Toward Kilogram‐Scale Preparation of Full‐Color Carbon Dots by Simply Stirring at Room Temperature in Air

Abstract

Large‐scale production of full‐color carbon dots (CDs) at room temperature under atmospheric pressure will promote their industrial application. Herein, o‐phenylenediamine is used as a single‐precursor carbon source and hydrogen peroxide as an oxidant. Kilogram‐scale CDs are obtained by stirring these reactants at room temperature in air for 30 min. After purification and acid treatment, blue‐, green‐, and red‐fluorescence CDs with photoluminescence peaks at 481, 539, and 625 nm are obtained with quantum yields of 21.76%, 27.12%, and 13.06%, respectively. Based on chemical structural characterizations, a reasonable formation mechanism is deduced, with blue, green, and red fluorescence arising from carbon nuclei stacked in conjugate planes containing fragments of quinoxaline, 2,3‐diaminophenazine (2,3‐DAPN), and protonated 2,3‐DAPN, respectively. High‐quality multi‐color and white light‐emitting diodes are successfully fabricated to demonstrate potential commercial applications in display and illumination.

Solvent-Engineered Synthesis of Multicolor Emissive Carbon Dots from Citric Acid and Cyanamide

“…The N 1s spectra can be fitted into three peaks at 399.1, 400.3, and 401.4 eV, attributed to pyridinic N, pyrrolic N/C–N, and graphitic N/N–H, respectively. , The results suggest the generation of amino groups on the surface of multicolor CDs except for Y-CDs, and no pyridinic N is observed in B-CDs. The O 1s spectra mainly contain two components related to CO (532.4 eV) and C–O (533.3 eV). , Overall, the diversities in the elemental content and functional groups of multicolor CDs can be ascribed to the different reaction processes of the precursors in different solvents, resulting in the generation of different carbon core structures and surface molecular fluorophores.…”

“…B-CDs and Y-CDs appear as single exponential decay with lifetimes of 6.15 and 8.64 ns, respectively, while decay traces of C-CDs and W-CDs follow a biexponential process with average lifetimes of 8.85 and 8.46 ns, respectively. The single exponential decay indicates that the fluorescence emission center of B-CDs and Y-CDs is relatively single, , while diverse fluorophores or energy levels such as recombination processes in core states or surface states, presented in C-CDs and W-CDs, could be responsible for their biexponential process. ,, Detailed PL decay data of multicolor CDs are displayed in Table S1. The above results suggest that different optical properties of multicolor CDs might originate from different surface fluorescent molecular states or core states formed from different reaction statuses or conditions.…”

“…Moreover, the testing results indicate that the CRI and correlated color temperature (CCT) of the white LED are 96.1 and 6015 K, respectively. The value of the CRI is high among previous reports. ,, The results suggest that CDs/polymer composites might be promising candidates for lighting devices.…”

Photoluminescence mechanism of red emissive carbon dots from a diaminobenzoic acid isomer

“…19 Subsequently, several research groups successfully synthesized OPD-based RCDs with similar emission peaks by adding low concentrations of strong acidic reagents or other precursors, such as dopamine, ionic liquids and dicyandiamide, in the hydrothermal process. [36][37][38][39] By performing systematic and complex purification, a large amount of quinoxalino [2,3-b]phenolizine-2,3-diamine (QXPDA) molecular fluorophore was found to be present in the RCDs, accounting for 80% of the total mass. When QXPDA was attached to the surface of the carbon core and aggregated, green and blue emission was observed.…”

Self-Precipitation of Highly Purified Red Emitting Carbon Dots as Red Phosphors

“…Among various types of precursors for production of the C-dots, o -PDA is one of the most important precursors for preparing R-C-dots benefiting from its self N-doping and built-in conjugation structure. − For example, Kostya et al prepared R-C-dots that exhibited an emission peak located at 620 nm with a PLQY of 1.9% using o -PDA as precursor with the addition of sodium sulfate as catalyst. They revealed that the protonation of 2,3-diaminophenazine (DAP) fluorophore was the reason for the luminescence property of R-C-dots .…”