Boron-doped TiO 2 nanoparticles were prepared by the sol-gel method and characterized by XRD, TEM, XPS, FT-IR, and UV-vis spectroscopy. XRD results showed that the doping of boron ions could efficiently inhibit the grain growth and facilitate the anatase-to-rutile transformation prior to the formation of diboron trioxide phase. FT-IR and XPS results revealed that the doped boron was present as the form of B 3+ in B-doped TiO 2 samples, forming a possible chemical environment like Ti-O-B. The lattice parameters at different boron contents and calcination temperatures indicated that B 3+ was likely to weave into the interstitial TiO 2 structure. The photocatalytic activity of the B-doped TiO 2 nanoparticles was evaluated by the photoregeneration of reduced nicotinamide adenine dinucleotide (NADH). All B-doped TiO 2 nanoparticles calcined at 500 °C showed higher photocatalytic activity than pure TiO 2 sample in the photocatalytic reaction of NADH regeneration under UV light irradiation. When the molar ratio of B to Ti was 5%, the TiO 2 nanoparticles could photocatalytically reproduce 94% NADH.

To utilize visible light more efficiently in photocatalytic reactions, carbon-doped TiO2 (C−TiO2), nitrogen-doped TiO2 (N−TiO2), and carbon and nitrogen co-doped TiO2 (C−N−TiO2) nanoparticles with different nitrogen and carbon contents were prepared by a sol−gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV−vis spectroscopy. XRD results showed that the doping of C and N atoms could suppress the crystal growth of TiO2, and the effect of C doping was more pronounced than that of N doping. XPS, UV−vis spectroscopy, and lattice parameter analysis revealed that N atoms could incorporate into the lattice of anatase through substituting the sites of oxygen atoms, while most C atoms could form a mixed layer of deposited active carbon and complex carbonate species at the surface of TiO2 nanoparticles. The photocatalytic activities of obtained C−TiO2, N−TiO2, and C−N−TiO2 samples with different C and N contents were evaluated by methylene blue degradation under visible light irradiation. It was found that C−N−TiO2 nanomaterials exhibited the highest photocatalytic activity, which could be assigned to the synergistic effect of doped C and N atoms.

Oxidoreductase is the largest class of enzymes and has broad applications in biotechnology since a number of bioconversions involve oxidation/reduction reactions. Coenzymes are always required in oxidoreductase-catalyzed reactions, where nicotinamide coenzymes, NAD(P)H/NAD(P) + , are the most commonly used. They undergo reactions with substrates in biocatalytic processes by converting into their reductive or oxidative forms. The efficient and economical regeneration of nicotinamide coenzymes is therefore of particular significance for industrial applications due to their high cost and large usage. The principal methods used for the regeneration of nicotinamide coenzymes, including enzymatic, chemical, electrochemical and photochemical regeneration methods are surveyed with emphasis on the crucial issues and the state-of-art research relevant to each method. Screening and improving the performance of the enzymes, designing and implementing efficient regeneration routes as well as retaining/recycling coenzymes are the three key issues for the enzymatic method. Development of efficient catalysts with high selectivity is the top priority of the chemical regeneration method. For the electrochemical regeneration method, improvement of the electrode by modification of either the nano-materials or electron mediators is the major concern. The focus of the photochemical regeneration method lies in the exploitation of efficient visible-light photosensitizers.

It is curial to develop a high-efficient, low-cost visible-light responsive photocatalyst for the application in solar energy conversion and environment remediation. Here, a three-dimensional (3D) porous g-C3N4/graphene oxide aerogel (CNGA) has been prepared by the hydrothermal coassembly of two-dimensional g-C3N4 and graphene oxide (GO) nanosheets, in which g-C3N4 acts as an efficient photocatalyst, and GO supports the 3D framework and promotes the electron transfer simultaneously. In CNGA, the highly interconnected porous network renders numerous pathways for rapid mass transport, strong adsorption and multireflection of incident light; meanwhile, the large planar interface between g-C3N4 and GO nanosheets increases the active site and electron transfer rate. Consequently, the methyl orange removal ratio over the CNGA photocatalyst reaches up to 92% within 4 h, which is much higher than that of pure g-C3N4 (12%), 2D hybrid counterpart (30%) and most of representative g-C3N4-based photocatalysts. In addition, the dye is mostly decomposed into CO2 under natural sunlight irradiation, and the catalyst can also be easily recycled from solution. Significantly, when utilized for CO2 photoreduction, the optimized CNGA sample could reduce CO2 into CO with a high yield of 23 mmol g(-1) (within 6 h), exhibiting about 2.3-fold increment compared to pure g-C3N4. The photocatalyst exploited in this study may become an attractive material in many environmental and energy related applications.

Hierarchically ordered macroporous networks (see Figure) composed of TiO2 tubes made of anatase nanocrystals have been fabricated by sol–gel coating of organic eggshell membrane consisting of interwoven shell membrane fibers. The unique hierarchical structure, together with the high surface area and substantial porosity, make this material attractive for a number of applications.