Nghiên cứu chế tạo, tính chất của vật liệu nano GdPO4 tb3+ và gd2o3 eu3+ định hướng ứng dụng trong y sinh tt tieng anh

MINISTRY OF EDUCATION
AND TRAINING

VIETNAM ACADEMY OF
SCIENCE AND TECHNOLOGY

----------------------------GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY

PHAM THI LIEN

RESEARCH ON THE SYNTHESIS, PROPERTIES OF
GdPO4:Tb3+ AND Gd2O3:Eu3+ NANOMATERIALS
ORIENTED FOR BIOMEDICAL APPLICATIONS
Major:
Code:

Optical, optoelectronic and photonic materials
62 44 01 27

SUMMARY OF DOCTORAL THESIS IN MATERIAL SCIENCE

Ha Noi - 2020


The thesis has been completed at:
Graduate University of Science and Technology Vietnam Academy of Science and Technology

Science supervisors:
1. Dr. Nguyen Thanh Huong
2. Prof. Dr. Le Quoc Minh

Reviewer 1:
Reviewer 2:
Reviewer 3:

The thesis was defended at Evaluation Council held at Graduate
University of Science and Technology - Vietnam Academy of
Science and Technology

on

, 2020.

Thesis can be further
referred at:
- The Library of Graduate University of Science and
Technology.
- National Library of Vietnam.


1
INTRODUCTION
1. 1. The necessity of the thesis
Luminescent nano-materials containing Rare Earth (RE-NP) have
received much attention in recent years. Notably, the materials GdPO4:
Tb3+ and Gd2O3:Eu3+ become the critical research tool for the wideranging biomedical applications in the diagnosis and treatment of
human disease. Magnetic resonance imaging (MRI) examination and
especially live-cell fluorescence microscopy are widely utilized in
hospitals and clinics.
In Vietnam, many research groups have focused on the synthesis
of luminescent materials as photonic biomarkers, creating the

analytical tool for assessing the quality of biologicals, foods and
vaccines. However, most of the biomedical applications are primarily
based on a single functional tool, e.g. either luminescent material as a
biomarker or magnetic material as a hyperthermia agent for enhancing
the contrast of image. Therefore, it is urgent to develop a
multifunctional

tool,

especially

simultaneously

possessing

fluorescence and magnetic properties in a single system to improve
the efficiency of diagnostic and treatment processes.
According to the latest reports in the field of rare-earth
luminescent materials, we decide to chose Terbium (Tb3+) and
Europium (Eu3+)-activated Gadolinium (Gd3+) compounds as research
objects. To our knowledge, these kinds of materials can meet the
requirement of multifunctional tool because Gd3+ ions simultaneously
exhibit fluorescence and magnetic properties, thus making them wellsuited to serve as nanoprobes in the diagnostic and treatment of human
disease.


2
To meet the requirement for diverse applications, the aim of our
thesis is to synthesize the luminescent nanomaterials with good
repeatability, well-controlled morphology, high solubility in water and

highly efficient luminescence. My doctoral thesis is entitled:
“Research on the synthesis, properties of GdPO4:Tb3+ and
Gd2O3:Eu3+ nanomaterials oriented for biomedical applications”.
2. Research objectives of the thesis
- Successful synthesis of GdPO4:Tb3+ nanorods and Gd2O3:Eu3+
nanospheres.
- Coating GdPO4:Tb3+ nanorods and Gd2O3:Eu3+ nanospheres with a
silica shell, functionalizing with NH2 functional group, conjugating
with anti-venom and anti-CEA antibodies for further biomedical
applications.
- Initial experimental application of the nanocomplexs based
GdPO4:Tb3+ nanorods

and

Gd2O3:Eu3+

nanospheres

using

immunofluorescence analysis method for labelling cells and
detecting the antigen of cobra venom and CEA antigen of colorectal
cancer cells.
3. Research contents of the thesis
In the following chapter 1, we present a brief overview of rareearth doped luminescent material; GdPO4:Tb3+/Gd2O3:Eu3+ based
luminescent materials and objects for biomedical application. Next,
we describe experimental methods and material characterizations used
in the thesis. We then present the material characterization results of
GdPO4:Tb3+ nanorods and Gd2O3:Eu3+ nanospheres. We also examine

and determine the magnetic hyperthermia property of GdPO4 and
GdPO4:Tb3+ nanorods. These nanomaterials were then conjugated


