Analysis Of Absorption Spectra Research Articles

A Smartphone-Based Sensing for Portable and Sensitive Visual Detection of Hg (II) via Nitrogen Doped Carbon Quantum Dots Modified Paper Strip.

The development of portable and cost-effective sensing system for Hg2+ quantitation is highly demanded for environmental monitoring. Herein, an on-site, rapid and portable smartphone readout device based Hg2+ sensing system integrating nitrogen-doped carbon quantum dots (NCDs) modified paper strip was proposed, and the physicochemical properties of NCDs were characterized by high resolution TEM, FTIR, UV-vis absorption spectrum and fluorescence spectral analysis. The modified paper strip was prepared via "ink-jet" printing technology and exhibits sensitive fluorescence response to Hg2+ with fluorescence color of bright blue (at the excitation/emission wavelength of 365/440nm). This portable smartphone-based sensing platform is highly selective and sensitive to Hg2+ with the limit of detection (LOD) of 10.6nM and the concentration range of 0-130nM. In addition, the recoveries of tap water and local lake water were in the range of 89.4% to 109%. The cost-effective sensing system based on smartphone shows a great potential for trace amounts of Hg2+ monitoring in environmental water samples.

Systematic Assessment of Phonon and Optical Characteristics for Gas-Source Molecular Beam Epitaxy-Grown InP1−xSbx/n-InAs Epifilms

Experimental and theoretical assessments of phonon and optical characteristics are methodically accomplished for comprehending the vibrational, structural, and electronic behavior of InP1−xSbx/n-InAs samples grown by Gas-Source Molecular Beam Epitaxy. While the polarization-dependent Raman scattering measurements revealed InP-like doublet covering optical modes (ωLOInP~350 cm−1, ωTOInP~304 cm−1) and phonons activated by disorders and impurities, a single unresolved InSb-like broadband is detected near ~195 cm−1. In InP1−xSbx, although no local vibrational (InSb:P; x → 1) and gap modes (InP:Sb; x → 0) are observed, the Raman line shapes exhibited large separation between the optical phonons of its binary counterparts, showing features similar to the phonon density of states, confirming “two-mode-behavior”. Despite the earlier suggestions of large miscibility gaps in InP1−xSbx epilayers for x between 0.02 and 0.97, our photoluminescence (PL) results of energy gaps insinuated achieving high-quality single-phase epilayers with x ~ 0.3 in the miscibility gap. Complete sets of model dielectric functions (MDFs) are obtained for simulating the optical constants of binary InP, InSb, and ternary InP1−xSbx alloys in the photon energy (0 ≤ E ≤ 6 eV) region. Detailed MDF analyses of refractive indices, extinction coefficients, absorption and reflectance spectra have exhibited results in good agreement with the spectroscopic ellipsometry data. For InP0.67Sb0.33 alloy, our calculated lowest energy bandgap E0 ~ 0.46 eV has validated the existing first-principles calculation and PL data. We feel that our results on Raman scattering, PL measurements, and simulations of optical constants provide valuable information for the vibrational and optical traits of InP1−xSbx/n-InAs epilayers and can be extended to many other technologically important materials.

EPR Spectrum Analysis of DPPH and MnCl2

This paper presents the findings of electron paramagnetic resonance (EPR) spectroscopy experiments conducted on two different samples: 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Manganese Chloride (MnCl2) dissolved in H2O. The experiments were conducted at Dr. D. Petasis EPR lab located in Allegheny College, Meadville, PA, USA. A Varian X-Band spectrometer was utilized for the analysis of the EPR absorption spectra. The primary objective was to determine the g-values and hyperfine structure of the two samples, which can be crucial in characterizing their electronic properties. The g-values obtained for both DPPH and MnCl2 were found to be remarkably close to the theoretically calculated values, suggesting the high accuracy and success of the experiments. This agreement validates the reliability of the EPR measurements and demonstrates the precision of the instruments and experimental procedures employed. For the MnCl2 sample, a hyperfine structure with 6 visible EPR lines was observed. By analyzing the number of EPR lines, the nuclear spin of the Mn(II) ion was determined to be I = 5/2, consistent with the expected value for Mn(II). The hyperfine constant (A) was also calculated from the field position differences between adjacent lines, providing further insights into the sample's magnetic properties. Comparisons were made between the obtained g-values and hyperfine constant with the expected values for Mn(II) in the literature, confirming the accuracy of the measurements and reinforcing the credibility of the experimental data. Overall, the EPR spectroscopy experiments conducted on DPPH and MnCl2 in H2O have provided valuable information about the electronic and magnetic properties of these paramagnetic materials. The results demonstrate the effectiveness of EPR spectroscopy as a powerful experimental technique for investigating various bio-chemical samples and understanding the effects of solvents on the EPR spectra of compounds. The close agreement between the experimental and theoretical values for the g-factors and hyperfine constants reinforces the reliability of the data obtained from the EPR experiments.

