Fig. 6: Selective ion detection and real time monitoring.

a Measured (symbols) V_M as a function of the potassium concentration for the potassium selective organic electrochemical transistor complementary amplifier. The full line is the linear least square fit to the measurements, and its slope gives a wide-range sensitivity S_M = 28 mV dec⁻¹. b Measured (symbols) V_O – c^K+ high sensitivity characteristics comprising the whole physiological range. Solid lines are the linear least square fit to the measurements, yielding S_A = 703 mV dec⁻¹, 952 mV dec⁻¹, 995 mV dec⁻¹, 1172 mV dec⁻¹. c, e Control experiment demonstrating the selectivity of the potassium-selective OECT complementary amplifier. V_O is measured over time and the Na⁺ (c) or Ca²⁺ (e) concentration is systematically increased every 60 s from 5.4 10⁻² M to 1 10⁻¹ M. In both cases the K⁺ concentration is constant and amounts to 5.4 10⁻² M. d, f Measured (symbols) steady state V_O as a function of c^Na+ (d) or c^Ca2+ (f). Solid line is the linear least square fit to the measurements and yields a cross-sensitivity S_CR,Na+ = 33 mV dec⁻¹ for Na⁺, and S_CR,Ca2+ = 20 mV dec⁻¹ for Ca²⁺, confirming the excellent selectivity of the output response.