Optimization of 2D Materials for Atmospheric Monitoring

Real time monitoring of chemical exposure events is crucial for occupational monitoring. However, current hand-held monitors are bulky, cannot identify the specific hazard, and are not designed for continuous use. Therefore, conformal wearable sensors and devices that can identify and quantitate hazardous compounds need to be further developed. Novel sensing materials are required to provide the requisite selectivity and sensitivity for next generation wearable atmospheric monitors. Two-dimensional (2D) materials are an emerging class of nanomaterials that have utility in diverse applications, including biochemical sensors. 2D materials, including graphene (Gr) and molybdenum disulfide (MoS2), have been demonstrated in a multitude of applications, including in biochemical sensing. Most commonly, 2D materials are deposited as nanoflakes, creating a crystalline network that can have its properties modified by the composition/blend of 2D materials selected. However, substantial work remains to understand how electrode material and electrode geometry impact sensor performance. Impedance spectroscopy (IS) provides a robust method towards material characterization. More specifically for nanomaterial inks, IS can interrogate and resolve intraflake resistance (Rintraflake), interflake resistance (Rinterflake), and intraflake capacitance (Cintraflake). This is especially important for atmospheric sensing, as the interfaces of these 2D materials are sensitive to the electrostatic environment, including absorbed analytes. Combining these 2D material electrodes with semi-selective barriers has the promise to enable creation of sensitive, selective atmospheric sensors. Here we present progress towards development of flexible, real-time atmospheric sensing through optimization of 1) the sensor, comprised of 2D materials, 2) the electrode geometry, 3) the interrogation parameters, and 4) the polymeric barrier. In this proceeding, we present specific examples of the importance of each of these parameters, as well as in-depth discussions of key achievements.