A Bis-Quinoline Appended Azobenzene Based Naked Eye Sensor for Selective Detection of Cd2+ Ion
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A new azobenzene chromophore (AZQU), appended with a bis-quinoline unit as a turn-on chemosensor for selective detection of Cd2+ ions, has been designed and synthesized. The fluorescent receptor AZQU has an excellent selectivity and sensitivity towards Cd2+ ions over other metal ions in CH3CN:H2O (80:20, v/v) solution. AZQU is red colored and non-fluorescent in the absence of Cd2+ ions, but upon addition of Cd2+ ions it turns colorless with appreciable fluorescence. This “off–on” type signaling behavior is attributed to the CHEF (chelation-enhanced fluorescence) effect of the quinoline unit and the change in color from red to yellow occurs by an ICT process with Cd2+. The association constant for AZQU + Cd2+ was calculated to be 1.68 × 105 L·mol−1 with binding in the 1:1 stoichiometric ratio.
KeywordsAzobenzene Chemosensor 8-Hydroxyquinoline Naked eye sensor
The author E.H thanks thank the Department of Science and Technology (DST), India for financial support (DST-SR/S1/PC-07/2010). The authors P.K and R.M are thankful to the Anna Centenary Research Fellowship (ACRF), Anna University, Chennai (CR/ACRF/2013/38). The instrumentation facility was provided to our department through DST-FIST and UGC-DRS from New Delhi.
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