A smart photonic crystal hydrogel sensor based on 18-crown-6/Ba2+ host–guest interactions for highly selective and visual Ba2+ detection

Barium ions (Ba 2+ ) contamination is a serious environmental problem worldwide. The currently existing Ba 2+ -detection techniques are generally expensive, time-consuming, and complicated. Therefore, the development of a simple, inexpensive, rapid, and effective strategy to detect Ba 2+ in water is of great importance. Herein, we first report a smart photonic crystal hydrogel (PCH) sensor for simple, highly selective, and naked-eye detection of Ba 2+ in water based on 18-crown-6/Ba 2+ host–guest interactions. This sensor was composed of a poly(benzo-18-crown-6-acrylamide- co - N -isopropylacrylamide- co -acrylamide) (PBCNA) intelligent hydrogel with embedding Fe 3 O 4 @SiO 2 colloidal photonic crystals (CPCs). The prepared PBCNA PCH sensor demonstrated pH and temperature-dependent Ba 2+ -detection performances. Besides, the Ba 2+ -responded PCH sensor could be easily regenerated via simple washing using hot/cold water at least 20 times without compromising its detection performance. Such a PCH sensor with obvious advantages of portability, ease of operation, cost-effectiveness, high selectivity and excellent regenerability, provides a simple and effective strategy to monitor Ba 2+ in contaminated water.