Urbach Energy Eu Research Articles

Effect of MWCNT addition on the optical band gap of PVA/CS transient biocomposites

In recent years, as a result of increasing environmental concerns, biodegradable materials have gained great attention. With the rapid development of electronic technology, the importance of innovation and development of low-cost, sustainable, transient bioelectronics materials is increasing. In this research, the preparation of Poly(Vinyl Alcohol) (PVA), Chitosan (CS), and Multi-Walled Carbon nanotube (MWCNT) biocomposite films have been described. The solution mixing, ultrasonic mixing, and spin coating techniques were used to prepare the PVA/CS/MWCNT biocomposite thin films. UV–Vis absorption spectroscopy and two-point probe resistivity measurement techniques were used to study the optical and electrical properties of the biocomposite thin films. Optical band gap energies ( Eg) of PVA/CS/MWCNT biocomposites were obtained using the Tauc and Absorbance Spectrum Fitting (ASF) methods. Results obtained with both methods were found to be exactly the same. Experimental results have shown that with increasing MWCNT concentration, electrical conductivity (σ) increases from 1.75x10−16 S to 2.94x10−3 S, and Eg decreases significantly. At the same time, the fundamental optical parameters such as band tail (Urbach) energy ( Eu), refractive index ( n), absorption ( α), and extinction ( k) coefficient of the PVA/CS/MWCNT biocomposites were investigated in the UV-VIS range. The improvement observed in the optical and electrical properties of PVA/CS/MWCNT biocomposite films shows that these composites could be used as bioelectronics materials.

Zinc-lead-borate glasses doped with dysprosium oxide: Structure, optical, and radiation shielding features

40PbO + 20ZnO + (40-x) B2O3 + xDy2O3 (where x = 0, 1, 2, 3, 4 and 5 wt%) glass samples were created via a traditional melt-quenching technique. The degree of structural compactness and the amendment of configurations in the glass network was verified by determining glass density. The linear optical properties of the samples were investigated by measuring U-V optical absorption over a spectral range of 190–900 nm. Both direct and indirect band gaps were found to decrease when the samples were doped with Dy2O3. The Urbach energy (Eu) yields increase as the number of doping materials in the samples increases. The gamma-ray shielding capacity of the samples was evaluated using MCNP-5 code. The simulated data found that the highest linear attenuation coefficient was obtained at 0.015 MeV. This attenuation varied between 2.84.43 and 346.33 cm−1 as the ratio of Dy2O3 rose from 0 to 5 wt%, respectively. Shielding factors like the half-value layer, the radiation protection efficiency and the transmission factor increased as more Dy2O3 was introduced.

Side-Chain Engineering for Enhancing the Molecular Rigidity and Photovoltaic Performance of Noncovalently Fused-Ring Electron Acceptors.

Side-chain engineering is an effective strategy to regulate the solubility and packing behavior of organic materials. Recently, a unique strategy, so-called terminal side-chain (T-SC) engineering, has attracted much attention in the field of organic solar cells (OSCs), but there is a lack of deep understanding of the mechanism. Herein, a new noncovalently fused-ring electron acceptor (NFREA) containing two T-SCs (NoCA-5) was designed and synthesized. Introduction of T-SCs can enhance molecular rigidity and intermolecular π-π stacking, which is confirmed by the smaller Stokes shift value, lower reorganization free energy, and shorter π-π stacking distance in comparison to NoCA-1. Hence, the NoCA-5-based device exhibits a record power conversion efficiency (PCE) of 14.82 % in labs and a certified PCE of 14.5 %, resulting from a high electron mobility, a short charge-extraction time, a small Urbach energy (Eu ), and a favorable phase separation.

Side‐Chain Engineering for Enhancing the Molecular Rigidity and Photovoltaic Performance of Noncovalently Fused‐Ring Electron Acceptors

AbstractSide‐chain engineering is an effective strategy to regulate the solubility and packing behavior of organic materials. Recently, a unique strategy, so‐called terminal side‐chain (T‐SC) engineering, has attracted much attention in the field of organic solar cells (OSCs), but there is a lack of deep understanding of the mechanism. Herein, a new noncovalently fused‐ring electron acceptor (NFREA) containing two T‐SCs (NoCA‐5) was designed and synthesized. Introduction of T‐SCs can enhance molecular rigidity and intermolecular π–π stacking, which is confirmed by the smaller Stokes shift value, lower reorganization free energy, and shorter π–π stacking distance in comparison to NoCA‐1. Hence, the NoCA‐5‐based device exhibits a record power conversion efficiency (PCE) of 14.82 % in labs and a certified PCE of 14.5 %, resulting from a high electron mobility, a short charge‐extraction time, a small Urbach energy (Eu), and a favorable phase separation.

