Role Of Oxygen In Formation Research Articles

Oxygen Effect on Magnetic Properties of Fullerenes

The role of oxygen in formation of magnetic properties of photolyzed fullerene is considered on the basis of ab initio calculations of oxygen energetics in fullerene matrix. A possibility of a formation of magnetically active species in oxygenated C60 and a polymerization of the fullerene matrix due to mono‐oxidation is considered. The optimized geometry and electronic structure of C60O isomers and C60‐O‐C60 oligomers in singlet and triplet spin states are calculated using DFT/B3LYP method.

Role of singlet oxygen in formation of nanoporous silicon

The effect of singlet oxygen on the formation of nanoporous silicon in the case of photoelectrochemical etching of p-Si is studied. Pulsed electrolysis was used to discriminate between chemical and electrochemical processes. The pulsed etching of silicon was accompanied by pulsed illumination coinciding either with current pulses or with zero-current periods. An analysis of the results obtained demonstrated that, as the number of silicon nanocrystals increases under illumination, singlet oxygen starts to be generated from molecular oxygen dissolved in the electrolyte. This process leads to oxidation of the surface of silicon nanocrystallites and to a change in its passivation.

The role of oxygen in formation of radiative recombination centers in ZnSe1−xTex crystals

The present study was aimed at revealing the influence of oxygen on formation of alloy ZnSe–ZnTe as well as on development of luminescence centers under thermal treatment of scintillators based on isovalently doped ZnSe crystals. The presence of oxygen in ZnSe(Te) crystals as ZnO phase has been shown to hinder formation of (V′ZnTexSe)′ type luminescence centers responsible for luminescence band peaked at 635–640 nm, which is the principal emission band of this scintillator. In ZnSe(Te) crystals doped by mechanically stimulated ion implantation with active forms of oxygen (O′, Ox, O′2, etc.), luminescence quenching effects are not observed. However, the luminescence band in these crystals is blueshifted towards 600–610 nm. Strong luminescence band peaked at λmax=590–610 nm is observed in Te-free ZnSe crystals doped with oxygen in active forms. The experimental results are interpreted by formation of centers (Zni⋅Oxi)⋅ or (Zni⋅OxSe)⋅. Having larger charge carrier capture cross-section than (Zn⋅iV′ZnTexSe)x, the oxygen-containing centers determine kinetics of luminescence in ZnSe1−xTex crystals (x<0.001) treated by active forms of oxygen during mechanical activation of the initial raw material for crystal growth.

Role of oxygen in formation and stabilization of SO− 3 and SO− 2 ion-radicals in thermal conversion of barium dithionate and barium sulfite

Role of oxygen in formation and stabilization of SO− 3 and SO− 2 ion-radicals in thermal conversion of barium dithionate and barium sulfite

95/06601 Role of oxygen in formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from carbon on fly ash

95/06601 Role of oxygen in formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from carbon on fly ash

Role of Oxygen in Formation of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans from Carbon on Fly Ash

Under an oxygen-deficient flow, no PCDD/F is formed from a carbon/fly ash mixture, but with a mixture of 1% O 2 in N 2 de novo synthesis of PCDD/F sets in. The O 2 concentration was varied 0-10%, formation was highest at 5-10% O 2 . The [PCDD] :[PCDF] ratio rises with increasing [O 2 ], but the average degree of chlorination of PCDD and PCDF does not depend on the O 2 concentration. Especially 3,4,6,7-substituted PCDD/F congeners are formed. Without a gas flow, carbon/fly ash mixtures can give PCDD/F formation too : the O 2 now enters the mixture by diffusion. This formation process can continue for several hours. Isomer distributions do not change with increased reaction times. Formation rates under conditions without a gas flow are higher than with a gas flow present, suggesting that O 2 diffusion into the fly ash bed is more efficient than the supply of O 2 through a gas flow.

The role of oxygen in the formation of titanium-based icosahedral phases and crystal approximants

Abstract The first report of an oxygen-stabilized quasicrystal is presented. Oxygen is shown to be essential for the formation of the icosahedral and 1/1 approximant phases in Ti-Mn-Si and Ti-Cr-Si alloys. Recent X-ray and neutron diffraction structural studies by us of the 1/1 approximant phase reveal specific sites for the oxygen in the Mackay icosahedral clusters. On the basis of these data, possible explanations for the role of oxygen in quasicrystal formation are considered. These include firstly the creation of a nucleation barrier for competing crystalline phases, secondly the stabilization of the fundamental Mackay icosahedral cluster and thirdly an adjustment of the electron-to-atom ratio to shift the Fermi surface into a minimum in the density of states.

Activation of molecular hydrogen by transition metal complexes. Communication 6. Role of molecular oxygen in formation of palladium complexes that are active in the hydrogenation of unsaturated compounds

1. In order to form complexes that will catalyze the hydrogenation of unsaturated hydro-carbons in a system consisting of (Ph3P)2Pd2, HOAc, and H2, the presence of oxygen is necessary. Under these conditions, the hydrogen and oxygen form water and H2O2, which oxidizes the bis-(triphenylphosphine)dipalladium to palladium acetate. The palladium acetate, by reaction with the bis(triphenylphosphine)dipalladium and hydrogen, gives a complex that is active in hydrogenation. 2. A cluster with the composition [(PPh)2Pd5]n, which is active in the hydrogenation of unsaturated hydrocarbons, has been isolated as an individual substance.