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  • 1. Ahrén, M.
    et al.
    Selegård, L.
    Söderlind, F.
    Linares, M.
    Kauczor, J.
    Norman, Patrick
    Käll, P. -O
    Uvdal, K.
    A simple polyol-free synthesis route to Gd 2O 3 nanoparticles for MRI applications: An experimental and theoretical study2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8, article id 1006Article in journal (Refereed)
    Abstract [en]

    Chelated gadolinium ions, e.g., Gd-DTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd 2O 3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r 1 and r 2 values almost as high as those for free Gd 3+ ions in water. The Gd 2O 3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI. © 2012 Springer Science+Business Media B.V.

  • 2.
    Fornara, Andrea
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Chiavarino, Annalisa
    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.
    Toprak, Muhammet
    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.
    PLGA-PEG multifunctional nanoparticles for simultaneous drug delivery and visualizationIn: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896XArticle in journal (Other academic)
  • 3.
    Liang, Lijun
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Kang, Zhengzhong
    Shen, Jia-Wei
    Translocation mechanism of C-60 and C-60 derivations across a cell membrane2016In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 18, no 11Article in journal (Refereed)
    Abstract [en]

    Carbon-based nanoparticles (NPs) such as fullerenes and nanotubes have been extensively studied for drug delivery in recent years. The permeation process of fullerene and its derivative molecules through membrane is essential to the utilization of fullerene-based drug delivery system, but the mechanism and the dynamics of permeation through cell membrane are still unclear. In this study, coarse-grained molecular dynamics simulations were performed to investigate the permeation process of functionalized fullerene molecules (ca. 0.72 nm) through the membrane. Our results show that single functionalized fullerene molecule in such nanoscale could permeate the lipid membrane in micro-second time scale. Pristine C-60 molecules prefer to aggregate into several small clusters while C60OH15 molecules could aggregate into one big cluster to permeate through the lipid membrane. After permeation of C-60 or its derivatives into membrane, all C-60 and C60OH15 molecules disaggregated and monodispersed in the lipid membrane.

  • 4.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Li, S
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Bitaraf Haghighi, Ehsan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn E
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Novel Nanofluids Based on Mesoporous Silica for Enhanced Heat Transfer2011In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, no 11, p. 6201-6206Article in journal (Refereed)
    Abstract [en]

    Nanofluids, which are liquids with engineered nanometer-sized particles suspensions, have drawn remarkable attraction from the researchers because of their enormous potential to enhance the efficiency in heat-transfer fluids. In the present study, water-based calcined mesoporous silica nanofluids were prepared and characterized. The commercial mesoporous silica (MPSiO2) nanoparticles were dispersed in deionized water by means of pH adjustment and ultrasonic agitation. MPSiO2 nanoparticles were observed to have an average particle size of 350 ± 100 nm by SEM analysis. The concentration of MPSiO2 was varied between 1 and 6 wt%. The physicochemical properties of nanofluids were characterized using various techniques, such as particle size analyzer, zeta-potential meter, TEM, and FT-IR. The thermal conductivity was measured by Transient Plane Source (TPS) method, and nanofluids showed a higher thermal conductivity than the base liquid for all the tested concentrations.

  • 5.
    Okoli, Chuka
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Rajarao-Kuttuva, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 10, p. 1194-Article in journal (Refereed)
    Abstract [en]

    Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO? ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MIONby washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

  • 6.
    Pradhan, Sulena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Tech Res Inst, Sweden.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Effect of sonication on particle dispersion, administered dose and metal release of non-functionalized, non-inert metal nanoparticles2016In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 18, no 9, article id 285Article in journal (Refereed)
    Abstract [en]

