If you need them in water media I suggest you the following publication, I recently tried it and it worked pretty well:

http://pubs.acs.org/doi/abs/10.1021/la201938u

I could achieve very good monodispersity for many different sizes.

Good luck!

One of the good methods for synthesising silver nanoparticles is by using microwave reduction techniques by using any of the stabilising agents like PVP. The solvents can be glycol and the silver nanoparticles are formed as colloid. In this method the nanoparticle formation can be visualised by a colour change and also the method is very efficient and rapid.

Which product you want to do?

@ wanderley monodispersed nanoparticles

The best way is what Leonardo suggested. You can get excellent results yield.

I forgot to mention that in the method I suggested before, the final capping agent is citrate, easy to exchange for further functionalization and/or application. Which size do you need to achieve?

@leonardo..around 15-20nm.

thanks alot

Then I suggest you to use the first procedure described in the paper; in 2-3 overgrown steps you should reach that size.

thanks Leonardo..

i will try my best