Poly(vinyl alcohol) hydrogel based fiber interferometer sensor for heavy metal cations

• Use of a compact fiber interferometer as transducer for hydrogel based heavy metal cation sensing.
• Facile method of poly(vinyl alcohol) thin hydrogel film formation on optical fiber with discussion on various design parameters.
• Transferability of sensor for other sensing applications.
• Potentials for continuous, remote sensing of water quality.

A Mach Zehnder fiber interferometer is demonstrated for sensing of the heavy metal cation, Ni2+ using a responsive poly(vinyl alcohol) (PVA) based hydrogel. The presence of Ni2+ increases degree of cross linkages within the hydrogel and increases its refractive index, leading to phase shift in the interferogram. Ni2+ concentration is monitored by the shifting of interference dips with a sensitivity of 0.214 nm/μM and limit of detection of 1 nM. Design of the PVA hydrogel to optimize sensitivity is discussed and the capability of the gel to immobilize various receptors enables a flexible platform for sensing applications.