A novel β-cyclodextrin-based molecular-responsive photonic hydrogel chemosensor for highly sensitive and visual detection of 2-naphthol

Abstract

Developing multifunctional materials for 2-naphthol (2-NAP) monitoring is in urgent demand since 2-NAP not only brings us convenience but also causes serious environmental and health issues. Herein, we report a novel β-cyclodextrin (β-CD)-based molecular-responsive photonic hydrogel chemosensor composed of a poly(N-isopropylacrylamide-co-maleic anhydride-β-cyclodextrin) (PNACD) hydrogel with embedded superparamagnetic Fe₃O₄ colloidal particle chains, for highly sensitive and visual detection of 2-NAP in aqueous solution. The Fe₃O₄ particle chains in the polymer matrix could strongly diffract visible light and transmit a 2-NAP concentration signal to the color change of the gel by changing the gel volume and lattice spacing of Fe₃O₄ particles. The rich β-CD groups attached to the polymer networks could specifically recognize and bind to 2-NAP by forming stable β-CD/2-NAP inclusion complexes. This specific molecular recognition expanded the gel, increased the particle spacing, and thus redshifted the reflection wavelengths of the gel and indicated the color changes of the gel. This photonic hydrogel exhibited remarkable thermo- and pH-dependent responsiveness to 2-NAP, a wider linear detection range of 0.01–500 μM and a comparatively lower detection concentration of 0.01 μM compared with the conventional instrument-based methods. Besides, it also demonstrated excellent regenerability and was applicable to monitor 2-NAP in a simulated contaminated river water sample. Such a multifunctional hydrogel with high sensitivity and selectivity toward 2-NAP as well as excellent recyclability holds great potential in sensitive, precise and naked-eye detection of aromatic pollutants in contaminated water bodies.