Carbon dot/TiO 2 nanocomposites for photocatalytic antibiotic degradation: interfacial engineering, degradation mechanisms, and environmental remediation

The widespread presence of antibiotic residues in aquatic environments contributes to ecological toxicity and accelerates antimicrobial resistance (AMR), highlighting the need for efficient and sustainable remediation technologies. Among advanced oxidation processes, TiO2-based photocatalysis has attracted considerable attention because of its chemical stability, low toxicity, and strong oxidative capability. However, the practical application of TiO2 is limited by poor visible-light absorption and rapid electron–hole recombination. Carbon dots (CDs) have emerged as highly promising interfacial modifiers owing to their tunable electronic structure, visible-light responsiveness, and efficient charge-transfer capability, enabling substantial enhancement of TiO2 photocatalytic performance. This review critically examines recent advances in CDs/TiO2 nanocomposites for photocatalytic antibiotic degradation, with particular emphasis on how heterointerface engineering governs charge-carrier dynamics, reactive oxygen species (ROS) generation, and degradation selectivity. The mechanistic roles of Ti–O–C interfacial bonding, band alignment, defect-state modulation, and interfacial electron transfer are systematically discussed in relation to photocatalytic activity across major antibiotic classes, including tetracyclines, fluoroquinolones, β-lactams, and sulfonamides. In addition, the effects of adsorption behavior, operational parameters, environmental matrix components, and reactor configuration on degradation efficiency and mineralization are critically evaluated. Special attention is devoted to degradation pathways, catalyst photostability, ecotoxicological considerations, and challenges associated with real-water applications and large-scale implementation. Current limitations, including insufficient mechanistic validation, lack of standardized benchmarking protocols, and limited long-term environmental safety assessment, are also highlighted. Finally, current research priorities involving mechanistic validation, predictive interfacial engineering, standardized benchmarking, environmental safety assessment, and solar-driven photocatalytic design are highlighted to guide the future development of sustainable antibiotic-remediation technologies.