Graphene quantum dots (GQDs) have been synthesized reproducibly by chemical oxidation (CO) of carbon nano-onions (nCNOs) and a one-step pulsed laser ablation (LA) of nCNOs in deionized water. The photoluminescence (PL) spectra show that the LA-GQDs have blue shifted emission relative to the CO-GQDs which is attributed to the effects of both particle sizes and surface functional groups. The CO-GQDs have an average diameter of 4.1(8) nm and a thickness corresponding to two or three graphene layers, while the LA-GQDs have an average diameter of 1.8(6) nm and a thickness comparable to a single layer of graphene. The CO-GQDs favor the presence of carboxylic groups and have a higher fraction of sp2 carbons, while the LA-GQDs prefer the presence of hydroxyl groups and have a higher fraction of sp3 carbons. PL lifetime data suggests that surface functional groups are the main source of radiative deactivation and the sp2 carbon domains are mainly responsible for non-radiative decay. PL lifetimes are measured to be 7.9(6) ns for the emission from the carboxylic groups and 3.18(10) ns from the hydroxyl groups. Compared to CO, liquid-phase LA is a faster and cleaner one-step method for producing GQDs with fewer starting chemicals and byproducts.
|Number of pages||9|
|Journal||Journal of Colloid and Interface Science|
|State||Published - Oct 1 2018|
Bibliographical noteFunding Information:
We acknowledge financial support from the National Science Foundation Division of Chemistry ( CHE-1362102 , DSY) and the University of Kentucky Research Challenge Trust Fund (RLC). DYK acknowledges the support from National Science Foundation under Cooperative Agreement No. 1355438 . The purchase of a new XPS system recently installed at the University of Kentucky was supported by the fund from the NSF EPSCoR grant (grant no. 0814194 ). We also acknowledge additional support from the Kentucky Science and Engineering Foundation.
- Graphene quantum dots
- Laser ablations
- Photoluminescence lifetime
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films
- Colloid and Surface Chemistry