Zhenjia Wang

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We find that giant surface-enhanced Raman scattering for adsorbates on silver surfaces is present only on surfaces that exhibit self-similar fractal topology as inferred from atomic force microscopy. The fractal character results in localizing the energy of incident photons to volumes of a few nanometers on a side, millions of times smaller than the(More)
We observe spectral and intensity fluctuations in Raman scattering from single molecules of 4-mercaptopyridine (4-Mpy) adsorbed on textured silver surfaces. We present evidence that the root cause of these fluctuations is thermal. Analysis of the spectra shows that in some cases the spectral changes are associated with molecular reorientation and in others(More)
We report that measurements of the Raman intensity versus applied voltage are sensitive to filling of the density of states and enable us to measure the second band gap in specific semiconducting single-walled carbon nanotubes (SWNTs). Raman scattering preferentially selects sets of SWNTs whose excitonic transitions are resonant with the incident or(More)
Dramatic localization of optical fields by interactions with surface plasmons on nanotextured metal surfaces allows us to record Raman spectra of individual chromophores on single chains of a high-molecular-weight model conjugated polymer, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene. The data are broadly consistent with two configurations of(More)
The photo-excitation and relaxation of a new cyclometalated complex, Ir(ppy)2fppy, is investigated through the measurement of absorption and photoluminescence spectra. Comparison of Ir(ppy)2fppy with Ir(ppy)3 reveals that the lowest energy excited state of Ir(ppy)2fppy is localised on the aldehyde-substituted ligand, thus giving the complex its(More)
Deposition of silver nanoparticles directly onto a Rhodamine Red monolayer covalently bound to glass is found to increase the photoluminescence by as much as 20 times depending on excitation wavelength and nanoparticle density. At the same time, the excited state lifetime is reduced by more than a factor of 2, the fluorescence spectrum is blue-shifted, and(More)
We report experiments on dendritic molecules with integrated conjugated chromophores that provide microscopic mechanistic information about their solvation dynamics. The fluorescence of a series of immobilized dendritically organized oligothiophenes is studied as they are exposed to good solvents. Initially, the pi-stacking of the oligothiophene units in(More)
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