Nghiên cứu tổng hợp, tính chất vật liệu cấu trúc lõi vỏ ceo2ppy =

MINISTRY OF EDUCATION AND TRAINING
HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY
---------------------------------------

LE THI HAI YEN

RESEARCH IN SYNTHESIZING, PROPERTIES OF
CeO2/Ppy CORE-SHELL NANOMATERIALS

THESIS OF THE MASTER OF SCIENCE
ENGINEERING PHYSICS
Hanoi – 2018


BỘ GIÁO DỤC VÀ ĐÀO TẠO
TRƯỜNG ĐẠI HỌC BÁCH KHOA HÀ NỘI
---------------------------------------

LÊ THỊ HẢI YẾN

NGHIÊN CỨU TỔNG HỢP, TÍNH CHẤT VẬT LIỆU
CẤU TRÚC LÕI VỎ CeO2/PPy

LUẬN VĂN THẠC SĨ KHOA HỌC
VẬT LÝ KỸ THUẬT

HƢỚNG DẪN KHOA HỌC:
TS PHẠM HÙNG VƯỢNG

Hà Nội – 2018

THESIS OF THE MASTER

STUDENT DECLARATION
I declare that the scientific results presented in this thesis are solely my own
work and have not been published by other authors.
Hanoi, 28th September 2018
Student

Le Thi Hai Yen

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THESIS OF THE MASTER

ACKNOWLEDGMENTS
I would first like to thank my supervisors - Associate Professor Phuong Dinh
Tam and Doctor Pham Hung Vuong of the Advanced Institute of Science and
Technology at Hanoi University of Science and Technology. The door to Prof. Phuong
Dinh Tam and Dr. Pham Hung Vuong’s offices were always opened whenever I ran
into a trouble spot or had a question about my research or writing. They consistently
allowed this paper to be my own work, but steered me in the right the direction
whenever they thought I needed it.
I would also like to acknowledge the friends who were involved this research
project: Mr. Nguyen Luong Hoang, Mr. Vu Y Doan, Mrs. Nguyen Thi Nguyet.
Without their passionate participation and helping, the thesis could not have been
successfully conducted.
I would also like to thank to the teachers of the Advanced Institute of Science
and Technology of the Hanoi University of Science and Technology as the second

readers of this thesis, and I am gratefully indebted to them for their very valuable
comments on this thesis.
This thesis is a part of Associate Professor Phuong Dinh Tam and Doctor Pham
Hung Vuong’s research that is funded by Vietnam National Foundation for Science
and Technology Development (NAFOSTED).
Last but not least, thanks for the kind support of my family during two years of
my Master program.

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TABLE OF CONTENTS
STUDENT DECLARATION ...........................................................................................................................3
ACKNOWLEDGMENTS ...............................................................................................................................4
LIST OF SYMBOLS AND SHORTENED WORDS ............................................................................................7
LIST OF FIGURES ........................................................................................................................................8
ABSTRACT ............................................................................................................................................... 10
CHAPTER 1: INTRODUCTION .................................................................................................................. 12
1.1.

Introduction of CeO2 nanomaterials ...................................................................................... 12

1.1.1.

Cerium (IV) oxide............................................................................................................ 12

1.1.2.

Introduction of polypyrrole ............................................................................................ 16

1.2.

CeO2/PPy core-shell nanocomposites .................................................................................... 17

1.2.1.

Core-shell nanomaterials ............................................................................................... 17

1.2.2.

Properties of CeO2/PPy core-shell nanocomposites ...................................................... 21

1.3.

CeO2 nanorods for biosensor application .............................................................................. 22

CHAPTER 2: EXPERIMENT....................................................................................................................... 25
2.1.

Chemicals and Equipment...................................................................................................... 25

2.2.

Synthesizing CeO2 nanorods .................................................................................................. 25

2.3.

Synthesizing CeO2/PPy core-shell nanocomposites ............................................................... 25

2.4.

Equipments use for materials properties checking ............................................................... 26

2.4.1.

