Self-Calibrating All-Solid-State Ion-Selective Electrodes without Reference Electrodes

Although considerable progress has been achieved in miniaturized devices based on all-solid-state ion-selective electrodes, there are still two crucial issues: the operational requirement of frequent calibration restricts industrial production and commercial applications, and the absence of standardized miniaturized reference electrodes may make the performance of reference electrodes fluctuated and thereby affect the potential stability of the sensor. This study presents a method for automatic calibration by analyzing the interfacial process kinetic parameters of ion-selective electrodes with membranes of different volumes and calculating the slope to generate a built-in standard curve. Since this method obtains interfacial process parameters from transient currents, it gets rid of the traditional detection system’s dependence on the stable potential provided by reference electrodes. This solution can offer universal adaptability under a unified workflow, making it compatible with diverse detection targets and transduction layer material systems. Taking carbon nanotubes as an example, this study established a standard model based on membranes with volumes of 1, 4, and 7 μL, achieving self-calibrating detection of sodium ions within a wide concentration range of 0.1–100 mM without a reference electrode (validated within a temperature range of 288–313 K). Experimental results show that the system demonstrates great stability (average relative standard deviation <4%) and accuracy (relative concentration error <3%). This work provides a solution for self-calibration ion detection systems without reference electrodes and also offers methodological support for the miniaturized design and practical application of wearable devices.