Synthesis of nano-particles of anatase-TiO2 and preparation of its optically transparent film in PVA

doi:10.1016/j.matlet.2007.03.064

Materials Letters

Volume 61, Issue 25, October 2007, Pages 4725-4730

https://doi.org/10.1016/j.matlet.2007.03.064 Get rights and content

Abstract

Anatase-TiO₂ nano-particles have been synthesized by using long-carbon chain carboxylic acid and titanium tetrachloride (TiCl₄). As-prepared powder has been calcined at 500 °C to obtain highly crystalline TiO₂. Broad X-ray diffraction (XRD) pattern of as-prepared as well as calcined powder showed all prominent peaks for tetragonal crystal structure representing anatase-TiO₂. The particle diameter by applying Scherrer formula was found to be about 20 nm. It was possible to load as-prepared particles in poly vinyl alcohol (PVA) for optical studies. Optically transparent film showed sharp absorption band for TiO₂ nano-particles at ∼ 300 nm. Photoluminescence (PL) studies of the solution showed emission wavelength at about 330 nm. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) revealed that the particles in the film have uniform distribution and even for the powder no agglomeration was observed. Thermal analysis (TGA) showed that the stability of host polymer is enhanced. FTIR spectra showed presence of carboxylate functional group in the powder.

Introduction

Titanium dioxide is mainly applied as pigments, adsorbents, and as catalyst particularly as photocatalyst. For almost all of applications, the size of the particles is an important factor. Therefore, much research has been focused upon the manipulation of particle size by various techniques including sol–gel method. The control of morphology, particle size, particle size distribution, phase composition and porosity of TiO₂ is a vital factor for determining the properties of final material. TiO₂ has three polymeric phases namely anatase, rutile and brookite. Among the three crystalline phases, anatase phase exhibits the highest photocatalytic activity. Rutile-TiO₂ is known as white pigment because of its high scattering effect which leads to protection from the ultraviolet light [1]. Anatase-TiO₂ has a band gap energy of about 3.2 eV and is used in solar energy conversion because of its high photoactivity [2], [3]. With unique characteristics in band position and surface structure, nano-sized TiO₂ provides, in addition to photocatalysis, a variety of other potential applications such as a smart material with self-cleaning and super-hydrophilic properties [4]. It is also known for its ability to act as an electrode material for light-sensitizers i.e. as an electro-chromophores, consisting of dye-sensitized solar cells [5], [6] and in electro-chromic devices [7]. TiO₂ thin films have been studied most extensively for various optical applications and have attracted considerable attention in many application oriented fields like photocatalyst, [8] gas sensor, opto-electronics and ceramic membrane [9].

Various wet chemical methods have been reported for the preparation of nano-sized TiO₂. Sol–gel route has been regarded as an excellent method to synthesize nano-sized metallic oxides [10] and has been widely employed for the preparation of titanium dioxide nano-particles [11], [12]. Use of hydroxyl and carboxyl group containing surfactants has been reported for the preparation of rutile-TiO₂ [13] where it was described that the quality of nano-sized TiO₂ in terms of particles shape, size and crystallinity may vary from one method to another. Sometime, even the preparation may not be re-producible by the same route, particularly when the preparation is scaled-up, i.e. the powder varies in size and morphology [14]. It is therefore, required carefully to design experimental strategy to obtain nano-particles with desired shape, size, morphology and crystallinity. We herein, present a simple one step method for the preparation of anatase-TiO₂ by the hydrolysis of titanium tetrachloride (TiCl₄) in the presence of myristic acid. In the present work, we have also presented loading of nano-particles in polymeric matrix and therefore creating possibility of the application in polymeric coating and in opto-electronics.

Section snippets

General

All the chemicals and reagents used were of analytical grade. Titanium tetra chloride (TiCl₄), poly vinyl alcohol (PVA) and myristic acid were purchased from local suppliers. The nano-powder obtained was characterized by various analytical tools. Scanning electron microscopy (SEM)/EDAX was done on Philips XL-30 instrument. Powder X-ray diffraction (XRD) patterns were measured using Cu-Kα radiation on a Miniflex Rigaku machine with a wavelength of radiation at λ = 1.5406 Å. UV–visible spectra of

Result and discussion

Long-carbon chain carboxylic acids are excellent surfactants for controlling particle growth in nano-particle synthesis. The use of mono-, di- or tri-carboxylic acids has been effectively described by us earlier also [15]. In fact, it has been described that oleic acid protected anatase-TiO₂ nano-particles of about less than 5 nm can be prepared with spherical morphology [16]. In the current synthesis we designed our experiment in such way to generate an intermediate that contains myristic

Conclusion

In the current synthesis an intermediate that contains myristic acid–titanium oxychloride precursor was converted to a gel-state followed by either complete evaporation to get a white powder or re-dissolving the as-prepared powder in aq. PVA to get the clear solution of TiO₂ in polymer. UV–Visible measurement showed that the onset of absorption was at around 300 nm which was in agreement with those reported by others for anatase-TiO₂ nano-powder. The blue shift of about 85 nm due to quantum

Acknowledgement

We thank, Executive Director, C-MET for encouragement and permission.

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Synthesis of nano-particles of anatase-TiO2 and preparation of its optically transparent film in PVA

Abstract

Introduction

Section snippets

General

Result and discussion

Conclusion

Acknowledgement

Mater. Chem. Phys.

Mater. Chem. Phys.

Appl. Surf. Sci.

Mat. Chem. Phys.

Mater. Lett.

Chem. Rev.

Chem Rev.

Nature

Nature

Nature

Synthesis of nano-particles of anatase-TiO₂ and preparation of its optically transparent film in PVA