Search Results (135)

This study synthesizes and comparatively investigates two squaric acid-based phthalocyanine-like dyes, SNF and its long-chain alkylated derivative LNF, to systematically elucidate the influence of peripheral hydrophobic groups on their third-order nonlinear optical (NLO) properties. The NLO characteristics were comprehensively characterized using femtosecond Z-scan and I-scan techniques at both 800 nm and 900 nm. Both dyes exhibited strong saturable absorption (SA), confirming their potential as saturable absorbers. Critically, the comparative analysis revealed that SNF exhibits a significantly greater nonlinear absorption coefficient (β) compared to LNF under identical conditions. For instance, at 800 nm, the β of SNF was approximately 3–5 times larger than that of LNF. This result conclusively demonstrates that the introduction of long hydrophobic alkyl chains attenuates the NLO response. Furthermore, I-scan measurements revealed excellent SA performance, with high modulation depths (e.g., LNF: 43.0% at 900 nm) and low saturation intensities. This work not only clarifies the structure–property relationship in these D-A-D dyes but also presents a clear strategy for modulating the NLO properties of organic chromophores for applications in near-infrared pulsed lasers. Full article

This study details how 3-(naphthalen-2-yl)-1-phenylprop-2-en-1-one (3NPEO) behaves in terms of photophysics when exposed to different solvents. The solvatochromic effect study reveals significant polarity shifts in the excited states of the 3NPEO compound, likely due to an intramolecular proton transfer mechanism. Measurements of dipole moments provide insight into their resonance structures in both ground and excited states. Electrochemical analysis revealed a reversible redox process, indicating a favorable charge transport potential. HOMO and LUMO energies of the compound were computed via oxidation and reduction potential standards. 3NPEO exhibits optimal one-photon and two-photon absorption characteristics, validating its suitability for visible wavelength laser applications in photonic devices. Furthermore, molecular docking and dynamics simulations demonstrated strong interactions between 3NPEO and the progesterone receptor enzyme, supported by structure–activity relationship (SAR) analyses. In vitro cytotoxicity assays on the MDAMB-231 breast cancer cell line showed moderate tumor cell inhibitory activity. Apoptosis studies confirmed the induction of both early and late apoptosis. These findings suggest that 3NPEO holds promise as a potential anticancer agent targeting the progesterone receptor in breast cancer cells. Overall, the findings highlight the substantial influence of solvent polarity on the photophysical properties and the design of more effective and stable therapeutic agents. Full article

This fundamental understanding of molecular structure–NLO property relationships provides critical design principles for next-generation optical limiting materials, quantum photonic devices, and ultrafast nonlinear optical switches, addressing the growing demand for high-performance organic optoelectronic materials in laser protection and photonic computing applications. In this study, it was observed that selenophene-incorporated fused D-A-D architectures exhibit a remarkable enhancement in two-photon absorption characteristics. By strategically modifying the heteroatomic composition of the Y6-derived fused-ring core, replacing thiophene (BDS) with selenophene (BDSe), the optimized system achieves unprecedented NLO performance. BDSe displays a nonlinear absorption coefficient (β) of 3.32 × 10⁻¹⁰ m/W and an effective two-photon absorption cross-section (σ_TPA) of 2428.2 GM under 532 nm with ns pulse excitation. Comprehensive characterization combining Z-scan measurements, transient absorption spectroscopy, and DFT calculations reveals that the heavy atom effect of selenium induces enhanced spin–orbit coupling, optimized intramolecular charge transfer dynamics and stabilized excited states, collectively contributing to the superior reverse saturable absorption behavior. It is believed that this molecular engineering strategy establishes critical structure–property relationships for the rational design of organic NLO materials. Full article

Organic–inorganic hybrid halide perovskites have emerged as promising optoelectronic materials owing to their exceptional optoelectronic properties and versatile crystal structures. The introduction of chiral organic ligands into perovskite frameworks, breaking the inversion symmetry of the structure, has attracted significant attention toward chiral perovskites. Herein, the recent advances in various synthesis strategies for chiral perovskite single crystals (SCs) are systematically demonstrated. Then, we elucidate an in-depth understanding of the chirality transfer mechanisms from chiral organic ligands to perovskite inorganic frameworks. Furthermore, representative examples of chiral perovskite SC-based applications are comprehensively discussed, including circularly polarized light (CPL) photodetection, nonlinear optical (NLO) responses, and other emerging chirality-dependent applications. In the end, an outlook for future challenges and research opportunities is provided, highlighting the transformative potential of chiral perovskites in next-generation optoelectronic devices. Full article

