Second-order Nonlinear Optical Properties Research Articles

Modeling of graphene like structure by utilizing phenanthrocarbazole for tailoring the second-order nonlinear optical properties

Lower band gap with excellent intramolecular charge transfer plays a pivotal role towards developing the strong nonlinear optical (NLO) properties in a molecule. In the current investigation, we have designed a series of graphene like molecules with promising organic fragments that we have strategically adjoin the phenanthrocarbazole and tetracyanobuta-1,3-dienes (TCBD) fragment. Density functional theory (DFT) approach with CAM-B3LYPP/6-311+G(d,p) were performed to evaluate the nonlinear optical properties of designed derivative. The NLO characteristics were analysed the static polarizability (α0), first order hyperpolarizabilities (βtot) and band gap. The calculated results revealed that the designed molecules have better NLO response and highest βtot were observed for molecule 10 (117871 au). Time dependent density functional based theories at the same level of theory were also performed to calculate the absorption spectra. The calculated results observed that there was a red shift trend with reduced band gap of designed derivative. Further, to substantiate our finding, we have also calculated density of states (DOS), molecular electrostatic potential (MESP) and transition density matrix (TDM) at the same level of theory. As a consequence the designed derivative shed light that the efficient TCBD group with graphene like molecular system and donor group can be utilized to design new molecular motif for NLO applications.

In-plane anisotropic dispersion property and second-harmonic generation of violet phosphorus with two-dimensional nano-interlocking structure

The unique one-dimensional chain structure of violet phosphorus provides an ideal platform for the study of second-order nonlinear optical properties. This also offers more possibilities for the further development of novel two-dimensional layered nanomaterials in the frequency domain. The research suggest that the highest occupied molecular orbital of monolayer phosphorene is characterized by a small effective mass and high hole mobility, while the lowest unoccupied molecular orbital exhibits opposite properties. This may be attributed to increased lattice scattering or electron-electron interactions in the conduction band. Monolayer violet phosphorus exhibits strong absorption capabilities in the near-ultraviolet light range, which can be utilized in UV spectroscopy technology for detecting harmful substances in water and air. Besides, its second harmonic generation response is also very strong within the visible light spectrum, and this response significantly varies with changes in angle. This provides theoretical guidance for optimizing the different stacking directions and heterojunction structures of violet phosphorus, more importantly, the sensitivity and directional selectivity of sensors can be improved. The work not only deepens the understanding of the electro-optical performance of violet phosphorus materials but also lays a theoretical foundation and guidance for the design and application of devices based on violet phosphorus.

The effect of metal-to-ligand charge transfer on linear and nonlinear optical properties of hexaphyrin and metallo-hexaphyrins

Charge transfer from metal to ligand has implications in various fields of chemistry, physics and biology. The manipulation of spin properties would be necessary for controlling charge transfer in spintronics and biological applications. Upon binding to the metal atoms (Ni, Cu, Au, etc.), the spin properties would be modulated in organic conjugated molecules of less intrinsic spin–orbit coupling (SOC) due to SOC coming from the heavy elements. Emission spectra calculation is necessary to validate them as suitable fluorescence quenchers. The nonlinear optical properties like first-order hyperpolarisability β and second-order hyperpolarisability γ calculations are important to find out their relation between fluorescence quenching and higher order nonlinear optical (NLO) properties. From the second-order NLO properties, we computed degenerate four-wave mixing (DFWM) component ( γ ( 2 ) ( − ω ; ω , ω , − ω )) and finally quadratic nonlinear refractive indices of the expanded porphyrins (EPs). How the linear and nonlinear optical properties are dependent on the SOC coming from the heavy materials (Ni, Cu, Au), and charge transfer process is the most interesting question to be addressed for their potential uses for various optoelectronic and spintronic applications.

Second-Order Nonlinear Switching and Photoluminescence Properties of Cd-Based Hybrid Perovskite with High-Temperature Phase Transition.