Scanning electron microscopy (SEM) ............................................................................. 26

2.4.2.

Transmission electron microscopy (TEM) ...................................................................... 27

2.4.3.

Fourier Transform Infrared (FTIR) Spectroscopy ........................................................... 27

2.4.4.

Cyclic voltammetry (C-V) ................................................................................................ 27

CHAPTER 3: RESULTS AND DISCUSSION ................................................................................................. 29
3.1.

Synthesizing CeO2 nanorods .................................................................................................. 29

3.1.1.
3.2.

Microstructure chracterization of CeO2 NRS ................................................................. 29

Synthesizing CeO2/PPy core-shell nanocomposites ............................................................... 32

3.2.1.

Microstructure characterization .................................................................................... 32

3.2.2.

Phase analysis ................................................................................................................ 33
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3.2.3.

Chemical bonding analysis, FTIR .................................................................................... 34

3.2.4.

Optical properties .......................................................................................................... 35

3.2.5.

Electrochemical properties ............................................................................................ 36

REFERENCES ..................................................................................................................................... 39

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LIST OF SYMBOLS AND SHORTENED WORDS
N.O

Shortened words

Full words

1

NMs

Nanomaterials

2

CSP

Core-shell polymer

3

NPs

Nanoparticles

4

NRs

Nanorods

5

CV

Cyclic voltametry

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THESIS OF THE MASTER

LIST OF FIGURES
N.O

Name of Figures

Page

1

Figure 1.1

Crystal structure of cerium (IV) oxide

12

2

Figure 1.2

TEM images (a–d) of CeO2 nanorods obtained

12

after 15h hydrothermal treatment at 220°C with
different initial CeCl3 concentrations: (a) 0.025M;
(b) 0.05 M; (c) 0.10 M; and (d) 0.20 M
3

Figure 1.3

TEM images (a–d) of CeO2 nanorods obtained

13

hydrothermal treatment (a) sphere shape, (b)
nanorods, (c) nanocubes and (d) CeO2 nanocubes
composed by CeO2 nanorods
4

Figure 1.4

Core – shell particle

15

5

Figure 1.5

Core–shell polymers (CSPs)

16

6

Figure 1.6

The common methods to prepare CSPs

19

7

Figure 2.1

The energy-dispersive x-ray spectrometry EDS

25

system Integrated in the scanning electron
microscopy (SEM), JEOL JSM-7600F (USA).
8

Figure 2.2

Cyclic voltammetry of the sensor equipment

26

9

Figure 3.1

FE-SEM images of the CeO2 materials

28

synthesized by hydrothermal method
(Ce(NO3)3.6H2O 0.1M; 12h) at 100 oC (a), 120 oC
(b), 150 oC (c) and 170 oC (d).
10

Figure 3.2

FE-SEM images of the CeO2 materials
synthesized by hydrothermal method (170 oC,
12h) with the concentration of Ce(NO3)3.6H2O:
0.1M (a); 0.02M (b); 0.01M (c); 0.005M (d);
8

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0.0025M (e).

11

Figure 3.3

FE-SEM images of the CeO2 materials

30

synthesized by hydrothermal method (170 oC,
Ce(NO3)3.6H2O 0,0025M ) with the different
reaction time: 1h (a); 1.5h (b); 2.5h (c); 3h (d); 6h
(e); 9h (f); 12h (g)
12

Figure 3.4

FE-SEM and TEM images of the pristine CeO2

33

nanorods (a,d), pure Ppy (b,e) and core-shell
CeO2 NRs@Ppy (c,f)
13

Figure 3.5

XRD patterns of the pristine (a) CeO2 nanorods,

34

(b) pure Ppy and (c) core-shell CeO2NRs@Ppy

14

Figure 3.6

FTIR spectra of (a) the pristine CeO2 nanorods,

35

(b) pure Ppy and (c) core-shell CeO2 NRs@Ppy
15

Figure 3.7

Photoluminescence spectroscopy of the pure Ppy,

36

pristine CeO2 NRs, and core-shell CeO2
NRs@Ppy
16

Figure 3.8

Cyclic voltammetry plots of (a) pure Ppy, (b)
CeO2 NRsand (c) CeO2 NRs@Ppy modifiedelectrode

