“…Smart hydrogel gratings made from stimuli-responsive hydrogels provide an advanced platform for efficient detection of trace threat analytes with easy operation and simple analysis. , Based on the analyte-responsive structural change of hydrogel networks, the hydrogel gratings can convert the signal of analyte concentration into easily detectable optical signals for quantitative detection. − Typically, with the smart hydrogel gratings, the change of analyte concentration can be converted into a variation of diffracted optical outputs, including the distance between the spots of zero-order and first-order diffraction lights, refractive index (RI), and diffraction efficiency (DE) . Such a signal conversion, based on the structural change of hydrogel gratings via their accumulated molecular–level interactions with the analytes, provides functions for efficient and quantitative detection of different substances, such as organic micropollutants, heavy metal ions, proteins, and viruses. − However, although hydrogel grating systems for detecting some heavy metal ions have been reported, development of a hydrogel grating detector for high-performance real-time detection of Cr(VI) ions in water is still highly desired.…”