共查询到20条相似文献,搜索用时 15 毫秒
1.
Based on calculations using density functional theory, we show that C60 can act as a chemical Faraday cage in which a highly magnetic metal cluster with a high chemical reactivity can be encapsulated. As an example, we find that C60 can encapsulate a Fe3 cluster, while it is much less likely to encapsulate a Fe2 cluster. Spin multiplicity (=9) of the Fe3@C60 is very high, being comparable to that (=11) of a free Fe3 cluster. Geometrically, the triangular plane of the cluster is perpendicular to a S6 axis of the fullerene. 相似文献
2.
In this work, we introduce the idea of cage formation probability, defined by considering the angular space needed by a particle in order to leave a cage given an average distance to its neighbors. Considering extreme fluctuations, two phases appear as a function of the number of neighbors and their distances to a central one: Solid and fluid. This allows us to construct an approximated phase diagram based on a geometrical approach. As an example, we apply this probability concept to hard disks in two dimensions and hard spheres in three dimensions. The results are compared with numerical simulations using a Monte Carlo method. 相似文献
3.
Sato Y Ohkoshi S Arai K Tozawa M Hashimoto K 《Journal of the American Chemical Society》2003,125(47):14590-14595
Solvent exchange caused reversible variations in color, magnetic properties, and the Faraday spectra of Co(II)(1.5)[Cr(III)(CN)(6)].7.5H2O (1) prepared in water. Compound 1 turned from peach to deep blue, which was due to a change in the coordination geometry on Co(II) ion from six-coordinate pseudo-octahedral (OhCo(II)) to four-coordinate pseudo-tetrahedral (TdCo(II)) geometries, when it was immersed in EtOH. The confirmed formula for the deep blue powder was Co(II)(1.5)[Cr(III)(CN)(6)].2.5H2O.2.0EtOH. The magnetic properties also changed; that is, the magnetic critical temperature, saturation magnetization, and coercive field went from 25 to 18 K, from 7.0 to 5.5 micro(B), and from 240 to 120 G, respectively. This solvatomagnetism is because the ferromagnetic magnetic coupling between OhCo(II) (S = 3/2) and Cr(III) (S = 3/2) is replaced by the antiferromagnetic coupling between TdCo(II) (S = 3/2) and Cr(III) (S = 3/2). Accompanying the solvatochromism and solvatomagnetism, the Faraday spectra drastically changed. The Faraday ellipticity (FE) spectrum of 1 had a distorted dispersive peak (A), which is due to the 4T1g --> 4T1g, 2T1g transitions of OhCo(II) ion, around 480 nm, but the FE spectra of 2 showed a new dispersive-shaped band (B) at 580 nm. The observed B band was assigned to the 4A2 --> 4T2 transition of the TdCo(II) ion. The Faraday spectra were well reproduced by a simulation that considers the ligand field splitting, spin-orbital coupling, and the ferromagnetic ordering. These solvatochromic effects were repeatedly observed. 相似文献
4.
Panov é. V. Pototskaya V. V. Gorodyskii A. V. 《Theoretical and Experimental Chemistry》1977,13(1):89-91
Theoretical and Experimental Chemistry - 相似文献
5.
T.R. Tuttle 《Chemical physics letters》1973,20(4):371-373
The Faraday effect for sodium dissolved in EDA indicates a magentic moment of about one Bohr magneton for the excited state involved in the 650 nm absorption. Comparison with results for iodide ion suggest a structure for the 650 nm band. A simple connection between ellipticity and derivative of absorption is pointed out and used in analyzing the data. 相似文献
6.
