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Sample records for magnetite nano-particle surface

  1. β-Cyclodextrin/thermosensitive containing polymer brushes grafted onto magnetite nano-particles for extraction and determination of venlafaxine in biological and pharmaceutical samples.

    PubMed

    Ahmad Panahi, Homayon; Alaei, Haniyeh Sadat

    2014-12-10

    In this paper, a novel nano-sorbent is fabricated by the surface grafting of poly[β-CD/allylamine-co-N-isopropylacrylamide] onto modified magnetite nano-particles by 3-mercaptopropyltrimethoxysilane. The polymer grafted magnetite nano-particles was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, scanning electron microscopy, and transmission electron microscopy. The feasibility of employing this nano-sorbent for extraction of trace venlafaxine in pharmaceutical samples and human biological fluids are investigated. The effect of various parameters such as pH, reaction temperature, and contact time was evaluated. The result revealed that the best sorption of venlafaxine by the magnetite nano-sorbent occurred at 35 °C at an optimum pH of 5. The kinetics of the venlafaxine shows accessibility of active sites in the grafted polymer onto the drug. The equilibrium data of venlafaxine by grafted magnetite nano-sorbent are well represented by the Langmuir and Freundlich isotherm models. The adsorption capacity of venlafaxine is found 142.8 mg g(-1) and indicated the homogeneous sites onto polymer grafted magnetite nano-sorbent surface. Nearly 80% of venlafaxine was released in simulated intestinal fluid, pH 7.4, in 30 h and 90% in simulated gastric fluid, pH 1.2, in 1 h. The venlafaxine loaded-polymer grafted magnetite nano-particles were successfully applied for the extraction in urine and pharmaceutical samples.

  2. Laser modification of ceramic surfaces with micro- and nano- particles

    NASA Astrophysics Data System (ADS)

    Rohde, Magnus

    2007-02-01

    Laser supported processes can be used to modify the electrical and thermal properties of ceramic substrates locally. These processes are characterised by a strong thermal interaction between the laser beam and the ceramic surface which leads to localised melting. During the dynamic melting process metal particles are introduced into the melt pool in order to modify the physical properties. Different alumina samples were treated with metal powders of tungsten, copper, and oxides of these metals. The interface between the metal and the ceramic can be designed by using selected combinations of metal- and metal-oxide-powders and also by a thermal post-processing. The application of nano-particles during the laser-dispersing process resulted in completely different characteristics of the micro-structure and the electrical properties compared to the conventional metal powders with an average grain size of 5 - 15 microns. The micron sized metal particles are embedded within the ceramic matrix as particle agglomerates or as distinct metal phase the nano-particle phase covers the grain boundaries of the ceramics leading to network of nano-scaled electrically conducting "wires". The resulting resistance of the laser tracks can be adjusted from semi-conducting to metallic behavior with a resistivity down to 2x10 -6W/m. The modified ceramic can be used for heating elements working at operation temperatures of up to 1000 °C, high current resistances which can be loaded with currents of up to 100 A.

  3. An optimized surface plasmon photovoltaic structure using energy transfer between discrete nano-particles.

    PubMed

    Lin, Albert; Fu, Sze-Ming; Chung, Yen-Kai; Lai, Shih-Yun; Tseng, Chi-Wei

    2013-01-14

    Surface plasmon enhancement has been proposed as a way to achieve higher absorption for thin-film photovoltaics, where surface plasmon polariton(SPP) and localized surface plasmon (LSP) are shown to provide dense near field and far field light scattering. Here it is shown that controlled far-field light scattering can be achieved using successive coupling between surface plasmonic (SP) nano-particles. Through genetic algorithm (GA) optimization, energy transfer between discrete nano-particles (ETDNP) is identified, which enhances solar cell efficiency. The optimized energy transfer structure acts like lumped-element transmission line and can properly alter the direction of photon flow. Increased in-plane component of wavevector is thus achieved and photon path length is extended. In addition, Wood-Rayleigh anomaly, at which transmission minimum occurs, is avoided through GA optimization. Optimized energy transfer structure provides 46.95% improvement over baseline planar cell. It achieves larger angular scattering capability compared to conventional surface plasmon polariton back reflector structure and index-guided structure due to SP energy transfer through mode coupling. Via SP mediated energy transfer, an alternative way to control the light flow inside thin-film is proposed, which can be more efficient than conventional index-guided mode using total internal reflection (TIR).

  4. Surface-plasmon resonances in indium nitride with metal-enriched nano-particles

    NASA Astrophysics Data System (ADS)

    Shubina, T. V.; Plotnikov, D. S.; Vasson, A.; Leymarie, J.; Larsson, M.; Holtz, P. O.; Monemar, B.; Lu, Hai; Schaff, W. J.; Kop'ev, P. S.

    2006-03-01

    Plasmonic resonances in In-enriched nano-particles, spontaneously formed during growth, can dramatically modify optical properties of InN. Experimental support for this is provided from detailed studies of absorption and infrared emission in InN. In particular, thermally detected optical absorption and photoluminescence excitation spectroscopy reveal a peak below the region of strong absorption in InN. A higher-energy part of the infrared emission having a noticeable p-polarization is markedly enhanced with excitation along the surface. These peculiarities are discussed in terms of the Mie resonances, arising in metallic spheroids with different aspect ratio, and their coupling with recombining states, whose strength depends on energy separation between the states and the resonances.

  5. Conditions for laser-induced plasma to effectively remove nano-particles on silicon surfaces

    NASA Astrophysics Data System (ADS)

    Han, Jinghua; Luo, Li; Zhang, Yubo; Hu, Ruifeng; Feng, Guoying

    2016-09-01

    Particles can be removed from a silicon surface by means of irradiation and a laser plasma shock wave. The particles and silicon are heated by the irradiation and they will expand differently due to their different expansion coefficients, making the particles easier to be removed. Laser plasma can ionize and even vaporize particles more significantly than an incident laser and, therefore, it can remove the particles more efficiently. The laser plasma shock wave plays a dominant role in removing particles, which is attributed to its strong burst force. The pressure of the laser plasma shock wave is determined by the laser pulse energy and the gap between the focus of laser and substrate surface. In order to obtain the working conditions for particle removal, the removal mechanism, as well as the temporal and spatial characteristics of velocity, propagation distance and pressure of shock wave have been researched. On the basis of our results, the conditions for nano-particle removal are achieved. Project supported by the National Natural Science Foundation of China (Grant No. 11574221).

  6. Enhancement of photo-response via surface plasmon resonance induced by Ag nano-particles embedded in ZnO

    NASA Astrophysics Data System (ADS)

    Li, Gaoming; Zhang, Jingwen; Chen, Guangde; Ye, Honggang; Duan, Xiangyang; Hou, Xun

    2016-09-01

    Surface plasmon resonance can be exploited to improve the performance of the photodetectors. However, it may cause the increase of dark current as a side effect. The enhancement of responsivity is highly dependent on the device structure involving SPR and the situations of the metal nano-particles. In this paper, we reported the responsivity enhancement of the ZnO UV detectors with SPR based on a structure in which Ag nano-particles are embedded in ZnO film, without the apparent increase of dark current. We found that the characteristic wavelength for SPR absorption is 380 nm, well predicted by Mie theory. And the spectral responsivity peak value increases from 472 mA/W to 10.522 A/W, by 22.3 times. The good matching between enhancement spectra and SPR absorption spectra confirms that the responsivity enhancement is resulted from SPR. Our results are of great importance in improving the photodetectors based on SPR effects, which may be widely used in light detection.

  7. Tuning the optical reflection property of metal surfaces via micro-nano particle structures fabricated by ultrafast laser

    NASA Astrophysics Data System (ADS)

    Fan, Peixun; Zhong, Minlin; Bai, Benfeng; Jin, Guofan; Zhang, Hongjun

    2015-12-01

    Optical functional surfaces are key components of nearly every optical device and they have become a special focus in both academia and industry. The no contact, one step, direct, and maskless laser surface texturing technique is one of the most encouraging approaches for realizing the surface functions. We use a high power and high repetition rate ultrafast laser system to produce micro-nano structures on metal surfaces. We demonstrate that metal surface micro-nano structures and correspondingly their optical responses can be facilely tailored by simple controlling the ultrafast laser processing parameters. Nano particles of tens to hundreds nm, sub-micro particles of 0.5-1 μm, fine-micro particles of 1-10 μm, micro particles of 10-50 μm, and coarse-micro particles larger than 50 μm have been fabricated on Cu surfaces. And surface reflection of copper surfaces has been tuned from 10% to 90% in spectra level and from UV to MIR in spectrum range, with unique optical properties like visible selective reflection, linear changing reflection, band reflection, and broadband absorption being achieved. The formation processes of those particle structures as well as the underlying mechanisms for their optical responses are discussed.

  8. Layer by Layer, Nano-particle "Only" Surface Modification of Filtration Membranes

    NASA Astrophysics Data System (ADS)

    Escobar-Ferrand, Luis

    Layer by Layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for the modification of polymeric micro and ultrafiltration (MF/UF) membranes to produce thin film composites (TFC) with potential nanofiltration (NF) and reverse osmosis (RO) capabilities.. A variety of porous substrate membranes with different membrane surface characteristics are employed, but exhibiting in common that wicking of water does not readily occur into the pore structure, including polycarbonate track etched (PCTE), polyethersulfone (PES) and sulfonated PES (SPEES) MF/UF membranes. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those reported by Lee et al. Appropriate selection of the pH's for anionic and cationic particle deposition enables the construction of nanoparticle only layers 100--1200 nm in thickness atop the original membrane substrates. The surface layer thickness varies monotonically with the number of bilayers (anionic/cationic deposition cycles) as expected. The deposition process is optimized to eliminate drying induced cracking and to improve mechanical durability via thickness control and post-deposition hydro-thermal treatment. The hydrodynamic permeability of these TFC membranes is measured to evaluate their performance under typical NF operating conditions using dead-end permeation experiments and their performance compared quantitatively with realistic hydrodynamic models, with favorable results. For track etched polycarbonate MF substrates, surface modification causes a permeability reduction of approximately two orders of magnitude with respect to the bare substrates, to values comparable to those for typical commercial NF membranes. Good quantitative agreement with hydrodynamic models with no adjustable parameters was also established for this case, providing indirect confirmation that the LbL deposited surface layers are largely defect (crack) free

  9. Surface enhanced Raman scattering of monolayer MX2 with metallic nano particles

    PubMed Central

    Zhang, Duan; Wu, Ye-Cun; Yang, Mei; Liu, Xiao; Coileáin, Cormac Ó; Abid, Mourad; Abid, Mohamed; Wang, Jing-Jing; Shvets, Igor; Xu, Hongjun; Chun, Byong Sun; Liu, Huajun; Wu, Han-Chun

    2016-01-01

    Monolayer transition metal dichalcogenides MX2 (M = Mo, W; X = S) exhibit remarkable electronic and optical properties, making them candidates for application within flexible nano-optoelectronics. The ability to achieve a high optical signal, while quantitatively monitoring strain in real-time is the key requirement for applications in flexible sensing and photonics devices. Surface-enhanced Raman scattering (SERS) allows us to achieve both simultaneously. However, the SERS depends crucially on the size and shape of the metallic nanoparticles (NPs), which have a large impact on its detection sensitivity. Here, we investigated the SERS of monolayer MX2, with particular attention paid to the effect of the distribution of the metallic NPs. We show that the SERS depends crucially on the distribution of the metallic NPs and also the phonon mode of the MX2. Moreover, strong coupling between MX2 and metallic NPs, through surface plasmon excitation, results in splitting of the and modes and an additional peak becomes apparent. For a WS2-Ag system the intensity of the additional peak increases exponentially with local strain, which opens another interesting window to quantitatively measure the local strain using SERS. Our experimental study may be useful for the application of monolayer MX2 in flexible nano-optoelectronics. PMID:27457808

  10. Surface enhanced Raman scattering of monolayer MX2 with metallic nano particles.

    PubMed

    Zhang, Duan; Wu, Ye-Cun; Yang, Mei; Liu, Xiao; Coileáin, Cormac Ó; Abid, Mourad; Abid, Mohamed; Wang, Jing-Jing; Shvets, Igor; Xu, Hongjun; Chun, Byong Sun; Liu, Huajun; Wu, Han-Chun

    2016-01-01

    Monolayer transition metal dichalcogenides MX2 (M = Mo, W; X = S) exhibit remarkable electronic and optical properties, making them candidates for application within flexible nano-optoelectronics. The ability to achieve a high optical signal, while quantitatively monitoring strain in real-time is the key requirement for applications in flexible sensing and photonics devices. Surface-enhanced Raman scattering (SERS) allows us to achieve both simultaneously. However, the SERS depends crucially on the size and shape of the metallic nanoparticles (NPs), which have a large impact on its detection sensitivity. Here, we investigated the SERS of monolayer MX2, with particular attention paid to the effect of the distribution of the metallic NPs. We show that the SERS depends crucially on the distribution of the metallic NPs and also the phonon mode of the MX2. Moreover, strong coupling between MX2 and metallic NPs, through surface plasmon excitation, results in splitting of the and modes and an additional peak becomes apparent. For a WS2-Ag system the intensity of the additional peak increases exponentially with local strain, which opens another interesting window to quantitatively measure the local strain using SERS. Our experimental study may be useful for the application of monolayer MX2 in flexible nano-optoelectronics. PMID:27457808

  11. Surface enhanced Raman scattering of monolayer MX2 with metallic nano particles

    NASA Astrophysics Data System (ADS)

    Zhang, Duan; Wu, Ye-Cun; Yang, Mei; Liu, Xiao; Coileáin, Cormac Ó.; Abid, Mourad; Abid, Mohamed; Wang, Jing-Jing; Shvets, Igor; Xu, Hongjun; Chun, Byong Sun; Liu, Huajun; Wu, Han-Chun

    2016-07-01

    Monolayer transition metal dichalcogenides MX2 (M = Mo, W; X = S) exhibit remarkable electronic and optical properties, making them candidates for application within flexible nano-optoelectronics. The ability to achieve a high optical signal, while quantitatively monitoring strain in real-time is the key requirement for applications in flexible sensing and photonics devices. Surface-enhanced Raman scattering (SERS) allows us to achieve both simultaneously. However, the SERS depends crucially on the size and shape of the metallic nanoparticles (NPs), which have a large impact on its detection sensitivity. Here, we investigated the SERS of monolayer MX2, with particular attention paid to the effect of the distribution of the metallic NPs. We show that the SERS depends crucially on the distribution of the metallic NPs and also the phonon mode of the MX2. Moreover, strong coupling between MX2 and metallic NPs, through surface plasmon excitation, results in splitting of the and modes and an additional peak becomes apparent. For a WS2-Ag system the intensity of the additional peak increases exponentially with local strain, which opens another interesting window to quantitatively measure the local strain using SERS. Our experimental study may be useful for the application of monolayer MX2 in flexible nano-optoelectronics.

  12. The Measurement of Surface Rheological and Surface Adhesive Properties of a PDMS Rubber using Micro- and Nano-Particle Embedment

    NASA Astrophysics Data System (ADS)

    Hutcheson, Stephen; McKenna, Gregory

    2009-03-01

    In previous work, we used particle embedment data to determine the rheological response of the surfaces of a polystyrene film, a phase separated copolymer and a commercially available polydimethylsiloxane (PDMS) rubber through the application of a viscoelastic contact mechanics model. The goal of the current research is to build off this analysis and use micro- and nano-sphere embedment experiments to probe the surface rheological behavior of PDMS in the rubbery state. The work includes measurements made with different particle diameters and chemistries. An atomic force microscope (AFM) is used to measure the embedment depth as nanoparticles are pulled into the surface by the thermodynamic work of adhesion. Present results show that silica probes of different sizes (500 nm and 300 nm) give different results for the surface adhesion properties and the surface rheological properties determined from the particle embedment data and at scales much larger than the nanometer size scale where one might expect such deviations. Possible water entrapment and effects of particle surface composition on the results will be discussed.

  13. The effect of surface modification on the magnetic properties of CoFe2O4 nano-particles synthesized by the hydrothermal method.

    PubMed

    Zhang, Yue; Fei, Chunlong; Liu, Yong; Wang, Rongjuan; Yan, Gaolin; Xiong, Rui; Shi, Jing

    2010-10-01

    Cobalt ferrite (CoFe2O4) nano-particles were synthesized by the hydrothermal method with the addition of a surfactant sodium bis(2-ethylhexyl) sulphosuccinate (AOT). Characterization measurements including X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy showed that all the final products were single-phase CoFe2O4 nano-crystals with AOT molecules bonding to the surfaces, the average crystallite sizes were all near 25 nm, and the lattice constant increased with the increasing mass of AOT. The magnetic hysteresis loops measured at room temperature indicated that the bonding of the AOT to the surfaces led to an increase of the saturation magnetization (Ms), the coercivity (Hc) and the remanence ratio (Mr/Ms). Furthermore, as the concentration of AOT reached the critical micelle concentration (CMC), turning points were observed in the the curves of Hc, Mr/Ms and K(eff) (effective magnetic anisotropy constants) versus. the mass of AOT due to the formation of the AOT micelles.

  14. Study of surface-modified PVP gate dielectric in organic thin film transistors with the nano-particle silver ink source/drain electrode.

    PubMed

    Yun, Ho-Jin; Ham, Yong-Hyun; Shin, Hong-Sik; Jeong, Kwang-Seok; Park, Jeong-Gyu; Choi, Deuk-Sung; Lee, Ga-Won

    2011-07-01

    We have fabricated the flexible pentacene based organic thin film transistors (OTFTs) with formulated poly[4-vinylphenol] (PVP) gate dielectrics treated by CF4/O2 plasma on poly[ethersulfones] (PES) substrate. The solution of gate dielectrics is made by adding methylated poly[melamine-co-formaldehyde] (MMF) to PVP. The PVP gate dielectric layer was cross linked at 90 degrees under UV ozone exposure. Source/drain electrodes are formed by micro contact printing (MCP) method using nano particle silver ink for the purposes of low cost and high throughput. The optimized OTFT shows the device performance with field effect mobility of the 0.88 cm2/V s, subthreshold slope of 2.2 V/decade, and on/off current ratios of 1.8 x 10(-6) at -40 V gate bias. We found that hydrophobic PVP gate dielectric surface can influence on the initial film morphologies of pentacene making dense, which is more important for high performance OTFTs than large grain size. Moreover, hydrophobic gate dielelctric surface reduces voids and -OH groups that interrupt the carrier transport in OTFTs.

  15. Damping-induced size effect in surface plasmon resonance in metallic nano-particles: Comparison of RPA microscopic model with numerical finite element simulation (COMSOL) and Mie approach

    NASA Astrophysics Data System (ADS)

    Kluczyk, K.; Jacak, W.

    2016-01-01

    We investigate metal nano-particle size influence on plasmon resonance within theoretical and numerical approaches and compare results with available experimental data in order to improve resolution of optical identification of metallic nano-particle size and shape. The developed microscopic approach is the quantum random phase approximation model of plasmons in metallic nano-particles including plasmon damping by electron scattering and by radiative losses (i.e., by the so-called Lorentz friction). The numerical approach is by the finite element method solution of Maxwell equations for incident planar wave in spherical (also nano-rod, spheroid) geometry upon the system COMSOL and Mie treatment, supplemented with phenomenologically modeled dielectric function of metallic nano-particle. Comparison with experimental data for light extinction in Au and Ag nano-particle colloidal solutions with different particle sizes is presented. The crucial role of the Lorentz friction in the size effect of plasmon resonance in large (e.g., 20-60 nm for Au in vacuum) metallic nanoparticles is evidenced.

  16. Advancing Sustainable Catalysis with Magnetite Surface Modification and Synthetic Applications

    EPA Science Inventory

    This article surveys the recent developments in the synthesis, surface modification, and synthetic applications of magnetitenanoparticles. The emergence of iron(II,III) oxide (triiron tetraoxide or magnetite; Fe3O4, or FeO•Fe2O3) nanoparticles as a sustainable support in het...

  17. Advancing Sustainable Catalysis with Magnetite Surface Modification and Synthetic Applications

    EPA Science Inventory

    This article surveys the recent developments in the synthesis, surface modification, and synthetic applications of magnetitenanoparticles. The emergence of iron(II,III) oxide (triiron tetraoxide or magnetite; Fe3O4, or FeO•Fe2O3) nanoparticles as a sustainable support in heteroge...

  18. Surface reactions kinetics between nanocrystalline magnetite and uranyl.

    PubMed

    Missana, Tiziana; Maffiotte, César; García-Gutiérrez, Miguel

    2003-05-01

    Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution.

  19. Oleic acid coated magnetic nano-particles: Synthesis and characterizations

    SciTech Connect

    Panda, Biswajit Goyal, P. S.

    2015-06-24

    Magnetic nano particles of Fe{sub 3}O{sub 4} coated with oleic acid were synthesized using wet chemical route, which involved co-precipitation of Fe{sup 2+} and Fe{sup 3+} ions. The nano particles were characterized using XRD, TEM, FTIR, TGA and VSM. X-ray diffraction studies showed that nano particles consist of single phase Fe{sub 3}O{sub 4} having inverse spinel structure. The particle size obtained from width of Bragg peak is about 12.6 nm. TEM analysis showed that sizes of nano particles are in range of 6 to 17 nm with a dominant population at 12 - 14 nm. FTIR and TGA analysis showed that -COOH group of oleic acid is bound to the surface of Fe{sub 3}O{sub 4} particles and one has to heat the sample to 278° C to remove the attached molecule from the surface. Further it was seen that Fe{sub 3}O{sub 4} particles exhibit super paramagnetism with a magnetization of about 53 emu/ gm.

  20. Surface site density, silicic acid retention and transport properties of compacted magnetite powder

    NASA Astrophysics Data System (ADS)

    Mayant, C.; Grambow, B.; Abdelouas, A.; Ribet, S.; Leclercq, S.

    In France, within the framework of investigations of the feasibility of deep geological disposal of high-level radioactive waste, studies on corrosion products of steel over packs are ongoing. Such studies concern silica and radionuclide retention. The objective of the present work is to study sorption of silicic acid on compacted magnetite in percolation cells to attempt to simulate confined site conditions. Potentiometric titration of commercial magnetite was carried out with both dispersed and compacted magnetite. The titration of the magnetite suspension has been made with two different methods: a batch method (several suspensions) and a direct fast method (one suspension). The Gran’s function gave 1.7 (±0.4) and 2.4 (±0.5) sorption sites nm -2 with these respective methods but site densities as high as 20/nm 2 could be obtained by modelling. The titration of magnetite compacted at 120 bars showed that the evolution of charge density on magnetite surfaces is similar for compacted and dispersed magnetite. Silicic acid sorption onto dispersed and compacted magnetite was similar with sorption site densities ranging between 2.2 and 4.4/nm 2.

  1. Nickel nano-particle modified nitrogen-doped amorphous hydrogenated diamond-like carbon film for glucose sensing

    SciTech Connect

    Zeng, Aiping; Jin, Chunyan; Cho, Sang-Jin; Seo, Hyun Ook; Kim, Young Dok; Lim, Dong Chan; Kim, Doo Hwan; Hong, Byungyou; Boo, Jin-Hyo

    2012-10-15

    Electrochemical method has been employed in this work to modify nitrogen-doped hydrogen amorphous diamond-like carbon (N-DLC) film to fabricate nickel nano-particle-modified N-DLC electrodes. The electrochemical behavior of the nickel nano-particle-modified N-DLC electrodes has been characterized at the presence of glucose in electrolyte. Meanwhile, the N-DLC film structure and the morphology of metal nano-particles on the N-DLC surface have been investigated using micro-Raman spectroscopy and atomic force microscopy. The nickel nano-particle-modified N-DLC electrode exhibits a high catalytic activity and low background current. This result shows that the nickel nano-particle deposition on N-DLC surface could be a promising method to fabricate novel electrode materials for glucose sensing.

  2. Nano-Particles in Cosmic Plasma Environments

    SciTech Connect

    Mann, Ingrid

    2008-09-07

    Astronomical observations and in-situ measurements point to the existence of cosmic nano-particles, but in most cases their material composition and structure are not known. Nano-dust interacts differently than larger dust with the cosmic radiation and plasma environment. Its dynamics and behavior upon collision is not well studied.

  3. Surface resistivity temperature dependence measures of commercial, multiwall carbon nanotubes (MWCNT), or silver nano-particle doped polyvinylidene difluoride (PVDF) and polyvinyl alcohol (PVA) films

    NASA Astrophysics Data System (ADS)

    Edwards, Matthew; Egarievwe, Stephen; Kukhtareva, Tatiana; Polius, Jemilia; Janen, Afef; Corda, John

    2014-10-01

    The detection of infrared radiation (IR) with pure and doped Polyvinylidene difluoride (PVDF) films has been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made from Polyvinyl Alcohol (PVA) have received considerable attention in recent years. The investigation of surface resistivities of both such films, to this point, has received far less consideration in comparison to pyroelectric effects. In this research, we report temperature dependent surface resistivity measurements of commercial, and of multiwall carbon nanotubes (MWCNT), or Ag-nanoparticle doped PVA films. Without any variation in the temperature range from 22°C to 40°C with controlled humidity, we found that the surface resistivity decreases initially, reaches a minimum, but rises steadily as the temperature continues to increase. This research was conducted with the combined instrumentation of the Keithley Model 6517 Electrometer and Keithley Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films. With the objective to quantify the suitability of PVDF and PVA films as IR detector materials, when using the surface resistivity phenomenon, instead of or in addition to the pyroelectricity, surface resistivity measurements are reported when considering bolometry. We find the surface resistivity of PVDF films to be in the range, which extends beyond the upper limit of our Keithley electrometer, but our measurements on PVA films were readily implemented.

  4. Controlled release study of an anti-carcinogenic agent, gallate from the surface of magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Ghotbi, Mohammad Yeganeh; bin Hussein, Mohd Zobir

    2012-07-01

    Immobilization of gallate anion, an anti-carcinogenic, anti-mutagenic, and anti-microbial agent on the surface of magnetite nanoparticles was accomplished by adsorption technique for the formation of a core-shell nanocomposite. A simple co-precipitation technique in the presence of poly vinyl pyrrolidone was successfully applied for the preparation of magnetite nanoparticles as core beads with narrow size distribution. The powders were characterized by X-ray diffraction, particle size analysis, magnetic measurements, atomic force microscope and also infrared spectroscopy. FTIR and CHNS results indicated that the gallate anion was actually adsorbed onto the surface of the magnetite nanoparticles. The release of the anion from the surface of the nanocomposite was found to be controllable by the selection of the release media.

  5. Using chromate to investigate the impact of natural organics on the surface reactivity of nanoparticulate magnetite.

    PubMed

    Swindle, Andrew L; Cozzarelli, Isabelle M; Elwood Madden, Andrew S

    2015-02-17

    Chromate was used as a chemical probe to investigate the size-dependent influence of organics on nanoparticle surface reactivity. Magnetite-chromate sorption experiments were conducted with ∼ 90 and ∼ 6 nm magnetite nanoparticles in the presence and absence of fulvic acid (FA), natural organic matter (NOM), and isolated landfill leachate (LL). Results indicated that low concentrations (1 mg/L) of organics had no noticeable impact on chromate sorption, whereas concentrations of 50 mg/L or more resulted in decreased amounts of chromate sorption. The adsorption of organics onto the magnetite surfaces interfered equally with the ability of the 6 and 90 nm particles to sorb chromate from solution, despite the greater surface area of the smaller particles. Results indicate the presence of organics did not impact the redox chemistry of the magnetite-chromate system over the duration of the experiments (8 h), nor did the organics interact with the chromate in solution. Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) results indicate that the organics blocked the surface reactivity by occupying surface sites on the particles. The similarity of results with FA and NOM suggests that coverage of the reactive mineral surface is the main factor behind the inhibition of surface reactivity in the presence of organics.

  6. Evaluation of minimum quantity lubrication grinding with nano-particles and recent related patents.

    PubMed

    Li, Changhe; Wang, Sheng; Zhang, Qiang; Jia, Dongzhou

    2013-06-01

    In recent years, a large number of patents have been devoted to developing minimum quantity lubrication (MQL) grinding techniques that can significantly improve both environmentally conscious and energy saving and costeffective sustainable grinding fluid alternatives. Among them, one patent is about a supply system for the grinding fluid in nano-particle jet MQL, which produced MQL lubricant by adding solid nano-particles in degradable grinding fluid. The MQL supply device turns the lubricant to the pulse drops with fixed pressure, unchanged pulse frequency and the same drop diameter. The drops will be produced and injected in the grinding zone in the form of jet flow under high pressure gas and air seal. As people become increasingly demanding on our environment, minimum quantity lubrication has been widely used in the grinding and processing. Yet, it presents the defect of insufficient cooling performance, which confines its development. To improve the heat transfer efficiency of MQL, nano-particles of a certain mass fraction can be added in the minimum quantity of lubricant oil, which concomitantly will improve the lubrication effects in the processing. In this study, the grinding experiment corroborated the effect of nano-particles in surface grinding. In addition, compared with other forms of lubrication, the results presented that the grinding force, the friction coefficient and specific grinding energy of MQL grinding have been significantly weakened, while G ratio greatly rose. These are attributed to the friction oil-film with excellent anti-friction and anti-wear performance, which is generated nano-particles at the wheel/workpiece interface. In this research, the cooling performance of nano-particle jet MQL was analyzed. Based on tests and experiments, the surface temperature was assayed from different methods, including flood lubricating oil, dry grinding, MQL grinding and nano-particle jet MQL grinding. Because of the outstanding heat transfer

  7. Evaluation of minimum quantity lubrication grinding with nano-particles and recent related patents.

    PubMed

    Li, Changhe; Wang, Sheng; Zhang, Qiang; Jia, Dongzhou

    2013-06-01

    In recent years, a large number of patents have been devoted to developing minimum quantity lubrication (MQL) grinding techniques that can significantly improve both environmentally conscious and energy saving and costeffective sustainable grinding fluid alternatives. Among them, one patent is about a supply system for the grinding fluid in nano-particle jet MQL, which produced MQL lubricant by adding solid nano-particles in degradable grinding fluid. The MQL supply device turns the lubricant to the pulse drops with fixed pressure, unchanged pulse frequency and the same drop diameter. The drops will be produced and injected in the grinding zone in the form of jet flow under high pressure gas and air seal. As people become increasingly demanding on our environment, minimum quantity lubrication has been widely used in the grinding and processing. Yet, it presents the defect of insufficient cooling performance, which confines its development. To improve the heat transfer efficiency of MQL, nano-particles of a certain mass fraction can be added in the minimum quantity of lubricant oil, which concomitantly will improve the lubrication effects in the processing. In this study, the grinding experiment corroborated the effect of nano-particles in surface grinding. In addition, compared with other forms of lubrication, the results presented that the grinding force, the friction coefficient and specific grinding energy of MQL grinding have been significantly weakened, while G ratio greatly rose. These are attributed to the friction oil-film with excellent anti-friction and anti-wear performance, which is generated nano-particles at the wheel/workpiece interface. In this research, the cooling performance of nano-particle jet MQL was analyzed. Based on tests and experiments, the surface temperature was assayed from different methods, including flood lubricating oil, dry grinding, MQL grinding and nano-particle jet MQL grinding. Because of the outstanding heat transfer

  8. Fabrication of carbon nano-tubes decorated with ultra fine superparamagnetic nano-particles under continuous flow conditions.

    PubMed

    Chin, Suk Fun; Iyer, K Swaminathan; Raston, Colin L

    2008-03-01

    Ultra fine (2-3 nm) magnetite (Fe(3)O(4)) nano-particles are uniformly deposited on single-walled carbon nano-tubes (SWCNTs) pre-functionalised with carboxylic acid groups using microwave radiation. The deposition process involves chemical precipitation associated with continuous flow spinning disc processing (SDP), as a rapid, environmentally friendly approach which is readily scalable for large scale synthesis. The resulting decorated SWCNTs are superparamagnetic with specific saturated magnetization of 30 emu g(-1). PMID:18305862

  9. Adsorption of alkenyl succinic anhydride from solutions in carbon tetrachloride on a fine magnetite surface

    NASA Astrophysics Data System (ADS)

    Balmasova, O. V.; Ramazanova, A. G.; Korolev, V. V.

    2016-06-01

    The adsorption of alkenyl succinic anhydride from a solution in carbon tetrachloride on a fine magnetite surface at a temperature of 298.15 K is studied using fine magnetite, which forms the basis of magnetic fluids, as the adsorbent. An adsorption isotherm is recorded and interpreted in terms of the theory of the volume filling of micropores (TVFM). Adsorption process parameters are calculated on the basis of the isotherm. It is shown that at low equilibrium concentrations, the experimental adsorption isotherm is linear in the TVFM equation coordinates.

  10. Surface modification of magnetite nanoparticles using lactobionic acid and their interaction with hepatocytes.

    PubMed

    Kamruzzaman Selim, K M; Ha, Yong-Soo; Kim, Sun-Jung; Chang, Yongmin; Kim, Tae-Jeong; Ho Lee, Gang; Kang, Inn-Kyu

    2007-02-01

    In the current study, superparamagnetic magnetite nanoparticles were surface-modified with lactobionic acid (LA) to improve their intracellular uptake and ability to target hepatocytes. Maltotrionic acid (MA)-modified nanoparticles were also synthesized as a control. Cell culture experiment showed that LA-modified nanoparticles were internalized into hepatocytes and atomic absorption spectrometer (AAS) measurement indicated that the uptake amount of LA-modified magnetite into hepatocytes was higher than that of unmodified and MA-modified nanoparticles. LA-modified nanoparticle solution was injected in rabbit and the magnetic resonance (MR) images obtained showed that LA-coated nanoparticles were selectively accumulated onto the hepatocytes. This result demonstrates that the LA-modified magnetite nanoparticles have a great potential to be used as contrast agent for liver diagnosis.

  11. Submicron writing by laser irradiation on metal nano-particle dispersed films toward flexible electronics

    NASA Astrophysics Data System (ADS)

    Watanabe, Akira; Aminuzzaman, Mohammod; Miyashita, Tokuji

    2009-02-01

    The requirement for microwiring technology by a wet process has significantly increased recently toward the achievement of printable and flexible electronics. We have developed the metal microwiring with a resolution higher than 1 μm by the laser direct writing technique using Ag and Cu nano-particle-dispersed films as precursors. The technique was applied to the microwiring on a flexible and transparent polymer film. The metallization is caused in a micro-region by focused laser beam, which reduces the thermal damage of the flexible polymer substrate during the metallization process. The laser direct writing technique is based on the efficient and fast conversion of photon energy to thermal energy by direct excitation of the plasmon absorption of a metal nano-particle, which provides Cu microwiring with a low resistivity owing to the inhibition of the surface oxidation of the Cu nano-particle.

  12. Room temperature water splitting at the surface of magnetite.

    PubMed

    Parkinson, Gareth S; Novotný, Zbyněk; Jacobson, Peter; Schmid, Michael; Diebold, Ulrike

    2011-08-17

    An array of surface science measurements has revealed novel water adsorption behavior at the Fe(3)O(4)(001) surface. Following room temperature exposure to water, a low coverage of hydrogen atoms is observed, with no associated water hydroxyl group. Mild annealing of the hydrogenated surface leads to desorption of water via abstraction of surface oxygen atoms, leading to a reduction of the surface. These results point to an irreversible splitting of the water molecule. The observed phenomena are discussed in the context of recent DFT calculations (Mulakaluri, N.; Pentcheva, R.; Scheffler, M. J. Phys. Chem. C 2010, 114, 11148), which show that the Jahn-Teller distorted surface isolates adsorbed H in a geometry that could kinetically hinder recombinative desorption. In contrast, the adsorption geometry facilitates interaction between water hydroxyl species, which are concluded to leave the surface following a reactive desorption process, possibly via the creation of O(2).

  13. Impact of surface coated magnetite used in magnetic drug delivery system on immune response

    NASA Astrophysics Data System (ADS)

    Oaku, Yoshihiro; Tamada, Junya; Mishima, Fumihito; Akiyama, Yoko; Osako, Mariana Kiomy; Koriyama, Hiroshi; Nakagami, Hironori; Nishijima, Shigehiro

    2015-05-01

    Magnetic drug delivery system (MDDS) is a technique to effectively accumulate drugs, which are combined with ferromagnetic particles, into the affected area using magnetic force control. This study intends to apply MDDS for immunotherapy by enhancing immune responses by a surface treatment of a ferromagnetic particle. The objective of this study is to give the adjuvant effect to a ferromagnetic particle by the surface treatment with alum, which is known as one of the common adjuvants that activates inflammasome pathway. First, magnetite was prepared as a ferromagnetic particle and coated with alum. Alum-coated magnetite increased the expression of caspase-1, which is an activated indicator of inflammasome, in the culture of human monocyte cell (THP-1 cell). To evaluate the potential of the surface coated particles, the particles were subcutaneously injected to mice with a peptide vaccine. As a result, the antibody titer was increased by the surface coated particles as assessed by ELISA. Although a magnetic force has not yet applied in this study, the administration experiment to mice using magnetic force control is our next step. In conclusion, we modified the immune response to magnetite by coating the surface with alum. This can lead to a clinical application for vaccine therapy in future.

  14. Co-ordinated functions of Mms proteins define the surface structure of cubo-octahedral magnetite crystals in magnetotactic bacteria.

    PubMed

    Arakaki, Atsushi; Yamagishi, Ayana; Fukuyo, Ayumi; Tanaka, Masayoshi; Matsunaga, Tadashi

    2014-08-01

    Magnetotactic bacteria synthesize magnetosomes comprised of membrane-enveloped single crystalline magnetite (Fe3 O4 ). The size and morphology of the nano-sized magnetite crystals (< 100 nm) are highly regulated and bacterial species dependent. However, the control mechanisms of magnetite crystal morphology remain largely unknown. The group of proteins, called Mms (Mms5, Mms6, Mms7, and Mms13), was previously isolated from the surface of cubo-octahedral magnetite crystals in Magnetospirillum magneticum strain AMB-1. Analysis of an mms6 gene deletion mutant suggested that the Mms6 protein plays a major role in the regulation of magnetite crystal size and morphology. In this study, we constructed various mms gene deletion mutants and characterized the magnetite crystals formed by the mutant strains. Comparative analysis showed that all mms genes were involved in the promotion of crystal growth in different manners. The phenotypic characterization of magnetites also suggested that these proteins are involved in controlling the geometries of the crystal surface structures. Thus, the co-ordinated functions of Mms proteins regulate the morphology of the cubo-octahedral magnetite crystals in magnetotactic bacteria.

  15. Surface modification of magnetite nanoparticles using gluconic acid and their application in immobilized lipase.

    PubMed

    Sui, Ying; Cui, Yu; Nie, Yong; Xia, Guang-Ming; Sun, Guo-Xin; Han, Jing-Tian

    2012-05-01

    Superparamagnetic magnetite nanoparticles (SMN) were surface-modified with gluconic acid (GLA) to improve their hydrophilicity and bio-affinity. Gluconic acid was successfully coated on the surface of magnetite nanoparticles and characterized using Fourier transform infrared spectroscopy (FT-IR). With water-soluble carbodiimide (EDC) as the coupling reagent, lipase was successfully immobilized onto the hydroxyl-functionalized magnetic nanoparticles. The immobilized lipase had better resistance to temperature and pH inactivation in comparison to the free form and hence widened the reaction pH and temperature range. Thermostability and storage stability of the enzyme improved upon covalent immobilization. Immobilized lipase showed higher activity after recycling when compared to the free one and could be recovered by magnetic separation.

  16. Study of the surface chemistry and morphology of single walled carbon nanotube-magnetite composites

    SciTech Connect

    Marquez-Linares, F.; Uwakweh, O.N.C.; Lopez, N.; Chavez, E.; Polanco, R.; Morant, C.; Sanz, J.M.; Elizalde, E.; Neira, C.; Nieto, S.; Roque-Malherbe, R.

    2011-03-15

    The study of the morphologies of the single walled carbon nanotube (SWCNT), magnetite nanoparticles (MNP), and the composite based on them was carried with combined X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). These techniques together with thermogravimetric analyses (TGA) and diffuse reflectance infrared transform spectroscopy (DRIFTS) confirmed the production of pure single phases, and that the composite material consisted of MNP attached to the outer surface of the SWCNT. The Moessbauer spectroscopy (MS) research showed the presence of a large quantity of Lewis acid sites in the highly dispersed magnetite particles supported on the SWCNT outer surface. The DRIFTS carbon dioxide adsorption study of the composites revealed significant adsorption of carbon dioxide, fundamentally in the Lewis acid sites. Then, the Lewis acid sites were observed to be catalytically active. Further, the electron exchange between the Lewis acid sites and the basic or amphoteric adsorbed molecules could influence the magnetic properties of the magnetite. Consequently, together with this first ever use of MS in the study of Lewis acid sites, this investigation revealed the potential of the composites for catalytic and sensors applications. -- Graphical abstract: A large amount of Lewis acid sites were found in the highly dispersed magnetite which is supported on the SWCNT outer surface. Display Omitted Research highlights: {yields} The obtained materials were completely characterized with XRD, Raman and SEM-TEM. {yields} DRIFT, TGA and adsorption of the composites allowed understand the material formation. {yields} This is the first report of a study of Lewis sites by Moessbauer spectroscopy.

  17. Subsurface cation vacancy stabilization of the magnetite (001) surface

    NASA Astrophysics Data System (ADS)

    Bliem, R.; McDermott, E.; Ferstl, P.; Setvin, M.; Gamba, O.; Pavelec, J.; Schneider, M. A.; Schmid, M.; Diebold, U.; Blaha, P.; Hammer, L.; Parkinson, G. S.

    2014-12-01

    Iron oxides play an increasingly prominent role in heterogeneous catalysis, hydrogen production, spintronics, and drug delivery. The surface or material interface can be performance-limiting in these applications, so it is vital to determine accurate atomic-scale structures for iron oxides and understand why they form. Using a combination of quantitative low-energy electron diffraction, scanning tunneling microscopy, and density functional theory calculations, we show that an ordered array of subsurface iron vacancies and interstitials underlies the well-known (2×2)R45° reconstruction of Fe3O4(001). This hitherto unobserved stabilization mechanism occurs because the iron oxides prefer to redistribute cations in the lattice in response to oxidizing or reducing environments. Many other metal oxides also achieve stoichiometry variation in this way, so such surface structures are likely commonplace.

  18. Galvanostatic interruption of lithium insertion into magnetite: Evidence of surface layer formation

    NASA Astrophysics Data System (ADS)

    Brady, Nicholas W.; Knehr, K. W.; Cama, Christina A.; Lininger, Christianna N.; Lin, Zhou; Marschilok, Amy C.; Takeuchi, Kenneth J.; Takeuchi, Esther S.; West, Alan C.

    2016-07-01

    Magnetite is a known lithium intercalation material, and the loss of active, nanocrystalline magnetite can be inferred from the open-circuit potential relaxation. Specifically, for current interruption after relatively small amounts of lithium insertion, the potential first increases and then decreases, and the decrease is hypothesized to be due to a formation of a surface layer, which increases the solid-state lithium concentration in the remaining active material. Comparisons of simulation to experiment suggest that the reactions with the electrolyte result in the formation of a thin layer of electrochemically inactive material, which is best described by a nucleation and growth mechanism. Simulations are consistent with experimental results observed for 6, 8 and 32-nm crystals. Furthermore, simulations capture the experimental differences in lithiation behavior between the first and second cycles.

  19. Galvanostatic interruption of lithium insertion into magnetite: Evidence of surface layer formation

    DOE PAGES

    Nicholas W. Brady; Takeuchi, Esther S.; Knehr, K. W.; Cama, Christina A.; Lininger, Christianna N.; Lin, Zhou; Marschilok, Amy C.; Takeuchi, Kenneth J.; West, Alan C.

    2016-05-05

    Magnetite is a known lithium intercalation material, and the loss of active, nanocrystalline magnetite can be inferred from the open-circuit potential relaxation. Specifically, for current interruption after relatively small amounts of lithium insertion, the potential first increases and then decreases, and the decrease is hypothesized to be due to a formation of a surface layer, which increases the solid-state lithium concentration in the remaining active material. Comparisons of simulation to experiment suggest that the reactions with the electrolyte result in the formation of a thin layer of electrochemically inactive material, which is best described by a nucleation and growth mechanism.more » Simulations are consistent with experimental results observed for 6, 8 and 32-nm crystals. As a result, simulations capture the experimental differences in lithiation behavior between the first and second cycles.« less

  20. Effect of surface charge of magnetite nanoparticles on their internalization into breast cancer and umbilical vein endothelial cells.

    PubMed

    Osaka, Tetsuya; Nakanishi, Takuya; Shanmugam, Sangaraju; Takahama, Shintaro; Zhang, Hong

    2009-07-01

    Internalization of magnetite nanoparticles with diameter of approximately 40 nm into normal and cancer cells was examined by microscopic observation and flow cytometry. Magnetite nanoparticles were synthesized by hydrolysis in an aqueous solution containing ferrous chloride with organic amines as a base. It was demonstrated that the difference in surface charge of magnetite nanoparticles brought about the difference in uptake efficiency. The nanoparticles with positive charge showed higher internalization into human breast cancer cells than the nanoparticles with negative charge, while the degree of internalization of the positively- and negatively-charged nanoparticles into human umbilical vein endothelial cells (HUVEC) was almost the same.

  1. Adsorption behavior of antimony(III) oxyanions on magnetite surface in aqueous organic acid environment

    NASA Astrophysics Data System (ADS)

    Mittal, Vinit K.; Bera, Santanu; Narasimhan, S. V.; Velmurugan, S.

    2013-02-01

    Antimony(III) adsorption is observed on magnetite (Fe3O4) surface under acidic and reducing condition through surface hydroxyl (SOH) groups bonding on Fe3O4 surface. Desorption of adsorbed Sb(III) is observed from Fe3O4 surface along with iron release in organic acid at 85 °C after 5 h of experiment. Tartaric acid (TA) shows minimum Sb(III) adsorption on Fe3O4 among the organic acid studied. The reason is TA having two sets of adjacent functional groups viz. Odbnd Csbnd OH and Csbnd OH which are responsible for the formation of five-membered bidendate chelate with Sb(III). Other oxyanions, cations or complexing agents along with TA influences the Sb(III) adsorption on Fe3O4. The surface of magnetite is modified by the addition of fatty acids viz. Lauric acid, benzoic acid to bind the Ssbnd OH groups present on the surface. This results in delaying the process of adsorption without changing the quantity of saturation adsorption of Sb(III) on Fe3O4 surface.

  2. Adsorption of gold subnano-structures on a magnetite(111) surface and their interaction with CO.

    PubMed

    Pabisiak, Tomasz; Winiarski, Maciej J; Ossowski, Tomasz; Kiejna, Adam

    2016-07-21

    Gold deposited on iron oxide surfaces can catalyze the oxidation of carbon monoxide. The adsorption of gold subnano-structures on the Fe-rich termination of the magnetite(111) surface has been investigated using density functional theory. The structural, energetic, and electronic properties of gold/magnetite systems have been examined for vertical and flattened configurations of adsorbed Aun (n = 1-4) species. Single gold adatoms strongly bonded to the iron atoms of the Fe3O4(111) surface appear to be negatively charged, and consequently increase the work function. For a more stable class of larger, flattened Aun structures the adsorption binding energy per adatom is substantially increased. The structures exhibit a net positive charge, with the Au atoms binding with the oxide having distinctly cationic character. A charge transfer from the larger gold structures to the substrate is consistent with the lowering of the work function. The bonding of a CO molecule to a Au monomer on the Fe3O4(111) surface has been found nearly as strong as that to the iron site of the bare Fe-terminated surface. However, CO bonding to larger, oxide supported Aun structures is distinctly stronger than that to the bare oxide surface. Upon CO adsorption all Aun structures are cationic and CO shows a tendency to bind to the most cationic atom of the Aun cluster.

  3. Real-space imaging of the Verwey transition at the (100) surface of magnetite

    NASA Astrophysics Data System (ADS)

    de la Figuera, Juan; Novotny, Zbynek; Setvin, Martin; Liu, Tijiang; Mao, Zhiqiang; Chen, Gong; N'Diaye, Alpha T.; Schmid, Michael; Diebold, Ulrike; Schmid, Andreas K.; Parkinson, Gareth S.

    2013-10-01

    Effects of the Verwey transition on the (100) surface of magnetite were studied using scanning tunneling microscopy and spin polarized low-energy electron microscopy. On cooling through the transition temperature TV, the initially flat surface undergoes a rooflike distortion with a periodicity of ˜0.5 μm due to ferroelastic twinning within monoclinic domains of the low-temperature monoclinic structure. The monoclinic c axis orients in the surface plane, along the [001]c directions. At the atomic scale, the charge-ordered (2×2)R45∘ reconstruction of the (100) surface is unperturbed by the bulk transition, and is continuous over the twin boundaries. Time resolved low-energy electron microscopy movies reveal the structural transition to be first order at the surface, indicating that the bulk transition is not an extension of the Verwey-like (2×2)R45∘ reconstruction. Although conceptually similar, the charge-ordered phases of the (100) surface and sub-TV bulk of magnetite are unrelated phenomena.

  4. Adsorption of gold subnano-structures on a magnetite(111) surface and their interaction with CO.

    PubMed

    Pabisiak, Tomasz; Winiarski, Maciej J; Ossowski, Tomasz; Kiejna, Adam

    2016-07-21

    Gold deposited on iron oxide surfaces can catalyze the oxidation of carbon monoxide. The adsorption of gold subnano-structures on the Fe-rich termination of the magnetite(111) surface has been investigated using density functional theory. The structural, energetic, and electronic properties of gold/magnetite systems have been examined for vertical and flattened configurations of adsorbed Aun (n = 1-4) species. Single gold adatoms strongly bonded to the iron atoms of the Fe3O4(111) surface appear to be negatively charged, and consequently increase the work function. For a more stable class of larger, flattened Aun structures the adsorption binding energy per adatom is substantially increased. The structures exhibit a net positive charge, with the Au atoms binding with the oxide having distinctly cationic character. A charge transfer from the larger gold structures to the substrate is consistent with the lowering of the work function. The bonding of a CO molecule to a Au monomer on the Fe3O4(111) surface has been found nearly as strong as that to the iron site of the bare Fe-terminated surface. However, CO bonding to larger, oxide supported Aun structures is distinctly stronger than that to the bare oxide surface. Upon CO adsorption all Aun structures are cationic and CO shows a tendency to bind to the most cationic atom of the Aun cluster. PMID:27332962

  5. The effect of humic acid adsorption on pH-dependent surface charging and aggregation of magnetite nanoparticles

    SciTech Connect

    Illes, E.; Tombacz, E.

    2006-03-01

    The pH-dependent adsorption of humic acid (HA) on magnetite and its effect on the surface charging and the aggregation of oxide particles were investigated. HA was extracted from brown coal. Synthetic magnetite was prepared by alkaline hydrolysis of iron(II) and iron(III) salts. The pH-dependent particle charge and aggregation, and coagulation kinetics at pH around to 4 were measured by laser Doppler electrophoresis and dynamic light scattering. The charge of pure magnetite reverses from positive to negative at pH around 8, which may consider as isoelectric point (IEP). Near this pH, large aggregates form, while stable sols exist further from it. In the presence of increasing HA loading, the IEP shifts to lower pH, then at higher loading, magnetite becomes negatively charged even at low pHs, which indicate the neutralization and gradual recharging positive charges on surface. In acidic region, the trace HA amounts are adsorbed on magnetite surface as oppositely charged patches, systems become highly unstable due to heterocoagulation. Above the adsorption saturation, however, the nanoparticles are stabilized in a way of combined steric and electrostatic effects. The HA coated magnetite particles form stable colloidal dispersion, particle aggregation does not occur in a wide range of pH and salt tolerance is enhanced.

  6. Synthesis and characterization of monosodium urate (MSU) nano particles

    NASA Astrophysics Data System (ADS)

    Tank, Nirali S.; Rathod, K. R.; Parekh, B. B.; Parikh, K. D.; Joshi, M. J.

    2016-05-01

    In Gout the deposition of crystals of Monosodium Urate (MSU) in various connective tissues and joints occurs, which is very painful with immflamation. The deposition likely to begin with nano particles form and expected to grow in to micro-paricles and hence it is important to synthesize and characrterize MSU nano-particles. The MSU nano particles were synthesized by wet chemical method using NaOH and uric acid (C5H4N4O3) and then characterized by powder XRD, TEM, FT-IR and thermal analysis. From the powder XRD the triclinic structure was found and 40 nm average particle size was estimated by using Scherrer's formula. From TEM the particle size was found to be in the range of 20 to 60 nm. The FT-IR spectrum for the MSU nano particles confirmed the presence of O-H stretching, N-H stretching, N-H rocking, C = O, C = C Enol or Keto and C = N vibrations. The thermal analysis was carried out from room temperature to 900°C. With comparison to the bulk MSU the thermal stability of MSU nano particles was slightly higher and 1.5 water molecules were found to be associated with MSU nano particles. Present results are compared with the bulk MSU.

  7. Surface-initiated atom transfer radical polymerization of methyl methacrylate from magnetite nanoparticles at ambient temperature.

    PubMed

    Raghuraman, G K; Dhamodharan, R

    2006-07-01

    The synthesis of methyl methacrylate (MMA) brush from the surface of magnetite nanoparticles (core-shell structure), from initiator moieties anchored covalently to the nanoparticles, via room temperature atom transfer radical polymerization (ATRP) is described. The surface-initiated polymerization was carried out from a surface-confined initiator containing a 2-bromoisobutyrate moiety with Cu(I)Br/PMDETA catalytic system. The initiator moiety was covalently anchored to the nanoparticles via a two step modification reaction scheme. Controlled polymerization was observed if ethyl-2-bromoisobutyrate (2-EiBrB) was added as a free/sacrificial initiator. A linear increase of molecular weight and a narrow molecular weight distribution of the PMMA formed in solution, provide evidence for a controlled surface-initiated polymerization, leading to surface-attached polymer brushes under mild conditions. The grafted PMMA provides good stability and dispersibility for the nanoparticles in organic solvents.

  8. Investigation on the antibacterial micro-porous titanium with silver nano-particles.

    PubMed

    Dong, Wei; Zhu, Yingchun; Zhang, Jingxian; Lu, Liqiang; Zhao, Chengjian; Qin, Lifeng; Li, Yingbin

    2013-10-01

    Micro-porous titanium is coated with silver nanoparticles by using a simple chemical reduction method that exhibits excellent antibacterial ability. Scanning electron microscopy (SEM) shows that the silver nanoparticles with average sizes of about 100 nm are formed homogeneously on the micro-porous titanium surface. After the micro-porous Ti coated with silver nano particles is treated by heating, the average size of the silver nano particles is slightly increased, but the nano particles are more uniformly dispersed on the surface of the micro-porous titanium. X-ray diffraction (XRD) indicates that those nanoparticles are metallic silver produced on the micro-porous titanium surface. The samples of micro-porous titanium coated with silver nanoparticles inhibit the growth of Escherichia coli. Our results show that the electrical double layer of the samples play an important role in the antibiosis and this study opens a new window for antibacterial mechanism which may be suitable for the other antibacterial metallic materials.

  9. EXAFS and HRTEM evidence for As(III)-containing surface precipitates on nanocrystalline magnetite: implications for As sequestration.

    PubMed

    Morin, Guillaume; Wang, Yuheng; Ona-Nguema, Georges; Juillot, Farid; Calas, Guillaume; Menguy, Nicolas; Aubry, Emmanuel; Bargar, John R; Brown, Gordon E

    2009-08-18

    Arsenic sorption onto iron oxide spinels such as magnetite could contribute to immobilization of arsenite (AsO3(3-)), the reduced, highly toxic form of arsenic in contaminated anoxic groundwaters, as well as to putative remediation processes. Nanocrystalline magnetite (<20 nm) is known to exhibit higher efficiency for arsenite sorption than larger particles, sorbing as much as approximately 20 micromol/m2 of arsenite. To improve our understanding of this process, we investigated the molecular level structure of As(III)-containing sorption products on two types of fine-grained magnetite: (1) a biogenic one with an average particle diameter of 34 nm produced by reduction of lepidocrocite (gamma-FeOOH) by Shewanella putrefaciens and (2) a synthetic, abiotic, nanocrystalline magnetite with an average particle diameter of 11 nm. Results from extended X-ray absorption spectroscopy (EXAFS) for both types of magnetite with As(III) surface coverages of up to 5 micromol/m2 indicate that As(III) forms dominantly inner-sphere, tridentate, hexanuclear, corner-sharing surface complexes (3C) in which AsO3 pyramids occupy vacant tetrahedral sites on octahedrally terminated {111} surfaces of magnetite. Formation of this type of surface complex results in a decrease in dissolved As(III) concentration below the maximum concentration level recommended by the World Health Organization (10 microg/L), which corresponds to As(III) surface coverages of 0.16 and 0.19 micromol/m2 in our experiments. In addition, high-resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray spectroscopy (EDXS) analyses revealed the occurrence of an amorphous As(III)-rich surface precipitate forming at As(III) surface coverages as low as 1.61 micromol/m2. This phase hosts the majority of adsorbed arsenite at surface coverages exceeding the theoretical maximum site density of vacant tetrahedral sites on the magnetite {111} surface (3.2 sites/nm2 or 5.3 micromol/m2). This finding

  10. Surface modification of monodisperse magnetite nanoparticles for improved intracellular uptake to breast cancer cells.

    PubMed

    Zhang, Yong; Zhang, Jing

    2005-03-15

    Nanoparticles have been widely used for a variety of biomedical applications and there is a growing need for highly specific and efficient uptake of the nanoparticles into target cells. Poly(ethylene glycol) (PEG), folic acid (FA), and their conjugate PEG-FA were attached to magnetite nanoparticles to compare their effects on the improvement of intracellular uptake of the nanoparticles to human breast cancer cells, BT-20. AFM and TEM results indicated that the nanoparticles after surface modification were monodisperse, with coatings on individual nanoparticles. The cell culture experiments showed that the PEG-FA coated nanoparticles were internalized into BT-20 cancer cells and exhibited higher efficiency of intracellular uptake than only PEG- or FA-coated nanoparticles. The surface modification protocols can also be used to modify the surfaces of other nanoparticles for targeting intracellular delivery.

  11. Development of functional nano-particle layer for highly efficient OLED

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Hyun; Kim, Min-Hoi; Choi, Haechul; Choi, Yoonseuk

    2015-12-01

    Organic light emitting diodes (OLEDs) are now widely commercialized in market due to many advantages such as possibility of making thin or flexible devices. Nevertheless there are still several things to obtain the high quality flexible OLEDs, one of the most important issues is the light extraction of the device. It is known that OLEDs have the typical light loss such as the waveguide loss, plasmon absorption loss and internal total reflection. In this paper, we demonstrate the one-step processed light scattering films with aluminum oxide nano-particles and polystyrene matrix composite to achieve highly efficient OLEDs. Optical characteristics and surface roughness of light scattering film was optimized by changing the mixing concentration of Al2O3 nano-particles and investigated with the atomic force microscopy and hazemeter, respectively.

  12. U(VI) sorption and reduction kinetics on the magnetite (111) surface.

    PubMed

    Singer, David M; Chatman, Shawn M; Ilton, Eugene S; Rosso, Kevin M; Banfield, Jillian F; Waychunas, Glenn A

    2012-04-01

    Sorption of contaminants onto mineral surfaces is an important process that can restrict their transport in the environment. In the current study, uranium (U) uptake on magnetite (111) was measured as a function of time and solution composition (pH, [CO(3)](T), [Ca]) under continuous batch-flow conditions. We observed, in real-time and in situ, adsorption and reduction of U(VI) and subsequent growth of UO(2) nanoprecipitates using atomic force microscopy (AFM) and newly developed batch-flow U L(III)-edge grazing-incidence X-ray absorption spectroscopy near-edge structure (GI-XANES) spectroscopy. U(VI) reduction occurred with and without CO(3) present, and coincided with nucleation and growth of UO(2) particles. When Ca and CO(3) were both present no U(VI) reduction occurred and the U surface loading was lower. In situ batch-flow AFM data indicated that UO(2) particles achieved a maximum height of 4-5 nm after about 8 h of exposure, however, aggregates continued to grow laterally after 8 h reaching up to about 300 nm in diameter. The combination of techniques indicated that U uptake is divided into three-stages; (1) initial adsorption of U(VI), (2) reduction of U(VI) to UO(2) nanoprecipitates at surface-specific sites after 2-3 h of exposure, and (3) completion of U(VI) reduction after ~6-8 h. U(VI) reduction also corresponded to detectable increases in Fe released to solution and surface topography changes. Redox reactions are proposed that explicitly couple the reduction of U(VI) to enhanced release of Fe(II) from magnetite. Although counterintuitive, the proposed reaction stoichiometry was shown to be largely consistent with the experimental results. In addition to providing molecular-scale details about U sorption on magnetite, this work also presents novel advances for collecting surface sensitive molecular-scale information in real-time under batch-flow conditions.

  13. Experimental study of combustion of decane, dodecane and hexadecane with polymeric and nano-particle additives

    NASA Astrophysics Data System (ADS)

    Ghamari, Mohsen; Ratner, Albert

    2015-11-01

    Recent studies have shown that adding combustible nano-particles could have promising effects on increasing burning rate of liquid fuels. Combustible nano-particles could enhance the heat conduction and mixing within the droplet. Polymers have also higher burning rate than regular hydrocarbon fuels because of having the flame closer to the droplet surface. Therefore adding polymeric additive could have the potential to increase the burning rate. In this study, combustion of stationary fuel droplets of n-Decane, n-Dodecane and n-Hexadecane doped with different percentages of a long chain polymer and also a very fine nano carbon was examined and compared with the pure hydrocarbon behavior. In contrast with hydrocarbon droplets with no polymer addition, several zones of combustion including a slow and steady burning zone, a strong swelling zone and a final fast and fairly steady combustion zone were also detected. In addition, increasing polymer percentage resulted in a more extended swelling zone and shorter slow burning zone in addition to a shorter total burning time. Addition of nano-particles also resulted in an overall increased burning rate and shortened burning time which is due to enhanced heat conduction within the droplet.

  14. Determination of anionic surface active agents using silica coated magnetite nanoparticles modified with cationic surfactant aggregates.

    PubMed

    Pena-Pereira, Francisco; Duarte, Regina M B O; Trindade, Tito; Duarte, Armando C

    2013-07-19

    The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica-magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10-C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10-C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8-1.9μgL(-1) for C10-C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N=6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples.

  15. NOVEL PREPARATION AND MAGNETO CHEMICAL CHARACTERIZATION OF NANO-PARTICLE MIXED ALCOHOL CATALYSTS

    SciTech Connect

    Seetala V. Naidu; Upali Siriwardane; Akundi N. Murty

    2004-02-23

    The preparation of Cu, Co, Fe, Cu/Co, Cu/Fe and Co/Fe nano-particle metal loaded mesoporous 1 mm spherical granular {gamma}-Al{sub 2}O{sub 3} catalysts, by combined sol-gel/oil-drop methods followed by calcination and hydrogenation steps, is accomplished. Parameters for calcination process were optimized using DTA. The properties of metal loaded {gamma}-Al{sub 2}O{sub 3} granules were compared for the preparations starting with two precursors: aluminum tri-sec-butoxide (ALTSB) and aluminum tri-iso-propoxide (ALTIP). Three sol-gel/oil-drop catalyst preparation methods; (1) Metal nitrate solutions co-entrapped-sol-gel (2) nano-particle metal oxide co-entrapped-sol-gel, and (3) Metal impregnation on preformed alumina granules, were used. Structure and composition of metal-loaded-granules were investigated using XRD, SEM, EDX, and surface area measurements (BET method). The nano-particle nature of catalysts was confirmed using SEM and X-ray diffraction. The reduction efficiency of hydrogenation of catalysts was examined by magnetic studies using a vibrating sample magnetometer (VSM). Catalysts could be effectively calcined at 450 C and the surface area values obtained were between 200-350 m{sup 2}/g, indicating the mesoporous nature of catalyst support. Parameters affecting the metal loading process were also studied, and the optimum conditions were identified and reported for reproducible synthesis of the metal loaded {gamma}-alumina granular particles. The catalyst activities of Fe, Co, and Co/Fe on alumina for the conversion of CO/H{sub 2} and CO{sub 2}/H{sub 2} mixtures were investigated using Gas chromatography (GC) with N{sub 2} as a standard carrier gas. Both, slurry-phase-batch and gas-phase-continuous-flow, reactors were used. Magnetization studies on reduced, CO/H{sub 2} post-reaction catalyst in both gas and slurry phase were performed using vibrating sample magnetometer (VSM). Magnetic studies of post-reaction Co and Fe nano-catalysts showed that the

  16. NOVEL PREPARATION AND MAGNETO CHEMICAL CHARACTERIZATION OF NANO-PARTICLE MIXED ALCOHOL CATALYSTS

    SciTech Connect

    Setala V. Naidu

    2003-01-01

    We have produced Co, Cu, and Fe nano-particles by Laser-induced solution deposition (LISD) as evidenced by TEM investigations. Sizes of the nano-particles created are in the order of 5 nm. The LISD system could generate nano-particles in quantities only in the order of a milligram. This may be mainly due to the limited photo induced reactions taking place on the surface of the solutions. We have designed experiments to use drop flow technique with LISD for nano-particle deposition on microreactors. Preliminary work has been done on Co and Fe thin film deposited microreactors. We are also investigating the catalytic properties of nano-particles of FeO and CoO prepared by ball milling and dispersed into sol-gel prepared alumina granules. We have continued our investigation of catalytic reactions of Cu, Co, Fe, Cu/Co, Cu/Fe and Co/Fe on alumina support. The metal oxides were first reduced with hydrogen and used for the conversion of CO/H{sub 2}. The surface area of the catalysts has been determined by nitrogen disorption. They are in the range of 200-300 m{sup 2}/g. Cu, Co, Fe, Co/Fe, Cu/Co and Cu/Fe showed increasing order of catalytic activity for CO/H{sub 2} conversion. We are also studying catalytic conversion rates for CO{sub 2}/H{sub 2} and CO/CO{sub 2}/H{sub 2} mixtures using these catalysts. Our investigations of Co and Fe thin film deposited microreactors showed higher CO/H{sub 2} conversion for Fe compared to Co. We have used vibrating sample magnetometer (VSM) to study the magnetic characteristics of as prepared, reduced, post-reaction catalysts. Comparative study of the ferromagnetic component of these samples gives the reduction efficiency and the changes in metal centers during catalytic reactions. Magnetic studies of post-reaction Co and Fe micro-reactors show that more carbide formation occurs for iron compared to cobalt.

  17. Synthesis of biomimetic poly[2-(methacryloyloxy)ethyl phosphorycholine]-coated magnetite nanoparticles via surface-initiated atom transfer radical polymerization.

    PubMed

    Sui, Jie-He; Cao, Chang-Yan; Cai, Wei

    2011-10-01

    Modification of magnetite nanoparticles with biomimetic poly[2-(methacryloyloxy)ethyl phosphorycholine] (poly(MPC)) via surface-initiated atom transfer radical polymerization (ATRP) was carried out. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analyses (TGA) and zeta potential studies indicated that well defined poly (MPC) was successfully grafted on the surface of magnetite nanoparticles. X-ray diffraction results showed the structure of magnetite nanoparticles after surface modification was not changed. The poly (MPC)-coated magnetite nanoparticles had a mean transmission electron microscopy (TEM) diameter of 11 +/- 1.5 nm. The resulting nanomaterials were superparamagnetic at room temperature, exhibited good colloidal stability in aqueous media and good responsibility to magnetic field. Such magnetite nanoparticles with biomimetic surface have potential application in prolonging circulation time in vivo.

  18. Microbial synthesis of magnetite and Mn-substituted magnetite nanoparticles: influence of bacteria and incubation temperature.

    PubMed

    Roh, Yul; Jang, Hee-Dong; Suh, Yongjae

    2007-11-01

    Microbial synthesis of magnetite and metal (Co, Cr, Ni)-substituted magnetites has only recently been reported. The objective of this study was to examine the influence of Mn ion on the microbial synthesis of magnetite nanoparticles. The reductive biotransformation of an akaganeite (beta-FeOOH) or a Mn-substituted (2-20 mol%) akaganeite (Fe(1-x)Mn(x)OOH) by Shewanella loiha (PV-4, 25 degrees C) and Thermoanaerobacter ethanolicus (TOR-39, 60 degrees C) was investigated under anaerobic conditions at circumneutral pH (pH = 7-8). Both bacteria formed magnetite nanoparticles using akaganeite as a magnetite precursor. By comparison of iron minerals formed by PV-4 and TOR-39 using Mn-mixed akaganeite as the precursor, it was shown that PV-4 formed siderite (FeCO3), green rust [Fe2+Fe3+(OH)16CO3 x 4H2O], and magnetite at 25 degrees C, whereas TOR-39 formed mainly nm-sized magnetite at 60 degrees C. The presence of Mn in the magnetite formed by TOR-39 was revealed by energy dispersive X-ray analysis (EDX) is indicative of Mn substitution into magnetite crystals. EDX analysis of iron minerals formed by PV-4 showed that Mn was preferentially concentrated in the siderite and green rust. These results demonstrate that coprecipitated/sorbed Mn induced microbial formation of siderite and green rust by PV-4 at 25 degrees C, but the synthesis of Mn-substituted magnetite nanoparticles proceeded by TOR-39 at 60 degrees C. These results indicate that the bacteria have the ability to synthesize magnetite and Mn-substituted magnetite nano-crystals. Microbially facilitated synthesis of magnetite and metal-substituted magnetites at near ambient temperatures may expand the possible use of specialized ferromagnetic nano-particles.

  19. Effect of hydroxyapatite nano-particles on morphology, rheology and thermal behavior of poly(caprolactone)/chitosan blends.

    PubMed

    Ghorbani, Fereshte Mohammad; Kaffashi, Babak; Shokrollahi, Parvin; Akhlaghi, Shahin; Hedenqvist, Mikael S

    2016-02-01

    The effect of hydroxyapatite nano-particles (nHA) on morphology, and rheological and thermal properties of PCL/chitosan blends was investigated. The tendency of nHA to reside in the submicron-dispersed chitosan phase is determined using SEM and AFM images. The presence of electrostatic interaction between amide sites of chitosan and ionic groups on the nHA surface was proved by FTIR. It is shown that the chitosan phase is thermodynamically more favorable for the nano-particles to reside than the PCL phase. Lack of implementation of Cox-Merz theory for this system shows that the polymer-nano-particle network is destructed by the flow. Results from dynamic rheological measurements and Zener fractional model show that the presence of nHA increases the shear moduli and relaxation time of the PCL/chitosan blends. DSC measurements showed that nHA nano-particles are responsible for the increase in melting and crystallization characteristics of the PCL/chitosan blends. Based on thermogravimetric analysis, the PCL/chitosan/nHA nano-composites exhibited a greater thermal stability compared to the nHA-free blends.

  20. Geometrical effects on the electron residence time in semiconductor nano-particles.

    PubMed

    Koochi, Hakimeh; Ebrahimi, Fatemeh

    2014-09-01

    We have used random walk (RW) numerical simulations to investigate the influence of the geometry on the statistics of the electron residence time τ(r) in a trap-limited diffusion process through semiconductor nano-particles. This is an important parameter in coarse-grained modeling of charge carrier transport in nano-structured semiconductor films. The traps have been distributed randomly on the surface (r(2) model) or through the whole particle (r(3) model) with a specified density. The trap energies have been taken from an exponential distribution and the traps release time is assumed to be a stochastic variable. We have carried out (RW) simulations to study the effect of coordination number, the spatial arrangement of the neighbors and the size of nano-particles on the statistics of τ(r). It has been observed that by increasing the coordination number n, the average value of electron residence time, τ̅(r) rapidly decreases to an asymptotic value. For a fixed coordination number n, the electron's mean residence time does not depend on the neighbors' spatial arrangement. In other words, τ̅(r) is a porosity-dependence, local parameter which generally varies remarkably from site to site, unless we are dealing with highly ordered structures. We have also examined the effect of nano-particle size d on the statistical behavior of τ̅(r). Our simulations indicate that for volume distribution of traps, τ̅(r) scales as d(2). For a surface distribution of traps τ(r) increases almost linearly with d. This leads to the prediction of a linear dependence of the diffusion coefficient D on the particle size d in ordered structures or random structures above the critical concentration which is in accordance with experimental observations.

  1. Geometrical effects on the electron residence time in semiconductor nano-particles

    SciTech Connect

    Koochi, Hakimeh; Ebrahimi, Fatemeh

    2014-09-07

    We have used random walk (RW) numerical simulations to investigate the influence of the geometry on the statistics of the electron residence time τ{sub r} in a trap-limited diffusion process through semiconductor nano-particles. This is an important parameter in coarse-grained modeling of charge carrier transport in nano-structured semiconductor films. The traps have been distributed randomly on the surface (r{sup 2} model) or through the whole particle (r{sup 3} model) with a specified density. The trap energies have been taken from an exponential distribution and the traps release time is assumed to be a stochastic variable. We have carried out (RW) simulations to study the effect of coordination number, the spatial arrangement of the neighbors and the size of nano-particles on the statistics of τ{sub r}. It has been observed that by increasing the coordination number n, the average value of electron residence time, τ{sup ¯}{sub r} rapidly decreases to an asymptotic value. For a fixed coordination number n, the electron's mean residence time does not depend on the neighbors' spatial arrangement. In other words, τ{sup ¯}{sub r} is a porosity-dependence, local parameter which generally varies remarkably from site to site, unless we are dealing with highly ordered structures. We have also examined the effect of nano-particle size d on the statistical behavior of τ{sup ¯}{sub r}. Our simulations indicate that for volume distribution of traps, τ{sup ¯}{sub r} scales as d{sup 2}. For a surface distribution of traps τ{sup ¯}{sub r} increases almost linearly with d. This leads to the prediction of a linear dependence of the diffusion coefficient D on the particle size d in ordered structures or random structures above the critical concentration which is in accordance with experimental observations.

  2. Diagnostics of Nano-Particle Formation in Process Plasmas

    NASA Astrophysics Data System (ADS)

    Kersten, Holger

    2015-09-01

    in the plasma during the growth cycles has been monitored by microwave interfereomtery and the nano-particle formation and deposition was observed in-situ by XPS and NEXAFS at a synchrotron beamline. In collaboration with E. von Wahl, A. Hinz, T. Strunskus, V. Schneider, and T. Trottenberg, Institute of Experimental and Applied Physics, University of Kiel, Kiel, Germany.

