IR Bands Research Articles

Degradation of Methyl Red (MR) dye via fabricated Y2O3–MgO/g-C3N4 nanostructures: Modification of band gap and photocatalysis under visible light

In this study, graphitic carbon nitride (g-C3N4) composites with metal oxide nanoparticles (Y2O3, MgO) and their combination (CN, YCN, MCN and YMCN) were synthesized by an ultrasonic technique and were then characterized by different tools such as UV–Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). From the XRD diffractograms of the YMCN ternary composite, the g-C3N4, cubic MgO and Y2O3 structural phases were identified. The morphology of the as prepared nanostructure from the SEM analysis revealed the dispersion of the metal oxides nanoparticles with the graphitic sheets and the presence of the corresponding elements were confirmed by the EDX and XPS data. The FT–IR bands confirmed the bonding of the metal oxides to the nitride host as indicated by the characteristic modes. A reduction of the band gap energies was confirmed by the UV–Vis to indicate its visible light possible photoactivity. Accordingly, its visible light driven photocatalytic performance was assessed for methyl red degradation. The degradation competence was highest for the ternary composite YMCN due to the coupling of the semiconductors which increases the absorption and the charge carriers’ separation as well. The kinetics of degradation was best described by pseudo-first-order, and the most active species were the holes and the hydroxyl radicals. Thus, the YMCN nanocomposite is a visible light-active photocatalyst which can be engaged in the degradation of organic pollutants.

Influence of the DEA Concentration on Structural and Optical Properties of Nanodot PbS Thin Films Growth by Chemical Solution Deposition: Unveiling Dual Optical Absorption Edges

The present paper presents a straightforward method for producing thin film layers of sulfide quantum dots (PbS-QDs) on a glass substrate using chemical solution deposition (CSD) assisted by dipcoating technique. The deposited PbS-QDs films were subjected to a comprehensive analysis using atomic force microscopy (AFM), energy dispersive X-ray (EDX) scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis–IR absorption, and photoluminescence spectroscopic (PL) techniques to investigate the effects of varying concentrations of diethanol amine (DEA) on their morphology, crystal structure, elemental composition, light absorption, and emission characteristics. The spherical shape of the PbS-QDs was confirmed by AFM and SEM images with average sizes around 100 and 50 nm, respectively. The energy dispersive X-ray (EDX) analysis provides evidence the existence of Pb and S elements within the PbS matrix. X-ray diffraction (XRD) results validate that the deposited films exhibit high crystallinity, with a preferential orientation along the (111) plane and a face-centered cubic lattice structure of PbS. The crystallite size of PbS is measured to be 46.6 nm. Based on the optical absorption measurements, we have determined the size range of PbS nanocrystals to be between 4.3 and 11.5 nm. The optical studies reveal the presence of two optical absorption edges within the visible and infrared spectrum, two direct band gap energy, two cut-off wavelengths, two confinement energy, two Urbach energy tail, and dual emission peaks of PbS-QDs at room temperature. The analysis reveals the presence of two distinct band gap energies, one in the visible range (1.3–2.28 eV) and the other in the infrared range (0.65–0.88 eV), which can be attributed to the formation of two distinct sizes of quantum dots situated in two different layers. The first layer, deposited directly on the glass substrate, comprises quantum dots with an average size of approximately 5.2 nm, while the second layer contains quantum dots with an average size of about 9.5 nm. This ability to tune the band gap of PbS in the visible range up to the IR band (0.65–2.28 eV) is a critical feature that holds the potential for the development of innovative optoelectronic devices.

Water-polymer interactions and mechanisms of water-driven glass transition decrease in non-isocyanate polyhydroxyurethanes with varying hydration sites

Non-isocyanate polyurethanes (NIPUs) with varying content of secondary amino groups along their chain were studied with respect to water absorption and plasticization. Secondary amino groups promote water uptake. Water sorption isotherms in the water activity range 0–0.97 are discussed in terms of various sorption models. Secondary amino groups act as additional hydration sites, increasing monolayer capacity. The red shift of the IR band assigned to the carbonyl of the urethane and the simultaneous blue shift of the urethane N–H bending band show cleavage of the polymer-polymer hydrogen bonds upon water uptake, due to strong interactions between water molecules and hydroxyurethanes constituting the primary hydration sites. A decrease in glass transition temperature (Tg) is observed with increasing water content. The effect is discussed in terms of plasticization and slaving mechanisms, while a peculiar decrease of Tg at very low hydrations is attributed to a mechanism not following common mixing laws.

