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The layer-by-layer assembly of silver nanoclusters with 3,3'-dithiodipropionic acid (DTDPA) as spacers was prepared through self-assembly on a gold foil and has been characterized by cyclic voltammetric and AFM techniques. The DTDPA molecules acting as spacers between the layers of silver serve as molecular interconnects for the four layers prepared in this work. The organization of layers was found to decrease with an increase in the number of layers. The layer-by-layer assembly of silver clusters motivated us to prepare silver nanowires stabilized by the bifunctional molecules DTDPA through template synthesis using cellulose nitrate membranes. The nanostructures formed by this method were characterized by SEM, TEM, AFM, FTIR, CV, and photoluminescence studies. It is observed that the DTDPA molecules, instead of forming molecular interconnects, protect the structures by self-assembling themselves along the edges of the nanostructures. The concept of self-assembly protecting the nanostructures is demonstrated in this work.

The monolayers of 2-mercaptobenzothiazole (MBT) on polycrystalline Au and Ag films have been studied by surface-enhanced Raman (SERS) and X-ray photoelectron (XPS) spectroscopies. Whereas MBT adsorbs with its molecular plane flat on Ag, its plane is perpendicular on Au. This difference in adsorbate geometry is manifested as differences in the intensities of certain vibrational peaks in the Raman spectra. Ab initio molecular orbital (MO) calculations suggest that MBT adsorbs on Au in the thione form and on Ag in the thiol form. The monolayers are stable up to a temperature of 473 K, much higher than most of the self-assembled monolayers (SAMs) studied so far. The adsorption geometry does not undergo any significant change when the monolayers are heated, although minor changes are observed in the SER spectra of the Ag monolayer. Raman intensities of all the bands increase with heating, and the enhanced intensity is preserved even after cooling. This is attributed to monolayer-induced coalescence of gold islands leading to the formation of an extended self-assembly. XPS studies confirm chemisorption, although structural details are not manifested. Copyright 1999 Academic Press.