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991.
激光单分子探测技术的研究 总被引:6,自引:1,他引:6
文中介绍利用激光激发分子荧光的方法探测液体中单个染料分子的新技术,以及作者自行设计和研制的激光单分子探测谱仪。通过探测“光子爆发”,把单个染料分子的荧光同很强的背景杂散光区别开来。进一步用82MHz高重复频率的锁模激光器和时间门符合技术,成功地消除了Raman散射光。目前该谱仪达到的检测限为灵敏区内仅有~7个R6G分子。 相似文献
992.
993.
Synthesis and characterization of Sr3Al2O6:Eu2+, Dy3+ phosphors prepared by sol-gel-combustion processing
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A type of red luminescent Sr3Al2O6:Eu2+, Dy3+ phosphor powder is synthesised by sol-gel-combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions. By tracing the formation process of the sol-gel, it is found that it is necessary to reduce the amount of NO3- by dropping ethanol into the solution for forming a stable and homogeneous sol-gel. Thermogravimetric and Differential Scanning Calorimeter Analysis, x-ray diffractionmeter, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the luminescent properties of the as-synthesised Sr3Al2O6:Eu2+, Dy3+. The results reveal that the Sr3Al2O6 crystallises completely when the combustion ash is sintered at 1250 C. The excitation and the emission spectra indicate that the excitation broadband lies mainly in a visible range and the phosphors emit a strong light at 618 nm under the excitation of 472 nm. The afterglow of (Sr0.94Eu0.03Dy0.03)3Al2O6 phosphors sintered at 1250 ℃ lasts for over 1000 s when the excited source is cut off. 相似文献
994.
Wen-Rong Liu 《中国物理 B》2022,31(3):37305-037305
The two-dimensional (2D) materials with nodal line band crossing have been attracting great research interest. However, it remains a challenge to find high-stable nodal line structure in 2D systems. Herein, based on the first-principles calculations and theoretical analysis, we propose that monolayer B6O possesses symmetry protected Dirac nodal line (DNL) state, with its Fermi velocity of 106 m/s in the same order of magnitude as that of graphene. The origin of DNL fermions is induced by coexistence of time-reversal symmetry and inversion symmetry. A two-band tight-binding model is further given to understand the mechanism of DNL. Considering its robustness against spin—orbit coupling (SOC) and high structural stability, these results suggest monolayer B6O as a new platform for realizing future high-speed low-dissipation devices. 相似文献
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996.
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998.
Chengxiang Lu Li Chen Ronggen Ye Xufu Cai 《Journal of Macromolecular Science: Physics》2013,52(5):986-999
The chain extension behaviors of 2,2′-(1,3-phenylene)bis(2-oxazoline) (MPBO) and 2,2′-bis(2-oxazoline) (BOZ) were studied to evaluate the coupling effect on polyamide 6 (PA6) in a Haake Rheocord mixer and an extruder. The coupling results showed that there existed an optimal dosage of chain extender, lack of which caused deficiency of chain extension and excess of which led to more blocking reaction. The effect of chain extension with MPBO was shown to be inferior to BOZ. When the optimum amount of chain extenders was added in PA6, the intrinsic viscosity of the polyamide 6 increased from 1.632dl/g to 1.787dl/g(MPBO) and 2.031dl/g(BOZ), respectively. The reaction time decreased very fast with an increase in the temperature. The chain-extended products dissociated at high temperature; the degradation is suggested to proceed from the onset of the chain extension reaction, as do the coupling and blocking reactions. Furthermore, the effects of MPBO and BOZ on the thermal and mechanical properties of chain-extended PA6 were also investigated. 相似文献
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