Fabrication, structure, physical and optical features of the 50B2O3 + 25Bi2O3 + (25-x) Li2O + xSrO2 glasses

The purpose of this investigation is to study the physical, structural and optical characteristics of a newly fabricated SrO2 doped lithium bismuth borate glass system. The current glass system was fabricated according to the chemical formula 50B2O3 + 25Bi2O3 + (25-x) Li2O + xSrO2, utilizing the solid state- conventional method. It was noticed that The glass density increased from 4.821 to 5.952 g cm−3 whilst the molar volume was decreasing in the range from 32.93 to 30.44 cm3 mol−1 with increase the SrO2 insertion from 0 (BBLSr0 glasses) to 25 (BBLSr25) respectively. The structure of the fabricated glasses was inspected utilizing X-ray diffraction method which clarified that the insertion of SrO2 didn’t affect the amorphous nature of the tested samples. Furthermore, the UV–vis absorption spectrum was utilized to study the UV absorption characteristics for the fabricated glasses. The UV–vis absorption spectrum showed that the absorption and transition bands increase with insertion of the SrO2 contents. Based on the UV/Vis data, several important optical features were calculated like the energy gap (Eg), Urbach energy (Eu), oscillator energy (Eo) and energy of distribution (Ed). Increasing the SrO2 substitution ratio led to increase the optical properties where the refractive index was found to increase from 3.056 to 5.710.

Synthesis, structural and optical characteristics of vanadium doped cerium dioxide layers

This research paper reports on spray pyrolysis deposited cerium dioxide (CeO2) thin films. Study consists of investigating the effect of Vanadium (V) doping on structural and optical characteristics of Ce1−xVxO2(0.02≤x≤0.06) layers using several characterization techniques. Indeed, X-ray diffraction patterns helped to estimate the crystallite size (D), micro-strain (ε), and dislocation density (δ). The crystallite size was found to decrease from 7 nm to 5 nm with the increase of V doping concentrations. The obtained dislocation density and micro-strain of the layers were found to be 1016 lines/m2 and 10−4 respectively. The micro-Raman results show the characteristic peak F2g of CeO2 at ~ 461 cm−1. The spectrum led to conclude that the peak intensity of the layers decreased in agreement with the increase in the V ratio. The atomic force micrograph showed a surface morphology transformation from spherical to flake upon doping. The surface roughness of the investigated thin layers was approximately 2-fold increased from 3.53 to 6.15 nm as a result of the increase in V doping proportions. The optical properties of the layers were studied in the wavelength range of 325–1000 nm and the overall transmittance of the layers was found to decrease with an increase in the V ratio. These results exhibit a slightly lower band-gap energy with the increase of V doping, from 3.19 eV to 3.08 eV. Optical parameters like refractive index (n), extinction coefficient (k), Urbach energy (Eu), optical conductivity (σ), and the real and imaginary part of dielectric constant (εr & εi) were estimated by using an UV-Visible spectrum.

Estimation of Structural and Optical Parameters of (Mg, B) co-doped ZnO Nanoparticles

Zn0.98-xMg0.02BxO nanoparticles with various dopant ratios (x = 0.00 - 0.05 with increments of 0.01) were grown by using the sol-gel technique. The samples were synthesized and the X-ray diffraction, scanning electron microscopy, optical reflectivity, and electron dispersive analyses were used to obtain the structural, electronic, and optical properties, respectively. Williamson–Hall procedure was utilized to obtain structural properties. The energy bandgap of the particles extracted from the absorption spectra was found to be ranging between 3.23 eV and 3.28 eV and decreasing with the boron concentration. The minimum dislocation density δ and Urbach energy Eu and the maximum bandgap Eg were obtained at 1% B concentration. The refractive index calculated by Moss’s model was found to be 2.3 and the maximum bandgap energy with a value of 3.28 eV suggests that these materials can be useful for infrared applications.

