Direct synthesis of Zn1−x Cd x S (0⩽x⩽1) quantum dots in aqueous solution and application in biology

A simple procedure was presented to directly synthesize Zn1-xCdxS (0≤x≤1) quantum dots (QDs) in aqueous solution. QDs’ structures and properties were characterized by TEM (transmission electron microscopy), XRD (X-ray diffraction) and fluorescence microscopy. For those as-synthesized Zn1-xCdxS QDs, when the molar ratio between Zn and Cd changed from 1 to 0, its photoluminescence (PL) emission peak shifted from 430 nm to 675 nm. PL emission quantum efficiency was up to 15%. The experiment results demonstrated that those alloyed QDs showed a good biocompatibility and could be used as labelling materials in cell biology.     

Synthesis and electrochemical performance of TiO2-B as anode material

TiO₂-B was synthesized by solid-state reaction. The structures, surface morphologies and electrochemical performances of TiO₂-B were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical measurement, respectively. The effects of calcining temperature, molar ratio of K₂O to TiO₂ and calcining time on the characteristics of TiO₂-B were investigated. The results show that the calcining time exerts a significant influence on the electrochemical performances of TiO₂-B. The TiO₂-B is obtained with good crystal structure and suitable size by using K₂Ti₄O₉, which is prepared at 950°C for 24 h under the condition of x(K₂O)/x(TiO₂)=1:3.5. The TiO₂-B delivers all initial discharge capacity of 231.6 mA·h/g. And the rate capacity is 73.2 mA·h/g at 1 675 mA/g, which suggests that TiO₂-B is a promising anode material for the lithium ion batteries.     

Preparation and effect of oxygen annealing on the electrical and magnetic properties of epitaxial (0001) Zn1−x Co x O thin films

Epitaxial (0001)-oriented Zn_1?x Co _x O ( _x = 0.01, 0.05 and 0.1) thin films were grown on c-sapphire substrates by pulsed laser deposition. The XRD analysis, optical transmittance and XPS measurements revealed that the Co²⁺ substituted Zn²⁺ ions were incorporated into the lattice of ZnO in Zn_1?x Co _x O thin films. The electrical properties measurements revealed that the Co concentration had a nonmonotonic influence on the electrical properties of the Zn_1?x Co _x O thin films due to the defects resulted from imperfections induced by Co substitution. The resistivity remarkably increased and the carrier concentration remarkably decreased in Zn_1?x Co _x O thin films after oxygen annealing at 600 ° under 15 Pa O₂ pressure for 60 mins. Room-temperature ferromagnetic was observed and the ferromagnetic Co amount was smaller than the nominal Co concentration for Zn_1?x Co _x O samples before oxygen annealing. After oxygen annealing, the Zn_1?x Co _x O thin films exhibited paramagnetic behavior. It is suggested that the room-temperature ferromagnetic of Zn_1?x Co _x O thin films may attribute to defects or carriers induced mechanism.     

Ti-based composite coatings with gradient TiC x reinforcements on TC4 titanium alloy prepared by laser cladding

TiC _x -NiTi₂/Ti cermet composite coatings C1 and C2 with gradient TiC _x reinforcements were prepared on TC4 titanium alloy by laser cladding method. The microstructure and phase compositions were analyzed by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) meter. The TiC _x exhibited a dendritic microstructure, and homogeneously dispersed in the Ti-based matrix where NiTi₂ was embedded. With increasing ingredient supercooling, temperature gradient and cooling temperature, the dendrites displayed a finer morphology with longer primary trunks and intensified side branches in the dilution zone. But the smoothed, coarse columnar ones became dominant in the upper clad layer due to the repeated energy input during multi-track cladding. The Vickers microhardness presented a linear change trend through the cross-sections, which well confirmed the gradient distribution of TiC _x . With more TiC _x , C1 presented higher hardness than C2.     

