Synthesis of Submicron-Sized Cu2O Crystals with Morphological Evolution from Cubic to Hexapod Structures and Their Comparative Photocatalytic Activity

立方體形態演繹至六足體之次微米大小氧化亞銅晶體的合成及其對應的光催化活性

何晉億(Jin-Yi Ho)

指導教授 ： 黃暄益

國立清華大學/理學院/化學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00290

摘要

本論文利用簡易的方法合成具系統性表面形貌變化的氧化亞銅(Cu2O)奈米晶體。經由改變加入含有氯化銅(CuCl2)、氫氧化鈉(NaOH)、以及界面活性劑十二烷基硫酸鈉(Sodium dodecyl sulfate)水溶液中還原劑鹽酸羥胺(hydroxylamine hydrochloride)的量，即可合成出具有立方體(cubic)、截角立方體(truncated cubic)、立方八面體(cuboctahedral)、截角八面體(truncated octahedral)、八面體(octahedral)、以及短六足體(short hexapod)結構，而合成長六足體(extended hexapod)結構則是經由稍微修改反應試劑的量。添加反應試劑的順序對於要合成出這些具有不同形態以及銳利面的晶體是非常重要的。所合成出來的晶體大小大約落在400到700奈米。
藉由X光繞射儀可以很明確的觀測到(111)及(200)面的相對繞射強度之間的轉換。在紫外光可見光吸收光譜圖中，可以發現散射帶(scattering band)主導了整個圖譜。晶體結構分析則指出氧化亞銅在{111}面上的銅原子具有懸浮鍵(dangling bond)，所以我們預測它與帶負電的分子有強烈的交互作用。經由對於帶負電甲基橙(methyl orange)分子做光降解(photodegradation)實驗則發現八面體以及長六足體具有催化活性，然而只有{100}面的立方體則沒有。相反的，如果經由對帶正電的甲基藍(methylene blue)分子做光降解，立方體和八面體則都沒有效果。八面體以及長六足體出乎預料的都不能在甲基藍溶液裡分散，而是逐漸地移動到溶液的表面。這些結果證實了氧化亞銅的{111}和{100}面在催化活性上有顯著不同的效果。

關鍵字

氧化亞銅

並列摘要

We report a facile method for the synthesis of cuprous oxide nanocrystals with systematic morphological evolution. Cubic, truncated cubic, cuboctahedral, truncated octahedral, octahedral, and short hexapod structures have been synthesized in an aqueous solution of CuCl2, NaOH, sodium dodecyl sulfate (SDS) surfactant, and hydroxylamine (NH2OH•HCl) reductant by simply varying the volume of hydroxylamine added to the reaction mixture. A slight modification in the volume of some reagents produced the extended hexapods. The order of the introduction of the reagents is important to the formation of these crystals with distinct morphologies and sharp faces. The sizes of these particles fall mostly in the range of 400–700 nm. Clear transition in the relative intensities of the (111) and the (200) reflection peaks in their XRD patterns was observed. Scattering bands dominate the UV–vis absorption spectra of these crystals. Crystal model analysis revealed that the {111} face contains surface copper atoms with dangling bonds, and is expected to interact more strongly with negatively charged molecules. Tests of photodegradation of negatively charged methyl orange showed that octahedra and the extended hexapods were catalytically active. The cubes with only the {100} faces were not active. On the contrary, both cubes and octahedra were not effective at photodecomposing positively charged methylene blue molecules. Surprisingly, octahedra and hexapods cannot be well suspended in the methylene blue solution; a significant amount of the crystals gradually moved to the surface of the solution with increasing stirring time. The results clearly demonstrate the dramatic differences in the catalytic activities of the {111} and {100} faces of Cu2O crystals for the first time.

並列關鍵字

cuprous oxide

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