Gram‐Scale Room‐Temperature Synthesis of Solid‐State Fluorescent Carbon Nanodots for Bright Electroluminescent Light Emitting Diodes

Abstract

The reaction conditions of high temperature and high pressure will introduce structural defects, high energy consumption, and security risks, severely hindering the industrial application of organic carbon nanodots (CDs). Moreover, the aggregation caused quenching effect also fundamentally limits the CDs based electroluminescent light emitting diodes (LEDs). Herein, for the first time, a rapid one‐step room temperature synthetic strategy is introduced to prepare highly emissive solid‐state‐fluorescent CDs (RT‐CDs). A strong oxidizing agent, potassium periodate (KIO4), is adopted as a catalyst to facilitate the cyclization of o‐phenylenediamine and 4‐dimethylamino phenol in aqueous solution at room temperature for only 5 min. The resultant organic molecule, 2‐(dimethylamino) phenazine, will self‐assemble kinetically to generate supramolecular‐structure CDs during crystallization. The elaborately arranged supramolecular structure (J aggregates) endows CDs with intense solid‐state‐fluorescence. Density functional theory (DFT) calculation shows that the excited state of RT‐CDs exhibits charge transfer characteristic owing to the unique donor‐Π‐acceptor structure. A high‐performance monochrome RT‐CDs based electroluminescent LEDs (2967 cd m−2 and 1.38 cd A−1) were fabricated via systematic optimizations of device engineering. This work provides a concrete and feasible avenue for the rapid and massive preparation of CDs, advancing the commercialization of CDs based optoelectronic devices.

Innovations in the Solid‐State Fluorescence of Carbon Dots: Strategies, Optical Manipulations, and Applications

“…Self‐assembled structures can also greatly limit vibrational rotation in CDs, which is the key to achieving solid‐state luminescence. [ 157–159 ]…”

“…[ 118 ] Alternatively, intermolecular forces can arrange small molecular precursors in J‐aggregation during carbonization, and this misaligned parallel arrangement can reduce or avoid direct π  π contact, thus allowing SSF (Figure 8b). 159 ]…”

Supramolecular Surface Engineering of Carbon Dots Enables Matrix‐Free Room Temperature Phosphorescence†

“…[ 7‐11 ] CDs have been widely used in sensing, in vitro / in vivo imaging, cancer therapy, catalysts and optoelectronic devices. [ 12‐19 ] Despite the well documented fluorescent properties, CDs with RTP have also been reported by several groups. [ 20 ] Lin and co‐workers reported the production of effective RTP by aggregation‐induced of CDs in trimellitic acid.…”

Spectral Regulation of Carbon Dots and the Realization of Single-Component Solar-Simulated White Light-Emitting Diodes

“…Carbon dots have attracted a significant amount of attention owing to their superior optical properties, , low toxicity, favorable biocompatibility, and stability, showing great potential in many applications, such as photocatalysts, optoelectronic devices, − biological imaging, chemical analysis, etc. Up to now, various methodologies for the synthesis of CDs like electrophoresis, the hydrothermal method, the microwave method, and the solvothermal method have been reported. − Benefiting from these methods above, many types of full-color CDs have been prepared, and the optical properties were deeply studied. , In 2018, Xiong et al reported a new solvent-controlled synthetic route, which achieved an effective regulation of the dehydration and carbonization processes by only changing the reaction solvent, resulting in highly luminescent CDs with PL emissions from 443 to 745 nm .…”