Abstract
Novel multifunctional fluorescent chemosensors composed of electrospun (ES) nanofibers with high sensitivity toward pH, mercury ions (Hg2+), and temperature were prepared from poly(N-Isopropylacrylamide-co-N-methylolacrylamide-co-rhodamine derivative) (poly(NIPAAm-co-NMA-co-RhBN2AM)) by employing an electrospinning process. NIPAAm and NMA moieties provide hydrophilic and thermo-responsive properties (absorption of Hg2+ in aqueous solutions), and chemical cross-linking sites (stabilization of the fibrous structure in aqueous solutions), respectively. The fluorescent probe, RhBN2AM is highly sensitive toward pH and Hg2+. The synthesis of poly(NIPAAm-co-NMA-co-RhBN2AM) with different compositions was carried on via free-radical polymerization. ES nanofibers prepared from sensory copolymers with a 71.1:28.4:0.5 NIPAAm:NMA:RhBN2AM ratio (P3 ES nanofibers) exhibited significant color change from non-fluorescent to red fluorescence while sensing pH (the λPL, max exhibited a 4.8-fold enhancement) or Hg2+ (at a constant Hg2+ concentration (10−3 M), the λPL, max of P3-fibers exhibited 4.7-fold enhancement), and high reversibility of on/off switchable fluorescence emission at least five times when Hg2+ and ethylenediaminetetraacetic acid (EDTA) were sequentially added. The P3 ES nanofibrous membranes had a higher surface-to-volume ratio to enhance their performance than did the corresponding thin films. In addition, the fluorescence emission of P3 ES nanofibrous membranes exhibited second enhancement above the lower critical solution temperature. Thus, the ES nanofibrous membranes prepared from P3 with on/off switchable capacity and thermo-responsive characteristics can be used as a multifunctional sensory device for specific heavy transition metal (HTM) in aqueous solutions.
Highlights
Some studies have demonstrated the adverse effects of exposure to heavy transition metal (HTM)cations on children’s health, such as low birth weight, low anogenital distance, and severe DNA and chromosome damage
The synthetic routes of RhBN2AM are shown in Scheme 2a, which are similar poly(NIPAAm-co-NMA-co-RhBN2AM) copolymers, which were composed of NIPAAm, NMA, and
The fluorescence emission of the RhBN2AM within the ES nanofibers was highly sensitive toward pH and Hg2+
Summary
Some studies have demonstrated the adverse effects of exposure to heavy transition metal (HTM)cations on children’s health, such as low birth weight, low anogenital distance, and severe DNA and chromosome damage. Selective and sensitive chromogenic or fluorogenic chemosensors for the detection of various HTM cations [4,5,6]. Recent studies have demonstrated the high potential of rhodamine B (RhB)-copolymer-based chemosensors for the sensing of temperature, pH, and certain HTM cations in aqueous solutions because of their water solubility, simplicity, ability to change color, and high selectivity [7,8,9,10]. Liu et al reported multifunctional fluorescent copolymers containing RhB moieties that could be used as ultrasensitive fluorometric chemosensors in aqueous media. Their multi-color emission can be effectively tuned by adjusting the temperature, pH [8], Zn2+
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