Symposium NM06 : Nanodiamonds---Synthesis, Characterization, Surface Chemistry and Applications

To begin exploration of molecular-sized nanodiamonds we introduce a high-yield technique based on controllable size reduction of conventional 4-6 nm DNDs via oxidative etching in air, which provides DNDs with the volumetric mean size around 2 nm (S. Stehlik et al., Sci.
Rep. 6 (2016) 38419). Analytical ultracentrifuge serves here as in particular useful and accurate tool for analyses and adjustment of size distribution of DNDs in colloidal dispersions on nanometer scale in contrast to conventional dynamic light scattering (DLS) method. We show that molecular-sized DNDs keep the specific DND structure and variable surface chemistry (e.g. hydrogenated to oxidized) and corresponding zeta potentials (positive to negative) down to 2 nm or below. This, among others, provides numerous opportunities to achieve a desired electrostatic interaction between 2 nm DND and a substrate. In particular, we show how to apply these novel 2 nm H-DNDs to form homogeneous, ultra-thin (2 nm), extremely dense (1.3 × 1013 cm-2) and smooth (RMS < 1 nm) nucleation layers for growing as thin as 5.5 nm continuous NCD films with distinct photoluminescence from SiV centers (S. Stehlik et al., ACS Appl. Mater. Interfaces 9 (2017) 38842–38853).

Last years, we have developed the synthesis of detonation nanodiamonds from nanostructured explosives. First results showed a relationship between the size of the explosive grain and the size of the synthesized nanodiamonds [1, 2]. The size of the explosive particles (RDX and TNT) were decreased down to 100-200 nm and below thanks to a spray flash evaporation process developed in the NS3E laboratory while they are usually found at the microscale. Sufficient quantities of submicron explosives could be elaborated in order to perform a complete study of different parameters such as the composition, the density, the size and the structure of the explosive charge.
The influence of these parameters will be discussed regarding the size of the obtained nanodiamonds. Overall, the nanodiamonds synthesized by using nanostructured explosives charge exhibit a smaller size and a more homogeneous size distribution than in the case of microstructured one.
These results are also analysed in order to try to understand the nanodiamond synthesis and the detonation mechanisms at a local scale. For this purpose, molecular dynamics are used in order to investigate the formation of the nanodiamonds under these extreme conditions.

[1] Pichot V., Risse B., Schnell F., Mory J., Spitzer D. Sci. Rep., 3, 2159, (2013).
[2] Pichot V., Comet M., Risse B., SpitzerD., Diamond and related Materials 54, 59-63 (2015).

Diamond nanoparticles (DNPs) are exciting candidates for various applications ranging from lubrication, semiconductor quantum dots, drug delivery, through globular protein mimics and reflectors for low-energy neutrons, to nucleation sites for chemical vapor deposition (CVD) of nanocrystalline diamond (NCD) films. For both biological applications using colloidal suspensions of DNPs and nanostructural applications based on solid-state substrate-supported DNP systems, a major drawback of DNPs is their tendency to form large, tightly bound aggregates. Since the technology to obtain monodisperse colloidal DNPs, having a narrow distribution of particle sizes centered on the core particle size (3 - 5 nm), was established in the first decade of the 21^th century, the biological applications using colloidal DNPs have rapidly progressed. Such ideal colloidal DNPs have directly been used in a technique called electrostatic self-assembly for nanostructural applications based on solid-state substrate-supported DNP systems. However, the sizes of the electrostatically self-assembled DNPs on substrate surfaces were typically much larger than the core particle size.
In this talk, the conventional electrostatic self-assembly, which was realized via the control of pH in the colloidal solutions and zeta potentials of DNPs and substrate surfaces, is firstly overviewed. The electrostatic self-assembly of non-aggregated DNPs onto substrate surfaces is then demonstrated by modifying the salt concentration in colloidal DNP solutions. Several salt concentrations of colloidal DNPs were prepared using KCl and were examined with respect to electrostatic self-assembly. In addition, the interaction energies between DNPs in each of the examined colloidal suspensions were considered on the basis of the DLVO theory. To further investigate the interaction between DNPs and SiO₂ surfaces in each of the examined colloidal suspensions, NCD-coated silica micro spheres attached to tipless cantilevers (k = 0.03 N/m) were fabricated, which readily allow probing the force interactions of diamond with different substrate materials by means of force spectroscopy. As a result of these measurements, it was clarified that the salt concentration of 1.0×10^–3 M drastically suppresses the re-aggregation of the DNPs during the electrostatic self-assembly onto SiO₂ surfaces and results in a successful formation of non-aggregated DNPs (5.6 nm in average size) on SiO₂ surfaces.
In the end, this salt-assisted electrostatic self-assembly was applied for the CVD of ultra-thin NCD films on Si substrates. Aside from the developed electrostatic self-assembly technique, suitable conditions of CVD were identified to promote rapid coalescence of NCD grains. Consequently, ~ 10 nm thick continuous NCD films, containing an extremely low density of pinholes, were successfully obtained and completely pinhole-free ~ 30 nm thick NCD films became reliably accessible via the salt-assisted electrostatic self-assembly.

Irradiation of synthetic and natural diamonds with high energy particles is known to produce optically active crystallographic defects that find many uses ranging from colorated specialty gemstones to a platform for quantum computing. Irradiation creates vacancies and self-interstitials that consequently form complexes with impurity atoms, particularly nitrogen, which is the most common natural and of a special importance impurity in diamond. Among the N-related family of optical-active defects, the nitrogen-vacancy (NV) consisting of a substitutional nitrogen atom and an adjacent vacancy is particularly important in view of numerous applications in both emerging and mature technologies. While irradiation with a number of different particles is known to cause defect formation in diamonds including formation of NV centers, e-beam method would yield just a few vacancies per electron and also cause lesser damage to the lattice than other irradiation methods. Furthermore, an e-beam procedure is expected to produce a more homogeneous distribution of the vacancies vs. those created along the shorter radiation tracks of heavier particles. Here we describe an optimization of the e-beam irradiation procedure with a particular focus on effects of the e-beam fluence on the efficiency of formation of paramagnetic NV⁻ centers in micrometer-sized HPHT diamond particles as studied by continuous wave (CW) electron paramagnetic resonance (EPR) spectroscopy at X-band (9.4 GHz) and pulsed EPR at X- and Q-bands (34 GHz). In these experiments e-beam fluence was varied up to 5 ×10¹⁹ e⁻/cm². EPR spectra of mostly “forbidden” Δm_s = 2 electronic spin transitions observed at g ≈ 4 (i.e., so-called half-field EPR spectra) reveal the presence of the main W15 triplet defects associated with the fluorescent negatively charged nitrogen-vacancy (NV⁻) centers as well as additional triplet spin centers identified as W16, W17, W18, and W33 that appear upon increasing the e-beam fluence. Consequent annealing at 1,400 °C significantly reduces the content of W17, W18, and W33 but not W15 and W16 defects. The efficacy of NV⁻ center fabrication as a function of fluence dependent e-beam irradiation is also reported. The EPR studies were also supported by photoluminescence data. The work has been funded in part by the NHLBI, Department of Health and Human Services, under Contract No. HHSN268201500010C.

Detonation nanodiamond (DND), diamond nanoparticles of size ranging 3-5nm, synthesized through detonation process, has recently demonstrated many exciting applications. It's small size, non-toxic and biocompatibility has drawn huge interests, particularly in the biomedical field. In order to capitalize the large total surface areas afforded by the small particle size, dispersing DND have been one of the endeavour for the better utilizing of DND for its applications.
DND has strong tendency to aggregate and form robust superstructures on the order of ~100 nm. Theoretical calculations have shown that such aggregation is due to both coherent (CICI) as well as incoherent (IICI) interfacial columbic interactions. The previous interaction should produce ordered configuration whereas the latter random aggregates.
Here we unambiguously demonstrate that DND in water, without any surface modifications, exhibits striking lacy network, formed by self-assembled chain-like superstructures. This was carried out by cryo-TEM imaging of cryo-plunged DND suspension samples. The cryo-plunge method immobilizes DND in water through rapid freezing of DND suspensions. Our analysis shows that the superstructure morphology has strong size and particle shape dependence. First principle calculations reveal that the origin of the superstructure formation is due to the electrostatic potential interaction from specific paring of surface facets of DNDs.
To further understand the relation of surface chemistry to the self-assemble behaviour, we have conducted further experiments using surface modified, hydrogenated and carboxylated DNDs. We found that surface chemistry has significant influence to the assembly as the sizes of the superstructures differ among the untreated, and surface modified DND.

