ANALYSIS OF MICRO AND NANOPLASTICS WITH X-RAY PHOTOELECTRON SPECTROSCOPY

• Autor(a) principal: Mendes, Ana Sofia Silva
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/155126
• topic: X-ray Photoelectron Spectroscopy; Microplastics; Oxide-hydroxide layer; Hydrocarbon contamination; Coverage; Surface analysis; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Microplastic pollution has become an increasingly relevant issue in recent years and thus there have been many studies on the analysis of these microparticles regarding their identification. The most used techniques for this purpose are Fourier-Transform Infrared Spectroscopy (FT-IR) and Raman Microspectroscopy (RM). X-ray Photoelectron Spectroscopy (XPS) is also utilised, although a lot less frequently because of its limitations when working with polymers, such as accumulation of charge on the sample, limited spectral resolution to identify specific functional groups and the difficulties associated with analysing a non-uniform sample, which is inevitable when working with microparticles. However, XPS is a highly surface sensitive technique and can be very useful in MP analysis. Namely, the application of XPS in this area is the study subject of this thesis. In this work, three industrial plastics were analysed with XPS: PVC, PA6 and PET. Reference samples of the indium substrate and the three plastics were prepared and analysed. The resulting spectra were fitted in accordance with literature. Afterwards, the relationship between the coverage of plastic in a sample and the signal intensities was studied by performing a calibration for each of the plastics, for which several samples were prepared with different percentages of coverage. As an additional necessary step, the thicknesses of the indium oxide-hydroxide and hydrocarbon contamination layers covering the metallic bulk indium were measured in order to properly account for the line intensity of indium, which was then used for the calibration. This way, a procedure is established for the quantification of different plastic particles deposited atop the indium surface.