I. I. Vlasov

Russian Academy of Sciences, Moskva, Moscow, Russia

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Publications (97)208.42 Total impact

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    ABSTRACT: In this paper, we report on the bulk modifications of type IIa single-crystal diamond with visible 10-ps pulses (at λ = 532 nm) and microstructural changes characterized by the appearance of several ‘unidentifiable’ vibrational modes in the frequency range of 1000–1400 cm−1 in the Raman spectra of laser-modified diamond. It is found that the new Raman modes are strongly pronounced in the spectra of high-stress regions in immediate proximity to the bulk microstructures in the absence of the G mode at ~1580 cm−1 characteristic of the sp2 phase. The high internal stresses are determined from the splitting of the triply degenerate diamond Raman line. The revealed structure transformation is localized within a narrow bulk layer near the bulk microstructures formed, and the stress relaxation is found to result in disappearance of the detected vibrational modes in the spectra. It is suggested that the formation of bulk regions with a sp3 carbon structure consisting of Z-carbon and hexagonal diamond is responsible for the appearance of new Raman modes in the spectra of laser-modified diamond. These findings evidence that the stress-assisted formation of novel metastable carbon phases or defect structures occur in the course of bulk modification of diamond with ps-laser pulses. In addition, we report the results of simulations of internal stresses in the system ‘graphitized cylinder-in-diamond’ to show (1) the effect of the mechanical properties of laser-modified diamond on the resulting stresses and (2) formation of bulk microscopic regions with high stresses of >10 GPa, i.e., the conditions at which various sp3 carbon allotropes and defect structures become more stable than graphite.
    Applied Physics A 06/2014; · 1.69 Impact Factor
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    ABSTRACT: The synthesis of a new class of fluorescent carbon nanomaterials, carbon-dot-decorated nanodiamonds (CDD-ND), is reported. These CDD-NDs are produced by specific acid treatment of detonation soot, forming tiny rounded sp2 carbon species (carbon dots), 1–2 atomic layers thick and 1–2 nm in size, covalently attached to the surface of the detonation diamond nanoparticles. A combination of nanodiamonds bonded with a graphitic phase as a starting material and the application of graphite intercalated acids for oxidation of the graphitic carbon is necessary for the successful production of CDD-ND. The CDD-ND photoluminescence (PL) is stable, 20 times more intense than the intrinsic PL of well-purified NDs and can be tailored by changing the oxidation process parameters. Carbon-dot-decorated DNDs are shown to be excellent probes for bioimaging applications and inexpensive additives for PL nanocomposites.
    Particle and Particle Systems Characterization 01/2014; · 0.86 Impact Factor
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    ABSTRACT: This work is devoted to the study of adsorption properties and adsorption mechanisms of the original (I6), modified (I6COOH) nanodiamonds and charcoal dispersed in water, with respect to dissolved ions (Cu2 +, Pb2 +, NO3 –, CH3COO –) using optical spectroscopy methods: Raman and IR spectroscopies, absorption, dynamic light scattering. Mechanisms of anions and cations adsorption were studied.
    JOURNAL OF NANO- AND ELECTRONIC PHYSICS. 12/2013; 5(4):2013.
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    ABSTRACT: Doping of carbon nanoparticles with impurity atoms is central to their application. However, doping has proven elusive for very small carbon nanoparticles because of their limited availability and a lack of fundamental understanding of impurity stability in such nanostructures. Here, we show that isolated diamond nanoparticles as small as 1.6 nm, comprising only ∼400 carbon atoms, are capable of housing stable photoluminescent colour centres, namely the silicon vacancy (SiV). Surprisingly, fluorescence from SiVs is stable over time, and few or only single colour centres are found per nanocrystal. We also observe size-dependent SiV emission supported by quantum-chemical simulation of SiV energy levels in small nanodiamonds. Our work opens the way to investigating the physics and chemistry of molecular-sized cubic carbon clusters and promises the application of ultrasmall non-perturbative fluorescent nanoparticles as markers in microscopy and sensing.
    Nature Nanotechnology 12/2013; · 31.17 Impact Factor
