Nghiên cứu chế tạo sợi nano αFe2O3 và ZnFe2O4 lai graphene khử từ ôxit graphene RGO bằng phương pháp phun tĩnh điện và ứng dụng cho cảm biến khí H2S

Nghiên cứu chế tạo sợi nano αFe2O3 và ZnFe2O4 lai graphene khử từ ôxit graphene RGO bằng phương pháp phun tĩnh điện và ứng dụng cho cảm biến khí H2S Nghiên cứu chế tạo sợi nano αFe2O3 và ZnFe2O4 lai graphene khử từ ôxit graphene RGO bằng phương pháp phun tĩnh điện và ứng dụng cho cảm biến khí H2S luận văn tốt nghiệp thạc sĩ

MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY Nguyen Van Hoang ELECTROSPINNING OF α-Fe2O3 AND ZnFe2O4 NANOFIBERS LOADED WITH REDUCED GRAPHENE OXIDE (RGO) FOR H2S GAS SENSING APPLICATION DOCTORAL DISSERTATION OF MATERIALS SCIENCE Hanoi – 2020 MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY Nguyen Van Hoang ELECTROSPINNING OF α-Fe2O3 AND ZnFe2O4 NANOFIBERS LOADED WITH REDUCED GRAPHENE OXIDE (RGO) FOR H2S GAS SENSING APPLICATION Major: Materials Science Code: 9440122 DOCTORAL DISSERTATION OF MATERIALS SCIENCE SUPERVISOR: PROF PhD NGUYEN VAN HIEU Hanoi – 2020 DECLARATION OF AUTHORSHIP This dissertation has been written in the basic of my researches carried out at Hanoi University of Science and Technology, under the supervision of Prof PhD Nguyen Van Hieu All the data and results in the thesis are true and were agreed to use in my thesis by co-authors The presented results have never been published by others Hanoi, 26th May 2020 Supervisor Prof PhD Nguyen Van Hieu PhD Student Nguyen Van Hoang ACKNOWLEDGMENTS First, I would like to express my deep gratitude to my supervisor, Prof Nguyen Van Hieu, for his devotion and inspiring supervision I would like to thank him for all his advice, support and encouragement throughout my postgraduate course I am grateful to Assoc Prof PhD Nguyen Duc Hoa, Assoc Prof PhD Nguyen Van Duy, PhD Dang Thi Thanh Le, PhD Chu Manh Hung, and PhD Nguyen Van Toan for their useful help, suggestions and comments I also would like to express my special thanks to PhD and Master Students at iSensors Group for their support and shared cozy working environment during my PhD course I am thankful to the leaders and staffs of International Training Institute for Materials Science (ITIMS), Graduate School for their help and given favorable working conditions I would like to thank my colleagues at Department of Materials Science and Engineering at Le Quy Don Technical University for their support during my PhD course I gratefully acknowledge the fund from Vietnam National Foundation for Science and Technology Development (NAFOSTED) under code 103.02-2017.25 and the 911 Scholarship of Ministry of Education and Training for the financial support for my research Last but not least, I am deeply thankful to my family for their endless love and unconditional support Without them, the work would have been impossible PhD Student Nguyen Van Hoang CONTENTS CONTENTS i ABBREVIATIONS AND SYMBOLS v LIST OF TABLES vii LIST OF FIGURES viii INTRODUCTION CHAPTER OVERVIEW ON SMO NFs AND THEIR LOADING WITH RGO FOR GAS-SENSING APPLICATION 1.1 Electrospinning for NFs fabrication 1.1.1 Background on electrospinning 1.1.2 Processing – structure relationships of electrospun NFs 1.2 NFs for gas-sensing application 10 1.2.1 Electrospun SMO NFs for gas-sensing application 10 1.2.2 Electrospun SMO NFs for H2S gas-sensing application 13 1.3 1.2.2.1 H2S gas 13 1.2.2.2 Electrospun SMO NFs for H2S gas-sensing application 13 NFs loading with RGO for gas-sensing application 14 1.3.1 Overview on RGO and its application in gas-sensing field 14 1.3.1.1 Overview on RGO 14 1.3.1.2 RGO in gas-sensing application 17 1.3.2 RGO-loaded SMO NFs in gas-sensing applications 19 1.3.2.1 RGO-loaded SMO gas sensor 19 1.3.2.2 RGO-loaded SMO NFs gas sensor 22 i 1.4 Gas-sensing mechanism 24 1.4.1 