Z-Scan

The effect of silver nanoparticles (AgNPs) that are adsorbed on the surface of the purple membranes of Halobacterium salinarium bacteria on the optical properties and functional peculiarities of the lightsensitive protein bacteriorhodopsin (BR) has been demonstrated for the first time. Two mechanisms of the effect of AgNPs on the protein photocycle have been demonstrated using Raman scattering, giant Raman scattering, flash photolysis, and atomic force microscopy. It has been shown that the nanoparticles in the immediate spatial vicinity of BR fix its photocycle at the stage where it was at the moment of interaction with the nanoparticles. At greater distances, which reach three radii of an AgNPs, they have a weaker effect on BR, under which it retains the ability to be involved in the photocycle, however, has its parameters significantly changed. Thus, in the case of wild-type BR the photocycle accelerates and for the BR-D96N mutant it becomes slower. The data that are obtained could be of significance for creation of such optoelectronic hybrid systems with BR, where the parameters of its photocycle can be controlled using NPs. The results of the study may also be used in the field of nanobioengineering research, which is directed to creation of unique materials with controlled properties for recording and storage of information, energy transformation, and identification and characterization of trace amounts of analytes.

In this paper, we will take a closer look at the state of the art of polydiacetylene, and metal-free phthalocyanine fills, in view of the microgravity impact on their optical properties, their nonlinear optical properties and their potential advantages for integrated optics. These materials have many attractive features with regard to their use in integrated optical circuits and optical switching. Thin films of these materials processed in microgravity environment show enhanced optical quality and better molecular alignment than those processed in unit gravity. Our studies of these materials indicate that microgravity can play a major role in integrated optics technologT. Polydiacetylene films are produced by UV irradiation of monomer solution throu_h an optical window. This novel technique of forming polydiacetylene thin fills has been modified for constructing sophisticated micro-structure integrated optical patterns using a pre-programmed UV-laser beam. Wave gxfiding through these thin films by the prism coupler technique has been demonstrated. The third order nonlinear parameters of these films have been evaluated. Metal-free phthalocyanine fills of good optical quality are processed in our laboratories by vapor deposition technique. Initial studies on these films indicate that they have excellent chemical, laser, and environmental stability. They have large nonlinear optical parameters and show intrinsic optical bistability. This bistability is essential for optical logic gates and optical switching applications. Waveguiding and device making investigations of these materials are underway.

The synthesis, chemical characterization and optical studies of three novel fluorene derivatives is reported. These compounds comprise a DeAeD architecture with fluorene moieties as donor groups and fluorenone or benzothiadiazole derivatives as acceptor groups. Theoretical analysis confirmed the existence and the nature of two principal electronic transitions (p / p* and intramolecular charge transfer). Spectroscopic studies in solution revealed that the intramolecular charge transfer character, and in turn the two-photon activity i.e., the fluorescence induced by two-photon absorption, is strongly affected by solvent polarity. The influence of specific solventesolute interactions over emission properties was also studied through LipperteMataga plot. Evaluation of the two-photon absorption cross-sections, gave a maximum value of 105 GM (1 GM ¼ 10 À50 cm 4 s) in toluene and a minimum value of 23 GM in THF solutions at 750 nm for the fluorenone derivative, a molecule with poor intramolecular charge transfer character and thus weak two-photon absorption; however the benzothiadiazole derivative, with stronger intramolecular charge transfer transition, produced a maximum value of 1000 GM in THF and a minimum value of 236 GM in methanol. Fluorescence quantum efficiency of these compounds was also affected by the medium, with fluorescence quenching in protic solvents such as methanol due to specific solvent interactions (i.e., hydrogen-bonding). Nevertheless, in a more polar medium such as water, nanoaggregates synthesized from the benzothiadiazole derivative exhibited good two-photon activity, i.e., w500 GM and fluorescence quantum efficiency of 0.83. Furthermore, these nanoaggregates exhibited more resistance against photodegradation processes than any of the organic solutions tested.

Third order nonlinearities of Mn(III)-Phthalocyanine chloride in dimethyl-sulphoxide under 50 fs pulses, operating at 94 MHz, by eliminating cumulative thermal effects have been investigated and reported by us. Modifications were done in data acquisition during Z-scan experiment, which included recording of time evolution waveform traces in an oscilloscope and not collection of Z versus transmission and utilization of a chopper of a suitable duty cycle. Time evolution traces were further processed analytically through MatLab® programming, which yielded Z-scan traces similar to what was obtained with single shot 50 fs pulse. We observed reverse saturable absorption at 800 nm owing to excited state absorption. We show that the nonlinear refractive index (γ) and nonlinear absorption coefficient (β) are over estimated almost 100 times, when MHz pulses are used compared to a situation, where thermo-optical nonlinearities are accounted. Illumination and dark periods are carefully set in a...

