Observation of Nucleation and Growth Mechanism of Bismuth Nano/Microparticles Prepared by Hot-Injection Method

Abstract

The growth mechanisms of the nanomaterials such as Bismuth (Bi) are investigated since the understanding of the factors that affect the kinetics is fundamental to tune the crystal growth and thus to achieve new types of nanostructures and new material properties. It is concluded that Bi nano/microparticles are grown in following: classical nucleation growth theory and then most possibly unclassical oriented attachment via two kinds of effective and noneffective collisions with mass transfer. Polycrystalline Bi nano/micropowders having variety forms such as nanocrystal, nanoplate, and nano/microparticle have been synthesized successfully in a non-coordinating solvent by using hot-injection method. The X-ray powder diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM), Fourier transform infrared (FTIR) spectroscopy, and energy dispersive X-ray (EDX) techniques are used to characterize the nanopowders. It is achieved that Bi particles synthesized during the reaction are accumulated via hit and stick mechanism and taken out of the solution as a conglomerate wet powder without need to centrifuge the solution. The Bi is formed in hexagonal phase with preferred orientation of (012) plane along with the XRD peak shape factor of ~0.44 which indicates more Lorentzian than Gaussian character. The average diameter of the synthesized nanocrystals is about 1.86 nm. The unit cell parameters calculated by Rietveld refinement are a=4.5474 Å and c=11.8612 Å in hexagonal phase. It is observed that hexagonal nanoplates are completely surrounded by nanocrystals. Twinkling of the spherical Bi nano/microparticles attached by nanoplates is observed under a white light illumination. All the steps from nucleation to the conglomerate structure formed are visualized and respectively proved experimentally.