D.G. Wang

Enhanced photocatalytic performances of CeO2/TiO2 nanobelt heterostructures.

CeO2 /TiO2 nanobelt heterostructures are synthesized via a cost-effective hydrothermal method. The as-prepared nanocomposites consist of CeO2 nanoparticles assembled on the rough surface of TiO2 nanobelts. In comparison with P25 TiO2 colloids, surface-coarsened TiO2 nanobelts, and CeO2 nanoparticles, the CeO2 /TiO2 nanobelt heterostructures exhibit a markedly enhanced photocatalytic activity in the degradation of organic pollutants such as methyl orange (MO) under either UV or visible light irradiation. The enhanced photocatalytic performance is attributed to a novel capture-photodegradation-release mechanism. During the photocatalytic process, MO molecules are captured by CeO2 nanoparticles, degraded by photogenerated free radicals, and then released to the solution. With its high degradation efficiency, broad active light wavelength, and good stability, the CeO2 /TiO2 nanobelt heterostructures represent a new effective photocatalyst that is low-cost, recyclable, and will have wide application in photodegradation of various organic pollutants. The new capture-photodegradation-release mechanism for improved photocatalysis properties is of importance in the rational design and synthesis of new photocatalysts.

Nanoheterostructures on TiO2 nanobelts achieved by acid hydrothermal method with enhanced photocatalytic and gas sensitive performance

Nanoheterostructures of TiO2 nanoparticles/TiO2 nanobelts and Ag/TiO2 nanoparticles/TiO2 nanobelts are prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The experimental parameters, including acid corrosion time and calcination temperature, are investigated in detail. Compared with TiO2 nanobelts, the single nanoheterostructure TiO2 nanoparticles/TiO2 nanobelts have a better photocatalytic activity. The double nanoheterostructure Ag/TiO2 nanoparticles/TiO2 nanobelts can further dramatically enhance photocatalytic properties of TiO2 nanobelts. The mechanisms for formation of the heterostructure and the enhanced photocatalytic effect of the heterostructure are discussed. The liquid continuous-flow photocatalysis based on TiO2 nanobelt nanopaper with different heterostructures is carried out, which has an efficient photocatalytic ability. At the same time, the obtained TiO2 nanobelt heterostructures have a good gas sensitive performance for ethanol.

Phase transformation of TiO2 nanobelts and TiO2(B)/anatase interface heterostructure nanobelts with enhanced photocatalytic activity

TiO2 nanobelts are very attractive due to their dimensional confinement and structurally well-defined physical and chemical properties. However, the obscure phase transformation mechanism and the low photocatalytic activity of TiO2 nanobelts limit their wide applications. Here, the phase transformations among H2Ti3O7, TiO2(B), anatase and rutile nanobelts were characterized in detail by X-ray powder diffraction, high resolution transmission electron microscopy, Raman spectroscopy and UV-Vis diffuse reflectance spectra. TiO2(B) is inevitable in the phase transformation of TiO2 nanobelts due to the shape limiting effort and the similar crystal structure between H2Ti3O7 and TiO2(B). TiO2 nanobelts have a good thermal stability for the crystal phase and nanostructures. TiO2(B)/anatase interface heterostructure nanobelts were obtained by calcining H2Ti3O7 nanobelts at 800 °C, which had an enhanced photocatalytic ability comparing with pure TiO2(B) and anatase nanobelts. The mechanisms of the phase transformation of TiO2 nanobelts and the enhanced photocatalytic activity of TiO2(B)/anatase interface heterostructure nanobelts were discussed. The self-transformed heterostructure nanobelts have good photocatalytic activity, stability and easy-recovery properties, which will have important practical applications.

UV-visible-light-activated photocatalysts based on Bi2O3/Bi4Ti3O12/TiO2 double-heterostructured TiO2 nanobelts

Surface engineering of TiO2 nanobelts by the controlled assembly of functional heterostructures represents an effective approach for the synthesis of high-performance photocatalysts. In this study, we prepared a novel Bi2O3/Bi4Ti3O12/TiO2 double-heterostructured nanobelt by depositing bismuth hydroxide onto the TiO2 nanobelt surface. A thermal annealing treatment led to the formation of a Bi4Ti3O12 interlayer that functioned as a bridge to link Bi2O3 and TiO2. The double-heterostructured TiO2 nanobelts exhibited better UV light photocatalytic performance than commercial P25. Importantly, the photocatalytic activity in the visible range was markedly better than that of Bi2O3 and Bi2O3/TiO2 heterostructured TiO2 nanobelts. The enhanced performance was accounted for by the material band structures where the matching was improved by the unique interlayer.

