Synthesis of N, F and S co-doped graphene quantum dots

Abstract

Graphene quantum dots (GQDs) are a promising category of materials with remarkable size dependent properties like tunable bandgap and photoluminescence along with the possibility of effective chemical functionalization. Doping of GQDs with heteroatoms is an interesting way of regulating their properties. Herein, we report a facile and scalable one-step synthesis of luminescent GQDs, substitutionally co-doped with N, F and S, of ∼2 nm average size by a microwave treatment of multi-walled carbon nanotubes in a customized ionic liquid medium. The use of an ionic liquid coupled with the use of a microwave technique enables not only an ultrafast process for the synthesis of co-doped GQDs, but also provides excellent photoluminescence quantum yield (70%), perhaps due to the interaction of defect clusters and dopants.

Tuning the Photoluminescence of Graphene Quantum Dots by Fluorination

“…Combined with the clear fluorine peak at 686 eV, the intense peak at 287.1 eV confirms the existence of C-F covalent bonding in F-GQDs [23]. Figure 2(d) reveals two kinds of bonding in the F 1s spectra, 685.9 eV owing to the semi-ionic C-F bonding and 688.6 eV is due to a covalent C-F bonding pattern [24]. Obviously, F is in the form of functional groups within the F-GQDs, not in the form of elemental crystal physically adsorbed or wrapped within them.…”

Recent Advances in Graphene Quantum Dots as Bioimaging Probes

“…So, dicyandiamide (DCD) [105,106,112], ammonium hydroxide [77,89,91,93,114,115,[129][130][131][132], diethylenetriamine (DETA) [133], urea [107], ethylenediamine (EDA) [111], dimethylformamide (DMF) [38,134] and hydrazine hydrate [123] are chosen as the nitrogen source for doping or modifying GQDs to synthesize nitrogen-functionalized GQDs, while 1,4-phenylene bis(boronic acid) [65], boron oxide (B 2 O 3 ) [76] and Na 2 B 4 O 7 [135] are employed as boron sources to prepare boron-functionalized GQDs. Also, nitrogen and sulfur co-functionalized GQDs are successfully obtained using nitrogen and sulfur containing compounds of 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl) imide [68], polythiophene [136] and thiourea [110]. Moreover, o-dichlorobenzene [128], ATP [119,120] and 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide [68] are utilized as sources to prepare chloride-, phosphorus-and fluoride-functionalized GQDs, respectively.…”

“…Also, nitrogen and sulfur co-functionalized GQDs are successfully obtained using nitrogen and sulfur containing compounds of 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl) imide [68], polythiophene [136] and thiourea [110]. Moreover, o-dichlorobenzene [128], ATP [119,120] and 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide [68] are utilized as sources to prepare chloride-, phosphorus-and fluoride-functionalized GQDs, respectively. The dimensions and heights of graphene sheets in the obtained GQDs range from 1.5 to 100 nm and 0.5 to 5 nm, respectively.…”

“…Generally, the approaches can be divided into two groups: top-down and bottom-up methods. In the top-down methods, GQDs are usually synthesized through the cleavage of relatively large bulk precursors, such as graphite [53][54][55], carbon black [56][57][58], coal [59][60][61], metal-organic framework (MOF) [40], 3D graphene [62], graphene oxide (GO) [63][64][65][66][67], carbon nanotubes [68][69][70], carbon fiber [53,[71][72][73] and C 60 [74,75] into small pieces of graphene sheets by chemical oxidation etching [76][77][78][79][80][81], electrochemical exfoliation [65,[82][83][84][85], Li/K intercalation [86,87], hydrothermal/solvothermal treatment [88][89][90][91][92][93][94], microwave irradiation [95...…”

Quantum dots in nanomedicine: recent trends, advances and unresolved issues

“…tuneable emission bands and amenability to targeted bio-functionalization. Doping of these graphene QDs with heteroatoms can further attenuate their optical qualities, permitting to achieve the photoluminescence quantum yield of up to 70% [39]. Chua et al have successfully used fullerene C60 to produce very small graphene QDs of 2e3 nm which demonstrated good dispersion qualities in aqueous suspension and exhibited strong luminescence emission at 460 nm, which could be shifted to red or blue areas of spectrum following customised chemical treatment with hydrazine hydrate and hydroxylamine [40].…”