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.

Correlating the Morphological Evolution of Individual Catalyst Particles to the Kinetic Behavior of Metallocene-Based Ethylene Polymerization Catalysts

“…Inspired by this, we used PiFM to characterize the cross-sections of a single 30 min prepolymerized SiO 2 /MAO/Hf particle at multiple locations and depths (Figures , S6, S7, S8, all cross-section 2; and S9, cross-section 1). Nanoscale infrared and topographic imaging ,,− yielded information on both the chemical composition and morphology of the sample at a sub-20 nm resolution.…”

Spectro‐Microscopic Techniques for Studying Nanoplastics in the Environment and in Organisms

“…As shown by ten Have et al., this so‐called AFM‐IR or nano‐IR technique (specifically, the authors used PiFM) facilitates the accurate detection of PS NPs down to 20 nm in size [65] . The surface sensitivity highlighted a change of spectrum after H 2 O 2 treatment of the (commercially obtained) PS beads.…”

“…[89,90] As shown by ten Have et al, this so-called AFM-IR or nano-IR technique (specifically, the authors used PiFM) facilitates the accurate detection of PS NPs down to 20 nm in size. [65] The surface sensitivity highlighted a change of spectrum after H 2 O 2 treatment of the (commercially obtained) PS beads. This is explained by sulfonate-containing surfactants used to stabilize the particles: at first there were S=O stretching vibrations visible in the spectrum but, after the treatment, these bands had disappeared.…”

“…Furthermore the C=C stretching and aliphatic C=C stretching vibrations indicate degradation of the particles after exposure to these saline conditions. Reproduced from ref [65]…”

Photo induced force microscopy: chemical spectroscopy beyond the diffraction limit

“…Using the characteristic acrylic and urethane absorption bands at 1730 cm −1 and 1705 cm −1 respectively, Chen et al used PiFM to map the distribution of the two components and establish acrylic domain sizes of ∼30–40 nm supporting the proposal that the enhanced physical behaviour of the hybrids is due to smaller domain sizes than is found in blends. Have et al 44 applied PiFM to a slightly different problem, comparing it with two commonly used light scattering techniques: nanoparticle tracking analysis and multi-angle dynamic light scattering, for the determination of nano-plastic particle size distributions and concentrations in seawater. The main drawback of PiFM's relatively slow throughput was offset by its ability to distinguish easily between nano-plastics and other nano-particles that interfere with the light scattering technique results.…”