Europium containing red light‑emitting fbers made by electrohydrodynamic casting

Red light-emitting polymeric micro- and nanofbers were made by electrohydrodynamic co-casting of two fuids. One fuid contains a 10 wt% concentration europium (III) complex dissolved in a dimethylformamide (DMF) solvent. The europium complex, an Eu3+ compound with the nominal formula of Eu(BA)3phen/PAN, consists of polyacrylonitrile (PAN), 1,10-phenanthroline (phen), and benzoic acid (BA). The other fuid consists of iron metal oxide nanoparticles dispersed in a solution containing 10 wt% polyacrylonitrile polymer in DMF solvent. The two fuids were electrohydrodynamically co-cast onto a soft tissue paper using a stainless steel coaxial nozzle. The intensity of the electric feld used for the co-casting was 1.5 kV/ cm. Scanning electron microscopic observation on the fbers obtained from the co-casting was made. The size of the fbers ranges from several hundreds of nanometers to several microns. Energy dispersive X-ray spectroscopic analysis of the fbers confrmed that the major elements included C, O, Fe, and Eu. The fuorescence of the two types of fbers was tested under the excitation of a UV light source. It was found that when the europium complex-containing solution was the sheath fuid and the iron-containing solution was the core, the prepared fbers showed red light-emitting behavior under ultraviolet light. Time-dependent fuorescence shows the two-stage decaying behavior. The frst stage lasts about 2000 s and the intensity of fuorescence decreases linearly. The second stage reveals the slow decaying behavior and it lasts longer than 3 h. Based on the bi-exponential data ftting using a processing MATLAB code, the fuorescence-related constants were extracted. A biexponential formula was proposed to describe the time-dependent fuorescence behavior of the fber made by the europium complex-containing solution as the sheath fuid. The decaying in the fuorescence shows two diferent stages. The frst stage lasts about 2000 s and it is characterized by a fast decaying model. The intensity of fuorescence decreases linearly. The second stage has a slow decaying feature. It takes over 3 h for the fuorescence to die out completely. Bi-exponential data ftting shows that the time constant for the decay of fuorescence is about 10,000 s.