Thiourea-enhanced bifunctional covalent organic framework triboelectric nanosensor for high-efficiency detection and visualization of Hg2+ ions

Abstract

The high toxicity and bioaccumulation of mercury (Hg²⁺) ions have raised concerns about the dynamic changes of trace Hg²⁺ ions in the environment. Although conventional Hg²⁺ ion detection techniques provide highly sensitive and specific results, complex sample pre-treatment damages the native aquatic environment for Hg²⁺ ions resulting in detection inaccuracy, and the need for a stable external power supply limits real-time detection of Hg²⁺ ions in the field where power is scarce. The triboelectric nanogenerator (TENG) with no pre-treatment and self-powering provide a sustainable solution for Hg²⁺ ion detection. In this work, a thiourea-enhanced bifunctional covalent organic framework triboelectric nanosensor (TENS) was proposed. The thiourea moiety not only enhances the electrical output performance of the COF-based TENG to improve the detection sensitivity, but also serves as a specific binding site to recognize Hg²⁺ ions. The prepared COF-based TENS had the advantages of low detection limit (31.6 pM), wide linear range (10⁻¹⁰ M to 10⁻⁴ M), high selectivity, reusability and stability. And it was suitable for the detection of Hg²⁺ ion concentration in real samples (drinking water, tap water, river water and lake water). The developed detection system was connected in series with LEDs without external power supply to realize LED-indicated Hg²⁺ ion detection in water samples. This study provided a novel implementation example of a COF-based TENS, which also provided a more convenient and sustainable idea for the detection of heavy metal pollution.