Minfang Chen

Synthesis of tunable ZnS–CuS microspheres and visible-light photoactivity for rhodamine B

Tunable ZnS–CuS microspheres were readily prepared via replacing the Zn2+ ions of solid ZnS microspheres with Cu2+ ions in an aqueous solution under a hydrothermal condition, and were then characterized by XRD, SEM, TEM, UV-Vis, PL and XPS techniques. The thickness of CuS shell on the surface of ZnS core can be controlled by changing the ion-exchange time, which plays an important role in the visible light photodegradation efficiency of rhodamine B in aqueous solution. Degradation rate can rapidly reach ca. 72% under visible light irradiation for 15 min and then ca. 98% after 60 min using the ZnS–CuS microspheres as the photocatalyst.

Preparation of various kinds of copper sulfides in a facile way and the enhanced catalytic activity by visible light

Various kinds of copper sulfides (CuS, a mixture of Cu7S4–CuS and Cu9S5) were synthesized by simply adjusting the amount of copper chloride and sodium sulfide in a solvothermal process. The different molar ratios of copper chloride and sodium sulfide result in the formation of different kinds of copper sulfides with various morphologies, such as tiny particle, hexagonal plate and octahedron. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. And the optical properties of the products were recorded by means of UV-Vis absorption and photoluminescence spectroscopy. Moreover, due to the presence of visible light, we found that the catalytic activities of the products for oxidation and decomposition of Rhodamine B with the assistance of hydrogen peroxide were enhanced, and the degradation efficiency of RhB was increased from 40% to 98% in 15 minutes at room temperature.

Microstructure and Properties of Biodegradable β-TCP Reinforced Mg-Zn-Zr Composites

Magnesium alloys have good biocompatibility, but their mechanical properties and corrosion resistance may not be satisfied for using as degradable materials within bone due to its high corrosion rate in the physiological environment. Nano β-TCP particles were added into Mg-Zn-Zr alloy to improve its microstructure and the properties. As-extruded Mg-3Zn-0.8Zr alloy and Mg-3Zn-0.8Zr/xβ-TCP (x=0.5%, 1.0% and 1.5%) composites were respectively fabricated. The grains of Mg-Zn-Zr/β-TCP composites were significantly refined. The results of the tensile tests indicate that the ultimate tensile strength and the elongation of composites were improved with the addition of β-TCP. The electrochemical test result in simulation body fluid shows that the corrosion resistance of the composites was strongly enhanced comparing with that of the alloy. The corrosion potential of Mg-3Zn0.8-Zr/1.0β-TCP composite is -1.547 V and its corrosion current density is 1.20×10^(-6) A/cm^2 .

In vivo comparative property study of the bioactivity of coated Mg–3Zn–0.8Zr alloy

In this in vivo study, degradable Mg-3Zn-0.8Zr cylinders were coated with a calcium phosphorus compound (Ca-P) layer or a magnesium fluoride (MgF2) layer; uncoated Mg-3Zn-0.8Zr alloy was used as a control. These were then implanted intramedullary into the femora of nine Japanese big-ear white rabbits for implantation periods of 1, 2 and 3 months. During the postoperative observation period with radiographic examination, the results showed that the MgF2-coated implants were tolerated well compared to the Ca-P-coated implants and uncoated implants. Moreover, large amounts of cells, rich fibrillar collagen and calcium and phosphorus products were found on the surface of the MgF2-coated implants using scanning electron microscopy. Micro-computed tomography further showed a slight decrease in volume (23.85%) and a greater increase in new bone mass (new bone volume fraction=11.56%, tissue mineral density=248.81 mg/cm(3)) for the MgF2-coated implants in comparison to uncoated and Ca-P compound-coated implants after 3 months of implantation.

Synthesis and characterization of air-stable Cu nanoparticles for conductive pattern drawing directly on paper substrates

Air-stable Cu nanoparticles (NPs) with an average diameter of 6.5xa0nm were synthesized under ambient conditions using polyvinylpyrrolidone and cetyltrimethylammonium bromide as a mixed capping agent, for preparing nano-Cu ink applicable for direct writing on photo paper using a roller pen. The size, morphology, and air-stability of the Cu NPs were characterized by TEM, SEM, XRD, etc. The mixed capping agent was effective in reducing the aggregation, size of the Cu NPs and improving their air-stability. The reduced size and enhanced air-stability of the Cu NPs resulted in an improved particle density upon sintering, which was mainly responsible for the increased conductivity of the Cu patterns. The resistivity of Cu patterns sintered at 160xa0°C for 2xa0h was 11xa0±xa00.8xa0μΩxa0cm, 6.40 times the bulk resistivity. A sample RFID antenna and a decorative logo were successfully made and the Cu patterns or lines exhibited excellent integrity and good conductivity, which were experimentally tested.

