High Current Gain Endowed by Heterojunction Engineering Coupling Interfacial Molecular Modulation: A Low-Ascorbic Acid-Dependent Organic Photoelectrochemical Transistor Aptasensing Platform.

To balance the "detection sensitivity" and "device stability" of the organic photoelectrochemical transistor (OPECT) aptasensors, it has become an urgent challenge for achieving effective signal modulation under low ascorbic acid (AA) conditions. To address this, our work proposed a collaborative optimization strategy by coupling heterojunction engineering with interfacial molecular modulation, to endow a high current gain of OPECT with low-AA -dependence. First, a CdZnS-SnIn4S8 heterojunction gate was constructed by in situ growth of CdZnS quantum dots (QDs) on SnIn4S8 nanoflowers, which enhanced the light trapping ability and photoelectric conversion efficiency of the photoactive gate. The constructing DNA double-strand embedding methylene blue (MB) at the sensing interface was then developed, enabling the directional transport of photogenerated carriers. By virtue of the synergistic signal modulation of CdZnS-SnIn4S8 heterojunction engineering and interface MB molecule sensitization, a high current gain of up to 3 orders of magnitude was obtained at low concentration of AA. As a proof of concept, the proposed OPECT system was employed to construct an aptasensor for detection of emerging antibiotics pollutant ofloxacin in water sample, with both excellent anti-interference ability and reliability. This work demonstrates an effective strategy to achieve a high current gain of OPECT at a low concentration AA, which provides a perspective for a new generation of OPECT systems with high-performance.