office: D43A Hildebrand
office phone: (510) 643-7371
office fax: (510) 642-6911
lab: D86-D79 Hildebrand
lab phone: (510) 642-2148, 643-4078
student/post doc office: D81 and D45 Hildebrand
(photo by LBL photographer Roy Kaltschmidt)
Prof. Alivisatos' research concerns the structural, thermodynamic, optical, and electrical properties of colloidal inorganic nanocrystals. He investigates the fundamental physical and chemical properties of nanocrystals and also works to develop practical applications of these new materials in biomedicine and renewable energy.
Nanocrystals: Building Blocks for Solid State Chemistry and Materials Design
Nanometer size inorganic crystals are playing an increasingly important role in solid state physics, chemistry, materials science, and even biology. Many fundamental properties of a crystal (e.g., ionization potential, melting point, band gap, saturation magnetization) depend upon the solid being periodic over a particular length scale, typically in the nm regime. By precisely controlling the size and surface of a nanocrystal, its properties can be tuned. Using techniques of molecular assembly, new nanocrystal based materials can in turn be created.
As the number of atoms in a cluster increases, there is a critical size above which one particular bonding geometry; characteristic of an extended solid "locks in." As more atoms are added, the total volume and the number of surface atoms change, but the basic nature of the chemical bonds in the cluster does not. In this regime, the properties of nanocrystals vary smoothly, slowly extrapolating to bulk values, according to scaling laws. Many scaling laws have been hypothesized, a few are verified. For instance, the band gap of a semiconductor, such as Si, InAs, or CdSe, all increase with size, roughly as 1/r2, and their melting temperatures all decrease with size, roughly as 1/r, and these observations can be described well theoretically. Other size dependent scaling laws are topics of current research: How long does it take for a crystal to isomerize between two stable bonding geometries? How do the selection rules for absorption and emission of light depend upon the crystal size (translational symmetry)? What is the largest crystal that can be made defect free? In our fundamental studies of nanocrystal physics, we employ a wide range of spectroscopic and structural experimental tools, as well as computer simulation.
The ability to make nanocrystals of high quality (uniform size, no defects except the ones we want, designed surface, etc.) is key to this area of science, and also interesting in its own right. We grow nanocrystals by injecting organometallic precursors into pure, hot surfactants. Some important questions of solid state chemistry can be addressed in the synthesis of nanocrystals. How does nucleation of a solid occur? What governs the rate of growth of a crystal? What is the stress and strain at the interface between a core and a shell of different materials? In addition to fundamental studies of nanocrystal synthesis, we are interested in developing automated, self-correcting nanocrystal syntheses, surface derivitization, and methods for nanocrystal characterization and assembly.
Materials Design Targets
- Nanocrystal/polymer composites for light emitting diodes and photovoltaics
- Single nanocrystal-single electron transistor (with P. McEuen, Physics)
- Nanocrystal/antibody conjugates as biological tag molecules (with S. Weiss, LBNL)
- DNA directed assembly of nanocrystal patterns (with P. Schultz)
- Nanocrystal photo-catalysis
- Mechanical properties of nanocrystal composites
Dr. Armand Paul Alivisatos is the University of California (UC) Berkeley's Executive Vice Chancellor and Provost and Samsung Distinguished Professor of Nanoscience and Nanotechnology. He is also the Founding Director of the Kavli Energy Nanoscience Institute (ENSI), a Sr. Faculty Scientist at Lawrence Berkeley National Laboratory, and holds professorships in UC Berkeley's departments of chemistry and materials science. In addition, he is a founder of two prominent nanotechnology companies, Nanosys and Quantum Dot Corp, now a part of Life Tech.
Groundbreaking contributions to the fundamental physical chemistry of nanocrystals are the hallmarks of Dr. Alivisatos' distinguished career. His research accomplishments include studies of the scaling laws governing the optical, electrical, structural, and thermodynamic properties of nanocrystals. He developed methods to synthesize size and shape controlled nanocrystals, and developed methods for preparing branched, hollow, nested, and segmented nanocrystals. In his research, he has demonstrated key applications of nanocrystals in biological imaging and renewable energy. He played a critical role in the establishment of the Molecular Foundry, a U.S. Department of Energy's Nanoscale Science Research Center; and was the facility's founding director. He is the founding editor of Nano Letters, a leading scientific publication of the American Chemical Society in nanoscience.
Dr. Alivisatos has been recognized for his accomplishments, with awards such as the Dan David Prize, the National Medal of Science, the Spiers Memorial Award, Axion Award, Wolf Prize in Chemistry, the Von Hippel Award, the Linus Pauling Medal, Computation and Engineering’s Nanoscience Prize, the Ernest Orlando Lawrence Award, the Rank Prize for Optoelectronics, the Eni Award for Energy and Environment, Colloid and Surface Chemistry Award, Coblentz Award for Molecular Spectroscopy and the Thomas Wilson Memorial Prize. He is a member of the National Academy of Sciences, the American Academy of Arts and Sciences and the American Philosophical Society.
Dr. Alivisatos received a Bachelor's degree in Chemistry in 1981 from the University of Chicago and Ph.D. in Chemistry from UC Berkeley in 1986. He began his career with UC Berkeley in 1988 and with Berkeley Lab in 1991.