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Prediction of Structural, Vibrational and Nonlinear Optical Properties of Small Organic Conjugated Molecules Derived From Pyridine
摘要： Nonlinear optical (NLO) effects of organic materials are caused by delocalized electrons and large polarization in molecules. In the present work, theoretical study by using the Density Functional Theory (DFT) at B3LYP/6-311G(d,p) level of theory on three types of pyridine derivates 2,6-dimethoxy-3,5-dinitropyridine (M1), 2-methoxy-3-nitropyridine (M2) and 2-methoxy-5-nitropyridine (M3) is reported. The nuclear magnetic resonance (1H- and 13C-NMR) chemical shifts of the title compounds were calculated using the Gauge Independent Atomic Orbital (GIAO) method and compared to the observed results. Both infrared absorption and Raman are complementary to provide characteristic fundamental vibrations that are necessary for the identification of the molecular structures. Electronic properties such as frontier molecular orbital (HOMO, LUMO), ionization potential (IPad) and electronic affinity (EAad) were determined to get better insight into the molecular properties. Using the Time-Dependent Density Functional Theory (TD-DFT), electronic absorption spectra have been predicted and closely matching the experimental findings. The natural bonding orbital (NBO) calculations were performed in order to elucidate various second order interactions in between the filled and vacant orbitals which are a measure of the intermolecular as well as the delocalization within the molecule. In addition, we have demonstrated that these molecular systems have large first static hyperpolarizabilities and may have potential applications in the development of NLO materials.
关键词： NLO properties,Electronic properties,DFT,Optical spectra,NBO
更新于2025-09-23 15:23:52
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Quantum chemical investigation of modified coumarin-based organic efficient sensitizers for optoelectronic applications
摘要： One of the most major features in the improvement of dye-sensitized solar cells (DSSCs) is the survey and plan of high-efficiency and low-cost dyes. In this paper, a new series of metal-free coumarin-based (NKX-2311) dye molecules, namely (D1–D4) are investigated for use in DSSC applications. The dye molecules contain three parts, electron-donor (D) connected by the π-conjugated linker as a spacer and electron-acceptor (A)/anchoring group. Molecular structure, electronic absorption spectra and photovoltaic (PV) parameters of the D1–D4 dyes have been performed by using density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches are employed. The effects of chemical modification on the spectra and PV properties of the coumarin-modified organic dyes have been revealed. The performance of three functionals (B3LYP, CAM-B3LYP and ωB97XD) has been evaluated to get an experimental absorption wavelength of NKX-2311. From the functionals, B3LYP method was better matched with the absorption wavelength of NKX-2311. Therefore, D1–D4 dye molecules excited state calculations of the absorption spectra have been investigated by using B3LYP functional with 6-31G(d) basis set. The results show that D1, D3 dyes are smaller energy gap and absorption spectra are systematically red-shifts. The theoretical results have a display that the lowest occupied molecular orbitals (LUMOs) and highest occupied molecular orbitals (HOMOs) of the D1–D4 dyes can be confirming positive response on the electron injection and dye regeneration process. The NLO property of the D1–D4 dyes can be derived as polarizability and first-order hyperpolarizability. The calculated values of D1 and D3 dyes are the best applicants for NLO performance. The conclusion of this study will deliver a useful reference to the future proposal and beneficial to get DSSCs with superior power conversion efficiency (PCE).
关键词： TD-DFT,coumarin-based dyes,DSSCs,NLO properties,DFT,photovoltaic properties
更新于2025-09-23 15:21:01
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First theoretical probe for efficient enhancement of nonlinear optical properties of quinacridone based compounds through various modifications
摘要： In this study, first attempt has been made for theoretical designing of quinacridone (QA) dye and new QA-based compounds (QA-1 to QA-9) were proposed by installing auxiliary donors (dimethylvinyl, methoxy, and N,N-dimethylamine), donor (diphenylamine) and acceptors (cyanoacrylic acid, CN and NO2) segments into fixed π-bridge QA. DFT and TDDFT calculations with B3LYP/6-31G(d,p) and CAM-B3LYP/6-31G(d,p) functional were used to shed light on the promising structure, charge transport and NLO properties. Introduction of auxiliary donors/donor and acceptor successfully modified the structure which led to superior NLO properties. An eye-catching NLO response was observed in all designed compounds. Interestingly, QA-9 exhibits appealingly large enhancement in NLO properties through ICT process with < α > and βtot computed to be 716.02 (a.u) and 128082.15 (a.u) respectively. UV–Vis results indicates the QA-9 most red shifted among all studied compounds with λmax = 489.02 nm. QA-1 to QA-9 showed narrow HOMO-LUMO energy gap as compared to QA which results in enhanced NLO response. NBO analysis confirms the formation of charge separation state in QA-1 to QA-9 due to successful migration of electrons from auxiliary donors/donor to acceptors via π-bridge. The present research evokes the scientific interest regarding the development of QA based tempting NLO compounds that can be beneficial in modern hi-tech applications.
