Absorption Experiments Research Articles

Geochemistry and mineralogy of legacy tailings under a composite cover

Remediation by a composite cover was implemented on partly oxidized sulfide-rich tailings in northern Ontario, Canada to reduce the production and release of acid mine drainage (AMD). The impact of the cover on sulfide oxidation rates and trace element mobility was initiated a decade after cover installation via multi-year measurements of pore-gas concentrations, pore-water and groundwater sampling and analysis, mineralogical studies of the tailings, selective chemical extractions, and synchrotron-based X-ray absorption experiments. Depleted pore-gas O2 concentrations, circumneutral pH, and improvement in water quality were observed at one detailed sampling location, suggesting that the cover decreased AMD generation and transport. Carbon and sulfur isotope ratios indicate sulfate reduction occurred at the base of the tailings. In contrast, near-atmospheric pore-gas O2 concentrations, low pH, and elevated aqueous concentrations of Fe, sulfate, Zn, Cu, As, and Pb were observed at another location, suggesting localized sulfide oxidation. Trace elements in the tailings are associated with secondary crystalline and amorphous Fe(III) oxyhydroxides, covellite, and Fe(III) hydroxysulfate phases, formed prior to cover installation. Substantial reductive dissolution of Fe(III) oxyhydroxides due to the isolation of the tailings from the atmosphere by the cover was not observed. Concentrations of Zn and Mn remained elevated due to limited sequestration under the current acidic to circumneutral pH. Although secondary Fe(III) oxyhydroxides contain As(V) and As(III), which were released by arsenopyrite oxidation, dissolved As persists. Due to localized sulfide oxidation, element remobilization, and limited capacity for sulfate reduction, diminished water quality, with elevated aqueous concentrations of sulfate, Zn, As, and Mn, may endure.

Diameter and gap controlled fabrication of periodic SiMW/SiNW arrays: A broadband absorber for high efficiency silicon solar cell

Vertically aligned and periodic silicon micro/nano-wire (SiMW/SiNW) arrays of different diameters were synthesized by combining lithography-free silica particle patterning, reactive ion etching (RIE), and modified metal-assisted chemical etching (MACE) methods. All required silica particles were synthesized, and process parameters were optimized to fabricate sub 50 nm SiNW to large size SiMW with the controlled inter-wire gap. Fabricated SiMW/SiNW array samples show a significant reduction of reflectance (7–9 %) in the silicon absorption band (300 nm–1000 nm). Additional absorption of 25–33 % compared to the planar silicon is observed in the sub-bandgap region of silicon (1100–2000 nm) for these samples, which signifies the effect of field confinement within these structures. The estimated short circuit current density (JSC) using the experimental absorption spectrum of SiMW is 49.96 mA/cm2, which is 16 % higher than the Lambertian limit of ∼43 mA/cm2. This result can lead to the theoretical efficiency of the solar cell up to 28.73 % without the inclusion of the surface passivation effect.

Determination of electromagnetic traveling path in polymer/multi‐walled carbon nanotube nanocomposite foams and analysis by Taguchi technique

AbstractThe attenuation of electromagnetic (EM) energy with polymeric nanocomposite foams is significant because the microwave energy is diminished by multiscattering of EM into microcellular structure. In this study, acrylonitrile butadiene styrene (ABS) and multi‐walled carbon nanotubes (MWCNTs) nanocomposite foams were fabricated via a chemical foaming in an injection‐molding process. It was demonstrated that the skin depth in foamed ABS/MWCNT specimens was fallen dramatically compared to their solid counterparts. The diminution of skin depth for foamed ABS/1 wt% of MWCNT nanocomposite was 21.7% compared to solid pure ABS. The reflectance of pure ABS was decreased by foaming but it was increased in foamed ABS/MWCNT nanocomposite. The absorption of microwave was improved by foaming and adding MWCNTs in ABS matrix. The utmost value of the experimental absorption shielding effectiveness (SEA. experimental), 14.26 dB, was found for the foamed ABS/1 wt% of MWCNT, holding pressure of 2 s and cooling time of 60 s F8, at 8.7 GHz. It was demonstrated that traveling path of EM wave was prolonged by the introduction of microcellular structure in ABS/MWCNT nanocomposite. Moreover, the contribution of MWCNT, holding pressure time, and cooling time to traveling path were achieved 76.7%, 8.5%, and 7.3%, respectively.Highlights ABS/MWCNTs nanocomposite foams were fabricated by chemical foaming process. Skin depth in foamed nanocomposite samples was fallen compared to solids. Reflectance of pure ABS was decreased by foaming. Absorption of microwave was improved by foaming and MWCNTs. Traveling path of EM wave was prolonged by microcellular structure.

