Solvent-regulated multicolor-emissive carbon dots and their application in multicolor light-emitting diodes

Abstract

Multicolor-emissive carbon dots (ME-CDs) have been extensively utilized in various fields such as optoelectronic devices, bioimaging, and sensing due to their tunable luminescence properties, solubility, stability, and biocompatibility. However, achieving ME-CDs in a straightforward manner remains a critical bottleneck hindering their wider industrial application. Herein, we report a facile method to prepare ME-CDs using p-phenylenediamine and urea as precursors by changing the type of reaction solvent. Specifically, when the solvents are formamide, deionized water, dimethylformamide, and ethanol, the fluorescence colors are blue, green, yellow, and red, respectively, covering the entire visible light range. The absolute fluorescence quantum yields and lifetimes are 63.02%/1.6 ns, 15.17%/3.4 ns, 16.82%/7.7 ns, and 17.81%/18.8 ns, respectively. The structure and photophysical properties of ME-CDs indicate that the emission of ME-CDs originates from different photoluminescence centers, namely clusteroluminescence, (n, π*) transition of heteroatom groups and (π, π*) transition of large π-conjugated structures. Furthermore, it is demonstrated that ME-CDs can be used as phosphors to fabricate multicolor light-emitting devices (LEDs). This study offers a simple and low-cost method to prepare ME-CDs and employ them as phosphors for LEDs.