A new series of non-aqueous phthalocyanines having 3,4,5-trimethoxy phenyl group at peripheral positions in which the central cavity possessing Cu(II), Zn(II), and without metals has been synthesized, and its absorption, fluorescence (steady-state and excited state lifetimes), electrochemical, and third-order nonlinear optical (NLO) properties were evaluated. Absorption studies data suggest that all three phthalocyanines obey Beer-Lambert's law, and the redox properties indicate that both oxidation and reduction reactions are macrocyclic centered. The singlet quantum yields were measured in different solvents and were found to be in the range of 0.2-0.5 in the case of free-base, whereas it was in the range of 0.1-0.5 in zinc derivative, while the timeresolved fluorescence data revealed lifetimes of typically a few ns. The third-order NLO properties were investigated using the Z-scan technique with kilohertz (for retrieving true electronic nonlinearities) and megahertz repetition rate femtosecond pulses at 800 nm. Intensity-dependent Z-scan studies revealed robust NLO coefficients for solutions and thin films (two-photon absorption cross-sections of 9,300-57,000 GM) of these molecules suggesting a strong potential for optical switching, imaging, and optical limiting applications.

Combining and coupling both magnetic and electric properties in one single phase multiferroic material has attracted high interest recently to enable a broad range of novel devices and applications. To evaluate one potential route toward new multiferroics, we have studied 0.5% Fe-doped BaTiO3 single crystals and measured the ferroelectric, magnetic, and multiferroic properties. X-ray absorption spectroscopy shows the presence of Fe3+, and magnetic measurements confirmed that this has a significant impact on the magnetic properties. Doping of iron introduces paramagnetism from lone iron atoms as well as what appears to be a weak ferromagnetism. Multiferroicity and magnetoelectric (ME) coupling were observed in the polarization-electric field hysteresis loops with an applied magnetic field, yet there was no direct evidence that ME coupling persists when the sample was in the defect dipole-aligned state.

Novel carbazole based styryl derivatives (6a-6c) having styryl group at third position and a methoxy substitution were synthesized by condensing 4-methoxy-9-methyl-9H-carbazole-3-carbaldehyde 3 and different active methylene derivatives (5a-5c). Evaluated photophysical properties of these synthesized novel chromophores, studied the effect of solvent polarity on absorption, emission and quantum yield of these styryl derivatives. DFT and TD-DFT computations are carried out to study structural, molecular, electronic and photophysical parameters of dyes. The ratio of ground state to excited state dipole moment was calculated using Bakhshiev and Kawski-Chamma-Viallet correlations.

Novel carbazole based styryl derivatives (6a-6c) having styryl group at third position and a methoxy substitution were synthesized by condensing 4-methoxy-9-methyl-9H-carbazole-3-carbaldehyde 3 and different active methylene derivatives (5a-5c). Evaluated photophysical properties of these synthesized novel chromophores, studied the effect of solvent polarity on absorption, emission and quantum yield of these styryl derivatives. DFT and TD-DFT computations are carried out to study structural, molecular, electronic and photophysical parameters of dyes. The ratio of ground state to excited state dipole moment was calculated using Bakhshiev and Kawski-Chamma-Viallet correlations.

The molecular structures and optical properties of six different N.dimethylphenylendiamino dyes were analyzed using a combination of DFT functionals (B3LYP and Cam-B3LYP/6-311+G(p,d)). The six dyes are D1-D6. The various parameters of the solvated phase, such as the polarizabilities, hyperpolarizabilities, peak absorption wavelengths, and HOMO-LUMO energy gaps, were calculated and analyzed. The results of the study are in agreement with the results of the NLO activity order thiophene linker > pyrrole bridge. Compared to the dipyrrole versions, the designed dithiophene-linker dyes exhibit longer absorption wavelengths and smaller HOMO-LUMO gaps. The predicted first hyperpolarisability of dyes D1-D3 are higher than that of D4-D5. This is mainly due to its enhanced electron-withdraw ability and the long p-conjugating action of the thiophene moiety. Highly elevated total hyperpolarisability of the designed dyes, suggests its potential application in organic NLO devices, which is expe...

The synthesis and characterization of new cyclometalated complex salts [M(C^N) 2 (4,4'-Cl 2 bpy)]PF 6 (M = Rh and Ir; C^N = 2-(p-tolyl)pyridinato (1 and 2), 2-phenyl-5-chloropyridinato (3 and 4); 4,4'-Cl 2 bpy = 4,4'-dichloro-2,2'-bipyridine) is described. Compounds 1-4 were obtained by reaction of 4,4'-dichloro-2,2'-bipyridine with the complexes [{M(µ-Cl)(C^N) 2 } 2 ] (M = Rh, Ir) in refluxing CH 2 Cl 2 /MeOH mixtures. The molecular structures of compounds 1 and 4 were confirmed by X-ray diffraction. The Ir compounds show phosphorescence in PMMA film and in solution at ambient temperature. Furthermore, all compounds display significant cytotoxicity against human cancer cell lines with the IC 50 values in the 0.4-2 µM range.

The title compound (9-ethyl-9H-carbazol-3-yl)carbamic acid tert-butyl ester was prepared from 3-amino-9ethylcarbazole and di-tert-butyldicarbonate (Boc anhydride) in good yield. It was characterized by elemental analysis, FT-NMR, FT-IR spectroscopy and subjected to single crystal X-ray diffraction studies. The compound crystallizes in monoclinic space group P21/c with unit cell dimensions are a = 13.5218(8) Å , b = 12.7624(7) Å , c = 10.1352 (6) Å , b = 100.784(6)°, V = 1718.15(17) Å 3 , D x = 1.200 Mg m-3 , and Z = 4. According to X-ray diffraction studies the molecule is in a non planar conformation except for the carbazole moiety and having a dihedral angle of 30.239(89)°b etween the plane of the carbazole and amide moieties. The molecules are packed in a zigzag manner and strong N-HÁÁÁO [C(4) motif] intermolecular hydrogen bonding, weak C-HÁÁÁp [C(5) motif] and p-p stacking interaction stabilize the crystal packing. The thermal analysis of single crystal was determined by DSC and TGA.

