Carbon dot photoluminescence: mechanisms, influencing factors, and modulation strategies — a review

Abstract

Carbon dots have become an important class of carbon nanomaterials that have been intensively studied in recent years due to their tunable photoluminescence, high photostability, low toxicity, and well‑developed surface chemistry. Nevertheless, a unified scientific approach to the nature of their photoluminescence has not yet been established, which limits the targeted regulation of carbon dot properties. This review article systematizes current research on the main approaches to the synthesis of carbon dots,  structural features, and mechanisms of photoluminescence formation. Models of quantum confinement, surface states, structural defects, and molecular states have been analyzed, and their advantages, limitations, and interrelationships have been compared. In addition, the role of surface functionalization and doping with heteroatoms such as nitrogen, sulfur, and fluorine in controlling photoluminescent properties has been examined. The applications of carbon dots in bioimaging, biosensing, theranostics, and optoelectronics have been analyzed in relation to their structure and photoluminescent properties. The scientific novelty of review lies in the unified scientific systematization of the main factors influencing the photoluminescence of carbon dots, critical analysis of the relationships between structural and surface chemical and optical properties, and identification of current approaches to the targeted control of photoluminescent properties and future research directions. The results of presented analysis can serve as a theoretical basis for development of carbon dots with predictable photoluminescent properties and their effective use in biomedical, sensor, and optoelectronic technologies.