A Quantum Mechanism-Centered Review of Carbon Dot-Based Theranostics

Despite advances in drug discovery, effective delivery and precise imaging still pose significant obstacles. Scientists have turned to zero-dimensional nanomaterials like carbon dots (CDs) to enable precision drug delivery. Due to their multidisciplinary appeal, there is extensive research on both the physical properties and biological applications of CDs, yet the fields rarely complement each other. This review applies a quantum-mechanistic framework to better understand CDs and unify the relationship between electronic structure, photophysical behavior, and theranostic performance. We first highlight the theranostic advantages of CDs over quantum dots, then discuss the quantum mechanisms behind a CD's imaging capabilities, including surface states, excitation-dependent photoluminescence, and the electronic origins of photostability. Through this physical lens, we then evaluate the effect of different precursors and doping strategies during synthesis on electronic structure and how dots are engineered to load, release, and track therapeutic cargo. Photodynamic therapy and surface functionalization strategies are also evaluated. Finally, we address the significance of renal clearance and translational bottlenecks such as heterogeneity.