Controlled etching of Au : SR cluster compounds

When Au:SR cluster compounds (R = (CH2)(5)CH3) with an Au metallic cluster core mass of similar to 14 kDa (similar to 75 atoms, 1.1 nm equivalent diam eter), are heated in neat dodecane-thiol solution under inert atmosphere, s pecies with smaller Au core masses are formed, presumably by the removal of Au atoms from the outermost surface layer of the cluster's Au core. This p rocess was monitored through laser desorption mass spectrometry, optical ab sorption spectroscopy, and X-ray diffraction, where all three methods indic ate a substantial decrease (>50%, by mass or number of Au atoms) in the siz e of the cluster compound's inorganic core. The optical absorption spectra and laser desorption mass spectra of the compounds generated by etching are strikingly similar to compounds previously separated without an etching st ep. The dual function of the thiol as both stabilizing adsorbate and effici ent etchant sets this cluster (or nanocrystal) system apart from other meta llic and semiconductor systems.