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In less than one minute the catalytic activity and selectivity of a single catalyst was measured in combinatorial libraries of ternary Rh-Pd-Pt-Cu alloys. Only slightly more than two hours were needed to complete a library with 136 elements. The elements of the libraries (ca. 2-4 μg of material) are contained in a two-dimensional array synthesized by a thin-film technique. The analysis was performed by a scanning mass spectrometer (see picture).

The trap-to-trap relaxation and recombination dynamics of photogenerated electron/hole pairs in MoS 2 nanoclusters have been studied. Static and time-resolved emission experiments have been performed on 3.0 and 4.5 nm diameter nanoclusters in ternary inverse micelles, acetonitrile, and octane at room temperature and at 20 K. The results indicate that, following synthesis in ternary inverse micelles, the nanoclusters have both shallow and deep traps. The deep traps are retained upon extraction into acetonitrile and passivated upon charge neutralization and reextraction into octane. The emission kinetics show that trap-to-trap relaxation is fast (<40 ps) at room temperature and slows (∼200 ps) at 20 K. A distributed kinetics model is presented that quantitatively describes electron/hole recombination. The trapped electron Bohr radius is found to be 2.0-2.5 nm in all cases. Charge neutralization and reextraction into octane passivates both the deep and the shallow traps on some nanoclusters, resulting in indirect band edge emission at 20 K.

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Combinatorial methodologies were used for the synthesis and screening of mixed metal oxide heterogeneous catalysts. Primary screening at low reactant conversions at a throughput of greater than 10,000 catalyst compositions per month was performed by using simultaneous MS and photothermal def lection spectroscopy on spatially separated thick film catalysts with Ϸ200 g per catalyst prepared by using automated liquid dispensing. Secondary screening under realistic operating conditions was performed at a throughput of greater than 3,000 catalyst compositions per month on Ϸ50 mg of catalyst in an array of fixed bed microreactors with gas chromatograph detection. The approach was validated by the discovery of catalysts with superior performance to those previously described for the oxidative dehydrogenation of ethane to ethylene. We show the full implementation and integration of combinatorial methodologies for synthesis, screening, discovery, and optimization of multicomponent heterogeneous catalysts.Although combinatorial methodologies are practiced routinely for drug discovery (1, 2), this general approach is compelling in other fields where predictive abilities also are restricted. Recently, combinatorial methods have been applied within several different areas of materials science, where increasing compositional or structural complexity often results in unique or otherwise improved properties (1-12). Structural and compositional complexity may result in systems consisting of several components functioning cooperatively. In these combinations, the synergy of the multicomponent system results in performance characteristics that are particularly difficult to predict à priori. Presently, the vast majority of complex inorganic solids and multicomponent materials remain unexplored (13), in part because composition-structure-property relationships for such systems are limited. The utility of combinatorial chemistry, i.e., the ability both to prepare and to screen vast numbers of compounds in a rapid fashion, may be most productively realized within such systems. Here, we describe an integrated combinatorial program that has resulted in the discovery of improved multicomponent heterogeneous catalysts for the oxidative dehydrogenation of ethane to ethylene. Bringing combinatorial methodologies to bear on this application is particularly appealing because catalyst discovery has relied traditionally on an iterative trial-and-error synthesis and characterization strategy that is both tedious and time consuming.The parallel synthesis of catalytic materials by the use of automation and miniaturization techniques is most efficient when preparing very small quantities (Ͻ1 mg) of catalysts. The characterization of such small amounts of catalytic materials frequently is hindered by the lack of sensitive high throughput screening methodologies, particularly for reactions of low probability such as the partial oxidation of hydrocarbons. These obstacles have been overcome in our laboratories, and an integrated combinatorial d...