Stabilization of silica-coated silver iodide nanoparticles by ethanol-washing

Yoshio Kobayashi, Tetsuya Ayame, Kyosuke Shibuya, Tomohiko Nakagawa, Yohsuke Kubota, Kohsuke Gonda, Noriaki Ohuchi

Research output: Contribution to journalArticlepeer-review


Purpose - This paper aims to propose a simple method for stabilizing silica-coated silver iodide (AgI/SiO2) core-shell particles, of which a colloid solution functions as an X-ray contrast agent. Design/methodology/approach - A colloid solution of AgI nanoparticles was prepared by mixing silver perchlorate and potassium iodide in water. The AgI/SiO2 nanoparticles were fabricated by a sol-gel method using NaOH, H2O and tetraethylorthosilicate in ethanol in the presence of AgI nanoparticles surface-modified with 3-mercaptopropyltrimethoxysilane. Findings - The silica shells of AgI/SiO2 particles were dissolved near the AgI nanoparticle surface, when they were washed by a process composed of centrifugation, removal of supernatant with decantation, addition of water as a washing solution and a shake with a vortex mixer. In contrast, the shells were not damaged by using ethanol as the washing solution, i.e. ethanol-washing. An X-ray photoelectron spectroscopy spectrum of the silica was changed after the ethanol-washing, which indicated that the ethanol-washing had an effect on the chemical bonds in silica. The effect also acted on the silica shells of AgI/SiO2 particles, which did not damage the core-shell structure, i.e. controlled the dissolution of shell. Originality/value - The paper demonstrates that the ethanol-washing is quite useful for stabilizing the core-shell structure composed of the silica shells.

Original languageEnglish
Pages (from-to)99-105
Number of pages7
JournalPigment and Resin Technology
Issue number2
Publication statusPublished - 2016 Mar 7


  • Coating
  • Nanotechnology
  • Silica


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