Sridhar Arun Siddarth, Chen Xiaoyu, Glossmann Tobias, Yang Ziming, Xu Yong, Lai Wei, Zeng Xiangqun
Department of Chemistry, Oakland University, Rochester Hills, Michigan 48309, United States.
Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan 48202, United States.
ACS Sens. 2023 Jan 27;8(1):197-206. doi: 10.1021/acssensors.2c02040. Epub 2023 Jan 11.
Continuous greenhouse gas monitoring at sub-zero temperatures is needed for monitoring greenhouse gas emission in cold environments such as the Arctic tundra. This work reports a single-frequency electrochemical impedance sensing (SF-EIS) method for real-time continuous monitoring of carbon dioxide (CO) at a wide range of temperatures (-15 to 40 °C) by using robust ionic liquid (IL) sensing materials and noninvasive, low-power, and low-cost impedance readout mechanisms since they cause minimal changes in the sensing interface, avoiding the baseline change for long-term continuous sensing. In addition, a miniaturized planar electrochemical sensor was fabricated that incorporates a hydrophobic 1-butyl-1-methylpyrrolidinium bis(trifluromethylsulfonyl)imide ([Bmpy][NTf]) IL electrolyte and Pt black electrode materials. The high viscosity of the ILs facilitates the formation of thin, ordered, and concentrated layers of ionic charges, and the inverse relationship of IL viscosity with temperature makes them especially suited for impedance sensing at low temperatures. The unique low-temperature properties of ILs together with EIS transduction mechanisms are shown to be sensitive and selective for continuously monitoring CO at a -15 to 40 °C temperature range via impedance changes at a specifically selected frequency at the open circuit potential (OCP). Molecular dynamics simulations revealed insights into the structure and dynamics of the IL at varying temperatures in the presence of methane and CO and provided potential explanations for the observed sensing results. The miniaturized and flexible planar electrochemical sensor with the [Bmpy][NTf] electrolyte was tested repeatedly at subzero temperatures over a 58-day period, during which good stability and repeatability were obtained. The CO impedance sensor was further tested for sensing CO from soil samples and shows promising results for their use in real-time monitoring of greenhouse gas emissions in cold temperatures such as permafrost soils.
在北极冻原等寒冷环境中监测温室气体排放需要在零下温度下进行连续的温室气体监测。这项工作报告了一种单频电化学阻抗传感（SF-EIS）方法，该方法通过使用坚固的离子液体（IL）传感材料以及无创、低功耗和低成本的阻抗读出机制，在很宽的温度范围（-15至40°C）内对二氧化碳（CO₂）进行实时连续监测，因为它们在传感界面引起的变化最小，避免了长期连续传感时基线的变化。此外，还制造了一种小型化平面电化学传感器，该传感器包含疏水性的1-丁基-1-甲基吡咯烷鎓双（三氟甲基磺酰）亚胺（[Bmpy][NTf]）离子液体电解质和铂黑电极材料。离子液体的高粘度有助于形成薄的、有序的和浓缩的离子电荷层，并且离子液体粘度与温度的反比关系使其特别适合于低温下的阻抗传感。结果表明，离子液体独特的低温特性与EIS转换机制在开路电位（OCP）下通过特定选择频率处的阻抗变化，在-15至40°C温度范围内对连续监测CO₂具有灵敏性和选择性。分子动力学模拟揭示了在存在甲烷和CO₂的情况下，离子液体在不同温度下的结构和动力学，并为观察到的传感结果提供了潜在解释。带有[Bmpy][NTf]电解质的小型化且灵活的平面电化学传感器在零下温度下经过58天的反复测试，在此期间获得了良好的稳定性和重复性。该CO₂阻抗传感器进一步用于检测土壤样品中的CO₂，并且在用于如多年冻土等寒冷温度下温室气体排放的实时监测方面显示出有前景的结果。