9

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THESIS OF THE MASTER

ABSTRACT
Two issues that our society cares deeply about are renewable energy generation
and health care. Renewable energy can allay air pollution and global warming
concerns, while effective medical treatments can increase the longevity and quality of
life. Developments in nanomaterial technology in the past decade has provided
scientists, engineers and medical doctors with new tools and techniques to tackle
pressing technological challenges in these areas.
Nanomaterials for biomedical applications can be deviced into imaging agents,
drug delivery vehicle, diagnostic tool, etc. to save human life along with other areas.
Biomedical engineering has decreased the gap between the conventional medicine and
biology by application of engineering skills in monitoring, surgical, diagnosis, therapy
and treatment etc. The smaller size and high surface to volume ratio of nanoparticles
are the main features which make them useful in the biomedical fields because of
development of many new properties, ease of functionalization, conjugation of biomolecules etc.. Recent years, the early diagnosis of many diseases such as diabetes,
cancer, Alzheimer’s disease, stroke and so on are the key focuses of biomedical field
in order to save human life. The application of nanotechnology in this field shows
further advancement in several specific areas such as bio-diagnostics, drug targeting,
genetic manipulation, bioimaging. The importance of nanotechnology in this field can
be evaluated from the attention of many research groups over the last decade.
Research in biomedical nanomaterials is now gravitating toward composite
nanomaterials. Core –shell materials is a type of Composite nanomaterials which is
including a core (inner material) made of a material coated with another material on

top of it and have demonstrated novel functionalities and advantageous properties in
comparision to single-component nanoparticles [1] [2]. In biological applications, core10


THESIS OF THE MASTER

shell nanoparticles have major advantages over simple nanoparticles leading to the
improvement of properties such as (i) less cytotoxicity [3], (ii) increase in
dispersibility, bio- and cyto-compatibility, (iii) better conjugation with other bioactive
molecules, (iv) increased thermal and chemical stability and so forth [4]. These coreshell nanoparticles are produced by many synthesis approaches like solvothermal
synthesis, hydrothermal synthesis,

emulsion polymerization, sol-gel method,

microemulsion polymerization, and so on. On the basis of the core and shell of the
materials, the synthesis techniques, their morphologies and properties can be modified.
[5-10].

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THESIS OF THE MASTER

CHAPTER 1: INTRODUCTION
1.1.

Introduction of CeO2 nanomaterials

1.1.1. Cerium (IV) oxide
1.1.1.1.

Introduction

Recent years, the oxides of rare-earth elements have been used in various
applications, for example: fuel cells, catalysis, medical applications, biomedical
applications, etc. Cerium oxide, a common rare earth oxides is widely developed,
especially in biomedical applications.
Cerium is an element of the rare earth family of metals having atomic symbol
Ce, atomic number 58, and atomic weight 140.12. The outer electron shell
configuration of cerium atoms is 4f26s2. There are two stable oxides of cerium named
cerium dioxide (CeO2) and cerium sesquioxide (Ce2O3) corresponding to two oxidation
states Ce3+ and Ce4+. Among them, CeO2 is known as the most stable oxide of cerium.
By heating cerium metal, cerium hydrate, or any of Ce(III) oxosalts such as oxalate,
nitrate or carbonate in air or oxygen, cerium (IV) oxide can be obtained.
1.1.1.2.

Crystal structure

Cerium (IV) oxide crystallizes in fluorite structure (FCC) which consist of a
face-centered cubic unit cell with lattice constant 5.411 A as shown in Figure 1.1.
In each unit cell, each Ce cation is coordinated by eight nearby neighbor oxygen
anions, while each oxygen anion is surrounded by four Ce. The eight coordination
sites are alternately empty and occupied by a Ce cation.