Gradient High-Q Dielectric Metasurfaces for Broadband Sensing and Control of Vibrational Light-Matter Coupling.

Surface-enhanced infrared absorption spectroscopy (SEIRA) has emerged as a powerful technique for ultrasensitive chemical-specific analysis. SEIRA can be realized by employing metasurfaces that can enhance light-matter interactions in the spectral bands of molecular vibrations. Increasing sample complexity emphasizes the need for metasurfaces that can operate simultaneously at different spectral bands, both accessing rich spectral information over a broad band, and resolving subtle differences in the absorption fingerprints through narrow-band resonances. Here, a novel concept of resonance-gradient metasurfaces is introduced, where the required spectral selectivity is achieved via local high-quality-factor (high-Q) resonances, while the continuous coverage of a broad band is enabled by the gradual adjustment of the unit-cell dimensions along the planar structure. The highly tailorable design of the gradient metasurfaces provides flexibility for shaping the spectral sampling density to match the relevant bands of target analytes while keeping a compact device footprint. The versatility of the gradient metasurfaces is demonstrated through several sensing scenarios, including polymer mixture deconvolution, detecting a multistep bioassay, and identification of the onset of vibrational strong coupling regime. The proposed gradient-resonance platform significantly contributes to the rapidly evolving landscape of nonlocal metasurfaces, enabling applications in molecular detection and analysis of fundamental light-matter interaction phenomena.

Probing calmodulin-NO synthase interactions via site-specific infrared spectroscopy: an introductory investigation.

Calmodulin (CaM) binds to a linker between the oxygenase and reductase domains of nitric oxide synthase (NOS) to regulate the functionalconformational dynamics. Specific residues on the interdomain interface guide the domain-domain docking to facilitate the electron transfer in NOS. Notably, the docking interface between CaM and the heme-containing oxygenase domain of NOS is isoform specific, which is only beginning to be investigated. Toward advancing understanding of the distinct CaM-NOS docking interactions by infrared spectroscopy, we introduced a cyano-group as frequency-resolved vibrational probe into CaM individually and when associated with full-length and abi-domain oxygenase/FMN construct of the inducible NOS isoform (iNOS). Site-specific, selective labeling with p-cyano-L-phenylalanine (CNF) by amber suppression of CaM bound to the iNOS has been accomplished by protein coexpression due to the instability ofrecombinant iNOS proteinalone. We introduced CNF at residue 108, which is at the putative CaM-heme (NOS) docking interface. CNF was also introduced at residue 29, which is distant from the docking interface. FT IR data show that the 108 site is sensitive to CaM-NOS complex formation, while insensitivity to its association with the iNOS protein or peptide was observed for the 29 site. Moreover, narrowing of the IR bands at residue 108 suggests the C≡N probe experiences a more limited distribution of environments, indicating side chain restriction apparent for the complex with iNOS. This initial work sets the stage for residue-specific characterizations of structural dynamics of the docked statesof NOS proteins.

Exploration of electronic and vibrational properties of sulfanilic acid through periodic and non-periodic DFT calculations.