Detonation of TNT/RDX in oxygen-deficient conditions produces nanodiamonds terminated by various oxygen containing surface functional groups, which enable single digit state dispersion in aqueous media via deaggregation methods, such as zirconia microbead milling. Centrifugation of aqueous dispersions of nanodiamonds purified by treatment with chromic acid yields a large amount of nanodiamond supernatant. We call the nanodiamond in this supernatant the water soluble nanodiamond since it exhibits outstanding dispersibility in aqueous media. Although water soluble nanodiamonds agglomerate when in a dry powder state, a mild sonication is capable of dispersing the powder into a transparent colloidal solution. To study the mechanism of the dispersibility of these water soluble nanodiamonds, the surface functional groups were quantified by Boehm titration and compared with various other nanodiamonds. Furthermore, the nanodiamond structure was investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on these results, we will discuss the origin and potential mechanisms of the outstanding dispersibility of the water soluble nanodiamonds in aqueous media.

Fluorescent nanodiamonds are biocompatible fluorescent particles with indefinite photo-stability that make them superior in vitro and in vivo imaging probes for a wide range of applications. Fluorescence arises from specific defect centers within the nanodiamond lattice, which permits the generation of fluorescent nanodiamonds with different emission wavelengths, or combinations of emission wavelengths. The negatively charged nitrogen-vacancy (NV^-) center is a defect in the diamond lattice consisting of a substitutional nitrogen and a lattice vacancy that form a nearest-neighbor pair. NV^- centers are fluorescent sources with remarkable optical properties including quantum efficiency near unity, indefinite photo-stability, i.e., no photo-bleaching or blinking, broad excitation spectra, and sensitive magnetic field-dependent fluorescence emission. In particular, their near infrared fluorescence makes them well-suited for in vivo imaging. However, producing, functionalizing, and characterizing small bright FNDs for biomedical applications remains challenging. We have developed multiple biocompatible functionalization schemes that permit the stabilization and specific labeling of fluorescent nanodiamonds for biological imaging applications. I will describe an approach to significantly increase the density of carboxylic acid groups on the surface of nanodiamonds and demonstrate subsequent functionalization of the nanodiamonds via carboxylic acid coupling schemes. I will also describe a complementary encapsulation approach in which nanodiamonds are coated with a conformal layer of polydopamine, which is subsequently covalently functionalized. I will illustrate uses of FNDs for high resolution three dimensional single-molecule imaging, in vivo background-free imaging through magnetic modulation of FND emission, and as superior fiducial markers for super-resolution microscopies.

Vascular endothelial growth factor (VEGF) is an overexpressed signal protein observed in cancerous cells and is responsible for the uncontrolled angiogenesis that promotes the growth and metastasis of virtually all forms of cancer. As a result, the overexpression of VEGF can be an important biomarker for indicating the presence of cancerous tissues. Fluorescent nanodiamonds have been functionalized via click chemistry mediated attachment with VEGF-A protein. Subsequent in vitro administration and analysis demonstrate effective conjugation and targeting of the VEGF modified diamond to VEGF cellular receptors (VEGF-R). Thus, an effective demonstration of click chemistry mediated conjugation and targeted in vitro administration of fluorescent nanodiamonds is shown, and the results show continued promise for the use of fluorescent nanodiamonds as a targeted fluorescent probe.

The utility of fluorescent nanodiamonds (FNDs) for in vivo bio-imaging was investigated. Fluorescence of ND as a function of size and concentration was measured via an in vivo imaging system to help determine optimal sizes for in vivo detection. This baseline analysis determines a threshold as to the expected imaging signal from whole-body imaging systems. ND was then administered via tail vain injection to nude BALB/c mice induced with a 4T1 mammary carcinoma to determine particle biodistribution via both whole-body imaging and supplemental ex vivo analysis. Due to ND stability against acidic conditions, tissues were digested and analyzed to provide quasi-quantitative assessment of tissue loading. In post-analysis microscopy of tissue, the unique spectral shape of nitrogen-vacancy induced fluorescence provided unambiguous determination of ND translocation to specific organs. Though particle sizes down to 60 nm are detectable via whole-body imaging systems if sufficiently concentrated, sizes above 170 nm are necessary to produce significant contrast in vivo after intravenous injection. These results are then placed in the context of FND for whole-body imaging and related applications.

Fluorescent nanodiamonds (FNDs) are biocompatible particles with indefinite photo-stability that have emerged as promising bioimaging probes. FNDs with negatively charged nitrogen-vacancy (NV^-) centers are superior imaging probes because they do not photobleach or blink, have a high quantum yield, large Stokes’ shift, long fluorescence lifetimes, and fluorescence emission that can be modulated by magnetic fields to improve signal:noise >100x. Their broad fluorescence emission in the near infrared region (lmax = 685 nm) can penetrate into the tissue with limited background signal from autofluorescence.

Results from the development of FNDs with specific terminal groups and bioconjugation chemistries for various in vitro and in vivo imaging applications will be presented. Bikanta’s probes (1) remain monodisperse and stable in liquid suspension unlike conventional nanodiamonds that aggregate into clusters, and (2) rather than having the typical unreactive surface, can be tightly bound to any targeting agent (e.g. aptamers, antibodies) and can therefore be tailored to detect specific diseases. Bikanta is also designing novel imaging instrumentation to improve detection capabilities. Nanodiamonds are exquisitely sensitive to magnetic fields and this sensitivity reduces background noise to improve visualization deeper into the body. Early results have already improved signal 100-fold over current methods.

Bikanta illustrates the unique features and potential uses of FNDs from single molecule to in vivo imaging with several applications: (1) high spatial and temporal resolution 3-D tracking over extended periods of time, (2) as stable fiducial markers for ultra high resolution microscopy across multiple wavelengths, (3) cell and generation tracking, (4) immunohistochemistry labeling, (5) tumor uptake, and (6) wide-field background-free imaging through magnetic modulation to image lymph node through tissue.

Despite of evident, in particular morphological differences, in terms of surface chemistry nanodiamond (ND) has much in common with graphene oxide (GO). Both of them have oxygenated functional groups on their surfaces. Among the most important and abundant ones are carboxylic groups COOH, which form the basis of functionalization chemistry for both ND and GO. Recently we tested a novel approach to GO functionalization, which allows for facile generation of a paramagnetic material by combining two diamagnetic components: GO and square-planar tetraazamacrocyclic cations [Ni(cyclam)]²⁺ and [Ni(tet b)]²⁺.¹ The underlying chemistry is the conversion of the square-planar diamagnetic complexes to pseudooctahedral paramagnetic ones when coordinated to COOH group under basic conditions, which implies the change from low-spin to high-spin state of nickel(II) ions. Based on the similarity between ND and GO surface chemistry, we attempted coordination functionalization of ND with the same tetraazamacrocyclic cations, under the same conditions as in the case of GO.¹ Nevertheless, the results we obtained were negative. DFT calculations (PBE functional with the empirical correction by Grimme) were employed to explain why our attempts to coordinatively functionalize ND failed. Our explanation is based on the comparison of calculated binding energies for low-spin (singlet) and high-spin (triplet) complexes of model carboxylates GO⁻ and ND⁻ with the two tetraazamacrocyclic cations. The calculated energies of complex formation were interpreted in terms of ΔΔE_3-1 values, which quantify the difference in stability for the triplet and singlet complexes: a negative ΔΔE_3-1 value means that triplet complex is more stable, and vice versa. The results obtained do not completely exclude the possibility of formation of high-spin [Ni(cyclam)]²⁺ carboxylate derivatives on ND. However, the comparison of ΔΔE_3-1 values in the case of [Ni(tet b)]²⁺ explicitly demonstrated that the formation of high-spin complex is highly unfavorable with ND⁻ contrary to GO⁻ model, for which ΔΔE_3-1 values obtained are 13.22 and -4.64 kcal/mol, respectively. In addition to binding energies, we analyzed the optimized complex geometries (in particular Ni−O distances), HOMO−LUMO parameters and spin density plots.
This work was supported by the projects CONACYT-250655 and UNAM DGAPA-IN200516.
(1) V. A. Basiuk, et al., Appl. Surf. Sci., 371, 16 (2016).

