I. I. Vlasov

Russian Academy of Sciences, Moskva, Moscow, Russia

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Publications (108)246.82 Total impact

  • Bulletin of the Lebedev Physics Institute 12/2015; 41(12):359-363. DOI:10.3103/S1068335614120057 · 0.29 Impact Factor
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    ABSTRACT: Recently reported photoluminescent nanographene oxides (nGO), i.e. nanographene oxidised with sulfuric to nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamonds (ND), graphene quantum dots (GQD), which all demonstrate a variety of properties that are attractive for biomedical imaging such as low toxicity and stable photoluminescence. In this study, the nGOs were organically surface-modified with poly(ethylene glycol) - poly(ethylene imine) (PEG-PEI) copolymers tagged with folic acid as affinity ligand for cancer cells expressing folate receptors. The functionalization enhanced both their cellular uptake and quantum efficiency of the photoluminescence as compared to non-modified nGOs. The nGOs exhibited an excitation dependent photoluminescence that facilitated their detection with a wide range of microscope configurations. The functionalized nGOs were non-toxic, they were retained in the stained cell population over a period of 8 days and they distributed equally between daughter cells. We have evaluated their applicability in in vitro and in vivo (chicken embryo CAM) models to visualize and track migratory cancer cells. The good biocompatibility and easy detection of the functionalized nGOs suggest that they could address the limitations faced with quantum dots and organic fluorophores in long-term in vivo biomedical imaging.
    Nanoscale 05/2015; 7(23):-. DOI:10.1039/C5NR01403D · 6.74 Impact Factor
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    ABSTRACT: We have studied the upper limits for incorporation of nitrogen and formation of arrays of nitrogen-vacancy (NV) color centers in optical-quality single-crystalline diamond synthesized by chemical vapor deposition (CVD). The CVD diamond samples were grown in a microwave plasma in methane-hydrogen mixtures with high content (200-2000 ppm) of the nitrogen dopant in the gas mixture, and were analyzed using Raman and photoluminescence spectroscopy. From the UV absorption spectra, we established that the solubility limit for substitutional nitrogen in the studied material is close to 2·1018 cm-3 (under typical synthesis conditions), which lets us in particular form arrays of NV center with similar concentrations by means of irradiation and annealing.
    Journal of Applied Spectroscopy 05/2015; 82(2):242-247. DOI:10.1007/s10812-015-0092-1 · 0.51 Impact Factor
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    ABSTRACT: Homoepitaxial single crystal diamond layers with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738 nm wavelength have been grown on (100) diamond substrates by a microwave plasma CVD using a controlled Si doping via adding silane to CH4H2 reaction gas mixture in the course of the deposition process. In the range of the silane concentrations SiH4/CH4 explored, from 0 to 2.4%, the SiV PL intensity shows a nonmonotonic behavior with silane addition, with a maximum at 0.6%SiH4/CH4, and a rapid PL quenching at higher Si doping. The maximum SiV concentration of ≈450 ppb in the samples has been determined from optical absorption spectra. It is found that the SiV PL intensity can strongly, an order of magnitude, increase within non-epitaxial inclusions in single crystal diamond film.
    Physica Status Solidi (A) Applications and Materials 05/2015; DOI:10.1002/pssa.201532174 · 1.53 Impact Factor
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    ABSTRACT: Nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) films with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738 nm have been grown using a microwave plasma CVD technique. The films were doped with Si via adding silane to CH4–H2 reaction gas mixture in the course of the deposition process. The dependence of SiV PL intensity on silane concentration in gas shows a maximum at SiH4/CH4 ratio of 0.2% and 0.6% for NCD and MCD films, respectively, the maximum intensity for MCD being an order of magnitude stronger compared with that for NCD. The PL quenching at higher CH4 addition occurs, however, no significant degradation of the film structure, such as Si-induced amorphous carbon formation, was observed within the SiH4 concentration range studied (0% – 0.9%). The higher PL efficiency of the MCD films is related to their less defective structure, as deduced from Raman spectroscopy analysis.
    Diamond and Related Materials 04/2015; 56. DOI:10.1016/j.diamond.2015.04.003 · 1.57 Impact Factor
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    ABSTRACT: Photoluminescence spectra show that silicon impurity is present in lattice of some nanodiamond grains (ND) of various chondrites as a silicon-vacancy (SiV) defect. The relative intensity of the SiV band in the diamond-rich separates depends on chemical composition of meteorites and on size of ND grains. The strongest signal is found for the size separates enriched in small grains; thus confirming our earlier conclusion that the SiV defects preferentially reside in the smallest (less than 2 nm) grains. The difference in relative intensities of the SiV luminescence in the diamond-rich separates of individual meteorites are due to variable conditions of thermal metamorphism of their parent bodies and/or uneven sampling of nanodiamonds populations. Annealing of separates in air eliminates surface sp2-carbon, consequently, the SiV luminescence is enhanced. Strong and well-defined luminescence and absorption of the SiV defect is a promising feature to locate cold (< 250 {\deg}C) nanodiamonds in space.
    02/2015; 50(6). DOI:10.1111/maps.12450
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    ABSTRACT: The method of epitaxial growth of localized photoluminescence sources in the form of the ordered microcolumn diamond structures with silicon-vacancy (SiV) color centers is implemented. The process is based on diamond deposition in microwave plasma in CH4-H2 mixtures in microwells in a silicon mask on a diamond single crystal substrate, where the Si mask itself is a silicon doping source. Strong photoluminescence of SiV centers at a wavelength of 738 nm is detected; the spatial distribution of luminescence completely coincides with the synthesized structure arrangement.
