Magnetic properties of single-crystalline preferential {001}-oriented Bi2Fe4O9nanosheets with thickness of about 13 nm, synthesized via a facile hydrothermal method, have been investigated through variable temperature...Magnetic properties of single-crystalline preferential {001}-oriented Bi2Fe4O9nanosheets with thickness of about 13 nm, synthesized via a facile hydrothermal method, have been investigated through variable temperature electron spin resonance measurement. A typical ferromagnetic state could be appeared in the measured temperature from 110 K to 300 K and the origin would be contributed to uncompensated surface spin due to its large surface-to-volume ratio and/or a few non-detectable impurities with strong magnetism. Interestingly, another weak ferromagnetic state could present below the temperature about 250 K, indicative of Neel temperature (TN) of antiferromagnetic state, which is slightly lower than that of bulksample of 265 K.展开更多
This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. ...This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. The phonon absorption and emission processes as well as the photon absorption and emission processes in all electron transition processes can be explained in an organized manner, and the result can be represented in a diagram that can provide intuition for the quantum dynamics of electrons in a solid. The temperature （T） dependence of electron spin relaxation times （T1） in silicon is T1 ∝ T-1.07 at low temperatures and T1 ∝ T-3.3 at high temperatures for acoustic deformation constant Pad = 1.4 × 10^7 eV and optical deformation constant Pod = 4.0 × 10^17 eV/m. This means that electrons are scattered by the acoustic deformation phonons at low temperatures and optical deformation phonons at high temperatures, respectively. The magnetic field （B） dependence of the relaxation times is T1 ∝ B-2.7 at 100 K and T1 ∝ B-2.3 at 150 K, which nearly agree with the result of Yafet, T1 ∝ B-3.0- B -2.5.展开更多
In order to f urther improve the photosensitizing activity of hypocrellin B(HB), the complex o f 5,8 di Br HB with Al 3+ was designed and synthesized in high yield. Th e complex of aluminium ion with 5,8 di Br HB is a...In order to f urther improve the photosensitizing activity of hypocrellin B(HB), the complex o f 5,8 di Br HB with Al 3+ was designed and synthesized in high yield. Th e complex of aluminium ion with 5,8 di Br HB is a new water soluble perylene quinonoid derivative with enhanced absorption over HB in the phototherapeutic wi ndow (600-900 nm). Electron paramagnetic resonance (EPR) measurement and 9,10 diphenyl anthracene bleaching methods were used to investigate the photosensiti zing activity of [Al 2(5,8 di Br HB)Cl 4] n in the prese nce of oxygen. Singlet oxygen, superoxide anion radical, hydroxyl radical can be generated by [Al 2(5,8 di Br HB)Cl 4] n photosensit ization. The results showed that the production of hydroxyl radical ( · OH) by [Al 2(5,8 di Br HB)Cl 4] n photosensitization comes from the Fenton Haber Weiss reaction and the decom position of DMPO 1O 2 adduct. Formation of H 2O 2 as one of main intermedi ates in the photogeneration of hydroxyl radical was detected by using the cataly zed oxidation of the DPD reagent by the POD enzyme method. Moreover, the experim ents of EPR spin trap and catalase enzyme excluded the effect of organoperoxide on DPD oxidization. These results further support the proposed mechanism of · OH formation.展开更多
文摘Magnetic properties of single-crystalline preferential {001}-oriented Bi2Fe4O9nanosheets with thickness of about 13 nm, synthesized via a facile hydrothermal method, have been investigated through variable temperature electron spin resonance measurement. A typical ferromagnetic state could be appeared in the measured temperature from 110 K to 300 K and the origin would be contributed to uncompensated surface spin due to its large surface-to-volume ratio and/or a few non-detectable impurities with strong magnetism. Interestingly, another weak ferromagnetic state could present below the temperature about 250 K, indicative of Neel temperature (TN) of antiferromagnetic state, which is slightly lower than that of bulksample of 265 K.
文摘This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. The phonon absorption and emission processes as well as the photon absorption and emission processes in all electron transition processes can be explained in an organized manner, and the result can be represented in a diagram that can provide intuition for the quantum dynamics of electrons in a solid. The temperature （T） dependence of electron spin relaxation times （T1） in silicon is T1 ∝ T-1.07 at low temperatures and T1 ∝ T-3.3 at high temperatures for acoustic deformation constant Pad = 1.4 × 10^7 eV and optical deformation constant Pod = 4.0 × 10^17 eV/m. This means that electrons are scattered by the acoustic deformation phonons at low temperatures and optical deformation phonons at high temperatures, respectively. The magnetic field （B） dependence of the relaxation times is T1 ∝ B-2.7 at 100 K and T1 ∝ B-2.3 at 150 K, which nearly agree with the result of Yafet, T1 ∝ B-3.0- B -2.5.
文摘In order to f urther improve the photosensitizing activity of hypocrellin B(HB), the complex o f 5,8 di Br HB with Al 3+ was designed and synthesized in high yield. Th e complex of aluminium ion with 5,8 di Br HB is a new water soluble perylene quinonoid derivative with enhanced absorption over HB in the phototherapeutic wi ndow (600-900 nm). Electron paramagnetic resonance (EPR) measurement and 9,10 diphenyl anthracene bleaching methods were used to investigate the photosensiti zing activity of [Al 2(5,8 di Br HB)Cl 4] n in the prese nce of oxygen. Singlet oxygen, superoxide anion radical, hydroxyl radical can be generated by [Al 2(5,8 di Br HB)Cl 4] n photosensit ization. The results showed that the production of hydroxyl radical ( · OH) by [Al 2(5,8 di Br HB)Cl 4] n photosensitization comes from the Fenton Haber Weiss reaction and the decom position of DMPO 1O 2 adduct. Formation of H 2O 2 as one of main intermedi ates in the photogeneration of hydroxyl radical was detected by using the cataly zed oxidation of the DPD reagent by the POD enzyme method. Moreover, the experim ents of EPR spin trap and catalase enzyme excluded the effect of organoperoxide on DPD oxidization. These results further support the proposed mechanism of · OH formation.
