Studies Of Fluorescence Optical Chemosensing Technique Based On Molecular Wire Polymer

The development of new analytical techniques for the determination of trace substance with high sensitivity and selectivity has always received much attention. Optical sensors are of considerable current interst in the trace substance analysis, and the sensitive material and analytical techniques are the key factors in improving the sensitivity and selectivity. This paper develops several approaches of ion determination with high selectivity, using molecule wire polymer as the sensitive material and measuring fluorescence recovery and anisotropy.The present thesis is composed of the following three parts:(1) The ion-induced aggregation of molecular wire polymer has been studied by several analytical methods, and the detection of Pd~2+ using fluorescence anisotropy with high selectivity has been developed based on the polymer aggregation.The ion-induced aggregation of molecular wire polymer is studied systematically by fluorescence intensity, fluorescence anisotropy and absorption spectra. The influence of structure modification, recognition site (pyridyle group)composition proportion and the length of side-substituted alkyl on the polymer aggregation has been investigated. The results indicate that the obvious intermolecule aggregation exists as Pd~2+ is added into the polymer PI, which exhibits an excellent selectivity toward Pd~2+. Many of metal ions such as alkali metals, alkaline-earth metals and transitional metal ions don't interfere with the detection of Pd~2+. A novel method for detecting Pd~2+ by fluorescence anisotropy has been developed based on the polymer aggregation. This study is expected to promote the exploitation of the ion sensors with high sensitivity and selectivity based on molecule wire polymer.(2) A competitive analysis method for the determination of cyanide anion based on the fluorescence restoral of molecule wire polymer.A new method has been developed for the determination of cyanide based on the competitive reaction. The fluorescence of molecule wire polymer is quenched due to ion-association with Pd~2+ and restored when cyanide is added into the system. The linear detection range is 5× 10~-6 M-2 × 10~-4 M and the detection limit is 1 × 10~-7 M for cyanide at optimal conditions. A possible mechanism of the method was proposed based on the studies of absorption spectra and fluorescence anisotropy. Thisstudy might create a new dimension for extensive application of molecular wire in the anion analysis.(3) The study of cyanide detection based on fluorescence anisotropy of molecule wire polymer.It is the first time that the determination of cyanide anion by fluorescence anisotropy of molecule wire polymer is reported. When Pd~2+ is added into the diluted polymer, the fluorescence anisotropy of Pyridine substitute molecule wire polymer increases due to the polymer aggregation induced by Pd~2+, and a larger-molecule-wight complex is formed. Subsequently the cyanide is added, cyanide is cooperated with Pd~2+ resulting in the recovery of fluorescence anisotropy because the aggregative polymer is disaggregated . The optimum is obtained through the orthogonal experiment. At the optimum conditions, the detection range is from 1 × 10~-6 M to 4 × 10~-4 M and the detection limit is 1 × 10~-6M. This approach is simple and rapid for the real time monitoring of cyanide anion.