研究奈米材料的昇華現象與機制對於材料的應用穩定性與合成設計上非常關鍵，而透過臨場加熱觀測材料在高溫下的昇華行為所得的即時影像，能夠對於材料在熱力學與動力學機制上進行更準確的分析。
在過去的研究結果中顯示，奈米顆粒的昇華與材料尺寸、表面能與外界環境如殼層包覆有密不可分的關係。本研究透過Ag立方顆粒(nanocube)與其核殼結構顆粒的臨場TEM加熱結果，探討銀顆粒在昇華過程中的形貌變化及殼層包覆對其熱穩定性的影響。有別於其他研究中小尺寸的Ag顆粒(<30 nm)在高溫下的結果，大尺寸的Ag立方顆粒(>50 nm)會在800 ℃環境中展現出三階段的形貌變化，分別為均勻(Ⅰ)-非均勻(Ⅱ)-均勻昇華(Ⅲ)，並以(110)與(100)面為Ⅰ、Ⅱ階段的主要昇華平面，而當反應至Ⅲ階段時，昇華速率反而會下降，推測是材料表能下降使昇華能障上升所導致。
在核-殼結構的加熱過程中，奈米顆粒的昇華行為則由Ⅱ階段開始進行，並且發現TiO2的包覆的Ag顆粒會因為殼層引發的局部加熱效應(local heating effect)在較低的溫度(700~750 ℃)下發生昇華反應；而C包覆的Ag則由於表面原子鈍化，抑制昇華的進行使熱穩定度有明顯的提升。

Uncovering the sublimation behavior and mechanism of nanomaterials is essential to their stability in applications and synthesis design. Through the in-situ observation of sublimation process under heating, we can analyze the behavior more precisely in thermodynamics and kinetics mechanism from the real-time reaction information.
According to the former research, sublimation behavior of nanoparticles is inseparable with the effects of particle size, surface energy and the external surroundings like shell coverage. In this study, Ag nanocubes and Ag-based core-shell structures are introduced to in-situ TEM heating system to investigate the sublimation-induced morphology change and influence of shell coverage in thermal stability. Different from other research with the results of Ag nanoparticles in small particle size (<30 nm), Ag nanocubes in large particle size (>50 nm) shows 3-stage sublimation-induced morphology change at 800 ℃ in the sequence of uniform (Ⅰ)-nonuniform (Ⅱ)- uniform (Ⅲ) sublimation. The (110) and (100) planes are the main sublimation planes from stage Ⅰ to Ⅱ. When the reaction comes to stage Ⅲ, the sublimation rate slows down due to the increase of sublimation energy barrier.
From the results of core-shell nanoparticles, the sublimation process begins with stage Ⅱ. Sublimation starts at lower temperature (700~750 ℃) in Ag with TiO2 shell because of local heating effect; while reaction is suppressed in the Ag with C shell by surface atom passivation, therefore enhancing the thermal stability.

