How does the skin sense sun light? An integrative view of light sensing molecules

The consensus on the effects of excessive sun exposure on human health has long emphasized the negative effects of solar UV radiation. Nevertheless, although UV radiation has been demonized, less is known about the consequences of sun exposure while using sunscreen, which can lead to high visible light exposure. UV and visible light play key roles in vitamin D synthesis, reduction of blood pressure, among other beneficial effects. In this review, we aim to provide a comprehensive view of the wide range of responses of the human skin to sunlight by revisiting data on the beneficial and harmful effects of UV and visible light. We start by exploring the interaction of photons in the skin at several levels including physical (depth of photon penetration), chemical (light absorption and subsequent photochemical events), and biological (how cells and tissues respond). Skin responses to sun exposure can only be comprehensively understood through a consideration of the light-absorbing molecules present in the skin, especially the light-sensing proteins called opsins. Indeed, many of the cellular responses to sun exposure are modulated by opsins, which act as the “eyes of the skin”.     

Recent Progress toward white organic light emitting diodes

An efficient and stable white organic light emitting diode (WOLED) is highly desirable in potential applications such as lighting, background light source, and full color display. A series of highly fluorescent dyes based on a dipyrazolopyridine skeleton, 1,7-diphenyl-1,7-dihydrodipyrazolo[3,4-b,4',3'-e]pyridine, were synthesized and evaluated as emitting as well as charge-transporting material in the fabrication of electroluminescent devices. Several of the blue derivatives are found to be …     

The XIth International symposium “polymers and light”

Information Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences Held with the Participation of the Russian Academy of Sciences

The XIth International symposium polymers and light     

Synthesis and light absorption of benzotellurazole crown ether cyanine dye

Various methods for synthesis of 2-methyl-5,6-(1,4,7,10,13-pentaoxatridecamethyl-ene)benzotellurazole (8) are described. Under different conditions, alkylation of compound 8 with methyl iodide gave telluronium salt 1,2-dimethyl-5,6-(1,4,7,10,13-pentaoxatridecamethylene)benzo-tellurazolium iodide (15) or quaternary ammonium salt 2,3-dimethyl-5,6-(1,4,7,10,13-pentaoxatri-decamethylene)benzotellurazolium iodide (14) in high yields, repectively. The cyanine dye 3,3'-dimethyl-5,6,5',6'-bis(1,4,7,10,13-pentaoxatridecamethylene)telluracarbocyanine iodide (16) is obtained by condensation of 14 with ethyl orthoformate in acetic anhydride. The visible absorption of the cyanine dye is also discussed.     

Cellulose-TiO2 nanocomposite with enhanced UV–Vis light absorption

TiO₂/N-cellulose nanocomposite was successfully prepared in the (cyclohexyl)hexyl-dimethylammonium acetate–dimethyl sulfoxide solution. The obtained composite was characterized with various techniques like UV–Vis/DR, FTIR/DRS, X-ray diffraction, thermogravimetric analysis, DLS method and BET SSA measurements. TiO₂/N-cellulose nanocomposite exhibited high UV–Vis light absorption with energy gap shifted to the visible region. Additive of TiO₂/N photocatalyst to cellulose-IL-DMSO solution leads to obtaining the material with higher thermostability and limited photoactivity.     

Rayleigh and Raman light scattering in hydrogen-bonded acetonitrile–water

The structure, vibrational frequencies, light scattering activities and binding energies of CH₃CNH₂O are obtained from ab initio methods. The hydrogen NH bond distance is calculated as 2.06 Å, the dipole moment as 5.77 D and our best estimate for the binding energy is 3.5 kcal mol^–1 (14.7 kJ mol^–1), after correcting for zero-point vibrations. The calculated average dipole polarizability is 39.67 au and the anisotropy is fairly large, corresponding to 21.78 au. The changes in intramolecular vibrational frequencies are analyzed. The scattering activities and depolarization of the Rayleigh and Raman light scattered are calculated. In the Raman case the depolarization due to the intense NC stretching vibration is increased by 20% after the hydrogen bond. For the OH symmetric stretch of water there is a large redshift of 75 cm^–1 and a great intensification of the Raman scattering activity by a factor of 2 and a considerable increase of the depolarization by a factor of nearly 4.From the Proceedings of the 28th Congreso de Químicos Teóricos de Expresión Latina (QUITEL 2002)     

Clustering properties of partly charged superfine particles in a light medium

This paper investigated average cluster sizes （ACS） and cluster size distributions （CSD） at different shear rates by Brownian dynamics in non-, bi-, and uni-polar systems with partly charged superfine particles, The investigation indicates that clusters in non- polar systems are the weakest and easiest to be damaged by increasing shear stresses; charged particles play important and different roles： in bi-polar system, it intends to strengthen clusters to some extent provided that the sign-like ions homogeneously arranged; in uni-polar system charged particles cracked the clusters into smaller ones, but the small clusters are strong to stand with larger shear stress. The relationship between ACS and shear rates follows power law with exponents in a range 0.18-0.28, these values are in a good agreement with experiment range but at the lower limit compared with other systems of non-metallic cluster particles.     