The present article demonstrates the optical linear and nonlinear studies of the chromophore 2,2'-(hexane-1,6-diylbis(9H-carbazole-9,3-diyl))bis(ethene-1,1,2-tricarbonitrile (HCzN). We have synthesized this molecule and the structure of this molecule has been con rmed via IR and NMR spectroscopies. The linear optical study has been done with the help of UV-Vis absorption and emission spectroscopies and we have measured the refractive index (n 0), and optical bandgap (E g) for this chromophore. We have explored the third-order nonlinear optical (NLO) characteristics of HCzN at the concentrations of 1, 2, 3, and 4 mM employing both closed and open-aperture Z-scan methods at 25 mW laser power. This chromophore evinces the self-defocusing and saturable absorption nature for closed and open aperture scans respectively. The calculated NLO parameters like the coe cient of nonlinear absorption (β) and refraction (n 2) are found to be of the order of 10 − 6 cm 2 /W and 10 − 3 cm/W respectively with the nonlinear optical susceptibility (χ (3)), and hyperpolarizability (γ) of the order of 10 − 5 esu, and 10-27 esu respectively. The magnitude of NLO parameters varies linearly with concentration.

The present article demonstrates the optical linear and nonlinear studies of the chromophore 2,2'-(hexane-1,6-diylbis(9H-carbazole-9,3-diyl))bis(ethene-1,1,2-tricarbonitrile (HCzN). We have synthesized this molecule and the structure of this molecule has been confirmed via IR and NMR spectroscopies. The linear optical study has been done with the help of UV-Vis absorption and emission spectroscopies and we have measured the refractive index (n0), and optical bandgap (Eg) for this chromophore. We have explored the third-order nonlinear optical (NLO) characteristics of HCzN at the concentrations of 1, 2, 3, and 4 mM employing both closed and open-aperture Z-scan methods at 25 mW laser power. This chromophore evinces the self-defocusing and saturable absorption nature for closed and open aperture scans respectively. The calculated NLO parameters like the coefficient of nonlinear absorption (β) and refraction (n2) are found to be of the order of 10− 6 cm2/W and 10− 3 cm/W respective...

In this paper we propose two types of polymeric materials synthesized by us suitable to interact by assembling with DNA in order to obtain new NLO biomaterials. The first polymer is a methacrylic chromophore with azobenzene groups and carbazolyl sequences known for their carrying principles while the second one is a copolymer of the methacrylic chromophore with a N-substituted amide. The Nsubstituted amide is N-acryloyl morpholine already used in biological application and also because is compatible with DNA. Spectral characterization of these materials showed charge transfer interactions depending on the solvent. The results obtained indicate that these new polymeric/copolymeric chromophores could interact with DNA in order to obtain biomaterials for photonic applications.

We present our experimental results on the measurement of third-order optical nonlinearity in the ns and ps domain, in Ž. Ž. several Tetra Tolyl Porphyrin molecules TTP , using degenerate four wave mixing DFWM and Z-Scan techniques. Our results indicate a very high value of nonlinearity for these molecules in the ns domain and reasonably high values in the ps domain. They are found to exhibit a strong nonlinear absorption at both 532 nm and 600 nm. The high value of nonlinearity for ns pulses is attributed to higher excited singlet and triplet states. Time-resolved studies indicate an ultra-fast temporal evolution of the nonlinearity in these molecules.

A series of heteroleptic bis-cyclometalated iridium(III) complexes, [Ir(cpbi) 2 (H 2 dcbpy)][PF 6 ] (1), [Ir(pbi) 2 (H 2 dcbpy)][PF 6 ] (2), and [Ir(mpbi) 2 (H 2 dcbpy)][PF 6 ] (3), where pbi = 1,2-diphenylbenzimidazole, cpbi = 2-(4-chlorophenyl)-1-phenylbenzimidazole, mpbi = 2-(3,4-dimethoxyphenyl)-1-phenylbenzimidazole, and H 2 dcbpy = 2,2 0-bipyridine-4,4 0-dicarboxylic acid has been synthesized and characterized by elemental analysis, 1 H, 31 P NMR, and high resolution mass-spectra. Molecular structure of complex 3 has been determined from single-crystal X-ray analysis. The complexes exhibit absorption up to 550 nm with molar absorptivities of 2500 M À1 cm À1. They have strong luminescence in broad yellow-to-red region in solutions at room temperature. While chloro-substituent (complex 1) causes a little hypsochromic shift of the absorption maxima compared to unsubstituted 2, introduction of two methoxy-groups (complex 3) gives rise to a bathochromic shift of about 100 nm. Alternating current voltammetry studies of the complexes indicates reversible oxidation and reduction potentials. Calculated excited state oxidation potentials for 1-3 are negative enough to efficiently inject electrons into the conduction band of TiO 2 (E F % À0.5 V). Thus, from the electrochemical point of view, all the complexes, especially 3, are good candidates for operation in DSSC as dyes.

