Optical Fiber-Based Heavy Metal Detection Using the Localized Surface Plasmon Resonance Technique

An innovative, reflection-based localized surface plasmon resonance (LSPR) fiber-optic sensor has been developed and demonstrated to detect the concentration of several heavy metal lead ions in an aqueous solution. By using a self-assembling technique, gold nanoparticles (Au NPs) have been immobilized on an optical fiber surface and functionalized with 1,1-Mercaptoundecanoic acid [MUA; HS(CH ₂ ) ₁₀ CO ₂ H] in order to make the fiber selective to each the important heavy metal ion, Pb ²⁺ or Cd ²⁺ . The concentration of the heavy metal then can be determined from the link between binding rate and the shift of the LSPR resonance wavelength. The Pb ²⁺ ion sensitivity of the sensor thus created has been determined to be 0.28 nm/mM, with a typical response time of 30 s. Importantly, the probe has been shown to be reversible through a simple process involving the use of ethylenedinitrilotetraacetic acid [EDTA;(HO ₂ CCH ₂ ) ₂ NCH ₂ CH ₂ N(CH ₂ CO ₂ H) ₂ ] chelator to remove the bound heavy metal ion.