Weak Band Research Articles

Effect of gas pre-decomposition device on the growth of GaN epitaxial layer

In previous studies, the influence of gas phase and surface reactions on the growth of GaN was mainly calculated through simulations. In this study, a novel gas pre-decomposition device (GPDD) was designed to experimentally investigate the effects of gas phase and surface reactions on GaN growth by changing the length and height of the isolation plates (IPs). By varying the structure of the GPDD, the effects on the growth rate and thickness uniformity of the GaN films were studied. The growth rate of the GaN sample slowed with the extension of the IPs because the longer partition plates led to insufficient gas mixing and premature consumption of the precursor trimethylgallium (TMG). The use of GPDD simultaneously achieves high crystal quality and smooth surface morphology of the GaN film. Owing to the use of GPDD, the decomposition of TMG in the pyrolysis pathway was promoted, which suppressed Ga vacancies and C impurities, resulting in weak yellow luminescence bands in the photoluminescence. This study provides a comprehensive understanding of the chemical reaction mechanism of GaN and plays an important role in promoting the development of metal-organic chemical vapor deposition equipment.

Mechanism of radial chain rockbursts in a deep granite TBM tunnel under the influence of weak band

Radial chain rockbursts (RCRs) in deep-buried TBM tunnels have prolonged durations and can pose significant safety risks. Further research is needed to deepen our understanding of the mechanisms of recurrence of rockbursts under the influence of structure plane. In this study, the geological characteristics, occurrence characteristics, microseismic (MS) activity laws, and rock mass fracture mechanism of several RCRs influenced by weak band were summarized to reveal the mechanism of recurrence of RCRs. Research shows that under the influence of weak band, (1) RCRs tends to occur in the area where the dip angle is large, and the strike intersects with the tunnel direction at a large angle and forms a small angle with the maximum principal stress. The width of the weak band typically ranges from 0.01 to 1 m, which is positively correlated with the final depth of rockburst pit. The strength of the weak band is relatively “soft” compared to the surrounding bedrock. (2) The depth of each rockburst pit in RCRs gradually decreases, the time interval between adjacent rockbursts gradually increases, and the maximum thickness of rock block in each rockburst gradually increases. (3) The maximum MS energy of MS events and the maximum apparent stress gradually decreased in the development process of RCRs. The region of stress concentration gradually extended to deeper zone, and the distance difference between stress concentration region and sidewall during each rockburst occurrence stage gradually decreased. (4) The effect of weak band on RCRs attributes to the excavation induced local stress concentration near the weak band, and the interface between the weak band and surrounding rock controls the boundary of the rockburst body. The “chain effect” of RCRs mainly shows that the promotion effect of the previous rockburst on the subsequent rockburst, by promoting the stress and rock fracture transferring to the deep zone, and the proportion of shear fractures increases.

MODIFICATION OF PINDIGA BENTONITE CLAY WITH DIDODECYLDIMETHYLAMMONIUM BROMIDES SURFACTANT FOR FOUNDRY USE

Bentonite clay from Pindiga, Gombe State, Nigeria, was surface modified with didodecyldimethylammonium bromides (DDAB) by the Base Exchange (cation exchange capacity) method for its possible use in foundries. The surfaces of the unmodified and modified Pindiga bentonite clay were characterised by means of spectroscopic, diffraction, and scanning methods (X-Ray fluorescence spectrometry (XRF)Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM).XRF showed that unmodified sample was rich of montmorillonite (MMt) with ca +2 as exchangeable cation, FTIR analysis revealed that unmodified water absorption causes stretching and bending vibrations for hydroxyl groups, with the most intense bands in the low-frequency region, while DDAB organo-bentonites showed slight changes in wave bands, with a strong methyl band and a weak methyl band indicative of long-chain linear aliphatic structure. The basal spacing of the unmodified bentonite sample was 1.52 nm, and after modification with DDAB, it improved to 2.1 nm as determined from the X-ray diffraction (XRD) analysis. Results of the SEM images revealed rougher surfaces with uniformly dispersed small particles of grain-like structures characteristic of the unmodified, while theorgano-modified bentoniterevealed clusters of different sizes and shapes, larger Fe 3+ ions replacing smaller Al 3+ ions at octahedral sites, discontinuous layers enveloping large grains, polygonal growth foams with octahedral and tetrahedral shapes, mixed layers of calcium bentonite, and particle sizes less than 200nm. The study concluded that modified bentonite with didodecyldimethylammonium bromides gives good microstructure, increases rigidity, and improve thermal stability, to the organoclays. Therefore, it is recommended that DDAB bentonite be used as binder for foundries.

