Synthesis and luminescent properties characterization of nanomaterials based on nayf4 matrices containing Er3+ and Yb3+ for biomedical application

line host materials do not partake in UC processes luminescent centers, referred to as activators, are required. Most Ln3+ species can theoretically be used to produce UC emissions as they have more than one excited 4f energy level (exceptions are La3+, Ce3+, Yb3+, and Lu3+). These Ln3+ species offer long-lived metastable excited states (up to 0.1s, due to low f-f transition probabilities), as well as multiple and equally spaced intermediate metastable energy levels in a ladder-like arrangement. This is exemplified, using the activators of Er3+. 1.2.2.3. Sensitizers Yb3+ has a larger absorption cross-section than those of the lanthanide activators. The 2F7/2 → 2F5/2 transition of Yb3+ is conveniently resonant with many f−f transitions of Er3+, Tm3+, and Ho3+, thus facilitating efficient energy transfer from Yb3+ to these ions. Thus, Yb3+ is often codoped with Er3+, Tm3+, or Ho3+ as a sensitizer to enhance upconversion emission. A CW 980 nm laser is applied as the excitation source to match the 2F7/2 → 2F5/2 transition of Yb3+ (Scheme 3). Additionally, in this review, we concentrate on summarizing 5 the advances in Yb3+ sensitized UCNPs, although some transition-metal ions have also been reported to serve as sensitizers or emitters to achieve upconversion emissions. 1.3. Several methods of synthesis luminescent nanomaterials contain rare earth ions for biomedical applications The chemical synthesis method controls the uniform size of the nanoparticle but usually produces only very small amounts, suitable for applications in sophisticated technology, such as in nano electronics, nano optics, and high-definition television, more recently in biomedical medicine. From different reaction conditions, it is possible to synthesize nanomaterials with diverse shapes such as particles, rods, fibers, disks, etc One of those products is light-emitting nano materials containing rare earth ions such as Y2O3: Eu3+; YVO4: Eu3+; NaYF4: Yb3+, Er3+ etc. In this thesis, we present three main chemical methods for synthesizing luminescent nanomaterials containing rare earth ions for biomedical application: hydrothermal, sol-gel and microwave. 1.4. Application of upconversion nanophosphors (UCNP) in biomedical engineering. 1.4.1. UCNP for Bioimaging Luminescent imaging is very useful for early diagnosis and treatment of some incurable diseases. Over the years, much research has been focused on developing new fluorescence imaging techniques and luminescent labels in order to improve the signal-to-noise ratio (SNR). Due to the special CW-excited upconversion process, upconversion emissive materials exhibit unique large anti-Stokes shifts. Thus, upconversion luminescence imaging with UCNPs as labels could be expected to completely eliminate autofluorescence from biotissues in bioimaging. To date, UCNPs have been successfully applied to the bioimaging of various biological samples, including living cells and small animals. Because of the high image contrast, in vitro and in vivo biological format applications of UCNP can be determined with high accuracy, especially in in vitro conditions. 