%0 Journal Article %A Skaltsas T.%A %A Ke X.%A %A Bittencourt C.%A %A Tagmatarchis N. %D 2013 %T Ultrasonication induces oxygenated species and defects onto exfoliated graphene %J Journal of Physical Chemistry C %V 117 %@ 1932-7447 %R 10.1021/jp4057048 %P 23272–23278 %N 44 %U https://hdl.handle.net/10442/17212 %X The effect of ultrasonication parameters, such as time and power applied, to exfoliate graphite in o-dichlorobenzene (o-DCB) and N-methyl-1,2-pyrrolidone (NMP) was examined. It was found that the concentration of graphene was higher in o-DCB, while its dispersibility was increased when sonication was applied for a longer period and/or at higher power. However, spectroscopic examination by X-ray photoelectron spectroscopy (XPS) revealed that ultrasonication causes defects and induces oxygen functional groups in the form of carboxylic acids and ethers/epoxides onto the graphene lattice. Additional proof for the latter arose from Raman, IR, and thermogravimetry studies. The carboxylic acids and ethers/epoxides onto exfoliated graphene were derived from air during ultrasonication and found independent of the solvent used for the exfoliation and the power and/or time ultrasonication applied. Quantitative evaluation of the amount of oxygenated species present on exfoliated graphene as performed by high-resolution XPS revealed that the relative oxygen percentage was higher when exfoliation was performed in NMP. Finally, the sonication time and/or power affected the oxygen content on exfoliated graphene, since extended ultrasonication resulted in a decrease in the oxygen content on exfoliated graphene, with a simultaneous increase of defected sp3 carbon atoms. %> Αποθετήριο Ήλιος / ΕΙΕ