    In this study, we elucidate the effect of different sonication techniques to efficiently prepare particle dispersions from selected non-functionalized NPs (Cu, Al, Mn, ZnO), and corresponding consequences on the particle dose, surface charge and release of metals. Probe sonication was shown to be the preferred method for dispersing non-inert, non-functionalized metal NPs (Cu, Mn, Al). However, rapid sedimentation during sonication resulted in differences between the real and the administered doses in the order of 30-80 % when sonicating in 1 and 2.56 g/L NP stock solutions. After sonication, extensive agglomeration of the metal NPs resulted in rapid sedimentation of all particles. DLVO calculations supported these findings, showing the strong van der Waals forces of the metal NPs to result in significant NP agglomeration. Metal release from the metal NPs was slightly increased by increased sonication. The addition of a stabilizing agent (bovine serum albumin) had an accelerating effect on the release of metals in sonicated solutions. For Cu and Mn NPs, the extent of particle dissolution increased from <1.6 to similar to 5 % after sonication for 15 min. A prolonged sonication time (3-15 min) had negligible effects on the zeta potential of the studied NPs. In all, it is shown that it is of utmost importance to carefully investigate how sonication influences the physicochemical properties of dispersed metal NPs. This should be considered in nanotoxicology investigations of metal NPs.

  • 7. Promnimit, S.
    et al.
    Baruah, S.
    Lamdub, U.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology, Thailand.
    Hydrothermal growth of ZnO hexagonal nanocrystals: Effect of growth conditions2013In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 21, p. 57-63Article in journal (Refereed)
    Abstract [en]

    Hexagonal ZnO nanocrystals were synthesized through a hydrothermal route under mild conditions (growth temperature of 90 degrees C at atmospheric pressure). Pre-synthesized ZnO nanoparticles were used to serve as nucleation sites for the growth of the nanocrystals. The growth of ZnO nanorods was found to be surface independent. The dimensions of the hexagonal ZnO nanocrystals were observed to be dependent on the concentration of the reactants used (sources of Zn2+ and OH- ions), pH of the growth bath and also on the duration of crystal growth. The average diameter and height of the ZnO nanocrystals was found to be directly proportional to the concentration of the reactants as well as hydrolysis time. The orientation of the nanocrystals was found to be dependent upon the seeding method employed. Hexagonal single crystals of a wide range of dimensions and aspect ratios could be successfully synthesized through a control of growth parameters.

  • 8.
    Qian, Zhao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Pathak, Biswarup
    Nisar, Jawad
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Oxygen- and nitrogen-chemisorbed carbon nanostructures for Z-scheme photocatalysis applications2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8, p. 895-Article in journal (Refereed)
    Abstract [en]

    Here focusing on the very new experimental finding on carbon nanomaterials for solid-state electron mediator applications in Z-scheme photocatalysis, we have investigated different graphene-based nanostructures chemisorbed by various types and amounts of species such as oxygen (O), nitrogen (N) and hydroxyl (OH) and their electronic structures using density functional theory. The work functions of different nanostructures have also been investigated by us to evaluate their potential applications in Z-scheme photocatalysis for water splitting. The N-, O-N-, and N-N-chemisorbed graphene-based nanostructures (32 carbon atoms supercell, corresponding to lattice parameter of about 1 nm) are found promising to be utilized as electron mediators between reduction level and oxidation level of water splitting. The O- or OH-chemisorbed nanostructures have potential to be used as electron conductors between H-2-evolving photocatalysts and the reduction level (H+/H-2). This systematic study is proposed to understand the properties of graphene-based carbon nanostructures in Z-scheme photocatalysis and guide experimentalists to develop better carbon-based nanomaterials for more efficient Z-scheme photocatalysis applications in the future.

