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Two‐dimensional polymers (2DPs) and their layer‐stacked 2D covalent organic frameworks have recently emerged as nonlinear optical (NLO) materials for potential applications in optics. However, the chemistry for designing third‐order NLO 2DP films with large nonlinear absorption coefficient (β) has remained a mystery. Herein, three highly crystalline porphyrin‐integrated 2D polyimines (named as 2DPI‐Zn‐Azo, 2DPI‐2H‐Azo, and 2DPI‐Zn), which are homogeneous films showing large lateral areas over cm2, uniform transparency, and thickness of tens of nanometers are reported. Particularly, the 2DPI‐Zn‐Azo film comprising zinc porphyrin and –NN– displays a large saturable absorption under 532 nm and the highest β (−1.88 × 105 cm GW−1) among the three 2D polyimines, that is also 2–5 orders of magnitude higher than the state‐of‐art performance of photoactive small molecules, porphyrin‐integrated 2DPs, and inorganic 2D materials. Control experiments in combination with theoretical calculation discover that the embedding of metal centers and –NN– results in highly delocalized π‐electrons and narrow bandgap in 2DPI‐Zn‐Azo, which enables fast transfer of the photogenerated electrons after the light‐excited charge separation, thus boosting the NLO performance. This work opens up a new path for the construction of highly efficient third‐order NLO film materials, and pushes the development of 2DPs for optics and optoelectronics. [ABSTRACT FROM AUTHOR]

In response to the limitations of current transparent window materials in γ-ray shielding scenarios, herein, high-lead equivalent (0.865 mmpb) Yb 2 Hf 2 O 7 transparent ceramics (YbHO-TCs) were prepared via a solid-state reaction and vacuum sintering. The fabricated YbHO-TC shows high transparency, where the in-line transmittance up to 78.9 % at 1200 nm, which is extremely close to their theoretical limit (79 %). Additionally, the linear absorption coefficient of YbHO-TC for γ-rays is 0.482, approximately twice that of the state-of-the-art lead glass materials widely employed in radiation-shielding windows. Remarkably, YbHO-TC displayed no discoloration, and its in-line transmittance exhibited little change even when exposed to a radiation dose as high as 800 kGy. The innovative developed YbHO-TC integrates high transparency and high-lead equivalent properties, not only rending them highly promising for deployment as γ-rays shielding windows but also inspiring the controllable design of high-performance optical windows tailored for use in radiation shielding applications. [ABSTRACT FROM AUTHOR]

Silver sulfide (Ag2S) chalcogenide compound can be a viable absorber in the applications of thin film solar cells owing to its optimum bandgap of 1.1 eV and high absorption coefficient. Herein, we propose a novel Ag2S‐based n‐CdS/p‐Ag2S/p+‐SnS double‐heterojunction solar cell. The numerical analysis of the device has been performed with SCAPS‐1D (Solar Cell Capacitance Simulator). In the case of single heterojunction, n‐CdS/p‐Ag2S manifests an efficiency of 19.75%, where VOC = 0.66 V, JSC = 36.99 mA/cm2 and FF = 81.50%. However, Ag2S‐based double‐heterojunction device with optimized structure provides the efficiency of 29.51% with VOC = 0.81 V, JSC = 42.81 mA/cm2 and FF =85.24%. The noteworthy augmentation of VOC and JSC in double‐heterojunction results from the reduction in surface recombination velocity and rise in built‐in voltage in the p‐Ag2S/p+‐SnS hetero‐interfaces that promote the higher efficiency of the device. These theoretical insights indicate a path for fabrication of an efficient Ag2S based thin film solar cell. [ABSTRACT FROM AUTHOR]

The authors studied Poly (methyl methacrylate) also called PMMA films with different concentrations of Poly (9, 9′-di-n-octylfuorenyl-2, 7-diyl) also called PFO and concluded that 1% PFO blended with PMMA is the best choice for opto-electronic applications. In the present study, the authors prepared nanocomposite films of PMMA + 1% PFO + different concentrations of TiO2 nanoparticles. The resulting films were subjected to FTIR, XRD, UV–visible, fluorescence and electrical conductivity studies. The polymer matrix undergoes modifications in its molecular and microstructural characteristics as evidenced by FTIR and XRD results. The addition of TiO2 nanoparticles leads to a uniform dispersion and good interaction with the blend matrix resulting in homogeneous films. The additional peaks were found at a wavenumber of 3620 cm−1 in FTIR can be attributed to stretching vibration of TiO2. The presence of TiO2 nanoparticles is confirmed by the distinctive diffraction peaks observed at 25.4°, 37.8°, 48.3°, 54.3°, 55.2°, and 62.8°. With a shift in the absorption peak towards higher wavelengths, the nanocomposites show greater absorption in the UV and visible regions. As the concentration of TiO2 increases, the optical parameters such as absorption coefficient, extinction coefficient, Urbach energy, refractive index and optical conductivity also increase. The direct optical band gap of the PNC films decreases from 5.03 to 3.06 eV and indirect band gap decreases from 4.52 to 1.92 eV at 10 wt% of TiO2 concentration. The addition of TiO2 nanoparticles to the PFO/PMMA matrix resulted in an increase in fluorescence emission intensity. The AC electrical conductivity exhibits increasing trend with frequency in Audio-Frequency range. Thus TiO2 nanoparticles improve the overall optical, electrical, and structural properties of PFO-PMMA nanocomposites. This means that they can be used in a variety of optoelectronic and advanced optical devices. [ABSTRACT FROM AUTHOR]

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This research introduces an innovative application of physics-informed neural networks (PINNs) to tackle the intricate challenges of radiative transfer (RT) modelling in exoplanetary atmospheres, with a special focus on efficiently handling scattering phenomena. Traditional RT models often simplify scattering as absorption, leading to inaccuracies. Our approach utilizes PINNs, noted for their ability to incorporate the governing differential equations of RT directly into their loss function, thus offering a more precise yet potentially fast modelling technique. The core of our method involves the development of a parametrized PINN tailored for a modified RT equation, enhancing its adaptability to various atmospheric scenarios. We focus on RT in transiting exoplanet atmospheres using a simplified 1D isothermal model with pressure-dependent coefficients for absorption and Rayleigh scattering. In scenarios of pure absorption, the PINN demonstrates its effectiveness in predicting transmission spectra for diverse absorption profiles. For Rayleigh scattering, the network successfully computes the RT equation, addressing both direct and diffuse stellar light components. While our preliminary results with simplified models are promising, indicating the potential of PINNs in improving RT calculations, we acknowledge the errors stemming from our approximations as well as the challenges in applying this technique to more complex atmospheric conditions. Specifically, extending our approach to atmospheres with intricate temperature-pressure profiles and varying scattering properties, such as those introduced by clouds and hazes, remains a significant area for future development. [ABSTRACT FROM AUTHOR]

The hydrophobic reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) was investigated as part of a cloud-point extraction (CPE) system for the spectrophotometric determination of Zn(II). In the system, complexes with different stoichiometries, including 1:1 and 2:2 (Zn:HTAR), are formed. Their ground-state equilibrium geometries were optimized at the B3LYP/6-31G level of theory. The obtained structures were then used to calculate vertical excitation energies in order to generate theoretical UV/Vis absorption spectra. The comparison between theoretical and experimental spectra demonstrated that, under optimal conditions, a binuclear complex containing oxygen-bridging atoms is the dominant species. The absorbance was found to be linearly dependent on the concentration of Zn(II) within the range of 15.7 to 209 ng mL−1 (R2 = 0.9996). The fraction extracted (%E), logarithm of the conditional extraction constant (log Kex), and molar absorption coefficient (ε) at λmax = 553 nm were calculated to be 98.3%, 15.9, and 4.47 × 105 L mol−1 cm−1, respectively. The method developed is characterized by simplicity, convenience, profitability, sensitivity, and ecological friendliness. It has been successfully applied to the analysis of pharmaceutical and industrial samples. [ABSTRACT FROM AUTHOR]

