Hello

What do you mean by increasing IEP? The Zp values can be tuned by changing the surface groups. The amino groups will take Zp towards positive and hydroxyl groups towards negative values. The IEP will vary accordingly.

Actually it is overall zero charge point. May be you refer to pH values. Add some information to your question.

I agree with the answer above, using aminopropyl silane will increase the iep, you may need treat the silica with aminopropyl silane rather than using it together with TEOS in the initial preparation of the silica.

see Langmuir 2012, 28, 20, 7598–7613.

alternatively you can adsorb a positively charged polyelectrolyte such as polyethyleneimine poly-lysine or polydimethyldiallylammonium chloride

Hi Alan,

I’m not an expert on Silica nanoparticles but I think these papers may help you:

Article molecules Morphological and Structural Properties of Amino-F...

Article Nano-Bio Interactions of Porous and Nonporous Silica Nanopar...

Article Effect of the surface charge of silica nanoparticles on oil ...

You may also find suggestions in the following link:

https://www.researchgate.net/post/How-can-I-acheive-positively-charged-mesoporous-silica-nanoparticles-MSNs-with-APTES

Good luck!!

AM

Thank you all for your answers!

Sushilkumar A. Jadhav sorry I meant having IEP at higher pH values. Typically for my silica nanoparticles I have an IEP at pH 2/3, but I am looking for silica nanoparticles with IEP at pH 7/8 in order to have zeta potential at -20/-30 mV without adding much conductivity.

Thanks to your suggestions Paul F Luckham and references in the literature, I notice that functionnalization with silane (diluted in solvent) after SiO2 synthesis is a good idea.

Thank you so much Amira Mahmoud for your unexpected and sweet help too!

Kind regards