Nanoporous SnO(2)-ZnO heterojunction nanocatalyst was prepared by a straightforward two-step procedure involving, first, the synthesis of nanosized SnO(2) particles by homogeneous precipitation combined with a hydrothermal treatment and, second, the reaction of the as-prepared SnO(2) particles with zinc acetate followed by calcination at 500 °C. The resulting nanocatalysts were characterized by X-ray diffraction (XRD), FTIR, Raman, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption analyses, transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectroscopy. The SnO(2)-ZnO photocatalyst was made of a mesoporous network of aggregated wurtzite ZnO and cassiterite SnO(2) nanocrystallites, the size of which was estimated to be 27 and 4.5 nm, respectively, after calcination. According to UV-visible diffuse reflectance spectroscopy, the evident energy band gap value of the SnO(2)-ZnO photocatalyst was estimated to be 3.23 eV to be compared with those of pure SnO(2), that is, 3.7 eV, and ZnO, that is, 3.2 eV, analogues. The energy band diagram of the SnO(2)-ZnO heterostructure was directly determined by combining XPS and the energy band gap values. The valence band and conduction band offsets were calculated to be 0.70 ± 0.05 eV and 0.20 ± 0.05 eV, respectively, which revealed a type-II band alignment. Moreover, the heterostructure SnO(2)-ZnO photocatalyst showed much higher photocatalytic activities for the degradation of methylene blue than those of individual SnO(2) and ZnO nanomaterials. This behavior was rationalized in terms of better charge separation and the suppression of charge recombination in the SnO(2)-ZnO photocatalyst because of the energy difference between the conduction band edges of SnO(2) and ZnO as evidenced by the band alignment determination. Finally, this mesoporous SnO(2)-ZnO heterojunction nanocatalyst was stable and could be easily recycled several times opening new avenues for potential industrial applications.

We report the electrical transport behavior of a series of redox-active conjugated molecular wires as a function of temperature and molecular length. The wires consist of covalently coupled ruthenium(II) bis(σ-arylacetylide) complexes (Ru1-Ru3) and range in length from 2.4 to 4.9 nm. The molecules are unique in that they contain multiple metal-redox centers that are well-coupled by conjugated ligands. The molecules were self-assembled and their films were extensively characterized using ellipsometry, X-ray photoelectron spectroscopy, reflectionabsorption infrared spectroscopy, and cyclic voltammetry. We probed their electrical properties using conducting probe atomic force microscopy and crossed-wire junctions. At room temperature, we found a very weak dependence of the wire resistance with molecular length, consistent with a high degree of electronic communication along the molecular backbone. In low-temperature (5 K) experiments, Coulomb blockadelike behavior was observed in junctions incorporating Ru3; direct tunneling appears to be the dominant transport mechanism in Ru1 and Ru2 junctions.

Nanoporous RuO 2 /TiO 2 heterostructures, in which ruthenium oxide acts as a quasi-metallic contact material enhancing charge separation under illumination, were prepared by impregnation of anatase TiO 2 nanoparticles in a ruthenium-(III) acetylacetonate solution followed by thermal annealing at 400 °C. Regardless of the RuO 2 amount (0.5−5 wt %), the asprepared nanocatalyst was made of a mesoporous network of aggregated 18 nm anatase TiO 2 nanocrystallites modified with RuO 2 according to N 2 sorption, TEM, and XRD analyses. Furthermore, a careful attention has been paid to determine the energy band alignment diagram by XPS and UPS in order to rationalize charge separation at the interface of RuO 2 /TiO 2 heterojunction. At first, a model experiment involving stepwise deposition of RuO 2 on the TiO 2 film and an in situ XPS measurement showed a shift of Ti 2p 3/2 core level spectra toward lower binding energy of 1.22 eV which was ascribed to upward band bending at the interface of RuO 2 /TiO 2 heterojunction. The band bending for the heterostructure RuO 2 /TiO 2 nanocomposites was then found to be 0.2 ± 0.05 eV. Photocatalytic decomposition of methylene blue (MB) in solution under UV light irradiation revealed that the 1 wt % RuO 2 /TiO 2 nanocatalyst led to twice higher activities than pure anatase TiO 2 and reference commercial TiO 2 P25 nanoparticles. This higher photocatalytic activity for the decomposition of organic dyes was related to the higher charge separation resulting from built-in potential developed at the interface of RuO 2 /TiO 2 heterojunction. Finally, these mesoporous RuO 2 −TiO 2 heterojunction nanocatalysts were stable and could be recycled several times without any appreciable change in degradation rate constant that opens new avenues toward potential industrial applications.

