Nghiên cứu chế tạo và so sánh đặc trưng nhạy khí giữa sợi nano ZnOSnO2 và zno sno2

MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY - PHAN HONG PHUOC COMPARATIVE STUDY OF GAS SENSING PROPERTIES BETWEEN ZnO/SnO2 AND ZnO-SnO2 NANOFIBERS NGHIÊN CỨU CHẾ TẠO VÀ SO SÁNH ĐẶC TRƯNG NHẠY KHÍ GIỮA SỢI NANO ZnO/SnO2 VÀ ZnO-SnO2 MASTER THESIS MATERIAL SCIENCE Hanoi - 2019 MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY - PHAN HONG PHUOC COMPARATIVE STUDY OF GAS SENSING PROPERTIES BETWEEN ZnO/SnO2 AND ZnO-SnO2 NANOFIBERS NGHIÊN CỨU CHẾ TẠO VÀ SO SÁNH ĐẶC TRƯNG NHẠY KHÍ GIỮA SỢI NANO ZnO/SnO2 VÀ ZnO-SnO2 Major: Material Science MASTER THESIS MATERIAL SCIENCE SUPERVISOR Associate professor Ph.D Nguyen Van Duy Hanoi - 2019 CỘNG HÒA XÃ HỘI CHỦ NGHĨA VIỆT NAM Độc lập – Tự – Hạnh phúc BẢN XÁC NHẬN CHỈNH SỬA LUẬN VĂN THẠC SĨ Họ tên tác giả luận văn: Phan Hồng Phước Đề tài luận văn: Nghiên cứu chế tạo so sánh đặc trưng nhạy khí sợi nano ZnO/SnO2 ZnO-SnO2 Chuyên ngành: Khoa học Kỹ thuật vật liệu Mã số SV: CB170310 Tác giả, người hướng dẫn khoa học Hội đồng chấm luận văn xác nhận tác giả sửa chữa, bổ sung luận văn theo biên họp Hội đồng ngày 30 tháng 10 năm 2019 với nội dung sau: - Tên đề tài luận văn chỉnh sửa từ “Nghiên cứu chế tạo sợi nano tổ hợp phương pháp phun tĩnh điện ứng dụng cho cảm biến khí” thành: “Nghiên cứu chế tạo so sánh đặc trưng nhạy khí sợi nano ZnO/SnO ZnO-SnO2” Tên tiếng anh: “Comparative gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers” - Tác giả chỉnh sửa cách diễn đạt, bình luận, đánh giá kích thước hạt đo SEM tính qua cơng thức Debye-Scherrer (trang 32) - Tác giả chỉnh sửa thích hình 1.5, 1.8, độ phân giải hình 3.6 c d - Tác giả xếp bảng kí hiệu viết tắt theo thứ tự abc bổ sung thêm số từ viết tắt PVP, TGA, DTG - Tác giả bổ sung thêm số kết vào phần introduction Hà Nội, ngày 12 tháng 11 năm 2019 Giáo viên hướng dẫn Tác giả luận văn PGS TS Nguyễn Văn Duy Phan Hồng Phước CHỦ TỊCH HỘI ĐỒNG PGS TS Nguyễn Phúc Dương Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers ACKNOWLEDGMENTS I would like to take this opportunity to express my gratitude to all persons who have given me their invaluable support and assistance I am profoundly grateful to Professor Ph.D Nguyen Van Hieu, Associate professor Ph.D Nguyen Van Duy, Associate professor Ph.D Nguyen Duc Hoa, Ph.D Chu Manh Hung for their scientific advice and insightful discussions I would like to thank Associate professor Ph.D Pham Anh Son (HUS-VNU), MSc Ta Ngoc Bach (VAST), MSc Nguyen Quang Hoa (HUS-VNU), MSc Pham Thi Nga (HUS-VNU) for their help in material characterization analysis I am very grateful to my colleague, Ph.D student Nguyen Van Hoang, who has dedicated so much time in helping me during all the time I my thesis I would like to say great thanks to my classmate, MSc student Tran Thi Mai Phuong who was giving me a lot of supports in two years I am doing my Master's degree at ITIMS Finally, but not least, I am deeply thankful to my family, my parents, for their love and encouragement I am heavily indebted to my younger brother and my maternal grandmother who passed away while I have to live far from home to this thesis Dedicated to the memory of my younger brother and my maternal grandfather, who have