An on-site colorimetric probe, based on gold nanoparticles incorporated into electrospun polystyrene nanofibres, for the detection of oestrogenic compounds, as represented by 17β-estradiol, in dairy effluents is presented. The probe exhibited a significant absorption peak at 542 nm, ascribed to surface plasmon resonance of Au nanoparticles (NPs). With increasing 17β-estradiol concentration the surface plasmon resonance (SPR) band shifted to a longer wavelength accompanied by a visual colour change from shades of pink to blue. The visible cut-off concentration was 100 ng/mℓ. Upon exposure to cholesterol and a series of compounds known to induce oestrogenic activity, p,p'-DDE, deltamethrin, 4-tert-octylphenol and nonylphenol, only 17β-estradiol could induce a pink colour observable by the naked eye, which is indicative that the proposed gold nanoparticles-incorporated electrospun polystyrene nanofibres could be employed as highly selective colorimetric strips to detect 17β-estradiol, with minor interference from other endocrine-disrupting compounds usually present in dairy effluents. The facile nature of the colorimetric probe and potential application in monitoring water quality was demonstrated.

A Ni 2+ based colorimetric probe based on glutathione-stabilized silver/copper nanoparticles (GSH-Ag-Cu alloy NPs) in an electrospun polymer matrix is reported. Glutathione-Ag-Cu alloy NPs were characterized by ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The freshly synthesized GSH-Ag-Cu alloy NPs in a polymer matrix were black in colour due to an intense surface plasmon absorption band at 424 nm. However the electrospun nanocomposite fibres were green in colour and in the presence of Ni 2+ the green GSH-Ag-Cu alloy NP fibres were discoloured. The sensitivity of the GSH-Ag-Cu alloy NPs towards other representative transition, alkali and alkali earth metal ions was negligible. The effect of the concentration of Ni 2+ on the nanocomposite fibres was evaluated and the 'eye-ball' limit of detection was found to be 5.8 μg/mL.