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The semiconductors based on lanthanum ferrite (LaFeO3) with perovskite structure have received increased attention for gas sensing, due to their stability and high gas-sensing response. However, it remains a challenge to design and fabricate LaFeO3-based gas sensors with high electrical conductivity and low prime working temperature. Based on this consideration, porous LaFeO3 hexagonal nano-sheets were prepared via thermal decomposition of La[Fe(CN)6]·5H2O, which was synthesized by a facile co-precipitation method. The LaFeO3 nano-sheets-based sensor possesses a relatively low resistance, which is 0.5 MΩ under air atmosphere at a low operating temperature of 100 °C, which means a low-power consumption. Moreover, the sensor exhibits an infrequent selectivity to n-propanol. This approach presents an effective way for the control and optimization of the rare earth perovskite nanomaterials for gas sensing. Gas sensor based on the fabricated porous LaFeO3 hexagonal nano-sheets presents a low resistance of 0.5 MΩ and a good sensing performance to n-propanol at a low working temperature of 100 °C. [ABSTRACT FROM AUTHOR]

Lithium iron phosphate (LiFePO4) membranes were fabricated by coating LiFePO4 particles dispersed in various dispersants on tin-diffused glass slides and alumina ceramic tubes for xylene gas detection. The influences of dispersants, including polyvinyl alcohol (PVA), sodium dodecylbenzene sulfonate (SDBS), and methyl methacrylate (MMA), on the optical properties and opto-electrical gas-sensing performance of the LiFePO4 particle-based membranes were investigated. The LiFePO4 particle-based membrane, prepared using PVA, exhibited less agglomeration, better transparency, optimum refractive index, and a higher response toward xylene gas at concentrations of 10 ppb to 1000 ppm in a planar optical waveguide sensor. However, in a resistance-type electrochemical sensing system at room temperature, the LiFePO4-PVA membrane exhibited low response even at high xylene concentrations. The membranes sensitivities increased in the order MMA < SDBS < PVA. After dispersing in PVA, the membrane sensitivity toward xylene was increased ~ 100 times, proving the positive effects of PVA on the optical properties and gas-sensing performance of LiFePO4 particles. [ABSTRACT FROM AUTHOR]

In this study, pure ZnO (ZnO-1, ZnO-2) with two different morphologies, and graphene doped ZnO-2 (G-ZnO-2) were synthesized using a simple hydrothermal process at 150 °C. The formaldehyde gas sensing performance of the G-ZnO-2 composite, synthesized by an in-situ method was investigated. The morphologies and the structures of the nanomaterials were characterized by X-ray diffraction, field emission scanning electronic microscopy, and transmission electron microscopy. The experimental results indicate that the G-ZnO-2 based sensor exhibits unique advantages for the sensing of formaldehyde gas at concentrations in the range of 2 to 2000 ppm, such as fast response/recovery time and good selectivity, at an optimal working temperature of 200 °C. The improved sensing performance of the G-ZnO-2 composite indicates that the addition of graphene is effective in improving the formaldehyde sensing performance of ZnO-based sensors. [ABSTRACT FROM AUTHOR]

The hierarchically porous Sn-Rh codoped ZnO, Sn-doped ZnO and pure ZnO nanosheets have been successfully synthesized through a simple hydrothermal reaction process without any surfactant or template at 180°C. The morphology and composition were carefully characterized by X-ray diffraction, energy dispersive X-ray spectrometer, field emission scanning electronic microscopy and BET. The gas-sensing testing results indicated that the Sn-Rh codoped ZnO nanosheets, with the specific surface area was 26.9 m/g, exhibited enhanced gas-sensing performance compared with that of pure ZnO and Sn-doped ZnO. The high sensitivity of the sensor based on Sn-Rh codoped ZnO was 149.38 to 100 ppm ethanol and the detection limit was less than 5 ppm (5.8). The response and recovery times were measured to be ∼3 s and ∼10 s when exposed to 100 ppm ethanol at the test temperature of 300°C. The good sensing performance of the Sn-Rh codoped ZnO sensor indicated that hierarchically porous Sn-Rh codoped ZnO could be a promising candidate for highly sensitive gas sensors. [ABSTRACT FROM AUTHOR]

Diamond-like carbon films with embedded copper nanocrystallites were deposited on SnO-coated glass substrates by using electrochemical technique. These composite films were subjected to sensing HS gas. Change in the intensity of the characteristic surface plasmon resonance (SPR) peak was recorded with time, and it was observed that the SPR peak disappeared within a short time after exposure to hydrogen sulphide gas. Sensing mechanism was critically analysed. [ABSTRACT FROM AUTHOR]

The stress-responsive bioprocess concept has been developed into an environmentally friendly biosensor with low energy consumption and high recovery yield. To improve chitosanase production during Streptomyces griseus cultivation, heat-stress was applied to the bioprocess with monitoring using an on-line gas sensing system. When exposed to heat-stress with liposomes, the chitosanase productivity was 2.6 times greater than for conventional cultivation. The mixed gas components could be distinguished using a principal component analysis during chitosanase production. The online-monitoring system reflected basic changes in growth conditions and metabolite formation in cells. The array type gas-sensing system was capable of detecting bacterial infection faster than conventional sensor systems. The gas sensor system can play a key role in monitoring and controlling stress levels in a stress-responsive bioprocess. [ABSTRACT FROM AUTHOR]