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    ABSTRACT: Raman and IR spectroscopy and thermal conductivity were employed to investigate the effects of simultaneous vacuum annealing on defect transformation processes in diamonds irradiated by fast neutrons and nanocrystalline diamond fi lms (DF) implanted with O or P ions. A correlation between the thermal conductivity at room temperature and the absorption coeffi cient near 13 μm was found in diamonds irradiated by neutron fl uence 2·1019 cm–2. It was found that two-phonon absorption in diamond IR spectra was sensitive to destruction of long-range ordering in the diamond crystal lattice. An absorption band with a shape characteristic of localized centers in the band gap (activation energy ~0.25 eV) was identifi ed in IR spectra of DF irradiated by neutrons and annealed at temperatures <900°C. It was shown that the optical and transport properties of the studied radiation-damaged DF were determined by multi-vacancy complexes and inclusions of a non-diamond phase.
    Journal of Applied Spectroscopy 11/2013; 80(5):707-714. · 0.69 Impact Factor
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    ABSTRACT: In this paper, the results of application of artificial neural networks for extraction of fluorescence contribution of nanoparticles used in biomedicine as biomarkers and drug carriers against the fluorescence background of inherent fluorophores of biological objects are presented. Principle possibility of solving this problem is shown. The used architectures of ANN allow detecting fluorescence of carbon dots against the background of proper fluorescence of egg protein with reasonably high accuracy-not worse than 0.002 mg/mL.
    Optical Memory and Neural Networks 07/2013; 22(3):156-165.
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    ABSTRACT: Recent advances within materials science and its interdisciplinary applications in biomedicine have emphasized the potential of using a single multifunctional composite material for concurrent drug delivery and biomedical imaging. Here we present a novel composite material consisting of a photoluminescent nanodiamond (ND) core with a porous silica (SiO2) shell. This novel multifunctional probe serves as an alternative nanomaterial to address the existing problems with delivery and subsequent tracing of the particles. Whereas the unique optical properties of ND allows for long-term live cell imaging and tracking of cellular processes, mesoporous silica nanoparticles (MSNs) have proven to be efficient drug carriers. The advantages of both ND and MSNs were hereby integrated in the new composite material, ND@MSN. The optical properties provided by the ND core rendered the nanocomposite suitable for microscopy imaging in fluorescence and reflectance mode, as well as super-resolution microscopy as a STED label; whereas the porous silica coating provided efficient intracellular delivery capacity, especially in surface-functionalized form. This study serves as a demonstration how this novel nanomaterial can be exploited for both bioimaging and drug delivery for future theranostic applications.
    Nanoscale 03/2013; · 6.73 Impact Factor
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    ABSTRACT: A multifunctional core-shell nanocomposite platform consisting of a photoluminescent nanodiamond (ND) core with uniform porous silica coatings is presented. This design intended for drug delivery applications allows simultaneous stable fluorescent imaging with high loading capacity of bioactive molecules. Despite irregularly shaped starting cores, well-dispersed and uniformly shaped nanocomposite particles can be produced. Moreover, after optimization of the silica source-to-diamond ratio, the thickness of the porous layer can be tuned by adjusting the ethanol amount, allowing rational nanoparticle size control. The ND key property, photoluminescence, is not quenched regardless of coating with thick silica layers. The high loading capacity for incorporation of active agents, provided by the introduced porous layer, is demonstrated by adsorption of a hydrophobic model drug into the composite particles. The loading degree, as compared to pure ND, increased with two orders of magnitude from 1wt-% for the
    Journal of Materials Chemistry B. 01/2013;
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    ABSTRACT: Optical absorption, photoluminescence, profilometry, and electron spin resonance (ESR) methods are used to study the effect of isochrononous vacuum annealing up to 1730 °C on the transformation of defects in chemical vapor deposited (CVD) diamonds implanted with deuterium ions (ion energy 350 keV, dose (2–12)⋅10^16 cm^–2). The grain boundaries in the diamonds are found to have no significant effect on the process of annealing and graphitization of the radiation-induced defects. The island graphitization typical of hydrogen isotope implantation in diamond is detected. Bands are observed in the photoluminescence spectra at 580 and 730 nm, which have not been observed before in diamonds, as well as a series of bands at 760–795 nm. A magnetic hysteresis is detected in the ESR spectra of the deuterium implanted CVD diamonds which indicates ordering of uncompensated electron spins. Deuterium- (hydrogen-) vacancy complexes are the most probable cause of the spin ordering.
