Linear Optical Activity Research Articles

Enhanced Circular Dichroism and Polarized Emission in an Achiral, Low Band Gap Bismuth Iodide Perovskite Derivative.

Lead halide perovskites and related main-group halogenido metalates offer unique semiconductor properties and diverse applications in photovoltaics, solid-state lighting, and photocatalysis. Recent advances in incorporating chiral organic cations have led to the emergence of chiral metal-halide semiconductors with intriguing properties, such as chiroptical activity and chirality-induced spin selectivity, enabling the generation and detection of circularly polarized light and spin-polarized electrons for applications in spintronics and quantum information. However, understanding the structural origin of chiroptical activity remains challenging due to macroscopic factors and experimental limitations. In this work, we present an achiral perovskite derivative [Cu2(pyz)3(MeCN)2][Bi3I11] (CuBiI; pyz = pyrazine; MeCN = acetonitrile), which exhibits remarkable circular dichroism (CD) attributed to the material's noncentrosymmetric nature. CuBiI features a unique structure as a poly-threaded iodido bismuthate, with [Bi3I11]2- chains threaded through a cationic two-dimensional coordination polymer. The material possesses a low, direct optical band gap of 1.70 eV. Notably, single crystals display both linear and circular optical activity with a large anisotropy factor of up to 0.16. Surprisingly, despite the absence of chiral building blocks, CuBiI exhibits a significant degree of circularly polarized photoluminescence, reaching 4.9%. This value is comparable to the results achieved by incorporating chiral organic molecules into perovskites, typically ranging from 3-10% at zero magnetic field. Our findings provide insights into the macroscopic origin of CD and offer design guidelines for the development of materials with high chiroptical activity.

Designing a Propellane-based Nonlinear Optically Active System Absorbing in Three Different Wavelength Regions.

The aim of this work is to demonstrate the possibility of using propellane in designing a molecule that can absorb in three different wavelength regions and their nonlinear optical (NLO) activity can be fine-tuned by varying the three wings. We considered 22 tailor-made propellane derivatives consisting of phenyl, naphthyl, and biphenyl wings for this purpose. Using the state-of-the-art linear and quadratic response methods within TD-DFT and RI-CC2 theories and a suitable generalized few-state model that quantifies the effect of orientation of different transition moments on NLO properties, we discussed how and why the linear and nonlinear optical activity of propellane vary when the three wings are assembled successively to construct a full-propellane.

Computational description of quantum chemical calculations and pharmacological studies of the synthesized chalcone derivative: A promising NLO material

The intended chalcone, (E)-1-(4-aminophenyl)-3-(4-ethoxyphenyl)-prop-2-en-1-one (4A3EP), was synthesized in an alkaline medium by the Claisen–Schmidt condensation reaction of 4-aminoacetophenone with 4-ethoxybenzaldehyde. Spectroscopic analytical techniques such as UV–visible, FT-IR, FT-RAMAN, 1H NMR, and 13C NMR investigations were used to analyze the molecular structure of the title molecule. The optimized molecular structure of the chalcone in gas phase vibrational frequencies and associated vibrational assignments were theoretically studied and compared with experimental results using the B3LYP/6–311++G techniques. All the experimental results were found to be in line with the theoretical values. The non linear optical activity of the title compound was proved from the hyperpolarizability calculations. In addition, EHOMO (−5.9038 eV), ELUMO (−2.2833 eV), energy gap (3.6205 eV) and electrophilicity index (4.628) were calculated to explore the reactivity, stability and bio activity of the title compound. The molecular electrostatic potential map was generated in order to spot the electrophilic and nucleophilic sites in the title compound. Natural bond orbital analysis was investigated in order to forecast the stability and charge transfer tendency of a title molecule. FUKUI FUNCTIONS were also calculated using DFT. Its anti-inflammatory, anti-diabetic, and anti-oxidant activities were also investigated. A molecular docking model was used to study the ligand-protein binding interactions of a synthetic chalcone derivative with the main protease of SARS-CoV-2 (the PDB code is 6yb7).

Theoretical study of linear and non-linear optical activity in dithienylethene-based photo-switch and its derivatives

In this contribution, our aim is to study the linear and non-linear optical activity and their variation with the addition/removal of electron withdrawing and electron donating groups in hexafluorinated dithienylethenes (HFDTE). By varying the terminal groups in the parent HFDTE, we have considered 16 closed-open pairs of substituted HFDTE and studied their electronic structures, one and two-photon absorption spectra and static first hyperpolarizability. All the calculations have been performed using the state-of-the-art linear and quadratic response theory within the framework of TD-DFT methods. RI-CC2 method is used as a reference to validate the applicability of TD-DFT method.

