Incorporation of designed extended chromophores into amphiphilic 4-helix bundle peptides for nonlinear optical biomolecular materials

Multipigment ensembles that feature (porphinato)metal components and appropriate ethyne- and oligoyne-based chromophore-to-chromophore connectivity can manifest large optical polarizabilities and hyperpolarizabilities by design. Their vectorial orientation and local environment are controlled upon incorporation into designed amphiphilic 4-helix bundle peptides via axial histidyl ligation without disturbing the peptide's helical secondary structure. The chromophore/peptide stoichiometry can be tuned by varying the peptide's oligomeric state. The chromophore/peptide complexes are thermally stable, making them ideal candidates for the fabrication of nonlinear optical biomolecular materials.     

Optical properties of porphyrin chromophores assembled in nano-lamellar zirconium phosphate

The supra-molecular assemblies and optical properties of the symmetrical neutral porphyrin chromophore, meso-tetra(4-pyridyl)porphine, bound to a modified alpha-zirconium phosphate framework have been studied. The interlayer distance of the cetyltrimethylammonium zirconium phosphate framework is 39.6 angstroms. After the addition of meso-tetra(4-pyridyl)porphine to the framework, the X-ray powder diffraction (XRPD) patterns show that the interlayer distance of the framework is 30.3 angstroms, demonstrating the formation of novel assemblies. In the framework, organic chromophores are assumed to align in a canted monolayer. The interaction of organic chromophores with the framework causes noticeable red shifts of the Soret absorption band from 416 to 427 nm. In contrast, the luminescence peak is blue shifted from 660 nm in aqueous media to 648 nm when meso-tetra(4-pyridyl)porphine is bound to the framework. Furthermore, the emission yield of the organic chromophore in the framework is dramatically enhanced compared to that of organic aqueous solutions. The spectroscopic change of meso-tetra(4-pyridyl)porphine is ascribed to the unique microenvironments of the nano-lamellar framework. The juxtaposition of the porphyrin chromophores in the framework tunes their electronic interactions. In comparison, the organic chromophores also attempted to bind with another modified alpha-zirconium phosphate, n-butylammonium zirconium phosphate. However, the chromophores could not enter into n-butylammonium zirconium phosphate due to its smaller interlayer distance (18.8 angstroms).     

Effects of chromophore dissociation on the optical properties of rare-Earth-doped polymers

The observed dissociation of tetrakis rare-earth chromophores in rare-earth-doped organic polymers is reported, and a time-resolved spectroscopic technique is presented to determine quantitatively the fractional concentrations of different chromophore species in various solvents. Based on this technique, the equilibrium constants of tetrakis rare-earth chromophores in rare-earth-doped polymers are determined. Thus, the equilibrium constants for tetrakis rare-earth compounds of benzoyltrifluoroacetonate (BTF), for example, Sm(BTF)(4)P and Eu(BTF)(4)P in methyl methacrylate monomer, are K = 4.7 ? 0.5 x 10(-4) M and K = 1.2 ? 0.5 x 10(-4) M, respectively. In contrast, the tetrakis rare-earth compounds of hexafluoroacetylacetonate (HFA), for example, Sm(HFA)(4)Net(4) and Eu(HFA)(4)Net(4), are quite stable and show no evidence of dissociation. We further characterize the dissociation of several chromophore systems and discuss the influence such dissociation has on overall optical performance. The results enable determination of optimal doping concentrations as well as preferred rare-earth chromophore preparation and doped polymer fabrication procedures.     

Enhanced electrooptical active materials based on n-hexyl group flexible isolation in NLO chromophores

Two principally novel organic nonlinear optical chromophores (1 and 2) with flexible (n-hexyl group) or rigid isolated (benzyl group) group are designed and successfully synthesized. The prepared chromophores were characterized by MS, ¹H-NMR and UV–Vis spectra. Their thermal stability was studied by thermal gravimetric analyzer and differential scanning calorimetry. Poled films of the chromophores doped in amorphous polycarbonate afford the maximum electro-optic tensor coefficient (r₃₃) equal to 39 pm/V, 63 pm/V for chromophore 1 and chromophore 2, respectively at the wavelength 1,064 nm. The reason of so large differences between these two chromophores’ linear electrooptics coefficients were explained within a framework of performed quantum chemical calculations and it is crucially dependent on distances between the chromophore molecules and the polymer chains.     

