RESUMO
To overcome obstacles such as low response and poor selectivity of pure ZnO and SnO2 gas sensors, the ZnO@SnO2 sensor was synthesized by hydrothermal synthesis. The samples were characterized by XRD, XPS, SEM, HRTEM, N2 adsorption-desorption and other techniques. The results show that ZnO@SnO2 forms an n-n-type heterostructure and presents a double-layer capsule with a size of 0.5-4 µm. The results show that compared with pure ZnO and SnO2, the ZnO@SnO2 sensor exhibits a higher response (138.9) to 50 ppm triethylamine (TEA) at 152°C, which is 19.56 times that of the pure ZnO sensor and 21.7 times that of the SnO2 sensor. It has a short response/recovery time (11/11 s), excellent selectivity and cycling stability. Compared with other volatile organic compounds or gases, it has higher selectivity for TEA detection.
Assuntos
Óxido de Zinco , Etilaminas , Gases , Compostos de EstanhoRESUMO
In this study, we have developed a simple and efficient single-nozzle electrospinning strategy involving the phase separation of polystyrene and poly(vinylpyrrolidone) to construct cable-like core-shell mesoporous SnO2 nanofibers. Compared with traditional multi-axial electrospinning approaches to the synthesis of core-shell nanofibers, the single-nozzle electrospinning process requires no complex multi-axial electrospinning setups or post-treatments, just drying and annealing after electrospinning. The obtained SnO2 nanofibers show promise as a sensing material for formaldehyde at low concentrations, the detection limit being about 1â ppm. Furthermore, the nanofibers exhibited good cycling stability and selectivity, with response and recovery times toward 10â ppm formaldehyde being approximately 18 and 196â s, respectively, at an operating temperature of 195 °C.
RESUMO
In this study, a simple and efficient strategy for the construction of hydrangea-like mesoporous WO3 nanoflowers templated using diblock copolymer PS119-PtBA129 was developed. The nanoflower shows good gas sensing properties, especially for 3-hydroxy-2-butanone (3H-2B), which is the signature metabolite of Listeria monocytogenes (L. monocytogenes). Therefore, the gas sensing of 3H-2B by hydrangea-like mesoporous WO3 nanoflowers can be used to detect L. monocytogenes. In the case of 25 ppm 3H-2B as target gas, the response (Ra/Rg) of the hydrangea-like mesoporous WO3 nanoflowers at 205 °C is 152, where Ra and Rg are the resistances of the sensing device in air and target gas, respectively, and the response and recovery times at 25 ppm are 25 s and 146 s, respectively. Schematic illustration of the formation of hydrangea-like mesoporous WO3 nanoflowers and its gas sensing implication.
RESUMO
Cobalt-based zeolitic imidazolate framework nanosheets (ZIF-67) with oxidase-like catalytic activities as an immunoprobe were employed to enhance the sensitivity of an immunoassay. ZIF-67 was synthesized via the solvothermal method using 2-methylimidazole and cobalt dichloride as substrates. A colorimetric immunoassay for Escherichia coli (E. coli) O157:H7 was designed. Preparation of the immunoprobe involved self-polymerized dopamine being applied for the surface modification of ZIF-67 nanosheets in order to bind to the antibody, which was used to identify E. coli O157:H7. ZIF-67 catalyze the oxidation of 3,3',5,5'-tetramethylbiphenyl (TMB) and produced a color change from colorless to blue. Upon reaction termination, the absorbance was measured at 450 nm. By combining ZIF-67@PDA catalyzed chromogenic reaction with antibody recognition and magnetic separation, the limit of determination is 12 CFU mL-1 and the linear range is 30 to 3.0 × 108 CFU mL-1. The proposed colorimetric immunoassay was successfully utilized to detect E. coli O157:H7 of spiked food samples. Graphical abstract.