Glass formation area of the CdO-CuCl2-V2O5 ternary system: optical properties as a function of CuCl2 content

Within the compositions triangle of the ternary system CdO-CuCl2-V2O5 a batch of 25 glasses were fabricated. In the corner of high CdO content the glass formation area (GFA), was found. For each group, the glass former (V2O5) content was constant and, the modifier oxides CdO, CuCl2were varied. All the fabricated glasses were analyzed by X-ray diffraction patterns, UV-Vis and Raman spectroscopies. In the border of the GFA all the samples presented the crystalline structure of the compound Cd2V2O7, meanwhile inside of the GFA, the samples contain amorphous Cd2V2O7. Into the GFA the samples were organized in 5 groups. For each group, taking as reference the CuCl2 content, the optical properties were analyzed. Under this point of view, the maximum of their Raman band associated with their amorphous structure, is being confined between 850 and 820 cm−1, depending on the CuCl2 content. By optical absorption the Eg values were determined in the 2.42 — 1.66 eV range, depending on the CuCl2 content. By the same spectroscopy the Urbach energy (Eu) for all the glasses was obtained and resulting to be in the 0.65 - 0.22 eV range. The refractive index for this group of samples, was obtained in the 2.57 – 2.90 range, also depending on the CuCl2 content. Finally, SEM images show a homogeneous distribution goticular into the amorphous matrix, for samples located in the border of the GFA.

A study on optical and thermal properties of natural polymer-based hemicellulose compounds

Films of husks of Plantango ovate, Cydonia oblonga, Mimosa pudica, Cochlospermum religiosum were prepared, delignified without protein and cellulose content, and their optical properties were evaluated. UV-Vis, FTIR TGA analysis revealed that these natural materials have strong potential in fiber optics, contact lenses and human transplantation infrastructure applications, where there is need of efficient transparency, high thermal stability and good conductivity with minimum light absorption. These natural polymeric films possess significant direct and indirect optical band gap values and better optical conductivity than currently in use synthetic polymeric materials. The Refractive index of these films is also found high in the visible region in comparison to pure or composite metal-doped synthetic films. Urbach energy (Eu), Dispersion energy (Ed), Average oscillation wavelength (λ0), and oscillation strength(S0) of this hemicellulose based natural polymeric films were found to be appropriate for such optical materials which are green, organic, economical and compatible to human systems.

Synthesis and optical properties of Er/Yb/Ag modified bismuth – tellurite based glasses

The Er2O3-Yb2O3 codoped TeO2-Bi2O3-Na2O-Glasses along with addition of AgNO3 in basic compositions glasses have been prepared by traditional melt quench method. Investigation of the synthesized glasses is done by DSC, XRD, and UV-Vis. spectroscopy. The glass transition temperature is observed by differential scanning calorimetry. The amorphous nature of the synthesized glasses is confirmed by X-ray diffractogram taken at room temperature. The fluid displacement method on the basis of the Archimedes principle was used to calculated density of prepared samples. The UV-Visible absorption characterizations have been done in the range of 200–1100 nm of synthesized glasses having different percentage of doping of Er2O/Yb2O3/AgNO3. The study of optical properties of the glasses such as the absorption coefficient (α), cut-off wavelength, forbidden energy band gap (Eopt), refractive index and Urbach Energy (Eu) have been done. The effect of Er2O/Yb2O3/AgNO3 on optical properties is observed.

Flexible Methyl Cellulose/Polyaniline/Silver Composite Films with Enhanced Linear and Nonlinear Optical Properties.

In order to potentiate implementations in optical energy applications, flexible polymer composite films comprising methyl cellulose (MC), polyaniline (PANI) and silver nanoparticles (AgNPs) were successfully fabricated through a cast preparation method. The composite structure of the fabricated film was confirmed by X-ray diffraction and infrared spectroscopy, indicating a successful incorporation of AgNPs into the MC/PANI blend. The scanning electron microscope (SEM) images have indicated a homogenous loading and dispersion of AgNPs into the MC/PANI blend. The optical parameters such as band gap (Eg), absorption edge (Ed), number of carbon cluster (N) and Urbach energy (Eu) of pure MC polymer, MC/PANI blend and MC/PANI/Ag films were determined using the UV optical absorbance. The effects of AgNPs and PANI on MC polymer linear optical (LO) and nonlinear optical (NLO) parameters including reflection extinction coefficient, refractive index, dielectric constant, nonlinear refractive index, and nonlinear susceptibility are studied. The results showed a decrease in the band gap of MC/PANI/AgNPs compared to the pure MC film. Meanwhile, the estimated carbon cluster number enhanced with the incorporation of the AgNPs. The inclusion of AgNPs and PANI has enhanced the optical properties of the MC polymer, providing a new composite suitable for energy conversion systems, solar cells, biosensors, and nonlinear optical applications.

