Self-assembled perylene diimide/CuO p-n heterojunction-enhanced photoelectrochemical platform for sensitive dopamine detection.

The development of a highly efficient photoelectrochemical (PEC) platform for the sensitive and selective detection of dopamine (DA) is of significant importance. In this study, an amine-propyl-functionalized perylene diimide (PA-PDI) self-assembly block material was fabricated and demonstrated a pronounced photoanodic current response under visible-light irradiation at 630 nm. Upon introduction of Cu2+, PA-PDI underwent structural reorganization from nanoflakes into nanobelts, leading to the in situ formation of a PA-PDI/CuO p-n heterojunction. This heterojunction markedly enhanced charge separation efficiency, resulting in a remarkable increase in photocurrent. Notably, the presence of DA triggered a substantial decrease in the photocurrent, which was proposed to arise from the likely formation of polydopamine (PDA) on the surface of PA-PDI/CuO via Cu2+-catalyzed oxidation of DA; the resulting PDA layer was suggested to act as an insulating layer and effective electron acceptor, thereby suppressing interfacial electron transfer within the heterojunction. Leveraging this proposed PEC transduction mechanism, a label-free PEC sensor was developed for the quantitative detection of DA, exhibiting a wide linear range from 10- 2 µM to 102 µM (R2 = 0.998) and a low limit of detection of 5.38 nM (S/N = 3). Furthermore, satisfactory recoveries (96.8-100.6%) were achieved in spiked human serum samples.