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This paper demonstrated a high-performance hydrogen gas sensor based on CuO-reduced graphene oxide (rGO)-CuO sandwiched nanostructure. The CuO-rGO-CuO nanostructure was examined by scanning electron microscopy, X-ray diffraction and transmission electron microscope. The gas sensing characteristics of the CuO-rGO-CuO film sensor were evaluated at room temperature against hydrogen over a wide concentration range, which are better than that of pristine CuO and rGO. High sensitivity, good repeatability, and response-recovery characteristics were achieved in this work. Furthermore, the possible sensing mechanism of the presented sensor was explored. [ABSTRACT FROM AUTHOR]

A metal oxide/graphene composite film-based sensor toward room-temperature detection of ppm-level nitrogen dioxide (NO) gas has been demonstrated. The sensor prototype was constructed on a PCB substrate with microelectrodes, and a tin oxide-reduced graphene oxide (SnO-rGO) composite as sensing film was prepared by one-step hydrothermal synthesis of tin tetrachloride pentahydrate solution in the presence of graphene oxide (GO). The SnO-rGO hybrid composite was examined by scanning electron microscope and x-ray diffraction (XRD). The gas sensing properties of the SnO-rGO composite were investigated at room temperature by exposing it to a wide concentration ranging from 1 ppm to 2000 ppm toward NO gas. The experiment results showed that the sensor exhibited a high response, superior selectivity, good repeatability, rapid response/recovery characteristics and low detection limit of 1 ppm, which exceeded that of a pure rGO sensor. The gas sensing mechanisms of the proposed sensor toward NO were possibly attributed to the nano-hybrid structures and n- p heterojunctions created at the interface of the SnO nanocrystals and rGO nanosheets. [ABSTRACT FROM AUTHOR]

This paper demonstrated a resistive-type humidity sensor with hierarchical ZnO/MWCNTs/ZnO nanocomposite film coated. Hydrothermally synthesized ZnO nanorods and functionalized multi-walled carbon nanotubes (MWCNTs) were utilized to construct a humidity sensor by using electrostatic layer-by-layer (ELbL) self-assembly technique. The characterization results including scanning electron microscope and X-ray diffraction confirmed the successful formation of as-prepared nanostructures. The electrical properties of the sensing films were investigated under different deposition time in the ELbL self-assembly process. The humidity sensing behaviors of the ZnO/MWCNTs/ZnO hierarchical hybrid film were investigated in a wide relative humidity (RH) range. It is found that the sensor exhibited an excellent linear response with RH, small hysteresis, acceptable repeatability and swift response-recovery characteristics. The possible sensing mechanism for the presented sensor was attributed to the nanostructure of ZnO/MWCNTs/ZnO and swelling effects between interlayers. This study provided a benchmark for humidity sensor fabrication using ELbL self-assembly technique. [ABSTRACT FROM AUTHOR]

In this paper, we synthetized a hybrid composite of zinc oxide (ZnO) nanocrystalline-decorated reduced graphene oxide (rGO) via a facile hydrothermal process, and fabricated a methane gas sensor by using the ZnO-rGO hybrid composite as sensing film coated on a ceramic tube with Ni-Cr heater. The presence of nanorod-shaped ZnO nanocrystalline and rGO nanosheets was characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance and photoluminescence spectra measurement. The sensing properties of the ZnO-rGO film sensor were investigated by exposing to various concentration of methane gas at different temperature. It was found that the presented sensor exhibited unique advantages in methane gas sensing with concentration spanning from 100 to 4000 ppm, such as outstanding repeatability, fast response-recovery time as well as good selectivity, at an optimal operating temperature of 190 °C. The gas response of the ZnO-rGO hybrid composite was superior to that of the pure ZnO and rGO counterpart in methane gas sensing. The possible and proposed sensing mechanism for the sensor is mainly attributed to its nano-hybrid structure and special interactions at p-n heterojunction. This observed results highlight the ZnO-rGO hybrid composite as a candidate material for constructing methane gas sensors. [ABSTRACT FROM AUTHOR]

This paper reported a multi-wall carbon nanotubes (MWNTs)/polymer film-based sensor for ethanol gas detection. The film sensor was fabricated using layer-by-layer self-assembly method on the substrate with interdigital electrodes structure. The surface morphology of the self-assembled membranes shows a high strength, dense and random network structures, and the electrical properties of MWNTs/polymer film sensor were investigated. Its ethanol gas-sensing properties with varying gas concentration are characterized at room temperature. The experiment results shown that carboxylic groups attached on the MWNTs surface and the expansion of polyelectrolyte interlayer lead to a prompt response and sensitive resistance change when the sensor exposed to ethanol gas, indicating the unique advantages of layer-by-layer self-assembly of MWNTs/polymer film sensors in prospective application. [ABSTRACT FROM AUTHOR]