Silole- and phosphole-containing polycyclic aromatic compounds have attracted significant attention in the field of organic functional materials. The structure of the aromatic units has great impact on the photophysical properties of the resulting silole- and phosphole-containing polycyclic aromatic compounds. Here, dibenzo-fused naphtho[2,3-b:6,7-b′]disilole (NDS) and naphtho[2,3-b:6,7-b′]diphosphole (NDP), where a naphthalene unit is arranged between two silole and phosphole units, respectively, were designed and synthesized. The solid-state structures of them were confirmed by X-ray crystallographic analysis. The photophysical properties were evaluated by UV−vis absorption and photoluminescence spectroscopies and compared with those of their related compounds, such as dibenzo-fused silolo[3,2-b]silole and benzo[1,2-b:4,5-b′]disilole, ever reported. The longest wavelength absorption band of a series of silole-fused compounds was found to be red-shifted in the order benzo[1,2-b:4,5-b′]disilole < NDS < silolo[3,2-b]silole derivatives. For a series of phosphole-fused compounds, π-extension from phospholo[3,2-b]phosphole to NDP derivatives induces the lower absorption coefficient of the longest wavelength absorption band and the red-shift of the second longest wavelength absorption band. Both NDS and NDP exhibit much lower fluorescence quantum yields than their related compounds. [ABSTRACT FROM AUTHOR]

Essential Climate Variables (ECVs) like ocean colour provide crucial information on the Optically Active Constituents (OACs) of seawater, such as phytoplankton, non-algal particles, and coloured dissolved organic matter (CDOM). The challenge in estimating these constituents through remote sensing is in accurately distinguishing and quantifying optical and biogeochemical properties, e.g., absorption coefficients and the concentration of chlorophyll a (Chla), especially in complex waters. This study evaluated the temporal and spatial variability of bio-optical properties in the coastal waters of the Western Iberian Coast (WIC), contributing to the assessment of satellite retrievals. In situ data from three oceanographic cruises conducted in 2019–2020 across different seasons were analyzed. Field-measured biogenic light absorption coefficients were compared to satellite estimates from Ocean-Colour Climate Change Initiative (OC-CCI) reflectance data using semi-analytical approaches (QAA, GSM, GIOP). Key findings indicate substantial variability in bio-optical properties across different seasons and regions. New bio-optical coefficients improved satellite data retrieval, reducing uncertainties and providing more reliable phytoplankton absorption estimates. These results highlight the need for region-specific algorithms to accurately capture the unique optical characteristics of coastal waters. Improved comprehension of bio-optical variability and retrieval techniques offers valuable insights for future research and coastal environment monitoring using satellite ocean colour data. [ABSTRACT FROM AUTHOR]

Diatomites are well-known mineral materials formed thousands of years ago from the skeletons of diatoms. They are found in many places around the world and have a wide range of applications. This article presents innovative research related to the possibility of using diatomite as a filler in composites to improve their sound absorption properties. The results of the study of the effect of diatomite processing (calcination) and its degree of fineness on the sound absorption coefficient of thermoplastic composites are presented. Three fractions of diatomite (0 ÷ 0.063 mm; 0.5 ÷ 3 mm; 2 ÷ 5 mm) and its variable mass proportion (0, 25, and 50 wt.%) were used. The composites were made with flax fibers as a reinforcement, polylactide as a matrix, and diatomite as an additional filler. This paper also presents the results of oxide chemical composition, diatomite mineral phase composition, morphology, and thermal conductivity coefficient of all diatomite fractions studied. In addition, the average particle size for diatomite powder was also determined. The most important of the studies was the determination of the acoustic properties of the aforementioned composites. As a result of the tests, it was found that the smallest fraction of diatomite particles and a variant without thermal treatment give the best effect in terms of sound absorption. [ABSTRACT FROM AUTHOR]

Material development in acoustic engineering plays a significant role in various applications, such as industrial noise control. It is important and relevant to consider alternative materials capable of reducing noise levels in different frequency ranges. One commonly used material in engineering structures is epoxy adhesive compositions. Favoring the use of adhesive compositions are their main characteristics, including weight reduction in structures, corrosion resistance, relatively low manufacturing costs, and high mechanical strength. This paper aims to discuss the relationship between the mechanical properties of modified epoxy adhesives, their structure, and sound absorption efficiency. The subjects of this study were specimens of an epoxy composition in the cured state. Acoustic absorption coefficients were evaluated using a dual-microphone impedance tube, and tensile, compressive, and bending strength properties were determined using a testing machine. The impact strength of the compositions was also investigated. An analysis of the structure of the adhesives in the cured state was carried out using a scanning electron microscope. The test specimens were made from Epidian 5 epoxy resin cured with a polyamide PAC curing agent. Nanobent ZR2 aluminosilicate in an amount of 1%, CaCO3 calcium carbonate in an amount of 5%, and CWZ-22 activated carbon in an amount of 20% were used as modifiers. The conducted studies revealed that the highest tensile strength was obtained for the adhesive composition with the addition of ZR2 filler. The highest compressive strength was exhibited by the adhesive composition with the addition of CWZ-22 filler. The highest flexural strength was demonstrated by the unmodified composition. For all the tested adhesive compositions, low sound absorption values were achieved, with a maximum of approximately 0.18. From the perspective of the reduction index R, it was observed that these samples performed better in reduction than in absorption. The best values were achieved in the compositions modified with CaCO3. [ABSTRACT FROM AUTHOR]

In the present communication, binary (ZnO:Ga 2 O 3 - 1:1 (ZGO), ZnO:Ga 2 O 3 - 2:1 (GaZn))/ternary (EZG (Eu 2 O 3 : ZnO: Ga 2 O 3 (1:1:1)), MZG (MgO: ZnO: Ga 2 O 3 (1:1:1)) NCs are synthesized by P i p e r b e t l e leaves extract as a reducing agent followed by calcination at 600 °C for 3 h. The Bragg reflections confirms the formation of single phase cubic symmetry with F d 3 m space group in ZGO NCs whereas reflections related individual metal oxides are observed in the GaZn, EZG and MZG NCs. The irregular size and shaped nanoparticles are observed in all the synthesized NCs. The tuned band gap was found to be in the range of 3.08 to 3.11 eV. The optical nonlinearity of the specimens was analyzed using the open aperture Z-scan technique. The material demonstrated reverse saturable absorption attributed to a two-photon absorption (2PA) process. The non linear absorption coefficient follows the order MZG > GaZn > ZGO > EZG. However, the optical limiting threshold follows the order ZGO > GaZn > MZG > EZG NCs with increase in energy band gap. These outcomes distinctly indicate the superior potential of GaZn binary NCs for optical limiting applications. This characteristic is advantageous for shielding sensors and the human eye, safeguarding them against the detrimental effects of intense green laser radiation. [ABSTRACT FROM AUTHOR]

This study demonstrates the use of computational methods to simulate the molecular dynamics involved in hemoglobin concentration sensing, utilizing Material Studio and the TCAD Silvaco device simulator. A non-invasive and flexible Graphene/MoS2 heterostructure has been proposed for sensing hemoglobin concentration in blood samples. The findings reveal a notable shift in the wavelength-dependent refractive index and extinction coefficient, as well as significant changes in the absorption coefficient and reflectivity of the Graphene/MoS2 heterostructure in response to different hemoglobin concentrations, specifically within an approximate range of 0.3 μm to 1 μm. Moreover, the spectral response of the heterostructure demonstrates that at a particular wavelength of approximately 600 nm, a maximum response is obtained. This wavelength can be considered optimal for detecting various levels of hemoglobin using this heterostructure. The anticipated outcome is a comprehensive understanding of the fundamental principles, ultimately resulting in the development of an exceptionally sensitive platform for detecting hemoglobin concentration. [ABSTRACT FROM AUTHOR]

