HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Fabrication of Zn2SnO4 nanostructures for gas sensor application LAI VAN DUY Duy.LVCA180178@sis.hust.edu.vn Specialized: Electronic materials Supervisor: Professor Ph.D Nguyen Duc Hoa Institute: International Training Institute for Materials Science (ITIMS) HANOI, 6/2020 HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Fabrication of Zn2SnO4 nanostructures for gas sensor application LAI VAN DUY Duy.LVCA180178@sis.hust.edu.vn Specialized: Electronic materials Supervisor: Professor Ph.D Nguyen Duc Hoa Institute: Signature of GVHD International Training Institute for Materials Science (ITIMS) HANOI, 6/2020 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: Lại Văn Duy Đề tài luận văn: Chế tạo vật liệu Zn2SnO4 cấu trúc nano ứng dụng cho cảm biến khí Chuyên ngành: Khoa học vật liệu-VLĐT Mã số SV: CA180178 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 30/06/2020 với nội dung sau: - Bổ sung thích hình 3.9, 3.10, 3.13 - Các cơng thức, phương trình phản ứng đánh số theo trình tự - Bảng danh mục chữ viết tắt xếp theo thứ tự alpha b - Chữ hình 3.2, 3.4, 3.6, 3.25 để kích thước lớn - Phần thích hình có dấu chấm sau số thứ tự hình - Chỉnh sửa lỗi tả, hành văn Ngày 09 tháng 07 năm 2020 Giáo viên hướng dẫn Tác giả luận văn GS TS Nguyễn Đức Hòa Lại Văn Duy CHỦ TỊCH HỘI ĐỒNG PGS TS Nguyễn Phúc Dương ĐỀ TÀI LUẬN VĂN Chế tạo vật liệu Zn2SnO4 cấu trúc nano ứng dụng cho cảm biến khí Học viên: Lại Văn Duy Chuyên ngành: Khoa học vật liệu-VLĐT Giáo viên hướng dẫn (Ký ghi rõ họ tên) GS TS Nguyễn Đức Hòa ACKNOWLEDGEMENT First of all, I would like to express my greatest gratitude to Prof PhD Nguyen Duc Hoa for his valuable scientific ideas, guidance and support of favorable conditions for me to complete this thesis His kindness and enthusiasm will be in my heart forever Simultaneously, I would like to express my sincere thanks to all staffs of the Laboratory for Research, Development, and Application of Nanosensors at ITIMS-HUST has always been enthusiastic about helping, sharing experiences and suggesting many important ideas for me to carry out the research of this thesis Moreover, I am also very grateful to my colleagues, PhD students, the iSensors’ graduated students who have always accompanied and assisted me in two years of doing my master thesis at ITIMS Finally, I would like to thank all my family, friends and colleagues who have always encouraged and shared me to complete this thesis SUMMARY OF MASTER THESIS In this project, we developed high-performance VOC gas sensors for breath analysis by focusing on the controlled synthesis of nanostructured Zn2SnO4 ternary metal oxides to maximize the gas sensitivity To archive the objective, we synthesised hollow structure ternary metal by hydrothermal technique with the assistance of soft template The thickness of the hollow cells was optimised to desire the highest VOC response By hydrothermal method, the author has successfully synthesized many nanostructures of Zn2SnO4 with different morphologies At the same time, the thesis also proves the application potential of Zn2SnO4 material in the gas sensor VOCs The sensor based on Zn2SnO4 materials could detect various VOCs gases such as acetone, ethanol, and methanol at low concentrations of ppb levels with high sensitivity STUDENT Lai Van Duy CONTENTS ABBREVIATIONS iii LIST OF FIGURES iv LIST OF TABLES viii INTRODUCTION 1 Foundation of the thesis Aims of the thesis 3 Research object and scope of the thesis 4 Research Methods The practical and scientific significance of the thesis New contributions of the thesis The structure of the thesis CHAPTER OVERVIEW 1.1 Volatile organic compounds 1.2 Overview of Zn2SnO4 material 1.2.1 Crystal structure of Zn2SnO4 material 1.2.2 Electrical properties of Zn2SnO4 material 11 1.2.3 Application of Zn2SnO4 material in gas sensors 12 1.2.4 Gas sensitivity mechanism of metal oxide for VOCs 17 1.3 Hydrothermal method 21 CHAPTER 2.1 EXPERIMENTAL APPROACH 25 The synthesis processes of nanostructured Zn2SnO4 materials with different morphologies by hydrothermal method 25 2.1.1 Equipment and chemicals 25 2.1.2 The synthesis process of Zn2SnO4 nanostructures with different morphologies by hydrothermal method 26 2.2 Sensor manufacturing processes 29 2.3 Morphological and microstructure analysis 30 2.4 Survey of gas sensitivity properties 30 i CHAPTER 3.1 