Dmitri Litvinov

Publications (6)31.62 Total impact

• Article: Development of Pinhole-Free Amorphous Aluminum Oxide Protective Layers for Biomedical Device Applications

  Julia Litvinov, Yi-Ju Wang, Jinnie George, Pawilai Chinwangso, Stanko Brankovic, Richard C. Willson, Dmitri Litvinov
  Surface and Coatings Technology 04/2013; · 1.87 Impact Factor
• Article: Light-induced covalent immobilization of monolayers of magnetic nanoparticles on hydrogen-terminated silicon.

  Gyu Leem, Shishan Zhang, Andrew C Jamison, Eduard Galstyan, Irene Rusakova, Bernd Lorenz, Dmitri Litvinov, T Randall Lee
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  ABSTRACT: Specifically tailored ω-alkenyl-1-carboxylic acids were synthesized for use as surfactants in the single-step preparation of manganese ferrite (MnFe2O4) nanoparticles (NPs). Monodisperse manganese ferrite NPs terminated with ω-alkenyl moieties were prepared via a one-pot reaction at high temperature without the need of ligand exchange. Using this approach, simple adjustment of the rate of heating allowed precise tuning of the size of the nanoparticles, which were characterized in bulk form by transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). These surfactant-coated magnetic nanoparticles were then deposited onto hydrogen-terminated silicon(111) wafers and covalently anchored to the surface by UV-initiated covalent bonding. Analysis by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) confirmed that the UV treatment led to covalent immobilization of the NPs on the silicon surface with a consistent packing density across the surface. The magnetic properties of the stable, surface-bound nanoparticle arrays were characterized using a superconducting quantum interference device (SQUID) magnetometer. The materials and methods described here are being developed for use in bit-patterned ultrahigh density magnetic recording media and nanoscale biomagnetic sensing.
  ACS Applied Materials & Interfaces 10/2010; 2(10):2789-96. · 4.53 Impact Factor
• Article: Surfactant-Controlled Size and Shape Evolution of Magnetic Nanoparticles

  Gyu Leem, Subhasis Sarangi, Shishan Zhang, Irene Rusakova, Audrius Brazdeikis, Dmitri Litvinov, T. Randall Lee
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  ABSTRACT: This manuscript describes a simple one-pot reaction that affords cuboid iron−manganese oxide nanoparticles with unprecedented dimensions as large as 33 ± 5 nm (average body-centered diagonal) in monodisperse form. Our unique synthetic method, which requires no multiple growth steps typical of other methods, utilizes the thermal decomposition of metal precursor complexes in the presence of specifically tailored surfactants and/or mixtures of surfactants. The size and shape of these unusually large magnetic nanoparticles (MNPs) can be manipulated at will simply by adjusting the surfactant composition, leading to enhanced control over the dimensions of the nanoparticles because of the surface-differentiating influence of the functional end groups. Our surfactant system utilizes two types of surface ligands: one strongly bound to the metal surface and the others loosely bound. This combination of ligands plays an important role in controlling particle size and morphology. With an eye toward potential biomedical applications, the magnetic properties of the MNPs were investigated through their M−H hysteresis loop behavior at 290 K. More importantly, when exposed to a magnetic field, relaxation measurements of these MNPs afforded Néel relaxation times of 3.4 s at an average body-centered diagonal size of 29 ± 4 nm.
  12/2008;
• Article: Facile synthesis, assembly, and immobilization of ordered arrays of monodisperse magnetic nanoparticles on silicon substrates.

  Gyu Leem, Andrew C Jamison, Shishan Zhang, Dmitri Litvinov, T Randall Lee
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  ABSTRACT: This paper outlines the preparation of monodisperse MnFe(2)O(4) nanoparticles modified with omega-alkenyl moieties in a one-pot reaction, requiring no ligand-exchange step, followed by deposition of the resulting surfactant-coated nanoparticles onto a hydrogen-terminated silicon (111) wafer and covalent anchoring to the surface via UV-initiated bonding, creating a stable two-dimensional array of monodisperse magnetic nanoparticles.
  Chemical Communications 11/2008; · 6.17 Impact Factor
• Source

  Available from: isivast.org.vn

  Article: Gold nanoparticle effects in polymerase chain reaction: favoring of smaller products by polymerase adsorption.

  Binh V Vu, Dmitri Litvinov, Richard C Willson
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  ABSTRACT: Gold nanoparticles were recently reported to reduce the formation of nonspecific products in polymerase chain reaction (PCR) at remarkably low temperatures, with hypothesized mechanisms including adsorption of DNA and heat-transfer enhancement. In contrast to these reports, we report that gold nanoparticles do not enhance the specificity of PCR but rather suppress the amplification of longer products while favoring amplification of shorter products, independent of specificity. Gold nanoparticles bearing a self-assembled monolayer of hexadecanethiol did not affect PCR, suggesting that surface interactions play an essential role. This role was further confirmed by experiments in which a similar effect on PCR was observed for the same total surface area of particles over a 100-fold range of per-particle surface area. The effect was seen with Taq and Tfl polymerases but not with Vent polymerase, and the effects of nanoparticles can be reversed by increasing the polymerase concentration or by adding bovine serum albumin (BSA). Transient high-temperature nanoparticle pre-exposure of PCR mix containing polymerase but not template or primers, followed by nanoparticle removal, modified subsequent nanoparticle-free PCR. Interaction between polymerase and gold nanoparticles was confirmed by changes in nanoparticle absorption spectrum and electrophoretic mobility in the presence of polymerase. Taken together, these results suggest that the nanoparticles nonspecifically adsorb polymerase, thus effectively reducing polymerase concentration.
  Analytical Chemistry 08/2008; 80(14):5462-7. · 5.86 Impact Factor
• Source

  Available from: uh.edu

  Article: Close-packed noncircular nanodevice pattern generation by self-limiting ion-mill process.

  Vishal A Parekh, Ariel Ruiz, Paul Ruchhoeft, Stanko Brankovic, Dmitri Litvinov
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  ABSTRACT: We describe a self-limiting, low-energy argon-ion-milling process that enables noncircular device patterns, such as squares or hexagons, to be formed using precursor arrays of uniform circular openings in poly(methyl methacrylate) defined using electron beam lithography. The proposed patterning technique is of particular interest for bit-patterned magnetic recording medium fabrication, where square magnetic bits result in improved recording system performance. Bit-patterned magnetic medium is among the primary candidates for the next generation magnetic recording technologies and is expected to extend the areal bit density limits far beyond 1 Tbit/in(2). The proposed patterning technology can be applied either for direct medium prototyping or for manufacturing of nanoimprint lithography templates or ion beam lithography stencil masks that can be utilized in mass production.
  Nano Letters 11/2007; 7(10):3246-8. · 13.20 Impact Factor