The development of intelligent materials that can respond to the application of an external stimulus is of major interest for the fabrication of artificial sensing devices able to sense and transmit information about the physical, chemical and/or biological changes produced in our environment. In addition, if these materials can be deposited or integrated on flexible and transparent substrates and processed employing low-cost techniques their appeal is greatly increased. It is well known that single crystals of molecular conductors, consisting of ion-radical salts (IRSs), typically based on tetrathiafulvalene (TTF) derivatives, exhibit striking conducting properties and that such properties are affected under applied pressure or temperature variations.
Here, we show that by using bilayer (BL) films, composed of a polymeric matrix with a toplayer formed by a crystalline network of a conducting molecular charge-transfer salt, it is possible to translate micrometer-scale elastic elongations of the film into reversible deformations of the soft organic charge-transfer salt crystals at the nanometer scale monitored by the change of the electrical resistance.[1-2] Highly reproducible and stable device operation of the prepared sensors is shown by continuous cycling them over a period of 9.5 h without any degradation effects.
Since the origin of the large electrical responses to film elongations can be originated either by the deformation of the crystallite themselves or by changes in the contacts among the crystallites, we investigated the structural and conducting changes occurring in these films under cyclic monoaxial deformations by means of XRD analysis finding the soft crystal structure of these materials as responsible for the high sensitivity.
Additionally a new set of sensors based on BL-Films able to detect different stimuli from our environment will be presented.[3,4,5] This sensor platform enables the combination of the high electrical performance of single crystals with the processing properties of polymers towards a simple, low-cost and high sensitive sensor platform for applications in human health care, aeronautics and medicine.
References
[1] a) E. E. Laukhina, et al. Synth. Met., 70, 797, (1995) b) E. Laukhina et al., Synth. Met., 102, 1785. (1999) c) E. Laukhina et al., J. Phys. I France, 7, 1665, (1997).
[2] E. Laukhina, et al. Advanced Materials., 21, 1-5, (2009).
[3] Lebedev, V., European Journal of Inorganic Chemistry, 24, 3927-3932, (2014)
[4] I. Sánchez, IOVS, Vol. 52, No. 11 (2011)
[5] R. Pfattner, et al. Sensors & Transducers, Vol. 18, Special Issue, January, pp. 128-133 (2013)

To pave the way towards an all organic complementary electronics the lack of compounds proving sufficiently high electron mobilities has imposed major constraints in the past. However, recent results have indicated several organic semiconductors showing promising electron transport properties, one of which being Cl₂-NDI (naphthalene diimide) [1], which has already proven technological relevance by its electron mobility of about 1 cm²/Vs measured in polycrystalline thin films [2]. Vice versa, studies of the electron mobility in corresponding macroscopic single crystal samples as function of temperature and spatial orientation provide detailed insights into the intrinsic transport mechanisms and their relation to morphology as well as static and dynamic lattice deformations on microscopic length scales.
For this reason, we have performed temperature dependent measurements of the anisotropic electron mobility tensor in the (001) plane of sublimation grown Cl₂-NDI single crystals between 175 K and 300 K. Upon cooling from room temperature to 175 K the electron mobility along the direction of preferred transport monotonously increases from 1.5 cm²/Vs to 2.8 cm²/Vs according to a distinct temperature relation of T^-1.3. At first glance, these characteristics allude to a coherent, i.e. band-like charge carrier transport predominantly governed by inelastic scattering with acoustic phonons. However, as we will demonstrate in this presentation, the experimental mobility data can be consistently described within the framework of an incoherent, hopping-type model based on Levich-Jortner rates. In this case, the decrease of the thermally activated mobility upon cooling is overcompensated by the much faster decay of the incoherent phonon scattering contribution to the electronic couplings. As a result, the effective electron mobility increases towards lower temperatures even though the underlying electron transport still relies on an incoherent charge carrier motion. Thus, in contrast to the general paradigm, the increase of mobility at lower temperatures proves to be a necessary but not sufficient criterion for a band-like motion of charge carriers. Furthermore, we show that the impact of thermally induced lattice effects and enhanced electron-phonon interaction on the anisotropic mobility tensor can be discriminated by their respective spatial variation with temperature.
[1] J. H. Oh, et. al., Adv. Funct. Mater. 20, 2148 (2010)
[2] T. He, et. al., Adv. Mater. 25, 6951 (2013)

This lecture will describe the design, synthesis, and study of molecules as electronic materials. We will describe new single molecule electronic measurements on designer molecules. These studies provided a foundation to create a new class of solid-state material that are formed from the
self-assembly of atomically defined clusters. These new solid-state materials have structures that are the same as traditional solid-state materials, but here the subunits are formed from new building blocks, we call superatoms.

Borrowing the idea from Si industry, where the properties of Si semiconductors can be greatly enhanced through the doping of heteroatoms (e.g. B, P, As, Sb), we believe that the properties of oligoacenes (or conjugated polycyclic hydrocarbons) could be tuned through inserting heteroatoms (e.g. B, N, O, S, P, As) into the backbone of oligoacenes. Moreover, the properties of as-obtained heteroacenes strongly depend on the number, positions, types, valence, and mixing of heteroatoms. Here, I will report the synthesis, optical and electrochemical properties, as well as fabrication of some devices for a series of heteroacenes (Scheme 1).
Reference:
[1] P.-Y. Gu, F. Zhou, J. Gao, G. Li, C. Wang, Q.-F. Xu, Q. Zhang,* J.-M. Lu* J. Am. Chem. Soc. 2013, 135 (38), 14086.
[2] G. Li, Y. Wu, J. Gao, C. Wang, J. Li, H. Zhang, Y. Zhao, Y. Zhao, Q. Zhang* J. Am. Chem. Soc. 2012, 134(50), 20298.
[3] J. Xiao, H. M. Duong, Y. Liu, W. Shi, L. Ji, G. Li, S. Li, X.-W. Liu, J. Ma, F. Wudl,* Q. Zhang*, Angew. Chem. Int. Ed 2012, 124, 6198.
[4] G. Li, Y. Wu, J. Gao, J. Li, Y. Zhao, Q. Zhang,* Chem. Asian J. 2013, 8(7), 1574.
[5] J. Li and Q. Zhang* Synlett, 2013, 24, 686-696 as Invited review.
[6] G. Li, K. Zheng, C. Wang, K. S. Leck, F. Hu,* X. W. Sun,* Q. Zhang* ACS Applied Materials & interface 2013,5(14),6458.
[7] G. Li, H. M. Duong, Z. Zhang, J. Xiao, L. Liu, Y. Zhao, H. Zhang, F. Huo, S. Li, J. Ma, F. Wudl, Q. Zhang,* Chem. Commun 2012, 48, 5974.
[8] Y. Wu, Z. Yin, J. Xiao, Y. Liu, F. Wei, K. J. Tan, C. Kloc, L. Huang, Q. Yan, F. Hu, H. Zhang, Q. Zhang*, ACS Appl. Mater. Interfaces 2012, 4, 1883.

Anthradithiophene (ADT) derivatives have proven to be a front runner in the world of small molecule semiconductors for organic electronics due for the most part to its stability, and its impressive device performances especially in organic field effect transistors (OFET)¹. Payne et al² have shown already the effect of functionalizing the ADT backbone with silylethynylgroup on its crystal packing and consequently its electronic properties. In this presentation we reveal a new generation of unsymmetrical ADT&’s that was engineered to stack in an alternating fashion using the R3Si group as a leading force to dictate its packing in the solid state. This reduced functionalization level allows us to study and observe the effect of the S-S interaction in the ADT core and its responsibility in reducing the sulfur scrambling in the solid state^3,4 . Additionally, from the early days ADT&’s and functionalized ADT&’s have been synthesized as isomeric mixtures; despite a few attempts to synthesize the syn isomer⁵, there hasn&’t been any successful approach to separate and obtain the syn and the anti compounds in isomerically pure form. Inspired by the same synthetic approach used to make the unsymmetrical ADT&’s, I will be showing a new and simple method that can separate the syn and anti isomers of the F TES ADT chromatographically. Anti F TES ADT isomer has demonstrated an improved average mobility of 4.7cm²/Vs compared to 3.1 cm²/Vs for the isomeric mixture, using cytop as a dielectric.

In this work we present our findings on structural features and trends observed in single crystal structural studies on a series of oligothiophene and ethylenedioxythiophene (EDOT) molecules substituted with a variety of groups. In particular we were interested in structures of molecules endowed with strong electron accepting groups including: halogens, nitro, cyano, dicyanovinyl and tricaynovinyl groups. The focus of the presentation will be on how these structural modifications impact planarity and packing of molecules with emphasis on the role of inter- and intra- molecular interactions in the observed crystal structures of these materials. In addition synthesis, electrochemistry and optical properties of these closely related molecules will be presented.

Molecular packing and morphology of organic semiconductors in the solid state are some of the most crucial yet the most unpredictable parameters controlling the performance of organic electronics. I will describe a new strategy for controlling the co-assembly of p- and n-type organic semiconductors through complementary hydrogen bonding. The dipyrrolopyridine heterocycle is introduced as a p-type (donor) semiconductor component capable of complementary H-bonding with naphthalenediimides (acceptor).^[1,2] I will show that the H bonding self-assembly process (i) modulates the charge transfer interactions between the donor and acceptor, (ii) allows for precise control over the heterojunction structure and (ii) leads to a combination of the charge-transport properties of the individual components. These studies provide a foundation for advanced solid state engineering in organic electronics, capitalizing on the complementary H-bonding interactions.
[1] H. T. Black, D. F. Perepichka, Angew. Chem. Int. Ed. 2014, 53, 2138-2141
[2] H.T. Black, H. Lin, F. Bélanger-Gariépy, D.F. Perepichka, Faraday Discuss.2014, DOI: 10.1039/C4FD00133H

A general principle in organic semiconductor design to derive materials with large charge-carrier mobilities is to increase intermolecular electronic couplings by reducing the packing distance and increasing the spatial overlap of neighboring conjugated backbones. Though synthetically tunable non-covalent interactions determine the molecular packing and resulting electronic, optical, and mechanical properties of materials derived from π-conjugated molecules and polymers, considerable synthetic effort remains solely focused on the electronic and redox characteristics of isolated molecular species. Here, quantum-chemical approaches are used to investigate relationships between intramolecular and intermolecular non-covalent interactions, with a particular focus on exchange repulsion, and intermolecular electronic couplings. The studies highlight that judicious synthetic strategies are needed to overcome exchange repulsion in order to design materials with the intermolecular electronic couplings necessary to push forward new generations of organic electronic materials

Among the various energy-producing alternatives to oil, nuclear power is in the limelight because it is cost effective and emits almost no greenhouse gases. On the other hand, the alpha-emitting radionuclide such as uranium from nuclear power plants could contaminate neighboring environments, especially water, soil, and air. Aside from this, the uranium is contained in ores above natural background rates due to the presence of naturally occurring radioactive materials (NORMs). The binding affinity of the uranium toward biomolecules could cause acute and/or chronic harmful effects by inhalation and ingestion of the uranium. Therefore, the detection and the determination of the uranium in an environmental sample are important from standpoint of health physics and environmental protection. To analyze the uranium in the sample using an alpha spectrometer, the uranium should be a form of a thin film. Among various methods to make the uranium thin film, electrodeposition is the most common technique due to advantages of high deposition yield and high qualities of the films obtained with simple and inexpensive equipment. The radioactivity concentration of the uranium in an environmental sample is very low. Therefore, to measure the very low-level activity concentration of the uranium with a high level of accuracy, a thin and pure uranium film should be fabricated. While various experimental parameters affecting the electrodeposition method have been studied from many diverse perspectives, the uranium-electrodeposited film has not been analyzed well.
Here, we focused our efforts on the crystal and surface analyses of the uranium-electrodeposited layer. The uranium was chemically extracted from a bauxite ore, and electrodeposited on a stainless steel disc. In X-ray diffraction (XRD) patterns of the uranium film on the stainless steel disc, peaks related with U and UOx was observed. In positive and negative time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra, the uranium oxide composite was also confirmed. The images obtained by the elemental mapping of TOF-SIMS exhibited the uniform distribution of the uranium oxide of the electrodeposited film. The thickness and the chemical-composition information on the depth of the electrodeposited layer were analyzed with X-ray photoelectron spectroscopy (XPS) depth profiling. The XPS study presented that the peaks corresponding to U(VI) and U(V) decreased significantly with the increase of the depth while the peaks for U(O) and U(IV) increased. The surface morphology was also observed with an atomic force microscope (AFM). The radioactivity concentrations of uranium isotopes were measured with an alpha-spectrometer.
We expect that our detailed analysis of the uranium-electrodeposited film could help to develop the electrodeposition method of uranium for the measurement of the low-level activity concentration of uranium with a high level of accuracy.

