Keywords: TiO2 nanoparticles Fabric Silane coupling agent Surface modification
abstract
Due to their excellent photo-catalytic activities making TiO2 nanoparticles applicable as self-cleaning and anti-bacterial agents, as well as for UV protection and environmental purification, a great potential for multi-functionalization of fabrics by TiO2 nanoparticles is considered. In order to improve the durability of nanoparticles at a fabric surface, the surface of commercial TiO2 nanoparticles was modified by 3-aminopropyltrimethoxysilane (APTMS) and 3-Isocyanatopropyltrimethoxysilane (IPTMS) by an aqueous process in this study. The grafting efficiency of agents to TiO2 nanoparticles at different reaction conditions was estimated by thermal gravimetric analysis. FTIR spectra confirmed that organic functional groups were successfully grafted onto the TiO2 nanoparticles surface both for APTMS-grafted TiO2 nanoparticles (A-TiO2) and IPTMS-grafted TiO2 nanoparticles (I-TiO2) through Ti O Si chemical bonds. After the surface modification of TiO2 nanoparticles, isoelectric point (IEP) of nanoparticles was shifted approximately from pH 6.4 to pH 9.4 and the zeta potential plateaus increased significantly which was explained by the protonation of NH2 groups in the acidic region. The significant reduction of particle hydrodynamic diameters and polydispersity index (PDI) indicated the particle dispersion stability was positively affected by an increase in particle zeta potential. With increasing the organosilane ratio from 0 wt.% to 200 wt.%, a slight decline of the rate constant of A-TiO2 photocatalytic activity and a rapid decrease for I-TiO2 were revealed, which was significantly dependent on the grafting efficiency.
Colloids and Surfaces A: Physicochem. Eng. Aspects 413 (2012) 273–279
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Colloids and Surfaces A: Physicochemical and Engineering Aspects
In recent years, several studies reported the promising potentials of TiO2 nanoparticles for offering multifunctional properties to different textile materials [5]. However, the major problem of nanoparticle application to textile materials is the maintenance of the adequate durability of obtained effects. The deposition of TiO2 nanoparticles onto fabrics is highly challenging due to the lack of chemical bonding between fabrics and TiO2 nanoparticles [10,11]. Therefore, developing a new generation of functional materials having photocatalytic and UV shielding properties and a long-term durability on textile substrates was the primary aim of many studies. On the one hand, a binder material can be used to create
∗ Corresponding author. Tel.: +31 53 489 2899; fax: +31 53 489 3849. E-mail address: j.zhao-1@utwente.nl (J. Zhao).
0927-7757/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2011.11.033
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
As a popular photocatalyst, TiO2 has been widely used because of its various merits, such as optical and electronic properties, low costs, high photocatalytic activity, chemical stability and nontoxicity, anti-bacterial agent, UV protection and environmental purification [1–5]. When TiO2 particle size is reduced to the nano scale, photocatalytic activity increases as a result of the expansion of light band-gap for quantum size and due to the enhancement of the effective surface area [2,6–9].
Hale Waihona Puke chemical linking between particles and substrates. Mihailovic et al. [10] reported the possibility of producing the multifunctional textile nanocomposite material using natural polysaccharide alginate as a binder to improve the durability of colloidal TiO2 nanoparticles on polyester fabrics. Qi et al. [12] introduced a new method to prepare anatase TiO2 nanoparticles in an aqueous solution through a sol–gel process with a small amount of acid, which prevented the loss of the mechanical strength of the cotton fabrics and improved the adhesion between the TiO2 thin film and cotton substrates. On the other hand, grafting active functional groups onto particle surface can increase the possibility of chemical bonds formation between modified particles and fabrics thereby improving their adhesion strength. Chen and Yakovlev [13] investigated the adsorption and interaction of organosilanes on TiO2 nanoparticles and confirmed the bonding of functional groups on particle surface was realized through Si O Ti bonds.