Electrogenerated chemiluminescence. 81. Influence of donor and acceptor substituents on the ECL of a spirobifluorene-bridged bipolar system

The electrochemistry and radical ion annihilation electrogenerated chemiluminescence (ECL) of 9,9'-spirobifluorene-bridged bipolar systems containing 1,3,4-oxadiazole-conjugated oligoaryl and triarylamine substituents were investigated. The stability of the oxidized spirobifluorenes was improved by functionalization with triarylamine centers. These donor-acceptor (DA) compounds exhibited a good fluorescence efficiency with an emission maximum that correlated with the potential difference between radical anion and cation formation, suggesting a charge transfer (CT) emission band. An ECL mechanism based on the formation of the CT excited state by radical ion annihilation or production of the triplet state followed by triplet-triplet annihilation, with perhaps some excimer contribution, is proposed.     

Effect of a magnetic field on thermostimulated chemiluminescence

Conclusions Effects, associated with relaxation of the spins and the rates of the electronic transitions as a function of the spin states, which determine the sensitivity of processes to an external magnetic field, can be observed in thermally stimulated chemical reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2355–2356, October, 1974.     

Effect of a magnetic field on the kinetics of the annihilation of triplet exciplexes

Conclusions The application of an external magnetic field leads to a lower rate of annihilation of triplet exciplexes in media with sufficiently high dielectric constant, in which the dissociation of the exciplexes to radical-ions is observed. The magnetic effect is explained in the framework of a hyperfine interaction mechanism for singlet-triplet transitions in radical pairs.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2611–2614, November, 1987.     

Unexpected sense dependence of the effect of a magnetic field on delayed fluorescence

Delayed fluorescence intensity from pyrene and methylene phenanthrene crystals alters when an applied, steady magnetic field is reversed. This sense dependence vanishes at high fields. It is maximum along the pyrene two-fold axis and zero in the mirror plane.     

Electrogenerated chemiluminescence. XVI. ECL of palladium and platinum α,β,γ,δ-tetraphenylporphyrin complexes

The electrochemistry of the Pt(II) and Pd(II) complexes with α,β,γ,δ-tetraphenylporphin (TPP) in dichloromethane solutions containing 0.1 M tetra-n-butylammonium perchlorate is characterized by one-electron transfers to form both oxidized and reduced species. The electron transfer reactions between these electrogenerated species lead to the emission of light. The radiating species has been identified as the lowest triplet state of the Pt(TPP) or Pd(TPP) by comparison with results of previous spectroscopic studies.     

Influence of a magnetic field on delayed fluorescence of aromatic hydrocarbons in solution: I. Dependence on temperature,solvent and solute

The relative magnetic field effects on the total triplet—triplet annihilation (TTA) rate constant, on the rate constant for production of a singlet monomer and on the rate constant for production of a singlet excimer have been measured in a magnetic field range from 0 to 6000 gauss for the hydrocarbons pyrene, 3,4-benzopyrene, 1,2-benzanthracene and phenanthrene in solvents of different polarity between room temperature and 120 K. A qualitative discussion of the experimental results yields the following information on the mechanism of TTA: (i) The ratio of singlet to triplet products decreases with decreasing temperature or increasing viscosity of the solvent. (ii) The magnetic field effect depends much more on viscosity than on temperature. (iii) Singlet monomers and excimers are predominantly formed from different initial triplet—triplet pair configurations. (iv) Ionic radical pair states do not seem to play an important role in the TTA mechanism between equal molecules.     

