A highly selective and sensitive recyclable colorimetric Hg2+ sensor based on the porphyrin-functionalized polyacrylonitrile fiber

Abstract

A colorimetric Hg²⁺ sensor based on the porphyrin-functionalized polyacrylonitrile fiber (CT_APP–PAN_AF) was prepared and investigated. This functional fiber sensor shows excellent selectivity and sensitivity towards Hg²⁺ over other common metal ions (Pb²⁺, Ba²⁺, Cd²⁺, Ag⁺, Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Fe³⁺, Mn²⁺, Cr³⁺, Ca²⁺, Al³⁺ and Mg²⁺). Upon the addition of Hg²⁺, a remarkable visual color change from red-brown to dark-green and significant detectable changes in the FTIR, UV and FL spectra of CT_APP–PAN_AF were observed. The naked-eye detection limit is as low as 20 ppb (1 × 10⁻⁷ mol L⁻¹), which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China. This functional fiber sensor also exhibits excellent reusability and recyclability and can be repeatedly used more than 50 times. The Hg²⁺ complexed sensor can be easily separated from the aqueous solution by simple filtration and reversed back by treating with dilute HCl. Furthermore, real water sample testing confirms the practical application of CT_APP–PAN_AF. In a word, the fiber sensor possesses the advantages of simplicity, rapidity, and reusability as well as high selectivity and sensitivity.