Electrochemically assisted flexible lanthanide upconversion luminescence sensing of heavy metal contamination with high sensitivity and selectivity

Heavy metal contamination in water can pose lethal threats to public health; therefore it is highly desired to develop a rapid and sensitive sensor for monitoring water quality. Owing to their superior optical features, upconversion nanoparticles (UCNPs) are widely explored to detect metal ions based on resonance energy transfer to dye quenchers. However, these schemes heavily rely on the optical properties of the molecules, which limits the flexibility of the probe design. Herein, a flexible carbon fiber cloth/UCNP composite probe was fabricated for sensing copper(ii) (Cu²⁺) ions and an electrochemical (E-chem) technique was implemented for the first time to enhance its sensing performance. By applying 0.3 V on the composite probe, Cu²⁺ ions can be effectively accumulated through oxidation, yielding a remarkable improvement in the selectivity and sensitivity. A more outstanding detection limit of the sensor was achieved at 82 ppb under the E-chem assistance, with 300-fold enhancement compared to the detection without the E-chem effect. This sensing approach can be an alternative to molecular quenchers and open up new possibilities for simple, rapid and portable sensing of metal ions.