  • 9. Salazar-Alvarez, German
    et al.
    Bjorkman, Eva
    Lopes, Cesar
    Eriksson, Anders
    Svensson, Soren
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Synthesis and nonlinear light scattering of microemulsions and nanoparticle suspensions2007In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 9, no 4, p. 647-652Article in journal (Refereed)
    Abstract [en]

    Microemulsions composed of normal or inverse micellar solutions and aqueous suspensions of pristine (uncoated) or silica-coated iron oxide nanoparticles, mainly gamma-Fe2O3, were synthesised and their optical limiting properties investigated. The microemulsions are colorless solutions with high transparency for visible wavelengths while the aqueous suspensions of iron oxide are of pale yellow colour. Optical limiting experiments performed in 2 mm cells using a f/5 optical system with a frequency doubled Nd:YAG laser delivering 5 ns pulses with 10 Hz repetition rate, showed clamping levels of similar to 3 mu J for the suspensions of both pristine and silica-coated iron oxide nanoparticles. A strong photoinduced nonlinear light scattering was observed for the water-in-oil microemulsion and the aqueous suspensions of nanoparticles while oil-in-water microemulsions did not show a significant nonlinear effect. Measurements carried out using an integrating sphere further verified that the photoinduced nonlinear light scattering is the dominating nonlinear mechanism while the nonlinear absorption of iron oxide nanoparticles is negligible at 532 nm.

  • 10. Sanchez-Dominguez, Margarita
    et al.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Solans, Conxita
    A novel approach to metal and metal oxide nanoparticle synthesis: the oil-in-water microemulsion reaction method2009In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 11, no 7, p. 1823-1829Article in journal (Refereed)
    Abstract [en]

    A novel and straightforward approach, based on oil-in-water (o/w) microemulsions, was developed for the synthesis of inorganic nanoparticles at ambient conditions. It implies the use of organometallic precursors dissolved in nanometre-scale oil droplets of o/w microemulsions. Addition of reducing or oxidizing/precipitating agents results in the formation of metallic or metal oxide nanoparticles, respectively. Nonionic o/w microemulsion systems were chosen, and several key compositions were selected for nanoparticle synthesis at 25 A degrees C. High Resolution Electron Microscopy revealed that small nanoparticles of metals (Pt, Pd and Rh) and nanocrystalline metal oxide (cerium (IV) oxide with cubic type crystalline structure confirmed by XRD), of less than 7 nm can be obtained in mild conditions.

  • 11. Singhal, Sonal
    et al.
    Chawla, Amit Kumar
    Nagar, Sandeep
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Gupta, Hari Om
    Chandra, Ramesh
    Photoluminescence measurements in the phase transition region of Zn1-x Cd (x) S films2010In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 12, no 4, p. 1415-1421Article in journal (Refereed)
    Abstract [en]

    Thin films of Zn1-x Cd (x) S (0.1 a parts per thousand currency sign x a parts per thousand currency sign 0.5) were prepared by using pulsed laser ablation technique on corning glass substrates. Phase transition from cubic to hexagonal in Zn1-x Cd (x) S films is determined by X-ray diffraction analysis. We observed a lowering in the phase transition temperature with increase in the cadmium concentration. Transmission electron microscopy suggests the crystalline nature of thin films with average particle size of 15 nm. The grown Zn1-x Cd (x) S samples show the high peak intensity ratio of the near band edge emission to the defect center luminescence even at room temperature, which indicates the small concentration of complex defects in the samples. Photoluminescence measurement show stoichiometric dependence of the energy band gap and is found to have quadratic dependence on x.

  • 12. Unal, B.
    et al.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Durmus, Z.
    Sozeri, H.
    Baykal, A.
    Synthesis, structural and conductivity characterization of alginic acid-Fe3O4 nanocomposite2010In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 12, no 8, p. 3039-3048Article in journal (Refereed)
    Abstract [en]

    Alginic acid-Fe3O4 nanocomposite is synthesized by the precipitation of Fe3O4 in the presence of alginic acid (AA). Structural, surface, morphological, thermal and electrical transport properties of the nanocomposite were performed by XRD, FT-IR, TEM-SEM, TGA and conductivity measurements respectively. FT-IR analysis revealed that Fe3O4 NPs are strongly capped with AA and TGA analysis showed that nanocomposite have 80% of Fe3O4 content. TEM analysis of Fe3O4 NPs show an average particle size of 9.5 nm, and upon nanocomposite formation with AA these particles are observed to form aggregates of similar to 150 nm. The frequency-dependency of the AC conductivity show electrode polarization effect. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled. DC electrical conductivity is strongly temperature dependent, and is classified into three regions over a limited temperature range of up to 100 A degrees C.