Gas-sensing mechanism of SMO NFs 24 1.4.2 Gas-sensing mechanism of RGO-loaded SMO NFs 25 1.4.3 H2S gas-sensing mechanism of SMO NFs and their loading with RGO… 27 Conclusion of chapter 28 CHAPTER EXPERIMENTAL APPROACH 29 2.1 Synthesis 29 2.1.1 RGO preparation 29 2.1.2 α-Fe2O3 NFs preparation 30 2.1.3 ZFO NFs preparation 31 2.1.4 Preparation of α-Fe2O3, ZFO NFs loading with RGO 32 2.2 Characterization Techniques 32 2.2.1 Raman spectroscopy 32 2.2.2 Thermal analysis 33 2.2.3 X-ray diffraction 33 2.2.4 SEM and EDX 34 2.2.5 TEM and SAED 34 2.3 Gas-sensing measurement 35 Conclusion of chapter 36 CHAPTER α-Fe2O3 NFs AND THEIR LOADING WITH RGO FOR H2S GASSENSING APPLICATION 37 3.1 Introduction 37 3.2 H2S gas sensors based on α-Fe2O3 NFs 39 3.2.1 Morphologies and structures of α-Fe2O3 NFs 39 ii 3.2.2 3.3 H2S gas-sensing properties of α-Fe2O3 NFs sensors 46 3.2.2.1 Effects of operating temperature 46 3.2.2.2 Effects of solution contents 48 3.2.2.3 Effects of annealing temperature and electrospinning time 50 3.2.2.4 Selectivity and stability 53 H2S gas sensors based on α-Fe2O3 NFs loaded with RGO 54 3.3.1 Morphologies and structures of α-Fe2O3 NFs loaded with RGO 54 3.3.2 H2S gas-sensing properties of RGO-loaded α-Fe2O3 NFs sensors 58 3.3.2.1 Effects of RGO contents 58 3.3.2.2 Effects of working temperature 61 3.3.2.3 Effects of annealing temperatures 62 3.3.2.4 Selectivity and stability 64 Conclusion of chapter 65 CHAPTER ZFO NFs AND THEIR LOADING WITH RGO FOR H2S GASSENSING APPLICATION 66 4.1 Introduction 66 4.2 H2S gas sensors based on ZFO NFs 68 4.2.1 Microstructure characterization 68 4.2.2 Gas-sensing properties 74 4.3 4.2.2.1 Effects of the operating temperature 74 4.2.2.2 Effects of the annealing temperature 76 4.2.2.3 Effects of annealing time and heating rate 79 4.2.2.4 Selectivity and stability 81 H2S gas sensors based on ZFO NFs loaded with RGO 82 4.3.1 Microstructure characterization 82 iii 4.3.2 Gas-sensing properties 86 4.3.2.1 Effects of RGO contents 86 4.3.2.2 Effects of operating temperature 88 4.3.2.3 Effects of annealing temperatures 89 4.3.2.4 Selectivity, stability and RH effects 91 Conclusion of chapter 94 CONCLUSIONS AND RECOMMENDATIONS 95 LIST OF PUBLICATIONS 97 REFERENCES 98 APPENDIX 117 iv ABBREVIATIONS AND SYMBOLS Meaning Abbreviations and symbols 1D 2D Two Dimension CVD Chemical Vapor Deposition DI Deionized Water DL Detection Limit DMF Dimethylformamide DTG Derivative Thermogravimetric EDX FE-SEM 10 FFT Energy Dispersive X-ray spectroscopy Field Emission Scanning Electron Microscope Fast Fourier Transform 11 GO Graphene Oxides 12 GP 13 HRTEM 14 IUPAC 15 JCPDS 16 NFs Graphene High Resolution Transmission Electron Microscope International Union of Pure and Applied Chemistry Joint Committee on Powder Diffraction Standards Nanofibers 17 NPs Nanoparticles 18 NRs Nanorods 19 NSs Nanosheets 20 NTs Nanotubes 21 NWs Nanowires 22 ppb Parts Per Billion 23 ppm Parts Per Million 24 PVA Poly(vinyl alcohol) 25 RGO Reduced Graphene Oxides 26 RH Ambient Relative Humidity 27 RT Room Temperature Number One Dimension v 28 SAED Selected Area Electron Diffraction 29 sccm Standard Cubic Centimeters Per Minute 30 SEM Scanning Electron Microscope 31 SMO Semiconductor Metal Oxides 32 TEM Transmission Electron Microscope 33 TGA Thermogravimetric Analysis 34 WF Work Function 35 XRD X-ray Diffraction 36 ZFO Zinc Ferrite, ZnFe2O4 37 Ra Sensor resistance in dry air 38 Rg Sensor resistance in tested gas 39 S Sensor Response 40 τres Response time 41 τrec Recovery time vi [109] S Abdolhosseinzadeh, H Asgharzadeh, and H Seop Kim (2015), “Fast and fully-scalable synthesis of reduced graphene oxide”, Sci Rep, Vol 5, pp 10160–10167 [110] A Abulizi, K Okitsu, and J J Zhu (2014), “Ultrasound assisted reduction of graphene oxide to graphene in l-ascorbic acid aqueous solutions: Kinetics and effects of various factors on the rate of graphene formation”, Ultrason Sonochem, Vol 21, pp 1174–1181 [111] M Iliut, C Leordean, V Canpean, C.