分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: A series of Sm-doped LDPE-Na2SO4 composites were successfully achieved by melt mixing and hot pressing methods. Their morphology, structure and luminescent properties were characterized by scanning electron microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and photoexcitation (PE), photoluminescence (PL) spectra, respectively. The sizes and concentrations of free volume cavities in composites were studied by positron annihilation lifetime spectroscopy (PALS). SEM micrographs showed that Na2SO4:Sm3+ particles were well-distributed in the polymer matrix. XRD analyses revealed that the addition of Na2SO4:Sm3+ had no effect on the original crystal structure of LDPE. The dominant photoexcitation peak was observed at about 402 nm. The photoluminescence spectra consisted of four main peaks at 563, 598, 644 and 706 nm which could be associated to the transitions 4G5/2→6HJ (J=5/2, 7/2, 9/2 and 11/2, respectively) within the 4f5 electronic configuration of Sm3+. The effect of different doping concentration of Na2SO4:Sm3+ on the luminescent properties of the composites was investigated. The luminescent intensity of the composites increased with phosphor concentration.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Four new coordination compounds, [Zn(bppc)2(H2O)2]·3H2O (1), [Zn2(bppc)2(m-bdc)(H2O)4]·7H2O (2), [Zn(bppc)2(H2O)2]n·n(m-Hbdc)·n(H2O) (3), [Zn2(bppc)(btc)(H2O)3]n·5nH2O (4) (Hbppc = 2,6-bis(pyrazin-2-yl)pyridine-4-carboxylate, H2(m-bdc) = 1,3-benzenedicarboxylic acid, H3btc = 1,3,5-benzene-tricarboxylic acid), have been hydrothermally synthesized and structurally characterized. Compound 1 shows a mononuclear structure and 2 shows a dinuclear structure. Compound 3 is a one-dimensional chain structure, which is extended into a 3D supramolecular network by intermolecular hydrogen interactions. In 4, a 1D loop-like chain is connected by (btc)3- anions to generate a 2D layer structure. The structure differences of 1~4 show that the pH and aromatic acid as auxiliary ligand have important influence on the final structures.[1]Additionally, the luminescent properties of 1~4 have been investigated with fluorescent spectra in the solid state, and 1~4 display a strong fluorescent emission at room temperature and have potential applications as fluorescent-emitting materials.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In order to do alignment between the timing signal and the synchrotron X-ray pulse on the sample spot in the time domain, measuring time structure of the storage ring on the sample spot inside the experimental hutch is a foundational step during the time-resolved experiments using the pulsed synchrotron X-rays with the time structure defined by the storage ring. In this work, the method of time-resolved X-ray excited optical luminescence (TRXEOL) was designed and implemented to do the measurement. It is based on the principle of time-correlated single photon counting techniques. The measurement system consists of a spectrometer with a detector of photomultiplier tube, a timing system, a set of nuclear instrument modules and a luminescent material of zinc oxide. The measurement was performed on the X-ray absorbed fine structure spectrum beamline at Shanghai Synchrotron Radiation Facility. The results show that this method can be used to measure the time structure of the storage ring with a precision of less than 1 ns. The measurement system can also be used for the time-resolved research for the optical luminescent materials.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-23
摘要: A comparative study on the morphology, structure and luminescence modifications of LDPE–Na2SO4:Sm3+ composite induced by gamma irradiation was reported for the first time. The composites were irradiated with irradiation doses of 10, 30, and 50 kGy in air at room temperature. Modifications on structural and luminescence properties of LDPE–Na2SO4:Sm3+ composites were investigated by using several analytical methods. The X-ray diffraction (XRD) patterns revealed that the cross-linking improved the crystallinity of the composites. Scanning electron microscope (SEM) images illustrated the surface modifications of composites induced by irradiation. Results of positron annihilation lifetime spectroscopy (PALS) suggested that gamma irradiation affected the free volumes concentrations in the samples. The photoluminescence (PL) spectra of non-irradiated and irradiated composites consisted of four main peaks at 563, 598, 644 and 706 nm which could be assigned to the 4G5/2 6HJ (J =5/2, 7/2, 9/2 and 11/2, respectively) transitions within the electronic configuration of Sm3+. Meanwhile, we observed an additional peak at about 686 nm in the irradiated composites, owing to the conversion of Sm3+ Sm2+. Concentrations of the Sm2+ centers linearly increased with gamma irradiation doses, which partly accounted for the degradation of PL intensity of Sm3+ peaks.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Two new coordination polymers, namely, {[Cd1.5(bc)2(HL)].H2O}2n (1) and [Mn(ip)(H2L)(H2O)]n (2) (H2L = 3-(1H-pyrazol-4-yl)-5-(pyridin-2-yl)-1,2,4-triazole, Hbc = benzoic acid, H2ip = isophthalic acid) were constructed by solvothermal reaction. The compounds were characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray diffraction. Compound 1 displays a two-dimensional plane structure consisting of [Cd3(bc)2(HL)] subunits. Compound 2 possesses a one-dimensional chain structure and is further extended into a 3-D supramolecular architecture via hydrogen bonds. Moreover, photoluminescence studies showed compound 1 exhibits luminescent emissions with emission maxima at 375 nm. Magnetic susceptibility measurements of 2 indicate that domain antiferromagnetic interactions exist between Mn(II) ions. In addition, thermogravimetric properties of 1 and 2 were also measured.