The degradation of cathodic Fe/N/C catalyst in PEMFCs: The evolution of remanent active sites after demetallation

The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells (PEMFCs). However, the major bottleneck is its significant activity decay in real-world PEMFC cells. The superposed “fast decay” and “slow decay” have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation. The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test. Nevertheless, it is still unclear how the remanent active sites evolve after demetallation. To this end, the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies (MEAs) after different operations. It is presented that 1 bar pressure and 80 °C temperature are the optimized conditions for Fe/N/C MEA. Particularly, the “fast decay” in the initial 15 h is immune to the various operating parameters, while the “slow decay” highly depends on the applied temperature and pressure. According to the X-ray absorption spectra (XAS) analysis and stability test of MEA, the gradual evolution of Fe-N coordination to Fe-O is found correlated with the “slow decay” and accounts for the catalyst decay after the demetallation process.

Ultraviolet-C persistent luminescence and defect properties in Ca2Al2SiO7:Pr3+

In recent years, significant attention has been focused on the study of materials with ultraviolet (UV) persistent luminescence (PersL) due to their prospective application possibilities. Although novel UV persistent phosphors are being developed, reports on defect properties and PersL mechanisms are limited. In this study, the incorporation of Pr3+ ions in Ca2Al2SiO7 is analyzed using X-ray diffraction (XRD) and X-ray absorption techniques, whereas PersL properties are characterized by photoluminescence (PL), thermostimulated luminescence (TSL) and electron paramagnetic resonance (EPR) methods. Analysis of the Pr L3-edge X-ray absorption spectra suggests that praseodymium atoms substitute for calcium atoms. The UV-C PersL of the host results from thermally assisted recombination of charge carriers with trap depths within the 0.50–0.87 eV range. Moreover, a partial correlation of PersL and TSL with the decay of X-ray-induced paramagnetic centers was observed. This study expands the knowledge base on the structure of Ca2Al2SiO7 and establishes the optimal Pr3+ concentration for efficient UV-C PersL.

Effects of temperature on factors relevant to laser operation near 1.6 µm wavelength in resonantly (in-band) pumped CaF2:Er and SrF2:Er crystals: a comparative study

Single crystals of CaF2 and SrF2 containing Er3+ ions with concentrations between 0.01 and 0.6 at% respectively, were grown using the temperature gradient technique (TGT). Absorption spectra related to the 4I15/2 → 4I13/2 transition of Er3+ ions were measured at 5 K to investigate the properties of the crystal field splitting of the 4I13/2 multiplet, and at several temperatures in the region 80 K – 300 K to determine the effect of temperature on the spectral bands. The 4I13/2 → 4I15/2 luminescence spectra were recorded within the same temperature range as for absorption measurement. The analysis of absorption and luminescence spectra provides an in-depth knowledge on the effect of temperature on the factors that govern the efficiency of resonant optical pumping near 1.6 µm and the resulting lasing ability of Er3+ ions imbedded in CaF2 and SrF2 hosts.

