A highly selective colorimetric sensor to Fe3+ and Co2+ in aqueous solutions
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Five aromatic azo dyes with hydroxyl groups (1–5) were designed and synthesized by coupling reactions. The relationships between structures of the compounds and the spectroscopic properties were investigated. The absorption spectra of these compounds upon titration with K+, Ca2+, Al3+, Mg2+, Ni2+, Mn2+, Cd2+, Cr3+, Fe3+, Cu2+, Zn2+, Co2+, Hg2+, and Pb2+ ions in neutral aqueous solutions were reported. The results are coincident with the calculation results using the density functional theory method. The high selectivity, excellent water solubility and simple synthetic process make 1-[(2-Hydroxyl)phenylazo]-2-naphthol (5) a potential sensor for sensing Fe3+ and Mn2+ with the naked eye. 1-[(2-hydroxyl)phenylazo]-2-naphthol-6-sulfonic acid (3) shows high selectivity for the colorimetric detection of Fe3+ and Co2+ among the tested metal ions. The detection limitations of 3 for determining Co2+ and Fe3+ were calculated to be 2.8 × 10−7 and 5.6 × 10−7 mol/L, respectively.
KeywordsAzo compounds Colorimetric sensing Metal ions Water-soluble DFT calculations
The authors are grateful for the financial support from National Natural Science Foundation of China (No. 21102037) and from the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of People’s Republic of China [No. 2008(890)].
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