Some Interesting Properties of Metals Confined in Time and Nanometer Space of Different Shapes

Mostafa El-Sayed received his B.Sc. from Ain Sham Uniiversity, Cairo, Egypt, and Ph.D. in 1959 from Florida State University (under M. Kasha). He was a Research Associate at Harvard University, Yale University, and California Institute of Technology before joining the University of California at Los Angeles. In 1994, he became the Julius Brown Chair and the director of the Laser Dynamics Laboratory at Georgia Institute of Technology, where he is now a Regents Professor. He is an elected member of the U.S. National Academy of Sciences and the Third World Academy of Sciences, and a Fellow of the American Academy of Sciences, the AAAS, and the American Physical Society. El-Sayed and his group have numerous publications. Using different laser spectroscopic techniques, they pursued research aimed at elucidating the molecular mechanisms involved in dynamical processes and energy conversion in molecules, in gaseous clusters, and in organic and inorganic solids as well as in photobiological systems. More recently, his group began active research on the ultrafast electron and hole dynamics in semiconductor nanoparticles and the thermal, photothermal and catalytic properties of metallic nanoparticles of different shapes.

The properties of a material depend on the type of motion its electrons can execute, which depends on the space available for them (i.e., on the degree of their spatial confinement). Thus, the properties of each material are characterized by a specific length scale, usually on the nanometer dimension. If the physical size of the material is reduced below this length scale, its properties change and become sensitive to its size and shape. In this Account we describe some of the observed new chemical, optical, and thermal properties of metallic nanocrystals when their size is confined to the nanometer length scale and their dynamical processes are observed on the femto- to picosecond time scale.