Enhanced linear and non-linear optical activity of lead onto l-threonine cadmium acetate crystal

Herein, we describe the growth and characterization of new crystal lead-doped l-threonine cadmium acetate (LTCA). The supramolecular coordination compounds are crystallized by slow evaporation technique at ambient temperature. The X-ray diffraction techniques confirm monoclinic crystal system. The presence of lead and the LTCA lattices were identified using EDAX analysis. l-Threonine amino acids have unique properties like zwitterionic nature and molecular chirality, which improve the optical properties of the lead-doped crystal. The linear optical parameters such as optical band gap and refractive indexes are estimated at lower cutoff wavelength from UV–Vis analysis. The variation of dielectric constant, dielectric loss with frequency is studied using LCR meter. Due to the electropositive character of lead the static permittivity increases. Magnetic behavior changes to paramagnetic nature due to the inclusion of lead. TG/DTA analysis suggests that the crystal is thermally stable up to 135.32 °C. Using Nd-YAG laser, the NLO property was studied and the lead-doped LTCA crystal shows higher SHG efficiency than the LTCA crystal.

Nonlinear chiral molecular photonics using twisted light: hyper-Rayleigh and hyper-Raman optical activity

Chiroptical and optical activity effects involve differential interactions between matter and light. Generally this involves chiral molecules absorbing or scattering right- and left-handed circularly polarized photons at different rates due to the chiroptical interplay of molecular and optical chirality. Laser light which propagates with a helical phase and twisted wavefront possesses optical orbital angular momentum. These optical vortices can twist either clockwise or anticlockwise, and as such they exhibit an optical handedness or chirality completely distinct from that of circular polarization. It has recently been established that the linear optical effects of single-photon absorption and scattering can exhibit optical activity and chiroptical interactions with respect to the optical vortex handedness. Here a fundamental mechanism of optical activity for twisted light is exhibited in nonlinear processes, with specific emphasis on hyper-Rayleigh and hyper-Raman scattering. In comparison to unstructured or plane-wave light, it is shown that using twisted photons produces novel scattering mechanisms dependent on parameters unique to optical vortex beams. Specifically, the scattered intensity for both hyper-Rayleigh and hyper-Raman optical activity is dependent on the sign and magnitude of the OAM of the incident twisted photons, as well as the transverse position of the chiral scatterer. Moreover, symmetry analysis reveals that, unlike the recently discovered linear optical activity effects with optical vortices, nonlinear scattering of twisted light by chiral molecules leads to a modification of scattering through uniquely weighted individual hyperpolarizability contributions.

Synthesis of promising nanocomposites from an antitumer and biologically active heterocyclic compound uploaded by clay and chitosan polymers

The innovative nanocomposites (NCs) of antibacterial and antitumor 2-amino-5-S-benzyl-1, 3, 4-thiadiazole (ABMT): binary (NC1): ABMT-clay as well as the ternary (NC2): ABMT-clay-chitosan have been prepared following the top-down approach method. The ABMT molecules have been efficiently uploaded on the inorganic polymer potassium montmorlinite clay polymer (MMT). The NC is homogenously dispersed in the aqueous solutions without crystallization of ABMT. However, the dispersity of the small particle size and the crystallinity of NC1 is greatly enhanced in the presence of the biopolymer chitosan. The nanocomposites showed good non linear optical activity with suitable band gaps indicated the electron confinement in the NC. The loading and entrapment efficiency of ABMT onto MMT reached 89.3% in NC1 during 6 h of contact time with the aqueous solution of pH 6.8. The enhanced redox characteristics of NC1 relative to that of MMT suggested the better biological (antibacterial and antitumor) activity of NC1. Chitosan enhanced the redox and the optical properties of NC1 and its ability to undergo intercharge transfer to any acceptor sites. Hence, chitosan may added synergestic electron donation and, hence antitumor activity to the binary NC1.