摘要 I
Abstract II
致謝 III
目錄 IV
圖目錄 VI
表目錄 XI
第一章 緒論與文獻探討 1
1.1. 奈米材料介紹 1
1.2. 零維奈米材料 2
1.3. 銀奈米顆粒 3
1.3.1. 特點與應用 3
1.3.2. 合成法 4
1.4. 銀-二氧化鈦核-殼奈米顆粒(Ag@TiO2 Core-Shell Nanoparticles) 7
1.4.1. 特點與應用 7
1.4.2. 合成法 9
1.5. 奈米材料反應 10
1.6. 奈米材料昇華反應 16
1.6.1. 零維奈米材料 16
1.6.2. 一維奈米材料 27
1.6.3. 二維奈米材料 29
1.7. 臨場電子顯微鏡觀測技術 31
1.8. 研究動機 34
第二章 實驗方法與儀器 35
2.1. 實驗架構與步驟 35
2.1.1. 實驗步驟 35
2.1.2. 奈米顆粒製備 36
2.1.3. 氮化矽薄膜與臨場觀測樣品製備 39
2.2. 儀器介紹 40
2.2.1. X光繞射分析儀 (X-Ray Diffractometer, XRD) 40
2.2.2. 掃描式電子顯微鏡 (Scanning Electron Microscope, SEM) 42
2.2.3. 穿透式電子顯微鏡 (Transmission Electron Microscope, TEM) 43
2.2.4. 能量色散X-射線光譜儀 (Energy-Dispersive X-Ray Spectroscopy, EDS) 45
2.2.5. 高解析X-射線電子能譜儀 (High resolution X-ray Photoelectron Spectrometer, HRXPS) 46
2.2.6. 電子顯微鏡臨場加熱系統 47
2.2.7. 單區加熱爐管 (Single Zone Furnace) 48
第三章 結果與討論 49
3.1. Ag與TiO2特徵分析 49
3.1.1. Ag與Ag@TiO2顆粒合成 49
3.1.2. Ag與Ag@TiO2顆粒結構分析 51
3.2. Ag奈米顆粒昇華行為探討 53
3.2.1. 臨場觀測結果 53
3.2.2. 反應階段與行為 54
3.2.3. 昇華熱力學模型 60
3.3. 不同殼層包覆對昇華的影響 66
3.3.1. Ag@C與Ag@TiO2 核-殼顆粒臨場觀測結果 66
3.3.2. 反應階段與行為 68
3.3.3. 昇華行為差異 73
3.3.4. Ag在TiO2中的擴散機制 75
第四章 結論 79
第五章 未來展望 80
參考文獻 81

1. Baig N, et al. Nanomaterials: A review of synthesis methods, properties, recent progress, and challenges. Materials Advances 2, 1821-1871 (2021).

2. Zhang D, et al. Controllable synthesis of carbon nanomaterials by direct current arc discharge from the inner wall of the chamber. Carbon 142, 278-284 (2019).

3. Murphy CJ, et al. Controlling the aspect ratio of inorganic nanorods and nanowires. Advanced Materials 14, 80-82 (2002).

4. Shah KA, et al. Synthesis of carbon nanotubes by catalytic chemical vapour deposition: A review on carbon sources, catalysts and substrates. Materials Science in Semiconductor Processing 41, 67-82 (2016).

5. Lyu B, et al. 2D MXene–TiO2 Core–Shell Nanosheets as a Data‐Storage Medium in Memory Devices. Advanced Materials 32, 1907633 (2020).

6. Kuc A, et al. Structural and electronic properties of graphene nanoflakes. Physical Review B 81, 085430 (2010).

7. Pomerantseva E, et al. Energy storage: The future enabled by nanomaterials. Science 366, eaan8285 (2019).

8. Tseng RJ, et al. Digital memory device based on tobacco mosaic virus conjugated with nanoparticles. Nature Nanotechnology 1, 72-77 (2006).

9. Nguyen CC, et al. Recent advances in the development of sunlight-driven hollow structure photocatalysts and their applications. Journal of Materials Chemistry A 3, 18345-18359 (2015).

10. Yang H, et al. Shaping Nanostructures for Applications in Energy Conversion and Storage. ChemSusChem 6, 1781-1783 (2013).

11. Wang L, et al. Zinc oxide core–shell hollow microspheres with multi-shelled architecture for gas sensor applications. Journal of Materials Chemistry 21, 19331-19336 (2011).

12. Chen Y, et al. Colloidal RBC‐shaped, hydrophilic, and hollow mesoporous carbon nanocapsules for highly efficient biomedical engineering. Advanced Materials 26, 4294-4301 (2014).

13. Pang X, et al. Strictly biphasic soft and hard Janus structures: synthesis, properties, and applications. Angewandte Chemie International Edition 53, 5524-5538 (2014).

