Could anyone suggest me the best capping agent for Silica. End goal is to have amines on the surface of silica nanoparticle after capping them. Have used APTES in the past.
You can modify the silica surface with amine groups by reacting 3-Aminopropyltrimethoxysilane (APTMS) or 3-Aminopropyltriethoxysilane (APTES). Should use a low concentration of APTMS (or APTES).
For your information:
Journal of Colloid and Interface Science 311 (2007) 507–513
You may get / or prepare several polyamine functionalized alkoxysilanes to graft on the surface of silica nanoparticles. Polyacrylamide grafting is also possible. You will get several literature reports on this.