本實驗室已在甲基橙之光降解中證實氧化亞銅之晶面效應，指出：氧化亞銅立方體無光催化活性；菱形十二面體具高度光催化活性；及八面體具中度光催化活性。為擴展此研究，本實驗室使用奈米金粒子修飾氧化亞銅表面；並藉由在氧化亞銅上生成半導體，例如氧化鋅、硫化鎘、硫化鋅及磷酸銀，以嘗試合成半導體-半導體之異質結構。本論文探討氧化亞銅晶體之有機分子表面修飾如何影響其能帶結構及光催化活性。

特別是對於4-乙炔基苯胺修飾之氧化亞銅立方體，使一般無活性的氧化亞銅立方體變得具有相當的光催化活性，在50分鐘內降解甲基橙至大約3 %。加入電子及電洞捕捉劑之後，甲基橙之降解受到抑制。EPR分析揭露了氫氧自由基之形成。EIS分析指出在4-乙炔基苯胺修飾後之電荷轉移電阻顯著的降低。Mott-Schottky分析顯示了價帶及導帶的位置有顯著的改變，解釋了氧化亞銅立方體之光催化活性。

We have already demonstrated the facet-dependent performance of Cu2O nanocrystals in the photocatalytic degradation of methyl orange, indicating that Cu2O cubes are photocatalytically inactive, while rhombic dodecahedra are highly photocatalytically active, and octahedra are moderately active. We extended our investigation to decorate Cu2O surfaces with gold nanoparticles and try to synthesize semiconductor‒semiconductor heterojunctions by growing semiconductor such as ZnS, CdS, ZnS, and Ag3PO4 on Cu2O crystals. This thesis explores how surface organic molecule modification of Cu2O crystals affect their band structures and photocatalytic activity.

Specifically for 4-ethynylaniline-modified Cu2O cubes, the normally inactive Cu2O cubes become fairly photocatalytically active, degrading methyl orange to almost 3 % in 50 min. Degradation of methyl orange was suppressed upon adding electron and hole scavengers. EPR analysis reveals the formation of hydroxyl radicals. EIS analysis indicates significantly reduced charge transfer resistance upon 4-ethynylaniline modification. Mott-Schottky analysis shows greatly tuned valance and conduction band positions, accounting for the observed photocatalytic activity of Cu2O cubes.

1. Ng, C. H. B.; Fan, W. Y. Shape evolution of Cu2O nanostructures via kinetic and thermodynamic controlled growth. J. Phys. Chem. B.2006, 110, 20801‒20807.
2. Chen, K.; Sun, C.; Xue, D. Morphology engineering of high performance binary oxide electrodes. Phys. Chem. Chem. Phys. 2015, 17, 732‒750.
3. Xu, H.; Wang, W.; Zhu, W. Shape evolution and size-controllable synthesis of Cu2O octahedra and their morphology-dependent photocatalytic properties. J. Phys. Chem. B. 2006, 110, 13829‒13834.
4. Kondo, J. N.; Domen, K. Cu2O as a photocatalyst for overall water splitting under visible light irradiation. Chem. Commun. 1998, 3, 357‒358.
5. Chanda, K.; Rej, S.; Huang, M. H. Facet-dependent catalytic activity of Cu2O nanocrystals in the one-pot synthesis of 1,2,3-triazoles by multicomponent click reactions. Chem. Eur. J. 2013, 19, 16036‒16043.
6. Zhang, Y.; Liu, J.; Peng, Q.; Wang, X.; Li, Y. Nearly monodisperse Cu2O and CuO nanospheres: Preparation and applications for sensitive gas sensors. Chem. Mater. 2006, 18, 867‒871.
7. McShane, C. M.; Siripala, W. P.; Choi, K.-S. Effect of junction morphology on the performance of polycrystalline Cu2O homojunction solar cells. J. Phys. Chem. Lett. 2010, 1, 2666‒2670.
8. Bao, H.; Zhang, W.; Hua, Q.; Jiang, Z.; Yang, J.; Huang, W. Crystal-plane-controlled surface restructuring and catalytic performance of oxide nanocrystals. Angew. Chem. Int. Ed. 2011, 50, 12294‒12298.