3
with anti-venom and anti-CEA antibodies for further biomedical
applications. Finally, we demonstrate the great potential of these
multifunctional nanocomplexs for detecting cobra venom antigen and
the CEA antigen of colorectal cancer cells. We conclude in the last
chapter.
In this thesis, the luminescent nanomaterials have been
synthesized by using hydrothermal process and multistep synthesis
approach. Surface morphology and structural characteristics of assynthesized nanomaterials were examined with field emission
scanning electron microscopy (FESEM), high-resolution transmission
electron microscopy (HRTEM), energy dispersive X-ray spectroscopy
(EDX). The optical properties of as-prepared samples were measured
with the spectrometers (iHR550, Acton SP2300i and Fluorolof FL32-2, Horiba (USA)). The magnetic properties were investigated with
magnetic field-dependent magnetization measurement using vibrating
sample magnetometer (VSM) system. The measurement of magnetic
induction heating is performed with the commercial RDO-HFI (IMS).
The biological experiments were performed at the Laboratory of
Molecular Biology (Vietnam Military Medical Academy).
Novel attribution of the thesis:
- Successful synthesis of GdPO4:Tb3+ nanorods with a length of 300–
500 nm and width of 10–30 nm through hydrothermal process and
Gd2O3:Eu3+ nanosphere with a diameter of 145–155 nm via multistep
synthesis approach.
- Successfully coating GdPO4:Tb3+ nanorods and Gd2O3:Eu3+
nanospheres with a silica shell, functionalizing with NH2 functional
group, conjugating with anti-venom antibodies and anti-CEA

4
antibodies to detect the cobra venom antigen and CEA antigen of
colorectal cancer cells.
- The magnetic inducting heater effect of GdPO4 and GdPO4:Tb3+
have been investigated, at 300 Oe, 390 kHz, the temperature reach
to 44 - 49 oC in 1500 s. The results indicating the synthesized
materials are well-suited for application in magnetic hyperthermia
therapy.
The thesis is divided into 4 chapters:
Chapter 1: Rare-earthe doped luminescent nanomaterials.
Chapter 2: Experimental methods.
Chapter 3: Synthesis of GdPO4:Tb3+ nanorods and the application of
GdPO4:Tb3+ nanocomplexs for the detection of cobra venom antigen.
Chapter 4: Synthesis of Gd2O3:Eu3+ nanospheres and the application
of Gd2O3:Eu3+ nanocomplexs for the detection of the CEA antigen
of colorectal cancer cells.
The main results of the thesis were published in 7 scientific papers.
CHAPTER 1: RARE EARTH ION-BASED LUMINESCENT
NANO MATERIALS
1.1. Introduction of luminescent nano materials
1.2. Rare earth ion-based fluorescente materials
1.2.1. Luminescent properties of rare earth compounds
1.2.1.1. Characteristics of Gd3+ ion
1.2.1.2. Characteristics of Tb3+ ion
1.2.1.3. Characteristics of Eu2+ and Eu3+ ions
1.2.2. Allowed electronic transition in RE3+ ion
1.2.3. Energy transfer process

5
(a)

(b)

Figure 1. 7. Energy level diagram and energy transfer mechanism of
Gd3+ ion to Eu3+ ion (a), Gd3+ ion to Tb3+ ion (b)
1.3 Features and applications of Gadolini
1.3.1. Gadolini material
1.3.2. The luminescent host material of Gd2O3
1.3.3. The luminescent host nanomaterial of GdPO4.
1.4. Characteristics of cobra venom and CEA antigens
1.4.1. Characteristics of Naja atra cobra venom
1.4.2. Characteristics of CEA colorectal cancer antigen
CHAPTER 2. EXPERIMENTAL METHOD
2.1. Chemical methods
2.1.1. Hydrothermal method
2.1.1.1. Introduction of hydrothermal method
Characteristics of material can tune by adjusting the following
parametrs: pH, temperature, speed of reaction, time of hydrolysis, and
crystallographic influence on morphology, magnitude and properties
of final products.
Synthesis process of GdPO4:Tb3+


