Transferring the released component of Z-scheme heterojunction onto opposite photoelectrode: A dual-electrode-cooperating signal amplification strategy in photo fuel cell for self-powered biosensing.

Exploration of signal amplification strategy is an important link during the development of self-powered photoelectrochemical biosensors (SPECs). Herein, we develop a dual-electrode-cooperating signal amplification mode by transferring the released component of Z-scheme heterojunction onto opposite photoelectrode, and integrate it with DNA entropy-driven amplification design for ultrasensitive SPECs bioanalysis. Specifically, microRNA-155, the model analyte triggers the entropy-driven DNA circuit to release large amounts of output DNAs, which can competitively hybridize with the partial complementary DNA double strand between TiO nanospheres and SbS/Au photoanode for initiating the release of TiO nanospheres. In this case, the formed Z-scheme heterojunction on photoanode will suffer destruction, generating a positive shift of photoanode potential and thus a decrease in the open circuit voltage (E) of SPECs. Meanwhile, the DNA on the surfaces of these liberated TiO nanospheres can further hybridize with the hairpin DNA anchored on CuO/CuO photocathode, leading to the formation of type-II heterojunction and the negative shift of photocathode potential. Therefore, an additional decrease in the E of SPECs can be realized for cascading signal amplification. This work adds a new member to the family of signal amplification strategies from dual-electrode-cooperating perspective, which will attract more attentions in the field of SPECs and even other fuel cells-based biosensor.