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Influence of Cr doping on the oxygen evolution potential of SnO2/Ti and Sb-SnO2/Ti electrodes
摘要： Oxygen evolution potential is the determining factor affecting the anode efficiency of the wastewater treatment process. In this study, we focus on increasing oxygen evolution potential of Cr-SnO2/Ti and Cr-Sb-SnO2/Ti electrodes with the pyrolytic method. XRD, SEM and XPS techniques had been applied to characterize the microstructures and chemical compositions of the samples. Electrochemical measurements had been performed to evaluate the oxygen evolution potential as a criterion of the wastewater treatment efficiency. The results show that co-doping of Sb and Cr improved the crystallinity and grain size of SnO2 coating, and Cr existed in the form of Cr(Ⅲ) valence states. The Cr doping treatment improved the electronic conductivity and the electrocatalytic activity of the electrodes. DFT calculation of the band-structure indicates Cr doped SnO2 had a superior electrical conductivity, where Cr atom acts as an acceptor providing vacancies for electron transportation. The DOS diagrams reveal the Cr doped SnO2 showing a p-type conductivity which would subsequently influence the built-in potential on metal-semiconductor interface. We proposed the mechanism of the increase of oxygen evolution potential is the doping of Cr expands the built-in potential.
关键词： Cr doping,oxygen evolution potential,DFT,wastewater treatment
更新于2025-09-10 09:29:36
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Red emitting coumarin based 4, 6-disubstituted-3-cyano-2-pyridones dyes – Synthesis, solvatochromism, linear and non-linear optical properties
摘要： New coumarin fluorescent based D-π-A-π-D dyes are synthesized and studied for their optical properties. Their show absorption and emission respectively are in the range of 471-504 nm and 506-550 nm. Viscosity induced emission intensity increase is examined with 0-100% PEG-400 in ethanol MLK 4 is good FMR as compared to the MLK 1-3 due to the presence of extra-π-conjugation. FMO analysis and Generalised Mulliken Hush analysis show a strong interaction of molecular charge transfer characteristics. The first (α), second (β) and third (γ) order polarizability of MLK 1-4 are calculated by the solvatochromic technique and corroborated by DFT calculations using CAM-B3LYP/6-31G(d) method. The outcomes found by solvatochromic technique are compared theoretically with DFT using B3LYP/6-31G(d) and CAM-B3LYP/6-31G(d) methods. These methods reveal that, CAM-B3LYP/6-31G(d) carry out for calculating α, β, γ. Photophysical data was also applied to establish the ground and excited state dipole moment ratio using Bakhshiev, Bilot-Kawski, and Liptay functions. Liptay function shows better correlations than the other two functions for all dyes.
关键词： Viscosity sensor,TD-DFT,Coumarin,NLO properties,Carbazole,Intramolecular charge transfer
更新于2025-09-10 09:29:36
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Photophysical and photocatalytic properties of corrophyll and chlorophyll
摘要： Tetrapyrrolic macrocycles are well known photosensitizers, absorbing light in the ultraviolet and visible region. The quantum e?ciency of these naturally occurring compounds in optical processes, and the possibility of altering their behavior by modifying its constituent features, make them promising candidates for applications as Dye Sensitized Solar Cells (DSSC) and photocatalytic reactions. The time-dependent density-functional theory (TD-DFT) were used to study the optical and redox properties of chlorophyll and corrin-related molecules (corrophyll). The in?uence of the substituents and metallic atoms in their properties have been investigated. Our results show lower reduction potentials for corrophyll molecules compared with chlorophyll. The optical absorbance spectra of corrophyll without a metallic atom at their central rings shows a signi?cant blue-shift, as compared to their chlorophyll counterparts. The presence of Co(I) ion species at the corrophyll core leads to oxidation potentials below than that of water, which puts corrophyll ahead of traditional chlorophyll pigments as photocatalysts. We show that the substituents and the ions coordinated to the macrocycles play an important role in this phenomena. These ?ndings show the great potential of tuning the spectroscopic and reactive properties of tetrapyrrole macrocycles for applications in photocatalysis and optoelectronic devices, while keeping their essential structural features intact.
关键词： Corrole,Photophysics,Porphyrin,Electronic structure,TD-DFT,Optical absorbance,Photocatalysis
更新于2025-09-10 09:29:36
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Electronic properties of Zigzag ZnO nanoribbons with Hydrogen and Magnesium passivations
摘要： In this study, the electronic properties of ZnO nanoribbons with zigzag edges (ZZnONr) have been investigated with Density Functional Theory (DFT). After a geometric optimization, the electronic band structures, the density of states (DOS) of ZZnONr passivated with Hydrogen (H) and Magnesium (Mg) atoms were calculated ZZnONr. It is shown that the increasing width of ZZnONrs has led to a decrement in energy band gap of the studied structures. While ZZnONr passivated with Mg for Zn-rich edge have not been shown a spin dependency, the structure passivated with Mg for O-rich edge have exhibited spin-dependent band structure. The energetically most stable structures have been determined as ZZnONr passivated with Mg for Zn-rich edge. ZZnONr passivated with Mg atoms for both edges have a graphene-like band structure especially for 8 and 10 atom width structures and this property of ZZnONrs could be important in terms of the electron transport for ZZnONrs.
