共查询到20条相似文献,搜索用时 15 毫秒
1.
Quite recently much attention has been devoted to the direct determination of hydration numbers of cations in both aqueous solutions and in mixed solvent systems by means of PMR (proton magnetic resonance).1-10 相似文献
2.
合成了窄分子量分布低聚壳聚糖(CS20)修饰的四(4-羧基苯基)锰(Ⅱ)卟啉(Mn-TCPP)功能配合物(Mn-TCPP-CS20)作为一种潜在的磁共振成像(MRI)造影剂。发现该锰基卟啉-壳聚糖配合物(Mn-TCPP-CS20)有良好的水溶性和分子结构稳定性。通过红外(FTIR)、紫外(UV-Vis)、质谱(MS)及电感耦合等离子体发射仪(ICP-AES)对其结构进行了表征。表明,低聚壳聚糖CS20通过酰胺键与Mn-TCPP共价链接。初步研究了功能配合物Mn-TCPP-CS20作为潜在的MRI造影剂的体外弛豫性能,发现其纵向弛豫率r1 (6.11 mmol-1·l·s-1)高于商用的MRI造影剂Gd-DTPA (r1=3.59 mmol-1·l·s-1),且在同等条件下体外成像效果更优。Mn-TCPP-CS20可作为潜在的具有组织靶向性的MRI造影剂。 相似文献
3.
Yu. S. Orlov S. V. Nikolaev S. G. Ovchinnikov 《Journal of Experimental and Theoretical Physics》2019,129(6):1062-1069
We analyze the influence of cooperative effects on the magnetic properties and spin crossover between the high-spin (HS) term S = 5/2 and low-spin (LS) term S = 1/2 in Mott–Hubbard dielectrics with 3d5 ions under high pressures. Two cooperation mechanisms (superexchange interaction and effective interaction via the elastic system) are considered. The sign of the exchange interaction changes because of the crossover from the antiferromagnetic in the HS state to the ferromagnetic in the LS state. In view of the large difference between the ionic radii of the HS and LS states, the systems with spin crossover acquire an additional strong coupling via the elastic system. Using the Hubbard operator representation and considering the electronic states of the two terms simultaneously, we obtain the effective Hamiltonian with allowance for the cooperative effects. The magnetic phase diagram and the spin crossover are investigated in the mean field approximation. It is shown that the inclusion of cooperative effects at low temperatures leads to a first-order phase transition between the antiferromagnetic HS state and the ferromagnetic LS state. At higher temperatures, more complicated sequences of phase transitions are possible upon an increase in pressure, including the HS paramagnet–HS antiferromagnet–LS paramagnet and HS antiferromagnet–LS paramagnet–LS ferromagnet transitions. 相似文献
4.
壳聚糖与五种过渡金属离子形成配合物的研究 总被引:7,自引:0,他引:7
差热分析法、红外光谱法研究了壳聚糖和5种过渡元素金属离子盐(Fe3 、Co2 、Ni2 、Cu2 、Zn2 )形成不同壳聚糖金属配合物变化特征.结果表明,由于壳聚糖分子中含有大量的-NH2、-OH基,与金属离子发生配位作用后,吸热和放热峰均发生了较大的位移,在3400cm-1羟基和氨基、1654.11cm-1处酰胺IR吸收峰均发生了相应的变化;而位于1379cm-1 C-H弯曲和-CH3对称变形振动吸收峰保持不变,表明壳聚糖与金属离子发生配位后稳定空间构象发生变化. 相似文献
5.
利用拉曼光谱仪测定L-半胱氨酸(L-Cys)的常规拉曼光谱(NRS)和表面增强拉曼光谱(SERS),发现L-Cys在纳米银棒上有明显的拉曼增强效应,对分子特征峰进行了归属,研究L-Cys在银纳米棒基底表面吸附机理,在固体NRS中在2 576 cm-1出处有明显的S-H伸缩振动峰,而SERS中没有出现,实验表明纳米银棒与L-Cys巯基上的S原子形成了Ag-S键,C-O和C-N伸缩振动有明显的增强。在不同pH值条件下,分析了L-Cys的拉曼光谱差异,探讨吸附行为的变化。在pH值为6时,S-H的伸缩振动峰基本消失,形成了稳定的S-Ag键;随着pH值增加趋于碱性时,羧基易失去H原子形成-COO-易与银发生吸附作用且振动峰增强。在pH值为7时,S原子与Ag形成稳定的S-Ag键,C-O和C-N的振动峰也最稳定。选择在pH值为7的条件下,在L-Cys溶液中加入Na+,Mg2+和Cu2+ 等10种金属盐,发现Al3+,Cu2+,Zn2+,Cd2+和Hg2+ 使L-Cys分子的结构发生了改变,金属离子与L-Cys另一端羧基发生作用,其中Cu2+,Zn2+,Cd2+和Hg2+随半径增大与S原子的孤电子发生作用越大。探讨了在不同pH值、不同比例和不同浓度下,金属离子与L-Cys作用SERS的变化,随着pH值、比例和浓度的增大,峰的强度有减小趋势。Cu2+与L-Cys作用的SERS信号很弱,Hg2+与L-Cys作用只出现了一个C-O的振动峰,说明Hg2+完全破坏了L-Cys的空间构型。该研究对蛋白质变性等的研究提供了重要参考信息。 相似文献
6.