Carbon nanomaterials, including nanodiamond (ND) and carbon nanotubes (CNTs) promise numerous and diverse applications. This makes their production steadily grow, which raised concerns on their potential impact on environmental systems and human health. These concerns resulted in a number of research reports on how ND and CNTs influence the growth, development and functions of different living organisms, with an emphasis on plants of agricultural importance. Unfortunately, the design of an adequate experimental setup is complicated, due to a considerable size of crop plants. As a result, only short-term assays are usually carried out, whereas long-term effects are inevitably overlooked.
Here we describe a new approach for the long-term assays of ND and CNTs phytotoxicity, employing three cactus species Parodia ayopayana, Ferocactus latispinus and Melocactus matanzanus. All of them are small and slow growing plants, which is very convenient for long-term phytotoxicity assays using the substrate volumes as small as tens of milliliters, contrary to the commonly reported experiments with crop species. The experimental setup of choice was a soil-based experiment. It allows for a better match of the real environmental situation, but, on the other hand, does not allow for direct observations of root development in vivo, contrary to the in vitro experiment performed in vertically-oriented Petri dishes on the plant culture medium solidified with the agar, which we reported previously.¹ After few-months observations of seedling growth, we concluded that pristine single-walled CNTs (SWNTs; synthesized by arc-discharge process) exhibited the strongest phytotoxic effect as compared to ND, pristine multi-walled CNTs (MWNTs; by CVD) and purified SWNTs, which can be attributed to a considerable fraction of impurities (amorphous carbon, graphitized particles, metal catalyst, etc.). Our results also showed that after first three months of exposure both ND and nanotubes might produce seemingly favorable effect on seedling growth. Nevertheless, this effect can invert after further exposure for one or more months. Therefore, careful evaluation of the possible phytotoxic effects of ND and other nanomaterials must include observations of the exposed plants for several months, whereas shorter, several week-long assays are definitely insufficient and might produce misleading results.
This work was supported by the projects CONACYT-250655 and UNAM DGAPA-IN200516.
(1) V. A. Basiuk, et al., Sci. Adv. Mater., 5, 1337 (2013).

Fluorescent nanodiamonds (FNDs) are a new class of carbon nanomaterials that offer great promise for biomedical imaging applications due to their superior optical stability. FNDs are widely used in biomedical application such as cell labeling, imaging, and sensing. However, they tend to precipitate in physiological buffers, and their surface modification can be difficult due in part to the inertness of diamond. Here, we demonstrate polydopamine (PDA) encapsulation of FNDs, which is inspired by the adhesion mechanism of marine mussels. The PDA shells are readily modified via Michael addition or Schiff base reactions with molecules presenting thiol or nitrogen derivatives. We describe modification of PDA shells by thiol terminated polyethylene glycol (PEG) molecules that enhance colloidal stability in biological solutions and biocompatibility of PDA coated FND (FND@PDA). The PEGylated FND@PDA nanoparticles were utilized as fluorescent probes for cell imaging with immature bone marrow derived dendritic cells. The FND@PDA nanoparticles were taken up by the cells, while exhibiting reduced nonspecific membrane adhesion. Moreover, biotin-PEG-SH functionalized FND@PDA was conjugated with biotinylated DNA via streptavidin, permitting long-term single-molecule fluorescence based tracking. The robust polydopamine encapsulation strategy that we present provides an avenue for the development of FND as multifunctional labels, drug delivery vehicles, and targeting agents for biomedical applications.

Primary amino group (-NH₂) on diamond surface is of significant for various applications. It will for instance serve as a scaffold to bind or adsorb proteins, DNAs, saccharides or small drug molecules for biomedical applications. In addition, it is recently reported that modification with nitrogen on the surface of bulk diamond stabilizes NV^- center. A lot of works to introduce primary amino group on the nanodiamond surface have been reported. In almost all of them, the processes were of the introduction of small molecules already possessing amino group, in which the amino group indirectly bound on the surface.
Here we will report about our attempts for fabrication of primary amino groups binding directly to surface carbon atoms of detonation nanodiamonds. We have worked on several modification reactions to introduce nitrogen atom on the surface, which are other than previously reported substitution reactions. We would like to discuss the results, as well as the properties of directly-bound amino group.

The addition of nano-particles to liquid lubricants often leads to a reduction in both friction and wear rates. While the lubricating properties of nano-particles are well documented, the detailed physical mechanisms remain to be fully explored. Results from prior experiments (Z. Liu, et al., RSC Advances 5, 78933 – 78940 (2015)) suggest that nano-diamond charge, as measured by the Zeta potential, can have a large influence on tribological performance. Using molecular dynamics simulations, we have characterized the interaction between charged nano-diamond particles and a gold surface in water. Two atomic models of octahedral nano-diamonds in an aqueous solution were created that mimic the negatively and positively charged experimental nano-diamonds, one with chemisorbed carboxyl groups (COO-) and Na+ counter ions, and one with chemisorbed amino groups (NH3+) and Cl- counter ions. To explore the influence of particle–surface electro-static interactions, the simulations were carried out with and without induced electrostatic forces between the nano-diamonds and the gold substrate. For both types of nano-diamond, the electro-static interactions enhance surface adhesion and increase the applied force needed to slide the nano-diamonds along the gold surface. However, the magnitude of these effects and their adhesion mechanisms were found to depend on the nano-diamond surface groups. The simulations predict that the positively charged nano-diamonds are both more strongly adhered to the gold (by a factor of almost three), and require a larger force for sliding (by a factor just greater than two). These results are consistent with the interpretation of the prior experimental studies from Liu et al. The relatively large size of surface carboxyl groups allows Na+ counter ions to reside in a thin water layer between the nano-diamond and gold substrate, which partially screens the nano-diamond/gold electrostatic interactions. In contrast, the positively charged nano-diamonds sit closer to the gold surface without the interface water layer and associated electro-static screening from the counter ions. This difference in electrostatic screening and in the thin water layer results in the different sliding and adhesion behavior.

Nanodiamonds produced by detonation and purified by oxidation have a large number of different oxygen-containing surface groups. A full control of surface chemistry is critically important in all applications of nanodiamonds. In particular, it has been found that nanodiamonds can be used as radical trapping stabilizers in thermal processing of polymers. To explain their radical trap action, we hypothesize that nanodiamonds have functional groups which are similar to conventional antioxidants, hindered phenols, but are stable up to 350 °C. In this research, the thermal stability of nanodiamond-polyether ether ketone (PEEK) composites was investigated. PEEK is well-known as one of the best engineering plastics with excellent mechanical and chemical resistance properties. However, at high temperatures, unwanted radical induced reactions such as cross-linking or extension of the chains occur, resulting in deteriorations of processibility and performances of the polymer. To date, no suitable thermal stabilizer has been found to suppress these undesired radical reactions. This is because conventional antioxidants are unstable over 350 °C, which is the processing temperature of PEEK. We developed a novel high temperature stable nanodiamond-PEEK composites. Rheometry and thermal gravimetric analysis (TGA) were used for characterization of the composites. Furthermore, Boehm titration was carried out to determine the phenolic hydroxyl groups on the nanodiamond surface, which are important functional groups to support our hypothesis about the mechanisms of nanodiamond induced thermal stabilization of polymer composites.

Nanodiamond powder produced by detonation synthesis is the most promising nanofiller for composites^1-2. It is made of diamond particles of ~5 nm in diameter, combining fully accessible surface with a rich and tailorable surface chemistry. Nanodiamond has unique optical, electrical, thermal, and mechanical properties, it is biocompatible and non-toxic. In order to fully benefit from the potential of nanodiamond in nanocomposites, several important issues must be addressed, such as uniformity of nanodiamond dispersion in the matrix, nanodiamond-matrix interface, and the properties of the interphase formed in the vicinity of nanoparticles. These issues can be addressed by different purification, dispersion³, and surface modification strategies. Proper surface chemistry and deaggreagtion strategies improve dispersions of nanodiamond in the matrix. Reactions of nanodiamond functional groups with the matrix can further be used to design a nanofiller-matrix interface and produce a significant volume of the interphase in the composite. The interphase formation depends on how nanodiamond changes the structure of the matrix in the vicinity of the nanoparticle. Incorporation of nanodiamond into composites may improve their mechanical, thermal, electrical, and optical properties for many practical applications.

