A new hydrothermal system has been designed to recycle waste WC–Co hardmetal with low cobalt (Co) content (3 %). In the solution system, nitric acid was designed to dissolve Co, H2O2 served as oxidant to accelerate the oxidation of the WC–Co hardmetals, and fluorine (F−) was designed to dissolve and recrystallize generated tungsten oxides, which were found to possess a layered structure using scanning electron microscopy and transmission electron microscopy. The obtained tungsten oxides were identified as WO3·0.33H2O by X-ray diffraction and their specific surface area was measured as 89.2 m2 g−1 via N2 adsorption–desorption techniques. The present layered structure tungsten oxides exhibited a promising capability for removing lead ion (Pb2+) and organic species, such as methyl blue. The adsorption model was found to be in agreement with Langmuir isotherm model. Given the facile synthesis procedure and promising properties of final products, this new approach should have great potential for refining some other waste hardmetals or tungsten products.

TiO2–Y2O3 core–shell nanoparticles for dye-sensitized solar cells (DSSCs) have been fabricated by a solvothermal technique. The heterostructure of TiO2 nanoparticles coated with porous Y2O3 is confirmed with transmission electron microscopy. The bonding of the Y2O3 coating on the TiO2 surface is quantitatively analyzed in terms of the Lifshitz–van der Waals and electrostatic contributions to the surface free energy of the particles. TiO2 and Y2O3 constitute a core–shell heterojunction because the Fermi levels merge; this increases the open-circuit voltage. Higher recombination resistances are obtained in DSSCs with porous Y2O3-coated TiO2 compared with those in the reference cells, indicating “backscattering” inhibition of the porous Y2O3 barrier on TiO2 nanoparticles. Moreover, smaller transport resistances and longer electron lifetimes are achieved in DSSCs with TiO2–Y2O3 core–shell nanoparticles. Compared with a reference cell, the VOC of a DSSC with a partial Y2O3 coating on the surface of the TiO2 nanoparticles improves from 683 to 738 mV and the Jsc from 14.15 to 15.35 mA·cm–2, whereas the conversion efficiency increases by 15.2%.Keywords: Backscattering barrier; Heterojunction; Photovoltage; Photovoltaic performance; Porous coating; Yttria;

TiO2 mesoporous nanoparticles (NPs) doped with yttrium (Y) ions are fabricated via an environmentally friendly and facile solvothermal method to serve as a photoanode for dye sensitized solar cells (DSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N2 adsorption–desorption tests are used to characterize the influence of yttrium dopant on the properties of TiO2 NPs. The prepared Y-doped TiO2 NPs show the anatase phase and exhibit Ti–O–Y bonds. The photovoltaic performance is primarily associated with the morphological parameters of the NPs. At the optimum Y concentration of 3 at%, the short circuit current density increased from 13.20 to 15.74 mA cm−2, full sun solar power conversion efficiencies increased from 6.09% up to 7.61% as compared to the blank DSSC.

Enhancing surface area is one of the efficient ways to improve photochromic sensitivity of WO3·0.33H2O. Hierarchical WO3·0.33H2O mesoporous nanorod assemblies were synthesized via proton exchange by adjusting the concentration of Na2WO4·2H2O. When the concentration of Na2WO4·2H2O is 2.0 g L−1, mesoporous nanorods with 10∼20 nm in diameter and an average pores size of about 4 nm were obtained. The novel WO3·0.33H2O porous structure possesses highly photochromic sensitivity and fatigue resistance properties. It exhibits visible-light-driven photochromic response due to large specific surface area originated from the mesoporous structure. The formation of mesopores is due to the volume decreasing in the transformation process from WO3·H2O to WO3·0.33H2O.Graphical abstractHierarchical WO3·0.33H2O mesoporous nanorod assemblies are synthesized through proton exchange route and exhibit highly photochromic sensitivity.Highlights► WO3·0.33H2O mesoporous nanorod assemblies was synthesized via proton exchange. ► It possesses highly photochromic sensitivity and fatigue resistance properties. ► The formation of mesopores is due to the volume decreasing.