  3. Influences of surface coating, UV irradiation and magnetic field on the algae removal using magnetite nanoparticles.

    PubMed

    Ge, Shijian; Agbakpe, Michael; Wu, Zhiyi; Kuang, Liyuan; Zhang, Wen; Wang, Xianqin

    2015-01-20

    Magnetophoretic separation is a promising and sustainable technology for rapid algal separation or removal from water. This work demonstrated the application of magnetic magnetite nanoparticles (MNPs) coated with a cationic polymer, polyethylenimine (PEI), toward the separation of Scenedesmus dimorphus from the medium broth. The influences of surface coating, UV irradiation, and magnetic field on the magnetophoretic separation were systematically examined. After PEI coating, zeta potential of MNPs shifted from −7.9 ± 2.0 to +39.0 ± 3.1 mV at a pH of 7.0, which improved MNPs-algae interaction and helped reduce the dose demand of MNPs (e.g., from 0.2 to 0.1 g·g(–1) while the harvesting efficiency (HE) of over 80% remained unchanged). The extended Derjaguin–Landau–Verwey–Overbeek theory predicted a strong attractive force between PEI-coated MNPs and algae, which supported the improved algal harvesting. Moreover, the HE was greater under the UV365 irradiation than that under the UV254, and increased with the irradiation intensity. Continuous application of the external magnetic field at high strength remarkably improved the algal harvesting. Finally, the reuse of MNPs for multiple cycles of algal harvesting was studied, which aimed at increasing the sustainability and lowering the cost. PMID:25486124

  4. Influences of surface coating, UV irradiation and magnetic field on the algae removal using magnetite nanoparticles.

    PubMed

    Ge, Shijian; Agbakpe, Michael; Wu, Zhiyi; Kuang, Liyuan; Zhang, Wen; Wang, Xianqin

    2015-01-20

    Magnetophoretic separation is a promising and sustainable technology for rapid algal separation or removal from water. This work demonstrated the application of magnetic magnetite nanoparticles (MNPs) coated with a cationic polymer, polyethylenimine (PEI), toward the separation of Scenedesmus dimorphus from the medium broth. The influences of surface coating, UV irradiation, and magnetic field on the magnetophoretic separation were systematically examined. After PEI coating, zeta potential of MNPs shifted from −7.9 ± 2.0 to +39.0 ± 3.1 mV at a pH of 7.0, which improved MNPs-algae interaction and helped reduce the dose demand of MNPs (e.g., from 0.2 to 0.1 g·g(–1) while the harvesting efficiency (HE) of over 80% remained unchanged). The extended Derjaguin–Landau–Verwey–Overbeek theory predicted a strong attractive force between PEI-coated MNPs and algae, which supported the improved algal harvesting. Moreover, the HE was greater under the UV365 irradiation than that under the UV254, and increased with the irradiation intensity. Continuous application of the external magnetic field at high strength remarkably improved the algal harvesting. Finally, the reuse of MNPs for multiple cycles of algal harvesting was studied, which aimed at increasing the sustainability and lowering the cost.

  5. Probing the interaction of lysozyme with ciprofloxacin in the presence of different-sized Ag nano-particles by multispectroscopic techniques and isothermal titration calorimetry.

    PubMed

    Pasban Ziyarat, Fatemeh; Asoodeh, Ahmad; Sharif Barfeh, Zahra; Pirouzi, Maliheh; Chamani, Jamshidkhan

    2014-04-01

    The binding of ciprofloxacin to lysozyme in the presence of three Ag nano-particles of varying sizes was for the first time investigated by multispectroscopic and isothermal titration calorimetry techniques at pH 7.4. The results indicated that ciprofloxacin quenched the fluorescence intensity of lysozyme through a static mechanism but in the presence of size-II Ag nano-particles, there were two kinds of interaction behaviors. The interaction between ciprofloxacin and lysozyme occurred via a second type of binding site, whereas in the presence of the Ag nano-particles, some changes occurred. The secondary structure of lysozyme-ciprofloxacin in the presence of Ag nano-particles was determined by circular dichroism. The thermodynamic parameters of the interaction between ciprofloxacin and lysozyme in the presence of Ag nano-particles were measured according to the van't Hoff equation. The enthalpy (ΔH(○)) and entropy (ΔS(○)) changes were calculated to be -49.7 (kJ mol(-1)) and -20.1 (J mol(-1) K(-1)), respectively, which indicated that the interaction of ciprofloxacin with lysozyme was driven mainly by van der Waals forces and hydrogen bonding. In the presence of the three different-sized Ag nano-particles, the enthalpic and the entropic changes were both negative which indicated that hydrogen bonding with van der Waals forces played major roles in the binding between ciprofloxacin and lysozyme. Recent developments in nano-materials offer new pathways for controlling the protein behavior through surface interactions. These data indicate that the recent research on nano-particle/protein interactions will emphasize the importance of such interactions in biological systems with applications including the diagnosis and treatment of human diseases.

  6. Fractures as Carriers for Colloid and Nano-Particles

    NASA Astrophysics Data System (ADS)

    Weisbrod, N.; Cohen, M.; Tang, X.; Zvikelsky, O.; Meron, H.

    2013-12-01

    One of the major questions in studies in which transport of colloids and nano particles (NPs) is being explored is whether or not they will be mobile on large scales and in large conduits such as fractures and cracks. While many studies explore the migration on a small scale and mostly in ideal porous media, less is known about this topic on larger scales and in fractured rocks or cracked soils. Fractures are likely to be favorable carriers for colloids and NPs due to their large aperture, enabling relatively high flow velocity and smaller tortuosity of the flow path. Transport of various colloids including microspheres, clay particles and viruses, as well as colloid-facilitated transport of lead and cesium was explored in a naturally discrete fractured chalk cores. Preliminary work exploring the transport of NZVIs and TiO2 NPs is being carried out through these cores as well. Our results indicate very high recovery of large microspheres (0.2 and 1 micron) and lower recovery of the small spheres (0.02 micron). It was observed that clay particles, with similar surface properties and sizes to that of the microspheres, show significantly lower recoveries (50 vs over 90%), probably due to the high density of clay particles in respect to the microspheres (2.65 vs. 1.05 g/cm3). High recovery of bacteriophages was also observed, but they exhibit some differences in respect to microspheres with similar properties. In all cases, including the 0.02 micron colloids exhibiting lower recovery rates, arrival times were earlier than that of the bromide that was used as a reference. It was found that colloid-facilitated transport played a major role in the migration of lead and cesium through the fracture. In practice, lead was found to be mobile only in a colloidal form. The on-going work on NP transport through fractures is still in a preliminary phase. Nevertheless, TiO2 recovery was found to be very low. In conclusion, it was observed that in many cases fractures are favorable

  7. Identification of simultaneous U(VI) sorption complexes and U(IV) nanoprecipitates on the magnetite (111) surface.

    PubMed

    Singer, David M; Chatman, Shawn M; Ilton, Eugene S; Rosso, Kevin M; Banfield, Jillian F; Waychunas, Glenn A

    2012-04-01

    Sequestration of uranium (U) by magnetite is a potentially important sink for U in natural and contaminated environments. However, molecular-scale controls that favor U(VI) uptake including both adsorption of U(VI) and reduction to U(IV) by magnetite remain poorly understood, in particular, the role of U(VI)-CO(3)-Ca complexes in inhibiting U(VI) reduction. To investigate U uptake pathways on magnetite as a function of U(VI) aqueous speciation, we performed batch sorption experiments on (111) surfaces of natural single crystals under a range of solution conditions (pH 5 and 10; 0.1 mM U(VI); 1 mM NaNO(3); and with or without 0.5 mM CO(3) and 0.1 mM Ca) and characterized surface-associated U using grazing incidence extended X-ray absorption fine structure spectroscopy (GI-EXAFS), grazing incidence X-ray diffraction (GI-XRD), and scanning electron microscopy (SEM). In the absence of both carbonate ([CO(3)](T), denoted here as CO(3)) and calcium (Ca), or in the presence of CO(3) only, coexisting adsorption of U(VI) surface species and reduction to U(IV) occurs at both pH 5 and 10. In the presence of both Ca and CO(3), only U(VI) adsorption (VI) occurs. When U reduction occurs, nanoparticulate UO(2) forms only within and adjacent to surface microtopographic features such as crystal boundaries and cracks. This result suggests that U reduction is limited to defect-rich surface regions. Further, at both pH 5 and 10 in the presence of both CO(3) and Ca, U(VI)-CO(3)-Ca ternary surface species develop and U reduction is inhibited. These findings extend the range of conditions under which U(VI)-CO(3)-Ca complexes inhibit U reduction.

  8. Silver nano particle formation on Ar plasma - treated cinnamyl alcohol

    SciTech Connect

    Dahle, S.; Marschewski, M.; Wegewitz, L.; Maus-Friedrichs, W.; Vioel, W.

    2012-02-01

    Metastable induced electron spectroscopy, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy are employed to study the adsorption of silver on cinnamyl alcohol films prepared on Au(111) substrates by thermal evaporation. Additionally, the impact of an Ar atmosphere dielectric barrier discharge plasma applied to the cinnamyl alcohol film preliminary to the Ag adsorption is investigated. In both cases silver nano particles with an average diameter of 9 nm are formed. These particles do not interact chemically with the underlying cinnamyl alcohol film. We do not find any influence of the preliminary Ar plasma-treatment on the adsorption behavior at all.

  9. Rapid laser sintering of metal nano-particles inks

    NASA Astrophysics Data System (ADS)

    Ermak, Oleg; Zenou, Michael; Bernstein Toker, Gil; Ankri, Jonathan; Shacham-Diamand, Yosi; Kotler, Zvi

    2016-09-01

    Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 μs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased.

  10. Rapid laser sintering of metal nano-particles inks.

    PubMed

    Ermak, Oleg; Zenou, Michael; Toker, Gil Bernstein; Ankri, Jonathan; Shacham-Diamand, Yosi; Kotler, Zvi

    2016-09-23

    Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 μs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased.

  11. Rapid laser sintering of metal nano-particles inks.

    PubMed

    Ermak, Oleg; Zenou, Michael; Toker, Gil Bernstein; Ankri, Jonathan; Shacham-Diamand, Yosi; Kotler, Zvi

    2016-09-23

    Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 μs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased. PMID:27514079

  12. Magnetite in CI carbonaceous meteorites - Origin by aqueous activity on a planetesimal surface

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.; Mackay, A. L.; Boynton, W. V.

    1979-01-01

    The composition and morphology of magnetite in CI carbonaceous meteorites appear incompatible with a nebular origin. Mineralization on the meteorite parent body is a more plausible mode of formation. The iodine-xenon age of this material therefore dates an episode of secondary mineralization on a planetesimal rather than the epoch of condensation in the primitive solar nebula.

  13. Preparation of biocompatible magnetite-carboxymethyl cellulose nanocomposite: Characterization of nanocomposite by FTIR, XRD, FESEM and TEM

    NASA Astrophysics Data System (ADS)

    Habibi, Neda

    2014-10-01

    The preparation and characterization of magnetite-carboxymethyl cellulose nano-composite (M-CMC) material is described. Magnetite nano-particles were synthesized by a modified co-precipitation method using ferrous chloride tetrahydrate and ferric chloride hexahydrate in ammonium hydroxide solution. The M-CMC nano-composite particles were synthesized by embedding the magnetite nanoparticles inside carboxymethyl cellulose (CMC) using a freshly prepared mixture of Fe3O4 with CMC precursor. Morphology, particle size, and structural properties of magnetite-carboxymethyl cellulose nano-composite was accomplished using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. As a result, magnetite nano-particles with an average size of 35 nm were obtained. The biocompatible Fe3O4-carboxymethyl cellulose nano-composite particles obtained from the natural CMC polymers have a potential range of application in biomedical field.

  14. Identification of magnetite in lunar regolith breccia 60016: Evidence for oxidized conditions at the lunar surface

    NASA Astrophysics Data System (ADS)

    Joy, Katherine H.; Visscher, Channon; Zolensky, Michael E.; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Kring, David A.

    2015-07-01

    Lunar regolith breccias are temporal archives of magmatic and impact bombardment processes on the Moon. Apollo 16 sample 60016 is an "ancient" feldspathic regolith breccia that was converted from a soil to a rock at ~3.8 Ga. The breccia contains a small (70 × 50 μm) rock fragment composed dominantly of an Fe-oxide phase with disseminated domains of troilite. Fragments of plagioclase (An95-97), pyroxene (En74-75, Fs21-22,Wo3-4), and olivine (Fo66-67) are distributed in and adjacent to the Fe-oxide. The silicate minerals have lunar compositions that are similar to anorthosites. Mineral chemistry, synchrotron X-ray absorption near edge spectroscopy (XANES) and X-ray diffraction (XRD) studies demonstrate that the oxide phase is magnetite with an estimated Fe3+/ΣFe ratio of ~0.45. The presence of magnetite in 60016 indicates that oxygen fugacity during formation was equilibrated at, or above, the Fe-magnetite or wüstite-magnetite oxygen buffer. This discovery provides direct evidence for oxidized conditions on the Moon. Thermodynamic modeling shows that magnetite could have been formed from oxidization-driven mineral replacement of Fe-metal or desulphurisation from Fe-sulfides (troilite) at low temperatures (<570 °C) in equilibrium with H2O steam/liquid or CO2 gas. Oxidizing conditions may have arisen from vapor transport during degassing of a magmatic source region, or from a hybrid endogenic-exogenic process when gases were released during an impacting asteroid or comet impact.

  15. NanoParticle Ontology for cancer nanotechnology research.

    PubMed

    Thomas, Dennis G; Pappu, Rohit V; Baker, Nathan A

    2011-02-01

    Data generated from cancer nanotechnology research are so diverse and large in volume that it is difficult to share and efficiently use them without informatics tools. In particular, ontologies that provide a unifying knowledge framework for annotating the data are required to facilitate the semantic integration, knowledge-based searching, unambiguous interpretation, mining and inferencing of the data using informatics methods. In this paper, we discuss the design and development of NanoParticle Ontology (NPO), which is developed within the framework of the Basic Formal Ontology (BFO), and implemented in the Ontology Web Language (OWL) using well-defined ontology design principles. The NPO was developed to represent knowledge underlying the preparation, chemical composition, and characterization of nanomaterials involved in cancer research. Public releases of the NPO are available through BioPortal website, maintained by the National Center for Biomedical Ontology. Mechanisms for editorial and governance processes are being developed for the maintenance, review, and growth of the NPO.

  16. Surface characterization of carbon-bearing magnetite (CBM) and carbon-bearing Ni(II)-ferrite (CBNF)

    SciTech Connect

    Sano, T.; Akanuma, K.; Tsuji, M.; Tamaura, Y.

    1994-12-31

    Oxygen-deficient magnetite (ODM; Fe{sub 3}O{sub 4{minus}{delta}}, {delta} > 0) synthesized by reduction of magnetite with H{sub 2} at 300 C decomposed CO{sub 2} to carbon with an efficiency of nearly 100% at 300 C. In this reaction, two oxygen ions of the CO{sub 2} were incorporated into the spinel structure of ODM and carbon was deposited on the surface of ODM with zero valence to form visible particles. The particles of carbon separated from ODM were studied by Raman, energy-dispersive X-ray and wave-dispersive X-ray spectroscopies. The carbon which had been deposited on the ODM was found to be a mixture of graphite and amorphous carbon in at least two levels of crystallization. X-ray photoelectron spectroscopy and X-ray diffraction patterns of the carbon-bearing magnetite (CBM) showed no indication of carbide (Fe{sub 3}C) or metallic iron ({alpha}-Fe) phase formation. In the C 1s XPS spectra of the CBM, no peaks were observed which could be assigned to CO{sub 2} or CO. X-ray diffractometry, chemical analysis and TG-MS measurement showed that the carbon-bearing Ni(II)-ferrite (CBNF) (Ni(II)/Fe{sub total} = 0.15) synthesized by the carbon deposition reaction from CO{sub 2} with the H{sub 2}-reduced Ni(II)-ferrite was represented by (Ni{sub 0.28}Fe{sub 2.72}O{sub 4.00}){sub 1{minus}{delta}} (Ni{sub 0.69}{sup 2+}Fe{sub 2.31}{sup 2+}O{sub 3.00}){sub {delta}}C{sub {tau}} ({delta} = 0.27, {tau} = 0.17). The carbon of the CBNF gave the CIOlayer-like oxide containing some Ni{sup 2+} ions.

  17. Size-dependent toxicity of silica nano-particles to Chlorella kessleri.

    PubMed

    Fujiwara, Kitao; Suematsu, Hitoshi; Kiyomiya, Emiko; Aoki, Motohide; Sato, Mamiko; Moritoki, Nobuko

    2008-08-01

    SiO(2) nano-particles were found to exhibit size-dependent toxicity toward the alga, Chlorella kessleri. Small SiO(2) nano-particles exhibit stronger toxicity: 50% inhibitory concentrations (IC(50)) value for 5 nm = 0.8 +/- 0.6%, 26 nm = 7.1 +/- 2.8%, and 78 nm = 9.1 +/- 4.7%. Enlargement of the cell body was observed by flow cytometry, which is due to the presence of structures that obstructed cell division. Optical and transmission microscopes were used to observe coagulated cells with incomplete division. Although the physiological effect of SiO(2) nano-particles was not clear, SiO(2) nano-particles are toxic, at least for algae in aquatic media. Under the transmission electron microscope, several amorphous structures appeared in the cells that were exposed to 5-nm silica nano-particles. PMID:18584432

  18. Enhancement of iron content in spinach plants stimulated by magnetic nano particles

    NASA Astrophysics Data System (ADS)

    Yulianto, Agus; Astuti, Budi; Amalia, Saptaria Rosa

    2016-04-01

    In our previous study, the iron content in spinach plants could be detected by magnetic susceptibility values. In the present work, magnetic nano particles were found from the iron sand. The magnetic nano particles are synthesis by using co-precipitation process and sol-gel technique. The stimulation of magnetic nano particles in the plant has been done by the provision of magnetic nano particles in growing media. After certain time, plant samples was characterized using susceptibility-meter MS2B and atomic absorption spectroscopy to measure the magnetic susceptibility and the amount of iron content that absorbed of the plant, respectively. The iron content in the spinach plants was increased when the magnetic nano particles was injected in the growing media.

  19. Simple Model for Gold Nano Particles Concentration Dependence of Resonance Energy Transfer Intensity

    NASA Astrophysics Data System (ADS)

    Hoa, N. M.; Ha, C. V.; Nga, D. T.; Lan, N. T.; Nhung, T. H.; Viet, N. A.

    2016-06-01

    Gold nano particles (GNPs) concentration dependence of the energy transfer occurs between the fluorophores and GNPs is investigated. In the case of theses pairs, GNPs can enhance or quench the fluorescence of fluorophores depending upon the relative magnitudes of two energy transfer mechanisms: i) the plasmonic field enhancement at the fluorophores emission frequencies (plasmon coupled fluorescence enhancement) and ii) the localized plasmon coupled Forster energy transfer from fluorescent particles to gold particles, which quenches the fluorescence. The competition of these mechanisms is depending on the spectral overlap of fluorophores and GNPs, their relative concentration, excitation wavelength. Simple two branches surface plasmon polariton model for GNPs concentration dependence of the energy transfer is proposed. The experimental data and theoretical results confirm our findings.

  20. Homeotropic nano-particle assembly on degenerate planar nematic interfaces: films and droplets.

    PubMed

    Londoño-Hurtado, Alejandro; Armas-Pérez, Julio C; Hernández-Ortiz, Juan P; de Pablo, Juan J

    2015-07-01

    A continuum theory is used to study the effects of homeotropic nano-particles on degenerate planar liquid crystal interfaces. Particle self-assembly mechanisms are obtained from careful examination of particle configurations on a planar film and on a spherical droplet. The free energy functional that describes the system is minimized according to Ginzburg-Landau and stochastic relaxations. The interplay between elastic and surface distortions and the desire to minimize defect volumes (boojums and half-Saturn rings) is shown to be responsible for the formation of intriguing ordered structures. As a general trend, the particles prefer to localize at defects to minimize the overall free energy. However, multiple metastable configurations corresponding to local minima can be easily observed due to the high energy barriers that separate distinct particle arrangements. We also show that by controlling anchoring strength and temperature one can direct liquid-crystal mediated nanoparticle self-assembly along well defined pathways. PMID:26027806

  1. Homeotropic nano-particle assembly on degenerate planar nematic interfaces: films and droplets.

    PubMed

    Londoño-Hurtado, Alejandro; Armas-Pérez, Julio C; Hernández-Ortiz, Juan P; de Pablo, Juan J

    2015-07-01

    A continuum theory is used to study the effects of homeotropic nano-particles on degenerate planar liquid crystal interfaces. Particle self-assembly mechanisms are obtained from careful examination of particle configurations on a planar film and on a spherical droplet. The free energy functional that describes the system is minimized according to Ginzburg-Landau and stochastic relaxations. The interplay between elastic and surface distortions and the desire to minimize defect volumes (boojums and half-Saturn rings) is shown to be responsible for the formation of intriguing ordered structures. As a general trend, the particles prefer to localize at defects to minimize the overall free energy. However, multiple metastable configurations corresponding to local minima can be easily observed due to the high energy barriers that separate distinct particle arrangements. We also show that by controlling anchoring strength and temperature one can direct liquid-crystal mediated nanoparticle self-assembly along well defined pathways.

  2. Formation and transformation of magnetite (Fe[sub 3]O[sub 4]) on steel surfaces under continuous and cyclic water fog testing

    SciTech Connect

    Nasrazadani, S. ); Raman, A. )

    1993-04-01

    Formation and transformation of magnetite on two selected low-alloy structural steels were studied using cyclic and continuous water fog tests. It is shown that continuous wetting of steel surfaces results in the formation of magnetite as the main constituent of rust formed. However, in wet/dry fog cycles with drying periods of more than 2 min in every 30-min cycle, a defective spinel phase similar to [gamma]-Fe[sub 2]O[sub 3] forms. Continuous wetting and fast rusting appear to be the main criteria for the stability of magnetite. Both the magnetite and the defective spinel phase [gamma]-Fe[sub 2]O[sub 3] transform to [gamma]-FeOOH first and to [alpha]-FeOOH ultimately under repeated drying conditions, mostly controlled by electrochemical oxidation process. Magnetite formed on steel surface in crevices in the open atmosphere is held stable by the lack of electrochemical oxidation conditions or activation energy for spontaneous oxidation in air.

  3. Fuel to Oxidizer Ratio Effects on La2O3 Nano Particles

    NASA Astrophysics Data System (ADS)

    Reddy, G. Balanagi; Bikshalu, K.; Rao, K. Venkateswara; Aparna, Y.; Shekar, M. Chandra; Prasad, K. Eswara

    2011-07-01

    The present paper deals with the synthesis of lanthanum oxide or lanthana (La2O3) nano particles. Lanthana nano particles were synthesized using chemical combustion synthesis based on glycine (C2H5NO2). The fuel glycine is varied for different fuel to oxidizer ratios (O/F). The starting material (oxidizer) is the lanthanum nitrate (La(NO3)3.9H2O). These lanthana nano particles were characterized by thermogravimetry (TG) and differential thermal analysis (DTA) for thermal studies, X-ray diffraction (XRD) for crystal structure analysis, Scanning electron microscopy (SEM) for morphological and particle size determination.

  4. Rotating Flow of Magnetite-Water Nanofluid over a Stretching Surface Inspired by Non-Linear Thermal Radiation

    PubMed Central

    Mustafa, M.; Mushtaq, A.; Hayat, T.; Alsaedi, A.

    2016-01-01

    Present study explores the MHD three-dimensional rotating flow and heat transfer of ferrofluid induced by a radiative surface. The base fluid is considered as water with magnetite-Fe3O4 nanoparticles. Novel concept of non-linear radiative heat flux is considered which produces a non-linear energy equation in temperature field. Conventional transformations are employed to obtain the self-similar form of the governing differential system. The arising system involves an interesting temperature ratio parameter which is an indicator of small/large temperature differences in the flow. Numerical simulations with high precision are determined by well-known shooting approach. Both uniform stretching and rotation have significant impact on the solutions. The variation in velocity components with the nanoparticle volume fraction is non-monotonic. Local Nusselt number in Fe3O4–water ferrofluid is larger in comparison to the pure fluid even at low particle concentration. PMID:26894690

  5. Rotating Flow of Magnetite-Water Nanofluid over a Stretching Surface Inspired by Non-Linear Thermal Radiation.

    PubMed

    Mustafa, M; Mushtaq, A; Hayat, T; Alsaedi, A

    2016-01-01

    Present study explores the MHD three-dimensional rotating flow and heat transfer of ferrofluid induced by a radiative surface. The base fluid is considered as water with magnetite-Fe3O4 nanoparticles. Novel concept of non-linear radiative heat flux is considered which produces a non-linear energy equation in temperature field. Conventional transformations are employed to obtain the self-similar form of the governing differential system. The arising system involves an interesting temperature ratio parameter which is an indicator of small/large temperature differences in the flow. Numerical simulations with high precision are determined by well-known shooting approach. Both uniform stretching and rotation have significant impact on the solutions. The variation in velocity components with the nanoparticle volume fraction is non-monotonic. Local Nusselt number in Fe3O4-water ferrofluid is larger in comparison to the pure fluid even at low particle concentration. PMID:26894690

  6. Aqueous dispersions of magnetite nanoparticles with NH3+ surfaces for magnetic manipulations of biomolecules and MRI contrast agents.

    PubMed

    Shieh, Dar-Bin; Cheng, Fong-Yu; Su, Chia-Hao; Yeh, Chen-Sheng; Wu, Ming-Ting; Wu, Ya-Na; Tsai, Chiau-Yuang; Wu, Chao-Liang; Chen, Dong-Hwang; Chou, Chen-Hsi

    2005-12-01

    In the current study, amine surface modified iron-oxide nanoparticles of 6 nm diameter without polymer coating were fabricated in an aqueous solution by organic acid modification as an adherent following chemical coprecipitation. Structure and the superparamagnetic property of magnetite nanoparticles were characterized by selected area electron diffraction (SAED) and superconducting quantum interference measurement device (SQUID). X-ray photoelectron spectrometer (XPS) and zeta potential measurements revealed cationic surface mostly decorated with terminal -NH(3)(+). This feature enables them to function as a magnetic carrier for nucleotides via electrostatic interaction. In addition, Fe(3)O(4)/trypsin conjugates with well-preserved functional activity was demonstrated. The nanoparticles displayed excellent in vitro biocompatibility. The NMR and the in vitro MRI measurements showed significantly reduced water proton relaxation times of both T(1) and T(2). Significantly reduced T(2) and T(2)*-weighted signal intensity were observed in a 1.5 T clinical MR imager. In vivo imaging contrast effect showed a fast and prolonged inverse contrast effect in the liver that lasted for more than 1 week. In addition, it was found that the spherical Fe(3)O(4) assembled as rod-like configuration through an aging process in aqueous solution at room temperature. Interestingly, TEM observation of the liver tissue revealed the rod-like shape but not the spherical-type nanoparticles being taken up by the Kupffer cells 120 h after tail vein infusion. Combining these results, we have demonstrated the potential applications of the newly synthesized magnetite nanoparticles in a broad spectrum of biomedical applications.

  7. Post-adsorption process of Yb phosphate nano-particle formation by Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Jiang, MingYu; Ohnuki, Toshihiko; Tanaka, Kazuya; Kozai, Naofumi; Kamiishi, Eigo; Utsunomiya, Satoshi

    2012-09-01

    In this study, we have investigated the post-adsorption process of ytterbium (Yb) phosphate nano-particle formation by Saccharomyces cerevisiae (yeast). The yeast grown in P-rich medium were exposed to 1.44 × 10-4 mol/L Yb(III) solution for 2-120 h, and 2 months at 25 ± 1 °C at an initial pH of 3, 4, or 5, respectively. Ytterbium concentrations in solutions decreased as a function of exposure time. Field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (FESEM), transmission electron microscopy (TEM), and synchrotron-based extended X-ray absorption fine structure (EXAFS) analyses revealed that nano-sized blocky Yb phosphate with an amorphous phase formed on the yeast cells surfaces in the solutions with Yb. These nano-sized precipitates that formed on the cell surfaces remained stable even after 2 months of exposure at 25 ± 1 °C around neutral pHs. The EXAFS data revealed that the chemical state of the accumulated Yb on the cell surfaces changed from the adsorption on both phosphate and carboxyl sites at 30 min to Yb phosphate precipitates at 5 days, indicating the Yb-phosphate precipitation as a major post-adsorption process. In addition, the precipitation of Yb phosphate occurred on cell surfaces during 7 days of exposure in Yb-free solution after 2 h of exposure (short-term Yb adsorption) in Yb solution. These results suggest that the released P from the inside of yeast cells reacted with adsorbed Yb on cell surfaces, resulting in the formation of Yb precipitates, even though no P was added to the exposure solution. In an abiotic system, the EXAFS data showed that the speciation of sorbed Yb on the reference materials, carboxymethyl cellulose and Ln resin, did not change even when the Yb was exposed to P solution, without forming Yb phosphate precipitates. This result strongly suggests that the cell surface of the yeast plays an important role in the Yb-phosphate precipitation process, not only as a carrier of the

  8. Fe adsorption on hematite (α-Fe{sub 2}O{sub 3}) (0001) and magnetite (Fe{sub 3}O{sub 4}) (111) surfaces

    SciTech Connect

    Pabisiak, Tomasz; Kiejna, Adam

    2014-10-07

    The structure and electronic properties of different terminations of hematite (0001) and magnetite (111) surfaces upon submonolayer Fe adsorption were studied using the spin-polarized density functional theory (DFT) including the Hubbard correction term U (DFT+U). On both oxides the Fe atoms were adsorbed on the most stable iron and oxygen terminated surfaces. The results show that Fe atoms bind strongly both to hematite and magnetite surfaces, however, the binding is distinctly stronger at the oxygen than at the iron terminated surfaces. For both oxides and surface terminations the binding energy of the Fe decreases with increasing coverage, which indicates substantial repulsive interactions between Fe adatoms. On the hematite surface, the most stable sites for Fe adsorption are bulk continuation sites which result in formation of the Fe-rich terminations. On the magnetite surface, the bulk continuation site is favored only for Fe adsorption on the oxygen terminated surface while on the iron terminated one Fe adsorbs in a position closer to the surface iron layer. Submonolayer coverages of Fe modify substantially the surface electronic structure of the oxides and, depending on the termination, can change its character from half-metallic to insulating one, and vice versa.

  9. Preparation of tourmaline nano-particles through a hydrothermal process and its infrared emission properties.

    PubMed

    Xue, Gang; Han, Chao; Liang, Jinsheng; Wang, Saifei; Zhao, Chaoyue

    2014-05-01

    Tourmaline nano-particles were successfully prepared via a hydrothermal process using HCl as an additive. The reaction temperature (T) and the concentration of HCI (C(HCl)) had effects on the size and morphology of the tourmaline nano-particles. The optimum reaction condition was that: T = 180 degrees C and C(HCl) = 0.1 mol/l. The obtained nano-particles were spherical with the diameter of 48 nm. The far-infrared emissivity of the product was 0.923. The formation mechnism of the tourmaline nano-particles might come from the corrosion of grain boundary between the tourmaline crystals in acidic hydrothermal conditions and then the asymmetric contraction of the crystals. PMID:24734669

  10. Preparation of tourmaline nano-particles through a hydrothermal process and its infrared emission properties.

    PubMed

    Xue, Gang; Han, Chao; Liang, Jinsheng; Wang, Saifei; Zhao, Chaoyue

    2014-05-01

    Tourmaline nano-particles were successfully prepared via a hydrothermal process using HCl as an additive. The reaction temperature (T) and the concentration of HCI (C(HCl)) had effects on the size and morphology of the tourmaline nano-particles. The optimum reaction condition was that: T = 180 degrees C and C(HCl) = 0.1 mol/l. The obtained nano-particles were spherical with the diameter of 48 nm. The far-infrared emissivity of the product was 0.923. The formation mechnism of the tourmaline nano-particles might come from the corrosion of grain boundary between the tourmaline crystals in acidic hydrothermal conditions and then the asymmetric contraction of the crystals.

  11. Synthesis of stabilized myrrh-capped hydrocolloidal magnetite nanoparticles.

    PubMed

    Atta, Ayman M; Al-Lohedan, Hamad A; Al-Hussain, Sami A

    2014-01-01

    Herein we report a new method for synthesizing stabilized magnetic nanoparticle (MNP) colloids. A new class of monodisperse water-soluble magnetite nano-particles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The ferrous and ferric ions were hydrolyzed at low temperature at pH 9 in the presence of iodine to produce iron oxide nanoparticles. The natural product myrrh gum was used as capping agent to produce highly dispersed coated magnetite nanoparticles. The structure and morphology of the magnetic nanogel was characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM), and X-ray diffraction (XRD) was used to examine the crystal structure of the produced magnetite nanoparticles. PMID:25090117

  12. Synthesis of stabilized myrrh-capped hydrocolloidal magnetite nanoparticles.

    PubMed

    Atta, Ayman M; Al-Lohedan, Hamad A; Al-Hussain, Sami A

    2014-07-31

    Herein we report a new method for synthesizing stabilized magnetic nanoparticle (MNP) colloids. A new class of monodisperse water-soluble magnetite nano-particles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The ferrous and ferric ions were hydrolyzed at low temperature at pH 9 in the presence of iodine to produce iron oxide nanoparticles. The natural product myrrh gum was used as capping agent to produce highly dispersed coated magnetite nanoparticles. The structure and morphology of the magnetic nanogel was characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM), and X-ray diffraction (XRD) was used to examine the crystal structure of the produced magnetite nanoparticles.

  13. Preparation of silver nano-particles immobilized onto chitin nano-crystals and their application to cellulose paper for imparting antimicrobial activity.

    PubMed

    Li, Zhihan; Zhang, Ming; Cheng, Dong; Yang, Rendang

    2016-10-20

    Immobilized silver nano-particles (Ag NPs) possess excellent antimicrobial properties due to their unique surface characteristics. In this paper, immobilized silver nano-particles were synthesized in the presence of chitin nano-crystals (CNC) based on the Tollens mechanism (reduction of silver ion by aldehydes in the chitosan oligosaccharides (COS)) under microwave-assisted conditions. The prepared Ag NPs-loaded CNC nano-composites were then applied onto the paper surface via coating for the preparation of antibacterial paper. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results confirmed that the Ag NPs were immobilized onto the CNC. The transmission electron microscope (TEM) and scanning electron microscopy (SEM) results further revealed that the spherical Ag NPs (5-12nm) were well dispersed on the surface of CNC. The coated paper made from the Ag NPs-loaded CNC nano-composites exhibited a high effectiveness of the antibacterial activity against E. coli or S. aureus.

  14. Preclinical spectral computed tomography of gold nano-particles

    NASA Astrophysics Data System (ADS)

    Roessl, Ewald; Cormode, David; Brendel, Bernhard; Jürgen Engel, Klaus; Martens, Gerhard; Thran, Axel; Fayad, Zahi; Proksa, Roland

    2011-08-01

    Today's state-of the art clinical computed tomography (CT) scanners exclusively use energy-integrating, scintillation detector technology, despite the fact that a part of the information carried by the transmitted X-ray photons is lost during the detection process. Room-temperature semiconductors, like CdTe or CZT, operated in energy-sensitive photon-counting mode provide information about the energy of every single X-ray detection event. This capability allows novel, promising approaches to selectively image abnormal tissue types like cancerous tissue or atherosclerotic plaque with the CT modality.In this article we report on recent dual K-edge imaging results obtained in the domain of pre-clinical, energy-sensitive photon-counting CT. In this approach, the tuning of threshold levels in the detector electronics to the K-edge energy in the attenuation of contrast agents (CA) offers highly specific, quantitative imaging of the distribution of the CA on top of the conventional, morphological image information. The combination of the high specificity of the K-edge imaging technique together with the powerful tool of targeting specific diseases in the human body by dedicated contrast materials might enrich the CT modality with capabilities of functional imaging known from the nuclear medicine imaging modalities, e.g., positron-emission-tomography but with the additional advantage of high spatial and temporal resolution. We also discuss briefly the technological difficulties to be overcome when translating the technique to human CT imaging and present the results of simulations indicating the feasibility of the K-edge imaging of vulnerable plaque using targeted gold nano-particles as contrast materials. Our experiments in the pre-clinical domain show that dual-K edge imaging of iodine and gold-based CAs is feasible while our simulations for the imaging of gold CAs in the clinical case support the future possibility of translating the technique to human imaging.

  15. Comparative study of three magnetic nano-particles (FeSO4, FeSO4/SiO2, FeSO4/SiO2/TiO2) in plasmid DNA extraction.

    PubMed

    Rahnama, H; Sattarzadeh, A; Kazemi, F; Ahmadi, N; Sanjarian, F; Zand, Z

    2016-11-15

    Recent updates on Magnetic Nano-Particles (MNPs) based separation of nucleic acids have received more attention due to their easy manipulation, simplicity, ease of automation and cost-effectiveness. It has been indicated that DNA molecules absorb on solid surfaces via hydrogen-bonding, and hydrophobic and electrostatic interactions. These properties highly depend on the surface condition of the solid support. Therefore, surface modification of MNPs may enhance their functionality and specification. In the present study, we functionalized Fe3O4 nano-particle surface utilizing SiO2 and TiO2 layer as Fe3O4/SiO2 and Fe3O4/SiO2/TiO2 and then compare their functionality in the adsorption of plasmid DNA molecules with the naked Fe3O4 nano-particles. The result obtained showed that the purity and amount of DNA extracted by Fe3O4 coated by SiO2 or SiO2/TiO2 were higher than the naked Fe3O4 nano-particles. Furthermore, we obtained pH 8 and 1.5 M NaCl as an optimal condition for desorption of DNA from MNPs. The result further showed that, 0.2 mg nano-particle and 10 min at 55 °C are the optimal conditions for DNA desorption from nano-particles. In conclusion, we recommended Fe3O4/SiO2/TiO2 as a new MNP for separation of DNA molecules from biological sources. PMID:27592192

  16. Comparative study of three magnetic nano-particles (FeSO4, FeSO4/SiO2, FeSO4/SiO2/TiO2) in plasmid DNA extraction.

    PubMed

    Rahnama, H; Sattarzadeh, A; Kazemi, F; Ahmadi, N; Sanjarian, F; Zand, Z

    2016-11-15

    Recent updates on Magnetic Nano-Particles (MNPs) based separation of nucleic acids have received more attention due to their easy manipulation, simplicity, ease of automation and cost-effectiveness. It has been indicated that DNA molecules absorb on solid surfaces via hydrogen-bonding, and hydrophobic and electrostatic interactions. These properties highly depend on the surface condition of the solid support. Therefore, surface modification of MNPs may enhance their functionality and specification. In the present study, we functionalized Fe3O4 nano-particle surface utilizing SiO2 and TiO2 layer as Fe3O4/SiO2 and Fe3O4/SiO2/TiO2 and then compare their functionality in the adsorption of plasmid DNA molecules with the naked Fe3O4 nano-particles. The result obtained showed that the purity and amount of DNA extracted by Fe3O4 coated by SiO2 or SiO2/TiO2 were higher than the naked Fe3O4 nano-particles. Furthermore, we obtained pH 8 and 1.5 M NaCl as an optimal condition for desorption of DNA from MNPs. The result further showed that, 0.2 mg nano-particle and 10 min at 55 °C are the optimal conditions for DNA desorption from nano-particles. In conclusion, we recommended Fe3O4/SiO2/TiO2 as a new MNP for separation of DNA molecules from biological sources.

  17. Electron Temperature and Density Variation Due To Temporal Evolution of Nano Particle Growth in RF Silane Plasma

    SciTech Connect

    Chai, K. B.; Seon, C. R.; Choe, W.; Park, S.; Chung, C. W.

    2008-09-07

    Nano particles, generated in various processing plasmas, have been extensively studied for applications in the fabrication of microelectronics devices. However, studies to find the relation between the particle parameters (particle size and density) and the plasma parameters (electron temperature and density) have been limited because of the availability of the appropriate diagnostic method. The utilization of Langmuir probes are limited in many cases due to the probe tip contamination and the presence of abundant negative ions and particles. In this work, measurements of electron temperature and ion density were performed in rf silane plasmas using a floating probe, which allows an accurate measurement even under harsh plasma environments. The size and density of nano particles were measured by the laser light scattering and the laser extinction method at various gas pressures. It was found that the temporal evolution of the particle growth played a significant role in changing the plasma parameters due to the electron and ion fluxes to the particles. The relation between the plasma parameters and the particle parameters was described by a power balance equation including the power loss to the particle surface.

  18. Coercivity enhancement of recycled Nd-Fe-B sintered magnets by grain boundary diffusion with DyH3 nano-particles

    NASA Astrophysics Data System (ADS)

    Ji, Weixiao; Liu, Weiqiang; Yue, Ming; Zhang, Dongtao; Zhang, Jiuxing

    2015-11-01

    The waste VCM magnets were disassembled from hard disk. After removing the coating of nickel by electrochemical method, the waste VCM magnets were recycled by grain boundary diffusion with DyH3 nano-particles. Compared to that of the original magnet, the coercivity of recycled magnets increases by 11.81 kOe, while the remanence keeps almost invariant. Investigation shows that Dy is preferentially enriched as (Nd,Dy)2Fe14B phase in the surface region of the Nd2Fe14B matrix grains indicated by the remarkable enhancement of the magneto-crystalline anisotropy field of the magnet. As a result, the magnet diffused with a small amount of DyH3 nano-particles possesses enhanced coercivity without remarkably sacrificing its magnetization.

  19. Direct Write Processing of Multi-micron Thickness Copper Nano-particle Paste on Flexible Substrates with 532 nm Laser Wavelength

    NASA Astrophysics Data System (ADS)

    Lopez-Espiricueta, Dunia; Fearon, Eamonn; Edwardson, Stuart; Dearden, Geoffrey

    The Laser Assisted Direct Write (LA-DW) method has been implemented in the development of different markets and material processing, recently also used for creating Printed Circuit Boards (PCB) or electrical circuitry. The process consists in the deposition of metallic nano-particle (NP) inks, which are afterwards cured or sintered by laser irradiation, thus creating conductive pathways; advantages are speed, accuracy and the protection of the heat affected zone (HAZ). This research will study the behaviour of the heat dissipation relatively within the Nano-particle Copper paste after being irradiated with 1064 nm and 532 nm wavelengths, research will be developed on different widths and depths deposited onto flat surfaces such as flexible PET. Comparisons to be made between resistivity results obtained from different wavelengths.

  20. A novel, generic, electroanalytical immunoassay format utilising silver nano-particles as a bio-label.

    PubMed

    Porter, Robert; Kabil, Alena; Forstern, Camilla; Slevin, Christopher; Kouwenberg, Katherine; Szymanski, Mateusz; Birch, Brian

    2009-01-01

    The aim of this study was to evaluate a novel, generic, sensitive electroanalytical platform method for binding reactions, such as immuno or DNA assays. It was thought that silver nano-particles of 40 nM when attached to the analyte of interest would give an electroanalytical amplification of approx. 10(6) resulting from silver ions produced by dissolution of the nano-particles by a mild chemical oxidant such as ferricyanide. Ferricyanide has been widely used in biochemical measurement and has been shown to relatively stable in a biosensor device. Here we have demonstrated the use of silver nano-particles as a bio-conjugate in a 96 well sandwich assay format for measuring human chorionic gonadotropin (hCG) to a concentration of 0.2 mIU.

  1. Catalytic Activity and Thermal Stability of Arc Plasma Deposited Pt Nano-Particles on CeO2-Al2O3.

    PubMed

    Jeong, Young Eun; Kumar, Pullur Anil; Choi, Hee Lack; Lee, Kwan-Young; Ha, Heon Phil

    2015-11-01

    In this study, catalytic activity and thermal stability of the arc plasma deposited (APD) Pt nano-particles on A12O3 and CeO2-Al2O3 were compared with that of the conventionally prepared Pt/Al2O3. All the catalysts were characterized by BET-surface area, transmission electron microscopy, X-ray photoelectron spectroscopy, CO-pulse chemisorption, H2-temperarture programmed reduction and X-ray absorption near edge spectroscopy. Through the quantum chemical calculations of different metal oxide support, CeO2 was identified as a suitable anchoring material with high energy level between the Pt species (Pt(0) and PtO(x)) on ceria. Subsequently, the results of XPS and XANES revealed the presence of abundant Pt(0) metal species in APD catalysts. The addition of ceria to Al2O3 support enhanced the dispersion of Pt nano-particles. The H2-TPR of Pt/CeO2-Al2O3 (APD) catalyst showed high-temperature reduction peaks corresponding to the interaction of Pt with ceria on alumina by Pt-O-Ce. Consequently, the Pt nano-particles deposited on CeO2-Al2O3 by APD attained strong thermal resistance at high temperatures. In addition, superior catalytic activities for CO and C3H6 oxidation and NO(x) reduction were obtained for the Pt/CeO2- Al2O3 (APD) catalyst.

  2. Improved light extraction with nano-particles offering directional radiation diagrams

    SciTech Connect

    Jouanin, A.; Hugonin, J. P.; Besbes, M.; Lalanne, P.

    2014-01-13

    We propose a unique approach for light extraction, using engineered nano-particles to efficiently decouple the light guided in transverse-magnetic guided modes into free-space radiation modes that leak out normally to the thin-film stacks. The underlying mechanism takes advantage of a small electric field variation at the nano-particle scale and induces a “polarization conversion,” which renders the induced dipole moment perpendicular to the polarization of the incident light. Our analysis is supported by 2D fully vectorial computational results. Potential applications for light emitting or photovoltaic devices are outlined.

  3. Synthesis and characterization of pure Cu and CuO nano particles by solution combustion synthesis

    NASA Astrophysics Data System (ADS)

    Patil, Sarika P.; Patil, Shital P.; Puri, V. R.; Jadhav, L. D.

    2013-06-01

    The Cu and CuO nano particles were prepared by using solution combustion technique with copper nitrate as an oxidizer and citric acid as the fuel. The solution combustion synthesis (SCS) method provides the advanced ceramics, nano-composites and catalyst materials and also produces homogeneous, crystalline and un-agglomerated multi-component oxides. The pure CuO nano particles were prepared for rich oxidant to fuel ratio. As prepared powder were further calcined at 600 °C for 2 hrs. The powder was characterized by different techniques such as XRD, TG-DTA, and SEM etc.

  4. Impact of the excitation source and plasmonic material on cylindrical active coated nano-particles.

    PubMed

    Arslanagic, Samel; Liu, Yan; Malureanu, Radu; Ziolkowski, Richard W

    2011-01-01

    Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced in the dielectric part of the nano-particle, whereas three different plasmonic materials (silver, gold, and copper) are employed and compared for the nano-shell layers.

  5. Biological Experiments in Microgravity Conditions Using Magnetic Micro- and Nano-Particles

    NASA Astrophysics Data System (ADS)

    Nechitailo, Galina S.; Kuznetsov, Anatoli; Kuznetsov, Oleg

    2016-07-01

    even for weak magnetic objects, and can have significant effects on multiple processes in living cells/organisms. It was reported, that such high gradient magnetic fields can affect cell differentiation and cell proliferation processes in ground-based experiments. To prevent oxidation of ultradisperse ferromagnetic particles in aqueous media, it is beneficial to coat their surface with carbon. Suitable protected metallic micro- and nano-particles can be produced by a variety of techniques (CVD, plasmachemistry, joint grinding, etc.). Ferro-carbon particles produced by plasmachemical technique have high sorption capacities for various organic and inorganic compounds (as well as for various cell metabolites), can be formed in rather stable aqueous suspensions, and be controlled (e.g., sedimented) by a magnetic field. This makes these particles a very interesting research tool. In our opinion, biological experiments with ferro-carbon nano-structured particles in microgravity will generate important scientific data and will allow creating new methods of negating the adverse effects of microgravity on living systems.

  6. Core-shell magnetite-silica dithiocarbamate-derivatised particles achieve the Water Framework Directive quality criteria for mercury in surface waters.

    PubMed

    Lopes, C B; Figueira, P; Tavares, D S; Lin, Z; Daniel-da-Silva, A L; Duarte, A C; Rocha, J; Trindade, T; Pereira, E

    2013-09-01

    The sorption capacity of nanoporous titanosilicate Engelhard titanosilicate number 4 (ETS-4) and silica-coated magnetite particles derivatised with dithiocarbamate groups towards Hg(II) was evaluated and compared in spiked ultra-pure and spiked surface-river water, for different batch factors. In the former, and using a batch factor of 100 m(3)/kg and an initial Hg(II) concentrations matching the maximum allowed concentration in an effluent discharge, both materials achieve Hg(II) uptake efficiencies in excess of 99 % and a residual metal concentration lower than the guideline value for drinking water quality. For the surface-river water and the same initial concentration, the Hg(II) uptake efficiency of magnetite particles is outstanding, achieving the quality criteria established by the Water Framework Directive (concerning Hg concentration in surface waters) using a batch factor of 50 m(3)/kg, while the efficiency of ETS-4 is significantly inferior. The dissimilar sorbents' Hg(II) removal efficiency is attributed to different uptake mechanisms. This study also highlights the importance of assessing the effective capacity of the sorbents under realistic conditions in order to achieve trustable results.

  7. Magnetite and its production

    SciTech Connect

    Koebbe, E.R.

    1993-12-31

    The supply of high quality magnetite for the cleaning of coal using dense medium cyclones and vessels is of concern to all coal preparation operations. This paper describes the production of high purity magnetite (Fe{sub 3}O{sub 4}) from a domestic underground mining operation in Missouri, Pea Ridge Iron Ore Company. Emphasis will be placed on the mining and processing of the magnetite ore into the various magnetite products required by coal preparation plants.

  8. ELECTROSTATIC CHARGE ON NANO-PARTICLES ACTIVATES CNS MACROPHAGES (MICROGLIA).

    EPA Science Inventory

    Nanometer size particles carry free radical activity on their surface and can produce oxidative stress (OS)-mediated damage upon impact to target cells. The initiating event of phage cell activation (i.e., the oxidative burst) is unknown, although many proximal events have been i...

  9. Peristaltic flow of a micropolar fluid with nano particles in small intestine

    NASA Astrophysics Data System (ADS)

    Akbar, Noreen Sher; Nadeem, S.

    2013-12-01

    The present article analyzed the peristaltic flow of a nanofluid in a uniform tube for micropolar fluid. The governing equations for proposed model are developed in cylindrical coordinates system. The flow is discussed in a wave frame of reference moving with velocity of the wave c. Under the assumptions of longwave length the reduced coupled nonlinear differential equations of momentum, energy, and concentrations are solved by Homotopy perturbation method is used to get the solutions for velocity, temperature, nano particle, microrotation component. The solutions consists Brownian motion number N b, thermophoresis number N t, local temperature Grashof number B r and local nano particle Grashof number G r . The effects of various parameters involved in the problem are investigated for pressure rise, pressure gradient, temperature and concentration profile. Five different waves are taken into account for analysis. Streamlines have been plotted at the end of the article.

  10. Neuroprotective effect of curcumin-loaded lactoferrin nano particles against rotenone induced neurotoxicity.

    PubMed

    Bollimpelli, V Satish; Kumar, Prashant; Kumari, Sonali; Kondapi, Anand K

    2016-05-01

    Curcumin is known to have neuroprotective role and possess antioxidant, anti-inflammatory activities. Rotenone, a flavonoid induced neurotoxicity in dopaminergic cells is being widely studied in Parkinson's Disease (PD) research. In the present study, curcumin loaded lactoferrin nano particles prepared by sol-oil chemistry were used to protect dopaminergic cell line SK-N-SH against rotenone induced neurotoxicity. These curcumin loaded nano particles were of 43-60 nm diameter size and around 100 nm hydrodynamic size as assessed by transmission electron microscopy, atomic force microscopy and dynamic light scattering analysis respectively. The encapsulation efficiency was 61.3% ± 2.4%. Cellular uptake of curcumin through these nano particles was confirmed by confocal imaging and spectrofluorimetric analysis. The curcumin loaded lactoferrin nanoparticles showed greater intracellular drug uptake, sustained retention and greater neuroprotection than soluble counterpart. Neuroprotective activity was characterized through viability assays and by estimating ROS levels. Furthermore rotenone induced PD like features were characterized by decrease in tyrosine hydroxylase expression and increase in α-synuclein expression. Taken together curcumin loaded lactoferrin nanoparticles could be a promising drug delivery strategy against neurotoxicity in dopaminergic neurons. PMID:26826319

  11. Effect of Silver Nano-particles on Tensile Strength of Acrylic Resins

    PubMed Central

    Ghaffari, Tahereh; Hamedi-rad, Fahimeh

    2015-01-01

    Background and aims. Polymethyl methacrylate (PMMA) is widely used for the fabrication of removable prostheses. Silver nano-particles (AgNps) have been added to PMMA because of their antimicrobial properties, but their effect on the mechanical properties of PMMA is unknown. The aim of this study was to investigate the effects of AgNps on the tensile strength of PMMA. Materials and methods. For this study, 12 specimens were prepared and divided into two groups. Group 1 included PMMA without AgNps and group 2 included PMMA mixed with 5 wt% of AgNps. Tensile strength of the specimens was measured by Zwick Z100 apparatus. Statistical analysis was carried out by SPSS using t-test. Statistical significance was defined at P<0.05. Results. This study showed that the mean tensile strength of PMMA in group 2 was significantly lower than that in group 1. Therefore, the tensile strength decreased significantly after incorporation of silver nano-particles. Conclusion. Within the limitations of this study, tensile strength of acrylic resin specimens was influenced by silver nano-particles. PMID:25973153

  12. Effects of Natural Organic Matter on Stability, Transport and Deposition of Engineered Nano-particles in Porous Media

    EPA Science Inventory

    The interaction of nano-particles and organic substances, like natural organic matter, could have significant influence on the fate, transport and bioavailability of toxic substances. Natural organic matter (NOM) is a mixture of chemically complex polyelectrolytes with varying m...

  13. Preparation of silver nano-particles immobilized onto chitin nano-crystals and their application to cellulose paper for imparting antimicrobial activity.

    PubMed

    Li, Zhihan; Zhang, Ming; Cheng, Dong; Yang, Rendang

    2016-10-20

    Immobilized silver nano-particles (Ag NPs) possess excellent antimicrobial properties due to their unique surface characteristics. In this paper, immobilized silver nano-particles were synthesized in the presence of chitin nano-crystals (CNC) based on the Tollens mechanism (reduction of silver ion by aldehydes in the chitosan oligosaccharides (COS)) under microwave-assisted conditions. The prepared Ag NPs-loaded CNC nano-composites were then applied onto the paper surface via coating for the preparation of antibacterial paper. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results confirmed that the Ag NPs were immobilized onto the CNC. The transmission electron microscope (TEM) and scanning electron microscopy (SEM) results further revealed that the spherical Ag NPs (5-12nm) were well dispersed on the surface of CNC. The coated paper made from the Ag NPs-loaded CNC nano-composites exhibited a high effectiveness of the antibacterial activity against E. coli or S. aureus. PMID:27474631

  14. Functional biocompatible magnetite-cellulose nanocomposite fibrous networks: Characterization by fourier transformed infrared spectroscopy, X-ray powder diffraction and field emission scanning electron microscopy analysis

    NASA Astrophysics Data System (ADS)

    Habibi, Neda

    2015-02-01

    The preparation and characterization of functional biocompatible magnetite-cellulose nano-composite fibrous material is described. Magnetite-cellulose nano-composite was prepared by a combination of the solution-based formation of magnetic nano-particles and subsequent coating with amino celluloses. Characterization was accomplished using X-ray powder diffraction (XRD), fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. The peaks of Fe3O4 in the XRD pattern of nanocomposite confirm existence of the nanoparticles in the amino cellulose matrix. Magnetite-cellulose particles exhibit an average diameter of roughly 33 nm as demonstrated by field emission scanning electron microscopy. Magnetite nanoparticles were irregular spheres dispersed in the cellulose matrix. The vibration corresponding to the Nsbnd CH3 functional group about 2850 cm-1 is assigned in the FTIR spectra. Functionalized magnetite-cellulose nano-composite polymers have a potential range of application as targeted drug delivery system in biomedical field.

  15. Transmission Electron Microscopy of Magnetite Plaquettes in Orgueil

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Han, J.; Zolensky, M.

    2016-01-01

    Magnetite sometimes takes the form of a plaquette - barrel-shaped stack of magnetite disks - in carbonaceous chondrites (CC) that show evidence of aqueous alteration. The asymmetric nature of the plaquettes caused Pizzarello and Groy to propose magnetite plaquettes as a naturally asymmetric mineral that can indroduce symmetry-breaking in organic molecules. Our previous synchrotron X-ray computed microtomography (SXRCT) and electron backscatter diffraction (EBSD) analyses of the magnetite plaquettes in fifteen CCs indicate that magnetite plaquettes are composed of nearly parallel discs, and the crystallographic orientations of the discs change around a rotational axis normal to the discs surfaces. In order to further investigate the nanostructures of magnetite plaquettes, we made two focused ion beam (FIB) sections of nine magnetite plaquettes from a thin section of CI Orgueil for transmission electron microscope (TEM) analysis. The X-ray spectrum imaging shows that the magnetite discs are purely iron oxide Fe3O4 (42.9 at% Fe and 57.1 at% O), which suggest that the plaquettes are of aqueous origin as it is difficult to form pure magnetite as a nebular condensate. The selected area electron diffraction (SAED) patterns acquired across the plaquettes show that the magnetite discs are single crystals. SEM and EBSD analyses suggest that the planar surfaces of the magnetite discs belong to the {100} planes of the cubic inverse spinel structure, which are supported by our TEM observations. Kerridge et al. suggested that the epitaxial relationship between magnetite plaquette and carbonate determines the magnetite face. However, according to our TEM observation, the association of magnetite with porous networks of phyllosilicate indicates that the epitaxial relationship with carbonate is not essential to the formation of magnetite plaquettes. It was difficult to determine the preferred rotational orientation of the plaquettes due to the symmetry of the cubic structure

  16. Immobilized molybdenum-thiosemicarbazide Schiff base complex on the surface of magnetite nanoparticles as a new nanocatalyst for the epoxidation of olefins

    NASA Astrophysics Data System (ADS)

    Mohammadikish, M.; Masteri-Farahani, M.; Mahdavi, S.

    2014-03-01

    In this work, a new magnetically recoverable nanocatalyst was developed by immobilization of thiosemicarbazide ligand on the surface of silica coated magnetite nanoparticles (SCMNPs) through Schiff base condensation and followed complexation with MoO2(acac)2. Characterization of the prepared nanocatalyst was performed with different physicochemical methods such as Fourier transform infrared (FT-IR) and atomic absorption spectroscopies, X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The prepared catalyst catalyzed the epoxidation of olefins and allyl alcohols with tert-butyl hydroperoxide (TBHP) and cumene hydroperoxide (CHP) quantitatively with excellent selectivity toward the corresponding epoxides under mild reaction conditions.

  17. Conductive polymer/reduced graphene oxide/Au nano particles as efficient composite materials in electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Shabani Shayeh, J.; Ehsani, A.; Ganjali, M. R.; Norouzi, P.; Jaleh, B.

    2015-10-01

    Polyaniline/reduced graphene oxide/Au nano particles (PANI/rGO/AuNPs) as a hybrid supercapacitor were deposited on a glassy carbon electrode (GCE) by cyclic voltammetry (CV) method as ternary composites and their electrochemical performance was evaluated in acidic medium. Scanning electron micrographs clearly revealed the formation of nanocomposites on the surface of the working electrode. Scanning electron micrographs (SEM) clearly revealed the formation of nanocomposites on the surface of working electrode. Different electrochemical methods including galvanostatic charge-discharge (CD) experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out in order to investigate the applicability of the system as a supercapacitor. Based on the cyclic voltammogram results obtained, PANI/rGO/AuNPs gave higher specific capacitance, power and energy values than PANI at a current density of 1 mA cm-2. Specific capacitance (SC) of PANI and PANI/rGO/AuNPs electrodes calculated using CV method are 190 and 303 F g-1, respectively. The present study introduces new nanocomposite materials for electrochemical redox capacitors with advantages including long life cycle and stability due to synergistic effects of each component.

  18. Photothermal investigation of the laser-induced modification of a single gold nano-particle in a silica film

    NASA Astrophysics Data System (ADS)

    Bertussi, B.; Natoli, J.-Y.; Commandre, M.; Rullier, J.-L.; Bonneau, F.; Combis, P.; Bouchut, P.

    2005-10-01

    Absorbing defects are believed to induce thermal effects that lead to laser damage, but the correlation between defect absorption and damage has not been clearly demonstrated. A model system consisting of a thin-film of silica containing gold nano-particles serving as nano-scale absorbing defects is investigated. For this purpose, a photothermal microscope coupled with a pulsed Nd:YAG laser allow us to follow the evolution of gold inclusion absorption before and after laser irradiation, without repositioning the sample. The "pre-damage" threshold had been defined previously as the laser fluence causing localized modification of the defect absorption without any surface modification. Thanks to the high sensitivity of photothermal microscopy, we find this threshold to be sevenfold less than that for the appearance of surface cracks. Numerical simulations are performed to evaluate the thermal evolution of the inclusion as a function of the laser fluence. From the comparison of experimental and theoretical results, we observe that the pre-damage threshold is closely linked to the melting of the metallic inclusion. Furthermore, the effect of repetitive shots on the evolution of gold inclusion absorption is examined experimentally and discussed.

  19. Using graphene nano-particle embedded in photonic crystal fiber for evanescent wave mode-locking of fiber laser.

    PubMed

    Lin, Yung-Hsiang; Yang, Chun-Yu; Liou, Jia-Hong; Yu, Chin-Ping; Lin, Gong-Ru

    2013-07-15

    A photonic crystal fiber (PCF) with high-quality graphene nano-particles uniformly dispersed in the hole cladding are demonstrated to passively mode-lock the erbium-doped fiber laser (EDFL) by evanescent-wave interaction. The few-layer graphene nano-particles are obtained by a stabilized electrochemical exfoliation at a threshold bias. These slowly and softly exfoliated graphene nano-particle exhibits an intense 2D band and an almost disappeared D band in the Raman scattering spectrum. The saturable phenomena of the extinction coefficient β in the cladding provides a loss modulation for the intracavity photon intensity by the evanescent-wave interaction. The evanescent-wave mode-locking scheme effectively enlarges the interaction length of saturable absorption with graphene nano-particle to provide an increasing transmittance ΔT of 5% and modulation depth of 13%. By comparing the core-wave and evanescent-wave mode-locking under the same linear transmittance, the transmittance of the graphene nano-particles on the end-face of SMF only enlarges from 0.54 to 0.578 with ΔT = 3.8% and the modulation depth of 10.8%. The evanescent wave interaction is found to be better than the traditional approach which confines the graphene nano-particles at the interface of two SMF patchcords. When enlarging the intra-cavity gain by simultaneously increasing the pumping current of 980-nm and 1480-nm pumping laser diodes (LDs) to 900 mA, the passively mode-locked EDFL shortens its pulsewidth to 650 fs and broadens its spectral linewidth to 3.92 nm. An extremely low carrier amplitude jitter (CAJ) of 1.2-1.6% is observed to confirm the stable EDFL pulse-train with the cladding graphene nano-particle based evanescent-wave mode-locking.

  20. A Proposed New "Nano-Particle" Theory of Light Based on Heat Transfer Principles

    NASA Astrophysics Data System (ADS)

    Das, Ashis

    2004-05-01

    Till date theories of light (visible and other radiations over electromagnetic scale) are divided into two classes viz. particle and wave theory. A particle on the classical view is a concentration of energy and other properties in space and time, whereas a wave is spread out over a larger region of space and time. It is generally understood that particle theory talks about corpuscles of finite measurable mass whereas wave theory is about packets of massless energy. This paper is a summary of thoughts collected so far on building a only - particle theory of light or other radiations assuming the Universe to be filled with "nano-particles" or very small particles and large particles. Although revolutionary and very thought provoking and unbelievably challenging the collected pointers outlined in this account appear very logical and mathematically sound although experiments are required to give this theory a firm basis for wide spread recognition in scientific forums. The major support for nano-particle theory comes from the observation of a term called "radiation pressure" which incorporates a sense of impact or pressure and therefore a force and so some particle impact although very feeble compared to normal large particle impact yielding noticeable effect on most pressure gauges measuring this. Similar feeble impact effects are possible in other phenomena like current, magnetic field etc. whose measurement will require very sensitive instruments. In this paper, I have explained that common method of estimation of momentum and heat transfer applied to very small mass nano-particles can explain at least three major phenomena of visble light viz. rectilinear propagation, reflection and refraction. Other phenomena such as diffraction, interference, polarization, diffusion etc will be presented in a future paper. This presentation is meant for collecting wide readership views to approve or deny this explanation of only particle theory after famous Compton scattering

  1. Mobilization and biodegradation of 2-methylnaphthalene by amphiphilic polyurethane nano-particle.

    PubMed

    Kim, Young-Bum; Kim, Ju-Young; Kim, Eun-ki

    2009-10-01

    Amphiphilic polyurethane (APU) nano-particle enhanced the mobilization of 2-methylnaphthalene (2-MNPT) in soil. Significant increase in the solubility of 2-MNPT was achieved. The molar solubilization ratio was 0.4 (mole 2-MNPT/mole APU). Simple precipitation of APU particle by 2 N CaCl(2) recovered 95% of APU particle and 92% of 2-MNPT simultaneously. Also, 2-MNPT, which was entrapped inside the APU particle, was directly degraded by Acinetobacter sp. as same efficiency as without APU particle. These results showed the potentials of APU particle in the mobilization and biodegradation of hydrophobic compounds from soil.

  2. Numerical analysis of micro- and nano-particle deposition in a realistic human upper airway.

    PubMed

    Farhadi Ghalati, Pejman; Keshavarzian, Erfan; Abouali, Omid; Faramarzi, Abolhassan; Tu, Jiyuan; Shakibafard, Alireza

    2012-01-01

    A computational model was developed for studying the flow field and particle deposition in a human upper airway system, including: nasal cavity, nasopharynx, oropharynx, larynx and trachea. A series of coronal CT scan images of a 24 year old woman was used to construct the 3D model. The Lagrangian and Eulerian approaches were used, respectively, to find the trajectories of micro-particles and concentration of nano-particles. The total and regional deposition fractions of micro/nanoparticles were evaluated and the major hot spots for the deposition of inhaled particles were found. PMID:22061046

  3. Mobilization and biodegradation of 2-methylnaphthalene by amphiphilic polyurethane nano-particle.

    PubMed

    Kim, Young-Bum; Kim, Ju-Young; Kim, Eun-ki

    2009-10-01

    Amphiphilic polyurethane (APU) nano-particle enhanced the mobilization of 2-methylnaphthalene (2-MNPT) in soil. Significant increase in the solubility of 2-MNPT was achieved. The molar solubilization ratio was 0.4 (mole 2-MNPT/mole APU). Simple precipitation of APU particle by 2 N CaCl(2) recovered 95% of APU particle and 92% of 2-MNPT simultaneously. Also, 2-MNPT, which was entrapped inside the APU particle, was directly degraded by Acinetobacter sp. as same efficiency as without APU particle. These results showed the potentials of APU particle in the mobilization and biodegradation of hydrophobic compounds from soil. PMID:19214790

  4. Some insights in the sonochemical preparation of cobalt nano-particles.

    PubMed

    Erasmus, Willem J; van Steen, Eric

    2007-09-01

    The preparation of cobalt nano-particles from a solution of Co(CO)(3)(NO) in n-decane under ultrasonication with a frequency of 20 kHz yielded cobalt particles of a size of ca. 5 nm. The presence of either silica or oleic acid in the solution reduced the particle size to ca. 3 and 2 nm, respectively. The resulting particle size is independent of the ultrasonication time, initial Co(CO)(3)(NO) concentration, ultrasound intensity and solution temperature. It is postulated that bubble collapse generates multiple nucleation sites resulting in the formation of cobalt particles with a rather uniform particle size distribution.

  5. Nitrogen doped TiO2 nano-particles: Phase control by solution combustion method

    NASA Astrophysics Data System (ADS)

    Bapna, Komal; Choudhary, R. J.; Phase, D. M.; Shastri, Sheetal; Prasad, R.; Ahuja, B. L.

    2016-05-01

    N-doped TiO2 nano powders were prepared by sol-gel solution combustion method. The influence of different fuels (urea and citric acid) used in obtaining N-TiO2 nano particles in similar conditions (heat treatment, amount of precursors) has been investigated. The growth of different phases of TiO2 (anatase and rutile) is strongly affected by the ligands and the dehydration reaction. Reduction in the band gap of TiO2 and features observed in the XPS spectra confirm the incorporation of N into TiO2 matrix.

  6. Removal of mercury (II) by dithiocarbamate surface functionalized magnetite particles: application to synthetic and natural spiked waters.

    PubMed

    Figueira, P; Lopes, C B; Daniel-da-Silva, A L; Pereira, E; Duarte, A C; Trindade, T

    2011-11-01

    In order to take advantage of the high affinity between mercury and sulphur, magnetite (Fe(3)O(4)) particles functionalized with dithiocarbamate groups (CS(2)(-)), were synthesized to be used as a new type of sorbent to remove Hg (II) from synthetic and natural spiked waters. The effectiveness of this type of sorbent was studied, and its potential as cleanup agent for contaminated waters was assessed. Batch stirred tank experiments were carried out by contacting a volume of solution with known amounts of functionalized Fe(3)O(4) particles, in order to study the effect of sorbent dose, salinity, and the kinetics and the equilibrium of this unit operation. A complete Hg (II) removal (ca. 99.8%) was attained with 6 mg/L of magnetic particles for an initial metal concentration of 50 μg/L. It was confirmed that highly complex matrices, such as seawater (ca. 99%) and river water (ca. 97%), do not affect the removal capacity of the functionalized magnetic particles. Concerning isotherms, no significant differences were observed between two- and three-parameter models (P = 0.05%); however, Sips isotherm provided the lowest values of SS and S(x/y), predicting a maximum sorption capacity of 206 mg/g, in the range of experimental conditions under study. The solid loadings measured in this essay surmount the majority of the values found in literature for other type of sorbents.

  7. One step facile synthesis of ferromagnetic magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Suppiah, Durga Devi; Abd Hamid, Sharifah Bee

    2016-09-01

    The ferromagnetic properties of magnetite (Fe3O4) were influenced by the nanoparticle size, hence importance were given to the synthesis method. This paper clearly shows that magnetite nanoparticles were successfully synthesized by employing one step controlled precipitation method using a single salt (Iron(II) sulfate) iron precursor. The acquired titration curve from this method provides vital information on the possible reaction mechanism leading to the magnetite (Fe3O4) nanoparticles formation. Goethite (α-FeOOH) was obtained at pH 4, while the continuous addition of hydroxyl ions (OH-) forms iron hydroxides (Fe(OH)2). This subsequently reacts with the goethite, producing magnetite (Fe3O4) at pH 10. Spectroscopy studies validate the magnetite phase existence while structural and morphology analysis illustrates cubic shaped magnetite with an average size of 35 nm was obtained. The synthesized magnetite might be superparamagnetic though lower saturation magnetization (67.5 emu/g) measured at room temperature as compared to bulk magnetite. However the nanoparticles surface anisotropy leads to higher remanence (12 emu/g) and coercivity (117.7 G) making the synthesized magnetite an excellent candidate to be utilized in recording devices. The understanding of the magnetite synthesis mechanism can not only be used to achieve even smaller magnetite nanoparticles but also to prepare different types of iron oxides hydroxides using different iron precursor source.

  8. Organophosphorous functionalization of magnetite nanoparticles.

    PubMed

    Kalska-Szostko, B; Rogowska, M; Satuła, D

    2013-11-01

    In this work magnetite nanoparticles covered by gold and silver shell were obtained. Analyzed particles were modified by two kinds of organophosphorous compounds: 3-phosphonopropionic acid and 16-phosphonohexadecanoic acid. Enzyme immobilization on particles modified in such a way was tested. The crystal structure of obtained nanoparticles was characterized by transmission electron microscopy and X-ray diffraction. Possible changes on the surfaces were analyzed by the use of infrared spectroscopy. Magnetic properties were studied by Mössbauer spectroscopy.

  9. Nano-Particle Formation of Mn/HA on the Ti-35Ta-xNb Alloy by Electrochemical Methods.

    PubMed

    Jo, Chae-Ik; Choe, Han-Cheol

    2015-08-01

    In this study, nano-particle formation of Mn/HA on the Ti-35Ta-xNb alloy by electrochemical methods has researched using various experiments. These alloys were performed by arc-melting furnace and then heat treated for 1000 °C at 12 h in Ar gas atmosphere and quenched at 0 °C water. Hydroxyapatite precipitation has been synthesized from 5 mM Ca(NO3)2 · 4 H2O+3 mM NH4H2PO4 at 80±1 °C. Manganese doped Hydroxyapatite precipitation has been synthesized from 4.95 mM Ca(NO3)2 · 4 H2O+3 mM NH4H2PO4+0.05 mM MnCl2 · 4 H2O at 80±1 °C. Morphology and structure were examined by FE-SEM, EDS and XRD. The microstructure of Ti-35Ta-xNb alloys was transformed from a phase to α phase as Nb content increased. The nano-scale HA shapes were plate-like precipitates and Mn doped HA shapes were net-like precipitates on Ti-35Ta-xNb alloys, and Ca, P and Mn peaks were detected on the Mn/HA deposited surface.

  10. Printed UHF RFID antennas with high efficiencies using nano-particle silver ink.

    PubMed

    Lee, Yongshik; Kim, Chung Hwan; Shin, Dong-Youn; Kim, Young Gook

    2011-07-01

    One of the most popular targets of conductive ink technology is to print RFID tag antennas. However, the printed RFID antennas, manufactured by conductive silver ink which is generally based on microsized silver particles, have lower conductivity and consequently lower radiation efficiency than those by conventional copper etching method. This work demonstrates nano-particle conductive silver ink that is capable of printing UHF RFID antennas with improved radiation efficiency. Compared with commercial micro-particle silver ink, the solid content of metal is much higher in the proposed nanoparticle silver ink, leading to better electrical properties. Two types of dipole antennas are printed with the proposed nano-particle as well as with commercial micro-particle inks. Also, the same antennas are fabricated by copper etching. With these conductive inks, a straight and a meandered dipole antennas are fabricated and their radiation efficiencies are measured with the Wheeler cap method. Experimental results show that the radiation efficiencies of the antennas based on nanoparticle silver ink are superior to those printed with the micro-particle silver ink, and are comparable to those of popular copper antennas.

