WIN Seminar Series: Professor Qing-Hua Xu

The Waterloo Institute for Nanotechnology (WIN) is pleased to present a WIN Seminar talk by Professor Qing-Hua Xu from the Department of Chemistry at the National University of Singapore.

Registration is required. If you have any questions or issues registering, please contact win-office@uwaterloo.ca 

Plasmon Enhanced Optical Properties and Their Biomedical Applications

Abstract

Noble metal nanoparticles (NPs) have been known to display unique localized surface plasmon resonance (LSPR) property, which could be utilized to significantly enhance optical responses of metal NPs themselves and nearby chromophores, such as Surface enhanced Raman scattering (SERS), metal enhanced fluorescence and Plasmon enhanced nonlinear optical (NLO) responses.

In this talk, I will present our group’s efforts on various Plasmon enhanced optical properties and their applications. I will focus on aggregation induced two-photon photoluminescence of metal NPs and aggregation induced emission (AIE) of chromophore conjugated metal NPs. Our group found an interesting phenomenon that two-photon photoluminescence of metal NPs were significantly enhanced upon formation of aggregates, up to >800-fold in the colloid solution and several orders of magnitude on single particle level. This phenomenon has been demonstrated to be universal for Plasmonic metal NPs, which has been further utilized to develop various two-photon-excitation based biomedical applications. We have also employed ultrafast spectroscopy and single particle spectroscopy to understand the underlying enhancement mechanisms. Taking advantages of giant local electric amplification of plasmon coupled nanostructures, we have developed a new type of AIE based on aggregation of metal-chromophore conjugates. The working principle of this new AIE scheme is based on aggregation induced plasmon coupling of metal NPs that help to enhance the excitation efficiency and emission quantum yield at the same time. We have further developed photosensitizer conjugated gold NPs that display significantly enhanced fluorescence, singlet oxygen generation and photothermal response, which allow applications for multimodal imaging and synergistic photothermal and photodynamic cancer therapy below the skin tolerance threshold.

Biography

Qing-Hua Xu received his B.S. from Zhejiang University (1993), M.S. from Peking University (1996) and University of Chicago (1997), and Ph.D. from UC Berkeley (2001). He conducted the postdoctoral research at Stanford University (2001-2002) and UC Santa Barbara (2002-2005). He joined NUS Chemistry in 2005 and became a tenured Associate Professor in 2011. His primary research interests focus on optical properties and dynamical processes of novel low-dimensional materials as well as their applications in biomedicine, optoelectronics, energy, and environmental areas. His research spans a broad range from materials preparation to practical applications as well as fundamental studies by using single particle spectroscopy and femtosecond time-resolved spectroscopy and microscopy. So far he has published ~230 peer reviewed articles with citations of >14,000 times and H-index of 71 (Google scholar). He was selected as top 2% of the most-cited scientists in the world for both year 2020 and 2021 (ranked by Stanford University).