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In this work, uniform BiOCl microspheres were used as self-sacrificed template to construct BiO/BiOCl heterojunctions by a simple alkaline treatment method. Details of structure and chemical properties were carefully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and Brunauer-Emmett-Teller techniques. The results indicated that BiOCl microspheres composed of numerous nanosheets transformed to rod-like BiO nanostructures during the alkaline treatment, which resulted in strong visible-light absorption. The as-obtained BiO/BiOCl heterojunctions exhibited remarkably enhanced photocatalytic performance for the degradation of methyl orange (MO) under visible-light irradiation, which was ~1.2 and 2.5 times as that of pure BiOCl and BiO, respectively. The formation of BiO/BiOCl heterojunctions facilitated the transfer and separation of photogenerated charge carriers which was further confirmed by the photocurrent measurement and photoluminescence spectra results. The finding reported here offers a valid in situ route for constructing heterojunction photocatalysts to effectively decompose the organic pollutants in aqueous solution. [ABSTRACT FROM AUTHOR]

The Cu, Co codoped ZnO multilayer films were deposited by magnetron sputtering on silicon (100) in different sputtering gas and the substrates were held at 500 °C. The oxygen content in the films were correlated with the oxygen prevailed in the sputter chamber. The influences of the oxygen content in the sputtering gas on structural, optical and magnetic properties of Cu, Co codoped ZnO multilayer films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, UV absorption spectrophotometer and vibrating sample magnetometer. The results indicated that Cu and Co ions would uniformly substitute into the Zn sites of ZnO lattice. The optical band gap of the films increased from 3.14 to 3.23 eV with increasing oxygen content of the sputtering gas. Oxygen concent have effected on the ferromagnetism of the samples. [ABSTRACT FROM AUTHOR]

Na-doped ZnCdO films [ZCO:Na] were grown on quartz substrates at different ratios of argon to oxygen gas flow (Ar:O) by the radio frequency magnetron sputtering method. The influence of Ar:O ratio on structure, electrical and optical properties was investigated by using X-ray diffraction, X-ray photoelectron spectroscopy, Transmission electron microscopy, Hall measurements (Hall), optical absorption spectra and Photoluminescence. Results indicated that all obtained ZCO:Na thin films possess the hexagonal wurtzite structure and free from the formation of secondary phases. As the Ar:O ratios change from 1:5 to 5:1, at first the E increases with the Ar:O ratios increasing and reaches a maximum value at the Ar:O ratio of 1:1, then decreases evidently with the Ar:O ratios increasing continually. It is found that the lower Ar:O ratio is propitious to obtain n-type ZCO:Na film, while the relative higher Ar:O ratio is required to obtain p-type ZCO:Na thin films. When the Ar:O ratio is 1:1, the ZCO:Na film shows the best p-type conduction characteristics, which has a hole concentration of 1.13 × 10 cm, Hall mobility of 2.54 cm V s and resistivity of 2.53 × 10 Ω cm. In addition, the mechanism of the influence of Ar:O ratio on the electrical and optical properties of the film as well as the mechanism of p-type conductivity was discussed in this work. [ABSTRACT FROM AUTHOR]

Ferroelectric glass-ceramics of the SrO-BaO-NbO-CaO-SiO-BO system with different nucleating agents CrO, BaF, ZrO, CaF and CeO, have been prepared by conventional melt casting followed by controlled crystallization processing. The effect of different nucleating agent additions on crystallization mechanism, crystallization behaviors, microstructures and dielectric properties of the glass-ceramics are studied using DTA, XRD techniques, SEM and LCR analyzer. The results show that the addition of different nucleating to the glass-ceramics decreases the crystallization temperatures, accelerates the secondary phase elimination and promotes the uniform distribution of grain size. The well development of microstructure promoted by the nucleating agents can result in the improvement of the dielectric constant as well as energy storage density remarkably. The sample with CeO as the optimum nucleating agent achieves the dielectric constant of 301, breakdown strength of 622 kV/cm and the highest energy storage density of 5.15 J/cm. [ABSTRACT FROM AUTHOR]

ZnCuVO nanoparticles have been successfully prepared by the sol-gel method and sintered in air at the different temperature. The effects of the annealing temperature on the structural, optical and magnetic properties of the obtained samples were studied. The X-ray diffraction (XRD) results showed that the ZnCuVO nanoparticles was single phase with the ZnO-like wurtzite structure when the annealing temperature was <700 °C. The photoluminescence (PL) spectra revealed that as the annealing temperature increased, the intensity of the UV emission increased and the green emission enhanced significantly. Magnetic measurements indicated that the samples exhibited ferromagnetism at the room temperature. The results of XRD, transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) revealed that there was no ferromagnetic-related secondary phase in ZnCuVO nanoparticles, the ferromagnetism of the ZnCuVO samples was originated from the fact that the Cu and V ions doped into the ZnO lattice. In addition, the saturation magnetization (Ms) increased with the enhancement of the annealing temperature. [ABSTRACT FROM AUTHOR]