14. Shafiee A, et al. Core–Shell Nanophotocatalysts: Review of Materials and Applications. ACS Applied Nano Materials, (2022).

15. Wang X, et al. Synthesis, properties, and applications of hollow micro-/nanostructures. Chemical Reviews 116, 10983-11060 (2016).

16. Zareei A, et al. Highly Conductive Copper–Silver Bimodal Paste for Low-Cost Printed Electronics. ACS Applied Electronic Materials 3, 3352-3364 (2021).

17. Qian T, et al. Enhanced thermal conductivity of PEG/diatomite shape-stabilized phase change materials with Ag nanoparticles for thermal energy storage. Journal of Materials Chemistry A 3, 8526-8536 (2015).

18. Shuai C, et al. Rivet-Inspired Modification of Carbon Nanotubes by In Situ-Reduced Ag Nanoparticles To Enhance the Strength and Ductility of Zn Implants. ACS Biomaterials Science & Engineering 7, 5484-5496 (2021).

19. Sun Y, et al. Anomalous sublimation passivation of nanotwinned silver particles. Materials Research Letters 8, 195-200 (2020).

20. Xu L, et al. Silver nanoparticles: Synthesis, medical applications and biosafety. Theranostics 10, 8996 (2020).

21. Khayati G, et al. The nanostructure evolution of Ag powder synthesized by high energy ball milling. Advanced Powder Technology 23, 393-397 (2012).

22. Tien DC, et al. Discovery of ionic silver in silver nanoparticle suspension fabricated by arc discharge method. Journal of Alloys and Compounds 463, 408-411 (2008).

23. Amendola V, et al. Laser ablation synthesis in solution and size manipulation of noble metal nanoparticles. Physical Chemistry Chemical Physics 11, 3805-3821 (2009).

24. Stagon SP, et al. Syntheses and applications of small metallic nanorods from solution and physical vapor deposition. Nanotechnology Reviews 2, 259-267 (2013).

25. Fiévet F, et al. The polyol process: a unique method for easy access to metal nanoparticles with tailored sizes, shapes and compositions. Chemical Society Reviews 47, 5187-5233 (2018).

26. Siekkinen AR, et al. Rapid synthesis of small silver nanocubes by mediating polyol reduction with a trace amount of sodium sulfide or sodium hydrosulfide. Chemical Physics Letters 432, 491-496 (2006).

27. Alqadi M, et al. pH effect on the aggregation of silver nanoparticles synthesized by chemical reduction. Materials Science-Poland 32, 107-111 (2014).

28. Zaarour M, et al. Photochemical preparation of silver nanoparticles supported on zeolite crystals. Langmuir 30, 6250-6256 (2014).

29. Khaydarov RA, et al. Electrochemical method for the synthesis of silver nanoparticles. Journal of Nanoparticle Research 11, 1193-1200 (2009).

30. Chung DS, et al. Microwave synthesis of silver nanoparticles using different pentose carbohydrates as reducing agents. J Chem 12, 1-10 (2018).

31. Darroudi M, et al. Green synthesis of colloidal silver nanoparticles by sonochemical method. Materials Letters 66, 117-120 (2012).

32. Ali J, et al. Revisiting the mechanistic pathways for bacterial mediated synthesis of noble metal nanoparticles. Journal of Microbiological Methods 159, 18-25 (2019).

33. Ottoni CA, et al. Screening of filamentous fungi for antimicrobial silver nanoparticles synthesis. AMB Express 7, 1-10 (2017).

34. Alassali A, et al. Methods for upstream extraction and chemical characterization of secondary metabolites from algae biomass. Advanced Techniques in Biology & Medicine, 1-16 (2016).

35. Galvez AM, et al. Bacterial exopolysaccharide-mediated synthesis of silver nanoparticles and their application on bacterial biofilms. Journal of Microbiology, Biotechnology and Food Sciences 2021, 970-978 (2021).