ExoMol line lists – LVIII. High-temperature molecular line list of carbonyl sulphide (OCS)

ABSTRACT A new molecular line list covering wavelengths λ > 1 μm (the 0–10 000 cm−1 range) for the main isotopologue of carbonyl sulphide 16O12C32S is presented. The OCS line list, named OYT8, contains almost 2.5 billion transitions between 2.4 million rotation-vibration energy levels with the total angular momentum up to J = 223. It is suitable for high-temperature environments up to T = 2000 K. Line list calculations were performed with the variational nuclear motion code trove in conjunction with a highly accurate, empirically refined potential energy surface and a newly computed ab initio dipole moment surface of OCS. The OYT8 line list is adapted for high-resolution applications by replacing computed energy levels with empirically derived values of OCS where available. Comparisons of the OYT8 line list with other OCS line lists and spectra yields excellent agreement for both strong and weak spectroscopic bands. The increased coverage of the OYT8 line list and the many new spectral features that are available will greatly facilitate the future observation of OCS on exoplanets. Carbonyl sulphide joins a growing number of sulphur-bearing molecules available from the ExoMol database. The OYT8 line list along with the associated temperature- and pressure-dependent molecular opacities can be downloaded from www.exomol.com and the CDS astronomical database.

Synergistic effects of β-NaFeO2 ferrite nanoparticles for photocatalytic degradation, antibacterial, and antioxidant applications.

Here, synthesis and thorough characterization of β-NaFeO2 nanoparticles utilizing a co-precipitation technique is presented. XRD analysis confirmed a hexagonal-phase structure of β-NaFeO2. SEM revealed well-dispersed spherical nanoparticles with an average diameter of 45 nm. The FTIR spectrum analysis revealed weak adsorption bands at 1054 cm-1 suggested metal-metal bond stretching (Fe-Na). UV-Visible spectroscopy indicates a 4.4 eV optical band gap. Colloidal stability of β-NaFeO2 was evidenced via Zeta potential (-28.5 mV) and Dynamic Light Scattering (DLS) measurements. BET analysis reveals a substantial 343.27 m2 g-1 surface area with mesoporous characteristics. Antioxidant analysis indicates efficacy comparable to standard antioxidants, while concentration-dependent antibacterial effects suggest enhanced efficacy against Gram-positive bacteria, particularly Streptococcus. The Photocatalytic activity of β-NaFeO2 showed significant pollutant degradation (>90% efficiency), with increased degradation rates at higher nanoparticle concentrations, indicating potential for environmental remediation applications.

A Discrete Element Model of High-Pressure Torsion Test to Assess the Effect of Particle Characteristics in the Interface

Abstract Sand particles have been used since the early stages of the railway industry to increase adhesion at the wheel–rail contact. However, there is a limited understanding of how sand particle characteristics affect the tribological performance of the wheel–rail contact. In this work, the high-pressure torsion test used as a small-scale simulation of the interface is numerically modeled using the discrete element method (DEM). The DEM model is then utilized to investigate the effect of different particle characteristics on the frictional performance of wheel–rail contact which can provide more insight into micromechanical observations. The effects of various particle characteristics including their size, their number, the number of fragments the particles break into, and the parameters defining the behavior of the bonds between particle fragments on the coefficient of traction (COT) are systematically investigated. Results show that, in dry contacts, the coefficient of traction decreases when the size or number of sand particles increases. This can be attributed to the formation of weak shear bands between the fragments. Further investigation is needed for wet- and leaf-contaminated contacts. It is also found that the COT is more sensitive to the stiffness of the bond between the fragments of a broken particle compared to the strength of the bond. A limiting value for bond strength was identified, beyond which the sand particles exhibited ductile behavior rather than the expected brittle fracture. The findings from this study can be useful for future research on adhesion management in wheel–rail contact and the modeling approach can be scaled up to the full contact.