In practical engineering, noise and impact hazards are pervasive, indicating the pressing demand for materials that can absorb both sound and stress wave energy simultaneously. However, the rational design of such multifunctional materials remains a challenge. Herein, inspired by cuttlebone, we present bioinspired architected metamaterials with unprecedented sound-absorbing and mechanical properties engineered via a weakly-coupled design. The acoustic elements feature heterogeneous multilayered resonators, whereas the mechanical responses are based on asymmetric cambered cell walls. These metamaterials experimentally demonstrated an average absorption coefficient of 0.80 from 1.0 to 6.0 kHz, with 77% of the data points exceeding the desired 0.75 threshold, all with a compact 21 mm thickness. An absorptance-thickness map is devised for assessing the sound-absorption efficiency. The high-fidelity microstructure-based model reveals the air friction damping mechanism, with broadband behavior attributed to multimodal hybrid resonance. Empowered by the cambered design of cell walls, metamaterials shift catastrophic failure toward a progressive deformation mode characterized by stable stress plateaus and ultrahigh specific energy absorption of 50.7 J/g—a 558.4% increase over the straight-wall design. After the deformation mechanisms are elucidated, a comprehensive research framework for burgeoning acousto-mechanical metamaterials is proposed. Overall, our study broadens the horizon for multifunctional material design. Noise and impact hazards are pervasive in engineering, necessitating materials capable of absorbing both sound and stress wave energy. Here, we present bioinspired metamaterials with exceptional sound-absorbing and mechanical properties using a weakly-coupled design strategy. These materials incorporate multi-layered resonators for superior acoustic performance and cambered cell walls for enhanced structural strength. They achieve an average absorption coefficient of 0.80 across the 1.0 to 6.0 kHz range, all within a sleek 21 mm thickness. Furthermore, the design transitions failure modes from catastrophic to progressive, resulting in a remarkable 558.4% increase in energy absorption compared to conventional designs. [ABSTRACT FROM AUTHOR]

The oxide and halide perovskite materials with a ABX3 structure exhibit a number of excellent properties, including a high dielectric constant, electrochemical properties, a wide band gap, and a large absorption coefficient. These properties have led to a range of applications, including renewable energy and optoelectronics, where high-performance catalysts are needed. However, it is difficult for a single structure of perovskite alone to simultaneously fulfill the diverse needs of multiple applications, such as high performance and good stability at the same time. Consequently, perovskite nanocomposites have been developed to address the current limitations and enhance their functionality by combining perovskite with two or more materials to create complementary materials. This review paper categorizes perovskite nanocomposites according to their structural composition and outlines their synthesis methodologies, as well as their applications in various fields. These include fuel cells, electrochemical water splitting, CO2 mitigation, supercapacitors, and optoelectronic devices. Additionally, the review presents a summary of their research status, practical challenges, and future prospects in the fields of renewable energy and electronics. [ABSTRACT FROM AUTHOR]

Significance: Developing stable, robust, and affordable tissue-mimicking phantoms is a prerequisite for any new clinical application within biomedical optics. To this end, a thorough understanding of the phantom structure and optical properties is paramount. Aim: We characterized the structural and optical properties of PlatSil SiliGlass phantoms using experimental and numerical approaches to examine the effects of phantom microstructure on their overall optical properties. Approach: We employed scanning electron microscope (SEM), hyperspectral imaging (HSI), and spectroscopy in combination with Mie theory modeling and inverse Monte Carlo to investigate the relationship between phantom constituent and overall phantom optical properties. Results: SEM revealed that microspheres had a broad range of sizes with average (13.47 ± 5.98) μm and were also aggregated, which may affect overall optical properties and warrants careful preparation to minimize these effects. Spectroscopy was used to measure pigment and SiliGlass absorption coefficient in the VIS-NIR range. Size distribution was used to calculate scattering coefficients and observe the impact of phantom microstructure on scattering properties. The results were surmised in an inverse problem solution that enabled absolute determination of component volume fractions that agree with values obtained during preparation and explained experimentally observed spectral features. HSI microscopy revealed pronounced single-scattering effects that agree with single-scattering events. Conclusions: We show that knowledge of phantom microstructure enables absolute measurements of phantom constitution without prior calibration. Further, we show a connection across different length scales where knowledge of precise phantom component constitution can help understand macroscopically observable optical properties. [ABSTRACT FROM AUTHOR]

A simplified model of the absorption coefficient of traditional Helmholtz resonators (THR) was established, and the influence of different geometric parameters on the absorption coefficient of THR was analyzed. To realize the low-frequency broadband acoustic structure design, an accurate theoretical model for the sound absorption coefficient of the curled acoustic metasurface (CAM) unit was established. Based on the complex frequency plane method (CFPM), the CAM units with perfect sound absorption at four discrete frequencies were designed. The low-frequency broadband acoustic metasurfaces in parallel under decoupled and coupled conditions were studied, and the thickness is only 12 mm. The high efficiency of sound absorption above 0.8 was achieved in the frequency range of 758 Hz–940 Hz. The experiment verifies the efficient sound absorption effect of the CAM unit and the broadband sound absorption effect under coupled conditions. The research in this paper has a certain potential applications for low-frequency broadband noise control technology. [ABSTRACT FROM AUTHOR]

A process for creating a macroporous silicon substrate on which a layer of titanium dioxide was deposited using the atomic-layer deposition method is described. Electrochemical etching was used to form the macroporous structure of the substrate. TiO2 was deposited using an SI PEALD setup. The morphology, structure, and optical properties of the deposited TiO2 film were assessed using scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy, spectral ellipsometry in the range 240–1000 nm, and Raman spectroscopy. Raman spectra revealed peaks at 144, 194, 397, and 639 cm–1 that were characteristic of the TiO2 anatase modification. The absorption coefficient and optical band gap width of the deposited film were determined based on the calculated ellipsometric parameters. [ABSTRACT FROM AUTHOR]

The formation of the stable layer below about 2 x 106 Pa pressure level (about 20 km altitude) of the atmosphere of Venus detected by in situ observations is investigated by the use of a radiative-convective equilibrium model. We demonstrate that, assuming mixing ratio profiles of absorbers to be at the upper limits of the observed ranges for H2O and SO2 and the lower limit for CO, a stable layer forms as a radiative-convective equilibrium state, but its stability is lower than the observed one. Also, increasing the continuum absorption coefficient of CO2 and/or H2O, which are not well constrained observationally or experimentally, results in the formation of a stable layer whose stability is comparable to the observed one. These results suggest a practical method to form the stable layer in the dynamical models of the Venus atmosphere. Further, these results indicate that the important targets of future observations and laboratory measurements are to obtain more precise profiles of the mixing ratios of H2O, CO, and SO2 in the Venus atmosphere, and to determine the continuum absorption coefficients of those. [ABSTRACT FROM AUTHOR]

