Ultraviolet light

About: Ultraviolet light is a research topic. Over the lifetime, 49494 publications have been published within this topic receiving 843151 citations.

5,6-Saturated thymine lesions in DNA: production by ultraviolet light or hydrogen peroxide

Abstract: Thymine analogs with saturated 5-6 bonds are important types of DNA damage that are recognized by the DNA N-glycosylase activity of E. coli endonuclease III. Seeking agents which could preferentially form 5,6-hydrated thymine residues in duplex DNA both in vivo and in vitro, we exposed purified duplex DNA to 325- or 313-nm light; however, after such exposure pyrimidine dimers greatly predominated over 5,6-hydrated thymine. Hydrogen peroxide, on the other hand, formed significant numbers of endonuclease III-sensitive sites in vitro which were not apurinic/apyrimidinic lesions and thus were likely to be 5,6-hydrated thymines.

Photocatalytic uphill conversion of natural gas beyond the limitation of thermal reaction systems

Abstract: Dry reforming of methane is one of the key reactions to exploit natural gas feedstocks by their catalytic conversion to synthesis gas (CH4 + CO2 → 2H2 + 2CO), which is used in the production of transportable liquid fuel. However, this reaction suffers from thermodynamic conversion limits and high thermal energy requirements. Herein we report that a SrTiO3-supported rhodium (Rh/STO) catalyst efficiently promotes methane reforming under ultraviolet light irradiation without heat supply at low temperatures, which cannot be achieved by conventional thermal catalysis. The photoexcited holes and electrons are used for CH4 oxidation over STO and CO2 reduction over rhodium, respectively. Isotope analysis clarified that the lattice oxygens (O2−) act as mediator to drive dry reforming of methane. The materials design of Rh/STO can be extended in principle to diverse uphill reactions that utilize photon energy to obtain valued products from different carbon resources. Despite its potential, catalytic dry reforming of methane has not yet reached practical application due to high thermal energy requirements. Now, a photocatalytic method is introduced based on strontium titanate-supported rhodium nanoparticles that afford syngas production solely under light irradiation.

Direct Splitting of Water under Visible Light Irradiation with an Oxide Semiconductor Photocatalyst.

Abstract: The photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting, or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide, were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light, which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium-tantalum-oxide with nickel yields a series of photocatalysts, In(1-x)Ni(x)TaO(4) (x = 0-0.2), which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66%. Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.

Praseodymium oxide nanostructures: novel solvent-less preparation, characterization and investigation of their optical and photocatalytic properties

Abstract: Praseodymium oxide (Pr6O11) nanostructures were prepared via a new simple solvent-less route. The nanostructures were synthesized by a heat treatment in air at 600 °C for 5 h, using [Pr L(NO3)2]NO3 (L = bis-(2-hydroxy phenyl methyl ketone)-dipropylene triamin Schiff base ligand), as a precursor, which was obtained by a solvent-free solid–solid reaction from different molar ratios of praseodymium nitrate and a Schiff base ligand. The as-prepared nanostructures were characterized by means of several techniques including X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), nuclear magnetic resonance spectroscopy (1H NMR) analysis, UV-vis diffuse reflectance spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The obtained results showed that the morphology and particle size of the final Pr6O11 could be dramatically affected via the molar ratio of praseodymium nitrate and the Schiff base ligand. The photocatalytic activity of the as-synthesized nanostructures was also investigated by the degradation of 2-naphthol as an organic contaminant under ultraviolet light irradiation.