Abstract
High-degree functionalization of graphene oxide (GO) nanoparticles (NPs) using polydopamine (PDA) was conducted to produce polydopamine functionalized graphene oxide nanoparticles (GO-PDA NPs). Aiming to explore their potential use as nanofiller in membrane separation processes, the spectral and structural properties of GO-PDA NPs were comprehensively analyzed. GO NPs were first prepared by the oxidation of graphite via a modified Hummers method. The obtained GO NPs were then functionalized with PDA using a GO:PDA ratio of 1:2 to obtain highly aminated GO NPs. The structural change was evaluated using XRD, FTIR-UATR, Raman spectroscopy, SEM and TEM. Several bands have emerged in the FTIR spectra of GO-PDA attributed to the amine groups of PDA confirming the high functionalization degree of GO NPs. Raman spectra and XRD patterns showed different crystalline structures and defects and higher interlayer spacing of GO-PDA. The change in elemental compositions was confirmed by XPS and CHNSO elemental analysis and showed an emerging N 1s core-level in the GO-PDA survey spectra corresponding to the amine groups of PDA. GO-PDA NPs showed better dispersibility in polar and nonpolar solvents expanding their potential utilization for different purposes. Furthermore, GO and GO-PDA-coated membranes were prepared via pressure-assisted self-assembly technique (PAS) using low concentrations of NPs (1 wt. %). Contact angle measurements showed excellent hydrophilic properties of GO-PDA with an average contact angle of (27.8°).
Highlights
Graphene and its based materials have been extensively researched recently owing to their unique and attractive properties
For graphene oxide (GO)-PDA, the 001 plane was shifted to 10.9◦ with the presence of several peaks confirming the structural change resulted from the functionalization reaction
The interlayer spacing of the 001 plane (d(001)-spacing) was calculated by Bragg’s equation to be 7.9 Å for GO which is close to the values reported for GO synthesized by modified Hummers methods [4,33,38]
Summary
Graphene and its based materials have been extensively researched recently owing to their unique and attractive properties. Graphene, which is extracted from natural graphite, is a two-dimensional material and is made of sp hybridized bonded carbon atoms arranged in a honeycomb structure [1]. One of the commonly explored graphene derivatives is graphene oxide (GO) that is usually produced from graphite sheets [2]. GO exhibits attractive optical, chemical, and electrical properties caused by the graphene skeleton and its oxygen content. The oxygenated functional groups located on the edges of GO sheets cause its hydrophilic properties and make the surface modifications easier to produce other graphene derivatives [1,3]. GO NPs are generally synthesized by the oxidation of graphite via the well-known Hummers method [2] and modified/improved Hummers methods that were developed later to improve the quality of GO NPs [4,5,6]
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