超声波-水热法合成Bi2Te3纳米管

以水为反应介质，NaBH4为还原剂，合成了BizTe3纳米管及纳米微粒。溶液首先在超声波发生器中预处理1h，然后置于150℃，水热反应釜中继续反应48h。XRD分析表明：合成产物主要物相为Bi2Te3；SEM观察可见产物中有纳米管生成，纳米管直径约为50-100nm，管壁厚约8-10nm，长度在500nm以上。EDS分析表明：纳米管成份为Bi2Te3。Bi2Te3纳米管可能的生长机制为纳米薄片-卷曲-闭合-纳米管。     

Facile synthesis of Bi2S3 nanoflowers arrays

Bi₂S₃ nanoflowers arrays have been synthesised by a facile hydrothermal method. The nanoflowers are composed of nanobelts. The Bi₂S₃ nanobelts are along [1?3?0] direction with a width of about 100?nm and a length of about 2?µm. It is found that the substrate, the height of the substrate in the autoclave and the reaction time play key roles for the formation of the nanoflowers arrays. The growth of the nanoflowers is attributed to the lowest interfacial tension and the growth of the nanobelts can be ascribed to the anisotropic growth of the Bi₂S₃ nanocrystals. The room temperature photoluminescence (PL) spectrum shows that there is a strong and broad PL band in the wavelength range from 650 to 800?nm. It is expected that the Bi₂S₃ nanoflowers arrays grown on the substrate could have potential application in optics and catalysts.     

Preparation and properties of Bi2−x As x S3 thin films by solution-gas interface technique

The solution gas interface technique by which thin films of Bi_2−x As _x S₃ were deposited is described in this paper. The semiconducting properties of the interface grown Bi_2−x As _x S₃ thin films are studied. The optical absorption, dark resistivity and thermoelectric power of the films were studied and results are reported.     

Microwave-assisted synthesis of Bi2Se3 /reduced graphene oxide nanocomposite as efficient catalytic counter electrodefordye-sensitized solar cell

Bi₂Se₃/reduced graphene oxide (rGO) composite was successfully synthesized by a facile microwave-assisted hydrothermal method and applied as a counter electrode for efficient dye-sensitized solar cells. By this means, the size and distribution of the formed Bi₂Se₃ nanoparticles onto a flexible graphene sheet were effectively controlled, which is crucial for achieving high electrocatalytic activity on I₃^? reduction. Mainly due to the homogeneous single-layer immobilization of Bi₂Se₃ nanoparticles on a graphene sheet with high density, BiG2 exhibited the highest catalytic activity and the lowest electrolyte diffusion resistance. Adye-sensitized solar cell with BiG2 as a counter electrode can yield 7.09% photoelectric conversion efficiency, which is comparable to that of the cell with a Pt-film counter electrode (6.23), exhibiting the application potential of BiG2 as a low cost non-Pt CE materials for DSSC.     

Facile synthesis of copper oxide nanotubes decorated by TiO2 nanoparticles,optical and photocatalytic activity in water

Copper oxide nanotubes decorated by TiO₂ nanoparticles (CNTNs) were fabricated by simple three-step method. First, deposition of copper onto cellulose fibres, then thermal oxidation of copper and cellulose fibres and last simply mixing copper oxide nanotubes and TiO₂ nanoparticles (NPs). Scanning electron microscopy, transmission electron microscopy and X-ray diffraction showed that the synthesised nanotubes were monoclinic-structured polycrystalline CuO with diameter and wall thickness of approximately 50～100 nm and 20～25 nm, respectively. Moreover, the diameter of the TiO₂ NPs is about 20～30 nm. Optical properties of the solutions containing copper oxide nanotubes decorated by TiO₂ NPs were studied. Discrete dipole approximation was used for the calculation of absorption, scattering and extinction cross sections of the deposited CNTNs on a glass substrate. Our simulation results show that there are good agreements between the experimental date and the simulation results. Moreover, the photocatalytic tests were done by methyl orange under visible light (λ = 633 nm) irradiation for prepared samples.     

