Sustainable Technology Turning Over a New Leaf: Brazilian Researchers Innovate with Eco-Friendly Sensors

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Scientists have innovated a sustainable method to create electrochemical sensors by laser printing on fallen tree leaves. This technique, which transforms leaf cellulose into functional graphite sensors through pyrolysis, has proven effective in detecting substances like dopamine and paracetamol.

Researchers in Brazil have developed a novel method for creating sensors by laser printing on fallen tree leaves. The process involves converting leaf cellulose into graphite through pyrolysis and then shaping it appropriately to function as a sensor. Initial testing has shown that these sensors can successfully measure concentrations of substances like dopamine and paracetamol.

The innovative technique combines the advantages of 3D printing, such as speed and design flexibility, with the sustainability of using natural waste as a substrate. This approach aligns with principles of the circular economy, turning typically discarded materials into valuable low-cost resources.

The project is led by Bruno Janegitz, professor at the Federal University of São Carlos (UFSCar) and head of its Laboratory for Sensors, Nanomedicines, and Nanostructured Materials (LSNANO), alongside Thiago Paixão, professor at the University of São Paulo (USP) and director of its Electronic Tongues and Chemical Sensors Lab (L2ESQ). The team's work represents a significant step forward in both environmental sustainability and sensor technology.

“We used a CO₂ laser to print the design of interest on a leaf by means of pyrolysis and carbonization. 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,” Janegitz said.

Simply put, the laser beam burns the leaf in a pyrolytic process that converts its cellulose into graphite, and the graphite body is printed on the leaf in a shape suited to functioning as a sensor. During the fabrication process, the parameters of the CO₂ laser, including laser power, pyrolysis scan rate and scan gap, are systematically adjusted to achieve optimal outcomes.

“The sensors were characterized by morphological and physicochemical methods, permitting exhaustive exploration of the novel carbonized surface generated on the leaves,” Janegitz said.

“Furthermore, the applicability of the sensors was confirmed by tests involving the detection of dopamine and paracetamol in biological and pharmaceutical samples. For dopamine, the system proved efficient in a linear range of 10–1,200 micromoles per liter, with a detection limit of 1.1 micromole per liter. For paracetamol, the system worked well in a linear range of 5-100 micromoles per liter, with a detection limit of 0.76.”

In the tests involving dopamine and paracetamol, conducted as proof of concept, the electrochemical sensors derived from fallen tree leaves attained a satisfactory analytical performance and noteworthy reproducibility, highlighting their potential as an alternative to conventional substrates.

Substituting fallen tree leaves for conventional materials yields significant gains in terms of cost-cutting and above all environmental sustainability. “The leaves would have been incinerated, or at best composted. Instead, they were used as a substrate for high value-added devices in a major advancement for the fabrication of next-generation electrochemical sensors,” Janegitz said.

Original Article: Green Fabrication and Analytical Application of Disposable Carbon Electrodes Made from Fallen Tree Leaves Using a CO2 Laser; ACS Sustainable Chemistry & Engineering; DOI:10.1021/acssuschemeng.3c06526

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