Extinction Coefficient Research Articles

Pressure-induced structural stability, metallization and optoelectronic properties of transition metal chalcogenide BaTiS3

The pressure effects on the structural stability, metallization and optoelectronic properties of transition metal chalcogenide BaTiS3 are investigated by performing ab-initio calculations. Our calculations show that BaTiS3 has a hexagonal structure at ambient pressure, which matches well with the available experimental values. As pressure increases, a transition from hexagonal to orthorhombic phase occurs at around 10.8 GPa. The band structure and density of states of hexagonal BaTiS3 have been calculated and analysed. Moreover, the effect of pressure on the optical properties has been studied in terms of dielectric function as well as absorption coefficient, reflectivity and extinction coefficient. The application of hydrostatic pressure has shifted the maximum absorption toward the visible range, revealing that hexagonal BaTiS3 can be used for high pressure optoelectronic applications.

Modeling and simulation of the structural, and optoelectronic properties of aluminum trihydride (β-[formula omitted]) for hydrogen storage

Hydrogen is a promising clean energy source, but its storage poses challenges. In this research, we conducted an in-depth study of the structural and optoelectronic properties of the β-AlH3 phase as a potential material for hydrogen storage. Using the density functional theory (DFT)-based Wien2k code, we optimized the structure of β-AlH3. Hydrogen storage properties show that β-AlH3 contains 10.1% hydrogen by weight, which is a significant amount. Electronic properties reveal that this material is a semiconductor with a wide indirect bandgap of 5.947 eV, obtained by the generalized gradient approximation with modified Becke-Johnson correction (GGA-mBJ). The optical response of β-AlH3 to photons with energies from 0 to 10 eV is also examined for a better understanding of this material. β-AlH3 exhibits a static dielectric permittivity value ε1(ω) of 2.1, indicative of its semiconducting nature. The optical conductivity σ1(ω) shows peaks at 7.25 eV and 8.5 eV, while the absorption coefficient α(ω) increases significantly above the band gap of 5.947 eV, with peaks at 7.2 eV and 9 eV. The refractive index n(ω) and extinction coefficient κ(ω) both display notable features at 7.2 eV and 9 eV, reflecting substantial electronic transitions and optical resonances.This research is crucial to understanding how this material can meet the technological demands of hydrogen storage. The results provide valuable insights into the potential of β-AlH₃ within the future energy landscape, highlighting both advances and challenges in this promising field.

CREST: a Climate Data Record of Stratospheric Aerosols

Abstract. Climate-related studies need information about the distribution of stratospheric aerosols, which influence the energy balance of the Earth's atmosphere. In this work, we present a merged dataset of vertically resolved stratospheric aerosol extinction coefficients, which is derived using data from six limb and occultation satellite instruments: SAGE (Stratospheric Aerosol and Gas Experiment) II on ERBS (Earth Radiation Budget Satellite), GOMOS (Global Ozone Monitoring by Occultation of Stars) and SCIAMACHY (Scanning Imaging Spectrometer for Atmospheric Chartography) on Envisat, OSIRIS (Optical Spectrograph and InfraRed Imaging System) on Odin, OMPS (Ozone Monitor Profiling Suite Limb Profiler) on Suomi NPP, and SAGE III on the ISS (International Space Station). The merging of aerosol profiles is performed via the transformation of the aerosol datasets from individual satellite instruments to the same wavelength (750 nm) and their de-biasing and homogenization by adjusting the seasonal cycles. After such homogenization, the data from individual satellite instruments are in good agreement. The merged aerosol extinction coefficient is computed as the median of the adjusted data from the individual instruments. The merged time series of vertically resolved monthly mean aerosol extinction coefficients at 750 nm is provided in 10° latitudinal bins from 90° S to 90° N, in the altitude range from 8.5 to 39.5 km. The time series of the stratospheric aerosol optical depth (SAOD) is created via the integration of aerosol extinction profiles from the tropopause to 39.5 km; it is also provided as monthly mean data in 10° latitudinal bins. The created aerosol climate record covers the period from October 1984 until December 2023, and it is intended to be extended in the future. The merged CREST aerosol dataset (v2) is available at https://doi.org/10.57707/fmib2share.dfe14351fd8548bcaca3c2956b17f665 (Sofieva et al., 2024a). It can be used in various climate-related studies.