Spectroscopic investigation and non linear optical activity study on 7,7,8,8-tetra cyano quino dimethane

Abstract FT-IR and FT-Raman spectra of 7,7,8,8-tetracyanoquinodimethane(TCNQ) was recorded and analyzed. The equilibrium geometry, various bonding features and harmonic vibrational wavenumbers of TCNQ and its related compounds have been performed using density functional theory(DFT) method with 6-311G(d,p) basis set. The detailed interpretation of the vibrational spectra has been carried out with the aid of Molvib program. The TD-DFT calculation has been compared with UV–Vis spectrum with different solvents. HOMO-LUMO energy gap, local softness and electrophlicity indices for selected atomic sites of the TCNQ and its related compounds were determined. The intermolecular interaction in the TCNQ were confirmed by using Hirshfeld surfaces. The NLO activity of molecule was confirmed by SHG analysis. The surface resistance and third-order nonlinear optical property of the crystal were studied by laser induced surface damage threshold and Z-scan techniques respectively using Nd:YAG laser with wavelength 532 nm.

Synthesis, Crystallization, Non Linear Optical and Anti-bacterial Activity of L-Alanine Sodium Nitrate Single Crystals

In this present work, L-Alanine Sodium Nitrate (LASN) single crystals were grown by spontaneous nucleation solution growth method. The cell parameters and crystalline structure of the LASN crystals were analysed using powder X-ray diffraction (PXRD) technique. The numerous functional groups in the LASN crystals were confirmed by FTIR analysis. SHG efficiency of the grown LASN crystal is 1.06 times superior to the reference crystalline material KDP. The antibacterial property of LASN crystals were assessed using by agar diffusion method.

Spectroscopic (FT-IR, FT-Raman), quantum mechanical and docking studies on methyl[(3S)-3-(naphthalen-1-yloxy)-3-(thiophen-2-yl)propyl]amine

The present research work explores the structural, vibrational, electronic, non linear optical, biological and thermodynamic properties of the title compound. The compound has been characterized using spectroscopic techniques like FT-IR and FT-Raman. The above results were compared with the data obtained from DFT (B3LYP) using 6-311++G(d,p) as basis set. The geometry of the title compound was optimized followed by the calculation of vibrational assignments and potential energy distribution (PED). All the experimental results were found to be in line with the theoretical values. The non linear optical activity of the title compound was proved from the hyperpolarizability calculations. In addition, EHOMO (−5.68 eV), ELUMO (−1.01 eV), energy gap (4.67eV) and electrophilicity index (2.39) were calculated to explore the reactivity, stability and bio activity of the title compound. The molecular electrostatic potential map was generated in order to spot the electrophilic and nucleophilic sites in the title compound. The paper further explains electron localization function (ELF) and Natural bond orbital (NBO) analysis of the said compound. Due to less side effects and good profile, the title compound can be used to treat various pathologies which have been confirmed through molecular docking studies.

Localized plasmonic fields of nanoantennas enhance second harmonic generation from two-dimensional molybdenum disulfide

Abstract

Circular Dichroism of Single Particles

Circular dichroism (CD) occurs in chiral molecules and nanostructures. It is manifested over a wide range of length scales, from molecules to crystals and large nanostructures. Being a weak phenomenon (typically a small fraction of absorption), CD is routinely measured on macroscopic quantities of matter in solutions, crystals, or arrays of fabricated meta-particles. These ensemble-averaged measurements mask the sensitivity of CD to small structural variations between individual nano-objects or to the possible coexistence of opposite enantiomers in the ensemble. We have developed far field extinction microcopy, which enables sensitive CD measurement on individual nano-objects, encompassing dramatic suppression of linear optical activity artifacts. Here, we report on CD of both chiral shaped plasmonic nanostructures (gold Gammadions) and achiral shaped inorganic nanocrystals having a chiral crystal lattice (HgS). CD spectra and spatial mapping were measured. Simulations on Gammadions, mimicking the experimental conditions, showed good correlation to the measurements. We have also demonstrated in simulations and experiments the high sensitivity of the measurements to minor misalignments of the experimental setup. This work extends the single-particle-spectroscopy toolbox to include CD spectroscopy and enables a unique diffraction limited imaging technique sensitive to chirality at the nanoscale.

Resonant nonlinear microscopy reveals changes in molecular level chirality in native biological tissues

Chirality is a fundamental property of biochemical molecules and often dictates their functionality. Conventionally, molecular chirality is studied by linear optical activity effects. However, poor contrast and artifacts due to anisotropy limit such studies to purified molecules not in their original microenvironments, potentially modifying their conformations. Here, we demonstrate that resonant second-harmonic-generation circular dichroism (SHG-CD) microscopy provides not only tissue imaging with improved chiral contrast, but also molecular chirality information of collagen, the most abundant protein in mammals, at its native state. Gradual protein denaturation shows that the resonant SHG-CD is dominated by the microscopic chirality related to collagen structures smaller than the spatial resolution of the microscope, i.e. to the protein conformation and microfibril organization, while the effects due to fiber orientation/anisotropy are mostly responsible of the non-resonant part. This result agrees well with a simple and intuitive model we propose to explain the resonant behavior and the consequent numerical SHG-CD simulations. Our results demonstrate the possibility to study molecular chirality in intact bio-tissues with nearly-unity contrast and sub-micrometer resolution, which will be useful in a broad range of biological and biochemical applications.

