Ytterbium-incorporated porphyrin nanostructure-modified carbon electrodes for ultra-sensitive detection of lead ions in water environments

Abstract

Simple modification of electrodes for sensitive Pb(II) detection is the key to the realization of electrochemical sensors for monitoring water pollution, but it remains a challenge. In this study, a novel ytterbium (Yb)-functionalized meso-tetra(4-carboxyphenyl)porphyrin (Yb-TCPP) composite was synthesized via a hydrothermal method to address this challenge. The excellent structure and properties of Yb-TCPP significantly enhance the sensitivity (783.58 μA μM⁻¹ cm⁻²) of electrochemical Pb(II) detection by the electrode. The Yb-TCPP-modified electrode exhibits a strong linear relationship in the Pb(II) concentration ranges of 5–300 μg L⁻¹ and 300–1000 μg L⁻¹, with a detection limit as low as 0.16 μg L⁻¹. The recovery rate obtained from repeated testing of actual water samples ranged from 98.93% to 100.63%. Density functional theory (DFT) was used to predict the structure of Yb-TCPP, which confirms that a large number of tetrapyrrolic cavities with strong adsorption to Pb are retained in the structure. The decrease in the structural energy gap further proves that Yb improves the conductivity of the material. The electron transfer in the system is revealed, and Yb-TCPP shows strong catalytic effects in both the reduction-enrichment and oxidation-stripping stages of Pb. This study discards the previous redundant modification process of multi-material composites and provides a new idea for the modification of a single-material electrode, which advances practical applications in environmental heavy metal monitoring.