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Sample records for ultrasmall cofe2o4 nanoparticles

  1. Enhanced dielectric and magnetic properties of polystyrene added CoFe2O4 magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Vadivel, M.; Babu, R. Ramesh; Ramamurthi, K.; Arivanandhan, M.

    2017-03-01

    In this work, a facile chemical synthesis of polystyrene (PS) added cobalt ferrite (CoFe2O4) magnetic nanoparticles by co-precipitation method is reported and the role of PS concentrations (1, 2, 3, 4 and 5 wt%) on the structural, morphological, dielectric and magnetic properties of CoFe2O4 nanoparticles is investigated. Formation of single phase cubic inverse spinel structure is confirmed by X-ray diffraction and Raman spectral analyses. Transmission electron microscopy studies show that the size of CoFe2O4 nanoparticles can be controlled by varying of PS concentration. Dielectric constant is enhanced due to increase in the PS concentrations in CoFe2O4 nanoparticles. Vibrating sample magnetometer measurements elucidate the enhanced saturation magnetization, coercivity and remanent magnetization in 1, 2 and 3 wt% of PS added CoFe2O4 nanoparticles. Hence the results obtained in this work evidently show that the addition of PS as a surfactant in the synthesis of CoFe2O4 nanoparticles remarkably modify the size of the particles.

  2. Monodisperse polyvinylpyrrolidone-coated CoFe2O4 nanoparticles: Synthesis, characterization and cytotoxicity study

    NASA Astrophysics Data System (ADS)

    Wang, Guangshuo; Ma, Yingying; Mu, Jingbo; Zhang, Zhixiao; Zhang, Xiaoliang; Zhang, Lina; Che, Hongwei; Bai, Yongmei; Hou, Junxian; Xie, Hailong

    2016-03-01

    In this study, monodisperse cobalt ferrite (CoFe2O4) nanoparticles were prepared successfully with various additions of polyvinylpyrrolidone (PVP) by sonochemical method, in which PVP served as a stabilizer and dispersant. The effects and roles of PVP on the morphology, microstructure and magnetic properties of the obtained CoFe2O4 were investigated in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). It was found that PVP-coated CoFe2O4 showed relatively well dispersion with narrow size distribution. The field-dependent magnetization curves indicated superparamagnetic behavior of PVP-coated CoFe2O4 with moderate saturation magnetization and hydrophilic character at room temperature. More importantly, the in vitro cytotoxicity testing exhibited negligible cytotoxicity of as-prepared PVP-CoFe2O4 even at the concentration as high as 150 μg/mL after 24 h treatment. Considering the superparamagnetic properties, hydrophilic character and negligible cytotoxicity, the monodisperse CoFe2O4 nanoparticles hold great potential in a variety of biomedical applications.

  3. Electron paramagnetic resonance, magnetic and electrical properties of CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Jnaneshwara, D. M.; Avadhani, D. N.; Daruka Prasad, B.; Nagabhushana, B. M.; Nagabhushana, H.; Sharma, S. C.; Shivakumara, C.; Rao, J. L.; Gopal, N. O.; Ke, Shyue-Chu; Chakradhar, R. P. S.

    2013-08-01

    CoFe2O4 nanoparticles were prepared by solution combustion method. The nanoparticle are characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). PXRD reveals single phase, cubic spinel structure with Fd3¯m (227) space group. SEM micrograph shows the particles are agglomerated and porous in nature. Electron paramagnetic resonance spectrum exhibits a broad resonance signal g=2.150 and is attributed to super exchange between Fe3+ and Co2+. Magnetization values of CoFe2O4 nanoparticle are lower when compared to the literature values of bulk samples. This can be attributed to the surface spin canting due to large surface-to-volume ratio for a nanoscale system. The variation of dielectric constant, dielectric loss, loss tangent and AC conductivity of as-synthesized nano CoFe2O4 particles at room temperature as a function of frequency has been studied. The magnetic and dielectric properties of the samples show that they are suitable for electronic and biomedical applications.

  4. Size selected synthesis of CoFe2O4 nanoparticles prepared in a chitosan matrix

    NASA Astrophysics Data System (ADS)

    Gurgel, A. L.; Soares, J. M.; Chaves, D. S.; Chaves, D. S.; Xavier, M. M.; Morales, M. A.; Baggio-Saitovitch, E. M.

    2010-05-01

    In this paper we report the synthesis and magnetic properties of CoFe2O4 nanoparticles. The nanoparticles with sizes ranging from 6 to 20 nm were prepared in a chitosan matrix. Size selection was achieved by introducing a nonionic surfactant Tween-X, where X={20, 60, 80, and 85}. Aqueous dispersions of Tween-X show micelles with increasing hydrodynamic sizes as X increases. Mössbauer spectroscopy measurements at 300 K show superparamagnetic behavior for the small particles, changing gradually to a blocked magnetic regime as the particle size increases. Magnetization measurements at 300 K show increasing values for the ratio Mr/MHmax and coercive fields (Hc).

  5. Relaxation phenomena in ensembles of CoFe 2O 4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Bittova, B.; Poltierova Vejpravova, J.; Morales, M. P.; Roca, A. G.; Mantlikova, A.

    2012-03-01

    Collective magnetic behavior of CoFe2O4 nanoparticles with diameters of 76, 16, 15 and 8 nm, respectively, prepared by different chemical methods has been investigated. Particle composition, size and structure have been characterized by inductive coupled plasma (ICP), transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD). Basic magnetic properties have been determined from the temperature dependence of magnetization and magnetization isotherms measurements. The three samples exhibit characteristic of a superparamagnetic system with the presence of strong interparticle interactions. Magnetic relaxation phenomena have been examined via frequency-dependent ac susceptibility measurements and aging and memory effect experiments. For the particles coated with oleic acid, it has been demonstrated that the sample reveals all attributes of a super-spin glass (SSG) system with strong interparticle interactions.

  6. A transmission electron microscopy study of CoFe2O4 ferrite nanoparticles in silica aerogel matrix using HREM and STEM imaging and EDX spectroscopy and EELS.

    PubMed

    Falqui, Andrea; Corrias, Anna; Wang, Peng; Snoeck, Etienne; Mountjoy, Gavin

    2010-04-01

    Magnetic nanocomposite materials consisting of 5 and 10 wt% CoFe2O4 nanoparticles in a silica aerogel matrix have been synthesized by the sol-gel method. For the CoFe2O4-10wt% sample, bright-field scanning transmission electron microscopy (BF STEM) and high-resolution transmission electron microscopy (HREM) images showed distinct, rounded CoFe2O4 nanoparticles, with typical diameters of roughly 8 nm. For the CoFe2O4-5wt% sample, BF STEM images and energy dispersive X-ray (EDX) measurements showed CoFe2O4 nanoparticles with diameters of roughly 3 +/- 1 nm. EDX measurements indicate that all nanoparticles consist of stoichiometric CoFe2O4, and electron energy-loss spectroscopy measurements from lines crossing nanoparticles in the CoFe2O4-10wt% sample show a uniform composition within nanoparticles, with a precision of at best than +/-0.5 nm in analysis position. BF STEM images obtained for the CoFe2O4-10wt% sample showed many "needle-like" nanostructures that typically have a length of 10 nm and a width of 1 nm, and frequently appear to be attached to nanoparticles. These needle-like nanostructures are observed to contain layers with interlayer spacing 0.33 +/- 0.1 nm, which could be consistent with Co silicate hydroxide, a known precursor phase in these nanocomposite materials.

  7. Structural, Optical, and Magnetic Properties of Zn-Doped CoFe2O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Tatarchuk, Tetiana; Bououdina, Mohamed; Macyk, Wojciech; Shyichuk, Olexander; Paliychuk, Natalia; Yaremiy, Ivan; Al-Najar, Basma; Pacia, Michał

    2017-02-01

    The effect of Zn-doping in CoFe2O4 nanoparticles (NPs) through chemical co-precipitation route was investigated in term of structural, optical, and magnetic properties. Both XRD and FTIR analyses confirm the formation of cubic spinel phase, where the crystallite size changes with Zn content from 46 to 77 nm. The Scherrer method, Williamson-Hall (W-H) analysis, and size-strain plot method (SSPM) were used to study of crystallite sizes. The TEM results were in good agreement with the results of the SSP method. SEM observations reveal agglomeration of fine spherical-like particles. The optical band gap energy determined from diffuse reflectance spectroscopy (DRS) varies increases from 1.17 to 1.3 eV. Magnetization field loops reveal a ferromagnetic behavior with lower hysteresis loop for higher Zn content. The magnetic properties are remarkably influenced with Zn doping; saturation magnetization (Ms) increases then decreases while both coercivity (HC) and remanent magnetization (Mr) decrease continuously, which was associated with preferential site occupancy and the change in particle size.

  8. The remanence ratio in CoFe2O4 nanoparticles with approximate single-domain sizes

    NASA Astrophysics Data System (ADS)

    Xu, Shitao; Ma, Yongqing; Geng, Bingqian; Sun, Xiao; Wang, Min

    2016-10-01

    Approximately single-domain-sized 9-, 13-, and 16-nm CoFe2O4 nanoparticles are synthesized using the thermal decomposition of a metal-organic salt. By means of dilution and reduction, the concentration, moment, and anisotropy of nanoparticles are changed and their influence on the magnetic properties is investigated. The relation of M r/ M s ∝ 1/lg H dip is observed, where M r/ M s is the remanence ratio and H dip is the maximum dipolar field. Especially, such relation is more accurate for the nanoparticle systems with higher concentration and higher moment, i.e., larger H dip. The deviation from M r/ M s ∝ 1/lg H dip appearing at low temperatures can be attributed to the effects of surface spins for the single-phase CoFe2O4 nanoparticles and to the pinning effect of CoFe2O4 on CoFe2 for the slightly reduced nanoparticles.

  9. Size dependent heating ability of CoFe2O4 nanoparticles in AC magnetic field for magnetic nanofluid hyperthermia

    NASA Astrophysics Data System (ADS)

    Çelik, Özer; Can, Musa Mutlu; Firat, Tezer

    2014-03-01

    We investigated the size dependent magnetic properties and heating mechanism of spinel CoFe2O4 nanoparticles, which synthesized using the nonhydrolytic thermal decomposition method. The size of CoFe2O4 nanoparticles was arranged with the variation of solvent type, reflux time, and reflux temperature. The optimum size range was determined for magnetic fluid hyperthermia. The particles with 9.9 ± 0.3 nm average diameter have the highest heating ability in the AC magnetic field having 3.2 kA/m amplitude and 571 kHz frequency. The maximum specific absorption rate of 22 W/g was obtained for 9.9 ± 0.3 nm sized CoFe2O4 nanoparticles. The calculations and experimental results showed the dominancy of Brownian relaxation at the heat production of synthesized 9.9 ± 0.3 nm nanoparticles. In contrary, the magneto-heating in 5.4 ± 0.2 nm particles mainly originated from Neel relaxation.

  10. Significantly improved dehydrogenation of ball-milled MgH2 doped with CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Shan, Jiawei; Li, Ping; Wan, Qi; Zhai, Fuqiang; Zhang, Jun; Li, Ziliang; Liu, Zhaojiang; Volinsky, Alex A.; Qu, Xuanhui

    2014-12-01

    CoFe2O4 nanoparticles are added to magnesium hydride (MgH2) by high-energy ball milling in order to improve its hydriding properties. The hydrogen storage properties and catalytic mechanism are investigated by pressure-composition-temperature (PCT), differential thermal analysis (DTA), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The nonisothermal desorption results show that the onset desorption temperature of the MgH2 + 7 mol% CoFe2O4 is 160 °C, which is 200 °C lower than of the as-received MgH2. The dehydrogenation process of the MgH2 doped with the CoFe2O4 nanoparticles includes two steps. DTA curves and XRD patterns reveal that a chemical reaction happens between MgH2 and CoFe2O4, forming the final products of the ternary combination, corresponding to Co3Fe7, MgO and Co. The onset desorption temperature of the ball-milled MgH2 doped with Co3Fe7, MgO and Co is about 260 °C, approximately 100 °C lower than the un-doped MgH2, demonstrating that the ternary combination (Co3Fe7, MgO, and Co) also has a great catalytic effect on the MgH2 hydrogen storage properties. It is also confirmed that the various methods of adding the ternary combination have different effects on the MgH2 hydriding-dehydriding process.

  11. Effect of cobalt ferrite (CoFe2O4) nanoparticles on the growth and development of Lycopersicon lycopersicum (tomato plants).

    PubMed

    López-Moreno, Martha L; Avilés, Leany Lugo; Pérez, Nitza Guzmán; Irizarry, Bianca Álamo; Perales, Oscar; Cedeno-Mattei, Yarilyn; Román, Félix

    2016-04-15

    Nanoparticles (NPs) have been synthetized and studied to be incorporated in many industrial and medical applications in recent decades. Due to their different physical and chemical properties compared with bulk materials, researchers are focused to understand their interactions with the surroundings. Living organisms such as plants are exposed to these materials and they are able to tolerate different concentrations and types of NPs. Cobalt ferrite (CoFe2O4) NPs are being studied for their application in medical sciences because of their high coercivity, anisotropy, and large magnetostriction. These properties are desirable in magnetic resonance imaging, drug delivery, and cell labeling. This study is aimed to explore the tolerance of Solanum lycopersicum L. (tomato) plants to CoFe2O4 NPs. Tomato plants were grown in hydroponic media amended with CoFe2O4 nanoparticles in a range from 0 to 1000mgL(-1). Exposure to CoFe2O4 NPs did not affect germination and growth of plants. Uptake of Fe and Co inside plant tissues increased as CoFe2O4 nanoparticle concentration was increased in the media. Mg uptake in plant leaves reached its maximum level of 4.9mgg(-1) DW (dry weight) at 125mgL(-1) of CoFe2O4 NPs exposure and decreased at high CoFe2O4 NPs concentrations. Similar pattern was observed for Ca uptake in leaves where the maximum concentration found was 10mgg(-1) DW at 125mgL(-1) of CoFe2O4 NPs exposure. Mn uptake in plant leaves was higher at 62.5mgL(-1) of CoFe2O4 NPs compared with 125 and 250mgL(-1) treatments. Catalase activity in tomato roots and leaves decreased in plants exposed to CoFe2O4 NPs. Tomato plants were able to tolerate CoFe2O4 NPs concentrations up to 1000mgL(-1) without visible toxicity symptoms. Macronutrient uptake in plants was affected when plants were exposed to 250, 500 and 1000mgL(-1) of CoFe2O4 NPs.

  12. Non-equilibrium cation distribution and enhanced spin disorder in hollow CoFe2O4 nanoparticles.

    PubMed

    Jaffari, G Hassnain; Ceylan, A; Bui, Holt P; Beebe, Thomas P; Ozcan, S; Shah, S Ismat

    2012-08-22

    We present magnetic properties of hollow and solid CoFe(2)O(4) nanoparticles that were obtained by annealing of Co(33)Fe(67)/CoFe(2)O(4) (core/shell) nanoparticles. Hollow nanoparticles were polycrystalline whereas the solid nanoparticles were mostly single crystal. Electronic structure studies were performed by photoemission which revealed that particles with hollow morphology have a higher degree of inversion compared to solid nanoparticles and the bulk counterpart. Electronic structure and the magnetic measurements show that particles have uncompensated spins. Quantitative comparison of saturation magnetization (M(S )), assuming bulk Néel type spin structure with cationic distribution, calculated from quantitative XPS analysis, is presented. The thickness of uncompensated spins is calculated to be significantly large for particles with hollow morphology compared to solid nanoparticles. Both morphologies show a lack of saturation up to 7 T. Moreover magnetic irreversibility exists up to 7 T of cooling fields for the entire temperature range (10-300 K). These effects are due to the large bulk anisotropy constant of CoFe(2)O(4) which is the highest among the cubic spinel ferrites. The effect of the uncompensated spins for hollow nanoparticles was investigated by cooling the sample in large fields of up to 9 T. The magnitude of horizontal shift resulting from the unidirectional anisotropy was more than three times larger than that of solid nanoparticles. As an indication signature of uncompensated spin structure, 11% vertical shift for hollow nanoparticles is observed, whereas solid nanoparticles do not show a similar shift. Deconvolution of the hysteresis response recorded at 300 K reveals the presence of a significant paramagnetic component for particles with hollow morphology which further confirms enhanced spin disorder.

  13. Tuneable magnetic properties of hydrothermally synthesised core/shell CoFe2O4/NiFe2O4 and NiFe2O4/CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Almeida, Trevor P.; Moro, Fabrizio; Fay, Michael W.; Zhu, Yanqiu; Brown, Paul D.

    2014-05-01

    Core/shell hetero-nanostructures of hydrothermally synthesised cobalt and nickel ferrites are shown to exhibit novel magnetic properties. The compositions and phase distributions of homogeneous Co0.5Ni0.5Fe2O4, and core/shell NiFe2O4-Core/CoFe2O4-Shell and CoFe2O4-Core/NiFe2O4-Shell nanoparticles (NPs) are confirmed using high-resolution transmission electron microscopy and electron energy loss spectroscopy. SQUID magnetometry investigations demonstrate that, at room temperature, homogeneous Co0.5Ni0.5Fe2O4 NPs ( 8 nm in diameter) are in the super-paramagnetic state, the magnetisation of NiFe2O4-Core/CoFe2O4-Shell NPs ( 11 nm in diameter) is partially blocked, whilst CoFe2O4-Core/NiFe2O4-Shell NPs ( 11 nm in diameter) are in a blocked state. In particular, NiFe2O4-Core/CoFe2O4-Shell NPs exhibit twice the out-of-phase χ″ susceptibility of CoFe2O4-Core/NiFe2O4-Shell NPs, being dominated by the magnetisation of the core ferrite phase. Hence, when exposed to a high-frequency magnetic field, it is considered that the high χ″ susceptibility of NiFe2O4-Core/CoFe2O4-Shell NPs will promote large magnetically induced heating effects, making these core/shell NPs strong candidates for hyperthermia applications.

  14. Monodisperse CoFe2O4 nanoparticles supported on Vulcan XC-72: High performance electrode materials for lithium-air and lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Şener, Tansel; Kayhan, Emine; Sevim, Melike; Metin, Önder

    2015-08-01

    Addressed herein is the preparation and the electrode performance of monodisperse CoFe2O4 nanoparticles (NPs) supported on Vulcan XC-72 for the Lithium-air battery (LAB) and Lithium-ion battery (LIB). Monodisperse CoFe2O4 NPs were synthesized by the thermal decomposition of cobalt(II) acetylacetonate and iron(III) acetylacetonate in oleylamine and oleic acid in the presence of 1,2-tetradecanediol and benzyl ether. As-prepared CoFe2O4 NPs with a particle size of 11 nm were then supported on Vulcan XC-72 (Vulcan-CoFe2O4) at different theoretical loadings (20, 40 and 60 wt % CoFe2O4 NPs) by using the simple liquid phase self assembly method. CoFe2O4 NPs dispersed on Vulcan-CoFe2O4 composites were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (PXRD) and atomic absorption spectroscopy (AAS). The AAS analyses indicated that the Vulcan-CoFe2O4 composites with different loadings were included 3.7, 8.1 and 16.4 wt % CoFe2O4 on the metal basis. The electrode performance of Vulcan-CoFe2O4 composites were evaluated as the anode active material for LIB and cathode active material for LABs by performing the galvanostatic charge-discharge tests. The highest discharge capacity for both LAB (7510 mAh g(Vulcan+CoFe2O4)-1; 13380 mAh gCoFe2O4-1 @ 0.1C) and LIB (863 mAh g(Vulcan+CoFe2O4)-1; 9330 mAh gCoFe2O4-1@ 0.1C) was investigated with 16.4 wt % CoFe2O4.

  15. Canted spin structure and the first order magnetic transition in CoFe2O4 nanoparticles coated by amorphous silica

    NASA Astrophysics Data System (ADS)

    Lyubutin, I. S.; Starchikov, S. S.; Gervits, N. E.; Korotkov, N. Yu.; Dmitrieva, T. V.; Lin, Chun-Rong; Tseng, Yaw-Teng; Shih, Kun-Yauh; Lee, Jiann-Shing; Wang, Cheng-Chien

    2016-10-01

    The functional polymer (PMA-co-MAA) latex microspheres were used as a core template to prepare magnetic hollow spheres consisting of CoFe2O4/SiO2 composites. The spinel type crystal structure of CoFe2O4 ferrite is formed under annealing, whereas the polymer cores are completely removed after annealing at 450 °C. Magnetic and Mössbauer spectroscopy measurements reveal very interesting magnetic properties of the CoFe2O4/SiO2 hollow spheres strongly dependent on the particle size which can be tuned by the annealing temperature. In the ground state of low temperatures, the CoFe2O4 nanoparticles are in antiferromagnetic state due to the canted magnetic structure. Under heating in the applied field, the magnetic structure gradually transforms from canted to collinear, which increases the magnetization. The Mössbauer data revealed that the small size CoFe2O4/SiO2 particles (2.2-4.3 nm) do not show superparamagnetic behavior but transit from the magnetic to the paramagnetic state by a jump-like magnetic transition of the first order This effect is a specific property of the magnetic nanoparticles isolated by inert material, and can be initiated by internal pressure creating at the particle surface. The suggested method of synthesis can be modified with various bio-ligands on the silane surface, and such materials can find many applications in diagnostics and bio-separation.

  16. Bioavailability of cobalt and iron from citric-acid-adsorbed CoFe2O4 nanoparticles in the terrestrial isopod Porcellio scaber.

    PubMed

    Romih, Tea; Drašler, Barbara; Jemec, Anita; Drobne, Damjana; Novak, Sara; Golobič, Miha; Makovec, Darko; Susič, Robert; Kogej, Ksenija

    2015-03-01

    The aim of this study was to determine whether citric acid adsorbed onto cobalt ferrite (CoFe2O4) nanoparticles (NPs) influences the bioavailability of their constituents Co and Fe. Dissolution of Co and Fe was assessed by two measures: (i) in aqueous suspension using chemical analysis, prior to application onto the food of test organisms; and (ii) in vivo, measuring the bioavailability in the model terrestrial invertebrate (Porcellio scaber, Isopoda, Crustacea). The isopods were exposed to citric-acid-adsorbed CoFe2O4 NPs for 2 weeks, and tissue accumulation of Co and Fe was assessed. This was compared to pristine CoFe2O4 NPs, and CoCl2 and Fe(III) salts as positive controls. The combined data shows that citric acid enhances free metal ion concentration from CoFe2O4 NPs in aqueous suspension, although in vivo, very similar amounts of assimilated Co were found in isopods exposed to both types of NPs. Therefore, evaluation of the dissolution in suspension by chemical means is not a good predictor of metal assimilation of this model organism; body assimilation of Co and Fe is rather governed by the physiological capacity of P. scaber for the uptake of these metals. Moreover, we propose that citric acid, due to its chelating properties, may hinder the uptake of Co that dissolves from citric-acid-adsorbed CoFe2O4 NPs, if citric acid is present in sufficient quantity.

  17. Magnetic interactions in silica coated nanoporous assemblies of CoFe2O4 nanoparticles with cubic magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Laureti, S.; Varvaro, G.; Testa, A. M.; Fiorani, D.; Agostinelli, E.; Piccaluga, G.; Musinu, A.; Ardu, A.; Peddis, D.

    2010-08-01

    Magnetic interactions in silica coated spherical nanoporous assemblies of CoFe2O4 nanoparticles have been investigated by low temperature field dependent remanent magnetization (MDCD and MIRM) and magnetization relaxation measurements. The synthesis procedure leads to the formation of spherical aggregates of about 50-60 nm in diameter composed of hexagonal shaped nanocrystals with shared edges. The negative deviation from the non-interacting case in the Henkel plot indicates the predominance of dipole-dipole interactions favouring the demagnetized state, although the presence of exchange interactions in the porous system cannot be excluded. The activation volume, derived from time dependent magnetization measurements, turns out to be comparable with the particle physical volume, thus indicating, in agreement with static and dynamic irreversible magnetization measurements, that the magnetization reversal actually involves individual crystals.

  18. Magnetic properties of CoFe2O4 and ZnFe2O4 nanoparticles synthesized by novel chemical route

    NASA Astrophysics Data System (ADS)

    Kharat, S. P.; Darvade, T. C.; Gaikwad, S. K.; Baraskar, B. G.; Kakade, S. G.; Kambale, R. C.; Kolekar, Y. D.

    2016-05-01

    CoFe2O4 and ZnFe2O4 nanoparticles were synthesized by modified and cost effective sol-gel autocombustion method. X-ray diffraction study confirms the spinel phase formation of face centered cubic lattice with space group Fd3m and without any impurity. Magnetic measurements demonstrate that the CoFe2O4 shows saturation magnetization of 2.73 µB/f.u. where as ZnFe2O4 shows paramagnetic behavior. Magnetic behavior of CoFe2O4 and ZnFe2O4 is confirmed from Mössbauer studies. Effect of sintering on structural, magnetic and cation occupancy of substituted cobalt ferrite is discussed in this paper.

  19. Magnetic and Mössbauer spectroscopy studies of hollow microcapsules made of silica-coated CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Lyubutin, I. S.; Gervits, N. E.; Starchikov, S. S.; Lin, Chun-Rong; Tseng, Yaw-Teng; Shih, Kun-Yauh; Wang, Cheng-Chien; Chen, I.-Han; Ogarkova, Yu L.; Korotkov, N. Yu

    2016-01-01

    The hollow microcapsules made of silica-coated CoFe2O4 nanoparticles were synthesized using chemical co-precipitation, followed by the sol-gel method. Poly(MMA-co-MAA) microspheres were used as a core template which can be completely removed after annealing at 450 °C. The microcapsules are monodisperse with the outer diameter of about 450 nm and the thickness of the shell is about 50 nm. The nanoparticles of Co-ferrite are single crystalline. The size of the nanoparticles and magnetic properties of CoFe2O4/SiO2 hollow spheres can be tuned with high accuracy at the annealing stage. The Mössbauer data indicate that CoFe2O4 ferrite is an inverse spinel, in which Fe3+ and Co2+ ions are distributed in both octahedral and tetrahedral sites with the inversion degree close to the bulk ferrite value. At low temperature the CoFe2O4/SiO2 nanoparticles are in antiferromagnetic (AFM) state due to the canted or triangular magnetic structure. Under heating in the applied field, AFM structure transforms to the ferrimagnetic (FM) structure, that increases the magnetization. The Mössbauer data revealed that the small size CoFe2O4/SiO2 particles do not show superparamagnetic behavior, but they transit to the paramagnetic state by the jump-like first order magnetic transition (JMT). This effect is a specific property of the magnetic nanoparticles isolated by inert material. The suggested method of synthesis can be modified with various bio-ligands on the silane surface, and such materials can find many applications in diagnostics and bio-separation.

  20. Quasi-static magnetic properties and high-frequency energy losses in CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Tykhonenko-Polishchuk, Yu. O.; Kulyk, N. N.; Yelenich, O. V.; Bečyte, V.; Mažeika, K.; Kalita, V. M.; Belous, A. G.; Tovstolytkin, A. I.

    2016-06-01

    Two series of nanosized cobalt spinel ferrites CoFe2O4 are synthesized from metal salts using high-energy ball milling with the addition of NaCl as a growth agent (series CFO-NaCl), and without (CFO Series). The particle properties are characterized using atomic force microscopy, as well as magnetic and calorimetric measurements. It is shown that the average sizes of the nanoparticles were ˜5.6 and ˜10.3 nm for CFO and CFO-NaCl series, respectively. We performed magnetostatic measurements and determined the parameters that are required to analyze the magnetic state and remagnetization processes of the nanoparticles. It is shown that the blocking temperature is ≈160 K for CFO samples and ≈300 K for the CFO-NaCl series. It was concluded that at 293 K the CFO series particles exhibit a superparamagnetic state, whereas the CFO-NaCl series are in the blocked state. The specific loss power that is scattered by the synthesized nanoparticle ensembles placed in an alternating magnetic field, is measured experimentally and theoretically assessed. The nature of the processes that determine the thermal characteristics of the nanoparticles is analyzed.

  1. Fabrication of Au nanoparticles supported on CoFe2O4 nanotubes by polyaniline assisted self-assembly strategy and their magnetically recoverable catalytic properties

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen; Jiang, Yanzhou; Chi, Maoqiang; Yang, Zezhou; Nie, Guangdi; Lu, Xiaofeng; Wang, Ce

    2016-02-01

    This article reports the fabrication of magnetically responsive Au nanoparticles supported on CoFe2O4 nanotubes through polyaniline (PANI) assisted self-assembly strategy which can be used as an efficient magnetically recoverable nanocatalyst. The central magnetic CoFe2O4 nanotubes possess a strong magnetic response under an externally magnetic field, enabling an easy and efficient separation from the reaction system for reuse. The thorn-like PANI layer on the surface of CoFe2O4 nanotubes provides large surface area for supporting Au nanocatalysts due to the electrostatic interactions. The as-prepared CoFe2O4/PANI/Au nanotube assemblies exhibit a high catalytic activity for the hydrogenation of 4-nitrophenol by sodium borohydride (NaBH4) at room temperature, with an apparent kinetic rate constant (Kapp) of about 7.8 × 10-3 s-1. Furthermore, the composite nanocatalyst shows a good recoverable property during the catalytic process. This work affords a reliable way in developing multifunctional nanocomposite for catalysis and other potential applications in many fields.

  2. Immobilization of glucose oxidase using CoFe2O4/SiO2 nanoparticles as carrier

    NASA Astrophysics Data System (ADS)

    Wang, Hai; Huang, Jun; Wang, Chao; Li, Dapeng; Ding, Liyun; Han, Yun

    2011-04-01

    Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe2O4/SiO2 NPs via cross-linking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, cross-linking time of 3 h, solution pH of 7.0 and 0.4 mg GOD (in 3.0 mg carrier). The immobilized GOD showed maximal catalytic activity at pH 6.5 and 40 °C. After immobilization, the GOD exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 80% of its initial activity after the incubation at 50 °C for 25 min, whereas free enzyme had only 20% of initial activity after the same incubation. After kept at 4 °C for 28 days, the immobilized and free enzyme retained 87% and 40% of initial activity, respectively. The immobilized GOD maintained approximately 57% of initial activity after reused 7 times. The KM (Michaelis-Menten constant) values for immobilized GOD and free GOD were 14.6 mM and 27.1 mM, respectively.

  3. Large Faraday rotation in magnetophotonic crystals containing SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Zamani, Mehdi; Hocini, Abdesselam

    2016-08-01

    This paper has focused on the potential of the SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles in order to achieve the high performance one-dimensional magnetophotonic crystals (MPCs) and to overcome the problem of integration of the magneto-optical devices. Because of importance of magneto-optical Faraday effect in most non-reciprocal optical components, we have investigated the capability of such silicon-based materials for providing large Faraday rotations. We have introduced some MPC structures containing SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles and by varying the concentration of magnetic nanoparticles, influence of volume fraction VF% on the Faraday rotation and transmittance of the structures has studied.

  4. Determination of the effective anisotropy constant of CoFe2O4 nanoparticles through the T-dependence of the coercive field

    NASA Astrophysics Data System (ADS)

    Carvalho, M. H.; Lima, R. J. S.; Meneses, C. T.; Folly, W. S. D.; Sarmento, V. H. V.; Coelho, A. A.; Duque, J. G. S.

    2016-03-01

    We present a systematic study of the coercive field of CoFe2O4-SiO2 nanocomposites. The samples were prepared via the sol-gel method by using the Tetraethyl Orthosilicate as starting reagent. Results of X-ray diffraction, transmission electron microscopy, and X-ray fluorescence confirm the dispersion of the magnetic nanoparticles inside the silica matrix. In addition, the shift in the maximum of Zero-Field-Cooled curves observed by varying the weight ratio of CoFe2O4 nanoparticles to the precursor of silica is consistent with the increasing of average interparticle distances. Because our samples present a particle size distribution, we have used a generalized model which takes account such parameter to fit the experimental data of coercive field extracted from the magnetization curves as a function of applied field. Unlike most of the coercive field results reported in the literature for this material, the use of this model provided a successful description of the temperature dependence of the coercive field of CoFe2O4 nanoparticles in a wide temperature range. Surprisingly, we have observed the decreasing of the nanoparticles anisotropy constant in comparison to the bulk value expected for the material. We believe that this can be interpreted as due to both the migration of the Co2+ from octahedral to tetrahedral sites.

  5. Nanoparticle-Based Magnetoelectric BaTiO3-CoFe2O4 Thin Film Heterostructures for Voltage Control of Magnetism.

    PubMed

    Erdem, Derya; Bingham, Nicholas S; Heiligtag, Florian J; Pilet, Nicolas; Warnicke, Peter; Vaz, Carlos A F; Shi, Yanuo; Buzzi, Michele; Rupp, Jennifer L M; Heyderman, Laura J; Niederberger, Markus

    2016-11-22

    Multiferroic composite materials combining ferroelectric and ferromagnetic order at room temperature have great potential for emerging applications such as four-state memories, magnetoelectric sensors, and microwave devices. In this paper, we report an effective and facile liquid phase deposition route to create multiferroic composite thin films involving the spin-coating of nanoparticle dispersions of BaTiO3, a well-known ferroelectric, and CoFe2O4, a highly magnetostrictive material. This approach offers great flexibility in terms of accessible film configurations (co-dispersed as well as layered films), thicknesses (from 100 nm to several μm) and composition (5-50 wt % CoFe2O4 with respect to BaTiO3) to address various potential applications. A detailed structural characterization proves that BaTiO3 and CoFe2O4 remain phase-separated with clear interfaces on the nanoscale after heat treatment, while electrical and magnetic studies indicate the simultaneous presence of both ferroelectric and ferromagnetic order. Furthermore, coupling between these orders within the films is demonstrated with voltage control of the magnetism at ambient temperatures.

  6. Magnetic hyperthermia and pH-responsive effective drug delivery to the sub-cellular level of human breast cancer cells by modified CoFe2O4 nanoparticles.

    PubMed

    Oh, Yunok; Moorthy, Madhappan Santha; Manivasagan, Panchanathan; Bharathiraja, Subramaniyan; Oh, Junghwan

    2017-02-01

    Magnetic iron oxide nanoparticles (MNPs) have been extensively utilized in a wide range of biomedical applications including magnetic hyperthermia agent. To improve the efficiency of the MNPs in therapeutic applications, in this study, we have synthesized CoFe2O4 nanoparticles and its surface was further functionalized with meso-2,3-dimercaptosuccinic acid (DMSA). The anticancer agent, Doxorubucin (DOX) was conjugated with CoFe2O4@DMSA nanoparticle to evaluate the combined effects of thermotherapy and chemotherapy. The drug delivery efficiency of the DOX loaded CoFe2O4@DMSA nanoparticles were examined based on magnetically triggered delivery of DOX into the subcellular level of cancer cells by using MDA-MB-231 cell line. The amine part of the DOX molecules were effectively attached through an electrostatic interactions and/or hydrogen bonding interactions with the carboxylic acid groups of the DMSA functionalities present onto the surface of the CoFe2O4 nanoparticles. The DOX loaded CoFe2O4@DMSA nanoparticles can effectively uptake with cancer cells via typical endocytosis process. After endocytosis, DOX release from CoFe2O4 nanoparticles was triggered by intracellular endosomal/lysosomal acidic environments and the localized heat can be generated under an alternating magnetic field (AMF). In the presence of AMF, the released DOX molecules were accumulated with high concentrations into the subcellular level at a desired sites and exhibited a synergistic effect of an enhanced cell cytotoxicity by the combined effects of thermal-chemotherapy. Importantly, pH- and thermal-responsive Dox-loaded CoFe2O4 nanoparticles induced significant cellular apoptosis more efficiently mediated by active mitochondrial membrane and ROS generation than the free Dox. Thus, the Dox-loaded CoFe2O4@DMSA nanoparticles can be used as a potential therapeutic agent in cancer therapy by combining the thermo-chemotherapy techniques.

  7. beta-cyclodextrins-based inclusion complexes of CoFe(2)O(4) magnetic nanoparticles as catalyst for the luminol chemiluminescence system and their applications in hydrogen peroxide detection.

    PubMed

    He, Shaohui; Shi, Wenbing; Zhang, Xiaodan; Li, Jian; Huang, Yuming

    2010-06-30

    beta-cyclodextrins (beta-CD)-based inclusion complexes of CoFe(2)O(4) magnetic nanoparticles (MNPs) were prepared and used as catalysts for chemiluminescence (CL) system using the luminol-hydrogen peroxide CL reaction as a model. The as-prepared inclusion complexes were characterized by XRD (X-ray diffraction), TGA (thermal gravimetric analysis) and FT-IR. The oxidation reaction between luminol and hydrogen peroxide in basic media initiated CL. The effect of beta-CD-based inclusion complexes of CoFe(2)O(4) magnetic nanoparticles and naked CoFe(2)O(4) magnetic nanoparticles on the luminol-hydrogen peroxide CL system was investigated. It was found that inclusion complexes between beta-CD and CoFe(2)O(4) magnetic nanoparticles could greatly enhance the CL of the luminol-hydrogen peroxide system. Investigation on the kinetic curves and the chemiluminescence spectra of the luminol-hydrogen peroxide system demonstrates that addition of CoFe(2)O(4) MNPs or inclusion complexes between beta-CD and CoFe(2)O(4) MNPs does not produce a new luminophor of the chemiluminescent reaction. The luminophor for the CL system was still the excited-state 3-aminophthalate anions (3-APA*). The enhanced CL signals were thus ascribed to the possible catalysis from CoFe(2)O(4) MNPs or inclusion complexes between beta-CD and CoFe(2)O(4) nanoparticles. The feasibility of employing the proposed system for hydrogen peroxide sensing was also investigated. Experimental results showed that the CL emission intensity was linear with hydrogen peroxide concentration in the range of 1.0 x 10(-7) to 4.0 x 10(-6) mol L(-1) with a detection limit of 2.0 x 10(-8) mol L(-1) under optimized conditions. The proposed method has been used to determine hydrogen peroxide in water samples successfully.

  8. CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles exhibit fast and selective adsorption of arsenic with high adsorption capacity

    NASA Astrophysics Data System (ADS)

    Yang, Ji-Chun; Yin, Xue-Bo

    2017-01-01

    In this study, we report the synthesis and application of mesoporous CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles (MNPs) for the simultaneous removal of inorganic arsenic (iAs). The hybrid adsorbent had a core-shell and mesoporous structure with an average diameter of 260 nm. The nanoscale size and mesoporous character impart a fast adsorption rate and high adsorption capacity for iAs. In total, 0.1 mg L‑1 As(V) and As(III) could be adsorbed within 2 min, and the maximum adsorption capacities were 114.8 mg g‑1 for As(V) and 143.6 mg g‑1 for As(III), higher than most previously reported adsorbents. The anti-interference capacity for iAs adsorption was improved by the electrostatic repulsion and size exclusion effects of the MIL-100(Fe) shell, which also decreased the zero-charge point of the hybrid absorbent for a broad pH adsorption range. The adsorption mechanisms of iAs on the MNPs are proposed. An Fe-O-As structure was formed on CoFe2O4@MIL-100(Fe) through hydroxyl substitution with the deprotonated iAs species. Monolayer adsorption of As(V) was observed, while hydrogen bonding led to the multi-layer adsorption of neutral As(III) for its high adsorption capacity. The high efficiency and the excellent pH- and interference-tolerance capacities of CoFe2O4@MIL-100(Fe) allowed effective iAs removal from natural water samples, as validated with batch magnetic separation mode and a portable filtration strategy.

  9. CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles exhibit fast and selective adsorption of arsenic with high adsorption capacity

    PubMed Central

    Yang, Ji-Chun; Yin, Xue-Bo

    2017-01-01

    In this study, we report the synthesis and application of mesoporous CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles (MNPs) for the simultaneous removal of inorganic arsenic (iAs). The hybrid adsorbent had a core-shell and mesoporous structure with an average diameter of 260 nm. The nanoscale size and mesoporous character impart a fast adsorption rate and high adsorption capacity for iAs. In total, 0.1 mg L−1 As(V) and As(III) could be adsorbed within 2 min, and the maximum adsorption capacities were 114.8 mg g−1 for As(V) and 143.6 mg g−1 for As(III), higher than most previously reported adsorbents. The anti-interference capacity for iAs adsorption was improved by the electrostatic repulsion and size exclusion effects of the MIL-100(Fe) shell, which also decreased the zero-charge point of the hybrid absorbent for a broad pH adsorption range. The adsorption mechanisms of iAs on the MNPs are proposed. An Fe-O-As structure was formed on CoFe2O4@MIL-100(Fe) through hydroxyl substitution with the deprotonated iAs species. Monolayer adsorption of As(V) was observed, while hydrogen bonding led to the multi-layer adsorption of neutral As(III) for its high adsorption capacity. The high efficiency and the excellent pH- and interference-tolerance capacities of CoFe2O4@MIL-100(Fe) allowed effective iAs removal from natural water samples, as validated with batch magnetic separation mode and a portable filtration strategy. PMID:28102334

  10. CoFe2O4 nanoparticles as oxidase mimic-mediated chemiluminescence of aqueous luminol for sulfite in white wines.

    PubMed

    Zhang, Xiaodan; He, Shaohui; Chen, Zhaohui; Huang, Yuming

    2013-01-30

    Recently, the intrinsic enzyme-like activity of nanoparticles (NPs) has become a growing area of interest. However, the analytical applications of the NP-based enzyme mimetic are mainly concentrated on their peroxidase-like activity; no attempts have been made to investigate the analytical applications based on the oxidase mimic activities of NPs. For the first time, we report that CoFe(2)O(4) NPs were found to possess intrinsic oxidase-like activity and could catalyze luminol oxidation by dissolved oxygen to produce intensified chemiluminescence (CL). The effect of sulfite on CoFe(2)O(4) NP oxidase mimic-mediated CL of aqueous luminol was investigated. It is very interesting that when adding sulfite to the luminol-CoFe(2)O(4) system, the role of sulfite in the luminol-CoFe(2)O(4) NP-sulfite system depends on its concentration. At a relatively low concentration level, sulfite presents an inhibition effect on the luminol-CoFe(2)O(4) NP system. However, it does have an enhancement effect at a higher concentration level. Investigations on the effect of the solution pH and luminol and CoFe(2)O(4) NP concentrations on the kinetic characteristics of the studied CL system in the presence of trace sulfite suggested that the enhancement and inhibition of the luminol-CoFe(2)O(4) NP-sulfite CL system also depended on the solution pH. It seems that the concentrations of luminol and CoFe(2)O(4) NPs did not influence the CL pathway. The possible mechanism of the luminol-CoFe(2)O(4) NP-sulfite CL system was also discussed. On this basis, a flow injection chemiluminescence method was established for the determination of trace sulfite in this study. Under the optimal conditions, the proposed system could respond down to 2.0 × 10(-8) M sulfite. The method has been applied to the determination of trace sulfite in white wine samples with satisfactory results. The results given by the proposed method are in good agreement with those given by the standard titration method.

  11. The effect of poly vinyl alcohol (PVA) surfactant on phase formation and magnetic properties of hydrothermally synthesized CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Jalalian, M.; Mirkazemi, S. M.; Alamolhoda, S.

    2016-12-01

    Nanoparticles of CoFe2O4 were synthesized by hydrothermal process at 190 °C with and without poly vinyl alcohol (PVA) addition using treatment durations of 1.5-6 h. The synthesized powders were characterized with X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), Field emission scanning electron microscope (FESEM) and vibration sample magnetometer (VSM) techniques. XRD results show presence of CoFe2O4 as the main phase and Co3O4 as the lateral phase in some samples. The results show that in the samples synthesized without PVA addition considerable amount of lateral phase is present after 3 h of hydrothermal treatment while with PVA addition this phase is undetectable in the XRD patterns of the sample synthesized at the same conditions. Microstructural studies represent increasing of particle size with increasing of hydrothermal duration and formation of coarser particles with PVA addition. The highest maximum magnetization (Mmax) values in both of the samples that were synthesized with and without PVA addition are about 59 emu/g that were obtained after 4.5 h of hydrothermal treatment. Intrinsic coercive field (iHc) value of the sample without PVA addition increases from 210 to 430 Oe. While with PVA addition the iHc value changes from 83 Oe to 493 Oe. The mechanism of changes in Mmax and iHc values has been explained.

  12. The anomalous memory effect related to the relaxation of surface and core moments observed in well-dispersed CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Huang, S.; Ma, Y. Q.; Xu, S. T.

    2015-12-01

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point, and characterized by XRD, TEM and detailed magnetic measurements. The moments of CoFe2O4 nanoparticles consist of the core and canted surface moments below 200 K, and the exchange-coupling between the surface and core spins enhanced the remanence (Mr) to saturation (Ms) magnetization ratio (Mr/Ms) at the temperature of 10 K. Interestingly, the anomalous memory effect was observed in a broad temperature range which can be attributed to the relaxation of surface spins below 200 K and the one from the moments of magnetically ordered entity larger than one particle above 200 K.

  13. Antigen-antibody interaction from quartz crystal microbalance immunosensors based on magnetic CoFe2O4/SiO2 composite nanoparticle-functionalized biomimetic interface.

    PubMed

    Chen, Zai-Gang; Tang, Dian-Yong

    2007-07-01

    A new quartz crystal microbalance immunoassay for the detection of carcinoembryonic antigen (CEA) was developed by means of immobilizing anti-CEA onto magnetic CoFe2O4/SiO2 composite nanoparticles-functionalized biomimetic interface. Under optimal conditions, the frequency shift was proportional to the CEA concentration in the range of 2.5-55 ng/mL with a detection limit of 0.5 ng/mL at a signal-to-noise ratio of 3. Moreover, the immunosensor system showed an acceptable reproducibility and stability. Clinical serum specimens were assayed with this method, and the results were in acceptable agreement with those obtained from ELISA. Compared with the conventional ELISA assay, the proposed immunoassay system was simple and rapid without multiple labeling and separation steps. Importantly, the developed immunoassay protocol could be further extended for the determination of other antigens.

  14. Comparison of the magnetic, radiolabeling, hyperthermic and biodistribution properties of hybrid nanoparticles bearing CoFe2O4 and Fe3O4 metal cores.

    PubMed

    Psimadas, D; Baldi, G; Ravagli, C; Comes Franchini, M; Locatelli, E; Innocenti, C; Sangregorio, C; Loudos, G

    2014-01-17

    Metal oxide nanoparticles, hybridized with various polymeric chemicals, represent a novel and breakthrough application in drug delivery, hyperthermia treatment and imaging techniques. Radiolabeling of these nanoformulations can result in new and attractive dual-imaging agents as well as provide accurate in vivo information on their biodistribution profile. In this paper a comparison study has been made between two of the most promising hybrid core-shell nanosystems, bearing either magnetite (Fe3O4) or cobalt ferrite (CoFe2O4) cores, regarding their magnetic, radiolabeling, hyperthermic and biodistribution properties. While hyperthermic properties were found to be affected by the metal-core type, the radiolabeling ability and the in vivo fate of the nanoformulations seem to depend critically on the size and the shell composition.

  15. Transforming single domain magnetic CoFe2O4 nanoparticles from hydrophobic to hydrophilic by novel mechanochemical ligand exchange

    NASA Astrophysics Data System (ADS)

    Munjal, Sandeep; Khare, Neeraj

    2017-01-01

    Single-phase uniform-sized ( 9 nm) cobalt ferrite (CFO) nanoparticles have been synthesized by hydrothermal synthesis using oleic acid as a surfactant. The as-synthesized oleic acid-coated CFO (OA-CFO) nanoparticles were well dispersible in nonpolar solvents but not dispersible in water. The OA-CFO nanoparticles have been successfully transformed to highly water-dispersible citric acid-coated CFO (CA-CFO) nanoparticles using a novel single-step ligand exchange process by mechanochemical milling, in which small chain citric acid molecules replace the original large chain oleic acid molecules available on CFO nanoparticles. The OA-CFO nanoparticle's hexane solution and CA-CFO nanoparticle's water solution remain stable even after 6 months and show no agglomeration and their dispersion stability was confirmed by zeta-potential measurements. The contact angle measurement shows that OA-CFO nanoparticles are hydrophobic whereas CA-CFO nanoparticles are superhydrophilic in nature. The potentiality of as-synthesized OA-CFO and mechanochemically transformed CA-CFO nanoparticles for the demulsification of highly stabilized water-in-oil and oil-in-water emulsions has been demonstrated.

  16. Effect of reaction time on particle size and dielectric properties of manganese substituted CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ranjith Kumar, E.; Jayaprakash, R.; ArunKumar, T.; Kumar, Sanjay

    2013-01-01

    An auto-combustion route was adopted for preparing nanosize manganese substituted cobalt ferrite. The synthesis of the nanoparticles was carried out using different fuel ratio for combustion process. The prepared samples were characterized using XRD and TEM. The impact of fuel ratio on the formation of Co0.6Mn0.4Fe2O4 nanoparticles was analyzed in terms of particle size. The particle is achieved towards smaller range of size as ˜3-51 nm only at the 50% fuel ratio. The 75% and 100% fuel combustion ratio are not supported to attain the particle size on these ranges. The dielectric loss and low value of dielectric constant have been measured in the frequency range of 50 Hz-1 MHz.

  17. Oleate-based hydrothermal preparation of CoFe2O4 nanoparticles, and their magnetic properties with respect to particle size and surface coating

    NASA Astrophysics Data System (ADS)

    Repko, Anton; Vejpravová, Jana; Vacková, Taťana; Zákutná, Dominika; Nižňanský, Daniel

    2015-09-01

    We present a facile and high-yield synthesis of cobalt ferrite nanoparticles by hydrothermal hydrolysis of Co-Fe oleate in the presence of pentanol/octanol/toluene and water at 180 or 220 °C. The particle size (6-10 nm) was controlled by the composition of the organic solvent and temperature. Magnetic properties were then investigated with respect to the particle size and surface modification with citric acid or titanium dioxide (leading to hydrophilic particles). The as-prepared hydrophobic nanoparticles (coated by oleic acid) had a minimum inter-particle distance of 2.5 nm. Their apparent blocking temperature (estimated as a maximum of the zero-field-cooled magnetization) was 180 K, 280 K and 330 K for the particles with size of 6, 9 and 10.5 nm, respectively. Replacement of oleic acid on the surface by citric acid decreased inter-particle distance to less than 1 nm, and increased blocking temperature by ca. 10 K. On the other hand, coating with titanium dioxide, supported by nitrilotri(methylphosphonic acid), caused increase of the particle spacing, and lowering of the blocking temperature by ca. 20 K. The CoFe2O4@TiO2 nanoparticles were sufficiently stable in water, methanol and ethanol. The particles were also investigated by Mössbauer spectroscopy and alternating-current (AC) susceptibility measurements, and their analysis with Vögel-Fulcher and power law. Effect of different particle coating and dipolar interactions on the magnetic properties is discussed.

  18. A facile and effective immobilization of glucose oxidase on tannic acid modified CoFe2O4 magnetic nanoparticles.

    PubMed

    Altun, Seher; Çakıroğlu, Bekir; Özacar, Münteha; Özacar, Mahmut

    2015-12-01

    This article presents a study of glucose oxidase (GOx) immobilization by employing tannic acid (TA) modified-CoFe2O4 (CFO) magnetic nanoparticles which demonstrates novel aspect for enzyme immobilization. By using the strong protein and tannic acid binding, GOx immobilization was carried out via physical adsorption in a simpler way compared with the other immobilization methods which require various chemicals and complicated procedures which is difficult, expensive, time-consuming, and destructive to the enzyme structure. CFO was synthesized by hydrothermal synthesis and modified with TA to immobilize GOx. The immobilized GOx demonstrated maximum catalytic activity at pH 6.5 and 45 °C. The samples were characterized by vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), zeta potential, and fourier transform infrared spectroscopy (FTIR), all of which confirm the surface modification of CFO and GOx immobilization. Also, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were performed to demonstrate the surface morphology and chemical structure of samples. According to the Lineweaver-Burk plot, GOx possessed lower affinity to glucose after immobilization, and the Michelis-Menten constant (KM) of immobilized and free GOx were found to be 50.05 mM and 28.00 mM, respectively. The immobilized GOx showed excellent reusability, and even after 8 consecutive activity assay runs, the immobilized GOx maintained ca. 60% of its initial activity.

  19. Novel electrochemical biosensor based on PVP capped CoFe2O4@CdSe core-shell nanoparticles modified electrode for ultra-trace level determination of rifampicin by square wave adsorptive stripping voltammetry.

    PubMed

    Asadpour-Zeynali, Karim; Mollarasouli, Fariba

    2017-06-15

    This work introduces a new electrochemical sensor based on polyvinyl pyrrolidone capped CoFe2O4@CdSe core-shell modified electrode for a rapid detection and highly sensitive determination of rifampicin (RIF) by square wave adsorptive stripping voltammetry. The new PVP capped CoFe2O4@CdSe with core-shell nanostructure was synthesized by a facile synthesis method for the first time. PVP can act as a capping and etching agent for protection of the outer surface nanoparticles and formation of a mesoporous shell, respectively. Another important feature of this work is the choice of the ligand (1,10-phenanthroline) for precursor cadmium complex that works as a chelating agent in order to increase optical and electrical properties and stability of prepared nanomaterial. The nanoparticles have been characterized by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV-vis, photoluminescence (PL) spectroscopy, FT-IR, and cyclic voltammetry techniques. The PL spectroscopy study of CoFe2O4@CdSe has shown significant PL quenching by the formation of CoFe2O4 core inside CdSe, this shows that CoFe2O4 NPs are efficient electron acceptors with the CdSe. It is clearly observed that the biosensor can significantly enhance electrocatalytic activity towards the oxidation of RIF, under the optimal conditions. The novelty of this work arises from the new synthesis method for the core-shell of CoFe2O4@CdSe. Then, the novel electrochemical biosensor was fabricated for ultra-trace level determination of rifampicin with very low detection limit (4.55×10(-17)M) and a wide linear range from 1.0×10(-16) to 1.0×10(-7)M. The fabricated biosensor showed high sensitivity and selectivity, good reproducibility and stability. Therefore, it was successfully applied for the determination of ultra-trace RIF amounts in biological and pharmaceutical samples with satisfactory recovery data.

  20. The effective peroxidase-like activity of chitosan-functionalized CoFe2O4 nanoparticles for chemiluminescence sensing of hydrogen peroxide and glucose.

    PubMed

    Fan, Yingwei; Huang, Yuming

    2012-03-07

    Here, we report a highly simple and general protocol for functionalization of the CoFe(2)O(4) NPs with chitosan polymers in order to make CoFe(2)O(4) NPs disperse and stable in solution. The functionalized CoFe(2)O(4) NPs (denoted as CF-CoFe(2)O(4) NPs) were characterized by scanning electron microscope (SEM), thermogravimetric (TG), X-ray diffraction (XRD) and FT-IR spectra. It was found that the CoFe(2)O(4) NPs were successfully decorated and uniformly dispersed on the surface of chitosan without agglomeration. The CF-CoFe(2)O(4) NPs were found to increase greatly the radiation emitted during the CL oxidation of luminol by hydrogen peroxide. Results of ESR spin-trapping experiments demonstrated that the CF-CoFe(2)O(4) NPs showed catalytic ability to H(2)O(2) decomposition into ˙OH radicals. On this basis, a highly sensitive and rapid chemiluminescent method was developed for hydrogen peroxide in water samples and glucose in blood samples. Under optimum conditions, the proposed method allowed the detection of H(2)O(2) in the range of 1.0 × 10(-9) to 4.0 × 10(-6) M and glucose in the range of 5.0 × 10(-8) to 1.0 × 10(-5) M with detectable H(2)O(2) as low as 500 pM and glucose as low as 10 nM, respectively. This proposed method has been successfully applied to detect H(2)O(2) in environmental water samples and glucose in serum samples with good accuracy and precision.

  1. CoFe2O4 magnetic nanoparticles as a highly active heterogeneous catalyst of oxone for the degradation of diclofenac in water.

    PubMed

    Deng, Jing; Shao, Yisheng; Gao, Naiyun; Tan, Chaoqun; Zhou, Shiqing; Hu, Xuhao

    2013-11-15

    A magnetic nanoscaled catalyst cobalt ferrite (CoFe2O4) was successfully prepared and used for the activation of oxone to generate sulfate radicals for the degradation of diclofenac. The catalyst was characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The effects of calcination temperature, initial pH, catalyst and oxone dosage on the degradation efficiency were investigated. Results demonstrated that CoFe2O4-300 exhibited the best catalytic performance and almost complete removal of diclofenac was obtained in 15 min. The degradation efficiency increased with initial pH decreasing in the pH range of 5-9. The increase of catalyst and oxone dosage both had the positive effect on the degradation of diclofenac. Moreover, CoFe2O4 could retain high degradation efficiency even after being reused for five cycles. Finally, the major diclofenac degradation intermediates were identified and the primary degradation pathways were proposed.

  2. Fatty acid as structure directing agent for controlled secondary growth of CoFe2O4 nanoparticles to achieve mesoscale assemblies: A facile approach for developing hierarchical structures

    NASA Astrophysics Data System (ADS)

    Saikia, K.; Kaushik, S. D.; Sen, D.; Mazumder, S.; Deb, P.

    2016-08-01

    Mesoscale hierarchical assemblies have emerged out as a new class of structures between fine dimension nanoparticles and bulk structures, having distinctly different physical properties from either side. Controlling the self-assembly process of primary nanoparticles and subsequent secondary growth mechanism is the key aspect for achieving such ordered structures. In this work, we introduce a new insight on achieving hierarchical assemblies of CoFe2O4 nanoparticles based on the temporal stability of the primary nanoparticles, where, the growth and stability of the primary particles are controlled by using oleic acid. It is found that the developed particles, at a critical concentration of oleic acid, prefer a secondary growth process, rather than promoting their individual growth. Domination of the attractive hydrophobic interaction over steric repulsion among the primary particles at this critical concentration of oleic acid is found to be the key factor for the initial aggregation of the primary particles, which eventually leads to the formation of spherical hierarchical assemblies via oriented attachment. It is also realized that the extremely well or poor stability conditions of the primary particles do not allow this secondary growth process. Estimated values of Co2+ distribution factor show that the cation distribution factor of CoFe2O4 system is not affected by the nature of dominant growth processes, when these are controlled. Interestingly, magnetic measurements reflect the stronger interparticle interaction in the hierarchical system and high magnetic moment values at low magnetic field.

  3. Morphology and magnetic properties of CoFe2O4 nanocables fabricated by electrospinning based on the Kirkendall effect

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengmei; Yang, Guijin; Wei, Jinxin; Bian, Haiqin; Gao, Jiming; Li, Jinyun; Wang, Tao

    2016-07-01

    CoFe2O4 nanocables have been successfully fabricated by electrospinning involving the nanoscale Kirkendall effect. The average diameters of the outer tubes and inner wires of CoFe2O4 nanocables are around 200 nm and 85 nm, respectively. The detailed formation process nanoscale morphology, structure and unique magnetic properties of CoFe2O4 nanocables have been studied comprehensively. Each fully calcined individual nanocable is composed of CoFe2O4 monocrystallites, which stacked along the longitudinal direction with random orientation. The coercivity (Hc) of the CoFe2O4 nanocables decreases from 11043 Oe at 10 K to 707 Oe at 300 K, and a spin reorientation has been detected at 5 K and 100 K, which is different from CoFe2O4 nanorods and nanoparticles.

  4. Impact of ignition temperature on particle size and magnetic properties of CoFe2O4 nanoparticles prepared by self-propagated MILD combustion technique

    NASA Astrophysics Data System (ADS)

    Kaliyamoorthy, Venkatesan; Rajan Babu, D.; Saminathan, Madeswaran

    2016-11-01

    We prepared nanocrystalline CoFe2O4 by changing its ignition temperatures, using moderate and intense low-oxygen dilution (MILD) combustion technique. The effect of ignition temperature on the particle size and its magnetic behavior was investigated by HR-TEM and VSM respectively. We observed a vast change in the structural behavior and the magnetic properties of the prepared samples. X-ray diffraction studies revealed that the resultant samples had single phase with different grain sizes from 23±5 nm to 16±5 nm, which was understood by observing the growth of the grains through heat released from the combustion reaction. FE-SEM analysis showed high porosity with heterogeneous distribution of the pore size based on the adiabatic temperature and EPMA analysis, which confirmed the elemental compositions of the prepared samples. The saturation magnetization values measured at room temperature, employing vibrating sample magnetometer (VSM) decreased gradually from 50 to 34 emu/g when the ignition temperature was increased from 243 °C to 400 °C. Some of Fe ions on the B sites moved periodically to the A sites because of quenching treatment. The presence of Fe2+ ions in the existing ferrite structure ruled the magnetic behavior of the sample, as confirmed by the Mössbauer analysis.

  5. Interfaces exchange bias and magnetic properties of ordered CoFe2O4/Co3O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, B. B.; Xu, J. C.; Wang, P. F.; Han, Y. B.; Hong, B.; Jin, H. X.; Jin, D. F.; Peng, X. L.; Li, J.; Yang, Y. T.; Gong, J.; Ge, H. L.; Wang, X. Q.

    2015-11-01

    Cobalt ferrites (CoFe2O4) nanoparticles were implanted into the ordered mesoporous cobaltosic oxide (Co3O4) nanowires to synthesize magnetic CoFe2O4/Co3O4 nanocomposites. X-ray diffraction (XRD), N2 physical absorption-desorption, transmission electron microscope (TEM) and energy disperse spectroscopy (EDS) were used to characterize the microstructure of mesoporous Co3O4 and CoFe2O4/Co3O4 nanocomposites. The percent of pore-volume of mesoporous Co3O4 nanowires was calculated to be about 41.99% and CoFe2O4 nanoparticles were revealed to exist in the mesopores of Co3O4. The magnetic behavior of both samples were investigated with superconducting quantum interference device (SQUID). Magnetization increased with the doping CoFe2O4 and decreasing temperature, while coercivity hardly changed. The exchange bias effect was obviously observed at 100 K and enhanced with the doping CoFe2O4. CoFe2O4 nanoparticles reinforced the interfaces magnetic interaction between antiferromagnetic Co3O4 and ferrimagnetic CoFe2O4.

  6. CoFe2O4 nano-particles functionalized with 8-hydroxyquinoline for dispersive solid-phase micro-extraction and direct fluorometric monitoring of aluminum in human serum and water samples.

    PubMed

    Abdolmohammad-Zadeh, Hossein; Rahimpour, Elaheh

    2015-06-30

    A simple dispersive solid-phase micro-extraction method based on CoFe2O4 nano-particles (NPs) functionalized with 8-hydroxyquinoline (8-HQ) with the aid of sodium dodecyl sulfate (SDS) was developed for separation of Al(III) ions from aqueous solutions. Al(III) ions are separated at pH 7 via complex formation with 8-HQ using the functionalized CoFe2O4 nano-particles sol solution as a dispersed solid-phase extractor. The separated analyte is directly quantified by a spectrofluorometric method at 370nm excitation and 506nm emission wavelengths. A comparison of the fluorescence of Al(III)-8-HQ complex in bulk solution and that of Al(III) ion interacted with 8-HQ/SDS/CoFe2O4 NPs revealed a nearly 5-fold improvement in intensity. The experimental factors influencing the separation and in situ monitoring of the analyte were optimized. Under these conditions, the calibration graph was linear in the range of 0.1-300ngmL(-1) with a correlation coefficient of 0.9986. The limit of detection and limit of quantification were 0.03ngmL(-1) and 0.10ngmL(-1), respectively. The inter-day and intra-day relative standard deviations for six replicate determinations of 150ngmL(-1) Al(III) ion were 2.8% and 1.7%, respectively. The method was successfully applied to direct determine Al(III) ion in various human serum and water samples.

  7. Room temperature magnetic ordering, enhanced magnetization and exchange bias of GdMnO3 nanoparticles in (GdMnO3)0.70(CoFe2O4)0.30

    NASA Astrophysics Data System (ADS)

    Mitra, A.; Mahapatra, A. S.; Mallick, A.; Chakrabarti, P. K.

    2017-02-01

    Nanoparticles of GdMnO3 (GMO) are prepared by sol-gel method. To enhance the magnetic property and also to obtain the magnetic ordering at room temperature (RT), nanoparticles of GMO are incorporated in the matrix of CoFe2O4 (CFO). Desired crystallographic phases of CFO, GMO and GMO-CFO are confirmed by analyzing X-ray diffractrograms (XRD) using Rietveld method. The average size of nanoparticles and their distribution, crystallographic phase, nanocrystallinity etc. are studied by high-resolution transmission electron microscope (HRTEM). Magnetic hysteresis loops (M-H) of GMO-CFO under zero field cooled (ZFC) and field cooled (FC) conditions are observed at different temperatures down to 5 K. Magnetization vs. temperature (M-T) under ZFC and FC conditions are also recorded. Interestingly, exchange bias (EB) is found at low temperature which suggests the encapsulation of the ferromagnetic (FM) nanoparticles of GMO by the ferrimagnetic nanoparticles of CFO below 100 K. Enhanced magnetization, EB effect and RT magnetic ordering of GMO-CFO would be interesting for both theoretical and experimental investigations.

  8. Effect of annealing on particle size, microstructure and gas sensing properties of Mn substituted CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, E. Ranjith; Kamzin, A. S.; Janani, K.

    2016-11-01

    Microstructure, morphological and gas sensor studies of Mn substituted cobalt ferrite nanoparticles synthesized by a simple evaporation method and auto- combustion method. The influence of heat treatment on phase and particle size of spinel ferrite nanoparticles were determined by X-ray diffraction and Mossbauer spectroscopy. The XRD study reveals that the lattice constant and crystallite size of the samples increases with the increase of annealing temperature. Last one was confirmed by Mossbauer data. The lowest size of particles of MnCoFe2O4 (~3 nm) is obtained by auto combustion method. The spherical shaped nanoparticles are recorded by TEM. Furthermore, conductance response of Mn-Co ferrite nanomaterial was measured by exposing the material to reducing gas like liquefied petroleum gas (LPG) which showed a sensor response of ~0.19 at an optimum operating temperature of 250 °C.

  9. Structural and magnetic studies of the nickel doped CoFe2O4 ferrite nanoparticles synthesized by the chemical co-precipitation method

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Yadav, Nisha; Rana, Dinesh S.; Kumar, Parmod; Arora, Manju; Pant, R. P.

    2015-11-01

    The physical properties of nickel doped cobalt ferrite nanoparticles NixCo1-xFe2O4 (x=0.5, 0.75, 0.9) derived by the chemical co-precipitation route are characterized by XRD, FTIR, TEM, EPR, search coil and ac susceptibility techniques to develop stable kerosene based ferrofluid. XRD patterns and TEM images confirm the single phase formation of NixCo1-xFe2O4 nanoparticles whose crystallite size increases and lattice parameters decreases with the increase in Ni content. EPR resonance signal peak-to-peak line width and resonance field value decreases with the increase in Ni concentration in these samples. The broad nature of resonance signal is attributed to the ferromagnetic nature of the as-prepared nanoparticles and the increase in super exchange interaction among Ni2+-O-Co2+ facilitate the shifting of resonance value to lower field. The hysteresis loops of these nickel doped cobalt ferrite analogs exhibits highly magnetic nature of these nanoparticles at ambient temperature whose saturation magnetization, coerecivity and remanence magnetization decreases linearly with the increase in Ni-concentration in cobalt ferrite. The magnetic susceptibility with temperature curve shows increasing trend of blocking temperature with rise in nickel ion concentration.

  10. Phase constituents and magnetic properties of the CoFe2O4 nanoparticles prepared by polyvinylpyrrolidone (PVP)-assisted hydrothermal route

    NASA Astrophysics Data System (ADS)

    Jalalian, M.; Mirkazemi, S. M.; Alamolhoda, S.

    2016-09-01

    In this research, nanoparticles of cobalt ferrite were synthesized by a simple hydrothermal process at 190 °C using different treatment durations with the assistance of polyvinylpyrrolidone (PVP) surfactant. The synthesized powders were characterized using X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope and vibration sample magnetometer techniques. The quantitative values of phase constituents and also inversion parameter of cobalt ferrite spinel structure were calculated by Rietveld method using XRD results. XRD results show formation of cobalt ferrite as the main phase in all samples and also the presence of small amounts of Co3O4 lateral phase in some cases. Raman spectroscopies also confirm the presence of this lateral phase. Microstructural studies represent formation of nanoparticles with a narrow particle size distribution. Magnetic measurements represent that maximum magnetization ( M max) values are in the range of 25-57 emu/g with changes in the hydrothermal treatment duration. Intrinsic coercivity force values ( i H c ) change from 0 to 487 Oe in different samples. The highest M max value of 57 emu/g was obtained in the sample after 3 h of hydrothermal treatment with PVP addition. The i H c value of this sample was 35 Oe, while without PVP addition, the high M max value of 60 emu/g is observed in a sample that has i H c value equal to 320 Oe.

  11. PEG-assisted hydrothermal synthesis of CoFe2O4 nanoparticles with enhanced selective adsorption properties for different dyes

    NASA Astrophysics Data System (ADS)

    Wu, Xiaofei; Wang, Wei; Li, Feng; Khaimanov, Spartak; Tsidaeva, Natalia; Lahoubi, Mahieddine

    2016-12-01

    Cobalt ferrite nanoparticles (CFO NPs) are synthesized by a facile and polyethylene glycol (PEG) assisted hydrothermal method. In the synthesis of cobalt ferrites, PEG is used as a surfactant. The formation of single-phase spinel structure in the samples is confirmed by XRD patterns. TEM images show that the addition of PEG results in the decrease in the size of the CFO NPs. When the amount of PEG is lower than 2.4 g, the particle sizes decrease, then, further increasing the concentration of PEG in the solution, the particle sizes begin to increase, for much more PEG will cover onto the surface of the nanoparticles. Here, the existence of PEG on the surface of CFO NPs is confirmed from the characteristic bands of PEG in FTIR spectra. All the samples are ferromagnetic, and their saturation magnetization (Ms) decreases with the increase in PEG concentration. The as-synthesized samples show highly selective adsorption characteristics for organic dyes. Compared with methyl orange (MO) and methyl blue (MB) dyes, good adsorption performance of the PEG/CoFe2O4 nanocomposites for Congo red (CR) dye is presented. Moreover, the addition of PEG greatly enhances their adsorption capacity (qe) for CR. The corresponding adsorption behavior fits well with the pseudo-second-order kinetic model and the Langmuir model. And the adsorption mechanism is investigated. This study suggests that the as-prepared products can be regarded as an excellent selective adsorbent to remove dyes from the wastewater.

  12. Magnetic and structural studies on CoFe2O4 nanoparticles synthesized by co-precipitation, normal micelles and reverse micelles methods

    NASA Astrophysics Data System (ADS)

    Sharifi, Ibrahim; Shokrollahi, H.; Doroodmand, Mohammad Mahdi; Safi, R.

    2012-05-01

    Cobalt ferrite nanoparticles were synthesized by the chemical co-precipitation, normal micelles and reverse micelles methods of iron and cobalt chlorides. X-ray diffraction analysis, Fourier Transform Infrared (FTIR) and Vibrating Sample Magnetometer were carried out at room temperature to study the structural and magnetic properties. X-ray patterns revealed the production of a broad single cubic phase with the average particle sizes of ∼12 nm, 5 nm and 8 nm for co-precipitation, normal micelles and reverse micelles methods, respectively. The FTIR measurements between 400 and 4000 cm-1 confirmed the intrinsic cation vibrations of spinel structure for each one of the three methods. Moreover, the average particle sizes were lower than the single domain size (128 nm) and higher than the super-paramagnetic size (2-3 nm) at room temperature. The results revealed that the magnetic properties depend on the particle size and cation distribution, whereas the role of particle size is more significant.

  13. Intrinsic dependence of the magnetic properties of CoFe2O4 nanoparticles prepared via chemical methods with addition of chelating agents

    NASA Astrophysics Data System (ADS)

    Mendonça, E. C.; Tenório, Mayara A.; Mecena, S. G.; Zucolotto, B.; Silva, L. S.; Jesus, C. B. R.; Meneses, C. T.; Duque, J. G. S.

    2015-12-01

    In this work, the effect of addition of different chelating agents on the magnetic properties of cobalt ferrite nanoparticles produced by the combining of both co-precipitation and hydrothermal methods is reported. The Rietveld analyses of X-ray diffraction patterns reveal that our samples are single phase (space group: Fd-3m) with small average sizes. The weight losses observed in the thermogravimetric measurements together with the M×H curves show that the organic contamination coming from chelating agent decomposition can give rise to misinterpretation of the magnetization measurements. Besides, analyses of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements and the M×H curves measured at room temperature allows us to state that both the average blocking temperature and particles size distribution are sensitive to the kind of chelating agent.

  14. Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Xu, S. T.; Ma, Y. Q.; Zheng, G. H.; Dai, Z. X.

    2015-04-01

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23 817 and 15 056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

  15. X-ray diffraction studies on crystallite size evolution of CoFe 2O 4 nanoparticles prepared using mechanical alloying and sintering

    NASA Astrophysics Data System (ADS)

    Waje, Samaila Bawa; Hashim, Mansor; Yusoff, Wan Daud Wan; Abbas, Zulkifly

    2010-03-01

    Nanosized cobalt ferrite spinel particles have been prepared by using mechanically alloyed nanoparticles. The effects of various preparation parameters on the crystallite size of cobalt ferrite which includes milling time; ball-to powder weight ratio (BPR) and sintering temperature, were studied using X-ray diffractometer (XRD). Scherrer's equation was used to study the crystallite size evolution of the as-prepared materials. The results of the as-milled sample revealed that both milling time and BPR plays a role in determining the crystallite size of the milled powder. However, where sintering is involved, the sintering temperature results in grain growth, and thus plays a dominant role in determining the final crystallite size of the samples sintered at higher temperature (above 900 °C). From the vibrating-sample magnetometer (VSM) measurement it was observed that the coercivity of the as-milled samples without sintering is almost negligible, which is a type characteristic of superparamagnetic material. However, for the sintered samples, the saturation increases while coercivity decreases with increases sintering temperature.

  16. Crystallographic and magnetic properties of the hyperthermia material CoFe2O4@AlFe2O4

    NASA Astrophysics Data System (ADS)

    Choi, Hyunkyung; An, Mijeong; Eom, Wonyoung; Lim, Sae Wool; Shim, In-Bo; Kim, Chul Sung; Kim, Sam Jin

    2017-01-01

    Hard/soft CoFe2O4@AlFe2O4 core/shell nanoparticles were prepared by using a high temperature thermal decomposition method with seed-mediated growth. The structural, magnetic and thermal properties of the nanoparticles were investigated by using X-ray diffraction, vibrating sample magnetometer, MagneTherm, and Mössbauer spectroscopy. The crystal structure of nanoparticles was determined to be cubic spinel ferrite with space group Fd-3m. The CoFe2O4 nanoparticles were found to show high magnetization and coercivity while AlFe2O4 nanoparticles were found to show low magnetization and coercivity. The CoFe2O4@AlFe2O4 core/shell nanoparticles showed intermediate values of magnetization and the coercivity between those of CoFe2O4 and AlFe2O4. Also, the blocking temperature ( T B ) of the nanoparticles (NPs) was observed to be 280, 50, and 225 K for CoFe2O4, AlFe2O4 and CoFe2O4@AlFe2O4, respectively. The core/shell ferrite shows a T B near 225 K, associated with the harder CoFe2O4 NPs. Temperatures below 225 K, the zero-field-cooled curves show changes in their slopes at a temperature near 50 K, corresponding to the second blocking temperature associated with the softer AlFe2O4 NPs.