Exploring HgO Effect on Structural, Dielectric, Optical, and Radiation Shielding Properties of Borate-based Glass

Abstract Glass samples in the system 60-xB2O3+20BaO+20K2O+xHgO (0≤x≤15 mol.%) were prepared via melt quenching method. Infrared spectroscopy revealed structural modifications with increasing HgO content, characterized by a shift in the BO4/BO3 ratio. Dielectric and impedance spectroscopy studies indicated enhanced ionic conductivity with higher HgO concentrations. Optical properties, including refractive index, extinction coefficient, and optical band gap, were determined. The optical absorption edge exhibited a red shift with increasing HgO, attributed to structural changes. Refractive index measurements showed an anomalous dispersion behavior at shorter wavelengths, followed by normal dispersion at longer wavelengths. Optical band gap calculations indicated a decrease with increasing HgO content, suggesting increased disorder. The mass attenuation coefficient (MAC) and linear attenuation coefficient (LAC) were calculated using the Phy-X/PSD software. Increasing HgO content led to a significant enhancement in both MAC and LAC values, particularly at lower energies. The mean free path (MFP) exhibited a corresponding decrease with higher HgO content. Overall, the results demonstrate the potential of these glasses as effective radiation shielding materials.

Investigation of Charge Transfer Mechanism and Dielectric Relaxation in CsCdCl3 Perovskite

ABSTRACTThe exceptional optoelectronic capabilities of all‐inorganic metal halide perovskite semiconductor components open up a multitude of possible applications. Among all the metal halides, the chloride of cesium cadmium has not been investigated in great detail. Here, we describe a straightforward method for creating CsCdCl3 perovskite single crystals using the slow evaporation solution growth approach. These were investigated by utilizing X‐ray powder diffraction, and optical and impedance spectroscopies. The creation of a single‐phase with a hexagonal‐type structure was verified by the X‐ray powder diffraction (XRPD) data. The compound's semiconductor characteristics were verified by the optical measurement, indicating a direct band‐gap value of about 3.16 eV. The absorption and reflectance spectrum was also used to calculate and explain the optical extinction coefficient, Urbach energy, and skin depth as functions of the input photon's wavelength. Besides, the impedance spectroscopy technique was employed to investigate the characteristics of this component, across a frequency range of 10−1 Hz to 106 Hz and at temperatures ranging from 313 K to 453 K. The frequency behavior of the AC conductivity, σac, was analyzed using the universal Jonscher law. The outcomes of the charge transport investigation on CsCdCl3 imply that the perovskite material possessed a quantum mechanical tunneling (QMT) model for T < 363 K and a large polaron tunneling (OLPT) paradigm for T > 363 K. A correlation between the ionic conductivity and the crystal structure was established and discussed. Ultimately, the low dielectric loss and high dielectric constant of CsCdCl3 make it a promising material for energy harvesting devices.

APPLICATION OF OPTIMIZATION METHOD IN MULTIDIMENSIONAL SPACE TO THE PROBLEM OF DETERMINING FULLERENE CONCENTRATION IN FULLERENE-CONTAINING MIXTURE

The work proposes a method for the quantitative processing of experimental data from ultraviolet spectroscopy of substituted fullerene mixtures, taking into account errors in the experimental data. This task can be written as a system of Vierordt equations (a system of linear equations). The coefficients of the system are the extinction coefficients of individual substituted fullerenes, which are difficult to measure accurately. Therefore, the mathematical model of the problem contains significant errors that affect the reliability and stability of the solution. To minimize the influence of errors, the work [1] proposes a method, which involves reducing the considered system of linear equations to a linear programming problem. This study generalizes the work [1] and proposes to use linear programming problems to find interval values of correction factors for parameters containing errors. Since decreasing the discrepancy reduces the solution error only for well-conditioned coefficient matrices, the values of correction coefficients that minimize the condition number of the coefficient matrix are found in the obtained intervals. The found correction values allowed to significantly improve the conditionality of the system coefficient matrix and obtain a more accurate solution. By using the refined extinction coefficients, the distribution of molar fractions of fullerene fragments and fullerene-containing compounds in the mixture of products formed by the attachment of cyanoisopropyl radicals was obtained, as well as the distribution of molar fractions of fullerene fragments of different degrees of substitution for samples of fullerene-containing polymethyl methacrylate and the distribution of molar fractions of fullerene fragments of different degrees of substitution for samples of fullerene-containing polystyrene. The results are correct and consistent with the theory, both for low-molecular-weight mixtures and for fullerene-containing polymers.