36. Khanna P, et al. Algae-based metallic nanoparticles: Synthesis, characterization and applications. Journal of Microbiological Methods 163, 105656 (2019).

37. Khan MA, et al. Applications of plant terpenoids in the synthesis of colloidal silver nanoparticles. Advances in Colloid and Interface Science 234, 132-141 (2016).

38. Khorrami S, et al. Selective cytotoxicity of green synthesized silver nanoparticles against the MCF-7 tumor cell line and their enhanced antioxidant and antimicrobial properties. International Journal of Nanomedicine 13, 8013 (2018).

39. Yang X, et al. Enhanced gas sensing performance based on the fabrication of polycrystalline Ag@ TiO2 core-shell nanowires. Sensors and Actuators B: Chemical 286, 483-492 (2019).

40. Zhang N, et al. Function-oriented engineering of metal-based nanohybrids for photoredox catalysis: exerting plasmonic effect and beyond. Chem 4, 1832-1861 (2018).

41. Cheng B, et al. Preparation and enhanced photocatalytic activity of Ag@ TiO2 core–shell nanocomposite nanowires. Journal of Hazardous Materials 177, 971-977 (2010).

42. Jia J, et al. On the crystal structural control of sputtered TiO2 thin films. Nanoscale Research Letters 11, 1-9 (2016).

43. Hanaor DA, et al. Review of the anatase to rutile phase transformation. Journal of Materials Science 46, 855-874 (2011).

44. Peckus D, et al. Hot electron emission can lead to damping of optomechanical modes in core–shell Ag@ TiO¬2 nanocubes. The Journal of Physical Chemistry C 121, 24159-24167 (2017).

45. Du P, et al. Synthesis of thermally stable Ag@ TiO2 core–shell nanoprisms and plasmon–enhanced optical properties for a P3HT thin film. RSC Advances 3, 6016-6021 (2013).

46. Zhang D, et al. Preparation and Characterization of Ag@TiO2 Core-Shell Nanoparticles in Water-in-Oil Emulsions. European Journal of Inorganic Chemistry 2005, 1643-1648 (2005).

47. Buffat P, et al. Size effect on the melting temperature of gold particles. Physical Review A 13, 2287 (1976).

48. Omar M. Models for mean bonding length, melting point and lattice thermal expansion of nanoparticle materials. Materials Research Bulletin 47, 3518-3522 (2012).

49. Qi W. Size effect on melting temperature of nanosolids. Physica B: Condensed Matter 368, 46-50 (2005).

50. Cai C, Han S, Wang Q, Gu M. Direct observation of yolk–shell transforming to gold single atoms and clusters with superior oxygen evolution reaction efficiency. ACS Nano 13, 8865-8871 (2019).

51. Huang X, et al. In Situ Atomic-Scale Observation of Surface-Tension-Induced Structural Transformation of Ag-NiPx Core–Shell Nanocrystals. ACS Nano 12, 7197-7205 (2018).

52. Connell JG, et al. Growth of Ge Nanowires from Au−Cu Alloy Nanoparticle Catalysts Synthesized from Aqueous Solution. The Journal of Physical Chemistry Letters 1, 3360-3365 (2010).

53. Jin B, et al. Structural evolution induced by Au atom diffusion in Ag2S. Chemical Communications 55, 13176-13178 (2019).

54. Wang D, et al. Migration of iron oxide nanoparticle through a silica shell by the redox-buffering effect. ACS Nano 12, 10949-10956 (2018).

55. Jeon KW, et al. Mechanistic insight into the conversion chemistry between Au-CuO heterostructured nanocrystals confined inside SiO2 nanospheres. Chemistry of Materials 29, 1788-1795 (2017).

56. Tang L, et al. A Novel Domain‐Confined Growth Strategy for In Situ Controllable Fabrication of Individual Hollow Nanostructures. Advanced Science 5, 1700213 (2018).

