Drying and Nondrying Layer-by-Layer Assembly for the Fabrication of Sodium Silicate/TiO2 Nanoparticle Composite Films

• Published in: Langmuir 2012-01, Vol.28 (3), p.1816-1823
• Main Authors: Zhang, Lianbin, Liu, He, Zhao, Engui, Qiu, Lingying, Sun, Junqi, Shen, Jiacong
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Microscopy, Atomic Force; Nanoparticles - chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Porosity; Porous materials; Silicates - chemistry; Titanium - chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la2043125

Influences of drying and nondrying steps on structures of layer-by-layer (LbL) assembled sodium silicate/TiO2 nanoparticles films (donated as silicate/TiO2 films) have been systematically investigated. The nondrying LbL assembly produces highly porous silicate/TiO2 films with large thickness. In contrast, the silicate/TiO2 films fabricated with a drying step after each layer deposition are flat and thin without porous structures. In situ atomic force microscopy (AFM) measurements confirm that the sodium silicate and TiO2 nanoparticles are deposited in their aggregated forms. A N2 drying step can disintegrate the aggregated silicate and TiO2 nanoparticles to produce thin silicate/TiO2 films with compact structures. Without the drying steps, the aggregated silicate and TiO2 nanoparticles are well retained, and their LbL assembly produces highly porous silicate/TiO2 films of large thickness. The highly porous silicate/TiO2 films are demonstrated to be useful as reusable film adsorbents for dye removal from wastewater because they can adsorb a large amount of cationic organic dyes and decompose them under UV irradiation. The present study is meaningful for exploring drying/nondrying steps for tailoring structure and functions of LbL assembled films.