Abstract
Despite the fact that there have been many studies of graphite exfoliation, none really addresses the issue of starting form of graphite. To address this issue various graphite forms (solid, powder and sooth) and graphite oxide (powder) are exfoliated in acetonitrile and studied via ultraviolet-visible (UV-Vis) spectroscopy. In different graphite forms two major absorbance peaks are observed at 223 nm and 273 nm corresponding to graphene oxide and graphene dispersions, respectively. The intensity change of the peaks refers to the layer number change. The intensity ratios of these peaks give information about the concentration of the exfoliation products. We observed that graphite oxide sample has the thinnest graphene dispersions among the compared samples, whereas graphite rod has the thickest. It appears that few layer graphene oxide dispersions exist more in graphite sooth and graphite oxide samples. Graphite oxide UV-Vis spectrum reveals two new absorbance peaks at 312 nm and 361 nm in addition to the graphene oxide and graphene dispersion peaks. To our knowledge these peaks were not observed before. We think that these new peaks are formed due to conjugated polyenes that affect π → π* plasmon peak.
Highlights
As our technology evolves, the need for new materials that possess superior qualities is very clear
When 5-min sonicated samples analyzed in Figure 10–14 with respect to their intensity for 223 nm peak, it is seen that graphite sooth and graphite oxide samples have absorbance intensities higher than 4.0, whereas graphite rod has about ∼3.3 and graphite powder has about ∼2.0
The UV-Vis technique is proven to be very effective in studying the number of layers exfoliated and detecting the difference in conjugated polyenes that affect π → π* plasmon peak
Summary
Absorbing a photon with energy about 4 eV. With an additional electron in the 2p orbital, carbon atom can form covalent bond with other carbon, hydrogen or oxygen atoms. Each carbon atom is connected to three other C atoms on the two dimensional plane via covalent σ bonds, the remaining single electron (π electron) is very mobile and located above or below the two dimensional plane. These π orbitals overlap with σ bonds, thereby enhancing the bonds (Figure 2). Since the strong acids introduce defects into the final product of graphene, in our study we tried to exfoliate different form of graphite directly with acetonitrile. Scanning Electron Microscopy (SEM) and optical microscopy are used to investigate the morphology These techniques helped us to visualize the extent of exfoliations for each sample. The samples had to be filtered via filter papers and dried before SEM and optical microscopy used
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