Hi,
I'm trying to coat magnetic nanoparticles with silica. I know that there are plenty of publications in the literature. But I still couldn't solve my problem.
There is a method I also use and unfortunately I couldn't get the same product in every reaction. I'm quite sure that I set exactly the same conditions, but the results are not the same. I need your help, I guess I have a problem with adding speed or temperature in the step of adding ethyl acetate and TEOS.
I transferred the magnetic nanoparticles into the aqueous medium with the help of CTAB as it is commonly present in literature. I dilute it with water containing NaOH and heat up the mixture to 70 C (the ref: Article Multifunctional Uniform Nanoparticles Composed of a Magnetit...
). I add TEOS and ethyl acetate into the mixture at 70 C in sequence or together after I dissolved TEOS in ethyl acetate.In this step, I tried adding slowly or quickly, but the result is always disappointing.
As you can see in the attached pictures taken from different syntheses, sometimes I get a ridiculous image while sometimes the core/shell structure is being formed. Although I tried many times, I could not understand why sometimes I lose the core/shell structure.
Is there any suggestion you can recommend to me so that I can produce a decent kernel/shell build? Why do you think I can't control some synths? should I decrease the temperature (like 50 C)?
I will look forward to your advice and suggestions,
Best regards
Hi, I have some questions
1. What method did you used to synthesized the magnetic nanoparticles?
2. Have you ever tried the lower temperature (for example 40 oC)?
3. Dropwise?
From my experience, I had synthesized the core-shell Fe3O4@SiO2 by using Fe3O4 NPs from co-precipitation method following with SiO2 shell encapsulate by adding TEOS in Fe3O4 aqueous solution (like ethanol) then heat it up at low temp with a gently stirring.
Yes try to reduce the temperature and compare your results. You will probably get something desirable.
Dear Kübra Solak
I read the article and they got a monodisperse material, which is really different from yours. Kittidhaj Dhanasiwawong asked you some important things that should be evaluated and I want to add another one:
Are you adding all of your TEOS content at the same time or are you using the equivalently fractionated drop method? If you are adding everything at the same time the final shell thicknesses changes and of course It is harder to have a monodisperse material, and It probably explains why you are having so much different results.
Best Regards,
Thank you all for your attention.
I produce the core MNP by the thermal decomposition method.
I tried adding both dropwise and quickly. I found that the result is the same.
When ethyl acetate is added to the reaction mixture, the core structure is separating from the water. Also, when the reaction is finished, I cannot see a homogeneous liquid when I pour the mixture into the centrifuge tubes. The structure collapses in the form of a cloud. I can't see core/shell structure in TEM when it is like this. Sometimes I obtain the homogenous mixture and at that time TEM images appear core/shell structure. Have you witnessed such a thing? Why do I get a phased mixture instead of a homogeneous mixture?
I also tried the temperature at 60 degrees but I haven't tried 40 degrees yet. Again, when I tried 60 degrees, the mixture lost its homogeneity and a phase was formed.
I am adding the TEOS in the reaction flask at once by dropwise.
Especially I wonder why I lose the homogeneity of the mixture when I used ethyl acetate?
I hope you can suggest to me the solutions.
Have a nice day,
Sincerely.
Kübra Solak maybe the fact that you are dropping the TEOS at once is the main reason that all of this is happening, especially losing the homogeneity of the mixture and in consequence losing the core-shell desired structure. I am not sure if this low temperature is going to play such an important role when we're talking about morphology with iron oxides and silica. I would recommend looking for equivalently fractionated drop method used for this kind of synthesis, sometimes it takes hours to drop all the TEOS content,
Please keep me update about
Best wishes,
Matheus
Matheus Mendes Thank you for your valuable comments.
I am going to try low reaction temperature and fractionated TEOS adding.
I will share the results.
Have a good day.
Dear Kübra Solak
I never used thermal decomposition method, however, is this technique required some surfactant during the reaction for example oleic acid, fatty acid?
If I'm not wrong, this mixture required fatty acid which might made your core structure separating while adding ethyl acetate
In addition, to form silica shell on your MNPs, the -OH group on MNPs surface is required, if your MNPs covered with surfactant (-CH3 group for example) the silica shell won't attached on MNPs surface.
Best wishes,
Kittidhaj
Thank you Kittidhaj Dhanasiwawong ,
Actually, I've tried producing silica-coated magnetic nanoparticles before but in a different way. The amount of nanoparticles I produced via my old method was very low. Therefore, I wanted to try the method in the reference I gave above. I thought I could produce a higher amount of NPs. However, the method sometimes works and sometimes it doesn't work. So stragen!
Your comment is very valuable. I will set experiments with different magnetic cores. As you said, there is oleylamine and oleic acid on the surface of the core structures that I produce by thermal decomposition.
Sincerly,
Have a nice day.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering