Shengli Zhu

Nanoporous CuS with excellent photocatalytic property.

We present the rational synthesis of nanoporous CuS for the first time by chemical dealloying method. The morphologies of the CuS catalysts are controlled by the composition of the original amorphous alloys. Nanoporous Cu2S is firstly formed during the chemical dealloying process, and then the Cu2S transforms into CuS. The nanoporous CuS exhibits excellent photocatalytic activity for the degradation of the methylene blue (MB), methyl orange (MO) and rhodamine B (RhB). The excellent photocatalytic activity of the nanoporous CuS is mainly attributed to the large specific surface area, high adsorbing capacity of dyes and low recombination of the photo generated electrons and holes. In the photo degradation process, both chemical and photo generated hydroxyl radicals are generated. The hydroxyl radicals are favor in the oxidation of the dye molecules. The present modified dealloying method may be extended for the preparation of other porous metal sulfide nanostructures.

Synthesis of Cu2O Octadecahedron/TiO2 Quantum Dot Heterojunctions with High Visible Light Photocatalytic Activity and High Stability.

Since p-n heterojunction photocatalysts with higher energy facets exposed usually possess greatly enhanced photocatalytic activities than single-phase catalysts, a novel Cu2O octadecahedron/TiO2 quantum dot (Cu2O-O/TiO2-QD) p-n heterojunctions composite was designed and synthesized in this study. Cu2O octadecahedra (Cu2O-O) with {110} facets and {100} facets exposed were synthesized first, then highly dispersed TiO2 quantum dots (TiO2-QDs) were loaded on Cu2O-O by the precipitation of TiO2-QDs sol in the presence of absolute ethanol. The morphology, crystal structure, chemical composition, optical properties, photocatalytic activity, and stability of Cu2O-O/TiO2-QD heterojunctions were characterized and investigated. It was found that TiO2-QDs were firmly anchored on Cu2O-O single crystals with good dispersibility. The Cu2O-O/TiO2-QD heterojunctions with partial coverage of TiO2-QDs showed a strong absorbance of visible light and exhibited an effective transfer of photoexcited electrons. The degradation of methyl orange (MO) under visible light irradiation indicated that the photocatalytic activity of Cu2O-O/TiO2-QD heterojunctions was significantly enhanced compared with that of Cu2O-O. This Cu2O-O/TiO2-QD heterojunctions composite exhibited high stability in MO degradation process and after storage in air. The high visible light photocatalytic activity and good stability were attributed to high utilization of light, effective separation of photoexcited electron-hole pairs, and instant scavenging of holes in the unique heterojunction structure.

Strontium incorporation to optimize the antibacterial and biological characteristics of silver-substituted hydroxyapatite coating

Infection in primary total joint prostheses is attracting considerable attention. In this study, silver (Ag) was incorporated into hydroxyapatite (HA) using a hydrothermal method in order to improve its antimicrobial properties. Strontium (Sr) was added as a second binary element to improve the biocompatibility. The substituted HA samples were fixed on titanium (Ti) substrates by dopamine-assisted immobilization in order to evaluate their antibacterial and biological properties. The results showed that Ag and Sr were successfully incorporated into HA without affecting their crystallinity. Further, the antibacterial tests showed that all the Ag-substituted samples had good anti-bacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Despite their good antibacterial ability, the Ag-substituted samples showed evidence of cytotoxicity on MG63 cells, characterized by low cell density and poor spreadability. The addition of Sr to the Ag-substituted samples considerably reduced the cytotoxicity of Ag. Although the viability of the cells grown on the surfaces of co-substituted HA was not as high as that of the cells grown on the HA surfaces, it is believed that excellent antibacterial properties and good biological activity can be achieved by balancing the dosage of Sr and Ag.

