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Abstract: Doping is an important and effective way to improve the gas-sensing properties of metal oxide semiconductors. ZnO-doped porous SnO2 hollow nanospheres were successfully synthesized by a controllable and scalable route in order to improve their sensor performance, and then characterized by X-ray diffraction (XRD), high-resolution electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS). The comparative gas-sensing properties of the pure porous SnO2 hollow nanospheres and ZnO-doped porous SnO2 hollow nanospheres were also investigated. The ZnO-doped porous SnO2 hollow nanospheres exhibited significantly enhanced ethanol sensing properties, including lower operating temperature, stronger sensitivity, faster response–recovery, and better selectivity. The response (R a/R g) of the prepared ZnO-doped porous SnO2 hollow nanospheres to 100ppm ethanol at 150°C is about 14.7, with the response and recovery times being about 10s and 23s, respectively. The possible gas-sensing mechanism was also discussed. [Copyright &y& Elsevier]

A novel stir bar-shaped ZnO (sb-ZnO)/nitrite-doped reduce grapheme oxide (N-rGO) nanocomposite (sb-ZnO/N-rGO) was facilely synthesized by using the hydrothermal route. Furthermore, a glassy carbon electrode (GCE) modified with the sb-ZnO/N-rGO nanocomposite was constructed and used as the non-enzymatic nitrite electrochemical sensor (sb-ZnO/N-rGO/GCE). Benefiting from the excellent catalytic activity to the electro-oxidation of nitrite as a result of the synergy of N-rGO and sb-ZnO, the modified electrode displayed a superior amperometric sensing performance toward nitrite detection including lower detection limit (LOD) of 0.13 μM, broad linearity range of 0.2 μM~1.2 mM and 1.5–7.8 mM, high sensitivity, rapid response, remarkable repeatability, outstanding durability, good storage stability and strong resistance against interfering substance. In addition, this sensor showed satisfying recovery between 96.0% and 103.0% to nitrite in practical application involved ham sausage, pickled vegetables as well as tap water. The as-synthesized sb-ZnO/N-rGO composite is a qualified candidate for fabricating nitrite electrochemical sensor, which would have promising application prospect in terms of food analysis and environmental monitoring. • stir bar-shaped ZnO/N-rGO nanocomposite was prepared by a facile hydrothermal method. • Systematic study of electrochemical sensing property of sb-ZnO/N-rGO for nitrite. • Sensor was used for detection of nitrite in ham sausage, pickle and tap water. • The electrochemical sensing mechanism of sb-ZnO/N-rGO for nitrite was explored. [ABSTRACT FROM AUTHOR]

Abstract: Uniform porous SnO2 hollow nanospheres with average diameters of about 100–200nm have been reproducibly synthesized via a facile template- and surfactant-free hydrothermal method, using hydrogen peroxide 30% and stannous sulfate as precursors. The morphology, composition and structure of the resultant products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy and nitrogen adsorption–desorption technique. Experimental results demonstrated that the formation of these porous SnO2 nanostructures is ascribed to an interfacial oxidation–dehydration mechanism. H2O2 usage has an important effect on both the morphology and purity of the final products. The gas sensing properties of the as-prepared porous SnO2 hollow nanospheres were investigated. By comparative gas sensing tests, the porous SnO2 hollow nanospheres exhibited superior gas sensing performances over commercial SnO2 nanopowders toward some typical volatile organic compounds (VOCs), implying their promising applications in gas sensors. [Copyright &y& Elsevier]

• Six ZnO materials with different morphology were synthesized by controlling solvent. • Practical application of stir bar-shaped ZnO/Nafion/GCE sensor for nitrite detection in water, ham, pickle. • A dependency between ZnO's sensing property and its morphology was revealed. • Study of ZnO's sensing mechanism for detecting nitrite. Excessive uptake of food or drinking water which is rich in nitrite has been demonstrated to be very hazardous to both the health of humans and animals, so it is of great significance to develop a reliable technique for low-concentration detection of nitrite. Herein, we reported the synthesized zinc oxide which is an excellent electrochemical material for the sensing of nitrite. Interestingly, the ZnO material exhibits a strong dependent relationship between the electrochemical sensing performance and its morphology controlled by the solvent employed in the solvo-thermal method. In particular, the stir-bar shaped ZnO nanorods, with a 40∼90 nm width and 50∼170 nm length, display significantly improved electrocatalytic performance to the electrochemical oxidation of nitrite which is benefited from the more reactive active sites based on the higher dispersion and smaller size. The sensor based on ZnO/Nafion modified glassy carbon electrode (ZnO/Nafion/GCE) shows a broad linear response within the range of 0.3 μM∼6.14 mM and 0.8 μM∼4.86 mM, respectively, for amperometry and linear sweep voltammetry (LSV), the corresponding limit of detection (LOD) were calculated to be 0.21 μM and 0.62 μM, respectively. Also the prepared sensor shows excellent sensitivity, reproducibility, stability and high anti-interference abilities. More importantly, the satisfactory recovery is obtained from ham sausage, pickle and running water, demonstrating the great application prospects of this sensor. In addition, the sensing mechanism of such ZnO sensing to nitrite is also discussed in detail. [ABSTRACT FROM AUTHOR]