Structural Evolution of Silver Nanoparticles duringWet-Chemical Synthesis.

Theformation of silver nanoparticles during the reduction withglucose in the presence of poly(N-vinyl pyrrolidone) as capping agentwas followed for more than 3000 min. First, spherical silver nanoparticlesare formed, but in later stages, an increasing fraction of nanotrianglesand also a few nanorods develop. Both spherical and trigonal nanoparticlesgrow with time, indicating separate nucleation pathways. The domainsize in the spherical nanoparticles increases proportionally to theparticle diameter and is always about 1/4ofthe diameter, indicating that twinned seeds are formed very earlyin the process and then simply grow by extending their domains. Thelattice constant of the nanoparticles is systematically increasedin comparison to microcrystalline silver (4.0877 vs 4.08635 Å)but did not change as a function of particle diameter. A thoroughanalysis of the texture coefficient, supported by transmission electronmicroscopy data, showed that the apparently spherical particles arein fact flattened pentagonal prisms, which typically lie on theirflat pentagonal face. Neither the presence of oxygen nor the presenceof ambient light had any influence on the particle properties. [ABSTRACT FROM AUTHOR]