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Microwave-assisted synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots: Raman characterization and their optical properties
摘要： In this report we will present completely new results on the improvement of the graphene quantum dots (GQDs) and nitrogen-doped graphene quantum dots (N-GQD) production method, using the microwave with different power levels and durations, from citric acid and urea. This is a new and unprecedented method of fabrication. The use of microwave has allowed ultra-fast fabrication of GQDs and nitrogen doped GQDs. These GQDs had their characteristics identi?ed by Raman scattering spectra for the characteristic C–C graphene vibration mode (G-peak) and defects of GQDs (D-peak). The absorption spectra of GQDs samples were fabricated under different conditions, with the expectation of different sizes, to be compared and analyzed. These absorption spectra were also compared with those of the N-GQD produced under the same conditions. The absorption mechanism of GQDs and N-GQD will be presented in detail. Measurements of the photoluminescence (PL) spectra in GQDs and N-GQD have also been recorded and analyzed. The ?uorescence mechanism will be presented, explained, and compared with other international publications of other authors. Some of the TEM and HR-TEM images of these two samples were also presented to con?rm the shape, size and in-plane spacing lattice of the GQD structure.
关键词： graphene quantum dots (GQDs),PL spectra,nitrogen-doped graphene quantum dots (N-GQD),microwave,Raman spectra,absorption spectra
更新于2025-11-19 16:56:42
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Application of polar solvent effects in absorption spectra for determination of lowest electron-excited states of phthalide
摘要： The optical absorption spectra of phthalide in polar (methanol) and nonpolar (n-hexane) solvents are recorded. The electronic phthalide spectrum was calculated by TDDFT B3LYP/6-311+G(d, p) using the polarisable continuum model. Based on an analysis of calculation data and the displacement of absorption bands in a polar solvent, it was established that the absorption bands of phthalide at energies of 3.51 and 3.96 eV correspond to singlet-triplet transitions to the T1 and T2 states, respectively.
关键词： Triplet excited states,Electronic absorption spectra,PCM TDDFT,Solvent effect,Phthalide
更新于2025-09-23 15:23:52
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High-temperature mid-infrared absorption spectra of methanol (CH3OH) and ethanol (C2H5OH) between 930 and 1170?cm-1
摘要： A methodology was recently developed with a broad-tuning, rapid-scan external-cavity quantum-cascade-laser in conjunction with shock tube facilities to measure the high-temperature mid-infrared absorption spectra of gaseous molecules. This technique is deployed to measure the cross section profiles in the C-O stretching band for methanol (CH3OH) and ethanol (C2H5OH) between 930 and 1170 cm-1. Methanol spectra are presented from 620 to 1304K between 0.98-3.30 atm with distinctive P, Q, and R branches of the ν8 vibrational band. At elevated temperatures, the emergence of hotbands and high-J ro-vibrational transitions are clearly observed. The absorption cross sections of ethanol are measured from 296 to 1018K between 0.90-3.27 atm. The peak strength decreases with temperature, with the peak location shifting to lower wavenumbers. These measurements are compared with existing empirical models, illustrating a strong need for the development of a high-temperature spectroscopic database.
关键词： Absorption spectra,Ethanol,Mid-infrared,High-temperature,Shock tube,Methanol
更新于2025-09-23 15:23:52
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4-{(Z)-[4-(Diethylamino)phenyldiazenyl]}phthalonitirle and Phthalocyanines Thereof
摘要： 4{(Z)-[4-(Diethylamino)phenyldiazenyl]}phthalonitrile was synthesized by diazotization and azo coupling and used to prepare tetrakis-4-(4-{(Z)-[4-(diethylamino)phenyl]diazenyl})phthalocyanine and its cobalt, nickel, zinc and magnesium complexes by template synthesis. The spectral properties of the synthesized compounds were studied.