    Journal of Applied Spectroscopy 09/2012; 79(4):600-609. · 0.69 Impact Factor
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    ABSTRACT: The interaction of nanodiamond (ND) particles produced by detonation synthesis with water molecules in ND water suspensions was studied using Raman and photoluminescence spectroscopy. To address the role of the surface chemistry of ND particles, NDs with heterogeneous surface groups as well as ND particles enriched with carboxyl-, hydroxyl-, and fluorine-containing surface groups were investigated. The influence of the nanodiamond particles on the shape and position of the water valence band in the Raman spectra of ND water suspensions was demonstrated for the first time. Changes in the water band parameters take place up to 1.5 mg/mL of NDs in all studied suspensions and are most pronounced for the ND functionalized with COOH groups. A correlation between increasing ND luminescence intensity and strengthening of hydrogen bonds formed at the interface of ND and water molecules in water suspensions of variously functionalized NDs was found. The most intense ND luminescence was detected for the ND functionalized with OH groups, forming the strongest hydrogen bonds among the studied samples.
    The Journal of Physical Chemistry C. 01/2012;
  • LPI Contributions. 05/2011;
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    ABSTRACT: The results of spectroscopic and structural studies of phase composition and defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) chondrites indicate that nitrogen atomic environment in meteoritic nanodiamonds (MND) is similar to that observed in synthetic counterparts produced by detonation and by the Chemical Vapor Deposition (CVD)-process. Most of the nitrogen in MND appears to be confined to lattice imperfections, such as crystallite/twin boundaries and other extended defects, while the concentration of nitrogen in the MND lattice is low. It is suggested that the N-rich sub-population of MND grains may have been formed with high growth rates in environments rich in accessible N (i.e., N in atomic form or as weakly bonded compounds). For the first time the silicon-vacancy complex (the “silicon” defect) is observed in MND by photoluminescence spectroscopy.
    Geochimica et Cosmochimica Acta 02/2011; · 3.88 Impact Factor
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    ABSTRACT: Production of nanodiamond particles containing substitutional nitrogen is important for a wide variety of advanced applications. In the current work nanodiamond particles synthesized from a mixture of graphite and hexogen were analyzed to determine the presence of substitutional nitrogen using pulsed electron paramagnetic resonance (EPR) spectroscopy. Nitrogen paramagnetic centers in the amount of 1.2 ppm have been identified. The spin relaxation characteristics for both nitrogen and surface defects are also reported. A new approach for efficient depletion of the strong non-nitrogen EPR signal in nanodiamond material by immersing nanodiamond particles into ice matrix is suggested. This approach allows an essential decrease of the spin relaxation time of the dominant non-nitrogen defects, while preserving the substitutional nitrogen spin relaxation time.
    Nanoscience and Nanotechnology Letters 01/2011; 3(1):63-67. · 1.44 Impact Factor
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    ABSTRACT: Precision measurements of the specific heat and spectral intensity I(ω) of Raman scattering for Lu N B12 single crystal samples with various boron isotopes (N = 10, 11, nat) have been performed at low and intermediate temperatures. A boson peak in the low-frequency part of the I(ω) spectrum has been observed for the first time for lutetium dodecaboride at liquid nitrogen temperatures. It has been shown that low-temperature anomalies in the specific heat, along with the features of Raman spectra, can be interpreted in terms of the transition to a cageglass state at T* = 50−70 K, which appears when Lu3+ ions are displaced from the centrosymmetric position in cavities of a rigid covalent boron sublattice towards the randomly located boron vacancies. The concentrations of various two-level systems that correspond to two types of vibrational clusters with correlation lengths of 12–15 and 18–22 Å, respectively, have been estimated. The vibrational density of states of LuB12 has been calculated from Raman spectra in the model of soft atomic potentials. An approach has been proposed to explain the dielectrization of the properties of the YbB12 compound at T < T*, as well as the features of the formation of magnetic structures in RB12 antiferromagnets (R = Tb, Dy, Ho, Er, Tm) and the suppression of superconductivity in LuB12.
    Journal of Experimental and Theoretical Physics 01/2011; 113(3):468-482. · 0.92 Impact Factor
