Polyelectrolyte multilayer film containing polydiacetylene vesicles for naked eye detection of aromatic compounds

Abstract

For preliminary analytical screening in the field test of toxic chemicals, it is desirable to have a sensing system which is inexpensive and convenient to use. Polydiacetylene is known to possess unique colorimetric sensing properties in which its color changing upon exposure to chemical stimulants can be easily observed by naked eyes. In this thesis study, a sensing system consisting of an active polydiacetylene agent, poly(10,12-pentacosadiynoic acid) (PCDA) vesicle, is constructed in a form of polyelectrolyte multilayer (PEM) film using a layer-by-layer deposition technique. The PEM film using PCDA as a polyanion and chitosan as a polycation has the most satisfactory film quality. The color of poly(PCDA)/chitosan PEM film can be induced from blue to red by aqueous solution of 10 mM α-cyclodextrin (α-CD). The α-CD induced color transition of poly(PCDA) PEM film can be inhibited by equimolar some aromatic compounds such as p-nitrophenol, benzoic acid and 2,4-dichlorophenoxyacetic acid (2,4-D) probably by the competitive inclusion complexation. There are some selectivity in the color transition inhibition of various aromatic compounds probably depended on their binding strength with α-CD. The multichannel chip constructed from the poly(PCDA)/chitosan PEM film and the polydimethylsiloxane channel show fast colorimetric response to α-CD that can provide a simultaneous test of multiple samples on the chip.