Diamond Annual Review 2023/24

40 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 3 / 2 4 Harmful environmental impact of microplastics adsorbing zinc oxide from sunscreens and microbeads from cleansers indicated In recent decades, there has been a dramatic increase in the manufacture of engineered nanomaterials (tiny, tiny particles about 1000 times thinner than a human hair), which has inevitably led to their environmental release. Similarly, Zinc oxide (ZnO) is among the more abundant nanomaterials fabricated due to its advantageous use in electronics, semiconducting, and for antibacterial purposes. At the same time, plastic waste has become ubiquitous andmay break down into smaller pieces called microplastics. These also are tiny, but ~100 times bigger than the nanomaterials. Because both these elements are getting disposed more often, A research team led by Diamond Researchers decided to study their fate when they are potentially being combined in freshwater and oceans and to help make environmental risk assessments more accurate. To make their study more relevant to the real world, the team tested a sunscreen containing zinc oxide which is commonly used to block UV-radiation. They let the sunscreen incubate in the different environmental solutions for a week and then added the microplastics for a day. The objective was to check if the zinc oxide could come out of the sunscreen and stick to these microplastics. They also followed the same procedure with a facial scrub containing tiny plastic beads. The team then examined these zinc oxide-covered microplastics at the I14 beamline, where they performed X-ray Fluorescence (XRF) and X-ray absorption near-edge structure spectroscopy (XANES) experiments. Their results show that the zinc oxide had transformed into different types of zinc-related particles. Some of these new particles (Zn-sulfide) were formed quickly, while others formed more slowly but were more stable (Zn-phosphate). This has worrying environmental implications for fish and other aquatic organisms in the food chain - which could swallow these microplastics and ingest zinc particles at the same time. Gomez-Gonzalez, M. A. et al. DOI: 10.1002/gch2.202300036 Figure: X-ray fluorescence (XRF, left) maps (100 nm pixel size) for the Zn signal and differential phase contrast (DPC, right) image for morphological inspection of the adsorbed structures measured at the hard X-ray nanoprobe (I14 beamline). Zn-particles from the sunscreen were deposited on the pristine microplastics after incubation in seawater (top row) while ZnO nanomaterials were deposited on the microplastics leached from the exfoliating cleanser after incubation in seawater as well (bottom row). Illuminating the future: a game-changing approach to quantumdot production In October 2023, the Nobel Prize in Chemistry was awarded to three scientists (Aleksey Yekimov, Louis Brus and Moungi Bawendi) for their roles in the discovery and development of quantum dots (QDs). At the nanoscale, the properties of matter are determined by quantum phenomena, and governed by size. QDs are nanoparticles of light-emitting semiconductors, so tiny that the wavelength of light they emit is determined by their size, not their chemistry. By carefully controlling the synthesis process, manufacturers can create QDs that emit light across the breadth of the visible spectrum and into the infrared. However, most are based on cadmium selenide, a toxic metal system that creates challenges for manufacturing, disposal and medical use. Indium phosphide (InP), already in commercial use, is a promising replacement. However, the standard synthesis of InP requires the use of tris(trimethylsilyl) phosphine, a highly reactive and dangerous phosphorous precursor. Researchers from King’s College London, the University of Oxford, the University of Cambridge, London South Bank University and Indiana University developed a significantly simpler synthetic methodology using a solid, air- and moisture-tolerant primary phosphine. In order to verify that that they had a crystalline structure, they used the electron Physical Science Imaging Centre (ePSIC), which is one of the few facilities where they can look at these particles under a microscope. They saw the particles, did an elemental analysis to see which elements were there, and where they were. The team need to do more analysis, but their initial results suggest that they have done exactly what they set out to do - make luminescent QDs using a safe phosphorus source. Wang, Y. et al. DOI:10.1039/D3NH00162H Figure: STEM HAADF image of (A) InZnP (InZnP, grown at 45 minutes/120 °C degassing followed by 10 minutes/220 °C growth). (B), (C) High angle annular dark field (HAADF) STEM images of InZnP/ZnS (InZnP/ZnS, core grown at 45 minutes/120 °C degassing followed by 10 minutes/220 °C growth, followed by shell addition). Imaging and Microscopy Science Highlights