Liquid-phase laser ablation synthesis of graphene quantum dots from carbon nano-onions: Comparison with chemical oxidation

Rosemary L Calabro; Dong-Sheng Yang; Doo Young Kim

doi:10.1016/j.jcis.2018.04.113

Liquid-phase laser ablation synthesis of graphene quantum dots from carbon nano-onions: Comparison with chemical oxidation

J Colloid Interface Sci. 2018 Oct 1:527:132-140. doi: 10.1016/j.jcis.2018.04.113. Epub 2018 May 9.

Authors

Rosemary L Calabro¹, Dong-Sheng Yang², Doo Young Kim³

Affiliations

¹ Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA.
² Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA. Electronic address: dyang0@uky.edu.
³ Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA. Electronic address: dooyoung.kim@uky.edu.

PMID: 29787949
DOI: 10.1016/j.jcis.2018.04.113

Abstract

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.

Keywords: Graphene quantum dots; Laser ablations; Photoluminescence lifetime.