Electronic Polarizability and Optical Basicity of BaO-B2O3-TeO2 Glass System

[(TeO2)0.7(B2O3)0.3]1-x (BaO)x, x = 0.00, 0.05, 0.10, 0.20, 0.25, 0.30 and 0.35 mol fraction glass series were successfully synthesized by conventional melt quenching method. Amorphous phase of all samples was confirmed through X-ray diffraction while optical properties were determined using UV-VIS spectrophotometer. Fourier Transform Infrared (FTIR) analysis showed that the glass structure consisted of TeO3, TeO4, TeO6, BO3 and BO4 structural units. The optical band gap energy, Eopt which was calculated from Tauc’ plots decreased as the amount of BaO increases, whereas, the Urbach energy value increased. The increase in Urbach energy value was attributed to the increase of defects in glass structure. The refractive indices of glass were found to increase along with the increased amount of BaO, due to the high polarization and high density of host material and glass modifier. The molar polarizability, αm, oxide ion polarizability, αo2- and optical basicity, Λ of the glasses are calculated by Lorentz-Lorenz equation. The glasses were found to possess αm values between 8.106 – 8.489 Å3, and αo2- values between 3.303 to 4.772. Meanwhile, optical basicity increases from 0.115 to 0.893.

Investigations on Structural and Optical Properties of Various Modifier Oxides (MO = ZnO, CdO, BaO, and PbO) Containing Bismuth Borate Lithium Glasses

Bismuth based quaternary glasses with compositions BiBLM: 50Bi2O3–20B2O3–15Li2O–15MO (where MO = ZnO, CdO, BaO, and PbO) were processed by conventional melt quenching. The effectiveness of various modifier oxides on the optical and structural properties of the developed glasses was studied systematically by XRD, DSC, FTIR, Raman, and optical absorption (OA) measurements. The synthesized glass specimens were characterized by XRD and the patterns demonstrated an amorphous nature. The physical characteristics such as molar mass, density, and OPD values were found to increase with an increase in the molar mass of the modifier oxides, while there was a decrement in oxygen molar volume, thus resulting in decrement of complete molar volume of the prepared glasses. From DSC analysis, incorrigible reduction and enhancement of Tg and thermal stability among various modifier oxides in the glass network was noticed. Optical absorption data for glass specimens have confirmed the decrease in both direct and indirect optical band gap values among various modifier oxides incorporation. These investigations support the obtained Urbach energy (UE) and metallization criteria of synthesized glasses. The ionic characteristic for the glass specimens were confirmed by the values of electronic polarizability and electronegativity. The Raman and FT-IR spectra of the glass specimens displayed the existence of BiO3, BiO6, ZnO4, CdO4, BaO4, BO3, PbO4, and BO4 structural units within the glass matrix. These structural results can support the applications of as-developed glasses in the area of photonics.

Epoxy/Silicone Blend Loaded with N-Doped CNT Composites: Study on the Optoelectronic Properties

Thin films of epoxy/silicone loaded with N-CNT were prepared by a method of sol-gel and deposited on ITO glass substrates at room temperature. The properties of the loaded monolayer samples (0.00, 0.07, 0.1, and 0.2 wt% N-CNTs) were analyzed by UV-visible spectroscopy. The transmittance for the unloaded thin films is 88%, and an average transmittance for the loaded thin film is about 42 to 67% in the visible range. The optical properties were studied from UV-visible spectroscopy to examine the transmission spectrum, optical gap, Tauc verified optical gap, and Urbach energy, based on the envelope method proposed by Swanepoel (1983). The results indicate that the adjusted optical gap of the film has a direct optical transition with an optical gap of 3.61 eV for unloaded thin films and 3.55 to 3.19 eV for loaded thin films depending on the loading rate. The optical gap is appropriately adapted to the direct transition model proposed by Tauc et al. (1966); its value was 3.6 eV for unloaded thin films and from 3.38 to 3.1 eV for loaded thin films; then, we determined the Urbach energy which is inversely variable with the optical gap, where Urbach’s energy is 0.19 eV for the unloaded thin films and varies from 0.43 to 1.33 eV for the loaded thin films with increasing rate of N-CNTs. Finally, nanocomposite epoxy/silicone N-CNT films can be developed as electrically conductive materials with specific optical characteristics, giving the possibility to be used in electrooptical applications.

