Influence of pH on the fluorescence properties of graphene quantum dots using ozonation pre-oxide hydrothermal synthesis

Abstract

Recent research into graphene-based materials is largely focused on graphene quantum dots (GQDs) and their optical properties. A facile method has been developed to extract GQDs from reduced graphene oxide (RGO) by the ozonation pre-oxide method. The as-prepared GQDs, which were 2-5 nm in diameter, exhibited strong fluorescence activity ranging from $355 nm to $440 nm. The prepared GQDs possessed strong fluorescence with quantum yields from 3.18% to 9.48%. What's more, the fluorescence properties of the GQDs could be determined by tuning the pH of the ozonation system. We speculated the mechanisms of ozonation, thermal and hydrothermal treatment. We found that pyrocatechol could lead to fluorescence quenching of the GQDs, which might produce novel potential for the detection of targets.

Preparation of graphene quantum dots based core-satellite hybrid spheres and their use as the ratiometric fluorescence probe for visual determination of mercury(II) ions

“…If the solution pH value is switched between 10.0 and 4.0, the fluorescence intensity of GQDs varies reversibly (Fig. 4C), in accordance with the spectra reported previously [55]. Fig.…”

Carbon Based Dots and Their Luminescent Properties and Analytical Applications

“…However, under acidic solutions, the zigzag sites in the CDs were protonated and inactive. Some other research groups also noticed similar pH-dependent PL from their obtained CDs [52,79,160]. However, most CDs exhibited different responses toward the change of pH value.…”

“…Therefore, a subsequent chemical oxidation was necessary to release the ultrafine pieces from the SWCNTs matrixes for obtaining CDs. Yang et al [79] developed an ozonation pre-oxide method to extract CDs from reduced GO. GO dispersed in DI water with hydrogen peroxide at different pH was first treated with ozone for 1 h. The obtained ozonized GO (O-GO) was thermally deoxidized in argon atmosphere before being oxidized by ozone again.…”

Graphene quantum dots in analytical science

“…Hydrothermal routes for GQD synthesis involve dissolving or dispersing an appropriate carbon-based raw material in water and heating at 180-200ºC at high pressure in a closed container (usually an autoclave) for 2-12 h [19,[26][27][28]. Solvothermal syntheses of GQDs use organic solvents {e.g., dimethylformamide (DMF) [29]}, and heating temperatures and times similar to those of hydrothermal routes.…”