Recently, organic-inorganic hybrid perovskites exhibiting facile structural phase transitions have accumulated significant attention due to their switchable second-order nonlinear optical (NLO) properties, which hold significant promise for next-generation intelligent optoelectronic devices. In this study, we present a novel one-dimensional hexagonal hybrid perovskite, (4-methoxypiperidinium)CdCl3, which undergoes a reversible high-temperature structural phase transition at 389 K. Notably, (4-methoxypiperidinium)CdCl3 demonstrates switchable second-order NLO and dielectric properties, accompanied by symmetry breaking from the centrosymmetric Pnma to noncentrosymmetric Pna21 space group. Variable-temperature structure analyses reveal that this transition is mainly driven by the order-disorder transformation of the 4-methoxypiperidinium cations. Furthermore, it also features a promising photoluminescence performance with blue-light emission and a long lifetime of 25.34 ns. It is anticipated that this study will expand the family of hybrid perovskites exhibiting high-temperature phase transitions and offer valuable guidance for the design of new NLO switching materials with superior optoelectronic properties.

Theoretical investigation of the electronic and second-order non-linear optical properties of [n]helicene derivatives

Designing and synthesizing nonlinear optical materials with excellent performance has always been a persistent goal pursued by material chemists. In paper, based on the reported [6]heliceno-bis(naphthalimides) 2, four new molecules are designed by introducing 2-dicyanomethylene-1,3-dithiole on the two middle benzene rings of the naphthalimide unit and replacing CH3 units on the R1 and R2 substituents with NH2/NO2 moieties, or their combination. The electronic spectra, reorganization energy and second-order nonlinear optical properties of the reported derivatives 1 and 2, as well as four newly designed derivatives, have been systematically investigated by means of (time-dependent) density functional theory calculations. Frontier molecular orbital analysis, electron excitation analysis, reorganization energy, and the calculation of the static and dynamic first hyperpolarizability all indicate that the studied system is greatly influenced by the number of benzene rings in helicene core and the terminal substituents attached at both ends of helicene core. Further analysis of depolarization, hyperpolarizability density and unit sphere representation reveals the nature of the nonlinear optical response of the studied system. Considering that the studied derivatives all have large static first hyperpolarizabilities (e.g., 210 × 10-30 esu for derivative 5) and small reorganization energy (e.g., 0.092 eV of hole reorganization energy and 0.118 eV of electron reorganization energy for derivative 3), they are expected to become potential nonlinear optical materials with excellent performance and bipolar transport materials. This work contributes to the rational design of high-performance molecules based on [n]helicenes derivatives and further explores their potential applications in optical materials.

Role of cation nature in crown ether appended 25-Oxasmaragdyrins with second-order NLO responses: As potential and selective metal ions detector

Crown ethers, known for their efficacy as metal ion traps, have garnered significant interest in optoelectronic applications due to their unique cavity structure and special binding ability with metals. Herein, we systematically designed and investigated the second-order nonlinear optical (NLO) properties of an intriguing compound, 18-crown-6 derivative appended with 25-oxasmaragdyrins (Cr-Prs), achieved through the incorporation of diverse metal ions into the crown ether ring. Significantly, the βtot values of compounds with alkaline earth metal ions (Mg2+, Ca2+) are greater than those compounds with alkali metal ions (Na+, K+). Interestingly, the Hg2+@Cr-Prs compound exhibits a tremendous second-order NLO property with the βtot value of 5.34 × 105 au. Further insights into substantial βtot values across all compounds were provided through a comprehensive analysis of the transition energies, the molecular orbitals, and the absorption spectra of the main excited states. The calculation results conclude that the second-order NLO properties of Cr-Prs can be modulated by incorporating metal ions into the crown ether ring. Crown ether emerges as a facilitator in detecting and identifying Hg2+ ions, serving as an effective NLO-based ion detector. These findings not only broaden the scope of cation detection and efficiency but also present innovative applications in analytical and optoelectronic research, encapsulating the essence of our study within a concise framework.

Optical and Electrical Properties of A3[VS4] (A = Na, K) Synthesized via a Straightforward and Scalable Solid-State Method.

Two literature-known sulfido vanadates, Na3[VS4] and K3[VS4], were obtained through a straightforward and scalable synthetic method. Highly crystalline powders of both compounds were obtained from the homogeneous molten phases of starting materials via a─comparably rapid─solid-state technique. Low-temperature structure determination, ambient temperature powder diffraction, and solid-state NMR spectroscopy verify previous structural reports and indicate purity of the obtained samples. Both compounds show semiconductivity with the optical band gap values in the range of 2.1 to 2.3 eV. Experimental values of the ionic conductivity and dielectric constants are σ = 2.41·10-5 mS·cm-1, k = 76.52 and σ = 1.36·10-4 mS·cm-1, k = 103.67 at ambient temperature for Na3[VS4] and K3[VS4], respectively. It is demonstrated that Na3[VS4] depicts second-order nonlinear optical properties, i.e., second harmonic generation over a broad wavelength spectrum. The results introduce new aspects of sulfido vanadates as multifunctional candidates for potential optical and electrical applications.