Abstract: Au–Cu bimetallic nanoparticles supported on SBA-15 have been reported to be much more active in CO oxidation than the corresponding monometallic counterparts in our previous work. In this work, in situ techniques including XRD, EPR, XANES, and FT-IR were employed to reveal the structural changes of the Au–Cu bimetallic particles during different pretreatment and reaction conditions, and to clarify the essence of the synergistic effect between gold and copper. The results showed that gold remained as Au0 in any treatment conditions, while copper was very sensitive to the treatment temperature and atmosphere. The freshly reduced catalyst was a mixture of Au3Cu1 intermetallic phase and Cu2O amorphous phase. In CO oxidation, the Au3Cu1 intermetallic phase was segregated into a gold core decorated with tiny CuO x patches, and CO adsorbed on Au0 reacted with active oxygen provided by the neighboring CuO x , thus enhancing greatly the activity for CO oxidation. [Copyright &y& Elsevier]

Abstract: Au–Cu bimetallic catalysts with Au/Cu ratios ranging from 3/1 to 20/1 were prepared on silica gel support by a two-step method. The catalysts were characterized by ICP, XRD and TEM. The results showed that, irrespective of Au/Cu ratios, all the bimetallic nanoparticles had significantly reduced particle sizes (3.0–3.6nm) in comparison with monometallic gold catalysts (5.7nm). Both CO oxidation and PROX reactions were employed to evaluate the catalytic activities of Au–Cu bimetallic catalysts. For CO oxidation, the alloy catalysts show non-monotonic temperature dependence showing a valley in the intermediate temperature range. The catalyst with Au/Cu ratio of 20/1 gave the highest activity at room temperature, but its activity showed the deepest valley with increasing the reaction temperature. On the other hand, the catalyst with Au/Cu ratio of 3/1 exhibited the best performance for PROX reaction. For the Au/Cu ratios investigated, the bimetallic catalysts showed superior performance to monometallic gold catalysts, demonstrating the synergy between gold and copper. [ABSTRACT FROM AUTHOR]

Abstract: ZnO nanoparticles (NPs) have been successfully synthesized by the chemical precipitation method in different atmospheres at 500°C. The annealing atmospheres were argon, forming gas (50% Ar/50% O2) and air, respectively. The effects of annealing atmosphere on the structure and optical properties of ZnO NPs were investigated in detail by X-ray diffraction, transmission electron microscope, photoluminescence and Raman scattering measurements. The results showed that the as-prepared ZnO NPs had a hexagonal wurtzite structure, and all the samples kept the overall crystal structure of bulk ZnO. From the Raman and photoluminescence spectra, it can be seen that the content of oxygen in different annealing atmospheres strongly influenced the crystallization and light emission of the ZnO NPs. The results revealed that the content of oxygen in air was the optimal condition for growing the ZnO NPs with the best crystalline quality and optical properties. Defect emission was significantly enhanced by annealing in Ar atmosphere, which indicated that the green defect emission was most likely due to oxygen vacancy. Moreover, the effect mechanism of annealing atmospheres on the structure and optical properties of ZnO NPs were also investigated. [Copyright &y& Elsevier]

Abstract: ZnO nanoparticles (NPs) have been successfully prepared by the chemical precipitation method at a low temperature of 200°C. X-ray diffraction (XRD), transmission electron microscope (TEM), photoluminescence (PL) and Raman were used to investigate the effect of annealing temperature on the structure and optical properties of ZnO NPs. The XRD analyses revealed that the average size of the as-prepared samples was about 8nm under 200°C, which had a good agreement with TEM images. Raman spectra showed that the E2 (high) mode became stronger and sharper with the increase of annealing temperature, but the intensity of phonon peak located at 580cm−1 was relatively suppressed. The position of ultraviolet (UV) emission peak in the room-temperature PL spectra showed a red-shift when the annealing temperature was increased. In addition, after annealing under 500°C, the intensity of the UV peak became strongest and the intensity of the green emission almost disappeared, which indicated that ZnO NPs have much better crystallization after annealing. [Copyright &y& Elsevier]

Ferroelectric nanowires have attracted great attention due to their excellent physical properties. We report the domain structure, ferroelectric, piezoelectric, and conductive properties of bismuth ferrite (BFO, short for BiFeO3) nanowires characterized by scanning probe microscopy (SPM). The X-ray diffraction (XRD) pattern presents single phase BFO without other obvious impurities. The piezoresponse force microscopy (PFM) results indicate that the nanowires possess a multidomain configuration, and the maximum piezoelectric coefficient (d33) of single BFO nanowire is 22.21 pm/V. Poling experiments and local switching spectroscopy piezoresponse force microscopy (SS-PFM) demonstrate that there is sufficient polarization switching behavior and obvious piezoelectric properties in BFO nanowires. The conducting atomic force microscopy (C-AFM) results show that the current is just hundreds of pA at 8 V. These lay the foundation for the application of BFO nanowires in nanodevices. [ABSTRACT FROM AUTHOR]

