Detecting mercury pollution could become a lot easier, thanks to a new visual technique developed by scientists in China.

When the gold nanoprobes come into contact with solutions containing mercury, their colour rapidly alters from red to purple

Chunhai Fan and colleagues at the Chinese Academy of Sciences and East China University in Shanghai have designed a new gold nanoprobe that changes colour when it comes into contact with mercury(II) ions.

The mercury(II) ion is the most stable form of inorganic mercury and is known to have detrimental effects on humans and the environment. Methods to detect mercury usually require lab-based instruments but there is an increasing demand for techniques that allow rapid mercury detection in drinking water, food and soil at the site of contamination.

The new technique, which combines micro- and nano-technologies, allows rapid, selective and portable detection of mercury within microfluidic channels at room temperature. When the gold nanoprobes come into contact with solutions containing mercury, their colour rapidly alters from red to purple. The higher the concentration of mercury, the greater the intensity of the colour change.

'Given its simplicity and low cost, we believe that this device provides a convenient approach for rapid mercury screening in the field detection of water pollution,' says Fan. He adds that the technique could be particularly useful for monitoring mercury contamination in developing countries.

Although the device currently has a mercury detection limit of only five micromolar, Fan expects that 'further design of the nanoprobe and the incorporation of signal amplification will significantly improve the sensitivity to meet more challenging requirements'.

Kathryn Lees