A universal dual-channel ratiometric photoelectrochemical sensing platform with integrated ionic liquid-sensitized In2S3@BiOBr0.8I0.2/PEDOT photoanode and Cu@Cu2O photocathode

The generation, separation and interfacial reaction of photogenerated carriers are crucial to realize efficient photoelectrochemical (PEC) detection. However, fast electron-hole recombination and slow interfacial reaction dynamics remain challenges for constructing advanced PEC platforms. Herein, ionic liquids (i.e. 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm]PF6)) are introduced as morphology modulator and supporting electrolyte into the synthesis of Cu@Cu2O and the heterogeneous combination of In2S3@BiOBr0.8I0.2 with electrochemically polymerized 3,4-ethylenedioxythiophene (PEDOT), for constructing a PEC sensing platform. As their unique microstructure, the formed p-n junction and the doped ionic liquids benefit the charge separation/transfer, the resulted [BMIm]BF4 − In2S3@BiOBr0.8I0.2/ [BMIm]PF6 − PEDOT/AuNPs (i.e. Au nanoparticles) photoanode material and [BMIm]PF6 − Cu@Cu2O photocathode material show enhanced interfacial reaction dynamics and photo-conversion efficiency. In order to improve the accuracy and reliability of PEC detection, the potentially responsive photocathode and photoanode materials are integrated on the same indium tin oxide electrode for potential-resolved two-channel ratiometric PEC detection. By tuning the bias voltage, the cathode and anode currents can be well distinguished, and dual signals can be obtained during a single detection run and used as reference for each other. Then, a biometric sensing platform for vascular endothelial growth factor and epithelial cell adhesion factor is constructed by combining with aptamers and it demonstrates excellent analytical performance. Compared with the traditional PEC biosensors, the platform can effectively eliminate the detection errors caused by the fluctuation of excitation light intensity and preparation conditions. In addition, the platform is universal, by changing the recognition element, it can be applied to the detection of a variety of biomarkers.