Degenerate third-order nonlinear optical (NLO) responses of organic molecules have a wide range of applications in science and engineering because they relate to the intensity-dependent refractive index (IDRI) and nonlinear absorption (NLA), such as two-photon absorption (TPA). Among the many molecular systems, open-shell molecular species such as intermediate singlet diradicaloids have attracted considerable attention because of their enhanced response, predicted theoretically by Nakano et al. Experimental studies for proofing and evaluating the enhanced nonlinearities play an important role in the development of the field. This tutorial review provides the solid fundamentals of the NLO processes of open-shell molecular species even to those who are not familiar with the experimental works. Its scope ranges from the basics of NLO responses, definitions, and interrelations of the key parameters of the responses, such as hyperpolarizability and TPA cross-section, to the experimental techniques used to evaluate them. Including the recent achievements, the evolution of experimental works on the TPA properties of singlet diradicaloids is also reviewed according to families of molecular structures. Full article

The optical and radiation shielding of PVA have been enhanced through embedding with ZnO/CuO/SWCNT (ZCS) nanocomposites. ZCS polymeric nanocomposites (PNCs) were prepared with the solution casting method. Scanning electron, optical microscopy and FT-IR procedures were performed to examine the surfaces’ morphology and structures’ modifications. UV–visible measurements were carried out to investigate the linear/nonlinear optical properties. The optical investigations show significant alterations in the optical parameters of PVA due to ZCS embedding. The UV–visible analysis shows that the optical parameters, including the transmittance, energy bandgap, refractive index, dielectric constants and optical conductivity of PVA, are tuned through ZCS embedding. The direct and indirect bandgap of PVA shrank from 5.42 eV and 4.99 eV (neat PVA) to 3.20 eV and 2.26 eV (10 wt.% ZCS PNCs). The nonlinear optical (NLO) constants (first order susceptibility (χ⁽¹⁾), third susceptibility (χ⁽³⁾) and refractive index (n₂)) of PVA were improved. Phy-X/PSD software was used to investigate the radiation shielding parameters of all samples. The linear attenuation coefficient (LAC), mean free path (MFP), half value layer (HVL), tenth value layer (TVL) and effective atomic number (Z_eff) of PVA were enhanced through ZCS embedding. It is found that the mass attenuation coefficient (MAC) of the neat PVA increased from 1.14 cm²/g to 7.96 cm²/g at 0.015 MeV. The HVL of PVA decreased from 30.2 cm to 20.6 cm, the TVL decreased from 100.3 cm to 68.5 cm and the MFP decreased from 43.6 cm to 29.8 cm upon embedding 10 wt.% of ZCS NCs at 15 MeV. The samples’ exposure buildup factor (EBF) and energy absorption buildup factor (EABF) in the photon energy range from 0.015 MeV to 15 MeV at 0.5 to 40 MFP values. This study proves that ZCS PNCs are advantageous for applications in optical and radiation shielding fields. Full article

Quasi-one-dimensional (quasi-1D) transition metal chalcogenides (TMCs), a subclass of low-dimensional materials, have attracted significant attention due to their unique optical and electronic properties, making them promising candidates for nonlinear photonics. In this work, NbTe₄, a quasi-1D transition metal tetrachalcogenide, was synthesized and employed for the first time as a broadband saturable absorber (SA) for pulsed laser applications. The nonlinear optical (NLO) properties of NbTe₄ were systematically characterized at 1.0 μm, 2.0 μm, and 3.0 μm, revealing saturation intensities of 59.53 GW/cm², 14 GW/cm², and 6.8 MW/cm², with corresponding modulation depths of 17.4%, 5.3%, and 21.5%. Utilizing NbTe₄-SA, passively Q-switched (PQS) pulses were successfully generated in the 1.0 μm and 2.0 μm bands, achieving pulse durations of 86 ns and 2 μs, respectively. Furthermore, stable mode-locked operation was demonstrated in an Er-doped fluoride fiber laser at 3.0 μm, yielding a pulse duration of 19 ps. These results establish NbTe₄ as a highly promising broadband SA material for next-generation ultrafast photonic devices and pave the way for the development of other quasi-1D materials in nonlinear optics. Full article