6

Figure 2.4: Schematic representation for synthesis process of
GdPO4:Tb3+

2.1.2 Multi-step chemical synthesis method
2.1.2.1 Introduction of a multi-step chemical synthesis method
2.1.2.2. Synthesis process of Gd2O3:Eu3+

Figure 2.5. Experimental diagram for preparation of Gd2O3: Eu3+
2.1.3. Synthetic method of biomedical nano compounds
GdPO4:Tb3+; Gd2O3:Eu3+.
2.1.3.1. Surface treatment method
2.1.3.2. Methods of surface functionalization and conjugation
between luminescent nanomaterials and biologically active
elements
2.1.3.3. Coating GdPO4: Tb3+ nanorods by Silica
2.1.3.4. Functionalizing GdPO4:Tb3+@Silica nanorods by -NH2


7

Figure 2. 7. Experimental diagram for wrapping and surface
functionalization of GdPO4:Tb3+ nanorods
2.1.3.5. Preparation of GdPO4:Tb3+@Silica-NH2 nano compound
with the snake venom antibody (IgG)

Figure 2. 8. Diagram of synthesizing nano compound by integrating
GdPO4:Tb3+@silica-NH2 with the snake venom antibody (IgG)
2.1.3.6. Coating Gd2O3:Eu3+ by silica
2.1.3.7. Functionalization of Gd2O3:Eu3+ @Silica by -NH2

Figure 2.9. Diagram of wrapping Gd2O3:Eu3+ by Silica and
integrating NH2 group

8
2.1.3.8. Synthesis of Gd2O3:Eu3+@Silica-NH2 nano compound with
the CEA antibody.

Figure 2.10. Schematic illustration for the synthesis of nano
compound by integrating Gd2O3:Eu3+@silica-NH2 with the CEA
antibody (IgG)
2.2. Methods of material analysis
CHAPTER 3: RESEARCHING RESULTS OF GdPO4:Tb3+
AND APPLICATION OF GdPO4:Tb3+ NANO COMPOUND TO
DETECT THE VENOM ANTIGEN
3.1. Crystal structure, morphology, optical and magnetic
properties of synthesized materials
3.1.1. FESEM analysis
3.1.1.1 FESEM images of GdPO4.
3.1.1.2. FESEM images of GdPO4: Tb3+
Figure 3.2 exhibits as-prepared materials have nanorod
morphology with the length of 300-500nm and the width of 10-30nm.
It can be seen the nanorods in the sample with [Tb3+]/[Gd3+] = 7% are
rather uniform and not clustered in bundles compared to others.


9

Figure 3.2. FESEM images of GdPO4:Tb3+
with the ratio of [Tb3+]/[Gd3+] = 0, 1, 3, 5, 7, 9%.
3.1.2 TEM images of GdPO4: Tb3+

Figure 3.3. Images of GdPO4: Tb3+ coated by silica

3.1.2. Powder XRD patterns of synthesized samples
As shown in figure 3.4, the X-ray diffraction peaks show that
synthesized materials have single-phase tetragonal structure with the
tetragonal shape and match with the peaks of standard 98-004-3396
for Gadolinium phosphate.

Figure 3. 4. The X-ray diffraction patterns of GdPO4, GdPO4:Tb3+
3.1.3. Optical properties
3.1.3.1. Luminescent spectra of GdPO4
3.1.3.2. Luminescent spectra of GdPO4:Tb3+


10
Figure 3.6 indicates the absorption peaks at 272 and 275nm,
which are strong absorption bands of Gd3+, corresponding to 8S – 6I
shift. The ones at 305 and 310nm corresponding to 8S – 6P shift are
main absorption peaks of Gd3+. The excitation bands at the
wavelengths of 350, 367 and 377 nm derive from Tb3+ ion which
correspond to f-f electronic transitions between energy levels
belonging to 4f configuration.

Figure 3. 6. PLE spectra of
GdPO4:Tb3+ (0- 9%).

