Hongquan Zhang

Porous tungsten trioxide nanolamellae with uniform structures for high-performance ethanol sensing

Tungsten trioxide nanostructures have received considerable attention due to their enhanced gas sensing properties and promising applications in the sensing field. Herein, tungsten oxide (WO3) with a lamellar structure was prepared by a facile but feasible hydrothermal process and applied for gas detection. The structures, morphologies and surface characteristics of the as-obtained products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller analysis. The uniform nanolamellae were constructed from many substructures, primarily nanoparticles, resulting in desirable porous structures. To highlight the potential applications, gas sensors based on the as-synthesized products were fabricated to test their sensing performance. The test data indicated that the porous WO3 nanolamellae had superb kinetic response and remarkable selectivity towards some volatile organic compounds (VOCs), particularly ethanol, at an operating temperature of 200 °C. As such, we believe that these porous WO3 nanolamellae are promising as a potential high-performance sensing material for ethanol detection.

Controllable synthesis and enhanced gas sensing properties of a single-crystalline WO3–rGO porous nanocomposite

In this paper, we report on a facile hydrothermal approach combined with a subsequent annealing process for the controllable synthesis of a single-crystalline WO3–rGO porous nanocomposite. The crystal structure, morphology and chemical composition of the as-obtained product were well-characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller analysis. The results indicate that this hybrid structure is composed of single-crystal WO3 porous nanoflakes with a size of 500 × 500 nm2 growing through or anchoring into a sheet-like rGO matrix. We explore the sensing performance of the gas sensor based on the as-synthesized product. Impressively, gas testing shows that the WO3–rGO nanocomposite exhibits an excellent kinetic response speed and good sensitivity toward NO2 and some volatile organic compound pollutants at a low temperature (90 °C). The pseudo 3-D structure provides many channels for gas diffusion and clearly enhances sensing properties. As such, this graphene-based composite shows promising potential as a high-performance gas sensing material for real-time gas detection.

Three-dimensional hierarchical Co3O4 nano/micro-architecture: synthesis and ethanol sensing properties

Recently, spinel cobalt oxide (Co3O4) nanostructure has received great interest because of its enhanced gas sensing properties and it offers many opportunities in the sensing field. In the research reported in this paper, spinel Co3O4 compounds with various morphologies were prepared by a simple solvothermal process and then applied for gas detection. The structure, morphology and surface characteristics of the as-obtained products were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscope, Brunauer–Emmett–Teller and inductively coupled plasma mass spectrometry analysis. These analyses revealed that the morphologies of the Co3O4 nanostructures could be accurately controlled by employing different solvents. To highlight their potential application, gas sensors based on the as-synthesized products were fabricated to test their sensing performances. The test data indicated that the needle-shaped Co3O4 compounds had a superb kinetic response and excellent selectivity towards some pollutant volatile organic compounds at an operating temperature of 170 °C, especially ethanol. As such, these hierarchical Co3O4 needle-shaped microspheres are a promising candidate for a high-performance gas sensing material.

Fabrication of CeO2/ZnCo2O4 n–p heterostructured porous nanotubes via electrospinning technology for enhanced ethanol gas sensing performance

Nanocomposite materials with a one-dimensional structure have rapidly developed in recent years. Metal oxides are applied in a wide range of daily applications. In this paper, pure CeO2 and composite CeO2/ZnCo2O4 nanotubes are successfully synthesized by single capillary electrospinning technology and post heat treatment. The structure and composition of pure CeO2 and the composite CeO2/ZnCo2O4 nanotubes are confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM) images identify the as-synthesized materials as hollow, mesoporous structures; the long nanotubes of both samples have a diameter around 60 nm, and the composite CeO2/ZnCo2O4 has a high porosity. The surface structure characteristics of these samples are characterized by N2 absorption–desorption isothermal analysis (Brunauer–Emmett–Teller, BET) and a large surface area is exhibited for the composite CeO2/ZnCo2O4 nanotubes of 80.989 m2 g−1. The QR-2 gas sensing system was used to measure the gas sensing properties of the test materials. We show an excellent improvement in the response and selectivity of the n–p heterojunction CeO2/ZnCo2O4 nanotubes in comparison with pure CeO2 nanotubes to ethanol gas at an optimal temperature of 180 °C. The gas sensing mechanism of the as-obtained materials toward ethanol gas is discussed. This material has promising potential in the gas sensing field.

Impact of addition sheet-like cobalt in ionic liquids mixture to detect oxygen

The incorporation of 1-alkyl-3-methylimidazolium hexafluorophosphate (AMIMPF6) and 1-vinlyimidazole (VIM) firstly served as electrolyte for oxygen sensor, which remarkably promoted response current. Moreover, the sheet-like structure of cobalt was deposited onto the surface of C@TiC nanowire (Co/C), which endowed the imidazole-based ionic liquid electrolyte with plentiful active sites and fast electron transfer rate for oxygen reduction reaction. There was little literature about the integration of AMIMPF6, VIM and Co/C as the electrolyte for oxygen sensor. The synergistic effect among all components was realized and maximized, leading to a superior performance of oxygen sensing compared to any component alone. The most important was that the composite material showed a fast response towards oxygen with an excellent linear relationship.

Economical, facile synthesis of network-like carbon nanosheets and their use as an enhanced electrode material for sensitive detection of ascorbic acid

A highly sensitive electrochemical sensor for the detection of ascorbic acid (AA) was first fabricated using network-like carbon nanosheets (NCN) as an enhanced electrode modifier. Novel carbon nanosheets were synthesized from willow catkin via a high temperature carbonization and chemical activation process with the aid of potassium hydroxide (KOH). The formation of porous and interconnected structures of the resulting product was characterized by various experiment techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and nitrogen isothermal adsorption–desorption technique. The network-like carbon nanosheet modified glassy carbon electrode (NCN/GCE) exhibited excellent electrocatalytic activity for the electrochemical oxidation of ascorbic acid owing to the unique network-like and partially graphitic structure. The amperometric curve of AA on the NCN/GCE showed a quick current response, a fine linear consistency of the peak current with the concentration of AA, a low detection limit and an excellent selectivity. Based on these excellent properties, a new sensing platform was developed and verified by the determination of ascorbic acid in commercial injections.