Table_1_Organic Electrochemical Transistors as Versatile Analytical Potentiometric Sensors.DOCX

Potentiometric transduction is an important tool of analytical chemistry to record chemical signals, but some constraints in the miniaturization and low-cost fabrication of the reference electrode are a bottleneck in the realization of more-advanced devices such as wearable and lab-on-a-chip sensors. Here, an organic electrochemical transistor (OECT) has been designed with an alternative architecture that allows to record the potentiometric signals of gate electrodes, which have been chemically modified to obtain Ag/AgnX interfaces (X = Cl−, Br−, I−, and S2−), without the use of a reference electrode. When the OECT is immersed in a sample solution, it reaches an equilibrium state, because PEDOT:PSS exchanges charges with the electrolyte until its Fermi level is aligned to the one of Ag/AgnX. The latter is controlled by Xn− concentration in the solution. As a consequence, in this spontaneous process, the conductivity of PEDOT:PSS changes with the electrochemical potential of the modified gate electrode without any external bias. The sensor works by applying only a fixed drain current or drain voltage and thus the OECT sensor operates with just two terminals. It is also demonstrated that, in this configuration, gate potential values extracted from the drain current are in good agreement with the ones measured with respect to a reference electrode being perfectly correlated (linear slope equal to 1.00 ± 0.03). In the case of the sulfide anion, the OECT performance overcomes the limit represented by the Nernst equation, with a sensitivity of 0.52 V decade−1. The presented results suggest that OECTs could be a viable option to fabricate advanced sensors based on potentiometric transduction.

电位转导（Potentiometric transduction）是分析化学领域用于记录化学信号的重要手段，但参比电极的小型化与低成本制备所存在的诸多限制，成为了可穿戴传感器、芯片实验室传感器等先进器件研发的核心瓶颈。本研究设计了一种新型架构的有机电化学晶体管（OECT），可无需依赖参比电极，直接记录经化学修饰得到Ag/AgₙX界面（X = Cl⁻、Br⁻、I⁻及S₂⁻）的栅电极电位信号。当OECT浸入样品溶液后，体系将达到平衡状态：聚(3,4-乙烯二氧噻吩):聚苯乙烯磺酸（PEDOT:PSS）与电解质发生电荷交换，直至其费米能级与Ag/AgₙX的费米能级对齐，而后者由溶液中的Xⁿ⁻浓度调控。因此，在该自发过程中，PEDOT:PSS的电导率会随修饰后栅电极的电化学势发生变化，且无需施加任何外部偏压。该传感器仅需施加固定的漏极电流或漏极电压即可工作，因此OECT传感器仅需两个端子即可实现运行。研究同时证实，在此构型下，从漏极电流中提取的栅极电位值与参比电极测得的电位值吻合度极佳，二者具有高度相关性（线性斜率为1.00 ± 0.03）。针对硫化物阴离子体系，该OECT的性能突破了能斯特方程（Nernst equation）的限制，灵敏度可达0.52 V·decade⁻¹。本研究结果表明，OECT可作为制备基于电位转导的先进传感器的可行方案。