Fluorescence-detected circular dichroism and circularly-polarized luminescence of a single molecule

PHYS 469

Ruthanne Hassey, rhassey@chem.umass.edu1, Ellen J. Swain, eswain@student.umass.edu1, Nathan I. Hammer, nhammer@chem.umass.edu1, Emily L. Richards, emily.richards@pnl.gov2, D. Venkataraman, dv@chem.umass.edu1, and Michael D. Barnes, mdbarnes@chem.umass.edu1. (1) Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant St, Amherst, MA 01003, (2) Environmental Technology Directorate/Field Hydrology, Pacific Northwest National Laboratory, P.O. Box 999, K6-96, Richland, WA 99352
We report the first observation of resonant chiroptical effects (fluorescence-detected circular dichroism, and circularly polarized luminescence) from single (bridged-triarylamine) helicene molecules. In the case of FDCD excited at 457 nm - an excitation wavelength where the bulk circular dichroism is negligible - single-molecule fluorescence from enantiomerically pure helicene samples shows a surprising distribution of dissymmetry (g)- parameters centered near zero but with significant contribution from molecules showing an almost perfectly pure response to either right or left circularly polarized light. Experiments combining a well-defined circularly polarized excitation (either right or left) field and decomposition of the fluorescence into right- and left-circular polarization components show only a weak correlation between the dissymmetry (sign and magnitude) of the CPL with the polarization state of the input. Current efforts are directed at both wavelength resolved CPL, and FDCD at wavelengths that are more closely matched to bulk circular dichroism features. These results provide new insights into chiroptical properties of chiral fluorophores at the single molecule level.

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006