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Domracheva N.E.,Zavoisky Kazan Physical Technical Institute | Morozov V.I.,RAS Arbuzov Institute of Organic and Physical Chemistry | Gruzdev M.S.,University of Bayreuth | Gruzdev M.S.,RAS Institute of Chemistry | And 3 more authors.
Macromolecular Chemistry and Physics | Year: 2010

Here, we report the first results of investigation the local structure and photoactive properties of iron-containing dendromesogens based on decyloxybenzoate substituted poly(propylene imine) dendrimers of the first to fifth generations. Iron ions existing in a high-spin state are coordinated in dendrimer ligands by two kinds of iron-complexing sites with an octahedral and a tetrahedral symmetry. Octahedral (high-symmetry) centers are located at the border of the dendrimeric core, while the tetrahedral centers with strong rhombic distortion of iron environment are distributed throughout all branching of the dendrimeric core. It has been found that all iron-containing dendromesogens exhibit light-harvesting and fluorescence properties. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Domracheva N.E.,Zavoisky Kazan Physical Technical Institute | Pyataev A.V.,Kazan Federal University | Manapov R.A.,Kazan Federal University | Gruzdev M.S.,RAS Institute of Chemistry
ChemPhysChem | Year: 2011

We present the first results of electron magnetic resonance (EMR) and Mössbauer spectroscopy studies of γ-Fe 2O 3 nanoparticles (NPs) incorporated into liquid-crystalline, second-generation dendrimers. The mean size of NPs formed in the dendrimers was around 2.5 nm. A temperature-driven transition from superparamagnetic to ferrimagnetic resonance was observed for the sample. Low-temperature blocking of the NP magnetic moments has been clearly evidenced in the integrated EMR line intensity and the blocking temperature was about 60 K. The physical parameters of magnetic NPs (magnetic moment, effective magnetic anisotropy) have been determined from analyses of the EMR data. The effective magnetic anisotropy constant is enhanced relative to bulk γ-Fe 2O 3 and this enhanced value is associated with the influence of the surface and shape effects. The angular dependence of the EMR signal position for the field-freezing sample from liquid-crystalline phase showed that NPs possessed uniaxial anisotropy, in contrast to bulk γ-Fe 2O 3. Mössbauer spectroscopy determined that fabricated NPs consisted of an α-Fe core and a γ-Fe 2O 3 shell. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Nikiforov V.G.,Zavoisky Kazan Physical Technical Institute
EPJ Web of Conferences | Year: 2015

We propose the implementation of the multiple-pulse excitation for manipulation of the molecular contributions to the optically-heterodyne-detected optical-Kerr-effect. The key parameters controlling the specificity of the multiple-pulse excitation scenarios are the pulses durations, the delays between pulses, the relation between the pump pulses amplitudes and the pulses polarizations. We model the high-order optical responses and consider some principles of the scenarios construction. We show that it is possible to adjust the excitation scenario in such a way that the some responses can be removed from detected signal along with the enhancement of the interested response amplitude. The theoretical analysis and first experimental data reveal that the multiple-pulse excitation technique can be useful for the selective spectroscopy of the molecular vibrations and rotations in liquid. © 2015 Owned by the authors, published by EDP Sciences. Source


Vorobeva V.E.,Zavoisky Kazan Physical Technical Institute | Domracheva N.E.,Zavoisky Kazan Physical Technical Institute | Gruzdev M.S.,RAS Institute of Chemistry | Pyataev A.V.,Kazan Federal University
Materials Science in Semiconductor Processing | Year: 2015

We are presenting the joint investigation of the optical and photoinduced superparamagnetic properties of a single-domain γ-Fe2O3 nanoparticles (NPs) formed in poly(propylene imine) (PPI)-dendrimer. The optical absorption studies indicated direct allowed transition with the band gap (4.5 eV), which is blue-shift with respect to the value of the bulk material. The influence of pulsed laser irradiation on the superparamagnetic properties of γ-Fe2O3 NPs was studied by Electron paramagnetic resonance (EPR) spectroscopy. It has been shown that irradiation of the sample in vacuo and cooled in zero magnetic field to 6.9 K leads to the appearance of a new EPR signal, which decays immediately after the irradiation is stopped. We suppose that the generation of conduction band electrons by irradiation into the band gap of the γ-Fe2O3 changes the superparamagnetic properties of NPs. © 2014 Elsevier Ltd. All rights reserved. Source


Domracheva N.E.,Zavoisky Kazan Physical Technical Institute | Vorobeva V.E.,Zavoisky Kazan Physical Technical Institute | Gruzdev M.S.,RAS Institute of Chemistry | Pyataev A.V.,Kazan Federal University
Journal of Nanoparticle Research | Year: 2015

Abstract: We are presenting the investigation of the optical, magnetic, and photoinduced superparamagnetic properties of single-domain γ-Fe2O3 nanoparticles (NPs) with diameters of about 2.5 nm formed in second-generation poly(propylene imine) dendrimer. The optical absorption studies indicated direct allowed transition with the band gap (4.5 eV), which is blue shift with respect to the value of the bulk material. Low-temperature blocking of the NPs magnetic moments at 18 K is determined by SQUID measurements. The influence of pulsed laser irradiation on the superparamagnetic properties of γ-Fe2O3 NPs was studied by EPR spectroscopy. It has been shown that irradiation of the sample held in vacuo and cooled in zero magnetic field to 6.9 K leads to the appearance of a new EPR signal, which decays immediately after the irradiation is stopped. The appearance and disappearance of this new signal can be repeated many times at 6.9 K when we turn on/turn off the laser. We suppose that the generation of conduction band electrons by irradiation into the band gap of the γ-Fe2O3 changes the superparamagnetic properties of NPs.Graphical Abstract: [Figure not available: see fulltext.]Features of the behavior of single-domain γ-Fe2O3 nanoparticles formed in dendrimer were found by UV-Vis and EPR spectroscopy: “blue” shift in optical absorption, a significant increase in the band gap width and variation of superparamagnetic properties under light irradiation. © 2015, Springer Science+Business Media Dordrecht. Source

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