always believed in my ability to be successful in the academic arena You are gone but your belief in me has made this journey possible I love you so much Hanoi, 30th September 2019 Phan Hong Phuoc PHAN HONG PHUOC i ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers COMMITTAL IN THE THESIS I confirm that this thesis is the result of my personal research and is solely my own work under the guidance of Associate professor Ph.D Nguyen Van Duy I declare that my scientific results are righteous I have responsibilities for my research results in this thesis Author Phan Hong Phuoc PHAN HONG PHUOC ii ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers TABLE OF CONTENTS ACKNOWLEDGMENTS i COMMITTAL IN THE THESIS ii TABLE OF CONTENTS iii List of Abbreviations v List of Figures vi List of Tables ix INTRODUCTION .1 Object for study Research objective Research method Organization of the Thesis Chapter LITERATURE REVIEW 1.1 Metal oxide semiconductor gas sensors 1.1.1 Gas sensors construction 1.1.2 Gas-sensing mechanisms 1.2 Nanofibers for gas sensors .7 1.2.1 Fabrication of nanofibers 1.2.2 Gas sensing mechanisms of nanofibers 10 1.2.3 Review of composite nanofibers for gas sensors 11 1.3 Effect of hetero-junction between ZnO and SnO2 nanofibers on gas sensing properties 13 1.3.1 Zinc oxide and Tin oxide properties .13 PHAN HONG PHUOC iii ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers 1.3.2 1.4 Hetero-junction between ZnO and SnO2 in gas sensing .15 Research orientation 17 Chapter EXPERIMENTAL 18 2.1 Chemicals preparation 18 2.2 Nanofibers synthesis 18 2.2.1 Preparation of the precursor solution for electrospinning 18 2.2.2 Electrospinning process 19 2.3 Material characterization .22 2.4 Gas sensing measurements 22 Chapter RESULTS AND DISCUSSIONS 25 3.1 Materials characterization 25 3.1.1 Thermogravimetric analysis 25 3.1.2 Morphological observation of nanofibers .26 3.1.3 Compositional and crystal properties of the nanofibers .29 3.2 Gas sensing properties of the nanofibers .34 3.2.1 H2S sensing results 34 3.2.2 NO2 sensing results .39 3.3 Gas sensing mechanisms .41 CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK .46 LIST OF PUBLICATIONS 47 REFERENCES 48 APPENDIX .56 PHAN HONG PHUOC iv ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers List of Abbreviations No Abbreviation Meaning 1D One-dimensional EDX Energy Dispersive X-ray Spectroscopy FESEM Field Emission Scanning Electron Microscopy HRTEM High-Resolution Transmission Electron Microscopy JCPDS Joint Committee on Powder Diffraction Standards MOS Metal Oxide Semiconductors NFs Nanofibers ppm Parts per million PVP Polyvinylpyrrolidone 10 Ra The resistances in the air 11 Rg The resistances in the gas 12 S Gas response 13 TG-DTA Thermal gravimetric and differential thermal analysis 14 resp Response time 15 recv Recovery time 16 XRD X-Ray Diffraction PHAN HONG PHUOC v ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers List of Figures Figure 1-1 The scheme of a typical resitive sensor system Figure 1-2 Band bending at an n-type semiconductor surface due to oxygen absorbtion [23] .5 Figure 1-3 The schematic of the on-chip fabrication of NF sensors by electrospinning [34] .7 Figure 1-4 The schematic illustration of the