Effects of gas produced by degradation of Mg–Zn–Zr Alloy on cancellous bone tissue

Mg-Zn-Zr alloy cylinders were implanted into the femoral condyles of Japanese big-ear white rabbits. X-ray showed that by 12 weeks following implantation the implant became obscure, around which the low-density area appeared and enlarged. By 24 weeks, the implant was more obscure and the density of the surrounding cancellous bone increased. Scanning electron microscopy examination showed bone tissue on the surface of the alloy attached by living fibers at 12 weeks. Micro-CT confirmed that new bone tissue on the surface of the residual alloy implant increased from 12 weeks to 24 weeks. By 12 weeks, many cavities in the cancellous bone tissue around the implant were noted with a CT value, similar to gas value, and increasing by 24 weeks (P<0.01). Histological examination of hard tissue slices showed that bone tissue was visibly attached to the alloy in the femoral condyle at 12 weeks. The trabecular bone tissues became more intact and dense, and the cavities were filled with soft tissue at 24 weeks. In general, gas produced by the degradation of the Mg-Zn-Zr alloy can cause cavitation within cancellous bone, which does not affect osteogenesis of Mg alloy.

Fabrication and characterization of a biodegradable Mg–2Zn–0.5Ca/1β-TCP composite

A biodegradable magnesium matrix and beta-tricalcium phosphate (β-TCP) particles reinforced composite Mg-2Zn-0.5Ca/1beta-TCP (wt.%) was fabricated for biomedical applications by the novel route of combined high shear solidification (HSS) and equal channel angular extrusion (ECAE). The as-cast composite obtained by HSS showed a fine and equiaxed grain structure with globally uniformly distributed β-TCP particles in aggregates of 2-25 μm in size. The ECAE processing at 300 °C resulted in further microstructural refinement and the improvement of β-TCP particle distribution. During ECAE, the β-TCP aggregates were broken into smaller ones or individual particles, forming a dispersion in the matrix. Such fabricated composite exhibited enhanced hardness and in vitro corrosion resistance. The enhanced hardness was attributed to both the addition of β-TCP particles and grain refinement while the development of a Ca-P rich surface layer from β-TCP during corrosion was responsible for the improvement in corrosion resistance. The composite was characterized in terms of microstructural evolution during fabrication, mechanical properties and electrochemical performance during polarization and immersion tests in a simulated body fluid. Discussions are made on the benefits of both HSS and ECAE and the mechanisms responsible for the enhanced corrosion resistance.

Preparation and adsorption capacity of porous MoS2 nanosheets

Layered porous MoS2 with high adsorption capacity was synthesized directly using molybdenum trioxide and potassium rhodanate as Mo and S sources in a facile hydrothermal method without any surfactant and sacrificial template. The influences of varying the hydrothermal temperature on the morphology and adsorptive properties of MoS2 are discussed. As-prepared MoS2 samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible spectrophotometry (UV-Vis), room-temperature photoluminescence spectroscopy (RT-PL), thermogravimetric analysis (TGA) and Brunauer–Emmet–Teller (BET) measurements. MoS2 samples exhibited an optimal nanostructure, specific surface area and thermal stability when the hydrothermal temperature was 190 °C, and the layered porous structure is comprised of many thin nanosheets. In addition, the final adsorption capacities of the layered MoS2 toward RhB, MB and MO were studied. The sample exhibited ultrafast adsorption for dye removal and could reach 163.0 mg g−1, 499.0 mg g−1 and 125.1 mg g−1 at 420 min, respectively. The adsorption mechanism was also studied. The results indicate that layered MoS2 structures possess a significant adsorption ability, which may be useful for further research and practical applications of the layered MoS2 adsorbent in wastewater treatment.

Direct writing of stable Cu–Ag-based conductive patterns for flexible electronics

Cu–Ag-based highly conductive patterns were drawn directly on a flexible substrate using a roller pen filled with Cu–Ag NPs ink. The particle packing density is important for the patterns conductivity. First, the addition of smaller Cu NPs (∼6.5 nm) between the larger Ag particles (∼16.5 nm) improves the particle packing density by filling the pores, which can help improve conductivity at lower temperatures. Furthermore, combination of temperature and stress by hot sintering & hot-pressure sintering makes the residual pore space decrease and improves the conductivity of the patterns. Finally, compared to bulk Cu wire (1.72 μΩ cm), the resistivity of the Cu–Ag patterns sintered at 160 °C is reduced to 6.2 ± 0.4 μΩ cm, which is acceptable for conductive patterns. Samples with a decorative logo drawn by the Cu–Ag NPs exhibited excellent conductive performance and mechanical integrity.

The Influence of Zn Content on the Corrosion and Wear Performance of Mg-Zn-Ca Alloy in Simulated Body Fluid

Mg-Zn-Ca alloy has been attracting increasing attention as a potential biodegradable implant material. In this paper, Mg-3Zn-0.2Ca and Mg-4Zn-0.2Ca alloys were prepared by means of vacuum melting and subsequent hot extrusion process. The influences of Zn content on the microstructure, mechanical properties, and corrosion and wear behavior of Mg-Zn-Ca alloys in simulated body fluid (SBF) were studied. The results show that with increased Zn content, the grain size and corrosion resistance were decreased, while the mechanical strength and wear resistance were increased, under both dry sliding and SBF-lubricated conditions. For the same Mg-Zn-Ca alloy, the wear loss rate under SBF lubrication was higher than dry sliding condition, indicating a strong corrosion-assisted wear effect of SBF to the Mg-Zn-Ca alloy.