Fig. 3

Function of each component in WJRP and the hydrochromic mechanism of WJRP. Variation of reflectance (R%) at 586 nm of WJRP integrated with ODB-2/developers (n/n 1/4) including a carboxylic acid derivatives and polyhydroxyls phenol derivatives and b developers with different logP before (blue dots) and after addition of water (red dots). c UV–vis reflection spectra of the mixture of ODB-2 and B4H on the glass before and after introduction of PEG and the mixture with PEG after adding water. d UV–vis reflection spectra of the mixture of ODB-2 and B4H on filter paper before and after addition of water. e UV–vis reflection spectra of ODB-2 alone dispersed on filter paper before and after addition of water as well as adding acid. f Schematic representation of WJRP based on the binary system writing with water and the erasing process (blue dashed line: supramolecular interaction, black dashed line: H-bonding)