Photonics of shungite quantum dots

TL;DR

This paper investigates the photonic properties of shungite quantum dots, revealing their fractal colloidal structures, dual emission centers, and presenting the first observation of photoluminescence spectra of individual GQDs in frozen dispersions.

Contribution

It provides new insights into the morphology and spectral behavior of shungite GQDs, including the first observation of their photoluminescence spectra in frozen dispersions.

Findings

GQDs form fractals with solvent-dependent structures

Spectral broadening due to colloidal inhomogeneity

First observation of photoluminescence of individual GQDs in frozen dispersions

Abstract

Shungite quantum dots are associated with nanosize fragments of reduced graphene oxide similarly to synthetic graphene quantum dots thus forming a common class of GQDs. Colloidal dispersions of powdered shungite in water, carbon tetrachloride, and toluene form the ground for the GQD photonic peculiarities manifestation. Morphological study shows a steady trend of GQDs to form fractals and a drastic change in the colloids fractal structure caused by solvent was reliably established. Spectral study reveals a dual character of emitting centers: individual GQDs are responsible for the spectra position while fractal structure of GQD colloids provides high broadening of the spectra due to structural inhomogeneity of the colloidal dispersions and a peculiar dependence on excitation wavelength. For the first time, photoluminescence spectra of individual GQDs were observed in frozen toluene dispersions which pave the way for a theoretical treatment of GQD photonics.