Flower-like Hydroxyfluoride-Sensing Platform toward NO₂ Detection

Abstract

We report for the first time using zinc hydroxyfluoride (ZnOHF) for efficient NO2 gas detection. The prepared ZnOHF had a unique flower-like architecture self-assembled by nanorods with a diameter of 150 nm and length of 2–3 μm. The sensing performance toward NO2 detection indicated that the prepared ZnOHF exhibited high response (82.71), short response/recovery time (13 s/35 s) to 10 ppm of NO2, and excellent selectivity at 200 °C, greatly outperforming the ZnO raw material. ZnOHF could work in a wide detection window ranging from 100 ppb to 50 ppm, implying its practical application prospects in both industry and daily life. The excellent sensing behavior of ZnOHF originated mainly from the negligible oxygen ions adsorbed on the material surface, which was caused by the higher work function of ZnOHF. Therefore, almost all conduction band electrons can be used in the NO2 gas sensing.

Decoupling the Conflicting Roles of Photoactivation and Boosting Chemiresistor Response by Pulsed UV Light Modulation

“…Based on the aforementioned analysis, herein, using the widely adopted ZnO as the photoactivated sensing material, ,, we have compared the NO 2 response characteristics under both CU and PULM modes. As present ZnO did not undergo sophisticated morphology/defect/heterostructure engineering, − or noble metal nanoparticle decoration, the response to 20 ppb NO 2 at RT (25 °C) under the optimized CU mode (365 nm UV light, 1.8 mW/cm 2 ) is only 1.9, while the response of the same device could be drastically boosted to 131.3 under PULM mode (UV-off envelope), which is comparable to or better than the state-of-the-art ZnO chemiresistors prepared via morphology/defect engineering or heterostructure coupling. ,− The limit of detection (LoD) of the chemiresistor could be noticeably reduced from 2.6 ppb (CU mode) to 0.8 ppb (PULM mode), which is much lower than the annual average standard of 53 ppb recommended by the US Environmental Protection Agency (EPA) and raises the hope of a real application of semiconductor chemiresistor in ambient air quality monitoring, which has strict requirements on high response for the trace target gas . Besides NO 2 , the response of the ZnO chemiresistor to trace H 2 S and trimethylamine (TMA), as well as the response of 2D MoSe 2 chemiresistor to NO 2 , could also be significantly amplified by PULM, implying a broad applicability of the present strategy for boosting the electrical response of RT chemiresistors toward trace (ppb-level) target gases.…”

SnO2 mesoporous nanoparticle-based gas sensor for highly sensitive and low concentration formaldehyde detection

“…When the sensor is placed in the HCHO test gas, they will be attached to the sensor surface, through the oxygen ions above the REDOX reaction, release electrons to the guide band, so the sensor resistance and surface potential barrier (Ø b ) drops. The reaction is as eqn (7) and (8):…”

“…Metal oxide semiconductors (MOSs) are considered the most excellent sensing materials due to their high sensitivity, good stability, low cost, non-toxic and easy synthesis. [4][5][6][7][8] As one of the earliest gas sensitive materials, SnO 2 (n-type semiconductor) is the most actively research semiconductor material with excellent sensing performances. Up to now, considerable effort has been devoted to maximize the number of coordinative surface sites which would improve the adsorption and catalytic property, 9 of which synthesizing material with porous structure is the preferred approach to increase specic surface area.…”

d-Band Center Optimization of Ti3C2Tx MXene Nanosheets for Ultrahigh NO2 Gas Sensitivity at Room Temperature

“…Nitrogen dioxide (NO 2 ) is an airborne pollutant responsible for a wide variety of human respiratory diseases such as bronchitis and asthma. − NO 2 not only threatens lives but also through photochemical reactions generates toxic smog. , Therefore, the development of highly sensitive and selective NO 2 gas sensors that can effectively identify and monitor toxic gases is in urgent demand.…”