Absorption Bands Research Articles

Optical, Structural, and Morphological Characterization of Titanium Oxide (TiO2) Nanoparticles from Laser Ablation in Deionized Water

In this research, we focus on the synthesis of titanium oxide (TiO2) nanoparticles using the Nd:Utilization of YAG laser pulse ablation technique in liquid environments, with pulse energies from 100 to 500 millijoules. The process employs a Nd:YAG laser operating at a frequency of 6 Hz and a wavelength of 1064 nm. (The TiO2 nanoparticles synthesized in this study could be used in different high-temperature environments, as they are characterized by favorable physical, chemical, and mechanical properties). The synthesized product was further treated by calcination for four hours at temperatures higher than 600°C which promoted crystalline structure in the lattice. Comprehensive analyses were carried out to determine the nanoparticles' features. Optical features were studied through UV-visible spectroscopy to examine the absorption spectrum and band gap. The detailed examination of the crystal and surface structures was done using X-ray diffraction and field emission scanning electron microscopy (FE-SEM), in order to obtain insight into the structural integrity and the morphology of the titanium oxide nanoparticles. The study provides a deeper insight into TiO2 nano particle production and their characteristics, thereby emphasizing their suitability for advanced material applications.

Effect of Natural Dye Extracts on the Absorbance Characteristics of TiO2 in Dye-Sensitized Solar Cells

Natural dye extracts from Chinese Ixora (Ixora chinensis) flower, Cassod flower (Cassia Siamea), Cassava leaf (Manihot Esculenta), purple heart (Tradescantia Pallida) and Copper leaf (Acalypha Wilkesiana) have been explored as sensitizers for the fabrication of dye-sensitized solar cells. The properties of the dyes were investigated using the FTIR and they all showed broad absorption bands in the 3800 to 3000cm-1 wavelenght and strong presence of intermolecular H-bonds. The effect of dye extracts on the absorbance and transmittance features of TiO2 was well studied by the UV-VIS and the absorbance peak was in the case of sensitization with Manihot Esculenta seen to radically improve above 1.0 at 350nm wavelength. Finally, the current and voltage characteristics of the DSSC were studied in sunlight and at a peak sunlight intensity of 601m/w2, the Manihot and Cassod sensitized devices exhibited maximum voltage values of 115 and 84mV respectively and maximum current values of 4.32 and 2.99mA. These plants have shown great potential for application in fabrication of cost effective and environmentally friendly DSSCs.

Helically Chiral π-Expanded Azocines Through Regioselective Beckmann Rearrangement and Their Charged States.

We report a synthetic approach to π-expanded [6]helicenes incorporating tropone and azocine units in combination with a 5-membered ring, which exhibit intriguing structural, electronic, and chiroptical properties. The regioselective Beckmann rearrangement allows the isolation of helical scaffolds containing 8-membered lactam, azocine, and amine units. As shown by X-ray crystallographic analysis, the incorporation of tropone or azocine units leads to highly distorted [6]helicene moieties, with distinct packing motifs in the solid state. The compounds exhibit promising optoelectronic properties with considerable photoluminescence quantum yields and tunable emission wavelengths depending on the relative position of the nitrogen center within the polycyclic framework. Separation of the enantiomers by chiral high-performance liquid chromatography (HPLC) allowed characterization of their chiroptical properties by circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopy. The azocine compounds feature manifold redox chemistry, allowing for the characterization of the corresponding radical anions and cations as well as the dications and dianions, with near-infrared (NIR) absorption bands extending beyond 3000 nm. Detailed theoretical studies provided insights into the aromaticity evolution upon reduction and oxidation, suggesting that the steric strain prevents the azocine unit from undergoing aromatization, while the indene moiety dominates the observed redox chemistry.