Synthesis and In vitro‐In silico Evaluation of Thiazolo‐triazole Hybrids as Anticancer Candidates

AbstractTo meet the growing need for stable and clinically effective chemotherapeutic agents, herein, we have synthesized a series of acyl‐functionalized thiazolo[3,2‐b]‐[1,2,4]triazole derivatives in highly efficient and regioselective manner. The structure of newly synthesized regioisomeric products was unambiguously characterized by multinuclear 2D‐NMR [(1H−13C) HMBC, (1H−13C) HMQC] spectroscopic data. To assess the anticancer and pharmacokinetic profile of the synthesized compounds, we performed in silico, and ex vivo binding studies of compounds with calf‐thymus deoxyribonucleic acid (ct‐DNA) and bovine serum albumin (BSA), respectively, and also tested their efficacy against five human cancer cell lines. viz., MCF‐7 (breast cancer), BT‐474 (breast cancer), A549 (lung cancer), MOLT4 (acute lymphoblastic leukemia), and BxPC3 (pancreatic cancer). Compounds (2‐(4‐chlorophenyl)‐6‐methylthiazolo[3,2‐b][1,2,4]triazol‐5‐yl)(4‐fluorophenyl)methanone 6 l, (4‐chlorophenyl)(2‐(4‐chlorophenyl)‐6‐methylthiazolo[3,2‐b][1,2,4]triazol‐5‐yl)methanone 6 m and (2‐(4‐chlorophenyl)‐6‐methylthiazolo[3,2‐b][1,2,4]triazol‐5‐yl)(4‐methoxyphenyl) methanone 6 q exhibited excellent anticancer potential among the screened derivatives. Furthermore, ex‐vivo mechanistic investigations showed the static mode of quenching and moderate bindings between the ligand and biomolecules; DNA (Kq=2.01‐2.24*1012 M−1 s−1) and BSA (Kq=2.25‐.2.72*1012 M−1 s−1). Moreover, fluorescence displacement assay demonstrated a groove binding mode of interaction with ct‐DNA, which was supported by UV‐Visible absorption spectrum, circular dichroism, and viscosity analysis.

Effect of doping SrTiO3 with Nb studied with wide-range spectroscopic ellipsometry

The low-temperature optical properties of a SrTiO3 crystal doped with 0.7% wt. Nb and a pure SrTiO3 reference crystal were studied using spectroscopic ellipsometry. The optical constants and dielectric functions were obtained in the spectral range of 0.8–8.8 eV at temperatures from 10 to 300 K, and the optical conductivity was obtained in the spectral range of 0.03–1 eV at 300 K. Analysis of the optical conductivity spectra in the infrared spectral range confirmed the presence of free electrons and additional absorption hump between 0.1 and 0.4 eV (806 and 3226 cm−1) in doped SrTiO3 and optical phonons in both doped and undoped SrTiO3. The performed analysis of optical absorption spectra in the range 0.8–8.8 eV revealed frustration of the indirect bandgap and an increase in the direct bandgap energy by ∼0.03 eV in Nb-doped SrTiO3, compared to undoped SrTiO3 over the whole temperature range. The energies of the peaks’ maxima of the dielectric function spectra did not significantly differ for doped and pure SrTiO3. For both Nb-doped and pure SrTiO3, temperature dependence of the direct bandgap energy and that of the index of refraction showed inflection between 100 and 150 K, which may be considered evidence of an antiferrodistortive phase transition from a cubic to a tetragonal structure.

Detection of germanium isotopes in biosynthesized Ge nanocrystals through different optical spectroscopy techniques

The current work aims to investigate the isotopic effect in biosynthesized Germanium nanocrystals (Ge NCs) through Raman and IR absorption spectra. By treating bulk germanium crystal with microorganisms in a weak magnetic field, Ge NCs with great chemical and isotopic purity are produced on its surface. Using various techniques, including X-ray diffraction, photoluminescence spectroscopy, micro-Raman spectroscopy, and FTIR spectroscopy, the structural and optical characteristics of the synthesized Ge NCs are studied. The PL, Raman, and IR peaks of synthesized material, which are recorded at various time intervals, are seen to have shifted. The PL peak shift of fabricated material is seen as a result of the quantum confinement effect. Raman and IR absorption spectra analysis, which are conducted at room temperature reveals the possible presence of germanium isotopes. It is observed that the phonon absorption peaks of synthesized germanium NC material shift to longer wavelengths with increasing average atomic mass of germanium. The observed optical properties of the synthesized Ge NCs have provided great help to study the change in structural and optical properties of the synthesized Ge crystal.

