A new simple, small molecule hydrazone was synthesized from1:1 condensation reaction of pyrene-1-aldehyde and 2-hydrazinobenzoic acid and was characterized by absorption, emission spectrometry, FTIR NMR and mass studies. It was investigated as a reversible, turn-on luminescent chemosensor for copper ion (Cu2+) in aqueous environment with a ratiometric change in emission pattern which may be explained due to due to intra ligand charge transfer transition (ILCT). The receptor shows a prominent colorimetric change from yellow to reddish brown, in presence of Cu2+ with a detection limit in the 10−8 M range. No significant spectral changes were observed in presence of other environmentally significant metal ions (Hg2+, Pb2+, Cd2+, Ni2+, Co2+, Fe2+, Fe3+, Mn2+, Zn2+, Al3+ and Cr3+). Interestingly in presence of Cu2+, the ligand exhibits reversible change in emission pattern with oxalate (C2O42-) and thus offers an interesting property of molecular ‘INHIBIT’ logic gate with Cu2+ and C2O42-as chemical inputs. In practical application, the receptor was used to detect Cu2+ in real samples by selective two phase liquid-liquid extraction using water-dichloromethane mixture (1:1). The systematic color change during Cu2+ extraction was monitored by a readily-usable smartphone as an analysis tool.