1. Mochalin, V. N.; Gogotsi, Y., Nanodiamond–polymer composites. Diam. Relat. Mat. 2015, 58, 161-171.
2. Mochalin, V. N.; Shenderova, O.; Ho, D.; Gogotsi, Y., The properties and applications of nanodiamonds. Nature Nanotechnology 2012, 7 (1), 11-23.
3. Turcheniuk, K.; Trecazzi, C.; Deeleepojananan, C.; Mochalin, V. N., Salt-Assisted Ultrasonic Deaggregation of Nanodiamond. ACS Applied Materials & Interfaces 2016, 8 (38), 25461-25468.

Detonation nanodiamonds are of vital significance to many areas of science and technology. However, their fluorescence properties have rarely been explored for applications and remain poorly understood. We demonstrate significant fluorescence from the visible to near-infrared spectral regions from deaggregated, single-digit detonation nanodiamonds dispersed in water produced via specific post synthesis oxidation conditions The excitation wavelength dependence of this fluorescence is analyzed in the spectral region from 400 nm to 700 nm as well as the particles’ absorption characteristics. We report a strong pH dependence of the fluorescence and compare our results to the pH dependent fluorescence of aromatic hydrocarbons. Our results significantly contribute to the current understanding of the fluorescence of carbon-based nanomaterials in general and detonation nanodiamonds in particular and pave the way towards the use of detonation nanodiamonds as pH sensors.

The chemical purification processes of detonation-synthesized nanodiamond (DND) has been very important in the industry because the process is very expensive and dangerous. Especially, the chemicals including carrier acid (e.g. H₂SO₄, HNO₃, etc.) and oxidant (e.g. HClO4, KMnO₄, etc.) are expensive and chemical waste disposal causes environmental issues. Therefore, the cost effective and environmentally friendly process of DND chemical purification is very attractive to the industry.
Here, we demonstrate the recycling process of DND chemical purification with H₂SO₄ and KMnO₄. We recycled H₂SO₄ with three times and characterized sp³/sp² carbon ratio of the purified DND. The results show consistent of sp³/sp² carbon ratio even though H₂SO₄ have been reused with three times. The details will be presented in this talk.

One of the long-lasting problems in nanobiomedical area is the virtual absence of chemiluminescence¹ in the elementary particles of detonation nanodiamond (EPDND, av. diameter of 2.6±0.5nm²), ideal material for biomarker or excitation source in ODMR. Attempted creation of NV color centers by the method of Chang mysteriously failed.
We happened to study MALDI-TOF-MS of EPDND and found a parent peak at 12K Dalton instead of 20K D predicted for EPDND from SCC-DFTB calculations.³ Drastic decrease in the parent mass is interpreted due to the fragmentation of graphene-island shell on the surface of EPDND particle and strained sp^2+x diamond carbon atoms near the core surface, while detecting continuous fragment peaks at 3-4K D region under LDI-TOF-MS conditions.² If NV centers required rigid and precise atomistic structure of the diamond structure, which is likely, then we must conclude that NV centers do not exist from the beginning near the surface of EPDND, nor it would be impossible to create the NV centers by ad hoc irradiation of high-energy beam like γ-ray onto EPDND.
We consider that the leaned parent peak from LDI-TOF-MS of EPDND corresponds to C₁₀₀₀ authentic diamond survived from intense UV laser irradiation but ionized due to the light mass. According to our geometry-optimized nanodiamond database, there is only one stable C₁₀₀₀ diamond predicted, which has a hexagonal structure consisting of sp³ carbon atoms and having only {100} facets, hence protected from diamond-graphite transition. Intense treatment of EPDND with hydrogen plasma could give C₁₀₀₀H₁₈₀, the first nanodiamondoid, in which NV centers can be generated.

Smith, R. S.; Inglis, D. W.; Sandnes, B.; Rabeau, J. R.; Zvyagin, A. V.; Gruber, D.; Noble, C. J.; Vogel, R.; Osawa, E.; Plakhotnik, T.Small, 2009, 5, 1649-1653. (2) Unpublished results. (3) Barnard, A. S.; Osawa, E. Nanoscale 2014, 6, 1188-1194.

Detonation nanodiamonds (DNDs) have unique physical and chemical properties that make them invaluable in many applications. However, DNDs are generally assumed to show weak fluorescence, if any, unless chemically modified with organic molecules. We demonstrate that detonation nanodiamonds exhibit significant and excitation wavelength dependent fluorescence from the visible to the near-infrared spectral region above 800 nm - even without the engraftment of organic molecules to their surfaces. We show that this fluorescence depends on the surface functionality of the DND particles. The investigated functionalized DNDs, produced from the same purified DND, are hydrogen, hydroxyl, carboxyl, ethylenediamine, octadecylamine terminated, as well as the as-received poly-functional starting material. All DNDs are investigated in-solution and on a silicon wafer substrate and compared to fluorescent high-pressure high-temperature nanodiamonds. The brightest fluorescence is observed from octadecylamine functionalized particles, which is more than 100 times brighter than the least fluorescent particles, carboxylated DNDs. The majority of photons emitted by all particle types likely originates from non-diamond carbon. However, we locally find bright and photostable fluorescence from nitrogen-vacancy centers in diamond in hydrogenated, hydroxylated and carboxylated detonation nanodiamonds. Our results contribute to understanding the effects of surface chemistry on the fluorescence of DNDs and enable the exploration of the fluorescent properties of DNDs for applications in theranostics, as non-toxic fluorescent labels, sensors, nanoscale tracers, and many others where chemically stable and brightly fluorescent nanoparticles with tailorable surface chemistry are needed.

Reference:
Reineck et al, The Effect of Surface Chemistry on the Fluorescence of Detonation Nanodiamonds, ACS Nano, 2017, accepted for publication

Detonation is a technique for manufacturing 5 nm diameter nanodiamonds, which are known as detonation nanodiamonds. Although these nanodiamonds are believed to have numerous NV centers, only a small fraction of them are optically active. As a result, the vast majority of detonation nanodiamond particles remain non-fluorescent for reasons that are not completely clear. On the other hand, bright and stable optically active NV fluorescent centers can be produced by irradiating microcrystalline diamonds that are synthesized by high pressure, high temperature (HPHT) processes. Reduction of size of these microcrystalline diamonds by milling yields brightly fluorescent NV nanodiamonds with the sizes down to 40 nm. However, milling of microcrystalline diamonds is a long and expensive process. Here, we investigate the possibility of producing smaller NV fluorescent nanodiamonds by mixing commercially available NV nanodiamonds with diameters ranging from 40 to 100 nm with explosives and detonating in the conditions typical for detonation nanodiamond synthesis. We purify and isolate the NV fluorescent nanodiamond nanoparticles, then determine their size and fluorescence after detonation. The behavior of NV fluorescent HPHT nanodiamonds in detonation environments and the potential to use detonation as a cheaper and faster way to reduce the size of NV fluorescent HPHT nanodiamonds below 40 nm will be discussed.

Nitrogen-vacancy centers (N-V) in nanocrystalline diamonds have been studied extensively for their interesting photoluminescence properties. Negatively-charged N-V centers (N-V-) can emit visible light that is readily detectable, even at room temperature. Observation of N-V centers, particularly the optically active N-V^-, has becoming routine using optical fluorescence microscopy. Combined with AFM, the locations of the N-V^- as well as the particle size can be measured. However, the questions remain as to what the effect of the host structure and the surface environment to the activation of the N-V centers. To answer this question, a technique that is capable of detecting both active and non-active N-V centers as well as the surrounding host structure is needed.
Here we demonstrate that we can measure the signals arising from the N-V centers in individual nanoparticles. The measurement is based on high-energy resolution electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Using EELS, we can measure the electronic transitions within the nanodiamond bandgap to detect N-V^- and N-V⁰ (and others). Such STEM can operate at low voltages (40-100kV) with both high spatial (~0.1 nm) and high-energy (16 meV) resolutions. Such capability allows us to observe the inter-band transition as well as the atomic structure of the particles at the same time.
Our initial result on a 70 nm nanodiamond confirms that we can indeed detect signals at 1.95 and 2.16 eV transitions in the particle. Interestingly, we found that not all particles exhibit these transition states. The reason, we then confirmed is due to the lack of nitrogen in the particle. These observations highlight the importance of dopant control for nanodiamond particles.

