Quantum Yield Enhancement in Graphene Quantum Dots via Esterification with Benzyl Alcohol

Suzuka Tachi,Misaki Takahashi,Shota Kuwahara,Takuya Hosokai,Toshiki Sugai,Hiroki Morita,Yusuke Okabayashi

doi:10.1038/s41598-019-50666-3

Abstract

The quantum yield of graphene quantum dots was enhanced by restriction of the rotation and vibration of surface functional groups on the edges of the graphene quantum dots via esterification with benzyl alcohol; this enhancement is crucial for the widespread application of graphene quantum dots in light-harvesting devices and optoelectronics. The obtained graphene quantum dots with highly graphene-stacked structures are understood to participate in π–π interactions with adjacent aromatic rings of the benzylic ester on the edges of the graphene quantum dots, thus impeding the nonradiative recombination process in graphene quantum dots. Furthermore, the crude graphene quantum dots were in a gel-like solid form and showed white luminescence under blue light illumination. Our results show the potential for improving the photophysical properties of nanomaterials, such as the quantum yield and band-gap energy for emission, by controlling the functional groups on the surface of graphene quantum dots through an organic modification approach.

Highlights

Graphene quantum dots (GQDs), carbon-based nanometre-sized materials, have a size-dependent photophysical property originating from the quantum confinement effect; many applications have been proposed, such as bioimaging probes, sensors, light emitting devices and solar cells[1,2,3,4,5,6,7,8]
In the case of GQD-Bn (W), a lattice parameter of 0.256 ± 0.023 nm was observed for the small particle, whereas no patterns appeared for the large round thin layer (Fig. 1b,d)
The esterification of GQDs with benzyl alcohol seems to result in formation of a highly stacked structure of large, round GQD layers that are soluble in toluene

Summary

Introduction

Graphene quantum dots (GQDs), carbon-based nanometre-sized materials, have a size-dependent photophysical property originating from the quantum confinement effect; many applications have been proposed, such as bioimaging probes, sensors, light emitting devices and solar cells[1,2,3,4,5,6,7,8]. We synthesized esterified GQDs with benzyl alcohol, a simple aromatic alcohol compared to the previously reported compounds for the edge modification of GQDs16–18, which exhibited a stacked structure of graphene sheets with an average diameter of 24.7 nm, and the absolute QYs reached to 0.25 in toluene.

Results

Conclusion