Theoretical calculation and experimental study of influence of oxygen vacancy on the electronic structure and hemocompatibility of rutile TiO2

In this work, the relationship between electronic structure and hemocompatibility of oxygen deficient rutile TiO_2?x was studied by both theoretical calculation and experimental study. Based on the local density functional theory, first-principals method was performed to calculate the electronic structure of rutile TiO₂ with different oxygen vacancy concentration. In the range of less than 10% of (or equal) physically realistic O vacancy concentration, the band gap of rutile TiO₂ increases with increasing O vacancy concentration, leading the TiO₂ changes from a p-type to an n-type semiconductor. The valance band of TiO₂ is predominated by O 2p orbital, while the conduction band is occupied by Ti 3d orbital for different O vacancy concentration. The O vacancy results in the occupation of electrons at the bottom of conduction band of TiO₂, and the donor density increases with increasing O vacancy concentration. When materials come in contact with blood, the n-type semiconductor feature of oxygen deficient TiO_2?x with the bottom of conduction band occupied by electrons would prevent charge transfer from fibrinogen into the surface of materials, thus inhibiting the aggregation and activation of platelets, therefore improving the hemocompatibility of rutile TiO_2-x .

     

Influence of surface finish and annealing treatment on oxidation behavior of Ti-48Al-8Cr-2Ag alloy

The effect of surface finish and annealing treatment on the oxidation behavior of Ti-48Al-8Cr-2Ag (molar fraction, %) alloy was investigated at 900 and 1 000 °C, respectively in air. Thermal gravimetric analysis (TGA) was conducted for the characterization of oxidation kinetics. The microstructures of oxide scales were studied by scanning electron microscopy (SEM) and transmission election microscopy (TEM) techniques. Unfavorable effect of the annealing treatment on the oxidation behavior of the coating was also investigated. The results indicate that the oxidation behavior of the alloy is influenced by surface finish and annealing treatment. The oxidation rate of ground sample is lower than that of the polished alloy at 1 000 °C in air. The former forms a scale of merely Al₂O₃, and the latter forms a scale of the mixture of Al₂O₃ and TiO₂. Annealing can improve the formation of TiO₂. Foundation item: Project(2007430028) supported by the Science and Technique Foundation of Henan Educational Committee, China     

Proposal and achievement of a relatively Al-rich interlayer for In-rich Al x In1−x N films deposition

Ternary In-rich Al _x In_1?x N films were successfully grown on Si (111) and (0001) sapphire substrates by radio-frequency magnetron sputtering on a relatively Al-rich Al _x In_1?x N layer after AlN buffer. X-ray diffraction (XRD) patterns of the films indicate highly c axis-oriented wurtzite structure and the indium content of about 0.76 has been evaluated according to the Vegard’s law. An Al-rich Al _x In_1?x N transition layer was formed between the ultimate In-rich Al _x In_1?x N film and the AlN buffer, which served as a further buffer to alleviate mismatch. X-ray photoelectron spectroscopy (XPS) depth profiling analyses confirm the alternative of indium and aluminum composition and the unavoidable oxygen impurities from surface to bulk. Owing to high indium content, obvious E ₂ ^H and InN-like A ₁ (LO) phonon model accompanying with slight AlN-like A ₁ (LO) phonon model are observed. Hall effect measurements demonstrate n-type electrical conductivity in these alloys with carrier concentrations n=10¹⁹ cm^?3. The strain in In-rich Al _x In_1?x N films can be significantly reduced by introducing an Al-rich interlayer, facilitating the improvement of film quality for diverse device applications.     

Laser cladding Al-Si/Al2O3-TiO2 composite coatings on AZ31B magnesium alloy

To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO₂ laser was used to investigate the laser surface cladding on AZ31B magnesium alloys with Al-Si/Al₂O₃ -TiO₂ composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mg₁₇Al₁₂, Al₃Mg₂, Mg₂Si, Al₂O₃, and TiO₂ phases. Compared to the average microhardness (50HV_0.05) of the AZ31B substrate, that of the composite coatings (230HV_0.05) is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCl solution.     