The nonlinear optical properties of zinc oxide nanoparticles (ZnONPs) in distilled water were measured using a femtosecond laser and the Z-scan technique. The ZnONPs colloids were created by the ablation of zinc bulk in distilled water with a 532 nm Nd: YAG laser. Transmission electron microscopy, an ultraviolet-visible spectrophotometer, and atomic absorption spectrophotometry were used to determine the size, shape, absorption spectra, and concentration of the ZnONPs colloids. The nonlinear absorption coefficient and nonlinear refractive index were measured at different excitation wavelengths and intensities. The nonlinear absorption coefficient of the ZnONPs colloids was found to be positive, caused by reverse saturable absorption, whereas the nonlinear refractive index was found to be negative due to self-defocusing in the ZnONPs. Both laser parameters, such as excitation wavelength and input intensity, and nanoparticle features, such as concentration and size, were found to infl...

Graphene acts as an excellent supporting material in the preparation of a variety of nanocomposites. In this study, thick sheets of graphene of differing nanometer sizes were prepared using a modified Hummer's method. CuCe 0.2 Fe 1.8 O 4 ferrite nanoparticles were fabricated using a facile co-precipitation technique. Subsequently, a hydrothermal method was employed for the fabrication of graphene-based CuCe 0.2 Fe 1.8 O 4 nanocomposites. We investigated the crystal structure, functional groups, thermal stability, morphology, and magnetic properties of CuFe 2 O 4 , CuCe 0.2 Fe 1.8 O 4 ferrite nanoparticles, and graphene-based CuCe 0.2 Fe 1.8 O 4 nanocomposites. Graphene was found to have distinct effects on the surface morphology, crystallite size, lattice strain, and thermal stability of the CuCe 0.2 Fe 1.8 O 4 nanocomposites. The average crystallite size and grain size were found to increase, whereas the lattice strain decreased, with the use of graphene and increased Ce 3+ content. The Vibrating Sample Magnetometer (VSM) results indicated that the saturation magnetization and coercivity were in the range of 11-30 emu/g and 690-1044 Oe, respectively. The direct effects of graphene on morphology, crystal structure, and thermal stability, as well as the improved magnetic properties, demonstrate that these nanoparticles and nanocomposites may be suitable for switching, electromagnetic wave absorbers, adsorbents, and catalytic applications.

A comprehensive investigation is presented on the photophysical and third-order nonlinear optical (NLO) properties of two thioalkyl-substituted tetrathiafulvalene molecules (referred here as G1 and G3) to understand their utility as photosensitizers for dyesensitized solar cell (DSSC) and optoelectronic applications. Both steady-state and time-resolved (in the fs−ns time regime) absorption and photoluminescence (PL) spectroscopy techniques were employed to comprehend the excited-state properties of the molecules in solution as well as in thin films deposited on both quartz and mesoporous TiO 2 layers. The spectroscopy measurements in solution and thin films deposited on quartz provided the excited-state properties of dye molecules. Time-resolved PL measurements at the dye−TiO 2 interface provided initial evidence of electron injection by fast PL quenching decay dynamics for both the molecules. Detailed target analysis of the femtosecond transient absorption spectroscopy (TAS) data of the dye−TiO 2 sample revealed a multistep ultrafast electron injection for both molecules with the fastest injection component being 374 and 314 fs for G1 and G3 molecules, respectively. The ultrafast NLO properties of G1 and G3 were studied using the Z-scan technique with 800 nm, ∼70 fs laser pulses. The open aperture measurements showed three-photon absorption with magnitudes of coefficients 4.7 × 10 −5 cm 3 /GW 2 and 5.2 × 10 −5 cm 3 /GW 2 , and the closed aperture measurements provided second hyperpolarizability (γ) values of 3.5 × 10 −31 esu and 4.2 × 10 −31 esu for G1 and G3, respectively. Additionally, the onset of optical limiting was estimated to be 5.8 × 10 −3 J/cm 2 and 5.7 × 10 −3 J/cm 2 for G1 and G3 molecules, respectively.

Reduced graphene oxide (rGO)-based transparent thin films including rGO, rGO/PVP and rGO/PVP/Ag (TFs) were prepared by drop casting method. The reduction process was performed using HI vapor. The physicochemical, morphological and structural characteristics of the prepared samples were studied using different characterization methods such as X-ray diffraction analysis, scanning electron microscopy and Raman spectroscopy. The linear and nonlinear optical properties of prepared samples were evaluated by Z-scan technique using a He-Ne laser (632 nm), respectively. Results showed that the nonlinear refraction index (n 2) and nonlinear absorption coefficient (β) of the prepared rGO/PVP thin film are higher than that reported before. Adding Ag NPs caused a considerable improvement in the NLO characteristics of rGO/PVP.

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under license by Materials Research Forum LLC.