Context: Myocardial infarction is one of the major health challenges. It is of great significance to develop potential delivery carriers for new anti-myocardial infarction drugs. In this paper, based on first-principles calculations, monolayer WS2 with excellent photoelectric properties was verified as a carrier for the anti-myocardial infarction drug amiodarone (AMD). Studies have shown that the WS2-adsorbed AMD system (WS2@AMD) maintains structural stability and produces an adsorption energy of—2.12 eV. Mulliken charge analysis shows that electrons are transferred from WS2 atoms to AMD atoms. Among them, C, N and O obtained the maximum values of 0.51,0.37 and 0.56 e electrons, respectively, while H and I lost the maximum values of 0.32 and 0.24 e electrons, respectively. The optical response of WS2 adsorbed AMD system is similar to that of WS2. The light absorption coefficients of the two materials in the near ultraviolet region and the visible region can reach the order of 105 cm−1 and 104 cm−1, and the strain makes the light absorption peak red-shifted. The feasibility of temperature-controlled release mechanism of WS2 as AMD carrier was discussed. This theoretical work helps to improve the performance of two-dimensional nanomaterials and make them better as drug delivery carriers to improve the therapeutic effect of myocardial infarction. These results indicate that the WS2 monolayer has potential applications in the development of drug delivery carriers. Methods: In this study, based on first-principles calculations, the CASTEP simulation software package was used to study the structure and properties of materials. The interaction between electrons and ions is considered by using Ultrasoft pseudopotentials. In order to eliminate the spurious interaction between adjacent structures caused by periodic calculations, a vacuum space no less than 18 Å is placed in the vertical direction if necessary. Different functions may produce different density functional calculation results. Due to the low sensitivity of the crystal structure to the calculation details, the PBE functional under the generalized gradient approximation (GGA) was initially used for structural optimization, and the energy cutoff value was set to 500 eV. Grimme 's dispersion correction was used to make the results more accurate. The Brillouin zone (BZ) is sampled by a 7 × 7 × 1 K-point grid to ensure the reliability of the original lattice calculation. The lattice vector and atomic coordinates are relaxed, and the tolerance of each atom is less than 0.01 eV/Å. The energy tolerance at the atomic position is less than 10–7 eV/atom. When calculating the band gap, the HSE06 hybrid functional is used to modify the optimized structure of the PBE functional to obtain more accurate results. Spin-polarized DFT calculations were performed to calculate the electronic structure. [ABSTRACT FROM AUTHOR]

The construction of anatase/rutile heterojunctions in TiO2 is an effective way of improving the CO2 photoreduction activity. Yet, the origin of the superior photocatalytic performance is still unclear. To solve this issue, the band edges between anatase and rutile phases were theoretically determined based on the three-phase atomic model of (112)A/II/(101)R, and simultaneously the CO2 reduction processes were meticulously investigated. Our calculations show that photogenerated holes can move readily from anatase to rutile via the thin intermediated II phase, while photoelectrons flowing in the opposite direction may be impeded due to the electron trapping sites at the II phase. However, the large potential drop across the anatase/rutile interface and the strong built-in electric field can provide an effective driving force for photoelectrons' migration to anatase. In addition, the II phase can better enhance the solar light utilization of (112)A/(100)II, including a wide light response range and an intensive optical absorption coefficient. Meanwhile, the mixed-phase TiO2 possesses negligible hydrogenation energy (CO2 to COOH*) and lower rate-limiting energy (HCOOH* to HCO*), which greatly facilitate CH3OH generation. The efficient charge separation, strengthened light absorption, and facile CO2 reduction successfully demonstrate that the anatase/rutile mixed-phase TiO2 is an efficient photocatalyst utilized for CO2 conversion. [ABSTRACT FROM AUTHOR]

Photodetectors converting light into electrical signals are crucial in various applications. The pursuit of high-performance photodetectors with high sensitivity and broad spectral range simultaneously has always been challenging in conventional semiconductor materials. Graphene, with its zero bandgap and high electron mobility, is an attractive candidate, but its low light absorption coefficient restricts its practical application in light detection. Integrating graphene with light-absorbing materials like PbS quantum dots (QDs) can potentially enhance its photodetection capabilities. Here, this work presents a broadband photodetector with enhanced sensitivity based on a graphene–PbS QD heterostructure. The device leverages the high carrier mobility of graphene and the strong light absorption of PbS QDs, achieving a wide detection range from ultraviolet to near-infrared. Employing a simple spinning method, the heterostructure demonstrates ultrahigh responsivity up to the order of 107 A/W and a specific detectivity on the order of 1013 Jones, showcasing significant potential for photoelectric applications. [ABSTRACT FROM AUTHOR]

This study is aimed to investigate the effects of introducing dysprosium (Dy) into Zn-based hydroxyapatite (HAp) at various concentrations (0.45, 0.90, 1.35 and 1.80%). The structural and optical properties of pure and doped HAp were thoroughly examined through theoretical and empirical analyses, including X-ray diffraction, Raman spectroscopy and Fourier transform infrared (FTIR) studies. The results confirmed the successful incorporation of Dy into the HAp lattice without significantly affecting its thermal stability or stoichiometry. The introduction of Dy into Zn-based HAp led to notable alterations in several material parameters. The lattice parameters, crystallinity, lattice stress, strain and anisotropic energy density varied with different Dy concentrations. In comparison with undoped HAp, all Dy-doped Zn-based HAps exhibited reduced crystallite size values, indicating a change in the microstructure. Furthermore, the material density increased from 3.159 to 3.228 g cm−3 with Dy doping. The band gap (BG), an important parameter for optical applications, is consistently decreased from 4.6 to 3.9 eV as the Dy concentration increased. This decrease in BG suggests the potential for improved photocatalytic or optoelectronic properties in Dy-doped Zn-based HAp. Additionally, the linear absorption coefficient (LAC) increased, indicating enhanced light absorption. Overall, this study provides a comprehensive understanding of structural and optical modifications induced by Dy doping in Zn-based HAp. These findings contribute to the potential application of Dy-doped Zn-based HAp in various fields, including biomedicine, photocatalysis and optoelectronics. [ABSTRACT FROM AUTHOR]

In this study, the optical properties of porous silicon (PSi), such as the dielectric function, absorption coefficient, bandgap, reflectivity and refractive index, were studied as a function of porosities ranging from 3% to about 40% by using a supercell model in an ab-initio pseudo-potential plane wave (PP-PW) method based on density functional theory (DFT). To validate these theoretical results, various PSi samples were prepared by varying the etching parameters to achieve similar porosities. The PSi samples were subjected to UV–vis spectrophotometry in order to measure their reflectivity. The refractive indexes predicted by DFT were compared to those obtained by the Fresnel equation and the effective medium approximation methods (EMA), particularly Bruggeman's, Looyenga's and del Rio's model (dRZW). These studies showed that the PSi dielectric constant decreases with increasing porosity, which is consistent with a decrease in the refractive index. In addition, as the porosity of PSi rises, the bandgap energy values increase, which is closely related to the decrease in the refractive index. For low porosity, DFT and Looyenga refractive indexes fit better than dRZW or Bruggeman. Furthermore, when the porosity is increased, DFT gives similar results as dRZW and is better than the Bruggeman method. Moreover, at medium porosity (28 or 40%), DFT and EMA models agree well with the experimental refractive indexes of PSi. [ABSTRACT FROM AUTHOR]

