Colloidal metal nanoparticles as a component of designed catalyst

Abstract

Recent advances in the synthesis of colloidal metal nanoparticles of controlled sizes and shapes that are relevant for catalyst design are reviewed. Three main methods, based on colloid chemistry techniques in solution, i.e., chemical reduction of metal salt precursors, electrochemical synthesis, and controlled decomposition of organometallic compounds and metal-surfactant complexes, are used to synthesize metal nanoparticles. Their catalytic activity and selectivity depend on the shape, size and composition of the metal nanoparticles, and the support effect, as shown for many reactions in quasi-homogeneous and heterogeneous catalysis. A specially designed type of thermally stable catalysts--"embedded" metal catalysts, in which metal nanoparticles are isolated by porous support shells so that metal sintering is effectively avoided at high temperatures, are also introduced. The utilization of pre-prepared colloidal metal nanoparticles with tuned size, shape and composition as components of designed catalysts opens up new field in catalysis.

Reusable and Flexible Heterogeneous Catalyst for Reduction of TNT by Pd Nanocube Decorated ZnO Nanolayers onto Electrospun Polymeric Nanofibers

“…This flexible template was further modified with alkoxy alkylthiol groups (MPTMS) for the selective anisotropic Pd NC decoration on the fiber surface. [22][23] Thiol group on the surface resulted in an effective affinity towards the deposition of Pd NC obtained by ligand and facet controlled thermal decomposition technique. Cubic shape provides advantages for a better surface attachment from geometrical perspective.…”

Active Site Elucidation in Heterogeneous Catalysis via In Situ X-Ray Spectroscopies

“…[12] The absence of a unified theory of heterogeneous catalysis has largely reflected difficulties in (i) synthesizing well defined, high surface area materials possessing a narrow distribution of coordination environments and oxidation states, and (ii) identifying the active surface species participating in the catalytic cycle. While advances in top-down [13][14][15][16] and bottom-up [17][18][19][20][21][22][23] engineering of nanocrystals and nanoporous solids are helping to address the former, a limited ability to directly observe surface reactions, coupled with reaction-induced restructuring, [24] has hampered past efforts to fingerprint and quantify structure-function relationships even in simple gas phase heterogeneously catalyzed processes such as CO [25,26] /alcohol oxidation [27] and alkene reduction. [28] This highlight paper illustrates how recent technical breakthroughs in X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES), are enabling researchers to visualize catalytic processes under in situ or operando (true working) conditions, and use the resulting insight to nanoengineer improved heterogeneous catalysts.…”

Properties and Customization of Sensor Materials for Biomedical Applications

“…Chemical synthesis is still one of the best approaches for their preparation, although other methods such as evaporation under vacuum or laser ablation (199) have also proven effective. Nanoparticles have been prepared using different metals such as gold, silver, platinum, and palladium, with each metal imparting specific catalytic and optical properties (200,201). In NP chemical synthesis, the choice of ligands, the metal to reducing agent ratio, time, and temperature all play an important role in determining the morphological aspects and properties of the resulting NPs (199).…”