Metal organic frameworks (MOFs) are an interesting class of extended crystalline materials that can be readily assembled by combining metal ions (components of nodes) and different organic ligands (structural linkers) via coordination chemistry, usually under solvothermal reaction conditions [1-3]. MOFs can be synthesized with particular porosity, shape, size, and volume. MOFs are frameworks with remarkably high surface areas of 6500 m² g^minus;1 and pore volumes of 3.6 cm³ g^minus;1. MOFs porosity are much higher than that of their corresponding inorganic zeolite analogues by 90% [1-3].
MOFs can be designed and systematically tuned by predesign in synthesis and post synthetic modifications. These modifications allow a simple optimization of the pore structure, surface functions, and other properties for specific applications such as novel desulfurization technology, biomimetic catalysis, and refinery catalysis [4-5]. Controlling the size and shape of the crystals is an evolving area in MOFs research, and they are means for optimizing the physical properties of MOFs for specific applications [6].
In this study the HKUST-1 metal organic framework (MOF) was modified from its extended crystalline structure into a nano-spherical metal organic framework. Also we present a facile synthesis of a nano-spherical MOF at room temperature using a capping agent via solvent-solvent methods. We investigated the ways of controlling the size and shape of MOFs crystals, since changing the physical properties of MOFs has lead to new magnetic, optoelectronic, gas adsorption, and catalytic properties. MOFs technology is a growing area in research focusing on controlling the size and shape of MOFs crystals. We studied the catalytic properties of the synthesized nano-sheperical MOF for the hydrodesulfurization reaction for the removal of sulfur from organo-sulfur compounds in crude oil.
[1] Camille Petit, Barbara Mendoza, and Teresa J. Bandosz. Reactive Adsorption of Ammonia on Cu-Based MOF/Graphene Composites. Langmuir 2010, 26(19), 15302-15309.
[2] Minh-Hao Pham, Gia-Thanh Vuong, Fre#769;de#769;ric-Georges Fontaine, and Trong-On Do. A Route to Bimodal Micro-Mesoporous Metalminus;Organic Frameworks Nanocrystals. Cryst. Growth Des. 2012, 12, 1008minus;1013
[3] Alberto Martinez Joaristi, Jana Juan-Alcan#771;iz, Pablo Serra-Crespo, Freek Kapteijn, and Jorge Gascon. Electrochemical Synthesis of Some Archetypical Zn^2+, Cu²⁺, and Al³⁺ Metal Organic Frameworks. Cryst. Growth Des. 2012, 12, 3489minus;3498.
[4] Shengqian Ma and Hong-Cai Zhou. A Metal-Organic Framework with Entatic Metal Centers Exhibiting High Gas Adsorption Affinity. J. Am. Chem. Soc. 2006, 128, 11734-11735
[5] Enrica Biemmi, Camilla Scherb, and Thomas Bein. Oriented Growth of the Metal Organic Framework Cu3(BTC)2(H2O)3*H2O Tunable with Functionalized Self-Assembled Monolayers. J. Am. Chem. Soc. 2007, 129, 8054-8055.
[6] Renzo, F. D. Zeolites as tailor-made catalysts: Control of the crystal size. Catal. Today 1998, 41, 37.

The Cd-Te oxides are the focus of many studies for their important non-linear optical properties [1]. Some electric properties of CdTe₂O₅ were introduced and investigated by Gorbenko et al [2]. CdTe semiconductors are being investigated for their efficiency in photovoltaic energy converters [3] and for their potential use as detectors for x-ray and γ- ray radiations [4]. CdTe oxides are very stable and can be used in solar cells in the same manner of using SiO₂ in electronic devices with Si base [5]. In particular, CdTeO₃ is used in photovoltaic p or n junctions to decrease or increase the open circuit voltage, respectively [6], and to form a non-reactive region on the interface [5]. Another excellent property is that the band gap of CdTe oxides can be varied from 1.5 eV to 3.8 eV according to the oxygen concentration [7].
A modified Bridgman growth approach was used to grow CdTe₂O₃ single crystals at a direction perpendicular to (001). Unlike the Czochralski method, which allows for the evaporation of CdO and TeO₂ during growth, the use of a modified Bridgman technique reduced that effect by covering the crucible or sealing it using a platinum foil. 33.3% CdO: 66.7% TeO₂ by mole were mixed in the jar mill, then pressed into small pellets and calcined for 24 hours at 650 #730;C. Melting the material briefly at 730 #730;C was used to test the thermal gradient reliability. Measured by a thermocouple on the side of the crucible, the material was then melted at a maximum temperature of 765 #730;C. Then the melt was cooled slowly at 2 #730;C /hr. Some optical and electrical measurements of the grown crystals were performed, including the dielectric constant, transmission/absorption spectra, and the electric resistivity. The stability of the crystal was tested at high temperatures using X-ray diffraction.
References
[1] V. Krämer, and G. Brandt, Act. Cryst., C41, 1152-1154, (1985).
[2] V. M. Gorbenko, A. Y. Kudzin, L. J. Sadovskaja, G. X. Sokoljanski, and V. P. Avramenko, Ferroelectrics, Vol. 110, 47 - 50, 1990.
[3] K. V. Krishna, V. Dutta, P. D. Paulson, Thin Solid Films: 444, 17 - 22, 2003.
[4] S. A. Awadallah, A. W. Hunt, R. B. Tjossem, K. G. Lynn, C. Szeles, and M. Bliss, Hard X-ray and Gamma Detector Physics III, Proceedings of SPIE: 4507, 2001.
[5] M. Y. El Azhari, M. Azizan, A. Bennouna, A. Outzourhit, E.L. Ameziane, and M. Burnel, Thin Solid Films, 366, 82 - 87, 2000.
[6] R. H. Bube, Photovoltaic Materials, Vol. 1, Imperial College Press, London, 1998, pp.144 - 146.
[7] A. Iribarren, E. Menèndez-Proupin, R. Castro_Rodr#943;guez, V. Sosa, J. L. Pe#328;a, and F.

High degree of sp³ hybridization and large mass density of carbon are considered as important prerequisites for superhard phase of carbon. The C₂₀ and C₃₆ are both small members in the fullerene family, offering the extreme curvature of the cage surface, which makes them easy to change the hybridization from sp² to sp³. Comparing with the other members of fullerene family, small fullerene molecules have large carbon mass density. In this work, new carbon allotropes have been uncovered by compressing C₂₀ and C₃₆ solid based on Self-Consistent-Charge Density Functional Tight Binding (SCC-DFTB) simulation. They are identified to be energetically more favorable and stable than corresponding molecule. The volume compression calculations suggest that the Phase III of C₂₀ has very high anti-compressibility with bulk modulus of 427 GPa and phase II of C₃₆ also shows good anti-compressibility with excellent high-pressure stability from 40 GPa to 400 GPa. Phase III of C₂₀ and phase II of C₃₆ are both semiconductors with 5.1 eV and 4.7 eV band gap, respectively, which indicates they are transparent. Our results indicate that small fullerene both C₂₀ and C₃₆ are excellent building blocks of superhard carbon materials and can be easily converted to transparent superhard material under cold compression, which provides a new idea to synthesize superhard carbon material.
Reference
1. LI Jianfu, ZHANG Rinqin. New superhard carbon allotropes based on C₂₀ fullerene. Carbon 63, 571-573 (2013).

Aluminum oxide is one of the high-k dielectric insulators commonly used in low voltage organic field effect transistors (OFETs). To enhance the crystallinity and carrier mobility, self-assembled monolayers (SAMs) are required to reduce the trap density and adjust the surface energy between the aluminum oxide and organic active layers. However, the conventional methods to deposit SAM are usually done by relatively time-consuming method and the deposition process would require hours or longer time. As a result, there is a strong need for fast printing of SAM with patterning capability in the applications of OFET.
Here we developed a novel time-saving and easy-to-pattern deposition method by gravure printing of SAM. The whole printing process on 2.5 cm × 2.5 cm substrate can be completed in 1 minute. The transistors based on Dinaphtho[2,3-b:2prime;,3prime;-f]thieno[3,2-b]thiophene (DNTT) using such SAM deposition approach exhibit an average field-effect mobility of 0.965 cm² V^-1s^-1 (highest is 1.05 cm² V^-1s^-1), which is higher than the control sample where SAM is deposited by submersion and the DNTT is deposited together. This fast pattering method of SAM deposition opens a way for printed circuits fabrication.
For the application of this patterned method, inverters were made by connecting two kinds of p-type transistors based on DNTT and 2,9-didecyl-dinaphtho-[2,3-b:2prime;,3prime;-f]thieno[3,2-b]thiophene (C10-DNTT) respectively. On those patterned areas with SAM, DNTT was deposited by thermal evaporation; and on those bare dielectric region, which is suitable for solution-processed organic semiconductor, single crystal C10-DNTT was deposited by drop casting. The overall performance of these inverters are analyzed and correlated to the quality of the SAM.

#12288;High-speed operating organic field-effect transistors (OFETs) fabricated by printing techniques have attracted much attention due to their promising potential for achieving flexible logic circuits over large area. Many attempts have been made to obtain single-crystalline active layers for use in OFETs having higher mobility. Performance variation in single-crystal OFETs, however, hinders their path to integrated-circuit applications, which is probably due to anisotropic charge transport in the active layers. To improve performance uniformity, the molecular orientation and crystalline morphology in the active layers should be artificially controlled. In this study 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) single-crystalline domains were deposited on SiO₂/Si substrates with Au strips using electrostatic spray deposition (ESD), and the correlation between the molecular orientation and the stripe direction was investigated by angle-dependent polarized Raman spectroscopy.
#12288;Au strips were defined on SiO₂/Si substrates via photolithography and liftoff. The width of Au stripes was 20 mu;m. TIPS pentacene was sprayed onto the substrates in air at 50 0C. TIPS pentacene molecules (0.1 wt%) were dissolved in a mixed solvent of 1,2-diclorobenzene (o-DCB) and acetone. The spraying time was 10 sec to study the initial growth stage. Raman spectroscopy was performed in a backscattering geometry using a single grating monochromator and a solid-state laser served for excitation at 532 nm. The incident laser radiation was linearly polarized (along the y direction). The sample stage was rotated around the optical axis of the incident laser (z direction). Raman spectra were taken at 100 rotation intervals. The polarization angle was defined as 00 when the polarization vector of the incident laser was parallel to the stripe direction. Since the acene planes in TIPS pentacene take an edge-on orientation on the substrates, C-C ring stretch modes can be used to probe the in-plane orientation. When the laser polarization aligns parallel to the long molecular axis of TIPS pentacene, a maximum Raman scattering intensity will be observed at 1578 cm^-1 (long-axis mode).
#12288;Single-crystalline domains nucleated at Au stripes were investigated. The Raman scattering intensities of the long-axis mode were highly dependent on the polarization angle and peaked at around the polarization angle of 500 or 1300, probably indicating that the [210] crystallographic axis was parallel to the stripe direction. This result demonstrates that the molecular orientation in TIPS pentacene single-crystalline domains can be controlled by the Au stripes like graphoepitaxy.

Precise control over the chirality of self-assembled structures remains one of the biggest challenges in crystal engineering. A process to control bulk, homochiral structures with predetermined handedness would have uses in many systems, from molecular scales - where nanochirality is found to be responsible for the large-scale formation of chiral cells, tissues, and organs - to metamaterials which can split light into circularly polarized components. By using Monte Carlo and Molecular Dynamics simulations, we propose two design strategies for self-assembly of 3D chiral crystals with and without a priori chirality bias: 1) by employing tailored isotropic pair-potentials, we show how spherical Brownian particles can have spontaneous chiral symmetry breaking during crystallization; and 2) by changing the shape of the particles to tailored chiral geometries, we show how the handedness can be now enforced and a priori guaranteed. We discuss the role of entropic force directionality for the formation of chiral crystals with desired handedness and suggest a new route for assembly of chiral structures in the nano, colloidal and mesoscale.