Simultaneous modification of emission spectrum and trap distribution for achieving self-trapped excitons-based white afterglow

The incommensurable differences between the feeding and actual doping ratios of luminescent dopants and excessive reliance on rare-earth ions become two key problems in halide perovskite-based afterglow materials, restricting the production cost and further application. Here, we prepare a series of novel lead- and rare-earth-free halide afterglow phosphors Cs2(Na0.9Ag0.1In)1-xZrxCl6 under an ambient condition, in which the Zr dopants modify the lattice thus tailoring the emission spectrum and trap distribution, simultaneously. The focused Cs2(Na0.9Ag0.1In)0.6Zr0.4Cl6 with mainly size distribution of ∼ 0.6–1.8 μm exhibits ∼ 350–850 nm ultrabroad white luminescence under ultra-violet excitation, and the introduced traps endow the white emission with a long-persistence of over 5 h after pre-irradiation. The absorption bands of self-trapped excitons (STEs) are observed in the steady-state absorption spectra during the afterglow process, suggesting the general accepted picosecond-scaled lifetimes of STEs have been successfully prolonged to hour-scale, which provide a potential opportunity for investigating the specific behavior of STEs.

Helically Chiral π‐Expanded Azocines Through Regioselective Beckmann Rearrangement and Their Charged States

We report a synthetic approach to p‐expanded [6]helicenes incorporating tropone and azocine units in combination with a 5‐membered ring, which exhibit intriguing structural, electronic, and chiroptical properties. The regioselective Beckmann rearrangement allows the isolation of helical scaffolds containing 8‐membered lactam, azocine, and amine units. As shown by X‐ray crystallographic analysis, the incorporation of tropone or azocine units leads to highly distorted [6]helicene moieties, with distinct packing motifs in the solid state. The compounds exhibit promising optoelectronic properties with considerable photoluminescence quantum yields and tunable emission wavelengths depending on the relative position of the nitrogen center within the polycyclic framework. Separation of the enantiomers by chiral high‐performance liquid chromatography (HPLC) allowed characterization of their chiroptical properties by circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopy. The azocine compounds feature manifold redox chemistry, allowing for the characterization of the corresponding radical anions and cations as well as the dications and dianions, with near‐infrared (NIR) absorption bands extending beyond 3000 nm. Detailed theoretical studies provided insights into the aromaticity evolution upon reduction and oxidation, suggesting that the steric strain prevents the azocine unit from undergoing aromatization, while the indene moiety dominates the observed redox chemistry.

Exciton Delocalization and Polarizability in Perylenetetracarboxylic Diimide Probed Using Electroabsorption and Fluorescence Spectroscopies.

Perylenetetracarboxylic diimide (PTCDI) is an n-type organic semiconductor molecule that has been widely utilized in numerous applications such as photocatalysis and field-effect transistors. Polarizability and dipole moment, which are inherent properties of molecules, are important parameters that determine their responses to external electric and optical fields, physical properties, and reactivity. These parameters are fundamentally important for the design of innovative materials. In this study, the effects of external electric fields on absorption and fluorescence spectra were investigated to obtain the PTCDI parameters. The PTCDI substituted by an octyl group (N,N'-Dioctyl-3,4,9,10-perylenedicarboximide) dispersed in a polymethyl methacrylate (PMMA) matrix was studied in this work. The features of vibronic progression in the absorption spectrum were analogous to those observed in solution. The red shift of the absorption band caused by the Stark effect was mainly observed in the presence of an external electric field. Changes in parameters such as the dipole moment and polarizability between the ground and the Franck-Condon excited states of the PTCDI monomer were determined. The fluorescence spectrum shows a contribution from a broad fluorescence band at wavelengths longer than the monomer fluorescence band. This broad fluorescence is ascribed to the excimer-like fluorescence of PTCDI. The effects of the electric field on the fluorescence spectrum, known as the Stark fluorescence or electrofluorescence spectrum, were measured. Fluorescence quenching is observed in the presence of an external electric field. The change in the polarizability of the monomer fluorescence band is in good agreement with that of the electroabsorption spectrum. A larger change in the polarizability was observed for the excimer-like fluorescence band than that for the monomer band. This result is consistent with exciton delocalization between PTCDI molecules in the excimer-like state.