Time resolved and site selective luminescence of M2Ln3Sb3O14 (M = Mg, Ca): Multisite Eu3+ environments

Time resolved and site selective spectra at low temperatures have been recorded for M2Ln3Sb3O14 (M = Mg, Ca) doped with Eu3+ at concentrations of 1 and 0.1 at.%. The M = Mg spectra can be interpreted in a model with Eu3+ situated at the La3+ C2h (2/m) site, although weaker bands are indicative of antisites at expected nearest La3+ neighbours. A minority of the Eu3+ ions in the M = Ca system are also situated at C2h sites, but structural disorder leads to most of the Eu3+ ions experiencing more varied spectra and lower site symmetry.

Photocatalytic degradation of organic dyes in water using semiconductor ZnO nanoparticles synthesized using Crataegus mexicana extract

In this work, the synthesis of zinc oxide (ZnO) nanoparticles was made using an eco-friendly methodology with a natural extract. The fruit of tejocote (Crataegus mexicana) was used as a stabilizing agent for synthesizing zinc oxide nanoparticles (NPs). Once the NPs were obtained, diverse characterization techniques were used to determine the physicochemical and optical properties of the ZnO NPs; the ultraviolet–visible spectroscopy was used to determine the uv absorption spectra of ZnO NPs and the bandgap of the material, the FT-IR spectrum of the ZnO NPs shows the presence of the Zn–O bond at 560 cm−1, XRD results show that the ZnO NPs exhibit a hexagonal crystal structure zincite type, the SEM confirms slight agglomerations between nanoparticles, Also from TEM results, the nanoparticles present a quasi-spherical morphology with sizes ranging from 18.25 nm to 36.88 nm, indicating an influence of the concentration of the Crataegus mexicana extract in the synthesis process of ZnO NPs. Photoluminescence spectroscopy of ZnO NPs shows strong emission bands in the visible spectrum around 425 nm, 467 nm, and 492 nm, and weak emission bands in the UV spectrum were observed. Finally, a photocatalytic study was realized for the photodegradation of 5 pollutant dyes: methylene blue (MB), malachite green (MG), congo red (CR), rhodamine b (RB), and methyl orange (MO). The results show degradation of the organic dyes after 180 min by a photodegradation process where ZnO nanoparticles act as a photocatalyst, indicating that the synthesized ZnO nanoparticles have excellent photocatalytic properties.

Hydrothermal synthesis of (C5H14N2)[CoCl4]⸳0.5H2O: Crystal structure, spectroscopic characterization, thermal behavior, magnetic properties and biological evaluation

The organic-inorganic compound (C5H14N2)[CoCl4]⸳0.5H2O, I, was characterized by various physicochemical techniques. The X-ray diffraction analysis revealed that the compound crystallizes in the centrosymmetric space group C2/c of the monoclinic system. The atomic arrangement the Co(II) complex is built from isolated [CoCl4]2– anions, 1-methylpiperazine-1,4-diium [C5H14N2]2+ cations and free water molecules. The crystal structure study showed that the cohesion of I is assured through N–H···Cl and N–H···O hydrogen bonds giving birth to a 3-D architecture. Hirshfeld surface analysis revealed that Cl···H/H···Cl and H···H (58.5 and 36.4%, respectively) are the most significant interactions between species. Minor O···H/H···O interactions are also present. The compound was characterized by thermal analysis, TGA-DTA showed the removal of the co-crystallized water before 100 °C and a first mass loss at around 120 °C. Magnetic measurements are in good agreement with isolated, S = 3/2, tetrahedral [CoCl4]2− anions. The negative Weiss constant of -1.35 indicates single-ion anisotropy and very weak antiferromagnetic interactions. UV–visible spectroscopy reveals three weak absorption bands in the visible range due to the d-d electronic transitions typical of the Co(II) tetra-coordinated. A bioassay showed antibacterial activity against the gram negative Klebsiella pneumonia and gram positive Bacillus ceureus, Listeria monocytogenes, and Micrococcus lutues.