Formation of TiO2/natural Melanin Nanostructure Hybrids with Enhanced Optical and Thermal Properties

Recently, with the progress of research in amending and developing the properties of inorganic materials, researchers have become focused on using inexpensive and environmentally friendly materials such as organic materials from natural sources that have proven effective in improving the properties of materials in various applications. In recent years, melanin has become an attractive topic for researchers due to its distinctive structural properties that have been distinguished in various application fields. Here, we report the use of ultrasonication under UV radiation for synthesis. The influence of natural melanin on the structural, optical and thermal properties of TiO2 nanoparticles was investigated by using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and UV–Vis spectroscopy. It was observed that incorporating natural melanin on TiO2 nanoparticles (TiO2-Mel) occurred at approximately 2.01 eV with low value of Urbach energy around 100 meV indicates improvement in crystalline structure. Thermal results showed that TiO2-Mel is stable even with temperatures up to 400°C. According to the results obtained by the thermal stability of melanin with titanium dioxide can makes it a good candidate in many application such as solar cells and optoelectronic that require optical efficiency and thermal stability for long periods.

Influence of KI Salt Concentration on The Hydroxypropyl Methylcellulose Films: Optical Study

Herein the optical properties of Hydroxypropylmethyl cellulose/Potassium iodide (HPMC/KI) composite films were determined. Casting technique was introduced to make HPMC/KI films with different KI salt concentrations (0.1–1) wt%. The absorbance model was used to determine parameters like absorption edge, refractive index, real and imaginary sections of dielectric function, extinction coefficient, Urbach energy, band gap and optical conductivity in the spectral range 200–800 nm. As shown by study, KI salt doping affects the optical properties of HPMC. The absorption edge (\({E}_{e}\)) was widely displaced towards a region of lower photonic energy. For the 1 wt% KI/HPMC film, the direct and indirect optical bandwidth gaps of pure HPMC were reduced from 5.6 eV to 2.56 eV and 5.86 to 2.5 eV respectively. The optical dielectric loss method was effectively employed as an alternate method for estimating the optical bandgap. In addition, the Tauc’s extrapolation method identified the kind of electronic transition. The variation of optical energy band gap and dielectric constant based on KI salt concentration was used to investigate the credibility of the Penn’s model. In salt-composite films, an increase in Urbach energy and optical conductivity were observed which may be evidence of large shift from tail-to-tail and band to tail. Meanwhile, X-ray diffraction (XRD) examination revealed that the KI salts damaged the HPMC polymer's crystalline phase. Lastly, the films were also subjected to Fourier transform infrared spectroscopy (FTIR). The considerable variation in transmittance and band change in FTIR spectra was exposed for doped films.

Investigation and Study of CaO-Borate Glass

Recent days the special interest towards Glasses is specifically due to their vast applications that they range. Glass series Calcium borate metallic glass (CaO–B2O3) has been prepared by melt quenching technique. CaO influences like density/molar volume ratio on the properties have analyzed and glass sample different modulus has found between them. The optical properties such as direct and indirect bandgap, Urbach energy, band gap, which also includes heat‐treated glasses, has studied by Fourier transform infrared spectroscopy and UV‐visible, respectively. According to this model elastic moduli increase, this is because of the CaO content increase. The Debye temperature, elastic moduli, other acoustic parameters and Poisson's ratio has acquired from experimental data. The obtained results show that the CaO enters into the glass network as a modifier by occupying increasing the nonbridging oxygen atoms (NBOs) and the interstitial spaces in the network.

A universal Urbach rule for disordered organic semiconductors

In crystalline semiconductors, absorption onset sharpness is characterized by temperature-dependent Urbach energies. These energies quantify the static, structural disorder causing localized exponential-tail states, and dynamic disorder from electron-phonon scattering. Applicability of this exponential-tail model to disordered solids has been long debated. Nonetheless, exponential fittings are routinely applied to sub-gap absorption analysis of organic semiconductors. Herein, we elucidate the sub-gap spectral line-shapes of organic semiconductors and their blends by temperature-dependent quantum efficiency measurements. We find that sub-gap absorption due to singlet excitons is universally dominated by thermal broadening at low photon energies and the associated Urbach energy equals the thermal energy, regardless of static disorder. This is consistent with absorptions obtained from a convolution of Gaussian density of excitonic states weighted by Boltzmann-like thermally activated optical transitions. A simple model is presented that explains absorption line-shapes of disordered systems, and we also provide a strategy to determine the excitonic disorder energy. Our findings elaborate the meaning of the Urbach energy in molecular solids and relate the photo-physics to static disorder, crucial for optimizing organic solar cells for which we present a revisited radiative open-circuit voltage limit.