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Departmental Colloquium

Noble Metal Materials at the Nanoscale: A Golden Key to Addressing Challenges in Solar Energy Conversion and Nanomedicine Development  
Guest Speaker
Wei Qian  
Guest Affiliation
IMRA America, Inc.  
Tuesday, February 14, 2012 4:00 pm - 5:00 pm  

In this talk, I will present two of research projects I have conducted, which shed some light on important roles of noble metal nanoparticles, such as gold and silver, in providing revolutionary solutions to intractable issues in a variety of areas from clean energy supply to disease control and prevention. In the first part of my talk, I will start with a brief discussion of ultrafast nonadiabatic electronic movements at conical intersection in silicon naphthalocyanine (SiNc) chromophores freely diffusing in solution studied at both low chromophore concentration (10 uM) and low pulse fluence (100 pJ) by using femtosecond polarized laser spectroscopy.  As one of naphthalocyanine derivatives, SiNc chromophore has gained interest from the scientific community because it has a similar chemical structure to biologically important porphyrins, such as chlorophyll, that play a vital role in photosynthesis. Then, I will move further to a study of chromophore confined in protein, which provides a unique and highly optimized environment for the photoinduced processes in chromophore. In our case, it is retinal enclosed inside pocket of Bacteriorhodopsin (bR). bR, biological solar cell for Halobacteria, is a paradigmatic system of transmembrane protein that functions as a light-driven vectorial proton pump. Following sub-picosecond photoisomerization of its retinal chromophore, bR visits a series of intermediates with different lifetimes ranging from femtosecond to millisecond and finally pumps a proton across a membrane. The photocycle of bR after absorbing a single photon in visible is among the most striking and beautiful phenomena in nature. I will discuss some experiments I did that showed how to manipulate the bR photocycle process by plasmonic field of a nearby metal nanoparticle. In the second part of my talk, I will first report a new instrument we have designed for live cell imaging via the detection of scattered light from metal nanoparticles. This new instrument is free of photobleaching and blinking problems suffered by fluorescence microscopy and  enables us to carry out continuous and intermittence-free light scattering imaging of live cell over 30 hours. Then,  I will demonstrate how advance in technique and instrumentation allow us to directly track the full cycle of cancer cells from birth to division and to investigate possible mechanism for cytokinesis arrested in cancer cells caused by nucleus-targeting gold nanoparticles.