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Optical photothermal infrared spectroscopy
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This review explains a new imaging technique that can chemically analyze incredibly tiny samples, even in water, without the usual interference problems. This matters because it can identify microplastics and their chemical makeup in tissues and cells with far greater precision than older methods, helping scientists better understand how these particles affect our bodies.
Optical photothermal infrared (O-PTIR) spectroscopy is an indirect form of infrared (IR) spectroscopy that enables submicrometre analysis. O-PTIR overcomes the diffraction limitations of IR microscopy through the use of a visible probe laser, which greatly improves spatial resolution. The probe laser’s scattering intensity is modulated by the sample’s photothermal response to pulses from an IR laser scanning across the mid-IR, a key region for identifying characteristic frequencies of functional groups and other covalently bonded or IR-active species. O-PTIR spectra also benefit from limited liquid water interference owing to the underlying physics of the photothermal response. This Primer discusses the theoretical background behind O-PTIR, the experimental set-up for O-PTIR spectral and imaging collection, signal theory and data acquisition, along with guidance for spectral interpretation. At present, O-PTIR has been used to generate IR spectra and images for challenging systems across the life, environmental and materials sciences. Examples of these applications are highlighted to show the capabilities of O-PTIR to provide spectra and images at resolutions that previously evaded the capabilities of traditional IR microscopy techniques. Lastly, approaches for improving data transparency and reproducibility are discussed, along with potential limitations, methods to optimize data collection and an outlook towards future O-PTIR development. Optical photothermal infrared spectroscopy is capable of submicrometre infrared analysis with minimal water interference and scattering artefacts. This indirect, non-contact pump–probe method circumvents the issues associated with direct infrared techniques and has been used to analyse a variety of systems, from hydrated tissue samples to microplastics and individual aerosol particles.
More Papers Like This
Characterization of microplastics in tap water by optical photothermal infrared
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Researchers used optical photothermal infrared spectroscopy to characterize microplastics in tap water, identifying particles as small as a few micrometers that conventional FTIR techniques cannot resolve. The higher detection sensitivity revealed that microplastic concentrations in drinking water are likely underestimated by standard methods.
Characterization of microplastics in tap water by optical photothermal infrared
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Researchers characterized microplastics in tap water using optical photothermal infrared spectroscopy, a technique that can identify particles smaller than 10 micrometers with high chemical specificity. The method detected a broader range of particle sizes than conventional FTIR microscopy, revealing higher microplastic concentrations in tap water than previously reported.
A tutorial on optical photothermal infrared (O-PTIR) microscopy
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This tutorial reviews optical photothermal infrared microscopy, a technique that achieves up to 30 times better spatial resolution than conventional infrared imaging. Researchers describe how this method enables chemical identification of materials at the sub-micrometer scale, with applications ranging from biomedical research to microplastics detection. The technology is particularly valuable for environmental scientists who need to identify and characterize extremely small plastic particles in complex samples.
Optical photothermal infrared spectroscopic assessment of microplastics in tissue models and non-digested human tissue sections
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Researchers developed a method using optical photothermal infrared spectroscopy to detect and map microplastics directly within tissue sections without requiring chemical or enzymatic digestion. The study suggests this approach preserves spatial information about where microplastics are located within tissue architecture, overcoming a key limitation of conventional digestion-based methods that can lose some particles.
Chemical characterization of microplastics from biosolids: a comparison of FTIR and O-PTIR microspectroscopy
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Researchers compared conventional FTIR microspectroscopy with the emerging Optical Photothermal Infrared (O-PTIR) technique for chemical characterization and polymer-type identification of microplastics extracted from biosolids, finding that O-PTIR's submicron resolution and artifact-free spectra offer advantages over traditional methods.
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