本研究以水熱法合成具有形狀控制的四氧化三鐵奈米晶體，並進行光學與磁性晶面效應的研究。在改變溶劑用量及鹼的濃度的情況下可以得到尺寸可調的八面體的四氧化三鐵，其對邊長分別為36奈米、45奈米及100奈米，以及可以得到243奈米的菱形十二面體。在電子顯微鏡下，小顆粒的八面體展現出較好的均勻性，但隨著尺寸變大均勻性會慢慢降低。並且透過X光繞射光譜、X射線光電子能譜學以及傅立葉轉換紅外光譜得知所合成出的奈米晶體為四氧化三鐵而非其他的鐵氧化物。在光學性質的量測上，四氧化三鐵的八面體之吸收峰隨晶體尺寸變小而藍移，而不同形狀之四氧化三鐵奈米晶體也展現了吸收值位移之現象。這兩種形狀之晶體在磁性的量測上也展現出晶面效應的現象，以及不同程度的遲滯現象。

This study investigates the optical and magnetic surface effects of shape-controlled iron(III) oxide (Fe3O4) nanocrystals synthesized using a hydrothermal method. By varying the solvent volume and alkaline concentration, size-tunable octahedra Fe3O4 nanocrystals with edge lengths of 36 nm, 45 nm, and 100 nm, as well as a rhombic dodecahedra with a size of 243 nm, were obtained. Under electron microscopy, the smaller octahedra particles exhibited better uniformity, but uniformity decreased as the size increased. Characterization techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy confirmed the synthesis of Fe3O4 nanocrystals rather than other iron oxide compounds. In terms of optical properties, the absorption peaks of the octahedral Fe3O4 shift towards the blue region as the crystal size decreased, and different shapes of Fe3O4 nanocrystals exhibit absorption wavelength shifts. Both crystal shapes show magnetic surface effects and varying degrees of hysteresis in magnetic measurements.

摘要…………………………………………………………………………….…….……ⅰ
Abstract………………………………………………………………………….…….…..ⅱ
致謝……………………………………………………………………………….………ⅲ
Table of Contents………………………………………………………….……………...ⅳ
List of Tables……………………………………………………………………….…….ⅶ
List of Figures……………………………………………………………………...……ⅷ
List of Schemes………………………………………………………….………………xⅳ
Chapter 1 Fe3O4 Crystals and Semiconductor Facet Effects………………………………1
1.1 Semiconductor Facet-Dependent Effects………………………………………...1
1.1.1 Facet-dependent electrical conductivity……………………………………1
1.1.2 Facet-dependent optical property…………………………………………..5
1.2 Introduction to iron(II) iron(III) oxide…………………………………………...7
1.3 Synthesis methods………………………………………………………………..8
1.4 Magnetic property………………………………………………………………11
1.5 Optical property…………………………………………………………………18
Chapter 2 Fe3O4 Octahedra and Rhombic Dodecahedra for Optical and Magnetic Characterization…………………………………………………………………………..23
2.1 Experimental section…………………………………………………………………23
2.1.1 Chemicals……………………………………………………………………..23
2.1.2 Synthesis of size-tunable Fe3O4 octahedra……………………………………24
2.1.3 Synthesis of Fe3O4 rhombic dodecahedra…………………………………….25
2.1.4 Instrumentation………………………………………………………………..26
2.2 Results and Discussion……………………………………………………………….27
2.2.1 Particle synthesis……………………………………………………………...27
2.2.2 Materials Characterization……………………………………………………28
2.2.2.1 Morphology and particle size determination…………………………..28
2.2.2.2 Crystal phase characterization using X-ray diffraction………………..30
2.2.2.3 Fourier transform infrared spectral analysis…………………………...35
2.2.2.4 Particle surface analysis……………………………………………….36
2.2.2.5 Crystal morphology and structure characterization through TEM…….38
2.3 Synthesis and characterization of Fe3O4 rhombic dodecahedra……………………...39
2.3.1 Particle synthesis……………………………………………………………...39
2.3.2 Materials Characterization……………………………………………………41
2.3.2.1 Morphology and particle size determination …………………….……41
2.3.2.2 Crystal phase characterization using X-ray diffraction………………..42
2.3.2.3 Fourier transform infrared spectral analysis…………………………...43
2.3.2.4 Particle surface analysis……………………………………………….44
2.4 Other shapes of Fe3O4 crystals…………………………………….…………………46
2.5 Size- and facet-dependent optical properties…………………………………………47
2.6 Magnetic property of Fe3O4 crystals…………………………………………………50
2.7 Conclusion……………………………………………………………………………57

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