This article reports on a study that obtained the surface enhanced Raman spectra of 4-mercaptopyridine on lead sulfide (PbS) quantum dots as a function of nanoparticle size and excitation wavelength.
The nanoparticle radii were selected to be less than the exciton Bohr radius of PbS, enabling the observation of quantum confinement effects on the spectrum. Researchers used the variation of non-totally symmetric modes of both b1 and b2 symmetry as compared to the totally symmetric a1 modes to measure the degree of charge-transfer between the molecule and quantum dot. The study found both size-dependent and wavelength-dependent resonances in the range of these measurements, and attributed them to charge-transfer resonances, which were responsible for the Raman enhancement. 23 references (publisher abstract modified)
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J. Chem. Phys. 134, 024707 (2011)