Simple synthesis of urchin-like In2S3 and In2O3 nanostructures

Without the assistance of any surfactant and template, urchin-like In₂S₃ microspheres constructed with nanoflakes of about 15–30 nm thickness were synthesized via the hydrothermal reaction of indium trichloride and thioacetamide in 6.25 vol.% acetic acid aqueous solution at 80 °C for 6–24 h. The as-synthesized nanostructured In₂S₃ could be completely transformed into In₂O₃ when subjected to heating in air at 600 °C for 5 h. The resultant In₂O₃ consisted of urchin-like microsphere built up by 20–30 nm thickness nanoflakes and 20–40 nm nanoparticles. X-ray diffraction, field emission scanning electronic microscope and energy dispersive X-ray spectroscopy have been used to characterize the In₂S₃ and In₂O₃ nanostructures obtained.     

Superconductivity of In5Bi3

Measurements of magnetic properties of superconducting In₅Bi₃ are reported. The single-crystal samples exhibit almost reversible magnetization curves and have resistivity ratios between 33 and 75. The results of the measurements in the superconducting state together with those of additional galvanomagnetic measurements allow estimates of some electronic constants of In₅Bi₃. The electron mean-free paths calculated in this way are about 20 times longer than the coherence length, i.e., the pure limit is approached very closely. This leads to the conclusion that In₅Bi₃ is an intrinsic type-II superconductor with a Ginzburg-Landau parameter =2.25±0.05. The transition temperature is 4.16±0.01 K and the thermodynamic critical field atT=0 is 340±5 Oe. A comparison of the temperature-dependent constants ₁ and ₂ with the predictions of the theory for the pure limit shows deviations up to 8% for ₁. For ₂ the agreement is good.This work was carried out while one of us (E.C.) held an A. von Humboldt Fellowship.Guest from Oak Ridge National Laboratory, Oak Ridge, Tennessee.Guest from Institutul de Fizica, Bucuresti, Romania.     

In situ high-temperature electron microscopy of 3DOM cobalt,iron oxide,and nickel

High-temperature electron microscopy was used to follow how the structure of two specimens of three-dimensionally ordered macroporous (3DOM) materials, also known as inverse opals, and one specimen of a precursor to a 3DOM material changed with temperature. The change in grain size with temperature of 3DOM cobalt and 3DOM iron oxide (as magnetite) was monitored in situ in the TEM by heating in stages to 900 and 1,000 °C, respectively. The two materials studied by TEM showed contrasting grain growth behavior. For 3DOM cobalt, carbon surrounding the nanometer-size grains led to slower grain growth in thinner sample areas than in areas in closer contact with other grains; a bimodal grain-size distribution was observed after heating above 700 °C for 90 min. The grains of the 3DOM iron oxide had no carbon coating and coarsened more evenly to give a unimodal size distribution. Line scans from selected-area diffraction (SAD) patterns were used for phase analysis and showed that traces of cobalt oxide present in the 3DOM cobalt sample at room temperature disappeared when the sample was heated above 500 °C. The transformation of a 3DOM precursor material, nickel(II) oxalate–polystyrene (PS) latex composites, was followed in situ by variable-temperature environmental scanning electron microscopy (ESEM) from room temperature to ca. 700 °C in 0.5–0.7 kPa O₂. The ESEM examination of the 3DOM precursors permitted real-time observation of the polymer template decomposition and the shrinkage that occurs upon calcination of these precursor materials.     