1.4.2. Lanthanide UCNP for biosensing Optical sensing and assays play vital roles in theranostics due to the capability to detect hint biochemical entities or molecular targets as well as to precisely monitor specific fundamental physiological processes. UCNPs are promising for these endeavors due to the unique frequency converting capability of biocompatible NIR light that is silent to tissues. They have the potential to reach a high detection sensitivity deeply located in the living body systems. However, the PL of UCNPs is not directly related to any biochemical property of a system except for temperature. Therefore, to be useful in a biochemical recognition process (the fundamental process in chemical sensing), UCNPs have to be used in combination with suitable recognition elements such as indicator dyes. The recognition element of a biosensor may consist of an enzyme, an antibody, a polynucleotide, or even living cells. Next, the process of biochemical recognition has to be transduced into an optical signal given by the UCNPs. The transduction was generally implemented by a FRET and/or LRET mechanism. In the following, we summarized UCNP-based in vitro temperature sensing, detection of ions (cyanide, mercury, etc.), sensing of small gas molecules (oxygen, carbon dioxide, ammonia, etc.), as well as UCNP-based bioassays for biomolecules (avidin, ATP, DNA, RNA, etc.). 1.4.3. Photothermal therapy (PTT) Photothermal therapy (PTT) employs photoabsorbers to generate heat from light absorption, leading to thermal ablation of cancer cells. In recent years, PTT has emerged as an increasingly recognized alternative to classical cancer therapies such as surgery, radiotherapy, and chemotherapy. Various nanomaterials with high optical absorbance have been highly successful in this application. 6 1.4.4. Photodynamic therapy (PDT) Photodynamic therapy (PDT) is a clinical treatment that utilizes phototriggered chemical drugs (photosensitizers) to produce singlet oxygen (1O2) to kill tumors. Typical PDT treatments involve three components: the photosensitizer, the light source, and the oxygen within the tissue at the disease site. Under appropriate light excitation (generally in the visible range), the photosensitizer can be excited from a ground singlet state to an excited singlet state, which undergoes intersystem crossing to a longer-lived triplet state and then reacts with a nearby oxygen molecule to produce highly cytotoxic 1O2. PDT has been used for therapy in prostate, lung, head and neck, or skin cancers. However, conventional PDT is limited by the penetration depth of visible light needed for its activation. NIR light in the “window of optical transparency” (750-1100 nm) of tissue can penetrate significantly deeper into tissues than the visible light, because absorbance and light scattering for most body constituents are minimal in this range. Importantly, UCNPs can efficiently convert the deeply penetrating near-infrared light to visible wavelengths that can excite photosensitizer to produce cytotoxic 1O, promising their use in PDT treatment of pertinent located deeply tumors. 7 CHAPTER 2. EXPERIMENTAL TECHNIQUES 2.1. Synthesis of NaYF4: Yb3+, Er3+ nanophosphors by hydrothermal method NaYF4:Yb3+, Er3+ nanophosphors were prepared by hydrothermal method 2.2. The ways of the synthesis of NaYF4: Yb3+, Er3+ biomedical nanocomposite complexes To make NaYF4: Yb3+, Er3+ biomedical nanocomposite complexes, it is necessary to first treat the surface of the material, then the functionalization and conjugation of materials with biological agents. 