Synthesis, characterization and the formation mechanism of magnesium- and strontium-substituted hydroxyapatite

Magnesium (Mg) and strontium (Sr) have been widely used in the field of implanted devices because of their excellent bioactivity. However, the local high ion concentration caused by the implant affects the growth of hydroxyapatite (Ca10(PO4)6(OH)2, HA), which is the main inorganic component of bone and teeth. Many studies have investigated the effect of Mg2+ and Sr2+ on the growth of HA, but no systematic research has been conducted to compare these two ions in terms of the growth of HA. In this study, the substitution of a series of Sr- and Mg-substituted HA was conducted through a conventional hydrothermal method. Comprehensive characterization techniques, including X-ray diffraction, inductive coupled plasma, field emission scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, thermo gravimetric-differential scanning calorimetry, and Fourier transform infrared spectroscopy, were used to examine the effects of Sr2+ and Mg2+ on the phase, morphology, crystallinity, chemical composition, thermal stability, and lattice parameters of HA. The results indicated that Mg ions partially substituted for calcium (Ca) ions in the apatite structure, thus decreasing the lattice parameters, partially adsorbing on the apatite surface that formed the amorphous phase, and inhibiting the crystal growth. By contrast, Sr ions fully substituted for Ca ions and increased the lattice parameters. Both Mg and Sr ions affected the morphology of HA. Crystallinity decreased with the addition of Mg ions (transition from the crystal to amorphous phase was between 30% and 40% Mg), but it was not affected by Sr ions. Thermostability decreased with the addition of Mg (a total weight loss from 8.06 wt% for 10% Mg to 25.81 wt% for 50% Mg), but it had no significant changes in the Sr-substituted samples.

Pd-loaded In2O3 nanowire-like network synthesized using carbon nanotube templates for enhancing NO2 sensing performance

Pd-loaded In2O3 nanowire (NW)-like networks were synthesized via electroless plating using carbon nanotubes (CNTs) as templates, followed by oxidation and removal of the CNTs at 550 °C. Palladium (Pd) was introduced to activate the surface of the CNTs for subsequent plating. Before calcination, Pd was loaded onto In2O3. The as-synthesized Pd-loaded In2O3 replicated the structure of the CNTs, forming a porous NW-like network with a very large specific surface area. Furthermore, the NO2 gas sensing properties of the Pd-loaded In2O3 NW-like network, porous Pd–In2O3 and porous unloaded-In2O3 were investigated. The results demonstrated that the Pd–In2O3 NW-like network exhibits superior sensitivity with short response and recovery times, and demonstrates a significant response when exposed to NO2 at concentrations as low as 5 ppm at a temperature of 110 °C. A synergy of electric and chemical effects has been proposed to explain the gas sensing enhancement.

MoO2–CoO coupled with a macroporous carbon hybrid electrocatalyst for highly efficient oxygen evolution

Cost-effective electrocatalysts for oxygen evolution reactions are attractive for energy conversion and storage processes. A high-performance oxygen evolution reaction (OER) electrocatalyst composed of 3D ordered microporous carbon and a MoO2 skeleton modified by cobalt oxide nanoparticles (MoO2-CoO-Carbon) is produced through a template method. This unique 3DOM structure finely combines the larger surface area of the 3D carbon skeleton and MoO2 as well as stablizes anchoring sites for CoO nanocrystals on the skeleton. The synergistic effect between the catalytic activity between MoO2 and CoO as well as the enhanced electron transport arising from the carbon skeleton contributed to superior electrocatalytic OER properties of MoO2-CoO-Carbon. The M200-C-Carbon hybrid with an overpotential as low as 0.24 V is among the best reported Mo-based OER catalysts. Moreover, the turnover frequency at an overpotential of 0.35 V is 6 times as high as that of commercial RuO2.

Incorporation of silver and strontium in hydroxyapatite coating on titanium surface for enhanced antibacterial and biological properties

Implant-related infection in primary total joint prostheses has attracted considerable research attention. As a measure to improve the antimicrobial properties of implant materials, silver (Ag) was incorporated into calcium phosphate (CaP) coatings on Titanium (Ti) via a hydrothermal method. Further, strontium (Sr) was added as a binary dopant to reduce the cytotoxicity of Ag in the coatings. Results showed that the CaP coatings were uniformly deposited on Ti with enhanced hydrophilicity and nanoscale surface roughness. Moreover, cell adhesion, proliferation, and differentiation were improved after the CaP coating deposition. The antibacterial properties of the coatings were distinctly improved by the incorporation of Ag, but the cell proliferation and differentiation were significantly decreased. Owing to the incorporation of Sr, the Ag-CaP coatings were able to effectively counteract the negative effects of Ag while maintaining good antibacterial properties. In summary, hydrothermally deposited CaP coatings doped with Ag and Sr exhibit excellent biocompatibility and antimicrobial activity. Thus, such co-doped CaP coatings have considerable potential for orthopaedic implant modification.