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Figure 1.1. Crystal structure of cerium (IV) oxide [1]

1.1.1.3.

Morphologies of CeO2 nanomaterials

CeO2 nanostructure posseses various applications in different areas, for example
catalysis, fuel cells and biomedical, etc. There are different shapes of CeO2
nanoconstructure, such as particles, cubes, rods, wires, and tubes. The more different
shapes in nanocrystal of CeO2, the more different crystal planes and surface properties
they possess. This can affect the interactions between the CeO2 surface and adsorbed
molecules, leading to the influencing of the performances in various systems.
In summary, different CeO2 moorphology could be obtained based on changing
the hydrothermal procesing such as precusor concentration, surfactant, hydrothermal
temperatures and pH value.

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THESIS OF THE MASTER

Figure.1.2 TEM images (a–d) of CeO2 nanorods obtained after 15h
hydrothermal treatment at 220°C with different initial CeCl3 concentrations:
(a) 0.025M; (b) 0.05 M; (c) 0.10 M; and (d) 0.20 M [ 11 ].

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THESIS OF THE MASTER

Figure.1.3 TEM images (a–d) of CeO2 nanorods obtained hydrothermal
treatment (a) sphere shape, (b) nanorods, (c) nanocubes and (d) CeO2 nanocubes

composed by CeO2 nanorods [ 12,13 ].
1.1.1.4.

Hydrothermal methods for cerium oxide nanostructures

Hydrothermal method is used to synthesize of crystallizing materials from
relative high temperature aqueous solutions at high pressures. The crystal growth is
took place in an autoclave including a steel pressure vessel, in which a solution is
prepared. Advantages of the hydrothermal method over other kinds of synthesized
methods is the ability to create crystalline phases that are not stable at the melting
point. The hydrothermal method could be used for materials which have a high vapour
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THESIS OF THE MASTER

pressure near their melting points to be grown. In addition, the method is specially
suitable for synthesis of large quality crystalline materials while maintaining control
over their composition. On the other hand, the disadvantages of this method is the
quantity of the synthesized materials is usually small because of the small volumn of
the autoclaves chamber.
1.1.1.5.

CeO2 nanorods formation mechanism

The evolution growth of CeO2 from a solution phase includes two crystallization
steps, which are nucleation and growth. It is proved that concentration of CeO2
precusor and a its diffusion coefficient are realy essential for the formation of 1D
CeO2 nanostructured materials. Small nuclei CeO2 tends to form

through

homogeneous nucleation of CeO2, but agglomeration can take place because of the
high surface energy of CeO2 nanoparticles.
1.1.2. Introduction of polypyrrole
Polypyrrole (PPy) is a one of the common

conductive polymer such as

polyacetylene, polyaniline, and polythiophene. Polypyrrole can be obatained in the
form of black powder by the oxidation polymerization of pyrrole with the presence of
ferric chloride as an oxidant as follows:
nC4H4NH + 2 FeCl3 → (C4H2NH)n + 2 FeCl2 + 2 HCl
The oxidized derivatives of the PPy families have good electrical conductivity
ranging from 2 to 100 S/cm. Reagents and conditions using in the oxidation process of
PPy are strongly influenced to the the conductivity of PPy. The larger the anions, the
higher conductivities of PPy can be achieved.

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THESIS OF THE MASTER

1.2.

CeO2/PPy core-shell nanocomposites

1.2.1. Core-shell nanomaterials
1.2.1.1.

Definication

Core-shell nanomaterials (NMs) are the combination of a core (inner material)
and a shell (outer layer material) made of different components. [4].