2.2.1. Functionalization Bio-compatible property of the UCNPs requires a core shell structure to protect the luminescent materials and the cells involved. Besides that, the biolabels need to have specific property to target a specific tumor such as its surface have to have proper ligands that bind to the cells. 2.2.2. Method of surface functionalization and conjugation between upconversion luminescent nanomaterials and biological agents. Surface silanization (or silica coating) is an inorganic surface treatment strategy to make nanoparticles water-dispersible and biocompatible. Silica is known to be highly stable, biocompatible, and optically transparent. When utilized as a coating material, surface silanization methods can flexibly offer abundant functional groups (e.g., -COOH, -NH, -SH, etc.) and thus satisfy various needs of conjugation with biological molecules (e.g., folic acid, peptides, proteins, DNA, succinimid, biotin etc.). There are two types of related chemistry to coat silica onto the nanoparticles, depending on the polar nature of the capping ligands on the particle surface. One is the Stober method, which can be utilized to coat silica on hydrophilic UCNPs. Tetraethyl silicate (TEOS) is added to an excess of water containing a low molar-mass ethanol and ammonia, together with the hydrophilic UCNPs. A precise control of the amounts of involved reagents as well the pH value can lead to a uniform growth of silica onto the UCNPs. 2.3. The structure, morphology and luminescent properties of materials. The morphological observation and crystalline phase identification of all prepared samples were carried out by the way of using Field Emission Scanning Electron Microscopy (FESEM, Hitachi, S-4800), (TEM, S-4800-HITACHI và JEOL-1010) and X-ray diffraction (XRD, Siemens. The luminescent properties of studied samples were measured on high-resolution steady-state photoluminescent setup based on luminescence spectrum photometer system, MicroSPEC-2356 với Laser He-Cd. FTIR were measured on IMPACT-410, NICOLET. The microsized images of the specimens which from the virus infected cells exposure with the conjugates from nanomaterials have been viewed by a fluorescent microscopic equipment Olympus BX-40 (Japan). 8 CHAPTER 3. THE RESULTS OF SYNTHESIS AND INVESTIGATE CHARACTERIZATION OF NAYF4: Yb3+, Er3+ UPCONVERSION NANPPHOSPHORS 3.1. The synthesis of NaYF4: Yb3+, Er3+ upconversion nanophosphors 3.1.1. Synthesis process of NaYF4: Yb 3+, Er3+ upconversion nanophosphors (Process 1) Synthesis process of nano materials containing rare earth ions NaYF4: Yb3+, Er3+ (process 1) by hydrothermal method is shown in Figure 3.1. C2H5OH + PEG Solution NaOH Stir / 30 minutes Solution A Solution B Solution C Stir / 120 minutes Solution D Solution NaF Centrifuge, wash, dry Powder NaYF4: Yb 3+, Er3+ Y3+ : Yb3+: Er3+ (79,5: 20,0: 0,5) 190 oC/ 24 hours (200; 4000; 6000; 20000) Fig 3.1. Synthesis process of nano materials containing rare earth ions NaYF4:Yb 3+, Er3 (process 1) NaYF4: Yb3+, Er3+ samples were synthesized according to process 1 and listed in Table 3.1. Table 3.1. The list of NaYF4: Yb 3+, Er3+samples were synthesized according to process 1. No. Samples Y3+ (% mol) Yb3+ (% mol) Er3+ (% mol) 1 M1 79,00 20,50 0,5 2 M2 79,25 20,25 0,5 3 M3 79,50 20,00 0,5 4 M4 79,75 19,75 0,5 3.1.2. The results of Investigate of the structure and morphology of NaYF4: Yb 3+, Er3+ upconversion nanophosphors according to process 1. 