Fast in Situ Ultrahigh-Voltage Electron Microscopy Observation of Crystal Nucleation and Growth in Amorphous Antimony Nanoparticles

Electron-irradiation-induced crystallization processes and the mechanisms in amorphous antimony nanoparticles have been investigated by microsecond temporal and picometer spatial resolution in situ observations. Electron irradiation experiments and the simultaneous in situ observations were carried out with an ultrahigh-voltage electron microscope operating at an accelerating voltage of 1 MV, which has a temporal resolution of 625 μs per frame. At the early stage of the crystallization in approximately 20 nm amorphous nanoparticles, a small crystal nucleus on the surface repeats between formation and annihilation. When the nucleus size becomes more than the critical size of 6.3 nm in diameter, crystal growth takes place in the whole nanoparticle. The crystal growth rate estimated was approximately 20 μm s^–1. The growth rate depends on the particle size, and it was confirmed that the smaller the particle size, the faster the growth rate. It was suggested that the crystallization driven by long-range elastic interaction due to small crystal nucleus formation in amorphous nanoparticles is induced by short-range atomic rearrangements

Fast in Situ Ultrahigh-Voltage Electron Microscopy Observation of Crystal Nucleation and Growth in Amorphous Antimony Nanoparticles

Electron-irradiation-induced crystallization processes and the mechanisms in amorphous antimony nanoparticles have been investigated by microsecond temporal and picometer spatial resolution in situ observations. Electron irradiation experiments and the simultaneous in situ observations were carried out with an ultrahigh-voltage electron microscope operating at an accelerating voltage of 1 MV, which has a temporal resolution of 625 μs per frame. At the early stage of the crystallization in approximately 20 nm amorphous nanoparticles, a small crystal nucleus on the surface repeats between formation and annihilation. When the nucleus size becomes more than the critical size of 6.3 nm in diameter, crystal growth takes place in the whole nanoparticle. The crystal growth rate estimated was approximately 20 μm s^–1. The growth rate depends on the particle size, and it was confirmed that the smaller the particle size, the faster the growth rate. It was suggested that the crystallization driven by long-range elastic interaction due to small crystal nucleus formation in amorphous nanoparticles is induced by short-range atomic rearrangements

Fast in Situ Ultrahigh-Voltage Electron Microscopy Observation of Crystal Nucleation and Growth in Amorphous Antimony Nanoparticles

Electron-irradiation-induced crystallization processes and the mechanisms in amorphous antimony nanoparticles have been investigated by microsecond temporal and picometer spatial resolution in situ observations. Electron irradiation experiments and the simultaneous in situ observations were carried out with an ultrahigh-voltage electron microscope operating at an accelerating voltage of 1 MV, which has a temporal resolution of 625 μs per frame. At the early stage of the crystallization in approximately 20 nm amorphous nanoparticles, a small crystal nucleus on the surface repeats between formation and annihilation. When the nucleus size becomes more than the critical size of 6.3 nm in diameter, crystal growth takes place in the whole nanoparticle. The crystal growth rate estimated was approximately 20 μm s^–1. The growth rate depends on the particle size, and it was confirmed that the smaller the particle size, the faster the growth rate. It was suggested that the crystallization driven by long-range elastic interaction due to small crystal nucleus formation in amorphous nanoparticles is induced by short-range atomic rearrangements

Fast in Situ Ultrahigh-Voltage Electron Microscopy Observation of Crystal Nucleation and Growth in Amorphous Antimony Nanoparticles

Electron-irradiation-induced crystallization processes and the mechanisms in amorphous antimony nanoparticles have been investigated by microsecond temporal and picometer spatial resolution in situ observations. Electron irradiation experiments and the simultaneous in situ observations were carried out with an ultrahigh-voltage electron microscope operating at an accelerating voltage of 1 MV, which has a temporal resolution of 625 μs per frame. At the early stage of the crystallization in approximately 20 nm amorphous nanoparticles, a small crystal nucleus on the surface repeats between formation and annihilation. When the nucleus size becomes more than the critical size of 6.3 nm in diameter, crystal growth takes place in the whole nanoparticle. The crystal growth rate estimated was approximately 20 μm s^–1. The growth rate depends on the particle size, and it was confirmed that the smaller the particle size, the faster the growth rate. It was suggested that the crystallization driven by long-range elastic interaction due to small crystal nucleus formation in amorphous nanoparticles is induced by short-range atomic rearrangements

Au-Protected Ag Core/Satellite Nanoassemblies for Excellent Extra-/Intracellular Surface-Enhanced Raman Scattering Activity

Silver nanoparticles (AgNPs) and their assembled nanostructures such as core/satellite nanoassemblies are quite attractive in plasmonic-based applications. However, one biggest drawback of the AgNPs is the poor chemical stability which also greatly limits their applications. We report fine Au coating on synthesized quasi-spherical silver nanoparticles (AgNSs) with few atomic layers to several nanometers by stoichiometric method. The fine Au coating layer was confirmed by energy-dispersive X-ray spectroscopy elemental mapping and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy. The optimized minimal thickness of Au coating layer on different sized AgNSs (22 nm [email protected] nm Au, 44 nm [email protected] nm Au, 75 nm [email protected] nm Au, and 103 nm [email protected] nm Au) was determined by extreme chemical stability tests using H₂O₂, NaSH, and H₂S gas. The thin Au coating layer on AgNSs did not affect their plasmonic-based applications. The core/satellite assemblies based on Ag@Au NPs showed the comparable SERS intensity and uniformity three times higher than that of noncoated Ag core/satellites. The Ag@Au core/satellites also showed high stability in intracellular SERS imaging for at least two days, while the SERS of the noncoated Ag core/satellites decayed significantly. These spherical Ag@Au NPs can be widely used and have great advantages in plasmon-based applications, intracellular SERS probes, and other biological and analytical studies