Highly optically and thermally stable carbon dots enabled by thermal annealing for laser illumination

Abstract

In order to obtain carbon dots (CDs) fluorescent materials with good optical and thermal properties for laser illumination, CDs with excellent fluorescence properties were synthesized by a hydrothermal method using 2,7-dihydroxynaphthalene and citric acid as raw materials, followed by thermal annealing to improve the graphitization degree of CDs, resulting in the red-shifted PL emission from 485 to 527 nm and increased thermal stability. The theoretical simulation verifies that the formation process of CDs can be divided into three stages, including decomposition, polymerization, and carbonization. The effect of the structure of CDs on their thermal stability was investigated using structural characterization and theoretical simulations, and the results show that the increase of the graphitization degree and the decrease of the oxygen element content are both beneficial to the improvement of CD thermal stability. The CDs were then dispersed in the aqueous solution of N-β-aminoethyl-γ-aminopropyl trimethoxysilane to form a fluorescent film, which was assembled with 450 nm laser diodes to construct a white laser illumination device with CIE coordinates of (0.42, 0.35), a correlated color temperature of 2822 K, and a color rendering index of 85. This research demonstrates that CDs possess good application prospects in the field of solid-state lighting, showing potential for realizing low cost and high efficiency laser illumination devices.