Novel Optical and Dynamic Properties and
Emerging Applications of Nanomaterials

Jin Z. Zhang
Department of Chemistry and Biochemistry
University of California Santa Cruz
Santa Cruz, CA 95064 USA
http://chemistry.ucsc.edu/zhang_j.html

Abstract
Nanomaterials are of strong interest for both fundamental and technological reasons. At the fundamental level, nanomaterials possess novel physical and chemical properties that differ from those of isolated atoms or molecules and bulk matter due to quantum confinement effects and exceedingly larger surface area relative to volume. These novel properties are highly promising for applications in emerging technologies such as nanoelectronics, nanophotonics, non-linear optics, miniaturized sensors and imaging devices, solar cells, and detectors.
Semiconductor nanoparticles have been studied extensively because of their potential application in electronic devices and the opportunity they offer to study the effects of quantum confinement. A unique subset of semiconductor nanoparticles is doped semiconductor nanoparticles. We have recently studied several doped semiconductor nanoparticle systems with the goal to understand the relation between their optical properties and the structure of the host nanoparticles as well as that of the dopant. In the case of Mn2+-doped ZnSe nanoparticles, we have found that the location of the Mn2+ significantly influences its optical emission properties. This understanding is important for designing new nanophotonics materials. We have also investigated the bioconjugation of silica-coated CdSe quantum dots to IgG proteins for potential applications in cancer biomarker detection and have found that the silica coating significantly enhance the stability of the CdSe quantum dots in buffer solutions based on photoluminescence properties.
Metal nanoparticles have also attracted considerable attention due to their interesting properties and potential applications. We have studied the optical and structural properties of different metal nanostructures including aggregates, nanorods, and nanoshells with the goal to optimize their SERS (surface-enhanced Raman scattering) activities. For example, we have very recently demonstrated SERS from single, hollow gold nanostructures. Exceptional sample homogeneity leads to a nearly tenfold increase in signal consistency over standard silver substrates. We have also discovered that it is possible to make long gold nanotubes using magnetic nanoparticles as templates. Unique hollow Au-Ag double nanoshell structures have been designed and successfully synthesized in our lab that show enhanced SERS activities over hollow gold nanoshells. SERS offers a unique combination of molecular specificity and extremely high sensitivity that few other analytical techniques can offer. SERS based on metal nanoparticles, in conjunction with photoluminescence from semiconductor quantum dots, have been exploited for detection of cancer biomarkers.
In addition, my lab has been engaged in the study of metal oxide nanostructures for solar energy applications based on photovoltaics, photocatalysis, or photoelectrochemistry. One example is hydrogen generation from photoelectrochemical splitting of water based on WO3 and TiO2 nanostructures doped with nitrogen or sensitized with quantum dots.

Brief Biography
Dr. Jin Z. Zhang received his B.Sc. degree in Chemistry from Fudan University, Shanghai, China, in 1983 and his Ph.D. in physical chemistry from University of Washington, Seattle, USA in 1989. His Ph.D. work focused on studies of molecular reaction dynamics in the gas phase. He was a postdoctoral research fellow at University of California Berkeley from 1989 to 1992, where he studied reaction dynamics in solutions. In 1992, he joined the faculty at University of California Santa Cruz, where he is currently full professor of chemistry and biochemistry. Zhang’s recent research interests focus on design, synthesis, characterization, and exploration of applications of advanced materials including semiconductor, metal and metal oxide nanomaterials. Dr. Zhang has authored over 110 publications including a book on “Self-assembled Nanostructures”, and he serves as a senior editor for the Journal of Physical Chemistry published by American Chemical Society.