Syntheses and Spectroscopic Characterization of Selected Methyl Quinolinylphosphonic and Quinolinylphosphinic Acids; Rationalized based on DFT Calculation

Abstract: The quinoline derivatives arouse interest due to their broad spectrum of activity. The phosphorus compounds under investigation, quinolinylphosphonic and -phosphinic acids and aminophenylphosphonic and -phosphinic acids, possess potent bioactive properties, mimicking amino acids, phosphate esters, anhydrides, or carboxylate groups in enzymes. Despite its potential value, there is no reported example of quinolinylphosphonic or - phosphinic acids with phosphonic or phosphinic functional groups connected directly to the benzene ring in quinoline constitution. The selected quinoline derivatives have been synthesized by adopting the Skraup-Doebner-Von Miller reaction. To this end, the syntheses of aminophenylphosphonic and -phosphinic acids were conducted and afforded the target products with high yield. All structures have been proven by the combination of NMR, IR, MS, and HRMS techniques and were rationalized based on DFT calculation. The structures of triphenylphosphane oxide (TPO), diphenylphosphosphinic acid (1c), (tert-butyl)phenylphosphinic acid (1d) and bis(3-nitrophenyl)phosphinic acid (2c) were determined by single-crystal X-ray diffraction measurements. The Hirshfeld surface analyses for 1c, 1d and 2c were performed to analyze the intermolecular interactions in their crystal structures. According to our findings, the presence of numerous intermolecular PO•••H, NO•••H, and CH•••O contacts stabilizes the crystal structures. The NO•••H interactions manifest in the IR spectrum of 2c crystal as a narrow band with a maximum at 3088 cm-1. The PO•••H intermolecular interactions are attributed to a weak experimental band at 1288 cm-1.

Investigation of Visceral Leishmaniasis and Coinfection of Intestinal Parasites in HIV-Positive Patients

Objective: Parasitic infections are more frequently observed in immunosuppressed cases, such as those infected with human immunodeficiency virus (HIV). Furthermore, compared to immunocompetent cases, a more severe clinical course is observed in the immunosuppressed patient group. HIV-positive individuals have increased pathogenicity of parasites and may exhibit a wide range of clinical symptoms of varying severity that may result in mortality. Visceral leishmaniasis (VL) is a vector-borne disease and an important opportunistic infection seen in HIV/Acquired Immune Deficiency Syndrome (AIDS) cases, most notably in Southern Europe and Africa, where both infections are endemic. Several parasites namely toxoplasmosis, cryptosporidiosis, isosporiasis, cyclosporiasis, amebiasis, giardiasis, plasmodium, and strongyloidiasis are infections posing significant risk factors for these patient groups. Materials and Methods: In this study, visceral leishmaniasis was investigated serologically in serum samples and parasitic infections were analyzed by conventional methods in fecal samples from HIV-positive cases. Results: 5 of the 42 cases included in the study were female. The mean age of these cases was 38.7 years (19-66). Blastocystis spp was detected in 5 fecal samples obtained from HIV-positive cases. The rK39 dipstick test with serum samples yielded a very weak band in one case, while none of the other tests yielded a positive band. Conclusion: The regional prevalence of these latent infections, which can be subclinical in HIV-positive patients, is important to know. However, the literature lacks sufficient data on the situation in Turkey. In this study, the prevalence of enteric parasitic infections in people with HIV infection in our region was found to be low and VL was not detected.

Theoretically predicted CO2 lines near 700 nm not observed

We present an experimental study of carbon dioxide absorption in the transparency window near 700 nm, where different calculations predicted several extremely weak bands. The measurements were done using the optical frequency comb-assisted cavity ring-down spectrometer reaching sensitivity (noise-equivalent absorption) of 3.1⋅10−12 cm−1. None of 21 lines, predicted by the most comprehensive calculations, were detected in five separate spectral regions near 700 nm. Our estimated detection limit ranges between 3 and 21 times lower than the expected peak absorption in the conditions of the experiment.

