The stratum corneum (SC) plays an important role in skin barrier function. it acts as a protective barrier against water loss, eliminates foreign substances and micro-organisms and acts against harmful effects of UVR. Our aim was to study the impact of suberythemal doses of UVA and UVB exposure on the molecular structure, organization and barrier function of the SC by following different Raman descriptors. Twenty female volunteers, aged 20–30 years, with healthy skin were enrolled. Doses of 95 mJ/cm2 UVA and 15 mJ/cm2 UVB were applied to volunteers’ forearms. In vivo Raman measurements were performed at irradiated and control regions. The impact of UVA and UVB irradiation was observed following several Raman descriptors, i.e. the ratio of vasymCH2/vsymCH2 (2885 cm−1/2850 cm−1) corresponding to the organizational order of the lipid bilayer. Water content and mobility descriptors were obtained by calculating vOH/vCH ratio. Finally, protein secondary structure was evaluated based on the 1670 cm−1/1650 cm−1 ratio related to β sheets and α helices, respectively. UVA induced a loosening of the lateral packing of lipids immediately after irradiation. in contrast, delayed impact caused a tightening of the lipid barrier, an increase in water content -mainly in the unbound water fraction and a higher relative amount of β sheets in SC proteins. Overall, these observations may explain the thickening of the SC observed in previous studies. A UVB dose of 15 mJ/cm2 was apparently below the threshold necessary to induce significant changes despite the trends observed in this study.

This study aims to explore the spectroscopic properties of a Sr1.0Ba2.0B6O12:O.5Sm(3+) phosphor synthesized using the solid-state reaction method. The morphology and elemental composition of the phosphor were determined using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. Phase changes and crystallite phases in the phosphor were studied using differential-scanning calorimetry and X-ray diffraction, respectively. Raman and Fourier-transform infrared spectra were used to identify the molecular vibrations in the phosphor. The energy bandgap and bonding nature of the phosphor were analyzed using the absorption spectrum. The nephelauxetic ratios determined from the absorption peaks revealed the presence of both ionic and covalent bonding in the phosphor. Judd-Ofelt parameters, along with radiative properties of the phosphor, were evaluated using the peaks in the absorption spectrum. Colorimetric analysis using the photoluminescence spectrum showed that the Sr1.0Ba2.0B6O12:0.5Sm(3+) phosphor emits a cool-white light. The higher values of the spectroscopic quality factor, stimulated-emission cross-section, quantum efficiency, and the white-light emission of the phosphor suggest that Sr1.0Ba2.0B6O12:0.5Sm(3+) is useful for display and lighting applications. (C) 2020 Elsevier B.V. All rights reserved.

AbstractOur work on new chemiluminescent substances related to the marine luciferin coelenterazine (λmax = 465 nm) led us to attempt the synthesis of four nitrogen-rich pyridopyrazine-bearing analogues. Accordingly, the preparation of the corresponding benzyl-bearing pyridopyrazinols is studied. By varying the conditions for the condensation of phenylpyruvic acid with 1,2-diaminopyridine or 3,4-diaminopyridine, all the possible pyridopyrazin-2-ol regioisomers are isolated and properly characterized, including by means of crystallographic studies. The ensuing syntheses of the halogenated pyridopyrazines are fraught with difficulties ranging from extensive decomposition to an unexpected ring contraction. In one instance, the inherently reductive mixture of phosphorus oxychloride and phosphorus trichloride provides 2-benzyl-3-chloropyrido[2,3-b]pyrazine. This precursor is then transformed into the target O-acetylated luciferin (6,8-dibenzylimidazo[1,2-a]pyrido[3,2-e]pyrazin-9-yl acetate). The ‘benzo’ derivative of this analogue (i.e., 2,12-dibenzylimidazo[1′,2′:1,6]pyrazino[2,3-c]isoquinolin-3-yl acetate) is also prepared and the chemiluminescence emission spectra of these compounds are determined in a phosphate buffer (λmax = 546 and 462 nm).

