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Au329(SR)84 nanomolecules: compositional assignment of the 76.3 kDa plasmonic faradaurates
1Department of Chemistry and Biochemistry, University of Mississippi , University, Mississippi 38677, United States.
Abstract:
The purpose of this work is to determine the chemical composition of the previously reported faradaurates, which is a large 76.3 kDa thiolated gold nanomolecule. Electrospray ionization quadrupole-time-of-flight (ESI Q-TOF) mass spectrometry of the title compound using three different thiols yield the 329:84 gold to thiol compositional assignment. The purity of the title compound was checked by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. Positive and negative mode ESI-MS spectra show identical peaks denoting that there are no counterions, further reinforcing the accuracy of the assigned composition. We intentionally added Cs(+) ions to show that the Au329(SR)84 is the base molecular ion, with several Cs(+) adducts. A comprehensive investigation including analysis of the title compound with three ligands, in positive and negative mode and Cs(+) adduction, leads to a conclusive composition of Au329(SR)84. This formula determination will facilitate the fundamental understanding of emergence of surface plasmon resonance in Au329(SR)84 with 245 free electrons.
