Colorimetric and fluorometric detection of copper ion (Cu2+) has attracted much attention because of the biological, environmental and medical significance of the Cu2+ion.

Designing an effective sensor molecule for the selective detection of analyte with dual sensitivity is an innovative approach and is expected to offer huge biological and environmental benefits. Contrary to other sensing process, the reversible recognition of two different analytes while varying the binding sites and signaling subunits is entirely a new concept as the metal ion present in the ensemble can be easily displaced in the presence of ionic or neutral analytes. A reversible strategy can also be employed in the simultaneous recognition and identification of two different analytes with the aid of highly selective and sensitive chemosensors. This review gives an overview of the recent inventions (from 2012 to 2017) in the field of colorimetric and fluorescent receptors towards the detection of two analytes via a relay recognition process. A special emphasis is placed on different mechanisms associated with the sensing process assisted by fluorescence induced receptors which will help to design an effective sensor system for the selective detection of anions or amino acids or metal ions.

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Probe R designed as tailor-fit triple action smart chemosensor for the sequential detection of CN− and Fe3+via colorimetric and fluorometric ‘on–off’ method and H2S through colorimetric method in semi-aqueous conditions.