Iron oxide nanoparticles are coated with PEG 5000 in liquid form and I need to make it powder for further study (such as XRD). As I do not want to change the structure of NPs, I need to find out the best temperature to make the NPs powder. Anyone has suggestion? Thanks
it must be about 50-55 °C. However, XRD would probably be unaffected by melting, even you had relatively large amounts of PEG. I would cetrifugate the liquid, collect the sediment, dry it at gentle conditions, and further use it.
According to Sigma Aldrich:
Melting point of PEG with an average molecular weight of 4600 (range 4400-4800) is 57 - 61 °C and with an average molecular weight of 6000 (range 5000-7000) 60 - 63 °C.
Therefore, melting point of PEG 5000 should be approx. 60 °C.
Dear Roman
I dried sample at 70°C, but it does not change to powder form and in fact, its very oily powder. The oily sample can not be used for some characterization experiment and I do not know how the sample will be completely powder. Do you have any suggestion? Thanks
You'll have to make a few tries, I don't know if any of the ideas below would work:
1. Try to spread your sample over a large area while drying - water can be better evaporated (I assume your solvent is water)
2. Try applying vacuum, something like rotational evaporator or vacuum drying oven
3. Try redispersing your particles in another more volatile solvent, for example ethanol, and then, if needed, you can again apply vacuum.
Probably you could try to perform a DSC cooling run to check at which temperature your sample turns out in solid state.
Well the oily behavior can be understood by the melting point of the PEG. If you melt the PEG the whole thing becomes very viscous.
So what do you exactly mean with PEG "coated". Can you wash the PEG off the particles or is the PEG grafted to the NP?
Data for PEG 4000 and PEG 6000 is readily available. The melting point should be between 51.5 and 58.7 C, respectively, if you accept DMA as an adequate measurement. See the following link, Figure 2:
http://www.perkinelmer.com/CMSResources/Images/44-74297APP_TgandMeltofPolyethylene.pdf
Dear Matthias
I am characterizing PEGylated versus non-PEGylated magnetic nanoparticles so that I do not want to wash away PEG from NPs, but I need to know what can I do with this oily behavior and how I will be able to do characterization? For some characterization experiments, such as XRD, FESEM, SEM, TGA, FTIR ..... we need a fine powder and the oily materials effect on results. Do you have any suggestion for that? Thanks
Dear Rozita,
Thermal analysis are the best method for determine of materials behavior during heating. Therefore, I suggest the DSC test. It can be useful for you.
Also, you can see the morphology of your particle by FE-SEM and TEM.
You can do the phase characterizations by XRD and FTIR methods.
With Bests
If you don't want to apply heat on it, you can go for freeze drying method to make it powder... It won't harm the structure of NPs too...
Dear Sakthivel
freeze drying method also gave me the same result, oily and sticky NPs which is not fine powder. Thanks
I do not follow your question. Do you want XRD of nanomagnetic powder coated with PEG or XRD of PEG. In former there is no problem. For letter there are available attachment for XRD.
Do not know whether it would help to mix it with an 'inert' powder to remove the stickiness?
Dear Titus
Which type of inert powder do you think that is work here? Is there any ref for that?
Thanks
I sought of NaCl, Na2SO4, CaSO4 and alike. However, not familiar with XRD.
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