Study on An Interaction between Titan Yellow and Orange S Indicators in Water and Ethanol by using Spectroscopy Technique

Charge transfer complex (CTC) of Orange S (donor) and Titan Yellow (acceptor) has been studied in ethanol, and water solvents at room temperature (20°C) using absorption spectrophotometer. The results indicate that formation of CTC in high polar solvent is high. The stoichiometry of the complex was found to be 1:1 ratio by straight-line method between donor and acceptor with maximum absorption bands and present of isosbestic point suggest this fact. The data are discussed in terms of formation constant (KCT), molar extinction coefficient (εCT), standard free energy (ΔGo), transition energy (ECT), and ionization potential (IP). The formation constant (KCT) for the complex was shown to be dependent upon the polarity of solvents that were used. Electronic absorption spectra, which indicate the CT interaction, associated with proton migration from the acceptor to the donor followed by hydrogen bonding.

Polarity in Liquid Crystals Formed by Self-Assembled Umbrella-Shaped Subphthalocyanine Mesogens.

We investigated the properties of p-type semiconducting columnar phases in self-assembled umbrella-shaped mesogens that have subphthalocyanine cores and oligo-thienyl arms. These compounds have nonswitchable phases that exhibit remanent electric polarization and nonlinear optical activity. Additionally, these compounds can generate photocurrents in the visible spectral range due to their wide absorption band. The photocurrent can be significantly increased by doping materials with fullerene. The charge mobility shows an anomalous field dependence, which decreases with the temperature.

Characterization of carbon dioxide on Ganymede and Europa supported by experiments: Effects of temperature, porosity, and mixing with water

The surfaces of icy moons are primarily composed of water ice that can be mixed with other compounds, such as carbon dioxide. The carbon dioxide (CO$_2)$ stretching fundamental band observed on Europa and Ganymede appears to be a combination of several bands that are shifting location from one moon to another. We investigate the cause of the observed shift in the CO$_2$ stretching absorption band experimentally. We also explore the spectral behaviour of CO$_2$ ice by varying the temperature and concentration. We analyzed pure CO$_2$ ice and ice mixtures deposited at 10 K under ultra-high vacuum conditions using Fourier-transform infrared (FTIR) spectroscopy and temperature programmed desorption (TPD) experiments. Laboratory ice spectra were compared to JWST observation of Europa's and Ganymede's leading hemispheres. The simulated IR spectra were calculated using density functional theory (DFT) methods, exploring the effect of porosity in CO$_2$ ice. Pure CO$_2$ and CO$_2$-water ice show distinct spectral changes and desorption behaviours at different temperatures, revealing intricate CO$_2$ and H$_2$O interactions. The number of discernible peaks increases from two in pure CO$_2$ to three in CO$_2$-water mixtures. The different CO$_2$ bands were assigned to $ nu $ (2351 cm$^ $, 4.25 mu m) caused by CO$_2$ dangling bonds (CO$_2$ found in pores or cracks) and $ nu $ (2345 cm$^ $, 4.26 mu m) due to CO$_2$ segregated in water ice, whereas $ nu $ (2341 cm$^ $, 4.27 mu m) is due to CO$_2$ molecules embedded in water ice. The JWST NIRSpec CO$_2$ spectra for Ganymede and for Europa can be fitted with two Gaussians attributed to $ nu $ and $ nu $. For Europa, $ nu $ is located at lower wavelengths due to a lower temperature. The Ganymede data reveal latitudinal variations in CO$_2$ bands, with $ nu $ dominating in the pole and $ nu $ prevalent in other regions. This shows that CO$_2$ is embedded in water ice at the poles and it is present in pores or cracks in other regions. Ganymede longitudinal spectra reveal an increase of the CO$_2$ $ nu $ band throughout the day, possibly due to ice cracks or pores caused by large temperature fluctuations.

Radical scavenging potential of spectrophotometric, spectroscopic, microscopic, and EDX observed zinc oxide nanoparticles from leaves, buds, and flowers extract of Bauhinia Variegata Linn: A thorough comparative insight.

