A new technique for observing the degradation of colloidal particles in real time


June 14, 2023

(Nanowerk News) In the early 2000s, scientists from the UK made the alarming discovery that the oceans are full of tiny particles of plastic (less than a millimeter in length) due to the continuous degradation of plastic waste. These microscopic plastic particles have become a major environmental concern. Scientists classify these tiny particles as microplastics or nanoplastics based on their size; the latter term is used exclusively for particles smaller than one micrometer.

These particles easily embed into the bodies of marine and freshwater animals, which has raised concerns over the widespread problem of micro- and nanoplastic pollution. Unfortunately, despite great efforts, researchers have yet to decipher the detailed mechanisms by which micro- and nanoplastics originate and change over time. The problem lies primarily with the techniques that have been used so far to observe the degradation process of plastic particles. Simply put, this method cannot observe degradation into single particles in real time.

Against this backdrop, a research team led by Associate Professor Daisuke Suzuki from Shinshu University in Japan set out to find a solution to this challenge. In their most recent study, published in Soft Matter (“Single microgel degradation regulated by heterogeneous nanostructures”), they demonstrated an innovative approach to observing the degradation processes of single microgel particles in real time with nanometric precision. This study was co-authored by Professor Takayuki Uchihashi of Nagoya University in Japan. Real-time high-altitude images of nanoplastics being degraded, captured using high-speed atomic force microscopy Real-time high-altitude images of nanoplastics being degraded, captured using high-speed atomic force microscopy. The left side shows water-containing particles, and the right side shows water-free particles.(Image: Daisuke Suzuki, Shinshu University) (click on image to enlarge)

The proposed approach has two main lines of inquiry. In the first part of the research, microgels were used as a model to understand the behavior of nanoplastic particles. The microgels used consist of polymers with cross-linked points that can be cleaved by a chemical reaction using an oxidizing agent. In other words, the bonds between molecules such as the long fibers that form tiny microgel balls can be broken in a semi-controlled manner by adjusting the temperature and chemical environment.

The second major line of research investigation is the development of state-of-the-art techniques to visualize microgel degradation in real time. The researchers used a carefully configured high-speed atomic force microscopy (HS-AFM) setup, which involves ‘touching’ the sample with an atomic-sized tip placed on the cantilever end and measuring its deflection. Thanks to HS-AFM, the team was able to observe changes in the shape of the microgels over time with very high precision.

After several experiments at different temperatures and microgel compositions, the researchers gained valuable insight into how nanoplastics originate and develop over time depending on the environment. “Experiments revealed that while water-containing nanoplastics easily allow chemical reactants to diffuse inside, nanoplastics in a water-free state do not allow reactants to diffuse. Thus, nanoplastics in different states show very different degradation behavior,” explained Prof. Suzuki.

Videos of microgels degrading in real time illustrate how useful this new approach can be for advancing the understanding of micro- and nanoplastics. Excited about the possible implications of their excellent work, Prof. Suzuki comments: “The approach presented has the potential to be extended into observational techniques that can assess not only temperature variations, but also other external stimuli encountered in everyday life, such as ultraviolet radiation. light and stress-free, enabling nanoscale observations in diverse environmental conditions.”

Overall, the results of this study will pave the way towards a better understanding of nanoplastics. In turn, this will give scientists and engineers a better opportunity to combat this elusive aspect of ocean pollution. Additionally, since micro and nanoplastics are important ingredients used in everyday products such as adhesives, paints and cosmetics, having a stronger understanding of their degradation processes will help develop guidelines for reducing their environmental impact. This knowledge will also be useful in advanced drug delivery systems, where gels play an important role as drug delivery agents.

Seeing a brighter future, Prof. Suzuki concluded: “It is hoped that this research will generate interest in the general public in micro- and nanoplastics, encouraging them to reconsider their use of plastics, a major source of nanoplastics.”


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