Investigation and synthesis of mos2 nanomaterial by probe ultrasonic vibration method for gas sensor at room temperature

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Investigation and synthesis of MoS2 nanomaterial by probe ultrasonic vibration method for gas sensor at room temperature HO HUU HAU Hau.HH202006M@sis.hust.edu.vn Materials Science Supervisor: Dr Chu Manh Hung Supervisor’s signature Institute: International Training Institute for Materials Science (ITIMS) Hanoi, 05/2022 SOCIALIST REPUBLIC OF VIETNAM Independence - Freedom - Happiness CONFIRMATION OF MASTER’S THESIS ADJUSTMENT Full name of author: Ho Huu Hau Investigation and synthesis of MoS2 nanomaterial by probe ultrasonic vibration method for gas sensor at room temperature Major: Materials Science Student ID: 20202006M The author, the supervisor, and the Committee confirmed that the author has adjusted and implemented the thesis according to the report of the Committee on May 19th, 2022 with the following contents: The thesis has been corrected for typographical errors and printing according to the opinions of the committee’s members Day month year 2022 Supervisor Author Dr Chu Manh Hung Ho Huu Hau COMMITTEE’S CHAIRMAN Assoc Prof Nguyen Van Quy DECLARATION OF AUTHORSHIP This thesis has been written on the basis of my research carried out at Hanoi University of Science and Technology, under the supervision of Dr Chu Manh Hung 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, May 2022 Supervisor Master student (Signature and full name) (Signature and full name) Dr Chu Manh Hung Ho Huu Hau ACKNOWLEDGMENTS First, I would like to express my deep gratitude to my supervisor, Dr Chu Manh Hung, 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 profoundly grateful to Prof Dr Nguyen Duc Hoa, Assoc Prof Dr Dang Thi Thanh Le, Assoc Prof Dr Nguyen Van Duy, Dr Nguyen Van Toan, and Dr Chu Thi Xuan for their scientific advice and insightful discussions I am very grateful to my colleague, MSc student Truong Tien Hoang Duong, who has dedicated so much time in helping me and giving me a lot of support during all the time I my thesis at ITIMS 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 Master course I am thankful to the leaders and staff of ITIMS, Hanoi University of Science and Technology (HUST), Academic Affairs Office for their help and given favorable working conditions Last but not least, I am deeply thankful to my family for their love, encouragement, and unconditional support Without them, the work would have been impossible Master student Ho Huu Hau CONTENTS CONTENTS i ABBREVIATIONS AND SYMBOLS iv LIST OF TABLES vi LIST OF FIGURES vii INTRODUCTION CHAPTER LITERATURE REVIEW 1.1 Liquid-phase exfoliation (LPE) for MoS2 NSs fabrication 1.1.1 Background on liquid-phase exfoliation 1.1.2 Processing-structure relationship of LPE for NSs 1.2 Hydrothermal for ZTO fabrication 1.3 MoS2 NSs for gas-sensing application 10 1.3.1 Overview on MoS2 10 1.3.2 MoS2 NSs in NO2 gas-sensing application 12 1.3.2.1 NO2 gas 12 1.3.2.2 MoS2 NSs in NO2 gas-sensing application 12 1.4 MoS2 combine with SMO (ZTO) for gas-sensing application 14 1.4.1 Overview on ZTO and its application in gas-sensing field 14 1.4.1.1 Overview on ZTO 14 1.4.1.2 ZTO in gas-sensing application 15 1.4.2 MoS2 combine with SMO (ZTO) for Triethylamine (TEA) gassensing application 16 1.4.2.1 MoS2 combine SMO for gas sensor 16 1.4.2.2 Triethylamine (TEA) gas 20 1.4.2.3 MoS2 combine SMO for TEA gas sensor 20 1.5 Gas-sensing mechanism 21 1.5.1 General sensing mechanisms of gas sensors 21 1.5.2 Sensing mechanisms of p-n heterojunction material-based gas sensors… 23 Conclusion of chapter 25 CHAPTER EXPERIMENTAL 26 2.1 Synthesis 26 i 2.1.1 MoS2 NSs preparation 26 2.1.2 ZTO porous octahedra preparation 27 2.1.3 Preparation MoS2 NSs combine with ZTO porous octahedra 28 2.2 Characterization Techniques 29 2.2.1 Raman spectroscopy 29 2.2.2 X-ray diffraction 30 2.2.3 SEM and EDX 30 2.2.4 TEM and SAED 31 2.3 Gas-sensing measurement 32 2.3.1 Dynamic measurement method 32 2.3.2 Static measurement method 32 2.3.3 Method to investigate the effect of relative humidity on the sensor and calculate the detection limit 34 Conclusion of chapter 34 CHAPTER RESULTS AND DISCUSSIONS 35 3.1 Introduction 35 3.2 NO2 gas sensors based on MoS2 NSs 36 3.2.1 Morphologies and structure of MoS2 NSs 36 3.2.1.1 Effects of ultrasonic vibration power 36 3.2.1.2 Effect of centrifugal speed 37 3.2.2 NO2 gas-sensing properties of MoS2 NSs sensors 41 3.2.2.3 Effects of ultrasonic vibration power 41 3.2.2.4 Effects of centrifugal speed 42 3.2.2.5 Selectivity, stability and RH effects 47 3.2.2.6 NO2 gas-sensing mechanism of MoS2 NSs 49 3.3 Triethylamine (TEA) gas sensors based on MoS2 NSs combine with ZTO porous octahedra 51 3.3.1 Morphologies and structure of MoS2 NSs combine with ZTO porous octahedra 51 3.3.2 Gas sensing properties 55 3.3.2.1 Effects of working temperature 55 3.3.2.2 Effects of MoS2 concentrations 57 3.3.2.3 Selectivity, stability and RH effects 59 ii 3.3.2.4 Triethylamine (TEA) gas-sensing mechanism of MoS2 NSs combine ZTO 62 Conclusion of chapter 64 CONCLUSIONS AND RECOMMENDATIONS 65 LIST OF PUBLICATIONS 66 REFERENCES 67 iii ABBREVIATIONS AND SYMBOLS Number Abbreviations and symbols Meaning 1D One Dimension 2D Two Dimension 3D Three Dimension CVD DI Deionized Water DL Detection Limit DMF Dimethylformamide EDX Energy Dispersive X-ray spectroscopy FE-SEM 10 GO Graphene Oxides 11 GP Graphene 12 HRTEM High Resolution Transmission Electron Microscope 13 IUPAC International Union of Pure and Applied Chemistry 14 JCPDS Joint Committee on Powder Diffraction Standards 15 NFs Nanofibers 16 NMP N-Methylpyrrolidone 17 NPs Nanoparticles 18 NRs Nanorods 19 NSs Nanosheets 20 NTs Nanotubes 21 NVP N-Vinylpyrrolidone 22 NWs Nanowires 23 ppb Parts Per Billion 24 ppm Parts Per Million 25 PVA Poly(vinyl alcohol) 26 Ra Sensor resistance in dry air 27 Rg Sensor resistance in tested gas 28 RGO Reduced Graphene Oxides 29 RH Ambient Relative Humidity Chemical Vapor Deposition Field Emission Scanning Electron Microscope iv 30 RT Room Temperature 31 S 32 SAED Selected Area Electron Diffraction 33 sccm Standard Cubic Centimeters Per Minute 34 SEM Scanning Electron Microscope 35 SMO Semiconductor Metal Oxides 36 TEA Triethylamine 37 TEM Transmission Electron Microscope 38 TMDs Transition Metal Dichalcogenide 39 WF 40 XRD X-ray Diffraction 41 ZTO Zinc Tin Oxide, Zn2SnO4 42 τrec Recovery time 43 τres Response time Sensor Response Work Function v LIST OF TABLES Table 1.1 Summary of advantages and disadvantages of TMDs and SMOs in terms of gas sensor application [55] 16 Table 2.1 Names and synthesis conditions for different samples of MoS2/Zn2SnO4 nanocomposites 29 Table 3.1 Comparison of the performance of the MoS2 nanosheets with that based on different MoS2 nanostructures to NO2 gas 50 Table 3.2 Comparison of the gas sensing performances of MoS2/Zn2SnO4 sensor with previous work 63 vi the response of the sensor is 304 times for 50 ppm of TEA gas at the working temperature of 150 °C due to the formation of heterojunctions between ZTO and MoS2 NSs Conclusion of chapter This chapter studies the effects of ultrasonic vibration power, centrifugation speed and dispersion solvent on the morphology and structure of the NSs MoS2 fabricated by liquid phase exfoliation method The optimal results showed that the NSs MoS2 sensor was delaminated at 420 W and centrifuged at 4000 rpm for 30 with a mixed solvent of ethanol and DI water with 45% ethanol/water mixture gave a response of to 5.3 with ppm to 0.5 ppm NO2, respectively at room temperature In addition, this chapter has optimized the concentration of MoS2 NSs when combined with ZTO by hydrothermal method MoS2 NSs enhanced the performance of ZTO sensors when combined with MoS2 NSs compared to pure ZTO-based sensors The ZTO sensor combined with 3ml of MoS2 solution at optimal fabrication conditions (ZM3) reached 657 to 200 ppm TEA at 150 °C (124 times higher than of pure ZTO at the same conditions) The results also confirm that besides improving the response, MoS2 NSs also reduce the operating temperature significantly of the pure ZTO-based sensor The optimum working condition of the pure ZTO-based sensor was 250 oC, while the optimal working temperature of the ZM3 sensor has been reduced to 150 oC These were significantly affected by the formation of heterojunctions between ZTO and MoS2 64 CONCLUSIONS AND RECOMMENDATIONS Conclusion Based on the above-mentioned research results, some conclusions were drawn and listed hereafter  MoS2 NSs and their combination with ZTO have been successfully fabricated by