Alfonso Zoleo Daria Confortin Nicola Dal Mina Marina Brustolon 《Applied magnetic resonance》2010,39(3):215-223
Samples from covers and endleaves of sixteenth to eighteenth century books in good conservation state from the Biblioteca
Nazionale Marciana in Venice have been investigated by means of electron paramagnetic resonance (EPR) spectroscopy and optical
microscopy to characterize the embedded paramagnetic species and to test differences and similarities of the materials in
the two types of book components. We detected the Mn(II), Fe(III), and Cu(II) paramagnetic ions, and analyzed their EPR signals
by comparing them with previous results in literature of EPR studies on paper. Interestingly, the Mn(II) EPR spectrum profile
appears as a fingerprint for samples coming from the same book, either from cover or endleaf, and it looks different for samples
extracted from different books. We discuss the role of EPR as a spectroscopic tool for characterizing the interaction of the
ions with the paper components and as possible agents of degradation. 相似文献
7.
Technical Physics - The initial composition and chemical state of nanopowder primary particles obtained by grinding natural diamond and detonation synthesis have been studied by X-ray photoelectron... 相似文献
8.
R. V. S. S. N. Ravikumar K. Kayalvizhi A. V. Chandrasekhar Y. P. Reddy J. Yamauchi K. Arunakumari P. S. Rao 《Applied magnetic resonance》2008,33(1-2):185-195
Electron paramagnetic resonance (EPR) and optical studies have been carried out on Cu(II)-, VO(II)- and Cr(III)-doped strontium
tetraborate glasses to understand the distortion and substitution of these ions. The EPR results of Cu(II) glass indicate
that g
∥ > g
⊥, typical for the tetragonally elongated octahedral site of the Cu(II) impurity. The evaluated covalency parameter 0.788 suggests
a moderate covalency for the bonding. By correlating EPR and optical results, the in-plane π-bonding β1
2 is evaluated as 0.715. In the vanadium-doped glasses, the distortion must be a tetragonally elongated octahedron, similar
to Cu(II). However, the EPR studies show that g
⊥ > g
∥ indicating the tetragonally compressed octahedral site for the ion. The site symmetry is C
4V. Supported by the optical absorption, evaluated parameters propose a moderate covalency. The EPR and optical results for
Cr(III) glass indicate the distorted octahedral site symmetry in the host lattice. These results further suggest that the
bonding between Cr(III) and the ligands is covalent.
Authors' address: Renduchintala V. S. S. N. Ravikumar, Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar
522510, India 相似文献
9.
2,6-二氨基吡啶(DAPD)衍生物都有较强的荧光。除DMHND(2,4-二甲基-7-羟基-1,8-萘啶)外,2,4-二甲基-7-胺基-1,8-萘啶(DMAND)和2,4-二甲基-7-丙烯酰胺基-1,8-萘啶(DMAAN)在加入过渡金属离子后,荧光强度增强,发射光谱红移,可以作为过渡金属离子的荧光探针。根据Irving-Williams顺序,以过渡金属中络合能力较强的Cu2+为代表,求算了DMAND和DMAAN与Cu2+的结合比,通过非线性拟合计算了结合常数,比较了它们与金属离子结合的强弱,DMAND较DMAAN为更灵敏的过渡金属离子荧光探针。 相似文献
10.
Helena Fridman Mahmud Diab Michael Volokh Alexander I. Shames Sofiya Kolusheva Taleb Mokari 《Particle & Particle Systems Characterization》2019,36(3)
A wide range of nanoparticle properties can be tuned by changing their surface characteristics, especially when dealing with ultrathin nanomaterials. Surface modification with transition‐metal ions may affect a variety of the nanoparticles' properties including the surface charge, the electronic structure, and the electrical and optical characteristics. In this work, a surface study of ceria nanoparticles modified by attachment of various transition‐metal ions to their surface is conducted. Characterization of the decorated particles as well as of the modifying transition‐metal ion is carried out using zeta potential in organic solution, UV–Vis absorption, and electron paramagnetic resonance measurements, together with isothermal titration calorimetry, X‐ray photoelectron spectroscopy, and energy dispersive X‐ray spectroscopy. All measurements confirm the attachment of the cation to the surface of ceria, both in solid state and in colloidal suspension. It is suggested that the modifying ion‐complex attaches to ceria both via chemical or strong physical interactions and weak physical interactions, demonstrated by a case‐study modification of ceria using a copper‐oleylamine complex. The metalization has a significant effect on the surface charge of the nanoparticles by shifting the zeta potential to more positive values and on the optical properties of the modifying transition‐metal ions by red‐shifting their absorption peak. 相似文献
11.
