Hexanethiolate monolayer protected 38 gold atom cluster.

The nucleation-growth-passivation Brust reaction has been modified so as to enrich the product in useful quantities of a 38-atom gold nanoparticle coated with a hexanethiolate monolayer. Two modifications are described, using -78 degrees C reduction temperature and a hyperexcess of thiol. Compositional evidence is presented that establishes the product as a Au38(C6)24 hexanethiolate monolayer protected cluster (MPC), based on transmission electron microscopy, laser ionization-desorption mass spectrometry, thermogravimetric analysis, and elemental analysis.

HPLC of monolayer-protected gold nanoclusters.

Polydisperse samples of Au nanoparticles protected with monolayers of hexanethiolate ligands (C6 MPCs) and with mixed monolayers of hexanethiolate and mercaptoundecanoic acid (C6/MUA MPCs) have been chromatographically separated using C8 120-A columns and acetone/ toluene mobile phase. The spectral details of eluted peaks and of quantized double-layer charging features in the differential pulse voltammetry of collected fractions were used to show that the elution orders of C6 MPC mixtures and of C6/MUA MPC mixtures were different. For C6 MPCs, the smallest MPCs were eluted first, whereas the smallest C6/MUA MPCs were eluted last.