关键词： ZnONr,Passivation,electronic properties,DFT
更新于2025-09-10 09:29:36
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Crystal Morphology and Phase Transformation of LiAlO <sub/>2</sub> : Combined Experimental and First-Principles Studies
摘要： Layered α-LiAlO2 matrix often suffers from detrimental structural and morphological changes during its lifetime, especially under H2 containing fuel inlet environments of molten carbonate fuel cell systems. However, the underlying mechanism of this phase and morphological transformations has rarely been explored. In this study, transmission electron microscopy (TEM) techniques were used to determine the changes in structure and morphology of LiAlO2 samples lifted by a focused ion beam (FIB). In accordance with X-ray diffraction (XRD) analysis, TEM images show that under H-rich conditions the rhombohedral α-LiAlO2 transforms to tetragonal γ-LiAlO2 phase with the appearance of the (101) terminated octahedral shaped γ-LiAlO2 crystallites. We further support, and plausibly rationalize, the observed transformations using density functional theory (DFT) calculation. The DFT computed surface energies of γ-LiAlO2 reveal that the {101} surface becomes the lowest energy surface upon H-adsorption, thus leading to formation of observed octahedral geometry. Contrary to stabilization of γ-LiAlO2 surfaces upon H passivation, DFT revealed H-adsorption on α-LiAlO2 surfaces to be energetically unfavorable. This contrasting behavior of α-LiAlO2 and γ-LiAlO2 under H-rich environments could be a potential driving force for the observed α-LiAlO2 to γ-LiAlO2 phase transformation.
关键词： morphology,phase transformation,TEM,DFT,LiAlO2,XRD
更新于2025-09-10 09:29:36
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STM and DFT Study of Chlorine Adsorption on the Ag(111)- <i>p</i> (4x4)-O Surface
摘要： Coadsorption of chlorine and oxygen on the Ag(111) surface has been studied with low-temperature scanning tunneling microscopy (LT-STM) in a combination with density functional theory (DFT) calculations. Room temperature adsorption of chlorine onto the Ag(111)-p(4×4)-O surface leads to the appearance of new bright objects located between protrusions of the 4×4 reconstruction. As chlorine adsorbs, objects form "rosettes" around corner holes. This configuration coincides with the configuration of the chlorine atoms in the Ag(111)-(3×3)-Cl reconstruction structure. We conclude that the adsorption of chlorine on the Ag(111)-p(4×4)-O surface occurs dissociatively, with chlorine atoms displacing oxygen atoms from the fourfold positions. Adsorption of chlorine at 77 K results in the formation of the mixed Cl–O species on the Ag6 triangles of the p(4×4) reconstruction. Both scenarios of chlorine adsorption are unexpected and cannot be explained within a commonly accepted Ag6 model of the p(4×4) reconstruction.
关键词： STM,DFT,Chlorine adsorption,Ag6 model,Ag(111)-p(4×4)-O surface
更新于2025-09-10 09:29:36
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Trialkylsilyl-Substituted Silole and Germole Dianions
摘要： The synthesis of dipotassio-2,5-bis(trialkylsilyl)-silacyclopentadienediides K2[3] and germacyclopentadienediides K2[4] is reported. The prepared silole dianions, 3, are characterized by a significantly deshielded silicon nuclei with 29Si NMR signals at very unusual low field positions for silicon anions (δ29Si = 148?169). The results of DFT calculations revealed that this deshielding is a consequence of the silylene-like frontier orbitals of silole dianions 3 and efficient hyperconjugation between the trialkylsilyl-substituents and the cyclic delocalized π-system. Solid-state structure determinations of potassium salts of silole and germole dianions revealed a novel polymeric bis-η5,bis-η1-coordination mode between heterole and potassium ions.
关键词： germole dianions,hyperconjugation,polymeric coordination,silole dianions,DFT calculations
更新于2025-09-10 09:29:36
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Synthesis and physico-chemical investigations of AgSbS2 thin films using Doehlert design and under DFT framework
摘要： Based on Doehlert matrix, Silver Antimony Sulfide (AgSbS2) thin films were prepared by chemical bath deposition (CBD) technique onto glass slides. Doehlert matrix was used to correlate between the effect of several factors and to predict the optimal condition of thickness (e=4 μm). XRD and SEM techniques were used to study the structural, microstructural and morphological properties of the obtained film. XRD data confirm the formation of the desired phase as well as their purity. SEM analysis reveals that the obtained film was formed by truncated-plate shaped grains morphology. AgSbS2 film shows good absorption coefficient (α) in the range of 104 cm-1. The optical band gap (Eg) of this film was determined based on transmittance and reflectance data and it was found to be equal to 1.65 eV. DFT calculation was applied to investigate the electronic structure their material and to confirm the experimental optical results. The obtained AgSbS2 film was examined as a new photocatalysis material for the degradation of MB dye. AgSbS2 shows good photocatalytic activity with a degradation efficiency of 80% for three hours.
