Eco-Friendly Disposable WS2 Paper Sensor for Sub-ppm NO2 Detection at Room Temperature

Abstract

We developed inexpensive and disposable gas sensors with a low environmental footprint. This approach is based on a biodegradable substrate, paper, and features safe and nontoxic electronic materials. We show that abrasion-induced deposited WS2 nanoplatelets on paper can be employed as a successful sensing layer to develop high-sensitivity and selective sensors, which operate even at room temperature. Its performance is investigated, at room temperature, against NO2 exposure, finding that the electrical resistance of the device drops dramatically upon NO2 adsorption, decreasing by ~42% (~31% half a year later) for 0.8 ppm concentration, and establishing a detection limit around~2 ppb (~3 ppb half a year later). The sensor is highly selective towards NO2 gas with respect to the interferents NH3 and CO, whose responses were only 1.8% (obtained for 30 ppm) and 1.5% (obtained for 8 ppm), respectively. Interestingly, an improved response of the developed sensor under humid conditions was observed (tested for 25% relative humidity at 23 °C). The high-performance, in conjunction with its small dimensions, low cost, operation at room temperature, and the possibility of using it as a portable system, makes this sensor a promising candidate for continuous monitoring of NO2 on-site.

High Gas Sensitivity to Nitrogen Dioxide of Nanocomposite ZnO-SnO2 Films Activated by a Surface Electric Field

“…The characteristics of NO 2 sensors based on other materials are presented in Table 5. Sensors operating at room temperature have long response/recovery times [82][83][84][89][90][91][92][93]. The advantage of such sensors is that there is no need for heating to operating temperature, and they can be used indoors.…”

“…Sensors with response/recovery times in the range of 30-180 s have a more complex technology for forming a gas-sensitive layer [86][87][88]93]. Some gas-sensitive materials are unstable over time, in particular metal sulfides [83,85,86].…”

Solvent-free fabrication of broadband WS₂ photodetectors on paper

“…change in the channel resistance due to the increase of temperature induced by light absorption, in the photocurrent generation. The linear power dependence and the slower response time of the devices in vacuum further support this scenario where light would be absorbed by the graphite electrodes, even for photons with energies lower than the WS 2 bandgap, and because of the low thermal conductivity of paper substrate the WS 2 film would start to increase its temperature that would lead to a decrease of its resistance 32 and thus an increase of the current flowing through the channel.…”

Optimization of multilayer graphene-based gas sensors by ultraviolet photoactivation

“…The responsiveness time can be evaluated using the τ 90 parameter, defined as the time required to achieve the 90 % of the response (Fig. S4) [33,47].…”