Abstract:
Using calorimetric techniques, we have shown that differences on surface energies of various phases lead to large changes in thermodynamic stability among phase assemblages, indeed sometimes startlingly, as small particles are stable in structures that are metastable in the bulk. These changes impact geochemical and biogeochemical processes, the transport of heavy metals in the environment, catalysis, and the optimization of materials for energy applications. Such effects will be illustrated in three families of materials: iron and manganese oxides, lithium battery cathode materials, and cluster compounds of elements ranging from aluminum to uranium.
Biography:
Alexandra Navrotsky was educated at the Bronx High School of Science and the University of Chicago (B.S., M.S., and Ph.D. in physical chemistry). After postdoctoral work in Germany and at Penn State University, she joined the faculty in chemistry at Arizona State University, where she remained till her move to the Department of Geological and Geophysical Sciences at Princeton University in 1985. She chaired that department from 1988 to 1991 and has been active in the Princeton Materials Institute. In 1997, she became an interdisciplinary professor of ceramic, earth and environmental materials chemistry at the University of California, Davis, and was appointed Edward Roessler Chair in Mathematical and Physical Sciences in 2001.
Her research interests have centered about relating microscopic features of structure and bonding to macroscopic thermodynamic behavior in minerals, ceramics and other complex materials. She has made contributions to mineral thermodynamics; mantle mineralogy and high pressure phase transitions; silicate melt and glass thermodynamics; order-disorder in spinels; framework silicates; and other oxides; ceramic processing; oxide superconductors; nanophase oxides, zeolites, nitrides, perovskites; and the general problem of structure-energy-property systematics. The main technical area of her laboratory is high temperature reaction calorimetry. She is director of the UC Davis Organized Research Unit on Nanomaterials in the Environment, Agriculture and Technology (NEAT-ORU). She has published over 700 scientific papers.
Honors include an Alfred P. Sloan Fellowship (1973); Mineralogical Society of America Award (1981); American Geophysical Union Fellow (1988); Vice-President, Mineralogical Society of America (1991-1992), President (1992-1993); Geochemical Society Fellow (1997). She spent five years (1986-1991) as editor of Physics and Chemistry of Minerals, and serves on numerous advisory committees and panels in both government and academia. She was elected to the National Academy of Sciences in 1993. In 1995, she received the Ross Coffin Purdy Award from the American Ceramic Society and was awarded the degree of Doctor Honoris Causa from Uppsala University, Sweden. In 2002, she was awarded the Benjamin Franklin Medal in Earth Science. In 2004, she was elected a Fellow of The Mineralogical Society (Great Britain) and awarded the Urey Medal (the highest career honor of the European Association of Geochemistry). In 2005, she was bestowed with the Spriggs Phase Equilibria award for her collaboration with Dr. Masao Morishita on the paper "Calorimetric Study of Nickel Molybdate: Heat Capacity, Enthalpy, and Gibbs Energy of Formation." In 2006, she received the Harry H. Hess Medal of the American Geophysical Union. In October 2009, she received the Roebling Medal, the highest honor of the Mineralogical Society of America. In 2011, she became a member of the American Philosophical Society.

Abstract
The demand of low cost materials has become one of the major challenges scientists face to address critical contemporary issues such as sustainable energy sources. For instance, one of the promising alternatives for the transition of fossil fuel-based energy to a clean and renewable technology relies on the widespread implementation of solar-related energy systems, however, the high cost of energy production poses an intrinsic limitation. In this context, low cost materials development is required to balance the necessary increase in power generation and conversion efficiency and the costs of implementation and operation. Furthermore, a better comprehensive understanding of materials growth and properties relationships using quantum confinement and nanoscale strategies to raise the theoretical limits by changing the fundamental physics and chemistry is the key to success. Such ideas will be demonstrated by the thermodynamic modeling and low-cost design of crystalline arrays of quantum rods- and dots-based oxides with controlled orientation, size, and shape onto various substrates at nano-, meso-, and micro-scale by aqueous chemical growth at low-temperature. Tailored dimensionality effects on their surface chemistry, electronic structure, and energetics for a low cost and sustainable generation of hydrogen from the two most abundant and geographically-balanced free resources available on this planet, that is the sun and seawater will also be presented.
