Why silver changes its color?

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Abhishek Das

Agglomeration leads to formation of larger particles wherein dipolar electronic oscillation which gives rise to surface plasmon ceases to occur. Thus the brown colour of silver nanoparticles is lost.

Harald G. Dill

Dear Mr. Mubarak Ali,

etching by light of different wave length is not uncommon in Ag-bearing chemical compounds and mainly used in Ag-S compounds [Ag2S] for diagnostic purposes . The intracrystalline bonding has also an impact on the process. I would like to refer for further reading to the classical textbook published by Ramdohr 1975 "The ore minerals and their intergrowth".

Best regards

Davoodbasha MubarakAli

Thanks Dr. Das

Dear Professor Harald

Thank you for the suggestion. Mine is Silver with polymer which turns metallic sheen from brown color. I am not sure that it was agglomerated. . Is it fact that color changes is due to Ag bond with thiol group. ?

Regards

Mubarak

Dear Davoodsbasha,

I am enganged in applied geosciences, in mineral exploration, economic geology and technical mineralogy (metallography). I am a reluctant to take further steps into your discipline which is marginal to mine. I would like to assist colleagues based upon my knowledge and experience but do not want to put them on the wrong scent.

I wish you all the best. Should you have further questions closer to my answer I would be glad to assist you.

if it is turning to metallic shine, it is definitely due to formation of bulk silver on agglomeration. Silver sulfide would turn black.

Dear colleagues,

it is common practice of silver items to turn dark or black as a result of a reaction with S compounds from the environment. Put a silver spoon into a soft boiled egg you will get the same chemical effect. Old silver coins and jeweler´s items do the same and increase the value (sometimes). Silver reacts at its surface with thio/S compounds and forms AgS (in nature argentite) coating the metal underneath. A similar but less pronounced reaction you will also find when using copper items. Many of these tarnishing reactions have been used in the past of distinguishing special chemical compounds, be it geogenic or anthropogenic.