本研究製備含rhodamine衍生物液晶球之感測系統，分子結構上以rhodamine作為分子辨識基團。首先，將摻混rhodamine衍生物之5CB液晶滴置於塗佈十八烷基三氯硅烷之玻璃基板上，再將待測水溶液滴於液晶上，並以偏光顯微鏡觀察加入金屬離子前後液晶滴紋理的變化，由於液晶滴紋理在加入金屬離子前後並無變化，因此，藉由界面活性劑的引入，以促進液晶滴紋理的變化。在低濃度界面活性劑的存在下，將不同金屬離子溶液加入純5CB液晶滴的系統，液晶分子的排列皆從平行變為垂直。結果顯示，此種液晶滴感測系統檢測金屬離子並無選擇性。
因此，開發了另一種感測系統。將具有反應性液晶單元RM257與RM105、無反應性液晶單元5CB以及合成的rhodamine衍生物單體的液晶混和物製成液晶滴。並將此液晶滴置於含有界面活性劑SDS的水溶液中進行光聚合反應，即可得到聚合液晶球。聚合後，以酒精洗去未反應的物質。
從UV-vis光譜儀的分析中可確認，所合成的rhodamine衍生物對銅離子的感測具有選擇性。將液晶球聚合物丟入含有銅離子的水溶液中，可觀察到顏色從淡粉紅色轉變為深粉紅。此現象為感測銅離子後，造成rhodamine分子結構開環，由於感測分子具有較長的共軛鏈，因而產生呈色現象。加入不同濃度的非反應性液晶單元5CB，造成液晶球的孔洞密度不同，進而影響銅離子擴散速度，造成感測速率的不同。然而此現象在酒精的加入後可被大幅削減，此舉有效地降低水的表面張力。液晶球聚合物對銅離子的偵測，在濃度為5×10-6M時仍可以清晰計測。感測後的液晶球聚合物，可經由加入氨水進行液晶球的回收再使用；加入胺水時，銅離子將形成[Cu(NH3)4]2+而被移除。

In this study, two sensing skills based on liquid crystal (LC) droplets and polymeric LC beads were developed and studied. To detect metal ions, sensing probe molecules derived from rhodamine B were synthesized. From the results of UV-vis analysis, the selective sensing of Cu2+ via the synthesized rhodamine B derivatives was confirmed. Firstly, the sensing system was built on LC droplet prepared from 4-cyano-4'-pentylbiphenyl (5CB) doped with the synthesized rhodamine B derivative. The LC droplets were set on octadecyltrichlorosilane (OTS)-coated glasses and sample aqueous solution was then dropped on the LC droplets. To promote the variation of POM texture, surfactants were introduced into the system. However, it was found that 5CB LC orientations transferred from parallel to perpendicular upon adding several metal ions in the presence of low concentration of surfactants. The results indicate that this LC droplet method is not a good way for the selective sensing of specific metal ions.
Furthermore, another detection method was developed. Recyclable polymeric LC beads were prepared from reactive mesogens of RM257 and RM105, nonreactive mesogen of 5CB and a rhodamine B derived monomer. In this study, LC monomeric droplets aligned in radial conformation were made by immersing the LC droplets in aqueous solution containing sodium dodecyl sulfate (SDS). After that, the LC monomeric droplets were UV-polymerized forming various sizes of polymeric liquid crystal beads. To remove unreacted chemicals, the fabricated beads were washed with ethanol thoroughly. The color of polymeric LC beads changed from light pink to deep pink after dropping the polymer beads into Cu2+ aqueous solution. The results were ascribed to the spiro ring-opening mechanism. Adding of nonreactive mesogen resulted in porous structure of polymeric LC beads. Depending on the amount of unreactive 5CB, a series of different pore density of polymeric LC beads revealing different detection rate were fabricated. However, this phenomenon was diminished significantly when the beads were immersed into DI water/ethanol sample solution. Adding of ethanol into deionized water decreases the surface tension drastically. The detection of 5×10-6M Cu2+ in DI water/ethanol (1:1 v/v) solution using the synthesized polymeric LC beads was confirmed. After detection, the fabricated polymeric LC beads were recycled via putting the polymeric LC beads into ammonia water. Removing of Cu2+ from polymeric LC beads is due to the formation of [Cu(NH3)4]2+.

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