A dual-channel optical fiber sensor based on surface plasmon resonance for heavy metal ions detection in contaminated water

Abstract A novel dual-channel optical fiber sensor based on surface plasmon resonance (SPR) is proposed experimentally. Different thicknesses of Ag are sputtered on two fiber channels first to generate two resonance dips firstly, achieving refractive index (RI) sensitivities of 1334.56 nm/RIU and 1730.88 nm/RIU respectively. Then the channel with thicker Ag is functionalized with chitosan (CS) and poly (acrylic acid) (PAA) through layer-by-layer (LBL) for the detection of heavy metal ions in contaminated water, and the channel with thinner Ag can be regarded as a reference, confirming whether the change of former channel is authentically caused by heavy metal ions or surrounding refractive index (SRI). With the concentration of Cu2+ increasing and other metal ions as experimental sample, the resonance dip caused by the channel functionalized with CS/PAA will have an obvious red shift at low concentration of ions. Experimental results demonstrate that Cu 2 + bind the CS/PAA layer more strongly, reaching to 0.249 nm/ μ M when the concentration is below 80 μ M, which means that this sensor has a high sensitivity for Cu 2 + in a low concentration.