Variables influencing coated nanoparticle sintering under dynamic compression

JMD Lane and TV Vu and TA Ho and HY Fan, MRS BULLETIN, 50, 1006-1012 (2025).

DOI: 10.1557/s43577-025-00933-8

Dynamic compression of ligand-coated gold nanoparticles is a novel approach to producing gold nanostructures in nanosecond times. The method has been experimentally demonstrated; however, optimizing synthesis will require better understanding of the complex response of both the particle cores and the ligand coatings. We show here that particle sintering depends critically on variables, such as ligand length, compression rate, and temperature, which alter ligand dynamics. We use all-atom molecular dynamics simulation to study the structure, mechanisms, and energy landscape of alkanethiol-coated gold nanoparticles under dynamic ramp and shock compression. We use a simple two-particle system to explore the importance of transverse constraints to ligand mobility and ordering, as well as a more realistic fcc superlattice to explore the role of compression rate and temperature. Simulation results suggest that alkanethiol ligands self-orient and tend to straighten their carbon chains under compression. The longer the ligand length, the more pronounced these effects. Longer ligand molecules tend to stabilize gold nanoparticles better than shorter ones, thus gold cores fuse more easily for nanoparticles with shorter alkanethiol ligands. We find that slower compression rates improve sintering, but temperature is a more important factor in ligand mobility and sintering. Interestingly, in shock compression, where compression rates are high one could expect poor sintering. However, we find that sintering can often proceed more readily because entropic shock heating overcomes rate effects. Our results indicate that preheated ramp compression with short ligand coatings should best promote nanostructure formation. This work may provide a guide to designing experiments for fabrication of complex gold nanostructures through the dynamic compression method.Impact statementThis study explores the dynamic compression of ligand-coated gold nanoparticles, offering insights into the mechanisms of nanoparticle sintering. By utilizing all-atom molecular dynamics simulations, we investigate how ligand length, compression rate, and temperature influence nanoparticle aggregation behavior under high pressure. Our results demonstrate that longer alkanethiol ligands stabilize gold nanoparticles more effectively, while slower compression rates enhance sintering. Surprisingly, high compression rates in shock compression can facilitate sintering due to entropic shock heating. This work provides valuable guidelines for optimizing nanoparticle synthesis, advancing the design of complex gold nanostructures through dynamic compression methods and informing future experimental approaches.

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