The light triggered dissolution of gold wires using potassium ferrocyanide solutions enables cumulative illumination sensing

Electronic systems with on-demand dissolution or destruction capabilities offer unusual opportunities in hardware-oriented security devices, advanced military spying and controlled biological treatment. Here, the dissolution chemistry of gold, generally known as inert metal, in potassium ferricyanide and potassium ferrocyanide solutions has been investigated upon light exposure. While a pure aqueous solution of potassium ferricyanide–K₃[Fe(CN)₆] does not dissolve gold, an aqueous solution of potassium ferrocyanide–K₄[Fe(CN)₆] irradiated with ambient light is able to completely dissolve a gold electrode within several minutes. Photo activation and dissolution kinetics were assessed at different initial pH values, light irradiation intensities and ferrocyanide concentrations. Addition of small amounts of the heavy metal thallium (260 ppb) also provides tunability of the dissolution kinetics. An investigation of the involved chemical and physical processes of photochemistry, cyanide diffusion and surface reaction results in an understanding of the rate limiting steps and yields an overall transformation of irradiated light energy to dissolved gold of 2.6%. A potential application of this novel gold dissolution method as a cumulative light sensor is demonstrated and discussed.