The catalytic performance of phosphate-stabilized WOx-ZrO2 compositions in gas-phase glycerol dehydration has been investigated. Results show that varying WO3 concentrations direct the process towards either acrolein or allyl alcohol formation. Catalysts with low WOx content exhibit strong Lewis acid sites (Zr4+ and W6+), where these metal ions likely function as redox sites, facilitating glycerol hydrogenolysis to produce allyl alcohol. Higher WOx concentrations (exceeding 20 wt %) lead to the shielding of some W6+ and Zr4+ sites by polytungstate surface complexes, which are strong Brønsted acid sites. This alteration promotes glycerol dehydration through the removal of two water molecules, thereby shifting the selectivity towards acrolein formation.
- Klíčová slova
- Acid sites, Acrolein, Allyl alcohol, Glycerol, Tungsten-zirconium oxide,
- Publikační typ
- časopisecké články MeSH
ZnO/ZrO2 catalysts have shown better activity in the CO2 hydrogenation to methanol compared with single component counterparts, but the interaction between ZnO and ZrO2 is still poorly understood. In particular, the effect of the ZrO2 support phase (tetragonal vs. monoclinic) was not systematically explored. Here, we have synthesized ZnO/ZrO2 catalysts supported on tetragonal ZrO2 (ZnO/ZrO2-t) and monoclinic ZrO2 (ZnO/ZrO2-m), which resulted in the formation of different ZnOx species, consisting of sub-nanometer ZnO moieties and large-sized ZnO particles, respectively. ZnO/ZrO2-t exhibited a higher methanol selectivity (81 vs. 39 %) and methanol yield (1.25 vs. 0.67 mmol g-1 h-1) compared with ZnO/ZrO2-m. The difference in performance was attributed to the redox state and degree of dispersion of Zn, based on spectroscopy and microscopy results. ZnO/ZrO2-t had a high density of ZnOx-ZrOy sites, which favored the formation of active HCOO* species and enhanced the yield and selectivity of methanol along the formate pathway. Such ZnO clusters were further dispersed on ZrO2-t during catalysis, while larger ZnO particles on ZnO/ZrO2-m remained stable throughout the reaction. This study shows that the phase of ZrO2 supports can be used to control the dispersion of ZnO and the catalyst surface chemistry, and lead to enhanced catalytic performance.
- Klíčová slova
- CO2 hydrogenation, Methanol, Support effects, Zinc oxide, Zirconia,
- Publikační typ
- časopisecké články MeSH
G-quadruplexes (G4 s), as non-canonical DNA structures, attract a great deal of research interest in the molecular biology as well as in the material science fields. The use of small molecules as ligands for G-quadruplexes has emerged as a tool to regulate gene expression and telomeres maintenance. Meso-tetrakis-(N-methyl-4-pyridyl) porphyrin (TMPyP4) was shown as one of the first ligands for G-quadruplexes and it is still widely used. We report an investigation comprising molecular docking and dynamics, synthesis and multiple spectroscopic and spectrometric determinations on simple cationic porphyrins and their interaction with different DNA sequences. This study enabled the synthesis of tetracationic porphyrin derivatives that exhibited binding and stabilizing capacity against G-quadruplex structures; the detailed characterization has shown that the presence of amide groups at the periphery improves selectivity for parallel G4 s binding over other structures. Taking into account the ease of synthesis, 5,10,15,20-tetrakis-(1-acetamido-4-pyridyl) porphyrin bromide could be considered a better alternative to TMPyP4 in studies involving G4 binding.
- Klíčová slova
- DNA, G-quadruplexes, Molecular dynamics, Molecular recognition, NMR,
- MeSH
- cirkulární dichroismus MeSH
- DNA * chemie MeSH
- G-kvadruplexy * MeSH
- ligandy MeSH
- porfyriny * chemie MeSH
- simulace molekulární dynamiky MeSH
- simulace molekulového dockingu * MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- DNA * MeSH
- ligandy MeSH
- porfyriny * MeSH
- tetra(4-N-methylpyridyl)porphine MeSH Prohlížeč
This work reports the effect of different processing parameters on the structural and morphological characteristics of MoSe2 layers grown by chemical vapour deposition (CVD), using MoO3 and Se powders as solid precursors. It shows the strong dependence of the size, shape and thickness of the MoSe2 layers on the processing parameters. The morphology of the samples was investigated by field emission scanning electron microscopy (FESEM) and the thickness of the deposited layers was determined by atomic force microscopy (AFM). Raman and photoluminescence (PL) spectroscopies were used to confirm the high quality of the MoSe2 layers. Surface composition was examined by photoelectron spectroscopy (XPS). Moreover, the MoSe2/SiOx/Si heterojunctions exhibit diode behaviour, with a rectification ratio of 10, measured at ±2.0 V, which is due to the p-i-n heterojunctions formed at the p-Si/SiOx/MoSe2 interface. A photovoltaic effect was observed with a short circuit current density (Jsc), open circuit voltage (VOC) and efficiency of -0.80 mA/cm2, 1.55 V and 0.5%, respectively. These results provide a guide for the preparation of p-i-n heterojunctions based on few-layer MoSe2 with improved photovoltaic response.
- Publikační typ
- časopisecké články MeSH
