Functionalized Silver Nano Particle Coated e-FBG Sensor for Specific and Rapid Detection of Chromium in Drinking Water

Hexavalent chromium [Cr (VI)], a widely used material in industry has raised alarm due to its genotoxicity and carcinogenic nature. This study focuses on developing an effective optical sensor for determining Cr (VI) in drinking water based on polyvinylpyrrolidone (PVP) functionalized silver nanoparticles (AgNp) coated and clad etched Fiber Bragg Grating (e-FBG). The lone pair electrons present in nitrogen (N) and oxygen (O) present in PVP contribute toward the specific binding of Cr (VI) on the sensor surface, causing a shift in the Bragg wavelength (
$\lambda _{\text {B}}$
) with Cr (VI) concentration. A liner relationship is observed in this study indicating the molar concentration of Cr (VI), with a limit of detection (LOD) of 0.1 pM (0.0000052 ppb), and a working range of 0.1 pM to
$100~\mu $
M (5.2 ppm), which is within the World Health Organization (WHO) permissible limit of 960 nM (50 ppb) in drinking water. The sensor is observed to be specific in nature when exposed to other interfering ions like arsenic [As (II)], mercury [Hg (II)], lead [Pb (II)], magnesium [Mg (II)], sodium [Na (I)], and trivalent chromium [Cr (III)]. The sensor’s accuracy has been reconfirmed with inductively coupled plasma mass spectroscopy (ICPMS), which showed an accuracy of (>96%). A good recovery percentage (>95%) for spiked drinking water samples highlights the sensor’s efficacy in the case of real water sample analysis. A portable sensor with real-time monitoring ability, combined with good reproducibility (
${S} \lt 10$
pM) and liner response, make the present sensor a potential onsite candidate for Cr (VI) determination in drinking water.