-M Teodorescu, and S Astilean (2013), “A new green, ascorbic acid-assisted method for versatile synthesis of Augraphene hybrids as efficient surface-enhanced Raman scattering platforms”, J Mater Chem C, Vol 1, pp 4094–4104 [112] B Fultz and J Howe (2007), “Transmission Electron Microscopy and Diffractometry of Materials”, Springer [113] N Van Hieu, N Van Duy, P T Huy, and N D Chien (2008), “Inclusion of SWCNTs in Nb/Pt co-doped TiO2 thin-film sensor for ethanol vapor detection”, Phys E, Vol 40, pp 2950–2958 [114] N Van Hieu, L Thi, B Thuy, and N Duc (2008), “Highly sensitive thin film NH3 gas sensor operating at room temperature based on SnO2/ MWCNTs composite”, Sensors Actuators B Chem, Vol 129, pp 888–895 [115] L A Currie (1999), “Nomenclature in evaluation of analytical methods including detection and quantifiation capabilities (IUPAC Recommendations 1995)”, Anal Chim Acta, Vol 391, pp 105–126 [116] V Van Quang, N Van Dung, N Sy Trong, N Duc Hoa, N Van Duy, and N Van Hieu (2014), “Outstanding gas-sensing performance of graphene/SnO2 nanowire Schottky junctions”, Appl Phys Lett, Vol 105, pp 1–5 [117] L Liao, Z Zheng, B Yan, J X Zhang, H Gong, J C Li, C Liu, Z X Shen, and T Yu (2008), “Morphology controllable synthesis of α-Fe2O3 1D nanostructures: Growth mechanism and nanodevice based on single nanowire”, J Phys Chem C, Vol 112, pp 10784–10788 [118] S Liang, H Bi, J Ding, J Zhu, Q Han, and X Wang (2015), “Synthesis of α -Fe2O3 with the aid of graphene and its gas-sensing property to ethanol”, 109 Ceram Int, Vol 41, pp 6978–6984 [119] W Wu, Z Wu, T Yu, C Jiang, and W S Kim (2015), “Recent progress on magnetic iron oxide nanoparticles: Synthesis, surface functional strategies and biomedical applications”, Sci Technol Adv Mater, Vol 16, pp 023501– 023544 [120] A Mirzaei, K Janghorban, B Hashemi, M Bonyani, S Gianluca, and G Neri (2016), “A novel gas sensor based on Ag/Fe2O3 core-shell nanocomposites”, Ceram Int, Vol 42, pp 18974–18982 [121] L Guo, N Xie, C Wang, X Kou, M Ding, H Zhang, Y Sun, H Song, Y Wang, and G Lu (2018), “Enhanced hydrogen sulfide sensing properties of Pt-functionalized α-Fe2O3 nanowires prepared by one-step electrospinning”, Sensors Actuators, B Chem, Vol 255, pp 1015–1023 [122] O Landau, A Rothschild, and E Zussman (2009), “Processingmicrostructure-properties correlation of ultrasensitive gas sensors produced by electrospinning”, Chem Mater, Vol 21, pp 9–11 [123] V D Nguyen, T T Le Dang, D T Nguyen, N D Hoang, M H Nguyen, V D Nguyen, D H Nguyen, and V H Nguyen (2016), “CuO Nanofibers Prepared by Electrospinning for Gas Sensing Application: Effect of Copper Salt Concentration”, J Nanosci Nanotechnol, Vol 16, pp 7910–7918 [124] A Khalil, J J Kim, H L Tuller, G C Rutledge, and R Hashaikeh (2016), “Gas sensing behavior of electrospun nickel oxide nanofibers: Effect of morphology and microstructure”, Sensors Actuators, B Chem, Vol 227, pp 54–64 [125] T Senthil and S Anandhan (2014), “Structure-property relationship of solgel electrospun ZnO nanofibers developed for ammonia gas sensing”, J Colloid Interface Sci, Vol 432, pp 285–296 [126] Y Wang, Y Wang, J Cao, F Kong, H Xia, J Zhang, B Zhu, S Wang, and S Wu (2008), “Low-temperature H2S sensors based on Ag-doped a-Fe2O3 nanoparticles”, Sensors Actuators, B Chem, Vol 131, pp 183–189 [127] Z Li, Y Huang, S Zhang, W Chen, Z Kuang, D Ao, W Liu, and Y Fu (2015), “A fast response & recovery H2S gas sensor based on α-Fe2O3 110 nanoparticles with ppb level detection limit”, J Hazard Mater, Vol 300, pp 167–174 [128] Y Huang, W Chen, S Zhang, Z Kuang, D Ao, N R Alkurd, W Zhou, W Liu, W Shen, and Z Li (2015), “A