Structural and optical study of perovskite nanoparticles MSnO3 (M = Ba, Zn, Ca) obtained by a wet chemical route

Perovskite nanoparticles MSnO3 (M = Ba, Zn, Ca) were synthesized at low temperature in a controllable and reproducible way, using the polymer complex method. The physicochemical, structural and optical characteristics of the mixed oxides were determined using DTA/GTA, XRD, FTIR, SEM/TEM, DRS and XPS. The pure crystalline phases were obtained between 700 and 800 °C, with particle size less than 80 nm, a spheroidal morphology in the BaSnO3 and ZnSnO3, and laminar in the CaSnO3. The band-gap energy between 3.4 and ~4.6 eV were obtained. Urbach energy (Eu) was calculated to determine the degree of disorder of the synthesized perovskites, with BaSnO3 giving the highest Eu value (417 meV). This result indicates the existence of defects, e.g. oxygen vacancies, a condition that was verified by deconvolution and analysis of XPS spectra. Considering the nature of the synthesis process and the results obtained, a mechanism was proposed to explain the formation of the perovskites.

PARTICLES SIZE AND LATTICE STRAIN EFFECT ON THE OPTICAL CONSTANTS OF Fe3O4 NANOPARTICLES

In the case of optical sensors such as the Surface Plasmon Resonance (SPR) sensor, the Fe3O4 nanoparticles play a role to boost the signal however they can increase the detection sensitivity of the biosensor. For this application, the optical properties of Fe3O4 nanoparticles need to be studied. The optical properties are described in terms of their optical constants. Therefore, this work was purposed to study the effect of the particle size and lattice strain on the optical constants of Fe3O4 nanoparticles. Samples were synthesized by using the coprecipitation technique. Two calcination temperatures, i.e., 150oC and 250oC for 4 hours were applied to the samples. Samples were characterized for their diffraction pattern and optical properties by using XRD and Specular UV-Vis Spectroscopy technique, consecutively. The particle size and lattice strain were estimated by using the Williamson-Hall (W-H) method. The effect of the particle size and their optical constants on the reflectance curve in the SPR sensor application was also performed toward a simulation by using Winspall 3.02 software. The results show that calcination temperature causes an increase in particle size and a decrease in lattice strain. The optical constants, such as absorbance (A), absorption coefficient (α), extinction coefficient (k), refractive index (n), dielectric constants (ε), optical conductivity (σ), and the Urbach energy (Eu) significantly depended on particles size and lattice strain. However, the particle size and optical constant were significantly influent the SPR angle in the reflectance curve of Fe3O4

Effects of Na2O on optical and radiation shielding properties of xNa2O-(20-x)K2O-30V2O5-50TeO2 mixed alkali glasses

In this study, the optical and gamma ray shielding properties of vanadotellurite-based quaternary glasses in the xNa2O-(20-x)K2O-30V2O5-50TeO2 system were examined. The optical band gap (Eopt) displayed an initial reduction from 2.33 to 2.30 eV (x ≤ 10 mol%), before increasing from 2.31 to 2.39 eV for x > 10 mol%, which indicated a change in non-bridging oxygen (NBO) concentration. There is an inverse relationship between Urbach energy (Eu) and Eopt. The refractive index (n) also showed an off-trend pattern within the same area (x = 10 mol%), which indicated a difference in polarizability due to changes in BO and NBO concentrations. The Phy-X software was used to analyse the radiation attenuation competence for the investigated glass systems. For the total interaction of photons between the 0.284 to 2.506 MeV energy range, the linear attenuation coefficients (LAC), the radiation protection efficiency (RPE), half-value layers (HVL) and mean free path (MFP) were determined. The increased Na2O content increased the values of LAC and RPE. The results demonstrated that the 20Na2O-30V2O5-50TeO2 composition had the most desired photon shielding properties.

