Design and Synthesis of Multi-Information Dyes for the Application of Optical Chemical Sensings

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Recently, the development of optical chemical sensors (optodes) have increased progressively, in an optode, dyes play an important role as a signal transducer component. Most of the dyes employed in the optodes were pH-indicator type dyes which can only tranduce one information which related to the proton dissociation-association. In this research, we developed multi-functional dyes that have capabilities to transduce many kind of informations (Multi- Information Dyes : MIDs) based on different color-changing mechanisms.The approach for designing the dye are as follows. 1) Introduction both positive and negative charges in the both ends of the large p-conjugated system of the dye molecule. This functional element is sensitive to the cange of the environment of the dye such as solvent polarity, the presence of ionic species, solvent viscousity, etc. 2) Introduction of electron donatings and/or electron withdrawing groups in the p-conjugated system, so that we can obatain dyes with difer … More ent pKa values. 3) Introduction of an immobilization site or a lipophilic terminal that is useful in the preparation of a sensing probe. Based on this concept, 12 dyes have been synthesized and their characteristics have been studied and discussed in relation to their chemical structures. The prospect of application of these MIDs into several kinds of chemical sensing system was investigated.The fundamental characteristic of the synthesized dyes based on the merosyanine-type (KDMl-KDM12) was studied spectrophotometrically. pH response profiles were determined in a methanol-water 1 : 1 (v/v) media and solvent-response profiles were studied using water (0.01 M NaOH)-contained methanol or THF.As a result, besides these dyes responded in the same characteristics as usual pH-indicator dyes, their lmax were shifted with the change of the polarity of the solvent. Accordingly, two dimensional informations could be gained from one spectrum.KD-M7 which has a small lmax shift was used in the application to an anion sensor using a proton-anion coextraction process in a chloroform-water system. The change of the absorbance of the dyes in the chloroform phase was measured and plotted against the concentration of the anion in phosphate-buffered aqueous phase. Moreover, PVC-based anion sensing membranes were constructed by dissolving the dyes in a membrane plasticizer (BEHS) and applied to measure perchlorate on in the aqueous solution. The experimental results showed that the absorbance of the dyes were varied with the concentration of the anions and the anionic selectivity was obeyed the Hoffmeister series. The PVC-based anion sensor was also exhibited absorbance changes with the anion concentration, and enabled to measure the concentration of an anion using this sensing system.KD-M5 which has large lmax shift and low pKa value was used in preparation of alcohol sensor. Experiment was conducted by extraction of the alcohol from the water phase with chloroform and measured the spectra of the dye in the chloroform phase. In addition, PVC-based alcohol sensing membranes were constructed by dissolving the dyes in a membrane plasticizer (BEHS) and applied to measure alcohol concentration in the aqueous solution. It was proved that lmax of the dye was shifted significantly with the change of the alcohol concentration in the water phase both in the extraction experiment and in PVC-based membrane sensor.From this result it would be possible to develop a novel cation optode based on different color changing mechanism using MID-type dyes. Less