RESUMEN
V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ËO2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability.
Asunto(s)
Tierra de Diatomeas , Titanio , Vanadio , Contaminantes Químicos del Agua/química , Adsorción , Catálisis , Colorantes/química , Tierra de Diatomeas/química , Tierra de Diatomeas/efectos de la radiación , Fotólisis , Reciclaje , Rodaminas/química , Luz Solar , Titanio/química , Titanio/efectos de la radiación , Vanadio/química , Vanadio/efectos de la radiación , Purificación del AguaRESUMEN
Eight alkali metal ion-mediated dioxidovanadium(v), [{V(V)O2L(1-6)}A(H2O)n]â, complexes for A = Li(+), Na(+), K(+) and Cs(+), containing tridentate aroylhydrazonate ligands coordinating via ONO donor atoms, are described. All the synthesised ligands and the metal complexes were successfully characterised by elemental analysis, IR, UV-Vis and NMR spectroscopy. X-ray crystallographic investigation of 3, 5-7 shows the presence of distorted NO4 coordination geometries for LVO2(-) in each case, and varying µ-oxido and/or µ-aqua bridging with interesting variations correlated with the size of the alkali metal ions: with small Li(+), no bridging-O is found but four ion aggregates are found with Na(+), chains for K(+) and finally, layers for Cs(+). Two (5) or three-dimensional (3, 6 and 7) architectures are consolidated by hydrogen bonding. The dioxidovanadium(v) complexes were found to exhibit DNA binding activity due to their interaction with CT-DNA by the groove binding mode, with binding constants ranging from 10(3) to 10(4) M(-1). Complexes 1-8 were also tested for DNA nuclease activity against pUC19 plasmid DNA which showed that 6 and 7 had the best DNA binding and photonuclease activity; these results support their good protein binding and cleavage activity with binding constants ranging from 10(4) to 10(5) M(-1). Finally, the in vitro antiproliferative activity of all complexes was assayed against the HeLa cell line. Some of the complexes (2, 5, 6 and 7) show considerable activity compared to commonly used chemotherapeutic drugs. The variation in cytotoxicity of the complexes is influenced by the various functional groups attached to the aroylhydrazone derivative.
Asunto(s)
Antineoplásicos , Complejos de Coordinación , Metales Alcalinos , Vanadio , Antineoplásicos/química , Antineoplásicos/farmacología , Antineoplásicos/efectos de la radiación , Supervivencia Celular/efectos de los fármacos , Dicroismo Circular , Complejos de Coordinación/química , Complejos de Coordinación/farmacología , Complejos de Coordinación/efectos de la radiación , ADN/química , ADN/metabolismo , División del ADN , Células HeLa , Humanos , Ligandos , Metales Alcalinos/química , Metales Alcalinos/farmacología , Metales Alcalinos/efectos de la radiación , Estructura Molecular , Unión Proteica , Albúmina Sérica Bovina/metabolismo , Albúmina Sérica Bovina/efectos de la radiación , Rayos Ultravioleta , Vanadio/química , Vanadio/farmacología , Vanadio/efectos de la radiaciónRESUMEN
A photoelectric switch with fast response to visible light (<200 µs), suitable photosensitivity and excellent repeatability is proposed based on the ultralong single crystalline V2O5 nanobelt, which are synthesized by chemical vapor deposition and its photoconductive mechanism can well be explained by small polaron hopping theory. Our results reveal that the switch has a great potential in next generation photodetectors and light-wave communications.
Asunto(s)
Electrónica , Nanopartículas/química , Nanopartículas/ultraestructura , Refractometría/instrumentación , Procesamiento de Señales Asistido por Computador/instrumentación , Vanadio/química , Vanadio/efectos de la radiación , Simulación por Computador , Diseño Asistido por Computadora , Campos Electromagnéticos , Diseño de Equipo , Análisis de Falla de Equipo , Luz , Modelos Teóricos , Dispersión de RadiaciónRESUMEN
YVO(4) photocatalysts with different grain sizes were obtained by annealing the YVO(4) nanopowders synthesized via microwave irradiation. The products were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), surface area and porosity analyzer, and ultraviolet-visible (UV-vis) spectrophotometer. Photocatalytic measurements showed that the YVO(4) nanopowders with grain size of about 5 nm possess superior photocatalytic properties in decolorization of methyl orange solution.
