No abstract

Catalytic transformation of glycerol to value-added products has attracted the attention of scientists all over the world. Among various transformations, selective oxidation of glycerol with molecular oxygen to dihydroxyacetone, glyceric acid, glyceraldehydes, and tartronic acid is challenging both from the viewpoint of academic research and industrial application. Herein, we review the recent progresses in the selective oxidation of glycerol under base-free conditions. Those catalysts widely reported for the selective oxidation of the terminal hydroxyl and secondary hydroxyl groups in glycerol, such as monometallic Au, Pt, and Pd NPs, and bimetallic Au-Pt, Au-Pd, Pt-Bi, Pt-Sb, and Pt-Cu, were compared and discussed in detail. The reaction mechanism over Pt-based catalysts, possible catalyst deactivation, and the corresponding improvements are presented. Further, the recent progresses in the continuous oxidation of glycerol in fixed bed reactors and its excellent selectivity in the formation of dihydroxyacetone are highlighted.

The first example of direct synthesis of 2-sulfonylquinolines through visible-light-induced deoxygenative C2-sulfonylation of quinoline N-oxides with organic dye as the catalyst and ambient air as the sole oxidant was developed.

The morphology of TiO2 nanotubes with nanowires directly formed on top (designed as TiO2 NTWs) would be a promising nanostructure in fabricating photoelectrochemical solar cells for its advantages in charge separation, electronic transport, and light harvesting. In this study, a TiO2 NTWs array film was prepared by a simple anodization method. The formation of CdS, CdSe, and ZnS quantum dots (QDs) sensitized TiO2 NTWs photoelectrode was carried out by successive ionic layer adsorption. The as-prepared materials were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. Our results indicate that the nanocrystals have effectively covered both inner and outer surfaces of TiO2 NTWs array. The interfacial structure of QDs/TiO2 was also investigated for the first time in our experiment, and the growth interface when annealed to 300 °C was verified. Under AM 1.5G illumination, we found the photoelectrodes have an optimum short-circuit photocurrent density of 4.30 mA/cm2 and corresponding energy conversation efficiency of 2.408%, which is 28 times higher than that of a bare TiO2 NTWs array. The excellent photoelectrochemical properties of our photoanodes suggest that the TiO2 NTWs array films (2.6–2.8 μm) cosensitized by CdS, CdSe, and ZnS nanoclusters have potential applications in solar cells.

The search for new inorganic electrides has attracted significant attention due to their potential applications in transparent conductors, battery electrodes, electron emitters, as well as catalysts for chemical synthesis. However, only a few inorganic electrides have been successfully synthesized thus far, limiting the variety of electride examples. Here, we show the stabilization of inorganic electrides in the Ti-rich Ti-O system through first-principles calculations in conjunction with swarm-intelligence-based CALYPSO method for structure prediction. Besides the known Ti-rich stoichiometries of Ti 2 O, Ti 3 O, and Ti 6 O, two hitherto unknown Ti 4 O and Ti 5 O stoichiometries are predicted to be thermodynamically stable at certain pressure conditions. We found that these Tirich Ti-O compounds are primarily zero-dimensional electrides with excess electrons confined in the atom-sized lattice voids or between the cationic layers playing the role as anions. The underlying mechanism behind the stabilization of electrides has been rationalized in terms of the excess electrons provided by Ti atoms and their accommodation of excess electrons by multiple cavities and layered atomic packings. The present results provide a viable direction for searching for practical electrides in the technically important Ti-O system.

Aryl radicals were generated for the first time from the cheap and easily available aryl acyl peroxides in eco-friendly ethyl acetate at ambient conditions under visible-light illumination in the absence...

Pressure is well-known to significantly change the bonding patterns of materials and lift the reactivity of elements, leading to the synthesis of unconventional compounds with fascinating properties. Titanium-oxygen (Ti-O) compounds (e.g., TiO) are attracting increasing attention due to their attractive electronic properties and extensive industrial applications (e.g., photocatalysis and solar cells). Using the effective CALYPSO structure searching method combined with first-principles calculations, we theoretically explored various oxygen-rich Ti-O compounds at pressures ranging from 0 to 200 GPa. Our results revealed, unexpectedly, that pressure stabilizes two hitherto unknown stoichiometric oxygen-rich TiO and TiO compounds. TiO crystallized in P-42 c structure, whose remarkable feature is that it contains a peroxide group (O2) with an O-O distance of 1.38 Å at 150 GPa. The trioxide TiO is an ionic metal and is the oxygen-richest compound known thus far in the Ti-O system. It adopts a high symmetry (space group Pm-3 n) structure consisting of a 12-fold coordinated face-sharing TiO icosahedron, where Ti has the highest coordination number with O among all Ti-O structures. The underlying mechanisms for the stabilization of TiO and TiO lie in the higher coordination number and denser structure packing. Our current results unravel the unusual oxygen-rich stoichiometry of Ti-O compounds and provide further insight into the diverse electronic properties of Ti oxides under high pressure.

Semiconductor/metal composite nanomaterials have been used as surface-enhanced Raman scattering (SERS) active substrates and have attracted increasing attention due to their widespread applications in both optical and material fields. Here, we report a facile strategy to prepare highly sensitive SERS substrates with excellent reproducibility and stability based on uniform and well-controlled Ag nanoparticle (NP) decorated Cu 2 O nanoframes. Our strategy is a unique one-pot procedure. Simply, hollow Cu 2 O/Ag composite nanoframes (Cu 2 O/Ag CNFs) with tunable silver content have been successfully designed and constructed by reduction of Ag + with sodium citrate in a 14 day old Cu 2 O-containing mother solution, and then a second component (Ag) was directly deposited onto primary nanomaterials (Cu 2 O nanoframes).There is an optimum amount of Ag NPs. When 0.40 mM AgNO 3 is used, the prepared Cu 2 O/Ag CNFs show significantly improved SERS properties with an enhancement factor of ~10 5 . Furthermore, the enhancement mechanism, reproducibility and stability of Cu 2 O/Ag CNFs are investigated in detail. The excellent properties of the prepared Cu 2 O/Ag CNFs suggest that this substrate has a potential application in SERS detection.