The structural, optical, and photocatalytic properties of Cd0.4Mn0.6XO nanocomposites with 50 wt% of X were investigated (X denotes ZnO, SnO, CuO, Al2O3, Fe2O3, NiO, and CoO). The crystal structure of Cd0.4Mn0.6XO nanocomposites is composed of the monoclinic Cd2Mn3O8 phase, along with other individual phases dependent on the type of X dopant. The crystallite sizes are between 11.07 nm for CoO and 23.65 nm for ZnO, whereas the particle sizes are between 9.75 nm for ZnO and 35.61 nm for Fe2O3. The SnO, NiO, and CoO nanocomposites had the highest values of the effective surface area of 29.71, 26.3, and 24.1 m(2)/g, respectively. The NiO and SnO nanocomposites had the highest and lowest absorbance, respectively, notably at wavelength below 400 nm. SnO, NiO, CuO, and Fe2O3 nanocomposites have the highest values of energy gap (Eg > 2 eV), whereas CoO, ZnO, and Al2O3 nanocomposites have the lowest Eg values (< 2 eV). The SnO nanocomposite exhibited the highest values of refractive index, q-factor, lattice dielectric constant (epsilon L), free carrier density (Nm & lowast;), and optical/electrical conductivity when compared to the other Cd0.4Mn0.6XO nanocomposites. Interestingly, the values of epsilon L and Nm & lowast; were enhanced to 21.2 and 4.9 x 10(57) cm(-3)g(-1) for SnO nanocomposite, followed by NiO and Fe2O3 nanocomposites. The photodegradation efficiency towards methylene blue (MB) using the Cd0.4Mn0.6XO catalysts after 3 h of UV-visible irradiation equals 97.94, 76.43, 74.43, 71.32, 65.98, 62.86, and 48.55 % for ZnO, NiO, SnO, Fe2O3, Al2O3, CuO and CoO nanocomposites, respectively. The photocatalytic performance of Cd0.4Mn0.6XO catalysts towards MB was compared to earlier investigations and a scavenger test was performed to validate the formation of reactive oxygen species. The features of Cd0.4Mn0.6XO nanocomposites are convenient for light-emitting diodes, solar cells, reduced electronic noise, high-power operation, and water purification.
