Improved Gas-sensing Performance Research Articles

Polythiophene-WO3 hybrid architectures for low-temperature H2S detection

This paper describes the low-temperature detection of hydrogen sulphide (H2S) using sensors based on organic–inorganic hybrids. Nanosheet-assembled WO3 architectures were prepared by a facile hydrothermal strategy using citric acid as capping agent. The resultant WO3 was further modified with polythiophene through in-situ polymerization of the adsorbed thiophene monomers on the surface of WO3 framework. The morphology, structure and thermal stability of obtained polythiophene-WO3 (PT-WO) hybrids were investigated in detail by FESEM, XRD, FT-IR, XPS and TG analysis. It is proved that there is a strong bonding interaction between PT and WO3 due to the electron transfer from S to W. Gas-sensing tests show that the PT-WO hybrids exhibit high response, good selectivity and fast recovery to ppm-level H2S at low operating temperature of 70°C. The improvement of gas-sensing performance is attributed to the formation of p–n junction at the interface between organic PT and inorganic WO3.

An MWCNT-doped SNO2 thin film NO2 gas sensor by RF reactive magnetron sputtering

An MWCNT-doped (multi-walled carbon nanotube) SnO2 thin film NO2 gas sensor, prepared by radio frequency reactive magnetron sputtering, showed a high sensitivity to ultra-low concentrations of NO2 in the parts per billion range. X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy (SEM) characterizations indicated that the MWCNTs were affected by the morphology of the SnO2 thin film and the particle size. The properties of the MWCNT-doped SnO2 sensor, such as sensitivity, selectivity, and response-recovery time, were investigated. Experimental results revealed that the MWCNT-doped SnO2 thin film sensor response to NO2 gas depended on the operating temperature, NO2 gas concentration, thermal treatment conditions, film thickness, and so on. The mechanism of the gas-sensing property of the MWCNT-doped Sn22 thin film sensor was investigated and showed that the improved gas-sensing performance should be attributed to the effects between MWCNTs (p-type) and SnO2 (n-type) semiconductors.

Inclusion of SWCNTs in Nb/Pt co-doped TiO 2 thin-film sensor for ethanol vapor detection

Nb-Pt co-doped TiO 2 and the hybrid SWCNTs/Nb-Pt co-doped TiO 2 thin films have been prepared by the sol–gel spin-coating process for gas-sensor fabrication. Field emission scanning electron microscope (FE-SEM, TEM and X-ray diffraction (XRD) characterizations indicated that the SWCNTs inclusion did not affect the morphology of the TiO 2 thin film and the particle size. Additionally, the SWCNTs were well embedded in the TiO 2 matrix. The gas-sensing properties of Nb–Pt co-doped TiO 2 thin films with and without SWCNTs inclusion were investigated. The hybrid sensors with the inclusion of different SWCNTs contents are examined to elucidate the effect of SWCNTs content on the gas-sensing properties. Experimental results revealed that the responses to ethanol of Nb–Pt co-doped TiO 2 sensors with SWNCTs inclusion increase by factors of 2–5 depending on the operating temperature and the ethanol concentration, compared to that of the sensor without SWCNTs inclusion. Moreover, all hybrid sensors can operate with high sensitivity and stability at a relatively low operating temperature (<335 °C). The responses of the hybrid sensors are greatly affected by SWCNTs content inclusion. The optimized SWCNTs content of 0.01% by weight was obtained for our experiment. The improved gas-sensing performance should be attributed to the additional formation of the p/n junction between SWCNTs (p-type) and TiO 2 (n-type).