Fig. 3: Sensing performance of single-channel extended gate field-effect transistor (EGFET).

a Schematic illustration of the operational process of the EGFET sensor. Abbreviations: metal-oxide-semiconductor field-effect transistor (MOSFET). b Transfer characteristic curves of the EGFET-pH sensor in buffer solutions with different pH values. c Transfer characteristic curves of the EGFET-DO sensor in aqueous ZnSO₄ electrolyte with different DO concentrations. d Channel current (I_DS) responses of the EGFET-pH sensor towards pH changes (V_ref. = −2.00 V, V_DS = −1.50 V). e Corresponding linear calibration curve of log(I_DS) versus pH. f Channel current (I_DS) responses to continuous DO concentration changes of the EGFET-DO sensor (V_ref. = −2.00 V, V_DS = −1.50 V). The red segment of the response curve represents the stabilization phase of DO concentration, with specific DO levels indicated by the arrows. g Corresponding linear calibration curve of log(I_DS) versus log(ρ_DO). h I_DS of the EGFET-pH & DO sensor (V_ref. = −2.00 V, V_DS = −1.50 V) in response to continuous changes of DO concentration. The initial and maximum concentrations of DO are marked with arrows. i I_DS of the EGFET-pH & DO sensor (V_ref. = −2.00 V, V_DS = −1.50 V) before and after sequential addition of H₂SO₄ (0.05 mol L⁻¹, 100 μL), and NaOH (0.1 mol L⁻¹, 200 μL). The arrow shows when the interference signal was added, and the pH values corresponding to the red segments on the I_DS–pH response curve are labeled. Error bar: the standard deviation calculated with five independent tests, and data are mean ± s.d.