Target Recognition-Triggered\nInterfacial Electron\nTransfer Model: Toward Signal-On Photoelectrochemical Aptasensing\nfor Efficient Detection of Staphylococcus aureus Using Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x&lt

Staphylococcus aureus (S. aureus) is one of the most common foodborne pathogens\nworldwide, which poses a great threat to public health. It is of utmost\nimportance to develop rapid, simple, and sensitive methods for the\ndetermination of S. aureus. A signal-on\nphotoelectrochemical (PEC) aptasensor is constructed herein based\non titanium carbide (Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>)-Au nanobipyramids (NBPs)/ZnO nanoarrays (NRs). The reliability\nand capability of the PEC aptasensor make it suitable for the sensitive\nand selective determination of S. aureus. First, the electrostatically self-assembled Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>-Au NBP nanomaterial was coated\non the ZnO NR surface by a spin-coating method. On the one hand, Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>-Au NBPs can broaden\nthe spectral absorption of ZnO NRs, resulting in Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>-Au NBPs/ZnO NR composites that\nexhibit a wide range of absorption from the ultraviolet to the infrared\nregion. On the other hand, Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> can reduce the agglomeration of nanoparticles, while\nAu NBPs can effectively fix the aptamer through the Au–S bond.\nSpecifically, the experimental results show that when S. aureus is present, the Au NBPs-aptamer-S. aureus complex is shed from the electrode surface,\naltering the interfacial electron transfer model and reducing the\nsteric hindrance. Consequently, an amplified photocurrent signal for\nthe quantitative determination of S. aureus is obtained. Under optimal experimental conditions, a linear correlation\nis observed between the current response of the aptasensor and the\nlogarithm of the S. aureus concentration\n(ranging from 1.0 to 1.0 × 10<sup>6</sup> CFU/mL), with an impressive\ndetection limit as low as 0.5 CFU/mL. Furthermore, the aptasensor\nhas been successfully employed for the detection of S. aureus in milk, with the recovery of 93.0%–99.0%.\nHence, this research offers a novel approach for the detection of\nfoodborne pathogens and other noxious substances.