RESULTS AND DISCUSSION 32 Morphology and crystal structure of zinc Stannate nanomaterials (Zn2SnO4) synthesized by hydrothermal method 32 3.1.1 Effect of hydrothermal temperatures on the morphology of Zinc Stannate (Zn2SnO4) materials .32 3.1.2 Effect of surfactant P123 on the morphology of Zn2SnO4 material 34 3.1.3 Effect of pH on the morphology of Zn2SnO4 materials .38 3.1.4 Crystal structure of synthesized Zn2SnO4 materials 44 3.2 Gas sensing properties of Zn2SnO4 materials with different morphological structures 49 3.2.1 Methanol gas-sensing properties of the fabricated sensors 50 3.2.2 Ethanol gas-sensing properties of the fabricated sensors 53 3.2.3 Acetone gas-sensing properties of the fabricated sensors 56 CONCLUSIONS AND RECOMMENDATIONS 68 LIST OF REFERENCES 69 LIST OF PUBLICATIONS 78 ii ABBREVIATIONS Number Abbreviations and symbols Meaning ads Adsorption BET Brunauer- Emnet-Teller CVD Chemical Vapour Deposition EDS/EDX Energy-dispersive X-ray spectroscopy HRTEM High Resolution Transmission Electron Microscope IoT Internet of Things ITIMS JCPDS P123 HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H 10 ppb Parts per billion 11 ppm Parts per million 12 Ra Rair 13 Rg Rgas 14 S Sensitivity 15 SEM Scanning Electron Microscope 16 TEM Transition Electron Microscope 17 VOCs Volatile Organic Compounds 18 XRD X-ray Diffraction International Training Institute for Materials Science Joint Committee on Powder Diffraction Standards iii LIST OF FIGURES Figure 1.1 VOCs in exhaled breath can be used as biomarkers for diseases diagnose [47] Figure 1.2 Crystal structures of zinc stannate (Zn2SnO4) [51] .9 Figure 1.3 Sublattices of zinc stannate (Zn2SnO4) 10 Figure 1.4 Schematic representation of the inverse spinel lattice of Zn2SnO4 [49] 10 Figure 1.5 Model explains the n-type semiconductor of Zn2SnO4 material [50] .11 Figure 1.6 A schematic diagram of reaction mechanism of SnO2-based sensor to HCHO: (a) in air, (b) in VOCs [73] 19 Figure 1.7 Schematic energy level diagram of a metal oxide before (a) and after exposure to a VOCs (b) [43] 19 Figure 1.8 A schematic of the sensing mechanism of (a) ZnO NPs and (b) ZnO QDs in air (left) and isoprene (right) [74] 20 Figure 2.1 Photos of some of the main equipment using synthesized Zn2SnO4 nanomaterials by a hydrothermal method such as thermos flask (1), magnetic stirrer (2), pH meter (3), centrifugal rotary machine (4) and annealing furnace (5) 26 Figure 2.2 Process diagram of synthesizing Zn2SnO4 nanomaterials with different morphological structures by hydrothermal method 27 Figure 2.3 The process diagram for making sensors on the basis of nano Zn2SnO4 material by small coating method .29 Figure 2.4 (A) Gas sensitive measuring system at ITIMS; (B) Diagram of the gas measuring system by static measurement method 31 Figure 3.1 SEM image of Zn2SnO4 samples synthesized by hydrothermal method with different hydrothermal temperature: (A, B) 160 ºC; (C, D) 180 ºC; (E, F) 200 ºC 33 Figure 3.2 General diagram of synthetic Zn2SnO4 materials with different morphology according to changes in hydrothermal temperature 34 Figure 3.3 SEM image of Zn2SnO4 samples synthesized by hydrothermal method with different amount of P123 surface-active agent (A, B) g; (C, D) 0.25 g; (E, F) 0,5 g; (G, H) 1,0 g 36 iv Figure 3.4 Schematic mechanism of synthesizing Zn2SnO4 materials with different morphology by the concentration of surfactants P123 by hydrothermal method 37 Figure 3.5 SEM image of Zn2SnO4 nanomaterial synthesized by hydrothermal method with different pH conditions: (A, B) pH = 8; (C, D) pH = 9; (E, F) pH = 10; (G, H) pH = 12; (I, K) pH = 13 40 Figure 3.6 General diagram of the synthesis of Zn2SnO4 materials with different morphology according to the pH change of the hydrothermal environment 41 Figure 3.7 TEM (A-D) images of the synthesized hollow cubic Zn2SnO4 Inset of (D) is correspondent SAED 43 Figure 3.8 (A) STEM image and (B-D) EDS mapping of the hollow cubic Zn2SnO4 43 Figure 3.9 XRD samples of Zn2SnO4 with condition pH = and pH = 13 at hydrothermal temperature of 180 °C/24h 44 Figure 3.10 XRD patterns of Zn2SnO4 with condition pH = and pH =13 hydrothermal temperature of 180 °C/24h after treatment heat at 550 °C for 2h in air 45 Figure 3.11 Raman and PL spectrum of synthesized Zn2SnO4 46 Figure 3.12 BET spectra of Zn2SnO4: (A) - Octahedron, (B) - Cubic, (C) – Nanoparticles 48 Figure 3.13 I-V