The present study incorporated an environment-friendly and cost-efficient green synthesis method for fabricating zinc oxide nanoparticles (ZnO-NPs) using various parts (leaves, buds, and flowers) of Bauhinia Variegate Linn. UV-Spectrophotometric analysis was used to confirm the synthesis of ZnO-NPs, which showed an absorption band within 360-380 nm range. Further techniques like FT-IR spectroscopy and (SEM) scanning electron microscopy equipped with a novel EDX were also included to confirm the synthesis, size, and shape of ZnO-NPs. Results obtained by FT-IR showed that the phytochemicals present in the ethanolic extract successfully acted as a capping agent. SEM micrographs confirmed irregularly shaped nanoparticles with an average size of 70-80 nm. The presence of Zinc and Oxygen peaks in EDX also confirmed the successful synthesis of ZnO nanoparticles. The radical scavenging (antioxidant) potential of prepared nanoparticles was also evaluated by DPPH radical assay. The ZnO-NPs obtained from the ethanolic extract of buds showed the highest %RSA (86%) as compared to the flowers (79%) and leaves (76%). The current study findings showed the versatile morphology of all parts of the plant with significant antioxidant potential, establishing the use of Bauhinia Variegate in biological systems for various biomedical applications. RESEARCH HIGHLIGHTS: A thorough comparative analysis of the radical scavenging power of major parts of the Bauhinia Variegate, which is 1st of its kind. Extensive characterization using UV-Vis spectrophotometry, FT-IR, SEM, and EDX to observe the conformational and morphological changes. Analysis of the reduction potential of leaves, buds, and flowers of a single plant for future directions in green synthesis.

Exploring the Influence of Cation and Halide Substitution in the Structure and Optical Properties of CH3NH3NiCl3 Perovskite.

This manuscript details a comprehensive investigation into the synthesis, structural characterization, thermal stability, and optical properties of nickel-containing hybrid perovskites, namely CH3NH3NiCl3, CsNiCl3, and CH3NH3NiBrCl2. The focal point of this study is to unravel the intricate crystal structures, thermal behaviors, and optical characteristics of these materials, thereby elucidating their potential application in energy conversion and storage technologies. X-ray powder diffraction measurements confirm that CH3NH3NiCl3 adopts a crystal structure within the Cmcm space group, while CsNiCl3 is organized in the P63/mmc space group, as reported previously. Such structural diversity underscores the complex nature of these perovskites and their potential for tailored applications. Thermal analysis further reveals the stability of CH3NH3NiCl3 and CH3NH3NiBrCl2, which begin to decompose at 260 °C and 295 °C, respectively. The optical absorption properties of these perovskites studied by UV-VIS-NIR spectroscopy revealed the bands characteristic of Ni2+ ions in an octahedral environment. Notably, these absorption bands exhibit subtle shifts upon bromide substitution, suggesting that optical properties can be finely tuned through halide modification. Such tunability is paramount for the design and development of materials with specific optical requirements. By offering a detailed examination of these properties, the study lays the groundwork for future advancements in material science, particularly in the development of innovative materials for sustainable energy technologies.

Features of obtaining composite material from hydrophobic clay with antimicrobic properties