  • 13. Uzun, K.
    et al.
    Cevik, E.
    Senel, M.
    Sozeri, H.
    Baykal, A.
    Abasiyanik, M. F.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Covalent immobilization of invertase on PAMAM-dendrimer modified superparamagnetic iron oxide nanoparticles2010In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 12, no 8, p. 3057-3067Article in journal (Refereed)
    Abstract [en]

    In this study, polyamidoamine (PAMAM) dendrimer was synthesized on the surface of superparamagnetite nanoparticles to enhance invertase immobilization. The amount of immobilized enzyme on the surface-hyperbranched magnetite nanoparticle was up to 2.5 times (i.e., 250%) as much as that of magnetite nanoparticle modified with only amino silane. Maximum reaction rate (V (max)) and Michaelis-Menten constant (K (m)) were determined for the free and immobilized enzymes. Various characteristics of immobilized invertase such as; the temperature activity, thermal stability, operational stability, and storage stability were evaluated and results revealed that stability of the enzyme is improved upon immobilization.

  • 14.
    Vogt, Carmen M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Laurent, Sophie
    University of Mons-Hainaut, Belgium.
    Bridot, Jean-Luc
    University of Mons-Hainaut, Belgium.
    Müller, Robert N.
    University of Mons-Hainaut.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    High quality and tuneable silica shell-magnetic core nanoparticles2010In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 12, no 4, p. 1137-1147Article in journal (Refereed)
    Abstract [en]

    Obtaining small (<50 nm), monodispersed, well-separated, single iron oxide core-silica SiO2) shell nanoparticles for biomedical applications is still a challenge. Preferably, they are synthesized by inverse microemulsion method. However, substantial amount of aggregated and multicore core- shell nanoparticles is the undesired outcome of the method. In this study, we report on the production of less than 50 nm overall size, monodispersed, free of necking, single core iron oxide-SiO2 shell nanoparticles with tuneable shell thickness by a carefully optimized inverse microemulsion method. The high degree of control over the process is achieved by understanding the mechanism of core-shell nanoparticles formation. By varying the reaction time and recursor concentration, the thickness of silica layer an the core nanoparticles can be finely adjusted from to 13 nm. Residual reactions during the workup were inhibited by a combination of pH control with hock freezing and ultracentrifuging. These highquality tuneable core-shell nanocomposite particles exhibit superparamagnetic character and sufficiently high magnetization with great potential for biomedical applications (e.g. MRI, cell separation and magnetically driven drug delivery systems) either as-prepared or by additional surface modification for improved biocompatibility.

  • 15. Wang, F. H.
    et al.
    Yoshitake, T.
    Kim, D. K.
    Muhammed, Mamoun
    KTH, Superseded Departments, Materials Science and Engineering.
    Bjelke, O.
    Kehr, J.
    Determination of conjugation efficiency of antibodies and proteins to the superparamagnetic iron oxide nanoparticles by capillary electrophoresis with laser-induced fluorescence detection2003In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 5, no 02-jan, p. 137-146Article in journal (Refereed)
    Abstract [en]