Aqueous precipitation and electrical properties of In2S3: characterization of the In2S3/polyaniline and In2S3/polypyrrole heterojunctions

The stability of indium sulphide aqueous supersaturated solutions at pH 2.50 and 25°C was investigated. Spontaneous precipitation proceeded at rates proportional to the solution supersaturation via a polynuclear mechanism and the phase formed was identified as In₂S₃. The absorption spectrum of In₂S₃ was measured from 190–800 nm and from the absorption threshold the optical energy gap was estimated to be E ₀ = (1.8 ± 0.1) eV. The thermal energy gap E _t = (1.6 ± 0.2)eV was determined from resistivity against temperature measurements and a thermopower coefficient S = –100VK^–1 at room temperature was found. Finally, In₂S₃/polyaniline and In₂S₃/polypyrrole heterojunctions were prepared and from the investigation of their I–V characteristics, the values of the ideality factor, n, the saturation current density, J ₀, and the effective barrier height, _B, were determined to be n = (15 ± 2), J ₀ = (38 ± 7) A m^–2 and _B = 0.56 eV for the polyaniline and n = (64 ± 8), J ₀ = (13 ± 2) A m^–2 and _B = 0.59 eV for the polypyrrole heterojunction.     

Preparation of InIn2O3Pb tunnel junctions

We describe a simple method for growing a homogeneous oxide layer on an indium film. This was earlier considered to be impossible. The method may be advantageous in laboratories with only simple equipment and may be even crucial in certain types of experiments.     

In、Ta共掺对BaCeO3烧结性能及稳定性的影响

采用改进的柠檬酸盐法制备了不同In、Ta掺杂量的BaCeO₃基质子导体粉体, 干压成型后分别在1150℃、1250℃和1350℃下进行烧结。采用X射线衍射仪、扫描电镜分别对质子导体的物相结构和微观形貌进行了表征, 并采用电化学工作站测定了样品不同温度下的电导率。结果表明, 1350℃烧结样品气孔率均小于10%, 并且In掺杂量越高越容易烧结。样品在CO₂和H₂O中的化学稳定性测试结果表明, 只掺杂In可以提高样品在水中的化学稳定性, 但是对粉末样品高浓度CO₂气氛下的稳定性影响不大。In、Ta共掺杂可以大幅度提高样品在CO₂中的稳定性, 且稳定性随着Ta掺杂量的增加而提高。但是样品在10%湿润氢气气氛下的电导率随着Ta含量的增加而降低, 其中, BaCe_0.7In_0.25Ta_0.05O_3-δ在800℃时湿氢气下的电导率为1.16×10^-3 S/cm。     

Coupled substitutions in In2O3: New transparent conductors In2−xM2x/3Sbx/3O3 (M = Cu,Zn)

Two solid solutions In_2−xM_2x/3Sb_x/3O₃ (M = Cu, Zn) with the bixbyite structure have been synthesized in air at 1300 °C. The homogeneity range is larger for Zn (x = 0.42) than for Cu (x = 0.20) and the cationic distribution of the Cu/Sb and Zn/Sb couples is weakly ordered. These new oxides appear to be transparent conductors. Even fully deprived of tin, they have good potential properties. These oxides are either semiconductors with a small band gap (Cu/Sb) or semimetals (Zn/Sb) with σ = 3 × 10² (Ω cm)⁻¹ at room temperature. These materials are more efficient than bulk ITO prepared under the same experimental conditions, i.e. without reducing treatment (σ = 50 (Ω cm)⁻¹).     

Effect of vacuum annealing on the phase composition of In/SnO/Si, In/SnO2/Si, and Sn/In2O3/Si heterostructures

The chemical interaction between indium and thin SnO and SnO₂ films and between tin and thin In₂O₃ films during vacuum annealing was studied. The metallic films were deposited onto single-crystal silicon substrates by magnetron sputtering, the SnO and SnO₂ films were produced by heat-treating the Sn film in flowing oxygen at 673 and 873 K, respectively, and the In₂O₃ film was produced by heat-treating the In film at 573 K. The results indicate that annealing of the In/SnO/Si and In/SnO₂/Si heterostructures in vacuum (residual pressure of 0.33 × 10^?2 Pa) at 773 K gives rise to the reduction of Sn and oxidation of In, whereas annealing of Sn/In₂O₃/Si causes partial tin substitution for indium in the cubic indium oxide lattice.     