Effect of UV radiation on the optical properties of PANI-Cu/PC and PANI-Cu/PC-PBT nanocomposites

Polyaniline-copper/Polycarbonate (PANI-Cu/PC) and polyaniline-copper/Polycarbonate-polyester (PANI-Cu/PC-PBT) nanocomposites (NCPs) were fabricated using chemical oxidative and casting techniques. The morphology of the prepared NCPs was studied using scanning electron microscopy. The optical absorption spectra of these NCP samples have been recorded in the wavelength range 250–850 nm at room temperature. Optical parameters such as Urbach energy (Eu ), optical bandgap (Eg ), refractive index (n), real (ϵ ′) and imaginary (ϵ ″) parts of complex permittivity have been evaluated. The induced modifications in the optical properties of the UV irradiated NCPs have been studied as a function of UV fluence. The values of optical bandgap of the blank PANI-Cu/PC and PANI-Cu/PC-PBT NCP samples were found to be 3.92 and 3.86 eV, respectively. These values decreased to 3.57 and 3.08 eV upon raising the UV fluence up to 120 J/cm2 due the dominance of crosslinking that destroys crystallinity and increases the amorphous phase. This was associated with an increase in Urbach energy, refractive index and dielectric constant. The obvious reduction in the optical bandgap of the UV irradiated PANI-Cu/PC-PBT NCPs makes it of great interest in optoelectronic devices applications.

Synthesis and characterization of Eu3+ doped TiO2 thin films deposited by spray pyrolysis technique for photocatalytic application

In this study, nanocrystalline TiO2: Eu3+ thin films are successfully formed by spray pyrolysis technique deposited on glass substrate. Structure, optical, electrical, surface morphology, and photocatalytic degradation of Methylene blue have been examined. The XRD analysis illustrate the tetragonal crystal structure of films with anatase phase and reduces crystallite size linearly with increasing Eu3+ concentration. The optical properties of the films are analyzed using transmittance and reflectance spectra, which are measured using UV–vis-NIR double-beam spectrophotometer. Optical properties such as refractive index (n), extinction coefficient (k), optical conductivity (σ) and Urbach energy (Eu) have been calculated as a function of Eu3+ concentration. Film thickness were evaluated using the refractive index dependence on wavelength. The films thickness were determined as 97.13, 122.62, 123.24, 117.14 and 128.25 nm, respectively, for Eu doped TiO2 at 0,4, 6, 8 and 10 wt % doping concentration. The band gap values raised from 3.29 to 3.42 eV with increasing the Eu3+ dopant concentration. The highest electrical conductivity was found to be 3.01 × 10−2(Ω·cm)−1 at high doping level with 10 wt% Eu3+. Scanning electron microscopy (SEM) analysis indicated consistent allocation of irregular and spherical shaped grains covering the substrate surface. The average grain size in range of 82.5—51.1 nm is observed and films show porous nature. The photocatalytic effect of TiO2: Eu3+ thin films is predicted from the degradation of methylene blue (MB) at room temperature under UV light irradiation. An enhancement in photocatalytic degradation observed by increasing the amount of Eu3+ due to increase in the (electron-hole) pair production and increase of film thickness. These results make TiO2: Eu3+ thin films as attractive candidate for photovoltaic cells and other optoelectronic device applications.

Optical studies and dielectric response of [DMA]2MCl4 (M = Zn and Co) and [DMA]2ZnBr4.