K 2 O–Na 2 O–Nb 2 O 5 –SiO 2 –B 2 O 3 glass-ceramics was prepared via melt-quenching and controlled crystallization route. To investigate the effect of crystallization treatment schedule on the dielectric properties of potassium sodium niobate (KNN) glass-ceramics, this report measured six glass samples with different crystallization treatment by XRD, SEM and LCR measurements. By means of changing heat-treatment schedule, it could be inferred that crystallization process and optimal treatment condition for KNN glass-ceramic with pore-free and high energy density. When the original glass samples crystallized at 707 °C for 2 h and 900 °C for 3 h, this crystallization treatment was beneficial to obtaining the glass-ceramic samples with purer perovskite structure K 0.1 Na 0.9 NbO 3 crystal phase and finer grains which possessed relative higher energy storage density (1.899 J/cm 3 ). The crystallization behavior and dielectric properties have exhibited a regular change at different crystallization temperature. Comprehensive results and analysis demonstrated that crystallization treatment played a role in dielectric properties of KNN glass-ceramics. In order to optimize energy storage, this experiment controlled transition from matrix glass phase of high breakdown strength (BDS) to ferroelectric crystal phase of high dielectric constant. [ABSTRACT FROM AUTHOR]

Bandgap engineering of Cu 2 In x Zn 1−x Sn(S,Se) 4 alloy films for photovoltaic application has been investigated. Cu 2 In x Zn 1−x Sn(S,Se) 4 (0 ≤ x ≤ 0.6) alloy films with different In contents and a single kieserite phase were fabricated by using a simple low-cost sol-gel method. The influence of In content on the structure, morphology, and optical and electrical properties of Cu 2 In x Zn 1−x Sn(S,Se) 4 films was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), X-Ray photoelectron spectroscopy (XPS), optical absorbance, and room-temperature Hall measurements. The results of XRD, TEM, and XPS demonstrated the substitution of some Zn atoms by In in Cu 2 In x Zn 1−x Sn(S,Se) 4 films. The Hall measurements show that the carrier concentration of the Cu 2 In x Zn 1−x Sn(S,Se) 4 (0 ≤ x ≤ 0.6) decreases with increasing In content and that the p-type Cu 2 In x Zn 1−x Sn(S,Se) 4 films with preferable electrical properties can be obtained by adjusting the In content during film deposition. The optical measurements indicate that the bandgap of Cu 2 In x Zn 1−x Sn(S,Se) 4 films with kesterite structure can be continuously tuned in the range of 1.13–1.01 eV as x is increased from 0 to 0.6. Our results show that the Cu 2 In x Zn 1−x Sn(S,Se) 4 alloy is a potentially applicable material for bandgap grading absorption layers in high-power-conversion-efficiency solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Hydrous hydrazine, such as hydrazine monohydrate (N2H4·H2O), is a promising hydrogen carrier material due to its high content of hydrogen (8.0wt%). The decomposition of hydrous hydrazine to H2 with a high selectivity and a high activity under mild conditions is the key to its potential usage as a hydrogen carrier material. Platinum-modified Ni/Al2O3 catalysts (NiPt x /Al2O3) were prepared starting from Ni–Al hydrotalcite and tested in the decomposition of hydrous hydrazine. Compared with Ni/Al2O3, the TOF was enhanced sevenfold over NiPt0.057/Al2O3; meanwhile, the selectivity to H2 was increased to 98%. Characterization results by means of HAADF-STEM, XRD, and EXAFS revealed the presence of surface Pt–Ni alloy in this Pt-promoted catalyst. The formation of Pt–Ni alloy could significantly weaken the interaction between adspecies produced (including H2 and NH x ) and surface Ni atoms, which is confirmed by microcalorimetry and TPD results. The weakening effect could account for the greatly enhanced reaction rate, as well as H2 selectivity on NiPt x /Al2O3 catalysts. [Copyright &y& Elsevier]

Abstract: Nanocrystalline samples of ZnS and Zn1−x Mn x S were synthesized by the solvothermal method without any surface-active agents and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), near-edge X-ray-absorption fine structure technique (XANES), photoluminescence (PL) and UV–vis. The results showed that the Mn2+ ions were substitutionally incorporated into the ZnS host and the size of the particles was decreased as the Mn doped-ratio increased. The yellow-orange emission from the Mn2+ 4T1–6A1 transition was observed in the PL spectra, the peak intensity ratio of which to that of sulfur vacancies increased with the increase of the Mn2+ concentration, and showed a maximum when the concentration of Mn2+ was kept at 3%. [Copyright &y& Elsevier]