Ultraviolet-visible spectroscopy structural characterization

Many metal complexes and clusters are colored and have distinctive ultraviolet-visible spectra. [80] The method offers the advantage of ease of application, but it has been used only seldom in the characterization of zeolite entrapped oigano-metallics. The spectra may provide evidence of metal-metal bonds, as has been shown for carbonyl clusters of Fe, Ru, and Os, [81, 82] but there are hardly any data for zeolite entrapped clusters. The absorption bands of dusters are shifted to lower energy as the cluster nudearity increases. [83] Ultraviolet-visible spectroscopy has been used to detect the formation of [HFe3(CO)n] in NaY zeolite [50] and of clusters suggested to be [Pt,(CO),g] in NaY zeolite. [40-42] Since the spectra do not provide highly spedfic structural information, the method is of secondary importance. 

There is a rapidly developng literature describing other metal oxides in zeolites, with Ti02 being well represented. [231-234] The characterization of these materials is largely based on ultraviolet-visible spectroscopy, and the structures are less than well understood. Whether the encaged spedes are clusters and whether they are uniform in structure remains to be determined. Similar statements can also be made about the materials described in the following sections (4.6.2.3 and 4.6.2.4). 

Whether laser flash photolysis (LFP) is used to detect RIs before they react, or matrix isolation at very low temperatures is employed to slow down or quench these reactions, spectroscopic characterization of RIs is frequently limited to infrared (IR) and/or ultraviolet-visible (UV-vis) spectroscopy. Nuclear magnetic resonance (NMR) spectroscopy, which is generally the most useful spectroscopic technique for unequivocally assigning structures to stable organic molecules, is inapplicable to many types of RI. 

Volumes 50 and 51 of the Advances, published in 2006 and 2007, respectively, were the first of a set of three focused on the physical characterization of solid catalysts in the functioning state. This volume completes the set. The six chapters presented here are largely focused on the determination of structures and electronic properties of components and surfaces of solid catalysts. The first chapter is devoted to photoluminescense spectroscopy it is followed by chapters on Raman spectroscopy ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy X-ray photoelectron spectroscopy X-ray diffraction and X-ray absorption spectroscopy. 

Elaborate synthetic approaches have been developed that enable significant control over the size and shape of palladium nanostructures. In order to understand the properties of the materials formed based on the preparation method, several characterization techniques have been used. These include electron microscopy, scanning probe microscopy (SPM), nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, infrared (IR) spectroscopy, electrochemistry, X-ray diffraction (XRD), thermogravimetric analysis (TGA), electron diffraction, photoelectron spectroscopy, dynamic light scattering (DLS), extended X-ray absorption fine structure (EXAFS), BET surface area analysis andX-ray reflectivity (XRR). In the following section we will describe the information provided by each of these characterization techniques. 

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