Noble metal

About: Noble metal is a research topic. Over the lifetime, 15113 publications have been published within this topic receiving 337947 citations.

Diffusion of metals in polymers

Abstract: First information on metal diffusion in polymers resulted from surface spectroscopies which mainly provided insight into chemical interactions of metals at polymer surfaces and into their growth mode. Medium energy ion scattering, electron microscopy, atomic force microscopy, and second-harmonic generation revealed a strong tendency of metals of low and intermediate reactivity to form clusters when deposited onto polymers. The interplay of diffusion and aggregation was also studied by Monte Carlo simulations. Metal diffusivities were obtained from radiotracer and Rutherford backscattering measurements. The available results show that reactive metals do not have any long-range mobility and are effective diffusion barriers. In contrast, isolated atoms of less reactive metals diffuse deep into polymers at elevated temperatures. However, the very pronounced aggregation tendency of these metals effectively impedes diffusion unless they are deposited at rates of the order of monolayers per minute or lower. Nevertheless, traces of noble metals always diffuse into polymers during the early stages of metal deposition, whereas no significant diffusion occurs from a continuous metal film. Even noble metal diffusivities are many orders of magnitude smaller than diffusivities of non-reactive gas molecules and largely decoupled from polymer dynamics. This is attributed to a pronounced reduction in the local chain mobility near metal atoms, e.g., by temporary metal-atom-induced crosslinking.

A General Approach to Noble Metal−Metal Oxide Dumbbell Nanoparticles and Their Catalytic Application for CO Oxidation

Abstract: Heterogeneous dumbbell-like nanoparticles represent an important type of composite nanomaterial that has attracted growing interest. Here we report a general approach to noble metal−metal oxide dumbbell nanoparticles based on seed-mediated growth. Metal oxides are grown over the presynthesized noble metal seeds by thermal decomposition of metal carbonyl followed by oxidation in air. The as-synthesized dumbbell nanoparticles have intrinsic epitaxial linkage between the metal and the oxide, providing enhanced heterojunction interactions. Moreover, the properties of one component are readily modified by the other in these nanoparticles, as demonstrated by the enhanced catalytic activity toward CO oxidation of such dumbbell nanoparticles in comparison with their counterparts prepared by conversional methods. The heterojunction effects provided in such nanostructures thus offer another degree of freedom for tailoring material properties. The developed synthetic strategy could also be generalized to other syste...

Ethanol Reactions over the Surfaces of Noble Metal/Cerium Oxide Catalysts

Abstract: environment through the air, water and soil. Hence seeking suitable, safer alternative chemicals and particularly fuels to replace conventional ones is an ongoing objective. There are several candidates for alternative fuels that can be derived from noncrude oil resources. These include natural gas, liquid petroleum gas (LPG), propane, methanol, ethanol, and hydrogen. Table I characterises various current and alternative fuels (1(a)).