Search

Abstract: We reported a facile and controllable route to prepare nest-like ZnO without any complicate experimental equipments, pressure and gas control procedures. The nest-like ZnO was made within a muffle furnace in air atmosphere under normal pressure through a simple carbon thermal reduction reaction. The product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), field emission scanning electron microscope (FESEM) and photoluminescence (PL). The results showed that the product was wurtzite ZnO and had an interesting hollow nest-like microstructure with a prickly porous shell. The shell consisted of ZnO nanospheres, and a few ZnO nanorods grew on the shell surface. The gas sensing test indicated that the nest-like ZnO had an excellent gas sensing behavior toward ethanol. The response of the sensor to 50ppm ethanol was about 100, which was at least four times more than other gases. Moreover, even down to 1ppm ethanol, the response still reached 3.8. Both the response time and recovery time of the sensor were short. All of these proved that the nest-like ZnO is a promising gas sensing material for ethanol detecting. [Copyright &y& Elsevier]

Measuring the concentration of oxynitride NO x (including NO and NO 2 ) can provide a scientific basis for determining its potential harm to the human body. The existing metal oxide semiconductor sensor arrays are greatly limited by high operating temperature and low integration. In this article, we report on a high-integration carbon nanotubes sensor array with two different electrode separations sensitive to oxynitride mixture at low temperature. The triple-electrode sensor array is comprised of a large carbon nanotube array cathode, two extracting electrodes and two collecting electrodes and worked at non-self-sustaining discharge state, which was determined by the study on current-voltage characteristic of a double-electrode structure sensor. Through studying the relationship between gas concentration and discharge current at 1 atm, we obtained the distinct sensitivities of the binary mixture in the concentration ranges of 0–1166 ppm NO and 0–712 ppm NO 2 using the sensor array at low operating voltages and 60 °C. Collecting currents of the two sensors in the array decreased with increasing NO and NO 2 concentration in the gas mixture. The repeatable characteristics and dynamical response tests of the sensors were also conducted. The proposed sensor array has potential for the direct detection of a NO-NO 2 mixture without separating the mixed gases. [ABSTRACT FROM AUTHOR]

NO 2 is the representative pollutant in air quality monitoring and power industry. Although numerous gas sensors have been employed for the accurate detection of NO 2 , a universal method sieving for the optimum sensor is still lacked. Herein, a strategy to acquire the optimal NO 2 -sensitive material has been proposed, and a series of tests verified its effectiveness. First, the serious noise would exist in the gas sensors with the high resistivity, so an appropriate baseline resistance is the basis for the practical application. Furthermore, the performances of SnCl 2 -In 2 O 3 doped with six metal oxides (CuO, NiO, TiO 2 , SnO 2 , WO 3 , ZnO) on NO 2 were investigated. The quantitative evaluation method that integrated the variation coefficient method (VCM), the technique for order preference by similarity to ideal solution (TOPSIS), and the grey correlation analysis (GRA) has been proposed to solve the imbalance of sensors' indices. Due to the highest comprehensive score, 10 wt% WO 3 -doped SnCl 2 -In 2 O 3 with high response value (5962.20%) was regarded as the optimum for NO 2 detection. Ultimately, an additional comparative test among the as-prepared sensors, previous investigations and commercial devices has demonstrated the great potential of the method in practice. • Verifying the gas-sensitive material needs proper resistance for practical use. • Providing a comprehensive evaluation method. [ABSTRACT FROM AUTHOR]

Monitoring the gas composition around power cables using gas sensors is a promising method for detecting their overheating. In this paper we screened the sensing performance in dry and humid conditions of a variety of commercial and homemade sensors. The target gases were 2-Ethylhexanol (2-EH), Dioctyl terephthalate (DOTP), and Benzene; they are the main gases evaporated from overheated polyvinyl chloride (PVC), which is the material of choice for the external insulation of power cables. We found that the tested sensors show different sensing performances to the three target gases, generally with a fast response and slow recovery, the latter especially for 2-EH and DOTP. We also found that the responses to DOTP and 2-EH are correlated and, generally, larger than the ones to benzene. We also showed that by combining the sensors into a sensor array and applying PCA it is possible to distinguish between 2-EH and DOTP, on the one hand, and benzene, on the other hand. However, a more refined pattern recognition method is needed to distinguish between 2-EH and DOTP. • Sensing performance of various sensors was examined for diagnosing the overheating of PVC insulators. • Sensing patterns for DOTP and 2-EH are quite similar and different from the ones corresponding to benzene. • Common functional groups in DOTP and 2-EH are vital. Benzene likely reacts with the surface material initially via π bond. • Best candidates seem to be commercially availables TGS822 and TS2620 and homemade sensors based on Pd-In 2 O 3 and Au-WO 3. [ABSTRACT FROM AUTHOR]