Eco-friendly curcumin-derived carbon quantum dots paired magnetic-carbon nitride for sustainable photocatalytic degradation of ciprofloxacin and antibacterial performance

Abstract

The persistent discharge of antibiotic contaminants into aquatic environments promotes antimicrobial resistance (AMR), posing significant ecological and public health risks. Toward this objective, ciprofloxacin (CIP)-contaminated water was treated via visible-light-assisted photocatalysis using curcumin-derived carbon quantum dots (Cur-CQDs) paired magnetic-carbon nitride lateral heterostructures (LMCN@Cur-CDs) to evaluate their degradation efficiency. The resulting lateral heterostructure (LHS) exhibited a larger surface area (S_BET=154.8 m²‧g^− 1), abundant defect sites (I_D/I_G=1.06), and yielded efficient peroxydisulfate (PDS) activation under visible light. Consequently, rapid CIP degradation (94.86% within 50 min; K₁ = 0.0505 min^− 1 at pH 7) was achieved through enhanced in-plane charge separation and reactive oxygen species‒ROS (SO₄^•‒, ^•O₂^–, ^•OH) generation, as confirmed by electron spin resonance (ESR) and quenching experiments. Density functional theory (DFT) and Fukui index analyses identified preferential radical attack sites (f^o: 0.06091–0.13296) on CIP molecules, whereas QSAR/TEST-based toxicity predictions indicated reduced toxicity of degraded products. Importantly, LMCN@Cur-CDs nearly cost $9.2761‧kg^− 1, comparable to activated carbon and lower than many noble-metal-based nanocatalysts. Furthermore, the LHS‒photocatalyst achieved ~ 99.99% antibacterial efficiency against multidrug-resistant‒MRSA-1369 and E. coli-25,922 strains under visible-light exposure, demonstrating comparable efficacy to standard antibiotic-CIP even at low dosages (50 µg‧mL^− 1). In-silico simulations further validated its antibacterial potential through strong interactions with DNA-gyrase^MRSA and β-lactamase^{E. coli} enzymes, while in-vitro MTT and hemolysis assays confirmed > 80% cytocompatibility. In short, this work provides a promising strategy for designing eco-friendly, efficient, and economical visible-light‒active LHS‒photocatalysts for sustainable antibiotic remediations and AMR mitigation toward public health protection.