Chromophores exhibiting nonlinearity–transparency–thermal stability trade-off: synthesis and nonlinear optical properties of two-dimensional chromophores containing nitro acceptors

Nonlinear optical multipolar chromophores with nitro acceptors were designed and synthesized. The target compounds were characterized by NMR, IR, UV and melting point. The decomposition temperature was determined with differential scanning calorimetry, and the absorption spectra were measured. The first hyperpolarizability of the chromophore were calculated via solvatochromic methods. The nonlinear optical properties of five compounds were discussed. Especially, the first-order hyperpolarizabilities of chromophores 2 and 3 come from their two-dimensional structure, the length of the conjugation bridge and the intramolecular proton transfer. The strong dihydroxyl donor of chromophores 4 and 5 expanded the first-order hyperpolarizabilities. These NLO chromophores exhibit large optical nonlinearity, good transparency and thermal stability.     

Preparation and nonlinear optical properties of hybrid films containing dicyanomethylenepyran-based chromophores

A new nonlinear optical (NLO) chromophore 4-dicyanomethylene-2-methyl-6- {4-[4-(N-ethyl-N-hydroxyethylamino)phenylazo]}styryl-4H-pyran (AZP), which features extended conjugated chain based on DCM laser dye, was synthesized and functionalized with alkoxysilane for materials processing. Hybrid films containing chromophore AZP and DCM were prepared via a sol-gel processing. The d₃₃ values of films containing AZP are 39-48 pm/V varying with concentration of chromophores, which is similar to that containing DCM. By tuning the organic content, the thermal stability of d₃₃ values can be significantly improved by about 30 °C, about 15 °C higher than those containing DCM. The residual rotational stress, along with cavity between chromophores and matrix, is proposed to contribute to the stability of NLO activity of hybrid films.     

Optical second order nonlinearities in new chromophores obtained by selective mono-reduction of dinitro precursors

Three new push–pull chromophores of potential interest in second order nonlinear optical applications were synthesized and characterized, also by EFISH determination of molecular second order NLO properties. The chromophores contain a phenyl-azo unit coupled with fluorenonic, stilbenic or 1,3,4-thia-diazolic groups and are OH-functionalized to prompt easy covalent insertion in polymer chains. The selective reduction of only one of the two chemically equivalent nitro groups in the starting precursors is the key step of the synthetic pathway affording the chromophores. These show good chemical and thermal stability. The X-ray structural determination of the fluorenone derived chromophore is also reported.     

Importance of chromophore environment on the near-infrared absorption of polymeric waveguides

The near-infrared absorption of two chromophore functionalized polymers and combinations of seventeen different guest chromophores in seven different organic polymer matrices were investigated to assess the effect of chromophore structure and environment on absorption. The near-infrared absorption losses were found to be dramatically larger by as much as 2-3 orders of magnitude in polymer matrices than in solution. Furthermore, the absorption of the long-wavelength tail appears to be related to the glass transition temperature of the polymer matrix that contains the chromophore. These results are interpreted in terms of inhomogeneous broadening.     

Two-dimensional correlation analysis study of the photo-induced molecular reorientations of photosensitive polyester film containing 1,4-phenylenediacryloyl units in the backbone

The photochemical reaction and molecular reorientation of a novel photosensitive polyester, poly[oxy(4-n-butyl-3,5-benzoate)oxy-1,4-phenylenediacryloyl] (PPDA-C4BZ), which contains n-butyl side groups and 1,4-phenylenediacryloyl units (PDA chromophores) in the main chain, are reported in detail. We applied two-dimensional (2D) correlation analysis for the infrared (IR) and ultraviolet (UV) absorption spectra of nanoscaled films of PPDA-C4BZ to establish the sequence of the photo-induced segmental reorientations that result from UV irradiation. The photochemical reaction was found to have a greater effect on the polymer's main chains than on its side groups and to induce the reorientation of the polymer molecules. In particular, a cycloaddition process occurs first in the PDA chromophore units and then the local reorientation of the polymer molecules is induced. Namely, such photodimerization of the PDA chromophores induces the molecular reorientations of the PDA chromophores and the benzoate units in the main chain. The photo-induced molecular reorientations occur in the following sequence: photodimerization --> benzoate units --> PDA chromophores --> n-butyl side groups. In addition, a two-dimensional map of the first derivatives of the UV absorption spectra with respect to the exposure energy provided evidence of the formation of head-to-head aggregates (i.e., H-aggregates) of PPDA-C4BZ molecules.     