57. Sambles JR, et al. An electron microscope study of evaporating small particles: the Kelvin equation for liquid lead and the mean surface energy of solid silver. Proceedings of the Royal Society of London A Mathematical and Physical Sciences 318, 507-522 (1970).

58. Asoro MA, et al. In situ transmission electron microscopy observations of sublimation in silver nanoparticles. ACS Nano 7, 7844-7852 (2013).

59. Li J, et al. In situ atomic‐scale observation of kinetic pathways of sublimation in silver nanoparticles. Advanced Science 6, 1802131 (2019).

60. He LB, et al. Surface energy and surface stability of Ag Nanocrystals at elevated temperatures and their dominance in sublimation‐induced shape evolution. Small 13, 1700743 (2017).

61. Chen C, et al. In-situ high-resolution transmission electron microscopy investigation of overheating of Cu nanoparticles. Scientific Reports 6, 1-8 (2016).

62. Yu Q, et al. In situ observation on dislocation-controlled sublimation of Mg nanoparticles. Nano letters 16, 1156-1160 (2016).

63. Tanigaki T, et al. Direct observation of sublimation process on a CdTe (111) surface using an ultrafine particle. Journal of Crystal Growth 260, 298-303 (2004).

64. Cheng F, et al. Sublimation and related thermal stability of PbSe nanocrystals with effective size control evidenced by in situ transmission electron microscopy. Nano Energy 75, 104816 (2020).

65. Tang L, et al. In situ observation of the solid solution-induced sublimation of CuAg Janus nanoparticles. Journal of Alloys and Compounds 877, 160168 (2021).

66. Hsin CL, et al. Direct observation of sublimation behaviors in one-dimensional In2Se3/In2O3 nanoheterostructures. Analytical Chemistry 87, 5584-5588 (2015).

67. Choi S, et al. Anisotropic atomistic evolution during the sublimation of polar InAs nanowires. Nanoscale 11, 6685-6692 (2019).

68. Luo C, et al. In Situ Interfacial Sublimation of Zn2GeO4 Nanowire for Atomic-Scale Manufacturing. ACS Applied Nano Materials 3, 4747-4754 (2020).

69. Buha J, et al. Thermal stability and anisotropic sublimation of two-dimensional colloidal Bi2Te3 and Bi2Se3 nanocrystals. Nano Letters 16, 4217-4223 (2016).

70. Liu X, et al. In situ thermal decomposition of exfoliated two-dimensional black phosphorus. The journal of Physical Chemistry Letters 6, 773-778 (2015).

71. Thummavichai K, et al. In situ investigations of the phase change behaviour of tungsten oxide nanostructures. Royal Society Open Science 5, 171932 (2018).

72. Luong MA, et al. In-Situ Transmission Electron Microscopy Imaging of Aluminum Diffusion in Germanium Nanowires for the Fabrication of Sub-10 Nm Ge Quantum Disks. ACS Applied Nano Materials 3, 1891-1899 (2020).

73. Huang JY, et al. In situ observation of graphene sublimation and multi-layer edge reconstructions. Proceedings of the National Academy of Sciences 106, 10103-10108 (2009).

74. Hsueh YH, et al. In situ TEM observations of void movement in Ag nanowires affecting the electrical properties under biasing. Chemical Communications 57, 11221-11224 (2021).

75. Ghodsi SM, et al. Advances in Graphene‐Based Liquid Cell Electron Microscopy: Working Principles, Opportunities, and Challenges. Small Methods 3, 1900026 (2019).

76. Wang CM, et al. Direct in situ TEM observation of modification of oxidation by the injected vacancies for Ni–4Al alloy using a microfabricated nanopost. ACS Applied Materials & Interfaces 7, 17272-17277 (2015).

77. Hauwiller MR, et al. Using graphene liquid cell transmission electron microscopy to study in situ nanocrystal etching. Journal of Visualized Experiments, e57665 (2018).

