Ultraviolet light

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

Photochromism of 1,2-Bis(2,5-dimethyl-3-thienyl)perfluoro- cyclopentene in a Single Crystalline Phase

Abstract: 1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (1a) was found to undergo photochromism in a single crystalline phase. Upon irradiation with ultraviolet light the colorless crystal turned red with keeping the crystal shape. The red color is due to the closed-ring form 1b. The red color was bleached by irradiation with visible light (λ > 450 nm). The intensity of the red color observed under polarized light dramatically changed by rotating the crystal sample, and the order parameter was as high as 0.84. The high order parameter confirmed that the molecules undergo photochromism in the crystalline lattice. The direction of the electronic transition moment of 1b estimated from the absorption anisotropy at 535 nm agreed with the long axis of 1a packed in the crystal, which was determined by X-ray crystallographic analysis. The movement of each atom of the molecule in the crystal during the cyclization reaction was estimated by comparing the structures of 1a and 1b, both of which were determined by X-ray ...

Synthesis of Graphene-ZnO-Au Nanocomposites for Efficient Photocatalytic Reduction of Nitrobenzene

Abstract: A simple hydrothermal method of preparing highly photocatalytic graphene-ZnO-Au nanocomposites (G-ZnO-Au NCs) has been developed. Zinc acetate and graphene oxide are reduced by catechin to form graphene-zinc oxide nanospheres (G-ZnO NSs; average diameter of (45.3 ± 3.7) nm) in the presence of ethylenediamine (EDA) as a stabilizing agent and gold nanorods (Au NRs) at 300 °C for 2 h. Then Au NRs are deposited onto as-formed G-ZnO NSs to form G-ZnO-Au NCs. Upon ultraviolet light activation, G-ZnO-Au NCs (4 mg mL–1) in methanol generates electron–hole pairs. Methanol (hydroxyl group) assists in trapping holes, enabling photogenerated electrons to catalyze reduction of nitrobenzene (NB) to aniline with a yield of 97.8% during a reaction course of 140 min. The efficiency of G-ZnO-Au NCs is 3.5- and 4.5-fold higher than those provided by commercial TiO2 and ZnO NSs, respectively. Surface assisted laser desorption/ionization mass spectrometry has been for the first time applied to detect the intermediates (nitros...

First occurrence of Culicoides obsoletus-transmitted Bluetongue virus epidemic in Central Europe

Abstract: In August 2006, Bluetongue virus disease (BTD) was detected for the first time in the Netherlands, Belgium, Germany and Northern France. Serological tests as well as reverse transcriptase polymerase chain reaction (RT-PCR) proved the occurrence of Bluetongue virus (BTV) in diseased sheep and cattle, and the virus was identified as serotype 8. Therefore, the search for possible vectors was immediately initiated in the outbreak region in Germany. Traps with automatically regulated ultraviolet light lamps were placed at two different farms with sero-positive cattle, and insect monitoring was done from August 2006 until January 2007. The caught arthropods were weekly determined, and it could be observed that midges of the dipteran family Ceratopogonidae occurred in large numbers, sometimes representing up to 40% of all individuals. The microscopical analysis of the wing morphology showed that the species (complex) Culicoides obsoletus was most abundant covering about 97% of the analysed midges. On the second place ranged C. pulicaris, while C. nubeculosus and C. festivipennis were found only as single individuals. Fed and unfed females were separated, sent to the National Reference Laboratory for Bluetongue disease (Friedrich-Loeffler-Institut, Isle of Riems, Germany) and investigated with a BTV-8-specific real-time RT-PCR. It could be demonstrated that at both farms both fed and unfed C. obsoletus were tested positive for BTV-8 genomes, while none of the other species scored positive. This finding strongly supports that the BTD-epidemic, which reached in the meantime wide regions of North Rhine-Westphalia in Germany and of the neighbouring countries with several hundreds of affected farms, is initiated by virus transmission during the blood meal of midges of the C. obsoletus complex. Since they were captured still at the 21st of December close to cattle with clinical signs, it must be feared that BTV-8 is now established in Central Europe, where it had been absent until now.

Synthesis and processing of silicon nanocrystallites using a pulsed laser ablation supersonic expansion method

Abstract: We report the preparation of nanometer sized crystallites of silicon by a pulsed laser ablation supersonic expansion technique. High resolution transmission electron microscopy is used to verify that particles with diameter in the range of ∼3 nm and greater are produced. Glancing angle x‐ray diffraction results confirm that the particles formed have the silicon diamond cubic crystal structure. Visible photoluminescence emission from self‐supporting thin films of agglomerated nanocrystallites is observed under excitation with ultraviolet light.