Using table sugar, researchers have synthesised carbon dots that can be used as a sensitive sensor for detecting minute traces of lead ions in drinking water1.
Carbon dots are carbon nanoparticles that are widely used to make light-emitting diodes, solar cells and even supercapacitors. Existing methods to make such nanodots are complex and time-consuming.
To find a simple green process, scientists from the University of Calicut, Kerala, in India heated a mixture of table sugar and diluted ammonia solution, and then exposed it to microwave irradiation. The solution was then cooled, filtered and freeze-dried to yield carbon nanodots.
Adding a solution of lead ions to the carbon nanodot solution turned the nanodot solution turbid, a state that can be detected by the naked eye.
When a mixture of metal ions such as those of cadmium, mercury, copper, potassium and sodium –without the lead ions – was added to the nanodot solution, the nanodot solution remained clear. When lead ions were added, the nanodot solution became turbid, showing that the nanodots are sensitive only to lead ions.
On being exposed to lead ions, the nanodots formed an aggregation that scattered light, turning the solution turbid. It was possible to measure the levels of lead ions in any water sample by measuring the turbidity of the solution.
The carbon nanodots successfully detected lead ion concentrations as low as 14 parts per billion in lead-containing real water samples.