While the study of dopants in diamond has generated wide-ranging applications in emerging quantum technologies and enabled the study of presolar and planetary chemistry, the rational control and study of high-pressure, high-temperature doping has remained elusive due to diamond’s low diffusion coefficient and extreme synthesis conditions. Here, we present recent work using well-defined hydrocarbon molecules containing nitrogen- and silicon- heteroatoms to dope nanodiamond at extreme high-pressure, high-temperature conditions. The extreme conditions are created using a laser-heated diamond anvil cell to convert an amorphous carbon precursor material to a nanocrystalline diamond phase. Photoluminescence demonstrates that nitrogen and silicon heteroatoms are incorporated within the carbon precursor and are converted into luminescent color centers within the recovered nanodiamond product without the need for ion implantation. Silicon-vacancy defects are investigated as potential optical pressure sensors in order to illustrate the potential applications of this novel, bottom-up method for color center generation in diamond.

This lecture will highlight our recent clinical trial to validate a nanodiamond-embedded biomaterial [1]. We will discuss the broad spectrum of efficacy, safety, characterization, and other studies that bridged in vitro with preclinical and downstream in-human studies. To provide an outlook for upcoming clinical studies, this talk will also highlight our work in augmented AI to develop globally optimized nanodiamond-modified therapy. Pairing nanodiamond platforms with augmented AI will lead to major advances in drug development and markedly improve response rates for a broad spectrum of disorders. This talk will also highlight our recent clinical trials using these powerful combination therapy optimization technologies and how they will usher in a new era of nanomedicine-based treatment [2].

1. Lee et al., Proceedings of the National Academy of Sciences, 2017
2. Zarrinpar et al., Science Translational Medicine, 2016

The constant emergence of new viruses with a global impact to public health and society at large together with the general absence of the availability of specific antiviral therapeutics for a variety of viruses have made the search for antiviral drugs and therapeutics a challenging research task. Viruses pose a considerable challenge to the body’s immune system as they hide inside cells making it difficult for antibodies to reach them. In contrast to bacterial infections, which are mostly treated using antibiotics, the immunization against viral infections is not always possible. Multivalent binding interactions have lately been considered for the development of new therapeutic strategies against bacterial and viral infections. Multivalent polymers, dendrimers and liposomes have successfully targeted pathogenic interactions. While a high synthetic effort is often needed for the development of such therapeutics, the integration of multiple ligands onto nanostructures turned to be a viable alternative. Particles modified with multiple ligands have the additional advantage of creating a high local concentration of binding molecules.
In this talk I will give several examples on the interest of carbon based nanostructures, notable C-dots and nanodiamonds for the treatment of viral and bacterial infections. Notable different glycan-modified nanodiamonds revealed themselves to be of great promise as useful nanostructures for combating microbial infections.

References:
1. R. Jijie, A. Barras, F. Teodorescu, R. Boukherroub, S. Szunerits, Molecular Systems Design & Engineering, 2017, DOI: 10.1039/C7ME00048K, Advancements on the molecular design of nanoantibiotics: current level of development and future challenges.

2. A. Barras, F. A. Martin, O. Bande, J.-S. Baumann, J.-M. Ghigo, R. Boukherroub, C. Beloin, A. Siriwardena, S. Szunerits, Nanoscale 2013, 5, 2307-2316, Glycan-functionalized diamond nanoparticles as potent E. coli anti-adhesives.

3.M. Khanal, F. Larsonneur, V. Raks, A. Barras, R. Boukherroub, J.-M. Ghigo, C. Ortiz Mellet, V. Zaitsev, J. M. Garcia Fernandez, C. Beloin, A. Siriwardena, S. Szunerits, Nanoscale 2015, 7, 2325-2335, Inhibition of Escherichia coli adhesion to biotic surfaces and of biofilm formation on abiotic surfaces by trimeric cluster mannosides conjugated to diamond nanoparticles.

4. M. Khanal, T. Vausellin, A. Barras, O. Bande; K. Turcheniuk, M. Benazza, Zaitsev, C. M. Teodurescu, R. Boukherroub, A. Siriwardena, J. Dubuisson, S. Szunerits, ACS Applied Materials & Interfaces 2013, 5, 12488-12498, Phenyl-acid-modified nanoparticles: potential antiviral therapeutics.

5. Barras, Q. Pagneux, F. Sané, R. Boukherroub, D. Hober, S. Szunerits, ACS Applied Materials & Interfaces 2016, 13, 9004-9013, Inhibition of Herpes simplex virus type 1 entry by functional carbon nanodots.

6. S. Szunerits, A. Barras, M. Khanal, Q. Pagneux, R. Boukherroub, Molecules 2015, 20, 14051-14081, Nanostructures for the inhibition of viral infections.

Nanodiamonds show great promise as photostable and biocompatible fluorescent markers and sensors for biological applications. Fluorescent defects in diamond particles can be employed to quantify for example magnetic fields and temperature at the nanoscale. Their versatile and robust surface chemistry allows for application specific surface termination and bio-functionalization. However, the use of fluorescent nanodiamonds in biologial systems beyond proof-of-principle experiments remains very limited. This presentation will discuss recent progress in the development of diamond nanomaterials for biological sensing and imaging applications. Material processing and the particles' optical properties will be addressed as well as bioconjugation strategies, the colloidal stability in complex media and targeted imaging approaches in vitro and in vivo.

Detonation nanodiamonds (NDs) behave suitable chemical and physical properties for bio-applications [1]. Well-controlled mass production provides NDs with a primary size of 5 nm made of a diamond-core and a shell-coating containing various surface terminations. Their surface chemistry can be adjusted via wet chemistry and physical treatments (annealing, plasma) [2]. Besides well-identified therapeutic and diagnosis applications of NDs such as drug nanocarriers or biomarkers, we proposed few years ago their use as an active nanoplatform, for which therapeutic effect can be triggered. Indeed, we reported on the radiosensitizing properties of H-NDs to enhance the effect of radiotherapy treatment on radio-resistant cell lines, which were shown to turn into senescence with a stopping of their proliferation [3]. This approach based on a carbon-based material represents a new alternative to metal-based nanoparticles which have not reached yet the clinical trial.
Here, we will summarize the studies conducted these last years in our group to better understand the mechanisms involved behind the reactivity of H-NDs in aqueous suspensions under irradiation. First, we will focus on the hydrogenation of nanodiamonds. Through the use of isotopes of hydrogen, we investigated qualitatively and quantitatively the hydrogenation process on detonation NDs according to the nature of the treatment, i.e. annealing or plasma. Then we will look at the colloidal properties of H-NDs and will report on their stability on short and long term. Finally, we will present our work on the behaviour of NDs suspended in water under ionizing radiations (X- and Gamma-rays). We investigated the production of hydroxyl radicals (HO^●) and solvated electrons (e^-_aq) during water radiolysis according to the concentration of H-NDs. We will demonstrate that H-NDs are at the origin of an overproduction of HO^● and e^-_aq compared to water radiolysis alone. On the contrary, no effect was measured for oxidized NDs from the same source [4]. The origin of the phenomenon will be discussed.
References
[1] Turcheniuk et al., Nanotechnology 28 (2017) 252001.
[2] Krueger et al., Adv. Funct. Mater. 22 (2012) pp 890
[3] Grall et al., Biomaterials 61 (2015) 290.
[4] Kurzyp et al., Chem. Comm. 53 (2017) 1237.

Nanodiamond powder produced by detonation synthesis has a great potential in different applications¹. However, the details of structure and structure-properties relations for this unique nanomaterial are still debated. Recently, interactions of nanodiamond with water became a subject of several studies that proposed different explanations of the details of nanodiamond-water interactions and nanodiamond-related changes to water structure. For applications including drug delivery, composites, and many others, it is important to understand the interactions of nanodiamond particles with the surrounding media, which can be a solvent, or a polymer or metal matrix, etc.
Here we present results of molecular modeling of nanodiamond in water. Structural and thermodynamic parameters of nanodiamond interactions with water will be discussed. This knowledge will advance our understanding of nanodiamond behavior in water, as well as in different liquids and polymers, which is important for drug delivery and composite applications.

