Currently, I drop cast 1mg/mL sonicated graphene oxide (GO) dispersion on mica substrate to prepare AFM samples. However, the GO dispersion is not uniform and mostly I fail to observe any GO particles. Coffee staining effect of GO suspension is another problem that I face. What is the possible way to prepare good GO samples for AFM? Is the success rate of of this analysis usually low?
I think its too concentrate (1 mg/mL) to make uniformly distributed sample on mica substrate because concentrated dispersion of GO agglomerates more faster than the dilute dispersion of GO. I would recommend to use 0.5 mg/mL. Just after sonication use the dispersion for drop casting on substrate and please remove the excess dispersion by agitation or micropipette from the substrate surface so that the GO particles do not get enough time to agglomerate or settle down in the basement of the droplets. you can also try spin or spray coating. Please dry the sample in a vacuum desiccator.
To avoid the effect of coffee stains, it is necessary to lower the concentration of GO and instead of drop casting, use spin coating
Hi, Nawshad,
The uniform thin films from dispersion solution of graphene oxide can also be formed using other coating techniques such as bar coating or blade coating. The concentration of solution is a key to obtain good quality films. Before you use AFM to examine your films, you had better to use microscope to look at the samples. You may have a quick idea what is going on with your samples.
All the best
Xuhua Wang
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