Pyrene or rhodamine derivative-modified surfaces of electrospun nanofibrous chemosensors for colorimetric and fluorescent determination of Cu2Â +, Hg2Â +, and pH

Novel fluorescent nanofibrous nonwoven-state sensors exhibiting high sensitivity to heavy metal ions were prepared from pyrene derivative (PyDAN2) or rhodamine B derivative (RhBN2)-modified poly(2-hydroxyethyl methacrylate-co-N-methylolacrylamide) (poly(HEMA-co-NMA)) electrospun (ES) nanofibers by employing a single-capillary spinneret. The HEMA moieties were designed to exhibit hydrophilic properties, and the NMA content substantially affected the stability of the ES nanofibers in water as well as enhanced their endurance in various organic solvents. PyDAN2 and RhBN2 grafted onto the cross-linked poly(HEMA-co-NMA) ES nanofibers through surface-initiated polymerization were denoted as Fiber-g-PyDAN2 and Fiber-g-RhBN2, respectively; they exhibited highly selective detection capabilities for copper (Cu2 +) and mercury (Hg2 +) ions/pH, respectively. The fluorescence emission colors of Fiber-g-PyDAN2 and Fiber-g-RhBN2 were initially nonfluorescent, but they transformed into strong fluorescence emissions with blue and orange-red colors when they detected Cu2 + and Hg2 +/pH, respectively. These sensors have high reversibility because their on-off switchable fluorescence emissions cycled several times upon the sequential addition of Cu2 +/Hg2 + and EDTA or acidic and alkaline media. The prepared chemosensors can be grafted onto ES nanofibrous membranes and can be used as “naked eye” sensors. They have potential applications in environmental sensing devices, especially in pollution sensors.