Water splitting on semiconductor photocatalysts has received much attention for the production of renewable hydrogen from solar energy and water. Alkali earth tantalum oxynitride perovskites, ATaO₂N (A = Ca, Sr, and Ba), are promising candidates for the photocatalytic splitting of water under visible light because they have smaller band gaps and are stable in aqueous solutions. In the present study, a special emphasis was put on BaTaO₂N as a suitable photoanode material since it can harvest visible light up to 660 nm and possesses enough high conduction band bottom for H₂ production. The IPCE value for BaTaO₂N was recently reported to be ca. 10 % at 1.2 V vs RHE under 600 nm, which is the highest among photoanode materials that can harvest light beyond 600 nm for water oxidation.¹ The ATaO₂N are generally fabricated by nitriding oxide precursors under high temperature using NH₃. Thermal decomposition of oxynitrides during high-temperature nitridation, introducing nitrogen vacancies in the crystalline product, makes it difficult to obtain highly crystalline ATaO₂N crystals with less defect density. Nitrogen vacancies formed produce a large band bending at the solid-liquid interface, forming a Schottky-type barrier that hinders the prompt migration of electrons from the bulk to the surface reaction sites.² To reduce the defect density in the oxynitride photocatalyst crystals, the improvement of a preparation method is considered to be essential. In this study, we applied a one-step NH₃-assisted flux method to grow ATaO₂N photocatalyst crystals with a less defect density. The effect of preparative conditions, such as flux type (chlorides, nitrates, carbonates, and sulfates), growth temperature (900-1000°C), holding time (0-10 h), and solute concentration (1-50 mol%) on the growth of BaTaO₂N crystals were investigated. To grow ATaO₂N crystals, BaCO₃ and Ta₂O₅ were mixed as solute with various fluxes for 30 min, a solute-flux mixture with the total mass of 3 g was placed in a Pt crucible, heated to 900-1000°C in a horizontal tube furnace with a heating rate of 10°Cmiddot;min^-1 and a holding time of 0-10 h under an NH₃ flow (200 ml/min). The flux-grown BaTaO₂N crystals were separated by washing the final product with hot water and dilute nitric acid, and dried at 100°C for 12 h. Single-phase BaTaO₂N crystals with the average size of 200 nm could be grown by a one-step NH₃-assisted flux method using only the KCl flux at 950°C for 10 h with 10 mol% solute concentration. It was found that KI, KF, MgCl₂, CaCl₂, K₂SO₄, K₂MoO₄, and KNO₃ were not suitable fluxes for the growth of BaTaO₂N crystals under the current experimental conditions. The photocatalytic activity of the flux-grown BaTaO₂N crystals for the sacrificial O₂ evolution was also investigated.
References
[1] Higashi et al., J. Am. Chem. Soc. 2013, 135, 10238.
[2] Maeda and Domen, J. Phys. Chem. C 2007, 111, 7851.

A series of expanded MOF-74 containing high-density open metal sites aligned along hexagonal channels were prepared by microwave-assisted or simple solvothermal reactions. The activated materials are structurally expanded when guest molecules or CO2 are introduced into the pores. The Lewis acidity of open metal sites varies in the order Mn < Co < Ni > Zn as probed by C=O stretching vibrations in the IR spectra, which is associated with the CO₂ adsorption enthalpy. The framework stability against water conditions coincides with the order of Lewis acidity. Among these series, the structural stability of Ni(dobpdc) is exceptional; it endured in water vapor, liquid water, and refluxing conditions for 1 month, while this solid remained intact upon exposure to solutions of pH 2 - 13.

Three-dimensional frameworks, [Zn(ethoxy-L)(bpy)](1) and [Zn(propoxy-L)(bpy)](2) were prepared via a solvothermal reaction using ethoxy-, propoxy-H₂L ligand (H₂L=biphenyl-4,4&’-dicarboxylic acid), and zinc(II) nitrate hexahydrate. Single crystal X-ray diffraction analysis reveals that 1 and 2 exhibit 5-fold interpenetrating network. Each Zn center is coordinated by two O atoms from H₂L and two N atoms from bpy. These compounds show highly selective sensing of nitrobenzene (NB) via fluorescence quenching mechanism. The initial fluorescence intensity was almost recovered after five cycles, suggesting reversibility of compounds for detection application. The structural transformation from 1 to 2 occurred via dissolution-recrystallization process, while the reverse conversion was not realized. This irreversible change is probably associated with their thermodynamic framework stability.

Laser-induced chemical vapor deposition (LCVD) can be employed to fabricate microstructures of different types and to grow large-area thin films. The high cooling rates and/or temperature gradients that can be achieved with certain laser parameters permit to deposit materials with nonequilibrium microstructures and/or to synthesize chemically new compounds that cannot be synthesized by any other technique. The decomposition of precursor molecules in LCVD can be activated thermally (pyrolytic LCVD) or non-thermally (photolytic LCVD) or by a combination of both (photophysical LCVD). In an effort to deposit localized heterostructures, a feasibility study was carried out using a continuous wave green laser (green) for high quality germanium crystalline thin film deposition on Si.
Before performing experiments, we have done modeling to determine the Si thermal profile influenced by laser beam parameters, including, power, shape, size, polarization and scan speed. Si wafer thickness and size highly impact on the thermal profile, as well. In this case, fixed wafer thickness and size were used. We also studied chemical kinetics for GeH₄ dissociation and Ge film deposition on Si, and identified the requirement of Si wafer temperature rise at least 450 °C to deposit Ge. Simulation task proposed the 532 nm laser parameters to obtain the Si wafer temperature change from 400 to 1400 °C.
Considering the computation feedback, experiments were set up for Ge deposition on Si using 30% GeH4 in H2 (500SCCM) at 400 Torr chamber pressure with a Gaussian laser beam of 5µm diameter, 532 nm wavelength, having power ranging from 0.2 to 1.25 W. Laser scan speed range was from 0.01 to 1 mm/s. 5 µm wide and 1 cm long Ge lines were deposited with different laser powers. Films were characterized by XRD, Raman and high resolution TEM. It has been observed that high purity, high crystalline Ge films can be deposited with high deposition rate by LCVD. This work proves the feasibility of laser to be a possible new energy source for thin film deposition.

The electronic properties of solution-processable small molecule organic semiconductors (OSCs) have rapidly improved in recent years, rendering them highly promising for various low-cost, large area, flexible, and transparent electronic applications such as displays, RFID tags, and integrated logic circuits. In order for these applications to be realized, nucleation and crystallization of OSCs must be carefully controlled so that the OSCs are patterned and precisely registered to within the transistor channel with uniform device properties over a large area—a task that that remains a significant challenge. In this presentation, we introduce a novel nucleation and crystallization technique known as CONNECT (Controlled OSC NucleatioN and Extension for CircuiTs) that utilizes differential surface energy and solution shearing to induce nucleation and crystal growth at specific points, resulting in self-patterned and self-registered OSC film within the channel region with well-aligned crystalline domains. The well-aligned crystals with minimal grain boundaries over the channel region resulted in low variability in device-to-device characteristics over a large area with average on-current density of 0.4 mu;A/mu;m and on/off ratio of 6.15 x 10(3). We have fabricated transistor density as high as 840 dpi, with a yield of 99%, previously unseen in literature. We have also built various logic gates and a 2-bit half adder circuit to demonstrate the feasibility of our technique in generating large-scale electronic circuits in a facile and economical manner.

Semiconducting organic crystals have been vigorously investigated for fabricating devices and applying to diverse applications. For the high performance OTFTs, single crystal phase is typically desired within a channel layer due to the fact that the transport of carriers mainly depends on the grain boundary as well as molecular ordering. Also, in order to control the position and orientation of organic single crystals with a densely packed molecular structure, several techniques such as inkjet printing and sheared deposition using a self-assembled monolayer pattern have been proposed. In this presentation, we used surface-mediated solvent vapor anneal (SMSVA) process of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) organic films, forming diverse patterns of their organic single crystals. Spatial-photochemical irradiation using deep ultraviolet (DUV) on a polymer dielectric film enables the determined organization of C8-BTBBT single crystals with desired position and orientation. In SMSVA process, C8-BTBT small molecules become mobile on soluble polymer layer and re-organized into micro rod-shaped single crystal only at pristine polymer dielectric region. Narrow trench of pristine polymer dielectric produced large arrays of C8-BTBT single crystals while their diverse patterns such as a simple line, square, triangle and zigzags were readily possible as well.
Based on these C8-BTBT single crystals, we fabricated high performance of organic single crystal transistor on 3-um-thick flexible film in which the saturation mobility of devices exceeds ~ 5 cm²/Vs. It was also found that the high performance of single crystal transistor remained functional without noticeable degradation following the aggressive bending test. More details will be presented at the conference.

Solution printing holds the promise to manufacture future electronic materials in an energy-efficient, low-cost, high-throughput fashion. However, major challenges remain, in controlling the morphology and molecular packing of the printed thin films, which critically impact the printed device performance. We introduce a new methodology to control thin film morphology during solution printing - flow enhanced crystal engineering, or FLUENCE, which leverage the unique characteristics of meniscus-guided solution coating methods, such as solution shearing and roll-to-roll printing. Using this approach, we have recently demonstrated for the first time large area coating of aligned single-crystalline thin films for organic field effect transistor applications. The high crystalline quality of FLUENCE printed thin films has enabled us to resolve the structures of newly discovered polymorphs of small molecule organic semiconductors, thereby uncovering that the charge carrier mobility can be altered by orders of magnitude among structurally similar crystal polymorphs.
We further extend the FLUENCE concept for controlling micro-phase separation in printed all-polymer solar cells. The design concept is verified via finite element based fluid simulations. The resulting morphology of the FLUENCE-printed thin films were characterized using resonant soft X-ray scattering to extract the domain size, and by grazing incidence X-ray diffraction to analyze the relative degree of crystallinity of the polymer donor. We found that FLUENCE significantly improved the crystallinity of the thin film, and reduced the characteristic length scale of microphase separation, both of which contributed to improved power conversion efficiency of the solar cell devices. We expect our strategy of flow-enhanced crystal engineering to go beyond printed transistors and photovoltaics to impact the greater community of crystal engineering.

We demonstrate that photoconductivity of pristine rubrene crystals exhibits several distinct regimes, in which photocurrent as a function of cw(continuous wave) excitation intensity is described by a power law with exponents sequentially taking values 1, 1/3 and frac14;. We show that this photocurrent is generated almost exclusively at the surface of pristine rubrene crystals, while the bulk photocurrent is dramatically smaller and follows a different set of exponents, 1 and ½. A model based on exciton fission, fusion and triplet-charge quenching is developed to describe these non-trivial effects in photoconductivity of highly ordered organic semiconductors.

This communication will display that single-crystal of organic semiconductors can see their properties tuned. They can also be used in various electronic devices. For example, a new transistor in the field of organic electronics will be introduced. If field-effect transistors are easily and commonly produced with organic semiconductors, the Bipolar Transistor has not yet been successfully made with organic materials. Here, single-crystals of P and N type of various organic semiconductors are laminated to form a PNP stacks. The two PN junctions shows typical IV responses. Such a simple device shows a bipolar transistor behaviour with some current amplication. If performances of such Organic Heterojunction Bipolar Transistors (OHBT) are still below those of inorganic-based ones, the research presented here opens a new route for the developpment of a new generation of organic semiconductor based circuitry.

Organic semiconductor research till now has developed mainly two kinds of organic field effect transistors (OFETs) i.e. single crystal transistors^1-3 and thin film transistors.¹ Organic thin film transistors (OTFTs) are very easy to fabricate using spin coating or evaporation methods and offer large area, flexibility and ease of production. Single crystal transistors however, are often tedious to prepare as it requires complex procedures for preparation of single crystals and accurate positioning of the crystal. There have been a great deal of research in single crystal transistors as it offers high mobility and better device performance as well as stability due to fewer defects or grain boundaries compared to thin films. Here we demonstrate a new kind of transistor which can be prepared with similar ease as thin films but is based on single crystals. We employ one additive deposition step of conducting pattern to produce the statistical transistor that is based on organic single crystallites statistical transistor (OSCST). Both n and p-type solution processable small molecules were prepared which can form microns size single crystals by annealing the thin film, of these molecules, at temperatures in the range of 90-150^oC. At these temperatures the molecules have enough mobility to find stable stacking position and hence can self-arrange¹.
To demonstrate the concept we make use of circular stencil mask pattern to deposit metallic islands, as the last fabrication step. The spatial pattern of these islands was designed to both avoid shorts and ensure inter-connectivity between the quasi-randomly distributed single crystallites and to the source/drain electrodes. The resulting effective mobility is found to be very close to that of single crystal transistor made of the same material suggesting that the use of the one additive step, which is of resolution suitable for printing, opens exciting opportunity for manufacturing single crystal like transistors, the OSCSTs. We will also show that the concept behind the organic single crystallite statistical transistor (OSCST) can be applied also to other material systems and act as performance booster.
References:
1.Kumar, P., Shivananda, K. N., Zajaqczkowski, W., Pisula, W. , Eichen, Y., & Tessler, N. The Relation between molecular packing or morphology and chemical structure or processing conditions: the effect on electronic properties. Adv. Funct. Mater. 24, 2530-2536 (2014)
2.Yi, H. T., Payne, M. M., Anthony, J. E. & Podzorov, V. Ultra-flexible solution-processed organic field-effect transistors. Nat. Commun. 3, 1259 (2012)
3.Katz, H. E., Lovinger, A. J., Johnson, J., Kloc, C., Siegrist, T., Li, W., Lin, Y.Y., Dodabalapur, A., A soluble and air-stable organic semiconductor with high electron mobility. Nature 404, 478-481 (2000)

OFETs based on single crystals afford excellent opportunities to examine fundamental connections between charge mobility, molecular structure, and crystal packing. A particularly exciting recent development is the increase in the number of single crystal materials that exhibit OFET mobilities near 10 cm²/Vs and band-like behavior in which mobility increases as the device temperature decreases (up to a point). Observations of such large mobilities suggest that in these systems the intrinsic mobility is approached. The first part of this talk will describe single crystal OFET measurements on a series of rubrene derivatives that have been designed so that the unit cell parameters are systematically tuned. The impact of the crystal structure on carrier mobility and the temperature dependence will be discussed. The second part of the talk will focus on transport in rubrene single crystal OFETs gated with electrolytes (e.g., ionic liquids) in order to achieve extremely large charge carrier densities, on the order of 0.3 holes/molecule. It will be shown that the carrier density can be confirmed by Hall measurements, and further, that the insulator-to-metal transition is very closely approached. Future prospects for understanding transport at high charge densities using electrolyte gating will be discussed.

