1. You can concentrate the commercial nanoparticles suspension using centrifugation/resuspension. This can be done up to a point since stability might become compromised.

2. You can reduce all the purchased gold to gold nanoparticles, the situation is that you must produce a stabilized suspension. This is why concentration of suspensions, commercial or home made, have similar particle concentrations.

Hi Omar. I have replaced citrate ligands with phosphine groups on commercially purchased citrate stabilised 1OD 10nm gold nanoparticles. I typically try and concentrate the 1 nanomolar solution to 100 nanomolars at least - this is expensive. I typically use a few milliliters of 1nm and concentrate down to ~20 microliters using NaCl reduction and methanol purification. I'm just wondering whether if I purchased a gram of Chloroauric, which costs the same as 25ml of 1 nanomolar au nanoparticles, I could use it to synthesise more than I could buy with the same figure commercially.

If you will synthesize gold nanoparticles from 1 g of chloroauric acid, then you need to take a large excess of citrate. 1 g is 0.0029 mol of acid. Take a 10-fold excess of a quotation of 0.02 moles and you will get about 0.0029 moles of 10 nm gold nanoparticles. This is 0.57 g of gold powder. During the synthesis it is necessary to take the concentrations that are known in the experiment.

Thank you Yuri Mirgorod. That's very helpful.

Hi. Gold nanospheres synthesis following the Turkevich´s method is a simple way to obtain monodisperse 10-12 nm nanoparticles, using only two reagents, HAuCl4 and sodium citrate. After the synthesis, you have solutions of 5 nM AuNSs.

Thank you so much Karen Bolanos thats very helpful.

Glad to help

Using the protocol steps 1-11 in the paper here: https://www.nature.com/articles/nprot.2006.51 starting with 500 ml of 1 mM hydrogen tetrochloroaurate (III) trihydrate in Nanopure water, I regularly get between 8-11 nM AuNPs of 13 nm size.