Preparation of amine free silica-coated Agl nanoparticles with modified Stöber method

Abstract

In recent years, the authors studied on fabrication of silica-coated AgI (AgI-SiO 2 ) nanoparticles with a Stö ber method toward new X-ray contrast agents. In the Stö ber method, amines are often used as catalysts for silica formation, so that it is probable that amine is left in the silica-coated particles. Since amines are harmful to the human body, amine free particles are desired for medical use. From this viewpoint, amine free AgI-SiO 2 nanoparticles were prepared with a modified Stö ber method using NaOH as a catalyst instead of amine in the present work. The AgI nanoparticles were prepared from AgClO 4 and KI with the use of 3-mercaptopropyltrimethoxysilane (MPS) as a silane coupling agent and NaOH catalyst for alkoxide hydrolysis. The silicacoating was performed at 4?5610 25 M MPS, 15-22?5M water, 0?0008-0?0024M NaOH and 0?0004-0?009M tetraethylorthosilicate at an AgI concentration of 0?001M. AgI-SiO 2 particles as small as ca. 30 nm could be successfully fabricated at the concentrations of 4?5610 25 M MPS, 20M water, 0?0011M NaOH, 0?001M AgI and 0?004M tetraethylorthosilicate.

Synthesis of High Concentration Colloid Solution of Silica-Coated AgI Nanoparticles

“…[6]. A freshly prepared AgClO 4 aqueous solution was added to a KI aqueous solution under vigorous stirring.…”

“…We also have developed an alternative method for silica-coating of AgI nanoparticles as iodide compounds over the last several years. [4][5][6][7] In our method, AgI nanoparticles, which were prepared by adding AgClO 4 aqueous solution to KI aqueous solution, were directly silica-coated with a modified * Author to whom correspondence should be addressed. Stöber method.…”

Synthesis of Silica-Coated AgI Nanoparticles and Immobilization of Proteins on Them

“…From this view point, our research group has proposed a method for producing silica-coated silver iodide (AgI/SiO 2 nanoparticles. [2][3][4] The AgI/SiO 2 particles revealed high contrast in X-ray imaging. 5 The contrast agents are desired to be adsorbed to the focus.…”

“…The present work studied on surfacemodification and protein-immobilization for the AgI/SiO 2 particles that were prepared referring to the previously proposed method. 4 After pH of the obtained colloid solution was adjusted to 5.5 using HCl, 6 ml of 0.12 g/l bovine serum albumin (BSA) aqueous solution was added to the colloid solution, and stirred for 4 h. Both the surface-modification and the protein-immobilization were also performed at 35 C.…”

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

“…24), 25) Since amines are, however, harmful to living bodies, 26),27) the amines are desired to be replaced with a different catalyst. From this view point, our group has examined an amine-free method for silica-coating of silver iodide (AgI) nanoparticles, 22) in which silica-coating was performed using 3-mercaptopropyltrimethoxysilane (MPS), sodium hydroxide (NaOH), water, tetraethylorthosilicate (TEOS) and ethanol in the presence of AgI nanoparticles prepared mixing silver perchlorate (AgClO 4 ) aqueous solution and potassium (KI) aqueous solution. Though AgI nanoparticles were successfully coated with silica shells, the silica-coated AgI (AgI/SiO 2 ) particles appeared poly-dispersed, compared to silica-coated nanoparticles that have been reported in our previous works.…”