Carbon nitride nanosheets (NS-C N ) were found to undergo robust binding with a binuclear ruthenium(II) complex (RuRu') even in basic aqueous solution. A hybrid material consisting of NS-C N (further modified with nanoparticulate Ag) and RuRu' promoted the photocatalytic reduction of CO to formate in aqueous media, in conjunction with high selectivity (approximately 98 %) and a good turnover number (>2000 with respect to the loaded Ru complex). These represent the highest values yet reported for a powder-based photocatalytic system during CO reduction under visible light in an aqueous environment. We also assessed the desorption of RuRu' from the Ag/C N surface, a factor that can contribute to a loss of activity. It was determined that desorption is not induced by salt additives, pH changes, or photoirradiation, which partly explains the high photocatalytic performance of this material.

Ag loaded Ga2O3 (Ag/Ga2O3) photocatalysts were prepared by an impregnation method, and examined for photocatalytic reduction of CO2 with water where CO, H2 and O2 were formed as products. TEM and X-ray absorption near edge structure (XANES) measurements revealed that around 1 nm sized Ag clusters were formed predominantly in an active Ag/Ga2O3 sample while partially oxidized large Ag particles with the size of several -several tens nm were observed in a less active Ag/Ga2O3 samples. Both Ag L3-edge and O K-edge XANES analysis suggested that the small Ag clusters accepted more electrons in the d-orbitals as the result of the strong interaction with the Ga2O3 surface. In-situ FT-IR measurements for the Ag/Ga2O3 samples showed CO3 stretching vibration bands assignable to monodentate bicarbonate and bidentate carbonate species chemisorbed on the Ga2O3 surface, and to monodentate carbonate species on the large Ag particles. Among these chemisorbed species, the monodentate bicarbonate and/or the bidentate carbonate species changed to bidentate formate species, as the reaction intermediate, under the UV light irradiation. The bidentate formate species was formed not by the plasmonic excitation of the Ag nanoparticles but by the photoexcitation of the Ga2O3 semiconductor, and the formation process would be promoted at the perimeter of the Ag clusters on the Ga2O3 surface by the effective separation of electronholes pairs. Catalysts preparation.Ag/Ga 2 O 3 samples were prepared by an impregnation method. A mixture of a Ga 2 O 3 powder (Kojundo Chemical Laboratory Co. Ltd. purity 99.99 %) and an aqueous solution of AgNO 3 (Kishida Chemical Co. Ltd. purity 99.8 %) was magnetically stirred and dried up, followed by calcination at 673 K for 2 h, which provided the Ag/Ga 2 O 3 samples. The loading amounts of Ag were 0.1, 0.2, 0.5 and 1.0 wt%.

6-[N-(4-vinylbenzyl)propylamino]-1,3,5-triazine-2,4-dithione (VBATDT) and 10-methacryloyloxydecyl dihydrogen phosphate (M10P) are functional monomers used for the surface treatment of dental alloys. The aim of our study was to clarify the role of a commercial metal primer containing both the monomers in adhesion between resin and various dental metals on a molecular level. We used surface-enhanced Raman scattering (SERS) and infrared reflection absorption (IRA) spectroscopy. An SERS measurement was performed with a 647 nm laser line for a mixture of aqueous Au colloid and the primer. IRA spectra were taken for cast films of the primer on Au, Ag, Cu, and Cr surfaces as a function of rinse time, and for self-assembled monolayer (SAM) films from dilute mixed solution of VBATDT and M10P. These spectra indicate that VBATDT in the primer is mainly chemisorbed on Au, Ag, and Cu surfaces with respect to thickness, whereas only M10P is adsorbed on Cr. We also examined the tensile bond strengths between resin and Au, Ag, Cu, and Cr plates treated by VBATDT, with and without M10P, and found that VBATDT effectively promotes the bond strength between resin and the metals except for Cr, whereas M10P is effective only for Cr. These adhesion characteristics are consistent with the chemisorbed species on each metal surface as shown in the spectroscopic evidence.

External infrared reflection absorption spectroscopy was used to study the carboxylate-counterion interactions and changes in these interactions during the photopolymerization of a long-chain diacetylene monocarboxylic acid, 10,12-pentacosadiynoic acid (DA), at air-water interfaces in the presence of divalent metal ions, Ba 2+ (pH 7.7), Cd 2+ (pH 6.8), and Pb 2+ (pH 6.0). Upon reducing the molecular area (0.80 f 0.18 nm 2 /molecule), the DA monolayer on each subphase exhibited discrete frequency changes of an IR band due to a carboxylate antisymmetric stretching vibration (ν as (COO -)), indicating discrete changes in the coordination and/or association states of the carboxylate groups. Ab initio molecular orbital calculations were applied to confirm the empirical relationships between the frequency differences of the asymmetric and symmetric stretching bands of the carboxylate group and the modes of coordination of the group to metal ions. On the basis of the relationships, it was proposed that, when the molecular area is reduced, the carboxylate group in the DA monolayer on the Ba 2+ subphase changes its coordination mode from a bridging state to a bidentate one, while the carboxylate group in the DA monolayer on the Cd 2+ subphase keeps a bidentate coordination state. It was also suggested that the DA monolayer on the Pb 2+ subphase exhibits a coordination change from a bridging to bidentate state upon compression. IR spectral changes in the ν as (COO -) and ν s (COO -) regions observed during UV-irradiation-induced polymerization of the DA monolayers were similar to the IR spectral changes observed by compressing the monolayers without irradiation. The results indicated that the polymerization induces more densely packed states of the carboxylate groups in the monolayers.

Vacuum-deposited films of a long-chain n-alkane, n-C44H90, tetratetracontane (TTC), on a Au(111) surface were investigated by infrared reflection absorption spectroscopy. We found four different structures for TTC on the Au surface. One is a “flat-on” structure formed by molecules in an all-trans conformation with the molecular plane composed of carbon atoms parallel to the surface. This structure was found in the first monolayer physisorbed on the surface. The second structure includes the gauche conformation, which shows a change in the orientation of the methylene groups with an increase in the thickness of TTC. The third structure is the crystalline state formed by all-trans molecules, which was found in the third and thicker layers with the molecular long axis parallel to the surface. These three structures were found for films deposited and measured at room temperature. With an increase in temperature after deposition at room temperature, the first and second structures were easily converted to another structure. This fourth structure consists of TTC molecules in the vicinity of the surface with their molecular axes parallel to the surface and their molecular planes tilted from the surface. The molecules in this structure interact with the Au(111) surface through some of their methylene groups, while the molecules in the flat-on structure contact the surface through all of their methylene groups. The appearance of these two structures is controlled by the balance of two kinds of interaction:  methylene group−Au surface interaction and the interaction among TTC molecules. In the second layer, the formation of TTC molecules including a gauche conformation is ascribed to the geometrical incompatibility between flat-on TTC and crystalline TTC.