Five-coordinated bis-dioxolene cobalt complexes with triphenylphosphine

Three novel five-coordinated bis-dioxolene cobalt complexes with triphenylphosphine were synthesized. Complexes differ by dioxolene ligands: 3,6-di-tert-butylcyclohexa-3,5-diene-1,2-dione (complex 1), 5,8-di-tert-butyl-2,3-dihydro-1,4-ethanoquinoxaline-6,7-dione (complex 2), 3,6-di-tert-butyl-4-methoxycyclohexa-3,5-diene-1,2-dione (complex 3). The geometry of the inner coordination core of all compounds is close to square pyramidal. The base of the pyramid is formed by oxygen atoms of the dioxolene ligands whereas phosphine occupies the apical position. The planes of dioxolenes are slightly bent relative to each other. The magnetic moment values at low temperatures correspond to one unpaired electron per molecule for all complexes. In the complex containing a methoxy group in the dioxolene ligand (3), an increase in the magnetic moment is observed upon heating above 250 K, which indicates the appearance of a fraction of molecules with a higher spin multiplicity. A slight elongation of the Co-O, Co-P distances and shortening of the CO bonds is observed at 353 K. DFT calculations using the TPSSh functional correctly reproduce geometries of the complexes as well as their electronic absorption and vibrational spectra. DFT predicts the doublet-state complexes to possess the lowest enthalpies. Gibbs free energy of sextet complex 3 in solution is lower than that of its doublet state. This agrees well with the experimental electronic absorption spectra. On the basis of TD DFT calculations, a strong NIR absorption band in the spectra of low-spin 1 and 2 is assigned to the transition involving charge transfer from cobalt to the dioxolene and PPh3 ligands (MLCT). The doublet molecules can be described by the (↑SQ—)(Co3+)(Cat2—) ↔ (Cat2—)(Co3+)(↑SQ—) resonance structures. The sextet state in all three systems represents the (↑SQ—)(↑↑↑Co2+)(PPh3)(↑SQ—) bis-semiquinonate complex of high-spin Co(II). On the basis of the conventional description the doublet → sextet transition in complexes can be interpreted as a VT/SCO transformation. The electron density analysis of the doublet → sextet transition in the 1 and 3 molecules reveals areas of both increase and decrease in the charge density near the Co and O atoms.

Computational study of self-trapped hole in KH2PO4–Si crystal

We use the DFT + U approach to investigate the properties of self-trapped holes (STHs) in silicon (Si)-doped potassium dihydrogen phosphate (KH2PO4) crystal. The calculated electronic structure and spin density indicate that the hole is trapped by an oxygen around the Si atom. The STH is stable under room temperature, as the self-trapped energy is as high as 0.50 eV. The optical properties of the localized and delocalized holes of KH2PO4-Si crystals are also calculated, and the results show that the emission energy of the STH [3.62 eV (343 nm)] is consistent with the experimental photoluminescence of KH2PO4 (342 nm), and the absorption peaks of the STH [3.58 eV (346 nm) and 5.56 eV (223 nm)] are located in the ultraviolet (UV) region, which indicates a close connection between the STH and the absorption band in the UV region. The absorption peak of the delocalized hole [3.44 eV (360 nm)] is consistent with the experimental absorption band (360 nm). Therefore, Si impurities result in UV absorption and a sharp decline of damage threshold in KH2PO4.

