I have prepared mixture of modified Fe3O4 and SiO2 nanoparticles and used 3-Aminopropyl triethoxysilane (APTES) to modify the surface of nanoparticles. Can anyone advice as how to estimate the number of amine functional groups present on the surface of above mixture?
check out this paper:
http://link.springer.com/article/10.1007%2FBF01204067
The total number of amino groups on the surface of SiO2nanoparticle were quantitatively analyzed by a simple acid-base back titration method and the effective number of amino groups for the successive chemical reactions was also determined by spectroscopic measurements after treating with fluorescent Rhodamine B isothiocyanate molecule, See:
http://www.hindawi.com/journals/jnm/2012/593471/
There are several ways. I've found the most reliable ones to be the Ninhidrin assay and NMR. For protocols see attached paper
http://www.nature.com/articles/srep17040
I would wash the dispersion serveral times, remove the magnetic nanoparticles and analyse both fractions as Yuri Mirgorad suggested. After washing you may also perfomr HATR-FT-IR measurments to control if the surface is modifed. (I suggest also to perfom such measurements before the modification)
Article Tuning the relaxation behaviour by changing the content of c...
If possible you can combine the quantitative analysis with ph-dependent zeta potential measurments.
Article Functionalized polymer colloids bearing primary amino groups
Thank you all for your great answers.
According some recommendations, there are several methods to determine the number of amine functional groups on the nanoparticles but I'm confusing that which one is the best. (1) XPS (2)TGA (3)Back titration (4) reaction of amine groups with salicylic aldehyde (5)Ninhidrin assay and NMR (6)FT-IR ...
In this case the "best" would depend on your particles. All of these methods have positive and negative traits and which one works for you would depend on your specific situation. Ultimately for excellence you would like to have at least two - three independent methods in a work. It would be best to use at least one non - colorimetric commonly available measure, say TGA and titration, one colorimetric assay, e.g. ninhidrin and one based off of spectroscopic data, NMR or FT - IR. If all of those different ways agree then you've got a water tight proof.
Hope this helps
Thank you so much for your suggestions. I will try the experiments and share my results in this discussion.
