Specific detection against PSA by using emission wavelength of carbon dots modulates TiO₂/In₂S₃-based...

Sensitive and precise detection of prostate-specific antigen (PSA) is essential for the early diagnosis and monitoring of prostate cancer. However, conventional detection methods often suffer from limited sensitivity, poor selectivity, highlighting the need for advanced sensing platforms. Photoelectrochemical (PEC) biosensing achieve for PSA accurate detection due to its high sensitivity, low background noise, and simplicity. Nonetheless, enhancing light absorption and charge separation efficiency remains a major challenge. In this study, we addressed this challenge by modulating the emission wavelength of carbon dots (CDs) and integrating them into a TiO₂/In₂S₃-based heterojunction. Three types of CDs, including blue, green and red-emitting CDs (B-CDs, G-CDs, and R-CDs) were synthesized via a hydrothermal method and systematically optimized for photophysical and electronic performance. Among them, R-CDs exhibited superior visible-light absorption, enhanced electron transport, and abundant surface functional groups. When incorporated into a TiO₂/In₂S₃ composite, R-CDs significantly boosted the photocurrent response (-112 μA), outperforming the B-CDs (-60 μA) and G-CDs (-88 μA) counterparts. Comprehensive characterizations confirmed the formation of a well-integrated ternary heterojunction with efficient charge separation and reactive oxygen species (ROS) generation. A PEC aptasensor was subsequently developed based on the optimized TiO₂/In₂S₃/R-CDs photoelectrode for PSA detection. The sensor demonstrated a wide linear detection range (0.002-100 ng/mL), an ultralow detection limit (5.0 pg/mL), and excellent selectivity. It also exhibited strong stability and reproducibility, with recovery rates of 96.6-100.4% in spiked serum samples. This study not only presents a highly sensitive PEC platform for clinical diagnostics but also underscores the critical role of emission-wavelength modulation of CDs in the rational design of advanced PEC biosensors.