curve of the sensor (A) - Octahedron, (B) - Cubic, (C) – Nanoparticles measured in air at 450 oC 49 Figure 3.14 Methanol sensing characteristics of nanoparticles Zn2SnO4 (ZTO_PH8): (A) transient resistance versus time upon exposure to different concentrations of methanol measured at different temperatures; (B) sensor response as a function of methanol; (C) respon and recovery time of sensor 52 Figure 3.15 Methanol sensing characteristics of hollow cubic Zn2SnO4 (ZTOP5_PH8): (A) transient resistance versus time upon exposure to different concentrations of methanol measured at different temperatures; (B) sensor response as a function of methanol; (C) respon and recovery time of sensor 52 Figure 3.16 Methanol sensing characteristics of hollow octahedron Zn2SnO4 (ZTOP5_PH13): (A) transient resistance versus time upon exposure to different v Figure 3.26 Selectivity of sensors ZTO_PH8, ZTOP5_PH8, and ZTOP5_PH13 when surveying with different gases: acetone (100 ppm), ethanol (100 ppm), methanol (100 ppm), NH3 (25 ppm), H2 (50 ppm) and CO (5 ppm) at 450 ºC Figure 3.26 shows the sensor ZTOP5_PH13 for higher response than sensors ZTO_PH8, ZTOP5_PH8 based on hollow octahedron Zn2SnO4 for acetone gas Specifically, the sensor ZTOP5_PH13 provides a response of 44.22 times at a concentration of 125 ppm, while the response of the sensor to ethanol, reducing gases (100 ppm), methanol (100 ppm), NH3 (25 ppm), H2 (50 ppm), CO (5 ppm) only gives a response respectively of 5.90, 7.83, 5.71, 1.84 and 1.48 times For ethanol gas, the sensor ZTOP5_PH8 based on hollow cubic Zn2SnO4 material has a higher response than the two sensors ZTO_PH8 and ZTOP5_PH13 Specifically, the ZTOP5_PH8 sensor has a response of about 13.50 times at a concentration of 125 ppm, while the sensor's response to reducing gases is methanol (100 ppm), NH3 (25 ppm), H2 (50 ppm), CO (5 ppm) only gives a response, respectively of 4.64, 3.78, 1.69, 1.16 times This proves that the sensors ZTOP5_PH8, ZTOP5_PH13 on the basis of hollow cubic and hollow octahedron materials are selective for ethanol and acetone reducing gases at a working temperature of 450 ºC Therefore, from the above gas-sensitive property analysis, we believe that ZTOP5_PH8, ZTOP_PH13 sensors built on 64 the basis of a hollow cubic, hollow octahedron materials can be applied in breath analysis to detect diabetes In addition to the selectivity, the effect of ambient relative humidity (RH) on the acetone sensing properties of the sensor were also tested Figure 3.27 shows the (A, B) transient resistance and (C, D) response value versus time upon exposure to 0.5 ppm acetone measured at 450 ºC in different values of humidity of the hollow cubic, hollow octahedron Zn2SnO4 sensor The based resistance is 396, 256, 148, 66 k and 1.07 M, 1.02 M, 953 k, 859 k for 10, 60, 70, and 90% HR, respectively The decrease of based resistance with increment of relative humidity indicate that that the adsorption of water molecule donates free electrons to the conduction band of Zn2SnO4 and decrease of based resistance The response value to 0.5 ppm acetone is 2.01, 3.57, 3.16, 2.96 and 3.67, 2.89, 2.78, 2.63 in 10, 60, 70, and 90 % RH, respectively The acetone response was influenced by the ambient humidity, but at high humidity of 70-90 % RH, the variation in acetone response was ignorable Such those characteristics ensure the reliable application of gas sensor in breath analysis [21] Figure 3.27 (A, B) transient resistance and (C, D) response value versus time upon exposure to 0.5 ppm acetone measured at 450 ºC in different values of humidity of the hollow cubic, hollow octahedron Zn2SnO4 sensor 65 The gas sensing mechanism is speculated as the resistance changes of the gas sensor before and after exposure to analytic gas For n-type semiconductor metal oxide-based gas sensors, the most widely accepted gas sensing mechanism is based on the change in resistance during the adsorption and desorption of gas molecules and chemical reactions on the surface of sensing materials [91] As shown in Fig 3.28, when the sensor was exposed to ambient air, oxygen molecules adsorbed on the surface of the sensing material (Eqs (3.4)-(3.7)) captured electrons in the conduction band of Zn2SnO4 to form O2-, O-, O2- species at around 350-450 °C then generated an electron depletion layer Because the wall of the hollow cube and hollow octahedron was formed from