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  • 1. Ahmed, Towfiq
    et al.
    Haraldsen, Jason T.
    Rehr, John J.
    Di Ventra, Massimiliano
    Schuller, Ivan
    Balatsky, Alexander V.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 12, p. 125705-Article in journal (Refereed)
    Abstract [en]

    Nanopore-based sequencing has demonstrated a significant potential for the development of fast, accurate, and cost-efficient fingerprinting techniques for next generation molecular detection and sequencing. We propose a specific multilayered graphene-based nanopore device architecture for the recognition of single biomolecules. Molecular detection and analysis can be accomplished through the detection of transverse currents as the molecule or DNA base translocates through the nanopore. To increase the overall signal-to-noise ratio and the accuracy, we implement a new 'multi-point cross-correlation' technique for identification of DNA bases or other molecules on the single molecular level. We demonstrate that the cross-correlations between each nanopore will greatly enhance the transverse current signal for each molecule. We implement first-principles transport calculations for DNA bases surveyed across a multilayered graphene nanopore system to illustrate the advantages of the proposed geometry. A time-series analysis of the cross-correlation functions illustrates the potential of this method for enhancing the signal-to-noise ratio. This work constitutes a significant step forward in facilitating fingerprinting of single biomolecules using solid state technology.

  • 2. Bell, D. C.
    et al.
    Lemme, Max C.
    Harvard University, Department of Physics.
    Stern, L. A.
    RWilliams, J.
    Marcus, C. M.
    Precision cutting and patterning of graphene with helium ions2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 45, p. 455301-Article in journal (Refereed)
    Abstract [en]

    We report nanoscale patterning of graphene using a helium ion microscope configured for lithography. Helium ion lithography is a direct-write lithography process, comparable to conventional focused ion beam patterning, with no resist or other material contacting the sample surface. In the present application, graphene samples on Si/SiO(2) substrates are cut using helium ions, with computer controlled alignment, patterning, and exposure. Once suitable beam doses are determined, sharp edge profiles and clean etching are obtained, with little evident damage or doping to the sample. This technique provides fast lithography compatible with graphene, with similar to 15 nm feature sizes.

  • 3.
    Belova, Lyubov M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Dahlberg, E. D.
    Riazanova, Anastasiia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Mulders, J. J. L.
    Christophersen, C.
    Eckert, J.
    Rapid electron beam assisted patterning of pure cobalt at elevated temperatures via seeded growth2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 14, p. 145305-Article in journal (Refereed)
    Abstract [en]

    A new method of direct, rapid nano- to micro-scale patterning of high purity cobalt is presented. The method utilizes a combination of electron beam induced deposition (EBID) and seeded growth at elevated temperatures below the temperature of spontaneous thermal decomposition. Dicobalt octacarbonyl Co-2(CO)(8) is used as the precursor and carbon as a seed layer. Seeded deposition is carried out in the substrate temperature range from 55 to 75 degrees C. Deposition yield is significantly higher than conventional EBID and magnetotransport measurements indicate that resistivity, 22 mu Omega cm, and saturation magnetization, 1.55 T, are much closer to the corresponding values for bulk Co than those for standard EBID.

  • 4.
    Benedict, Samatha
    et al.
    Indian Inst Sci, Ctr Nano Sci & Engn, Bangalore, Karnataka, India..
    Lumdee, Chatdanai
    Univ Gothenburg, Dept Phys, Gothenburg, Sweden..
    Dmitriev, Alexandre
    Univ Gothenburg, Dept Phys, Gothenburg, Sweden..
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bhat, Navakanta
    Indian Inst Sci, Ctr Nano Sci & Engn, Bangalore, Karnataka, India..
    Colloidal lithography nanostructured Pd/PdOx core-shell sensor for ppb level H2S2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 25, article id 255502Article in journal (Refereed)
    Abstract [en]

    In this work we report on plasma oxidation of palladium (Pd) to form reliable palladium/palladium oxide (Pd/PdOx) core-shell sensor for ppb level H2S detection and its performance improvement through nanostructuring using hole-mask colloidal lithography (HCL). The plasma oxidation parameters and the sensor operating conditions are optimized to arrive at a sensor device with high sensitivity and repeatable response for H2S. The plasma oxidized palladium/palladium oxide sensor shows a response of 43.1% at 3 ppm H2S at the optimum operating temperature of 200 degrees C with response and recovery times of 24 s and 155 s, respectively. The limit of detection (LoD) of the plasma oxidised beam is 10 ppb. We further integrate HCL, a bottom-up and cost-effective process, to create nanodiscs of fixed diameter of 100 nm and varying heights (10, 15 and 20 nm) on 10 nm thin Pd beam which is subsequently plasma oxidized to improve the H2S sensing characteristics. The nanostructured Pd/PdOx sensor with nanodiscs of 100 nm diameter and 10 nm height shows an enhancement in sensing performance by 11.8% at same operating temperature and gas concentration. This nanostructured sensor also shows faster response and recovery times (15s and 100s, respectively) compared to the unstructured Pd/PdOx counterpart together with an experimental LoD of 10 ppb and the estimated limit going all the way down to 2 ppb. Material characterization of the fabricated Pd/PdOx sensors is done using UV-vis spectroscopy and x-ray photoemission spectroscopy.

  • 5.
    Bruhn, Benjamin
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Valenta, Jan
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Controlled fabrication of individual silicon quantum rods yielding high intensity, polarized light emission2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 50, p. 1-5Article in journal (Refereed)
    Abstract [en]

    Elongated silicon quantum dots (also referred to as rods) were fabricated using a lithographic process which reliably yields sufficient numbers of emitters. These quantum rods are perfectly aligned and the vast majority are spatially separated well enough to enable single-dot spectroscopy. Not only do they exhibit extraordinarily high linear polarization with respect to both absorption and emission, but the silicon rods also appear to luminesce much more brightly than their spherical counterparts. Significantly increased quantum efficiency and almost unity degree of linear polarization render these quantum rods perfect candidates for numerous applications.

  • 6. Buscaglia, M. T.
    et al.
    Buscaglia, V.
    Viviani, M.
    Petzelt, J.
    Savinov, M.
    Mitoseriu, L.
    Testino, A.
    Nanni, P.
    Harnagea, C.
    Zhao, Zhe
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Nygren, M.
    Ferroelectric properties of dense nanocrystalline BaTiO3 ceramics2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 9, p. 1113-1117Article in journal (Refereed)
    Abstract [en]

    Dense BaTiO3 ceramics with 50 nm average grain size obtained by spark plasma sintering were investigated. The dielectric data show a broad ferro-para phase transition with a maximum permittivity of approximate to1100 at 390 K and 1 kHz. The local ferroelectric switching behaviour was investigated by piezoresponse force microscopy. Typical piezoelectric hysteresis loops were recorded at different positions of the sample. The present results provide experimental evidence for polarization switching at the local scale, indicating that the critical grain size for the disappearance of ferroelectric behaviour in dense, bulk BaTiO3 nanocrystalline ceramics is below 50 nm.

