Bi-doped CoTe nanoparticles for nonlinear and optoelectronic applications

The exceptional properties and broad applicability of CoTe nanoparticles make them highly relevant for various technological applications, particularly in optoelectronics. Introducing a metal dopant into a nanomaterial matrix has been shown to enhance its characteristics, thereby expanding its potential use. This study presents a straightforward hydrothermal synthesis method for Bi-doped CoTe nanoparticles, wherein four different samples were synthesized by varying the Bi doping concentration. Structural characterization via X-ray diffraction confirmed the presence of the hexagonal CoTe phase, with noticeable phase shifts attributed to Bi incorporation. Raman spectroscopy provided insights into the vibrational modes of CoTe, while transmission electron microscopy further verified the CoTe phase and measured interplanar spacing. A field emission scanning electron microscopy morphological study revealed a constant nanoparticle-like structure that did not alter as the concentration of Bi increased. Elemental composition was examined through X-ray photoelectron spectroscopy, confirming the composition of the expected material. Additionally, UV-Vis spectroscopy revealed a bandgap reduction in the range of 3.35–1.64 eV, suggesting modifications in the material's optical properties. Meanwhile, the refractive index value of the material gradually increased in the range of 2.00–3.08. The photoresponse study showed a photocurrent ranging from 229 to 810 μA, with the highest observed in the Bi-3 sample. Additionally, a maximum nonlinear absorption coefficient (β) of 1.448 cm W⁻¹ was recorded. These results indicate the material's strong potential for nonlinear photonics and optoelectronic applications.