aggregated nanocrystals, the surface of the Zn2SnO4 formed on a high potential barrier between the adjacent nanograins, leading to an increase in the resistance of the sensing material Subsequently, the VOC gas molecule reacts with pre-adsorbed oxygen species on the surface of the sensor, and the electrons were released back to the conduction band (Eq (3.9)), resulting in an increase in surface electrons and conductivity and a decrease in resistance [43, 90] O2 (gas) → O2 (ads) (3.4) O2 (ads) + e- → O2- (3.5) O2 (ads) + 2e- → 2O- (3.6) O2 (ads) + 4e- → 2O2- (3.7) VOC (gas) → (3.8) VOC (ads) VOCs + nOx- → aCO2 + bH2O + ne- (3.9) The hollow structure of the Zn2SnO4 cubic and octahedron was beneficial for the total exposure of analytic gas on the outer and inner surfaces of the sensing material The hollow structure also enhanced the diffusion rate of gas molecules to the inside of the sensing material, thereby improving the sensing performance Recovery of the sensor was obtained after stop flowing analytic VOC gas, and again exposure to ambient air When the sensor was exposed to ambient air, oxygen molecules again adsorbed on the surface of the Zn2SnO4 cube and ionized to negatively charged surface-adsorbed oxygen species by capturing free electrons from the conducting band of the Zn2SnO4 cubic [52], as shown in Eqs 66 (3.4)–(3.7) As a result, the resistance of sensor recovers to the initial value after stop flowing analytic gas Figure 3.28 Schematic of the VOCs gas-sensing mechanism of the Zn2SnO4 67 CONCLUSIONS AND RECOMMENDATIONS Based on the results and analyses presented above, we have some conclusions: Successfully fabrication of Zn2SnO4 material with various structures of nanoparticles, hollow cubic, and hollow octahedron by hydrothermal method The obtained Zn2SnO4 materials had a uniformly hollow cubic and hollow octahedron structure with an average size of approximately µm and a wall thickness of about 150 nm formed from nanocrystals of around 28 nm Particularly for Zn2SnO4 nanoparticles, the average particle size is about 21 nm The gas sensing properties of Zn2SnO4 material with acetone, ethanol, methanol, NH3, H2, and CO were tested The results showed that the sensors ZTOP5_PH8 and ZTOP5_PH13 based on hollow cubic and hollow octahedron materials gave relatively good selectivity to VOCs The responses respectively, of ZTOP5_PH8 and ZTOP5_PH13 sensors to 125 ppm acetone were 34 and 44.52 times at the optimum working temperature of 450 °C The sensor's detection limit reaches 175 and 0.67 (ppb) We also explained the gas sensitivity mechanism of cubic and octahedron materials through the electron depletion region model The porous structure of hollow cubic and hollow octahedron enables gas diffusion, and thus enhance the gas sensing performance Although we have tried to make the research project as complete as possible, however, there are still many other issues that need to be addressed for further improvement Therefore, we have proposed further research directions, including: Continuing to study the effect of hydrothermal conditions on the formation of different structural morphologies of Zn2SnO4 materials, thereby elucidating the mechanism of material formation and simultaneously investigating the influence of light on the sensor parameters Study on denaturation of Zn2SnO4 material with some catalyst metals such as Pt, Pd, and Pt-Pd alloy or with some other metal oxides such as MoS2 to improve the gas-sensitive properties of the material With the remarkable advantages of Zn2SnO4 material, we expected to successfully develop a high-performance VOC sensor for breath analysis application 68 LIST OF REFERENCES [1] D Assante, A Caforio, M Flamini, and E Romano, “Smart Education in the context of Industry 4.0,” in 2019 IEEE Global Engineering Education Conference (EDUCON), 2019, pp 1140–1145 [2] J Nagy, J Oláh, E Erdei, D Máté, and J Popp, “The Role and Impact of Industry 4.0 and the Internet of Things on the Business Strategy of the Value Chain—The Case of Hungary,” Sustainability, vol 10, no 10, p 3491, Sep 2018 [3] T Adhikary, A D Jana, A Chakrabarty, and S K Jana, “The Internet of Things (IoT) Augmentation in Healthcare: An Application Analytics,” in ICICCT 2019 – System Reliability, Quality Control, Safety, Maintenance and Management, Singapore: Springer Singapore, 2020, pp 576–583 [4] C Perera, C H Liu, and S Jayawardena, “The