The second-order nonlinear optical (NLO) properties of the known heteroleptic complex [Cu(1,10-phenanthroline)xantphos][PF₆] (complex 1) and the related new complexes [Cu(5-NO₂-1,10-phenanthroline)xantphos][PF₆] and [Cu(5-NO₂-1,10-phenanthroline)(dppe)][PF₆] (dppe = 1,2-bis(diphenylphosphino)ethane) (complexes 2 and 3) were investigated in solution by the EFISH (Electric Field-Induced Second Harmonic generation) technique, working at a non-resonant wavelength of 1907 nm. It turned out that they are characterized by large μβ values (957–1100 × 10⁻⁴⁸ esu), much higher than that of the Disperse Red One benchmark. Unexpectedly, the homoleptic complex [Cu(2-mesityl-1,10-phenanthroline)₂][PF₆] (complex 4) shows a similar high second-order NLO response. Quantum chemical calculations based on Density Functional Theory (DFT) methods have been carried out to give insight into the electronic structure of the investigated complexes in relation to NLO properties. This investigation, which represents the first EFISH study on copper(I) complexes, opens a convenient route for the development of low-cost dipolar NLO-active heteroleptic [Cu(P^P)(N^N)][PF₆] and homoleptic [Cu(N^N)₂][PF₆] complexes. Full article

The exploitation of high-performance third-order nonlinear optical (NLO) materials that have a favorable optical limit (OL) threshold is essential due to a rise in the application of ultra-intense lasers. In this study, a Cu-based MOF (denoted as Cu-bpy) was synthesized, and its third-order NLO and OL properties were investigated using the Z-scan technique with the nanosecond laser pulse excitation set at 532 nm. The Cu-bpy exhibits a typical rate of reverse saturable absorption (RSA) with a third-order nonlinear absorption coefficient of 100 cm GW⁻¹ and a favorable OL threshold of 0.75 J cm⁻² (at a concentration of 1.6 mg mL⁻¹), which is lower than that of most NLO materials that have been reported on so far. In addition, a DFT calculation was performed and was in agreement with our experimental results. Furthermore, the mechanism of the third-order NLO properties was illustrated as one-photon absorption (1PA). These results investigate the relationship between the structure and the nonlinear optical properties of Cu-bpy, and provide an experimental and theoretical basis for its use in optical limiting applications. Full article

In this report, the nonlinear optical (NLO) properties of titanium dioxide nanoparticles (TiO₂ NPs) have been explored experimentally using femtosecond laser light along with the Z-scan approach. The synthesis of TiO₂ NPs was carried out in distilled water through nanosecond second harmonic Nd:YAG laser ablation. Characterization of the TiO₂ NPs colloids was conducted using UV-visible absorption spectroscopy, transmission electron microscopy (TEM), inductively coupled plasma (ICP), and energy-dispersive X-ray spectroscopy (EDX). The TEM analysis indicated that the size distribution and average particle size of the TiO₂ NPs varied from 8.3 nm to 19.1 nm, depending on the laser ablation duration. The third-order NLO properties of the synthesized TiO₂ NPs were examined at different excitation laser wavelengths and incident powers through both open- and closed-aperture Z-scan techniques, utilizing a laser pulse duration of 100 fs and a high repetition rate of 80 MHz. The nonlinear absorption (NLA) coefficient and nonlinear refractive (NLR) index of the TiO₂ NPs colloidal solutions were found to be influenced by the incident power, excitation wavelength, average size, and concentration of TiO₂ NPs. Maximum values of 4.93 × 10⁻⁹ cm/W for the NLA coefficient and 15.39 × 10⁻¹⁵ cm²/W for the NLR index were observed at an excitation wavelength of 800 nm, an incident power of 0.6 W, and an ablation time of 15 min. The optical limiting (OL) effects of the TiO₂ NPs solution at different ablation times were investigated and revealed to be concentration and average size dependent. An increase in concentration results in a more limiting effect. Full article

