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Donor/acceptor substitutions of a series of naphthyl bi-substituted 2-pyrazolines at accurate positions leads to large variations of their optical properties. An insightful discussion, supported by theoretical density functional theory (DFT) calculations, is presented on how the intrinsic polarization of the 2-pyrazoline core influences dipole moment, charge transfer, and optical properties, with distinct patterns based on substituent attachment enhancing either second or third harmonic generation. In particular, this study highlights the importance of the juxtaposition of electron-releasing sub-units within small molecules for modulating their second and third-order susceptibilities in PMMA films. The DFT calculations corroborated these experimental findings, underscoring the importance of substituent effects, enriching our understanding and enabling the development of novel materials with customizable optical functions. [ABSTRACT FROM AUTHOR]

We demonstrate a hybrid nanocomposite combining mesoporous silica, p SiO 2 , as a host medium and guest lithium niobate LiNbO 3 nanocrystals embedded into tubular silica nanochannels by calcination of the precursor mixed solution of lithium and niobium salts. High-resolution transmission electron microscopy, X-ray diffraction and Raman scattering techniques reveal trigonal LiNbO 3 nanocrystals within the p SiO 2 nanochannels, indicating their random texture morphology. Annealing at high temperatures (950 ∘ C) during calcination also leads to partial crystallization of the p SiO 2 matrix with the formation of trigonal α - SiO 2 nanocrystals. The Raman microscopy analysis of the p SiO 2 : LiNbO 3 nanocomposite reveals three structural crystalline phases, α - SiO 2 , LiNbO 3 and a mixed phase which involves the α - SiO 2 phase of host membrane and LiNbO 3 nanocrystals embedded into the membrane. The finite size of the LiNbO 3 nanocrystals results in specific features of the LO-TO phonon frequency splitting, which are investigated by Raman microscopy. In the transmission geometry, the second harmonic generation emission exhibits no Maker fringes and is characterized by a broad angular diagram of diffusely scattered light. The second harmonic generation response is independent of the polarization direction of the incident pump light, thus indicating a spatial isotropy of the nonlinear optical conversion in the p SiO 2 : LiNbO 3 composite, consistent with the randomly oriented textural morphology of the deposited LiNbO 3 nanocrystals. The contribution of the guest LiNbO 3 nanocrystals to the second harmonic generation effect was found to be strongly dominant compared to the partially crystallized host p SiO 2 matrix. The nanocomposite p SiO 2 : LiNbO 3 membrane, set in the 90 ∘ nonlinear optical geometry, shows unusually high diffusely transmitted second harmonic generation light (back-reflected emission), apparently supported by internal light reflection from the tubular nanochannel network. Despite the fundamental interest, the revealed anomalous back-reflected second harmonic generation emission from p SiO 2 : LiNbO 3 nanocomposite membranes expands the prospects for their photonic and nonlinear optical applications. [ABSTRACT FROM AUTHOR]

The presented work concerns computational investigations of the physical properties of composite materials based on polymer matrix and nonlinear optical (NLO) active chromophores. The structural, electronic, and optical properties of selected tetrathiafulvalene (TTF)-based chromophores have been calculated using quantum chemical methods. The polymer matrix changes the physical properties of the inserted chromophores influencing their optical parameters. To explain the mechanism of the NLO signal occurrence from the composites based on poly(methyl methacrylate) (PMMA) matrix and TTF chromophores, their structures are modeled using the classical molecular dynamics. In consequence, the structural properties of the composites are discussed according to the NLO requirements. By developing the theoretical model based on a discrete multipole local field approach, the impact of polymer matrix on the optical properties of chromophores is explained. [ABSTRACT FROM AUTHOR]

The nonlinear optical (NLO) properties of differently structured organic materials, such as low-weight dyes, macromolecular chains, or those functionalized by metal ions, have been widely investigated and are crucial for various applications in fields such as photonics, optical sensing, and data transmission. In this study, we explore the use of a 1,3,5-triazine core for constructing new azo/stilbene-based octupolar NLO chromophores (NLOPhores) and investigate their linear, second-order, and third-order NLO properties. Specifically, we examine their all-optical switching, causing remote optical anisotropy of the refractive index through the global re-ordering of photochromic molecules in host–guest polymeric thin films using the Optical Kerr effect. Additionally, NLOPhores were analyzed experimentally using the Z-scan methodology, as well as the comparative techniques defining the second and third harmonics of light generation (SHG and THG). These comprehensive studies demonstrate the significant potential of azo/stilbene-based octupolar chromophores with an embedded 1,3,5-triazine core in optoelectronics and quantum optics applications. [ABSTRACT FROM AUTHOR]

