Valence-tautomeric infinite coordination polymer nanoparticles for encapsulation of rhodamine B and its potential application for colorimetric and fluorescence dual mode sensing of hypochlorite

In this work, we for the first time developed a visual and fluorescent dual probe for hypochlorite (ClO−) based on stimuli-responsive valence-tautomeric infinite coordination polymer (ICP) nanoparticles encapsulated with a fluorescent dye, i.e., rhodamine B (RhB). In the absence of ClO−, the as-formed RhB@{Co(3,5-dbsq)(3,5-dbcat)(bix)} ICP nanoparticles are well dispersed and quite stable in aqueous solution. However, the addition of ClO− into the dispersion of RhB@{Co(3,5-dbsq)(3,5-dbcat)(bix)} destroys the {Co(3,5-dbsq)(3,5-dbcat)(bix)} network structure, resulting in the release of RhB from ICP nanoparticles into the solvent. As a consequence, the color of the dispersion changed from purple to orange-red and, in the meantime, the fluorescence of RhB turns on, which constitutes a new mechanism for colorimetric and fluorescence dual-model sensing of ClO−. With the method demonstrated here, the ClO− in tap water can be easily visualized by the naked eye and detected quantitatively through double channels. This study not only offers a new method for on-the-spot visible detection of ClO− in environmental samples, but also provides a strategy for designing dual mode sensing mechanisms based on the stimulus response of valence-tautomeric ICP nanomaterials.