  17. Towards high performance CoFe2O4 isotropic nanocrystalline powder for permanent magnet applications

    NASA Astrophysics Data System (ADS)

    Pedrosa, F. J.; Rial, J.; Golasinski, K. M.; Guzik, M. N.; Quesada, A.; Fernández, J. F.; Deledda, S.; Camarero, J.; Bollero, A.

    2016-11-01

    We report on a comparative study of high performance isotropic cobalt ferrite (CoFe2O4) powder processed by dry and surfactant assisted (wet) ball milling. Milling times as short as 1.5 min (dry) and 6 min (wet) have resulted in a 4-fold increase in coercivity, with a maximum achieved value above 318 kA/m (4 kOe). The use of surfactant is shown to be advantageous in the formation of a more homogeneous structure constituted by non-agglomerated and strained nanoparticles. A record (BH) max value of 18.6 kJ m - 3 (2.34 MGOe) has been obtained for isotropic powder after post-processing annealing. This magnetic performance combined with the required short processing times and the unnecessary requirement of oxygen avoidance in the milling process, makes this CoFe2O4 powder a good candidate for permanent magnet applications.

  18. Magnetic properties of the nanocomposite CoFe2O4/FeCo-FeO at a high H/T regime

    NASA Astrophysics Data System (ADS)

    Machado, F. L. A.; Soares, J. M.; Conceição, O. L. A.; Choi, E. S.; Balicas, L.

    2017-02-01

    The low temperature magnetic properties of nanopowders of CoFe2O4 and of CoFe2O4/FeCo-FeO with average particle size of about 6 nm were investigated for temperatures down to 5 K and for applied magnetic fields up to 350 kOe. Highly enhanced coercive fields were obtained for the CoFe2O4 nanoparticles. The values of the saturation magnetization MS and of the anisotropy constant K1 were also found to be enhanced for the nanocomposite powder sample. The overall results are discussed in terms of a particle model which takes into account a thin amorphous layer present in the CoFe2O4 particles and due to a FeCo-FeO layer grown during an annealing procedure. Moreover, the temperature dependence of K1 was found to be in good agreement with a model proposed by Tachiki.

  19. Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres

    NASA Astrophysics Data System (ADS)

    Gonçalves, R.; Martins, P.; Moya, X.; Ghidini, M.; Sencadas, V.; Botelho, G.; Mathur, N. D.; Lanceros-Mendez, S.

    2015-04-01

    Magnetoelectric 0-1 composites comprising CoFe2O4 (CFO) nanoparticles in a polyvinylidene fluoride (PVDF) polymer-fibre matrix have been prepared by electrospinning. The average diameter of the electrospun composite fibres is ~325 nm, independent of the nanoparticle content, and the amount of the crystalline polar β phase is strongly enhanced when compared to pure PVDF polymer fibres. The piezoelectric response of these electroactive nanofibres is modified by an applied magnetic field, thus evidencing the magnetoelectric character of the CFO/PVDF 0-1 composites.

  20. Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres.

    PubMed

    Gonçalves, R; Martins, P; Moya, X; Ghidini, M; Sencadas, V; Botelho, G; Mathur, N D; Lanceros-Mendez, S

    2015-05-07

    Magnetoelectric 0-1 composites comprising CoFe2O4 (CFO) nanoparticles in a polyvinylidene fluoride (PVDF) polymer-fibre matrix have been prepared by electrospinning. The average diameter of the electrospun composite fibres is ∼325 nm, independent of the nanoparticle content, and the amount of the crystalline polar β phase is strongly enhanced when compared to pure PVDF polymer fibres. The piezoelectric response of these electroactive nanofibres is modified by an applied magnetic field, thus evidencing the magnetoelectric character of the CFO/PVDF 0-1 composites.

  1. Conduction mechanism and gas sensing properties of CoFe2O4 nanocomposite thick films for H2S gas.

    PubMed

    Bodade, Anjali B; Bodade, Archana B; Wankhade, H G; Chaudhari, G N; Kothari, D C

    2012-01-30

    Nanocrystalline 10 wt% Ni and 0.2 wt% Sm doped CoFe(2)O(4) was prepared by sol-gel citrate method and calcined at different temperatures. The CoFe(2)O(4) nanoparticles were characterized by X-ray diffraction (XRD), electrical properties were studied by impedance analysis. The XRD of CoFe(2)O(4) shows cubic structure with grain growth of 40 nm. The ac conductivity was studied for the sample 10 wt% Ni and 0.2 wt% Sm doped CoFe(2)O(4) calcined at 650°C, at temperature range from 100 to 700°C over a wide range of frequencies from 50 Hz to 200 kHz. The result indicates that the ac conductivity depend on temperature, frequency and concentration of dopant. Nanocrystalline 10 wt% Ni and 0.2 wt% Sm doped CoFe(2)O(4) was found to be good H(2)S sensor with high sensitivity and selectivity.

  2. Building of CoFe2/CoFe2O4/MgO architectures: Structure, magnetism and surface functionalized by TiO2

    NASA Astrophysics Data System (ADS)

    Wang, M.; Ma, Y. Q.; Sun, X.; Geng, B. Q.; Wu, M. Z.; Zheng, G. H.; Dai, Z. X.

    2017-01-01

    Well-dispersed uniform CoFe2O4 nanoparticles were prepared and then coated by MgO through thermal decomposition of a metal-organic salt in organic solvent. Then CoFe2O4/MgO were reduced in a H2/N2 mixture gas and subsequently oxidized in an ambient atmosphere in order to build CoFe2/CoFe2O4/MgO architectures with high magnetization, good chemical stability and dispersivity, which are useful in some practical applications. MgO can be dissolved by the HCl solution. The surfaces of CoFe2O4, CoFe2/MgO, CoFe2 and CoFe2/CoFe2O4 magnetic particles were functionalized by TiO2 to prepare the magnetically separable photocatalysts. The rattle-type particles were obtained without the assistance of template and etchant. The photocatalytic activity of these photocatalysts in degradation of methylene blue and the magnetic separability were investigated: The nanosheet-shaped TiO2 and rattle-type particles exhibited good photocatalytic performance; The highest degradation efficiency reaches 93% for the CoFe2/TiO2 sample which has the highest magnetization value of 42 emu/g, beneficial for the recovery of catalyst after degradation.

  3. Microemulsion synthesis and magnetic properties of hydroxyapatite-encapsulated nano CoFe2O4

    NASA Astrophysics Data System (ADS)

    Foroughi, Firoozeh; Hassanzadeh-Tabrizi, S. A.; Amighian, Jamshid

    2015-05-01

    Hydroxyapatite-encapsulated cobalt ferrite (CoFe2O4) nanopowders were synthesized by one step microemulsion method. The powders were characterized by X-ray Diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. TEM results showed that nanoparticles calcined at 700 °C have core-shell morphology. It was found that the resultant phases, morphology and magnetic properties of the samples depend on calcining temperature. The synthesized nanoparticles showed a maximum saturation magnetization of 7.8 emu/g with a wasp-waisted hysteresis loop. The magnetion was reduced by increasing calcining temperature to 900 °C. This reduction is due to the reaction of cobalt ferrite with hydroxyapatite which leads to CaFe12(PO4)8(OH)12 phase.

  4. ZnO supported CoFe2O4 nanophotocatalysts for the mineralization of Direct Blue 71 in aqueous environments.

    PubMed

    Sathishkumar, Panneerselvam; Pugazhenthiran, Nalenthiran; Mangalaraja, Ramalinga Viswanathan; Asiri, Abdullah M; Anandan, Sambandam

    2013-05-15

    In this study, an attempt was made to render both the magnetic and photocatalytic properties in a semiconductor material to enhance the efficiency of degradation and recycling possibility of magnetic nanophotocatalysts. CoFe2O4 and CoFe2O4 loaded ZnO nanoparticles were prepared by a simple co-precipitation method and characterized using various analytical tools and in addition to check its visible light assisted photocatalytic activity. CoFe2O4/ZnO nanocatalyst coupled with acceptor, peroxomonosulphate (PMS) showed 1.69-fold enhancement in Direct Blue 71 (triazo dye; DB71) mineralization within 5h. The accomplished enrichment in decolorization was due to the production of more number of non-selective and active free radicals at the catalyst surface.

  5. A simple aloe vera plant-extracted microwave and conventional combustion synthesis: Morphological, optical, magnetic and catalytic properties of CoFe2O4 nanostructures

    NASA Astrophysics Data System (ADS)

    Manikandan, A.; Sridhar, R.; Arul Antony, S.; Ramakrishna, Seeram

    2014-11-01

    Nanocrystalline magnetic spinel CoFe2O4 was synthesized by a simple microwave combustion method (MCM) using ferric nitrate, cobalt nitrate and Aloe vera plant extracted solution. For the comparative study, it was also prepared by a conventional combustion method (CCM). Powder X-ray diffraction, energy dispersive X-ray and selected-area electron diffraction results indicate that the as-synthesized samples have only single-phase spinel structure with high crystallinity and without the presence of other phase impurities. The crystal structure and morphology of the powders were revealed by high resolution scanning electron microscopy and transmission electron microscopy, show that the MCM products of CoFe2O4 samples contain sphere-like nanoparticles (SNPs), whereas the CCM method of samples consist of flake-like nanoplatelets (FNPs). The band gap of the samples was determined by UV-Visible diffuse reflectance and photoluminescence spectroscopy. The magnetization (Ms) results showed a ferromagnetic behavior of the CoFe2O4 nanostructures. The Ms value of CoFe2O4-SNPs is higher i.e. 77.62 emu/g than CoFe2O4-FNPs (25.46 emu/g). The higher Ms value of the sample suggest that the MCM technique is suitable for preparing high quality nanostructures for magnetic applications. Both the samples were successfully tested as catalysts for the conversion of benzyl alcohol. The resulting spinel ferrites were highly selective for the oxidation of benzyl alcohol and exhibit important difference among their activities. It was found that CoFe2O4-SNPs catalyst show the best performance, whereby 99.5% selectivity of benzaldehyde was achieved at close to 93.2% conversion.

  6. Preparation and adsorption properties of magnetic CoFe2O4-chitosan composite microspheres

    NASA Astrophysics Data System (ADS)

    Lian, Qi; Zheng, Xue-Fang; Hu, Tie-Feng

    2015-11-01

    Magnetic chitosan microspheres made from novel polymer materials show outstanding applied characteristics. Magnetic chitosan microspheres are rather cheap, non-toxic, tasteless, alkali resistant, corrosion resistant, easily degradable, easily recyclable, and so on. It can be widely used in many fields. In this paper, magnetic CoFe2O4/chitosan core-shell microspheres are prepared by means of emulsification cross-linking technique using CoFe2O4 as core and glutaric dialdehyde as crosslinking agent. The results demonstrated that the different calcining temperature of magnetic (CoFe2O4) particles, CoFe2O4/chitosan ratio and stirring time of the suspension medium are the most effective parameters that control the size, size distribution, morphology and magnetism of the described microspheres. Finally, the size, morphology and chemical structure of the prepared materials are studied by different methods. The results show that the optimal calcination temperature of magnetic particles is 700°C, the optimal ratio of CoFe2O4/chitosan is 1: 1, ultrasonic dispersion time is 30 min. The prepared chitosan magnetic microspheres have small size and are well dispersed when the stirring time is 3 h. The prepared magnetic chitosan microspheres are well shaped spheres with a diameter from 1 to 50 μm, in which CoFe2O4 particles are dispersed uniformly. The magnetic chitosan microspheres show excellent magnetic response and have good adsorption characteristics.

  7. Synthesize and characterization of a novel anticorrosive cobalt ferrite nanoparticles dispersed in silica matrix (CoFe2O4-SiO2) to improve the corrosion protection performance of epoxy coating

    NASA Astrophysics Data System (ADS)

    Gharagozlou, M.; Ramezanzadeh, B.; Baradaran, Z.

    2016-07-01

    This study aimed at studying the effect of an anticorrosive nickel ferrite nanoparticle dispersed in silica matrix (NiFe2O4-SiO2) on the corrosion protection properties of steel substrate. NiFe2O4 and NiFe2O4-SiO2 nanopigments were synthesized and then characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscope (TEM). Then, 1 wt.% of nanopigments was dispersed in an epoxy coating and the resultant nanocomposites were applied on the steel substrates. The corrosion inhibition effects of nanopigments were tested by an electrochemical impedance spectroscopy (EIS) and salt spray test. Results revealed that dispersing nickel ferrite nanoparticles in a silica matrix (NiFe2O4-SiO2) resulted in the enhancement of the nanopigment dispersion in the epoxy coating matrix. Inclusion of 1 wt.% of NiFe2O4-SiO2 nanopigment into the epoxy coating enhanced its corrosion protection properties before and after scratching.

  8. Effect of starting solution acidity on the characteristics of CoFe2O4 powders prepared by solution combustion synthesis

    NASA Astrophysics Data System (ADS)

    Pourgolmohammad, B.; Masoudpanah, S. M.; Aboutalebi, M. R.

    2017-02-01

    Cobalt ferrite (CoFe2O4) nanoparticles were synthesized at the different pH values of starting solution, adjusted by NH4OH, using solution combustion method. Theoretical calculations and Fourier transform infrared spectroscopy analysis were carried out for determination and controlling the chelated species in solution. The phase evolution, surface area, morphology and magnetic properties of the combusted CoFe2O4 powders have been investigated by thermal analysis, X-ray diffractometry, electron microscopy, adsorption-desorption and vibrating sample magnetometer. The combustion rate mainly depends on pH which affects the phase and crystallite size. Furthermore, the specific surface area of the porous CoFe2O4 powders decreases from 66.25 to 27.09 m2/g by the increase of pH from 2 to 10. The combusted CoFe2O4 powders exhibit ferromagnetic properties which the highest saturation magnetization of 63.7 emu/g was achieved at pH of 2. Furthermore, the coercivity increases from 1112 to 1225 Oe by the increase of pH due to the decreasing of crystallite size.

  9. Effect of Gd3+ substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe2O4

    NASA Astrophysics Data System (ADS)

    Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Kumar, Arun; Singh, Mahavir

    2017-03-01

    Nanoparticles of CoGdxFe2-xO4 with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd3+ substitution effect on different properties of nanocrystalline CoFe2O4 has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd3+ ions occupy the octahedral site in CoFe2O4. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd3+ substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd3+ substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd3+ substitution for Fe3+ at the octahedral sites. Low dielectric loss suggested the applicability of Gd3+ doped CoFe2O4 nanoparticles for high frequency microwave device applications.

  10. Self-oriented CoFe2O4 composites for non-reciprocal microwave components

    NASA Astrophysics Data System (ADS)

    Tchangoulian, A.; Abou Diwan, E.; Vincent, D.; Neveu, S.; Nader, C.; Habchy, R.

    2014-07-01

    In telecommunication systems, heavy bulky magnets are used to establish the proper functioning of a circulator by ensuring the uniform orientation of the ferrite material's magnetic moment. Thus to develop an unbiased coplanar microwave circulator, the approach based on "ferromagnetic nanowired composite substrates" was promising. The idea was to do a magnetophoretic deposition of nanocoloidal cobalt ferrite nanoparticles into porous alumina membranes and permanently orient them uniformly. Therefore, in order to check the orientation possibility of the nanoparticle, samples of magnetic thin films on glass substrates were synthetized from CoFe2O4 nanoparticles dispersed in a silica sol-gel matrix using the dip-coating technique with and without a uniformly applied magnetic field. To investigate the magnetic behavior of the prepared samples, the Faraday rotation as a function of the applied magnetic field was measured using a spectral polarimeter. The unambiguous qualitative difference between the Faraday rotation hysteresis loops shows a large variation of coercive (μ0Hc) and remanent field (Mr/Ms) values, thus proving the orientation of the nanoparticles. Such nanocomposite is a promising candidate for future miniature microwave circulators fabrication.

  11. Structural and magnetic properties of turmeric functionalized CoFe2O4 nanocomposite powder

    NASA Astrophysics Data System (ADS)

    Mehran, E.; Farjami Shayesteh, S.; Sheykhan, M.

    2016-10-01

    The structural and magnetic properties of the synthesized pure and functionalized CoFe2O4 magnetic nanoparticles (NPs) are studied by analyzing the results from the x-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR spectroscopy, thermogravimetry (TG), and vibrating sample magnetometer (VSM). To extract the structure and lattice parameters from the XRD analysis results, we first apply the pseudo-Voigt model function to the experimental data obtained from XRD analysis and then the Rietveld algorithm is used in order to optimize the model function to estimate the true intensity values. Our simulated intensities are in good agreement with the experimental peaks, therefore, all structural parameters such as crystallite size and lattice constant are achieved through this simulation. Magnetic analysis reveals that the synthesized functionalized NPs have a saturation magnetization almost equal to that of pure nanoparticles (PNPs). It is also found that the presence of the turmeric causes a small reduction in coercivity of the functionalized NPs in comparison with PNP. Our TGA and FTIR results show that the turmeric is bonded very well to the surface of the NPs. So it can be inferred that a nancomposite (NC) powder of turmeric and nanoparticles is produced. As an application, the anti-arsenic characteristic of turmeric makes the synthesized functionalized NPs or NC powder a good candidate for arsenic removal from polluted industrial waste water. Project supported by the University of Guilan and the Iran Nanotechnology Initiative Council.

  12. Spin Hall magnetoresistance in CoFe2O4/Pt films

    DOE PAGES

    Wu, Hao; Qintong, Zhang; Caihua, Wan; ...

    2015-05-13

    Pulse laser deposition and magnetron sputtering techniques have been employed to prepare MgO(001)//CoFe2O4/Pt samples. Cross section transmission electron microscope results prove that the CoFe2O4 film epitaxially grew along (001) direction. X-ray magnetic circular dichroism results show that magnetic proximity effect in this sample is negligible. Magnetoresistance (MR) properties confirm that spin Hall MR (SMR) dominates in this system. Spin Hall effect-induced anomalous Hall voltage was also observed in this sample. Lastly, these results not only demonstrate the universality of SMR effect but also demonstrate the utility in spintronics of CoFe2O4 as a new type of magnetic insulator.

  13. Magnetoelectricity in CoFe2O4 nanocrystal-P(VDF-HFP) thin films

    PubMed Central

    2013-01-01

    Transition metal ferrites such as CoFe2O4, possessing a large magnetostriction coefficient and high Curie temperature (Tc > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0–3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 μm. We describe the synthesis and structural characterization of the nanocrystals and composite films by XRD, TEM, HRTEM, STEM, and SEM, as well as dielectric and magnetic properties, in order to identify evidence of cooperative interactions between the two phases. The CoFe2O4 polymer nanocomposite thin films exhibit composition-dependent effective permittivity, loss tangent, and specific saturation magnetization (Ms). An enhancement of the effective permittivity and saturation magnetization of the CoFe2O4-P(VDF-HFP) films was observed and directly compared with CoFe2O4-polyvinylpyrrolidone, a non-ferroelectric polymer-based nanocomposite prepared by the same method. The comparison provided evidence for the observation of a magnetoelectric effect in the case of CoFe2O4-P(VDF-HFP), attributed to a magnetostrictive/piezoelectric interaction. An enhancement of Ms up to +20.7% was observed at room temperature in the case of the 10 wt.% CoFe2O4-P(VDF-HFP) sample. PMID:24004499

  14. Fabrication of CoFe2O4 ferrite nanowire arrays in porous silicon template and their local magnetic properties

    NASA Astrophysics Data System (ADS)

    Hui, Zheng; Man-Gui, Han; Long-Jiang, Deng

    2016-02-01

    CoFe2O4 ferrite nanowire arrays are fabricated in porous silicon templates. The porous silicon templates are prepared via metal-assisted chemical etching with gold (Au) nanoparticles as the catalyst. Subsequently, CoFe2O4 ferrite nanowires are successfully synthesized into porous silicon templates by the sol-gel method. The magnetic hysteresis loop of nanowire array shows an isotropic feature of magnetic properties. The coercivity and squareness ratio (Mr/Ms) of ensemble nanowires are found to be 630 Oe (1 Oe, = 79.5775 A·m-1 and 0.4 respectively. However, the first-order reversal curve (FORC) is adopted to reveal the probability density function of local magnetostatic properties (i.e., interwire interaction field and coercivity). The FORC diagram shows an obvious distribution feature for interaction field and coercivity. The local coercivity with a value of about 1000 Oe is found to have the highest probability. Project supported by the National Natural Science Foundation of China (Grant No. 61271039), the Scientific Projects of Sichuan Province, China (Grant No. 2015HH0016), and the Natural Science Foundations of Zhejiang Province, China (Grant Nos. LQ12E02001 and Y107255).

  15. THz conductivity of semi-insulating and magnetic CoFe2O4 nano-hollow structures through thermally activated polaron

    NASA Astrophysics Data System (ADS)

    Rakshit, Rupali; Serita, Kazunori; Tonouchi, Masayoshi; Mandal, Kalyan

    2016-11-01

    Herein, terahertz (THz) time domain spectroscopy is used to measure the complex conductivity of semi-insulating CoFe2O4 nanoparticles (NPs) and nano-hollow spheres (NHSs) with different diameters ranging from 100 to 350 nm having a nanocrystalline shell thickness of 19 to 90 nm, respectively. Interestingly, the magnitude of conductivity for CoFe2O4 NPs and NHSs of same average diameter (˜100 nm) for a given frequency of 0.3 THz is found to be 0.33 S/m and 9.08 S/m, respectively, indicating that the hollow structure exhibits greater THz conduction in comparison to its solid counterpart. Moreover, THz conductivity can be tailored by varying the nano-shell thickness of NHSs, and a maximum conductivity of 15.61 S/m is observed at 0.3 THz for NHSs of average diameter 250 nm. A detailed study reveals that thermally activated polaronic hopping plays the key role in determining the electrical transport property of CoFe2O4 nanostructures, which is found to solely depend on their magnitude of THz absorptivity. The non-Drude conductivity of all CoFe2O4 nanostructures is well described by the Polaron model instead of the Drude-Smith model, which is relevant for backscattering of free electrons in a nanostructured material. The Polaron model includes intra-particle and interparticle polaronic conductivities for closely spaced magnetic nanostructures and provides a mean free path of 29 nm for CoFe2O4 NPs of diameter 100 nm, which is comparable with its average crystallite size, indicating the applicability of the developed model for nanomaterials where charge transport is determined by polaronic hopping. Finally, we have demonstrated the morphology and size dependent magnetic measurements of ferrimagnetically aligned CoFe2O4 nanostructures through a vibrating sample magnetometer in the temperature range of 80-250 K, revealing that the disordered surface spin layer of nanostructures significantly controls their magnetism.

  16. Magnetoreflection of light in CoFe2O4 magnetostrictive spinel

    NASA Astrophysics Data System (ADS)

    Sukhorukov, Yu. P.; Telegin, A. V.; Nosov, A. P.; Bessonov, V. D.; Buchkevich, A. A.

    2016-09-01

    The reflection and magnetoreflection of natural light within the infrared spectral range is studied in single crystals of CoFe2O4 ferrimagnetic ferrite spinel. Correlation between the reflection of light and magnetoelastic characteristics of this spinel is found. It is shown that the most significant magnetic-field-induced changes in the magnetoreflection of the spinel occur near the fundamental absorption edge and within the range of the phonon spectrum.

  17. Simultaneous Presence Of Ferroelectricity And Magnetism In Mo-Doped CoFe2O4

    NASA Astrophysics Data System (ADS)

    Dwivedi, G. D.; Tseng, K. F.; Chan, C. L.; Shahi, P.; Chatterjee, B.; Ghosh, A. K.; Yang, H. D.; Chatterjee, Sandip

    2010-12-01

    Signature of ferroelectricity has been observed for the first time in magnetically ordered Co(Fe1-xMox)2O4. The structural property of Co(Fe1-xMox)2O4 (x ranges from 0 to 0.1) indicates that Mo goes into the tetrahedral site. The frequency dependent P-E loop indicates the existence of weak ferroelectricity in Mo-doped CoFe2O4.

  18. Flux growth of high-quality CoFe 2O 4 single crystals and their characterization

    NASA Astrophysics Data System (ADS)

    Wang, W. H.; Ren, X.

    2006-04-01

    We report the growth of high-quality CoFe 2O 4 single crystals using a borax flux method. The crystals were characterized by powder X-ray diffraction, electron probe microanalysis and Raman spectroscopy. We found the crystals are flux-free and highly homogeneous in composition. X-ray rocking curves of the CoFe 2O 4 single crystals showed a full-width at half-maximum of 0.15°. The saturation magnetization of the CoFe 2O 4 single crystals was measured to be 90 emu/g or equivalently 3.65 μ B/f.u. at 5 K.

  19. Preparation and microwave absorption property of graphene/BaFe12O19/CoFe2O4 nanocomposite

    NASA Astrophysics Data System (ADS)

    Yang, Haibo; Ye, Ting; Lin, Ying; Liu, Miao

    2015-12-01

    The graphene/BaFe12O19/CoFe2O4 nanocomposite powders were successfully synthesized by a deoxidation technique. The phase composition, morphology and electromagnetic properties of the nanocomposites were characterized by various instruments. The as-prepared graphene/BaFe12O19/CoFe2O4 nanocomposite exhibits a saturated magnetization of 50.42 emu/g. The electromagnetic parameters of graphene/BaFe12O19/CoFe2O4 nanocomposite were investigated in the 2-18 GHz range. The graphene/BaFe12O19/CoFe2O4 nanocomposite exhibits better microwave absorbing properties than BaFe12O19/CoFe2O4 nanocomposite. The excellent microwave absorbing property is achieved and the minimum reflection loss of the nanocomposite can reach -32.4 dB, which is obviously enhanced compared with that of the BaFe12O19/CoFe2O4 nanocomposite.

  20. On the microstructural and magnetic properties of fine-grained CoFe2O4 ceramics produced by combining polyol process and spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Gaudisson, T.; Artus, M.; Acevedo, U.; Herbst, F.; Nowak, S.; Valenzuela, R.; Ammar, S.

    2014-12-01

    Starting from polyol-made CoFe2O4 ferrite nanoparticles of different aggregation states, high-density fine-grained ceramics were produced using Spark Plasma Sintering technique at 600 and 500 °C, under vacuum and applying a uniaxial pressure of more than 80 MPa. The grain growth of thus produced ceramics appears to be proportional to the temperature plateau and inversely proportional to the aggregation state of the initial powders. Average grain sizes ranging between about 50 and 350 nm were obtained. In all the cases, magnetic measurements evidenced a ferrimagnetic behavior at room temperature with non-zero coercivity, while their starting powders exhibited superparamagnetic features.

  1. The magnetization reversal in CoFe2O4/CoFe2 granular systems

    NASA Astrophysics Data System (ADS)

    Jin, J.; Sun, X.; Wang, M.; Ding, Z. L.; Ma, Y. Q.

    2016-12-01

    The temperature-dependent field cooling (FC) and zero-field cooling (ZFC) magnetizations, i.e., M FC and M ZFC, measured under different magnetic fields from 500 Oe to 20 kOe have been investigated on two exchange-spring CoFe2O4/CoFe2 composites with different relative content of CoFe2. Two samples exhibit different magnetization reversal behaviors. With decreasing temperature, a progressive freezing of the moments in two composites occurs at a field-dependent irreversible temperature T irr. For the sample with less CoFe2, the curves of - d( M FC - M ZFC)/ dT versus temperature T exhibit a broad peak at an intermediate temperature T 2 below T irr , and the moments are suggested not to fully freeze till the lowest measuring temperature 10 K. However, for the - d( M FC - M ZFC)/ dT curves of the sample with more CoFe2, besides a broad peat at an intermediate temperature T 2, a rapid rise around the low temperature T 1 15 K is observed, below which the moments are suggested to fully freeze. Increase of magnetic field from 2 kOe leads to the shift of T 2 and T irr towards a lower temperature, and the shift of T 2 is attributable to the moment reversal of CoFe2O4.

  2. Research Update: Facile synthesis of CoFe2O4 nano-hollow spheres for efficient bilirubin adsorption

    NASA Astrophysics Data System (ADS)

    Rakshit, Rupali; Pal, Monalisa; Chaudhuri, Arka; Mandal, Madhuri; Mandal, Kalyan

    2015-11-01

    Herein, we report an unprecedented bilirubin (BR) adsorption efficiency of CoFe2O4 (CFO) nanostructures in contrast to the commercially available activated carbon and resin which are generally used for haemoperfusion and haemodialysis. We have synthesized CFO nanoparticles of diameter 100 nm and a series of nano-hollow spheres of diameter 100, 160, 250, and 350 nm using a simple template free solvothermal technique through proper variation of reaction time and capping agent, oleylamine (OLA), respectively, and carried out SiO2 coating by employing Stöber method. The comparative BR adsorption study of CFO and SiO2 coated CFO nanostructures indicates that apart from porosity and hollow configuration of nanostructures, the electrostatic affinity between anionic carboxyl group of BR and cationic amine group of OLA plays a significant role in adsorbing BR. Finally, we demonstrate that the BR adsorption capacity of the nanostructures can be tailored by varying the morphology as well as size of the nanostructures. We believe that our developed magnetic nanostructures could be considered as a potential material towards therapeutic applications against hyperbilirubinemia.

  3. The magnetization of epitaxial nanometric CoFe2O4(001) layers

    NASA Astrophysics Data System (ADS)

    Rigato, F.; Geshev, J.; Skumryev, V.; Fontcuberta, J.

    2009-12-01

    We have studied the magnetic anisotropy of nanometric CoFe2O4 (CFO) thin films grown on (100)SrTiO3 (STO) substrates. It has been found that epitaxial substrate-induced compressive strain makes the normal-to-film axis harder than the in-plane directions. In agreement with some previous reports, the magnetization loops are found to display a characteristic shrinking at low fields. Detailed structural and microstructural analyses, together with a modeling of the magnetization loops, revealed that the microstructure of the films, namely, the coexistence of a continuous CFO and a distribution of pyramidal CFO huts emerging from the surface, are responsible for this peculiar feature. We argue that this behavior, which significantly impacts the magnetic properties, could be a general trend of spinel films grow on (001)STO substrates.

  4. Flexible Heteroepitaxy of CoFe2O4/Muscovite Bimorph with Large Magnetostriction.

    PubMed

    Liu, Heng-Jui; Wang, Chih-Kuo; Su, Dong; Amrillah, Tahta; Hsieh, Ying-Hui; Wu, Kun-Hong; Chen, Yi-Chun; Juang, Jenh-Yih; Eng, Lukas M; Jen, Shien-Uang; Chu, Ying-Hao

    2017-03-01

    A bimorph composed of ferrimagnetic cobalt ferrite (CoFe2O4, CFO) and flexible muscovite was fabricated via van der Waals epitaxy. The combination of X-ray diffraction and transmission electron microscopy was conducted to reveal the heteroepitaxy of the CFO/muscovite system. The robust magnetic behaviors against mechanical bending were characterized by hysteresis measurements and magnetic force microscopy, which maintain a saturation magnetization (Ms) of ∼120-150 emu/cm(3) under different bending states. The large magnetostrictive response of the CFO film was then determined by digital holographic microscopy, where the difference of magnetostrction coefficient (Δλ) is -104 ppm. The superior performance of this bimorph is attributed to the nature of weak interaction between film and substrate. Such a flexible CFO/muscovite bimorph provides a new platform to develop next-generation flexible magnetic devices.

  5. Flexible Heteroepitaxy of CoFe 2 O 4 /Muscovite Bimorph with Large Magnetostriction

    DOE PAGES

    Liu, Heng-Jui; Wang, Chih-Kuo; Su, Dong; ...

    2017-02-03

    Van der Waals epitaxy was used to fabricate a bimorph composed of ferrimagnetic cobalt ferrite (CoFe2O4, CFO) and flexible muscovite. The combination of X-ray diffraction and transmission electron microscopy was conducted to reveal the heteroepitaxy of the CFO/muscovite system. The robust magnetic behaviors against mechanical bending were characterized by hysteresis measurements and magnetic force microscopy, which maintain a saturation magnetization (Ms) of ~120–150 emu/cm3 under different bending states. The large magnetostrictive response of the CFO film was then determined by digital holographic microscopy, where the difference of magnetostrction coefficient (Δλ) is -104 ppm. We attribute the superior performance of thismore » bimorph to the nature of weak interaction between film and substrate. Such a flexible CFO/muscovite bimorph provides a new platform to develop next-generation flexible magnetic devices.« less

  6. Thickness dependence of exchange coupling in epitaxial Fe3O4/CoFe2O4 soft/hard magnetic bilayers

    NASA Astrophysics Data System (ADS)

    Lavorato, G.; Winkler, E.; Rivas-Murias, B.; Rivadulla, F.

    2016-08-01

    Epitaxial magnetic heterostructures of (soft -) Fe3O4/(hard -) CoFe2O4(001 ) have been fabricated with a varying thicknesses of soft ferrite from 5 to 25 nm. We report a change in the regime of magnetic interaction between the layers from rigid-coupling to exchange-spring behavior, above a critical thickness of the soft magnetic Fe3O4 layer. We show that the symmetry and epitaxial matching between the spinel structures of CoFe2O4 and Fe3O4 at the interface stabilize the Verwey transition close to the bulk value even for 5-nm-thick Fe3O4 . The large interface exchange-coupling constant estimated from low-temperature M (H ) data confirmed the good quality of the ferrite-ferrite interface and the major role played by the interface in the magnetization dynamics. The results presented here constitute a model system for understanding the magnetic behavior of interfaces in core/shell nanoparticles and magnetic oxide-based spintronic devices.

  7. Toxicity of cobalt ferrite (CoFe2O4) nanobeads in Chlorella vulgaris: interaction, adaptation and oxidative stress.

    PubMed

    Ahmad, Farooq; Yao, Hongzhou; Zhou, Ying; Liu, Xiaoyi

    2015-11-01

    The potential toxicity of CoFe2O4 nanobeads (NBs) in Chlorella vulgaris was observed up to 72h. Algal cell morphology, membrane integrity and viability were severely compromised due to adsorption and aggregation of NBs on algal surfaces, release of Fe(3+) and Co(2+) ions and possible mechanical damage by NBs. Interactions with NBs and effective decrease in ions released by aggregation and exudation of algal cells as a self defense mechanism were observed by Fourier transform infrared attenuated total reflectance (FTIR-ATR) and inductively coupled plasma mass spectrometry (ICP-MS). The results corroborated CoFe2O4 NBs induced ROS triggered oxidative stress, leading to a reduction in catalase activity, activation of the mutagenic glutathione s-transferase (mu-GST) and acid phosphatase (AP) antioxidant enzymes, and an increase in genetic aberrations, metabolic and cellular signal transduction dysfunction. Circular dichroism (CD) spectra indicated the weak interactions of NBs with BSA, with slight changes in the α-helix structure of BSA confirming conformational changes in structure, hence the potential for functional interactions with biomolecules. Possible interferences of CoFe2O4 NBs with assay techniques and components indicated CoFe2O4 NBs at lower concentration do not show any significant interference with ROS, catalase, mu-GST and no interference with CD measurements. This study showed ROS production is one of the pathways of toxicity initiated by CoFe2O4 NBs and illustrates the complex processes that may occur between organisms and NBs in natural complex ecosystem.

  8. FTIR and UV-vis diffuse reflectance spectroscopy studies of the wet chemical (WC) route synthesized nano-structure CoFe(2)O(4) from CoCl(2) and FeCl(3).

    PubMed

    Habibi, Mohammad Hossein; Parhizkar, Hadi Janan

    2014-06-05

    Nano-structure CoFe(2)O(4) has been fabricated by wet chemical route using CoCl2 and FeCl3 as simple precursors. The prepared nano-structure samples was calcined at 600°C and characterized by fourier transform infrared spectra (FTIR), UV-vis diffuse reflectance spectroscopy (DRS), X-ray powder diffractometry (XRD), and field emission scanning electron microscopy (FESEM). X-ray diffraction patterns confirmed the presence of the spinel phases with average crystallite sizes of 47nm. Field emission scanning electron microscopy investigations showed spherical morphology of nanoparticles with average particle size of 46nm. The FTIR spectra of CoFe(2)O(4) nanoparticles showed absorption bands at about 594cm(-1) and 401cm(-1) due to the stretching vibrations of Co-O and Fe-O respectively. Investigation of the optical properties of the produced nano-structure CoFe(2)O(4) confirmed its semiconducting properties by revealing two optical band gaps at 1.4 and 2.0eV.

  9. In situ chemical vapor deposition growth of carbon nanotubes on hollow CoFe2O4 as an efficient and low cost counter electrode for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Yuan, Hong; Jiao, Qingze; Zhang, Shenli; Zhao, Yun; Wu, Qin; Li, Hansheng

    2016-09-01

    The composites of hollow CoFe2O4 and carbon nanotubes (h-CoFe2O4@CNTs) are successfully prepared by using a simple hydrothermal process coupling with the in-situ chemical vapor deposition (CVD) as electrocatalytic materials for counter electrode of dye-sensitized solar cells. The CNTs are uniformly grown on the surface of hollow CoFe2O4 particles verified by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) measurements. The electrochemical performances of hollow CoFe2O4@CNTs composites are evaluated by the EIS, Tafel polarization and CV measurements, and exhibiting high electrocatalytic performance for the reduction of triiodide. The presence of conductive polypyrrole nanoparticles could further improve the conductivity and catalytic performance of the resultant composites. Controlling the thickness of composites film, the optimum photovoltaic conversion efficiency of 6.55% is obtained, which is comparable to that of the cells fabricated with Pt counter electrode (6.61%). In addition, the composites exhibit a good long-term electrochemical stability in I3-/I- electrolyte.

  10. Tuning the formation and functionalities of ultrafine CoFe2O4 nanocrystals via interfacial coherent strain.

    PubMed

    Hsieh, Ying-Hui; Kuo, Ho-Hung; Liao, Sheng-Chieh; Liu, Heng-Jui; Chen, Ying-Jiun; Lin, Hong-Ji; Chen, Chien-Te; Lai, Chih-Huang; Zhan, Qian; Chueh, Yu-Lun; Chu, Ying-Hao

    2013-07-21

    Complex oxide nanocrystals with a spinel structure show their remarkable optical, electronic, mechanical, thermal, and magnetic properties. In this study, we present a simple yet versatile strategy to grow self-assembled epitaxial CoFe2O4 nanocrystals with well-controlled size (less than 10 nm) and single orientation. CoFe2O4 nanocrystals were fabricated via phase separation in a BiFeO3-CoF2O4 ultrathin film by pulsed laser deposition. The coherent strain at the BiFeO3-CoF2O4 interface suppressed the growth of the nanocrystals regardless of substrate temperatures. This strain also resulted in the ferromagnetic anisotropy and interesting conducting behaviors of ultrafine CFO nanocrystals.

  11. A facile hydrothermal synthesis, characterization and magnetic properties of mesoporous CoFe2O4 nanospheres

    NASA Astrophysics Data System (ADS)

    Reddy, M. Penchal; Mohamed, A. M. A.; Zhou, X. B.; Du, S.; Huang, Q.

    2015-08-01

    Mesoporous CoFe2O4 nanospheres with an average size of 180 nm were fabricated via a facile hydrothermal process using ethylene glycol as solvent and sodium acetate (NaAc) as electrostatic stabilizer. In this method, ethylene glycol plays a vital role in the formation of cobalt nanoospheres as a solvent and reducing agent. The structure and morphology of the prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The nanospheres exhibited ferromagnetic properties with high saturation magnetization value of about 60.19 emu/g at room temperature. The BET surface area of the nanospheres was determined using the nitrogen absorption method. The porous CoFe2O4 nanospheres displayed good magnetic properties, which may provide a very promising candidate for their applications in target drug delivery.

  12. Pillar shape modulation in epitaxial BiFeO3-CoFe2O4 vertical nanocomposite films

    NASA Astrophysics Data System (ADS)

    Kim, Dong Hun; Aimon, Nicolas M.; Ross, C. A.

    2014-08-01

    Self-assembled epitaxial CoFe2O4-BiFeO3 nanocomposite films, in which pillars of CoFe2O4 grow within a single crystal BiFeO3 matrix, show both ferrimagnetism and ferroelectricity. The pillars typically have a uniform cross-section, but here two methods are demonstrated to produce a width modulation during growth by pulsed laser deposition. This was achieved by growing a blocking layer of BiFeO3 to produce layers of separated pillars or pillars with constrictions, or by changing the temperature during growth to produce bowling-pin shaped pillars. Modulated nanocomposites showed changes in their magnetic anisotropy compared to nanocomposites with uniform width. The magnetic anisotropy was interpreted as a result of magnetoelastic and shape anisotropies.

  13. Metal-insulator-metal transition in NdNiO3 films capped by CoFe2O4

    NASA Astrophysics Data System (ADS)

    Saleem, M. S.; Song, C.; Peng, J. J.; Cui, B.; Li, F.; Gu, Y. D.; Pan, F.

    2017-02-01

    Metal-insulator transition features as a transformation from a highly charge conductive state to another state where the charge conductivity is greatly suppressed when decreasing the temperature. Here, we demonstrate two consecutive transitions in NdNiO3 films with CoFe2O4 capping, in which the metal-insulator transition occurs at ˜85 K, followed by an unprecedented insulator-metal transition below 40 K. The emerging insulator-metal transition associated with a weak antiferromagnetic behavior is observed in 20 unit cell-thick NdNiO3 with more than 5 unit cell CoFe2O4 capping. Differently, the NdNiO3 films with thinner CoFe2O4 capping only exhibit metal-insulator transition at ˜85 K, accompanied by a strong antiferromagnetic state below 40 K. Charge transfer from Co to Ni, instead of from Fe to Ni, formulates the ferromagnetic interaction between Ni-Ni and Ni-Co atoms, thus suppressing the antiferromagnetic feature and producing a metallic conductive behavior. Furthermore, a phase diagram for the metal-insulator-metal transition in this system is drawn.

  14. Could microwave induced catalytic oxidation (MICO) process over CoFe2O4 effectively eliminate brilliant green in aqueous solution?

    PubMed

    Ju, Yongming; Wang, Xiaoyan; Qiao, Junqin; Li, Guohua; Wu, You; Li, Yuan; Zhang, Xiuyu; Xu, Zhencheng; Qi, Jianying; Fang, Jiande; Dionysiou, Dionysios D

    2013-12-15

    In this study, we adopted the chemical co-precipitation (CP) method and sol-gel method followed by calcination at temperatures of 100-900°C for 12h to synthesize CoFe2O4 materials, which were further characterized by TEM, XRD and XPS techniques. The properties of CoFe2O4 materials were evaluated in a microwave (MW) induced catalytic oxidation (MICO) process for the elimination of brilliant green (BG). The results showed that: (1) the removal rates of BG gradually decreased over a series of CoFe2O4 materials prepared by CP method and calcinated with 100-700°C (except 900°C) for 12h within three reuse cycles; for comparison, no removal of BG was obtained over CoFe2O4 synthesized by sol-gel method and CoFe2O4-900 (CP); (2) no hydroxyl radicals were captured with salicylic acid used as molecular probe in the MICO process; (3) MW irradiation enhanced the release of residual NaOH within the microstructure of CoFe2O4 and further discolored BG, because BG is sensitive to pH; (4) granular activated carbon (GAC), an excellent MW-absorbing material possessing higher dielectric loss tangent compared to that of a series of CoFe2O4 materials, could not remove BG in suspensions at a higher efficiency, even if the loading amount was 20 g L(-1). Accordingly, MICO process over CoFe2O4 materials and GAC could not effectively eliminate BG in suspensions.

  15. Enhanced photo-Fenton-like process over Z-scheme CoFe2O4/g-C3N4 Heterostructures under natural indoor light.

    PubMed

    Yao, Yunjin; Wu, Guodong; Lu, Fang; Wang, Shaobin; Hu, Yi; Zhang, Jie; Huang, Wanzheng; Wei, Fengyu

    2016-11-01

    Low-cost catalysts with high activity and stability toward producing strongly oxidative species are extremely desirable, but their development still remains a big challenge. Here, we report a novel strategy for the synthesis of a magnetic CoFe2O4/C3N4 hybrid via a simple self-assembly method. The CoFe2O4/C3N4 was utilized as a photo-Fenton-like catalyst for degradation of organic dyes in the presence of H2O2 under natural indoor light irradiation, a green and energy-saving approach for environmental cleaning. It was found the CoFe2O4/C3N4 hybrid with a CoFe2O4: g-C3N4 mass ratio of 2:1 can completely degrade Rhodamine B nearly 100 % within 210 min under room-light irradiation. The effects of the amount of H2O2 (0.01-0.5 M), initial dye concentration (5-20 mg/L), solution pH (3.08-10.09), fulvic acid concentration (5-50 mg/L), different dyes and catalyst stability on the organic dye degradation were investigated. The introduction of CoFe2O4 on g-C3N4 produced an enhanced separation efficiency of photogenerated electron - hole pairs by a Z-scheme mechanism between the interfaces of g-C3N4 and CoFe2O4, leading to an excellent activity as compared with either g-C3N4 or CoFe2O4 and their mixture. This study demonstrates an efficient way to construct the low-cost magnetic CoFe2O4/C3N4 heterojunction as a typical Z-scheme system in environmental remediation.

  16. Directed self-assembly of epitaxial CoFe2O(4)-BiFeO3 multiferroic nanocomposites.

    PubMed

    Comes, Ryan; Liu, Hongxue; Khokhlov, Mikhail; Kasica, Richard; Lu, Jiwei; Wolf, Stuart A

    2012-05-09

    CoFe(2)O(4) (CFO)-BiFeO(3) (BFO) nanocomposites are an intriguing option for future memory and logic technologies due to the magnetoelectric properties of the system. However, these nanocomposites form with CFO pillars randomly located within a BFO matrix, making implementation in devices difficult. To overcome this, we present a technique to produce patterned nanocomposites through self-assembly. CFO islands are patterned on Nb-doped SrTiO(3) to direct the self-assembly of epitaxial CFO-BFO nanocomposites, producing square arrays of CFO pillars.

  17. Synthesis of ordered mesoporous CoFe2O4-containing silica by self-assembly process

    NASA Astrophysics Data System (ADS)

    Yuan, Xiaoyan; Cheng, Laifei; Liu, Wen; Zhang, Litong

    2013-04-01

    Magnetic CoFe2O4-containing silica with an ordered mesoporous structure was prepared by the self-assembly associated with triblock copolymer, tetraethyl orthosilicate, ferric nitrate and cobalt nitrate. Ammonia water was added to adjust the pH value for collecting the mixture, and then the products were obtained at various temperatures in air. The final products were investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption isotherm, and vibrating sample magnetometer measurements. As a result, the as-prepared magnetically hybrid porous silica possesses ordered 2-D hexagonal (p6mm) mesoporosity with uniform pore-size distribution and high surface areas (up to 283 m2/g at 1000 °C). A pure CoFe2O4 with a high degree of crystallization was formed in the amorphous silica matrix at 1000 °C. In addition, this self-assembly method can be applied to prepare other composites with highly ordered mesostructures. Such nanocomposites with hydrophilic and magnetic framework showed a good dispersibility in water and an easy separation procedure.

  18. Magnetic and magnetostrictive behavior of Dy 3+ doped CoFe 2O 4 single crystals grown by flux method

    NASA Astrophysics Data System (ADS)

    Kambale, Rahul C.; Song, K. M.; Won, C. J.; Lee, K. D.; Hur, N.

    2012-02-01

    We studied the effect of Dy 3+ content on the magnetic properties of cobalt ferrite single crystal. The single crystals of CoFe 1.9Dy 0.1O 4 were grown by the flux method using Na 2B 4O 7.10 H 2O (Borax) as a solvent (flux). The black and shiny single crystals were obtained as a product. The X-ray diffraction analysis at room temperature confirmed the spinel cubic structure with lattice constant a=8.42 Å of the single crystals. The compositional analysis endorses the presence of constituents Co, Fe and Dy elements after sintering at 1300 °C within the final structure. The magnetic hysteresis measurements at various temperatures viz. 10 K, 100 K, 200 K and 300 K reveal the soft ferrimagnetic nature of the single crystal than that of for pure CoFe 2O 4. The observed saturation magnetization ( Ms) and coercivity ( Hc) are found to be lower than that of pure CoFe 2O 4 single crystal. The magnetostriction ( λ) measurement was carried out along the [001] direction. The magnetic measurements lead to conclude that the present single crystals can be used for magneto-optic recording media.

  19. Magnetic studies of CoFe2O4/SiO2 aerogel and xerogel nanocomposites.

    PubMed

    da Silva, J B; Mohallem, N D S; Sinnecker, E; Novak, M A; Alburquerque, A S; Ardisson, J D; Macedo, W A

    2009-10-01

    The evolution of the structural and magnetic properties of nanocomposites formed by cobalt ferrite particles dispersed in xerogel and aerogel silica matrices (CoFe2O4/SiO2) have been studied as a function of the temperature of preparation and the amount of ferrite dispersed in the matrix. Wet samples with different amounts of CoFe2O4 in SiO2 matrix were prepared by sol-gel process in monolithic form. Xerogel and aerogel samples were prepared by controlled and hypercritical drying, respectively, and heated at various temperatures between 300 and 1100 degrees C. Superparamagnetic behavior has been observed by magnetization studies at room temperature for xerogels prepared at low temperature. Aerogel samples showed significant superparamagnetic fractions for all thermal treatment temperatures as determined by Mössbauer spectroscopy. Magnetization of the nanocomposites at 10 KOe applied field varied from 1 to 19 emu/g and the coercivity from 90 to 2320 Oe, respectively, for the different morphologies and textures of the analyzed material. The results show that besides the magnetization and coercivity depend on crystallite size, parameters such as ferrite content, porosity and drying conditions greatly influence the nanocomposite magnetic behavior.

  20. Preparation and characterization of self-assembled percolative BaTiO3-CoFe2O4 nanocomposites via magnetron co-sputtering.

    PubMed

    Yang, Qian; Zhang, Wei; Yuan, Meiling; Kang, Limin; Feng, Junxiao; Pan, Wei; Ouyang, Jun

    2014-04-01

    BaTiO3-CoFe2O4 composite films were prepared on (100) SrTiO3 substrates by using a radio-frequency magnetron co-sputtering method at 750 °C. These films contained highly (001)-oriented crystalline phases of perovskite BaTiO3 and spinel CoFe2O4, which can form a self-assembled nanostructure with BaTiO3 well-dispersed into CoFe2O4 under optimized sputtering conditions. A prominent dielectric percolation behavior was observed in the self-assembled nanocomposite. Compared with pure BaTiO3 films sputtered under similar conditions, the nanocomposite film showed higher dielectric constants and lower dielectric losses together with a dramatically suppressed frequency dispersion. This dielectric percolation phenomenon can be explained by the 'micro-capacitor' model, which was supported by measurement results of the electric polarization and leakage current.

  1. Magnetic Properties of Liquid-Phase Sintered CoFe2O4 for Application in Magnetoelastic and Magnetoelectric Transducers

    PubMed Central

    de Brito, Vera Lúcia Othéro; Cunha, Stéphanie Alá; Lemos, Leonardo Violim; Nunes, Cristina Bormio

    2012-01-01

    Cobalt ferrite is a ferrimagnetic magnetostrictive ceramic that has potential application in magnetoelastic and magnetoelectric transducers. In this work, CoFe2O4 was obtained using a conventional ceramic method and Bi2O3 was used as additive in order to obtain liquid-phase sintered samples. Bi2O3 was added to the ferrite in amounts ranging from 0.25 mol% to 0.45 mol% and samples were sintered at 900 °C and 950 °C. It was observed the presence of Bi-containing particles in the microstructure of the sintered samples and the magnetostriction results indicated microstructural anisotropy. It was verified that it is possible to get dense cobalt ferrites, liquid-phase sintered, with relative densities higher than 90% and with magnetostriction values very close to samples sintered without additives. PMID:23112589

  2. The resistive switching memory of CoFe2O4 thin film using nanoporous alumina template

    PubMed Central

    2014-01-01

    A novel conductive process for resistive random access memory cells is investigated based on nanoporous anodized aluminum oxide template. Bipolar resistive switching characteristic is clearly observed in CoFe2O4 thin film. Stable and repeatable resistive switching behavior is acquired at the same time. On the basis of conductive filament model, possible generation mechanisms for the resistive switching behaviors are discussed intensively. Besides, the magnetic properties of samples (before and after the annealing process) are characterized, and the distinct changes of magnetic anisotropy and coercive field are detected. The present results provide a new perspective to comprehend the underlying physical origin of the resistive switching effect. PACS 68.37.-d; 73.40.Rw; 73.61.-r PMID:25404869

  3. Dwell time effects on high coercivity CoFe2O4 thin films deposited by the solution processing

    NASA Astrophysics Data System (ADS)

    Tang, Xianwu; Jin, Linghua; Chen, Fangchu; Wei, Renhuai; Yang, Jie; Dai, Jianming; Song, Wenhai; Zhu, Xuebin; Sun, Yuping

    2016-10-01

    High room temperature coercivity CoFe2O4 (CFO) thin films are desirable in view of many applications, which is seldom achieved over 3 kOe in solution deposited CFO thin films. Herein, grain growth kinetic is investigated in the solution derived CFO thin films with coercivity larger than 4 kOe, showing a relaxation mechanism. The coercivity and magnetization increase initially and then decrease with increasing dwell time. The high coercivity is originated mainly from the critical grain size and the growth strain induced by the small crystallites and poorly developed grains. The results will provide a route to fabricate larger-area CFO thin films with high coercivity on silicon wafers by low-cost solution processing.

  4. Influence of La doping and synthesis method on the properties of CoFe2O4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Mansour, S. F.; Hemeda, O. M.; El-Dek, S. I.; Salem, B. I.

    2016-12-01

    Nanocrystals of La doped CoFe2O4 were synthesized using three different techniques: flash autocombustion, citrate-nitrate and the standard ceramic technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the obtained nanocrystals. All samples were crystallized in a spinel structure with cubic symmetry. The decrease in the lattice constant was endorsed to the large difference in ionic radii of both La+3 (1.216 Å) and Fe (0.65 Å) in 6-f coordination. The citrate method displayed superior Ms values amongst all techniques. The coercivity was found to exhibit largest values for the citrate method and then the flash while smallest values are associated with ceramic technique.

  5. Comparative study of nano-sized particles CoFe2O4 effects on superconducting properties of Y-123 and Y-358

    NASA Astrophysics Data System (ADS)

    Slimani, Y.; Hannachi, E.; Ben Salem, M. K.; Hamrita, A.; Varilci, A.; Dachraoui, W.; Ben Salem, M.; Ben Azzouz, F.

    2014-10-01

    The effects of nano-sized CoFe2O4 particles (10 nm) addition on the structural and the normal state resistivity of YBa2Cu3O7 (noted Y-123) and Y3Ba5Cu8O18 (noted Y-358) polycrystalline were systematically studied. Samples were synthesized in oxygen atmosphere using a standard solid state reaction technique by adding CoFe2O4 up to 2 wt%. Phases, microstructure and superconductivity have been systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical measurements ρ(T). XRD results reveal that the lattice parameters change for both Y-123 and Y-358 phases. SEM observations reveal that the grain size is reduced with increasing the content of CoFe2O4. The measurements for the resistivity dependence of temperature show that the depression in superconducting temperature is more pronounced for CoFe2O4 addition in Y-358 compound than in Y-123 one. These results may be attributed to the existence of much more disorder due to a greater number of Cu sites to be substituted by Fe and Co in Y-358 compared to Y-123.

  6. Structural, electronic and magnetic properties of RE3+-doping in CoFe2O4: A first-principles study

    NASA Astrophysics Data System (ADS)

    Hou, Y. H.; Huang, Y. L.; Hou, S. J.; Ma, S. C.; Liu, Z. W.; Ouyang, Y. F.

    2017-01-01

    RE3+(RE=La, Ce, Pr, Nd, Eu, Gd) doped cobalt ferrite (CoFe2O4) have been studied systematically by the first-principles calculations based on density functional theory within the generalized gradient approximation with Hubbard corrections (GGA+U) . The significant effects of RE3+doping on the crystal structure, electronic and magnetic properties of CoFe2O4 have been explored. The calculated results show that the RE ions prefer substituting Fe3+ located at the octahedral sites. And the lattice constant of CoFe1.875RE0.125O4 (RE=La, Ce, Pr, Nd, Eu and Gd) decreases due to the decreasing ionic radius of RE as the atomic number increases. The magnetic properties depend on the unpaired 4f electrons of RE3+ ions. The net magnetic moment of CoFe2O4 increases by doping with Eu and Gd, the reason is that there are more unpaired 4f electrons for Eu3+and Gd3+. However, the net magnetic moment of CoFe2O4 decreases by doping with La, Ce, Pr, and Nd, due to the reason that these RE ions prefer their low spin configurations.

  7. Label-free electrochemical immunosensor based on enhanced signal amplification between Au@Pd and CoFe2O4/graphene nanohybrid

    PubMed Central

    Zhang, Yong; Li, Jiaojiao; Wang, Zhiling; Ma, Hongmin; Wu, Dan; Cheng, Qianhe; Wei, Qin

    2016-01-01

    The improvement of sensitivity of electrochemical immunosensor can be achieved via two approaches: increasing loading capacities of antibody and enlarging responding electrochemical signals. Based on these, CoFe2O4/graphene nanohybrid (CoFe2O4/rGO) as support was firstly used for preparing electrochemical biosensor, and with the addition of Au@Pd nanorods (NRs) as mimic enzyme, a label-free electrochemical immunosensor was prepared. Due to the high electrical conductivity, open porous structure and large loading capacities of CoFe2O4/rGO, the enhanced signal amplification between Au@Pd NRs and CoFe2O4/rGO was studied. Fabricated as a novel substrate, the prepared immunosensor had a good analytical performance and exhibited a wide linear range from 0.01 to 18.0 ng·mL−1 with a low detection limit of 3.3 pg·mL−1 for estradiol, which was succeeded in applying to detect estradiol in the natural water. PMID:26987503

  8. Direct formation of reusable TiO2/CoFe2O4 heterogeneous photocatalytic fibers via two-spinneret electrospinning.

    PubMed

    Li, Cong-Ju; Wang, Jiao-Na; Wang, Bin; Gong, Jian Ru; Lin, Zhang

    2012-03-01

    A reusable photocatalytic TiO2/CoFe2O4 composite nanofiber was directly formed by using a vertical two-spinneret electrospinning process and sol-gel method, followed by heat treatment at 550 degrees C for 2 h. The high photocatalytic activity of the composite nanofibers depends on the good morphology of the fibers and the appropriate calcination temperature. The crystal structure and magnetic properties of the fibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The photocatalytic activity of the TiO2/CoFe2O4 fibers was investigated through ultraviolet-visible absorbance following the photo-oxidative decomposition of phenol. Meanwhile, the presence of CoFe2O4 not only broadens the response region of visible light, but also enhances the absorbance of UV light. Furthermore, these fibers displayed photocatalytic activity associated with magnetic activity of CoFe2O4 ferrites, allowing easy separated of the photocatalysts after the photo-oxidative process and effectively avoided the secondary pollution of the treated water.

  9. Induced ferromagnetism and magnetoelectric coupling in ion-beam synthesized BiFeO3-CoFe2O4 nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Modarresi, H.; Lazenka, V.; Menéndez, E.; Lorenz, M.; Bisht, M.; Volodin, A.; Van Haesendonck, C.; Grundmann, M.; Van Bael, M. J.; Temst, K.; Vantomme, A.

    2016-08-01

    Ferrimagnetic CoFe2O4 (cobalt ferrite) is formed within an epitaxial BiFeO3 (bismuth ferrite) thin film matrix by Co channeled ion implantation and subsequent annealing. The presence of nanoscale CoFe2O4 crystals in the matrix is confirmed by x-ray diffraction using synchrotron radiation. The significantly increased magnetic moment and the low-temperature coercive field of the composite system evidence the formation of ferrimagnetic cobalt ferrite and its nanoscale character, respectively. The results demonstrate that ion beam synthesis is an appropriate method to controllably transform a planar system into a granular one, increasing the interface area between cobalt ferrite and bismuth ferrite. The ferroelectric nature of the BiFeO3-CoFe2O4 composite is confirmed by several scanning probe microscopy techniques. At room temperature, the composite exhibits a magnetoelectric voltage coefficient of α ME  =  17.5 V (cm · Oe)-1, while a single-phase BiFeO3 thin film shows a α ME value of 4.2 V (cm · Oe)-1. The high magnetoelectric voltage coefficient is interpreted to be the result of the interfacial interaction between the ferrimagnetic CoFe2O4 nanocrystallites and the multiferroic BiFeO3 matrix.

  10. CoFe2O4 and/or Co3Fe7 loaded porous activated carbon balls as a lightweight microwave absorbent.

    PubMed

    Li, Guomin; Wang, Liancheng; Li, Wanxi; Ding, Ruimin; Xu, Yao

    2014-06-28

    In order to prepare a lightweight and efficient microwave absorbent, porous activated carbon balls (PACB) were used to load Fe(3+) and Co(2+) ions, because the PACB carrier has a high specific surface area of 800 m(2) g(-1) and abundant pores, including micropores and macropores. The loaded Fe(3+) and Co(2+) ions in the PACB composite were transformed into magnetic CoFe2O4 and/or Co3Fe7 particles during subsequent heat-treatment under an Ar atmosphere. According to the XRD and SEM results, the magnetic particles were embedded in the PACB macropores and showed different crystalline phases and morphologies after heat-treatment. CoFe2O4 flakes with spinel structure were obtained at approximately 450 °C, and were then transformed into loose quasi-spheres between 500 °C and 600 °C, where CoFe2O4 and Co3Fe7 coexisted because of the partial reduction of CoFe2O4. Co3Fe7 microspheres appeared above 700 °C. The density of the magnetic PACB composites was in the range of 2.2-2.3 g cm(-3). The as-synthesized PACB composites exhibited excellent microwave absorbability, which was mainly attributed to the magnetism of CoFe2O4 and Co3Fe7, as well as the presence of graphitized carbon. The minimum reflection loss value of the CoFe2O4-Co3Fe7-PACB composite reached -32 dB at 15.6 GHz, and the frequency of microwave absorption obeyed the quarter-wavelength matching model, showing a good match between dielectric loss and magnetic loss. The microwave reflection loss (RL) value could be modulated by adjusting the composition and thickness of the PACB composite absorbent. PACB composites with CoFe2O4-Co3Fe7 are a promising candidate for lightweight microwave absorption materials.

  11. Nanolamellar Magnetoelectric BaTiO3-CoFe2O4 Bicrystal

    DTIC Science & Technology

    2009-10-13

    Ma, L. Mohaddes-Ardabili, T . Zhao, L. Salamanca-Riba, S. R. Shinde , S. B. Ogale, F. Bai, D. Viehland, D. G. Schlom, M. Wuttig, and R. Ramesh, Science...and N. D. Mathur, Nature Mater. 6, 348 2007. 14S. Q. Ren, L. Q. Weng, S. H. Song, and F. Li, J . Mater. Sci. 40, 4375 2005. 15R. D. Burbank and H. T ...nanoparticles in ultra-low magnetic fields J . Appl. Phys. 113, 043911 (2013) Edge-induced flattening in the fabrication of ultrathin freestanding

  12. High-coercivity CoFe2O4 thin films on Si substrates by sol-gel

    NASA Astrophysics Data System (ADS)

    Tang, Xianwu; Jin, Linghua; Wei, Renhuai; Zhu, Xiaoguang; Yang, Jie; Dai, Jianming; Song, Wenhai; Zhu, Xuebin; Sun, Yuping

    2017-01-01

    CoFe2O4 (CFO) thin films with high coercivity HC are desirable in applications. The difficulty in achieving large-area CFO thin films with high coercivity by sol-gel has hindered the development of CFO thin films. Herein, polycrystalline CFO thin films with the room temperature out-of-plane and in-plane coercivity HC respectively reached ~5.9 and 3.6 kOe has been achieved on the silicon substrate by sol-gel. The room-temperature maximum magnetic energy product (BH)max and remanence ratio Mr/Ms are of 1.66 MG Oe and 0.58 respectively, which are also the largest values amongst the CFO thin films prepared by solution methods. At the same time, annealing temperature and thickness effects on the HC, (BH)max and Mr/Ms of the derived CFO thin films have been investigated. It is observed that grain size and residual tensile strain in the derived films play an important role in the variations of HC and Mr/Ms. These results will provide an effective route for fabricating larger-area high-coercivity CFO thin films with low-cost by sol-gel on silicon wafers.

  13. Strain-controlled easy axis orientation of epitaxial CoFe2O4 films by He implantation

    NASA Astrophysics Data System (ADS)

    Herklotz, Andreas; Wong, Antony T.; Rus, Stefania F.; Ward, Thomas Z.

    2015-03-01

    Heteroepitaxial strain engineering is an essential tool in the strongly correlated systems for investigating fundamental coupling effects and for more practical control of thin film properties. Here, we use strain doping by He implantation as an alternative technique to control thin film functionalities. We demonstrate the tuning of the magnetic anisotropy of CoFe2O4 (CFO) films through He implantation. Compressively strained thin films of CFO are grown coherently on MgO substrates and show pronounced out-of-plane magnetic anisotropy. Successive doping of the CFO films with He using a commercial ion gun results in an expansion of the out-of-plane lattice parameter while maintaining in-plane epitaxial lock to the substrate. We observe a continuous rotation of the magnetic easy axis towards the film plane with increasing unit cell tetragonality. The results are in agreement with the strain-induced change of the magnetic anisotropy due to the large negative magnetostriction of CFO and demonstrate that strain doping via He implantation is an elegant path to tune desired characteristics of transition metal oxide thin films. This work was supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division.

  14. Reusable nanocomposite of CoFe2O4/chitosan-graft-poly(acrylic acid) for removal of Ni(II) from aqueous solution

    NASA Astrophysics Data System (ADS)

    Nguyen, Van Cuong; Huynh, Thi Kim Ngoc

    2014-06-01

    In this paper, CoFe2O4/chitosan-graft-poly(acrylic acid) (CoFe2O4/CS-graft-PAA) nanocomposites were prepared successfully by coprecipitation of the compounds in alkaline solution and were used for removal of nickel (II) ions from aqueous solution. The sorption rate was affected significantly by the initial concentration of the solution, sorbent amount, and pH value of the solution. Batch experiments were conducted to investigate the adsorption capacity under different initial concentration (ranging from 25 to 150 mg L-1), solution pH (4.1, 5.3, 6.4 and 7.6), and contact time. These nanocomposites can be recycled conveniently from water with the assistance of an external magnet because of their exceptional properties. The prepared nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), x-ray powder diffraction (XRD), and thermogravimetric analysis (TGA).

  15. Multiferroic properties of CoFe2O4/Bi3.4La0.6Ti3O12 bilayer structure at room temperature

    NASA Astrophysics Data System (ADS)

    Charris-Hernández, A.; Melgarejo, R.; Barrionuevo, D.; Kumar, A.; Tomar, M. S.

    2013-07-01

    Bi3.4La0.6Ti3O12/CoFe2O4 bilayer films were synthesized by chemical solution method and deposited by spin coating on Pt (Pt/TiO2/SiO2/Si) substrate. X-ray diffraction of the bilayer system revealed the composite-like structure. The leakage current is less than 10-7 A at electric field below100 kV/cm, and it shows the ohmic behavior. Dielectric constant decreases with increasing frequency and reaches to 140 at 10-6 Hz. Bi3.4La0.6Ti3O12/CoFe2O4 system shows the co-existence of ferroelectric polarization (Pr) = 51 μC/cm2 and magnetization (Mr) = 206 emu/cm3 at room temperature. Observed ferromagnetic and ferroelectric responses in bilayer system may be useful for bi-functional devices.

  16. Development of novel exchange spring magnet by employing nanocomposites of CoFe2O4 and CoFe2

    NASA Astrophysics Data System (ADS)

    Safi, Rohollah; Ghasemi, Ali; Shoja-Razavi, Reza; Tavoosi, Majid

    2016-12-01

    CoFe2O4sbnd CoFe2 hard-soft nanocomposites were prepared via reduction of the cobalt ferrite CoFe2O4 in hydrogen atmosphere at different temperature. The structure and the room temperature magnetization of the samples were characterized by X-ray diffraction, field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM). It was found that the saturation magnetization of the nanocomposite powders increases by reduction temperature while their coercivity decreases. The highest Mr/Ms ratio of 0.52 was obtained for sample reduced at 550 °C. Single smooth hysteresis loops of nanocomposites show that these nanocomposites behave as the single-phase materials. This result indicates the presence of exchange coupling between two different hard and soft phases.

  17. Magnetization-induced enhancement of photoluminescence in core-shell CoFe2O4@YVO4:Eu3+ composite

    NASA Astrophysics Data System (ADS)

    Jia, Yanmin; Zhou, Zhihua; Wei, Yongbin; Wu, Zheng; Chen, Jianrong; Zhang, Yihe; Liu, Yongsheng

    2013-12-01

    After the core-shell CoFe2O4@YVO4:Eu3+ composite synthesized through a facile sol-gel method was magnetized under an external magnetic field of 0.25 T for 4 h, an enhancement of ˜56% in photoluminescence intensity was observed. The remanent magnetization of the CoFe2O4 core increases the intensity of the excited charge transfer transition of VO43- group in YVO4:Eu3+ shell, which may enhance the probability related to the Eu3+ radiative transition 5D0-7F2, yielding to a high photoluminescence. The obvious remanent-magnetization-induced enhancement in photoluminescence is helpful in developing excellent magnetic/luminescent material for the practical display devices.

  18. Tuning the coercive field of CoFe2 in hard/soft CoFe2O4/CoFe2 bilayers

    NASA Astrophysics Data System (ADS)

    Sayed Hassan, R.; Mény, C.; Viart, N.; Ulhaq, C.; Versini, G.; Loison, J. L.; Pourroy, G.

    2007-10-01

    The sensitivity of magnetoresistive devices, i.e. their ability to be switched by very small fields, depends on the softness of their soft electrode. In this paper, we show the possibility to tune the coercive field of the CoFe2 alloy, commonly used as a soft electrode, from intrinsic values down to zero, by varying the pulsed laser ablation conditions of CoFe2/CoFe2O4 bilayers. This tuning possibility relies on the existence of a frustration of the spins of the CoFe2 layer originating from both the ferrimagnetic nature of the CoFe2O4 layer and the oxide/metal interface roughness.

  19. Magnetoelectric coupling effect in lead-free Bi4Ti3O12/CoFe2O4 composite films derived from chemistry solution deposition

    NASA Astrophysics Data System (ADS)

    Tang, Zhehong; Chen, Jieyu; Bai, Yulong; Zhao, Shifeng

    2016-08-01

    Lead-free magnetoelectric composite films combining Bi4Ti3O12 and CoFe2O4 were synthesized by chemical solution deposition on Pt (100)/Ti/SiO2/Si substrate. Morphological and electrical domain structure, ferroelectric, leakage, dielectric, piezoelectric, magnetic and magnetoelectric properties were investigated for Bi4Ti3O12/CoFe2O4 composite films. Well-defined interfaces between Bi4Ti3O12 and CoFe2O4 film layers and electrical domain structure were observed. The composite films show the coexistence of ferroelectric and ferromagnetic orders at room temperature. Larger piezoelectric coefficient and magnetization are obtained for the composite films, which is contributed to the magnetoelectric effect since it originates from the interface coupling through mechanical strain transfer. This work presents a feasible way to modulate the magnetoelectric coupling in ferromagnetic/ferroelectric composite films for developing lead-free micro-electro-mechanical system and information storage devices.

  20. Coin-like α-Fe2O3@CoFe2O4 core-shell composites with excellent electromagnetic absorption performance.

    PubMed

    Lv, Hualiang; Liang, Xiaohui; Cheng, Yan; Zhang, Haiqian; Tang, Dongming; Zhang, Baoshan; Ji, Guangbin; Du, Youwei

    2015-03-04

    In this paper, we designed a novel core-shell composite for microwave absorption application in which the α-Fe2O3 and the porous CoFe2O4 nanospheres served as the core and shell, respectively. Interestingly, during the solvothermal process, the solvent ratio (V) of PEG-200 to distilled water played a key role in the morphology of α-Fe2O3 for which irregular flake, coin-like, and thinner coin-like forms of α-Fe2O3 can be produced with the ratios of 1:7, 1:3, and 1:1, respectively. The porous 70 nm diameter CoFe2O4 nanospheres were generated as the shell of α-Fe2O3. It should be noted that the CoFe2O4 coating layer did not damage the original shape of α-Fe2O3. As compared with the uncoated α-Fe2O3, the Fe2O3@CoFe2O4 composites exhibited improved microwave absorption performance over the tested frequency range (2-18 GHz). In particular, the optimal reflection loss value of the flake-like composite can reach -60 dB at 16.5 GHz with a thin coating thickness of 2 mm. Furthermore, the frequency bandwidth corresponding to the RLmin value below -10 dB was up to 5 GHz (13-18 GHz). The enhanced microwave absorption properties of these composites may originate from the strong electron polarization effect (i.e., the electron polarization between Fe and Co) and the electromagnetic wave scattering on this special porous core-shell structure. In addition, the synergy effect between α-Fe2O3 and CoFe2O4 also favored balancing the electromagnetic parameters. Our results provided a promising approach for preparing an absorbent with good absorption intensity and a broad frequency that was lightweight.

  1. General design of hollow porous CoFe2O4 nanocubes from metal-organic frameworks with extraordinary lithium storage

    NASA Astrophysics Data System (ADS)

    Guo, Hong; Li, Tingting; Chen, Weiwei; Liu, Lixiang; Yang, Xiangjun; Wang, Yapeng; Guo, Yicheng

    2014-11-01

    Hollow porous CoFe2O4 nanocubes from metal-organic frameworks were fabricated through a general facile strategy. The intrinsic hollow nanostructure can shorten the lengths for both electronic and ionic transport, enlarge the surface area of electrodes, and improve accommodation of the volume change during Li insertion/extraction cycling. The hybrid multi-elements characteristics allow the volume change to take place in a stepwise manner during the electrochemical cycle. Therefore, the as-prepared CoFe2O4 electrode exhibits outstanding performance as anode materials for lithium ion batteries. The stable capacity arrives at 815 mA h g-1 for 20 C. Subsequently, a specific capacity of ca. 1043 mA h g-1 is recovered when the current rate reduces back to 1 C after 200 cycles. This general strategy may shed light on a new avenue for large-scale synthesis of hollow porous hybrid nanocubes via MOFs for energy storage, environmental remediation and other novel applications.Hollow porous CoFe2O4 nanocubes from metal-organic frameworks were fabricated through a general facile strategy. The intrinsic hollow nanostructure can shorten the lengths for both electronic and ionic transport, enlarge the surface area of electrodes, and improve accommodation of the volume change during Li insertion/extraction cycling. The hybrid multi-elements characteristics allow the volume change to take place in a stepwise manner during the electrochemical cycle. Therefore, the as-prepared CoFe2O4 electrode exhibits outstanding performance as anode materials for lithium ion batteries. The stable capacity arrives at 815 mA h g-1 for 20 C. Subsequently, a specific capacity of ca. 1043 mA h g-1 is recovered when the current rate reduces back to 1 C after 200 cycles. This general strategy may shed light on a new avenue for large-scale synthesis of hollow porous hybrid nanocubes via MOFs for energy storage, environmental remediation and other novel applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04422c

  2. Magnetic and electric properties of Ru-substituted CoFe2O4 thin films fabricated by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Iwamoto, Fujiyuki; Seki, Munetoshi; Tabata, Hitoshi

    2012-11-01

    Epitaxial thin films of Ru-substituted CoFe2O4 with a cubic spinel structure were fabricated on α-Al2O3 (001) substrates using pulsed laser deposition, and their magnetic and electric properties were investigated. The films showed room temperature ferrimagnetic behavior with hard magnetic features similar to those of non-Ru-substituted cobalt ferrite films. The electrical conductivity of the films was dramatically enhanced by the substitution of Ru. The anomalous Hall effect was observed in all films even at 300 K suggesting that carriers in the films are highly spin-polarized at room temperature as expected from a first-principles calculation.

