synthesis and comparative photocatalytic study of znmn₂o₄ nanocomposite thin films via sol-gel and urea combustion methods for direct red 28 azo dye degradation

In this study, znmn₂o₄ nanocomposites were synthesized using two different methods: sol-gel and urea combustion. thin films of these nanocomposites were then fabricated using the doctor blade technique to evaluate their photocatalytic performance in degrading direct red 28 dye. a comprehensive set of characterization techniques including x-ray diffraction (xrd), fourier-transform infrared spectroscopy (ft-ir), ultraviolet-visible (uv-vis) spectroscopy, and field emission scanning electron microscopy (fesem) were employed to assess the structural, optical, and morphological properties of the catalysts. both synthesis routes resulted in a tetragonal spinel structure. however, the urea combustion method produced nanocomposites with smaller particle sizes, higher crystallinity, and a larger surface area, which are crucial factors for enhancing photocatalytic activity. photocatalytic tests under uv light demonstrated that the znmn2o4 thin film prepared via the sol-gel method reduced the absorbance of direct red 28 from approximately 0.35 to 0.10 over 140 minutes, while the thin film synthesized by urea combustion achieved a more pronounced reduction, reaching an absorbance as low as 0.03-0.04 in the same time frame. kinetic studies based on the pseudo-first-order model further confirmed that the urea combustion catalyst exhibited faster degradation rate. these findings suggest that, although both methods provide effective photocatalytic degradation of direct red 28, the urea combustion route offers superior performance due to its favorable structural and morphological characteristics.