The preferential generation of anionic nanoparticles of mass around 30 kamu from thiol-derivatized gold nanoparticles and its significance

Abstract

Thiol-derivatized gold nanoparticles have been prepared by the reduction of gold cations in an ethanol solvent in the presence of alkanethiols such as dodecanethiol and nonanethiol. Negative ion laser ablation time-of-flight mass spectra (LA-TOF-MS) of the as-prepared samples indicate the presence of a single predominant peak at around 30 kamu even for samples prepared using widely different gold to thiol molar ratios in the reactant mix. The preponderant observation of such nanoparticles in the mass spectra is attributed to a region of especially high thermodynamic stability existing in this mass range for negative ions derived from nanoparticles prepared from the Au–RSH material combine. These studies also support the assertion that the thiol-derivatized gold nanoparticles prepared by the method of Murthy et al. are qualitatively different than that prepared by the method of Brust et al.

Keywords:

• monolayer protected clusters
• mass spectrometry
• thiol-derivatized gold nanoparticles

Acknowledgements

This work was performed in the laboratories of the Georgia Institute of Technology, Atlanta, GA, USA. The materials preparation and mass spectrometric work was performed in the laboratory of Prof. R. L. Whetten. Members of the Whetten group participated in the preparation and the processing of the nanoparticle material. LA-TOF-MS was performed by members of the Whetten group. The assistance of the Wang group in TEM studies is also acknowledged. The suggestions of one of the referees are also gratefully acknowledged.

Notes

Formerly at the School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA