Lu Yu-Xuan, Chen Guan-Ying, Lin Fang-Min, Tsai Ming-Hsiu, Lin Chih-Ting
Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106319, Taiwan.
Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei 106319, Taiwan.
ACS Sens. 2025 Sep 26;10(9):6634-6644. doi: 10.1021/acssensors.5c01138. Epub 2025 Jun 17.
Most graphene-sensor researches have focused on direct graphene modifications to enhance performance. However, supporting-substrate effects on graphene sensing mechanisms remain underexplored. Because of graphene 2D architecture, substrates affect its surface potential, wettability, and molecular adsorption. These effects intensify in the presence of polar molecules, e.g., water molecules, further complicating the sensing characteristics. To explore these effects, this study investigates the influence of substrate on the sensing capabilities and mechanisms of graphene field-effect transistors (GFETs) in organic solvents through electrical-transport measurements. Specifically, we compare partially suspended graphene FETs (PS-GFETs) and oxide-supported graphene FETs (OS-GFETs) in response to dimethyl sulfoxide (DMSO), ethanol, and isopropanol (IPA) at different concentrations. By quantifying Dirac-point hysteresis, we experimentally show that the hysteresis correlates with molecular polarity, following the trend DMSO < ethanol < IPA. Moreover, OS-GFETs exhibit a 1.5-fold sensitivity enhancement compared to PS-GFETs when detecting organic solution concentrations. Employing the two-dimensional hydrogen bond network (2D-HBNS) model, we theoretically illustrate that hydrophobic PS-GFET surfaces maintain equilibrium through hydration shell and 2D-HBNS formation. In contrast, hydrophilic OS-GFET surfaces disrupt this balance, enhancing van der Waals interactions and attracting organic molecules. This leads to superior sensitivity in OS-GFETs. To further validate this hypothesis, we introduced poly(methyl methacrylate) (PMMA) and polytetrafluoroethylene (PTFE) layers on the SiO substrate. The experiments show it changes graphene-surface hydrophilicity and graphene-sensor sensitivity. These findings establish a theoretical and experimental framework for optimizing graphene-based sensors. This framework elucidates a solute-solvent interfacial interaction model for polar liquids, aiming to improve the sensing characteristics of 2D materials.
大多数石墨烯传感器研究都集中在直接对石墨烯进行改性以提高性能。然而，支撑衬底对石墨烯传感机制的影响仍未得到充分探索。由于石墨烯的二维结构，衬底会影响其表面电位、润湿性和分子吸附。在极性分子（如水分子）存在的情况下，这些影响会加剧，进一步使传感特性变得复杂。为了探究这些影响，本研究通过电输运测量研究了衬底对有机溶剂中石墨烯场效应晶体管（GFET）传感能力和机制的影响。具体而言，我们比较了部分悬空的石墨烯场效应晶体管（PS-GFET）和氧化物支撑的石墨烯场效应晶体管（OS-GFET）对不同浓度的二甲基亚砜（DMSO）、乙醇和异丙醇（IPA）的响应。通过量化狄拉克点滞后现象，我们通过实验表明，滞后现象与分子极性相关，遵循DMSO＜乙醇＜IPA的趋势。此外，在检测有机溶液浓度时，OS-GFET的灵敏度比PS-GFET提高了1.5倍。采用二维氢键网络（2D-HBNS）模型，我们从理论上说明了疏水性PS-GFET表面通过水合壳层和2D-HBNS的形成保持平衡。相比之下，亲水性OS-GFET表面会破坏这种平衡，增强范德华相互作用并吸引有机分子。这导致OS-GFET具有更高的灵敏度。为了进一步验证这一假设，我们在SiO衬底上引入了聚甲基丙烯酸甲酯（PMMA）和聚四氟乙烯（PTFE）层。实验表明，这会改变石墨烯表面的亲水性和石墨烯传感器的灵敏度。这些发现为优化基于石墨烯的传感器建立了一个理论和实验框架。该框架阐明了极性液体的溶质-溶剂界面相互作用模型，旨在改善二维材料的传感特性。
