Saeed Shahbaz

I suspect it's hydrolyzed to 'Si(OH)x' or SiO2 and these are the white particles... You need to replace with new.

Buy new. Hydrolysis, for sure. Normally much faster in chlorosilanes, but also happens with ethoxysilanes.

If you cannot work in a glovebox, try to fill the APTES container with inert gas before sealing it as well as you can. And/orr put it in a larger container, filled with drying material. In this way, you reduce the moisture a bit.

Article Synthesis of mesoporous silica nanoparticles derived from ri...

Read this article and I have functionalized silica in two possible pathways such as co-synthesis and post-grafting

If there is no resource to compare another reagent at the moment, I suggest a procedure, which I have already performed, to recover the reagent (partially). He follows:

a) Filter the reagent with a 0.45 filter

b) drying the reagent with a type 4A molecular sieve.

c) Store in a bottle with a septum.