Gold-based sensor helps detect ‘forever chemicals’ in water

A new gold-based sensor is able to detect pollution from ‘forever chemicals’ in water through luminescence.

PFAS or ‘forever chemicals’ are manufactured fluorine chemicals that are used widely in different industries—from food packaging to semiconductor production and car tires. They are non-degradable and accumulate in the environment. Concerns regarding the toxic pollution they cause, particularly in water, have been rising in recent years.

According to the researchers behind the development, current methods for measurement of these contaminants are difficult, time-consuming, and expensive. In addition to this, it’s hard to carry out the measurements on-site to aid containment and remediation, especially at (ultra)trace concentrations.

In a paper published in the journal Analytical Chemistry, the scientists present their prototype model which detects the ‘forever chemical’ perfluorooctanoic acid (PFOA). The approach uses luminescent metal complexes attached to a sensor surface. If the device is dipped in contaminated water, it detects PFOA by changes in the luminescence signal given off by the metals.

A small gold chip

“The sensor works by using a small gold chip grafted with iridium metal complexes,” Zoe Pikramenou, a professor at the University of Birmingham who co-led the development of the sensor, said in a media statement. “UV light is then used to excite the iridium, which gives off red light. When the gold chip is immersed in a sample polluted with the ‘forever chemical,’ a change of the signal in the luminescence lifetime of the metal is observed to allow the presence of the ‘forever chemical’ at different concentrations to be detected.”

Pikramenou pointed out that, so far, the sensor has been able to detect 220 micrograms of PFAS per litre of water, which works for industrial wastewater, but for drinking water, they would need the approach to be much more sensitive and be able to detect nanogram levels of PFAS.

“Advanced imaging surface analyses are essential for the development of dedicated chemical nanostructures on customized sensor chips to ensure optimal performance,” Dan Hodoroaba, co-author of the paper and a surface and sensor scientist at Germany’s Federal Institute for Materials Research and Testing, said.

Pikramenou, Hodoroaba and their colleagues now intend to refine and integrate the prototype sensor gold chip to make it portable and more sensitive so it can be used on the site of spills and to determine the presence of chemicals in drinking water.

“PFAS are used in industrial settings due to their useful properties for example in stain-proofing fabrics. But if not disposed of safely these chemicals pose a real danger to aquatic life, our health, and the broader environment,” Pikramenou said.

“This prototype is a big step forward in bringing an effective, quick, and accurate way to detect this pollution, helping to protect our natural world and potentially keep our drinking water clean.”