Biography
Born in 1968, Lionel Vayssieres obtained a MSc. in Physical Chemistry (1990) and a Ph.D. in Chemistry (1995) from the Université Pierre & Marie Curie, Paris, France for his research on the interfacial thermodynamic growth control of metal oxide nanoparticles in aqueous solutions. Thereafter, he joined Uppsala University, Sweden as a researcher where he pioneered nanorod-based oxide structures for photoelectrochemical applications. He was a visiting scientist at University of Texas at Austin; UNESCO Centre for Macromolecules & Materials, Stellenbosch University, and iThemba LABS, South Africa; Lawrence Berkeley National Laboratory; Texas Materials Institute; Ecole Polytechnique Fédérale de Lausanne, Switzerland; University of Queensland, Australia, and Nanyang Technological University, Singapore as well as an independent scientist at the National Institute for Materials Science, Japan for 8 years working on quantum-confined oxide nanodevices. Since 2012, he is a full time 1000-talent scholar Professor, co-founder and co-director of the International Research Center for Renewable Energy at Xi&’an Jiaotong University, China http://ircre.xjtu.edu.cn/ . He&’s also, since 2003, the founding editor-in-chief of the International Journal of Nanotechnology and a guest scientist at Lawrence Berkeley National Laboratory. He has published 100+ publications which have generated over 7700 citations since the year 2000 including highly cited papers in Materials Science, Chemistry, Physics, and Environment fields and presented over 320 lectures in 28 countries.

In the last two decades, the wet-chemical synthesis of colloidal semiconductor nanocrystals of II-VI, IV-VI and III-V compounds has taken a high flight. This led to a word wide access to suspensions of nanocrystals with specific size and shape, various surface capping and bright emission. Compared to the typical solid state quantum dots, colloidal quantum dots have several advantages: they are quantum objects that do NOT interact with each other, they are available in high quantities, and they can be used as building blocks for more complex materials.
The optical spectroscopy on ensembles and single colloidal nanocrystals resulted in the demonstration and partial understanding of emission blinking, bi-exciton vs. exciton emission, and type I vs. type II quantum dots. On the other hand, electron-tunnelling spectroscopy on single quantum dots revealed the discrete energy levels of these systems and the degree of quantum coupling for quantum dots in an array.
Due to their monodisperse size and shape, small dimensions, and opto-electrical function, colloidal nanocrystals are of huge interest for the study of colloid self-assembly and the fabrication of nanostructured materials with novel opto-electric or thermo-electric functions. I would like to distinguish the non-reactive self-assembly of inert nanocrystals, driven by dispersion forces and entropy, from the reactive assembly driven by facet-to-facet chemical bonding.
The first type of self-assembly has led to a plethora of single-component and binary nanocrystal superlattices with considerable structural diversity. From a materials viewpoint, new electric, magnetic, and optical properties have been demonstrated. Reactive self-assembly has resulted into two-dimensional atomically coherent semiconductors with remarkable geometry. Of special interest are honeycomb semiconductors, since theory predicts Dirac-type electronic conduction and valence bands, and the occurrence of the quantum spin Hall effect. The electronic properties of these systems are presently under investigation.
References to publications of my group and many other research groups will be provided during the lecture.
Biography
Daniel Vanmaekelbergh was born in Brugge (Belgium) on 18 august 1958. After his high school he studied Chemistry at the University of Gent, and obtained his masters degree in Science (Chemistry) “Cum Laude” in 1980. He promoted “Cum Laude” to a Ph.D. in Science (Chemistry) at the University of Gent, under the guidance of Prof. Walter Gomes and Felix Cardon, with the thesis “Investigations on the mechanism of photoelectrochemical reactions at n-type III-V semiconductor electrodes” in 1984.
After his military service and a few post-doc years he became a staff member at Utrecht University in the Netherlands: assistant professor in 1989, associate professor in 1991 and full professor in 2002. He is currently leading the group “Chemistry and Physics of Nanostructures” in the Debye Institute for Nanomaterials Science at the University of Utrecht.
The research of the group of Vanmaekelbergh is directed to the synthesis of colloidal semiconductor nanocrystals, the self-assembly of these to prepare 2-D nanostructured semiconductor systems with tunable electronic band structure, and scanning tunneling micro-spectroscopy, atomic force microscopy and optical spectroscopy of these systems.
The major mission of his research is finding a direct relation between the atomic structure of a nano-system on one hand and its electronic structure and magneto-optical properties on the other hand. Besides STM, also advanced atomic force microscopy is used to image the atomic structure of 2-D semiconductors, and real and artificial graphene nanostructures. One of the final goals is to prepare 2-D honeycomb semiconductors in which charge carries have a Dirac-like nature as in graphene and in which strong spin-orbit coupling results in the topological properties such as the quantum spin Hall effect. His research can find applications in new materials for opto-electronic devices, from spin-transistors to photovoltaic cells.
More information is available on http://www.staff.science.uu.nl/~vanma101/.