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Photophysical features and semiconducting properties of propeller-shaped oligo(styryl)benzenes
摘要： Electronic, optical, and semiconducting properties of a series of propeller-shaped oligo(styryl)benzenes have been systematically investigated to monitor the effect of the number of styryl branches (three, four, and six) around a central benzene core. In order to clarify the relationships between their structures and properties, Density Functional Theory calculations were carried out at several levels of theory considering solvents with different polarity. Absorption and vibrational Raman spectroscopies showed that cruciform, four-branched derivatives present the most effective π-conjugation in agreement with the lowest calculated bond length alternation and bandgap. Deviations from the mirror image symmetry between absorption and fluorescence spectra were related to changes in the molecular conformation upon electronic excitation. Furthermore, in order to investigate the semiconducting behavior of oligo(styryl)benzenes, molecular structure changes and different electronic properties related to ionization processes were calculated and analyzed. Hole and electron reorganization energies were also computed to provide a first approximation on the n- or p-type character of these compounds. In some cases, electron reorganization energies comparable to common n-type semiconductors were found.
关键词： photophysical properties,Density Functional Theory,charge transport,Raman spectroscopy,oligo(styryl)benzenes,semiconducting properties
更新于2025-11-20 15:33:11
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Mg Doped Perovskite LaNiO <sub/>3</sub> Nanofibers as an Efficient Bifunctional Catalyst for Rechargeable Zinc–Air Batteries
摘要： Rational design of efficient and durable bifunctional catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is important for rechargeable zinc-air batteries. Herein, Mg doped perovskite LaNiO3 (LNO) nanofibers (LNMO NFs) were prepared by a facile electrospinning method combined with subsequent calcination. LNMO NFs show a more positive half-wave potential of 0.69V and a lower overpotential of 0.45 V at a current density of 10 mA cm-2 than those of the pristine LNO NFs. As an air electrode for zinc-air battery, the cell with LaNi0.85Mg0.15O3 NFs catalyst is able to deliver a high specific capacity of 809.9 mAh g-1 at a current density of 5 mA cm-2. It also shows an excellent cycling stability over 110 h at a current density of 10 mA cm?2. DFT calculation results demonstrate that the LNMO surface binds oxygen stronger than LNO, which contributes to enhanced OER activity as observed in our experiments. The results indicate that LNMO NFs is an efficient and durable bifunctional catalyst for zinc-air batteries.
关键词： bi-functional catalyst,Mg doped LaNiO3 nanofibers,electrospinning,density functional theory calculation,zinc-air batteries
更新于2025-11-14 17:04:02
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Defective ZnS nanoparticles anchored in situ on N-doped carbon as a superior oxygen reduction reaction catalyst
摘要： Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions. However, the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking. In this study, ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst. These catalysts were prepared via a one-step method at 900 °C. Amazingly, the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles. These facilitated the catalyst synthesis, and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium, including a lower onset potential, lower mid-wave potential, four electron transfer process, and better durability compared with 20 wt% Pt/C. More importantly, the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH ? from ?OO toward oxygen reduction reaction. Therefore, the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells, given the novel catalyst’s resulting performance.
关键词： Density functional theory calculations,Oxygen reduction reaction,Zn vacancy,Electrocatalyst,Defective ZnS nanoparticle
更新于2025-11-14 17:03:37
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Density functional theory for investigation of optical and spectroscopic properties of zinc-quinonoid complexes as semiconductor materials
摘要： Three Zn(II) complexes of a new organic compound [(E)-4-methyl-N1-((E)-4-methyl-6-(p-tolylimino) cyclohex-3-en-1-ylidene)-N2-(p-tolyl) benzene-1, 2-diamine] (HMBD) were prepared and characterized by various techniques, including Fourier transform infrared (FTIR), UV–visible measurements, 1H-NMR, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The data revealed that the HMBD ligand has an ONS tridentate-forming structure, while the complex of HMBD with zinc metal has a distorted octahedral structure, providing sp3d2 hybridization type. The geometry, HOMO, LUMO, polarizability, and other energetic parameters were evaluated by density functional theory (DFT) on Materials Studio package. Optical band gap (Eg) was estimated by DFT theory and optical properties for [Zn(MBD)(Cl)(H2O)2].2H2O (1), [Zn(MBD)](NO3)2H2O].2H2O (2), and [Zn(MBD)(CH3COO)(H2O)].3H2O (3) thin films as well, revealing that [Zn(MBD)(CH3COO)(H2O)].3H2O (3) thin film has the smallest energy gap and can be considered a highly efficient photovoltaic material. The resulting band gap energy values from both methods were found to be close to each other. Thin films of the ligand and zinc complexes were successfully fabricated by spin coating method. The optical constants, refractive index (n), and the absorption index (k) over the spectral range of the thin films were determined.