Effects of atmospheres and precursors on MnO x /TiO2 catalysts for NH3-SCR at low temperature

The effects of atmospheres and precursors on MnO _x /TiO₂ catalysts were studied, which were prepared by the impregnation method and tested for their NO _x conversion activity in ammonia selective catalytic reduction (NH₃-SCR) reactions. Results showed that the manganese carbonate (MC) precursor caused mainly Mn₂O₃, while the manganese nitrate (MN) precursor resulted primarily in MnO₂ and the manganese sulfate (MS) precursor was unchanged. The manganese acetate (MA) precursor leaded obtaining a mixture of Mn₂O₃ and Mn₃O₄. NO _x conversion decreased in the following order: MA/TiO₂ > MC/TiO₂ > MN/TiO₂ > MS/TiO₂ > P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO₃ was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO _x conversion decreased with calcination atmospheres: Nitrogen> Air> Oxygen. Meanwhile, amorphous Mn₂O₃ turned into crystalline Mn₂O₃, when the temperatures increased from 673 to 873 K.     

Influence of annealing temperature on the properties of TiO2 films annealed by ex situ and in situ TEM

TiO₂ thin films were deposited on quartz substrates by DC reactive magnetron sputtering of a pure Ti target in Ar/O₂ plasma at room temperature. The TiO₂ films were annealed at different temperatures ranging from 300 to 800 °C in a tube furnace under flowing oxygen gas for half an hour each. The effect of annealing temperatures on the structure, optical properties, and morphologies were presented and discussed by using X-ray diffraction, optical absorption spectrum, and atomic force microscope. The films show the presence of diffraction peaks from the (101), (004), (200) and (105) lattice planes of the anatase TiO₂ lattice. The direct band gap of the annealed films decreases with the increase of annealing temperature. While, the roughness of the films increases with the increases of annealing temperature, and some significant roughness changes of the TiO₂ film surfaces were observed after the annealing temperature reached 800 °C. Moreover, the influences of annealing on the microstructures of the TiO₂ film were investigated also by in situ observation in transmission electron microscope.     

Moisture-proof and enhanced effect of inorganic coating on porous Si<Subscript>3</Subscript>N<Subscript>4</Subscript> ceramic

Inorganic coating was fabricated on the surface of the porous Si₃N₄ ceramic by polymer derived (PD) and spraying technology, via using vinyl-polysilazane (PSN-1) as a preceramic polymer and Si₃N₄ and lithium aluminosilicate (LAS) powders as fillers. The phase and microstructure of the coatings were analyzed by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM), respectively. The effect of the coatings on mechanical property and humidity resistance of the porous Si₃N₄ ceramic was investigated. The experimental results showed that we successfully fabricated the uniform and dense coating which preferably combined with the substrate upon the addition of fillers. The bending strength of the porous Si₃N₄ ceramic sprayed the coating increased by more than 18%, and the surface hardness increased by 1.7 times. The apparent porosity of the materials reduced by an average of 97.7%, and water absorption was below 0.5%. Therefore, the prepared coating with preferable density had an obviously moisture-proof and enhanced effect on the porous Si₃N₄ ceramic.     

Photocatalytic activity of bauxite-tailings supported nano-TiO2

TiO₂/bauxite-tailings (TiO₂/BTs) composites were prepared via a chemical liquid deposition method and characterized by X-ray diffractometry (XRD), scanning electronic microscopy (SEM) and N₂ adsorption analysis. The photocatalytic performance of TiO₂/BTs composites was evaluated with UV-Vis spectrophotometer following the changes of phenol concentration under different illumination time. Effects of the calcination temperature, the pH and the cycles on the photocatalytic activity of TiO₂/BTs composites were investigated. The composites calcined at 500 and 600 °C exhibit the best photocatalytic performance, and the phenol degradation ratios reacting for 40 and 160 min reach 35% and 78% respectively under the same conditions, higher than those of 29% and 76% of the Degussa P25(TiO₂). The ability of TiO₂/BTs₅₀₀ (BTs₅₀₀ represents bauxite-tailings calcined at 500 °C) composites to degrade phenol increases with decreasing pH.     

