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Single-Particle Analysis of the Photodegradation of Submicron Polystyrene Particles Using Infrared Photothermal Heterodyne Imaging.

Environmental science & technology 2024 Score: 35 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.
Ozioma Nwachukwu, Kirill Kniazev, Angela Abarca Perez, Masaru Kuno, Kyle Doudrick

Summary

Researchers used a new infrared imaging technique to observe how submicron polystyrene particles physically and chemically degrade under UV light, finding significant chemical changes within just 6 hours. This is one of the first methods capable of tracking photodegradation of very small plastic particles, improving our understanding of how nanoplastics form and age in the environment.

Polymers

Sunlight irradiation is the predominant process for degrading plastics in the environment, but our current understanding of the degradation of smaller, submicron (<1000 nm) particles is limited due to prior analytical constraints. We used infrared photothermal heterodyne imaging (IR-PHI) to simultaneously analyze the chemical and morphological changes of single polystyrene (PS) particles (∼1000 nm) when exposed to ultraviolet (UV) irradiation (λ = 250-400 nm). Within 6 h of irradiation, infrared bands associated with the backbone of PS decreased, accompanied by a reduction in the particle size. Concurrently, the formation of several spectral features due to photooxidation was attributed to ketones, carboxylic acids, aldehydes, esters, and lactones. Spectral outcomes were used to present an updated reaction scheme for the photodegradation of PS. After 36 h, the average particle size was reduced to 478 ± 158 nm. The rates of size decrease and carbonyl band area increase were -24 ± 3.0 nm h and 2.1 ± 0.6 cm h, respectively. Using the size-related rate, we estimated that under peak terrestrial sunlight conditions, it would take less than 500 h for a 1000 nm PS particle to degrade to 1 nm.

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