The synthesis of nanoparticle arrays has been described previously . In brief, silicon nitride membranes were functionalized with HMDS and precursor inks were prepared by adding PEO-b-P2VP, metal precursors, and HNO3, at desired ratios in deionized water. Plasma-treated DPN pen arrays were mounted onto an AFM (Park Systems XE-150) at a relative humidity of 80% and coated with the precursor ink. Nanoreactors were deposited onto the functionalized silicon nitride membranes by repeatedly bringing the cantilever tips in contact with the surface. Nanoparticles were formed from the nanoreactors through thermal annealing in a H2 atmosphere.