Supporting characterization spectroscopies

A catalyst supported on y-AFO was prepared from Re2Pt(CO)i2l (Fig. 70) and characterized by IR. X-ray photoelectron spectroscopy (XPS), and TPR. The chemi.sorbed cluster was treated with H2 at about 150 C resulting in fragmentation and formation of rhenium subcarbonyls at 400 C the sample was completely decarbonylated. A catalyst prepared from a mixture of Re3(//-H)3(CO)i2l and PtMe2(// -cod)] and treated under equivalent conditions showed the rhenium to... 

X-ray absorption spectroscopy was used for situ characterization of active, supported Pt catalysts. 

Characterization of Supported Iron Oxide Particles Using Mdssbauer Spectroscopy and Magnetic Susceptibility... 

Scheme 2, vide infra for characterization of these structures) [15]. At an intermediate temperature of 500 °C, a 65/35 mixture of these two complexes is obtained [16]. The proposed structure is further confirmed by the mass balance analysis since hydrolysis or ethanolysis of the resulting solid yields the complementary amounts of neopentane, these are 2 and 3 equiv. of neopentane/Ta for [(=SiO)2Ta(= CHlBu)(CH2fBu)] and [(=SiO)Ta(= CH(Bu)(CH2fBu)2], respectively. Moreover, elemental analysis provides further information indeed, 4.2 wt % of Ta grafted onto sihca partially dehydroxylated at 700 °C corresponds to 0.22 mmol of Ta/g of sofid [ 17,18]. This is comparable to the amount of silanol present on this support (0.26 mmol OH/g), which shows that most of them have reacted during grafting (as observed by IR spectroscopy). 

The longer metal-oxygen distances of about 2.6 A observed by EXAFS spectroscopy for these and related supported metal clusters suggest weak interactions between the metal and surface oxygen atoms these EXAFS contributions are not determined with as much confidence as those characterized by the shorter distances, and the interactions are not well understood. 

Fig. 3 Ir4 cluster supported at the six-ring of zeolite NaX as represented by density functional theory samples were characterized by Extended X-ray absorption fine structure (EXAFS) spectroscopy and other techniques [32]...

Fig. 4 Osmium clusters supported on MgO(OOl) a OssC/MgisOs and b OS5C at a surface point Vs defect site [33] these were represented by density functional theory, and the samples were characterized by EXAFS spectroscopy, transmission electron microscopy, and other techniques [15]...

Much remains to be done to develop the chemistry of organic hgands on supported metal clusters, and substantial progress is to be expected as the samples are well suited to characterization, by IR, NMR, and neutron scattering (F. Li, J. Eckert, and B.C. Gates, unpubhshed results) spectroscopies, as well as density functional theory. 

Burns, A. R., Frankel, D. J. and Buranda, T. (2005) Local mobility in hpid domains of supported bilayers characterized by atomic force microscopy and fluorescence correlation spectroscopy. Biophys. J., 89, 1081-1093. 

The XRD and TEM showed that the bimetallic nanoparticles with Ag-core/Rh-shell structure spontaneously form by the physical mixture of Ag and Rh nanoparticles. Luo et al. [168] carried out structure characterization of carbon-supported Au/Pt catalysts with different bimetallic compositions by XRD and direct current plasma-atomic emission spectroscopy. The bimetallic nanoparticles were alloy. Au-core/Pd-shell structure of bimetallic nanoparticles, prepared by co-reduction of Au(III) and Pd(II) precursors in toluene, were well supported by XRD data [119]. Pt/Cu bimetallic nanoparticles can be prepared by the co-reduction of H2PtClg and CuCl2 with hydrazine in w/o microemulsions of water/CTAB/ isooctane/n-butanol [112]. XRD results showed that there is only one peak in the pattern of bimetallic nanoparticles, corresponding to the (111) plane of the PtCu3 bulk alloy. 

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)... 

Information on the chemical state of iridium on going from the molecular precursors, and its adsorption on the surface of the support can be obtained by Ir Mossbauer spectroscopy. It allows to estimate the composition of the Ir-containing alloys that are possibly formed during the activation treatment of supported bimetallic systems. The main results obtained in the application of Ir Mossbauer spectroscopy to characterize two Ir-containing bimetallic supported nanoparticles, i.e., Pt-Ir on amorphous silica and Fe-Ir on magnesia are presented and discussed... 

Three series of Au nanoparticles on oxidic iron catalysts were prepared by coprecipitation, characterized by Au Mossbauer spectroscopy, and tested for their catalytic activity in the room-temperature oxidation of CO. Evidence was found that the most active catalyst comprises a combination of a noncrys-taUine and possibly hydrated gold oxyhydroxide, AUOOH XH2O, and poorly crystalhzed ferrihydrate, FeH0g-4H20 [421]. This work represents the first study to positively identify gold oxyhydroxide as an active phase for CO oxidation. Later, it was confirmed that the activity in CO2 production is related with the presence of-OH species on the support [422]. 

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