From controllable attached isolation moieties to possibly highly efficient nonlinear optical main-chain polyurethanes containing indole-based chromophores

For the first time, the indole-based NLO chromophores were embedded into the polymer main chain, and different isolation groups were attached to their donor side with the efforts of adjusting the NLO properties of the resultant main-chain polyurethanes, according to the site isolation principle. Thanks to the main-chain structure and the advantages of the indole-based chromophores, all the polymers show excellent transparency, good processability, thermal stability, and relatively good NLO effects. The tested NLO properties of the polymers demonstrate that there is a suitable isolation group present for the sulfonyl-based chromophore to boost its microscopic beta value to a possibly higher macroscopic NLO property efficiently.     

Facile synthesis and electro‐optic activities of new polycarbonates containing tricyanofuran‐based nonlinear optical chromophores

Two series of novel electro‐optic (EO) polycarbonates containing two different kinds of nonlinear optical (NLO) chromophores with tricyanofurane (TCF) electron acceptor have been successfully prepared through the facile polycondensation between diol NLO chromophore and bisphenol A bis(chloroformate). These new polycarbonates which were characterized by ¹H‐NMR and Fourier transform infrared exhibited good solubility in common polar organic solvents. They also showed glass transition temperatures (T_g) in the range of 124–156 °C. The morphology studies indicated that these polycarbonates had good film quality before and after corona poling. The EO coefficients (r₃₃) of two polycarbonates films were up to 45 pm/V (PC‐TCFC‐2) and 75 pm/V (PC‐DFTC‐3) at the wavelength of 1310 nm. Moreover, good temporal stability of the poling‐induced dipole alignment was also achieved, and the resulting poled films of PC‐TCFC‐2 and PC‐DFTC‐3 could retain 90 and 80% of the initial EO activities at 85 °C for more than 500 h, respectively. Both EO activity and temporal stability results were better than the guest–host EO polymers containing the same concentration chromophores, which indicated that such kind of polycarbonates could effectively suppress the intermolecular electrostatic interaction and translate microscopic molecular hyperpolarizability into macroscopic EO activity. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2841–2849.     

High performance nonlinear optical chromophores

Both the linear and nonlinear optical properties of our newly designed high temperature electrooptic chromophores are discussed. In addition to the charge separated mechanism for the new chromophores, isomer effects are equally important in determining the optical properties of the new class.     

Facile synthesis of silver nano particles with highly efficient anti-microbial property

A simple surfactant assisted aqueous solution approach, based on the conventional Tollen’s reaction has been applied for the facile syntheses of silver nano-assembly. Nano particle morphologies strongly depend on the temperature adopted during the synthesis. Two-dimensional (2 D) nano-disks and three-dimensional (3D) nano-globules with “Cauliflower” like morphology were observed. The unique and distinctive feature of the synthesized silver nano particle in solution is its very high anti-microbial activity. This is evident in very low (4 μg/ml) inhibitory concentration (MIC) value for Escherichia coli, Vibrio cholerae, Shigella flexneri, Salmonella typhimurium and three varieties of Staphylococcus aureus. This low MIC value is comparable to that of Penicillin and in the cases of E. coli and S. aureus (ML 422), the MIC value is as low as 2 μg/ml which beats even Penicillin.     

Synthesis and characterization of new thienylpyrrolyl-benzothiazoles as efficient and thermally stable nonlinear optical chromophores

The synthesis and full characterization of new chromophores with second-order nonlinearities containing thienylpyrrolyl and benzothiazolyl moieties are reported. The solvatochromic behavior of the compounds was investigated. The hyperpolarizabilities β of derivatives 4-6 were measured using hyper-Rayleigh scattering and thermogravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that strong nonlinearity is balanced by good thermal stability especially for chromophores 6b and 6c, making them good candidates for NLO applications.     