3.1.2.1. XRD pattern of the nanophosphors of NaYF4: Yb 3+, Er3+ were synthesized according to process1. XRD pattern of the nanophosphors of NaYF4: Yb3+, Er3+ at 190 oC, 24 hours with different Yb3+/Y3+ ratios : M1 (20,5/79) - line 1; M2 (20,25/79,25) - line 2; M3 (20/79,5) - line 3 and M4 (19,75/79,75) - line 4 were synthesized according to procedure 1 presented in Figure 3.2 . 9 The phase structures of NaYF4:Yb3+, Er3+ nanophosphors were investigated by X-ray diffraction (XRD) and the results are showed in Fig. 3.2. In the XRD pattern of the sample, there are diffraction peaks at 2: 29.5o; 30.8o; 34.7o; 39.5o; 43.5o; 53.2o; 59.8o; 61.2o; 62.2o; 68.3o; 71o; 78.95o equal to hexagonal phase of NaYF4 (JCPDS card No. 28-1192); at 2: 28,3 o; 32,8 o; 46,9 o; 55,7 o; 58,4 ; 75,7o, 78,06 o and 87,50 o. equal to hexagonal phase of NaYF4 (JCPDS card No. 77-2042 of α – NaYF4 (cubic). We found that all measured peaks are belonging to this standard pattern. 20 40 60 (4) (3) (2) In te n s it y ( a .u ) 2- Theta (degree) (1) M1 (2) M2 (3) M3 (4) M4 Cubic NaYF4 Hex NaYF4 (1) Fig 3.2. XRD pattern of the nanophosphors of NaYF4: Yb 3+, Er3+ at 190 oC, 24 hours with different Yb3+/Y3+ ratios: M1 (20,5/79); M2 (20,25/79,25); M3 (20/79,5) và M4 (19,75/79,75) 3.1.2.2. The morphology of NaYF4: Yb 3+, Er3+ were synthesized according to process 1 FESEM images of the nanophosphors of NaYF4: Yb3+, Er3+ with different Yb3+/Y3+ ratios 20,5/79 (M1); 20,25/ 79,25 (M2); 20,0/79,5 (M3); 19,75/ 79,75 (M4) were presented in Figure 3. 3. The results showed that all samples were in the form of square blocks with dimensions of about 100 nm 300 nm. Fig. 3.3. FESEM images of the nanophosphors of NaYF4: Yb 3+, Er3+ with different Yb3+/Y3+ ratios 20,5/79 (M1); 20,25/ 79,25 (M2); 20,0/79,5 (M3); 19,75/ 79,75 (M4) 3.1.2.3. The upconversion luminescence (UCL) spectra of NaYF4: Yb 3+, Er3+ were synthesized according to process 1. Combining morphological and structural studies, we continue to investigate the luminescent properties of NaYF4: Yb3+, Er3+ samples through upconversion luminescence (UCL) spectra. M1 M2 M3 M4 10 The results of The upconversion luminescence (UCL) spectra analysis in Figure 3.4 show that when excited at 980 nm, all samples have a fluorescence effect that converts in reverse with blue at wavelengths (510 nm ÷ 570 nm) and red at wavelengths (630 nm ÷ 700 nm) corresponding to 2H11/2 → 4I15/2; 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 of Er3+ ions. Thus, from the results of the upconversion luminescence (UCL) spectra, the red zone emission of the M3 sample (NaYF4: Yb3+, Er3+ with molar ratio Yb3+ / Y3+ = 20.0 / 79.5 is dominant). 500 550 600 650 700 750 4 F 9 /2 - 4 I 1 5 /2 4 S 3 /2 - 4 I 1 5 /2 M3 M4 M2I n d e n s it y ( a .u ) Wavelength (nm) M1 M2 M3 M4 M1 2 H 1 1 /2 - 4 I 1 5 /2 Fig 3.4. The upconversion luminescence (UCL) spectra of the nanophosphors of NaYF4: Yb 3+, Er3+ with different Yb3+/Y3+ ratios: 20,5/79 (M1); 20,25/ 79,25 (M2); 20,0/79,5 (M3) and 19,75/ 79,75 (M4) under NIR laser excitation at 980 nm Schematic diagram of energy, radiation and non-radiation processes of Yb3+/ Er3+codoped materials were shown in Figure 3.5. Fig. 3.5. Schematic diagram of energy, radiation and non-radiation processes of Yb3+/Er3+codoped materials 3.2. The synthesis of NaYF4: Yb 3+, Er3+ upconversion nanophosphors assisted soft template PEG 3.2.1. Synthesis process of NaYF4: Yb 3+, Er3+ upconversion nanophosphors assisted soft template PEG Synthesis process of NaYF4: Yb3+, Er3+ upconversion nanophosphors assisted soft template PEG is shown in Figure 3.7. 