  • 7. Chen, S
    et al.
    Svedendahl, M
    Käll, M
    Gunnarsson, L
    Dmitriev, A
    Ultrahigh sensitivity made simple: nanoplasmonic label-free biosensing with an extremely low limit-of-detection for bacterial and cancer diagnostics.2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 43Article in journal (Refereed)
    Abstract [en]

    We present a simple and robust scheme for biosensing with an ultralow limit-of-detection down to several pg cm(-2) (or several tens of attomoles cm(-2)) based on optical label-free biodetection with localized surface plasmon resonances. The scheme utilizes cost-effective optical components and comprises a white light source, a properly functionalized sensor surface enclosed in a simple fluidics chip, and a spectral analyzer. The sensor surface is produced by a bottom-up nanofabrication technique with hole mask colloidal lithography. Despite its simplicity, the method is able to reliably detect protein-protein binding events at low picomolar and femtomolar concentrations, which is exemplified by the label-free detection of the extracellular adherence protein (EAP) found on the outer surface of the bacterium Staphylococcus aureus and of prostate-specific antigen (PSA), which is believed to be a prostate cancer marker. These experiments pave the way towards an ultra-sensitive yet compact biodetection platform for point-of-care diagnostics applications.

  • 8.
    Elfström, Niklas
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Biomolecule detection using a silicon nanoribbon: Accumulation mode versus inversion mode2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 23, p. 235201-Article in journal (Refereed)
    Abstract [en]

    Silicon nanoribbons were fabricated using standard optical lithography from silicon on insulator material with top silicon layer thicknesses of 100, 60 and 45 nm. Electrically these work as Schottky-barrier field-effect transistors and, depending on the substrate voltage, electron or hole injection is possible. The current through the nanoribbon is extremely sensitive to charge changes at the oxidized top surface and can be used for biomolecule detection in a liquid. We show that for detection of streptavidin molecules the response is larger in the accumulation mode than in the inversion mode, although not leading to higher detection sensitivity due to increased noise. The effect is attributed to the location in depth of the conducting channel, which for holes is closer to the screened surface charges of the biomolecules. Furthermore, the response increases for decreasing silicon thickness in both the accumulation mode and the inversion mode. The results are verified qualitatively and quantitatively through a two-dimensional simulation model on a cross section along the nanoribbon device.

  • 9.
    Fang, Mei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 14, p. 145601-Article in journal (Refereed)
    Abstract [en]

    Magnetite nanoparticles have been prepared by co-precipitation using a custom-designed jet mixer to achieve rapid mixing (RM) of reactants in a timescale of milliseconds. The quick and stable nucleation obtained allows control of the particle size and size distribution via a more defined growth process. Nanoparticles of different sizes were prepared by controlling the processing temperature in the first few seconds post-mixing. The average size of the nanoparticles investigated using a Tecnai transmission electron microscope is found to increase with the temperature from 3.8 nm at 1 +/- 1 degrees C to 10.9 nm for particles grown at 95 +/- 1 degrees C. The temperature dependence of the size distribution follows the same trend and is explained in terms of Ostwald ripening of the magnetite nanoparticles during the co-precipitation of Fe2+ and Fe3+. The magnetic properties were studied by monitoring the blocking temperature via both DC and AC techniques. Strikingly, the obtained RM particles maintain the high magnetization (as high as similar to 88 A m(2) kg(-1) at 500 kA m(-1)) while the coercivity is as low as similar to 12 A m(-1) with the expected temperature dependence. Besides, by adding a drop of tetramethylammonium hydroxide, aqueous ferrofluids with long term stability are obtained, suggesting their suitability for applications in ferrofluid technology and biomedicine.

  • 10.
    Forchheimer, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Borysov, Stanislav S.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Platz, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. Max-Planck-Institute for the Physics of Complex Systems, Germany.
    Haviland, David B.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Determining surface properties with bimodal and multimodal AFM2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 48, p. 485708-Article in journal (Refereed)
    Abstract [en]

    Conventional dynamic atomic force microscopy (AFM) can be extended to bimodal and multimodal AFM in which the cantilever is simultaneously excited at two or more resonance frequencies. Such excitation schemes result in one additional amplitude and phase images for each driven resonance, and potentially convey more information about the surface under investigation. Here we present a theoretical basis for using this information to approximate the parameters of a tip-surface interaction model. The theory is verified by simulations with added noise corresponding to room-temperature measurements.

  • 11.
    Forsberg, Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Reversible logic based on electron waveguide Y-branch switches2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 4, p. S298-S302Article in journal (Refereed)
    Abstract [en]

    The lower bound of the energy required to change the state of an electron waveguide Y-branch switch is not thermally limited, and the theoretical limit is orders of magnitude lower than the energy cost of information erasure. Thus as the power dissipation due to information erasure can be avoided by the use of logically reversible gates, such gates based on electron waveguide Y-branch switches promise circuits with extremely low power dissipation. In this paper, reversible logic based on electron waveguide Y-branch switches is proposed and discussed.

  • 12.
    Fransson, Jonas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Formation of pure two-electron triplet states in weakly coupled quantum dots attached to ferromagnetic leads2006In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 17, no 21, p. 5344-5348Article in journal (Refereed)
    Abstract [en]

    Weakly coupled quantum dots in the Pauli spin blockade regime are considered with respect to spin-dependent transport. By attaching one half-metallic and one non-magnetic lead, the Pauli spin blockade is formed by a pure triplet state with spin moment S-z = 1 or -1. Furthermore, additional spin blockade regimes emerge because of full occupation in states with opposite spin to that of the half-metallic lead.

  • 13. Gholami, M.
    et al.
    Haratizadeh, H.
    Esmaeili, M.
    Amiri, R.
    Holtz, P. O.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Alternation of band gap and localization of excitons in InGaNAs nanostructures with low nitrogen content2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 31Article in journal (Refereed)
    Abstract [en]

    Continuous wave photoluminescence (cw PL) spectroscopy has been used to study the optical properties of a set of InGaNAs epilayers and single quantum wells with nitrogen concentration less than a few per cent at different temperatures and different excitation powers. We found that nitrogen has a critical role on the emission light of InGaNAs nanostructures and the recombination mechanism. The incorporation of a few per cent of nitrogen leads to shrinkage of the InGaNAs band gap. The physical origin of such band gap reduction has been investigated both experimentally and theoretically by using a band anticrossing model. We have found that localization of excitons that have been caused by incorporation of a few per cent of nitrogen in these structures is the main explanation of such anomalous behavior observed in the low-temperature photoluminescence spectra of these nanostructures. The localization energies of carriers have been evaluated by studying the variation of the quantum well (QW) emission versus temperature, and it was found that the localization energy increases with increasing nitrogen composition. Our data also show that, with increasing excitation intensity, the PL peak position moves to higher energies (blue shift) due to the filling of localized states and capture centers for excitons by photo-generated carriers.

  • 14. Gowtham, S.
    et al.
    Scheicher, R. H.
    Pandey, R.
    Karna, S. P.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    First-principles study of physisorption of nucleic acid bases on small-diameter carbon nanotubes2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 12Article in journal (Refereed)
    Abstract [en]

    We report the results of our first-principles study based on density functional theory on the interaction of the nucleic acid base molecules adenine ( A), cytosine ( C), guanine ( G), thymine ( T), and uracil ( U), with a single-walled carbon nanotube (CNT). Specifically, the focus is on the physisorption of base molecules on the outer wall of a ( 5, 0) metallic CNT possessing one of the smallest diameters possible. Compared to the case for CNTs with large diameters, the physisorption energy is found to be reduced in the high-curvature case. The base molecules exhibit significantly different interaction strengths and the calculated binding energies follow the hierarchy G > A > T > C > U, which appears to be independent of the tube curvature. The stabilizing factor in the interaction between the base molecule and CNT is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study provides an improved understanding of the role of the base sequence in deoxyribonucleic acid ( DNA) or ribonucleic acid ( RNA) in their interactions with carbon nanotubes of varying diameters.

