Researchers Turn Fallen Leaves Into Working Electrochemical Sensors — By Blasting Them with Lasers

Researchers from the Federal University of São Carlos, Universidade de São Paulo, and the State University of Campinas have come up with an extremely eco-friendly source of sensor materials: leaves fallen from trees, blasted with a carbon dioxide laser.

"We used a CO₂ [carbon dioxide] laser to print the design of interest on a leaf by means of pyrolysis and carbonization," explains project lead Bruno Janegitz in an interview with José Tadeu Arantes at project sponsor FAPESP. "We thereby obtained an electrochemical sensor for use in determining levels of dopamine and paracetamol. It’s very easy to operate. A drop of the solution containing one of these compounds is placed on the sensor, and the potentiostat to which it's coupled displays the concentration."

The sensors themselves are built by gathering leaves that have already fallen from trees, typically seen as a waste material suitable only for composting or burning, and burning a particular pattern onto the surface with a carbon dioxide laser on an XY gantry — carbonizing the cellulose in the leaves and creating a fully-functional eco-friendly electrochemical sensor.

In testing, the team found that the sensors thus created were able to detect the presence of dopamine and acetaminophen within a range of 10-1,200 micromoles per liter and 5-100 micromoles per liter each — delivering what the team describes as "satisfactory analytical performance." The sensors themselves, meanwhile, are described as showing "remarkable reproducibility" — suggesting that fallen leaves could truly offer an alternative to less environmentally-friendly sensor substrates.

"The leaves would have been incinerated, or at best composted," Janegitz told Arantes at FAPESP of the materials used in the project. "Instead, they were used as a substrate for high value-added devices in a major advancement for the fabrication of next-generation electrochemical sensors."

The team's work has been published in the journal ACS Sustainable Chemistry & Engineering under closed-access terms.