Two-dimensional colloidal crystals are promising targets for numerous technological applications, including data storage and manipulation of light, and they are unique model systems for the investigation of crystallization processes. Two-dimensional crystallization of spherical colloidal particles can be achieved by the application of alternating current electric fields produced by electrodes arranged in a coplanar geometry. Devices with this configuration provoke the formation of linear chains of colloidal particles aligned parallel to the electric field as a consequence of polarization of the individual particles and the associated dipole-dipole interactions. If the dielectric constant of the particles is less than that of the surrounding medium, as in the case of polymer-based colloids dispersed in water, these chains aggregate to the center of the device where the electric field strength is at a minimum, thereby forming stable hexagonal close-packed crystals with the maximum achievable packing fraction, phi;, of 0.91. In this device configuration, crystalline phases with lower packing fractions, such as square-packed crystals, are inaccessible. Larger electric field strengths, the only direct handle for regulating particle assembly in these devices, create an upward dielectrophoretic force that overcomes the downward gravitational force, thus disrupting the colloidal 2D crystals. Investigations in our laboratory, however, have discovered that an array of dielectric barriers in the device channel permits the formation of different 2D packings of colloidal spheres owing to local potential wells that trap the particles and stabilize them on the device surface, even at high electric fields. At applied electric field strengths of 400 V/cm or lower, particles aggregate in the potential wells and form hexagonal close-packed crystals. When the applied electric field strength is increased beyond 400 V/cm, induced dipole interactions between particles causes a phase transition in the confined crystals to a square-packed phase with a lower packing fraction of phi; = 0.79. The presence of defects in these crystals, such as vacancies and insertions, was observed to affect the crystalline phase at high electric field strengths. When a single vacancy is present, for example, rhombohedral-packed crystals with a packing fraction of phi; = 0.66 are observed, while crystals with two or more vacancies form mixed square- and hexagonal-packed crystalline phases at high electric field strengths. These defect-dependent phase transitions in colloidal crystals are reminiscent of the observed effect of lattice imperfections on phase transitions in ferroelectric materials, indicating that the factors governing crystalline phase transitions can span multiple length scales.

Advances in synthesis techniques have produced colloids and nanoparticles in a
diverse array of shapes that can be assembled into bulk crystals. That bulk
structure is strongly affected by particle shape in idealized systems is widely
established in the literature. However, this literature leaves open three key
questions: (i) We know that shape affects structure, but how? (ii) Does shape
matter in experimental systems where other interactions are present? (iii) How
do we tailor particle shape for a target structure? In this talk we discuss
recent work [1,2] aimed at answering these questions.
[1] G. van Anders, N.K. Ahmed, R. Smith, M. Engel, and S.C. Glotzer, ACS Nano 8, 931 (2014).
[2] G. van Anders, D. Klotsa, N.K. Ahmed, M. Engel, and S.C. Glotzer, PNAS, in press (2014).

Sub-lithographic sizes, defect-free structures, unique geometries, remarkable mechanical and electronic properties; these have all been the superior features enjoyed by chalcogenide nanocrystals, making them promising candidates for energy storage devices, non-volatile memory devices, topological insulators, thermo-electrics and optoelectronics. However, the actual industrialization relies substantially on the ability to control the position and properties of the deposited nanocrystals. Selective growth of single nanocrystals is therefore of paramount importance.
Here we show that using chemical vapor deposition (CVD) with custom-synthesized single source precursors, we are able to selectively deposit a variety of chalcogenide crystals (TiSe₂, SnSe₂, Bi₂Te₃, and Sb₂Te₃) into TiN holes of the lithographically patterned TiN/SiO2 substrates [1-3]. Furthermore, this high level of selectivity remains when the TiN hole are reduce to sub-micrometer size for Bi₂Te₃ and Sb₂Te₃, resulting in single nanocrystals being deposited in each TiN hole with no deposition on the surrounding SiO₂. We demonstrate the control over the preferred orientation of the deposited single nanocrystals by adjusting the TiN hole size. Scanning Electron Microscopy (SEM) images show that the nanocrystals lie flat in the TiN holes with diameter larger than 1um, showing the <0 0 1> preferred orientation. For those of 100-500 nm holes, the individual nanocrystals stand on a side, showing strongly preferred <1 1 0> orientation. We will report the growth, materials, and electronic properties of the above compounds. SEM, AFM, X-ray diffraction, Raman spectroscopy, Hall and Seebeck measurements will be presented. The origin of the selective growth will be discussed.
[1] Highly Selective Chemical Vapor Deposition of Tin Diselenide Thin Films onto Patterned Substrates via Single Source Diselenoether Precursors, C. H. de Groot, C. Gurnani, A. L. Hector, R. Huang, M Jura, W Levason, and G. Reid, Chemistry of Materials, 24, 4442-4449 (2012).
[2]Area Selective Growth of Titanium Diselenide Thin Films into Micropatterned Substrates by Low-Pressure Chemical Vapor Deposition, S. L. Benjamin, C. H. de Groot, C. Gurnani, A. L. Hector, R. Huang, K. Ignatyev, W. Levason, S. J. Pearce, F. Thomas, and G. Reid, Chemistry of Materials, 25, 4719minus;4724 (2013)
[3] Controlling the Nanostructure of Bismuth Telluride by Selective Chemical Vapour Deposition from a Single Source Precursor, SL Benjamin, CH de Groot, C Gurnani, AL Hector, R. Huang, E. Koukharenko, W. Levason and G. Reid Journal of Materials Chemistry A, 2, 4865-4869 (2014)

For centuries, crystals have been considered to be the purest form of matter and crystallisation is used as a major technique for purification. Crystals are characterised by a set of strictly defined properties, such as morphology, hardness and colour.¹ Recent investigations challenge these classical views and show that minerals derived from biological systems are often enriched with proteins that modify the morphology of growing crystals and enhance their mechanical properties.² In this work we exploit the observation that amino acids can be incorporated within calcite single crystals to successfully dye calcite crystals. While calcite co-precipitated with dye molecules alone remains completely colourless, we demonstrate that calcite can be efficiently coloured by co-precipitation with dyes and amino acids. Importantly, a given dye can only be incorporated using very specific amino acids, where effective combinations were rapidly determined using an automated pipetting robot programmed to follow a genetically inspired algorithm.
The possibility of guiding the colorant along specific crystallographic directions using mixtures of amino acids was also investigated, where control over the crystallization conditions resulted in the formation of coloured geometrical patterns within the crystals (e.g. hourglass or Maltese cross motifs). Stained crystals could also be used as seeds in further crystal growth, resulting in crystals containing complex patterns of dye. The generality of this novel experimental strategy was then demonstrated by using it to dye crystals of Sr(NO₃)₂, SrCO₃ and BaCO₃. The successful encapsulation of dyes within certain oxides (such as ZnO or TiO₂) may significantly enhance the efficiency of currently existing photovoltaic devices, such as dye-sensitised solar cells. The structure of the dyed crystals was further evaluated using SEM, TEM and synchrotron PXRD in order to establish links beteween the strain introduced to crystal lattices and the amount of incorporated organic molecules.
This work therefore demonstrates that colour does not have to be an intrinsic property and can be introduced into crystals using a biomimetic approach. A further important feature of the resultant composite crystals is that the organic component is protected from solar UV radiation and atmospheric oxygen therefore it should not degrade after a prolonged period of time. The reported method is expected to be equally applicable to other organic compounds which do not exhibit natural colouration, such as active pharmaceutinal ingreedients or anti-fungal agents.
1. P. Atkins and J. de Paula, Physical Chemistry, IX edn., W. H. Freeman, 2009.
2. S. Mann, D. D. Archibald, J. M. Didymus, T. Douglas, B. R. Heywood, F. C. Meldrum and N. J. Reeves, Science, 1993, 261, 1286-1292.

Lyotropic chromonic liquid crystals (LCLCs) are formed by soluble small molecule mesogens. LCLCs are named after the anti-asthmatic drug disodium chromoglycate, the most-well studied such compound in recent years. However, a handful of LCLCs have languished in the literature since the early part of the 20th Century. Unlike typical lyotropic phases, the components of LCLCs lack long chains and are not micelle-forming amphiphiles. At present, the lyotropic behavior of small molecules has been observed in a number dyes and drugs, each discovered serendipitously. Here we explore whether it is possible to recognize the features of small molecules leading to ordered fluids and thereby design such phases.
One of the most well known LCLCs is the dye sunset yellow (SSY, disodium 6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonate). Our interest in this compound stems from our research in growing mixed crystals that contain dye molecules such as SSY. These mixed crystals grow at concentrations of SSY known to favor the formation of dimers and trimers, on their way to chromonic aggregates. We have undertaken a theoretical study of the structures and dynamics of dimers and higher oligomers of sunset yellow. Initially gas phase vdW-DFT simulations of seven possible dimer configurations were performed and the structures and energies of these compared to results from a force field model. Excellent agreement between the two techniques was obtained with the largest deviation of only 3 kJ/mol. Confident that the potential model was of excellent quality, molecular dynamics and metadynamics simulations of dimers and higher oligomers in solution were undertaken to establish the dynamical behaviour of SSY molecules in water. We observed a remarkable correspondence between solution structure and crystal structure.
With these tools in hand, we set out to design a minimal LCLC mesogen that has all of the characteristics necessary to form an anisotropic fluid. That exploration will be described herein.

Intramolecular motion in the solid state can be tailored to occur from kHz to GHz rates by synthesizing organic molecules with dumbbell-like architectures. In the first part of the talk, recent advances that contribute to the understanding of segmental motion in crystals will be discussed. Those studies helped us to devise new ways to employ molecular rotation in order to obtain organic materials with modulated properties, i.e. solid state emission.
Our interest in luminogenic organic compounds is based on their potential technological applications like sensors, biological probes and organic light-emitting diodes, among others. Strong fluorescence of organic molecules in the solid state is often related to the restriction of the intramolecular rotations upon crystallization that would otherwise occur in solution, a phenomenon known as Aggregation-Induced Emission (AIE). The second part of this presentation will feature our current efforts towards the synthesis of π-conjugated molecules designed to present fast molecular reorientations in the solid state. Exploring the molecular dynamics in the crystals of this highly conjugated systems may help us to understand better the mechanism of the AIE phenomenon and to generate novel organic materials with controllable emission.

Single crystals of organic charge transfer compounds with low concentration of imperfections and high purity are outstanding objects for the study of relation between charge transfer and physical properties. The degree of charge transfer in compounds impacts antiferromagnetism, superconductivity, electron-phonon interactions and energy storage.
Crystal growth of binary compounds made from organic donors and acceptors is more complicated than that of monomolecular crystals. For studies of charge transfer degree, compounds with multiple stoichiometries are especially desired. However, systems with multiple stoichiometries are rare. Due to the different physical properties (solubilities, sublimation temperatures) of donors and acceptors, the stoichiometry of the synthesized compounds may differ from the stoichiometry of the starting materials.
In this study we observed an interesting phenomenon: the final stoichiometries of single crystal P1T1 (perylene1:TCNQ1) and P3T1 (perylene3:TCNQ1) are not affected by the stoichiometry of the starting materials, but by the solvent in which the perylene-TCNQ crystals were grown. The P1T1 crystals were grown from toluene, whereas the P3T1 crystals were grown from benzene regardless of the acceptor/donor stoichiometry in the starting materials. The solubility data were employed to analyse the effect of solvent on the stoichiometry of the perylene-TCNQ charge transfer single crystals. Steady-state optical spectra and time-resolved fluorescence measured in a mixture of perylene and TCNQ in toluene and benzene, confirmed selective crystallization of P1T1 and P3T1 from toluene and benzene.
In contrast to solution growth, when utilizing the physical vapour transport (PVT) method, a mixture of monomolecular crystals, P1T1 (perylene1:TCNQ1), P2T1 (perylene2:TCNQ1) and P3T1 (perylene3:TCNQ1) is obtained. P2T1 is a new discovered structure. The charge transfer degrees of P1T1, P2T1 and P3T1 have been measured and calculated. Field-effect transistors on the single crystals&’ surfaces of P1T1, P2T1 and P3T1have been made. The results reveal thatP1T1 is typically an n-type semiconductor, P3T1 showed p type behaviour, whereas P2T1 showed ambipolar properties.