Nanoparticle size-dependent lowering of temperature for phase transition from In(OH)3 to In2O3

Phase transformation of In(OH)3 to In2O3 has been studied as a function of nanoparticle size without any alteration of nanoparticle size during transformation. Chemically capped In(OH)3 nanoparticles having sizes of 15, 11, and 8 nm transform to In2O3 at temperatures of 285, 272, and 255 degrees C, respectively. This first-time unambiguous observation of size-dependent lowering of transformation temperature represents a thermodynamic characteristic of the nanoparticle system. The results have been explained in terms of a lower cohesive energy of surface atoms and an increase in surface-to-volume ratio with a decrease in nanoparticle size.     

Sorptive properties of antimony-doped In2O3

O₂, Cl₂, and SO₂ chemisorption on the surface of nanocrystalline In₂O₃ doped with antimony (0.2 and 2.7 at %) has been studied at temperatures from 22 to 200°C. The results indicate that antimony prevents the formation of nonconducting indium chlorides on the surface of nanocrystalline In₂O₃ during Cl₂ chemisorption. The logarithm of the conductivity of Sb-doped In₂O₃ is a nearly linear function of the surface coverage with chlorine, which makes it a candidate chlorine-sensing material. At the same time, antimony doping reduces the SO₂ response of In₂O₃.     

The study of optical properties of In2O3 and of mixed oxides In2O3−MoO3 system deposited by coevaporation

A discussion of the optical properties of two systems of dielectric films i.e. In₂O₃ and of mixed oxides In₂O₃−MoO₃ system is presented. Film thickness, substrate temperature, annealing and composition (in molar%) have a profound effect on the structure and optical properties of these films. The decrease in optical band gap with the increase in film thickness of In₂O₃ is interpreted in terms of incorporation of oxygen vacancies in the In₂O₃ lattice. The decrease in optical band gap with the increase in substrate temperature and annealing of In₂O₃ thin films is ascribed to the release of trapped electrons by thermal energy or by the outward diffusion of the oxygen-ion vacancies, which are quite mobile even at low temperature. For the mixed oxides In₂O₃−MoO₃ system the results are found to be compatible with the reduction in the value of optical band gap of these materials as the molar fraction of MoO₃ increases in the In₂O₃ thin films and is attributed to the incorporation of Mo(VI) ions in an In₂O₃lattice that causes the indium orbital to become a little less tightly bound. The decrease in optical band gap of mixed oxides In₂O₃−MoO₃ system, with increasing film thickness is interpreted in terms of incorporation of oxygen vacancies in both In₂O₃ and MoO₃ lattice which are also believed to be the source of conduction electrons in In₂O₃–MoO₃ complex. The decrease in optical band gap with increasing substrate temperature and annealing of mixed oxides In₂O₃−MoO₃ system is due to the increasing concentration of oxygen vacancies, formation of indium and molybdenum species of lower oxidation state and indium interstitials. The blue colouration of mixed oxides In₂O₃–MoO₃ samples is due to the inter-electron transfer from oxygen 2p to molybdenum 4d level due to which Mo species of lower oxidation states are formed.     

Synthesis of In2O3 nanostructures: from pyramidal monuments, nanotowers to nanopencils

We report on the synthesis of In2O3 nanostructures grown at three different growth temperatures by using the thermal evaporation method. The obtained nanostructural morphologies of In2O3 were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In2O3 nanopencils and pyramidal monument-like structures were reported. The reaction temperature and the difference of temperature between the central heating zones and the product deposition zones, the reaction time, and the surface energies of different growth planes are all responsible for the final crystalline morphologies of the In2O3 nanostructures. A growth mechanism proposed to elucidate the kinetic factors leading the growth of In2O3 nanostructures. The obtained results may not only assist the investigation of new approaches of preparing various nanostructures for potential technical applications and how to modulate the desired morphology, but also give a deeper understanding of the fundamental physical and chemical processes of CVD methods.     