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: The comprehensive structural and luminescence study of Sm-doped SiO2-Na2SO4 composite materials are reported. The samples were synthesized by melt-mixing mixture of Na2SO4 and SmF3 into the SiO2 matrix at 1050 C for 30 min. X-ray di raction (XRD) pattern shows the characteristic structure of the SiO2 and addition of 20% Na2SO4:Sm has no e ect on the basic crystal structure of the SiO2. Scanning electron microscopy (SEM) shows the clear di erence in morphological structure between the composite and host SiO2. From photoexcitation (PE) spectra of the as-synthesized composite, the highest excitation e ciency was observed at 402 nm. The photoluminescence (PL) spectra of as-synthesized composite phosphors obtained under 402 nm excitation consist of five narrow emission bands with peaks at 563, 598, 644, 704 and 784 nm. These are assigned to the 4G5=2 ! 6HJ (J=5/2, 7/2, 9/2, 11/2 and 13/2, respectively) transitions within 4f5 electronic configuration of Sm3+. Highest luminescence intensity was observed with SiO2-10%Na2SO4:Sm.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Two alkaline earth metal coordination polymers [M(2-Hstp)(H2O)] (M = Ca2+ (1) and Sr2+ (2), 2-H3stp = 2-sulfoterephthalate) were synthesized under hydrothermal conditions by the precursor [Mn(2-Hstp)2(4,4΄-Hbpy)2] and alkaline earth metal salts. The two alkaline earth complexes are not isomorphic. Complex 1 crystallizes in the monoclinic space group P21/m, while 2 in the monoclinic space group P21/c, despite of their similar formulas. In 1, the Ca2+ ion lies in a seven-coordinated pentagon bipyramidal configuration, coordinated with five 2-Hstp2- anions and one water molecule. However, the Sr2+ ion in 2 is coordinated by nine oxygen atoms to form a single-capped square antiprism polyhedron. Both 1 and 2 exhibit π-π* emission of the 2-sulfoterephthalate ligand.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: One two-dimensional coordination polymer with a formula of {[Cd(L)(imidazole)(H2O)](H2O)}n (1) was obtained by the synthetic reactions in aqueous solution using a newly synthesized H2L (H2L = methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate) ligand. Compound 1 crystallizes in monoclinic system, space group C2/c with a = 18.3176(11), b = 8.5366(9), c = 8.4152(5) Å, β = 101.789(6)º, V = 2797.1(3) Å3, Dc = 1.979 g/cm3, C10H12N2O7SCd, Mr = 416.68, F(000) = 1648, μ = 1.745 mm-1, F(000) = 1648, the final R = 0.0323 and wR = 0.0604 for 2604 observed reflections with I > 2s(I). Structure analyses reveal that the compound is constructed by dinuclear Cd(II) clusters bridged by two hydroxyl oxygens of L2- anions, which features a two-dimensional network with 4-connected sql topology. Furthermore, the compound exhibits high thermal stability and intense fluorescent emission, and could be explored for potential luminescent materials.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Switching luminescence of lanthanide-based molecules through an external electric field is considered as a promising approach toward novel functional molecule-based devices. Classic routes use casted films and liquid electrolyte as media for redox reactions. Such protocol, even if efficient, is relatively hard to turn into an effective solid-state device. In this work, we explicitly synthesize lanthanide-based dimers whose luminescent behavior is affected by the presence of Cu2+ ions. Excellent evaporability of the dimers and utilization of Cu2+- based solid-state electrolyte makes it possible to reproduce solution behavior at the solid state. Reversible modulation of Cu2+ ions transport can be achieved by an electric field in a solid-state device, where lanthanide-related luminescence is driven by an electric field. These findings provide a proof-of-concept alternative approach for electrically driven modulation of solid-state luminescence and show promising potential for information storage media in the future.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: We obtained a single phase BLS:Eu2+, Ce3+, Mn2+ phosphor by solid-state reactions. Eu2+, Ce3+, and Mn2+ gives rise to the blue, green, and red emission, respectively. The Mn2+ red emission can be effectively enhanced via energy transfers from both Eu2+ and Ce3+. Thus a tunable full color emission from 410 to 750 nm was realized in this single phosphor. The Eu2+ ! Mn2+ energy transfer mechanism was investigated by the fluorescence decay curves. This single phosphor exhibits an efficient excitation band covering from 390 to 410 nm, which matches well with the emission light of the efficient NUV chips. The optimized BLS:Eu2+, Ce3+, Mn2+ phosphor shows a high quantum efficient of $62% and a good color stability. When this single phosphor was combined with a 395 nm NUV-chip, an ideal white LED with a high color render index (CRI) of 85 and a correlated color temperature (CCT) of 6300 K was obtained. This demonstrates the promising application of the BLS:Eu2+, Ce3+, Mn2+ single phosphor for the NUV-based white LEDs.