Transport kinetics of protium and deuterium in titanium: Experiments and modeling

We conducted absorption experiments on Ti using hydrogen isotopes, protium and deuterium, to gain insights into the kinetics of hydrogen atoms, particularly across the Ti surface. Rather than relying on various surface pretreatments, we identified the initial temperature of Ti in vacuum as the determining factor in achieving a high absorption rate and content. Specifically, we found that the initial Ti temperatures of approximately 900 and 980 °C are optimal for protium and deuterium, respectively, likely due to sufficient removal of the native surface oxide on Ti. The dependence of the absorption rate and amount of hydrogen isotopes on the temperature during absorption was partially explained by the phase transformation and exothermicity of the hydrogenation reaction. Moreover, this dependence strongly indicated the existence of a tunneling transport process. Additionally, we developed a kinetic model for hydrogen isotope transport in Ti to conduct numerical simulations. The absorption curves, calculated using the developed model, closely matched a series of experimental curves obtained at different temperatures. These curves were from an identical set of equations and kinetic parameters for both protium and deuterium. Our numerical kinetic model has the potential to serve as a valuable simulation tool for various applications, such as the design of high-performance hydrogen storage systems and maintenance strategies against hydrogen embrittlement of structural materials.

Inverse design of chiral functional films by a robotic AI-guided system

Artificial chiral materials and nanostructures with strong and tuneable chiroptical activities, including sign, magnitude, and wavelength distribution, are useful owing to their potential applications in chiral sensing, enantioselective catalysis, and chiroptical devices. Thus, the inverse design and customized manufacturing of these materials is highly desirable. Here, we use an artificial intelligence (AI) guided robotic chemist to accurately predict chiroptical activities from the experimental absorption spectra and structure/process parameters, and generate chiral films with targeted chiroptical activities across the full visible spectrum. The robotic AI-chemist carries out the entire process, including chiral film construction, characterization, and testing. A machine learned reverse design model using spectrum embedded descriptors is developed to predict optimal structure/process parameters for any targeted chiroptical property. A series of chiral films with a dissymmetry factor as high as 1.9 (gabs ~ 1.9) are identified out of more than 100 million possible structures, and their feasible application in circular polarization-selective color filters for multiplex laser display and switchable circularly polarized (CP) luminescence is demonstrated. Our findings not only provide chiral films with the highest reported chiroptical activity, but also have great fundamental value for the inverse design of chiroptical materials.

Extension of Judd-Ofelt theory: Application on Eu3+, Nd3+ and Er3+

We present a modified version of the Judd-Ofelt theory, which describes the intensities of f-f transitions for trivalent lanthanide ions (Ln3+) in solids. In our model, the properties of the dopant are calculated with well-established atomic-structure techniques, while the influence of the crystal-field potential is described as a perturbation, by three adjustable parameters. Compared to our previous work (Hovhannesyan et al., 2022 [28]), the spin-orbit interaction within the first excited configuration 4fw−15d is described in a perturbative way, whereas it is exactly taken into account in the ground configuration 4fw, using all the eigenvector components of the free-ion levels. Moreover, the wavelength-dependence of the refractive index of the host material is also accounted for. We test the validity of our model on three ions: Eu3+, Nd3+ and Er3+. The results of the extension are satisfactory, we are able to give a physical insight into all the transitions within the ground electronic configuration, and also to reproduce quantitatively experimental absorption oscillator strengths. We also performed calculations of standard JO parameters, and the results are in good agreement with the values reported in the literature. The code used to make the calculations is available on GitLab.

Does the Traditional Band Picture Describe the Electronic Structure of Doped Conjugated Polymers? TD-DFT and Natural Transition Orbital Study of Doped P3HT.