Let the light be a guide: Chromophore communication in metal-organic frameworks

The photonic characteristics of chromophore-containing metal-organic frameworks(MOFs)have led to extensive photophysical studies in an effort to capitalize on the potency of precisely controlled chromophore ensembles.Several examples have laid the foundation that demonstrates how photophysical properties of chromophores can be manipulated by tuning their communications(interactions)through integration within a MOF matrix.The main focus of this review is on harnessing the versatile MOF platform to accentuate the photophysical properties of integrated chromophores.In particular,this review will highlight chromophore dynamics that enhance,alter,or tune the photoluminescence response of single-and multi-chromophore-containing scaffolds,as well as alignment-guided anisotropic fluorescence.Building upon this groundwork,utilization of a hybrid crystalline motif can induce preferential orientation of chromophores resulting in enhanced communication and tailored behavior compared to randomly oriented emissive molecules.Moreover,frameworks that produce upconverted emission via sensitized triplet-triplet annihilation(sTTA),excited-state absorption(ESA),energy transfer upconversion(ETU),multi-photon absorption(MPA),or second-harmonic generation(SHG)can invoke dynamic control of material properties using photochromic linkers and will be discussed herein with a focus on the effects of chromophore alignment.Integration within a framework is a vehicle tofuse chromophores into solid-state platforms,opening an avenue for chromophore utilization in applications such as portable electronics that require solids or thin films.For those reasons,the design of chromophore-containing MOFs with desirable properties that rely on the alignment and communication of hundreds of chromophores within a single platform is a pressing demand for the development of futuristic technologies.     

Surface-enhanced resonance Raman scattering of black inkjet dyes in solution and in situ printed onto paper

Understanding the changes that occur when dyes are absorbed onto paper is crucial for the design of new inkjet dyes. This problem is particularly difficult for black dyes that have complex chromophores, and as a result, spectroscopic information on electronic and structural changes can be of importance. Surface-enhanced resonance Raman scattering (SERRS) and electronic structure calculations were used to probe in situ changes in the chromophore in black di-azo dyes printed onto paper. The data indicate that the low-energy chromophore is due mainly to the hydrazone group and the high-energy chromophore to both the azo and hydrazone groups. A comparison of SERRS from the dyes adsorbed onto silver particles in suspension and from the dyes on paper demonstrated a broadening of the chromophore into the red for both dyes and evidence of a structural change in one dye.     

TiO2纳米晶半导体电极及有机-无机电致变色器件的研究

通过丝网印刷工艺，制备了具有高的比表面积的纳米晶氧化钛薄膜，通过有机／无机复合，在氧化钛薄膜表面吸附了单层的电变色子，制备成纳米晶电极并且装配成三明治结构的电致变色器件．通过紫外可见分光光度计表征，该器件的着色态透过率为4％，退色态透过率为85％．其在智能窗、平板显示器、电子书和电子报纸等领域具有潜在的应用前景．     

Silver nanocrystal-modified silicon nanowires as substrates for surface-enhanced Raman and hyper-Raman scattering

Metal catalyzed, CVD-grown silicon nanowires decorated by chemical assembly of closely spaced Ag nanocrystals were modified with the well-known "silver mirror" reaction and investigated as substrates for surface-enhanced Raman (SERS) and hyper-Raman (SEHRS) spectroscopy. Four chromophores were examined: Rhodamine 6G, crystal violet, a cyanine dye, and a cationic donor-acceptor substituted stilbene. After soaking the substrates overnight in 10(-4) M aqueous chromophore solutions, all four chromophores gave good-quality SERS spectra in < or =60 s using <1 microW of 458-nm cw laser power, and SEHRS spectra are obtained in < or =120 s using <1 mW of mode-locked 916-nm laser power. Results from this substrate are compared with those on colloidal silver nanoparticles deposited as a film, as well as surfaces grown by the silver mirror reaction.     

Fluorescence polarization of triple-chromophore complexes with energy transfer

The formula for the determination of a fluorescence polarization degree is derived for triple-chromophore complexes with energy transfer: P = (3B - 1 + 2A)/(3 + B + 4A). In this formula B = q(12) cos(2)(?(12)) + q(13) cos(2)(?(13)) + q(23) cos(2)(?(23)) and parameters A and q(ij) are dependent on the kinetic parameters of energy exchange and the chromophore spectroscopic parameters. The angle ?ij is the angle between the transition dipole moments of the i and j chromophores. The formula was tested for the particular case of the C-phycocyanin (C-PC) of the blue-green algae Agmenellum quadruplicatum, which contain three chromophores, α-84, β-84, and β155. Polarized spectra were calculated for both the emission and the excitation spectra of C-PC β subunits and monomers.     

Circularly-induced χ(2) grating in the CHBrClF incorporated within the olygoetheracrylate photopolymer matrices

We have found that CHBrClF chromophore incorporated into olygoetheracrylate photopolymer matrices might be considered like promising materials for optical poling excited by circularly polarized bicolor coherent light. The maximally-achieved value of the second-order optical susceptibility caused by circularly polarized light for the wavelength 1760 nm was equal to about 0.82 pm/V. Maximal susceptibility is achieved for the 4.65% of chromophores. The further increase of the second-order susceptibility is limited by appearance of the chromophore CHBrClF agglomerates. The investigated composites possess long-lived χ⁽²⁾ grating which decreases by not more than 24% after 800 min of laser treatment.     