A chiral π-stacked vinyl polymer emitting white circularly polarized light

An optically active, π-stacked poly[2,7-bis(4-tert-butylphenyl)dibenzofulvene] having a preferred-handed helical conformation was synthesized by anionic polymerization. A thin film sample of the polymer exhibited broad-band white circularly polarized light (CPL) emission on photo excitation.     

Dynamical and allosteric regulation of photoprotection in light harvesting complex Ⅱ

Major light-harvesting complex of photosystem Ⅱ(LHCⅡ) plays a dual role in light-harvesting and excited energy dissipation to protect photodamage from excess energy. The regulatory switch is induced by increased acidity, temperature or both. However,the molecular origin of the protein dynamics at the atomic level is still unknown. We carried out temperature-jump time-resolved infrared spectroscopy and molecular dynamics simulations to determine the energy quenching dynamics and conformational changes of LHCⅡ trimers. We found that the spontaneous formation of a pair of local α-helices from the 310-helix E/loop and the C-terminal coil of the neighboring monomer, in response to the increased environmental temperature and/or acidity, induces a scissoring motion of transmembrane helices A and B, shifting the conformational equilibrium to a more open state, with an increased angle between the associated carotenoids. The dynamical and allosteric conformation change leads to close contacts between carotenoid lutein 1 and chlorophyll pigment 612, facilitating the fluorescence quenching. Based on these results, we suggest a unified mechanism by which the LHCⅡ trimer controls the dissipation of excess excited energy in response to increased temperature and acidity, as an intrinsic result of intense sun light in plant photosynthesis.     

A pure blue light emitting binaphthyl derivative：Synthesis and properties

A binaphthyl derivative with pyrene on 3 and 3＇ positions was synthesized and characterized via Suzuki coupling reaction. Emission maximum in solution was located at 390 nm with a quantum efficiency of 68% by taking 9,10-diphenyl anthracene as reference,while it is shifted to 450 nm with FWHM of 104 nm resulting from aggregation state in solid film.Glass transition temperature（Tg）and decomposition temperature were measured to be 184 and 447℃,respectively,by DSC and TGA.Unlike its photoluminescence spectrum,electroluminescent spectrum peaked at about 460 nm and shows a FWHM of 69 nm corresponding to a pure blue emission.The turn-on voltage,luminance and efficiency maximum were 5 V,2953 cd/m^2 and 1.37cd/A with CIE color coordinate of（0.16,0.15）,in the device structure of ITO/NPB（40nm）/PY-BN-PY（15nm）/BPhen（40nm）/Mg：Ag.     

Hindered amine light stabilisers—Interactions with transition and non-transition metals

Experiments have shown that hindered amine light stabilisers (HALS) are able to complex strongly with transition metal ions. During this reaction, in air, there is a marked tendency for oxidation of the metal ion species and the reaction is shown to be general across the first transition series. Using these results, in addition to evidence from other work, a scheme is proposed whereby these HALS, because of their complexing ability, will act as photo-oxidation stabilisers for polymers.Preliminary results show that HALS are also able to complex with non-transition metals.     

CCQM primary methods symposium: how far does the light shine?

The Consultative Committee for Amount of Substance (CCQM) has the task of organizing a comprehensive set of international comparisons to establish the technical basis for the mutual recognition of measurement capabilities among the national measurement institutes (NMIs) in the field of chemical measurement. The challenge that the CCQM faces is to identify, design, and conduct a limited number of key comparisons to enable the assessment of measurement comparability among NMIs across the entirety of ’chemical measurement space’. This is no easy task because the field of chemical metrology is extremely diverse and multidimensional, owing to the number of measurand types, concentrations, and matrix types of importance. The ”CCQM primary methods symposium: how far does the light shine?” was organized to provide information and initiate discussions to assist in this challenge, and clarify how the concept of a primary method of measurement could be instrumental in achieving this goal.     

