Ag quantum dots decorated ultrathin g-C3N4 nanosheets for boosting degradation of pharmaceutical contaminants: Insight from interfacial electric field induced by local surface plasma resonance

The design of photocatalysts that can generate local surface plasmon resonance effect (LSPR) is expected to be an effective strategy for improving photocatalytic activity. However, the photocatalytic mechanism of interfacial electric field induced by quantum dot plasma is still unclear. Herein, different amount of Ag quantum dots was loaded on ultrathin carbon nitride sheets (Ag/UCN) to construct Schottky junction. The 1:1 Ag/UCN Schottky junction exhibits excellent photocatalytic activity in ofloxacin degradation with 95.2% removal, and is highly stable during four consecutive photocatalytic cycles. Ag/UCN can also effectively mineralize ofloxacin with 65.8% TOC removal, and NH4+, F- and NO3- were detected in the degradation solution of ofloxacin. Moreover, Ag/UCN shows high antibacterial activity and is effective in pharmaceutical wastewater treatment. The enhanced visible-light absorption of Ag/UCN nanocomposites is attributed to the LSPR effect of Ag quantum dots. Finite difference time domain (FDTD) simulations, density functional theory (DFT) calculations and surface potential confirm that the interfacial electric field drives the photogenerated carriers to cross the Schottky barrier, thus effectively accelerating the electron transfer rate at Ag/UCN interface. The photocatalytic mechanism of the interfacial electric field induced by LSPR effect was also revealed, which provides a new insight for design of LSPR-promoted photocatalyst with interfacial electric field induced by quantum dots.