Figure1.4. Core – shell particle [14]

Recently, core-shell nanomaterials have paid a lot of attention because they
possess the novel functionalities and advantageous properties in comparision to singlecomponent of materials in different applications such as catalysis, biology and sensors
[15-17]. Hughes and Brown could be the first researcher who did a research on the
properties and morphologies of core – shell nanomaterials in 1961 [18]. The properties
and characteristics of both core and shell are mixed together, for example the surface
properties of the shell are leaded to the core which brings new functionalities for the
materials [19]. Core-shell polymers (CSPs) also possess these mixed properties of
core-shell nanomaterials that leads to their various applications in environtments
treatments, coatings, catalysis, printing, sensing, and drug delivery [20-21]. Usually,
CSPs are synthesized in

spherical form consisting of an inner core located at the

centre, and the polymers forming the outer shell layer as shown in Fig. 1.2. The nature
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THESIS OF THE MASTER

of materials form the CSPs depends on the targeted application [5][20]. The core part
might be formed from liquid, solid, or gas and the shell is commonly formed from a
solid. Various techniques

such

as dispersion, emulsion

polymerization, and

precipitation, etc. have been used to prepared the CSPs [4].

Figure 1.5. Core–shell polymers (CSPs) [22]
1.2.1.2.

Classification

Core-shell nanomaterials have been explored in various structure including
metal-metal, metal-oxide, metal- polymer, oxide-polymer core-shell nanomaterials
[4]. It is possible to be changed materials that forms the core and the shell of the above
kinds of core-shell nanomaterials. It also can obtain an other type of core-shell
nanomaterials which is multishell nanostructure consisting of some shells around a
core nanoparticle [6][24].
1.2.1.3.

Properties

The properties and characteristics of core-shell nanomaterials depend on their
shell thickness and their core size [25]. Core-shell structures have different chemical,
biological, and physical properties on the basis of tenability of the composition, surface
morphology and structural order of nanomaterials.
a) Physical Properties
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THESIS OF THE MASTER

There are a wide range of advancement properties of core-shell nanostructure
and the surface functionalization of core-shell nanomaterials, for example dielectric,
and electrical conductivity properties [27].
b) Physicochemical properties
The core-shell nanomaterial is demonstrated to possess some physicochemical
properties such as magnetic resonance Imaging and catalytic behavior.
c) Biological Properties
Surface modification and biocompatibility properties, thermoresponsive
properties, pH Responsive properties, Surface functionalization,… are mail biological
properties which make core-shell nanomaterial become more common in research
today especially in biosensor applications.
1.2.1.4.

Synthesizing methods

There are different methods have been used to synthesized CSPs such as
precipitation polymerization sequences, dispersion or emulsion with different types of
monomer [22-23]. Synthesis of CSPs particles is required multi-step procedures which
uses seed particles as a core material, and the another materials is coated to form the
outer shell. The seed core can not only be synthesized in a individual step but also
form during the in situ polymerization. Beside the advantages, these techniques still
possess the several limitations such as time consuming and expensive, because of the
using multiple step procedures. The polymer particles with core–shell morphology can
be synthesized easier by using one-stage reaction [28]. Another technique that can
produces polymer particles in the range of 1–15 mm which is dispersion
polymerization. It is also known as a class of precipitation polymerization. The formed
polymers are insoluble in continuous phase (e.g. methanol, ethanol, water). However,

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THESIS OF THE MASTER

the obtanined polymer particles possess irregular shape and larger particles via
precipitation polymerization. Moreover, emulsion polymerization is the main process
for the synthesizing of commercial emulsion, which involves a monomer that has
limited solubility in water. The common methods that have been used to synthesize
CSPs described by Li and Stover indicates in Fig. 1.3 [22].

Figure 1.6. The common methods to prepare CSPs [22]
The most method used in synthesizing CSPs is two stage emulsion
polymerization (a). The emulsion polymerization using reactive surfactants were also
used to synthesize CSP particles (b). The formation of core–shell particles by step-wise
inducing of smaller cationic polymer particles onto larger anionic polymer particles,
followed by heat treatment has also been documented (c). The obtained copolymers can
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THESIS OF THE MASTER

also be used to synthesis core–shell polymer nanospheres by block copolymerization
(d).
1.2.1.5.

