Oxygen adsorbed quartz

This conclusion is in agreement with experiments in which a smootb quartz and cellulose were used as substrates. For above materials the transfer of excitation energy of the dye into the substrate is low which is confirmed by intensive luminescence of adsorbed tripaflavine. Note, that the activation energy of emission of singlet oxygen is close for zinc oxide oxidized by oxygen atoms, quartz and cellulose and amounts to 5-10 kcal/mol [83]. 

We used polycrystalline films of ZnO and Sn02 as adsorbents. The films were deposited from the water suspension of respective oxides on quartz substrates. These substrates contained initially sintered contacts made of platinum paste. The gap between contacts was of about lO" cm. All samples were initially heated in air during one hour at T 500 C. We used purified molecular oxygen an acceptor particle gas. H and Zn atoms as well as molecules of CO were used as donor particles. We monitored both the kinetics of the change of ohmic electric conductivity and the tangent of inclination angle of pre-relaxation VAC caused by adsorption of above gases and the dependence of stationary values of characteristics in question as functions of concentrations of active particles. 

The existence of free radicals seemed likely when Ilin, Kiselev, and Krasil nikov 178) and Krasil nikov, Kiselev, and Sysoev 268) observed that oxygen was adsorbed by silica after heating to 300-900°. Solonitsyn 269) observed adsorption of oxygen when silica gel or quartz was... 

In a solution containing oxygen, photolysis yields a mixture of 6,12-, 1,6-, and 3,6-diones. Nitration by nitrogen dioxide forms 6-nitro-, 1-nitro-, and 3-nitrobenzo[a]pyrene. When benzo [a] pyrene in methanol (1 g/L) was irradiated at 254 nm in a quartz flask for 1 h, the solution turned pale yellow. After 2 h, the solution turned yellow and back to clear after 4 h of irradiation. After 4 h, 99.67% of benzo[a]pyrene was converted to polar compounds. One of these compounds was identified as a methoxylated benzo[a]pyrene (Lu et al, 1977). A carbon dioxide yield of 26.5% was achieved when benzo [a] pyrene adsorbed on silica gel was irradiated with light (A, >290 nm) for 17 h (Freitag et al, 1985). 

On the crystalline quartz on the other hand the gases are but feebly adsorbed and the rate is governed by the probability of reaction between oxygen atoms and carbon monoxide on adjoining elementary... 

In principle, in oxygen containing carrier gases also oxyhalides can be synthesized. However, for group-4 elements little is know about these compounds. It was observed that ZrOCl2 and HfOCl2 decompose to tetrachlorides and the oxide under elevated temperatures [6]. An alternative process is substitutive adsorption of the pure halides on the surface of the quartz chromatography column where oxychloride formation is possible in the adsorbed state only. 

The nature of the silica-water interface is determined by adsorption/desorption of the species in the water. When a silicon oxide, e.g., quartz, is fractured, the initial surface is composed of dangling silicon and oxygen bonds (Fig. 4.30a) which are not stable and hydroxylate easily with available waterThe hydroxylated surface is dominated by SiOH groups (Fig. 4.30b). The initial adsorbed water adjacent to the surface is oriented and has properties different from the bulk water. As this adsorbed water layer increases to more than three monolayers, its properties become more like bulk water. The surface potential changes as a result of the adsorption of the ionic species in the water. °... 

Prior to each reaction test and spectroscopic measurement, the sample was treated with 100 Torr oxygen (1 Torr = 133.3 N m ) at 673 K for 1 h, followed by evacuation at 673 K for 1 h. The photooxidation of propene was performed with a conventional closed system (123 cm ). The sample (200 mg) was spread on the flat bottom (12.6 cm ) of the quartz vessel. Propene (100 pmol, 15 Torr) and oxygen (200 pmol, 30 Torr) were introduced into the vessel, and the sample was irradiated by a 200 W Xe lamp. After collecting the products in gas phase, the catalyst bed was heated at 573 K in vacuo to collect the products adsorbed on the catalyst by a liquid nitrogen trap. These products were separately analyzed by GC. The results presented here are the sum of each product yield. 

In addition to reactive oxygen species, nitric oxide may be a potential mediator of sihca-induced toxicity (Castranova et al. 1996). Nitric oxide adsorbed readily to DQ12 quartz (Robertson et al. 1982). At room temperature it remained adsorbed for up to several weeks. Thermal desorption of NO was much lower (43 %) than of NOj (67 %). Vallya-THAN et al. (1997) studied the kinetic clearance of instilled stable nitroxide radicals (2,2,6,6-tetra-methyl piperidine N-oxyl) and showed an oxidative stress in adult male Sprague-Dawley rats exposed to 10 mg Min-U-Sil quartz <5 im. The generation of reactive oxygen species increased by sihca was associated with enhanced levels of superoxide dismu-tase (P<0.05) and lipid peroxidation. 

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