Controlled release behaviour and antibacterial effects of antibiotic-loaded titania nanotubes.

Bacterial infections have been identified as the main cause of orthopaedic implant failure. Owing to their high antibiotic delivery efficiency, titania nanotubes loaded with antibiotics constitute one of the most promising strategies for suppressing bacterial infections. However, it is difficult to control the drug-release behaviour of such nanotubes. Although sealing the nanotubes with a polymer solution provides sustained release effects to a certain extent, it inevitably influences their initial antibacterial activity. This study reports on the controlled release of gentamicin sulphate (GS) from titania nanotube surfaces whereby their initial antibacterial activity remains unaffected. Titania nanotubes were fabricated via electrochemical anodization and loaded with GS through physical adsorption. Experimental results showed that this loading method is feasible and efficient. The GS-loaded titania nanotubes were further covered by a thin film comprising a mixture of GS and chitosan (GSCH). The release kinetics confirmed that the drug release could be controlled by this thin film. Moreover, such a film was shown to not only inhibit initial bacterial adherence owing to its strong antibacterial properties but also enhance cell viability. Thus, GS-loaded titania nanotubes coated with GSCH have considerable potential as biomaterials for preventing initial release and peri-implant infection in the field of orthopaedics.

Ni- and Be-free Zr-based bulk metallic glasses with high glass-forming ability and unusual plasticity.

We developed Ni- and Be-free Zr(45+x)Cu(40-x)Al₇Pd₅Nb₃ bulk metallic glasses with large glass-forming ability and unusual plasticity. The alloys have large critical diameters (larger than 10 mm) in a wide composition range (x=0-20). The Zr₅₀Cu₃₅Al₇Pd₅Nb₃ and Zr₅₅Cu₃₀Al₇Pd₅Nb₃ alloys exhibit the largest critical diameter (between 18 and 20 mm). The Zr(45+x)Cu(40-x)Al₇Pd₅Nb₃ bulk metallic glasses also have large plastic elongation in wide composition range (x=10-17). The Zr₆₂Cu₂₃Al₇Pd₅Nb₃ bulk metallic glass exhibits significant plasticity (over 20% of plastic elongation). With increasing Zr content, the compressive strength decreases except for the Zr₆₇Cu₁₈Al₇Pd₅Nb₃ alloy. The fragility parameters were calculated to evaluate the glass-forming ability and plasticity. The fragility exhibits more sensitive correlation with plasticity than glass-forming ability. The ZrCuAlPdNb bulk metallic glasses have high crystallization activation energies of above 300 kJ/mol. The ZrCuAlPdNb bulk metallic glasses are favorable for application to biomaterials.

Development and Applications of Highly Functional Al-based Materials by Use of Metastable Phases

This paper reviews the features of alloy components, structure and mechanical properties, physical and chemical properties of metastable Al-based alloys developed by use of various liquid or vapor quenching-induced phases such as amorphous, quasicrystalline, nanocrystalline, nanocomposite, supersaturated solid solution and structure gradient phases. As advantages of the metastable Al-based alloys, one can exemplify a high tensile strength of 1500 MPa for amorphous alloys, high elevated temperature strength of 364 MPa at 573 K for nanoquasicrystalline alloys, high strength of 1000 MPa at room temperature and 520 MPa at 473 K for nanocrystalline alloys, relatively high strength of 596 MPa with large elongation of 16% for nanocomposite alloys and high strength of 900 MPa and distinct elongation of 5% for supersaturated fcc-Al solid solution. These highly functional properties, which have not been obtained for conventional crystalline Al-based alloys, have enabled the commercialization of metastable Al-based alloys as structural, machinery and sporting goods materials. Owing to the significant increase of various fundamental properties caused by the essential differences in the structures, the engineering importance of the metastable Al-based alloys is expected to increase steadily in the future low carbon and nature harmonious society.