Eco-friendly synthesis of size-controllable amine-functionalized graphene quantum dots with antimycoplasma properties

Abstract

Size-controllable amine-functionalized graphene quantum dots (GQDs) are prepared by an eco-friendly method with graphene oxide sheets, ammonia and hydrogen peroxide as starting materials. Using a Sephadex G-25 gel column for fine separation, for the first time we obtain GQDs with either single or double layers. By atomic force microscopy characterization, we confirm that hydrogen peroxide and ammonia play a synergistic role on graphene oxide (GO), in which the former cuts the GO into small pieces and the latter passivates the active surface to give amine-modified GQDs. Due to the low cytotoxicity and excellent biocompatibility of the obtained amine-functionalized GQDs, besides the multiwavelength imaging properties of GQDs, for the first time we find that this kind of GQD exhibits good antimycoplasma properties. Given the superior antimycoplasma effect of the GQDs and their eco-friendly mass production with low cost, these new GQDs may offer opportunities for the development of new antimycoplasma agents, thus extending their widespread application in biomedicine.

Photoluminescent and superparamagnetic reduced graphene oxide–iron oxide quantum dots for dual-modality imaging, drug delivery and photothermal therapy

“…This emission value is slightly lower than that (420 nm) observed for the GQDs prepared by the same hydrothermal method [40]. Quantum yield measurements (using Equation 1) gave a value of 7.9% for the MGQDs, similar to the published literature for GQDs (5.5-14%) prepared by other groups [20,23,24,75] and slightly lower than the GQDs prepared using the same method (9.4%) [40]. These suggest the presence of IO slightly quenches the luminescence of GQDs.…”

“…The cell viability of nanoparticles at higher concentrations can be improved upon by passivation with a coating of a biocompatible organic compound, with amine functionalized GQDs [23] and IO functionalized by pullulan [87] significantly improving the cell viability of the respective nanoparticles. Chitosan could also act as a passivation agent as previous work has shown that chitosan functionalized rGO was more stable in simulated body fluids than pristine GO [89], and that chitosan functionalized graphene nanosheets are biocompatible and do promote the proliferation of cells [90].…”

“…This led to the development of biocompatible carbon-based QDs, with QDs derived from carbohydrates [20], nanodiamonds [21], and graphene [22][23][24][25]. Graphene QDs (GQDs) can be created by ultrasonication [22], chemical reduction [23], photo-reduction [24], and hydrothermal cutting [25].…”

Recent Advances in Graphene Quantum Dots as Bioimaging Probes

“…Furthermore, doping and/or surface passivation are effective methods to modulate the electronic density of bulk semiconductor materials and to tune their optical and electrical properties. 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].…”

“…In contrast to unfunctionalized GQDs, the specially functionalized GQDs can label cells more efficiency and specifically [149,150]. For instance, Jiang et al [130] synthesized single-or double-layered size-controllable amine-functionalized GQDs by an eco-friendly method with graphene oxide sheets, ammonia and hydrogen peroxide as starting materials, and found a negligible toxicity to HeLa cells for amine-functionalized GQDs. In addition, Chen et al [151] prepared the pyrrole-ring surface-functionalized graphene quantum dots (p-GQDs) by a twostep hydrothermal approach under microwave irradiation of graphene oxide in an ammonia medium.…”