2023, Trechera, Pedro, Garcia-Marlès, Meritxell, Liu, Xiansheng, Reche, Cristina, Pérez, Noemí, Savadkoohi, Marjan, Beddows, David, Salma, Imre, Vörösmarty, Máté, Casans, Andrea, Casquero-Vera, Juan Andrés, Hueglin, Christoph, Marchand, Nicolas, Chazeau, Benjamin, Gille, Grégory, Kalkavouras, Panayiotis, Mihalopoulos, Nikos, Ondracek, Jakub, Zikova, Nadia, Niemi, Jarkko V., Manninen, Hanna E., Green, David C., Tremper, Anja H., Norman, Michael, Vratolis, Stergios, Eleftheriadis, Konstantinos, Gómez-Moreno, Francisco J., Alonso-Blanco, Elisabeth, Gerwig, Holger, Wiedensohler, Alfred, Weinhold, Kay, Merkel, Maik, Bastian, Susanne, Petit, Jean-Eudes, Favez, Olivier, Crumeyrolle, Suzanne, Ferlay, Nicolas, Martins Dos Santos, Sebastiao, Putaud, Jean-Philippe, Timonen, Hilkka, Lampilahti, Janne, Asbach, Christof, Wolf, Carmen, Kaminski, Heinz, Altug, Hicran, Hoffmann, Barbara, Rich, David Q., Pandolfi, Marco, Harrison, Roy M., Hopke, Philip K., Petäjä, Tuukka, Alastuey, Andrés, Querol, Xavier

The 2017–2019 hourly particle number size distributions (PNSD) from 26 sites in Europe and 1 in the US were evaluated focusing on 16 urban background (UB) and 6 traffic (TR) sites in the framework of Research Infrastructures services reinforcing air quality monitoring capacities in European URBAN & industrial areaS (RI-URBANS) project. The main objective was to describe the phenomenology of urban ultrafine particles (UFP) in Europe with a significant air quality focus. The varying lower size detection limits made it difficult to compare PN concentrations (PNC), particularly PN10-25, from different cities. PNCs follow a TR > UB > Suburban (SUB) order. PNC and Black Carbon (BC) progressively increase from Northern Europe to Southern Europe and from Western to Eastern Europe. At the UB sites, typical traffic rush hour PNC peaks are evident, many also showing midday-morning PNC peaks anti-correlated with BC. These peaks result from increased PN10-25, suggesting significant PNC contributions from nucleation, fumigation and shipping. Site types to be identified by daily and seasonal PNC and BC patterns are: (i) PNC mainly driven by traffic emissions, with marked correlations with BC on different time scales; (ii) marked midday/morning PNC peaks and a seasonal anti-correlation with PNC/BC; (iii) both traffic peaks and midday peaks without marked seasonal patterns. Groups (ii) and (iii) included cities with high insolation. PNC, especially PN25-800, was positively correlated with BC, NO2, CO and PM for several sites. The variable correlation of PNSD with different urban pollutants demonstrates that these do not reflect the variability of UFP in urban environments. Specific monitoring of PNSD is needed if nanoparticles and their associated health impacts are to be assessed. Implementation of the CEN-ACTRIS recommendations for PNSD measurements would provide comparable measurements, and measurements of <10 nm PNC are needed for full evaluation of the health effects of this size fraction.

2020, Hussein, Haytham E. M., Amari, Houari, Breeze, Ben G., Beanland, Richard, Macpherson, Julie V.

By changing the mole fraction of water (χwater) in the solvent acetonitrile (MeCN), we report a simple procedure to control nanostructure morphology during electrodeposition. We focus on the electrodeposition of palladium (Pd) on electron beam transparent boron-doped diamond (BDD) electrodes. Three solutions are employed, MeCN rich (90% v/v MeCN, χwater = 0.246), equal volumes (50% v/v MeCN, χwater = 0.743) and water rich (10% v/v MeCN, χwater = 0.963), with electrodeposition carried out under a constant, and high overpotential (−1.0 V), for fixed time periods (50, 150 and 300 s). Scanning transmission electron microscopy (STEM) reveals that in MeCN rich solution, Pd atoms, amorphous atom clusters and (majority) nanoparticles (NPs) result. As water content is increased, NPs are again evident but also elongated and defected nanostructures which grow in prominence with time. In the water rich environment, NPs and branched, concave and star-like Pd nanostructures are now seen, which with time translate to aggregated porous structures and ultimately dendrites. We attribute these observations to the role MeCN adsorption on Pd surfaces plays in retarding metal nucleation and growth.

2021, Ortega, Eduardo, Nicholls, Daniel, Browning, Nigel D., de Jonge, Niels

Scanning transmission electron microscopy (STEM) provides structural analysis with sub-angstrom resolution. But the pixel-by-pixel scanning process is a limiting factor in acquiring high-speed data. Different strategies have been implemented to increase scanning speeds while at the same time minimizing beam damage via optimizing the scanning strategy. Here, we achieve the highest possible scanning speed by eliminating the image acquisition dead time induced by the beam flyback time combined with reducing the amount of scanning pixels via sparse imaging. A calibration procedure was developed to compensate for the hysteresis of the magnetic scan coils. A combination of sparse and serpentine scanning routines was tested for a crystalline thin film, gold nanoparticles, and in an in-situ liquid phase STEM experiment. Frame rates of 92, 23 and 5.8 s-1 were achieved for images of a width of 128, 256, and 512 pixels, respectively. The methods described here can be applied to single-particle tracking and analysis of radiation sensitive materials.