11 C2H5OH + PEG Solution NaOH Stir / 30 minutes Solution A Solution B Solution C Stir / 120 minutes Solution D Solution NaF Centrifuge, wash, dry Powder NaYF4: Yb 3+, Er3+ Y3+ : Yb3+: Er3+ (79,5: 20,0: 0,5) 190 oC/ 24 hours (200; 4000; 6000; 20000) Fig 3.7. Synthesis process of NaYF4: Yb 3+, Er3+nanomaterials assisted soft template PEG NaYF4: Yb3+, Er3+ - PEG samples were synthesized according to process 1 and listed in Table 3.4. Table 3.4. The list of NaYF4: Yb 3+, Er3+ (Y3+/ Yb3+/ Er3+ = 79,5/ 20/ 0,5) with PEG =200; 4000; 6000; 20000 were synthesized according to procedure 1. No. Sample % Y3+ % Yb3+ % Er3+ MPE G 1 M3 79,5 0 20 0,5 2 MP2 79,5 0 20 0,5 200 3 MP4 79,5 0 20 0,5 400 0 4 MP6 79,5 0 20 0,5 600 0 5 MP20 79,5 0 20 0,5 200 00 3.2.2. The results of Investigate of the structure and morphology of NaYF4: Yb 3+, Er3+ - PEG 3.2.2.1. XRD pattern of the nanophosphors of NaYF4: Yb 3+, Er3+ - PEG 12 30 40 50 60 70 (5) (4) (3) (2) In te n s it y ( a .u ) 2-Theta (degree) (1) M3 (2) MP2 (3) MP4 (4) MP6 (5) MP20 Cubic-NaYF 4 Hexa-NaYF 4 (1) Fig 3.8. XRD pattern of the nanophosphors of NaYF4: Yb 3+, Er3+ at 190 oC, 24 hours (M1 - line 1) , NaYF4:Yb 3+, Er3+ - PEG 200 (MP2 - line 2); PEG 4000 (MP4 - line 3); PEG 6000 (MP6 - line 4); PEG 20000 (MP20 - line 5) NaYF4: Yb3+, Er3+ assisted soft template PEG with NaYF4: Yb3+, Er3+ at 190 oC, 24 hours (M1 - line 1), NaYF4:Yb3+, Er3+ - PEG 200 (MP2 - line 2); PEG 4000 (MP4 - line 3); PEG 6000 (MP6 - line 4); PEG 20000 (MP20 - line 5) are showed in Fig. 3.8. The analysis results on the X-ray diffraction diagram in Figure 3.10 show the phase structure of M3 (line 1), MP2 (line 2), MP4 (line 3), MP6 (line 4) and MP20 (line 5) models. ) still has a two-phase mixed structure α, -NaYF4. The diffraction peaks on the diagram are all sharp to show that the samples are crystallized. This proves that the presence of PEG in the sample does not change the phase structure of the material. 3.2.2.2. FESEM images of the nanophosphors of NaYF4: Yb 3+, Er3+ - PEG After investigating the structure of the material, we continue to investigate the effect of PEG on the morphology of NaYF4 materials: Yb3+, Er3+ (Figures 3.11 and 3.12). Fig 3.9. FESEM images of the nanophosphors of NaYF4: Yb 3+, Er3+ - PEG 200 (a) and PEG 4000 (b) FESEM image in Figure 3.9 of the MP2, MP4 samples and Figure 3.10 of the MP6 and MP20 samples show that the samples are still in the square shape with the size of about 100 nm ÷ 300 nm. This proves that the presence of soft-forming agent PEG does not change the morphology of the material. (a) (b) 13 Fig. 3.10. FESEM images of the nanophosphors of NaYF4: Yb 3+, Er3+ - PEG 6000 (a) and PEG 20000 (b) 3.2.3. The luminescent properties of the nanophosphors of NaYF4: Yb 3+, Er3+ - PEG Under NIR laser excitation at 980 nm, the upconversion luminescence (UCL) spectra of NaYF4: Yb3+, Er3+ - PEG were shown in Figure 3.11. Observing the spectra on the samples MP2, MP4, MP6, MP20 all appear emission peaks in the region with wavelength from 400  700 nm. The emission peaks wavelength range from 510  570 nm and from 630  700 nm, corresponding to 2H11/2 → 4I15/2; (520nm), 4S3/2 → 4I15/2 (540nm) and 4F9/2 → 4I15/2 (650nm) of Er3+ ions. 500 