Photovoltaic generation has stepped up within the last decade from outsider status to one of the important contributors of the ongoing energy transition, with about 1.7% of world electricity provided by solar cells. Progress in materials and production processes has played an important part in this development. Yet, there are many challenges before photovoltaics could provide clean, abundant, and cheap energy. Here, we review this research direction, with a focus on the results obtained within a Japan–French cooperation program, NextPV, working on promising solar cell technologies. The cooperation was focused on efficient photovoltaic devices, such as multijunction, ultrathin, intermediate band, and hot-carrier solar cells, and on printable solar cell materials such as colloidal quantum dots.

Earth-abundant NiO/anatase TiO 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 TiO nanoparticles were characterized by X-ray diffraction, electron microscopy, Raman and UV-visible spectroscopy and N 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 TiO heterojunction nanoparticles. Furthermore, these heterojunction photocatalysts exhibited an improved photocatalytic activity in H production by methanol photoreforming compared to pure anatase TiO and commercial P25. Thus, an average H production rate of 2693 μmol h g was obtained for the heterojunction of a 1 wt% NiO/anatase photocatalyst, which is one of the most efficient NiO/anatase TiO 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 TiO p-n heterojunctions is suggested to be the reason of this enhanced photocatalytic activity.

Two methodologies of C-C bond formation to achieve organometallic complexes with 7 or 9 conjugated carbon atoms are described. A C7 annelated trans-[Cl(dppe)2Ru=C=C=C-CH=C(CH2)-C[triple bond]C-Ru(dppe)2Cl][X] (X = PF6, OTf) complex is obtained from the diyne trans-[Cl(dppe)2Ru-(C[triple bond]C)2-R] (R = H, SiMe3) in the presence of [FeCp2][PF6] or HOTf, and C7 or C9 complexes trans-[Cl(dppe)2Ru-(C[triple bond]C)n-C(CH3)=C(R1)-C(R2)=C=C=Ru(dppe)2Cl][X] (n = 1, 2; R1 = Me, Ph, R2 = H, Me; X = BF4, OTf) are formed in the presence of a polyyne trans-[Cl(dppe)2Ru-(C[triple bond]C)n-R] (n = 2, 3; R = H, SiMe3) with a ruthenium allenylidene trans-[Cl(dppe)2Ru=C=C=C(CH2R1)R2][X]. These reactions proceed under mild conditions and involve cumulenic intermediates [M+]=(C=)nCHR (n = 3, 5), including a hexapentaenylidene. A combination of chemical, electrochemical, spectroscopic (UV-vis, IR, NIR, EPR), and theoretical (DFT) techniques is used to show the influence of the nature and conformation of the bridge on the properties of the complexes and to give a picture of the electron delocalization in the reduced and oxidized states. These studies demonstrate that the C7 bridging ligand spanning the metal centers by almost 12 angstroms is implicated in both redox processes and serves as a molecular wire to convey the unpaired electron with no tendency for spin localization on one of the halves of the molecules. The reactivity of the C7 complexes toward protonation and deprotonation led to original bis(acetylides), vinylidene-allenylidene, or carbyne-vinylidene species such as trans-[Cl(dppe)2Ru[triple bond]C-CH=C(CH3)-CH=C(CH3)-HC=C=Ru(dppe)2Cl][BF4]3.

The ground-state electronic structure and the lowest-lying excited states of the cationic mixed-valent dinuclear complexes [(η2-dppe)(η5-C5Me5)Fe[CC-1,4-(C6H4)CC]Ru(η2-dppe)2(X)][PF6] (X = Cl, 2; X = CC(4-C6H4NO2), 5) are discussed, with particular emphasis on the photoinduced intramolecular electron transfer between the ruthenium and iron centers. The location and intensities of the low-lying absorptions exhibited in the near-infrared (near-IR) range by these heterodinuclear mixed-valent (MV) complexes correlate with predictions based on the Hush model, strongly suggesting that they correspond to intervalence charge-transfer (IVCT) bands.

The preparation and properties of novel ruthenium carbon-rich complexes for molecular electronics are reported. The synthetic procedure used in this work led to the first series of neutral redox-active conjugated molecular wires including mono-, bi-, and trimetallic bis(σ-arylacetylide) complexes (Ru n NC and CNRu n NC, n ) 1-3) having 1,4-diethynylbenzene spacers and one or two isocyanide terminal groups for surface binding. An analogous cationic σ-arylacetylide-allenylidene molecule (AllRuNC + ) is also reported. These new structurally rigid complexes have lengths ranging from 1.8 to 4.5 nm and are excellent candidates for the building of alternative metal-molecule-metal junctions. Indeed, the molecules uniquely contain up to three metal-redox centers that are efficiently coupled by conjugated ligands to provide significant electronic communication along the molecular backbone, as indicated by the optical and electrochemical properties. Furthermore, the wires offer multiple low potential redox states that can lead to unusual current-voltage behavior and efficient charge conduction. Overall, these molecules will open a route to establish the structure-property relationships of conductive molecular wires and to gain valuable insights into the correlation between charge transport and molecular length.