Doping effect of Europium (Eu³⁺) on flower-like ZnO nanostructures: shape variations, optical properties and its applicability in electrochemical sensing of heavy metal (Lead) ion detection

Hydrothermal synthesis has been effectively used to create pure and Europium (Eu³⁺) doped (1, 3 & 5%) ZnO nanostructures. The as-synthesized structures were analyzed using a range of spectroscopic and microscopic techniques such as X-ray, UV–Vis, FTIR, PL, and SEM analysis. It was discovered that the shape of the fabricated flower-like ZnO nanostructures made of mixed compact clustered nanorods could be meticulously governed by changing the Eu³⁺ dopant amount within the desired threshold. The distinctive photoluminescence (PL) properties indicate that energy is transferred from excited ZnO material, precisely at its band-gap (3.17 eV), to the Eu³⁺ states through the luminescent defects present in the nanoparticles. Considering, the increasing presence of heavy metal ions poses a continuous risk to both human health and ecosystems, we introduced for the first time, an electrochemical spectroscopy analysis of Europium-doped ZnO (Eu³⁺: ZnO) as modifications to the glassy carbon electrodes for lead (Pb²⁺) heavy metal ion detection. Electrochemical impedance spectroscopy, cyclic voltammetry, and square wave voltammetry were used to test the sensor’s sensing ability. Differential pulse voltammetry reveals the remarkable sensitivity towards Pb²⁺ ions with a 0.002 µM detection limit.