Using Infrared Photothermal Heterodyne Imaging to Characterize Micro- and Nanoplastics in Complex Environmental Matrices
Using Infrared Photothermal Heterodyne Imaging to Characterize Micro- and Nanoplastics in Complex Environmental Matrices
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DOI：
10.1021/acs.est.1c05181
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发表时间：
2021-12-07
影响因子：
11.4
通讯作者：
Kuno, Masaru
中科院分区：
文献类型：
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作者：
Kniazev, Kirill;Pavlovetc, Ilia M.;Kuno, Masaru
解决环境中的微米和纳米塑料（MNP）的一个关键挑战是能够表征它们在复杂基质中的化学性质，形态和数量。目前的技术，如傅里叶变换红外光谱，提供了这些广泛的表征，但不适合研究MNP在光谱拥挤或复杂的化学环境。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具有类似于300 nm的空间分辨率，可以在单次分析中以高灵敏度确定MNP的化学身份、形态和数量。样品在环境条件下支撑在CaF 2盖玻片上，其中我们（1）在25和95 ℃下浸泡在超纯水中后定量尼龙茶袋中的MNP，（2）在95 ℃下浸泡后鉴定MNP化学或形态变化，以及（3）化学鉴定筛分道路灰尘中的MNP。在所有情况下，不需要特殊的样品制备。在25 ℃下从尼龙茶袋释放的MNP是纤维状的，并且具有对应于热挤出尼龙的特征IR频率。在95 ° C下，通过酰胺基团IR频率的消失观察到尼龙化学结构的降解，表明尼龙主链的断链。通过形态学变化也观察到这种降解，其中MNP将形状从纤维状改变为准球形。在道路灰尘中，IR-PHI分析揭示了大量聚集体和单个颗粒的存在（
A key challenge for addressing micro- and nano-plastics (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 similar to 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 degrees C, (2) identify MNP chemical or morphological changes after steeping at 95 degrees 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 degrees C were fiber-like and had characteristic IR frequencies corresponding to thermally extruded nylon. At 95 degrees 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 (