Hydrogel sensors for detection of metal ions

A method for using hydrogels to detect metal ions, including transition metal ions, comprises contacting the hydrogel in any order, with a sample potentially containing metal ions, and a solution comprising a fluorescent dye, nanoparticle, colorimetric tag, or combination thereof. The presence of metal ions in the sample may be detected by one or more suitable techniques, such as determining the color, conductivity, Raman, infrared spectrum, and/or size and/or mass change of the hydrogel. The method may be useful for detecting corrosion and/or failure of protective coating of metal structures including outdoor sculptures, building, bridges, ships, and the like.