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

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/mu M 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. (C) 2014 Elsevier B.V. All rights reserved.