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The UV absorbance bands of 1,4-distyrylbenzene (1,4-Bis[(E)-2-phenylethenyl]benzene, DSB) are investigated by Synchrotron Radiation Linear Dichroism (SRLD) spectroscopy using stretched polyethylene as an anisotropic solvent. The observed polarization data provide information on the transition moment directions of the observed spectral features. The investigation covers the range 15,000-58,000 cm-1 (667-172 nm), thereby providing new information on the transitions of DSB in the vacuum UV region. The observed spectrum is characterized by four main band systems centered at 27,600, 41,000, 49,800, and 57,500 cm-1 (362, 244, 201, and 174 nm). In general, the observed bands and their polarization directions are well predicted by the results of quantum chemical calculations using Time-Dependent Density Functional Theory (TD-DFT) with the functional CAM-B3LYP, and with the semiempirical all-valence-electrons method LCOAO.

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We present results of experimental and theoretical studies of excited state dynamics in two alkyl derivatives of fluorescein, MitoFluo and C8-Fl in solutions with liposomes. The liposomes DOPC and soybeanPC + 20% Cardiolipin (Azo-Cl), modelling cellular and inner mitochondrial membranes, respectively, were used in experiments. Both types of liposomes were shown to reduce significantly the fluorescence quantum yield as compared to that of pure fluorescein derivatives in solutions, while DOPC liposomes also caused a noticeable (ca 10 nm) red shift of fluorescence maximum. The study of fluorescence polarization decay has been carried out where important fluorescence parameters: polarization anisotropy, fluorescence lifetimes, and rotational diffusion times have been determined. It was shown that the isotropic fluorescence decay of C8-Fl in liposome containing solutions was single-exponential and the anisotropic decay was double-exponential for both types of lyposomes. In the case of MitoFluo both isotropic and anisotropic fluorescence decays were fitted satisfactory only with double-exponential functions. The interpretation of the experimental data obtained was supported by ab initio calculations of the structure and excitation properties of MitoFluo and C8-Fl in aqueous solution. The analysis of anisotropic fluorescence decay allowed for isolation of the contributions of fluorescein derivatives free in solution from those embedded in liposomes. Also, the experimental data suggest that MitoFluo interacts with liposomes more effectively than C8-Fl. Basing on the experimental and theoretical results obtained we conclude that free C8-Fl and MitoFluo molecules in solution were mostly in their dimer forms.

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We report the optical imaging and absorption spectroscopy on atomically precise armchair graphene nanoribbons (GNRs) on insulating fused silica substrates. This is achieved by controlling light polarization on macroscopically aligned GNRs which greatly enhances the optical contrast of the submonolayer GNRs on the insulating substrates. We measure the linear absorption spectra of 7-armchair and 9-armchair GNRs in this study, and the experimental data agree qualitatively with ab inito calculation results. The polarization spectroscopy technique enables an unambiguous optical identification of GNRs and provides a rapid tool to characterize the transferred film over a large area.

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We demonstrate quantitative measurements of methane (CH4) mole fractions in a low-pressure fuel-rich premixed dimethyl ether/oxygen/argon flat flame (Φ = 1.87, 37 mbar) using mid-infrared (IR) polarization spectroscopy (IRPS). Non-intrusive in situ detection of CH4, acetylene (C2H2), and ethane (C2H6) in the flame was realized by probing the fundamental asymmetric C-H stretching vibration bands in the respective molecules in the spectral range 2970-3340 cm-1. The flame was stabilized on a McKenna-type porous plug burner hosted in a low-pressure chamber. The temperature at different heights above the burner (HAB) was measured from the line ratio of temperature-sensitive H2O spectral lines recorded using IRPS. Quantitative measurements of CH4 mole fractions at different HAB in the flame were realized by a calibration measurement in a low-pressure gas flow of N2 with a small admixture of known amount of CH4. A comprehensive study of the collision effects on the IRPS signal was performed in order to quantify the flame measurement. The concentration and temperature measurements were found to agree reasonably well with simulations using Chemkin. These measurements prove the potential of IRPS as a sensitive, non-intrusive, in situ technique in low pressure flames.

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This paper compares the signal-to-noise ratio obtained using an InSb photodiode for infrared (IR) polarization spectroscopy to that obtained using an upconversion detector, and shows a factor 64 improvement by the change. Upconversion detection is based on using sum frequency generation to move the IR optical signal to near-visible wavelengths to improve the sensitivity.

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We discuss the internal status of rubber composites consisting of an insulating rubber matrix and conductive carbon black (CB) fillers ("black rubber") using polarization-sensitive terahertz time-domain spectroscopy (THz-TDS). The black rubber composites under stretched conditions exhibit a large optical anisotropy or birefringence in the terahertz regime. From systematic studies, it is revealed that the large birefringence of black rubbers is due to the orientation distribution of anisotropically shaped CB aggregates in the rubber matrix and the orientation distribution is strongly linked to the mechanical deformation of the black rubber. A model simulation based on this relation between deformation and reorientation allows conversion of the birefringence (optical) information into strain (mechanical) information. In addition, the spectroscopic information obtained using the THz-TDS technique is useful to evaluate the changes in the internal conductive filler network caused by the mechanical deformation. Our findings demonstrate that the terahertz polarization spectroscopy is a promising nondestructive inspection method for contactless investigation of the internal condition of black rubber composites.