Azo-azulene derivatives as second-order nonlinear optical chromophores

The molecular and solid state nonlinear optical (NLO) properties of several (phenylazo)-azulenes are investigated. In particular, (4-nitrophenylazo)-azulene (2b) exhibits a quadratic hyperpolarizability (beta(vec)) of 80 x 10(-30) cm5esu recorded at 1.907 microm by the electric field-induced second-harmonic (EFISH) technique. This molecular material, which crystallizes in the monoclinic noncentrosymmetric space group Pc, exhibits an efficiency 420 times that of urea in second-harmonic generation. The origin of the optical nonlinearity in azo-azulene is discussed in relation with crystal structures and semiempirical calculations within the INDO/SOS formalism, and compared with that of the well known disperse red one (DR1) organic dye.     

Three-dimensional nonlinear optical chromophores based on through-space delocalization

Six permutations of 4-fold donor and/or acceptor substitution of paracyclophane at the 4, 7, 12, and 15 positions were synthesized to probe the phenomenon of three-dimensional delocalization on the nonlinear optical properties of organic materials. The interplay between through-bond intramolecular charge transfer (ICT) as well as three-dimensional, or through-space, ICT processes gives rise to large quadratic hyperpolarizability values. The determination of dipolar (beta(J)(=1)) and octupolar (beta(J)(=3)) irreducible tensor contributions to the overall beta tensor value is made possible by the polarized harmonic light scattering technique at 1.32 microm. The electric field-induced second-harmonic generation technique was also used at 1.91 microm for comparison. Significant experimental beta values for members of the series made of two centrosymmetric benzene-like units are a clear signature of a purely through-space ICT between two aryl subunits. The two configurational isomers that pair two dipolar donor-acceptor chromophores also exhibit octupolar character. Analysis of these two with an additive model for beta(J)(=1) and beta(J)(=3) reveals a strong three-dimensional inter-ring charge transfer.     

Synthesis and nonlinear optical properties of chromophores for photorefractive polymer materials

The synthesis and nonlinear optical (NLO) properties of a series of nitrostilbene-, dinitrostilbene-, and dicyanomethylenedihydrofuran-based chromophores potentially useful in photorefractive multifunctional polymers are reported. Electronic absorption spectra have been measured in different solvents. Electric field induced second harmonic (EFISH) generation results show that the 2-dicyanomethylen-3-cyano-5,5-dimethyl-2,5-dihydrofuran moieties lead to the best NLO performances. Dinitrophenyl-based chromophores have shown a reduced nonlinear response as compared with the mononitro analogues. Nonlinear optical properties of a selected nitro-dinitro couple have been also determined theoretically.     

Facile one-step synthesis of Ru doped NiCoP nanoparticles as highly efficient electrocatalysts for oxygen evolution reaction

Transition metal phosphides (TMPs) as ever-evolving electrocatalytic materials have attracted increasing attention in water splitting reactions owing to their cost-effective, highly active and stable catalytic properties. This work presents a facile synthetic route to NiCoP nanoparticles with Ru dopants which function as highly efficient electrocatalysts for oxygen evolution reaction (OER) in alkaline media. The Ru dopants induced a high content of Ni and Co vacancies in NiCoP nanoparticles, and the more defective Ru doped NiCoP phase than undoped NiCoP ones led to a greater number of catalytically active sites and improved electrical conductivity after undergoing electrochemical activation. The Ru doped NiCoP catalyst exhibited high OER catalytic performance in alkaline media with a low overpotential of 281 mV at 10 mA cm⁻² and a Tafel slope of 42.7 mV dec⁻¹.     

Influence of thiazole regioisomerism on second-order nonlinear optical chromophores

Two series of matched and mismatched donor–thiazole–acceptor chromophores have been synthesized to disclose the role that the orientation of the thiazole ring plays on their second-order nonlinear optical (NLO) properties. Whereas previous theoretical studies predict that the matched systems show markedly higher NLO responses, our experimental results do not parallel this trend, showing differences between regioisomers much lower than those predicted.     

Facile synthesis of highly functionalized ethyltrifluoroborates

Organotrifluoroborates are generating increased interest because of their ease of preparation and purification and indefinite shelf life. Herein we report the preparation of organotrifluoroborates bearing functional groups that can be manipulated at different stages of the synthetic route, exploiting the inertness of their carbon-boron bonds. The alkylation of 2,2-dicyanoethyltrifluoroborate with a variety of electrophiles and of (EWG)2CH2 with potassium iodomethyltrifluoroborate resulted in di- and trisubstituted ethyltrifluoroborates in good to excellent yields.     

