Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
J Am Chem Soc. 2010 Dec 8;132(48):17149-56. doi: 10.1021/ja104850n. Epub 2010 Nov 15.
Field-effect transistors based on single-walled carbon nanotubes (SWNTs) and graphene can function as highly sensitive nanoscale (bio)sensors in solution. Here, we compare experimentally how SWNT and graphene transistors respond to changes in the composition of the aqueous electrolyte in which they are immersed. We show that the conductance of SWNTs and graphene is strongly affected by changes in the ionic strength, the pH, and the type of ions present, in a manner that can be qualitatively different for graphene and SWNT devices. We show that this sensitivity to electrolyte composition results from a combination of different mechanisms including electrostatic gating, Schottky-barrier modifications, and changes in gate capacitance. Interestingly, we find strong evidence that the sensor response to changes in electrolyte composition is affected by a high density of ionizable groups on both the underlying substrate and the carbon surfaces. We present a model based on the (regulated) surface charge associated with these ionizable groups that explains the majority of our data. Our findings have significant implications for interpreting and optimizing sensing experiments with nanocarbon transistors. This is particularly true for complex biological samples such as cell extracts, growth media, or bodily fluids, for which the complete composition of the solution needs to be considered.
基于单壁碳纳米管 (SWNTs) 和石墨烯的场效应晶体管可以在溶液中用作高度灵敏的纳米级（生物）传感器。在这里，我们通过实验比较了 SWNT 和石墨烯晶体管对其所处的水基电解质组成变化的响应。我们表明，SWNTs 和石墨烯的电导强烈受到离子强度、pH 值和存在的离子类型变化的影响，这种影响在石墨烯和 SWNT 器件中可能是定性不同的。我们表明，这种对电解质组成的敏感性源自于包括静电门控、肖特基势垒修饰和栅电容变化在内的不同机制的组合。有趣的是，我们发现有强有力的证据表明，电解质组成变化对传感器响应的影响取决于底层衬底和碳表面上的高浓度可离子化基团。我们提出了一个基于与这些可离子化基团相关的（调节）表面电荷的模型，该模型解释了我们的大部分数据。我们的发现对解释和优化使用纳米碳晶体管的传感实验具有重要意义。对于细胞提取物、生长培养基或体液等复杂生物样本尤其如此，因为需要考虑溶液的完整组成。
