We have developed a facile, fast, and one-step synthetic method to prepare graphene quantum dots (GQDs) simultaneously with nitrogen (N) doping via pulsed laser ablation. The N-doped GQDs (N-GQDs) with an average size around 3 nm and an N/C atomic ratio of 33% have been obtained. The N-GQDs emit blue photoluminescence (PL), where the PL intensity enhances as the N doping increases. The PL enhancement for the N-GQDs with a factor as high as 25 has been achieved as compared to GQDs. The origin of the PL enhancement in GQDs after N doping is attributed to the increased densities of pyridinic and graphitic N.
Modulation
of the photoluminescence (PL) properties in graphene
oxide quantum dots (GOQDs) is important for fundamental research and
applications in bioimaging and optoelectronic devices. Herein, the
synthesis of GOQDs doped with diethylenetriamine (DETA)
was implemented by one-pot synthesis via oil bath heating. The PL
intensity in the GOQDs was increased by an enhancement factor of ∼13.2
following the DETA doping. The band gap of the GOQDs increased with
the increase in DETA doping, producing tunable PL from red to blue
emission with a wavelength change of ∼265 nm. The significant
tuning of the PL wavelength in the GOQDs was attributed to the variation
of pyrrolic and/or graphitic N in the C–N bonding configuration.
The synthesized GOQDs were found to inject carriers into the gallium
nitride (GaN) epilayer in the GOQD/GaN composite, which in turn enhance
the PL in the GaN epilayer. Our observations provide effective approaches
for tuning the PL wavelength in GOQDs and enhancing the PL intensity
in GaN; these are promising developments for applications in optoelectronic
devices such as light-emitting diodes and solar cells.
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