Synthesis of Strongly Fluorescent Graphene Quantum Dots by Cage-Opening Buckminsterfullerene

Abstract

Graphene quantum dots is a class of graphene nanomaterials with exceptional luminescence properties. Precise dimension control of graphene quantum dots produced by chemical synthesis methods is currently difficult to achieve and usually provides a range of sizes from 3 to 25 nm. In this work, fullerene C60 is used as starting material, due to its well-defined dimension, to produce very small graphene quantum dots (∼2-3 nm). Treatment of fullerene C60 with a mixture of strong acid and chemical oxidant induced the oxidation, cage-opening, and fragmentation processes of fullerene C60. The synthesized quantum dots were characterized and supported by LDI-TOF MS, TEM, XRD, XPS, AFM, STM, FTIR, DLS, Raman spectroscopy, and luminescence analyses. The quantum dots remained fully dispersed in aqueous suspension and exhibited strong luminescence properties, with the highest intensity at 460 nm under a 340 nm excitation wavelength. Further chemical treatments with hydrazine hydrate and hydroxylamine resulted in red- and blue-shift of the luminescence, respectively.

Sensitivity to Heavy-Metal Ions of Unfolded Fullerene Quantum Dots

“…1d) confirmed that the as-prepared UFQDs had a relatively narrow size distribution with <2RH> 3.5 ± 1.0 nm, in agreement with the data of Ref. [38] and in reasonable agreement with the expected dimensions of monodisperse unfolded fullerene. Comparable PL quenching effects, with different values of sensitivity to the ion concentration, were also observed in the presence of Pb 2+ and As(III) (Figs.…”

“…1a) were similar to those of Ref. [38] and, along with the absorption curve and the dependence of the emission peak on the excitation wavelength (Fig. 1b,c), showed the characteristic spectral features found in regular GOQDs synthesized from graphite or citric acid [28][29][30][31][32][33][34] [35].…”

“…Within this framework, we have recently investigated [37] a novel type of graphene-like quantum dots synthesized by low-temperature oxidation and unfolding of C60 buckminsterfullerene [38]. Due to the peculiar structure of buckminsterfullerene¸ the carbon nanosheets synthesized with this technique have a lattice made of both hexagons and pentagons, which could give rise to a different configuration for the sp 2 domains, the content and location of defects and the functional groups.…”

“…UFQDs were prepared from C60 fullerene by a chemical oxidation trough modified Hummers method, as reported elsewhere [38]. Briefly, the fullerene was oxidized using NaNO3, KMnO4 and H2SO4.…”

“…Aqueous suspensions of UFQDs were prepared by oxidation and cage-opening of C60 buckminsterfullerene according to the reported method [38]. The obtained stable aqueous suspension appeared with the characteristic brownish colour, no appreciable Tyndall effect and UVinduced photoluminescence (Fig.…”