Photoinduced Force Microscopy as an Efficient Method Towards the Detection of Nanoplastics

Abstract

The degradation of plastic waste in aquatic environments, leading to plastic particles at the micro- and nanoscale is of growing concern. However, conventional analytical techniques either lack sufficient spatial resolution or the necessary spectroscopic means to investigate individual plastic nanoparticles. Both are however necessary to understand how macro- and micro-sized plastic particles break down into nanometer-sized particles. Here we show that a hybrid analytical technique, combining the spatial resolution of atomic force microscopy (AFM) with the chemical information from infrared (IR) spectroscopy, meets these requirements. We studied nanometer-sized particles of polystyrene (PS), a plastic that is extensively used worldwide. We demonstrate that we can detect and quantify these so-called nanoplastics down to 20 nm in size and discuss their physicochemical properties. We show that in saline aqueous environments, in the absence of light, oxidative degradation and chain scission are the main mechanisms to form and degrade PS micro- and nanoplastics.