Emerging Internet of Things Marketplace From an Industrial Perspective: A Survey,” IEEE Trans Emerg Top Comput., vol 3, no 4, pp 585–598, Dec 2015 [5] L M Dang, M J Piran, D Han, K Min, and H Moon, “A Survey on Internet of Things and Cloud Computing for Healthcare,” Electronics, vol 8, no 7, p 768, Jul 2019 [6] A Nayyar and V Puri, “Data Glove: Internet of Things (IoT) Based Smart Wearable Gadget,” Br J Math Comput Sci., vol 15, no 5, pp 1–12, Jan 2016 [7] A H Jalal, F Alam, S Roychoudhury, Y Umasankar, N Pala, and S Bhansali, “Prospects and Challenges of Volatile Organic Compound Sensors in Human Healthcare,” ACS Sensors, vol 3, no 7, pp 1246–1263, Jul 2018 [8] X Shi et al., “State-of-the-Art Internet of Things in Protected Agriculture,” Sensors, vol 19, no 8, p 1833, Apr 2019 [9] Y Shiv, R Kumar, V Kumar, and M Wairiya, “A Lightweight Authentication Scheme for Wearable Medical Sensors,” in 2018 8th International Conference on Cloud Computing, Data Science & Engineering (Confluence), 2018, pp 366–370 [10] T Lin, X Lv, Z Hu, A Xu, and C Feng, “Semiconductor Metal Oxides as 69 Chemoresistive Sensors for Detecting Volatile Organic Compounds,” Sensors, vol 19, no 2, p 233, Jan 2019 [11] X Gao and T Zhang, “An overview: Facet-dependent metal oxide semiconductor gas sensors,” Sensors Actuators B Chem., vol 277, pp 604–633, Dec 2018 [12] C Zhang, L Li, L Hou, and W Chen, “Fabrication of Co3O4 nanowires assembled on the surface of hollow carbon spheres for acetone gas sensing,” Sensors Actuators B Chem., vol 291, pp 130–140, Jul 2019 [13] T T Le Dang, M Tonezzer, and V H Nguyen, “Hydrothermal Growth and Hydrogen Selective Sensing of Nickel Oxide Nanowires,” J Nanomater., vol 2015, pp 1–8, 2015 [14] C Su et al., “Controllable synthesis of crescent-shaped porous NiO nanoplates for conductometric ethanol gas sensors,” Sensors Actuators B Chem., vol 296, p 126642, Oct 2019 [15] H Nguyen and S A El-Safty, “Meso- and Macroporous Co3O4 Nanorods for Effective VOC Gas Sensors,” J Phys Chem C, vol 115, no 17, pp 8466–8474, May 2011 [16] S Agarwal et al., “Gas sensing properties of ZnO nanostructures (flowers/rods) synthesized by hydrothermal method,” Sensors Actuators B Chem., vol 292, pp 24–31, Aug 2019 [17] P Bindra and A Hazra, “Selective detection of organic vapors using TiO2 nanotubes based single sensor at room temperature,” Sensors Actuators B Chem., vol 290, pp 684–690, Jul 2019 [18] X Yang et al., “One step synthesis of branched SnO2/ZnO heterostructures and their enhanced gas-sensing properties,” Sensors Actuators B Chem., vol 281, pp 415–423, Feb 2019 [19] Y Li et al., “Enhanced acetone sensing performance based on hollow coral-like SnO2–ZnO composite nanofibers,” J Mater Sci Mater Electron., vol 30, no 16, pp 15734–15743, Aug 2019 [20] X Wang et al., “Dispersed WO3 nanoparticles with porous nanostructure for ultrafast toluene sensing,” Sensors Actuators B Chem., vol 289, pp 195–206, Jun 2019 70 [21] M Righettoni, A Amann, and S E Pratsinis, “Breath analysis by nanostructured metal oxides as chemo-resistive gas sensors,” Mater Today, vol 18, no 3, pp 163–171, Apr 2015 [22] D Zhang et al., “Highly sensitive BTEX sensors based on hexagonal WO3 nanosheets,” Sensors Actuators B Chem., vol 293, pp 23–30, Aug 2019 [23] J.-W Yoon and J.-H Lee, “Toward breath analysis on a chip for disease diagnosis using semiconductor-based chemiresistors: recent progress and future perspectives,” Lab Chip, vol 17, no 21, pp 3537–3557, 2017 [24] A Mirzaei, J.-H Kim, H W Kim, and S S Kim, “Resistive-based gas sensors for detection of benzene, toluene and xylene (BTX) gases: a review,” J Mater Chem C, vol 6, no 16, pp 4342–4370, 2018 [25] R Li et al., “Gas sensing selectivity of oxygen-regulated SnO2 films with different microstructure and texture,” J Mater Sci Technol., vol 35, no 10, pp 2232–2237, Oct 2019 [26] A Mirzaei, S S Kim, and H W Kim, “Resistance-based H2S gas sensors using metal oxide nanostructures: A review of recent advances,” J Hazard Mater., vol 357, pp 314–331, Sep 2018 [27] N Van Hoang, C M Hung, N D Hoa, N Van Duy, and N Van Hieu, “Facile on-chip electrospinning of ZnFe2O4 nanofiber sensors with excellent sensing performance to H2S down ppb level,” J Hazard Mater., vol 360, pp 6–16, Oct 2018 [28] N Van Hoang, C M Hung, N D Hoa, N Van Duy, I Park, and N Van Hieu, “Excellent detection of H2S gas at ppb concentrations using ZnFe2O4 