关键词： AgSbS2,DFT,Doehlert Matrix,Photocatalysis,Chemical bath deposition
更新于2025-09-10 09:29:36
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Reconciling Structural and Spectroscopic Fingerprints of the Oxygen Evolving Complex of Photosystem II: A Computational Study of the S <sub/>2</sub> State
摘要： The catalytic cycle of photosynthetic water oxidation occurs at the Mn4CaO5 oxygen-evolving complex (OEC) of Photosystem II (PSII). Extensive spectroscopic data have been collected on the intermediates, especially the S2 (Kok) state, although the proton and electron inventories (Mn oxidation states) are still uncertain. The “high-oxidation” paradigm, assigns S2 Mn oxidation level (III, IV, IV, IV) or (IV, IV, IV, III), whereas a “low-oxidation” paradigm posits two additional electrons. Here we investigate the geometric (XRD, EXAFS) and spectroscopic (EPR, ENDOR) properties of the S2 state using quantum chemical DFT calculations, focusing on the neglected low paradigm. Two interconvertible electronic spin configurations are predicted as ground states, producing multiline (S = 1/2) and broad (S = 5/2) EPR signals in the low paradigm oxidation state (III, IV, III, III) and with W2 as OH– and O5 as OH–. They have “open” (S = 5/2) and “closed” (S = 1/2) Mn3CaO4-cubane geometries. Other energetically accessible isomers with ground spin states 1/2, 7/2, 9/2, or 11/2 can be obtained through perturbations of hydrogen-bonding networks (e.g. H+ from His337 to O3 or W2), consistent with experimental observations. Conformers with the low oxidation state configuration (III, IV, IV, II) also become energetically accessible when the protonation state is O5 (OH–), W2 (H2O) and neutral His337. The configuration with (III, IV, III, III) agrees well with earlier low temperature EPR and ENDOR interpretations, while the MnII-containing configuration agrees partially with recent ENDOR data. However, the low-oxidation paradigm does not yield isotropic ligand hyperfine interactions in good agreement with observed values. We conclude that the low Mn oxidation state proposal for the OEC can closely fit most of the available structural and electronic data for S2 at accessible energies.
关键词： EPR,low-oxidation paradigm,oxygen-evolving complex,ENDOR,Photosystem II,DFT calculations,S2 state
更新于2025-09-10 09:29:36
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Nitrato, Pseudohalo-Linked Zn(II)/Cd(II) Schiff-Base Complexes with 1,3-Diimine Spacer Group: Syntheses, Crystal Structures, DFT, TD-DFT and Fluorescence Studies
摘要： Self assemblies of (N2O4) salen-type bi-compartmental ligand (H2L°Me) [N,N’-Bis(3-methoxysalicylidenimino)-1,3-diaminopropane] afforded two series of complexes, a trinuclear nitrate [Cd3(L°Me)2(NO3)2] (1) and a dinuclear [Zn2(L°Me)(η1-N3)2(CH3OH)2] (2). Elemental analysis, UV-visible and Fourier transform Infrared spectroscopic methods were employed successfully to characterize the complexes. Single-crystal X-ray studies reveal that complex 1 consists of planar trinuclear Cd(II)3 core coordinated by two fully deprotonated dianionic ligands [L1]2(cid:0) and nitrato (NO3(cid:0)) bridging but complex 2 is a centrosymmetric hexacoordinated Zn(II) double end-on azide (η1-N3) with methanol as co-ligands. Both complexes satisfied a common 4-membered M(II)2(μ2-O)2 basic core. Fluorescence properties in DMSO solvent reveal that complexes enhance appreciably the fluorescence behavior over free salen-type ligand (H2L°Me). Complexes are optimized using Density functional theory calculated at B3LYP/TZVP level of theory to obtain insights into optimized structure, Frontier molecular orbital, Electrostatic potential maps, charge analyses gives an insight into the electronic structure and charge/potential distribution in the molecule etc. which substantiate the experimentally observed supramolecular interactions. Existing different non-covalent supramolecular interactions have been explained by means of Hirshfeld surface and 2D fingerprint plot analysis. Further the observed experimental electronic spectra of both complexes were explained by using Time-dependent density functional theory level of calculations.
关键词： Cd(II)/Zn(II) Complex,Fluorescence,TD-DFT,DFT,Azide
更新于2025-09-09 09:28:46