30, 3.30, and 3.26 eV, respectively, as shown in the inset of Figure  3. The absorbance spectra and their corresponding first and second derivatives are drawn in Figure  4a,b,c, and the bandgaps of 3.30, 3.28, and 3.24 were estimated for ZnO, ZB10, and ZB20 nanoparticles, respectively. It can be seen that the bandgap of the ZnO nanoparticles decreased by adding barium. As mentioned earlier, the crystallite size of the prepared nanoparticles increased by adding barium, resulting to redshifting of the absorption edge due to the quantum this website confinement and

size effects. The bandgap is estimated from the absorption spectrum; therefore, the value of the obtained bandgap decreased for the barium-added samples. Considering the results obtained from the methods, it can be concluded that there is a better agreement between the derivative method with the observed blueshift in reflectance spectra and the Kubelka-Munk method due to the less approximations of the derivative method. Figure 4 Optical bandgap value of the synthesized (a) ZnO, (b) PRN1371 order ZB10, and (c) ZB20 nanoparticles. The absorbance is shown in the inset. Method of optical constant calculations In the complex refractive index, N = n - ik, n is the refractive index and k is the Savolitinib molecular weight extinction coefficient. The extinction coefficient is related to the absorption coefficient by k = λα/4π. According to the Fresnel formula, the reflectance as a function of the refractive index n and the absorption

index k is given as [31] (3) As mentioned above, the extinction coefficient is obtained using k = λα/4π, where the absorption coefficient is calculated from Equation 3. Therefore, by calculating α and then k, the refractive index can be obtained from (4) According to the obtained results for n and k, the real

and imaginary parts Smoothened of the dielectric function can be calculated by the following equations [32]: (5) The obtained results for the optical properties are presented in Figures  5 and 6. Figure 5 The behavior of the refractive indexes and extinction coefficients calculated near the absorption edge. (a) ZnO, (b) ZB10, and (c) ZB20 nanoparticles. Figure 6 The behavior of the real and imaginary parts of permittivity calculated near the absorption edge. (a) ZnO, (b) ZB10, and (c) ZB20 nanoparticles. Auger spectroscopy of ZnO/BaCO3 nanocomposites Auger spectroscopy is a helpful method to be used for element detection of compounds. Figure  7 shows the high-resolution N(E) (blue line) and related derivative (red line) AES of the ZB-NPs calcined at 650°C. The Auger spectra of barium, oxygen, carbon, and zinc were indexed in the Auger spectrum. The derivative AES spectrum of barium indicates peaks at 56 and 494 eV, corresponding to the MVV and KLL derivative Auger electron emission from barium. In the middle part of the figure, which relates to oxygen, the Auger spectrum indicates peaks at 470, 485, and 505 eV. These peaks can be attributed to the KLL Auger electron emission of oxygen [33].