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Abstract: N-type Fe2O3 nanobelts and P-type LaFeO3 nanobelts were prepared by electrospinning. The structure and micro-morphology of the materials were characterized by X-ray diffraction (XRD) and scanning of electron microscopy (SEM). The gas sensing properties of the materials were investigated. The results show that the optimum operating temperature of the gas sensors fabricated from Fe2O3 nanobelts is 285°C, whereas that from LaFeO3 nanobelts is 170°C. Under optimum operating temperatures at 500ppm ethanol, the response of the gas sensors based on these two materials is 4.9 and 8.9, respectively. The response of LaFeO3-based gas sensors behaves linearly with the ethanol concentration at 10–200ppm. Sensitivities to different gases were examined, and the results show that LaFeO3 nanobelts exhibit good selectivity to ethanol, making them promising candidates as practical detectors of ethanol. [Copyright &y& Elsevier]

Abstract: KCl-doped ZnO nanofibers are synthesized via an electrospinning method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The humidity sensing properties of these nanofibers are investigated by screen-printing them on a ceramic substrate with a pair of Ag–Pd interdigitated electrodes. The experimental results show that the 5.7wt% KCl-doped ZnO nanofibers hold super-rapid response and recovery, high response value, good reproducibility, linearity, selectivity, and stability at 100Hz. Especially, the response time and recovery time is only about 2 and 1s, respectively. These results demonstrate the potential application of KCl-doped ZnO nanofibers for fabricating high performance humidity sensors. [Copyright &y& Elsevier]

Abstract: Dumbbell-like ZnO microcrystals have been obtained through a facile solution method. The structure, morphology and optical properties of the as-prepared ZnO microcrystals have been characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and photoluminescence. The as-prepared ZnO microcrystals exhibit excellent sensing properties against acetone at an operating temperature of 300°C. The response and recovery times are found to be 1.5 and 3s, respectively. Moreover, the sensor holds the successful discrimination between acetone and ethanol, which makes our product a good candidate in fabricating highly selective sensors in practice. [Copyright &y& Elsevier]

Abstract: Pure and Sm2O3-doped SnO2 are prepared through a sol–gel method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The sensor based on 6wt% Sm2O3-doped SnO2 displays superior response at an operating temperature of 180°C, and the response magnitude to 1000ppm C2H2 can reach 63.8, which is 16.8 times larger than that of pure SnO2. This sensor also shows high sensitivity under various humidity conditions. These results make our product be a good candidate in fabricating C2H2 sensors. [Copyright &y& Elsevier]

Graphical abstract Highlights • In this work, the obtained Zn 2 SnO 4 -RGO hybrids exhibited outstanding sensing performance for detecting oxidizing gases (NO 2 and O 3) with very low cross sensitivities to reducing gases, such as C 2 H 5 OH, CH 3 COCH 3 and CO. • The Zn 2 SnO 4 -RGO based sensors exhibited high response values of up to 3.50 for 500 ppb NO 2 , which is higher than that for detection of 500 ppb O 3 (1.78) at 30 °C under 50% relative humidity (RH). • The surface reaction between Zn 2 SnO 4 -RGO hybrids and NO 2 can be concluded from Operando diffuse reflectance infrared Fourier transformed spectroscopy (Operando DRIFT). Abstract Highly selective oxidizing gas sensors are of great importance for environmental pollution monitoring. In this work, a hybrid material containing Zn 2 SnO 4 nanoparticles (NPs) and immobilized reduced graphene oxide (Zn 2 SnO 4 -RGO) was developed as a high performance gas sensing material for the detection of ppb-levels of oxidizing gases (NO 2 and O 3). The structural, morphological and compositional properties of the Zn 2 SnO 4 -RGO hybrids were systematically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), which demonstrated the successful anchoring of Zn 2 SnO 4 NPs on RGO nanosheets. The obtained Zn 2 SnO 4 -RGO hybrids exhibited outstanding sensing performance for detecting oxidizing gases (NO 2 and O 3) with very low cross sensitivities to reducing gases, such as C 2 H 5 OH, CH 3 COCH 3 and CO. The Zn 2 SnO 4 -RGO based sensors exhibited high response values of up to 3.50 for 500 ppb NO 2 , which is higher than that for detection of 500 ppb O 3 (1.78) at 30 °C under 50% relative humidity (RH). Moreover, the NO 2 sensing performances of Zn 2 SnO 4 -RGO-based sensors were investigated under various RH. In all cases, the sensors based on RGO and Zn 2 SnO 4 -RGO hybrids presented p-type behavior. The sensors based on Zn 2 SnO 4 -RGO hybrids also exhibited high response values of up to 3.62 for 1 ppm NO 2 at 50 °C in 80% RH, which is much higher than that of pure RGO (1.31). The excellent sensing performances are mainly ascribed to the synergetic effect of Zn 2 SnO 4 NPs and RGO. Furthermore, the surface reaction between Zn 2 SnO 4 -RGO hybrids and NO 2 can be concluded from Operando diffuse reflectance infrared Fourier transformed spectroscopy (Operando DRIFT). [ABSTRACT FROM AUTHOR]

