Novel issues of morphology, size, and structure of Pt nanoparticles in chemical engineering: Surface attachment, aggregation or agglomeration, assembly, and structural changes

In this paper, the polyhedral Pt nanoparticles were prepared by a modified polyol method using AgNO₃ as a nanostructure-shaping agent. TEM and HRTEM images of Pt nanoparticles show the particle size in the 10 nm range for the well-controlled case. In contrast, Pt nanoparticles have the particle size in the 50 nm range for the uncontrolled case. To understand the important issues of morphology, size, surface and structure, the as-prepared Pt nanoparticles were investigated through UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution (HR)TEM measurements. In the two cases, the as-prepared Pt nanoparticles with and without the control procedures exhibit surface attachment, aggregation or agglomeration and assembly. The mechanisms can lead to the formation of the ultra-porous mesostructure of the as-prepared Pt nanoparticles by using various sophisticated control methods. Therefore, the experimental findings and observations showed the formations of the porous Pt nanostructures as the new Pt textures from self-aggregation or self-agglomeration and self-assembly of extreme importance in designing great superlattices under experimentally chemical and physical methods. This also proved the important role of PVP polymer in the protection of the as-prepared nanoparticles. In particular, a new phenomenon was found in the randomly natural collapse and self-breaking in the Pt nanostructures originating from the naked Pt nanoparticles without protective polymer agents. As a result, a porous meso-nanostructure was formed by the structural changes of Pt nanoparticles without stabilization of the PVP polymer. Finally, the discoveries of surface structure changes of polyhedral Pt shapes and morphologies in future are very important in further catalysis investigation.