Polarons and bipolarons are created when one or two electrons are removed from the π-system of a p-type conjugated polymer, respectively. In the traditional band picture, the creation of a polaron causes two electronic energy levels to move into the band gap. The removal of a second electron to form a bipolaron causes the two intragap states to move further into the gap. Several groups, however, who looked at the energies of the Kohn-Sham orbitals from DFT calculations, have recently argued that the traditional band picture is incorrect for explaining the spectroscopy of doped conjugated polymers. Instead, the DFT calculations suggest that polaron creation causes only one unoccupied state to move into the band gap near the valence band edge while half-filled state in the valence band and the conduction band bend downward in energy. To understand the discrepancy, we performed TD-DFT calculations of polarons and bipolarons on poly(3-hexylthiophene) (P3HT). Not only do the TD-DFT-calculated absorption spectra match the experimental absorption spectra, but an analysis using natural transitional orbitals (NTOs), which provides an approximate one-electron picture from the many-electron TD-DFT results, supports the traditional band picture. Our TD-DFT/NTO analysis indicates that the traditional band picture also works for bipolarons, a system for which DFT calculations were unable to determine the electronic structure.

Efficient capture of benzene and its homologues volatile organic compounds with protic [MIM][NTF2] and aprotic [EMIM][NTF2] ionic liquids: Experimental and computational thermodynamics

Using new green solvents to effectively capture volatile organic compounds (VOCs) is considered as an attractive green sustainable chemical development route. In this work, benzene, toluene, ethylbenzene and p-xylene (BTEX) were selected as typical aromatic VOCs. The gas absorption performance of proton [MIM][NTF2] and aprotic [EMIM][NTF2] ionic liquids (ILs) for BTEX were studied by computational thermodynamics combined with gas absorption experiments. Absorption experiments of BTEX and regeneration experiments of ILs were carried out at different temperatures, and ILs had good stability. The interaction type and intensity were determined by Interaction Region Indicator (IRI) analysis of IL-BTEX blend systems. The C-H···π and π-π interaction between imidazole ring and BTEX were the direct reason why ILs can efficiently absorb BTEX. Molecular dynamics simulations were performed to explore the diffusion behavior of gas in ILs. The increase of methyl group increases the interaction strength of the system, and the fractional free volume of IL-BTEX blend systems decreases gradually, which limits the diffusion of BTEX. Non-bond interaction analysis shows that van der Waals interaction was the main driving force of BTEX absorption in ILs.

Anharmonicity and deuteration in the IR absorption and emission spectrum of phenylacetylene

Anharmonic cascade emission simulations, herein evinced by full reproduction and deep insights into recent emission spectroscopy experiments of phenylacetylene, are integral to the future successful analysis of JWST observational spectra. Experimental infrared absorption experiments conducted in this study reveal a complex spectrum dominated by quantum effects that are uncovered by anharmonic computational analysis. From this work, it becomes clear that phenylacetylene exhibits strong resonance coupling between fundamental and two-quanta combination modes as well as giving indication for coupling with higher-order, three-quanta combination bands. This study benchmarks the development of advanced computational methods that will be extended to larger systems of astronomical relevance and those including isotopic substitution and side group functionalization with groups such as acetylene. The astrophysical implications of these results, including the potential for detection of acetylenic C–H stretches in space, are discussed in the vein of the impact polycyclic aromatic hydrocarbons have on astronomical infrared emission bands.

Exciting lattice oxygen of nickel–iron bi-metal alkoxide for efficient electrochemical oxygen evolution reaction

High efficiency, cost-effective and durable electrocatalysts are of pivotal importance in energy conversion and storage systems. The electro-oxidation of water to oxygen plays a crucial role in such energy conversion technologies. Herein, we report a robust method for the synthesis of a bimetallic alkoxide for efficient oxygen evolution reaction (OER) for alkaline electrolysis, which yields current density of 10 mA cm−2 at an overpotential of 215 mV in 0.1 M KOH electrolyte. The catalyst demonstrates an excellent durability for more than 540 h operation with negligible degradation in activity. Raman spectra revealed that the catalyst underwent structure reconstruction during OER, evolving into oxyhydroxide, which was the active site proceeding OER in alkaline electrolyte. In-situ synchrotron X-ray absorption experiment combined with density functional theory calculation suggests a lattice oxygen involved electrocatalytic reaction mechanism for the in-situ generated nickel–iron bimetal-oxyhydroxide catalyst. This mechanism together with the synergy between nickel and iron are responsible for the enhanced catalytic activity and durability. These findings provide promising strategies for the rational design of non-noble metal OER catalysts.

