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 polymer template. The approach is of general applicability to other metals and various oxides. In the first step, polymeric micelles with a polar core were generated by dissolution of poly(styrene)-block-poly(2-vinylpyridine) in toluene. These micelles were used as nanocompartments that were loaded with 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 the embedded equally large particles became arranged in a mesoscopic quasihexagonal 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 monomicellar film. A modified procedure in which the precursor salt was not reduced before the plasma treatment yielded clusters of identical size and in the same 2-D order. The size (height) of the clusters could be varied between 1 and 15 nm depending on the concentration of the metal salt. The interparticle distance could be varied between 30 and 140 nm by using block copolymers with different lengths of the blocks. Such lattices of Au particles have been used to bind streptavidin proteins in an ordered array.

Formation and structural transformation of inverse poly(styrene)-block-poly(2-vinylpyridine) micelles whose polyvinylpyridine core was loaded with HAuCl4 or with elementary gold nanoclusters was studied by combined static and dynamic light scattering. A transformation in the morphology from spherical particles (small R g/R h ratio) to large anisomeric objects (large R g/R h ratio) was observed by decreasing the concentration of the block copolymer below the critical micelle concentration. At this point, the polymer chains are molecularly dispersed and no longer able to prevent uncontrolled growth of the gold nanoclusters.

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Controlled mineralization of the transformation allowed the following ticle per micelle, 2) aggregated micelles gold nanoparticles has been performed in stages of the mineralization/coagulation containing two or three gold particles, a microemulsion of polystyrene-block-process to be stabilized: 1) one gold par-and 3) a state in which empty micelles copoly(2-vinylpyridine) . The starting point exist with larger polymer-stabilized gold was the formation of a thermodynamicalparticles. Distinctive variations in the ly stable dispersion of HAuCI, in inverse spectra were observed dependending on micelles of the block copolymer in Woc the particle size and whether two particles toluene, which became metastable when had formed a couple with orientationization dependent dipolar interactions. the gold was reduced. Kinetic control of

structure of such materials varies from spherical, interconnected pores, to a bicontinuous type arrangement of silica, to an assembly of spherical particle aggregates loosely bonded together. We are currently investigating quantitatively the evaporation kinetics of both solvents alongside the temporal changes in structure during the process of formation of these porous solids. ExperimentalMaterials: Water was passed through a reverse osmosis unit and then a Milli-Q reagent water system. Toluene (Fisher, > 99.9 %), hexane (Sigma, > 99 %) and decane (Sigma > 99 %) were passed twice through a chromatographic alumina column before use. The fumed silica powders were from Wacker-Chemie (Munich), with primary particle diameters of between 10 and 30 nm, and surface areas of 200±250 m 2 g ±1 . The silanol content of the different particles is 100 % (N20), 76 % (SLM 079) and 50 % (H30), with the coating reagent being dichlorodimethylsilane.Methods: Dispersions of hydrophilic silica-in-water, or of hydrophobic silicain-oil, were prepared by dispersing a known mass of powder into the liquid using a high intensity ultrasonic vibracell processor (Sonics & Materials) of tip diameter 0.3 cm, operating at 20 kHz and up to 10 W for 2 min. In some experiments, both hydrophilic and hydrophobic particles were dispersed simultaneously in oil initially. Emulsions were made in glass vessels by mixing the appropriate particle dispersion with the second liquid phase using a Janke & Kunkel Ultra Turrax homogenizer (rotor-stator), with a 1.8 cm head operating at 13 500 rpm for 2 min. Their type was assessed using conductivity and droptest measurements. Drop-size distributions were determined using a Malvern MasterSizer MS20 particle sizer and checked with optical microscopy (Nikon Labophot). Emulsions of different particle concentrations, oil/water volume ratios, and oil and particle hydrophobicities were prepared. They were left in air at room temperature to allow evaporation of oil and water. Such systems dry first to a gel and subsequently to the solid phase. In many cases, a tablet-like material forms that retains the shape of the container. In other cases, small angular solid fragments result. After drying to constant weight, the solid samples were mounted on aluminum studs using epoxy resin, and gently scraped with paper to expose a fresh fracture surface. This was coated with a thin (20 nm) layer of carbon and examined using a Cambridge Instruments S360 scanning electron microscope. The details of the freeze fracture field emission SEM method of liquid emulsion samples were given previously [16].