Here is the refernce:

Langmuir, 2006, 22 (6), pp 2731–2737

Also http://193.146.160.29/gtb/sod/usu/$UBUG/repositorio/10320106_Neumeyer.pdf

Nanomedicine: Nanotechnology, Biology, and Medicine 7(2011) 410-419.

hre is another publication : Langmuir 2012, 28, 209–218

Thank you al for your answers. We did try using PEG as coating to prevent agglomeration during the synthesis but it seems that rhodamine might react with the polymer and give some non-nanoparticulate material (seen in TEM images).

I will try the click chemistry routes and will tell you the results.

Thanks once again.

Did you try silane copling agents? They are excellent for SiO2.

I hope you can definitely get a solution if you scan the nano particle by Small Angle X-ray Scattering (SAXS). IT GIVES MOST STATISTICAL AVERAGE PARTICLE SIZE, So it is the best way to confirm the size.

Try silane coupling chemistry with either (3-amino propyl)-triethoxy-silane (APTES) or (3-mercaptopropyl)-trimethoxy-silane (MPTMS). Mptms can couple the sulfur specific region of the isothiocyanate to SiO2 surface while Aptes can couple the amino region of the isothiocyanate to SiO2.

Here is the link for one of my publication in which we have conjugated the fluorophore in the ORMOSIL matrix with size being around 20nm.

http://www.ncbi.nlm.nih.gov/pubmed/19206569

Thanks.

You can try microemulsion method to prepare the silica nanoparticles, it should be less than 100nm.

Please proceed for the SAXS scan of the nano system to have an clear idea on size scale of your expected particle size and if any difficulty ask me for any help in this regard with out any hesitation. I hope you will resolve this problem in a much meaningful and judicious manner.