Ordered deposition of inorganic clusters from micellar block copolymer films

A method is presented for generating quasiregular arrays of nanometer-sized noble metal and metal oxide clusters on flat substrates by the use of a po lymer template. The approach is of general applicability to other metals an d various oxides. In the first step, polymeric micelles with a polar core w ere generated by dissolution of poly(styrene)-block-poly(2-vinylpyridine) i n toluene, These micelles were used as nanocompartments that were loaded wi th a defined amount of a metal precursor. The metal ions can be reduced in such a way that exactly one elemental or oxidic particle is formed in each micelle, where each particle is of equal size. By dipping a flat substrate into a dilute solution, a monolayer of the micelles was obtained whereby th e embedded equally large particles became arranged in a mesoscopic quasihex agonal two-dimensional (2-D) lattice. Exposure to an oxygen plasma allowed removal of the polymer completely, leaving the naked metal particles firmly attached to the substrate in the same quasihexagonal order as in the monom icellar film. A modified procedure in which the precursor salt was not redu ced before the plasma treatment yielded clusters of identical size and in t he same 2-D order. The size (height) of the clusters could be varied betwee n 1 and 15 nm depending on the concentration of the metal salt. The interpa rticle distance could be varied between 30 and 140 nm by using block copoly mers with different lengths of the blocks. Such lattices of Au particles ha ve been used to bind streptavidin proteins in an ordered array.