Figure 3.7. PL spectra of
GdPO4:Tb3+ with the ratio of 0, 1,
3, 5, 7, 9% excited at 272nm.
As shown in figure 3.7, GdPO4:Tb3+ (0- 9%) samples emit the blue
light due to the 5D4→7FJ (J = 6, 5, 4, 3) transition of Tb3+. The
5

D4→7F6, 5D4→7F5, 5D4→7F4 and 5D4→7F3 transtions of Tb3+
correspond to the wavelengths of 488nm, 543, 586 and 620 nm,
respectively. The strongest emission band occurs at 543 nm.
3.1.3.4. Luminescent spectra of GdPO4:Tb3+ @ silica integrated amin
functional group and IgG antibody
The luminescent intensity of the samples decreases in turn after
functionalization, binding to the amine and IgG groups. However,
such luminescent intensity slightly declines at the last step of binding
to IgG, which is a favorable condition for the application of this
material in the rapid detection of the cobra venom antigen.


11

Figure 3. 8. PL spectra of GdPO4:Tb3+(1), GdPO4:Tb3+@silica (2),
GdPO4:Tb3+@silica –NH2 (3), GdPO4:Tb3+@silica –NH2-IgG (4).
3.1.4. Infrared (IR) spectra

Figure 3.9. IR spectra of GdPO4:Tb3+(a), GdPO4:Tb3+@silica (b)
GdPO4:Tb3+@silica-NH2 (c) và GdPO4:Tb3+@silica-NH2-IgG (d).
The absorption bands of C-H (1400 cm-1), O-H of H2O (3500cm-1
and 1600 cm-1) and PO43- (1043, 622 and 545 cm-1) are observed in the
IR spectrum of the samples, see figure 3.9. The presence of O-Si-O
(1100-900 cm-1) and N-H (2200-2000 cm-1 and 3450 cm-1) bands
proves the silica coating and surface functionalization by NH2 group
were successful.


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3.1.5. Magnetism of GdPO4 and GdPO4:Tb3+

Figure 3.10. Magnetic curves of
GdPO4:Tb3+ with the ratio
[Tb3+]/[Gd3+] of 0, 1, 3, 5, 7, 9%.

Figure 3.11. The magnetic
inducting heater effect of
GdPO4:Tb3+ with [Tb3+]/[Gd3+]:
0, 1, 3, 5, 7, 9%
It can be seen from figure 3.10 that the magnetization of GdPO4

reaches the highest value of 1,7 emu/g which is twice larger than that
of Zhang’s work and as much as that of Xu’s work. The magnetization
of Tb3+ doped samples decrease, nevertheless the lowest value of
GdPO4:9%Tb3+ also achieves 0,8 emu/g equivalent to the value of
Zhang’s group. Therefore, GdPO4:Tb3+ can be used to increase the
contrast level of the magnetic resonance image MRI.
The magnetic inducting heater effect of GdPO4 and GdPO4:Tb3+
have been investigated, at 300 Oe, 390 kHz (figure 3.11), the
temperature reach to 44 - 49 oC in 1500 s. The results indicating the
synthesized materials are well-suited for application in magnetic
hyperthermia therapy.
3.2. Application of GdPO4:Tb3+ in the detection of Naja atra
venom antigen
The

experiment

of

detecting

the

venom

antigen

of

GdPO4:Tb @silica-NH2-IgG nano compound is shown in figure 3.12.
3+


13

Figure 3. 12. Diagrammatic illustration for detection of the venom
antigen by Gd2O3:Tb3+@silica-NH2-IgG fluorescent nano compund
1. Attaching simultaneously the snake venom antigen and nano
compound on the 6-disc wells.
2. Incubating the nano compound integrated the antivenom
antibody with the venom antigen.
3. After washing, only the nano compound integrated the
antibody and antigen of the venom.
4. The nano compound emits blue luminescence with excitation
wavelength at 405nm
3.2.1. Evaluation of conjugating of nano material – IgG antigen
based on FTIR spectra

Figure 3. 13. FTIR spectra of IgG antibody samples before and after

conjugating luminescent material.


14
The line (a) in figure 3.13 indicates the presence of the O-H (3459
cm ), N-H (2078 cm−1), C=O (1639 cm−1 to1442 cm−1) and the bond
−1

of N-H in the first amine group of carbonyl (C-N) group. The peak at
1389cm-1 in the line (b) is due to the formation of C - N bond by means
of the aldehyd group (O = C - H) reaction of GDA bond with NH2 of
IgG. As a consequence, the combination of luminescent nanorods and
anti-venom antibodies were formed.
3.2.2. Evaluating the ability of GdPO4:Tb3+@silica-NH2-IgG nano
compound in the detection Naja atra venom antigen.

