Cinchona alkaloid copolymers as fluorimetric INHIBIT and colorimetric AND logic gates for detection of iodide

Abstract

Four cinchona alkaloid-acrylamide water soluble copolymers with a mean hydrodynamic diameter of 3 nm were synthesised by free radical polymerization. The copolymers were characterised by ¹H NMR, FTIR, GPC, DLS, UV-vis and fluorescence spectroscopy. A blue emission is observed with H⁺ switching of 185 and 175-fold for the quinidine and quinine copolymers, and 21 and 11-fold for the cinchonine and cinchonidine copolymers, while the presence of Cl⁻, Br⁻ or I⁻ causes fluorescence quenching. In emission mode, the copolymers function as fluorescent H⁺, X⁻-driven INHIBIT logic gates (where X = Cl⁻, Br⁻ or I⁻). In absorbance mode, the copolymers function as colorimetric H⁺, I⁻-driven AND logic gates in 1:1 (v/v) THF/water with a 76-fold enhancement. The solution colour changes from colourless to yellow with formation of new absorbance bands at 288 nm and 353 nm due to a π-anion non-covalent charge transfer interaction. The copolymers may be useful as selective iodide sensors for medical and analytical diagnostics.