关键词： Optical properties,Semiconductor materials,Density functional theory,Thin film,Zinc-quinonoid complexes
更新于2025-11-14 15:19:41
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Optical, charge transport and magnetic properties of palladium retrieved from photometric measurements: approaching the quantum mechanics background
摘要： A parametric Drude–Lorentz (DL) model is used to describe the spectral variation of the dielectric functions of bulk palladium samples at low and room temperature. In addition to the contribution of conduction electrons, the contribution of holes is also explicitly accounted for in the model. A simulated annealing method is applied to obtain the optimized values of the parameters involved in the model: volume plasma frequency of conduction electrons, high frequency dielectric constant, collision frequency of holes and corresponding relaxation time, and two additional parameters from which the effective mass of holes and collision frequency of conduction electrons are evaluated. Oscillatior strengths, resonance frequencies, and widths entering in the Lorentz contribution to the dielectric function are also optimized. Renormalization of the oscillator strengths requires the introduction of a new parameter in the context of the DL model: the ratio between number density of conduction electrons and number density of metal atoms, whose optimized value ?ts very well with its evaluation from band structure calculations and from independent measurements. Inclusion of this parameter in the framework allows us to evaluate additional quantities related to the charge-carrier transport: average effective masses, Fermi energies and electronic densities of states at the corresponding Fermi energies, intrinsic electrical resistivity, intrinsic mean free paths, heat capacities, mobilities, as well as paramagnetic and diamagnetic susceptibilities, for both electrons and holes. The optimized resonance frequencies are compared with energy differences between plausible interband transitions, in accordance with reported band structure diagrams and with our own band structure obtained from density functional theory calculations.
关键词： Drude–Lorentz model,palladium,density functional theory,simulated annealing,metal thin ?lms
更新于2025-11-14 15:19:41
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Full color carbon dots through surface engineering for constructing white light-emitting diodes
摘要： White light-emitting diodes (WLEDs) devices are replacing the filament lamp and they can provide a light close to the natural sunlight, which have thus drawn considerable attention in these recent years. It remains a scientific challenge to develop WLEDs using environmentally friendly, easy-to-process and cost-effective phosphors. Here we synthesized blue-, green- and red-carbon dots (denoted as B-, G- and R-CDs) by a facile solvothermal method with high dispersity both in aqueous and organic solvent. The quantum yield (QY) of the R-CDs achieved up to 24.7%. These CDs can be easily dissolved in polyvinylpyrrolidone (PVP) colloid, leading to the production of ultraviolet (UV)-excited LED devices to avoid the retinal damage caused by blue ray excitation. The fluorescence emission of the WLED has a wide band, covering the whole visible light region. Importantly, the influence of doping that gives rise to the change of emissive colors has been elucidated by X-ray photoelectron spectroscopy (XPS) combined with a computation method in order to provide a systematic controllable tuning on the functionalization of CDs. As such, WLEDs were demonstrated with color coordinates of (0.33, 0.33), a color temperature of 5612 K in the CIE chromaticity diagram with good anti-photobleaching and a color rendering index (CRI) of 89.
关键词： polyvinylpyrrolidone,White light-emitting diodes,solvothermal method,UV-excited LED devices,density functional theory,quantum yield,X-ray photoelectron spectroscopy,carbon dots
更新于2025-11-14 15:18:02
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Structural, electronic and optical properties of pulsed laser deposited Cu2SnS3 photo absorber thin films: A combined experimental and computational study
摘要： Pulsed laser deposited thin films of Cu2SnS3 (CTS) are characterized for the structural, electronic and optical properties using X-ray diffraction, Raman, UV–Vis-NIR spectroscopy, scanning electron microscopic techniques, and density functional theory. It is observed that thin-film samples annealed at low temperature have a metastable tetragonal structure, whereas the films annealed at 450 °C have a predominant stable monoclinic phase. A direct band gap of 1.1 eV, measured from the transmittance spectra, in close agreement with the theoretical band gap value of 0.89 eV obtained from density functional theory calculations. Optical properties reveal that CTS has a large absorption coefficient ~0.5 × 104 cm?1 at 1.5 eV which is comparable to other CuS based materials like CuInS2 and Cu2ZnSnS4. The direct band gap and large absorption coefficient make CTS as one of the potential alternative absorber materials for thin-film solar cell applications.