Devices based on organic materials are currently attracting great attention for applications where low-cost, large area coverage and flexibility are required. In addition, the versatility of organic synthesis allows to chemically modify their molecular structure and functionality, the solid state structure and the resulting macroscopic properties, for the preparation of tailored materials for specific uses.[1]
Tetrathiafulvalenes (TTF) have shown to exhibit excellent OFET mobility (up to 6 cm²/Vs) as well as easy processability.[2,3] Thus, TTFs offer a suitable platform to perform structure-mobility correlation studies, due to the fact that their chemistry is very well-known. It is possible to synthesize a large variety of very similar molecules exhibiting different solid-state organization or different electronic structure.
Here we will describe our recent work related to explore the influence of crystal structure i.e polymorphism [4] on the charge transport properties, electronic structure fusing electron withdrawing groups to the TTF core to achieve ambipolar behaviour [5,6] and device configurations in TTF OFETs employing different architectures and electrodes.[7-9]
References
[1] M. Mas-Torrent, et al. Chem. Rev., 111, 4833, (2011)
[2] M. Mas-Torrent, et al. J. Mater.Chem., 16, 433, (2006)
[3] M. Mas-Torrent, et al. JACS., 126, 8546, (2004)
[4] R. Pfattner, et al. Adv.Mater., 22, 4198, (2010)
[5] C. Moreno et al. J. Mater.Chem., 22, 345, (2012)
[6] F. Otoacute;n et al. CrystEngComm, 13, 6597, (2011)
[7] R. Pfattner, et al. J. Mater. Chem., 22, 16011, (2012)
[8] R. Pfattner, et al., Org. Electr., 15, 211, (2014)
[9] R. Pfattner, et al., Phys. Chem. Chem. Phys., (2014), DOI: 10.1039/c4cp03492a

In this presentation we will discuss recent progress in applying molecular engineering to optimize the properties of dendrimers employed in light-emitting diodes. We synthesized hole-transporting dendrimeric molecules containing dioctylfluorene and spirobi(fluorene) as the core unit and different numbers of carbazole and thiophene moieties as the peripheral groups. The photophysical properties were investigated by UV-Vis absorption and photoluminescence measurements in dilute chlorobenzene solution as well as in thin film. The electrochemical behavior of the dendrimers were investigated by cyclic voltammetry (CV). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal behavior of the materials. All dendrimers exhibited bright green light emission between 512-528 nm. Finally, we explain the differences in performance among the dendrimers via DFT calculations and electronic structure determination.

Yujing Liu^1,2,3 and Hanying Li^1,2,3,*
1MOE Key Laboratory of Macromolecular Synthesis and Functionalization, ²State Key Laboratory of Silicon Materials, ³Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China. E-mail: [email protected]
Synthetic single-crystals are usually homogeneous solids. Biogenic single-crystals,^1,2 however, can incorporate biomacromolecules and become inhomogeneous solid so that their properties are also extrinsically regulated by the incorporated materials.^3,4 The discrepancy between synthetic and biogenic single-crystals inspires an idea to modify the internal structure of synthetic crystals to achieve non-intrinsic properties by foreign material incorporation. Here, Au and/or Fe₃O₄ nanoparticles were incorporated, through a gel-grown crystallization method, into calcite single-crystals and, as a result, the intrinsically colorless and diamagnetic calcite single-crystals were turned into colored and paramagnetic solids.⁵ The gel growth media instead of solutions are necessary to induce the nanoparticle incorporations during which crystals incorporate the gel network and also the nanoparticles trapped in the gels. This result suggests that the nanoparticles are “glued” into the crystals by the gel polymers. Similarly, CdTe quantum dots, Carbon nanotubes and Graphene Oxide nanosheets were incorporated by this gel method to endow single-crystals with other non-intrinsic properties such as photoluminescence . As such, our work extends the long-history gel method for crystallization into a platform to functionalize single-crystalline materials to expand their potential application.
Aizenberg, J., Hanson, J., Koetzle, T. F., Weiner, S. & Addadi, L. Control of Macromolecule Distribution within Synthetic and Biogenic Single Calcite Crystals. J. Am. Chem. Soc.119, 881-886 (1997).
Veis, A. A Window on Biomineralization. Science307, 1419-1420 (2005).
Li, H. Y., Xin, H. L., Muller, D. A. & Estroff, L. A. Visualizing the 3-D Internal Structure of Calcite Single Crystals Grown in Agarose Hydrogels. Science326, 1244-1247 (2009).
Kim, Y. Y., Ganesan, K., Yang, P. C., Kulak, A. N., Borukhin, S., Pechook, S., Ribeiro, L., Kroger, R., Eichhorn, S. J., Armes, S. P., Pokroy, B., Meldrum, F. C.. An artificial biomineral formed by incorporation of copolymer micelles in calcite crystals. Nature Mater. 10, 890-896 (2011).
Y. J. Liu, W. T. Yuan, Y. Shi, X. Q. Chen, Y. Wang, H. Z. Chen and H. Y. Li. Functionalizing Single-Crystals: Nanoparticles Incorporation Inside Gel-Grown Calcite Crystals. Angew. Chem. Int. Edn., 53, 4127-4131 (2014).

Large scale and high density nanowires can be grown by thermal oxidation. The growth mechanism has been under intense investigation. Herein, we report nanowire self-nanowelding process. CuO nanowires were grown by thermal oxidation. During growth process, we provided opportunities for CuO nanowires to contact with other CuO nanowires and observed formation of nanowire junctions. The high resolution TEM results reveals the nanotwin formation in the transient area of the junctions. The junction synthesis process has been discussed in detail. Silver nanowire coated on sample surface would casue large scale formation of nanowire junctions. This process was also applied to form junction together with carbon nanotubes and graphene.

One of today&’s challenges for high-performance organic devices is the ability to control crystallization in molecular semiconductors. Here we show that light influences molecular growth and can be used to gain control over polymorphism in vacuum deposited films. We report on a direct influence of light on the molecular crystal structure and focus on the two well-studied molecules alpha-sexithiophene (6T) and pentacene (PEN), which are known to exhibit bimodal growth in thin films with two coexisting crystal phases.
We study the growth behavior of PEN and 6T thin films by the means of in-situ real time x-ray diffraction measurements accompanied by atomic force microscopy (AFM). We find that influence of light on the crystal structure cannot be explained in terms of simple annealing or thermal sample heating. Therefore we discuss various mechanisms for the increased phase purity such as excited state crystallization, differences in the optical absorption properties and the cohesive energies of the respective crystal polymorphs.
Pentacene films grown on silicon substrates with native oxide layer form a substrate surface induced thin film phase in addition to the simultaneously growing pentacene bulk polymorph. This bimodal growth reduces the thin film&’s structural quality, and thereby reduces for example hole mobilities in transistors. We show that irradiation with visible light smoothes the pentacene surface and reduces the formation of crystallites in the bulk structure, thereby increasing phase purity.
For 6T we find that the two most prominent crystal structures, the low temperature (LT) and high temperature (HT) polymorph coexist in films deposited on potassium chloride (KCl). Irradiating the film during growth with visible light of moderate intensity (1.5 W/m²) suppresses the nucleation and formation of the HT crystallites in the growing film.
The two findings show that light can serve as an additional control parameter in molecular crystal growth to optimize the structural quality of molecular thin films. In the future this may lead to micro-patterning since light can be applied locally on the absorbing molecules.

Solution coating of semiconducting polymers (SPs) provides great potential for low-cost fabrication of large-area and flexible electronics. Morphology and molecular packing of SP films are crucial to their electrical performance. Self-assembly of SPs into ordered supramolecular structures commensurate with efficient charge transport has been achieved by tuning a range of processing parameters (e.g. film formation methods, different solvents (low or high boiling point), polymer-dielectric interface treatment, and solution treatments such as ultrasonication or UV irradiation). However, these strategies present limitations for achieving highly ordered crystalline SPs, including uniform, rapid processing, and continuous fabrication of devices.
Here, fluid-flow enhanced oriented crystallization of SPs with high charge transport characteristics is demonstrated. Fluid flow provides for enhanced intramolecular ordering of solubilized polymer chains, and thereby effects formation of anisotropic supramolecular polymer assemblies via favorable π-π stacking (intermolecular interaction). Molecular ordering is thus dramatically enhanced with concomitant, enhanced charge transport characteristics of corresponding films. Furthermore, we combine the microfluidic treatment strategy with a blade coating method to achieve continuous and large scale preparation of FET (field-effect transistor) devices with enhanced performance. Because our findings can be applied to various SPs and solvent, laminar fluid-flow enhanced oriented crystallization technology is universally applicable and is expected to yield high-performance printable electronics.

Conjugated organic polymers are very promising materials for flexible electronics and energy storage devices. The effectiveness of π-conjugated devices depends significantly on the way the polyene chains pack together in a material as well as the chemical structure of the material. Although remarkable improvement in their structure and morphological order has been achieved, preparing high molecular weight polymer single crystals remains a major challenge. We report a novel method for the preparation of parallel-extended chains of polyacetylene by photochemical conversion of a reactive molecule (1,4-diiodo-1,3-butadiene, DIBD) constrained within the parallel channels of a urea inclusion complex (UIC).
Solid-state photopolymerization method was used to synthesize macroscopic-size polyacetyelene arrays with stereoregular chain structures. This method, as applied to inclusion complexes, is novel. Organo-iodine compounds like DIBD absorb at 260 nm leading to photochemical homolytic breakage of the carbon-iodine bond.¹ The end-to-end arrangement of the DIBD guest molecules in the linear urea host tunnels² suggested that photopolymerization occurs through iodine diffusion from the crystal followed by carbon-carbon bond formation. Continuation of this process results in long polyacetylene chains.
We used Raman spectroscopy to probe the resulting conjugated polyene chains. Irradiation results in new resonance-enhanced Raman modes around 1120 and 1500 cm^-1. The same products were observed after the DIBD/UIC single-crystals were subjected to 254 nm, 532 nm, or broadband Hg/Xe arc radiation. The Raman spectra of the resulting confined polyene chains are nearly identical to spectra of trans-polyacetylene prepared by solution methods. The structural, spectral and photochemical properties of the resulting hybrid polyacetylene material will be presented.
Preparations of polyacetylene³ have been interpreted as having an extended backbone structure, in spite of the evidence that polyacetylene samples are heterogeneous mixtures of relatively short conjugated chains with considerable defects. We speculate that the physical properties of polyacetylene in this idealized extended conformation, including its conductivity, may differ considerably from those of the material prepared by standard methods. The argument that this material will be a room temperature superconductor will be discussed.
1. P. J. Kropp, Acc. Chem. Res. 17, 131 (1984).
2. A. F. Lashua, T. M. Smith, H.Hu, L. Wei, D. G. Allis, M. B. Sponsler, and B. S. Hudson, Cryst. Growth Des. 13, 3852 (2013).
3. A. J. Heeger, Angew. Chem. Int. Ed. 40, 2591 (2001).

One of the biggest challenges in the field of semiconducting polymers is the exact determination of their solid-state crystal structure. The generally high degree of disorder, large unit cells, and lack of diffraction peaks are some of the many limitations for these materials. Unlike small molecule organic semiconductors, polymers also cannot be grown into single crystals. The exact details regarding the atomic positions, the side chain dynamics and conformation, and the rigidity of the backbone, however, all play an important role in polymer crystallization and can have a dramatic impact on the overall electronic charge transport. In this work, we present a detailed study on the crystal structure of a model polymer system, poly(3-ethylhexylthiophene) (P3EHT). Unlike its more popular counterpart, poly(3-hexylthiophene) (P3HT), P3EHT has been shown to exhibit more diffraction peaks and a somewhat unconventional triclinic unit cell. Further, the addition of an ethyl group to the side chain decreases the mobility by 2 orders of magnitude. By using a combination of x-ray diffraction refinement, density functional theory and molecular dynamics refinements, and solid-state nuclear magnetic resonance (NMR) measurements, we are able to study detailed properties of the P3EHT crystal structure. Specifically, we are able to comment on the chain-to-chain stacking distance, the degree of sliding and tilting between adjacent chains, and the overall symmetry of individual crystals. Also analyzed are the differences in molecular mobility between the thiophene backbone and the alkyl side chains in both amorphous and crystalline polymer domains. Finally, we comment on the effects of crystal structure on the transport properties of the polymer.

