本研究之目的在於合成不同辨識基團在不同位置的香豆素衍生物作為重金屬離子之感測應用,我們利用香豆素(coumarin)作為其訊號讀出單元,合成在間位為冠狀醚的化合物1(18-monoazacrown-6 ether);另外合成在對位具有硫原子冠狀醚的化合物2,藉以研究辨識單元結構及原子種類對於金屬離子選擇性之影響。由螢光滴定實驗結果可知,化合物1對鈣、鋇、鉛離子有很強的結合性,並使得螢光強度增強。在化合物2中,我們引進了硫原子在冠狀醚中,則應對電子密度較低之金屬有較好的結合能力,實驗結果顯示了此分子對銅離子有相當好的選擇性和結合能力,螢光增加可達60倍;同時由紅外光吸收光譜和核磁共振光譜滴定實驗可確知,香豆素衍生物上的兩個羰基(carbonyl group)對金屬離子的選擇性及結合上扮演相當重要的角色。 再者,我們合成香豆素衍生物3、4、5,並將其修飾在金及二氧化矽奈米粒子的表面,希望利用化合物分子對鉛離子的高選擇及多配位的特性,應用在不同材質之奈米粒子感測材料的研發上。
In recently, the need for selective and sensitive sensors able to monitor in real-time and real-space is nowadays generally accepted. Because metal ions play a important role in our daily life. In our study, we synthesized a series of coumarin-derivatives for sensing heavy metal ions. We designed coumarin group as signal readout unit, and combined different positions and sizes of recognition sites: “crown-ether”. They displayed a highly specificity and fluorescence-enhancement to the hard metal ions: lead ion. In the titration experiment of NMR and IR spectroscopy, we can understand how sensors binding with metal ions: the two carbonyl group and crown ether group cooperated in binding with metal ions. Furthermore, by altering the “oxygen” atoms of crown ether to “sulfur”, we can change the binding affinity to the soft metal: cupper. It shows 60-fold enhancement of fluorescence. According to the high specificity and multivalent binding to the lead ions, we synthesized compound 3, 4, 5 with alkyl-chain thiol and alkyl-chain triethoxysilane group. By modifying them to the different carriers, gold and silica nanoparticles, we can develope new materials for sensing metal ions.