Gas nanosensors for health and safety applications in mining

Abstract

The ever-increasing demand for accurate, miniaturized, and cost-effective gas sensing systems has eclipsed basic research across many disciplines. Along with the rapid progress in nanotechnology, the latest development in gas sensing technology is dominated by the incorporation of nanomaterials with different properties and structures. Such nanomaterials provide a variety of sensing interfaces operating on different principles ranging from chemiresistive and electrochemical to optical modules. Compared to thick film and bulk structures currently used for gas sensing, nanomaterials are advantageous in terms of surface-to-volume ratio, response time, and power consumption. However, designing nanostructured gas sensors for the marketplace requires understanding of key mechanisms in detecting certain gaseous analytes. Herein, we provide an overview of different sensing modules and nanomaterials under development for sensing critical gases in the mining industry, specifically for health and safety monitoring of mining workers. The interactions between target gas molecules and the sensing interface and strategies to tailor the gas sensing interfacial properties are highlighted throughout the review. Finally, challenges of existing nanomaterial-based sensing systems, directions for future studies, and conclusions are discussed.

Fig. 1. Schematic representation of a typical nanosensor interface, the gases of concern in coal mines, the common sensing methods utilized for mine monitoring, and the advantages of nanosensing interfaces. Nanoparticles and nanowires (grey objects) are predominantly used in nanosensor interfaces.

Fig. 2. (A) Illustration of a typical underground coal mine. (B) Typical devices carried by miners. Reprinted with permission from ref. .

Fig. 3. (A) Scheme of the chemical sensitization effect of noble metals incorporated into the sensing interface to improve the sensitivity of MOS sensors. Reproduced with permission from ref. Copyright 2022 Elsevier. (B) Methane sensing mechanism of Cr-doped SnO₂ structures based on successive methane oxidation and a decrease in the width of the depletion layer. Adapted with permission from ref. Copyright 2019 Elsevier. (C) Charge carrier transport across dispersed SnO₂ sites and nonporous graphene with a high surface area, enabling sensitive methane detection. Reprinted with permission from ref. Copyright 2019 Elsevier. (D) Application of 2D vanadium carbide MXene for resistive methane sensing through the interaction of physisorbed methane with the surface functional groups of MXenes. Reproduced with permission from ref. Copyright 2019 American Chemical Society. (E) Methane sensing achieved by the catalytic function and redox cycling of Pt sites in the SWCNTs/Pt-POM composite. Reproduced with permission from ref. Copyright 2020 Proceedings of the National Academy of Sciences.

Fig. 4. (A) Electrochemical methane sensing using IL-based electrolytes. CO₂ generated by successive methane oxidation on the WE, and active oxygen species were used as an internal standard. Adapted with permission from ref. Copyright 2014 Royal Society of Chemistry. (B) Scheme showing a multilayered electrochemical device based on solid-state electrolyte Nafion for methane sensing. Reprinted with permission from ref. Copyright 2018 American Chemical Society.

Fig. 5. (A) Room-temperature CO₂ sensing by a Ag-doped ZnO–CuO (p–n) heterojunction where the charge carrier movement provides more electrons for oxygen chemisorption. This is followed by a reduction in the HAL upon exposure to CO₂. Reprinted with permission from ref. Copyright 2023 Elsevier. (B) Illustration showing the CO₂ sensing mechanism using Ru–WS₂/Au electrodes. Adapted with permission from ref. Copyright 2020 Institute of Physics. (C) EIS-based CO₂ sensing via disruption of the IL assembly at the electrode interface due to CO₂ inclusion. Reproduced with permission from ref. Copyright 2023 American Chemical Society. (D) A FET sensor developed for CO₂ sensing based on an electrolyte-gated mode using an IL and In₂O₃ as the electrolyte and channel forming layer, respectively. Reprinted with permission from ref. Copyright 2020 Elsevier.

Fig. 6. (A) Zeolitic imidazolate framework-derived n-ZnO/p-Co₃O₄ nanomaterials for CO sensing. The sensing nanomaterial presents many oxygen vacancies and enables strong chemisorption. Reprinted with permission from ref. Copyright 2023 Elsevier. (B) Schematic of a potentiometric O₂ sensor based on YSZ solid electrolyte. Adapted with permission from ref. Copyright 2003 Springer. (C) A typical configuration of a mixed mode potentiometric–amperometric O₂ sensor. Reprinted with permission from ref. Copyright 2022, The Authors, under Creative Commons Attribution (CC-BY) license, published by Multidisciplinary Digital Publishing Institute.

Fig. 7. (A) Schematic illustration of molecular packing in TTF-TCNQ CTC. Adapted with permission from ref. Copyright 2009 Institute of Physics. (B) Seed-mediated controlled growth of potassium tetracyanoplatinate sesquihydrate nanowires on gold nanoparticles. Reprinted with permission from ref. Copyright 2017 Taylor & Francis. (C) Substrate-directed electrocrystallization of tetrathiafulvalene bromide (TTFBr) nanowires on patterned gold electrodes. Reprinted with permission from ref. Copyright 2023 John Wiley & Sons, Inc.