Fachgebiet Nanotechnologie, Technische Universität Ilmenau, 98693, Ilmenau, Germany.
School of Civil Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia.
Mikrochim Acta. 2022 Apr 21;189(5):196. doi: 10.1007/s00604-022-05254-0.
To meet requirements in air quality monitoring, sensors are required that can measure the concentration of gaseous pollutants at concentrations down to the ppb and ppt levels, while at the same time they exhibiting high sensitivity, selectivity, and short response/recovery times. Among the different sensor types, those employing metal oxide semiconductors (MOSs) offer great promises as they can be manufactured in easy/inexpensive ways, and designed to measure the concentration of a wide range of target gases. MOS sensors rely on the adsorption of target gas molecules on the surface of the sensing material and the consequent capturing of electrons from the conduction band that in turn affects their conductivity. Despite their simplicity and ease of manufacturing, MOS gas sensors are restricted by high limits of detection (LOD; which are typically in the ppm range) as well as poor sensitivity and selectivity. LOD and sensitivity can in principle be addressed by nanostructuring the MOSs, thereby increasing their porosity and surface-to-volume ratio, whereas selectivity can be tailored through their chemical composition. In this paper we provide a critical review of the available techniques for nanostructuring MOSs using chemiresistive materials, and discuss how these can be used to attribute desired properties to the end gas sensors. We start by describing the operating principles of chemiresistive sensors, and key material properties that define their performance. The main part of the paper focuses on the available methods for synthesizing nanostructured MOSs for use in gas sensors. We close by addressing the current needs and provide perspectives for improving sensor performance in ways that can fulfill requirements for air quality monitoring.
为了满足空气质量监测的要求，需要能够测量气体污染物浓度达到 ppb 和 ppt 水平的传感器，同时具有高灵敏度、选择性和短的响应/恢复时间。在不同的传感器类型中，那些采用金属氧化物半导体 (MOS) 的传感器具有很大的应用前景，因为它们可以通过简单/廉价的方式制造，并设计用于测量广泛范围内的目标气体浓度。MOS 传感器依赖于目标气体分子在传感材料表面的吸附以及从导带捕获电子，这反过来又影响它们的电导率。尽管它们简单易用，但 MOS 气体传感器受到高检测限 (LOD; 通常在 ppm 范围内) 的限制，以及灵敏度和选择性差的限制。通过纳米结构化 MOS，可以在一定程度上解决 LOD 和灵敏度问题，从而提高其孔隙率和表面积与体积比，而选择性可以通过其化学成分来调整。在本文中，我们提供了使用化学电阻材料对 MOS 进行纳米结构化的现有技术的批判性综述，并讨论了如何将这些技术用于为最终的气体传感器赋予所需的特性。我们首先描述了化学电阻传感器的工作原理以及决定其性能的关键材料特性。本文的主要部分重点介绍了用于气体传感器的纳米结构化 MOS 的现有合成方法。最后，我们讨论了当前的需求，并提供了改进传感器性能的观点，以满足空气质量监测的要求。
