Using Infrared Photothermal Heterodyne Imaging to Characterize Micro- and Nanoplastics in Complex Environmental Matrices,Environmental Science & Technology

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Using Infrared Photothermal Heterodyne Imaging to Characterize Micro- and Nanoplastics in Complex Environmental Matrices
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2021-11-08 , DOI: 10.1021/acs.est.1c05181
Kirill Kniazev ₁ , Ilia M Pavlovetc ₁ , Shuang Zhang ₂ , Junyeol Kim _{3,

4} , Robert L Stevenson ₂ , Kyle Doudrick ₃ , Masaru Kuno _{1,

5}

Affiliation

A key challenge for addressing micro- and nanoplastics (MNPs) in the environment is being able to characterize their chemical properties, morphologies, and quantities in complex matrices. Current techniques, such as Fourier transform infrared spectroscopy, provide these broad characterizations but are unsuitable for studying MNPs in spectrally congested or complex chemical environments. Here, we introduce a new, super-resolution infrared absorption technique to characterize MNPs, called infrared photothermal heterodyne imaging (IR-PHI). IR-PHI has a spatial resolution of ∼300 nm and can determine the chemical identity, morphology, and quantity of MNPs in a single analysis with high sensitivity. Specimens are supported on CaF₂ coverslips under ambient conditions from where we (1) quantify MNPs from nylon tea bags after steeping in ultrapure water at 25 and 95 °C, (2) identify MNP chemical or morphological changes after steeping at 95 °C, and (3) chemically identify MNPs in sieved road dust. In all cases, no special sample preparation was required. MNPs released from nylon tea bags at 25 °C were fiber-like and had characteristic IR frequencies corresponding to thermally extruded nylon. At 95 °C, degradation of the nylon chemical structure was observed via the disappearance of amide group IR frequencies, indicating chain scission of the nylon backbone. This degradation was also observed through morphological changes, where MNPs altered shape from fiber-like to quasi-spherical. In road dust, IR-PHI analysis reveals the presence of numerous aggregate and single-particle (<3 μm) MNPs composed of rubber and nylon.

中文翻译：

使用红外光热外差成像表征复杂环境基质中的微塑料和纳米塑料

解决环境中微塑料和纳米塑料 (MNP) 的一个关键挑战是能够在复杂基质中表征它们的化学性质、形态和数量。当前的技术，如傅里叶变换红外光谱，提供了这些广泛的表征，但不适合在光谱拥挤或复杂的化学环境中研究 MNP。在这里，我们介绍了一种新的超分辨率红外吸收技术来表征 MNP，称为红外光热外差成像 (IR-PHI)。IR-PHI 的空间分辨率约为 300 nm，可以在一次分析中以高灵敏度确定 MNP 的化学特性、形态和数量。CaF ₂支持样本环境条件下的盖玻片，我们 (1) 在 25°C 和 95°C 的超纯水中浸泡后量化尼龙茶袋中的 MNP，(2) 在 95°C 浸泡后确定 MNP 的化学或形态变化，以及 (3) 化学鉴定过筛后的道路灰尘中的 MNP。在所有情况下，都不需要特殊的样品制备。在 25 °C 时从尼龙茶包中释放的 MNP 是纤维状的，并且具有与热挤出尼龙相对应的特征红外频率。在 95 °C 时，通过酰胺基 IR 频率的消失观察到尼龙化学结构的降解，表明尼龙主链发生断链。这种降解也通过形态变化观察到，其中 MNP 将形状从纤维状改变为准球形。在道路尘土中，

更新日期：2021-12-07

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