  • 15. He, Zeming
    et al.
    Stiewe, Christian
    Platzek, Dieter
    Karpinski, Gabriele
    Mueller, Eckhard
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nano ZrO2/CoSb3 composites with improved thermoelectric figure of merit2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 23, p. 235602-Article in journal (Refereed)
    Abstract [en]

    Nano ZrO2/CoSb3 composites with different ZrO 2 contents were prepared using hot pressing. The phase purity, the microstructure and the temperature-dependent transport parameters of the composites were investigated. The dimensionless figure of merit (ZT) of 0.18 of the non-dispersed CoSb3 preponderates the maximal value (0.17) of pure CoSb3 reported in the literature, which is attributed to the prepared sample having higher electrical conductivity due to the existence of a small amount of metallic Sb and lower thermal conductivity due to the fine-grained structure. Compared to non-dispersed CoSb3, a further improvement of 11% on ZT (0.20) was achieved in the composite with 0.05ZrO 2 inclusions, which resulted from the enhanced ratio of electrical conductivity to thermal conductivity and the Seebeck coefficient. The nanodispersion method provides an effective approach to improving a material's thermoelectric properties and performance.

  • 16.
    Hollertz, Rebecca
    et al.
    EMPA, Switzerland .
    Chatterjee, S
    Gutmann, H
    Geiger, T
    Nüesch, F A
    Chu, B T T
    Improvement of toughness and electrical properties of epoxy composites with carbon nanotubes prepared by industrially relevant processes2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 12, p. 125702-Article in journal (Refereed)
    Abstract [en]

    The addition of carbon nanotubes (CNTs) to polymeric matrices or master batches has the potential to provide composites with novel properties. However, composites with a uniform dispersion of CNTs have proved to be difficult to manufacture, especially at an industrial scale. This paper reports on processing methods that overcome problems related to the control and reproducibility of dispersions. By using a high pressure homogenizer and a three-roll calendaring mill in combination, CNT reinforced epoxies were fabricated by mould casting with a well dispersed nanofiller content from 0.1 to 2 wt%. The influence of the nano-carbon reinforcements on toughness and electrical properties of the CNT/epoxies was studied. A substantial increase of all mechanical properties already appeared at the lowest CNT content of 0.1 wt%, but further raising the nanofiller concentration only led to moderate further changes. The most significant enhancement was obtained for fracture toughness, reaching up to 82%. The low percolation thresholds were confirmed by electrical conductivity measurements on the same composites yielding a threshold value of only about 0.01 wt%. As corroborated by a thorough microscopic analysis of the composites, mechanical and electrical enhancement points to the formation of an interconnected network of agglomerated CNTs.

  • 17.
    Hussain, T.
    et al.
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia.;Univ Queensland, Ctr Theoret & Computat Mol Sci, Australian Inst Bioengn & Nanotechnol, Brisbane, Qld 4072, Australia..
    Vovusha, H.
    KAUST, Phys Sci & Engn Div PSE, Thuwal 239556900, Saudi Arabia..
    Kaewmaraya, T.
    Khon Kaen Univ, Integrated Nanotechnol Res Ctr, Dept Phys, Khon Kaen, Thailand..
    Karton, A.
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia..
    Amornkitbamrung, V
    Khon Kaen Univ, Integrated Nanotechnol Res Ctr, Dept Phys, Khon Kaen, Thailand..
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, Box 516, S-75120 Uppsala, Sweden.
    Graphitic carbon nitride nano sheets functionalized with selected transition metal dopants: an efficient way to store CO22018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 41, article id 415502Article in journal (Refereed)
    Abstract [en]

    Proficient capture of carbon dioxide (CO2) is considered to be a backbone for environment protection through countering the climate change caused by mounting carbon content. Here we present a comprehensive mechanism to design novel functional nanostructures capable of capturing a large amount of CO2 efficiently. By means of van der Waals corrected density functional theory calculations, we have studied the structural, electronic and CO2 storage properties of carbon nitride (g-C6N8) nano sheets functionalized with a range of transition metal (TM) dopants ranging from Sc to Zn. The considered TMs bind strongly to the nano sheets with binding energies exceeding their respective cohesive energies, thus abolishing the possibility of metal cluster formation. Uniformly dispersed TMs change the electronic properties of semiconducting g-C6N8 through the transfer of valence charges from the former to the latter. This leaves all the TM dopants with significant positive charges, which are beneficial for CO2 adsorption. We have found that each TM's dopants anchor a maximum of four CO2 molecules with suitable adsorption energies (-0.15 to -1.0 eV) for ambient condition applications. Thus g-C6N8 nano sheets functionalized with selected TMs could serve as an ideal sorbent for CO2 capture.

  • 18.
    Hussain, Tanveer
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden and University of Queensland, Australia.
    Islam, M. S.
    Rao, G. S.
    Panigrahi, P.
    Gupta, D.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden and Dongguk University, Korea.
    Hydrogen storage properties of light metal adatoms (Li, Na) decorated fluorographene monolayer2015In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 27, article id 275401Article in journal (Refereed)
    Abstract [en]

    Owing to its high energy density, the potential of hydrogen (H-2) as an energy carrier has been immense, however its storage remains a big obstacle and calls for an efficient storage medium. By means of density functional theory (DFT) in spin polarized generalized gradient approximation (GGA), we have investigated the structural, electronic and hydrogen storage properties of a light alkali metal (Li, Na) functionalized fluorographene monolayer (FG). Metal adatoms bind to the FG with significantly high binding energy, much higher than their cohesive energies, which helps to achieve a uniform distribution of metal adatoms on the monolayer and consequently ensure reversibility. Due to a difference of electronegativities, each metal adatom transfers a substantial amount of its charge to the FG monolayer and attains a partial positive state, which facilitates the adsorption of multiple H-2 molecules around the adatoms by electrostatic as well as van der Waals interactions. To get a better description of H-2 adsorption energies with metal-doped systems, we have also performed calculations using van der Waals corrections. For both the functionalized systems, the results indicate a reasonably high H-2 storage capacity with H2 adsorption energies falling into the range for the practical applications.

  • 19. Hussain, Tanveer
    et al.
    Kaewmaraya, Thanayut
    Khan, Mehwish
    Chakraborty, Sudip
    Islam, Muhammad Shafiq
    Amornkitbamrung, Vittaya
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uppsala University, Sweden.
    Improved sensing characteristics of methane over ZnO nano sheets upon implanting defects and foreign atoms substitution2017In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 28, no 41, article id 415502Article in journal (Refereed)
    Abstract [en]

    Thanks to the growing interests of metal oxide sensors in environmental and industrial uses, this study presents the sensing mechanism of methane gas (CH4) on recently synthesized two-dimensional form of ZnO, ZnO nano sheets (ZnO-NS). The adsorption energy of CH4 on pristine ZnO-NS, calculated by means of van derWaals corrected first-principles calculations, is found to be insufficient restricting its application as an efficient nano sensor. However, the creation of (O/Zn) vacancies and the substitution of foreign dopants into ZnO-NS considerably intensify the binding energy of CH4. Through a comprehensive energetic analysis, it is observed that among all the substituents, boron (B), sulphur (S) and gallium (Ga) improves the binding of CH4 to 2.75, 6.1 and 7.5 times respectively than its values on pristine ZnO-NS. In addition to the CH4 binding energies falling ideally between physisorption and chemisorption range, a prominent variation in the electronic properties before and after CH4 exposure indicates the promise of substituted Zn-NS as a useful nano sensors.