关键词： azo chromophore,4-aminophthalonitrile,electronic absorption spectra,metal phthalocyanines
更新于2025-09-23 15:21:21
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A general approach for the calculation and characterization of x-ray absorption spectra
摘要： We present a general approach for the calculation and assignment of X-ray absorption spectra based on electronic wavepacket propagations performed using explicitly time-dependent electronic structure calculations. Such calculations have the appeal of yielding the entire absorption spectrum for the cost of a single set of electronic wavepacket propagations, obviating the need to explicitly calculate large numbers of core-excited states. The spectrum can either be calculated from the Fourier transform of the time-dependent dipole moment or from the Fourier transform of the wavepacket autocorrelation function. We propose that calculating the absorption spectrum using the latter approach will generally be the preferred option. This method has two important advantages. First, the autocorrelation functions can be obtained for twice the propagation time, resulting in a halving of the computational effort required to calculate the spectrum relative to the time-dependent dipole moment approach. Second, using the tools of filter diagonalisation, the autocorrelation functions may be used to determine the time-independent final core-excited states underlying the peaks of interest in the spectrum. The proposed scheme is validated by calculating and characterizing the X-ray absorption spectra of benzene and trifluoroacetonitrile at the time-dependent second-order algebraic diagrammatic construction level of theory.
关键词： time-dependent electronic structure calculations,X-ray absorption spectra,core-excited states,electronic wavepacket propagations,filter diagonalisation
更新于2025-09-23 15:21:01
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Growth and characterization of Cs2LiLaCl6:Ce single crystals
摘要： Cs2LiLaCl6:Ce (CLLC) is a promising scintillator material for dual gamma/neutron detection. The vertical Bridgman technique, with a LiCl-rich melt and high axial temperature gradient, was used to grow transparent CLLC crystals for the first time. The stoichiometric CLLC powder melted incongruently with a melting range of 343-442 oC. Additional LiCl suppressed the formation of Cs3LaCl6 second phase, which was identified in crystals grown from stoichiometric melts. CLLC was found to have a Stokes shift of about 1358 cm-1 and a photoluminescence decay time of 34.6 ns. Direct electron-hole capture by Ce3+ ions and core-valence luminescence were the main contributors to the X-ray induced luminescence spectrum. A 9×8 mm3 cylinder of the CLLC crystal with 0.5at% Ce had an energy resolution of 7.1% at 662 keV. The scintillation decay times of the CLLC crystal excited with 662 keV gammas were 79 ns and 1491 ns.
关键词： A1. Absorption spectra,B2. Scintillator materials,B1. Cs2LiLaCl6:Ce,B3. Neutron detection,A2. Bridgman technique
更新于2025-09-23 15:21:01
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Deep Learning for Optoelectronic Properties of Organic Semiconductors
摘要： Atomistic modeling of the optoelectronic properties of organic semiconductors (OSCs) requires a large number of excited-state electronic-structure calculations, a computationally daunting task for many OSC applications. In this work, we advocate the use of deep learning to address this challenge and demonstrate that state-of-the-art deep neural networks (DNNs) are capable of accurately predicting various electronic properties of an important class of OSCs, i.e., oligothiophenes (OTs), including their HOMO and LUMO energies, excited-state energies and associated transition dipole moments. Among the tested DNNs, SchNet shows the best performance for OTs of different sizes, achieving average prediction errors in the range of 20-80meV. We show that SchNet also consistently outperforms shallow feed-forward neural networks, especially in difficult cases with large molecules or limited training data. We further show that SchNet could predict the transition dipole moment accurately, a task previously known to be difficult for feed-forward neural networks, and we ascribe the relatively large errors in transition dipole prediction seen for some OT configurations to the charge-transfer character of their excited states. Finally, we demonstrate the effectiveness of SchNet by modeling the UV-Vis absorption spectra of OTs in dichloromethane and a good agreement is observed between the calculated and experimental spectra.
关键词： optoelectronic properties,organic semiconductors,transition dipole moment,SchNet,oligothiophenes,deep learning,UV-Vis absorption spectra
更新于2025-09-23 15:19:57
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Effects of near-field electromagnetic coupling in dimers of nanoparticles with a silver core and a J-aggregate dye shell
摘要： We report a theoretical study of the plasmon – exciton coupling effect on the absorption spectra of pairs of closely spaced double-layer hybrid nanoparticles consisting of a metallic core and a J-aggregate dye shell. The effect of frequency conversion of plasmonic lines due to the near-field interaction between plasmons and Frenkel excitons of the organic shell is demonstrated. The effect leads to the appearance of additional spectral lines in the long-wavelength part of the spectrum of the system of hybrid particles. The shapes and the relative intensities of the additional lines exactly reproduce the specific features of the original spectrum of plasmonic absorption bands in uncoated metallic nanoparticles. The discovered phenomenon can be used to design new types of high-sensitivity nanosensors, based on plasmon – exciton effects and principles of near-field optics.