High-level studies of the singlet states of quadricyclane, including analysis of a new experimental vacuum ultraviolet absorption spectrum by configuration interaction and density functional calculations.

A synchrotron-based vacuum ultraviolet absorption spectrum (VUV) of quadricyclane (QC) is reported with energies up to 10.8eV. Extensive vibrational structure has been extracted from the broad maxima by fitting short energy ranges of the VUV spectrum to high level polynomial functions and processing the regular residuals. Comparison of these data with our recent high-resolution photoelectron spectral of QC showed that this structure must be attributed to Rydberg states (RS). Several of these appear before the valence states at higher energies. Both types of states have been calculated by configuration interaction, including symmetry-adapted cluster studies (SAC-CI) and time dependent density functional theoretical methods (TDDFT). There is a close correlation between the SAC-CI vertical excitation energies (VEE) and both Becke 3-parameter hybrid functional (B3LYP), especially Coulomb-attenuating method-B3LYP determined ones. The VEE for several low-lying s-, p, d-, and f-RS have been determined by SAC-CI and adiabatic excitation energies by TDDFT methods. Searches for equilibrium structures for 11,3A2 and 11B1 states for QC led to rearrangement to a norbornadiene structure. Determination of the experimental 00 band positions, which show extremely low cross-sections, has been assisted by matching features in the spectra with Franck-Condon (FC) fits. Herzberg-Teller (HT) vibrational profiles for the RS are more intense than the FC ones, but only at high energy, and are attributed to up to ten quanta. The vibrational fine structure of the RS calculated by both FC and HT procedures gives an easy route to generating HT profiles for ionic states, which usually require non-standard procedures.

Complexation of copper algaecide and algal organic matter in algae-laden water: Insights into complex metal–organic interactions

Copper-based algicides have been widely used to suppress algae blooms; however, the release of algal organic matter (AOM) on account of cell lysis may cause significant changes in the mitigation, transformation, and bioavailability of Cu(II). In the present work, the binding characteristics of Cu(II) with AOM were explored via combinative characterization methods, such as high-performance size exclusion chromatography, differential absorption spectra analysis, and joint applications of two-dimensional correlation spectroscopy (2D-COS), as well as heterospectral 2D-COS and moving window 2D-COS analyses of UV, synchronous fluorescence, and FTIR spectra. Carboxyl groups displayed a preferential interaction to Cu(II) binding, followed by polysaccharides. The spectral changes of C]O stretching occur after the change of chromophores in complexation with Cu(II). The AOM chromophores exhibit obvious conformations at Cu(II) concentrations higher than 120 μM, while AOM fluorophores and functional groups exhibit the greatest changes at Cu(II) concentrations lower than 20 μM. All these observations have verified the presence of binding heterogeneity and indicate that AOM could interact with Cu(II) through diverse functional moieties. Therefore, our study contributes to the better understanding of the fate of Cu(II)–AOM complexes in aquatic systems.

Prompt and effective purification for thin single wall carbon nanotubes by dry process using ferric chloride

For the removal of iron catalyst nanoparticles, the dry purification of as-grown thin single wall carbon nanotubes (SWCNTs) with different mean tube-diameters of 0.9 and 1.3 nm by using FeCl3 was investigated. Based on the comparison studies on the purification efficiency and the various characteristics of these SWCNTs purified under different conditions, it was proved that the present dry-process can promptly proceed the purification reaction within a few 10 min with the high purity of more than 95 mass% as carbon content. Furthermore, the analysis of optical absorption spectra showed that the degradation of thinner SWCNTs with 0.9 nm diameter occurs on the dry purification at the temperature of higher than 900 °C even within the short duration (∼5 min) of FeCl3-treatment, while it is not observed in case of SWCNTs with 1.3 nm diameter.

