Metal cation detection based on a stable n-channel accumulation organic electrochemical transistor

Abstract

Organic electrochemical transistors (OECTs) have become promising candidates for biosensors due to their favorable aqueous stability, low operating voltage, and inherent amplification capability. Monitoring the levels of metal cations such as Na⁺ and K⁺ holds significant importance in human health. Most previous works on ion detection have predominantly focused on OECTs utilizing PEDOT:PSS that operates in depletion mode. Herein, we report a high-performance n-channel accumulation OECT constructed with a highly ordered fullerene derivative film, exhibiting excellent electrical performance and long-term stability in the water environment. The optimized n-channel OECT demonstrates a high performance in response to a wide range of concentrations of Na⁺, K⁺, and Ca²⁺, with a minimum detection concentration of 100 nM. The sensitivities, as determined by the normalized current variation vs. the concentration, are respectively 17.35 ± 0.98/dec(Na⁺), 7.21 ± 0.12/dec(K⁺), and 4.62 ± 0.18/dec(Ca²⁺), which are comparable to most reported ion sensors. The detected ion concentrations encompass the corresponding range for human sweat, thus making them suitable for cation detection in sweat. By incorporating a selective membrane, enhanced selectivity can be achieved. This flexible and highly sensitive electrochemical transistor holds immense potential for the development of flexible and skin-friendly sweat biosensors.