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Novel multifunctional fluorescent chemosensors composed of electrospun (ES) nanofibers with high sensitivity toward pH, mercury ions (Hg²⁺), and temperature were prepared from poly(<i>N</i>-Isopropylacrylamide-<i>co</i>-<i>N</i>-methylolacrylamide-<i>co</i>-rhodamine derivative) (poly(NIPAAm-<i>co</i>-NMA-<i>co</i>-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-<i>co</i>-NMA-<i>co</i>-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 (<b>P3</b> ES nanofibers) exhibited significant color change from non-fluorescent to red fluorescence while sensing pH (the &#955;_{PL, max} exhibited a 4.8-fold enhancement) or Hg²⁺ (at a constant Hg²⁺ concentration (10^&#8722;3 M), the &#955;_{PL, max} of <b>P3-fibers</b> 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 <b>P3</b> 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 <b>P3</b> ES nanofibrous membranes exhibited second enhancement above the lower critical solution temperature. Thus, the ES nanofibrous membranes prepared from <b>P3</b> 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.