[MOS] March 29, 2011

[Zina M Queen]

Seminar on

 Modern Optics and Spectroscopy



Probing submillisecond dynamics in the fluorescence spectra of single semiconductor nanocrystals

Lisa Marshall,MIT

Tuesday, March 29, 2011

12:00 – 1:00 p.m.
Single-molecule fluorescence spectroscopy is temporally limited by the  need to detect enough photons to measure a spectrum and generally reserved for chromophores isolated on a substrate.These limitations are  particularly troubling for systems like colloidal quantum dots, where spectral dynamics are observed on the slower time scales of conventional camera-based measurements and assumed to be present at faster time scales as well. Here, we use the recently developed Photon-Correlation Fourier Spectroscopy to circumvent both of these limitations.By replacing the beam splitter in a standard Hanbury Brown and Twiss setup with a Michelson interferometer, we are able to compute time-dependent spectral correlations from intensity correlations in the interference pattern from the emission of a single chromophore. We then combine our method with Fluorescent Correlation Spectroscopy (FCS) to extract spectral  dynamics of single chromophores freely diffusing in solution.We apply our technique to colloidal quantum dots both at room temperature in solution and at liquid helium temperatures and explore the spectrum of single particles on timescales not feasible with conventional fluorescence measurements.
Grier Room, MIT Bldg 34-401
Refreshments served after the lecture
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