Amphiphilic water-soluble poly(alkyl aryl ether) dendrimers Gn (n = 1-3) with charge-neutral tetraethylene glycol monomethyl ethers at their periphery were synthesized as microreactors to control the photochemical reactions of dibenzyl ketone derivatives in aqueous solutions. Photophysical studies demonstrated that Gn can encapsulate organic molecules and provide a hydrophobic microenvironment. The product distribution of photolysis of dibenzyl ketone derivatives can be successfully controlled by encapsulating the substrates within dendrimers, and an unsurpassed cage effect of 1.00 is reached in high generation dendrimers, revealing that a thick and compact "shell" was formed at the periphery of the dendrimers. The cage effect is also significantly influenced by the substituent at the para-position of the guest molecules. The higher generation dendrimers exhibit a better confined microenvironment and the aggregates possess more compact cavities to "lock" the guests than the corresponding unimolecular dendrimers. After photolysis, the separation of products can be easily achieved by extracting from the dendrimer solutions and the dendrimers are simply recovered and reused. 相似文献
7.
In some systems, the donor of a triplet—triplet energy transfer can be sensitized in its singlet state through a singlet—singlet energy transfer (Dexter mechanism), where the donor is the acceptor of the triplet transfer itself. As a consequence an extra acceptor molecule in the triplet energy transfer is present in the vicinity of the donor, thus enhancing the efficiency of the transfer process. Experiments show clearly this effect and a diffusional model gives semi-quantitative agreement with the experimental data. 相似文献
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9.
A computer experiment on a two-dimensional Lorentz gas is described for which the autocorrelation function of the induced dipole moment exhibits an extremely long positive tail. It is argued that this tail can be ascribed to the trapping of particles in irregular cages. 相似文献
10.
The photodissociation of iodine has been studied in the gas phase by laser flash photolysis. The decrease of the quantum yield with increasing ethane and propane pressure has been interpreted in terms of the cage effect. As the temperature is increased a less pronounced cage effect is observed. The trends in the measured quantum yields with changing temperature and pressure agree with model calculations for dissociation in a viscous continuum. However the simple model applied is not useful for quantitative predictions. A small decrease of the second order rate constant for iodine atom recombination has been observed with increasing temperature. 相似文献
11.
Kuniyuki Kitagawa Toshiki Nanya Shin Tsuge 《Spectrochimica Acta Part B: Atomic Spectroscopy》1981,36(1):9-20
The atomic Faraday effect has been applied to the trace determination of lead in NBS Orchard Leaves, human blood, and volcanic ashes. Suspensions of powder samples and diluted whole blood are directly pipetted into a graphite tube atomizer. Spectroscopic and practical features are discussed of the atomic Faraday effect of lead. The inherent feature of insensitivity to background scattering makes the present technique suitable for practical analysis. The problem associated with loss of transmitted optical energy caused by non-atomic species was overcome by a correction method. Consequently, the present technique enabled us to perform rapid analyses, gave a detection limit of 5 × 10?11 g and fair accuracy, at least satisfactory for practical analysis. Some problems arise from residue build-up in the atomizer. 相似文献
12.
Masaaki Kubota Yoshimasa Fujishiro Ryohei Ishida 《Spectrochimica Acta Part B: Atomic Spectroscopy》1981,36(7):697-710
A strict, comparative investigation of published transition probabilities for thermometric lines and an experimental study of determinations of plasma temperatures were made for improving the accuracy in temperature measurements by the well-known slope method. Four sets of FeI lines which satisfy the requirements for the thermometric lines were selected in the wavelength region of 200–400 nm. A statistical method was used to evaluate degrees of agreement among different sets of transition probabilities. In the experimental study, excitation temperatures of a stabilized arc plasma were determined from relative line-intensities recorded by photoelectric scanning spectrometry. In conclusion, two recommended combinations of lines and transition probability data are presented for the slope temperature measurement. Line pairs used in combination of selected transition probabilities suitable for the two-line method are also given. 相似文献
13.