9. Huang, W.-C.; Lyu, Y.-C.; Yang, Y.-C.; Huang, M. H. Synthesis of Cu2O nanocrystals from cubic to rhombic dodecahedral structures and their comparative photocatalytic activity. J. Am. Chem. Soc. 2012, 134, 1261‒1267.
10. Tan, C.-S.; Hsu, S.-C.; Ke, W.-H.; Chen, L.-J.; Huang, M. H. Facet-dependent electrical conductivity properties of Cu2O crystals. Nano Lett. 2015, 15, 2155‒2160.
11. Chen, Y.-J.; Chiang, Y.-W.; Huang, M. H. Synthesis of diverse Ag2O crystals and their facet-dependent photocatalytic activity examination. ACS Appl. Mater. Interfaces 2016, 8, 19672‒19679.
12. Tan, C.-S.; Chen, Y.-J.; Hsia, C.-F.; Huang, M. H. Facet-dependent electrical conductivity properties of silver oxide crystals. Chem. Asian J. 2017, 12, 293‒297.
13. Tan, C.-S.; Chen, H.-S.; Chiu, C.-Y.; Wu, S.-C.; Chen, L.-J.; Huang, M. H. Facet-dependent electrical conductivity properties of PbS nanocrystals. Chem. Mater. 2016, 28, 1574‒1580.
14. Hsieh, M.-S.; Su, H.-J.; Hsieh, P.-L.; Chiang, Y.-W.; Huang, M. H. Synthesis of Ag3PO4 crystals with tunable shapes for facet-dependent optical property, photocatalytic activity, and electrical conductivity examinations. ACS Appl. Mater. Interfaces 2017, 9, 39086‒39093.
15. Yuan, G.-Z.; Hsia, C.-F.; Lin, Z.-W.; Chiang, Y.-W.; Huang, M. H. Highly Facet-dependent photocatalytic properties of Cu2O crystals established through the formation of Au-decorated Cu2O heterostructures. Chem. Eur. J. 2016, 22, 12548‒12556.
16. Su, Y.; Li, H.; Ma, H.; Robertson, J.; Nathan, A. Controlling surface termination and facet orientation in Cu2O nanoparticles for high photocatalytic activity: A combined experimental and density functional theory study. ACS Appl. Mater. Interfaces 2017, 9, 8100‒8106.
17. Li, C.; Koenigsmann, C.; Ding, W.; Rudshteyn, B.; Yang, K.-R.; Regan, K. P. Konezy, S. J.; Batista, V. S.; Brudvig, G. W.; Schmuttenmaer, C. A.; Kim, J.-H. Facet-dependent photoelectrochemical performance of TiO2 nanostructures: An experimental and computational study. J. Am. Chem. Soc. 2015, 137, 1520‒1529.
18. Lei, W.; Zhang, T.; Gu, L.; Liu, P.; Rodriguez, J. A.; Liu, G.; Liu, M. Surface-structure sensitivity of CeO2 nanocrystals in photocatalysis and enhancing the reactivity with nanogold. ACS Catal. 2015, 5, 4385‒4393.
19. Shang, Y.; Guo, L. Facet-controlled synthetic strategy of Cu2O-based crystals for catalysis and sensing. Adv. Sci. 2015, 2, 1500140.
20. Wang, G.; Ma, X.; Huang, B.; Cheng, H.; Wang, Z.; Zhan, J.; Qin, X.; Zhang, X.; Dai, Y. Controlled synthesis of Ag2O microcrystals with facet-dependent photocatalytic activities. J. Mater. Chem. 2012, 22, 21189‒21194.
21. Rej, S.; Chanda, K.; Chiu, C.-Y.; Huang, M. H. Control of regioselectivity over gold nanocrystals of different surfaces for the synthesis of 1,4-disubstituted triazole through the click reaction. Chem. Eur. J. 2014, 20, 15991‒15997.
22. Madasu, M.; Hsia, C.-F.; Huang, M. H. Au-Cu core-shell nanocube-catalyzed click reactions for efficient synthesis of diverse triazoles. Nanoscale 2017, 9, 6970‒6974.
23. Zhou, Q.; Li, X.; Fan, Q.; Zhang, X.; Zheng, J. Charge transfer between metal nanoparticles interconnected with a functionalized molecule probed by surface-enhanced raman spectroscopy. Angew. Chem. Int. Ed. 2006, 45, 3970‒3973.