  11. Microstructure Changes of Copper Nano Particles via Polymer Solution and Reduction Firing Processes.

    PubMed

    Han, Young-Min; Jung, Choong-Hwan; Lee, Sang-Jin

    2016-02-01

    Cu nano particles were fabricated at a very low temperature via polymer solution and reduction firing processes using a polyvinyl alcohol (PVA) and Ar-4%H2 gas mixture. In the process, copper nitrate and 5 wt% PVA solution were dissolved in D.I. water and the organic-inorganic precursor sols were dried to porous gels. The precursor gels were calcined in an air atmosphere, and then refired at 250 degrees C-300 degrees C under an Ar-4%H2 atmosphere for the reduction of CuO. The morphology of precursor gels and CuO and Cu powders was strongly dependent on the PVA content, and the as- calcined CuO readily deoxidized to Cu with minimal residual carbon. The polymer also contributed to an atomic-scale copper cation distribution, which resulted in nano-sized CuO and Cu powders. The Cu powder synthesized with PVA content in a 4:1 ratio showed a crystallite size of about 20 nm or less. In this paper, the microstructure changes of Cu nano particles at each set of processing conditions were examined by SEM and TEM observations.

  12. Magnetite pollution nanoparticles in the human brain.

    PubMed

    Maher, Barbara A; Ahmed, Imad A M; Karloukovski, Vassil; MacLaren, Donald A; Foulds, Penelope G; Allsop, David; Mann, David M A; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

    2016-09-27

    Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health. PMID:27601646

  13. Magnetite pollution nanoparticles in the human brain.

    PubMed

    Maher, Barbara A; Ahmed, Imad A M; Karloukovski, Vassil; MacLaren, Donald A; Foulds, Penelope G; Allsop, David; Mann, David M A; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

    2016-09-27

    Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

  14. Observation the Distribution of Titanium Dioxide Nano-particles in an Experimental Tumor Tissue by a Raman Microscope

    NASA Astrophysics Data System (ADS)

    Bibin, Andriana B.; Kume, Kyo; Tsutumi, Kotaro; Fukunaga, Yukihiro; Ito, Shinnji; Imamura, Yoshiaki; Miyoshi, Norio

    2011-12-01

    One of the most important technologies of the 21st century is nanotechnology. Many researchers will have been focusing to employ nanotechnology for medical purpose. Our team was interested in focusing to the application of titanium dioxide (TiO2), as nano-particles, for medical purpose especially drug delivery for the cancer and tumor. The administrations of TiO2 nano-particle via the oral administration of the interface layer particles into the mouse transplanted squamous-cell-carcinoma (SCC) have already conducted. Histology study and Raman spectroscope data were applied to the serial section of frozen tumor tissue in order to observe the distribution of TiO2 nano-particle within the SCC tissue. We used near infrared laser Raman microscopy system, the wavelength is 785 nm. Hematoxyline & eosin stained image and the Raman microscopy system were also used for analyzing the photodynamic therapy (PDT) with 5-ALA and TiO2-particle-sol [TiO2]-ALA-treated tumor samples. As the result, we demonstrated the distribution of TiO2, where TiO2 particles were detected to be distributed in the blood vessel at the bleeding in the SCC tumor tissue. PDT with TiO2 nano-particles that is presented in the SCC-transplanted mouse tumor model can cause the enhancement of photodynamic reaction by nano-particles. Therefore, the combinations of PDT with TiO2 nano-particles may have a possibility to be introduced to the human body in near future for diagnose and PDT treatment of the tumor.

  15. Support vector machine to predict diesel engine performance and emission parameters fueled with nano-particles additive to diesel fuel

    NASA Astrophysics Data System (ADS)

    Ghanbari, M.; Najafi, G.; Ghobadian, B.; Mamat, R.; Noor, M. M.; Moosavian, A.

    2015-12-01

    This paper studies the use of adaptive Support Vector Machine (SVM) to predict the performance parameters and exhaust emissions of a diesel engine operating on nanodiesel blended fuels. In order to predict the engine parameters, the whole experimental data were randomly divided into training and testing data. For SVM modelling, different values for radial basis function (RBF) kernel width and penalty parameters (C) were considered and the optimum values were then found. The results demonstrate that SVM is capable of predicting the diesel engine performance and emissions. In the experimental step, Carbon nano tubes (CNT) (40, 80 and 120 ppm) and nano silver particles (40, 80 and 120 ppm) with nanostructure were prepared and added as additive to the diesel fuel. Six cylinders, four-stroke diesel engine was fuelled with these new blended fuels and operated at different engine speeds. Experimental test results indicated the fact that adding nano particles to diesel fuel, increased diesel engine power and torque output. For nano-diesel it was found that the brake specific fuel consumption (bsfc) was decreased compared to the net diesel fuel. The results proved that with increase of nano particles concentrations (from 40 ppm to 120 ppm) in diesel fuel, CO2 emission increased. CO emission in diesel fuel with nano-particles was lower significantly compared to pure diesel fuel. UHC emission with silver nano-diesel blended fuel decreased while with fuels that contains CNT nano particles increased. The trend of NOx emission was inverse compared to the UHC emission. With adding nano particles to the blended fuels, NOx increased compared to the net diesel fuel. The tests revealed that silver & CNT nano particles can be used as additive in diesel fuel to improve complete combustion of the fuel and reduce the exhaust emissions significantly.

  16. Formation of Li3O4 nano particles in the discharge products of non-aqueous lithium-oxygen batteries leads to lower charge overvoltage.

    PubMed

    Shi, L; Xu, A; Zhao, T S

    2015-11-28

    Density functional theory calculations are made for bulk thermodynamic properties and surface energies of Li2O2, a primary discharge product, and Li3O4, a possible byproduct in the discharge products, of the non-aqueous lithium-oxygen batteries. Results show that the standard formation Gibbs free energy of bulk Li3O4 is marginally higher than that of Li2O2, but the surface energy of Li3O4 is much lower. Low surface energy results in both lowered nucleation energy and formation Gibbs free energy in the nanometer regime, allowing the Li3O4 nano particles to nucleate ahead of Li2O2 during the discharge process and to exist stably when particle sizes are smaller than about 40 nm. The scanning transmission electron microscopy (STEM) image of Li3O4 crystals is simulated and compared with the measured STEM image of the discharge product particles. The consistency between the simulated and measured STEM images suggests that the Li3O4 phase can exist stably as a discharge product. The energy profile of the oxygen evolution reaction (OER) occurring on the most abundant surfaces of Li3O4 is also calculated. The predicted overpotential for the OER on the {0001} surface (0.30 V) shows a good agreement with experimental data. The presence of more electronically conductive Li3O4 nano particles in the primary discharge product Li2O2 tends to decrease the charge overvoltage of the batteries, explaining why the lower voltage area (<3.5 V) was widely observed during the charging of the batteries. An increase in the oxygen pressure or a decrease in temperature enhances the stability of the Li3O4 phase and increase the proportion of the Li3O4 phase in the discharge products, consequently leading to a lower overall charge overvoltage.

  17. Thermal Analysis of Acicular Shaped Magnetite

    NASA Technical Reports Server (NTRS)

    Lauer, H. V., Jr.; Ming, D. W.; Golden, D. C.

    2003-01-01

    We are in the process of developing a database on the thermal properties of well-characterized Martian analog materials in support of future Mars surface missions. The database contains the thermal behaviors of these analog materials under reduced and Earth ambient pressures. Magnetite in planetary materials has received considerable attention in recent years since the identification of fine grain single-domain magnetite in Martian meteorite ALH84001 and their possible link to past life on Mars (i.e., possible biominerals of magnetotactic bacteria). Because of its possible importance to Mars science, we report here the thermal properties of magnetite particles with acicular morphology, i.e., needle-shaped magnetite. Acicular shaped magnetite can be commercially produced from goethite (FeOOH) as the starting material via a H2 reduction process. However, instead of using this process or procedure, we report here on the thermal characterization of acicular magnetite formed under reducing conditions from well-characterized needle-shaped goethite at low temperature in controlled CO-CO2 1-bar atmosphere gas mixing furnaces.

  18. Enhancing Asphalt Binder's Rheological Behavior and Aging Susceptibility Using Nano-Particles

    NASA Astrophysics Data System (ADS)

    Walters, Renaldo C.

    The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment of UV rays. UV rays cause asphalt to oxidize faster which results in deterioration of asphalt rheological characteristics that can lead to pavement distresses. This study investigates the impact that nano-particles and bio modification have on the aging susceptibility of asphalt binder. As such, the following hypothesis was investigated: Introduction of nano particles to asphalt binder will reduce asphalt oxidation aging by increasing the inter layer spacing of the nano particles. Two nano scale materials were used for this study, nano-clay and bio-char as well as one micro scale material, silica fume. Nano-clay (Cloisite 30B) is a naturally occurring inorganic mineral. Bio-char is the waste product from bio-binder production. Bio-binder is produced from swine manure using a thermochemical conversion process. This process is then followed by a filtration procedure where the bio-char is produced. Chemical and physical properties of bio-char showed a significant presence of carbon which could in turn reduce the rate of asphalt oxidation. Silica Fume is an ultra-fine powder collected as a by-product of silicon and ferrosilicon alloy production and consists of spherical particles. In this study several mixtures are designed and evaluated using RV testing (Rotational Viscometer), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Nano-clay is blended at 2% and 4% by weight of dry mass, with and without bio-binder (5% by weight of dry mass). Bio-char is grinded to nano scale and added to the virgin asphalt binder (PG 64-22) at 2%, 5% and 10% by weight of dry mass. Silica Fume is added to virgin asphalt binder (PG 64-22) at 2%, 4% and 8% by weight of dry mass. The optimum percent of nano scale material that is added to virgin asphalt binder is expected to reduce aging susceptibility of asphalt binder, extending its service life.

  19. Thermal treatment of magnetite nanoparticles

    PubMed Central

    Wykowska, Urszula; Satula, Dariusz; Nordblad, Per

    2015-01-01

    Summary This paper presents the results of a thermal treatment process for magnetite nanoparticles in the temperature range of 50–500 °C. The tested magnetite nanoparticles were synthesized using three different methods that resulted in nanoparticles with different surface characteristics and crystallinity, which in turn, was reflected in their thermal durability. The particles were obtained by coprecipitation from Fe chlorides and decomposition of an Fe(acac)3 complex with and without a core–shell structure. Three types of ferrite nanoparticles were produced and their thermal stability properties were compared. In this study, two sets of unmodified magnetite nanoparticles were used where crystallinity was as determinant of the series. For the third type of particles, a Ag shell was added. By comparing the coated and uncoated particles, the influence of the metallic layer on the thermal stability of the nanoparticles was tested. Before and after heat treatment, the nanoparticles were examined using transmission electron microscopy, IR spectroscopy, differential scanning calorimetry, X-ray diffraction and Mössbauer spectroscopy. Based on the obtained results, it was observed that the fabrication methods determine, to some extent, the sensitivity of the nanoparticles to external factors. PMID:26199842

  20. Synthesis of zinc oxide nano-particles by mechano-thermal route

    NASA Astrophysics Data System (ADS)

    Karimi, S.; Ataie, A.; Nozari, A.

    2012-09-01

    ZnO nano-particles were synthesized via mechano-thermal route using ZnSO4.H2O and Na2CO3 as starting materials. The mixture of powders was milled for 5, 10 and 15 in a high energy planetary ball mill, then heat treated at 300 °C for 1 hour. XRD results of the heat treated sample at 300 °C revealed a single phase nano-crystalline ZnO phase with a mean crystallite size of 18 nm. FESEM micrographs of the heat treated sample showed that mean particle size of the ZnO decreased from 150 nm for 5-hour milled sample to 25 nm for 15-hour milled sample. It was also found that the optical properties of the samples varied as a function of milling time.

  1. Graphene supported nano particles of Pt-Ni for CO oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Lv, Wei; Yang, Quanhong; Liu, Yuan

    2012-08-01

    In this study, a series of graphene supported Pt, Ni and Pt-Ni nano particles were successfully synthesized by a simple impregnation method. The resultant composites were characterized using SEM, XRD, HRTEM, XPS and TPR techniques and their catalytic performance for the oxidation of carbon monoxide was tested. It was shown that in the prepared metal/graphene composite, metal particles were highly dispersed on the graphene sheets (GS) with an average particle size of 1-3 nm. The results of catalytic performance tests indicate that the activity decreases in the order of Pt-Ni/GS, Pt/GS and Ni/GS. In the sample of Pt-Ni/GS, Pt-Ni alloy was formed, which contributed to the high activity of Pt-Ni/GS for CO oxidation.

  2. Interfacial Structure of Composites of Poly(m-xylylen adipamide) and Silica Nano-Particles

    NASA Astrophysics Data System (ADS)

    Achiwa, Osamu; Kyogoku, Yoshitaka; Matsuda, Yasuhiro; Tasaka, Shigeru

    2012-10-01

    Interfacial structure of composites of poly(m-xylylen adipamide) (MXD6) and silica nano-particles (SNPs) was investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and infrared (IR) spectroscopy. In the DSC curves of the composites, changes in specific heat similar to a glass transition behavior (sub-Tg) were detected at 0-40 °C, and sub-Tg decreased with the increase in the weight fraction of SNPs. Crystallization temperature (Tc) decreased, and XRD peaks became sharper with the increase in the weight fraction of SNPs. The IR spectra suggest that the hydrogen bonds between MXD6 chains were weakened by the addition of SNPs.

  3. Development of CMC hydrogels loaded with silver nano-particles for medical applications.

    PubMed

    Hebeish, Ali; Hashem, M; El-Hady, M M Abd; Sharaf, S

    2013-01-30

    Innovative CMC-based hydrogels with great potentials for usage in medical area were principally synthesized as per two strategies .The first involved reaction of epichlorohydrin in alkaline medium containing silver nitrate to yield silver nano-particles (AgNPs)-loaded CMC hydrogel. While CMC acted as stabilizing for AgNPs, trisodium citrate was added to the reaction medium to assist CMC in establishing reduction of Ag(+) to AgNPs. The second strategy entailed preparation of CMC hydrogel which assists the in situ preparation of AgNPs under the same conditions. In both strategies, factors affecting the characterization of AgNPs-loaded CMC hydrogels were studied. Analysis and characterization of the so obtained hydrogels were performed through monitoring swelling behavior, FTIR spectroscopy, SEM, EDX, UV-vis spectrophotometer and TEM. Antimicrobial activity of the hydrogels was examined and mechanisms involved in their synthesis were reported.

  4. Enhanced copper micro/nano-particle mixed paste sintered at low temperature for 3D interconnects

    NASA Astrophysics Data System (ADS)

    Dai, Y. Y.; Ng, M. Z.; Anantha, P.; Lin, Y. D.; Li, Z. G.; Gan, C. L.; Tan, C. S.

    2016-06-01

    An enhanced copper paste, formulated by copper micro- and nano-particles mixture, is reported to prevent paste cracking and obtain an improved packing density. The particle mixture of two different sizes enables reduction in porosity of the micro-paste and resolves the cracking issue in the nano-paste. In-situ temperature and resistance measurements indicate that the mixed paste has a lower densification temperature. Electrical study also shows a ˜12× lower sheet resistance of 0.27 Ω/sq. In addition, scanning electron microscope image analysis confirms a ˜50% lower porosity, which is consistent with the thermal and electrical results. The 3:1 (micro:nano, wt. %) mixed paste is found to have the strongest synergistic effect. This phenomenon is discussed further. Consequently, the mixed paste is a promising material for potential low temperature 3D interconnects fabrication.

  5. Modifying Si-based consolidants through the addition of colloidal nano-particles

    NASA Astrophysics Data System (ADS)

    Ksinopoulou, E.; Bakolas, A.; Moropoulou, A.

    2016-04-01

    The modification of silicon-based stone consolidants has been the subject of many scientific studies aiming to overcome the commonly reported drawbacks of these materials, such as the tendency to shrink and crack during drying. The addition of nano-particle dispersions into silica matrix has been found to enhance their effectiveness in several ways. Objective of the current research was to study the preparation of particle-modified consolidants (PMC), consisting of an ethyl silicate matrix (TEOS) loaded with colloidal silica (SiO2) nano-particles and oxide titania (TiO2) particles. The effect of the polyacrylic acid on the dispersion stability was also investigated, by varying its concentration into PMC samples. The prepared materials were allowed to dry in two different relative humidity environments and then evaluated based on their stability in the sol phase, the aggregation sizes, determined through dynamic light scattering, the % solids content and their morphological characteristics, observed via scanning electron microscopy (SEM-EDAX). Mercury intrusion porosimetry was also applied to investigate the microstructural characteristics and differences between the prepared consolidants. Significant role in the final form of the material is played by both the initial molar ratios in the mixtures, as well as the conditions where the drying and aging takes place. Based on the results, the three-component PMCs appear to be promising in stone consolidation, as they show a reduction in cracking and shrinkage during drying and a more porous network, compared with the siliceous material, or the two-component TEOS-SiO2 formulation.

  6. Enhanced selectivity and capacity of clinoptilolite for Cd2+ removal from aqueous solutions by incorporation of magnetite nanoparticles and surface modification with cysteine.

    PubMed

    Sharifi, Masumeh; Baghdadi, Majid

    2016-01-01

    In this study, magnetic zeolite (MZ) nanocomposite modified with cysteine was developed in order to enhance selectivity and capacity of clinoptilolite for cadmium ion. The prepared MZ nanocomposite is containing clinoptilolite and magnetite nanoparticles with weight ratio of 3:1. The synthesized nanocomposite was characterized by transmission electron microscopy, X-ray diffraction and vibrating sample magnetometer. Surface modification was confirmed by Fourier transform infrared spectrometer. Experiments were carried out to find the optimum conditions for modification of clinoptilolite and to investigate the effective parameters (pH, adsorbent dosage, contact time, and temperature) on the adsorption of Cd(2+) ion by modified clinoptilolite. The results showed enhanced selectivity of modified MZ in the presence of other naturally occurring cations (Na(+), K(+), Ca(2+) and Mg(2+)) and ammonium. Kinetic and equilibrium data were well fitted by a pseudo second-order and Langmuir model, respectively, with high correlation coefficients. The maximum adsorption capacities of the modified and non-modified clinoptilolite were found to be 20.0 mg/g and 5.2 mg/g, respectively. Thermodynamic parameters revealed that the adsorption process is spontaneous and endothermic under studied conditions. PMID:27148732

  7. Kinetic and isotherm analyses for thorium (IV) adsorptive removal from aqueous solutions by modified magnetite nanoparticle using response surface methodology (RSM)

    NASA Astrophysics Data System (ADS)

    Karimi, Mohammad; Milani, Saeid Alamdar; Abolgashemi, Hossein

    2016-10-01

    In this study, the ability and the adsorption capacity of magnetite/aminopropyltriethoxysilane/glutaraldehyde (Fe3O4/APTES/GA) adsorbent were evaluated for the adsorption of thorium (IV) ions from aqueous solutions. The influence of the several variables such as pH (1-5), Th (IV) initial concentration (50-300 mg L-1) and adsorbent concentration (1-5 g L-1) on the Th (IV) adsorption were investigated by response surface methodology (RSM). The results showed that the highest absorption capacity (q) was 107.23 mg g-1 with respect to pH = 4.5, initial concentration of 250 mg L-1 and adsorbent concentration of 1 g L-1 for 90 min. Modeling equilibrium sorption data with the Langmuir, Freundlich and Dubinin-Radushkevich models pointed out that the results were in good agreement with Langmuir model. The experimental kinetic data were well fitted to pseudo-second-order equation with R2 = 0.9739. Also thermodynamic parameters (ΔGo, ΔHo, ΔSo) declared that the Th (IV) adsorption was endothermic and spontaneous.

  8. The nano-particle dispersion strengthening of V-4Cr-4Ti alloys for high temperature application in fusion reactors

    NASA Astrophysics Data System (ADS)

    Zheng, Pengfei; Chen, Jiming; Xu, Zengyu; Duan, Xuru

    2013-10-01

    V-4Cr-4Ti was identified as an attractive structural material for Li blanket in fusion reactors. However, both high temperature and irradiation induced degradation are great challenges for this material. It was thought that the nano-particles with high thermal stability can efficiently strengthen the alloy at elevated temperatures, and accommodate the irradiation induced defects at the boundaries. This study is a starting work aiming at improving the creep resistance and reducing the irradiation induced degradation for V-4Cr-4Ti alloy. Currently, we focus on the preparation of some comparative nano-particle dispersion strengthened V-4Cr-4Ti alloys. A mechanical alloying (MA) route is used to fabricate yttrium and carbides added V-4Cr-4Ti alloys. Nano-scale yttria, carbides and other possible particles have a combined dispersion-strengthening effect on the matrices of these MA-fabricated V-4Cr-4Ti alloys. High-temperature annealing is carried out to stabilize the optimized nano-particles. Mechanical properties are tested. Microstructures of the MA-fabricated V-4Cr-4Ti alloys with yttrium and carbide additions are characterized. Based on these results, the thermal stability of different nano-particle agents are classified. ITER related China domestic project 2011GB108007.

  9. Cellular uptake of beta-carotene from protein stabilized solid lipid nano-particles prepared by homogenization-evaporation method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using a homogenization-evaporation method, beta-carotene (BC) loaded nano-particles were prepared with different ratios of food-grade sodium caseinate (SC), whey protein isolate (WPI), or soy protein isolate (SPI) to BC and evaluated for their physiochemical stability, in vitro cytotoxicity, and cel...

  10. Development of a gold nano-particle-based fluorescent molecular beacon for detection of cystic fibrosis associated mutation.

    PubMed

    Beni, Valerio; Hayes, Karen; Lerga, Teresa Mairal; O'Sullivan, Ciara K

    2010-10-15

    Cystic fibrosis is one of the most common genetically inherited diseases in Northern Europe, consisting of an inherited defect of chloride transport in the epithelium. Of the several mutations related to CF, the ΔF508 mutation occurs in ca. 70% of the cases. In this work the use of a gold nano-particle supported fluorescence molecular beacon was investigated as an optical sensing platform for the detection of the ΔF508 cystic fibrosis associated mutation. Different parameters such as molecular beacon design, Au nano-particle size, molecular beacon-nano-particle conjugation protocol, molecular beacon loading as well as experimental conditions were evaluated. A 31-base long molecular beacon, containing a 15-base recognition sequence specific for the mutant target, was linked via a thiol modified poly thymine linker (10 bases long) to a 13 nm gold nano-particle and was exposed to mutant and wild type targets, and a clear differentiation was achieved at target concentrations as low as 1 nM.

  11. Cobalt doped antimony oxide nano-particles based chemical sensor and photo-catalyst for environmental pollutants

    NASA Astrophysics Data System (ADS)

    Jamal, Aslam; Rahman, Mohammed M.; Khan, Sher Bahadar; Faisal, Mohd.; Akhtar, Kalsoom; Rub, Malik Abdul; Asiri, Abdullah M.; Al-Youbi, Abdulrahman O.

    2012-11-01

    Cobalt doped antimony oxide nano-particles (NPs) have been synthesized by hydrothermal process and structurally characterized by utilizing X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Fourier transforms infrared spectrophotometer (FT-IR) which revealed that the synthesized cobalt antimony oxides (CoSb2O6) are well crystalline nano-particles with an average particles size of 26 ± 10 nm. UV-visible absorption spectra (˜286 nm) were used to investigate the optical properties of CoSb2O6. The chemical sensing of CoSb2O6 NPs have been primarily investigated by I-V technique, where dichloromethane is used as a model compound. The analytical performance of dichloromethane chemical sensor exhibits high sensitivity (1.2432 μA cm-2 mM-1) and a large linear dynamic range (1.0 μM-0.01 M) in short response time (10 s). The photo catalytic activity of the synthesized CoSb2O6 nano-particles was evaluated by degradation of acridine orange (AO), which degraded 58.37% in 200 min. These results indicate that CoSb2O6 nano-particles can play an excellent research impact in the environmental field.

  12. Synthesis and spectroscopic investigations of iron oxide nano-particles for biomedical applications in the treatment of cancer cells

    NASA Astrophysics Data System (ADS)

    Atta, Aly H.; El-ghamry, Mosad A.; Hamzaoui, Adel; Refat, Moamen S.

    2015-04-01

    Recently, upon the great importance of synthesized nano-particles especially ferric oxides on medicinal applications, these nano-particles have been prepared here using friendly and low cost biological precursors moieties via a thermal decomposition method. The Fe2O3 nano-particles preparation method is based on thermal degradation of ferric complexes of hippuric acid, itaconic acid, or tyrosine amino acid at 600 °C. The used precursors were characterized by several characterization techniques such as microanalysis, conductance, infrared spectra, electronic spectra, and thermogravimetric (TG/DTG). The calcinations stages were identified from the thermogravimetric analyses of ferric complexes. The narrow size distribution in nano-scale range for the Fe2O3 crystals have been studied using X-ray powder diffraction (XRD), scanning electron microscope (SEM), X-ray energy dispersive spectrometer (EDX) and transmission electron microscopy (TEM) analyzer. XRD data indicate that a single phase Fe2O3 nano-particles are obtained with particle size ranging from 20 to 60 nm. The cytotoxic activity of the Fe2O3 nanoparticles was tested against the breast carcinoma cells (MCF-7 cell line). The results of inhibitory concentration fifty (IC50) were existed within the 3.10-3.81 μg limit.

  13. Mechanism of in situ surface polymerization of gallic acid in an environmental-inspired preparation of carboxylated core-shell magnetite nanoparticles.

    PubMed

    Tóth, Ildikó Y; Szekeres, Márta; Turcu, Rodica; Sáringer, Szilárd; Illés, Erzsébet; Nesztor, Dániel; Tombácz, Etelka

    2014-12-30

    Magnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic resonance imaging) contrasting, magnetic hyperthermia treatments, and drug delivery systems. The spontaneous surface induced polymerization of dissolved organic matter on environmental mineral particles inspired us to prepare carboxylated core-shell MNPs by using a ubiquitous polyphenolic precursor. Through the adsorption and in situ surface polymerization of gallic acid (GA), a polygallate (PGA) coating is formed on the nanoparticles (PGA@MNP) with possible antioxidant capacity. The present work explores the mechanism of polymerization with the help of potentiometric acid-base titration, dynamic light scattering (for particle size and zeta potential determination), UV-vis (UV-visible light spectroscopy), FTIR-ATR (Fourier-transformed infrared spectroscopy by attenuated total reflection), and XPS (X-ray photoelectron spectroscopy) techniques. We observed the formation of ester and ether linkages between gallate monomers both in solution and in the adsorbed state. Higher polymers were formed in the course of several weeks both on the surface of nanoparticles and in the dispersion medium. The ratio of the absorbances of PGA supernatants at 400 and 600 nm (i.e., the E4/E6 ratio commonly used to characterize the degree of polymerization of humic materials) was determined to be 4.3, similar to that of humic acids. Combined XPS, dynamic light scattering, and FTIR-ATR results revealed that, prior to polymerization, the GA monomers became oxidized to poly(carboxylic acid)s due to ring opening while Fe(3+) ions reduced to Fe(2+). Our published results on the colloidal and chemical stability of PGA@MNPs are referenced thoroughly in the present work. Detailed studies on biocompatibility, antioxidant property, and biomedical applicability of the particles will be published.

  14. Synthesis and characterization of magnetite/silver/antibiotic nanocomposites for targeted antimicrobial therapy.

    PubMed

    Ivashchenko, Olena; Lewandowski, Mikołaj; Peplińska, Barbara; Jarek, Marcin; Nowaczyk, Grzegorz; Wiesner, Maciej; Załęski, Karol; Babutina, Tetyana; Warowicka, Alicja; Jurga, Stefan

    2015-10-01

    The article is devoted to preparation and characterization of magnetite/silver/antibiotic nanocomposites for targeted antimicrobial therapy. Magnetite nanopowder was produced by thermochemical technique; silver was deposited on the magnetite nanoparticles in the form of silver clusters. Magnetite/silver nanocomposite was investigated by XRD, SEM, TEM, AFM, XPS, EDX techniques. Adsorptivity of magnetite/silver nanocomposite towards seven antibiotics from five different groups was investigated. It was shown that rifampicin, doxycycline, ceftriaxone, cefotaxime and doxycycline may be attached by physical adsorption to magnetite/silver nanocomposite. Electrostatic surfaces of antibiotics were modeled and possible mechanism of antibiotic attachment is considered in this article. Raman spectra of magnetite, magnetite/silver and magnetite/silver/antibiotic were collected. It was found that it is difficult to detect the bands related to antibiotics in the magnetite/silver/antibiotic nanocomposite spectra due to their overlap by the broad carbon bands of magnetite nanopowder. Magnetic measurements revealed that magnetic saturation of the magnetite/silver/antibiotic nanocomposites decreased on 6-19 % in comparison with initial magnetite nanopowder. Pilot study of antimicrobial properties of the magnetite/silver/antibiotic nanocomposites were performed towards Bacillus pumilus.

  15. Fabrication of docetaxel surfaced Fe3O4 magnetite nanoparticles and their cytotoxicity on 4 T1 breast cancer cells

    PubMed Central

    2012-01-01

    Background In the recent years, there is an increasing attention to the using of Fe3O4 magnetite nanoparticles (MNPs) as drug delivery systems. Application of this nanoparticles could profit advantages of nanomedicine to enhance biological activity of pharmaceutical ingredients. Methods Fe3O4 MNPs were synthesised by a chemical method and characterized by transmission electron microscopy and energy-dispersive spectroscopy techniques. In the next step, docetaxel-coated Fe3O4 MNPs were prepared, using percipitation method. The surface chemistry of docetaxel-coated Fe3O4 MNPs as well as their thermal decomposition characteristics were examined using fourier transform infrared spectroscopy and thermogravimetric analyzer equipment, respectively. The cytotoxicity assay was conducted on 4 T1 breast cancer carsinoma by MTT assay to evaluate the possible in vitro antiproliferative effects of docetaxel-coated Fe3O4 MNPs. Results During precipitation process, docetaxel molecules were precipitated on the surface of Fe3O4 MNPs by the ratio of 3:100 w/w which indicates that each milligram of coated Fe3O4 MNPs averagely contained 30 μg pure docetaxel compound. Docetaxel showed aniproliferative effects against mentioned cell line. The higestest concentartion of docetaxel (80 μg/ml) caused about 80% cell death. However, the results demostarted that much lower amounts of docetaxel will be needed in combination of Fe3O4 MNPs to produce the potent antiproliferative effect compared to docetaxel alone. Dose response cytotoxicity assay of docetaxel-coated Fe3O4 MNPs against 4 T1 breast cancer cells showed that lower amount of docetaxel (0.6 μg/ml) can exhibit higher cytotoxic effect against this cancer cell line (90% cell death). PMID:23351643

  16. Role of plant growth promoting rhizobacteria and Ag-nano particle in the bioremediation of heavy metals and maize growth under municipal wastewater irrigation.

    PubMed

    Khan, Naeem; Bano, Asghari

    2016-01-01

    The investigation evaluated the role of plant growth promoting rhizobacteria (PGPR) and Ag-nano particle on the growth and metabolism of maize irrigated with municipal wastewater (MW). Three PGPR isolated from MW were identified on the basis of 16S-rRNA gene sequence analyses as Pseudomonas sp., Pseudomonas fluorescence, and Bacillus cereus. The municipal waste water was used to irrigate the maize seeds inoculated with 3 isolated PGPR. The isolated PGPR had catalase and oxidase enzymes, solubilize insoluble bound phosphate and exhibit antifungal and antibacterial activities. The colony forming unit (cfu) of the PGPR was inhibited by Ag-nano particle, but was stimulated by the municipal wastewater. The Ag-nano particles augmented the PGPR induced increase in root area and root length. The root-shoot ratio was also changed with the Ag-nano particles. The plants irrigated with municipal wastewater had higher activities of peroxidase and catalase which were further augmented by Ag-nano particle. The Ag- nano particle application modulated level of ABA (34%), IAA (55%), and GA (82%), increased proline production (70%) and encountered oxidative stress and augmented the bioremediation potential of PGPR for Pb, Cd, and Ni. Municipal wastewater needs to be treated with PGPR and Ag nano particle prior to be used for irrigation. This aims for the better growth of the plant and enhanced bioremediation of toxic heavy metals.

  17. Acute toxicity of virgin and used engine oil enriched with copper nano particles in the earthworm

    NASA Astrophysics Data System (ADS)

    Khodabandeh, M.; Koohi, M. K.; Roshani, A.; Shahroziyan, E.; Badri, B.; Pourfallah, A.; Shams, Gh; Hobbenaghi, R.; Sadeghi-Hashjin, G.

    2011-07-01

    In spite of development of nanotechnology and creation of new opportunities for industry, new applications and products initiated by this technology may cause harmful effects on human health and environment. Unfortunately, there is no sufficient information on the harmful effects caused by application of some nano materials; the current knowledge in this field is limited solely to the nano particles but not the final products. Nano cupper particles, as one of the common materials produced in industrial scale is widely used as additives into engine oil to reduce friction and improve lubrication. However, the difference between the effects of virgin and used conventional engine oil (CEO) and the engine oil containing cupper nano particles (NEO) on the environment is not known. Earthworm, as a one of the species which could live and survive in different sorts of earth and has a certain role in protecting the soil structure and fertility, was used in this experiment. In accordance with the recommended method of OECD.1984, Filter Paper test in 24 and 48 h based on 8 concentrations in the range of 3×10-3 - 24×10-3 ml/cm2 and Artificial Soil test in 7 and 14 days based on 7 concentrations in the range of 0.1 mg/kg - 100 g/kg were carried out to study earthworms in terms of lifetime (LC50), morphology and pathology. It was shown that the 48 h LC50 for virgin CEO, virgin NEO, used CEO(8000 km) and used NEO (8000 km) were 6×10-3, 23×10-3, 24×10-3 and 16×10-3 ml/cm2 respectively. Furthermore, 14-day LC50 in artificial soil for all cases were above 100 g/kg. It is concluded that virgin CEO is more toxic than virgin NEO. Meanwhile, the CEO shows significant reduction in toxicity after consumption and the used NEO shows more toxicity in comparison to virgin product. It seems that more investigations on the effects of final products specifically after consumption is necessary because the products after consumption have the most contact with environment and subsequently

  18. Chemical characterization, nano-particle mineralogy and particle size distribution of basalt dust wastes.

    PubMed

    Dalmora, Adilson C; Ramos, Claudete G; Oliveira, Marcos L S; Teixeira, Elba C; Kautzmann, Rubens M; Taffarel, Silvio R; de Brum, Irineu A S; Silva, Luis F O

    2016-01-01

    Understanding the geochemistry of basalt alteration is central to the study of agriculture systems. Various nano-minerals play an important role in the mobilization of contaminants and their subsequent uptake by plants. We present a new analytical experimental approach in combination with an integrated analytical protocol designed to study basalt alteration processes. Recently, throughout the world, ultra-fine and nano-particles derived from basalt dust wastes (BDW) during "stonemeal" soil fertilizer application have been of great concern for their possible adverse effects on human health and environmental pollution. Samples of BDW utilized were obtained from companies in the Nova Prata mining district in southern Brazil for chemical characterization and nano-mineralogy investigation, using an integrated application of advanced characterization techniques such as X-ray diffraction (XRD), High Resolution-Transmission Electron microscopy (HR-TEM)/Energy Dispersive Spectroscopy (EDS)/(selected-area diffraction pattern) SAED, Field Emission-Scanning Electron Microscopy (FE-SEM/EDS), and granulometric distribution analysis. The investigation has revealed that BDW materials are dominated by SiO2, Al2O3, and Fe2O3, with a complex micromineralogy including alkali feldspar, augite, barite, labradorite, hematite, heulandrite, gypsum, kaolinite, quartz, and smectite. In addition, we have identified a number of trace metals such as Cd, Cu, Cr, and Zn, that are preferentially concentrated into the finer, inhalable, dust fraction and, thus, could present a health hazard in the urban areas around the basalt mining zone. The implication of this observation is that use of these nanometric-sized particulates as soil fertilizer may present different health challenges to those of conventional fertilizers, inviting future work regarding the relative toxicities of these materials. Our investigation on the particle size distribution, nano-particle mineralogy and chemical composition in

  19. Chemical characterization, nano-particle mineralogy and particle size distribution of basalt dust wastes.

    PubMed

    Dalmora, Adilson C; Ramos, Claudete G; Oliveira, Marcos L S; Teixeira, Elba C; Kautzmann, Rubens M; Taffarel, Silvio R; de Brum, Irineu A S; Silva, Luis F O

    2016-01-01

    Understanding the geochemistry of basalt alteration is central to the study of agriculture systems. Various nano-minerals play an important role in the mobilization of contaminants and their subsequent uptake by plants. We present a new analytical experimental approach in combination with an integrated analytical protocol designed to study basalt alteration processes. Recently, throughout the world, ultra-fine and nano-particles derived from basalt dust wastes (BDW) during "stonemeal" soil fertilizer application have been of great concern for their possible adverse effects on human health and environmental pollution. Samples of BDW utilized were obtained from companies in the Nova Prata mining district in southern Brazil for chemical characterization and nano-mineralogy investigation, using an integrated application of advanced characterization techniques such as X-ray diffraction (XRD), High Resolution-Transmission Electron microscopy (HR-TEM)/Energy Dispersive Spectroscopy (EDS)/(selected-area diffraction pattern) SAED, Field Emission-Scanning Electron Microscopy (FE-SEM/EDS), and granulometric distribution analysis. The investigation has revealed that BDW materials are dominated by SiO2, Al2O3, and Fe2O3, with a complex micromineralogy including alkali feldspar, augite, barite, labradorite, hematite, heulandrite, gypsum, kaolinite, quartz, and smectite. In addition, we have identified a number of trace metals such as Cd, Cu, Cr, and Zn, that are preferentially concentrated into the finer, inhalable, dust fraction and, thus, could present a health hazard in the urban areas around the basalt mining zone. The implication of this observation is that use of these nanometric-sized particulates as soil fertilizer may present different health challenges to those of conventional fertilizers, inviting future work regarding the relative toxicities of these materials. Our investigation on the particle size distribution, nano-particle mineralogy and chemical composition in

  20. Magnetic solid phase extraction of gemfibrozil from human serum and pharmaceutical wastewater samples utilizing a β-cyclodextrin grafted graphene oxide-magnetite nano-hybrid.

    PubMed

    Abdolmohammad-Zadeh, Hossein; Talleb, Zeynab

    2015-03-01

    A magnetic solid phase extraction method based on β-cyclodextrin (β-CD) grafted graphene oxide (GO)/magnetite (Fe3O4) nano-hybrid as an innovative adsorbent was developed for the separation and pre-concentration of gemfibrozil prior to its determination by spectrofluorometry. The as-prepared β-CD/GO/Fe3O4 nano-hybrid possesses the magnetism property of Fe3O4 nano-particles that makes it easily manipulated by an external magnetic field. On the other hand, the surface modification of GO by β-CD leads to selective separation of the target analyte from sample matrices. The structure and morphology of the synthesized adsorbent were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The experimental factors affecting the extraction/pre-concentration and determination of the analyte were investigated and optimized. Under the optimized experimental conditions, the calibration graph was linear in the range between 10 and 5000 pg mL(-1) with a correlation coefficient of 0.9989. The limit of detection and enrichment factor for gemfibrozil were 3 pg mL(-1) and 100, respectively. The maximum sorption capacity of the adsorbent for gemfibrozil was 49.8 mg g(-1). The method was successfully applied to monitoring gemfibrozil in human serum and pharmaceutical wastewaters samples with recoveries in the range of 96.0-104.0% for the spiked samples.

  1. Improved electrical properties of cadmium substituted cobalt ferrites nano-particles for microwave application

    NASA Astrophysics Data System (ADS)

    Ahmad, Rabia; Hussain Gul, Iftikhar; Zarrar, Muhammad; Anwar, Humaira; khan Niazi, Muhammad Bilal; Khan, Azim

    2016-05-01

    Cadmium substituted cobalt ferrites with formula CdxCo1-xFe2O4 (x=0.0, 0.2, 0.35, 0.5), have been synthesized by wet chemical co-precipitation technique. Electrical, morphological and Structural properties of the samples have been studied using DC electrical resistivity and Impedance analyzer, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. XRD, SEM and AFM have been used to study the structural parameters such as measured density, lattice constant, X-ray density, crystallite size and morphology of the synthesized nano-particles. Debye-Scherrer formula has been used for the estimation of crystallite sizes. The estimated crystallite sizes were to be 15-19±2 nm. Hopping length of octahedral and tetrahedral sites have been calculated using indexed XRD data. The porosity and lattice constant increased as Cd2+concentration increases. DC electrical resistivity was performed using two probe technique. The decrease of resistivity with temperature confirms the semiconducting nature of the samples. The dielectric properties variation has been studied at room temperature as a function of frequency. Variation of dielectric properties from 100 Hz to 5 MHz has been explained on the basis of Maxwell and Wagner's model and hoping of electrons on octahedral sites. To separates the grains boundary and grains of the system CdxCo1-xFe2O4 the impedance analysis were performed.

  2. Enhanced dielectric breakdown performances of propylene carbonate modified by nano-particles under microsecond pulses

    NASA Astrophysics Data System (ADS)

    Hou, Yanpan; Zhang, Jiande; Zhang, Zicheng

    2016-06-01

    Propylene carbonate shows appealing prospects as an energy storage medium in the compact pulsed power sources because of its large permittivity, high dielectric strength, and broad operating temperature range. In this paper, TiO2 nano-particles coated with γ-aminopropyltriethoxylsilane coupling agent are homogeneously dispersed into propylene carbonate and these nano-fluids (NFs) exhibit substantially larger breakdown voltages than those of pure propylene carbonate. It is proposed that interfaces between nano-fillers and propylene carbonate matrix may provide myriad trap sites for charge carriers. The charge carriers can be easily captured at the interfaces between NFs and the electrode, resulting in an increased barrier height and suppressed charge carriers injection, and in the bulk of NFs, the charge carriers' mean free path can be greatly shortened by the scattering effect. As a result, in order for charge carriers acquiring enough energy to generate a region of low density (the bubble) and initiate breakdown in NFs, much higher applied field is needed.

  3. Theory of molecule metal nano-particle interaction: Quantum description of plasmonic lasing

    SciTech Connect

    Zhang, Yuan May, Volkhard

    2015-06-14

    The recent quantum description of a few molecules interacting with plasmon excitations of a spherical metal nano-particle (MNP) as presented in the work of Zhang and May [Phys. Rev. B 89, 245441 (2014)] is extended to systems with up to 100 molecules. We demonstrate the possibility of multiple plasmon excitation and describe their conversion into far-field photons. The calculation of the steady-state photon emission spectrum results in an emission line-narrowing with an increasing number of molecules coupled to the MNP. This is considered as an essential criterion for the action of the molecule-MNP system as a nano-laser. To have exact results for systems with up to 20 molecules, we proceed as recently described by Richter et al. [Phys. Rev. B 91, 035306 (2015)] and study a highly symmetric system. It assumes an equatorial and regular position of identical molecules in such a way that their coupling is dominated by that to a single MNP dipole-plasmon excitation. Changing from the exact computation of the system’s complete density matrix to an approximate theory based on the reduced plasmon density matrix, systems with more than 100 molecules can be described. Finally, nonlinear rate equations are proposed which reproduce the mean number of excited plasmons in their dependence of the number of molecules and of the used pump rate. The second order intensity correlation function of emitted photons is related to the respective plasmon correlation function which approaches unity when the system starts lasing.

  4. Recent patents on amylose-flavor inclusion complex nano particles preparation and their application.

    PubMed

    Feng, Tao; Zhuang, Hai N; Xiao, Zuo B; Tian, Huai X

    2011-09-01

    Lipophilic and hydrophilic compounds that are solubilized in the form of nano-sized particles, or "nanoparticles", can be used in pharmacology, in the production of food additives, cosmetics, and agriculture, as well as in pet foods and veterinary products, amongst other uses. This review focuses on nanoparticles and methods for the production of soluble nanoparticles and, in particular, inclusion complexes of water-insoluble lipophilic and water-soluble hydrophilic organic materials, especially flavor compounds. The host molecule is namely V-amylose or modified starch molecule, which could form a cavity to fix or secure guest molecules. Thus, the V-amylose molecular properties and the molecular inclusion complex formation mechanism is firstly introduced, then amylose-other ingredients inclusion complex preparation and application are listed, finally amylose-flavor molecular inclusion complex preparations and its application have been overviewed. Through this review, it is concluded that amylose-small chemical molecule inclusion complexes, especially amylose-flavor inclusion complexes have a marvelous application prospect and have great significance to develop the nano-product application field. This paper reviews the recent patents on amylose-flavour inclusion complex nano particles preparation and their application.

  5. Fate and effect of tire rubber ash nano-particles (RANPs) in cucumber.

    PubMed

    Moghaddasi, Sahar; Hossein Khoshgoftarmanesh, Amir; Karimzadeh, Fatholah; Chaney, Rufus

    2015-05-01

    There are growing interests on effects of nano-materials on living organisms including higher plants. No report is available on positive and negative effects of rubber ash nano-particles (RANPs) on edible plants. Recently, we reported the possibility of using waste tire rubber and rubber ash as zinc (Zn) fertilizer for plants. In this nutrient solution culture study, for the first time, root uptake and the effects of RANPs on growth and Zn, cadmium (Cd), and lead (Pb) concentration in cucumber was investigated. Various Zn levels (0, 1, 5, 25, 125mgL(-1)) were applied in the form of RANPs or ZnSO4. The root RANPs uptake was visualized by light (LA), scanning electron (SEM), and transmission electron microcopies (TEM). At all Zn levels, cucumber plants supplied with RANPs produced higher shoot and root biomass compared with those supplied with ZnSO4. In addition, the RANPs resulted in higher accumulation of Zn in cucumber tissues in comparison with ZnSO4; although phytotoxicity of Zn from ZnSO4 was greater than that from RANPs. Clear evidence of the RANPs penetration into the root cells was obtained by using SEM and TEM. Filaments of RANPs were also observed at the end of roots by LM and TEM. Further research is needed to clarify the fate of the RANPs in plant cells and their possible risks for food chain.

  6. Investigation on Tc tuned nano particles of magnetic oxides for hyperthermia applications.

    PubMed

    Giri, Jyotsnendu; Ray, Amlan; Dasgupta, S; Datta, D; Bahadur, D

    2003-01-01

    Superparamagnetic as well as fine ferrimagnetic particles such as Fe3O4, have been extensively used in magnetic field induced localized hyperthermia for the treatment of cancer. The magnetic materials with Curie temperature (Tc) between 42 and 50 degrees C, with sufficient biocompatibility are the best candidates for effective treatment such that during therapy it acts as in vivo temperature control switch and thus over heating could be avoided. Ultrafine particles of substituted ferrite Co(1-a)Zn(a)Fe2O4 and substituted yttrium-iron garnet Y3Fe(5-x)Al(x)O12 have been prepared through microwave refluxing and citrate-gel route respectively. Single-phase compounds were obtained with particle size below 100 nm. In order to make these magnetic nano particles biocompatible, we have attempted to coat these above said composition by alumina. The coating of alumina was done by hydrolysis method. The coating of hydrous aluminium oxide has been done over the magnetic particles by aging the preformed solid particles in the solution of aluminium sulfate and formamide at elevated temperatures. In vitro study is carried out to verify the innocuousness of coated materials towards cells. In vitro biocompatibility study has been carried out by cell culture method for a period of three days using human WBC cell lines. Study of cell counts and SEM images indicates the cells viability/growth. The in vitro experiments show that the coated materials are biocompatible.

  7. Fiber Bragg grating filter using evaporated induced self assembly of silica nano particles

    NASA Astrophysics Data System (ADS)

    Hammarling, Krister; Zhang, Renyung; Manuilskiy, Anatoliy; Nilsson, Hans-Erik

    2014-03-01

    In the present work we conduct a study of fiber filters produced by evaporation of silica particles upon a MM-fiber core. A band filter was designed and theoretically verified using a 2D Comsol simulation model of a 3D problem, and calculated in the frequency domain in respect to refractive index. The fiber filters were fabricated by stripping and chemically etching the middle part of an MM-fiber until the core was exposed. A mono layer of silica nano particles were evaporated on the core using an Evaporation Induced Self-Assembly (EISA) method. The experimental results indicated a broader bandwidth than indicated by the simulations which can be explained by the mismatch in the particle size distributions, uneven particle packing and finally by effects from multiple mode angles. Thus, there are several closely connected Bragg wavelengths that build up the broader bandwidth. The experimental part shows that it is possible by narrowing the particle size distributing and better control of the particle packing, the filter effectiveness can be greatly improved.

  8. Biopolymer nano-particles and natural nano-carriers for nano-encapsulation of phenolic compounds.

    PubMed

    Faridi Esfanjani, Afshin; Jafari, Seid Mahdi

    2016-10-01

    Phenolic compounds are major micronutrients in our diet,(1) and evidence for their role in the prevention of degenerative diseases such as cancer, inflammation and neurodegenerative diseases is emerging. The easily destruction against environment stresses and low bioavailability of phenolics are main limitations of their application. Therefore, nano-encapsulated phenolics as a fine delivery system can solve their restrictions. Polymeric nanoparticles and natural nano-carriers are one of the most effective and industrial techniques which can be used for protection and delivery of phenolics. In this review, preparation, application and characterization of polymeric based nano-capsules and natural nano-carriers for phenolics have been considered and discussed including polymeric nanoparticles, polymeric complex nanoparticles, cyclodextrins, nano-caseins, nanocrystals, electrospun nano-fibers, electro-sprayed nano-particles, and nano-spray dried particles. Our main goal was to cover the relevant recent studies in the past few years. Although a number of different types of polymeric and natural based nano-scale delivery systems have been developed, there are relatively poor quantitative understanding of their in vivo absorption, permeation and release. Also, performing toxicity experiments, residual solvent analysis and studying their biological fate during digestion, absorption, and excretion of polymeric nanoparticle and natural nano-carriers containing phenolics should be considered in future researches. In addition, future investigations could focus on application of phenolic nano-scale delivery systems in pharmaceuticals and functional foods. PMID:27419648

  9. Biopolymer nano-particles and natural nano-carriers for nano-encapsulation of phenolic compounds.

    PubMed

    Faridi Esfanjani, Afshin; Jafari, Seid Mahdi

    2016-10-01

    Phenolic compounds are major micronutrients in our diet,(1) and evidence for their role in the prevention of degenerative diseases such as cancer, inflammation and neurodegenerative diseases is emerging. The easily destruction against environment stresses and low bioavailability of phenolics are main limitations of their application. Therefore, nano-encapsulated phenolics as a fine delivery system can solve their restrictions. Polymeric nanoparticles and natural nano-carriers are one of the most effective and industrial techniques which can be used for protection and delivery of phenolics. In this review, preparation, application and characterization of polymeric based nano-capsules and natural nano-carriers for phenolics have been considered and discussed including polymeric nanoparticles, polymeric complex nanoparticles, cyclodextrins, nano-caseins, nanocrystals, electrospun nano-fibers, electro-sprayed nano-particles, and nano-spray dried particles. Our main goal was to cover the relevant recent studies in the past few years. Although a number of different types of polymeric and natural based nano-scale delivery systems have been developed, there are relatively poor quantitative understanding of their in vivo absorption, permeation and release. Also, performing toxicity experiments, residual solvent analysis and studying their biological fate during digestion, absorption, and excretion of polymeric nanoparticle and natural nano-carriers containing phenolics should be considered in future researches. In addition, future investigations could focus on application of phenolic nano-scale delivery systems in pharmaceuticals and functional foods.

  10. Theory of molecule metal nano-particle interaction: Quantum description of plasmonic lasing.

    PubMed

    Zhang, Yuan; May, Volkhard

    2015-06-14

    The recent quantum description of a few molecules interacting with plasmon excitations of a spherical metal nano-particle (MNP) as presented in the work of Zhang and May [Phys. Rev. B 89, 245441 (2014)] is extended to systems with up to 100 molecules. We demonstrate the possibility of multiple plasmon excitation and describe their conversion into far-field photons. The calculation of the steady-state photon emission spectrum results in an emission line-narrowing with an increasing number of molecules coupled to the MNP. This is considered as an essential criterion for the action of the molecule-MNP system as a nano-laser. To have exact results for systems with up to 20 molecules, we proceed as recently described by Richter et al. [Phys. Rev. B 91, 035306 (2015)] and study a highly symmetric system. It assumes an equatorial and regular position of identical molecules in such a way that their coupling is dominated by that to a single MNP dipole-plasmon excitation. Changing from the exact computation of the system's complete density matrix to an approximate theory based on the reduced plasmon density matrix, systems with more than 100 molecules can be described. Finally, nonlinear rate equations are proposed which reproduce the mean number of excited plasmons in their dependence of the number of molecules and of the used pump rate. The second order intensity correlation function of emitted photons is related to the respective plasmon correlation function which approaches unity when the system starts lasing.

  11. Magnetic separation of encapsulated islet cells labeled with superparamagnetic iron oxide nano particles.

    PubMed

    Mettler, Esther; Trenkler, Anja; Feilen, Peter J; Wiegand, Frederik; Fottner, Christian; Ehrhart, Friederike; Zimmermann, Heiko; Hwang, Yong Hwa; Lee, Dong Yun; Fischer, Stefan; Schreiber, Laura M; Weber, Matthias M

    2013-01-01

    Islet cell transplantation is a promising option for the restoration of normal glucose homeostasis in patients with type 1 diabetes. Because graft volume is a crucial issue in islet transplantations for patients with diabetes, we evaluated a new method for increasing functional tissue yield in xenogeneic grafts of encapsulated islets. Islets were labeled with three different superparamagnetic iron oxide nano particles (SPIONs; dextran-coated SPION, siloxane-coated SPION, and heparin-coated SPION). Magnetic separation was performed to separate encapsulated islets from the empty capsules, and cell viability and function were tested. Islets labeled with 1000 μg Fe/ml dextran-coated SPIONs experienced a 69.9% reduction in graft volume, with a 33.2% loss of islet-containing capsules. Islets labeled with 100 μg Fe/ml heparin-coated SPIONs showed a 46.4% reduction in graft volume, with a 4.5% loss of capsules containing islets. No purification could be achieved using siloxane-coated SPIONs due to its toxicity to the primary islets. SPION labeling of islets is useful for transplant purification during islet separation as well as in vivo imaging after transplantation. Furthermore, purification of encapsulated islets can also reduce the volume of the encapsulated islets without impairing their function by removing empty capsules.

  12. Fe atom exchange between aqueous Fe2+ and magnetite.

    PubMed

    Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M

    2012-11-20

    The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite.

  13. Dose limited reliability of quantitative annular dark field scanning transmission electron microscopy for nano-particle atom-counting.

    PubMed

    De Backer, A; Martinez, G T; MacArthur, K E; Jones, L; Béché, A; Nellist, P D; Van Aert, S

    2015-04-01

    Quantitative annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique to characterise nano-particles on an atomic scale. Because of their limited size and beam sensitivity, the atomic structure of such particles may become extremely challenging to determine. Therefore keeping the incoming electron dose to a minimum is important. However, this may reduce the reliability of quantitative ADF STEM which will here be demonstrated for nano-particle atom-counting. Based on experimental ADF STEM images of a real industrial catalyst, we discuss the limits for counting the number of atoms in a projected atomic column with single atom sensitivity. We diagnose these limits by combining a thorough statistical method and detailed image simulations.

  14. The effect of acid-base clustering and ions on the growth of atmospheric nano-particles

    NASA Astrophysics Data System (ADS)

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J.; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K.; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P.; Ruuskanen, Taina; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N.; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E.; Wagner, Paul E.; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Virtanen, Annele; Donahue, Neil M.; Carslaw, Kenneth S.; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R.; Kulmala, Markku

    2016-05-01

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

  15. Gd-DTPA Adsorption on Chitosan/Magnetite Nanocomposites

    NASA Astrophysics Data System (ADS)

    Pylypchuk, Ie. V.; Kołodyńska, D.; Kozioł, M.; Gorbyk, P. P.

    2016-03-01

    The synthesis of the chitosan/magnetite nanocomposites is presented. Composites were prepared by co-precipitation of iron(II) and iron(III) salts by aqueous ammonia in the 0.1 % chitosan solution. It was shown that magnetite synthesis in the chitosan medium does not affect the magnetite crystal structure. The thermal analysis data showed 4.6 % of mass concentration of chitosan in the hybrid chitosan/magnetite composite. In the concentration range of initial Gd-DTPA solution up to 0.4 mmol/L, addition of chitosan to magnetite increases the adsorption capacity and affinity to Gd-DTPA complex. The Langmuir and Freundlich adsorption models were applied to describe adsorption processes. Nanocomposites were characterized by scanning electron microscopy (SEM), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and specific surface area determination (ASAP) methods.

  16. Synthesis, characterisation and application of silica-magnetite nanocomposites

    NASA Astrophysics Data System (ADS)

    Bruce, Ian J.; Taylor, James; Todd, Michael; Davies, Martin J.; Borioni, Enrico; Sangregorio, Claudio; Sen, Tapas

    2004-12-01

    -phosphorylated analogue 2-deoxyguanosine (G) and a range of sequence defined oligonucleotides (NAs) and sheared salmon sperm DNA. It was found that magnetite readily adsorbed GMP via the GMP phosphate anion in water, whereas silica did not, due to electrostatic repulsion between the negatively charged surface of silica and the GMP. Both magnetite and silica magnetite were further tested in adsorption studies of G and GMP in different chaotropic media, 4 M sodium chloride or 4 M ammonium sulphate. The high salt conditions aided binding of GMP silica magnetite but inhibited adsorption to magnetite presumably due to competition for binding sites on the magnetite's surface by the chaotrope anions. Interestingly, the results from NAs binding studies indicated that sequence appeared to play an important role in adsorption of the different species to silica-magnetite composites. This may indicate a contribution by hydrophobic interactions to the binding mechanism. Multiple depositions of silica onto magnetite performed by deposition from silicic acid at pH 10 did not appear to greatly increase the composite percentage represented by silica whilst composite produced by the acid hydrolysis of TEOS at 90 °C did. However, it appeared that the silica deposited by the first method represented a complete coating of the magnetite core whilst the second method yielded a porous or incomplete coating. In comparison with commercially available silica-magnetite composite in DNA adsorption and elution, the material was observed to perform approximately 10% more efficiently. These findings indicate that it is possible to produce a consistent and cheap silica-magnetite nanoparticle on relatively large scale (greater than 20 g batch size) which is at least as good as, if not better than, a commercially available alternative.

  17. Biogeochemical role of magnetite in urban soils (Review of publications)

    NASA Astrophysics Data System (ADS)

    Vodyanitskii, Yu. N.

    2013-03-01

    The surface horizons of urban soils are enriched in technogenic magnetite Fe3O4 accumulated from emissions. Its content there reaches 3-4% and more, whereas it does not exceed 0.1% in the back-ground soils. In urban soils, large spherical magnetite particles of pseudo-single-domain and multidomain fabric predominate; the cavities in magnetic spherules decrease their chemical stability and increase their reactivity. Magnetite is most often destroyed in urban soils due to complexing; its destruction may be initiated by mineral salts entering the soil with deicing mixtures and by organic acids excreted by roots (e.g., by oxalic acid). The high solubility of magnetite with ammonium oxalate should be taken into account when using Tamm's reagent for the analysis of urban soils. Magnetite is a mineral carrier of some heavy metals. Therefore, its content (as determined from the magnetic susceptibility) serves as an indirect index of soil pollution. In addition, magnetite may affect many soil properties as a reducer and sorbent. It adsorbs phosphorus thus preventing the penetration of this nutrient into rivers and lakes. Magnetite also oxidizes Cl-containing aliphatic hydrocarbons and purifies the soil. Although magnetite enters urban soils as a pollutant, its influence on the soil properties cannot be unambiguously judged as only negative.

  18. Effects of oxidation on the magnetization of nanoparticulate magnetite.

    PubMed

    Rebodos, Robert L; Vikesland, Peter J

    2010-11-16

    Synthetic nanomagnetite has been suggested as a potential reactant for the in situ treatment of contaminated groundwater. Although the application of magnetite nanoparticles for environmental remediation is promising, a full understanding of particle reactivity has been deterred by the propensity of the nanoparticles to aggregate and become colloidally unstable. Attractive magnetic interactions between particles are partially responsible for their aggregation. In this study, we characterized the magnetic behavior of magnetite by determining the saturation magnetization, coercivity, remanent magnetization, susceptibility, and blocking temperature of synthetic magnetite using a superconducting quantum interference device (SQUID). We show how these properties vary in the presence of surface-associated solutes such as tetramethylammonium (TMA(+)) and ferrous (Fe(II)) cations. More importantly, because magnetite readily reacts with O(2) to produce maghemite, we analyzed the effect of oxidation on the magnetic properties of the particles. Because maghemite has a reported magnetic saturation that is less than that of magnetite, we hypothesized that oxidation would decrease the magnitude of the magnetic attractive force between adjacent particles. The presence of TMA(+) and Fe(II) caused a change in the magnetic properties of magnetite potentially because of alterations in its crystalline order. Magnetite oxidation caused a decrease in saturation magnetization, resulting in less significant magnetic interactions between particles. Oxidation, therefore, could lead to the decreased aggregation of magnetite nanoparticles and a potential enhancement of their colloidal stability.

  19. EBSD analysis of electroplated magnetite thin films

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Teng, C. L.; Ryan, M. P.; Hartmann, U.; Mücklich, F.

    2010-05-01

    By means of electron backscatter diffraction (EBSD), we analyse the crystallographic orientation of electroplated magnetite thin films on Si/copper substrates. Varying the voltage during the electroplating procedure, the resulting surface properties are differing considerably. While a high voltage produces larger but individual grains on the surface, the surfaces become smoother on decreasing voltage. Good quality Kikuchi patterns could be obtained from all samples; even on individual grains, where the surface and the edges could be measured. The spatial resolution of the EBSD measurement could be increased to about 10 nm; thus enabling a detailed analysis of single magnetite grains. The thin film samples are polycrystalline and do not exhibit a preferred orientation. EBSD reveals that the grain size changes depending on the processing conditions, while the detected misorientation angles stay similar.

  20. Degeneration of biogenic superparamagnetic magnetite.

    PubMed

    Li, Y-L; Pfiffner, S M; Dyar, M D; Vali, H; Konhauser, K; Cole, D R; Rondinone, A J; Phelps, T J

    2009-01-01

    Magnetite crystals precipitated as a consequence of Fe(III) reduction by Shewanella algae BrY after 265 h incubation and 5-year anaerobic storage were investigated with transmission electron microscopy, Mössbauer spectroscopy and X-ray diffraction. The magnetite crystals were typically superparamagnetic with an approximate size of 13 nm. The lattice constants of the 265 h and 5-year crystals are 8.4164A and 8.3774A, respectively. The Mössbauer spectra indicated that the 265 h magnetite had excess Fe(II) in its crystal-chemistry (Fe(3+) (1.990)Fe(2+) (1.015)O(4)) but the 5-year magnetite was Fe(II)-deficient in stoichiometry (Fe(3+) (2.388)Fe(2+) (0.419)O(4)). Such crystal-chemical changes may be indicative of the degeneration of superparamagnetic magnetite through the aqueous oxidization of Fe(II) anaerobically, and the concomitant oxidation of the organic phases (fatty acid methyl esters) that were present during the initial formation of the magnetite. The observation of a corona structure on the aged magnetite corroborates the anaerobic oxidation of Fe(II) on the outer layers of magnetite crystals. These results suggest that there may be a possible link between the enzymatic activity of the bacteria and the stability of Fe(II)-excess magnetite, which may help explain why stable nano-magnetite grains are seldom preserved in natural environments.

  1. Bioinspired synthesis of magnetite nanoparticles.

    PubMed

    Mirabello, Giulia; Lenders, Jos J M; Sommerdijk, Nico A J M

    2016-09-21

    Magnetite (Fe3O4) is a widespread magnetic iron oxide encountered in many biological and geological systems, and also in many technological applications. The magnetic properties of magnetite crystals depend strongly on the size and shape of its crystals. Hence, engineering magnetite nanoparticles with specific shapes and sizes allows tuning their properties to specific applications in a wide variety of fields, including catalysis, magnetic storage, targeted drug delivery, cancer diagnostics and magnetic resonance imaging (MRI). However, synthesis of magnetite with a specific size, shape and a narrow crystal size distribution is notoriously difficult without using high temperatures and non-aqueous media. Nevertheless, living organisms such as chitons and magnetotactic bacteria are able to form magnetite crystals with well controlled sizes and shapes under ambient conditions and in aqueous media. In these biomineralization processes the organisms use a twofold strategy to control magnetite formation: the mineral is formed from a poorly crystalline precursor phase, and nucleation and growth are controlled through the interaction of the mineral with biomolecular templates and additives. Taking inspiration from this biological strategy is a promising route to achieve control over the kinetics of magnetite crystallization under ambient conditions and in aqueous media. In this review we first summarize the main characteristics of magnetite and what is known about the mechanisms of magnetite biomineralization. We then describe the most common routes to synthesize magnetite and subsequently will introduce recent efforts in bioinspired magnetite synthesis. We describe how the use of poorly ordered, more soluble precursors such as ferrihydrite (FeH) or white rust (Fe(OH)2) can be employed to control the solution supersaturation, setting the conditions for continued growth. Further, we show how the use of various organic additives such as proteins, peptides and polymers allows

  2. Bioinspired synthesis of magnetite nanoparticles.

    PubMed

    Mirabello, Giulia; Lenders, Jos J M; Sommerdijk, Nico A J M

    2016-09-21

    Magnetite (Fe3O4) is a widespread magnetic iron oxide encountered in many biological and geological systems, and also in many technological applications. The magnetic properties of magnetite crystals depend strongly on the size and shape of its crystals. Hence, engineering magnetite nanoparticles with specific shapes and sizes allows tuning their properties to specific applications in a wide variety of fields, including catalysis, magnetic storage, targeted drug delivery, cancer diagnostics and magnetic resonance imaging (MRI). However, synthesis of magnetite with a specific size, shape and a narrow crystal size distribution is notoriously difficult without using high temperatures and non-aqueous media. Nevertheless, living organisms such as chitons and magnetotactic bacteria are able to form magnetite crystals with well controlled sizes and shapes under ambient conditions and in aqueous media. In these biomineralization processes the organisms use a twofold strategy to control magnetite formation: the mineral is formed from a poorly crystalline precursor phase, and nucleation and growth are controlled through the interaction of the mineral with biomolecular templates and additives. Taking inspiration from this biological strategy is a promising route to achieve control over the kinetics of magnetite crystallization under ambient conditions and in aqueous media. In this review we first summarize the main characteristics of magnetite and what is known about the mechanisms of magnetite biomineralization. We then describe the most common routes to synthesize magnetite and subsequently will introduce recent efforts in bioinspired magnetite synthesis. We describe how the use of poorly ordered, more soluble precursors such as ferrihydrite (FeH) or white rust (Fe(OH)2) can be employed to control the solution supersaturation, setting the conditions for continued growth. Further, we show how the use of various organic additives such as proteins, peptides and polymers allows

  3. Protection of cisplatin-induced spermatotoxicity, DNA damage and chromatin abnormality by selenium nano-particles

    SciTech Connect

    Rezvanfar, Mohammad Amin; Rezvanfar, Mohammad Ali; Shahverdi, Ahmad Reza; Ahmadi, Abbas; Baeeri, Maryam; Mohammadirad, Azadeh; Abdollahi, Mohammad

    2013-02-01

    Cisplatin (CIS), an anticancer alkylating agent, induces DNA adducts and effectively cross links the DNA strands and so affects spermatozoa as a male reproductive toxicant. The present study investigated the cellular/biochemical mechanisms underlying possible protective effect of selenium nano-particles (Nano-Se) as an established strong antioxidant with more bioavailability and less toxicity, on reproductive toxicity of CIS by assessment of sperm characteristics, sperm DNA integrity, chromatin quality and spermatogenic disorders. To determine the role of oxidative stress (OS) in the pathogenesis of CIS gonadotoxicity, the level of lipid peroxidation (LPO), antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) and peroxynitrite (ONOO) as a marker of nitrosative stress (NS) and testosterone (T) concentration as a biomarker of testicular function were measured in the blood and testes. Thirty-two male Wistar rats were equally divided into four groups. A single IP dose of CIS (7 mg/kg) and protective dose of Nano-Se (2 mg/kg/day) were administered alone or in combination. The CIS-exposed rats showed a significant increase in testicular and serum LPO and ONOO level, along with a significant decrease in enzymatic antioxidants levels, diminished serum T concentration and abnormal histologic findings with impaired sperm quality associated with increased DNA damage and decreased chromatin quality. Coadministration of Nano-Se significantly improved the serum T, sperm quality, and spermatogenesis and reduced CIS-induced free radical toxic stress and spermatic DNA damage. In conclusion, the current study demonstrated that Nano-Se may be useful to prevent CIS-induced gonadotoxicity through its antioxidant potential. Highlights: ► Cisplatin (CIS) affects spermatozoa as a male reproductive toxicant. ► Effect of Nano-Se on CIS-induced spermatotoxicity was investigated. ► CIS-exposure induces oxidative sperm DNA damage

  4. Hot Extruded Polycrystalline Mg2Si with Embedded XS2 Nano-particles (X: Mo, W)

    NASA Astrophysics Data System (ADS)

    Bercegol, A.; Christophe, V.; Keshavarz, M. K.; Vasilevskiy, D.; Turenne, S.; Masut, R. A.

    2016-08-01

    Due to their abundant, inexpensive and non-toxic constituent elements, magnesium silicide and related alloys are attractive for large-scale thermoelectric (TE) applications in the 500-800 K temperature range, in particular for energy conversion. In this work, we propose a hot extrusion method favorable for large-scale production, where the starting materials (Mg2Si and XS2, X: W, Mo) are milled together in a sealed vial. The MoS2 nano-particles (0.5-2 at.%) act as solid lubricant during the extrusion process, thus facilitating material densification, as confirmed by density measurements based on Archimedes' method. Scanning electron microscopy images of bulk extruded specimens show a wide distribution of grain size, covering the range from 0.1 μm to 10 μm, and energy dispersive spectroscopy shows oxygen preferentially distributed at the grain boundaries. X-ray diffraction analysis shows that the major phase is the expected cubic structure of Mg2Si. The TE properties of these extruded alloys have been measured by the Harman method between 300 K and 700 K. Resistivity values at 700 K vary between 370 μΩ m and 530 μΩ m. The ZT value reaches a maximum of 0.26 for a sample with 2 at.% MoS2. Heat conductivity is reduced for extruded samples containing MoS2, which most likely behave as scattering centers for phonons. The reason why the WS2 particles do not bring any enhancement, for either densification or heat transfer reduction, might be linked to their tendency to agglomerate. These results open the way for further investigation to optimize the processing parameters for this family of TE alloys.

  5. Nondestructive optical testing of 3D disperse systems with micro- and nano-particles

    NASA Astrophysics Data System (ADS)

    Bezrukova, Alexandra G.

    2005-04-01

    Nondestructive testing and analysis of three-dimensional (3D) disperse systems (DS) with micro- and nano-particles of different nature by complex of optical compatible methods can provide further progress in on-line control of water and air. The simultaneous analysis of 3D-DS by refractometry, absorbency, fluorescence and by different types of light scattering can help to elaborate the sensing elements for specific impurity control. In our research we have investigated by complex of optical methods different 3D-DS such as: proteins, nucleoproteids, lipoproteids, liposomes, viruses, virosomes, lipid emulsions, blood substitutes, latexes, liquid crystals, biological cells with various form and size (including bacterial cells), metallic powders, clays, kimberlites, zeolites, oils, crude oils, etc., and mixtures -- proteins with nucleic acids, liposomes and viruses, liquid crystals with surfactants, mixtures of clay with bacterial cells, samples of natural and water-supply waters, etc. This experience suggests that the set of optical parameters of so called second class is unique for each 3D-DS. In another words each DS can be characterized by n-dimensional vector in n-dimensional space of optical parameters. Mixtures can be considered as polycomponent and polymodal 3D-DS (such as natural water and air). Due to the fusion of various optical data it is possible to indicate by information statistical theory the inverse physical problem on the presence of impurities in mixtures (viruses, bacteria, oil, metallic particles, etc.), and in this case polymodality of particle size distribution is not an obstacle. Bank of optical data for 3D-DS is the base for analysis by information-statistical method.

  6. Controlled aggregates of magnetite nanoparticles for highly sensitive MR contrast agent.

    PubMed

    Jeon, Bong-Sik; Cho, Eun-Jin; Yang, Hee-Man; Suh, Jin-Suck; Huh, Yong-Min; Kim, Jong-Duk

    2009-12-01

    We have prepared a magnetite encapsulated polymer nanocomposite (MEPN) by an emulsification-diffusion technique and found that the encapsulation efficiency could be precisely controlled according to the portion of magnetite and the capping ligand that covers the surface of the magnetite nanoparticles. The field-dependence and temperature dependence on magnetization, measured by a superconducting quantum interference device, demonstrate that there was no size effect of the magnetite nanoparticles on the encapsulation behavior. The size distribution and T2 relaxivity of prepared MEPNs were measured using magnetic resonance imaging for analysis of the effect of aggregation and it was verified that aggregates of the magnetite nanoparticles provide enhanced relaxation ability.

