Melissa A. Summers

Single molecule spectroscopy of tetrahedral oligophenylenevinylene molecules

Abstract We probe the fluorescence from single molecules of a new class of tetrahedral oligo(phenylenevinylene) (OPV) molecules. Our results show that the tetrahedral molecules contain multiple chromophores with limited inter-arm coupling, but significant molecular motion about the central carbon results in fluctuations in the polarizability axis of the molecule. Loss in luminescence intensity is also observed during the fluctuations which is attributed to inter-arm coupling occurring when adjacent arms come close together. These fluctuations occur on the timescale of 100 ms to 10 s and are shown to be absent in the ‘arm’ molecules alone.

Variable-ambient scanning stage for a laser scanning confocal microscope

A variable-ambient scanning stage for a laser scanning confocal microscope was designed and tested. The stage allows for facile observation of both thin films and single molecule samples under inert conditions. High precision images have been acquired up to 174 μm2 using a single piezoceramic tube. The vacuum seal is achieved by simply placing the sample side of a standard 25×25 mm glass coverslip face down onto a Buna o ring and gently clamping it in place with a Teflon cap. Tests show that the stage holds a vacuum of at least 3×10−6 Torr. Fluorescence experiments performed on films of an organic dye, DiIC12, as well as single molecule experiments performed on air sensitive oligo(phenylenevinylene) molecules, effectively demonstrate the ability of the scanner to reduce photo-oxidation rates.

Optical Microscopy of Polycrystalline Oligo(phenylenevinylene) Films

Laser scanning confocal microscopy (LSCM) has been used to characterize the emission properties of polycrystalline films of a phenylenevinylene oligomer. The emission profiles obtained from different crystalline regions are distinct and indicate that different molecular environments exist within the films. The spectra obtained from polycrystalline films contain a broad low energy component that is not observed in non-crystalline oligomer samples, and is consistent with excimer emission.