Degradation of Argan Oils Used in Edible and Cosmetic Applications After Exposure to UV Light.

This study investigates for the first time the effects of UV light exposure on the chemical composition of artisanal and cold-pressed culinary and cosmetic argan oils, as well as their quality and biological activities. We ascertained the oxidative stability of both types of oil through measurements of the peroxide value, acidity, UV-spectrophotometric indexes (E232 and E270), and iodine value. Over the course of eight hours at room temperature, the impact of UV light on the breakdown of tocopherols, polyphenols, chlorophylls, and carotenoid pigments was examined. The findings showed that during photo-oxidation, acidity, peroxide value, and particular extinction coefficients (E232 and E270) gradually increased. On the other hand, a decline in the content of polyphenols, tocopherols, carotenoid, and chlorophyll was noted. Interestingly, iodine levels failed to improve. Although after an eight-hour degradation, the physicochemical profile of Argan oils remained exceptional. DPPH• (1,1-Diphenyl-2-picrylhydrazyl) antioxidant activity tests showed a gradual decrease in radical inhibition over time, which was attributed to lower levels of tocopherol and polyphenol. However, roasted oils showed antifungal action against Botrytis cinerea fungus, while Argan vegetable oils showed no activity against Escherichia coli, Microbacterium resistens, Staphylococcus saprophyticus, and Raoultella ornithinolytica, according to antimicrobial assays.

Surface Plasmon Modulation in Cu3-xP Nanocrystals.

We demonstrate modulation of the surface plasmon resonance in nonstoichiometric copper phosphide nanocrystals using spectroelectrochemical methods. Application of an anodic potential resulted in a blue-shift of the surface plasmon resonance and an incremental increase in its extinction coefficient. Conversely, upon application of a cathodic potential, the surface plasmon band red-shifted and reduced in intensity. These changes were found to be reversible over multiple cycles of anodic and cathodic potential steps. We also discuss how the postsynthetic ligand treatment impacts the surface plasmon peak and the structure of Cu3-xP nanocrystals. For example, the addition of alkylthiols resulted in the chemical decomposition of the nanocrystals. This work demonstrates how the surface plasmon peak in Cu3-xP can be used to probe changes in the structure and carrier density in these nanocrystals.

First principles investigation of structural, electronic, optical, transport properties of double perovskites X2TaTbO6 (X= Ca, Sr, Ba) for optoelectronic and energy harvesting applications

Structural, electrical, optical, thermoelectric response of X2TaTbO6 (X = Ca, Sr, Ba) double perovskites oxides are studied by using WIEN2k that is based on quantum mechanical calculations employing PBE-GGA approximation under the framework of DFT. We present electronic attributes including band gaps and density of states, and explain the electronic properties of all three oxide double perovskite materials which proved that they belong to directly forbidden band gap materials family. The cubic compounds Ba2TaTbO6, Sr2TaTbO6, and Ca2TaTbO6 have respective direct band gaps of 2.35 eV, 2.15eV, and 2.25 eV. Optical conductivity σ(ω), reflection R(ω), complex dielectric constants, refractive index ƞ(ω), absorbance α(ω), loss parameter L(ω) and extinction coefficient K(ω) are all utilized to explore light dependent characteristics of studied compounds. Thermoelectric parameter like, Number of Seebeck effect (S), charge carrier (n), magnetic susceptibility, power factor (PF), electrical conductivity (σ/t), thermal conductivity K/t, and heat capacity are key characteristics for materials to study its ability of thermal behavior. These thermoelectric parameters were determined by using BoltzTraP code. By studying the numbers on various material properties, scientists are uncovering new possibilities for creating sustainable materials for sustainable gadgets.

