| dc.description.abstract | The occurrence of nanoplastics has recently gained awareness as a potential environmental concern. This
has emphasized the necessity to better understand their formation pathways. A relatively new nano-IR tool,
photo-induced force microscopy (PiFM), can provide a way to investigate this; offering a combination of highly
space-resolved topographic and chemical information.
We developed a spectral degradation series using the surface sensitive grazing incidence attenuated total
reflectance (GI-ATR)-IR spectroscopy, in order to better understand the information gathered from PiFM nano-
IR hyper maps of UV-degraded PET films. Spectral features indicative for carboxylic acid end groups were
found to be formed in the film upon UV exposure. These features were additionally found on the outer surface
of the film with PiFM. Yet, their presence showed to be inconsistent over multiple PiFM scans. Also, initial
indications were found in the PiFM scans suggesting differences in the spectral features that may arise from
other (degradative) processes, such as through changes in crystallinity. These results demonstrate the usefulness
of PiFM to differentiate chemical information at the nanoscale, and may help to unravel the formation process
of nanoplastics. However, the observed variability, inconsistency, and proneness to many measurement variables also
underline its complexity.
Furthermore, the development of morphological features measured by the atomic force microscopy (AFM)
scans suggested the initial presence and growth of spherulite-like structures upon UV exposure. Over time, and
upon submergence in water, these morphologies were transformed into more lamellar-like ridge structures which
were elongated in a preferred orientation, seemingly inherent to the structure of the film. For the assessment
of the spectral relation to topography, a tangible methodology was developed. This revealed the heterogeneous
distribution of spectral features and structural properties to the surface topography. In this regard, the most
exemplary observation was a frequently observed asymmetrical distribution of spectral features with respect to
the formed cracks. | |
