Structural, optical and dielectric properties of transition metal doped ZnO nanoparticles and its enhanced electrochemical properties: role of atomic number of the dopant

The transition metal-doped ZnO nanoparticles (Zn_1−xM_xO; M is a transition metal – Mn, Fe, Co, Ni and Cu) are prepared by the chemical precipitation method. The significance of the atomic number of the dopant is scrutinized to unveil the structural, optical, and dielectric attributes of the prepared nanoparticles. The transition metals with atomic numbers ranging from 25 to 29 are considered as dopants in the work. Debye-Scherrer’s formula, Williamson-Hall equation and Halder-Wagner methods are employed to find the crystallite size of the prepared nanoparticles. Cu-doped ZnO nanoparticles have low crystallite size as compared with undoped and other transition metal-doped ZnO. As the atomic number of the dopant increases, the dislocation density is enhanced. The band gap and Hall coefficient have minimum value when the atomic number of the dopant is high. The electron and hole concentrations also depend on the dopant and the dielectric properties depend on the atomic number of the dopant. The cyclic voltametric technique is employed to study its electrochemical properties. The transition metal-doped ZnO nanoparticles show a higher specific capacitance than undoped ZnO. In this study, Cu-doped ZnO nanoparticles have a high specific capacitance of ~ 419 F/g.