  • 20.
    Hussain, Tanveer
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden.
    Panigrahi, Puspamitra
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden.
    Sensing propensity of a defected graphane sheet towards CO, H2O and NO22014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 32, p. 325501-Article in journal (Refereed)
    Abstract [en]

    We have used density functional theory to investigate the sensing property of a hydrogenated graphene sheet (graphane) towards CO, H2O and NO2 gas molecules. Though the pristine graphane sheet is found not to have sufficient affinity towards the mentioned gas molecules, the defected sheet (removing few surface H atoms) has a strong affinity towards the gas molecules. While CO and H2O are found to be weakly physisorbed, the NO2 molecules are found to be strongly chemi-sorbed to the defected graphane sheet. With NO2, the N(p) and O(p) states are found to have strong hybridization with the most active C(p) states which lie at the defected site of the graphane sheet. While increasing the coverage effect of the mentioned gas molecules toward the defected sheet, the adsorption energies do not change significantly. At the same time, the work function of the defected graphane sheet shows an increasing trend while adsorbed with CO, H2O and NO2 gas molecules, opening up the possibilities for a future gas sensor.

  • 21. Hwang, F. H.
    et al.
    Kim, Do-Kyung
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yoshitake, T.
    Johansson, S. M.
    Bjelke, B.
    Muhammed, M.
    Kehr, J.
    Diffusion and clearance of superparamagnetic iron oxide nanoparticles infused into the rat striatum studied by MRI and histochemical techniques2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 1, p. 015103-Article in journal (Refereed)
    Abstract [en]

    The purpose of the present study was to investigate, by MRI and histochemical techniques, the diffusion and clearance abilities of superparamagnetic iron oxide nanoparticles (SPION) coated with dextran (Dextran-SPION) and gold (Au-SPION) following their local infusions into the rat brain. In separate groups of anesthetized rats, the Dextran-SPION and Au-SPION were infused at concentrations of 0.01, 0.1, 1 and 5 mu g Fe/0.5 mu l and at the flow rate of 0.5 mu l min(-1) into the left and right striata, respectively. Repetitive T2-weighted spin-echo MRI scans were performed at time intervals of 1, 6, 12, 24, 48, 72 h, and one, two and eight weeks after inoculation. Following infusion of Dextran-SPION (0.1 mu g and 1 mu g Fe), the maximal distribution volume was observed at about 12-24 h after inoculation and two weeks later the Fe signals were undetectable for the lower dose. On the other hand, Au-SPION remained tightly localized in the closest vicinity of the infusion site as revealed by unchanged MRI signal intensities and strong histochemical staining of Fe2+ and Fe3+ ions in the corresponding brain slices. Immunohistochemical staining of astrocytic and microglial reactions revealed that there were no marked differences in GFAP, VIM or OX-42 labeling observed between the nanoparticle types, however the astrocytic reaction was more pronounced in rats receiving nanoparticles compared to the control (aCSF-infused) rats. In conclusion, the present data demonstrate that the viral-sized Dextran-SPION were able to diffuse freely through the interstitial space of the brain being progressively cleared out from the infusion site within two weeks. Thus, Dextran-SPION could be beneficially used in MRI-guided diagnostic applications such as in experimental oncology or as labels and carriers for targeted drug delivery, whereas Au-SPION could be used for labeling and tracking the transplanted stem cells in experimental MRI.

  • 22. Jafri, S. H. M.
    et al.
    Blom, T.
    Leifer, K.
    Stromme, M.
    Lofas, H.
    Grigoriev, A.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Welch, K.
    Assessment of a nanoparticle bridge platform for molecular electronics measurements2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 43, p. 435204-Article in journal (Refereed)
    Abstract [en]

    A combination of electron beam lithography, photolithography and focused ion beam milling was used to create a nanogap platform, which was bridged by gold nanoparticles in order to make electrical measurements and assess the platform under ambient conditions. Non-functionalized electrodes were tested to determine the intrinsic response of the platform and it was found that creating devices in ambient conditions requires careful cleaning and awareness of the contributions contaminants may make to measurements. The platform was then used to make measurements on octanethiol (OT) and biphenyldithiol (BPDT) molecules by functionalizing the nanoelectrodes with the molecules prior to bridging the nanogap with nanoparticles. Measurements on OT show that it is possible to make measurements on relatively small numbers of molecules, but that a large variation in response can be expected when one of the metal-molecule junctions is physisorbed, which was partially explained by attachment of OT molecules to different sites on the surface of the Au electrode using a density functional theory calculation. On the other hand, when dealing with BPDT, high yields for device creation are very difficult to achieve under ambient conditions. Significant hysteresis in the I-V curves of BPDT was also observed, which was attributed primarily to voltage induced changes at the interface between the molecule and the metal.

  • 23.
    Jayakumar, Ganesh
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Legallais, Maxime
    Hellström, Per-Erik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Mouis, Mireille
    Pignot-Paintrand, Isabelle
    Stambouli, Valérie
    Ternon, Céline
    Östling, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Wafer-scale HfO 2 encapsulated silicon nanowire field effect transistor for efficient label-free DNA hybridization detection in dry environment2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 18Article in journal (Refereed)
  • 24.
    Jayakumar, Ganesh
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Östling, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Pixel-based biosensor for enhanced control: silicon nanowires monolithically integrated with field-effect transistors in fully depleted silicon on insulator technology2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 22, article id 225502Article in journal (Refereed)
    Abstract [en]

    Silicon nanowires (SiNWs) are a widely used technology for sensing applications. Complementary metal-oxide-semiconductor (CMOS) integration of SiNWs advances lab-on-chip (LOC) technology and offers opportunities for read-out circuit integration, selective and multiplexed detection. In this work, we propose novel scalable pixel-based biosensors exploiting the integration of SiNWs with CMOS in fully-depleted silicon-on-insulator technology. A detailed description of the wafer-scale fabrication of SiNW pixels using the CMOS compatible sidewall-transfer-lithography as an alternative to widely investigated time inefficient e-beam lithography is presented. Each 60 nm wide SiNWs sensor is monolithically connected to a control transistor and novel on-chip fluid-gate forming an individual pixel that can be operated in two modes: biasing transistor frontgate (V-G) or substrate backgate (V-BG). We also present the first electrical results of single N and P-type SiNW pixels. In frontgate mode, N and P-type SiNW pixels exhibit subthreshold slope (SS) approximate to 70-80 mV/dec and I-on/I-off approximate to 10(5). The N-type and P-type pixels have an average threshold voltage, Vth of -1.7 V and 0.85 V respectively. In the backgate mode, N and P-type SiNW pixels exhibit SS approximate to 100-150 mV/dec and I-on/I-off approximate to 10(6). The N and P-type pixels have an average V-th of 5 V and -2.5 V respectively. Further, the influence of the backgate and frontgate voltage on the switching characteristics of the SiNW pixels is also studied. In the frontgate mode, the Vth of the SiNW pixels can be tuned at 0.2 V for 1 V change in V-BG for N-type or at -0.2 V for -1 V change in V-BG for P-type pixels. In the backgate mode, it is found that for stable operation of the pixels, the V-G of the N and P-type transistors must be in the range 0.5-2.5 V and 0 V to -2.5 V respectively.

