copper coordinated congo-red as a solvent assisted selective fluorometric and colorimetric chemosensor for determination and naked-eye detection of multiple analytes in nanomolar scale: a reversible fluorescent cn−/co32− switch that works as keypad lock

A new diazo based, congo-red-cu , was developed to act as an ‘off–on’ reversible fluorescent probe for cn− detection. the changes in solvent composition has been shown greatly effective on selectivity of anion sensing through eliminate of sulfite interference. increasing the amount of ethanol up to 5% (v/v) cause a dramatic development in selectivity of cn−via inhibitory effect on sulfite interferent. the chemosensing behavior of the cr-cu has been demonstrated through fluorescence, absorption, visual color changes and ft-ir studies. this chemosensor (cr-cu) has been shown a significant visible color change and displays a remarkable fluorescent switch on in the presence of cn− ions. the ‘in situ’ prepared cn− complexes of cr-cu shows high “turn-off” selectivity toward co32− over the other anions. the detection limits for cn− were 90 and 20 nm for colorimetric and fluorometric methods respectively, that is far lower than the who guideline of 1.9 µm. the complex of cn− with cr-cu also displayed ability to detect up to 15 nm co32− among other competing anions through a fast response time of less than 30 s which is much lower than most recently reported chemosensor probes. it has been possible to build an inhibit logic gate for two binary inputs viz., cn− and co32− by monitoring the fluorescence emission band at 446 nm as output. the development of fluorometric an ‘‘off–on’’ reversible switch for three chemical inputs cu2+, cn− and co32− ions and mimics a molecular level keypad lock.