Metal nanoparticles chemical environment

Size reduction of metal particles results in several changes of the physico-chemical properties. The primary change is observed in the electronic properties of the metal particles which can be characterized by ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS, respectively) as well as Auger-electron spectroscopy (AES) measurements. Furthermore, morphology of the metal nanoparticles is highly sensitive to the environment, such as ion-metal interaction (e.g. metal-support interaction)... 

Structure and morphology of supported metal nanoparticles may differ drastically, depending on (i) their size, (ii) their interaction with support, (iii) the (electro)chemical environment, and, (iv) since very often particles do not attain equUibrium shapes, also on the preparation conditions and sample prehistory. 

The mobility of metal atoms in bare metal clusters and small metallic nanoparticles (NPs) is of fundamental importance to cluster science and nanochemistry. Atomic mobility also has significant implications in the reactivity of catalysts in heterogeneous transformation [6]. Surface restmcturing in bimetallic NP and cluster catalysts is particularly relevant because changes in the local environment of a metal atom can alter its chemical activity [7, 8]. 

AuNPs in Liquid-State Environment Solute pure and monolayer-coated ( capped ) AuNPs are central targets in colloid and surface science also with a historical dimension [258-262]. Facile chemical syntheses introduced by Schmid et al. [260] and by Brust et al. [263] have boosted AuNP and other metal nanoparticle science towards characterization of the physical properties and use of these nanoscale metallic entities by multifarious techniques and in a variety of environments. Physical properties in focus have been the surface plasmon optical extinction band [264—269], scanning and transmission electron microscopy properties, and electrochemical properties of surface-immobilized coated AuNPs [173, 268-276], To this can be added a variety of AuNP crosslinked molecular and biomolecular... 

Metal nanoparticles housed in zeolites and aluminosilicates can be regarded as arrays of microelectrodes placed in a solid electrolyte having shape and size selectivity. Remarkably, the chemical and electrochemical reactivity of metal nanoparticles differ from those displayed by bulk metals and are modulated by the high ionic strength environment and shape and size restrictions imposed by the host framework. In the other extreme end of the existing possibilities, polymeric structures can be part of the porous materials from electropolymerization procedures as is the case of polyanilines incorporated to microporous materials. The electrochemistry of these types of materials, which will be termed, sensu lato, hybrid materials, will be discussed in Chapter 8. 

Section III focuses on metal or metal oxide nanoparticle catalysts. By controlling the nanoparticle size and the environment where the nanoparticle is formed, several examples are described to show how the metal or metal oxide nanopartcle catalysts can be formed and how their unique structure and properties affect the chemical reaction they catalyze. These examples provide clues for understanding the nanoparticle catalysts, which may guide the future generation catalysts development. 

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