(a)

(b)

(c)

Figure 3. 14. Image of Naja atra venom antigen under the visible
light (a); Naja atra antigen combined with nano material under the
visible light (b); Naja atra antigen combined with nano material
under the visible light observed under fluorescence microscope of
405nm, the magnification of 40x and eyepiece of 10x (c).
The results showed that the wells incubated with nanorods-antibodies
provided a green image and nanoparticles distributed uniformly
throughout the field green light under a 40x fluorescence microscope

(Figure 3.14 (c)). This result shows that these wells have a specific
association between the nanorods-antibodies and the Naja atra cobra
antigen so that when it was washed, it does not wash away.
Meanwhile, other emissions were not green due to the absence of a
combination of antibody-coated nanoparticles and Naja atra cobra
venom antigens so they were washed away during washing. Based on


15
these results, it could be concluded that this Naja atra venom detection
procedure can shorten the time needed for early diagnosis and improve
the efficacy of treatment and thus could facilitate early treatment of
snake bite and save lives. Thus, with respect to other green-emitting
luminescent materials like Yb, Er-codoped NaYF4 or TbPO4·H2Obased nanomaterials, our synthesized immunoglobulin G-conjugated
GdPO4·nH2O:Tb3+ nanorods are compatible for detection of antigenantibody reaction.

CHAPTER 4: RESEARCHING RESULTS OF Gd2O3:Eu3+
AND APPLICATION OF Gd2O3:Eu3+ NANO COMPOUND

TO DETECT THE CEA ANTIGEN OF COLORECTAL
CANCER CELLS
4.1. The analyses of structure, morphology, optical and magnetic
properties of samples
4.1.1. FESEM images
• FESEM images of Gd(OH)CO3.H2O:Eu3+ with the different
ratio of [Urê]/ [Gd3++ Eu3+]

Figure 4.1. FESEM images of Gd(OH)CO3.H2O:Eu3+ with the ratio
[Urê]/[Gd3+ + Eu3+] of 20 (a), 25 (b), 30 (c), 35 (d), 40 (e)
All samples obtained have nanospherical shape as seen in Figure

4.1. The diameter of such nanospheres increases with the increase of
molar ratio [Urê]/ [Gd3+ + Eu3+]. Typically, the average diameter of


16
nanospheres is 140, 190, 210, 240 and 270nm corresponding to the
molar ratio [Urê]/[Gd3+ + Eu3+] of 20, 25, 30, 35 and 40, respectively.
With the ratio [Urê]/[Gd3+ + Eu3+] of 25, the nanospheres are generally
the most uniform. As a consequence, this ratio is used to synthesize
Eu3+-doped Gd2O3 with the molar ratio Eu3+/ Gd3+ of 3,5; 5; 6; 7; 7,5
and 8%.
• FESEM images of Gd(OH)CO3.H2O: Eu3+ dried at 70oC

Figure 4.3. FESEM images of Gd(OH)CO3.H2O:Eu3+ dried at 70oC
with the ratio [Urê]/[Gd3++Eu3+] of 0 (a); 3,5(b); 5(c); 6(d); 7(e);
7.5(f) and 8%(g)
As shown in Figure 4.3, when Eu3+ is not doped, the nanospheres
are quite uniform with the diameter of about 157-173nm (Figure 4.3a).
When doping Eu3+ with different molar ratios Eu3+/Gd3 + of 3.5; 5; 6;
7; 7.5 and 8%, the nanospheres have the diameter in the range of 100230nm. From FESEM images, for Eu3+-doped sample with the
concentration of 6%, the nanospheres are rather uniform with the
diameter of 185-195 nm compared to others. As a result, this sample
is selected for next experiments.
4.1.2. Thermogravimetric analysis (TGA)
From Figure 4.4, one can observe 4 phases including: Phase 1 (25200oC): the weight of sample decreases 5.79% due to the evaporation


17
of water molecules; Phase 2 (200-380oC): the 8.13 wt % loss is
observed because of the decomposition of OH group. Phase 3: the

decomposition of cacbonate group in the range of 380-550oC results
in 15.21wt% loss. Phase 4: a further 28.49 wt% loss between 550 and
1000oC is caused by the disintegration of cacbonate group. In all 4
phases, there are strong points of heat absorption at 170, 319, 427 and
609 oC. These can be considered as the phase transition points,
yielding to can be selected suitable processing temperature to obtain
the material with a stable phase structure. Therefore, we choose the
sample processing temperature of 650 oC, at this temperature the
product obtained will be Gd2O3:Eu3+.

