When graphite undergoes chemical reaction to form graphene or graphene oxide, which bonds break and what changes happen in the electron density of carbon rings?
What caused that graphene sheets to be stable and prevent them from aggregation?
The hybridization of carbon changes from sp2 to sp3, and results in many negatively charged oxygen-containing groups on the monolayer carbon to prevent them from aggreation.
Functional groups on the graphene oxide prevent the sheet stacking by electronic repulsion .This is the reason why the graphene oxide have larger interlayer distance then graphene.
thanks dear Yongfeng bu and K.P. Annamalai for answers. but I have another question, in which place does functionalization occurs? in borders or all surface?
Functionalization will be facile on the edges of the graphene sheet.Thats what if you load some nanoparticles or some positivly charged materials on graphene, it will likely attach on the edges of the graphene sheet rather than on plane.
Well when we oxidize graphene, different bonds are formed depending upon the environment. These include -OH, -COOH, -C-O-C bonds.
Also as far as know when these bonds are formed at the edges of graphene sheet they carry charges and presence of these charges lead to stabilization of graphene oxide sheets
When graphite (3D) undergoes to graphene (2D) changes the hybridization. Weak Van der Waals dispersion forces hold graphite layers together and it is very easy to break them through ultrasonication. Thus, it is very difficult to be reagregated.
When graphite undergoes to graphene oxide the hybridization changes too. In that case, there are also weak Van der Waals bonds between the layers of graphite oxide that break also through ultrasonication. This is the reason that Hummers' method is the most preferable than Staudenmaier's or Hoffman's. Hummers' method adds more functional groups between the layers and therefore facilitates them to be drawn away.
To conclude, -COOH and -OH are placed at the edges, while -C-O-C- (epoxy) and -OH are placed on the main planar surface of graphene oxide sheets. These functional groups prevent the reagregation.
In fact the hybridization of carbon atoms in graphene is the same as graphite(sp2) .In graphene oxide, however, some of the carbon atoms which are functionalized have sp3 hybidization.
@Minas M. Stylianakis sir, would you please provide some research articles in reference to your conclusion. How the hybridization (from sp2 to sp3) changes when pristine graphene converted to graphene oxide? How the orbital movement happens?
In graphene each carbon has an odd electron and each one is triangular planar sp2 hybridised 2d plane. During oxidation some of the terminal carbons are converted into -COOH, -C-O-C- (epoxy) and -OH placed at the edges, because the C=O group is predominantly introduced by utilising the odd electron of all converted functional groups. Rearranged electronic sp3 configuration (from sp2)of each carbon = oxygen , introduction of 3 dimensional 2p y and 2p z orbitals in tetrahedral symmetry results.
Due to oxidation some (around 40%)of the sp2 bonds converted to sp3 bonds. For reference follow the link
https://pubs.acs.org/doi/10.1021/nl8034256
@samit karmakar i hope you got the answer
Thank you guys for this discussion. Just a quick one, I am doing some XPS analysis on graphene oxide (GO) and by deconvoluting the C1S peak, I can see that most of the carbon species have been come up hybridised into sp3 by 30% and sp2 come with
Dear Meysam Nobakht
I agree to Minas M. Stylianakis , in addition you can find some related details in Article Metal-Free, Graphene Oxide-Based Tunable Soliton and Plasmon...
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