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I put a drop of aqueous red colloidal gold on a glass. After the drop dried I saw that remaining nanoparticles were black instead of red. Why black? Does it mean that plasmon resonance is so strong and extends over all optical wavelengths? Is the effect due to something other than plasmon resonance?

This is picture of said structure:

said structure

user46147
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1 Answers1

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"Black Gold: Plasmonic Colloidosomes with Broadband Absorption Self-Assembled from Monodispersed Gold Nanospheres by Using a Reverse Emulsion System" describes a similar phenomena of red gold nanoparticles assembling into black 3D structures, except they had to go through more steps than just drying them.

ignacio
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