The Influence of Annealing Temperature on the Structure and Properties of TiO2 Films Prepared by Sputtering

The TiO₂ films were prepared on slides by dc reactive magnetron sputtering, then the samples were annealed at 300°C, 350°C, 400°C, 450°C, 500°C and 550°C, respectively. X-ray diffraction (XRD) was used to obtain the TiO₂ film crystalline structure; X-ray photoelectron spectroscopy (XPS) was used to study the film surface stoichiometries; surface morphologies were studied by scanning electron microscopy (SEM); the contact angle was tested to indicate the TiO₂ film wettability; and the photocatalytic activity testing was conducted to evaluate the photocatalysis properties. The photocatalytic activity and contact angle testing results were correlated with the crystallinity, surface morphologies and surface ·OH concentration of TiO₂ films. The samples with a higher polycrystalline anatase structure, rough surface and high ·OH concentration displayed a better photoinduced hydrophilicity and a stronger photocatalysis. Funded by the National “863” Project Foundation (No. 2003LG0034)     

Inhibition of bacterial adherence on the surface of biliary stent materials modified with chitosan

Bacterial infection plays an important role in the initiation of biliary sludge formation. Bacterial adherence and biofilm formation on the surface of a material have been considered as one of the main factors of stent re-occlusion in clinic. This work reported preventing bacterial adherence and bacterial biofilm formation on the surface of biliary stent material using chitosan film. The chitosan film was deposited on 316 L stainless steel (SS) plate by electrophoresis method and was characterized by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). The ability of inhibiting bacterial adherence was investigated by incubating in human fresh bile adding E. coli and Enterobacter at 37±1 ℃ . Scanning electron microscopy (SEM) and fluorescence staining were used for observing bacterial colonization and biofilm formation. The results show that chitosan film was uniformly deposited on material surface, and the composition of the film did not change through cross-linking, but the crystallinity of chitosan film become well. Comparing to un-modified sample, the E. coli and Enterococcus adhesion amount and colonization on the surface of modified sample were significantly decreased by fluorescence staining and SEM. It is suggested that chitosan could be applied to biliary stent in clinical because of its antimicrobial activities.     

Effects of Substrate Temperatures on the Structure and UV-shielding Properties of TiO2-CeO2 Films Deposited on Glass by Radio-frequency Magnetron Sputtering

TiO2-CeO2 films were deposited on soda-lime glass substrates at varied substrate temperatures by rf magnetron sputtering using 40% molar TiO2-60% molar CeO2 ceramic target in Ar：O2=95：5 atmosphere.The structure,surface composition,UV-visible spectra of the films were measured by scanning electron microscopy and X-ray diffraction,and X-ray photoelectron spectroscopy,respectively.The experimental results show that the films are amorphous,there are only Ti^4＋ and Ce^4＋ on the surface of the films,the obtained TiO2-CeO2 films shou a good uniformity and high densification,and the films deposited on the glass can shield ultraviolet light without significant absorpition of visible light,the films deposited on substrates at room temperature and 220℃ absorb UV effectively.     

Acid/base treatment of monolithic activated carbon for coating silver with tunable morphology

Silver coatings on the exterior surface of monolithic activated carbon (MAC) with different morphology were prepared by directly immersing MAC into [Ag(NH₃)₂]NO₃ solution. Acid and base treatments were employed to modify the surface oxygenic groups of MAC, respectively. The MACs’ Brunauer-Emmett-Teller (BET) surface area, surface groups, and silver coating morphology were characterized by N₂ adsorption, elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), respectively. The coating morphology was found to be closely related to the surface area and surface functional groups of MAC. For a raw MAC which contained a variety of oxygenic groups, HNO₃ treatment enhanced the relative amount of highly oxidized groups such as carboxyl and carbonates, which disfavored the deposition of silver particles. By contrast, NaOH treatment significantly improved the amount of carbonyl groups, which in turn improved the deposition amount of silver. Importantly, lamella silver was produced on raw MAC while NaOH treatment resulted in granular particles because of the capping effect of carbonyl groups. At appropriate [Ag(NH₃)₂]NO₃ concentrations, silver nanoparticles smaller than 100 nm were homogeneously dispersed on NaOH-treated MAC. The successful tuning of the size and morphology of silver coatings on MAC is promising for novel applications in air purification and for antibacterial or aesthetic purposes.     

