The ability of graphene to transduce an adsorption event of ions into a detectable electrical signal has sparked a lot of interest for its use in sensors. However, a low concentration of the chemically active sites for binding analytes on the graphene surface has significantly prevented its applications so far. Here, we report on implementation of the van der Waals heterostructure based on a monolayer graphene and an ∼1-nm-thick molecular carbon nanomembrane (CNM) in a solution-gated field-effect transistor (FET) for pH sensing. The nondestructive functionalization of a graphene FET with the amino-terminated CNM (NH₂-CNM) enables the induction of chemically active groups in the vicinity of the graphene sheet, maintaining its charge carrier transport properties. We applied complementary characterization techniques, including Raman spectroscopy, x-ray photoelectron spectroscopy, and optical and atomic force microscopy as well as field-effect and electrical impedance measurements to characterize the engineered NH₂-CNM/graphene devices. We demonstrate their high pH resolution with a minimum detectable pH change of ∼0.01 at pH 2 and ∼0.04 at pH 12, with a response time in the range of seconds, and we apply an electrical double-layer model to rationalize the experimentally observed performance theoretically. The developed device concept enables the engineering of microscale pH sensors for applications in biological and environmental sciences.

中文翻译：

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基于端氨基碳纳米膜和单层石墨烯范德华异质结构的 pH 传感器

石墨烯将离子的吸附事件转换为可检测的电信号的能力引起了人们对其在传感器中使用的兴趣。然而，迄今为止，石墨烯表面上用于结合分析物的低浓度化学活性位点已大大阻碍了其应用。在这里，我们报告了基于单层石墨烯和~1nm 厚的分子碳纳米膜 (CNM) 在用于 pH 传感的溶液门控场效应晶体管 (FET) 中的范德华异质结构的实现。具有氨基封端的 CNM (NH ₂-CNM) 能够在石墨烯片附近诱导化学活性基团，保持其电荷载流子传输特性。我们应用了互补的表征技术，包括拉曼光谱、X 射线光电子能谱、光学和原子力显微镜以及场效应和电阻抗测量来表征工程化的 NH ₂-CNM/石墨烯器件。我们证明了它们的高 pH 分辨率，在 pH 2 时可检测到的最小 pH 变化为 ~0.01，在 pH 12 时为 ~0.04，响应时间在几秒钟的范围内，我们应用双电层模型来合理化实验观察到的性能理论上。开发的设备概念使微型 pH 传感器工程能够应用于生物和环境科学。