Temporal evolution of beam fanning in LiNbO(3):Fe, In crystals

We investigated the temporal evolution of light-induced scattering in LiNbO(3):Fe, In crystals with different doping concentrations. A special behavior of the beam fanning was found when the intensity of the incident light was relatively weak. In this case the beam fanning became stronger at the beginning of the illumination and then was greatly reduced, which was observed only at strong incident light intensities. This phenomenon was analyzed on the basis of the saturation space-charge field. The intensity threshold effect and the concentration threshold effect were successfully explained.     

Synthesis and characterisation of In(OH)3 and In2O3 nanoparticles by sol-gel and solvothermal methods

Indium hydroxide nanostructures were synthesised by sol-gel and hydrothermal processes from indium acetate and sodium hydroxide as precursors and polyvinyl alcohol, polyvinyl pyrrolidone or polydimethylsiloxane as stabilisers. Calcination of the In(OH)₃ nanostructures at 500°C in air yielded In₂O₃ nanoparticles. The morphology, crystallinity and thermal behaviour of the obtained products of each method were investigated by X-ray diffraction, scanning electron microscopy and thermal gravimetry analysis and differential thermal analysis.     

Selective, electrochemically activated biofunctionalization of In2O3 nanowires using an air-stable surface modifier

Selective electrochemically activated biofunctionalization of In(2)O(3) nanowires (NWs) has been achieved, using monolayer coatings of p-dimethoxybenzene derivatives. Monolayer coatings of 4-(2,5-dimethoxyphenyl)butyl-phosphonic acid (DMP-PA) were deposited on planar indium-tin oxide (ITO) electrodes and In(2)O(3) NWs. The electrochemical behavior of the monolayer coating was first studied using ITO electrodes, as a model system for In(2)O(3) nanowires. When a potential of 950 mV vs a Ag/AgCl reference electrode is applied to an ITO electrode coated with DMP-PA in PBS buffer, the p-dimethoxyphenyl groups are converted to p-benzoquinone (BQ). The electrochemically formed benzoquinone groups react readily with alkyl thiol groups via a Michael addition. The reaction strategy optimized on ITO was applied to an In(2)O(3) NW mat sample coated with DMP-PA. Applying a potential of 950 mV to metal electrodes deposited on NWs converts the DMP-PA NW coating to BQ-PA, which reacts with a thiol-terminated 20-base oligonucleotide. These NWs showed strong fluorescence response after paring with the dye labeled compliment, demonstrating that the probe was bound to the NW surface and that it remained active toward hybridization with its compliment. The unactivated DMP-PA coated NWs showed no response, demonstrating the selective electrochemical functionalization of NWs and the potential of using them in multiplex sensing. We also compared the p-dimethoxybenzene derivative to the conventional hydroquinone analog. The results show that the former can largely enhance the selectivity during the functionalization of both ITO and In(2)O(3) NWs.     

In2O3纳米纤维的制备及其导电性研究

利用静电纺丝技术结合热处理方法制备了一维多孔结构的In2O3纳米纤维。借助扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察纳米纤维的形貌结构;利用热重分析仪(TGA)分析前驱体复合纳米纤维的热处理过程;采用X射线衍射仪(XRD)分析不同煅烧温度下所得In2O3的晶体结构;利用四探针测试In2O3纳米纤维的导电性,并探讨煅烧温度对其导电性的影响。结果表明:静电纺前驱体复合纳米纤维成型良好,且经不同温度煅烧后产物仍保持纤维结构,但纤维直径明显减小。不同温度下煅烧所得In2O3均为立方铁锰矿型,随着煅烧温度的升高,In2O3纳米颗粒逐渐增大,晶体更加完整,导电性逐渐增强。     

纳米In_2O_3的制备与结构表征

介绍了以同纯精铟为原料,采用化学沉淀法在一定的实验条件下制备纳米级In2O3粉体的实验过程,通过XRD、TEM、BET及化学分析等多种检测及分析手段对所制得的粉体的性能进行了初步表征,结果表明:采用化学沉淀法制备的In2O3为高纯单相类球形的黄色粉末,其平均粒径小于30nm。