CdS-Based Photocatalysts for Antimicrobial Applications: From Quantum Dots to Z-Scheme Heterojunctions—Mechanisms, Challenges, and Future Perspectives

The chronic overuse of antibiotics has accelerated the emergence of antibiotic-resistant bacteria, creating a global public health crisis as conventional therapies fail against multidrug-resistant pathogens spreading through water and food chains. Cadmium sulfide (CdS) has been established as an important visible-light-driven photocatalyst for antibacterial applications. This brief review systematically examines the structure–property relationships governing CdS-based antibacterial materials, including crystallographic polymorphs (cubic sphalerite and hexagonal wurtzite), morphological diversity from quantum dots to hierarchical architectures, and synthesis methodologies that critically influence particle size, crystallinity, and surface chemistry. The mechanisms of antibacterial action are elucidated, encompassing photocatalytic reactive oxygen species (ROS) generation, controlled Cd2+ ion release, and membrane disruption. A detailed tabulated analysis is presented across three material classes: pristine CdS, binary composites, and ternary Z-scheme heterostructures. Density functional theory (DFT) calculations and molecular docking simulations provide atomic-level insights into charge transfer dynamics and enzyme inhibition mechanisms. Finally, critical challenges, photocorrosion, toxicity, biocompatibility concerns, and scalability limitations are addressed. This review bridges fundamental materials science with antimicrobial applications to guide rational design of next-generation CdS-based antibacterial materials.