SnSb 2 S 4 thin films have been deposited by thermal evaporation technique on non-heated glass substrates and subsequently annealed at 473 and 673K. The influence of annealing temperature on the structural, morphological, optical and electrical properties was analyzed by X-ray diffraction, atomic force microscopy (AFM), spectrophotometer and hot probe method, respectively. The as-deposited and annealed films were polycrystalline in nature with preferential growth along (621) plane. The SnSb 2 S 4 films annealed at 673K exhibited an optical transmittance of 30% and a direct band gap of 1.4eV. The dispersion behavior of the refractive index was studied in terms of the single-oscillator Wemple-DiDomenico and Cauchy models, and the optical parameters such as refractive index, extinction coefficient, oscillator energy, dispersion energy and Cauchy's constants were found. The electrical free carrier susceptibility and the carrier concentration on the effective masse ratio were estimated according to the model of Spitzer and fan.

We report the wavelength-dependent nonlinear absorption (NLA) of InN film grown on anr-plane sapphire by molecular beam epitaxy technique. In order to understand the nonlinear optical properties of InN, the Z-scan measurement was performed at two different wavelengths, the photon energies of which are near (resonant excitation) and much higher (non-resonant excitation) than the bandgap of InN, respectively. Under non-resonant excitation, band-filling effect leads the dominant saturable absorption, while under resonant excitation, reverse saturable absorption dominates the nonlinear absorption. From the open-aperture Z-scan measurement under resonant excitation, we found that InN exhibits more than one nonlinear absorption process simultaneously. Particularly, under relatively weak resonant excitation, the transformation from saturable absorption to 2PA through the intermediate excitation state absorption was observed as the sample approaches the beam focus. The close-aperture Z-scan signals of InN show valley-peak response, implying that the nonlinear refraction in InN is caused by the self-focusing of the Gaussian laser beam. Using the Z-scan theory, the corresponding nonlinear parameters, such as saturation intensity, 2PA coefficient, and nonlinear refractive index, of InN were estimated.

The electronic properties of 4,4¢-bis(3-ethyl-N-carbazolyl)-1,1¢-biphenyl (ECBP) have been studied using time-dependent density functional theory. The non-linear optical (NLO) properties and dipole moments were investigated to understand the optical behavior of ECBP. Frontier molecular orbitals were determined to define the energetic properties of the title molecule. The total density of states, partial density of states, and overlap population electronic density of states of ECBP were calculated and analyzed. Experimental and semi-theoretical parameters such as the optical density, transmittance, absorbance band edge, optical bandgap, refractive index, incidence angle, and refraction angle of ECBP at 3 mM, 10 mM, 21 mM, and 70 mM were obtained. The results indicate that this molecule is a suitable material for NLO, optical, and optoelectronic devices.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

In this paper we present the nonlinear optical characterization of Au/Pd nanoparticles in order to obtain the nonlinear refractive indices using the Z-scan technique. The experiments were performed using a 514 nm laser beam Ar + , with 14 Hz of modulation frequency, as excitation source. By using a lens the excitation beam was focused to a small spot and the sample was moved across the focal region along the z-axis by a motorized translation stage. Seven samples with different concentration ratio of Au/Pd nanoparticles were prepared by simultaneous reduction of gold and palladium ions in presence of poly (N-vinyl-2-pirrolidone) (PVP) using ethanol as a reducing agent. In this work, we report the application of the Z-scan technique, to generate optical transmission of laser light as a function of the z position for solutions containing bimetallic nanoparticles of Au (core)/Pd (shell) with average sizes ranging from 3 to 5 nm. The magnitude of the obtained nonlinear refractive index was in the order of 10 −8 cm 2 /W. Our results show that the nonlinear refractive index has a nonlinear behavior when the (Au/Pd) ratio was increased.

Two photon absorption cross-section s 2PA CAM-B3LYP BHandHLYP Bond length alternation (BLA) Bond order alternation (BOA) Hyperpolarizability Mulliken-Hush charge transfer a b s t r a c t The linear and nonlinear optical (NLO) properties of new fluorescent styryl dyes based on anchoring ester containing carbazole as donor appended to different acceptor groups to have a conjugated p-system with push-pull geometry are studied. The NLO properties have been determined using solvatochromic and computational methods. Three different TD-DFT functional are used namely, B3LYP, BHandHLYP, and CAM-B3LYP, with aim of elucidating better functional for NLOphores. Further, the two photon properties (s 2PA) have been described theoretically by two level model considering the dipole moment difference between the ground and the final electronic states and bypassing the intermediated resonance state. The compounds with a high charge transfer from the acceptor group to the carbazole ring have relatively high two-photon absorption cross-sections (60e317 GM). The linear polarizability (a CT), first order hyperpolarizability (b) and second order hyperpolarizability (ɣ) for 4c dye was the highest among the studied dyes which is attributed to the lesser energy gap evident by both the methods. But in contrary, the s 2PA cross-section value was low for dye 4c which is due to the presence of freely rotatable twisted phenyl ring in the conjugation path, pulling the electron density towards itself and thus lead to decrease in s 2PA cross-section. Structure-property relationship is better understood by the correlation of bond length alternation/bond order alternation (BLA/BOA) with NLO properties of dyes. Thus by simple solvatochromic method and computational method, we have screened the carbazole styryls as NLO candidates with good first order hyperpolarizability and good two photon cross-section.

