Selective detection of lead in water using etched fiber Bragg grating sensor

In this work, we demonstrate a maleic acid (MA) functionalized gold nanoparticle (AuNP) coated, clad etched-fiber Bragg grating (e-FBG) sensor, capable of detecting lead metal ion (Pb2+) in water. The self-assembled carboxylic group in MA-AuNP shows an assertive coordination behavior towards Pb2+ for selective detection through a Bragg wavelength shift. The limit of detection (LOD) is found to be 10 femtomolar (fM, 0.0000002 ppb) with a dynamic range up to 100 nanomolar (nM, 20.72 ppb), which is within the acceptable limit stipulated by the World Health Organization (WHO) for safe drinking water (10 ppb). The sensor's recovery concentration is > 90% for spiked real water samples. A good reproducibility (standard error < 10 pm) and specificity along with portability, small footprint and real time response make e-FBG sensor an ideal optical probe for drinking water.