  3. Monolithic integration of room-temperature multifunctional BaTiO3-CoFe2O4 epitaxial heterostructures on Si(001)

    NASA Astrophysics Data System (ADS)

    Scigaj, Mateusz; Dix, Nico; Gázquez, Jaume; Varela, María; Fina, Ignasi; Domingo, Neus; Herranz, Gervasi; Skumryev, Vassil; Fontcuberta, Josep; Sánchez, Florencio

    2016-08-01

    The multifunctional (ferromagnetic and ferroelectric) response at room temperature that is elusive in single phase multiferroic materials can be achieved in a proper combination of ferroelectric perovskites and ferrimagnetic spinel oxides in horizontal heterostructures. In this work, lead-free CoFe2O4/BaTiO3 bilayers are integrated with Si(001) using LaNiO3/CeO2/YSZ as a tri-layer buffer. They present structural and functional properties close to those achieved on perovskite substrates: the bilayers are fully epitaxial with extremely flat surface, and exhibit robust ferromagnetism and ferroelectricity at room temperature.

  4. Monolithic integration of room-temperature multifunctional BaTiO3-CoFe2O4 epitaxial heterostructures on Si(001)

    PubMed Central

    Scigaj, Mateusz; Dix, Nico; Gázquez, Jaume; Varela, María; Fina, Ignasi; Domingo, Neus; Herranz, Gervasi; Skumryev, Vassil; Fontcuberta, Josep; Sánchez, Florencio

    2016-01-01

    The multifunctional (ferromagnetic and ferroelectric) response at room temperature that is elusive in single phase multiferroic materials can be achieved in a proper combination of ferroelectric perovskites and ferrimagnetic spinel oxides in horizontal heterostructures. In this work, lead-free CoFe2O4/BaTiO3 bilayers are integrated with Si(001) using LaNiO3/CeO2/YSZ as a tri-layer buffer. They present structural and functional properties close to those achieved on perovskite substrates: the bilayers are fully epitaxial with extremely flat surface, and exhibit robust ferromagnetism and ferroelectricity at room temperature. PMID:27550543

  5. Multiferroic CoFe2O4-Pb(Zr0.52Ti0.48)O3 core-shell nanofibers and their magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Xie, Shuhong; Ma, Feiyue; Liu, Yuanming; Li, Jiangyu

    2011-08-01

    Multiferroic CoFe2O4-Pb(Zr0.52Ti0.48)O3 core-shell nanofibers have been synthesized by coaxial electrospinning in combination with a sol-gel process. The core-shell configuration of nanofibers has been verified by scanning electron microscopy and transmission electron microscopy, and the spinel structure of CoFe2O4 and perovskite structure of Pb(Zr0.52Ti0.48)O3 have been confirmed by X-ray diffraction and selected area electron diffraction. The multiferroic properties of core-shell nanofibers have been demonstrated by magnetic hysteresis and piezoresponse force microscopy, and their magnetoelectric coupling has been confirmed by evolution of piezoresponse under an external magnetic field, showing magnetically induced ferroelectric domain switching and changes in switching characteristics. The lateral magnetoelectric coefficient is estimated to be 2.95 × 104 mV/cmOe, two orders of magnitude higher than multiferroic thin films of similar composition.

  6. On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Tileli, Vasiliki; Duchamp, Martial; Axelsson, Anna-Karin; Valant, Matjaz; Dunin-Borkowski, Rafal E.; Alford, Neil Mcn.

    2014-11-01

    The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces.The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces. Electronic supplementary information (ESI) available: Magnetic moment data of the structure, linear decomposition graph of the interface layer in its constituent components of CoFe2O4 and BaTiO3, reference Fe L3,2 EEL data used for MLLS analysis of the Fe oxidation and coordination variation, and a table detailing the partial ionization cross-sections used for quantitative MLLS analysis. See DOI: 10.1039/c4nr04339a

  7. Carbon dioxide-induced homogeneous deposition of nanometer-sized cobalt ferrite (CoFe2O4) on graphene as high-rate and cycle-stable anode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Lingyan; Zhuo, Linhai; Zhang, Chao; Zhao, Fengyu

    2015-02-01

    In the preparation of metal oxide composite materials, the common organic solvents limit the homogenous dispersion of guest component on substrate for their high viscosity, surface tension and low diffusivity. Herein, we take advantage of the unique properties of supercritical carbon dioxide (scCO2) to successfully deposit uniform CoFe2O4 nanoparticles (CFO NPs) on the surface of graphene without need of surfactants or precipitants. The obtained CFO NPs are 8-10 nm in size and homogeneously anchored on graphene sheets as spacers to reduce the degree of graphene restacking. Additionally, the effects of pressure and solvent on the crystallinity, dispersion and particle size of the NPs are discussed. The CFO@G-CE composite synthesized in scCO2-expanded ethanol exhibits excellent cyclability and significantly improved rate capability than the CFO@G-E in pure ethanol and CFO@G-NE in the mixture of high pressure nitrogen and ethanol. It is certified, by the structural and morphological analyses of the intermediates and phase observations, that the reaction medium greatly affects the dispersion and size of the particles, and thus influences their electrochemical performances. The proposed strategy is shortcut (reaction time: 2 h) and effective in execution, hence, we hope that the presented strategy would encourage further studies on other hybrid nanomaterials fabrication.

  8. Hyperfine interaction and tuning of magnetic anisotropy of Cu doped CoFe2O4 ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Batoo, Khalid Mujasam; Salah, Dina; Kumar, Gagan; Kumar, Arun; Singh, Mahavir; Abd El-sadek, M.; Mir, Feroz Ahmad; Imran, Ahamad; Jameel, Daler Adil

    2016-08-01

    Ferrimagnetic oxides may contain single or multi domain particles which get converted into superparamagnetic state near a critical size. To explore the existence of these particles, we have made Mössbauer and magnetic studies of Cu2+ substitution effect in CoFe2-xO4 Ferrites (0.0, 0.1, 0.2, 0.3, 0.4, and 0.5). All the samples have a cubic spinel structure with lattice parameters increasing linearly with increase in Cu content. The hysteresis loops yield a saturation magnetization, coercive field, and remanent magnetization that vary significantly with Cu content. The magnetic hysteresis curves shows a reduction in saturation magnetization and an increase in coercitivity with Cu2+ ion substitution. The anisotropy constant, K1, is found strongly dependent on the composition of Cu2+ ions. The variation of saturation magnetization with increasing Cu2+ ion content has been explained in the light of Neel's molecular field theory. Mössbauer spectra at room temperature shows two ferrimagnetically relaxed Zeeman sextets. The dependence of Mössbauer parameters such as isomer shift, quadrupole splitting, line width and hyperfine magnetic field on Cu2+ ion concentration have been discussed.

  9. Annealing control of magnetic anisotropy and phase separation in CoFe2O4-BaTiO3 nanocomposite films

    NASA Astrophysics Data System (ADS)

    Rafique, Mohsin; Herklotz, A.; Guo, E.-J.; Roth, R.; Schultz, L.; Dörr, K.; Manzoor, Sadia

    2013-12-01

    Multiferroic heteroepitaxial nanocomposite films of BaTiO3 and CoFe2O4 (CFO) have been grown by pulsed laser deposition employing alternating ablation of two ceramic targets. Films grown at temperatures between 650 °C and 710 °C contain columnar CFO grains about 10-20 nm in diameter embedded in a BaTiO3 matrix. The very strong vertical compression of these grains causes large perpendicular magnetic anisotropy. Post-growth annealing treatments above the growth temperature gradually release the compression. This allows one to tune the stress-induced magnetic anisotropy. Additionally, annealing leads to substantial enhancement of the saturation magnetization MS. Since MS of a pure CFO film remains unchanged by a similar annealing procedure, MS is proposed to depend on the volume fraction of the obtained CFO phase. We suggest that MS can be utilized to monitor the degree of phase separation in nanocomposite films.

  10. Multiferroics properties in BiFeO3/CoFe2O4 heterostructures thin films deposited on (111) SrTiO3

    NASA Astrophysics Data System (ADS)

    Singh, Gulab; Singh, Manoj K.; Kumar, Aditya; Dussan, S.; Katiyar, Ram S.

    2016-05-01

    The multiferroic properties of BiFeO3-CoFe2O4 (BFO-CFO) heterostructures thin film grown on (111) SrTiO3 (STO) substrates by employing pulsed laser deposition (PLD) method, have been studied.X ray diffraction analysis reveals the presence of BFO and CFO in two separate phases. The heterostructures BFO/CFO/STO(111) thin films show well - shaped hysteresis loop with saturated magnetization and coercive field, which are much larger than pure BFO/STO thin film. The frequency dependent dielectric anomalies in BFO-CFO multilayer are attributed to the interfacial effect across the presence of CFO as a separate phase embedded in BFO matrix.

  11. Fabrication of magnetic alginate beads with uniform dispersion of CoFe2O4 by the polydopamine surface functionalization for organic pollutants removal

    NASA Astrophysics Data System (ADS)

    Li, Xiaoli; Lu, Haijun; Zhang, Yun; He, Fu; Jing, Lingyun; He, Xinghua

    2016-12-01

    A simple and efficient method for production of magnetic composites by decorating CoFe2O4 with polydopamine (PDA) through oxidative polymerization of dopamine was conducted. Further, magnetic alginate beads with porous structure containing well-dispersed CoFe2O4-PDA were fabricated by ionic crosslinking technology. The resulting SA@CoFe2O4-PDA beads were characterized using scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffractometer, vibrating sample magnetometer and X-ray photoelectron spectroscopy. Adsorption potential of SA@CoFe2O4-PDA beads for organic dyes including Methylene Blue (MB), Crystal Violet (CV) and Malachite Green (MG) was evaluated. SA@CoFe2O4-PDA beads exhibited excellent adsorption performances due to the composite effect, large surface area and porous structure. Organic dyes could be removed from water solution with high efficiency in a wide pH range of 4.0-9.0. Moreover, it exhibited much higher adsorptivity towards MB and CV with the maximum adsorption capacities of 466.60 and 456.52 mg/g, respectively, which were much higher than that of MG (248.78 mg/g). Ca-electrolyte had obvious adverse effects on MB and CV adsorption than MG. FTIR and XPS demonstrated that carboxylate, catechol, hydroxyl and amine groups might be involved in adsorption of organic dyes. The characteristics of wide pH range, high adsorption capacity and convenient magnetic separation would make SA@CoFe2O4-PDA beads as effective adsorbent for removal of organic dyes from wastewater.

  12. Evaluation of SiO2@CoFe2O4 nano-hollow spheres through THz pulses

    NASA Astrophysics Data System (ADS)

    Rakshit, Rupali; Pal, Monalisa; Serita, Kazunori; Chaudhuri, Arka; Tonouchi, Masayoshi; Mandal, Kalyan

    2016-05-01

    We have synthesized cobalt ferrite (CFO) nanoparticles (NPs) of diameter 100 nm and nano-hollow spheres (NHSs) of diameter 100, 160, 250, and 350 nm by a facile one step template free solvothermal technique and carried out SiO2 coating on their surface following Stöber method. The phase and morphology of the nanostructures were confirmed by X-ray diffraction and transmission electron microscope. The magnetic measurements were carried out by vibrating sample magnetometer in order to study the influence of SiO2 coating on the magnetic properties of bare CFO nanostructures. Furthermore, we have applied THz time domain spectroscopy to investigate the THz absorption property of these nanostructures in the frequency range 1.0-2.5 THz. Detailed morphology and size dependent THz absorption study unfolds that the absorption property of these nanostructures sensitively carries the unique signature of its dielectric property.

  13. Regulation of the forming process and the set voltage distribution of unipolar resistance switching in spin-coated CoFe2O4 thin films.

    PubMed

    Mustaqima, Millaty; Yoo, Pilsun; Huang, Wei; Lee, Bo Wha; Liu, Chunli

    2015-01-01

    We report the preparation of (111) preferentially oriented CoFe2O4 thin films on Pt(111)/TiO2/SiO2/Si substrates using a spin-coating process. The post-annealing conditions and film thickness were varied for cobalt ferrite (CFO) thin films, and Pt/CFO/Pt structures were prepared to investigate the resistance switching behaviors. Our results showed that resistance switching without a forming process is preferred to obtain less fluctuation in the set voltage, which can be regulated directly from the preparation conditions of the CFO thin films. Therefore, instead of thicker film, CFO thin films deposited by two times spin-coating with a thickness about 100 nm gave stable resistance switching with the most stable set voltage. Since the forming process and the large variation in set voltage have been considered as serious obstacles for the practical application of resistance switching for non-volatile memory devices, our results could provide meaningful insights in improving the performance of ferrite material-based resistance switching memory devices.

  14. Enhanced electrocatalytic activity of PANI and CoFe2O4/PANI composite supported on graphene for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Mohanraju, Karuppannan; Sreejith, Vasudevan; Ananth, Ramaiyan; Cindrella, Louis

    2015-06-01

    New catalysts of reduced graphene oxide (rGO) with poly aniline (PANI) and cobalt ferrite (CF) have been successfully prepared by simple chemical reduction method. Their electrocatalytic activity for oxygen reduction reaction (ORR) was evaluated. Semi-crystalline nature of CF was analyzed by X-ray diffraction (XRD) study. Surface morphology by HR-SEM showed features of CF particles and PANI film on graphene sheets. FT-IR studies revealed changes in C-N and Cdbnd N stretching vibrations of PANI confirming bonding of PANI to graphene sheets. Raman spectrum showed presence of PANI on distorted graphene layers. TG/DTA revealed thermal stability and extent of loading of CF in composite. ORR performance was studied using catalyst modified rotating disc electrode (RDE). A maximum kinetic current density of -3.46 mA cm-2 at -0.2 V was obtained for CF/PANI/rGO. Tafel slope, onset and half wave potentials for the catalyst were obtained from ORR response. Durability studies showed that synthesized electrocatalyst has better stability and methanol tolerance than commercial Pt/C catalyst. To the best of our knowledge, this is the first study aiming enhancement of ORR activity using PANI and CoFe2O4 on graphene support. A trace amount of Pt in the composite boosted the performance of single PEM fuel cell.

  15. Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film.

    PubMed

    Shirsath, Sagar E; Liu, Xiaoxi; Yasukawa, Yukiko; Li, Sean; Morisako, Akimitsu

    2016-07-20

    Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate.

  16. Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film

    NASA Astrophysics Data System (ADS)

    Shirsath, Sagar E.; Liu, Xiaoxi; Yasukawa, Yukiko; Li, Sean; Morisako, Akimitsu

    2016-07-01

    Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate.

  17. Thin (111) oriented CoFe2O4 and Co3O4 films prepared by decomposition of layered cobaltates

    NASA Astrophysics Data System (ADS)

    Buršík, Josef; Soroka, Miroslav; Uhrecký, Róbert; Kužel, Radomír; Mika, Filip; Huber, Štěpán

    2016-07-01

    The formation and structural characterization of highly (111)-oriented Co3O4 and CoFe2O4 films prepared by a novel procedure from 00l-oriented NaCoO2 and Na(CoFe)O2 is reported. The Na(CoFe)O2 films were deposited on MgO, SrTiO3, LaAlO3, and Zr(Y)O2 single crystals with (100) and (111) orientations by chemical solution deposition method and crystallized at 700 °C. Subsequently they were transformed into (111)-oriented spinel phase during post-growth annealing at 800-1000 °C. Morphology and structure of the films was investigated by means of scanning electron microscopy and X-ray diffraction. While all spinel films exhibit pronounced out-of-plane orientation irrespective of substrate, the rate of in-plane orientation strongly depend on lattice misfit values. Different epitaxial phenomena ranging from true one-to-one epitaxy to the existence of many-to-one epitaxy involving two or more orientations were determined by full 3D texture analysis.

  18. Tuning the photovoltaic effect of multiferroic CoFe2O4/Pb(Zr, Ti)O3 composite films by magnetic fields

    NASA Astrophysics Data System (ADS)

    Pan, Dan-Feng; Chen, Guang-Yi; Bi, Gui-Feng; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

    2016-05-01

    The 0-3 type CoFe2O4-Pb(Zr,Ti)O3 (CFO-PZT) multiferroic composite films have been prepared by a sol-gel process and spin-coating technique. A confirmable photovoltaic effect is observed under ultraviolet light irradiation. Moreover, this photovoltaic effect can be tuned by external magnetic fields. The maximum magnetic modulation ratios of short-circuit current density and open-circuit voltage can reach as high as 13.7% and 12.8% upon the application of 6 kOe DC magnetic field. Through remnant polarization measurements under various magnetic fields and detailed analysis of the energy band structures, we elucidate the mechanism of tuning photovoltaic effect by magnetic fields and attribute it to the combination of two factors. One is the decreased ferroelectric-polarization-induced depolarization electric field and another is the band structure reconstruction at CFO-PZT interfaces, both of which are dominated by the magnetoelectric coupling via interfacial stress transferring at nanoscale. This work makes some attempts of coupling photo-induced effects with magnetoelectric effect in multiferroic materials and will widen the practical ranges of multiferroic-based applications.

  19. Connectivity between electrical conduction and thermally activated grain size evolution in Ho-doped CoFe2O4 ferrite

    NASA Astrophysics Data System (ADS)

    Panneer Muthuselvam, I.; Bhowmik, R. N.

    2010-11-01

    Ho-doped CoFe2O4 spinel ferrite has been synthesized by a combination of mechanical alloying and subsequent annealing of the alloyed powder in the temperature range 950 °C <= TAN <= 1200 °C. The grains of the nanocrystalline samples have been found in the single domain/pseudo-single domain state for TAN <= 1050 °C and multi-domain state for TAN >= 1100 °C. The room temperature Fourier transform infrared spectroscopy spectrum of the samples indicated substantial changes in the tetrahedral sites of the cubic spinel structure while the alloyed powder was annealed at different temperatures. Ac conductivity of the nano-grained samples has been studied in the frequency range 1 Hz-3 MHz and temperature range 303-523 K. This work has been specifically designed to highlight the properties of electrical conductivity in the annealed samples. Experimental results revealed a strong connectivity between electrical conduction and the single domain and multi-domain states of the grains.

  20. Fabrication of three-dimensional ordered macroporous spinel CoFe2O4 as efficient bifunctional catalysts for the positive electrode of lithium-oxygen batteries.

    PubMed

    Kim, Jong Guk; Noh, Yuseong; Kim, Youngmin; Lee, Seonhwa; Kim, Won Bae

    2017-04-07

    Three-dimensionally ordered macroporous (3DOM) CoFe2O4 (CFO) catalysts were prepared by using the colloidal crystal templating method to be used as bifunctional catalysts of Li-O2 battery positive electrodes. In order to study the relationship between the macropore diameter and charge/discharge behavior, 3DOM CFO catalysts with two different pore diameters of 140 and 60 nm were prepared. The physicochemical properties of the 3DOM CFO catalysts were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. When the 3DOM CFO catalyst with a pore diameter of 140 nm (CFO@140) was used in the O2-electrode of Li-O2 batteries, it exhibited a substantially enhanced discharge capacity (ca. 11 658.5 mA h g(-1)) in the first cycle. Moreover, the Li-O2 cells with the CFO@140 catalyst showed cycling stability over 47 cycles at a limited capacity of 500 mA h g(-1) with a reduced potential polarization of 1.13 V, as compared with that with Ketjen Black carbon and the 3DOM CFO of 60 nm pore diameter (CFO@60). Their high cycling stability, low overpotential, high round-trip efficiency, and high rate performance suggest that these 3DOM CFO catalysts could be promising O2-electrode catalysts for next-generation lithium-oxygen batteries.

  1. Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film

    PubMed Central

    Shirsath, Sagar E.; Liu, Xiaoxi; Yasukawa, Yukiko; Li, Sean; Morisako, Akimitsu

    2016-01-01

    Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate. PMID:27435010

  2. Luminol-silver nitrate chemiluminescence enhancement induced by cobalt ferrite nanoparticles.

    PubMed

    Shi, Wenbing; Wang, Hui; Huang, Yuming

    2011-01-01

    CoFe(2)O(4) nanoparticles (NPs) could stimulate the weak chemiluminescence (CL) system of luminol and AgNO(3), resulting in a strong CL emission. The UV-visible spectra, X-ray photoelectron spectra and TEM images of the investigated system revealed that AgNO(3) was reduced by luminol to Ag in the presence of CoFe(2)O(4) NPs and the formed Ag covered the surface of CoFe(2)O(4) NPs, resulting in CoFe(2)O(4)-Ag core-shell nanoparticles. Investigation of the CL reaction kinetics demonstrated that the reaction among luminol, AgNO(3) and CoFe(2)O(4) NPs was fast at the beginning and slowed down later. The CL spectra of the luminol - AgNO(3) - CoFe(2)O(4) NPs system indicated that the luminophor was still an electronically excited 3-aminophthalate anion. A CL mechanism has been postulated. When the CoFe(2)O(4) NPs were injected into the mixture of luminol and AgNO(3), they catalyzed the reduction of AgNO(3) by luminol to produce luminol radicals and Ag, which immediately covered the CoFe(2)O(4) NPs to form CoFe(2)O(4)-Ag core-shell nanoparticles, and the luminol radicals reacted with the dissolved oxygen, leading to a strong CL emission. With the continuous deposition of Ag on the surface of CoFe(2)O(4) NPs, the catalytic activity of the core-shell nanoparticles was inhibited and a decrease in CL intensity was observed and also a slow growth of shell on the nanoparticles.

  3. Ligand-induced evolution of intrinsic fluorescence and catalytic activity from cobalt ferrite nanoparticles.

    PubMed

    Pal, Monalisa; Kundu, Anirban; Rakshit, Rupali; Mandal, Kalyan

    2015-06-08

    To develop CoFe(2)O(4) as magneto-fluorescent nanoparticles (NPs) for biomedical applications, it would be advantageous to identify any intrinsic fluorescence of this important magnetic material by simply adjusting the surface chemistry of the NPs themselves. Herein, we demonstrate that intrinsic multicolor fluorescence, covering the whole visible region, can be induced by facile functionalization of CoFe(2)O(4) NPs with Na-tartrate. Moreover, the functionalized CoFe(2)O(4) NPs also show unprecedented catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, pioneering the potential application of these NPs in therapeutics and wastewater treatment. Detailed investigation through various spectroscopic tools unveils the story behind the emergence of this unique optical property of CoFe(2)O(4) NPs upon functionalization with tartrate ligands. We believe our developed multifunctional CoFe(2)O(4) NPs hold great promise for advanced biomedical and technological applications.

  4. Thickness dependence of magnetoelectric response for composites of Pb(Zr0.52Ti0.48)O3 films on CoFe2O4 ceramic substrates

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Wu, Xia; Peng, Renci; Wang, Jianjun; Deng, Chaoyong; Zhu, Kongjun

    2014-08-01

    Using chemical solution spin-coating we grew Pb(Zr0.52Ti0.48)O3 films of different thicknesses on highly dense CoFe2O4 ceramics. X-ray diffraction revealed no other phases except Pb(Zr0.52Ti0.48)O3 and CoFe2O4. In many of these samples we observed typical ferroelectric hysteresis loops, butterfly-shaped piezoelectric strains, and the magnetic-field-dependent magnetostriction. These behaviors caused appreciable magnetoelectric responses based on magnetic-mechanical-electric coupling. Our results indicated that the thickness of the Pb(Zr0.52Ti0.48)O3 film was important in obtaining strong magnetoelectric coupling.

  5. Photocatalytic activity of magnetically anatase TiO2 with high crystallinity and stability for dyes degradation: Insights into the dual roles of SiO2 interlayer between TiO2 and CoFe2O4

    NASA Astrophysics Data System (ADS)

    Yang, Zewei; Shi, Yingying; Wang, Bing

    2017-03-01

    A novel magnetically separable photocatalyst comprising hollow TiO2-SiO2-CoFe2O4 (TSC) was prepared. In the TSC photocatalyst, an SiO2 interlayer between CoFe2O4 core and TiO2 shell is used to both weaken adverse influence of the magnetic core on photocatalysis and increase the temperature of the transition from anatase to rutile phase TiO2, thus increasing the anatase TiO2 crystallinity. Such an interlayer promotes photocatalytic activity by changing the competition between the injecting process and reacting process of the photogenerated carriers. The photocatalytic activity of TSC was determined for degradation of dye molecules in water under either UV or visible light. The photocatalytic reaction of cationic dyes was governed by rad OH radicals, while O2rad - was the main active species in the initial photoreaction of anionic dyes.

  6. Investigation on multiferroic, optical and photoluminescence properties of CoFe2O4/(Pb1-xSrx)TiO3 nanostructured composite thin films

    NASA Astrophysics Data System (ADS)

    Bala, Kanchan; Sharma, Pankaj; Negi, N. S.

    2016-11-01

    Multiferroic nanostructured composite thin films consisting of CoFe2O4 (CFO) and Pb1-xSrxTiO3 (PST; x = 0.1, 0.2, 0.3, 0.4 and 0.5) layers have been deposited on Pt/TiO2/SiO2/Si and quartz substrates by using metallo-organic decomposition process and spin coating. The effect of Sr content on the multiferroic and optical properties have been investigated. The phase purity such as spinel structure of CFO and perovskite structure of PST has been verified by X-ray diffraction. Cross-sectional scanning electron microscopy images revealed clear interface between CFO and PST layers without any noticeable diffusion. The multiferroic properties of CFO/PST composite films have been confirmed by magnetic and ferroelectric hysteresis loops with low leakage current density. The residual strain sensitivity of multiferroic and optical properties has been observed in the composite films. The decrease in saturation magnetization and saturation polarization with increase in Sr content has been observed which could be attributed to the decrease in residual strain of CFO/PST composite films. The magnetic phase transition temperature of the CFO/PST composite films is also reduced. The optical refractive index decreases with increase of amount of Sr content. The photoluminescence spectra of the CFO/PST composite films possess a blue shift which can be attributed to the Pb and oxygen vacancies as localized sensitizing centers. We show that the multiferroic and optical properties of the CFO/PST composite films are highly sensitive to the heterostructure strains which can be controlled by Sr content.

  7. Magnetic, magnetoelectric and dielectric behavior of CoFe2O4-Pb(Fe1/2Nb1/2)O3 particulate and layered composites

    NASA Astrophysics Data System (ADS)

    Kulawik, J.; Szwagierczak, D.; Guzdek, P.

    2012-09-01

    Magnetic, magnetoelectric and dielectric properties of multiferroic CoFe2O4-Pb(Fe1/2Nb1/2)O3 composites prepared as bulk ceramics were compared with those of tape cast and cofired laminates consisting of alternate ferrite and relaxor layers. X-ray diffraction analysis and Scanning Electron Microscope observations of ceramic samples revealed two-phase composition and fine grained microstructure with uniformly distributed ferrite and relaxor phases. High and broad maxima of dielectric permittivity attributed to dielectric relaxation were found for ceramic samples measured in a temperature range from -55 to 500 °C at frequencies 10 Hz-2 MHz. Magnetic hysteresis, zero-field cooled (ZFC) and field cooled (FC) curves, and dependencies of magnetization on temperature for both magnetoelectric composites were measured with a vibrating sample magnetometer in an applied magnetic field up to 80 kOe at 4-400 K. The hysteresis loops obtained for composites are typical of a mixture of the hard magnetic material with a significant amount of the paramagnet. The bifurcation of ZFC-FC magnetizations observed for both composites implies spin-glass behavior. Magnetoelectric properties at room temperature were investigated as a function of dc magnetic field (0.3-7.2 kOe) and frequency (10 Hz-10 kHz) of ac magnetic field. Both types of composites exhibit a distinct magnetoelectric effect. Maximum values of magnetoelectric coefficient attained for the layered composites exceed 200 mV/(cm Oe) and are almost three times higher than those for particulate composites.

  8. Preparation of silica coated cobalt ferrite magnetic nanoparticles for the purification of histidine-tagged proteins

    NASA Astrophysics Data System (ADS)

    Aygar, Gülfem; Kaya, Murat; Özkan, Necati; Kocabıyık, Semra; Volkan, Mürvet

    2015-12-01

    Surface modified cobalt ferrite (CoFe2O4) nanoparticles containing Ni-NTA affinity group were synthesized and used for the separation of histidine tag proteins from the complex matrices through the use of imidazole side chains of histidine molecules. Firstly, CoFe2O4 nanoparticles with a narrow size distribution were prepared in an aqueous solution using the controlled co-precipitation method. In order to obtain small CoFe2O4 agglomerates, oleic acid and sodium chloride were used as dispersants. The CoFe2O4 particles were coated with silica and subsequently the surface of these silica coated particles (SiO2-CoFe2O4) was modified by amine (NH2) groups in order to add further functional groups on the silica shell. Then, carboxyl (-COOH) functional groups were added to the SiO2-CoFe2O4 magnetic nanoparticles through the NH2 groups. After that Nα,Nα-Bis(carboxymethyl)-L-lysine hydrate (NTA) was attached to carboxyl ends of the structure. Finally, the surface modified nanoparticles were labeled with nickel (Ni) (II) ions. Furthermore, the modified SiO2-CoFe2O4 magnetic nanoparticles were utilized as a new system that allows purification of the N-terminal His-tagged recombinant small heat shock protein, Tpv-sHSP 14.3.

  9. Adsorption of cobalt ferrite nanoparticles within layer-by-layer films: a kinetic study carried out using quartz crystal microbalance.

    PubMed

    Alcantara, Gustavo B; Paterno, Leonardo G; Afonso, André S; Faria, Ronaldo C; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2011-12-28

    The paper reports on the successful use of the quartz crystal microbalance technique to assess accurate kinetics and equilibrium parameters regarding the investigation of in situ adsorption of nanosized cobalt ferrite particles (CoFe(2)O(4)--10.5 nm-diameter) onto two different surfaces. Firstly, a single layer of nanoparticles was deposited onto the surface provided by the gold-coated quartz resonator functionalized with sodium 3-mercapto propanesulfonate (3-MPS). Secondly, the layer-by-layer (LbL) technique was used to build multilayers in which the CoFe(2)O(4) nanoparticle-based layer alternates with the sodium sulfonated polystyrene (PSS) layer. The adsorption experiments were conducted by modulating the number of adsorbed CoFe(2)O(4)/PSS bilayers (n) and/or by changing the CoFe(2)O(4) nanoparticle concentration while suspended as a stable colloidal dispersion. Adsorption of CoFe(2)O(4) nanoparticles onto the 3-MPS-functionalized surface follows perfectly a first order kinetic process in a wide range (two orders of magnitude) of nanoparticle concentrations. These data were used to assess the equilibrium constant and the adsorption free energy. Alternatively, the Langmuir adsorption constant was obtained while analyzing the isotherm data at the equilibrium. Adsorption of CoFe(2)O(4) nanoparticles while growing multilayers of CoFe(2)O(4)/PSS was conducted using colloidal suspensions with CoFe(2)O(4) concentration in the range of 10(-8) to 10(-6) (moles of cobalt ferrite per litre) and for different numbers of cycles n = 1, 3, 5, and 10. We found the adsorption of CoFe(2)O(4) nanoparticles within the CoFe(2)O(4)/PSS bilayers perfectly following a first order kinetic process, with the characteristic rate constant growing with the increase of CoFe(2)O(4) nanoparticle concentration and decreasing with the rise of the number of LbL cycles (n). Additionally, atomic force microscopy was employed for assessing the LbL film roughness and thickness. We found the film

  10. Water dispersible superparamagnetic Cobalt iron oxide nanoparticles for magnetic fluid hyperthermia

    NASA Astrophysics Data System (ADS)

    Salunkhe, Ashwini B.; Khot, Vishwajeet M.; Ruso, Juan M.; Patil, S. I.

    2016-12-01

    Superparamagnetic nanoparticles of Cobalt iron oxide (CoFe2O4) are synthesized chemically, and dispersed in an aqueous suspension for hyperthermia therapy application. Different parameters such as magnetic field intensity, particle concentration which regulates the competence of CoFe2O4 nanoparticle as a heating agents in hyperthermia are investigated. Specific absorption rate (SAR) decreases with increase in the particle concentration and increases with increase in applied magnetic field intensity. Highest value of SAR is found to be 91.84 W g-1 for 5 mg. mL-1 concentration. Oleic acid conjugated polyethylene glycol (OA-PEG) coated CoFe2O4 nanoparticles have shown superior cyto-compatibility over uncoated nanoparticles to L929 mice fibroblast cell lines for concentrations below 2 mg. mL-1. Present work provides the underpinning for the use of CoFe2O4 nanoparticles as a potential heating mediator for magnetic fluid hyperthermia.

  11. Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na0.5Bi0.5TiO3)-magnetostrictive (CoFe2O4) particulate composite

    NASA Astrophysics Data System (ADS)

    Srinivas, A.; Krishnaiah, R. V.; Karthik, T.; Suresh, P.; Asthana, Saket; Kamat, S. V.

    2012-08-01

    A particulate composite consisting of 65 mol. % Na0.5Bi0.5TiO3 and 35 mol. % CoFe2O4 was synthesized, and it's structure, microstructure, ferroelectric, magnetostrictive, magnetic, and direct/indirect magnetoelectric properties were studied. The composite showed different magnetization behaviour under electrically poled and un-poled conditions. The percentage change in magnetization as a result of poling is approximately -15% at 500 Oe magnetic field. Magnetostriction measurements displayed a value of λ11 = -57 × 10-6 and piezomagnetic coefficient δλ11/δH = 0.022 × 10-6 kOe-1 at 2.2 kOe for the composite. The maximum magnetoelectric output varied from 1350 mV/cm to 2000 mV/cm with change in the electrical poling conditions.

  12. Multiferroic and magnetoelectric properties of Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4 core-shell nanocomposite

    NASA Astrophysics Data System (ADS)

    Kumar, Ajith S.; Lekha, C. S. Chitra; Vivek, S.; Saravanan, Venkata; Nandakumar, K.; Nair, Swapna S.

    2016-11-01

    Lead-free magnetoelectric (ME) composites with remarkable ME coupling are required for the realization of eco-friendly multifunctional devices. This work demonstrates the ME properties of Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4 (BCZT-CFO) core-shell composites synthesized via co-sol-gel technique. Room temperature ferroelectric and ferromagnetic characterization have shown that the samples are magnetic and ferroelectric along with an adequate magnetoelectric coupling of 12.15 mV/(cm Oe). The strong dependence of electric parameters on applied magnetic DC bias fields demonstrated in ferroelectric and magnetoelectric measurements provide a framework for the development of potential magnetoelectric devices. Also, the high sensitivity of magnetoelectric coupling towards the applied AC magnetic field can be used for its application in magnetoelectric sensors.

  13. Size-dependent antimicrobial properties of the cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Žalnėravičius, Rokas; Paškevičius, Algimantas; Kurtinaitiene, Marija; Jagminas, Arūnas

    2016-10-01

    The growing resistance of bacteria to conventional antibiotics elicited considerable interest to non-typical drugs. In this study, antimicrobial investigations were performed on low-size dispersion cobalt ferrite nanoparticles (Nps) fabricated by co-precipitation approach in several average sizes, in particular, 15.0, 5.0, and 1.65 nm. A variety of experimental tests demonstrated that the size of these Nps is determinant for antimicrobial efficiency against S. cerevisiae and several Candida species, in particular, C. parapsilosis, C. krusei, and C. albicans. The small and ultra-small fractions of CoFe2O4 Nps possess especially strong antimicrobial activity against all tested microorganisms. The possible reasons are discussed. Nps were characterized by means of transmission and high-resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and atomic force microscopy, chemical analysis and magnetic measurements.

  14. Effects of magnetic cobalt ferrite nanoparticles on biological and artificial lipid membranes

    PubMed Central

    Drašler, Barbara; Drobne, Damjana; Novak, Sara; Valant, Janez; Boljte, Sabina; Otrin, Lado; Rappolt, Michael; Sartori, Barbara; Iglič, Aleš; Kralj-Iglič, Veronika; Šuštar, Vid; Makovec, Darko; Gyergyek, Sašo; Hočevar, Matej; Godec, Matjaž; Zupanc, Jernej

    2014-01-01

    Background The purpose of this work is to provide experimental evidence on the interactions of suspended nanoparticles with artificial or biological membranes and to assess the possibility of suspended nanoparticles interacting with the lipid component of biological membranes. Methods 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid vesicles and human red blood cells were incubated in suspensions of magnetic bare cobalt ferrite (CoFe2O4) or citric acid (CA)-adsorbed CoFe2O4 nanoparticles dispersed in phosphate-buffered saline and glucose solution. The stability of POPC giant unilamellar vesicles after incubation in the tested nanoparticle suspensions was assessed by phase-contrast light microscopy and analyzed with computer-aided imaging. Structural changes in the POPC multilamellar vesicles were assessed by small angle X-ray scattering, and the shape transformation of red blood cells after incubation in tested suspensions of nanoparticles was observed using scanning electron microscopy and sedimentation, agglutination, and hemolysis assays. Results Artificial lipid membranes were disturbed more by CA-adsorbed CoFe2O4 nanoparticle suspensions than by bare CoFe2O4 nanoparticle suspensions. CA-adsorbed CoFe2O4-CA nanoparticles caused more significant shape transformation in red blood cells than bare CoFe2O4 nanoparticles. Conclusion Consistent with their smaller sized agglomerates, CA-adsorbed CoFe2O4 nanoparticles demonstrate more pronounced effects on artificial and biological membranes. Larger agglomerates of nanoparticles were confirmed to be reactive against lipid membranes and thus not acceptable for use with red blood cells. This finding is significant with respect to the efficient and safe application of nanoparticles as medicinal agents. PMID:24741305

  15. Second harmonic generation in microcrystallite films of ultrasmall Si nanoparticles

    SciTech Connect

    Nayfeh, M. H.; Akcakir, O.; Belomoin, G.; Barry, N.; Therrien, J.; Gratton, E.

    2000-12-18

    We dispersed crystalline Si into a colloid of ultrasmall nano particles ({approx}1 nm), and reconstituted it into microcrystallites films on device-quality Si. The film is excited by near-infrared femtosecond two-photon process in the range 765--835 nm, with incident average power in the range 15--70 mW, focused to {approx}1 {mu}m. We have observed strong radiation at half the wavelength of the incident beam. The results are analyzed in terms of second-harmonic generation, a process that is not allowed in silicon due to the centrosymmetry. Ionic vibration of or/and excitonic self-trapping on novel radiative Si--Si dimer phase, found only in ultrasmall nanoparticles, are suggested as a basic mechanism for inducing anharmonicity that breaks the centrosymmetry.

  16. Synthesis of monodisperse FeCo nanoparticles by reductive salt-matrix annealing.

    PubMed

    Poudyal, Narayan; Chaubey, Girija S; Rong, Chuan-Bing; Cui, Jun; Liu, J Ping

    2013-08-30

    We report here a novel synthetic method to prepare monodisperse air-stable FeCo nanoparticles with average sizes of 8, 12 and 20 nm. CoFe2O4 nanoparticles of different sizes were first synthesized by a chemical solution method. The as-synthesized CoFe2O4 nanoparticles were then mixed with ball-milled NaCl powders and heated to 400-500 ° C in forming gas (Ar 93%+H2 7%). The salt powder worked as a separating medium that prevents the CoFe2O4 nanoparticles from agglomerating during the heat treatment while the forming gas reduces the CoFe2O4 nanoparticles to FeCo nanoparticles. Monodisperse FeCo nanoparticles were recovered by dissolving the NaCl in water and subsequently washing with ethanol and acetone. Structural analyses confirmed that FeCo nanoparticles retained the same size as their oxide precursors. The size of the FeCo nanoparticles can be well tuned by controlling the size of the CoFe2O4 nanoparticles. The saturation magnetization of FeCo nanoparticles is size dependent and increases with size.

  17. Hydrothermal Synthesis of Ultrasmall Pt Nanoparticles as Highly Active Electrocatalysts for Methanol Oxidation

    PubMed Central

    Ji, Wenhai; Qi, Weihong; Tang, Shasha; Peng, Hongcheng; Li, Siqi

    2015-01-01

    Ultrasmall nanoparticles, with sizes in the 1–3 nm range, exhibit unique properties distinct from those of free molecules and larger-sized nanoparticles. Demonstrating that the hydrothermal method can serve as a facile method for the synthesis of platinum nanoparticles, we successfully synthesized ultrasmall Pt nanoparticles with an average size of 2.45 nm, with the aid of poly(vinyl pyrrolidone) (PVP) as reducing agents and capping agents. Because of the size effect, these ultrasmall Pt nanoparticles exhibit a high activity toward the methanol oxidation reaction.

  18. Strain and Ferroelectric-Field Effects Co-mediated Magnetism in (011)-CoFe2O4/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 Multiferroic Heterostructures.

    PubMed

    Wang, Ping; Jin, Chao; Zheng, Dongxing; Li, Dong; Gong, Junlu; Li, Peng; Bai, Haili

    2016-09-14

    Electric-field mediated magnetism was investigated in CoFe2O4 (CFO, deposited by reactive cosputtering under different oxygen flow rates) films fabricated on (011)-Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrates. Ascribed to the volatile strain effect of PMN-PT, the magnetization of the CFO films decreases along the [01-1] direction whereas it increases along the [100] direction under the electric field, which is attributed to the octahedron distortion in the spinel ferrite. Moreover, a nonvolatile mediation was obtained in the CFO film with low oxygen flow rate (4 sccm), deriving from the ferroelectric-field effect, in which the magnetization is different after removing the positive and negative fields. The cooperation of the two effects produces four different magnetization states in the CFO film with low oxygen flow rate (4 sccm), compared to the only two different states in the CFO film with high oxygen flow rate (10 sccm). It is suggested that the ferroelectric-field effect is related to the oxygen vacancies in CFO films.

  19. Magnetoelectric properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 - CoFe2O4 particulate composites

    NASA Astrophysics Data System (ADS)

    Paul Praveen, J.; Vinitha Reddy, M.; Das, Dibakar

    2016-05-01

    0.7[(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3)]-0.3[CoFe2O4] multiferroic particulate ceramic composite with (0-3) connectivity has been synthesized by wet chemical methods. BCZT-CFO composite showed both polarization-electric field and magnetic hysteresis loops simultaneously at room temperature. A high dielectric constant of 2160 and tangent loss factor of 0.6 has been obtained. Magnetoelectric (ME) voltage coefficient (αME =dE/dH) of the composite was measured as a function of applied d.c magnetic field at different frequencies. At resonance frequency (365kHz) the composite showed a maximum αME of 102mV/cm.Oe. It was observed that the transverse ME coefficient is 1.8 times higher than the longitudinal ME coefficient. The magnetoelectric properties of this composite has been studied in detail in this work and correlated with its structure.

  20. Manipulating the exchange bias effect of Pb(Zr0.52Ti0.48)O3/CoFe2O4/NiO heterostructural films by electric fields

    NASA Astrophysics Data System (ADS)

    Li, Yong-Chao; Pan, Dan-Feng; Wu, Jun; Li, Ying-bin; Wang, Guang-hou; Liu, Jun-Ming; Wan, Jian-Guo

    2016-10-01

    The Pb(Zr0.52Ti0.48)O3/CoFe2O4/NiO heterostructural films with exchange bias (EB) effect have been prepared on Pt/Ti/SiO2/Si wafers using a sol-gel process, and reversible manipulation of EB effect by electric fields has been realized. Compared with the exchange bias field (Heb = -75 Oe) at as-grown state, the modulation gain of Heb by electric fields can reach 83% (Heb = -12.5 Oe) in the case of +5.0 V and 283% (Heb = -287.5 Oe) in the case of -5.0 V, respectively. Moreover, such electrically tunable EB effect is repeatable and has good endurance and retention. Through analyzing the energy band structures in different electric treatment states, we discuss the mechanism of such electric-field-tunable EB effect. Two factors, i.e., the filling (or releasing) of electrons into (or from) the defect levels produced by oxygen vacancies at positive (or negative) electric voltages, and the redistribution of electrons due to the ferroelectric polarization, both of which give rise to the variation of the strength of exchange interaction in the CFO layer, have been revealed to be responsible for the electric modulation of EB effect. This work provides a promising avenue for electrically manipulating the EB effect and developing high-performance memory and storage devices with low power consumption.

  1. Ultrasmall inorganic nanoparticles: State-of-the-art and perspectives for biomedical applications.

    PubMed

    Zarschler, Kristof; Rocks, Louise; Licciardello, Nadia; Boselli, Luca; Polo, Ester; Garcia, Karina Pombo; De Cola, Luisa; Stephan, Holger; Dawson, Kenneth A

    2016-08-01

    Ultrasmall nanoparticulate materials with core sizes in the 1-3nm range bridge the gap between single molecules and classical, larger-sized nanomaterials, not only in terms of spatial dimension, but also as regards physicochemical and pharmacokinetic properties. Due to these unique properties, ultrasmall nanoparticles appear to be promising materials for nanomedicinal applications. This review overviews the different synthetic methods of inorganic ultrasmall nanoparticles as well as their properties, characterization, surface modification and toxicity. We moreover summarize the current state of knowledge regarding pharmacokinetics, biodistribution and targeting of nanoscale materials. Aside from addressing the issue of biomolecular corona formation and elaborating on the interactions of ultrasmall nanoparticles with individual cells, we discuss the potential diagnostic, therapeutic and theranostic applications of ultrasmall nanoparticles in the emerging field of nanomedicine in the final part of this review.

  2. Robust, ultrasmall organosilica nanoparticles without silica shells

    NASA Astrophysics Data System (ADS)

    Murray, Eoin; Born, Philip; Weber, Anika; Kraus, Tobias

    2014-07-01

    Traditionally, organosilica nanoparticles have been prepared inside micelles with an external silica shell for mechanical support. Here, we compare these hybrid core-shell particles with organosilica particles that are robust enough to be produced both inside micelles and alone in a sol-gel process. These particles form from octadecyltrimethoxy silane as silica source either in microemulsions, resulting in water-dispersible particles with a hydrophobic core, or precipitate from an aqueous mixture to form particles with both hydrophobic core and surface. We examine size and morphology of the particles by dynamic light scattering and transmission electron microscopy and show that the particles consist of Si-O-Si networks pervaded by alkyl chains using nuclear magnetic resonance, infrared spectroscopy, and thermogravimetric analysis.

  3. Stimulated blue emission in reconstituted films of ultrasmall silicon nanoparticles

    SciTech Connect

    Nayfeh, M. H.; Barry, N.; Therrien, J.; Akcakir, O.; Gratton, E.; Belomoin, G.

    2001-02-19

    We dispersed electrochemical etched Si into a colloid of ultrabright blue luminescent nanoparticles (1 nm in diameter) and reconstituted it into films or microcrystallites. When the film is excited by a near-infrared two-photon process at 780 nm, the emission exhibits a sharp threshold near 10{sup 6}W/cm{sup 2}, rising by many orders of magnitude, beyond which a low power dependence sets in. Under some conditions, spontaneous recrystallization forms crystals of smooth shape from which we observe collimated beam emission, pointing to very large gain coefficients. The results are discussed in terms of population inversion, produced by quantum tunneling or/and thermal activation, and stimulated emission in the quantum confinement-engineered Si--Si phase found only on ultrasmall Si nanoparticles. The Si--Si phase model provides gain coefficients as large as 10{sup 3}--10{sup 5}cm{sup -1}.

  4. Ultrasmall lanthanide-doped nanoparticles as multimodal platforms

    NASA Astrophysics Data System (ADS)

    Yust, Brian G.; Pedraza, Francisco J.; Sardar, Dhiraj K.

    2014-03-01

    Recently, there has been a great amount of interest in nanoparticles which are able to provide a platform with high contrast for multiple imaging modalities in order to advance the tools available to biomedical researchers and physicians. However, many nanoparticles do not have ideal properties to provide high contrast in different imaging modes. In order to address this, ultrasmall lanthanide doped oxide and fluoride nanoparticles with strong NIR to NIR upconversion fluorescence and a strong magnetic response for magnetic resonance imaging (MRI) have been developed. Specifically, these nanoparticles incorporate gadolinium, dysprosium, or a combination of both into the nano-crystalline host to achieve the magnetic properties. Thulium, erbium, and neodymium codopants provide the strong NIR absorption and emission lines that allow for deeper tissue imaging since near infrared light is not strongly absorbed or scattered by most tissues within this region. This also leads to better image quality and lower necessary excitation intensities. As a part of the one pot synthesis, these nanoparticles are coated with peg, pmao, or d-glucuronic acid to make them water soluble, biocompatible, and bioconjugable due to the available carboxyl or amine groups. Here, the synthesis, morphological characterization, magnetic response, NIR emission, and the quantum yield will be discussed. Cytotoxicity tested through cell viability at varying concentrations of nanoparticles in growth media will also be discussed.

  5. Molecularly stabilised ultrasmall gold nanoparticles: synthesis, characterization and bioactivity

    NASA Astrophysics Data System (ADS)

    Leifert, Annika; Pan-Bartnek, Yu; Simon, Ulrich; Jahnen-Dechent, Willi

    2013-06-01

    Gold nanoparticles (AuNPs) are widely used as contrast agents in electron microscopy as well as for diagnostic tests. Due to their unique optical and electrical properties and their small size, there is also a growing field of potential applications in medical fields of imaging and therapy, for example as drug carriers or as active compounds in thermotherapy. Besides their intrinsic optical properties, facile surface decoration with (bio)functional ligands renders AuNPs ideally suited for many industrial and medical applications. However, novel AuNPs may have toxicological profiles differing from bulk and therefore a thorough analysis of the quantitative structure-activity relationship (QSAR) is required. Several mechanisms are proposed that cause adverse effects of nanoparticles in biological systems. Catalytic generation of reactive species due to the large and chemically active surface area of nanomaterials is well established. Because nanoparticles approach the size of biological molecules and subcellular structures, they may overcome natural barriers by active or passive uptake. Ultrasmall AuNPs with sizes of 2 nm or less may even behave as molecular ligands. These types of potential interactions would imply a size and ligand-dependent behaviour of any nanomaterial towards biological systems. Thus, to fully understand their QSAR, AuNPs bioactivity should be analysed in biological systems of increasing complexity ranging from cell culture to whole animal studies.

  6. Synthesis and properties MFe2O4 (M = Fe, Co) nanoparticles and core-shell structures

    NASA Astrophysics Data System (ADS)

    Yelenich, O. V.; Solopan, S. O.; Greneche, J. M.; Belous, A. G.

    2015-08-01

    Individual Fe3-xO4 and CoFe2O4 nanoparticles, as well as Fe3-xO4/CoFe2O4 core/shell structures were synthesized by the method of co-precipitation from diethylene glycol solutions. Core/shell structure were synthesized with CoFe2O4-shell thickness of 1.0, 2.5 and 3.5 nm. X-ray diffraction patterns of individual nanoparticles and core/shell are similar and indicate that all synthesized samples have a cubic spinel structure. Compares Mössbauer studies of CoFe2O4, Fe3-xO4 nanoparticles indicate superparamagnetic properties at 300 K. It was shown that individual magnetite nanoparticles are transformed into maghemite through oxidation during the synthesis procedure, wherein the smallest nanoparticles are completely oxidized while a magnetite core does occur in the case of the largest nanoparticles. The Mössbauer spectra of core/shell nanoparticles with increasing CoFe2O4-shell thickness show a gradual decrease in the relative intensity of the quadrupole doublet and significant decrease of the mean isomer shift value at both RT and 77 K indicating a decrease of the superparamagnetic relaxation phenomena. Specific loss power for the prepared ferrofluids was experimentally calculated and it was determined that under influence of ac-magnetic field magnetic fluid based on individual CoFe2O4 and Fe3-xO4 particles are characterized by very low heating temperature, when magnetic fluids based on core/shell nanoparticles demonstrate higher heating effect.

  7. On Ultrasmall Nanocrystals

    PubMed Central

    McBride, James R.; Dukes, Albert D.; Schreuder, Michael A.; Rosenthal, Sandra J.

    2010-01-01

    Ultrasmall nanocrystals are a growing sub-class of traditional nanocrystals that exhibit new properties at diameters typically below 2 nm. In this review, we define what constitutes an ultrasmall nanoparticle while distinguishing between ultrasmall and magic-size nanoparticles. After a brief overview of ultrasmall nanoparticles, including ultrasmall gold clusters, our recent work is presented covering the optical properties, structure, and application of ultrasmall CdSe nanocrystals. This unique material has potential application in solid state lighting due to its balanced white emission. This section is followed by a discussion on the blurring boundary between what can be considered a nanoparticle and a molecule. PMID:21132106

  8. Ultra-small Palladium Nanoparticle Decorated Carbon Nanotubes: Conductivity and Reactivity.

    PubMed

    Li, Xiuting; Batchelor-McAuley, Christopher; Tschulik, Kristina; Shao, Lidong; Compton, Richard G

    2015-08-03

    Carbon nanotubes decorated with ultra-small metal nanoparticles are of great value in catalysis. We report that individual multiwalled carbon nanotubes decorated with ultra-small palladium nanoparticles can be detected by using the nano-impacts method. The high conductivity and reactivity of each decorated carbon nanotube is directly evidenced; this is achieved through studying the proton-reduction reaction for the underpotential deposition of hydrogen onto the nanoparticles decorated on the carbon nanotube walls. The reductive spikes from current amplification are analyzed to estimate the approximate length of the decorated carbon nanotubes, revealing that the decorated carbon nanotubes are electroactive along its entire length of several micrometers.

  9. Use of magnetic nanoparticles to enhance bioethanol production in syngas fermentation.

    PubMed

    Kim, Young-Kee; Lee, Haryeong

    2016-03-01

    The effect of two types of nanoparticles on the enhancement of bioethanol production in syngas fermentation by Clostridium ljungdahlii was examined. Methyl-functionalized silica and methyl-functionalized cobalt ferrite-silica (CoFe2O4@SiO2-CH3) nanoparticles were used to improve syngas-water mass transfer. Of these, CoFe2O4@SiO2-CH3 nanoparticles showed better enhancement of syngas mass transfer. The nanoparticles were recovered using a magnet and reused five times to evaluate reusability, and it was confirmed that their capability for mass transfer enhancement was maintained. Both types of nanoparticles were applied to syngas fermentation, and production of biomass, ethanol, and acetic acid was enhanced. CoFe2O4@SiO2-CH3 nanoparticles were more efficient for the productivity of syngas fermentation due to improved syngas mass transfer. The biomass, ethanol, and acetic acid production compared to a control were increased by 227.6%, 213.5%, and 59.6%, respectively by addition of CoFe2O4@SiO2-CH3 nanoparticles. The reusability of the nanoparticles was confirmed by reuse of recovered nanoparticles for fermentation.

  10. Biointeractions of ultrasmall glutathione-coated gold nanoparticles: effect of small size variations

    NASA Astrophysics Data System (ADS)

    Sousa, Alioscka A.; Hassan, Sergio A.; Knittel, Luiza L.; Balbo, Andrea; Aronova, Maria A.; Brown, Patrick H.; Schuck, Peter; Leapman, Richard D.

    2016-03-01

    Recent in vivo studies have established ultrasmall (<3 nm) gold nanoparticles coated with glutathione (AuGSH) as a promising platform for applications in nanomedicine. However, systematic in vitro investigations to gain a more fundamental understanding of the particles' biointeractions are still lacking. Herein we examined the behavior of ultrasmall AuGSH in vitro, focusing on their ability to resist aggregation and adsorption from serum proteins. Despite having net negative charge, AuGSH particles were colloidally stable in biological media and able to resist binding from serum proteins, in agreement with the favorable bioresponses reported for AuGSH in vivo. However, our results revealed disparate behaviors depending on nanoparticle size: particles between 2 and 3 nm in core diameter were found to readily aggregate in biological media, whereas those strictly under 2 nm were exceptionally stable. Molecular dynamics simulations provided microscopic insight into interparticle interactions leading to aggregation and their sensitivity to the solution composition and particle size. These results have important implications, in that seemingly small variations in size can impact the biointeractions of ultrasmall AuGSH, and potentially of other ultrasmall nanoparticles as well.Recent in vivo studies have established ultrasmall (<3 nm) gold nanoparticles coated with glutathione (AuGSH) as a promising platform for applications in nanomedicine. However, systematic in vitro investigations to gain a more fundamental understanding of the particles' biointeractions are still lacking. Herein we examined the behavior of ultrasmall AuGSH in vitro, focusing on their ability to resist aggregation and adsorption from serum proteins. Despite having net negative charge, AuGSH particles were colloidally stable in biological media and able to resist binding from serum proteins, in agreement with the favorable bioresponses reported for AuGSH in vivo. However, our results revealed disparate

  11. Fabrication and Characterization of Cobalt Iron Oxide Nanoparticles by a Reverse Micelle Process

    NASA Astrophysics Data System (ADS)

    Bae, D. S.

    2013-12-01

    The preparation of CoFe2O4 nanoparticles in Igepal CO-520-cyclohexane-water reverse micelle solutions has been studied. Transmission electron microscopy and X-ray diffraction pattern analyses revealed the resultant particles to be CoFe2O4. The average size and distribution of synthesized particles calcined at 6000C for 2 hrs were in the range of 30 to 70 nm and broaden, respectively. The phase of synthesized particles was crystalline. The magnetic behavior of the synthesized particles was ferromagnetism. The effects of synthesis parameters, such as the molar ratio of water to surfactant and calcination temperature, are discussed.

  12. Ultrasmall iron oxide nanoparticles for biomedical applications: improving the colloidal and magnetic properties.

    PubMed

    Costo, Rocio; Bello, Valentina; Robic, Caroline; Port, Marc; Marco, Jose F; Puerto Morales, M; Veintemillas-Verdaguer, Sabino

    2012-01-10

    A considerable increase in the saturation magnetization, M(s) (40%), and initial susceptibility of ultrasmall (<5 nm) iron oxide nanoparticles prepared by laser pyrolysis was obtained through an optimized acid treatment. Moreover, a significant enhancement in the colloidal properties, such as smaller aggregate sizes in aqueous media and increased surface charge densities, was found after this chemical protocol. The results are consistent with a reduction in nanoparticle surface disorder induced by a dissolution-recrystallization mechanism.

  13. Facile method to synthesize dopamine-capped mixed ferrite nanoparticles and their peroxidase-like activity

    NASA Astrophysics Data System (ADS)

    Mumtaz, Shazia; Wang, Li-Sheng; Abdullah, Muhammad; Zajif Hussain, Syed; Iqbal, Zafar; Rotello, Vincent M.; Hussain, Irshad

    2017-03-01

    A facile single-step strategy to prepare stable and water-dispersible dopamine-functionalized ultra-small mixed ferrite nanoparticles MFe2O4-DOPA (where M is a bivalent metal atom i.e. Fe, Co Cu, Mn and Ni) at room temperature is described. The nanoparticles formed have narrow size distribution as indicated by their characterization using transmission electron microscopy (TEM) and dynamic light scattering. The surface chemistry of these nanoparticles was probed by FTIR spectroscopy indicating their successful capping with dopamine ligands, which was further confirmed using zetapotential measurements and thermogravimetric analysis. The comparative horseradish peroxidase (HRP)—like activity of these cationic mixed ferrites nanoparticles was studied at pH 4.6 using a negatively-charged 2, 2‧-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) as a chromogenic substrate in the presence of hydrogen peroxide. A time-dependent relative peroxidase-like activity follows the following order CoFe2O4-DOPA  >  MnFe2O4-DOPA  >  CuFe2O4-DOPA  >  NiFe2O4-DOPA  >  Fe3O4-DOPA. This diversity in HRP-like activity may be attributed to the different redox properties of ferrite nanoparticles when doped with M (Fe, Co Cu, Mn and Ni).

  14. Ultrasmall nanoparticles induce ferroptosis in nutrient-deprived cancer cells and suppress tumour growth

    PubMed Central

    Kim, Sung Eun; Zhang, Li; Ma, Kai; Riegman, Michelle; Chen, Feng; Ingold, Irina; Conrad, Marcus; Turker, Melik Ziya; Gao, Minghui; Jiang, Xuejun; Monette, Sebastien; Pauliah, Mohan; Gonen, Mithat; Zanzonico, Pat; Quinn, Thomas; Wiesner, Ulrich; Bradbury, Michelle S.; Overholtzer, Michael

    2016-01-01

    The design of cancer-targeting particles with precisely-tuned physiocochemical properties may enhance delivery of therapeutics and access to pharmacological targets. However, molecular level understanding of the interactions driving the fate of nanomedicine in biological systems remains elusive. Here, we show that ultrasmall (< 10 nm in diameter) poly(ethylene glycol) (PEG)-coated silica nanoparticles, functionalized with melanoma-targeting peptides, can induce a form of programmed cell death known as ferroptosis in starved cancer cells and cancer-bearing mice. Tumor xenografts in mice intravenously injected with nanoparticles using a high-dose multiple injection scheme exhibit reduced growth or regression, in a manner that is reversed by the pharmacological inhibitor of ferroptosis, liproxstatin-1. These data demonstrate that ferroptosis can be targeted by ultrasmall silica nanoparticles and may have therapeutic potential. PMID:27668796

  15. Ultrasmall nanoparticles induce ferroptosis in nutrient-deprived cancer cells and suppress tumour growth.

    PubMed

    Kim, Sung Eun; Zhang, Li; Ma, Kai; Riegman, Michelle; Chen, Feng; Ingold, Irina; Conrad, Marcus; Turker, Melik Ziya; Gao, Minghui; Jiang, Xuejun; Monette, Sebastien; Pauliah, Mohan; Gonen, Mithat; Zanzonico, Pat; Quinn, Thomas; Wiesner, Ulrich; Bradbury, Michelle S; Overholtzer, Michael

    2016-11-01

    The design of cancer-targeting particles with precisely tuned physicochemical properties may enhance the delivery of therapeutics and access to pharmacological targets. However, a molecular-level understanding of the interactions driving the fate of nanomedicine in biological systems remains elusive. Here, we show that ultrasmall (<10 nm in diameter) poly(ethylene glycol)-coated silica nanoparticles, functionalized with melanoma-targeting peptides, can induce a form of programmed cell death known as ferroptosis in starved cancer cells and cancer-bearing mice. Tumour xenografts in mice intravenously injected with nanoparticles using a high-dose multiple injection scheme exhibit reduced growth or regression, in a manner that is reversed by the pharmacological inhibitor of ferroptosis, liproxstatin-1. These data demonstrate that ferroptosis can be targeted by ultrasmall silica nanoparticles and may have therapeutic potential.

  16. Ultrasmall nanoparticles induce ferroptosis in nutrient-deprived cancer cells and suppress tumour growth

    NASA Astrophysics Data System (ADS)

    Kim, Sung Eun; Zhang, Li; Ma, Kai; Riegman, Michelle; Chen, Feng; Ingold, Irina; Conrad, Marcus; Turker, Melik Ziya; Gao, Minghui; Jiang, Xuejun; Monette, Sebastien; Pauliah, Mohan; Gonen, Mithat; Zanzonico, Pat; Quinn, Thomas; Wiesner, Ulrich; Bradbury, Michelle S.; Overholtzer, Michael

    2016-11-01

    The design of cancer-targeting particles with precisely tuned physicochemical properties may enhance the delivery of therapeutics and access to pharmacological targets. However, a molecular-level understanding of the interactions driving the fate of nanomedicine in biological systems remains elusive. Here, we show that ultrasmall (<10 nm in diameter) poly(ethylene glycol)-coated silica nanoparticles, functionalized with melanoma-targeting peptides, can induce a form of programmed cell death known as ferroptosis in starved cancer cells and cancer-bearing mice. Tumour xenografts in mice intravenously injected with nanoparticles using a high-dose multiple injection scheme exhibit reduced growth or regression, in a manner that is reversed by the pharmacological inhibitor of ferroptosis, liproxstatin-1. These data demonstrate that ferroptosis can be targeted by ultrasmall silica nanoparticles and may have therapeutic potential.

  17. Ultradispersed Cobalt Ferrite Nanoparticles Assembled in Graphene Aerogel for Continuous Photo-Fenton Reaction and Enhanced Lithium Storage Performance

    NASA Astrophysics Data System (ADS)

    Qiu, Bocheng; Deng, Yuanxin; Du, Mengmeng; Xing, Mingyang; Zhang, Jinlong

    2016-07-01

    The Photo-Fenton reaction is an advanced technology to eliminate organic pollutants in environmental chemistry. Moreover, the conversion rate of Fe3+/Fe2+ and utilization rate of H2O2 are significant factors in Photo-Fenton reaction. In this work, we reported three dimensional (3D) hierarchical cobalt ferrite/graphene aerogels (CoFe2O4/GAs) composites by the in situ growing CoFe2O4 crystal seeds on the graphene oxide (GO) followed by the hydrothermal process. The resulting CoFe2O4/GAs composites demonstrated 3D hierarchical pore structure with mesopores (14~18 nm), macropores (50~125 nm), and a remarkable surface area (177.8 m2 g‑1). These properties endowed this hybrid with the high and recyclable Photo-Fenton activity for methyl orange pollutant degradation. More importantly, the CoFe2O4/GAs composites can keep high Photo-Fenton activity in a wide pH. Besides, the CoFe2O4/GAs composites also exhibited excellent cyclic performance and good rate capability. The 3D framework can not only effectively prevent the volume expansion and aggregation of CoFe2O4 nanoparticles during the charge/discharge processes for Lithium-ion batteries (LIBs), but also shorten lithium ions and electron diffusion length in 3D pathways. These results indicated a broaden application prospect of 3D-graphene based hybrids in wastewater treatment and energy storage.

  18. Ultradispersed Cobalt Ferrite Nanoparticles Assembled in Graphene Aerogel for Continuous Photo-Fenton Reaction and Enhanced Lithium Storage Performance

    PubMed Central

    Qiu, Bocheng; Deng, Yuanxin; Du, Mengmeng; Xing, Mingyang; Zhang, Jinlong

    2016-01-01

    The Photo-Fenton reaction is an advanced technology to eliminate organic pollutants in environmental chemistry. Moreover, the conversion rate of Fe3+/Fe2+ and utilization rate of H2O2 are significant factors in Photo-Fenton reaction. In this work, we reported three dimensional (3D) hierarchical cobalt ferrite/graphene aerogels (CoFe2O4/GAs) composites by the in situ growing CoFe2O4 crystal seeds on the graphene oxide (GO) followed by the hydrothermal process. The resulting CoFe2O4/GAs composites demonstrated 3D hierarchical pore structure with mesopores (14~18 nm), macropores (50~125 nm), and a remarkable surface area (177.8 m2 g−1). These properties endowed this hybrid with the high and recyclable Photo-Fenton activity for methyl orange pollutant degradation. More importantly, the CoFe2O4/GAs composites can keep high Photo-Fenton activity in a wide pH. Besides, the CoFe2O4/GAs composites also exhibited excellent cyclic performance and good rate capability. The 3D framework can not only effectively prevent the volume expansion and aggregation of CoFe2O4 nanoparticles during the charge/discharge processes for Lithium-ion batteries (LIBs), but also shorten lithium ions and electron diffusion length in 3D pathways. These results indicated a broaden application prospect of 3D-graphene based hybrids in wastewater treatment and energy storage. PMID:27373343

  19. Ultra-small lipid-polymer hybrid nanoparticles for tumor-penetrating drug delivery

    NASA Astrophysics Data System (ADS)

    Dehaini, Diana; Fang, Ronnie H.; Luk, Brian T.; Pang, Zhiqing; Hu, Che-Ming J.; Kroll, Ashley V.; Yu, Chun Lai; Gao, Weiwei; Zhang, Liangfang

    2016-07-01

    Lipid-polymer hybrid nanoparticles, consisting of a polymeric core coated by a layer of lipids, are a class of highly scalable, biodegradable nanocarriers that have shown great promise in drug delivery applications. Here, we demonstrate the facile synthesis of ultra-small, sub-25 nm lipid-polymer hybrid nanoparticles using an adapted nanoprecipitation approach and explore their utility for targeted delivery of a model chemotherapeutic. The fabrication process is first optimized to produce a monodisperse population of particles that are stable under physiological conditions. It is shown that these ultra-small hybrid nanoparticles can be functionalized with a targeting ligand on the surface and loaded with drug inside the polymeric matrix. Further, the in vivo fate of the nanoparticles after intravenous injection is characterized by examining the blood circulation and biodistribution. In a final proof-of-concept study, targeted ultra-small hybrid nanoparticles loaded with the cancer drug docetaxel are used to treat a mouse tumor model and demonstrate improved efficacy compared to a clinically available formulation of the drug. The ability to synthesize a significantly smaller version of the established lipid-polymer hybrid platform can ultimately enhance its applicability across a wider range of applications.

  20. Rechargeable Mg batteries with graphene-like MoS₂ cathode and ultrasmall Mg nanoparticle anode.

    PubMed

    Liang, Yanliang; Feng, Rujun; Yang, Siqi; Ma, Hua; Liang, Jing; Chen, Jun

    2011-02-01

    The combination of a highly exfoliated, graphene-like MoS₂ cathode and ultrasmall Mg nanoparticle anode is proposed, for the first time, for rechargeable Mg batteries. Such a configuration exhibits an operating voltage of 1.8 V and a well reversible discharge capacity of ca. 170 mA h g−1, emphasizing the necessity of rational morphological control of electrode materials and opening up new opportunities for rechargeable Mg batteries.

  1. In Vitro Toxicological Assessment of Cobalt Ferrite Nanoparticles in Several Mammalian Cell Types.

    PubMed

    Abudayyak, Mahmoud; Altincekic Gurkaynak, Tuba; Özhan, Gül

    2017-02-01

    Nanoparticles have been widely used in various fields due to the superior physicochemical properties and functions. As a result, human exposure to nanoparticles increases dramatically. Previous researches have shown that nanoparticles could travel through the respiratory, digestive system, or skin into the blood and then to the secondary organs such as the brain, heart, and liver. Besides, the nanoparticle toxicity is controversial and dependent on the sensitivity of the cell type, route of exposure, and condition, as well as their characteristics. Similarly, cobalt ferrite nanoparticles (CoFe2O4-NPs) have been used in different industrial fields, and have also various application possibilities in medical and biomedical fields. CoFe2O4-NPs induce toxic responses in various organisms such as human, mice, and algae. However, there is a serious deficit of information concerning their effects on human health and the environment. We aimed to investigate the toxic effects of CoFe2O4-NPs on liver (HepG2), colon (Caco-2), lung (A549), and neuron (SH-SY5Y) cells, which reflect different exposure routes in vitro, by using various toxicological endpoints. The cytotoxicity, genotoxicity, oxidative damage, and apoptosis induction of CoFe2O4-NPs (39 ± 17 nm) were evaluated. After 24 h, the nanoparticles decreased cell viability at ≤100 μg/mL, while increasing viability at >100 μg/mL. CoFe2O4-NPs induced DNA and oxidative damage with increased malondialdehyde (MDA) and 8-hydroxy deoxyguanosine (8-OHdG) levels and decreased glutathione (GSH) levels with no change in protein carbonyl (PC) levels. CoFe2O4-NPs had apoptotic effect in HepG2 and Caco-2 cells in a concentration-dependent manner and necrotic effects on SH-SY5Y and A549 cells. Consequently, the adverse effects of CoFe2O4-NPs should raise concern about their safety in consumer products.

  2. Probing the interaction induced conformation transitions in acid phosphatase with cobalt ferrite nanoparticles: Relation to inhibition and bio-activity of Chlorella vulgaris acid phosphatase.

    PubMed

    Ahmad, Farooq; Zhou, Xing; Yao, Hongzhou; Zhou, Ying; Xu, Chao

    2016-09-01

    The present study explored the interaction and kinetics of cobalt ferrite nanoparticles (NPs) with acid phosphatase (ACP) by utilizing diverse range of spectroscopic techniques. The results corroborate, the CoFe2O4 NPs cause fluorescence quenching in ACP by static quenching mechanism. The negative values of van't Hoff thermodynamic expressions (ΔH=-0.3293Jmol(-1)K(-1) and ΔG=-3.960kJmol(-1)K(-1)) corroborate the spontaneity and exothermic nature of static quenching. The positive value of ΔS (13.2893Jmol(-1)K(-1)) corroborate that major contributors of higher and stronger binding affinity among CoFe2O4 NPs with ACP were electrostatic. In addition, FTIR, UV-CD, UV-vis spectroscopy and three dimensional fluorescence (3D) techniques confirmed that CoFe2O4 NPs binding induces microenvironment perturbations leading to secondary and tertiary conformation changes in ACP to a great extent. Furthermore, synchronous fluorescence spectroscopy (SFS) affirmed the comparatively significant changes in microenvironment around tryptophan (Trp) residue by CoFe2O4 NPs. The effect of CoFe2O4 NPs on the activation kinetics of ACP was further examined in Chlorella vulgaris. Apparent Michaelis constant (Km) values of 0.57 and 26.5mM with activation energy values of 0.538 and 3.428kJmol(-1) were determined without and with 200μM CoFe2O4 NPs. Apparent Vmax value of -7Umml(-1) corroborate that enzyme active sites were completely captured by the NPs leaving no space for the substrate. The results confirmed that CoFe2O4 NPs ceased the activity by unfolding of ACP enzyme. This suggests CoFe2O4 NPs perturbed the enzyme activity by transitions in conformation and hence the metabolic activity of ACP. This study provides the pavement for novel and simple approach of using sensitive biomarkers for sensing NPs in environment.

  3. Stimulated blue emission in reconstituted films of ultra-small silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Nayfeh, M.; Barry, N.; Therrien, J.; Akcakir, O.; Gratton, E.; Belomoin, G.

    2000-03-01

    We dispersed electro-chemical etched Si into a colloid of enriched blue emitting ultra-small (1 nm in diameter) nano particles, and reconstituted it into micro crystallites or uniform films on device quality Si. When the film is excited by near-infrared two photon process at 780 nm, we observe an extremely strong blue band that exhibits a sharp threshold near 106 W/cm2, rising by many orders of magnitude, beyond which a low power dependence sets in. We also observe directed blue beams between faces of the micro crystallites. The results are analyzed in terms of population inversion and stimulated emission in quantum confinement-induced Si-Si dimer phase, found only on ultra-small Si nanoparticles.

  4. Magnetoelectric studies on CoFe2O4/0.5(BaTi0.8Zr0.2O3)-0.5(Ba0.7Ca0.3TiO3) lead-free bilayer thin films derived by the chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Venkata Ramana, E.; Zavašnik, Janez; Graça, M. P. F.; Valente, M. A.

    2016-08-01

    Lead-free multiferroic bilayer thin films were fabricated on (111)Pt/Si substrate via a simple sol-gel chemical solution deposition, by altering the position of piezoelectric (Ba0.85Ca0.15) (Ti0.9Zr0.1)O3 (BCTZO) and ferromagnetic CoFe2O4 (CFO). Single layer BCTZO experiences the out-of-plane compressive stress, while this layer is under tensile strain in both the bilayers. The microstructural study confirms the formation of bilayers with expected chemical composition composed of multiple well-developed crystallites having no crystallographic dependencies. Thin films of BCTZO and CFO/BCTZO exhibited saturated ferroelectric hysteresis loops at room temperature with a Pr of 7.2 and 5.6 μC/cm2. The magnetic field induced shift in phonon vibrations coupled with direct magnetoelectric (ME) measurements demonstrated a stress-mediated coupling mechanism in the bilayers. We found a superior ME coefficient (105 MV/cm Oe) and dielectric tunability (˜52%) for CFO/BCTZO bilayer compared to the BCTZO/CFO bilayer, which demonstrates that the modification of strain state in bilayers is useful for the desired ME coupling. The BCTZO having piezoelectricity on par with that of lead-based ones can be useful to tailor lead-free ME applications.

