Sensitive and selective Cd²⁺ sensing with a hydrogel-functionalized Fabry-Pérot fiber sensor

Area of Science:

• Environmental Science
• Materials Science
• Analytical Chemistry

Background:

• Detecting ultra-low concentrations of cadmium ions (Cd²⁺) in water is crucial for environmental safety and public health.
• Existing methods for Cd²⁺ detection often face challenges in sensitivity, selectivity, and real-time monitoring.

Purpose of the Study:

• To develop a novel, highly sensitive fiber-optic sensor for the detection of trace cadmium ions (Cd²⁺) in water.
• To integrate a Cd²⁺-responsive hydrogel with a refractive-index-sensitive Fabry-Pérot (F-P) interferometer for enhanced sensing capabilities.

Main Methods:

• Fabrication of a Fabry-Pérot (F-P) interferometer using large-offset fusion splicing.
• Synthesis of a Cd²⁺-responsive hydrogel from allylthiourea/acrylic acid/acrylamide monomers.
• Integration of the hydrogel with the F-P interferometer for Cd²⁺ detection.

Main Results:

• The developed sensor achieved ultrahigh sensitivity (8.58 × 10⁷ nm/(mol/L)) and an ultra-low detection limit (9.435 × 10^-10 mol/L, 0.1057 ppb).
• Demonstrated excellent selectivity, stability, and consistency, with a detection limit significantly below WHO drinking water standards.
• The hydrogel exhibited specific adsorption towards Cd²⁺ and formed a robust bond with the F-P fiber interferometer.

Conclusions:

• The proposed fiber-optic sensor offers a reliable solution for in situ monitoring of trace Cd²⁺ in environmental waters.
• The sensor shows significant potential for real-time environmental monitoring applications, ensuring water safety.
• This novel approach advances the field of optical sensing for heavy metal ion detection.