Micro- and nanoplastics (MNP) are ubiquitous, but little is known about the risks they pose to human health. Currently available data are of limited use for developing relevant risk assessments due to poor quality control, the lack of a standardised approach to particle characterisation and environmental analysis, and the use of test materials that do not reflect those found in the environment. A set of well-characterised MNP test materials would greatly alleviate this. Here, we present a robust method to produce, fractionate and characterise such test materials of PP and PVC. Initial size reduction of commercial powders to 500 µm was performed using a centrifugal mill under cryogenic conditions. Further ball-milling between room temperature and − 50°C in 1-propanol was then performed to reach the final particle sizes. Fractionation into size ranges of < 1, 1–5, 5–10, 10–90, 90–180 and 180–300 µm was performed by sedimentation and filtration. Characterisation of the reference materials through SLS, SEM-EDX, XRF and TGA demonstrated that the fractions were of the desired size and levels of contamination from the procedure were < 1 wt%. Stability testing in both 1-propanol and 0.05 wt% BSA solution showed that whilst some agglomeration occurred during storage in 1-propanol the suspensions were stable in BSA over 9 months and some of the previous agglomeration was reversed.

A new method is developed to produce mesoporous titania thin films at room temperature using the enzyme papain in a dip‐coating procedure, providing low‐cost titania films in a sustainable manner. Quartz crystal microbalance, positron annihilation Doppler broadening and lifetime spectroscopy, scanning electron microscopy, and X‐ray diffraction are used to determine the deposition and structural properties of the films. As‐deposited films have low densities ρ ≈ 0.6 g cm−3, contain small micropores and proteins, and exhibit corrugated surfaces. Annealing at temperatures of 300 °C or higher leads to the destruction and evaporation of most of the organic material, resulting in a thickness decrease of 50–60%, more pure titania films with increased density, an increase in micropore size and a decrease in the concentration and size of atomic‐scale vacancies. Up to 50 layers could be stacked, allowing easy control over the total layer thickness. Based on these titania films, first test devices consisting of natural dye‐sensitized solar cells are produced, that show photovoltaic activity and indicate possibilities for low‐cost, accessible, organic production of solar cells. Given the wide range of other applications for titania, this new method is a promising candidate for improving the fabrication of those products with respect to cost, sustainability, and production speed.

Micro- and nanoplastics (MNP) are ubiquitous, but little is known about the risks they pose to human health. Currently available data are of limited use for developing relevant risk assessments due to poor quality control, the lack of a standardised approach to particle characterisation and environmental analysis, and the use of test materials that do not reflect those found in the environment. A set of well-characterised MNP test materials would greatly alleviate this. Here, we present a robust method to produce, fractionate and characterise such test materials of PP and PVC. Initial size reduction of commercial powders or pellets to 500 µm was performed using a centrifugal mill under cryogenic conditions. Further ball-milling between room temperature and -50 °C in 1-propanol was then performed to reach the final particle sizes. Fractionation into size ranges of < 1, 1–5, 5–10, 10–30, 90–180 and 180–300 µm was performed by sedimentation and filtration. Characterisation of the reference materials through SLS, SEM–EDX, XRF and TGA demonstrated that the fractions were of the desired size and levels of contamination from the procedure were < 1 wt%. Stability testing in both 1-propanol and 0.05 wt% BSA solution showed that whilst some agglomeration occurred during storage in 1-propanol the suspensions were stable in BSA over 9 months and some of the previous agglomeration was reversed.