24. Wu, S.-C.; Tan, C.-S.; Huang, M. H. Strong facet effects on interfacial charge transfer revealed through the examination of photocatalytic activities of various Cu2O-ZnO heterostructures. Adv. Funct. Mater. 2017, 27, 1604635.
25. Huang, J.-Y.; Hsieh, P.-L.; Naresh, G.; Tsai, H.-Y.; Huang, M. H. Photocatalytic activity suppression of CdS nanoparticle-decorated Cu2O octahedra and rhombic dodecahedra. J. Phys. Chem. C 2018, 122, 12944‒12950.
26. Naresh, G.; Hsieh, P.-L.; Meena, V.; Lee, S.-K.; Chiu, Y.-H.; Madasu, M.; Lee, A.-T.; Tsai, H.-Y.; Lai, T.-H.; Hsu, Y.-J.; Lo, Y.-C.; Huang, M. H. Facet-dependent photocatalytic behaviors of ZnS-decorated Cu2O polyhedra arising from tunable interfacial band alignment. ACS Appl. Mater. Interfaces 2019, 11, 3582‒3589.
27. Naresh, G.; Lee, A.-T.; Meena, V.; Satyanarayana, M.; Huang, M. H. Photocatalytic activity suppression of Ag3PO4-deposited Cu2O octahedra and rhombic dodecahedra. J. Phys. Chem. C 2019, 123, 2314‒2320.
28. Kuo, C.-H.; Huang, M. H. Facile synthesis of Cu2O nanocrystals with systematic shape evolution from cubic to octahedral structures. J. Phys. Chem. C 2008, 112, 18355.
29. Ho, J.-Y.; Huang, M. H. Synthesis of submicrometer-sized Cu2O crystals with morphological evolution from cubic to hexapod structures and their comparative photocatalytic activity. J. Phys. Chem. C 2009, 113, 14159.
30. Huang, W.-C.; Lyu, L.-M.; Yang, Y.-C.; Huang, M. H. Synthesis of Cu2O nanocrystals from cubic to rhombic dodecahedral structures and their comparative photocatalytic activity. J. Am. Chem. Soc. 2012, 134, 1261‒1267.
31. Huang, C.; Li, A.; Li, L.-J.; Chao, Z.-S. Synthesis of quinolines from aniline and propanol over modified USY zeolite: catalytic performance and mechanism evaluated by in situ Fourier transform infrared spectroscopy. RSC Adv. 2017, 7, 24950‒24962.
32. Lin, J.; Hao, W.; Shang, Y.; Wang, X.; Qiu, D.; Ma, G.; Chen, C.; Li, S.; Guo, L. Direct experimental observation of facet-dependent SERS of Cu2O polyhedral. Small 2017, 1703274.
33. Chu, C.-Y.; Huang, M. H. Facet-dependent photocatalytic properties of Cu2O crystals probed by electron, hole and radical scavengers. J. Mater. Chem. A 2017, 5, 15116‒15123.
34. Pieper, G. M.; Felix, C. C.; Kalyanaraman, B.; Turk, M.; Roza, A. M. Detection by ESR of DMPO hydroxyl adduct formation from islets of Langerhans. Free Radic. Biol. Med. 1995, 19, 219‒225.
35. Yang, Y.; Xu, D.; Wu, Q.; Diao, P. Cu2O/CuO bilayered composite as a high-efficiency photocathode for photoelectrochemical hydrogen evolution reaction. Sci. Rep. 2016, 6, 35158.
36. Hodby, J. W.; Jenkins, T. E.; Schwab, C; Tamura, H; Trivich, D. Cyclotron resonance of electrons and of holes in cuprous oxide, Cu2O. J.Phys. C Solid State Phys. 1976, 9, 1429.
37. Huang, Q.; Kang, F.; Liu, H.; Li, Q.; Xiao, X. Highly aligned Cu2O/CuO/TiO2 core/shell nanowire arrays as photocathodes for water photoelectrolysis. J. Mater. Chem. A 2013, 1, 2418‒2425.
38. An, X.-Q.; Li, K.-F.; Tang, J.-W. Cu2O/reduced graphene oxide composites for the photocatalytic conversion of CO2. Chem. Sus. Chem. 2014, 7, 1086‒1093.