BỘ MINISTRY OF EDUCATION
AND TRAINING
VIETNAM ÂCDEMY OF
SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY
……..….***…………
NGUYEN THI MAI HUONG
Study the fabrication and photocatalytic, hydrophilic
properties of TiO
2
/SiO
2
and TiO
2
/PEG thin films by
sol-gel method
Major: Solid State Physics
Code: 9 44 01 04
SUMMARY OF THE THESIS
Hà Nội – 2018
The thesis is completed at: Graduate University of Sciences and
Technology, Vietnam Academy of Science and Technology
Supervisors: 1) Dr. Nguyen Trong Tinh
2) Dr. Nghiem Thi Ha Lien
Reviewer 1: …
Reviewer 2: …
Reviewer 3: ….
- 1 -
A. INTRODUCTION
TiO
2
is known as a photocatalytic and hydrophilic
semiconductor material when excited by light. That is why TiO
2
is
considered to be a functional material that has the potential to
create self-cleaning materials for practical applications. The
hydrophilic nature of the material surface under optical excitiation
is closely related to the material properties, surface configuration
and stimulus. For this reason, the study on the hydrophilicity of the
material is a very academically attractive subject in studying the
properties as well as physical processes on the surface.
In the world, recent studies show the relationship between the
hydrophilicity of the solid surface and surface energy. Exciation by
light produces a change in surface energy, leading to a change in
hydrophilicity.
The systematic and quantitative study of the changes in
surface energy under the differentiation of TiO
2
with different
nano-structures promises to bring further information to the
photocatalytic mechanism and super-hydrophilic effects of TiO
2
material.
In Vietnam, there are a few studies related to hydrophilicity or
surface energy of materials, especially hydrophilicity under the
Exciation of the light. Therefore, the objectives of the thesis are
presented as follows:
The objectives of the thesis:
Study on materials fabrication technology; structural -
photocatalytic properties of TiO
2
material, and TiO
2
as the
nanostructured variant. On the basis of such material system, the
systematic and quantitative study on hydrophilicity or, in other
words, the study of surface energy of material systems under
Exciation of UV light radiation. Further clarification of the
correlation between photocatalytic activity, self-cleaning and
hydrophobicity of TiO
2
nanostructured materials.
Research subjects: The thesis focuses on two structural
systems on the basis of nanostructured and anatse-shaped TiO
2
: The
complex nano-structure TiO
2
/SiO
2
and Nano-porous TiO
2
/PEG.
- 2 -
Main study contents:
Fabrication of TiO
2
/SiO
2
, TiO
2
/PEG material systems and
experimental study on the structural properties as well as the
photocatalytic properties of the two material systems.
The hydrophilicity or surface energy of TiO
2
/SiO
2
, TiO
2
/PEG
nanostructured films is studied by contact angle measurement and
semi-quantitative techniques based on micro-theoretical models of
solid surface under the presence of the stimulus.
The practical and theoretical significance of the thesis
The technology of fabrication of nanostructured TiO
2
material
is controlled by sol-gel method. The nanostructures of TiO2 thin
films are controlled. The phase transition is inhibited from the
anatase configure with high photocatalytic activity of Anatase to
Rutile phase into Rutile phase with low photocatalytic activity at
high temperature.
A new methodology is developed for calculation and
quantification of solid phase surface energy quantification based on
micro theory of solid-state physics. Based on this methodology, it
is possible to calculate and quantify the solid surface energy based
on experimental data of measuring the liquid-solid phase contact
angle by contact angle measurement technique.
Quantitative study of surface energy of nanostructured TiO
2
photocatalytic film under the Exciation of UV radiation. This
provides empirical evidence about a physical effect: optical
Exciation can change the surface energy of the photocatalyst.
The correlation between the photocatalytic mechanism and
the super-hydrophilic mechanism of the nano-structured TiO
2
material system is demonstrated. Quantitative empirical data is
provided, contributing to consolidate the hypothesis of the origin of
the mechanism of super-hydrophilic effect of the TiO
2
material
system.
Layout of the thesis: The thesis consists of the introduction,
5 chapters and the conclusion. The results are published in five
journals including 03 international publications and 02 national
publications.
- 3 -
B. CONTENTS OF THE THESIS
Chapter 1
OVERVIEW OF TITANIUM DIOXIDE NANOMATERIALS
(TIO2)
1.1. Titanium Dioxide Nanomaterials
1.1.1. Introduction.
In recent years, Nano TiO
2
powder in the rutile, anatase, or
mixture of rutile and anatase and brookite mixtures have been
studied for use in the fields of solar cells, manufacturing electronic
device, sensing head, etc. With high photocatalytic activity, TiO
2
nano-material are applied in the fields of environmental treatment
such as: decomposition of toxic organic compounds, water
treatment, bactericidal, mildew-proof. Especially, in combination
with hydrophobicity when exposed to light, TiO
2
is developed as a
self-cleaning material. With durable and non-toxic structure, TiO
2
material is considered to be the most promising material to address
many serious environmental problems and challenges of pollution.
Phase-pure TiO
2
nanoparticles:
TiO
2
has four forms of formation. In addition to amorphous
form, it has three crystalline forms, including: anatase, rutile and
brookite (Figure 1.1).
Anatase
Rutile
Brookite
Figure 1.1: The Crystal structure of TiO
2
Differences in network structure lead to differences in
electronic density between the two rutile and anatase forms of TiO
2
and this is the cause of difference in nature between them. The
nature and application of TiO
2
is highly dependent on the
crystalline structure of the forms and particle size of such forms.
Among the forms of TiO
2
, the anatase exhibits higher
photocatalytic activity than the rest.