Yellow Fluorescent Nitrogen and Bromine Co-doped Graphene Quantum Dots for Bioimaging

Abstract

Currently, the large-scale commercial/industrial application of graphene quantum dots (GQDs) is generally limited by their low production and lack of diverse photoluminescence (PL) properties such as GQDs with long-wavelength emissions and high quantum yields. Herein, for the first time, a facile deflagration method was developed for the ultrafast and gram-scale synthesis of N and Br co-doped GQDs (NBr-GQDs) with bright yellow PL emissions. NBr-GQDs exhibited an excitation-independent emission property with a central PL wavelength of ∼579 nm. The results of theoretical calculations revealed that N and Br co-doping may reduce the band gap between the excited singlet states and decrease the intersystem crossing effect of excited electrons from the singlet to the triplet state, thus considerably improving the quantum yield (as high as 52%). Moreover, a series of experiments were performed, and their results showed that the synthesized NBr-GQDs achieved excellent pH tolerance, long PL lifetime, and low cytotoxicity. Using HeLa cells as specimens, it was demonstrated that NBr-GQDs could successfully enter the HeLa cytoplasm and achieve high-quality fluorescent labeling, indicating their great potential in the bioimaging field.

Sustainable Nanomaterials for Biomedical Applications

“…In another work, Gong et al synthesized N and Br co-doped GQDs using a rapid and large-scale approach. The results showed high cellular uptake and high-quality fluorescence labeling ability, suggesting their great promise for cellular bioimaging [ 110 ]. Since these nanomaterials have hydrophilic surface groups (carboxylic and amine), the covalent or non-covalent surface modification strategies can be used to attach targeting and drug molecules on the surface of CDs and GQDs for designing targeted drug delivery platforms for the treatment of cancerous diseases [ 108 ].…”

Graphene‐Based Nano Materials: Biomedical Applications

“…Gong et al 72] prepared nitrogen and bromine doped graphene quantum dots (NBr-GQDs) using ultrafast deflagration method, which results in excitation independent emission at a wavelength of 579 nm. The composite exhibits excellent pH…”

Halogen-Doped Carbon Dots: Synthesis, Application, and Prospects

“…Gong et al [ 88 ] first designed a deflagration method for the rapid synthesis of NBr-GQDs (average diameter: 3.5 nm, thickness: <2 nm) that emit yellow fluorescence owing to their PL ( Figure 7 D). Because of the N and Br co-doping, the band gap between the excited singlet states and their crossover with triplet states are reduced; hence, the GQDs exhibit a high QY (52%).…”

“…Copyright 2014, 2018, 2020, and 2021 copyright RSC. Reprinted/adapted with permission from [ 88 , 89 ]. Copyright 2015, 2021 American Chemical Society.…”