The electronic, discrete water solvation, and vibrational properties of zwitterionic sulfanilic acid were thoroughly investigated using periodic and non-periodic DFT approaches. The periodic-DFT results, obtained by employing the PBE-TS functional (Perdew-Burke-Ernzerhof (PBE) functional with the Tkatchenko and Scheffler (TS) dispersion correction) were first presented in order to analyze the band structures of the studied crystal. An attentive reading of the predicted band structures has shown three lowest gap energies calculated at 4.23, 4.24, and 4.29eV arising from the Γ→Γ, Γ→Z, and Γ→S transitions, respectively. Then, non-periodic calculations were carried out, at the B3LYP-D3 level of theory (B3LYP functional with the D3 Grimme dispersion correction) in order to optimize the sulfanilic acid-(H2O)10 complex. Starting from the optimized structure, non-covalent interaction calculations were performed and the H-bonding, van der Waals, and steric effect interactions were identified. Finally, the PBE-TS calculations were strengthened by conducting anharmonic B3LYP-D3 calculations in order to achieve a complete decryption of the experimental IR spectrum of sulfanilic acid. The spectral analysis is not limited only to the interpretation of both the NH/CH stretching and fingerprint regions but also extended to the 1800-2600cm-1 region, which is characterized by a strong anharmonic effect. In the latter wavenumber region, the large experimental IR band centered at 1937cm-1 is reproduced theoretically employing the anharmonic B3LYP-D3 calculations. The similarity of this band with those usually considered as a fingerprint of zwitterionic amino acids is observed, and its origin is elucidated theoretically. In the vibrational spectroscopy field, the calculations presented in this study are probably the most appropriate for achieving vast analysis and accurate assignments of vibrational spectra of hydrogen bonding compounds recorded in the solid state. The periodic and non-periodic calculations were conducted within the Density Functional Theory (DFT) using the Generalized Gradient Approximation (GGA) at the PBE-TS level of theory and B3LYP-D3 functional with the 6-311++G(d,p) basis set, respectively. The PBE-TS and B3LYP-D3/6-311++G(d,p) calculations were performed using the CASTEP and Gaussian 09 programs, respectively. In addition, The non-covalent interactions were calculated by the Multiwfn 3.8 software. The obtained results for different calculations were visualized by employing the visualization tools in Materials Studio, GaussView, VMD, and Gnuplot programs.

Water Adsorption on π-Surfaces of Open-Fullerenes.

Understanding the water adsorptive behavior of fullerenes is of particular importance for their material application in aqueous media. The conventional fullerenols usually provide complex physical pictures of water adsorption due to their uncontrollable hydroxylation degree and substitution pattern. Herein, we focus on poorly hydroxylated fullerenes with well-defined structures. The water adsorptive behavior was examined by synchrotron IR spectroscopy and computational studies. As a result, three types of IR bands were observed for adsorbed water. The population of the three states was considerably altered by the orientational difference of the hydroxy groups. Nevertheless, water adsorption could not occur for 9-fluorenol and catechol. This indicates that the Lewis acidic fullerene π-surface plays a prominent role in water adsorption, while the rather Lewis basic π-surface of 9-fluorenol is unable to attract much water at a boundary with humid air.

The impact of indium and manganese modifiers on the catalytic properties of zinc-alumina propane dehydrogenation catalysts

Supported zinc-containing catalysts are considered as a viable alternative to the currently-deployed Cr-based (toxic) and Pt-based (costly) catalysts of alkane dehydrogenation, as reflected also in the increased number of reports related to the Zn-based catalysts in recent years. Here, we present a study of alumina-supported Zn-In and Zn-Mn propane dehydrogenation (PDH) catalysts prepared by the tailored methods. Specifically, the introduction of zinc relied on the chemical vapor deposition (CVD, using Zn vapor) onto alumina or alumina-supported indium or manganese materials, the latter two prepared by the impregnation of alumina with aqueous solutions of the respective metal nitrates followed by the calcination and hydrogen treatment. Alternatively, both zinc and indium were introduced by the co-impregnation of alumina with aqueous zinc and indium nitrates. The PDH tests revealed that the “dilution” of the active Zn2+ surface sites with In+ cations lead to a significant improvement in the catalytic performance, i.e., the introduction of In+ increased propene selectivity and attenuated the undesirable cracking and hydrogenolysis side reactions as well as decreased coke formation. In contrast, Mn2+ cations improved the catalytic properties of Zn2+ surface sites to a lesser extent than In+ cations. All prepared catalysts were characterized by DRIFT (diffuse reflectance infrared Fourier transform) spectroscopy of the adsorbed CO and H2 probe molecules. It was found that surface In+ and Mn2+ cations affect Zn2+ sites (electronic and geometric effect), which can be assessed from the position of the IR bands of zinc hydridespecies, formed due to the heterolytic hydrogen dissociation on the Zn2+ active sites. The effect of In and Mn dopants also was confirmed by the molecular DFT simulation.