  5. Geometrically confined ultrasmall gadolinium oxide nanoparticles boost the T1 contrast ability

    NASA Astrophysics Data System (ADS)

    Ni, Kaiyuan; Zhao, Zhenghuan; Zhang, Zongjun; Zhou, Zijian; Yang, Li; Wang, Lirong; Ai, Hua; Gao, Jinhao

    2016-02-01

    High-performance magnetic resonance imaging (MRI) contrast agents and novel contrast enhancement strategies are urgently needed for sensitive and accurate diagnosis. Here we report a strategy to construct a new T1 contrast agent based on the Solomon-Bloembergen-Morgan (SBM) theory. We loaded the ultrasmall gadolinium oxide nanoparticles into worm-like interior channels of mesoporous silica nanospheres (Gd2O3@MSN nanocomposites). This unique structure endows the nanocomposites with geometrical confinement, high molecular tumbling time, and a large coordinated number of water molecules, which results in a significant enhancement of the T1 contrast with longitudinal proton relaxivity (r1) as high as 45.08 mM-1 s-1. Such a high r1 value of Gd2O3@MSN, compared to those of ultrasmall Gd2O3 nanoparticles and gadolinium-based clinical contrast agents, is mainly attributed to the strong geometrical confinement effect. This strategy provides new guidance for developing various high-performance T1 contrast agents for sensitive imaging and disease diagnosis.High-performance magnetic resonance imaging (MRI) contrast agents and novel contrast enhancement strategies are urgently needed for sensitive and accurate diagnosis. Here we report a strategy to construct a new T1 contrast agent based on the Solomon-Bloembergen-Morgan (SBM) theory. We loaded the ultrasmall gadolinium oxide nanoparticles into worm-like interior channels of mesoporous silica nanospheres (Gd2O3@MSN nanocomposites). This unique structure endows the nanocomposites with geometrical confinement, high molecular tumbling time, and a large coordinated number of water molecules, which results in a significant enhancement of the T1 contrast with longitudinal proton relaxivity (r1) as high as 45.08 mM-1 s-1. Such a high r1 value of Gd2O3@MSN, compared to those of ultrasmall Gd2O3 nanoparticles and gadolinium-based clinical contrast agents, is mainly attributed to the strong geometrical confinement effect. This strategy

  6. Nanoencapsulation of ultra-small superparamagnetic particles of iron oxide into human serum albumin nanoparticles

    PubMed Central

    Altinok, Mahmut; Urfels, Stephan; Bauer, Johann

    2014-01-01

    Summary Human serum albumin nanoparticles have been utilized as drug delivery systems for a variety of medical applications. Since ultra-small superparamagnetic particles of iron oxide (USPIO) are used as contrast agents in magnetic resonance imaging, their encapsulation into the protein matrix enables the synthesis of diagnostic and theranostic agents by surface modification and co-encapsulation of active pharmaceutical ingredients. The present investigation deals with the surface modification and nanoencapsulation of USPIO into an albumin matrix by using ethanolic desolvation. Particles of narrow size distribution and with a defined particle structure have been achieved. PMID:25551054

  7. Use of a polyol liquid collection medium to obtain ultrasmall magnetic nanoparticles by laser pyrolysis.

    PubMed

    Martínez, G; Malumbres, A; Mallada, R; Hueso, J L; Irusta, S; Bomatí-Miguel, O; Santamaría, J

    2012-10-26

    The present work addresses the main bottleneck in the synthesis of magnetic nanoparticles by laser pyrolysis. Since the introduction of laser pyrolysis for the production of nanoparticles nearly three decades ago, this method has been repeatedly presented as a highly promising alternative, on account of two main characteristics: (i) its flexibility, since nanoparticles can be formed from a wide variety of precursors in both gas and liquid phase, and (ii) its continuous nature, avoiding the intrinsic variability of batch processing. However, the results reported to date invariably show considerable aggregation of the obtained nanoparticles, which strongly limits their application in most fields. In this work, we have been able to circumvent this problem by collecting the particles in a polyol liquid medium. This method prevents the formation of aggregates and renders a uniform distribution of well dispersed ultrasmall nanoparticles (<4 nm) in a water-compatible solvent. We consider that the effectiveness of this novel collection method for the production of well-dispersed magnetic nanoparticles will be of high interest to a wide range of scientists working in the nanoparticle synthesis field and may enable new applications wherever there is a strict requirement for non-agglomerated nanoparticles.

  8. Ultrasmall Gold Nanoparticles as Carriers for Nucleus-Based Gene Therapy Due to Size-Dependent Nuclear Entry

    PubMed Central

    2015-01-01

    The aim of this study was to determine the size-dependent penetration ability of gold nanoparticles and the potential application of ultrasmall gold nanoparticles for intranucleus delivery and therapy. We synthesized gold nanoparticles with diameters of 2, 6, 10, and 16 nm and compared their intracellular distribution in MCF-7 breast cancer cells. Nanoparticles smaller than 10 nm (2 and 6 nm) could enter the nucleus, whereas larger ones (10 and 16 nm) were found only in the cytoplasm. We then investigated the possibility of using ultrasmall 2 nm nanoparticles as carriers for nuclear delivery of a triplex-forming oligonucleotide (TFO) that binds to the c-myc promoter. Compared to free TFO, the nanoparticle-conjugated TFO was more effective at reducing c-myc RNA and c-myc protein, which resulted in reduced cell viability. Our result demonstrated that the entry of gold nanoparticles into the cell nucleus is critically dependent on the size of the nanoparticles. We developed a strategy for regulating gene expression, by directly delivering TFOs into the nucleus using ultrasmall gold nanoparticles. More importantly, guidelines were provided to choose appropriate nanocarriers for different biomedical purposes. PMID:24824865

  9. Geometrically confined ultrasmall gadolinium oxide nanoparticles boost the T(1) contrast ability.

    PubMed

    Ni, Kaiyuan; Zhao, Zhenghuan; Zhang, Zongjun; Zhou, Zijian; Yang, Li; Wang, Lirong; Ai, Hua; Gao, Jinhao

    2016-02-14

    High-performance magnetic resonance imaging (MRI) contrast agents and novel contrast enhancement strategies are urgently needed for sensitive and accurate diagnosis. Here we report a strategy to construct a new T1 contrast agent based on the Solomon-Bloembergen-Morgan (SBM) theory. We loaded the ultrasmall gadolinium oxide nanoparticles into worm-like interior channels of mesoporous silica nanospheres (Gd2O3@MSN nanocomposites). This unique structure endows the nanocomposites with geometrical confinement, high molecular tumbling time, and a large coordinated number of water molecules, which results in a significant enhancement of the T1 contrast with longitudinal proton relaxivity (r1) as high as 45.08 mM(-1) s(-1). Such a high r1 value of Gd2O3@MSN, compared to those of ultrasmall Gd2O3 nanoparticles and gadolinium-based clinical contrast agents, is mainly attributed to the strong geometrical confinement effect. This strategy provides new guidance for developing various high-performance T1 contrast agents for sensitive imaging and disease diagnosis.

  10. Oleylamine as a beneficial agent for the synthesis of CoFe₂O₄ nanoparticles with potential biomedical uses.

    PubMed

    Georgiadou, Violetta; Kokotidou, Chrysoula; Le Droumaguet, Benjamin; Carbonnier, Benjamin; Choli-Papadopoulou, Theodora; Dendrinou-Samara, Catherine

    2014-05-07

    The multifunctional role of oleylamine (OAm) as a versatile and flexible reagent in synthesis as well as a desired surface ligand for the synthesis of CoFe2O4 nanoparticles (NPs) is described. CoFe2O4 NPs were prepared by a facile, reproducible and scalable solvothermal approach in the presence of pure OAm. By monitoring the volume of OAm, different shapes of NPs, spherical and truncated, were formed. The syntheses led to high yields of monodispersed and considerably small (9-11 nm) CoFe2O4 NPs with enhanced magnetization (M(s) = 84.7-87.5 emu g(-1)). The resulting hydrophobic CoFe2O4 NPs were easily transferred to an aqueous phase through the formation of reverse micelles between the hydrophobic chains of OAm and cetyltrimethylammonium bromide (CTAB) and transverse relaxivities (r2) were measured. The spherical NPs had a greater effect on water proton relaxivity (r2 = 553 mM(-1) s(-1)) at an applied magnetic field of 11.7 T. The NPs became fluorescent probes by exploiting the presence of the double bond of OAm in the middle of the molecule; a thiol-ene "click" reaction with the fluorophore bovine serum albumin (FITC-BSA) was achieved. The labeled/biofunctionalized CoFe2O4 NPs interacted with cancer (HeLa and A549) and non-cancer cell lines (MRC5 and dental MSCS) and cell viability was estimated. A clear difference of toxicity between the cancer and non-cancer cells was observed while low cytotoxicity in living cells was supported. Confocal laser microscopy showed that NPs entered the cell membranes and were firstly localized close to them provoking a membrane expansion and were further accumulated perinuclearly without entering the nuclei.

  11. Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Europium(III) DO3A as a Bimodal Imaging Probe.

    PubMed

    Carron, Sophie; Bloemen, Maarten; Vander Elst, Luce; Laurent, Sophie; Verbiest, Thierry; Parac-Vogt, Tatjana N

    2016-03-18

    A new prototype consisting of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles decorated with europium(III) ions encapsulated in a DO3A organic scaffold was designed as a platform for further development of bimodal contrast agents for MRI and optical imaging. The USPIO nanoparticles act as negative MRI contrast agents, whereas the europium(III) ion is a luminophore that is suitable for use in optical imaging detection. The functionalized USPIO nanoparticles were characterized by TEM, DLS, XRD, FTIR, and TXRF analysis, and a full investigation of the relaxometric and optical properties was conducted. The typical luminescence emission of europium(III) was observed and the main red emission wavelength was found at 614 nm. The relaxometric study of these ultrasmall nanoparticles showed r2 values of 114.8 mM(-1) Fes(-1) at 60 MHz, which is nearly double the r2 relaxivity of Sinerem(®).

  12. Differential hERG ion channel activity of ultrasmall gold nanoparticles.

    PubMed

    Leifert, Annika; Pan, Yu; Kinkeldey, Anne; Schiefer, Frank; Setzler, Julia; Scheel, Olaf; Lichtenbeld, Hera; Schmid, Günter; Wenzel, Wolfgang; Jahnen-Dechent, Willi; Simon, Ulrich

    2013-05-14

    Understanding the mechanism of toxicity of nanomaterials remains a challenge with respect to both mechanisms involved and product regulation. Here we show toxicity of ultrasmall gold nanoparticles (AuNPs). Depending on the ligand chemistry, 1.4-nm-diameter AuNPs failed electrophysiology-based safety testing using human embryonic kidney cell line 293 cells expressing human ether-á-go-go-Related gene (hERG), a Food and Drug Administration-established drug safety test. In patch-clamp experiments, phosphine-stabilized AuNPs irreversibly blocked hERG channels, whereas thiol-stabilized AuNPs of similar size had no effect in vitro, and neither particle blocked the channel in vivo. We conclude that safety regulations may need to be reevaluated and adapted to reflect the fact that the binding modality of surface functional groups becomes a relevant parameter for the design of nanoscale bioactive compounds.

  13. Detection of luminescent single ultrasmall silicon nanoparticles using fluctuation correlation spectroscopy

    SciTech Connect

    Akcakir, O.; Therrien, J.; Belomoin, G.; Barry, N.; Muller, J. D.; Gratton, E.; Nayfeh, M.

    2000-04-03

    We dispersed electrochemical etched Si into a colloid of ultrasmall blue luminescent nanoparticles, observable with the naked eye, in room light. We use two-photon near-infrared femtosecond excitation at 780 nm to record the fluctuating time series of the luminescence, and determine the number density, brightness, and size of diffusing fluorescent particles. The luminescence efficiency of particles is high enough such that we are able to detect a single particle, in a focal volume, of 1 pcm3. The measurements yield a particle size of 1 nm, consistent with direct imaging by transmission electron microscopy. They also yield an excitation efficiency under two-photon excitation two to threefold larger than that of fluorescein. Detection of single particles paves the way for their use as labels in biosensing applications. (c) 2000 American Institute of Physics.

  14. Differential hERG ion channel activity of ultrasmall gold nanoparticles

    PubMed Central

    Leifert, Annika; Pan, Yu; Kinkeldey, Anne; Schiefer, Frank; Setzler, Julia; Scheel, Olaf; Lichtenbeld, Hera; Schmid, Günter; Wenzel, Wolfgang; Jahnen-Dechent, Willi; Simon, Ulrich

    2013-01-01

    Understanding the mechanism of toxicity of nanomaterials remains a challenge with respect to both mechanisms involved and product regulation. Here we show toxicity of ultrasmall gold nanoparticles (AuNPs). Depending on the ligand chemistry, 1.4-nm-diameter AuNPs failed electrophysiology-based safety testing using human embryonic kidney cell line 293 cells expressing human ether-á-go-go-Related gene (hERG), a Food and Drug Administration-established drug safety test. In patch-clamp experiments, phosphine-stabilized AuNPs irreversibly blocked hERG channels, whereas thiol-stabilized AuNPs of similar size had no effect in vitro, and neither particle blocked the channel in vivo. We conclude that safety regulations may need to be reevaluated and adapted to reflect the fact that the binding modality of surface functional groups becomes a relevant parameter for the design of nanoscale bioactive compounds. PMID:23630249

  15. Charge-controlled nanoprecipitation as a modular approach to ultrasmall polymer nanocarriers: making bright and stable nanoparticles.

    PubMed

    Reisch, Andreas; Runser, Anne; Arntz, Youri; Mély, Yves; Klymchenko, Andrey S

    2015-05-26

    Ultrasmall polymer nanoparticles are rapidly gaining importance as nanocarriers for drugs and contrast agents. Here, a straightforward modular approach to efficiently loaded and stable sub-20-nm polymer particles is developed. In order to obtain ultrasmall polymer nanoparticles, we investigated the influence of one to two charged groups per polymer chain on the size of particles obtained by nanoprecipitation. Negatively charged carboxylate and sulfonate or positively charged trimethylammonium groups were introduced into the polymers poly(d,l-lactide-co-glycolide) (PLGA), polycaprolactone (PCL), and poly(methyl methacrylate) (PMMA). According to dynamic light scattering, atomic force and electron microscopy, the presence of one to two charged groups per polymer chain can strongly reduce the size of polymer nanoparticles made by nanoprecipitation. The particle size can be further decreased to less than 15 nm by decreasing the concentration of polymer in the solvent used for nanoprecipitation. We then show that even very small nanocarriers of 15 nm size preserve the capacity to encapsulate large amounts of ionic dyes with bulky counterions at efficiencies >90%, which generates polymer nanoparticles 10-fold brighter than quantum dots of the same size. Postmodification of their surface with the PEG containing amphiphiles Tween 80 and pluronic F-127 led to particles that were stable under physiological conditions and in the presence of 10% fetal bovine serum. This modular route could become a general method for the preparation of ultrasmall polymer nanoparticles as nanocarriers of contrast agents and drugs.

  16. Ultrasmall cationic superparamagnetic iron oxide nanoparticles as nontoxic and efficient MRI contrast agent and magnetic-targeting tool

    PubMed Central

    Uchiyama, Mayara Klimuk; Toma, Sergio Hiroshi; Rodrigues, Stephen Fernandes; Shimada, Ana Lucia Borges; Loiola, Rodrigo Azevedo; Cervantes Rodríguez, Hernán Joel; Oliveira, Pedro Vitoriano; Luz, Maciel Santos; Rabbani, Said Rahnamaye; Toma, Henrique Eisi; Poliselli Farsky, Sandra Helena; Araki, Koiti

    2015-01-01

    Fully dispersible, cationic ultrasmall (7 nm diameter) superparamagnetic iron oxide nanoparticles, exhibiting high relaxivity (178 mM−1s−1 in 0.47 T) and no acute or subchronic toxicity in Wistar rats, were studied and their suitability as contrast agents for magnetic resonance imaging and material for development of new diagnostic and treatment tools demonstrated. After intravenous injection (10 mg/kg body weight), they circulated throughout the vascular system causing no microhemorrhage or thrombus, neither inflammatory processes at the mesentery vascular bed and hepatic sinusoids (leukocyte rolling, adhesion, or migration as evaluated by intravital microscopy), but having been spontaneously concentrated in the liver, spleen, and kidneys, they caused strong negative contrast. The nanoparticles are cleared from kidneys and bladder in few days, whereas the complete elimination from liver and spleen occurred only after 4 weeks. Ex vivo studies demonstrated that cationic ultrasmall superparamagnetic iron oxide nanoparticles caused no effects on hepatic and renal enzymes dosage as well as on leukocyte count. In addition, they were readily concentrated in rat thigh by a magnet showing its potential as magnetically targeted carriers of therapeutic and diagnostic agents. Summarizing, cationic ultrasmall superparamagnetic iron oxide nanoparticles are nontoxic and efficient magnetic resonance imaging contrast agents useful as platform for the development of new materials for application in theranostics. PMID:26251595

  17. Ultrasmall and phase-pure W2C nanoparticles for efficient electrocatalytic and photoelectrochemical hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Gong, Qiufang; Wang, Yu; Hu, Qi; Zhou, Jigang; Feng, Renfei; Duchesne, Paul N.; Zhang, Peng; Chen, Fengjiao; Han, Na; Li, Yafei; Jin, Chuanhong; Li, Yanguang; Lee, Shuit-Tong

    2016-10-01

    Earlier research has been primarily focused on WC as one of the most promising earth-abundant electrocatalysts for hydrogen evolution reaction (HER), whereas the other compound in this carbide family--W2C--has received far less attention. Our theoretical calculations suggest that such a focus is misplaced and W2C is potentially more HER-active than WC. Nevertheless, the preparation of phase pure and sintering-free W2C nanostructures represents a formidable challenge. Here we develop an improved carburization method and successfully prepare ultrasmall and phase-pure W2C nanoparticles. When evaluated for HER electrocatalysis, W2C nanoparticles exhibit a small onset overpotential of 50 mV, a Tafel slope of 45 mV dec-1 and outstanding long-term cycling stability, which are dramatically improved over all existing WC-based materials. In addition, the integration of W2C nanoparticles with p-type Si nanowires enables highly active and sustainable solar-driven hydrogen production. Our results highlight the great potential of this traditionally non-popular material in HER electrocatalysis.

  18. Optical Observation of Plasmonic Nonlocal Effects in a 2D Superlattice of Ultrasmall Gold Nanoparticles.

    PubMed

    Shen, Hao; Chen, Li; Ferrari, Lorenzo; Lin, Meng-Hsien; Mortensen, N Asger; Gwo, Shangjr; Liu, Zhaowei

    2017-04-12

    The advances in recent nanofabrication techniques have facilitated explorations of metal structures into nanometer scales, where the traditional local-response Drude model with hard-wall boundary conditions fails to accurately describe their optical responses. The emerging nonlocal effects in single ultrasmall silver nanoparticles have been experimentally observed in single-particle spectroscopy enabled by the unprecedented high spatial resolution of electron energy loss spectroscopy (EELS). However, the unambiguous optical observation of such new effects in gold nanoparticles has yet not been reported, due to the extremely weak scattering and the obscuring fingerprint of strong interband transitions. Here we present a nanosystem, a superlattice monolayer formed by sub-10 nm gold nanoparticles. Plasmon resonances are spectrally well-separated from interband transitions, while exhibiting clearly distinguishable blueshifts compared to predictions by the classical local-response model. Our far-field spectroscopy was performed by a standard optical transmission and reflection setup, and the results agreed excellently with the hydrodynamic nonlocal model, opening a simple and widely accessible way for addressing quantum effects in nanoplasmonic systems.

  19. Ultrasmall and phase-pure W2C nanoparticles for efficient electrocatalytic and photoelectrochemical hydrogen evolution

    PubMed Central

    Gong, Qiufang; Wang, Yu; Hu, Qi; Zhou, Jigang; Feng, Renfei; Duchesne, Paul N.; Zhang, Peng; Chen, Fengjiao; Han, Na; Li, Yafei; Jin, Chuanhong; Li, Yanguang; Lee, Shuit-Tong

    2016-01-01

    Earlier research has been primarily focused on WC as one of the most promising earth-abundant electrocatalysts for hydrogen evolution reaction (HER), whereas the other compound in this carbide family—W2C—has received far less attention. Our theoretical calculations suggest that such a focus is misplaced and W2C is potentially more HER-active than WC. Nevertheless, the preparation of phase pure and sintering-free W2C nanostructures represents a formidable challenge. Here we develop an improved carburization method and successfully prepare ultrasmall and phase-pure W2C nanoparticles. When evaluated for HER electrocatalysis, W2C nanoparticles exhibit a small onset overpotential of 50 mV, a Tafel slope of 45 mV dec−1 and outstanding long-term cycling stability, which are dramatically improved over all existing WC-based materials. In addition, the integration of W2C nanoparticles with p-type Si nanowires enables highly active and sustainable solar-driven hydrogen production. Our results highlight the great potential of this traditionally non-popular material in HER electrocatalysis. PMID:27752046

  20. Optical characterization of ultrasmall, hydrogen-terminated and carboxyl-functionalized silicon nanoparticles in aqueous environments

    NASA Astrophysics Data System (ADS)

    Eckhoff, Dean Alan

    The primary theme of this dissertation is to characterize the optical and chemical properties of ultrasmall (˜1 nm) silicon nanoparticles (Si-np) in aqueous environments, focusing on their potential for use as luminescent markers in biophysical and biological applications. Two systems are presented in detail: hydrogen-terminated Si-np prepared through electrochemical dispersion of a crystalline Si wafer and carboxyl-functionalized Si-np prepared via thermal hydrosilylation of surface Si-H bonds with an o-ester 1-alkene. Chemical and physical characterizations are done using nuclear magnetic resonance, size exclusion chromatography, and infrared spectroscopy. Optical characterization is done via absorption and steady-state photoluminescence (PL) and using capillary electrophoresis coupled with laser-induced fluorescence detection. The behavior of the hydrogen-terminated Si-np is studied over time as-prepared in isopropanol and during treatments with water, NaOH, HCl, and H2O 2. The PL spectra show three distinct, near-Gaussian states with a FWHM ˜0.45 eV and their respective emissions in the UV-B (˜305 nm), UV-A (˜340 nm), and 'hard-blue' (˜400 nm) regions of the spectrum. The 'hard-blue' emission is shown to have a simple pH dependence with a pKa ˜3, demonstrating the possibility of using Si-np as environmental probes. These results offer some promise for tailoring the PL properties of ultrasmall Si-np through control of their surface chemistry. In the second part, three central elements establish that the carboxyl-functionalized Si-np have excellent potential for use as a luminescent marker in aqueous systems. First, they are shown to be ultrasmall, with a diameter of ˜1 nm, comparable to that of common organic fluorophores. Second, they are shown to have narrow PL in the near-UV with a nearly-symmetric lineshape and a FWHM as small as 30 nm. Third, it is shown that standard chemical means can be used to functionalize the Si-np with carboxyl groups, giving

  1. RGD-functionalized ultrasmall iron oxide nanoparticles for targeted T1-weighted MR imaging of gliomas

    NASA Astrophysics Data System (ADS)

    Luo, Yu; Yang, Jia; Yan, Yu; Li, Jingchao; Shen, Mingwu; Zhang, Guixiang; Mignani, Serge; Shi, Xiangyang

    2015-08-01

    We report a convenient approach to prepare ultrasmall Fe3O4 nanoparticles (NPs) functionalized with an arginylglycylaspartic acid (RGD) peptide for in vitro and in vivo magnetic resonance (MR) imaging of gliomas. In our work, stable sodium citrate-stabilized Fe3O4 NPs were prepared by a solvothermal route. Then, the carboxylated Fe3O4 NPs stabilized with sodium citrate were conjugated with polyethylene glycol (PEG)-linked RGD. The formed ultrasmall RGD-functionalized nanoprobe (Fe3O4-PEG-RGD) was fully characterized using different techniques. We show that these Fe3O4-PEG-RGD particles with a size of 2.7 nm are water-dispersible, stable, cytocompatible and hemocompatible in a given concentration range, and display targeting specificity to glioma cells overexpressing αvβ3 integrin in vitro. With the relatively high r1 relaxivity (r1 = 1.4 mM-1 s-1), the Fe3O4-PEG-RGD particles can be used as an efficient nanoprobe for targeted T1-weighted positive MR imaging of glioma cells in vitro and the xenografted tumor model in vivo via an active RGD-mediated targeting pathway. The developed RGD-functionalized Fe3O4 NPs may hold great promise to be used as a nanoprobe for targeted T1-weighted MR imaging of different αvβ3 integrin-overexpressing cancer cells or biological systems.We report a convenient approach to prepare ultrasmall Fe3O4 nanoparticles (NPs) functionalized with an arginylglycylaspartic acid (RGD) peptide for in vitro and in vivo magnetic resonance (MR) imaging of gliomas. In our work, stable sodium citrate-stabilized Fe3O4 NPs were prepared by a solvothermal route. Then, the carboxylated Fe3O4 NPs stabilized with sodium citrate were conjugated with polyethylene glycol (PEG)-linked RGD. The formed ultrasmall RGD-functionalized nanoprobe (Fe3O4-PEG-RGD) was fully characterized using different techniques. We show that these Fe3O4-PEG-RGD particles with a size of 2.7 nm are water-dispersible, stable, cytocompatible and hemocompatible in a given concentration

  2. Kinetically-controlled synthesis of ultra-small silica nanoparticles and ultra-thin coatings

    NASA Astrophysics Data System (ADS)

    Ding, Tao; Yao, Lin; Liu, Cuicui

    2016-02-01

    The understanding of silica as a polymer-like globule allows us to synthesize ultra-small silica nanoparticles (NPs) via a kinetic controlled process. The synthetic system is quite simple with Tetraethyl orthosilicate (TESO) as the precursor and H2O as the solvent and reactant. The reaction conditions are gentle with a temperature of around 35 to 60 °C with an incubation time of 7-12 hours. The final product of the silica NPs is very uniform and could be as small as 10 nm. The silica NPs can further grow up to 18 nm under the controlled addition of the precursors. Also, these silica NPs can be used as seeds to generate larger silica NPs with sizes ranging from 20 to 100 nm, which can be a useful supplement to the size range made by the traditional Stöber method. Moreover, these ultra-small Au NPs can be used as a depletion reagent or as building blocks for an ultrathin silica coating, which has significant applications in fine-tuning the plasmons of AuNPs and thin spacers for surface enhanced spectroscopies.The understanding of silica as a polymer-like globule allows us to synthesize ultra-small silica nanoparticles (NPs) via a kinetic controlled process. The synthetic system is quite simple with Tetraethyl orthosilicate (TESO) as the precursor and H2O as the solvent and reactant. The reaction conditions are gentle with a temperature of around 35 to 60 °C with an incubation time of 7-12 hours. The final product of the silica NPs is very uniform and could be as small as 10 nm. The silica NPs can further grow up to 18 nm under the controlled addition of the precursors. Also, these silica NPs can be used as seeds to generate larger silica NPs with sizes ranging from 20 to 100 nm, which can be a useful supplement to the size range made by the traditional Stöber method. Moreover, these ultra-small Au NPs can be used as a depletion reagent or as building blocks for an ultrathin silica coating, which has significant applications in fine-tuning the plasmons of Au

  3. Clinical translation of an ultrasmall inorganic optical-PET imaging nanoparticle probe

    PubMed Central

    Phillips, Evan; Penate-Medina, Oula; Zanzonico, Pat B.; Carvajal, Richard D.; Mohan, Pauliah; Ye, Yunpeng; Humm, John; Gönen, Mithat; Kalaigian, Hovanes; Schöder, Heiko; Strauss, H. William; Larson, Steven M.; Wiesner, Ulrich; Bradbury, Michelle S.

    2015-01-01

    A first-in-human clinical trial of ultrasmall inorganic hybrid nanoparticles, “C dots” (Cornell dots), in patients with metastatic melanoma is described for the imaging of cancer. These renally excreted silica particles were labeled with 124I for positron emission tomography (PET) imaging and modified with cRGDY peptides for molecular targeting. 124I-cRGDY–PEG–C dot particles are inherently fluorescent, containing the dye, Cy5, so they may be used as hybrid PET-optical imaging agents for lesion detection, cancer staging, and treatment management in humans. However, the clinical translation of nanoparticle probes, including quantum dots, has not kept pace with the accelerated growth in minimally invasive surgical tools that rely on optical imaging agents. The safety, pharmacokinetics, clearance properties, and radiation dosimetry of 124I-cRGDY–PEG–C dots were assessed by serial PET and computerized tomography after intravenous administration in patients. Metabolic profiles and laboratory tests of blood and urine specimens, obtained before and after particle injection, were monitored over a 2-week interval. Findings are consistent with a well-tolerated inorganic particle tracer exhibiting in vivo stability and distinct, reproducible pharmacokinetic signatures defined by renal excretion. No toxic or adverse events attributable to the particles were observed. Coupled with preferential uptake and localization of the probe at sites of disease, these first-in-human results suggest safe use of these particles in human cancer diagnostics. PMID:25355699

  4. Synthesis of core/shell spinel ferrite/carbon nanoparticles with enhanced cycling stability for lithium ion battery anodes

    NASA Astrophysics Data System (ADS)

    Jin, Yun-Ho; Seo, Seung-Deok; Shim, Hyun-Woo; Park, Kyung-Soo; Kim, Dong-Wan

    2012-03-01

    Monodispersed core/shell spinel ferrite/carbon nanoparticles are formed by thermolysis of metal (Fe3+, Co2+) oleates followed by carbon coating. The phase and morphology of nanoparticles are characterized by x-ray diffraction and transmission electron microscopy. Pure Fe3O4 and CoFe2O4 nanoparticles are initially prepared through thermal decomposition of metal-oleate precursors at 310 °C and they are found to exhibit poor electrochemical performance because of the easy aggregation of nanoparticles and the resulting increase in the interparticle contact resistance. In contrast, uniform carbon coating of Fe3O4 and CoFe2O4 nanoparticles by low-temperature (180 °C) decomposition of malic acid allowed each nanoparticle to be electrically wired to a current collector through a conducting percolative path. Core/shell Fe3O4/C and CoFe2O4/C nanocomposite electrodes show a high specific capacity that can exceed 700 mAh g-1 after 200 cycles, along with enhanced cycling stability.

  5. Superparamagnetic MFe2O 4 (M = Ni, Co, Zn, Mn) nanoparticles: synthesis, characterization, induction heating and cell viability studies for cancer hyperthermia applications.

    PubMed

    Sabale, Sandip; Jadhav, Vidhya; Khot, Vishwajeet; Zhu, Xiaoli; Xin, Meiling; Chen, Hongxia

    2015-03-01

    Superparamagnetic nanoferrites are prepared by simple and one step refluxing in polyol synthesis. The ferrite nanoparticles prepared by this method exhibit particle sizes below 10 nm and high degree of crystallinity. These ferrite nanoparticles are compared by means of their magnetic properties, induction heating and cell viability studies for its application in magnetic fluid hyperthermia. Out of all studied nanoparticles in present work, only ZnFe2O4 and CoFe2O4 MNPs are able to produce threshold hyperthermia temperature. This rise in temperature is discussed in detail in view of their magneto-structural properties. Therefore ZnFe2O4 and CoFe2O4 MNPs with improved stability, magnetic induction heating and cell viability are suitable candidates for magnetic hyperthermia.

  6. Near-field light concentration of ultra-small metallic nanoparticles for absorption enhancement in a-Si solar cells

    NASA Astrophysics Data System (ADS)

    Cai, Boyuan; Jia, Baohua; Shi, Zhengrong; Gu, Min

    2013-03-01

    Near-field light concentration from plasmonic nanostructures was predicted to significantly improve solar cell conversion efficiency since the inception of plasmonic solar cells. However the challenge remains in designing effective nanostructures for useful near-field enhancement much exceeding the detrimental ohmic loss and light blockage losses in solar cells. We propose and demonstrate ultra-small (a few nanometers) gold nanoparticles integrated in amorphous silicon solar cells between the front electrode and the photoactive layer. Significant enhancements in both the photocurrent (14.1%) and fill factor (12.3%) have been achieved due to the strong plasmonic near-field concentration and the reduced contact resistance, respectively.

  7. Relaxation behavior study of ultrasmall superparamagnetic iron oxide nanoparticles at ultralow and ultrahigh magnetic fields.

    PubMed

    Wang, Wei; Dong, Hui; Pacheco, Victor; Willbold, Dieter; Zhang, Yi; Offenhaeusser, Andreas; Hartmann, Rudolf; Weirich, Thomas E; Ma, Peixiang; Krause, Hans-Joachim; Gu, Zhongwei

    2011-12-15

    Ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) have attracted attention because of their current and potential usefulness as contrast agents for magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR). USPIOs are usually used for their significant capacity to produce predominant proton relaxation effects, which result in signal reduction. However, most previous studies that utilized USPIOs have been focused on the relaxation behavior at commonly used magnetic fields of clinical MRI systems (typically 1-3 T). In this paper, magnetic relaxation processes of protons in water surrounding the USPIOs are studied at ultralow (≤10 mT) and ultrahigh magnetic fields (14.1 T). USPIOs used in our experiments were synthesized with a core size of 6 nm, and transferred from organic to water by ligand exchange. The proton spin-lattice relaxation time (T(1)) and spin-spin relaxation time (T(2)) were investigated at ultralow (212 μT for T(2) and 10 mT for T(1)) and at 14.1 T with different iron concentrations. At all of the fields, there is a linear relationship between the inverse of relaxation times and the iron concentration. The spin-spin relaxivity (r(2)) at 14.1 T is much larger than that value of the ultralow field. At ultralow field, however, the spin-lattice relaxivity (r(1)) is larger than the r(1) at ultrahigh field. The results provide a perspective on potential in vivo and in vitro applications of USPIOs in ultralow and ultrahigh field NMR and MRI.

  8. Effects of the synthesis temperature on the crystalline structure and the magnetic properties of cobalt ferrite nanoparticles prepared via coprecipitation

    NASA Astrophysics Data System (ADS)

    Hutamaningtyas, Evangelin; Utari; Suharyana; Purnama, Budi; Wijayanta, Agung Tri

    2016-08-01

    The effects of the synthesis temperature on the crystalline structure and the magnetic properties of cobalt ferrite (CoFe2O4) nanoparticles prepared via coprecipitation are discussed. The synthesis was conducted at temperatures of 75 °C, 85 °C and 95 °C. Fourier transform infrared spectroscopy characterization related to a stretching vibration at a wavenumber of 590 cm-1 indicated the formation of a CoFe2O4 metal oxide. In addition, powder X ray diffraction (XRD) characterization proved that the metal oxide was CoFe2O4. Crystallite sizes calculated using the Scherer formula at the strongest peak of the XRD spectra of the samples synthesized at 75 °C, 85 °C and 95 °C were 32 nm, 43 nm and 50.4 nm, respectively. Finally, the results of the vibrating sample magnetometer characterization showed that the saturation magnetization decreased with increasing synthesis temperature, which is related to the dominant preference of Co2+ over Fe3+ cations at the octahedral sites.

  9. In Situ Growth Strategy to Integrate Up-Conversion Nanoparticles with Ultrasmall CuS for Photothermal Theranostics.

    PubMed

    Lv, Ruichan; Yang, Piaoping; Hu, Bo; Xu, Jiating; Shang, Wenting; Tian, Jie

    2017-01-24

    In the theranostic field, a near-infrared (NIR) laser is located in the optical window, and up-conversion nanoparticles (UCNPs) could be potentially utilized as the imaging agents with high contrast. Meanwhile, copper sulfide (CuS) has been proposed as a photothermal agent with increased temperature under a NIR laser. However, there is still no direct and effective strategy to integrate the hydrophobic UCNPs with CuS until now. Herein, we propose an in situ growth routine based on the hydrophobic core/shell UCNPs combined with ultrasmall water-soluble CuS triggered by single 808 nm NIR irradiation as the theranostic platform. Hydrophobic NaYF4:Yb,Er@NaYF4,Nd,Yb could be turned hydrophilic with highly dispersed and biocompatible properties through conjunction with transferred dopamine. The as-synthesized ultrasmall CuS (3 and 7 nm) served as a stable photothermal agent even after several laser-on/off cycles. Most importantly, comparing with the mix routine, the in situ growth routine to coat UCNPs with CuS is meaningful, and the platform is uniform and stable. Green luminescence-guided hyperthermia could be achieved under a single 808 nm laser, which was evidenced by in vitro and in vivo assays. This nanoplatform is applicable as a bioimaging and photothermal antitumor agent, and the in situ growth routine could be spread to other integration processes.

  10. Synergistic Effect between Ultra-Small Nickel Hydroxide Nanoparticles and Reduced Graphene Oxide sheets for the Application in High-Performance Asymmetric Supercapacitor

    PubMed Central

    Liu, Yonghuan; Wang, Rutao; Yan, Xingbin

    2015-01-01

    Nanoscale electrode materials including metal oxide nanoparticles and two-dimensional graphene have been employed for designing supercapacitors. However, inevitable agglomeration of nanoparticles and layers stacking of graphene largely hamper their practical applications. Here we demonstrate an efficient co-ordination and synergistic effect between ultra-small Ni(OH)2 nanoparticles and reduced graphene oxide (RGO) sheets for synthesizing ideal electrode materials. On one hand, to make the ultra-small Ni(OH)2 nanoparticles work at full capacity as an ideal pseudocapacitive material, RGO sheets are employed as an suitable substrate to anchor these nanoparticles against agglomeration. As a consequence, an ultrahigh specific capacitance of 1717 F g−1 at 0.5 A g−1 is achieved. On the other hand, to further facilitate ion transfer within RGO sheets as an ideal electrical double layer capacitor material, the ultra-small Ni(OH)2 nanoparticles are introduced among RGO sheets as the recyclable sacrificial spacer to prevent the stacking. The resulting RGO sheets exhibit superior rate capability with a high capacitance of 182 F g−1 at 100 A g−1. On this basis, an asymmetric supercapacitor is assembled using the two materials, delivering a superior energy density of 75 Wh kg−1 and an ultrahigh power density of 40 000 W kg−1. PMID:26053847

  11. Ferrofluids based on Co-Fe-Si-B amorphous nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Tianqi; Bian, Xiufang; Yang, Chuncheng; Zhao, Shuchun; Yu, Mengchun

    2017-03-01

    Magnetic Co-Fe-Si-B amorphous nanoparticles were successfully synthesized by chemical reduction method. ICP, XRD, DSC, and TEM were used to investigate the composition, structure and morphology of Co-Fe-Si-B samples. The results show that the Co-Fe-Si-B samples are amorphous, which consist of nearly spherical nanoparticles with an average particle size about 23 nm. VSM results manifest that the saturation magnetization (Ms) of Co-Fe-Si-B samples ranges from 46.37 to 62.89 emu/g. Two kinds of ferrofluids (FFs) were prepared by dispersing Co-Fe-Si-B amorphous nanoparticles and CoFe2O4 nanoparticles in kerosene and silicone oil, respectively. The magnetic properties, stability and viscosity of the FFs were investigated. The FFs with Co-Fe-Si-B samples have a higher Ms and lower coercivity (Hc) than FFs with CoFe2O4 sample. Under magnetic field, the silicone oil-based FFs exhibit high stability. The viscosity of FFs under different applied magnetic fields was measured by a rotational viscometer, indicating that FFs with Co-Fe-Si-B particles present relative strong response to an external magnetic field. The metal-boride amorphous alloy nanoparticles have potential applications in the preparation of magnetic fluids with good stability and good magnetoviscous properties.

  12. Magnetic Characterization of Ferrite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Bryan, Matthew; Sokol, Paul; Gumina, Greg; Bronstein, Lyudmila; Dragnea, Bogdan

    2011-03-01

    Magnetic nanoparticles (NPs) of different compositions (FeO/ Fe 3 O4 , g- Fe 2 O3 , FePt, and CoFe 2 O4) have been synthesized using high temperature organometallic routes described elsewhere. NPs (16.6 nm in diameter) of a mixed FeO/ Fe 3 O4 (wuestite/magnetite) composition were prepared by thermal decomposition or iron oleate in the presence of oleic acid as a surfactant in dodocane at 370C in argon atmosphere. After the thermal treatment of the reaction solution at 200 C under air for 2 hours these NPs are transformed into maghemite (g- Fe 2 O3) , the magnetization of which is significantly enhanced. NPs of CoFe 2 O4 (8 nm) have been prepared by simultaneous decomposition of Co(II) and Fe(III) acetylacetonates in the presence of oleic acid and oleylamine. The X-ray diffraction profile of these NPs is characteristic of cobalt ferrite. Alternatively, alloyed 1.8 nm FePt NPs prepared by simultaneous decomposition of Fe and Pt acetylacetonates in the reductive environment demonstrate a completely disordered structure, which is reflected in their magnetic properties. SQUID magnetometry was used to measure the magnetization of NPs at high and low temperatures. Zero-field cooling and field-cooling measurements were taken to demonstrate superparamagnetic behavior and an associated blocking temperature.

  13. Synthesis of ultra-small cysteine-capped gold nanoparticles by pH switching of the Au(I)-cysteine polymer.

    PubMed

    Cappellari, Paula S; Buceta, David; Morales, Gustavo M; Barbero, Cesar A; Sergio Moreno, M; Giovanetti, Lisandro J; Ramallo-López, José Martín; Requejo, Felix G; Craievich, Aldo F; Planes, Gabriel A

    2015-03-01

    We report a synthetic approach for the production of ultra-small (0.6 nm) gold nanoparticles soluble in water with a precise control of the nanoparticle size. Our synthetic approach utilizes a pH-depending Au-cysteine polymer as a quencher for the AuNPs grown. The method extends the synthetic capabilities of nanoparticles with sizes down to 1 nm. In addition to the strict pH control, the existence of free -SH groups present in the mixture of reaction has been observed as a key requirement for the synthesis of small nanoparticles in mild conditions. UV-Vis, SAXS, XANES, EXAFS and HR-TEM, has been used to determinate the particle size, characterization of the gold precursor and gold-cysteine interaction.

  14. Tuning the magnetism of ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Viñas, S. Liébana; Simeonidis, K.; Li, Z.-A.; Ma, Z.; Myrovali, E.; Makridis, A.; Sakellari, D.; Angelakeris, M.; Wiedwald, U.; Spasova, M.; Farle, M.

    2016-10-01

    The importance of magnetic interactions within an individual nanoparticle or between adjacent ones is crucial not only for the macroscopic collective magnetic behavior but for the AC magnetic heating efficiency as well. On this concept, single-(MFe2O4 where M=Fe, Co, Mn) and core-shell ferrite nanoparticles consisting of a magnetically softer (MnFe2O4) or magnetically harder (CoFe2O4) core and a magnetite (Fe3O4) shell with an overall size in the 10 nm range were synthesized and studied for their magnetic particle hyperthermia efficiency. Magnetic measurements indicate that the coating of the hard magnetic phase (CoFe2O4) by Fe3O4 provides a significant enhancement of hysteresis losses over the corresponding single-phase counterpart response, and thus results in a multiplication of the magnetic hyperthermia efficiency opening a novel pathway for high-performance, magnetic hyperthermia agents. At the same time, the existence of a biocompatible Fe3O4 outer shell, toxicologically renders these systems similar to iron-oxide ones with significantly milder side-effects.

  15. Direct isolation of flavonoids from plants using ultra-small anatase TiO2 nanoparticles

    PubMed Central

    Kurepa, Jasmina; Nakabayashi, Ryo; Paunesku, Tatjana; Suzuki, Makoto; Saito, Kazuki; Woloschak, Gayle E.; Smalle, Jan A.

    2013-01-01

    Summary Surface functionalization of nanoparticles has become an important tool for the in vivo delivery of bioactive agents to their target sites. Here we describe the reverse strategy, nanoharvesting, in which nanoparticles are used as a tool to isolate and enrich bioactive compounds from living cells. Anatase TiO2 nanoparticles smaller than 20 nm form strong bonds with molecules carrying enediol and especially catechol groups. We show that these nanoparticles can enter plant cells, conjugate enediol and catechol group-rich flavonoids in situ, and exit plant cells as flavonoid-nanoparticle conjugates. The source plant tissues remain viable after treatment. As predicted by the surface chemistry of anatase TiO2 nanoparticles, the quercetin-based flavonoids were enriched amongst the nanoharvested flavonoid species. Nanoharvesting eliminates the use of organic solvents, allows spectral identification of the isolated compounds, and offers a new avenue for the use of nanomaterials for the coupled isolation and testing of bioactive properties of plant-made compounds. PMID:24147867

  16. Synthesis of magnetic cobalt ferrite nanoparticles with controlled morphology, monodispersity and composition: the influence of solvent, surfactant, reductant and synthetic conditions

    NASA Astrophysics Data System (ADS)

    Lu, Le T.; Dung, Ngo T.; Tung, Le D.; Thanh, Cao T.; Quy, Ong K.; Chuc, Nguyen V.; Maenosono, Shinya; Thanh, Nguyen T. K.

    2015-11-01

    In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(iii) and Co(ii) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications.In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(iii) and Co(ii) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications. Electronic

  17. Ultra-small rhenium nanoparticles immobilized on DNA scaffolds: An excellent material for surface enhanced Raman scattering and catalysis studies.

    PubMed

    Anantharaj, S; Sakthikumar, K; Elangovan, Ayyapan; Ravi, G; Karthik, T; Kundu, Subrata

    2016-12-01

    Highly Sensitive and ultra-small Rhenium (Re) metal nanoparticles (NPs) were successfully stabilized in water by the staging and fencing action of the versatile biomolecule DNA that resulted in two distinct aggregated chain-like morphologies with average grain sizes of 1.1±0.1nm and 0.7±0.1nm for the very first time within a minute of reaction time. Re NPs are formed by the borohydride reduction of ammonium perrhenate (NH4ReO4) in the presence of DNA at room temperature (RT) under stirring. The morphologies were controlled by carefully monitoring the molar ratio of NH4ReO4 and DNA. The synthesized material was employed in two potential applications: as a substrate for surface enhanced Raman scattering (SERS) studies and as a catalyst for the reduction of aromatic nitro compounds. SERS study was carried out by taking methylene blue (MB) as the probe and the highest SERS enhancement factor (EF) of 2.07×10(7) was found for the aggregated chain-like having average grain size of 0.7±0.1nm. Catalytic reduction of 4-nitro phenol (4-NP), 2-nitro phenol (2-NP) and 4-nitroaniline (4-NA) with a rate constant value of 6×10(-2)min(-1), 33.83×10(-2)min(-1) and 37.4×10(-2)min(-1) have testified the excellent catalytic performance of our Re NPs immobilized on DNA. The overall study have revealed the capability of DNA in stabilizing the highly reactive Re metal at nanoscale and made them applicable in practice. The present route can also be extended to prepare one dimensional (1-D), self-assembled NPs of other reactive metals, mixed metals or even metal oxides for specific applications in water based solutions.

  18. Ultra-small lipid nanoparticles promote the penetration of coenzyme Q10 in skin cells and counteract oxidative stress.

    PubMed

    Lohan, Silke B; Bauersachs, Sonja; Ahlberg, Sebastian; Baisaeng, Nuttakorn; Keck, Cornelia M; Müller, Rainer H; Witte, Ellen; Wolk, Kerstin; Hackbarth, Steffen; Röder, Beate; Lademann, Jürgen; Meinke, Martina C

    2015-01-01

    UV irradiation leads to the formation of reactive oxygen species (ROS). An imbalance between the antioxidant system and ROS can lead to cell damage, premature skin aging or skin cancer. To counteract these processes, antioxidants such as coenzyme Q10 (CoQ10) are contained in many cosmetics. To improve and optimize cell/tissue penetration properties of the lipophilic CoQ10, ultra-small lipid nanoparticles (usNLC) were developed. The antioxidant effectiveness of CoQ10-loaded usNLC compared to conventional nanocarriers was investigated in the human keratinocyte cell line HaCaT. Using confocal laser scanning microscopy investigations of the carriers additionally loaded with nile red showed a clear uptake into cells and their distribution within the cytoplasm. By use of the XTT cell viability test, CoQ10 concentrations of 10-50 μg/ml were shown to be non-toxic, and the antioxidant potential of 10 μg/ml CoQ10 loaded usNLC in the HaCaT cells was analyzed via electron paramagnetic resonance spectroscopy after cellular exposure to UVA (1J/cm(2)) and UVB (18 mJ/cm(2)) irradiation. In comparison with the CoQ10-loaded conventional carriers, usNLC-CoQ10 demonstrated the strongest reduction of the radical formation; reaching up to 23% compared to control cells without nanocarrier treatment. Therefore, usNLC-CoQ10 are very suitable to increase the antioxidant potential of skin.

  19. Differential stress reaction of human colon cells to oleic-acid-stabilized and unstabilized ultrasmall iron oxide nanoparticles

    PubMed Central

    Schütz, Catherine A; Staedler, Davide; Crosbie-Staunton, Kieran; Movia, Dania; Chapuis Bernasconi, Catherine; Kenzaoui, Blanka Halamoda; Prina-Mello, Adriele; Juillerat-Jeanneret, Lucienne

    2014-01-01

    Therapeutic engineered nanoparticles (NPs), including ultrasmall superparamagnetic iron oxide (USPIO) NPs, may accumulate in the lower digestive tract following ingestion or injection. In order to evaluate the reaction of human colon cells to USPIO NPs, the effects of non-stabilized USPIO NPs (NS-USPIO NPs), oleic-acid-stabilized USPIO NPs (OA-USPIO NPs), and free oleic acid (OA) were compared in human HT29 and CaCo2 colon epithelial cancer cells. First the biophysical characteristics of NS-USPIO NPs and OA-USPIO NPs in water, in cell culture medium supplemented with fetal calf serum, and in cell culture medium preconditioned by HT29 and CaCo2 cells were determined. Then, stress responses of the cells were evaluated following exposure to NS-USPIO NPs, OA-USPIO NPs, and free OA. No modification of the cytoskeletal actin network was observed. Cell response to stress, including markers of apoptosis and DNA repair, oxidative stress and degradative/autophagic stress, induction of heat shock protein, or lipid metabolism was determined in cells exposed to the two NPs. Induction of an autophagic response was observed in the two cell lines for both NPs but not free OA, while the other stress responses were cell- and NP-specific. The formation of lipid vacuoles/droplets was demonstrated in HT29 and CaCo2 cells exposed to OA-USPIO NPs but not to NS-USPIO NPs, and to a much lower level in cells exposed to equimolar concentrations of free OA. Therefore, the induction of lipid vacuoles in colon cells exposed to OA utilized as a stabilizer for USPIO NPs is higly amplified compared to free OA, and is not observed in the absence of this lipid in NS-USPIO NPs. PMID:25092978

  20. Selective Removal of Hemoglobin from Blood Using Hierarchical Copper Shells Anchored to Magnetic Nanoparticles

    PubMed Central

    Wang, Yaokun; Yan, Mingyang

    2017-01-01

    Hierarchical copper shells anchored on magnetic nanoparticles were designed and fabricated to selectively deplete hemoglobin from human blood by immobilized metal affinity chromatography. Briefly, CoFe2O4 nanoparticles coated with polyacrylic acid were first synthesized by a one-pot solvothermal method. Hierarchical copper shells were then deposited by immobilizing Cu2+ on nanoparticles and subsequently by reducing between the solid CoFe2O4@COOH and copper solution with NaBH4. The resulting nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. The particles were also tested against purified bovine hemoglobin over a range of pH, contact time, and initial protein concentration. Hemoglobin adsorption followed pseudo-second-order kinetics and reached equilibrium in 90 min. Isothermal data also fit the Langmuir model well, with calculated maximum adsorption capacity 666 mg g−1. Due to the high density of Cu2+ on the shell, the nanoparticles efficiently and selectively deplete hemoglobin from human blood. Taken together, the results demonstrate that the particles with hierarchical copper shells effectively remove abundant, histidine-rich proteins, such as hemoglobin from human blood, and thereby minimize interference in diagnostic and other assays. PMID:28316987

  1. Structural and Magnetic Response in Bimetallic Core/Shell Magnetic Nanoparticles

    PubMed Central

    Nairan, Adeela; Khan, Usman; Iqbal, Munawar; Khan, Maaz; Javed, Khalid; Riaz, Saira; Naseem, Shahzad; Han, Xiufeng

    2016-01-01

    Bimagnetic monodisperse CoFe2O4/Fe3O4 core/shell nanoparticles have been prepared by solution evaporation route. To demonstrate preferential coating of iron oxide onto the surface of ferrite nanoparticles X-ray diffraction (XRD), High resolution transmission electron microscope (HR-TEM) and Raman spectroscopy have been performed. XRD analysis using Rietveld refinement technique confirms single phase nanoparticles with average seed size of about 18 nm and thickness of shell is 3 nm, which corroborates with transmission electron microscopy (TEM) analysis. Low temperature magnetic hysteresis loops showed interesting behavior. We have observed large coercivity 15.8 kOe at T = 5 K, whereas maximum saturation magnetization (125 emu/g) is attained at T = 100 K for CoFe2O4/Fe3O4 core/shell nanoparticles. Saturation magnetization decreases due to structural distortions at the surface of shell below 100 K. Zero field cooled (ZFC) and Field cooled (FC) plots show that synthesized nanoparticles are ferromagnetic till room temperature and it has been noticed that core/shell sample possess high blocking temperature than Cobalt Ferrite. Results indicate that presence of iron oxide shell significantly increases magnetic parameters as compared to the simple cobalt ferrite. PMID:28335200

  2. Synthesis of ultrasmall magnetic iron oxide nanoparticles and study of their colloid and surface chemistry

    PubMed Central

    Goloverda, Galina; Jackson, Barry; Kidd, Clayton; Kolesnichenko, Vladimir

    2009-01-01

    Colloidal nanoparticles of Fe3O4 (4 nm) were synthesized by high-temperature hydrolysis of chelated iron (II) and (III) diethylene glycol alkoxide complexes in a solution of the parent alcohol (H2DEG) without using capping ligands or surfactants: [Fe(DEG)Cl2]2- + 2[Fe(DEG)Cl3]2- + 2H2O + 2OH- → Fe3O4 + 3H2DEG + 8Cl- The obtained particles were reacted with different small-molecule polydentate ligands, and the resulting adducts were tested for aqueous colloid formation. Both the carboxyl and α-hydroxyl groups of the hydroxyacids are involved in coordination to the nanoparticles’ surface. This coordination provides the major contribution to the stability of the ligand-coated nanoparticles against hydrolysis. PMID:20161232

  3. Ultra-small Co3O4 nanoparticles-reduced graphene oxide nanocomposite as superior anodes for lithium-ion batteries.

    PubMed

    Lou, Yongbing; Liang, Jing; Peng, Yinglian; Chen, Jinxi

    2015-04-14

    Reducing the particle size of active component in electrode material could significantly improve the electrochemical performance of lithium-ion batteries. Herein, we report a facile method for preparing cobalt oxide nanoparticles-reduced graphene oxide (Co3O4-RGO) nanocomposite, which was composed of ultra-small Co3O4 nanoparticles (∼12.5 nm in size) anchored on RGO nanosheets, as anode material for lithium-ion batteries. Both of the Co3O4-RGO nanocomposite and Co3O4 nanoparticles showed very high specific surface areas of ∼149.5 m(2) g(-1) and ∼107.4 m(2) g(-1). The Co3O4-RGO nanocomposite showed excellent coulombic efficiency, high lithium storage capacity and good rate capability. With an optimum weight percentage of RGO (∼40 wt%), the nanocomposite displayed a high reversible discharge capacity of 830.7 mA h g(-1) after 75 cycles at 200 mA g(-1), and a reversible capacity of 680.9 mA h g(-1) after 30 cycles at 200 mA g(-1) and 100 consecutive cycles at 500 mA g(-1). After each eight cycles at 50, 100, 200, and 500 mA g(-1), the nanocomposite showed high reversible specific capacities of about 1153.2, 961.0, 851.4 and 736.4 mA h g(-1), respectively. These results show the importance of anchoring ultra-small nanoparticles on graphene nanosheets for maximum utilization of electrochemically active Co3O4 nanoparticles and graphene for energy storage applications in high-performance lithium-ion batteries.

  4. Iridium ultrasmall nanoparticles, worm-like chain nanowires, and porous nanodendrites: One-pot solvothermal synthesis and catalytic CO oxidation activity

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Li, Shuai-Chen; Zhu, Wei; Ke, Jun; Yu, Jing-Wen; Zhang, Zhi-Ping; Dai, Lin-Xiu; Gu, Jun; Zhang, Ya-Wen

    2016-06-01

    We report a facile one-pot solvothermal synthesis of monodisperse iridium (Ir) ultrasmall (1.5-2.5 nm in diameter) nanoparticles (NPs), worm-like chain nanowires (NWs), and porous nanodendrites (NDs), for which CO oxidation reaction has been employed as a probe reaction to investigate the effects of nanoparticle size and surface-capping organics on the catalytic activities. Time-dependent experiments revealed that an oriented attachment mechanism induced by the strong adsorption of halide anions (Br- and I-) on specific facet of Ir nanoclusters or by decreasing the reduction rate of Ir precursors with changing their concentrations during the synthesis was responsible for the formation of Ir NWs and NDs. Annealing tests indicated that an O2-H2 atmosphere treatment turned out to be an effective measure to clean up the surface-capping organics of Ir NPs supported on commercial SiO2. Catalytic CO oxidation reaction illustrated that a significant improvement in the catalytic activity of CO oxidation reaction was achieved together with the changing of activation energies after such atmosphere treatment for the supported catalysts of the ultrasmall Ir NPs. It is noteworthy that this enhancement in catalytic activity could be ascribed to the changes in the surface status (including populations of Ir species in metallic and oxidized states, removal of surface capping organics, the variety of active sites, and total effective active site number) for the supported nanocatalysts during the atmosphere treatment.

  5. Maghemite decorated with ultra-small palladium nanoparticles (γ-Fe2O3–Pd): applications in the Heck–Mizoroki olefination, Suzuki reaction and allylic oxidation of alkenes

    EPA Science Inventory

    A nanocatalyst comprising ultra-small Pd/PdO nanoparticles (<5 nm) supported on maghemite was prepared by a co-precipitation protocol using inexpensive raw materials and was deployed successfully in various significant synthetic transformations, namely the Heck–Mizoroki olefinati...

  6. Enhancing the antimicrobial activity of natural extraction using the synthetic ultrasmall metal nanoparticles

    PubMed Central

    Li, Huanhuan; Chen, Quansheng; Zhao, Jiewen; Urmila, Khulal

    2015-01-01

    The use of Catechin as an antibacterial agent is becoming ever-more common, whereas unstable and easy oxidation, have limited its application. A simple and low-energy-consuming approach to synthesize highly stable and dispersive Catechin-Cu nanoparticles(NPs) has been developed, in which the stability and dispersivity of the NPs are varied greatly with the pH value and temperature of the reaction. The results demonstrate that the optimal reaction conditions are pH 11 at room temperature. As-synthesized NPs display excellent antimicrobial activity, the survival rates of bacterial cells exposed to the NPs were evaluated using live/dead Bacterial Viability Kit. The results showed that NPs at the concentration of 10 ppm and 20 ppm provided rapid and effective killing of up to 90% and 85% of S. aureus and E. coli within 3 h, respectively. After treatment with 20 ppm and 40 ppm NPs, the bacteria are killed completely. Furthermore, on the basis of assessing the antibacterial effects by SEM, TEM, and AFM, it was found the cell membrane damage of the bacteria caused by direct contact of the bacteria with the NPs was the effective mechanism in the bacterial inactivation. PMID:26046938

  7. Synthesis of stable ultra-small Cu nanoparticles for direct writing flexible electronics

    NASA Astrophysics Data System (ADS)

    Li, Wei; Chen, Minfang

    2014-01-01

    In this study, pure Cu nanoparticles (NPs) have been successfully synthesized and the Cu nano-ink was prepared for direct writing on photo paper using a roller pen. The tri-sodium citrate was used as initial reducing-cum-surfactant agent followed by hydrazine as a second massive reducing agent and cetyltrimethylammonium bromide (CTAB) as extra surfactant agent. From the XRD, TEM, and HR-TEM analyses, the synthesized particles are confirmed to be Cu in spherical shape with sizes range of 2.5 ± 1.0 nm. By analyzing the FT-IR spectroscopy and TGA curves, it was found that the obtained particles capped with tri-sodium citrate and CTAB layers are stable to oxidation up to the temperature 228 °C. The reduced size and enhanced air-stability of the Cu NPs result in an improved particle density upon sintering, which is mainly responsible for the increased conductivity of the Cu patterns. The resistivity of Cu patterns sintered in Ar at 160 °C for 2 h is 7.2 ± 0.6 μΩ cm, which is 4.40 times the bulk Cu resistivity. The drawn Cu lines exhibited excellent integrity and good conductivity, which were experimentally tested. Moreover, a Cu electrode and a sample RFID antenna were successfully made.

  8. Magnetization reversal in epitaxial highly anisotropic CoFe2O4 hetero-structures

    NASA Astrophysics Data System (ADS)

    Lisfi, A.; Pokharel, S.; Morgan, W.; Salamanca-Riba, L.; Wuttig, M.

    2015-05-01

    Magnetization reversal in epitaxial cobalt ferrite films grown on (110) MgO substrate has been investigated through angular studies of hysteresis loop and DCD remanence curve. The angular dependences of the coercivity and the switching field of these films strongly deviate from those typically known for coherent and incoherent rotation modes. However, the best fit for these angular curves suggests that domain wall nucleation is the appropriate mode for the magnetization reversal in these hetero-structures.

  9. Grain size effect on activation energy in spinel CoFe2O4 ceramic

    NASA Astrophysics Data System (ADS)

    Supriya, Sweety; Kumar, Sunil; Kar, Manoranjan

    2016-05-01

    Cobalt ferrite of different average crystallites (from nanocrystallite to micro crystallites) has been prepared by the Sol-Gel Method. The X-ray diffraction (XRD) analysis confirms the cubic spinel phase with no trace of impurity phases. The effect of annealing temperature on micro structure and electric transport properties as a function of frequency and temperature has been studied. It is observed that the electric impedance and conductivity are strongly dependent on grain size. The impedance spectroscopic study is employed to understand the electrical transport properties of cobalt ferrite.

  10. Signature of ferroelectricity in magnetically ordered Mo-doped CoFe2O4

    NASA Astrophysics Data System (ADS)

    Dwivedi, G. D.; Tseng, K. F.; Chan, C. L.; Shahi, P.; Lourembam, J.; Chatterjee, B.; Ghosh, A. K.; Yang, H. D.; Chatterjee, Sandip

    2010-10-01

    Coexistence of both magnetic ordering and ferroelectricity (with giant dielectric constant) have been observed for the first time in Co(Fe1-xMox)2O4 . The magnetization of Co(Fe1-xMox)2O4 ( x ranges from 0 to 0.1) was found to increase with doping concentration of Mo. The magnetic properties indicate that Mo goes into the tetrahedral site. The giant dielectric constant may be attributed to the Maxwell-Wagner relaxation mechanism.

  11. Neutron diffraction study of multiferroic Mo-doped CoFe2O4

    NASA Astrophysics Data System (ADS)

    Das, A.; Dwivedi, G. D.; Kumari, Poonam; Shahi, P.; Yang, H. D.; Ghosh, A. K.; Chatterjee, Sandip

    2015-04-01

    Neutron diffraction measurements have been carried out to study the coexistence of magnetic ordering and ferroelectricity at room temperature in CoFe1.8Mo0.2O4. It is observed from this study that the Mo6+ preferentially occupies the octahedral site and it converts some of the Fe3+ ions into Fe2+ ions in the tetrahedral site. The conversion of Fe3+ ions into Fe2+ ions modulate the Fe-Fe distances which in effect induce the ferroelectricity in magnetically ordered CoFe1.8Mo0.2O4.

  12. Ultrasmall Fe2O3 nanoparticles/MoS2 nanosheets composite as high-performance anode material for lithium ion batteries

    PubMed Central

    Qu, Bin; Sun, Yue; Liu, Lianlian; Li, Chunyan; Yu, Changjian; Zhang, Xitian; Chen, Yujin

    2017-01-01

    Coupling ultrasmall Fe2O3 particles (~4.0 nm) with the MoS2 nanosheets is achieved by a facile method for high-performance anode material for Li-ion battery. MoS2 nanosheets in the composite can serve as scaffolds, efficiently buffering the large volume change of Fe2O3 during charge/discharge process, whereas the ultrasmall Fe2O3 nanoparticles mainly provide the specific capacity. Due to bigger surface area and larger pore volume as well as strong coupling between Fe2O3 particles and MoS2 nanosheets, the composite exhibits superior electrochemical properties to MoS2, Fe2O3 and the physical mixture Fe2O3+MoS2. Typically, after 140 cycles the reversible capacity of the composite does not decay, but increases from 829 mA h g−1 to 864 mA h g−1 at a high current density of 2 A g−1. Thus, the present facile strategy could open a way for development of cost-efficient anode material with high-performance for large-scale energy conversion and storage systems. PMID:28218313

  13. Ultrasmall Fe2O3 nanoparticles/MoS2 nanosheets composite as high-performance anode material for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Qu, Bin; Sun, Yue; Liu, Lianlian; Li, Chunyan; Yu, Changjian; Zhang, Xitian; Chen, Yujin

    2017-02-01

    Coupling ultrasmall Fe2O3 particles (~4.0 nm) with the MoS2 nanosheets is achieved by a facile method for high-performance anode material for Li-ion battery. MoS2 nanosheets in the composite can serve as scaffolds, efficiently buffering the large volume change of Fe2O3 during charge/discharge process, whereas the ultrasmall Fe2O3 nanoparticles mainly provide the specific capacity. Due to bigger surface area and larger pore volume as well as strong coupling between Fe2O3 particles and MoS2 nanosheets, the composite exhibits superior electrochemical properties to MoS2, Fe2O3 and the physical mixture Fe2O3+MoS2. Typically, after 140 cycles the reversible capacity of the composite does not decay, but increases from 829 mA h g‑1 to 864 mA h g‑1 at a high current density of 2 A g‑1. Thus, the present facile strategy could open a way for development of cost-efficient anode material with high-performance for large-scale energy conversion and storage systems.

  14. One-step synthesis of monodisperse, water-soluble ultra-small Fe3O4 nanoparticles for potential bio-application.

    PubMed

    Shen, Li-hua; Bao, Jian-feng; Wang, Dong; Wang, Yi-xiao; Chen, Zhi-wei; Ren, Lei; Zhou, Xi; Ke, Xue-bin; Chen, Min; Yang, An-qi

    2013-03-07

    We report that ultra-small, monodisperse, water-dispersible magnetite (Fe(3)O(4)) nanoparticles can be synthesized by a facile one-pot approach using trisodium citrate as crystal grain growth inhibitor and stabilizer in polyol solution. The resultant Fe(3)O(4) nanoparticles exhibit an excellent long-term colloidal stability in various buffer solutions without any modification. They are also superparamagnetic at room temperature and their magnetic property relies heavily on their size. Due to the low magnetization and good water-dispersibility, the 1.9 nm-sized Fe(3)O(4) nanoparticles reveal a low r(2)/r(1) ratio of 2.03 (r(1) = 1.415 mM(-1) s(-1), r(2) = 2.87 mM(-1) s(-1)), demonstrating that they can be efficient T(1) contrast agents. On the other hand, because of the excellent magnetic responsivity, the 13.8 nm-sized Fe(3)O(4) nanoparticles can be readily modified with nitrilotriacetic acid and used to separate the protein simply with the assistance of a magnet. In addition, these Fe(3)O(4) nanoparticles may be useful in other fields, such as hyperthermia treatment of cancer and targeted drug delivery based on their size-dependent magnetic property and excellent stability.

  15. Au Nanocage Functionalized with Ultra-small Fe3O4 Nanoparticles for Targeting T1–T2Dual MRI and CT Imaging of Tumor

    NASA Astrophysics Data System (ADS)

    Wang, Guannan; Gao, Wei; Zhang, Xuanjun; Mei, Xifan

    2016-06-01

    Diagnostic approaches based on multimodal imaging of clinical noninvasive imaging (eg. MRI/CT scanner) are highly developed in recent years for accurate selection of the therapeutic regimens in critical diseases. Therefore, it is highly demanded in the development of appropriate all-in-one multimodal contrast agents (MCAs) for the MRI/CT multimodal imaging. Here a novel ideal MCAs (F-AuNC@Fe3O4) were engineered by assemble Au nanocages (Au NC) and ultra-small iron oxide nanoparticles (Fe3O4) for simultaneous T1–T2dual MRI and CT contrast imaging. In this system, the Au nanocages offer facile thiol modification and strong X-ray attenuation property for CT imaging. The ultra-small Fe3O4 nanoparticles, as excellent contrast agent, is able to provide great enhanced signal of T1- and T2-weighted MRI (r1 = 6.263 mM‑1 s‑1, r2 = 28.117 mM‑1 s‑1) due to their ultra-refined size. After functionalization, the present MCAs nanoparticles exhibited small average size, low aggregation and excellent biocompatible. In vitro and In vivo studies revealed that the MCAs show long-term circulation time, renal clearance properties and outstanding capability of selective accumulation in tumor tissues for simultaneous CT imaging and T1- and T2-weighted MRI. Taken together, these results show that as-prepared MCAs are excellent candidates as MRI/CT multimodal imaging contrast agents.

  16. Au Nanocage Functionalized with Ultra-small Fe3O4 Nanoparticles for Targeting T1–T2Dual MRI and CT Imaging of Tumor

    PubMed Central

    Wang, Guannan; Gao, Wei; Zhang, Xuanjun; Mei, Xifan

    2016-01-01

    Diagnostic approaches based on multimodal imaging of clinical noninvasive imaging (eg. MRI/CT scanner) are highly developed in recent years for accurate selection of the therapeutic regimens in critical diseases. Therefore, it is highly demanded in the development of appropriate all-in-one multimodal contrast agents (MCAs) for the MRI/CT multimodal imaging. Here a novel ideal MCAs (F-AuNC@Fe3O4) were engineered by assemble Au nanocages (Au NC) and ultra-small iron oxide nanoparticles (Fe3O4) for simultaneous T1–T2dual MRI and CT contrast imaging. In this system, the Au nanocages offer facile thiol modification and strong X-ray attenuation property for CT imaging. The ultra-small Fe3O4 nanoparticles, as excellent contrast agent, is able to provide great enhanced signal of T1- and T2-weighted MRI (r1 = 6.263 mM−1 s−1, r2 = 28.117 mM−1 s−1) due to their ultra-refined size. After functionalization, the present MCAs nanoparticles exhibited small average size, low aggregation and excellent biocompatible. In vitro and In vivo studies revealed that the MCAs show long-term circulation time, renal clearance properties and outstanding capability of selective accumulation in tumor tissues for simultaneous CT imaging and T1- and T2-weighted MRI. Taken together, these results show that as-prepared MCAs are excellent candidates as MRI/CT multimodal imaging contrast agents. PMID:27312564

  17. Metal-induced self-assembly of peroxiredoxin as a tool for sorting ultrasmall gold nanoparticles into one-dimensional clusters

    NASA Astrophysics Data System (ADS)

    Ardini, Matteo; Giansanti, Francesco; di Leandro, Luana; Pitari, Giuseppina; Cimini, Annamaria; Ottaviano, Luca; Donarelli, Maurizio; Santucci, Sandro; Angelucci, Francesco; Ippoliti, Rodolfo

    2014-06-01

    Nanomanipulation of matter to create responsive, ordered materials still remains extremely challenging. Supramolecular chemistry has inspired new strategies by which such nanomaterials can be synthesized step by step by exploiting the self-recognition properties of molecules. In this work, the ring-shaped architecture of the 2-Cys peroxiredoxin I protein from Schistosoma mansoni, engineered to have metal ion-binding sites, is used as a template to build up 1D nanoscopic structures through metal-induced self-assembly. Chromatographic and microscopic analyses demonstrate the ability of the protein rings to stack directionally upon interaction with divalent metal ions and form well-defined nanotubes by exploiting the intrinsic recognition properties of the ring surfaces. Taking advantage of such behavior, the rings are then used to capture colloidal Ni2+-functionalized ultrasmall gold nanoparticles and arrange them into 1D arrays through stacking into peapod-like complexes. Finally, as the formation of such nano-peapods strictly depends on nanoparticle dimensions, the peroxiredoxin template is used as a colloidal cut-off device to sort by size the encapsulated nanoparticles. These results open up possibilities in developing Prx-based methods to synthesize new advanced functional materials.Nanomanipulation of matter to create responsive, ordered materials still remains extremely challenging. Supramolecular chemistry has inspired new strategies by which such nanomaterials can be synthesized step by step by exploiting the self-recognition properties of molecules. In this work, the ring-shaped architecture of the 2-Cys peroxiredoxin I protein from Schistosoma mansoni, engineered to have metal ion-binding sites, is used as a template to build up 1D nanoscopic structures through metal-induced self-assembly. Chromatographic and microscopic analyses demonstrate the ability of the protein rings to stack directionally upon interaction with divalent metal ions and form well

  18. Colorimetric gas detection by the varying thickness of a thin film of ultrasmall PTSA-coated TiO2 nanoparticles on a Si substrate

    PubMed Central

    Joost, Urmas; Šutka, Andris; Visnapuu, Meeri; Tamm, Aile; Lembinen, Meeri; Antsov, Mikk; Utt, Kathriin; Smits, Krisjanis; Nõmmiste, Ergo

    2017-01-01

    Colorimetric gas sensing is demonstrated by thin films based on ultrasmall TiO2 nanoparticles (NPs) on Si substrates. The NPs are bound into the film by p-toluenesulfonic acid (PTSA) and the film is made to absorb volatile organic compounds (VOCs). Since the color of the sensing element depends on the interference of reflected light from the surface of the film and from the film/silicon substrate interface, colorimetric detection is possible by the varying thickness of the NP-based film. Indeed, VOC absorption causes significant swelling of the film. Thus, the optical path length is increased, interference wavelengths are shifted and the refractive index of the film is decreased. This causes a change of color of the sensor element visible by the naked eye. The color response is rapid and changes reversibly within seconds of exposure. The sensing element is extremely simple and cheap, and can be fabricated by common coating processes. PMID:28243561

  19. Colorimetric gas detection by the varying thickness of a thin film of ultrasmall PTSA-coated TiO2 nanoparticles on a Si substrate.

    PubMed

    Joost, Urmas; Šutka, Andris; Visnapuu, Meeri; Tamm, Aile; Lembinen, Meeri; Antsov, Mikk; Utt, Kathriin; Smits, Krisjanis; Nõmmiste, Ergo; Kisand, Vambola

    2017-01-01

    Colorimetric gas sensing is demonstrated by thin films based on ultrasmall TiO2 nanoparticles (NPs) on Si substrates. The NPs are bound into the film by p-toluenesulfonic acid (PTSA) and the film is made to absorb volatile organic compounds (VOCs). Since the color of the sensing element depends on the interference of reflected light from the surface of the film and from the film/silicon substrate interface, colorimetric detection is possible by the varying thickness of the NP-based film. Indeed, VOC absorption causes significant swelling of the film. Thus, the optical path length is increased, interference wavelengths are shifted and the refractive index of the film is decreased. This causes a change of color of the sensor element visible by the naked eye. The color response is rapid and changes reversibly within seconds of exposure. The sensing element is extremely simple and cheap, and can be fabricated by common coating processes.