The basic theoretical ideas about the influence of the magnetic susceptibility of the sample material on the nuclear magnetic resonance line position and width of powder samples are discussed. Three different effects may occur the respective influence of which could be derived from multiple-pulse line-narrowing experiments with and without rapid magic-angle sample spinning using powder samples mixed from polymer and metal powders. Measures to avoid the influence of the susceptibility effects are proposed. 相似文献
12.
设计合成了用以检测过渡金属离子的荧光化学敏感器体系,它们是由1,8-萘二酰亚胺为荧光团,多胺衍生物为金属离子受体组成.在室温下对其光物理性质的研究中发现,在没有加入过渡金属离子时,由于体系内存在有效的光诱导电子转移过程使得荧光团的荧光被淬灭.加入过渡金属离子后,金属离子受体中的氮原子和过渡金属离子之间的配位作用阻断了光诱导电子转移过程,体系的荧光增强.不同的金属离子受体表现出了和过渡金属离子不同的配位识别能力,并且通过荧光的变化传递出受体-金属离子作用的信息. 相似文献
13.
Orlov Yu. S. Nikolaev S. V. Ovchinnikov S. G. 《Journal of Experimental and Theoretical Physics》2020,131(2):374-374
Journal of Experimental and Theoretical Physics - erratum 相似文献
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16.
运用傅里叶变换红外光谱技术,对DL-2-氨基-4-磺酸基丁酸(DLH)与Na+,Cu2+,Zn2+和Ni2+ 形成的配合物进行了研究,并用元素分析的方法确定配合物的组成。红外光谱显示DLH分子中的—COOH,—NH+3和—SO-3 基团均可与金属离子发生直接或间接的相互作用。不同过渡金属离子与氨基、羧基相互作用的强度顺序均为: Cu2+>Zn2+>Ni2+,其中羧基与不同离子可能采取了不同的配位方式。 相似文献
17.
采用高温固相法制备了Na8 Al6 Si6 O24 Cl2∶M n和Na8 Al6 Si6 O24 Cl2∶Fe近红外发光材料。测定了荧光粉的X射线粉末衍射(XRD ),及室温下的光致近红外发射光谱和激发光谱。在400 nm紫外光和602 nm可见光的激发下,Na8 Al6 Si6 O24 Cl2∶M n粉末中的M n5+(3 A2-3 T2,3 A2-1 E)发射了主发射峰位于1200 nm的近红外光谱。实验发现,M n和S共掺提高了该粉末的近红外发光强度,文中对此提出了S2--M n5+之间的能量传递机理。在334和500 nm的激发下,Na8 Al6 Si6 O24 Cl2∶Fe粉末中的Fe2+(3 T1-5 E)发射了主发射峰位于1000 nm的红外光谱,该现象对提高硅太阳能电池的效率可能具有积极意义。 相似文献
18.
The process of the multilayer growth of Pt on Pt (111) is studied by using a Monte Carlo model with realistic physical parameters. The effects of the substrate temperature, the ES barrier, and the deposition rate
on the growth mode have been investigated. Gradual transitions of the
surface roughness from oscillatory
to non-oscillatory behavior and then back to oscillatory behavior are observed while increasing the substrate
temperature from 270 K to 620 K. It is found that the growth mode depends
strongly on ES barrier over the whole temperatures and the deposition rate
of atoms effectively affects the growth mode. The simulation results are
consistent with many experimental observations for homoexpitaxy on a Pt (111) substrate. 相似文献
19.
The process of the multilayer growth of Pt on Pt (111) is studied by using a Monte Carlo model with realistic physical parameters. The effects of the substrate temperature, the ES barrier, and the deposition rate on the growth mode have been investigated. Gradual transitions of the surface roughness from oscillatory to non-oscillatory behavior and then back to oscillatory behavior are observed while increasing the substrate temperature from 270 K to 620 K. It is found that the growth mode depends strongly on ES barrier over the whole temperatures and the deposition rate of atoms effectively affects the growth mode. The simulation results are consistent with many experimental observations for homoexpitaxy on a Pt (111) substrate. 相似文献