nanofibers loaded with reduced graphene oxide,” Sensors Actuators B Chem., vol 282, pp 876–884, Mar 2019 [29] K Al-Attafi et al., “Cubic aggregates of Zn2SnO4 nanoparticles and their application in dye-sensitized solar cells,” Nano Energy, vol 57, pp 202– 213, Mar 2019 [30] P P Das, A Roy, M Tathavadekar, and P S Devi, “Photovoltaic and photocatalytic performance of electrospun Zn2SnO4 hollow fibers,” Appl Catal B Environ., vol 203, pp 692–703, Apr 2017 [31] Y R Lim et al., “Zn2GeO4 and Zn2SnO4 nanowires for high-capacity 71 lithium- and sodium-ion batteries,” J Mater Chem A, vol 4, no 27, pp 10691–10699, 2016 [32] H X Thanh et al., “On-chip growth of single phase Zn2SnO4 nanowires by thermal evaporation method for gas sensor application,” J Alloys Compd., vol 708, pp 470–475, Jun 2017 [33] J Yang, S Wang, L Zhang, R Dong, Z Zhu, and X Gao, “Zn2SnO4 doped SnO2 hollow spheres for phenylamine gas sensor application,” Sensors Actuators B Chem., vol 239, pp 857–864, Feb 2017 [34] H M Chen et al., “Hollow Platinum Spheres with Nano-Channels: Synthesis and Enhanced Catalysis for Oxygen Reduction,” J Phys Chem C, vol 112, no 20, pp 7522–7526, May 2008 [35] X Yang et al., “Enhanced gas sensing properties of monodisperse Zn2SnO4 octahedron functionalized by PdO nanoparticals,” Sensors Actuators B Chem., vol 266, pp 302–310, Aug 2018 [36] H M Yang et al., “Synthesis of Zn2SnO4 hollow spheres by a template route for high-performance acetone gas sensor,” Sensors Actuators B Chem., vol 245, pp 493–506, Jun 2017 [37] D An et al., “Synthesis of Zn2SnO4 via a co-precipitation method and its gas-sensing property toward ethanol,” Sensors Actuators B Chem., vol 213, pp 155–163, Jul 2015 [38] K A Bhabu, J Theerthagiri, J Madhavan, T Balu, and T R Rajasekaran, “Synthesis and Characterization of Zinc Stannate Nanomaterials by SolGel Method,” Mater Sci Forum, vol 832, pp 144–157, Nov 2015 [39] C M Hung, H V Phuong, N Van Duy, N D Hoa, and N Van Hieu, “Comparative effects of synthesis parameters on the NO2 gas-sensing performance of on-chip grown ZnO and Zn2SnO4 nanowire sensors,” J Alloys Compd., vol 765, pp 1237–1242, Oct 2018 [40] Y.-Q Jiang, X.-X Chen, R Sun, Z Xiong, and L.-S Zheng, “Hydrothermal syntheses and gas sensing properties of cubic and quasicubic Zn2SnO4,” Mater Chem Phys., vol 129, no 1–2, pp 53–61, Sep 2011 [41] T.-T Xu, X.-F Zhang, X Dong, Z.-P Deng, L.-H Huo, and S Gao, 72 “Enhanced H2S gas-sensing performance of Zn2SnO4 hierarchical quasimicrospheres constructed from nanosheets and octahedra,” J Hazard Mater., vol 361, pp 49–55, Jan 2019 [42] G Ma et al., “Phase-controlled synthesis and gas-sensing properties of zinc stannate (ZnSnO3 and Zn2SnO4) faceted solid and hollow microcrystals,” CrystEngComm, vol 14, no 6, p 2172, 2012 [43] A Mirzaei, S G Leonardi, and G Neri, “Detection of hazardous volatile organic compounds (VOCs) by metal oxide nanostructures-based gas sensors: A review,” Ceram Int., vol 42, no 14, pp 15119–15141, Nov 2016 [44] C Yang et al., “Abatement of various types of VOCs by adsorption/catalytic oxidation: A review,” Chem Eng J., vol 370, pp 1128–1153, Aug 2019 [45] J Park, “Nanostructured semiconducting metal oxides for use in gas sensors,” Manager, 2010 [46] A Rydosz, “Sensors for Enhanced Detection of Acetone as a Potential Tool for Noninvasive Diabetes Monitoring,” Sensors, vol 18, no 7, p 2298, Jul 2018 [47] I Nardi-Agmon et al., “Exhaled Breath Analysis for Monitoring Response to Treatment in Advanced Lung Cancer,” J Thorac Oncol., vol 11, no 6, pp 827–837, Jun 2016 [48] T Ivetić, “Zinc-Tin-Oxide-Based Porous Ceramics: Structure, Preparation and Properties,” in Recent Advances in Porous Ceramics, InTech, 2018 [49] V Šepelák et al., “Nonequilibrium structure of Zn2SnO4 spinel nanoparticles,” J Mater Chem., vol 22, no 7, p 3117, 2012 [50] J Lee, Y Kang, C S Hwang, S Han, S.-C Lee, and J.-H Choi, “Effect of oxygen vacancy on the structural and electronic characteristics of crystalline Zn2SnO4,” J Mater Chem C, vol 2, no 39, pp 8381–8387, 2014 [51] T Tharsika, A S M A Haseeb, S A Akbar, M F M Sabri, and Y H Wong, “Gas sensing properties of zinc stannate (Zn2SnO4) nanowires prepared by carbon assisted thermal evaporation process,” J Alloys 73 Compd., vol 618, pp 455–462, Jan 2015 [52] D An et al., “Ethanol gas-sensing characteristic of the Zn2SnO4 nanospheres,” Ceram Int., vol 42, no 2, pp 3535–3541, Feb 2016 [53] L Wang, T Zhou, R Zhang, Z Lou, J Deng, and T Zhang, “Comparison of toluene sensing performances of zinc stannate with different morphology-based gas sensors,” Sensors Actuators B Chem., vol 227, pp 448–455, May 2016 [54] T.