The microstructure and properties of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramic system

The microstructure and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3(x=0,0.04,0.08,0.12,0.16) ceramic system were investigated.The Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics were prepared by the traditional solid-state reaction method and were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and Raman spectrometer.The sintering ability and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 were found to be improved with the doping of Mn4+ and W6+ ions.The densification temperature of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics decreased from 1 080 ℃ to 1 000 ℃ when x increased from 0 to 0.16.Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramic was found to have the best dielectric properties when x=0.08,larger permittivity(■=547) and smaller dielectric loss(tan■=0.00156).     

Preparation, characterization and photocatalytic property of Ag-loaded TiO2 powders using photodeposition method

The Ag particles were photodeposited on TiO₂ powder surface. The X-ray diffraction (XRD), Raman spectroscopy, transmittance electron microscopy (TEM), UV-vis diffused reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectrophotoscopy were used to investigate the structure and morphologies of the samples. It is found that the loaded Ag particles have no effect on the XRD patterns, and the Raman scattering becomes much stronger due to the surface Raman enhancing effect. The TEM images show that the TiO₂ grains are in the shape of short sticks, and the spherical Ag particles with hexagonal structure are adhered to the TiO₂ grain surface tightly. XPS result shows that the loaded Ag particles can not affect the chemical states of Ti and O, and they are mainly in the form of metal Ag. A wide plasmon absorption appears on the UV-vis spectra after Ag photodeposition. The loaded Ag further greatly decreases the PL intensity, which partly indicates the electron transfer from TiO₂ to Ag. The photocatalytic activities firstly increase with the content of loaded Ag, and then sharply decrease. Finally, the photocatalytic mechanism related to Ag-loaded TiO₂ powders was discussed in detail. Funded by the National Natural Science Foundation of China (No. 50702041), and the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT, IRT0547), Ministry of Education, China     

Preparation of TiO2 Thin Film and Its Antibacterial Activity

TiO2 nanometer thin films with photocatalytic antibacterial activity were prepared by the sol-gel method on fused quartz and soda lime glass precoated with a SiO2 layer. The thin films were characterized by X-ray photoelectron spectroscopy ( XPS ), scanning electron microscopy (SEM), and X- ray diffraction ( XRD ). The results show that sodium and calcium diffusion into nascent TiO2 film is effectively retarded by the SiO2 layer precoated on the soda lime glass, The antibacterial activity of the films was determined. The crystalline of TiO2 nanometer thin film has important effects on the antibacterial activity of the film.     

Study on the thermal stability and electrical properties of the high-k dielectrics (ZrO2)x(SiO2)1?x

(ZrO₂) _x (SiO₂)_1−x (Zr-Si-O) films with different compositions were deposited on p-Si(100) substrates by using pulsed laser deposition technique. X-ray photoelectron spectra (XPS) showed that these films remained amorphous after annealing at 800°C with RTA process in N₂ for 60 s. The XPS spectra indicated that Zr-Si-O films with x=0.5 suffered no obvious phase separation after annealing at 800°C, and no interface layer was formed between Zr-Si-O film and Si substrate. While Zr-Si-O films with x >0.5 suffered phase separation to precipitate ZrO₂ after annealing under the same condition, and SiO₂ was formed at the interface. To get a good interface between Zr-Si-O films and Si substrate, Zr-Si-O films with bi-layer structure (ZrO₂)_0.7(SiO₂)_0.3/(ZrO₂)_0.5(SiO₂)_0.5/Si was deposited. The electrical properties showed that the bi-layer Zr-Si-O film is of the lowest equivalent oxide thickness and good interface with Si substrate. Supported by the National Nature Science Foundation of China (Grant No. 60636010) and the National Basic Research Program of China (“973” Program) (Grant No. 2004CB619004)