Detection of copper ions in an aqueous solution by a dual-peak long period fiber grating functionalized with a polypyrrole–chitosan composite

Abstract

A dual-peak long period fiber grating (DP-LPFG) sensor functionalized by polypyrrole–chitosan composite was proposed for sensitive detection of Cu2+ ions in aqueous solution. The nitrogen atom on the polypyrrole ring and the amino group on the chitosan chain in the complex matrix can chelate the Cu2+ ions. Thus, the refractive index of the overlay changed and further modulated the transmission spectrum of DP-LPFG. After special design, the double peaks can move in opposite directions with the increase of Cu2+ ion concentration, thereby greatly improving detection sensitivity. The linear sensitivity of the fabricated sensor was measured to be 9.12 and 2.14 nm/ppm (0.61 and 0.14 nm/µM) for concentrations of 0.1–0.5 (1.5 µM-7.5 µM) and 0.5–2 ppm (7.5 µM-30 µM), respectively. In addition, the Langmuir isothermal model was used to evaluate the overall response of the sensor to Cu2+ ions quantitatively, and the detection limit was determined to be 0.05 ppb (0.75 nM). This ingenious sensor offers a new solution for sensitive detection of heavy metal ions in environmental water.

Angularly Cascaded Long-Period Fiber Grating for Curvature and Temperature Detection

“…Due to the high response of the cladding mode to change in the environment, LPFGs have higher sensitivity than other types of optical fiber grating [ 1 ]. Recently, R&D LPFG-based sensors have been developed to measure many environmental parameters closely related to our daily lives, such as strain, force, torsion, curvature, magnetic field, surrounding refractive index, and so on [ 2 , 3 , 4 ]. Regardless of the type of parameter being measured, the temperature crosstalk limits the practical application of LPFG-based sensors.…”