Rational design and investigation of nonlinear optical response properties of pyrrolopyrrole aza-BODIPY-based novel push-pull chromophores.

Intramolecular charge transfer (ICT)-based chromophores are highly sought after for designing near-infrared (NIR) absorbing and emitting dyes as well as for designing materials for nonlinear optical (NLO) applications. The properties of these 'push-pull' molecules can easily be modified by varying the electronic donor (D) and acceptor (A) groups as well as the π-conjugation linker. This study presents a methodical approach and employs quantum chemical analysis to explore the relationship between the structural features, electro-optical properties, and the NLO characteristics of molecules with D-π-A framework. The one- and two-photon absorption (2PA), linear polarizability (α), and first hyperpolarizability (β) of some novel chromophores, consisting of a dimeric aza-Boron Dipyrromethene (aza-BODIPY) analogue, called, pyrrolopyrrole aza-BODIPY (PPAB), serving as the acceptor, have been investigated. The electronic donors used in this study are triphenylamine (TPA) and diphenylamine (DPA), and they are conjugated to the acceptor via thienyl or phenylene π-linkers. Additionally, the Hyper-Rayleigh Scattering (βHRS), which enables direct estimation of the second-order NLO properties, is calculated for the studied chromophores with 1064 nm excitation in acetonitrile. The β value shows a significant increase with increasing solvent polarity, indicating that the ICT plays a crucial role in shaping the NLO response of the studied molecules. The enhancement of the 2PA cross-section of the investigated molecules can also be achieved by modulating the combinations of donors and linkers. The results of our study indicate that the novel D-π-A molecules designed in this work demonstrate considerably higher hyperpolarizability values than the standard p-nitroaniline, making them promising candidates for future NLO applications.

Room-Temperature Phase Transition Material with Switchable Second-Order Nonlinear Optical Properties.

Phase transition materials with switchable second-order nonlinear optical (NLO) properties have attracted extensive attention because of their great application potential in photoelectric switches, sensors, and modulators, while metal-free organics with NLO switchability near room temperature remain scarce. Herein, we report a hydrogen-bonded metal-free organic crystal, 2-methylpropan-2-aminium 2,2-dimethylpropanoate (1), exhibiting a room-temperature phase transition and favorable NLO switchability. Through investigations on its thermal anomalies, dielectric properties, and crystal structures, we uncover that 1 holds a near-room-temperature phase transition at 303 K from noncentrosymmetric point group C2v to centrosymmetric one D2h, which is attributed to the order-disorder transformations of both tert-butylamine cations and dimethylpropionic acid anions. Accompanied by symmetry change during the phase transition, 1 exhibits reversible and repeatable NLO "on-off" switchability with a desirable switching contrast ratio of ca. 19 between high and low NLO states. This discovery demonstrates a metal-free organic crystal with NLO switching behavior near room temperature, serving as a promising candidate in smart and ecofriendly photoelectric functional materials and devices.

Crystallization of SrB4O7 in a glass tape and its electrical, dielectric, ferroelectric and nonlinear optical properties

This paper presents the results of an investigation of the electrical, dielectric, ferroelectric, and second-order nonlinear optical properties of SrB4O7 synthesized by methods of both solid-state reaction (SSR) and crystallization of a glass tape (GT). To obtain GTs of SrB4O7, the melt consisting of appropriate precursors was rapidly cooled using a twin-roller. The prepared GTs were crystallized at 730°C for different durations and analyzed by X-ray diffraction. The formation of “extended” crystals in the central part of GTs due to the application of the GT technology is discussed. The investigation of the current-voltage characteristic of the sample prepared by SSR showed that its breakdown voltage is higher than 1000 V. The measurements of the dielectric parameters in the frequency range of 1 KHz–1 MHz showed that the dielectric constant is about 7.5, and the dielectric loss varies from 0.002 to 0.0008. These parameters are sufficiently stable in the temperature range from room temperature to 150°C. The ferroelectric properties of the GT crystallized at 730°C for 3 h were also investigated. At 20 kV/cm, a remnant polarization of 0.18 μC/cm2 was measured. Optical measurements showed that the intensity of second-harmonic generation in the GT crystallized at 730°C for 3 h is 5.4 times higher than that of KH2PO4 (KDP).