Many meta-substituted derivatives of 1,3-bis diphenylurea grow as concomitant mixtures of polymorphs. In some cases, phase selectivity can be achieved through the use of appropriate 2D templates which encourage heterogeneous nucleation. The role of solvent in the heterogeneous nucleation process is not well understood and can complicate the analysis of interactions at the template/crystal interface. In the present study we compare various crystallization configurations both in solvent and under solvent-free conditions in order to gain a more complete picture of interfacial structure-directing effects.

The study of nucleation is of paramount importance because it represents the seminal event in the growth of a solid phase from solution. Organothiol self-assembled monolayers (SAMs) have been utilized as a model system to mimic biological templates, with which to investigate the underlying mechanisms by which organic matrices control nucleation. There exist many long-standing questions surrounding templated nucleation due to a lack of experimental approaches suitable for probing this seminal event in mineral formation. Of particular interest is the formation pathway that takes the mineral from its solvated state to the final, oriented calcite crystal. Whether mineralization pathways on organic templates differ from pathways in purely inorganic calcite formation is currently unknown. Resolving this question is of great importance to understanding the mechanisms by which organic matrices exert control over the organization of minerals.
In recent years developments in transmission electron microscopy (TEM) have produced platforms allowing observation of fluid environments. Here we use fluid cell TEM to investigate calcium carbonate nucleation. During nucleation in the absence of organic templates, we observe direct formation of amorphous calcium carbonate (ACC), as well as the three predominant crystalline phases: calcite, vaterite, and aragonite. The direct formation of the crystalline phases is observed under conditions in which ACC readily forms. These observations provide direct evidence that multiple phases of calcium carbonate can form without the intermediate stage of ACC. For all phases measured, radial/edge growth rates following nucleation are constant, showing growth is limit by reaction kinetics.
In addiiton to direct formation pathways, in a purely inorganic system we observe transformation from ACC to aragonite and vaterite, but, significantly, not to calcite. ACC transforms directly to the crystalline phases starting on or just beneath the surface, rather than via dissolution and reprecipitation through distinct nucleation events. These formation pathways are confirmed by collecting diffraction information of the various phases of calcium carbonate.
We show how this approach can be modified to investigate CaCO₃ nucleation on SAMs of γ-substituted alkanethiols, and compare initial results of our observations on CaCO₃ nucleation pathways on carboxyl-terminated alkanethiol SAMs organized on gold to the formation pathways observed in the absence of a SAM.

Magnetocaloric effect (MCE) provides an interesting way of realizing the refrigeration for a given range of temperature. With the increase of applied field, magnetic entropies decrease and heat is radiated from the magnetic system into the environment through an isothermal process, while with the decrease of applied field, magnetic entropies increase and heat is absorbed from the lattice system into the magnetic system through an adiabatic process. Both the large isothermal entropy change and the adiabatic temperature change characterize the prominent MCE.
In the ~1 to 10 K range, thanks to their gravity independency, MCE based systems are considered as serious alternatives to ³He - ⁴He dilution refrigerators. Among the explored materials for such a purpose, R₃M₅O₁₂ garnets (R = Nd, Gd, and Dy, M = Ga and Al) [1,2] and paramagnetic rare earth salts such as Gd₂(SO₄)₃.8H₂O [3,4] are the most studied. In this context, we purpose to prepare metal-organic hybrid materials with valuable magnetic properties, framework robustness, weak density and real ability to function in conditions of microgravity. These hybrids are obtained by reacting 3d and 4f transition metallic salts in a polyalcohol, typically a diethyleneglycol. They consist of mixed glycolates in which divalent cobalt and trivalent rare earth (R = Nd, Sm, Eu, Gd, Ho) cations are coupled to deprotonated diethyleneglycol molecules. They typically adopt the general CoRCl[(O(C₂H₄)₂O₂]₂ chemical formula and crystallize in a monoclinic unit cell (space group C2/c) in which Co²⁺ and R³⁺ cations exhibit non-conventional five and seven coordination spheres, respectively. Their magnetic properties change with the nature of R cation, from a single ion magnet for R = Eu to a 1D canted ferrimagnet for the others. Measuring the thermal variation (from 1.8 to 20 K) of their magnetic entropy for different applied magnetic field (from 1 to 5 T) a maximal value was measured for R = Gd at ~2 K, comparable to those reported on the best Mn-Gd based low temperature magnetocaloric coordination compounds [5].
References
[1] R. Li, T. Numazawa, T. Hashimoto et al., Adv. Cryog. Eng. 32 (1986) 287.
[2] R.D McMichael, J. J. Ritter, R. D. Shull, J. Appl. Phys. 73 (1993) 6946.
[3] W.F. Giauque, J. Amer. Chem. Soc. 49 (1927) 1864.
[4] W.F. Giauque, I.P.D. McDougall, Phys. Rev. 43 (1933) 768.
[5] J.W. Sharples, D. Collison, Polyhedron 54 (2013) 91.

We previously reported converting in situ the structure of nanoscale manganese oxide (MnOx) conformally coating the carbon walls in 3D nanofoam paper from a layered (2D) birnessite-like structure (MnOx@C) to a 3D tunnel structure consistent with lithium spinel (LiMnOx@C) [1]. We now report the results from neutron pair-distribution function (nPDF) analyses that track this topotactic conversion of the MnOx within the carbon nanofoam from 1) an initial Na⁺-compensated birnessite form to 2) a Li⁺-compensated birnessite to 3) disordered Li⁺-compensated spinel and finally to 4) crystalline LiMnOx@C. Manganese oxides are widely used for electrochemical energy storage, providing the active material in the positive electrode of the alkaline battery and offering enhanced capacitive energy storage for pulse power. Electrochemical utilization of the innate redox capacity of Mn(IV)Ox can be improved by (nano)engineering the oxide to increase surface area and optimize electron hand-off between the oxide and its 3D carbon current-collecting substrate. The crystallographic engineering of the birnessite phase to the spinel phase via composites (1)-(4) creates a device-ready 3D electrode that can charge/discharge in tens of seconds—similar to a capacitor—while displaying lithium-ion insertion behavior similar to that of a battery [1]. The nPDF study tracks specific changes over a long range (nanometers) in atomic environments of semicrystalline materials, especially with the X-ray-insensitive chemical agents (Li⁺, Na⁺, H₂O) that direct the phase engineering of MnOx@C to LiMnOx@C. Deciphering such structural conversion through structures (1)-(4) provides possible routes to further optimize MnOx-modified energy-storing architectures.
[1] M.B. Sassin, S.G. Greenbaum, P.E. Stallworth, A.N. Mansour, B.P. Hahn, K.A. Pettigrew, D.R. Rolison, J.W. Long, Journal of Materials Chemistry A 23 (2013) 2431-2440.

Detailed knowledge of the role of mechanical strain on workfunction in organic semiconductors is very important not only for understanding the electrical properties of organic semiconductor films, which are typically in intrinsic and/or extrinsic strain states, but also for the development of flexible organic electronic devices. However, to the best of our knowledge, fundamental relationships between mechanical strain and workfunction are not yet established in any organic semiconductors. Rubrene single crystals, with their high degrees of structural order and material purity, have served as a model material platform for fundamental studies of the physics of organic semiconductors, including the intrinsic transport properties and structure-property relationships. Here we use rubrene single crystal as a model system to investigate the correlation between mechanical strain and workfunction. To induce strain in rubrene, ultrathin crystals (1-5 mu;m) are electrostatically attached to substrates with distinct coefficients of thermal expansion than rubrene, namely, polydimethylsiloxane (PDMS) and silicon. Varied strains can be consistently induced within rubrene crystals upon heating and are quantified by temperature-dependent X-ray diffraction (XRD). The corresponding workfunction change of the crystal is measured by scanning Kelvin probe microscopy (SKPM) at different temperatures. It is found that the workfunction of rubrene significantly increases with in-plane tensile strain, i.e., increase of over 200 meV with about 0.2% strain in the π-stacking direction of rubrene crystal. A large hysteresis of workfunction change (approximately 100 meV) with strain is also observed upon cooling and is attributed to plastic deformation of the crystal beyond the yield point.

Crystals and crystalline films are the ideal medium to probe the impact of small changes in functionalization on stability and electronic properties of small-molecule chromophores. Subtle changes in substitution can induce a variety of changes in intermolecular arrangements in a crystalline compound, and the impact of these changes can be measured by photophysical changes in the material, or by changes in charge transport properties. In some instances, it is possible to alter functionalization without impacting solid-state arrangements, in which case it becomes possible to probe how changes in the electronic nature of the individual chromophores impact issues such as stability or transport. Further, the precise molecular arrangement of singlet fission chromophores in the solid state can have a significant impact on the rate and efficiency of that process. In this talk, I will survey a wide range of crystalline materials, discuss trends in the impact of functionalization change on crystal packing, and describe how subtle tuning of functionalization can alter crystal growth rate, electronic transport properties, and the photophysical properties of the solid.

Polymorphism - the existence of more than one crystal form for some well-defined chemical entity - is a common phenomenon in molecular crystals. Indeed, polymorphs are probably rather more common than many of us would like to admit. In the field of organic electronics, device performance is intimately related to the relative positioning of molecules, i.e. to the manner in which molecules pack in the solid state. Even small changes in crystal packing can have profound effects on electronic and other physical properties. It therefore stands to reason that different polymorphs are likely to exhibit dramatically different properties. Polymorphs may be produced intentionally or unintentionally by changes in crystal growth conditions, but they may also occur as a result of phase transitions. The phenomena of polymorphism and phase transitions, and especially their occurrence in electronically active organic materials, will be described using a few examples encountered in the author's laboratory.

As a new class of magnetic materials, metal-organic framework (MOF) has been studied widely because of their functionality and porosity that can provide diverse magnetic phenomena by means of the host-guest chemistry. Using density functional calculations, we observe that the O₂ adsorption does not change the ferromagnetic (FM) ordering along the 1D chain of the bare Fe-MOF-74, unlike the adsorption of ethylene which changes the magnetism to antiferromagnetic (AFM) ordering. We find that this distinct magnetism behavior of O₂ vs. olefin adsorption is attributed to the different electronic effects, namely the spin-dependent charge transfer effects. This prediction offers us a hint about the possible usage of Fe-MOF-74 for a magnetic sensor to identify the adsorbed gases in Fe-MOF-74. Furthermore, the suggested mechanism can be used to control the magnetic properties of MOFs using the guest molecules.

The formation of covalently bound, two-dimensional materials has been a subject of study as early as the 1930&’s; quite recently, the existence of ordered covalent two-dimensional networks was confirmed by single-crystal X-ray diffraction (Nat. Chem., 2014, 6, 757-759). In addition to interest arising from the synthetic challenges associated with such networks, they might also possess electronic, magnetic, or optical properties unique to their dimensionality.
The most well-studied two-dimensional covalent material is graphene; it has the highest charge carrier mobility known, among other remarkable electronic and physical properties. However, the band structure of graphene poses difficulties in employing it as a semiconductor, where its near-zero bandgap at room temperature precludes its use in devices such as transistors or those based on p-n junctions. The successful bottom-up synthesis of conjugated, covalent, two-dimensional, ordered network polymers might yield materials having both formidable charge carrier transport properties and compatibility with existing semiconductor device technologies. Progress has been made in this direction (Nat. Chem., 2013, 5, 453-465), but obtaining large-area films of such materials on technologically relevant substrates remains a significant challenge.
In this presentation, we describe progress made towards the synthesis, characterization, and integration into devices of ordered covalent, conjugated, two-dimensional films from small molecule precursors. Our synthetic route brings together concepts from previous interfacial polymerization methods and more recent reports of conjugated covalent organic frameworks. We are able to form films of varying thickness over large (> 1 cm²) areas composed of two-dimensional sheets. These films can be physically transferred to any substrate, easing integration of the materials into electronic devices such as organic thin-film transistors. Furthermore, we discuss progress and extant challenges in the characterization of such films.

Controlling the crystalline morphology of polymeric thin films at a molecular level has been increasingly important due to their potential as the active layer in organic electronics. The preferential molecular orientation achieved via crystallization can greatly improve the performance of such devices including transistors, photovoltaics, and sensors. Typically, the crystalline morphology is achieved via thermal annealing or melt-crystallization of spin-cast polymer films where the molecules are mutually entangled. Here, the crystallization propagates to the whole polymer domain in a relatively short time, leading to a spherulitic morphology where the crystalline lamellae grow in all directions. This approach, therefore, is often challenged in obtaining specific film morphology where the crystalline lamellae need to be preferentially aligned.
Here, we propose an alternative approach to make crystalline polymer films via Matrix Assisted Pulsed Laser Evaporation (MAPLE). Using polyethylene oxide (PEO) as a model polymer, we show that the preferential orientation of crystalline lamellae can be controlled during the film growth. In MAPLE, the polymer of interest is kinetically ejected from a frozen dilute solution under high vacuum by an incident pulsed laser beam, and deposits on a substrate as nanometer-sized droplets. We find that uncrystallized PEO was transferred to the substrate from the frozen solution target. The crystallization of deposited liquid PEO droplets was achieved at a sufficiently low substrate temperature. Due to the nanometer confinement of liquid PEO droplets, the preferential orientation of lamellae formed during crystallization was strongly affected by the interfacial energy of the substrate. Flat-on crystals were formed on the surface of silicon wafers, and the seed crystals formed at the early deposition stage directed the crystallization of PEO deposited at later times. In contrast, edge-on crystals were formed on the surface of octadecyltrichlorosilane (OTS)-coated silicon wafers. Mimicking the epitaxial growth of metallic films, this novel polymer deposition technique can enable the engineering of film properties in a way not achievable in bulk.

