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An efficient formaldehyde (HCHO) gas sensor system based on nickel-doped tin oxide (Ni-doped SnO2) nanoparticle sensor and back-end circuit has been developed. Ni-doped SnO2 nanoparticles are prepared by a simple one-step hydrothermal method. To complete the function of detecting HCHO gas in real time, a back-end circuit suitable for resistance measurement of nanoparticle sensors and an organic light emitting diode screen which can display the output of gas concentration data are integrated as a portable device. Compared with the traditional HCHO detection device, this designed system exhibits better stability, excellent selectivity, and high response. Its detection limit is as low as 90 ppb. The gas response to 50 ppm HCHO is 67.63. Further for the quantitative evaluation, we refer to and modify the existing HCHO diffusion model, then carry out a practical test on the HCHO diffusion at the same time. The comparison between the theoretical fitting curve and the actual test curve matched well enough to reflect the potential of this system for the practical HCHO evaluation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bimetallic MOFs-derived hierarchical WO 3 /ZnWO 4 /CoWO 4 heterostructures are gained. • Morphology and sensing behavior of the samples are tuned by the amounts of ZIFs. • Good selectivity and stability of WO 3 -based composites can be observed at 25 °C. • Abundant polyoxometalate electron acceptors are distributed on the coarse surface. • Sensing mechanism is relied on the rapid transport of carriers and plentiful POMs. Bimetallic MOFs-derived hierarchical WO 3 /ZnWO 4 /CoWO 4 heterostructures were prepared by electrospinning for achieving superior n-butanol-sensing property at low operating temperatures. Porous chain-like structures can gradually transformed into porous mulberry-like structures composed of various accumulated particles as increasing the additive amount of Zn/Co-ZIFs. High selectivity and stability of WO 3 -based composites to 100 ppm n-butanol can be observed at 25 °C, including the large sensitivity of 32 and the fast response/recovery times of 115/179 s. The enhanced gas-sensing performance is primarily ascribed to the increased specific surface area, plentiful polyoxometalate, and effective heterojunctions, obviously promoting surface/interface absorption behavior and electron transport process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low temperature TEA-sensing SnS 2 /MnS microflowers are originally fabricated. • DFT simulation shows the transformation from semiconductive to metallic nature. • SnS 2 /MnS-3 % exhibits high responses of 17.85/23.67 to 100 ppm TEA at 30/40 ℃. • The enhanced metallicity plays a vital role of the enhanced gas-sensing behavior. • New strategy for gaining effective sulfide RT gas-sensing materials is presented. The development of low-temperature SnS 2 -based sensitive elements with unique surface adsorption and transport regulation for triethylamine (TEA) has always been an intractable challenge. In the present work, ultrathin SnS 2 /MnS microflowers with enhanced metallicity have been prepared by a facile one-step hydrothermal method, which is especially beneficial for achieving superior TEA-sensing performance under room temperature (RT) condition. Compared with pure SnS 2 , the SnS 2 /MnS-3 % can obviously exhibit higher responses of 17.85 and 23.67, faster response/recovery times of 165/506 and 156/344 s, and the enhanced gas selectivity and stability to 100 ppm TEA at 30 and 40 ℃, respectively. Taking account of density functional theory (DFT) calculation, the transformation of SnS 2 -based sensors from semiconductive to metallic nature plays a critical role of the enhanced gas-sensing behavior with the increased gas molecules absorption and electron transport efficiency, which can provide a new strategy for constructing novel and effective sulfide RT gas-sensing composites. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have received emerging attention due to their rich active sites, layered structure, and suitable electronic structure for gas sensing at room temperature (25 °C). However, the sensitivity, recoverability, stability and selectivity of TMDs-based gas sensors have remained a grand challenge. Herein, a novel 2D/0D molybdenum disulfide (MoS 2)/zinc sulfide (ZnS) based gas sensor was rationally designed via a two-step solution process, enabling high-performance detection of nitrogen dioxide (NO 2) gas at room temperature. Specifically, the MoS 2 /ZnS heterostructures manifest a greatly enhanced response performance (S = 7.2) to 5 ppm NO 2 in comparison with the bare MoS 2 nanosheets. The gas sensor can be completely recovered after re-exposing to the air for 4.6 min at room temperature without using any external auxiliary treatments. Our optimized gas sensor not only exhibits an ultra-low theoretical limit of detection (14 ppb), but also shows an ultrahigh selectivity and outstanding stability. We further showed that the greatly enhanced gas sensing performance of 2D/0D MoS 2 /ZnS can be ascribed to the unique structure as well as the synergistic effects between MoS 2 nanosheets and ZnS nanoparticles from the geometrical, charge transfer, equivalent resistance, and chemical aspects. This work provides a promising approach to the fabrication of high-performance gas sensing materials for environmental monitoring at room temperature. • MoS 2 /ZnS heterostructures were synthesized through wet chemical growth of ZnS nanoparticles on MoS 2 nanosheets. • MoS 2 /ZnS-based gas sensor shows high response of 7.2 towards 5 ppm NO 2 and excellent recoverability at room temperature. • The MoS 2 /ZnS-based gas sensor demonstrates an ultra-low theoretical limit (14 ppb), superb selectivity and stability. • The mechanisms are discussed from the aspects of geometrical, charge transfer, equivalent resistance, and chemical effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • The uniformly dispersed ZnS NPs hinder the accumulation of rGO flakes and enlarge the specific surface area, while the heterojunction barrier effect realizes the high-efficiency response recovery of NO 2 at room temperature. • Flexible sensor shows low power consumption and good anti-bending and anti-fatigue performance. • Developed a watch-type wearable room temperature NO 2 detection device, which realizes real-time monitoring of target gas by smart terminals through Bluetooth wireless transmission. Wearable electronics consists of mechanically flexible sensor networks and the corresponding circuit system can provide real-time monitoring and recording of toxic gases. In this work, we present a convenient watch-type wearable nitrogen dioxide (NO 2) sensor based on ZnS nanoparticles/nitrogen-doped reduced graphene oxide (ZnS NPs/N-rGO) as a flexible device. The power consumption of the flexible sensor is as low as 0.52 μW. The response value of the device for 10 ppm NO 2 is 2.2; while the recovery time is 724 s, with a low theoretical limit of detection at 69 ppb, with the device maintaining stable mechanical durability. By reading and analyzing the signal data through wireless bluetooth transmission, the device can provide timely monitoring and early warning for NO 2 leakage. Furthermore, the impressive room-temperature sensing performance of ZnS NPs/N-rGO is attributed to factors of geometrical and electronic effects. More specifically, ZnS NP uniformly dispersed on rGO greatly expands the effective contact area with the target gas molecules, and the built-in electric field formed by the strong charge interaction between them also effectively improves the detection sensitivity. The successful development of this type of wireless wearable sensor provides an effective reference for the future application and development of high-performance, low-power, and lightweight sensing equipment. [ABSTRACT FROM AUTHOR]