title: Nonlinear Interactions of Zinc Phthalocyanine-Graphene Quantum Dots Nanocomposites: Investigation of Effects of Surface Functionalization with Heteroatoms.
abstract: This study reports the development of functional optical limiting materials composed of pristine graphene (GQDs), nitrogen-doped (NGQDs) and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots covalently linked to mono-amino substituted zinc phthalocyanine (Pc). Open aperture Z-scan technique was employed to monitor the behaviour of the conjugates under tightly focussed Gaussian laser beam using a mode-locked Nd:YAG laser delivering 10 nanosecond (FWHM) pulses at 532 nm wavelength. Nonlinear effect due to reverse saturable absorption was the predominant mechanism; and was attributed to the moderately enhanced triplet population. The major factor(s) responsible for the enhanced nonlinearities in the Pc-NGQDs and Pc-SNGQDs was fully described and attributed to the surface defects caused by the presence of heteroatoms of N and S.
authors.affiliation: Department of Chemistry, Rhodes University, Grahamstown, 6140, South Africa.
authors.forename: Owolabi M
authors.initials: OM
authors.lastname: Bankole
authors.affiliation: Department of Chemistry, Rhodes University, Grahamstown, 6140, South Africa.
authors.forename: Ojodomo J
authors.initials: OJ
authors.lastname: Achadu
authors.affiliation: Department of Chemistry, Rhodes University, Grahamstown, 6140, South Africa. t.nyokong@ru.ac.za.
authors.forename: Tebello
authors.initials: T
authors.lastname: Nyokong
keywords: 3rd order susceptibility; Graphene quantum dots; Hyperpolarizability; Nonlinear optics; Phthalocyanine