  7. Reduction of Hg(II) to Hg(0) by magnetite.

    PubMed

    Wiatrowski, Heather A; Das, Soumya; Kukkadapu, Ravi; Ilton, Eugene S; Barkay, Tamar; Yee, Nathan

    2009-07-15

    Mercury (Hg) is a highly toxic element, and its contamination of groundwater presents a significant threat to terrestrial ecosystems. Understanding the geochemical processes that mediate mercury transformations in the subsurface is necessary to predict its fate and transport. In this study, we investigated the redox transformation of mercuric Hg (Hg[II]) in the presence of the Fe(II)/Fe(III) mixed valence iron oxide mineral magnetite. Kinetic and spectroscopic experiments were performed to elucidate reaction rates and mechanisms. The experimental data demonstrated that reaction of Hg(II) with magnetite resulted in the loss of Hg(II) and the formation of volatile elemental Hg (Hg[0]). Kinetic experiments showed that Hg(II) reduction occurred within minutes, with reaction rates increasing with increasing magnetite surface area (0.5 to 2 m2/L) and solution pH (4.8 to 6.7), and decreasing with increasing chloride concentration (10(-6) to 10(-2) mol/L). Mössbauer spectroscopic analysis of reacted magnetite samples revealed a decrease in Fe(II) content, corresponding to the oxidation of Fe(II) to Fe(III) in the magnetite structure. X-ray photoelectron spectroscopy detected the presence of Hg(II) on magnetite surfaces, implying that adsorption is involved in the electron transfer process. These results suggest that Hg(II) reaction with solid-phase Fe(II) is a kinetically favorable pathway for Hg(II) reduction in magnetite-hearing environmental systems.

  8. Extracellular synthesis of magnetite and metal-substituted magnetite nanoparticles.

    PubMed

    Roh, Y; Vali, H; Phelps, T J; Moon, J W

    2006-11-01

    We have developed a novel microbial process that exploits the ability of Fe(III)-reducing microorganisms to produce copious amounts of extracellular magentites and metal-substituted magnetite nanoparticles. The Fe(III)-reducing bacteria (Theroanaerobacter ethanolicus and Shewanella sp.) have the ability to reduce Fe(III) and various metals in aqueous media and form various sized magnetite and metal-substituted magnetite nano-crystals. The Fe(III)-reducing bacteria formed metalsubstituted magnetites using iron oxide plus metals (e.g., Co, Cr, Mn, Ni) under conditions of relatively low temperature (<70 degrees C), ambient pressure, and pH values near neutral to slightly basic (pH = 6.5 to 9). Precise biological control over activation and regulation of the biosolid-state processes can produce magnetite particles of well-defined size (typically tens of nanometers) and crystallographic morphology, containing selected dopant metals into the magnetite (Fe(3-y)XyO4) structure (where X = Co, Cr, Mn, Ni). Magnetite yields of up to 20 g/L per day have been observed in 20-L vessels. Water-based ferrofluids were formed with the nanometer sized, magnetite, and metal-substituted biomagnetite particles.

  9. Influence of magnetite stoichiometry on Fe(II) uptake and nitrobenzene reduction.

    PubMed

    Gorski, Christopher A; Scherer, Michelle M

    2009-05-15

    Magnetite (Fe3O4) is a common biomineralization product of microbial iron respiration and is often found in subsurface anoxic environments, such as groundwater aquifers where aqueous Fe(II) is present We investigated the reaction between aqueous Fe(II) and magnetite using the isotopic selectivity of 57Fe Mössbauer spectroscopy and revisited the reduction of nitrobenzene by magnetite. Similar to our previous findings with Fe3+ oxides, we did not observe the formation of a stable sorbed Fe(II) species; instead, we observed oxidation of the Fe(II) to a partially oxidized magnetite phase. Oxidation of Fe(II) was accompanied by reduction of the octahedral Fe3+ atoms in the underlying magnetite to octahedral Fe2+ atoms. The lack of a stable, sorbed Fe(II) species on magnetite prompted us to reevaluate what is controlling the extent of Fe(II) uptake on magnetite, as well as contaminant reduction in the presence of magnetite and Fe(II). Uptake of Fe(II) by magnetite appears to be limited by the stoichiometry of the magnetite particles, rather than the surface area of the particles. More oxidized (or less stoichiometric) magnetite particles take up more Fe(II), with the formation of stoichiometric magnetite (Fe2+/Fe3+ = 0.5) limiting the extent of Fe(II) uptake. We also showthat stoichiometric magnetite, in the absence of aqueous Fe(II), can rapidly reduce nitrobenzene. Based on these results, we speculate that contaminant reduction that was previously attributed to Fe(II) sorbed on magnetite is due to a process similar to negative (n) doping of a solid, which increases the stoichiometry of the magnetite and alters the bulk redox properties of the particle to make reduction more favorable. PMID:19544872

  10. Bimodal porous silica microspheres decorated with polydopamine nano-particles for the adsorption of methylene blue in fixed-bed columns.

    PubMed

    Ataei-Germi, Taher; Nematollahzadeh, Ali

    2016-05-15

    Bimodal meso/macro-porous silica microspheres (MSM) were synthesized by a modified sol-emulsion-gel method and then the surface was coated with polydopamine (PDA) nano-particles of 39nm in size. Focusing on the encouraging properties of the synthesized adsorbent, such as high specific surface area (612.3m(2)g(-1), because of mesopores), fast mass transfer (0.9-2.67×10(-3)mLmin(-1)mg, because of macropores), and abundant "adhesive" functional groups of PDA, it was used for the removal of methylene blue (MB) from aqueous solution in a fixed-bed column. The effect of different parameters such as pH, initial concentration, and flow rate was studied. The results revealed that an appropriate sorption condition is an alkaline solution of MB (e.g., pH 10) at low flow rate (less than 5mLmin(-1)). Furthermore, the compatibility of the experimental data with mathematical models such as Thomas and Adams-Bohart was investigated. Both of the models showed a good agreement with the experimental data (R(2)=0.9954-0.9994), and could be applied for the prediction of the column properties and breakthrough curves. Regeneration of the column was performed by using HCl solution with a concentration of 0.1M as an eluent. PMID:26943002

  11. Crystallography of Magnetite Plaquettes and their Significance as Asymmetric Catalysts for the Synthesis of Chiral Organics in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.

    2015-01-01

    We have previously observed the magnetite plaquettes in carbonaceous chondrites using scanning electron microscope (SEM) imaging, examined the crystal orientation of the polished surfaces of magnetite plaquettes in CI Orgueil using electron backscattered diffraction (EBSD) analysis, and concluded that these magnetite plaquettes are likely naturally asymmetric materials. In this study, we expanded our EBSD observation to other magnetite plaquettes in Orgueil, and further examined the internal structure of these remarkable crystals with the use of X-ray computed microtomography.

  12. Tuning of platinum nano-particles by Au usage in their binary alloy for direct ethanol fuel cell: Controlled synthesis, electrode kinetics and mechanistic interpretation

    NASA Astrophysics Data System (ADS)

    Dutta, Abhijit; Mondal, Achintya; Datta, Jayati

    2015-06-01

    Understanding of the electrode-kinetics and mechanism of ethanol oxidation reaction (EOR) is of considerable interest for optimizing electro-catalysis in direct ethanol fuel cell (DEFC). This work attempts to design Pt based electro-catalyst on carbon support, tuned with gold nano-particles (NPs), for their use in DEFC operating in alkaline medium. The platinum-gold alloyed NPs are synthesized at desired compositions and size (2-10 nm) by controlled borohydride reduction method and successfully characterized by XRD, TEM, EDS and XPS techniques. The kinetic parameters along with the activation energies for the EOR are evaluated over the temperature range 20-80 °C and the oxidation reaction products estimated through ion chromatographic analysis. Compared to single Pt/C catalyst, the over potential of EOR is reduced by ca. 500 mV, at the onset during the reaction, for PtAu/C alloy with only 23% Pt content demonstrating the ability of Au and/or its surface oxides providing oxygen species at much lower potentials compared to Pt. Furthermore, a considerable increase in the peak power density (>191%) is observed in an in-house fabricated direct ethanol anion exchange membrane fuel cell, DE(AEM)FC using the best performing Au covered Pt electrode (23% Pt) compared to the monometallic Pt catalyst.

  13. The effect of acid–base clustering and ions on the growth of atmospheric nano-particles

    DOE PAGES

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; et al

    2016-05-20

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted formore » in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. Furthermore, we bring these observations into a coherent framework and discuss their significance in the atmosphere.« less

  14. Study on the Particle Size Distribution Nano-Particles of Mining Minerals on Whiteness of Triaxial Body

    NASA Astrophysics Data System (ADS)

    Mathur, Ravi; Soni, Aditi

    White wares produced worldwide represent the foundation of much of the ceramic industry; Porcelain bodies fabricated from triaxial mixtures of clay, quartz and feldspar with different size and amounts of nano particles were investigated. Although the purity of raw materials has a strong effect on the colour of the fired bodies, the particle size of raw materials also effect the whiteness The raw material mining minerals china Clay, Feldspar, quarts were prepared of various sized nano particles contains 10.60 -20.22%, 56.84- 70.80 % and 34.87-50.76 % of 100nm respectively. The fired bodies of raw mining minerals and triaxial bodies were subjected to colour measurement. The differences in whiteness were compared and discussed. The studies so far carried out is upto 400 mesh size while the present study has included up to 100nm particle size. A statistical correlation between whiteness of feldspar and triaxial body was also carried out. The correlation between china clay and triaxial body are 0.53, 0.57 and 0.66 for china clay similarly correlation for feldspar is 0.49, 0.73 and 0.83 for triaxial body it are 0.97, 0.84 and 0.75 for A1, A2 and A3 samples. Correlation between china clay and feldspar with triaxial body are 0.79 and 0.92 respectively.

  15. The effect of acid-base clustering and ions on the growth of atmospheric nano-particles.

    PubMed

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J; Dunne, Eimear M; Flagan, Richard C; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P; Ruuskanen, Taina; Santos, Filipe D; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E; Wagner, Paul E; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M; Virtanen, Annele; Donahue, Neil M; Carslaw, Kenneth S; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R; Kulmala, Markku

    2016-05-20

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

  16. Use of TiO2 nano particles in Sulfur electrodes to enhance cyclability of Li-S batteries

    NASA Astrophysics Data System (ADS)

    Dharmasena, Ruchira; Sumanasekera, Gamini; Jasinski, Jacek; Thapa, Arjun; Sunkara, Mahendra

    Herein we investigate a novel and facile technique to fabricate Sulfur cathode for Li-S batteries with better cyclability and higher stable gravimetric capacity of around 750 mAh/g over 50 cycles. In this study we have experimented the use of TiO2 nano particles to prevent polysulfide dissolution into the electrolyte. Absorption and adsorption properties of TiO2 nano particles are used to trap Lithium Polysulfides. Excellent electrical conductivity property of carbonized polyacrylonitrile (PAN) carbon fibers is effectively used in this technique to establish better electrical connection to Sulfur in the bulk electrode. The thermal annealing technique we use in this work introduces a facile way to load Sulfur into the electrode. Mechanical properties of the Sulfur electrode is improved using a relatively easy way to sustain expansion and contraction at stable coulombic capacity with almost 100 % efficiency. The mechanism of the said Sulfur electrode is discussed in detail using cyclic voltammetry and Impedance spectrum analysis. Funded by KY EPSCoR, Project Number T1 2014-2019.

  17. The effect of acid–base clustering and ions on the growth of atmospheric nano-particles

    PubMed Central

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J.; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K.; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P.; Ruuskanen, Taina; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N.; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E.; Wagner, Paul E.; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Virtanen, Annele; Donahue, Neil M.; Carslaw, Kenneth S.; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R.; Kulmala, Markku

    2016-01-01

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere. PMID:27197574

  18. The effect of acid-base clustering and ions on the growth of atmospheric nano-particles.

    PubMed

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J; Dunne, Eimear M; Flagan, Richard C; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P; Ruuskanen, Taina; Santos, Filipe D; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E; Wagner, Paul E; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M; Virtanen, Annele; Donahue, Neil M; Carslaw, Kenneth S; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R; Kulmala, Markku

    2016-01-01

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere. PMID:27197574

  19. Nano-particle based scattering layers for optical efficiency enhancement of organic light-emitting diodes and organic solar cells

    NASA Astrophysics Data System (ADS)

    Chang, Hong-Wei; Lee, Jonghee; Hofmann, Simone; Hyun Kim, Yong; Müller-Meskamp, Lars; Lüssem, Björn; Wu, Chung-Chih; Leo, Karl; Gather, Malte C.

    2013-05-01

    The performance of both organic light-emitting diodes (OLEDs) and organic solar cells (OSC) depends on efficient coupling between optical far field modes and the emitting/absorbing region of the device. Current approaches towards OLEDs with efficient light-extraction often are limited to single-color emission or require expensive, non-standard substrates or top-down structuring, which reduces compatibility with large-area light sources. Here, we report on integrating solution-processed nano-particle based light-scattering films close to the active region of organic semiconductor devices. In OLEDs, these films efficiently extract light that would otherwise remain trapped in the device. Without additional external outcoupling structures, translucent white OLEDs containing these scattering films achieve luminous efficacies of 46 lm W-1 and external quantum efficiencies of 33% (both at 1000 cd m-2). These are by far the highest numbers ever reported for translucent white OLEDs and the best values in the open literature for any white device on a conventional substrate. By applying additional light-extraction structures, 62 lm W-1 and 46% EQE are reached. Besides universally enhancing light-extraction in various OLED configurations, including flexible, translucent, single-color, and white OLEDs, the nano-particle scattering film boosts the short-circuit current density in translucent organic solar cells by up to 70%.

  20. Modeling Magnetite Reflectance Spectra Using Hapke Theory and Existing Optical Constants

    NASA Technical Reports Server (NTRS)

    Roush, T. L.; Blewett, D. T.; Cahill, J. T. S.

    2016-01-01

    Magnetite is an accessory mineral found in terrestrial environments, some meteorites, and the lunar surface. The reflectance of magnetite powers is relatively low [1], and this property makes it an analog for other dark Fe- or Ti-bearing components, particularly ilmenite on the lunar surface. The real and imaginary indices of refraction (optical constants) for magnetite are available in the literature [2-3], and online [4]. Here we use these values to calculate the reflectance of particulates and compare these model spectra to reflectance measurements of magnetite available on-line [5].

  1. [Interaction of fibrinogen with magnetite nanoparticles].

    PubMed

    Bychkova, A V; Sorokina, O N; Kovarskiĭ, A L; Shapiro, A B; Leonova, V B; Rozenfel'd, M A

    2010-01-01

    The interaction between fibrinogen and magnetite nanoparticles in solution has been studied by the methods of spin labeling, ferromagnetic resonance, dynamic and Rayleigh light scattering. It was shown that protein molecules adsorb on the surface of nanoparticles to form multilayer protein covers. The number of molecules adsorbed on one nanoparticle amounts to approximately 65 and the thickness of the adsorption layer amounts to approximately 27 nm. Separate nanoparticles with fibrinogen covers (clusters) form aggregates due to interactions of the end D-domains of fibrinogen. Under the influence of direct magnetic field, nanoparticles with adsorbed proteins form linear aggregates parallel to force lines. It was shown that the rate of protein coagulation during the formation of fibrin gel under the action of thrombin on fibrinogen decreases approximately 2 times in the presence of magnetite nanoparticles, and the magnitude of the average fiber mass-length ratio grows.

  2. Kinetic modeling of the formation and growth of inorganic nano-particles during pulverized coal char combustion in O2/N2 and O2/CO2 atmospheres

    DOE PAGES

    Shaddix, Christopher R.; Niu, Yanqing; Hui, Shi'en; Wang, Shuai

    2016-08-01

    In this formation of nano-particles during coal char combustion, the vaporization of inorganic components in char and the subsequent homogeneous particle nucleation, heterogeneous condensation, coagulation, and coalescence play decisive roles. Furthermore, conventional measurements cannot provide detailed information on the dynamics of nano-particle formation and evolution, In this study, a sophisticated intrinsic char kinetics model that considers ash effects (including ash film formation, ash dilution, and ash vaporization acting in tandem), both oxidation and gasification by CO2 and H2O, homogeneous particle nucleation, heterogeneous vapor condensation, coagulation, and and coalescence mechanisms is developed and used to compare the temporal evolution of themore » number and size of nano-particles during coal char particle combustion as a function of char particle size, ash content, and oxygen content in O2/N2 and O2/CO2 atmospheres .« less

  3. Surface plasmons induced in Al spherical nanoparticles by Auger effect

    NASA Astrophysics Data System (ADS)

    García Gallardo, J.; Gervasoni, J. L.; Kövér, L.

    2016-02-01

    In this work we study the surface plasmon generation by electron-hole interaction in an aluminum spherical nano-particle due to the Auger electron-hole interaction by means of the Hamiltonian formalism.

  4. Adaptive neuro-fuzzy inference system (ANFIS) to predict CI engine parameters fueled with nano-particles additive to diesel fuel

    NASA Astrophysics Data System (ADS)

    Ghanbari, M.; Najafi, G.; Ghobadian, B.; Mamat, R.; Noor, M. M.; Moosavian, A.

    2015-12-01

    This paper studies the use of adaptive neuro-fuzzy inference system (ANFIS) to predict the performance parameters and exhaust emissions of a diesel engine operating on nanodiesel blended fuels. In order to predict the engine parameters, the whole experimental data were randomly divided into training and testing data. For ANFIS modelling, Gaussian curve membership function (gaussmf) and 200 training epochs (iteration) were found to be optimum choices for training process. The results demonstrate that ANFIS is capable of predicting the diesel engine performance and emissions. In the experimental step, Carbon nano tubes (CNT) (40, 80 and 120 ppm) and nano silver particles (40, 80 and 120 ppm) with nanostructure were prepared and added as additive to the diesel fuel. Six cylinders, four-stroke diesel engine was fuelled with these new blended fuels and operated at different engine speeds. Experimental test results indicated the fact that adding nano particles to diesel fuel, increased diesel engine power and torque output. For nano-diesel it was found that the brake specific fuel consumption (bsfc) was decreased compared to the net diesel fuel. The results proved that with increase of nano particles concentrations (from 40 ppm to 120 ppm) in diesel fuel, CO2 emission increased. CO emission in diesel fuel with nano-particles was lower significantly compared to pure diesel fuel. UHC emission with silver nano-diesel blended fuel decreased while with fuels that contains CNT nano particles increased. The trend of NOx emission was inverse compared to the UHC emission. With adding nano particles to the blended fuels, NOx increased compared to the net diesel fuel. The tests revealed that silver & CNT nano particles can be used as additive in diesel fuel to improve combustion of the fuel and reduce the exhaust emissions significantly.

  5. Magnetite: from synthesis to applications.

    PubMed

    Unsoy, Gozde; Gunduz, Ufuk; Oprea, Ovidiu; Ficai, Denisa; Sonmez, Maria; Radulescu, Marius; Alexie, Mihaela; Ficai, Anton

    2015-01-01

    In this review the synthesis, functionalization and some applications of magnetite nanoparticles (MNPs) were highlighted. It is our intention to highlight the correlations between the synthesis routes, related synthesis parameters, functionalization strategies and the properties expected for the materials containing MNPs. The uses of MNPs are strongly influenced by the properties of the materials. Therefore this review is trying to discuss the applications of the magnetite and magnetite based nanomaterials by taking into account all the factors that can influence the properties of the final materials and consequently their potential applications. PMID:25877083

  6. Using a biomimetic membrane surface experiment to investigate the activity of the magnetite biomineralisation protein Mms6† †Electronic supplementary information (ESI) available: Including Mms6 protein and peptide sequences, additional QCM-D and SEM data and protein modelling. See DOI: 10.1039/c5ra16469a Click here for additional data file.

    PubMed Central

    Bird, Scott M.; Rawlings, Andrea E.; Galloway, Johanna M.

    2016-01-01

    Magnetotactic bacteria are able to synthesise precise nanoparticles of the iron oxide magnetite within their cells. These particles are formed in dedicated organelles termed magnetosomes. These lipid membrane compartments use a range of biomineralisation proteins to nucleate and regulate the magnetite crystallisation process. A key component is the membrane protein Mms6, which binds to iron ions and helps to control the formation of the inorganic core. We have previously used Mms6 on gold surfaces patterned with a self-assembled monolayer to successfully produce arrays of magnetic nanoparticles. Here we use this surface system as a mimic of the interior face of the magnetosome membrane to study differences between intact Mms6 and the acid-rich C-terminal peptide subregion of the Mms6 protein. When immobilised on surfaces, the peptide is unable to reproduce the particle size or homogeneity control exhibited by the full Mms6 protein in our experimental setup. Moreover, the peptide is unable to support anchoring of a dense array of nanoparticles to the surface. This system also allows us to deconvolute particle binding from particle nucleation, and shows that Mms6 particle binding is less efficient when supplied with preformed magnetite nanoparticles when compared to particles precipitated from solution in the presence of the surface immobilised Mms6. This suggests that Mms6 binds to iron ions rather than to magnetite surfaces in our system, and is perhaps a nucleating agent rather than a controller of magnetite crystal growth. The comparison between the peptide and the protein under identical experimental conditions indicates that the full length sequence is required to support the full function of Mms6 on surfaces. PMID:27019707

  7. Origins of magnetite nanocrystals in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; McKay, D. S.; Gibson, E. K.; Wentworth, S. J.

    2009-11-01

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe 3O 4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

  8. Electrochemistry and dissolution kinetics of magnetite and ilmenite

    USGS Publications Warehouse

    White, A.F.; Peterson, M.L.; Hochella, M.F.

    1994-01-01

    Natural samples of magnetite and ilmenite were experimentally weathered in pH 1-7 anoxic solutions at temperatures of 2-65 ??C. Reaction of magnetite is described as [Fe2+Fe23+]O4(magnetite) + 2H+ ??? ??[Fe23+]O3(maghemite) + Fe2+ + H2O. Dynamic polarization experiments using magnetite electrodes confirmed that this reaction is controlled by two electrochemical half cells, 3[Fe2+Fe23+]O4(magnetite) ??? 4??[Fe23+]O3(maghemite) + Fe2+ + 2e- and [Fe2+Fe23+]O4(magnetite) + 8 H+ + 2e- ??? 3Fe2+ + 4H2O, which result in solid state Fe3+ reduction, formation of an oxidized layer and release of Fe(II) to solution. XPS data revealed that iron is present in the ferric state in the surfaces of reacted magnetite and ilmenite and that the Ti Fe ratio increased with reaction pH for ilmenite. Short-term (<36 h) release rates of Fe(II) were linear with time. Between pH 1 and 7, rates varied between 0.3 and 13 ?? 10-14 mol ?? cm-2 ?? s-1 for magnetite and 0.05 and 12.3 ?? 10-14 mol ?? cm-2 ?? s-1 for ilmenite. These rates are two orders of magnitude slower than electrochemical rates determined by Tafel and polarization resistance measurements. Discrepancies are due to both differences in geometric and BET surface area estimates and in the oxidation state of the mineral surface. In long-term closed-system experiments (<120 days), Fe(II) release slowed with time due to the passivation of the surfaces by increasing thicknesses of oxide surface layers. A shrinking core model, coupling surface reaction and diffusion transport, predicted that at neutral pH, the mean residence time for sand-size grains of magnetite and ilmenite will exceed 107 years. This agrees with long-term stability of these oxides in the geologic record. ?? 1994.

  9. Growth mechanism and magnetic properties of magnetite nanoparticles during solution process

    NASA Astrophysics Data System (ADS)

    Iwamoto, Takashi; Kinoshita, Toshiya; Takahashi, Kazuma

    2016-05-01

    We investigated the growth mechanism of magnetite nanoparticles during chemical synthesis by analyzing their physicochemical properties. The transformation from metallic precursor to particles and the growth of the particle occurred during chemical synthesis. During the transformation process, Fe(acac)3, which was used as a metallic precursor, was decomposed, fabricating an Fe oleate. The Fe oleates then agglomerated to each other to form Fe oleate clusters. Finally, the Fe oleate cluster was reduced, and a magnetite nanoparticle was fabricated. During the growth process of the magnetite nanoparticle, the diameter of the magnetite nanoparticles increased as the reaction temperature increased. Then, the Fe oleates on the surface of the magnetite nanoparticle were reduced at a constant rate, and as a result, the magnetite nanoparticle grew significantly.

  10. Fourier transform infrared and Raman spectroscopy studies on magnetite/Ag/antibiotic nanocomposites

    NASA Astrophysics Data System (ADS)

    Ivashchenko, Olena; Jurga-Stopa, Justyna; Coy, Emerson; Peplinska, Barbara; Pietralik, Zuzanna; Jurga, Stefan

    2016-02-01

    This article presents a study on the detection of antibiotics in magnetite/Ag/antibiotic nanocomposites using Fourier transform infrared (FTIR) and Raman spectroscopy. Antibiotics with different spectra of antimicrobial activities, including rifampicin, doxycycline, cefotaxime, and ceftriaxone, were studied. Mechanical mixtures of antibiotics and magnetite/Ag nanocomposites, as well as antibiotics and magnetite nanopowder, were investigated in order to identify the origin of FTIR bands. FTIR spectroscopy was found to be an appropriate technique for this task. The spectra of the magnetite/Ag/antibiotic nanocomposites exhibited very weak (for doxycycline, cefotaxime, and ceftriaxone) or even no (for rifampicin) antibiotic bands. This FTIR "invisibility" of antibiotics is ascribed to their adsorbed state. FTIR and Raman measurements show altered Csbnd O, Cdbnd O, and Csbnd S bonds, indicating adsorption of the antibiotic molecules on the magnetite/Ag nanocomposite structure. In addition, a potential mechanism through which antibiotic molecules interact with magnetite/Ag nanoparticle surfaces is proposed.

  11. Synthesis and characterization of magnetite particles covered with α-trietoxysilil-polydimethylsiloxane

    NASA Astrophysics Data System (ADS)

    Durdureanu-Angheluta, Anamaria; Pricop, Lucia; Stoica, Iuliana; Peptu, Catalina-Anisoara; Dascalu, Andrei; Marangoci, Narcisa; Doroftei, Florica; Chiriac, Horia; Pinteala, Mariana; Simionescu, Bogdan C.

    2010-10-01

    New silicon magnetite ferrofluids were prepared by dispersing siloxane-coated magnetite particles in polydimethylsiloxane with low or high molecular weights. Ferrofluids are stable colloidal dispersions of ultra fine covered magnetite particles, which may be selected for a specific application. We demonstrated new methods of stabilizing the magnetic particles by reacting the hydroxyl groups on the surface of magnetite particles with terminal ethoxy groups of polydimethylsiloxane, followed by their dispersion in silicon fluids. The new silicon ferrofluids were tested from the morphology, magnetic properties/losses, and rheological properties point of view.

  12. The effect of metal nano particle on optical absorption coefficient of multi-layer spherical quantum dot

    NASA Astrophysics Data System (ADS)

    Zamani, N.; Keshavarz, A.; Nadgaran, H.

    2016-06-01

    In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge-Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.

  13. Photodegradation of luminescence in organic-ligand-capped Eu{sup 3+}:LaF{sub 3} nano-particles

    SciTech Connect

    King, Gavin G. G.; Taylor, Luke R.; Longdell, Jevon J.; Clarke, David J.; Quilty, J. W.

    2014-01-28

    The luminescence from europium doped lanthanum trifluoride (Eu{sup 3+}:LaF{sub 3}) nano-crystals can be greatly enhanced by capping with β-diketonate organic ligands. Here, we report on photo-stability measurements for the case of nano-crystals capped with thenoyltrifluroacetone (TTA) and compared with those capped with an inactive ligand, oleic acid. With exposure to UV pump light, we observed significant decrease in fluorescence and change in emission spectrum of the TTA-capped nano-particles whilst the fluorescence lifetime remained approximately constant. After a dose of order 70 kJ cm{sup −2}, the luminescence level was similar to that of oleic acid capped nano-crystals. We discuss possible mechanisms.

  14. Optically sensitive devices based on Pt nano particles fabricated by atomic layer deposition and embedded in a dielectric stack

    SciTech Connect

    Mikhelashvili, V.; Padmanabhan, R.; Eisenstein, G.; Meyler, B.; Yofis, S.; Weindling, S.; Salzman, J.; Atiya, G.; Cohen-Hyams, Z.; Kaplan, W. D.; Ankonina, G.

    2015-10-07

    We report a series of metal insulator semiconductor devices with embedded Pt nano particles (NPs) fabricated using a low temperature atomic layer deposition process. Optically sensitive nonvolatile memory cells as well as optical sensors: (i) varactors, whose capacitance-voltage characteristics, nonlinearity, and peak capacitance are strongly dependent on illumination intensity; (ii) highly linear photo detectors whose responsivity is enhanced due to the Pt NPs. Both single devices and back to back pairs of diodes were used. The different configurations enable a variety of functionalities with many potential applications in biomedical sensing, environmental surveying, simple imagers for consumer electronics and military uses. The simplicity and planar configuration of the proposed devices makes them suitable for standard CMOS fabrication technology.

  15. In-situ synthesis of Au nano particles of co-existing morphologies in liquid crystalline matrix

    NASA Astrophysics Data System (ADS)

    Dan, Kaustabh; Datta, Alokmay

    2015-06-01

    The present study describes the in-situ synthesis of Au nano particles (Au-NP) in the room temperature nematic liquid crystalline (LC) substance MBBA (N-4 methoxybenzylidene 4 butylaniline) without any external reducing or stabilizing agents. UV-Visible absorption and fluorescence spectroscopy clearly show formation of Au-NP within the LC matrix through the plasmon resonance peak for the NPs and EDAX measurements confirm this formation. Transmission electron Microscopy shows co-existence of spherical and prismatic NPs. FTIR spectroscopy shows a considerable shift in the C=N stretch band pointing to the location of the growth centre of the NPs. Polarization microscopy data indicates a definite phase ordering and texture transformation from Nematic to highly ordered smectic mesophase.

  16. Using Silver Nano-Particle Ink in Electrode Fabrication of High Frequency Copolymer Ultrasonic Transducers: Modeling and Experimental Investigation

    PubMed Central

    Decharat, Adit; Wagle, Sanat; Jacobsen, Svein; Melandsø, Frank

    2015-01-01

    High frequency polymer-based ultrasonic transducers are produced with electrodes thicknesses typical for printed electrodes obtained from silver (Ag) nano-particle inks. An analytical three-port network is used to study the acoustic effects imposed by a thick electrode in a typical layered transducer configuration. Results from the network model are compared to experimental findings for the implemented transducer configuration, to obtain a better understanding of acoustical effects caused by the additional printed mass loading. The proposed investigation might be supportive of identification of suitable electrode-depositing methods. It is also believed to be useful as a feasibility study for printed Ag-based electrodes in high frequency transducers, which may reduce both the cost and production complexity of these devices. PMID:25903552

  17. Optically sensitive devices based on Pt nano particles fabricated by atomic layer deposition and embedded in a dielectric stack

    NASA Astrophysics Data System (ADS)

    Mikhelashvili, V.; Padmanabhan, R.; Meyler, B.; Yofis, S.; Atiya, G.; Cohen-Hyams, Z.; Weindling, S.; Ankonina, G.; Salzman, J.; Kaplan, W. D.; Eisenstein, G.

    2015-10-01

    We report a series of metal insulator semiconductor devices with embedded Pt nano particles (NPs) fabricated using a low temperature atomic layer deposition process. Optically sensitive nonvolatile memory cells as well as optical sensors: (i) varactors, whose capacitance-voltage characteristics, nonlinearity, and peak capacitance are strongly dependent on illumination intensity; (ii) highly linear photo detectors whose responsivity is enhanced due to the Pt NPs. Both single devices and back to back pairs of diodes were used. The different configurations enable a variety of functionalities with many potential applications in biomedical sensing, environmental surveying, simple imagers for consumer electronics and military uses. The simplicity and planar configuration of the proposed devices makes them suitable for standard CMOS fabrication technology.

  18. Significantly enhanced impulse breakdown performances of propylene carbonate modified by TiO2 nano-particles

    NASA Astrophysics Data System (ADS)

    Hou, Yanpan; Zhang, Zicheng; Zhang, Jiande

    2016-10-01

    Nano-fluids with KH550-grafted TiO2 nano-particles homogenously dispersed into propylene carbonate exhibit substantially enhanced dielectric properties compared with the base liquid. Specifically, the breakdown stability of nano-fluids is dramatically improved for a small high-voltage electrode potential increasing rate, which has a potential to increase the reliability of the pulsed power system. On the other hand, the mean breakdown voltage of nano-fluids is more than 30% larger than that of base liquid when the high-voltage electrode potential increasing rate equals to 6 kV/μs, which will lead to a great increase in energy storage density of the pulsed power system.

  19. In-situ synthesis of Au nano particles of co-existing morphologies in liquid crystalline matrix

    SciTech Connect

    Dan, Kaustabh Datta, Alokmay

    2015-06-24

    The present study describes the in-situ synthesis of Au nano particles (Au-NP) in the room temperature nematic liquid crystalline (LC) substance MBBA (N-4 methoxybenzylidene 4 butylaniline) without any external reducing or stabilizing agents. UV-Visible absorption and fluorescence spectroscopy clearly show formation of Au-NP within the LC matrix through the plasmon resonance peak for the NPs and EDAX measurements confirm this formation. Transmission electron Microscopy shows co-existence of spherical and prismatic NPs. FTIR spectroscopy shows a considerable shift in the C=N stretch band pointing to the location of the growth centre of the NPs. Polarization microscopy data indicates a definite phase ordering and texture transformation from Nematic to highly ordered smectic mesophase.

  20. Effect of UV radiations to control particle size of Mn-Zn spinel ferrite nano-particles

    NASA Astrophysics Data System (ADS)

    Ameen Ramiza, F.; Ajmal, S. K.; Khan, M. B.; Nasim, A.; Jamil, Y.; Kashif, K.; Amira, S.

    2016-08-01

    MnxZn1-xFe2O4 (0.0 < x < 1.0) ferrite nano particles were synthesized for concentration varying from 0.27 to 0.87 to obtain chemically homogenous powder for obtaining fine particle size by co precipitation technique. Keeping in view the interest of scientists for particle size, the present work focus on the impact of UV radiation to control the particle size of prepared fine magnetic particles. The particles were digested for ninety minutes at a temperature of 90oC. The samples were divided into four equal quantities and were subjected to different doses of UV radiation. The chemically produced samples of Mn-Zn ferrite nano particles were analyzed by XRD which confirmed cubic spinel structure of the material. The average crystallite size (t), lattice parameter (a) and other structural parameters of UV-irradiated MnxZni-xFe2O4 spinel ferrite were calculated from XRD data. The spinel peak of the irradiated sample when compared with the control sample, shifted from 35.38 to 35.15. In few samples, additional peaks supporting the ferrite structure were also observed. The variation in the particle sizes observed for various doses of UV irradiation were in the range of 17.6 to 6.2 nm, whereas the particle size of the control was 8.82nm. The experiment was repeated for different concentrations, at the same digestion temperature and time revealed the similar results indicating that UV radiations can have a remarkable effect to control the phase and size of nano size fine magnetic ferrite particles. The present work successfully document the impact of UV to control the particle size.

  1. Optical micro resonance based sensor schemes for detection and identification of nano particles and biological agents in situ

    NASA Astrophysics Data System (ADS)

    Saetchnikov, Vladimir A.; Tcherniavskaia, Elina A.; Schweiger, Gustav; Ostendorf, Andreas

    2010-05-01

    A novel emerging technique for the label-free analysis of nano particles including biomolecules using optical micro cavity resonance is being developed. Various schemes based on a mechanically fixed microspheres as well as microspheres melted by laser on the tip of a standard single mode fiber have been investigated to make further development for microbial application. Water solutions of ethanol, HCl, glucose, vitamin C and biotin have been used to test refractive index changes by monitoring the magnitude of the whispering gallery modes spectral shift. Particular efforts were made for effective fixing of the micro spheres in the water flow, an optimal geometry for micro resonance observation and material of microsphere the most appropriate for microbial application. Optical resonance in free micro spheres from PMMA fixed in micro channels produced by photolithography has been observed under the laser power of less then 1 microwatt. Resonance shifts of C reactive protein water solutions as well as albumin solutions in pure water and with HCl modelling blood have been investigated. Introducing controlled amount of glass gel nano particles into sensor microsphere surrounding were accompanied by both correlative resonance shift (400 nm in diameter) and total reconstruct of resonance spectra (57 nm in diameter). Developed schemes have been demonstrated to be a promising technology platform for sensitive, lab-on-chip type sensor of diagnostic tools for different biological molecules, e.g. proteins, oligonucleotides, oligosaccharides, lipids, small molecules, viral particles, cells as well as in different experimental contexts e.g. proteomics, genomics, drug discovery, and membrane studies.

  2. Force interactions between magnetite, silica, and bentonite studied with atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Dobryden, I.; Potapova, E.; Holmgren, A.; Weber, H.; Hedlund, J.; Almqvist, N.

    2015-04-01

    Iron ore pellets consist of variety of mineral particles and are an important refined product used in steel manufacturing. Production of high-quality pellets requires good understanding of interactions between different constituents, such as magnetite, gangue residues, bentonite, and additives. Much research has been reported on magnetite, silica, and bentonite surface properties and their effect on pellet strength but more scant with a focus on a fundamental particle-particle interaction. To probe such particle interaction, atomic force microscopy (AFM) using colloidal probe technique has proven to be a suitable tool. In this work, the measurements were performed between magnetite-magnetite, bentonite-magnetite, silica-bentonite, and silica-magnetite particles in 1 mM CaCl2 solution at various pH values. The interaction character, i.e., repulsion or attraction, was determined by measuring and analyzing AFM force curves. The observed quantitative changes in interaction forces were in good agreement with the measured zeta-potentials for the particles at the same experimental conditions. Particle aggregation was studied by measuring the adhesion force. Absolute values of adhesion forces for different systems could not be compared due to the difference in particle size and contact geometry. Therefore, the relative change of adhesion force between pH 6 and 10 was used for comparison. The adhesion force decreased for the magnetite-magnetite and bentonite-silica systems and slightly increased for the magnetite-bentonite system at pH 10 as compared to pH 6, whereas a pronounced decrease in adhesion force was observed in the magnetite-silica system. Thus, the presence of silica particles on the magnetite surface could have a negative impact on the interaction between magnetite and bentonite in balling due to the reduction of the adhesion force.

  3. Preparations of nano-particles, nano-composites and fibers of ZnO from an amide precursor: Photocatalytic decomposition of (CH{sub 3}){sub 2}S{sub 2} in a continuous flow reactor

    SciTech Connect

    Daniele, Stephane . E-mail: daniele@catalyse.cnrs.fr; Ghazzal, Mohamed N.; Hubert-Pfalzgraf, Liliane G.; Duchamp, Christian; Guillard, Chantal; Ledoux, Gilles

    2006-12-14

    High surface area hexagonal ZnO nano-particles were obtained at room temperature from hydrolysis of the amide derivative Zn[N(SiMe{sub 3}){sub 2}]{sub 2}. The same procedure applied on silica or cellulose substrates led to homogeneous crack-free hybrid materials for which micro- down to nano-meter replication into ZnO cloth was achieved by calcination at 700 deg. C. These materials were characterized by FT-IR, UV-vis, photoluminescence, X-ray diffraction (XRD) and transmission electron microscopy (TEM). They demonstrated enhanced photocatalytic degradation of a tough pollutant such as CH{sub 3}SSCH{sub 3} compared with commercial ZnO powder.

  4. High saturation magnetization of γ-Fe2O3 nano-particles by a facile one-step synthesis approach

    PubMed Central

    Cao, Derang; Li, Hao; Pan, Lining; Li, Jianan; Wang, Xicheng; Jing, Panpan; Cheng, Xiaohong; Wang, Wenjie; Wang, Jianbo; Liu, Qingfang

    2016-01-01

    We have demonstrated the synthesis of γ-Fe2O3 nano-particles through a facile and novel calcination process in the air. There is no pH regulation, gas atmosphere, additive, centrifugation or other complicated procedures during the preparing process. A detailed formation process of the nano-particles is proposed, and DMF as a polar solvent may slower the reaction process of calcination. The structures, morphologies, and magnetic properties of γ-Fe2O3 nano-particles were investigated systematically, and the pure γ-Fe2O3 nano-particles obtained at 200 °C display uniform morphology good magnetic property. The saturation magnetization of obtained pure γ-Fe2O3 is about 74 emu/g, which is comparable with bulk material (76 emu/g) and larger than other results. In addition, the photocatalytic activity for degradation of methylene blue is also studied, which shows proper photocatalytic activity. PMID:27581732

  5. High saturation magnetization of γ-Fe2O3 nano-particles by a facile one-step synthesis approach.

    PubMed

    Cao, Derang; Li, Hao; Pan, Lining; Li, Jianan; Wang, Xicheng; Jing, Panpan; Cheng, Xiaohong; Wang, Wenjie; Wang, Jianbo; Liu, Qingfang

    2016-01-01

    We have demonstrated the synthesis of γ-Fe2O3 nano-particles through a facile and novel calcination process in the air. There is no pH regulation, gas atmosphere, additive, centrifugation or other complicated procedures during the preparing process. A detailed formation process of the nano-particles is proposed, and DMF as a polar solvent may slower the reaction process of calcination. The structures, morphologies, and magnetic properties of γ-Fe2O3 nano-particles were investigated systematically, and the pure γ-Fe2O3 nano-particles obtained at 200 °C display uniform morphology good magnetic property. The saturation magnetization of obtained pure γ-Fe2O3 is about 74 emu/g, which is comparable with bulk material (76 emu/g) and larger than other results. In addition, the photocatalytic activity for degradation of methylene blue is also studied, which shows proper photocatalytic activity. PMID:27581732

  6. High saturation magnetization of γ-Fe2O3 nano-particles by a facile one-step synthesis approach

    NASA Astrophysics Data System (ADS)

    Cao, Derang; Li, Hao; Pan, Lining; Li, Jianan; Wang, Xicheng; Jing, Panpan; Cheng, Xiaohong; Wang, Wenjie; Wang, Jianbo; Liu, Qingfang

    2016-09-01

    We have demonstrated the synthesis of γ-Fe2O3 nano-particles through a facile and novel calcination process in the air. There is no pH regulation, gas atmosphere, additive, centrifugation or other complicated procedures during the preparing process. A detailed formation process of the nano-particles is proposed, and DMF as a polar solvent may slower the reaction process of calcination. The structures, morphologies, and magnetic properties of γ-Fe2O3 nano-particles were investigated systematically, and the pure γ-Fe2O3 nano-particles obtained at 200 °C display uniform morphology good magnetic property. The saturation magnetization of obtained pure γ-Fe2O3 is about 74 emu/g, which is comparable with bulk material (76 emu/g) and larger than other results. In addition, the photocatalytic activity for degradation of methylene blue is also studied, which shows proper photocatalytic activity.

  7. Functionalized magnetite particles for adsorption of colloidal noble metal nanoparticles.

    PubMed

    Lopes, Joana L; Marques, Karine L; Girão, Ana V; Pereira, Eduarda; Trindade, Tito

    2016-08-01

    Magnetite (inverse spinel type) particles have been surface-modified with siliceous shells enriched in dithiocarbamate groups. The deposition of colloidal noble metal nanoparticles (Au, Ag, Pt, Pd) onto the modified magnetites can be performed by treating the respective hydrosols with the magnetic sorbents, thus allowing their uptake from water under a magnetic gradient. In particular, for Au colloids, these magnetic particles are very efficient sorbents that we ascribe to the strong affinity of sulfur-containing groups at the magnetite surfaces for this metal. Considering the extensive use of Au colloids in laboratorial and industrial contexts, the approach described here might have an impact on the development of nanotechnologies to recover this precious metal. En route to these findings, we varied several operational parameters in order to investigate this strategy as a new bottom-up assembly method for producing plasmonic-magnetic nanoassemblies. PMID:27156089

  8. Functionalized magnetite particles for adsorption of colloidal noble metal nanoparticles.

    PubMed

    Lopes, Joana L; Marques, Karine L; Girão, Ana V; Pereira, Eduarda; Trindade, Tito

    2016-08-01

    Magnetite (inverse spinel type) particles have been surface-modified with siliceous shells enriched in dithiocarbamate groups. The deposition of colloidal noble metal nanoparticles (Au, Ag, Pt, Pd) onto the modified magnetites can be performed by treating the respective hydrosols with the magnetic sorbents, thus allowing their uptake from water under a magnetic gradient. In particular, for Au colloids, these magnetic particles are very efficient sorbents that we ascribe to the strong affinity of sulfur-containing groups at the magnetite surfaces for this metal. Considering the extensive use of Au colloids in laboratorial and industrial contexts, the approach described here might have an impact on the development of nanotechnologies to recover this precious metal. En route to these findings, we varied several operational parameters in order to investigate this strategy as a new bottom-up assembly method for producing plasmonic-magnetic nanoassemblies.

  9. Observations of magnetite dissolution in poorly drained soils

    USGS Publications Warehouse

    Grimley, D.A.; Arruda, N.K.

    2007-01-01

    Dissolution of strongly magnetic minerals is a common and relatively rapid phenomenon in poorly drained soils of the central United States, resulting in low magnetic susceptibility (MS). Low Eh reducing conditions are primarily responsible for magnetic mineral dissolution; a process likely mediated by iron-reducing bacteria in the presence of soil organic matter. Based on transects across drainage sequences from nine sites, natural magnetic minerals (>5 ??m) extracted from surface soil consist of 54% ?? 18% magnetite, 21% ?? 11% titanomagnetite, and 17% ?? 14% ilmenite. Magnetite and titanomagnetite dissolution, assessed by scanning electron microscopy on a 0-to-3 scale, inversely correlates with surface soil MS (r = 0.53), a proxy for soil drainage at studied transects. Altered magnetite typically displays etch pits 5 ??m) include 26% ?? 18% anthropogenic fly ash that also exhibits greater dissolution in low MS soils (r = 0.38), indicating detectable alteration can occur within 150 years in low Eh soils. Laboratory induced reduction of magnetite, titanomagnetite, and magnetic fly ash, with a citrate-bicarbonate- dithionite solution, resulted in dissolution textures similar to those of in situ soil particles. Although experiments indicate that reductive dissolution of magnetite can occur abiotically under extreme conditions, bacteria likely play an important role in the natural environment. ?? 2007 Lippincott Williams & Wilkins, Inc.

  10. Natural Magnetite: an efficient catalyst for the degradation of organic contaminant

    PubMed Central

    HE, Hongping; ZHONG, Yuanhong; LIANG, Xiaoliang; TAN, Wei; ZHU, Jianxi; Yan WANG, Christina

    2015-01-01

    Iron (hydr)oxides are ubiquitous earth materials that have high adsorption capacities for toxic elements and degradation ability towards organic contaminants. Many studies have investigated the reactivity of synthetic magnetite, while little is known about natural magnetite. Here, we first report the reactivity of natural magnetites with a variety of elemental impurities for catalyzing the decomposition of H2O2 to produce hydroxyl free radicals (•OH) and the consequent degradation of p-nitrophenol (p-NP). We observed that these natural magnetites show higher catalytic performance than that of the synthetic pure magnetite. The catalytic ability of natural magnetite with high phase purity depends on the surface site density while that for the magnetites with exsolutions relies on the mineralogical nature of the exsolved phases. The pleonaste exsolution can promote the generation of •OH and the consequent degradation of p-NP; the ilmenite exsolution has little effect on the decomposition of H2O2, but can increase the adsorption of p-NP on magnetite. Our results imply that natural magnetite is an efficient catalyst for the degradation of organic contaminants in nature. PMID:25958854

  11. Natural Magnetite: an efficient catalyst for the degradation of organic contaminant.

    PubMed

    He, Hongping; Zhong, Yuanhong; Liang, Xiaoliang; Tan, Wei; Zhu, Jianxi; Wang, Christina Yan

    2015-01-01

    Iron (hydr)oxides are ubiquitous earth materials that have high adsorption capacities for toxic elements and degradation ability towards organic contaminants. Many studies have investigated the reactivity of synthetic magnetite, while little is known about natural magnetite. Here, we first report the reactivity of natural magnetites with a variety of elemental impurities for catalyzing the decomposition of H2O2 to produce hydroxyl free radicals (•OH) and the consequent degradation of p-nitrophenol (p-NP). We observed that these natural magnetites show higher catalytic performance than that of the synthetic pure magnetite. The catalytic ability of natural magnetite with high phase purity depends on the surface site density while that for the magnetites with exsolutions relies on the mineralogical nature of the exsolved phases. The pleonaste exsolution can promote the generation of •OH and the consequent degradation of p-NP; the ilmenite exsolution has little effect on the decomposition of H2O2, but can increase the adsorption of p-NP on magnetite. Our results imply that natural magnetite is an efficient catalyst for the degradation of organic contaminants in nature.

  12. Origins of Magnetite Nanocrystals in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Mckay, David S.; Gibson, Everett K.; Wentworth, Susan J.

    2009-01-01

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of mag- netite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterized of the compo- sitional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the car- bonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

  13. Magnetic microbes: Bacterial magnetite biomineralization.

    PubMed

    Prozorov, Tanya

    2015-10-01

    Magnetotactic bacteria are a diverse group of prokaryotes with the ability to orient and migrate along the magnetic field lines in search for a preferred oxygen concentration in chemically stratified water columns and sediments. These microorganisms produce magnetosomes, the intracellular nanometer-sized magnetic crystals surrounded by a phospholipid bilayer membrane, typically organized in chains. Magnetosomes have nearly perfect crystal structures with narrow size distribution and species-specific morphologies, leading to well-defined magnetic properties. As a result, the magnetite biomineralization in these organisms is of fundamental interest to diverse disciplines, from biotechnology to astrobiology. This article highlights recent advances in the understanding of the bacterial magnetite biomineralization.

  14. Magnetic microbes: Bacterial magnetite biomineralization

    SciTech Connect

    Prozorov, Tanya

    2015-09-14

    Magnetotactic bacteria are a diverse group of prokaryotes with the ability to orient and migrate along the magnetic field lines in search for a preferred oxygen concentration in chemically stratified water columns and sediments. These microorganisms produce magnetosomes, the intracellular nanometer-sized magnetic crystals surrounded by a phospholipid bilayer membrane, typically organized in chains. Magnetosomes have nearly perfect crystal structures with narrow size distribution and species-specific morphologies, leading to well-defined magnetic properties. As a result, the magnetite biomineralization in these organisms is of fundamental interest to diverse disciplines, from biotechnology to astrobiology. As a result, this article highlights recent advances in the understanding of the bacterial magnetite biomineralization.

  15. Synthesis and characterization of magnetite/PLGA/chitosan nanoparticles

    NASA Astrophysics Data System (ADS)

    Ibarra, Jaime; Melendres, Julio; Almada, Mario; Burboa, María G.; Taboada, Pablo; Juárez, Josué; Valdez, Miguel A.

    2015-09-01

    In this work, we report the synthesis and characterization of a new hybrid nanoparticles system performed by magnetite nanoparticles, loaded in a PLGA matrix, and stabilized by different concentrations of chitosan. Magnetite nanoparticles were hydrophobized with oleic acid and entrapped in a PLGA matrix by the emulsion solvent evaporation method, after that, magnetite/PLGA/chitosan nanoparticles were obtained by adding dropwise magnetite/PLGA nanoparticles in chitosan solutions. Magnetite/PLGA nanoparticles produced with different molar ratios did not show significant differences in size and the 3:1 molar ratio showed best spherical shapes as well as uniform particle size. Isothermal titration calorimetry studies demonstrated that the first stage of PLGA-chitosan interaction is mostly regulated by electrostatic forces. Based on a single set of identical sites model, we obtained for the average number of binding sites a value of 3.4, which can be considered as the number of chitosan chains per nanoparticle. This value was confirmed by using a model based on the DLVO theory and fitting zeta potential measurements of magnetite/PLGA/chitosan nanoparticles. From the adjusted parameters, we found that an average number of chitosan molecules of 3.6 per nanoparticle are attached onto the surface of the PLGA matrix. Finally, we evaluated the effect of surface charge of nanoparticles on a membrane model of endothelial cells performed by a mixture of three phospholipids at the air-water interface. Different isotherms and adsorption curves show that cationic surface of charged nanoparticles strongly interact with the phospholipids mixture and these results can be the basis of future experiments to understand the nanoparticles- cell membrane interaction.

  16. Micro-CT molecular imaging of tumor angiogenesis using a magnetite nano-cluster probe.

    PubMed

    Liu, Ping; Li, Jing; Zhang, Chunfu; Xu, Lisa X

    2013-06-01

    Due to its high resolution, micro-CT is desirable for molecular imaging of tumor angiogenesis. However, the sensitivity of micro-CT to contrast agents is relatively low. Therefore, the purpose of this study is to develop high micro-CT sensitive molecular imaging probes for direct visualization and dynamic monitoring of tumor angiogenesis. To this end, Arg-Gly-Asp (RGD) peptides conjugated magnetite nano clusters (RGD-MNCs) were developed by assembling individual magnetite nano particles into clusters with amphiphilic (maleimide) methoxypoly(ethylene glycol)-b-poly(lactic acid) ((Mal)mPEG-PLA) copolymer and subsequently encoding RGD peptides onto the clusters for specific targeting alpha(v)beta3 integrin. The hydrodynamic size of RGD-MNCs was about 85 nm. To test its specificity, alpha(v)beta3 positive cells (H1299) were incubated with magnetite nano clusters (MNCs), RGD-MNCs or RGD-MNCs competition with free RGD peptides. Prussian Blue staining and inductively coupled plasma optical emission spectrometer (ICP-OES) measurements indicated that the cell uptake of RGD-MNCs was significantly more than that of MNCs, which could be inhibited by free RGD peptides. For detection of tumor angiogenesis, mice bearing H1299 tumors were injected intravenously with RGD-MNCs at the dose of 400 micro mol Fe/kg. Tumor angiogenic hot spots as well as individual angiogenic vessels could be clearly manifested by micro-CT imaging 12 h post injection, which was dynamically monitored with the extension of probe circulation time. Subsequent histological studies of tumor tissues verified that RGD-MNCs registered tumor angiogenic vessels. Our study demonstrated that RGD-MNC probes fabricated in this study could be used to effectively target alpha(v)beta3 integrin. Using high resolution micro-CT in combination with the probes, tumor angiogenesis could be studied dynamically.

  17. Magnetite and Magnetotaxis in Algae

    PubMed Central

    de Araujo, F. F. Torres; Pires, M. A.; Frankel, R. B.; Bicudo, C. E. M.

    1986-01-01

    Magnetotactic algae of the genus Anisonema (Euglenophyceae) have been isolated from a coastal mangrove swamp in northeastern Brazil. The magnetotactic response is based on a permanent magnetic dipole moment per cell ∼7 10-10 emu. Each cell contains many magnetite (Fe3O4) particles organized in chains. ImagesFIGURE 2FIGURE 1FIGURE 3 PMID:19431684

  18. Biogenic Magnetite and EMF Effects

    NASA Astrophysics Data System (ADS)

    Kirschvink, Joseph L.

    1996-03-01

    Magnetite biomineralization is a genetically-controlled biochemical process through which organisms make perfect ferrimagnetic crystals, usually of single magnetic domain size. This process is an ancient one, having evolved about 2 billion years ago in the magnetotactic bacteria, and presumably was incorporated in the genome of higher organisms, including humans. During this time, DNA replication, protein synthesis, and many other biochemical processes have functioned in the presence of strong static fields of up to 400 mT adjacent to these magnetosomes without any obvious deleterious effects. Recent behavioral experiments using short but strong magnetic pulses in honeybees and birds demonstrates that ferromagnetic materials are involved in the sensory transduction of geomagnetic field information to the nervous system, and both behavioral and direct electrophysiological experiments indicate sensitivity thresholds to DC magnetic fields down to a few nT. However, far more biogenic magnetite is present in animal tissues than is needed for magnetoreception, and the biological function of this extra material is unknown. The presence of ferromagnetic materials in biological systems could provide physical transduction mechanisms for ELF magnetic fields, as well for microwave radiation in the .5 to 10 GHz band where magnetite has its peak ferromagnetic resonance. Elucidation of the cellular ultrastructure and biological function(s) of magnetite might help resolve the question of whether anthropogenic EMFs can cause deleterious biological effects. This work has been supported by grants from the NIH and EPRI.

  19. Cu-Ni nano-alloy: mixed, core-shell or Janus nano-particle?

    NASA Astrophysics Data System (ADS)

    Guisbiers, Grégory; Khanal, Subarna; Ruiz-Zepeda, Francisco; Roque de La Puente, Jorge; José-Yacaman, Miguel

    2014-11-01

    Bimetallic nanoparticles like Cu-Ni are particularly attractive due to their magnetic and catalytic properties; however, their properties depend strongly on the structure of the alloy i.e. mixed, core-shell or Janus. To predict the alloy structure, this paper investigates the size and shape effects as well as the surface segregation effect on the Cu-Ni phase diagram. Phase maps have been plotted to determine the mixing/demixing behavior of this alloy according the particle shape. Cu-Ni nanoalloy can form a mixed particle or a Janus one depending on the synthesis temperature. Surface segregation is also considered and reveals a nickel surface-enrichment. Finally, this paper provides a useful roadmap for experimentalists.Bimetallic nanoparticles like Cu-Ni are particularly attractive due to their magnetic and catalytic properties; however, their properties depend strongly on the structure of the alloy i.e. mixed, core-shell or Janus. To predict the alloy structure, this paper investigates the size and shape effects as well as the surface segregation effect on the Cu-Ni phase diagram. Phase maps have been plotted to determine the mixing/demixing behavior of this alloy according the particle shape. Cu-Ni nanoalloy can form a mixed particle or a Janus one depending on the synthesis temperature. Surface segregation is also considered and reveals a nickel surface-enrichment. Finally, this paper provides a useful roadmap for experimentalists. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05739b

  20. Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics.

    PubMed

    Wang, Fuliang; Mao, Peng; He, Hu

    2016-02-17

    Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10(-8) (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10(-8) to 5.08 × 10(-8) (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved.

  1. The role of silver nano-particles and silver thiosulfate on the longevity of cut carnation (Dianthus caryophyllus) flowers.

    PubMed

    Hashemabadi, Davood

    2014-07-01

    The purpose of this study was to evaluate the efficacy of silver nano-particles (SNP) and silver thiosulfate (STS) in extending the vase life of cut carnation (Dianthus caryophyllus L. cv. 'Tempo') flowers. Pulse treatments of SNP @ 0, 5, 10 and 15 mg l(-1) and STS @ 0, 0.1, 0.2 and 0.3 mM were administered to carnation flowers for 24 hr. The longest vase life (16.1 days) was observed in flowers treated with 15 mg l(-1) of SNP + 0.2 mM STS. The least chlorophyll was destroyed in flowers treated with 15 mg I(-1) of SNP + 0.3 mM STS. Our findings showed that the 15 mg l(-1) SNP treatment inhibited bacterial growth in the preservative solution. The control flowers bloomed faster than the treated flowers. The maximum peroxidase activity and the minimum lipid peroxidation were obtained in cut flowers that were treated with 15 mg l(-1) of SNP and 0.3 mM STS. Overall, results of the study revealed that SNP and STS treatment extended the longevity of cut carnation 'Tempo' flowers by reducing oxidative stress, improving anti-oxidant system, reducing bacterial populations and delaying flowering.

  2. Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics.

    PubMed

    Wang, Fuliang; Mao, Peng; He, Hu

    2016-01-01

    Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10(-8) (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10(-8) to 5.08 × 10(-8) (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved. PMID:26883558

  3. Selective, direct detection of acetylcholine in PBS solution, with self-assembled fluorescent nano-particles: experiment and modelling.

    PubMed

    Erieau-Peyrard, Lisa; Coiffier, Claire; Bordat, Patrice; Bégué, Didier; Chierici, Sabine; Pinet, Sandra; Gosse, Isabelle; Baraille, Isabelle; Brown, Ross

    2015-02-14

    We report synthesis, characterisation and molecular modelling of a new fluorescent cyclotriveratrylene probe for acetylcholine in aqueous media, with emission around 430 nm thanks to extended conjugation. The probe discriminates acetylcholine from choline, with respective binding constants 540 and 240 M(-1) in PBS buffered saline solution, an order of magnitude improvement over the previous best performance. Dynamic light scattering and transmission electron microscopy show the new probe self-assembles in ca. 5 nm diameter particles in PBS medium. Molecular modelling suggests that the high fluorescence quantum yield of the probe, 20% in aqueous media, is due to features of the molecular arrangement in the nano-particles, contributing both to exposure of the complexation site and to shielding of the fluorescent π system from quenching by water. Titration data for other quaternary ammoniums and modelling indicate that recognition of acetylcholine vs. choline depends on specific electrostatic interactions, and to a lesser extent on exclusion of water by hydrophobic-hydrophilic segregation. Probe-substrate interactions enhance the fluorescence of the probe by shielding against water and by flattening the π system.

  4. Nondestructive testing of 3D disperse systems with micro- and nano-particles: N-dimensional space of optical parameters

    NASA Astrophysics Data System (ADS)

    Bezrukova, Alexandra G.

    2006-04-01

    The simultaneous analysis of 3D disperse systems (DS) with micro- and nano- particles by refractometry, absorbency, fluorescence and by different types of light scattering, can help to elaborate the sensing elements for specffic impurity control. Our research has investigated by complex of optical methods different 3D DS such as: proteins, nucleoproteids, lipoproteids, liposomes, viruses, virosomes, lipid emulsions, blood substitutes, latexes, liquid crystals, biological cells with various form and size (including bacterial cells), metallic powders, clays, kimberlites, zeolites, oils, crude oils, samples of natural and water-supply waters, etc. This experience suggests that each 3D DS can be charactensed by N-dimensional vector in N-dimensional space of optical parameters. Due to the fusion of various optical data it is possible to solve the inverse physical problem on the presence of impurity in mixtures of 3D DS by information statistical theory methods. It is important that in this case polymodality of particle size distribution is not an obstacle.

  5. Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics

    NASA Astrophysics Data System (ADS)

    Wang, Fuliang; Mao, Peng; He, Hu

    2016-02-01

    Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10-8 (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10-8 to 5.08 × 10-8 (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved.

  6. White top-emitting organic light-emitting diodes with solution-processed nano-particle scattering layers

    SciTech Connect

    Schaefer, Tim; Schwab, Tobias; Lenk, Simone; Gather, Malte C.

    2015-12-07

    A random scattering approach to enhance light extraction in white top-emitting organic light-emitting diodes (OLEDs) is reported. Through solution processing from fluorinated solvents, a nano-particle scattering layer (NPSL) can be deposited directly on top of small molecule OLEDs without affecting their electrical performance. The scattering length for light inside the NPSL is determined from transmission measurements and found to be in agreement with Mie scattering theory. Furthermore, the dependence of the light outcoupling enhancement on electron transport layer thickness is studied. Depending on the electron transport layer thickness, the NPSL enhances the external quantum efficiency of the investigated white OLEDs by between 1.5 and 2.3-fold. For a device structure that has been optimized prior to application of the NPSL, the maximum external quantum efficiency is improved from 4.7% to 7.4% (1.6-fold improvement). In addition, the scattering layer strongly reduces the undesired shift in emission color with viewing angle.

  7. Effect of addition of BaTiO3 nano particles on the electrical transport properties of YBCO superconductor

    NASA Astrophysics Data System (ADS)

    Rejith, P. P.; Vidya, S.; Thomas, J. K.

    2015-02-01

    The flux pinning properties of YBCO bulk superconductors synthesized by conventional solid state route and are added with different weight% (x=0, 0.5, 1, 2, 3, 5) of nano BaTiO3 which are prepared by a modified combustion route are studied systematically. The phase analysis of the samples was done by using X-ray diffraction and scanning electron microscopy. Temperature-resistivity measurements, magnetic field dependence of critical current density (Jc-B Characteristics) and flux pinning force calculations were done at 77 K. From the SEM images the microstructure of the sample showed a relative uniform distribution of the nano-particles within the specimen. We found that, even though the transition temperature (Tc) does not change considerably with the BaTiO3 addition, both the critical current density (Jc) and flux pinning force (Fp) increased systematically up to 2 wt% BaTiO3 in the composite, in the presence of magnetic field ranging between 0 and 0.6 T. The Jc value in 2 wt% BaTiO3 added sample showed at least 250% larger than that of the pure YBCO. Also the flux pinning force calculated for the 2 wt% BaTiO3 added is found to be enhanced more than 9 times that of pure YBCO. These observations suggest that the BaTiO3 addition to the Y-123- compounds improve the electrical connection between superconducting grains to result in the increase in Jc.

  8. Preparation of ZrC nano-particles reinforced amorphous carbon composite coating by atmospheric pressure chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Sun, W.; Xiong, X.; Huang, B. Y.; Li, G. D.; Zhang, H. B.; Xiao, P.; Chen, Z. K.; Zheng, X. L.

    2009-05-01

    To eliminate cracks caused by thermal expansion mismatch between ZrC coating and carbon-carbon composites, a kind of ZrC/C composite coating was designed as an interlayer. The atmospheric pressure chemical vapor deposition was used as a method to achieve co-deposition of ZrC and C from ZrCl 4-C 3H 6-H 2-Ar source. Zirconium tetrachloride (ZrCl 4) powder carrier was especially made to control accurately the flow rate. The microstructure of ZrC/C composite coating was studied using analytical techniques. ZrC/C coating shows same morphology as pyrolytic carbon. Transmission electron microscopy (TEM) shows ZrC grains with size of 10-50 nm embed in turbostratic carbon. The formation mechanism is that the growth of ZrC crystals was inhibited by surrounding pyrolytic carbon and kept as nano-particles. Fracture morphologies imply good combination between coating and substrate. The ZrC crystals have stoichiometric proportion near 1, with good crystalline but no clear preferred orientation while pyrolytic carbon is amorphous. The heating-up oxidation of ZrC/C coating shows 11.58 wt.% loss. It can be calculated that the coating consists of 74.04 wt.% ZrC and 25.96 wt.% pyrolytic carbon. The average density of the composite coating is 5.892 g/cm 3 by Archimedes' principle.

  9. Synthesis, structural characterization and study of blue shift in optical properties of zinc oxide nano particles prepared by chemical route method

    NASA Astrophysics Data System (ADS)

    Taunk, P. B.; Das, R.; Bisen, D. P.; Tamrakar, Raunak Kumar

    2015-12-01

    We report the synthesis and optical properties of ZnO nano particle using TEA (Tri Ethanol Amine) and without TEA by chemical route method. By decreasing the concentration of TEA, reaction rate is decreases and inter planner spacing d is increases, band gap is increased from 4.1 to 4.8 eV. In case of without TEA band gap is obtained 3.4 eV. Morphology, growth and the nature of crystalline of the powder samples were performed by X- ray Diffraction (XRD); UV spectrophotometer, scanning electron microscope (SEM) and Photoluminescence (PL). Luminescence properties are discussed by probing the photoluminescence properties of ZnO nano particles with TEA at different molar concentrations.

  10. Effect of Au nano-particle aggregation on the deactivation of the AuCl3/AC catalyst for acetylene hydrochlorination

    PubMed Central

    Dai, Bin; Wang, Qinqin; Yu, Feng; Zhu, Mingyuan

    2015-01-01

    A detailed study of the valence state and distribution of the AuCl3/AC catalyst during the acetylene hydrochlorination deactivation process is described and discussed. Temperature-programmed reduction and X-ray photoelectron spectral analysis indicate that the active Au3+ reduction to metallic Au0 is one reason for the deactivation of AuCl3/AC catalyst. Transmission electron microscopy characterization demonstrated that the particle size of Au nano-particles increases with increasing reaction time. The results indicated that metallic Au0 exhibits considerable catalytic activity and that Au nano-particle aggregation may be another reason for the AuCl3/AC catalytic activity in acetylene hydrochlorination. PMID:25994222

  11. Arsenic sorption by nanocrystalline magnetite: an example of environmentally promising interface with geosphere.

    PubMed

    Bujňáková, Z; Baláž, P; Zorkovská, A; Sayagués, M J; Kováč, J; Timko, M

    2013-11-15

    In this paper, the sorption of arsenic onto nanocrystalline magnetite mineral Fe3O4 was studied in a model system. Nanocrystalline magnetite was produced by mechanical activation in a planetary ball mill from natural microcrystalline magnetite. As a consequence of milling, the specific surface area increased from 0.1m(2)/g to 11.9 m(2)/g and the surface site concentration enhanced from 2.2 sites/nm(2) to 8.4 sites/nm(2). These changes in surface properties of magnetite lead to the enhancement of arsenic removal from model system. The best sorption ability was achieved with magnetite sample activated for 90 min. In this case the sample was able to absorb around 4 mg/g. The structural changes of magnetite were also observed and the new hematite phase was detected after 120 min of milling. A good correlation between the decreasing particle size, increasing specific surface area and reduction of saturation magnetization was found. In desorption study, KOH and NaOH were found as the best eluents where more than 70% of arsenic was released back into the solution. The principal novelty of the paper is that mineral magnetite, truly one nature's gift can be used after "smart" milling (mechanical activation) as an effective arsenic sorbent.

  12. Arsenic sorption by nanocrystalline magnetite: an example of environmentally promising interface with geosphere.

    PubMed

    Bujňáková, Z; Baláž, P; Zorkovská, A; Sayagués, M J; Kováč, J; Timko, M

    2013-11-15

    In this paper, the sorption of arsenic onto nanocrystalline magnetite mineral Fe3O4 was studied in a model system. Nanocrystalline magnetite was produced by mechanical activation in a planetary ball mill from natural microcrystalline magnetite. As a consequence of milling, the specific surface area increased from 0.1m(2)/g to 11.9 m(2)/g and the surface site concentration enhanced from 2.2 sites/nm(2) to 8.4 sites/nm(2). These changes in surface properties of magnetite lead to the enhancement of arsenic removal from model system. The best sorption ability was achieved with magnetite sample activated for 90 min. In this case the sample was able to absorb around 4 mg/g. The structural changes of magnetite were also observed and the new hematite phase was detected after 120 min of milling. A good correlation between the decreasing particle size, increasing specific surface area and reduction of saturation magnetization was found. In desorption study, KOH and NaOH were found as the best eluents where more than 70% of arsenic was released back into the solution. The principal novelty of the paper is that mineral magnetite, truly one nature's gift can be used after "smart" milling (mechanical activation) as an effective arsenic sorbent. PMID:23531452

  13. Formation of nanoscale structures through driven flow of nano-particles in microchannels

    NASA Astrophysics Data System (ADS)

    Verberg, Rolf; Yeomans, Julia; Balazs, Anna

    2005-03-01

    Using a computational model, we consider an isothermal binary fluid that contains tracer particles, which are advected by the fluid within a microchannel. The flow is modeled directly using a Lattice Boltzmann algorithm for a binary fluid. We then introduce nanoparticles that travel along trajectories that obey a stochastic differential equation, such that the concentration of nanoparticles in the bulk obeys a standard convection-diffusion equation. To simulate the affinity of the nanoparticles to one of the components, we modified the stochastic diffusion equation in order to include a drift term that contains the gradient of the order parameter. Reactions with the solid boundaries will be incorporated by introducing a reaction probability when the particle's trajectory crosses the solid-fluid surface. The results provide guidelines for creating microfluidic devices with surfaces that contain well-controlled spatial patterns on the nanometer to micron range.

  14. Megacity pollution by modern Diesel cars: New insights into the nature and formation of volatile nano-particles with high lung intrusion efficiency

    NASA Astrophysics Data System (ADS)

    Arnold, F.; Reichl, U.; Muschik, Ch.; Roiger, A.; Schlager, H.; Pirjola, L.; Rönkkö, T.; Keskinen, J.; Rothe, D.; Lähde, T.

    2009-04-01

    Aerosol particles generated by Diesel vehicles represent mayor health affecting air pollutants in cities and near motor ways. To mitigate the Diesel particle pollution problem, Diesel vehicles become increasingly fitted or retro-fitted with modern exhaust after treatment systems (ATS), which remove most engine-generated primary particles, particularly soot. Unfortunately however, ATS have undesired side effects including also the formation of low vapour pressure gases, which may undergo nucleation and condensation leading to volatile nucleation particles (NUP). NUP are substantially smaller (diameters: 5-15 nm) than soot particles (diameters: 40-100 nm), and therefore may be termed real nano-particles. NUP can intrude with maximum efficiency the lowest, least protected, and most vulnerable compartment of the human lung. However, the chemical nature and mechanism of formation of NUP are only poorly explored. Using a novel mass spectrometric method, we have made the first on line and off line measurements of low vapour pressure NUP precursor gases in the exhaust of a modern heavy duty Diesel vehicle engine, operated with and without ATS and combusting low and ultra-low sulphur fuels including also bio fuel. In addition, we have made accompanying NUP measurements and NUP model simulations. The on line measurements involved a CIMS (Chemical Ionization Mass Spectrometry) method originally developed by MPIK. They took place directly in the Diesel exhaust and had a large sensitivity and a fast time response (1 s). The off line measurements involved adsorption of exhaust gases on stainless steel, followed by thermo desorption and detection of desorbed exhaust molecules by CIMS. We find that modern Diesel ATS strongly increase the formation of hydroxyl radicals, which induce conversion of fuel sulphur to the important NUP precursor gaseous sulphuric acid. We also find that appreciable amounts of di-carboxylic acids survive the passage of the ATS or are even formed by the

  15. Electrochemical capacitor of magnetite in aqueous electrolytes

    NASA Astrophysics Data System (ADS)

    Wu, Nae-Lih; Wang, Shi-Yu; Han, Chih-Yu; Wu, Dien-Shi; Shiue, Lih-Ren

    The capacitive behaviours of magnetite nanocrystallites, along with conductive carbon black additive, in aqueous electrolytes, including sodium sulphite, sulphate, chloride, and phosphate, and potassium hydroxide, have been characterised by means of cyclic voltammetry and chrono-potentiometry. The behaviour can be categorised into three groups. Sodium sulphate and chloride electrolytes give capacitances (˜5 F/g-Fe 3O 4) close to the space-charge capacitance of the oxide. Potassium hydroxide and sodium phosphate gave rise to a higher capacitance (˜7 F/g) which can in part be attributed to a surface redox reaction which involves hydroxide ions. Sodium sulphite results in the highest capacitances, which depend heavily on the dispersion of magnetite crystallites on the conductive matrix and range from ˜30 to 510 F/g-Fe 3O 4 with an operation voltage range of 1.2 V. Correlation between rest potential and anion-concentration gives strong indication of potential-determining process which involve either OH under extremely alkaline conditions (pOH<3) or SO 32- in the sulphite electrolyte.

  16. Rapid reduction of titanium dioxide nano-particles by reduction with a calcium reductant

    NASA Astrophysics Data System (ADS)

    Kikuchi, Tatsuya; Yoshida, Masumi; Matsuura, Shiki; Natsui, Shungo; Tsuji, Etsuji; Habazaki, Hiroki; Suzuki, Ryosuke O.