Optical properties of poly(N-vinylcarbazole)-based guest-host photorefractive polymer systems

The photorefractive properties of poly(N-vinylcarbazole) doped with a variety of nonlinear optical chromophores and sensitizing agents are surveyed. Steady-state diffraction efficiencies of greater than 10(-3) and two-beam coupling gain exceeding the absorption loss are found in six materials combinations. The effect of the structure of the nonlinear optical chromophore on the photorefractive properties is discussed.     

Nonlinear Optical Properties of Correlated Chromophores in Organic Mesoscopic Superstructures

A new design strategy for enhanced nonlinear optical properties, based on a simple vector model and situated at the mesoscopic level, between the microscopic molecular level and the macroscopic bulk, is explained and exemplified by a number of organic superstructures. The second-order nonlinear optical properties of the structures are analyzed in terms of the corresponding properties of the individual monomeric chromophores that constitute the structure. The chromophores can be considered as electronically independent with a high symmetry. A simple vector model can then account for the large secondorder nonlinear optical polarizability of the mesoscopic superstructure. Another important advantage that is clear from the vector analysis is the improved chromophore alignment, owing to the enlarged mesoscopic dipole moment.     

Assembly, structure and optical response of three-dimensional dynamically tunable multicomponent superlattices

We report the successful fabrication of optically active three-dimensional (3D) superlattices that incorporate DNA-encoded components, metallic nanoparticles, and molecular chromophores in well-defined positions. A DNA linker with three distinct binding sites serves as an assembly agent and dynamically tunable structural element for the superlattice. Using small angle X-ray scattering we have revealed the organization of particle-chromophore 3D arrays and monitored their reversible contractions and expansions that were modulated by ionic strength changes. As the distance between the molecular chromophores and plasmonic nanoparticles in the superlattice was regulated in situ, we were able to uncover the relationship between experimentally determined structure and optical response of the system. This dynamical tunability of superlattice results in a dramatic optical response: nearly a three times change of emission rate of the chromophore. The evolution of lifetime with structural changes reasonably agrees with the calculations based on a cumulitative coupling of chromophores with metallic nanoparticles in different coordination shells.     

Modelling photosystem I as a complex interacting network

In this paper, we model the excitation energy transfer (EET) of photosystem I (PSI) of the common pea plant Pisum sativum as a complex interacting network. The magnitude of the link energy transfer between nodes/chromophores is computed by Forster resonant energy transfer (FRET) using the pairwise physical distances between chromophores from the PDB 5L8R (Protein Data Bank). We measure the global PSI network EET efficiency adopting well-known network theory indicators: the network efficiency (Eff) and the largest connected component (LCC). We also account the number of connected nodes/chromophores to P700 (CN), a new ad hoc measure we introduce here to indicate how many nodes in the network can actually transfer energy to the P700 reaction centre. We find that when progressively removing the weak links of lower EET, the Eff decreases, while the EET paths integrity (LCC and CN) is still preserved. This finding would show that the PSI is a resilient system owning a large window of functioning feasibility and it is completely impaired only when removing most of the network links. From the study of different types of chromophore, we propose different primary functions within the PSI system: chlorophyll a (CLA) molecules are the central nodes in the EET process, while other chromophore types have different primary functions. Furthermore, we perform nodes removal simulations to understand how the nodes/chromophores malfunctioning may affect PSI functioning. We discover that the removal of the CLA triggers the fastest decrease in the Eff, confirming that CAL is the main contributors to the high EET efficiency. Our outcomes open new perspectives of research, such comparing the PSI energy transfer efficiency of different natural and agricultural plant species and investigating the light-harvesting mechanisms of artificial photosynthesis both in plant agriculture and in the field of solar energy applications.     

Nonlinear optical properties and performance optimization of the pro-aromatic chromophores for NLO materials

Geometric structures and nonlinear optical properties (NLO) of the pro-aromatic chromophores, comprising indoline moiety as an electron donor and azo linker as a π-conjugated bridge, have been investigated by means of quantum chemistry method and the response theory. Three solvent models were used to study the short-range interaction and long-range interaction between solvent and solution in order to simulate the experimental spectra. Simulated absorption used by the polarizable continuum model gave a well agreement with experimental measurement. The micro-mechanisms of first hyperpolarizability were explained on the basis of the two-level models, and charge difference density methods demonstrated that the chromophore (4f), which indoline moiety acts as an electron donor and N,N-dimethyl formamide as an acceptor bridged by azo bridge, displays an efficient intramolecular charge transfer properties amplifying the NLO response. Calculations of two-photon absorption (TPA) for the indoline chromophore were performed to develop their potential application on TPA materials. Additionally, some molecules were designed by replacing electron donor and introducing additional heteroatoms to tune the NLO parameters. The results show 4f-a with 1,4-phenylenediamine donor unit and introducing one heteroatom display well NLO character.