基于荧光共轭聚合物的金属离子传感研究

Investigation of Conjugated Polymers for Metal Ion Sensing

设计合成了一系列结构相似的共轭主链含5%苯并噻二唑结构单元及侧链带胺类金属离子螯合基团的阴离子型水溶性共轭聚合物PFA,PFBTA和PFBTNA,并对它们在不同极性溶剂中的光物理性质进行了研究.利用分子主链含适量苯并噻二唑共聚单元的聚芴衍生物聚集态不同荧光光谱及颜色发生显著变化这一特性,研究了这一系列水溶性聚芴衍生物在水/甲醇(9/1)溶液中对金属离子的荧光响应过程.结果表明,金属离子不仅能通过能量及电荷转移猝灭聚合物荧光,还可以通过静电相互作用力使聚合物聚集态发生改变,进而影响聚合物的光学性质.同时分子链上引入金属离子螯合基团能够显著提高体系的检测灵敏度,聚合物PFBTA和PFBTNA可以特异性识别Cu2+离子,并且可做为其它金属离子的广谱型比色法检测材料.

Two carboxylate-containing fluorene-based anoinic water-soluble conjugated polymers, which are specially de signed to link fluorene with alternating moieties such as 5% benzo[2,1,3]thiadiazole （BT） and amine groups have been syn thesized via the Pd-catalyzed Suzuki-coupling reaction, respectively. The optical properties of the neutral precursory poly mers in CHCI3 and final carboxylic-anionic conjugated polyelectrolytes in aqueous solution were investigated. These poly mers had good solubility in water and showed different responses for metal ions in aqueous environments. The fluorescence of carboxylic-anionic polyfluorene （PFA） can be quenched by most of metal ions selected （except K, Li） in H20/CH3OH solution （9/1）. The carboxylic acid-functionalized polyfluorene containing benzo[2,1,3]thiadiazole （PFBTA） showed good quenching with the addition of Cu2. ions and had a little response for K, Li. While addition of other metal ions selected results in a change in the emission color of PFBTA from blue to orange. These spectral changes can be ascribed to increased interchain contacts in aggregated structures of PFBTA and increased levels of fluorescence resonance energy transfer （FRET） from the fluorene segments to BT units. The carboxylic acid-functionalized polyfluorene containing benzo[2,1,3]thiadiazole and amine group （PFBTNA） had similar responses for all metal ions selected with PFBTA in H20/CH3OH solution （9/1）. Moreover, PFBTNA showed improved sensitivity to most of metal ions selected, which may be contributed to the interaction between amine group and metal ions. After investigation of the UV-vis absorption spectra and PL emission spectra, we found that the energy or electron-transfer reactions were the main reason for ionochromic fluorescence quenching of these poly- mers. On the other hand, interchain aggregation caused by metal ions also lead to fluorescence quenching for these polymers. Moreover, the results also indicated that introduction of recognition group can obviously increase the sensitivity of the poly mers and suggested the potential application for polymer PFBTA and PFBTNA as novel colorimetric and universal chemosensor with higher sensing sensitivity for many metal ions in aqueous environments.