Excitation-Dependent Photostability and High Fluorescence Quantum Yield of Cr-Doped Carbon Polymer Dots for Sensors, Anticounterfeiting Inks, and Light-Emitting Devices

Carbon polymer dots (CPDs) show incredible potential due to their outstanding optical characteristics, simple synthesis using low-cost precursors, and diverse applications. This study aimed to develop chromium-doped CPDs (Cr-CPDs) using an efficient one-step microwave method for fluorescence sensing and optoelectronic devices. The one-pot microwave synthesis used citric acid, urea, C6H9O6Cr, and N,N-dimethylformamide. The resulting Cr-CPDs demonstrated excitation-dependent photostability with a high fluorescence quantum yield of 15.56%, making them promising for fluorescence-based applications. Our experiments showed that the Cr-CPDs' fluorescence could be effectively quenched in the presence of Fe3+ ions, allowing detection down to 0.52 μM concentration. By combination with PVA, flexible composite films were created for visual ion sensing. Static quenching and IFE dynamics work synergistically to underpin the selective and sensitive fluorescent detection function of Cr-CPDs for Fe3+. These Cr-CPDs further served as colorful inks for multifunctional information encoding. Most significantly, incorporating the Cr-CPDs into PVA films and assembling them on light-emitting devices (LEDs) led to efficient blue- and green LEDs. This study opens new possibilities for cost-effective luminescent materials and next-gen electronics.