The synthesis procedure shown here was adapted by Steve Ng and Chris Johnson from a procedure
developed by S.D. Solomon, M. Bahadory, A.V. Jeyarajasingam, S.A. Rutkowsky, C. Boritz, and L.
Mulfinger, Journal of Chemical Education, 84, 322-325, (2007).
The formation of silver nanoparticles can be observed by a change in color since small
nanoparticles of silver are yellow. A layer of absorbed borohydride anions on the surface of
the nanoparticles keep the nanoparticles separated. When sodium cholride (NaCl) is added the
nanoparticles aggregate and the suspension turns cloudy gray. The addition of a small amount of
polyvinyl pyrrolidone will prevent aggregation.
Wear eye protection
Never look directly into a laser or shine a laser at another person
Step 1. Add 30 mL of 0.002M sodium borohydride (NaBH4) to an Erlenmeyer flask. Make sure the
solution is made fresh right before the experiment. Add a magnetic stir bar and place the flask
in an ice bath on a stir plate. Stir. Keeping the sodium borohydride (NaBH4) on ice will reduce
the rate of decomposition during the experiment.
Step 2. Drip 2 mL of 0.001M silver nitrate (AgNO3) into the stirring NaBH4 solution at
approximately 1 drop per second. Stop stirring as soon as all of the AgNO3 is added.
Step 3. The presence of a colloidal suspension can be detected by the reflection of a laser
beam from the particles.
Step 4. Transfer a small portion of the solution to a test tube. The addition of a few drops
of 1.5 M sodium chloride (NaCl) solution causes the suspension to turn darker yellow, then gray
as the nanoparticles aggregate.
Step 5. Transfer a small portion of the solution to a test tube. The addition of a few drops of
1.5 M sodium chloride (NaCl) solution causes the suspension to turn darker yellow, then gray as
the nanoparticles aggregate.
Step 6. Transfer a small portion of the solution to a test tube. Add a drop of 0.3% polyvinyl
pyrrolidone (PVP). PVP prevents aggregation. Addition of NaCl solution then has no effect on the
color of the suspension.
Step 7. Add enough solid polyvinyl alcohol (PVA) to give a 4% solution. To get the PVA to dissolve
you will need to SLOWLY add it to the strirred, hot, silver colloid solution.
Step 8. Silver nanoparticles color the yellow stained glass in medieval churches. To make "stained
glass" decant the mixture into a mold leaving air bubbles and undissolved PVA in the beaker.
9. Evaporate in a toaster oven for 30 minutes. Alternatively the solution can be left in a hood
over two days to evaporate.
Stock Solutions for 8 batches
0.001M AgNO3: Dissolve 0.017 g of AgNO3 into 100 mL distilled water. This solution can be kept
for later usage.
0.002M NaBH4: Dissolve 0.0189 g of NaBH4 into 250 mL distilled water. This solution must be made
fresh before the experiment.
0.3% PVP solution: Dissolve 0.1 g of PVP into 33 mL distilled water.
Small Erlenmeyer flask
Large dish of ice
1" stir bar
Toaster oven or overnight drying