1. Mochalin, V. N.; Shenderova, O.; Ho, D.; Gogotsi, Y., The properties and applications of nanodiamonds. Nature Nanotechnology 2012, 7 (1), 11-23.

Applications of nanomaterials are numerous as they can play major roles in improving electronic device capabilities or in reducing pollutants by catalytic reactions for example. In nanomedicine, metallic nanoparticles and detonation nanodiamonds were shown to improve significantly the effects of irradiation in cellulo and in vivo^(1,2). Considering the equivalent mass-energy absorption coefficients μ/ρ between carbon and water, no enhancement is expected. As for gold, considering the quantities of nanoparticles, the order of magnitude of the enhancement is, in many cases, not consistent with μ/ρ values. This leads us to investigate the nanomaterials-ionizing radiation interaction through radicals generation.
For that, we developed a protocol to obtain absolute quantification of solvated electrons and hydroxyl radicals in solution⁽³⁾. Based on coumarin fluorescence, this method was adapted to avoid several pitfalls often encountered in the presence of nanoparticles. This allowed us to quantify the solvated electrons produced as a function of nanoparticle concentration, during irradiation under X-rays (17 keV) and Gamma rays (1.17 MeV) ⁽⁴⁾. Behaviours of gold nanoparticles and detonation nanodiamonds with different surface chemistries were compared. Due to this quantitative approach, we were able to propose a crucial role played by interfacial water in radicals’ production by nanoparticles under irradiation.



References
(1) Hainfeld, J.; Slatkin, D.; Smilowitz, H., The Use of Gold Nanoparticles to Enhance Radiotherapy. Phys Med Biol 2004, 49, 309 - 315.
(2) R. Grall, H. A. Girard, L. Saad, T. Petit, C. Gesset, M. Combis-Schlumberger, V. Paget, J. Delic, J. C.
Arnault, S. Chevillard, Biomaterials 2015 61,290.
(3) Sicard-Roselli, C.; Brun, E.; Gilles, M.; Baldacchino, G.; Kelsey, C.; McQuaid, H.; Polin, C.; Wardlow, N.; Currell, F., A New Mechanism for Hydroxyl Radical Production in Irradiated Nanoparticle Solutions. Small 2014, 10, 3338-3346.
(4) Kurzyp, M.; Girard, H. A.; Cheref, Y.; Brun, E.; Sicard-Roselli, C. Saadaa, S.and Arnault, J.-C. Chem. Commun., 2017, 53, 1237.

Tribological systems are an integral part of any moving mechanical assembly, from nanoscale microelectromechanical systems to macroscale automotive and aerospace applications. Minimizing friction and wear-related mechanical failures in order to allow superior performance and long-lasting operation of moving mechanical systems remains the one of today’s greatest challenges. Despite intense research efforts superlubricity, or near zero friction, has seldom been achieved at engineering scales or in practical systems. Much of the difficulty has often been due to the very complex physical, chemical, and mechanical interactions that occur simultaneously at sliding interfaces of mechanical systems.
In this study we evaluate tribological performance of carbon nanomaterials [1-2], and demonstrate realization of superlubricity regime at macroscale in an all-carbon-based ensemble when diamond nanoparticles are mixed with graphene and slide against diamond-like carbon (DLC) surface [3]. We show that during sliding in dry atmosphere, graphene patches wrap around tiny diamond nanoparticles and form nanoscrolls, thus dramatically reducing the contact area with a perfectly incommensurate DLC surface. The coefficient of friction reaches ultralow values (0.004) thus demonstrating the long-lasting superlubric regime. This superlubricity is stable over a range of temperature, load, and sliding velocity conditions. Our large-scale molecular dynamic simulations elucidate the mesoscopic link between nanoscale mechanics and macroscopic experimental observations.
The highlighted carbon-based superlubricity provides a fundamental basis for developing universal friction mechanism and offers a direct pathway for designing smart frictionless tribological systems for practical applications of industrial interest.

References:
[1] D. Berman, et al., special issue in Diamond and Related Materials, 54, 91 (2015).
[2] D. Berman, et al., Materials Today 17 (2014) 31-42.
[3] D. Berman, et al., Science, 348 (2015) 1118-1122

Development of new lubricants and lubricant additives is critical from both energy conservation and environmental impact viewpoints. Current oil-based technologies, which were developed with a focus on wear reduction, rely heavily on sulfur, phosphorous and/or chlorine based additives that have a propensity for bioaccumulation and environmental toxicity. Another key additive in lubricant formulations are antioxidants which are geared toward minimizing the content of acids, alcohols, aldehydes, ketones, esters and peroxides formed as a result of high temperature oxidation of hydrocarbon chains. Conventional antioxidant components often contain toxic elements. Recent studies have shown that nanocarbon based additives to lubricants can provide significant performance enhancement while mitigating environmental concerns. It was demonstrated that lubricant formulations containing detonation nanodiamond (ND) particles with small aggregate sizes are capable of reducing friction and wear at sliding interfaces due to nano-polishing [1], while fullerene (C60) nanoparticles show antioxidant effects upon addition to oils [2]. A goal of the present work was to investigate if a combination of NDs and C60 can provide a synergism of enhanced tribological and antioxidant properties of polyalphaolefin (PAO) and mineral oils.
Oxidation properties of mineral oil I-20A and PAO-6 oil containing NDs, detonation soot or commercial additives containing ND or detonation soot (ADDO, Karat-5, D-Tribo) has been examined and compared with the oil containing C60 and a conventional antioxidant (N-Phenyl-2-naphthylamine) upon heating at 180^oC for 6 hours. The degradation characteristics of the base oils were determined by physical and chemical tests and through FTIR spectroscopy in the region 1800–1650 cm^-1. Tests of physical and chemical properties included determination of changes in viscosity and the total acid number (TAN).Both fullerene C60 and ND (but not detonation soot) showed antioxidant properties in the mineral oil and PAO at high temperature. The effects of ND deagglomeration approaches and a method of preparation of colloidal ND in oil on their antioxidant properties will also be discussed. The effect of co-additives (ND and ND/C60) in PAO-6 oil on the tribological properties of the formulation are also reported.

References
M Ivanov, O Shenderova, Nanodiamond-based nanolubricants for motor oils, Current Opinion in Solid State and Materials Science, 21 (1), p.17-24 (2017)
Zmarzly, D.; Dobry, D. Analysis of properties of aged mineral oil doped with C60 fullerenes. IEEE Trans. Dielectr. Electr. Insul. 2014, 21, 1119–1126.

Individual color centers in diamond are bright, photo-stable emitters of fluorescence. Whereas e.g. nitrogen vacancy (NV) centers additionally offer electronic spins that can be coherently manipulated and read-out conveniently at room temperature, silicon vacancy (SiV) centers offer especially narrow emission (zero-phonon-line, ZPL) at room temperature. Color centers in diamond are versatile sensors, e.g. NV spins are highly-sensitive to electric and magnetic fields [1], while SiV centers have been recently used as optical temperature sensors [2]. The high stability of color centers also makes them promising candidates for novel scanning near field microscopy techniques [3]. To fully harness the potential of atomic-sized color centers as sensors, it is mandatory to create individual color centers close to the diamond surface and to bring them near (< 100 nm) the sample under investigation. Simultaneously, all techniques mentioned above are using the fluorescence of the color centers to read out the sensor. Thus, the approach of choice to obtain truly nanoscale resolution, not limited by optical resolution, is to incorporate single color centers into nanophotonic structures to enhance fluorescence collection and use them in a scanning probe geometry [4,5].

The talk discusses tip-like nanophotonic structures for scanning probe sensing. I will cover the optimization of these structures via simulations as well as different strategies for their fabrication (bottom up and top down, [6]). Due to the proximity of the color centers to the surface (typically < 10 nm), it is highly crucial to chemically control the termination of the surface to stabilize the charge state and to avoid any damage during nanofabrication processes. We will discuss our results on these topics considering color centers in nanostructures.

Finally, we will summarize our steps towards novel sensing approaches with color centers, including experiments to establish near field based energy transfer (FRET) with color centers inside a diamond single crystal.