  • 25.
    Jo, Yunsuk
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Kim, M. C.
    Kim, Do-Kyung
    KTH, Superseded Departments, Materials Science and Engineering.
    Kim, C. J.
    Jeong, Y. K.
    Kim, K. J.
    Muhammed, Mamoun
    KTH, Superseded Departments, Materials Science and Engineering.
    Mathematical modelling on the controlled-release of indomethacin-encapsulated poly(lactic acid-co-ethylene oxide) nanospheres2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 9, p. 1186-1194Article in journal (Refereed)
    Abstract [en]

    The in vitro release behaviour of indomethacin (IMC, 1-[p-chlorobenzoyl]-2-methyl-5-methoxy-3-indoleacetic acid) encapsulated in poly(lactic acid-co-ethylene oxide) (PLA-PEO) nanospheres is investigated based on two mathematical models: the diffusion model derived from Fick's law and the dissolution model from the mass balance of IMC. A dual chamber transport system (DCTS) is designed and used for the in vitro experiment. The release behaviour of IMC from the PLA-PEO drug delivery systems (DDSs) is compared to the mathematical models suggested in this work. The synthesis of PLA-PEO and the fabrication of the IMC-loaded PLA-PEO DDSs are discussed and characterized by H-1 NMR, transmission electron microscopy (TEM) and quasi-elastic light scattering (QELS) spectroscopy. Spherical PLA-PEO nanospheres are well prepared as a model DDS as suggested by the characterization results. The overall releasing behaviour of the model drug can be manipulated by varying several key parameters including the volumetric ratio between the organic and the aqueous phase (V-r), the partition coefficient (K-p) and the encapsulation efficiency (EE). Modelling results show that the releasing mechanism is different depending on the particle size. When large PLA-PEO nanospheres are fabricated, the dissolution mechanism can be effective, as the dissolution of IMC can be a rate-determining step due to its high hydrophobicity in an aqueous surrounding medium. In this manner, the optimum DDS can be suitably designed and the releasing profile can be also estimated by considering several major factors for a specific type of substance and its purpose.

  • 26. Kumar, R. T. R.
    et al.
    Badel, X.
    Vikor, G.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schuch, R.
    Fabrication of silicon dioxide nanocapillary arrays for guiding highly charged ions2005In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 16, no 9, p. 1697-1700Article in journal (Refereed)
    Abstract [en]

    This paper demonstrates the fabrication of a membrane permeated by a silicon dioxide nanocapillary array for manipulating highly charged ions at the nanoscale. The fabrication method involves (i) the formation of pores at the nanoscale on lithographically patterned, n-type silicon using photo-assisted electrochemical etching, followed by (ii) thermal oxidation, (iii) bulk silicon back etching and (iv) oxide etching using silicon micromachining technology. The electrochemical etching parameters were chosen to form arrays of straight pores with a diameter of about 250 nm, a length of 30 mu m and interpore distances of I and 1.4 mu m. The back side of the pore arrays was etched in potassium hydroxide and tetramethyl ammonium hydroxide. Finally, the inside of the pores was thermally oxidized to yield SiO2 capillary arrays. The present method could allow the fabrication of capillaries with further smaller dimensions by increasing the thermally grown oxide thickness.

  • 27.
    Lemme, Max C.
    et al.
    AMO GmbH, AMICA, Aachen, Germany.
    Moormann, C.
    Lerch, H.
    Moller, M.
    Vratzov, B.
    Kurz, H.
    Triple-gate metal-oxide-semiconductor field effect transistors fabricated with interference lithography2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 4, p. S208-S210Article in journal (Refereed)
    Abstract [en]

    In this work, n-type triple-crate metal-oxide-semiconductor field effect transistors (MOSFETs) are presented, where laser interference lithography (LIL) is integrated into a silicon-on-insulator (SOI) CMOS process to provide for the critical definition of the transistor channels. A mix and match process of optical contact lithography and LIL is developed to achieve device relevant structures. The triple-gate MOSFETs are electrically characterized to demonstrate the feasibility of this low cost fabrication process.

  • 28.
    Li, Shanghua
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Qin, Jian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Fornara, Andrea
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Kim, Do Kyung
    Synthesis and magnetic properties of bulk transparent PMMA/Fe-oxide nanocomposites2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 18Article in journal (Refereed)
    Abstract [en]

    PMMA/Fe-oxide nanocomposites are fabricated by a chemical method. Monodispersed Fe-oxide nanoparticles are well dispersed in the PMMA matrix by in situ polymerization, resulting in a bulk transparent polymeric nanocomposite. The magnetic behavior of the PMMA/Fe-oxide nanocomposites is investigated. The transparent PMMA/Fe-oxide nanocomposite has potentially interesting magneto-optic applications without compromising the advantages of a lightweight, noncorrosive polymeric material with very high transparency even for bulk samples.

  • 29. Li, X.
    et al.
    Qian, J.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Impact of the self-assembly of multilayer polyelectrolyte functionalized gold nanorods and its application to biosensing2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 35Article in journal (Refereed)
    Abstract [en]

    Multilayered polyelectrolyte functionalized gold nanorods (GNRs) are reported for the conjugation of and sensitive detection of bio-molecules. Multilayered polyelectrolyte functionalized GNRs can significantly improve the biocompatibility of cetyltrimethylammonium bromide ( CTAB) coated GNRs in a bio-environment and can diminish the toxicity induced by CTAB. Biotin, bovine serum albumin (BSA)-biotin and streptavidin are conjugated to polyelectrolyte functionalized GNRs, and the conjugates can serve as a platform for many biotin-streptavidin-based biological applications. Through the robust self-assembly effect of GNRs, biotin-conjugated GNRs are also utilized as a very sensitive probe for the detection of a small amount of streptavidin.

  • 30. Li, Zhuang-Zhi
    et al.
    Baca, Javier
    Yun, Sang Ho
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Wu, Judy
    Gold/boron core-shell nanocables synthesized from gold-boron eutectic droplets2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 5, p. 055606-Article in journal (Refereed)
    Abstract [en]

    Metal/semiconductor coreshell coaxial nanocables are promising building blocks for nanoelectronic devices while in situ growth of these nanocables remains challenging due to the distinctly different synthesis temperature ranges required for metals and semiconductors. To overcome this difficulty, we have developed a vaporliquidsolid and oxide-assisted bimodal competition growth strategy for in situ metal/semiconductor coreshell nanocable growth. Using this process, gold/boron coreshell nanocables were obtained. A coreshell Au-B/BOx eutectic droplet formed via hydrogen gas-assisted rapid cooling was found critical for initiation of the nanocable growth. In addition, the large difference in the boron nanowire growth rates in the vapor-liquid-solid and oxide-assisted mechanisms facilitates the layered growth in the nanocables. The compatibility of this method with the vapor-liquid-solid process applied widely for semiconductor nanowire growth allows in situ connection of metal/semiconductor nanocables with semiconductor nanowires.