A method for obtaining a nanocomposite from hydrophobic clays with bactericidal properties is considered, which plays the role of a drug matrix intercalated agar-agar. Such nanocomposite materials are increasingly used in medicine as matrices for medicines and vitamins using their adsorption properties and long-term exposure. It was established using TEM analysis that halloysite particles from Beloye Glinische deposit are nanoscale and have a cylindrical shape with a length from 200 nm to 1000 nm and a diameter of nanoparticles from 50 nm to 80 nm. The first stage of the bionanocomposites manufacturing process was the treatment of halloysite nanoparticles with silver ions to impart antimicrobial properties, and hydrophobization with a cationic surfactant was carried out at the next stage. It was established by the X-ray diffraction method that the interlayer space of HNT has been expanded from 9.998 Å to 17.5 Å on the result of the cationic adsorption on the HNT. FTIR spectroscopy also proved the adsorption of surfactant molecules on halloysite by the presence of an appropriate absorption band. The adsorption of silver on a nanotube made of halloysite was revealed by the method of energy-dispersive X-ray spectroscopy. Antimicrobial properties of silver-treated and organophilic halloysite have been established and proved by in vitro analyses in microbiological laboratories about Escherichia coli. Hydrophobic samples of these organophilic clays had edge angles higher than 90° and this proves that all samples are hydrophobic. The resulting organophilic clays were intercalated into an agar-agar matrix and were thrown into a solution of calcium chloride, which gave them stability in a liquid medium. It has been practically established that the most optimal bionanocomposite microsphere is a 50% ratio of organohalloysite and agar-agar.

Bi3+/Mn4+ co-doped Y2MgTiO6 dual-emitting phosphors for plant growth lighting and temperature sensor

Novel Bi3+/Mn4+ co-doped Y2MgTiO6 dual-emitting phosphors were synthesized using a high-temperature solid-phase method. The crystal structure and luminescence properties of phosphors were systematically investigated by experimental characterization and theoretical calculation. Under excitation at 375 nm, Y2MgTiO6:Bi3+, Mn4+ phosphors exhibit two emission bands located at 410 nm and 696 nm (blue and red), which can well be matched with the absorption bands of chlorophylls a, b and phytochrome. The Y2MgTiO6: Bi3+, Mn4+ luminescence remains at 66.2 % intensity at 423 K and quantum yield is 52.06 %. Optical temperature properties of Y2MgTiO6:Bi3+, Mn4+ were investigated using fluorescence intensity ratio (FIR) analysis and were found to reach a maximum relative sensitivity of 2.93 % K−1 at 498 K. The study suggests that this material could be a potential option for indoor plant culture and optical temperature sensing.

Molecular Probing of the Microscopic Pressure at Contact Interfaces.

Obtaining insights into friction at the nanoscopic level and being able to translate these into macroscopic friction behavior in real-world systems is of paramount importance in many contexts, ranging from transportation to high-precision technology and seismology. Since friction is controlled by the local pressure at the contact it is important to be able to detect both the real contact area and the nanoscopic local pressure distribution simultaneously. In this paper, we present a method that uses planarizable molecular probes in combination with fluorescence microscopy to achieve this goal. These probes, inherently twisted in their ground states, undergo planarization under the influence of pressure, leading to bathochromic and hyperchromic shifts of their UV-vis absorption band. This allows us to map the local pressure in mechanical contact from fluorescence by exciting the emission in the long-wavelength region of the absorption band. We demonstrate a linear relationship between fluorescence intensity and (simulated) pressure at the submicron scale. This relationship enables us to experimentally depict the pressure distribution in multiasperity contacts. The method presented here offers a new way of bridging friction studies of the nanoscale model systems and practical situations for which surface roughness plays a crucial role.

Cr3+‐doped far‐red phosphors with zero thermal quenching and excellent spectral matching for plant lighting application

AbstractFar‐red‐emitting (700−740 nm) phosphors are essential for the fabrication of plant lighting phosphor‐converted light‐emitting diodes (pc‐LEDs). However, the development of highly efficient, thermally stable, and spectrally matched far‐red phosphors still remains a challenge. Herein, far‐red GdAlO3:Cr3+ (GAO:Cr3+) phosphors were synthesized via solid‐state reaction and investigated for plant lighting pc‐LED applications. A low‐temperature flux‐assisted synthesis strategy was adopted to improve the crystalline quality, suppress the defect formation, and maintain the valence state of Cr3+ in the phosphors, finally leading to significant luminescent enhancement (∼10 times). The GAO:Cr3+ phosphors show the 2E sharp‐line emissions around 730 nm, which is highly matched with the far‐red absorption band of plants. The optimized GAO:0.01Cr3+ phosphor exhibits a high internal quantum efficiency of 98.3% and zero thermal quenching even up to 250°C. The fabricated pc‐LED can generate an overall output power of 78.1 mW at 100 mA drive current, with a high energy conversion efficiency of 25.3%. The findings demonstrate the great potential of GAO:Cr3+ as far‐red‐emitting phosphor materials for plant growth pc‐LED applications.