Applications

The core-shell nanomaterials have been used in different applications in medical
areas such as dental materials, prosthetic materials, extracorporeal devices, implants,

dressings, encapsulants, tissue engineered products, polymeric drug delivery systems,
and orthodoses as that of ceramics and metal substituents. Due to the advantage of
chemical and physical properties over single-component counterpart, the core-shell
nanoparticles have also shown a wide range of applications in the fields of bioscience
[29-33], chemistry [34-35], and material sciences [36-37]. They also play an essential
roles in developing medical and biological applications.
1.2.2. Properties of CeO2/PPy core-shell nanocomposites
Polypyrrole (PPy) is one of most prospect conducting polymeric electrode
materials for a supercapacitor due to its intriguing properties like high specific
capacitance, high electrical conductivity, and low cost. Unluckily, its poor cycling
performance is limitted severely the practice application because of the big volume
changes and degradation at high potential during the long charge/discharge process.
The most important factor for the design of the nanocomposites might be the
interface between the conducting polymers and the inorganic nanomaterials. The
interfacial property of the PPy-based nanocomposites could be improved by the
modified surface modified of inorganic nanomaterials. The carbon nanomaterials, for
exaple, were used after oxidization, or treatment with surfactants. By using different
modifiers such as dyes, surfactant, or functional silane, the well-defined structured
nanocomposites could be obtained.

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THESIS OF THE MASTER

1.3.

CeO2 nanorods for biosensor application
Ornastka et al studied Pd-doped CeO2 based sensor to detect glucose [38]. Due

to the synergetic effect between Pd and CeO2, an electrocatalytic response current
towards glucose oxidation is presented by Pd-CeO2. However, un-doped CeO2 does not
have electrolytic response towards the oxidation of glucose. Moreover, the presence of
Pd in CeO2 enlarges the rate of electron transport that leads to improvement of
electrochemical properties. The combination of GOx and CeO2-NPs in a filter paper
via salinization method to create a glucose sensor was introduced by Ornastka et al.
The enzymatically introduced hydrogen peroxide induces a visual color from
whiteyellowish to dark orange change of immobilized CeO2-NPs during sensing.
In order to immobilize GOx for the selective detection of glucose, CeO2
nanorods synthesized by non-isothermal precipitates were added to ITO. The
electrochemical sensing studies of GOx/CeO2/ITO glucose showed a low detection
limit of 100μM with correlation coefficient of 0.99 and a response time of 2s,
sensitivity is 0.165 μA mM−1 cm−2, a linear range of 2 to 26 mM. The oxidation of
glucose occurs in the presence of oxygen and enzymatically generated H2O2 detection
during glucose sensing. Moreover, pulsed laser deposition method is invested to
synthesized thin film of CeO2 onto Pt coated glass plated for the immobilization of
GOx in order to detect glucose. A sol-gel derived CeO2 nanostructured film was added
to Au electrode by Ansari et al in order to immobilize GOx via physical adsorption for
selective detection of glucose. The GOx/CeO2/Au bioelectrode sensor showed a
linearity of 50–400 mg/dL, a low detection limit of 12.0 µM and shelf-life of 12 weeks.
CeO2/graphene composite was added to glossy carbon electrode in order to
create an enzyme based electro-generated chemiluminescence cholesterol biosensor.
This composite shown a high catalytic activity and sensitivity towards cholesterol. A
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THESIS OF THE MASTER

sol-gel derived nano CeO2 film is used to immobilize cholesterol oxidase (ChOx)
enzyme. Nano CeO2 supplies ideal electro-active surface and enlarges rate of electron