Effect of Al-, In-, and Mg-doping in the ZnO on the structural, electrical, and optical properties of ZnO/CH3NH3PbI3 heterostructure

The creation of ZnO/CH3NH3PbI3 heterostructures with Aluminum (Al), Magnesium (Mg), and Indium (In) doped ZnO serving as an electron transport layer is the aim of this work. A favorable orientation for the CH3NH3PbI3 absorber layer crystallizes in the tetragonal phase [220], while ZnO crystallizes in the hexagonal phase [100]. This information is yielded by x-ray diffraction analysis. Al, In, and Mg doping of the transport layer has a significant effect on the optical characteristics like absorption and extinction coefficients, optical gaps, and optical and electrical conductivity. The UV-visible characterization of the heterostructures reveals that n-type doping can raise ZnO gap energy from 3.15 to 3.42 eV. The band gap energy of CH3NH3PbI3 is around 1.53-1.55 eV. Additionally, the absorption coefficient of each sample is high, it exceeds 105 cm-1. The ZnO thin films, both undoped and doped (with Al, In and Mg) exhibit an increase in refractive index from 1.97 to 2.13. The best dopant is found to be In. The refractive index of films composed of CH3NH3PbI3 is 3.13.

Investigation of UV-blocking and photon-down conversion characteristics of PMMA@ CH3NH3PbBr3:WO3 polymer nanocomposites

Herein, methyl ammonium lead bromide: Tungsten trioxide (CH3NH3PbBr3:WO3) nano heterojunction and polymethyl methacrylate (PMMA) polymer composite films of different weight percentage (wt%) proportions of CH3NH3PbBr3:WO3 nanoparticles (0, 0.5, 1.0, 1.5 and 2.0 wt%) were prepared. The structure, morphology and thermal features of CH3NH3PbBr3:WO3 heterojunctions and PMMA@CH3NH3PbBr3:WO3 nanocomposites were investigated using X-ray diffraction (XRD), Fourier Transform-Infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM) and Differential scanning calorimetry (DSC) techniques. The characterization data revealed decrease in crystallinity (up to 7.97%) and glass transition temperature (Tg) with increase in the concentration of CH3NH3PbBr3:WO3 nanoparticles in PMMA nanocomposites. The UV-visible absorbance and transmittance data of PMMA nanocomposites recorded using UV-visible spectroscopy was used to mathematically deduct the optical characteristics such as absorption coefficient, optical band gap, refractive index, extinction coefficient, finesse coefficient, optical conductivity and Urbach energy. The deducted data revealed improved UV-shielding, refractive index and optical conductivity values while the optical band gap and Urbach energy was found to decrease with concentration of dopant. The experimental data of different PMMA@CH3NH3PbBr3:WO3 composite films showed excellent UV- blocking properties in the wider wavelength range of 259-322nm(4.80eV-3.850eV). The PMMA nanocomposites with 2.0 wt% CH3NH3PbBr3:WO3 filler composition exhibited highest UV-shielding behavior with maximum UV-absorption in the wavelength range of 260 to 300nm. The pristine PMMA films showed a PL emission peak at 410nm while the PMMA nanocomposites exhibited strong emissions in the wavelength range of 485-520nm. The observed hydrophobicity, redshift and longer lifetime decay of 34.3 ns for PMMA nanocomposites is attributed to the incorporated CH3NH3PbBr3:WO3 heterojunction nanoparticles. The chromaticity profile suggested that the emission color changed from blue to green as the filler dose of CH3NH3PbBr3:WO3 varied from 0 to 2.0 wt%. Additionally, the findings from the study reveal that incorporation of CH3NH3PbBr3:WO3 into the PMMA matrix enhances UV-absorption, optical conductivity, hydrophobicity, thermal stability, electrical conductivity and photon-down conversion properties of PMMA which make the material suitable for photonic, photovoltaic, optoelectronic and light emitting diode applications.

