A fluorescent nanofiber probe for the determination of Ni 2+ was developed via the electrospinning of a covalently functionalized pyridylazo-2-naphthol-poly(acrylic acid) polymer. Fluorescent nanofibers with diameters in the range 230-800 nm were produced with uniformly dispersed fluorophores. The excitation and emission fluorescence were at wavelengths 479 and 557 nm respectively, thereby exhibiting a good Stokes' shift. This Ni 2+ probe that employs fluorescence quenching in a solid receptor-fluorophore system exhibited a good correlation between the fluorescence intensity and nickel concentration up to 1.0 mg mL À1 based on the Stern-Volmer mechanism. The probe achieved a detection limit (3d/S) of 0.07 ng mL À1 and a precision, calculated as a relative standard deviation (RSD) of <4% (n ¼ 8). The concentration of Ni 2+ in a certified reference material (SEP-3) was found to be 0.8986 mg mL À1 , which is significantly comparable with the certified value of 0.8980 mg mL À1 . The accuracy of the determinations, expressed as a relative error between the certified and the observed values of certified reference groundwater was #0.1%. The versatility of the nanofiber probe was demonstrated by affording simple, rapid and selective detection of Ni 2+ in the presence of other competing metal ions by direct analysis, without employing any further sample handling steps.

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