Ultrasonication Induces Oxygenated Species and Defects onto Exfoliated Graphene

Abstract

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.

Graphene Ink Film Based Electrochemical Detector for Paracetamol Analysis

“…Similar phenomena were reported by other studies as well [36][37][38]. It is well known that the graphene used for ink preparation was usually produced using top-down exfoliation methods in order to control the cost [39,40]. However, the exfoliation technique inevitably introduced many defects into graphene.…”

Insights into the superhydrophobicity of metallic surfaces prepared by electrodeposition involving spontaneous adsorption of airborne hydrocarbons

“…The O 1s spectrum in Fig. 2(d) is resolved into three peaks centered at 530.8, 532.0, and 533.2 eV from CuO, OH, and C O species [51][52][53][54]. These XPS analyses reveal that besides copper oxides, there were organic contaminations on the micro/nanostructured Cu surface.…”

“…The C 1s spectrum shown in Fig. 2(c) is resolved into four peaks with binding energies of 284.5, 285.3, 286.6 and 288.7 eV, and they correspond to C C, C C/C H, C O C/C O and COOH/C O, respectively [53,54], where hydrocarbons (C C, C C/C H) predominate. The O 1s spectrum in Fig.…”

“…The O 1s spectrum in Fig. 3(d) is resolved into three peaks centered at 531.8, 532.9, and 533.6 eV from OH, C O and C O C species, respectively [53,54,57], and no Au O was detected because Au is stable under room temperature. These results also demonstrate that organic contaminations occurred on the prepared Au surface, which also made contribution for the superhydrophobicity of micro/nanostructured Au by decreasing the surface energy.…”

Rapid fabrication of SERS substrate and superhydrophobic surface with different micro/nano-structures by electrochemical shaping of smooth Cu surface

“…The C 1s spectrum of XPS shown in Fig. S2a (Supplementary data) is resolved into four peaks with binding energies of 284.78 eV, 285.68 eV, 286.45 eV, and 288.28 eV, attributed to C C, C-C/C-H, C-O-C/C-OH, and O-C O, respectively [31,34], where hydrocarbons (C C and C-C/C-H) predominate. The XPS analyses reveal that organic contaminations from air were inevitable, they spontaneously and rapidly adsorbed on the micro/nano-structured Cu surfaces while dried in air [16].…”