关键词： near-field electromagnetic coupling,nanophotonics,Frenkel excitons,dimers of metalorganic nanoparticles,plasmon – exciton interaction,molecular J-aggregates,localised plasmons,absorption spectra
更新于2025-09-19 17:15:36
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Tracking small heterogeneity in binary mixtures of aliphatic and aromatic hydrocarbons: NIR spectroscopic, 2DCOS and MCR-ALS studies
摘要： To our best knowledge, this is the ?rst spectroscopic study of small heterogeneity at a molecular level in binary mixtures of aliphatic and aromatic hydrocarbons. The composition-dependent spectra of benzene/toluene, benzene/n hexane, benzene/cyclohexane, n hexane/n heptane and n hexane/cyclohexane mixtures were recorded by NIR transmission technique in the whole range of mole fractions. A comprehensive exploration of the experimental data was performed by two-dimensional correlation analysis (2DCOS) and chemometric methods. In addition, we calculated excess NIR molar absorption spectra and parameter of ER, which allows for comparison of the degree of deviation from ideality for various mixtures. Our results reveal that all studied mixtures deviate from the ideal mixture. The extent of these deviations is small for the mixtures were both components are aromatic or aliphatic and increases for aromatic/aliphatic mixtures. In addition, molecular shapes have an important effect on the degree of deviation from the ideal mixture. As expected, benzene/n hexane is the most non-ideal mixture, while behavior of n hexane/n heptane and benzene/toluene mixtures is close to the ideal one. Our results suggest that in the mixtures with the largest deviations from ideality are present homoclusters of both components and heteroclusters. The heteroclusters exist in the whole range of compositions, while the homoclusters appears above a certain concentration limit. If both components of the mixture are similar, the molecules with equal probability form the homo- and heteroclusters. In the case of unlike components, the molecules prefer to form the homoclusters. The homoclusters of both components in the mixture are similar as those observed in bulk constituents. This means that deviation from the ideal mixture results from presence of the heteroclusters.
关键词： Aliphatic/aromatic hydrocarbons,NIR,Clustering,MCR-ALS,Binary mixtures,2DCOS,Chemometrics,Excess absorption spectra,Microheterogeneity
更新于2025-09-19 17:15:36
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Substitutional effect of different bridging groups on optical and charge transfer properties of small bipolar molecules for OLEDs
摘要： In this work, a series of eight different bipolar molecules were designed and calculated using density functional theory (DFT) and time‐dependent functional theory (TD‐DFT) for organic light emitting diodes (OLEDs) as efficient luminescent and charge transfer materials. The eight donor‐π‐donor type small molecules (D1‐D8) were composed of triphenylamine (TPA) donor (D) unit connected to 1,8‐naphthalimides (NI) acceptor (A) unit though different π‐conjugated or R‐groups (as π‐spacer). The effect of substitutions made in π‐spacer was investigated on optical, electronic, and stability properties. This calculation analysis showed that different substitutions in π‐spacer resulted smaller Eg (range from 1.63 to 2.00 eV), broader absorption with the lowest excitation energy covering both visible and near infrared regions of solar spectrum, especially D3, D4, D5, and D6 molecules. The analyses of local densities of states, frontier molecular orbitals, and natural population analysis of orbitals revealed that studied molecules exhibited π‐π* electronic transitions of absorption in singlet excited states, but D5 and D6 also show intramolecular charge transfer (ICT) characteristics. The study of chemical indices, molecular electrostatic potential (MEP) surfaces, and charge transfer properties turned out that D4, D5, and D6 are expected to show good potential for luminescent and hole transport materials in the favor of OLEDs.
关键词： DFT,organic light emitting diodes (OLEDs),optical properties,absorption spectra,electronic structures
更新于2025-09-19 17:13:59