In our work on the design and studies of luciferins related to the blue-hued coelenterazine, we undertook the synthesis of heterocyclic analogues susceptible to produce a photon, possibly at a different wavelength. We describe here the synthesis of O-acetylated derivatives of imidazo[1,2-b]pyridazin-3(5H)-one, imidazo[2,1-f][1,2,4]triazin-7(1H)-one, imidazo[1,2-a]pyridin-3-ol, imidazo[1,2-a]quinoxalin-1(5H)-one, benzo[f]imidazo[1,2-a]quinoxalin-3(11H)-one, imidazo[1',2':1,6]pyrazino[2,3-c]quinolin-3(11H)-one and 5,11-dihydro-3H-chromeno[4,3-e]imidazo[1,2-a]pyrazin-3-one thanks to an extensive use of the Buchwald-Hartwig N-arylation. The acidic hydrolysis of these derivatives then gave solutions of the corresponding luciferin analogues which we studied. Not too unexpectedly, even if these were "dressed" with substituents found in actual substrates of the nanoKAZ/NanoLuc luciferase, no bioluminescence was observed with these compounds. However, in a phosphate buffer, all produced a light signal, by chemiluminescence, with extensive variations in their respective intensity and this could be increased by adding a quaternary ammonium salt in the buffer. This aspect was actually instrumental to determine the emission spectra of many of these luciferin analogs.

Three new copper(I) complexes [Cu(LX)2]+(PF6-) (where LX stands for 2,9-dihalo-1,10-phenanthroline and X = Cl, Br, and I) have been synthesized in order to study the impact of halogen substituents tethered in the α position of the chelating nitrogen atoms on their physical properties. The photophysical properties of these new complexes (hereafter named Cu-X) were characterized in both their ground and excited states. Femtosecond ultrafast spectroscopy revealed that early photoinduced processes are faster for Cu-I than for Cu-Cl or Cu-Br, both showing similar behaviors. Their electronic absorption and electrochemical properties are comparable to benchmark [Cu(dmp)2]+ (where dmp stands for 2,9-dimethyl-1,10-phenanthroline); furthermore, their optical features were fully reproduced by time-dependent density functional theory and ab initio molecular dynamics calculations. All three complexes are luminescent at room temperature, showing that halogen atoms bound to positions 2 and 9 of phenanthroline are sufficiently bulky to prevent strong interactions between the excited Cu complexes and solvent molecules in the coordination sphere. Their behavior in the excited state, more specifically the extent of the photoluminescence efficiency and its dependence on the temperature, is, however, strongly dependent on the nature of the halogen. A combination of ultrafast transient absorption spectroscopy, temperature-dependent steady-state fluorescence spectroscopy, and computational chemistry allows one to gain a deeper understanding of the behavior of all three complexes in their excited state.

While copper(I)-bis(diimine) complexes [Cu-I(L)(2)](+) are considered as potent substitutes for [Ru-II(bpy)(3)](2+), they exhibit low molar extinction coefficients with respect to ruthenium parent analogues. One interesting possibility to improve the light collection ability of [Cu-I(L)(2)](+) consists in increasing the length of the Cu-L dipole. In order to achieve this goal, we propose in this contribution to fuse aromatic rings onto the 2,9-di-nbutyl-1,10-phenanthroline core and examine how the properties of the corresponding copper(I) complexes are impacted. Electrochemical, absorption and emission properties are assessed; rewardingly, the envisioned approach was successful since extinction coefficients above 10,000 M-1.cm(-1) were measured. All copper(I) complexes remain photoluminescent, with emission maxima greatly varying from 725 to 815 nm, strongly affected by the molecular structures. A rationale to explain the variations of the emission quantum yields is proposed. (C) 2017 Elsevier Ltd. All rights reserved.

An important aspect of the biomechanical behaviour of the stratum corneum (SC) is the drying stresses that develop with water loss. These stresses act as a driving force for damage in the form of chapping and cracking. Betasitosterol is a plant sterol with a structure similar to cholesterol, a key component in the intercellular lipids of the outermost layer of human skin, the SC. Cholesterol plays an important role in stabilizing the SC lipid structure, and altered levels of cholesterol have been linked with SC barrier abnormalities. Betasitosterol is currently applied topically to skin for treatment of wounds and burns. However, it is unknown what effect betasitosterol has on the biomechanical barrier function of skin. Here, by analysing the drying stress profile of SC generated during a kinetics of dehydration, we show that betasitosterol, in combination with two emollient molecules, isocetyl stearoyl stearate (ISS) and glyceryl tri-2-ethylhexanoate (GTEH), causes a significant modulation of the drying stress behaviour of the SC by reducing both the maximal peak stress height and average plateau of the drying stress profile. Raman spectra analyses demonstrate that the combination of betasitosterol with the two emollients, ISS and GTEH, allows a high water retention capacity within the SC, while the lipid conformational order by increasing the amount of trans conformers. Our study highlights the advantage of combining a biomechanical approach together with Raman spectroscopy in engineering a suitable combination of molecules for alleviating dryness and dry skin damage.