Tunable resonance hyper-Raman spectroscopy of second-order nonlinear optical chromophores

Two-photon-resonant hyper-Raman spectra are reported for three "push-pull" conjugated organic chromophores bearing -NO(2) acceptor groups, two dipolar and one octupolar. The excitation source is an unamplified picosecond mode-locked Ti:sapphire laser tunable from 720 to 950 nm. The linear resonance Raman spectra of the same molecules are measured using excitation from the laser second harmonic. Excitation on resonance with the lowest-lying band in the linear absorption spectrum yields nearly identical resonance Raman and resonance hyper-Raman spectra. However, excitation into a region that appears to contain more than one electronic transition gives rise to different intensity patterns in the linear and nonlinear spectra, indicating that different transitions contribute differently to the one-photon and two-photon oscillator strength. The promise of the hyper-Raman technique for examining electronic transitions that are both one- and two-photon allowed is discussed.     

Preparation of polymer optical fibers doped with nonlinear optical active organic chromophores

We synthesized two novel organic nonlinear optical chromophores—chiral S(+)‐N‐[p‐(4‐nitrostyryl) phenyl] prolinol and non‐chiral [p‐(4‐nitrostyryl) phenyl] piperdine—as potential laser‐active dyes for photonic applications. Both materials show good optical transmittance in the telecommunication frequency region, desirable solubility in acrylic polymer optical fiber matrices, and attractive fluorescence properties that are advantageous for laser‐gain materials and devices. Subsequently, these two chromophores were incorporated into poly(methyl methacrylate) and poly(ethyl methacrylate) and drawn into polymer optical fibers. The relevant properties of these organic dye‐doped fibers have been studied, revealing essential attributes of laser‐active characteristics. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1794–1801, 2001     

Enhanced poling efficiency in rigid-flexible dendritic nonlinear optical chromophores

Naringenin is a flavonoid specific to citrus fruits and possesses anti-inflammatory, anticarcinogenic, and antitumour effects. But due to a lower half-life and rapid clearance from the body, frequent administration of the molecule is required. To improve the bioavailability and prolong its duration in body system, its phospholipid complexes were prepared by a simple and reproducible method. Naringenin was complexed with phosphatidylcholine in equimolar ratio, in presence of dichloromethane. The prepared Phytosomes (naringenin–phospholipid complex) were evaluated for various physical parameters like FT-IR spectroscopy, Differential Scanning Calorimetry (DSC), X-ray powder diffractometry (XRPD), Solubility, Scanning Electron Microscopy (SEM) and the in vitro drug release study. These phospholipid complexes of naringenin were found to be irregular and disc shaped with rough surface in SEM. Drug content was found to be 91.7% (w/w). FTIR, ¹H NMR, DSC and XRPD data confirmed the formation of phospholipid complex. Water solubility of naringenin improved from 43.83 to 79.31 μg/mL in the prepared complex. Unlike the free naringenin (which showed a total of only 27% drug release at the end of 10 h), naringenin complex showed 99.80% release at the end of 10 h of dissolution study. Thus it can be concluded that the phospholipid complex of naringenin may be of potential use for improving bioavailability.     

Photorefractive polymer composites based on nanosized nonlinear optical chromophores

Photorefractive (PR) polymer composites based on polymers with a high glass transition temperature in which the random distribution of a photosensitizer and a nonlinear optical chromophore as dopants is “frozen” were designed. In the case of the random distribution of chromophores, only the third-order electric susceptibility has a nonzero value. Therefore, nanosized structures having high third-order polarizability due to an extended conjugated-bond system (or cooperative electronic excitation) were used as nonlinear chromophores. Good PR characteristics are displayed by polymeric composites containing nanosized structures, such as cyanine dye J aggregates, supramolecular assemblies of ruthenium(II) complexes, and single-wall carbon nanotubes. The use of extended nanosized chromophores as simultaneous spectral sensitizers allowed polymer composites with PR sensitivity in the near IR region at 1064 and 1550 nm to be designed.     

