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An inorganic-organic hybrid of SnO 2 -reduced graphene oxide (rGO)-polyaniline (SGP) nanocomposite has been successfully synthesized from surfactant-free precursor by a low temperature solution process. The SGP nanocomposite is found to form from in situ synthesized SnO 2 -rGO (SG) and polyaniline (PANI), generated via polymerization of aniline monomer at 5–10 °C. The structural properties of SGP have been analyzed by X-ray diffraction, transmission electron and atomic force microscopes. The chemical interaction existed in the nanocomposite has been examined by X-ray photoelectron, Fourier transform infrared and Raman spectroscopies. Compare to pristine SnO 2 and SG, the SGP sample shows an enhanced ammonia gas sensing at room temperature. At an optimum content of PANI, high sensitivity, fast response and good selectivity of the gas sensing are observed in the nanocomposite. This enhanced sensing performance can be attributed to well-defined p-n hetero junction formation in the hybridized polyaniline and rGO with nano SnO 2 in SGP as confirmed from structural characterization of the sample. It is also seen that the presence of PANI layers in SGP, enhances the chemical stability as reflected from the observation of negligible decrease in the sensing performance of sample up to 30 days period. This facile process can create an avenue for development of various metal oxide semiconductor-graphene-polyaniline nanocomposites for improving room temperature stable ammonia gas sensor. [ABSTRACT FROM AUTHOR]

Cd-Sn oxide nanocomposite powders were synthesized by a facile gel calcination method, starting from precursor sol having Cd:Sn ratio as 2:1. The powders were characterized in terms of their phase formation behaviour and morphological features using X-ray diffractometer, FTIR, UV-visible spectra and FESEM analyses. Sensor fabricated from nanocomposite calcined at 1050 °C exhibited excellent ethanol sensing performance, ~86 % for 50 ppm ethanol vapour. It also revealed quite a good sensitivity at concentration down to 5 ppm vapour. Sensors were quite stable and selective towards ethanol vapour. A possible mechanism for enhanced performance due to formation of preferential perovskite cadmium stannite phase has been discussed. [ABSTRACT FROM AUTHOR]

Metal oxide nanocomposite sensors based on γ-Fe 2 O 3 and WO 3 were investigated in acetone vapor of various concentrations (1–100 ppm) at operating temperatures between 250 and 350 °C. The composites were prepared by simple solid state mixing and porous thick-film gas sensors were fabricated on alumina substrates. The γ-Fe 2 O 3 :WO 3 (50:50) nanocomposite showed a marked enhancement in sensing response down to 1 ppm acetone vapor detection at 300 °C. The response was ~2-fold better compared to pure WO 3 or pure γ-Fe 2 O 3 with a very fast response (1 s) and very short recovery time (3 s). No appreciable sensitivity was observed towards alcohol vapor (an interfacing agent for diabetics) and in moisture (present in breath). The enhanced performance was due to n–n heterojunction effect. [ABSTRACT FROM AUTHOR]

• A ternary nanocomposite containing 3 wt% rGO decorated ZnO-SnO 2 was prepared using a facile sol-gel procedure. • Pristine ZnO-SnO 2 nanocomposite sensor exhibited ~ 60% response towards 10 ppm acetone at operating temperature of 300°C. • ~3wt% rGO addition enhanced the response upto ~ 91% for 10 ppm acetone as well as operating temperature reduced to 150°C. • rGO decorated sensor was capable to detect very low concentration (~1 ppm) of VOCs with fast response and recovery time. • The sensor shows reproducible performance over time with negligible sensing response in other reducing gases. [Display omitted] A ternary p-n-n heterojunction has been prepared by introducing reduced graphene oxide (rGO) in ZnO-SnO 2 nanocomposite and its ppm level volatile organic compounds (VOCs) sensing properties have been exploited. Using a simple, facile sol-gel process, initially, ZnO-SnO 2 nanocomposites containing different concentrations of ZnO and SnO 2 were prepared and subsequently this was followed by rGO incorporation. The as-synthesized powders were well characterized through XRD, FTIR, Raman spectroscopy, FESEM, TEM, and XPS analyses. The sensing study revealed that, the ternary nanocomposite sensor delineated ~91% n-type sensing response towards ~10 ppm acetone gas at an optimum working temperature of 150 °C. Even it could sense ~1 ppm acetone with appreciable sensing response of ~71%. Additionally, the sensor displayed fast response (~10 s) and recovery time (~100 s) suitable for detection of multiple pulses in short time duration. It also exhibited a considerable ~65% sensing response towards ~10 ppm ethanol at 150 °C. These superior sensing performances of rGO decorated ZnO-SnO 2 nanocomposite illustrated with band structure modification. Our results indicated that, the fabricated rGO decorated ZnO-SnO 2 sensor, with remarkable high sensing response, minimum interference from other toxic, inflammable gases and profound long term stability, could be considered as a prolific candidate for real time detection of low concentration VOCs in versatile commercial applications. [ABSTRACT FROM AUTHOR]

In the present work, reduced graphene oxide (rGO) decorated NiO-SnO 2 nanocomposites were synthesized by using a facile sol-gel process and their structural (XRD, FTIR, Raman), morphological (BET, FESEM, TEM), and optical (UV-Vis, PL) characterizations were carried out. The as-synthesized NiO-SnO 2 nanocomposite exhibited an enhancement of surface area after the incorporation of rGO and this substantial increment was expected to be beneficial for gas sensing at room temperature. Therefore, Taguchi-type sensors were fabricated and deployed for the detection of VOCs. The optimized sensor containing ∼ 3 wt% rGO in NiO-SnO 2 nanocomposite demonstrated an excellent sensing response (R g /R a ∼ 7.8) towards ∼ 10 ppm acetone at room temperature (30 ± 5 °C) with response and recovery time of ∼ 10 s and ∼ 30 s respectively. It also exhibited good reproducibility and stability over ∼ 3 months. Additionally, this sensor selectively detected trace concentration (< 1 ppm) of acetone in exhaled human breath (ethanol present in a healthy person's exhaled breath is insignificant), which is a non-invasive biomarker of diabetes. The sensing performance was analyzed from an electronic transportation point-of-view and consequent band structure modulation. The electrical property of the sensing material was illustrated using impedance spectroscopy to support the sensing mechanism. [Display omitted] • rGO decorated NiO-SnO 2 nanocomposites were prepared using sol-gel process. • Optimized Taguchi type sensor showed ∼ 7.8 response in ∼10 ppm acetone at ∼ 30 °C. • Sensor showed reproducible sensing performance and cross sensitivity was negligible. • Optimized sensor used to detect acetone (biomarker of diabetes) in exhaled breath. • The electrical properties of sensors were elucidated by impedance spectroscopy. [ABSTRACT FROM AUTHOR]