For optical characterization, reflectivity is recorded from the (111) plane of the crystals. Figure 3 shows the reflection spectra of the PSS PhC templates and inverted ZnO PhC measured in (111) direction at the incident angles of 10°, 20°, 30°,

40°, and 50°. The inset presents the measured conditions in this study. An inspection of this figure reveals that the spectrum of PSS PhC templates measured at the incident angle of 10° exhibits a maximum reflection of 34% at the wavelength of 432 nm. The calculated wavelength of the reflection peak is 432 nm according to the modified Bragg’s law [10] by considering the colloidal-sphere diameter to be 193 nm. The reflectivity of the inverted ZnO PhC can correspond to the Bragg reflection from the ordered porous structures. The reflectivity of the inverted ZnO

PhC can still be identified using the angle-dependent phenomenon. The reflectivity peak of the inverted ZnO PhC find more shifts with increasing incident angle towards high energy band. Maybe the broadband reflectivity is caused by the non-stoichiometry of this inverted ZnO PhC. When the angle of incident light increases, the reflection spectral Vistusertib peak shifts towards the short wavelength range. The shift of the reflection spectrum with increasing angle of incident light indicates the pseudo-band gap nature of the PhC. Fabry-Perot (F-P) oscillations are observed on both sides of the reflection maximum. The estimated thickness of the PSS PhC from the F-P oscillation is 2 μm, with 13 numbers of periodic arrangement layers [11]. The reflection spectra of the PSS PhC template and inverted ZnO PhC CYT387 concentration structures are shown in Sitaxentan Figure 4. The spectral position of the reflection maximum λ = 432 nm (in Figure 4) in the PSS PhC template corresponds to the Bragg condition λ = 2dn eff with the effective value of refraction index, n eff = 1.37, in fair agreement with the calculation from the following Equation (1). In our case of the fcc lattice, the plane-to-plane distance is d = (2/3)1/2 D

PS along the <111 > direction, where D PS = 193 nm and D inverted ZnO = 200 nm are the diameters of the PS spheres and inverted ZnO PhC structure, respectively. In the general case of the three-component system, n eff is governed by the relation [12] (1) where n 1 = 1.48, n 2 = 2.0, n 3 = 1; f 1, f 2, and f 3 are the refraction indices and volume proportions of PSS, ZnO, and air, respectively (f 1 + f 2 + f 3 = 1). It should be taken into account that for the volumetric proportion of PSS, f 1 = 0.67, the porosity being f 3 = 0.33 (f 2 = 0) as contrasted from the inverted ZnO PhC structure, where f 2 = 0.42 and f 3 = 0.58 (removed PSS, f 1 = 0) [12]. From Equation (1), calculate the filling fraction. The calculated effective index of refraction of the inverted ZnO PhC structure is n eff = 1.42. The reflection maximum of such a structure ought to be at 465 nm for D inverted ZnO = 200 nm.