    The method based on capillary electrophoresis with laser-induced fluorescence detection (CE/LIF) was developed for determination of magnetic iron oxide nanoparticles (hydrodynamic diameters of 100 nm) functionalized with molecules containing primary amino groups. The magnetic nanoparticles with carboxylic or aminopropyltrimethoxysilane groups at their surface were conjugated to the model proteins ( bovine serum albumin, BSA; streptavidin or goat anti-rabbit immunoglobulin G, IgG) using carbodiimide as a zero-length cross-linker. The nanoparticle-protein conjugates ( hydrodynamic diameter 163 - 194 nm) were derivatized with naphthalene-2,3- dicarboxaldehyde reagent and separated by CE/LIF with a helium - cadmium laser ( excitation at 442 nm, emission at 488 nm). The separations were carried out by using a fused-silica capillary ( effective length 48 cm, inner diameter 75 mum) and 100 mM sodium borate buffer ( pH 9.2), the potential was 30 kV. The detection limit for BSA-conjugate was 1.3 pg/10 nl, i.e. about 20 amol. The present method provides an efficient and fast tool for sensitive determination of the efficacy of biomolecular functionalization of magnetic nanoparticles. The CE/LIF technique requires only negligible sample volumes for analysis, which is especially suitable for controlling the process of preparation of functionalized nanoparticles with unique properties aimed to be used for diagnostic or therapeutic purposes.

  • 16.
    Wang, Xiaodi
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Ma, Ying
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Sugunan, Abhilash
    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.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis of uniform quasi-octahedral CeO2 mesocrystals via a surfactant-free route2011In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, no 11, p. 5879-5885Article in journal (Refereed)
    Abstract [en]

    A facile surfactant-free nonaqueous method is presented to prepare uniform quasi-octahedral ceria, CeO 2 , mesocrystals, in which only Ce(NO 3 ) 3 and octanol were used as the reactants at a reaction temperature of 150 °C. CeO 2 sample synthesized using this technique consists of well-dispersed quasi-octahedrons and exhibits an uniform size and morphology. Based on structural characterization, it is proposed that the CeO 2 mesostructure was formed by self-assembly of primary nanocrystals based on unique 3D oriented-attachment mechanism. Optical characterization exhibited a strong quantum confinement, revealing small size of primary nanocrystals. The thermal stability and UV–Vis study reveal CeO 2 mesocrystal has various potential for high temperature applications and optical apparatus applications.

  • 17.
    Yar, Mazher Ahmed
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Wahlberg, Sverker
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Abuelnaga, Mohammad Omar
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Johnsson, Mats
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Processing and Sintering of Yttrium-Doped Tungsten Oxide Nano-powdersIn: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896XArticle in journal (Other academic)
    Abstract [en]

    Innovative chemical methods are capable of fabricating nanoscale tungsten oxide compoundsd oped with various rare-earth elements with high purity and homogeneity, which can be processed under hydrogen into nanostructured oxide-dispersed tungsten composite powders having several potential applications. However, hydrogen reduction of doped-tungsten oxide compounds is rather complex, affecting the morphology and composition of the final powder. In this study we have investigated the reduction of tungstic acid in the presence of Y and weprovide the experimental evidence that Y2O3 can be separated from Y-doped tungstic acid via hydrogen reduction to produce Y2O3-W powders. The processed powders were further consolidated by spark plasma sintering at different temperatures and holding times at 75 MPa pressure and characterized. The optimized SPS conditions suggest sintering at 1400 °C for 3 min holding time to achieve higher density composites with an optimum finer grain size (3 μm) and a hardness value up to 420 HV. Major grain growth takes place at temperatures above 1300 °C during sintering. From the density values obtained, it is recommend to apply higher pressure before 900 °C to obtain maximum density. Oxides inclusions present in the matrix were identified as Y2O3•3WO3 and Y2O3•WO3 during high resolution microscopici nvestigations.