high performance hydrogen sulfide gas sensor based on porous α-Fe2O3 operates at room-temperature”, Appl Surf Sci, Vol 351, pp 1025–1033 [129] S Liang, J Zhu, C Wang, S Yu, H Bi, X Liu, and X Wang (2014), “Fabrication of α-Fe2O3@graphene nanostructures for enhanced gas-sensing property to ethanol”, Appl Surf Sci, Vol 292, pp 278–284 [130] M Arias, V M Pantojas, O Perales, and W Otaño (2011), “Synthesis and characterization of magnetic diphase ZnFe2O4/γ-Fe2O3 electrospun fibers”, J Magn Magn Mater, Vol 323, pp 2109–2114 [131] J M Yang and F S Yen (2008), “Evolution of intermediate phases in the synthesis of zinc ferrite nanopowders prepared by the tartrate precursor method”, J Alloys Compd, Vol 450, pp 387–394 [132] H Shao, X Zhang, S Liu, F Chen, J Xu, and Y Feng (2011), “Preparation of pure iron nanofibers via electrospinning”, Mater Lett, Vol 65, pp 1775– 1777 [133] S W Choi, J Y Park, and S S Kim (2011), “Growth behavior of nanograins in NiO fibers”, Mater Chem Phys, Vol 127, pp 16–20 [134] Y Cheng, W Huang, Y Zhang, L Zhu, Y Liu, X Fan, and X Cao (2010), “Preparation of TiO2 hollow nanofibers by electrospining combined with sol– gel process”, CrystEngComm, Vol 12, pp 2256–2260 [135] X Yang, C Shao, H Guan, X Li, and J Gong (2004), “Preparation and characterization of ZnO nanofibers by using electrospun PVA/zinc acetate composite fiber as precursor”, Inorg Chem Commun, Vol 7, pp 176–178 [136] M W Ahn, K S Park, J H Heo, D W Kim, K J Choi, and J G Park (2009), “On-chip fabrication of ZnO-nanowire gas sensor with high gas sensitivity” , Sensors Actuators, B Chem, Vol 138, pp 168–173 [137] L V Thong, N D Hoa, D T T Le, D T Viet, P D Tam, A T Le, and N Van Hieu (2010), “On-chip fabrication of SnO2-nanowire gas sensor: The 111 effect of growth time on sensor performance”, Sensors Actuators B Chem, Vol 146, pp 361–367 [138] D Zhang, Z Liu, C Li, T Tang, X Liu, S Han, and B Lei (2004), “Detection of NO2 down to ppb Levels Using Individual and Multiple In2O3 Nanowire Devices”, Nano Lett, Vol 4, pp 1919–1924 [139] G Sakai, N Matsunaga, K Shimanoe, and N Yamazoe (2001), “Theory of gas-diffusion controlled sensitivity for thin film semiconductor gas sensor”, Sensors Actuators B Chem, Vol 80, pp 125–131 [140] Y Xiao, Q Yang, Z Wang, R Zhang, Y Gao, P Sun, Y Sun, and G Lu (2016), “Improvement of NO2 gas sensing performance based on discoid tin oxide modified by reduced graphene oxide”, Sensors Actuators B Chem, Vol 227, pp 419–426 [141] L Tang, Y Wang, Y Li, H Feng, J Lu, and J Li (2009), “Preparation, structure, and electrochemical properties of reduced graphene sheet films”, Adv Funct Mater, Vol 19, pp 2782–2789 [142] Z Fan, K Wang, T Wei, J Yan, L Song, and B Shao (2010), “An environmentally friendly and efficient route for the reduction of graphene oxide by aluminum powder”, Carbon N Y, Vol 48, pp 1686–1689 [143] S Stankovich, D A Dikin, R D Piner, K A Kohlhaas, A Kleinhammes, Y Jia, Y Wu, S B T Nguyen, and R S Ruoff (2007), “Synthesis of graphenebased nanosheets via chemical reduction of exfoliated graphite oxide”, Carbon N Y, Vol 45, pp 1558–1565 [144] P Cui, J Lee, E Hwang, and H Lee (2011), “One-pot reduction of graphene oxide at subzero temperatures”, Chem Commun, Vol 47, pp 12370–12372 [145] Y Zhou, Q Bao, L A L Tang, Y Zhong, and K P Loh (2009), “Hydrothermal dehydration for the ‘green’ reduction of exfoliated graphene oxide to graphene and demonstration of tunable optical limiting properties”, Chem Mater, Vol 21, pp 2950–2956 [146] A C Ferrari and J Robertson (2000), “Interpretation of Raman spectra of disordered and amorphous carbon”, Phys Rev B, Vol 61, pp 14095–14107 [147] M Fu, Q Jiao, and Y Zhao (2013), “In situ fabrication and characterization 112 of cobalt ferrite nanorods/graphene composites”, Mater Charact, Vol 86, pp 303–315 [148] K Satheesh and R Jayavel (2013), “Synthesis and electrochemical properties of reduced graphene oxide via chemical reduction using thiourea as a reducing agent”, Mater Lett, Vol 113, pp 5–8 [149] J Shi, Z Cheng, L Gao, Y Zhang, J Xu, and H Zhao (2016), “Facile synthesis of reduced graphene oxide/hexagonal WO3 nanosheets composites with enhanced H2S sensing properties”, Sensors Actuators, B Chem, Vol 230, pp 736–745 [150] R J Zou, G J He, K B Xu, Q Liu, Z Y Zhang, and J Q Hu (2013), “ZnO nanorods on reduced graphene sheets with excellent field emission, gas sensor and photocatalytic properties” , J Mater Chem A, Vol 1, pp 8445– 8452 [151] S Singkammo, A Wisitsoraat, C Sriprachuabwong, A Tuantranont, S Phanichphant, and C Liewhiran (2015), “Electrolytically exfoliated graphene-loaded flame-made Ni-doped SnO2 composite film for acetone sensing”, ACS Appl Mater Interfaces, Vol 7, pp 3077–3092 [152] R C V Gopal, S V Manorama, V J Rao, and C V G Reddy (2000), “Preparation and characterization of ferrites as gas sensor materials”, J Mater Sci Lett, Vol 9, pp 775–778 [153] V D Kapse (2015), “Preparation of Nanocrystalline Spinel-type oxide Materials for Gas sensing applications”, ResJChemSci, Vol 5, pp 7–12 [154] A Sutka and K A Gross (2016), “Spinel ferrite oxide semiconductor gas sensors”, Sensors Actuators B, Vol 222, pp 95–105 [155] Z Sun, L Liu, D zeng Jia, and W Pan (2007), “Simple synthesis of CuFe2O4 nanoparticles as gas-sensing materials”, Sensors Actuators, B Chem, Vol 125, pp 144–148 [156] J Y Patil, D Y Nadargi, J L Gurav, I S Mulla, and S S Suryavanshi (2014), “Synthesis of glycine combusted NiFe2O4 spinel ferrite: A highly versatile gas sensor”, Mater Lett, Vol 124, pp 144–147 [157] S Ayyappan, G Paneerselvam, M P Antony, and J Philip (2011), 113 “Structural stability of ZnFe2O4 nanoparticles under different annealing conditions”, Mater Chem Phys, Vol 128, pp 400–404 [158] P Ghosh, A Mukherjee, M Fu, S Chattopadhyay, and P Mitra (2015), “Influence of particle size on H2 and H2S sensing characteristics of nanocrystalline nickel ferrite”, Phys E Low-dimensional Syst Nanostructures, Vol 74, pp 570–575 [159] C J Belle, A Bonamin, U Simon, J Santoyo-Salazar, M Pauly, S BéginColin, and G Pourroy (2011), “Size dependent gas sensing properties of spinel iron oxide nanoparticles”, Sensors Actuators, B Chem, Vol 160, pp 942–950 [160] A Katoch, S W Choi, J H Kim, J H Lee, J S Lee, and S S Kim (2015), “Importance of the nanograin size on the H2S-sensing properties of ZnO-CuO composite nanofibers”, Sensors Actuators, B Chem, Vol 214, pp 111–116 [161] F Lu, Y Liu, M Dong, and X Wang (2000), “Nanosized tin oxide as the novel material with simultaneous detection towards CO, H2 and CH4”, Sensors Actuators B, Vol 66, pp 225–227 [162] S G Ansari, S R Sainkar, R N Karekar, R C Aiyer, and S K Kulkarni (1997), “Grain size effects on H2 gas sensitivity of thick film resistor using SnO2 nanoparticles”, Thin Solid Films, Vol 295, pp 271–276 [163] Y.-F Sun, S.-B Liu, F.-L Meng, J.-Y Liu, Z Jin, L.-T Kong, and J.-H Liu (2012), “Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review”, Sensors, Vol 12, pp 2610–2631 [164] G Korotcenkov (2008), “The role of morphology and crystallographic structure of metal oxides in response of conductometric-type gas sensors”, Mater Sci Eng R Reports, Vol 61, pp 1–39 [165] X Zhou, J Liu, C Wang, P Sun, X Hu, X Li, K Shimanoe, N Yamazoe, and G Lu (2015), “Highly sensitive acetone gas sensor based on porous ZnFe2O4 nanospheres”, Sensors Actuators, B Chem, Vol 206, pp 577–583 [166] A F S Abu-Hani, S T Mahmoud, F Awwad, and A I Ayesh (2017), “Design, fabrication, and characterization of portable gas sensors based on spinel ferrite nanoparticles embedded in organic membranes”, Sensors 114 Actuators B Chem, Vol 241, pp 