  • 31. Liao, Yufeng
    et al.
    Li, Wenjiang
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Properties of CdSe quantum dots coated with silica fabricated in a facile way2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 37Article in journal (Refereed)
  • 32. Liu, Zhengjun
    et al.
    Iltanen, Kari
    Chekurov, Nikolai
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Grigoras, Kestutis
    Tittonen, Ilkka
    Aluminum oxide mask fabrication by focused ion beam implantation combined with wet etching2013In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 24, no 17, p. 175304-Article in journal (Refereed)
    Abstract [en]

    A novel aluminum oxide (Al2O3) hard mask fabrication process with nanoscale resolution is introduced. The Al2O3 mask can be used for various purposes, but in this work it was utilized for silicon patterning using cryogenic deep reactive ion etching (DRIE). The patterning of Al2O3 is a two-step process utilizing focused ion beam (FIB) irradiation combined with wet chemical etching. Gallium (Ga+) FIB maskless patterning confers wet etch selectivity between the irradiated region and the non-irradiated one on the Al2O3 layer, and mask patterns can easily be revealed by wet etching. This method is a modification of Ga+ FIB mask patterning for the silicon etch stop, which eliminates the detrimental lattice damage and doping of the silicon substrate in critical devices. The shallow surface gallium FIB irradiated Al2O3 mask protects the underlying silicon from Ga+ ions. The performance of the masking capacity was tested by drawing pairs consisting of a line and an empty space with varying width. The best result was seven such pairs for 1 mu m. The smallest half pitch was 59 nm. This method is capable of arbitrary pattern generation. The fabrication of a freestanding single-ended tuning fork resonator utilizing the introduced masking method is demonstrated.

  • 33. Makhal, Abhinandan
    et al.
    Sarkar, Soumik
    Bora, Tanujjal
    Baruah, Sunandan
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Raychaudhuri, A K
    Pal, Samir Kumar
    Dynamics of light harvesting in ZnO nanoparticles2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 26, p. 265703-1Article in journal (Refereed)
    Abstract [en]

    We have explored light harvesting of the complex of ZnO nanoparticles with the biological probe Oxazine 1 in the near-infrared region using picosecond-time-resolved fluorescence decay studies. We have used ZnO nanoparticles and Oxazine 1 as a model donor and acceptor, respectively, to explore the efficacy of the Förster resonance energy transfer (FRET) in the nanoparticle–dye system. It has been shown that FRET from the states localized near the surface and those in the bulk of the ZnO nanoparticles can be resolved by measuring the resonance efficiency for various wavelengths of the emission spectrum. It has been observed that the states located near the surface for the nanoparticles (contributing to visible emission at λ≈550 nm) can contribute to very high efficiency (>90%) FRET. The efficiency of light harvesting dynamics of the ZnO nanorods has also been explored in this study and they were found to have much less efficiency (~40%) for energy transfer compared to the nanoparticles. The possibility of an electron transfer reaction has been ruled out from the picosecond-resolved fluorescence decay of the acceptor dye at the ZnO surface.

  • 34. Mikkelsen, A.
    et al.
    Eriksson, J.
    Lundgren, E.
    Andersen, J. N.
    Weissenrieder, Jonas
    Lund University.
    Seifert, W.
    The influence of lysine on InP(001) surface ordering and nanowire growth2005In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 16, no 10, p. 2354-2359Article in journal (Refereed)
    Abstract [en]

    We report on high resolution photoelectron core level spectroscopy (HRCLS) and scanning tunnelling microscopy (STM) measurements of the decomposition of lysine adsorbed on InP(001) substrates. We find that components from the lysine can be present on the InP surface even after annealing to 600 degrees C and desorption of the native surface oxide. We further observe that while a crystalline surface phase can be observed on the epi-ready surface after annealing, the lysine treated surface still appears rough. We conclude that lysine residues inhibit the formation of a flat crystalline structure on the InP(001) surface. These results are discussed in terms of the lysine promotion of [001] nanowire growth.

  • 35. Mohanty, B.
    et al.
    Verma, Anita K.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Bohidar, H. B.
    Physical and anti-microbial characteristics of carbon nanoparticles prepared from lamp soot2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 44Article in journal (Refereed)
    Abstract [en]

    Soot originating from the burning of butter and mustard oil in a lamp with a cotton wick was collected on a brass plate and dispersed in water and carbon tetrachloride (CCl4) as naked, and as Gum Arabic (GA, a anionic polyelectrolyte)-coated nanoparticles in water. They were physically characterized, and their anti-bacterial activities were probed on gram positive and negative bacterial colonies. TEM data revealed the presence of 35-55 nm diameter spherical carbon nanoparticles in water and CCl4. The dynamic light scattering determined the average hydrodynamic diameter for the same samples, which was found to be approximate to 100 nm ( in CCl4) and approximate to 240 nm ( in water), implying the packing of these nanoparticles into clusters. GA-coated particles yielded stable suspensions in water, but the clusters were almost the same in size (approximate to 250 nm). The zeta potential distributions of the naked and the GA-coated nanoparticles were found to be unimodal and bimodal, respectively, with both yielding mean zeta potential values nearly equal to zero. Results of energy-dispersive x-ray analysis (EDAX) confirmed the absence of toxic metallic elements inside the specimen. X-ray diffraction study confirmed the presence of amorphous as well as graphitized carbon in these nanostructures. The anti-microbial activities in terms of growth inhibition for the carbon nanoparticles against Staphylococcus aureus, ATCC 13709 ( native strain) and Klebsiella pneumonia ATCC 29655 ( native strain) were assayed in agar gel. In vitro testing revealed significant anti-microbial activity against Klebsiella pneumonia, but carbon nanoparticles were unable to kill Staphylococcus aureus.

  • 36. Moosburger, J.
    et al.
    Kamp, M.
    Forchel, A.
    Ferrini, R.
    Leuenberger, D.
    Houdre, R.
    Anand, Srinivasan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Berggren, J.
    Nanofabrication of high quality photonic crystals for integrated optics circuits2002In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 13, no 3, p. 341-345Article in journal (Refereed)
    Abstract [en]

    In this paper we report on the fabrication and characterization of two-dimensional photonic crystals. They are realized as a hexagonal array of air holes etched in GaAs or InP based slab waveguide heterostructures. The fabrication steps are discussed, with a focus on the development of suitable dry etching processes. Holes with a depth of I mum on GaAs and 4 Mm on InP were fabricated, which results in a good overlap of the guided mode with the photonic crystal patterns and low losses. The optical quality of the structures is assessed by transmission spectroscopy of photonic crystal blocks and photonic crystal-based waveguides.

  • 37. Mulders, J. J. L.
    et al.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Riazanova, Anastasiia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Electron beam induced deposition at elevated temperatures: compositional changes and purity improvement2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 5, p. 055302-Article in journal (Refereed)
    Abstract [en]

    Thermally assisted electron beam induced deposition can result in an improvement of the purity of nano-scale depositions. Six commonly used organic precursors were examined: W(CO) 6, TEOS (tetraethylorthosilicate), MeCpPtMe3, Co(CO)(3)NO, Co-2(CO)(8), and Me(2)Auacac. The last two precursors were also tested on two different instruments to confirm reproducibility of the results. The influence of the substrate temperature on the composition of the deposition has been quantified systematically in the temperature range 25-360 degrees C. It has been shown that most purities improve when applying an elevated temperature, while the shape of the deposition remains intact. The purity improvement is achieved at the cost of a lower deposition yield. The amount of improvement is different for each precursor. Within the maximum temperature range of 360 degrees C, the best improvement was found for W(CO)(6): from 36.7 at.% at 25 degrees C to 59.2 at.% at 280 degrees C. For both cobalt precursors an additional transition region between patterned electron beam induced deposition (EBID) and thermal thin film growth has been identified. In this region seeded growth occurs with strongly increased growth rates.