A detailed study of linear and nonlinear optical (NLO) properties obtained by spectroscopy and DFT computations of carbazole-based D-p-A (mono) and A-p-D-p-A (bis) extended styryl dyes is presented. Four different DFT functionals, B3LYP, MO6, BHandHLYP, and CAM-B3LYP are used for computations. The structure-property relationship is examined by correlating bond length alternation/bond order alternation with NLO properties of the dyes. The bis-carbazole styryl dyes possess a higher second-order hyperpolarizability (b) than the mono-carbazole styryl dyes. An increase in the polarity of the environment causes an increase in the first-order hyperpolarizability (b CT or b 0) and second-order hyperpolarizability (c) of the mono-and bis-carbazole styryl compounds. The NLO properties calculated by the CAM-B3LYP and BHandHLYP functionals show good agreement with the spectroscopic results. Keywords Carbazole Á Nonlinear properties Á CAM-B3LYP Á BHandHLYP Á Bond length alternation (BLA) Á Bond order alternation (BOA) Á Hyperpolarizability Electronic supplementary material The online version of this article (

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Pure (ZnSe) and europium doped (ZnSe:Eu) zinc selenide films were evaporated onto glass substrates using the close-spaced vacuum sublimation (CSVS) technique at different deposition conditions (substrate temperature). The fundamental optical parameters such as optical density, extinction coefficient, refraction index, real and imaginary parts of optical dielectric constant, band gap were evaluated in transparent region of transmittance and absorbance spectrum. Optical spectroscopy analysis shown that in both cases deposited films had a high level of transmittance values (55-65 % for ZnSe films and 80-90 % for ZnSe:Eu films). Moreover, evaluated values of the films optical band gap were in the range of Eg  (2.63-2.69) eV for ZnSe films and Eg  (2.77-2.81) eV for ZnSe:Eu for films with increasing of the films substrate temperature. Fourier-transformed infra-red (FTIR) analysis of deposited ZnSe and ZnSe:Eu films shown that all investigated samples are well-crystalline and identified vibrations are typical for II-VI semiconductors.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

A series of luminescent isocyanorhenium(I) complexes with chelating acyclic diaminocarbene ligands (N^C) has been synthesized and characterized. Two of these carbene complexes have also been structurally characterized by X-ray crystallography. These complexes show blue-to-red phosphorescence, with the emission maxima not only considerably varied with a change in the number of ancillary isocyanide ligands but also extremely sensitive to the electronic and steric nature of the substituents on the acyclic diaminocarbene ligand. A detailed study with the support of density functional theory calculations revealed that the lowestenergy absorption and phosphorescence of these complexes in a degassed CH 2 Cl 2 solution are derived from the predominantly metal-to-ligand charge-transfer [dπ(Re) → π*(N^C)] excited state. The unprecedented anion-binding and CO 2-capturing properties of the acyclic diaminocarbene have also been described.

Binuclear platinum(II) complexes with strong Pt−Pt interactions are an interesting class of luminescent materials, of which photophysical properties could be controlled via multiple ways through organic ligands and Pt− Pt distance. While a number of binuclear platinum(II) complexes have been developed with tunable emissions, achieving high photoluminescence quantum efficiency (PLQE) remains challenging and of great interest. Here we report the synthesis and characterization of a series of binuclear 2,4-difluorophenylpyridine platinum(II) complexes bridged by thiazol-2-thiolate ligands with different bulkiness. The three complexes were found to have short Pt−Pt distances ranging from 2.916 to 2.945 Å. The strong Pt−Pt interactions lead to pronounced metal−metal-to-ligand charge transfer (MMLCT) absorptions between 450 and 500 nm, and strong 3 MMLCT emissions in the orange/red region. The PLQEs of the new complexes are in the ranges of 2−31% in solution and 26−100% in solid state. These complexes also exhibit excellent stability in halogenated solvents.

Starting from proligand 1-methyl-2-(phenyl)imidazo[1,5-a]pyridine-2-iumchloride (1.HCl), 1-methyl-2-(phenyl)imidazo[1,5-a]pyridine silver(I) chloride, (2) has been prepared. Synthesis, structures and photophysical properties of (2,2 / −bipyridyl)-1-methyl-2-(phenyl)imidazo[1,5-a]pyridinesilver(I) hexaflurophosphate, (3), 1-methyl-2-(phenyl)imidazo[1,5-a]pyridinesilver(I) carbazolate, (4) and 1-methyl-2-(phenyl)imidazo[1,5-a]pyridinegold(I)carbazolate, (5) are focused. Herein we have first reported the NHC-Ag-(bpy/carbazole). All the complexes have been characterized by elemental analysis, various spectroscopic studies and finally screened for luminescent properties. All the complexes are strongly emissive. Solid state structures of 2, 3, 4 and 5 have been determined by X-ray diffraction studies. Conventionally, complex 2 adopts linear geometry whereas complex 3 embraces triangular planar geometry around Ag; complex 4 and 5 clinches linear geometry around Ag/Au. All the complexes absorb light within 275-343 nm. Complex 3 is luminous at~407 mn, whereas complex 4 and 5 luminous at~360 nm having short life time 1.00-6.97 ns. The quantum yield (Φ em) of the complexes varies 0.106-0.186. It is expected variation of luminescence arises due to change of metal and the chromophore (bpy/carbazole). Density Functional Theory (DFT) and Temparature Dependent Density Functional Theory (TDDFT) calculations were performed to verify crystallographically derived parameters and to calculate the UV-Vis properties of the ground state as well as of the first excited state of the complexes.

