The structural, optical, magnetic, and photocatalytic properties of NiO/SiO2(x) nanoparticles with different SiO2 concentration (x) = 0%, 30%, 50%, 60%, and 70% have been investigated. XRD confirmed that the phase formation of NiO nanoparticles and the average crystallite size decreased with increasing SiO2 concentration. FTIR spectra confirmed the presence of Ni - O and Si - O - Si symmetric and asymmetric bands at 440, 800, and 1050 cm−1, respectively. The one-phonon (1P) optical mode in Raman spectra revealed the presence of interstitial oxygen defects, whereas the two-magnon (2M) peak indicates antiferromagnetic (AFM) ordering in x = 0% and 30% nanoparticles due to the large average crystallite size. The 2M peak at 1472 cm−1 diminished for x = 50%, 60%, and 70% nanoparticles, which confirmed the magnetic transition from AFM to a superparamagnetic (SPM) state. The magnetic data also confirmed the AFM to SPM transition in these nanoparticles. It is clear from diffuse reflectance spectra that x = 70% nanoparticles showed higher and wide absorbance spectra due to the presence of a large amount of fused SiO2. The HRTEM images showed that the crystalline NiO nanoparticles are well dispersed in a fused amorphous SiO2 matrix, which served as the UV wave guiding medium to activate NiO nanoparticles as a photocatalyst. The photocatalytic activity of x = 70% nanoparticles was found maximum due to their ability to absorb a wide range of UV/Vis light, and this is attributed to a higher concentration of SiO2 and oxygen defects at the surface of the nanoparticles. Therefore, a higher SiO2 concentration is beneficial for enhancing the photocatalytic performance and achieving SPM in NiO nanoparticles.
ASJC Scopus subject areas
- Physics and Astronomy(all)