Long‐Term Impact of Impurities on the Optical and Morphological Properties of Polymer Dot, Carbon Polymer Dot, and Carbon Quantum Dots

The role of impurities and molecular fluorophores in carbon dots (CDs) is often overlooked, yet they can significantly mislead interpretations of optical properties. This study systematically examines their long-term impact on the optical and morphological characteristics of carbon quantum dots (CQD), carbon polymer dots (CPD), and polymer dots (PD), synthesized from citric acid and urea under controlled hydrothermal conditions. Pronounced variations in photoluminescence and structural stability across the three CD types are directly linked to impurity incorporation. These findings highlight the necessity of rigorous purification and precise molecular identification, offering critical insights into impurity-driven modulation of CD performance and reliability.