transfer for the immobilization of ChOx. The calculated low Km suggested the strong
affinity of ChOx towards cholesterol. This type of nano CeO2 bio-electrode is
profitable biosensor for clinical diagnosis. However, in order to improve the sensing
performance, composite of nano CeO2 and CH is used to immobilize ChOx instead of
CeO2/graphene composite due to electrostatic interaction and hydrogen bonding
between CeO2 nanoparticles and -NH/OH groups of CH. This cholesterol biosensor
presented a high sensitivity of 47 μA/mg dL-1 cm-2, a detection limit of 10 mg dL-1, a
response time of 10s and a wide detection range of 10-400 mg dL-1.[39]
Others enzymatic biosensor based on nano CeO2 have been introduced for other
catalytic sensing application. Catalysts of nano CeO2 and nano CeO2 were prepared
using precipitation and co-precipitation method. This sensor showed a detection limit
for phenol as 5.6×10-9 M and 9.0×10-9 M in the absence and presence of oxygen.
Nevertheless, the detection limit for dopamine is 4.2×10-8 M and 3.4×10-8 M. The
estimated sensitivities for dopamine are 14.9 mAM-1 and 14.8 mAM-1 and in case of
phenol in absence and presence of oxygen the sensitivities are as 86 mAM-1 and 65
mAM-1, respectively.
Desired nano CeO2 with good electrochemical and functionality properties
have been developed for DNA biosensor to detect related target analyte. The DNA
biosensors performance is improved by doping of electroactive nanomaterials and
making organicinorganic hybrid nanocomposite for instance Pt and CNTs to enhance
electrochemical sensing performance. Feng et al combine the properties of nano CeO2
and CH in order to immobilize DNA [40]. Authors found that the advantages and
synergetic effect of nano CeO2 with CH to understand DNA loading and enhanced
signal to obtained biosensor response. For developing an effective platform, TBA
probe is immobilized onto nano CeO2 which is modified with MWCNTs to enhance
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THESIS OF THE MASTER

the sensitivity of the DNA-based sensors. These DNA biosensors are used to detect
Pb2+ using TBA as a molecular recognition element and ionic liquid supported CeO2
nanoparticles–MWNTs composite. This developed DNA biosensor presented
sensitivity of (1.13 μA μM-1) and 1.26 μA μM-1 and detection limit as 10 and 20 nM
for guanine and adenine, respectively.
An electrochemical DNA biosensor to detect fusion gene of CML in methylene
blue medium was prepared by a composite of nano CeO2 including CH and MWCNTs
using DPV technique. It is shown that this biosensor presented a detection limit of
5x10-13 M. Further, CaMV35S gene DNA biosensor is also fabricated using
MWCNTs/CeO2/CHIT composite system.

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THESIS OF THE MASTER

CHAPTER 2: EXPERIMENT
2.1.

Chemicals and Equipment
Ce(NO3)3.6H2O was provide by Invitrogen Co. Phosphate-buffered saline (PBS

1×, pH 7.4), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC),
sulfo-N-hydroxysuccinimide (NHS), bovine serum albumin BSA, H2SO4 98%,
KCr2O7, and 3-aminopropyl triethoxy-silane (APTES) were purchased from SigmaAldrich. Potassium ferrocyanide and potassium derricyanide were purchased from
Beijing Chemical Reagent (China). All solutions were prepared with de-ionized (DI)
water.
2.2.

Synthesizing CeO2 nanorods

Ce(NO3)3.6H2O (0.025 mol) was dissolved into a solution containing 30ml HCl

1%, 1ml KHPO4:K2HPO4 and 29 ml distilled water. The mixture was stirred for 30
minutes before being transferred into a 100 ml Teflon lined stainless steel autoclave
that was placed into a furnace. The temperature was controlled to react at 170°C for
12h. After that, the autoclave was cooled down to room temperature naturally. The
obtained product was precipitated in Teflon lined stainless steel autoclave.
Subsequently, the nanomaterial could be washed in ethanol and distilled water several
times. The products were dried in a vacuum oven for 6h at 60°C.
2.3.

Synthesizing CeO2/PPy core-shell nanocomposites
Synthesis of the core-shell CeO2/ppy nanohybrid was prepared by the in situ

chemical oxidative polymerization of pyrrole on the CeO2 nanorods in the presence of
FeCl3.6H2O as an oxidant. A certain amount of the CeO2 nanorods was added in
FeCl3.6H2O solution under magnetic stirred for 30 minutes. Then, the monomer
25