Silver nanoparticles structural evolution with time

August 31, 2023

Silver nanoparticles, major environmental pollutants, have been synthetized in vacuum, exposed to ambient air and investigated by atomic resolution imaging and ab initio calculations. Temperature, gaseous atmospheric pressure and surface contamination effects on nanoparticles morphology have been disentangled, paving the way to the understanding of nanoparticle ageing in environmental conditions at the atomic scale.

Metallic nanoparticles are widely used in industry, medicine and household goods and are of large interest for research activities in catalysis, optics, biosensing, cosmetics etc. Among them, silver nanoparticles (Ag NPs) have been developed intensively, especially due to their antimicrobial properties. Hence, they are a major source of environmental pollutants, with an evolutive toxicity level depending on their fate.

To date, very little is known about Ag NPs stability and structural evolution at the atomic scale, when exposed to environment. In the present studies, silver clusters have been synthetized in vacuum, exposed to ambient air and investigated by atomic resolution imaging (ac-STEM) to obtain isomer distribution statistics. Ag NPs exposed to air have been modelled by DFT and ab initio molecular dynamics (Ø = 1.66-1.80 nm). Temperature, gaseous atmospheric pressure and surface contaminant effects have been included in our simulations in order to determine Ag NPs thermodynamic stability and morphological changes, at short timescale (before ageing).  Being able to untangle all these effects on the morphological changes of Ag NPs is a prerequisite to a rational design of efficient devices safer for environment.

Our key results show that Ag NPs exposed to air keep their metallic integrity all along the molecular dynamics simulations at room temperature. They are sensitive to the environment at various levels: (1) temperature determines the existence of a given morphology and structure; (2) shells of coadsorbed surface contaminants play a crucial role on the competition between Ag NPs morphologies; (3) nitrogen pressure exhibits a minority effect.

Our theoretical results agree with the experimental statistics and paves the way to the understanding of nanoparticle ageing in environmental conditions at the atomic scale.

Publications:

Influence of Air Exposure on Structural Isomers of Silver Nanoparticles
J. Vernieres, N. Tarrat, S. Lethbridge, E. Watchorn-Rokutan, T. Slater, D. Loffreda, and R. E. Palmer
Communications Chemistry, 2023, 6, 19
https://doi.org/10.1038/s42004-023-00813-9

Morphological Sensitivity of Silver Nanoparticles to Environment
N. Tarrat and D. Loffreda
Environmental Science: Nano, 2023, 10, 1754
https://doi.org/10.1039/D2EN01129H

Contact:
Nathalie Tarrat | nathalie.tarrat[at]cemes.fr