A fluorescent aminoacid was designed for selective and sensitive detection of Cu(II) in aqueous solution. The designing of this Cu(II) fluorescent chemosensing molecule, N (1 naphthyl)~aminoacetic acid (NAA), was based on the binding of Cu(II) to aminoacetic acid and the novel charge transfer photophysics of 1 aminonaphthalenes. The fluorescence of NAA was found quenched by Cu(II) and several other metal ions of similar electronic structure such as Co(II), Ni(II) and Zn(II). The quenching was shown to occur via electron transfer within the metal NAA complex, which required an optimal combination of high binding affinity and favorable redox properties of the components in the metal NAA complex and hence afforded selective fluorometric detection of Cu(II). The calibration graph obeyed Stern Volmer theory and was shown for Cu(II) over the range of 0—2 75×10 -4 mol/L. The quenching constant of Cu(II) was measured as 8 0×10 3 mol/L that was two orders of magnitude higher than those of Co(II), Ni(II) and Zn(II). The 3SD limit of detection for Cu(II) was 8 00×10 -6 mol/L with a coefficient of variation of 1 65%. Linear range for quantitative detection of Cu(II) was 2 67×10 -5 —2 75×10 -4 mol/L. The method was applied to synthetic sample measurements which gave recoveries of 105%—112%. A fluorescent aminoacid was designed for selective and sensitive detection of Cu (II) in aqueous solution. The designing of this Cu (II) fluorescent chemosensing molecule, N (1 naphthyl) ~ aminoacetic acid (NAA), was based on the binding of Cu (II) to aminoacetic acid and the novel charge transfer photophysics of 1 aminonaphthalenes. The fluorescence of NAA was found quenched by Cu (II) and several other metal ions of similar electronic structure such as Co (II), Ni (II) and Zn (II). The quenching was shown to occur via electron transfer within the metal NAA complex, which required an optimal combination of high binding affinity and favorable redox properties of the components in the metal NAA complex and hence afforded selective fluorometric detection of Cu (II The quenching constant of Cu (II) was measured as 8 × 10 3 mol. The quenching constant of Cu (II) was measured as 8 × 10 3 mol / L that was two orders of magnitude hig The 3SD limit of detection for Cu (II) was 8 00 × 10 -6 mol / L with a coefficient of variation of 1 65%. range for quantitative detection of Cu (II) was 2 67 × 10 -5 -2 75 × 10 -4 mol / L The method was applied to synthetic sample measurements which gave recoveries of 105% -112%.