Invited Speech:

Plasmonic Enhancement of Chemical Reactions

Prof. Jianfang Wang Professor Department of Physics, The Chinese University of Hong Kong E-mail: jfwang@phy.cuhk.edu.hk

 

Date: 12 Dec 2016 (Mon)
Time: 11:45am - 12:15pm
Venue: TY Wong Hall, 5/F, Ho Sin Hang Engineering Building, CUHK

 

Abstract:

Noble metal nanocrystals, possessing localized surface plasmon resonance, can interact strongly with light, efficiently converting light into heat and generating hot electrons and holes. Both plasmonic photothermal conversion and generation of hot charge carriers can accelerate chemical reactions. While the acceleration of chemical reactions by photothermal conversion is straightforward, the acceleration of chemical reactions by plasmonic hot charge carriers represents a new research field. Plasmonic hot charge carriers can not only enhance the reaction yield and selectivity, but also introduce new reaction pathways. A full understanding of the latter process requires the knowledge of localized plasmon, electron/hole dynamics, charge transfer, and electron/hole-induced reactions. The study of plasmonic enhancement of chemical reactions will be rewarding in both fundamental and technological aspects.

The lifetime of plasmonic hot charge carriers is on the femtosecond scale. Without utilization, they will rapidly relax, converting their energy into heat. Two approaches have mainly been developed to facilitate the utilization of plasmonic hot charge carriers. The first is the integration of Au or Ag nanocrystals with Pd or Pt nanoparticles. Au and Ag nanocrystals possess strong localized plasmon resonance, while Pd and Pt nanoparticles are excellent catalysts for a variety of chemical reactions. A combination of the two types of metal nanocrystals can lead to efficient light absorption and generation of plasmonic hot charge carriers, which can subsequently inject into molecules that are adsorbed on the Pd component. The second is the integration of plasmonic metals with semiconductors. A barrier is formed at the interface. The generated hot electrons and holes can quickly inject into the conduction or valence band and therefore get separated. The injected charge carriers can then promote chemical reactions. We have synthesized bimetallic nanocrystals as well as metal/semiconductor hybrid nanostructures to demonstrate plasmonic enhancement of chemical reactions by both approaches.

 

About speaker:

Jianfang Wang obtained BS (inorganic chemistry and software design) from University of Science and Technology of China in 1993, MS (inorganic chemistry) from Peking University in 1996, and PhD (physical chemistry) from Harvard University in 2002. He did postdoctoral study in University of California, Santa Barbara from February 2002 to July 2005. He joined in Department of Physics of The Chinese University of Hong Kong (CUHK) as an assistant professor in 2005 and became an associate professor in 2011 and a full professor in 2015. His current research interests focus on metal nanocrystals for nanoplasmonics and nanophotonics, and metal oxide nanostructures for photocatalysis. He has published ~150 papers, with a total citation number of ~15,000 and an h-index of 55.