Evaluation of the thermal stability of some nonlinear optical chromophores

Optical data storage is poised to benefit from a new class of advanced polymeric materials engineered to exhibit photorefractivity. Likewise, the transmission and processing of data will also benefit from a related class of materials with electro-optic activity. Organic chromophores are critical constituents of these materials which function due to a change of index of refraction in response to an electric field. However, a number of materials and processing problems remain to be solved before devices incorporating these optically nonlinear chromophores are practical. For example, for electrooptical applications the NLO waveguide should be able to withstand short duration processing temperatures in excess of 300°C and long duration use temperatures of at least 80°C. The requirement for thermochemical stability follows from the need to implement highT _g matrices to provide stability of the orientational or polar order required for long-term device performance and reliability. As a result, the thermal stability of chromophores is now more closely evaluated in addition to their transparency and optical nonlinearity properties. Some chromophore classes, such as the azo dyes studied here, have attractive properties for these applications but further enhancements in overall properties are needed. Identification of the fundamental chemical processes in thermal decomposition of these dyes should lead to introduction of structural changes which provide better stability. Here thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA/MS) is used to provide an assay of thermochemical stability with an added benefit that insight into the mechanisms of thermal decomposition may by identified. In this initial study diaryl substitution of the amine in derivatives of 4-amino-4-nitroazobenzene was observed to greatly enhance thermal stability relative to dialkyl substitution. Substitution of phenyl for alkyl eliminates structural features involved in the most facile degradation mechanism available to the alkyl derivative.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe authors acknowledge contributions by colleagues at IBM including H. Truong and R. Siemens for the thermal analysis. This work was supported by the Air Force Office of Scientific Research and the National Institute of Science and Technology Advanced Technology Program.     

Facile synthesis of highly fluorescent Boranil complexes

Complexation of a large variety of Anils (aniline-imines) with boron(III) precursors provides stable Boranils, some of which have been structurally characterized. Analysis of their optical properties reveals that the fluorescence stems from an intraligand charge transfer (ILCT) state with the best quantum yields reaching 90%. Chemistry on the Boranils allows grafting of photoactive modules acting as energy antennae for borondipyrromethene (Bodipy) and subphtalocyanine (SubPc) fluorophores.     

Hyper-Rayleigh scattering measurements of nonlinear optical chromophores at 1907 nm

Hyper-Rayleigh scattering measurements are performed on nonlinear optical chromophores using an excitation wavelength of 1907 nm. This wavelength is the longest that has yet been reported for the hyper-Rayleigh scattering experiment and allows measurements of the first hyperpolarizability of chromophores that are free of contributions from two-photon absorption induced fluorescence and reduces one and two photon resonance enhancement to a minimum. Using the 1907 nm setup we demonstrate good agreement between our results and those obtained with the electric field induced second harmonic generation (EFISHG) technique previously performed at this wavelength.     

Facile synthesis of zirconia supported nanomaterials for efficient photocatalytic applications

The recent study enlightens the synthesis and characterization of zirconia (ZrO₂), Fe-doped ZrO₂ (Fe@ZrO₂), and Ni-doped ZrO₂ (Ni@ZrO₂) catalysts having new-fangled morphology with tuned band gap as photocatalysts for degradation of textile wastewater dyes methylene blue (MB), malachite green (MG), and their mixtures. SEM imaging of Fe@ZrO₂ and Ni@ZrO₂ is interestingly varied from ZrO₂ as well as doping of transition metals greatly affects the morphology of composites. The optimization study depicts that the pH, time (min) and catalyst amount (g) have a direct relation with degradation efficiency, while the dye concentration (mg/L) has an indirect relation as well. The photocatalytic studies depict that the degradation of MB and MG follows oxidation pathway via hydroxyl radicals (OH^•) and holes. Reusability of catalysts corresponds to a little decrease in degradation efficiency in the first two cycles and decreases to about ∼10% (Ni@ZrO₂) and ∼12% (Fe@ZrO₂) in next three cycles.