A Study of the Electronic and Geometric Structure of Colloidal Ti⁰·0.5THF

Abstract

The reduction of TiBr4·2THF using K[BEt3H] yields the hydrogen-free organosol Ti·0.5THF. According to the HRTEM (high-resolution transmission electron microscopy), EDX (energy-dispersive X-ray) fluorescence, XPS (X-ray photoelectron spectroscopy), XANES (X-ray absorption near edge structure), and EXAFS (extended X-ray absorption fine structure) data, this nanoparticulate metal colloid consists of very small Ti particles in the zerovalent state, stabilized by intact THF molecules.

An X-Ray Photoelectron and X-Ray Absorption Spectroscopic Study of Colloidal [Mn0·0.3THF]x

“…However, the constant intensity ratio A/B after different sputtering cycles allow the hypothesis that peak B results from the outermost Mn atoms of the colloid particles, interacting with oxygen from the coordinated THF molecule, while peak A represents the innermost atoms. This peak assignment agrees with our structural model of the metal colloid particles [1,2] and confirms that the sample under study consists mainly of intact, non-oxidized metal colloid particles and a partly oxidized sample area. Note that we have observed that only the outermost spherical region of the sample was brown coloredÐ an indication of MnO 2 Ðwhile the inner region was black.…”

“…[2] Here we discuss the synthesis of the hydrogen-free organosol [Mn × 0.3THF] x together with a detailed characterization of the product by a combination of physical methods. The use of MnBr 2 × 2THF as the starting material for the salt reduction and a subsequent cooling step to ±78 C allows more than 95 % of the insoluble byproduct KBr to be removed from the manganese sol.…”

“…Besides TEM as a standard technique for the characterization of the particle size of nano-sized materials, XAS and XPS were found to be powerful tools for the investigation of the chemical state and the geometric and electronic structure of small metallic nanoparticles. [2,4,5] The spectroscopic features near the absorption edge (XANES: X-ray absorption near-edge structure) result from strongly localized electronic excitations of core electrons into unoccupied states above the Fermi level. [6] From the presence, intensity, and energy position of distinct absorption features, information about the chemical state and the geometry of the coordination polyhedron of the absorbing atom can be derived.…”

“…[2,3] One of the objectives of current research is to prepare metal or semiconductor nanocrystals of equal size and to connect them to defined surroundings. In principle, it is possible to make clusters electrically active by connecting them to a conducting polymer.…”

EXAFS/XANES, chemisorption and IR investigations of colloidal Pt/Rh bimetallic catalysts

“…X-ray absorption spectroscopy (XAS) has been proven to be a spectroscopic technique especially well suited for the investigation of the electronic and geometric structure of small metallic particles in the absence of welldefined crystal structures. 4,5 While this holds especially for the detailed analysis of the extended x-ray absorption fine structure (EXAFS) and its rich information content on structure parameters such as bonding lengths and coordination numbers, 6 the additional information exposed by the X-ray absorption near-edge structure (XANES) has often been disregarded.…”