Quantum Confinement Effect in the Absorption Spectra of Graphene Quantum Dots
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.18
Quantum Confinement Effect in the Absorption Spectra of Graphene Quantum Dots Leon Yang1, Devon Reed1, Kofi W. Adu1,2, Ana Laura Elias Arriaga2
1
Pennsylvania State University, Altoona, PA, 16601, U. S. A.
2
Pennsylvania State University, University Park, PA 16802, U. S. A.
ABSTRACT
Our preliminary investigation of the absorption and the photoluminescence response of selectively separated graphene quantum dots using centrifugation indicate that the photoluminescence is more sensitive to the size of the quantum dot than the absorption. We observed ~143nm blueshift from 623nm to 480nm in the visible region of the photoluminescence with increasing successive centrifugation (decreasing size) and not in the corresponding absorption spectra in the visible region. However, for the first time, we observed a blueshift in the absorption spectra in the UV regions that is tentatively attributed to quantum confinement. Further detailed work is underway to confirm the blueshift in the absorption and correlate with deep UV photoluminescence and morphological quantification of the quantum dots size distribution using high resolution transmission electron microscope.
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INTRODUCTION Semiconductors nanostructures offer several potential technological applications, especially in optics and electro-optics due to quantum size effects with enhanced photoluminescence(PL) stability[1-3]. Furthermore, they can serve as a scaffold for grafting molecules or macromolecules[4-6]. However, they pose several challenges, most importantly, these semiconductor compounds are very toxic and there is no single compound that can produce the range of wavelengths within the UV-vis-IR spectrum. Over the past decade, graphene quantum dots(GQDs) have emerged as functional material for such applications due to their unique properties such as deep ultraviolet and blue to green luminescence[7–11, 16-19], two-photon induced fluorescence[12] minimal to no toxicity[8], chemical and photostability[12,13] and biocompatibility[12,14]. These attractive properties of GQDs are mainly due to the bandgap opening of two-dimensional graphene[14], quantum confinement effects[12], edge effects[12] surface functionalization[9,13] and doping[15]. One of the obstacles that is hindering the development and application of graphene quantum dots in optoelectronics, photonics and bioimaging is the limited number of emission colors, with only blue [8,10,11], green [7,8,11] and deep UV[16-19] being reported. Most of these were achieved through either doping or functionalization[16-19]. Obviously, the main interest is to produce graphene quantum dots that can provide emissions ranging from IR to UV using quantum size effect. In general, GQDs can be prepared usi
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