Mechanisms of emissions, especially electrochemiluminescence (ECL), for graphene quantum dots (GQDs) are poorly understood, which makes near-infrared (NIR)-emitting GQDs difficult to create. To explore this poorly understood NIR ECL, two GQDs, nitrogen-doped GQDs (GQD-1) and nitrogenand sulfur-doped ones (GQD-2), were prepared by a simple onestep solvothermal reaction with similar core structures but different surface states. The GQDs were analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and highresolution transmission electron microscopy. Photoluminescence results, with a comparable quantum efficiency of 13% to strong luminophores in aqueous media, suggested a mechanism that the emission mainly depends on the core structure while slightly adjusted by the heteroatom doping. ECL of GQD-2 dispersed in aqueous media with K 2 S 2 O 8 as the coreactant was measured by means of ECL−voltage curves and ECL spectroscopy, demonstrating strong NIR emissions between 680 and 870 nm, with a high ECL efficiency of 13% relative to that of the Ru(bpy) 3 2+ /K 2 S 2 O 8 system. Interestingly, ECL is generated by surface excited states emitting light at a much longer wavelength in the NIR region. The easily prepared GQD-2 has several advantages such as low cost and quite strong NIR-ECL in aqueous media, with which wide applications in biodetection are anticipated.

An N-annulated perylene diimide dimer, tPDI 2 Nhex, a graphene model compound with atomic precision, was investigated for luminescence applications. Electrochemiluminescence (ECL) of tPDI 2 N-hex was studied with tri-n-propylamine (TPrA) as a reducing coreactant. ECL-voltage curves along with spooling ECL spectra provided details of light generation mechanisms. The relative ECL quantum efficiency of the Ru(bpy) 3 (PF 6 ) 2 /TPrA system was calculated to be 64%, which is superior to that of many other organic molecules because of the desired excited state in the absence of surface states. An organic light-emitting diode (OLED) fabricated with tPDI 2 N-hex displayed bright orange-red emission with a low color temperature, which is very desirable. It is plausible that the sterically constrained and thus orthogonal aromatic moieties in the tPDI 2 N-hex structure, with atomic precision graphene layer characteristics, lead to the excellent luminescence performances. The ECL and OLED studies of tPDI 2 N-hex showcase great application potentials of tPDI 2 Nhex in both solution-based ECL probes and solid-state light devices.