| 研究生: |
張桂敏 Teo, Gui-Min |
|---|---|
| 論文名稱: |
利用陽性-陰性離子型界面活性劑系統合成各種新奇型態中孔洞氧化矽 Synthesis of Mesoporous Silica in Various Novel Morphologies Using Cationic-Anionic Binary Surfactant Mixture |
| 指導教授: |
林弘萍
Lin, Hong-Ping |
| 學位類別: |
碩士 Master |
| 系所名稱: |
理學院 - 化學系 Department of Chemistry |
| 論文出版年: | 2007 |
| 畢業學年度: | 95 |
| 語文別: | 中文 |
| 論文頁數: | 77 |
| 中文關鍵詞: | 中孔洞氧化矽 、離子型界面活性劑 、生物成礦 |
| 外文關鍵詞: | catanionic mixtures, biomineralization, silica |
| 相關次數: | 點閱:78 下載:1 |
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有機-無機複合材料,是經由分子自組裝過程而形成。分子自組裝的行為普遍存在於生物系統中,是各種複雜生物結構形成的基礎。本研究將此觀念應用於合成奈米結構材料,期盼能合成出與自然界矽藻相似的型態,藉此了解自然界生物成礦的原理。
本研究所選用的有機物為界面活性劑,無機物來源為易溶於水的矽酸鈉溶液。由界面活性劑化學得知,陽性-陰性離子型界面活性劑所組成的系統,可形成各種微胞結構和介尺度液晶相,適合作為合成中孔洞氧化矽的多元化模板。本研究採用陽離子型界面活性劑 (CnTMAX,n = 14-18,X = Br或Cl)及陰離子型界面活性劑(SDS)所形成的混合型界面活性劑系統作為有機模板,結合低濃度的矽酸鈉(Sodium Silicate)溶液在pH 2及近室溫(40℃)條件下,藉由調控陽性-陰性離子型界面活性劑間組份比(SDS/CTAB莫耳比,S)製備各種新奇型態的中孔洞氧化矽材料。
實驗結果依照氧化矽的型態分為三部份:一、微米尺度的花瓣型氧化矽,其型態的特殊及絢麗可媲美自然界矽藻的型態;二、長達數百微米的大柱狀氧化矽,其尺度之大是分子自組裝系統中極少見的;三、纖維狀氧化矽,長度可達數微米,經由無機物水量的控制可選擇合成實心纖維狀(直徑50~150 nm)或空心纖維狀(直徑100~300 nm),有趣的是空心纖維狀氧化矽皆由環狀的奈米管所組成。
本研究探討各種實驗變因對氧化矽型態的影響,包括氧化矽寡聚物尺度、合成pH值、有機模板系統的組份種類、各組份間比例、濃度、溫度、攪拌時間等。利用實驗結果,找出各種型態氧化矽最佳合成條件,並推測合成機制。
本研究的合成方法簡單,產率高,實驗再現性良好。因此,本研究成果對於自然界生物成礦的形成機制及基礎理論,具有很高的參考價值。
Organic-inorganic nanao-composite materials are formed via molecular self-assembly process. Molecular self-assembly behaviour generally exists in the living systems of complex structural forms. Extending the biomineralization concepts, in which organic molecules manipulate the growth of the inorganic systems, can inspire new biomimetic approaches for the synthesis of inorganic materials. Our approach is focused on understanding the biomineralization of the diatoms and proposed new strategies in preparation of mesoporous silicas in novel morphologies.
It is well known that there are many different mesophases and morphologies in a mixture of cationic and anionic surfactants (i.e. catanionic surfactant). Therefore, the catanionic surfactants can be used as a versatile template to synthesize the mesoporous silica in various spectacular morphologies similar to the diatoms in nature. We utilized a mixture of alkyltrimethylammonium bromide (CnTMAX , n = 14-18 , X=Br or Cl) and sodium dodecylsulfate (SDS) as organic template, incorporated a highly-dilute sodium silicate solution at near room temperature (40℃) to synthesize mesoporous silica. The pH value of reaction was adjusted to 2.0. The morphology of silica is strongly dependent on SDS/CnTMAX molar ratio.
According to the experimental results, there are three parts regarding to different silica morphologies in this thesis. In first part, flower-like mesoporous silicas in micro-size have been synthesized at SDS/CTAB = 0.20. Second part, hundred-micrometer mesoporous silica pillars with diameter in tens micrometer was prepared at SDS/CTAB = 0.50. This morphology in such scale is seldom found among the mesoporous silica formed from the self-assembling of surfactant and silica. Third part, the mesoporous silica fibers and tubes with length in few microns were generated at SDS/CTAB = 0.35. Silica fibers (diameter: 50~150 nm) or silica tube (diameter: 100~300 nm) can be selected by control the water content of the synthetic compositions. Interestingly, the nanochannel’s direction in the tubes is perpendicular to the longitudinal direction of the tubes to avoiding the contact between the hydrophobic tails and water.
In addition, we also explored variation of silica morphologies by changing a series of experimental conditions including pH value, CTAB/SDS molar ratio, surfactant concentration, temperature, stirring rate and so on. Using the experimental result, we tried to find out the best synthesis condition for the mesoporous silica in the desired morphology, and extrapolation the synthesis mechanism.
In brief, CnTMAX/SDS catanionic surfactants can be used as a new template to prepare many spectacular mesoporous silicas, which provide more information to understand the biomineralization in nature. This synthetic method is simple, and the results are reproducible. Therefore, our research results have high referencing values for understanding biomineralization concepts and theories.
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