Self-assembly behaviour and colorimetric cysteine sensor of a mercury-bridged cytosine-containing polydiacetylene

Abstract

Supramolecular self-assembled structures, formed via non-covalent interactions, impart diverse functional properties to materials. Herein, we designed and fabricated cytosine-mercury coordination-mediated self-assembled polydiacetylene (PDA) structures. The cooperative mercury-cytosine coordination and hydrogen bonding interactions drive the self-assembly into polymerisable arrangements, generating blue-phase polymeric PDA. The interaction between mercury and cytosine facilitates the trans-to-cis transition of the diacetylene monomer (DACy) during the self-assembly process, resulting in a hierarchical supramolecular assembly. Upon UV irradiation, the monomer (DACy-Hg-DACy) undergoes photopolymerisation, resulting a brilliant blue-phase polydiacetylene (PDCy-Hg-PDCy). A simple PDA-immobilised paper-based colorimetric sensor was fabricated, which exhibits selective detection of cysteine with a brilliant blue-to-red colour transition. The sensory response and mechanistic insights into the colour transition were studied using spectroscopic methods.