Miniaturized photoelectrochemical sensing system for reusable detection of macromolecules and its applications for unattended environmental monitoring

Photoelectrochemical (PEC) sensors are widely employed in biochemical detection due to their accuracy and speed, but most PEC measurement systems face challenges with bulky instruments and complex operations. Current miniaturized systems based on Potentiostat and constant light are limited in accuracy and application ranges. PEC systems based on mod/demod signal processing offer high SNR and accuracy but struggles with miniaturization due to complex algorithms of Lock-in amplifier. Herein, discrete Fourier transform (DFT) algorithm instead of Lock-in algorithm was used for the photocurrent demodulation in PEC system. After functional verification, coordinate rotation digital computer (CORDIC) algorithm was used to implement DFT demodulation to further reduce resource occupancy. Afterwards, the spectral leakage was reduced by applying Hanning window, which improves the SNR and accuracy of photocurrent demodulation. Subsequently, a miniaturized, low-cost, low-power and high-accuracy PEC measurement system was obtained by integrating designed Hanning-CORDIC-DFT module, Potentiostat, light source driver and other miniaturized modules. The performances of miniaturized PEC measurement system were compared with that of the commercial PEC measurement system based on Lock-in amplifier by using the same MIP-PEC sensor, validating the feasibility and accuracy of designed miniaturized PEC system. Then, the performance of MIP-PEC sensor was investigated in detail. The results showed that MIP-PEC sensor has good sensitivity, stability, selectivity and recyclability for detecting MC-LR. The reliability of MIP-PEC sensor was further confirmed by the recovery test of MC-LR in lake water. Finally, long-term, cyclic and unattended measurements of microcystin-LR were achieved by designed miniaturized PEC system and MIP-PEC sensor under different conditions, verifying the practicality of the system for field monitoring. The designed measurement system provides a new method for constructing miniaturized PEC sensing platform, and a new solution for continuous biochemical detection in complex environments.