Enhancing the Fluorescence of Graphene Quantum Dots with a Oxidation Way

Abstract

It is a facile and efficient way to produce grapheme quantum dots (GQDs) through photo-Fenton reaction. However, the fluorescence of the as-generated GQDs is weak. Here, bright yellow-green fluorescent graphene quantum dots (GQDs) were prepared by post-oxidation of the GQDs with H2O2. The fluorescence quantum yields of the post-oxidized GQDs (O-GQDs) increased from 0.08% to 3.3% and the maximum emission wavelength shifted from 450 to 510 nm. The O-GQDs exhibit excitation-independent and pH-dependent photoluminescence behaviors. The increase of the photoluminescence intensity is attributed to the more carbonyl and carboxyl groups after the post-oxidation. The post-oxidation treatment offers a simple pathway to enhance the fluorescence of GQDs.

Chemical Nature of Redox-Controlled Photoluminescence of Graphene Quantum Dots by Post-Synthesis Treatment

“…For example, Wang and co-workers had stated that the common green luminescence emission centers in these GQDs synthesized by bottom-up and top-down methods can be unambiguously assigned to special edge states consisting of several carbon atoms on the edge of carbon backbone and functional groups with CO (carbonyl and carboxyl groups) . Meanwhile, based on other studies (shown as Figures S7–S10), − a similar conclusion can be drawn. For the G–OH hybridized states, Yang et al pointed out that they mainly contribute to the blue emission and increase the electron density of the π structure in GQDs .…”

Graphene quantum dots in analytical science

“…Recent studies have shown that surface oxidation [73] or reduction [11,74] effectively alters the PL properties of GDQs and improves their optical performance. Post-synthesis hydrothermal treatments have also proved useful for regulating the PL properties of GQDs obtained by using various routes and bulk materials as a result of their removing epoxy and hydroxyl groups from the GQD surface ( Fig.…”

“…Surface functionalization with small organic molecules, such as alcohols, diamines, thiols, ionic liquids (ILs) and glutathione (GSH) [12,18,20,73], is also useful to modulate the PL of GQDs. Recent studies have shown that surface oxidation [73] or reduction [11,74] effectively alters the PL properties of GDQs and improves their optical performance.…”

The Enhanced Photoluminescence Properties of Carbon Dots Derived from Glucose: The Effect of Natural Oxidation

“…Several studies have found that the QY of CDs can be substantially enhanced by removing oxygen-related groups through violent reduction reaction treatments [12][13][14]. However, contrary findings have also been reported by other researchers [15][16][17]. Additionally, the emission wavelength of CDs tends to redshift with an increase in oxygen-containing groups, as the optical bandgap of CDs narrows after incorporating these species [18,19].…”

“…Based on these ultrafiltration results, we consider that the blue emission primarily originates from small carbonaceous materials. Moreover, the change in the surface configurations and particle sizes of the CDs tailored through different oxidation methods (chemical or natural) may impart distinct optical properties to the CDs [14][15][16][17]. Xu's group used an HNO3 reflexing method to oxidize the CDs and noted that the oxidation not only increased the oxygen content but also led to the formation of an oxygen-containing loose shell on the surface of the CDs [14].…”