Thank you Dr. Punckt

Please, is it possible that the original micelle structure is preserved even after solvent evaporation in AFM?

Dear Ahmed,

In order to get better sight into your surfactant/Au surface system you are advised to study phenomenon of surfactant adsorption onto Au surfaces. If surfactant concentration is around its CMC the case is easier. If it is higher than you can get surfactant monolayer or even bilayer. the unperturbated micelles could be adsorbed on Au surfaces over already existing layers. This micelles could be of the same shape as in the solutions.  However, it is dependent on many factors (the nature of Au surface which I suppose you did  not change. After one surfactant layer is adsorbed on Au polar surface your polar surface is changed into hydrophobic one. When second layer is formed polar surface is recovered. The adsorption of whole micelles is dependent on polarity of the layer on the Au surfaces. It is strongly influenced by surfactant nature and structural characteristics of surfactant molecules. Properties of water medium also influences the adsorption (pH, presence of salt, some other additives).

The opinion of Christian Punckt  is very instructive and useful. Only, I would exclude the possibility to have the same micelle shape both in water medium and on the Au surfaces covered by a bilayer (then you could have attraction forces between adsorption layer and the micelles.

We all could proceed with discussion if you give us more data.

I would also like to draw your attention to look at research gate base of papers you will find the papers useful for you

We all could proceed with discussion if you give us more data.

I would also like to draw your attention to look at reserch gate base of papers you will find the papers usefull for you.

Petar Dokic

Thank you Dr. Waleed and Dr. Dokic

I think I could not express my question as well so let me represent my enquiry.

My aim was to study the micelles shape and size of a novel surfactant I have synthesized. I think cryo_TEM is the best method but it is unavailable so I think of AFM.

Au substrate was immersed in a surfactant solution at its CMC for 6 hours then it was removed, washed, dried by a Nitrogen flow and examined using AFM.

The images showed hemispheres or domes of about 50 nm diameter.

Do these hemispheres represent micelles of the surfactant? If the answer is yes, is it possible for micelles to preserve their shape and size after the drying of Au substrate under Nitrogen?

Thanks

as answered above, whole starts with agglomerates at interface likely do not have same identity as micelles in solution. Even if the micelles were adsorbed onto a first adsorption layer, they would be removed by washing. Could be on the images you see collapsed hemimicelles adsorbed in first adsorption step. By washing you further should remove all  surfactant molecules directed with polar groups towards aqueous phase. Would be surprised if your dried surface is not hydrophobic.

In summary, you should not have expected that something at dried surface is representative for micelles in aqueous solution.

Every substrate, boundary (interface), or solvent have own nature and peculiarities of interactions with surfactants (as well as other molecules) and it is no need to find conditions when micelles will be the same. Better to discribe and explain the differencies due to different kind of interactions. This information will be useful for everybody. 

Thank you very much for your answers. I appreciate all your help, but let me tell you that I found a disagreement of these answers with this paper "Polymeric Micelle Assembly for Preparation of Large-Sized Mesoporous Metal Oxides with Various Compositions" [It is available in ResearchGate]. In page 654, The authors said "The formation of micelles was further directly confirmed by AFM (Figure 3b-2). Polymeric micellar solution containing 100 μL of HCl solution was casted on silicon substrate. THF can be easily evaporated from the system due to its low boiling temperature. After drying, the spherical micelles were uniformly distributed (Figure 3c). The original spherical micelle structure was preserved even after solvent evaporation, indicating the formation of stable and robust micelles in the solution"

Do you have any explanation for this?

Thanks,,,

It is not correct to speak about micelles without indication the kind of solution: aqueous or nonaqueous. There are different driving forces for micellization in water and organic solvents and different kinds of micelles can be formed. What kind of micelles were formed in THF? May be in this case the micelles are not break because the environment stay nonpolar.