    2014-09-01

    Micro-, submicron-, and nano-scale titanium dioxide particles were reduced by reduction with a metallic calcium reductant in calcium chloride molten salt at 1173 K, and the reduction mechanism of the oxides by the calcium reductant was explored. These oxide particles, metallic calcium as a reducing agent, and calcium chloride as a molten salt were placed in a titanium crucible and heated under an argon atmosphere. Titanium dioxide was reduced to metallic titanium through a calcium titanate and lower titanium oxide, and the materials were sintered together to form a micro-porous titanium structure in molten salt at high temperature. The reduction rate of titanium dioxide was observed to increase with decreasing particle size; accordingly, the residual oxygen content in the reduced titanium decreases. The obtained micro-porous titanium appeared dark gray in color because of its low surface reflection. Micro-porous metallic titanium with a low oxygen content (0.42 wt%) and a large surface area (1.794 m2 g-1) can be successfully obtained by reduction under optimal conditions.

  17. The use of visible light and metal oxide nano particles for pathogen inactivation

    NASA Astrophysics Data System (ADS)

    Lubart, R.; Lipovski, A.; Gedanken, A.

    2012-09-01

    Since the effectiveness of antibiotic treatment is decreasing due to the development of resistant strains, alternative approaches for destroying microorganisms are needed. In this review we summarize new technologies that might be effective for pathogen inactivation. In the past we found that intense blue light could be used for bacterial eradication. The phototoxic effect correlated with the amount of reactive oxygen species (ROS) generated by the bacteria due to illumination. Recently it has been shown that the effect of light can be enhanced by introducing metal oxide nanoparticles (nps) to the bacteria prior to irradiation. This led us to suggest combining nanoparticles with visible light irradiation for pathogen eradication. We have shown that combination of illumination with the nanoparticles (ZnO or TiO2) resulted in a marked increase in the reduction of bacterial viability to a mean reduction of 80-90% for both nanoaprticles. As a matter of fact metal oxide nps alone can be used for bacteria destruction. The advantage of our approach is the use of lower concentrations of nps, combined with reduced light intensity that is less toxic to the host tissue. To further avoid the toxicity of metal oxides nps on healthy tissue it is possible to coat their surfaces with various substrates including ceramics and polymers. Recently Zinc oxide nanoparticles have been synthesized and deposited on the surface of cotton fabrics using ultrasound irradiation. Thus in the future we will try to treat infected wounds with transparent bandages coated with ZnO that will be applied to the wounds prior to irradiation.

  18. Raman spectroscopy investigation of magnetite nanoparticles in ferrofluids

    NASA Astrophysics Data System (ADS)

    Slavov, L.; Abrashev, M. V.; Merodiiska, T.; Gelev, Ch.; Vandenberghe, R. E.; Markova-Deneva, I.; Nedkov, I.

    2010-07-01

    Raman spectroscopy is used to investigate magnetite nanoparticles dispersed in two types of β-cyclodextrin suspensions. An approach is presented for characterization of the magnetic core in liquid surrounding at room temperature and atmospheric pressure. The effect of elevating laser power on the structural stability and chemical composition of magnetite in the ferrofluids is discussed. The data are compared with data from dry by-products from the fluids. Powder samples undergo total phase transition from magnetite to hematite at laser power of 1.95 mW. The same nanoparticles in the fluid undergo transformation at 9 mW, but no hematite positions appear throughout that investigation. The Raman spectra revealed that the main phase of the magnetic core in the fluids is magnetite. That is indicated by a strong and non-diminishing in intensity peak at 670 cm -1. A second phase is present at the nanoparticle's surface with Raman spectroscopy unveiling maghemite-like and small fractions of goethite-like structures. The Fourier transform infrared spectroscopy investigations confirm deviations in the surface structure and also point to the fact that the oxidation process starts at an early stage after formation of the nanoparticles. The analyses of the infrared data also show that β-cyclodextrin molecules retain their cyclic character and the coating does not affect the oxidation process once the particles are evicted from the fluids. A Mössbauer spectroscopy measurement on a ferrofluidic sample is also presented.

  19. Magnetic microbes: Bacterial magnetite biomineralization

    DOE PAGES

    Prozorov, Tanya

    2015-09-14

    Magnetotactic bacteria are a diverse group of prokaryotes with the ability to orient and migrate along the magnetic field lines in search for a preferred oxygen concentration in chemically stratified water columns and sediments. These microorganisms produce magnetosomes, the intracellular nanometer-sized magnetic crystals surrounded by a phospholipid bilayer membrane, typically organized in chains. Magnetosomes have nearly perfect crystal structures with narrow size distribution and species-specific morphologies, leading to well-defined magnetic properties. As a result, the magnetite biomineralization in these organisms is of fundamental interest to diverse disciplines, from biotechnology to astrobiology. As a result, this article highlights recent advances inmore » the understanding of the bacterial magnetite biomineralization.« less

  20. Nano-particle enhanced impedimetric biosensor for detedtion of foodborne pathogens

    NASA Astrophysics Data System (ADS)

    Kim, G.; Om, A. S.; Mun, J. H.

    2007-03-01

    Recent outbreaks of foodborne illness have been increased the need for rapid and sensitive methods for detection of these pathogens. Conventional methods for pathogens detection and identification involve prolonged multiple enrichment steps. Even though some immunological rapid assays are available, these assays still need enrichment steps result in delayed detection. Biosensors have shown great potential for rapid detection of foodborne pathogens. They are capable of direct monitoring the antigen-antibody reactions in real time. Among the biosensors, impedimetric biosensors have been widely adapted as an analysis tool for the study of various biological binding reactions because of their high sensitivity and reagentless operation. In this study a nanoparticle-enhanced impedimetric biosensor for Salmonella enteritidis detection was developed which detected impedance changes caused by the attachment of the cells to the anti-Salmonella antibodies immobilized on interdigitated gold electrodes. Successive immobilization of neutravidin followed by anti-Salmonella antibodies was performed to the sensing area to create a biological detection surface. To enhance the impedance responses generated by antigen-antibody reactions, anti-Salmonella antibody conjugated nanoparticles were introduced on the sensing area. Using a portable impedance analyzer, the impedance across the interdigital electrodes was measured after the series of antigen-antibody bindings. Bacteria cells present in solution attached to capture antibodies and became tethered to the sensor surface. Attached bacteria cells changed the dielectric constant of the media between the electrodes thereby causing a change in measured impedance. Optimum input frequency was determined by analyzing frequency characteristics of the biosensor over ranges of applied frequencies from 10 Hz to 400 Hz. At 100 Hz of input frequency, the biosensor was most sensitive to the changes of the bacteria concentration and this frequency

  1. Dissolution and reduction of magnetite by bacteria

    NASA Technical Reports Server (NTRS)

    Kostka, J. E.; Nealson, K. H.

    1995-01-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis.

  2. Dissolution and reduction of magnetite by bacteria.

    PubMed

    Kostka, J E; Nealson, K H

    1995-10-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis. PMID:11539843

  3. MULTI-STAGE DELIVERY NANO-PARTICLE SYSTEMS FOR THERAPEUTIC APPLICATIONS

    PubMed Central

    Serda, Rita E.; Godin, Biana; Blanco, Elvin; Chiappini, Ciro; Ferrari, Mauro

    2010-01-01

    Background The daunting task for drug molecules to reach pathological lesions has fueled rapid advances in Nanomedicine. The progressive evolution of nanovectors has led to the development of multi-stage delivery systems aimed at overcoming the numerous obstacles encountered by nanovectors on their journey to the target site. Scope of Review This review summarizes major findings with respect to silicon-based drug delivery vectors for cancer therapeutics and imaging. Based on rational design, well established silicon technologies have been adapted for the fabrication of nanovectors with specific shapes, sizes, and porosities. These vectors are part of a multi-stage delivery system that contains multiple nano-components, each designed to achieve a specific task with the common goal of site-directed delivery of therapeutics. Major Conclusions Quasi-hemispherical and discoidal silicon microparticles are superior to spherical particles with respect to margination in the blood, with particles of different shapes and sizes having unique distributions in vivo. Cellular adhesion and internalization of silicon microparticles is influenced by microparticle shape and surface charge, with the latter dictating binding of serum opsonins. Based on in vitro cell studies, the internalization of porous silicon microparticles by endothelial cells and macrophages is compatible with cellular morphology, intracellular trafficking, mitosis, cell cycle progression, cytokine release, and cell viability. In vivo studies support superior therapeutic efficacy of liposomal encapsulated siRNA when delivered in multi-stage systems compared to free nanoparticles. PMID:20493927

  4. Micro/nano-particle decorated metal wire for cutting soft matter

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Feng, Liang-liang; Wu, Fan; Zhang, Run-run; Wu, Cheng-wei

    2016-09-01

    To cut soft materials such as biological tissues with minimal damage and reduced positional error is highly desired in medical surgery and biomechanics. After years of natural selection and evolution, mosquitoes have acquired the ability to insert their proboscises into human skin with astonishingly tiny forces. This can be associated with the unique structure of their proboscises, with micro/nano sawteeth, and the distinctive insertion manner: high frequency reciprocating saw cutting. Inspired by these, this communication describes the successful implantation of metal oxide particles onto molybdenum wire surfaces through a sol-calcination process, to form a biomimetic sawblade with a high density of micro/nano saw teeth, where the acidification is essential in terms of generating active anchoring sites on the wire. When used as a sawblade in conjunction with reciprocating action to cut the viscoelastic gel, both the cut-in force and cut-in displacement could be decreased substantially. The cutting speed and frequency of reciprocating action are important operating parameters influencing cut-in force.

  5. Effects of strain on phonon interactions and phase nucleation in several semiconductor and nano particle systems

    NASA Astrophysics Data System (ADS)

    Tallman, Robert E.

    Raman scattering is utilized to explore the effects of applied pressure and strain on anharmonic phonon interactions and nucleation of structural transitions in several bulk and nanoparticle semiconductor systems. The systems investigated are bulk ZnS and ZnSe in several isotopic compositions, InP/CdS core/shell nanoparticles exhibiting confined and surface optical Raman modes, and amorphous selenium films undergoing photo-induced crystallization. The anharmonic decay of long-wavelength optical modes into two-phonon acoustic combinations modes is studied in 64Zn32S, 64Zn34S, natZnatS bulk crystals by measuring the TO(Gamma) Raman line-shape as a function of applied hydrostatic pressure. The experiments are carried out at room temperature and 16K for pressures up to 150 kbars using diamond-anvil cells. The most striking effects occur in 68Zn32S where the TO(Gamma) peak narrows by a factor of 10 and increases in intensity at pressures for which the TO(Gamma) frequency has been tuned into a gap in the two-phonon density of states (DOS). In all the isotopic compositions, the observed phonon decay processes can be adequately explained by a second order perturbation treatment of the anharmonic coupling between TO(Gamma) and TA + LA combinations at various critical points, combined with an adiabatic bond-charge model for the phonon DOS and the known mode Gruneisen parameters. Bulk ZnSe crystals exhibit very different behavior. Here we find that anharmonic decay alone can not explain the excessive (˜ 60 cm-1 ) broadening in the TO(Gamma) Raman peak observed as the pressure approaches to within 50kbar of the ZB -> B1 phase transition (at P ˜ 137 kbar). Rather the broadening appears to arise from antecedent nucleation of structural changes within nanoscopic domains, with the mechanism for line-shape changes being mode mixing via localization and disorder instead of anharmonicity. To sort out these contributions, pressure experiments on natural ZnSe and on isotopically pure

  6. Micro/nano-particle decorated metal wire for cutting soft matter.

    PubMed

    Zhang, Wei; Feng, Liang-Liang; Wu, Fan; Zhang, Run-Run; Wu, Cheng-Wei

    2016-09-01

    To cut soft materials such as biological tissues with minimal damage and reduced positional error is highly desired in medical surgery and biomechanics. After years of natural selection and evolution, mosquitoes have acquired the ability to insert their proboscises into human skin with astonishingly tiny forces. This can be associated with the unique structure of their proboscises, with micro/nano sawteeth, and the distinctive insertion manner: high frequency reciprocating saw cutting. Inspired by these, this communication describes the successful implantation of metal oxide particles onto molybdenum wire surfaces through a sol-calcination process, to form a biomimetic sawblade with a high density of micro/nano saw teeth, where the acidification is essential in terms of generating active anchoring sites on the wire. When used as a sawblade in conjunction with reciprocating action to cut the viscoelastic gel, both the cut-in force and cut-in displacement could be decreased substantially. The cutting speed and frequency of reciprocating action are important operating parameters influencing cut-in force.

  7. Micro/nano-particle decorated metal wire for cutting soft matter.

    PubMed

    Zhang, Wei; Feng, Liang-Liang; Wu, Fan; Zhang, Run-Run; Wu, Cheng-Wei

    2016-09-01

    To cut soft materials such as biological tissues with minimal damage and reduced positional error is highly desired in medical surgery and biomechanics. After years of natural selection and evolution, mosquitoes have acquired the ability to insert their proboscises into human skin with astonishingly tiny forces. This can be associated with the unique structure of their proboscises, with micro/nano sawteeth, and the distinctive insertion manner: high frequency reciprocating saw cutting. Inspired by these, this communication describes the successful implantation of metal oxide particles onto molybdenum wire surfaces through a sol-calcination process, to form a biomimetic sawblade with a high density of micro/nano saw teeth, where the acidification is essential in terms of generating active anchoring sites on the wire. When used as a sawblade in conjunction with reciprocating action to cut the viscoelastic gel, both the cut-in force and cut-in displacement could be decreased substantially. The cutting speed and frequency of reciprocating action are important operating parameters influencing cut-in force. PMID:27456430

  8. The use of nano-particles to produce iridescent metallic effects on ancient ceramic objects.

    PubMed

    Fermo, P; Padeletti, G

    2012-11-01

    Nano-sized materials have been often used in the past to realize objects with particular characteristics. One of the most outstanding examples is represented by luster pottery, showing shining surfaces with particular optical properties. Luster was one of the most sophisticated technique for the decoration of majolicas. It consists of a thin metallic film containing silver, copper and other substances, like iron oxide and cinnabar, applied in a reducing atmosphere on a previously glazed ceramic. In such a way, beautiful iridescent reflections of different colours (in particular gold and ruby-red) are obtained. This technique, at first developed in Iraq, was introduced in Italy from Spain. In Italy the potters of the two centres of Gubbio and Deruta, in central Italy, became so expert that nowadays modern artisans are not able to reproduce the wonderful effects obtained during Renaissance. A complete characterization by means of numerous techniques has been carried out on a great number of shards and precious work of arts conserved in many important museums. This allowed to draw some correlations between the preparation technique and the obtained nano-structure.

  9. Calcium alginate beads encapsulated PMMA-g-CS nano-particles for α-chymotrypsin immobilization.

    PubMed

    Abd El-Ghaffar, M A; Hashem, M S

    2013-02-15

    Chitosan grafted with polymethyl methacrylate (PMMA-g-CS) was prepared via a free-radicals polymerization technique as a carrier for enzyme immobilization. α-Chymotrypsin (CT), as an enzyme model in this study, was immobilized onto the prepared PMMA-g-CS via covalent bonding. Calcium alginate (CA) beads were developed for encapsulating PMMA-g-CS-CT to produce PMMA-g-CS-CT/CA composite beads. Morphology and size of PMMA-g-CS particles were investigated by TEM and found to be in the nanoscale. The structure and surface morphology of the beads before and after immobilization process were characterized by FT-IR and SEM, respectively. Both the bound CT content and relative activity of immobilized enzyme were measured. A higher retained activity (about 97.7%) obtained for the immobilized CT at pH 9 for 24 h. The results indicated that immobilized CT maintained excellent performance even after 25 reuses and retained 75% from its original activity after 60 days of storage at 25 °C.

  10. Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics

    PubMed Central

    Wang, Fuliang; Mao, Peng; He, Hu

    2016-01-01

    Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10−8 (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10−8 to 5.08 × 10−8 (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved. PMID:26883558

  11. Electrical conductivity modification using silver nano particles of Jatropha Multifida L. and Pterocarpus Indicus w. extracts films

    NASA Astrophysics Data System (ADS)

    Diantoro, Markus; Hidayati, Nisfi Nahari Sani; Latifah, Rodatul; Fuad, Abdulloh; Nasikhudin, Sujito, Hidayat, Arif

    2016-03-01

    Natural polymers can be extracted from leaf or stem of plants. Pterocarpus Indicus W. (PIW) and Jatropha Multifida L. (JIL) plants are good candidate as natural polymer sources. PIW and JIW polymers contain chemical compound so-called flavonoids which has C6-C3-C6 carbons conjugated configuration. The renewable type of polymer as well as their abundancy of flavonoid provide us to explore their physical properties. A number of research have been reported related to broad synthesis method and mechanical properties. So far there is no specific report of electrical conductivity associated to PIW and JIL natural polymers. In order to obtain electrical conductivity and its crystallinity of the extracted polymer films, it was induced on them a various fraction of silver nano particles. The film has been prepared by means of spin coating method on nickel substrate. It was revealed that FTIR spectra confirm the existing of rutine flavonoid. The crystallinity of the samples increase from 0.66%, to 4.11% associated to the respective various of silver fractions of 0.1 M to 0.5 M. SEM images show that there are some grains of silver in the film. The nature of electric conductivity increases a long with the addition of silver. The electrical conductivity increase significantly from 3.22 S/cm, to 542.85 S/cm. On the other hand, PIW films also shows similar trends that increase of Ag induce the increase its crystallinity as well as its electrical conductivity at semiconducting level. This result opens a prospective research and application of the green renewable polymer as optoelectronic materials.

  12. [Construction of 3D tissue-like structure using functional magnetite nanoparticles].

    PubMed

    Ito, Akira; Honda, Hiroyuki; Kamihira, Masamichi

    2008-01-01

    Magnetic nanoparticles for medical applications have been developed by many researchers. Since these nanoparticles have unique magnetic features not present in other materials, they can be applied to special medical techniques. Magnetite cationic liposomes (MCLs), one group of the cationic magnetic particles, can be used as carriers to introduce magnetite nanoparticles into target cells since their positively charged surface interacts with the negatively charged cell surface. Magnetite nanoparticles conjugated with antibodies (antibody-conjugated magnetoliposomes, AMLs) are applicable to introduce magnetite nanoparticles specifically into target cells, even when target cells coexist with other kinds of cells. Since the cells labeled with magnetite nanoparticles could be manipulated using magnets, we applied this technique to tissue engineering and termed it ;magnetic force-based tissue engineering (Mag-TE)'. Both magnetic force and functionalized magnetite nanoparticles were used in a process of tissue engineering: construction of multilayered cell sheet-like structures and tubular structures. Thus, the applications of these functionalized magnetite nanoparticles with their unique features will further improve tissue engineering techniques.

  13. Microreactor and electron spectroscopy studies of Fischer-Tropsch synthesis on magnetite

    SciTech Connect

    Krebs, H.J.; Bonzel, H.P.; Schwarting, W.; Gafner, G.

    1981-12-01

    The Fischer-Tropsch synthesis from CO and H/sub 2/ (1:3 mixture) at 1 bar total pressure and 570 K has been studied in a differential microreactor system on reduced and unreduced Fe/sub 3/O/sub 4/ (magnetite). The catalytic reactivity data were complemented by surface analytical measurements using Auger electron and x-ray photoelectron spectroscopy (XPS, ESCA). XPS measurements showed evidence of carbon deposition, mostly in the form of graphite on all samples. The rate of methanation on reduced magnetite was characterized by a maximum and subsequent decrease. Both features were dependent on the reduction history of the sample. All samples gave rise to the production of higher-molecular-weight species. The selectivity of reduced magnetite tended towards the formation of saturated hydrocarbons while that of the unreduced magnetite favoured the formation of alkenes. It was concluded that the reduction of magnetite led to a considerable increase in surface area and porosity and that secondary reactions of the alkenes caused the primary product spectrum to shift from alkenes to alkanes. Accordingly the polymerisation probability increased from 0.3 for unreduced magnetite (also for clean foil) to greater than or equal to 0.42 for reduced magnetite.

  14. Magnetite as a prokaryotic biomarker: A review

    NASA Astrophysics Data System (ADS)

    Jimenez-Lopez, Concepcion; Romanek, Christopher S.; Bazylinski, Dennis A.

    2010-06-01

    Over the years, nanometer-sized magnetite (Fe3O4) crystals have been recovered from many modern and ancient environments including sediments and soils and even meteorites. In some cases these crystals have been used as "magnetofossils" for evidence of the past presence of specific microbes. Magnetite nanocrystals can be formed by a number of different biological and inorganic mechanisms resulting in crystals with different physical and magnetic characteristics. Prokaryotes (bacteria) biomineralize magnetite through two methods that differ mechanistically, including: biologically induced mineralization (BIM) and biologically controlled mineralization (BCM). Magnetite nanocrystals produced by BIM are known to be synthesized by the dissimilatory iron-reducing bacteria, are deposited external to the cell, and generally are physically indistinguishable from magnetite particles formed inorganically. BCM magnetites, in contrast, are synthesized by the magnetotactic bacteria and some higher organisms and are precipitated intracellularly as membrane-bounded structures called magnetosomes. These magnetites appear to have unique crystal morphologies and a narrow size range leading to their original use as magnetofossils. Because of the discovery of nanometer-sized crystals of magnetite in the Martian meteorite ALH84001, the use of these criteria for the determination of whether magnetite crystals could constitute a prokaryotic biomarker was questioned. Thus, there is currently great debate over what criteria to use in the determination of whether specific magnetite crystals are biogenic or not. In the last decade, additional criteria have been established (e.g., the Magnetite Assay for Biogenicity), and new tools and technologies have been developed to determine the origin of specific types of magnetite crystals.

  15. Sonochemical synthesis of versatile hydrophilic magnetite nanoparticles.

    PubMed

    Marchegiani, G; Imperatori, P; Mari, A; Pilloni, L; Chiolerio, A; Allia, P; Tiberto, P; Suber, L

    2012-07-01

    Hydrophilic magnetite nanoparticles in the size range 30-10nm are easily and rapidly prepared under ultrasonic irradiation of Fe(OH)(2) in di- and tri-ethylene glycol/water solution with volume ratio varying between 7:3 and 3:7. Structural (XRD) and morphological (SEM) characterization reveal good crystalline and homogeneous particles whereas, when solvothermally prepared, the particles are inhomogeneous and aggregated. The sonochemically prepared particles are versatile, i.e. well suited to covalently bind molecules because of the free glycol hydroxylic groups on their surface or exchange the diethylene or triethylene glycol ligand. They can be easily transferred in hydrophobic solvents too. Room-temperature magnetic hysteresis properties measured by means of Vibrating Sample Magnetometer (VSM) display a nearly superparamagnetic character. The sonochemical preparation is easily scalable to meet industrial demand.

  16. Benefaction studies on the Hasan Celebi magnetite deposit, Turkey

    USGS Publications Warehouse

    Pressler, Jean W.; Akar, Ali

    1972-01-01

    Bench-scale and semicontinuous tests were performed on surface, trench, and diamond drill core samples from the Hasan Celebi low-grade magnetite deposit to determine the optimum benefication procedures utilizing wet magnetic separation techniques. Composite core samples typically contain about 27 percent recoverable magnetite and require crushing and grinding through 1 mm in size to insure satisfactory separation of the gangue from the magnetite. Regrinding and cleaning the magnetite concentrate to 80 percent minus 150-mesh is necessary to obtain an optimum of 66 percent iron. Semicontinuous pilot-plant testing with the wet magnetic drum using the recycled middling technique indicates that as much as 83 percent of the acid-soluble iron can be recovered into a concentrate containing 66 percent iron, with minimum deleterious elements. This represents 27 weight percent of the original ore. Further tests will continue when the Maden Tetkik ve Arama Enstitusu (MTA) receives 24 tons of bulk sample from an exploratory drift and cross-cut now being driven through a section of the major reserve area.

  17. Some Properties of Magnetite Nanoparticles Produced Under Different Conditions

    NASA Astrophysics Data System (ADS)

    Khan, Umar Saeed; Khattak, Nazir Shah; Manan, Abdul; Rahman, Aminur; Khan, Faridullah; Rahim, Abdur

    2015-01-01

    Temperature, stirring rate, stirring time, reaction pH, and concentration of precursors during synthesis were found to be crucial in determining the size of the magnetite nanoparticles (NPs) obtained. The relationship between synthetic conditions and the crystal structure, particle size, and size distribution of the NPs was studied. Surface coating of iron oxide NPs was performed in two steps. Magnetite NPs were prepared by coprecipitation then coated with silica by use of a sol-gel process. Saturation magnetization of the magnetite NPs increased from 47.23 to 49.12 emu/g when their size was increased from 8.89 to 9.39 nm. Magnetite NPs in the size range 11-12 nm, coated with silica, are monodispersed and their corresponding saturation magnetization is 40.67 emu/g (11 nm) and 34.65 emu/g (12 nm). The decrease in the saturation magnetization of the coated samples is attributed to the increase in the amount of tetraethyl orthosilicate.

  18. Electrokinetic characterization of magnetite nanoparticles functionalized with amino acids.

    PubMed

    Viota, J L; Arroyo, F J; Delgado, A V; Horno, J

    2010-04-01

    The synthesis of nanoparticles consisting of a magnetite core coated with one or more layers of amino acid (L-arginine, L-lysine, glycine, and L-glutamine) is described in this paper. For all the amino acids it is found that adsorption increases with concentration in solution in the range 0.5-10 mg/mL. The adsorption, however, differs substantially from one amino acid to another, depending on the length of the hydrocarbon chain and the polarity and charge of the side group. Thus, for given concentration and pH, adsorption is found to increase in the order L-arginine < L-lysine < L-glutamine < glycine. This order corresponds roughly to amino acids with decreasing chain length; in addition, the presence of the less polarizable guanidine group in the arginine molecule may explain why this amino acid is slightly less adsorbed than lysine. The pH dependence of the adsorption of each amino acid is reasonably explained considering the surface charge of magnetite and the charge of the amino acid molecules for different pHs, indicating a significant role of electrostatics in adsorption. This is further checked by means of determinations of the electrophoretic mobility of amino acid-coated magnetite as a function of pH: the results indicate a shift of the isoelectric point of the raw magnetite toward more basic pHs, an indication of adsorption of positive species, as confirmed by the tendency of the mobility of amino acid-coated magnetite toward more positive values below neutral pH. The electrophoretic mobility of coated particles was also measured as a function of the concentration of amino acid, and it was found that for low concentrations the four amino acids provoke charge inversion and overcharging of the magnetite surface at pH 6. Finally, the dependence of the electrophoretic mobility on the ionic strength indicated that from an electrophoretic point of view, the functionalized magnetite-amino acid particles do not behave as soft particles, and that the amino acid

  19. Sonochemical coating of magnetite nanoparticles with silica.

    PubMed

    Dang, Feng; Enomoto, Naoya; Hojo, Junichi; Enpuku, Keiji

    2010-01-01

    Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating.

  20. Magnetite nanoparticles as-prepared and dispersed in Copaiba oil: study using magnetic measurements and Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Oshtrakh, Michael I.; Ushakov, Mikhail V.; Semenova, Anna S.; Kellerman, Dina G.; Šepelák, Vladimir; Rodriguez, Alfonso F. R.; Semionkin, Vladimir A.; Morais, Paulo C.

    2013-04-01

    Study of magnetite nanoparticles, as-prepared and dispersed in Copaiba oil as magnetic fluid, by means of magnetic measurement and Mössbauer spectroscopy at various temperatures demonstrated differences in the saturation magnetization and Mössbauer hyperfine parameters which were related to the interactions of Copaiba oil polar molecules with iron cations on magnetite nanoparticle's surface.

  1. Dependence of microbial magnetite formation on humic substance and ferrihydrite concentrations

    NASA Astrophysics Data System (ADS)

    Piepenbrock, Annette; Dippon, Urs; Porsch, Katharina; Appel, Erwin; Kappler, Andreas

    2011-11-01

    Iron mineral (trans)formation during microbial Fe(III) reduction is of environmental relevance as it can influence the fate of pollutants such as toxic metal ions or hydrocarbons. Magnetite is an important biomineralization product of microbial iron reduction and influences soil magnetic properties that are used for paleoclimate reconstruction and were suggested to assist in the localization of organic and inorganic pollutants. However, it is not well understood how different concentrations of Fe(III) minerals and humic substances (HS) affect magnetite formation during microbial Fe(III) reduction. We therefore used wet-chemical extractions, magnetic susceptibility measurements and X-ray diffraction analyses to determine systematically how (i) different initial ferrihydrite (FH) concentrations and (ii) different concentrations of HS (i.e. the presence of either only adsorbed HS or adsorbed and dissolved HS) affect magnetite formation during FH reduction by Shewanella oneidensis MR-1. In our experiments magnetite formation did not occur at FH concentrations lower than 5 mM, even though rapid iron reduction took place. At higher FH concentrations a minimum fraction of Fe(II) of 25-30% of the total iron present was necessary to initiate magnetite formation. The Fe(II) fraction at which magnetite formation started decreased with increasing FH concentration, which might be due to aggregation of the FH particles reducing the FH surface area at higher FH concentrations. HS concentrations of 215-393 mg HS/g FH slowed down (at partial FH surface coverage with sorbed HS) or even completely inhibited (at complete FH surface coverage with sorbed HS) magnetite formation due to blocking of surface sites by adsorbed HS. These results indicate the requirement of Fe(II) adsorption to, and subsequent interaction with, the FH surface for the transformation of FH into magnetite. Additionally, we found that the microbially formed magnetite was further reduced by strain MR-1 leading to

  2. Removal of hexavalent chromium [Cr(VI)] from aqueous solutions by the diatomite-supported/unsupported magnetite nanoparticles.

    PubMed

    Yuan, Peng; Liu, Dong; Fan, Mingde; Yang, Dan; Zhu, Runliang; Ge, Fei; Zhu, JianXi; He, Hongping

    2010-01-15

    Diatomite-supported/unsupported magnetite nanoparticles were prepared by co-precipitation and hydrosol methods, and characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the unsupported and supported magnetite nanoparticles are around 25 and 15 nm, respectively. The supported magnetite nanoparticles exist on the surface or inside the pores of diatom shells, with better dispersing and less coaggregation than the unsupported ones. The uptake of hexavalent chromium [Cr(VI)] on the synthesized magnetite nanoparticles was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium [Cr(III)]. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed a pseudo-second-order model. The adsorption data of diatomite-supported/unsupported magnetite fit well with the Langmuir isotherm equation. The supported magnetite showed a better adsorption capacity per unit mass of magnetite than unsupported magnetite, and was more thermally stable than their unsupported counterparts. These results indicate that the diatomite-supported/unsupported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.

  3. Montmorillonite-supported magnetite nanoparticles for the removal of hexavalent chromium [Cr(VI)] from aqueous solutions.

    PubMed

    Yuan, Peng; Fan, Mingde; Yang, Dan; He, Hongping; Liu, Dong; Yuan, Aihua; Zhu, JianXi; Chen, TianHu

    2009-07-30

    Montmorillonite-supported magnetite nanoparticles were prepared by co-precipitation and hydrosol method. The obtained materials were characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the magnetite nanoparticles without and with montmorillonite support are around 25 and 15 nm, respectively. The montmorillonite-supported magnetite nanoparticles exist on the surface or inside the interparticle pores of clays, with better dispersing and less coaggregation than the ones without montmorillonite support. Batch tests were carried out to investigate the removal mechanism of hexavalent chromium [Cr(VI)] by these synthesized magnetite nanoparticles. The Cr(VI) uptake was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed the Pseudo-second-order model. The adsorption data of unsupported and clay-supported magnetite nanoparticles fit well with the Langmuir and Freundlich isotherm equations. The montmorillonite-supported magnetite nanoparticles showed a much better adsorption capacity per unit mass of magnetite (15.3mg/g) than unsupported magnetite (10.6 mg/g), and were more thermally stable than their unsupported counterparts. These fundamental results demonstrate that the montmorillonite-supported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.

  4. Magnetite (Fe3O4) microcapsules prepared using a glass membrane and solvent removal.

    PubMed

    Omi, S; Kanetaka, A; Shimamori, Y; Supsakulchai, A; Nagai, M; Ma, G H

    2001-01-01

    Fine magnetite powders dispersed in polymer solution were encapsulated from an oil-in-water emulsion prepared by an emulsification process employing a porous glass membrane and subsequent evaporation of the solvent. Styrene-based copolymers were dissolved in a magnetic fluid, and then continuously pushed through the pores of glass membrane into the aqueous phase, which had dissolved polyvinyl alcohol (PVA) and sodium dodecyl sulphate (SDS) as a mixed stabilizer. P(styrene-co-acrylic acid) (PS-AA), P(stryrene-co-butyl acrylate) (PS-BA) and styrene-butadiene rubber (SBR) were dissolved in the specially ordered magnetite fluid (25 wt% magnetite dispersed in toluene) separately or as a mixture, and uniform droplets suspending the magnetic particles were obtained. After the evaporation of toluene, PS-AA capsules retained a spherical shape and uniformity, whereas PS-AA/PS-BA capsules revealed a creased surface and broader size distribution. The microcapsules entrapped 30-40 wt% of magnetite, and the encapsulation yield of magnetite was 20-40%. Glass membranes with 9.5, 5.25 and 1.42 microm pore size were employed and 5-40 microm microcapsules were obtained depending on the pore size. When magnetite suspended in chloroform was used, magnetite capsules with broader size distributions were obtained because of the sticking of the droplets to the membrane wall. The advantage of the membrane emulsification which provides uniform sized droplets was lost. PMID:11695639

  5. Antimicrobial Properties of Lysosomal Enzymes Immobilized on NH₂Functionalized Silica-Encapsulated Magnetite Nanoparticles.

    PubMed

    Bang, Seung Hyuck; Sekhon, Simranjeet Singh; Cho, Sung-Jin; Kim, So Jeong; Le, Thai-Hoang; Kim, Pil; Ahn, Ji-Young; Kim, Yang-Hoon; Min, Jiho

    2016-01-01

    The immobilization efficiency, antimicrobial activity and recovery of lysosomal enzymes on NH2 functionalized magnetite nanoparticles have been studied under various conditions. The immobi- lization efficiency depends upon the ratio of the amount of enzyme and magnetite and it shows an increase with magnetite concentration which is due to the presence of amine group at the magnetite surface that leads to a strong attraction. The optimized reaction time to immobilize the lysosomal enzymes on magnetite was determined by using a rolling method. The immobilization efficiency increases with reaction time and reached a plateau after 5 minutes and then remained constant for 10 minutes. However, after 30 minutes the immobilization efficiency decreased to 85%, which is due to the weaker electrostatic interactions between magnetite and detached lysosomal enzymes. The recovery and stability of immobilized lysosomal enzymes has also been studied. The antimicrobial activity was almost 100% but it decreased upon reuse and no activity was observed after its reuse for seven times. The storage stability of lysosomal enzymes as an antimicrobial agent was about 88%, which decreased to 53% after one day and all activity of immobilized lysosomal enzymes was maintained after five days. Thus, the lysosomal enzymes immobilized on magnetite nanoparticles could potentially be used as antimicrobial agents to remove bacteria. PMID:27398573

  6. Antimicrobial Properties of Lysosomal Enzymes Immobilized on NH₂Functionalized Silica-Encapsulated Magnetite Nanoparticles.

    PubMed

    Bang, Seung Hyuck; Sekhon, Simranjeet Singh; Cho, Sung-Jin; Kim, So Jeong; Le, Thai-Hoang; Kim, Pil; Ahn, Ji-Young; Kim, Yang-Hoon; Min, Jiho

    2016-01-01

    The immobilization efficiency, antimicrobial activity and recovery of lysosomal enzymes on NH2 functionalized magnetite nanoparticles have been studied under various conditions. The immobi- lization efficiency depends upon the ratio of the amount of enzyme and magnetite and it shows an increase with magnetite concentration which is due to the presence of amine group at the magnetite surface that leads to a strong attraction. The optimized reaction time to immobilize the lysosomal enzymes on magnetite was determined by using a rolling method. The immobilization efficiency increases with reaction time and reached a plateau after 5 minutes and then remained constant for 10 minutes. However, after 30 minutes the immobilization efficiency decreased to 85%, which is due to the weaker electrostatic interactions between magnetite and detached lysosomal enzymes. The recovery and stability of immobilized lysosomal enzymes has also been studied. The antimicrobial activity was almost 100% but it decreased upon reuse and no activity was observed after its reuse for seven times. The storage stability of lysosomal enzymes as an antimicrobial agent was about 88%, which decreased to 53% after one day and all activity of immobilized lysosomal enzymes was maintained after five days. Thus, the lysosomal enzymes immobilized on magnetite nanoparticles could potentially be used as antimicrobial agents to remove bacteria.

  7. Magnetism of Al-substituted magnetite reduced from Al-hematite

    NASA Astrophysics Data System (ADS)

    Jiang, Zhaoxia; Liu, Qingsong; Zhao, Xiang; Roberts, Andrew P.; Heslop, David; Barrón, Vidal; Torrent, José

    2016-06-01

    Aluminum-substituted magnetite (Al-magnetite) reduced from Al-substituted hematite or goethite (Al-hematite or Al-goethite) is an environmentally important constituent of magnetically enhanced soils. In order to characterize the magnetic properties of Al-magnetite, two series of Al-magnetite samples were synthesized through reduction of Al-hematite by a mixed gas (80% CO2 and 20% CO) at 395°C for 72 h in a quartz tube furnace. Al-magnetite samples inherited the morphology of their parent Al-hematite samples, but only those transformed from Al-hematite synthesized at low temperature possessed surficial micropores, which originated from the release of structural water during heating. Surface micropores could thus serve as a practical fingerprint of fire or other high-temperature mineralogical alteration processes in natural environments, e.g., shear friction in seismic zones. In addition, Al substitution greatly affects the magnetic properties of Al-magnetite. For example, coercivity (Bc) increases with increasing Al content and then decreases slightly, while the saturation magnetization (Ms), Curie temperature (Tc), and Verwey transition temperature (Tv) all decrease with increasing Al content due to crystal defect formation and dilution of magnetic ions caused by Al incorporation. Moreover, different trends in the correlation between Tc and Bc can be used to discriminate titanomagnetite from Al-magnetite, which is likely to be important in environmental and paleomagnetic studies, particularly in soil.

  8. Magnetite Nanoparticles Stabilized Under Physiological Conditions for Biomedical Application

    NASA Astrophysics Data System (ADS)

    Hajdãº, A.; Tombácz, E.; Illés, E.; Bica, D.; Vékás, L.

    The biomedical application of water based magnetic fluids (MFs) is of great practical importance. Their colloidal stability under physiological conditions (blood pH ˜ 7.2-7.4 and salt concentration ˜0.15 M) and more in high magnetic field gradient is crucial. Magnetite or maghemite nanoparticles are used in general. In the present work, magnetite nanoparticles were stabilized with different compounds (citric acid (CA) and phosphate) and sodium oleate (NaO) as the most used surfactant in the stabilization of MFs. The adsorption and overcharging effect were quantified, and the enhancement in salt tolerance of stabilized systems was studied. Adsorption, electrophoretic mobility and dynamic light scattering (DLS) measurements were performed. The electrolyte tolerance was tested in coagulation kinetic measurements. Above the adsorption saturation, the nanoparticles are stabilized in a way of combined steric and electrostatic effects. The aim was to research these two important effects and demonstrate that none of them alone is enough. The phosphate was not able to stabilize the ferrofluid in spite of our expectation, but the other two additives proved to be effective stabilizing agents. The magnetite was well stabilized by the surface complexation of CA above pH ˜ 5, however, the salt tolerance of citrate stabilized MFs remained much below the concentration of physiological salt solution, and more the dissolution of magnetite nanocrystals was enhanced due to Fe-CA complexation in aqueous medium, which may cause problems in vivo. The oleate double layers were able to stabilize magnetite nanoparticles perfectly at pH ˜ 6 preventing particle aggregation effectively even in physiological salt solution.

  9. Preparation of magnetite aqueous dispersion for magnetic fluid hyperthermia

    NASA Astrophysics Data System (ADS)

    Kikuchi, Teppei; Kasuya, Ryo; Endo, Shota; Nakamura, Akira; Takai, Toshiyuki; Metzler-Nolte, Nils; Tohji, Kazuyuki; Balachandran, Jeyadevan

    2011-05-01

    An aqueous magnetic suspension was prepared by dispersing amphiphilic co-polymer-coated monodispersed magnetite nanoparticles synthesized through thermal decomposition of iron acetylacetonate (Fe(acac) 3) in a mixture of oleic acid and oleylamine. The average diameter of narrow-size-distributed magnetite nanoparticles varied between 5 and 12 nm depending on the experimental parameters such as reaction temperature, metal salt concentration and oleic acid/oleylamine ratio. Though the as-synthesized particles were coated with oleate and were dispersible in organic solvent, their surfaces were modified using amphiphilic co-polymers composed of poly(maleic anhydride-alt-1-octadecene) and polyethylene glycol-methyl ether and made dispersible in water. Infrared spectra of the sample indicated the existence of -COOH groups on the surface for further conjugation with biomolecules for targeted cancer therapy.

  10. Polyaniline stabilized magnetite nanoparticle reinforced epoxy nanocomposites.

    PubMed

    Gu, Hongbo; Tadakamalla, Sruthi; Huang, Yudong; Colorado, Henry A; Luo, Zhiping; Haldolaarachchige, Neel; Young, David P; Wei, Suying; Guo, Zhanhu

    2012-10-24

    Magnetic epoxy polymer nanocomposites (PNCs) reinforced with magnetite (Fe(3)O(4)) nanoparticles (NPs) have been prepared at different particle loading levels. The particle surface functionality tuned by conductive polyaniline (PANI) is achieved via a surface initiated polymerization (SIP) approach. The effects of nanoparticle loading, surface functionality, and temperature on both the viscosity and storage/loss modulus of liquid epoxy resin suspensions and the physicochemical properties of the cured solid PNCs are systematically investigated. The glass transition temperature (T(g)) of the cured epoxy filled with the functionalized NPs has shifted to the higher temperature in the dynamic mechanical analysis (DMA) compared with that of the cured pure epoxy. Enhanced mechanical properties of the cured epoxy PNCs filled with the functionalized NPs are observed in the tensile test compared with that of the cured pure epoxy and cured epoxy PNCs filled with as-received NPs. The uniform NP distribution in the cured epoxy PNCs filled with functionalized NPs is observed by scanning electron microscope (SEM). These magnetic epoxy PNCs show the good magnetic properties and can be attached by a permanent magnet. Enhanced interfacial interaction between NPs and epoxy is revealed in the fracture surface analysis. The PNCs formation mechanism is also interpreted from the comprehensive analysis based on the TGA, DSC, and FTIR in this work.

  11. Arsenic(III) and arsenic(V) speciation during transformation of lepidocrocite to magnetite.

    PubMed

    Wang, Yuheng; Morin, Guillaume; Ona-Nguema, Georges; Brown, Gordon E

    2014-12-16

    Bioreduction of As(V) and As-bearing iron oxides is considered to be one of the key processes leading to arsenic pollution in groundwaters in South and Southeast Asia. Recent laboratory studies with simple aqueous media showed that secondary Fe(II)-bearing phases (e.g., magnetite and green rust), which commonly precipitate during bioreduction of iron oxides, captured arsenic species. The aim of the present study was to follow arsenic speciation during the abiotic Fe(II)-induced transformation of As(III)- and As(V)-doped lepidocrocite to magnetite, and to evaluate the influence of arsenic on the transformation kinetics and pathway. We found green rust formation is an intermediate phase in the transformation. Both As(III) and As(V) slowed the transformation, with the effect being greater for As(III) than for As(V). Prior to the formation of magnetite, As(III) adsorbed on both lepidocrocite and green rust, whereas As(V) associated exclusively with green rust, When magnetite precipitated, As(III) formed surface complexes on magnetite nanoparticles and As(V) is thought to have been incorporated into the magnetite structure. These processes dramatically lowered the availability of As in the anoxic systems studied. These results provide insights into the behavior of arsenic during magnetite precipitation in reducing environments. We also found that As(V) removal from solution was higher than As(III) removal following magnetite formation, which suggests that conversion of As(III) to As(V) is preferred when using As-magnetite precipitation to treat As-contaminated groundwaters.

  12. High stable suspension of magnetite nanoparticles in ethanol by using sono-synthesized nanomagnetite in polyol medium

    SciTech Connect

    Bastami, Tahereh Rohani; Entezari, Mohammad H.

    2013-09-01

    Graphical abstract: - Highlights: • The sonochemical synthesis of magnetite nanoparticles was carried out in EG without any surfactant. • The nanoparticles with sizes ∼24 nm were composed of small building blocks with sizes ∼2 nm. • The hydrophilic magnetite nanoparticles were stable in ethanol even after 8 months. • Ultrasonic intensity showed a crucial role on the obtained high stable magnetite nanoparticles in ethanol. - Abstract: The sonochemical synthesis of magnetite nanoparticles was carried out at relatively low temperature (80 °C) in ethylene glycol (EG) as a polyol solvent. The particle size was determined by transmission electron microscopy (TEM). The magnetite nanoparticles with an average size of 24 nm were composed of small building blocks with an average size of 2–3 nm and the particles exhibited nearly spherical shape. The surface characterization was investigated by using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The stability of magnetite nanoparticles was studied in ethanol as a polar solvent. The nanoparticles showed an enhanced stability in ethanol which is due to the hydrophilic surface of the particles. The colloidal stability of magnetite nanoparticles in ethanol was monitored by UV–visible spectrophotometer. According to the results, the nanoparticles synthesized in 30 min of sonication with intensity of 35 W/cm{sup 2} (50%) led to a maximum stability in ethanol as a polar solvent with respect to the other applied intensities. The obtained magnetite nanoparticles were stable for more than12 months.

  13. Mechanical properties of natural chitosan/hydroxyapatite/magnetite nanocomposites for tissue engineering applications.

    PubMed

    Heidari, Fatemeh; Razavi, Mehdi; E Bahrololoom, Mohammad; Bazargan-Lari, Reza; Vashaee, Daryoosh; Kotturi, Hari; Tayebi, Lobat

    2016-08-01

    Chitosan (CS), hydroxyapatite (HA), and magnetite (Fe3O4) have been broadly employed for bone treatment applications. Having a hybrid biomaterial composed of the aforementioned constituents not only accumulates the useful characteristics of each component, but also provides outstanding composite properties. In the present research, mechanical properties of pure CS, CS/HA, CS/HA/magnetite, and CS/magnetite were evaluated by the measurements of bending strength, elastic modulus, compressive strength and hardness values. Moreover, the morphology of the bending fracture surfaces were characterized using a scanning electron microscope (SEM) and an image analyzer. Studies were also conducted to examine the biological response of the human Mesenchymal Stem Cells (hMSCs) on different composites. We conclude that, although all of these composites possess in-vitro biocompatibility, adding hydroxyapatite and magnetite to the chitosan matrix can noticeably enhance the mechanical properties of the pure chitosan.

  14. Characterization of magnetite-organic complex nanoparticles by metal-reducing bacteria.

    PubMed

    Kim, Yumi; Jang, Heedong; Suh, Yongjae; Roh, Yul

    2011-08-01

    Magnetite nanoparticles exhibit clear technological potential for biomedical applications. The objectives of this study were to synthesize magnetite-organic complex nanoparticles through the use of metal-reducing bacteria and characterize the mineralogical and surface chemical properties of these nanoparticles as well as to test their potential applications in biomedical technology with regards to their protein immobilization capacity. The microbially formed magnetite nanoparticles had a size of around 10 nm with a spherical shape and were coated with organics containing an abundance of reactive carboxyl groups without any chemical process for functionalizing them. These microbial processes may lead to a simple preparation of functional magnetite-organic complex nanoparticles which have benefits for biomedical applications.

  15. Magnetic and Structural Properties of Magnetite in Radular Teeth of Chiton Acanthochiton Rubrolinestus

    NASA Astrophysics Data System (ADS)

    Han, Y. N.; Liu, C. L.; Yao, L. D.; Wang, Y.; Han, X. F.

    2008-03-01

    The major radular lateral teeth of Polyplacophora Chiton comprise a magnetite biomineral cap.We have investigated the structure and magnetic properties of the biomineralized magnetite crystallites in mature teeth of Chiton Acanthochiton Rubrolinestus. From the measurement of magnetic properties of tooth particles using SQUID magnetometry we find that the saturation magnetization and the Verwey transition temperature (Tv) are 78.4 emu/g and 105 K, respectively. An in situ examination of the structure of magnetite-bearing region within individual tooth using the high resolution TEM, together with electron diffraction (ED) pattern and energy-dispersive X-ray (EDX) analyses indicates magnetite microcrystal form electron-dense polycrystalline sheets with typical length 800 nm and width 150 nm or so. These polycrystalline sheets are arranged regularly along the longitude direction of the tooth cutting surface. Furthermore, the microcrystallites in polycrystalline sheet take on the generally good crystallinity.

  16. Evidence for exclusively inorganic formation of magnetite in Martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Brearley, A. J.; Lauer, H. V., Jr.; Treiman, A. H.; Zolensky, M. E.; Schwandt, C. S.; Lofgren, G. E.

    2004-01-01

    globules in Martian meteorite ALH84001 is replicated by an inorganic process; and (2) the most common crystal morphology for biogenic (MV-1) magnetite is distinctly different from that in both ALH84001 and our inorganic laboratory products. Therefore, [111]-elongated magnetite crystals in ALH84001 do not constitute, as previously claimed, a robust biosignature and, in fact, an exclusively inorganic origin for the magnetite is fully consistent with our results. Furthermore, the inorganic synthesis method, i.e., the thermal decomposition of hydrothermally precipitated Fe-rich carbonate, is a process analogue for formation of the magnetite on Mars. Namely, precipitation of carbonate globules from carbonate-rich hydrothermal solutions followed at some later time by a thermal pulse, perhaps in association with meteoritic impact or volcanic processes on the Martian surface.

  17. Magnetite and magnetite/silver core/shell nanoparticles with diluted magnet-like behavior

    SciTech Connect

    Garza-Navarro, Marco; Gonzalez, Virgilio; Ortiz, Ubaldo; De la Rosa, Elder

    2010-01-15

    In the present work is reported the use of the biopolymer chitosan as template for the preparation of magnetite and magnetite/silver core/shell nanoparticles systems, following a two step procedure of magnetite nanoparticles in situ precipitation and subsequent silver ions reduction. The crystalline and morphological characteristics of both magnetite and magnetite/silver core/shell nanoparticles systems were analyzed by high resolution transmission electron microscopy (HRTEM) and nanobeam diffraction patterns (NBD). The results of these studies corroborate the core/shell morphology and the crystalline structure of the magnetite core and the silver shell. Moreover, magnetization temperature dependent, M(T), measurements show an unusual diluted magnetic behavior attributed to the dilution of the magnetic ordering in the magnetite and magnetite/silver core/shell nanoparticles systems. - Graphical abstract: Biopolymer chitosan was used as stabilization media to synthesize both magnetite and magnetite/silver core/shell nanoparticles. Results of HRTEM and NBD patterns confirm core/shell morphology of the obtained nanoparticles. It was found that the composites show diluted magnet-like behavior.

  18. Magnetite nanoparticles-chitosan composite containing carbon paste electrode for glucose biosensor application.

    PubMed

    Kavitha, A L; Prabu, H Gurumallesh; Babu, S Ananda; Suja, S K

    2013-01-01

    This work was aimed to develop reusable magnetite chitosan composite containing carbon paste electrode for biosensor application. Glucose oxidase (GOx) enzyme was used to prepare GOx-magnetite-chitosan nanocomposite containing carbon paste electrode for sensitive detection of glucose. The immobilized enzyme retained its bioactivity, exhibited a surface confined reversible electron transfer reaction, and had good stability. The surface parameters like surface coverage (tau), Diffusion coefficient (D0), and rate constant (kS) were studied. The carbon paste modified electrode virtually eliminated the interference during the detection of glucose. The excellent performance of the biosensor is attributed to large surface-to-volume ratio, high conductivity and good biocompatibility of chitosan, which enhances the enzyme absorption and promotes electron transfer between redox enzymes and the surface of electrode. The shelf life of the developed electrode system is about 12 weeks under refrigerated conditions. We report for the first time in the fabrication of carbon paste bioelectrode containing magnetite-chitosan-GOx.

  19. Acceleration of microwave-assisted enzymatic digestion reactions by magnetite beads.

    PubMed

    Chen, Wei-Yu; Chen, Yu-Chie

    2007-03-15

    In this study, we demonstrated that microwave-assisted enzymatic digestion could be greatly accelerated by multifunctional magnetite beads. The acceleration of microwave-assisted enzymatic digestion by the presence of the magnetite beads was attributable to several features of the beads. Their capacity to absorb microwave radiation leads to rapid heating of the beads. Furthermore, their negatively charged functionalities cause adsorption of proteins with opposite charges onto their surfaces by electrostatic interactions, leading to a concentration on the surfaces of the beads of proteins present in trace amounts in the solution. The adsorbed proteins are denatured and hence rendered vulnerable to enzymatic digestion and are digested on the beads. For microwave heating, 30 s was sufficient for carrying out the tryptic digestion of cytochrome c, in the presence of magnetite beads, while 1 min was adequate for tryptic digestion of myoglobin. The digestion products were characterized by MALDI-MS. This rapid enzymatic digestion allowed the entire time for identification of proteins to be greatly reduced. Furthermore, specific proteins present in trace quantities were enriched from the sample on the magnetite beads and could be rapidly isolated from the sample by employing an external magnetic field. These multiple roles of magnetite beads, as the absorber for microwave irradiation, the concentrating probe, and the agent for unfolding proteins, contributed to their capability of accelerating microwave-assisted enzymatic digestion. We also demonstrated that trypsin immobilized magnetite beads were suitable for use in microwave-assisted enzymatic digestion.

  20. Structure-function studies of the magnetite-biomineralizing magnetosome-associated protein MamC.

    PubMed

    Nudelman, Hila; Valverde-Tercedor, Carmen; Kolusheva, Sofiya; Perez Gonzalez, Teresa; Widdrat, Marc; Grimberg, Noam; Levi, Hilla; Nelkenbaum, Or; Davidov, Geula; Faivre, Damien; Jimenez-Lopez, Concepcion; Zarivach, Raz

    2016-06-01

    Magnetotactic bacteria are Gram-negative bacteria that navigate along geomagnetic fields using the magnetosome, an organelle that consists of a membrane-enveloped magnetic nanoparticle. Magnetite formation and its properties are controlled by a specific set of proteins. MamC is a small magnetosome-membrane protein that is known to be active in iron biomineralization but its mechanism has yet to be clarified. Here, we studied the relationship between the MamC magnetite-interaction loop (MIL) structure and its magnetite interaction using an inert biomineralization protein-MamC chimera. Our determined structure shows an alpha-helical fold for MamC-MIL with highly charged surfaces. Additionally, the MamC-MIL induces the formation of larger magnetite crystals compared to protein-free and inert biomineralization protein control experiments. We suggest that the connection between the MamC-MIL structure and the protein's charged surfaces is crucial for magnetite binding and thus for the size control of the magnetite nanoparticles. PMID:26970040

  1. Structure-function studies of the magnetite-biomineralizing magnetosome-associated protein MamC.

    PubMed

    Nudelman, Hila; Valverde-Tercedor, Carmen; Kolusheva, Sofiya; Perez Gonzalez, Teresa; Widdrat, Marc; Grimberg, Noam; Levi, Hilla; Nelkenbaum, Or; Davidov, Geula; Faivre, Damien; Jimenez-Lopez, Concepcion; Zarivach, Raz

    2016-06-01

    Magnetotactic bacteria are Gram-negative bacteria that navigate along geomagnetic fields using the magnetosome, an organelle that consists of a membrane-enveloped magnetic nanoparticle. Magnetite formation and its properties are controlled by a specific set of proteins. MamC is a small magnetosome-membrane protein that is known to be active in iron biomineralization but its mechanism has yet to be clarified. Here, we studied the relationship between the MamC magnetite-interaction loop (MIL) structure and its magnetite interaction using an inert biomineralization protein-MamC chimera. Our determined structure shows an alpha-helical fold for MamC-MIL with highly charged surfaces. Additionally, the MamC-MIL induces the formation of larger magnetite crystals compared to protein-free and inert biomineralization protein control experiments. We suggest that the connection between the MamC-MIL structure and the protein's charged surfaces is crucial for magnetite binding and thus for the size control of the magnetite nanoparticles.

  2. Microstructures Resulting from Uniaxial Deformation of Magnetite

    NASA Astrophysics Data System (ADS)

    Lindquist, A. K.; Feinberg, J. M.

    2012-12-01

    Researchers rely on the magnetic record preserved in magnetite when investigating magnetic field reversals, reconstructing past tectonic plate locations, and studying changes in the strength of the earth's magnetic field. Despite the extensive use of magnetite in scientific studies, the effects of dislocations on magnetite's remanence and magnetic stability are poorly understood, yet are crucial to understanding how magnetite records and maintains past magnetic field directions and intensities. To begin to address this need, we have studied the dislocation and defect structures in magnetite that form after controlled deformation. We have also measured major hysteresis loops to investigate the changes in remanence and coercivity that result from each of these deformation events. A single magnetite octahedron was cut into roughly equal bar-shaped pieces, and each was deformed uniaxially along a <121> direction at one atmosphere using a variety of temperature and pressure conditions, each selected to fall within the dislocation glide regime. Slices were cut from each deformed bar after deformation and investigated using a transmission electron microscope to characterize the types of deformation structures resulting from each of the temperature-pressure combinations. A variety of deformation structures were observed, especially dislocations and deformation bands. Dislocations were more common in samples deformed below 875°C. Hysteresis loops were measured for each sample with a field direction perpendicular to the deformation axis. Surprisingly, there is no significant difference in the bulk coercivity of a deformed and undeformed piece of magnetite.

  3. Adsorption of arsenic to magnetite nanoparticles: effect of particle concentration, pH, ionic strength, and temperature.

    PubMed

    Shipley, Heather J; Yean, Sujin; Kan, Amy T; Tomson, Mason B

    2009-03-01

    Little work has been conducted on the adsorption of arsenic to the mixed iron [Fe(II)/(III)] oxide magnetite and the effect that environmental parameters, such as pH, ionic strength, and temperature, have on adsorption. Magnetite nanoparticles are unique because of their affinity for both arsenate and arsenite and increased adsorption capacity from their bulk counterparts. This article shows the effect of various magnetite nanoparticle concentrations on arsenic adsorption kinetics. The adsorption data show the ability of the magnetite nanoparticles to remove arsenate and arsenite from solution in both synthetic and natural waters, and the data fit a first-order rate equation. Because of the increased surface area of these particles, less than 1 g/L of magnetite nanoparticles was needed. The results suggest that arsenic adsorption to the nanoparticles was not significantly affected by the pH, ionic strength and temperature in the ranges tested, which are typical of most potable water sources.

  4. Preparation of magnetite-fullerene nanocomposite with enzyme immobilization.

    PubMed

    Kalska-Szostko, B; Rogowska, M

    2012-09-01

    This study presents modification of magnetite nanoparticles and fullerene for biocompatibility. It show also specific fabrication of magnetite-carbon nanocomposite with immobilized biomolecule. The composites were created by joining individual components step-by-step manner (fullerene to magnetite and glucose oxidase or glucose oxidase to magnetite and fullerene). The resulting nanocomposites were characterized by infrared spectroscopy (IR) and transmission electron microscopy (TEM).

  5. The distinct effects of Mn substitution on the reactivity of magnetite in heterogeneous Fenton reaction and Pb(II) adsorption.

    PubMed

    Liang, Xiaoliang; He, Zisen; Wei, Gaoling; Liu, Peng; Zhong, Yuanhong; Tan, Wei; Du, Peixin; Zhu, Jianxi; He, Hongping; Zhang, Jing

    2014-07-15

    In this study, a series of Mn substituted magnetites were synthesized and used in catalyzing the heterogeneous Fenton degradation of acid orange II and Pb(II) adsorption, in order to investigate the effect of Mn substitution on the reactivity of magnetite. The valence and local environment of both Fe and Mn in the spinel structure of magnetite were investigated by X-ray absorption fine structure (XAFS) spectroscopy. The incorporation of Mn did not change the valence and local structure of Fe in the synthetic magnetite, while Mn was in the valences of +2 and +3. The Mn distribution on the octahedral sites of magnetite surface increased with the increase in Mn content. The Mn introduction led to an improvement of catalytic activity of magnetite. The sample with the minimum Mn content displayed the best efficiency in OH production and the degradation of acid orange II, while the other substituted samples did not show obvious difference in their catalytic performance. The adsorption capacity of magnetite samples toward Pb(II) gradually increased with the increase in Mn content. The above influences of Mn substitution on the reactivity of magnetite were discussed in views of the variations in microstructural environment and physicochemical properties.

  6. Magnetic and structural properties of magnetite in radular teeth of chiton Acanthochiton rubrolinestus.

    PubMed

    Han, Yunan; Liu, Chuanlin; Zhou, Dong; Li, Fashen; Wang, Yong; Han, Xiufeng

    2011-04-01

    The teeth of the Polyplacophora Chiton Acanthochiton Rubrolinestus contain biomineralized magnetite crystallites whose biological functions in relation to structure and magnetic properties are not well understood. Here, using superconducting quantum interference device (SQUID) magnetometry, we find that the saturation magnetization (σ(s)) and the Verwey transition temperature (T(v)) of tooth particles are 78.4 emu/g and 105 K, respectively. These values are below those of the stoichiometric magnetite. An in situ examination of the structure of the magnetite-bearing region within an individual tooth using high-resolution transmission electron microscopy indicates magnetite microcrystals form electron dense polycrystalline sheets with typical lengths of about 800 nm and widths of about 150 nm. These polycrystalline sheets are arranged regularly along the longitudinal direction of the tooth cutting surface. In addition, the crystallites in polycrystalline sheets take on generally good crystallinity. The magnetic microstructures of in situ magnetic force microscopy demonstrate that the [111] easy direction of magnetite microcrystals are aligned along the length of the tooth, whereas the [111] direction is parallel to the thickness of the tooth. Both Mössbauer spectra and magnetization versus temperature measurements under field cooled and zero-field cooled conditions do not detect superparamagnetic magnetite crystallites in the mature major lateral tooth particles of this chiton.

  7. Magnetic and structural properties of magnetite in radular teeth of chiton Acanthochiton rubrolinestus.

    PubMed

    Han, Yunan; Liu, Chuanlin; Zhou, Dong; Li, Fashen; Wang, Yong; Han, Xiufeng

    2011-04-01

    The teeth of the Polyplacophora Chiton Acanthochiton Rubrolinestus contain biomineralized magnetite crystallites whose biological functions in relation to structure and magnetic properties are not well understood. Here, using superconducting quantum interference device (SQUID) magnetometry, we find that the saturation magnetization (σ(s)) and the Verwey transition temperature (T(v)) of tooth particles are 78.4 emu/g and 105 K, respectively. These values are below those of the stoichiometric magnetite. An in situ examination of the structure of the magnetite-bearing region within an individual tooth using high-resolution transmission electron microscopy indicates magnetite microcrystals form electron dense polycrystalline sheets with typical lengths of about 800 nm and widths of about 150 nm. These polycrystalline sheets are arranged regularly along the longitudinal direction of the tooth cutting surface. In addition, the crystallites in polycrystalline sheets take on generally good crystallinity. The magnetic microstructures of in situ magnetic force microscopy demonstrate that the [111] easy direction of magnetite microcrystals are aligned along the length of the tooth, whereas the [111] direction is parallel to the thickness of the tooth. Both Mössbauer spectra and magnetization versus temperature measurements under field cooled and zero-field cooled conditions do not detect superparamagnetic magnetite crystallites in the mature major lateral tooth particles of this chiton. PMID:21365666

  8. Properties of intracellular magnetite crystals produced by Desulfovibrio magneticus strain RS-1

    NASA Astrophysics Data System (ADS)

    Pósfai, Mihály; Moskowitz, Bruce M.; Arató, Balázs; Schüler, Dirk; Flies, Christine; Bazylinski, Dennis A.; Frankel, Richard B.

    2006-09-01

    Desulfovibrio magneticus strain RS-1 is an anaerobic sulfate-reducing bacterium. Cells form intracellular nanocrystals of magnetite but are only weakly magnetotactic. In order to understand the unusual magnetic response of this strain, we studied magnetite crystals within cells grown with fumarate and sulfate. Many cells grown under either condition did not form magnetic crystals while others contained only 1 to 18 small (˜ 40 nm) magnetite-containing magnetosomes. Bulk magnetic measurements of whole cells showed a superparamagnetic-like behavior, indicating that many of the magnetite crystals are too small to have a permanent magnetic moment at ambient temperature. The temperature of the Verwey transition is lower (˜ 86 K) than of magnetite from other magnetotactic strains, likely indicating partial oxidation of magnetite into maghemite. As a result of the small size and small number of magnetite magnetosomes, the magnetic moments of most cells grown anaerobically with fumarate or sulfate are insufficient for magnetotaxis. In addition to intracellular magnetite, in some cultures another iron oxide, hematite, formed on the surfaces of cells. The hematite grains are embedded in an extracellular polymeric material, indicating that the crystals likely resulted from a biologically-induced mineralization process. Although the hematite particles appear to consist of aggregations of many small (5 to 10 nm) grains, the grains have a consensus orientation and thus the whole particle diffracts as a single crystal. The aligned arrangement of nanoparticles within larger clusters may reflect either a templated nucleation of hematite crystallites in an extracellular organic matrix, or result from a self-assembling process during the crystallization of hematite from ferric gels or ferrihydrite.

  9. Is magnetite a universal memory molecule?

    PubMed

    Størmer, Fredrik C

    2014-11-01

    Human stem cells possess memory, and consequently all living human cells must have a memory system. How memory is stored in cells and organisms is an open question. Magnetite is perhaps the best candidate to be a universal memory molecule. Magnetite may give us a clue, because it is the Earth's most distributed and important magnetic material. It is found in living organisms with no known functions except for involvement in navigation in some organisms. In humans magnetite is found in the brain, heart, liver and spleen. Humans suffer from memory dysfunctions in many cases when iron is out of balance. Anomalous concentrations of magnetite is known to be associated with a neurodegenerative disorder like Alzheimer's disease. Due to the rapid speed and accuracy of our brain, memory and its functions must be governed by quantum mechanics.

  10. "Clickable", trifunctional magnetite nanoparticles and their chemoselective biofunctionalization.

    PubMed

    Das, Manasmita; Bandyopadhyay, Debarati; Mishra, Debasish; Datir, Satyajit; Dhak, Prasanta; Jain, Sanyog; Maiti, Tapas Kumar; Basak, Amit; Pramanik, Panchanan

    2011-06-15

    A multifunctional iron oxide based nanoformulation for combined cancer-targeted therapy and multimodal imaging has been meticulously designed and synthesized using a chemoselective ligation approach. Novel superparamagnetic magnetite nanoparticles simultaneously functionalized with amine, carboxyl, and azide groups were fabricated through a sequence of stoichiometrically controllable partial succinylation and Cu (II) catalyzed diazo transfer on the reactive amine termini of 2-aminoethylphosphonate grafted magnetite nanoparticles (MNPs). Functional moieties associated with MNP surface were chemoselectively conjugated with rhodamine B isothiocyanate (RITC), propargyl folate (FA), and paclitaxel (PTX) via tandem nucleophic addition of amine to isothithiocyanates, Cu (I) catalyzed azide--alkyne click chemistry and carbodiimide-promoted esterification. An extensive in vitro study established that the bioactives chemoselectively appended to the magnetite core bequeathed multifunctionality to the nanoparticles without any loss of activity of the functional molecules. Multifunctional nanoparticles, developed in the course of the study, could selectively target and induce apoptosis to folate-receptor (FR) overexpressing cancer cells with enhanced efficacy as compared to the free drug. In addition, the dual optical and magnetic properties of the synthesized nanoparticles aided in the real-time tracking of their intracellular pathways also as apoptotic events through dual fluorescence and MR-based imaging.

  11. [Adsorption of methylene blue onto vanadium-doped magnetite].

    PubMed

    Zhong, Yuan-Hong; Liang, Xiao-Liang; Zhu, Jian-Xi; He, Hong-Ping; Yuan, Peng

    2010-06-01

    A series of vanadium-doped magnetite (Fe3-x VxO4, x < 0.4) synthesized by an oxidation-precipitation method, were characterized using chemical analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as thermogravimetric and differential scanning calorimetry (TG-DSC) analyses. The obtained results show that the synthetic Fe3-x VxO4 has spinel structure while vanadium mostly replaces Fe3+ in the octahedral sites. The synthetic Fe3-x VxO4 is magnetic material, with crystal size ranging from 28 to 35 nm. The substitution of vanadium in the magnetite structure increases the amount of surface hydroxyls. The experimental adsorption results indicate that, in neutral pH condition, the maximum adsorption capacities of Fe3-x VxO4 increase obviously with the increase of vanadium concentration in magnetite while the adsorption isotherm complies well with the Langmuir model. The adsorption of methylene blue (MB) on Fe3-x VxO4 can get equilibrium in the first 25 min, supporting a pseudo-second order equation. Moreover, the rise of the solution pH value results in an increase of the adsorption capability of MB on Fe3-x VxO4.

  12. The Verwey structure of a natural magnetite.

    PubMed

    Perversi, G; Cumby, J; Pachoud, E; Wright, J P; Attfield, J P

    2016-04-01

    A remarkably complex electronic order of Fe(2+)/Fe(3+) charges, Fe(2+) orbital states, and weakly metal-metal bonded Fe3 units known as trimerons, was recently discovered in stoichiometric magnetite (Fe3O4) below the 125 K Verwey transition. Here, the low temperature crystal structure of a natural magnetite from a mineral sample has been determined using the same microcrystal synchrotron X-ray diffraction method. Structure refinement demonstrates that the natural sample has the same complex electronic order as pure synthetic magnetite, with only minor reductions of orbital and trimeron distortions. Chemical analysis shows that the natural sample contains dopants such as Al, Si, Mg and Mn at comparable concentrations to extraterrestrial magnetites, for example, as reported in the Tagish Lake meteorite. Much extraterrestrial magnetite exists at temperatures below the Verwey transition and hence our study demonstrates that the low temperature phase of magnetite represents the most complex long-range electronic order known to occur naturally. PMID:26908195

  13. Effect of concentration of sodium silicate solution in the synthesis of silica-coated magnetite nanoparticles by ultrasonication

    NASA Astrophysics Data System (ADS)

    Fajaroh, Fauziatul; Sumari, Nazriati

    2016-02-01

    An ex-situ silica coating of magnetite nanoparticles synthesized electrochemically had been successfully carried out by ultrasonication. An aqueous solution of sodium silicate had been used as silica source.The Si-O-Si, Si-O and Fe-O-Si bonds on the surface of the silica-coated magnetite had been successfully identified using FTIR. Reduction in particle size due to the influence of ultrasound was studied using SEM. Enhancement in the specific surface area of the particles due to the silica coating and reduction in particle size was learned through BET analysis. The Characters of the resulting silica-coated magnetite were influenced by the concentration of sodium silicate solution. The greater the concentration of sodium silicate solution, the smaller the particle crystallinity and the larger the particles surface area was produced. The resulting silica-coated magnetite has a surface area of 38.171 to 67.993 m2/g, otherwise the non-coated particles only has a surface area of 27.894 m2/g. This silica-coated magnetite nanoparticles has more potent as an adsorbent than that of the bare magnetite. Besides that, the presence of silanol groups on its surface makes an opportunity for further functionalization needed for some applications.

  14. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered). PMID:14577885

  15. Submicron Magnetite Grains and Carbon Compounds in Martian Meteorite ALH84001: Inorganic, Abiotic Formation by Shock and Thermal Metamorphism

    NASA Astrophysics Data System (ADS)

    Treiman, Allan H.

    2003-06-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe3O4, reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  16. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  17. Evaluation of cytotoxic, genotoxic and inflammatory responses of micro- and nano-particles of granite on human lung fibroblast cell IMR-90.

    PubMed

    Ahmad, Iqbal; Khan, Mohd Imran; Patil, Govil; Chauhan, L K S

    2012-02-01

    Occupational exposure of granite workers is well known to cause lung impairment and silicosis. Toxicological profiles of different size particles of granite dust, however, are not yet understood. Present evaluation of micro- and nano-particles of granite dust as on human lung fibroblast cells IMR-90, revealed that their toxic effects were dose-dependent, and nanoparticles in general were more toxic. In this study we first demonstrated that nanoparticles caused oxidative stress, inflammatory response and genotoxicity, as seen by nearly 2 fold induction of ROS and LPO, mRNA levels of TNF-α and IL-1β, and induction in micronuclei formation. All these were significantly higher when compared with the effect of micro particles. Thus, the study suggests that separate health safety standards would be required for granite particles of different sizes.

  18. Characterization and nonlinear optical properties of PVP/TiO2 nano-fibers doping with Ag colloid nano-particles

    NASA Astrophysics Data System (ADS)

    Majles Ara, M. H.; Naderi, H.; Mobasheri, A.; Rajabi, M. H.; Malekfar, R.; Koushki, E.

    2013-02-01

    We synthesized PVP/TiO2 nano-fibers doping with Ag colloid nano-particles by electro-spinning method. These nano-fibers were characterized by UV/visible/NIR spectroscopy, SEM and XRD. The image of SEM showed that the synthesized nano-fibers were monotonous and without knot and had a diameter about 150 nm. We also measured the nonlinear refractive and absorption indexes of the sample in three different intensities using the single beam Z-scan method by a continuous wave (CW) He-Ne laser at 632.8 nm wavelength. The nonlinear refraction indexes of these nano-fibers were measured in order of 10-7 (cm2/W) with negative sign and the nonlinear absorption coefficient was obtained in order of 10-3 (cm/W).

