Optical sensor based on hydrogel films with 2D colloidal arrays attached on both the surfaces: anti-curling performance and enhanced optical diffraction intensity

An interesting strategy to create free standing hydrogel composite films with colloidal monolayers attached on both the surfaces, which could act as visualizing sensors with high diffraction intensity, is developed. Owing to the balanced stress on both the surfaces, the colloidal monolayer-hydrogel composite films overcome the curling problem of traditional hydrogel films loaded with a colloidal monolayer on one side. They also display enhanced diffraction intensity compared to those with the attachment of only a single 2D colloidal monolayer due to a multi-diffraction effect. Such sensing hydrogel composite films with anticurling performance and enhanced optical diffraction intensity are very helpful to improve their practical applications in visual and quantitative detection. In addition, this strategy is universal and could be suitable for fabricating various functional hydrogel films loaded with different nanosphere arrays for novel optical sensors.