  20. Bcl-2-functionalized ultrasmall superparamagnetic iron oxide nanoparticles coated with amphiphilic polymer enhance the labeling efficiency of islets for detection by magnetic resonance imaging

    PubMed Central

    Yang, Bin; Cai, Haolei; Qin, Wenjie; Zhang, Bo; Zhai, Chuanxin; Jiang, Biao; Wu, Yulian

    2013-01-01

    Based on their versatile, biocompatible properties, superparamagnetic iron oxide (SPIO) or ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are utilized for detecting and tracing cells or tumors in vivo. Here, we developed an innoxious and concise synthesis approach for a novel B-cell lymphoma (Bcl)-2 monoclonal antibody-functionalized USPIO nanoparticle coated with an amphiphilic polymer (carboxylated polyethylene glycol monooleyl ether [OE-PEG-COOH]). These nanoparticles can be effectively internalized by beta cells and label primary islet cells, at relatively low iron concentration. The biocompatibility and cytotoxicity of these products were investigated by comparison with the commercial USPIO product, FeraSpin™ S. We also assessed the safe dosage range of the product. Although some cases showed a hypointensity change at the site of transplant, a strong magnetic resonance imaging (MRI) was detectable by a clinical MRI scanner, at field strength of 3.0 Tesla, in vivo, and the iron deposition/attached in islets was confirmed by Prussian blue and immunohistochemistry staining. It is noteworthy that based on our synthesis approach, in future, we could exchange the Bcl-2 with other probes that would be more specific for the targeted cells and that would have better labeling specificity in vivo. The combined results point to the promising potential of the novel Bcl-2-functionalized PEG-USPIO as a molecular imaging agent for in vivo monitoring of islet cells or other cells. PMID:24204136

  1. One-step synthesis of amino-functionalized ultrasmall near infrared-emitting persistent luminescent nanoparticles for in vitro and in vivo bioimaging

    NASA Astrophysics Data System (ADS)

    Shi, Junpeng; Sun, Xia; Zhu, Jianfei; Li, Jinlei; Zhang, Hongwu

    2016-05-01

    Near infrared (NIR)-emitting persistent luminescent nanoparticles (NPLNPs) have attracted much attention in bioimaging because they can provide long-term in vivo imaging with a high signal-to-noise ratio (SNR). However, conventional NPLNPs with large particle sizes that lack modifiable surface groups suffer from many serious limitations in bioimaging. Herein, we report a one-step synthesis of amino-functionalized ZnGa2O4:Cr,Eu nanoparticles (ZGO) that have an ultrasmall size, where ethylenediamine served as the reactant to fabricate the ZGO as well as the surfactant ligand to control the nanocrystal size and form surface amino groups. The ZGO exhibited a narrow particle size distribution, a bright NIR emission and a long afterglow luminescence. In addition, due to the excellent conjugation ability of the surface amino groups, the ZGO can be easily conjugated with many bio-functional molecules, which has been successfully utilized to realize in vitro and in vivo imaging. More importantly, the ZGO achieved re-excitation imaging using 650 nm and 808 nm NIR light in situ, which is advantageous for long-term and higher SNR bioimaging.Near infrared (NIR)-emitting persistent luminescent nanoparticles (NPLNPs) have attracted much attention in bioimaging because they can provide long-term in vivo imaging with a high signal-to-noise ratio (SNR). However, conventional NPLNPs with large particle sizes that lack modifiable surface groups suffer from many serious limitations in bioimaging. Herein, we report a one-step synthesis of amino-functionalized ZnGa2O4:Cr,Eu nanoparticles (ZGO) that have an ultrasmall size, where ethylenediamine served as the reactant to fabricate the ZGO as well as the surfactant ligand to control the nanocrystal size and form surface amino groups. The ZGO exhibited a narrow particle size distribution, a bright NIR emission and a long afterglow luminescence. In addition, due to the excellent conjugation ability of the surface amino groups, the ZGO can be

  2. Monitoring Endothelial and Tissue Responses to Cobalt Ferrite Nanoparticles and Hybrid Hydrogels

    PubMed Central

    Terzuoli, Erika; Donnini, Sandra; Uva, Marianna; Ziche, Marina; Morbidelli, Lucia

    2016-01-01

    Iron oxide nanoparticles (NPs) have been proposed for many biomedical applications as in vivo imaging and drug delivery in cancer treatment, but their toxicity is an ongoing concern. When NPs are intravenously administered, the endothelium represents the first barrier to tissue diffusion/penetration. However, there is little information about the biological effects of NPs on endothelial cells. In this work we showed that cobalt-ferrite (CoFe2O4) NPs affect endothelial cell integrity by increasing permeability, oxidative stress, inflammatory profile and by inducing cytoskeletal modifications. To overcome these problems, NPs have be loaded into biocompatible gels to form nanocomposite hybrid material (polysaccharide hydrogels containing magnetic NPs) that can be further conjugated with anticancer drugs to allow their release close to the target. The organic part of hybrid biomaterials is a carboxymethylcellulose (CMC) polymer, while the inorganic part consists of CoFe2O4 NPs coated with (3-aminopropyl)trimethoxysilane. The biological activity of these hybrid hydrogels was evaluated in vitro and in vivo. Our findings showed that hybrid hydrogels, instead of NPs alone, were not toxic on endothelial, stromal and epithelial cells, safe and biodegradable in vivo. In conclusion, biohydrogels with paramagnetic NPs as cross-linkers can be further exploited for antitumor drug loading and delivery systems. PMID:28036325

  3. Monitoring Endothelial and Tissue Responses to Cobalt Ferrite Nanoparticles and Hybrid Hydrogels.

    PubMed

    Finetti, Federica; Terzuoli, Erika; Donnini, Sandra; Uva, Marianna; Ziche, Marina; Morbidelli, Lucia

    2016-01-01

    Iron oxide nanoparticles (NPs) have been proposed for many biomedical applications as in vivo imaging and drug delivery in cancer treatment, but their toxicity is an ongoing concern. When NPs are intravenously administered, the endothelium represents the first barrier to tissue diffusion/penetration. However, there is little information about the biological effects of NPs on endothelial cells. In this work we showed that cobalt-ferrite (CoFe2O4) NPs affect endothelial cell integrity by increasing permeability, oxidative stress, inflammatory profile and by inducing cytoskeletal modifications. To overcome these problems, NPs have be loaded into biocompatible gels to form nanocomposite hybrid material (polysaccharide hydrogels containing magnetic NPs) that can be further conjugated with anticancer drugs to allow their release close to the target. The organic part of hybrid biomaterials is a carboxymethylcellulose (CMC) polymer, while the inorganic part consists of CoFe2O4 NPs coated with (3-aminopropyl)trimethoxysilane. The biological activity of these hybrid hydrogels was evaluated in vitro and in vivo. Our findings showed that hybrid hydrogels, instead of NPs alone, were not toxic on endothelial, stromal and epithelial cells, safe and biodegradable in vivo. In conclusion, biohydrogels with paramagnetic NPs as cross-linkers can be further exploited for antitumor drug loading and delivery systems.

  4. Differential magnetic catch and release: Separation, purification, and characterization of magnetic nanoparticles and particle assemblies

    NASA Astrophysics Data System (ADS)

    Beveridge, Jacob S.

    Magnetic nanoparticles uniquely combine superparamagnetic behavior with dimensions that are smaller than or the same size as molecular analytes. The integration of magnetic nanoparticles with analytical methods has opened new avenues for sensing, purification, and quantitative analysis. Applied magnetic fields can be used to control the motion and properties of magnetic nanoparticles; in analytical chemistry, use of magnetic fields provides methods for manipulating and analyzing species at the molecular level. The ability to use applied magnetic fields to control the motion and properties of magnetic nanoparticles is a tool for manipulating and analyzing species at the molecular level, and has led to applications including analyte handing, chemical sensors, and imaging techniques. This is clearly an area where significant growth and impact in separation science and analysis is expected in the future. In Chapter 1, we describe applications of magnetic nanoparticles to analyte handling, chemical sensors, and imaging techniques. Chapter 2 reports the purification and separation of magnetic nanoparticle mixtures using the technique developed in our lab called differential magnetic catch and release (DMCR). This method applies a variable magnetic flux orthogonal to the flow direction in an open tubular capillary to trap and controllably release magnetic nanoparticles. Magnetic moments of 8, 12, and 17 nm diameter CoFe2O4 nanoparticles are calculated using the applied magnetic flux density and experimentally determined force required to trap 50% of the particle sample. Balancing the relative strengths of the drag and magnetic forces enable separation and purification of magnetic CoFe2 O4 nanoparticle samples with < 20 nm diameters. Samples were characterized by transmission electron microscopy to determine the average size and size dispersity of the sample population. DMCR is further demonstrated to be useful for separation of a magnetic nanoparticle mixture, resulting

  5. One-pot synthesis of pegylated ultrasmall iron-oxide nanoparticles and their in vivo evaluation as magnetic resonance imaging contrast agents.

    PubMed

    Lutz, Jean-François; Stiller, Sabrina; Hoth, Ann; Kaufner, Lutz; Pison, Ulrich; Cartier, Régis

    2006-11-01

    A well-defined copolymer poly(oligo(ethylene glycol) methacrylate-co-methacrylic acid) P(OEGMA-co-MAA) was studied as a novel water-soluble biocompatible coating for superparamagnetic iron oxide nanoparticles. This copolymer was prepared via a two-step procedure: a well-defined precursor poly(oligo(ethylene glycol) methacrylate-co-tert-butyl methacrylate), P(OEGMA-co-tBMA) (M(n) = 17300 g mol(-1); M(w)/M(n) = 1.22), was first synthesized by atom-transfer radical polymerization in the presence of the catalyst system copper(I) chloride/2,2'-bipyridyl and subsequently selectively hydrolyzed in acidic conditions. The resulting P(OEGMA-co-MAA) was directly utilized as a polymeric stabilizer in the nanoparticle synthesis. Four batches of ultrasmall PEGylated magnetite nanoparticles (i.e., with an average diameter below 30 nm) were prepared via aqueous coprecipitation of iron salts in the presence of variable amounts of P(OEGMA-co-MAA). The diameter of the nanoparticles could be easily tuned in the range 10-25 nm by varying the initial copolymer concentration. Moreover, the formed PEGylated ferrofluids exhibited a long-term colloidal stability in physiological buffer and could therefore be studied in vivo by magnetic resonance (MR) imaging. Intravenous injection into rats showed no detectable signal in the liver within the first 2 h. Maximum liver accumulation was found after 6 h, suggesting a prolongated circulation of the nanoparticles in the bloodstream as compared to conventional MR imaging contrast agents.

  6. Synthesis of cobalt ferrite nanoparticles from thermolysis of prospective metal-nitrosonaphthol complexes and their photochemical application in removing methylene blue

    NASA Astrophysics Data System (ADS)

    Tavana, Jalal; Edrisi, Mohammad

    2016-03-01

    In this study, cobalt ferrite (CoFe2O4) nanoparticles were synthesized by two novel methods. The first method is based on the thermolysis of metal-NN complexes. In the second method, a template free sonochemical treatment of mixed cobalt and iron chelates of α-nitroso-β-naphthol (NN) was applied. Products prepared through method 1 were spherical, with high specific surface area (54.39 m2 g-1) and small average crystalline size of 13 nm. However, CoFe2O4 nanoparticles prepared by method 2 were in random shapes, a broad range of crystalline sizes and a low specific surface area of 25.46 m2 g-1 though highly pure. A Taguchi experimental design was implemented in method 1 to determine and obtain the optimum catalyst. The structural and morphological properties of products were investigated by x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, Brunauer-Emmett-Teller and dynamic laser light scattering. The crystalline size calculations were performed using Williamson-Hall method on XRD spectrum. The photocatalytic activity of the optimum nanocrystalline cobalt ferrite was investigated for degradation of a representative pollutant, methylene blue (MB), and visible light as energy source. The results showed that some 92% degradation of MB could be achieved for 7 h of visible light irradiation.

  7. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

    PubMed

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-09-14

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.

  8. Synthesis and dose interval dependent hepatotoxicity evaluation of intravenously administered polyethylene glycol-8000 coated ultra-small superparamagnetic iron oxide nanoparticle on Wistar rats.

    PubMed

    Rajan, Balan; Sathish, Shanmugam; Balakumar, Subramanian; Devaki, Thiruvengadam

    2015-03-01

    Superparamagnetic iron oxide nanoparticles are being used in medical imaging, drug delivery, cancer therapy, and so on. However, there is a direct need to identify any nanotoxicity associated with these nanoparticles. However uncommon, drug-induced liver injury (DILI) is a major health concern that challenges pharmaceutical industry and drug regulatory agencies alike. In this study we have synthesized and evaluated the dose interval dependent hepatotoxicity of polyethylene glycol-8000 coated ultra-small superparamagnetic iron oxide nanoparticles (PUSPIOs). To assess the hepatotoxicity of intravenously injected PUSPIOs, alterations in basic clinical parameters, hematological parameters, hemolysis assay, serum levels of liver marker enzymes, serum and liver lipid peroxidation (LPO) levels, enzymatic antioxidant levels, and finally histology of liver, kidney, spleen, lung, brain, and heart tissues were studied in control and experimental Wistar rat groups over a 30-day period. The results of our study showed a significant increase in the aspartate transaminase (AST) enzyme activity at a dose of 10mg/kg b.w. PUSPIOs twice a week. Besides, alanine transaminase (ALT), alkaline phosphatase (ALP), and gamma-glutamyl transferase (γGT) enzyme activity showed a slender increase when compared with control experimental groups. A significant increase in the serum and liver LPO levels at a dose of 10mg/kg b.w. PUSPIOs twice a week was also observed. Histological analyses of liver, kidney, spleen, lung, brain and heart tissue samples showed no obvious uncharacteristic changes. In conclusion, PUSPIOs were found to posses excellent biocompatibility and Wistar rats showed much better drug tolerance to the dose of 10mg/kg b.w. per week than the dose of 10mg/kg b.w. twice a week for the period of 30 days.

  9. Microwave synthesis and characterization of Co-ferrite nanoparticles.

    PubMed

    Bensebaa, F; Zavaliche, F; L'Ecuyer, P; Cochrane, R W; Veres, T

    2004-09-01

    Stable CoFe(2)O(4) nanoparticles have been obtained by co-precipitation using a microwave heating system. Transmission electron microscopy images analysis shows an agglomeration of particles with an average size of about 5 nm, and X-ray diffraction reveals the presence of a pure ferrite nanocrystalline phase. X-ray photoelectron spectroscopy and thermal gravimetric analysis show the presence of organic matter in the range of about 16 wt%. The magnetic response in DC fields is typical for an assembly of single-domain particles. The measured saturation magnetization is slightly larger than the bulk value, probably due to the presence of small amounts of Co and Fe. AC magnetization data indicate the presence of magnetic interactions between the nanoparticles.

  10. Cobalt ferrite nanoparticles in a mesoporous silicon dioxide matrix

    NASA Astrophysics Data System (ADS)

    Komogortsev, S. V.; Patrusheva, T. N.; Balaev, D. A.; Denisova, E. A.; Ponomarenko, I. V.

    2009-10-01

    We have studied magnetic nanoparticles of cobalt ferrite obtained by the extraction-pyrolysis method in a mesoporous silicon dioxide (MSM-41) molecular sieve matrix. The X-ray diffraction data show evidence for the formation of CoFe2O4 particles with a coherent scattering domain size of ˜40 nm. Measurements of the magnetization curves showed that powders consisting of these nanoparticles are magnetically hard materials with a coercive field of H c(4.2 K) = 9.0 kOe and H c(300 K) = 1.8 kOe and a reduced remanent magnetization of M r/ M s(4.2 K) = 0.83 and M r/ M s(300 K) = 0.49. The shape of the low-temperature (4.2 K) magnetization curves is adequately described in terms of the Stoner-Wohlfarth model for randomly oriented single-domain particles with a cubic magnetic anisotropy.

  11. Achieving magneto-elasto-electroporation and cell transport using core-shell magnetoelectric nanoparticles (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Betal, Soutik; Dutta, Moumita; Shrestha, Binita; Saha, Amit; Tang, Liang; Ramasubramanian, Ananad K.; Bhalla, Amar S.; Guo, Ruyan

    2016-09-01

    Magneto-Elasto-Electroporation (MEEP) is a magnetically controlled acoustic-electroporation observed while core-shell Magneto-electric nanoparticles interact with Biological Cells. The surface polarity change of the piezoelectric coating (BaTiO3) due to absorption of pressure created due magneto-striction of core (CoFe2O4) in AC magnetic field results in electric field (Uext) change at the external vicinity of the cell membrane when nanoparticles are nearby. This results in transmembrane Voltage (Um) change which is basically the difference in Cell's internal potential (Uint) and external potential. The nonlinear permeability change of cell membrane due to change in Um opens the nano-pores on the membrane. The magnetic moment of the nanoparticles further helps in penetration of the Magneto-electric nanoparticles inside the cell through these magneto-electrically controlled newly opened nano-pores on cell's membrane. MEEP is analyzed through in-vitro analysis and Mathematical equations are formulated for numerically expressing its fundamental effect. TEM imaging, XRD analysis, Zeta-potentiometer measurement and AFM imaging are confirming the coating of the piezoelectric layer on Magneto-stricitve nanoparticles, Acoustic measurements confirms the photo-acoustic and magneto-acoustic property of CoFe2O4 nanoparticles and Fluorescence microscopy as well as Confocal microscopy are confirming the penetration of particle inside the Human Epithelial cells (HEP2). Further on application of repulsive magnetic field, nanoparticles are observed to transport a group of cells in controlled boundary conditions in microfluidic chamber. Hence these nanoparticles can be used for accurate and efficient drug delivery as well as cell transport applications

  12. Labeling adipose derived stem cell sheet by ultrasmall super-paramagnetic Fe3O4 nanoparticles and magnetic resonance tracking in vivo.

    PubMed

    Zhou, Shukui; Yin, Ting; Zou, Qingsong; Zhang, Kaile; Gao, Guo; Shapter, Joseph G; Huang, Peng; Fu, Qiang

    2017-02-21

    Cell sheet therapy has emerged as a potential therapeutic option for reparation and reconstruction of damaged tissues and organs. However, an effective means to assess the fate and distribution of transplanted cell sheets in a serial and noninvasive manner is still lacking. To investigate the feasibility of tracking Adipose derived stem cells (ADSCs) sheet in vivo using ultrasmall super-paramagnetic Fe3O4 nanoparticles (USPIO), canine ADSCs were cultured and incubated with USPIO and 0.75 μg/ml Poly-L-Lysine (PLL) for 12 h. Labeling efficiency, cell viability, apoptotic cell rate were assessed to screen the optimum concentrations of USPIO for best labeling ADSCs. The results showed ADSCs were labeled by USPIO at an iron dose of 50 μg/ml for a 12 h incubation time, which can most efficiently mark cells and did not impair the cell survival, self-renewal, and proliferation capacity. USPIO-labeled ADSCs sheets can be easily and clearly detected in vivo and have persisted for at least 12 weeks. Our experiment confirmed USPIO was feasible for in vivo labeling of the ADSCs sheets with the optimal concentration of 50 μg Fe/ml and the tracing time is no less than 12 weeks.

  13. Labeling adipose derived stem cell sheet by ultrasmall super-paramagnetic Fe3O4 nanoparticles and magnetic resonance tracking in vivo

    PubMed Central

    Zhou, Shukui; Yin, Ting; Zou, Qingsong; Zhang, Kaile; Gao, Guo; Shapter, Joseph G.; Huang, Peng; Fu, Qiang

    2017-01-01

    Cell sheet therapy has emerged as a potential therapeutic option for reparation and reconstruction of damaged tissues and organs. However, an effective means to assess the fate and distribution of transplanted cell sheets in a serial and noninvasive manner is still lacking. To investigate the feasibility of tracking Adipose derived stem cells (ADSCs) sheet in vivo using ultrasmall super-paramagnetic Fe3O4 nanoparticles (USPIO), canine ADSCs were cultured and incubated with USPIO and 0.75 μg/ml Poly-L-Lysine (PLL) for 12 h. Labeling efficiency, cell viability, apoptotic cell rate were assessed to screen the optimum concentrations of USPIO for best labeling ADSCs. The results showed ADSCs were labeled by USPIO at an iron dose of 50 μg/ml for a 12 h incubation time, which can most efficiently mark cells and did not impair the cell survival, self-renewal, and proliferation capacity. USPIO-labeled ADSCs sheets can be easily and clearly detected in vivo and have persisted for at least 12 weeks. Our experiment confirmed USPIO was feasible for in vivo labeling of the ADSCs sheets with the optimal concentration of 50 μg Fe/ml and the tracing time is no less than 12 weeks. PMID:28220818

  14. Antibiotic-free nanotherapeutics: ultra-small, mucus-penetrating solid lipid nanoparticles enhance the pulmonary delivery and anti-virulence efficacy of novel quorum sensing inhibitors.

    PubMed

    Nafee, Noha; Husari, Ayman; Maurer, Christine K; Lu, Cenbin; de Rossi, Chiara; Steinbach, Anke; Hartmann, Rolf W; Lehr, Claus-Michael; Schneider, Marc

    2014-10-28

    Cystic fibrosis (CF) is a genetic disease mainly manifested in the respiratory tract. Pseudomonas aeruginosa (P. aeruginosa) is the most common pathogen identified in cultures of the CF airways, however, its eradication with antibiotics remains challenging as it grows in biofilms that counterwork human immune response and dramatically decrease susceptibility to antibiotics. P. aeruginosa regulates pathogenicity via a cell-to-cell communication system known as quorum sensing (QS) involving the virulence factor (pyocyanin), thus representing an attractive target for coping with bacterial pathogenicity. The first in vivo potent QS inhibitor (QSI) was recently developed. Nevertheless, its lipophilic nature might hamper its penetration of non-cellular barriers such as mucus and bacterial biofilms, which limits its biomedical application. Successful anti-infective inhalation therapy necessitates proper design of a biodegradable nanocarrier allowing: 1) high loading and prolonged release, 2) mucus penetration, 3) effective pulmonary delivery, and 4) maintenance of the anti-virulence activity of the QSI. In this context, various pharmaceutical lipids were used to prepare ultra-small solid lipid nanoparticles (us-SLNs) by hot melt homogenization. Plain and QSI-loaded SLNs were characterized in terms of colloidal properties, drug loading, in vitro release and acute toxicity on Calu-3 cells. Mucus penetration was studied using a newly-developed confocal microscopy technique based on 3D-time-lapse imaging. For pulmonary application, nebulization efficiency of SLNs and lung deposition using next generation impactor (NGI) were performed. The anti-virulence efficacy was investigated by pyocyanin formation in P. aeruginosa cultures. Ultra-small SLNs (<100nm diameter) provided high encapsulation efficiency (68-95%) according to SLN composition, high burst in phosphate buffer saline compared to prolonged release of the payload over >8h in simulated lung fluid with minor burst. All

  15. Towards hybrid biocompatible magnetic rHuman serum albumin-based nanoparticles: use of ultra-small (CeLn)3/4+ cation-doped maghemite nanoparticles as functional shell

    NASA Astrophysics Data System (ADS)

    Israel, Liron L.; Kovalenko, Elena I.; Boyko, Anna A.; Sapozhnikov, Alexander M.; Rosenberger, Ina; Kreuter, Jörg; Passoni, Lorena; Lellouche, Jean-Paul

    2015-01-01

    Human serum albumin (HSA) is a protein found in human blood. Over the last decade, HSA has been evaluated as a promising drug carrier. However, not being magnetic, HSA cannot be used for biomedical applications such as magnetic resonance imaging (MRI) and magnetic drug targeting. Therefore, subsequent composites building on iron oxide nanoparticles that are already used clinically as MRI contrast agents are extensively studied. Recently and in this context, innovative fully hydrophilic ultra-small CAN-stabilized maghemite ((CeLn)3/4+-γ-Fe2O3) nanoparticles have been readily fabricated. The present study discusses the design, fabrication, and characterization of a dual phase hybrid core (rHSA)-shell ((CeLn)3/4+-γ-Fe2O3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeLn)3/4+-γ-Fe2O3 NPs enabled to exploit both rHSA (protein functionalities) and (CeLn)3/4+-γ-Fe2O3 NP surface functionalities (COOH and ligand L coordinative exchange) in addition to very effective MRI contrast capability due to optimal accessibility of H2O molecules with the outer magnetic phase. Resulting hybrid nanoparticles might be used as a platform modular system for therapeutic (drug delivery system) and MR diagnostic purposes.

  16. Noninvasive monitoring of early antiangiogenic therapy response in human nasopharyngeal carcinoma xenograft model using MRI with RGD-conjugated ultrasmall superparamagnetic iron oxide nanoparticles

    PubMed Central

    Cui, Yanfen; Zhang, Caiyuan; Luo, Ran; Liu, Huanhuan; Zhang, Zhongyang; Xu, Tianyong; Zhang, Yong; Wang, Dengbin

    2016-01-01

    Purpose Arginine-glycine-aspartic acid (RGD)-based nanoprobes allow specific imaging of integrin αvβ3, a protein overexpressed during angiogenesis. Therefore, this study applied a novel RGD-coupled, polyacrylic acid (PAA)-coated ultrasmall superparamagnetic iron oxide (USPIO) (referred to as RGD-PAA-USPIO) in order to detect tumor angiogenesis and assess the early response to antiangiogenic treatment in human nasopharyngeal carcinoma (NPC) xenograft model by magnetic resonance imaging (MRI). Materials and methods The binding specificity of RGD-PAA-USPIO with human umbilical vein endothelial cells (HUVECs) was confirmed by Prussian blue staining and transmission electron microscopy in vitro. The tumor targeting of RGD-PAA-USPIO was evaluated in the NPC xenograft model. Later, mice bearing NPC underwent MRI at baseline and after 4 and 14 days of consecutive treatment with Endostar or phosphate-buffered saline (n=10 per group). Results The specific uptake of the RGD-PAA-USPIO nanoparticles was mainly dependent on the interaction between RGD and integrin αvβ3 of HUVECs. The tumor targeting of RGD-PAA-USPIO was observed in the NPC xenograft model. Moreover, the T2 relaxation time of mice in the Endostar-treated group decreased significantly compared with those in the control group both on days 4 and 14, consistent with the immunofluorescence results of CD31 and CD61 (P<0.05). Conclusion This study demonstrated that the magnetic resonance molecular nanoprobes, RGD-PAA-USPIOs, allow noninvasive in vivo imaging of tumor angiogenesis and assessment of the early response to antiangiogenic treatment in NPC xenograft model, favoring its potential clinical translation. PMID:27895477

  17. Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

    NASA Astrophysics Data System (ADS)

    Qi, B.; Andrew, J. S.; Arnold, D. P.

    2017-03-01

    This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain ( 100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe66Co34) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe2O4) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

  18. Detection sensitivity of MRI using ultra-small super paramagnetic iron oxide nano-particles (USPIO) in biological tissues.

    PubMed

    Oghabian, M A; Guiti, M; Haddad, P; Gharehaghaji, N; Saber, R; Alam, N R; Malekpour, M; Rafie, B

    2006-01-01

    Today, by injecting iron oxide based nanoparticles (USPIO) as MRI contrast agents, it is possible to study lymphatic system and some specific tumors and their metastasis. The type of surface coating, and coating characteristics of the nanoparticles are important factors for the biological properties of nanoparticles and their destination target. On the other hand, these properties contribute to different signal intensities. This may confine application of all types of USPIO based contrast agents in routine daily experiments. In this study, the ability of detecting these particles having various sizes and coating properties was evaluated for MRI applications. Signal intensity changes after administration of these particles into tissues have been studied and their detection sensitivity was evaluated using a liver phantom and animal model (rat). IO based nanoparticles of various sizes (8-30 nm) functionalized and coated with various surface polymers such as dextran and starch, amine and hydroxide groups, and bear IO particles were used to investigate the signal changes. The optimized pulse sequences for proper demonstration of lymph nodes using these contrast agents were found (T2* FSPGR protocol with fat suppressions). A detection sensitivity of 98% was achieved in most experiments during applying a proper MR protocol. However, the type of surface coating, and coating characteristics such as thickness were shown to be essential factors for MRI signal intensity in both T1 and T2 protocols.

  19. Mechanisms of cell penetration and cytotoxicity of ultrasmall Au nanoparticles conjugated to doxorubicin and/or targeting peptides

    NASA Astrophysics Data System (ADS)

    Nadeau, Jay; Poon, Wilson; Zhang, Xuan

    2015-03-01

    The goals of this work were to determine whether conjugation of any of four selected peptides to Au nanoparticles improved their delivery to B16 melanoma in vitro and in vivo. In in vitro cytotoxicity assays, peptides and conjugates were endocytosed but did not escape from endosomes. None of the peptides showed any cytotoxicity, with or without conjugation to the nanoparticles. The combination of peptides and doxorubicin did not improve upon the cytotoxicity of gold-doxorubicin alone. We then tested targeting in vivo using inductively coupled plasma mass spectrometry to quantify the concentration of Au in the organs of B16 tumor-bearing mice 4, 24, and 72 h after intravenous Au nanoparticle injection. These experiments showed that in some cases, peptide conjugation improved upon the enhanced permeability and retention (EPR) effect. A peptide based upon the myxoma virus and the cyclic RGD peptide were both effective at tumor targeting; myxoma was more effective with un-PEGylated particles, and cRGD with PEGylated particles. The FREG and melanocyte stimulating hormone (MSH) peptides did not improve targeting. These results suggest that these peptides may improve delivery of Au particles to tumors, but also may prevent entry of particles into cell nuclei.

  20. Strain Field in Ultrasmall Gold Nanoparticles Supported on Cerium-Based Mixed Oxides. Key Influence of the Support Redox State.

    PubMed

    López-Haro, Miguel; Yoshida, Kenta; Del Río, Eloy; Pérez-Omil, José A; Boyes, Edward D; Trasobares, Susana; Zuo, Jian-Min; Gai, Pratibha L; Calvino, José J

    2016-05-03

    Using a method that combines experimental and simulated Aberration-Corrected High Resolution Electron Microscopy images with digital image processing and structure modeling, strain distribution maps within gold nanoparticles relevant to real powder type catalysts, i.e., smaller than 3 nm, and supported on a ceria-based mixed oxide have been determined. The influence of the reduction state of the support and particle size has been examined. In this respect, it has been proven that reduction even at low temperatures induces a much larger compressive strain on the first {111} planes at the interface. This increase in compression fully explains, in accordance with previous DFT calculations, the loss of CO adsorption capacity of the interface area previously reported for Au supported on ceria-based oxides.

  1. Ultrasmall Li2S Nanoparticles Anchored in Graphene Nanosheets for High-Energy Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Wang, Lijiang; Hu, Zhe; Cheng, Fangyi; Chen, Jun

    2014-09-01

    Li2S has a high theoretical capacity of 1166 mAh g-1, but it suffers from limited rate and cycling performance. Herein we reported in-situ synthesis of thermally exfoliated graphene-Li2S (in-situ TG-Li2S) nanocomposite and its application as a superior cathode material alternative to sulfur. Li2S nanoparticles with the size of ~8.5 nm homogeneously anchored in graphene nanosheets were prepared via chemical reduction of pre-sublimed sulfur by lithium triethylborohydride (LiEt3BH). The in-situ TG-Li2S nanocomposite exhibited an initial capacity of 1119 mAh g-1 Li2S (1609 mAh g-1 S) with a negligible charged potential barrier in the first cycle. The discharge capacity retained 791 mAh g-1 Li2S (1137 mAh g-1 S) after 100 cycles at 0.1C and exceeded 560 mAh g-1 Li2S (805 mAh g-1 S) at a high rate of 2C. Moreover, coupling the composite with Si thin film anode, a Li2S/Si full cell was produced, delivering a high specific capacity of ~900 mAh g-1 Li2S (1294 mAh g-1 S). The outstanding electrode performance of in-situ TG-Li2S composite was attributed to the well dispersed small Li2S nanoparticles and highly conductive graphene nanosheets, which provided merits of facile ionic and electronic transport, efficient utilization of the active material, and flexible accommodation of volume change.

  2. Ultrasmall Li2S Nanoparticles Anchored in Graphene Nanosheets for High-Energy Lithium-Ion Batteries

    PubMed Central

    Zhang, Kai; Wang, Lijiang; Hu, Zhe; Cheng, Fangyi; Chen, Jun

    2014-01-01

    Li2S has a high theoretical capacity of 1166 mAh g−1, but it suffers from limited rate and cycling performance. Herein we reported in-situ synthesis of thermally exfoliated graphene−Li2S (in-situ TG−Li2S) nanocomposite and its application as a superior cathode material alternative to sulfur. Li2S nanoparticles with the size of ~8.5 nm homogeneously anchored in graphene nanosheets were prepared via chemical reduction of pre-sublimed sulfur by lithium triethylborohydride (LiEt3BH). The in-situ TG−Li2S nanocomposite exhibited an initial capacity of 1119 mAh g−1 Li2S (1609 mAh g−1 S) with a negligible charged potential barrier in the first cycle. The discharge capacity retained 791 mAh g−1 Li2S (1137 mAh g−1 S) after 100 cycles at 0.1C and exceeded 560 mAh g−1 Li2S (805 mAh g−1 S) at a high rate of 2C. Moreover, coupling the composite with Si thin film anode, a Li2S/Si full cell was produced, delivering a high specific capacity of ~900 mAh g−1 Li2S (1294 mAh g−1 S). The outstanding electrode performance of in-situ TG−Li2S composite was attributed to the well dispersed small Li2S nanoparticles and highly conductive graphene nanosheets, which provided merits of facile ionic and electronic transport, efficient utilization of the active material, and flexible accommodation of volume change. PMID:25253198

  3. Acid-functionalized nanoparticles for biomass hydrolysis

    NASA Astrophysics Data System (ADS)

    Pena Duque, Leidy Eugenia

    Cellulosic ethanol is a renewable source of energy. Lignocellulosic biomass is a complex material composed mainly of cellulose, hemicellulose, and lignin. Biomass pretreatment is a required step to make sugar polymers liable to hydrolysis. Mineral acids are commonly used for biomass pretreatment. Using acid catalysts that can be recovered and reused could make the process economically more attractive. The overall goal of this dissertation is the development of a recyclable nanocatalyst for the hydrolysis of biomass sugars. Cobalt iron oxide nanoparticles (CoFe2O4) were synthesized to provide a magnetic core that could be separated from reaction using a magnetic field and modified to carry acid functional groups. X-ray diffraction (XRD) confirmed the crystal structure was that of cobalt spinel ferrite. CoFe2O4 were covered with silica which served as linker for the acid functions. Silica-coated nanoparticles were functionalized with three different acid functions: perfluoropropyl-sulfonic acid, carboxylic acid, and propyl-sulfonic acid. Transmission electron microscope (TEM) images were analyzed to obtain particle size distributions of the nanoparticles. Total carbon, nitrogen, and sulfur were quantified using an elemental analyzer. Fourier transform infra-red spectra confirmed the presence of sulfonic and carboxylic acid functions and ion-exchange titrations accounted for the total amount of catalytic acid sites per nanoparticle mass. These nanoparticles were evaluated for their performance to hydrolyze the beta-1,4 glycosidic bond of the cellobiose molecule. Propyl-sulfonic (PS) and perfluoropropyl-sulfonic (PFS) acid functionalized nanoparticles catalyzed the hydrolysis of cellobiose significantly better than the control. PS and PFS were also evaluated for their capacity to solubilize wheat straw hemicelluloses and performed better than the control. Although PFS nanoparticles were stronger acid catalysts, the acid functions leached out of the nanoparticle during

  4. Ultra-small Nd3+-doped nanoparticles as near-infrared luminescent biolabels of hemin in bacteria

    NASA Astrophysics Data System (ADS)

    Xi, Yonglan; Chang, Zhizhou; Ye, Xiaomei; Huang, Hongying; Huang, Yanan; Xiao, Qingbo; Lin, Hongzhen

    2016-01-01

    Near-infrared (NIR) luminescent Nd3+-doped nanoparticles (NPs) have attracted considerable attention in bioimaging and biodetection. Here, we demonstrate sub-6 nm NaGdF4:Nd3+,Fe3+ NPs as luminescent biolabels of hemin molecules that act as the exogenous electron carriers in microbial communities. Contrary to the severe quenching of the visible luminescence for either upconverting or downconverting NPs, the Nd3+-doped NPs show superior properties in avoiding the optical absorption of hemin within the UV and visible spectral regions. A detailed examination showed that the Nd3+-doped NPs exhibit no obvious toxic effects on the microbial communities and show scarce influence on the characteristics of labeled hemin molecules in enhancing the reducing power of the fermentation system. More importantly, by monitoring the NIR luminescence of Nd3+-doped NPs, the selective accumulation of exogenous electron carriers in bacteria that are lacking reducing power has been revealed for the first time. The application of Nd3+-doped NPs as biolabels in bacteria would provide new opportunities for further unravelling the role of exogenous electron carriers in anaerobic digestion.Near-infrared (NIR) luminescent Nd3+-doped nanoparticles (NPs) have attracted considerable attention in bioimaging and biodetection. Here, we demonstrate sub-6 nm NaGdF4:Nd3+,Fe3+ NPs as luminescent biolabels of hemin molecules that act as the exogenous electron carriers in microbial communities. Contrary to the severe quenching of the visible luminescence for either upconverting or downconverting NPs, the Nd3+-doped NPs show superior properties in avoiding the optical absorption of hemin within the UV and visible spectral regions. A detailed examination showed that the Nd3+-doped NPs exhibit no obvious toxic effects on the microbial communities and show scarce influence on the characteristics of labeled hemin molecules in enhancing the reducing power of the fermentation system. More importantly, by

  5. Ultrasmall PdmMn1-mOx binary alloyed nanoparticles on graphene catalysts for ethanol oxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Ahmed, Mohammad Shamsuddin; Park, Dongchul; Jeon, Seungwon

    2016-03-01

    A rare combination of graphene (G)-supported palladium and manganese in mixed-oxides binary alloyed catalysts (BACs) have been synthesized with the addition of Pd and Mn metals in various ratios (G/PdmMn1-mOx) through a facile wet-chemical method and employed as an efficient anode catalyst for ethanol oxidation reaction (EOR) in alkaline fuel cells. The as prepared G/PdmMn1-mOx BACs have been characterized by several instrumental techniques; the transmission electron microscopy images show that the ultrafine alloyed nanoparticles (NPs) are excellently monodispersed onto the G. The Pd and Mn in G/PdmMn1-mOx BACs have been alloyed homogeneously, and Mn presents in mixed-oxidized form that resulted by X-ray diffraction. The electrochemical performances, kinetics and stability of these catalysts toward EOR have been evaluated using cyclic voltammetry in 1 M KOH electrolyte. Among all G/PdmMn1-mOx BACs, the G/Pd0.5Mn0.5Ox catalyst has shown much superior mass activity and incredible stability than that of pure Pd catalysts (G/Pd1Mn0Ox, Pd/C and Pt/C). The well dispersion, ultrafine size of NPs and higher degree of alloying are the key factor for enhanced and stable EOR electrocatalysis on G/Pd0.5Mn0.5Ox.

  6. Magnetic nanoparticles for "smart liposomes".

    PubMed

    Nakayama, Yoshitaka; Mustapić, Mislav; Ebrahimian, Haleh; Wagner, Pawel; Kim, Jung Ho; Hossain, Md Shahriar Al; Horvat, Joseph; Martinac, Boris

    2015-12-01

    Liposomal drug delivery systems (LDDSs) are promising tools used for the treatment of diseases where highly toxic pharmacological agents are administered. Currently, destabilising LDDSs by a specific stimulus at a target site remains a major challenge. The bacterial mechanosensitive channel of large conductance (MscL) presents an excellent candidate biomolecule that could be employed as a remotely controlled pore-forming nanovalve for triggered drug release from LDDSs. In this study, we developed superparamagnetic nanoparticles for activation of the MscL nanovalves by magnetic field. Synthesised CoFe2O4 nanoparticles with the radius less than 10 nm were labelled by SH groups for attachment to MscL. Activation of MscL by magnetic field with the nanoparticles attached was examined by the patch clamp technique showing that the number of activated channels under ramp pressure increased upon application of the magnetic field. In addition, we have not observed any cytotoxicity of the nanoparticles in human cultured cells. Our study suggests the possibility of using magnetic nanoparticles as a specific trigger for activation of MscL nanovalves for drug release in LDDSs.

  7. PSynthesis, characterization and electromagnetic properties of Zn-substituted CoFe2O4 via sucrose assisted combustion route

    NASA Astrophysics Data System (ADS)

    Gabal, M. A.; Al-Juaid, A. A.; Al-Rashed, S. M.; Hussein, M. A.; Al-Marzouki, F.

    2017-03-01

    Nanocrystalline Co1-xZnxFe2O4 ferrites (0.0≤x≤0.1) were synthesized via simple, economic and environmentally friend sucrose auto-combustion method. An appropriate mechanism for complexation process as well as ferrites formation was suggested and discussed. The detailed structural studies were estimated through X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) measurements. The results confirmed the formation of mixed spinel phase with cubic structure and exhibited a gradual decrease in the crystal size from 58 nm to 20 nm by the addition of zinc. Based on the obtained structural parameters, an appropriate cation distribution was suggested and reinforced via electrical and magnetic properties measurements. Hysteresis loops measurements, indicated ferromagnetic characteristics, with hard magnetic properties, for the samples with 0.0≤x≤0.6. The samples with higher Zn-content exhibited paramagnetic properties. The changes in the magnetization and coercivity by the addition of zinc can be discussed in the view of the influence of cationic stoichiometry and magneto-crystalline anisotropy, respectively. The huge decrease in the magnetization value at x≥0.8 suggested a shift from ferromagnetic to paramagnetic characteristics. Ac-conductivity as well as dielectric constant behaviors reinforced this magnetic transition. The obtained Curie transition temperatures (TC) were gradually shifted to lower temperatures by the addition of zinc. The addition of zinc results in the substitution of Co2+ ions in the octahedral sites thus, decreases B-B hopping probability, decreases conductivity and consequently increases activation energy. The most predominant conduction mechanisms in the ferromagnetic and paramagnetic regions are expected to be due to electron hoppings between different valence state ions and small positive polaron migration, respectively.

  8. Directed Self-Assembly of Epitaxial CoFe2O4-BiFeO3 Multiferroic Nanocomposites

    DTIC Science & Technology

    2012-04-09

    been found to demonstrate magnetoelectric coupling, allowing for electrical control of the magnetic anisotropy of the CFO pillars.6,7 Based on these...etching processes to improve resolution. It is worthwhile to characterize the magnetic and ferroelectric properties of the composite as a means of...nanopillars with pitches of 100, 150, and 200 nm have been fabricated, and their structural properties have been characterized. It is shown that for

  9. Mechanical alloyed Ho3+ doping in CoFe2O4 spinel ferrite and understanding of magnetic nanodomains

    NASA Astrophysics Data System (ADS)

    Panneer Muthuselvam, I.; Bhowmik, R. N.

    2010-04-01

    We doped Ho3+ in CoFe1.95Ho0.05O4 spinel ferrite by mechanical alloying and subsequent annealing at different temperatures (600-1200 °C). We understood the structural and magnetic properties of the samples using X-ray diffraction, SEM, Thermal analysis (TGA and DTA), and VSM measurement. The samples have shown structural stabilization within cubic spinel phase for the annealing temperature (TAN)≥800 °C. Thermal activated grain growth kinetics has been accompanied with the substantial decrease in lattice strain. The gain size dependent magnetism is evident from the variation of magnetic moment, remanent magnetization and coercivity of the material. The paramagnetic to ferrimagnetic transition temperature TC (˜805 K) seems to be grain size independent in the present material. The magnetic nanograins, either single domain/pseudo-single domain (50-64 nm) or multi-domain (above 64 nm) regime, showed superparamagnetic blocking below Tm, which is below TC (805 K) and also well above the room temperature.

  10. Enhanced biomedical heat-triggered carriers via nanomagnetism tuning in ferrite-based nanoparticles

    NASA Astrophysics Data System (ADS)

    Angelakeris, M.; Li, Zi-An; Hilgendorff, M.; Simeonidis, K.; Sakellari, D.; Filippousi, M.; Tian, H.; Van Tendeloo, G.; Spasova, M.; Acet, M.; Farle, M.

    2015-05-01

    Biomedical nanomagnetic carriers are getting a higher impact in therapy and diagnosis schemes while their constraints and prerequisites are more and more successfully confronted. Such particles should possess a well-defined size with minimum agglomeration and they should be synthesized in a facile and reproducible high-yield way together with a controllable response to an applied static or dynamic field tailored for the specific application. Here, we attempt to enhance the heating efficiency in magnetic particle hyperthermia treatment through the proper adjustment of the core-shell morphology in ferrite particles, by controlling exchange and dipolar magnetic interactions at the nanoscale. Thus, core-shell nanoparticles with mutual coupling of magnetically hard (CoFe2O4) and soft (MnFe2O4) components are synthesized with facile synthetic controls resulting in uniform size and shell thickness as evidenced by high resolution transmission electron microscopy imaging, excellent crystallinity and size monodispersity. Such a magnetic coupling enables the fine tuning of magnetic anisotropy and magnetic interactions without sparing the good structural, chemical and colloidal stability. Consequently, the magnetic heating efficiency of CoFe2O4 and MnFe2O4 core-shell nanoparticles is distinctively different from that of their counterparts, even though all these nanocrystals were synthesized under similar conditions. For better understanding of the AC magnetic hyperthermia response and its correlation with magnetic-origin features we study the effect of the volume ratio of magnetic hard and soft phases in the bimagnetic core-shell nanocrystals. Eventually, such particles may be considered as novel heating carriers that under further biomedical functionalization may become adaptable multifunctional heat-triggered nanoplatforms.

  11. Structural, electrical, and optomagnetic tweaking of Zn doped CoFe2-xZnxO4-δ nanoparticles

    NASA Astrophysics Data System (ADS)

    Agrawal, Shraddha; Parveen, Azra; Azam, Ameer

    2016-09-01

    Nanoparticles of pure and Zn doped CoFe2O4 of the composition CoFe2-xZnxO4-δ (x=0, 0.05, 0.10, 0.15) have been successfully synthesized by microwave gel combustion. The microstructural and compositional analyses were carried out by X-ray diffraction, Scanning Electron Microscopy. The crystallite size was found to increase with the increase in the Zn content. The dielectric constant (ε) and A.C. conductivity were studied as a function of frequency and temperature and were explained on the basis of Maxwell-Wagner model and electron hopping respectively. The energy band gap was found to decrease gradually with Zn doping. The magnetic measurements, depicts an increase in magnetization with the increase in Zn concentration, which in turn shows a strong dependency on the particle size. The magnetic hysteresis loop confirms the ferromagnetic nature.

  12. In situ synthesis of cobalt ferrite nanoparticle/polymer hybrid from a mixed Fe-Co methacrylate for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Hayashi, Koichiro; Maeda, Kazuki; Moriya, Makoto; Sakamoto, Wataru; Yogo, Toshinobu

    2012-09-01

    Hyperthermic CoFe2O4 nanoparticle (CFO NP)/polymer hybrids were synthesized by hydrolysis-condensation from a complex of Co and Fe possessing methacrylate ligands. Single-crystal analysis revealed that the complex consisted of two Co and four Fe metal atoms coordinated by methacrylate and 2-methoxyethoxy groups. The complex was copolymerized with 2-hydroxyethyl methacrylate (HEMA) and the resulting copolymer was then hydrolyzed to form a CFO NP/copolymer of poly(methacrylate) and poly(2-hydroxyethyl methacrylate) hybrid. Copolymerization with HEMA enhanced the stability of the hybrid in water. The size and magnetic properties of CFO in the hybrid were controlled by adjusting the hydrolysis conditions. Moreover, the hybrid generated heat under an alternating current magnetic field; its exothermal properties depended on the magnetic properties of the hybrid, the strength of the applied field, and the CFO NP content in the agar phantom matrix.

  13. Influence of nanoparticle-membrane electrostatic interactions on membrane fluidity and bending elasticity.

    PubMed

    Santhosh, Poornima Budime; Velikonja, Aljaž; Perutkova, Šarka; Gongadze, Ekaterina; Kulkarni, Mukta; Genova, Julia; Eleršič, Kristina; Iglič, Aleš; Kralj-Iglič, Veronika; Ulrih, Nataša Poklar

    2014-02-01

    The aim of this work is to investigate the effect of electrostatic interactions between the nanoparticles and the membrane lipids on altering the physical properties of the liposomal membrane such as fluidity and bending elasticity. For this purpose, we have used nanoparticles and lipids with different surface charges. Positively charged iron oxide (γ-Fe2O3) nanoparticles, neutral and negatively charged cobalt ferrite (CoFe2O4) nanoparticles were encapsulated in neutral lipid 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine lipid mixture. Membrane fluidity was assessed through the anisotropy measurements using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. Though the interaction of both the types of nanoparticles reduced the membrane fluidity, the results were more pronounced in the negatively charged liposomes encapsulated with positively charged iron oxide nanoparticles due to strong electrostatic attractions. X-ray photoelectron spectroscopy results also confirmed the presence of significant quantity of positively charged iron oxide nanoparticles in negatively charged liposomes. Through thermally induced shape fluctuation measurements of the giant liposomes, a considerable reduction in the bending elasticity modulus was observed for cobalt ferrite nanoparticles. The experimental results were supported by the simulation studies using modified Langevin-Poisson-Boltzmann model.

  14. Dendrimer-Templated Ultrasmall and Multifunctional Photothermal Agents for Efficient Tumor Ablation.

    PubMed

    Zhou, Zhengjie; Wang, Yitong; Yan, Yang; Zhang, Qiang; Cheng, Yiyun

    2016-04-26

    Ultrasmall and multifunctional nanoparticles are highly desirable for photothermal cancer therapy, but the synthesis of these nanoparticles remains a huge challenge. Here, we used a dendrimer as a template to synthesize ultrasmall photothermal agents and further modified them with multifunctional groups. Dendrimer-encapsulated nanoparticles (DENPs) including copper sulfide, platinum, and palladium nanoparticles possessed a sub-5 nm size and exhibited an excellent photothermal effect. DENPs were further modified with TAT or RGD peptides to facilitate their cellular uptake and targeting delivery to tumors. They were also decorated with fluorescent probes for real-time imaging and tracking of the particles' distribution. The in vivo study revealed RGD-modified DENPs efficiently reduced the tumor growth upon near-infrared irradiation. In all, our study provides a facile and flexible scaffold to prepare ultrasmall and multifunctional photothermal agents.

  15. Embryotoxicity of cobalt ferrite and gold nanoparticles: a first in vitro approach.

    PubMed

    Di Guglielmo, Claudia; López, David Ramos; De Lapuente, Joaquín; Mallafre, Joan Maria Llobet; Suàrez, Miquel Borràs

    2010-09-01

    Nanoparticles (NPs) are emerging as promising biomedical tools thanks to their peculiar characteristics. Our purpose was to investigate the embryotoxicity of cobalt ferrite and gold NPs through the Embryonic Stem Cell Test (EST). The EST is an in vitro standard assay, which permits to classify substances as strongly, weakly or non-embryotoxic. Due to the particular physical-chemical nature of nanoparticles, we introduced a modification to the standard protocol exposing the Embryonic Stem Cells (ES-D3) to nanoparticles only during the first 5 days of the assay. Moreover, we proposed a method to discriminate and compare the embryotoxicity of the substances within the weakly embryotoxic range. Our ID(50) results permit to classify cobalt ferrite nanoparticles coated with gold and silanes as non-embryotoxic. The remaining nanoparticles have been classified as weakly embryotoxic in this decreasing order: gold salt (HAuCl(4).3H(2)O)>cobalt ferrite salt (CoFe(2)O(4))>cobalt ferrite nanoparticles coated with silanes (Si-CoFe)>gold nanoparticles coated with hyaluronic acid (HA-Au).

  16. Dynamics of magnetic nanoparticles in viscoelastic media

    NASA Astrophysics Data System (ADS)

    Remmer, Hilke; Roeben, Eric; Schmidt, Annette M.; Schilling, Meinhard; Ludwig, Frank

    2017-04-01

    We compare different models for the description of the complex susceptibility of magnetic nanoparticles in an aqueous gelatin solution representing a model system for a Voigt-Kelvin scheme. The analysis of susceptibility spectra with the numerical model by Raikher et al. [7] is compared with the analysis applying a phenomenological, modified Debye model. The fit of the models to the measured data allows one to extract the viscoelastic parameter dynamic viscosity η and shear modulus G. The experimental data were recorded on single-core thermally blocked CoFe2O4 nanoparticles in an aqueous solution with 2.5 wt% gelatin. Whereas the dynamic viscosities obtained by fitting the model - extended by distributions of hydrodynamic diameters and viscosities - agree very well, the derived values for the shear modulus show the same temporal behavior during the gelation process, but vary approximately by a factor of two. To verify the values for viscosity and shear modulus obtained from nanorheology, macrorheological measurements are in progress.

  17. Enigmatic, ultrasmall, uncultivated Archaea

    SciTech Connect

    Baker, Brett J.; Comolli, Luis; Dick, Gregory J.; Hauser, Loren John; Hyatt, Philip Douglas; Dill, Brian; Land, Miriam L; Verberkmoes, Nathan C; Hettich, Robert {Bob} L; Banfield, Jillian F.

    2010-01-01

    Metagenomics has provided access to genomes of as yet uncultivated microorganisms in natural environments, yet there are gaps in our knowledge particularly for Archaea that occur at relatively low abundance and in extreme environments. Ultrasmall cells (<500 nm in diameter) from lineages without cultivated representatives that branch near the crenarchaeal/euryarchaeal divide have been detected in a variety of acidic ecosystems. We reconstructed composite, near-complete 1-Mb genomes for three lineages, referred to as ARMAN (archaeal Richmond Mine acidophilic nanoorganisms), from environmental samples and a biofilm filtrate. Genes of two lineages are among the smallest yet described, enabling a 10% higher coding density than found genomes of the same size, and there are noncontiguous genes. No biological function could be inferred for up to 45% of genes and no more than 63% of the predicted proteins could be assigned to a revised set of archaeal clusters of orthologous groups. Some core metabolic genes are more common in Crenarchaeota than Euryarchaeota, up to 21% of genes have the highest sequence identity to bacterial genes, and 12 belong to clusters of orthologous groups that were previously exclusive to bacteria. A small subset of 3D cryo-electron tomographic reconstructions clearly show penetration of the ARMAN cell wall and cytoplasmic membranes by protuberances extended from cells of the archaeal order Thermoplasmatales. Interspecies interactions, the presence of a unique internal tubular organelle [Comolli, et al. (2009) ISME J 3:159 167], and many genes previously only affiliated with Crenarchaea or Bacteria indicate extensive unique physiology in organisms that branched close to the time that Cren- and Euryarchaeotal lineages diverged.

  18. Enigmatic, ultrasmall, uncultivated Archaea

    SciTech Connect

    Baker, Brett J.; Comolli, Luis; Dick, Gregory J.; Hauser, Loren John; Hyatt, Philip Douglas; Dill, Brian; Land, Miriam L; Verberkmoes, Nathan C; Hettich, Robert {Bob} L; Banfield, Jillian F.

    2010-01-01

    Metagenomics has provided access to genomes of as yet uncultivated microorganisms in natural environments, yet there are gaps in our knowledge-particularly for Archaea-that occur at relatively low abundance and in extreme environments. Ultrasmall cells (<500 nm in diameter) from lineages without cultivated representatives that branch near the crenarchaeal/euryarchaeal divide have been detected in a variety of acidic ecosystems. We reconstructed composite, near-complete similar to 1-Mb genomes for three lineages, referred to as ARMAN (archaeal Richmond Mine acidophilic nanoorganisms), from environmental samples and a biofilm filtrate. Genes of two lineages are among the smallest yet described, enabling a 10% higher coding density than found genomes of the same size, and there are noncontiguous genes. No biological function could be inferred for up to 45% of genes and no more than 63% of the predicted proteins could be assigned to a revised set of archaeal clusters of orthologous groups. Some core metabolic genes are more common in Crenarchaeota than Euryarchaeota, up to 21% of genes have the highest sequence identity to bacterial genes, and 12 belong to clusters of orthologous groups that were previously exclusive to bacteria. A small subset of 3D cryo-electron tomographic reconstructions clearly show penetration of the ARMAN cell wall and cytoplasmic membranes by protuberances extended from cells of the archaeal order Thermoplasmatales. Interspecies interactions, the presence of a unique internal tubular organelle [Comolli, et al. (2009) ISME J 3: 159-167], and many genes previously only affiliated with Crenarchaea or Bacteria indicate extensive unique physiology in organisms that branched close to the time that Cren- and Euryarchaeotal lineages diverged.

  19. Enigmatic, ultrasmall, uncultivated Archaea.

    PubMed

    Baker, Brett J; Comolli, Luis R; Dick, Gregory J; Hauser, Loren J; Hyatt, Doug; Dill, Brian D; Land, Miriam L; Verberkmoes, Nathan C; Hettich, Robert L; Banfield, Jillian F

    2010-05-11

    Metagenomics has provided access to genomes of as yet uncultivated microorganisms in natural environments, yet there are gaps in our knowledge-particularly for Archaea-that occur at relatively low abundance and in extreme environments. Ultrasmall cells (<500 nm in diameter) from lineages without cultivated representatives that branch near the crenarchaeal/euryarchaeal divide have been detected in a variety of acidic ecosystems. We reconstructed composite, near-complete approximately 1-Mb genomes for three lineages, referred to as ARMAN (archaeal Richmond Mine acidophilic nanoorganisms), from environmental samples and a biofilm filtrate. Genes of two lineages are among the smallest yet described, enabling a 10% higher coding density than found genomes of the same size, and there are noncontiguous genes. No biological function could be inferred for up to 45% of genes and no more than 63% of the predicted proteins could be assigned to a revised set of archaeal clusters of orthologous groups. Some core metabolic genes are more common in Crenarchaeota than Euryarchaeota, up to 21% of genes have the highest sequence identity to bacterial genes, and 12 belong to clusters of orthologous groups that were previously exclusive to bacteria. A small subset of 3D cryo-electron tomographic reconstructions clearly show penetration of the ARMAN cell wall and cytoplasmic membranes by protuberances extended from cells of the archaeal order Thermoplasmatales. Interspecies interactions, the presence of a unique internal tubular organelle [Comolli, et al. (2009) ISME J 3:159-167], and many genes previously only affiliated with Crenarchaea or Bacteria indicate extensive unique physiology in organisms that branched close to the time that Cren- and Euryarchaeotal lineages diverged.

  20. Metabolic Effects of Cobalt Ferrite Nanoparticles on Cervical Carcinoma Cells and Nontumorigenic Keratinocytes.

    PubMed

    Oliveira, Ana Beatriz Bortolozo; de Moraes, Fabio Rogério; Candido, Natalia Maria; Sampaio, Isabella; Paula, Alex Silva; de Vasconcellos, Adriano; Silva, Thais Cerqueira; Miller, Alex Henrique; Rahal, Paula; Nery, Jose Geraldo; Calmon, Marilia Freitas

    2016-12-02

    The cytotoxic response, cellular uptake, and metabolomic profile of HeLa and HaCaT cell lines treated with cobalt ferrite nanoparticles (CoFe2O4 NPs) were investigated in this study. Cell viability assays showed low cytotoxicity caused by the uptake of the nanoparticles at 2 mg/mL. However, metabolomics revealed that these nanoparticles impacted cell metabolism even when tested at a concentration that presented low cytotoxicity according to the cell viability assay. The two cell lines shared stress-related metabolic changes such as increase in alanine and creatine levels. A reduced level of fumarate was also observed in HeLa cells after treatment with the nanoparticles, and this alteration can inhibit tumorigenesis. Fumarate is considered to be an oncometabolite that can inhibit prolyl hydroxylase, and this inhibition stabilizes HIF1α, one of the master regulators of tumorigenesis that promotes tumor growth and development. In summary, this study showed that nanoparticle-treated HeLa cells demonstrated decreased concentrations of metabolites associated with cell proliferation and tumor growth. The results clearly indicated that treatment with these nanoparticles might cause a perturbation in cellular metabolism.

  1. Structural and magnetic properties of cobalt-doped iron oxide nanoparticles prepared by solution combustion method for biomedical applications.

    PubMed

    Venkatesan, Kaliyamoorthy; Rajan Babu, Dhanakotti; Kavya Bai, Mane Prabhu; Supriya, Ravi; Vidya, Radhakrishnan; Madeswaran, Saminathan; Anandan, Pandurangan; Arivanandhan, Mukannan; Hayakawa, Yasuhiro

    2015-01-01

    Cobalt-doped iron oxide nanoparticles were prepared by solution combustion technique. The structural and magnetic properties of the prepared samples were also investigated. The average crystallite size of cobalt ferrite (CoFe2O4) magnetic nanoparticle was calculated using Scherrer equation, and it was found to be 16±5 nm. The particle size was measured by transmission electron microscope. This value was found to match with the crystallite size calculated by Scherrer equation corresponding to the prominent intensity peak (311) of X-ray diffraction. The high-resolution transmission electron microscope image shows clear lattice fringes and high crystallinity of cobalt ferrite magnetic nanoparticles. The synthesized magnetic nanoparticles exhibited the saturation magnetization value of 47 emu/g and coercivity of 947 Oe. The anti-microbial activity of cobalt ferrite nanoparticles showed better results as an anti-bacterial agent. The affinity constant was determined for the nanoparticles, and the cytotoxicity studies were conducted for the cobalt ferrite nanoparticles at different concentrations and the results are discussed.

  2. Structural and magnetic properties of cobalt-doped iron oxide nanoparticles prepared by solution combustion method for biomedical applications

    PubMed Central

    Venkatesan, Kaliyamoorthy; Rajan Babu, Dhanakotti; Kavya Bai, Mane Prabhu; Supriya, Ravi; Vidya, Radhakrishnan; Madeswaran, Saminathan; Anandan, Pandurangan; Arivanandhan, Mukannan; Hayakawa, Yasuhiro

    2015-01-01

    Cobalt-doped iron oxide nanoparticles were prepared by solution combustion technique. The structural and magnetic properties of the prepared samples were also investigated. The average crystallite size of cobalt ferrite (CoFe2O4) magnetic nanoparticle was calculated using Scherrer equation, and it was found to be 16±5 nm. The particle size was measured by transmission electron microscope. This value was found to match with the crystallite size calculated by Scherrer equation corresponding to the prominent intensity peak (311) of X-ray diffraction. The high-resolution transmission electron microscope image shows clear lattice fringes and high crystallinity of cobalt ferrite magnetic nanoparticles. The synthesized magnetic nanoparticles exhibited the saturation magnetization value of 47 emu/g and coercivity of 947 Oe. The anti-microbial activity of cobalt ferrite nanoparticles showed better results as an anti-bacterial agent. The affinity constant was determined for the nanoparticles, and the cytotoxicity studies were conducted for the cobalt ferrite nanoparticles at different concentrations and the results are discussed. PMID:26491320

  3. Encapsidation of nanoparticles by red clover necrotic mosaic virus.

    PubMed

    Loo, LiNa; Guenther, Richard H; Lommel, Steven A; Franzen, Stefan

    2007-09-12

    Icosahedral virus capsids demonstrate a high degree of selectivity in packaging cognate nucleic acid genome components during virion assembly. The 36 nm icosahedral plant virus Red clover necrotic mosaic virus (RCNMV) packages its two genomic ssRNAs via a specific capsid protein (CP) genomic RNA interaction. A 20-nucleotide hairpin structure within the genomic RNA-2 hybridizes with RNA-1 to form a bimolecular complex, which is the origin of assembly (OAS) in RCNMV that selectively recruits and orients CP subunits initiating virion assembly. In this Article, an oligonucleotide mimic of the OAS sequence was attached to Au, CoFe2O4, and CdSe nanoparticles ranging from 3 to 15 nm, followed by addition of RNA-1 to form a synthetic OAS to direct the virion-like assembly by RCNMV CP. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements were consistent with the formation of virus-like particles (VLPs) comparable in size to native RCNMV. Attempts to encapsidate nanoparticles with diameters larger than 17 nm did not result in well-formed viral capsids. These results are consistent with the presence of a 17 nm cavity in native RCNMV. Covalent linkage of the OAS to nanoparticles directs RNA-dependent encapsidation and demonstrates that foreign cargo can be packaged into RCNMV virions. The flexibility of the RCNMV CP to encapsidate different materials, as long as it is within encapsidation constraint, is a critical factor to be considered as a drug delivery and diagnostic vehicle in biomedical applications.

  4. Strong and moldable cellulose magnets with high ferrite nanoparticle content.

    PubMed

    Galland, Sylvain; Andersson, Richard L; Ström, Valter; Olsson, Richard T; Berglund, Lars A

    2014-11-26

    A major limitation in the development of highly functional hybrid nanocomposites is brittleness and low tensile strength at high inorganic nanoparticle content. Herein, cellulose nanofibers were extracted from wood and individually decorated with cobalt-ferrite nanoparticles and then for the first time molded at low temperature (<120 °C) into magnetic nanocomposites with up to 93 wt % inorganic content. The material structure was characterized by TEM and FE-SEM and mechanically tested as compression molded samples. The obtained porous magnetic sheets were further impregnated with a thermosetting epoxy resin, which improved the load-bearing functions of ferrite and cellulose material. A nanocomposite with 70 wt % ferrite, 20 wt % cellulose nanofibers, and 10 wt % epoxy showed a modulus of 12.6 GPa, a tensile strength of 97 MPa, and a strain at failure of ca. 4%. Magnetic characterization was performed in a vibrating sample magnetometer, which showed that the coercivity was unaffected and that the saturation magnetization was in proportion with the ferrite content. The used ferrite, CoFe2O4, is a magnetically hard material, demonstrated by that the composite material behaved as a traditional permanent magnet. The presented processing route is easily adaptable to prepare millimeter-thick and moldable magnetic objects. This suggests that the processing method has the potential to be scaled-up for industrial use for the preparation of a new subcategory of magnetic, low-cost, and moldable objects based on cellulose nanofibers.

  5. Core/Shell and High Aspect Ratio Magnetic Oxide Nanoparticles for Antenna Applications

    NASA Astrophysics Data System (ADS)

    Ekiert, Thomas F., Jr.; O'Malley, Matthew; Yocum, Brandon; Lippold, Jennifer; Lyle, Mallory; Griner, Angela; Flynn, Cory; Nickel, Anna; Alexander, Max D., Jr.

    2012-02-01

    Improved antenna gain, reduced antenna aperture size, and improved bandwidth are of interest to an increasingly mobile world. To obtain these improvements our efforts are directed at developing new magnetic oxide nanoparticle/polymer composites with modifiable permeability and permittivity and low electrical losses. Our approach consists of producing core/shell and shape controlled magnetic nanoparticles. Methods of synthesis utilize microwave and traditional heating to perform hydrothermal and solvothermal reactions. Decomposition of metal acetylacetonates is performed using various alcohols resulting in spherical nanoparticles with diameters of 8-16 nm and 3-7 nm for Fe3O4 and CoFe2O4, respectively. Microwave methods result in similar particles, but are produced in an hour or less as compared to 48 hrs via the traditional solvothermal method. Successive growths are used to produce larger monolithic particles as well as core/shell systems where exchange coupling between the core and shell is observed. Hexaferrite particles have been produced via hydrothermal synthesis, while high aspect ratio Fe3O4 nanoparticles ( 10-100 nm) produced via hydrothermal synthesis result in nanoneedles with high μr.

  6. Tri-iodide reduction activity of ultra-small size PtFe nanoparticles supported nitrogen-doped graphene as counter electrode for dye-sensitized solar cell.

    PubMed

    Nechiyil, Divya; Vinayan, B P; Ramaprabhu, S

    2017-02-15

    Efficient and cost effective counter electrode (CE) is pre-requisite for the commercialization of dye-sensitized solar cell (DSSC). Present work investigates ultra small size platinum-iron alloy nanoparticles dispersed over nitrogen-doped graphene (PtFe/NG) as an effective counter electrode for DSSC. Hereby we achieve low loading of Pt by alloying with Fe accompanied by superior electrocatalytic activity towards the iodide-triiodide (I(-)/I3(-)) mechanism. Enhancement in electrocatalytic performance of PtFe/NG has been shown by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization analysis. PtFe/NG counter electrode exhibits higher power conversion efficiency (∼6.12%) with lower charge transfer resistance, which helps in faster diffusion of I(-)/I3(-) ions as compared to NG and Pt/NG counter electrodes. The increased electrocatalytic activity of PtFe/NG is due to the collective effect of intrinsic electronic effects by alloying, uniform dispersion of small PtFe alloy nanoparticles over nitrogen doped graphene, and additional catalytic sites offered by nitrogen-doped graphene.

  7. Hemolysin coregulated protein 1 as a molecular gluing unit for the assembly of nanoparticle hybrid structures

    PubMed Central

    Pham, Tuan Anh; Schreiber, Andreas; Sturm (née Rosseeva), Elena V

    2016-01-01

    Summary Hybrid nanoparticle (NP) structures containing organic building units such as polymers, peptides, DNA and proteins have great potential in biosensor and electronic applications. The nearly free modification of the polymer chain, the variation of the protein and DNA sequence and the implementation of functional moieties provide a great platform to create inorganic structures of different morphology, resulting in different optical and magnetic properties. Nevertheless, the design and modification of a protein structure with functional groups or sequences for the assembly of biohybrid materials is not trivial. This is mainly due to the sensitivity of its secondary, tertiary and quaternary structure to the changes in the interaction (e.g., hydrophobic, hydrophilic, electrostatic, chemical groups) between the protein subunits and the inorganic material. Here, we use hemolysin coregulated protein 1 (Hcp1) from Pseudomonas aeruginosa as a building and gluing unit for the formation of biohybrid structures by implementing cysteine anchoring points at defined positions on the protein rim (Hcp1_cys3). We successfully apply the Hcp1_cys3 gluing unit for the assembly of often linear, hybrid structures of plasmonic gold (Au NP), magnetite (Fe3O4 NP), and cobalt ferrite nanoparticles (CoFe2O4 NP). Furthermore, the assembly of Au NPs into linear structures using Hcp1_cys3 is investigated by UV–vis spectroscopy, TEM and cryo-TEM. One key parameter for the formation of Au NP assembly is the specific ionic strength in the mixture. The resulting network-like structure of Au NPs is characterized by Raman spectroscopy, showing surface-enhanced Raman scattering (SERS) by a factor of 8·104 and a stable secondary structure of the Hcp1_cys3 unit. In order to prove the catalytic performance of the gold hybrid structures, they are used as a catalyst in the reduction reaction of 4-nitrophenol showing similar catalytic activity as the pure Au NPs. To further extend the functionality

  8. Synthesis, characterization and magnetic properties of carbon nanotubes decorated with magnetic MIIFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ali, Syed Danish; Hussain, Syed Tajammul; Gilani, Syeda Rubina

    2013-04-01

    In this study, a simple, efficient and reproducible microemulsion method was applied for the successful decoration of carbon nanotubes (CNTs) with magnetic MIIFe2O4 (M = Co, Ni, Cu, Zn) nanoparticles. The structure, composition and morphology of the prepared nanocomposite materials were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The magnetic properties were investigated by the vibrating sample magnetometer (VSM). The SEM results illustrated that large quantity of MIIFe2O4 nanoparticles were uniformly decorated around the circumference of CNTs and the sizes of the nanoparticles ranged from 15 to 20 nm. Magnetic hysteresis loop measurements revealed that all the MIIFe2O4/CNTs nanocomposites displayed ferromagnetic behavior at 300 K and can be manipulated using an external magnetic field. The CoFe2O4/CNTs nanocomposite showed maximum value of saturation magnetization which was 37.47 emu g-1. The as prepared MIIFe2O4/CNTs nanocomposites have many potential application in magnetically guided targeted drug delivery, clinical diagnosis, electrochemical biosensing, magnetic data storage and magnetic resonance imaging.

  9. Preliminary evaluation of a 99mTc labeled hybrid nanoparticle bearing a cobalt ferrite core: in vivo biodistribution.

    PubMed

    Psimadas, Dimitrios; Baldi, Giovanni; Ravagli, Costanza; Bouziotis, Penelope; Xanthopoulos, Stavros; Franchini, Mauro Comes; Georgoulias, Panagiotis; Loudos, George

    2012-08-01

    Magnetic nanoparticles have become important tools for imaging a wide range of diseases, improving drug delivery and applying hyperthermic treatment. Iron oxide based nanoparticles have been widely examined, unlike cobalt ferrite based ones. Herein, monodisperse and stable CoFe2O4 nanoparticles have been produced, coated and further stabilized using ethyl 12-(hydroxyamino)-12-oxododecanoate, poly(lactic-co-glycolic acid) and bovine serum albumin. The final product, NBRh1, was fully characterized and has been directly radiolabeled with 99mTc using SnCl1 as the reducing agent in high yields. In vitro stability and hyperthermic properties of 99mTC-NBRh1 were encouraging for further application in low frequencies hyperthermia and biomagnetic applications. In vivo evaluation followed after injection in healthy mice. The planar and SPECT imaging data as well as the biodistribution results were in accordance, showing high liver and spleen uptake as expected starting almost immediately after administration. In conclusion the preliminary results for nanoparticles bearing a cobalt ferrite core justify further investigations towards potential hyperthermic applications, drug transportation and liver or spleen imaging.

  10. Liquid-phase syntheses of cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Sinkó, Katalin; Manek, Enikő; Meiszterics, Anikó; Havancsák, Károly; Vainio, Ulla; Peterlik, Herwig

    2012-06-01

    The aim of the present study was to synthesize cobalt-ferrite (CoFe2O4) nanoparticles using various liquid phase methods; sol-gel route, co-precipitation process, and microemulsion technique. The effects of experimental parameters on the particle size, size distribution, morphology, and chemical composition have been studied. The anions of precursors (chloride and nitrate), the solvents (water, n-propanol, ethanol, and benzyl alcohol), the precipitating agent (ammonia, sodium carbonate, and oxalic acid), the surfactants (polydimethylsiloxane, ethyl acetate, citric acid, cethyltrimethylammonium bromide, and sodium dodecil sulfate), their concentrations, and heat treatments were varied in the experiments. The smallest particles (around 40 nm) with narrow polydispersity and spherical shape could be achieved by a simple, fast sol-gel technique in the medium of propanol and ethyl acetate. The size characterization methods have also been investigated. Small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and scanning electron microscopy (SEM) provide the comparison of methods. The SAXS data correspond with the sizes detected by SEM and differ from DLS data. The crystalline phases, morphology, and chemical composition of the particles with different shapes have been analyzed by X-ray diffraction, SEM, and energy dispersive X-ray spectrometer.

  11. Magnetic and electrical properties of In doped cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Nongjai, Razia; Khan, Shakeel; Asokan, K.; Ahmed, Hilal; Khan, Imran

    2012-10-01

    Nanoparticles of CoFe2O4 and CoIn0.15Fe1.85O4 ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In3+ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric constant (ɛ') and dielectric loss (tan δ) are also studied as a function of frequency and temperature. The variation of dielectric properties ɛ', tan δ, and ac conductivity (σac) with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe2+ and Fe3+ as well as between Co2+ and Co3+ ions at B-sites. Magnetization and electrical property study showed its dominant dependence on the grain size.

