Structural Investigation of Vanadyl-Acetylacetonate-Containing Precursors of TiOx−VOx Mixed Oxides on SBA-15

V2O5/SBA-15 nanocatalysts for the selective synthesis of 2,3,5-trimethyl-1,4-benzoquinone at room temperature

The molecular designed dispersion method yielded monodispersed nanoscale (4–7.5 nm sized) V₂O₅ dimeric species on SBA-15, which oxidized TMP into TMBQ with H₂O₂ under green conditions.

Effects of copper and vanadium deposition in multi-walled hydrogen trititanate and mixed-phase anatase/trititanate nanotubes

Metal incorporation and doping is one of the routes commonly explored to improve visible light photocatalytic activity of titania and related materials. In this work, we explore the effect of copper and vanadium deposition and incorporation in multi-walled hydrogen trititanate and mixed-phase anatase/trititanate nanotubes. The molecular designed dispersion method is used to introduce the metals in the materials. Electron paramagnetic resonance facilitates a full characterization of the metal sites before and after calcination and allows determining the UV- and visible-light-induced formation of paramagnetic intermediates. Vanadium or copper deposition on the tubes leads to increased formation of F(+) centres under visible or UV illumination. The EPR results are linked to the activity towards rhodamine 6G photobleaching of the different materials.

Structure and bonding of [V(IV)O(acac)(2)] on the surface of AlF(3) as studied by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy

Well defined isolated [V(IV)O(acac)(2)] surface complexes have been prepared on aluminium trifluoride, alpha-AlF(3), as solid support by equilibrium adsorption from liquid solution. The paramagnetic vanadium(iv) surface complexes were studied by pulsed electron spin resonance spectroscopy in combination with quantum chemical calculations using density functional theory. (19)F and (27)Al ligand hyperfine interactions with the nuclei of the AlF(3) support observed by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy experiments verify the direct chemical bonding between the vanadium and a surface fluorine atom. Detailed analysis of the ligand hyperfine couplings supported by quantum chemical calculations indicates that the axial position of [V(IV)O(acac)(2)]trans to the oxo ligand is bound directly to a terminal fluorine atom of the support. Analysis of the (1)H ligand hyperfine interaction revealed that an acidic H(+) of the AlF(3) surface protonated a donor oxygen of the acetylacetone ligand in the surface complex.

Vanadium Silicalite-1 Nanoparticles Deposition onto the Mesoporous Walls of SBA-15. Mechanistic Insights from a Combined EPR and Raman Study

Continuous Wave (CW) and pulsed Electron Paramagnetic Resonance (EPR) spectroscopy in conjunction with Raman spectroscopy are used to investigate the properties of Vanadium Silicalite-1 (VS-1) nanoparticles dispersed onto the mesoporous walls of SBA-15 silica. The properties of the deposited zeolite nanoparticles are found to be remarkably different from those of the full grown VS-1 zeolite. Monitoring of the local VO(2+) environment in the noncalcined nanoparticles in SBA-15 reveals that, in contrast to the full grown zeolite case, these sites are highly hydrophilic. Also, the stability of the TPAOH template is found to be affected by acidification of the nanoparticles. These results promise to be of great importance in elucidating the formation mechanism of TPAOH-templated zeolitic nanoparticles and their incorporation in mesoporous silica materials.

Complementary use of Fourier transform laser microprobe mass spectrometry and time-of-flight static secondary ion mass spectrometry for the study of the surface adsorption of organic dyes on silicate materials

The adsorption of organic ionic dyes on different pore size engineered silica materials with potential application for industrial wastewater treatment has been investigated using Fourier transform laser microprobe mass spectrometry (FT-LMMS) and time-of-flight secondary ion mass spectrometry (TOF-S-SIMS). The complementary use of the two methods with different information depth allowed data on the subsurface distribution and pore penetration of the adsorbed organic compounds. Macroscopic methods were employed to determine the amount adsorbed on the particles and the specific external surface area. Local MS analysis allows identification of the organic dyes exclusively at the outer particle surface when the pore size is inferior to the size of the adsorbing molecule, or at the surface of the channels inside the material. Specifically, the monolayer information depth of TOF-S-SIMS causes a signal to refer essentially to the adsorbate at the outer particle surface, which is only a fraction of the total adsorption in mesoporous materials, while FT-LMMS allowed detection of the presence of adsorbates at the outer surface as well as inside the subsurface of 10 to 50 nm depending on the material under study. The observed data open perspectives for the molecular monitoring of the adsorption behaviour of different materials at the (sub) microm scale.