关键词： Annealing,Raman spectroscopy,Thin films,Density functional theory,Pulsed laser deposition,Optical properties
更新于2025-10-22 19:40:53
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A reaction-based turn-on fluorescent sensor for the detection of Cu (II) with excellent sensitivity and selectivity: Synthesis, DFT calculations, kinetics and application in real water samples
摘要： A reaction-based turn-on fluorescent chemosensor RhB-Cu, starting from rhodamine B (RhB), for Cu2+ was easily synthesized in two steps. The sensor could selectively detect Cu2+ with a 100-fold fluorescence enhancement among the common metal ions, exhibiting an extremely low detection limit of 4.7 nM. To the best of our knowledge, this was the best record for the detection of Cu2+ with organic fluorescent sensors. There was a 1:1 binding stoichiometry between RhB-Cu and Cu2+ with an association constant of 6.42 × 104 M-1. Noteworthy, it could distinguish Cu2+ from Cu+, which was hard to realize in the previous studies. In addition, the detection mechanism was proposed based on mass spectrometric analysis and density functional theory (DFT) calculations. Kinetic studies were conducted to obtain the activation energy, enthalpy and entropy, so as to elucidate the solvent effect. Interestingly, the kinetic compensation effect (KCE) was uncovered in this work. Finally, RhB-Cu was proved to have the capability to work in real water samples. It would highly contribute to the even better design of fluorescent sensor for Cu2+ in future.
关键词： fluorescent sensor,solvent effect,kinetic compensation effect (KCE),copper,density functional theory (DFT),PET mechanism
更新于2025-10-22 19:38:57
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Domino Reaction for the Sustainable Functionalization of Few-Layer Graphene
摘要： The mechanism for the functionalization of graphene layers with pyrrole compounds was investigated. Liquid 1,2,5-trimethylpyrrole (TMP) was heated in air in the presence of a high surface area nanosized graphite (HSAG), at temperatures between 80 °C and 180 °C. After the thermal treatments solid and liquid samples, separated by centrifugation, were analysed by means of Raman, Fourier Transform Infrared (FT-IR) spectroscopy, X-Rays Photoelectron Spectroscopy (XPS) and 1H-Nuclear Magnetic Resonance (1H NMR) spectroscopy and High Resolution Transmission Electron Microscopy (HRTEM). FT-IR spectra were interpreted with the support of Density Functional Theory (DFT) quantum chemical modelling. Raman findings suggested that the bulk structure of HSAG remained substantially unaltered, without intercalation products. FT-IR and XPS spectra showed the presence of oxidized TMP derivatives on the solid adducts, in a much larger amount than in the liquid. For thermal treatments at T ≥ 150 °C, IR spectral features revealed not only the presence of oxidized products but also the reaction of intra-annular double bond of TMP with HSAG. XPS spectroscopy showed the increase of the ratio between C(sp2)N bonds involved in the aromatic system and C(sp3)N bonds, resulting from reaction of the pyrrole moiety, observed while increasing the temperature from 130 °C to 180 °C. All these findings, supported by modeling, led to hypothesize a cascade reaction involving a carbocatalyzed oxidation of the pyrrole compound followed by Diels-Alder cycloaddition. Graphene layers play a twofold role: at the early stages of the reaction, they behave as a catalyst for the oxidation of TMP and then they become the substrate for the cycloaddition reaction. Such sustainable functionalization, which does not produce by-products, allows us to use the pyrrole compounds for decorating sp2 carbon allotropes without altering their bulk structure and smooths the path for their wider application.
关键词： infrared spectroscopy,Density Functional Theory,pyrrole compounds,quantum chemical modelling,graphene layers,Functional Groups
更新于2025-09-23 15:23:52
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Edge-dependent reflection and inherited fine structure of higher-order plasmons in graphene nanoribbons
摘要： We investigate higher-order plasmons in graphene nanoribbons, and we present how electronic edge states and wave-function fine structure influence the graphene plasmons. Based on nearest-neighbor tight-binding calculations, we find that a standing-wave model based on nonlocal bulk plasmon dispersion is surprisingly accurate for armchair ribbons of widths even down to a few nanometers, and we determine the corresponding phase shift upon edge reflection and an effective ribbon width. Wider zigzag ribbons exhibit a similar phase shift, whereas the standing-wave model describes few-nanometer zigzag ribbons less satisfactorily, to a large extent because of their edge states. We directly confirm that also the larger broadening of plasmons for zigzag ribbons is due to their edge states. Furthermore, we report a prominent fine structure in the induced charges of the ribbon plasmons, which for armchair ribbons follows the electronic wave-function oscillations induced by intervalley coupling. Interestingly, the wave-function fine structure is also found in our analogous density-functional theory calculations, and both these and tight-binding numerical calculations are explained quite well with analytical Dirac theory for graphene ribbons.
关键词： plasmons,edge states,tight-binding,density-functional theory,Dirac theory,graphene nanoribbons
更新于2025-09-23 15:23:52