Principles-based investigation of lithium-based halide perovskite X2LiAlH6 (X=K, Mn) for hydrogen storage, optoelectronic, and radiation shielding applications

Scientists devote their time and energy to studying and developing hydrogen storage devices to address the energy crisis and climate change. Because of this, investigations are conducted to reveal the optoelectronic, structural, bader charge, electronic charge density, and hydrogen storage properties of X2LiAlH6 (X = K, Mn) within the framework of density functional theory, and calculations of the structural characteristics were carried out utilizing local and nonlocal, and hybrid functionals. An additional onsite Coulomb parameter (GGA + U), which includes the Hubbard parameter, was used to apply the potential. Calculations based on the Kramer-Kroning principle were used to determine the dielectric function, refractive index, extinction coefficient, and energy loss function. The results indicate that K2LiAlH6 and Mn2LiAlH6 are highly suitable for hydrogen storage applications. The gravimetric ratios of hydrogen storage capacities for both investigated materials are 5.2 wt %, and 7.5 wt %, respectively. The interaction of the Mn-d, Li-s, K-s, and H-s/p orbitals was the cause of hybridization, according to the optoelectronic characteristics. Compound stability is indicated by the negative computed formation energy of the materials under investigation. The electronic charge density analysis showed a mixed-bond semiconductor with low ionicity and high covalence. In addition, the radiation shielding properties of Mn2LiAlH6 and K2LiAlH6 were investigated using Phy-X software, showing promising results in linear attenuation, half-value layer, and mean free path, particularly for Mn2LiAlH6 due to its higher atomic number. This groundbreaking study represents a pioneering computational exploration of X2LiAlH6, offering promising advancements for future research in hydrogen storage applications.

Effect of substrate temperature on the physical and sensing properties of nanostructured Fe2O3 thin films

Using Chemical Bath Deposition (CBD) Method and various substrate temperatures, Fe2O3 films were successfully deposited. The produced film thickness was around (320 nm). Using X-ray diffraction, researchers may examine the polycrystalline structure of Fe2O3 thin films. These nanofilms contain strong peaks at 2θ =32.21, suggesting a preferred orientation along the (110) plane, and the grain size increases with substrate temperature, according to XRD tests. When the base temperature was raised from 350 to 450 o C, the strain parameter decreased from 31.35 to 28.43. AFM testing of the surface morphology of the deposition of material yields excellent homogenous coatings. The findings show that the average particle size of the nanoparticles ranges from (69.8 to 32.7) nm. SEM images show Fe2O3 films at (350, 400, 450) °C. Increased temperature reduces grain size, influencing morphology variations. The absorbance increases with substrate temperatures and decreases rapidly at short wavelengths, which correspond to the energy gap. The transmittance increases with increasing wavelength range. It decreases with rising substrate temperatures. The band gap values vary from 2.17 eV to 2.06 eV by increasing the substrate temperatures from 350 to 450 o C. It was discovered that the band gap reduces as the temperature of the Fe2O3 substrate increases. In addition, the optical constants for all films, including the absorption coefficient, the refractive index, and the extinction coefficient, were computed. Fe2O3 film's resistance over time at 350, 400, and 450°C for 300 ppm NO2 demonstrates oxidation effect and temperature sensitivity. Sensitivity decreases with higher base temperature due to charge carrier recombination, affecting NO2 response.

First principles calculations of physical properties of the CeCu2Si2 material

Using local density approximation functional computations, LSDA (local spin density approximation) and mBJ (modified Becke-Johnson) for exchange-correlation interactions, we examined the combination CeCu2Si2, concentrating on its many physical properties. This work used the WC-GGA method to compute the elastic characteristics of CeCu2Si2 material, and the results indicate that unstrained CeCu2Si2 is more brittle. The density of states exhibits the metallic character of the chemical, in agreement with the inference made from the band structure. We also assessed several optical characteristics, such as real and imaginary optical conductivity, electronic energy loss, absorption coefficient, refractive index, and extinction coefficient. We also looked at the electronic components of thermal conductivity, electrical conductivity, Seebeck coefficient, and electronic conductivity. The compound's Seebeck coefficient values are negative, indicating p-type behavior. A thorough analysis of the data is presented, along with important details regarding the CeCu2Si2 compound's characteristics.