Isocyanides as Catalytic Electron Acceptors in the Visible Light Promoted Oxidative Formation of Benzyl and Acyl Radicals.

The recent disclosure of the ability of aromatic isocyanides to harvest visible light and act as single electron acceptors when reacting with tertiary aromatic amines has triggered a renewed interest in their application to the development of green photoredox catalytic methodologies. Accordingly, the present work explores their ability to promote the generation of both alkyl and acyl radicals starting from radical precursors such as Hantzsch esters, potassium alkyltrifluoroborates, and α-oxoacids. Mechanistic studies involving UV-visible absorption and fluorescence experiments, electrochemical measurements of the ground-state redox potentials along with computational calculations of both the ground- and the excited-state redox potentials of a set of nine different aromatic isocyanides provided key insights to promote a rationale design of a new generation of isocyanide-based organic photoredox catalysts. Importantly, the green potential of the investigated chemistry has been herein demonstrated by a direct and easy access to deuterium labeled compounds.

Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms.

Nicotinamide adenine dinucleotide (NADH) is an important enzyme cofactor with emissive properties that allow it to be used in fluorescence microscopies to study cell metabolism. Its oxidized form NAD+, on the other hand, is considered to produce negligible fluorescence. In this contribution, we describe the photophysics of the isolated nicotinamidic system in both its reduced and oxidized states. This was achieved through the study of model molecules that do not carry the adenine nucleotide since its absorbance would overlap with the absorption spectrum of the nicotinamidic chromophores. We studied three model molecules: nicotinamide (niacinamide, an oxidized form without nitrogen substitution), the oxidized chromophore 1-benzyl-3-carbamoyl-pyridinium bromide (NBzOx), and its reduced form 1-benzyl-1,4-dihydronicotinamide (NBz). For a full understanding of the dynamics, we performed both femtosecond-resolved emission and transient absorption experiments. The oxidized systems, nicotinamide and NBzOx, have similar photophysics, where the originally excited bright state decays on an ultrafast timescale of less than 400 fs. The depopulation of this state is followed by excited-state positive absorption signals, which evolve in two timescales: the first one is from 1 to a few picoseconds and is followed by a second decaying component of 480 ps for nicotinamide in water and of 80-90 ps for nicotinamide in methanol and NBzOx in aqueous solution. The long decay times are assigned as the S1 lifetimes populated from the original higher-lying bright singlet, where this state is nonemissive but can be detected by transient absorption. While for NBzOx in aqueous solution and for nicotinamide in methanol, the S1 signal decays to the solvent-only level, for the aqueous solutions of nicotinamide, a small transient absorption signal remains after the 480 ps decay. This residual signal was assigned to a small population of triplet states formed during the slower S1 decay for nicotinamide in water. The experimental results were complemented by XMS-CASPT2 calculations, which reveal that in the oxidized forms, the rapid evolution of the initial π-π* state is due to a direct crossing with lower-energy dark n-π* singlet states. This coincides with the experimental observation of long-lived nonemissive states (80 to 480 ps depending on the system). On the other hand, the reduced model compound NBz has a long-lived emissive π-π* S1 state, which decays with a 510 ps time constant, similarly to the parent compound NADH. This is consistent with the XMS-CASPT2 calculations, which show that for the reduced chromophore, the dark states lie at higher energies than the bright π-π* S1 state.