[1] E. Bernardi et al Crystals 7(5), 124 (2017)
[2] C. Ngyuen et al. Arxiv 1708.05419 (2017)
[3] Sekatsitkii et al., Faraday Discuss., 2015, 184, 51-69, Tisler et al., Nano Lett., 2013, 13, 3152
[4] Appel et al., Review of Scientific Instruments, 2016, 87, 063703
[5] E. Neu et al., Appl Phys Lett 104, 153108 (2014)
[6] R. Nelz et al., Appl Phys Lett 109, 193105 (2016)

Quantum sensors based on the spin-dependent photoluminescence of nitrogen-vacancy (NV) centers in diamond offer great potential in sensing applications for life sciences. In this talk we show how diamond color centers can be applied for nanoscale NMR. We also discuss potential of color centers in diamond for hyperpolarization of nuclear spins.

CVD diamond is considered as a new interesting conventional wide bandgap (E_g ~ 5.5 eV) semiconducting material having both n- and p-type dopants, which makes it attractive for numerous applications. For instance, nitrogen has one extra valence electron and thus substituting carbon with nitrogen will make diamond conductive, via the motion of free electrons in the conduction band. However, nitrogen substituting for carbon undergoes a Jahn-Teller distortion which generates a deep donor level at 1.7 eV below the conduction band. Nitrogen–vacancy (NV) defects give diamond a pink hue and arise when a nitrogen atom replaces a carbon atom at a position in the diamond lattice next to a vacant site. These systems are rapidly becoming a front-runner for use as the basic unit of quantum information, the ‘qubit’ in a solid-state quantum computer and have been investigated as solid-state sources of single photons.
Since formation energies of neutral N impurities in diamond is -3.4 eV, it explains the prevalence of N in natural diamond. In the present work, we have employed hot filament chemical vapour deposition (HFCVD) method to create NV centers in diamond. Photoluminescence (PL) studies using excitation wavelength λ_ex = 532 nm reveal the presence of NV^- center having zero phonon line (ZPL) at 637 nm along with Silicon-vacancy (Si-V) color center having ZPL at 738 nm.

We have systematically investigated the effects of oxidation on the microstructure and photoluminescent properties of nanocrystalline diamond films. We found that the films exhibited PL peak after oxidation under different temperatures and times. C=O bonds supply important role in the PL. We also prepared a series single crystal diamond in the size of micrometer. The effects of crystal planes on the PL were investigated. The results show that Fabry-Perot resonance is observed in the cubo-octahedral diamond crystals and <111> planes prefer to increase the PL intensity. The crystals were applied in the bio-imaging.

Surface chemistry of detonation nanodiamonds (DND) is an important factor for dispersibility and/or application performance, which can be controlled by various modification methods. Not only the condition of surface functional groups but also the state of sp² carbon on the surface is affected.
X-ray absorption near-edge structure spectroscopy (XANES) is a powerful tool to analyze the state of sp² carbon. In this paper, we will report the states of sp² carbon of DND samples treated by various techniques such as gas phase oxidation, hydrogenation, annealing and so on. CK and OK-edge XANES measurements were carried out at BL10 in the NewSUBARU Synchrotron Radiation Facility, University of Hyogo. We compared the amounts of sp² carbon among different samples estimated from the peak ratio of π*(285.5 eV)/σ*(293 eV), as well as the edge carbon proportions in sp² carbon by detailed analysis of π* peaks. Oxidation state was evaluated as well by the peak ratio of σ* peaks between OK and CK-edge XANES. We will discuss the correlation between the states of sp² carbon and performances.

Elementary particles of detonation nanodiamond (EPDND) were first revealed by DFT calculations, consisting of some patches of sp²(G-patch), a mantle of sp^2+x(F-mantle), and a core of sp³ carbons (D-core)[1]. However, its emprical confirmation has been delayed because of difficulties in isolating pure samples. The elaborate attrition milling of nanodiamond (ND) agglutinates by NanoCarbon Research Institute (NCR) produced a pure well-dispersed solution of single-nano(~3nm) sized EPDND[1], thus giving us its evidence. Korepanov demonstrated by the phonon confinement analysis of Raman spectra that G-core from the solution is nearly 1.6 nm in size[3] and Tristan confirmed the G-patches only in the solution by X-ray absorption[4]. We consider that the solution contains the EPDND that are predicted by the calculations. Hence, any further experimental evidence is appreciated.
Laser desorption ionization mass spectra (LDI MS) demonstrate herein that a G-core of EPDND contains nearly 1000 sp³ carbon atoms. The positive ion mass peak of ~12k Da (~C₁₀₀₀) was first reported three years ago [5] and, among five positive-peaks (<0.5kDa: C_n⁺, 1~5kDa: C_2n⁺, ~12kDa: broad, ~40kDa: broad, ~120kDa:broad) observed, it was assigned to a remnant D-core after losing all the G-patches and F-mantles[6,7]. Abundant C_n⁺ and C_2n⁺peaks are the fragments from the G-patches or F-mantles through thermal or photochemical decomposition at their surfaces because they were observed with the lower laser power threshold which cannot give G-core ions. Little change in the D-core peak from a linear to a reflector mode also indicates the stability of D-core ions as the remnant. Although the solution was dried before measurements, G-core ions were observed from the solution and not from raw agglutinates without milling. We think that D-core ion is generated from the micro colloidal crystals that can be precipitated at air-drying only from the well-dispersed solution. Such a stable D-core ion furthermore should be the cubic diamond that corresponds to be one of the energy-minimized model structures simulated by DFT calculations. The high sp³ content of the cube reaching 76% is unique in the structures, thus explaining the size and stability observed.
[1] A. S. Barnard, E. Osawa; Nanoscale 6, 1188 (2014). [2] E. Osawa, D. Ho, H. Huang, M. V. Korobov, N. N. Rozhkova; Diam. Rel. Mat. 18, 904 (2009). [3] V. I. Korepanov, H. Witek,H. Okajima, E. Osawa, H. Hamaguchi; J. Chem. Phys. 140, 41107 (2014). [4] P. Tristan, H. Yuzawa, M.Nagasaka, R.Yamanoi, E.Osawa, N.Kosugi, E.F.Aziz; JPC Lett. 6, 20909 (2015). [5] T. Tanaka, R. Yamanoi, E.Osawa; 48^th FNTG, Abstract Book,19 (2015). [6] T. Tanaka, M.Fukaya, A.S.Barnard, E.Osawa; 52^th FNTG, Abstract Book, 31(2017). [7] T. Tanaka, M.Fukaya, A.S.Barnard, T.Aoyama, Y.F.Miura, E.Osawa; submitted for publication.

The C 1s peak’s electron binding energy in X-ray photoelectron spectroscopy (XPS) analysis of crystalline diamond and diamond films has been extensively investigated. The splitting of the C 1s peak is usually reported as the combination of C 1s/sp³ and C 1s/sp² bonding in the sample. In this work, we present a systematic XPS C 1s study of the polycrystalline diamond films as well as single crystal diamond (SCD). We demonstrate that the lower energy peak, present in C 1s, and usually related to sp² bonding, is the result of Ar incorporation in the sp3 lattice, identified in this paper as C_D-Ar peak. The correlation of the C_D-Ar peak and the Ar+ beam energy as well as the concentration of Ar in the lattice is discussed. The incorporation of Ar in the samples have been demonstrated as well with high resolution transmission electron microscopy (HRTEM) and Rutherford back scattering (RBS).

