| Abstract
| - Novel gold nanoparticles, passivated by monolayers of benzenethiol, biphenylthiol, and similar derivatives,have been synthesized and characterized using UV/vis, NMR, and Fourier transform infrared (FTIR)spectroscopies. The nanoparticle sizes have been evaluated using transmission electron microscopy andUV/vis spectroscopy; they show diameters between 2.1 and 4.7 nm, depending on the method of synthesisand the monolayer protecting group. Femtosecond transient absorption measurements show that thenanoparticles possess optical properties on the boundary between molecular and nanoparticle behavior. Thesmaller systems based on benzenethiol exhibit long-lived excited states with lifetimes on the order of a fewnanoseconds, resembling those of small gold molecular type clusters. The larger nanoparticles protected withbiphenylthiol and benzylthiol groups relax much more rapidly on a picosecond time scale, similarly to relatedcitrate stabilized systems reported in the literature.
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