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 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 THESIS OF THE MASTER TABLE OF CONTENTS STUDENT DECLARATION ACKNOWLEDGMENTS .4 LIST OF SYMBOLS AND SHORTENED WORDS LIST OF FIGURES 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 THESIS OF THE MASTER 3.2.3 Chemical bonding analysis, FTIR 34 3.2.4 Optical properties 35 3.2.5 Electrochemical properties 36 REFERENCES 39 THESIS OF THE MASTER LIST OF SYMBOLS AND SHORTENED WORDS N.O Shortened words Full words NMs Nanomaterials CSP Core-shell polymer NPs Nanoparticles NRs Nanorods CV Cyclic voltametry THESIS OF THE MASTER LIST OF FIGURES N.O Name of Figures Page Figure 1.1 Crystal structure of cerium (IV) oxide 12 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 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 Figure 1.4 Core – shell particle 15 Figure 1.5 Core–shell polymers (CSPs) 16 Figure 1.6 The common methods to prepare CSPs 19 Figure 2.1 The energy-dispersive x-ray spectrometry EDS 25 system Integrated in the scanning electron microscopy (SEM), JEOL JSM-7600F (USA) Figure 2.2 Cyclic voltammetry of the sensor equipment 26 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); 29 THESIS OF THE MASTER 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 37 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 It is clearly seen that the lower the concentration of CeO2 is, the lower the width of CeO2 nanorods being collected In figure 3.2 (a, b), the CeO2 nanorods which were collected by using 0.1M; 0.02M and 0.01M precusor concentrations are quite big and short with about 0.5-1 µm width and µm length When the precusor concentration was decreased to 0.005M and 0.0025M, there was a slight decline in the width of CeO2 nanorods (about 100-200 nm) while the length of them rose significantly 3.1.1.3 Effect of reaction time Figure 3.3 FE-SEM images of the CeO2 materials 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) 31 THESIS OF THE MASTER Figure 3.3 witnessed the changes in morphology of CeO2 nanorods synthesized by hydrothermal method in different periods of time As it can see in Figure 3.3(a), the CeO2 nanorods were formed though the size was still big (more than 100 nm) and the length was quite short In Figure 3.3(b), when the reaction time was 1.5h, there were some nanorods being formed with smaller size but non-uniform The reaction time was increased to 2.5h and 3h, there were more CeO2 nanorods which had more uniform shape and higher length appeared as shown in figure 3.3(c,d) Figure 3.3(e,f) illustrated the reduction in the width of CeO2 nanorod (about 30-70 nm) when the reaction time was risen to 6h and 9h We continued to rise the reaction time to 12h, the nanorods that was collected had quite uniform shape with 30 nm width and several micrometres length as shown in Figure 3.3(g) 3.2 Synthesizing CeO2/PPy core-shell nanocomposites 3.2.1 Microstructure characterization The morphology the CeO2 nanorods, pure PPy and CeO2/PPy core-shells nanohybrid samples was investigated by FE- SEM and TEM as presented in Fig 3.4 Fig 3.4 (a) showed the FE-SEM images of the CeO2 NRs, which has uniform rodlike structure This can be also seen clearly rod-like morphology of CeO2 NRs in the TEM image as illustrated in Fig 3.4 (d) The diameters of these NRs are about 25-30 nm The Fig 3.4 (b) and (e) showed FE-SEM and TEM images of the pure PPy that showed the amorphous and aggregative structure like a cauliflower The morphology of core-shell nanostructured CeO2@Ppy indicated in Fig 3(c) and (f) It is clearly observed that Ppy nanoparticles are uniformly anchored on the surface of CeO2 NRs (Fig 3.4 (c) Moreover, the TEM image (Fig 3.4 (f)) also displays a quite uniform layer coats on surface of nanorods, which constructs a core-shell structure 32 THESIS OF THE MASTER Figure 3.4 FE-SEM and TEM images of the pristine CeO2 nanorods (a,d), pure Ppy (b,e) and core-shell CeO2NRs@Ppy (c,f) 3.2.2 Phase analysis The XRD patterns of the CeO2 nanorods, pure PPy, and the core-shells nanostructured CeO2NRs@PPy are shown in Fig 3.5 As indicated in Fig 3.5 (a), the diffraction peaks for CeO2 nanorods at 28.6, 33.1, 47.6, 56.5 are corresponded to the (111), (200), (220), (311) planes, which has cubic fluorite structure This is matched with the diffraction pattern of CeO2 indexed in the JCPD card No 34-0394 The XRD pattern of CeO2 nanorods shows the good crystalline nature of the prepared material Fig 3.5 (b) indicates X-ray diffraction pattern of the pure PPy, which is amorphous in nature because no peaks can be defined in the XRD pattern of pure PPy The X-ray diffraction pattern of core-shell nanostructured CeO2@Ppy is shown in Fig 3.5 (c) It has same profile as observed in the pure CeO2 nanorods, indicating that the crystal structure of CeO2 NRs was not modified by Ppy This result also confirm that polypyrrole is amorphous in the nanohybrid material When Ppy is absorbed on the 33 THESIS OF THE MASTER CeO2 nanorod, the diffraction peak intensity of the core-shell nanostructured CeO2@PPy decreased comparing to pristine CeO2 nanorods due to the