Fig. 2

Detection performance and mechanism of the field-effect transistor (FET) sensor. a Schematic diagram of the •OH detection. b Liquid gate transfer curves of a FET device of pristine graphene (black), after step iii (red), after step iv (10⁻⁴ M Cd²⁺, green), and after step v (10⁻⁴ M •OH, blue), when liquid gate voltage (V_lg) varies from −400 to 800 mV. c, d Real-time electrical responses of a graphene/Au/Cys-PP FET device upon successive addition of 1 × 10⁻⁵ M Cd²⁺ (step iv) and subsequent 1 × 10⁻⁴ M •OH (step v). e Selectivity of a graphene/Au/Cys-PP-Cd²⁺ FET sensor (modified in 10⁻⁴ M Cd²⁺) toward •OH (10⁻⁶ M) and metal ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe²⁺, Mn²⁺, Co²⁺, Fe³⁺, Ag⁺, Zn²⁺, Cu²⁺, Pb²⁺, Ni²⁺, 10⁻⁶ M). f Selectivity of a graphene/Au/Cys-PP-Cd²⁺ FET sensor (modified in 10⁻⁴ M Cd²⁺) toward •OH (10⁻⁶ M) and other reactive oxygen species (H₂O₂, ROO⁻, ¹O₂, ClO⁻, O₂•⁻, phosphate-buffered saline, 10⁻⁶ M). g The response of a pristine graphene channel (without modification) upon successive addition of 1 × 10⁻⁴ M •OH. The error bars are defined by the standard deviation of the results from three parallel experiments