Study of nonlinear optical properties of ZnCo₂O₄/GQD nanocomposite and their correlation with microstructure

In this study, ZnCo 2 O 4 /Graphene quantum dots (ZCO/GQDs) nanocomposite was fabricated by carbonization and hydrothermal methods in four volume ratios (40.0 ml/0.0, 37.5 ml/2.5 ml, 35.0 ml/5.0 ml, and 32.5 ml /7.5 ml) of ZCO/GQD where the total volume was fixed at 40 ml. To characterize the structural, morphological, and optical properties of the nanocomposites, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, UV-visible spectrometry, and Z-scan analysis were conducted. The variance and Williamson-Smallman methods were applied to calculate the microstructure features. The results illustrate that the crystallite size and strain are minimum while the dislocation density has a maximum value for 37.5 ml/2.5 ml of volume ratio. Band gap and nonlinear optical coefficients were obtained by Tauc and Z-scan techniques and the results show they are maximum in this ratio. These results confirm a correlation between microstructure and optical properties. Such a correlation can be applied to improve the optoelectronic applications of the nanocomposite.