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Abstract: In this paper, the shape evolution and thermal stability of Ag nanoparticles (NPs) on spherical SiO2 substrates were investigated by means of in situ transmission electron microscopy (TEM) imaging and differential scanning calorimetry (DSC). The initial Ag NPs at room temperature were semispherical-like, with an average size of 9nm in half-height width, well-dispersed on spherical SiO2 substrates. No obvious shape change was observed when the semispherical NPs of Ag were heated at temperature lower than 550°C. The shape of the semispherical Ag NPs changed gradually into a spherical one in the temperature range of 550–700°C, where surface diffusion and surface premelting took place. When the heating temperature was increased up to 750°C, the spherical Ag NPs were found to desquamate from the substrates due to the decreases of the contact area and the binding force between Ag NPs and SiO2 substrates. A possible mechanism for the desquamation of Ag NPs from the SiO2 sphere surface is proposed according to the results of in situ TEM observation and DSC analysis. [Copyright &y& Elsevier]

Abstract: Silica–silver core–shell composite particles with uniform thin silver layers were successfully synthesized by a facile and one-step ultrasonic electrodeposition method. By electrolysis of the slurry consisting of preformed silica spheres and silver perchlorate without any additives, the homogenous composite particles can be prepared. The average size of single silver crystals in the composite is about 12nm and the thickness of silver layer is 14±2nm. Moreover, the continuity of Ag distribution, the surface roughness and the thickness of silver layer are controllable by adjusting the current density (I), the concentration of electrolyte (C) and the reaction time (t). Optical properties of the composite particles with different silver content were also investigated. [Copyright &y& Elsevier]