  19. Effects of common groundwater ions on chromate removal by magnetite: Importance of chromate adsorption

    DOE PAGES

    Meena, Amanda H.; Arai, Yuji

    2016-04-29

    Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (< a few hr) reduction of soluble Cr(VI) to insoluble Cr(III) species by Fe(II) in magnetite has been the primary focus of the Cr(VI) removal process in the past. However, the contribution of simultaneous Cr(VI) adsorption processes in aged magnetite has been largely ignored, leaving uncertainties in evaluating the application of in situ Cr remediation technologies for aqueous systems. In this study, effects of common groundwater ions (i.e., nitrate and sulfate) on Cr(VI) sorption to magnetite were investigated using batchmore » geochemical experiments in conjunction with X-ray absorption spectroscopy. As a result, in both nitrate and sulfate electrolytes, batch sorption experiments showed that Cr(VI) sorption decreases with increasing pH from 4 to 8. In this pH range, Cr(VI) sorption decreased with increasing ionic strength of sulfate from 0.01 to 0.1 M whereas nitrate concentrations did not alter the Cr(VI) sorption behavior. This indicates the background electrolyte specific Cr(VI) sorption process in magnetite. Under the same ionic strength, Cr(VI) removal in sulfate containing solutions was greater than that in nitrate solutions. This is because the oxidation of Fe(II) by nitrate is more thermodynamically favorable than by sulfate, leaving less reduction capacity of magnetite to reduce Cr(VI) in the nitrate media. X-ray absorption spectroscopy analysis supports the macroscopic evidence that more than 75 % of total Cr on the magnetite surfaces was adsorbed Cr(VI) species after 48 h. In conclusion, this experimental geochemical study showed that the adsorption process of Cr(VI) anions was as important as the reductive precipitation of Cr(III) in describing the removal of Cr(VI) by magnetite, and these interfacial adsorption processes could be impacted by common groundwater ions like sulfate and nitrate. The

  20. Three-Dimensional Morphological Analysis of ALH84001 Magnetite Using Electron Tomography

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Shimmin, Joel; Morphew, Mary; McIntosh, J. Richard; Bazylinski, Dennis A.; Kirschvink, Joseph L.; Wentworth, Susan J.; McKay, David S.; Vali, Hojatollah

    2003-01-01

    We report here the crystal morphologies of MV-1 and ALH84001 magnetites as calculated by back-projection using electron tomography. In the present study, we used a 300 keV TEM with a field emission gun (Tecnai F-30 from FEI Inc.), equipped with a 2048 x 2048 pixel CCD camera from Gatan Inc. to image magnetite crystals over tilt ranges of approx. +/- 72 deg in 2 deg tilt intervals. The images were aligned for back-projection, either manually, or through the use of fiducial 5 nm Au spheres affixed to the specimen prior to microscopy. Three-dimensional (3-D) reconstructions were computed using weighted back-projection of the tilted views. The tomograms were viewed and analyzed as a series of slices 1.0 nm thick, taken parallel to the specimen-supporting grid, using the IMOD software package. The shape of each magnetite crystal was determined by defining the external contour of a given magnetite in each slice and assembling a stack of these contours in 3-D. To aid in visualization, the stacked contour array was reduced to an optimal mesh by Delaunay triangulation. The surface normal to each of the triangles in the mesh was calculated and the triangle faces colored according to the orientation of that surface normal relative to the principal crystallographic axis of magnetite. Green surfaces correspond to {111} orientations, blue surfaces to {100} orientations, and red surfaces to {110} orientations. Triangles whose surface normal did not correspond to one of the principal axes were colored gray. Within the experimental and numerical uncertainties of the deconvolution, the tomographic reconstruction of both MV-1 and ALH84001 magnetites are equivalent and correspond to a truncated hexa-octahedral morphology.

  1. The chemistry of hydrothermal magnetite: a review

    USGS Publications Warehouse

    Nadoll, Patrick; Angerer, Thomas; Mauk, Jeffrey L.; French, David; Walshe, John

    2014-01-01

    Magnetite (Fe3O4) is a well-recognized petrogenetic indicator and is a common accessory mineral in many ore deposits and their host rocks. Recent years have seen an increased interest in the use of hydrothermal magnetite for provenance studies and as a pathfinder for mineral exploration. A number of studies have investigated how specific formation conditions are reflected in the composition of the respective magnetite. Two fundamental questions underlie these efforts — (i) How can the composition of igneous and, more importantly, hydrothermal magnetite be used to discriminate mineralized areas from barren host rocks, and (ii) how can this assist exploration geologists to target ore deposits at greater and greater distances from the main mineralization? Similar to igneous magnetite, the most important factors that govern compositional variations in hydrothermal magnetite are (A) temperature, (B) fluid composition — element availability, (C) oxygen and sulfur fugacity, (D) silicate and sulfide activity, (E) host rock buffering, (F) re-equilibration processes, and (G) intrinsic crystallographic controls such as ionic radius and charge balance. We discuss how specific formation conditions are reflected in the composition of magnetite and review studies that investigate the chemistry of hydrothermal and igneous magnetite from various mineral deposits and their host rocks. Furthermore, we discuss the redox-related alteration of magnetite (martitization and mushketovitization) and mineral inclusions in magnetite and their effect on chemical analyses. Our database includes published and previously unpublished magnetite minor and trace element data for magnetite from (1) banded iron formations (BIF) and related high-grade iron ore deposits in Western Australia, India, and Brazil, (2) Ag–Pb–Zn veins of the Coeur d'Alene district, United States, (3) porphyry Cu–(Au)–(Mo) deposits and associated (4) calcic and magnesian skarn deposits in the southwestern United

  2. Distinctive arsenic(V) trapping modes by magnetite nanoparticles induced by different sorption processes.

    PubMed

    Wang, Yuheng; Morin, Guillaume; Ona-Nguema, Georges; Juillot, Farid; Calas, Georges; Brown, Gordon E

    2011-09-01

    Arsenic sorption onto iron oxide spinels such as magnetite may contribute to arsenic immobilization at redox fronts in soils, sediments, and aquifers, as well as in putative remediation and water treatment technologies. We have investigated As(V) speciation resulting from different sorption processes on magnetite nanoparticles, including both adsorption and precipitation, using X-ray absorption fine structure (XAFS) spectroscopy and transmission electron microscopy (TEM). XAFS results suggest that AsO(4) tetrahedra form predominantly inner-sphere bidentate corner-sharing ((2)C) complexes and outer-sphere complexes on magnetite in the adsorption experiments. In the precipitation experiments, an increasing fraction of AsO(4) tetrahedra appears to be incorporated in clusters having a magnetite-like local structure with increasing As loading, the remaining fraction of As being adsorbed at the surface of magnetite particles. In the sample with the highest As loading (15.7 μmol/m(2)) XAFS data indicate that As(V) is fully incorporated in such clusters. Such processes help to explain the significantly higher arsenic uptake in precipitation samples compared to those generated in adsorption experiments. In addition, for the precipitation samples, TEM observations indicate the formation of amorphous coatings and small (~3 nm) nanoparticles associated with larger (~20-40 nm) magnetite nanoparticles, which are absent in the adsorption samples. These results suggest that As(V) could form complexes at the surfaces of the small nanoparticles and could be progressively incorporated in their structure with increasing As loading. These results provide some of the fundamental knowledge about As(V)-magnetite interactions that is essential for developing effective water treatment technologies for arsenic.

  3. Aqueous ferrofluid of magnetite nanoparticles: Fluorescence labeling and magnetophoretic control.

    PubMed

    Sahoo, Yudhisthira; Goodarzi, Alireza; Swihart, Mark T; Ohulchanskyy, Tymish Y; Kaur, Navjot; Furlani, Edward P; Prasad, Paras N

    2005-03-10

    A method is presented for the preparation of a biocompatible ferrofluid containing dye-functionalized magnetite nanoparticles that can serve as fluorescent markers. This method entails the surface functionalization of magnetite nanoparticles using citric acid to produce a stable aqueous dispersion and the subsequent binding of fluorescent dyes to the surface of the particles. Several ferrofluid samples were prepared and characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), BET surface area analysis, transmission electron microscopy (TEM), and SQUID magnetometry. In addition, confocal fluorescence microscopy was used to study the response of the fluorescent nanoparticles to an applied magnetic field and their uptake by cells in vitro. Results are presented on the distribution of particle sizes, the fluorescent and magnetic properties of the nanoparticles, and the nature of their surface bonds. Biocompatible ferrofluids with fluorescent nanoparticles enable optical tracking of basic processes at the cellular level combined with magnetophoretic manipulation and should be of substantial value to researchers engaged in both fundamental and applied biomedical research. PMID:16851439

  4. Core Amino Acid Residues in the Morphology-Regulating Protein, Mms6, for Intracellular Magnetite Biomineralization

    PubMed Central

    Yamagishi, Ayana; Narumiya, Kaori; Tanaka, Masayoshi; Matsunaga, Tadashi; Arakaki, Atsushi

    2016-01-01

    Living organisms produce finely tuned biomineral architectures with the aid of biomineral-associated proteins. The functional amino acid residues in these proteins have been previously identified using in vitro and in silico experimentation in different biomineralization systems. However, the investigation in living organisms is limited owing to the difficulty in establishing appropriate genetic techniques. Mms6 protein, isolated from the surface of magnetite crystals synthesized in magnetotactic bacteria, was shown to play a key role in the regulation of crystal morphology. In this study, we have demonstrated a defect in the specific region or substituted acidic amino acid residues in the Mms6 protein for observing their effect on magnetite biomineralization in vivo. Analysis of the gene deletion mutants and transformants of Magnetospirillum magneticum AMB-1 expressing partially truncated Mms6 protein revealed that deletions in the N-terminal or C-terminal regions disrupted proper protein localization to the magnetite surface, resulting in a change in the crystal morphology. Moreover, single amino acid substitutions at Asp123, Glu124, or Glu125 in the C-terminal region of Mms6 clearly indicated that these amino acid residues had a direct impact on magnetite crystal morphology. Thus, these consecutive acidic amino acid residues were found to be core residues regulating magnetite crystal morphology. PMID:27759096

  5. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens.

    PubMed

    Byrne, J M; Telling, N D; Coker, V S; Pattrick, R A D; van der Laan, G; Arenholz, E; Tuna, F; Lloyd, J R

    2011-11-11

    The bioproduction of nanoscale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction analysis indicates that controlled production of a number of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) reduction and total concentration and rate of Fe(II) produced by the bacteria during the reduction process. Relative cation distributions within the structure of the nanoparticles have been investigated by x-ray magnetic circular dichroism and indicate the presence of a highly reduced surface layer which is not observed when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of organics, radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimized biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently to the less harmful trivalent form.

  6. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens

    NASA Astrophysics Data System (ADS)

    Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; van der Laan, G.; Arenholz, E.; Tuna, F.; Lloyd, J. R.

    2011-11-01

    The bioproduction of nanoscale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction analysis indicates that controlled production of a number of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) reduction and total concentration and rate of Fe(II) produced by the bacteria during the reduction process. Relative cation distributions within the structure of the nanoparticles have been investigated by x-ray magnetic circular dichroism and indicate the presence of a highly reduced surface layer which is not observed when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of organics, radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimized biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently to the less harmful trivalent form.

  7. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens

    SciTech Connect

    Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; Laan, G. van der; Arenholz, E.; Tuna, F.; Lloyd, J. R.

    2011-08-02

    The bioproduction of nano-scale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens, by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction analysis indicates that controlled production of a number of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) reduction and total concentration and rate of Fe(II) produced by the bacteria during the reduction process. Relative cation distributions within the structure of the nanoparticles has been investigated by X-ray magnetic circular dichroism and indicates the presence of a highly reduced surface layer which is not observed when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of organics, radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimised biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently in the less harmful trivalent form.

  8. Sticking polydisperse hydrophobic magnetite nanoparticles to lipid membranes.

    PubMed

    Paulus, Michael; Degen, Patrick; Brenner, Thorsten; Tiemeyer, Sebastian; Struth, Bernd; Tolan, Metin; Rehage, Heinz

    2010-10-19

    The formation of a layer of hydrophobic magnetite (Fe(3)O(4)) nanoparticles stabilized by lauric acid is analyzed by in situ X-ray reflectivity measurements. The data analysis shows that the nanoparticles partially disperse their hydrophobic coating. Consequently, a Langmuir layer was formed by lauric acid molecules that can be compressed into an untilted condensed phase. A majority of the nanoparticles are attached to the Langmuir film integrating lauric acid residue on their surface into the Langmuir film. Hence, the particles at the liquid-gas interface can be identified as so-called Janus beads, which are amphiphilic solids having two sides with different functionality.

  9. Sticking polydisperse hydrophobic magnetite nanoparticles to lipid membranes.

    PubMed

    Paulus, Michael; Degen, Patrick; Brenner, Thorsten; Tiemeyer, Sebastian; Struth, Bernd; Tolan, Metin; Rehage, Heinz

    2010-10-19

    The formation of a layer of hydrophobic magnetite (Fe(3)O(4)) nanoparticles stabilized by lauric acid is analyzed by in situ X-ray reflectivity measurements. The data analysis shows that the nanoparticles partially disperse their hydrophobic coating. Consequently, a Langmuir layer was formed by lauric acid molecules that can be compressed into an untilted condensed phase. A majority of the nanoparticles are attached to the Langmuir film integrating lauric acid residue on their surface into the Langmuir film. Hence, the particles at the liquid-gas interface can be identified as so-called Janus beads, which are amphiphilic solids having two sides with different functionality. PMID:20873726

  10. Rheological Study of Dextran-Modified Magnetite Nanoparticle Water Suspension

    NASA Astrophysics Data System (ADS)

    Józefczak, A.; Hornowski, T.; Rozynek, Z.; Skumiel, A.; Fossum, J. O.

    2013-04-01

    The aim of this work is to investigate the effect of surface modification of superparamagnetic magnetite nanoparticles (sterically stabilized by sodium oleate) by the dextran biocompatible layer on the rheological behavior of water-based magnetic fluids. The flow curves were measured as a function of the magnetic field strength by means of rheometry. The measured viscosity is generally dependent on both the particle concentration and the geometrical factors such as the particle shape and thickness of the adsorbed layers. The rheological properties of the magnetic fluids studied show the effect of the magnetic field strength and the presence of the surfactant second layer (dextran) on their viscosity.

  11. Superexchange coupling on oleylsarcosine-coated magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Bakuzis, A. F.; Pereira, A. R.; Santos, J. G.; Morais, P. C.

    2006-04-01

    Room temperature ferromagnetic resonance was used to investigate particle-particle interaction in magnetic fluid samples containing magnetite nanoparticles surface coated with dimercaptosuccinic acid (DMSA) or oleylsarcosine (OLEL). The DMSA sample showed a decrease of the magnetic resonance field (MRF) increasing the nanoparticle concentration (phi), whereas the OLEL sample showed the opposite behavior. The DMSA MRF concentration dependence was explained using a dipolar interaction model beyond the point dipole approximation. In addition, the magnetic resonance spectra of the OLEL sample showed an optical mode suggesting an antiferromagnetic superexchange coupling between magnetic nanoparticles forming dimers.

  12. Strong oxide-oxide interactions in silica-supported magnetite catalysts. IV. Catalytic consequences of the interaction in water-gas shift

    SciTech Connect

    Lund, C.R.F.; Dumesic, J.A.

    1982-07-01

    Water-gas shift was studied at 663 K and 0.1 MPa over a series of silica-supported magnetite (Fe/sub 3/O/sub 4/) catalysts having magnetite particles from ca. 10 to 160 nm in size. The surface sites on these catalysts were titrated using NO adsorption at 273 K and adsorption from a CO/sub 2//CO gas mixture (CO/sub 2/:CO = 85:15) at 663 K. For these silica-supported catalysts, the water-gas shift turnover frequency, based on NO adsorption for site titration, decreased with decreasing particle size. In contrast, unsupported magnetite did not show this particle size dependence. For the smallest silica-supported magnetite particles, the turnover frequency was three orders of magnitude lower than over unsupported magnetite. The extent of CO and CO/sub 2/ adsorption, per surface site as titrated by NO, was also observed to decrease with decreasing particle size; and, the water-gas shift turnover frequency, based on CO/sub 2//CO adsorption for site titration, is independent of particle size. Thus, while NO adsorption can be used to measure the magnetite surface area of silica-supported samples, the CO/sub 2//CO adsorption uptake is proportional to the number of active sites on the magnetite surface. Compared to unsupported magnetite, the origin of the low catalytic activity of silica-supported magnetite (based on NO adsorption for site titration) is interpreted as being due to the effects of Si/sup 4 +/ substitution into the surface of magnetite, which causes the iron cations at the surface to become electron deficient and coordinatively more saturated with oxygen anions. 2 figures, 1 table.

  13. Pond sediment magnetite grains show a distinctive microbial community.

    PubMed

    Song, H-K; Sonkaria, S; Khare, V; Dong, K; Lee, H-T; Ahn, S-H; Kim, H-K; Kang, H-J; Lee, S-H; Jung, S P; Adams, J M

    2015-07-01

    Formation of magnetite in anaerobic sediments is thought to be enhanced by the activities of iron-reducing bacteria. Geobacter has been implicated as playing a major role, as in culture its cells are often associated with extracellular magnetite grains. We studied the bacterial community associated with magnetite grains in sediment of a freshwater pond in South Korea. Magnetite was isolated from the sediment using a magnet. The magnetite-depleted fraction of sediment was also taken for comparison. DNA was extracted from each set of samples, followed by PCR for 16S bacterial ribosomal RNA (rRNA) gene and HiSeq sequencing. The bacterial communities of the magnetite-enriched and magnetite-depleted fractions were significantly different. The enrichment of three abundant operational taxonomic units (OTUs) suggests that they may either be dependent upon the magnetite grain environment or may be playing a role in magnetite formation. The most abundant OTU in magnetite-enriched fractions was Geobacter, bolstering the case that this genus is important in magnetite formation in natural systems. Other major OTUs strongly associated with the magnetite-enriched fraction, rather than the magnetite-depleted fraction, include a Sulfuricella and a novel member of the Betaproteobacteria. The existence of distinct bacterial communities associated with particular mineral grain types may also be an example of niche separation and coexistence in sediments and soils, which cannot usually be detected due to difficulties in separating and concentrating minerals. PMID:25592636

  14. Pond sediment magnetite grains show a distinctive microbial community.

    PubMed

    Song, H-K; Sonkaria, S; Khare, V; Dong, K; Lee, H-T; Ahn, S-H; Kim, H-K; Kang, H-J; Lee, S-H; Jung, S P; Adams, J M

    2015-07-01

    Formation of magnetite in anaerobic sediments is thought to be enhanced by the activities of iron-reducing bacteria. Geobacter has been implicated as playing a major role, as in culture its cells are often associated with extracellular magnetite grains. We studied the bacterial community associated with magnetite grains in sediment of a freshwater pond in South Korea. Magnetite was isolated from the sediment using a magnet. The magnetite-depleted fraction of sediment was also taken for comparison. DNA was extracted from each set of samples, followed by PCR for 16S bacterial ribosomal RNA (rRNA) gene and HiSeq sequencing. The bacterial communities of the magnetite-enriched and magnetite-depleted fractions were significantly different. The enrichment of three abundant operational taxonomic units (OTUs) suggests that they may either be dependent upon the magnetite grain environment or may be playing a role in magnetite formation. The most abundant OTU in magnetite-enriched fractions was Geobacter, bolstering the case that this genus is important in magnetite formation in natural systems. Other major OTUs strongly associated with the magnetite-enriched fraction, rather than the magnetite-depleted fraction, include a Sulfuricella and a novel member of the Betaproteobacteria. The existence of distinct bacterial communities associated with particular mineral grain types may also be an example of niche separation and coexistence in sediments and soils, which cannot usually be detected due to difficulties in separating and concentrating minerals.

  15. Synthesis of Environmentally Friendly Highly Dispersed Magnetite Nanoparticles Based on Rosin Cationic Surfactants as Thin Film Coatings of Steel

    PubMed Central

    Atta, Ayman M.; El-Mahdy, Gamal A.; Al-Lohedan, Hamad A.; Al-Hussain, Sami A.

    2014-01-01

    This work presents a new method to prepare monodisperse magnetite nanoparticles capping with new cationic surfactants based on rosin. Core/shell type magnetite nanoparticles were synthesized using bis-N-(3-levopimaric maleic acid adduct-2-hydroxy) propyl-triethyl ammonium chloride (LPMQA) as capping agent. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the nanoparticles chemical structure. Transmittance electron microscopies (TEM) and X-ray powder diffraction (XRD) were used to examine the morphology of the modified magnetite nanoparticles. The magnetite dispersed aqueous acid solution was evaluated as an effective anticorrosion behavior of a hydrophobic surface on steel. The inhibition effect of magnetite nanoparticles on steel corrosion in 1 M HCl solution was investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Results obtained from both potentiodynamic polarisation and EIS measurements reveal that the magnetite nanoparticle is an effective inhibitor for the corrosion of steel in 1.0 M HCl solution. Polarization data show that magnetite nanoparticles behave as a mixed type inhibitor. The inhibition efficiencies obtained from potentiodynamic polarization and EIS methods are in good agreement. PMID:24758936

  16. Synthesis of environmentally friendly highly dispersed magnetite nanoparticles based on rosin cationic surfactants as thin film coatings of steel.

    PubMed

    Atta, Ayman M; El-Mahdy, Gamal A; Al-Lohedan, Hamad A; Al-Hussain, Sami A

    2014-04-22

    This work presents a new method to prepare monodisperse magnetite nanoparticles capping with new cationic surfactants based on rosin. Core/shell type magnetite nanoparticles were synthesized using bis-N-(3-levopimaric maleic acid adduct-2-hydroxy) propyl-triethyl ammonium chloride (LPMQA) as capping agent. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the nanoparticles chemical structure. Transmittance electron microscopies (TEM) and X-ray powder diffraction (XRD) were used to examine the morphology of the modified magnetite nanoparticles. The magnetite dispersed aqueous acid solution was evaluated as an effective anticorrosion behavior of a hydrophobic surface on steel. The inhibition effect of magnetite nanoparticles on steel corrosion in 1 M HCl solution was investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Results obtained from both potentiodynamic polarisation and EIS measurements reveal that the magnetite nanoparticle is an effective inhibitor for the corrosion of steel in 1.0 M HCl solution. Polarization data show that magnetite nanoparticles behave as a mixed type inhibitor. The inhibition efficiencies obtained from potentiodynamic polarization and EIS methods are in good agreement.

  17. Did an Impact Make the Mysterious Microscopic Magnetite Crystals in ALH 84001?

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2007-10-01

    Fervent debate swirls around microscopic crystals of magnetite (Fe3O4) in Martian meteorite ALH 84001. Some investigators suggest that the crystals are evidence of past life on Mars, citing magnetite crystals of similar chemical compositions and sizes made by magnetotactic bacteria on Earth. Others cite assorted experiments and observations to argue that the important little crystals formed entirely by non-biological processes, hence say nothing about life on Mars. One of those processes is the decomposition of iron carbonate (the mineral siderite), which occurs in ALH 84001. Researchers argue that heating this mineral causes it to decompose into magnetite and CO2 gas. Experiments showing this were done by heating siderite and observing that it decomposed and formed magnetite, but nobody had shock-heated siderite to see if magnetite crystals formed. (Shock is a rapid, strong rise and fall in pressure. It happens under many circumstances, including meteorite impacts.) The lack of shock experiments has been solved by Mary Sue Bell (University of Houston and Jacobs Engineering). She experimentally shocked samples of siderite at the Experimental Impact Laboratory at the Johnson Space Center. She shows that magnetite crystals of the right size and composition formed when samples were shocked to 49 GPa (about 500,000 times the pressure at the Earth's surface). This is more evidence for a non-biological origin for the magnetite crystals in ALH 84001 and is consistent with what we know about the impact history of the rock. There seems to be growing evidence against a biological origin, but don't expect these results to completely settle the debate!

  18. High Efficiency DNA Extraction by Graphite Oxide/Cellulose/Magnetite Composites Under Na+ Free System

    NASA Astrophysics Data System (ADS)

    Akceoglu, Garbis Atam; Li, Oi Lun; Saito, Nagahiro

    2016-04-01

    DNA extraction is the key step at various research areas like biotechnology, diagnostic development, paternity determination, and forensic science . Solid support extraction is the most common method for DNA purification. In this method, Na+ ions have often been applied as binding buffers in order to obtain high extraction efficiency and high quality of DNA; however, the presence of Na+ ions might be interfering with the downstream DNA applications. In this study, we proposed graphite oxide (GO)/magnetite composite/cellulose as an innovative material for Na+-free DNA extraction. The total wt.% of GO was fixed at 4.15% in the GO/cellulose/magnetite composite . The concentration of magnetite within the composites were controlled at 0-3.98 wt.%. The extraction yield of DNA increased with increasing weight percentage of magnetite. The highest yield was achieved at 3.98 wt.% magnetite, where the extraction efficiency was reported to be 338.5 ng/µl. The absorbance ratios between 260 nm and 280 nm (A260/A280) of the DNA elution volume was demonstrated as 1.81, indicating the extracted DNA consisted of high purity. The mechanism of adsorption of DNA was provided by (1) π-π interaction between the aromatic ring in GO and nucleobases of DNA molecule, and (2) surface charge interaction between the positive charge magnetite and anions such as phosphates within the DNA molecules. The results proved that the GO/cellulose/magnetite composite provides a Na+-free method for selective DNA extraction with high extraction efficiency of pure DNA.

  19. Trichloroethylene degradation by persulphate with magnetite as a heterogeneous activator in aqueous solution.

    PubMed

    Ruan, Xiaoxin; Gu, Xiaogang; Lu, Shuguang; Qiu, Zhaofu; Sui, Qian

    2015-01-01

    Iron oxide-magnetite (Fe3O4) as a heterogeneous activator to activate persulphate anions (S2O8(2-)) for trichloroethylene (TCE) degradation was investigated in this study. The experimental results showed that TCE could be completely oxidized within 5 h by using 5 g L(-1) magnetite and 63 mM S2O8(2-), indicating the effectiveness of the process for TCE removal. Various factors of the process, including. (S2O8(2-) and magnetite dosages, and initial solution pH, were evaluated, and TCE degradation fitted well to the pseudo-first-order kinetic model. The calculated kinetic rate constant was increased with increasing S2O8(2-) and magnetite dosages, but it was independent of solution pH. In addition, the changes of magnetite morphology examined by scanning electron microscopy and X-ray powder diffraction, respectively, confirmed the slight corrosion with α-Fe2O3 coated on the magnetite surface. The probe compounds tests clearly identified the generation of the reactive oxygen species in the system. While the free radical quenching studies further demonstrated that •SO4- and •OH were the major radicals responsible for TCE degradation, whereas •O2- contributed less in the system, and therefore the roles of reactive oxygen species on TCE degradation mechanisms were proposed accordingly. To our best knowledge, this is the first time the performance and mechanism of magnetite-activated persulphate oxidation for TCE degradation are reported. The findings of this study provided a new insight into the heterogeneous catalysis mechanism and showed a great potential for the practical application of this technique in in situ TCE-contaminated groundwater remediation.

  20. Oxidation of pyrite in coal to magnetite

    USGS Publications Warehouse

    Thorpe, A.N.; Senftle, F.E.; Alexander, C.C.; Dulong, F.T.

    1984-01-01

    When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393-455 ??C, pyrite (FeS2) in coal is partially converted to magnetite (Fe304). The maximum amount of Fe304 formed during the time of heating corresponds to 5-20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains. The fact that the magnetic properties of the pyrite grains are substantially increased by the magnetite crust suggests that pyrite can be separated from coal by use of a low magnetic field. In a laboratory test, 75% removal is obtained by means of a 500 Oe magnet on three samples, and 60% on a fourth sample. ?? 1984.

  1. Scaffold of Asymmetric Organic Compounds - Magnetite Plaquettes

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.; Martinez, J.

    2015-01-01

    Life on Earth shows preference towards the set of organics with particular spatial configurations, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life prefers the left- (L-) form over the right- (D-) form of amino acids, resulting in an L-enantiomeric excess (L-ee). Recent studies have shown Lee for alpha-methyl amino acids in some chondrites. Since these amino acids have limited terrestrial occurrence, the origin of their stereoselectivity is nonbiological, and it seems appropriate to conclude that chiral asymmetry, the molecular characteristic that is common to all terrestrial life form, has an abiotic origin. A possible abiotic mechanism that can produce chiral asymmetry in meteoritic amino acids is their formation with the presence of asymmetric catalysts, as mineral crystallization can produce spatially asymmetric structures. Magnetite is shown to be an effective catalyst for the formation of amino acids that are commonly found in chondrites. Magnetite 'plaquettes' (or 'platelets'), first described by Jedwab, show an interesting morphology of barrel-shaped stacks of magnetite disks with an apparent dislocation-induced spiral growth that seem to be connected at the center. A recent study by Singh et al. has shown that magnetites can self-assemble into helical superstructures. Such molecular asymmetry could be inherited by adsorbed organic molecules. In order to understand the distribution of 'spiral' magnetites in different meteorite classes, as well as to investigate their apparent spiral configurations and possible correlation to molecular asymmetry, we observed polished sections of carbonaceous chondrites (CC) using scanning electron microscope (SEM) imaging. The sections were also studied by electron backscattered diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.

  2. Rock magnetism linked to human brain magnetite

    NASA Astrophysics Data System (ADS)

    Kirschvink, Joseph L.

    Magnetite has a long and distinguished career as one of the most important minerals in geophysics, as it is responsible for most of the remanent magnetization in marine sediments and the oceanic crust. It may come as a surprise to discover that it also ranks as the third or fourth most diverse mineral product formed biochemically by living organisms, and forms naturally in a variety of human tissues [Kirschvink et al., 1992].Magnetite was discovered in teeth of the Polyplacophora mollusks over 30 years ago, in magnetotactic bacteria nearly 20 years ago, in honey bees and homing pigeons nearly 15 years ago, but only recently in human tissue.

  3. Crystal growth of bullet-shaped magnetite in magnetotactic bacteria of the Nitrospirae phylum.

    PubMed

    Li, Jinhua; Menguy, Nicolas; Gatel, Christophe; Boureau, Victor; Snoeck, Etienne; Patriarche, Gilles; Leroy, Eric; Pan, Yongxin

    2015-02-01

    Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth's magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB group. We observed a multiple-step crystal growth of MYR-1 magnetite: initial isotropic growth forming cubo-octahedral particles (less than approx. 40 nm), subsequent anisotropic growth and a systematic final elongation along [001] direction. During the crystal growth, one major {111} face is well developed and preserved at the larger basal end of the crystal. The basal {111} face appears to be terminated by a tetrahedral-octahedral-mixed iron surface, suggesting dimensional advantages for binding protein(s), which may template the crystallization of magnetite. This study offers new insights for understanding magnetite biomineralization within the Nitrospirae phylum.

  4. Aqueous dispersions of magnetite nanoparticles complexed with copolyether dispersants: experiments and theory.

    PubMed

    Zhang, Qian; Thompson, M Shane; Carmichael-Baranauskas, Anita Y; Caba, Beth L; Zalich, Michael A; Lin, Yin-Nian; Mefford, O Thompson; Davis, Richey M; Riffle, Judy S

    2007-06-19

    Magnetite (Fe3O4) nanoparticles have been synthesized and complexed with carboxylate-functional block copolymers, and then aqueous dispersions of the complexes were investigated as functions of their chemical and morphological structures. The block copolymer dispersants had either poly(ethylene oxide), poly(ethylene oxide-co-propylene oxide), or poly(ethylene oxide-b-propylene oxide) outer blocks, and all of them had a polyurethane center block that contained pendent carboxylate groups. The complexes were formed through interactions of the carboxylates with the surfaces of the magnetite nanoparticles. The magnetite cores of the magnetite-copolymer complexes were near 10 nm in diameter, and the particles were superparamagnetic. Complexes with mass ratios of polymer to magnetite varying from 50:50 to 85:15 were studied. One of our objectives is to design complexes that form stable dispersions of discrete particles in water, yet that can be actuated (moved together) upon exposure to a uniform magnetic field. DLVO calculations that accounted for magnetic attractive interparticle forces, as well as van der Waals, steric, and electrostatic forces are presented. Compositions were identified wherein a shallow, attractive interparticle potential minimum appears once the magnetic term is applied. This suggests that it may be possible to tune the structures of superparamagnetic nanoparticle shells to allow discrete dispersions without a field, yet weak flocculation could be induced upon exposure to a field.

  5. Biogenic Magnetite Formation through Anaerobic Biooxidation of Fe(II)

    PubMed Central

    Chaudhuri, Swades K.; Lack, Joseph G.; Coates, John D.

    2001-01-01

    The presence of isotopically light carbonates in association with fine-grained magnetite is considered to be primarily due to the reduction of Fe(III) by Fe(III)-reducing bacteria in the environment. Here, we report on magnetite formation by biooxidation of Fe(II) coupled to denitrification. This metabolism offers an alternative environmental source of biogenic magnetite. PMID:11375205

  6. Vortex magnetic structure in framboidal magnetite reveals existence of water droplets in an ancient asteroid

    NASA Astrophysics Data System (ADS)

    Kimura, Yuki; Sato, Takeshi; Nakamura, Norihiro; Nozawa, Jun; Nakamura, Tomoki; Tsukamoto, Katsuo; Yamamoto, Kazuo

    2013-10-01

    The majority of water has vanished from modern meteorites, yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important, because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method, applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure, a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid.

  7. Synthesis of functionalized magnetite nanoparticles to use as liver targeting MRI contrast agent

    NASA Astrophysics Data System (ADS)

    Yazdani, Farshad; Fattahi, Bahare; Azizi, Najmodin

    2016-05-01

    The aim of this research was the preparation of functionalized magnetite nanoparticles to use as a liver targeting contrast agent in magnetic resonance imaging (MRI). For this purpose, Fe3O4 nanoparticles were synthesized via the co-precipitation method. The synthesized nanoparticles were coated with silica via the Stober method and finally the coated nanoparticles were functionalized with mebrofenin. Formation of crystalline magnetite particles was confirmed by X-ray diffraction (XRD) analysis. The Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray analyzer (EDX) of the final product showed that silica had been effectively bonded onto the surface of the magnetite nanoparticles and the coated nanoparticles functionalized with mebrofenin. The magnetic resonance imaging of the functional nanoparticles showed that the Fe3O4-SiO2-mebrofenin composite is an effective MRI contrast agent for liver targeting.

  8. Magnetite nanoparticles doped photoresist derived carbon as a suitable substratum for nerve cell culture.

    PubMed

    Zhu, Zanzan; Rezhdo, Olijora; Perrone, Matthew; Bao, Zhengzheng; Munir, Ahsan; Wang, Jianlong; Zhou, H Susan; Shao, Jiahui

    2013-02-01

    A method which alters the substrate's physical and electrochemical properties by doping photoresist derived carbon with magnetite nanoparticles has been developed to enhance the existing substrate's ability to foster cell growth. Cyclic voltammetry, scanning electron microscopy and atomic force microscopy are used to evaluate the characters of the prepared film. And then, the magnetite nanoparticles doped carbon film is used as substrate for the growth of nerve cell. Here, rat pheochromocytoma cells are used for culture to test substrate-cell interactions. The results showed an increase in cell concentration and average neurite length with the increase of nanoparticle concentration on the surface. Importantly, the nerve cells can be grown on the magnetite nanoparticles doped carbon even in the absence of nerve growth factor. This finding will potentially provide a new material for nerve regeneration.

  9. Vortex magnetic structure in framboidal magnetite reveals existence of water droplets in an ancient asteroid.

    PubMed

    Kimura, Yuki; Sato, Takeshi; Nakamura, Norihiro; Nozawa, Jun; Nakamura, Tomoki; Tsukamoto, Katsuo; Yamamoto, Kazuo

    2013-01-01

    The majority of water has vanished from modern meteorites, yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important, because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method, applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure, a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid. PMID:24149376

  10. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles.

    PubMed

    Byrne, James M; van der Laan, Gerrit; Figueroa, Adriana I; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M; Kappler, Andreas

    2016-01-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100-200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments. PMID:27492680

  11. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles

    PubMed Central

    Byrne, James M.; van der Laan, Gerrit; Figueroa, Adriana I.; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I.; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M.; Kappler, Andreas

    2016-01-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100–200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments. PMID:27492680

  12. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles

    NASA Astrophysics Data System (ADS)

    Byrne, James M.; van der Laan, Gerrit; Figueroa, Adriana I.; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I.; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M.; Kappler, Andreas

    2016-08-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100–200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments.

  13. Magnetically recyclable magnetite-palladium (Nanocat-Fe-Pd) nanocatalyst for the Buchwald-Hartwig reaction

    EPA Science Inventory

    The immobilization of Pd on magnetite surface afforded (Nanocat-Fe-Pd) using inexpensive precursors and its catalytic role in the Buchwald-Hartwig reaction for arylation of amines and amides was investigated; C-N bond formation was achieved in moderate to excellent yields and the...

  14. Polyhedral magnetite nanocrystals with multiple facets: facile synthesis, structural modelling, magnetic properties and application for high capacity lithium storage.

    PubMed

    Su, Dawei; Horvat, Josip; Munroe, Paul; Ahn, Hyojun; Ranjbartoreh, Ali R; Wang, Guoxiu

    2012-01-01

    Polyhedral magnetite nanocrystals with multiple facets were synthesised by a low temperature hydrothermal method. Atomistic simulation and calculations on surface attachment energy successfully predicted the polyhedral structure of magnetite nanocrystals with multiple facets. X-ray diffraction, field emission scanning electron microscopy, and high resolution transmission microscopy confirmed the crystal structure of magnetite, which is consistent with the theoretical modelling. The magnetic property measurements show the superspin glass state of the polyhedral nanocrystals, which could originate from the nanometer size of individual single crystals. When applied as an anode material in lithium ion cells, magnetite nanocrystals demonstrated an outstanding electrochemical performance with a high lithium storage capacity, a satisfactory cyclability, and an excellent high rate capacity.

  15. Magnetite in Black Sea Turtles (Chelonia agassizi)

    NASA Astrophysics Data System (ADS)

    Fuentes, A.; Urrutia-Fucugauchi, J.; Garduño, V.; Sanchez, J.; Rizzi, A.

    2004-12-01

    Previous studies have reported experimental evidence for magnetoreception in marine turtles. In order to increase our knowledge about magnetoreception and biogenic mineralization, we have isolated magnetite particles from the brain of specimens of black sea turtles Chelonia agassizi. Our samples come from natural deceased organisms collected the reserve area of Colola Maruata in southern Mexico. The occurrence of magnetite particles in brain tissue of black sea turtles offers the opportunity for further studies to investigate possible function of ferrimagnetic material, its mineralogical composition, grain size, texture and its location and structural arrangement within the host tissue. After sample preparation and microscopic examination, we localized and identified the ultrafine unidimensional particles of magnetite by scanning electron microscope (SEM). Particles present grain sizes between 10.0 to 40.0Mm. Our study provides, for the first time, evidence for biogenic formation of this material in the black sea turtles. The ultrafine particles are apparently superparamagnetic. Preliminary results from rock magnetic measurements are also reported and correlated to the SEM observations. The black turtle story on the Michoacan coast is an example of formerly abundant resource which was utilized as a subsistence level by Nahuatl indigenous group for centuries, but which is collapsing because of intensive illegal commercial exploitation. The most important nesting and breeding grounds for the black sea turtle on any mainland shore are the eastern Pacific coastal areas of Maruata and Colola, in Michoacan. These beaches are characterized by important amounts of magnetic mineral (magnetites and titanomagnetites) mixed in their sediments.

  16. Magnetite biomineralization and ancient life on Mars.

    PubMed

    Frankel, R B; Buseck, P R

    2000-04-01

    Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate. PMID:10742183

  17. Originof magnetite in martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Scott, E.; Fuller, M.

    2003-04-01

    The magnetization of ALH84001 is predominantly carried by single domain magnetite, which is found in association with carbonate. The magnetite is found in topotactic relationship with the carbonate in regions of iron rich carbonate, whereas in magnesium richer areas periclase is found. The magnetite formed from the carbonate by thermal decomposition of siderite at elevated temperature in a major impact event at about 4.0 Gyr. Chromite is also present in large amounts, but it is predominantly paramagnetic at room temperature with a Neel point close to 100^oK. Carbonate with associated magnetite is also found in the martian meteorite Nakhla. Experiments and theory show that siderite is a major product of percolation and evaporation of brines generated under pressures of more than 0.1bar of carbon dioxide. This is the preferred explanation for the carbonate in nakhla, as well as in ALH84001. Thermal decomposition of siderite may result from deep burial, magmatic heat sources, or as in the case of ALH84001, impact heating.

  18. Magnetite biomineralization and ancient life on Mars.

    PubMed

    Frankel, R B; Buseck, P R

    2000-04-01

    Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate.

  19. Magnetite Nanoparticles Prepared By Spark Erosion

    NASA Astrophysics Data System (ADS)

    Maiorov, M.; Blums, E.; Kronkalns, G.; Krumina, A.; Lubane, M.

    2016-08-01

    In the present research, we study a possibility of using the electric spark erosion method as an alternative to the method of chemical co-precipitation for preparation of magnetic nanoparticles. Initiation of high frequency electric discharge between coarse iron particles under a layer of distilled water allows obtaining pure magnetite nanoparticles.

  20. Bisphosphonate release profiles from magnetite microspheres.

    PubMed

    Miyazaki, Toshiki; Inoue, Tatsuya; Shirosaki, Yuki; Kawashita, Masakazu; Matsubara, Takao; Matsumine, Akihiko

    2014-10-01

    Hyperthermia has been suggested as a novel, minimally invasive cancer treatment method. After implantation of magnetic nano- or microparticles around a tumour through blood vessels, irradiation with alternating magnetic fields facilitates the efficient in situ hyperthermia even for deep-seated tumours. On the basis of this idea, if the microspheres are capable of delivering drugs, they could be promising multifunctional biomaterials effective for chemotherapy as well as hyperthermia. In the present study, magnetite microspheres were prepared by aggregation of the iron oxide colloid in water-in-oil (W/O) emulsion. The release behaviour of alendronate, a typical bisphosphonate, from the microspheres was examined in vitro as a model of the bone tumour prevention and treatment system. The alendronate was successfully incorporated onto the porous magnetite microspheres in vacuum conditions. The drug-loaded microspheres maintained their original spherical shapes even after shaking in ultrapure water for 3 days, suggesting that they have sufficient mechanical integrity for clinical use. It was attributed to high aggregation capability of the magnetite nanoparticles through van der Waals and weak magnetic attractions. The microspheres showed slow release of the alendronate in vitro, resulting from tight covalent or ionic interaction between the magnetite and the alendronate. The release rate was diffusion-controlled type and well controlled by the alendronate concentration in drug incorporation to the microspheres.

  1. Bisphosphonate release profiles from magnetite microspheres.

    PubMed

    Miyazaki, Toshiki; Inoue, Tatsuya; Shirosaki, Yuki; Kawashita, Masakazu; Matsubara, Takao; Matsumine, Akihiko

    2014-10-01

    Hyperthermia has been suggested as a novel, minimally invasive cancer treatment method. After implantation of magnetic nano- or microparticles around a tumour through blood vessels, irradiation with alternating magnetic fields facilitates the efficient in situ hyperthermia even for deep-seated tumours. On the basis of this idea, if the microspheres are capable of delivering drugs, they could be promising multifunctional biomaterials effective for chemotherapy as well as hyperthermia. In the present study, magnetite microspheres were prepared by aggregation of the iron oxide colloid in water-in-oil (W/O) emulsion. The release behaviour of alendronate, a typical bisphosphonate, from the microspheres was examined in vitro as a model of the bone tumour prevention and treatment system. The alendronate was successfully incorporated onto the porous magnetite microspheres in vacuum conditions. The drug-loaded microspheres maintained their original spherical shapes even after shaking in ultrapure water for 3 days, suggesting that they have sufficient mechanical integrity for clinical use. It was attributed to high aggregation capability of the magnetite nanoparticles through van der Waals and weak magnetic attractions. The microspheres showed slow release of the alendronate in vitro, resulting from tight covalent or ionic interaction between the magnetite and the alendronate. The release rate was diffusion-controlled type and well controlled by the alendronate concentration in drug incorporation to the microspheres. PMID:24854985

  2. Adsorption of zinc on magnetite pellets

    SciTech Connect

    Cargnel, D.A.; Cole, C.A.

    1995-12-31

    Zinc is a common contaminant in wastewater electroplating, metal finishing, and many other industrial processes. This paper presents the results of work which is intended to be the first step in an evaluation of the use of concentrated and pelletized magnetite for the adsorption of metals from industrial wastewater. The magnetite used is a cold carbon bonded material which is formulated for the steel industry as a complete product ready for feed to the furnaces. The specific objective of this work was to determine the zinc adsorption capacity of the prepared magnetite pellets through batch tests that were designed to allow the development of an adsorption isotherm. Future work would explore the potential for use of the spent adsorbent in the steel making process, thereby allowing the recovered metals to be recycled into steel products, while avoiding spent adsorbent disposal costs. Although not evaluated in this study, an additional advantage of the use of magnetite as an adsorbent is that it can be magnetically separated from the wastewater.

  3. Metallic nano-particles in lustre glazed ceramics from the 15th century in Seville studied by PIXE and RBS

    NASA Astrophysics Data System (ADS)

    del Rio, A. Polvorinos; Castaing, J.; Aucouturier, M.

    2006-08-01

    Lustre ceramics, found in a workshop located in Triana (Sevilla), have been analysed to determine the composition of glazes including the metallic particle layers giving rise to the lustre effect. PIXE and RBS were used for the elemental composition and the sub-surface concentration profiles, respectively. Copper and silver at the origin of the lustre are detected by PIXE. RBS gives access to the detailed distribution of the elements in the surface layers. The simulation of RBS spectra confirms the occurrence of thin layers (less than 300 nm) containing metallic silver and/or copper. The results are compared with those obtained on other types of lustre ceramics.

  4. Dual layer hollow fiber PVDF ultra-filtration membranes containing Ag nano-particle loaded zeolite with longer term anti-bacterial capacity in salt water.

    PubMed

    Shi, Huyan; Xue, Lixin; Gao, Ailin; Zhou, Qingbo

    2016-01-01

    Dual layer polyvinylidene fluoride (PVDF), antibacterial, hollow fiber, ultra-filtration composite membranes with antibacterial particles (silver (Ag) nano-particles loaded zeolite (Z-Ag)) in the outer layer were prepared with high water flux and desired pore sizes. The amounts of Ag(+) released from the composite membranes, freshly made and stored in water and salt solution, were measured. The result indicated that dual layer PVDF antibacterial hollow fiber containing Z-Ag (M-1-Ag) still possessed the ability of continuous release of Ag(+) even after exposure to water with high ionic content, showing a longer term resistance to bacterial adhesion and antibacterial activity than membrane doped with Z-Ag(+) (M-1). Results from an anti-adhesion and bacteria killing test with Escherichia coli supported that the antibacterial efficiency of dual hollow fiber PVDF membranes with Z-Ag was much higher than those with Z-Ag(+) after long time storage in water or exposure to phosphate buffered saline (PBS) solution. This novel hollow fiber membrane may find applications in constructing sea water pretreatment devices with long term antifouling capability for the desalination processes.

  5. Gold nano-particles (AuNPs) carrying anti-EBV-miR-BART7-3p inhibit growth of EBV-positive nasopharyngeal carcinoma

    PubMed Central

    Wang, Jianguo; Lyu, Xiaoming; Chen, Yuxiang; Liu, Jinkun; Cai, Hongbing; Wang, Ying; Li, Xin

    2015-01-01

    Epstein-Barr virus (EBV) infection is a major etiological factor for nasopharyngeal carcinoma (NPC). Several EBV-encoded BART miRNAs have been associated with viral latency, immune escape, cell survival, cell proliferation and apoptosis. Here, we report that EBV-miR-BART7-3p, an EBV-encoded BART miRNA highly expressed in NPC, was correlated with cell-cycle progression in vitro and increased tumor formation in vivo. This viral miRNA stimulated the PTEN/PI3K/Akt pathway and induced c-Myc and c-Jun. Knockdown of PTEN mimicked EBV-miR-BART7-3p-induced tumorigenic phenotype. Based on these results, we conducted a therapeutic experiment by using gold nano-particles (AuNPs) carrying anti-EBV-miR-BART7-3p. Silencing of EBV-miR-BART7-3p reduced tumor growth in animal model. We conclude that EBV-miR-BART7-3p favors carcinogenesis, representing a potential target for miRNA-based therapy. PMID:25691053

  6. Computation of emission characteristics of Ar-Fe arc plasma column during the synthesis of nano particles of Fe-oxides

    NASA Astrophysics Data System (ADS)

    Banerjee, I.; Sahasrabudhe, S. N.; Bhoraskar, S. V.; Das, A. K.

    2006-08-01

    The article reports the results of the computationally determined radiative emission characteristics of a transferred arc argon plasma source used in plasma-assisted nano particles synthesis of Fe-oxides. A thermodynamic code uses a spectroscopic database to compute internal partition functions and densities of various charged states in argon-iron vapor plasma system during the synthesis of Fe-oxides. The net amount of radiation emitted by the plasma at different axial positions along the column has been monitored by optical emission spectroscopy. It was also used to determine the amount of metal vapors mixing inside the plasma column during the synthesis process. The net emission coefficient estimated along a certain line of sight shows an effective increase even for a small inclusion of Fe vapors (0.11%) inside the column. It has been noticed that the radiations emitted by the plasma inside the reactor chamber might also be one of the factors, controlling the crystalline phase of Fe-oxide particles.

  7. Modification of carbon paste electrode with Fe(III)-clinoptilolite nano-particles for simultaneous voltammetric determination of acetaminophen and ascorbic acid.

    PubMed

    Sharifian, Samira; Nezamzadeh-Ejhieh, Alireza

    2016-01-01

    A novel carbon paste electrode (CPE) modified with Fe(III)-exchanged clinoptilolite nano-particles (Fe(III)-NClino/CPE) was constructed and used for simultaneous voltammetric (CV, SqW and chronoamperometry) determination of ascorbic acid and acetaminophen. Raw and modified zeolites were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The square wave peak current was linearly increased in the concentration ranges of 1.0 × 10(-9)-1.0 × 10(-2) mol L(-1) for ascorbic acid and 1.0 × 10(-10-)1.0 × 10(-2) mol L(-1) for acetaminophen with detection limits of 1.8 × 10(-9) mol L(-1) and 9.9 × 10(-10) mol L(-1), respectively. The detection limits of 2.4 × 10(-10) mol L(-1) and 2.5 × 10(-11) mol L(-1) were also obtained for AA and AC in chronoamperometric measurements, respectively. The diffusion coefficients of 7.5 × 10(-5) cm(2) s(-1) and 2.4 × 10(-5) cm(2) s(-1) were respectively calculated for the oxidation of AC and AA by chronoamperometry. The proposed electrode exhibited high sensitivity and good stability, and would be valuable for the clinical assay of ascorbic acid and acetaminophen.

  8. Dual layer hollow fiber PVDF ultra-filtration membranes containing Ag nano-particle loaded zeolite with longer term anti-bacterial capacity in salt water.

    PubMed

    Shi, Huyan; Xue, Lixin; Gao, Ailin; Zhou, Qingbo

    2016-01-01

    Dual layer polyvinylidene fluoride (PVDF), antibacterial, hollow fiber, ultra-filtration composite membranes with antibacterial particles (silver (Ag) nano-particles loaded zeolite (Z-Ag)) in the outer layer were prepared with high water flux and desired pore sizes. The amounts of Ag(+) released from the composite membranes, freshly made and stored in water and salt solution, were measured. The result indicated that dual layer PVDF antibacterial hollow fiber containing Z-Ag (M-1-Ag) still possessed the ability of continuous release of Ag(+) even after exposure to water with high ionic content, showing a longer term resistance to bacterial adhesion and antibacterial activity than membrane doped with Z-Ag(+) (M-1). Results from an anti-adhesion and bacteria killing test with Escherichia coli supported that the antibacterial efficiency of dual hollow fiber PVDF membranes with Z-Ag was much higher than those with Z-Ag(+) after long time storage in water or exposure to phosphate buffered saline (PBS) solution. This novel hollow fiber membrane may find applications in constructing sea water pretreatment devices with long term antifouling capability for the desalination processes. PMID:27148717

  9. Invited paper: Sintering mechanism of vapor self-assembled multilayer (VSAM) coated Cu nano particles for application in Cu nano ink

    NASA Astrophysics Data System (ADS)

    Haque, Md. Mominul; Park, Shinyoung; Her, Jaehak; Park, Joong-Hak; Lee, Caroline Sunyong

    2011-09-01

    Oxidation preventive Cu nano ink was prepared using a vapor self-assembed multi-layer coating method (VSAMs). These particles were prepared using 100 nm Cu nano particles coated with 1-octanethiol under ultrahigh vacuum condition with octanol used as a solvent. Octanol-based non-oxidized 10% (wt.) nano ink was well-dispersed without any surfactant. The conductive ink had good dispersion and remains stable for more than 6 weeks. It also has a low viscosity rating of 8.3 cPs. In addition, 5 μL of copper nano ink was dropped into a 1 cm × 1 cm glass substrate to form a copper pattern. The copper pattern was then sintered at 350°C in a tube furnace in a H2 gas atmosphere. The resistivity of the film using the fabricated ink was determined to be 5.8 × 10-6 Ωcm. The results show that the non-oxidized oxidation-preventive copper nano ink is suitable for ink-jet printing.

  10. Electrochemical performance of La2O3/Li2O/TiO2 nano-particle coated cathode material LiFePO4.

    PubMed

    Wang, Hong; Yang, Chi; Liu, Shu-Xin

    2014-09-01

    Cathode material, LiFePO4 was modified by coating with a thin layer of La2O3/Li2O/TiO2 nano-particles for improving its performance for lithium ion batteries. The morphology and structure of the modified cathode material were characterized by powder X-ray diffraction, scanning electron microcopy and AES. The performance of the battery with the modified cathode material, including cycling stability, C-rate discharge was examined. The results show that the battery composed of the coated cathode materials can discharge at a large current density and show stable cycling performance in the range from 2.5 to 4.0 V. The rate of Li ion diffusion increases in the battery with the La2O3/Li2O/TiO2-coated LiFePO4 as a cathode and the coating layer may acts as a faster ion conductor (La(2/3-x)Li(3x)TiO3).

  11. Adsorption-desorption mechanism of phosphate by immobilized nano-sized magnetite layer: interface and bulk interactions.

    PubMed

    Zach-Maor, Adva; Semiat, Raphael; Shemer, Hilla

    2011-11-15

    Phosphate adsorption mechanism by a homogenous porous layer of nano-sized magnetite particles immobilized onto granular activated carbon (nFe-GAC) was studied for both interface and bulk structures. X-ray Photoelectron Spectroscopy (XPS) analysis revealed phosphate bonding to the nFe-GAC predominantly through bidentate surface complexes. It was established that phosphate was adsorbed to the magnetite surface mainly via ligand exchange mechanism. Initially, phosphate was adsorbed by the active sites on the magnetite surface, after which it diffused into the interior of the nano-magnetite layer, as indicated by intraparticle diffusion model. This diffusion process continues regardless of interface interactions, revealing some of the outer magnetite binding sites for further phosphate uptake. Desorption, using NaOH solution, was found to be predominantly a surface reaction, at which hydroxyl ions replace the adsorbed phosphate ions only at the surface outer biding sites. Five successive fix-bed adsorption/regeneration cycles were successfully applied, without significant reduction in the nFe-GAC adsorption capacity and at high regeneration efficiency.

  12. Detection and differentiation of Salmonella serotypes using Surface Enhanced Raman Scattering (SERS) technique.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface Enhanced Raman Scattering (SERS) can detect pathogens rapidly and accurately. The metal surface for the SERS spectroscopy was a silver nano-particle encapsulated biopolymer polyvinyl alcohol nano-colloid deposited on a stainless steel plate. Salmonella Typhimurium and Salmonella Enteritidis...

  13. Moessbauer Characterization of Magnetite/Polyaniline Magnetic Nanocomposite

    SciTech Connect

    Rodriguez, Anselmo F. R.; Faria, Fernando S. E. D. V.; Lopez, Jorge L.; Mesquita, Antonio G. G.; Coaquira, Jose A. H.; Oliveira, Aderbal C.; Morais, Paulo C.; Azevedo, Ricardo B.; Araujo, Ana C. V. de; Alves, Severino Jr.; Azevedo, Walter M. de

    2010-12-02

    Aniline surface coated Fe{sub 3}O{sub 4} nanoparticles have been successfully synthesized by UV irradiation varying the time and the acid media (HCl, HNO{sub 3}, or H{sub 2}SO{sub 4}). The synthesized material represents a promising platform for application in nerve regeneration. XRD patterns are consistent with the crystalline structure of magnetite. Nevertheless, for UV irradiation times longer than 2 h, extra XRD lines reveal the presence of goethite. The mean crystallite size of uncoated particles is estimated to be 25.4 nm, meanwhile that size is reduced to 19.9 nm for the UV irradiated sample in HCl medium for 4 h. Moessbauer spectra of uncoated nanoparticles reveal the occurrence of thermal relaxation at room temperature, while the 77 K-Moessbauer spectrum suggests the occurrence of electron localization effects similar to that expected in bulk magnetite. The Mossbauer spectra of UV irradiated sample in HCl medium during 4 h, confirms the presence of the goethite phase. For this sample, the thermal relaxation is more evident, since the room temperature spectrum shows larger spectral area for the nonmagnetic component due to the smaller crystallite size. Meanwhile, the 77 K-Moessbauer spectrum suggests the absence of the electron localization effect above 77 K.

  14. A Disposable Organophosphorus Pesticides Enzyme Biosensor Based on Magnetic Composite Nano-Particles Modified Screen Printed Carbon Electrode

    PubMed Central

    Gan, Ning; Yang, Xin; Xie, Donghua; Wu, Yuanzhao; Wen, Weigang

    2010-01-01

    A disposable organophosphorus pesticides (OPs) enzyme biosensor based on magnetic composite nanoparticle-modified screen printed carbon electrodes (SPCE) has been developed. Firstly, an acetylcholinesterase (AChE)-coated Fe3O4/Au (GMP) magnetic nanoparticulate (GMP-AChE) was synthesized. Then, GMP-AChE was absorbed on the surface of a SPCE modified by carbon nanotubes (CNTs)/nano-ZrO2/prussian blue (PB)/Nafion (Nf) composite membrane by an external magnetic field. Thus, the biosensor (SPCE│CNTs/ZrO2/PB/Nf│GMP-AChE) for OPs was fabricated. The surface of the biosensor was characterized by scanning electron micrography (SEM) and X-ray fluorescence spectrometery (XRFS) and its electrochemical properties were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The degree of inhibition (A%) of the AChE by OPs was determined by measuring the reduction current of the PB generated by the AChE-catalyzed hydrolysis of acetylthiocholine (ATCh). In pH = 7.5 KNO3 solution, the A was related linearly to the concentration of dimethoate in the range from 1.0 × 10−3–10 ng·mL−1 with a detection limit of 5.6 × 10−4 ng·mL−1. The recovery rates in Chinese cabbage exhibited a range of 88%–105%. The results were consistent with the standard gas chromatography (GC) method. Compared with other enzyme biosensors the proposed biosensor exhibited high sensitivity, good selectivity with disposable, low consumption of sample. In particular its surface can be easily renewed by removal of the magnet. The convenient, fast and sensitive voltammetric measurement opens new opportunities for OPs analysis. PMID:22315558

  15. Biofouling inhibition and enhancing performance of microbial fuel cell using silver nano-particles as fungicide and cathode catalyst.

    PubMed

    Noori, Md T; Jain, Sumat C; Ghangrekar, M M; Mukherjee, C K

    2016-11-01

    Morphological analysis of biofouling developed on cathode surface in an air-cathode microbial fuel cell (MFC) was performed. For sustaining power production and enhancing Coulombic efficiency (CE) of MFC, studies were conducted to inhibit cathode biofouling using different loadings of silver nanoparticles (Ag-NPs) with 5% and 10% Ag in carbon black powder. In MFC without using Ag-NPs in cathode (MFC-C), cathode biofouling increased the charge transfer resistance (Rct) from 1710Ω.cm(2) to 2409Ω.cm(2), and reduced CE by 32%; whereas in MFC with 10% Ag in cathode Rct increased by only 5%. Power density of 7.9±0.5W/m(3) in MFC using 5% Ag and 9.8±0.3W/m(3) in MFC using 10% Ag in cathode was 4.6 and 5.7-folds higher than MFC-C. These results suggest that the Ag-NPs effectively inhibit the fungal biofouling on cathode surface of MFCs and enhanced the power recovery and CE by improving cathode kinetics.

  16. Performance of iron nano particles and bimetallic Ni/Fe nanoparticles in removal of amoxicillin trihydrate from synthetic wastewater.

    PubMed

    Yazdanbakhsh, Ahmad Reza; Daraei, Hasti; Rafiee, Mohamad; Kamali, Hosein

    2016-01-01

    In the present study, the degradation of amoxicillin trihydrate (AMT), using synthesized nanoscale zero-valent iron (nZVI) and bimetallic Fe and Ni nanoparticles stabilized with chitosan (Cs-Fe/Ni), in water was investigated. A central composite design combined with response surface methodology and optimization was utilized for maximizing the AMT reduction by the nanoparticles-water system. The importance of the various variables and their interactions were analyzed using analysis of variance and t-test. The effects of independent parameters were tested and the results showed that the initial concentration of AMT, pH, and nanoparticles dosage were all significant factors. Field-emission scanning electron microscopy images indicated that chitosan acts as a stabilizer preventing the agglomeration of nanoparticles. Also, chitosan and Ni increased the specific surface area of Cs-Fe/Ni. X-ray diffraction confirmed the existence of Fe(0) in fresh samples and the presence of Fe(II) and Fe(III) after the reaction with AMT. This study demonstrates that the nZVI technology could be a promising approach for antibiotic wastewater treatment. PMID:27332846

  17. Biofouling inhibition and enhancing performance of microbial fuel cell using silver nano-particles as fungicide and cathode catalyst.

    PubMed

    Noori, Md T; Jain, Sumat C; Ghangrekar, M M; Mukherjee, C K

    2016-11-01

    Morphological analysis of biofouling developed on cathode surface in an air-cathode microbial fuel cell (MFC) was performed. For sustaining power production and enhancing Coulombic efficiency (CE) of MFC, studies were conducted to inhibit cathode biofouling using different loadings of silver nanoparticles (Ag-NPs) with 5% and 10% Ag in carbon black powder. In MFC without using Ag-NPs in cathode (MFC-C), cathode biofouling increased the charge transfer resistance (Rct) from 1710Ω.cm(2) to 2409Ω.cm(2), and reduced CE by 32%; whereas in MFC with 10% Ag in cathode Rct increased by only 5%. Power density of 7.9±0.5W/m(3) in MFC using 5% Ag and 9.8±0.3W/m(3) in MFC using 10% Ag in cathode was 4.6 and 5.7-folds higher than MFC-C. These results suggest that the Ag-NPs effectively inhibit the fungal biofouling on cathode surface of MFCs and enhanced the power recovery and CE by improving cathode kinetics. PMID:27567479

  18. Preparation and application of crosslinked poly(sodium acrylate)--coated magnetite nanoparticles as corrosion inhibitors for carbon steel alloy.

    PubMed

    Atta, Ayman M; El-Mahdy, Gamal A; Al-Lohedan, Hamad A; El-Saeed, Ashraf M

    2015-01-14

    This work presents a new method to prepare poly(sodium acrylate) magnetite composite nanoparticles. Core/shell type magnetite nanocomposites were synthesized using sodium acrylate as monomer and N,N-methylenebisacrylamide (MBA) as crosslinker. Microemulsion polymerization was used for constructing core/shell structures with magnetite nanoparticles as core and poly(sodium acrylate) as shell. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the nanocomposite chemical structure. Transmittance electron microscopy (TEM) was used to examine the morphology of the modified poly(sodium acrylate) magnetite composite nanoparticles. These particle will be evaluated for effective anticorrosion behavior as a hydrophobic surface on stainless steel. The composite nanoparticles has been designed by dispersing nanocomposites which act as a corrosion inhibitor. The inhibition effect of AA-Na/magnetite composites on steel corrosion in 1 M HCl solution was investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Polarization measurements indicated that the studied inhibitor acts as mixed type corrosion inhibitor. EIS spectra exhibit one capacitive loop. The different techniques confirmed that the inhibition efficiency reaches 99% at 50 ppm concentration. This study has led to a better understanding of active anticorrosive magnetite nanoparticles with embedded nanocomposites and the factors influencing their anticorrosion performance.

  19. Design, Characterization and Application of Biocompatible Micro- and Nano-Particles for Dynamic X-ray Visual Imaging

    NASA Astrophysics Data System (ADS)

    Ahn, Sungsook; Jung, Sung Yong; Lee, Sang Joon

    2010-03-01

    For a dynamic X-ray visual imaging, contrast agents in particle forms are developed in micro- and nano-scales. First, water- soluble contrast agents are encapsulated into biocompatible polymeric microparticles. The fabricated polymeric microparticles are controlled in terms of the size, degree of crosslinking and encapsulation efficiency of the X-ray contrast agent. Second, gold is designed into functionalized nanoparticles. Properly controlled aggregates or encapsulated into human red blood cell (RBC), the surface modified gold nanoparticles are used as excellent X-ray contrast agent. The behaviors of the particles in the solution state are described by hydrodynamic size (DH) and zeta-potential (?-potential). The microscopic structures of the gold nanoparticle aggregates are determined by scanning electron microscopy (SEM) and zone-plate X-ray microscopy. The designed particulate biocompatible tracers are successfully used as excellent X-ray imaging tracers which enable the dynamic study in various biological fluid flows.

  20. Comparing gold nano-particle enhanced radiotherapy with protons, megavoltage photons and kilovoltage photons: a Monte Carlo simulation.

    PubMed

    Lin, Yuting; McMahon, Stephen J; Scarpelli, Matthew; Paganetti, Harald; Schuemann, Jan

    2014-12-21

    Gold nanoparticles (GNPs) have shown potential to be used as a radiosensitizer for radiation therapy. Despite extensive research activity to study GNP radiosensitization using photon beams, only a few studies have been carried out using proton beams. In this work Monte Carlo simulations were used to assess the dose enhancement of GNPs for proton therapy. The enhancement effect was compared between a clinical proton spectrum, a clinical 6 MV photon spectrum, and a kilovoltage photon source similar to those used in many radiobiology lab settings. We showed that the mechanism by which GNPs can lead to dose enhancements in radiation therapy differs when comparing photon and proton radiation. The GNP dose enhancement using protons can be up to 14 and is independent of proton energy, while the dose enhancement is highly dependent on the photon energy used. For the same amount of energy absorbed in the GNP, interactions with protons, kVp photons and MV photons produce similar doses within several nanometers of the GNP surface, and differences are below 15% for the first 10 nm. However, secondary electrons produced by kilovoltage photons have the longest range in water as compared to protons and MV photons, e.g. they cause a dose enhancement 20 times higher than the one caused by protons 10 μm away from the GNP surface. We conclude that GNPs have the potential to enhance radiation therapy depending on the type of radiation source. Proton therapy can be enhanced significantly only if the GNPs are in close proximity to the biological target.

  1. Oxidative degradation of nalidixic acid by nano-magnetite via Fe2+/O2-mediated reactions.

    PubMed

    Ardo, Sandy G; Nélieu, Sylvie; Ona-Nguema, Georges; Delarue, Ghislaine; Brest, Jessica; Pironin, Elsa; Morin, Guillaume

    2015-04-01

    Organic pollution has become a critical issue worldwide due to the increasing input and persistence of organic compounds in the environment. Iron minerals are potentially able to degrade efficiently organic pollutants sorbed to their surfaces via oxidative or reductive transformation processes. Here, we explored the oxidative capacity of nano-magnetite (Fe3O4) having ∼ 12 nm particle size, to promote heterogeneous Fenton-like reactions for the removal of nalidixic acid (NAL), a recalcitrant quinolone antibacterial agent. Results show that NAL was adsorbed at the surface of magnetite and was efficiently degraded under oxic conditions. Nearly 60% of this organic contaminant was eliminated after 30 min exposure to air bubbling in solution in the presence of an excess of nano-magnetite. X-ray diffraction (XRD) and Fe K-edge X-ray absorption spectroscopy (XANES and EXAFS) showed a partial oxidation of magnetite to maghemite during the reaction, and four byproducts of NAL were identified by liquid chromatography-mass spectroscopy (UHPLC-MS/MS). We also provide evidence that hydroxyl radicals (HO(•)) were involved in the oxidative degradation of NAL, as indicated by the quenching of the degradation reaction in the presence of ethanol. This study points out the promising potentialities of mixed valence iron oxides for the treatment of soils and wastewater contaminated by organic pollutants.

  2. Multiple morphologies of gold-magnetite heterostructure nanoparticles are effectively functionalized with protein for cell targeting.

    PubMed

    Krystofiak, Evan S; Mattson, Eric C; Voyles, Paul M; Hirschmugl, Carol J; Albrecht, Ralph M; Gajdardziska-Josifovska, Marija; Oliver, Julie A

    2013-08-01

    Nanoparticles composed of a magnetic iron oxide core surrounded by a metal shell have utility in a broad range of biomedical applications. However, the presence of surface energy differences between the two components makes wetting of oxide with metal unfavorable, precluding a "core-shell" structure of an oxide core completely surrounded by a thin metal shell. Three-dimensional island growth followed by island coalescence into thick shells is favored over the two-dimensional layer-by-layer growth of a thin, continuous metal coating of a true core-shell. Aqueous synthesis of gold-coated magnetite nanoparticles with analysis by infrared, energy-dispersive X-ray, and electron energy loss spectroscopies; high-resolution transmission electron microscopy; selected area electron diffraction; and high-angle annular dark-field scanning transmission electron microscopy showed two distinct morphologies that are inconsistent with an idealized core-shell. The majority were isolated ~16-22-nm-diameter nanoparticles consisting of ~7-nm-diameter magnetite and a thick deposition of gold, most often discontinuous, with some potentially "sandwiched" morphologies. A minority were aggregates of agglomerated magnetite decorated with gold but displaying significant bare magnetite. Both populations were successfully conjugated to fibrinogen and targeted to surface-activated platelets, demonstrating that iron oxide-gold nanoparticles produced by aqueous synthesis do not require an ideal core-shell structure for biological activity in cell labeling and targeting applications.

  3. Uranium (VI) recovery from aqueous medium using novel floating macroporous alginate-agarose-magnetite cryobeads.

    PubMed

    Tripathi, Anuj; Melo, Jose Savio; D'Souza, Stanislaus Francis

    2013-02-15

    This study presents a novel development of a floating polymeric-magnetite cryobead for the recovery of hexavalent uranium from the aqueous sub-surfaces. The alginate-agarose-magnetite cryobeads were synthesized by the process of cryotropic-gelation at subzero-temperature. The physico-chemical properties of cryobeads showed high surface area and high interconnected porosity (≈ 90%). Low density of these cryobeads explains their floating property in the aqueous medium. The rheological analysis of cryobeads showed its stability and increased stiffness after uranium adsorption. The presence of magnetite nanoparticles in the porous cryobeads facilitates the recovery of these beads by applying an external magnetic field. Maximum uranium adsorption (97 ± 2%) was observed in the pH range of 4.5-5.5. The thermodynamic parameters suggest passive endothermic adsorption behaviour. HCl was found to be an efficient eluent for the uranium desorption. Five repeated cycles for the desorption of uranium from biosorbent showed 69 ± 3% of uranium recovery. These results suggest stability of these novel floating magnetite-cryobeads under environmental conditions with potential for the recovery of uranium from contaminated aqueous subsurfaces.

  4. Morphologies and Chemical Composition of Individual Magnetite Grains in CI and CM Chondrites: A Potential Genetic Link to their Origin?

    NASA Astrophysics Data System (ADS)

    Lohn, B.; El Goresy, A.

    1992-07-01

    Magnetite occurs in CI and CM chondrites as plaquettes, framboids, and radially structured spherolites (Jedwab, 1967, 1971). Recent ion microprobe investigations of the O-isotopic compositions of individual magnetite grains in Orgueil, Alais, Ivuna, and Revelstoke revealed enormous variations in delta^18O (-25 to +25) in the same meteorite (Hyman et al., (1991)). A planetary process involving water should lead to formation of grains of similar O-isotopic composition. Individual magnetites in Alais (CI1), Orgueil (CI1), Y-82162 (CI2), Essebi (CM2) and Acfer-207 have been studied in detail by us (e.g., more than 300 electron microprobe analyses). The fact that all morphological types occur together in clusters make an in situ formation not very probable. The stacking morphology of the plaquettes is in fact the strongest argument against epitaxial growth of magnetite along the rhombohedral surfaces of carbonates as suggested by Kerridge et al. (1979). The stacks occur as rounded or oval discs with the top and bottom discs displaying several oblique crystal surfaces and one perpendicular to the axis of the disc stacking. Epitaxial growth should--in contrast to the encountered plaquette morphology--produce three sets of stacks every one parallel to two opposing surfaces of the rhombohedral faces with diminishing disc sizes towards the centre of the rhombohedron. This epitaxial growth would also produce plaquettes with rhombohedral outlines and not circular or oval ones. In none of the studied meteorites were three directional rhombohedral magnetite plaquettes encountered. In Alais a sequence of formation: Magnetite--pyrrhotite--carbonate was found. The magnetites in all C-chondrites studied, are pure Fe3O4 regardless of their morphology and the assemblage in which they occur. Only the magnetites in Y-82162 are enriched in MgO and some of them in MnO. The present investigations, variability of the chemical composition of magnetite in Y-82162 and the oxygen isotopic

  5. Initial Test Determination of Cosmogenic Nuclides in Magnetite

    NASA Astrophysics Data System (ADS)

    Matsumura, H.; Caffee, M. W.; Nagao, K.; Nishiizumi, K.

    2014-12-01

    Long-lived radionuclides, such as 10Be, 26Al, and 36Cl, are produced by cosmic rays in surficial materials on Earth, and used for determinations of cosmic-ray exposure ages and erosion rates. Quartz and limestone are routinely used as the target minerals for these geomorphological studies. Magnetite also contains target elements that produce abundant cosmogenic nuclides when exposed to the cosmic rays. Magnetite has several notable merits that enable the measurement of cosmogenic nuclides: (1) the target elements for production of cosmogenic nuclides in magnetite comprise the dominant mineral form of magnetite, Fe3O4; (2) magnetite can be easily isolated, using a magnet, after rock milling; (3) multiple cosmogenic nuclides are produced by exposure of magnetite to cosmic-ray secondaries; and (4) cosmogenic nuclides produced in the rock containing the magnetite, but not within the magnetite itself, can be separated using nitric acid and sodium hydroxide leaches. As part of this initial study, magnetite was separated from a basaltic sample collected from the Atacama Desert in Chili (2,995 m). Then Be, Al, Cl, Ca, and Mn were separated from ~2 g of the purified magnetite. We measured cosmogenic 10Be, 26Al, and 36Cl concentrations in the magnetite by accelerator mass spectrometry at PRIME Lab, Purdue University. Cosmogenic 3He and 21Ne concentrations of aliquot of the magnetite were measured by mass spectrometry at the University of Tokyo. We also measured the nuclide concentrations from magnetite collected from a mine at Ishpeming, Michigan as a blank. The 10Be and 36Cl concentrations as well as 3He concentration produce concordant cosmic ray exposure ages of ~0.4 Myr for the Atacama basalt. However, observed high 26Al and 21Ne concentrations attribute to those nuclides incorporation from silicate impurity.

