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In this work, the mesomorphic, morphologic, thermotropic, thermooptical, and thermodynamical properties of 4-(octyloxy)-N-(4-hexylphenyl)-2-hydroxybenzalimine thermotropic liquid crystalline compound, which was synthesized by our group, have been studied in detail. This compound displays smectic C and nematic mesophases. These mesophases are enantiotropic and exhibit specific confocal and schlieren textures, respectively.

Thermotropic, thermooptical, and thermodynamical properties of the compound at direct and reverse phase transitions between smectic C and nematic mesophases and also between nematic mesophase and isotropic liquid have been investigated. The peculiarities of the bistable heterophase regions of these phase transitions have been studied.

We explore the charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of the charge transport in TG4 DNA. The consecutive TG4 (CTG4) is semiconducting with 0.2 ~ 0.3 eV energy gap. Charges transfer favorably in the CTG4, but are trapped in the nonconsecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly ~ 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

In a comprehensive study, structural properties, electronic structure and optical response of crystalline o-phenanthroline were investigated. Our results show that in generalized gradient approximation (GGA) approximation, o-phenanthroline is a direct bandgap semiconductor of 2.60 eV. In the framework of many-body approach, by solving the Bethe–Salpeter equation (BSE), dielectric properties of crystalline o-phenanthroline were studied and compared with phenanthrene. Highly anisotropic components of the imaginary part of the macroscopic dielectric function in o-phenanthroline show four main excitonic features in the bandgap region. In comparison to phenanthrene, these excitons occur at lower energies. Due to smaller bond lengths originated from the polarity nature of bonds in presence of nitrogen atoms, denser packing, and therefore, a weaker screening effect, exciton binding energies in o-phenanthroline were found to be larger than those in phenanthrene. Our results showed that in comparison to the independent-particle picture, excitonic effects highly redistribute the oscillator strength.

Succinonitrile (SCN)–2 wt% Camphor (CAMP) alloy was unidirectionally solidified with a constant temperature gradient (G = 3.01 K/mm) at different growth rates (V = 6.5–113 μm/s) and with a constant growth rate (V = 6.5 μm/s) at different temperature gradients (G = 1.93 - 3.01 K/mm). Microstructural parameters (primary dendrite arm spacings, λ₁, secondary dendrite arm spacings, λ₂, dendrite tip radius, R, and mushy zone depth, d) were measured as a function of growth rate and temperature gradient. The experimental results have been compared with theoretical models and previous experimental works. The stability constant (σ) for this alloy system was calculated and compared with similar experimental results.

Needle-shaped nanostructured tris(8-hydroxyquinoline) aluminum nanowires (Alq₃) have been obtained by annealing Alq₃ amorphous films at 150^∘C which is lower than the glass transition temperature of Alq₃ (172^∘C). The growth of Alq₃ nanowires is attributed to the migration and stacking of Alq₃ molecules which acquire thermal energy from the annealing process. X-ray diffraction analysis and scanning electronic microscopy spectra show that the Alq₃ nanowires are composed of the well-known $\alpha$-phase Alq₃. The intensity of the photoluminescence spectra firstly increases and then decreases as the annealing time increases, along with a spectral blue shift. The optical transmittance spectra of the annealed Alq₃ films show a smaller average absorption in the visible range and a wider optical bandgap compared with that of the amorphous films, as a result of the decrease of $\pi$ overlapping in the Alq₃ molecules.

We performed structural optimization of a selective emitter with two-dimensional silicon based gratings coated by platinum as a thermal radiator to promote methane steam reforming reaction. The structural parameters were optimized by numerical calculation to radiate high thermal power in a vibrational absorption band of methane molecule at 3.3 μm. Optical property of the fabricated optimum selective emitter with periodicity Λ = 2.6 μm found that the emission peak was resonant with this absorption band. The amount of hydrogen produced by the methane steam reforming process using the optimized selective emitter became four times greater than that obtained by the flat emitter.

We have studied the electronic structure and optical responses of both molecular and bulk phases of 3-nitroaniline (m-NA) using density functional theory (DFT). We have developed our calculations within the framework of band structure theory for both phases. The results of current simulation are also useful for comparison between solids and vapors. Findings show that the crystalline m-NA has an indirect bandgap which is smaller than its molecular counterpart. Due to the weak intermolecular interactions, the crystalline band structure shows very low dispersions and hence the crystalline spectra are very similar to those of molecules, especially at lower energies. This resemblance is extended to lower wavelengths in linear regime, but limited to higher wavelengths in nonlinear one. This study shows that the substituent groups play major roles in the band structure and charge transfer excitations. The optical spectra show higher intensity and more splitting, especially in nonlinear regime, when we go from molecular phase to bulk phase. Findings show that the electron energy loss structures in vapor phase are very close to ${\epsilon }_2$, hence energy loss spectroscopy is a direct way for measuring dielectric function of vapors. According to our results, the crystalline phase exhibits plasmon resonances at much higher energies compared to those of vapor phase. For example, the energy loss spectrum of m-NA molecule shows plasmon peak around 17eV which is about 10eV lower than the crystalline counterpart. The comparison between nonlinear spectra and the linear spectra (as functions of both $\omega$ and 2$\omega$) reveals the significant resemblance between linear and nonlinear structures in both phases. This study shows that the molecular-based models for investigating optical properties of organic crystals are only suitable for low energy regions. Finally, our simulation reproduces the experimental results very well.