Spectroscopic investigations using density functional theory on 2-methoxy- 4(phenyliminomethyl)phenol: A non linear optical material

Single crystals of 2-methoxy-4(phenyliminomethyl)phenol were grown from ethanol by slow evaporation solution growth technique. Single crystal X-ray diffraction experiment reveals the crystallization in orthorhombic system having non-centrosymmetric space group C2221. Geometrical optimization by density functional theory method was carried out using Gaussian program and compared with experimental results. Detailed experimental and theoretical vibrational analyses were carried out and the results were correlated to find close agreement. Thermal analyses show the material is thermally stable with a melting point of 159 °C. Natural bond orbital analysis was carried out to explain charge transfer interactions through hydrogen bonding. Relatively smaller HOMO-LUMO band gap favors the non linear optical activity of the molecule. Natural population analysis and molecular electrostatic potential calculations visualize the charge distribution in an isolated molecule. Calculated first-order molecular hyperpolarizability and preliminary second harmonic generation test carried out using Kurtz-Perry technique establish 2-methoxy-4(phenyliminomethyl)phenol crystal as a good non linear optical material. Z-scan proposes the material for reverse saturable absorption.

Comparative studies on molecular structure, vibrational spectra and hyperpolarizabilies of NLO chromophore Ethyl 4-Dimethylaminobenzoate

The molecular structure, vibrational spectra and polarizabilities of Ethyl 4-Dimethylaminobenzoate (EDAB) was investigated by density functional theory employing Becke's three parameter hybrid exchange functional with Lee–Yang–Parr (B3LYP) co-relational functional involving 6-311++G(d,p) basis set and compared with some other levels. A detailed interpretation of the IR and Raman spectra of EDBA have been reported and analyzed. Complete vibrational assignments of the vibrational modes have been done on the basis of the potential energy distribution (TED) using VEDA software. The molecular electrostatic potential mapped onto total density surface has been obtained. A study on the electronic properties, such as absorption wavelength, and frontier molecular orbitals energy, was performed using DFT approach. The stability of the molecule arising from hyper conjugative interactions and accompanying charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The natural and Mulliken charge also calculated and compared with different level of calculation. The dipole moment, polarizability and first, second order hyperpolarizabilities of the title molecule were calculated and compared with the experimental values. The energy gap between frontier orbitals has been used along with electric moments and first order hyperpolarizability, to understand the non linear optical (NLO) activity of the molecule. The NLO activity of molecule was confirmed by SHG analysis.

Polarization-dependent laser autofluorescence of the polycrystalline networks of blood plasma films in the task of liver pathology differentiation.

Current research presents the results of the investigation of diagnostic efficiency of laser polarization autofluorescence for the set of endogenous fluorophores of blood plasma polycrystalline films in two spectral regions (0.5-0.53 μm and 0.63-0.67 μm) under the excitation of laser radiation with a wavelength of 0.405 μm. A model of generalized optical anisotropy of protein networks of blood plasma polycrystalline films is proposed for the purpose of defining laser autofluorescence processes. Both phase (linear birefringence and optical activity) and amplitude (linear and circular dichroisms) anisotropies have been considered. Interconnections between the optimal condition of probing beam polarization state and the efficiency of induction laser autofluorescence have been found. Statistical analysis of coordinate distributions of laser polarization autofluorescence intensities is suggested by means of determination of the quantitative criteria (statistical moments of the 1st-4th orders). The efficiency of laser polarization autofluorescence of polycrystalline networks in the task of differentiation of nonalcoholic fatty liver disease and chronic hepatitis of human liver has been analyzed.