Cosensitization of a Tetraethylene Glycol‐Substituted Unsymmetrical Zinc Phthalocyanine Sensitized Solar Cells with D131 Auxiliary Dye Exhibited Enhanced Efficiency

AbstractAn asymmetric zinc phthalocyanine dye (ZnPcT3C), bearing three tetraethylene glycol donor groups and one carboxylic acid anchoring group, was synthesized as a photosensitizer dye for dye‐sensitized solar cells (DSSCs). The tetraethylene glycol (TEG), consisting of four ethoxy units, works as an amphiphilic long‐chain donor group that greatly helped in reducing the molecular aggregation. Carboxylic acid group, on the other hand, an acceptor, together with TEG in ZnPcT3C functions as a ‘push–pullʼ system suitable for DSSCs. Absorption spectra of ZnPcT3C in DMSO showed a strong sharp Q band in the infrared region 600–700 nm with (λmax = 682 nm) and a less intense soret band appeared in the region 300–400 nm with λmax = 340 nm. The zinc phthalocyanine (ZnPcT3C) exhibited molar extinction coefficient (ε) of 72,727 L mol−1cm−1. The emission was observed at λem = 695 nm upon excitation at 650 nm and exhibited a fluorescence decay of 2.82 ns. The ZnPcT3C dye sensitised solar cell (c = 1 mM) exhibited the power conversion efficiency (η) of 3.52% in chloroform in I−/I3 electrolyte under simulated 100% brightness. Cosensitization of ZnPcT3C with another auxiliary dye D131 in 1:1 ratio in a cocktail‐type DSSC attained the power conversion efficiency of twice as high as η = 6.27% in an identical condition. A mixture of D131 (λmax = 470 nm) dye with the ZnPcT3C phthalocyanine harvests sunlight across the visible spectra, enabling DSSCs to attain a large photocurrent and photovoltage, enhancing power conversion efficiency.

A Hemicyanine‐Based Highly Sensitive and Selective Near‐Infrared Fluorescent Probe for Fe3+ in Aqueous Media

ABSTRACTFerric ion is widely distributed in human cells and an important component of hemoglobin, which can promote the transportation of blood in the human body. Its ability to bind with oxygen is essential for participating in oxidation reactions and enzymatic reactions. Deficiency of iron (III) and excessive accumulation of iron in the blood can cause many health problems in the body, such as anemia, loss of appetite, fibrosis, reduced work routines, and decreased immunity. As a fluorescent dye, cyanine has the advantages of high fluorescence quantum yield, good optical and chemical stability, excitation and emission wavelengths in the near‐infrared region, high molar extinction coefficient, and small influence on pH variation. It is a fluorescent dye that modern scholars choose more. A new near‐IR hemicyanine derivative bearing 1,3‐dithiane moiety was developed as an efficient fluorescence probe 1 for the detection of Fe3+ in aqueous medium (THF/H2O, 1:1, v:v). This near‐IR fluorescence probe 1 exhibits high sensitivity and selectivity toward Fe3+ sensing with detection limit of 0.5 μM under lager scope of pH value (pH = 2–12).

The mechanistic origin of amber pigmentation of Perithemis tenera (Say, 1840) wings (Odonata: Libellulidae) and its function in conspecific signalling

Animal coloration serves various signaling and non-signaling functions. In damselflies and dragonflies (Odonata), such colors may not only play photoprotective and/or thermoregulatory roles but also serve as visual signals during courtship and/or agonistic interactions. Here, we analyzed the coloration of Perithemis tenera wings, a potential secondary sexual ornament, applying spectrophotometry and visual modeling to gain a deeper understanding of their color mechanisms and functions. The amber coloration of the P. tenera wings results from the interaction of light with both the melanized chitin matrix and possibly ommochrome pigments. Additionally, by fitting the absorbance curve of P. tenera wings to the extinction coefficient of different melanins, we deduced that pheomelanin is likely the pigment embedded in the wing’s chitinous matrix. The amber coloration of P. tenera wings stands out against their natural habitat, making it detectable by conspecifics. Finding multiple pigments in the P. tenera wings not only enhances our understanding of the functional roles of pigmentation in Odonata but also offer broader insights into how structural and pigment-based colorations evolve as multifunctional traits.