Enhancement of the sensing performance and stability of a MOF based-molecularly imprinted polymer by utilizing dual-ligands and triethanolamine catalysis

In this work, a terbium MOF-based molecularly imprinted polymer (Tb-MOF@SiO2@MIP) was prepared using two ligands as organic linkers and triethanolamine (TEA) as a catalyst to improve the sensing performance and stability of the fluorescence sensors. The obtained Tb-MOF@SiO2@MIP was then characterized using a transmission electron microscope (TEM), energy dispersive spectroscopy (EDS) Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The results revealed that Tb-MOF@SiO2@MIP was successfully synthesized with a thin imprinted layer of 76nm. The synthesized Tb-MOF@SiO2@MIP maintained 96% of its original fluorescence intensity after 44 days in aqueous environments because of appropriate coordination models between the imidazole ligands as a nitrogen donor and Tb (Ⅲ). Furthermore, TGA analysis results indicated that an increase in the thermal stability of Tb-MOF@SiO2@MIP was attributed to the thermal barrier from a MIP layer. The Tb-MOF@SiO2@MIP sensor responded well to the addition of imidacloprid (IDP) in the range of 2.07-150ngmL-1 with a low detection limit of 0.67ngmL-1. In vegetable samples, the sensor can quickly detect IDP levels with the average recovery ranging from 85.10 to 99.85% and RSD values ranging from 0.59 to 5.82%. The UV-vis absorption spectrum and density functional theory analysis results revealed that the inner filter effect and dynamic quenching process both contributed to the sensing process of Tb-MOF@SiO2@MIP.

Active Site Descriptors from 95Mo NMR Signatures of Silica-Supported Mo-Based Olefin Metathesis Catalysts.

The olefin metathesis activity of silica-supported molybdenum oxides depends strongly on metal loading and preparation conditions, indicating that the nature and/or amounts of the active sites vary across compositionally similar catalysts. This is illustrated by comparing Mo-based (pre)catalysts prepared by impregnation (2.5-15.6 wt % Mo) and a model material (2.3 wt % Mo) synthesized via surface organometallic chemistry (SOMC). Analyses of FTIR, UV-vis, and Mo K-edge X-ray absorption spectra show that these (pre)catalysts are composed predominantly of similar isolated Mo dioxo sites. However, they exhibit different reaction properties in both liquid and gas-phase olefin metathesis with the SOMC-derived catalyst outperforming a classical catalyst of a similar Mo loading by ×1.5-2.0. Notably, solid-state 95Mo NMR analyses leveraging state-of-the-art high-field (28.2 T) measurement conditions resolve four distinct surface Mo dioxo sites with distributions that depend on the (pre)catalyst preparation methods. The intensity of a specific deshielded 95Mo NMR signal, which is most prominent in the SOMC-derived catalyst, is linked to reducibility and catalytic activity. First-principles calculations show that 95Mo NMR parameters directly manifest the local strain and coordination environment: acute (SiO-Mo(O)2-OSi) angles and low coordination numbers at Mo lead to highly deshielded 95Mo chemical shifts and small quadrupolar coupling constants, respectively. Natural chemical shift analyses relate the 95Mo NMR signature of strained species to low LUMO energies, which is consistent with their high reducibility and corresponding reactivity. The 95Mo chemical shifts of supported Mo dioxo sites are thus linked to their specific electronic structures, providing a powerful descriptor for their propensity toward reduction and formation of active sites.

Cost-effective electrodes based on mixed iridium-zirconium oxides for vanadium electrolyte rebalancing cell

Developing the mixed metal oxide (MMO) electrodes with high electrocatalytic activity, low cost of materials and long service life is an important and relevant task for various applications including the vanadium electrolyte rebalancing. In this work, the cost-effective electrodes based on mixed iridium-zirconium oxides were fabricated using the Pechini method followed by thermal decomposition. The Raman and XPS analysis of mixed IrO2–ZrO2 electrodes showed a partially crystalline (IrO2 and ZrO2) and partially amorphous (IrOx and ZrOx) structure. Conducted electrochemical tests demonstrated the high electrocatalytic performance of the electrodes with 15–30 mol% of Zr addition comparable to Ir-based electrodes toward the OER. Successful proceeding of the electrochemical reduction in the rebalancing cell was proved using operando absorbance spectra analysis of the reducing vanadium electrolyte. The results of a prolonged vanadium electrolyte electroreduction showed more effective performance of the cell with 70Ir–30Zr electrode than the same cell with 70Ir electrode under a high current density of 250 mA cm−2. This approach allows reducing the electrode cost with reducing the Ir loading without sacrificing the electrocatalytic properties with Zr adding.

