Published in JACS, the Murray Group reports how 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 Au144L60 and Au146L59, present in the sample as a mixture.
The improved resolution is based on lowering m/z by exchanging multiple [−SC11H22N(CH2CH3)3+] ligands into the original [−S(CH2)5CH3] 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.
As published in JACS, researchers in the Murray Group show how oxidation of dissolved 1.6 ± 0.6 nm (dia.) IrIVOx nanoparticles in pH 13 solutions leads to a 100% current efficient oxidation of water to O2, at a modest overpotential η of only 0.29 V, relative to thermodynamic expectations for the four electron H2O→O2 reaction.
Each nanoparticle contains an average of 66 Ir sites; all are electroactive, so that the nanoparticles act, effectively, as 66 electron transfer mediators in the water oxidation. Each Ir site has a turnover frequency (TO, mol O2/Ir sites/s) of 8−11 s−1, which is nearly the same as observed for films of IrIVOx nanoparticle composed of similar nanoparticles, and providing the first comparison of electrocatalysis by nanoparticle films with redox catalysis by dissolved, diffusing nanoparticles.