Gaussian-Fitting-Enabled High-Accuracy pH Detection for Light-Addressable Potentiometric Sensor

A light-addressable potentiometric sensor (LAPS) is a low-cost and versatile semiconductor field-effect pH sensor. In practical application, typical pH detection based on LAPS usually adopts the method of normalizing the voltage-photocurrent (V-I) characteristic to solve the working point. However, this method not only needs to obtain the data of the whole V-I characteristic, which leads to slow and time-consuming measurement, but the selection of the working point is also greatly influenced by the shape and noise of the V-I characteristic. In view of this, a new pH measurement method is proposed in this paper, which reduces the impact of noise fluctuations by fitting a Gaussian function to the local depletion region of the V-I characteristic and is almost unaffected by some measurement points distortions of the V-I characteristic, and the measurement results are directly obtained from robust morphological parameters of the fitted function. The experimental results show that the new measurement method can not only obtain pH detection with high sensitivity, high linearity and strong specificity but also further improve the detection speed by shortening the range of the bias voltage, reducing the number of measurement points, and increasing the step value of the bias voltage. At the same time, the measurement method has strong anti-interference ability when the light source fluctuates and is applicable to a variety of waveform excitation scenarios. In practical application, this measurement method has low errors in the pH detection of sewage samples. The measurement method expands the measurement mode of LAPS and provides a new idea for high-precision, rapid pH detection and other biochemical species detection marked by pH.