Competitive coordination assisted scalable fabrication of FITC­nickel frameworks anchored nanofiber paper for colorimetric/fluorescent monitoring of shrimp freshness.

ABSTRACT

A novel type of colorimetric/fluorescent nanopaper indicator has been developed from the melt-extruded poly (vinyl alcohol-co-ethylene) nanofibers with surface anchored metal-organic frameworks (MOFs) by an interfacial coordination strategy. Specifically, the fluorescein isothiocyanate molecules could be anchored to the nanofiber surface by nickel ions and co-assembled into a hydrophilic nanocoating via a dynamic water/alcohol solvent evaporation method. Interestingly, this hydrophilic surface enables fast adsorption of moistures and interaction with biological amine vapors, resulting a saffron cake-layer of MOF nanocrystals with ultra-sensitive colorimetric/fluorescent responses based on an alkaline pH/ammonia induced competitive coordination mechanism. Finally, these porous nanofibrous matrix and active nanocoating make the nano-paper an ultra-sensitive optical platform for in-situ monitoring of the shrimp freshness from mins to weeks. Therefore, this composite film shows great potential into advanced paper-based indicators for food quality control and safety in processing industry.