Production of gold cluster ions by laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry

We report a simple method for generating large gold cluster ions, Au^+/-, by laser desorption Fourier-transform ion cyclotron resonance (LD FT-ICR) mass spectrometry. The gold clusters are generated from peptide-covered thin gold films coated on glass plates to ≈ 10 nm thickness to provide for high optical absorbance at the Nd:YAG laser fundamental wavelength, 1064 nm. Abundant negatively charged gold clusters up to Au^-₄₆ are produced when gramicidin S peptide is overcoated on the gold film. These gold cluster ions are the largest reported to date by laser desorption without use of a supersonic jet expansion source.