Design of an ocu‐Metal‐Organic Framework for a Photocatalysis Reaction

AbstractEmpowered by reticular chemistry, an ocu‐metal‐organic framework (MOF) catalyst has been created for the first time. The catalyst, SYD‐1, was rationally designed and successfully synthesised by assembling 8‐c prismatic zirconium oxo‐clusters and 6‐c octahedral Ru(bpy)32+‐based metalloligands into a three‐dimensional structure. Catalytically active metal sites were then attached to the coordinatively unsaturated sites on the Zr oxo‐clusters postsynthetically via a sequential practice of solvent‐assisted ligand exchange and metalation processes, giving rise to SYD‐1‐CuNi. SYD‐1‐CuNi was thoroughly characterised via an array of X‐ray diffraction, 77 K N2 sorption experiments, nuclear magnetic resonance measurements, microscopic analysis, optical absorption spectra analysis and electrochemical measurements to demonstrate the successful synthesis of the targeted SYD‐1‐CuNi and its potential in photocatalysis. The photocatalytic performance of SYD‐1‐CuNi was illustrated by driving a model reaction, namely photocatalytic CO2 reduction reaction (yield of CH4 19.2 μmol g−1 h−1)/hydrogen evolution reaction (yield of H2 200.4 μmol g−1 h−1) concomitantly with oxidation of benzyl alcohol to benzaldehyde (286.6 μmol g−1 h−1). The present work highlights the power and potential of reticular chemistry in the at‐will synthesis of MOF materials for a specific application.

Impactive cadmium modifications to enhance the structural-optical relationship in nickel borate glasses

Cadmium-doped borate glass composition was prepared via the melt-quenching technique. The nature of the glass structure was detected by X-ray diffraction (XRD). The physical parameters, such as density (ρ) from Archimedes’ principle, molar volume (Vm), Cd2+ ions concentration (NCd), and inter-atomic distance (Ri) were evaluated, providing structural information on glass samples. Fourier transform infrared (FT-IR) analysis was used to study the fundamental vibrational modes of structural units, confirming the conversion of BO3 to BO4 units, indicating a strongly bonded and high connectivity of the network. Some important optical findings were extracted from the analysis of optical absorption spectra. For example, the mitigation in the optical band gap, the increase in Urbach energy, the deterioration in the metallization criterion, and the enhancement in the electron-phonon interaction were obtained with cadmium oxide addition. The nonlinearity characteristics were enhanced, making these glass samples have viability in the non-linear optics sector. The obtained data from the electron spin resonance (ESR) revealed that the nickel ions exist in a divalent oxidation state with octahedral symmetry. Interestingly, the optical absorption transitions of Ni2+ ions were accurately deconvoluted and assigned to octahedral and tetrahedral positions. The equations of ligand field parameters of octahedral Ni2+ ions were correctly presented. The equation of Racah C parameter was deduced for the first time. Then, the ligand field parameters, such as the ligand field strength (10 Dq), Racah parameters (B and C), and other related parameters, were precisely assessed. The covalent nature between Ni2+ ions and the ligands was detected from the nephelauxetic effect.

Phase Transition and Energy Storage Density in Lead-Free Ferroelectric Ba1−xSrxTiO3 (x = 0.1, 0.3, and 0.7) Capacitors

Structure, phonon, and energy storage density in Sr2+-substituted lead-free ferroelectric Ba1−xSrxTiO3 (BSTx) for compositions x = 0.1, 0.3, and 0.7 were investigated using X-ray diffraction, Raman, and ferroelectric polarization measurements as a function of temperature. The samples were tetragonal for x = 0.1 with a large c/a ratio. The tetragonal anisotropy was decreased upon increasing x and transforming to cubic for x = 0.7. The changes in structural and ferroelectric properties were found to be related to the c/a ratios. The temperature-dependent phonon spectroscopy results indicated a decrease in tetragonal–cubic phase transition temperature, Tc, upon increasing x due to a reduction in the lattice anisotropy. The intensity of ~303 cm−1 E(TO2) mode decreased gradually with temperature and finally disappeared around the tetragonal ferroelectric to cubic paraelectric phase at about 100 ℃ and 40 ℃ for x = 0.1 and 0.3, respectively. A gradual reduction in the band gap Eg of BSTx with x was evident from the analysis of UV-visible absorption spectra. The energy storage density (Udis) of the ferroelectric capacitors for x = 0.7 was ~0.20 J/cm3 with an energy storage efficiency of ~88% at an applied electric field of 104.6 kV/cm. Nearly room temperature transition temperatures TC and reasonably fair energy storage density of the BSTx capacitors were found.