Selected Recent Publications
1. A.M. Schwartzberg, C.D. Grant, T. van Buuren,, J. Z. Zhang, “The Reduction of HAuCl4 by Na2S Revisited: The case for gold nanoparticle aggregates and against Au2S/Au core/shell particles ”, JPCB, in press (on web), 2007.
2. Leo Seballos, T. Olson, and J. Z. Zhang, “Effects of Chromophore Orientation and Molecule Conformation on Surface-enhanced Raman Scattering Studied with Alkanoic Acids and Colloidal Silver Nanoparticles”, J. Chem. Phys. 125, 234706, 2006.
3. A. Wolcott, T. R. Kuykendall. W. Chen, S. Chen, J.Z. Zhang, “Synthesis and Characterization of Ultrathin WO3 Nanodiscs Utilizing Long Chain Polyethylene Glycol”, JPCB, 110, 25288-2529, 2006.
4. A.M. Schwartzberg, T. Y. Olson, C. Talley, J. Z. Zhang, “Synthesis, characterization and tunable optical properties of hollow gold nanospheres”, J. Phys. Chem. B, 110, 19935-19944, 2006.
5. Adam Schwartzberg, Tammy Y. Olson, J.Z. Zhang, Thomas Huser, and Chad Talley, “Improving nanoprobes using surface-enhanced Raman scattering from 30 nm hollow gold particles”, Analytical Chemistry Communications, 78, 4732-4736, 2006
6. Yi Zhang, Claire Gu, Adam Schwartzberg, Shaowei Chen, Jin Z. Zhang, “Optical Trapping and Light Induced Agglomeration of Gold Nanoparticle Aggregates”, Phys. Rev. B, 73, 1654051-1654059, 2006.
7. Abraham Wolcott, Daniele Gerionb, Micah Visconte, Jia Sun, Adam Schwartzberg, Shaowei Chen, and Jin Z. Zhang, "Silica Coated CdTe Quantum Dots Functionalized with Thiols for Bioconjugation to IgG Proteins", J. Phys. Chem. B, 110, 5779-5789, 2006.
8. Yiwen Chu, Jianhua Hu, Wuli Yang, Changchun Wang, and Jin Z. Zhang, “Growth and Characterization of Highly Branched Nanostructures of Magnetic Nanoparticles under Solid State Condition”, J. Phys. Chem. B, 110, 3135-3139, 2006.

9. L Seballos, R. Sutphen, J.Z. Zhang, “Surface-enhanced Raman Scattering Detection of Lysophosphatidic Acid”, Anal. Bioanal. Chem., 383, 763-767, 2005.
10. Jin Z. Zhang, Adam M. Schwartzberg, Thaddeus Norman, Jr., Christian D. Grant, Jun Liu, Frank Bridges, Tony van Buuren, "Comment on 'gold nanoshells improve single nanparticle molecular sensors'", Nano Letters, 5, 809-810, 2005.
11. A.M. Schwartzberg, C.D. Grant, A. Wolcott, C. Talley, T. Huser, R. Bogomolni, J.Z. Zhang, "Unique gold nanoparticle aggregates as a highly active surface-enhanced Raman scattering substrate", J. Phys. Chem. B, 108, 19191-19197, 2004.
12. J. Woo, H.B. Na, T. Yu, Y.W. Kim, F. Wu, J.Z. Zhang, T. Hyeon, “A generalized and facile synthesis of semiconducting metal sulfide nanocrystals” J. Am. Chem. Soc., 125, 11100-11105, 2003.
13. J. Joo, T. Yu, Young W. Kim, H. M. Park, F. Wu, J. Z. Zhang, and T. Hyeon, “Multi-gram scale synthesis and characterization of monodisperse tetragonal zirconia nanocrystals”, J. Am. Chem. Soc., 125, 6553-6557, 2003.
14. T. Norman, Jr, C. Grant, D. Magana, D. Cao, F. Bridges, J. Liu, T. van Buuren, J. Z. Zhang, "Near infrared absorption of gold nanoparticle aggregates", J. Phys. Chem. B 106, 7005-7012, 2002.
15. J.Z. Zhang, “Interfacial charge carrier dynamics of colloidal semiconductor nanoparticles”, J. Phys. Chem. B, 104, 7239-7253, 2000 (invited feature article).
16. J. Z. Zhang, "Ultrafast studies of electron dynamics in semiconductor and metal colloidal nano-particles: effects of size and surface,” Acc. Chem. Res. 30, 423-429, 1997. (invited review)