Nucleation of isotactic polypropylene (PP) crystallization by gold particles with various sizes and shapes was studied. The morphology of gold particles ranged from microcrystals with well-developed crystal facets (AuMC) to vacuum-sputtered 5 nm gold nanoparticles (AuNP), 30 nm gold nanoislands (AuNI), and compact gold nanolayer (AuNL). To minimize agglomeration of Au particles in molten PP, the nucleated crystallization was studied by means of the improved sandwich method, which consisted in the controlled deposition of a homogeneous nucleant layer between similar to 100 mu m PP films, followed by the careful thermal treatment and the evaluation of the nucleation activity by three independent methods: polarized-light microscopy, two-dimensional wide-angle X-ray scattering, and differential scanning calorimetry. It was demonstrated that the nucleating activity of gold strongly depended on its morphology: The nucleation effect of microcrystalline AuMC resulted in a transcrystallization comparable to that caused by a strong commercial a-nucleant (Hyperform HPN-68), whereas the effect of vacuum-sputtered layers of nanocrystalline AuNL, AuNI, and AuNP was extremely weak. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012