Spectroscopic investigation and chemical properties analysis on anticancer compound; α,α,ά,ά-Tetrabromo-p-Xylene with computational analysis

In order to explore the pharmaceutical applications, the vibrational spectra of α,α,ά,ά-Tetrabromo-p-Xylene (4αBX) were recorded using IR, Raman and NMR spectrometer with FT technique. The modified optimized structural bond parameters and vibrational group wavenumbers of molecule based on substitutional bonds, Mulliken atomic charge distribution, frontier molecular orbital levels, chemical properties, temperature dependence of thermodynamic parameters, NLO studies and natural bond orbital calculations of the molecule were performed using the HF and DFT model theories. The intense observation was made over the excitations between the electronic energy levels within the molecule which enable to explore the electronic properties. The distribution of Mulliken charges of present molecule were calculated and were interrelated with the architecture of the molecular bonds. The charge transformation over the frontier molecular orbitals between the ligand and rings has been thoroughly observed. The average Polarizability first order diagonal hyperpolarizability have been calculated and from which the linear and non linear optical activity of the molecule is interpreted in detail. The reactive site of the molecule was predicted from the molecular electrostatic potential contour map. From the thermodynamical analysis, it was found that, the values of thermo dynamic parameters were increasing with increasing temperature.

Influence of rare earth doping on the spectral, thermal, morphological, and optical properties of nonlinear optical single crystals of manganese mercury thiocyanate, MnHg(SCN)4

Good optical grade single crystals of pure, lanthanum (La3+) and neodymium (Nd3+) doped manganese mercury thiocyanate (MMTC) crystals were grown from aqueous solution by slow solvent evaporation technique at room temperature. Single crystal X-ray diffraction (XRD) data reveal that the grown crystals belong to the tetragonal system with space group I4¯. The crystals were characterized using Optical absorption (UV–vis–NIR), Fourier Transform Infrared (FT-IR), Fourier Transform Raman (FT-Raman) spectral studies, Scanning Electron Microscope (SEM), Energy Dispersive X-ray analysis (EDAX), Dielectric and Thermal studies. The second harmonic generation (SHG) efficiencies of the grown crystals were also measured using Kurtz and Perry powder technique. The non linear optical (NLO) activity of the pure MMTC was slightly enhanced due to rare earth dopants.

Vibrational [FT-IR, FT-Raman] analysis, NMR and mass – Spectroscopic investigation on 3,6-Dimethylphenanthrene using computational calculation

In this research work, in order to the vibrational, physical and chemical properties, a thorough investigation has been made by recording FT-IR, FT-Raman, Mass and 13C and 1H NMR spectra of pharmaceutically important compound; 3,6-Dimethylphenanthrene. The altered geometrical parameters of Phenanthrene due to the addition of methyl groups have been calculated using HF and DFT (B3LYP and B3PW91) methods with 6–31++G(d,p) and 6–311++G(d,p) basis sets and the discussion are made on their corresponding results. The alternation of the vibrational pattern of the molecule due to the injection of the substitutions; CH3 is investigated. The keen observation is made over the excitations between the electronic energy levels of the molecule which lead to the study of electronic properties. The alternation of distribution of Mulliken charges after the formation of present molecule has been correlated with the vibrational pattern of the molecular bonds. The charge transformation over the frontier molecular orbitals between the ligand and rings has been studied. The cause of the linear and non linear optical activity of the molecule is interpreted in detail from the average Polarizability first order diagonal hyperpolarizability calculations. The variation of thermodynamic properties; heat capacity, entropy, and enthalpy of the present compound at different temperatures are calculated using NIST thermodynamical function program and interpreted.

Evans hole and non linear optical activity in Bis(melaminium) sulphate dihydrate: A vibrational spectral study

Bis(melaminium) sulphate dihydrate (BMSD), an interesting melaminium derivative for nonlinear optical activity, has been subjected to vibrational spectral analysis using FT IR and FT Raman spectra. The analysis has been aided by the Potential Energy Distribution (PED) of vibrational spectral bands, derived using density functional theory (DFT) at B3LYP/6-31G(d) level. The geometry is found to correlate well with the XRD structure and the band profiles for certain vibrations in the finger print region have been theoretically explained using Evans hole. The detailed Natural Bond Orbital (NBO) analysis of the hydrogen bonding in BMSD has also been carried out to understand the correlation between the stabilization energy of hyperconjugation of the lone pair of donor with the σ∗ orbital of hydrogen-acceptor bond and the strength of hydrogen bond. The theoretical calculation shows that BMSD has NLO efficiency, 2.66times that of urea. The frontier molecular orbital analysis points to a charge transfer, which contributes to NLO activity, through N–H…O intermolecular hydrogen bonding between the melaminium ring and the sulphate. The molecular electrostatic potential (MEP) mapping has also been performed for the detailed analysis of the mutual interactions between melaminium ring and sulphate ion.