Raman Spectroscopic Studies of Novel Gold-Containing Nanomaterials

Tsang, Lemuel Shui-Lun (2017) Raman Spectroscopic Studies of Novel Gold-Containing Nanomaterials. Undergraduate thesis, under the direction of Nathan Hammer from Chemistry and Biochemistry, The University of Mississippi.

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Abstract

The thiolate-protected gold nanocluster (AuNP) Au38(SCH2CH2Ph)24 was studied using Raman spectroscopy with particular attention to the vibrational modes of the gold-sulfur interface. Such studies of AuNPs are non-trivial, as these materials are weak scatterers that burn and fluoresce readily. Previous works have successfully studied this class of materials using a rolling circle filter to subtract fluorescence backgrounds, but we set out to develop a method which would suppress fluorescence using more fundamental means. For Au38(SCH2CH2Ph)24, it was found that data acquisition was most effective using lower-energy excitation wavelengths, which could be predicted based on the UV-Vis absorption spectrum of the cluster. When forced to use higher-energy lasers, significant cooling of samples was required to prevent local heating, i.e. at a temperature of 173 K, a low power of 450 μW using 633 nm excitation was enough to burn a sample of Au38(SCH2CH2Ph)24. Here, we present the findings of the process by which we developed another method for Raman characterization of AuNPs.

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