With its excellent anticorrosion and biocompatibility, tantalum, as a promising endosseous implant or implant coating, is attracting more and more attention. For improving physicochemical property and biocompatibility, the research of tantalum surface modification has increased. Tantalum oxide (Ta2O5) nanotube films can be produced on tantalum by controlling the conditions of anodization and annealing. The objective of our present study was to investigate the influence of Ta2O5 nanotube films on pure tantalum properties related with anticorrosion, protein adsorption, and biological function of rabbit bone mesenchymal stem cells (rBMSCs). The polarization curve was measured, the adsorption of bovine serum albumin and fibronectin to Ta2O5 nanotubes was detected, and the morphology and actin cytoskeletons of the rBMSCs were observed via fluorescence microscopy, and the adhesion and proliferation of the rBMSCs, as well as the osteogenic differentiation potential on tantalum specimens, were examined quantificationally by MTT and real-time PCR technology. The results showed that Ta2O5 nanotube films have high anticorrosion capability and can increase the protein adsorption to tantalum and promote the adhesion, proliferation, and differentiation of rBMSCs, as well as the mRNA expression of osteogenic gene such as Osterix, ALP, Collagen-I, and Osteocalcin on tantalum. This study suggests that Ta2O5 nanotube films can improve the anticorrosion, biocompatibility, and osteoinduction of pure tantalum, which provides the theoretical elaboration for development of tantalum endosseous implant or implant coating to a certain extent.Keywords: anticorrosion; biocompatibility; bone mesenchymal stem cell; osteogenesis-related genes; protein adsorption; Ta2O5 nanotube array;

Based on their photoinduced hydrophilicity, titanium dioxide (TiO2) thin films have many promising applications, such as anti-fog, self-cleaning, capillary pump and so on. Microchannels were prepared on glass substrates by wet-etching methods and highly uniform TiO2 thin films were deposited into the micro-channels using pulsed laser deposition (PLD). The crystallite was determined as anatase by X-ray diffraction (XRD); the thickness and the particle size were calculated to be 200 nm and 25 nm respectively. The light absorbance and a contact angle were also investigated using a UV–Visible spectrometer and contact angle analysis system, respectively. The results show that the obtained TiO2 thin films exhibit hydrophilicity. The minimum contact angle was about 10° (highly hydrophilicity) under UV (253.7 nm) light irradiation. The contact angle increased gradually after the light was cut off. The flow velocity of the water in the microchannels was also investigated. The results indicate that the microchannels decorated with TiO2 thin films have promising application in capillary pumps.Highlights► Unique TiO2 thin films were deposited into the microchannels on glass substrates using pulse laser deposition. ► The microchannels deposited TiO2 exhibits super-hydrophilic properties under UV light irradiation. ► The photo-induced hydrophilic capability produced a water fluid rate of 48 mm/s, which can be used to drive fluids.

The multi-layer TiO2 nanotube array thin films have been formed by anodic oxidation method via adjusting the outer voltage during oxidation process in glycerol electrolyte containing 0.3% NH4HF2. The diameter of the nanotube array increases with the outer voltage, and the length of nanotube in every layer increases with the anodic oxidation time. These multi-layers bring new possibilities to tailor the properties of the TiO2 nanotube array thin films formed via anodic oxidation method. Further, such multi-layer structure provide a new approach to evaluate the growth rate of TiO2 nanotube, which will help us to understand more deeply the formation mechanism of the TiO2 nanotubes. The growth rate of TiO2 nanotube array is respectively 1.2 and 3.6 μm/h under the anodic voltage of 30 V and 60 V. These multi-layer TiO2 nanotube array thin films may exhibit lots of potential applications in photoelectrochemical fields.

TiO2 mesoporous nanoparticles (NPs) doped with yttrium (Y) ions are fabricated via an environmentally friendly and facile solvothermal method to serve as a photoanode for dye sensitized solar cells (DSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N2 adsorption–desorption tests are used to characterize the influence of yttrium dopant on the properties of TiO2 NPs. The prepared Y-doped TiO2 NPs show the anatase phase and exhibit Ti–O–Y bonds. The photovoltaic performance is primarily associated with the morphological parameters of the NPs. At the optimum Y concentration of 3 at%, the short circuit current density increased from 13.20 to 15.74 mA cm−2, full sun solar power conversion efficiencies increased from 6.09% up to 7.61% as compared to the blank DSSC.