Salicylic acid doped silica nanoparticles as a fluorescent nanosensor for the detection of Fe3+ in aqueous solution

A novel organic–inorganic hybrid nanosensor (SASP) was prepared by a one-step sol–gel method and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, N2 adsorption–desorption, fluorescence spectroscopy, etc. The nanosensor showed almost 3-fold fluorescence emission quenching upon excitation with a 293 nm wavelength in the presence of 20 μM Fe3+ ions. The presence of 18 other metal ions had no observable effect on the sensitivity and selectivity of the nanosensor. A fluorescence analysis method based on the SASP for the selective detection of Fe3+ was established under optimal conditions. The results showed that there was a linear relationship between the log luminescence value and the concentration of Fe3+ over the range of 2.0 × 10−7–9.0 × 10−5 mol L−1 with a detection limit (3σ) of 2.5 × 10−8 mol L−1. Furthermore, the proposed method was successfully applied for the determination of trace Fe3+ in fetal bovine serum without the interference of other molecules and ions. Good recovery (96.5–104.5%) and a relative standard deviation of less than 8.6% were obtained from serum samples spiked with four levels of Fe3+. Additionally, the nanosensor showed a good reversibility; the fluorescence could be switched “off” and “on” in two ways, by adjusting the pH of the solution and adding metal chelating agent EDTA.