  6. Origin of magnetite crystals in Martian meteorite ALH84001 carbonate disks

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, Kathie; Clemett, Simon; McKay, David; Gibson, Everett; Wentworth, Susan

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. In-timately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate [1,2]. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate [3,4]. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our ob-servations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates [5]. [1] McKay et al. (1996) Science 273, 924-930. [2] Thomas-Keprta et al. (2001) Proc. Natl. Acad. Sci. 98, 2164

  7. Experimental Shock Decomposition of Siderite to Magnetite

    NASA Technical Reports Server (NTRS)

    Bell, M. S.; Golden, D. C.; Zolensky, M. E.

    2005-01-01

    The debate about fossil life on Mars includes the origin of magnetites of specific sizes and habits in the siderite-rich portions of the carbonate spheres in ALH 84001 [1,2]. Specifically [2] were able to demonstrate that inorganic synthesis of these compositionally zoned spheres from aqueous solutions of variable ion-concentrations is possible. They further demonstrated the formation of magnetite from siderite upon heating at 550 C under a Mars-like CO2-rich atmosphere according to 3FeCO3 = Fe3O4 + 2CO2 + CO [3] and they postulated that the carbonates in ALH 84001 were heated to these temperatures by some shock event. The average shock pressure for ALH 84001, substantially based on the refractive index of diaplectic feldspar glasses [3,4,5] is some 35-40 GPa and associated temperatures are some 300-400 C [4]. However, some of the feldspar is melted [5], requiring local deviations from this average as high as 45-50 GPa. Indeed, [5] observes the carbonates in ALH 84001 to be melted locally, requiring pressures in excess of 60 GPa and temperatures > 600 C. Combining these shock studies with the above inorganic synthesis of zoned carbonates it seems possible to produce the ALH 84001 magnetites by the shock-induced decomposition of siderite.

  8. Magnetite biomineralization in the human brain.

    PubMed

    Kirschvink, J L; Kobayashi-Kirschvink, A; Woodford, B J

    1992-08-15

    Although the mineral magnetite (Fe3O4) is precipitated biochemically by bacteria, protists, and a variety of animals, it has not been documented previously in human tissue. Using an ultrasensitive superconducting magnetometer in a clean-lab environment, we have detected the presence of ferromagnetic material in a variety of tissues from the human brain. Magnetic particle extracts from solubilized brain tissues examined with high-resolution transmission electron microscopy, electron diffraction, and elemental analyses identify minerals in the magnetite-maghemite family, with many of the crystal morphologies and structures resembling strongly those precipitated by magnetotactic bacteria and fish. These magnetic and high-resolution transmission electron microscopy measurements imply the presence of a minimum of 5 million single-domain crystals per gram for most tissues in the brain and greater than 100 million crystals per gram for pia and dura. Magnetic property data indicate the crystals are in clumps of between 50 and 100 particles. Biogenic magnetite in the human brain may account for high-field saturation effects observed in the T1 and T2 values of magnetic resonance imaging and, perhaps, for a variety of biological effects of low-frequency magnetic fields.

  9. Infra Red Dye and Endostar Loaded Poly Lactic Acid Nano Particles as a Novel Theranostic Nanomedicine for Breast Cancer.

    PubMed

    Zhang, Qian; Du, Yang; Jing, Lijia; Liang, Xiaolong; Li, Yaqian; Li, Xiaofeng; Dai, Zhifei; Tian, Jie

    2016-03-01

    Endostar, a novel recombinant human endostatin, has been proven to inhibit tumor angiogenesis and is utilized as an anticancer drug. While free drugs can display limited efficacy, nanoscaled anticancer drugs have been fabricated and proven to possess superior therapeutic effects. Poly(lactic acid) (PLA) is a FDA-approved biomaterial displaying excellent biocompatibility and low toxicity. In this study, Endostar-loaded PLA nanoparticles (EPNPs) were first prepared, and a near-infrared (NIR) dye, IRDye 800CW, was conjugated to the surface for detecting nanoparticle biodistribution through fluorescence molecular imaging (FMI) using an orthotopic breast tumor mouse model. The antitumor efficacy of EPNPs was examined using bioluminescence imaging (BLI) and immunohistology. To further improve the antitumor effects, we combined EPNPs with zoledronic acid monohydrate (ZA), which is known to decrease the tumor-associated macrophages (TAM) and inhibit tumor progression. We found that EPNPs decreased human umbilical vein endothelial cell (HUVEC) viability by inhibiting tumor growth gene expression more significantly than free Endostar in vitro. In vivo, EPNPs displayed better tumor growth inhibitory effects compared with free Endostar, and the combination of EPNPs with ZA exhibited more significant antitumor effects. As confirmed by CD31 and CD11b immunohistochemistry, the combination of EPNPs and ZA showed synergistic effects in reducing tumor angiogenesis and TAM accumulation in tumor regions. Taken together, this study presents a novel and effective form of nanoscaled Endostar for the treatment of breast cancer that displays synergistic antitumor effects in combination with ZA. PMID:27280247

  10. Spin-resolved electron spectroscopies of epitaxial magnetite (001) (abstract)

    NASA Astrophysics Data System (ADS)

    Shaw, Kimberly A.; Lochner, Eric; Lind, David M.; DiBari, Rebecca C.; Stoyanov, Plamen; Singer, Brian

    1996-04-01

    We will present the first spin-resolving electron spectroscopic studies of a magnetite (Fe3O4)(001) surface. Magnetite is a semimetal with a high density of states in the minority band, but a large band gap in the majority states at the Fermi energy. The polarization of the secondary emission cascade is measured using spin-resolved secondary electron emission spectroscopy (SRSEES), and reflects the semimetallic spin structure of Fe3O4. The polarization plateau of spin-resolved secondary emission (29.8%) matches the average 3D band polarization of stoichiometric Fe3O4 as determined from spin-resolved band structure calculations (34.2%). An enhancement of the polarization of the secondary electrons at lowest energies will also be discussed. Spin-resolved Auger emission spectroscopy (SRAES) of the Fe3O4 films have been measured and show correlation effects in the valence-valence Auger transitions. Suppressed intensity and polarization of M23M45M45 Auger emission relative to M1M45M45 Auger emission is observed, as well as strong resonant emission with shake-up. Conversely, no spin polarization is detected in the spin-resolved oxygen LMM Auger features, although oxygen Auger emission (in which we can distinguish between adsorbed and bonded oxygen) is used to verify surface cleanliness of the samples. The synthesis of Fe3O4 films grown on magnesium oxide (001) substrates using oxygen plasma-assisted molecular beam epitaxy will be discussed, as will thin-film characterization using SQUID magnetometry and x-ray and electron diffraction. A unique angle-, energy-, and spin-resolved electron spectrometer has been designed and built for the study of magnetic surfaces, and these studies represent its' first use. That spectrometer is based on a tandem configuration of an energy-dispersive energy analyzer and Mott spin polarimeter.

  11. A novel electrochemical biosensor based on the hemin-graphene nano-sheets and gold nano-particles hybrid film for the analysis of hydrogen peroxide.

    PubMed

    Song, Haiyan; Ni, Yongnian; Kokot, Serge

    2013-07-25

    Hydrogen peroxide is an important analyte in biochemical, industrial and environmental systems. Therefore, development of novel rapid and sensitive analytical methods is useful. In this work, a hemin-graphene nano-sheets (H-GNs)/gold nano-particles (AuNPs) electrochemical biosensor for the detection of hydrogen peroxide (H2O2) was researched and developed; it was constructed by consecutive, selective modification of the GCE electrode. Performance of the H-GNs/AuNPs/GCE was investigated by chronoamperometry, and AFM measurements suggested that the graphene flakes thickness was ~1.3 nm and that of H-GNs was ~1.8 nm, which ultimately indicated that each hemin layer was ~0.25 nm. This biosensor exhibited significantly better electrocatalytic activity for the reduction of hydrogen peroxide in comparison with the simpler AuNPs/GCE and H-GNs/GCE; it also displayed a linear response for the reduction of H2O2 in the range of 0.3 μM to 1.8 mM with a detection limit of 0.11μM (SN(-1)=3), high sensitivity of 2774.8 μA mM(-1) cm(-2), and a rapid response, which reached 95% of the steady state condition within 5s. In addition, the biosensor was unaffected by many interfering substances, and was stable over time. Thus, it was demonstrated that this biosensor was potentially suitable for H2O2 analysis in many types of sample.

  12. Incorporation of photosenzitizer hypericin into synthetic lipid-based nano-particles for drug delivery and large unilamellar vesicles with different content of cholesterol

    NASA Astrophysics Data System (ADS)

    Joniova, Jaroslava; Blascakova, Ludmila; Jancura, Daniel; Nadova, Zuzana; Sureau, Franck; Miskovsky, Pavol

    2014-08-01

    Low-density lipoproteins (LDL) and high-density lipoproteins (HDL) are attractive natural occurring vehicles for drug delivery and targeting to cancer tissues. The capacity of both types of the lipoproteins to bind hydrophobic drugs and their functionality as drug carriers have been examined in several studies and it has been also shown that mixing of anticancer drugs with LDL or HDL before administration led to an increase of cytotoxic effects of the drugs in the comparison when the drugs were administered alone. However, a difficult isolation of the lipoproteins in large quantity from a biological organism as well as a variability of the composition and size of these molecules makes practical application of LDL and HDL as drug delivery systems quite complicated. Synthetic LDL and HDL and large unilamellar vesicles (LUV) are potentially suitable candidates to substitute the native lipoproteins for targeted and effective drug delivery. In this work, we have studied process of an association of potent photosensitizer hypericin (Hyp) with synthetic lipid-based nano-particles (sLNP) and large unilamellar vesicles (LUV) containing various amount of cholesterol. Cholesterol is one of the main components of both LDL and HDL particles and its presence in biological membranes is known to be a determining factor for membrane properties. It was found that the behavior of Hyp incorporation into sLNP particles with diameter ca ~ 90 nm is qualitatively very similar to that of Hyp incorporation into LDL (diameter ca. 22 nm) and these particles are able to enter U-87 MG cells by endocytosis. The presence of cholesterol in LUV influences the capacity of these vesicles to incorporate Hyp into their structure.

  13. Nano-particle vaccination combined with TLR-7 and -9 ligands triggers memory and effector CD8⁺ T-cell responses in melanoma patients.

    PubMed

    Goldinger, Simone M; Dummer, Reinhard; Baumgaertner, Petra; Mihic-Probst, Daniela; Schwarz, Katrin; Hammann-Haenni, Anya; Willers, Joerg; Geldhof, Christine; Prior, John O; Kündig, Thomas M; Michielin, Olivier; Bachmann, Martin F; Speiser, Daniel E

    2012-11-01

    Optimal vaccine strategies must be identified for improving T-cell vaccination against infectious and malignant diseases. MelQbG10 is a virus-like nano-particle loaded with A-type CpG-oligonucleotides (CpG-ODN) and coupled to peptide(16-35) derived from Melan-A/MART-1. In this phase IIa clinical study, four groups of stage III-IV melanoma patients were vaccinated with MelQbG10, given (i) with IFA (Montanide) s.c.; (ii) with IFA s.c. and topical Imiquimod; (iii) i.d. with topical Imiquimod; or (iv) as intralymph node injection. In total, 16/21 (76%) patients generated ex vivo detectable Melan-A/MART-1-specific T-cell responses. T-cell frequencies were significantly higher when IFA was used as adjuvant, resulting in detectable T-cell responses in all (11/11) patients, with predominant generation of effector-memory-phenotype cells. In turn, Imiquimod induced higher proportions of central-memory-phenotype cells and increased percentages of CD127(+) (IL-7R) T cells. Direct injection of MelQbG10 into lymph nodes resulted in lower T-cell frequencies, associated with lower proportions of memory and effector-phenotype T cells. Swelling of vaccine site draining lymph nodes, and increased glucose uptake at PET/CT was observed in 13/15 (87%) of evaluable patients, reflecting vaccine triggered immune reactions in lymph nodes. We conclude that the simultaneous use of both Imiquimod and CpG-ODN induced combined memory and effector CD8(+) T-cell responses. PMID:22806397

  14. Effects of acido-basic support properties on the catalytic hydrogenation of acetylene on gold nano-particles

    NASA Astrophysics Data System (ADS)

    Manda, Abdullah Ahmed

    Metallic gold nanoparticles supported on gamma-Al2O 3 and magnesia-alumina mixed oxide, with different magnesia content have been prepared by sol-gel method and characterized by different techniques (inductive coupled plasma-mass spectroscopy (ICP-MS), XRD, BET surface area analysis, transmission electron microscopy (TEM), CO2 and NH 3 temperature programmed desorption (TPD), H2 temperature programmed reduction (TPR) and FTIR of adsorbed CO2). Such systems were found to produce catalysts with controllable acidity, varying from catalyst possessing large density of acidic and low density of basic sites, others with acidic and basic sites of equal strength and density, and others with large basic and low acid sites densities, respectively. The catalytic assessment of the generated acidity was carried out using 2-propanol decomposition as a test reaction. The results obtained indicate that the presence of magnesia and reduced gold nanopartilces has imparted the catalysts, 1%Au/4%Mg-Al 2O3 and 1%Au/8%Mg-Al2O3, with significant base-catalytic properties. Acetylene hydrogenation and formation of coke deposits were investigated on a gold catalyst supported on gamma-Al2O3 and gold supported on alumina-magnisia mixed oxide with different gold content; 1%Au/gamma-Al 2O3, 1%Au/15%Mg-Al2O3, 2%Au/15%Mg-Al 2O3 and 4%Au/15%Mg-Al2O3. The effect of the H2/C2H2 ratio was studied over a range of values. The catalytic activity and selectivity towards ethylene and other products were investigated at different reaction temperatures. Acetylene hydrogenation was investigated in the presence and absence of ethylene in stream. It is investigated that the adsorption of the triple bond is preferred over the double bond and during selective catalytic (SCR) of C2H2 the two hydrocarbons do not compete for the same adsorption sites. The deactivation of catalysts was studied by temperature programmed oxidation (TPO). Higher content of coke over 1%Au/Al2O3 catalyst was investigated in contrast to

  15. Production of magnetite by electrolytic reduction of ferric oxyhydroxide

    NASA Astrophysics Data System (ADS)

    Manrique-Julio, J.; Machuca-Martinez, F.; Marriaga-Cabrales, N.; Pinzon-Cardenas, M.

    2016-03-01

    Magnetite (Fe3O4) particles were prepared by electrolytic synthesis without the use of a surfactant. Various techniques were used to evaluate the effect of two parameters, the current density and the separation between electrodes, in the formation process of ferrimagnetic magnetite particles. The crystallite sizes can be controlled by adjusting the current density. Particle formation was favored below a critical separation distance between the electrodes. Finally, a formation mechanism for magnetite was proposed based on the partial reduction of lepidocrocite.

  16. Biomimetic Magnetite Formation: From Biocombinatorial Approaches to Mineralization Effects

    PubMed Central

    2014-01-01

    Biological materials typically display complex morphologies and hierarchical architectures, properties that are hardly matched by synthetic materials. Understanding the biological control of mineral properties will enable the development of new synthetic approaches toward biomimetic functional materials. Here, we combine biocombinatorial approaches with a proteome homology search and in vitro mineralization assays to assess the role of biological determinants in biomimetic magnetite mineralization. Our results suggest that the identified proteins and biomimetic polypeptides influence nucleation in vitro. Even though the in vivo role cannot be directly determined from our experiments, we can rationalize the following design principles: proteins, larger complexes, or membrane components that promote nucleation in vivo are likely to expose positively charged residues to a negatively charged crystal surface. In turn, components with acidic (negatively charged) functionality are nucleation inhibitors, which stabilize an amorphous structure through the coordination of iron. PMID:24499323

  17. Biofunctionalized magnetic hydrogel nanospheres of magnetite and κ-carrageenan

    NASA Astrophysics Data System (ADS)

    Daniel-da-Silva, Ana L.; Fateixa, Sara; Guiomar, António J.; Costa, Benilde F. O.; Silva, Nuno J. O.; Trindade, Tito; Goodfellow, Brian J.; Gil, Ana M.

    2009-09-01

    Magnetic hydrogel κ-carrageenan nanospheres were successfully prepared via water-in-oil (w/o) microemulsions combined with thermally induced gelation of the polysaccharide. The size of the nanospheres (an average diameter (∅) of about 50 and 75 nm) was modulated by varying the concentration of surfactant. The nanospheres contained superparamagnetic magnetite nanoparticles (∅8 nm), previously prepared by co-precipitation within the biopolymer. Carboxyl groups, at a concentration of about 4 mmol g-1, were successfully grafted at the surface of these magnetic nanospheres via carboxymethylation of the κ-carrageenan. The carboxylated nanospheres were shown to be thermo-sensitive in the 37-45 °C temperature range, indicating their potential as thermally controlled delivery systems for drugs and/or magnetic particles at physiological temperatures. Finally, preliminary results have been obtained for IgG antibody conjugation of the carboxylated nanospheres and the potential of these systems for bio-applications is discussed.

  18. In situ formation of magnetite reactive barriers in soil for waste stabilization

    DOEpatents

    Moore, Robert C.

    2003-01-01

    Reactive barriers containing magnetite and methods for making magnetite reactive barriers in situ in soil for sequestering soil contaminants including actinides and heavy metals, organic materials, iodine and technetium are disclosed. According to one embodiment, a two-step reagent introduction into soil takes place. In the first step, free oxygen is removed from the soil by separately injecting into the soil aqueous solutions of iron (II) salt, for example FeCl.sub.2, and base, for example NaOH or NH.sub.3 in about a 1:1 volume ratio. Then, in the second step, similar reagents are injected a second time (however, according to about a 1:2 volume ratio, iron to salt) to form magnetite. The magnetite formation is facilitated, in part, due to slow intrusion of oxygen into the soil from the surface. The invention techniques are suited to injection of reagents into soil in proximity to a contamination plume or source allowing in situ formation of the reactive barrier at the location of waste or hazardous material. Mixing of reagents to form. precipitate is mediated and enhanced through movement of reagents in soil as a result of phenomena including capillary action, movement of groundwater, soil washing and reagent injection pressure.

  19. Sorptive uptake of selenium with magnetite and its supported materials onto activated carbon.

    PubMed

    Kwon, Jae H; Wilson, Lee D; Sammynaiken, R

    2015-11-01

    Kinetic and equilibrium uptake studies of selenite in aqueous solution with synthetic magnetite (Mag-P), commercial magnetite (Mag-C), goethite, activated carbon (AC), and a composite material containing 19% magnetite supported on activated carbon (CM-19) were investigated. Kinetic uptake studies used a one-pot setup at pH 5.26 at variable temperature. Sampling of unbound selenite in-situ was achieved with analytical detection by atomic absorbance. The sorptive uptake at equilibrium and kinetic conditions are listed in descending order: goethite>Mag-P>Mag-C>CM-19. Kinetic uptake parameters reveal that Mag-P showed apparent negative values for the activation energy (E(a)) and the enthalpy of activation (ΔH(‡)), in agreement with a multi-step process for the kinetic uptake of selenite. By contrast, Mag-C, CM-19, and goethite showed positive values for E(a) and ΔH(‡). The uptake properties of the various sorbent materials with selenite are in accordance with the formation of inner- and out-sphere complexes. Leaching of iron from the composite material (CM-19) was attenuated due to the stabilizing effect of the magnetite within the pore sites and the surface of AC. Supported iron oxide nanomaterial composites represent a unique sorbent material with tunable uptake properties toward inorganic selenite in aqueous solution.

  20. Adsorption of Oxyanions from Industrial Wastewater using Perlite-Supported Magnetite.

    PubMed

    Verbinnen, Bram; Block, Chantal; Vandecasteele, Carlo

    2016-05-01

    Most studies on oxyanion adsorption focus on their removal from synthetic solutions. It is often claimed that the considered adsorbents can be used to treat real (industrial) wastewaters, but this is seldom tested. Perlite-supported magnetite was characterized first by determining its specific surface area, magnetite content and by examining the coating. Tests on a synthetic solution showed that at the ideal pH values (pH 3 to 5), the order of adsorption is Mo(VI) > As(V) > Sb(V) > Cr(VI) > Se(VI). Most oxyanions can be removed for more than 75% with an adsorbent dosage of 1 g/l. Furthermore, perlite-supported magnetite has a higher removal efficiency for oxyanions than commercially available adsorbents and comparable adsorbents described in literature. Perlite-supported magnetite is suitable for treating real wastewaters: it can remove several oxyanions simultaneously from the considered industrial wastewater, but the adsorption order changes due to the presence of interfering anions.

  1. Structure and superparamagnetic behaviour of magnetite nanoparticles in cellulose beads

    SciTech Connect

    Correa, Jose R.; Bordallo, Eduardo; Canetti, Dora; Leon, Vivian; Otero-Diaz, Luis C.; Negro, Carlos; Gomez, Adrian; Saez-Puche, Regino

    2010-08-15

    Superparamagnetic magnetite nanoparticles were obtained starting from a mixture of iron(II) and iron(III) solutions in a preset total iron concentration from 0.04 to 0.8 mol l{sup -1} with ammonia at 25 and 70 {sup o}C. The regeneration of cellulose from viscose produces micrometrical spherical cellulose beads in which synthetic magnetite were embedded. The characterization of cellulose-magnetite beads by X-ray diffraction, Scanning and Transmission Electron Microscopy and magnetic measurement is reported. X-ray diffraction patterns indicate that the higher is the total iron concentration and temperature the higher is the crystal size of the magnetite obtained. Transmission Electron Microscopy studies of cellulose-magnetite beads revealed the distribution of magnetite nanoparticles inside pores of hundred nanometers. Magnetite as well as the cellulose-magnetite composites exhibit superparamagnetic characteristics. Field cooling and zero field cooling magnetic susceptibility measurements confirm the superparamagnetic behaviour and the blocking temperature for the magnetite with a mean size of 12.5 nm, which is 200 K.

  2. Activation of persulfate by irradiated magnetite: implications for the degradation of phenol under heterogeneous photo-Fenton-like conditions.

    PubMed

    Avetta, Paola; Pensato, Alessia; Minella, Marco; Malandrino, Mery; Maurino, Valter; Minero, Claudio; Hanna, Khalil; Vione, Davide

    2015-01-20

    We show that phenol can be effectively degraded by magnetite in the presence of persulfate (S2O8(2–)) under UVA irradiation. The process involves the radical SO4(–•), formed from S2O8(2–) in the presence of Fe(II). Although magnetite naturally contains Fe(II), the air-exposed oxide surface is fully oxidized to Fe(III) and irradiation is required to produce Fe(II). The magnetite + S2O8(2–) system was superior to the corresponding magnetite + H2O2 one in the presence of radical scavengers and in a natural water matrix, but it induced phenol mineralization in ultrapure water to a lesser extent. The leaching of Fe from the oxide surface was very limited, and much below the wastewater discharge limits. The reasonable performance of the magnetite/persulfate system in a natural water matrix and the low levels of dissolved Fe are potentially important for the removal of organic contaminants in wastewater.

  3. Magnetite in Desert Varnish and Applications to Rock Varnish on Mars

    NASA Astrophysics Data System (ADS)

    Mancinelli, R. L.; Bishop, J. L.; de, S.

    2002-03-01

    Magnetite in desert varnish is characterized here using DTA, IR and SEM. The presence of magnetite in desert varnish is significant because of the oxidizing environment. This situation is similar to that of Mars where magnetite may also be present.

  4. Viscosity studies of water based magnetite nanofluids

    NASA Astrophysics Data System (ADS)

    Anu, K.; Hemalatha, J.

    2016-05-01

    Magnetite nanofluids of various concentrations have been synthesized through co-precipitation method. The structural and topographical studies made with the X-Ray Diffractometer and Atomic Force Microscope are presented in this paper. The density and viscosity studies for the ferrofluids of various concentrations have been made at room temperature. The experimental viscosities are compared with theoretical values obtained from Einstein, Batchelor and Wang models. An attempt to modify the Rosensweig model is made and the modified Rosensweig equation is reported. In addition, new empirical correlation is also proposed for predicting viscosity of ferrofluid at various concentrations.

  5. The contribution of vanadium and titanium on improving methylene blue decolorization through heterogeneous UV-Fenton reaction catalyzed by their co-doped magnetite.

    PubMed

    Liang, Xiaoliang; Zhong, Yuanhong; Zhu, Sanyuan; Ma, Lingya; Yuan, Peng; Zhu, Jianxi; He, Hongping; Jiang, Zheng

    2012-01-15

    This study investigated the methylene blue (MB) decolorization through heterogeneous UV-Fenton reaction catalyzed by V-Ti co-doped magnetites, with emphasis on comparing the contribution of V and Ti cations on improving the adsorption and catalytic activity of magnetite. In the well crystallized spinel structure, both Ti(4+) and V(3+) occupied the octahedral sites. Ti(4+) showed a more obvious effect on increasing specific surface area and superficial hydroxyl amount than V(3+) did, resulting in a significant improvement of the adsorption ability of magnetite to MB. The UV introduction greatly accelerated MB degradation. And magnetite with more Ti and less V displayed better catalytic activity in MB degradation through heterogeneous UV-Fenton reaction. The transformation of degradation products and individual contribution from vanadium and titanium on improving adsorption and catalytic activity of magnetite were also investigated. These new insights are of high importance for well understanding the interface interaction between contaminants and metal doped magnetites, and the environmental application of natural and synthetic magnetites.

  6. [Preparation of Gold Nano-Particles as Surface-Enhanced Raman Scattering Sensors for Analysis of Banned Food Dye Chrysoidin in Yuba].

    PubMed

    Xu, Xue-qin; Liu, Qiong-hua; Yang, Fang; Qian, Jiang; Chen, Jian; Lin, Zhen-yu; Qiu, Bin

    2015-11-01

    Chrysoidin is a kind of banned food dye, and it has been illegally used for coloring food. A rapid detection and quantification method is developed and applied in analysis chrysoidin in yuba. Gold nanoparticles are synthesized by using hexadecyl trimethyl ammonium bromide (CTAB) as the bifunctional ligand to link the solid substrate and the AuNPs. The laser wavelength used for quantitative is 1594 cm⁻¹. Significant differences between different concentrations of chrysoidin are verified by multiple variable analysis. A relationship between the logarithm of the concentrations and the intensity of laser is proved using univariate analysis method. The calibration curves showed good linearity in the range of 0.001-0.5 mmol · L⁻¹ with correlation coefficients r = 0.995. The method is successfully applied to the determination of chrysoidin in yuba. The average recoveries of the drugs spiked at 50 and 500 µg · g⁻¹ levels are 82.4% and 116.9%, and the relative standard deviations (RSD) are 3.8% and 4.0%. The method is simple, rapid, sensitive and accurate in the determination of chrysoidin. PMID:26978915

  7. Synthesis of thoria nano-particles at low temperature through base electrogeneration on steel 316L surface: Effect of current density

    NASA Astrophysics Data System (ADS)

    Yousefi, Taher; Torab-Mostaedi, Meisam; Mobtaker, Hossein Ghasemi; Keshtkar, Ali Reza

    2016-10-01

    The strategy developed in this study, offers significant advantages (simplicity and cleanness of method and also a product purity and new morphology of the product) over the conventional routes for the synthesis of ThO2 nanostructure. The effect of current density on morphology was studied. The synthesized powder was characterized by means of Powder X-ray Diffraction (PXRD), Transmission Electron Microscopy (TEM, Phillips EM 2085) Brunauer-Emmett-Teller (BET) and Fourier Transform Infrared (FT-IR) spectroscopy. The results show that the current density has a great effect on the morphology of the samples. The average size of the particles decreases as the applied current density increases and the average size of the samples decreases from 50 to 15 nm when the current density increases from 2 to 5 mA cm-2.

  8. A first test of the hypothesis of biogenic magnetite-based heterogeneous ice-crystal nucleation in cryopreservation.

    PubMed

    Kobayashi, Atsuko; Golash, Harry N; Kirschvink, Joseph L

    2016-06-01

    An outstanding biophysical puzzle is focused on the apparent ability of weak, extremely low-frequency oscillating magnetic fields to enhance cryopreservation of many biological tissues. A recent theory holds that these weak magnetic fields could be inhibiting ice-crystal nucleation on the nanocrystals of biological magnetite (Fe3O4, an inverse cubic spinel) that are present in many plant and animal tissues by causing them to oscillate. In this theory, magnetically-induced mechanical oscillations disrupt the ability of water molecules to nucleate on the surface of the magnetite nanocrystals. However, the ability of the magnetite crystal lattice to serve as a template for heterogeneous ice crystal nucleation is as yet unknown, particularly for particles in the 10-100 nm size range. Here we report that the addition of trace-amounts of finely-dispersed magnetite into ultrapure water samples reduces strongly the incidence of supercooling, as measured in experiments conducted using a controlled freezing apparatus with multiple thermocouples. SQUID magnetometry was used to quantify nanogram levels of magnetite in the water samples. We also report a relationship between the volume change of ice, and the degree of supercooling, that may indicate lower degassing during the crystallization of supercooled water. In addition to supporting the role of ice-crystal nucleation by biogenic magnetite in many tissues, magnetite nanocrystals could provide inexpensive, non-toxic, and non-pathogenic ice nucleating agents needed in a variety of industrial processes, as well as influencing the dynamics of ice crystal nucleation in many natural environments. PMID:27087604

  9. A first test of the hypothesis of biogenic magnetite-based heterogeneous ice-crystal nucleation in cryopreservation.

    PubMed

    Kobayashi, Atsuko; Golash, Harry N; Kirschvink, Joseph L

    2016-06-01

    An outstanding biophysical puzzle is focused on the apparent ability of weak, extremely low-frequency oscillating magnetic fields to enhance cryopreservation of many biological tissues. A recent theory holds that these weak magnetic fields could be inhibiting ice-crystal nucleation on the nanocrystals of biological magnetite (Fe3O4, an inverse cubic spinel) that are present in many plant and animal tissues by causing them to oscillate. In this theory, magnetically-induced mechanical oscillations disrupt the ability of water molecules to nucleate on the surface of the magnetite nanocrystals. However, the ability of the magnetite crystal lattice to serve as a template for heterogeneous ice crystal nucleation is as yet unknown, particularly for particles in the 10-100 nm size range. Here we report that the addition of trace-amounts of finely-dispersed magnetite into ultrapure water samples reduces strongly the incidence of supercooling, as measured in experiments conducted using a controlled freezing apparatus with multiple thermocouples. SQUID magnetometry was used to quantify nanogram levels of magnetite in the water samples. We also report a relationship between the volume change of ice, and the degree of supercooling, that may indicate lower degassing during the crystallization of supercooled water. In addition to supporting the role of ice-crystal nucleation by biogenic magnetite in many tissues, magnetite nanocrystals could provide inexpensive, non-toxic, and non-pathogenic ice nucleating agents needed in a variety of industrial processes, as well as influencing the dynamics of ice crystal nucleation in many natural environments.

  10. Magnetic Dinner Salads: The Role of Biogenic Magnetite in Cryopreservation for Common Food Plants

    NASA Astrophysics Data System (ADS)

    Chaffee, T. M.; Kirschvink, J. L.; Kobayashi, A. K.

    2015-12-01

    Biogenically-precipitated magnetite has been found in organisms ranging from Bacteria, single-celled protists, and many of the animal phyla, where its major function is navigation and magnetoreception. To date there is but a single report of biogenic magnetite in plants (essentially, magnetoferritin), and that is in common grass (Festuca species, from Gajdardziska-Josifovska et. al. doi:10.1127/0935-1221/2001/0013/0863). Recent developments in cryopreservation suggest that ~ 1 mT, ~ 10 Hz oscillating magnetic fields can drastically reduce ice nucleation during freezing, promote supercooling, and minimize cellular damage in living tissues (e.g., Kaku et al., doi: 10.1016/j.cryobiol.2012.02.001). Kobayashi & Kirschvink (2014, doi:10.1016/j.cryobiol.2013.12.002) suggest that biogenic magnetite crystals could be the nucleating site for damaging ice crystals, and that they would be driven magneto-mechanically to rotate in those oscillating fields which could inhibit the ice crystal nucleation process. This prompted our investigation into the magnetite content of ordinary fruit and vegetable food products, as knowledge of the natural levels of biogenic magnetite in the human food supply could guide the selection of which foods might work for this type of cryopreservation. Our study involved a range of common foods including avocados, bananas, garlic, and apples. Samples were prepared in a clean lab environment kept free of contaminant particles, and subjected to a variety of standard rock-magnetic tests including IRM and ARM acquisition, and the corresponding Af demagnetization, on a standard 2G™ SRM. Results are consistent with moderately interacting single-domain magnetite (see figure), with moderate inter-particle interaction effects. Typical magnetite concentrations in these samples are in the range of .1 to 1 ng/g for room temperature samples, increasing to the range of 1-10 ng/g when measured frozen (to inhibit thermal rotation of small particles and clumps). If

  11. Coating of magnetite with mercapto modified rice hull ash silica in a one-pot process.

    PubMed

    Nuryono, Nuryono; Mutia Rosiati, Nur; Rusdiarso, Bambang; Sakti, Satya Candra Wibawa; Tanaka, Shunitz

    2014-01-01

    In this research, mercapto-silica coated magnetite (Fe3O4-SiO2-SH) has been prepared in aqueous solution through a simple approach so called a one-pot process. The Fe3O4-SiO2-SH was prepared in nitrogen condition by mixing magnetite, 3-mercaptopropyltrimethoxysilane (MPTMS), and sodium silicate (Na2SiO3) solution extracted from rice hull ash, and adjusting the pH of 7.0 using hydrochloric acid. The residue was washed with deionized water, dried at 150°C and separated with an external magnetic field. In that work, the volume of MPTMS and Na2SiO3 was varied and the total amount of Si represented as silica was kept constant. Characters of the material including the functional group presence, the structure, the porosity, the morphology and stability toward various solvents were identified and evaluated. Results of characterization indicated that mercapto-silica has been coated magnetite particle with a simple one-pot process. Coating mercapto-silica on magnetite increases particle size, surface area, and chemical stability. Additionally, Fe3O4-SiO2-SH also shows high stability toward various organic solvents. The magnetic property of magnetite does not change after coating and the addition of nonmagnetic material still gives high value of maximum saturation magnetization. The presence of mercapto groups effective for interaction with heavy metal ions, the high chemical stability without removing the magnetic property promises the prospective application of Fe3O4-SiO2-SH in the future such as for separation and removal of heavy metal ions from aquatic environments.

  12. Fabrication of triple-layered magnetite-hydrogel-gold nanocomposites for biomedical applications.

    PubMed

    Lim, Sera; Lee, Sang-Wha

    2012-02-01

    Magnetite-hydrogel-gold nanocomposites with optical-active, thermo-responsive, and magnetism have been prepared by the following consecutive steps. Hydrogel-encapsulated magnetites were first synthesized by the combination of sol-gel reaction and radical polymerization process, and the resulting magnetic hydrogels were subsequently bound with nano-sized Au (1-3 nm) via a molecular linkage of diamine ligand which was covalently bonded to the carboxylic groups on the hydrogel surface. Au seeds anchored on the magnetic hydrogels were further reduced into nano-scale Au layer which induced the distinct red-shift of absorption band into NIR region. The optical properties and surface morphology of the nanocomposites were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). PMID:22629930

  13. An original route to stabilize and functionalize magnetite nanoparticles for theranosis applications

    NASA Astrophysics Data System (ADS)

    Forge, D.; Laurent, S.; Gossuin, Y.; Roch, A.; Vander Elst, L.; Muller, R. N.

    2011-03-01

    A versatile method for the introduction of cyano groups onto the surface of iron oxide nanoparticles has been developed. This protocol is based on the hydrolysis and the condensation of cyanoethyltrimethoxysilane (CES) on the magnetite surface. The optimal concentration of silane coupling agent was determined ([Fe]/[CN] ratio=0.4) in order to obtain an appropriate surface density of activating groups on the nanoparticles. The size distribution of the particles was also optimized by a magnetic size sorting procedure. An adequate surface with cyano groups could facilitates their use in biomedical applications by improving the cellular labeling and the cell targeting.

  14. Magnetic process for removing heavy metals from water employing magnetites

    DOEpatents

    Prenger, F. Coyne; Hill, Dallas D.

    2006-12-26

    A process for removing heavy metals from water is provided. The process includes the steps of introducing magnetite to a quantity of water containing heavy metal. The magnetite is mixed with the water such that at least a portion of, and preferably the majority of, the heavy metal in the water is bound to the magnetite. Once this occurs the magnetite and absorbed metal is removed from the water by application of a magnetic field. In most applications the process is achieved by flowing the water through a solid magnetized matrix, such as steel wool, such that the magnetite magnetically binds to the solid matrix. The magnetized matrix preferably has remnant magnetism, but may also be subject to an externally applied magnetic field. Once the magnetite and associated heavy metal is bound to the matrix, it can be removed and disposed of, such as by reverse water or air and water flow through the matrix. The magnetite may be formed in-situ by the addition of the necessary quantities of Fe(II) and Fe(III) ions, or pre-formed magnetite may be added, or a combination of seed and in-situ formation may be used. The invention also relates to an apparatus for performing the removal of heavy metals from water using the process outlined above.

  15. Magnetic process for removing heavy metals from water employing magnetites

    DOEpatents

    Prenger, F. Coyne; Hill, Dallas D.; Padilla, Dennis D.; Wingo, Robert M.; Worl, Laura A.; Johnson, Michael D.

    2003-07-22

    A process for removing heavy metals from water is provided. The process includes the steps of introducing magnetite to a quantity of water containing heavy metal. The magnetite is mixed with the water such that at least a portion of, and preferably the majority of, the heavy metal in the water is bound to the magnetite. Once this occurs the magnetite and absorbed metal is removed from the water by application of a magnetic field. In most applications the process is achieved by flowing the water through a solid magnetized matrix, such as steel wool, such that the magnetite magnetically binds to the solid matrix. The magnetized matrix preferably has remnant magnetism, but may also be subject to an externally applied magnetic field. Once the magnetite and associated heavy metal is bound to the matrix, it can be removed and disposed of, such as by reverse water or air and water flow through the matrix. The magnetite may be formed in-situ by the addition of the necessary quantities of Fe(II) and Fe(III) ions, or pre-formed magnetite may be added, or a combination of seed and in-situ formation may be used. The invention also relates to an apparatus for performing the removal of heavy metals from water using the process outlined above.

  16. Intermediate magnetite formation during dehydration of goethite

    NASA Astrophysics Data System (ADS)

    Özdemir, Özden; Dunlop, David J.

    2000-04-01

    The dehydration of goethite has been studied by low-temperature induced magnetization (LTIM) and X-ray diffraction on well-characterized acicular crystals. Fresh samples were heated in air to temperatures between 155°C and 610°C. Goethite and hematite were the magnetically dominant phases after all runs except 500°C and 610°C, for which only hematite was found. However, partially dehydrated goethites after the 238-402°C runs had broad peaks or inflections in the LTIM curves around 120 K, suggesting the formation of an intermediate spinel phase. These samples were next given a saturation remanence in a field of 2 T at 10 K and the remanence was measured continuously during zero-field warming to 300 K. There was a decrease in remanence at the Verwey transition (120 K), diagnostic of magnetite. The possible formation of a small amount of magnetite is of serious concern in studies of goethite-bearing sediments and rocks. Chemical remanent magnetization (CRM) of this strongly magnetic spinel phase could significantly modify the direction as well as the intensity of the original goethite CRM. As well, it would be a new source of paleomagnetic noise as far as primary remanence carried by other mineral phases is concerned.

  17. Curcumin associated magnetite nanoparticles inhibit in vitro melanoma cell growth.

    PubMed

    de Souza, Fernanda França; dos Santos, Michelly Christine; dos Passos, Debora Cristina Silva; Lima, Emilia Celma de Oliveira; Guillo, Lidia Andreu

    2011-09-01

    Curcumin is a natural product possessing therapeutic properties but the low water solubility of this compound limits its use. We have successfully incorporated curcumin into a bilayer of dodecanoic acid attached to magnetite nanoparticles in an effort to maximize solubility and delivery efficiency. Curcumin/magnetite nanoparticles were characterized using diffused reflectance infra-red fourier transform spectroscopy (DRIFTS) and X-ray powder diffraction (XRD). Moreover curcumin associated magnetite nanoparticles inhibited in vitro melanoma cell growth. An inhibitory concentration (IC50) of 66.0 +/- 3.0 microM (48 +/- 2.2 microg-iron/mL) was observed for the curcumin/magnetite nanoparticles. Fluorescent microscopy revealed that curcumin associated magnetite nanoparticles were internalized by the melanoma cells and remained in the cytoplasm. The curcumin/magnetic nanoparticles synthesized in this study possess magnetic and water solubility properties making this a novel curcumin formulation with therapeutic potential.

  18. Redox cycling of Fe(II) and Fe(III) in magnetite by Fe-metabolizing bacteria

    SciTech Connect

    Byrne, James; Klueglein, Nicole; Pearce, Carolyn I.; Rosso, Kevin M.; Appel, Erwin; Kappler, Andreas

    2015-03-26

    Despite the regular occurrence of both magnetite and iron-metabolizing bacteria in the same environments, it is currently unknown whether the iron(II) and iron(III) in magnetite can be cycled between different bacteria and whether or how magnetic properties are affected by this metabolic activity. We show through magnetic and spectroscopic measurements that the phototrophic Fe(II)-oxidizer Rhodopseudomonas palustris TIE-1 can oxidize solid-phase magnetite nanoparticles using light energy, leading to a decrease in the measured magnetic susceptibility (MS). This process likely occurs at the surface and is reversible in the dark by the Fe(III)-reducer Geobacter sulfurreducens resulting in an increase in MS. These results show that iron ions bound in highly crystalline mineral magnetite are bioavailable as electron stores and electron sinks under varying environmental conditions, making magnetite a potential “biogeobattery” during day/night cycles. These findings are relevant for environmental studies and reinforce the impact of microbial redox processes on the global iron cycle.

  19. Modifying magnetic properties of ultra-thin magnetite films by growth on Fe pre-covered MgO(001)

    SciTech Connect

    Schemme, T. Krampf, A.; Kuepper, K.; Wollschläger, J.; Bertram, F.; Kuschel, T.

    2015-09-21

    Iron oxide films were reactively grown on iron buffer films, which were deposited before on MgO(001) substrates to analyze the influence of the initial iron buffer layers on the magnetic properties of the magnetite films. X-ray photoelectron spectroscopy and low energy electron diffraction showed that magnetite films of high crystalline quality in the surface near region were formed by this two-step deposition procedure. The underlying iron film, however, was completely oxidized as proved by x-ray reflectometry and diffraction. The structural bulk quality of the iron oxide film is poor compared to magnetite films directly grown on MgO(001). Although the iron film was completely oxidized, we found drastically modified magnetic properties for these films using the magnetooptic Kerr effect. The magnetite films had strongly increased coercive fields, and their magnetic in-plane anisotropy is in-plane rotated by 45∘ compared to magnetite films formed directly by one step reactive growth on MgO(001)

  20. One-step synthesis and functionalization of hydroxyl-decorated magnetite nanoparticles.

    PubMed

    Mondini, Sara; Cenedese, Simone; Marinoni, Giorgio; Molteni, Giorgio; Santo, Nadia; Bianchi, Claudia L; Ponti, Alessandro

    2008-06-01

    Magnetite nanoparticles covered by a layer of omega-hydroxycarboxylic acid were synthesized in one step by high-temperature decomposition of iron(III) omega-hydroxycarboxylates in tri- and tetra-ethylene glycol. The nanoparticles were characterized by TEM, XRD, IR, XPS and NMR techniques in order to show that they comprise a crystalline magnetite core and actually bear on the outer surface terminal hydroxy groups. The latter ones are convenient "handles" for further functionalization as opposed to the chemically-inert aliphatic chains which cover conventionally synthesized nanoparticles. This was shown by several examples in which the hydroxy groups on the nanoparticle surface were easily transformed in other functional groups or reacted with other molecules. For instance, the hydroxyl-decorated nanoparticles were made water soluble by esterification with a PEGylated acetic acid. The reactive behavior of the surfactant monolayer was monitored by degrading the nanoparticles with aqueous acid and isolating the surfactant for NMR characterization. In general, the reactivity of the terminal hydroxyl groups on the nanoparticle surface parallels that observed in the free surfactants. The reported hydroxyl-decorated magnetite nanoparticles can be thus considered as pro-functional nanoparticles, i.e., a convenient starting material to functionalized magnetic nanoparticles.

  1. Origin of magnetite in oxidized CV chondrites: in situ measurement of oxygen isotope compositions of Allende magnetite and olivine.

    PubMed

    Choi, B G; McKeegan, K D; Leshin, L A; Wasson, J T

    1997-01-01

    Magnetite in the oxidized CV chondrite Allende mainly occurs as spherical nodules in porphyritic-olivine (PO) chondrules, where it is associated with Ni-rich metal and/or sulfides. To help constrain the origin of the magnetite, we measured oxygen isotopic compositions of magnetite and coexisting olivine grains in PO chondrules of Allende by an in situ ion microprobe technique. Five magnetite nodules form a relatively tight cluster in oxygen isotopic composition with delta 18O values from -4.8 to -7.1% and delta 17O values from -2.9 to -6.3%. Seven coexisting olivine grains have oxygen isotopic compositions from -0.9 to -6.3% in delta 18O and from -4.6 to -7.9% in delta 17O. The delta 17O values of the magnetite and coexisting olivine do not overlap; they range from -0.4 to -2.6%, and from -4.0 to -5.7%, respectively. Thus, the magnetite is not in isotopic equilibrium with the olivine in PO chondrules, implying that it formed after the chondrule formation. The delta 17O of the magnetite is somewhat more negative than estimates for the ambient solar nebula gas. We infer that the magnetite formed on the parent asteroid by oxidation of metal by H2O which had previously experienced minor O isotope exchange with fine-grained silicates.

  2. Origin of magnetite in oxidized CV chondrites: in situ measurement of oxygen isotope compositions of Allende magnetite and olivine

    NASA Technical Reports Server (NTRS)

    Choi, B. G.; McKeegan, K. D.; Leshin, L. A.; Wasson, J. T.

    1997-01-01

    Magnetite in the oxidized CV chondrite Allende mainly occurs as spherical nodules in porphyritic-olivine (PO) chondrules, where it is associated with Ni-rich metal and/or sulfides. To help constrain the origin of the magnetite, we measured oxygen isotopic compositions of magnetite and coexisting olivine grains in PO chondrules of Allende by an in situ ion microprobe technique. Five magnetite nodules form a relatively tight cluster in oxygen isotopic composition with delta 18O values from -4.8 to -7.1% and delta 17O values from -2.9 to -6.3%. Seven coexisting olivine grains have oxygen isotopic compositions from -0.9 to -6.3% in delta 18O and from -4.6 to -7.9% in delta 17O. The delta 17O values of the magnetite and coexisting olivine do not overlap; they range from -0.4 to -2.6%, and from -4.0 to -5.7%, respectively. Thus, the magnetite is not in isotopic equilibrium with the olivine in PO chondrules, implying that it formed after the chondrule formation. The delta 17O of the magnetite is somewhat more negative than estimates for the ambient solar nebula gas. We infer that the magnetite formed on the parent asteroid by oxidation of metal by H2O which had previously experienced minor O isotope exchange with fine-grained silicates.

  3. Water treatment using activated carbon supporting silver and magnetite.

    PubMed

    Valušová, Eva; Vandžurová, Anna; Pristaš, Peter; Antalík, Marián; Javorský, Peter

    2012-01-01

    Recent efforts in water purification have led to the development of novel materials whose unique properties can offer effective biocidal capabilities with greater ease of use and at lower cost. In this study, we introduce a novel procedure for the preparation of activated carbon (charcoal) composite in which magnetite and silver are incorporated (MCAG); we also describe the use of this material for the disinfection of surface water. The formation process of magnetic MCAG composite was studied using ultraviolet-visible spectroscopy. The results demonstrated the high sorption efficiency of AgNO₃ to magnetic activated carbon. The antimicrobial capabilities of the prepared MCAG were examined and the results clearly demonstrate their inhibitory effect on total river water bacteria and on Pseudomonas koreensis and Bacillus mycoides cultures isolated from river water. The bacterial counts in river water samples were reduced by five orders of magnitude following 30 min of treatment using 1 g l⁻¹ of MCAG at room temperature. The removal of all bacteria from the surface water samples implies that the MCAG material would be a suitable disinfectant for such waters. In combination with its magnetic character, MCAG would be an excellent candidate for the simple ambulatory disinfection of surface water.

  4. Effects of heavy metals and oxalate on the zeta potential of magnetite.

    PubMed

    Erdemoğlu, Murat; Sarikaya, Musa

    2006-08-15

    Zeta potential is a function of surface coverage by charged species at a given pH, and it is theoretically determined by the activity of the species in solution. The zeta potentials of particles occurring in soils, such as clay and iron oxide minerals, directly affect the efficiency of the electrokinetic soil remediation. In this study, zeta potential of natural magnetite was studied by conducting electrophoretic mobility measurements in single and binary solution systems. It was shown that adsorption of charged species of Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+), and Cd(2+) and precipitation of their hydroxides at the mineral surface are dominant processes in the charging of the surface in high alkaline suspensions. Taking Pb(2+) as an example, three different mechanisms were proposed for its effect on the surface charge: if pH<5, competitive adsorption with H(3)O(+); if 5surface precipitation; and if pH>6, precipitation of heavy metal hydroxides prevails. Oxalate anion changed the associated surface charge by neutralizing surface positive charges by complexing with iron at the surface, and ultimately reversed the surface to a negative zeta potential. Therefore the adsorption ability of heavy metal ions ultimately changed in the presence of oxalate ion. The changes in the zeta potentials of the magnetite suspensions with solution pH before and after adsorption were utilized to estimate the adsorption ability of heavy metal ions. The mechanisms for heavy metals and oxalate adsorption on magnetite were discussed in the view of the experimental results and published data. PMID:16707134

  5. Simple synthesis of functionalized superparamagnetic magnetite/silica core/shell nanoparticles and their application as magnetically separable high-performance biocatalysts

    SciTech Connect

    Lee, Jinwoo; Lee, Youjin; Youn, Jongkyu; Na, Hyon Bin; Yu, Taekyung; Kim, Hwan O.; Lee, Sang-mok; Koo, Yoon-mo; Kwak, Ja Hun; Park, Hyun-Gyu; Chang, Ho Nam; Hwang, Misun; Park, Je-Geun; Kim, Jungbae; Hyeon, Taeghwan

    2008-01-01

    We report on the facile large-scale synthesis of magnetite@silica core-shell nanoparticles by a simple addition of tetraethyl orthosilicate (TEOS) into reverse micelles during the formation of uniformly-sized magnetite nanoparticles. The size of magnetic core was determined by the ratio of solvent and surfactant in reverse micelle solution while the thickness of silica shell could be easily controlled by adjusting the amount of added TEOS. Amino group functional groups were grafted to the magnetic nanoparticles, and crosslinked enzyme clusters (CEC) were fabricated on the surface of magnetite@silica nanoparticles. The resulting hybrid materials of magnetite and CEC were magnetically separable, highly active, and stable enough to show no decrease of enzyme activity under rigorous shaking for more than 15 days.

  6. Magnetite mineral nanoparticles synthesized naturally in an iron ore deposit

    NASA Astrophysics Data System (ADS)

    Rivas-Sanchez, M. L.; Alva-Valdivia, L. M.

    2013-05-01

    We performed a mineralogical characterization and mineral magnetism study of the Peña Colorada iron ore, Mexico. The ore is formed partly by intergranular magnetite intergrowed with berthierine (Fe,Mg,Al)6(Si,Al)4O10(OH)8. The magnetite nanoparticles are forming aggregates of wide grain size spectra, from micro to nanometer scale. The smallest aggregates are formed by magnetite nanoparticles 2 to 30 grain size range, showing unusual physical and chemical behavior. The continuous agglomeration of nanoparticles formed more denser and compact magnetite microparticles. A magnetite concentrate to micrometric scale was reduced and divided into distinct range sizes: 85-56 μm, 56-30 μm, 30-22 μm, 22-15 μm, 15-10 μm, 10-7 μm and 7-1 μm. Nanometric-scale magnetite 2-30 nm was identified by using high resolution Transmission Electron Microscopy (HRTEM). The magnetite and minerals associated were characterized by X-ray diffraction, transmitted and reflected light polarization, microscope and electron probe X-ray micro-analyzer, differential thermal analysis, gravimetric thermal analysis, and high-resolution transmission electron microscopy. Besides, results of Mössbauer spectroscopy, frequency-dependent magnetic susceptibility, isothermal remanent magnetization and magnetic susceptibility versus temperature were important in the research related to the origin of this deposit. To study magnetite nanoparticles, agglomeration processes and temperature effect implications, we developed an experimental process to re-create the environmental conditions that originated this nanoparticles. These processes start with direct precipitation to synthesize magnetite nanoparticles through a thermal and dehydration treatment of the berthierine base mineral, using diverse temperature ranges, from 360 °C to 750 °C and treatment time of two hours. This process allowed the nucleation and crystalline growth of a high number of magnetite nano-crystals with average size of 2 to 6 nm

  7. Did the massive magnetite "lava flows" of El Laco (Chile) form by magmatic or hydrothermal processes? New constraints from magnetite composition by LA-ICP-MS

    NASA Astrophysics Data System (ADS)

    Dare, Sarah A. S.; Barnes, Sarah-Jane; Beaudoin, Georges

    2015-06-01

    The El Laco magnetite deposits consist of more than 98 % magnetite but show field textures remarkably similar to mafic lava flows. Therefore, it has long been suggested that they represent a rare example of an effusive Fe oxide liquid. Field and petrographic evidence, however, suggest that the magnetite deposits represent replacement of andesite flows and that the textures are pseudomorphs. We determined the trace element content of magnetite by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from various settings at El Laco and compared them with magnetite from both igneous and hydrothermal environments. This new technique allows us to place constraints on the conditions under which magnetite in these supposed magnetite "lava flows" formed. The trace element content of magnetite from the massive magnetite samples is different to any known magmatic magnetite, including primary magnetite phenocrysts from the unaltered andesite host rocks at El Laco. Instead, the El Laco magnetite is most similar in composition to hydrothermal magnetite from high-temperature environments (>500 °C), such as iron oxide-copper-gold (IOCG) and porphyry-Cu deposits. The magnetite trace elements from massive magnetite are characterised by (1) depletion in elements considered relatively immobile in hydrothermal fluids (e.g. Ti, Al, Cr, Zr, Hf and Sc); (2) enrichment in elements that are highly incompatible with magmatic magnetite (rare earth elements (REE), Si, Ca, Na and P) and normally present in very low abundance in magmatic magnetite; (3) high Ni/Cr ratios which are typical of magnetite from hydrothermal environments; and (4) oscillatory zoning of Si, Ca, Mg, REE and most high field strength elements, and zoning truncations indicating dissolution, similar to that formed in hydrothermal Fe skarn deposits. In addition, secondary magnetite in altered, brecciated host rock, forming disseminations and veins, has the same composition as magnetite from the massive

  8. Growth of nano-particles of Al{sub 2}O{sub 3}, AlN and iron oxide with different crystalline phases in a thermal plasma reactor

    SciTech Connect

    Kulkarni, Naveen V.; Karmakar, Soumen; Banerjee, Indrani; Sahasrabudhe, S.N.; Das, A.K.; Bhoraskar, S.V.

    2009-03-05

    The paper presents the experimental results showing that the crystalline phase of the nano-particles, synthesized in a DC transferred arc thermal plasma reactor, critically depend on the operating pressure in the reaction zone. The paper reports about the changes in crystalline phases of three different compounds namely: aluminium oxide (Al{sub 2}O{sub 3}), aluminium nitride (AlN) and iron oxide (Fe{sub x}O{sub y}) synthesized at 760 Torr and 500 Torr of operating pressures. The major outcome of the present work is that the phases having higher defect densities are more probable to form at the sub-atmospheric operating pressures. The variations in the crystalline structures are discussed on the basis of the change in the temperature during the nucleation process, prevailing at the boundary of the plasma, on account of the ambient pressures. The as-synthesized nano-particles were examined by X-ray diffraction analysis and transmission electron microscopy. In addition, the confirmatory analysis of the crystalline phases of iron oxides was carried out with the help of Moessbauer spectroscopy.

  9. Functional titanium oxide nano-particles as electron lifetime, electrical conductance enhancer, and long-term performance booster in quasi-solid-state electrolyte for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Lue, Shingjiang Jessie; Wu, Yun-Ling; Tung, Yung-Liang; Shih, Chao-Ming; Wang, Yi-Chun; Li, Jun-Ruei

    2015-01-01

    This research investigates the design of a quasi-solid-state electrolyte for improving the photovoltaic efficiency and long-term performance stability of dye-sensitized solar cells (DSSCs). In this study, agarose gel and titanium oxide (TiO2) nano-particles are incorporated into an iodine/iodide electrolyte solution in a 1-methyl-2-pyrrolidinone (NMP)/3-methoxypropionitrile (MPN) solvent mixture to fabricate quasi-solid-state electrolytes for 2.0-cm2 DSSCs. The electrolyte also contains an ionic liquid, 1-methyl-3-propylimidazolium iodide, and a co-additive, 1-methylbenzimidazole. The negatively charged TiO2 nano-particles exhibit an anatase crystal structure. Without agarose and TiO2, the control cell's photovoltaic efficiency drops by more than 50% over 2400 h of aging due to a significant decrease in the short-circuit current. Incorporating 1% agarose into the electrolyte not only enhances the retention of the solvent but also maintains the short-circuit current. Furthermore, adding 0.5% TiO2 to 1% agarose electrolyte provides sufficient ion and electron transfer routes and improves the fill factor of the corresponding DSSC. The photoconversion efficiency of the agarose/TiO2-containing DSSC monotonically increases from an initial value of 5.08% to 6.48% within 2400 h. The improved cell efficiency is correlated to the longer electron lifetime in the DSSC, higher ion diffusivity, and the smaller electrical resistance of the electrolyte.

  10. Controlled cobalt doping in biogenic magnetite nanoparticles

    PubMed Central

    Byrne, J. M.; Coker, V. S.; Moise, S.; Wincott, P. L.; Vaughan, D. J.; Tuna, F.; Arenholz, E.; van der Laan, G.; Pattrick, R. A. D.; Lloyd, J. R.; Telling, N. D.

    2013-01-01

    Cobalt-doped magnetite (CoxFe3 −xO4) nanoparticles have been produced through the microbial reduction of cobalt–iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe2+ site with Co2+, with up to 17 per cent Co substituted into tetrahedral sites. PMID:23594814

  11. Magnetite morphology and life on Mars.

    PubMed

    Buseck, P R; Dunin-Borkowski, R E; Devouard, B; Frankel, R B; McCartney, M R; Midgley, P A; Pósfai, M; Weyland, M

    2001-11-20

    Nanocrystals of magnetite (Fe(3)O(4)) in a meteorite from Mars provide the strongest, albeit controversial, evidence for the former presence of extraterrestrial life. The morphological and size resemblance of the crystals from meteorite ALH84001 to crystals formed by certain terrestrial bacteria has been used in support of the biological origin of the extraterrestrial minerals. By using tomographic and holographic methods in a transmission electron microscope, we show that the three-dimensional shapes of such nanocrystals can be defined, that the detailed morphologies of individual crystals from three bacterial strains differ, and that none uniquely match those reported from the Martian meteorite. In contrast to previous accounts, we argue that the existing crystallographic and morphological evidence is inadequate to support the inference of former life on Mars. PMID:11717421

  12. Magnetite morphology and life on Mars

    PubMed Central

    Buseck, Peter R.; Dunin-Borkowski, Rafal E.; Devouard, Bertrand; Frankel, Richard B.; McCartney, Martha R.; Midgley, Paul A.; Pósfai, Mihály; Weyland, Matthew

    2001-01-01

    Nanocrystals of magnetite (Fe3O4) in a meteorite from Mars provide the strongest, albeit controversial, evidence for the former presence of extraterrestrial life. The morphological and size resemblance of the crystals from meteorite ALH84001 to crystals formed by certain terrestrial bacteria has been used in support of the biological origin of the extraterrestrial minerals. By using tomographic and holographic methods in a transmission electron microscope, we show that the three-dimensional shapes of such nanocrystals can be defined, that the detailed morphologies of individual crystals from three bacterial strains differ, and that none uniquely match those reported from the Martian meteorite. In contrast to previous accounts, we argue that the existing crystallographic and morphological evidence is inadequate to support the inference of former life on Mars. PMID:11717421

  13. Refractory Behaviors of Magnetite-Kaolin Bricks

    NASA Astrophysics Data System (ADS)

    Adeosun, S. O.; Akpan, E. I.; Gbenebor, O. P.; Taiwo, O. O.; Eke, I. J.

    2016-09-01

    In this work, the suitability of using kaolin-magnetite-plastic clay to produce refractory bricks has been experimentally explored. Thirty bricks of different compositions were produced and fired at 1200°C. The density, shrinkage moisture content, loss on ignition, porosity and permeability of the bricks were examined. Results show that the bricks remained stable during firing and thus possess good insulating characteristics. The highest (2.23 g/cm3) and lowest (2.00 g/cm3) bulk densities obtained in this study are higher than the highest bulk density reported for Al dross-filled refractories (1.23 g/cm3). The bricks also possessed very low effective moisture content (10-23%) and very high compression modulus (16-100 MPa) desirable in insulating refractory bricks with high resistance to abrasion.

  14. Verwey transition in single magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Mottaghizadeh, A.; Wang, H.; Ulysse, C.; Zimmers, A.; Rebuttini, V.; Pinna, N.; Aubin, H.

    2014-08-01

    We present a tunnel spectroscopy study of the electronic spectrum of single magnetite Fe3O4 nanoparticles trapped between nanometer-spaced electrodes. The Verwey transition is clearly identified in the current-voltage characteristics where we find that the transition temperature is electric field dependent. The data show the presence of localized states at high energy, ɛ ˜0.6 eV, which can be attributed to polaron states. At low energy, the density of states (DOS) is suppressed at the approach of the Verwey transition. Below the Verwey transition, a gap, Δ ˜300 meV, is observed in the spectrum. In contrast, no gap is observed in the high temperature phase, implying that electronic transport in this phase is possibly due to polaron hopping with activated mobility.

  15. A comparison between acoustic properties and heat effects in biogenic (magnetosomes) and abiotic magnetite nanoparticle suspensions

    NASA Astrophysics Data System (ADS)

    Józefczak, A.; Leszczyński, B.; Skumiel, A.; Hornowski, T.

    2016-06-01

    Magnetic nanoparticles show unique properties and find many applications because of the possibility to control their properties using magnetic field. Magnetic nanoparticles are usually synthesized chemically and modification of the particle surface is necessary. Another source of magnetic nanoparticles are various magnetotactic bacteria. These biogenic nanoparticles (magnetosomes) represent an attractive alternative to chemically synthesized iron oxide particles because of their unique characteristics and a high potential for biotechnological and biomedical applications. This work presents a comparison between acoustic properties of biogenic and abiotic magnetite nanoparticle suspensions. Experimental studies have shown the influence of a biological membrane on the ultrasound properties of magnetosomes suspension. Finally the heat effect in synthetic and biogenic magnetite nanoparticles is also discussed. The experimental study shows that magnetosomes present good heating efficiency.

  16. LA-ICP-MS of magnetite: Methods and reference materials

    USGS Publications Warehouse

    Nadoll, P.; Koenig, A.E.

    2011-01-01

    Magnetite (Fe3O4) is a common accessory mineral in many geologic settings. Its variable geochemistry makes it a powerful petrogenetic indicator. Electron microprobe (EMPA) analyses are commonly used to examine major and minor element contents in magnetite. Laser ablation ICP-MS (LA-ICP-MS) is applicable to trace element analyses of magnetite but has not been widely employed to examine compositional variations. We tested the applicability of the NIST SRM 610, the USGS GSE-1G, and the NIST SRM 2782 reference materials (RMs) as external standards and developed a reliable method for LA-ICP-MS analysis of magnetite. LA-ICP-MS analyses were carried out on well characterized magnetite samples with a 193 nm, Excimer, ArF LA system. Although matrix-matched RMs are sometimes important for calibration and normalization of LA-ICP-MS data, we demonstrate that glass RMs can produce accurate results for LA-ICP-MS analyses of magnetite. Cross-comparison between the NIST SRM 610 and USGS GSE-1G indicates good agreement for magnetite minor and trace element data calibrated with either of these RMs. Many elements show a sufficiently good match between the LA-ICP-MS and the EMPA data; for example, Ti and V show a close to linear relationship with correlation coefficients, R2 of 0.79 and 0.85 respectively. ?? 2011 The Royal Society of Chemistry.

  17. Magnetite/poly(alkylcyanoacrylate) (core/shell) nanoparticles as 5-Fluorouracil delivery systems for active targeting.

    PubMed

    Arias, José L; Gallardo, Visitación; Ruiz, M A Adolfina; Delgado, Angel V

    2008-05-01

    In this article, a reproducible emulsion polymerization process is described to prepare core/shell colloidal nanospheres, loaded with 5-Fluorouracil, and consisting of a magnetic core (magnetite) and a biodegradable polymeric shell [poly(ethyl-2-cyanoacrylate), poly(butylcyanoacrylate), poly(hexylcyanoacrylate), or poly(octylcyanoacrylate)]. The heterogeneous structure of these carriers can confer them both the possibility of being used as drug delivery systems and the responsiveness to external magnetic fields, allowing an active drug targeting without a concurrent systemic distribution. Zeta potential determinations as a function of ionic strength showed that the surface behaviour of the core/shell particles is similar to that of pure cyanoacrylate particles. The first magnetization curve of both magnetite and magnetite/polymer particles demonstrated that the polymer shell reduces the magnetic responsiveness of the particles, but keeps unchanged their ferrimagnetic character. Two drug loading mechanisms were studied: absorption or entrapment in the polymeric network, and surface adsorption. We found that the acidity of the medium had significant effects on the drug absorption per unit mass of polymer, and needs to be controlled to avoid formation of macroaggregates and to reach significant 5-Fluorouracil absorption. The type of polymer and the drug concentration are also main factors determining the drug incorporation to the core/shell particles. 5-Fluorouracil release evaluations showed a biphasic profile affected by the type of polymeric shell, the type of drug incorporation and the amount of drug loaded.

  18. Synthesis, performance, and modeling of immobilized nano-sized magnetite layer for phosphate removal.

    PubMed

    Zach-Maor, Adva; Semiat, Raphael; Shemer, Hilla

    2011-05-15

    A homogeneous layer of nano-sized magnetite particles (<4 nm) was synthesized by impregnation of modified granular activated carbon (GAC) with ferric chloride, for effective removal of phosphate. A proposed mechanism for the modification and formation of magnetite onto the GAC is specified. BET results showed a significant increase in the surface area of the matrix following iron loading, implying that a porous nanomagnetite layer was formed. Batch adsorption experiments revealed high efficiency of phosphate removal, by the newly developed adsorbent, attaining maximum adsorption capacity of 435 mg PO(4)/g Fe (corresponding to 1.1 mol PO(4)/mol Fe(3)O(4)). It was concluded that initially phosphate was adsorbed by the active sites on the magnetite surface, and then it diffused into the interior pores of the nanomagnetite layer. It was demonstrated that the latter is the rate-determining step for the process. Innovative correlation of the diffusion mechanism with the unique adsorption properties of the synthesized adsorbent is presented.

  19. Porphyrin-magnetite nanoconjugates for biological imaging

    PubMed Central

    2011-01-01

    Background The use of silica coated magnetic nanoparticles as contrast agents has resulted in the production of highly stable, non-toxic solutions that can be manipulated via an external magnetic field. As a result, the interaction of these nanocomposites with cells is of vital importance in understanding their behaviour and biocompatibility. Here we report the preparation, characterisation and potential application of new "two-in-one" magnetic fluorescent nanocomposites composed of silica-coated magnetite nanoparticles covalently linked to a porphyrin moiety. Method The experiments were performed by administering porphyrin functionalised silica-coated magnetite nanoparticles to THP-1 cells, a human acute monocytic leukaemia cell line. Cells were cultured in RPMI 1640 medium with 25 mM HEPES supplemented with heat-inactivated foetal bovine serum (FBS). Results We have synthesised, characterised and analysed in vitro, a new multimodal (magnetic and fluorescent) porphyrin magnetic nanoparticle composite (PMNC). Initial co-incubation experiments performed with THP-1 macrophage cells were promising; however the PMNC photobleached under confocal microscopy study. β-mercaptoethanol (β-ME) was employed to counteract this problem and resulted not only in enhanced fluorescence emission, but also allowed for elongated imaging and increased exposure times of the PMNC in a cellular environment. Conclusion Our experiments have demonstrated that β-ME visibly enhances the emission intensity. No deleterious effects to the cells were witnessed upon co-incubation with β-ME alone and no increases in background fluorescence were recorded. These results should present an interest for further development of in vitro biological imaging techniques. PMID:21477294

  20. Comparative evaluation of the three different surface treatments – conventional, laser and Nano technology methods in enhancing the surface characteristics of commercially pure titanium discs and their effects on cell adhesion: An in vitro study

    PubMed Central

    Vignesh; Nayar, Sanjna; Bhuminathan; Mahadevan; Santhosh, S.

    2015-01-01

    The surface area of the titanium dental implant materials can be increased by surface treatments without altering their shape and form, thereby increasing the biologic properties of the biomaterial. A good biomaterial helps in early cell adhesion and cell signaling. In this study, the commercially pure titanium surfaces were prepared to enable machined surfaces to form a control material and to be compared with sandblasted and acid-etched surfaces, laser treated surfaces and titanium dioxide (20 nm) Nano-particle coated surfaces. The surface elements were characterized. The biocompatibility was evaluated by cell culture in vitro using L929 fibroblasts. The results suggested that the titanium dioxide Nano-particle coated surfaces had good osteoconductivity and can be used as a potential method for coating the biomaterial. PMID:26015762

  1. Comparative evaluation of the three different surface treatments - conventional, laser and Nano technology methods in enhancing the surface characteristics of commercially pure titanium discs and their effects on cell adhesion: An in vitro study.

    PubMed

    Vignesh; Nayar, Sanjna; Bhuminathan; Mahadevan; Santhosh, S

    2015-04-01

    The surface area of the titanium dental implant materials can be increased by surface treatments without altering their shape and form, thereby increasing the biologic properties of the biomaterial. A good biomaterial helps in early cell adhesion and cell signaling. In this study, the commercially pure titanium surfaces were prepared to enable machined surfaces to form a control material and to be compared with sandblasted and acid-etched surfaces, laser treated surfaces and titanium dioxide (20 nm) Nano-particle coated surfaces. The surface elements were characterized. The biocompatibility was evaluated by cell culture in vitro using L929 fibroblasts. The results suggested that the titanium dioxide Nano-particle coated surfaces had good osteoconductivity and can be used as a potential method for coating the biomaterial.

  2. Comparative evaluation of the three different surface treatments - conventional, laser and Nano technology methods in enhancing the surface characteristics of commercially pure titanium discs and their effects on cell adhesion: An in vitro study.

    PubMed

    Vignesh; Nayar, Sanjna; Bhuminathan; Mahadevan; Santhosh, S

    2015-04-01

    The surface area of the titanium dental implant materials can be increased by surface treatments without altering their shape and form, thereby increasing the biologic properties of the biomaterial. A good biomaterial helps in early cell adhesion and cell signaling. In this study, the commercially pure titanium surfaces were prepared to enable machined surfaces to form a control material and to be compared with sandblasted and acid-etched surfaces, laser treated surfaces and titanium dioxide (20 nm) Nano-particle coated surfaces. The surface elements were characterized. The biocompatibility was evaluated by cell culture in vitro using L929 fibroblasts. The results suggested that the titanium dioxide Nano-particle coated surfaces had good osteoconductivity and can be used as a potential method for coating the biomaterial. PMID:26015762

  3. Magnetite as Possible Template for the Synthesis of Chiral Organics in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.