  12. Micrometric periodic assembly of magnetotactic bacteria and magnetic nanoparticles using audio tapes

    NASA Astrophysics Data System (ADS)

    Godoy, M.; Moreno, A. J.; Jorge, G. A.; Ferrari, H. J.; Antonel, P. S.; Mietta, J. L.; Ruiz, M.; Negri, R. M.; Pettinari, M. J.; Bekeris, V.

    2012-02-01

    We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum magneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and of superparamagnetic Fe3O4 and ferromagnetic CoFe2O4 nanoparticles in aqueous suspensions using periodically magnetized audio tapes. The distribution of the stray magnetic field at the surface of the tapes was determined analytically and experimentally by magneto-optic imaging. Calculations showed that the magnetic field close to the tape surface was of the order of 100 mT, and the magnetic field gradient was larger than 1 T mm-1. Drops of aqueous solutions were deposited on the tapes, and bacteria and particles were trapped at locations where magnetic energy is minimized, as observed using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treated with formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated that magnetic forces dominate over self-propelling forces in these experiments, in accordance with calculated values. The behavior of the different types of samples is discussed.

  13. Targeted and controlled anticancer drug delivery and release with magnetoelectric nanoparticles

    NASA Astrophysics Data System (ADS)

    Rodzinski, Alexandra; Guduru, Rakesh; Liang, Ping; Hadjikhani, Ali; Stewart, Tiffanie; Stimphil, Emmanuel; Runowicz, Carolyn; Cote, Richard; Altman, Norman; Datar, Ram; Khizroev, Sakhrat

    2016-02-01

    It is a challenge to eradicate tumor cells while sparing normal cells. We used magnetoelectric nanoparticles (MENs) to control drug delivery and release. The physics is due to electric-field interactions (i) between MENs and a drug and (ii) between drug-loaded MENs and cells. MENs distinguish cancer cells from normal cells through the membrane’s electric properties; cancer cells have a significantly smaller threshold field to induce electroporation. In vitro and in vivo studies (nude mice with SKOV-3 xenografts) showed that (i) drug (paclitaxel (PTX)) could be attached to MENs (30-nm CoFe2O4@BaTiO3 nanostructures) through surface functionalization to avoid its premature release, (ii) drug-loaded MENs could be delivered into cancer cells via application of a d.c. field (~100 Oe), and (iii) the drug could be released off MENs on demand via application of an a.c. field (~50 Oe, 100 Hz). The cell lysate content was measured with scanning probe microscopy and spectrophotometry. MENs and control ferromagnetic and polymer nanoparticles conjugated with HER2-neu antibodies, all loaded with PTX were weekly administrated intravenously. Only the mice treated with PTX-loaded MENs (15/200 μg) in a field for three months were completely cured, as confirmed through infrared imaging and post-euthanasia histology studies via energy-dispersive spectroscopy and immunohistochemistry.

  14. Targeted and controlled anticancer drug delivery and release with magnetoelectric nanoparticles

    PubMed Central

    Rodzinski, Alexandra; Guduru, Rakesh; Liang, Ping; Hadjikhani, Ali; Stewart, Tiffanie; Stimphil, Emmanuel; Runowicz, Carolyn; Cote, Richard; Altman, Norman; Datar, Ram; Khizroev, Sakhrat

    2016-01-01

    It is a challenge to eradicate tumor cells while sparing normal cells. We used magnetoelectric nanoparticles (MENs) to control drug delivery and release. The physics is due to electric-field interactions (i) between MENs and a drug and (ii) between drug-loaded MENs and cells. MENs distinguish cancer cells from normal cells through the membrane’s electric properties; cancer cells have a significantly smaller threshold field to induce electroporation. In vitro and in vivo studies (nude mice with SKOV-3 xenografts) showed that (i) drug (paclitaxel (PTX)) could be attached to MENs (30-nm CoFe2O4@BaTiO3 nanostructures) through surface functionalization to avoid its premature release, (ii) drug-loaded MENs could be delivered into cancer cells via application of a d.c. field (~100 Oe), and (iii) the drug could be released off MENs on demand via application of an a.c. field (~50 Oe, 100 Hz). The cell lysate content was measured with scanning probe microscopy and spectrophotometry. MENs and control ferromagnetic and polymer nanoparticles conjugated with HER2-neu antibodies, all loaded with PTX were weekly administrated intravenously. Only the mice treated with PTX-loaded MENs (15/200 μg) in a field for three months were completely cured, as confirmed through infrared imaging and post-euthanasia histology studies via energy-dispersive spectroscopy and immunohistochemistry. PMID:26875783

  15. On the correlation between nanoscale structure and magnetic properties in ordered mesoporous cobalt ferrite (CoFe2O4) thin films.

    PubMed

    Quickel, Thomas E; Le, Van H; Brezesinski, Torsten; Tolbert, Sarah H

    2010-08-11

    In this work, we report the synthesis of periodic nanoporous cobalt ferrite (CFO) that exhibits tunable room temperature ferrimagnetism. The porous cubic CFO frameworks are fabricated by coassembly of inorganic precursors with a large amphiphilic diblock copolymer, referred to as KLE. The inverse spinel framework boasts an ordered open network of pores averaging 14 nm in diameter. The domain sizes of the crystallites are tunable from 6 to 15 nm, a control which comes at little cost to the ordering of the mesostructure. Increases in crystalline domain size directly correlate with increases in room temperature coercivity. In addition, these materials show a strong preference for out-of-plane oriented magnetization, which is unique in a thin film system. The preference is explained by in-plane tensile strain, combined with relaxation of the out-of-plane strain through flexing of the mesopores. It is envisioned that the pores of this ferrimagnet could facilitate the formation of a diverse range of exchange coupled composite materials.

  16. Raman scattering spectra, magnetic and ferroelectric properties of BiFeO3-CoFe2O4 nanocomposite thin films structure

    NASA Astrophysics Data System (ADS)

    Tyagi, Mintu; Kumari, Mukesh; Chatterjee, Ratnamala; Sharma, Puneet

    2014-09-01

    Multiferroic (1-x)BiFeO3(BFO)-xCoFe2O4(CFO) (x=0 and 0.1) nanocomposite thin films were deposited on ITO coated glass using sol-gel spin coating technique. X-ray diffraction and transmission electron microscopy examinations confirm the coexistence of both perovskite BFO and spinel CFO phases. The effect of addition of CFO in BFO matrix has been studied on Raman spectra, magnetic and ferroelectric properties. BFO/CFO nanocomposite showed good magnetic behavior (Ms 40.3 emu/cm3, Mr 12.9 emu/cm3, Hc 90 Oe) with no change in ferroelectric properties. The strain analysis carried out by Raman spectroscopy reveals that both BFO and CFO bands are found to be strained in BFO/CFO composite nanostructure. The strain of the bands is discussed on the basis of lattice mismatch (interfacial stress) between CFO (a=0.839 nm) and BFO (a=0.396 nm) phases.

  17. Tuning magnetoelectric coupling using porosity in multiferroic nanocomposites of ALD-grown Pb(Zr,Ti)O3 and templated mesoporous CoFe2O4

    NASA Astrophysics Data System (ADS)

    Chien, Diana; Buditama, Abraham N.; Schelhas, Laura T.; Kang, Hye Yeon; Robbennolt, Shauna; Chang, Jane P.; Tolbert, Sarah H.

    2016-09-01

    In this manuscript, we examine ways to create multiferroic composites with controlled nanoscale architecture. We accomplished this by uniformly depositing piezoelectric lead zirconate titanate (PZT) into templated mesoporous, magnetostrictive cobalt ferrite (CFO) thin films to form nanocomposites in which strain can be transferred at the interface between the two materials. To study the magnetoelectric coupling, the nanostructure was electrically poled ex situ prior to magnetic measurements. No samples showed a change in in-plane magnetization as a function of voltage due to substrate clamping. Out-of-plane changes were observed, but contrary to expectations based on total PZT volume fraction, mesoporous CFO samples partially filled with PZT showed more change in out-of-plane magnetization than the sample with fully filled pores. This result suggests that residual porosity in the composite adds mechanical flexibility and results in greater magnetoelectric coupling.

  18. Local Probing of Magnetoelectric Coupling and Magnetoelastic Control of Switching in BiFeO3-CoFe2O4 Thin-Film Nanocomposite

    DTIC Science & Technology

    2013-07-25

    hysteresis loop: the inset shows the remanent phase change as a function of magnetic field; (b) average amplitude-voltage butterfly loop; (c) measured...at remanent state (Fig. 4(d)). The obtained ME coefficient (the highest value we measure is 102 mV/ cm/Oe) and is comparable to that of bulk PZT-CFO

  19. The converse magnetoelectric characteristics of Mn and Mg doped CoFe2O4-PbTiO3 composites

    NASA Astrophysics Data System (ADS)

    Liu, Ting-ting; Wang, Zhi; Mao, Jun; Cheng, Ning-ning; Ni, Li-jun

    2014-05-01

    Electric-field-induced magnetization characteristics are demonstrated in xCo0.6Mg0.2Mn0.2Fe2O4-(1 - x) PbTiO3 (x = 0.4, 0.5, 0.6, and 0.7) composites synthesized by sol-gel method. The converse magnetoelectric effect (CME) with driving frequency in a range of 4-16 kHz was measured at room temperature. The composite of 0.6Co0.6Mg0.2Mn0.2Fe2O4-0.4PbTiO3 exhibits the maximum CME coefficient at electromechanical resonance frequency of 13 kHz. Doping Mn and Mg into CFO enhances CME coefficients and resistivity of compositions, which provide great opportunities for electric field tunable microwave devices.

  20. Formation and evolution of crystalline magnetic phases of CoFe2O4 with temperature depending on the nature of the diol used

    NASA Astrophysics Data System (ADS)

    Thomas, Dippong; Zoita, Berinde; Ivan, Pauliuc

    2013-05-01

    An organic precursor was obtained from cobalt nitrate and iron nitrate with different diols (etilendiol, 1,2-propanediol and 1,3-propanediol). The precursor was observed through thermal analysis and FT-IR spectrometry, techniques aimed at tracking the formation of carboxylate type complex combinations and establishing the optimal synthesis temperature. The formation of magnetic crystalline phases is observed through advanced heat treatments.

  1. Fabrication of Porous Anodic Alumina with Ultrasmall Nanopores

    PubMed Central

    2010-01-01

    Anodization of Al foil under low voltages of 1–10 V was conducted to obtain porous anodic aluminas (PAAs) with ultrasmall nanopores. Regular nanopore arrays with pore diameter 6–10 nm were realized in four different electrolytes under 0–30°C according to the AFM, FESEM, TEM images and current evolution curves. It is found that the pore diameter and interpore distance, as well as the barrier layer thickness, are not sensitive to the applied potentials and electrolytes, which is totally different from the rules of general PAA fabrication. The brand-new formation mechanism has been revealed by the AFM study on the samples anodized for very short durations of 2–60 s. It is discovered for the first time that the regular nanoparticles come into being under 1–10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultrasmall nanopores. Under higher potentials from 10 to 40 V, the surface nanoparticles will be less and less and nanopores transform into general PAAs. PMID:20676199

  2. Fabrication of Porous Anodic Alumina with Ultrasmall Nanopores

    NASA Astrophysics Data System (ADS)

    Ding, Gu Qiao; Yang, Rong; Ding, Jian Ning; Yuan, Ning Yi; Zhu, Yuan Yuan

    2010-08-01

    Anodization of Al foil under low voltages of 1-10 V was conducted to obtain porous anodic aluminas (PAAs) with ultrasmall nanopores. Regular nanopore arrays with pore diameter 6-10 nm were realized in four different electrolytes under 0-30°C according to the AFM, FESEM, TEM images and current evolution curves. It is found that the pore diameter and interpore distance, as well as the barrier layer thickness, are not sensitive to the applied potentials and electrolytes, which is totally different from the rules of general PAA fabrication. The brand-new formation mechanism has been revealed by the AFM study on the samples anodized for very short durations of 2-60 s. It is discovered for the first time that the regular nanoparticles come into being under 1-10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultrasmall nanopores. Under higher potentials from 10 to 40 V, the surface nanoparticles will be less and less and nanopores transform into general PAAs.

  3. Arrays of ultrasmall metal rings

    NASA Astrophysics Data System (ADS)

    Singh, Deepak K.; Krotkov, Robert V.; Xiang, Hongqi; Xu, Ting; Russell, Thomas P.; Tuominen, Mark T.

    2008-06-01

    In this paper, we present a simple method to fabricate ultra-high-density hexagonal arrays of ferromagnetic nanorings having 13 nm outer diameter, 5 nm inner diameter and 5 nm thickness. Cobalt magnetic nanorings were fabricated using a self-assembled diblock copolymer template with an angular evaporation of metal followed by an ion-beam etching. Magnetic measurements and theoretical calculations suggest that, at low fields, only the single domain and vortex states are important for rings of this size. The measured magnetization as a function of applied field shows a hysteresis that is consistent. These ultrasmall ferromagnetic rings have potential use in magnetic memory devices due to the simplicity of the preparation coupled with the ultra-high-density and geometry-controlled switching. This fabrication technique can be extended to other materials for applications in optics, sensing and nanoscale research.

  4. Effects of CeO2 Nanoparticles on Terrestrial Isopod Porcellio scaber: Comparison of CeO2 Biological Potential with Other Nanoparticles.

    PubMed

    Malev, Olga; Trebše, Polonca; Piecha, Małgorzata; Novak, Sara; Budič, Bojan; Dramićanin, Miroslav D; Drobne, Damjana

    2017-02-01

    Nano-sized cerium dioxide (CeO2) particles are emerging as an environmental issue due to their extensive use in automobile industries as fuel additives. Limited information is available on the potential toxicity of CeO2 nanoparticles (NPs) on terrestrial invertebrates through dietary exposure. In the present study, the toxic effects of CeO2 NPs on the model soil organism Porcellio scaber were evaluated. Nanotoxicity was assessed by monitoring the lipid peroxidation (LP) level and feeding rate after 14-days exposure to food amended with nano CeO2. The exposure concentration of 1000 μg of CeO2 NPs g(-1) dry weight food for 14 days significantly increased both the feeding rate and LP. Thus, this exposure dose is considered the lowest observed effect dose. At higher exposure doses of 2000 and 5000 μg of CeO2 NPs g(-1) dry weight food, NPs significantly decreased the feeding rate and increased the LP level. Comparative studies showed that CeO2 NPs are more biologically potent than TiO2 NPs, ZnO NPs, CuO NPs, CoFe2O4 NPs, and Ag NPs based on feeding rate using the same model organism and experimental setup. Based on comparative metal oxide NPs toxicities, the present results contribute to the knowledge related to the ecotoxicological effects of CeO2 NPs in terrestrial invertebrates exposed through feeding.

  5. Surface spin-glass in cobalt ferrite nanoparticles dispersed in silica matrix

    NASA Astrophysics Data System (ADS)

    Zeb, F.; Sarwer, W.; Nadeem, K.; Kamran, M.; Mumtaz, M.; Krenn, H.; Letofsky-Papst, I.

    2016-06-01

    Surface effects in cobalt ferrite (CoFe2O4) nanoparticles dispersed in a silica (SiO2) matrix were studied by using AC and DC magnetization. Nanoparticles with different concentration of SiO2 were synthesized by using sol-gel method. Average crystallite size lies in the range 25-34 nm for different SiO2 concentration. TEM image showed that particles are spherical and elongated in shape. Nanoparticles with higher concentration of SiO2 exhibit two peaks in the out-of-phase ac-susceptibility. First peak lies in the high temperature regime and corresponds to average blocking temperature of the nanoparticles. Second peak lies in the low temperature regime and is attributed to surface spin-glass freezing in these nanoparticles. Low temperature peak showed SiO2 concentration dependence and was vanished for large uncoated nanoparticles. The frequency dependence of the AC-susceptibility of low temperature peak was fitted with dynamic scaling law which ensures the presence of spin-glass behavior. With increasing applied DC field, the low temperature peak showed less shift as compared to blocking peak, broaden, and decreased in magnitude which also signifies its identity as spin-glass peak for smaller nanoparticles. M-H loops showed the presence of more surface disorder in nanoparticles dispersed in 60% SiO2 matrix. All these measurements revealed that surface effects become strengthen with increasing SiO2 matrix concentration and surface spins freeze in to spin-glass state at low temperatures.

  6. Use of oleic-acid functionalized nanoparticles for the magnetic solid-phase microextraction of alkylphenols in fruit juices using liquid chromatography-tandem mass spectrometry.

    PubMed

    Viñas, Pilar; Pastor-Belda, Marta; Torres, Aitor; Campillo, Natalia; Hernández-Córdoba, Manuel

    2016-05-01

    Magnetic nanoparticles of cobalt ferrite with oleic acid as the surfactant (CoFe2O4/oleic acid) were used as sorbent material for the determination of alkylphenols in fruit juices. High sensitivity and specificity were achieved by liquid chromatography and detection using both diode-array (DAD) and electrospray-ion trap-tandem mass spectrometry (ESI-IT-MS/MS) in the selected reaction monitoring (SRM) mode of the negative fragment ions for alkylphenols (APs) and in positive mode for ethoxylate APs (APEOs). The optimized conditions for the different variables influencing the magnetic separation procedure were: mass of magnetic nanoparticles, 50mg, juice volume, 10mL diluted to 25mL with water, pH 6, stirring for 10min at room temperature, separation with an external neodymium magnet, desorption with 3mL of methanol and orbital shaking for 5min. The enriched organic phase was evaporated and reconstituted with 100µL acetonitrile before injecting 30µL into a liquid chromatograph with a mobile phase composed of acetonitrile/0.1% (v/v) formic acid under gradient elution. Quantification limits were in the range 3.6 to 125ngmL(-1). The recoveries obtained were in the 91-119% range, with RSDs lower than 14%. The ESI-MS/MS spectra permitted the correct identification of both APs and APEOs in the fruit juice samples.

  7. High longitudinal relaxivity of ultra-small gadolinium oxide prepared by microsecond laser ablation in diethylene glycol

    SciTech Connect

    Luo Ningqi; Xiao Jun; Hu Wenyong; Chen Dihu; Tian Xiumei; Yang Chuan; Li Li

    2013-04-28

    Ultra-small gadolinium oxide (Gd{sub 2}O{sub 3}) can be used as T{sub 1}-weighted Magnetic Resonance Imaging (MRI) contrast agent own to its high longitudinal relaxivity (r{sub 1}) and has attracted intensive attention in these years. In this paper, ultra-small Gd{sub 2}O{sub 3} nanoparticles of 3.8 nm in diameter have been successfully synthesized by a microsecond laser ablating a gadolinium (Gd) target in diethylene glycol (DEG). The growth inhibition effect induced by the large viscosity of DEG makes it possible to synthesize ultra-small Gd{sub 2}O{sub 3} by laser ablation in DEG. The r{sub 1} value and T{sub 1}-weighted MR images are measured by a 3.0 T MRI spectroscope. The results show these nanoparticles with a high r{sub 1} value of 9.76 s{sup -1} mM{sup -1} to be good MRI contrast agents. We propose an explanation for the high r{sub 1} value of ultra-small Gd{sub 2}O{sub 3} by considering the decreasing factor (surface to volume ratio of the nanoparticles, S/V) and the increasing factor (water hydration number of the Gd{sup 3+} on Gd{sub 2}O{sub 3} surface, q), which offer a new look into the relaxivity studies of MRI contrast agents. Our research provides a new approach to preparing ultra-small Gd{sub 2}O{sub 3} of high r{sub 1} value by laser ablation in DEG and develops the understanding of high relaxivity of ultra-small Gd{sub 2}O{sub 3} MRI contrast agents.

  8. Ultrasmall near-infrared gold nanoclusters for tumor fluorescence imaging in vivo

    NASA Astrophysics Data System (ADS)

    Wu, Xu; He, Xiaoxiao; Wang, Kemin; Xie, Can; Zhou, Bing; Qing, Zhihe

    2010-10-01

    In this paper, we explore the possibility of using ultrasmall near-infrared (NIR) gold nanoclusters (AuNCs) as novel contrast imaging agents for tumor fluorescence imaging in vivo. The fluorescence imaging signal of the tail vein administrated AuNCs in living organisms can spectrally be well distinguished from the background with maximum emission wavelength at about 710 nm, and the high photostability of AuNCs promises continuous imaging in vivo. The uptake of AuNCs by the reticuloendothelial system is relatively low in comparison with other nanoparticle-based contrast imaging agents due to their ultrasmall hydrodynamic size (~2.7 nm). Through the body weight change analysis, the results show that the body weight of the mice administrated with AuNCs has not been changed obviously in comparison with that of the control mice injected with PBS. Furthermore, using MDA-MB-45 and Hela tumor xenograft models, in vivo and ex vivo imaging studies show that the ultrasmall NIR AuNCs are able to be highly accumulated in the tumor areas, thanks to the enhanced permeability and retention (EPR) effects. And the tumor-to-background ratio is about 15 for 6 h postinjection. The results indicate that the ultrasmall NIR AuNCs appear as very promising contrast imaging agents for in vivo fluorescence tumor imaging.

  9. Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles.

    PubMed

    Girgis, Emad; Wahsh, Mohamed Ms; Othman, Atef Gm; Bandhu, Lokeshwar; Rao, Kv

    2011-07-20

    The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

  10. Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles

    PubMed Central

    2011-01-01

    The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications. PMID:21774807

  11. Well-Combined Magnetically Separable Hybrid Cobalt Ferrite/Nitrogen-Doped Graphene as Efficient Catalyst with Superior Performance for Oxygen Reduction Reaction.

    PubMed

    Lu, Lei; Hao, Qingli; Lei, Wu; Xia, Xifeng; Liu, Peng; Sun, Dongping; Wang, Xin; Yang, Xujie

    2015-11-18

    Catalysts with low-cost, high activity and stability toward oxygen reduction reaction (ORR) are extremely desirable, but its development still remains a great challenge. Here, a novel magnetically separable hybrid of multimetal oxide, cobalt ferrite (CoFe2O4), anchored on nitrogen-doped reduced graphene oxide (CoFe2O4/NG) is prepared via a facile solvothermal method followed by calcination at 500 °C. The structure of CoFe2O4/NG and the interaction of both components are analyzed by several techniques. The possible formation of Co/Fe-N interaction in the CoFe2O4/NG catalyst is found. As a result, the well-combination of CoFe2O4 nanoparticles with NG and its improved crystallinity lead to a synergistic and efficient catalyst with high performance to ORR through a four-electron-transfer process in alkaline medium. The CoFe2O4/NG exhibits particularly comparable catalytic activity as commercial Pt/C catalyst, and superior stability against methanol oxidation and CO poisoning. Meanwhile, it has been proved that both nitrogen doping and the spinel structure of CoFe2O4 can have a significant contribution to the catalytic activity by contrast experiments. Multimetal oxide hybrid demonstrates better catalysis to ORR than a single metal oxide hybrid. All results make the low-cost and magnetically separable CoFe2O4/NG a promising alternative for costly platinum-based ORR catalyst in fuel cells and metal-air batteries.

  12. Magneto-electric Nanoparticles to Enable Field-controlled High-Specificity Drug Delivery to Eradicate Ovarian Cancer Cells

    NASA Astrophysics Data System (ADS)

    Guduru, Rakesh; Liang, Ping; Runowicz, Carolyn; Nair, Madhavan; Atluri, Venkata; Khizroev, Sakhrat

    2013-10-01

    The nanotechnology capable of high-specificity targeted delivery of anti-neoplastic drugs would be a significant breakthrough in Cancer in general and Ovarian Cancer in particular. We addressed this challenge through a new physical concept that exploited (i) the difference in the membrane electric properties between the tumor and healthy cells and (ii) the capability of magneto-electric nanoparticles (MENs) to serve as nanosized converters of remote magnetic field energy into the MENs' intrinsic electric field energy. This capability allows to remotely control the membrane electric fields and consequently trigger high-specificity drug uptake through creation of localized nano-electroporation sites. In in-vitro studies on human ovarian carcinoma cell (SKOV-3) and healthy cell (HOMEC) lines, we applied a 30-Oe d.c. field to trigger high-specificity uptake of paclitaxel loaded on 30-nm CoFe2O4@BaTiO3 MENs. The drug penetrated through the membrane and completely eradicated the tumor within 24 hours without affecting the normal cells.

  13. Enhancement of specific absorption rate by exchange coupling of the core-shell structure of magnetic nanoparticles for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Phadatare, M. R.; Meshram, J. V.; Gurav, K. V.; Hyeok Kim, Jin; Pawar, S. H.

    2016-03-01

    Conversion of electromagnetic energy into heat by nanoparticles (NPs) has the potential to be a powerful, non-invasive technique for biomedical applications such as magnetic fluid hyperthermia, drug release, disease treatment and remote control of single cell functions, but poor conversion efficiencies have hindered practical applications so far. In this paper, an attempt has been made to increase the efficiency of magnetic thermal induction by NPs. To increase the efficiency of magnetic thermal induction by NPs, one can take advantage of the exchange coupling between a magnetically hard core and magnetically soft shell to tune the magnetic properties of the NP and maximize the specific absorption rate, which is the gauge of conversion efficiency. In order to examine the tunability of magnetocrystalline anisotropy and its magnetic heating power, a representative magnetically hard material (CoFe2O4) has been coupled to a soft material (Ni0.5Zn0.5Fe2O4). The synthesized NPs show specific absorption rates that are of an order of magnitude larger than the conventional one.

  14. Ultra-small particles of iron oxide as peroxidase for immunohistochemical detection

    NASA Astrophysics Data System (ADS)

    Wu, Yihang; Song, Mengjie; Xin, Zhuang; Zhang, Xiaoqing; Zhang, Yu; Wang, Chunyu; Li, Suyi; Gu, Ning

    2011-06-01

    Dimercaptosuccinic acid (DMSA) modified ultra-small particles of iron oxide (USPIO) were synthesized through a two-step process. The first step: oleic acid (OA) capped Fe3O4 (OA-USPIO) were synthesized by a novel oxidation coprecipitation method in H2O/DMSO mixing system, where DMSO acts as an oxidant simultaneously. The second step: OA was replaced by DMSA to obtain water-soluble nanoparticles. The as-synthesized nanoparticles were characterized by TEM, FTIR, TGA, VSM, DLS, EDS and UV-vis. Hydrodynamic sizes and Peroxidase-like catalytic activity of the nanoparticles were investigated. The hydrodynamic sizes of the nanoparticles (around 24.4 nm) were well suited to developing stable nanoprobes for bio-detection. The kinetic studies were performed to quantitatively evaluate the catalytic ability of the peroxidase-like nanoparticles. The calculated kinetic parameters indicated that the DMSA-USPIO possesses high catalytic activity. Based on the high activity, immunohistochemical experiments were established: using low-cost nanoparticles as the enzyme instead of expensive HRP, Nimotuzumab was conjugated onto the surface of the nanoparticles to construct a kind of ultra-small nanoprobe which was employed to detect epidermal growth factor receptor (EGFR) over-expressed on the membrane of esophageal cancer cell. The proper sizes of the probes and the result of membranous immunohistochemical staining suggest that the probes can be served as a useful diagnostic reagent for bio-detection.

  15. Ultrasmall dopamine-coated nanogolds: preparation, characteristics, and CT imaging

    PubMed Central

    Yu, Yao; Wu, Youshen; Liu, JiaJun; Zhan, Yonghua; Wu, Daocheng

    2016-01-01

    ABSTRACT Water-dispersible ultrasmall nanogolds (WDU AuNPs) and their dopamine-coated nanogolds (WDU AuNPs@DPAs) were prepared by a reduction method with sodium borohydride as a reducing agent and a stabilised agent of 2-mercaptosuccinic acid in aqueous solution. The effects of these nanoparticles on computed tomography (CT) imaging were evaluated. The size distributions and Zeta potential of the nanoparticles were measured with a Malvern size analyser, and nanoparticle morphology was observed by transmission electron microscopy. These characteristics were confirmed by Fourier transform spectroscopy and ultraviolet/visible spectra. It was found that WDU AuNPs@DPAs were 5.4 nm in size with clear core–shell structure. The 3-(4, 5-Dimethyl-2-thiazolyl)-2, 5-diphenyltetrazolium bromide assay results showed that the WDU AuNPs and WDU AuNPs@DPAs were hypotoxic to different cells. The WDU AuNPs@DPAs showed a much longer circulation time and a larger CT attenuation coefficient than iohexol and could be excreted by the kidney and bladder. These nanoparticles showed considerable potential for future application in CT imaging. PMID:27366201

  16. Pinned emission from ultrasmall cadmium selenide nanocrystals.

    PubMed

    Dukes, Albert D; Schreuder, Michael A; Sammons, Jessica A; McBride, James R; Smith, Nathanael J; Rosenthal, Sandra J

    2008-09-28

    We report pinning of the emission spectrum in ultrasmall CdSe nanocrystals with a diameter of 1.7 nm and smaller. It was observed that the first emission feature ceased to blueshift once the band edge absorption reached 420 nm, though the band edge absorption continued to blueshift with decreasing nanocrystal diameter.

  17. Structural, electrical, magnetic and dielectric properties of rare-earth substituted cobalt ferrites nanoparticles synthesized by the co-precipitation method

    NASA Astrophysics Data System (ADS)

    Nikumbh, A. K.; Pawar, R. A.; Nighot, D. V.; Gugale, G. S.; Sangale, M. D.; Khanvilkar, M. B.; Nagawade, A. V.

    2014-04-01

    Pure nanoparticles of the rare-earth substituted cobalt ferrites CoRExFe2-xO4 (where RE=Nd, Sm and Gd and x=0.1 and 0.2) were prepared by the chemical co-precipitation method. X-ray diffraction, Transmission electron microscopy (TEM), d.c. electrical conductivity, Magnetic hysteresis and Thermal analysis are utilized in order to study the effect of variation in the rare-earth substitution and its impact on particle size, magnetic properties like MS, HC and Curie temperature. The phase identification of the materials by X-ray diffraction reveals the single-phase nature of the materials. The lattice parameter increased with rare-earth content for x≤0.2. The Transmission electron micrographs of Nd-, Sm- and Gd-substituted CoFe2O4 exhibit the particle size 36.1 to 67.8 nm ranges. The data of temperature variation of the direct current electrical conductivity showed definite breaks, which corresponds to ferrimagnetic to paramagnetic transitions. The thermoelectric power for all compound are positive over the whole range of temperature. The dielectric constant decreases with frequency and rare-earth content for the prepared samples. The magnetic properties of rare-earth substituted cobalt ferrites showed a definite hysteresis loop at room temperature. The reduction of coercive force, saturation magnetization, ratio MR/MS and magnetic moments may be due to dilution of the magnetic interaction.

  18. Optimizing magnetic anisotropy of La1-xSrxMnO3 nanoparticles for hyperthermia applications

    NASA Astrophysics Data System (ADS)

    Rashid, Amin ur; Manzoor, Sadia

    2016-12-01

    Maximizing the magnetothermal response of magnetic nanoparticles (MNP's) for hyperthermia applications is a complex problem, because it depends sensitively upon interrelated magnetic and structural parameters. The task is somewhat simpler for systems with fixed composition, e.g. Fe3O4 or CoFe2O4, in which the particle size is the only means of modifying the magnetic anisotropy, and hence the magnetothermal response. In the La1-xSrxMnO3 system however, the magnetic interactions as well as the particle size both change with the Sr concentration x, which makes it a much more complex system for which to optimize the hyperthermia response. We have investigated the effect of magnetic anisotropy on the magnetothermal response of La1-xSrxMnO3 nanoparticles as a function of the particle size as well as the Sr concentration x where 0.20≤x≤0.45. The optimum particle size range is 25-30 nm for all concentrations, where the specific absorption rate (SAR) has a maximum. The linear response theory (LRT) has been applied to this system and good agreement has been found between the experimental and theoretically determined values of the SAR for samples lying in the single domain regime and having large enough anisotropy energies. The agreement is much better for the intermediate concentrations of 0.27 and 0.33, because of their large anisotropy as compared to other concentrations. It is concluded that the LRT can be successfully used to predict the SAR of these nanoparticles, provided they possess large enough effective anisotropies. Values of the ILP have been obtained for these samples and found to be comparable to those of magnetite and some commercial ferrofluids.

  19. Controlling transport and chemical functionality of magnetic nanoparticles.

    PubMed

    Latham, Andrew H; Williams, Mary Elizabeth

    2008-03-01

    A wide range of metal, magnetic, semiconductor, and polymer nanoparticles with tunable sizes and properties can be synthesized by wet-chemical techniques. Magnetic nanoparticles are particularly attractive because their inherent superparamagnetic properties make them desirable for medical imaging, magnetic field assisted transport, and separations and analyses. With such applications on the horizon, synthetic routes for quickly and reliably rendering magnetic nanoparticle surfaces chemically functional have become an increasingly important focus. This Account describes common synthetic routes for making and functionalizing magnetic nanoparticles and discusses initial applications in magnetic field induced separations. The most widely studied magnetic nanoparticles are iron oxide (Fe2O3 and Fe3O4), cobalt ferrite (CoFe 2O4), iron platinum (FePt), and manganese ferrite (MnFe 2O4), although others have been investigated. Magnetic nanoparticles are typically prepared under either high-temperature organic phase or aqueous conditions, producing particles with surfaces that are stabilized by attached surfactants or associated ions. Although it requires more specialized glassware, high-temperature routes are generally preferred when a high degree of stability and low particle size dispersity is desired. Particles can be further modified with a secondary metal or polymer to create core-shell structures. The outer shells function as protective layers for the inner metal cores and alter the surface chemistry to enable postsynthetic modification of the surfactant chemistry. Efforts by our group as well as others have centered on pathways to yield nanoparticles with surfaces that are both easily functionalized and tunable in terms of the number and variety of attached species. Ligand place-exchange reactions have been shown quite successful for exchanging silanes, acids, thiols, and dopamine ligands onto the surfaces of some magnetic particles. Poly(ethylene oxide

  20. Evaluation of humidity sensing properties of TMBHPET thin film embedded with spinel cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Zafar, Qayyum; Azmer, Mohamad Izzat; Al-Sehemi, Abdullah G.; Al-Assiri, Mohammad S.; Kalam, Abul; Sulaiman, Khaulah

    2016-07-01

    In this study, we report the enhanced sensing parameters of previously reported TMBHPET-based humidity sensor. Significant improved sensing performance has been demonstrated by coupling of TMBHPET moisture sensing thin film with cobalt ferrite nanoparticles (synthesized by eco-benign ultrasonic method). The mean size of CoFe2O4 nanoparticles has been estimated to be 6.5 nm. It is assumed that the thin film of organic-ceramic hybrid matrix (TMBHPET:CoFe2O4) is a potential candidate for humidity sensing utility by virtue of its high specific surface area and porous surface morphology (as evident from TEM, FESEM, and AFM images). The hybrid suspension has been drop-cast onto the glass substrate with preliminary deposited coplanar aluminum electrodes separated by 40 µm distance. The influence of humidity on the capacitance of the hybrid humidity sensor (Al/TMBHPET:CoFe2O4/Al) has been investigated at three different frequencies of the AC applied voltage ( V rms 1 V): 100 Hz, 1 kHz, and 10 kHz. It has been observed that at 100 Hz, under a humidity of 99 % RH, the capacitance of the sensor increased by 2.61 times, with respect to 30 % RH condition. The proposed sensor exhibits significantly improved sensitivity 560 fF/ % RH at 100 Hz, which is nearly 7.5 times as high as that of pristine TMBHPET-based humidity sensor. Further, the capacitive sensor exhibits improved dynamic range (30-99 % RH), small hysteresis ( 2.3 %), and relatively quicker response and recovery times ( 12 s, 14 s, respectively). It is assumed that the humidity response of the sensor is associated with the diffusion kinetics of water vapors and doping of the semiconductor nanocomposite by water molecules.

  1. Atomic scale dynamics of ultrasmall germanium clusters.

    PubMed

    Bals, S; Van Aert, S; Romero, C P; Lauwaet, K; Van Bael, M J; Schoeters, B; Partoens, B; Yücelen, E; Lievens, P; Van Tendeloo, G

    2012-06-12

    Starting from the gas phase, small clusters can be produced and deposited with huge flexibility with regard to composition, materials choice and cluster size. Despite many advances in experimental characterization, a detailed morphology of such clusters is still lacking. Here we present an atomic scale observation as well as the dynamical behaviour of ultrasmall germanium clusters. Using quantitative scanning transmission electron microscopy in combination with ab initio calculations, we are able to characterize the transition between different equilibrium geometries of a germanium cluster consisting of less than 25 atoms. Seven-membered rings, trigonal prisms and some smaller subunits are identified as possible building blocks that stabilize the structure.

  2. RGD-conjugated iron oxide magnetic nanoparticles for magnetic resonance imaging contrast enhancement and hyperthermia.

    PubMed

    Zheng, S W; Huang, M; Hong, R Y; Deng, S M; Cheng, L F; Gao, B; Badami, D

    2014-03-01

    The purpose of this study was to develop a specific targeting magnetic nanoparticle probe for magnetic resonance imaging and therapy in the form of local hyperthermia. Carboxymethyl dextran-coated ultrasmall superparamagnetic iron oxide nanoparticles with carboxyl groups were coupled to cyclic arginine-glycine-aspartic peptides for integrin α(v)β₃ targeting. The particle size, magnetic properties, heating effect, and stability of the arginine-glycine-aspartic-ultrasmall superparamagnetic iron oxide were measured. The arginine-glycine-aspartic-ultrasmall superparamagnetic iron oxide demonstrates excellent stability and fast magneto-temperature response. Magnetic resonance imaging signal intensity of Bcap37 cells incubated with arginine-glycine-aspartic-ultrasmall superparamagnetic iron oxide was significantly decreased compared with that incubated with plain ultrasmall superparamagnetic iron oxide. The preferential uptake of arginine-glycine-aspartic-ultrasmall superparamagnetic iron oxide by target cells was further confirmed by Prussian blue staining and confocal laser scanning microscopy.

  3. Study of magnetic and structural properties of ferrofluids based on cobalt-zinc ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    López, J.; González-Bahamón, L. F.; Prado, J.; Caicedo, J. C.; Zambrano, G.; Gómez, M. E.; Esteve, J.; Prieto, P.

    2012-02-01

    Ferrofluids are colloidal systems composed of a single domain of magnetic nanoparticles with a mean diameter around 30 nm, dispersed in a liquid carrier. Magnetic Co(1-x)ZnxFe2O4 (x=0.25, 0.50, 0.75) ferrite nanoparticles were prepared via co-precipitation method from aqueous salt solutions in an alkaline medium. The composition and structure of the samples were characterized through Energy Dispersive X-ray Spectroscopy and X-ray diffraction, respectively. Transmission Electron Microscopy (TEM) studies permitted determining nanoparticle size; grain size of nanoparticle conglomerates was established via Atomic Force Microscopy. The magnetic behavior of ferrofluids was characterized by Vibrating Sample Magnetometer (VSM); and finally, a magnetic force microscope was used to visualize the magnetic domains of Co(1-x)ZnxFe2O4 nanoparticles. X-ray diffraction patterns of Co(1-x)ZnxFe2O4 show the presence of the most intense peak corresponding to the (311) crystallographic orientation of the spinel phase of CoFe2O4. Fourier Transform Infrared Spectroscopy confirmed the presence of the bonds associated to the spinel structures; particularly for ferrites. The mean size of the crystallite of nanoparticles determined from the full-width at half maximum of the strongest reflection of the (311) peak by using the Scherrer approximation diminished from (9.5±0.3) nm to (5.4±0.2) nm when the Zn concentration increases from 0.21 to 0.75. The size of the Co-Zn ferrite nanoparticles obtained by TEM is in good agreement with the crystallite size calculated from X-ray diffraction patterns, using Scherer's formula. The magnetic properties investigated with the aid of a VSM at room temperature presented super-paramagnetic behavior, determined by the shape of the hysteresis loop. In this study, we established that the coercive field of Co(1-x)ZnxFe2O4 magnetic nanoparticles, the crystal and nanoparticle sizes determined by X-ray Diffraction and TEM, respectively, decrease with the

  4. High β phase content in PVDF/CoFe2O4 nanocomposites induced by DC magnetic fields

    NASA Astrophysics Data System (ADS)

    Jiang, Shenglin; Wan, Hongyan; Liu, Huan; Zeng, Yike; Liu, Jianguo; Wu, Yunyi; Zhang, Guangzu

    2016-09-01

    Flexible ferroelectrics being exploited as energy harvesting and conversion materials are highly desirable for wearable and skin-mountable electronic devices. As one of the most typical ferroelectric polymers, poly(vinylidene fluoride) (PVDF) has been widely used in modern electronic systems and devices, whose ferroelectric performance relies heavily on its β phase content. In this work, to achieve high-β-phase-content PVDF, we first introduced CoFe2O4 nanoparticles into PVDF. With the incorporation of CoFe2O4 nanoparticles used as an effective polymer nucleation agent, the percentage of the β phase in the PVDF has been significantly enhanced, e.g., 84% in the nanocomposite with 5 wt. % CoFe2O4 versus only 73% in the pure PVDF. In order to further increase the β phase content in PVDF, we subsequently proposed an easily realized strategy. By applying DC magnetic fields during the solution-casting process of the PVDF/CoFe2O4 nanocomposites, a further improved β phase content as high as 95% can be achieved. The further improvement of the β phase content is attributable to the tensile stress at the CoFe2O4/PVDF interfaces created by the coupling of magnetic field and CoFe2O4 by means of the magnetostriction effect. The high β-phase content makes the PVDF/CoFe2O4 nanocomposites a promising candidate for flexible and wearable electronic device applications.

  5. Ultrasmall all-optical plasmonic switch and its application to superresolution imaging

    PubMed Central

    Wu, Hsueh-Yu; Huang, Yen-Ta; Shen, Po-Ting; Lee, Hsuan; Oketani, Ryosuke; Yonemaru, Yasuo; Yamanaka, Masahito; Shoji, Satoru; Lin, Kung-Hsuan; Chang, Chih-Wei; Kawata, Satoshi; Fujita, Katsumasa; Chu, Shi-Wei

    2016-01-01

    Because of their exceptional local-field enhancement and ultrasmall mode volume, plasmonic components can integrate photonics and electronics at nanoscale, and active control of plasmons is the key. However, all-optical modulation of plasmonic response with nanometer mode volume and unity modulation depth is still lacking. Here we show that scattering from a plasmonic nanoparticle, whose volume is smaller than 0.001 μm3, can be optically switched off with less than 100 μW power. Over 80% modulation depth is observed, and shows no degradation after repetitive switching. The spectral bandwidth approaches 100 nm. The underlying mechanism is suggested to be photothermal effects, and the effective single-particle nonlinearity reaches nearly 10−9 m2/W, which is to our knowledge the largest record of metallic materials to date. As a novel application, the non-bleaching and unlimitedly switchable scattering is used to enhance optical resolution to λ/5 (λ/9 after deconvolution), with 100-fold less intensity requirement compared to similar superresolution techniques. Our work not only opens up a new field of ultrasmall all-optical control based on scattering from a single nanoparticle, but also facilitates superresolution imaging for long-term observation. PMID:27063920

  6. Magnetic behavior of core shell particles

    NASA Astrophysics Data System (ADS)

    Lin, Chun-Rong; Wang, Cheng-Chien; Chen, I.-Han

    2006-09-01

    We have prepared composite magnetic core-shell particles using the process of soap-free emulsion polymerization and the co-precipitation method. The shell of the synthesized composite sphere is cobalt ferrite (CoFe 2O 4) nanoparticles and the core consists of poly(styrene-co-methacrylic acid) polymer. The mean crystallite sizes of the coated CoFe 2O 4 nanoparticles were controlled in the range of 2.4-6.7 nm by the concentration of [NH 4+] and heated temperature. The magnetic properties of the core-shell spherical particles can go from superparamagnetic to ferromagnetic behavior depending on the crystalline sizes of CoFe 2O 4.

  7. Design of an ultrasmall aspect ratio concentrator

    NASA Astrophysics Data System (ADS)

    Cheng, Ying; Fang, Fengzhou; Zhang, Xiaodong

    2014-11-01

    The concentrated photovoltaic (CPV) can be employed to improve the efficiency of solar cells and reduce the system cost of power generation, which is the primary part of the CPV system. Based on the demands for the concentrators to have an ultrathin and ultralight design, a design of ultrasmall aspect ratio concentrators is proposed. The concentrator is formed by a lens array and a freeform reflector to precisely control the light. The solar cell is placed at the side of the concentrator, which greatly reduces the overall thickness of the concentrator. The design can reduce the aspect ratio of concentrator by a considerable amount. The freeform reflector can shape the light beam and achieve a uniform distribution of light energy.

  8. Studying the effect of Zn-substitution on the magnetic and hyperthermic properties of cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Mameli, V.; Musinu, A.; Ardu, A.; Ennas, G.; Peddis, D.; Niznansky, D.; Sangregorio, C.; Innocenti, C.; Thanh, Nguyen T. K.; Cannas, C.

    2016-05-01

    The possibility to finely control nanostructured cubic ferrites (MIIFe2O4) paves the way to design materials with the desired magnetic properties for specific applications. However, the strict and complex interrelation among the chemical composition, size, polydispersity, shape and surface coating renders their correlation with the magnetic properties not trivial to predict. In this context, this work aims to discuss the magnetic properties and the heating abilities of Zn-substituted cobalt ferrite nanoparticles with different zinc contents (ZnxCo1-xFe2O4 with 0 < x < 0.6), specifically prepared with similar particle sizes (~7 nm) and size distributions having the crystallite size (~6 nm) and capping agent amount of 15%. All samples have high saturation magnetisation (Ms) values at 5 K (>100 emu g-1). The increase in the zinc content up to x = 0.46 in the structure has resulted in an increase of the saturation magnetisation (Ms) at 5 K. High Ms values have also been revealed at room temperature (~90 emu g-1) for both CoFe2O4 and Zn0.30Co0.70Fe2O4 samples and their heating ability has been tested. Despite a similar saturation magnetisation, the specific absorption rate value for the cobalt ferrite is three times higher than the Zn-substituted one. DC magnetometry results were not sufficient to justify these data, the experimental conditions of SAR and static measurements being quite different. The synergic combination of DC with AC magnetometry and 57Fe Mössbauer spectroscopy represents a powerful tool to get new insights into the design of suitable heat mediators for magnetic fluid hyperthermia.The possibility to finely control nanostructured cubic ferrites (MIIFe2O4) paves the way to design materials with the desired magnetic properties for specific applications. However, the strict and complex interrelation among the chemical composition, size, polydispersity, shape and surface coating renders their correlation with the magnetic properties not trivial to predict

  9. Brine assemblages of ultrasmall microbial cells within the ice cover of Lake Vida, Antarctica.

    PubMed

    Kuhn, Emanuele; Ichimura, Andrew S; Peng, Vivian; Fritsen, Christian H; Trubl, Gareth; Doran, Peter T; Murray, Alison E

    2014-06-01

    The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (≤0.2-μm) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 μm in length. Fluorescent DNA staining, electron microscopy (EM) observations, elemental analysis, and extraction of high-molecular-weight genomic DNA indicated that a significant portion of these ultrasmall particles are cells. A continuous electron-dense layer surrounding a less electron-dense region was observed by EM, indicating the presence of a biological membrane surrounding a cytoplasm. The ultrasmall cells are 0.192 ± 0.065 μm, with morphology characteristic of coccoid and diplococcic bacterial cells, often surrounded by iron-rich capsular structures. EM observations also detected the presence of smaller unidentified nanoparticles of 0.020 to 0.140 μm among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-μm-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-μm-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-μm-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-μm-size fraction led to the isolation of Actinobacteria-affiliated genera Microbacterium and Kocuria. Based on phylogenetic relatedness and microscopic observations, we hypothesize that the ultrasmall cells in Lake Vida brine are ultramicrocells that are likely in a reduced size state as a result of environmental stress or life cycle-related conditions.

  10. Brine Assemblages of Ultrasmall Microbial Cells within the Ice Cover of Lake Vida, Antarctica

    PubMed Central

    Kuhn, Emanuele; Ichimura, Andrew S.; Peng, Vivian; Fritsen, Christian H.; Trubl, Gareth; Doran, Peter T.

    2014-01-01

    The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (≤0.2-μm) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 μm in length. Fluorescent DNA staining, electron microscopy (EM) observations, elemental analysis, and extraction of high-molecular-weight genomic DNA indicated that a significant portion of these ultrasmall particles are cells. A continuous electron-dense layer surrounding a less electron-dense region was observed by EM, indicating the presence of a biological membrane surrounding a cytoplasm. The ultrasmall cells are 0.192 ± 0.065 μm, with morphology characteristic of coccoid and diplococcic bacterial cells, often surrounded by iron-rich capsular structures. EM observations also detected the presence of smaller unidentified nanoparticles of 0.020 to 0.140 μm among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-μm-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-μm-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-μm-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-μm-size fraction led to the isolation of Actinobacteria-affiliated genera Microbacterium and Kocuria. Based on phylogenetic relatedness and microscopic observations, we hypothesize that the ultrasmall cells in Lake Vida brine are ultramicrocells that are likely in a reduced size state as a result of environmental stress or life cycle-related conditions. PMID:24727273

  11. Studying the effect of Zn-substitution on the magnetic and hyperthermic properties of cobalt ferrite nanoparticles.

    PubMed

    Mameli, V; Musinu, A; Ardu, A; Ennas, G; Peddis, D; Niznansky, D; Sangregorio, C; Innocenti, C; Thanh, Nguyen T K; Cannas, C

    2016-05-21

    The possibility to finely control nanostructured cubic ferrites (M(II)Fe2O4) paves the way to design materials with the desired magnetic properties for specific applications. However, the strict and complex interrelation among the chemical composition, size, polydispersity, shape and surface coating renders their correlation with the magnetic properties not trivial to predict. In this context, this work aims to discuss the magnetic properties and the heating abilities of Zn-substituted cobalt ferrite nanoparticles with different zinc contents (ZnxCo1-xFe2O4 with 0 < x < 0.6), specifically prepared with similar particle sizes (∼7 nm) and size distributions having the crystallite size (∼6 nm) and capping agent amount of 15%. All samples have high saturation magnetisation (Ms) values at 5 K (>100 emu g(-1)). The increase in the zinc content up to x = 0.46 in the structure has resulted in an increase of the saturation magnetisation (Ms) at 5 K. High Ms values have also been revealed at room temperature (∼90 emu g(-1)) for both CoFe2O4 and Zn0.30Co0.70Fe2O4 samples and their heating ability has been tested. Despite a similar saturation magnetisation, the specific absorption rate value for the cobalt ferrite is three times higher than the Zn-substituted one. DC magnetometry results were not sufficient to justify these data, the experimental conditions of SAR and static measurements being quite different. The synergic combination of DC with AC magnetometry and (57)Fe Mössbauer spectroscopy represents a powerful tool to get new insights into the design of suitable heat mediators for magnetic fluid hyperthermia.

  12. Novel and easy access to highly luminescent Eu and Tb doped ultra-small CaF2, SrF2 and BaF2 nanoparticles - structure and luminescence.

    PubMed

    Ritter, Benjamin; Haida, Philipp; Fink, Friedrich; Krahl, Thoralf; Gawlitza, Kornelia; Rurack, Knut; Scholz, Gudrun; Kemnitz, Erhard

    2017-02-28

    A universal fast and easy access at room temperature to transparent sols of nanoscopic Eu(3+) and Tb(3+) doped CaF2, SrF2 and BaF2 particles via the fluorolytic sol-gel synthesis route is presented. Monodisperse quasi-spherical nanoparticles with sizes of 3-20 nm are obtained with up to 40% rare earth doping showing red or green luminescence. In the beginning luminescence quenching effects are only observed for the highest content, which demonstrates the unique and outstanding properties of these materials. From CaF2:Eu10 via SrF2:Eu10 to BaF2:Eu10 a steady increase of the luminescence intensity and lifetime occurs by a factor of ≈2; the photoluminescence quantum yield increases by 29 to 35% due to the lower phonon energy of the matrix. The fast formation process of the particles within fractions of seconds is clearly visualized by exploiting appropriate luminescence processes during the synthesis. Multiply doped particles are also available by this method. Fine tuning of the luminescence properties is achieved by variation of the Ca-to-Sr ratio. Co-doping with Ce(3+) and Tb(3+) results in a huge increase (>50 times) of the green luminescence intensity due to energy transfer Ce(3+) → Tb(3+). In this case, the luminescence intensity is higher for CaF2 than for SrF2, due to a lower spatial distance of the rare earth ions.

  13. Ultrasmall, water dispersible, TWEEN80 modified Yb:Er:NaGd(WO4)2 nanoparticles with record upconversion ratiometric thermal sensitivity and their internalization by mesenchymal stem cells.

    PubMed

    Cascales, Concepcion; Paino, Carlos; Bazán, Eulalia; Zaldo, Carlos

    2017-03-21

    This work presents the synthesis by coprecipitation of diamond shaped Yb:Er:NaGd(WO4)2 crystalline nanoparticles (NPs) with diagonal dimensions in the 5-7 nm × 10-12 nm range which have been modified with TWEEN80 for their dispersion in water, and their interaction with mesenchymal stem cells (MSCs) proposed as cellular NP vehicles. These NPs belong to a large family of tetragonal Yb:Er:NaT(XO4)2 (T=Y, La, Gd, Lu; X= Mo, W) compounds with green (2H11/2+4S3/24I15/2) Er-related upconversion (UC) efficiency comparable to that of Yb:Er:β-NaYF4 reference compound, but with a ratiometric thermal sensitivity (S) 2.5-3.5 times larger than that of the fluoride. At the temperature range of interest for biomedical applications (~293-317 K / 20-44 ºC) S= 108-118 × 10-4 K-1 for 20at%Yb:5at%Er:NaGd(WO4)2 NPs, being the largest values so far reported using the 2H11/2/4S3/2 Er intensity ratiometric method. Cultured MSCs, incubated with these water NP emulsions, internalize and accumulate the NPs enclosed in endosomes/lysosomes. Incubations with up to 10 μg of NPs per ml of culture medium maintain cellular metabolism at 72 h. A thermal assisted excitation path is discussed as responsible for the UC behavior of Yb:Er:NaT(XO4)2 compounds.

  14. THE THICKNESS DEPENDENCE OF OXYGEN PERMEABILITY IN SOL-GEL DERIVED CGO-COFE2O4 THIN FILMS ON POROUS CERAMIC SUBSTRATES: A SPUTTERED BLOCKING LAYER FOR THICKNESS CONTROL

    SciTech Connect

    Brinkman, K

    2009-01-08

    Mixed conductive oxides are a topic of interest for applications in oxygen separation membranes as well as use in producing hydrogen fuel through the partial oxidation of methane. The oxygen flux through the membrane is governed both by the oxygen ionic conductivity as well as the material's electronic conductivity; composite membranes like Ce{sub 0.8}Gd{sub 0.2}O{sub 2-{delta}} (CGO)-CoFe{sub 2}O{sub 4} (CFO) use gadolinium doped ceria oxides as the ionic conducting material combined with cobalt iron spinel which serves as the electronic conductor. In this study we employ {approx} 50 nm sputtered CeO{sub 2} layers on the surface of porous CGO ceramic substrates which serve as solution 'blocking' layers during the thin film fabrication process facilitating the control of film thickness. Films with thickness of {approx} 2 and 4 microns were prepared by depositing 40 and 95 separate sol-gel layers respectively. Oxygen flux measurements indicated that the permeation increased with decreasing membrane thickness; thin film membrane with thickness on the micron level showed flux values an order of magnitude greater (0.03 {micro}mol/cm{sup 2} s) at 800 C as compared to 1mm thick bulk ceramic membranes (0.003 {micro}mol/cm{sup 2}).

  15. Synthesis and characterization of a mixture of CoFe2O4 and MgFe2O4 from layered double hydroxides: Band gap energy and magnetic responses

    NASA Astrophysics Data System (ADS)

    Agú, Ulises A.; Oliva, Marcos I.; Marchetti, Sergio G.; Heredia, Angélica C.; Casuscelli, Sandra G.; Crivello, Mónica E.

    2014-11-01

    A mixture of nanocrystals of cobalt ferrite and magnesium ferrite was obtained from Layered Double Hydroxides (LDH) through a co-precitation method with a theoretical molar ratio M2+:Fe3+=3:1, where M2+represents Mg2+ and/or Co2+. The molar ratios between Co2+:Fe3+ were 0.0 (0Co), 0.2 (5Co), and 0.4 (10Co). In order to assess the effect on the properties of the LDH and their oxides, the molar percentages were 0, 5 and 10%. Two different synthesis methods were evaluated; (i) ageing at room temperature (rt), and (ii) hydrothermal ageing at 200 °C in autoclave (ht), both methods needed 15 h of ageing. Then, these LDH were calcined in air atmosphere at 550 °C for 10 h. The calcined materials were characterized by X-ray diffraction (XRD), thermogravymetric analysis (TGA), temperature-programmed reduction (TPR), infrared spectroscopy with Fourier transform (FTIR), Diffuse Reflectance UV-visible spectroscopy (UV-vis-DRS), Mössbauer spectroscopy and inductively coupled plasma optical emission spectroscopy (ICP-OES). The magnetic response was analyzed using a vibrating sample magnetometer (VSM). The band gap energy of the iron oxides was determined through the UV-vis-DRS analysis. Through these studies it was possible to identify the presence of a mixture of cobalt ferrite and magnesium ferrite. Samples did not show hematite and cobalt oxides, but the presence of MgO in the periclase phase was determined. This magnesium oxide promoted a good dispersion of the ferrites. Moreover, when a single ferrite phase of Co or Mg was formed, a diminution of the crystal size with consequent enlarged values of band gap energy was observed. Thus, materials synthesized by room temperature ageing promoted the superparamagnetic behaviour of samples, attributed to the content of the cobalt ferrite structure in nanocrystals. In regard to the estimated band gap energy, all samples exhibited low levels. These results indicate that these solids would be suitable for photocatalysts use in all visible light range, and that they could be easily removed from the reaction medium by a simple magnetic separation procedure.

  16. Cobalt iron oxide nanoparticles induce cytotoxicity and regulate the apoptotic genes through ROS in human liver cells (HepG2).

    PubMed

    Ahamed, Maqusood; Akhtar, Mohd Javed; Khan, M A Majeed; Alhadlaq, Hisham A; Alshamsan, Aws

    2016-12-01

    Cobalt iron oxide (CoFe2O4) nanoparticles (CIO NPs) have been one of the most widely explored magnetic NPs because of their excellent chemical stability, mechanical hardness and heat generating potential. However, there is limited information concerning the interaction of CIO NPs with biological systems. In this study, we investigated the reactive oxygen species (ROS) mediated cytotoxicity and apoptotic response of CIO NPs in human liver cells (HepG2). Diameter of crystalline CIO NPs was found to be 23nm with a band gap of 1.97eV. CIO NPs induced cell viability reduction and membrane damage, and degree of induction was dose- and time-dependent. CIO NPs were also found to induce oxidative stress revealed by induction of ROS, depletion of glutathione and lower activity of superoxide dismutase enzyme. Real-time PCR data has shown that mRNA level of tumor suppressor gene p53 and apoptotic genes (bax, CASP3 and CASP9) were higher, while the expression level of anti-apoptotic gene bcl-2 was lower in cells following exposure to CIO NPs. Activity of caspase-3 and caspase-9 enzymes was also higher in CIO NPs exposed cells. Furthermore, co-exposure of N-acetyl-cysteine (ROS scavenger) efficiently abrogated the modulation of apoptotic genes along with the prevention of cytotoxicity caused by CIO NPs. Overall, we observed that CIO NPs induced cytotoxicity and apoptosis in HepG2 cells through ROS via p53 pathway. This study suggests that toxicity mechanisms of CIO NPs should be further investigated in animal models.

  17. Magnetic ionic liquids produced by the dispersion of magnetic nanoparticles in 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf2).

    PubMed

    Medeiros, Anderson M M S; Parize, Alexandre L; Oliveira, Vanda M; Neto, Brenno A D; Bakuzis, Andris F; Sousa, Marcelo H; Rossi, Liane M; Rubim, Joel C

    2012-10-24

    ̀This paper reports on the advancement of magnetic ionic liquids (MILs) as stable dispersions of surface-modified γ-Fe(2)O(3), Fe(3)O(4), and CoFe(2)O(4) magnetic nanoparticles (MNPs) in a hydrophobic ionic liquid, 1-n-butyl 3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf(2)). The MNPs were obtained via coprecipitation and were characterized using powder X-ray diffraction, transmission electron microscopy, Raman spectroscopy and Fourier transform near-infrared (FT-NIR) spectroscopy, and magnetic measurements. The surface-modified MNPs (SM-MNPs) were obtained via the silanization of the MNPs with the aid of 1-butyl-3-[3-(trimethoxysilyl)propyl]imidazolium chloride (BMSPI.Cl). The SM-MNPs were characterized by Raman spectroscopy and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and by magnetic measurements. The FTIR-ATR spectra of the SM-MNPs exhibited characteristic absorptions of the imidazolium and those of the Fe-O-Si-C moieties, confirming the presence of BMSPI.Cl on the MNP surface. Thermogravimetric analysis (TGA) showed that the SM-MNPs were modified by at least one BMSPI.Cl monolayer. The MILs were characterized using Raman spectroscopy, differential scanning calorimetry (DSC), and magnetic measurements. The Raman and DSC results indicated an interaction between the SM-MNPs and the IL. This interaction promotes the formation of a supramolecular structure close to the MNP surface that mimics the IL structure and is responsible for the stability of the MIL. Magnetic measurements of the MILs indicated no hysteresis. Superparamagnetic behavior and a saturation magnetization of ~22 emu/g could be inferred from the magnetic measurements of a sample containing 50% w/w γ-Fe(2)O(3) SM-MNP/BMI.NTf(2).

  18. Investigation of phase formation of (Zn, Mg)0.5Co0.5Fe2O4 nanoferrites

    NASA Astrophysics Data System (ADS)

    Msomi, J. Z.; Dlamini, W. B.; Moyo, T.; Ezekiel, P.

    2015-01-01

    Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 nanoparticles have been prepared through high energy ball milling of single phase mixtures of ZnFe2O4 and CoFe2O4 or MgFe2O4 and CoFe2O4 nanosized oxides. The Mössbauer spectra of the milled products ZnFe2O4/CoFe2O4 and MgFe2O4/CoFe2O4 reveal the presence of Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4, respectively. In an alternative route, Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 compounds were prepared directly from metal chloride solutions through glycol-thermal reaction. The coercive fields of the Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 oxides produced by glycol-thermal reaction were found to be about 100 Oe and 161 Oe, respectively. Larger coercive fields of about 184 Oe and 255 Oe have been observed for the milled ZnFe2O4/CoFe2O4 and MgFe2O4/CoFe2O4 oxides.

  19. Ultrasmall Black Phosphorus Quantum Dots: Synthesis and Use as Photothermal Agents.

    PubMed

    Sun, Zhengbo; Xie, Hanhan; Tang, Siying; Yu, Xue-Feng; Guo, Zhinan; Shao, Jundong; Zhang, Han; Huang, Hao; Wang, Huaiyu; Chu, Paul K

    2015-09-21

    Black phosphorus quantum dots (BPQDs) were synthesized using a liquid exfoliation method that combined probe sonication and bath sonication. With a lateral size of approximately 2.6 nm and a thickness of about 1.5 nm, the ultrasmall BPQDs exhibited an excellent NIR photothermal performance with a large extinction coefficient of 14.8 L g(-1) cm(-1) at 808 nm, a photothermal conversion efficiency of 28.4%, as well as good photostability. After PEG conjugation, the BPQDs showed enhanced stability in physiological medium, and there was no observable toxicity to different types of cells. NIR photoexcitation of the BPQDs in the presence of C6 and MCF7 cancer cells led to significant cell death, suggesting that the nanoparticles have large potential as photothermal agents.

  20. [Effectiveness of ultrasmall doses of endogenous bioregulators and immunoactive compounds].

    PubMed

    Ashmarin, I P; Karazeeva, E P; Lelekova, T V

    2005-01-01

    The data and hypotheses on the mechanisms of action of ultrasmall doses (USD) and ultralow concentrations (ULC) of endogenous bioregulators and immunoactive compounds (regulatory peptides, cytokines, etc.) are presented. The reliability of the published data on the effectiveness of USD and ULC within the concentration limits 10(-13) - 10(-24) M and lower is considered.

  1. Cobalt ferrite nanoparticles decorated on exfoliated graphene oxide, application for amperometric determination of NADH and H2O2.

    PubMed

    Ensafi, Ali A; Alinajafi, Hossein A; Jafari-Asl, M; Rezaei, B; Ghazaei, F

    2016-03-01

    Here, cobalt ferrite nanohybrid decorated on exfoliated graphene oxide (CoFe2O4/EGO) was synthesized. The nanohybrid was characterized by different methods such as X-ray diffraction spectroscopy, scanning electron microscopy, energy dispersive X-ray diffraction microanalysis, transmission electron microscopy, FT-IR, Raman spectroscopy and electrochemical methods. The CoFe2O4/EGO nanohybrid was used to modify glassy carbon electrode (GCE). The voltammetric investigations showed that CoFe2O4/EGO nanohybrid has synergetic effect towards the electro-reduction of H2O2 and electro-oxidation of nicotinamide adenine dinucleotide (NADH). Rotating disk chronoamperometry was used for their quantitative analysis. The calibration curves were observed in the range of 0.50 to 100.0 μmol L(-1) NADH and 0.9 to 900.0 μmol L(-1) H2O2 with detections limit of 0.38 and 0.54 μmol L(-1), respectively. The repeatability, reproducibility and selectivity of the electrochemical sensor for analysis of the analytes were studied. The new electrochemical sensor was successfully applied for the determination of NADH and H2O2 in real samples with satisfactory results.

  2. Metal-Organic Framework Templated Synthesis of Ultrasmall Catalyst Loaded ZnO/ZnCo2O4 Hollow Spheres for Enhanced Gas Sensing Properties

    PubMed Central

    Koo, Won-Tae; Choi, Seon-Jin; Jang, Ji-Soo; Kim, Il-Doo

    2017-01-01

    To achieve the rational design of nanostructures for superior gas sensors, the ultrasmall nanoparticles (NPs) loaded on ternary metal oxide (TMO) hollow spheres (HS) were synthesized by using the polystyrene (PS) sphere template and bimetallic metal-organic framework (BM-MOFs) mold. The zinc and cobalt based zeolite imidazole frameworks (BM-ZIFs) encapsulating ultrasmall Pd NPs (2–3 nm) were assembled on PS spheres at room temperature. After calcination at 450 °C, these nanoscale Pd particles were effectively infiltrated on the surface of ZnO/ZnCo2O4 HSs. In addition, the heterojunctions of Pd-ZnO, Pd-ZnCo2O4, and ZnO-ZnCo2O4 were formed on each phase. The synthesized Pd-ZnO/ZnCo2O4 HSs exhibited extremely high selectivity toward acetone gas with notable sensitivity (S = 69% to 5 ppm at 250 °C). The results demonstrate that MOF driven ultrasmall catalyst loaded TMO HSs were highly effective platform for high performance chemical gas sensors. PMID:28327599

  3. Metal-Organic Framework Templated Synthesis of Ultrasmall Catalyst Loaded ZnO/ZnCo2O4 Hollow Spheres for Enhanced Gas Sensing Properties

    NASA Astrophysics Data System (ADS)

    Koo, Won-Tae; Choi, Seon-Jin; Jang, Ji-Soo; Kim, Il-Doo

    2017-03-01

    To achieve the rational design of nanostructures for superior gas sensors, the ultrasmall nanoparticles (NPs) loaded on ternary metal oxide (TMO) hollow spheres (HS) were synthesized by using the polystyrene (PS) sphere template and bimetallic metal-organic framework (BM-MOFs) mold. The zinc and cobalt based zeolite imidazole frameworks (BM-ZIFs) encapsulating ultrasmall Pd NPs (2–3 nm) were assembled on PS spheres at room temperature. After calcination at 450 °C, these nanoscale Pd particles were effectively infiltrated on the surface of ZnO/ZnCo2O4 HSs. In addition, the heterojunctions of Pd-ZnO, Pd-ZnCo2O4, and ZnO-ZnCo2O4 were formed on each phase. The synthesized Pd-ZnO/ZnCo2O4 HSs exhibited extremely high selectivity toward acetone gas with notable sensitivity (S = 69% to 5 ppm at 250 °C). The results demonstrate that MOF driven ultrasmall catalyst loaded TMO HSs were highly effective platform for high performance chemical gas sensors.

  4. Coupling efficiency of ultra-small gradient-index fiber probe

    NASA Astrophysics Data System (ADS)

    Wang, Chi; Sun, Jianmei; Sun, Fan; Zhu, Jun; Yuan, Zhiwen; Asundi, Anand

    2017-04-01

    In this paper, the coupling efficiency of ultra-small GRIN fiber probe is studied for its focusing performance. Based on the light transmission characteristics of a Gaussian beam and the principle of optical imaging, with the analytical methods, the theoretical formula is deduced for the coupling efficiency of ultra-small GRIN fiber probe. Experiments were set-up and conducted for verification. Per the experimental results, for an ultra-small GRIN fiber probe with the focal length of 0.4 mm, the coupling efficiency measured at the focusing position was 57%, and above 44% within the 0-0.6 mm range. However, for a single-mode fiber, the coupling efficiency dropped to 17% when the distance increased to 0.2 mm. Thus, the ultra-small GRIN fiber probe boasts a superior focusing performance and coupling efficiency. This paper provides a theoretical basis for the application and research on ultra-small GRIN fiber probe.

  5. Field emission properties of ultrasmall Zr spots on W

    SciTech Connect

    Fursey, G.N.; Glazanov, D.V.

    1995-05-01

    The aims of the investigation were to obtain small and supersmall Zr/ZrO spots on W surface, estimating the limit emission capabilities of such systems, and to analyze their physical mechanisms, which determine their stability. Ultrasmall Zr spots with radii of {approximately} 100 {Angstrom} were obtained. For such spots field emission current densities of {approximately} 10{sup 9} A/cm{sup 2} were achieved in stationary regime. The numerical simulation of the emitter heating in the three-dimensional axial-symmetrical model showed good qualitative agreement with the experimental results for both localized and nonlocalized emission. 25 refs., 6 figs.

  6. Bright White Light Emission from Ultrasmall Cadmium Selenide Nanocrystals

    SciTech Connect

    Rosson, Teresa; Claiborne, Sarah; McBride, James; Stratton, Benjamin S; Rosenthal, Sandra

    2012-01-01

    A simple treatment method using formic acid has been found to increase the fluorescence quantum yield of ultrasmall white light-emitting CdSe nanocrystals from 8% to 45%. Brighter white-light emission occurs with other carboxylic acids as well, and the magnitude of the quantum yield enhancement is shown to be dependent on the alkyl chain length. Additionally, the nanocrystal luminescence remains enhanced relative to the untreated nanocrystals over several days. This brightened emission opens the possibility for even further quantum yield improvement and potential for use of these white-light nanocrystals in solid-state lighting applications.

  7. Bright white light emission from ultrasmall cadmium selenide nanocrystals.

    PubMed

    Rosson, Teresa E; Claiborne, Sarah M; McBride, James R; Stratton, Benjamin S; Rosenthal, Sandra J

    2012-05-16

    A simple treatment method using formic acid has been found to increase the fluorescence quantum yield of ultrasmall white light-emitting CdSe nanocrystals from 8% to 45%. Brighter white-light emission occurs with other carboxylic acids as well, and the magnitude of the quantum yield enhancement is shown to be dependent on the alkyl chain length. Additionally, the nanocrystal luminescence remains enhanced relative to the untreated nanocrystals over several days. This brightened emission opens the possibility for even further quantum yield improvement and potential for use of these white-light nanocrystals in solid-state lighting applications.

  8. Synthesis, kinetics and photocatalytic study of "ultra-small" Ag-NPs obtained by a green chemistry method using an extract of Rosa 'Andeli' double delight petals.

    PubMed

    Suárez-Cerda, Javier; Alonso-Nuñez, Gabriel; Espinoza-Gómez, Heriberto; Flores-López, Lucía Z

    2015-11-15

    This paper reports the effect of different concentrations of Rosa 'Andeli' double delight petals aqueous extract (PERA) in the synthesis of silver nanoparticles (Ag-NPs), using an easy green chemistry method. Its kinetics study and photocatalytic activity were also evaluated. The Ag-NPs were obtained using an aqueous silver nitrate solution (AgNO3) with 9.66% w/v, 7.25% w/v, and 4.20% w/v PERA as both reducing-stabilizing agent. The formation of the Ag-NPs was demonstrated by analysis of UV-vis spectroscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). TEM analysis shows spherical nanoparticles in shape and size between ∼0.5 and 1.4nm. A comparative study was done to determine which concentration was the best reducing-stabilizing agent, and we found out that "ultra-small" nanoparticles (0.5-1.1nm) were obtained with 9.66% w/v of PERA. The size of the Ag-NPs depends on the concentration of PERA and Ag(I). The reaction of formation of "ultra-small" Ag-NPs, proved to be first order for metallic precursor (silver) and second order for reducing-stabilizing agent (PERA). The Ag-NPs showed photocatalytic activity, in degradation of commercial dye with an efficiency of 95%.

  9. Physicochemical characterization of ultrasmall superparamagnetic iron oxide particles (USPIO) for biomedical application as MRI contrast agents.

    PubMed

    Di Marco, Mariagrazia; Sadun, Claudia; Port, Marc; Guilbert, Irene; Couvreur, Patrick; Dubernet, Catherine

    2007-01-01

    Ultrasmall superparamagnetic iron oxide (USPIO) particles are maghemite or magnetite nanoparticles currently used as contrast agent in magnetic resonance imaging. The coatings surrounding the USPIO inorganic core play a major role in both the in vitro stability and, over all, USPIO's in vivo fate. Different physicochemical properties such as final size, surface charge and coating density are key factors in this respect. Up to now no precise structure--activity relationship has been described to predict entirely the USPIOs stability, as well as their pharmacokinetics and their safety. This review is focused on both the classical and the latest available techniques allowing a better insight in the magnetic core structure and the organic surface of these particles. Concurrently, this work clearly shows the difficulty to obtain a complete physicochemical characterization of USPIOs particles owing to their small dimensions, reaching the analytical resolution limits of many commercial instruments. An extended characterization is therefore necessary to improve the understanding of the properties of USPIOs when dispersed in an aqueous environment and to set the specifications and limits for their conception.

  10. Ultra-small, highly stable, and membrane-impermeable fluorescent nanosensors for oxygen

    NASA Astrophysics Data System (ADS)

    Wang, Xu-dong; Stolwijk, Judith A.; Sperber, Michaela; Meier, Robert J.; Wegener, Joachim; Wolfbeis, Otto S.

    2013-09-01

    We report on the preparation of ultra-small fluorescent nanosensors for oxygen via a one-pot approach. The nanoparticles have a hydrophobic core capable of firmly hosting hydrophobic luminescent oxygen probes. Their surface is composed of a dense and long-chain poly(ethylene glycol) shell, which renders them cell-membrane impermeable but yet highly sensitive to oxygen, and also highly stable in aqueous solutions and cell culture media. These features make them potentially suitable for sensing oxygen in extracellular fluids such as blood, interstitial and brain fluid, in (micro) bioreactors and micro- or nanoscale fluidic devices. Four kinds of nanosensors are presented, whose excitation spectra cover a wide spectral range (395-630 nm), thus matching many common laser lines, and with emission maxima ranging from 565 to 800 nm, thereby minimizing interference from background luminescence of biomatter. The unquenched lifetimes are on the order of 5.8-234 μs, which—in turn—enables lifetime imaging and additional background separation via time-gated methods.