CeO2 cores are encapsulated by the PPy shell Figure 3.5 XRD patterns of the pristine (a) CeO2 nanorods, (b) pure Ppy and (c) coreshell CeO2NRs@Ppy 3.2.3 Chemical bonding analysis, FTIR Fig 3.6 shows the FTIR spectra of (a)the pristine CeO2 nanorods, (b) pure Ppy and (c)core-shell CeO2 NRs@Ppy For CeO2 nanorods (Fig 3.6 (a)),the band at 521 cm1 is corresponding to Ce-O stretching vibration The band at 1635 cm-1 is attributed to the bending mode of hydroxyl group, which may be due to the presence of the moisture in the sample In the FTIR spectrum of pure polypyrrole exhibits a peak at 3427 cm-1corresponding to N-H stretching vibration in the pyrrole ring The bands at 1035 and 1299 cm1 areassociated with C-H deformation and C-N bonds Peak at 1385 cm-1 assisted C-N stretching The band at 1635 cm-1 is attributed to the bending mode of hydroxyl group 34 THESIS OF THE MASTER (Fig 3.6 (b)) The FTIR spectrum CeO2 NRs@Ppy has the same peaks as compared to the peaks of pure Ppy as indicated in Fig 3.6 (c) Additionally, it found peak at 1541 cm-1 to be associated with C-C stretching vibration in the pyrrole ring The peak at 780 cm-1 indicates the doping state of Ppy Beside, Ce-O stretching vibration was also found at 521 cm-1 This confirms that pyrrole was successfully coated onto CeO2 nanorods Figure 3.6 FTIR spectra of (a) the pristine CeO2 nanorods, (b) pure Ppy and (c) core-shell CeO2NRs@Ppy 3.2.4 Optical properties Figure 3.7 shows photoluminescence spectra (PL) of pure Ppy, pristine CeO2 nanorods and CeO2 NRs@Ppy monitoring at excitation wavelength of 350 nm at room temperature As shown in Fig 3.7, the pristine CeO2 NRs displays strong emission bands in the visible region around 356 nm correspond to the 5d1→4f1 transition for 35 THESIS OF THE MASTER Ce3+ ions [41] Without the presence of CeO2 NRs, pure Ppy exhibits very low signal of PL For CeO2 NRs@Ppy, the obtained results showed that PL intensity was decreased in comparision to pristine CeO2 NRs, which might due to interaction between Ppy shell and CeO2 NRs core In onther word, Ppy can reduce number of phonons which were absorbed by CeO2 NRs leading to decrease in recombination rate of excited electrons and holes Figure 3.7 Photoluminescence spectroscopy of (a) the pure Ppy, (b)pristine CeO2 NRs, and (c) core-shell CeO2NRs@Ppy 3.2.5 Electrochemical properties In order to study the electrochemical characteristic of the CeO2 NRs@Ppy modified-electrode, the cyclic voltammetry of CeO2 NRs@Ppy modified-electrode was recorded in PBS solution at a scan rate of 100mV/s versus an Ag/AgCl reference 36 THESIS OF THE MASTER electrode The electrochemical properties of pure Ppy and CeO2 nanorods were also studied for comparison The obtained results are illustrated in Fig 3.8 As presented in Fig 3.8 (a), no redox peak for pure Ppy modified-electrode was observed due to Ppy has low conducting However, anoxidation peak could be found at potential of 0.27V with the current obviously increased up to 25µA when electrode is modified with pristine CeO2 nanorods as illustrated in Fig 3.8 (b) An increase in the peak current up to 39µA and a separation of the potential of 0.3V were also observed for CeO2 NRs@Ppy modified-electrode, confirming that CeO2 NRs@Ppy modifiedelectrode has better electrochemical behavior than CeO2NRs modified-electrode Figure 3.8 Cyclic voltammetry plots of (a) pure Ppy, (b) CeO2 NRs and (c) CeO2 NRs@Ppy modified- electrode 37 THESIS OF THE MASTER CONCLUSION From all results above, there are some conclusions being given: The CeO2 nanorods were successful synthesized by hydrothermal method with approx 5µm of length and 30 nm of width at 170 oC for 12h with 0.0025M precusor concentration The core-shell nanostructured CeO2@Ppy was synthesized via in situ polymerization The obtained results showed that PPy was amorphous, while the CeO2 nanorods maintained their cubic crystal structure The characterization of TEM images indicates that the CeO2 nanorods were embedded in the Ppy shell forming the coreshell structure The electrochemical properties of core-shell material was also studied, which indicated CeO2 NRs@Ppy modified-electrode has better electrochemical behavior than that of CeO2 NRs modified-electrode Further research directions: - Optimizing the reaction conditions in order to synthesize the CeO2@Ppy coreshell nanomaterials - Using this materials for synthesizing DNA biosensor 38 THESIS OF THE MASTER REFERENCES [1] Clemens Burda, Xiaobo Chen, Radha Narayanan, and Mostafa A El-Sayed, “Chemistry and properties of nanocrystals of different shapes,” Chemical Reviews, vol 105, pp 1025-1102, 2005 [2] Salvatore Sortino, “Photoactivated 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, Phuong Dinh Tam , “Highly sensitive DNA sensors based on cerium oxide nanorods”, Journal of Physics and Chemistry of Solids, 115 (2018) 18–25 45 ... 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... Vƣợng, Vũ Văn Thú, Hoàng Lan, Đinh Văn Tuấn , Nguyễn Thị Thuỷ , Phƣơng Đình Tâm, Trần Trung, “NGHIÊN CỨU TỔNG HỢP MÀNG CeO2 BẰNG PHƢƠNG PHÁP ĐIỆN HÓA”, Proceeding of Workshop on advanced nanomaterials