Far Infrared/Terahertz Spectroscopy as a Complementary Method for the Analysis of the Spectral Features of Thymol and Carvacrol Structural Isomers

Objective: The conventional method for the characterization of volatile compounds has been mostly limited to the use of gas chromatography. This work offers an alternative method to address the limitations that might be encountered with the use of the gas chromatography method. Furthermore, this work addresses the scarcity of the analysis of these materials in the far infrared/terahertz region as previous studies have been focused mainly on the mid-infrared region. Methods: The far infrared/terahertz spectra of carvacrol and thymol were analyzed using the Fourier transform infrared (FTIR) and gas chromatography-mass spectroscopy (GC-MS). Density function theory (DFT) calculations were employed for the interpretation of the FTIR experimental spectra. Results: Thymol and carvacrol spectra were characterized by distinct absorption bands in the 200-600 cm−1 (6-18 THz). There were appearances of bands at similar energies for these isomers. These bands appeared at 320.7 cm−1 (9.6 THz), 439.2 cm−1 (13.2 THz), 525.2 cm−1 (15.8 THz), and 586.8 cm−1 (17.6 THz) for thymol and at 313.6 cm−1 (9.4 THz), 419.8 cm−1 (12.6 THz), 521.2 cm−1 (15.7 THz), and 566.9 cm−1 (17.0 THz) for carvacrol. Despite these similarities, there were also significant differences in the spectra of these materials. The theoretical peak frequencies were in agreement with the experimental absorption band frequencies. Two seemingly common absorption bands were observed in the spectra of thymol and carvacrol. However, peak assignments revealed that these bands have different vibrational modes. The GC-MS results show that the retention time of thymol and carvacrol are very close at 18.5 and 18.8 respectively. Conclusion: This work underscores the ability of far infrared/terahertz waves in identifying materials with similar structural features. Furthermore, it supplements the limited studies of these isomers in the far infrared/terahertz region. The GC-MS results emphasize the need for a complementary method that can improve the characterization of these materials.

Spectroscopic studies of Eu doped CaF2 single crystal

The Eu-doped CaF2 crystal is investigated for potential use in visible-region solid-state lasers. The single-crystal Eu: CaF2 has an FCC crystal structure and belongs to the space group Fm-3 m, as confirmed by single-crystal X-ray diffraction. A Raman shift of 324 cm−1 has been observed in a single crystal of Eu: CaF2. The vibrational mode at low frequency is suitable for minimizing non-radiative emissions and increasing radiative emissions. Eu: CaF2 crystal has two absorption bands, at 399 nm and 415 nm, corresponding to the 7F0→5L6 and 7F0→5D3 transitions, respectively. The strongest absorption peak (399 nm) is associated with the 7F0→5L6 electronic transition. The orange-red emission was observed at 588 nm (5D0→7F1), 612 nm (5D0→7F2), 648 (5D0→7F3), and 685(5D0→7F4) when excited at 399 nm. Measurements of the luminescence intensity ratio (R) between the 5D0→7F2 (electric dipole) transition and the 5D0→7F1 (magnetic dipole) transition predict that Eu3+ ions are situated at the symmetric sites in CaF2. The radiative parameters for the Eu: CaF2 crystal are calculated using the JOES code using the Judd-Ofelt theory. The calculated total radiative transition probability (AR) is 64.54 s−1, and the radiative lifetime (τR) is 15.57 ms. Radiative transition probabilities are 43.41,7.02 and 14.10, and branching ratios are 67.26 %,10.88 % and 21.85 % for 5D0→7F1, 5D0→7F25D0→7F4 transitions respectively.