Thin films of ZnS have found extensive applications in various optical, electrical, and optoelectronic devices. In this present work ZnS thin films have been deposited by simple and inexpensive Successive Ionic Layer Adsorption and Reaction (SILAR) technique on glass substrates at room temperature. The precursor solution is composed of ZnCl 2 and Na 2 S. The annealing effects on the optical and electrical properties of the films have been investigated. Xray diffraction technique was used to investigate the structural properties of films. The XRD shows that the films exhibit polycrystalline cubic structure oriented in (111) direction. The crystallite size was found to be 26.75nm. From the optical absorption measurements, the band gaps energies at room temperature, 100 o C, 150 o C, 200 o C and 250 o C were found to be 3.74eV, 3.66eV, 3.57eV 3.5eV and 3.46eV respectively. The band gap decreased as the temperature increases. The two point probe method was used for the investigation of electrical properties of the films and it was found that current decreased as the temperature increases, thus, the annealed films were found to be more resistance than the as-grown films. The optical transmission measurement revealed that the films exhibit good transmission of 95% in the infrared region for ZnS annealed.

Pulsed laser ablation of copper in distilled water is used to synthesize copper nanoparticles as a function of duration of laser ablation and incident laser energy. Increase in the ablation time from 15 to 60 min at fixed incident laser energy of 30 mJ resulted in blue shift of the surface plasmon resonance peak from 641 to 626 nm along with a broadening of the plasmon bandwidth from 127 to 165 nm, respectively. The increase in incident laser energy from 30 to 70 mJ at fixed duration of 60 min ablation induced a similar blue shift in the plasmon peak from 626 to 617 nm and a corresponding increase in the bandwidth from 165 to 209 nm, respectively. These observations are due to reduction in the size of the nanoparticles as also confirmed by the transmission electron microscopic images. Nearly uniform particle size distribution is observed for an ablation time of 60 min. An increase in laser energy from 30 to 70 mJ keeping the ablation time fixed for 60 min resulted in decrease in the average size of the nanoparticles from 20 to 7 nm, respectively. The structural studies via selected area electron diffraction and Raman analysis revealed that the extent of oxidation taking place in the synthesized nanoparticles of Cu@Cu x O also varies with the laser ablation duration and incident laser energy. For the samples prepared with 30 mJ of incident laser energy and laser ablation duration upto 30 min, Cu 2 O phase of the nanoparticles is dominant whereas for an increased duration of 60 min at the same laser energy, there is an appearance of CuO phase. The increase in laser energy upto 70 mJ for 60 min of ablation duration resulted in CuO as the dominating phase. It has been established that by merely varying the laser ablation duration and the incident energy, particle size, plasmonic response and structural properties of the synthesized nanoparticles can be effectively tuned.

Organic optoelectronic materials with high fluorescence quantum yield, both in solution and in the solid state, have attracted considerable interest in recent years. In this work, we designed and synthesized three triarylborane-terminalized branched p-conjugative compounds, including two C 3-symmetric p-3A(acceptor) triarylboron dyes: 2,7,12-tri(5-(dimesitylboryl)thiophen-2-yl)-5,5 0 ,10,10 0 ,15,15 0-hexaethyltruxene and 2,7,12-tri((5-(dimesitylboryl)thiophen-2-yl)ethynyl)-5,5 0 ,10,10 0 ,15,15 0-hexaethyltruxene, and a 2D(donor)-p-A asymmetric dye: 2,7-di(N,N-diphenylamino)-12-(5-(dimesitylboryl)thiophen-2-yl)-5,5 0 ,10,10 0 ,15,15 0-hexaethyltruxene. The three compounds displayed prominent optical properties. The ethynyl spaced thiophene analogue emitted intense fluorescence both in the THF solution and in the solid state with excellent quantum yields. Interestingly, their solid powders showed a very different fluorescence colour from their respective THF solution. The results of theoretical calculations were in good agreement with the experimental absorption and CV spectra. The high reversibility of the three boron-containing dyes in their redox process indicates substantial stability of the produced species, which make them promising light-emitting materials.

A series of bis-cyclometalated iridium(III) complexes, [Ir(LH) 2 (H 2 dcbpy)][PF 6 ] (1), [Ir(LMe) 2 (H 2 dcbpy)][PF 6 ] (2), and [Ir(LPh) 2 (H 2 dcbpy)][PF 6 ] (3), where LH = 1-H-2-phenylbenzimidazole, LMe = 1-methyl-2-phenylbenzimidazole, LPh = 1,2-diphenylbenzimidazole, and H 2 dcbpy = 2,2′-bipyridine-4,4′-dicarboxylic acid, has been synthesized and fully characterized by elemental analysis, 1 H and 31 P NMR spectroscopy, mass spectrometry, and single-crystal X-ray analysis. The complexes show strong luminescence in the yellow-orange region in ethanol at room temperature (quantum yield is up to 22 %), and

