Simultaneous Colorimetric Sensing of Anion (I−) and Cation (Fe2+) by Protein Functionalized Silver Nanoparticles in Real Samples

Spherical shaped silver nanoparticles with the average size of 68.7 nm were synthesized from eco-friendly and environmentally safe approach using serum carrier protein 'fetuin-A' as stabilizing agent (named as F-AgNPs). Protein capping provided excellent stability at variable temperature (~ 25–85 °C), pH (~ 4–8), salt concentrations (~ 1.5 M) and storage period (≥ 3 months). Synthesized F-AgNPs were extensively characterized using UV–visible, Fourier transform infrared, circular dichroism and intrinsic fluorescence spectroscopy, dynamic light scattering, atomic force and scanning electron microscopy, energy dispersive spectroscopic measurements. F-AgNPs were proved as highly sensitive and selective colorimetric dual sensor for iodide (I−) and ferrous (Fe2+) ions with significant linearity (1–8 and 1–10 µM, respectively), detection limits (LOD = 0.5 and 0.47 µM, respectively) and percent recoveries in real environmental (tap water) and biological (human plasma and urine) samples with adequate test performance. Cumulatively, obtained results revealed that this simple and biocompatible nanosensor has great potential for applications not only in analytical chemistry but also for biological investigations.