Core–shell Au@PtAg modified TiO2–Ti3C2 heterostructure and target-triggered DNAzyme cascade amplification for photoelectrochemical detection of ochratoxin A

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Efficient charge separation and utilization are critical factors to obtain a high initial signal in photoelectrochemical (PEC) aptasensor. Reports demonstrate that constructing metal/semiconductor Schottky junction can effectively improve the charge separation efficiency. Herein, a photoelectrode Au@PtAg/TiO2–Ti3C2 Schottky junction is successfully synthesized. Specifically, the Schottky junction between core–shell Au@PtAg and TiO2–Ti3C2 facilitates the efficiency of photogenerated electron transfer and enables the transfer of photogenerated electrons from TiO2–Ti3C2 to Au@PtAg. Noteworthy, the core–shell Au@PtAg acts as a photoelectron receiver to capture and store electrons, which further facilitates the separation of photogenerated electron–hole pairs, resulting enhanced photocurrent generation without sacrificial agents. Moreover, through the Mg2+-dependent DNAzyme cascade amplification, the sensitivity of the PEC aptasensor is further improved. Hence, we report an ultrasensitive PEC aptasensor for ochratoxin A (OTA) assy based on Au@PtAg/TiO2–Ti3C2 Schottky junction and Mg2+-dependent DNAzyme cascade amplification. As a result, the established PEC aptasensor exhibits excellent photocurrent performance in the range of 5 fg mL−1–10 ng mL−1 with a detection limit as low as 1.73 fg mL−1, showing high sensitivity, selectivity as well as stability. This strategy provides a versatile and promising avenue for the development of high-performance PEC aptasensor.