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The Ni-doped CdSe nanostructured thin films during the deposition procedure that govern the altering of the optical transitions have been investigated. The concentration of Ni as doping inside CdSe from 0.01, 0.02 to 0.03mol in the form of nanostructured thin layers have been fabricated through a simple chemical solution deposition approach. Doping of the Ni to CdSe adds the new transitions related to NiSe, which means the tiny concentration of Ni ions creates the new transition to CdSe that sample has multiple optical bandgaps. There is an order in band gap changing with doping concentration raising so that increasing the Ni${}^{2+}$ ions decreases the optical band gap to 1.59eV although the optical band gap for CdSe in bulk state is 1.74eV, so doping procedure decreases optical bandgap of CdSe that is mean doping procedure creates the new structure. It has shown that it’s possible to determine the Urbach energy of the samples from the absorption spectrum without the need to determine the adsorption coefficient from the determination of thickness. Degradation efficiency for pure CdSe is 86% while a sample of Ni-doped CdSe enhanced degradation efficiency until 93%.

The fundamental absorption edge of SnO₂ amorphous thin films has been investigated. It has been observed that the optical energy gap decreases with the increase in film thickness, substrate temperature and post deposition annealing. The results are analysed by assuming optical absorption by non-direct transition. The decrease in optical band gap with increase in film thickness may be interpreted in terms of the incorporation of oxygen vacancies in the SnO₂ lattice. The decrease in optical energy due to the increase in substrate temperature may be ascribed to the release of trapped electrons by thermal energy or by the outward diffusion of the oxygen-ion vacancies, which are quite mobile even at low temperatures. The decrease in optical band gap due to annealing may be due to the formation of tin species of lower oxidation state.

Zinc-phosphate glasses with the addition of B₂O₃ were prepared by using the melt quench technique. These glasses had a mol% composition of 30ZnO-xB₂O₃-(70-x)P₂O₅. The quantity x had values of 10–40 mol%. The mass density of these glasses was found to be in the range of 2.4912–3.0142 g/cm³. The oxygen packing density and molar volume were estimated to lie in the range 192.385–286.026 g-atom/liter and 46.78–31.46 cm³ respectively. The absorption spectra of these glasses were recorded in the range of 190 to 1100 nm. No sharp edges were found in the optical spectra, which confirms the amorphous nature of these glasses. The optical band gap energies were determined to be in the range of 2.40–3.00 eV. A decreasing behavior in optical band gap energy was seen due to the increasing concentration of B₂O₃. The extent of band tailing was worked out from the Urbach plots, which showed an exponential dependence of absorption coefficients on photon energies.

Optical transmittance of Ba_1-xCa_xTi₂O₅ (x=0, 0.01, 0.03) bulk glasses of ferroelectric BaTi₂O₅ is measured at room temperature in the wavelength range 190–800 nm. The fundamental absorption edge located in the ultraviolet (UV) region tends to shift toward the longer wavelength region on increasing x. The optical band gap of 3.31 eV estimated for x=0 decreases on increasing x. The decrease in the optical band gap energy is related to the creation of non-bridging oxygen ions, which increase on Ca substitution. The observed increase in the Urbach energy with increasing x is associated with the possible increase of structural disorder in the ferroelectric BaTi₂O₅-based bulk glass occurred by substituting Ca for Ba.

Quaternary glasses were successfully fabricated using melt quenching technique based on the chemical compound composition ($x$)Bi₂O₃–($0.5-x$) ZnO–(0.2)B₂O₃–(0.3)SiO₂, where ($x=0.1$, 0.2, 0.3, 0.4, 0.45) mole. The sources of SiO₂ was produced from rice husk ash (RHA) at 99.36% of SiO₂. The Urbach energy was increased from 0.16eV to the 0.29eV as the mole of Bi₂O₃ increased in the glass structure. The indirect energy band gap is indicated in decrement pattern with 3.15eV towards 2.51eV. The results of Urbach energy and band gap energy that were obtained are due to the increment of Bi${}^{3+}$ ion in the glass network. The refractive indexes for the prepared glasses were evaluated at 2.36 to 2.54 based on the Lorentz–Lorentz formulation which correlated to the energy band gap. The calculated of molar polarizability, electronic polarizability and optical basicity exemplify fine complement to the Bi₂O₃ addition in the glass network. The glass sample was indicated in amorphous state.

CdSe is an important II-VI, n-type direct band gap semiconductor with wide band gap (bulk band gap of 2.6 eV) and an attractive host for the development of doped nanoparticles. Poly vinyl alcohol (PVA) is used as a capping agent to stabilize the CdSe nanoparticles. The optical properties of Co (II) ion doped PVA capped CdSe nanoparticles grown at room temperature are studied in the wavelength region of 200-1400 nm. The spectrum of Co (II) ion doped PVA capped CdSe nanoparticles exhibit five bands at 1185, 620, 602, 548 and 465 nm (8437, 16125, 16607, 18243 and 21499 cm^-1). The bands observed at 1185, 548 and 465 nm are correspond to the three spin allowed transitions ⁴T_1g (F) → ⁴T_2g (F), ⁴T_1g (F) → ⁴A_2g (F) and ⁴T_1g (F) → ⁴T_1g (P) respectively. The other bands observed at 602 nm and 620 nm are assigned to spin forbidden transitions ⁴T_1g (F) → ²T_2g (G), ⁴T_1g (F) → ²T_1g (G). The small value of the Urbach energy indicates greater stability of the prepared sample.

TiO₂ is a highly potential, photoactive and dye-sensitive photocatalyst but its optical properties are further enhanced in the presence of different types of dyes. Dye-modified TiO₂ was prepared by the modified sol–gel method. The dyes are methyl orange (MO), potassium permanganate (KMnO₄) and beetroot. Analysis was conducted to study the physical, linear and nonlinear optical properties. XRD result suggests that the prepared TiO₂ is synthesized in the pure anatase phase. The bandgap is decreased in all the dye-modified TiO₂ samples. The dielectric constant, interband transition strength, energy loss functions, Urbach energy, optical conductivity and electrical conductivity were determined. Further, the dispersion parameter of refractive index was discussed as per the single-oscillator model proposed by Wemple and DiDomenico. Moreover, the analyses of nonlinear dispersions like first-order and third-order optical susceptibilities, electrical susceptibilities, nonlinear refractive index and reflection loss were performed. To further investigate the electronic properties, the plasma energy, Penn gap and Fermi energy were also determined.