Preparation of multilayered silica–Gd–silica core-shell particles and their magnetic resonance images

A preparation method for multilayered silica–Gd–silica core-shell particles is proposed. Silica particles with an average size of 30.9 nm were prepared by the Stöber method. Silica–Gd core-shell particles with a size of 57.4 nm were synthesized by a homogeneous precipitation method at 80 °C in water/propanol solution with 27.7 M H2O, 0.001 M Gd(NO3)3, 0.5 M urea and 1 g/l polyvinylpyrrolidone in the presence of 0.001 vol.% suspension of the silica particles. Succeeding silica-coating of the silica–Gd core-shell particles was performed with 0.0133 M TEOS and 0.002 M NaOH in the presence of a suspension of silica–Gd core-shell particles. Consequently, multilayered silica–Gd–silica core-shell particles with an average size of 71.2 nm could be obtained. These particles exhibited clear enhancement in magnetic resonance images. These nanoparticles are expected to a novel magnetic resonance contrast agents.