Effect of Polyelectrolyte Dispersants on the Preparation of Silica-Coated Zinc Oxide Particles in Aqueous Media

• Published in: Journal of the American Ceramic Society Vol. 85; no. 8; pp. 1937 - 1940
• Main Authors: Wang, Hongzhi, Nakamura, Hiroyuki, Yao, Ken, Uehara, Masato, Nishimura, Satoshi, Maeda, Hideaki, Abe, Eiichi
• Format: Journal Article
• Language: English
• Published: Westerville, Ohio American Ceramics Society 01.08.2002; Blackwell; Wiley Subscription Services, Inc
• Subjects: Chemistry; Colloidal state and disperse state; Cross-disciplinary physics: materials science; rheology; dispersants/dispersion; Exact sciences and technology; General and physical chemistry; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Powders; silica; zinc oxide; Inorganic compounds; Photocatalysis; Transition element compounds; Oxides; Dispersant; Experimental study; Polyelectrolyte; Zinc oxides; II-VI semiconductors; Aqueous solutions; Silicon oxides; Polymers; Protective coatings; Growth from solution; Sodium silicates
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1151-2916.2002.tb00384.x

Sodium silicate was utilized to obtain a SiO2 coating on ZnO particles to prevent a photocatalytic reaction between ZnO and phenol. During the coating process, pH control is important to avoid dissolution of the ZnO as well as to obtain a good dispersion. Two kinds of polyelectrolyte dispersants were used to control the surface charge of the ZnO particles in aqueous media. As a result, poly(ethylenimine) (PEI) shifted the isoelectric point of ZnO from pH 9 to pH 10, whereas poly(ammonium acrylate) (PAA) made the surface charge of ZnO negative between pH 6 and pH 11. The change in the ZnO surface charge produced by adding polyelectrolyte dispersants makes it possible to obtain uniform silica–coated ZnO particle in aqueous media. UV–irradiation experiments showed that PEI, which can make the surface charge opposite to that of SiO2, is more effective in obtaining a thick silica coating on ZnO.