The effect of laser energy density on the properties of Graphene dots

Abstract

The structural and optical properties of dots based on graphene oxide (GO) obtained by laser ablation method with various energy densities of radiation were studied. It was shown that after laser ablation, the average lateral size of GO sheets was decreased from 1280–1900 nm to 230±95 nm and 110±42 nm for samples prepared at a laser radiation with energy density of E~15 and 21 mJ/cm2, respectively. Raman spectroscopy data showed that after ablation, the ID/IG ratio decreased from 1.04 to 0.97, indicating an increase in the number of sp2- hybridized domains in GO after ablation. A change in the energy density has practically no effect on a change in its functionalization, as well as the ordering of sp2 domains inside a GO sheet. The optical density of GO dispersions and the intensity of their fluorescence depend on the ablation conditions. For non-ablated dispersions along with the luminescence band at 450 nm, additional band appears in the spectrum with a maximum at about 600 nm. After ablation the distribution of particles becomes more uniform, as evidenced by both the change in the shape of the GO luminescence band and the constancy of the fluorescence lifetime upon registration at different wavelength.