利用嵌合劑與界面活性劑控制氧化亞銅結晶的表面型貌之研究

One-Pot Synthesis of Cu2O Particles via Surfactants and Chelating Agents

陳敬舜(Ching-Shun Chen)

指導教授 ： 陳建瑞 ； 鄧希平

國立清華大學/工學院/材料科學工程學系/碩士(2009年)

摘要

晶體的表面型貌對於能隙及催化效果的影響已經得到證實，所以，在應用端，操控物質的型貌與大小變成一個重要的課題。氧化亞銅屬p型半導體，具有高激子結合能及穩定性高的優點。此外，其能隙為2.17eV，落於可見光區，在光觸酶的應用上亦備受期待。本論文中藉由化學合成法，提出一個簡單、穩定、均一性高且價格低廉的方法以生成氧化亞銅粉末。
本研究以葡萄糖做為還原劑，將水溶液中的硝酸銅還原成氧化亞銅晶體，其研究內容可分成三個部份。第一部份的目的在找出各項物理參數對於晶體成長的影響，改變檸檬酸(嵌合劑)、葡萄糖及碳酸鈉的濃度與反應時間等參數，以便釐清其成長機制。在研究中發現嵌合劑對於成長特定晶形的結構決定性的影響，而高葡萄糖濃度會使得反應速率過快進而出現孿生晶的現象。此外，以檸檬酸離子做為嵌合劑時，晶體會由削平面八面體成長至立方體，又過多的碳酸根離子會佔據在(111)面上，使得晶體成長受到阻礙而出現角落崩毀的現象；第二部份則是探討嵌合劑種類對於晶體成長的影響。在研究成果中發現，檸檬酸離子雖能穩定(111)面，但(100)面為其熱力學最穩定的結果。而EDTA在穩定(100)面的功效卓越，酒石酸離子則能協助氧化亞銅形成八面體的晶形。三種嵌合劑對於氧化亞銅晶體的成長機制亦被解開；第三部份是探討溶液中添加的界面活性劑的影響。發現具有氧原子的官能基，如S-O鍵，C-O-C鍵，C-O鍵等…，僅在極高濃度時才能顯現出其穩定(100)面的能力，並不適用於操控氧化亞銅晶體的外觀。而有機銨鹽僅有四級銨鹽能幫助氧化亞銅往<111>方向成長，且效果非常卓越，並隨著長碳鏈的複雜度增加，其效果亦增強。
綜合而論，本論文對於氧化亞銅表面型貌的控制有深入的探討及證據。對於此材料在應用上有實質的幫助。

關鍵字

氧化亞銅 ； 嵌合劑 ； 界面活性劑 ； 碳酸根 ； 葡萄糖 ； 表面型貌

並列摘要

The morphology of crystal plays an important role to influence the band gap and the effect of catalysis has been announced. Based on this concept, the control of the morphology became an important issue. Cuprous oxide is a p-type semiconductor with a direct band gap about 2.17eV. It’s a potential material in photocatalyst and solar cell because of its high exciton binding energy and stability.
We report a stable, low cost, nontoxic and high uniformity approach to manufacture the Cu2O powder. There’re four reactants in the experiment, which is the chelating agent, the reductant(glucose), the base(sodium carbonate) and the cupric ion(cupric nitrate). In this dissertation, it divides into three parts. In the first part, we try to find out the effect of the reagent concentration on the crystal morphology. By adjusting the citrate concentration, we demonstrate that the existence of chelating agent is crucial for producing well-crystallizing Cu2O particle. The higher glucose concentration would cause the twin-crystal because of the faster reducing rate. Besides, we observe an interesting phenomenon. Under the surplus carbonate ion of the environment, the Cu2O cubes show the impairment on the corner. Base on the aging experiment and the base source replacement, we demonstrate that impairment is caused by the adsorption of carbonate ion on (111) plane. In the part two, we discuss the influence on crystal growth of the different chelating agent. The citrate ion stabilize the (100) plane and the (111) plane, but the (100) plane is more thermodynamically stable. EDTA is a strong agent to ensure the Cu2O crystal to be cube shape even on the edge and the corner. And the tartrate ion is with high stability of (111) to Cu2O. The crystal growth mechanism with different chelating agent is figured out too. In the part three, the surfactant is introduced. When the functional group is with oxygen atom such as S-O bond, C-O-C bond and C-O bond, it’s hard to produce the Cu2O with preferred orientation. The oxygen base functional group would increase the (100) plane stability only on the extremely high concentration. The quaternary alkylammonium salt is powerful to accelerate the growth rate in <111> direction, but the primary alkylammonium salt shows no use. When the long carbon chain is more complex, the growth rate in <111> direction is faster.
Generally, this dissertation is useful in understanding the grow mechanism of Cu2O crystal. Based on the conclusion, Cu2O exhibits higher application potential in the semiconductor industry in the future.

並列關鍵字

Cu2O ； chelating agent ； surfactant ； carbonate ； glucose ； surface morphology

參考文獻

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