Electrochemical impedance characterization of ZnO semiconductor nanoparticles biosynthesized with Verbascum thapsus

The present work analyzes the electrochemical properties of ZnO nanoparticles synthesized with the help of Verbascum thapsus as a reducing agent with different aggregation percentages. The synthesized nanoparticles had Band gap values of 2.71, 2.66, and 2.58 eV for the ZnO-1%, ZnO-2%, and ZnO-4% samples, respectively, which is related to their average crystal sizes of 24, 22, and 20 nm. It was also observed that the different samples maintain a Wurtzite-type phase, with a quasi-spherical nanoparticle morphology (sizes between 66.3 and 36.5 nm approximately) and composition of only Zn and O elements. Furthermore, the ATR-IR study showed the vibration peak of Zn–O and a zone that corresponds to the organic molecules of the extract used in biosynthesis. From the electrochemical analysis, it was found that the sample labeled as ZnO-4% has a significantly smaller impedance value than the other two samples. The tests show that the variation in the extract modified the reactance and resistivity of the materials that can be associated to the individual values of the capacitances and resistances expressed in the electrical model of equivalent impedance.