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Black gold, but no oil: A nanoporous black gold film was formed by the anodization of gold in oxalate solution. The film had a spongelike porous configuration with a uniform hole size of approximately 20 nm (see picture). The formation mechanism has not yet been clarified, but carbonaceous matter produced by the anodic reaction of oxalate ions likely contributes to the growth of numerous nanopores on the gold anode.
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