High ethanol sensitivity of Palladium/TiO2 nanobelt surface heterostructures dominated by enlarged surface area and nano-Schottky junctions

TiO(2) nanobelts were prepared by the hydrothermal growth method. The surface of the nanobelts was coarsened by selective acid corrosion and functionalized with Pd catalyst particles. Three nanobelt samples (TiO(2) nanobelts, surface-coarsened TiO(2) nanobelts and Pd nanoparticle/TiO(2) nanobelt surface heterostructures) were configured as gas sensors and their sensing ability was measured. Both the surface-coarsened nanobelts and the Pd nanoparticle-decorated TiO(2) nanobelts exhibited dramatically improved sensitivity to ethanol vapor. Pd nanoparticle-decorated TiO(2) nanobelts with surface heterostructures exhibited the best sensitivity, selectivity, working temperature, response/recovery time, and reproducibility. The excellent ethanol sensing performance is attributed to the large surface area and enhancement by Schottky barrier-type junctions between the Pd nanoparticles and TiO(2) nanobelts.

PdO/TiO2 and Pd/TiO2 heterostructured nanobelts with enhanced photocatalytic activity.

Heterostructures play an important role not only in the manufacture of semiconductor devices, but also in the field of catalysis. Herein, we report the synthesis of PdO/TiO2 and Pd/TiO2 heterostructured nanobelts by means of a simple co-precipitation method, followed by a reduction process using surface-modified TiO2 nanobelts as templates. The as-obtained heterostructures were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and UV/Vis diffuse reflectance spectroscopy. PdO and Pd nanoparticles with a size of about 1.3 and 1.6 nm were assembled uniformly on the surface of TiO2 nanobelts, respectively. Compared with TiO2 nanobelts, PdO/TiO2 and Pd/TiO2 hybrid nanobelts exhibit enhanced photocatalytic activity upon UV and visible-light irradiation. Photoelectrochemical technology was used to study the heterostructure effect on enhanced photocatalytic activity. Our mechanistic investigation revealed that energy-band matching is the major factor in the observed enhancement of photocatalytic activity.

Surface Charge Regulation of Osteogenic Differentiation of Mesenchymal Stem Cell on Polarized Ferroelectric Crystal Substrate

Polarized ferroelectric crystal lithium niobate wafers with different cuts are selected to offer differently charged surfaces. By induction of the mesenchymal stem cells differentiation into osteoblasts on different charged surfaces, the specific osteogenic-associated markers are assessed and the results illustrate that the positively charged wafer surface enhances rBMMSCs osteogenic differentiation.

Improvement of corrosion and biological properties of microarc oxidized coatings on Mg-Zn-Zr alloy by optimizing negative power density parameters.

Corrosion and biological properties of microarc oxidized calcium phosphate (CaP) coatings on Mg-Zn-Zr alloy were improved by optimizing negative power density parameters. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) were employed to characterize the coating morphology and phase composition. The in vitro cytotoxicity and systemic toxicity tests were carried out to evaluate the coating biocompatibility. The degradability and bioactivity of the coatings were determined by in vitro simulated body fluid (SBF) immersion test. The coating microstructure, thickness and growth rate can be influenced by negative power density through changing direction of ions movements, rate of ions exchanges and affecting formation of plasma. The CaP coatings reduced the substrate degradation rate. Calcium phosphates, such as hydroxyapatite (Ca10(PO4)6(OH)2, HA) and calcium pyrophosphate (Ca2P2O7, CPP), etc., were induced after 30 days SBF immersion, indicating that the coatings have bioactivity. The CaP coatings have no toxicity to cell and living mice, indicating that the coatings are safe to serve as implants.

Effect of various additives on microstructure, mechanical properties, and in vitro bioactivity of sodium oxide-calcium oxide-silica-phosphorus pentoxide glass-ceramics.

The partial substitution of MgO, TiO2, or CaF2 for CaO in the Na2O-CaO-SiO2-P2O5 (45S5) system was conducted by the sol-gel method and a comparative study on structural, mechanical properties, and bioactivity of the glasses was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass-ceramic properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and so on, and the bioactivity of the glass-ceramic was evaluated by in vitro assays in simulated body fluid (SBF). Results indicate that with the partial substitution of MgO, TiO2, CaF2 for CaO in glass composition, the mechanical properties of the glass-ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization and the crystallization does not inhibit the glass-ceramic bioactivity. All samples possess bioactivity; however, the bioactivity of these glass-ceramics is quite different. Compared with 45S5, the introduction of MgO decreases the ability of apatite induction. The addition of TiO2 does not significantly improve the bioactivity, and the replacement of CaO by CaF2 shows a higher bioactivity.

Crystallization, mechanical properties and in vitro bioactivity of sol–gel derived Na2O–CaO–SiO2–P2O5 glass–ceramics by partial substitution of CaF2 for CaO

The partial substitution of CaF2 for CaO in the Na2O–CaO–SiO2–P2O5 system was conducted by the sol–gel method and a comparison of the glass–ceramic properties was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass–ceramic properties were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectrometer and so on, and the bioactivity of the glass–ceramic was evaluated by in vitro assays in simulated body fluid. Results indicate that with the partial substitution of CaF2 for CaO in glass composition, the volume density, apparent porosity, bending strength and microhardness of the glass–ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization which does not inhibit the glass–ceramic bioactivity.