Optical spectra in pure-silica-core single mode optical fibers after high-fluence reactor irradiation

The paper describes the study of radiation-induced attenuation (RIA) spectra in reactor-irradiated single mode at λ=1.55 μm optical fibers (OFs) with differente high-temperature coatings (polyimyde, aluminum and copper). The OFs were previously irradiated up to fast neutron fluence 1.8·1020 n/cm2 and gamma dose 2.32 GGy. After three years of storage at room temperature (RT), the RIA spectra were examined in the range of 650–1700 nm. All RIA mechanisms acting in this spectral range were identified: a tail of non-bridging oxygen hole center, a long-wavelength RIA (LWRIA) band with a maximum at λ > 1600 nm, unstructured “grey” loss due to coating microbendings or damage, and an absorption band peaking at 930 nm (E=1.33 eV). It was found out that the LWRIA can be significantly annealed at RT in polyimide-coated OFs. Grey loss were found to be more stable than those causing LWRIA.The LWRIA arising in reactor- and gamma-irradiated OFs have close thermal stability at RT and exhibit a similar shapes, which close to the absorption band of self-trapped holes (STH). This suggests a STH-like nature of the LWRIA.

High FoM quad‐band THz perfect metamaterial absorber‐based RI sensor for gas sensing applications

AbstractHere, a novel design of a microstructured quad‐band terahertz metamaterial absorber is presented consisting of a copper‐based merged circular and square split ring resonator‐integrated over a lead glass substrate intended to detect changes in the surrounding medium's refractive index for gas sensing applications through THz spectroscopy. Outstanding performance is shown by the suggested absorber, which achieves a maximum absorption rate of 99.4%, 98.7%, 99.2%, and 99.4%, at resonance frequencies of 8.055 (), 8.423 (), 9.257 (), and 9.507 () THz, respectively. The quality factors (Q‐factors) attained are 201, 129, 298, and 271 for these four absorption bands. The obtained sensitivity values at these four distinct bands are 3898, 2927, 4719, and 4102 GHz per refractive index unit with high figure of merits (FoM) of 97, 95, 152, and 117, respectively, throughout a range of refractive indices from n = 1.00 to n = 1.05 (with a step size of 0.005). The study's novelty lies in its novel design and remarkable ability to excel in gas sensing with high sensitivity and high FoM across not just one but four distinct THz bands. Furthermore, each band demonstrates significantly superior performance in sensitivity, Q‐factor, and FoM, among other parameters compared to prior research in both gas detection and RI monitoring scenarios, hence exhibiting its potential across a wide range of applications.

Achieving high-efficiency electromagnetic wave absorption performance in a 3-layer hierarchical porous magneto-dielectric nanocomposite

Hierarchical porous structures along with micro- and nanoparticles of magneto-dielectric components in sandwich structure design have superior potential applications in the field of electromagnetic wave absorption, due to high active dissipation phenomena such as multiple scatterings and reflections between components, 3D network pores and layers, coupling interactions between each layer, promotion of interfacial polarization, and so on. The Sandwich-Structure absorber composed of hierarchical porous Bi2MoO6, Cu microparticles, and FeNi nanoparticles was effectively constructed with optimization in layer thickness and low filler loading percentage. The microwave absorption characteristics of absorber samples varied in thickness but all less than 1.6 mm in total thickness were thoroughly examined. The as-prepared sandwich structure displayed a unique microwave absorbing behavior due to the multiple-layer structure, the dielectric dissipation property of both Bi2MoO6, Cu microparticles and the magnetic dissipation feature of FeNi nanoparticles, as well as the complementary effect between particles and layers. Minimum reflection loss (RLmini) of −45.5 dB at 5.5 GHz is obtained with proper optimization of layer order and thickness in a resin base 3-layer absorber sample with Bi2MoO6 placed as a top layer with 0.4 mm thickness, FeNi placed as a middle layer with 0.5 mm thickness, and finally Cu placed as a bottom layer with 0.7 mm thickness. The results show that the as-prepared 3-layer nanocomposite sample has a high potential for usage in microwave absorption in the low-frequency band.