Molecular dynamic simulations of the formation of Ag nanoparticles assisted by PVP

BALBUENA, CRISTIAN; GIANETTI, MELISA; SOULE, EZEQUIEL

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Año: 2021 vol. 23

1463-9076

Understanding the formation mechanisms of nanoparticles is essential in the synthesis of nanomaterials with controlled properties. In solution synthesis, capping agents are used to mediate this process and control the final size and shape of particles. In this work, synthesis of silver nanoparticles, with polyvynylpirrolidone (PVP) as a capping agent, is studied through molecular dynamics simulations. Nucleation of clusters of atoms and subsequent growth to form nanoparticles is analyzed, with focus on the role of PVP. No finite critical nucleus is detected, and amorphous particles seem to form by spinodal growth. In this timescale, PVP seem to have no effect on particle growth, which is ascribed to a competition between the protective effect, and ?bridging? (where a molecule of PVP is adsorbed to two different clusters, bringing them together) As the process evolves a sequence of ordered structures appear within the particles: icosahedral, BCC, FCC, the last one being the equilibrium configuration of bulk silver. In addition, for low PVP an apparent acceleration is observed in particle growth after these ordered phases appears, indicating that growth of ordered particles from solution is faster than growth of amorphous particles. For high PVP content this acceleration is not observed, indicating that the protective effect prevails on particle growth in this regime. In addition, due to bridging effect, the final overall configuration is strongly dependent of PVP content. For no PVP, large but dispersed particles are observed. For low PVP content, due to strong bridging, particles form agglomerates (with no strong coalescence in the timescale of simulations). For large enough PVP content, particles are smaller in size and do not show a strong tendency to agglomerate.