Monitoring and protecting flowing watercourses is a complex and challenging task that requires the collaboration and coordination of various stakeholders such as governments, industries, farmers, consumers and environmental groups. The study of the dynamics of the concentration of polluting factors and especially the concentrations of heavy metals and highlighting a seasonal variation is a necessary element from this point of view. In this article, we present the results of our analyses carried out in two measurement campaigns executed in 10 monitoring points along the Danube River, between Braila city and Isaccea city in the pre-deltaic area, during the summer season and autumn season 2022. The importance of this area is given by the fact that the Danube Delta is part of the UNESCO heritage, and the monitoring of polluting factors is a necessity in the desire to protect this area. The data measured during the July and August 2022 campaign cover a wide range of chemical species: Phosphate, CCO, CBO5, NH4+, N-NO2, N-NO3−, N-Total, P-PO4 3−, SO42−, Cl−, phenols, as well as metals with a harmful effect: Al, As, Cd, Cr, Fe. The study includes an evaluation based on the statistical approach of the results to highlight the significant correlations and differences identified between the two data sets. Next, to highlight the obtained results, a numerical model was considered using HEC-RAS and ESRI ArcGIS applications in a two-dimensional unsteady flow model in order to obtain the non-homogenous concentrations' distributions in the studied area. These two-dimensional models have been less studied in the specialized literature. In this way, interesting results could be obtained, and prediction methods regarding the dynamics of metal concentrations could be structured. The data obtained were used for the terrain model from the USGS service, and the flows of the Danube and its two tributaries were simulated using the data provided by the national services. In this work, we present the results obtained for the dynamics of the concentrations of the metals Al, As, Cd, Cr and Fe and the evaluation of the specific absorption coefficients for the explanation and correlation with the results of the measurements. Except for the numerical model presented, we would like to highlight the existence of some contributions of the main tributaries of the Danube in the study area. Such a systematic study has not been carried out due to conditions imposed by the border authorities. From this point of view, this study has an element of originality. The study is part of a more complex project in which the spatio-temporal distribution of the polluting factors in the water was evaluated, and the habitats in the study area were inventoried—especially those of community interest. In this way, we were able to expose the self-purification capacity of the Danube and highlight the existence of a concentration reduction gradient along the course of the river. The aspects related to the influence of the distribution of polluting factors on the state of health will be the subject of another article. [ABSTRACT FROM AUTHOR]

Effective sound absorption is crucial in environments like schools and hospitals. This study evaluates open-pore polyurethane foam and perforated onyx panels, which attenuate noise via distinct mechanisms: porous materials convert sound energy to heat through viscous and thermal losses, while perforated panels use resonant behaviour for energy dissipation. The impact of hole geometries and panel orientations on the sound absorption coefficient and noise reduction coefficient was investigated using COMSOL Multiphysics 6.0 for finite element analysis and ISO 10534-2 compliant impedance tube experiments. Six perforated panel configurations were 3D-printed with varying hole diameters and backed by a 24 mm polyurethane foam layer. Both 'forward' and 'reverse' configurations were assessed. A tapered hole from 4 mm to 2 mm showed the highest sound absorption across the 100–4000 Hz range, with a noise reduction coefficient of 0.444, excelling in both orientations. Reverse designs generally performed less, underscoring the importance of hole geometry and orientation. Experimental results aligned with FEA simulations, validating the computational model. This study elucidates sound absorption mechanisms of porous and perforated materials, providing a validated framework for material selection in noise-sensitive settings and highlighting 3D-printing's potential in noise control. [ABSTRACT FROM AUTHOR]

Copyright of Environmental & Social Management Journal / Revista de Gestão Social e Ambiental is the property of Environmental & Social Management Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We used a vacuum ultraviolet (VUV) spectrophotometer to measure the spectral transmittance of epoxy resin in the 140–220-nm region. This study used dielectric materials that are commonly used in electronic devices. We assessed the penetration of VUV light with a central wavelength of 172 nm from an excimer lamp into the depth direction of the resin and evaluated it based on the absorption coefficient. The epoxy resin was irradiated with a consistent amount of VUV light. Subsequently, attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) was used to observe the changes in the internal chemical state. By measuring the decrease in the peak at 1100 cm−1 on FTIR-ATR, we identified the relationship between the quantity of 172-nm photons absorbed and the number of reacting ether bonds. Further, the surface of the irradiated epoxy resin was analyzed by x-ray photoelectron spectroscopy (XPS) to evaluate the functional group concentration after exposure to different doses of VUV light. The difference in principle between FTIR-ATR and XPS analyses was used as the basis to examine the depth-wise effects of epoxy resin irradiated with VUV light. [ABSTRACT FROM AUTHOR]

This study explores the effects of gamma irradiation on the properties of polyvinyl chloride (PVC):(50 nm)/CeO2:(10 nm)/TiO2 nanocomposite films. Gamma irradiation significantly enhances the optical conductivity (σopt) of the films, signifying increased light‐to‐current conversion efficiency. This improvement is attributed to a reduction in the bandgap and increased light absorption induced by irradiation. X‐ray diffraction (XRD) analysis reveals a decrease in crystallinity due to disrupted atomic order within the nanocomposite. Williamson–Hall (W‐H) plots show a dose‐dependent reduction in crystallite size and a corresponding rise in lattice strain with increasing irradiation dose. Infrared (IR) spectroscopy suggests potential bond breaking of O‐H groups and modifications in C=O functional groups upon irradiation. The absorption coefficient and binding energy exhibit a nonmonotonic response with increasing dose, reaching an optimum at around 100 kGy. These findings demonstrate the potential of gamma irradiation for tailoring the optoelectronic properties of PVC:(50 nm)/CeO2:(10 nm)/TiO2 nanocomposites. This work paves the way for the development of next‐generation optoelectronic devices with optimized functionalities. [ABSTRACT FROM AUTHOR]

Halogenation of Y‐series small‐molecule acceptors (Y‐SMAs) is identified as an effective strategy to optimize photoelectric properties for achieving improved power‐conversion‐efficiencies (PCEs) in binary organic solar cells (OSCs). However, the effect of different halogenation in the 2D‐structured large π‐fused core of guest Y‐SMAs on ternary OSCs has not yet been systematically studied. Herein, four 2D‐conjugated Y‐SMAs (X‐QTP‐4F, including halogen‐free H‐QTP‐4F, chlorinated Cl‐QTP‐4F, brominated Br‐QTP‐4F, and iodinated I‐QTP‐4F) by attaching different halogens into 2D‐conjugation extended dibenzo[f,h]quinoxaline core are developed. Among these X‐QTP‐4F, Cl‐QTP‐4F has a higher absorption coefficient, optimized molecular crystallinity and packing, suitable cascade energy levels, and complementary absorption with PM6:L8‐BO host. Moreover, among ternary PM6:L8‐BO:X‐QTP‐4F blends, PM6:L8‐BO:Cl‐QTP‐4F obtains a more uniform and size‐suitable fibrillary network morphology, improved molecular crystallinity and packing, as well as optimized vertical phase distribution, thus boosting charge generation, transport, extraction, and suppressing energy loss of OSCs. Consequently, the PM6:L8‐BO:Cl‐QTP‐4F‐based OSCs achieve a 19.0% efficiency, which is among the state‐of‐the‐art OSCs based on 2D‐conjugated Y‐SMAs and superior to these devices based on PM6:L8‐BO host (17.70%) and with guests of H‐QTP‐4F (18.23%), Br‐QTP‐4F (18.39%), and I‐QTP‐4F (17.62%). The work indicates that halogenation in 2D‐structured dibenzo[f,h]quinoxaline core of Y‐SMAs guests is a promising strategy to gain efficient ternary OSCs. [ABSTRACT FROM AUTHOR]