78. Dai S, et al. In situ observation of Rh-CaTiO3 catalysts during reduction and oxidation treatments by transmission electron microscopy. ACS Catalysis 7, 1579-1582 (2017).

79. Huang Y, et al. In situ mechanical properties of individual ZnO nanowires and the mass measurement of nanoparticles. Journal of Physics: Condensed Matter 18, L179 (2006).

80. Gu H, et al. Considerable knock-on displacement of metal atoms under a low energy electron beam. Scientific Reports 7, 1-10 (2017).

81. Duan X, et al. Formation of alumina nanocapsules by high-energy-electron irradiation of na-dawsonite nanorods. Scientific Reports 3, 1-4 (2013).

82. Feng W, et al. Solid‐to‐hollow single‐particle manipulation of a self‐assembled luminescent NaYF4: Yb, Er nanocrystal monolayer by electron‐beam lithography. Small 5, 2057-2060 (2009).

83. Luo B, et al. Improved stability of metal nanowires via electron beam irradiation induced surface passivation. ACS Applied Materials & Interfaces 11, 12195-12201 (2019).

84. Liu M, et al. Heating effect of electron beam bombardment. Scanning 16, 1-5 (1994).

85. Lee S, et al. Electron‐Beam‐Induced Phase Transformations from Metakaolinite to Mullite Investigated by EF‐TEM and HRTEM. Journal of the American Ceramic Society 84, 2096-2098 (2001).

86. Herman DA, et al. How hollow structures form from crystalline iron–iron oxide core–shell nanoparticles in the electron beam. Chemical Communications 49, 6203-6205 (2013).

87. Wang CM, et al. In situ transmission electron microscopy observation of microstructure and phase evolution in a SnO2 nanowire during lithium intercalation. Nano Letters 11, 1874-1880 (2011).

88. Pennycook S, et al. Scanning transmission electron microscopy for nanostructure characterization. In: Scanning Microscopy for Nanotechnology. Springer (2006).

89. Ayache J, et al. The different observation modes in electron microscopy (SEM, TEM, STEM). In: Sample Preparation Handbook for Transmission Electron Microscopy. Springer (2010).

90. Skrabalak SE, et al. Facile synthesis of Ag nanocubes and Au nanocages. Nature Protocols 2, 2182-2190 (2007).

91. Seh ZW, et al. Janus Au‐TiO2 photocatalysts with strong localization of plasmonic near‐fields for efficient visible‐light hydrogen generation. Advanced Materials 24, 2310-2314 (2012).

92. Abdulla-Al-Mamun M, et al. Synergistic cell-killing by photocatalytic and plasmonic photothermal effects of Ag@ TiO2 core–shell composite nanoclusters against human epithelial carcinoma (HeLa) cells. Applied Catalysis A: General 398, 134-142 (2011).

93. Kirz J, et al. X-ray data booklet. X-Ray Data Booklet, 13 (1986).

94. Xiong S, et al. Modeling size effects on the surface free energy of metallic nanoparticles and nanocavities. Physical Chemistry Chemical Physics 13, 10648-10651 (2011).

95. Galanakis I, et al. Applicability of the broken-bond rule to the surface energy of the fcc metals. Surface Science 511, 1-12 (2002).

96. Han Z, et al. Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review. Progress in polymer science 36, 914-944 (2011).

97. Touloukian YS, et al. Thermophysical properties of matter-the tprc data series. volume 2. thermal conductivity-nonmetallic solids.(reannouncement). data book.). Purdue Univ., Lafayette, IN (United States). Thermophysical and Electronic (1971).

98. He Q, et al. Au@ TiO2 yolk-shell nanostructures for enhanced performance in both photoelectric and photocatalytic solar conversion. Applied Surface Science 441, 458-465 (2018).

99. Bartosewicz B, et al. Fabrication of Ag-modified hollow titania spheres via controlled silver diffusion in Ag–TiO2 core–shell nanostructures. Beilstein Journal of Nanotechnology 11, 141-146 (2020).