1179–1187 [167] Y Cao, D Jia, P Hu, and R Wang (2013), “One-step room-temperature solid-phase synthesis of ZnFe2O4 nanomaterials and its excellent gas-sensing property”, Ceram Int, Vol 39, pp 2989–2994 [168] Y Yan, P Nizamidin, G Turdi, N Kari, and A Yimit (2017), “Roomtemperature H2S Gas Sensor Based on Au-doped ZnFe2O4”, Anal Sci, Vol 33, pp 945–951 [169] H Qiao, Z Xia, Y Fei, L Cai, R Cui, Y Cai, Q Wei, and Q Yao (2017), “Electrospinning combined with hydrothermal synthesis and lithium storage properties of ZnFe2O4-graphene composite nanofibers”, Ceram Int, Vol 43, pp 2136–2142 [170] S Yang, X Song, P Zhang, and L Gao (2015), “Heating-Rate-Induced Porous α ‑ Fe2O3 with Controllable Pore Size and Crystallinity Grown on Graphene for Supercapacitors”, ACS Appl Mater Interfaces, Vol 7, pp 75−79 [171] J M Chem, P F Teh, Y Sharma, S Pramana, and M Srinivasan (2011), “Nanoweb anodes composed of one-dimensional, high aspect ratio, size tunable electrospun ZnFe2O4 nanofibers for lithium ion batteries”, J Mater Chem, Vol 21, pp 14999–15008 [172] K Wu, J Li, and C Zhang (2019), “Zinc ferrite based gas sensors: A review”, Ceram Int, Vol 45, pp 11143–11157 [173] J Y Park, K Asokan, S W Choi, and S S Kim (2011), “Growth kinetics of nanograins in SnO2 fibers and size dependent sensing properties”, Sensors Actuators, B Chem, Vol 152, pp 254–260 [174] M Zong, Y Huang, H Wu, Y Zhao, Q Wang, and X Sun (2014), “One-pot hydrothermal synthesis of RGO/CoFe2O4 composite and its excellent microwave absorption properties”, Mater Lett, Vol 114, pp 52–55 [175] H Zhang, A Xie, C Wang, H Wang, Y Shen, and X Tian (2013), “Novel rGO/α-Fe2O3 composite hydrogel: synthesis, characterization and high performance of electromagnetic wave absorption”, J Mater Chem A, Vol 1, pp 8547–8552 115 [176] S K Pandey, K.-H Kim, and K.-T Tang (2012), “A review of sensor-based methods for monitoring hydrogen sulfide”, TrAC Trends Anal Chem, Vol 32, pp 87–99 [177] A Mirzaei, S S Kim, and H W Kim (2018), “Resistance-based H2S gas sensors using metal oxide nanostructures: A review of recent advances”, J Hazard Mater, Vol 357, pp 314–331 [178] L Guo, X Kou, M Ding, C Wang, L Dong, H Zhang, C Feng, Y Sun, Y Gao, P Sun, and G Lu (2017), “Reduced graphene oxide/α-Fe2O3 composite nanofibers for application in gas sensors”, Sensors Actuators B Chem, Vol 244, pp 233–242 [179] Jiwei Deng, Jianmin Ma, L Mei, Y Tang, Y Chen, T Lv, Z Xu, and T Wang (2013), “Porous α-Fe2O3 nanosphere-based H2S sensor with fast response, high selectivity and enhanced sensitivity”, J Mater Chem A, Vol 1, pp 12400–12403 [180] Z U Abideen, H W Kim, and S S Kim (2015), “An ultra-sensitive hydrogen gas sensor using reduced graphene oxide-loaded ZnO nanofibers”, Chem Commun, Vol 51, pp 15418–15421 [181] S Ferrari, R S Kumar, F Grinblat, J C Aphesteguy, F D Saccone, and D Errandonea (2016), “In-situ high-pressure X-ray diffraction study of zinc ferrite nanoparticles”, Solid State Sci, Vol 56, pp 68–72 116 APPENDIX 1.04 Pure α- Fe2O3 NFs@ air & 350 oC Pure α- Fe2O3 NFs@ air & 350 oC Fifth-order polynomial fit RSS = 3.66E-5 Linear Fit Slope = 5.53 (a) 10 o 0.5 wt.% RGO @ air & 350 C Fifth-order polynomial fit (b) RSS = 3.03E-5 Resp Base (Ra/Rg) 1.00 10 o 0.5 wt.% RGO @ air & 350 C Linear Fit Slope = 6.76 0.98 (g) 0.96 1.08 o 1.0 wt.% RGO@ air & 350 C Fifth-order polynomial fit (c) RSS = 2.4E-5 1.06 10 o 1.0 wt.% RGO@ air & 350 C Linear Fit Slope = 8.66 Resp (Ra/Rg) (f) 1.02 (h) 1.04 1.02 o 1.5 wt.% RGO@ air & 350 C (d) Fifth-order polynomial fit RSS = 1.34E-5 1.00 1.5 wt.% RGO@ air & 350 oC Linear Fit Slope = 2.44 (i) 0.98 0 10 0.00 0.25 0.50 0.75 1.00 H2S conc (ppm) Time (s) Figure A3.1 Fitted values of RSS and slope for DL calculation of sensors based on α-Fe2O3 NFs loaded with different contents of RGO of (a, e), 0.5 (b, f), 1.0 (c, g), and 1.5 wt.