Figure 4. 4. TG-DTG curves of the as-prepared
Gd(OH)CO3.H2O:Eu3+
Figure 4.5 shows the diameter of Gd2O3 nanospheres (a) after
annealing at 650oC with the diameter of about 104-130nm. The
diameter of nanospheres in the sample containing 3.5% Eu3+ (b), 5%
Eu3+ (c), 6% Eu3+ (d), 7% Eu 3+ (e), 7.5% Eu3+ (f ) and 8% Eu 3+ (g) is
about 105-143nm, 117-130nm, 145 -155nm, 136-150nm, 99-130nm
and 176-200nm, respectively.


18

Figure 4.5. FESEM của vật liệu Gd2O3:Eu3+ khi ủ ở nhiệt độ 650oC
với tỷ lệ [Eu3+]/[Gd3+] là 0 (a); 3,5(b); 5(c); 6(d); 7(e); 7.5(f);8%(g).
4.1.3. TEM images of Gd2O3: 6%Eu3+

Figure 4.6. TEM images of Gd2O3: 6%Eu3+ (a)
and Gd2O3: 6%Eu3+@silica (b).
Figure 4.6 exhibits that the nanospheres are uniformly synthesized
with the diameter of about 145-155 nm which is similar to the FESEM

results (Figure 4.6a). The diameter of such nanospheres increase
significantly after coating silica, around 155-165nm. The silica shell
can be easily observed by naked eyes (Figure 4.6b).
4.1.4. Powder XRD patterns of as-synthesized samples
The sample of Gd(OH)CO3.H2O:6%Eu3+ is almost amorphous
annealed at 200oC. However, X-ray diffraction peaks are observed at
2θ: 28,70; 33,10; 47,60; 56,40; and 59.10º, in agreement with the
standard of JCPDS:110604, when annealing at 650oC. This can be
confirmed that the material obtained is cubic crystal.


19

Figure 4. 8. The X-ray diffraction patterns of
Gd(OH)CO3.H2O:6%Eu3+ heated at 200oC and 650oC.
4.1.5. EDX spectrum analysis
Through EDX spectrum analysis, it can be seen that the
synthesized sample includes the chemical elements Gd, O, Eu. Such
sample hence can be considered to be pure. The EDX spectrum of
Gd2O3: Eu3+@silica indicates the presence of Si atom.
4.1.6. FTIR spectra
Figure 4.11 plots the infrared spectra of Gd2O3: 6% Eu 3+ calcined
at 650oC with and without silica shell. The specific absorption regions
of Gd2O3 are represented at 415.49; 449.66 and 542.9 cm-1, see Figure
4.11a. The oscillation of 543 cm-1 can be attributed to the strain
oscillation of Gd-O, which confirms the formation of Gd2O3. Strong
absorption regions at 3446 and 1634 cm-1 specify for the typical bonds
of hydroxyl (OH) group and water hydration in structure. Figure 4.11b
is the infrared spectrum of Gd2O3:6%Eu3+@silica, the feature
oscillations of OH and Si-O-Si bonds are observed at the regions of

1050 – 1250 cm-1 và 650 – 800 cm-1, respectively. Combining the
results of EDX and FTIR analysis can confirm that the silica is coated
on the outer shell of the nanospheres.