In this work, the nonlinear optical (NLO) properties of CuO nanoparticles (CuO NPs) were studied experimentally using the pulsed laser ablation (PLA) technique. A nanosecond Nd: YAG laser was employed as the ablation excitation source to create CuO NPs in distilled water. Various CuO NPs samples were prepared at ablation periods of 20, 30, and 40 min. Utilizing HR-TEM, the structure of the synthesized CuO NPs samples was verified. In addition, a UV–VIS spectrophotometer was used to investigate the linear features of the samples. The Z-scan technique was utilized to explore the NLO properties of CuO NPs samples, including the nonlinear absorption coefficient ($\beta$) and nonlinear refractive index ($n_2$). An experimental study on the NLO features was conducted at a variety of excitation wavelengths (750–850 nm), average excitation powers (0.8–1.2 W), and CuO NPs sample concentrations and sizes. The reverse saturable absorption (RSA) behavior of all CuO NPs samples differed with the excitation wavelength and average excitation power. In addition, the CuO NPs samples demonstrated excellent optical limiters at various excitation wavelengths, with limitations dependent on the size and concentration of CuO NPs. Full article

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. Full article

In recent years, the phenomenon of optical second harmonic generation (SHG) has attracted significant attention as a pivotal nonlinear optical effect in research. Notably, in low-dimensional materials (LDMs), SHG detection has become an instrumental tool for elucidating nonlinear optical properties due to their pronounced second-order susceptibility and distinct electronic structure. This review offers an exhaustive overview of the generation process and experimental configurations for SHG in such materials. It underscores the latest advancements in harnessing SHG as a sensitive probe for investigating the nonlinear optical attributes of these materials, with a particular focus on its pivotal role in unveiling electronic structures, bandgap characteristics, and crystal symmetry. By analyzing SHG signals, researchers can glean invaluable insights into the microscopic properties of these materials. Furthermore, this paper delves into the applications of optical SHG in imaging and time-resolved experiments. Finally, future directions and challenges toward the improvement in the NLO in LDMs are discussed to provide an outlook in this rapidly developing field, offering crucial perspectives for the design and optimization of pertinent devices. Full article

In this paper, we first optimized the structures of Cl benzaldehydes using Gaussian 09 software with the B3LYP/631-G’ (d,p) basis set. The title compound’s polarizability and hyperpolarizabilities values have been computed, along with an examination of its nonlinear optical characteristics. The title molecule’s total initial static hyperpolarizability as determined by DFT studies may be a topic for future NLO content that is appealing. Full article

The present study elaborates on the synthesis, crystal structure, and computational studies of two new ionic liquids. In the crystal structure, [C₅H₁₂N][C₂₁H₁₄ClN₂O₂S] (4a), the anions form chains along the a-axis direction through C—H···π(ring) interactions. These are connected into layers that run approximately parallel to the ac plane by a variety of hydrogen bonds. In the compound structure, [C₅H₁₂N][C₁₈H₁₅N₂O₂S] (4b), the two ions are primarily associated by an N—H···N hydrogen bond. In the crystal structure, layers parallel to the bc plane are formed by pairs of C—H···O and N—H···S hydrogen bonds and by C—H···π(ring) interactions. A theoretical study reveals that 4a has lower energy than 4b and is more stable. The NBO and DOS studies further confine the liquids’ structural reactivity and electronic properties. The quantum theory of atoms in a molecule (QTAIM) analysis reveals the important non-covalent interactions among the fragments and charge transfer. The global reactivity descriptors indicate their molecular reactivity relationship with the presence of functional groups. The remarkable polarizability (α_o) and hyperpolarizability (β_o) values indicate their optical and nonlinear optical (NLO) properties. Furthermore, the analysis performed by CrystalExplorer shows the intermolecular interactions and reactive sites between cations and anions in ionic liquids. The 2D fingerprint plots and Hirshfeld surfaces indicate the major interactions of crystals with neighboring elements in crystal packing. For both compounds, the H···H interactions are significantly higher than the other element interactions. Full article