Pyridazine derivative as potent antihyperglycemic agent: Synthesis, crystal structure, α-amylase and α-glucosidase inhibition and computational studies

In this study, a pyridazine derivative (PDZ-1) was synthesized and characterized by using 13C NMR, 1H NMR, FT-IR, UV–Vis, HRMS-ESI and single-crystal X-ray diffraction analysis (XRD). Density functional theory methods at the B3LYP/6–311++G** level of theory predict very good correlations in the geometrical parameters and spectra when they are compared with the corresponding experimental ones. The presence of dimer explains the broad IR band due to CH···O interactions. The scaled force constants and the 75 vibration modes of PDZ-1 have been completely assigned using the scaled quantum mechanical force field (SQMFF) methodology. The deactivating character of Cl atom probably explains that the densities of pyridazine rings in both media are higher than that corresponding to chlorobenzyl, as revealed by AIM study while NBO calculations show that the derivative is most stable in gas phase than ethanol solution. Frontier orbital studies reveal that PDZ-1 is most reactive in ethanol than in the gas phase. The title compound showed a potent α-glucosidase and α-amylase inhibition compared to Acarbose (IC50 = 113.6 ± 1.17 µM, 124.5 ± 0.64 µM, respectively) with IC50 values of 17.32 ± 0.76 and 109.41± 0.87 µM, respectively. In addition, molecular docking studies were performed to determine the binding modes and energies between PDZ-1 and the target enzymes.

Mechanism of autoxidation of the chromium(II) porphyrins. In situ infrared spectroscopic detection of the peroxo- intermediate

The reaction of Cr(II)(TPP) (TPP is meso-tetraphenylporphyrinato dianion) in solid sublimed layers with dioxygen at 50 K results in formation of a single IR band at 1142 cm−1. The IR spectrum of the sublimated Cr (II)(TPP) exposed to the dioxygen at 77 K exhibits two IR bands at 1142 and 935 cm−1, which are shifted to 1078 and 883 cm−1 respectively by 16O2/18O2 substitution. When heated to 130 K, the bands at 1142 cm−1 (1078 cm−1) are completely transformed into bands at 935 cm−1 (883 cm−1) and this transformation is irreversible. Based on IR frequencies analysis, isotopic dioxygen substitution and DFT calculations the band at 1142 cm−1 is assigned to the end-on type base-free dioxygen adduct, whereas the band at and 935 cm−1 is attributed to the side-on peroxo- intermediate. Following warm-up revealed further changes in IR spectra giving at room temperature well known chromyl O = Cr(IV)(TPP) compound with IR frequencies at 1020 cm−1 (980 cm−1).

Ir metal nanoparticles and IrO2 for acidic oxygen evolution reaction: Insight from Raman spectroscopy

Due to their high activity and stability, Ir-based materials are state-of-the-art electrocatalysts for oxygen evolution reaction (OER) under acidic conditions. However, many factors such as the influence of the activation/conditioning protocol and the resulting oxidation state or the effect of electrolyte adsorption on activity are still debated or overlooked. Herein, Raman spectroscopy was performed on commercial Ir black and IrO2 nanopowders to reveal differences in the samples after activation, as well as adsorption of perchlorates. Specifically, three different activation protocols were performed, 0.05 to 1.45 VRHE (activated), 0.05 to 1.6 VRHE (activated-long range (l.r.)), and 1.1 to 1.6 VRHE (activated-short range (s.r.)), resulting in different OER activity as well as different Raman spectra. However, only Ir(IV) bands remain visible in the ex situ Raman experiments, which was not sufficient to reveal the hydrated phases in the iridium samples. Therefore, mimicked in situ experiments were performed, which allowed the observation of the hydrated phase, particularly for Ir black, but also showed adsorption of perchlorate anions. In addition, the influence of solvation on Raman band shifts is revealed - along with DFT calculations. Overall, this work paves the way for our future in situ Raman spectroscopy experiments with iridium-based electrocatalysts during activation and OER.