  • 18.
    Yar, Mazher Ahmed
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Wahlberg, Sverker
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Pintsuk, Gerald
    Johnsson, Mats
    Linke, Jochem
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Micro-mechanical and high heat load testing of W-Y2O3 ODS armourmaterials fabricated by novel chemical method and SPSIn: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896XArticle in journal (Other academic)
    Abstract [en]

    Oxide-dispersed strengthened (ODS) - tungsten based composites can be fabricated using several methods. In this study W-Y2O3 composite powders were synthesized by an innovative chemical process yielding ultrafine to micron range grains that were subsequently compacted using spark plasma sintering (SPS). Micro-mechanical tests were conducted to investigate the elastic and fracture properties of sintered compacts with grain size from ultrafine to several microns. For the evaluation of the developed material for plasma facing armour application in the fusion reactor, high heat load tests have been performed in an electron beam test facility. Surface effects, i.e. roughening, particle erosion and crack formation in dependence of base temperature and power density, were determined for an applied number of 100 ELM like loads with a pulse duration of 1 ms. The crack paths at the surface and particularly versus the bulk material were investigated to determine the resistance of the material to the formation of cracks parallel to the surface which finally would limit the thermal transfer and lead to local overheating and probably melting. Furthermore, the thermal stability of material, i.e. the resistance to recrystallization was determined by thermal annealing up to 1800 °C and during the electron beam tests by applying heat loads that lead to a surface temperature increase of> 2000°C.

  • 19.
    Ye, Fei
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Qin, Jian
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Muhammed, Mamoun
    KTH, School of Engineering Sciences (SCI), Applied Physics, Functional Materials, FNM.
    Multifunctional core-shell nanoparticles: superparamagnetic, mesoporous, and thermosensitive2011In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, no 11, p. 6157-6167Article in journal (Refereed)
    Abstract [en]

    Multifunctional core-shell composite nanoparticles (NPs) have been developed by the combination of three functionalities into one entity, which is composed of a single Fe3O4 NP as the magnetic core, mesoporous silica (mSiO2) with cavities as the sandwiched layer, and thermosensitive poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAAm-co-AAm)) copolymer as the outer shell. The mSiO2-coated Fe3O4 NPs (Fe3O4@mSiO2) are monodisperse and the particle sizes were varied from 25 to 95 nm by precisely controlling the thickness of mSiO2-coating layer. The P(NIPAAm-co-AAm) were then grown onto surface-initiator-modified Fe3O4@mSiO2 NPs through free radical polymerization. These core-shell composite NPs (designated as Fe3O4@mSiO2@P(NIPAAm-co-AAm)) were found to be superparamagnetic with high r2 relaxivity. To manipulate the phase transition behavior of these thermosensitive polymer-coated NPs for future in vivo applications, the characteristic lower critical solution temperature (LCST) was subtly tuned by adjusting the composition of the monomers to be around the human body temperature (i.e. 37 °C), from ca. 34 to ca. 42 °C. The thermal response of the core-shell composite NPs to the external magnetic field was also demonstrated. Owing to their multiple functionality characteristics, these porous superparamagnetic and thermosensitive NPs may prove valuable for simultaneous magnetic resonance imaging (MRI), temperature-controlled drug release, and temperature-programed magnetic targeting and separation applications.

  • 20. Zagorodni, Andrei A.
    et al.
    Salazar-Alvarez, German
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Bar-shaped nanoparticles of iron(II) hydroxide2008In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 10, no 2, p. 377-381Article in journal (Refereed)
    Abstract [en]

    Formation of elongated nanoparticles was observed when FE3O4 was precipitated from solutions containing excess of Fe2+. The average diameter of the particles was 23 nm; the length to diameter ratio was up to 14. This shape was an unexpected phenomenon because bar- or needle-like nanoparticles have been earlier reported only for Fe(III)-based materials. Chemical analysis revealed Fe(OH)(2) nature of the obtained particles. In addition, this conclusion was verified with a new simple method for quantitative evaluation of the particle morphology. Application of this method to the mixed Fe(OH)(2/)Fe3O4 samples allowed to distinguish between the two different compounds and to attribute different morphologies to Fe(OH)(2) or Fe3O4. Results indicate that bars are frequent shapes of nano-sized iron oxides/hydroxides.

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