关键词： Density functional theory,Molecular modeling,Quinacridone-based dyes,Donor and acceptor units,NLO properties,Two-state model
更新于2025-09-23 15:21:01
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Nonlinear optical properties of colloidal CdSe/ZnS quantum dots in PMMA
摘要： The colloidal CdSe/ZnS quantum dots (QDs) in the PMMA polymer film with different QDs concentrations were fabricated. The influence of QDs concentration and excitation pump energy on nonlinear optical (NLO) properties of PMMA capped CdSe/ZnS QDs was investigated by the Z-scan technique with nanosecond laser pulses in the near-infrared spectral band. A large effective nonlinear absorption coefficient (βeff～?10?13 esu) due to the saturable absorption was observed. It was found that the appropriate concentration could lead to the reinforcement of NLO effect. In addition, the impact of the excitation energy on the nonlinear refractive index n2, real and imaginary parts of the third-order nonlinear optical susceptibility was also performed. This study involving the light–matter interactions in the colloidal quantum dots will benefit potential NLO-based applications of optoelectronics, optical modulation and photonics.
关键词： nanophotonics,semiconductor colloidal quantum dots,impact behavior,Z-scan technique,nonlinear optical (NLO) properties
更新于2025-09-23 15:19:57
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Molecular modelling and optical properties of a novel fluorinated chalcone
摘要： Chalcones exhibit a broad spectrum of biological activities, mainly due to a,b-unsaturated ketone, and are precursors of the biosynthesis of flavonoids present in plants. These compounds have been shown to be useful in the biological approach, proven by the broad spectrum of biological activities reported, and also in the technological approach, considering their potential as nonlinear optic (NLO) material. In this context, this work aimed to examine the crystallization and characterization of fluorinated chalcone (E)-1-(4-fluorophenyl)-3-(4-isopropylphenyl)prop-2-en-1-one (DFC). A comprehensive structural study of DFC was carried out to understand the process of stabilizing the crystalline lattice through X-ray diffraction, infrared spectroscopy, and molecular modeling studies. Finally, the electrical properties of DFC were calculated by using the supermolecule method (SM). DFC molecules are connected by means of CAH···O and CAH···F intermolecular contacts, forming dimers which play an important role in the stabilization of crystal packing. Molecular modeling studies indicated that this compound could act as an anti-tuberculosis ligand because of its high binding affinity with the M. tuberculosis enoyl-acyl carrier protein, InhA. On the other hand, theoretical calculations were performed to evaluate the NLO properties of DFC and indicated that it showed good potential.
关键词： NLO properties,Molecular modeling,Fluorinated chalcone
更新于2025-09-23 15:19:57
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UV irradiation induce NLO modulation in photochromic Styrylquinoline-Based Polymers: Computational and Experimental Studies
摘要： Functionalized photochromic materials have attracted a growing interest during the last few decades since they are promising materials to be used in optoelectronics and photonics. In this paper, the results of the nonlinear optical (NLO) investigation (second and third harmonic generation) of spin deposited high-quality thin films of styrylquinoline containing methacrylic polymers studied by using Maker fringes technique employing 30 ps laser pulses at fundamental wavelength of 1064 nm are presented. Photochromic styrylquinoline units were oriented in the thin films by corona poling technique promoting second order NLO activity. Strong dependence of the NLO response upon the structure of the polymers has been found, which is related to the different charge transfer within the styrylquinoline fragments. These investigations were completed by theoretical studies using HOMO-LUMO energy levels theory and the first and second order hyperpolarizability values. Good compatibility has been achieved between the theoretical and experimental results. Studied styrylquinoline-based polymers showed the contrast in NLO response after their trans-cis photoisomerization making them interesting for using in photonic devices.
关键词： NLO properties,second and first order hyperpolarizability,harmonic generation,functionalized polymers,DFT and TDHF calculations,styrylquinoline
更新于2025-09-23 15:19:57
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Ultraviolet Absorption Spectra, Solvent Effect and Non-Linear Optical Properties of Tetrahydroxy-1,4-quinone Hydrate by Hartee-Fock and Density Functional Theory
摘要： In present work, the ultraviolet absorption spectrum of tetrahydroxy-1,4-quinone hydrate (TH,1,4-QH) has been carried out experimentally (in water, methanol dimethyl sulfoxide, acetonitrile and chloroform) and theoretically in the range 3500-2300 cm-1 in the solution phase. Predicted electronic absorption spectra from time dependent density functional theory (TD-DFT) calculation have been analyzed and compared with the experimental UV-visible spectrum. The effects of hydroxy group substituent in benzoquinone ring have been analyzed. The electronic properties such as excitation energy, wavelength corresponding to absorption maxima (λmax), oscillator strength (f), HOMO and LUMO energies are calculated by time-dependent density functional theory (TD-DFT) using HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) as basis sets. The electric dipole moment (μ), α (polarizability) and β (first hyperpolarizability) have been computed to evaluate the NLO (non-linear optical) response of the investigated compound by Hartree-Fock (HF) and density functional theory (DFT) with B3LYP basis sets. Mulliken atomic charges of the atoms are calculated by DFT (B3LYP). In addition natural bond orbital (NBO) analysis has been done using TD-DFT with B3LYP/6-311++G(d,p) basis sets.
关键词： Tetrahydroxy-1,4-quinone hydrate,Density Functional Theory,NLO properties,Hartee-Fock,Ultraviolet spectrum
更新于2025-09-11 14:15:04
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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