Soybean seeds are susceptible to damage from the Riptortus pedestris, which is a significant factor affecting the quality of soybean seeds. Currently, manual screening methods for soybean seeds are limited to visual inspection, making it difficult to identify seeds that are phenotypically defect-free but have been punctured by stink bugs on the sub-surface. To facilitate the convenient and efficient identification of healthy soybean seeds, this paper proposes a soybean seed pest detection method based on spatial frequency domain imaging combined with RL-SVM. Firstly, soybean optical data is obtained using single integration sphere technique, and the vigor index of soybean seeds is obtained through germination experiments. Then, based on the above two data items using feature extraction algorithms (the successive projections algorithm and the competitive adaptive reweighted sampling algorithm), the characteristic wavelengths of soybeans are identified. Subsequently, the spatial frequency domain imaging technique is used to obtain the sub-surface images of soybean seeds in a forward manner, and the optical coefficients such as the reduced scattering coefficient μ ′ s and absorption coefficient μ a of soybean seeds are inverted. Finally, RL-MLR, RL-GRNN, and RL-SVM prediction models are established based on the ratio of the area of insect-damaged sub-surface to the entire seed, soybean varieties, and μ a at three wavelengths (502 nm, 813 nm, and 712 nm) for predicting and identifying soybean the stinging and sucking pest damage levels of soybean seeds. The experimental results show that the spatial frequency domain imaging technique yields small errors in the optical coefficients of soybean seeds, with errors of less than 15% for μ a and less than 10% for μ ′ s . After parameter adjustment through reinforcement learning, the Macro-Recall metrics of each model have improved by 10%-15%, and the RL-SVM model achieves a high Macro-Recall value of 0.9635 for classifying the pest damage levels of soybean seeds. [ABSTRACT FROM AUTHOR]

The Two-Photon Absorption–Transient Current Technique (TPA-TCT) is a device characterisation technique that enables three-dimensional spatial resolution. Laser light in the quadratic absorption regime is employed to generate excess charge carriers only in a small volume around the focal spot. The drift of the excess charge carriers is studied to obtain information about the device under test. Neutron-, proton-, and gamma-irradiated p-type pad silicon detectors up to equivalent fluences of about 7 × 1015  n eq / c m 2 and a dose of 186   M r a d are investigated to study irradiation-induced effects on the TPA-TCT. Neutron and proton irradiation lead to additional linear absorption, which does not occur in gamma-irradiated detectors. The additional absorption is related to cluster damage, and the absorption scales according to the non-ionising energy loss. The influence of irradiation on the two-photon absorption coefficient is investigated, as well as potential laser beam depletion by the irradiation-induced linear absorption. Further, the electric field in neutron- and proton-irradiated pad detectors at an equivalent fluence of about 7 × 1015  n eq / c m 2 is investigated, where the space charge of the proton-irradiated devices appears inverted compared to the neutron-irradiated device. [ABSTRACT FROM AUTHOR]

Silica aerogel incorporated Cementitious composites (AICs) are extensively utilized in construction, yet their long-term effectiveness is compromised by significant capillary water absorption. Notably, research seldom explores how varying amounts of aerogel affect these properties through changes in the material's internal pore structure, compounded by a scarcity of experimental data. Consequently, this study investigates the impact of silica aerogel incorporation on the water content distribution and capillary water absorption characteristics of AICs, utilizing SEM, MIP, and BET characterization techniques. The findings indicate that the water absorption profile of AICs typically follows a three-phase pattern: a rapid increase, a slow rise, and a relatively stable phase. Despite an increase in the static contact angle, neither the capillary absorption coefficient (Scap) nor the diffusion coefficient of liquid water (DL) decreased with higher aerogel content. Instead, there was an increase in the percentage of micro-mesoporous pore volume within the AICs, along with a more tortuous pore structure, which restricted the movement of water molecules through the pore channels, thereby progressively diminishing the material's capillary water absorption. These results may provide both a theoretical and experimental foundation for enhancing the long-term performance of AICs in building applications. [ABSTRACT FROM AUTHOR]

We report on the spatial distributions and optical characteristics of chromophoric dissolved organic matter (CDOM) in the sea surface microlayer (SML), subsurface seawater (SSW), and water column profiles down to 500 m across a range of Atlantic Ocean biogeochemical provinces during two cruises of the UK Atlantic Meridional Transect program (AMT24 and AMT25). We measured the CDOM absorption coefficient at 300 nm, aCDOM(300), and determined CDOM spectral slopes across two UV wavelength ranges: S1 (275-295 nm) and S2 (350-400 nm). We used spectral slope ratios (SR: S1/S2) to infer CDOM source characteristics and transformation history. During both cruises, SML aCDOM(300) was highest in the Northern Hemisphere, particularly in the North Atlantic Drift Region (NADR). CDOM was always enriched in the SML, with enrichment factors (SML aCDOM (300) / SSW aCDOM(300)) ranging from 1.03 to 2.00, reflecting preferential accumulation of CDOM in the SML. We also found a significant inverse correlation between aCDOM(300) and S1 in both the SML (Spearman's rank correlation coefficient, r2 = -0.75, p < 0.001, n = 114) and water column profiles (r2 = -0.74, p < 0.001, n = 845). Biogeochemical province-dependent variations in the relationships between CDOM and chlorophyll a were also observed. In high-latitude regions, elevated aCDOM(300) and low SR values indicated a dominance of terrestrially-derived CDOM, whereas oligotrophic subtropical areas showed lower aCDOM(300) and higher SR values, suggestive of aged, refractory, and photodegraded biologically-derived CDOM. Taken together, these findings reveal a complexity of drivers affecting CDOM distributions and spectral properties, which may limit the use of CDOM in predictive relationships in the oceans. However, the potential use of chlorophyll a as a CDOM proxy may prove most successful in open ocean regions devoid of terrestrial inputs, where biological production predominates. [ABSTRACT FROM AUTHOR]

Achieving ultra-low and ultra-broad-band sound absorption and full-band sound insulation is a major challenge. Here, we propose a composite structure of a multilayer micro-perforated plate and acoustic black holes to achieve this purpose. Combining the stable sound absorption effect of the multilayer micro-perforated plate in the full frequency band and the sound insulation effect of the acoustic black hole in the low frequency and the excellent sound absorption effect in the high frequency, the excellent sound control effect of 600–3150 Hz absorption coefficient greater than 0.8 and 100–3150 Hz sound transmission loss greater than 50 dB is achieved. The acoustic properties of different components and different acoustic black hole outlet were evaluated by finite element method, and the principles of sound absorption and insulation of the composite structure were elaborated. Finally, the results of finite element method are verified by impedance tube experiments. This work can make further progress in elucidating the acoustic properties of the ABH and open up new avenues in the control of ultra-low and ultra-wide frequency acoustic waves. [ABSTRACT FROM AUTHOR]

The use of semiconductors based on abundant and less expensive materials in photovoltaic industry has grown since electricity consumption has increased, alloys such as Cu2ZnSn(S1-xSex)4 have recently attracted attention, due to its structural, optical and electronic properties which make it a very promising candidate as an absorber layer in photovoltaic applications. The lattice mismatch of Cu2ZnSn(S1-xSex)4 with Cu2NiGeS4 as substrate for solar cell architecture reveals that low Se content (0.1≤x≤0.4) is favorable, and thus, by reducing Se content from 40 to 10% induces a decrease in optical parameters such as refractive index from 5.475 to 3.834 for near-infrared wavelengths, and both extinction and absorption coefficients are from 0.478 to 0.211 and from 7.956×104 to 6.912×104 cm-1, respectively, for almost along the visible spectrum. Additionally, the bandgap energy of Cu2ZnSn(S1-xSex)4 in kesterite structure increases from 1.267 to 1.442 eV at room temperature, while the compressive strain of the epitaxial layer reduces from 3.93 to 2.39% and from 4.62 to 3.17% on the growth plane and following the direction of growth, respectively. [ABSTRACT FROM AUTHOR]