Surface Modification of NiO‐Al2O3 Nanocomposites using Stearic Acid as a Modifier and their Applications in Self‐cleaning and Removal of Dyes

AbstractIn the present study, a quick surface modification method has been developed for the modification NiO‐Al2O3 nanocomposites using stearic acid (SA). The surface modification of NiO‐Al2O3 nanocomposites with stearic acid was confirmed by various analytical techniques (FT‐IR spectroscopy, thermal gravimetry (TG), carbon and hydrogen (CH) and XPS). There is no change in XRD patterns, and FE‐SEM and TEM images of NiO‐Al2O3 nanocomposites after modification with SA. FT‐IR analysis of SA modified NiO‐Al2O3 nanocomposites shows characteristic IR bands of carboxylate group. TG and CH analyses also confirm the presence of SA in the NiO‐Al2O3 nanocomposites. XPS analysis of SA modified NiO‐Al2O3 nanocomposites shows the presence of carbon atoms of stearic acid. The SA modified NiO‐Al2O3 nanocomposites show water contact angle greater than 90° which suggests their hydrophobic nature. The SA modified NiO‐Al2O3 nanocomposites were explored for self‐cleaning and also as adsorbent for the removal of crystal violet and rhodamine B dyes from aqueous solutions. The SA modified NiO‐Al2O3 nanocomposites remove the dyes within 30 minutes. The effect of various adsorption parameters (adsorbent dosage, contact time, pH, and temperature) was investigated to understand the optimum adsorption conditions. The SA modified NiO‐Al2O3 nanocomposites show better self‐cleaning property as compared to unmodified NiO‐Al2O3 nanocomposites.

Raman–Infrared Spectral Correlation of an Artificially Space-Weathered Carbonaceous Chondrite Meteorite

Raman and infrared measurements of the same locations were conducted on a northwest African (NWA) 10580 CO3 meteorite sample, before and after three proton irradiations (1 keV ion energy using 1011, 1014, and 1017 ion/cm2 fluent values), to simulate space weathering effects. In the case of Raman spectroscopy, both FWHM and peak positions of the major olivine and pyroxene bands changed after the irradiation, and the minor bands disappeared. In the FTIR spectra, the minor bands of olivine and pyroxene also disappeared; meanwhile, major IR bands of pyroxene remained visible, demonstrating both positive and negative peak shifts, and the olivines were characterised only by negative peak shifts. The olivines were characterised by negative FWHM changes for major bands, but positive FWHM changes for minor bands. The pyroxenes were characterised by elevated FWHM changes for minor bands after the irradiation. The disappearance of minor bands both of IR and Raman spectra indicates the amorphization of minerals. The negative peak shift in IR spectra indicates Mg loss for olivine and pyroxene, in agreement with the literature. The Raman spectra are characterised by positive peak shift and positive FWHM changes; the IR spectra are characterised by a negative peak shift. The Mg loss, which was detected by negative peak shifts of FTIR bands, may be caused by distortion of the crystal structure, which could be detected by a positive peak shift in Raman spectra. This joint observation and interpretation has not been formulated in the literature, but indicates further possibilities in the confirmation of mineral changes by different instruments. Shock alteration-based observations by other researchers could be used as a reference for irradiation experiments as irradiation makes a similar structural alteration, like a low-grade shock metamorphism.