Pt-loaded mesoporous WO 3 was fabricated by nanocasting method. Mesoporous structure provided ordered tunnel which was convenient for gas diffusion and the large specific surface area which could offer more active sites. The noble metal (Pt) improved the catalytic efficiency which played crucial role in enhancing the performance of the gas sensor. The obtained materials were characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Characterization indicated that the synthesized materials had ordered mesoporous structure with excellent crystallinity and the pore size was about 10.6 nm. Static test system was employed to measure ammonia sensing properties for the as-prepared samples. The sensor based on Pt-loaded WO 3 presented higher sensitivity, quicker response-recovery rates, excellent repeatability and selectivity. It indicated that the Pt-loaded mesoporous WO 3 was a potential ammonia gas sensor material. [ABSTRACT FROM AUTHOR]

The development of graphene-based room temperature gas sensors has drawn massive attention due to their unique advantage of gas sensing at room temperature. In this paper, in pursuit of developing high-performance graphene-based gas sensors, a NO 2 gas sensor has been successfully fabricated using sulfonated reduced graphene oxide (S-rGO) anchoring with SnO 2 nanoparticles as sensing materials. The SnO 2 nanoparticles modified S-rGO (SnO 2 /S-rGO) hybrids were prepared by deposition of SnO 2 nanoparticles on the surface of S-rGO through hydrothermal synthesis method. The combined characterizations of X-ray diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive spectroscopy, as well as N 2 sorption isotherm indicate the successful preparation of SnO 2 /S-rGO hybrids with porous structure. Most importantly, SnO 2 /S-rGO hybrids exhibit good sensing performances for detection of NO 2 at room temperature, such as high response, fast response and recovery rate, and good selectivity. The sensor based on SnO 2 /S-rGO hybrids exhibits better sensing performances than the previously reported rGO-based gas sensors. Furthermore, the excellent sensing performances of sensor based on SnO 2 /S-rGO also render it suitable for development of high performance gas sensors operated at room temperature. [ABSTRACT FROM AUTHOR]

A facile and effective strategy has been successfully developed to synthesize reduced graphene oxide-multiwalled carbon nanotubes-tin oxide nanoparticles (rGO-CNT-SnO 2 ) hybrids by hydrothermal method. The combined characterizations of X-ray diffraction, Raman spectrum and Transmission electron microscopy were used to characterize the samples thus obtained, indicating the successful preparation of rGO-CNT-SnO 2 hybrids. A room temperature NO 2 sensor was fabricated by dropping the dispersion of rGO-CNT-SnO 2 hybrids on the surface of ceramic substrate previously printed Au electrodes. Most importantly, the sensor based on rGO-CNT-SnO 2 hybrids shows high response, fast response and recovery rate, high selectivity and good stability, which are much better than NO 2 sensors based on pure rGO and rGO-SnO 2 hybrids. [ABSTRACT FROM AUTHOR]

Highly sensitive and selective toluene sensors based on ordered mesoporous Co3O4 have been successfully developed. The combined characterizations of X-ray diffraction (XRD) patterns, nitrogen adsorption–desorption isothermal, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) indicate that mesoporous Co3O4 with ordered mesoporous structure and high surface area has been successfully prepared by the nanocasting method using mesoporous silica (SBA-15) as hard template and Co(NO3)2·6H2O as cobalt source. It is also found that mesoporous Co3O4 thus obtained shows good response toward toluene with the concentrations ranging from 1ppm to 1000ppm. Furthermore, mesoporous Co3O4 also exhibits high selectivity for detection of toluene, compared to other interferences, such as ethanol, formaldehyde, ethanol, acetone, methanol and ammonia. Most importantly, mesoporous Co3O4 exhibits better sensing performance than that of non-porous Co3O4 obtained by direct calcination of Co(NO3)2·6H2O in the absence of any templates, which can be attributed to unique properties of mesopotous Co3O4, such as high surface area, open mesoporous structure as well as relatively small crystal size. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous LaFeO3 with high surface area and pore volume was prepared through a nanocasting route by using mesoporous silica SBA-15 as a hard template. The structure and chemical composition of the sample were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS). The humidity sensing properties of the mesoporous LaFeO3 were investigated. Impedance greatly changes by more than five orders magnitude (1.7×106 to 4.5kΩ) when the relative humidity varies from 11% to 98% at 10Hz, and it also exhibits the satisfactory response time, hysteresis and stability. The sensor utilizing mesoporous LaFeO3 via nanocasting method displays superior humidity performance compared to that using bulk LaFeO3 via sol–gel technique. Such sensing behavior of the mesoporous LaFeO3 can be attributed to the high surface area (83.2m2/g) and porosity, which lead to highly effective interaction between the water molecules and the surface active sites. A possible mechanism is discussed to explain the excellent performance of the humidity sensing device using the mesoporous LaFeO3. [Copyright &y& Elsevier]

Abstract: Hollow ZnSnO3 microspheres were successfully prepared by hydrothermal method at 160°C for 12h. The prepared material was characterized by field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and X-ray diffraction measurements (XRD). The average diameter of the hollow ZnSnO3 microspheres was in the range of 400–600nm. Compared with solid ZnSnO3 microspheres structure, the hollow ZnSnO3 microspheres showed better response (S) to butane. To 500ppm butane, the sensor response (S) of the hollow ZnSnO3 microspheres was 5.79 at the optimum operating temperature of 380°C, and the response and recovery time were 0.3s and 0.65s, respectively. The sensitivities of sensors based on this material were linear with the concentration of butane in the range of 100–1000ppm. [Copyright &y& Elsevier]