% (d, h), respectively The sensors are tested with H2S gas at operating temperature of 350°C Table A3.1 Calculation table of DL to H2S of sensors based on α-Fe2O3 NFs loaded with different contents of RGO from to 1.5 wt% RGO at operating temperature of 350°C Samples RSS rmsnoise Slope DL (ppb) 3.66E-05 0.001913113 5.53 1.04 0.5 3.03E-05 0.00174069 6.76 0.78 2.40E-05 0.001549193 8.66 0.54 1.5 1.34E-05 0.001157584 2.44 1.42 117 α−Fe2O3 Cal 400 oC@ H2S & 350 oC Fifth-order polynomial fit RSS = 1.31E-5 Linear Fit Slope = 4.15 (a) (f) 1.00 Cal 500 oC@ air & 350 oC Fifth-order polynomial fit RSS = 5.12E-6 1.04 Resp Base (Ra/Rg) 1.02 1.00 1.04 Cal 600 oC@ air & 350 oC Fifth-order polynomial fit RSS = 3.66E-5 1.02 Cal 700 oC@ air & 350 oC Fifth-order polynomial fit RSS = 2.34E-5 0.98 0.96 1.04 Cal 800 oC@ air & 350 oC Fifth-order polynomial fit RSS = 1.77E-5 1.02 Cal 500 oC@ H2S & 350 oC (b) (c) (d) (e) Linear Fit Slope = 2.76 (g) Cal 600 oC@ H2S & 350 oC Linear Fit Slope = 5.53 (h) Cal 700 oC@ H2S & 350 oC Linear Fit Slope = 4.48 Resp (Ra/Rg) 1.02 α- Fe2O3 Cal 400 oC@ air&350 oC (i) Cal 800 oC@ H2S & 350 oC Linear Fit Slope = 0.83 (j) 1.00 0 10 0.00 Time (s) 0.25 0.50 0.75 H2S conc (ppm) 1.00 Figure A3.2 Fitted values of RSS and slope for DL calculation of α-Fe2O3 NFs sensors calcined at various annealing temperatures of 400 (a, f), 500 (b, g), 600 (c, h), 700 (d, i), and 800°C (e, j), respectively The sensors are tested with H2S gas at operating temperature of 350°C Table A3.2 Calculation table of DL to H2S of α-Fe2O3 NFs sensors calcined at annealing temperatures from 400°C to 800°C at operating temperature of 350°C Samples RSS rmsnoise Slope DL (ppb) 400oC 1.31E-05 0.001144552 4.15 0.83 500oC 5.12E-06 0.000715542 2.76 0.78 600oC 3.66E-05 0.001913113 5.53 1.04 700oC 2.34E-05 0.001529706 4.48 1.02 800oC 1.77E-05 0.001330413 0.83 4.81 118 wt% RGO Cal 400 oC@ air&350 oC Fifth-order polynomial fit (a) RSS = 1.67E-5 1.02 Resp Base (Ra/Rg) 1.00 0.98 1.04 1.00 1.04 Cal 800 oC@ air & 350 oC Fifth-order polynomial fit RSS = 9.0E-6 1.02 10 (g) 10 Cal 600 oC@ H2S & 350 oC Linear Fit Slope = 8.66 Cal 700 oC@ air & 350 oC (d) Fifth-order polynomial fit RSS = 4.0E-5 1.02 (f) Linear Fit Slope = 3.68 Cal 600 oC@ air & 350 oC Fifth-order polynomial fit (c) RSS = 2.40E-5 1.06 10 Linear Fit Slope = 6.00 Cal 500 oC@ H2S & 350 oC Cal 500 oC@ air & 350 oC Fifth-order polynomial fit (b) RSS = 1.21E-5 1.02 wt.% RGO Cal 400 oC@H2S&350oC (h) 10 Cal 700 oC@ H2S & 350 oC (i) Linear Fit Slope = 3.15 10 Cal 800 oC@ H2S & 350 oC (e) Resp (Ra/Rg) 1.04 (j) Linear Fit Slope = 0.14 1.00 0 Time (s) 10 0.00 0.25 0.50 0.75 H2S conc (ppm) 1.00 Figure A3.3 Fitted values of RSS and slope for DL calculation of 1.0 wt.% RGO-loaded αFe2O3 NFs sensors calcined at various annealing temperatures of 400 (a, f), 500 (b, g), 600 (c, h), 700 (d, i), and 800°C (e, j), respectively The sensors are tested with H2S gas at operating temperature of 350°C Table A3.3 Calculation table of DL to H2S of 1.0 wt.% RGO-loaded α-Fe2O3 NFs sensors calcined at annealing temperatures from 400°C to 800°C at operating temperature of 350°C Samples RSS rmsnoise Slope DL (ppb) 400oC 1.67E-05 0.001292285 0.65 500oC 1.21E-05 0.0011 3.68 0.90 600oC 2.40E-05 0.001549193 8.66 0.54 700oC 4.05E-05 0.002012461 3.12 1.94 800oC 9.00E-06 0.000948683 0.14 20.33 119 Table A4.1 Average nanograin sizes determined by Scherrer formula and integrated intensity of (311) diffraction peak of ZFO-NFs calcined at different conditions β (FWHM) Samples Crystallite sizes (nm) (radian) Integrated intensity 400oC 0.62 13.53 20.24 500oC 0.55 15.16 22.44 600oC 0.46 18.08 35.39 700oC 0.35 23.92 84.24 0.5 h 0.51 16.32 24.68 3h 0.46 18.08 35.39 12 h 0.38 21.82 69.01 48 h 0.36 23.28 108.82 0.5oC/min 0.46 18.08 35.39 