Ambient Degradation Anisotropy and Mechanism of van der Waals Ferroelectric NbOI2.

The spontaneous centrosymmetry-breaking and robust room-temperature ferroelectricity in niobium oxide dihalides spurs a flurry of explorations into its promising second-order nonlinear optical properties, and promises potential applications in nonvolatile electro-optical and optoelectronic devices. However, the ambient stability of the niobium oxide dihalides remains questionable, which overshadows their future development. In this work, the chemical degradation of NbOI2 is comprehensively investigated using combined chemical and optical microscopies in conjunction with spectroscopies. We unveil the highly anisotropic degradation kinetics of NbOI2 driven by the hydrolysis process of the unstable dangling iodine bonds dominantly on the (010) facet and progressing along the c axis. Knowing its degradation mechanism, the NbOI2 flake can then be stabilized by the hexagonal boron nitride encapsulation, which isolates the air moisture. These findings provide direct insights into the ambient instability of NbOI2, and they deliver possible solutions to circumvent this issue, which are essential for its practical integration in photonic and electronic devices.

A theoretical study on the second-order nonlinear optical properties of Pt(II) bis-acetylide complexes: substituent and redox effects.

Density functional theory studies on the geometric and electronic structures, UV-vis absorption spectra, and second-order nonlinear optical (NLO) properties of four-coordinate Pt(II) bis-acetylide complexes, cis-[Pt(CNtBu)(ADC)(CCR)2] , have been employed. The effects of ligand variation and the single electron redox process on the structures and NLO response of complexes have also been investigated. It shows that the variations of the ligand and electron have little effect on the geometries of the complexes, but there is a significant effect on their electronic structures and NLO responses. The introduction of a single -NO2 group in acetylide ligands increases the first hyperpolarizability of complex 12 times, while one electron lost in five complexes enhances the first hyperpolarizability 496 times at the most. Both methods are considered effective ways for improving the NLO response of Pt(II) bis-acetylide complexes. Based on the analysis of the electronic and optical properties of fifteen studied complexes, the increase of NLO response is mainly ascribed to strong oscillator strengths, lower electron transition energy, and well-directed effective charge transfer. This work reveals some underlying relationships between the NLO responses and electronic structures of complexes, which is helpful for the design and synthesis of high-performance NLO materials of Pt(II) bis-acetylide complexes.

Second-order nonlinear optical properties of X-shaped pyrazine derivatives.

This work reports an investigation of the second-order NLO properties of two isomer series of X-shaped pyrazine derivatives, by means of HRS measurements and DFT calculations. The systems differ in the relative position of the donor and acceptor substituents with respect to the axis formed by the nitrogen atoms of the central pyrazine ring. Although the magnitude of the second harmonic signal is similar, HRS measurements revealed that the anisotropy of the NLO response strongly differs in the two chromophore series, the one of the 2,3-isomers being strikingly dipolar, while the one of the 2,6-isomers is mostly octupolar. The experimental observations are well supported by DFT calculations. In particular, the sum-over-states approach allows us to rationalize the different NLO anisotropies observed in the two isomer series through a detailed analysis of the symmetry of the low-lying excited states.

Investigation of the electronic and optical properties of Al13–dianhydride complexes by (time-dependent) density functional theory

The second-order nonlinear optical properties of inorganic–organic complexes constructed from Al13 and dianhydrides were investigated using (time-dependent) density functional theory.

Two multifunctional Dy(iii)-based metal–organic frameworks exhibiting proton conduction, magnetic properties and second-harmonic generation

Two novelty Dy-MOFs were synthesized using H4DTTP-2OMe ligand. MOF 1 displays a more superior proton conductivity, field-induced single molecule magnets behavior and obvious second-order nonlinear optical properties.

Effect of substitution on second-order nonlinear optical properties of ferrocene appended donor–π–acceptor Y-shaped trifluoromethyl imidazole chromophores

Substitution of an imidazole ring creates a steric effect and restricts the intramolecular charge-transfer (ICT) process, resulting in the feeble quadratic hyperpolarizability of the chromophore.

