A new Fe-selective, sensitive, and dual-channel turn-on probe based on rhodamine carrying thiophenecarboxaldehyde: Smartphone application and imaging in living cells.

A new dual-channel probe based on rhodamine B derivative (MSB) was successfully designed, synthesized, characterized by Nuclear Magnetic Resonance (NMR) Spectroscopy, Fourier Transform Infrared Spectrophotometer (FTIR), Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS), X-ray Photoelectron Spectroscopy (XPS), and Single Crystal X-rayDiffraction, and the sensing abilities toward Fe cation have been demonstrated and the probe was successfully utilized for fluorescence imaging of Fe in living cells. The probe demonstrated quite fast, sensitive, and selective response to Fe by causing an extreme enhancement in UV-vis and fluorescence spectroscopy techniques in the buffered aqueous media which makes MSB a dual-channel probe. While the color of MSB solution was initially light yellow, it turned pink in the presence of Fe, which provided highly selective naked-eye determination among several ions as alkaline, alkaline-earth, and transition metal ions. After that, the probe was easily applied to paper strips and real samples such as drinking waters and supplementary iron tablets for sensing Fe in an aqueous solution. The detection limit (LOD) and the response time of the probe were determined as 4.85x10 M and 4 min, respectively, which are quite lower compared with other rhodamine based Fe sensors in the literature. According to Job's plot, H NMR titration, MALDI-TOF MS, XPS, and DFT study techniques, the complexation ratio between MSB and Fe was found as 1:1. Moreover, the spectral response was reversible with alternately addition of Fe or NaEDTA to the MSB solution. In addition, fluorescence imaging in NIH/3T3 mouse fibroblast cells and studies in real samples with a quite high recovery rate exhibited that the probe is qualified for detection of Fe ion with multiple practical usages.