D0 ferromagnetic display of zirconia nanocrystallites and the impact of gold doping on their structural, optical, and magnetic properties

[Formula: see text] ferromagnetism is currently under extensive investigation as an alternative to transition metal-doped dilute magnetic semiconductors in the continuously evolving field of spintronics and optoelectronic applications. The literature contains numerous conflicting sources regarding its origin, specifically in materials such as oxides, making it a subject of ongoing controversy. This work mainly centers on the interplay among gold doping, oxygen concentration, and resulting changes in the structural, optical, and magnetic characteristics, with a specific focus on [Formula: see text] ferromagnetism and room temperature ferromagnetism in sol–gel synthesized zirconia nanocrystals. The powder samples crystallized in a mixed monoclinic-tetragonal phase. The weak absorbance band around 280[Formula: see text]nm and the O-1s peak in X-ray photoelectron spectroscopy provide insights into the metastable tetragonal phase’s stability, attributed to oxygen vacancies. The bandgap slightly increases from 4.6[Formula: see text]eV to 5.0[Formula: see text]eV due to the transformation from a tetragonal to a monoclinic phase. Magnetic studies reveal room-temperature ferromagnetism induced by oxygen vacancies in undoped zirconia, while a shift from ferromagnetic to paramagnetic behavior occurs in gold-infused zirconia samples.

Water‐Ice Dominated Spectra of Saturn's Rings and Small Moons From JWST

AbstractJWST measured the infrared spectra of Saturn's rings and several of its small moons (Epimetheus, Pandora, Telesto, and Pallene) as part of Guaranteed Time Observation program 1247. The NIRSpec instrument obtained near‐infrared spectra of the small moons between 0.6 and 5.3 microns, which are all dominated by water‐ice absorption bands. The shapes of the water‐ice bands for these moons suggests that their surfaces contain variable mixes of crystalline and amorphous ice or variable amounts of contaminants and/or sub‐micron ice grains. The near‐infrared spectrum of Saturn's A ring has exceptionally high signal‐to‐noise between 2.7 and 5 microns and is dominated by features due to highly crystalline water ice. The ring spectrum also confirms that the rings possess a 2%–3% deep absorption at 4.13 microns due to deuterated water ice previously seen by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft. This spectrum also constrains the fundamental absorption bands of carbon dioxide and carbon monoxide and may contain evidence for a weak aliphatic hydrocarbon band. Meanwhile, the MIRI instrument obtained mid‐infrared spectra of the rings between 4.9 and 27.9 microns, where the observed signal is a combination of reflected sunlight and thermal emission. This region shows a strong reflectance peak centered around 9.3 microns that can be attributed to crystalline water ice. Since both the near and mid‐infrared spectra are dominated by highly crystalline water ice, they should provide a useful baseline for interpreting the spectra of other objects in the outer solar system with more complex compositions.

The GeoCarb greenhouse gas retrieval algorithm: simulations and sensitivity to sources of uncertainty

Abstract. The Geostationary Carbon Cycle Observatory (GeoCarb) was selected as NASA's second Earth Venture Mission (EVM-2). The scientific objectives of GeoCarb were to advance our knowledge of the carbon cycle, in particular, land–atmosphere fluxes of the greenhouse gases carbon dioxide (CO2) and methane (CH4) and the effects of these fluxes on the Earth's radiation budget. GeoCarb would retrieve column-integrated dry-air mole fractions of CO2 (XCO2), CH4 (XCH4) and CO (XCO), important for understanding tropospheric chemistry), in addition to solar-induced fluorescence (SIF), from hyperspectral resolution measurements in the O2 A-band at 0.76 µm, the weak CO2 band at 1.6 µm, the strong CO2 band at 2.06 µm, and a CH4/CO band at 2.32 µm. Unlike its predecessors (OCO-2/3, GOSAT-1/2, TROPOMI), GeoCarb would be in a geostationary orbit with a sub-satellite point centered over the Americas. This orbital configuration combined with its high-spatial-resolution imaging capabilities would provide an unprecedented view of these quantities on spatial and temporal scales accurate enough to resolve sources and sinks to improve land–atmosphere CO2 and CH4 flux calculations and reduce the uncertainty of these fluxes. This paper will present a description of the GeoCarb instrument and the L2 retrieval algorithms which will be followed by simulation experiments to determine an error budget for each target gas. Several sources of uncertainty will be explored, including that from the instrument calibration parameters for radiometric gain, the instrument line shape (ILS), the polarization, and the geolocation pointing, in addition to forward model parameters including meteorology and spectroscopy, although there are some other instrument-related sources of uncertainty that are left out for this study, including that from “smile”, the keystone effect, stray light, detector persistence, and scene inhomogeneity. The results indicate that the errors (1σ) are less than the instrument's multi-sounding precision requirements of 1.2 ppm, 10 ppb, and 12 ppb (10 %), for XCO2, XCH4, and XCO, respectively. In particular, when considering the sources of uncertainty separately and in combination (all sources included), we find overall RMSEs of 1.06 ppm for XCO2, 8.2 ppb for XCH4, and 2.5 ppb for XCO, respectively. Additionally, we find that, as expected, errors in XCO2 and XCH4 are dominated by forward model and other systematic errors, while errors in XCO are dominated by measurement noise. It is important to note that the GeoCarb mission was canceled by NASA; however, the instrument is still in development and will be delivered to NASA, in full, with the hope that it will eventually be adopted in a future mission proposal.

