High-resolution time-of-flight mass spectra of alkanethiolate-coated gold nanocrystals

Alkanethiolate-coated gold nanocrystals have been laser desorbed from a solid film, ionized, and analyzed by time-of-flight mass spectrometry. A previously unresolved distribution of peaks is observed and the number of gold and sulfur atoms associated with each feature can be assigned. Alkyl chains are not evident in these high-resolution spectra. Experiments using spatially and temporally separated light pulses demonstrate that more of the desorbed nanocrystals are neutral than are ionized. Pure gold cluster ions of various sizes can be generated from these neutral molecules in the two-laser experiment.