550 600 650 700 750 4 F 9 /2 - 4 I 1 5 /2 4 S 3 /2 - 4 I 1 5 /2 (2)(1) (3) In te n s it y ( a .u ) Wavelength (nm) (1) MP2 (2) MP4 (3) MP6 (4) MP20 (4) 2 H 1 1 /2 - 4 I 1 5 /2 λexc = 980 nm Fig 3.11. The upconversion luminescence (UCL) spectra of the nanophosphors of NaYF4: Yb 3+, Er3+- PEG 200 (MP2 - line 1); PEG 4000 (MP4 - line 2); PEG 6000 (MP6 - line 3) and PEG 20000 (MP20 - line 4) under NIR laser excitation at 980 nm. Observing the emission peaks between the red and blue regions shows that the red zone emission is more dominant, especially the emission intensity of NaYF4:Yb3+, Er3+ - PEG 20000 emitting red is much higher than intensity NaYF4: Yb3+, Er3+ - PEG nanomaterial emissions have low molecular weight under NIR laser excitation at 980 nm. The β-NaYF4 hexagonal structure material has the ability to luminesce reverse conversion about 10 times larger than the -NaYF4 form. In order to synthesize materials with hexagonal structure β-NaYF4, a number of factors can be changed such as reaction time, annealing temperature, concentration of sensitizers, luminescent center concentration, pH, etc. In the thesis, in order to synthesize materials with the desired β- (a) 14 NaYF4 hexagonal structure, we have changed the order of creating NaYF4 matrices in the process of material synthesis. 3.3. The synthesis of NaYF4: Yb3+, Er3+ upconversion nanophosphors with NaYF4 matrices order change. 3.3.1. Synthesis process of NaYF4: Yb 3+, Er3+ upconversion nanophosphors with NaYF4 matrices order change (process 2) Table 3.5. The list of NaYF4: Yb 3+, Er3+samples were synthesized according to process 2 No. Samples % Y3+ % Yb3+ % Er3+ MPEG 1 EY1 79,75 20,0 0,25 20.000 2 EY2 79,50 20,0 0,50 20.000 3 EY3 79,00 20,0 1,00 20.000 4 EY4 78,00 20,0 2,00 20.000 NaYF4: Yb3+, Er3+ - PEG 20000 samples were synthesized according to process 2 (Fig 3.13) was listed in Table 3.5 C2H5OH + PEG Y3+ + NaF SolutionNaOH Stir / 30 minutes Solution A Solution B Solution C Stir / 120 minutes SolutionD Centrifuge, wash, dry Powder NaYF4: Yb 3+, Er3+ Solution RE3+ (Yb3+ + Er3+) 190 oC/ 24 hours Fig 3.13. Synthesis process of nanomaterials containing rare earth ions NaYF4: Yb 3+, Er3+ with NaYF4 matrices order change (Process 2) 3.3.2. The result of Investigate of the structure and morphology of NaYF4: Yb 3+, Er3+ upconversion luminescent nanomaterials according to process 2 3.3.2.1. XRD pattern of the nanophosphors of NaYF4: Yb 3+, Er3+ were synthesized according to process 2. 15 The results of XRD diagram analysis of EY2 sample presented in Figure 3.14 show at the 2 angles: 17,1  ; 29,9 ; 30,8 ; 34,7 ; 43,5 ; 46,5 ; 53,2 ; 55,3 ; 62,3 ; 71,03 ; 86,7 . There are diffraction peaks equivalent to the -NaYF4 hexagonal. The XRD schema results of the EY2 model match the results on the JCPDS standard card number 00-028-1192. In addition to the diffraction peaks of the  -NaYF4 phase, on the XDR diagram of the sample, no strange peaks were observed. This shows that NaYF4:Yb3+, Er3+ samples with PEG 20000 were synthesized according to the structured procedure 2 with the desired -NaYF4 phase structure. 