Hydrazine-assisted hydrothermal synthesis of NiTe and NiTe₂ nanorods

Herein, we report nanostructures of NiTe and NiTe₂ nanorods (NRs) with stoichiometric chemical compositions grown in an efficient one-pot hydrothermal approach. In the synthesis, hydrazine hydrate played multiple roles, such as a dissolving agent, reductant, and structure-directing agent. The samples were characterized using various analytical methods, such as X-ray diffraction, high-resolution transmission electron microscopy (HR-TEM), nitrogen adsorption/desorption measurements, energy-dispersive X-ray spectrometer (EDX), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and UV–Vis diffuse reflectance spectroscopy consequently. Adjustment of the Ni:Te (1:1, 1:2) precursors molar ratio reflected the results as desirable stoichiometric crystal structures of NiTe (hexagonal, P6 ₃/ mmc ) and NiTe₂ (trigonal, P3 ¯ m 1 ); further, the FE-SEM images displayed the evolution of nanorod morphology with an intermediate of tellurium template by the influence of the Kirkendall effect. The TEM pictures are likely to show the formation of two distinguished nanorods with different particle sizes. Both NiTe NRs and NiTe₂ NRs were developed along the hexagonal direction; however, NiTe NRs include relatively small particles, and NiTe₂ NRs considerably larger ones. The high-resolution XPS spectra revealed the surface structure and chemical composition of the Ni–Te system under Ni 2p and Te 3d spectra with the characteristic peaks of Ni²⁺, Ni⁰, Te²⁻, and Te⁴⁺ assigned based on the influence of hydrazine reduction and surface oxidation, respectively. Therefore, the optical band gap value of the prepared NiTe and NiTe₂ NRs phases was found to be 3.25 and 3.0 eV, showing the semiconductor properties and potential for a wide range of applications.