  11. Engineering ultrasmall water-soluble gold and silver nanoclusters for biomedical applications.

    PubMed

    Luo, Zhentao; Zheng, Kaiyuan; Xie, Jianping

    2014-05-25

    Gold and silver nanoclusters or Au/Ag NCs with core sizes smaller than 2 nm have been an attractive frontier of nanoparticle research because of their unique physicochemical properties such as well-defined molecular structure, discrete electronic transitions, quantized charging, and strong luminescence. As a result of these unique properties, ultrasmall size, and good biocompatibility, Au/Ag NCs have great potential for a variety of biomedical applications, such as bioimaging, biosensing, antimicrobial agents, and cancer therapy. In this feature article, we will first discuss some critical biological considerations, such as biocompatibility and renal clearance, of Au/Ag NCs that are applied for biomedical applications, leading to some design criteria for functional Au/Ag NCs in the biological settings. According to these biological considerations, we will then survey some efficient synthetic strategies for the preparation of protein- and peptide-protected Au/Ag NCs with an emphasis on our recent contributions in this fast-growing field. In the last part, we will highlight some potential biomedical applications of these protein- and peptide-protected Au/Ag NCs. It is believed that with continued efforts to understand the interactions of biomolecule-protected Au/Ag NCs with the biological systems, scientists can largely realize the great potential of Au/Ag NCs for biomedical applications, which could finally pave their way towards clinical use.

  12. Synthesis and magnetic characterization of cobalt-substituted ferrite (Co xFe 3-xO 4) nanoparticles

    NASA Astrophysics Data System (ADS)

    Calero-DdelC, Victoria L.; Rinaldi, Carlos

    2007-07-01

    Cobalt-substituted ferrite nanoparticles were synthesized with a narrow size distribution using reverse micelles formed in the system water/AOT/isooctane. Fe:Co ratios of 3:1, 4:1, and 5:1 were used in the synthesis, obtaining cobalt-substituted ferrites (Co xFe 3-xO 4) and some indication of γ-Fe 3O 4 when 4:1 and 5:1 Fe:Co ratios were used. Inductively coupled plasma mass spectroscopy (ICP-MS) verified the presence of cobalt in all samples. Fourier transform infrared (FTIR) showed bands at ˜560 and ˜400 cm -1, characteristic of the metal-oxygen bond in ferrites. Transmission electron microscopy showed that the number median diameter of the particles was ˜3 nm with a geometric deviation of ˜0.2. X-ray diffraction (XRD) confirmed the inverse spinel structure typical of ferrites with a lattice parameter of a=8.388 Å for Co 0.61Fe 0.39O 4, which is near that of CoFe 2O 4 ( a=8.394 Å). Magnetic properties were determined using a superconducting quantum interference device (SQUID). Coercivities higher than 8 kOe were observed at 5 K, whereas at 300 K the particles showed superparamagnetic behavior. The anisotropy constant was determined based on the Debye model for a magnetic dipole in an oscillating field and an expression relating χ' and the temperature of the in-phase susceptibility peak. Anisotropy constant values in the order of ˜10 6 erg/cm 3 were determined using the Debye model, whereas anisotropy constants in the order of ˜10 7 erg/cm 3 were calculated assuming Ωτ=1 at the temperature peak of the in-phase component of the susceptibility curve as commonly done in the literature. Our analysis demonstrates that the assumption Ωτ=1 at the temperature peak of χ' is rigorously incorrect.

  13. Ultrasmall hollow gold-silver nanoshells with extinctions strongly red-shifted to the near-infrared.

    PubMed

    Vongsavat, Varadee; Vittur, Brandon M; Bryan, William W; Kim, Jun-Hyun; Lee, T Randall

    2011-09-01

    Hollow gold-silver nanoshells having systematically varying sizes between 40 and 100 nm were prepared. These particles consist of a hollow spherical silver shell surrounded by a thin gold layer. By varying the volume of the gold stock solution added to suspensions of small silver-core templates, we tailored the hollow gold-silver nanoshells to possess strong tunable optical extinctions that range from the visible to the near-IR spectral regions, with extinctions routinely centered at ∼950 nm. The size and morphology of these core/shell nanoparticles were characterized by dynamic light scattering (DLS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Separately, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used for measuring their elemental composition; UV-vis spectroscopy was used to evaluate their optical properties. Given their relatively small size compared to other nanoparticles that absorb strongly at near IR wavelengths, these easy-to-synthesize particles should find use in applications that require ultrasmall nanoparticles with extinctions comfortably beyond visible wavelengths (e.g., medicinal therapies, diagnostic imaging, nanofluidics, and display technologies).

  14. New directions in developing ultrasmall fiber-optic ion sensors

    SciTech Connect

    Shortreed, M.R.; Kopelman, R.; Bakker, E.

    1995-12-31

    We have recently investigated the fluorescent properties of a number of pH-selective chromoionophores and evaluated their potential for use in cation exchange optode membranes. Three approaches were developed to monitor the response of these bulk-optodes. The Nile Blue derivative, ETH 5350, shows the greatest promise exhibiting bright fluorescence and an emission peak shift upon protonation. Another Nile Blue derivatives, ETH 2439, has sufficient molar absorptivity to act as an inner-filter for the highly lipophilic fluorescent membrane label, DiIC{sub 18}. These chromogenic systems, used in traditional, PVC-based, liquid polymer membranes along with ionophores and lipophilic charge sites, are placed on the end of optical fibers. An ultra-small optode capable of measuring cytosolic levels of sodium at physiological pH has been constructed based on a highly lipophilic bridged-calixarene. Progress in the construction of analogous anion-selective optodes will also be presented.

  15. Perfect spin filtering effect in ultrasmall helical zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Zi-Yue

    2017-02-01

    The spin-polarized transport properties of helical zigzag graphene nanoribbons (ZGNRs) are investigated by first-principles calculations. It is found that although all helical ZGNRs have similar density of states and edge states, they show obviously different transport characteristics depending on the curling manners. ZGNRs curled along zigzag orientation exhibit perfect spin filtering effect with a large spin-split gap near the Fermi level, while ZGNRs curled along armchair orientation behave as conventional conductors for both two spin channels. The spin filtering effect will be weakened with the increase of either ribbon width or curling diameter. The results suggest that ultrasmall helical ZGNRs have important potential applications in spintronics and flexible electronics.

  16. Anodic Stripping Voltametry at Mercury Film Deposited on Ultrasmall Carbon Ring Electrodes

    DTIC Science & Technology

    1990-11-05

    ABSTRACT ’Mas-,im 2?0 wC!OS) Anodic stripping voltammetry of lead and cadmium without deliberately added electrolytes has been studied at ultrasmall...ANODIC STRIPPING VOLTAMMETRY AT MERCURY FILMS DEPOSITED ON ULTRASMALL CARBON RING ELECTRODES ABSTRACT Anodic stripping voltammetry of lead and cadmium ...electroac- tive species to the electrode region then arises. Golas and Osteryoung [11,12] have performed anodic stripping square - wave voltam- metry in

  17. Yafet-Kittel-type magnetic order in Zn-substituted cobalt ferrite nanoparticles with uniaxial anisotropy

    NASA Astrophysics Data System (ADS)

    Topkaya, R.; Baykal, A.; Demir, A.

    2013-01-01

    Zn-substituted cobalt ferrite (Zn x Co1- x Fe2O4 with 0.0 ≤ x ≤ 1.0) nanoparticles coated with triethylene glycol (TREG) were prepared by the hydrothermal technique. The effect of Zn substitution on temperature-dependent magnetic properties of the TREG-coated Zn x Co1- x Fe2O4 nanoparticles has been investigated in the temperature range of 10-400 K and in magnetic fields up to 9 T. The structural, morphological, and magnetic properties of TREG-coated Zn x Co1- x Fe2O4 NPs were examined using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The average crystallite size estimated from X-ray line profile fitting was found to be in the range of 7.0-10 nm. The lattice constant determined using the Nelson-Riley extrapolation method continuously increases with the increase in Zn2+ content, obeying Vegard's law. TEM analysis revealed that the synthesized particles were nearly monodisperse, roughly spherical shaped nanoparticles in the size range of 9.0-15 nm. FT-IR spectra confirm that TREG is successfully coated on the surface of nanoparticles (NPs). The substitution of non-magnetic Zn2+ ions for magnetic Co2+ ions substantially changes the magnetic properties of the TREG-coated Zn x Co1- x Fe2O4 NPs. The saturation magnetization and the experimental magnetic moment are observed to initially increase (up to x = 0.2), which is explained by Néel's collinear two-sublattice model, and then continuously decrease with further increase in Zn content x. This decrease obeys the three-sublattice model suggested by Yafet-Kittel (Y-K). While the Y-K angle is zero for the CoFe2O4 NPs coated with TREG, it increases gradually with increasing Zn concentrations and extrapolates to 82.36° for ZnFe2O4 NPs coated with TREG. The increase in spin canting angles (Y-K angles) suggests the existence of triangular (or canted) spin arrangements in all the samples (except for the samples with x

  18. Ultrasmall SnO2 Nanocrystals: Hot-bubbling Synthesis, Encapsulation in Carbon Layers and Applications in High Capacity Li-Ion Storage

    PubMed Central

    Ding, Liping; He, Shulian; Miao, Shiding; Jorgensen, Matthew R.; Leubner, Susanne; Yan, Chenglin; Hickey, Stephen G.; Eychmüller, Alexander; Xu, Jinzhang; Schmidt, Oliver G.

    2014-01-01

    Ultrasmall SnO2 nanocrystals as anode materials for lithium-ion batteries (LIBs) have been synthesized by bubbling an oxidizing gas into hot surfactant solutions containing Sn-oleate complexes. Annealing of the particles in N2 carbonifies the densely packed surface capping ligands resulting in carbon encapsulated SnO2 nanoparticles (SnO2/C). Carbon encapsulation can effectively buffer the volume changes during the lithiation/delithiation process. The assembled SnO2/C thus deliver extraordinarily high reversible capacity of 908 mA·h·g−1 at 0.5 C as well as excellent cycling performance in the LIBs. This method demonstrates the great potential of SnO2/C nanoparticles for the design of high power LIBs. PMID:24732294

  19. Influence of pH on the structural and magnetic behavior of cobalt ferrite synthesized by sol-gel auto-combustion

    NASA Astrophysics Data System (ADS)

    Kakade, S. G.; Kambale, R. C.; Kolekar, Y. D.

    2015-06-01

    Cobalt ferrite (CoFe2O4) shown to be promising candidate for applications such as high-density magnetic recording, enhanced memory storage, magnetic fluids and catalysts. Utility of ferrite nanoparticles depends on its size, dispersibility in solutions, and magnetic properties. We have investigated the structural properties of synthesized cobalt ferrite nanoparticles synthesized by sol gel auto combustion for uncontrolled, acidic, neutral and basic pH values. X-ray diffraction (XRD) study confirms the cubic spinel phase formation with lattice constant 8.38 Å. In this study, we have optimized the pH value to synthesize homogenous cobalt ferrite nanoparticles with enhanced magnetic behavior. The surface morphology has been investigated by employing SEM images and the confirmation of spinel ferrite was also supported by using IR spectroscopy. Magnetic measurements for CoFe2O4 compositions (with pH <1, pH = 3, 7, 10) were investigated using VSM measurements.

  20. Structure and magnetic properties of Co and Ni nano-ferrites prepared by a two step direct microemulsions synthesis

    NASA Astrophysics Data System (ADS)

    Pulišová, P.; Kováč, J.; Voigt, A.; Raschman, P.

    2013-09-01

    Nano-particles of CoFe2O4, NiFe2O4 and Co0.5Ni0.5Fe2O4 were synthesized by a two step microemulsion precipitation where inverse micelles of water in hexanol were stabilized using cetyltrimethylammonium bromide. Powder X-ray diffraction analysis and Transmission electron microscopy measurements provided data to clarify the crystal structure and size of the produced nano-particles. Different measurements of magnetic properties at low temperatures of 2 K revealed that nano-particles of NiFe2O4 represent magnetically soft ferrite with a coercivity ∼40 kA/m, whereas nano-particles of CoFe2O4 and Co0.5Ni0.5Fe2O4 were magnetically harder with a coercivity of 815 and 947 kA/m, respectively. Additionally zero field cooling and field cooling measurements provided data for estimating the blocking temperature of the materials produced. For NiFe2O4 this temperature is lower, 23 K. The blocking temperature of CoFe2O4 of 238 K and Co0.5Ni0.5Fe2O4 of 268 K are higher in comparison with NiFe2O4.

  1. Hydrogen gas sensing with networks of ultra-small palladium nanowires formed on filtration membranes.

    SciTech Connect

    Zeng, X. Q.; Latimer, M. L.; Xiao, Z. L.; Panuganti, S.; Welp, U.; Kwok, W. K.; Xu, T.

    2010-11-29

    Hydrogen sensors based on single Pd nanowires show promising results in speed, sensitivity, and ultralow power consumption. The utilization of single Pd nanowires, however, face challenges in nanofabrication, manipulation, and achieving ultrasmall transverse dimensions. We report on hydrogen sensors that take advantage of single palladium nanowires in high speed and sensitivity and that can be fabricated conveniently. The sensors are based on networks of ultrasmall (<10 nm) palladium nanowires deposited onto commercially available filtration membranes. We investigated the sensitivities and response times of these sensors as a function of the thickness of the nanowires and also compared them with a continuous reference film. The superior performance of the ultrasmall Pd nanowire network based sensors demonstrates the novelty of our fabrication approach, which can be directly applied to palladium alloy and other hydrogen sensing materials.

  2. Gold Nanoparticles for Neural Prosthetics Devices

    PubMed Central

    Zhang, Huanan; Shih, Jimmy; Zhu, Jian; Kotov, Nicholas A.

    2012-01-01

    Treatments of neurological diseases and the realization of brain-computer interfaces require ultrasmall electrodes which are “invisible” to resident immune cells. Functional electrodes smaller than 50μm are impossible to produce with traditional materials due to high interfacial impedance at the characteristic frequency of neural activity and insufficient charge storage capacity. The problem can be resolved by using gold nanoparticle nanocomposites. Careful comparison indicates that layer-by-layer assembled films from Au NPs provide more than threefold improvement in interfacial impedance and one order of magnitude increase in charge storage capacity. Prototypes of microelectrodes could be made using traditional photolithography. Integration of unique nanocomposite materials with microfabrication techniques opens the door for practical realization of the ultrasmall implantable electrodes. Further improvement of electrical properties is expected when using special shapes of gold nanoparticles. PMID:22734673

  3. Measuring and controlling the transport of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Stephens, Jason R.

    Despite the large body of literature describing the synthesis of magnetic nanoparticles, few analytical tools are commonly used for their purification and analysis. Due to their unique physical and chemical properties, magnetic nanoparticles are appealing candidates for biomedical applications and analytical separations. Yet in the absence of methods for assessing and assuring their purity, the ultimate use of magnetic particles and heterostructures is likely to be limited. For magnetic nanoparticles, it is the use of an applied magnetic flux or field gradient that enables separations. Flow based techniques are combined with applied magnetic fields to give methods such as magnetic field flow fractionation and high gradient magnetic separation. Additional techniques have been explored for manipulating particles in microfluidic channels and in mesoporous membranes. This thesis further describes development of these and new analytical tools for separation and analysis of colloidal particles is critically important to enable the practical use of these, particularly for medicinal purposes. Measurement of transport of nanometer scale particles through porous media is important to begin to understand the potential environmental impacts of nanomaterials. Using a diffusion cell with two compartments separated by either a porous alumina or polycarbonate membrane as a model system, diffusive flux through mesoporous materials is examined. Experiments are performed as a function of particle size, pore diameter, and solvent, and the particle fluxes are monitored by the change in absorbance of the solution in the receiving cell. Using the measured extinction coefficient and change in absorbance of the solution as a function of time, the fluxes of 3, 8, and 14 nm diameter CoFe2O4 particles are determined as they are translocated across pores with diameters 30, 50, 100, and 200 nm in hexane and aqueous solutions. In general, flux decreases with increasing particle size and

  4. nanoparticles

    NASA Astrophysics Data System (ADS)

    Andreu-Cabedo, Patricia; Mondragon, Rosa; Hernandez, Leonor; Martinez-Cuenca, Raul; Cabedo, Luis; Julia, J. Enrique

    2014-10-01

    Thermal energy storage (TES) is extremely important in concentrated solar power (CSP) plants since it represents the main difference and advantage of CSP plants with respect to other renewable energy sources such as wind, photovoltaic, etc. CSP represents a low-carbon emission renewable source of energy, and TES allows CSP plants to have energy availability and dispatchability using available industrial technologies. Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 500°C. Their main drawbacks are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve thermal properties of fluids is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. In this work, solar salt used in CSP plants (60% NaNO3 + 40% KNO3) was doped with silica nanoparticles at different solid mass concentrations (from 0.5% to 2%). Specific heat was measured by means of differential scanning calorimetry (DSC). A maximum increase of 25.03% was found at an optimal concentration of 1 wt.% of nanoparticles. The size distribution of nanoparticle clusters present in the salt at each concentration was evaluated by means of scanning electron microscopy (SEM) and image processing, as well as by means of dynamic light scattering (DLS). The cluster size and the specific surface available depended on the solid content, and a relationship between the specific heat increment and the available particle surface area was obtained. It was proved that the mechanism involved in the specific heat increment is based on a surface phenomenon. Stability of samples was tested for several thermal cycles and thermogravimetric analysis at high temperature was carried out, the samples being stable.

  5. Ultra-Small Reader/Writer with Multiple Contactless Interfaces on a Flexible Circuit Board

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hideaki; Ikeda, Minoru; Hosoda, Yasuhiro

    In order to incorporate the reader/writers (RWs) into mobile electronic devices, miniaturization and flexibility are required. To meet these requirements, we fabricate an ultra-small RW with multiple contactless interfaces by mounting main unit circuits inside the antenna coil and using flexible multi-layer circuit board.

  6. Design of an ultrasmall Au nanocluster-CeO2 mesoporous nanocomposite catalyst for nitrobenzene reduction.

    PubMed

    Chong, Hanbao; Li, Peng; Xiang, Ji; Fu, Fangyu; Zhang, Dandan; Ran, Xiaorong; Zhu, Manzhou

    2013-08-21

    In this work we are inspired to explore gold nanoclusters supported on mesoporous CeO2 nanospheres as nanocatalysts for the reduction of nitrobenzene. Ultrasmall Au nanoclusters (NCs) and mesoporous CeO2 nanospheres were readily synthesized and well characterized. Due to their ultrasmall size, the as-prepared Au clusters can be easily absorbed into the mesopores of the mesoporous CeO2 nanospheres. Owing to the unique mesoporous structure of the CeO2 support, Au nanoclusters in the Au@CeO2 may effectively prevent the aggregation which usually results in a rapid decay of the catalytic activity. It is notable that the ultrasmall gold nanoclusters possess uniform size distribution and good dispersibility on the mesoporous CeO2 supports. Compared to other catalyst systems with different oxide supports, the as-prepared Au nanocluster-CeO2 nanocomposite nanocatalysts showed efficient catalytic performance in transforming nitrobenzene into azoxybenzene. In addition, a plausible mechanism was deeply investigated to explain the transforming process. Au@CeO2 exhibited efficient catalytic activity for reduction of nitrobenzene. This strategy may be easily extended to fabricate many other heterogeneous catalysts including ultrasmall metal nanoclusters and mesoporous oxides.

  7. Enzymatic- and temperature-sensitive controlled release of ultrasmall superparamagnetic iron oxides (USPIOs)

    PubMed Central

    2011-01-01

    Background Drug and contrast agent delivery systems that achieve controlled release in the presence of enzymatic activity are becoming increasingly important, as enzymatic activity is a hallmark of a wide array of diseases, including cancer and atherosclerosis. Here, we have synthesized clusters of ultrasmall superparamagnetic iron oxides (USPIOs) that sense enzymatic activity for applications in magnetic resonance imaging (MRI). To achieve this goal, we utilize amphiphilic poly(propylene sulfide)-bl-poly(ethylene glycol) (PPS-b-PEG) copolymers, which are known to have excellent properties for smart delivery of drug and siRNA. Results Monodisperse PPS polymers were synthesized by anionic ring opening polymerization of propylene sulfide, and were sequentially reacted with commercially available heterobifunctional PEG reagents and then ssDNA sequences to fashion biofunctional PPS-bl-PEG copolymers. They were then combined with hydrophobic 12 nm USPIO cores in the thin-film hydration method to produce ssDNA-displaying USPIO micelles. Micelle populations displaying complementary ssDNA sequences were mixed to induce crosslinking of the USPIO micelles. By design, these crosslinking sequences contained an EcoRV cleavage site. Treatment of the clusters with EcoRV results in a loss of R2 negative contrast in the system. Further, the USPIO clusters demonstrate temperature sensitivity as evidenced by their reversible dispersion at ~75°C and re-clustering following return to room temperature. Conclusions This work demonstrates proof of concept of an enzymatically-actuatable and thermoresponsive system for dynamic biosensing applications. The platform exhibits controlled release of nanoparticles leading to changes in magnetic relaxation, enabling detection of enzymatic activity. Further, the presented functionalization scheme extends the scope of potential applications for PPS-b-PEG. Combined with previous findings using this polymer platform that demonstrate controlled drug

  8. ²⁰¹Tl⁺-labelled Prussian blue nanoparticles as contrast agents for SPECT scintigraphy.

    PubMed

    Perrier, M; Busson, M; Massasso, G; Long, J; Boudousq, V; Pouget, J-P; Peyrottes, S; Perigaud, Ch; Porredon-Guarch, C; de Lapuente, J; Borras, M; Larionova, J; Guari, Y

    2014-11-21

    Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive (201)Tl(+) to obtain new nanoprobes as radiotracers for 201-thallium-based imaging.

  9. Response of iron oxide on hetero-nanostructures of soft and hard ferrites

    NASA Astrophysics Data System (ADS)

    Khan, U.; Adeela, N.; Wan, C. H.; Irfan, M.; Naseem, S.; Riaz, S.; Iqbal, M.; Han, X. F.

    2016-04-01

    Core-shell nanostructures of Zinc and Cobalt ferrites synthesized by solution evaporation route are observed to perform novel magnetic response. The structural and morphological analyses of ZnFe2O4-core/Fe3O4-shell and CoFe2O4-core/Fe3O4-shell nanoparticles (NPs) are confirmed with X-ray diffractometer (XRD) and high resolution transmission electron microscopy (HRTEM). Physical properties measurement system (PPMS) investigations at room temperature reveal that the synthesized core-shell NPs (∼8 nm in diameter) are in super-paramagnetic state. The coercivity of ZnFe2O4/Fe3O4 is much lower than that of CoFe2O4/Fe3O4 NPs (e.g., at 5 K: Hc = 0.6kOe for ZnFe2O4/Fe3O4 and Hc = 18kOe for CoFe2O4/Fe3O4. Fe3O4 is preferable to reduce magnetic hardness for Zinc ferrite and enhance for Cobalt Ferrite.

  10. Design and synthesis of ternary cobalt ferrite/graphene/polyaniline hierarchical nanocomposites for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Xiong, Pan; Huang, Huajie; Wang, Xin

    2014-01-01

    A ternary cobalt ferrite/graphene/polyaniline nanocomposite (CGP) is designed and fabricated via a facile two-step approach: cobalt ferrite nanoparticles dispersed on graphene sheets are achieved by a hydrothermal method, followed by coating with polyaniline (PANI) through in situ polymerization process. Electrochemical measurements demonstrate that the specific capacitance of the resulting ternary hybrid (CGP) is up to 1133.3 F g-1 at a scan rate of 1 mV s-1 and 767.7 F g-1 at a current density of 0.1 A g-1 using a three-electrode system, while 716.4 F g-1 at a scan rate of 1 mV s-1 and 392.3 F g-1 at a current density of 0.1 A g-1 using a two-electrode system, which are significantly higher than those of pure CoFe2O4, graphene and PANI, or binary CoFe2O4/graphene, CoFe2O4/PANI and graphene/PANI hybrids. In addition, over 96% of the initial capacitance can be retained after repeating test for 5000 cycles, demonstrating a high cycling stability. The extraordinary electrochemical performance of the ternary CGP nanocomposite can be attributed to its well-designed nanostructure and the synergistic effects of the individual components.

  11. General Approach for MOF-Derived Porous Spinel AFe2O4 Hollow Structures and Their Superior Lithium Storage Properties.

    PubMed

    Yu, Hong; Fan, Haosen; Yadian, Boluo; Tan, Huiteng; Liu, Weiling; Hng, Huey Hoon; Huang, Yizhong; Yan, Qingyu

    2015-12-09

    A general and simple approach for large-scale synthesis of porous hollow spinel AFe2O4 nanoarchitectures via metal organic framework self-sacrificial template strategy is proposed. By employing this method, we can successfully synthesize uniform NiFe2O4, ZnFe2O4, and CoFe2O4 hollow architectures that are hierarchically assembled by nanoparticles. When these hollow microcubes were tested as anode for lithium ion batteries, good rate capability and long-term cycling stability can be achieved. For example, high specific capacities of 636, 449, and 380 mA h g(-1) were depicted by NiFe2O4, ZnFe2O4, and CoFe2O4, respectively, at a high current density of 8.0 A g(-1). NiFe2O4 exhibits high specific capacities of 841 and 447 mA h g(-1) during the 100th cycle when it was tested at current densities of 1.0 and 5.0 A g(-1), respectively. Discharge capacities of 390 and 290 mA h g(-1) were delivered by the ZnFe2O4 and CoFe2O4, respectively, during the 100th cycle at 5.0 A g(-1).

  12. Graphene stabilized ultra-small CuNi nanocomposite with high activity and recyclability toward catalysing the reduction of aromatic nitro-compounds

    NASA Astrophysics Data System (ADS)

    Fang, Hao; Wen, Ming; Chen, Hanxing; Wu, Qingsheng; Li, Weiying

    2015-12-01

    Nowadays, it is of great significance and a challenge to design a noble-metal-free catalyst with high activity and a long lifetime for the reduction of aromatic nitro-compounds. Here, a 2D structured nanocomposite catalyst with graphene supported CuNi alloy nanoparticles (NPs) is prepared, and is promising for meeting the requirements of green chemistry. In this graphene/CuNi nanocomposite, the ultra-small CuNi nanoparticles (~2 nm) are evenly anchored on graphene sheets, which is not only a breakthrough in the structures, but also brings about an outstanding performance in activity and stability. Combined with a precise optimization of the alloy ratios, the reaction rate constant of graphene/Cu61Ni39 reached a high level of 0.13685 s-1, with a desirable selectivity as high as 99% for various aromatic nitro-compounds. What's more, the catalyst exhibited a unprecedented long lifetime because it could be recycled over 25 times without obvious performance decay or even a morphology change. This work showed the promise and great potential of noble-metal-free catalysts in green chemistry.Nowadays, it is of great significance and a challenge to design a noble-metal-free catalyst with high activity and a long lifetime for the reduction of aromatic nitro-compounds. Here, a 2D structured nanocomposite catalyst with graphene supported CuNi alloy nanoparticles (NPs) is prepared, and is promising for meeting the requirements of green chemistry. In this graphene/CuNi nanocomposite, the ultra-small CuNi nanoparticles (~2 nm) are evenly anchored on graphene sheets, which is not only a breakthrough in the structures, but also brings about an outstanding performance in activity and stability. Combined with a precise optimization of the alloy ratios, the reaction rate constant of graphene/Cu61Ni39 reached a high level of 0.13685 s-1, with a desirable selectivity as high as 99% for various aromatic nitro-compounds. What's more, the catalyst exhibited a unprecedented long lifetime

  13. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    NASA Astrophysics Data System (ADS)

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew; Krishnan, Kannan M.

    2014-11-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  14. Studies on ultrasmall bacteria in relation to the presence of bacteria in the stratosphere

    NASA Astrophysics Data System (ADS)

    Alshammari, Fawaz; Wainwright, Milton; Alabri, Khalid; Alharbi, Sulamain A.

    2011-04-01

    Recent studies confirm that bacteria exist in the stratosphere. It is generally assumed that these bacteria are exiting from Earth, although it is possible that some are incoming from space. Most stratospheric bacterial isolates belong to the spore-forming genus Bacillus, although non-spore formers have also been isolated. Theoretically, the smaller a bacterium is, the more likely it is to be carried from Earth to the stratosphere. Ultrasmall bacteria have been frequently isolated from Earth environments, but not yet from the stratosphere. This is an anomalous situation, since we would expect such small bacteria to be over represented in the stratosphere-microflora. Here, we show that ultrasmall bacteria are present in the environment on Earth (i.e. in seawater and rainwater) and discuss the paradox of why they have not been isolated from the stratosphere.

  15. Ultra-small NLC for improved dermal delivery of coenyzme Q10.

    PubMed

    Schwarz, Julia C; Baisaeng, Nuttakorn; Hoppel, Magdalena; Löw, Monika; Keck, Cornelia M; Valenta, Claudia

    2013-04-15

    Coenzyme Q10 (CoQ10) acts as an antioxidant in the skin and is frequently contained in anti-aging products. In previous studies, it could be shown that nano-structured lipid carriers (NLC) with a size of about 230 nm are beneficial for the dermal delivery of CoQ10. They increased Q10 skin penetration when compared to equally sized nanoemulsion. In this study, ultra-small NLC were prepared with even smaller mean particles sizes of around 80 nm. The influence of this decrease of particle size was investigated in terms of skin permeation and penetration as well as physicochemical stability of the NLC. Improved dermal delivery of CoQ10 by ultra-small NLC could be achieved.

  16. Sustained high external quantum efficiency in ultrasmall blue III–nitride micro-LEDs

    NASA Astrophysics Data System (ADS)

    Hwang, David; Mughal, Asad; Pynn, Christopher D.; Nakamura, Shuji; DenBaars, Steven P.

    2017-03-01

    Ultrasmall blue InGaN micro-light-emitting diodes (µLEDs) with areas from 10‑4 to 0.01 mm2 were fabricated to study their optical and electrical properties. The peak external quantum efficiencies (EQEs) of the smallest and largest µLEDs were 40.2 and 48.6%, respectively. The difference in EQE was from nonradiative recombination originating from etching damage. This decrease is less severe than that in red AlInGaP LEDs. The efficiency droop at 900 A/cm2 of the smallest µLED was 45.7%, compared with 56.0% for the largest, and was lower because of improved current spreading. These results show that ultrasmall µLEDs may be fabricated without a significant loss in optical or electrical performance.

  17. Ultra-small volume interdigital sensors for the measurement of human breast milk

    NASA Astrophysics Data System (ADS)

    Keating, A.; Pang, W. W.; Lai, C. T.; Hartmann, P.

    2007-12-01

    A palm-size interdigital impedance sensor incorporating a 10 μL sample reservoir, temperature sensor and hybrid heater was fabricated to determine the feasibility of measuring macronutrients in ultra-small volumes of human breast milk. Comparisons with previous measurements of homogenized cows milk show excellent agreement with fat measurement. Human breast milk however shows no correlation with fat but a surprising correlation with protein. Our investigations and proposed methods to improve the correlation and measurement accuracy are discussed.

  18. An insight into the metabolic responses of ultra-small superparamagnetic particles of iron oxide using metabonomic analysis of biofluids

    NASA Astrophysics Data System (ADS)

    Feng, Jianghua; Liu, Huili; Zhang, Limin; Bhakoo, Kishore; Lu, Lehui

    2010-10-01

    Ultra-small superparamagnetic particles of iron oxides (USPIO) have been developed as intravenous organ/tissue-targeted contrast agents to improve magnetic resonance imaging (MRI) in vivo. However, their potential toxicity and effects on metabolism have attracted particular attention. In the present study, uncoated and dextran-coated USPIO were investigated by analyzing both rat urine and plasma metabonomes using high-resolution NMR-based metabonomic analysis in combination with multivariate statistical analysis. The wealth of information gathered on the metabolic profiles from rat urine and plasma has revealed subtle metabolic changes in response to USPIO administration. The metabolic changes include the elevation of urinary α-hydroxy-n-valerate, o- and p-HPA, PAG, nicotinate and hippurate accompanied by decreases in the levels of urinary α-ketoglutarate, succinate, citrate, N-methylnicotinamide, NAG, DMA, allantoin and acetate following USPIO administration. The changes associated with USPIO administration included a gradual increase in plasma glucose, N-acetyl glycoprotein, saturated fatty acid, citrate, succinate, acetate, GPC, ketone bodies (β-hydroxybutyrate, acetone and acetoacetate) and individual amino acids, such as phenylalanine, lysine, isoleucine, glycine, glutamine and glutamate and a gradual decrease of myo-inositol, unsaturated fatty acid and triacylglycerol. Hence USPIO administration effects are reflected in changes in a number of metabolic pathways including energy, lipid, glucose and amino acid metabolism. The size- and surface chemistry-dependent metabolic responses and possible toxicity were observed using NMR analysis of biofluids. These changes may be attributed to the disturbances of hepatic, renal and cardiac functions following USPIO administrations. The potential biotoxicity can be derived from metabonomic analysis and serum biochemistry analysis. Metabonomic strategy offers a promising approach for the detection of subtle

  19. Ultrasmall particle detection using a submicron Hall sensor

    SciTech Connect

    Kazakova, O.; Gallop, J.; Panchal, V.; See, P.; Cox, D. C.; Spasova, M.; Cohen, L. F.

    2010-05-15

    We demonstrate detection of a single FePt nanoparticle (diameter 150 nm, moment {approx}10{sup 7} {mu}{sub B}) using an ultrasensitive InSb Hall sensor with the bar lateral width of 600 nm. The white noise of a typical nanodevice, S{sub V}{sup 1/2{approx_equal}}28 nV/{radical}Hz, is limited only by two-terminal resistance of the voltage leads which results in a minimum field sensitivity of the device B{sub min}=0.87 {mu}T/{radical}Hz. To detect a single FePt bead, we employed a phase-sensitive method based on measuring the ac susceptibility change in a bead when exposed to a switched dc magnetic field. Such nano-Hall devices, enabling detection of potentially even smaller moments, are of considerable significance both for nanomagnetic metrology and high sensitivity biological and environmental detectors.

  20. Ultrasmall particle detection using a submicron Hall sensor

    NASA Astrophysics Data System (ADS)

    Kazakova, O.; Panchal, V.; Gallop, J.; See, P.; Cox, D. C.; Spasova, M.; Cohen, L. F.

    2010-05-01

    We demonstrate detection of a single FePt nanoparticle (diameter 150 nm, moment ˜107 μB) using an ultrasensitive InSb Hall sensor with the bar lateral width of 600 nm. The white noise of a typical nanodevice, SV1/2≈28 nV/√Hz, is limited only by two-terminal resistance of the voltage leads which results in a minimum field sensitivity of the device Bmin=0.87 μT/√Hz. To detect a single FePt bead, we employed a phase-sensitive method based on measuring the ac susceptibility change in a bead when exposed to a switched dc magnetic field. Such nano-Hall devices, enabling detection of potentially even smaller moments, are of considerable significance both for nanomagnetic metrology and high sensitivity biological and environmental detectors.

  1. A new method for the aqueous functionalization of superparamagnetic Fe2O3 nanoparticles.

    PubMed

    Herranz, Fernando; Morales, Ma Puerto; Roca, Alejandro G; Vilar, Ramón; Ruiz-Cabello, Jesús

    2008-01-01

    A new methodology for the synthesis of hydrophilic iron oxide nanoparticles has been developed. This new method is based on the direct chemical modification of the nanoparticles' surfactant molecules. Using this methodology both USPIO (ultrasmall super paramagnetic iron oxide) (hydrodynamic size smaller than 50 nm) and SPIO (super paramagnetic iron oxide) (hydrodynamic size bigger than 50 nm) were obtained. In addition, we also show that it is possible to further functionalize the hydrophilic nanoparticles via covalent chemistry in water. The magnetic properties of these nanoparticles were also studied, showing their potential as MRI contrast agents.

  2. Reducing Capsule Based on Electron Programming: Versatile Synthesizer for Size-Controlled Ultra-Small Metal Clusters.

    PubMed

    Kambe, Tetsuya; Imaoka, Takane; Yamamoto, Kimihisa

    2016-11-07

    Controlled reducing capsules with a specific number of reducing electrons were achieved by appropriately placed BH3 units in the dendritic polyphenylazomethines (DPAs). Using the 1:1 coordination fashion on their basic branches with radius affinity gradient, the 4th generation DPA (DPAG4) possessing four BH3 units in the central positions was prepared as a template synthesizer for size-controlled ultra-small metal clusters. This was well-demonstrated by reduction of Ag, Pt, and other metal ions resulting in monodispersed ultra-small clusters.

  3. Holographic interferometry of ultrasmall-pressure-induced curvature changes of bilayer lipid membranes

    SciTech Connect

    Picard, G.; Schneider-Henriquez, J.E.; Fendler, J.H. )

    1990-01-25

    Two-exposure interferometric holograms have been shown to sensitively report ultrasmall-pressure (10 natm)-induced curvature changes in glyceryl monooleate (GMO) bilayer lipid membranes (BLMs). The number of concentric fringes observed, and hence the lateral distance between the plane of the Teflon and the BLM, increased linearly with increasing transmembrane pressure and led to a value of 1.1 {plus minus} 0.05 dyn/cm for the surface tension of the BLM. BLMs with appreciable Plateau-Gibbs borders have been shown to undergo nonuniform deformation; the bilayer portion is distorted less than the surrounding Plateau-Gibbs border upon the application of a transmembrane pressure gradient.

  4. Concepts of the mosaic array of numerous ultra-small lens (MANUL) design

    NASA Astrophysics Data System (ADS)

    Pál, A.; Mészáros, L.

    2016-08-01

    In order to provide a continuous, multi-color time-domain surveying of the brightest regime of the naked-eye optical sky, we designed the Mosaic Array of Numerous Ultrasmall Lens (MANUL). This device is a palm-sized "astronomical observatory," featuring optics, filters and all necessary electronics (including a TCP/IP-based downlink), all are mounted on 2-inch printed circuit boards. Based on these units, a modular and mosaic arrangement of CMOS imaging sensors with an effective resolution of 1'/pixel can be built. Here we introduce the main design concepts, the early prototyping and the results of the preliminary photometric quality analysis of this initiative.

  5. Decorating in situ ultrasmall tin particles on crumpled N-doped graphene for lithium-ion batteries with a long life cycle

    NASA Astrophysics Data System (ADS)

    Liu, Lianjun; Huang, Xingkang; Guo, Xiaoru; Mao, Shun; Chen, Junhong

    2016-10-01

    The practical application of Sn, a promising anode material for lithium-ion batteries, is hindered primarily by its huge volume change (up to 260%) upon lithiation. To tackle this obstacle, here we report a facile one-pot method, i.e., pyrolysis of a mixture of GO, SnCl4, and cyanamide at elevated temperatures to create in situ a novel mesoporous structure of Sn@N-doped graphene (Sn@NG). In the constructed architecture, the ultrasmall Sn nanoparticles (2-3 nm) are uniformly embedded in the NG network while the crumpled NG provides good electronic conductivity, abundant defects, high surface area, and large mesopore volume. Due to the combination of these merits, Sn@NG exhibits extremely long-term cycling stability, even at high rates, retaining a capacity of 568 mAh g-1 at 1 A g-1 (90% retention) and 535 mAh g-1 at 2 A g-1 (91.6% retention) after 1000 and 900 cycles, respectively. This performance is superior to that of Sn@G (without N-doping) and Sn//NG prepared using a two-step process with large particle sizes (>30 nm) and uneven dispersion of Sn. The findings from this work will shed light on the design of efficient and stable Sn and other metal-based materials for energy storage and conversion.

  6. Active-target T1-weighted MR Imaging of Tiny Hepatic Tumor via RGD Modified Ultra-small Fe3O4 Nanoprobes

    PubMed Central

    Jia, Zhengyang; Song, Lina; Zang, Fengchao; Song, Jiacheng; Zhang, Wei; Yan, Changzhi; Xie, Jun; Ma, Zhanlong; Ma, Ming; Teng, Gaojun; Gu, Ning; Zhang, Yu

    2016-01-01

    Developing ultrasensitive contrast agents for the early detection of malignant tumors in liver is highly demanded. Constructing hepatic tumors specific targeting probes could provide more sensitive imaging information but still faces great challenges. Here we report a novel approach for the synthesis of ultra-small Fe3O4 nanoparticles conjugated with c(RGDyK) and their applications as active-target T1-weighted magnetic resonance imaging (MRI) contrast agent (T1-Fe3O4) for imaging tiny hepatic tumors in vivo. RGD-modified T1-Fe3O4 nanoprobes exhibited high r1 of 7.74 mM-1s-1 and ultralow r2/r1 of 2.8 at 3 T, reflecting their excellent T1 contrast effect at clinically relevant magnetic field. High targeting specificity together with favorable biocompatibility and strong ability to resist against non-specific uptake were evaluated through in vitro studies. Owing to the outstanding properties of tumor angiogenesis targeting with little phagocytosis in liver parenchyma, hepatic tumor as small as 2.2 mm was successfully detected via the T1 contrast enhancement of RGD-modified T1-Fe3O4. It is emphasized that this is the first report on active-target T1 imaging of hepatic tumors, which could not only significantly improve diagnostic sensitivity, but also provide post therapeutic assessments for patients with liver cancer. PMID:27570550

  7. Accelerator mass spectrometry of ultra-small samples with applications in the biosciences

    NASA Astrophysics Data System (ADS)

    Salehpour, Mehran; Håkansson, Karl; Possnert, Göran

    2013-01-01

    An overview is presented covering the biological accelerator mass spectrometry activities at Uppsala University. The research utilizes the Uppsala University Tandem laboratory facilities, including a 5 MV Pelletron tandem accelerator and two stable isotope ratio mass spectrometers. In addition, a dedicated sample preparation laboratory for biological samples with natural activity is in use, as well as another laboratory specifically for 14C-labeled samples. A variety of ongoing projects are described and presented. Examples are: (1) Ultra-small sample AMS. We routinely analyze samples with masses in the 5-10 μg C range. Data is presented regarding the sample preparation method, (2) bomb peak biological dating of ultra-small samples. A long term project is presented where purified and cell-specific DNA from various part of the human body including the heart and the brain are analyzed with the aim of extracting regeneration rate of the various human cells, (3) biological dating of various human biopsies, including atherosclerosis related plaques is presented. The average built up time of the surgically removed human carotid plaques have been measured and correlated to various data including the level of insulin in the human blood, and (4) In addition to standard microdosing type measurements using small pharmaceutical drugs, pre-clinical pharmacokinetic data from a macromolecular drug candidate are discussed.

  8. Ultra-small photoluminescent silicon-carbide nanocrystals by atmospheric-pressure plasmas.

    PubMed

    Askari, Sadegh; Ul Haq, Atta; Macias-Montero, Manuel; Levchenko, Igor; Yu, Fengjiao; Zhou, Wuzong; Ostrikov, Kostya Ken; Maguire, Paul; Svrcek, Vladimir; Mariotti, Davide

    2016-10-06

    Highly size-controllable synthesis of free-standing perfectly crystalline silicon carbide nanocrystals has been achieved for the first time through a plasma-based bottom-up process. This low-cost, scalable, ligand-free atmospheric pressure technique allows fabrication of ultra-small (down to 1.5 nm) nanocrystals with very low level of surface contamination, leading to fundamental insights into optical properties of the nanocrystals. This is also confirmed by their exceptional photoluminescence emission yield enhanced by more than 5 times by reducing the nanocrystals sizes in the range of 1-5 nm, which is attributed to quantum confinement in ultra-small nanocrystals. This method is potentially scalable and readily extendable to a wide range of other classes of materials. Moreover, this ligand-free process can produce colloidal nanocrystals by direct deposition into liquid, onto biological materials or onto the substrate of choice to form nanocrystal films. Our simple but efficient approach based on non-equilibrium plasma environment is a response to the need of most efficient bottom-up processes in nanosynthesis and nanotechnology.

  9. Ultrasmall volume molecular isothermal amplification in microfluidic chip with advanced surface processing

    NASA Astrophysics Data System (ADS)

    Huang, Guoliang; Ma, Li; Yang, Xiaoyong; Yang, Xu

    2011-01-01

    In this paper, we developed a metal micro-fluidic chip with advanced surface processing for ultra-small volume molecular isothermal amplification. This method takes advantages of the nucleic acid amplification with good stability and consistency, high sensitivity about 31 genomic DNA copies and bacteria specific gene identification. Based on the advanced surface processing, the bioreaction assays of nucleic acid amplification was dropped about 392nl in volume. A high numerical aperture confocal optical detection system was advanced to sensitively monitor the DNA amplification with low noise and high power collecting fluorescence near to the optical diffraction limit. A speedy nucleic acid isothermal amplification was performed in the ultra-small volume microfluidic chip, where the time at the inflexions of second derivative to DNA exponential amplified curves was brought forward and the sensitivity was improved about 65 folds to that of in current 25μl Ep-tube amplified reaction, which indicates a promising clinic molecular diagnostics in the droplet amplification.

  10. Ultrasmall peptides self-assemble into diverse nanostructures: morphological evaluation and potential implications.

    PubMed

    Lakshmanan, Anupama; Hauser, Charlotte A E

    2011-01-01

    In this study, we perform a morphological evaluation of the diverse nanostructures formed by varying concentration and amino acid sequence of a unique class of ultrasmall self-assembling peptides. We modified these peptides by replacing the aliphatic amino acid at the C-aliphatic terminus with different aromatic amino acids. We tracked the effect of introducing aromatic residues on self-assembly and morphology of resulting nanostructures. Whereas aliphatic peptides formed long, helical fibers that entangle into meshes and entrap >99.9% water, the modified peptides contrastingly formed short, straight fibers with a flat morphology. No helical fibers were observed for the modified peptides. For the aliphatic peptides at low concentrations, different supramolecular assemblies such as hollow nanospheres and membrane blebs were found. Since the ultrasmall peptides are made of simple, aliphatic amino acids, considered to have existed in the primordial soup, study of these supramolecular assemblies could be relevant to understanding chemical evolution leading to the origin of life on Earth. In particular, we propose a variety of potential applications in bioengineering and nanotechnology for the diverse self-assembled nanostructures.

  11. Ultraviolet saturable absorption and ultrafast carrier dynamics in ultrasmall black phosphorus quantum dots.

    PubMed

    Wang, Y W; Liu, S; Zeng, B W; Huang, H; Xiao, J; Li, J B; Long, M Q; Xiao, S; Yu, X F; Gao, Y L; He, J

    2017-02-02

    Understanding the photoexcited carrier-relaxation actions in ultrasmall black phosphorus quantum dots (BPQDs) will play a crucial role in the fields of electronics and optoelectronics. Herein, we report the ultraviolet (UV) saturable absorption and ultrafast photoexcited carrier-relaxation dynamics of BPQDs. The ultrasmall BPQDs are synthesized using a facile liquid-exfoliation method and possess a diameter of 3.8 ± 0.6 nm and a thickness of 1.5 ± 0.4 nm. Femtosecond open-aperture (OA) Z-scan measurements showed typical saturable absorption properties in the UV band. A negative nonlinear optical (NLO) absorption coefficient of -(1.4 ± 0.3) × 10(-3) cm GW(-1) and a saturable intensity of 6.6 ± 1.3 GW cm(-2) were determined. Using a degenerate pump-probe technique, an ultrafast photoexcited carrier-recombination time was observed in the range of 216-305 fs, which was 3 orders of magnitude faster than that of BP nanosheets. Such an ultrafast relaxation component may be attributable to the edge- and step-mediated recombination and was confirmed by our density functional theory (DFT) calculations. This work provides fundamental insight into the underlying mechanism of the photoexcited carrier relaxation dynamic action in BPQDs which can enable UV photonic devices.

  12. Ultrasmall Quantum Dots: A Tool for in Vitro and in Vivo Fluorescence Imaging

    NASA Astrophysics Data System (ADS)

    Linkov, Pavel; Vokhmintcev, Kirill V.; Samokhvalov, Pavel S.; Nabiev, Igor

    2017-01-01

    Fluorescence bioimaging is an increasingly popular approach in biomedical research and diagnosis, where semiconductor nanocrystals or quantum dots (QDs) have proved to be excellent fluorescent labels. The use of ultrasmall QDs in nanoprobes extends the possibilities of bioimaging owing to an enhanced capacity for penetrating through cell membranes. However, the QDs synthesis is accompanied by the rapid growth of nanocrystals in colloidal medium what prevents obtaining sufficiently small QDs prepared by conventional approaches. Here, a one-pot injection technique of QD synthesis in an organic medium, with the reaction terminated at an early crystal growth stage and excess precursors eliminated by gel permeation chromatography, is proposed. This technique yields defect-free cadmium selenide QD cores about 1.5 nm in size emitting at the wavelengths less than 500 nm. Coating of these QDs with epitaxial shells of different compositions ensures a photoluminescence quantum yield approaching 100%. The resultant ultrasmall QDs are promising components of nanoprobes to be used for imaging intracellular and intranuclear events down to the molecular level.

  13. Ultrasmall quantum dots for fluorescent bioimaging in vivo and in vitro

    NASA Astrophysics Data System (ADS)

    Linkov, P. A.; Vokhmintcev, K. V.; Samokhvalov, P. S.; Nabiev, I. R.

    2017-01-01

    Photoluminescent semiconductor quantum dots (QDs) are widely used in many branches of diagnostics and biomedicine. Using ultrasmall QDs for designing fluorescent nanoprobes increases their capacity for penetrating through cell membranes, which allows one to use them for tracking intracellular processes at the molecular level. Obtaining small-size QDs is usually impeded due to the fast kinetics of reactions of their formation and growth in a colloidal medium. We propose a method of synthesizing defectless CdSe QDs with a diameter of 1.5 nm based on the injection reaction in an organic medium, with superfast termination of the growth of QDs at the early stage of their formation. Separation of QDs by means of gel-permeation chromatography allows one to completely remove the excess of cadmium precursors not entering the reaction, which ensures the subsequent obtaining of QDs with a controllable fluorescence wavelength and high quantum yield in the process of depositing protective epitaxial shells of different compositions. The obtained ultrasmall QDs may find application in developing photoluminescent nanoprobes for visualizing intranuclear processes in cells.

  14. Synthesis of ultrasmall Li-Mn spinel oxides exhibiting unusual ion exchange, electrochemical, and catalytic properties.

    PubMed

    Miyamoto, Yumi; Kuroda, Yoshiyuki; Uematsu, Tsubasa; Oshikawa, Hiroyuki; Shibata, Naoya; Ikuhara, Yuichi; Suzuki, Kosuke; Hibino, Mitsuhiro; Yamaguchi, Kazuya; Mizuno, Noritaka

    2015-10-12

    The efficient surface reaction and rapid ion diffusion of nanocrystalline metal oxides have prompted considerable research interest for the development of high functional materials. Herein, we present a novel low-temperature method to synthesize ultrasmall nanocrystalline spinel oxides by controlling the hydration of coexisting metal cations in an organic solvent. This method selectively led to Li-Mn spinel oxides by tuning the hydration of Li(+) ions under mild reaction conditions (i.e., low temperature and short reaction time). These particles exhibited an ultrasmall crystallite size of 2.3 nm and a large specific surface area of 371 ± 15 m(2) g(-1). They exhibited unique properties such as unusual topotactic Li(+)/H(+) ion exchange, high-rate discharge ability, and high catalytic performance for several aerobic oxidation reactions, by creating surface phenomena throughout the particles. These properties differed significantly from those of Li-Mn spinel oxides obtained by conventional solid-state methods.

  15. Synthesis of ultrasmall Li–Mn spinel oxides exhibiting unusual ion exchange, electrochemical, and catalytic properties

    PubMed Central

    Miyamoto, Yumi; Kuroda, Yoshiyuki; Uematsu, Tsubasa; Oshikawa, Hiroyuki; Shibata, Naoya; Ikuhara, Yuichi; Suzuki, Kosuke; Hibino, Mitsuhiro; Yamaguchi, Kazuya; Mizuno, Noritaka

    2015-01-01

    The efficient surface reaction and rapid ion diffusion of nanocrystalline metal oxides have prompted considerable research interest for the development of high functional materials. Herein, we present a novel low-temperature method to synthesize ultrasmall nanocrystalline spinel oxides by controlling the hydration of coexisting metal cations in an organic solvent. This method selectively led to Li–Mn spinel oxides by tuning the hydration of Li+ ions under mild reaction conditions (i.e., low temperature and short reaction time). These particles exhibited an ultrasmall crystallite size of 2.3 nm and a large specific surface area of 371 ± 15 m2 g−1. They exhibited unique properties such as unusual topotactic Li+/H+ ion exchange, high-rate discharge ability, and high catalytic performance for several aerobic oxidation reactions, by creating surface phenomena throughout the particles. These properties differed significantly from those of Li–Mn spinel oxides obtained by conventional solid-state methods. PMID:26456216

  16. Ultrasmall Peptides Self-Assemble into Diverse Nanostructures: Morphological Evaluation and Potential Implications

    PubMed Central

    Lakshmanan, Anupama; Hauser, Charlotte A.E.

    2011-01-01

    In this study, we perform a morphological evaluation of the diverse nanostructures formed by varying concentration and amino acid sequence of a unique class of ultrasmall self-assembling peptides. We modified these peptides by replacing the aliphatic amino acid at the C-aliphatic terminus with different aromatic amino acids. We tracked the effect of introducing aromatic residues on self-assembly and morphology of resulting nanostructures. Whereas aliphatic peptides formed long, helical fibers that entangle into meshes and entrap >99.9% water, the modified peptides contrastingly formed short, straight fibers with a flat morphology. No helical fibers were observed for the modified peptides. For the aliphatic peptides at low concentrations, different supramolecular assemblies such as hollow nanospheres and membrane blebs were found. Since the ultrasmall peptides are made of simple, aliphatic amino acids, considered to have existed in the primordial soup, study of these supramolecular assemblies could be relevant to understanding chemical evolution leading to the origin of life on Earth. In particular, we propose a variety of potential applications in bioengineering and nanotechnology for the diverse self-assembled nanostructures. PMID:22016623

  17. Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

    PubMed Central

    2011-01-01

    Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the crystallinity and size of CoFe2O4 nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results showed that the well-established silica network provided nucleation locations for CoFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an ideal nucleation environment to disperse CoFe2O4 nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even more versatile. PMID:21486494

  18. Thermodynamics and Charging of Interstellar Iron Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hensley, Brandon S.; Draine, B. T.

    2017-01-01

    Interstellar iron in the form of metallic iron nanoparticles may constitute a component of the interstellar dust. We compute the stability of iron nanoparticles to sublimation in the interstellar radiation field, finding that iron clusters can persist down to a radius of ≃4.5 Å, and perhaps smaller. We employ laboratory data on small iron clusters to compute the photoelectric yields as a function of grain size and the resulting grain charge distribution in various interstellar environments, finding that iron nanoparticles can acquire negative charges, particularly in regions with high gas temperatures and ionization fractions. If ≳10% of the interstellar iron is in the form of ultrasmall iron clusters, the photoelectric heating rate from dust may be increased by up to tens of percent relative to dust models with only carbonaceous and silicate grains.

  19. 201Tl+-labelled Prussian blue nanoparticles as contrast agents for SPECT scintigraphy

    NASA Astrophysics Data System (ADS)

    Perrier, M.; Busson, M.; Massasso, G.; Long, J.; Boudousq, V.; Pouget, J.-P.; Peyrottes, S.; Perigaud, Ch.; Porredon-Guarch, C.; de Lapuente, J.; Borras, M.; Larionova, J.; Guari, Y.

    2014-10-01

    Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive 201Tl+ to obtain new nanoprobes as radiotracers for 201-thallium-based imaging.Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive 201Tl+ to obtain new nanoprobes as radiotracers for 201-thallium-based imaging. Electronic supplementary information (ESI) available: Experimental details and procedures, toxicological data, PXRD, TEM images, kinetics and adsorption isotherms, SPECT/CT images, Tl+ captation profiles. See DOI: 10.1039/c4nr03044c

  20. Clinical applications of iron oxide nanoparticles for magnetic resonance imaging of brain tumors.

    PubMed

    Iv, Michael; Telischak, Nicholas; Feng, Dan; Holdsworth, Samantha J; Yeom, Kristen W; Daldrup-Link, Heike E

    2015-01-01

    Current neuroimaging provides detailed anatomic and functional evaluation of brain tumors, allowing for improved diagnostic and prognostic capabilities. Some challenges persist even with today's advanced imaging techniques, including accurate delineation of tumor margins and distinguishing treatment effects from residual or recurrent tumor. Ultrasmall superparamagnetic iron oxide nanoparticles are an emerging tool that can add clinically useful information due to their distinct physiochemical features and biodistribution, while having a good safety profile. Nanoparticles can be used as a platform for theranostic drugs, which have shown great promise for the treatment of CNS malignancies. This review will provide an overview of clinical ultrasmall superparamagnetic iron oxides and how they can be applied to the diagnostic and therapeutic neuro-oncologic setting.

  1. Actinomycetes mediated biogenic synthesis of metal and metal oxide nanoparticles: Progress and challenges.

    PubMed

    Manimaran, Manickavelu; Kannabiran, Krishnan

    2017-03-07

    Actinomycetes mediated biogenic synthesis of metal nanoparticles and their antimicrobial activities are well documented. Actinomycetes facilitate both intracellular and extracellular metal nanoparticles synthesis and are efficient candidates for the production of polydispersed, stable and ultra-small size metal nanoparticles. Secondary metabolites and new chemical entities derived from actinomycetes have not been extensively studied for the synthesis of metal/ metal oxide nanoparticles. The present review focuses on biogenic synthesis of metal nanoparticles from actinomycetes and the scope for exploring actinomycetes derived compounds (enzymes, organics acids and bioactive compounds) as metal and metal oxide reducing agents for the synthesis of desired nanoparticles. This review also focuses on challenges faced in the applications nanoparticles and the methods to synthesise biogenic metal nanoparticles with desired physiochemical properties such as ultra-small size, large surface to mass ratio, high reactivity etc. Methods to evade their toxicity and unique interactions with biological systems to improve their chance as an alternative therapeutic agent in medical and pharmaceutical industry are also discussed. This article is protected by copyright. All rights reserved.

  2. Ultra-Small Dualband Dualmode Microstrip Antenna Based on Novel Hybrid Resonator

    NASA Astrophysics Data System (ADS)

    Zhu, Ji-Xu; Bai, Peng; Zheng, Hao-Zhong

    2016-11-01

    A novel hybrid resonator consists of right handed patch+composite right and left handed transmission line (RH+CRLH) is proposed for the first time aiming at both compactness and frequency manipulation. A demonstration with theoretical dispersion relations and EM simulation is provided for the correctness and efficiency. According to the new method, an ultra-small and dualband antenna operating around 2.4 GHz (n=0, Bluetooth band) and 3.5 GHz (n=+1, Wimax band) is designed, fabricated and measured, whose occupied area is only of 0.158 λ_0. Numerical and experimental results indicate that the antenna exhibits a good impendence match, low cross-polarization and comparable radiation gains in both bands. Excellent performances of the antennas based on hybrid resonators predict promising applications in multifunction wireless communication systems.

  3. Ultrasmall-angle X-ray scattering analysis of photonic crystal structure

    SciTech Connect

    Abramova, V. V.; Sinitskii, A. S.; Grigor'eva, N. A.; Grigor'ev, S. V.; Belov, D. V.; Petukhov, A. V.; Mistonov, A. A.; Vasil'eva, A. V.; Tret'yakov, Yu. D.

    2009-07-15

    The results of an ultrasmall-angle X-ray scattering study of iron(III) oxide inverse opal thin films are presented. The photonic crystals examined are shown to have fcc structure with amount of stacking faults varying among the samples. The method used in this study makes it possible to easily distinguish between samples with predominantly twinned fcc structure and nearly perfect fcc stacking. The difference observed between samples fabricated under identical conditions is attributed to random layer stacking in the self-assembled colloidal crystals used as templates for fabricating the inverse opals. The present method provides a versatile tool for analyzing photonic crystal structure in studies of inverse opals made of various materials, colloidal crystals, and three-dimensional photonic crystals of other types.

  4. Manipulating superconducting fluctuations by the Little-Parks-de Gennes effect in ultrasmall Al loops.

    PubMed

    Staley, Neal E; Liu, Ying

    2012-09-11

    The destruction of superconducting phase coherence by quantum fluctuations and the control of these fluctuations are a problem of long-standing interest, with recent impetus provided by the relevance of these issues to the pursuit of high temperature superconductivity. Building on the work of Little and Parks, de Gennes predicted more than three decades ago that superconductivity could be destroyed near half-integer-flux quanta in ultrasmall loops, resulting in a destructive regime, and restored by adding a superconducting side branch, which does not affect the flux quantization condition. We report the experimental observation of this Little-Parks-de Gennes effect in Al loops prepared by advanced e-beam lithography. We show that the effect can be used to restore the lost phase coherence by employing side branches.

  5. Ultra-small Fabry-Perot cavities in tapered optical fibers

    NASA Astrophysics Data System (ADS)

    Warren-Smith, Stephen C.; André, Ricardo M.; Dellith, Jan; Bartelt, Hartmut

    2016-11-01

    The small dimensions of optical fiber sensors are of interest to biological applications, given the ability to penetrate relatively inaccessible regions. However, conventional optical fibers are larger than biological material such as cells, and thus there is a need for further miniaturization. Here we present the fabrication of ultra-small Fabry-Perot cavities written into optical micro-fibers using focused ion beam (FIB) milling. We have fabricated cavities as small as 2.8 μm and demonstrated their use for measuring refractive index. In order to achieve sensitive measurements we interrogate at visible wavelengths, thereby reducing the free spectral range of the interferometer (relative to infra-red interrogation), increasing the number of interference fringes, and allowing for the implementation of the Fourier shift method.

  6. Ultra-small and anionic starch nanospheres: formation and vitro thrombolytic behavior study.

    PubMed

    Huang, Yinjuan; Ding, Shenglong; Liu, Mingzhu; Gao, Chunmei; Yang, Jinlong; Zhang, Xinjie; Ding, Bin

    2013-07-25

    This paper is considered as the first report on the investigation of nattokinase (NK) release from anionic starch nanospheres. The ultra-small and anionic starch nanospheres were prepared by the method of reverse micro-emulsion crosslinking in this work. Starch nanospheres were characterized through Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). Effects of preparation conditions on particle size were studied. The cytotoxicity, biodegradable and vitro thrombolytic behaviors of nattokinase (NK) loaded anionic starch nanospheres were also studied. The results showed that the anionic starch nanospheres are non-toxic, biocompatible and biodegradable. Moreover, the anionic starch nanospheres can protect NK from fast biodegradation hence prolongs the circulation in vivo and can reduce the risk of acute hemorrhage complication by decreasing the thrombolysis rate.

  7. Amorphous RE–Fe–B–Na colloidal nanoparticles: High temperature solution synthesis and magnetic properties

    SciTech Connect

    Jia, Li-Ping; Yan, Bing

    2015-04-15

    Graphical abstract: RE–Fe–B–Na (RE = Nd–Er) colloidal nanoparticles by high-temperature solution synthesis are ultra-small monodisperse and air-stable amorphous, whose size and magnetic dependence are studied. - Highlights: • RE–Fe–B–Na nanoparticles are obtained by high-temperature solution synthesis. • These colloidal nanoparticles are monodisperse and size controlled. • The magnetism dependence and possible magnetic coupling mechanism are studied. - Abstract: RE–Fe–B–Na (RE = Nd–Er) colloidal nanoparticles are prepared by high-temperature solution synthesis. These nanoparticles are ultra-small monodisperse, air-stable and amorphous, whose particle size and magnetic property are characterized by transmission electron microscope and superconducting quantum interference device. Taking Nd–Fe–B–Na nanoparticle as an example, it is found that the particle size can be controlled in less than 7 nm. Besides, the magnetic properties of RE–Fe–B–Na colloidal nanoparticles can be compared for different rare earth elements. Based on the bulk ferromagnetic coupling, other possible magnetic coupling mechanism is discussed.

  8. Size dependence of magnetorheological properties of cobalt ferrite ferrofluid

    SciTech Connect

    Radhika, B.; Sahoo, Rasmita; Srinath, S.

    2015-06-24

    Cobalt Ferrite nanoparticles were synthesized using co-precipitation method at reaction temperatures of 40°C and 80°C. X-Ray diffraction studies confirm cubic phase formation. The average crystallite sizes were found to be ∼30nm and ∼48nm for 40°C sample and 80°C sample respectively. Magnetic properties measured using vibrating sample magnetometer show higher coercivety and magnetization for sample prepared at 80°C. Magnetorheological properties of CoFe2O4 ferrofluids were measured and studied.

  9. Surface modification of Cobalt ferrite nano-hollowspheres for inherent multiple photoluminescence and enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Talukdar, Souvanik; Mandal, Dipika; Mandal, Kalyan

    2017-03-01

    Nano-hollow spheres (NHSs) are the new drift in magnetic nanostructures as they provide more surface area at nano length scale with enhanced magnetic properties compared to their nanoparticle counterpart. Here we reported the synthesis of biocompatible CoFe2O4 NHSs of diameter around 250 nm and emergence of intrinsic multiple photoluminescence from blue, green to red on modifying their surface with small organic ligands like tartrate. The surface modified NHSs also showed notable photocatalytic activity towards the degradation of environmentally malefic dyes like Methylene Blue and Rhodamine B. The surface modified NHSs are found to exhibit superior magnetic properties.

  10. Novel hybrid multifunctional magnetoelectric porous composite films

    NASA Astrophysics Data System (ADS)

    Martins, P.; Gonçalves, R.; Lopes, A. C.; Venkata Ramana, E.; Mendiratta, S. K.; Lanceros-Mendez, S.

    2015-12-01

    Novel multifunctional porous films have been developed by the integration of magnetic CoFe2O4 (CFO) nanoparticles into poly(vinylidene fluoride)-Trifuoroethylene (P(VDF-TrFE)), taking advantage of the synergies of the magnetostrictive filler and the piezoelectric polymer. The porous films show a piezoelectric response with an effective d33 coefficient of -22 pC/N-1, a maximum magnetization of 12 emu g-1 and a maximum magnetoelectric coefficient of 9 mV cm-1 Oe-1. In this way, a multifunctional membrane has been developed suitable for advanced applications ranging from biomedical to water treatment.

  11. Size dependence of magnetorheological properties of cobalt ferrite ferrofluid

    NASA Astrophysics Data System (ADS)

    Radhika, B.; Sahoo, Rasmita; Srinath, S.

    2015-06-01

    Cobalt Ferrite nanoparticles were synthesized using co-precipitation method at reaction temperatures of 40°C and 80°C. X-Ray diffraction studies confirm cubic phase formation. The average crystallite sizes were found to be ˜30nm and ˜48nm for 40°C sample and 80°C sample respectively. Magnetic properties measured using vibrating sample magnetometer show higher coercivety and magnetization for sample prepared at 80°C. Magnetorheological properties of CoFe2O4 ferrofluids were measured and studied.

  12. Multifunctional wood materials with magnetic, superhydrophobic and anti-ultraviolet properties

    NASA Astrophysics Data System (ADS)

    Gan, Wentao; Gao, Likun; Sun, Qingfeng; Jin, Chunde; Lu, Yun; Li, Jian

    2015-03-01

    Multifunctional wood materials with magnetic, superhydrophobic and anti-ultraviolet properties were obtained successfully by precipitated CoFe2O4 nanoparticles on the wood surface and then treated with a layer of octadecyltrichlorosilane (OTS). The as-fabricated wood composites exhibited excellent magnetic property and the water contact angle of the OTS-modified magnetic wood surface reached as high as 150°, revealed the superhydrophobic property. Moreover, accelerated aging tests suggested that the treated wood composites also have an excellent anti-ultraviolet property.

  13. Quantum Tunneling of Magnetization in Ultrasmall Half-Metallic V3O4 Quantum Dots: Displaying Quantum Superparamagnetic State

    NASA Astrophysics Data System (ADS)

    Xiao, Chong; Zhang, Jiajia; Xu, Jie; Tong, Wei; Cao, Boxiao; Li, Kun; Pan, Bicai; Su, Haibin; Xie, Yi

    2012-10-01

    Quantum tunneling of magnetization (QTMs), stemming from their importance for understanding materials with unconventional properties, has continued to attract widespread theoretical and experimental attention. However, the observation of QTMs in the most promising candidates of molecular magnets and few iron-based compounds is limited to very low temperature. Herein, we first highlight a simple system, ultrasmall half-metallic V3O4 quantum dots, as a promising candidate for the investigation of QTMs at high temperature. The quantum superparamagnetic state (QSP) as a high temperature signature of QTMs is observed at 16 K, which is beyond absolute zero temperature and much higher than that of conventional iron-based compounds due to the stronger spin-orbital coupling of V3+ ions bringing high anisotropy energy. It is undoubtedly that this ultrasmall quantum dots, V3O4, offers not only a promising candidate for theoretical understanding of QTMs but also a very exciting possibility for computers using mesoscopic magnets.

  14. Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities.

    PubMed

    Jin, Rongchao; Zeng, Chenjie; Zhou, Meng; Chen, Yuxiang

    2016-09-28

    Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1-3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the stability, metal-ligand interfacial bonding, ligand assembly on particle surfaces, aesthetic structural patterns, periodicities, and emergence of the metallic state) and to develop a range of potential applications such as in catalysis, biomedicine, sensing, imaging, optics, and energy conversion. Although most of the research activity currently focuses on thiolate-protected gold nanoclusters, important progress has also been achieved in other ligand-protected gold, silver, and bimetal (or alloy) nanoclusters. All of these types of unique nanoparticles will bring unprecedented opportunities, not only in understanding the fundamental questions of nanoparticles but also in opening up new horizons for scientific studies of nanoparticles.

  15. Ultra-small Tetrametallic Pt-Pd-Rh-Ag Nanoframes with Tunable Behavior for Direct Formic Acid/Methanol Oxidation.

    PubMed

    Saleem, Faisal; Ni, Bing; Yong, Yang; Gu, Lin; Wang, Xun

    2016-10-01

    Reversible tuning of ultra-small multimetallic Pt-Pd-Rh-Ag nanoframes is achieved. These nanoframes showed tunable and reversible modes for the oxidation of small organic molecules by simply inducing segregation with adsorbates, such as SO4(2-) and OH(-) . This is the first example of reversible segregation under electrocatalytic conditions in atomic-sized electrocatalysts. These nanoframes also showed a controllable activity and good stability for the oxidation of small organic molecules.

  16. Ultrasmall Glutathione-Protected Gold Nanoclusters as Next Generation Radiotherapy Sensitizers with High Tumor Uptake and High Renal Clearance

    PubMed Central

    Zhang, Xiao-Dong; Luo, Zhentao; Chen, Jie; Song, Shasha; Yuan, Xun; Shen, Xiu; Wang, Hao; Sun, Yuanming; Gao, Kai; Zhang, Lianfeng; Fan, Saijun; Leong, David Tai; Guo, Meili; Xie, Jianping

    2015-01-01

    Radiotherapy is often the most straightforward first line cancer treatment for solid tumors. While it is highly effective against tumors, there is also collateral damage to healthy proximal tissues especially with high doses. The use of radiosensitizers is an effective way to boost the killing efficacy of radiotherapy against the tumor while drastically limiting the received dose and reducing the possible damage to normal tissues. Here, we report the design and application of a good radiosensitizer by using ultrasmall Au29–43(SG)27–37 nanoclusters (<2 nm) with a naturally-occurring peptide (e.g., glutathione or GSH) as the protecting shell. The GSH-coated Au29–43(SG)27–37 nanoclusters can escape the RES absorption, leading to a good tumor uptake (~8.1% ID/g at 24 h post injection). As a result, the as-designed Au nanoclusters led to a strong enhancement for radiotherapy, as well as a negligible damage to normal tissues. After the treatment, the ultrasmall Au29–43(SG)27–37 nanoclusters can be efficiently cleared by the kidney, thereby avoiding potential long-term side-effects caused by the accumulation of gold atoms in the body. Our data suggest that the ultrasmall peptide-protected Au nanoclusters are a promising radiosensitizer for cancer radiotherapy. PMID:25727895

  17. Ultrasmall Glutathione-Protected Gold Nanoclusters as Next Generation Radiotherapy Sensitizers with High Tumor Uptake and High Renal Clearance

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Dong; Luo, Zhentao; Chen, Jie; Song, Shasha; Yuan, Xun; Shen, Xiu; Wang, Hao; Sun, Yuanming; Gao, Kai; Zhang, Lianfeng; Fan, Saijun; Leong, David Tai; Guo, Meili; Xie, Jianping

    2015-03-01

    Radiotherapy is often the most straightforward first line cancer treatment for solid tumors. While it is highly effective against tumors, there is also collateral damage to healthy proximal tissues especially with high doses. The use of radiosensitizers is an effective way to boost the killing efficacy of radiotherapy against the tumor while drastically limiting the received dose and reducing the possible damage to normal tissues. Here, we report the design and application of a good radiosensitizer by using ultrasmall Au29-43(SG)27-37 nanoclusters (<2 nm) with a naturally-occurring peptide (e.g., glutathione or GSH) as the protecting shell. The GSH-coated Au29-43(SG)27-37 nanoclusters can escape the RES absorption, leading to a good tumor uptake (~8.1% ID/g at 24 h post injection). As a result, the as-designed Au nanoclusters led to a strong enhancement for radiotherapy, as well as a negligible damage to normal tissues. After the treatment, the ultrasmall Au29-43(SG)27-37 nanoclusters can be efficiently cleared by the kidney, thereby avoiding potential long-term side-effects caused by the accumulation of gold atoms in the body. Our data suggest that the ultrasmall peptide-protected Au nanoclusters are a promising radiosensitizer for cancer radiotherapy.

  18. Photocatalytic activities of ultra-small β-FeOOH and TiO{sub 2} heterojunction structure under simulated solar irradiation

    SciTech Connect

    Chowdhury, Mahabubur Ntiribinyange, Mary; Nyamayaro, Kudzanai; Fester, Veruscha

    2015-08-15

    Highlights: • Ultra small β-FeOOH with TiO{sub 2} in heterojunction showed good photocatalytic activity under simulated solar irradiation. • Significant improvement of photocatalytic activity compared to pristine TiO{sub 2}. • The as prepared catalyst decoloured industrial textile effluent within 30 min. - Abstract: Photocatalytic performance of β-FeOOH/TiO{sub 2} heterojunction structure, created from ultra-small β-FeOOH nanorods (2–6 nm diameter) and spherical anatase phase of TiO{sub 2} nanoparticles (∼100 nm), is reported in this study. Three different β-FeOOH mol% of (2, 5 and 10%) β-FeOOH/TiO{sub 2} composite was prepared. 5% β-FeOOH/TiO{sub 2} composite material showed the highest photocatalytic activity. XRD, high temperature XRD, FTIR, TEM, UV–vis diffuse reflectance spectra (DRS) were used to characterise the prepared catalyst. The developed catalyst showed excellent photocatalytic activity in photodegradation of methyl orange (MO) than β-FeOOH and TiO{sub 2} under simulated solar irradiation. Two commercial metal complex dyes and real textile effluent were efficiently photodegraded under identical conditions. The developed catalyst exhibited good recyclability without the need of sintering. No significant loss in efficiency was observed during the recycling cycle. These characteristics highlight the potential application of the developed photocatalyst in textile effluent treatment via photocatalysis. The enhanced photocatalytic activity was attributed to the relative energy band positions and very good electron, e{sup −} and hole, h{sup +} conduction ability of TiO{sub 2} and β-FeOOH particles respectively.