A comprehensive study on carbon capture potential of lactic acid based deep eutectic solvents at wide process conditions

This study explores the solubility and absorption kinetics of CO2 in novel Natural Deep Eutectic Solvents (NADES) with a focus on three systems: carvone-lactic acid (1:1), cineole-lactic acid (3:1), and cineole-lactic acid (1:1). The CO2 absorption experiments were carried out in the pressure range of 4.5 to 37 bar at 25 °C and 35 °C isotherms. The absorbed CO2 was quantified as a mole fraction in the NADES and demonstrated that the absorption was positively influenced by pressure and inversely by temperature. Among the systems, cineole-lactic acid (3:1) showed the highest CO2 absorption capacity at both isotherms. The experimental data were compared with the COSMO-RS predictions, revealing a systematic deviation, with all experimental results being higher than the predictions. The deviation increased with the decrease of temperature and the increase of pressure. Absorption kinetics was also studied, revealing that pressure increase accelerates the absorption process. Furthermore, cineole-lactic acid (1:1) absorption was notably faster at 35 °C than at 25 °C, possibly due to a reduction in viscosity. The study also calculated the heat of absorption for each system using the Clausius-Clapeyron equation. The heat of absorption values fell within the physi-sorbents heat of absorption range and were lower than traditional monoethanolamine (MEA), indicating less energy-intensive regeneration for these NADES. Overall, these findings point to the potential of these NADES for CO2 capture with efficient energy utilization and reduced environmental impact.

Tunable Rydberg–Rydberg transitions in helium with reduced sensitivity to dc electric fields by two-colour microwave dressing

The difference in the static electric dipole polarizabilities of the and Rydberg levels in helium has been eliminated by dressing the atom with a microwave field near resonant with the single-photon transition. For an amplitude dressing field, detuned by from the zero-field transition frequency, the dc Stark shift of the two-photon transition between these states remained within for electric fields up to . This transition was probed by single-color two-photon microwave spectroscopy, and by two-color two-photon spectroscopy with one strong additional dressing field and a weak probe field. For all measurements, the transition frequencies and Stark shifts were compared, and found to be in excellent quantitative agreement with the results of Floquet calculations of the energy-level structure of the Rydberg states in the presence of the dressing fields and applied dc electric fields. The two-color microwave dressing scheme demonstrated, with one field applied to null the differential polarizability of the Rydberg–Rydberg transition, and the second exploited to allow the two-photon transition to be employed to achieve tunable absorption of single-photons from a weak probe field, will facilitate improved coherence times and tunable single-photon absorption in hybrid cavity QED experiments with Rydberg atoms and superconducting microwave circuits.

Statistical and experimental study on microcrack of mortar by a self-healing agent of bacteria adsorbed by expanded perlite

PurposeThe purpose of this paper is to add expanded perlite (EP) immobilized microorganisms that replace part of the standard sand in mortar to improve the self-healing ability of mortar cracks and reduce the water absorption of mortar after healing.Design/methodology/approachBacillus pseudofirmus spores were immobilized with EP particles as self-healing agents. The effects of adding self-healing agents on the compressive strength of mortar specimens were observed. The ability of mortar specimens to heal cracks was evaluated using crack microscopic observation and water absorption experiments. The filler at the cracks was microscopically analyzed by scanning electron microscope and X-ray diffraction experiments.FindingsFirst, the internal curing effect of EP promotes the hydration of cement in mortar, which generates more amount and denser crystal structure of Ca(OH)2 at mortar cracks and improves the self-healing ability of mortar. Second, the self-healing ability of mortar improves with the increase of self-healing agent admixture. Adding a self-healing agent of high admixture makes the planar undulation of calcite crystal accumulation at mortar cracks more significant. Finally, the initial crack widths that can be completely healed by adding EP and self-healing agents to the mortar are 200 µm and 600 µm, respectively.Originality/valueThe innovation points of this study are as follows. (1) The mechanism of the internal curing effect of EP particles on the self-healing ability of mortar cracks was revealed by crack microscopic observation tests and microscopic experiments. (2) The effect of different self-healing agent amounts on the self-healing ability of mortar cracks has been studied. (3) The effects of EP particles and self-healing agents on healing different initial widths were elucidated by crack microscopic observation tests.Graphical abstract

Anharmonic IR absorption spectra of the prototypical interstellar PAHs phenanthrene, pyrene, and pentacene in their neutral and cation states

