Efficient self-assembly of transition metal oxide nanoclusters on silicon substrates

Self-assembled monolayers (SAMs) of nanoclusters (< 10 nm) on silicon wafer have been prepared via simply immersing the substrate into a FeCl3/HCl solution. The clusters are hydrous iron oxide resulting from the hydrolysis of FeCl3, and their deposition is driven by the electrostatic attraction between the clusters and the substrate, the surface groups of which are oppositely charged at suitable pH value. HCl is used to enhance the repulsive force among the clusters and cause them uniformly distributed; in this regard, it can be replaced by KCl, NH4Cl, or NH2·HCl. This result provides a general guidance to prepare self-assemblies of transition metal oxide nanoclusters onto silicon substrates and others with appropriate hydroxyl (-OH) groups.