Xiaoyong is working on a joint project with Dr. Kahen's group at Kodak, mainly on the optical characterizations of single nanocrystal quantum dots by means of blinking dynamics and ultrafast spectroscopy. A Coherent laser system, including a Verdi 10 green laser, a femtosecond Ti:Sapphire laser with its SHG & THG, a tunable OPO with its SHG, and a pulse picker, is being used as the excitation source. Individual quantum dots on a confocal scanning optical microscope are excited by the laser beam focused to the diffraction limit (~300 nm) by an oil immersion objective (NA = 1.5). Optical emissions from single quantum dots are collected by the same objective and sent either to a CCD for the photoluminescence spectral and image measurements, or to a time correlated single photon counting system (PicoHarp 300) with two single photon APDs for the time-resolved measurements. The above optical setup will also be used for the optical studies of single carbon nanotubes and the folding, stability and conformational dynamics of proteins.
Intensity versus time trace showing blinking for a single quantum dot
