Abstract
The ever-increasing complexity of environmental pollutants urgently
warrants the development of new detection technologies. In this context,
sensors based on the optical properties of hydrogels enabling fast and
easy in situ detection are attracting increasing attention. Herein, the
target recognition and sensing mechanisms of two main types of optical
hydrogels (OHs) are reviewed and discussed: photonic crystal hydrogels
(PCHs) and fluorescent hydrogels (FHs). For PCHs, the environmental
stimulus response, target receptors, inverse opal structures, and
molecular imprinting techniques related to PCHs are reviewed and
summarized. Furthermore, the different types of fluorophores (i.e.,
compound probes, biomacromolecules, quantum dots, and luminescent
microbes) of FHs are summarized. Finally, the data from 138 papers about
different OHs are extracted for secondary statistical analysis. The
detection performance and potential of various OH types in different
environmental pollutant detection scenarios are evaluated, and compared
them to those obtained using the standard detection method. Based on
this analysis, some possible development directions are proposed,
including the fusion of various OHs, introduction of more hydrogel
technologies from the biomedical field to the environmental pollutant
detection field, and development of multifunctional sensor arrays.