CRDS line-shape study of the (7–0) band of CO

We present the results of the spectral line-shape study of the first measurement of the extremely weak (7–0) band of the 12C16O molecule. Measurements were done with a highly sensitive cavity ring-down spectrometer. Collisional narrowing, analyzed in terms of speed-dependent effects, was observed for the first time for transitions with line intensities below 2⋅10−29 cm/molecule at 296 K. We provide a full set of line-shape parameters of the speed-dependent and regular Voigt profile analysis for 14 transitions from P and R branches. Experimental verification of a strong vibrational dependence of the pressure shifting described by the Hartmann model (Hartmann, 2009) is extended up to the sixth overtone highly sensitive to the model parameter.

ZnO nanomaterials with enhanced antimicrobial activity obtained by Eichhornia crassipes aqueous extract‐mediated synthesis

AbstractBACKGROUNDZinc oxide nanoparticles (ZnO NPs) were obtained through precipitation synthesis, using aqueous water hyacinth leaf extract (Eichhornia crassipes) under alkaline conditions. The effect of the extract on the physicochemical and antimicrobial properties of the ZnO was evaluated starting from concentrated extract (labeled as E100) and performing two dilutions of this concentrated extract at 50% and 25% in water (E50, and E25).RESULTSThe FTIR spectra revealed strong peaks at ≈3440 cm−1, corresponding to vibrations from OH stretching, and medium‐intense peaks at 1384 and 1327 cm−1, assigned to CC, COOH and COC vibrations, which are related to the presence of the extract; a weak band at 884 cm−1 and a broad band in the region below 600 cm−1 indicate the presence of ZnO. The hydrodynamic size of the ZnOE100, ZnOE50 and ZnOE25 samples were 202, 244 and 313 nm, respectively. No significant variations on the Eg value were observed. Field emission scanning electron microscopy images showed that the ZnO NPs have triangular‐like shapes and agglomeration of the NPs synthesized for the ZnOE25 sample. The minimum inhibitory concentration (MIC) of the ZnO NPs showed no significant effects related to the concentration the plant extract used.CONCLUSIONSVariations in particle size and zeta potential can be introduced in ZnO by varying the content of the extract; the presence of organic groups from the extract, along with a positive zeta potential value, can promote the bactericide effect of ZnO nanomaterials prepared by bio‐assisted synthesis. © 2024 Society of Chemical Industry (SCI).

