Photothermal infrared imaging: identification and visualization of micro- and nanoplastics in environmental matrices

Pavlovetc, Ilia M.; Kniazev, Kirill; Kim, Junyeol; Doudrick, Kyle; Kuno, Masaru

doi:10.1117/12.2577003

Cited by 2 publications

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“…Vibrational optical spectroscopies stand as important, label-free imaging modalities for the complete structural and functional characterization of chemical, environmental and biological specimens. − Two major embodiments involve Raman scattering and infrared (IR) absorption spectroscopy. Raman microscopy possesses a relatively high spatial resolution of ∼300 nm.…”

Section: Introductionmentioning

confidence: 99%

Hyperspectral and Nanosecond Temporal Resolution Widefield Infrared Photothermal Heterodyne Imaging

et al. 2023

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Label-free, bond-selective imaging offers new opportunities for fundamental and applied studies in chemistry, biology, and materials science. Preventing its broader application to investigating spatially-congested specimens are issues related to low sensitivity as well as low spatial and temporal resolution. Here, we demonstrate a widefield, mid-infrared (MIR) photothermal imaging technique, called widefield Infrared Photothermal Heterodyne imaging (wIR-PHI), that massively parallelizes acquisition of MIR absorption data through use of a high-speed complementary metal-oxide-semiconductor camera. wIR-PHI possesses notable features that include: spatial resolution significantly below the MIR diffraction limit, hyperspectral imaging capabilities, high sensitivity, and ∼100 ns temporal resolution. The first two features are highlighted by hyperspectral imaging of proximally close poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanoparticles where clear, bond-specific imaging of nanoparticles, separated by less than the MIR diffraction limit, is demonstrated. Sensitivity is highlighted by imaging individual PMMA and PS nanoparticles with radii between r = 97−556 nm. This leads to a current, peak absorption cross-section limit-of-detection of σ abs = 1.9 × 10 −16 cm 2 . wIR-PHI's 100 ns temporal resolution is simultaneously demonstrated by observing the decay of photothermal contrast on individual nanoparticles on a ∼200−6200 ns timescale. In whole, wIR-PHI's dramatic increase in acquisition speed opens opportunities for future MIR kinetic imaging and spectroscopic studies of important chemical, biological, and material processes.

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Section: Introductionmentioning

confidence: 99%

Hyperspectral and Nanosecond Temporal Resolution Widefield Infrared Photothermal Heterodyne Imaging

et al. 2023

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Deep image restoration for infrared photothermal heterodyne imaging

Kuno

Zhang

Kniazev

et al. 2021

The Journal of Chemical Physics

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Infrared photothermal heterodyne imaging (IR-PHI) is an all-optical table top approach that enables super-resolution mid-infrared microscopy and spectroscopy. The underlying principle behind IR-PHI is the detection of photothermal changes to specimens induced by their absorption of infrared radiation. Because detection of resulting refractive index and scattering cross section changes is done using a visible (probe) laser, IR-PHI exhibits a spatial resolution of ∼300 nm. This is significantly below the mid-infrared diffraction limit and is unlike conventional infrared absorption microscopy where spatial resolution is of order ∼5μm. Despite having achieved mid-infrared super-resolution, IR-PHI’s spatial resolution is ultimately limited by the visible probe laser’s diffraction limit. This hinders immediate application to studying samples residing in spatially congested environments. To circumvent this, we demonstrate further enhancements to IR-PHI’s spatial resolution using a deep learning network that addresses the Abbe diffraction limit as well as background artifacts, introduced by experimental raster scanning. What results is a twofold improvement in feature resolution from 300 to ∼150 nm.

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Photothermal infrared imaging: identification and visualization of micro- and nanoplastics in environmental matrices

Cited by 2 publications

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Hyperspectral and Nanosecond Temporal Resolution Widefield Infrared Photothermal Heterodyne Imaging

Hyperspectral and Nanosecond Temporal Resolution Widefield Infrared Photothermal Heterodyne Imaging

Deep image restoration for infrared photothermal heterodyne imaging

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