Band alignment investigations of heterostructure NiO/TiO2 nanomaterials used as efficient heterojunction earth-abundant metal oxide photocatalysts for hydrogen production.

Earth-abundant NiO/anatase TiO2 heteronanostructures were prepared by a straightforward one-pot sol-gel synthetic route followed by a suitable thermal post-treatment. The resulting 0.1-4 wt% NiO-decorated anatase TiO2 nanoparticles were characterized by X-ray diffraction, electron microscopy, Raman and UV-visible spectroscopy and N2 sorption analysis, and showed both nanocrystallinity and mesoporosity. The careful determination of the energy band alignment diagram by a suitable combination of XPS/UPS and absorption spectroscopy data revealed significant band bending at the interface of the p-n NiO/anatase TiO2 heterojunction nanoparticles. Furthermore, these heterojunction photocatalysts exhibited an improved photocatalytic activity in H2 production by methanol photoreforming compared to pure anatase TiO2 and commercial P25. Thus, an average H2 production rate of 2693 µmol h-1 g-1 was obtained for the heterojunction of a 1 wt% NiO/anatase photocatalyst, which is one of the most efficient NiO/anatase TiO2 systems ever reported. An enhanced dissociation efficiency of the photogenerated electron-hole pairs resulting from an internal electric field developed at the interface of the NiO/anatase TiO2 p-n heterojunctions is suggested to be the reason of this enhanced photocatalytic activity.

Functional crosslinked polymer particles synthesized by precipitation polymerization for liquid chromatography.

Highly crosslinked functional polymer particles with narrow size distribution have been produced by precipitation copolymerization of divinylbenzene, ethylene glycol dimethacrylate and vinylbenzyl chloride using a simple reflux protocol. After establishing the satisfactory synthesis conditions, we produced uniform chlorobenzyl particles with different size depending on the polymerization times. The porosity of those particles was modulated from microporous to mesoporous structure by using various porogens such as toluene, dodecanol, cyclohexanol and polypropylene glycol. These particles were tested as stationary phase in high-performance liquid chromatography for the separation of polycyclic aromatic hydrocarbons in reversed-phase mode. The separation was observed even for elution 100% organic (methanol) without any participation of water fraction in the eluent composition. The influences of particles size, specific surface area and packing conditions on the separation behavior were investigated.

New Fluorinated Stannic Compounds as Precursors of F-Doped SnO(2) Materials Prepared by the Sol-Gel Route.

Dialkoxydi(beta-diketonate)tin(IV) compounds react either with difluorodi(beta-diketonate)tin(IV) or with butanoyl fluoride to yield novel tin complexes Sn(OR(1))F(R(2)COCHCOR(2))(2) 1 (R(1) = tert-amyl, isopropyl, ethyl; R(2) = methyl, tert-butyl). Multinuclear (1)H, (13)C, (19)F, and (119)Sn NMR spectroscopic characterization showed that complexes 1 are octahedral in solution with a cis configuration for the fluorine and the alkoxide group. Kinetics of configurational rearrangements were studied by variable-temperature (13)C NMR spectroscopy. The hydrolytic behavior of 1 was determined for different hydrolysis ratios h = [H(2)O]/[1]. For R(1) = tert-amyl, a dimeric fluorinated species was mainly obtained for h = 0.5, and addition of 2 mol equiv of water led to a fluorinated stannic oxopolymer soluble in CH(3)CN. In the latter case, the powder obtained after solvent elimination and treatment in air at 550 degrees C consisted of crystalline SnO(2) cassiterite particles containing the required amount (3 mol %) of doping fluorine and exhibiting electronic conductivity comparable to that of Sn-doped In(2)O(3). Complexes 1 are the first precursors of F-doped SnO(2) materials prepared by the sol-gel route.