liquid-phase exfoliation combined with a simple hydrothermal method  Solvent dispersion, ultrasonic vibration power, centrifugal rotation speed which strongly influence the morphology, microstructure and gas sensing performance of the MoS2 NSs, were optimized Optimized MoS2 NSs have approximately times to ppm NO2 response at room temperature, corresponding to 3-layer MoS2 nanosheets, significantly improving the gassensitive performance compared with the multi-layer bulk MoS2  The effect of MoS2 concentration on the morphology, crystal structure and gas sensing performance of ZTO, was also optimized  MoS2 NSs enhanced the sensing properties The response increased about 124 times (5.3 with pure ZTO and 657 with MoS2/ZTO to 200 ppm TEA at 150 ºC) and the working temperature was also significantly improved from 250 ºC to 150 ºC under optimal conditions  The sensor of MoS2/ZTO under optimal conditions also exhibits high sensitivity, excellent selectivity and long-term stability, making it suitable for TEA gas sensors for food quality control applications Recommendations for future works The liquid-phase exfoliation and hydrothermal method is a simple technique to fabricate NSs few layers from bulk materials and composite with various materials Whereas, it is quite easy to mix TMDs structures with other SMO, which has significant impacts on SMO structure, composition and gas-sensing properties Thus, some directions for future research were suggested as follows:  Investigation to combine other TMDs such as WS2, MoSe2 with other SMOs to improve gas sensing performance  Doping noble metals such as Pt, Pd, Au, etc with TMDs structure and TMD/SMO structure  Investigation on combining types of TMDs with each other and with SMO for gas sensors 65 LIST OF PUBLICATIONS Ho Huu Hau, Truong Tien Hoang Duong, Nguyen Khac Man, Tran Thi Viet Nga, Chu Thi Xuan, Dang Thi Thanh Le, Nguyen Van Toan*, Chu Manh Hung*, Nguyen Van Duy, Nguyen Van Hieu, Nguyen Duc Hoa, “Enhanced NO2 gassensing performance at room temperature using exfoliated MoS2 nanosheets”, Sensors and Actuators A: Physical, Volume 332, (2021) 113137, Q1, [IF2021: 3.407] Tran Thi Ngoc Hoa, Nguyen Van Duy*, Chu Manh Hung, Nguyen Van Hieu, Ho Huu Hau and Nguyen Duc Hoa*, “Dip-coating decoration of Ag2O nanoparticles on SnO2 nanowires for high-performance H2S gas sensors”, RSC Advances 10 (2020) 17713–17723, Q1, [IF2021: 3.361] PUBLICATIONS IN PROGRESS Ho Huu Hau, Truong Tien Hoang Duong, Chu Manh Hung*, Dang Thi Thanh Le, Nguyen Van Duy, Nguyen Van Hieu, Nguyen Duc Hoa*, “Highly sensitive and dual-functional NO2 and NH3 toxic gas selective at low temperature gas sensor using WS2 nanosheets” (Complete manuscript for submission-Q1) Ho Huu Hau, Truong Tien Hoang Duong, Chu Manh Hung*, Dang Thi Thanh Le, Nguyen Van Duy, Nguyen Duc Hoa, “Ultrasensitive triethylamine gas sensing performance based on P-N heterostructural MoS2/Zn2SnO4 nanocomposites composed of porous octahedra and nanosheets for food quality assessment” (Complete manuscript for submission-Q1) Truong Tien Hoang Duong, Ho Huu Hau, Le Thi Hong, Chu Manh Hung*, Nguyen Van Duy, Le Anh Vu, Nguyen Duc Hoa*, “Pt-decorated MoS2 ultrathin nanoflowers for enhanced NH3 gas sensing”, Materials Science in Semiconductor Processing (Revision-Q2) Ho Huu Hau, Truong Tien Hoang Duong, Chu Manh Hung*, Dang Thi Thanh Le, Nguyen Van Duy, Nguyen Duc Hoa, “WS2 nanosheets synthesized via ultrasonic vibration probe method application for NO2 gas sensor”, The 11th Vietnam National Conference of Solid Physics and Materials Science, 2021 (Submitted) Truong Tien Hoang Duong, Ho Huu Hau, Chu Manh Hung*, Dang Thi Thanh Le, Nguyen Van Duy, Nguyen Duc Hoa, “Synthesis and investigation of SnO2 nanowires/MoS2 nanosheets heterojunction”, The 11th Vietnam National Conference of Solid Physics and Materials Science, 2021 (Submitted) 66 REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] A Dey, “Semiconductor metal oxide gas sensors: A review,” Mater Sci Eng B Solid-State Mater Adv Technol., vol 229, no December 2017, pp 206–217, 2018, 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gas sensors... 3.2.1.1 Effects of ultrasonic vibration power To study the effect of ultrasonic vibration power on the size and morphology of the materials, we performed MoS2 ultrasonic vibration at power levels,