Effect of complexing agent on growth process and properties of nanostructured Bi2S3 thin films deposited by chemical bath deposition method

Nanostructured Bi₂S₃ thin films have been prepared onto amorphous glass substrates by chemical bath deposition method at room temperature using bismuth nitrate and sodium thiosulphate as cationic and anionic precursors with EDTA as complexing agent in aqueous medium. The X-ray diffraction study reveals that the films deposited without the complexing agent are amorphous in nature and becomes nanocrystalline in the presence of EDTA. The resistivity for the films prepared from EDTA complexed bath is decreased due to the improvement in grain structure. The decrease in optical bandgap and activation energy is observed as the thickness of the film varies from 45 to 211 nm on account of the variation of the volume of complexing agent in reaction bath. Studies reveal that the growth mechanism of Bi₂S₃ gets affected in the presence of complexing agent EDTA and shows impact on structural, electrical and optical properties.     

High-pressure synthesis,crystal structure,and magnetic properties of KSbO3-type 5d oxides K0.84OsO3 and Bi2.93Os3O11

5d Solid-state oxides K_0.84OsO₃ (Os^5.16+; 5d ^2.84) and Bi_2.93Os₃O₁₁ (Os^4.40+; 5d ^3.60) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500–1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5d electronic properties and tunnel-like structure motifs were investigated. A KSbO₃-type structure with a space group of Im-3 and Pn-3 was determined for K_0.84OsO₃ and Bi_2.93Os₃O₁₁, respectively. The magnetic and electronic transport properties of the polycrystalline compounds were compared with those obtained theoretically. It was revealed that the 5d tunnel-like structures are paramagnetic with metallic charge conduction at temperatures above 2 K. This was similar to what was observed for structurally relevant 5d oxides, including Bi₃Re₃O₁₁ (Re^4.33+; 5d ^2.66) and Ba₂Ir₃O₉ (Ir^4.66+; 5d ^4.33). The absence of long-range magnetic order seems to be common among 5d KSbO₃-like oxides, regardless of the number of 5d electrons (between 2.6 and 4.3 per 5d atom).     

Synthesis and characterization of β type solid solution in the binary system of Bi2O3-Eu2O3

We have investigated Bi₂O₃-Eu₂O₃ binary system by doping with Eu₂O₃ in the composition range from 1 to 10 mole% via solid state reactions and succeeded to stabilize β-Bi₂O₃ phase which is metastable when pure. Stability of β-Bi₂O₃ polymorph was influenced by heat treatment temperature. Tetragonal type solid solution was obtained in 3–6 mole% addition range when annealed at 750°C and the range was 2–7 mole% when annealed at 800°C. We have also carried out investigations on lattice parameters, microstructural properties and elemental compositions of this β type solid solution for each doping ratio. Lattice parameters increased with amount of Eu₂O₃ addition. Our experimental observations strongly suggested that oxygen deficiency type non-stoichiometry is present in doped β type solid solutions.     

Facile synthesis of Bi2S3 nanocrystalline-modified TiO2: Fe nanotubes hybrids and their photocatalytic activities in dye degradation

Interface-induced effects and large specific area of heteronanostructures are attracting much attention due to applications in photocatalysis. In this work, ultrafine bismuth sulfide (Bi₂S₃) nanocrystalline-modified Fe-doped TiO₂ nanotubes (NTs) were fabricated with facile methods. The effect of the ratio of Bi₂S₃ to the Fe-doped TiO₂ NTs on the microstructural, optical, and photocatalytic properties of the NTs and hybrids was studied. The NTs showed an actual Fe content of ～ 2.93 at.%. The optical bandgap of the NTs and hybrids was ～2.90 eV and ～2.46–2.88 eV, respectively, and decreased with increasing Bi₂S₃/NTs ratio. The specific surface area of the NTs was ～333 m² · g^?1; whereas the hybrids showed obviously larger specific surface area of ～ 527–689 m² · g^?1 than the NTs because of well-controlled formation process of Bi₂S₃ nanoparticles. The sunlight-excited degradation experiments of dyes in the water indicated that the photocatalytic activity of the hybrids was higher than that of the NTs and increased with increasing Bi₂S₃/NTs ratio. Moreover, the degradation rates of two dyes at different initial pH values were very different. The high photocatalytic activity of the hybrids was mainly ascribed to the narrow bandgap, large specific surface area, and effective heterojunction.     

