The role of reductant oxidation state in the formation and function of gold nanoparticle aggregates for SERS applications

摘要

Sodium sulfide used to produce gold nanoparticle aggregates has been shown to require aging, however, until this work, few studies have attempted to ascertain the nature of this aging effect. UV-vis spectroscopy and other experimental evidence suggest that chemical changes take place during the aging process. NEXAFS has helped determine that sodium sulfide is oxidized over time to form, at least partially, sodium thiosulfate. Experiments performed with sodium thiosulfate yield similar results spectroscopically, however, in SERS experiments it is apparent that the surface chemistry is substantially different. This is likely due to both a lack of sodium sulfide and an increase in thiosulfate concentration. It has also been found that thiosulfate can be utilized for the reduction of several other metal salts into metal and, in some cases, metal sulfide nanoparticles, including copper, platinum, palladium, and silver.