Electron Spin Resonance Study on γ-Ray-Induced Ethyl Radical in Ethane Hydrate

Abstract

An ultrasonically assisted two-step polyol process was established to fabricate polycrystalline ZnO nanotubes. Thus one-dimensional (1D) precursors were prepared from an ethylene glycol (EG) solution containing 0.3 M of zinc acetate in the presence of ultrasonic irradiation. The ZnO nanotubes were obtained by calcination of the precursors at proper temperatures. The precursors and polycrystalline ZnO nanotubes obtained at various calcination temperatures were characterized by means of scanning electron microscopy (SEM), Fourier transformation infrared spectrometry (FTIR), x-ray diffraction (XRD, together with temperature-resolved XRD), and transmission electron microscopy (TEM). It was found that the precursors were extremely sensitive to atmospheric moisture and instantly transformed to layered hydroxide zinc acetate (LHS-Zn) after being exposed to air, accompanied by the erosion and deformation of the one-dimensional structure. After being calcined at proper temperatures, the precursors were completely transformed into polycrystalline tubular ZnO, and the sizes of the resulting ZnO nanocrystallites increased with increasing calcination temperature, implying that polycrystalline tubular ZnO of desired sizes could be fabricated using the present method by properly controlling the calcination temperature. However, the tubular structures were destroyed at a calcination temperature of 400 • C and above, owing to the growth of polycrystalline ZnO. Moreover, the present method could be used to synthesize other tubular metal oxides, and tubular ZnO might find promising applications in gas-sensitive sensors and catalysis as well.

Intermolecular Hydrogen Transfer in Isobutane Hydrate

“…These values are in agreement with the literature [10,11]. Other than isobutyl and tert-butyl radicals, the signals of H and D atoms were also observed at 120 K. OD radicals were not observed even at 77 K, which is consistent with the previous reports on the γ-ray-irradiated methane [1], ethane [3], and propane [4] hydrates. To quantify the amounts of each butyl radical, the ESR spectrum was deconvoluted based on the ESR parameters determined at each temperature.…”

“…We have reported the thermal stabilities of methyl, ethyl, and propyl radicals in the γ-ray-irradiated simple methane [1,2], ethane [3], and propane [4] hydrate systems. The radicals in other clathrate hydrates have been investigated [5][6][7].…”

Characterization of Free Radicals in Clathrate Hydrates of Furan, 2,3-Dihydrofuran, and 2,5-Dihydrofuran by Muon Spin Spectroscopy

“…The study of controlled reactions in clathrate hydrates has led to the suggestion that they be used as "nano-reactors". 7 Free radicals can be created in clathrate hydrates by photolysis of either the guest 8 or the host water molecules, 9 but most studies employ γ-irradiation, [10][11][12][13][14][15][16] and thence reaction of guest molecules with the transient products (H, OH, e -) of water radiolysis. At low temperature hydrogen atoms (H or D) can be detected by electron spin resonance (ESR).…”

“…Free radicals can be created in clathrate hydrates by photolysis of either the guest or the host water molecules, but most studies employ γ-irradiation − and, thus, reaction of guest molecules with the transient products (H, OH, e – ) of water radiolysis. At low temperature, hydrogen atoms (H or D) can be detected by electron-spin resonance (ESR). , Organic free radicals can also be characterized by ESR, and monitoring their signal intensities in temperature-annealing studies has provided evidence for H atom transfer reactions. − …”

Reactions of HOCO radicals through hydrogen-atom hopping utilizing clathrate hydrates as an observational matrix

“…The guest molecules interact weakly with the water molecules of the cages through only van der Waals forces, 15 and we have already studied the thermal stabilities of gamma-ray induced radicals in clathrate hydrates using ESR measurements. [16][17][18][19] In the case of gamma-ray irradiated hydrocarbon hydrates, alkyl radicals induced from alkanes in hydrate cages seem to be stable below the three-phase (i.e., hydrate, ice and gas phase) equilibrium temperature of each hydrocarbon hydrate at atmospheric pressure. For example, the methyl radical in the methane hydrate is relatively stable in comparison with that in water ice, and this trend has also been observed in other hydrocarbon hydrate systems.…”