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Kinetics and Mechanism of Metal Nanoparticle Growth via Optical Extinction Spectroscopy and Computational Modeling: The Curious Case of Colloidal Gold
An overarching computational framework unifying several optical theories to describe the temporal volution of gold nanoparticles (GNPs) during a seeded growth process is presented. To achieve this, we sed the inexpensive and widely available optical extinction spectroscopy, to obtain quantitative kinetic data. In situ spectra collected over a wide set of experimental conditions were regressed using the hysical model, calculating light extinction by ensembles of GNPs during the growth process. This model rovides temporal information on the size, shape, and concentration of the particles, and any electromagnetic interactions between them. Consequently, we were able to describe the mechanism of GNP growth and divide the process into distinct genesis periods. We provide explanations for several longstanding mysteries, e.g., the phenomena responsible for the purple-greyish hue during the early stages of GNP growth, the complex interactions between nucleation, growth and aggregation events, and a clear distinction between agglomeration and electromagnetic interactions. The presented theoretical formalism has been developed in a generic fashion so that it can readily be adapted to other nanoparticulate formation scenarios such as the genesis of various metal nanoparticles.
Chemically mapping ice forming particles
Scientists have just nucleated ice in an X-ray microscope for the first time and they created chemical maps of those responsible.
2018 Highly Cited Researchers
Three LAC researchers were highly cited in 2018.
Breakthrough - electron crystallography for everyone
Recent advances in electron crystallography published in Angewandte Chemie and highlighted by Science, Chemical & Engineering News and ScienceNews!Under the lead of LSK member, "Rapid structure determination of microcrystalline molecular compounds using electron diffraction", published in Angewandte Chemie International Edition https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201811318 has attracted great attention in the chemistry community.
Les causes de la fin du Petit Âge glaciaire au milieu du XIXe siècle
Au cours de la première moitié du XIXe siècle, une série de fortes éruptions volcaniques dans les Tropiques a provoqué temporairement un refroidissement global du climat terrestre. Le fait que les glaciers ont progressé pendant la phase finale du Petit Âge glaciaire, avant de reculer à nouveau, était un phénomène naturel. C’est ce qu’ont montré des chercheurs du PSI au moyen de carottes de glace.
Brennstoffzellen zum Durchbruch verhelfen
Wasserstoff gilt als vielversprechende Alternative für eine Zukunft ohne fossile Energieträger. Um Brennstoffzellen weiterzuentwickeln und für einen Markteintritt vorzubereiten, verstärkt die Empa die Zusammenarbeit mit der H2 Energy Holding AG und dem Paul Scherrer Institut (PSI).
Light from the particle accelerator helps to understand ozone decomposition
PSI researchers have developed an experimental chamber in which they can recreate atmospheric processes and probe them with unprecedented precision, using X-ray light from the Swiss Light Source SLS. In the initial experiments, they have studied the production of bromine, which plays an essential role in the decomposition of ozone in the lower layers of the atmosphere. In the future, the new experiment chamber will also be available for use by researchers from other scientific fields.
Coexistence of Physisorbed and Solvated HCl at Warm Ice Surfaces
The interfacial ionization of strong acids is an essential factor of multiphase and heterogeneous chemistry in environmental science, cryospheric science, catalysis research and material science. Using Near Ambient Pressure X-ray Photoelectron (NAPP) spectroscopy, we directly detected a low surface coverage of adsorbed HCl at 253 K in both molecular and dissociated states and interpret the results as physisorbed molecular HCl at the outermost ice surface and dissociation occurring upon solvation deeper in the interfacial region. This study gives clear evidence for nonuniformity across the air−ice interface and questions the use of acid−base concepts in interfacial processes.
Gasoline cars produce more carbonaceous particulate matter than modern filter-equipped diesel cars
In contrast to nitrogen oxides, modern gasoline cars emit much more cancerogenic primary soot (black carbon + primary organic aerosol) and lead to more toxic secondary organic aerosol than modern diesel vehicles.