Synthesis of triphenylamine-containing conjugated polyelectrolyte and fabrication of fluorescence color-changeable, paper-based sensor strips for biothiol detection

A new water-soluble conjugated polyelectrolyte containing triphenylamine groups with aldehyde pendants was synthesized, which featured distinctly different emission colors according to its states, in aqueous solution and in the solid. Paper-based strips containing the polymer were prepared by simple immersion of filter paper in the polyelectrolyte solution for practical and efficient detection of biothiols including cysteine and homocysteine. The presence of aldehyde groups enables us to demonstrate noticeable fluorescence emission color changes (green-to-blue) because of the alterations in electron push–pull structure in the polymer via a reaction between the aldehyde group of the polymer and the aminothiol moiety in biothiol compounds. The presence of an aldehyde group and a sulfonate side chain was found to be indispensable for the cysteine reaction site and for a hydrophilic environment allowing the easy approach of cysteine, respectively, resulting in a simple and easy detection protocol for biothiol compounds.