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    The Journal of Physical Chemistry C 01/2011; 115:14014-14024. · 4.84 Impact Factor
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    ABSTRACT: We have studied the IR absorption spectra of samples of porous ultrananocrystalline diamond (UNC diamond) obtained by selective etching of the sp 2 phase in UNC diamond films. We show that the surface of porous UNC diamond is polyfunctional. We have studied the behavior of surface hydride, carbonyl, carboxyl, and hydroxyl groups as a function of annealing temperature in air and the time kept under normal conditions for UNC diamond films previously oxidized at 430°C–450°C. In the range from a few minutes to a few months, we studied the kinetics for establishment of the steady state for the functional adsorbed layer on the diamond surface under normal conditions. The observed growth in the intensity of the transmission bands due to hydride (CH x ) and other hydrogen-containing functional groups is explained by dissociation of water molecules on the surface of the UNC diamond films. Keywordsdiamond–hydrogen–infrared spectrum–hydroxyl group–surface chemistry
    Journal of Applied Spectroscopy 01/2011; 78(4):563-571. · 0.69 Impact Factor
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    ABSTRACT: Diamond structures with inverse and direct three-dimensional opal lattices with period of 250–530 nm were grown by microwave plasma deposition in methane-hydrogen mixtures using porous SiO2 opal matrix and its Si replica as templates, respectively. The Si templates can be filled with diamond to the depth as large as 80 layers of the spheres.
    Physics of the Solid State 01/2011; 53(6):1131-1134. · 0.77 Impact Factor
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    ABSTRACT: Expandable graphite of two types was synthesized by (1) hydrolysis of graphite nitrate of II stage and (2) anodic polarization of graphite in 60% HNO3. Exfoliated graphite samples were produced by thermal shock of expandable graphite samples in air at 900 °C. A comparative study of microstructural distinctions of both expandable and exfoliated graphite samples was carried out using X-ray diffraction, Raman spectroscopy, electron energy loss spectroscopy and high resolution transmission electron microscopy.
    Carbon. 05/2010; 48(6):1862–1865.
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    ABSTRACT: An efficient method to investigate the microstructure and spatial distribution of nitrogen and nitrogen-vacancy (N-V) defects in detonation nanodiamond (DND) with primary particle sizes ranging from approximately 3 to 50 nm is presented. Detailed analysis reveals atomic nitrogen concentrations as high as 3 at% in 50% of diamond primary particles with sizes smaller than 6 nm. A non-uniform distribution of nitrogen within larger primary DND particles is also presented, indicating a preference for location within the defective central part or at twin boundaries. A photoluminescence (PL) spectrum with well-pronounced zero-phonon lines related to the N-V centers is demonstrated for the first time for electron-irradiated and annealed DND particles at continuous laser excitation. Combined Raman and PL analysis of DND crystallites dispersed on a Si substrate leads to the conclusion that the observed N-V luminescence originates from primary particles with sizes exceeding 30 nm. These findings demonstrate that by manipulation of the size/nitrogen content in DND there are prospects for mass production of nanodiamond photoemitters based on bright and stable luminescence from nitrogen-related defects.
    Small 03/2010; 6(5):687-94. · 7.82 Impact Factor
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    ABSTRACT: Diamond films of different structures were deposited on quartz, WC-Co, and molybdenum substrates in a microwave plasma torch discharge in an argon-hydrogen-methane gas mixture in a sealed chamber at pressures close to atmospheric by using the chemical vapor deposition technique. Images of diamond polycrystal films and separate crystals, as well as results of Raman spectroscopy, are presented. The spectra of optical plasma radiation recorded during film deposition demonstrate the presence of intense Hα hydrogen and C2 radical bands known as Swan bands.
    Plasma Physics Reports 01/2010; 36(13):1272-1277. · 0.66 Impact Factor

Publication Stats

354 Citations
208.42 Total Impact Points

Institutions

  • 1997–2013
    • Russian Academy of Sciences
      • • Prokhorov General Physics Institute
      • • A.N. Frumkin Institute of Physical chemistry and Electrochemistry
      Moskva, Moscow, Russia
  • 2008
    • Radiation Monitoring Devices, Inc
      Watertown, Massachusetts, United States
  • 2003
    • Central Research Institute of Epidemiology
      Moskva, Moscow, Russia
  • 1999
    • Max Planck Institute of Microstructure Physics
      Halle-on-the-Saale, Saxony-Anhalt, Germany