Control of shell thickness in silica-coating of Au nanoparticles and their X-ray imaging properties

• Published in: Journal of colloid and interface science 2011-06, Vol.358 (2), p.329-333
• Main Authors: Kobayashi, Yoshio, Inose, Hiromitsu, Nakagawa, Tomohiko, Gonda, Kohsuke, Takeda, Motohiro, Ohuchi, Noriaki, Kasuya, Atsuo
• Format: Article
• Language: English
• Subjects: absorption; Catalysis; catalysts; centrifugation; Chemistry; citrates; Coated Materials, Biocompatible - chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Colloids; Colloids - chemistry; computed tomography; Core–shell; Exact sciences and technology; General and physical chemistry; Gold; image analysis; Image contrast; Mathematical models; Metal Nanoparticles - chemistry; nanogold; Nanoparticle; Nanoparticles; Physical and chemical studies. Granulometry. Electrokinetic phenomena; prediction; Shells; Silica; Silicon dioxide; Silicon Dioxide - chemistry; sodium hydroxide; sol-gel processing; Surface plasmon resonance; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Tomography, X-Ray Computed; wavelengths; X-radiation; X-ray imaging; X-rays
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2011.01.058

Photograph (a) and X-ray image (b) of the concentrated Au/SiO 2 particle colloid solution. TEM image of the Au/SiO 2 particles in the colloid solution is also shown in (c). [Display omitted] ► Shell thickness of silica-coated Au nanoparticles was precisely controlled. ► Optical properties of the particles were approximately predicted by Mie theory. ► The particle colloid solution revealed a computed tomography value of 1329.7 ± 52.7 HU. This paper describes a performance of precise control of shell thickness in silica-coating of Au nanoparticles based on a sol–gel process, and an investigation into X-ray imaging properties for the silica-coated Au (Au/SiO 2) particles. The Au nanoparticles with a size of 16.9 ± 1.2 nm prepared through a conventional citrate reduction method were used as core particles. The Au nanoparticles were silica-coated with a sol–gel reaction using tetraethylorthosilicate (TEOS) as a silica source, sodium hydroxide (NaOH) as a catalyst, and (3-aminopropyl) trimethoxysilane (APMS) as a silane coupling agent. An increase in TEOS concentration resulted in an increase in shell thickness. Under certain concentrations of Au, H 2O, NaOH, and APMS, the Au/SiO 2 particles with silica shell thickness of 6.0–61.0 nm were produced with varying TEOS concentration. Absorption peak wavelength of surface plasmon resonance of the Au/SiO 2 colloid solution depended on silica shell thickness, which agreed approximately with the predictions by Mie theory. The as-prepared colloid solution could be concentrated up to an Au concentration of 0.19 M with salting-out and centrifugation. The concentrated colloid solution showed an X-ray image with high contrast, and a computed tomography value for the colloid solution with an Au concentration of 0.129 M was achieved 1329.7 ± 52.7 HU.