Hydrolysis of Poly(ester urethane): In-depth Mechanistic Pathway Determination through Thermal and Chemical Characterization

Many structure/property relationships of hydrolyzed poly(ester urethane) (PEU) – a thermoplastic polymer have been reported. Examples include changes in molecular weight vs. elongation at break and crosslink density vs. mechanical strength. However, the effect of molecular weight reduction on some physical, thermal, and chemical properties of hydrolyzed PEU have not been reported. Therefore, a large set of hydrolyzed PEU (Estane®5703) samples were obtained from two aging experiments: 1) accelerated aging conducted under various environments (air, nitrogen, moisture) and at 64°C and below for almost three years, and 2) natural aging conducted under ambient conditions for more than four decades. The hydrolyzed samples were characterized via multi-detection gel permeation chromatography (GPC), thermogravimetric analysis (TGA), modulated differential scanning colorimetry (mDSC), UV-vis spectroscopy, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy techniques. Hydrolysis of ester linkages in the soft-segments decreases both the molecular weight of the polymer and the melting point of Estane from ∼55°C to 39°C. Aging above this melting temperature (Tm), increased mobility of polymer chains and water diffusivity alter the PEU degradation pathway from those expected at aging temperatures below Tm and have significant bearing on the critical molecular weight (MC) at which the physical, chemical, thermal, and mechanical properties of Estane change abruptly. While a MC value of 20 kDa is found for PEU hydrolysis at mild temperatures (e.g., below 39°C), the MC increases with increasing aging temperature. To complement the existing structure/property relationships reported in the literature, more correlations are obtained, which include the effect of Mw on polydispersity, intrinsic viscosity (Mark-Houwink equation), UV extinction coefficient, and dn/dc (GPC analysis) values. Furthermore, we seek to augment previously reported aging models for PEU by developing a practical model with which the extent of degradation and material performance can be predicted based on aging under different temperature ranges both above and below the melting point of the hard-segments.

The Extraction of Alcea Rosea Organic Dye and Its Characterization of Optical Properties

In the present study, the optical properties of a natural dye extracted from Alcea rosea flowers were investigated. The color extraction procedure was performed using a nontoxic solvent ethanol to enhance human safety and the ecological framework. Fourier transform infrared spectroscopy was employed to determine the functional groups of the natural dye obtained from Alcea rosea flowers. The optical properties of dye were achieved by the directed thin film using UV-Vis spectroscopy and analyzed absorption spectra, coefficients, refractive indices, extinction coefficients, and optical energy bandgap. A broad absorption band occurs over an extensive waveband with peak at 380 nm. The occurrence of a low indirect bandgap in a thin film was discerned at 3.9 eV, with Urbach energy noticed in a state of 0.23 eV.

Optical and stress properties of ZrO2/SiO2 and TiO2/SiO2 anti-reflective coatings deposited by ion-beam-assisted deposition on a flexible substrate

Dielectric films of ZrO2,TiO2, and SiO2 were deposited on flexible polycarbonate (PC) and polyethylene terephthalate (PET) substrates by using ion-beam-assisted deposition (IBAD). Each layer had a thickness ranging from 30 to 210 nm. The optical and anisotropic stress properties were investigated. Two anti-reflective coatings (ARCs), ZrO2/SiO2 and TiO2/SiO2, were selected and deposited on the PET flexible substrate. The anisotropic stresses of the single layer and ARCs were measured using a phase-shifting moiré interferometer. Experimental results showed that the optimal oxygen flow rates for the ZrO2,TiO2, and SiO2 films deposited with IBAD were 10, 10, and 15 sccm, respectively. The refractive index (n) was TiO2(2.37)>ZrO2(2.05)>SiO2(1.46), and the extinction coefficient (k) for all samples was below 10−3. The thermal expansion coefficient of the PC substrate was three times that of the PET substrate, and the high-refraction ZrO2 and TiO2 single-layer films presented cracks and distortions on the PC substrate. Only the low-refractive-index SiO2 sample did not present cracks. The three dielectric films did not crack or distort when deposited on the PET substrate. The anisotropic stress analysis provided the maximum principal and shear stresses for the three dielectric films on the PET substrate. Therefore, the maximum principal stress of the 210 nm single-layer film on a PET substrate is TiO2>ZrO2>SiO2. It was also discovered that the principal stress of the AR multilayer film is significantly decreased due to the damping stacking effect (DSE) of the high- and low-refractive-index materials, ZrO2/SiO2 ARC (−297.3MPa)>TiO2/SiO2ARC(−132.6MPa). Thus, the high packing density of TiO2 gives a better DSE than ZrO2.