2,4- 1Particle Laboratory, Department of Process Engineering, Eawag (Swiss Federal Institute of Aquatic Science and Technology), Ueberlandstrasse 133, 8600 Dübendorf, Switzerland (ralf.kaegi@eawag.ch)
- 2Particles and Aerosols Laboratory, Federal Institute of Metrology METAS, Lindenweg 50, 3003 Bern, Switzerland
- 3Laboratory for Transport at Nanoscale Interfaces, Empa (Swiss Federal Laboratories for Materials Science and Technology), Ueberlandstrasse 129, 8600 Dübendorf, Switzerland
- 4Laboratory for Air Pollution and Environmental Technology, Empa (Swiss Federal Laboratories for Materials Science and Technology), Ueberlandstrasse 129, 8600 Dübendorf, Switzerland
Whereas the presence of microplastic particles (1µm – 1mm) have been documented all around the globe, the evidence for plastic particles in the submicrometer size range (<1µm) and especially in the nano size range (NPs<100nm) falls short.1,2 This is, on the one hand, related to the lack of suitable sampling methods which allow a representative collection of plastic particles in the respective size range and, on the other hand, to the lack of analytical techniques providing sufficient lateral resolution and chemical specificity. The lateral resolution of commonly used vibrational spectroscopy methods such as infrared (IR) or Raman spectroscopy are diffraction limited to a few micrometers (IR) or slightly below 1µm (Raman) and are therefore not suitable for the analysis of submicron or nano sized plastic particles. Thus, other methods, either using shorter wavelengths (e.g. electron microscopy) or relying on non-optical effects (e.g., atomic force microscopy (AFM)) have to be used. In this study, we assessed the potential of AFM-IR to detect and quantify submicron and nanoscale plastic particles. We evaluated different substates for their suitability to conduct AFM-IR analysis and found silicon (Si) wafers most suitable. Other substrates such as mica were well suited to image particles using the AFM but led to artefacts or high background contributions during AFM-IR analysis. Size detection limits depended on the polymer types and were as low as 80nm for polystyrene.
Synthetic aerosols containing major particulate components of the urban atmosphere including photochemically aged soot, organic compounds, geogenic dust and salts were collected using an electrostatic sampling device. This approach allowed a representative collection of individual aerosol particles directly on laser cut Si wafers with a diameter of 3mm.3 AFM-IR analysis of individual particles demonstrated the high specificity of the method and allowed identifying the different particle and polymer types in complex (aerosol) mixtures. After removing water soluble compounds such as salts in an initial washing step, particles collected electrostatically from the urban atmosphere were dominated by soot, whereas NPs were not detected. Based on our dataset, the maximum possible atmospheric concentration of NPs in the analyzed air sample was estimated at 9 NPs per cm3. Future studies will be dedicated to a selective enrichment of NPs to further constrain the concentration of NPs in ambient air.
References
(1) R. C. Thompson, W. Courtene-Jones, J. Boucher, S. Pahl, K. Raubenheimer and A. A. Koelmans, Twenty years of microplastic pollution research-what have we learned?, Science, 2024, 386, eadl2746.
(2) N. P. Ivleva, Chemical Analysis of Microplastics and Nanoplastics: Challenges, Advanced Methods, and Perspectives, Chem Rev, 2021, 121, 11886-11936.
(3) R. Kaegi, M. Fierz and B. Hattendorf, Quantification of Nanoparticles in Dispersions Using Transmission Electron Microscopy, Microsc Microanal, 2021, 27, 557-565.
How to cite: Kaegi, R., Kummer, N., Horender, S., Kulmala, T. S., Vasilatou, K., and Hueglin, C.: AFM-IR as a tool to detect nanoplastic particles in aerosols, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18546, https://doi.org/10.5194/egusphere-egu26-18546, 2026.
