A highly selective and sensitive colorimetric Hg²⁺ sensor based on hemicyanine-functionalized polyacrylonitrile fiber

In this work, we have synthesized a novel hemicyanine-modified polyacrylonitrile fiber (HDBA-PAN_AF) as a colorimetric Hg²⁺ sensor. The color is observed from dark red to orange by the naked eye only when the fiber is exposed to Hg²⁺. Positively, the HDBA-PAN_AF shows high selectivity and sensitivity for Hg²⁺ compared with other metal ions such as Na⁺, Mg²⁺, Al³⁺, Ca²⁺, Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺ and Pb²⁺. Furthermore, the obtained fiber has a wide pH application range from 3 to 11 and also processes a lower detection limit of 1 × 10⁻⁶ mol L⁻¹ for Hg²⁺. Moreover, the HDBA-PAN_AF undergoes an obvious color change toward Hg²⁺ even containing an excess of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) in the solution, indicating that the fiber has a stronger complexation affinity for Hg²⁺ than EDTA-2Na. Hence, the fiber sensor possesses the merits of low cost, high selectivity, low detection limit and environment-friendly property, which shows that it is a promising candidate for Hg²⁺ detection in water.