Layer-by-Layer Assembly of Gold Nanoclusters Modified with Self-Assembled Monolayers
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The formation of ordered monolayers and multilayers of both organic and inorganic materials on solid substrates with various functionalities has been a subject of intensive research in view of the possible applications in a wide variety of fields in nanotechnology and nanoscience.
Metal and semiconductor nanoclusters are the good candidates as building blocks for the multilayer formation because they have various interesting characteristics, which are different from those of the bulk materials. Since the report by Brust et al., gold nanoclusters (GNCs) covered by self-assembled monolayers (SAMs) of alkanethiols have attracted many research groups because SAM-covered GNCs have a high stability and those of a certain size with a narrow size distribution can be prepared relatively easily. Gold nanocluster with special functionalities can be constructed by using thiol molecules with special functional groups. One can utilize the rich references on alkanethiol SAMs with various functionalities including ours.
Structurally organized GNC multilayers have been constructed on solid substrates by various wet processes, including bond formation between a sulfur atom of an alkanedithiol, a linker, and metal atoms of a substrate as well as of a nanocluster and the Langmuir–Blodgett (LB) method. The electrostatic layer-by-layer (LBL) assembly method, which was initially developed for thin film fabrication of pure polymeric materials of oppositely charged polyelectrolytes, has been extended to the construction of alternate multilayer assemblies composed of oppositely charged nanoparticles and polyions. The simplicity and versatility of the LBL technique as well as the resulting high-quality films provide broad perspectives in both fundamental and applied research in nanostructure systems.