Abstract
Graphene quantum dots (GQDs), a novel type of zero-dimensional fluorescent materials, have gained considerable attention owing to their unique optical properties, size and quantum confinement. However, their high cost and low yield remain open challenges for practical applications. In this work, a low cost, green and renewable biomass resource is utilised for the high yield synthesis of GQDs via microwave treatment. The synthesis approach involves oxidative cutting of short range ordered carbon derived from pyrolysis of biomass waste. The GQDs are successfully synthesised with a high yield of over 84%, the highest value reported to date for biomass derived GQDs. As prepared GQDs are highly hydrophilic and exhibit unique excitation independent photoluminescence emission, attributed to their single-emission fluorescence centre. As prepared GQDs are further modified by simple hydrothermal treatment and exhibit pronounced optical properties with a high quantum yield of 0.23. These modified GQDs are used for the highly selective and sensitive sensing of ferric ions (Fe3+). A sensitive sensor is prepared for the selective detection of Fe3+ ions with a detection limit of as low as 2.5 × 10–6 M. The utilisation of renewable resource along with facile microwave treatment paves the way to sustainable, high yield and cost-effective synthesis of GQDs for practical applications.
Highlights
Graphene quantum dots (GQDs), as a zero-dimensional derivates of graphene, have ignited tremendous research interests in recent years[1,2,3,4,5,6]
GQDs were successfully synthesised by oxidative cutting of a biomass-derived carbon rich precursor using nitric acid (HNO3) as an oxidising agent via microwave heating of 15–180 min duration
The PL intensity increases with an increase in the treatment time up to 120 min and decreases thereafter (Fig. 2b). These results suggest that increase in power and process time intensify the cleavage of carbon domains into nanosized GQDs leading to enhanced optical emission, while increasing the power and time over a certain limit may cause the destruction of the surface and structure of GQDs resulting in diminished PL emission
Summary
Graphene quantum dots (GQDs), as a zero-dimensional derivates of graphene, have ignited tremendous research interests in recent years[1,2,3,4,5,6]. GQDs offer significant advantages of low cost, high water solubility, stable fluorescence, tunable bandgap, low toxicity and good b iocompatibility[8,9,10,11], and making them a legitimate competitor to the traditional semiconductor quantum dots (QDs) (e.g. ZnS, TiO, CdSe, CdS, CdTe), which are expensive, cytotoxic, and show low-biocompatibility[12]. A high product yield of ~ 84% was achieved with increasing the reaction time or microwave power These GQDs were modified by simple hydrothermal treatment and displayed enhanced optical properties for the selective and sensitive detection of metal ions. This procedure is generic and applicable to any other biomass waste which can yield carbon rich precursor by pyrolysis treatment
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