[wm334]

We have made silica nanoparticles via stober method,

I understand that this does hydrolysis and condensation reactions and this will increase the silica chains and make si-0-si-o etc

I dont understand how these are any different from a sodium silicate chain

and how they are nanoparticles, I have seen the microscopy pictures of the spheres

does the size of the chain decide the size of the nanoparticle?

thanks

[P]

I dont understand how these are any different from a sodium silicate chain

Is there any sodium in your si-o-si-o network?

[/quote]

does the size of the chain decide the size of the nanoparticle?

I do not think so..  I would imagine that you are measuring the size of the clumps of particles stuck together rather than the size of individual macro molecules, but I am not 100% certain in your case.

Hope that helps.

P.

[P]

and how they are nanoparticles, I have seen the microscopy pictures of the spheres

How large are the particles?  450 nm can still be defined as a nano particle. It doesn't have to be 1nm across to be a nano particle.

[Intanjir]

The question is a bit confusing. The Stober process uses alkoxides of silica and does not involve sodium silicate. It is cheaper to make the nanosilica with a sodium silicate process but I don't know if this has a special name. I think you must have meant this instead of Stober.

A sodium silicate chain is a linear polymer. Each silicon is attached to 4 oxygens but only one of them will be available to be attached to another silicon. The two other sides are populated with hydroxide or O- groups. The overall negative charge keeps silicate molecules apart as long as the pH remains high enough. This state of affairs is no longer stable once you lower the pH as the O- groups will tend to find an available H+. In this situation each silicon has all 4 oxygens available to be linked and so you will get a 3 dimensional network of tetrahedrons.

The size of the linear sodium silicate chains you start with shouldn't have too much to do with the size of the final particles. The growth pH and concentration of silicons would be more relevant. You can even get really big particles if you first 'seed' with nanoparticles before you lower the pH.