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.