[DMA]2ZnCl4, [DMA]2CoCl4 and [DMA]2ZnBr4 crystallized in the monoclinic system, in the P21/n, P21/n and P21/c space groups, respectively. The optical properties of [DMA]2MCl4 (M = Zn and Co) and [DMA]2ZnBr4 were studied using ultraviolet-visible (UV-Vis) spectroscopy in the range of 200–800 nm. The Tauc model was used to determine the band gap energy of each hybrid compound. The calculated values of the direct and indirect band gaps (Egd, Egi) for all samples were found to be in the range of 1.91 eV to 4.29 eV for [DMA]2ZnCl4, 4.76 eV to 5.34 eV for [DMA]2ZnBr4 and 1.77 eV to 3.84 eV for [DMA]2CoCl4. The Urbach energy (Eu), extinction coefficient (k) and refractive index (n) of each compound was calculated. On the other hand, the dispersion of (n) is discussed in terms of the single oscillator Wemple–DiDomenico model. The single oscillator energy (E0), the dispersion energy (Ed), and both the real εr and imaginary parts εi of the dielectric permittivity were estimated. The variation of optical conductivity with the incident photon energy has also been studied. We employed impedance spectroscopy to thoroughly investigate the dipolar dynamics in the prepared materials. The evolution of the dielectric loss, as a function of frequency, showed a distribution of relaxation times, which probably could be of a Maxwell–Wagner type interfacial polarization relaxation, possibly attributed to grain boundary effects or blocking at the contacts. In fact, the current work opens an efficient path to high quality organic–inorganic halide perovskites with good optical properties, which makes them suitable for application in nonlinear optoelectronic devices.

Synthesis and optical properties of ternary TeO2-Bi2O3-Na2O glass system

The glasses with composition TBN: 80TeO2-10Bi2O3-10Na2O in mol% have been prepared by using a conventional melt-quench and pressing technique. Investigation of the prepared sample is done by XRD, EDS and UV–Visible spectroscopy. The glassy nature of prepared sample is confirmed by X-ray diffraction at room temperature and composition is verified by EDS. The density was calculated using the fluid displacement method on the basis of the Archimedes principle. UV–Visible absorption measurements have been taken in the range of 200–1100 nm of TBN glasses having different thickness for the study of optical properties. For the evaluation of optical properties of the samples such as the absorption coefficient (α), cut-off wavelength, forbidden energy band gap (Eopt), refractive index and Urbach Energy (Eu) have been done. The effect of thickness on optical properties is observed.

Influence of gamma ray on optical and structural properties of commercial glass enriched with copper oxide

Commercial glass with composition SiO2 ≈ 71.9, Na2O ≈ 14.25, CaO ≈ 8.6, MgO ≈ 4.05, Al2O3 ≈ 0.66, K2O ≈ 0.037, TiO2 ≈ 0.025, Fe2O3 ≈ 0.08, SO3 ≈ 0.32 mixed with X CuO (X ≥ 0.01) were synthesized by melt-casting method. After that, effects of gamma ray on glass samples were investigated by optical absorption, transmission %, FTIR and ESR spectra. The optical absorption and ESR studies suggested that, Cu-ions exist as Cu2+ valence state and act as modifiers by raising the degree of disorder in the glass network. Physical parameters such as optical energy gap (Eopt), Urbach energy (Eu), refractive index (n) and electrical constant were also calculated to sustain the results obtained from optical absorption measurements. Results show that there are considerable variations in number of NBOs in the structural glass due to the influence of CuO and gamma irradiation. Calibration curve of Commercial window glass containing 0.05 mol % CuO exhibited dosimeter behavior in long dose range among 2.5–80 kGy. Also, characteristic fading curve over a period of 50 days at room temperature has been taken into consideration. Our study showed that the recycled commercial window glass doped with 0.05% CuO could be candidate for radiation dosimeter application.

Optical and dielectric studies of CdI2-doped silver borotelurate glass system

This paper treaty with the preparation, characterization, and Optical and Dielectric studies of xCdI2–(100 − x)[0.444 Ag2SO4–0.555 (0.4TeO2–0.6B2O3) glass system, where x is the wt% of CdI2 varying from 0 to 25 with step 5. These systems were prepared by melt quenching method and characterized by Differential scanning calorimeter (DSC), X-ray diffraction (XRD), and Fourier transforms infrared (FTIR) spectra. Physical parameters such as the density of materials, molar volume, average molecular weight, refractive index, oxygen mole present, polarizability, field strength, and Cd and Ag ions concentration were calculated. Based on optical absorption results, direct band gap Eg was premeditated by comparing Tauc’s plots and the ASF method. From these optical absorption results, Urbach energy (Eu) also calculated. Second-order deformation potential and free energy of the system have been resoluted by expending relation between Eu and Eg. Variation of these factors by changing the CdI2 composition is deliberated in detail. Refractive index, dielectric constant at optical and electrical frequencies have been discussed in detail.