An understanding of the mechanisms of size and shape evolution during nanocrystal growth is significant to colloidal synthesis with precise control. It is known that surfactants play an important role during nanocrystal growth, however, their effects on nanocrystal shape evolution has not been fully understood due to the lack of direct observation. We study the growth of platinum iron nanocrystals in solution with different surfactant concentration by real time imaging using transmission electron microscopy (TEM). we observed the growth of platinum iron nanoparticles follow different trajectories with diverse shape evolution. With 20% of oleylamine, three stages of growth are observed (I) the nucleation and growth of platinum iron nanoparticles in the precursor solution; (II) nanowire formation by nanoparticle attachment; (III) Break down or shrinkage of nanowires into individual nanoparticles with a large size distribution. With 30% oleylamine, formation of platinum iron nanowires similar to the first two stages of growth in the above is observed. However, nanowires do not break down or shrink, which suggests nanowires are stabilized by surfactants on the surface. With 50% of oleylamine, after the individual nanoparticles are formed they do not merge into nanowires. Shape of the nanoparticle is strongly influenced by the neighboring nanoparticles due to the stereo-hindrance effects. Real time observation of the dynamic growth process deepens our understanding of nanocrystal growth mechanisms and shed light on the futuresynthesis of nanomateials with desired functions.References: 1. H. G. Liao, L. Cui, S. Whitelam, H. Zheng, 'Real time imaging Pt3Fe nanorod growth in solution' Science 336, 1011 (2012).2. H. G. Liao, H. Zheng, ' Surfactant effects on platinum iron nanocrystal growth and shape evolution' submitted.

In situ TEM study of platinum iron nanocrystal growth and shape evolution

245th National Meeting (2013)

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