Fabrication and Surface-Modification of Silica/GadoliniumCompound/Silica Core-Shell Nanoparticles

Abstract

The present work describes methods for fabricating multilayered core-shell nanoparticles composed of silica (SiO 2 ) as a core, gadolinium compound (GdC) as an inner shell, and SiO 2 as an outer shell (SiO 2 /GdC/SiO 2 ), and for surface-modifying the SiO 2 /GdC/SiO 2 nanoparticles.SiO 2 nanoparticles with an average size of 28.6±12.6nm were produced by a sol-gel method using tetraethylorthosilicate (TEOS) and methylamine in water/ethanol solution.GdC-coated SiO 2 nanoparticles(SiO 2 /GdC) with an average particle size of 107.0±23.0nm and an average GdC shell thickness of 35.9±4.9 nm were synthesized by a homogeneous precipitation method at 80°C in water/propanol solution containing Gd(NO 3 ) 3 , urea and polyvinylpyrrolidone in the presence of the SiO 2 nanoparticles.Succeeding SiO 2 -coating of the SiO 2 /GdC nanaoparticles was performed by using TEOS and NaOH in the presence of SiO 2 /GdC nanoparticles.Consequently, SiO 2 /GdC/SiO 2 nanoparticles with an average particle size of 119.0±39.0nm and an average SiO 2 shell thickness of 8.5±2.7 nm could be obtained.The SiO 2 /GdC/SiO 2 nanoparticles were successfully surface-modified by using 3-aminopropyltrimethoxysilane for amination, and by followingly using succinic anhydride for carboxylation.