effect of increasing the surface charge on drop deformation [36] .8 Figure 1-5 (a) The schematic diagram of the path of an electrospinning jet (b) The schematic illustration of the Earnshaw instability leading to bending of an electrified jet [41],[43] Figure 1-6 The schematic of the gas-sensing mechanism of NFs: (a) in air, and (b) in H2S gas [46] .10 Figure 1-7 (a) SEM images of SnO2/In2O3 hetero-NFs, (b) Gas responses of SnO2, In2O3 and SnO2/In2O3 sensors to 10 ppm formaldehyde as a function of operating temperature [13] 11 Figure 1-8 (a) SEM images of SnO2-ZnO NFs (the inset shows the corresponding high magnification images), and (b) Comparison the gas response of ZnO, SnO2ZnO and SnO2 NFs to 100 ppm ethanol at different operating temperatures (200 °C - 400 °C) [9] 12 Figure 1-9 ZnO unit cell with wurtzite structure [49] 13 Figure 1-10 Bulk structures of the SnO2 polymorphs (gray and red colors represent Sn and O atoms, respectively) [57] 14 Figure 1-11 The schematic diagrams of the energy band structure of ZnO and SnO2: (a) before contact, and (b) after-contact 16 PHAN HONG PHUOC vi ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers Table 3-2 Properties of several gas molecules [80], [81] Gas type H2S NO2 NH3 H2 CO Bond H-SH NO-O H-NH2 H-H C-O Bond energy (kJ/mol) 381 305 435 436 1076 PHAN HONG PHUOC 45 ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK  In summary, two types of the composite structure of ZnO-SnO2 NFs and ZnO/SnO2 NFs, as well as pure ZnO NFs and SnO2 NFs were successfully synthesized through facile on-chip electrospinning method  The gas sensing characteristic of NF sensors was investigated carefully towards reducing H2S gas and oxidizing NO2 gas Highly sensitive result of NF sensors were explained by two main combined factors including the modulation of the resistance along with the surface depletion layer and the grain boundaries  The results displayed that the composite NFs with different structures of ZnO-SnO2 NFs and ZnO/SnO2 NFs exhibited higher sensitivity compared to that of pure ZnO NFs and SnO2 NFs, in which, the ZnO-SnO2 NFs indicated the highest sensitivity towards reducing H2S gas and NO2 gas at all operating temperatures from 250 °C - 450 °C Moreover, the ZnO-SnO2 NFs showed the fastest response  Overall, the finding demonstrates that the high response of fibers is mainly governed by potential barriers at the intergranular contact in NFs (internal-junction)  Since the gas sensing mechanisms of n-type MOS and p-type MOS are somewhat contradictory The p-type composite NFs with two structures need to be prepared and investigated to comparare the effects of internal-junction and externaljunction on their gas sensing performance PHAN HONG PHUOC 46 ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers LIST OF PUBLICATIONS [1] Phan Hong Phuoc, Chu Manh Hung, Nguyen Van Toan, Nguyen Van Duy, Nguyen Duc Hoa, and Nguyen Van Hieu, “One-step fabrication of SnO2 porous nanofiber gas sensors for sub-ppm H2S detection”, Sensors & Actuators: A Physical, 2019 [2] Phan Hong Phuoc, Nguyen Van Duy, Chu Manh 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properties between ZnO/SnO2 and ZnO-SnO2 nanofibers (a) (b) 100 ZnO/SnO2 NFs H2S@250oC&1ppm