The crystals N-(2-chlorophenyl)-(1-propanamide) (NCP) appropriate for nonlinear optical (NLO) and electro–optic appliances were grown full-fledged by the slow cooling method. The solubility and metastable zone width range of NCP specimen were studied. The specimen crystallizes in the monoclinic crystal system with noncentrosymmetric space group of P2₁. The crystal morphology study also elucidates supplementary excellence of the as-grown NCP crystal. The optical precision in the whole visible region was found to be superior for NLO claim. The crystallinity of the full-fledged crystal is determined by etching and HRXRD. Laser harm threshold and photoluminescence studies delegate the grown crystal comprises extremely less imperfections. The mechanical deeds of NCP sample at assorted temperatures were examined to decide the hardness solidity of the grown specimen. The piezoelectric behavior and the comparative second harmonic generation for assorted particle sizes of the material were also deliberate. The third-order nonlinear ocular possessions of NCP crystal specimen were determined by Z-scan method. The optical homogeneity of the solitary crystal was assessed using customized channel spectrum technique. The thermal structures of NCP solitary crystal have been studied using photopyroelectric method. The half-wave voltage of the full-fledged crystal was intended from the electro–optic experimentation. Photoconductivity nature of the grown crystal outlined consummate inducing dipoles due to strong incident radiation and further revealed the nonlinear deeds of the grown material.

By using the slow evaporation solution growth technique, the 2-amino 6-methyl pyridinium 4-methyl benzoate (2A6MP4MB) is crystallized in a single, high-quality crystal. Single crystal X-ray diffraction (SXRD) was used to determine the crystal structure. The different functional groups of the substances were identified using Fourier Transform Infrared Spectroscopy (FTIR) analysis. The 2A6MP4MB crystal exhibits a significant optical transmittance throughout the complete visible spectrum and a lowered UV cutoff wavelength, according to studies conducted using UV-Vis spectrometers. The optical band gap energy (Eg) of a single crystal of 2A6MP4MB is 4.768eV. The compound’s photoluminescence (PL) spectrum in the title illustrates the green emission technique. We analyze the produced single crystal’s dielectric tensorial behavior at various frequencies. The produced 2A6MP4MB crystal’s third-order susceptibility, nonlinear refraction, and nonlinear absorption coefficient were evaluated using the $Z$-scan technique. A Vickers hardness tester was used to assess the created crystal’s mechanical stability.

To study the effect of terminal groups substituent on the two-photon absorption (TPA) properties of $D$-$\pi$-$A$-$\pi$-$D$ structural dyes with diketo-pyrrolo-pyrrole (DPP) as central electron acceptor group, linear/transient absorption spectroscopy, one/two-photon fluorescence spectra, open-aperture $Z$-scan, and excited states quantum chemical calculations have been performed to systematically study the intermediate product electron acceptor J0 as well as three $D$-$\pi$-$A$-$\pi$-$D$ structural dyes using benzene, triphenylamine and 2,3-methoxy-triphenylamine as terminal electron donors, named as J1, J2, and J3, respectively. The intermediate product electron acceptor itself exhibits a relatively large TPA response, which indicates the DPP group has a large conjugated system. J2, with strong electron-donating ability groups triphenylamine as terminal groups, shows a large TPA cross-section of 534GM, which is approximately 10 times larger than that of J1 with weak electron pushing/pulling abilities groups benzene as terminal groups (51GM). The result indicates that the electron-donating abilities of terminal groups do play a key role in TPA response. Furthermore, methoxy substituent on the terminal triphenylamine groups can further effectively increase the TPA response, J3 exhibits a 15-fold enhancement compared with that of J1. Transient absorption spectra and quantum chemical calculation results are well accorded with the experimental results. Terminal substituents with strong electron donor groups are beneficial for the formation of intramolecular charge transfer (ICT) process. Besides, methoxy substituent in the terminal of triphenylamine groups can further enhance the degree of ICT and induce AIE characteristics in the molecule.

An organic nonlinear optical (NLO) crystal of Guanidinium carbonate (GUCT) was synthesized by the slow evaporation solution growth method using water as solvent. The GUCT crystalized in the tetragonal crystal system with non-centrosymmetric space group P4₃2₁2, which has been confirmed by single-crystal X-ray diffraction. The crystalline perfection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The UV-Vis-NIR spectrum studies have been carried out to identify the optical transmittance, lower cut off wavelength and optical band gap energy of GUCT crystal. The luminescence spectrum of crystal contains a green emission band with λ_max, 545 nm. From thermo-gravimetric analysis (TGA), the thermal stability of the grown crystal is found to be 117°C. The dielectric tensor components ε₁₁ and ε₂₂ of the grown crystal were evaluated as a function of frequency at 40°C. The mechanical strength and its parameters of the grown crystals have been determined by Vickers' microhardness test. The Kurtz-powder technique reveals that the second harmonic generation (SHG) efficiency of the grown crystal is 5.2 times greater than that of KDP.