Haoshuang Gu

Sol-gel-derived c-axis oriented ZnO thin films

c-Axis oriented zinc oxide thin films were prepared by sol-gel process on fused quartz substrates. The structure, optical and electrical properties of ZnO films were investigated. Growth of the thin films strongly depends on heat-treatment conditions. The c-axis lattice constants of the thin films and the band gap are a little bigger than that of ZnO crystal. The differences between the thin film and crystal might be attributable to the grain boundaries and imperfections in thin films.

Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors.

Recent Development of Sandwich Assay Based on the Nanobiotechnologies for Proteins, Nucleic Acids, Small Molecules, and Ions

Nanobiotechnologies for Proteins, Nucleic Acids, Small Molecules, and Ions Juwen Shen, Yuebin Li,†,§,⊥ Haoshuang Gu, Fan Xia,*,† and Xiaolei Zuo*,‡ †Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China ‡Division of Physical Biology and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 201800, China Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Faculty of Physical and Electronic Sciences, Hubei University, Wuhan 430062, China Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China

Synthesis and optical properties of highly c-axis oriented Bi4Ti3O12 thin films by sol-gel processing

Abstract Highly c -axis oriented Bi 4 Ti 3 O 12 thin films have successfully been prepared on fused quartz substrates by sol-gel processing. The orientation degree of the thin film was about 87%. The thin film exhibits good optical transmission. The optical-absorption properties of the thin films have been measured. The variation of bandgap with annealing temperature is studied.

Facile preparation, formation mechanism and microwave absorption properties of porous carbonyl iron flakes

An easy and flexible two-step approach consisting of annealing and subsequently selective pitting corrosion has been developed to prepare porous carbonyl iron flakes (CIFs). Based on the dependence of the morphologies and compositions of the resultant CIFs on the annealing temperature and corrosion time, a formation mechanism for the porous CIFs has been substantiated. In our protocol, the annealing process carried out as the first step in the formation process causes an increase in the grain size and forces the Fe nanocrystals to react with the N impurities in the raw CIFs to generate dispersed Fe4N domains. These domains subsequently induce selective pitting corrosion, resulting in porous CIFs. As a result of the porous structure, the as-obtained porous CIFs have a specific surface area of 16.92 m2 g−1, a saturation magnetization of 140 emu g−1 and a coercivity of 61 Oe. Compared with the raw CIFs, they have a large permeability at high frequencies and a modest permittivity. Consequently, composites containing 20 vol% of the porous CIFs in paraffin wax display a reflection loss ≤−20 dB over a wide frequency range of 2.9–20 GHz when the thickness is varied between 0.9 and 4.5 mm. The results reported here suggest a facile approach to preparing porous nanocrystalline metals. Our results offer a promising strategy for the fabrication of absorbents for thin-thickness and strong-absorption microwave absorbing materials with working frequencies adjustable over a wide range simply by varying the thickness.

Photoluminescence and Raman scattering studies on PbTiO3 nanowires fabricated by hydrothermal method at low temperature

PbTiO3 nanowires have been successfully fabricated by a hydrothermal method at 200°C. X-ray diffraction result shows that the PbTiO3 nanowires have a tetragonal perovskite structure without any other impurity phase. Scanning electron microscopy and transmission electron microscopy investigations exhibit that the as-prepared samples are made up of large quantity nanowires with diameters of about 10–20nm and lengths reaching up to 3μm and single crystalline in nature. Photoluminescence study at room temperature for wavelength between 400 and 650nm reveals a strong blue-green emission band peaking at ca. 471.4nm (2.63eV). Raman spectroscopy study of the nanowires at room temperature demonstrates that the lifetime of the phonons is shorter compare to that of bulk materials.

Synthesis, growth mechanism and optical properties of (K,Na)NbO3 nanostructures

(K1−xNax)NbO3 (KNN) nanomaterials with various morphologies, including nanorods, step-like structures etc. were synthesized through a hydrothermal route. For KNN nanomaterials, the phase structures changed from orthorhombic to monoclinic as the x value increased from 0.27 to 0.66. Oriented attachment and aggregation are the major formation mechanism of the nanorods and the step-like structures, respectively. The compositional change in KNN induced a series of shifts of the Raman bands, of which the mechanisms are briefly discussed. A UV/vis absorption study shows that, for K0.50Na0.50NbO3 nanorods, two interband transitions from O2p electron states to empty Nb4d electron states and two intraband transitions in relation to Nb5+ cations are revealed, and the band gap is about 3.09 eV.

Lead-free In2O3-doped (Bi0.5Na0.5)0.93Ba0.07TiO3 ceramics synthesized by direct reaction sintering

Lead-free (Bi0.5Na0.5)0.93Ba0.07TiO3–xwt%In2O3 ceramics synthesized by direct reaction sintering have been studied. X-ray diffraction reveals that all (Bi0.5Na0.5)0.93Ba0.07TiO3–xwt%In2O3 ceramics are of a perovskite structure with coexistence of rhombohedral and tetragonal phases. It is found that the direct reaction sintering promotes growing of ceramic grains while doping of In2O3 contributes to inhibit and homogenize the grain growth, as shown by scanning electron microscopy. The ceramics show excellent piezoelectric and dielectric properties with thickness electromechanical coupling factor kt=0.503, piezoelectric constant d33=205pC∕N, dielectric constant e33T∕e0=1046, and loss tangent tanδ=0.036.

Synthesis of bismuth ferrite nanoparticles via a wet chemical route at low temperature

Nanoparticles (NPs) of multiferroic bismuth ferrite (BiFeO3) with narrow size distributions were synthesized via a wet chemical route using bismuth nitrate and iron nitrate as starting materials and excess tartaric acid and citric acid as chelating agent, respectively, followed by thermal treatment. It was found that BiFeO3 NPs crystallized at ∼350°C when using citric acid as chelating agent. Such crystallization temperature is much lower than that of conventional chemical process in which other types of chelating agent are used. BiFeO3 NPs with different sizes distributions show obvious ferromagnetic properties, and the magnetization is increased with reducing the particle size.

Highly Responsive Room-Temperature Hydrogen Sensing of α-MoO3 Nanoribbon Membranes

[001]-Oriented α-MoO3 nanoribbons were synthesized via hydrothermal method at temperature from 120 to 200 °C and following assembled a membrane on interdigital electrodes to form sensors. The sensitivity, response speed, and recovery speed of the sensor improve with the increasing hydrothermal temperature. Among them, the sample obtained at 200 °C exhibits a room-temperature response time of 14.1 s toward 1000 ppm of H2. The nanoribbons also show good selectivity against CO, ethanol, and acetone, as well as high sensitivity to H2 with a concentration as low as 500 ppb. The hydrogen sensing behavior is dependent on the redox reaction between the H2 and chemisorbed oxygen species. Higher hydrothermal temperature creates larger specific surface area and higher Mo(5+) content, leading to increased chemisorbed oxygen species on the nanoribbon surface.