Transforming Carbon Quantum Dots Synthesis: Innovative Continuous Hydrothermal Flow Methods for Environmental Advancements and Beyond

Carbon quantum dots (CQDs) are an emerging class of nanomaterials exhibiting unique sizedependent optical and electronic properties. Owing to their high photoluminescence, chemical stability, low toxicity, and surface functionalization capabilities, CQDs show tremendous potential for diverse applications in energy harvesting, sensing, optoelectronics, and biomedicine. However, conventional CQD synthesis methods involve toxic organic solvents, high energy consumption, long reaction times, and poor control over particle size distribution and properties. This PhD research focused on the continuous hydrothermal flow synthesis (CHFS) of CQDs from renewable precursors as a rapid, sustainable, and scalable production route. A systematic investigation was undertaken to establish relationships between synthesis conditions (precursor composition, dopant concentrations) and final CQD characteristics. State-of-the-art spectroscopic and microscopic characterisation techniques provided fundamental insights into nucleation, growth mechanisms, and surface chemistry during CQD formation via CHFS. By tuning the CHFS parameters, photoluminescent CQDs with uniform size distribution, tailored surface chemistry, and reproducible optoelectronic properties were synthesised. This thesis demonstrates the first comprehensive study utilising CHFS for controlled and optimized synthesis of CQDs. The fundamental understanding of CQD formation mechanisms and structure-property correlations established here will aid the customised design of CQDs for diverse cutting-edge applications in sensing, catalysis and beyond.