Currently, the most reliable approach to reconstruct optical properties, namely absorption coefficient, reduced scattering coefficient, scattering coefficient and asymmetry factor, of turbid media is through inverse Monte Carlo simulation. To determine these optical properties, three measurements are required: total transmission, total reflection and collimated transmission. However, the accurate determination of the collimated transmission is very difficult. To overcome the difficulty of measuring the collimated transmission, it is proposed to measure the total transmission and total reflection of the same sample with two different thicknesses instead. To prove this alternative solution, machine learning is used to prove that the repeated measurement for two different thicknesses carries all the necessary information. As a result, all four optical properties can be measured with high accuracy, particularly for interpolation problems where the test data fall within the range of the training data. For extrapolation problems, high accuracy can be achieved in the determination of at least the absorption coefficient, reduced scattering coefficient and scattering coefficient. Hence, these results allow that in the future, an easier and therefore more precise reconstruction of the optical properties is possible, potentially even with inverse Monte Carlo simulations as the current standard. [ABSTRACT FROM AUTHOR]

A novel reagent derived from salicylaldehyde has been synthesized and characterized by determining its crystalline structure through X-ray diffraction analysis. The complex formation of this reagent with iron(III) has been investigated by spectrophotometric methods. The dissociation constant of the reagent was determined by potentiometry in an aqueous–ethanolic medium, yielding pK = 9.66 ± 0.02. The interaction of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol in the presence and absence of diantipyrylmethane (DAM), diantipyrylphenylmethane (DAPhM), and diantipyrylpropylmethane (DAPrM) has been thoroughly studied. Optimal conditions for complex formation (λopt, pHopt) were found. Iron(III) forms colored mixed-ligand complexes with the reagent in the presence of the third component—DAM, DAPhM, or DAPrM,—resulting in a hypsochromic shift in the absorption spectrum. The maximum yield of complexes was achieved in a more acidic medium compared to the binary complex. Molar absorption coefficients of the complexes and the ranges of compliance with Beer's law were determined. Component ratios in the homogeneous and mixed-ligand complexes were established using isomolar series methods, as well as the relative yield of the Starik–Barbanel and equilibrium shift methods. These analyses revealed that the component ratio of Fe(III)–R in the binary complex is 1 : 2, while in the mixed-ligand complexes Fe(III)–R–DAM, Fe(III)–R–DAPhM, and Fe(III)–R–DAPrM, the ratios are 1 : 2 : 1, 1 : 1 : 1, and 1 : 1 : 2, respectively. The mixed-ligand complexes of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol exhibit favorable chemical-analytical characteristics. The developed procedure was successfully applied to the determination of trace amounts of iron(III) in oil sludge. [ABSTRACT FROM AUTHOR]

This study examined the self-cleaning and mechanical properties of basalt fiber–reinforced ground granulated blast furnace slag (GGBS)-based geopolymer mortar containing nano TiO2. The nano TiO2 and basalt fiber in mixtures were used at 0%, 0.25%, 0.5%, and 1% by weight of GGBS. The cubes (50×50×50 mm) and prisms (40×40×160 mm) samples containing nano TiO2 and basalt fiber were produced and cured in the oven for 24 h at 60°C. Then, these samples were kept at room temperature at 23°C±2°C for 28 days. Lastly, the compressive strength, flexural strength, ultrasonic pulse velocity, capillary water absorption, and self-cleaning tests of GGBS-based geopolymer mortars were carried out. In this study, the Rhodamine-B test was used to determine self-cleaning. This study showed that the compressive strength, flexural strength, and ultrasonic pulse velocity values of the GGBS-based geopolymer mortars increased as the nano TiO2 and basalt fiber ratios increased, but their capillary water absorption coefficient decreased. Also, this study found that the self-cleaning rate of GGBS-based geopolymer mortars containing 1% nano TiO2 was obtained as 50.62% at 28 days. [ABSTRACT FROM AUTHOR]

Broadband adjustable sound absorbers are desired for controlling the acoustic conditions within enclosed spaces. Existing studies on acoustic absorbers, either passive or active, aim to maximize the sound absorption coefficients over an extended frequency band. By contrast, this paper introduces a tunable acoustic absorber, whose working frequency band and sound absorption characteristics can be defined by users for different applications. The approach leverages an error signal that can be synthesized using a standing wave separation technique. The error signal encodes different target reflection coefficients, leading to arbitrary absorption coefficients between 0 and 1. Experimental validation is conducted in a one-dimensional standing wave tube, demonstrating that the proposed active absorber achieves near-perfect absorption within the 150–1600 Hz frequency range, boasting an average absorption coefficient of 0.98. Adjustable absorption is demonstrated across three octave bands, aligning closely with theoretical predictions. Furthermore, when coupled with a shaping filter, the absorber exhibits spectrally tunable broadband absorption capabilities, selectively reflecting specific frequency bands while effectively absorbing others. These outcomes underscore the versatile tunability of the proposed active acoustic absorber, which is expected to pave the way for personalized regulating of the indoor acoustic environment. [ABSTRACT FROM AUTHOR]

Laser-induced ultrasound is based on the thermo-elastic conversion of absorbed short light pulses to pressure pulses. In the work presented here, laser-induced ultrasound in a planar structure of interconnected layers with variations in optical, thermal, and mechanical properties is studied. Layered structures can be used for generating wideband ultrasonic pulses specific to a chosen application. An analytical time-domain solution is derived for the resulting pressure transmitted from the layered structure. The solution is derived for an arbitrary number of layers with an arbitrary optical absorption profile. Free space Green's functions with image sources are used to derive the solution. A solution employing the Beer–Lambert law is also proposed. The simplification with reflections only at the boundaries is in agreement with previous published results. The spectral properties of the generated pulse are derived, where the effects of optical absorption coefficients and layer thicknesses are shown. The analytical solution is compared to one-dimensional (1D) simulations and a three-dimensional (3D) simulation, realised as a two-dimensional (2D) axially symmetric case, using the matlab toolbox k-Wave. The 3D simulation on-axis pressure agrees well with the 1D analytical solution when the diameter of the laser beam is larger by approximately 1 order of magnitude than the thickness of the planar layered structure. [ABSTRACT FROM AUTHOR]

High Spectral Spatial Frequency Domain Imaging (HSFDI) combines high spectral imaging and spatial frequency domain imaging techniques, offering advantages such as wide spectral range, non-contact, and differentiated imaging depth, making it well-suited for measuring the optical properties of agricultural products. The diffuse reflectance spectra of the samples at spatial frequencies of 0 mm - 1 ( R d 0 ) and 0.2 mm - 1 ( R d 0 ) were obtained using the three-phase demodulation algorithm. The pixel-by-pixel inversion was performed to obtain the absorption coefficient ( μ a ) spectra and the reduced scattering coefficient ( μ s ′ ) spectra of the pears. For predicting the SSC and firmness of the pears, these optical properties and their specific combinations were used as inputs for partial least squares regression (PLSR) modeling by combining them with the wavelength selection algorithm of competitive adaptive reweighting sampling (CARS). The results showed that μ a had a stronger correlation with SSC, whereas μ s ′ exhibited a stronger correlation with firmness. Taking the plane diffuse reflectance R d 0 as the comparison object, the prediction results of SSC based on both μ a and the combination of diffuse reflectance at two spatial frequencies ( R d ) were superior (the best R p 2 of 0.90 and R M S E P of 0.41%). Similarly, in the prediction of firmness, the results of μ s ′ , μ a × μ s ′ , and R d 1 were better than that of R d 0 (the best R p 2 of 0.80 and R M S E P of 3.25%). The findings of this research indicate that the optical properties represented by HSFDI technology and their combinations can accurately predict the internal quality of pears, providing a novel technical approach for the non-destructive internal quality evaluation of agricultural products. [ABSTRACT FROM AUTHOR]

