Nuclear fast red-based colorimetric sensors for sensitive and selective detection of Ag ions

The reduction of nuclear fast red (NFR) stain by sodium tetrahydroboron was catalyzed in the presence of silver ions (Ag⁺ ). The fluorescence properties of reduced NFR differed from that of NFR. The product showed fluorescence emission at 480 nm with excitation at 369 nm. Furthermore, the fluorescence intensity of the mixture increased strongly in the presence of Ag⁺ and Britton-Robinson buffer at pH 4.78. There was a good linear relationship between increased fluorescence intensity (ΔI) and Ag⁺ concentration in the range 5.0 × 10^-9 to 5.0 × 10^-8  M. The correlation coefficient was 0.998, and the detection limit (3σ/k) was 1.5 × 10^-9  M. The colour of the reaction system changed with variation in Ag⁺ concentration over a wide range. Based on the colour change, a visual semiquantitative detection method for recognition and sensing of Ag⁺ was developed for the range 1.0 × 10^-8  to 5.0 × 10^-4  M, with an indicator that was visible to the naked eye. Therefore, a sensitive, simple method for determination of Ag⁺ was developed. Optimum conditions for Ag⁺ detection, the effect of other ions and the analytical application of Ag⁺ detection of synthesized sample were investigated.