Carbon nanodots with intense emission from green to red and their multifunctional applications

In this report, carbon nanodots (CDs) with tunable full-color emission were successfully synthesized by a solvothermal method. By changing the carbon source (p-phenylenediamine or o-phenylenediamine) and the concentration, green, yellow, orange and red CDs (GCDs, YCDs, OCDs and RCDs) were successfully fabricated. As the concentration of the starting materials was increased, the emission peak was red-shifted. The shifted peaks showed strong intensity and an obvious color change. This concentration-dependent effect was attributed to the reabsorption phenomenon. Carbon source was critical in determining the fluorescence properties and the quantum yield (QY) of full-color CDs was high. The CDs also presented a distinct pH sensitivity. The PL intensity of RCDs showed linear decreases over decreasing pH from 11 to 4 and from 4 to 2. Fluorescent oil carrying CDs was successfully applied for various purposes such as anti-counterfeiting, information encryption and storage purposes. An RCD film was successfully fabricated that could improve the correlated color temperature and color rendering index of white light-emitting diodes.