<p style="text-align:justify">Quantum dots (QDs) are incredibly important in nanotechnology due to their unique, size-tunable optical and electronic properties arising from quantum confinement. Carbon Quantum Dots (CQDs) are carbon-based nanomaterials under 10 nm known for their unique photoluminescent properties and biocompatibility. They exhibit tunable fluorescence due to quantum confinement, making them suitable for diverse applications.</p> <p style="text-align:justify">This book introduces CQDs, discusses their structural features and synthesis methods, including ecofriendly approaches, and highlights their advantages over traditional quantum dots in terms of safety. Top-down approaches include techniques like laser ablation, arc discharge, and electrochemical oxidation, which break down larger carbon structures into quantum dots. Bottom-up methods, such as hydrothermal synthesis, microwave-assisted synthesis, and thermal decomposition, involve the assembly of smaller molecules into CQDs under controlled conditions. Despite their numerous advantages, concerns regarding the safety and environmental impact of the synthesis methods have emerged. These concerns include the use of hazardous chemicals, high-energy processes, and the generation of waste during production.</p> <p style="text-align:justify">This book helps to explore the various synthesis methods of CQDs and evaluate their sustainability, toxicity, and efficiency. Key applications include bioimaging, drug delivery, sensing, photovoltaics, Quantum computing and light-emitting devices, Security and Anti-Counterfeiting. In essence, carbon quantum dots bridge the gap between bulk materials and individual atoms, offering a unique set of properties that can be precisely engineered at the nanoscale. This tunability and their superior optical and electronic characteristics make them a powerful tool driving innovation across numerous areas of nanotechnology.</p>