A very simple and low cost route to Bi2S3 nanorods bundles and dandelion-like nanostructures

Bi₂S₃ nanorods bundles as well as three-dimensional dandelion-like nanostructures were synthesized in high yield at lower temperature (room temperature or ambient temperature of 15 °C) in a very simple system composed only of Bi(NO₃)₃, thioacetamide (TAA), hydrochloride acid and distilled water. It is the first report to obtain such nanostructures at such a low temperature and by such a simple method, and the reaction does not demand any additional energy such as heating or agitation. A splitting crystal growth and self-assemble mechanism should be responsible for the formation of these structures. This kind of novel Bi₂S₃ nanostructures may find potential applications in hydrogen storage, high-energy batteries, as well as luminescence and catalysis fields.     

Hydrothermal synthesis of single-crystalline Bi2Te3 nanoplates

Novel Bi₂Te₃ nanoplates with about 0.2-1 μm in diagonal and 100 nm in thickness have been facilely synthesized via hydrothermal routes in the presence of polyvinylpyrrolidone (PVP). Various techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform infrared spectrometry (FT-IR) have been used to characterize the obtained products. The results show that the existence of PVP is vital to the formation of the plate-like morphology. Other factors, such as the reaction temperature and the different surfactants also have influence on the morphology of the final products to some extent.     

Incommensurate fluctuations in Bi2Sr2CaCu2O8

A special neutron scattering technique has been used to discover an incommensurate fluctuation in Bi₂Sr₂CaCu₂O₈ that appears below T_c. The fluctuation is identified as a dynamic charge density wave since its scattering intensity appears to increase with increasing momentum transfer. The fluctuation is found at a wavevector near 2k_F and could be associated with a dynamic stripe phase.     

Evidence for supercooling across a vortex-matter phase transition: studies on CeRU2 and Bi2Sr2CaCu2O8

We present DC magnetization data indicating a first-order phase transition in the vortex state of CeRu₂, with the higher entropy phase exhibiting enhanced pinning. Minor hysteresis loops show evidence of supercooling of the higher entropy phase as the phase boundary is crossed both isothermally as well as at constant field. These features are shown to be absent across the Bragg-glass to vortex-glass transition in Bi₂Sr₂CaCu₂O₈. The supercooling is more persistent in the constant field case.     

The fabrication of the antibacterial paste based on TiO2 nanotubes and Ag nanoparticles-loaded TiO2 nanotubes powders

ABSTRACT

We successfully synthesised TiO₂ nanotubes (TNTs) and silver nanoparticles (Ag NPs)-loaded TiO₂ nanotubes paste. These were coated on a glass substrate by spin coating method, and their antibacterial activities were surveyed. The morphology of materials was defined by transmission electron microscopy (TEM) image; the crystalline structure and the composition of the materials were determined by X-ray diffraction (XRD) pattern and X-ray photoelectron spectroscopy (XPS). Vibrational properties of the molecules existing in the sample were investigated by Fourier transform infrared (FTIR) spectroscopy, and the transmittances of films were determined by UV–Vis transmittance spectroscopy. This research shows that the structure and morphology of TNTs did not change after they underwent the processes of paste preparing and film coating on a glass substrate. Furthermore, the transmittance of TNTs film (about 75%) is higher than Ag NPs-loaded TiO₂ nanotubes (Ag/TNTs) film (about 65%) in the visible region. Moreover, the antibacterial property of Ag/TNTs film shows its effectiveness against Escherichia coli bacteria, and the antibacterial efficiency is 99.06% for 24 h-incubation period in the dark condition.     

Superconductivity in Na-doped Bi2Sr2CaCu2O y system

Samples with the nominal composition Bi₂Sr₂Ca_1−x Na _x Cu₂O _y (x=0, 0·1, 0·2 and 0·3) were prepared by solid-state reaction of the individual compounds. X-ray diffraction patterns indicate that the samples have a majority 2212 phase with 2223 also being present. From the DC four-probe resistance data, we have observed that the furnace-cooled samples show metallic behaviour while the quenched samples show superconductivity up to 97 K.     