Photocatalytic activity of sea water using TiO₂ catalyst under solar light

Wastewater is generally released into the rivers and streams in developing countries. Industrial wastewater usually contains highly toxic pollutants, cyanides, chlorinated compounds. Ultraviolet (UV) radiation from sunlight also decomposes organic compounds by oxidation process. However, the process is less effective due to large amount of toxic effluent entering in the main stream of water. The solar radiation can effectively be applied to accelerate the process by using suitable catalyst for economically cleaning the water sources. This paper describes the photocatalytic degradation of the sea water using novel approach of photoelectrochemical (PEC) reactor module consisting of nine photoelectrochemical cells equipped with spray deposited TiO? catalysts under solar light. The resulted water samples were studied for physicochemical and bacteriological analysis. The complete mineralization of degraded sample was confirmed by total organic carbon (TOC) analysis, COD measurement and estimation of the formation of inorganic ions such as NH?(+), NO??, Cl? and SO2??. Microbiological examinations are performed to determine the bacterial analysis. This implies that photoelectrocatalysis could be a promising way for improving water quality in developing countries with low cost and clean energy reliable resource.     

Advances in the determination of hindered amine light stabilizers – A review

Within this paper we discuss analytical strategies for the characterization and quantitation of hindered amine light stabilizers (HALS) an important sub-group of polymer additives. For the determination of monomeric HALS a range of mature and reliable techniques exists, allowing their determination in polymer extracts. If qualitative or semi-quantitative information suffices, certain techniques are capable of sampling directly from the polymer surface with limited or no sample preparation. Different strategies for the determination of complex oligomeric HALS in extracts from polymer samples are discussed. Here, approaches providing only a sum parameter including all HALS oligomers have been distinguished from more sophisticated technologies allowing the determination of single oligomers, their degradation and by-products. Particularly, the latter issue is facing increased interest as it provides important information for polymers aging studies. A tabulated overview provides comprehensive information on different analytical techniques suitable for HALS determination.     

Visible light photocatalysis by a Titania–Rhodium(III) complex

Titania hybrid photocatalysts containing 0.5, 1.0, 2.0, and 5.0 wt% of rhodium(III) were prepared by chemisorption of RhCl₃ × 3H₂O onto anatase hydrate powder (TH). Analytical data suggest that a titania–trichlororhodate complex is produced containing a [TiO₂]–O–Rh bond.Similar results are found in the case of modification by RhBr₃ × 3H₂O. Diffuse reflectance spectra exhibit an absorption shoulder throughout the visible region down to 700 nm. Photoelectrochemical measurements indicate that the quasi-Fermi level of electrons is gradually shifted to more anodic potentials with increasing rhodium loading reaching a value of ?0.34 V at pH 7 (vs. NHE) in the case of 5.0%RhCl₃/TH. This is more anodic by 210 mV as compared to unmodified TH. Upon visible light irradiation this photocatalyst induces a fast mineralization of 4-chlorophenol whereas cyanuric acid, which is known to be mineralized in the presence of the analogous Pt(IV) modified titania, is not degraded.     

Simple preparation of Mn–N-codoped titania photocatalyst with visible light response

Mn–N-codoped TiO₂ nanocrystal photocatalysts responsive to visible light were synthesized for the first time by a simple hydrothermal synthesis method. X-ray powder diffraction (XRD) measurement indicated that all the photocatalysts have an anatase crystallite structure, and that increase of the doping concentration had little effect on the structure and particle size. Compared to N-doped TiO₂, a shift of the absorption edge of Mn–N-codoped TiO₂ to a lower energy and a stronger absorption in the visible light region were observed. The Mn–N-codoped TiO₂ showed higher photocatalytic reactivity than undoped TiO₂ or N-doped TiO₂ for the photodegradation of rhodamine B (RhB) under visible light irradiation. The highest photocatalytic activity was achieved on 0.4 mol% Mn–N–TiO₂ calcined at 673 K.     

A new spectrum technique based on direct detection of light intensity absorbed

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Synthesis, characterization and antibacterial properties of multifunctional hindered amine light stabilizers

A series of novel hindered amine light stabilizers containing an N-halamine moiety were designed and synthesized. Their structures were characterized by FT-IR, 1H NMR, and MS. The compounds were tested for antibacterial activity against Candida albicans, Staphylococcus aureus, and Escherichia coll. At a concentration of 0.5 mmol/L, these compounds all exhibited satisfactory antibacterial activity against all the three types of bacteria.     

Visible light–driven photoelectrocatalytic semiconductor heterojunction anodes for water treatment applications

Research interest in photoelectrocatalysis or photoelectrochemical oxidation processes for water treatment is on the increase. This is because this method has the ability to abate a wide range of recalcitrant organic pollutants from wastewater. The application of visible or solar light, which has the potential to reduce cost, increase safety, and increase sustainability, is a recent direction in this novel electrochemical technology for water treatment. This review focuses on the use of semiconductor heterojunctions as a way of tuning the photoanode towards visible light activation. The classifications, preparations and various applications of semiconductor heterojunction for the removal of organic pollutants from water in the past two years are presented with concluding remarks and future perspective.