Doping effect of Europium (Eu${}^{3+}$) 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 (Eu${}^{3+}$) 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 Eu${}^{3+}$ 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 Eu${}^{3+}$ 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 (Eu${}^{3+}$: ZnO) as modifications to the glassy carbon electrodes for lead (Pb${}^{2+}$) 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 Pb${}^{2+}$ ions with a 0.002 µM detection limit.