Carbazole benzaldehyde: A highly selective and sensitive turn-off fluorometric sensor for Fe3+ detection

Abstract

In this study, 4-(9'-hexylcarbazol-3'-yl)benzaldehyde (probe C) with the structure of donor-pi-acceptor was studied as a new sensor. The selectivity and sensitivity properties of probe C against various analytes were investigated by using absorption (UV-Vis) and fluorescence (PL) spectroscopy. Only with the addition of Fe3+ and Fe2+, the absorption spectrum of probe C slightly changed, while the maximum emission intensity at 482 nm of probe C dramatically changed in the presence of various interfering analytes. Hence, probe C exhibited high selectivity towards Fe3+ with the limit of detection (LOD) value of 2.3 nM. This LOD value lies in among the best values reported so far for the carbazole-based fluorescent sensors. The binding stoichiometry, stoichiometric interaction ratio and binding site between probe C and Fe3+ were established by Job's plot, H-1-NMR, HRMS and FT-IR analyses. Job's plot indicated that the stoichiometric ratio between probe C and Fe3+ was 2:1. H-1-NMR and FT-IR spectra showed that Fe3+ formed a complex with probe C via the non-bonding electron pair on the oxygen atom of the formyl group. Probe C was tested for the detection of Fe3+ in 3 different real water samples by spike and recovery method. It was observed that probe C worked successfully in the detection of Fe3+. From these, it was concluded that probe C can be successfully used as a turn-off fluorometric sensor for the detection of Fe3+.