In this study, it is considered three anthracene derivatives, characterized meticulously in terms of their chemical structure and product purity. Extensive quantum chemical calculations are conducted to elucidate their optical and nonlinear optical properties, shedding light on the mechanism of photoinduced conformational transformation, a pivotal discovery in this research. Experimental analyses encompassed fundamental optical properties and advanced nonlinear optical phenomena, including z‐scan experiments, second harmonic generation (SHG), and third harmonic generation (THG). Remarkably, a groundbreaking all‐optical switching phenomenon in these materials is experimentally validated, marking a significant advancement and contributing to their potential applications. [ABSTRACT FROM AUTHOR]

This article covers selected properties of organic–inorganic thin films of hybrid perovskites with the summary formulas CH3NH3MI3, where M = Pb, Cd, Ge, Sn, Zn. The paper discusses not only the history, general structure, applications of perovskites and the basics of the theory of nonlinear optics, but also the results of experimental research on their structural, spectroscopic, and nonlinear optical properties. The samples used in all presented studies were prepared in the physical vapor deposition process by using co-deposition from two independent thermal sources containing the organic and inorganic parts of individual perovskites. Ultimately, thin layers with a thickness of the order of nanometers were obtained on glass and crystalline substrates. Their structural properties were characterized by atomic force microscopy imaging. Spectroscopic tests were used to confirm the tested films' transmission quality and determine previously unknown physical parameters, such as the absorption coefficient and refractive index. Experimental results of the nonlinear optical properties were obtained by studying the second and third harmonic generation processes and using initial sample polarization in the so-called Corona poling process. The obtained experimental results allowed us to determine the second- and third-order nonlinear optical susceptibility of the tested materials. [ABSTRACT FROM AUTHOR]

In this work, a novel experimental investigation of photoluminescence properties of Znq2 thin films co-doped with different concentrations of DCM were performed. The thin films were successfully deposited on glass substrates with different compositions, under high vacuum, by using the vacuum evaporation technique. For all compositions, the photoluminescence was measured at room temperature and also at low temperature in a wide range from 77 to 300 K with a step of 25 K in a high vacuum. The lifetime of the sample studied in real time was also measured using the decay time technique. The results obtained confirm that the doping influences the intensity of the DCM photoluminescence and also shows a complete energy transfer occurred from Znq2 to DCM which may have shifted the photoluminescence peak from Znq2 to the orange wavelength region which is related to DCM. The lifetime of the sample studied in real time was about 4.47 ns for Znq2 and while all the other samples showed two decay time components. As a result, the doping influences the optical properties of Znq2 and makes it a potential candidate for optoelectronic applications. [ABSTRACT FROM AUTHOR]

The synthesis of nanosized organic benzil (C 6 H 5 CO) 2 crystals within the mesoporous SiO 2 host matrix was investigated via X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and ab initio lattice dynamics analysis. Combining these methods, we have proved that the main structural properties of benzil nanocrystals embedded into SiO 2 host membranes with pore diameters of 6.0, 7.8, 9.4, and 13.0 nm are preserved compared to a bulk benzil crystal. Space confinement has an insignificant impact on the lattice vibrational properties of benzil crystals implanted into the host matrices. The ab initio lattice dynamics calculation of the phonon spectrum in the Brillouin zone center shows the mechanical and dynamical stability of benzil lattice, revealing very low optical frequency of 11 cm − 1 at point Γ. [ABSTRACT FROM AUTHOR]

The dependency of CO2 reduction rate in acetonitrile-Bu4NClO4 solution on cathodes, which were modified by laser induction of a copper surface, was studied. The topography of laser-induced periodic surface structures (LIPSS) → grooves → spikes was successively formed by a certain number of pulses. It was proved that for a higher number of laser pulses, the surface area of the copper cathode increases and preferred platy orientation of the copper surface on [022] crystallografic direction and larger fluence values increase. At the same time, the content of copper (I) oxide on the surface of the copper cathode increases. Also, the tendency to larger fluency values is observed. It promotes the increase of cathodic current density for CO2 reduction, which reaches values of 14 mA cm-2 for samples with spikes surface structures at E = − 3.0 V upon a stable process. [ABSTRACT FROM AUTHOR]