Highly confined plasmon modes in nanostructured graphene can be used to detect tiny quantities of biological and gas molecules. In biosensing, a specific biomarker can be concentrated close to graphene, where the optical field is enhanced, by using an ad-hoc functional layer (e.g., antibodies). Inspired by this approach, in this paper we exploit the chemical and gas adsorption properties of an ultrathin polymer layer deposited on a nanostructured graphene surface to demonstrate a new gas sensing scheme. A proof-of-concept experiment using polyethylenimine (PEI) that is chemically reactive to CO₂ molecules is presented. Upon CO₂ adsorption, the sensor optical response changes because of PEI vibrational modes enhancement and shift in plasmon resonance, the latter related to polymer-induced doping of graphene. We show that the change in optical response is reversed during CO₂ desorption. The demonstrated limit of detection (LOD) of 390 ppm corresponds to the lowest value detectable in ambient atmosphere, which can be lowered by operating in vacuum. By using specific adsorption polymers, the proposed sensing scheme can be easily extended to other relevant gases, for example, volatile organic compounds.

中文翻译：

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使用可逆化学掺杂调谐的石墨烯等离子体中红外气体传感

纳米结构石墨烯中的高度受限等离子体激元模式可用于检测极少量的生物和气体分子。在生物传感中，可以通过使用临时功能层（例如抗体）将特定的生物标记物集中在石墨烯附近，从而增强光场。受这种方法的启发，本文利用沉积在纳米结构石墨烯表面的超薄聚合物层的化学和气体吸附特性，展示了一种新的气体传感方案。提出了使用对CO ₂分子具有化学反应性的聚乙烯亚胺（PEI）的概念验证实验。当CO ₂吸附后，由于PEI振动模式的增强和等离振子共振的移动，传感器的光学响应发生了变化，后者与聚合物诱导的石墨烯掺杂有关。我们表明，在CO ₂解吸过程中，光学响应的​​变化是相反的。证明的390 ppm的检测限（LOD）对应于在环境大气中可检测到的最低值，可通过在真空中操作降低该最低值。通过使用特定的吸附聚合物，建议的检测方案可以轻松扩展到其他相关气体，例如挥发性有机化合物。