分类: 地球科学 >> 地理学 提交时间: 2019-08-30 合作期刊: 《干旱区科学》
摘要: Riverine sand dunes develop as a result of fluvial-aeolian interactions. The primarily barchan dune chains along the Xiangshui River (a branch of the Xar Moron River in the western part of the Horqin Sandy Land of China) form a typical riverine dune field. We collected a series of samples from the riverine sand dunes parallel to the direction of the prevailing wind and investigated the sand sources and formation mechanisms of these dunes by determining the grain size, heavy mineral content and optically stimulated luminescence (OSL) of the samples. The sand of the near-river dunes was coarser than the sand of the dunes distant from the river, indicating that coarse sand of the valley mainly deposited on near-river dunes. The heavy mineral analysis suggested that wind-sand activity levels were intense on the upwind dunes, but relatively weak on the downwind dunes. This indicated that the sand sources for the near-river dunes were more abundant than those of the distant dunes. Our OSL analysis of samples suggested that the deposition rates on dunes near the river were greater than the deposition rates on dunes distant from the river. The development of dunes along the river indicated that the river played an important role in dune formation and development. In addition, airflow fluctuation and the formation of the waveform dunes had a type of feedback relationship. Grain size, heavy mineral and OSL analyses are widely used methods in wind-sand research. Sand dune grain size characteristics reflect the effects of airflow on the transport and separation of sand materials, as well as the physical characteristics of the sand sources. Heavy mineral characteristics are often used to investigate the relationships between sediments and sand sources. OSL indicates dune age, revealing formation of dunes. Therefore, it is useful to explore dune sand sources, as well as the mechanisms underlying dune formation, by determining grain size, heavy mineral content and OSL. This study investigated the sand sources of riverine dunes and provided new information about riverine dune formation and development.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: Isoenzyme c of horseradish peroxidase (HRP-C) is widely used in enzyme immunoassay combined with chemiluminescence (CL) detection. For this application, HRP-C activity measurement is usually based on luminol oxidation in the presence of hydrogen peroxide (H2O2). However, this catalysis reaction was enhancer dependent. In this study, we demonstrated that Jatropha curcas peroxidase (JcGP1) showed high efficiency in catalyzing luminol oxidation in the presence of H2O2. Compared with HRP-C, the JcGP1-induced reaction was enhancer independent, which made the enzyme-linked immunosorbent assay (ELISA) simpler. In addition, the JcGP1 catalyzed reaction showed a long-term stable CL signal. We optimized the conditions for JcGP1 catalysis and determined the favorable conditions as follows: 50 mM Tris buffer (pH 8.2) containing 10 mM H2O2, 14 mM luminol and 0.75 M NaCl. The optimum catalysis temperature was 30 degrees C. The detection limit of JcGP1 under optimum condition was 0.2 pM. Long-term stable CL signal combined with enhancer-independent property indicated that JcGP1 might be a valuable candidate peroxidase for clinical diagnosis and enzyme immunoassay with CL detection. Copyright (C) 2014 John Wiley & Sons, Ltd.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: A d-f heteronuclear metal-organic framework (MOF), {[Tm3Zn6(bipy2)2(mimda)7 (H2O)3]·(H2O)5}n (1, H3mimda = 2-methyl-1-H-imidazole-4,5-dicarboxylic acid, and bipy = 4,4΄-bipyridine), has been synthesized under solvothermal conditions, and structurally characterized by elemental analysis, IR spectra and X-ray single-crystal diffraction. It crystallizes in orthorhombic system, space group Pnma with a = 16.1102(9), b = 33.5805(19), c = 16.8593(10) Å, β = 97.344(11)°, V = 9120.7(9) Å3, Z = 4, F(000) = 5184, the final R = 0.0530 and wR = 0.1306. In complex 1, the Tm(III) ions adopt two types of coordination fashions. Complex 1 shows one-dimensional (1-D) Tm-Zn heteronuclear zigzag chains, and these chains are further linked by H3mimda ligands into Tm-Zn heteronuclear 2-D lattice-like arrays. The 2-D heteronuclear units were connected through [Zn6(mimda)6] rings to give rise to the Tm-Zn heteronuclear cages. Finally, H3mimda ligands connected the cages into a 3-D heterometallic framework by the combination of [TmO7]n and Tm-Zn heteronuclear cages. In addition, the thermal stability and luminescent property have been investigated.