Organic-inorganic nanoflowers, methods of synthesis, and uses of the nanoflowers are described. It has been found that organic-inorganic nanoflowers can be grown in the presence of a solid substrate containing copper without the requirement for added copper ion. The method includes exposing bacteria to a solid substrate containing copper in the presence of an aqueous solution that contains phosphate ions. The aqueous solution can additionally contain chloride ions, similar to that of a phosphate-buffered saline composition. The solid substrate can be an alloy of copper and tin, and the substrate can have phosphorus incorporated into it.