    Bulletin of the Lebedev Physics Institute 02/2015; 42(2):63-66. DOI:10.3103/S1068335615020062 · 0.29 Impact Factor
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    ABSTRACT: Bifunctional detonation nanodiamonds (NDs) were obtained by vacuum annealing at 750 °C of NDs previously oxidized in ozone (ND-ozone). Raman investigations demonstrate a significantly higher amount of sp2 carbon compared to ND with polyfunctional surface (ND-NRI) annealed in vacuum under the same conditions. In addition to sp2 carbon caps, thermal desorption mass spectroscopy analysis revealed a higher oxygen concentration at the ND-ozone surface with abundant carbonyl and carboxylic acid anhydride groups. The supernatant of ND-ozone annealed in vacuum exhibits a positive zeta potential (+50 mV at pH 6.5), while the starting sample has a high negative zeta potential (−60 mV). This supports the oxygen hole-doping model previously proposed to explain the positive zeta potential of NDs after vacuum annealing.
    Physica Status Solidi (A) Applications and Materials 12/2014; 211(2):2739-2743. DOI:10.1002/pssa.201431397 · 1.53 Impact Factor
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    Journal of Biomedical Optics 11/2014; 19(11):117007. DOI:10.1117/1.JBO.19.11.117007 · 2.75 Impact Factor
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    ABSTRACT: Nanodiamond particles are widely recognized candidates for biomedical applications due to their excellent biocompatibility, bright photoluminescence based on color centers and outstanding photostability. Recently, more complex architectures with a nanodiamond core and an external shell or nanostructure which provides synergistic benefits have been developed, and their feasibility for biomedical applications has been demonstrated. This review is aimed at summarizing recent achievements in the fabrication and functional demonstrations of nanodiamond-based composite structures, along with critical considerations that should be taken into account in the design of such structures from a biomedical point of view. A particular focus of the review is core/shell structures of nanodiamond surrounded by porous silica shells, which demonstrate a remarkable increase in drug loading efficiency; as well as nanodiamonds decorated with carbon dots, which have excellent potential as bioimaging probes. Other combinations are also considered, relying on the discussed inherent properties of the inorganic materials being integrated in a way to advance inorganic nanomedicine in the quest for better health-related nanotechnology.
    Journal of Nanoscience and Nanotechnology 09/2014; 15(2):959-971. DOI:10.1166/jnn.2015.9742 · 1.34 Impact Factor
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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; 116(2). DOI:10.1007/s00339-014-8530-0 · 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 05/2014; 31(5). DOI:10.1002/ppsc.201300251 · 0.54 Impact Factor
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    ABSTRACT: This paper presents results of a study of adsorption properties of the original (I6) and carboxyl-modified (I6COOH) detonation nanodiamonds (DNDs) dispersed in aqueous solutions, with respect to dissolved ions: Cu2+, Pb2+, . Application of complementary spectroscopic methods allows comparative analysis of the adsorption activity of DNDs in aqueous solutions of metal salts. It was shown that both types of functionalized NDs readily adsorb nitrate ions and metal cations, and the adsorption efficiency of I6COOH is approx. three times higher than that of I6. Hypothetic mechanism of nitrate and copper ions adsorption on NDs surface is proposed.
    Journal of Alloys and Compounds 02/2014; 586:S436-S439. DOI:10.1016/j.jallcom.2013.01.055 · 2.73 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.
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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; DOI:10.1038/nnano.2013.255 · 33.27 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. DOI:10.1007/s10812-013-9830-4 · 0.51 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. DOI:10.3103/S1060992X13030077
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    ABSTRACT: The peculiarities of wettability of diamond that was obtained in a nanostructured form as ultrananocrystalline diamond (UNCD) films by deposition from a gas phase are considered. Surface hydrogenation leads to hydrophobicity: advancing contact angle θ for UNCD films reaches 106 ± 1° (for diamond single crystals θ = 93°). Even higher values of θ equal to 124 ± 3° were detected for nanoporous samples of UNCD, in which a graphite-like component was removed by etching. High hydrophobicity is achieved owing to the specific surface morphology of the nanostructured diamond (anisotropic, with high content of nanopores) and chemical modification, which on the whole provides for very low values of free surface energy of the films. It was shown that laser-drilled microholes in polycrystalline diamond also can enhance the hydrophobicity. The wetting behavior of the nanostructured surfaces agrees well with the Cassie-Baxter equation for heterophase porous surfaces. The oxidation and hydrogenation of UNCD films allows controlling of θ in considerably wider ranges compared to single crystal diamond.
    Protection of metals and physical chemistry of surfaces 05/2013; 49(3):325-331. DOI:10.1134/S2070205113030118 · 0.68 Impact Factor
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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; DOI:10.1039/c3nr33926b · 6.74 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; DOI:10.1039/C3TB20308E · 4.73 Impact Factor

Publication Stats

915 Citations
246.82 Total Impact Points

Institutions

  • 1997–2014
    • Russian Academy of Sciences
      • • Prokhorov General Physics Institute
      • • Institute of Chemistry
      • • A.N. Frumkin Institute of Physical chemistry and Electrochemistry
      Moskva, Moscow, Russia
  • 1999
    • Max Planck Institute of Microstructure Physics
      Halle-on-the-Saale, Saxony-Anhalt, Germany