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The assemblies of cross-linked gold nanoparticles (AuNP) attract lot of scientific attention due to feasible perspectives of their use for development of scaled contact electrodes. Here, we developed and tested method of solid-state formation of dimers created from small AuNP (~18 nm) cross-linked with 1.9-nonadithiol (NDT) molecules. The morphology of created coating of a glass surface and its optical-polarization properties have been studied in detail by combination of scanning electron microscopy, atomic force microscopy, UV-visible spectroscopy, and modulation-polarization spectroscopy.The modification of localized surface plasmon resonance (LSPR) of single AuNP and their assemblies were studied by measuring of the spectral characteristics of polarization difference at all stages of synthesis. The radiative and nonradiative modes of LSPR have been analyzed in detail at different angles of incidence light. This allowed establishing relation between surface morphology of the coating and its optical properties.

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Myricetin (3,3',4',5,5',7'-hexahydroxyflavone) was investigated by linear dichroism spectroscopy on molecular samples partially aligned in stretched poly(vinyl alcohol) (PVA). At least five electronic transitions in the range 40,000-20,000cm-1 were characterized with respect to their wavenumbers, relative intensities, and transition moment directions. The observed bands were assigned to electronic transitions predicted with TD-B3LYP/6-31+G(d,p).

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Polyfluorene and its derivatives have been recognized as efficient light-emitting semiconductors. However, directional alignment of polyfluorene copolymers at a large scale has rarely been observed, in particular for the two relatively more amorphous members of poly-9,9-dioctylfluorene-co-bethiadisazole (F8BT) and poly-(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N0-diphenyl)-N,N'di(p-butyl-oxy-pheyl)-1,4-diamino-benzene) (PFB) molecules. Furthermore, the directional alignment of PFB has not been observed so far due to the triphenylamine units in its molecular structures. We present, in this work, a solution-processible method to achieve large-scale alignment of F8BT and PFB molecules into fibers as long as millimeters in a defined direction. Spin-coating the polymer film on to a glass substrate patterned by one-dimensional dielectric nano-grating structures through interference lithography and subsequent modification using 1,5-pentanediol have been used in all of the preparation procedures. Polymer fibers have been obtained in an arrangement parallel to the grating lines. The microscopic, spectroscopic, and photoconductive performances verified the formation and the quality of these directionally-aligned polymeric fibers.

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Visible and Near Infrared (Vis-NIR) Spectroscopy is a powerful non destructive analytical method used to analyze major compounds in bulk materials and products and requiring no sample preparation. It is widely used in routine analysis and also in-line in industries, in-vivo with biomedical applications or in-field for agricultural and environmental applications. However, highly scattering samples subvert Beer-Lambert law's linear relationship between spectral absorbance and the concentrations. Instead of spectral pre-processing, which is commonly used by Vis-NIR spectroscopists to mitigate the scattering effect, we put forward an optical method, based on Polarized Light Spectroscopy to improve the absorbance signal measurement on highly scattering samples. This method selects part of the signal which is less impacted by scattering. The resulted signal is combined in the Absorption/Remission function defined in Dahm's Representative Layer Theory to compute an absorbance signal fulfilling Beer-Lambert's law, i.e. being linearly related to concentration of the chemicals composing the sample. The underpinning theories have been experimentally evaluated on scattering samples in liquid form and in powdered form. The method produced more accurate spectra and the Pearson's coefficient assessing the linearity between the absorbance spectra and the concentration of the added dye improved from 0.94 to 0.99 for liquid samples and 0.84-0.97 for powdered samples.

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Photoactive Yellow Protein (PYP), a phototaxis photoreceptor from Ectothiorhodospira halophila, is a small water-soluble protein that iscrystallisable and excellently photo-stable. It can be activated with light(λ(max)= 446 nm), to enter a series of transientintermediates that jointly form the photocycle of this photosensor protein.The most stable of these transient states is the signalling state forphototaxis, pB.The spatial structure of the ground state of PYP, pG and the spectralproperties of the photocycle intermediates have been very well resolved.Owing to its excellent chemical- and photochemical stability, also the spatialstructure of its photocycle intermediates has been characterised with X-raydiffraction and multinuclear NMR spectroscopy. Surprisingly, the resultsobtained showed that their structure is dependent on the molecular contextin which they are formed. Therefore, a large range of diffraction-,scattering- and spectroscopic techniques is now being employed to resolvein detail the dynamical changes of the structure of PYP while it progressesthrough its photocycle. This approach has led to considerable progress,although some techniques still result in mutually inconsistent conclusionsregarding aspects of the structure of particular intermediates.Recently, significant progress has also been made with simulations withmolecular dynamics analyses of the initial events that occur in PYP uponphoto activation. The great challenge in this field is to eventually obtainagreement between predicted dynamical alterations in PYP structure, asobtained with the MD approach and the actually measured dynamicalchanges in its structure as evolving during photocycle progression.