Order in purely organic network polymers is hard to achieve, as reversible, dynamic covalent bond formation is required. Strategies focused on thermodynamic controlled transformations, as kinetics would not seemingly favour reversibility. Herein, we report formation of crystalline network polymers under kinetically favoured conditions by using quaternary ammonium salt linked networks. Charged bulky bridges align, even under fast reaction times (20 minutes) if the rotational freedom is granted. Adding vicinal methyl substituents block the ordering, hence form amorphous networks. Raman experiments and SEM images reveal stacking of 2D layers.

A large diversity of π-systems exists, the vast majority of them transport electrical charges but only a few molecular structures qualify as best-performing organic semiconductors with mu; ge; 10 cm²/V.s. But charge carrier mobility is a materials and not a molecular property. One has, thus, to consider supramolecular order at all lengthscales. The best organic semiconductors self-organize into large plate-like monocrystals as evidenced in a recent review paper devoted to the question: “What Currently Limits Charge Carrier Mobility in Crystals of Molecular Semiconductors?” G. Schweicher, Y. Olivier, V. Lemaur, Y. H. Geerts, Isr. J. Chem.2014, 54, 595-620. Due to their electronic properties but also to their favorable crystalline morphology, BTBT derivatives exhibit record charge carrier mobility above 10 cm²/V.s. We will report our latest results on the molecular and supramolecular engineering of BTBT semiconductors, including: design by theory, synthesis, crystal engineering, calculation and observation of crystal morphology, and processing into single crystal thin films for transistor fabrication

Cocrystallization, the formation of a crystal containing multiple neutral compounds in a defined stoichiometry within a single crystal lattice, has the potential to afford many of the targeted qualities for novel energetic materials. In particular, the cocrystallization of energetic materials offers a means to direct crystal packing, enhance intermolecular forces, reduce electron density of functional groups, and improve the oxygen balance of an energetic. While many of these properties can be engineered into single component systems, cocrystallization is unique in being able to leverage existing manufacturing infrastructure for energetic materials. With all these potential advantages, the challenges of actually obtaining energetic cocrystals with useful properties must be addressed. In short, the most reliable strategies for molecular cocrystal design can not be generally implemented for energetic materials because one must rely on the existing set of energetic compounds and their functional groups fall outside of those reliably used in cocrystallization. Progress will be discussed.

The unregulated crystallization of uric acid in vivo is associated with diseases such as kidney stones formation and gout. This talk will describe the inclusion of various dopants in uric acid dihydrate single crystals and the striking differences in the physical/material properties which result.

In the last decade there has been a lot of interest in inorganic nanosystems that exhibit chirality and chiroptical activity.¹ Three different approaches have been demonstrated for that purpose. First, induction of weak chiroptical effects in the plasmon or exciton resonances of nanocrystals of achiral materials with achiral shapes (such as gold, silver and cadmium/zinc chalcogenides), when these are capped with chiral surfactant molecules. Second, formation of chiral shaped nanostructures, mostly by lithographic or vapor deposition methods. Third, assembly of achiral nanocrystals into chiral superstructures. In all these systems the lattice symmetry is high and the crystal structure itself is achiral. More recently we have demonstrated an alternative approach for realization of chirality and stronger chiroptical effects in inorganic nanostructures. In our work we study inorganic materials that crystallize in chiral space groups, such as mercury sulfide,² tellurium and selenium.³ The handedness of the crystal can be controlled when nanocrystals of these materials are grown in the presence of strongly binding chiral biomolecules. Furthermore, in the case of tellurium, the lattice chirality can be translated to the overall shape, on a 100 nm scale. Hence, control over chirality at two different size hierarchies is achieved. This is a unique demonstration of formation of chiral shapes in colloidal synthesis of inorganic nanocrystals. The chiral inorganic systems evolve by initial formation of very small clusters followed by a unique self-assembly process. As a result, interesting analogies to molecular crystals could be looked at. Different stages of nucleation and growth can be conveniently monitored by spectroscopic measurements in solution (as opposed to bulk crystals where this is more challenging). The shape and crystal structure are also easily imaged on the nanometer scale by electron microscopy (as opposed to organic crystals where this is more challenging). These new materials should be useful for a range of applications such as metamaterials fabrication, optics and asymmetric catalysis. On a more fundamental level, we believe that these are excellent model systems for studies of chiral crystallization and separation, and the interaction of chiral biomolecules with chiral crystals.
1.Ben-Moshe, A.; Maoz, B. M.; Govorov, A. O.; Markovich, G. "Chirality and Chiroptical Effects in Inorganic Nanocrystal Systems with Plasmon and Exciton Resonances" Chem. Soc. Rev. 42, 7028-7041 (2013).
2.Ben-Moshe, A.; Govorov, A. O.; Markovich, G. "Enantioselective Synthesis of Intrinsically Chiral Mercury Sulfide Nanocrystals" Angew. Chem. Int. Ed.52, 1275-1279 (2013)
3.Ben-Moshe, A.; Wolf, S. G.; Bar-Sadan, M.; Houben, L.; Fan, Z.; Govorov, A. O.; Markovich, G. "Enantioselective control of lattice and shape chirality in inorganic nanocrystals using chiral biomolecules" Nat. Comm. 5, 4302 (2014)

Over the past 30 years, integral membrane protein crystallization within ordered nanostructured lipid self-assembly materials has facilitated the structural determination of a number of biologically relevant integral membrane proteins including, recently, several human G-protein coupled receptors (GPCRs). The unique amphiphilic three-dimensional structure of these materials makes them ideal for the encapsulation of membrane proteins during crystal growth and there is increasing evidence to show that the material properties can affect the control and functionality of proteins which are embedded within it. However, the extremely large variable physiochemical space for crystallization has proved resistant to traditional experimental methods and, despite the importance of membrane proteins as drug targets, success rates for their structural determination remain extremely low. A suite of new high-throughput techniques developed within our laboratory to formulate bicontinuous cubic phases for in meso crystallisation, and structurally characterize their evolving nanostructure during the period of crystal growth using synchrotron small angle x-ray scattering (SSAXS) will be presented. It will also be shown how his high-throughput approach informs the identification of key factors that are important for the promotion of integral membrane crystallisation.

The mineralization of the collagenous matrix in bone is among the most important factors governing bone growth and quality. Here, a novel class of biodegradable Mg alloy has been used to provide structural support after bone fracture. After sufficient time the implants gradually degrade and by that a second operation to remove the implant can be avoided. This is especially important when fracture healing and bone growth are overlapping, such as it is in the case of e.g. children.
The response of bone mineralization upon a degradable Mg implant was monitored in a rat model (Sprague-Dawley rat, two weeks old) over a growth period from 1 to 18 months. Alterations in the bone nano- and mineral structure were investigated by means of synchrotron methods such as small-angle x-ray scattering (SAXS) and diffraction (XRD) , x-ray fluorescence (XRF), as well as x-ray absorption spectroscopy (XAS) at a spatial resolution of about 3 µm.
The combined investigations unveiled not only nanostructural changes such as altered mineral crystal size in response to the implant degradation but also impact on the bone mineral structure by the presence of Mg ions from the implant. The implant-bone interface shows Mg enrichment in the context of new bone formation, indicating that Mg is predominantly incorporated into the bone mineral by bone remodeling. Interestingly, increased concentrations of Mg were also observed in the vicinity of blood vessels several hundreds of µm away from the bone-implant interface from the earliest points in time. This may indicate that resorbed Mg was re-deposited into the bone matrix via the blood-vessel pore network of the bone
The electronic state of the bone constituents phosphorus and magnesium was investigated by means of synchrotron x-ray absorption near - and extended edge spectroscopy. A gradual change between different mineral phases could be observed at bone regions adjacent to the implant, underlining the impact of Mg on the local bone structure and its influence during the bone formation.
Our study therefore helps towards understanding the degradation kinetics of Mg implants and potentially allows for optimizing custom-tailored implants meeting the patient&’s specific needs.

Thymine, one of the four nucleic acid base pairs in DNA, is known to crystallize in both a monohydrate (TMH) and an anhydrous (T) phase. Single crystals of TMH were found to undergo a single crystal to single crystal phase transformation at ~ 200K, to a lower symmetry phase. At elevated temperatures, TMH also irreversibly dehydrates to polycrystalline T. The internal and external factors which affect both of these phase changes will be discussed.

Metal-organic frameworks are crystalline solids with high surface area and various pore properties. The framework structure can be transformed into other phases that consist of different topologies. A reversible or irreversible structural conversion is realized depending on factors such as framework components, dimensionality, and reaction media, for instance. Three Zn(II) frameworks are commonly based on the adamantanoid 3D networks that are mutually entangled to form 3-fold (1) to 4-fold (2) to 5-fold interpenetrating dia structure (3). The solvent pairs used in the reactions are primarily responsible for the variation of such interpenetration degree. Interestingly, 2 reveals the reversible structural transformation during the activation-resolvation process where the solid can be activated through two routes (solvent exchange/desolvation and direct desolvation). On the other hand, a three-dimensional Zn(II) framework (4) with three-fold interpenetration is uniquely converted to the two-dimensional Cu phase with no interpenetration, reflecting a drastic dimensionality variation.

The modular assembly of discrete, intrinsically porous organic molecules is an alternative to extended networks porous materials such as zeolites and MOFs that are chemically bonded in 3-dimensions.[1] Their modular nature has further allowed multicomponent porous molecular systems to be formed, whereby property tuning is achieved through varying the component ratios. Here we present a computational investigation into how this property tuning is occurring on an atomistic level, finding that subtle effects such as dynamic pore connectivity[2] are responsible. Furthermore, we demonstrate that we can predict the dependence of gas uptake across the multicomponent series through a simple statistical model.
The ternary porous organic cage system[3] has three component imine cages that differ only by the functionalisation of their vertex; CC1 (ethane group), CC3 (cyclohexane group) and CC4 (cyclopentane group). All have four windows that small gases can diffuse through, and whilst all component crystals contain 50% CC1, the variation of the proportion of CC3 and CC4 modules results in a pronounced variation in the sorption properties. Indeed, the CC1:CC3 has a Brunauer-Emmett-Teller (BET) surface area of ~373 m² g^-1, which increases as the CC4 module is incorporated up until a surface area of ~670 m² g^-1.[3] All the multicomponent systems crystallize isostructurally in a cubic space group with window-to-window packing. Thus an analysis of their void structures from the crystal structure alone would suggest that all systems should have approximately the same surface area (~700 m² g^-1). Using a combination of sorption simulations, gas diffusion simulations and our newly developed approach for studying dynamic pore connectivity[2], we are able to show that it is the increased accessibility of formally isolated voids as the proportion of CC4 increases that is responsible for the observed behaviour. This is an example of the phenomenon of “porosity without pores”.[4]
We conclude by consideration of the potential for in silico design to assist chemical intuition[5] in the field of crystal engineering, particularly if property prediction is combined with structure prediction[6,7,8].
References
[1] T. Tozawa, J. T. A. Jones, S. I. Swamy, S. Jiang, A. I. Cooper et al. Nature Materials, 2009, 8 973.
[2] D. Holden, K. E. Jelfs, A. Trewin, D. J. Willock, M. Haranczyk, A. I. Cooper, J. Phys. Chem. C.2014, 118 (24) 12734.
[3] T. Hasell, S. Y. Chong, M. Schmidtmann, D. J. Adams, A. I. Cooper, Angew. Chem. Int. Ed.2012, 51, 7154.
[4] L. J. Barbour, Chem. Comm.2006, 11, 1163.
[5] G. R. Desiraju, J. Am. Chem. Soc. 2013, 135, 9952.
[6] J. T. A. Jones, T. Hasell, X. Wu, J. Bacsa, K. E. Jelfs, A. I. Cooper et al. Nature 2011, 367 474.
[7] K. E. Jelfs, E. G. B. Eden, J. L. Culshaw, S. Shakespeare, A. I. Cooper et al.J. Am. Chem. Soc.2013, 135, 9307.
[8] S. L. Price, Chem. Soc. Rev.2014, 43, 2098.