Asunto(s)
Nanopartículas/química , Vanadio/química , Itrio/química , Compuestos Azo/química , Compuestos Azo/efectos de la radiación , Catálisis , Color , Colorantes/química , Colorantes/efectos de la radiación , Microondas , Nanopartículas/efectos de la radiación , Fotoquímica , Polvos , Rayos Ultravioleta , Vanadio/efectos de la radiación , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/efectos de la radiación , Purificación del Agua/métodos , Itrio/efectos de la radiaciónRESUMEN
Methane activation by group 5 transition-metal atoms in excess argon and the matrix infrared spectra of reaction products have been investigated. Vanadium forms only the monohydrido methyl complex (CH3-VH) in reaction with CH4 and upon irradiation. On the other hand, the heavier metals form methyl hydride and methylidene dihydride complexes (CH3-MH and CH2=MH2) along with the methylidyne trihydride anion complexes (CHMH3-). The neutral products, particularly the methylidene complex, increase markedly on irradiation whereas the anionic product depletes upon UV irradiation or addition of a trace of CCl4 or CBr4 to trap electrons. Other absorptions that emerge on irradiation and annealing increase markedly at higher precursor concentration and are attributed to a higher-order product ((CH3)2MH2)). Spectroscopic evidence suggests that the agostic Nb and Ta methylidene dihydride complexes have two identical metal-hydrogen bonds.
Asunto(s)
Metano/química , Niobio/química , Compuestos Organometálicos/síntesis química , Compuestos Organometálicos/efectos de la radiación , Tantalio/química , Vanadio/química , Argón/química , Rayos Láser , Metano/efectos de la radiación , Niobio/efectos de la radiación , Compuestos Organometálicos/química , Tantalio/efectos de la radiación , Rayos Ultravioleta , Vanadio/efectos de la radiaciónRESUMEN
K2NaScF6 crystals codoped with V3+ and Er3+ exhibit some novel cooperative near-IR to visible upconversion processes at cryogenic temperatures. V3+ mainly acts as a broadband sensitizer. The V3+ 3T1g --> 3T2g excitation between 13,500 and 15,500 cm(-1), after fast relaxation to V3+ 1T2g, can be transferred to Er3+ 4I(11/2), and then upconversion takes place. Four upconversion mechanisms are identified and characterized. For narrow-band laser excitation the overall efficiency of the upconversion processes is low. However, at 12 K for broadband excitation, such as in a lamp, between 12,000 and 14,500 cm(-1) the number of emitted visible photons is roughly doubled by codoping V3+ in addition to Er3+.
Asunto(s)
Erbio/química , Minerales/química , Vanadio/química , Erbio/efectos de la radiación , Transferencia Lineal de Energía , Minerales/efectos de la radiación , Dosis de Radiación , Vanadio/efectos de la radiaciónRESUMEN
High-resolution mass spectrometry indicates that the isotopic abundance of 50V of the Late Cretaceous La Luna petroleum asphaltenes of marine origin (highly enriched with V > 2000 ppm) is higher by about 3.5% than that of the inorganic source (VOSO4 x 5H2O, Merck). We propose that the difference in the 50V/51V values between the La Luna petroleum asphaltenes and the inorganic source can be best ascribed to the biological processing of seawater vanadium. The fact that the V isotopic compositions of petroleum asphaltenes vary over a very narrow range (2.46-2.52) suggests essentially the same (or similar) and fixed biological source of vanadium.
Asunto(s)
Hidrocarburos/química , Petróleo , Vanadio/química , Isótopos , Espectrometría de Masas/métodos , Vanadio/efectos de la radiación , VenezuelaRESUMEN
A companion paper describes a predictive ion parametric resonance (IPR) model of magnetic field interactions with biological systems based on a selective relation between the ratio of the flux density of the static magnetic field to the AC magnetic field and the charge-to-mass ratio of ions of biological relevance. Previous studies demonstrated that nerve growth factor (NGF)-stimulated neurite outgrowth (NO) in PC-12 cells can be inhibited by exposure to magnetic fields as a function of either magnetic field flux density or AC magnetic field frequency. The present work examines whether the PC-12 cell response to magnetic fields is consistent with the quasi-periodic, resonance-based predictions of the IPR model. We tested changes in each of the experimentally controllable variables [flux densities of the parallel components of the AC magnetic field (Bac) and the static magnetic field (Bdc) and the frequency of the AC magnetic field] over a range of exposure conditions sufficient to determine whether the IPR model is applicable. A multiple-coil exposure system independently controlled each of these critical quantities. The perpendicular static magnetic field was controlled to less than 2 mG for all tests. The first set of tests examined the NO response in cells exposed to 45 Hz Bac from 77 to 468 mG(rms) at a Bdc of 366 mG. Next, we examined an off-resonance condition using 20 mG Bdc with a 45 Hz AC field across a range of Bac between 7.9 and 21 mG(rms). Finally, we changed the AC frequency to 25 Hz, with a corresponding change in Bdc to 203 mG (to tune for the same set of ions as in the first test) and a Bac range from 78 to 181 mG(rms). In all cases the observed responses were consistent with predictions of the IPR model. These experimental results are the first to support in detail the validity of the fundamental relationships embodied in the IPR model.