Preparation of silica-coated AgI nanoparticles by an amine-free process and their X-ray imaging properties

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AgI nanoparticles coated with silica shell (AgI/SiO2) were prepared with an amine-free process, i.e. a modified Stöber method. A colloid solution of 3.9 × 10−4 M AgI nanoparticles was prepared mixing silver perchlorate at 3.9 × 10−4 M and potassium iodide at 7.8 × 10−4 M. A silica-coating was performed at 4.5 × 10−6 M 3-mercaptopropyltrimethoxysilane, 0.1 × 10−3–2.0 × 10−3 M NaOH, 11–25 M H2O, and 0.4 × 10−3–80 × 10−3 M tetraethylorthosilicate (TEOS) in the presence of 1.0 × 10−4 M AgI nanoparticles in ethanol. The AgI/SiO2 particles with a size of 53.2 ± 9.3 nm and an AgI core size of 13.5 ± 4.2 nm were prepared at 1.2 × 10−3 M NaOH, 15 M H2O, and 4.0 × 10−3 M TEOS. The AgI concentration of 1.0 × 10−4 M in the as-prepared colloid solution was increased up to an AgI concentration of 0.32 M by salting-out and centrifugation. The core–shell structure of AgI/SiO2 particles was undamaged, and the colloid solution was still colloidally stable, even after the condensation. The concentrated AgI/SiO2 colloid solution showed a high-contrast X-ray image, and its computed tomography value was 2908 ± 37 HU. Internal organs in a mouse could be imaged injecting the concentrated colloid solution into it.