20

Figure 4. 11. FTIR spectra of (a) Gd2O3:6%Eu3+ and
(b) Gd2O3:6%Eu3+@Silica.
4.1.7. Luminescent properties

Figure 4. 12. PLE spectrum of Gd2O3:6%Eu3+
Figure 4.12 shows the PLE spectrum of Gd2O3:6%Eu3+
observed at the emission wavelength of 611nm. The strong absorption
band at 266 nm is a charge-transfer band of Eu3+- O2, the weak
absorption peaks of 272 and 275nm correspond to the shift of 8S – 6I,
the absorption peaks at 305 and 310 nm correspond to the
displacement of 8S – 6P. All absorption peaks above are the
characteristic of Gd3+. The excitation bands at 394, 467 and 534 nm
are derived from the Eu3+ centers corresponding to the electron f-f
transitions between the energy levels belonging to the configuration
4f6 of Eu3+.
The PL spectra of Gd2O3:X%Eu (X=3,5; 5; 6; 7; 8%) excitated at
270nm wavelength are plotted in Figure 4.13. Strong emission peak at
611 nm corresponds to the shift of Eu3+ ion from 5Do →7F2. Other
peaks at 590, 625, 650 and 705nm have lower intensity and they


21
correspond to the shift of 5D0 → 7F1; 5D0 → 7F2; 5D0 → 7F3 and 5D0

→ 7F4.

Figure 4. 13. PL spectra of Gd2O3:X%Eu
(X=3,5; 5; 6; 7; 8%)
In Fig.4.14 it can be seen the photoluminescence spectra of
Gd2O3:6%Eu3+coated with silica shell in different thickness. First, the
photoluminescence intensity of Gd2O3:6%Eu3+@silica nanospheres
dried at 70ºC before being coated and annealed at 650ºC was stronger
than that of pure core phosphor. When the silica coating in the
emission range from 611 to 621nm belonging to the 5D0 – 7F2
displacement occurs interaction on the orbit, the crystal field
degenerates the energy level to make the line. With the sample coated
with one layer of silica, maximum separation occurs in the 5D0 – 7F2
emission range due to its low crystal symmetry. When coated with 2
layers, 3 layers at high crystal field symmetry leads to separate less.
When the crystal field is large, the average energy shifts towards the
high energy, the emission peak of 621nm thus increases with
increasing silica thickness.


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Figure 4.14. PL spectra of Gd2O3:6%Eu containing 1, 2 and 3 layers.
4.2. Combining Gd2O3:Eu3+@Silica-NH2 luminescent material
with IgG antbody to detect CEA.
4.2.1. Evaluation of the ability to detect CEA antigen by nano
compound.

Figure 4.16. Diagrammatic illustration for detection of CEA by
Gd2O3:Eu3+@Silica-NH2-IgG nano fluorescent compound.

(a)
(b)
(c)
(d)
Figure 4. 17. Fluorescent microscopy images of samples: Ref1 (a),
disc 3 (b), disc 4 (c), disc 5 (d) under the fluorescence microscope at
405nm wavelength, 40x magnification, 10x eyepiece.
Figure 4.17 is the images for detecting the CEA antigen by
Gd2O3:Eu3+@silica-NH2-IgG nano compound under the fluorescence
microscope with the magnification of 40x, the eyepiece of 10x. As
observed, reference disc 1 (Figure 4.17a) is only the image of pure


23
CEA without glowing red. Reference disc 2 do not recognize the
image due to the nano compound being lost during washing. For discs
3, 4 and 5 when the concentration of nano compounds increases from
3 to 10 mg / ml (Figure 4.17b, c, d), it is easy to observe the increase
of red luminescent points, the most obviously observation occurs for
the nano compound with the concentration of 10 mg/ml. This indicates
that an immunofluorescent reaction has occurred between the nano
compound and the CEA antigen.
4.2.2. Evaluation of the ability to detect CEA antigen of the
colorectal cancer cells HT-29 by nano compound.
After evaluating the results of detection of pure CEA antigen, we
test on colorectal cancer HT-29 containing CEA antigen.

(a)
(b)

(c)
(d)
Figure 4. 18. Fluorescence microscopy image of Ref1 (a), disk 3 (b),
disc 4 (c), disc 5 (d), under the fluorescence microscope at 405nm
wavelength, 40x magnification, 10x eyepiece.
The results obtained show that reference dics 1 (Figure 4.18a)
with only the CEA antigens is not red luminescence. Reference dics 2
can not observe the image because the drifting elements were not
conjugated during the washing process. Discs 3, 4 and 5 (Figure 4.18
b, c, d) corresponding to the volumes of nano complex of 50µl (b),
75µl (c) and 100µl (d) record luminescent images. The color becomes
strong with increasing the volume of nano compound. This proves that
there is a conjugation between nano compound and cancer cell's CEA