Synthesis and characterizations of MgxNixO2 nanoparticles doped (CMC /PVP) polymeric blend thin films

In this work, pure MgO nanoparticles and Ni-doped MgO (MgₓNiₓO2) nanoparticles with different Ni-to-Mg ratios (1:0.25, 1:0.5, and 1:1) were successfully synthesized using a simple, non-toxic, and low-cost sol–gel route. Flexible nanocomposite thin films were subsequently fabricated by incorporating (9 wt%) of the synthesized nanoparticles into a CMC/PVP polymeric blend matrix. The structural, morphological, and optical properties of the prepared samples were investigated using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and UV–Vis spectroscopy. FE-SEM analysis revealed the formation of semi-spherical MgO nanoparticles with an average particle size of approximately (50 nm). The incorporation of Ni resulted in the formation of more defined MgₓNiₓO2 nanoparticles with reduced particle sizes at lower Ni contents (1:0.25 and 1:0.5), while higher Ni content (1:1) led to particle growth, which may be associated with enhanced agglomeration effects. XRD results confirmed the formation of a cubic MgO crystal structure, with no detectable secondary phases upon Ni incorporation, indicating the preservation of the host lattice structure. EDX analysis verified the presence of Mg, Ni, and O elements with compositions consistent with the intended synthesis ratios. FT-IR spectra confirmed effective blending between CMC and PVP polymers and demonstrated favorable interactions between the polymer matrix and the embedded nanoparticles. The optical analysis revealed that the reported optical band gap values correspond to the effective optical band gap of the CMC/PVP–MgₓNiₓO2 nanocomposite thin films, rather than the intrinsic electronic band gap of bulk MgO. The incorporation of MgO and Ni-doped MgO nanoparticles led to a noticeable reduction in optical transmittance across the visible and near-infrared regions, attributed to enhanced light absorption and scattering effects. Furthermore, increasing Ni content resulted in a progressive reduction of the effective optical band gap, which is associated with the formation of localized electronic states and interfacial effects within the polymer–nanoparticle system. A corresponding increase in both the refractive index and extinction coefficient was also observed with higher Ni incorporation. These findings demonstrate that CMC/PVP–MgₓNiₓO2 nanocomposite thin films exhibit tunable optical properties and show potential for application in optoelectronic and photonic device.