Guest molecules confined inside hollow confined space show unexpected structural behaviors compared to unprotected environment. Cyclobutadiene (CBD), the smallest cyclic hydrocarbon bearing double bonds, has long intrigued chemists, but the parent compound and intermediates have eluded crystallographic characterization. The CBD precursor, 4,6-dimethyl-α-pyrone has been captured in a crystalline network. UV irradiation of the crystals transforms the 4,6-dimethyl-α-pyrone into a 4,6-dimethyl-β-lactone Dewar that is kinetically stable under the confined conditions to allow a conventional structure by X-ray diffraction. Further irradiation pushes the reaction to completion, enabling the structure determination of 1,3-dimethylcyclobutadiene Me₂CBD. Another special case is the coiling behavior of alkane chains in rigid molecular cages. It has been found that coiling may occur and a large number of possible conformers have been theoretically and spectroscopically described. No direct evidence concerning the exact conformation of the chains has been presented. We present here the compression mechanisms of linear of 1,omega;-diammonium-alkanes, confined with different degrees of compression, within a molecular cage. The exact coiling behavior is determined from atomic resolution X-ray diffraction and shows crenel-like conformations in the compressed states which are possibly assisted by slight attractive dihydrogen contacts. These findings may provide insight in areas ranging from nanomechanics to biological pathways.
References
Y.M. Legrand, A. van der Lee, M. Barboiu, Single-crystal X-ray structure of 1,3-dimethylcyclobutadiene by confinement in a crystalline matrix, Science, 2010, 329, 299-302.
Y.M. Legrand, A. Gilles, E. Petit, A. van der Lee, M. Barboiu, Unprecedented synthesis of 1,3-dimethyl-cyclobutadiene in solid state and aqueous solution, Chem. Eur J. 2011, 17, 10021-10028.
D. Dumitrescu, Y.M. Legrand,, E. Petit, A. van der Lee, M. Barboiu, Progressive compression of alkane chains inside a rigid crystalline molecular cage, Chem. Commun., 2014, 50, 14086-14088.

Supramolecular assemblies of self-templated metal organic chalcogenides can be synthesized by harnessing the competition between covalent and intermolecular interactions. These hybrid metal organic chalcogenide (MOC) crystals exhibit single atom control and tailorable optoelectronic properties. Low-dimensional metal chalcogenides have emerged as a class of materials with interesting properties including high-mobility semiconductors, superionics, superconductors and topological insulators. Material control at the few-atom level for chalcogenides is highly desirable. Here we explore the synthesis and structure of low-dimensional metal chalcogenides with anisotropic arrangement of atoms driven by competitively strong van der Waals forces between directing diamondoid cage ligands. We examine the optoelectronic and electrical properties of different MOCs and highlight the diversity and tunability of MOCs by ligand, metal, and chalcogen. Lastly, we demonstrate the influence of metal and chalcogen atoms on the anisotropic electrical conductivity within these molecularly confined hybrid chalcogenide structures.

Crystal engineering via organic ligand design is a route towards synthetic intervention into the structure/function relationship of conductive nanomaterials. Hybrid organic/inorganic metal chalcogenides provide an opportunity to direct structure and connectivity in a material class with diverse optoelectronic properties, including semiconductors, superconductors, and topological insulators. However, small geometric differences between ligands can have large effect on emergent crystal structures, and structural prediction is a considerable challenge. Here we use isogeometric carboranethiol isomers and examine various self-assembling metal chalcogenide nanostructures as a function of carborane molecular dipole orientation. We find that materials can be manipulated across atomic, supramolecular, and macroscales by dipole selection.

Glasses play an important role in modern technology and raise fundamental questions regarding what properties are possible in a solid. The large number of local packing arrangements in glasses underlies their important properties, including macroscopic homogeneity (e.g., the clarity of window glass) and the ability to be tuned by composition changes. A problem with glasses, also associated with their local disorder, is that they are unstable with respect to lower energy glasses and crystalline states. We have used physical vapor deposition and the mobility of glassy surfaces to prepare what are likely the most stable glasses on the planet. Our materials have the properties expected for “million-year-old” glasses, including high density, low enthalpy, and high mechanical moduli. We have discovered deposition conditions that combine high stability with substantial molecular orientation. Such materials combine some of the most useful features of glasses and crystals. These developments present significant opportunities to expand our understanding of amorphous packing and to design new classes of anisotropic solids for applications such as organic electronics.

Glasses are generally prepared by cooling from a liquid state, to temperatures below the glass transition. Recent experimental work has shown that glasses can also be prepared through a process of physical vapor deposition (PVD), leading to materials with exceptional thermal and kinetic stability. The resulting materials could offer advantages over ordinary glasses in demanding applications, including photovoltaic or organic electronic devices, and it is therefore of interest to understand the origins of their enhanced stability. Molecular simulations of model glass formers have allowed us to gain insights into the process of glass formation by PVD. In this presentation, I will provide a general overview of past computational studies aimed at describing vapor-deposited glasses, along with new results from our own laboratory regarding the emergence of local order during physical vapor deposition, the origins of orientational anisotropy in vapor-deposited glasses, and the relation between local order and enhanced thermal and kinetic stability in this new class of materials.

Glasses are amorphous materials that combine the mechanical stability of solids with the microscopic spatial uniformity of liquids, making them ideal for many applications. Amorphous solids, however, are unstable, and can crystallize over time. Recent studies have discovered that as organic liquids are cooled to become glasses, fast modes of crystal growth can emerge. One such mode (the glass-to-crystal or GC mode) exists in the bulk and causes the rate of crystal growth to exceed by several orders of magnitude the prediction of standard models. An even faster mode of crystal growth emerges at the free surface, causing surface crystals to grow much faster than bulk crystals. We report that the general condition for GC growth to exist is that liquid diffusion be slow relative to crystal growth according to D/u < 7 pm. This condition holds for all liquids exhibiting GC growth whose growth rates span 4 orders of magnitude and suggests that the phenomenon is a solid-state process terminated by fluidity. During their active growth, surface crystals rise above the amorphous surface while spreading laterally and are surrounded by depressed grooves whose dimensions are determined by surface diffusivity and crystallization flux. Similar to GC growth, surface crystal growth terminates if glasses are heated to gain fluidity. Upon heating, the growth becomes slower, sometimes unstable. This damage is stronger on segregated needles than on crystals growing in compact domains because the onset of liquid flow causes wetting and embedding of upward-growing surface crystals. Our results suggest that both processes are solid-state phenomena terminated by fluidity. These findings are important for understanding and predicting the stability of organic glasses.
Reference
D. Musumeci, C. T. Powell, M. D. Ediger, and L. Yu, J. Phys. Chem.Lett., 2014, 5 (10), 1705-1710.
M. Hasebe, D. Musumeci, T. Powell, T. Cai, E. Gunn, L. Zhu, and L. Yu, J. Phys. Chem. B, 2014, 118, 7638-7646

Amorphous solids and glasses have important applications in bio-preservation, organic electronics, and the delivery of poorly soluble drugs. We report recent progress in measuring surface diffusion on molecular glasses.^1,2 Surface diffusion is at least one million times faster than bulk diffusion, and remains fast after significant bulk aging.³ This high surface mobility is responsible for the fast surface crystal growth on molecular glasses⁴ and the formation of ultra-stable glasses by vapor deposition.⁵ Relying on rapid surface equilibration, vapor deposition can build glasses layer-by-layer to achieve exceptionally low energy and high density. References: (1) Zhu, L.; Brian, C.; Swallen, S. F.; Straus, P. T.; Ediger, M. D.; Yu, L. Phys. Rev. Lett.2011, 106, 256103. (2) Brian, C. W.; Yu, L. J. Phys. Chem. A. 2013, 117, 13303. (3) Brian, C. W.; Zhu, L.; Yu, L. J. Chem. Phys.2014, 140, 054509. (4) Sun, Y.; Zhu, L.; Kearns, K. L.; Ediger, M. D.; Yu, L. Proc. Natl. Acad. Sci. U. S. A.2011, 108, 5990. (5) Swallen, S.; Kearns, K.; Mapes, M.; McMahon, R.; Kim, S.; Ediger, M.; Yu, L.; Wu, T.; Satija, S. Science2007, 315, 353.

A new strategy is proposed for protein crystallization methods in solution-growth or gel-growth by using different crystal growth devices applying electric (in the range of micro-Amperes) and magnetic fields (from 7 to 12 Tesla). The effect of combining both electric and magnetic fields is shown and is reviewed. Proteins with differing contents of a-helices and b-sheets, and crystallized in different crystallographic space groups are studied. The crystal quality is improved by using an electric field to electro-migrate ions to the ITO electrodes, and to orientate protein molecules by using a strong magnetic field in either solution or gel-growth to control the transport phenomena. Some advantages to increase the crystal quality for crystals from marginal conditions for X-ray diffraction are discussed. Finally, in order to separate the nucleation and the crystal growth processes (by using these electromagnetic fields), the obtainment of either large amount of small crystals for Powder X-ray Diffraction or big single crystals for the classic X-ray Crystallography (or Neutron Diffraction Crystallography) is also evaluated.
Acknowledgements: The author (A.M.) gratefully acknowledges financial support from CONACYT-Mexico Project No. 175924.

The prediction of structure and polymorphism in molecular crystals is a problem of importance in areas ranging from pharmaceuticals to industrial and high-energy materials. Because of the challenges associated with performing extensive, high-quality experiments on molecular crystals, theory and computation can play a significant role in this area provided the models and structure prediction algorithms are of sufficient accuracy and efficiency. In this talk, I will describe the efforts we are making to develop new free-energy based enhanced sampling computational strategies for predicting structure and polymorphism in molecular crystals and the mapping out the associated free energy landscapes. I will demonstrate the performance of the approach in a series of organic molecular crystals, several of which are blind predictions in which the crystal structures are not known a priori.

Icosahedral quasicrystals (IQCs) are a form of matter that is ordered but not periodic in any direction. IQCs have the highest symmetry of all crystals and therefore exhibit orientationally highly uniform properties. This makes them candidates for materials with a complete photonic bandgap or as specialized alloys. All reported IQCs are intermetallic compounds and either of face-centered-icosahedral or primitive-icosahedral type, and the positions of their atoms have been resolved from diffraction data. However, unlike other quasicrystals, which have been observed experimentally in micellar or nanoparticle systems and suggested in bi-layer water, silicon, and mesoporous silica, IQCs have not been discussed in the context of non-intermetallic systems.
In this contribution, we demonstrate the first self-assembly of an IQC by means of molecular dynamics simulations. The IQC self-assembles rapidly and reproducibly from a fluid phase in a one-component system of particles interacting via a tunable, isotropic pair potential extending only to the-third neighbor shell [1]. It is body-centered icosahedral, and in parameter space neighbors clathrates and other tetrahedrally bonded crystals. We provide a crystallographic structure model and show the presence of a diffusion mechanism not available in periodically ordered solids. Our finding is an important step towards addressing a central remaining question in the theory of crystal growth: How do atoms (or other elementary building blocks) arrange themselves rapidly, and with near structural perfection, into a long-range ordered configuration without the guidance of a unit cell? Finally, we suggest routes to search for the IQC and design it in soft matter and nanoscale systems.
[1] M. Engel, P.F. Damasceno, P.L. Phillips, S.C. Glotzer, Nature Materials, in press (2014).

The development of in-situ techniques to explore details of crystallization processes from solution promises to yield significant new insights on fundamental aspects of such processes. With this motivation, we recently developed a new in-situ solid-state NMR technique [1-3] that exploits the ability of NMR to selectively detect the solid phase in heterogeneous solid/liquid systems (of the type that exist during crystallization from solution), with the liquid phase “invisible” to the measurement. As a consequence, the technique allows the first solid particles produced during crystallization to be observed and identified, and allows the evolution of different solid phases (e.g. polymorphs) present during the crystallization process to be monitored as a function of time. This in-situ NMR strategy has been shown [3] to be a powerful approach for establishing the sequence of solid phases produced during crystallization [1,2] (for example, see Figure 1) and for the discovery of new polymorphs [4].
In our most recent development of this in-situ NMR technique, we exploit the fact that NMR spectroscopy can study both the liquid phase and the solid phase in heterogeneous solid/liquid systems using the same instrument, simply by changing the pulse sequence used to record the data. Thus, by alternating between two different pulse sequences during an in-situ NMR study of crystallization, alternate solid-state NMR and liquid-state NMR spectra are recorded, yielding essentially simultaneous information on the time-evolution of both the solid phase and the liquid phase (Figure 2). This new strategy is called CLASSIC NMR (Combined Liquid- And Solid-State In-situ Crystallization NMR). We have shown [5] that the CLASSIC NMR strategy significantly extends the scope and capability of in-situ NMR monitoring of crystallization processes, particularly as it provides complementary information on the changes that occur in both the solid phase and the liquid phase as a function of time during the crystallization process.