High Performance CuO Nanorectangles-Based Room Temperature Flexible NH3 Sensor

Here, we report the fabrication of a flexible room temperature ammonia gas sensor using surfactant-free hydrothermally synthesized copper oxide (CuO) nanorectangles. The structural analysis revealed that the CuO nanorectangles possessed monoclinic structure with an average length and breadth of 950 and 450 nm, respectively. The specific surface area of CuO nanorectangles was determined to be 29 m 2 /g. The sensor was fabricated on a flexible polyethylene terephthalate substrate by screen printing technique. The room temperature ammonia sensing measurement exhibited significant response down to 5 ppm of ammonia with a quick response time of 90 s and recovered to baseline within 120 s. Maximum response of 0.99 was recorded for 100 ppm of ammonia. The rate constants for adsorption and desorption were estimated for 6.5 to 100 ppm of ammonia from the exponential conductance changes during response and recovery process. The sensor showed appreciable stability and reproducibility of the sensing performance over a period of three months. The fabricated flexible sensor demonstrated its ability to detect a wide range of ammonia concentrations at room temperature irrespective of the mechanical deformations applied. Thus, the fabricated sensor is promising and can be suitably employed for practical applications in environments where efficient gas sensing is vitally important

Printed flexible electrochemical pH sensors based on CuO nanorods

Nanostructured metal oxides have attracted significant interest in a range of areas in electrochemical applications such as sensors, supercapacitors, and battery electrodes etc. Printing of these materials on flexible substrates will open new applications for the fabrication of sensors for monitoring the biological-food-medicine-agricultural systems. This paper presents the printed CuO based flexible electrochemical pH sensors. The sensors with interdigitated electrodes, screen printed on flexible substrates, are based on CuO nanostructures having nanorods (NR) morphology. The morphology influences the charge transfer phenomena and hence the sensor performance, as confirmed by the electrochemical studies. The NR based sensors have better stability with respect to conventional nanoflowers (NF). The structural analysis shows NRs exhibit high crystallinity and low surface roughness (130 nm) with respect to NF (192 nm). The sensor capacitance in the test frequency range (20 Hz–10 MHz) decreases exponentially with increase in pH. The CuO NR based sensor exhibits a sensitivity of 0.64 μF/pH in the range pH 5–8.5. The sensor performance towards interfrence to other ions and analytes such as Na+, K+, glucose, and urea was found to have negligible influence (±1.5 nF) on the sensing electrode. The capacitance of sensors is also found to vary with different bending conditions

ZnO/Graphene Composite from Solvent-Exfoliated Few-Layer Graphene Nanosheets for Photocatalytic Dye Degradation under Sunlight Irradiation

ZnO/graphene nanocomposites were prepared using a facile approach. Graphene nanosheets were prepared by ultrasonication-based liquid phase exfoliation of graphite powder in a low boiling point organic solvent, 1,2-Dichloroethane, for the preparation of ZnO/graphene nanocomposites. Structural properties of the synthesized ZnO/graphene nanocomposites were studied through powder XRD and micro-Raman analysis. The characteristic Raman active modes of ZnO and graphene present in the micro-Raman spectra ensured the formation of ZnO/graphene nanocomposite and it is inferred that the graphene sheets in the composites were few layers in nature. Increasing the concentration of graphene influenced the surface morphology of the ZnO nanoparticles and a flower shape ZnO was formed on the graphene nanosheets of the composite with high graphene concentration. The efficiencies of the samples for the photocatalytic degradation of Methylene Blue dye under sunlight irradiation were investigated and 97% degradation efficiency was observed. The stability of the nanocomposites was evaluated by performing five cycles, and 92% degradation efficiency was maintained. The observed results were compared with that of ZnO/graphene composite derived from other methods