Alkali and mixed alkali effect: Spectral investigations on Sm3+ and Dy3+ ions doped zinc tungstate borophosphate glasses

In this study, we provide the spectra data of borophosphate zinc tungstate glasses doped with Sm3+or Dy3+ ions based on alkali and mixed alkali oxides. In order to describe the spectroscopic properties of the manufactured Sm3+ and Dy3+ glasses, we used XRD, EDAX, FT-IR, FT-Raman, Absorption, and PL Spectra. The amorphous nature of glass has been studied by looking at its X-ray diffraction data. Glasses that have been doped with Sm3+ and Dy3+ ions have been shown to exhibit significant absorption bands at 401 nm in the Vis-NIR range, as well as three weak bands at 360, 373, and 473 nm, and bands centered at roughly 1079, 1216, 1363, and 1455 nm in the NIR area. Multiple absorption bands at various wavelengths, from 796 nm to 1667 nm, are present in both series C and D glasses. After being excited at 402 nm, the emission spectra of Sm3+ doped glasses show three emission transitions at 562, 598, and 645 nm. The transition at 598 nm has been proven to produce brilliant orange-red light. Excitation at 350 nm in the emission spectra of Dy3+ doped glasses causes three emission transitions to occur at 482, 574, and 664 nm. The 574 nm emission band offers the clearest evidence of yellow emission. Energy level diagrams have been used to describe the emission process that occurs in these glasses.

Determining the Structural Properties and Vibrational Modes of Annealed Lead Composite Material Deposit

Techniques for effectively harnessing lead (Pb) deposits for optimum utilization have attracted a lot of research interest. Results obtained from investigating the elemental composition, vibrational modes, and structural properties of a fired Pb composite deposit, which is purified using an electric kiln furnace and further annealed in palladium‐diffused hydrogen ambient, are reported in the present study. Both atomic force microscopy and scanning electron microscopy analysis on the deposit indicate that the Pb composite is composed of crystal‐like morphology. The vibrational modes obtained from the material are identical to the Raman spectrum reported for PbSO4. Also, data acquired from the energy‐dispersive X‐ray analysis of the annealed Pb composite material confirm the presence of zinc, carbon, silicon, sulfur, and oxygen in the material. At the same time, Pb appears to be the primary constituent with reference to its weight percentage composition compared to other elements. The findings from the present study may be vital for providing an improved understanding of the electronic and structural properties of the annealed Pb composite deposit while promoting the development of a feasible approach for the recovery and recycling of Pb for future related applications.

Molecular engineering of D-π-A-type structures based on nitrobenzofurazan (NBD) derivatives for both organic solar cells and nonlinear optical response

The electronic, photo-physical, and nonlinear optical (NLO) properties of small molecules from nitrobenzofurazan (NBD) derivatives have been fine-tuned through the introduction of various electron-donating groups (OH, OCH3, and N(CH3)2). These designed small molecules follow a donor-linker-acceptor (D-π-A) motif, featuring p-phenylene as the electron donor, thiophene as the π-conjugated bridge, and NBD as the electron acceptor. To achieve this, we conducted density functional theory (DFT) and its time-dependent counterpart, TD-DFT calculations. Our exploration of the structure–property relations among the molecular parameters revealed that the introduction of donor groups has a notable influence on lowering the highest occupied molecular orbital (HOMO) energy levels. Analysis of the absorption–emission spectra showed a prominent π → π* band followed by a weaker n → π* band.Remarkably, three compounds substituted with electron-donor group’s exhibit anti-Stokes fluorescence (ASF) emission. Moreover, the relatively weak emission band associated with the charge transfer n → π* transition of the nitro-functionalized molecules is quenched, similar to the π → π* electronic transition. Consequently, these compounds display a lower bandgap energy, resulting in a broad optical absorption profile with emissions spanning from green to yellow. Notably, when tuning the NLO properties, push-type groups exhibit demonstrate exceptionally high hyperpolarizabilities. Furthermore, our investigation unveiled excellent photovoltaic properties, with these compounds achieving an impressive power conversion efficiency (PCE) of approximately 7 %.Additionally, we conducted complementary topological analyses, including Molecular Electrostatic Potential (MEP), Quantum Theory of Atoms in Molecules (QTAIM), Reduced Density Gradient (RDG), Electron Localization Function (ELF), and the Localized Orbital Locator (LOL), to gain insights into both intra- and intermolecular interactions. These findings strongly underscore the effectiveness of modifying the electron-donating group capability in D-π-A conjugated systems as a strategy for enhancing the optoelectronic properties of organic photovoltaic (PV) devices, as well as their NLO responses.