  19. Highly Efficient Antibacterial and Pb(II) Removal Effects of Ag-CoFe2O4-GO Nanocomposite.

    PubMed

    Ma, Shuanglong; Zhan, Sihui; Jia, Yanan; Zhou, Qixing

    2015-05-20

    Ag-CoFe2O4-graphene oxide (Ag-CoFe2O4-GO) nanocomposite was synthesized by doping silver and CoFe2O4 nanoparticles on the surface of GO, which was used to purify both bacteria and Pb(II) contaminated water. The Ag-CoFe2O4-GO nanomaterial was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), cyclic voltammetry (CV), and magnetic property tests. It can be found that Ag-CoFe2O4-GO nanocomposite exhibited excellent antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus compared with CoFe2O4, Ag-CoFe2O4, and CoFe2O4-GO composite. This superior disinfecting effect was possibly attributed to the combination of GO nanosheets and Ag nanoparticles. Several antibacterial factors including temperature, time, and pH were also investigated. It was obvious that E. coli was more susceptible than S. aureus toward all the four types of nanomaterials. The structural difference of bacterial membranes should be responsible for the resistant discrepancy. We also found that Ag-CoFe2O4-GO inactivated both bacteria in an irreversibly stronger manner than Ag-CoFe2O4 and CoFe2O4-GO. The Pb(II) removal efficiency with all the nanomaterials showed significant dependence on the surface area and zeta potential of the materials. In this work, not only did we demonstrate the simultaneous superior removal efficiency of bacteria and Pb(II) by Ag-CoFe2O4-GO but also the antibacterial mechanism was discussed to have a better understanding of the interaction between Ag-CoFe2O4-GO and bacteria. In a word, taking into consideration the easy magnetic separation, bulk availability, and irreversibly high antibacterial activity of Ag-CoFe2O4-GO, it is the very promising candidate material for advanced antimicrobial or Pb(II) contaminated water treatment.

  20. Bio-NCs - the marriage of ultrasmall metal nanoclusters with biomolecules

    NASA Astrophysics Data System (ADS)

    Goswami, Nirmal; Zheng, Kaiyuan; Xie, Jianping

    2014-10-01

    Ultrasmall metal nanoclusters (NCs) have attracted increasing attention due to their fascinating physicochemical properties. Today, functional metal NCs are finding growing acceptance in biomedical applications. To achieve a better performance in biomedical applications, metal NCs can be interfaced with biomolecules, such as proteins, peptides, and DNA, to form a new class of biomolecule-NC composites (or bio-NCs in short), which typically show synergistic or novel physicochemical and physiological properties. This feature article focuses on the recent studies emerging at the interface of metal NCs and biomolecules, where the interactions could impart unique physicochemical properties to the metal NCs, as well as mutually regulate biological functions of the bio-NCs. In this article, we first provide a broad overview of key concepts and developments in the novel biomolecule-directed synthesis of metal NCs. A special focus is placed on the key roles of biomolecules in metal NC synthesis. In the second part, we describe how the encapsulated metal NCs affect the structure and function of biomolecules. Followed by that, we discuss several unique synergistic effects observed in the bio-NCs, and illustrate them with examples highlighting their potential biomedical applications. Continued interdisciplinary efforts are required to build up in-depth knowledge about the interfacial chemistry and biology of bio-NCs, which could further pave their ways toward biomedical applications.

  1. Ultra-small plutonium oxide nanocrystals: an innovative material in plutonium science.

    PubMed

    Hudry, Damien; Apostolidis, Christos; Walter, Olaf; Janssen, Arne; Manara, Dario; Griveau, Jean-Christophe; Colineau, Eric; Vitova, Tonya; Prüssmann, Tim; Wang, Di; Kübel, Christian; Meyer, Daniel

    2014-08-11

    Apart from its technological importance, plutonium (Pu) is also one of the most intriguing elements because of its non-conventional physical properties and fascinating chemistry. Those fundamental aspects are particularly interesting when dealing with the challenging study of plutonium-based nanomaterials. Here we show that ultra-small (3.2±0.9 nm) and highly crystalline plutonium oxide (PuO2 ) nanocrystals (NCs) can be synthesized by the thermal decomposition of plutonyl nitrate ([PuO2 (NO3 )2 ]⋅3 H2 O) in a highly coordinating organic medium. This is the first example reporting on the preparation of significant quantities (several tens of milligrams) of PuO2 NCs, in a controllable and reproducible manner. The structure and magnetic properties of PuO2 NCs have been characterized by a wide variety of techniques (powder X-ray diffraction (PXRD), X-ray absorption fine structure (XAFS), X-ray absorption near edge structure (XANES), TEM, IR, Raman, UV/Vis spectroscopies, and superconducting quantum interference device (SQUID) magnetometry). The current PuO2 NCs constitute an innovative material for the study of challenging problems as diverse as the transport behavior of plutonium in the environment or size and shape effects on the physics of transuranium elements.

  2. Ultrasmall superparamagnetic particles of iron oxide (USPIO) MR imaging of infarcted myocardium in pigs.

    PubMed

    Kroft, L J; Doornbos, J; van der Geest, R J; van der Laarse, A; van der Meulen, H; de Roos, A

    1998-09-01

    The purpose of this study is to assess the potential value of ultrasmall superparamagnetic iron oxide (USPIO) for the detection of acute myocardial infarction by magnetic resonance (MR) imaging. Spin-echo magnetic resonance imaging of the heart was performed before, immediately after, and approximately 35 and 90 min after 30 micromol Fe/kg of USPIO administration in seven pigs with surgically induced myocardial infarction. Gradient-echo sequences were used to identify contraction abnormalities at the site of infarction. Myocardial signal intensities were measured using region-of-interest analysis in normal and infarcted myocardium. In addition, liver and lung signal intensities were measured. Pathologic correlation was performed after sacrificing the animals. The infarct area was located with wall-motion analysis. The site of infarction was confirmed at pathologic examination. The signal-intensity ratio between infarcted and normal myocardium was not significantly changed after USPIO administration at equilibrium stages (immediately after injection p = 0.64, at 35 min p = 0.32, at 90 min p = 0.73). The signal intensity of the liver decreased significantly after contrast administration (p < 0.05). For the lung, the change in signal intensity after USPIO administration was not significant. This pig model is well suited to study wall motion abnormalities after induction of acute myocardial infarction. USPIO-enhanced magnetic resonance imaging does not improve the visualization of acute myocardial infarction at equilibrium stage.

  3. Shrinking of the Cooper Pair Insulator Phase in Thin Films with Ultrasmall Superconducting Islands

    NASA Astrophysics Data System (ADS)

    Joy, J. C.; Zhang, X.; Zhao, C.; Valles, J. M., Jr.; Fernandes, G.; Xu, J. M.

    The ubiquity of the bosonic Cooper Pair Insulator (CPI) phase near the two-dimensional superconductor to insulator transition (SIT) is a long standing question. While a number of two dimensional materials exhibit bosonic insulating phases similar to the Mott Insulator in arrays of ultrasmall, Josephson coupled superconducting islands, others show behaviors consistent with a fermionic insulating phase. Utilizing specially prepared anodized aluminum oxide substrates, we are able to fabricate films reminiscent of arrays of superconducting islands whose properties are tunable by varying the substrate morphology. Our recent work has focused on arrays of islands which possess an energy level spacing comparable to the mean field superconducting gap, where one expects pair breaking followed by fermionic Anderson Localization as the dominant mechanism by which superconductivity is destroyed. Early results show that the paradigmatic bosonic insulator exists only very near the disorder tuned SIT, while films only marginally deeper in the insulating phase exhibit transport distinct from the CPI's reentrant, activated transport. We are grateful for the support of NSF Grant No. DMR-1307290, the AFOSR, and the AOARD. Currently at Northwestern Polytechnical University, Xian, China.

  4. High-Throughput Fabrication of Resonant Metamaterials with Ultrasmall Coaxial Apertures via Atomic Layer Lithography.

    PubMed

    Yoo, Daehan; Nguyen, Ngoc-Cuong; Martin-Moreno, Luis; Mohr, Daniel A; Carretero-Palacios, Sol; Shaver, Jonah; Peraire, Jaime; Ebbesen, Thomas W; Oh, Sang-Hyun

    2016-03-09

    We combine atomic layer lithography and glancing-angle ion polishing to create wafer-scale metamaterials composed of dense arrays of ultrasmall coaxial nanocavities in gold films. This new fabrication scheme makes it possible to shrink the diameter and increase the packing density of 2 nm-gap coaxial resonators, an extreme subwavelength structure first manufactured via atomic layer lithography, both by a factor of 100 with respect to previous studies. We demonstrate that the nonpropagating zeroth-order Fabry-Pérot mode, which possesses slow light-like properties at the cutoff resonance, traps infrared light inside 2 nm gaps (gap volume ∼ λ(3)/10(6)). Notably, the annular gaps cover only 3% or less of the metal surface, while open-area normalized transmission is as high as 1700% at the epsilon-near-zero (ENZ) condition. The resulting energy accumulation alongside extraordinary optical transmission can benefit applications in nonlinear optics, optical trapping, and surface-enhanced spectroscopies. Furthermore, because the resonance wavelength is independent of the cavity length and dramatically red shifts as the gap size is reduced, large-area arrays can be constructed with λresonance ≫ period, making this fabrication method ideal for manufacturing resonant metamaterials.

  5. Effects of Ultrasmall Orifices on the Electro-generation of Femtoliter-Volume Aqueous Droplets

    PubMed Central

    He, Mingyan; Kuo, Jason S.; Chiu, Daniel T.

    2008-01-01

    The ability to generate individual picoliter- and femtoliter-volume aqueous droplets on-demand is useful for encapsulating and chemically manipulating discrete chemical and biological samples. This paper characterizes the effects of orifice dimensions and material choices on generating such droplets in an immiscible oil phase using single high-voltage pulses with various amplitudes and durations. We have examined microfluidic orifices as small as 1.7 μm in equivalent radii, and found that the electrohydrodynamic jet lengths and the subsequent formation of droplets are affected by the axial aspect ratios of the orifices (length of an orifice divided by its equivalent radius). As higher voltages were used to compensate for the increased capillary pressure and hydrodynamic resistance in ultrasmall orifices, we observed secondary jet protrusions and droplet formations that were not of classical electrohydrodynamic origin. The droplets generated from secondary jets traveled at relatively lower velocities as compared to those of electrohydrodynamic origin, and these slow individual droplets are potentially more useful for applications in microscale chemical reactions. PMID:16800707

  6. Fabrication of Si Thermoelectric Nanomaterials Containing Ultrasmall Epitaxial Ge Nanodots with an Ultrahigh Density

    NASA Astrophysics Data System (ADS)

    Yamasaka, Shuto; Nakamura, Yoshiaki; Ueda, Tomohiro; Takeuchi, Shotaro; Yamamoto, Yuta; Arai, Shigeo; Tanji, Takayoshi; Tanaka, Nobuo; Sakai, Akira

    2015-06-01

    A Si-based nanomaterial is proposed for use as a thermoelectric material. Ultrasmall epitaxial Ge nanodots (NDs) with an ultrahigh density are introduced into Si films as phonon scatterers using an ultrathin SiO2 film technique. The nanomaterial has the stacked structure Si/Ge NDs/Si on Si substrates. Reflection high-energy electron diffraction reveals epitaxial growth of the Ge NDs and Si layers in all of the stacking stages. Sharp interfaces of the Ge NDs/Si in the stacked structures were observed by high-angle annular field scanning transmission electron microscopy. The Ge NDs were controlled in terms of their composition and strain: main parts of the NDs did not alloy with Si, and the elastic strain was relaxed. These features were confirmed by Raman scattering and x-ray diffraction measurements. The fabrication techniques used to make the simple Si-based stacked structure with strain-relaxed almost pure Ge NDs are useful to develop thermoelectric nanomaterials.

  7. Ultrasmall near-infrared Ag2Se quantum dots with tunable fluorescence for in vivo imaging.

    PubMed

    Gu, Yi-Ping; Cui, Ran; Zhang, Zhi-Ling; Xie, Zhi-Xiong; Pang, Dai-Wen

    2012-01-11

    A strategy is presented that involes coupling Na(2)SeO(3) reduction with the binding of silver ions and alanine in a quasi-biosystem to obtain ultrasmall, near-infrared Ag(2)Se quantum dots (QDs) with tunable fluorescence at 90 °C in aqueous solution. This strategy avoids high temperatures, high pressures, and organic solvents so that water-dispersible sub-3 nm Ag(2)Se QDs can be directly obtained. The photoluminescence of the Ag(2)Se QDs was size-dependent over a wavelength range from 700 to 820 nm, corresponding to sizes from 1.5 ± 0.4 to 2.4 ± 0.5 nm, with good monodispersity. The Ag(2)Se QDs are less cytotoxic than other nanomaterials used for similar applications. Furthermore, the NIR fluorescence of the Ag(2)Se QDs could penetrate through the abdominal cavity of a living nude mouse and could be detected on its back side, demonstrating the potential applications of these less toxic NIR Ag(2)Se QDs in bioimaging.

  8. High-Throughput Fabrication of Resonant Metamaterials with Ultrasmall Coaxial Apertures via Atomic Layer Lithography

    PubMed Central

    2016-01-01

    We combine atomic layer lithography and glancing-angle ion polishing to create wafer-scale metamaterials composed of dense arrays of ultrasmall coaxial nanocavities in gold films. This new fabrication scheme makes it possible to shrink the diameter and increase the packing density of 2 nm-gap coaxial resonators, an extreme subwavelength structure first manufactured via atomic layer lithography, both by a factor of 100 with respect to previous studies. We demonstrate that the nonpropagating zeroth-order Fabry-Pérot mode, which possesses slow light-like properties at the cutoff resonance, traps infrared light inside 2 nm gaps (gap volume ∼ λ3/106). Notably, the annular gaps cover only 3% or less of the metal surface, while open-area normalized transmission is as high as 1700% at the epsilon-near-zero (ENZ) condition. The resulting energy accumulation alongside extraordinary optical transmission can benefit applications in nonlinear optics, optical trapping, and surface-enhanced spectroscopies. Furthermore, because the resonance wavelength is independent of the cavity length and dramatically red shifts as the gap size is reduced, large-area arrays can be constructed with λresonance ≫ period, making this fabrication method ideal for manufacturing resonant metamaterials. PMID:26910363

  9. Ultrasmall polymeric nanocarriers for drug delivery to podocytes in kidney glomerulus.

    PubMed

    Bruni, R; Possenti, P; Bordignon, C; Li, M; Ordanini, S; Messa, P; Rastaldi, M P; Cellesi, F

    2017-04-07

    We explored the use of new drug-loaded nanocarriers and their targeted delivery to the kidney glomerulus and in particular to podocytes, in order to overcome the failure of current therapeutic regimens in patients with proteinuric (i.e. abnormal amount of proteins in the urine) diseases. Podocytes are glomerular cells which are mainly responsible for glomerular filtration and are primarily or secondarily involved in chronic kidney diseases. Therefore, the possibility to utilise a podocyte-targeted drug delivery could represent a major breakthrough in kidney disease research, particularly in terms of dosage reduction and elimination of systemic side effects of current therapies. Four-arm star-shaped polymers, with/without a hydrophobic poly-ε-caprolactone core and a brush-like polyethylene glycol (PEG) hydrophilic shell, were synthesised by controlled/living polymerisation (ROP and ATRP) to allow the formation of stable ultrasmall colloidal nanomaterials of tuneable size (5-30nm), which are able to cross the glomerular filtration barrier (GFB). The effects of these nanomaterials on glomerular cells were evaluated in vitro. Nanomaterial accumulation and permeability in the kidney glomerulus were also assessed in mice under physiological and pathological conditions. Drug (dexamethasone) encapsulation was performed in order to test loading capacity, release kinetics, and podocyte repairing effects. The marked efficacy of these drug-loaded nanocarriers in repairing damaged podocytes may pave the way for developing a cell-targeted administration of new and traditional drugs, increasing efficacy and limiting side effects.

  10. Ultrasmall Nanoplatforms as Calcium-Responsive Contrast Agents for Magnetic Resonance Imaging.

    PubMed

    Moussaron, Albert; Vibhute, Sandip; Bianchi, Andrea; Gündüz, Serhat; Kotb, Shady; Sancey, Lucie; Motto-Ros, Vincent; Rizzitelli, Silvia; Crémillieux, Yannick; Lux, Francois; Logothetis, Nikos K; Tillement, Olivier; Angelovski, Goran

    2015-10-07

    The preparation of ultrasmall and rigid platforms (USRPs) that are covalently coupled to macrocycle-based, calcium-responsive/smart contrast agents (SCAs), and the initial in vitro and in vivo validation of the resulting nanosized probes (SCA-USRPs) by means of magnetic resonance imaging (MRI) is reported. The synthetic procedure is robust, allowing preparation of the SCA-USRPs on a multigram scale. The resulting platforms display the desired MRI activity—i.e., longitudinal relaxivity increases almost twice at 7 T magnetic field strength upon saturation with Ca(2+). Cell viability is probed with the MTT assay using HEK-293 cells, which show good tolerance for lower contrast agent concentrations over longer periods of time. On intravenous administration of SCA-USRPs in living mice, MRI studies indicate their rapid accumulation in the renal pelvis and parenchyma. Importantly, the MRI signal increases in both kidney compartments when CaCl2 is also administrated. Laser-induced breakdown spectroscopy experiments confirm accumulation of SCA-USRPs in the renal cortex. To the best of our knowledge, these are the first studies which demonstrate calcium-sensitive MRI signal changes in vivo. Continuing contrast agent and MRI protocol optimizations should lead to wider application of these responsive probes and development of superior functional methods for monitoring calcium-dependent physiological and pathological processes in a dynamic manner.

  11. Bio-NCs--the marriage of ultrasmall metal nanoclusters with biomolecules.

    PubMed

    Goswami, Nirmal; Zheng, Kaiyuan; Xie, Jianping

    2014-11-21

    Ultrasmall metal nanoclusters (NCs) have attracted increasing attention due to their fascinating physicochemical properties. Today, functional metal NCs are finding growing acceptance in biomedical applications. To achieve a better performance in biomedical applications, metal NCs can be interfaced with biomolecules, such as proteins, peptides, and DNA, to form a new class of biomolecule-NC composites (or bio-NCs in short), which typically show synergistic or novel physicochemical and physiological properties. This feature article focuses on the recent studies emerging at the interface of metal NCs and biomolecules, where the interactions could impart unique physicochemical properties to the metal NCs, as well as mutually regulate biological functions of the bio-NCs. In this article, we first provide a broad overview of key concepts and developments in the novel biomolecule-directed synthesis of metal NCs. A special focus is placed on the key roles of biomolecules in metal NC synthesis. In the second part, we describe how the encapsulated metal NCs affect the structure and function of biomolecules. Followed by that, we discuss several unique synergistic effects observed in the bio-NCs, and illustrate them with examples highlighting their potential biomedical applications. Continued interdisciplinary efforts are required to build up in-depth knowledge about the interfacial chemistry and biology of bio-NCs, which could further pave their ways toward biomedical applications.

  12. Ultrasmall Pt Nanoclusters as Robust Peroxidase Mimics for Colorimetric Detection of Glucose in Human Serum.

    PubMed

    Jin, Lihua; Meng, Zheng; Zhang, Yongqing; Cai, Shijie; Zhang, Zaihua; Li, Cong; Shang, Li; Shen, Yehua

    2017-02-28

    In this work, a new type of ultrasmall Pt nanoclusters (Pt NCs) has been prepared via a facile one-pot approach by using yeast extract as the reductant and stabilizer. Besides their excellent water-solubility, these yeast extract-stabilized Pt NCs also possess attractive peroxidase mimics property. They can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the coexistence of hydrogen peroxide (H2O2). Catalytic mechanism analysis suggested that the peroxidase mimics activity of these Pt NCs might originate from their characteristic of accelerating electron transfer between TMB and H2O2, and their enzymatic kinetics followed typical Michaelis-Menten theory. Based on these findings, we developed a new highly sensitive colorimetric method for glucose detection, and the limit of detection was calculated as low as 0.28 μM (S/N = 3). Further application of the present system for glucose detection in human serum has been successfully demonstrated, suggesting its promising utilization as robust peroxidase mimics in the clinical diagnosis, pharmaceutical and environmental chemistry fields.

  13. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    PubMed Central

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew

    2014-01-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy. PMID:25422526

  14. Mixed lanthanide oxide nanoparticles as dual imaging agent in biomedicine

    NASA Astrophysics Data System (ADS)

    Xu, Wenlong; Bony, Badrul Alam; Kim, Cho Rong; Baeck, Jong Su; Chang, Yongmin; Bae, Ji Eun; Chae, Kwon Seok; Kim, Tae Jeong; Lee, Gang Ho

    2013-11-01

    There is no doubt that the molecular imaging is an extremely important technique in diagnosing diseases. Dual imaging is emerging as a step forward in molecular imaging technique because it can provide us with more information useful for diagnosing diseases than single imaging. Therefore, diverse dual imaging modalities should be developed. Molecular imaging generally relies on imaging agents. Mixed lanthanide oxide nanoparticles could be valuable materials for dual magnetic resonance imaging (MRI)-fluorescent imaging (FI) because they have both excellent and diverse magnetic and fluorescent properties useful for dual MRI-FI, depending on lanthanide ions used. Since they are mixed nanoparticles, they are compact, robust, and stable, which is extremely useful for biomedical applications. They can be also easily synthesized with facile composition control. In this study, we explored three systems of ultrasmall mixed lanthanide (Dy/Eu, Ho/Eu, and Ho/Tb) oxide nanoparticles to demonstrate their usefulness as dual T2 MRI-FI agents.

  15. Multiscale investigation of USPIO nanoparticles in atherosclerotic plaques and their catabolism and storage in vivo.

    PubMed

    Maraloiu, Valentin-Adrian; Appaix, Florence; Broisat, Alexis; Le Guellec, Dominique; Teodorescu, Valentin Serban; Ghezzi, Catherine; van der Sanden, Boudewijn; Blanchin, Marie-Genevieve

    2016-01-01

    The storage and catabolism of Ultrasmall SuperParamagnetic Iron Oxide (USPIO) nanoparticles were analyzed through a multiscale approach combining Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM) at different times after intravenous injection in an atherosclerotic ApoE(-/-) mouse model. The atherosclerotic plaque features and the USPIO heterogeneous biodistribution were revealed down from organ's scale to subcellular level. The biotransformation of the nanoparticle iron oxide (maghemite) core into ferritin, the non-toxic form of iron storage, was demonstrated for the first time ex vivo in atherosclerotic plaques as well as in spleen, the iron storage organ. These results rely on an innovative spatial and structural investigation of USPIO's catabolism in cellular phagolysosomes. This study showed that these nanoparticles were stored as non-toxic iron compounds: maghemite oxide or ferritin, which is promising for MRI detection of atherosclerotic plaques in clinics using these USPIOs. From the Clinical Editor: Advance in nanotechnology has brought new contrast agents for clinical imaging. In this article, the authors investigated the use and biotransformation of Ultrasmall Super-paramagnetic Iron Oxide (USPIO) nanoparticles for analysis of atherosclerotic plagues in Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM). The biophysical data generated from this study could enable the possible use of these nanoparticles for the benefits of clinical patients.

  16. Massive dielectric properties enhancement of MWCNTs/CoFe2O4 nanohybrid for super capacitor applications

    NASA Astrophysics Data System (ADS)

    Khan, Muhammad Zarrar; Gul, Iftikhar Hussain; Anwar, Humaira; Ameer, Shahid; Khan, Ahmad Nawaz; Khurram, Aqeel Ahsan; Nadeem, Kashif; Mumtaz, Muhammad

    2017-02-01

    Nanohybrids of CoFe2O4/MWCNTs with increasing MWCNTs loading from 0.0%, 0.5%, 1%, 1.5%, 2% and 5% by weight were prepared by a novel method of dispersion using ortho-xylene as a dispersive medium for the first time. In our current research, nanoparticles of cobalt ferrite were synthesized via wet chemical co-precipitation route. Non-magnetic MWCNTs matrix was dispersed uniformly in the synthesized ferrite nanoparticles using ortho-xylene as a polar solvent. and Impedance Analyzer were utilized to effectively investigate the synthesized nanohybrid. The obtained X-Ray Powder Diffraction (XRD) images confirm the pure Face Centered Cubic (FCC) single phase of CoFe2O4/MWCNTs nanohybrid. The average crystallite size remains within the range of 26±6 nm. Scanning Electron Microscopy (SEM) results showed aggregation of ferrite nanoparticles on MWCNTs. Fourier Transform Infrared Spectroscopy (FTIR) was utilized to study the band positions. The dielectric properties were found to be massively enhanced with increased loadings of MWCNTs. The dielectric constant (ε/) was massively enhanced from 45 for pure cobalt ferrites to 4.32×1012 for 5% MWCNTs loading at 100 Hz. The dielectric and tangent losses also increased from 21 and 0.47 for pure cobalt ferrites to 2.33×1017 and 5.39×104 at 100 Hz for 5% MWCNTs loading respectively indicating that this area of research should further be exploited in the realm of super capacitors applications.

  17. A novel and facile synthesis of porous SiO2-coated ultrasmall Se particles as a drug delivery nanoplatform for efficient synergistic treatment of cancer cells

    NASA Astrophysics Data System (ADS)

    Liu, Xijian; Deng, Guoying; Wang, Yeying; Wang, Qian; Gao, Zhifang; Sun, Yangang; Zhang, Wenlong; Lu, Jie; Hu, Junqing

    2016-04-01

    A novel and facile synthetic route has been developed to fabricate porous SiO2-coated ultrasmall Se particles (Se@SiO2 nanospheres) as a drug delivery nanoplatform which combines Se quantum dots and doxorubicin (DOX) for efficient synergistic treatment of cancer cells.A novel and facile synthetic route has been developed to fabricate porous SiO2-coated ultrasmall Se particles (Se@SiO2 nanospheres) as a drug delivery nanoplatform which combines Se quantum dots and doxorubicin (DOX) for efficient synergistic treatment of cancer cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02298g

  18. Imaging of activated complement using ultrasmall superparamagnetic iron oxide particles (USPIO) - conjugated vectors: an in vivo in utero non-invasive method to predict placental insufficiency and abnormal fetal brain development

    PubMed Central

    Girardi, G; Fraser, J; Lennen, R; Vontell, R; Jansen, M; Hutchison, G

    2015-01-01

    In the current study, we have developed a magnetic resonance imaging-based method for non-invasive detection of complement activation in placenta and foetal brain in vivo in utero. Using this method, we found that anti-complement C3-targeted ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles bind within the inflamed placenta and foetal brain cortical tissue, causing a shortening of the T2* relaxation time. We used two mouse models of pregnancy complications: a mouse model of obstetrics antiphospholipid syndrome (APS) and a mouse model of preterm birth (PTB). We found that detection of C3 deposition in the placenta in the APS model was associated with placental insufficiency characterised by increased oxidative stress, decreased vascular endothelial growth factor and placental growth factor levels and intrauterine growth restriction. We also found that foetal brain C3 deposition was associated with cortical axonal cytoarchitecture disruption and increased neurodegeneration in the mouse model of APS and in the PTB model. In the APS model, foetuses that showed increased C3 in their brains additionally expressed anxiety-related behaviour after birth. Importantly, USPIO did not affect pregnancy outcomes and liver function in the mother and the offspring, suggesting that this method may be useful for detecting complement activation in vivo in utero and predicting placental insufficiency and abnormal foetal neurodevelopment that leads to neuropsychiatric disorders. PMID:25245499

  19. Biofunctional polymer nanoparticles for intra-articular targeting and retention in cartilage

    NASA Astrophysics Data System (ADS)

    Rothenfluh, Dominique A.; Bermudez, Harry; O'Neil, Conlin P.; Hubbell, Jeffrey A.

    2008-03-01

    The extracellular matrix of dense, avascular tissues presents a barrier to entry for polymer-based therapeutics, such as drugs encapsulated within polymeric particles. Here, we present an approach by which polymer nanoparticles, sufficiently small to enter the matrix of the targeted tissue, here articular cartilage, are further modified with a biomolecular ligand for matrix binding. This combination of ultrasmall size and biomolecular binding converts the matrix from a barrier into a reservoir, resisting rapid release of the nanoparticles and clearance from the tissue site. Phage display of a peptide library was used to discover appropriate targeting ligands by biopanning on denuded cartilage. The ligand WYRGRL was selected in 94 of 96 clones sequenced after five rounds of biopanning and was demonstrated to bind to collagen II α1. Peptide-functionalized nanoparticles targeted articular cartilage up to 72-fold more than nanoparticles displaying a scrambled peptide sequence following intra-articular injection in the mouse.

  20. Complete Exchange of the Hydrophobic Dispersant Shell on Monodisperse Superparamagnetic Iron Oxide Nanoparticles

    PubMed Central

    2015-01-01

    High-temperature synthesized monodisperse superparamagnetic iron oxide nanoparticles are obtained with a strongly bound ligand shell of oleic acid and its decomposition products. Most applications require a stable presentation of a defined surface chemistry; therefore, the native shell has to be completely exchanged for dispersants with irreversible affinity to the nanoparticle surface. We evaluate by attenuated total reflectance−Fourier transform infrared spectroscopy (ATR−FTIR) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) the limitations of commonly used approaches. A mechanism and multiple exchange scheme that attains the goal of complete and irreversible ligand replacement on monodisperse nanoparticles of various sizes is presented. The obtained hydrophobic nanoparticles are ideally suited for magnetically controlled drug delivery and membrane applications and for the investigation of fundamental interfacial properties of ultrasmall core–shell architectures. PMID:26226071

  1. Near-infrared electrogenerated chemiluminescence of ultrasmall Ag2Se quantum dots for the detection of dopamine.

    PubMed

    Cui, Ran; Gu, Yi-Ping; Bao, Lei; Zhao, Jing-Ya; Qi, Bao-Ping; Zhang, Zhi-Ling; Xie, Zhi-Xiong; Pang, Dai-Wen

    2012-11-06

    The near-infrared (NIR) electrogenerated chemiluminescence (ECL) of water-dispersed Ag(2)Se quantum dots (QDs) with ultrasmall size was presented for the first time. The Ag(2)Se QDs have shown a strong and efficient cathodic ECL signal with K(2)S(2)O(8) as coreactant on the glassy carbon electrode (GCE) in aqueous solution. The ECL spectrum exhibited a peak at 695 nm, consistent with the peak in photoluminescence (PL) spectrum of the Ag(2)Se QDs solution, indicating that the Ag(2)Se QDs had no deep surface traps. Dopamine was chosen as a model analyte to study the potential of Ag(2)Se QDs in the ECL analytical application. The ECL signal of Ag(2)Se QDs can also be used for the detection of the dopamine concentration in the practical drug (dopamine hydrochloride injection) containing several adjuvants such as edetate disodium, sodium bisulfite, sodium chloride and so on. The Ag(2)Se QDs could be a promising candidate emitter of ECL biosensors in the future due to their fantastic features, such as ultrasmall size, low toxicity, good water solubility, and near infrared (NIR) fluorescent emission.

  2. Wedge hybrid plasmonic THz waveguide with long propagation length and ultra-small deep-subwavelength mode area

    PubMed Central

    Gui, Chengcheng; Wang, Jian

    2015-01-01

    We present a novel design of wedge hybrid plasmonic terahertz (THz) waveguide consisting of a silicon (Si) nanowire cylinder above a triangular gold wedge with surrounded high-density polyethylene as cladding. It features long propagation length and ultra-small deep-subwavelength mode confinement. The mode properties of wedge hybrid plasmonic THz waveguide are comprehensively characterized in terms of propagation length (L), normalized mode area (Aeff /A0), figure of merit (FoM), and chromatic dispersion (D). The designed wedge hybrid plasmonic THz waveguide enables an ultra-small deep-subwavelength mode area which is more than one-order of magnitude smaller compared to previous rectangular one. When choosing the diameter of Si nanowire cylinder, a smaller diameter (e.g. 10 μm) is preferred to achieve longer L and higher FoM, while a larger diameter (e.g. 60 μm) is favorable to obtain smaller Aeff /A0 and higher FoM. We further study the impacts of possible practical fabrication errors on the mode properties. The simulated results of propagation length and normalized mode area show that the proposed wedge hybrid plasmonic THz waveguide is tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, variation of wedge tip angle, and variation of wedge tip curvature radius. PMID:26155782

  3. Manganese (II) Chelate Functionalized Copper Sulfide Nanoparticles for Efficient Magnetic Resonance/Photoacoustic Dual-Modal Imaging Guided Photothermal Therapy

    PubMed Central

    Liu, Renfa; Jing, Lijia; Peng, Dong; Li, Yong; Tian, Jie; Dai, Zhifei

    2015-01-01

    The integration of diagnostic and therapeutic functionalities into one nanoplatform shows great promise in cancer therapy. In this research, manganese (II) chelate functionalized copper sulfide nanoparticles were successfully prepared using a facile hydrothermal method. The obtained ultrasmall nanoparticles exhibit excellent photothermal effect and photoaoustic activity. Besides, the high loading content of Mn(II) chelates makes the nanoparticles attractive T1 contrast agent in magnetic resonance imaging (MRI). In vivo photoacoustic imaging (PAI) results showed that the nanoparticles could be efficiently accumulated in tumor site in 24 h after systematic administration, which was further validated by MRI tests. The subsequent photothermal therapy of cancer in vivo was achieved without inducing any observed side effects. Therefore, the copper sulfide nanoparticles functionalized with Mn(II) chelate hold great promise as a theranostic nanomedicine for MR/PA dual-modal imaging guided photothermal therapy of cancer. PMID:26284144

  4. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe{sub 3}O{sub 4} nanoparticle rings

    SciTech Connect

    Takeno, Yumu; Murakami, Yasukazu E-mail: kannanmk@uw.edu; Shindo, Daisuke; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Ferguson, R. Matthew; Krishnan, Kannan M. E-mail: kannanmk@uw.edu

    2014-11-03

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe{sub 3}O{sub 4} nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  5. Manganese (II) Chelate Functionalized Copper Sulfide Nanoparticles for Efficient Magnetic Resonance/Photoacoustic Dual-Modal Imaging Guided Photothermal Therapy.

    PubMed

    Liu, Renfa; Jing, Lijia; Peng, Dong; Li, Yong; Tian, Jie; Dai, Zhifei

    2015-01-01

    The integration of diagnostic and therapeutic functionalities into one nanoplatform shows great promise in cancer therapy. In this research, manganese (II) chelate functionalized copper sulfide nanoparticles were successfully prepared using a facile hydrothermal method. The obtained ultrasmall nanoparticles exhibit excellent photothermal effect and photoaoustic activity. Besides, the high loading content of Mn(II) chelates makes the nanoparticles attractive T1 contrast agent in magnetic resonance imaging (MRI). In vivo photoacoustic imaging (PAI) results showed that the nanoparticles could be efficiently accumulated in tumor site in 24 h after systematic administration, which was further validated by MRI tests. The subsequent photothermal therapy of cancer in vivo was achieved without inducing any observed side effects. Therefore, the copper sulfide nanoparticles functionalized with Mn(II) chelate hold great promise as a theranostic nanomedicine for MR/PA dual-modal imaging guided photothermal therapy of cancer.

  6. How size evaluation of lymph node is protocol dependent in MRI when using ultrasmall superparamagnetic iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Gharehaghaji, Nahideh; Oghabian, Mohammad Ali; Sarkar, Saeed; Darki, Fahimeh; Beitollahi, Ali

    2009-05-01

    In this study, the volume of susceptibility artifact was evaluated in T1 and T2-weighted spin echo (SE) and gradient echo (GRE) images at various parameters using registration and subtraction methods. In order to state an important misinterpretation problem in lymphography, it was demonstrated that a lymph node size may be enlarged approximately 10 times when a T2*-weighted GRE protocol is used. To overcome this problem a technical consideration using multisequence (GRE and SE) paradigm was suggested to ensure both lymph node detection and metastasis identification in lymphatic system. The paradigm was also extended by post-processing manipulation of the SE images using a registration and subtraction approach for detection of lymphatic lesions.

  7. Molecular magnetic resonance imaging of activated hepatic stellate cells with ultrasmall superparamagnetic iron oxide targeting integrin αvβ3 for staging liver fibrosis in rat model

    PubMed Central

    Zhang, Caiyuan; Liu, Huanhuan; Cui, Yanfen; Li, Xiaoming; Zhang, Zhongyang; Zhang, Yong; Wang, Dengbin

    2016-01-01

    Purpose To evaluate the expression level of integrin αvβ3 on activated hepatic stellate cells (HSCs) at different stages of liver fibrosis induced by carbon tetrachloride (CCl4) in rat model and the feasibility to stage liver fibrosis by using molecular magnetic resonance imaging (MRI) with arginine-glycine-aspartic acid (RGD) peptide modified ultrasmall superparamagnetic iron oxide nanoparticle (USPIO) specifically targeting integrin αvβ3. Materials and methods All experiments received approval from our Institutional Animal Care and Use Committee. Thirty-six rats were randomly divided into three groups of 12 subjects each, and intraperitoneally injected with CCl4 for either 3, 6, or 9 weeks. Controls (n=10) received pure olive oil. The change in T2* relaxation rate (ΔR2*) pre- and postintravenous administration of RGD-USPIO or naked USPIO was measured by 3.0T clinical MRI and compared by one-way analysis of variance or the Student’s t-test. The relationship between expression level of integrin αvβ3 and liver fibrotic degree was evaluated by Spearman’s ranked correlation. Results Activated HSCs were confirmed to be the main cell types expressing integrin αvβ3 during liver fibrogenesis. The protein level of integrin αv and β3 subunit expressed on activated HSCs was upregulated and correlated well with the progression of liver fibrosis (r=0.954, P<0.001; r=0.931, P<0.001, respectively). After injection of RGD-USPIO, there is significant difference in ΔR2* among rats treated with 0, 3, 6, and 9 weeks of CCl4 (P<0.001). The accumulation of iron particles in fibrotic liver specimen is significantly greater for RGD-USPIO than naked USPIO after being injected with equal dose of iron. Conclusion Molecular MRI of integrin αvβ3 expressed on activated HSCs by using RGD-USPIO may distinguish different liver fibrotic stages in CCl4 rat model and shows promising to noninvasively monitor the progression of the liver fibrosis and therapeutic response to

  8. A new approach to quantification of metamorphism using ultra-small and small angle neutron scattering.

    SciTech Connect

    Anovitz, Lawrence {Larry} M; Lynn, Gary W; Cole, David R

    2009-12-01

    In this paper we report the results of a study using small angle and ultra-small angle neutron scattering techniques (SANS and USANS) to examine the evolution of carbonates during contact metamorphism. Data were obtained from samples collected along two transects in the metamorphosed Hueco limestone at the Marble Canyon, Texas, contact aureole. These samples were collected from the igneous contact out to {approx}1700 m. Scattering curves obtained from these samples show mass fractal behavior at low scattering vectors, and surface fractal behavior at high scattering vectors. Significant changes are observed in the surface and mass fractal dimensions as well as the correlation lengths (pore and grain sizes), surface area to volume ratio and surface Gibbs Free energy as a function of distance, including regions of the aureole outside the range of classic metamorphic petrology. A change from mass-fractal to non-fractal behavior is observed at larger scales near the outer boundary of the aureole that implies significant reorganization of pore distributions early in the metamorphic history. Surface fractal results suggest significant smoothing of grain boundaries, coupled with changes in pore sizes. A section of the scattering curve with a slope less than -4 appears at low-Q in metamorphosed samples, which is not present in unmetamorphosed samples. A strong spike in the surface area to volume ratio is observed in rocks near the mapped metamorphic limit, which is associated with reaction of small amounts of organic material to graphite. It may also represent an increase in pore volume or permeability, suggesting that a high permeability zone forms at the boundary of the aureole and moves outwards as metamorphism progresses. Neutron scattering data also correlate well with transmission electron microscopic (TEM) observations, which show formation of micro- and nanopores and microfractures during metamorphism. The scattering data are, however, quantifiable for a bulk rock

  9. Development of carbon nanotubes/CoFe2O4 magnetic hybrid material for removal of tetrabromobisphenol A and Pb(II).

    PubMed

    Zhou, Lincheng; Ji, Liqin; Ma, Peng-Cheng; Shao, Yanming; Zhang, He; Gao, Weijie; Li, Yanfeng

    2014-01-30

    Multi-walled carbon nanotubes (MWCNTs) coated with magnetic amino-modified CoFe2O4 (CoFe2O4-NH2) nanoparticles (denoted as MNP) were prepared via a simple one-pot polyol method. The MNP composite was further modified with chitosan (CTS) to obtain a chitosan-functionalized MWCNT/CoFe2O4-NH2 hybrid material (MNP-CTS). The obtained hybrid materials were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectrogram (FT-IR) Analysis and X-ray Photoelectron Spectroscopy (XPS) Analysis, Vibrating Sample Magnetometer (VSM) Analysis and the Brunauer-Emmett-Teller (BET) surface area method, respectively. The composites were tested as adsorbents for tetrabromobisphenol A (TBBPA) and Pb(II), and were investigated using a pseudo-second-order model. The adsorption of TBBPA was well represented by the Freundlich isotherm; the Langmuir model better described Pb(II) absorption. MNP-CTS adsorbed both TBBPA and Pb(II) (maximum adsorption capacities of 42.48 and 140.1mgg(-1), respectively) better than did MNP without CTS. Magnetic composite particles with adsorbed TBBPA and Pb(II) could be regenerated using 0.2M NaOH solution and were separable from liquid media using a magnetic field.

  10. Use of Nanoparticles As Contrast Agents for the Functional and Molecular Imaging of Abdominal Aortic Aneurysm

    PubMed Central

    Emeto, Theophilus I.; Alele, Faith O.; Smith, Amy M.; Smith, Felicity M.; Dougan, Tammy; Golledge, Jonathan

    2017-01-01

    Abdominal aortic aneurysm (AAA) is a degenerative disease of the aorta common in adults older than 65 years of age. AAA is usually imaged using ultrasound or computed tomography. Molecular imaging technologies employing nanoparticles (NPs) have been proposed as novel ways to quantify pathological processes, such as inflammation, within AAAs as a means to identify the risk of rapid progression or rupture. This article reviews the current evidence supporting the role of NP-based imaging in the management of AAA. Currently, ultrasmall superparamagnetic NPs enhanced magnetic resonance imaging appears to hold the greatest potential for imaging macrophage-mediated inflammation in human AAA. PMID:28386544

  11. Use of Nanoparticles As Contrast Agents for the Functional and Molecular Imaging of Abdominal Aortic Aneurysm.

    PubMed

    Emeto, Theophilus I; Alele, Faith O; Smith, Amy M; Smith, Felicity M; Dougan, Tammy; Golledge, Jonathan

    2017-01-01

    Abdominal aortic aneurysm (AAA) is a degenerative disease of the aorta common in adults older than 65 years of age. AAA is usually imaged using ultrasound or computed tomography. Molecular imaging technologies employing nanoparticles (NPs) have been proposed as novel ways to quantify pathological processes, such as inflammation, within AAAs as a means to identify the risk of rapid progression or rupture. This article reviews the current evidence supporting the role of NP-based imaging in the management of AAA. Currently, ultrasmall superparamagnetic NPs enhanced magnetic resonance imaging appears to hold the greatest potential for imaging macrophage-mediated inflammation in human AAA.

  12. Soluble Metal-Nanoparticle-Decorated Porous Coordination Polymers for the Homogenization of Heterogeneous Catalysis.

    PubMed

    Huang, Yuan-Biao; Wang, Qiang; Liang, Jun; Wang, Xusheng; Cao, Rong

    2016-08-17

    Ultrasmall metal nanoparticles (MNPs) were decorated on soluble porous coordination polymers (PCPs) with high metal loadings. The solubility of the composite and the size of the MNPs can be controlled by varying the ratio of the precursors to the supports. The soluble PCPs can serve as a platform to homogenize heterogeneous MNPs catalysts, which exhibited excellent activity and recyclability in C-H activation and Suzuki reactions. This strategy combines the advantages of homogeneous and heterogeneous catalysis and may bring new inspiration to catalysis.

  13. Synthesis of Water Dispersible and Catalytically Active Gold-Decorated Cobalt Ferrite Nanoparticles.

    PubMed

    Silvestri, Alessandro; Mondini, Sara; Marelli, Marcello; Pifferi, Valentina; Falciola, Luigi; Ponti, Alessandro; Ferretti, Anna Maria; Polito, Laura

    2016-07-19

    Hetero-nanoparticles represent an important family of composite nanomaterials that in the past years are attracting ever-growing interest. Here, we report a new strategy for the synthesis of water dispersible cobalt ferrite nanoparticles (CoxFe3-xO4 NPs) decorated with ultrasmall (2-3 nm) gold nanoparticles (Au NPs). The synthetic procedure is based on the use of 2,3-meso-dimercaptosuccinic acid (DMSA), which plays a double role. First, it transfers cobalt ferrite NPs from the organic phase to aqueous media. Second, the DMSA reductive power promotes the in situ nucleation of gold NPs in proximity of the magnetic NP surface. Following this procedure, we achieved a water dispersible nanosystem (CoxFe3-xO4-DMSA-Au NPs) which combines the cobalt ferrite magnetic properties with the catalytic features of ultrasmall Au NPs. We showed that CoxFe3-xO4-DMSA-Au NPs act as an efficient nanocatalyst to reduce 4-nitrophenol to 4-aminophenol and that they can be magnetically recovered and recycled. It is noteworthy that such nanosystem is more catalytically active than Au NPs with equal size. Finally, a complete structural and chemical characterization of the hetero-NPs is provided.

  14. Bifunctional non-noble metal oxide nanoparticle electrocatalysts through lithium-induced conversion for overall water splitting

    PubMed Central

    Wang, Haotian; Lee, Hyun-Wook; Deng, Yong; Lu, Zhiyi; Hsu, Po-Chun; Liu, Yayuan; Lin, Dingchang; Cui, Yi

    2015-01-01

    Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, including oxygen evolution reaction and hydrogen evolution reaction, is important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanoparticles (∼20 nm) are electrochemically transformed into ultra-small diameter (2–5 nm) nanoparticles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanoparticles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10 mA cm−2 water-splitting current at only 1.51 V for over 200 h without degradation in a two-electrode configuration and 1 M KOH, better than the combination of iridium and platinum as benchmark catalysts. PMID:26099250

  15. Cytotoxicity, tumor targeting and PET imaging of sub-5 nm KGdF4 multifunctional rare earth nanoparticles

    NASA Astrophysics Data System (ADS)

    Cao, Xinmin; Cao, Fengwen; Xiong, Liqin; Yang, Yang; Cao, Tianye; Cai, Xi; Hai, Wangxi; Li, Biao; Guo, Yixiao; Zhang, Yimin; Li, Fuyou

    2015-08-01

    Ultrasmall sub-5 nm KGdF4 rare earth nanoparticles were synthesized as multifunctional probes for fluorescent, magnetic, and radionuclide imaging. The cytotoxicity of these nanoparticles in human glioblastoma U87MG and human non-small cell lung carcinoma H1299 cells was evaluated, and their application for in vitro and in vivo tumor targeted imaging has also been demonstrated.Ultrasmall sub-5 nm KGdF4 rare earth nanoparticles were synthesized as multifunctional probes for fluorescent, magnetic, and radionuclide imaging. The cytotoxicity of these nanoparticles in human glioblastoma U87MG and human non-small cell lung carcinoma H1299 cells was evaluated, and their application for in vitro and in vivo tumor targeted imaging has also been demonstrated. Electronic supplementary information (ESI) available: Details of the experimental section as well as EDXA, XRD, zeta potential, FTIR, TGA, stability, TEM, Z scanning, ICP-MS, and MicroPET/CT images. See DOI: 10.1039/c5nr03374h

  16. Thermal decomposition of [Co(en)3][Fe(CN)6]∙ 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation

    PubMed Central

    2013-01-01

    Background The Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored. In this paper, the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ∙∙ 2H2O (1a) is elucidated, including the topotactic dehydration, valence and spins exchange mechanisms suggestion and the formation of a mixture of CoFe2O4-Co3O4 (3:1) as final products of thermal degradation. Results The course of thermal decomposition of 1a in air atmosphere up to 600°C was monitored by TG/DSC techniques, 57Fe Mössbauer and IR spectroscopy. As first, the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ∙∙ 1/2H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-ray diffraction analysis. The consequent thermal decomposition proceeded in further four stages including intermediates varying in valence and spin states of both transition metal ions in their structures, i.e. [FeII(en)2(μ-NC)CoIII(CN)4], FeIII(NH2CH2CH3)2(μ-NC)2CoII(CN)3] and FeIII[CoII(CN)5], which were suggested mainly from 57Fe Mössbauer, IR spectral and elemental analyses data. Thermal decomposition was completed at 400°C when superparamagnetic phases of CoFe2O4 and Co3O4 in the molar ratio of 3:1 were formed. During further temperature increase (450 and 600°C), the ongoing crystallization process gave a new ferromagnetic phase attributed to the CoFe2O4-Co3O4 nanocomposite particles. Their formation was confirmed by XRD and TEM analyses. In-field (5 K / 5 T) Mössbauer spectrum revealed canting of Fe(III) spin in almost fully inverse spinel structure of CoFe2O4. Conclusions It has been found

  17. Quantum Suppression of Alignment in Ultrasmall Grains: Microwave Emission from Spinning Dust will be Negligibly Polarized

    NASA Astrophysics Data System (ADS)

    Draine, B. T.; Hensley, Brandon S.

    2016-11-01

    The quantization of energy levels in small, cold, free-flying nanoparticles suppresses dissipative processes that convert grain rotational kinetic energy into heat. For interstellar grains small enough to have ˜GHz rotation rates, the suppression of dissipation can be extreme. As a result, alignment of such grains is suppressed. This applies both to alignment of the grain body with its angular momentum {\\boldsymbol{J}}, and to alignment of {\\boldsymbol{J}} with the local magnetic field {\\boldsymbol{B}} 0. If the anomalous microwave emission is rotational emission from spinning grains, then it will be negligibly polarized at GHz frequencies, with P ≲ 10-6 at ν > 10 GHz.

  18. Targeting of peptide conjugated magnetic nanoparticles to urokinase plasminogen activator receptor (uPAR) expressing cells

    NASA Astrophysics Data System (ADS)

    Hansen, Line; Unmack Larsen, Esben Kjær; Nielsen, Erik Holm; Iversen, Frank; Liu, Zhuo; Thomsen, Karen; Pedersen, Michael; Skrydstrup, Troels; Nielsen, Niels Chr.; Ploug, Michael; Kjems, Jørgen

    2013-08-01

    Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are currently being used as a magnetic resonance imaging (MRI) contrast agent in vivo, mainly by their passive accumulation in tissues of interest. However, a higher specificity can ideally be achieved when the nanoparticles are targeted towards cell specific receptors and this may also facilitate specific drug delivery by an enhanced target-mediated endocytosis. We report efficient peptide-mediated targeting of magnetic nanoparticles to cells expressing the urokinase plasminogen activator receptor (uPAR), a surface biomarker for poor patient prognosis shared by several cancers including breast, colorectal, and gastric cancers. Conjugation of a uPAR specific targeting peptide onto polyethylene glycol (PEG) coated USPIO nanoparticles by click chemistry resulted in a five times higher uptake in vitro in a uPAR positive cell line compared to nanoparticles carrying a non-binding control peptide. In accordance with specific receptor-mediated recognition, a low uptake was observed in the presence of an excess of ATF, a natural ligand for uPAR. The uPAR specific magnetic nanoparticles can potentially provide a useful supplement for tumor patient management when combined with MRI and drug delivery.Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are currently being used as a magnetic resonance imaging (MRI) contrast agent in vivo, mainly by their passive accumulation in tissues of interest. However, a higher specificity can ideally be achieved when the nanoparticles are targeted towards cell specific receptors and this may also facilitate specific drug delivery by an enhanced target-mediated endocytosis. We report efficient peptide-mediated targeting of magnetic nanoparticles to cells expressing the urokinase plasminogen activator receptor (uPAR), a surface biomarker for poor patient prognosis shared by several cancers including breast, colorectal, and gastric cancers. Conjugation of a uPAR specific

  19. Magnetoelectric ‘spin’ on stimulating the brain

    PubMed Central

    Guduru, Rakesh; Liang, Ping; Hong, J; Rodzinski, Alexandra; Hadjikhani, Ali; Horstmyer, Jeffrey; Levister, Ernest; Khizroev, Sakhrat

    2015-01-01

    Aim: The in vivo study on imprinting control region mice aims to show that magnetoelectric nanoparticles may directly couple the intrinsic neural activity-induced electric fields with external magnetic fields. Methods: Approximately 10 µg of CoFe2O4–BaTiO3 30-nm nanoparticles have been intravenously administrated through a tail vein and forced to cross the blood–brain barrier via a d.c. field gradient of 3000 Oe/cm. A surgically attached two-channel electroencephalography headmount has directly measured the modulation of intrinsic electric waveforms by an external a.c. 100-Oe magnetic field in a frequency range of 0–20 Hz. Results: The modulated signal has reached the strength comparable to that due the regular neural activity. Conclusion: The study opens a pathway to use multifunctional nanoparticles to control intrinsic fields deep in the brain. PMID:25953069

  20. Simulation of Ultra-Small MOSFETs Using a 2-D Quantum-Corrected Drift-Diffusion Model

    NASA Technical Reports Server (NTRS)

    Biegal, Bryan A.; Rafferty, Connor S.; Yu, Zhiping; Ancona, Mario G.; Dutton, Robert W.; Saini, Subhash (Technical Monitor)

    1998-01-01

    corrections do not have a large effect on the IN characteristics of electronic devices without heteroj unction s. On the other hand, ultra-small MOSFETs certainly exhibit important quantum effects that the DG model will include: quantum repulsion of the inversion and gate charges from the oxide interfaces, and quantum tunneling through thin gate oxides. We present initial results of 2-D DG simulations of ultra-small MOSFETs. Subtle but important issues involving the specification of the model, boundary conditions, and interface constraints for DG simulation of MOSFETs will also be illuminated.

  1. Aqueous phase preparation of ultrasmall MoSe2 nanodots for efficient photothermal therapy of cancer cells

    NASA Astrophysics Data System (ADS)

    Yuwen, Lihui; Zhou, Jiajia; Zhang, Yuqian; Zhang, Qi; Shan, Jingyang; Luo, Zhimin; Weng, Lixing; Teng, Zhaogang; Wang, Lianhui

    2016-01-01

    Photothermal therapy (PTT) is a promising cancer treatment with both high effectiveness and fewer side effects. However, an ideal PTT agent not only needs strong absorption of near-infrared (NIR) light and high photothermal conversion efficiency, but also needs good biocompatibility, stability, and small size, which makes the design and preparation of a novel PTT agent a great challenge. In this work, we developed an ultrasonication-assisted liquid exfoliation method for the direct preparation of ultrasmall (2-3 nm) MoSe2 nanodots (NDs) in aqueous solution and demonstrated their superior properties as a PTT agent. The as-prepared MoSe2 NDs have strong absorption of NIR light and high photothermal conversion efficiency of about 46.5%. In vitro cellular experiments demonstrate that MoSe2 NDs have negligible cytotoxicity and can efficiently kill HeLa cells (human cervical cell line) under NIR laser (785 nm) irradiation.Photothermal therapy (PTT) is a promising cancer treatment with both high effectiveness and fewer side effects. However, an ideal PTT agent not only needs strong absorption of near-infrared (NIR) light and high photothermal conversion efficiency, but also needs good biocompatibility, stability, and small size, which makes the design and preparation of a novel PTT agent a great challenge. In this work, we developed an ultrasonication-assisted liquid exfoliation method for the direct preparation of ultrasmall (2-3 nm) MoSe2 nanodots (NDs) in aqueous solution and demonstrated their superior properties as a PTT agent. The as-prepared MoSe2 NDs have strong absorption of NIR light and high photothermal conversion efficiency of about 46.5%. In vitro cellular experiments demonstrate that MoSe2 NDs have negligible cytotoxicity and can efficiently kill HeLa cells (human cervical cell line) under NIR laser (785 nm) irradiation. Electronic supplementary information (ESI) available: Characterization, size distribution and EDS spectrum of MoSe2 NDs, calculation of

  2. Electrical detection of surface plasmon resonance phenomena by a photoelectronic device integrated with gold nanoparticle plasmon antenna

    NASA Astrophysics Data System (ADS)

    Hashimoto, Tatsuya; Fukunishi, Yurie; Zheng, Bin; Uraoka, Yukiharu; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2013-02-01

    We have proposed a concept of a photoelectronic hybrid device utilizing gold nanoparticles (GNPs), which are supposed to function not only as the plasmon antenna but also as the sensing part. The photocurrent in the fabricated device, consisting of a transparent Nb-doped TiO2 channel and Au electrodes, was enhanced more than eight times at a specific wavelength with GNP arrays located between the electrodes, indicating that surface plasmon resonance was electrically detected with the hybrid device. This result will open new doors for ultra-small biosensor chips integrated with multi-functional solid-state devices.

  3. Bubble-Free Propulsion of Ultrasmall Tubular Nanojets Powered by Biocatalytic Reactions

    PubMed Central

    2016-01-01

    The motion of self-propelled tubular micro- and nanojets has so far been achieved by bubble propulsion, e.g., O2 bubbles formed by catalytic decomposition of H2O2, which renders future biomedical applications inviable. An alternative self-propulsion mechanism for tubular engines on the nanometer scale is still missing. Here, we report the fabrication and characterization of bubble-free propelled tubular nanojets (as small as 220 nm diameter), powered by an enzyme-triggered biocatalytic reaction using urea as fuel. We studied the translational and rotational dynamics of the nanojets as functions of the length and location of the enzymes. Introducing tracer nanoparticles into the system, we demonstrated the presence of an internal flow that extends into the external fluid via the cavity opening, leading to the self-propulsion. One-dimensional nanosize, longitudinal self-propulsion, and biocompatibility make the tubular nanojets promising for future biomedical applications. PMID:27718566

  4. Bubble-Free Propulsion of Ultrasmall Tubular Nanojets Powered by Biocatalytic Reactions.

    PubMed

    Ma, Xing; Hortelao, Ana C; Miguel-López, Albert; Sánchez, Samuel

    2016-10-26

    The motion of self-propelled tubular micro- and nanojets has so far been achieved by bubble propulsion, e.g., O2 bubbles formed by catalytic decomposition of H2O2, which renders future biomedical applications inviable. An alternative self-propulsion mechanism for tubular engines on the nanometer scale is still missing. Here, we report the fabrication and characterization of bubble-free propelled tubular nanojets (as small as 220 nm diameter), powered by an enzyme-triggered biocatalytic reaction using urea as fuel. We studied the translational and rotational dynamics of the nanojets as functions of the length and location of the enzymes. Introducing tracer nanoparticles into the system, we demonstrated the presence of an internal flow that extends into the external fluid via the cavity opening, leading to the self-propulsion. One-dimensional nanosize, longitudinal self-propulsion, and biocompatibility make the tubular nanojets promising for future biomedical applications.

  5. Nanoparticle cluster gas sensor: Pt activated SnO2 nanoparticles for NH3 detection with ultrahigh sensitivity.

    PubMed

    Liu, Xu; Chen, Nan; Han, Bingqian; Xiao, Xuechun; Chen, Gang; Djerdj, Igor; Wang, Yude

    2015-09-28

    Pt activated SnO2 nanoparticle clusters were synthesized by a simple solvothermal method. The structure, morphology, chemical state and specific surface area were analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2-sorption studies, respectively. The SnO2 nanoparticle cluster matrix consists of tens of thousands of SnO2 nanoparticles with an ultra-small grain size estimated to be 3.0 nm. And there are abundant random-packed wormhole-like pores, caused by the inter-connection of the SnO2 nanoparticles, throughout each cluster. The platinum element is present in two forms including metal (Pt) and tetravalent metal oxide (PtO2) in the Pt activated SnO2 nanoparticle clusters. The as-synthesized pure and Pt activated SnO2 nanoparticle clusters were used to fabricate gas sensor devices. It was found that the gas response toward 500 ppm of ammonia was improved from 6.48 to 203.44 through the activation by Pt. And the results indicate that the sensor based on Pt activated SnO2 not only has ultrahigh sensitivity but also possesses good response-recovery properties, linear dependence, repeatability, selectivity and long-term stability, demonstrating the potential to use Pt activated SnO2 nanoparticle clusters as ammonia gas sensors. At the same time, the formation mechanisms of the unique nanoparticle clusters and highly enhanced sensitivity are also discussed.

  6. NMR-based metabonomic analyses of the effects of ultrasmall superparamagnetic particles of iron oxide (USPIO) on macrophage metabolism

    NASA Astrophysics Data System (ADS)

    Feng, Jianghua; Zhao, Jing; Hao, Fuhua; Chen, Chang; Bhakoo, Kishore; Tang, Huiru

    2011-05-01

    The metabonomic changes in murine RAW264.7 macrophage-like cell line induced by ultrasmall superparamagnetic particles of iron oxides (USPIO) have been investigated, by analyzing both the cells and culture media, using high-resolution NMR in conjunction with multivariate statistical methods. Upon treatment with USPIO, macrophage cells showed a significant decrease in the levels of triglycerides, essential amino acids such as valine, isoleucine, and choline metabolites together with an increase of glycerophospholipids, tyrosine, phenylalanine, lysine, glycine, and glutamate. Such cellular responses to USPIO were also detectable in compositional changes of cell media, showing an obvious depletion of the primary nutrition molecules, such as glucose and amino acids and the production of end-products of glycolysis, such as pyruvate, acetate, and lactate and intermediates of TCA cycle such as succinate and citrate. At 48 h treatment, there was a differential response to incubation with USPIO in both cell metabonome and medium components, indicating that USPIO are phagocytosed and released by macrophages. Furthermore, information on cell membrane modification can be derived from the changes in choline-like metabolites. These results not only suggest that NMR-based metabonomic methods have sufficient sensitivity to identify the metabolic consequences of murine RAW264.7 macrophage-like cell line response to USPIO in vitro, but also provide useful information on the effects of USPIO on cellular metabolism.

  7. Hierarchical Pore Morphology of Cretaceous Shale: A Small-Angle Neutron Scattering and Ultrasmall-Angle Neutron Scattering Study

    SciTech Connect

    Bahadur, J.; Melnichenko, Y. B.; Mastalerz, Maria; Furmann, Agnieszka; Clarkson, Chris R.

    2014-09-25

    Shale reservoirs are becoming an increasingly important source of oil and natural gas supply and a potential candidate for CO2 sequestration. Understanding the pore morphology in shale may provide clues to making gas extraction more efficient and cost-effective. The porosity of Cretaceous shale samples from Alberta, Canada, collected from different depths with varying mineralogical compositions, has been investigated by small- and ultrasmall-angle neutron scattering. Moreover these samples come from the Second White Specks and Belle Fourche formations, and their organic matter content ranges between 2 and 3%. The scattering length density of the shale specimens has been estimated using the chemical composition of the different mineral components. Scattering experiments reveal the presence of fractal and non-fractal pores. It has been shown that the porosity and specific surface area are dominated by the contribution from meso- and micropores. The fraction of closed porosity has been calculated by comparing the porosities estimated by He pycnometry and scattering techniques. There is no correlation between total porosity and mineral components, a strong correlation has been observed between closed porosity and major mineral components in the studied specimens.

  8. Hierarchical Pore Morphology of Cretaceous Shale: A Small-Angle Neutron Scattering and Ultrasmall-Angle Neutron Scattering Study

    DOE PAGES

    Bahadur, J.; Melnichenko, Y. B.; Mastalerz, Maria; ...

    2014-09-25

    Shale reservoirs are becoming an increasingly important source of oil and natural gas supply and a potential candidate for CO2 sequestration. Understanding the pore morphology in shale may provide clues to making gas extraction more efficient and cost-effective. The porosity of Cretaceous shale samples from Alberta, Canada, collected from different depths with varying mineralogical compositions, has been investigated by small- and ultrasmall-angle neutron scattering. Moreover these samples come from the Second White Specks and Belle Fourche formations, and their organic matter content ranges between 2 and 3%. The scattering length density of the shale specimens has been estimated using themore » chemical composition of the different mineral components. Scattering experiments reveal the presence of fractal and non-fractal pores. It has been shown that the porosity and specific surface area are dominated by the contribution from meso- and micropores. The fraction of closed porosity has been calculated by comparing the porosities estimated by He pycnometry and scattering techniques. There is no correlation between total porosity and mineral components, a strong correlation has been observed between closed porosity and major mineral components in the studied specimens.« less

  9. Current oscillations in ultra-small superconducting Nb-Nb junctions formed by STM at mK temperatures

    NASA Astrophysics Data System (ADS)

    Dreyer, Michael; Roychowdhury, Anita; Dana, Rami

    2014-03-01

    Using etched Nb STM tips we formed ultra-small tunnel junctions on a Nb crystal at an effective temperature of ~ 200 mK using an Oxford dilution refrigerator. The Nb crystal was prepared in UHV and then transferred into the mK STM. The resulting superconductor-insulator-superconductor (SIS) junction displayed several sub-gap features from multiple Andreev reflections to a zero bias conductance peak. The latter showed features of a Josephson junction in the phase diffusion limit with side structures due to the electrical environment. Upon microwave irradiation the peak split into multiple peaks in accordance with theory, verifying Josephson tunneling. In addition we observed bias dependent oscillations of the tunneling current. The oscillations where recorded at a rate of 10 kS/s while acquiring conventional dI/dV or I(V) spectroscopic curves. Histograms of the current for each bias voltage step then reveal the nature of the oscillation. It ranges from multiple states in certain bias regions through pure oscillations to supercurrent-normal switching. Fourier transform of the current show in some cases a bias dependence of the main frequencies. Possible causes will be discussed.

  10. Generation of ultra-small InN nanocrystals by pulsed laser ablation of suspension in organic solution

    NASA Astrophysics Data System (ADS)

    Kurşungöz, Canan; Uzcengiz Şimşek, Elif; Tuzaklı, Refik; Ortaç, Bülend

    2017-03-01

    Nanostructures of InN have been extensively investigated since nano-size provides a number of advantages allowing applications in nanoscale electronic and optoelectronic devices. It is quite important to obtain pure InN nanocrystals (InN-NCs) to reveal the characteristic features, which gain interest in the literature. Here, we proposed a new approach for the synthesis of ultra-small hexagonal InN-NCs by using suspension of micron-sized InN powder in ethanol with pulsed laser ablation method. The liquid environment, laser energy and ablation time were optimized and a post-synthesis treatment, centrifugation, was performed to achieve InN-NCs with the smallest size. Besides, the micron-sized InN powder suspension, as a starting material, enabled us to obtain InN-NCs having diameters smaller than 5 nm. We also presented a detailed characterization of InN-NCs and demonstrated that the formation mechanism mainly depends on the fragmentation due to laser irradiation of the suspension.

  11. Solvent-like ligand-coated ultrasmall cadmium selenide nanocrystals: strong electronic coupling in a self-organized assembly.

    PubMed

    Lawrence, Katie N; Johnson, Merrell A; Dolai, Sukanta; Kumbhar, Amar; Sardar, Rajesh

    2015-07-21

    Strong inter-nanocrystal electronic coupling is a prerequisite for delocalization of exciton wave functions and high conductivity. We report 170 meV electronic coupling energy of short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals (SNCs) in solution. Cryo-transmission electron microscopy analysis showed the formation of a pearl-necklace assembly of nanocrystals in solution with regular inter-nanocrystal spacing. The electronic coupling was studied as a function of CdSe nanocrystal size where the smallest nanocrystals exhibited the largest coupling energy. The electronic coupling in spin-cast thin-film (<200 nm in thickness) of poly(ethylene glycol) thiolate-coated CdSe SNCs was studied as a function of annealing temperature, where an unprecedentedly large, ∼400 meV coupling energy was observed for 1.6 nm diameter SNCs, which were coated with a thin layer of poly(ethylene glycol) thiolates. Small-angle X-ray scattering measurements showed that CdSe SNCs maintained an order array inside the films. The strong electronic coupling of SNCs in a self-organized film could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device application.

  12. Protein fibrillation and nanoparticle interactions: opportunities and challenges

    NASA Astrophysics Data System (ADS)

    Mahmoudi, Morteza; Kalhor, Hamid R.; Laurent, Sophie; Lynch, Iseult

    2013-03-01

    Due to their ultra-small size, nanoparticles (NPs) have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. NPs are recognized as promising and powerful tools to fight against the human brain diseases such as multiple sclerosis or Alzheimer's disease. In this review, after an introductory part on the nature of protein fibrillation and the existing approaches for its investigations, the effects of NPs on the fibrillation process have been considered. More specifically, the role of biophysicochemical properties of NPs, which define their affinity for protein monomers, unfolded monomers, oligomers, critical nuclei, and other prefibrillar states, together with their influence on protein fibrillation kinetics has been described in detail. In addition, current and possible-future strategies for controlling the desired effect of NPs and their corresponding effects on the conformational changes of the proteins, which have significant roles in the fibrillation process, have been presented.

  13. Oxidized silicon nanoparticles for radiosensitization of cancer and tissue cells.

    PubMed

    Klein, Stefanie; Dell'Arciprete, Maria L; Wegmann, Marc; Distel, Luitpold V R; Neuhuber, Winfried; Gonzalez, Mónica C; Kryschi, Carola

    2013-05-03

    The applicability of ultrasmall uncapped and aminosilanized oxidized silicon nanoparticles (SiNPs and NH2-SiNPs) as radiosensitizer was studied by internalizing these nanoparticles into human breast cancer (MCF-7) and mouse fibroblast cells (3T3) that were exposed to X-rays at a single dose of 3 Gy. While SiNPs did not increase the production of reactive oxygen species (ROS) in X-ray treated cells, the NH2-SiNPs significantly enhanced the ROS formation. This is due to the amino functionality as providing positive surface charges in aqueous environment. The NH2-SiNPs were observed to penetrate into the mitochondrial membrane, wherein these nanoparticles provoked oxidative stress. The NH2-SiNPs induced mitochondrial ROS production was confirmed by the determination of an increased malondialdehyde level as representing a gauge for the extent of membrane lipid peroxidation. X-ray exposure of NH2-SiNPs incubated MCF-7 and 3T3 cells increased the ROS concentration for 180%, and 120%, respectively. Complementary cytotoxicity studies demonstrate that these silicon nanoparticles are more cytotoxic for MCF-7 than for 3T3 cells.

  14. Synthesis Characterization and Photocatalytic Studies of Cobalt Ferrite-Silica-Titania Nanocomposites

    PubMed Central

    Greene, David; Serrano-Garcia, Raquel; Govan, Joseph; Gun’ko, Yurii K.

    2014-01-01

    In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating of cobalt ferrite nanoparticles with the double SiO2/TiO2 layer using metallorganic precursors. The Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis (EDX), Vibrational Sample Magnetometer (VSM) measurements and Raman spectroscopy results confirm the presence both of the silica and very thin TiO2 layers. The core-shell nanoparticles have been sintered at 600 °C and used as a catalyst in photo-oxidation reactions of methylene blue under UV light. Despite the additional non-magnetic coatings result in a lower value of the magnetic moment, the particles can still easily be retrieved from reaction mixtures by magnetic separation. This retention of magnetism was of particular importance allowing magnetic recovery and re-use of the catalyst.

  15. Comparison of drug delivery potentials of surface functionalized cobalt and zinc ferrite nanohybrids for curcumin in to MCF-7 breast cancer cells

    NASA Astrophysics Data System (ADS)

    Sawant, V. J.; Bamane, S. R.; Shejwal, R. V.; Patil, S. B.

    2016-11-01

    The functionalization and surface engineering of CoFe2O4 and ZnFe2O4 nanoparticles were performed by coating with PEG and Chitosan respectively using simple wet co-precipitation. Then multiactive therapeutic drug curcumin was loaded to form drug delivery nanohybrids by precipitation. These nanohybrids were characterized separately using UV-vis, FTIR, PL spectroscopy, XRD, VSM, SEM and TEM analysis. The moderate antibacterial activities of the nanohybrids were elaborated by in vitro antibacterial screening on Escherichia coli and Staphylococcus aureus. The anticancer potentials, apoptotic effects and enhanced drug delivery properties of these nanohybrids were confirmed and compared on MCF-7 cells by in vitro MTT assay. The drug delivery activities for hydrophobic drug and anticancer effects of chitosan coated zinc ferrite functionalized nanoparticles were higher than PEG coated cobalt ferrite nanohybrids.

  16. FTIR and structural properties of co-precipitated cobalt ferrite nano particles

    NASA Astrophysics Data System (ADS)

    Hutamaningtyas, E.; Utari; Suharyana; Wijayanta, A. T.; Purnama, B.

    2016-11-01

    The FTIR and structural properties in co-precipitated cobalt ferrite (CoFe2O4) nanoparticles are discussed in this paper. The synthesis was conducted at temperatures of 75°C and 95°C following post annealing at 1200°C for 5 hours. Other modification samples were synthesis at temperature of 95°C and then annealing at temperature of 1000°C and 1200°C for 5 hours. For both modification of synthesis and annealing temperature, FTIR result showed a metal oxide at a wave number of 590 cm-1 which indicated cobalt ferrite nanoparticles. The crystalline structure was confirmed using x-ray diffraction that the high purity of cobalt ferrite was realized. Calculation of the cation distribution by using comparison I220/I222 and I422/I222 show that the synthesis and annealing temperature succesfully modify cation occupy the site octahedral and tetrahedral.

  17. The High Radiosensitizing Efficiency of a Trace of Gadolinium-Based Nanoparticles in Tumors

    NASA Astrophysics Data System (ADS)

    Dufort, Sandrine; Le Duc, Géraldine; Salomé, Murielle; Bentivegna, Valerie; Sancey, Lucie; Bräuer-Krisch, Elke; Requardt, Herwig; Lux, François; Coll, Jean-Luc; Perriat, Pascal; Roux, Stéphane; Tillement, Olivier

    2016-07-01

    We recently developed the synthesis of ultrasmall gadolinium-based nanoparticles (GBN), (hydrodynamic diameter <5 nm) characterized by a safe behavior after intravenous injection (renal clearance, preferential accumulation in tumors). Owing to the presence of gadolinium ions, GBN can be used as contrast agents for magnetic resonance imaging (MRI) and as radiosensitizers. The attempt to determine the most opportune delay between the intravenous injection of GBN and the irradiation showed that a very low content of radiosensitizing nanoparticles in the tumor area is sufficient (0.1 μg/g of particles, i.e. 15 ppb of gadolinium) for an important increase of the therapeutic effect of irradiation. Such a promising and unexpected result is assigned to a suited distribution of GBN within the tumor, as revealed by the X-ray fluorescence (XRF) maps.

  18. The High Radiosensitizing Efficiency of a Trace of Gadolinium-Based Nanoparticles in Tumors

    PubMed Central

    Dufort, Sandrine; Le Duc, Géraldine; Salomé, Murielle; Bentivegna, Valerie; Sancey, Lucie; Bräuer-Krisch, Elke; Requardt, Herwig; