Colloidal Silica Particles with Bimodal Final Size Distribution: Ion-Induced Nucleation Mechanism

Abstract

Colloidal silica particles, Bimodal size distribution, Nucleation Abstract. Colloidal silica particles with bimodal size distribution have been prepared by the hydrolysis of tetraethylorthosilicate in alcoholic solutions of water and ammonia as catalyst. Experimental conditions such as concentration of NaCl, amount of water and reaction temperature were investigated to reveal the formation mechanism of the colloidal silica particles. The nucleation process of colloidal silica particles with bimodal size distribution depends on the hydrolysis rate of TEOS and the ionic strength of reaction media. The hydrolysis reaction is the rate-limiting step during the nucleation process. Nucleation involving background ions generated by TEOS hydrolysis reaction and addition of electrolyte(NaCl) is another potentially important factor for nucleation process of electrically charged clusters. A critical value of ionic strength exists in the reaction to form bimodal size distribution particles.

Preparation and surface modification of porous hollow organosilica particles for biomedical applications

“…The Stöber technique was used to create a bimodal SNP sample (denoted as SNPs22) with an average particle size of 50 nm to 100 nm [135][136][137]. Typically, in a 20 mL scintillation vial (WHEATON®, VWR International, Budapest, Hungary), 10 mL of ethanol was mixed for 10 minutes with 600 uL of ammonium hydroxide solution, and then 300 uL of TEOS solution was quickly added while stirring the solution at 500 rpm.…”