TY - JOUR ID - 10442/17212 A1 - Skaltsas T. A1 - A1 - Ke X. A1 - A1 - Bittencourt C. A1 - A1 - Tagmatarchis N. Y1 - 2013/// T1 - Ultrasonication induces oxygenated species and defects onto exfoliated graphene JF - Journal of Physical Chemistry C VL - 117 IS - 44 SN - 1932-7447 U3 - 10.1021/jp4057048 SP - 23272–23278EP - UR - https://hdl.handle.net/10442/17212 N2 - 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. ER -