Graphene acts as an excellent supporting material in the preparation of a variety of nanocomposites. In this study, thick sheets of graphene of differing nanometer sizes were prepared using a modified Hummer's method. CuCe 0.2 Fe 1.8 O 4 ferrite nanoparticles were fabricated using a facile co-precipitation technique. Subsequently, a hydrothermal method was employed for the fabrication of graphene-based CuCe 0.2 Fe 1.8 O 4 nanocomposites. We investigated the crystal structure, functional groups, thermal stability, morphology, and magnetic properties of CuFe 2 O 4 , CuCe 0.2 Fe 1.8 O 4 ferrite nanoparticles, and graphene-based CuCe 0.2 Fe 1.8 O 4 nanocomposites. Graphene was found to have distinct effects on the surface morphology, crystallite size, lattice strain, and thermal stability of the CuCe 0.2 Fe 1.8 O 4 nanocomposites. The average crystallite size and grain size were found to increase, whereas the lattice strain decreased, with the use of graphene and increased Ce 3+ content. The Vibrating Sample Magnetometer (VSM) results indicated that the saturation magnetization and coercivity were in the range of 11-30 emu/g and 690-1044 Oe, respectively. The direct effects of graphene on morphology, crystal structure, and thermal stability, as well as the improved magnetic properties, demonstrate that these nanoparticles and nanocomposites may be suitable for switching, electromagnetic wave absorbers, adsorbents, and catalytic applications.

In this paper, we investigate the linear and nonlinear (NL) optical properties of gold nanoparticles (Au-NPs) with different sizes. A colloidal gold nanoparticles solution has prepared to utilize the chemical reduction method by interacting gold chloride solution HAuCl4 with trisodium citrate solution. By using a hotplate and vigorous stirring the flask, which has the mixture solution, was heated to produce a 0.05 mg/ml of colloidal gold nanoparticles. The characterization of gold nanoparticles is executed by the utilization of different techniques. The information about nanoparticles size was achieved from the spectra measured by transmission electron microscopy (TEM). As well as the compositional characteristics are obtained using FTIR and XRD techniques. Finally, the Surface Plasmon Resonance (SPR) peaks were measured using a UV-Vis spectrophotometer. A Z-scan technique was utilized to study the nonlinear optical properties of Au nanoparticles. From the preparation of the nanoparticles, the shape of gold nanoparticles was almost spherical and has two different sizes. The nonlinear refractive index of Au nanoparticles was obtained in the order of 10-10 cm 2 /w extracted from a closed aperture z-scan. The nonlinear absorption of these nanoparticles was measured at 10-5 cm/w range obtained from an open aperture z-scan technique.

The free-carrier absorption cross-section σ of a magnetic colloid composed of magnetite nanoparticles dispersed in oil is obtained by using the Z-scan technique in different experimental conditions of the laser beam. We show that it is possible to obtain σ with picosecond pulsed and millisecond chopped beams with pulse frequencies smaller than about 30 Hz. For higher pulse frequencies, the heating of the colloidal system triggers the appearance of the Soret effect. This effect artificially increases the value of σ calculated from the experimental results. The limits of the different experimental setups are discussed.

In the present work, the nonlinear optical properties of some single-and few-layered graphene dispersions under femtosecond laser excitation were studied using the Z-scan technique and are compared in order to evaluate the effect of the number of graphenic layers and the influence of the laser excitation conditions on the measurements. The experimental evidences obtained indicate that the nonlinear optical response of these graphenes' dispersions under low repetition rate laser excitation conditions (i.e., 10 Hz) is several orders of magnitude lower than that reported using higher repetition rate laser excitation conditions (as e.g., kHz, MHz). To further investigate these experimental findings, Z-scan combined with a thermal lensing measurement technique was used to study the presence and the building of thermal/cumulative effects occurring under high repetition rate conditions. It was shown that thermal/cumulative effects were dominant, obscuring entirely the observation of the electronic origin nonlinear optical response. The contributions of both mechanisms were evaluated and unambiguously distinguished. To the best of our knowledge, this is the first work, investigating the nonlinear optical properties of single-and few-layered graphene, under low and high repetition rate laser excitation, providing a more accurate insight about the nonlinear optical response of graphene.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

In the present work, the nonlinear optical properties of some single-and few-layered graphene dispersions under femtosecond laser excitation were studied using the Z-scan technique and are compared in order to evaluate the effect of the number of graphenic layers and the influence of the laser excitation conditions on the measurements. The experimental evidences obtained indicate that the nonlinear optical response of these graphenes' dispersions under low repetition rate laser excitation conditions (i.e., 10 Hz) is several orders of magnitude lower than that reported using higher repetition rate laser excitation conditions (as e.g., kHz, MHz). To further investigate these experimental findings, Z-scan combined with a thermal lensing measurement technique was used to study the presence and the building of thermal/cumulative effects occurring under high repetition rate conditions. It was shown that thermal/cumulative effects were dominant, obscuring entirely the observation of the electronic origin nonlinear optical response. The contributions of both mechanisms were evaluated and unambiguously distinguished. To the best of our knowledge, this is the first work, investigating the nonlinear optical properties of single-and few-layered graphene, under low and high repetition rate laser excitation, providing a more accurate insight about the nonlinear optical response of graphene.