  • 38.
    Naureen, Shagufta
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
    Shahid, Naeem
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
    Dev, Apurba
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
    Generation of substrate-free III-V nanodisks from user-defined multilayer nanopillar arrays for integration on Si2013In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 24, no 22, p. 225301-Article in journal (Refereed)
    Abstract [en]

    High material quality InP-based multilayer nanopillar (NP) arrays are fabricated using a combination of self-assembly of silica particles for mask generation and dry etching. In particular, the NP arrays are made from user-defined epitaxial multilayer stacks with specific materials and layer thicknesses. An additional degree of flexibility in the structures is obtained by changing the lateral diameters of the NP multilayer stacks. Pre-defined NP arrays made from InGaAsP/InP and InGaAs/InP NPs are then used to generate substrate-free nanodisks of a chosen material from the stack by selective etching. A soft-stamping method is demonstrated to transfer the generated nanodisks with arbitrary densities onto Si. The transferred nanodisks retain their smooth surface morphologies and their designed geometrical dimensions. Both InP and InGaAsP nanodisks display excellent photoluminescence properties, with line-widths comparable to unprocessed reference epitaxial layers of similar composition. The multilayer NP arrays are potentially attractive for broad-band absorption in third-generation solar cells. The high optical quality, substrate-free InP and InGaAsP nanodisks on Si offer a new path to explore alternative ways to integrate III-V on Si by bonding nanodisks to Si. The method also has the advantage of re-usable III-V substrates for subsequent layer growth.

  • 39. Nisar, J.
    et al.
    Jiang, Xue
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Pathak, B.
    Zhao, J.
    Kang, T. W.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Semiconducting allotrope of graphene2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 38, p. 385704-Article in journal (Refereed)
    Abstract [en]

    From first-principles calculations, we predict a planar stable graphene allotrope composed of a periodic array of tetragonal and octagonal (4, 8) carbon rings. The stability of this sheet is predicted from the room-temperature molecular dynamics study and the electronic structure is studied using state-of-the-art calculations such as the hybrid density functional and the GW approach. Moreover, the mechanical properties of (4, 8) carbon sheet are evaluated from the Youngs modulus and intrinsic strength calculations. We find this is a stable planar semiconducting carbon sheet with a bandgap between 0.43 and 1.01eV and whose mechanical properties are as good as graphenes.

  • 40.
    Palmgren, Pål
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Hennies, F.
    Yu, S.
    Nilson, K.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Thermal effects on order at organic/inorganic interfaces: TiOPc on IOnSb(001)c(8x2)2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528Article in journal (Other academic)
  • 41.
    Panigrahi, P.
    et al.
    Hindustan Inst Technol & Sci, Clean Energy & Nano Convergence Ctr, Madras 603103, Tamil Nadu, India..
    Dhinakaran, A. K.
    Hindustan Inst Technol & Sci, Clean Energy & Nano Convergence Ctr, Madras 603103, Tamil Nadu, India..
    Naqvi, S. R.
    Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, Box 516, S-75120 Uppsala, Sweden..
    Gollu, S. R.
    Nanyang Technol Univ, Sch Elect & Elect Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, Box 516, S-75120 Uppsala, Sweden..
    Hussain, T.
    Univ Queensland, Australian Inst Bioengn & Nanotechnol, Ctr Theoret & Computat Mol Sci, Brisbane, Qld 4072, Australia.;Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia..
    Light metal decorated graphdiyne nanosheets for reversible hydrogen storage2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 35, article id 355401Article in journal (Refereed)
    Abstract [en]

    The sensitive nature of molecular hydrogen (H-2) interaction with the surfaces of pristine and functionalized nanostructures, especially two-dimensional materials, has been a subject of debate for a while now. An accurate approximation of the H-2 adsorption mechanism has vital significance for fields such as H2 storage applications. Owing to the importance of this issue, we have performed a comprehensive density functional theory (DFT) study by means of several different approximations to investigate the structural, electronic, charge transfer and energy storage properties of pristine and functionalized graphdiyne (GDY) nanosheets. The dopants considered here include the light metals Li, Na, K, Ca, Sc and Ti, which have a uniform distribution over GDY even at high doping concentration due to their strong binding and charge transfer mechanism. Upon 11% of metal functionalization, GDY changes into a metallic state from being a small band-gap semiconductor. Such situations turn the dopants to a partial positive state, which is favorable for adsorption of H-2 molecules. The adsorption mechanism of H-2 on GDY has been studied and compared by different methods like generalized gradient approximation, van der Waals density functional and DFT-D3 functionals. It has been established that each functionalized system anchors multiple H-2 molecules with adsorption energies that fall into a suitable range regardless of the functional used for approximations. A significantly high H-2 storage capacity would guarantee that light metal-doped GDY nanosheets could serve as efficient and reversible H-2 storage materials.

  • 42.
    Pardon, Gaspard
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Gatty, Hithesh K.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Roxhed, Niclas
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores2013In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 24, no 1, p. 015602-Article in journal (Refereed)
    Abstract [en]

    Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al2O3) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al2O3 layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 mu m thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al2O3 using ALD.

  • 43. Parekh, Kinnari
    et al.
    Upadhyay, Ramesh V.
    Belova, Lyubov M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Rao, K. V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Ternary monodispersed Mn0.5Zn0.5Fe2O4 ferrite nanoparticles: preparation and magnetic characterization2006In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 17, no 24, p. 5970-5975Article in journal (Refereed)
    Abstract [en]

    A ternary system of Mn0.5Zn0.5Fe2O4 has been synthesized for the first time using thermal decomposition of metal acetylacetonate in the presence of a high temperature boiling point solvent and fatty acids. Unlike the results of synthesis of this material by other techniques, we obtain nearly monodispersed nanoparticles, rendering them ideal for applications like in hyperthermia. The crystal structure and morphology of the particles obtained using x-ray diffraction (XRD) and transmission electron microscopy (TEM) are those of a single phase spinel structure with no other impurity phases. The particles are of 7 nm average diameter, with a very narrow (< 10%) size distribution. The oleic acid surfactant on the particles shows a 28% weight loss in thermo-gravimetric analyses (TGAs), which corresponds to a monolayer thickness of the coating. Magnetic measurements show the particles to be superparamagnetic with a characteristic blocking temperature of around 50 K.

  • 44.
    Platz, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Forchheimer, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tholén, Erik A.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Haviland, David B.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    The role of nonlinear dynamics in quantitative atomic force microscopy2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 26, p. 265705-Article in journal (Refereed)
    Abstract [en]

    Various methods of force measurement with the atomic force microscope are compared for their ability to accurately determine the tip-surface force from analysis of the nonlinear cantilever motion. It is explained how intermodulation, or the frequency mixing of multiple drive tones by the nonlinear tip-surface force, can be used to concentrate the nonlinear motion in a narrow band of frequency near the cantilever's fundamental resonance, where accuracy and sensitivity of force measurement are greatest. Two different methods for reconstructing tip-surface forces from intermodulation spectra are explained. The reconstruction of both conservative and dissipative tip-surface interactions from intermodulation spectra are demonstrated on simulated data.