-T Xu, Y.-M Xu, X.-F Zhang, Z.-P Deng, L.-H Huo, and S Gao, “Enhanced H2S Gas-Sensing Performance of Zn2SnO4 Lamellar MicroSpheres,” Front Chem., vol 6, May 2018 [55] T.-T Xu, X.-F Zhang, Z.-P Deng, L.-H Huo, and S Gao, “Synthesis of Zn2SnO4 octahedron with enhanced H2S gas-sensing performance,” Polyhedron, vol 151, pp 510–514, Sep 2018 [56] Y Tie et al., “Formaldehyde sensing characteristics of hydrothermally synthesized Zn2SnO4 nanocubes,” Mater Lett., vol 259, p 126896, Jan 2020 [57] S Shu, M Wang, W Yang, and S Liu, “Synthesis of surface layered hierarchical octahedral-like structured Zn2SnO4/SnO2 with excellent sensing properties toward HCHO,” Sensors Actuators B Chem., vol 243, pp 1171–1180, May 2017 [58] F Liu et al., “Fabrication of 1D Zn2SnO4 nanowire and 2D ZnO nanosheet hybrid hierarchical structures for use in triethylamine gas sensors,” Sensors Actuators B Chem., vol 291, pp 155–163, Jul 2019 [59] W Wang, H Chai, X Wang, X Hu, and X Li, “Ethanol gas sensing performance of Zn2SnO4 nanopowder prepared via a hydrothermal route with different solution pH values,” Appl Surf Sci., vol 341, pp 43–47, Jun 2015 [60] Z Chen, M Cao, and C Hu, “Novel Zn2SnO4 Hierarchical Nanostructures and Their Gas Sensing Properties toward Ethanol,” J Phys Chem C, vol 115, no 13, pp 5522–5529, Apr 2011 [61] Y Yu, Y Xia, W Zeng, and R Liu, “Synthesis of multiple networked NiO nanostructures for enhanced gas sensing performance,” Mater Lett., 74 vol 206, pp 80–83, Nov 2017 [62] Y Zhang, W Zeng, H Ye, and Y Li, “Enhanced carbon monoxide sensing properties of TiO2 with exposed (001) facet: A combined firstprinciple and experimental study,” Appl Surf Sci., vol 442, pp 507–516, Jun 2018 [63] Y.-F Sun et al., “Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review,” Sensors, vol 12, no 3, pp 2610–2631, Feb 2012 [64] C Chen, G Li, J Li, and Y Liu, “One-step synthesis of 3D flower-like Zn2SnO4 hierarchical nanostructures and their gas sensing properties,” Ceram Int., vol 41, no 1, pp 1857–1862, Jan 2015 [65] X Chu et al., “Preparation and gas sensing properties of grapheneZn2SnO4 composite materials,” Sensors Actuators B Chem., vol 251, pp 120–126, Nov 2017 [66] Y Li et al., “In situ decoration of Zn2SnO4 nanoparticles on reduced graphene oxide for high performance ethanol sensor,” Ceram Int., vol 44, no 6, pp 6836–6842, Apr 2018 [67] X Yang et al., “Highly efficient ethanol gas sensor based on hierarchical SnO2/Zn2SnO4 porous spheres,” Sensors Actuators B Chem., vol 282, pp 339–346, Mar 2019 [68] X Xin et al., “UV-activated porous Zn2SnO4 nanofibers for selective ethanol sensing at low temperatures,” J Alloys Compd., vol 780, pp 228– 236, Apr 2019 [69] L H Hoang et al., “Temperature-dependent Raman scattering study of multiferroic MnWO4,” J Raman Spectrosc., vol 41, no 9, pp 1005–1010, Sep 2010 [70] N Van Minh, N M Hung, D T Xuan Thao, M Roeffaers, and J Hofkens, “Structural and Optical Properties of ZnWO4 :Er3+ Crystals,” J Spectrosc., vol 2013, pp 1–5, 2013 [71] L H Hoang, P Van Hai, N H Hai, P Van Vinh, X.-B Chen, and I.-S Yang, “The microwave-assisted synthesis and characterization of Zn1−xCoxO nanopowders,” Mater Lett., vol 64, no 8, pp 962–965, Apr 2010 75 [72] G Korotcenkov, Handbook of Gas Sensor Materials, vol 2014 [73] Y Li, N Chen, D Deng, X Xing, X Xiao, and Y Wang, “Formaldehyde detection: SnO2 microspheres for formaldehyde gas sensor with high sensitivity, fast response/recovery and good selectivity,” Sensors Actuators B Chem., vol 238, pp 264–273, Jan 2017 [74] Y Park et al., “Highly sensitive and selective isoprene sensing performance of ZnO quantum dots for a breath analyzer,” Sensors Actuators B Chem., vol 290, pp 258–266, Jul 2019 [75] H Bian et al., “Improvement of acetone gas sensing performance of ZnO nanoparticles,” J Alloys Compd., vol 658, pp 629–635, Feb 2016 [76] T Zhou, X Liu, R Zhang, Y Wang, and T Zhang, “Shape control and selective decoration of Zn2SnO4 nanostructures on 1D nanowires: Boosting chemical–sensing performances,” Sensors Actuators B Chem., vol 290, pp 210–216, Jul 2019 [77] X Hu et al., “Hydrothermal synthesis, characterization and enhanced visible-light photocatalytic activity of Co-doped Zn2SnO4 nanoparticles,” Chem Phys., vol 490, pp 38–46, Jun 2017 [78] Y Bing et al., “Assembly of hierarchical ZnSnO3 hollow microspheres from ultra-thin nanorods and the enhanced ethanol-sensing performances,” Sensors Actuators B Chem., vol 190, pp 370–377, Jan 2014 [79] S Sun and S Liang, “Morphological zinc stannate: synthesis, fundamental properties and applications,” J Mater Chem A, vol 5, no 39, pp 20534– 20560, 2017 [80] M Miyauchi, Z Liu, Z.