I'm preparing silica NP controlling the size by using different concentration of NH4OH.
1- 16.75 ml ethanol.
2-0.5 ml TEOS.
3- NH4OH (0.3- 0.5- 0.75- 1 ml)
mixed for 24 hr then evaporate the ethanol to get a silica powder.
When i did the DLS to measure the size i took 100ul immediately when i stop the reaction and and mix it with 1ml ethanol. I found the targeted size (30-50 nm) but after i dried the silica i prepare another sample (1:10 in ethanol) and i found the size above 200 nm.
is that due to aggregation?
Dear Hajar Alghamdi, the following documents deal with the pecularities of Stoeber process and the different parameters involved. My Regards
https://doi.org/10.1016/j.spmi.2013.06.004
https://link.springer.com/article/10.1007/s10971-013-3175-6
https://www.researchgate.net/publication/333268478_Revising_the_synthesis_of_Stober_silica_nanoparticles_A_multivariate_assessment_study_on_the_effects_of_reaction_parameters_on_the_particle_size
Dear Hajar Alghamdi, the following documents deal with the pecularities of Stoeber process and the different parameters involved. My Regards
https://doi.org/10.1016/j.spmi.2013.06.004
https://link.springer.com/article/10.1007/s10971-013-3175-6
https://www.researchgate.net/publication/333268478_Revising_the_synthesis_of_Stober_silica_nanoparticles_A_multivariate_assessment_study_on_the_effects_of_reaction_parameters_on_the_particle_size
Stober process is a relative reaction to pH and solvent volume, especially for nanoparticle size.
Please adjust for the ethanol fraction and pH by NH4OH.
I would like to give a paper for the reaction.
These are open access papers.
https://matsc.ktu.lt/index.php/MatSc/article/view/26643
https://publications.aston.ac.uk/id/eprint/40029/1/Controlling_particle_size_in_the_St_ber_process.pdf
Best regards,
Simon K.H. Kim
Hajar Alghamdi
Once dried your particles are no longer ‘nano’ - they contain no free, independent, discrete particles < 100 nm in size. You have, as you state, a mix of fused aggregates and looser agglomerates. Keep them in suspension to retain their ‘nano- ness’...
@ Alan F Rawle
Dear Alan,
Is it mean that the size of the precipitates related to duration time?
Would you mind letting me know?
Regards,
Simon K.H.
What method should I use to re-disperse Hajar's dried aggregated nanoparticles? Just curious.
Will the aggregated silica particles never break down again into their individual diameters because of the drying process?
Thanks for the answers,
My supervisor suggest to keep it on suspension but in this way, how i would purify the silica and use it in further reaction. I need to coat it with PEG and load my drug on it. So, i think i will need to have it in a powder form?
@Alan F Rawle
Eric Dickson You can’t recover the original suspension from the dried particle. Period. Take a look at this webinar (registration needed):
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
@Eric Dickson , I agree with Rawle's opinion. I think returning to a nano from the dried state must be physically crushed or dissolved back into a solution.
Best regards,
Simon K.H.
Eric Dickson KangHyung Kim
Look at slides 40 and 41 in the above webinar and memorize the quotations!
Alan F Rawle Dear Dr. Rawle,
There was a hint that the energy barrier to redistribution is greater after drying. This allowed me to understand why the particles get bigger after drying.
Thank you for your kind advice.
Dear Hajar Alghamdi, you don't need to isolate the SiNP's into a powder then redispersed it again, pleinty of procedures are available where all is done in situ, i.e., SiNP's, drug loading, and PEGylation. Please see the following exemple. My Regards
https://doi.org/10.1016/j.ijpharm.2014.07.049
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