The physics and applications of Ultrananocrystalline Diamond (UNCD) films are been investigated due to their unique combination of properties such as high wear resistance, highest hardness relative to any other film, lowest friction coefficient compared with metal and ceramic coatings, chemical inertness^{1 2}, negative electron affinity, low work function, and the high electrical conductivity for boron doped and nitrogen incorporated diamond films. The combination of these properties make doped diamond films suitable for many applications like electrodes for water purification, thermionic and field emission devices, and high power electronic devices^{3 4 5 6 7}. Boron doping of UNCD films during growth has the drawback of Boron contamination of the chamber where the film is grown, which can only be used for the growth of B-doped diamond films.
This presentation will focus on describing the results from research and development of a novel process for Boron doping large area UNCD films by thermal diffusion after growth, thus eliminating the problem of Boron contamination of the diamond film growth chamber. The research is focused on understanding the chemical, structural and electrical properties of the UNCD films before and after doping with Boron by thermal diffusion. The UNCD films were grown by Microwave Plasma Chemical Vapor Deposition (MPCVD) technique on a (1 0 0) Silicon substrate. Subsequently, a 200-nm thick Boron doped Polycrystalline Silicon film was grown on top of the UNCD film as a boron source and protective layer to avoid the C-based UNCD film being exposed, at the high temperature needed for Boron diffusion, to oxygen present in the oven where the Boron doping is produced, which would etch the UNCD film, during the process to induced diffusion of Boron atoms from the Silicon layer into the UNCD film. The diffusion process was carried in an atmospheric furnace at 800^oC with a constant N₂ flow of 4L/min (the furnace was expose to atmosphere during the process) for 1 hour. Once the diffusion process was over, the silicon layer was removed by CF₄ RIE etching. The boron doped and as deposited films were characterized by Raman, XRD, XPS, 4-point probe and C-V analysis. Raman and XRD characterizations were done to confirm that there was no induced graphitization or damage in the films during the diffusion process, while XPS, 4-point probe and C-V characterizations were carried to confirm the boron doping and the change in electrical properties (sheet resistance, charge carrier concentration) during the diffusion process.

Diamond is a wide bandgap (5.5 eV) semiconductor with many attractive properties such as high directioanlity, high hardness (100 GPa) and high thermal conductivity (2000 W/mK). It shows superconductivity when doped with boron. Heavily boron doped diamond becomes a superconductor when the boron concentration is raised beyond 4.5 x 10²¹ cm^-3. It is imperative to obtain critical information on how doping of boron in diamond changes the surface, electronic and superconducting properties in the nanocrystalline regime. Both microscopic and the macroscopic electrical measurements have been employed to study the effect of grain boundaries and of the doping level in superconducting nanocrystalline boron doped diamond (BNCD) films. Conducting atomic force microscopy (CAFM) study has been employed to investigate the local conductivity of the superconducting BNCD films (T_c = 4.3 K). CAFM study revealed that the grain boundaries are more conducting then the individual sp^{<span style="font-size:10.8333px">3</span>} bonded grains. Probing of empty states in BNCD using X-ray absorption spectroscopy (XAS) revealed impurity band formation at 282.8 eV and 284.1 eV, above and below the valence band maximum, resepectively, which are responsible for superconductivity.

I will present some new routes to synthesis of nanodiamonds. The work at this time is unpublished, thus the abstract is brief.

Raman spectroscopy is known as a method of choice for the analysis of carbon materials and carbon nanostructures, allowing, among other, the identification of the type of bonding and estimations of the size of coherent domains. This method is now widely used for the characterization of detonation nanodiamond (DND) of various sources.
The Raman spectrum of purified DND usually consists of several characteristic features: (i) the first-order Raman mode of the cubic diamond lattice which is broadened and red-shifted by about 3-8 cm^-1 compared to bulk diamond, (ii) broad features with two apparent maxima in the 500-1250 cm^-1 range, and (iii) a broad asymmetric line peaking in the 1600-1650 cm^-1 (hereafter named “1650 cm^-1 peak”) range, depending on the sample origin and its purification. Depending on the excitation wavelength, another feature peaking at about 1750 cm^-1 is more or less clearly identified. This Raman spectrum does not strongly depend on the origin of the nanodiamond. In this study, we will focus on the 1650 cm^-1 broad band. Indeed, there is still no true consensus for its origin.
For such a purpose, annealing under different atmospheres may be used to modify the surface properties of DND. These treatments confer different surface properties, in particular in terms of surface terminations and surface charge. These treatments are also usual starting points for further complex surface modifications. The modifications induced by different gases can be divided into three categories: in reductive atmospheres, e.g. hydrogen; in an oxidative atmosphere (air, oxygen) and in inert atmospheres: argon or in vacuum. Isotopic labelling (deuterium, ¹⁸O) was also considered. In specific cases, high resolution TEM images allowed a better understanding of the observed line shapes.
New experimental conditions were adapted to minimize laser-induced effects on DND and to increase the signal to noise ratio of the spectra, in particular when using excitation wavelengths in the deep UV range (325 nm). However, even for the lowest power levels, subtle signal modifications versus time are still observed, especially for the longest exposure durations. Thus, in this study, we also address the problem of the stability of DND under the UV excitations used for the Raman analysis of detonation nanodiamonds.

Controlled- and high-ratio of sp3/sp2 carbon of the detonation-synthesized nanodiamond (DND) might play a very important role in many applications. Here, we demonstrate an atmospheric-pressure process of chemical purification using perchloric acid (HClO4) and identify the control parameters including the reaction temperature, ND loading amount, and processing time. The sp3/sp2 carbon ratio was characterized using UV-Raman spectroscopy (325 nm) and is evaluated based on the intensity ratio (IDia/IG) of the diamond peak and G band peak at 1324 cm-1 and 1590 cm-1, respectively. Through the control of process parameters, we successfully fine-tuned the sp3/sp2 carbon ratio with the range from 0.28 to 1.5 and achieved 15.5 % higher sp3 ratio compared with commercial DND. In addition, we also measured electrical conductivity of DND powder as function of the sp3/sp2 carbon ratio and it shown that sp2 carbon ratio directly affects to enhance the electrical conductivity.
Furthermore, we will also demonstrate a new approach for purifying DND using an atmospheric-pressure plasma jet. Oxygen gas is continuously dissociated in the plasma jet and generates reactive oxygen, which plays a key role in removing non-diamond carbon, including graphite and amorphous carbon. The purification process was evaluated by UV-Raman (325 nm) and X-ray photoelectron spectroscopy. This technique was applied to create a high purity nanodiamond pattern in the polymeric system of polyvinyl alcohol (PVA) and nanodiamonds using a localized plasma jet. The plasma-assisted purification of nanodiamonds enabled to the fabrication of patterns with low electrical conductivity and high thermal conductivity.

The Global market of Nano-Diamond (ND) powders was investigated and the main factors restricting the industrial implementation of ND with the average size of 4-5 nm have been defined: non-constant quality and surface reactivity of commercially available ND, the absence of industrial technologies for dispersing ND in solvents and polymers and insufficient number of ND formulations validated by potential ND consumers. The solution proposed for overcoming the barriers combines the fabrication of pure, uniform and low-cost ND produced by Light Hydro-Dynamic Pulse (LHDP) technology, the industrial Production of Advanced Nano-Diamond Additives (PANDA) in forms of ready-to-use modified ND powders, slurries and masterbatches and the validation of ND formulations by academia and industrial consumers. Technological and economic feasibility of industrial LHDP implementation was investigated and the possibility of 200-fold increase in the process productivity was confirmed. Experimental ND samples were produced varying the intensity of laser irradiation and the obtained ND were characterized by X-Ray diffraction and weighted. It was found, that the minimal power density in the spot needed for ND synthesis by the LHDP was 10^6 W/cm2; 40 % of this powder had the diamond cubic structure, while the rest part was the amorphous carbon. The power density of 10^7 W/cm2 provided 100 % diamond crystallinity not affecting the average size of 4.5 nm. Enhancing the power density from 10^7 to 10^10 resulted in the 2-fold output increase and not affected the ND structure. The power density close to 10^11 W/cm2 leaded to the appearance of 20-30 nm ND particles (~15 %) in the powder of 4-5 nm. The optimization of lthe process enabled to attract a commercially available laser system for industrial fabrication of ND powder with the projected ND output of 600 g/hour.
A technological chain for PANDA consists of the laser ND synthesis manufacturing line and the line for fabrication of ready-to-use ND additives in the form of modified ND powders suluble in numerous fluids, stable colloids based on diverse solvents (aqua, acetone, cyclohexane, NMP, IPA, etc.) and masterbatches based on polyester oil, wax, stearic acid, epoxy resins and other polymers by ND surface modification, disaggregation and uniform incorporation within various media.
Preliminary results of testing ND additives in new applications: 3D printing, thermal management, high refractive index of polymers and energy storage, are presented.
Approaches for the accelerating of ND uptake in traditional applications (coatings, lubricants, polishing and polymers) and scientific issues for ND characterization, validation and new applications development (for bio-medicine, thermal management and high refractive index of polymers, EMI shielding, etc.) are discussed. A new approach of effective treatment of cancer and other severe diseases with modified ND is proposed.