    2014-01-01

    The main goal of the Japanese Aerospace Ex-ploration Agency (JAXA) Hayabusa-2 mission is to visit and return to Earth samples of a C-type asteroid (162173) 1999 JU3 in order to understand the origin and nature of organic materials in the Solar System. Life on Earth shows preference towards the set of organics with particular spatial arrangements, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life 'determines' to use the left- (L-) form over the right- (D-) form of amino acids, resulting in a L-enantiomeric excess (ee). Recent studies have shown that L-ee is found within the alpha-methyl amino acids in meteorites [1, 2], which are amino acids with rare terrestrial occurrence, and thus point towards a plausible abiotic origin for ee. One of the proposed origins of chiral asymmetry of amino acids in meteorites is their formation with the presence of asymmetric catalysts [3]. The catalytic mineral grains acted as a surface at which nebular gases (CO, H2 and NH3) were allowed to condense and react through Fisher Tropsch type (FTT) syntheses to form the organics observed in meteorites [4]. Magnetite is shown to be an effective catalyst of the synthesis of amino acids that are commonly found in meteorites [5]. It has also taken the form as spiral magnetites (a.k.a. 'plaquettes'), which were found in various carbonaceous chondrites (CCs), including C2s Tagish Lake and Esseibi, CI Orgueil, and CR chondrites [e.g., 6, 7, 8]. In addition, L-ee for amino acids are common in the aqueously altered CCs, as opposed to the unaltered CCs [1]. It seems possible that the synthesis of amino acids with chiral preferences is correlated to the alteration process experienced by the asteroid parent body, and related to the configuration of spiral magnetite catalysts. Since C-type asteroids are considered to be enriched in organic matter, and the spectral data of 1999 JU3 indicates a certain de-gree of aqueous alteration [9], the Hayabusa-2 mission serves as

  4. Trace elements in magnetite from massive iron oxide-apatite deposits indicate a combined formation by igneous and magmatic-hydrothermal processes

    NASA Astrophysics Data System (ADS)

    Knipping, Jaayke L.; Bilenker, Laura D.; Simon, Adam C.; Reich, Martin; Barra, Fernando; Deditius, Artur P.; Wälle, Markus; Heinrich, Christoph A.; Holtz, François; Munizaga, Rodrigo

    2015-12-01

    Iron oxide-apatite (IOA) deposits are an important source of iron and other elements (e.g., REE, P, U, Ag and Co) vital to modern society. However, their formation, including the namesake Kiruna-type IOA deposit (Sweden), remains controversial. Working hypotheses include a purely magmatic origin involving separation of an Fe-, P-rich, volatile-rich oxide melt from a Si-rich silicate melt, and precipitation of magnetite from an aqueous ore fluid, which is either of magmatic-hydrothermal or non-magmatic surface or metamorphic origin. In this study, we focus on the geochemistry of magnetite from the Cretaceous Kiruna-type Los Colorados IOA deposit (∼350 Mt Fe) located in the northern Chilean Iron Belt. Los Colorados has experienced minimal hydrothermal alteration that commonly obscures primary features in IOA deposits. Laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) transects and electron probe micro-analyzer (EPMA) wavelength-dispersive X-ray (WDX) spectrometry mapping demonstrate distinct chemical zoning in magnetite grains, wherein cores are enriched in Ti, Al, Mn and Mg. The concentrations of these trace elements in magnetite cores are consistent with igneous magnetite crystallized from a silicate melt, whereas magnetite rims show a pronounced depletion in these elements, consistent with magnetite grown from an Fe-rich magmatic-hydrothermal aqueous fluid. Further, magnetite grains contain polycrystalline inclusions that re-homogenize at magmatic temperatures (>850 °C). Smaller inclusions (<5 μm) contain halite crystals indicating a saline environment during magnetite growth. The combination of these observations are consistent with a formation model for IOA deposits in northern Chile that involves crystallization of magnetite microlites from a silicate melt, nucleation of aqueous fluid bubbles on magnetite surfaces, and formation and ascent of buoyant fluid bubble-magnetite aggregates. Decompression of the fluid-magnetite aggregate

  5. Evidence for a relationship between hydrocarbons and authigenic magnetite

    NASA Astrophysics Data System (ADS)

    Elmore, R. D.; Engel, M. H.; Crawford, L.; Nick, K.; Imbus, S.; Sofer, Z.

    1987-01-01

    Establishing a relationship between hydrocarbon migration and the precipitation of authigenic magnetite in sedimentary rocks is of significant interest with respect to (1) elucidating mechanisms for remagnetization and establishing the origin of secondary magnetizations residing in magnetite, (2) developing a method to date hydrocarbon migration events by determining the time of remanence acquisition by palaeomagnetic methods, and (3) evaluating whether searching for anomalous concentrations of diagenetic magnetic minerals and/or aeromagnetic anomalies is justified as a relatively inexpensive exploration tool. The direct association of hydrocarbon migration and the precipitation of authigenic magnetite has, however, not been established. In this paper we report palaeomagnetic, rock magnetic, petrographic and geochemical results of a study of samples from Permian spelebthems and gilsonite found in the Ordovician Arbuckle Group in southern Oklahoma. The results indicate that there is a genetic relationship between hydrocarbon migration and the precipitation of authigenic magnetite.

  6. Bioinspired magnetite formation from a disordered ferrihydrite-derived precursor.

    PubMed

    Dey, Archan; Lenders, Jos J M; Sommerdijk, Nico A J M

    2015-01-01

    We show that by reacting ferrihydrite (FeH) with Fe((II)) ions and subsequently increasing the pH, magnetite is formed through a multi-step nucleation process mediated by monodisperse FeH-Fe((II)) primary particles. The interaction of these primary particles with a transient green rust phase leads to the formation of smaller secondary particles which form the feedstock for magnetite formation. Surprisingly, the presence of a polypeptide additive prevents the formation of green rust as an Fe((II))-rich intermediate phase, and leads to the formation of amorphous aggregates of FeH-Fe((II)) particles which subsequently transform into the final magnetite nanocrystals. The observation of multiple transitions and the involvement of disordered precursor phases in this bioinspired crystallization route is important for our understanding of the nucleation of magnetite in geological and biological environments, and may lead to new approaches in the sustainable synthesis of this technologically important mineral.

  7. Magnetite Plaquettes Provide an Extraterrestrial Source of Asymmetric Components

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.; Martinez, J. E.

    2015-01-01

    Molecular selectivity is a crucial criterion for life. A possible abiotic mechanism that can produce chiral asymmetry in meteoritic amino acids is their formation with the presence of asymmetric catalysts. Magnetite (Fe3O4), a common mineral in some carbonaceous chondrites (CCs), has been shown to be an effective catalyst for the formation of amino acids that are commonly found in these meteorites. Magnetite sometimes takes the form of plaquettes that consist of barrel-shaped stacks of magnetite disks that resemble a spiral. However, a widely accepted description of the internal morphology of this particular magnetite form is still lacking, which is necessary in order to confirm or disprove the spiral configuration.

  8. The Search for 60Fe in Secondary Magnetite and Fayalite

    NASA Astrophysics Data System (ADS)

    Donohue, P. H.; Huss, G. R.; Nagashima, K.; Telus, M.

    2016-08-01

    Secondary phases produced by aqueous alteration may record fossil iron-60 signatures and also avoid issues with redistribution of Fe and Ni. We investigated fayalite and magnetite from Semarkona and Kaba and will report our results.

  9. Electrophoretic mobility of magnetite particles in high temperature water

    SciTech Connect

    Vidojkovic, Sonja; Rodriguez-Santiago, V; Fedkin, Mark V.; Wesolowski, David J; Lvov, Serguei N.

    2011-01-01

    Magnetite(Fe3O4) isoneofthemostcommonoxidesformingdepositsandparticulatephasesin industrialhightemperaturewatercircuits.Itscolloidalcharacteristicsplayaprincipalroleinthe mechanismofdepositformationandcanbeusedascontrollingfactorstopreventorminimizedeposit formationanddamageofindustrialpipelinesduetounder-depositcorrosion.Inthisstudy,ahigh temperatureparticleelectrophoresistechniquewasemployedtomeasurethezetapotentialatthe magnetite/waterinterface the parameterthatcontrolscolloidalstabilityofparticles,theiraggrega- tion, anddeposition.Themeasurementsweremadeattemperaturesupto200 1C overawiderangeofpH. The isoelectricpointsofmagnetite,atwhichthedepositionofparticlesisincreased,weredeterminedatpH 6.35, 6.00,5.25,and5.05fortemperatures25,100,150,and200 1C, respectively.Theobserved temperaturedependenceofzetapotentialandtheisoelectricpHpointofmagnetitecanhelptoexplain the extentofinteractionsbetweenthecolloidalparticlesandthesteelwallsurfacesunderhydro- thermalconditions,andindicatemethodsforcontrollingandmitigatingoxidedepositioninhigh temperaturewatercycles.

  10. Controls on Soluble Pu Concentrations in PuO2/Magnetite Suspensions

    SciTech Connect

    Felmy, Andrew R.; Moore, Dean A.; Pearce, Carolyn I.; Conradson, Steven D.; Qafoku, Odeta; Buck, Edgar C.; Rosso, Kevin M.; Ilton, Eugene S.

    2012-11-06

    Time-dependent reduction of PuO2(am) was studied over a range of pH values in the presence of aqueous Fe(II) and magnetite (Fe3O4) nanoparticles. At early time frames (up to 56 days) very little aqueous Pu was mobilized from PuO2(am), even though measured pH and redox potentials, coupled to equilibrium thermodynamic modeling indicated the potential for significant reduction of PuO2(am) to relatively soluble Pu(III). Introduction of Eu(III) or Nd(III) to the suspensions as competitive cations to displace possible sorbed Pu(III) resulted in the release of significant concentrations of aqueous Pu. However, the similarity of aqueous Pu concentrations that resulted from the introduction of Eu(III)/Nd(III) to suspensions with and without magnetite indicated that the Pu was displaced from the PuO2(am), not from magnetite. The fact that soluble forms of Pu can be displaced from the surface of PuO2(am) represents a potential, but previously unidentified, source of Pu to aqueous solution or subsurface groundwaters.

  11. Adsorption behavior of some aromatic compounds on hydrophobic magnetite for magnetic separation.

    PubMed

    Sasaki, Takahiro; Tanaka, Shunitz

    2011-11-30

    In this study, a hydrophobic magnetite coated with an alkyl chain or a phenyl group on the surface was prepared and used as an adsorbent to investigate the adsorption behavior of aromatic compounds having various values of log P(ow) (phenol 1.46, benzonitrile 1.56, nitrobenzene 1.86, benzene 2.13, toluene 2.73, chlorobenzene 2.84 and o-dichlorobenzene 3.38) onto hydrophobic magnetite. The hydrophobic magnetites were modified with stearic acid and phenyltrimethoxysilane, and the modification amounts were 9.84 × 10(-3) and 4.17 × 10(-2)mmol/g, respectively. The aromatic compounds used in this study were divided into 3 groups depending on the log P(ow): 1magnetite at an initial concentration of 100 ppm were 3.62 × 10(-3) (nitrobenzene), 1.92 × 10(-2) (phenol), 1.13 × 10(-1) (chlorobenzene), 2.42 × 10(-1) (benzene), and 3.10 × 10(-1)mmol/g (dichlorobenzene), respectively. This indicates that the adsorption behaviors depend on the strength of hydrophobicity of aromatic compounds. The adsorption mechanism for 2

  12. In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

    NASA Astrophysics Data System (ADS)

    Wang, Yongliang; Li, Baoqiang; Zhou, Yu; Jia, Dechang

    2009-09-01

    Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS-Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4 and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3 and hydroxyapatite.

  13. Effect of cation trapping on thermal stability of magnetite nanoparticles.

    PubMed

    Pati, S S; Philip, John

    2014-06-01

    We investigate the effect of sodium trapping on thermal stability of magnetite (Fe3O4) nanoparticles. The pure magnetite nanoparticles incubated in sodium hydroxide solutions and subsequently washed with water to remove the excess sodium. The amount of sodium in magnetite is measured using atomic absorption spectroscopy. The size distribution obtained from Small angle X-ray scattering measurements show that particles are fairly monodisperse. The FTIR spectra of nanoparticles show transmission bands at 441 and 611 cm(-1) are due to the symmetric stretching vibrations (v) of Fe-O in octahedral and tetrahedral sites respectively. With 500 ppm of sodium ions (Na+) in magnetite, the cubic ferrite structure of maghemite (gamma-Fe2O3) to hexagonal hematite (alpha-Fe2O3) phase transition is enhanced by -150 degrees C in air. The Rietveld analysis of sodium doped magnetite nanoparticles show that above 99% of metastable gamma-Fe2O3 is converted to a thermodynamically stable alpha-Fe2O3 after air annealing at 700 degrees C. A decrease in enthalpy observed in doped magnetite unambiguously confirms that the activation energy for maghemite to hematite transition is increased due to the presence of trapped sodium ions. These results suggest that the trapped cations in ferrite nanoparticles can stabilize them by increasing the activation energy.

  14. The Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K., Jr.

    2012-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.

  15. Magnetite impregnation effects on the sorbent properties of activated carbons and biochars.

    PubMed

    Han, Zhantao; Sani, Badruddeen; Mrozik, Wojciech; Obst, Martin; Beckingham, Barbara; Karapanagioti, Hrissi K; Werner, David

    2015-03-01

    This paper discusses the sorbent properties of magnetic activated carbons and biochars produced by wet impregnation with iron oxides. The sorbents had magnetic susceptibilities consistent with theoretical predictions for carbon-magnetite composites. The high BET surface areas of the activated carbons were preserved in the synthesis, and enhanced for one low surface area biochar by dissolving carbonates. Magnetization decreased the point of zero charge. Organic compound sorption correlated strongly with BET surface areas for the pristine and magnetized materials, while metal cation sorption did not show such a correlation. Strong sorption of the hydrophobic organic contaminant phenanthrene to the activated carbon or biochar surfaces was maintained following magnetite impregnation, while phenol sorption was diminished, probably due to enhanced carbon oxidation. Copper, zinc and lead sorption to the activated carbons and biochars was unchanged or slightly enhanced by the magnetization, and iron oxides also contributed to the composite metal sorption capacity. While a magnetic biochar with 219 ± 3.7 m(2)/g surface area nearly reached the very strong organic pollutant binding capacity of the two magnetic activated carbons, a magnetic biochar with 68 ± 2.8 m(2)/g surface area was the best metal sorbent. Magnetic biochars thus hold promise as more sustainable alternatives to coal-derived magnetic activated carbons.

  16. Effect of dissolved organic matter on the stability of magnetite nanoparticles under different pH and ionic strength conditions.

    PubMed

    Hu, Jun-Dong; Zevi, Yuniati; Kou, Xiao-Ming; Xiao, John; Wang, Xue-Jun; Jin, Yan

    2010-07-15

    Upon release of engineered nanoparticles (NPs) into the subsurface environment, their fate and transport and hence their potential environmental and public health impacts will largely depend on how stable these NPs are as suspended particles in the natural environment. In this study, we systematically examine the effect of humic acid (HA) on surface charge status and aggregation potential of magnetite (Fe(3)O(4)) NPs, selected as a model for metal oxide NPs, over a wide range of solution pH and ionic strength. Through zeta potential (ZP) measurements, we found that HA can adsorb to magnetite particles hence modifying their surface charge status. At low loadings, the presence of HA can induce a shift in the point zero of charge of due to partial neutralization of the positive charges on magnetite NPs. At high loadings, however, HA is capable of completely cover magnetite particles giving rise to a suspension ZP profile similar to its own (observed in presence of 20 mg L(-)(1) HA). These impacts on surface charge correspond well with the observed aggregation behaviors in the absence and presence of HA. From the dynamic light scattering (DLS) measurements, fast aggregation, which is independent of solution chemistry, took place when the pH is close to the point zero charge (PZC) and the ionic strength is above the critical coagulation concentration (CCC). At high ionic strength, a small dose (2 mg L(-)(1)) of HA stabilized the NPs' suspension significantly. This stabilization effect is substantially enhanced with increasing HA concentration. The calculated DLVO (Derjaguin-Landau-Verwey-Overbeek) interaction energy profiles, using experimentally determined values of Hamaker constant, adequately support the experimental observations. The DLVO analysis further reveals the possible presence of secondary energy minima and the possibility of deaggregation of magnetite agglomerates. The complexation of HA-NPs and the HA effects on NPs aggregations were confirmed by atomic

  17. Atomic layer deposition of superparamagnetic and ferrimagnetic magnetite thin films

    SciTech Connect

    Zhang, Yijun; Liu, Ming E-mail: wren@mail.xjtu.edu.cn Ren, Wei E-mail: wren@mail.xjtu.edu.cn; Zhang, Yuepeng; Chen, Xing; Ye, Zuo-Guang E-mail: wren@mail.xjtu.edu.cn

    2015-05-07

    One of the key challenges in realizing superparamagnetism in magnetic thin films lies in finding a low-energy growth way to create sufficiently small grains and magnetic domains which allow the magnetization to randomly and rapidly reverse. In this work, well-defined superparamagnetic and ferrimagnetic Fe{sub 3}O{sub 4} thin films are successfully prepared using atomic layer deposition technique by finely controlling the growth condition and post-annealing process. As-grown Fe{sub 3}O{sub 4} thin films exhibit a conformal surface and poly-crystalline nature with an average grain size of 7 nm, resulting in a superparamagnetic behavior with a blocking temperature of 210 K. After post-annealing in H{sub 2}/Ar at 400 °C, the as-grown α−Fe{sub 2}O{sub 3} sample is reduced to Fe{sub 3}O{sub 4} phase, exhibiting a ferrimagnetic ordering and distinct magnetic shape anisotropy. Atomic layer deposition of magnetite thin films with well-controlled morphology and magnetic properties provides great opportunities for integrating with other order parameters to realize magnetic nano-devices with potential applications in spintronics, electronics, and bio-applications.

  18. Nano-structured and functionalized surfaces for cytocompatibility improvement and bactericidal action.

    PubMed

    Slepicka, Petr; Kasalkova, Nikola Slepickova; Siegel, Jakub; Kolska, Zdenka; Bacakova, Lucie; Svorcik, Vaclav

    2015-11-01

    The field of material surface modification with the aim of biomaterial construction involves several approaches of treatments that allow the preparation of materials, which positively influence adhesion of cells and their proliferation and thus aid and improve tissue formation. Modified materials have a surface composition and morphology intended to interact with biological systems and cellular functions. Not only surface chemistry has an effect on material biological response, surface structures of different morphology can be constructed to guide a desirable biological outcome. Nano-patterned material surfaces have been tested with the aim of how surface geometry and physical properties on a micro- and nano-scale can affect cellular response and influence cell adhesion and proliferation. Biological functionality of solid state substrates was significantly improved by the irradiation of material with plasma discharge or laser treatment. Commonly used "artificial" polymers (e.g. polyethylene (PE), polystyrene (PS), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN)) and biopolymers (e.g. Poly-l-Lactic acid (PLLA), polymethylpentene (PMP)) were treated with aim of biocompatibility improvement. The treatment of polymer/biopolymer substrates leads to formation of ripple or wrinkle-like structures, supported also with heat treatment or other subsequent surface processing. Several types of chemically different substances (e.g. metal or carbon nano-particles, proteins) were grafted onto material surfaces or built into material structures by different processes. Surface physico-chemical properties (e.g. chemistry, charge, morphology, wettability, electrical conductivity, optical and mechanical properties) of treated surfaces were determined. The enhancement of adhesion and proliferation of cells on modified substrates was investigated in vitro. Bactericidal action of noble metal nano-particles (e.g. Au, Ag) on polymers was

  19. XAS signatures of Am(III) adsorbed onto magnetite and maghemite

    NASA Astrophysics Data System (ADS)

    Finck, N.; Radulescu, L.; Schild, D.; Rothmeier, M.; Huber, F.; Lützenkirchen, J.; Rabung, T.; Heberling, F.; Schlegel, M. L.; Dideriksen, K.; Nedel, S.; Geckeis, H.

    2016-05-01

    Trivalent americium was adsorbed on magnetite and maghemite under similar chemical conditions and the local environment probed by EXAFS spectroscopy. In both samples, partially hydrated Am(III) binds the surface but slightly different surface complexes were identified. On Fe3O4, Am(III) forms monomeric tridentate surface complexes similar to that reported for Pu(III) at the (111) surface. In contrast, the lower number of detected Fe atoms may suggest that Am(III) forms monomeric bidentate surface complexes on γ-Fe2O3. Alternatively, the lower Fe coordination number can also be due to the presence of vacancies in maghemite. XPS data imply very similar binding environments for Am at both Fe oxide surfaces.

  20. Electrochemical and spectroscopic evidence on the one-electron reduction of U(VI) to U(V) on magnetite

    SciTech Connect

    Yuan, Ke; Ilton, Eugene S.; Antonio, Mark R.; Li, Zhongrui; Cook, Peter J.; Becker, Udo

    2015-05-19

    Reduction of U(VI) to U(IV) on mineral surfaces has been considered as a one-step two electron process. However, stabilized U(V), with no evidence of U(IV), found in recent studies indicates U(VI) can undergo a one electron reduction to U(V) without further progression to U(IV). We investigated the mechanisms of uranium reduction by reducing U(VI) electrochemically on a magnetite electrode at pH 3.4 . The one electron reduction of U(VI) was first confirmed using the cyclic voltammetry method. Formation of nano-size uranium precipitates on the surface of magnetite at reducing potentials and dissolution of the solids at oxidizing potentials were observed by in situ electrochemical AFM. XPS analysis of the magnetite electrodes polarized in uranium solutions at voltages from 0.1 ~ 0.9 V (vs. Ag/AgCl) showed the presence of only U(V) and U(VI). The highest amount of U(V) relative to U(VI) was prepared at 0.7 V, where the longest average U–Oaxial distance of 2.05 ± 0.01 Å was evident in the same sample revealed by EXAFS analysis. The results demonstrate that the electrochemical reduction of U(VI) on magnetite only yields U(V), even at a potential of 0.9 V, which favors the one-electron reduction mechanism. U(V) did not disproportionate but stabilized on magnetite through precipitation of mixed-valence state U(VI)/U(V) solids.

  1. Nano silver and nano zinc-oxide in surface waters - exposure estimation for Europe at high spatial and temporal resolution.

    PubMed

    Dumont, Egon; Johnson, Andrew C; Keller, Virginie D J; Williams, Richard J

    2015-01-01

    Nano silver and nano zinc-oxide monthly concentrations in surface waters across Europe were modeled at ~6 x 9 km spatial resolution. Nano-particle loadings from households to rivers were simulated considering household connectivity to sewerage, sewage treatment efficiency, the spatial distribution of sewage treatment plants, and their associated populations. These loadings were used to model temporally varying nano-particle concentrations in rivers, lakes and wetlands by considering dilution, downstream transport, water evaporation, water abstraction, and nano-particle sedimentation. Temporal variability in concentrations caused by weather variation was simulated using monthly weather data for a representative 31-year period. Modeled concentrations represent current levels of nano-particle production.Two scenarios were modeled. In the most likely scenario, half the river stretches had long-term average concentrations exceeding 0.002 ng L(-1) nano silver and 1.5 ng L(-1) nano zinc oxide. In 10% of the river stretches, these concentrations exceeded 0.18 ng L(-1) and 150 ng L(-1), respectively. Predicted concentrations were usually highest in July. PMID:25463731

  2. Nano silver and nano zinc-oxide in surface waters - exposure estimation for Europe at high spatial and temporal resolution.

    PubMed

    Dumont, Egon; Johnson, Andrew C; Keller, Virginie D J; Williams, Richard J

    2015-01-01

    Nano silver and nano zinc-oxide monthly concentrations in surface waters across Europe were modeled at ~6 x 9 km spatial resolution. Nano-particle loadings from households to rivers were simulated considering household connectivity to sewerage, sewage treatment efficiency, the spatial distribution of sewage treatment plants, and their associated populations. These loadings were used to model temporally varying nano-particle concentrations in rivers, lakes and wetlands by considering dilution, downstream transport, water evaporation, water abstraction, and nano-particle sedimentation. Temporal variability in concentrations caused by weather variation was simulated using monthly weather data for a representative 31-year period. Modeled concentrations represent current levels of nano-particle production.Two scenarios were modeled. In the most likely scenario, half the river stretches had long-term average concentrations exceeding 0.002 ng L(-1) nano silver and 1.5 ng L(-1) nano zinc oxide. In 10% of the river stretches, these concentrations exceeded 0.18 ng L(-1) and 150 ng L(-1), respectively. Predicted concentrations were usually highest in July.

  3. One-step continuous synthesis of functionalized magnetite nanoflowers

    NASA Astrophysics Data System (ADS)

    Thomas, G.; Demoisson, F.; Chassagnon, R.; Popova, E.; Millot, N.

    2016-04-01

    For the first time, functionalized magnetite nanoparticles (Fe3O4 NPs) that form aggregates with a nanoflower morphology were synthesized using a rapid (11 s) one-step continuous hydrothermal process, which was recently modified, and their application as a T 2 magnetic resonance imaging (MRI) contrast agent was evaluated. The nanoparticles functionalized with 3,4-dihydroxy-L-phenylalanine (LDOPA) or 3,4-dihydroxyhydrocinnamic acid (DHCA) consisted of small crystallites of approximately 15 nm of diameter that assembled to form flower-shaped aggregate structures. The Fe3O4-LDOPA nanoflowers exhibited a high transverse relaxivity, r 2 of 418 ± 10 l mmolFe -1 s-1 at 3 T owing to magnetic dipolar interactions, which is twice as that of the commercial Feridex®/Endorem®. The prepared nanostructures were compared with bare Fe3O4 NPs and citrated Fe3O4 NPs. DHCA, LDOPA, and citric acid (CA) were found to have an anti-oxidizing effect and to influence the crystallite size and the lattice parameter of the NPs. DHCA and LDOPA increased the crystallite size, whereas CA decreased it. Surface modification increased the colloidal stability of NPs as compared to bare NPs. Nanoflower suspensions of Fe3O4-LDOPA NPs were found to be stable in the phosphate-buffered saline, saline medium, and minimal essential medium and formed aggregates of sizes smaller than 120 nm. All samples were found to be superparamagnetic in nature and the highest saturation magnetization was obtained for the Fe3O4-LDOPA samples. These NPs can bind to polymers such as PEG, and to fluorescent and chelating agents owing to the presence of free -NH2 or -COOH groups on the surface of NPs, allowing their use in dual imaging applications.

  4. Uniform mesoporous dye-doped silica nanoparticles decorated with multiple magnetite nanocrystals for simultaneous enhanced magnetic resonance imaging, fluorescence imaging, and drug delivery.

    PubMed

    Lee, Ji Eun; Lee, Nohyun; Kim, Hyoungsu; Kim, Jaeyun; Choi, Seung Hong; Kim, Jeong Hyun; Kim, Taeho; Song, In Chan; Park, Seung Pyo; Moon, Woo Kyung; Hyeon, Taeghwan

    2010-01-20

    Highly versatile nanocomposite nanoparticles were synthesized by decorating the surface of mesoporous dye-doped silica nanoparticles with multiple magnetite nanocrystals. The superparamagnetic property of the magnetite nanocrystals enabled the nanoparticles to be used as a contrast agent in magnetic resonance (MR) imaging, and the dye molecule in the silica framework imparted optical imaging modality. Integrating a multitude of magnetite nanocrystals on the silica surface resulted in remarkable enhancement of MR signal due to the synergistic magnetism. An anticancer drug, doxorubicin (DOX), could be loaded in the pores and induced efficient cell death. In vivo passive targeting and accumulation of the nanoparticles at the tumor sites was confirmed by both T2 MR and fluorescence imaging. Furthermore, apoptotic morphology was clearly detected in tumor tissues of mice treated with DOX loaded nanocomposite nanoparticles, demonstrating that DOX was successfully delivered to the tumor sites and its anticancer activity was retained.

  5. Production Rate of Cosmogenic 10Be in Magnetite

    NASA Astrophysics Data System (ADS)

    Granger, D. E.; Rogers, H. E.; Riebe, C. S.; Lifton, N. A.

    2013-12-01

    Cosmogenic 10Be is widely used for determining exposure ages, soil production rates, and catchment-wide erosion rates. To date, measurements have been almost exclusively in the mineral quartz (SiO2), which is resistant to weathering and easily cleaned of meteoric 10Be contamination. However, this limits the method to quartz-bearing rocks and requires specialized laboratories due to the need for large quantities of hydrofluoric acid (HF). Here, we present initial results for 10Be production in the mineral magnetite (Fe3O4). Magnetite offers several advantages over quartz; it is (1) present in mafic rocks, (2) easily collected in the field, (3) quickly and easily separated in the lab, and (4) digested without HF. In addition, 10Be can be measured in both detrital quartz and magnetite from the same catchment to yield information about the intensity of chemical weathering (Rogers et al., this conference). The 10Be production rate in magnetite relative to quartz was determined for a granitic boulder from Mt. Evans, Colorado, USA. The boulder was crushed and homogenized to facilitate production rate comparisons among various minerals. We separated magnetite using a combination of hand magnets, froth flotation, and a variety of selective chemical dissolutions in dithionite-citrate-bicarbonate solution, 5% nitric acid (HNO3) and 1% HF/HNO3. Six aliquots of magnetite were analyzed for 10Be and compared to quartz. Three aliquots that were not exposed to 1% HF/HNO3 were contaminated with meteoric 10Be, probably associated with residual mica. Three aliquots that were exposed to 1% HF/HNO3 treatments agreed to within 2% measurement uncertainty. Our preliminary results indicate that the relative production rate by mass of 10Be in magnetite and quartz is 0.462 × 0.012. Our results are similar to theoretically predicted values. Recently updated excitation functions for neutron and proton spallation reactions allow us to partition 10Be production in quartz and magnetite among

  6. Iron isotopic fractionation factor between magnetite and hydrous silicic melt

    NASA Astrophysics Data System (ADS)

    Huang, F.; Lundstrom, C. C.

    2006-12-01

    A "thermal migration" experiment was conducted in the piston cylinder to investigate the changes in composition of a wet andesitic bulk composition in a temperature gradient at 0.5 GPa. A homogeneous andesite powder (AGV-1 containing 4 wt.% H2O was sealed in a AuPd double capsule with the hot end at 950°C and the bottom end 350°C for 66 days. The charge changes from 100% melt at the top to the progressively more crystalline with the sequential appearance of apatite, magnetite, amphibole, biotite, plagioclase, quartz, and K-feldspar. We microdrilled 5 samples along the temperature gradient and analyzed these for Fe isotope ratios by double spike MC-ICP-MS at UIUC. Results show that the 100% melt area is depleted in heavy Fe isotopes relative to all more crystalline portions of the experiment (4 samples) with the offset in {δ}^{56/54}FeIRMM of about 1.7‰. This does not appear to reflect Fe loss in the experiment as the Fe content and isotopes mass balance and no detectable Fe was found in the capsule after the experiment. Instead the offset is interpreted to reflect the combination of diffusive fractionation of Fe moving by diffusion and possible equilibrium fractionations between melt and magnetite that occurs throughout the crystalline portion of the experiment. However, both the isotopic fractionation factor between magnetite and melt and the effect of diffusion on Fe isotopes remains unknown. We are currently investigating Fe isotopic fractionation factor between magnetite and melt and effects of melt diffusion on Fe isotopes. To assess diffusion, we will microdrill and analyze melt-melt diffusion couples from Lundstrom(G-Cubed, 2003). To assess magnetite-melt fractionation, we have begun piston cylinder experiments at 0.5 GPa and 800°C using a starting material synthesized based on the melt composition within the thermal migration experiment. Initial experiments produce a layer of 100% melt on top of a 2-phase mush of magnetite-melt. This will allow

  7. Abnormal elastic and vibrational behaviors of magnetite at high pressures.

    PubMed

    Lin, Jung-Fu; Wu, Junjie; Zhu, Jie; Mao, Zhu; Said, Ayman H; Leu, Bogdan M; Cheng, Jinguang; Uwatoko, Yoshiya; Jin, Changqing; Zhou, Jianshi

    2014-01-01

    Magnetite exhibits unique electronic, magnetic, and structural properties in extreme conditions that are of great research interest. Previous studies have suggested a number of transitional models, although the nature of magnetite at high pressure remains elusive. We have studied a highly stoichiometric magnetite using inelastic X-ray scattering, X-ray diffraction and emission, and Raman spectroscopies in diamond anvil cells up to ~20 GPa, while complementary electrical conductivity measurements were conducted in a cubic anvil cell up to 8.5 GPa. We have observed an elastic softening in the diagonal elastic constants (C11 and C44) and a hardening in the off-diagonal constant (C12) at ~8 GPa where significant elastic anisotropies in longitudinal and transverse acoustic waves occur, especially along the [110] direction. An additional vibrational Raman band between the A1g and T2g modes was also detected at the transition pressure. These abnormal elastic and vibrational behaviors of magnetite are attributed to the occurrence of the octahedrally-coordinated Fe(2+)-Fe(3+)-Fe(2+) ions charge-ordering along the [110] direction in the inverse spinel structure. We propose a new phase diagram of magnetite in which the temperature for the metal-insulator and distorted structural transitions decreases with increasing pressure while the charge-ordering transition occurs at ~8 GPa and room temperature. PMID:25186916

  8. Abnormal Elastic and Vibrational Behaviors of Magnetite at High Pressures

    PubMed Central

    Lin, Jung-Fu; Wu, Junjie; Zhu, Jie; Mao, Zhu; Said, Ayman H.; Leu, Bogdan M.; Cheng, Jinguang; Uwatoko, Yoshiya; Jin, Changqing; Zhou, Jianshi

    2014-01-01

    Magnetite exhibits unique electronic, magnetic, and structural properties in extreme conditions that are of great research interest. Previous studies have suggested a number of transitional models, although the nature of magnetite at high pressure remains elusive. We have studied a highly stoichiometric magnetite using inelastic X-ray scattering, X-ray diffraction and emission, and Raman spectroscopies in diamond anvil cells up to ~20 GPa, while complementary electrical conductivity measurements were conducted in a cubic anvil cell up to 8.5 GPa. We have observed an elastic softening in the diagonal elastic constants (C11 and C44) and a hardening in the off-diagonal constant (C12) at ~8 GPa where significant elastic anisotropies in longitudinal and transverse acoustic waves occur, especially along the [110] direction. An additional vibrational Raman band between the A1g and T2g modes was also detected at the transition pressure. These abnormal elastic and vibrational behaviors of magnetite are attributed to the occurrence of the octahedrally-coordinated Fe2+-Fe3+-Fe2+ ions charge-ordering along the [110] direction in the inverse spinel structure. We propose a new phase diagram of magnetite in which the temperature for the metal-insulator and distorted structural transitions decreases with increasing pressure while the charge-ordering transition occurs at ~8 GPa and room temperature. PMID:25186916

  9. Magnetic Separations with Magnetite: Theory, Operation, and Limitations

    SciTech Connect

    G. B. Cotten

    2000-08-01

    This dissertation documents the theory development and experimental plan followed to describe how a magnetite-based column under the influence of an external magnetic field functions as a magnetic separator. Theoretical simulations predict that weekly paramagnetic particles in the sub-micron range can be magnetically separated while diamagnetic particles as large as 2 microns in diameter may pass. Magnetite-based columns were evaluated as magnetically-controllable enhanced filtration devices. There was no evidence of enhanced filtration for diamagnetic particles by the magnetite-based bed. Magnetite-based magnetic separators have proven to be effective in specific laboratory experiments, indicating a potential feasibility for scale-up operations. Column media-filter type filtration effects indicate a magnetite-based column would not be suitable for treatment of a waste stream with a high diamagnetic solids content or high volume throughput requirements. Specific applications requiring removal of sub-micron para- or ferromagnetic particles under batch or Stokes flow conditions would be most applicable.

  10. Biogeochemical Conditions Favoring Magnetite Formation during Anaerobic Iron Reduction

    PubMed Central

    Bell, P. E.; Mills, A. L.; Herman, J. S.

    1987-01-01

    Several anaerobic bacteria isolated from the sediments of Contrary Creek, an iron-rich environment, produced magnetite when cultured in combinations but not when cultured alone in synthetic iron oxyhydroxide medium. When glucose was added as a carbon source, the pH of the medium decreased (to 5.5) and no magnetite was formed. When the same growth medium without glucose was used, the pH increased (to 8.5) and magnetite was formed. In both cases, Fe2+ was released into the growth medium. Geochemical equilibrium equations with Eh and pH as master variables were solved for the concentrations of iron and inorganic carbon that were observed in the system. Magnetite was predicted to be the dominant iron oxide formed at high pHs, while free Fe2+ or siderite were the dominant forms of iron expected at low pHs. Thus, magnetite formation occurs because of microbial alteration of the local Eh and pH conditions, along with concurrent reduction of ferric iron (direct biological reduction or abiological oxidation-reduction reactions). PMID:16347480

  11. Functionalization of Magnetite Nanoparticles as Oil Spill Collector

    PubMed Central

    Atta, Ayman M.; Al-Lohedan, Hamad A.; Al-Hussain, Sami A.

    2015-01-01

    In the present study, a new magnetic powder based on magnetite can be used as a petroleum crude oil collector. Amidoximes based on rosin as a natural product can be prepared from a reaction between hydroxylamine and rosin/acrylonitrile adducts. The produced rosin amidoximes were used as capping agents for magnetite nanoparticles to prepare hydrophobic coated magnetic powders. A new class of monodisperse hydrophobic magnetite nanoparticles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The structure and morphology of magnetite capped with rosin amidoxime were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential, thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The magnetic properties were determined from vibrating sample magnetometer (VSM) analyses. These prepared magnetite nanoparticles were tested as bioactive nanosystems and their antimicrobial effects were investigated. The prepared nanomaterials were examined as a crude oil collector using magnetic fields. The results show promising data for the separation of the petroleum crude oil from aqueous solution in environmental pollution cleanup. PMID:25822876

  12. Functionalization of magnetite nanoparticles as oil spill collector.

    PubMed

    Atta, Ayman M; Al-Lohedan, Hamad A; Al-Hussain, Sami A

    2015-03-26

    In the present study, a new magnetic powder based on magnetite can be used as a petroleum crude oil collector. Amidoximes based on rosin as a natural product can be prepared from a reaction between hydroxylamine and rosin/acrylonitrile adducts. The produced rosin amidoximes were used as capping agents for magnetite nanoparticles to prepare hydrophobic coated magnetic powders. A new class of monodisperse hydrophobic magnetite nanoparticles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The structure and morphology of magnetite capped with rosin amidoxime were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential, thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The magnetic properties were determined from vibrating sample magnetometer (VSM) analyses. These prepared magnetite nanoparticles were tested as bioactive nanosystems and their antimicrobial effects were investigated. The prepared nanomaterials were examined as a crude oil collector using magnetic fields. The results show promising data for the separation of the petroleum crude oil from aqueous solution in environmental pollution cleanup.

  13. Fabrication of chitosan-magnetite nanocomposite strip for chromium removal

    NASA Astrophysics Data System (ADS)

    Sureshkumar, Vaishnavi; Kiruba Daniel, S. C. G.; Ruckmani, K.; Sivakumar, M.

    2016-02-01

    Environmental pollution caused by heavy metals is a serious threat. In the present work, removal of chromium was carried out using chitosan-magnetite nanocomposite strip. Magnetite nanoparticles (Fe3O4) were synthesized using chemical co-precipitation method at 80 °C. The nanoparticles were characterized using UV-visible spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction spectrometer, atomic force microscope, dynamic light scattering and vibrating sample magnetometer, which confirm the size, shape, crystalline nature and magnetic behaviour of nanoparticles. Atomic force microscope revealed that the particle size was 15-30 nm and spherical in shape. The magnetite nanoparticles were mixed with chitosan solution to form hybrid nanocomposite. Chitosan strip was casted with and without nanoparticle. The affinity of hybrid nanocomposite for chromium was studied using K2Cr2O7 (potassium dichromate) solution as the heavy metal solution containing Cr(VI) ions. Adsorption tests were carried out using chitosan strip and hybrid nanocomposite strip at different time intervals. Amount of chromium adsorbed by chitosan strip and chitosan-magnetite nanocomposite strip from aqueous solution was evaluated using UV-visible spectroscopy. The results confirm that the heavy metal removal efficiency of chitosan-magnetite nanocomposite strip is 92.33 %, which is higher when compared to chitosan strip, which is 29.39 %.

  14. Functionalization of magnetite nanoparticles as oil spill collector.

    PubMed

    Atta, Ayman M; Al-Lohedan, Hamad A; Al-Hussain, Sami A

    2015-01-01

    In the present study, a new magnetic powder based on magnetite can be used as a petroleum crude oil collector. Amidoximes based on rosin as a natural product can be prepared from a reaction between hydroxylamine and rosin/acrylonitrile adducts. The produced rosin amidoximes were used as capping agents for magnetite nanoparticles to prepare hydrophobic coated magnetic powders. A new class of monodisperse hydrophobic magnetite nanoparticles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The structure and morphology of magnetite capped with rosin amidoxime were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential, thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The magnetic properties were determined from vibrating sample magnetometer (VSM) analyses. These prepared magnetite nanoparticles were tested as bioactive nanosystems and their antimicrobial effects were investigated. The prepared nanomaterials were examined as a crude oil collector using magnetic fields. The results show promising data for the separation of the petroleum crude oil from aqueous solution in environmental pollution cleanup. PMID:25822876

  15. One-pot reaction to synthesize PEG-coated hollow magnetite nanostructures with excellent magnetic properties.

    PubMed

    Gao, Qian; Zhang, Jilin; Hong, Guangyan; Ni, Jiazuan

    2010-10-01

    We first demonstrate a simple "one-pot" method to synthesis uniform Fe3O4 hollow microspheres in the presence of PEG in ethylene glycol by using urea to control their morphologies. The interior cavity of the hollow spheres can be tunable by reaction time. The Lamer model was used to explain the formation of magnetite hollow spherical structures based on the experimental observations. The obtained hollow Fe3O4 microspheres showing superparamagnetism with a high saturation magnetization of ca. 86.4 emu/g, and also had an enrichment surface of -OH groups, which will be favorable to the further modification with other biomedical molecules.

  16. Synthesis of magnetite magnetic nanoparticles and measurement of magneto-optical effects

    NASA Astrophysics Data System (ADS)

    Lin, Jing-Fung; Lee, Meng-Zhe

    2014-06-01

    In the present study, magnetite (Fe3O4) magnetic nanoparticles (MNPs) were prepared by an improved chemical co-precipitation method. The effects of the pH value of the solution after titration, the reaction temperature in surface coating, and the molar concentration of Fe3+/Fe2+ salts in dispersibility and size of MNPs are studied. Characterization of the dispersibility and size in MNPs involved using transmission electronic microscope and X-ray diffractometry. Above all, the measurement of magneto-optical effect including the linear birefringence and dichroism of magnetic fluid are executed by a Stokes polarimeter.

  17. An experimental study of the mechanism of the replacement of magnetite by pyrite up to 300 °C

    NASA Astrophysics Data System (ADS)

    Qian, Gujie; Brugger, Joël; Skinner, William M.; Chen, Guorong; Pring, Allan

    2010-10-01

    We present the results of an experimental study into the sulfidation of magnetite to form pyrite/marcasite under hydrothermal conditions (90-300 °C, vapor saturated pressures), a process associated with gold deposition in a number of ore deposits. The formation of pyrite/marcasite was studied as a function of reaction time, temperature, pH, sulfide concentration, solid-weight-to-fluid-volume ratio, and geometric surface area of magnetite in polytetrafluoroethylene-lined autoclaves (PTFE) and a titanium and stainless steel flow-through cell. Marcasite was formed only at pH 21°C <4 and was the dominant Fe disulfide at pH 21°C 1.11, while pyrite predominated at pH 21°C >2 and formed even under basic conditions (up to pH 21°C 12-13). Marcasite formation was favored at higher temperatures. Fine-grained pyrrhotite formed in the initial stage of the reaction together with pyrite in some experiments with large surface area of magnetite (grain size <125 μm). This pyrrhotite eventually gave way to pyrite. The transformation rate of magnetite to Fe disulfide increased with decreasing pH (at 120 °C; pH 120°C 0.96-4.42), and that rate of the transformation increased from 120 to 190 °C. Scanning electron microscope (SEM) imaging revealed that micro-pores (0.1-5 μm scale) existed at the reaction front between the parent magnetite and the product pyrite, and that the pyrite and/or marcasite were euhedral at pH 21°C <4 and anhedral at higher pH. The newly formed pyrite was micro-porous (0.1-5 μm); this micro-porosity facilitates fluid transport to the reaction interface between magnetite and pyrite, thus promoting the replacement reaction. The pyrite precipitated onto the parent magnetite was polycrystalline and did not preserve the crystallographic orientation of the magnetite. The pyrite precipitation was also observed on the PTFE liner, which is consistent with pyrite crystallizing from solution. The mechanism of the reaction is that of a dissolution

  18. Arsenic chemistry with sulfide, pyrite, zero-valent iron, and magnetite

    NASA Astrophysics Data System (ADS)

    Sun, Fenglong

    The aim of this thesis is to study the immobilization reactions of arsenic in water. Since compounds containing iron or sulfide are common in most natural and engineered systems, the research focused on the redox reactions and adsorption of arsenic with sulfide, pyrite, zero-valent iron (ZVI), and magnetite which were studied through wet chemistry methods and spectroscopic techniques. The kinetic and thermodynamic information of the reactions of As(V) with S(-II), As(V)/As(III) with pyrite and surface-oxidized pyrite, As(V) with ZVI and acid-treated ZVI, As(III) with magnetite was used to identify mechanisms. The necessity to maintain strictly anoxic conditions was emphasized for the study of arsenic redox chemistry with sulfides and ZVI. The major findings of this research can be stated as follows. First, dissolved sulfide reduced As(V) to lower valences to form a yellow precipitate at acidic pH. The reaction involved the formation of thioarsenic intermediate species. Dissolved O2, granular activated carbon (GAC) and dissolved Fe(II) inhibited the removal of As(V) by sulfide. Elemental sulfur catalyzed the reduction of As(V) by sulfide, which implied the possible benefit of using sulfur-loaded GAC for arsenic removal. Possible reaction mechanisms were discussed. Second, As(III) adsorbed on pristine pyrite over a broader pH range than on surface-oxidized pyrite, while As(V) adsorbed over a narrower pH range with pristine pyrite. As(V) was completely reduced to As(III) on pristine pyrite at acidic pH but not at higher pH. The reduction was first-order with respect to As(V). As(V) was not reduced on surface-oxidized pyrite at pH = 4--11. The different behaviors of As(V) and As(III) on pristine and surface oxidized pyrite determines the toxicity and mobility of arsenic under oxic/anoxic environments. Third, commercial ZVI reduced As(V) to As(III) at low pH (<9) but not at higher pH. Acid-treated ZVI reduced As(V) to As(0), indicated by wet chemical analyses and by

  19. Imaging faces of shadowed magnetite (Fe(3)O(4)) crystals from magnetotactic bacteria with energy-filtering transmission electron microscopy.

    PubMed

    Lins, U; Kachar, B; Farina, M

    We used energy-filtering transmission electron microscopy to image magnetite crystals isolated from uncultured magnetotactic bacteria. These magnetite crystals were shadowed in high vacuum with platinum at 45 degrees. The shadowed crystals were observed in a Zeiss (Thornwood, NY) CEM902 transmission electron microscope. Imaging shadowed crystals with inelastically scattered electrons provided information of the decoration pattern of small platinum particles over crystal surfaces, and thus information on surface characteristics of crystals. Results were comparable to those obtained from scanning electron microscopy using a field emitter gun. Electron energy loss spectra of the crystals as well as of the supporting film were recorded to evaluate variations of image contrast with energy losses. Results indicated that the contrast is attenuated with inelastic imaging and that the effect of contrast tuning caused a contrast inversion at a given point between 100 and 150 eV. We believe this approach can be useful for studying multilayered materials by transmission electron microscopy.

  20. Dried calcium alginate/magnetite spheres: a new support for chromatographic separations and enzyme immobilization

    SciTech Connect

    Burns, M.A.; Kvesitadze, G.I.; Graves, D.J.

    1985-02-01

    Dried spheres made from an alginate solution containing magnetite particles have excellent potential as a support for enzyme immobilization and chromatographic applications. The beads were found to be much stronger than gels such as polyacrylamide and dextran, indicating that high flow rates and pressures could be used in column separations. The support withstood not only temperatures of up to 120/sup 0/C, but also most pH values and common solvents. While some solutions, such as phosphate buffers, dissolved the spheres, stabilization with Tyzor TE eliminated this problem. The physical properties of the beads include a glasslike density of 2.2 g/mL, excellent sphericity, low porosity, and a narrow size distribution. The magnetite present in the support allows the beads to be used for magnetic separations such as high gradient magnetic filtration. Their high degree of microroughness provides a large exposed surface area for enzyme and ligand binding. Mixed Actinomyces fradiae proteases and Aspergillus niger ..cap alpha..-amylase, two enzymes representative of classes which attack large substrates, were immobilized on the bead's surface with high activity and stability. A cyanuric dye which can be used in chromatographic applications (Cibacron Blue F3GA) was also readily coupled to the surface of this support with good yield.

  1. Synthesis of highly stable folic acid conjugated magnetite nanoparticles for targeting cancer cells

    NASA Astrophysics Data System (ADS)

    Mohapatra, S.; Mallick, S. K.; Maiti, T. K.; Ghosh, S. K.; Pramanik, P.

    2007-09-01

    A new approach towards the design of folic acid conjugated magnetic nanoparticles for enhancing their site specific intracellular uptake against a folate receptor overexpressing cancer cells is reported. Magnetite nanoparticles were prepared by coprecipitation from an Fe3+ and Fe2+ solution followed by surface modification with 2-carboxyethyl phosphonic acid to form carboxyl group terminated nanoparticles. Then folic acid and fluorescein isothiocyanate (FITC) were conjugated with carboxylic acid functionalized magnetite nanoparticles using 2,2'-(ethylenedioxy)-bis-ethylamine. These folate-conjugated nanoparticles were characterized in terms of their size by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Surface functional groups and surface composition were analyzed by Fourier transform infrared (FTIR) spectroscopy and x-ray photoelectron spectroscopy (XPS), respectively. Vibration sample magnetometry (VSM) measurements showed the superparamagnetic nature of the particles at room temperature. Folate-conjugated magnetic nanoparticles are noncytotoxic and receptor mediated internalization by HeLa and B16 melanoma F0 cancer cells was confirmed by flow cytometry and confocal microscopy.

  2. Magnetite solubility and phase stability in alkaline media at elevated temperatures

    SciTech Connect

    Ziemniak, S.E.; Jones, M.E.; Combs, K.E.S.

    1994-05-01

    Magnetite, Fe{sub 3}O{sub 4}, is the dominant oxide constituent of the indigenous corrosion layers that form on iron base alloys in high purity, high temperature water. The apparent simultaneous stability of two distinct oxidation states of iron in this metal oxide is responsible for its unique solubility behavior. The present work was undertaken to extend the experimental and theoretical bases for estimating solubilities of an iron corrosion product (Fe{sub 3}O{sub 4}/Fe(OH){sub 2}) over a broader temperature range and in the presence of complexing, pH-controlling reagents. These results indicate that a surface layer of ferrous hydroxide controls magnetite solubility behavior at low temperatures in much the same manner as a surface layer of nickel(II) hydroxide was previously reported to control the low temperature solubility behavior of NiO. The importance of Fe(III) ion complexes implies not only that most previously-derived thermodynamic properties of the Fe(OH){sub 3}{sup {minus}} ion are incorrect, but that magnetite phase stability probably shifts to favor a sodium ferric hydroxyphosphate compound in alkaline sodium phosphate solutions at elevated temperatures. The test methodology involved pumping alkaline solutions of known composition through a bed of Fe{sub 3}O{sub 4} granules and analyzing the emerging solution for Fe. Two pH-controlling reagents were tested: sodium phosphate and ammonia. Equilibria for the following reactions were described in thermodynamic terms: (a) Fe(OH){sub 2}/Fe{sub 3}O{sub 4} dissolution and transformation, (b) Fe(II) and Fe(III) ion hydroxocomplex formation (hydrolysis), (c) Fe(II) ion amminocomplex formation, and (d) Fe(II) and Fe(III) ion phosphatocomplex formation. 36 refs.

  3. Prolonged in vivo circulation time by zwitterionic modification of magnetite nanoparticles for blood pool contrast agents.

    PubMed

    Xiao, Wangchuan; Lin, Jiang; Li, Mingli; Ma, Yongjie; Chen, Yuxin; Zhang, Chunfu; Li, Dan; Gu, Hongchen

    2012-01-01

    Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron oxide particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoparticles via EDC/NHS [N-(3-dimethylaminopropyl)-N'-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic particles demonstrated five times lower macrophage cell uptake than the original particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoparticles had much longer in vivo circulation time than the original particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoparticles with carboxyl surface and to prolong their circulating time.

  4. Simple and Rapid Synthesis of Magnetite/Hydroxyapatite Composites for Hyperthermia Treatments via a Mechanochemical Route

    PubMed Central

    Iwasaki, Tomohiro; Nakatsuka, Ryo; Murase, Kenya; Takata, Hiroshige; Nakamura, Hideya; Watano, Satoru

    2013-01-01

    This paper presents a simple method for the rapid synthesis of magnetite/hydroxyapatite composite particles. In this method, superparamagnetic magnetite nanoparticles are first synthesized by coprecipitation using ferrous chloride and ferric chloride. Immediately following the synthesis, carbonate-substituted (B-type) hydroxyapatite particles are mechanochemically synthesized by wet milling dicalcium phosphate dihydrate and calcium carbonate in a dispersed suspension of magnetite nanoparticles, during which the magnetite nanoparticles are incorporated into the hydroxyapatite matrix. We observed that the resultant magnetite/hydroxyapatite composites possessed a homogeneous dispersion of magnetite nanoparticles, characterized by an absence of large aggregates. When this material was subjected to an alternating magnetic field, the heat generated increased with increasing magnetite concentration. For a magnetite concentration of 30 mass%, a temperature increase greater than 20 K was achieved in less than 50 s. These results suggest that our composites exhibit good hyperthermia properties and are promising candidates for hyperthermia treatments. PMID:23629669

  5. Study of magnetite nanoparticle suspensions by photometry and NMR relaxometry

    NASA Astrophysics Data System (ADS)

    Bogachev, Yu. V.; Gareev, K. G.; Matyushkin, L. B.; Moshnikov, V. A.; Naumova, A. N.

    2013-12-01

    A method has been described for preparation of suspensions of magnetite nanoparticles stabilized by porous silicon dioxide. The process of sedimentation of nanoparticles in suspensions of different compositions and concentrations has been analyzed by transmission coefficient measurements. Spectra of the transmission coefficient have been obtained for suspensions containing composite nanoparticles, the initial silicon dioxide, and macroscopic magnetite particles. The average effective radius of nanoparticles has been calculated from the time dependences of the transmission coefficient. It has been demonstrated that the synthesized nanoparticles possess magnetic-resonance contrast properties.

  6. Plagioclase-Hosted Magnetite Inclusions From the Bushveld Complex

    NASA Astrophysics Data System (ADS)

    Feinberg, J. M.; Scott, G. R.; Renne, P. R.; Wenk, H.

    2004-12-01

    Gabbros from the Main Zone of the 2.064 Ga Bushveld Complex have long been known to possess unusually stable magnetizations due to the presence of high coercivity, exsolved magnetite inclusions in plagioclase and clinopyroxene. The paleomagnetic pole for these rocks has been used to anchor apparent polar wander paths for the Kaapval craton during the Early-Mid Proterozoic. To better understand the rock magnetic properties of silicate-hosted magnetite inclusions, oriented paleomagnetic samples of gabbro were collected from quarries near Belfast and Rustenberg, South Africa, sampling the eastern and western limbs of the Complex, respectively. Plagioclase composition at both sites ranges from An55 (rims) to An65 (cores) based on optical and electron microprobe data. Four kinds of inclusions are present within the plagioclase: elongate magnetite needles, nanometer-scale magnetite particles (responsible for the "cloudy" appearance of some crystals), translucent brown hematite/ilmenite platelets, and colorless euhedral inclusions of pyroxene and/or feldspar. Magnetite inclusions are most abundant at the cores of the plagioclase crystals. Orientations of the needles and the platelets are crystallographically controlled by the silicate host. Although the elongation direction of the magnetite inclusions can occur in any of five possible orientations, only two or three of these directions dominates each plagioclase crystal. Alternating field demagnetization of bulk samples (NRM = 1.5 x 101 A m-1) shows univectorial remanence with average median destructive fields (MDF) of 115 mT (Belfast) and 90 mT (Rustenberg). AF demagnetization of single plagioclase crystals (NRM = 100 A m-1) also shows single component remanence with average MDFs >150 mT. The NRM coercivity spectra of single plagioclase crystals are indistinguishable from that of the bulk samples. When normalized to their abundance in bulk samples the magnetite-bearing plagioclase fully accounts for the NRM of Bushveld

  7. Formation of "Chemically Pure" Magnetite from Mg-Fe-Carbonates Implications for the Exclusively Inorganic Origin of Magnetite and Sulfides in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, Douglas W.; Lauer, H. V., Jr.; Morris, R. V.; Trieman, A. H.; McKay, G. A.

    2006-01-01

    Magnetite and sulfides in the black rims of carbonate globules in Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al. that they are biogenic in origin. However, exclusively inorganic (abiotic) processes are able to account for the occurrence of carbonate-sulfide-magnetite assemblages in the meteorite. We have previously precipitated chemically zoned and sulfide-bearing carbonate globules analogous to those in ALH84001 (at less than or equal to 150 C) from multiple fluxes of variable-composition Ca-Mg-Fe-CO2-S-H2O solutions. Brief heating of precipitated globules to approx. 470 C produced magnetite and pyrrhotite within the globules by thermal decomposition of siderite and pyrite, respectively. We have also shown that morphology of magnetite formed by inorganic thermal decomposition of Fe-rich carbonate is similar to the morphology of so-called biogenic magnetite in the carbonate globules of ALH84001. Magnetite crystals in the rims of carbonate globules in ALH84001 are chemically pure [Note: "Chemically pure" is defined here as magnetite with Mg at levels comparable or lower than Mg detected by [8] in ALH84001 magnetite]. A debate continues on whether or not chemically pure magnetite can form by the thermal decomposition of mixed Mg-Fe-carbonates that have formed under abiotic conditions. Thomas-Keprta et al. argue that it is not possible to form Mg-free magnetite from Mg-Fe-carbonate based on thermodynamic data. We previously suggested that chemically pure magnetite could form by the thermal decomposition of relatively pure siderite in the outer rims of the globules. Mg-Fe-carbonates may also thermally decompose under conditions conducive for formation of chemically pure magnetite. In this paper we show through laboratory experiments that chemically pure magnetite can form by an inorganic process from mixed Mg-Fe-carbonates.

  8. Chemical states in XPS and Raman analysis during removal of Cr(VI) from contaminated water by mixed maghemite-magnetite nanoparticles.

    PubMed

    Chowdhury, Saidur Rahman; Yanful, Ernest K; Pratt, Allen R

    2012-10-15

    Mixed maghemite-magnetite has been used as adsorbent for Cr(VI) removal in this study. Results show that the adsorption capacity is enhanced with an increase in reaction temperature and decrease in free energy change. Thermodynamic study shows that Cr(VI) adsorption on the mixed maghemite and magnetite is endothermic in nature and is dependent on solution pH between 3 and 6. X-ray photoelectron spectroscopy (XPS) results demonstrate the theoretical multiplet peaks for iron and chromium adsorbed iron at the surface of the γ-Fe(2)O(3) and Fe(3)O(4) mixture. Theoretical multiplet analysis shows that during Cr adsorption, the amount of maghemite increases (from 70 to 89%). In magnetite spectra, the relative content of Fe(II) decreases from 8.2 to 3.6% indicating the reduction of magnetite in the mixture particles. In Raman spectroscopy studies, clear peaks of chromium on iron oxide were generated at 826 cm(-1), which could be attributed to chemical interactions between chromium compound and iron oxide. From the results of Raman and XPS studies, electrostatic attraction and oxidation-reduction between chromium and mixed maghemite-magnetite are postulated as mechanisms for the removal of Cr(VI) from aqueous solutions. PMID:22902142

  9. Nano-magnetite (Fe3O4) as a support for recyclable catalysts in the development of sustainable methodologies.

    PubMed

    Gawande, Manoj B; Branco, Paula S; Varma, Rajender S

    2013-04-21

    Surface functionalization of nano-magnetic nanoparticles is a well-designed way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles (MNPs) in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation. Magnetite is a well-known material, also known as ferrite (Fe3O4), and can be used as a versatile support for functionalization of metals, organocatalysts, N-heterocyclic carbenes, and chiral catalysts. It is used as a support for important homogeneous catalytically active metals such as Pd, Pt, Cu, Ni, Co, Ir, etc. to obtain stable and magnetically recyclable heterogeneous catalysts. Homogeneous organocatalysts can be successfully decorated with linkers/ligands on the surface of magnetite or alternatively the organocatalysts can be directly immobilized on the surface of magnetite. The functionalized magnetically retrievable catalysts or nanocatalysts that are increasingly being used in catalysis, green chemistry and pharmaceutically significant reactions are summarized in this review.

  10. Nano silver and nano zinc-oxide in surface waters – Exposure estimation for Europe at high spatial and temporal resolution

    PubMed Central

    Dumont, Egon; Johnson, Andrew C.; Keller, Virginie D.J.; Williams, Richard J.

    2015-01-01

    Nano silver and nano zinc-oxide monthly concentrations in surface waters across Europe were modeled at ∼6 × 9 km spatial resolution. Nano-particle loadings from households to rivers were simulated considering household connectivity to sewerage, sewage treatment efficiency, the spatial distribution of sewage treatment plants, and their associated populations. These loadings were used to model temporally varying nano-particle concentrations in rivers, lakes and wetlands by considering dilution, downstream transport, water evaporation, water abstraction, and nano-particle sedimentation. Temporal variability in concentrations caused by weather variation was simulated using monthly weather data for a representative 31-year period. Modeled concentrations represent current levels of nano-particle production. Two scenarios were modeled. In the most likely scenario, half the river stretches had long-term average concentrations exceeding 0.002 ng L−1 nano silver and 1.5 ng L−1 nano zinc oxide. In 10% of the river stretches, these concentrations exceeded 0.18 ng L−1 and 150 ng L−1, respectively. Predicted concentrations were usually highest in July. PMID:25463731

  11. Elongated prismatic magnetite crystals in ALH84001 carbonate globules: potential Martian magnetofossils.

    PubMed

    Thomas-Keprta, K L; Bazylinski, D A; Kirschvink, J L; Clemett, S J; McKay, D S; Wentworth, S J; Vali, H; Gibson, E K; Romanek, C S

    2000-12-01

    Using transmission electron microscopy (TEM), we have analyzed magnetite (Fe3O4) crystals acid-extracted from carbonate globules in Martian meteorite ALH84001. We studied 594 magnetites from ALH84001 and grouped them into three populations on the basis of morphology: 389 were irregularly shaped, 164 were elongated prisms, and 41 were whisker-like. As a possible terrestrial analog for the ALH84001 elongated prisms, we compared these magnetites with those produced by the terrestrial magnetotactic bacteria strain MV-1. By TEM again, we examined 206 magnetites recovered from strain MV-1 cells. Natural (Darwinian) selection in terrestrial magnetotactic bacteria appears to have resulted in the formation of intracellular magnetite crystals having the physical and chemical properties that optimize their magnetic moment. In this study, we describe six properties of magnetite produced by biologically controlled mechanisms (e.g., magnetotactic bacteria), properties that, collectively, are not observed in any known population of inorganic magnetites. These criteria can be used to distinguish one of the modes of origin for magnetites from samples with complex or unknown histories. Of the ALH84001 magnetites that we have examined, the elongated prismatic magnetite particles (similar to 27% of the total) are indistinguishable from the MV-1 magnetites in five of these six characteristics observed for biogenically controlled mineralization of magnetite crystals. PMID:11543573

  12. Iron site occupancies in magnetite-ulvospinel solid solution: A new approach using XMCD

    SciTech Connect

    Pearce, C. I.; Henderson, C. M. B.; Telling, N. D.; Pattrick, R. A.D.; Vaughan, D. J.; Charnock, J. M.; Arenholz, E.; Tuna, F.; Coker, V.S.; Laan, G. van der

    2009-06-22

    Ordering of Fe{sup 3+} and Fe{sup 2+} between octahedral (Oh) and tetrahedral (Td) sites in synthetic members of the magnetite (Fe{sub 3}O{sub 4}) - ulvoespinel (Fe{sub 2}TiO{sub 4}) solid-solution series was determined using Fe L{sub 2,3}-edge X-ray magnetic circular dichroism (XMCD) coupled with electron microprobe and chemical analysis, Ti L-edge spectroscopy, Fe K-edge EXAFS and XANES, Fe{sub 57} Moessbauer spectroscopy, and unit cell parameters. Microprobe analysis, cell edges and chemical FeO determinations showed that the bulk compositions of the samples were stoichiometric magnetite-ulvoespinel solid-solutions. Surface sensitive XMCD showed that the surfaces of these oxide minerals were more sensitive to redox conditions and some samples required re-equilibration with suitable solid-solid buffers. Detailed site-occupancy analysis of these samples gave XMCD-Fe{sup 2+}/Fe{sup 3+} ratios very close to stoichiometric values. L{sub 2,3}-edge spectroscopy showed that Ti{sup 4+} was restricted to Oh sites. XMCD results showed that significant Fe{sup 2+} only entered Td when the Ti content was > 0.40 apfu while Fe{sup 2+} in Oh increased from 1 a.p.f.u in magnetite to a maximum of {approx}1.4 apfu in USP45. As the Ti content increased from this point, the steady increase in Fe{sup 2+} in Td sites was clearly observable in the XMCD spectra, concurrent with a slow decrease in Fe{sup 2+} in Oh sites. Calculated magnetic moments showed a steady decrease from magnetite (4.06 {mu}{sub B}) to USP45 (1.5 {mu}{sub B}) and then a slower decrease towards the value for ulvoespinel (0 {mu}{sub B}). Two of the synthesized samples were also partially maghemitized by re-equilibrating with an oxidizing Ni-NiO buffer and XMCD showed that Fe{sup 2+} oxidation only occurred at Oh sites, with concomitant vacancy formation restricted to this site. This study shows the advantage of using XMCD as a direct measurement of Fe oxidation state in these complex magnetic spinels. These results

  13. Preparation and characterization of chondroitin-sulfate-A-coated magnetite nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Tóth, Ildikó Y.; Illés, Erzsébet; Szekeres, Márta; Tombácz, Etelka

    2015-04-01

    Polysaccharides are promising candidates for manufacturing biocompatible core-shell nanoparticles with potential in vivo use. Superparamagnetic magnetite nanoparticles (MNPs) have prospective application in both diagnosis and therapy, and so developing a novel polysaccharide shell on MNP core is of great challenge. MNPs were prepared by co-precipitation, then the surface of purified MNPs was coated with chondroitin-sulfate-A (CSA) to obtain core-shell structured magnetite nanoparticles (CSA@MNP). The effect of the added amount of CSA on the surface charging and the aggregation state of MNPs at various pHs and 10 mM NaCl was measured by electrophoresis and dynamic light scattering. The amphoteric behavior of MNPs was fundamentally modified by adsorption of CSA polyanions. A very low CSA-loading induces the aggregation of MNPs, while four times more stabilizes the dispersions over the whole pH-range studied. The coagulation kinetics experiments measured at pH=6.3±0.3 showed that salt tolerance of CSA@MNPs rises up to ~150 mM NaCl.

  14. Tegafur loading and release properties of magnetite/poly(alkylcyanoacrylate) (core/shell) nanoparticles.

    PubMed

    Arias, José L; Ruiz, M Adolfina; Gallardo, Visitación; Delgado, Angel V

    2008-01-01

    In this work, we describe a reproducible method to prepare polymeric colloidal nanospheres of poly(ethyl-2-cyanoacrylate), poly(butylcyanoacrylate), poly(hexylcyanoacrylate) and poly(octylcyanoacrylate) with a magnetite core, and loaded with the anticancer drug Tegafur. The method is based on the emulsion polymerization procedure, often used in the synthesis of poly(alkylcyanoacrylate) nanospheres for drug delivery. The heterogeneous structure of the particles confer them both magnetic-field responsiveness and potential applicability as drug carriers. In order to investigate to what extent is this target achieved, we compare the surface electrical properties of the core/shell particles with those of both the nucleus and the coating material. The hysteresis cycles of both magnetite and composite particles demonstrate that the polymer shell reduces the magnetic responsiveness of the particles, but keeps their soft ferrimagnetic character unchanged. A detailed investigation of the capabilities of the core/shell particles to load this drug is shown. We found, by means of spectrophotometric and electrophoretic measurements, the existence of two drug loading mechanisms: absorption or entrapment in the polymeric network, and surface adsorption. The type of polymer, the pH and the drug concentration are the main factors determining the drug incorporation to the nanoparticles. The release studies showed a biphasic profile affected by the type of polymeric shell, the type of drug incorporation and the amount of drug loaded.

  15. Laser spectroscopy of finite size and covering effects in magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Nikiforov, V. N.; Ignatenko, A. N.; Ivanov, A. V.; Irkhin, V. Yu

    2016-02-01

    Experiments on the impact of the size of magnetite clusters on various magnetic properties (magnetic moment, Curie temperature, blocking temperature etc) have been carried out. The methods of magnetic separation and centrifugation of water suspensions of biocompatible iron oxide nanoparticles (NPs) allow one to produce fractions with diameters of nanoparticles in the range of 4-22 nm. The size of the NPs is controlled by the methods of dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). For the first time the DLS method is applied in real time to control the size during the process of the separation of the NPs in aqueous suspensions. The changes of the size of NPs cause a shift in the Curie temperature and changes in the specific magnetic properties of the iron NPs. The experimental data is interpreted on the basis of Monte Carlo simulations for the classical Heisenberg model with different bulk and surface magnetic moments. It is demonstrated experimentally and by theoretical modeling that the magnetic properties of magnetite NPs are determined not only by their sizes, but also by their surface spin states, while both growing and falling dependences of the magnetic moment (per Fe3O4 formula unit) are possible, depending on the number of magnetic atoms in the nanoparticle. NPs that are both clean and covered with bioresorbable layer clusters have been investigated.

  16. Scale-up of the production of highly reactive biogenic magnetite nanoparticles using Geobacter sulfurreducens

    PubMed Central

    Byrne, J. M.; Muhamadali, H.; Coker, V. S.; Cooper, J.; Lloyd, J. R.

    2015-01-01

    Although there are numerous examples of large-scale commercial microbial synthesis routes for organic bioproducts, few studies have addressed the obvious potential for microbial systems to produce inorganic functional biomaterials at scale. Here we address this by focusing on the production of nanoscale biomagnetite particles by the Fe(III)-reducing bacterium Geobacter sulfurreducens, which was scaled up successfully from laboratory- to pilot plant-scale production, while maintaining the surface reactivity and magnetic properties which make this material well suited to commercial exploitation. At the largest scale tested, the bacterium was grown in a 50 l bioreactor, harvested and then inoculated into a buffer solution containing Fe(III)-oxyhydroxide and an electron donor and mediator, which promoted the formation of magnetite in under 24 h. This procedure was capable of producing up to 120 g of biomagnetite. The particle size distribution was maintained between 10 and 15 nm during scale-up of this second step from 10 ml to 10 l, with conserved magnetic properties and surface reactivity; the latter demonstrated by the reduction of Cr(VI). The process presented provides an environmentally benign route to magnetite production and serves as an alternative to harsher synthetic techniques, with the clear potential to be used to produce kilogram to tonne quantities. PMID:25972437

  17. Electrostatic powder spraying process for the fabrication of stable superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Gu, Guotuan; Tian, Yuping; Li, Zhantie; Lu, Dongfang

    2011-03-01

    Nano-sized Al2O3 particles were modified by heptadecafluorodecyl trimethoxysilane and 2,3-epoxy propoxy propyl trimethoxysilicane to make it both hydrophobic and reactive. The reactive nano-particles were mixed with polyester resin containing curing agents and electrostatic sprayed on stainless steel substrates to obtain stable superhydrophobic coatings after curing. The water contact angle (WCA) on the hybrid coating is influenced by the content of Al2O3 particles in the coating. As the Al2O3 concentration in the coating was increased from 0% to 8%, WCA increased from 68° to 165°. Surface topography of the coatings was examined using scanning electron microscopy (SEM). Nano-particles covered on the coating surface formed continuous film with greatly enhanced roughness, which was found to be responsible for the superhydrophobicity. The method is simple and cost effective and can be used for preparing self-cleaning superhydrophobic coating on large areas.

  18. Microbial preparation of metal-substituted magnetite nanoparticles.

    PubMed

    Moon, Ji-Won; Roh, Yul; Lauf, Robert J; Vali, Hojatollah; Yeary, Lucas W; Phelps, Tommy J

    2007-07-01

    A microbial process that exploits the ability of iron-reducing microorganisms to produce copious amounts of extra-cellular metal (M)-substituted magnetite nanoparticles using akaganeite and dopants of dissolved form has previously been reported. The objectives of this study were to develop methods for producing M-substituted magnetite nanoparticles with a high rate of metal substitution by biological processes and to identify factors affecting the production of nano-crystals. The thermophilic and psychrotolerant iron-reducing bacteria had the ability to form M-substituted magnetite nano-crystals (M(y)Fe(3-y)O(4)) from a doped precursor, mixed-M iron oxyhydroxide, (M(x)Fe(1-x)OOH, x< or =0.5, M is Mn, Zn, Ni, Co and Cr). Within the range of 0.01< or =x< or =0.3, using the mixed precursor material enabled the microbial synthesis of more heavily substituted magnetite compared to the previous method, in which the precursor was pure akaganeite and the dopants were present as soluble metal salts. The mixed precursor method was especially advantageous in the case of toxic metals such as Cr and Ni. Also this new method increased the production rate and magnetic properties of the product, while improving crystallinity, size control and scalability.

  19. SEPARATION OF TECHNETIUM FROM AQUEOUS SOLUTIONS BY COPRECIPITATION WITH MAGNETITE

    DOEpatents

    Rimshaw, S.J.

    1961-10-24

    A method of separating technetium in the 4+ oxidation state from an aqueous basic solution containing products of uranium fission is described. The method consists of contacting the solution with finely divided magnetite and recovering a technetium-bearing precipitate. (AEC)

  20. Enhancing of Fe removal in pyrophyllite using magnetite ore susceptor

    NASA Astrophysics Data System (ADS)

    Hack Lim, Dae; Myung, Eun Ji; Kim, Hyun Soo; Choul Choi, Nag; Cho, Kang Hee; Park, Cheon Young

    2016-04-01

    Pyrite and hematite are an impurity that reduces the grade of pyrophyllite in the final products. Because the impurity in pyrophyllite which was associated with hydrothermally altered rocks. Microwave has been extensively explored in various fields of materials processing. This technology exhibits unique characteristics including volumetric and selective heating, which eventually lead to many exceptional advantages over conventional processing methods including both energy and cost savings, improved product quality and faster processing. The aim of this study was to investigate the application possibility of microwave process for Fe removal in pyrophyllite. The pyrite and quartz of the pyrophyllite was determined by reflected light microscopy and XRD. The result of Fe removal experiment in pyrophyllite using microwave susceptor(magnetite ore included ilmenite and magnetite) showed to decrease of Fe content in pyrophyllite. The Fe removal of 93.62% and parameters were obtained under the following conditions by magnetite ore was 20.0 g, the pyrophyllite was 10.0 g, and the microwave heating time was 10.0 min. By means of microwave, Fe removal in pyrophyllite can be rapidly and efficiently pyrolyze. if some of the magnetite ore, which acts as a microwave susceptor, is mixed with the raw material. Acknowledgment : This subject is supported by Korea Ministry of Environment as "Advanced Technology Program for Environmental Industry"