Mixtures of elementary oxides, MgO–Al2O3, were used to fabricate transparent polycrystalline magnesium aluminate spinel specimens by means of the spark plasma sintering technique. A sintering aid, 1 wt% of LiF, was added to the mixed powder. The presence of the additive promotes the synthesis of spinel that starts at 900°C and is completed at 1100°C. The LiF additive wets spinel on its melting and promotes densification, which is completed at 1600°C. LiF vapor plays a cardinal role in eliminating residual carbon contamination and in the fully dense state, allows attaining a 78% level of optical transmittance. The optimal conditions for achieving adequate transparency were determined and the role of the LiF addition in the various stages of the process is discussed.

Self-assembled nanocomplexes composed of individual molecules that spontaneously connect via noncovalent interactions have recently emerged as versatile alternatives to conventional controlled drug delivery systems because of their unique bioinspired properties (responsiveness, dynamics, etc.). Characterization of such nanocomplexes typically includes their size distribution, surface charge, morphology, drug entrapment efficiency, and verification of the coexistence of labeled components within the nanocomplexes using a colocalization study. Less common is the direct examination of the molecular interactions between the different components in the coassembled nanocomplex, especially in nanocomplexes composed of hygroscopic components, because convenient methods are still lacking. Here, we present a detailed experimental protocol for determining the surface composition and the chemical bonds by X-ray photoelectron spectroscopy (XPS) after drying the deposit hygroscopic sample overnight under UHV. We applied this method to investigate the surface chemistry of binary Ca 2+ -siRNA nanocomplexes and ternary nanocomplexes of hyaluronan-sulfate (HAS)-Ca 2+ -siRNA, deposited on a wafer. Notably, we showed that the protocol can be implemented to study the surface composition and interactions of the deposited nanocomplexes with a traditional XPS instrument, and it requires only a relatively small amount of the nanocomplex suspension.

Three materials containing Ni 2 P, Ni 12 P 5 , and Ni 3 P phases on silica gel with surface area 320 m 2 /g at loadings of 32-37 wt % and the crystal size of Ni x P phases 30, 9, and 13 nm, respectively, were prepared by a combination of impregnation and TPR methods and tested in hydrodesulfurization (HDS) and adsorptive desulfurization (ADS) of diesel fuel. There were established opposite trends in changing the DS efficiency in two processes: The HDS rate constant decreased while the ADS sulfur capacity (breakthrough at 1 ppmw) increased with increasing the Ni to P ratio in Ni x P from 2 to 3. The observed behavior was attributed to the specific features of the densities of states (DOS) obtained from the density functional theory calculations of total and partial DOS for Ni and P in Ni x P phases and revealed in XPS measurements of binding energy of Ni 2p 3/2 -and P 2p-electrons. This attribution was consistent with the analysis of the relative part of d-electrons of Ni participating in bonding with p-electrons of phosphorus in these phases.

We report on a combined investigation of the structure and chemical bonding in fluorinated detonation nanodiamond by means of nuclear magnetic resonance, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and Raman measurements. The results of these methods are found to be consistent with each other and evidence formation of different fluorocarbon groups on the nanodiamond surface, which substitutes for hydrocarbon and hydroxyl groups. The data obtained provide detailed information about the structure and bonding in the fluorinated diamond nanoparticle. The fluorinated sample has a significant number of paramagnetic defects (∼10 20 spin/g) located mainly near the surface of the diamond nanoparticle, resulting in fast 19 F and 13 C nuclear spin-lattice relaxation.

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