A dodecapeptide (AMRKLPDAPGMH) functionalized with a tetramethylrhodamine (TAMRA) chromophore at the N-terminus was immobilized on nanocrystalline TiO2. The optical and binding properties of the peptide layer immobilized on the titania surface were characterized by UV-vis absorption, steady-state fluorescence and X-ray photoelectron spectroscopies. Circular Dichroism experiments and Molecular Mechanics calculations showed that the predominant conformation populated by the peptide scaffold brings Arg3, Lys4 and Asp7 in the correct position for linking the TiO2 surface. Photocurrent generation experiments were therefore carried out to determine the photon-to-current conversion efficiency (IPCE) of a Gratzel-like Dye Sensitized Solar Cell (DSSC), the photoactive unit of which is formed by TAMRA-AMRKLPDAPGMH/TiO2. The measured IPCE amounted to 0.65%, a value that is definitely low, but superior to those previously repoited for similar bioinspired DSSCs. This result can be ascribed to the light-harvesting properties of the TAMRA chromophore and to the unique structural properties of the peptide spacer. (C) 2017 Elsevier B.V. All rights reserved.

BACKGROUND:In vivo Raman spectroscopy is a powerful tool for real-time analysis and in situ evaluation of tissues such as the skin. The efficiency of this technique has been widely demonstrated as a label-free method for in vivo evaluation of the skin. The aim of this study is to gather information about inter- and intra-individual variations in the spectral descriptors of water content and structure, organization of the lipid barrier and structure of proteins in the stratum corneum (SC).METHODS:In vivo SC measurements were performed on 17 female volunteers aged 20-30 years (phototypes I and II). For intra-individual variability, spectral collection was performed on 5 successive days per volunteer. Shapiro-Wilk and Cochran tests were applied to check the normality and the homoscedasticity of variances. ANOVA was then applied to evaluate intra- and intergroup variability.RESULTS:ANOVA was performed on the spectral descriptors of water content and structure, organization of the lipid barrier and secondary structure of proteins in the SC. No significant intra- and interday variability was observed for all volunteers. Despite the low value of the total relative standard deviation, a highly significant variation was observed between volunteers.CONCLUSION:Interindividual variability for Raman measurements is significant for a set of volunteers with normal nondiseased SC and close phototypes. This variability should be taken into consideration as a threshold for significant variance when working in vivo.

Stratum Corneum (SC) is the most superficial layer of the epidermis. It plays the main barrier role against water loss and the aggression of external chemical and biological substances. Thermal treatment in warm purified water followed by trypsin incubation of excised human skin is a well‐established in vitro method for SC removal. Different protocols can be found in literature, but little is described about the effect of temperature and trypsin during isolation process on its barrier function.

The degradation mechanisms of Reverse Bias (RB) stressed Dye Solar Cells (DSCs), sensitized with cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium (N719, Red Dye) and with cis-dicyano-bis(2,2′-bipyridyl-4,4′-dicarboxylic acid) ruthenium(II) (Ru505, Orange Dye) have been studied by means of resonance micro-Raman and UV-Vis spectroscopy. For N719 sensitized devices, the visible degradation induced by the stress tests involves both electrolytic solution and the sensitizer: the electrolyte suffers gas bubble formation and loss of solvent, while the dye cannot be regenerated and undergoes irreversible chemical changes. Confocal Raman imaging and UV-Vis absorption spectra confirmed that in regions where the electrolyte was absent, the detachment of the thiocyanate ligand (SCN−) from the dye is favored. On the other hand, measurements carried out on DSCs realized with the bis-cyano dye (Ru505) do not show dye modifications during the RB stress. We also clarify that the apparent N719 dye bleaching in particular zones of the cell active area, is not related to dye desorption from the TiO2 layer, but to loss of solvent and to dye chemical changes, which are responsible for a characteristic blue shift in the absorption spectrum.

