Application of Optical Hydrogels in Environmental Sensing

Abstract

The ever‐increasing complexity of environmental pollutants urgently warrants the development of new detection technologies. Sensors based on the optical properties of hydrogels enabling fast and easy in situ detection are attracting increasing attention. In this paper, the data from 138 papers about different optical hydrogels (OHs) are extracted for statistical analysis. The detection performance and potential of various types of OHs in different environmental pollutant detection scenarios were evaluated and compared to those obtained using the standard detection method. Based on this analysis, the target recognition and sensing mechanisms of two main types of 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 discussed. Finally, the potential academic research directions to address the challenges of applying and developing OHs in environmental sensing are proposed, including the fusion of various OHs, introduction of the latest technologies in various fields to the construction of OHs, and development of multifunctional sensor arrays.

Recent progress in low‐swellable polymer‐based smart photonic crystal sensors

“…[129] Specifically, stimulusresponse hydrogels can change their swelling ratio in response to changes in external conditions, such as pH and temperature. [130] However, some emerging applications have put forward more stringent requirements for the swelling properties of hydrogels. Such as mechanical and dimensional stability, rather than large expansion.…”

“…Since then, a large number of SPCSs have been developed. [11,48,130,234] Due to the adjustable lattice spacing, only a limited swelling can meet the maximum reflection wavelength of PC in the visible range. To prevent excessive swelling of the system, usually, LSPs can meet the material requirements of the relevant SPCSs.…”