The Remarkable Predictive Power of Infrared Data of Blazars

Blazars are the brightest and most abundant persistent sources in the extragalactic γ-ray sky. Due to their significance, they are often observed across various energy bands, where the data of which can be used to explore potential correlations between emission at different energies, yielding valuable insights into the emission processes of their powerful jets. In this study we utilized IR data at 3.4 and 4.6 μm from the Near-Earth Object Wide-field Infrared Survey Explorer Reactivation Mission, spanning 8 yr of observations, X-ray data from the Neil Gehrels Swift Observatory collected throughout the satellite’s lifetime, and 12 years of γ-ray measurements from the Fermi Large Area Telescope’s all-sky survey. Our analysis reveals that the IR spectral slope reliably predicts the peak frequency and maximum intensity of the synchrotron component of blazar spectral energy distributions, provided it is uncontaminated by radiation unrelated to the jet. A notable correlation between the IR and γ-ray fluxes was observed, with the BL Lacertae subclass of blazars displaying a strong correlation coefficient of r = 0.80. IR band variability is more pronounced in flat spectrum radio quasars than in BL Lacertae objects, with mean fractional variability values of 0.65 and 0.35, respectively. We also observed that the synchrotron peak intensity of intermediate-high-energy-peaked objects can forecast their detectability at very high γ-ray energies. We used this predicting power to identify objects in current catalogs that could meet the detection threshold of the Cerenkov Telescope Array extragalactic survey, which should encompass approximately 180 blazars.

VCD spectra of chiral naphthalene-1-carboxamides in the solid-state

The VCD spectra of chiral 2,3-dihydro-1H-benzo[de]isoquinolin-1-one (8-substituted naphthalene-1-carboxamide, BIQ) were studied in KBr pellets. The X-ray diffractometry revealed that the Me, Ph, and pClPh BIQs crystalize in the monoclinic P21, while nBu, pMePh, and oMeOPh BIQs in the orthorhombic P212121 space group. Only the Me-BIQ crystal exhibits the presence of cyclic amide dimers, while the others contain chains of the amid group hydrogen bonds. For all BIQs, except pMePh, the most intense IR band in the 1750–1550 cm−1 region is located at ca. 1680 cm−1 and is accompanied by two weak ones at ca. 1618 and 1590 cm−1. For the pMePh derivative, four almost equally intense IR bands at 1662, 1639, 1614, and 1588 cm−1 are observed. This region of the IR spectra of BIQs, but pMePh, is well reproduced by calculations based on BIQ monomers. On the other hand, the complex IR pattern of pMePh is computationally reproduced when larger crystal fragments, like octamers, are considered. Registration of the VCD spectra enabled recognizing the complexity of IR contours at ca. 1680 cm−1 by the corresponding VCD motives. For (i) Me, Ph and pClPh (R)-enantiomers, two (+)(–) bands were distinguished and for (ii) nBu and pMePh ones, one VCD band with right-side asymmetry was found. For (iii) oMeOPh the VCD pattern cannot be unambiguously assigned. Thus, the VCD spectra in the ν(C=O) range diverse the studied compounds. Among the set of molecules, pMePh has exceptional crystal geometry. Therefore, its most intense ν(C=O) band position and shape can be connected with the geometry of the hydrogen bonds, interactions, and crystal packing. Interpretation of the VCD spectra is based on linear and packed BIQ octamers. This cluster model can reproduce the main features of the solid-state VCD of BIQs.

A transparent broadband flexible metamaterial absorber for radar infrared-compatible stealth

The iterative upgrading of the means of warfare has promoted the development of detection technology, and military activities are increasingly demanding target stealth. In this paper, a multifunctional metamaterial absorber is recommended, which simultaneously realizes the integrated stealth functions of ultra-wideband radar wave absorption, low infrared emission, and optically transparent. The structure is composed of an infrared shield, a radar-absorbing layer, and a reflective layer. Simulation results indicate that the absorption bandwidth in the radar band (1.81–20.4 GHz) is more than 90%, and the infrared emissivity is as low as 0.271 in the IR band (3–14 μm). Moreover, it has the features of flexibility, angle stability (0–45°), polarization insensitivity (0–90°), and so on. Furthermore, the electric field current distribution and equivalent circuit model of the structure are analyzed, and a 180 mm*180 mm sample is built and tested; the results show that the simulated and actual measurements are in agreement, and it is expected that such absorbers will be used in areas such as aircraft.

