2-Mercaptobenzothiazole protected Au and Ag clusters

Nanometer sized gold and silver clusters protected with 2-mercaptobenzothia zole monolayers have been prepared and characterized by various spectroscop ic methods. Optical absorption spectra show features assigned to charge-tra nsfer excitation between the monolayer and the cluster, in addition to a re d shifting and reduction of plasmon absorption. The monolayers on clusters are compared with the corresponding 2D-monolayers investigated previously. The dominant adsorbate geometries on these clusters are different. Whereas the temperature dependent dynamics are minimal for 2D-SAMs, they are signif icant for monolayers on 3D surfaces, which is attributed to the decreased p acking density on the cluster surfaces. The thermal stability of these mono layers is high and comparable to that of alkanethiolate monolayers. The mon olayers undergo irreversible structural changes upon heating, which have be en studied by differential scanning calorimetry and IR spectroscopy.