  • 45.
    Qian, Zhao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Sa
    Pathak, Biswarup
    Araujo, C. Moyses
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Jena, Puru
    C-60-mediated hydrogen desorption in Li-N-H systems2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 48, p. 485406-Article in journal (Refereed)
    Abstract [en]

    Hydrogen desorption from a LiH + NH3 mixture is very difficult due to the formation of the stable LiNH4 compound. Using cluster models and first-principles theory, we demonstrate that the C-60 molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH4. The hydrogen desorption following the path of LiNH4-C-60 -> LiNH3-C-60 + 1/2H(2) is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH4 compound cannot desorb hydrogen at room temperature in the absence of C-60. The introduction of C-60 also helps to restrain the NH3 gas which is poisonous in proton exchange membrane fuel cell applications.

  • 46.
    Qu, Muchao
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;BPI, Key Lab Adv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Schubert, Dirk W.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;BPI, Key Lab Adv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Novel definition of the synergistic effect between carbon nanotubes and carbon black for electrical conductivity2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 24, article id 245703Article in journal (Refereed)
    Abstract [en]

    Anisotropic ternary composites comprising poly(methy-methacrylate) (PMMA), carbon black (CB), and carbon nanotubes (CNTs) were extruded using a capillary rheometer and the electrical conductivities of the composites were measured and presented in a detailed contour plot covering a large range of filler fractions (up to 30 vol% CNTs, 20 vol% CB). A recent generic conductivity model for ternary composites was successfully validated using the conductivity measurements. When analyzing the conductivity measurements using four traditional definitions of 'synergy' between two conductive fillers, no clear synergetic effect was observed between CB and CNT. Also, when all the conductivity data for ternary CNT/CB composites from the existing literature was carefully gathered and analyzed, the number of confirmed occurrences of strong and convincing CNT/CB synergies was surprisingly low. Finally, a novel definition of synergy based on the physical aspect, in particular, its maximum, the 'synergasm', was defined in order to obtain a more precise instrument for revealing regions of potential synergy.

  • 47. Rao, G. S.
    et al.
    Hussain, Tanveer
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden; University of Queensland, Australia.
    Islam, M. S.
    Sagynbaeva, M.
    Gupta, D.
    Panigrahi, P.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden.
    Adsorption mechanism of graphene-like ZnO monolayer towards CO2 molecules: enhanced CO2 capture2016In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 27, no 1, article id 015502Article in journal (Refereed)
    Abstract [en]

    This work aims to efficiently capture CO2 on two-dimensional (2D) nanostructures for effective cleaning of our atmosphere and purification of exhausts coming from fuel engines. Here, we have performed extensive first principles calculations based on density functional theory (DFT) to investigate the interaction of CO2 on a recently synthesized ZnO monolayer (ZnO-ML) in its pure, defected and functionalized form. A series of rigorous calculations yielded the most preferential binding configurations of the CO2 gas molecule on a ZnO-ML. It is observed that the substitution of one oxygen atom with boron, carbon and nitrogen on the ZnO monolayer resulted into enhanced CO2 adsorption. Our calculations show an enriched adsorption of CO2 on the ZnO-ML when substituting with foreign atoms like B, C and N. The improved adsorption energy of CO2 on ZnO suggests the ZnO-ML could be a promising candidate for future CO2 capture.

  • 48.
    Riazanova, Anastasia V.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Aristov, Andrey
    Aix Marseille University.
    Rikers, Yuri G. M.
    FEI Electron Optics.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Mulders, Johannes J. L.
    FEI Electron Optics.
    Kabashin, Andrei V.
    Aix Marseille University.
    Belova, Lyubov M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Gas-assisted electron-beam-induced nanopatterning of high-quality Si-based insulator2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 15, p. 155301-Article in journal (Refereed)
    Abstract [en]

    An oxygen-assisted electron-beam-induced deposition (EBID) process, in which an oxygen flow and the vapor phase of the precursor, tetraethyl orthosilicate (TEOS), are both mixed and delivered through a single needle, is described. The optical properties of the SiO(2+delta) (-0.04 <= delta <= +0.28) are comparable to fused silica. The electrical resistivity of both single-needle and double-needle SiO(2+delta) are comparable (greater than 7 G Omega cm) and a measured breakdown field is greater than 400 V mu m(-1). Compared to the double-needle process the advantage of the single-needle technique is the ease of alignment and the proximity to the deposition location, which facilitates fabrication of complex 3D structures for nanophotonics, photovoltaics, micro- and nano-electronics applications.

  • 49.
    Riazanova, Anastasiia V.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Costanzi, B. N.
    Aristov, A. I.
    Rikers, Y. G. M.
    Mulders, J. J. L.
    Kabashin, A. V.
    Dahlberg, E. Dan
    Belova, Liubov M.
    FEI Electron Opt, Netherlands.
    Gas-assisted electron-beam-induced nanopatterning of high-quality titanium oxide2016In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 27, no 11, article id 115304Article in journal (Refereed)
    Abstract [en]

    Electron-beam-induced deposition of titanium oxide nanopatterns is described. The precursor is titanium tetra-isopropoxide, delivered to the deposition point through a needle and mixed with oxygen at the same point via a flow through a separate needle. The depositions are free of residual carbon and have an EDX determined stoichiometry of TiO2.2. High resolution transmission electron microscopy and Raman spectroscopy studies reveal an amorphous structure of the fabricated titanium oxide. Ellipsometric characterization of the deposited material reveals a refractive index of 2.2-2.4 RIU in the spectral range of 500-1700 nm and a very low extinction coefficient (lower than 10(-6) in the range of 400-1700 nm), which is consistent with high quality titanium oxide. The electrical resistivity of the titanium oxide patterned with this new process is in the range of 10-40 G Omega cm and the measured breakdown field is in the range of 10-70 V mu m(-1). The fabricated nanopatterns are important for a variety of applications, including field-effect transistors, memory devices, MEMS, waveguide structures, bio-and chemical sensors.

  • 50. Saeed, Saba
    et al.
    Buters, Frank
    Dohnalova, Katerina
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Gregorkiewicz, Tom
    Structural and optical characterization of self-assembled Ge nanocrystal layers grown by plasma-enhanced chemical vapor deposition2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 40, p. 405705-Article in journal (Refereed)
    Abstract [en]

    We present a structural and optical study of solid-state dispersions of Ge nanocrystals prepared by plasma-enhanced chemical vapor deposition. Structural analysis shows the presence of nanocrystalline germanium inclusions embedded in an amorphous matrix of Si-rich SiO2. Optical characterization reveals two prominent emission bands centered around 2.6 eV and 3.4 eV, and tunable by excitation energy. In addition, the lower energy band shows an excitation power-dependent blue shift of up to 0.3 eV. Decay dynamics of the observed emission contains fast (nanosecond) and slow (microseconds) components, indicating contributions of several relaxation channels. Based on these material characteristics, a possible microscopic origin of the individual emission bands is discussed.

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