本研究合成以雙邊Rhodamine基團為主體的化學感測器，分子結構設計上以Rhodamine及希夫鹼做為分子辨識基團。本研究合成的化學感測器在可見光-紫外光分光光譜及螢光光譜的量測下，對鈀離子皆具有高度的選擇性及靈敏度。且在同時具有其他金屬離子的狀況下，鈀離子的感測性亦不會受到影響，顯示BRI對鈀離子具有優異的選擇性。實驗結果顯示，隨著鈀離子數量的增加，固定感測器分子濃度之溶液吸收度及螢光亮度亦隨之增加；尤其吸收度與增加的鈀離子數量呈現良好量化趨勢，代表其穩定的感測特性。而在感測分子鍵結模型部分，本研究以Job’s plot測定化學感測器分子與鈀離子形成錯合物的鍵結數目。由核磁共振氫譜與紅外光光譜推得，分子中的酮基與希夫鹼上的氮原子會與鈀離子螯合，進而生成開環結構體。開環BRI分子具有較長的共軛鏈，因而可改變顏色且發出螢光，此光學特性使BRI分子具有離子感測功能。本研究合成的化學感測器之感測機制是可逆反應，加入硫化鈉水溶液可使感測器釋放鈀離子，回復至原先的閉環分子結構。

A bis-rhodamine appended Schiff base derivative (BRI) has been designed as colorimetric as well as fluorescent sensor for the selective detection of Pd2+. The synthesis and the spectroscopic sensing characterization of the BRI probe were carried out. The probe BRI exhibited high sensitivity and selectivity towards Pd2+ in solution of acetonitrile/water (3:2, v/v). In the presence of Pd2+, BRI exhibited obvious absorption at 556.5 nm and fluorescence emission at 591 nm. Those peaks increased with increasing of Pd2+ concentration. Results of ion selectivity show that the intensity of the BRI-Pd2+ complex was not affected by the presence of other metal ions. 1H-NMR and FT-IR spectroscopic investigations of BRI and BRI-Pd2+ revealed that the -C=N- groups and spirolactam of rhodamine B are capable of coordinating cation guest species. Furthermore, Job’s plot profile exhibited that each BRI may coordinate with 1.8 Pd2+ ions under the conditions. Based on these results, a schematic representation of BRI coordinated with two Pd2+ ions was proposed. It was found that coordination of BRI with Pd2+ ions caused ring opening of BRI. Emission of fluorescence could be due to the formation of long conjugation construction of ring-opening BRI. The coordination behaviors of BRI were reversible. Addition of sodium sulfide into the system may cause the releasing of Pd2+ leads to the ring-closing of BRI probe.

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