H2S@300oC&1ppm o 0.1 H2S@350 C&1ppm Resistance (MW) Resistance (MW) 10 10 ZnO-SnO2 NFs H2S@250oC&1ppm H2S@300oC&1ppm H2S@350oC&1ppm 0.1 o H2S@400oC&1ppm H2S@400 C&1ppm o H2S@450 C&1ppm 0.01 500 1000 1500 H2S@450oC&1ppm 0.01 2000 500 10 SnO2 NFs o H2S@250 C&1ppm o H2S@300 C&1ppm o H2S@350 C&1ppm o H2S@400 C&1ppm Resistance (MW) Resistance (MW) (c) 0.1 1000 1500 2000 Temperature (oC) Time (s) (d) ZnO NFs H2S@250oC&1ppm 0.1 H2S@300oC&1ppm H2S@350oC&1ppm 0.01 H2S@400oC&1ppm o H2S@450oC&1ppm H2S@450 C&1ppm 0.001 200 400 600 800 Time (s) 200 400 600 800 Time (s) Figure A2 Dynamic response of the (a) ZnO/SnO2 NFs, (b) ZnO-SnO2 NFs, (c) ZnO NFs, and (d) SnO2 NFs toward ppm H2S gas at various operating temperatures PHAN HONG PHUOC 57 ITIMS 2017-2019 Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers NO2@10ppm&450oC 10 ppm NO2@10ppm&350oC NO2@10ppm&300oC NO2@10ppm&250oC 10 ZnO/SnO2 NFs (a) Response (Ra/Rg) 100 Resistance (MW) 1000 NO2@10ppm&400oC NO2@10ppm&450oC 10 ppm NO2@10ppm&400oC NO2@10ppm&350oC NO2@10ppm&300oC 100 NO2@10ppm&250oC ZnO-SnO2 NFs (b) 10 100 200 300 400 100 200 Time (s) 100 NO2@10ppm&450oC 10 ppm 300 600 NO2@10ppm&450oC 10 ppm NO2@10ppm&400oC o NO2@10ppm&350oC NO2@10ppm&350 C o NO2@10ppm&300 C o NO2@10ppm&250 C SnO2 nanofibers (c) Resistance (MW) Response (Rg/Ra) 500 o NO2@10ppm&400 C 10 400 Time (s) NO2@10ppm&300oC 10 NO2@10ppm&250oC ZnO nanofibers (d) 1 200 400 600 800 Time (s) 200 400 600 800 Time (s) Figure A3 Dynamic response of the (a) ZnO/SnO2 NFs, (b) ZnO-SnO2 NFs, (c) SnO2 NFs, and (d) ZnO NFs toward 10 ppm NO2 gas at various operating temperatures PHAN HONG PHUOC 58 ITIMS 2017-2019 CO@350 oC &200 ppm H2@350 oC &250 ppm 100 Response (Ra/Rg or Rg/Ra) Response (Ra/Rg or Rg/Ra) Comparative study of gas sensing properties between ZnO/SnO2 and ZnO-SnO2 nanofibers NH3@350 oC & 250 ppm NO2@350 oC &5 ppm H2S@350 oC &1 ppm 10 ZnO/SnO2 nanofibers (a) CO@350 oC &200 ppm H2@350 oC &250 ppm NH3@350 oC & 250 ppm 100 NO2@350 oC &5 ppm H2S@350 oC &1 ppm 10 ZnO-SnO2 nanofibers (b) 200 400 600 800 100 200 CO@350 oC &200 ppm H2@350 oC &250 ppm NH3@350 oC & 250 ppm NO2@350 oC &5 ppm H2S@350 oC &1 ppm 10 300 400 500 600 700 Time (s) Response (Ra/Rg or Rg/Ra) Response (Ra/Rg or Rg/Ra) Time (s) SnO2 nanofibers (c) CO@350 oC &200 ppm H2@350 oC &250 ppm 100 NH3@350 oC & 250 ppm NO2@350 oC &5 ppm H2S@350 oC &1 ppm 10 ZnO nanofibers (d) 1 100 200 300 400 500 Time (s) 100 200 300 400 500 Time (s) Figure A4 Dynamic response of (a) ZnO/SnO2 NFs, (b) ZnO-SnO2 NFs, (c) SnO2 NFs, and (d) ZnO NFs to 200 ppm CO, 250 ppm H2, 250 ppm NH3, ppm NO2, and ppm H2S at 350 °C PHAN HONG PHUOC 59 ITIMS 2017-2019 ... BETWEEN ZnO/ SnO2 AND ZnO- SnO2 NANOFIBERS NGHIÊN CỨU CHẾ TẠO VÀ SO SÁNH ĐẶC TRƯNG NHẠY KHÍ GIỮA SỢI NANO ZnO/ SnO2 VÀ ZnO- SnO2 Major: Material Science MASTER THESIS MATERIAL SCIENCE SUPERVISOR Associate... chỉnh sửa từ ? ?Nghiên cứu chế tạo sợi nano tổ hợp phương pháp phun tĩnh điện ứng dụng cho cảm biến khí? ?? thành: ? ?Nghiên cứu chế tạo so sánh đặc trưng nhạy khí sợi nano ZnO/ SnO ZnO- SnO2? ?? Tên tiếng... to 450 °C ZnO- SnO2 nanofibers ZnO/ SnO2 nanofibers ZnO nanofibers SnO2 nanofibers H2S @ ppm resp (s) 50 40 30 (a) 20 1600 ZnO- SnO2 nanofibers ZnO/ SnO2 nanofibers ZnO nanofibers SnO2 nanofibers