Real-time monitoring of geosmin based on an aptamer-conjugated graphene field-effect transistor

In this paper, we propose a novel field-effect transistor (FET) using graphene, which is a two-dimensional (2D) nanomaterial, capable of evaluating water quality, and immobilizing the surface of a graphene micropatterned transistor with a highly responsive bioprobe for a water contamination indicator, geosmin, with high selectivity. A high-quality bioprobe-immobilized graphene FET (GFET) was fabricated for the real-time monitoring of geosmin using a liquid-gate measurement configuration. Immobilization was confirmed by measuring the change in the electrical characteristics of the platform (slope of the current-voltage (I–V) curve) and fluorescence images. In addition, a selectivity test showed remarkable implementation of the highly sensitive sensing platform with an insignificant signal when a nontarget was added. Using the fabricated device, the linear range for geosmin detection was determined to be from 0.01 nM - 1 μM with a detection limit of 0.01 nM. In addition, geosmin concentrations as low as 10 nM could be determined from river water samples with the sensor platform. This sensor can be utilized to immediately determine the presence of odorous substances by analyzing a water supply source without additional pretreatment. Another advantage is that the sensor device is a promising tool that does not have special equipment that requirs careful maintenance. In addition, the device provides a new platform for detecting harmful substances in various water sources by varying the bioprobes that are empolyed.