Spectroscopic characterization of the interactions between poly(2-(trimethylamino)ethyl methacrylate) chloride and the xanthene dyes, 2′, 7′-difluorofluorescein and 2, 4, 5, 7-tetraiodofluorescein

Intermolecular interactions in buffered aqueous solution between the polycation, poly(2-(trimethylamino)ethyl methacrylate) chloride (pTMAEMC) and two anionic xanthene dyes, 2′, 7′-difluorofluorescein (Oregon Green 488) and 2, 4, 5, 7-tetraiodofluorescein (Erythrosin B), are characterized using multiple optical spectroscopic methods. Visible absorption spectroscopy indicates the formation of ground-state pTMAEMC-dye complexes. Benesi-Hildebrand binding isotherm analysis of visible absorption spectra for pTMAEMC-dye mixtures quantifies the strength of binding interactions producing the complexes. For both Oregon Green 488 (OG) and Erythrosin B (EB) in mixtures with pTMAEMC, the concentration of the solution’s sodium acetate buffer at a fixed pH alters the binding constants, Kb, suggesting that ionic strength plays a key role in determining the binding affinity of pTMAEMC for the dyes. Comparison of Kb, for the dyes indicates stronger binding of EB under all solution conditions. Steady-state fluorescence emission spectroscopy, fluorescence quenching, excited-state fluorescence lifetime measurements and fluorescence correlation spectroscopy provide complementary data for the interactions between pTMAEMC and the dyes. Mixtures of pTMAEMC with the dyes produce fluorescence enhancements and fluorescence quenching which exhibit a dependence on the buffer concentration used in the mixture. Excited-state lifetime analysis indicates that OG interacts with pTMAEMC through ground-state interactions while EB exhibits both ground-state and excited-state interactions with pTMAEMC. The spectroscopic measurements suggest that a polyelectrolyte effect for pTMAEMC due to ionic strength variation produced by the buffer concentration affects the dye binding profile of the polycation. This conclusion is supported by fluorescence correlation spectroscopy (FCS) analyses of the hydrodynamic diameter changes in pTMAEMC-OG binding in low buffer concentration (low ionic strength) solution. FCS analyses of pTMAEMC-OG mixtures also reveal diversity in the complexes formed in low ionic strength solution suggesting that other xanthene dyes will exhibit similar binding behaviors in mixtures with pTMAEMC as a function of solution ionic strength.

The effect of zinc oxide on the physical and optical characteristics of calcium oxide containing boro-tellurite glasses

Glassy system with a chemical compositions of xZnO-10CaO-30TeO2-(60-x)B2O3 (x = 0 to 20 mol% with stepwise 5 mol%) was synthesized by conventional melt quenching method. The non-crystallinecharacter of the produced glasses was verified by X-ray diffraction analysis. Variations in the molar concentration of additional ZnO resulted in a densityrange of 3.19–3.77 g/cm3 for the current glasses. Through analysis of Ultraviolet Absorption spectrum, optical properties like cut-off (λc) optical energy band gap (Eopt), Urbach energy (ΔE),refractive index were determined. The cut-off wave length (λc) was increased, whereas, indirect band gap energy decreased with addition of ZnO content. The Urbach energy (ΔE) of the present glasses increased with ZnO content which confirms more disorderness. As the amount of ZnO in the glass system changed, the refractive index shifted from 2.23 to 2.30 with changing of ZnO content. The FTIR spectra confirmed the structural changes with increasing ZnO content. The higher refractive index values of the studied glasses and the presence TeO2 and ZnO enables the prominence of the glasses for NLO and antimicrobial applications.