In this study, we report on novel optical chemosensors containing benzothiazole moeity, namely, 2‐(6‐chloro‐benzothiazol‐2‐yl azo)‐4‐methyl‐phenol (CBAMP) and 1‐(6‐chloro‐benzothiazol‐2‐yl azo)‐naphthalen‐2‐ol (CBAN), which were synthesized and characterized by Fourier transform infrared spectroscopy (FT‐IR), 1H‐NMR, 13C‐NMR, and mass spectrometry. The solvatochromic behavior was explored in different solvents of various polarities to explore the active fluorescent tautomer, and the photophysical parameters have been measured. The naked eyes, as well as ultraviolet–visible (UV–Vis) and fluorescence spectroscopy, were used to study the colorimetric and optical sensing properties of CBAMP and CBAN toward various metal ions and anions. These chemosensors have a strong detecting ability, with excellent sensitivity and selectivity for certain of the metal ions investigated, as well as CO32− and CN− over other anions. The Benesi–Hildebrand and Job's plots were used to determine the binding constants and stoichiometry of the formed metal ions–sensor complexes, respectively. Co2+ and Cu2+ ions have lower detection limits in CBAMP and CBAN than other metal ions (6.4 × 10−7 and 8.4 × 10−7 M, respectively). Furthermore, fluorescent imaging investigations for Co2+ and Cu2+ ions in living cells reveal CBAMP and CBAN's promise for biological chemosensing.
Herein, we synthesized three novel benzothiazole azo dyes, including 4-chloro-2-(4-methyl-benzothiazol-2-ylazo)-phenol (CMBTAP), 1-(6-chloro-benzothiazol-2-ylazo)-naphthalen-2-ol (CBAN), and 2-(6-chloro-benzothiazol-2-ylazo)-4-methyl-phenol (CBAMP), and investigated their corrosion inhibition effect on carbon steel. The dyes were characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR), 13C NMR, and mass spectroscopy. Weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization measurements were performed to investigate the corrosion inhibition effect of the dyes on carbon steel in a 1.0 M HCl solution. The synergistic effects of the dyes with potassium iodide (KI) were also investigated. The inhibition efficiency (IE%) was enhanced by increasing the dose of the dyes (1 × 10–5 to 2 × 10–4 M) and decreased as the temperature increased from 25 to 45 °C. The addition of KI to a 1.0 M HCl solution containing the dyes improved the performance and efficiency as iodide ions promoted the formation of inhibition films on the surface of carbon steel. The dyes are mixed-type inhibitors, according to Tafel polarization. Scanning electron microscopy and energy dispersive X-ray analysis were used to evaluate the surface morphology of carbon steel sheets. Quantum theory calculations were utilized to evaluate the relationship between the dyes’ chemical structures and their inhibitory efficiency, which confirmed the experimental results. The calculations revealed that the dyes have low energy gap and Milliken and Fukui indices. Among all of the dyes, CMBTAP showed the highest adsorption energy. The corrosion IE was in the order CMBTAP > CBAMP > CBAN.
Heavy metals are extremely toxic, causing harm to aquatic and human life. Thus, this study focused on developing simple, colorimetric, and low-cost optical sensors for detection of metal ions with high selectivity and sensitivity. Here, a novel benzothiazole azo-dye, namely, 4-chloro-2-(4 0 -methyl-benzothiazol-2 0 -ylazo)-phenol (CMBTAP) was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), 1 H-nuclear magnetic resonance (NMR), 13 C-NMR, and mass spectroscopic techniques. This azo-dye has been anchored into the amino-functionalized mesoporous TiO 2 which synthesized using pluornic123 and cetyltrimethylammonium bromide as templates to yield CMBTAP-M-TiO 2 (1) and CMBTAP-M-TiO 2 (2), respectively. The designed nanosensors were characterized by FT-IR, transmission electron microscopy, nitrogen adsorption-desorption isotherms, X-ray diffraction, and thermogravimetric analyses. The colorimetric and optical sensing behavior of CMBTAP and its nanosensor analogs toward different metal ions like Ba 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Cd 2+ , Hg 2+ , and Al 3+ were explored using naked-eye observations, steady-state absorption, and emission techniques. Significant changes in colors, the absorption and emission spectra were observed. The action of these nanosensors is reversible where on adding ethylenediaminetetraacetic acid to the formed complexes, the original absorption and emission spectra of the free sensors are restored, demonstrating that the chelation process is reversible. For CMBTAP and the nanosensors, the binding constants of the complexes formed with the used metal ions, and limit of detection (LOD) were calculated. In comparison with CMBTAP, the results revealed that the nanosensors exhibited a stronger binding affinity, selectivity, sensitivity, and lower LODs for the studied metal ions, implying that the sensing efficiency of CMBTAP is improved after loading onto the nanostructured TiO 2 . Thus, we have successfully converted the hazardous azo dye into an environmentally safe optical sensor for detection of toxic metal ions in wastewater with high sensitivity.
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