荧光共轭聚合物金属离子传感的机理研究

Study of the Fluorescent Conjugated Polymers on Metal Ion Sensing

含金属离子识别单元犤2,2'-联吡啶(bpy)、1,10-菲洛啉(phen)等犦的荧光共轭聚合物金属离子传感的机理主要是引入金属离子所引起的聚合物主链构象的变化或是电子能级的变化.本文报导了两种属于这类荧光共轭聚合物的芴共聚物P1和P2在溶液中和固体薄膜状态下的金属离子传感性质,并研究了这类荧光共轭聚合物金属离子传感的机理.聚合物P1和P2分别是有20°二面角的bpy和平面的phen与芴交替共聚而成.研究发现P1、P2与金属离子络合后能够使吸收光谱红移,荧光猝灭,同时P2表现出更灵敏的金属离子传感性质.尤其是P2在固体状态下的高灵敏金属离子传感性质为金属离子荧光传感器的应用提供一种新的思路.P2的金属离子识别单元是平面的phen,在与离子响应过程中不需要发生构型转变,从而可以说明这类主链含金属离子识别单元的聚合物在与金属离子作用时,金属离子配位诱导聚合物电子能级的改变是金属离子传感的决定性因素.

The effects of the rigidity of molecu lar recognition sites in fluorene-b ased conjugated polymers P1and P2in solution on metal ion sensing have been investigated.The structures o f polymer P1and P2have twisted 2,2'-bipyridine and planar1,10-phenanthroline units,respec tively,which alternate with one flu orene monomer unit.It is found that absorp tion and emission bands of 1,10-phen anthroline-based polymer P2exposed to metal ions can be red -shifted up to30nm,and emission intensity can be q uenched up to 100%,depending on metal ions present,which is very sim ilar to the behavoir of 2,2'-bipyrid ine-based analog P1.And P2shows much higher sensitivity to metal ion than that of P1.The origins of ionochromic effects of 2,2'-bipyridine-based conjugated polymer due to the metal i on chelation have been attributed to both conformational changes and electron density variations on the p olymer chains caused by introducing positively charged metal ions.Base d on the fact that conformational changes are not required in the ion responsive process of phen ion-recognition u nit,we demonstrate that the electron den sity variations play more important roles in metal ion induced red shifts in absorption and fluorescence quench ing in photoluminescence.The higher sensitivity of P2films to metal ions compared with P1suggest the use of rigid units as mole cular recognition sites in the fluor escent ions-sensory conjugated polymer for achieving hi gher sensing sensitivity,which is a lso significant for studying the nature of ionchromatic effect of conjugated p olymer.The study present herein has,to a certain degree,elucidated the nature of metal ion and polymer interactions and demonstrated a new appro ach to improve the metal ions sensing properties of conjugated polymer.