Combination band and overtone transitions of polycyclic aromatic hydrocarbon (PAH) cations in the 2000–2900 cm-1 (5-3.5 µm) region are implicated as carriers of the ‘quasi-continuum’ observed in the near-infrared (IR) emission spectra of many astronomical objects. In neutral PAHs, the strongest absorption features are concentrated in the 700–900 cm-1 (14–11 µm) range, which are associated with CH out-of-plane bending motions. Upon ionization, this shifts to the 1000–1600 cm-1 (10–6 µm) range, where bands are associated with C=C stretches and CH in-plane bends. Anharmonicity is required to accurately characterize the IR absorption spectrum of PAHs, indicated herein by the ability to directly assign the bands in high-resolution experimental absorption spectra of neutral and cationic phenanthrene, pyrene, and pentacene. Neutral PAHs are indicated as the source of the strong 3.3 and 11.2 µm astronomical PAH features, while the broad features in the 6–10 µm region and the ‘quasi-continuum’ from 3.5–5 µm stem from PAH cations. This study reinforces the need for including anharmonicity in the computation of IR absorption and emission spectra of larger and more complex PAHs. This is particularly pertinent to the interpretation of data returned by JWST.

Comprehensive investigation of Co(II), Ni(II) and Cu(II) complexes derived from a novel Schiff base: Synthesis, characterization, DNA interactions, ADME profiling, molecular docking, and in-vitro biological evaluation

Here, anisidine-based ligand (HL) and its cobalt (1a), nickel (1b) and copper (1c) complexes were synthesized and characterized by various spectroscopic techniques such as NMR, mass, IR, UV–visible, magnetic moments, ESR and TGA. The synthesized [Ni(L)2] and [Cu(L)2] complexes demonstrated square planar geometry around the metal centers, while the cobalt complex [Co(L)2(H2O)2] adopted six coordinated octahedral geometries. The DNA interaction studies of the complexes revealed an intercalative mode of binding, as evidenced by UV absorption, emission, and viscosity experiments, and the binding constant (Kb) follows the order of 1c > 1a > 1b. When exposed to oxidative and photolytic methods, the complexes demonstrated better efficacy in cleaving double-stranded pBR322 DNA compared to their parent Schiff base. When tested for cytotoxicity against A549 and MCF7 cell lines, complexes showed more activity than their parent ligand. In-vitro studies of the complexes' antimicrobial and antioxidant properties shown that they are far more effective than the parent ligand. Further, the biological efficiency of the ligand (HL) and complexes were verified by computational methods, including molecular docking (against protein data bank PDB ID: 2ADO.pdb) and pharmacokinetic studies, both the ligand (HL) and complexes have demonstrated significant potency. This promising result indicated their potential as therapeutic agents for treating pathogen-induced deformities.

THz time-domain spectroscopy modulated with semiconductor plasmonic perfect absorbers.

Terahertz time-domain spectroscopy (THz-TDS) at room temperature and standard atmosphere pressure remains so far the backbone of THz photonics in numerous applications for civil and defense levels. Plasmonic microstructures and metasurfaces are particularly promising for improving THz spectroscopy techniques and developing biomedical and environmental sensors. Highly doped semiconductors are suitable for replacing the traditional plasmonic noble metals in the THz range. We present a perfect absorber structure based on semiconductor III-Sb epitaxial layers. The insulator layer is GaSb while the metal-like layers are Si doped InAsSb (∼5·1019 cm-3). The doping is optically measured in the IR with polaritonic effects at the Brewster angle mode. Theoretically, the surface can be engineered in frequency selective absorption array areas of an extensive THz region from 1.0 to 6.0 THz. The technological process is based on a single resist layer used as hard mask in dry etching defined by electron beam lithography. A wide 1350 GHz cumulative bandwidth experimental absorption is measured in THz-TDS between 1.0 and 2.5 THz, only limited by the air-exposed reflectance configuration. These results pave the way to implement finely tuned selective surfaces based on semiconductors to enhance light-matter interaction in the THz region.