A DFT study on the Ag-decorated ZnO graphene-like nanosheet as a chemical sensor for ethanol: Explaining the experimental observations

Intertwining Density Functional Theory and Experiments in the Investigation of Gas Sensing Mechanisms: A Review

In this review, we present the last ten years of progress in evaluation of gas sensing mechanisms. We focus mostly on the studies joining theoretical modeling of gas adsorption by density functional theory method with advanced experimental characterization of sensing materials. We provide the background about important aspects that should be taken into account during the design of the effective sensing device and an overview of the most recently studied sensing materials and analytes. Using the exemplary works, we next show how theory and experiment intertwine in revealing how the sensing mechanism serves to improve the device performance. In the end, we summarize the progress already made despite the existing difficulties, and provide an outlook for future methodological development.

Boosting Gaseous Acetone Detection by Nanoheterojunctions of p-Type MWCNTs/PANI Integrated into 3D Flame-Synthesized n-Type ZnO

Accurate methods for detecting volatile organic compounds (VOCs) are essential for noninvasive disease diagnosis, with breath analysis providing a simpler, user-friendly alternative to traditional diagnostic tools. However, challenges remain in low-temperature VOC solid-state sensors, especially concerning their selectivity and functionality at room temperature. Herein, we present key insights into optimizing multiwalled carbon nanotubes (MWCNTs)/polyaniline (PANI) and ZnO nanocomposites for efficient, light-free selective acetone sensing. We showcased novel nanocomposites prepared by integrating p-type MWCNTs/PANI into a porous 3D network of n-type ZnO nanoparticles, synthesized via flame spray pyrolysis, and varying the weight ratios between ZnO and MWCNTs/PANI (namely 1:1, 8:1, 32:1, 64:1). The 32:1 nanocomposite exhibited superior acetone selectivity over toluene and ethanol, resulting in promise even at room temperature. As such, a potential sensing mechanism was proposed, which involves nanoheterojunction formation between p-type MWCNTs/PANI and n-type ZnO, creating an accumulation layer that enhances the gas response. Moreover, the incorporation of MWCNTs improved the overall conductivity and carrier mobility. Hence, we believe that this work offers valuable insights for optimizing MWCNTs/PANI and ZnO nanocomposites for efficient, low-temperature, light-free gas sensors.

A DFT Study of Volatile Organic Compounds Detection on Pristine and Pt-Decorated SnS Monolayers

Real-time monitoring of volatile organic compounds (VOCs) is crucial for both industrial production and daily life. However, the non-reactive nature of VOCs and their low concentrations pose a significant challenge for developing sensors. In this study, we investigated the adsorption behaviors of typical VOCs (C2H4, C2H6, and C6H6), on pristine and Pt-decorated SnS monolayers using density functional theory (DFT) calculations. Pristine SnS monolayers have limited charge transfer and long adsorption distances to VOC molecules, resulting in VOC insensitivity. The introduction of Pt atoms promotes charge transfer, creates new energy levels, and increases the overlap of the density of states, thereby enhancing electron excitation and improving gas sensitivity. Pt-decorated SnS monolayers exhibited high sensitivities of 241,921.7%, 35.7%, and 74.3% towards C2H4, C2H6, and C6H6, respectively. These values are 142,306.9, 23.8, and 82.6 times higher than those of pristine SnS monolayers, respectively. Moreover, the moderate adsorption energies of adsorbing C2H6 and C6H6 molecules ensure that Pt-decorated SnS monolayers possess good reversibility with a short recovery time at 298 K. When heated to 498 K, C2H4 molecules desorbs from the surface of Pt-decorated SnS monolayer in 162.33 s. Our results indicate that Pt-decorated SnS monolayers could be superior candidates for sensing VOCs with high selectivity, sensitivity, and reversibility.