A bioinspired approach is applied to photoelectric conversion devices. A 3(10)-helical hexapeptide bearing a pyrene unit is immobilized on a gold-covered TiO2 surface. The device is integrated for the first time in a dye-sensitized solar cell, exhibiting stability after several measurements. The approach could have promising applications in the field of optoelectronics.

We show that SiGe islands are transformed into nanoholes and rings solely by annealing treatments and without Si capping. Rings are produced by a rapid flash heating at temperatures higher than the melting point of Ge, whereas nanoholes are produced by several minutes of annealing. The rings are markedly rich in Si with respect to the pristine islands, suggesting that the evolution path from islands to rings is driven by the selective dissolution of Ge occurring at high temperatures. (C) 2013 Elsevier B.V. All rights reserved.

In this work, the effect of reverse bias stress tests on Dye Solar Cells (DSCs) based on N719 dye was investigated in detail using resonant micro-Raman spectroscopy. First the Raman lines were assigned to vibrations from the different constituents in a fresh solar cell. Then the mechanism of thiocyanato (SCN−) loss under stress conditions was reported.

We have prepared new polyesters containing quadratic, nonlinear optical (NLO) active chromophores covalently incorporated into the main chain. In these polymers, the sequence of the chromophore units along the main chain is rigorously head to tail. All the polyesters are processable, both in the melt and in solution. For one polyester, a full second-order NLO characterization has been performed. An out-of-resonance d(33) coefficient of 21 pm/V at 1368 nm has been measured. (c) 2007 Wiley Periodicals, Inc.

Polymethacrylate and polycondensated polymers based on chromophores containing the s-triazolo[3,4-b]-thiadiazole heterocycle were synthesized. Chromophore and polymer preparations are described. Second order NLO measurements are reported for polymers and for one functionalized chromophore. The maximum value of second harmonic generation coefficient (d33) measured is 11.5pm/V at incident laser wavelength of 1368nm. For the most active polymer, 85% of the initial d33 value is retained after 27 days at 80°C.

A guest-host polymer system with potential use in electro-optic devices is discussed. The polymer host is a high Tg, fully aromatic polyimide and the guest chromophore is disperse red 19. Relaxation mechanisms of polar order after electric field alignment procedure have been investigated by measuring the isothermal decay of the macroscopic nonlinear optical coefficient d333 at different temperatures below glass transition temperature (Tg), upon the removal of the poling electric field. All the decay curves can be fitted by a double exponential function. Below Tg, the slower relaxation time shows an Arrhenius temperature dependence. An extrapolation to room temperature allows to predict the time stability which results to be longer than 30years. In addition, absorption spectra measurements of the films were performed before and immediately after poling procedure to estimate independently the polar order of the dipoles through the decrease of the absorption coefficients.

Two NLO azo-benzimidazolic chromophores, bis-ethanol, 2,2′-[[4-[[4-(1-ethyl-6-nitro-1H-benzimidazol-2-yl)phenyl]azo]phenyl]imino] (BZI1) and bis-ethanol, 2,2′-[[4-[[4-[(1E)-2-(1-ethyl-6-nitro-1H-benzimidazol-2-yl)ethenyl]phenyl]azo]phenyl]imino] (BZI2), properly functionalised for polycondensation reactions, have been used for the synthesis of new NLO polyurethanes and polyesters. The polymers have high thermal stability and Tg ranging between 146 and 173°C. Thin films of polymers have been prepared and oriented by electrical poling. The resonance free NLO activity has been measured at a fundamental wavelength of 1368nm by second harmonic generation (SHG) and a maximum d33 of 2.3 pm/V has been observed. Polymers containing the less active chromophore (BZI1, μβ=950×10−48esu) show higher d33 value than the analogous polymers containing BZI2 chromophore (μβ=1400×10−48). A theoretical analysis suggests that this unexpected behaviour can be only partially attributed to thermodynamic effects, dynamical effects should also play a role.