Qiuyue Yang

A low temperature operating gas sensor with high response to NO2 based on ordered mesoporous Ni-doped In2O3

The ordered mesoporous Ni-doped In2O3 and undoped In2O3 nanostructures have been synthesized via a nanocasting method, which is an easy, repeatable and friendly route. The structure of the as-prepared product was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen physisorption and scanning electron microscopy (SEM). The results of XRD and TEM revealed the ordered structure of undoped and Ni-doped In2O3. The wide-angle XRD of the samples revealed that Ni incorporation may lead to lattice deformation without destroying the original crystal structure. Gas sensors based on undoped and Ni-doped In2O3 were fabricated and their gas sensing properties were tested. The Ni-doped In2O3 based sensor showed excellent selectivity toward NO2 at the operating temperature of 58 °C and the detection limit was 10 ppb. The response of the sensor based on mesoporous Ni-doped In2O3 was nearly 4 times higher than that of the sensor based on mesoporous undoped In2O3.

Highly sensitive and humidity-independent ethanol sensors based on In2O3 nanoflower/SnO2 nanoparticle composites

As an ethanol sensing material, the composites of In2O3–SnO2 were composed of In2O3 microflowers and SnO2 nanoparticles. Both In2O3 microflowers and SnO2 nanoparticles were synthesized by hydrothermal method and then mixed in an ultrasonic environment. The morphology and phase composition of the as-synthesized samples were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results on gas sensing properties showed that when the mass ratio of In2O3 and SnO2 was 2 : 1, the sensor based on the as-prepared In2O3–SnO2 composite exhibited high response and good selectivity to ethanol at 250 °C. The response to 100 ppm ethanol gas was 53.2. UV illumination stabilized the responses of the sensors while the relative humidity increased. The gas sensing mechanism proposed was that the addition of SnO2 to In2O3 enhanced the catalytic activity for the ethanol reaction, which changed the electrical resistance of the materials. Besides, the morphology was helpful to the gas reaction on the surface of the sensing materials.

Monodisperse WO3 hierarchical spheres synthesized via a microwave assisted hydrothermal method: time dependent morphologies and gas sensing characterization

Monodisperse WO3 hierarchical spheres were successfully synthesized via a microwave assisted hydrothermal method and a subsequent annealing process. The synthesis was performed using peroxopolytungstic acid as a precursor in the presence of sodium sulfate. The effects of hydrothermal reaction time on the microstructure were also investigated and discussed. It is found that the reaction time influences the morphologies in terms of particle sizes and dispersities. A gas sensor based on the as-prepared WO3 was fabricated and tested. The results revealed that the sensor showed relatively good selectivity and repeatability to acetone vapour. When the acetone concentration was in the range of 100 to 1000 ppm, the relationship between the response and the acetone concentration exhibited a good linearity.