Metal-organic frameworks of rare earth metals embedded side-by-side nanofiber as a switchable luminescent sensor for Fe3+ and Cu2+ in aqueous media

Europium metal-organic frameworks (Eu-MOFs) and terbium metal-organic frameworks (Tb-MOFs) incorporated side-by-side nanofibrous membrane (Eu//Tb SBS NFs) was successfully fabricated by electrospinning. Eu-MOFs or Tb-MOFs emitting red or green light, respectively, were adjusted on each side, and a luminescent sensor with yellow luminescence was prepared by adjusting the ratio of the two MOFs. Eu//Tb SBS NFs have high luminescence efficiency and show sequential changes in luminescence color (yellow-green-gray). To investigate whether it is possible to detect metal ions reliably in aqueous media, we evaluated the wettability of the samples by contact angle measurement and luminescence stability in different pH conditions. Eu//Tb SBS NFs showed selective detection of Fe3+ and Cu2+ in aqueous solutions containing various metal ions. The quenching effect constant (Ksv) for Fe3+ was calculated as 7.62 x 103 M−1 (the limit of detection = 1.6 x 10−7 M), indicating high sensitivity for Fe3+. The luminescence changes of the Eu//Tb SBS NFs resulting from the presence of the metal ions and varying concentrations of the targeted metal ions were confirmed with the naked eye. This is the first report of a nanofibrous membrane with a unique side-by-side structure designed as a luminescence switchable dual sensor for Fe3+ and Cu2+. The superiority of Eu//Tb SBS NFs as luminescent sensors is discussed in this paper.