-G Zhao, S Anandan, and K Hara, “Single crystalline zinc stannate nanoparticles for efficient photo-electrochemical devices,” Chem Commun., vol 46, no 9, p 1529, 2010 [81] M.-J Kim, S.-H Park, and Y.-D Huh, “Photocatalytic Activities of Hydrothermally Synthesized Zn2SnO4,” Bull Korean Chem Soc., vol 32, no 5, pp 1757–1760, May 2011 [82] Q Zhao, X Deng, M Ding, J Huang, D Ju, and X Xu, “Synthesis of hollow cubic Zn2SnO4 sub-microstructures with enhanced photocatalytic performance,” J Alloys Compd., vol 671, pp 328–333, Jun 2016 76 [83] N D Thien, L M Quynh, L Van Vu, and N N Long, “Phase transformation and photoluminescence of undoped and Eu3+-doped zinc stannate (Zn2SnO4) nanocrystals synthesized by hydrothermal method,” J Mater Sci Mater Electron., vol 30, no 2, pp 1813–1820, Jan 2019 [84] J.-W Zhao, L.-R Qin, and L.-D Zhang, “Single-crystalline Zn2SnO4 hexangular microprisms: Fabrication, characterization and optical properties,” Solid State Commun., vol 141, no 12, pp 663–666, Mar 2007 [85] Q R Hu et al., “Synthesis and photoluminescence of Zn2SnO4 nanowires,” J Alloys Compd., vol 484, no 1–2, pp 25–27, Sep 2009 [86] N D Hoa and S A El-Safty, “Gas nanosensor design packages based on tungsten oxide: mesocages, hollow spheres, and nanowires,” Nanotechnology, vol 22, no 48, p 485503, Dec 2011 [87] C M Hung, N D Hoa, N Van Duy, N Van Toan, D T T Le, and N Van Hieu, “Synthesis and gas-sensing characteristics of α-Fe2O3 hollow balls,” J Sci Adv Mater Devices, vol 1, no 1, pp 45–50, Mar 2016 [88] S Lee, “Electrodes for Semiconductor Gas Sensors,” Sensors, vol 17, no 4, p 683, Mar 2017 [89] S.-J Choi et al., “Selective diagnosis of diabetes using Pt-functionalized WO3 hemitube networks as a sensing layer of acetone in exhaled breath,” Anal Chem., vol 85, no 3, pp 1792–1796, 2013 [90] H M Tan et al., “Novel self-heated gas sensors using on-chip networked nanowires with ultralow power consumption,” ACS Appl Mater Interfaces, vol 9, no 7, pp 6153–6162, 2017 [91] X Kou et al., “Superior acetone gas sensor based on electrospun SnO2 nanofibers by Rh doping,” Sensors Actuators B Chem., vol 256, pp 861– 869, Mar 2018 [92] X Xing et al., “CdO-Ag-ZnO nanocomposites with hierarchically porous structure for effective VOCs gas-sensing properties,” Ceram Int., vol 45, no 4, pp 4322–4334, Mar 2019 77 LIST OF PUBLICATIONS Nguyen Hong Hanh, Lai Van Duy, Chu Manh Hung, Nguyen Van Duy, Young-Woo Heo, Nguyen Van Hieu, Nguyen Duc Hoa*, "VOC gas sensor based on hollow cubic assembled nanocrystal Zn2SnO4 for breath analysis", Sensors and Actuators A 302 (2020) 111834-111839 [IF2018: 2.73] Lai Van Duy, Nguyen Hong Hanh, Dang Ngoc Son, Pham Tien Hung, Chu Manh Hung*, Nguyen Van Duy, Nguyen Duc Hoa*, Nguyen Van Hieu, “Facile hydrothermal synthesis of two-dimensional porous ZnO nanosheets for highly sensitive ethanol sensor”, Journal of Nanomaterials 2019 (2019) 1-7 [IF2018: 2.23] Lai Van Duy, Nguyen Hong Hanh, Nguyen Duc Hoa+, Chu Manh Hung*, “Hydrothermal Synthesis of Zn2SnO4 Nanoparticles for Ethanol sensor”, Journal of Science & Technology 135 (2019) 067-071 Nguyen Hong Hanh, Lai Van Duy, Chu Manh Hung, Nguyen Van Duy, Nguyen Van Hieu, Nguyen Duc Hoa “Synthesis of octahedron Zn2SnO4 by hydrothermal method for high performance ethanol senser”, Vietnam Academy of Science and Technology, vol 58, No (2020) 78 ... tên tác giả luận văn: Lại Văn Duy Đề tài luận văn: Chế tạo vật liệu Zn2SnO4 cấu trúc nano ứng dụng cho cảm biến khí Chuyên ngành: Khoa học vật liệu- VLĐT Mã số SV: CA180178 Tác giả, Người hướng... PGS TS Nguyễn Phúc Dương ĐỀ TÀI LUẬN VĂN Chế tạo vật liệu Zn2SnO4 cấu trúc nano ứng dụng cho cảm biến khí Học viên: Lại Văn Duy Chuyên ngành: Khoa học vật liệu- VLĐT Giáo viên hướng dẫn (Ký ghi rõ... block for VOC gas sensor applications Therefore, this thesis targets to the ? ?Fabrication of Zn2SnO4 nanostructures for gas sensor application? ?? Aims of the thesis - To successfully fabricate Zn2SnO4