L-cysteine grafted fiber-optic chemosensor for heavy metal detection

In this work, we have demonstrated metal ion detection using L-Cysteine functionalised gold-coated tilted fiber Bragg grating (Au-TFBG). L-cysteine (L-cys) is a semi-essential amino acid that has high tendency to form Au-S bond via thiol group on the gold surface of the sensor whereas the amine groups and carboxyl groups of the L-cys molecules can serve as surface ligands that bind with the metal ions in the test analyte. The findings indicate that the sensor was reactive and sensitive to different metal ions including Co2+, Cd2+, Cu2+, Pb2+, Ni2+ and Zn2+. By adopting the two-step procedure in the measurement, the refractive index noise can be effectively discriminated from the signal and the functionality of the L-cysteine grafted Au-TFBG sensor can be validated. The selectivity test results show that the sensor has high affinity towards Cu2+ metal ion and the measured LOD is 0.19 µM.

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