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“O-PTIR spectroscopy demonstrated its potential to provide further insights into surface properties and behavior, uniquely identifying organic and inorganic constituents at the microscale level.”
In this study, the authors address the critical challenge of characterizing the variability in chemical composition and physical properties of indoor particles and surfaces across different dwellings in the United States. This research became particularly relevant during the COVID-19 pandemic, as increased time spent indoors heightened exposure to indoor pollutants. Utilizing microspectroscopic techniques, specifically and optical photothermal infrared spectroscopy (O-PTIR) and Raman microspectroscopy, the authors analyzed particles deposited on glass slides positioned in various residential rooms over periods ranging from hours to weeks.
The authors report that O-PTIR spectroscopy provided clear, distinct, and sensitive identification of organic compounds, predominantly characterized by vibrations from functional groups such as C–H stretching and carbonyl (C=O) functionalities.
The O-PTIR method revealed detailed spectral variability between samples, often linked to specific activities like cooking, highlighting differences not only between homes but also among rooms within the same residence.
Data indicated substantial organic contributions, particularly in kitchen environments, correlating deposited particles with cooking oils. Spectroscopic evidence clearly demonstrated that indoor particle deposition occurs heterogeneously, primarily forming discrete particle layers rather than uniform films.
Importantly, O-PTIR spectroscopy uniquely identified particles containing both inorganic (e.g., nitrates) and organic components, thus demonstrating the technique’s comprehensive analytical capability.
Further supporting their conclusions, three-dimensional optical profilometry reinforced the microspectroscopic findings by visualizing particle morphology and deposition unevenness on sampled surfaces.
In conclusion, the authors emphasize the powerful capabilities of the O-PTIR technique, underscoring its exceptional sensitivity and specificity in identifying diverse chemical species present in indoor environments. This research highlights O-PTIR’s significant potential in accurately characterizing and understanding indoor surface chemistry, essential for improving indoor air quality models and mitigating human exposure to harmful indoor pollutants.
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Authors:
Alison M. Fankhauser, a Jana L. Butman, b Madeline E. Cooke, a Yekaterina Fyodorova,a Yangdongling Liu,b Rachel E. O’Brien, cd V. Faye McNeill, *ef Franz M. Geiger, *b Vicki H. Grassian *g and Andrew P. Ault *a
a Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA. b Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60660, USA. c Department of Chemistry, William & Mary, Williamsburg, Virginia 23185, USA d Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA e Department of Chemical Engineering, Columbia University, New York, New York 10027, USA. f Department of Earth and Environmental Sciences, Columbia University, New York, New York 10027, USA g Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA.
