- 學位論文
脫層蒙脫石在奈米複合材料中的應用
Novel Applications of the Exfoliated Montmorillonite on Nanocomposites
摘要
本論文研究主題專注於脫層型蒙脫石的創新研究。首先利用過去實驗室方法製備 聚(甲基丙烯酸甲酯) (PMMA)/ 脫層蒙脫石 之奈米複合材料，再利用溶劑萃取法將脫層蒙脫石萃取出來，形成可供研究之水溶液。本論文分為兩部分，第一部分將專注於脫層蒙脫石的基本吸附研究，第二部分則為脫層蒙脫石在染料敏化太陽能電池電解液中的應用。 在第一部分，利用正電型染料分子如亞甲基藍(methylene blue)與三聯吡啶釕(II) (tris(bipyridine) ruthenium-(II))做為吸附的陽離子，由於脫層蒙脫石的表面帶有負電荷,故可與陽離子藉由庫侖作用力相互吸附。其吸附曲線利用染料分子的濃度變化測得,可知脫層型蒙脫石之吸附量較一般基本蒙脫石來得少，此原因推測可能是源於殘留在脫層蒙脫石上的PMMA 所造成吸附量的下降；同時，藉由穿透式電子顯微鏡與X-ray繞射分析可知脫層蒙脫石的奈米矽片會因為加入正電荷的分子而重疊聚集，變回類似基本蒙脫石的結構。更進一步，我們將聚乙烯亞胺 (poly(ethylene imine)(PEI))與脫層蒙脫石混合，其奈米複合材料型態與毒性試驗將同時被檢驗；在有混合脫層蒙脫石的PEI複合材料中，可以看出其毒性明顯下降，故推測可以成為良好的基因傳導材料。 在第二部分，利用離子液體與脫層蒙脫石相混製備染料敏化太陽能電池的電解質。令人驚奇的是脫層蒙脫石可以做為凝膠因子(gelator)，流動態的離子液體因此與脫層蒙脫石形成凝膠，在效率的表現上有提升的效果；同時，利用交流阻抗分析其電解質的基本電化學，分析出脫層蒙脫石影響電解質之因素。更進一步為了追求更好的效率，我們利用奈米碳管與脫層蒙脫石相混再加入離子液體，此時同樣成為凝膠，更令人振奮的是其效率的表現可達到平均7.8%。在長時期穩定度的測試中，此電解液也保持著相當良好的穩定性，利用此凝膠態離子液體電解液，或許可使染料敏化太陽能電池成為有競爭性的太陽能電池商品。
並列摘要
In this thesis, we fabricated the exfoliated montmorillonite (MMT) nanoplatelets by solvent extraction from PMMA/exfoliated MMT nanocomposites, and focused on their novel applications. In the first part, the basic adsorption isotherms of exfoliated MMT was studied by cationic ruthenium dye and methylene blue; it showed less amount of dye molecules adsorbed on exfoliated MMT than pristine MMT reported on literature, so we proposed that it resulted from the remaining PMMA on the nanoplatelets. Moreover, the dye molecules would make the exfoliated MMT nanoplatelets re-stacking back to lamellar structure similar to pristine MMT, which had been revealed by transmitting electron microscopy and X-ray diffraction. The fast adsorption process was observed and the formed separating phase would immediately float on the solution, this made the exfoliated MMT become a promising material for heavy metal removal. Moreover, the cationic poly (ethylene imine) (PEI) was also mixed with exfoliated MMT to form a new biomaterial for gene delivery, the morphology of this nanocomposite was investigated by TEM, and cytoxicity test was carried out by MTT assay; it was inspiring that the toxicity of PEI/ exfoliated MMT nanocomposites were lower than that of the pristine PEI, which might be an optimistic biomaterial suitable for gene delivery. In the second part, we applied the exfoliated MMT nanoplatelets to the electrolyte system of dye-sensitized solar cell (DSSC). As the exfoliated MMT was added into ionic liquid of 1-methyl-3-propylimidazolium iodide (MPII), the whole mixture became gels. The performance of ionic liquid-based electrolyte system incorporating exfoliated MMT was evaluated. The efficiency of resulting DSSC was higher than that with the original ionic liquid; the photoelectrochemical properties were also studied by electrochemical impedance spectroscopy (EIS). Furthermore, in order to increase the efficiency of DSSC, we added carbon nanotubes to the MMT containing ionic liquid-based electrolyte system. The performance of DSSC with this novel electrolyte could reach 7.8% conversion efficiency in average. This well-performed DSSC also showed a very stable long-term stability, which made this device possible to join the competition of commercial solar cell industry.