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Synthesis of Silver Nanoparticles

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.


Safety:

Wear eye protection

Never look directly into a laser or shine a laser at another person

Procedure:

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.


Materials:

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.

PVA solid

Equipment

Small Erlenmeyer flask

Large dish of ice

Stirrer hotplate

1" stir bar

Droppers

Laser pointer

Mold

Toaster oven or overnight drying


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