FeOOH/Cu2O/CuS photocathode-enabled simultaneous promotion on charge carrier separation and electron acceptor reduction for lab-on-paper homogeneous cathodic photoelectrochemical bioassay

• Paper-based Cu 2 O photocathode was collaboratively modified with FeOOH and CuS. • Both the charge carrier separation and electron acceptor reduction were promoted. • Dual-hydrophilic-walls hollow channel was used for promoting homogeneous reaction. • Lab-on-paper homogeneous photocathodic bioassay of microRNA was proposed. Herein, a simple but effective photocathodic signal enhancement strategy was developed based on FeOOH/Cu 2 O/CuS photocathode-enabled simultaneous promotion on charge carrier separation and electron acceptor reduction, and applied to construct lab-on-paper homogeneous cathodic photoelectrochemical (PEC) bioassay via dual-hydrophilic-walls hollow channel (DHWHC) design and target-triggered all-in-one hemin@G-rich DNA release. More concretely, FeOOH as hole extraction layer fleetly extracted photogenerated holes from Cu 2 O, while the photogenerated electrons rapidly transferred to CuS, as electron transfer/consumption accelerator, by photoinduced interfacial charge transfer (IFCT), achieving the efficient charge carrier separation. In the IFCT process, the Cu(II) in CuS was reduced to Cu(I) and it could be oxidized back to Cu(II) by electron acceptor (O 2 ), forming a Cu(II)/Cu(I) redox circular reaction, which could effectively accelerate the transfer/consumption of photogenerated electrons and further promote electron acceptor reduction. Thus, the simultaneous promotion on charge carrier separation and electron acceptor reduction was fulfilled by FeOOH/Cu 2 O/CuS photocathode, producing a strongly enhanced photocathodic signal. On account of the high mass-transfer rates of DHWHC, the mediation of electron acceptor generation through target-triggered hemin@G-rich DNA release, and the proposed signal enhancement strategy, the ultrasensitive lab-on-paper homogeneous PEC microRNA-141 detection was realized with high selectivity, reproducibility, and stability. This work rendered practical guidelines for developing high-performance lab-on-paper cathodic PEC bioanalysis systems.