奈米粒子應用在鋁離子、吡啶二羧酸與薑黃素感測之研究

奈米材料由於具有獨特的光學性質、易合成及易被官能化與小尺寸等特性已被廣泛應用在化學與生物感測的研究。舉例而言，在可見光下呈現紅色而被穀胱甘肽包覆的金奈米粒子與在紫外燈照射下呈現橙紅色螢光而被穀胱甘肽包覆的金奈米團簇上均可透過一鍋反應輕易地將這些奈米材料合成出來。雖然這兩種奈米材料已是廣為熟知的奈米探針，但這兩種奈米探針與金屬離子間的特殊相互作用仍在化學感測的發展上吸引起相當大的興趣。此外，因為奈米碳量子點具有高亮度螢光與低毒性的特性，奈米碳量子點在化學感測方法的開發已被公認為是很好的感測探針之一。因此，開發簡易的合成方法來製造高亮度螢光的奈米碳量子點仍具有相當重要性。在本論文的第一部分，我開發了以穀胱甘肽包覆的金奈米粒子做為感測鋁離子的螢光探針之感測方法。鋁是地殼上第三豐富的元素，也被我們廣泛地使用日常生活中。然而，有研究顯示鋁離子在人體內的累積會造成神經毒性，因此發展快速檢測鋁離子的方法有其必要性。在此所開發的方法中雖然不用加入額外的遮蔽劑減低一般常見金屬離子的干擾，但所發展的感測方法仍對鋁離子的選擇性相當好，且偵測極限可達100 nM左右，此偵測極限遠低於世界衛生組織所允許的飲用水中鋁離子的最高容許濃度(~7.4 µM)。而在本論文的第二及第三部分，我則分別以穀胱甘肽包覆的金奈米粒子與穀胱甘肽包覆的金奈米團簇為感測探針發展感測吡啶二羧酸的方法。吡啶二羧酸被認為是可用來當作檢測如產孢子的病原體像炭疽芽孢桿菌和蠟狀芽孢桿菌之類的微生物之生物標幟分子。穀胱甘肽包覆的金奈米團簇的螢光在銅離子的存在下會被淬熄，由於銅離子和吡啶二羧酸具有高親和力(log K= 7.97)，在加入吡啶二羧酸後，螢光被銅離子淬熄的金奈米團簇可恢復螢光亮度，利用這種關-開的感測機制成功開發出對吡啶二羧酸的感測方法，對吡啶二羧酸的偵測極限為90 nM左右，感測效果可和現有方法相抗衡。此外，我也研究利用穀胱甘肽包覆的金奈米粒子為吡啶二羧酸的感測探針的比色檢測方法。穀胱甘肽包覆的金奈米粒子在鈣離子存在下會造成可見光吸收光譜中吸收帶的紅位移造成顏色由紅色變為紫色。由於鈣離子和吡啶二羧酸具有高形成常數(log K= 4.4)，當加入吡啶二羧酸至含鈣離子的穀胱甘肽包覆的金奈米粒子懸浮液，則懸浮液顏色會由紫色變回紅色。雖然此感測方法對吡啶二羧酸的偵測極限僅約在幾個μM左右，但可以輕易透過肉眼輕易觀察感測吡啶二羧酸的結果。在論文的第四部分則開發了一種簡單且經濟的奈米碳量子點的合成方法，我使用了便宜且容易獲得的雞蛋蛋白為製備碳量子點的原料，將雞蛋蛋白溶液直接在加熱板上加熱到攝氏兩百度並持續反應四小時後，可產生高亮度的奈米碳量子點，其螢光量子產率可高達百分之四十三左右。也以實驗證明可用所製備的碳量子點為細菌的螢光標記試劑及做為薑黃中活性化合物薑黃素的感測探針。綜上所述，本論文開發了數種適合感測鋁離子、吡啶二羧酸和薑黃素的化學感測方法。由於所使用感測機制非常相似，因此預期未來能開發一種能夠同時檢測數種標的物的感測探針。

關鍵字

納米粒子；鋁；吡啶二羧酸；薑黃素

並列摘要

Nanomaterials have been widely used in chemical and biosensing research owing to their unique optical properties, ease of generation/functionalization, and small sizes. Glutathione (GSH) capped gold nanoparticles (Au@GSH NPs) and gold nanoclusters (Au@GSH NCs) possess red color and orange-reddish fluorescence, respectively, which can be easily generated from one-pot reactions. Although these two nanomaterials are well-known nanoprobes, the unique interactions between these nanoprobes and metal ions still attract considerable attention in the development of chemical sensing. In addition, carbon-dots (C-dots) with bright fluorescence and relatively low toxicity have also been considered as good sensing probes when developing chemical sensing methods. Thus, to explore simple and straightforward synthesis methods to obtain C-dots with bright fluorescence is also meaningful. In the first part of this dissertation, a sensing method based on the use of Au@GSH NCs as turn-on fluorescence probes toward aluminum ions was explored. Aluminum is the third most abundant element on earth crust. It has been extensively used in our daily life. Nevertheless, studies have shown that accumulations of aluminum ions in the body can cause neurotoxicity. Thus, rapid sensing methods for detection of Al3+ are needed.The developed method showed good selectivity towards Al3+ without adding additional masking agents to reduce the interference from common metal ions. The limit of detection (LOD) toward Al3+ using the developed method was ~100 nM, which was lower than the maximum level (~7.4 µM) of Al3+ in drinking water permitted by the World Health Organization. In the second and third parts of this dissertation, sensing methods fordetection of dipicolinic acid (DPA) were developed based on the use of Au@GSH NCs and Au@GSH NPs as the sensing probes, respectively. DPA has been recognized as a biomarker for detection of spore-forming pathogens such as Bacillus anthracis and Bacillus cereus. The fluorescence of Au@GSH NCs is quenched in the presence of Cu2+. Owing to the high affinity between Cu2+ and DPA (log K= 7.97), the fluorescence of the quenched Au@GSH NCs can be switched-on in the presence of DPA. On the basis of this off-on phenomenon, a sensitive sensing method toward DPA was successfully developed. The LOD of the sensing method toward DPA was as low as ~90 nM, which is comparable to that obtained from existing methods.In addition, a colorimetric sensing method against DPA based on the use of Au@GSH NPs as the sensing probes was explored. The presence of Ca2+in the Au@GSH NPs suspension caused a red shift of the absorption band in the resultant ultraviolet-visible (UV-Vis) spectrum to have a purple color. Given thatthe high formation constant (log K= 4.4) arises between Ca2+ and DPA, the color of theAu@GSH NP-Ca2+ suspension changed from purple to red in the presence of DPA. Although the LOD was only in low µM, the sensing results can be easily visualized by the naked eye. In the fourth part of this dissertation, a simple and green synthesis method for generation of C-dots was developed. Chicken egg whites, which are inexpensive and easily available, were used as the starting materials for generation of C-dots. C-dots were generated by simply heating chicken egg whites on a hot-plate (200 oC) for 4 h. The as-generated C-dots were quite bright with the quantum yield as high as~43%.The usefulness of using the as-prepared C-dots as the fluorescence labeling agents for bacteria and the sensing probes for curcumin, which is an active compound in turmeric, was demonstrated. In conclusion, several chemical sensing methods that are suitable for detection of Al3+, DPA, and curcumin have been developed in this dissertation. Given that the sensing mechanisms are quite similar, to develop one type of sensing probes that are capable of detecting multiplex targets is anticipated.