The wet-season atmosphere in the central Amazon resembles natural conditions with minimal anthropogenic influence, making it one of the rare preindustrial-like continental areas worldwide. Previous long-term studies have analyzed the properties and sources of the natural Amazonian background aerosol. However, the vertical profile of the planetary boundary layer (PBL) has not been assessed systematically. Since 2017, such a profile assessment has been possible with the 325 m high tower at the Amazon Tall Tower Observatory (ATTO), located in a largely untouched primary forest in the central Amazon. This study investigates the variability of submicrometer aerosol concentration, size distribution, and optical properties at 60 and 325 m in the Amazonian PBL. The results show significant differences in aerosol volumes and scattering coefficients in the vertical gradient. The aerosol population was well-mixed throughout the boundary layer during the daytime but became separated upon stratification during the nighttime. We also found a significant difference in the spectral dependence of the scattering coefficients between the two heights. The analysis of downdrafts and the related rainfall revealed changes in the aerosol populations before and after rain events, with absorption and scattering coefficients decreasing as optically active particles are removed by wet deposition. The recovery of absorption and scattering coefficients is faster at 325 m than at 60 m. Convective events were concomitant with rapid increases in the concentrations of sub-50 nm particles, which were likely associated with downdrafts. We found that the aerosol population near the canopy had a significantly higher mass scattering efficiency than at 325 m. There was also a clear spectral dependence, with values for λ=450 , 525, and 635 nm of 7.74±0.12 , 5.49±0.11 , and 4.15±0.11 m 2 g -1 , respectively, at 60 m , while at 325 m the values were 5.26±0.06 , 3.76±0.0 5, and 2.46±0.04 m 2 g -1 , respectively. The equivalent aerosol refractive index results, which were obtained for the first time for the wet season in the central Amazon, show slightly higher scattering (real) components at 60 m compared to 325 m of 1.33 and 1.27, respectively. In contrast, the refractive index's absorptive (imaginary) component was identical for both heights, at 0.006. This study shows that the aerosol physical properties at 60 and 325 m are different, likely due to aging processes, and strongly depend on the photochemistry, PBL dynamics, and aerosol sources. These findings provide valuable insights into the impact of aerosols on climate and radiative balance and can be used to improve the representation of aerosols in global climate models. [ABSTRACT FROM AUTHOR]

K9 glass is a classical transparent material widely used in high-power optical systems due to its high-temperature resistance. However, the precision machining of K9 glass is difficult. The laser processing method, characterized by being non-contact, having a small heat-affected zone, and having high processing precision, is commonly employed for processing intricate structures. In this study, the vector diffraction model is employed to simulate the internal electric field inside the material when focused by objective lenses with varying numerical apertures. Furthermore, the temperature field is simulated. The simulation considered the nonlinear absorption of the material, the stretching of the focal dot due to spherical aberration, and the energy loss of the laser during the focusing process. The experiment indicated that the ablated area consists of numerous small, ablated dots and that multiple ablated areas emerged under an NA of 0.6. This study can provide valuable references for the research of the interaction between lasers and glass materials. [ABSTRACT FROM AUTHOR]

We have studied the variations in the temperature-dependent absorption edge of a bulk InSe-layered semiconductor using photoconductivity (PC) measurements. From both the X-ray diffraction (XRD) and Raman experimental results, the structural phase of the as-prepared InSe sample was confirmed to be γ-polytype. Upon heating from 15 K to 300 K, the absorption edge of PC spectra was found to shift significantly toward lower energy, and the absorption edge as a function of temperature was further analyzed by the Varshni's relationship and Bose–Einstein empirical equation. The Urbach energy as a function of temperature was obtained by fitting the absorption tail below the absorption coefficient of the PC spectrum, and the effective phonon energy can be derived from the temperature-dependent steepness parameter associated with Urbach energy. Our study indicates that the broadening of the absorption edge in the as-synthesized bulk γ-InSe is caused by a combination of electron/exciton–phonon interactions and thermal/structural disorder. [ABSTRACT FROM AUTHOR]

This study investigates the potential of Ho3+ doped BaTiO3 perovskite phosphor, synthesized via the sol–gel method. X-ray diffraction (XRD) analysis confirmed a hexagonal crystallographic structure (P63/mmc), consistent with JCPDS card no. 82-1175. The shifts in the XRD pattern suggest that the concentration of Ho3+ ions influence the structure. Fourier transform infrared (FT-IR) spectroscopy is used to study the vibrational behavior of the synthesized perovskite phosphor. The diffuse reflectance spectra (DRS) presented several bands in the UV–Vis regions due to Ho3+ ions. The bandgap for Ho3+-doped BaTiO3 was calculated as 2.8 eV, which aligns with the literature values. This value was derived from fitting the Tauc equation to the absorption coefficient data. Extensive photoluminescence (PL) spectroscopy revealed sharp excitation and emission spectra. The PL spectrum, corresponding to an excitation wavelength of 456 nm, exhibited a dominant green emission at 540 nm that corresponds to the 5F4/5S2 → 5I8 transition, suggesting its suitability for a green-emitting phosphor. Concentration quenching optimization occurred beyond 0.015 mol Ho3+ ions. The CIE color coordinates and color purity analysis confirmed the phosphor's suitability for green-emitting applications. Preliminary results suggest that this research highlights the potential of the phosphor for green light generation and advancing solid-state lighting technology. [ABSTRACT FROM AUTHOR]

Bismuth layered structure ferroelectrics (BLSFs), also known as Aurivillius phase materials, are ideal for energy-efficient applications, particularly for solar cells. This work reports the first comprehensive detailed theoretical study on the fascinating structural, electronic, and optical properties of XNb2Bi2O9 (X = Ca, Ba, Be, Mg, Sr). The Perdew–Burke–Ernzerhof approach and generalized gradient approximation (GGA) are implemented to thoroughly investigate the structural, bandgap, optical, and electronic properties of the compounds. The optical conductivity, band topologies, dielectric function, bandgap values, absorption coefficient, reflectivity, extinction coefficient, refractive index, and partial and total densities of states are thoroughly investigated from a photovoltaics standpoint. The material exhibits distinct behaviors, including significant optical anisotropy and an elevated absorption coefficient > 105 cm−1 in the region of visible; ultraviolet energy is observed, the elevated transparency lies in the visible and infrared regions for the imaginary portion of the dielectric function, and peaks in the optical spectra caused by inter-band transitions are detected. According to the data reported, it becomes obvious that XNb2Bi2O9 (X = Ca, Ba, Be, Mg, and Sr) is a suitable candidate for implementation in solar energy conversion applications. [ABSTRACT FROM AUTHOR]

Electromagnetic scattering is a routine tool for rapid, non-contact characterization of particle media. In previous work, the interaction targets of scattering intensity, scattering efficiency, and extinction efficiency of Bessel pincer light-sheet beams were all aimed at dielectric spheres. However, most particles in nature are charged. Considering the boundary condition on a charged sphere, the beam shape coefficients (BSCs) ( p m n , q m n ) of the charged spherical particle illuminated by a Bessel pincer light-sheet beam are obtained. The extinction, scattering, and absorption efficiencies are derived under the generalized Lorenz–Mie theory (GLMT) framework. This study reveals the significant differences in scattering characteristics of Bessel pincer light-sheet beams on a charged particle compared to traditional beams. The simulations show a few apparent differences in the far-field scattering intensity and efficiencies between charged and natural spheres under the influence of dimensionless size parameters. As dimensionless parameters increase, the difference between the charged and neutral spheres decreases. The effects of refractive index and beam parameters on scattering, extinction, and absorption coefficients are different but tend to converge with increasing dimensionless parameters. When applied to charged spheres with different refractive indices, the scattering, extinction, and absorption efficiencies of Bessel pincer light-sheet beams change with variations in surface charge. However, once the surface charge reaches saturation, these efficiencies become stable. This study is significant for understanding optical manipulation and super-resolution imaging in single-molecule microbiology. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)