We describe a general method for the entrapment of enzymes within bulk metallic gold. This is a new approach for the immobilization of enzymes on metals, which is commonly carried out by 2D adsorption or covalent biding, that is, the enzyme is in contact with the metal at a specific contact zone of the enzyme, while most of the rest of it remains exposed to the environment. The 3D metallic encaging of the enzymes is quite different: the enzyme is in contact with the metallic cage walls all around it and is well protected inside. The porous nature of the metallic matrix enables substrate molecules to diffuse inside, reach the active site, and let product molecules diffuse out. The generality of the approach was proven by the successful entrapment of five enzymes representing different classes and different bio- and medical applications: l-asparaginase (Asp), collagenase, horseradish peroxidase (HRP), laccase and glucose oxidase (GOx). GOx–gold conjugates have been of particular interest in the literature. The main challenge we had to solve was how to keep the enzyme active in the process of gold-synthesis from its cation – this required careful tailoring of reaction conditions, which are detailed in the paper. The gold entrapped enzymes gain thermal stability and protectability against harsh conditions. For instance, we could keep Asp alive at the extreme pH of 13, which normally kills the enzyme instantly. The entrapped enzymes obey the Michaelis–Menten kinetics, and activation energies were determined. Good recyclability for eight cycles was found. Multi-enzymatic reactions by combinations of the off-the-shelf bioactive enzyme@gold powders are possible, as demonstrated for the classical detection of GOx activity with HRP. Detailed material characterization and proposed mechanisms for the 3D protectability of the enzymes are provided. The new enzyme immobilization method is of wide potential uses in medicine, biotechnology, bio-fuel cells and enzymatic (electro)sensing applications.We describe a general method for the entrapment of enzymes within bulk metallic gold. 相似文献
14.
No solvent cage effect could be found in the reduction of 4-aminocyclohexanone 3 by Shvo's hydroxycyclopentadienyl ruthenium hydride 2. No preference was observed in the complex formation from trapping by aminoalcohol product 4 over external trapping by aminoketone 3 or by Shvo hydride 2. A solvent cage effect has previously been proposed to support an outer-sphere mechanism in the reduction of imines by 2; this was based on the observation that there was >90% preference for complexation of the newly formed amine over an external amine. Since alcohols form stronger hydrogen bonds than amines a larger cage effect would be expected in the present study. The lack of a cage effect in the present reduction suggests that the previous results from imine reduction require an additional explanation (other than a solvent cage effect). 相似文献
15.
《Analytical letters》2012,45(6):1050-1057
16.
Nuclear spin optical rotation (NSOR) of linearly polarized light, due to the nuclear spins through the Faraday effect, provides a novel probe of molecular structure and could pave the way to optical detection of nuclear magnetization. We determine computationally the effects of the liquid medium on NSOR and the Verdet constant of Faraday rotation (arising from an external magnetic field) in water, using the recently developed theory applied on a first-principles molecular dynamics trajectory. The gas-to-liquid shifts of the relevant antisymmetric polarizability and, hence, NSOR magnitude are found to be -14% and -29% for (1)H and (17)O nuclei, respectively. On the other hand, medium effects both enhance the local electric field in water and, via bulk magnetization, the local magnetic field. Together these two effects partially cancel the solvation influence on the single-molecular property. We find a good agreement for the hydrogen NSOR with a recent pioneering experiment on H(2)O(l). 相似文献
17.
Expressions for a resonance dependence of geminate recombination probability of radical pairs on the intensity of an external steady magnetic field in the presence of a high-frequency magnetic field normal to it have been obtained Numerical calculations of the above dependence have been performed for the cases involving Δg and hyperfine coupling mechanisms of spin conversion. 相似文献
18.
The photolysis of iodine has been studied in the gas phase using laser flash photolysis at 6943 A. The dependence of the quantum yield on the pressure has been investigated in the range 0.1–1000 atm for several inert gases. For Kr, Xe, O2, CO2, CH4, C2H6 and C3H8 a decrease of the quantum yield with increasing pressure was obtained; for He, Ne, Ar and H2 no effect could be observed. These results may correspond to a photolycitc cage effect of iodine in the gas phase analogous to that known from the liquid phase. 相似文献
19.