Effect of external field on phase behavior of ternary systems involving polypeptide

Phase behavior of ternary systems comprising arigid-rod polymer, a randomly coiled polymer, and asolvent was first studied by Flory on the basis of thelattice model[1]. According to the theory, above a criti-cal polymer concentration the ternary solution …     

Effect of a weak magnetic field on hematite sol in stationary and flowing systems

The effect of a weak magnetic field on the aggregation state and electrophoretic mobility of hematite sol was studied in flowing (dynamic) systems as a function of time and electrolyte concentration (0–60 mmol/dm³ KCl) and compared with the effect of the field in stationary (static) systems and flow in the absence of the field. During the entire treatment period, the pH remained almost constant (4.06–4.24). Conductance varied with KCl concentration, but except for minor fluctuations appeared to be unaffected by any form of treatment. While aggregation of hematite was observed during dynamic magnetic treatment (change in turbidity, scattered light intensity, and photon correlation spectroscopy), little effect on aggregation state was observed for the static systems or for the flowing systems in the absence of the field. Mobility also increased during the first 30 min of static and dynamic magnetic treatment. After longer treatment periods (90–120 min), the mobility decreased, but in almost all cases remained larger than in the case of untreated systems. Changes in both mobility and particle aggregation state also showed a significant dependence on electrolyte concentration. These effects are discussed in terms of a magnetohydrodynamic interaction between the magnetic field and the charged colloidal particles, which results only when the particles are made to pass rapidly through the field.     

Effect of high magnetic fields on intramolecular exciplex fluorescence of pyrene and dimethylaniline systems

The effect of high magnetic fields (〈13 T) on the intramolecular exciplex fluorescence generated from chain-linked pyrene and dimethylaniline systems is studied in acetonitrile. On increasing the magnetic field from 0 to ca. 1 T, the exciplex fluorescence intensity increases and then decreases gradually for fields up to ca. 8 T. The exciplex fluorescence lifetime exhibits a magnetic field dependence similar to that for the intensity (〈13 T). The reversal of the effect in the high magnetic field region is interpreted in terms of a Δg mechanism.     

Magnetic field effects on the fluorescence of intramolecular electron-donor-acceptor systems

The external magnetic field effects on the exciplex fluorescence of α-(4-dimethylaminophenyl)-ω-(9-phenanthryl)alkanes have been studied by photostationary, time-resolved, and magnetic field modulation fluorescence spectroscopy. The singlet-triplet degeneracy of the radical ion pair is suggested to occur at a methylene chain length of about ten.     

The influence of a magnetic field on the fluorescence and photolysis rate of carbon disulfide vapour

The effect of a magnetic field on the fluorescence of carbon disulphide vapour under stationary excitation by light with λ = 3130±30 Å has been investigated at 0.014–165.1 Torr. Over the whole range of pressure, the magnetic effect does not depend on the gas pressure. A magnetic field has been found to affect the photolysis rate of carbon disulphide vapour in light with λ>2900 Å. The magnetic effect does not vary with pressure from 2.6–90 Torr.     

基于生物条形码的粘蛋白和特定细胞电化学发光适配体生物传感方法研究

本文基于适配体识别和生物条形码放大策略,以MCF-7细胞和粘蛋白(MUC1)为目标物,MUC1的特异性适配体(rcDNA)为分子识别物质,Ru(phen)32+为信号物质,rcDNA通过巯基自组装于金电极表面作为传感界面,发卡DNA (hpDNA)和rcDNA通过巯基自组装在金纳米粒子(AuNP)表面合成的hpDNA/...     

Effect of the magnetic field on the hydrodynamic permeability of a membrane

The present paper concerns the influence of the magnetic field on the permeability of a membrane of solid cylindrical particles covered with porous layer. Here, we have considered the flow along the axis of cylinder and the alignment of uniform magnetic field is assumed to be perpendicular to the axis. The Brinkman equation is used for flow through porous region and Stokes equation is used for flow through clear fluid region. To model flow through assemblage of particles, cell model technique has been used i.e. the porous cylindrical shell is assumed to be confined within a hypothetical cell of same geometry. The stress jump condition has been employed at the fluid-porous interface and all four alternative conditions Happel, Kuwabara, Kvashnin and Mehta-Morse/Cunningham are used at the hypothetical cell. Effect of the Hartmann number on the hydrodynamic permeability of the membrane is discussed.     

