Scientists have developed a new film, sensitised with ruthenium dye, which is capable of rapidly detecting low levels of toxic mercury in water-based solutions.

The sensor utilises a mesoporous nanocrystalline TiO₂ film, which is then sensitized with a commercially available ruthenium dye.

The film, developed by researchers at Imperial College London, then changes from red to orange if it comes into contact with mercuric salts in water.

'There is no previous report of TiO₂ films being used for detecting metal salts,' Emilio Palomares, one of the scientists involved, told Chemical and Engineering News.

'Because of its excellent optical transparency, high surface area, and the ease of modifying the surface, TiO₂ is an ideal material on which to build colorimetric sensors.'

According to the research team, the dye-sensitized film can detect mercuric salt concentrations as low as 20 µM with the naked eye, whilst spectrophotometric detection using the film can identify concentrations of 0.3 µM or 0.5 ppm.

The new sensor holds a number of advantages over existing ones, for example it is less complicated than many, operates at room temperature and is more sensitive.