How can we avoid the restacking of graphene, without the use of composites or adding functional groups? I am asking for reduced graphene oxide prepared by a chemical method.
I've synthesized GO by chemical method, experienced the same problem and found that if we'll leave sample for several days without washing, it will re-stake due to presence of sulfur etc as I used sulfuric acid as cleaving agent. In the 2nd attempt I synthesized the sample and washed it by 1 M HCl de-ionized water soon after the synthesis using centrifuge and prepared pure GO. So I'll suggest you not to leave the sample after preparation and wash it as soon as possible. It may be helpful for you.
Hello if your majority is restacking try ionic liquids and start from graphite but as you know they are expensive
I've synthesized GO by chemical method, experienced the same problem and found that if we'll leave sample for several days without washing, it will re-stake due to presence of sulfur etc as I used sulfuric acid as cleaving agent. In the 2nd attempt I synthesized the sample and washed it by 1 M HCl de-ionized water soon after the synthesis using centrifuge and prepared pure GO. So I'll suggest you not to leave the sample after preparation and wash it as soon as possible. It may be helpful for you.
Polar solvents such as N-Methyl-2-pyrrolidone (NMP) are very effective at separating sheets of graphene from bulk graphite and maintaining their isolation to form a colloidal-like solution .
References: Hernandez, Y., Nicolosi, V., Lotya, M., Blighe, F. M., Sun, Z., De, S., … Coleman, J. N. (2008). High-yield production of graphene by liquid-phase exfoliation of graphite. Nature nanotechnology, 3(9), 563–8. doi:10.1038/nnano.2008.215
If you maintain the liquid state graphene, we can limit the stacking behaviour. if you want to get solid product , freeze drying or supercritical drying is the best.
Thank you for your query.
There are some of following ways to control restaking in graphene
1. Graphene should be re-stacking because of vander waals interactions. So, One can increase the inter layer distance between 2 adjacent layers. It can be done by introducing ionic liquid intercalates in interlayer spaces of 2 adjacent layers. So, you can try this.
2. Since you kindly suggested for rGO case. You must be very very careful about pH. The re-stacking rate is very high at highly acidic pH that decrease towards shift pH values to 7. So, After preparing rGO, washed the rGO sample repeatedly until it come to pH near to 7. It assure you removal of all acidic residues and your rGO restack lesser.
3. Another possibility is using NMP solvent as suggested by Qaiser Ali sir. Its best to exfoliate or keeping the layers apart as demonstrated by JN Coleman et al in their Nature paper. NMP is expensive but some relatively good and cheaper solvents can be DMF, di-choloro methane etc....Poorest are Acetone etc. We have found that the NMP based suspension is extremely stable (suspended sample does not settle even after months).
4. Another possibility could be a very high temperature treatment resulting thermal expansion of your rGO.
Thanks, Vineet
@ Vineet kumar, High temperature treamtents highly improve the stacking probablity, Due to this draw back , freeze drying emerged into material science field. As you said expansion will happen but only along the sheet not between the sheets.If one need to get poorly stacked graphene sheet in solid state in cost effective manner, should do some composites to intercalate between the sheets and consequenc chemical reductions.
if you reduce the graphene oxide with out direct contact , we can avoid stacking i mean just keep the graphene oxide in petri dish and put this petri dish into bigger one,the bigger petridish should have hydrazine then close the whole setup put into hotplate heat to 45 degree ,in this way you can avoid stacking.Hydrazine vapour will reduce the graphene oxide. vapours mostly doesnt detoriate the stuctural features of graphene.
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