Hydrogel- and organohydrogel-based stretchable, ultrasensitive, transparent, room-temperature and real-time NO2 sensors and the mechanism. Issue 7 (10th May 2022)

• Record Type: Journal Article
• Authors: Wei, Yaoming; Wang, Hao; Ding, Qiongling; Wu, Zixuan; Zhang, He; Tao, Kai; Xie, Xi; Wu, Jin
• Is Part Of: Environmental science. Volume 9:Issue 7(2022)
• Page Start: 1921
• Page End: 1934
• Publication Date: 2022-05-10
• Subjects: Environmental sciences -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/d2mh00284a
• Languages: English
• ISSNs: 2051-8153

Abstract

Abstract : Highly stretchable, transparent, ultrasensitive, selective and room-temperature NO2 sensors are created by using ion-conductive hydrogels/organohydrogels. The electrodes play a key role in sensing performances and NO2 tend to react at the cathode. Abstract : Highly stretchable, sensitive and room-temperature nitrogen dioxide (NO2 ) sensors are fabricated by exploiting intrinsically stretchable, transparent and ion-conducting hydrogels and active metals as the novel transducing materials and electrodes, respectively. The NO2 sensor exhibits high sensitivity (60.02% ppm −1 ), ultralow theoretical limit of detection (6.8 ppb), excellent selectivity, linearity and reversibility at room temperature. Notably, the sensitivity can be maintained even under 50% tensile strain. For the first time, it's found that the metal electrodes significantly impact the sensing performance. Specifically, the sensitivity is boosted from 31.18 to 60.02% ppm −1 by replacing the anodic silver with copper–tin alloy. Importantly, by applying specially designed sensing tests, and microscopic and composition analyses, we have obtained the inherent NO2 sensing mechanism: the anodic metal tends to be oxidized and the NO2 molecules tend to react in the cathode–gel interface. The introduction of glycerol converts the hydrogel into the organohydrogel with remarkably enhanced anti-drying and anti-freezing capacities and toughness, which effectively improved the long-time stability of the sensors. Importantly, we execute sound/light alarms and a wireless smartphone alarm by utilizing a designed circuit board and applet. This work gives an incisive investigation for the preparation, performance improvement, mechanism and application of hydrogel-based NO2 sensors, promoting the evolution of hydrogel ionotronics.