30 40 50 60 70 In te n s it y ( a .u ) 2 - Theta (degree) EY2 Hexagonal NaYF 4 JCPDS No.28-1192 Fig 3.14. XRD pattern of the nanophosphors of NaYF4:Yb 3+, Er3+ - PEG20000 (EY2) at 190 oC, 24 hours synthesized according to process 2 We continue to investigate the effect of the molar ratio of Er3+ / Y3+ on the crystal structure of the synthesized samples according to process 2 (Fig 3.15). The results showed that, with the change of the molar ratio of Er3+/ Y3+, the samples still showed diffraction peaks equivalent to the -NaYF4 hexagonal phase structure, indicating that the molar ratio of Er3+/ Y3+ did not affect the structure crystal of material. 20 40 60 (4) (3) (2) In te n s it y ( a .u ) 2 - Theta (degree) (1) EY1 (2) EY2 (3) EY3 (4) EY4 Hex NaYF4 (1) Fig . 3.15: XRD pattern of the nanophosphors of NaYF4:Yb 3+, Er3+ - PEG20000 (EY2) at 190 oC, 24 hours with change of Er3+/ Y3+ ratio synthesized according to process 2 ( EY1 = 0,25/ 79,75; EY2 = 0,5/ 79,5; EY3 = 1,0/ 79,0; EY4 =2,0/ 78,0) Thus, changing the matricies order in the synthesis process obtained NaYF4: Yb3+, Er3+ materials with desired hexagonal structure  -NaYF4. 3.3.2.2. The morphology of NaYF4: Yb 3+, Er3+ has the structure of β-NaYF4 FE-SEM images of the nanophosphors were presented in Figure 3.17. The FE-SEM image of the NaYF4:Yb3+, Er3+ indicates that the nanorods have bundles shape with the lengths of rod about 300  800 nm and diameter of rod about 100  200 nm. 16 (a) (b) (c) (d) Fig. 3.17. FESEM images of the nanophosphors of EY1 (a), EY2 (b) , EY3 (c) và EY4 (d) with β-NaYF4 (synthesized according to process 2) 3.3.3. Luminescent properties of NaYF4:Yb 3+, Er3+ has the structure of β-NaYF4 Luminescent properties of NaYF4:Yb3+, Er3+-PEG has the structure of β-NaYF4 with change of Er3+/ Y3+ ratio were investigated. Fig.3.18 shows the upconversion luminescence (UCL) spectra of the samples EY1, EY2, EY3 and EY4. The results showed that the samples emitted blue and red areas corresponding to the transitions of Er3+, the red emission rate of EY2 was strongest (EY2 compared to EY1 is 1.53 times; compared to EY3 is 4.58 times). 450 500 550 600 650 700 750 2 H 1 1 /2 - 4 I 1 5 /2 4 F 9 /2 - 4 I 1 5 /2 4 S 3 /2 - 4 I 1 5 /2 (4) (3) (2) In te n s it y ( a .u ) Wavelength (nm) (1) EY1- 0,25% Er3+ (2) EY2 - 0,5% Er 3+ (3) EY3 - 1,0% Er 3+ (4) EY4 - 2,0% Er 3+ (1) Fig 3.18. The upconversion luminescence (UCL) spectra of the nanophosphors of NaYF4:Yb 3+, Er3+ with change of Er3+/ Y3+ ratio synthesized according to process 2, under NIR laser excitation at 980 nm 17 CHAPTER 4. THE RESULT OF SYNTHESIS AND APPLICATION OF UPCONVERSION NANPPHOSPHORS CONTAINING RARE EARTH IONS FOR MARKING, IDENTIFICATION BREAST CANCER CELLS MCF7 4.1. Surface treatment, functionalization and conjugation of NaYF4 materials containing Yb3+ and Er3+ ions 4.1.1. Surface treatment of NaYF4 material containing Yb3+ and Er3+ ions with silica (TEOS: TetraEthylOcthorSilicate) Stir / 6 hours TEOS + C2H5OH Solution A NaYF4: Yb 3+, Er3+@NaYF4 + C2H5OH Solution B Powder NaYF4: Yb 3+, Er3+@NaYF4@silica Solution NaYF4:Yb 3+, Er3+ @NaYF4 @silica Centrifuge, wash, dry Stir /30 minutes Stir / 15 minutes CH3COOH + H2O Fig.4.1. Surface treatment process of NaYF4:Yb 3+, Er3+ with silica 4.1.2. Functionalization of NaYF4: Yb 3+, Er3+@silica with APTMS NaYF4: Yb 3+, Er3+@NaYF4@silica + C2H5OH + H2O APTMS + C2H5OH Solution 1 Solution 2 Mixture Stir/ 20 minutesStir/ 20 minutes NaYF4: Yb 3+, Er3+@NaYF4@silica-NH2 Centrifuge, wash Stir / 12 hours APTMS (3-aminopropyltrimethoxysilane) NaYF4: Yb 3+, Er3+@NaYF4@silica-NH2 NaYF4: Yb 3+, Er3+@NaYF4@silica Hydrolysis Silanol condensation Fig. 4.2. Functionalization process of NaYF4: Yb 3+, Er3+@silica with APTMS Fig. 4.3. Reaction