Weak transverse magnetic field effect on the viscosity of water at several temperatures

Experiments performed at 10, 20, 25, 30, 35, 40 and 50°C show that a transversally applied magnetic field H (H ranges from 0 to 12 kG) weakly increases the viscosity of distilled water. The largest value of this increase occurs at the applied magnetic field strength of 12 kg at the vicinity of a temperature of 25°C.     

Effects of extremely low frequency magnetic field on the antioxidant defense system in mouse brain: a chemiluminescence study

Among the putative mechanisms, by which extremely low frequency (ELF) magnetic field (MF) may affect biological systems is that of increasing free radical life span in organisms. To test this hypothesis, we investigated whether ELF (60 Hz) MF can modulate antioxidant system in mouse brain by detecting chemiluminescence and measuring superoxide dismutase (SOD) activity in homogenates of the organ. Compared to sham exposed control group, lucigenin-initiated chemiluminescence in exposed group was not significantly increased. However, lucigenin-amplified t-butyl hydroperoxide (TBHP)-initiated brain homogenates chemiluminescence, was significantly increased in mouse exposed to 60 Hz, MF, 12 G for 3 h compared to sham exposed group. We also measured SOD activity, that plays a critical role of the antioxidant defensive system in brain. In the group exposed to 60 Hz, MF, 12 G for 3 h, brain SOD activity was significantly increased. These results suggest that 60 Hz, MF could deteriorate antioxidant defensive system by reactive oxygen species (ROS), other than superoxide radicals. Further studies are needed to identify the kind of ROS generated by the exposure to 60 Hz, MF and elucidate how MF can affect biological system in connection with oxidative stress.     

Effect of a d.c. electric field on the fluorescence spectra of cationic polymethine dyes in a polymer film

We have observed that in an external d.c. electric field, in the differential fluorescence spectra of both symmetric and asymmetric polymethine dyes in a polymer film, the intensity of the emission in the long-wavelength region of the band increases while the intensity in the short-wavelength region decreases. In symmetric polymethines, these effects are opposite to those in the differential absorption spectra, while in asymmetric polymethines they are symbatic. The spectral effects were interpreted by a change in the probability of the vibronic transitions due to redistribution of electron density in the chromophore, in the ground state and the excited state of the dye, in an external electric field. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 343–347, November–December, 2008.     

Effect of a homogeneous magnetic field on the mechanical behavior of soft magnetic elastomers under compression

The mechanical properties of new magnetic composite materials were studied. The above materials represent rubbery silicon matrices filled with magnetic microparticles of metallic iron or magnetite. In homogeneous magnetic fields with an intensity of up to 0.4 T, the shear modulus of the composites was abnormally high (up to 10 000%). The variation of elastic properties of new materials on the type and volume content of the magnetic filler was investigated. In the presence of a sufficiently strong magnetic field, the above composites were shown to behave as elastoplastic materials with strengthening.     

The effect of encounters involving ions,excited molecules,and neutral radicals in a track on the delayed fluorescence of irradiated alkane solutions

A computer model has been developed to simulate the processes of the excited states formation in irradiated alkane solutions. The model includes the charge and energy transfer reactions as well as intratrack encounters involving excess electrons, radical ions, the excited states of molecules, and neutral radicals including spin effects. The model is applied to visualize the contact interactions and to establish their effect on the delayed fluorescence decay in nanosecond time domain after pulsed irradiation. The model predicts no significant influence of neutral alkyl radicals on the delayed fluorescence.     

Effect of a magnetic field on the rheological properties of cellulose ether solutions

Application of a magnetic field is shown to be accompanied by an increase in the viscosity of hydroxyethyl cellulose and ethyl cellulose solutions and an additional assembly of macromolecules, as is evident from a gain in the radii of light-scattering particles. The concentration dependences of supramolecular-particle radius and solution viscosity in the presence of a magnetic field are described by curves with maxima.