Silver Deposition on Alumina Membranes

Tuesday, June 28, 2005

Electroless Silver Plating

Electroless Ag deposition on alumina membranes

Silver and gold nanowires can be made using a process called electroless deposition. Using Whatman commercial alumina membranes containing 200nm pores, silver and gold can be deposited in the pores by immersing an activated membrane in a silver or gold plating solution. Also, it can be done by using either pulsed or ac electrodeposition.
When this experiment was conducted I used the electroless silver plating process. This requires that a membrane be activated by first placing it in an initiator solution. The initiator solution contained 1g tin (II) chloride, 1mL trifluoroacetic acid, 100mL distilled water, and 100mL methanol. Once the membrane had been immersed in 30mL of initiator solution for 5 minutes it was washed three times using 200 proof ethanol.
The membrane was then placed in 50mL of the silver plating solution. This solution contained 0.6749g silver nitrate, 1.55g cobalt sulfate, 9.91g ammonium sulfate, 16.33mL ammonia liquor (ammonium hydroxide), and 50mL distilled water. After making sure all the solids had been dissolved by using sonication, the membrane was placed in the silver plating solution. Then I placed the solution with the membrane on the wrist action shaker.
After doing trials of various times (15, 30, 45, 60, 120 min.), the membranes were washed using distilled water then dried with a kimwipe. The membranes were then prepared for SEM microscope viewing by chemical etching. The chemical etching solution I used contained 2g iron(II)chloride dissolved in 100mL distilled water. After swabbing the membrane with the solution for several minutes chemical polishing was observed. The membranes changed from greenish before polishing to a darker silver color. Upon viewing the membranes using the SEM microscope silver deposition was not uniform throughout the nanopores.

This image shows how the pores (dark areas) are not completely filled with silver particles.

This is a cross section of the membrane; again silver is not continuous thoughout the pores.

This membrane appears not to be chemically polished enough. There is still silver on top of the membrane.


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