2oC/min 0.68 12.25 29.19 5oC/min 0.61 13.63 35.29 20oC/min 0.55 15.23 46.58 120 Table A4.2 Response and response-recovery time to ppm H2S gas at the operating temperature of 350°C of the ZFO NFs sensors calcined at different annealing temperatures (400−700°C), annealing time (0.5−48 h), heating rates (0.5−20°C/min), electrospinning time (10−120 min) S τres τrec 1ppm (s) (s) 400oC 8.5 47 423 500oC 61 261 600oC 102 206 700oC 21.8 129 0.5 h 34 217 3h 102 206 12 h 42.3 63 48 h 15.4 40 0.5oC/min 102 206 2oC/min 19.9 53 5oC/min 53.4 68 20oC/min 7.4 12 122 Samples 121 Cal 400 oC@ H2S & 350 oC Cal 400 oC@ air & 350 oC Fifth-order polynomial fit RSS = 1.37E-5 (a) Linear Fit Slope = 8.32664 Resp Base (Ra/Ra) 1.04 Cal 500 oC@ air & 350 oC Fifth-order polynomial fit RSS = 3.69E-5 (b) 1.02 10 (e) Cal 500 oC@ H2S & 350 oC 50 Linear Fit Slope = 67.70817 (f) 1.00 25 o o o Cal 600 C@ H2S & 350 C Cal 600 C@ air & 350 C Fifth-order polynomial fit RSS = 3.28E-5 (c) 1.02 o Linear Fit Slope = 113.96252 100 (g) 1.00 50 (d) 1.02 o Cal 700 oC@ H2S & 350 oC o Cal 700 C@ air & 350 C Fifth-order polynomial fit RSS = 4.78E-6 20 Linear Fit Slope = 22.34538 (h) 1.00 10 0 10 0.00 0.25 0.50 0.75 1.00 H2S conc (ppm) Time (s) Figure A4.1 Fitted values of RSS and slope for DL calculation of the sensors based on ZFO NFs calcined at various annealing temperatures of 400 (a,e), 500 (b,f), 600 (c,g), and 700°C (d,h), respectively The sensors are tested with H2S gas at the operating temperature of 350°C Table A4.3 Calculation table of DL to H2S of the ZFO NFs sensors calcined at the annealing temperature from 400°C to 700°C at the operating temperature of 350°C Samples RSS rmsnoise Slope DL (ppb) 400oC 1.37E-05 0.00117161 8.32664 0.422 500oC 3.69E-05 0.00192032 67.70817 0.085 600oC 3.28E-05 0.001810392 113.96252 0.048 700oC 4.78E-06 0.002185514 22.34538 0.093 122 Resp (Ra/Rg) 1.06 Cal 400 oC@ air & 350 oC Fifth-order polynomial fit RSS = 5.05E-5 (a) 1.00 50 Cal 400 oC@ H2S & 350 oC Linear Fit Slope = 48.94 (e) 25 1.02 Cal 500 oC@ air & 350 oC Fifth-order polynomial fit RSS = 5.57E-5 (b) 1.00 0.98 1.04 o o Cal 600 C@ air & 350 C Fifth-order polynomial fit RSS = 3.28E-5 (c) 1.02 75 o o Cal 500 C@ H2S & 350 C Linear Fit Slope = 86.58 50 (f) 25 Resp (Ra/Rg) Resp Base (Ra/Ra) 0.98 150 Cal 600 oC@ H2S & 350 oC Linear Fit Slope = 164.15 100 (g) 50 1.00 Cal 700 oC@ air & 350 oC Fifth-order polynomial fit RSS = 5.2E-5 (d) 1.06 Cal 700 oC@ H2S & 350 oC Linear Fit Slope = 15.25 (h) 20 10 1.04 0 10 0.00 0.25 0.50 0.75 1.00 H2S conc (ppm) Time (s) Figure A4.2 Fitted values of RSS and slope for DL calculation of the sensors based on wt% RGO loaded ZFO NFs calcined at various annealing temperatures of 400 (a,e), 500 (b,f), 600 (c,g), and 700°C (d,h), respectively The sensors are tested with H2S gas at the operating temperature of 350°C Table A4.4 Calculation table of DL to H2S of the wt% RGO-loaded ZFO NFs sensors calcined at annealing temperatures from 400°C to 700°C at the operating temperature of 350°C Samples RSS rmsnoise Slope DL (ppb) 400oC 5.05E-05 0.002247221 48.94 0.14 500oC 5.57E-05 0.002360085 86.58 0.08 600oC 3.28E-05 0.001811077 164.15 0.03 700oC 5.20E-06 0.002280351 15.25 0.44 123 ... Standards Nanofibers 17 NPs Nanoparticles 18 NRs Nanorods 19 NSs Nanosheets 20 NTs Nanotubes 21 NWs Nanowires 22 ppb Parts Per Billion 23 ppm Parts Per Million 24 PVA Poly(vinyl alcohol) 25 RGO Reduced... of RGO in α-Fe2O3 and ZFO NFs for enhanced H2S gas-sensing performance Therefore, the thesis titled “Electrospinning of α-Fe2O3 and ZnFe2O4 nanofibers loaded with reduced graphene oxide (RGO) ... (a,b) RGO- loaded ZnO NFs and (c-d) RGOloaded SnO2; Sensor response of (e) RGO- loaded ZnO NFs and (f) RGO- loaded SnO2; (g) Comparision of of pure SnO2 NFs, pure ZnO NFs, rGO- loaded SnO2 NFs and rGOloaded