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Article
Journal of
Nanoscience and Nanotechnology
Vol. 16, 504–514, 2016
www.aspbs.com/jnn
Microstructure, Optical and Photocatalytic Properties of
TiO
2
Thin Films Prepared by Chelating-Agent
Assisted Sol–Gel Method
Lenka Matˇ ejová
1 ∗
, Monika Cieslarová
1
, Zdenˇ ek Matˇ ej
2
, Stanislav Daniš
2
, Pavlína Peikertová
1 3
,
Marcel Šihor
3
, Jaroslav Lang
1 3
, and Vlastimil Matˇ ejka
1
1
Nanotechnology Centre, VŠB-Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava, Czech Republic
2
Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University in Prague,
Ke Karlovu 5, 121 16 Prague 2, Czech Republic
3
Institute of Environmental Technology, VŠB-Technical University of Ostrava, 17. listopadu 15,
708 33 Ostrava, Czech Republic
Single and multilayer TiO
2
thin films coated on two types of soda-lime glass substrates (micro-
scope slides and cylinders) were prepared by a chelating agent-assisted sol–gel method, using
ethyl acetoacetate as a chelating agent, dip-coating and calcination at 500
C for 2 h in air. Phase
composition, microstructural, morphological and optical properties of thin films were comprehen-
sively investigated by using XRF, advanced XRD analysis, Raman and UV-vis spectroscopy and
AFM. It was found out that the thickness of thin films increases linearly with increasing number of
deposited layers, indicating a good adhesion of the titania solution to a glass substrate as well as to
a previously calcined layer. 1 layer film crystallized to anatase-TiO
2
(B) mixture with minor/negligible
amount of nanosized brookite, 2–4 layers films crystallized to anatase-brookite-TiO
2
(B) mixture. In
contrast to other multilayers films, 4 layers film was highly inhomogeneous. The different phase
composition of thin films was clarified based on the crystallization via titanate/s and metastable
monoclinic TiO
2
(B) as a consequence of several phenomena; the diffusion of Na
+
ions from a soda-
lime glass substrate, acidic conditions and repeated thermal treatment. The multilayer films were
in average highly transparent (80–95%) in the visible light region with the sharp absorption edge
in the UV light region. Additionally, the photocatalytic properties of selected multilayer films were
compared in AO7 photodegradation. Photocatalytic experiments showed that thicker 4 layers film of
tricrystalline anatase-brookite-TiO
2
(B) phase mixture was similarly active as thinner 3 layers film of
similar phase composition, which may be a consequence of the inhomogeneity of the thicker film.
Keywords: TiO
2
, Multilayer Thin Film, Chelating Agent Assisted Sol–Gel, Monoclinic TiO
2
(B),
Microstructure.
1. INTRODUCTION
Due to excellent photo-chemical performance and
other photo-induced phenomena under UV light (with
wavelength < 390 nm) TiO
2
(titanium dioxide, titania)
belongs among keenly investigated semiconductor mate-
rials. Up to now it has been explored in various macro-
scopic forms such as nanoparticulate powders, thin films,
aerogel blocks or monoliths for many application areas;
1–4
e.g., as additives to textile, construction materials and
∗
Author to whom correspondence should be addressed.
paints introducing their antimicrobial, antifungal and self-
cleaning activity of surfaces,
5 6
an electrode material in
electrochromic devices,
7–9
as adsorbent and photocata-
lyst for mitigation of various organic pollutants
10 11
and
greenhouse gasses,
3 12
catalysts support into technologi-
cal oxidation units
13–15
etc. Since in last decade due to
ambitious plans related to TiO
2
to integrate it as a part
of ‘hybrid’ waste water or waste air treatment technolo-
gies in the form of cleaning surfaces, guaranteeing no
release of nanoparticles to purified medium, thin films
of TiO
2
have become very attractive. There have been
504 J. Nanosci. Nanotechnol. 2016, Vol. 16, No. 1 1533-4880/2016/16/504/011 doi:10.1166/jnn.2016.10684