A carbon nanotube electrochemical sensor detects pollutants in water using electricity, opening a new frontier.

When we think of 'plastic pollution We imagine islands floating in the ocean, small colorful fragments crowded on a fingertip, and old beached containers. Yet, as often happens, the most insidious threat is the one we can't see. In a word: nanoplastics.

When plastic fragments to the point of reaching nanometer dimensions, it stops behaving like simple debris and begins to move like a biological particle, escaping the pull of gravity to respond to molecular dynamics that make it nearly impossible to track. New Italian research, however, may have found the key to making the invisible visible using electrical signals.

How to detect nanoplastics in aquatic environments?

Sometimes, size becomes a substantial feature. When they go down below the micrometer, for example, fragments of plastic materials not only become invisible to optical microscopes, but are transformed into particles that stop behaving as inert sediments, which have the ability to penetrate cell membranes and can remain suspended indefinitely in water without sinking or following the currents, because at certain scales the force of gravity is almost irrelevant compared to the forces of molecular collisions.

Thus it happens that nanoplastics spread quite uniformly throughout the water column, albeit in minimal quantities – impossible to avoid, almost impossible to distinguish from organic molecules. To "capture" them, today, membrane filters with nanometric pores are used; then, to isolate them, algae and other residues must be eliminated using oxidizing agents, acids, or enzymes that only attack molecules of biological origin. Only then is it possible study isolated particlesThis can only be done with nanoscale analysis technologies such as scanning electron microscopy, DLS (Dynamic Light Scattering), and spectroscopic techniques that reveal the chemical identity of the sample by shining lasers or infrared light on it. In short, this is far from easy and extremely expensive work, as well as being subject to a high risk of external contamination.

The search for Free University of Bozen-Bolzano and of the Smart Materials Lab of theItalian Institute of Technology It was created precisely to find an answer to these limitations, which make nanoplastics a threat perhaps even more serious than the now well-known threat of microplastics.

A new sensor to detect nanoplastics in the sea

The new study, published in the journal ACS Applied Materials & Interfaces, was born from the intuition of a team of researchers from the Faculty of Engineering of the University of Bolzano: the young biotechnologist Giulia Elli and the professors of the Sensing Technologies Lab Paul Lugli e Luisa Petti. Looking for alternatives to complex and expensive techniques such as spectroscopy, researchers have developed a innovative sensor, fast and easy to use based on a carbon nanotube field-effect transistor.

The device, they explain, exploits the non-covalent interactions between the carbon nanotubes and polystyrene nanoplastics, offering a more accessible method to detect these dangerous particles: the nanoplastics present in the water interact with the carbon nanotubes present on the sensor surface, inducing a increase in current generated. The higher the concentration of nanoplastics, the greater the current produced.

From laboratory simulation to environmental monitoring

The research, so far, has been conducted entirely in the laboratory, reproducing the characteristics of sea, river, and lake water – in order to test the behavior and effectiveness of the sensors in marine and brackish environments.

As a model material, the researchers used polystyrene nanoparticles. Now, the University of Paris Cité is studying the selectivity of sensors, which in the future will also be able to identify what type of nanoplastics a watercourse area is contaminated with. The next step, clearly, will consist in try the new sensors outside the laboratory to carry out surveys in nature and sample waterways and stretches of sea:

"Studying engineering subjects isn't just about designing the future, it's also about protecting it: the sensors developed in Bolzano demonstrate how innovation can become an essential weapon in fighting invisible pollution and safeguarding our planet."

underlines the Professor Luisa PettiThis new electrochemical approach, in fact, could revolutionize the monitoring of nanoplastic pollution.

"One nanoplastic at a time, we can all defeat pollution. Even if our actions seem as small as microparticles, each one of them can improve our planet."

concludes the researcher Giulia Elli.

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