UV–visible absorption edge energy of heteropolyacids (HPAs) as a probe of catalytic performance of HPAs in the oxidative dehydrogenation of isobutyric acid

2006 ◽  
Vol 252 (1-2) ◽  
pp. 252-255 ◽  
Author(s):  
Heesoo Kim ◽  
Min Hye Youn ◽  
Ji Chul Jung ◽  
In Kyu Song
Keyword(s):  
Oxidative Dehydrogenation ◽  
Absorption Edge ◽  
Catalytic Performance ◽  
Isobutyric Acid ◽  
Visible Absorption ◽  
Absorption Edge Energy ◽  
Uv Visible

scholarly journals Polymer Composites with 0.98 Transparencies and Small Optical Energy Band Gap Using a Promising Green Methodology: Structural and Optical Properties

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1648
Author(s):  
Muaffaq M. Nofal ◽  
Shujahadeen B. Aziz ◽  
Jihad M. Hadi ◽  
Wrya O. Karim ◽  
Elham M. A. Dannoun ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Polymer Composites ◽  
Amorphous Phase ◽  
Absorption Edge ◽  
Complex Form ◽  
Bandgap Energy ◽  
Optical Parameters ◽  
Visible Spectroscopy ◽  
Uv Visible

In this work, a green approach was implemented to prepare polymer composites using polyvinyl alcohol polymer and the extract of black tea leaves (polyphenols) in a complex form with Co2+ ions. A range of techniques was used to characterize the Co2+ complex and polymer composite, such as Ultraviolet–visible (UV-Visible) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The optical parameters of absorption edge, refractive index (n), dielectric properties including real and imaginary parts (εr, and εi) were also investigated. The FRIR and XRD spectra were used to examine the compatibility between the PVA polymer and Co2+-polyphenol complex. The extent of interaction was evidenced from the shifts and change in the intensity of the peaks. The relatively wide amorphous phase in PVA polymer increased upon insertion of the Co2+-polyphenol complex. The amorphous character of the Co2+ complex was emphasized with the appearance of a hump in the XRD pattern. From UV-Visible spectroscopy, the optical properties, such as absorption edge, refractive index (n), (εr), (εi), and bandgap energy (Eg) of parent PVA and composite films were specified. The Eg of PVA was lowered from 5.8 to 1.82 eV upon addition of 45 mL of Co2+-polyphenol complex. The N/m* was calculated from the optical dielectric function. Ultimately, various types of electronic transitions within the polymer composites were specified using Tauc’s method. The direct bandgap (DBG) treatment of polymer composites with a developed amorphous phase is fundamental for commercialization in optoelectronic devices.

Remarkable kinetic stability of α-thiocarbamoyl substituted 4-methoxybenzylcations

1998 ◽  
Vol 76 (12) ◽  
pp. 1910-1915 ◽  
Author(s):  
Robert A McClelland ◽  
Victoria E Licence ◽  
John P Richard ◽  
Kathleen B Williams ◽  
Shrong-Shi Lin
Keyword(s):  
Key Words ◽  
Strong Interaction ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Visible Absorption ◽  
Methyl Group ◽  
Thioamide Group ◽  
Azide Ion ◽  
Uv Visible ◽  
Leaving Groups

4-Methoxybenzyl cations bearing α-(N,N-dimethylcarbamoyl) and α-(N,N-dimethylthiocarbamoyl) substituents have been generated photochemically upon irradiation of precursors with pentafluorobenzoate or 4-methoxybenzoate leaving groups. The ions have been observed with flash photolysis in 40:60 acetonitrile:water and in 50:50 methanol:water, and rate constants were measured for their decay in solvent alone and for their capture by azide ion. The cations so studied and their lifetimes in 40% acetonitrile are 6, ArC+H-CONMe2, 0.6 μs; 2, ArC+H-CSNMe2, 7 ms; and 4, ArC+(CH3)-CSMe2, 6 ms, where Ar = 4-MeOC6H4. The cation 4 reacts with solvent by elimination of a proton from the α-methyl group, and the rate constant for solvent addition must be less than 1 s-1. The CSNMe2 substituted cations are 105-107-fold longer lived than analogs where the thioamide group has been replaced with an α-methyl. The UV-visible absorption spectra of these two cations also show significant differences from those of typical 4-methoxybenzyl cations. Thus, both the lifetimes and spectra point to a strong interaction of the benzylic centre with the thioamide group. Key words: flash photolysis, thiocarbamoyl stabilized carbocation, photosolvolysis.

scholarly journals Water-soluble β-aminobisulfonate building blocks for pH and Cu2+ indicators

RSC Advances ◽  
2016 ◽  
Vol 6 (88) ◽  
pp. 84712-84721 ◽  
Author(s):  
Maria A. Cardona ◽  
Marina Kveder ◽  
Ulrich Baisch ◽  
Michael R. Probert ◽  
David C. Magri
Keyword(s):  
Nmr Spectroscopy ◽  
Building Blocks ◽  
Water Soluble ◽  
Visible Absorption ◽  
H Nmr ◽  
Uv Visible

Two phenyl β-aminobisulfonate ligands characterised by UV-visible absorption, EPR and 1H NMR spectroscopy exhibit evidence for binding with Cu2+ in water and methanol.

Valence variation of phase-pure M1 MoVNbTe oxide by plasma treatment for improved catalytic performance in oxidative dehydrogenation of ethane

RSC Advances ◽  
2015 ◽  
Vol 5 (111) ◽  
pp. 91295-91301 ◽  
Author(s):  
Xin Chen ◽  
Qianli Yang ◽  
Bozhao Chu ◽  
Hang An ◽  
Yi Cheng
Keyword(s):  
Surface Modification ◽  
Metal Oxide ◽  
Plasma Treatment ◽  
Oxidative Dehydrogenation ◽  
Oxidation State ◽  
Active Sites ◽  
Oxygen Plasma ◽  
Catalyst Surface ◽  
Catalytic Performance ◽  
Phase Pure

This work presents a new method of catalyst surface modification by using oxygen plasma to change the oxidation state of active sites in metal oxide catalysts.

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