Electrospray lonization Mass Spectrometry of Intrinsically Cationized Nanoparticles,[Au_(144/146)(SC_(11)H_(22)N(CH_2CH_3)_3~+)_x(S(CH_2)_5CH_3)_y]~(x+)

摘要

Electrospray ionization triple-quadrupole mass spectrometry of ca. 1.6 nm diameter thiolate-protected gold nanoparticles has been achieved at higher resolution than in previous reports. The results reveal the presence of nanoparticles with formulas Au_(144)U_(60) and Au_(146)L_(59), present in the sample as a mixture. The improved resolution is based on lowering m/z by exchanging multiple [-SC_(11)H_(22)N(CH_2CH_3)_3~+] ligands into the original [-S(CH_2)_5CH_3] ligand shell. The nanoparticles are thus intrinsically cationized and appear as a series of 10+ to 15+ mass spectral peaks. The assigned state of charge was confirmed by a collision-induced dissociation measurement.