Near-Infrared Laser Irradiation-Modulated High-Temperature Solid-Contact Ion-Selective Electrodes: Potentiometric...

The high-temperature potentiometry operated by nonisothermal heating is a promising way to break through the traditional potentiometric responses of ion-selective electrodes (ISEs) at room temperature. Herein, a locally heated strategy through near-infrared region (NIR) laser irradiation upon the photothermal mesoporous carbon material placed between the ion-selective membrane and the glassy carbon substrate is introduced to obtain the high-temperature potentiometric performance of a solid-contact Ca²⁺-ISE for detection of Ca²⁺ in seawater. Based on the light-to-heat conversion of the mesoporous carbon-based solid contact, the temperature of the solid-contact Ca²⁺-ISE upon continuous NIR laser irradiation can be increased from room temperature to 60-70 °C, and the slope of the electrode is promoted up to about 30% according to the thermodynamic steady-state potentiometric response. The pulsed potentiometric response of the solid-contact Ca²⁺-ISE upon a pulsed NIR laser irradiation of 5 s also shows a linear change as a function of Ca²⁺ activities, and the improved slope from 27.1 ± 0.6 to 38.1 ± 0.9 mV/dec can be obtained under dual control of the temperature of the electrode and the transient current induced by the pulsed NIR laser irradiation. As compared to the traditional potentiometric measurement under zero-current conditions at room temperature, the NIR laser-modulated high-temperature potentiometric response provides an alternative way for measurement of the solid-contact ISEs.