High heat-reflective and superhydrophobicity properties functional fabrics

Infrared reflective materials are pivotal in reducing bicarbon emission and have emerged as a global research focus. This study presents the preparation of kilogram-scale weakly Tb-doped cerium oxide nanocomposites, utilizing a green synthesis approach combining ball milling and high-temperature calcination. Integrating first-principles calculations with experiments analysis, we demonstrate that Tb doping enhances the band gap of cerium oxide, significantly improving its reflective properties. The resulting terbium-doped cerium oxide nanoparticles have good absorption in the visible range while maintaining excellent IR reflectance in the IR band. The near-infrared solar reflectance reaches 85.54 %. Additionally, we developed CeO2:Tb–SiO2 polyester fabrics using an impregnation method. These fabrics show superior IR infrared barrier efficiency (76.58 %) and a notable reduction in inner-surface temperature compared to standard polyester fabrics. The barrier efficiency is enhanced by 27.59 %, and the temperature difference reaches up to 6.1 °C, underscoring their exceptional thermal insulating properties. Moreover, the fabric exhibits remarkable superhydrophobicity, with a contact angle of 152.1°. This novel heat-reflective, self-cleaning, stable rare-earth nano-insulating coating along with its application in polyester fabrics, paves the way for effective temperature regulation. Its potential applications in fabric stain and sun protection are promising, contributing to energy saving and sustainable development.

How Aqueous Solvation Impacts the Frequencies and Intensities of Infrared Absorption Bands in Flavin: The Quest for a Suitable Solvent Model.

FTIR spectroscopy accompanied by quantum chemical simulations can reveal important information about molecular structure and intermolecular interactions in the condensed phase. Simulations typically account for the solvent either through cluster quantum mechanical (QM) models, polarizable continuum models (PCM), or hybrid quantum mechanical/molecular mechanical (QM/MM) models. Recently, we studied the effect of aqueous solvent interactions on the vibrational frequencies of lumiflavin, a minimal flavin model, using cluster QM and PCM models. Those models successfully reproduced the relative frequencies of four prominent stretching modes of flavin's isoalloxazine ring in the diagnostic 1450-1750 cm-1 range but poorly reproduced the relative band intensities. Here, we extend our studies on this system and account for solvation through a series of increasingly sophisticated models. Only by combining elements of QM clusters, QM/MM, and PCM approaches do we obtain an improved agreement with the experiment. The study sheds light more generally on factors that can impact the computed frequencies and intensities of IR bands in solution.

Characteristics of multi-absorption bands in near IR based on a 1D photonic crystal comprising two composite metamaterials

The Matlab program has been utilized in this study to examine the absorption spectral properties of a one-dimensional photonic crystal (1DPCs) comprising two composite metamaterials through near IR wavelengths. The composite metamaterials are designed from Ag of a gyroidal geometry (layer A) and hyperbolic metamaterial (layer B). Therefore, the introduced design is labeled as [ABn]m\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${[A{B}^{n}]}^{m}$$\\end{document} with n and m to define the periodicity of the hyperbolic metamaterial and the whole structure, respectively. The numerical findings have been introduced in the vicinity of the effective medium theory, transfer matrix method and the Drude model as well. In this regard, the numerical results demonstrate the appearance of some spectral absorption bands ranging from 0.7 µm to 3 µm for both TM and TE polarizations. Additionally, these bands are almost insensitive to the changes in the angle of incidence. Interestingly, we have considered the role played by some parameters such as the permittivities and thicknesses of both layers on the introduced absorption bands. Finally, we believe that the investigated results could be promising through many applications such as wavelength selective absorbers, solar energy, and smart windows as well.

Design of narrowband infrared emitters by hybridizing guided-mode resonance structures with van der Waals materials

In this paper, narrowband emitters have been designed using particle swarm optimization (PSO) in the 10–20 μm infrared range. The device structure consists of an anisotropic α-MoO3 layer combined with the one- and two-dimensional guided-mode resonance structures. Well-defined absorption lines are present in the reflection spectrum for both TE and TM polarizations, thereby yielding narrowband emissivity at desired wavelengths. The band structure of the designed emitters under TM polarization demonstrates distinct features unlike its TE counterpart. These features are attributed to the interaction between guided-mode resonances and phonon polaritons. The results are relevant for applications in active and passive photonic elements in mid- and long-wave IR bands.