Hello, Osim;

Basically you gonna need an ice bath, silver nitrate, PVP (or sodium citrate) and NaBH4.

This article on anex will help you.

Article

I used to use this concentrations;

AgNO3 = 0,0025 g in 10 mL Mili-Q water  (1,47x10-3 M)

NaBH4 = 0,0011 g in 5 mL Mili-Q Water (5,8x10-3 M)

Na3C6H5.2H2O = 0,0160 g in 10 mL mili-Q water (5,45x10-3 M)

http://ac.els-cdn.com/S0928493108003640/1-s2.0-S0928493108003640-main.pdf?_tid=2cbfe1b8-2cbf-11e6-8227-00000aab0f02&acdnat=1465311208_2d3bbe80a68395e09e5483249cab2a17

In biological synthesis 90 mL of 2 mmol/L silver nitrate solution in water will be added to 10 mL of plant extract at room temperature and kept for 30 min. You will get Ag+ ions into Ag0. Dark brown colored reaction mixture of biologically synthesized Ag NPs will be centrifuged at 5000 to 8000 r/min for 15 min and resulting pellet will be redispersed in sterile water followed by filtration through millipore filter.

For chemical synthesis equimolar amount of salts and reductant solution will be added. 50 mL 2 mmol/L of silver nitrate solution will be taken, then added 20 mL of 2 mmol/L of surfactant/stabilizer (twin80, CTAB) followed by addition of 2 mmol/L of 50 mL reducing agent (i.e. sodium borohydride). You will get Ag NPs.

NaBH4 and AgNO3

Very small concentrations (1 to 0.1 mM) of each of them.

cool down both solutions by putting them on ice or in the fridge.

Slowly add AgNO3 to NaBH4 solution using a burette

Let the solution change to yellow and you have particles in the size range of 50 nm