Protonated 1,10-Phenanthroline as a Fluorescent Sensor for Fe(II) at Micro Molar Level Detections

Pristine 1,10-phenanthroline is widely known for the formation of non-fluorescent complexes with Fe(II). Although lot of studies have been done on 1,10-phenanthroline and Fe(II), studies on Fe(II) with a pronated core of phenanthroline are very scarce. Thus, in this work, Fe(II)'s effect on the absorption and emission spectra of protonated 1,10-phenanthroline was investigated. Protonated 1,10-phenanthroline was developed as a sensitive and selective turn off fluorescent sensor for Fe(II) quantification. The excitation and emission wavelengths of protonated 1,10-phenanthroline are 273 nm and 415 nm, respectively. The intensity of the emission peak at 415 nm was remarkably decreased upon the addition of Fe(II). Temperature studies along with charge transfer spectra were evidence for a static quenching process. The limit of detection and the limit of quantification of the probe at 3.3 σ and 25 °C was 0.31 μmol/L and 0.65 μmol/L respectively. The sensitivity of the protonated fluorescent sensor was increased in acidic media while the highest sensitivity was observed at pH 2.81. The interference from Ni(II) and Cu(II) at this pH was at a minute level.