Simple method for synthesis of carbon nanotubes over Ni-Mo/Al2O3 catalyst via pyrolysis of polyethylene waste using a two-stage process

Synthesis of valuable multi-walled carbon nanotubes (MWCNTs) by thermal pyrolysis of low-density polyethylene (LDPE) waste was investigated via a two-stage process. The first stage was the thermal pyrolysis of LDPE to gaseous hydrocarbons, and the second stage was the catalytic decomposition of the pyrolysis gases over Ni-Mo/Al₂O₃ catalysts. Two catalysts with the compositions of 5.2%Ni-10.96%Mo/Al₂O₃ and 10%Ni-9.5%Mo/Al₂O₃ were tested for carbon nanotubes (CNTs) formation. The catalyst containing 10%Ni showed better activity in terms of CNTs production. Accordingly, the impact of either pyrolysis or decomposition temperatures was investigated using the 10%Ni-9.5%Mo/Al₂O₃ catalyst. TEM, XRD, Raman spectroscopy, TGA, TPR, and BET analysis tools were used to characterize the fresh catalysts as well as the obtained carbon nanomaterials. TEM images proved that MWCNTs with various morphological structures were obtained at all pyrolysis and decomposition temperatures. Moreover, cup-stacked carbon nanotubes (CS-CNTs) were observed at the decomposition temperature of 600°C. MWCNTs with the best quality were produced at decomposition temperature of 750°C. The optimum pyrolysis and decomposition temperatures in terms of CNTs production were at 700 and 650°C, respectively.     

Synthesis and photocatalytic property of SnO2/TiO2 nanotubes composites

SnO2/TiO2 nanotubes composite photocatalysts with different SnO2 contents were successfully synthesized by means of a simple solvothermal process. The synthesized products were characterized physically by X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The composite photocatalysts can not only make the target pollutant, methylene blue (MB), adsorbed at a high concentration level around the surface of the composites but also decrease the recombination rate of electron-hole pairs so as to achieve good photocatalytic performance. The effect of SnO2 contents on the photocatalytic activities of the composites was also investigated. The results showed that the SnO2/TiO2 nanotubes composite photocatalyst with 5 wt.% SnO2 loading had the highest photocatalytic efficiency.     

Microwave-assisted synthesis of hierarchical Bi2O3 spheres assembled from nanosheets with pore structure

Hierarchical Bi₂O₃ spheres assembled from nanosheets with nanopore structure have been successfully synthesized by thermal decomposition of the precursor at 400 °C for 3 h in air, which was prepared using Bi(NO₃)₃·5H₂O and poly(vinylpyrrolidone) (PVP) by a microwave-assisted heating method in ethylene glycol (EG) at 150 °C for 10 min. The morphology of Bi₂O₃ is similar to that of the precursor. The products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TG) and differential scanning calorimetric analysis (DSC). XRD pattern showed that the product had a high degree of crystallinity. FE-SEM micrograph indicated that hierarchical Bi₂O₃ spheres had sizes around 10 μm.     

Photocatalytic activities of Mo-doped Bi2WO6 three-dimensional hierarchical microspheres

The Mo-doped Bi₂WO₆ three-dimensional (3D) hierarchical microspheres from nanoplates have been synthesized by a hydrothermal route. The products were characterized in detail by multiform techniques: X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDS), scanning electron microscopy (SEM), and UV-vis absorption spectrum. The results of the photocatalytic degradation of Rhodamine-B (RhB) in aqueous solution showed that molybdenum ions doping greatly improved the photocatalytic efficiency of Bi₂WO₆ 3D hierarchical microspheres. The Mo-doped Bi₂WO₆ microspheres with atomic ratio of Mo-W of 0.05 had the best activity in photodegradation of RhB in aqueous solution under 500 W Xe lamp light irradiation.     

Efficient Bi → Nd energy transfer in Gd2O3:Bi,Nd

Bi³⁺,Nd³⁺ co-doped Gd₂O₃ were prepared by solid state reaction and the optical properties were investigated. The results show that the near-infrared emission of Nd³⁺ ions is significantly enhanced by the introducing of Bi³⁺ in co-doped samples. An efficient energy transfer from Bi³⁺ to Nd³⁺ corresponds to the near-infrared emission enhancement. The energy transfer efficiency reaches 64.1% for the sample with the strongest near-infrared emission, which has the optimized doping concentrations of 0.5% for Bi³⁺ and 2% for Nd³⁺. The interesting optical properties make Bi³⁺,Nd³⁺ co-doped Gd₂O₃ promising as the luminescent down-conversion layers in front of c-Si solar cells to enhance the performance of the solar cells.