Quantum Mechanical Calculations, Hirshfeld Surface Analysis, Molecular Docking, ADME and Toxicology Studies of the Ethyl 4-chloro-2-[(4-nitrophenyl)hydrazono]-3-oxobutrate Compound

The theoretical chemical activity parameters of the compound Ethyl 4-chloro-2-[(4-nitrophenyl)hydrazono]-3-oxobutrate, which had previously been synthesized and crystallographically studied, were determined using Density Functional Theory (DFT). With Hirshfeld surface analysis, the effects of molecular interactions on the surface were defined with surface maps and the percentage contribution of the interactions of atoms with each other was determined. In addition, second-order nonlinear optical properties (NLO) and thermodynamic parameters were examined at temperatures between 100 and 1000 K. In addition, molecular docking study was carried out by downloading structure of a B-DNA dodecamer (PDB ID: 1BNA) from PDB (Protein Data Bank). ADME and toxicology properties were examined using the complex, in-silico method and it was discussed whether it had drug properties.

First hyperpolarizability of the di-8-ANEPPS and DR1 nonlinear optical chromophores in solution. An experimental and multi-scale theoretical chemistry study

The solvent effects on the linear and second-order nonlinear optical properties of an aminonaphtylethenylpyridinium (ANEP) dye are investigated by combining experimental and theoretical chemistry methods. On the one hand, deep near infrared (NIR) hyper-Rayleigh scattering (HRS) measurements (1840–1950 nm) are performed on solutions of di-8-ANEPPS in deuterated chloroform, dimethylformamide, and dimethylsulfoxide to determine their first hyperpolarizablity (βHRS). For the first time, these HRS experiments are carried out in the picosecond regime in the deep NIR with very moderate (≤3 mW) average input power, providing a good signal-to-noise ratio and avoiding solvent thermal effects. Moreover, the frequency dispersion of βHRS is investigated for Disperse Red 1 (DR1), a dye commonly used as HRS external reference. On the other hand, these are compared with computational chemistry results obtained by using a sequential molecular dynamics (MD) then quantum mechanics (QM) approach. The MD method allows accounting for the dynamical nature of the molecular structures. Then, the QM part is based on TDDFT/M06-2X/6-311+G* calculations using solvation models ranging from continuum to discrete ones. Measurements report a decrease of the βHRS of di-8-ANEPPS in more polar solvents and these effects are reproduced by the different solvation models. For di-8-ANEPPS and DR1, comparisons show that the use of a hybrid solvation model, combining the description of the solvent molecules around the probe by point charges with a continuum model, already achieves quasi quantitative agreement with experiment. These results are further improved by using a polarizable embedding that includes the atomic polarizabilities in the solvent description.

Second harmonic responses of clickable azobenzenes in solution: Comparative Hyper-Rayleigh scattering and density functional theory studies

The linear and second-order nonlinear optical (NLO) properties of clickable azobenzene derivatives are investigated in chloroform solution by means of UV/Visible and Hyper-Rayleigh scattering (HRS) spectroscopies. Their absorption properties are also monitored along time in order to characterize the rate and kinetics of the E-Z photoswitching reaction. The magnitude and symmetry of the first hyperpolarizability of the compounds are rationalized with the help of DFT calculations, which support well the experimental data. We demonstrate that the second harmonic generation (SHG) intensity of the E form, as well as its variation upon photoisomerization, can be tuned by varying the nature of the peripheral substituents. A fully characterized library of ready-to-click switchable compounds displaying large hyperpolarizability contrasts, and differing in the amplitude and orientation in their dipole moments is provided. This library expands the database of photoswitching compounds for further anchorage into polymer matrices or nano- or micro-sized solid substrates.

Design, Synthesis and Second-Order Nonlinear Optical Properties of Azobenzene-Based Polysiloxanes.

To study the effect of polymeric structures on second-order nonlinear optical properties, polysiloxanes materials based on azobenzene as chromophore have been designed and synthesized successfully. Herein, the siloxane monomer is directly bonded to azobenzene units by palladium catalysis, which avoids the influence of flexible chains on the photoelectric properties of azobenzene. According to the different positions of azobenzene units in the polymers, it is divided into side-chain, main-chain, and alternative-type polymers. The chemical structures of obtained polysiloxanes are confirmed by nuclear magnetic resonance spectra and mass spectra. Three polymers present high thermal decomposition temperatures and the medium glass transition temperatures. The effects of polymeric structures on the second-order nonlinear properties are compared. The main-chain polysiloxane possesses the highest thermal stability because of its rigid architecture. The side-chain polysiloxane shows the fastest isomerization transformation rate due to the large free volume. Besides, the alternative polysiloxane displays the best second-order nonlinear performance with second harmonic generation coefficient (d33 ) value of 47.6 pm V-1 , which is 3 times higher than the side-chain one.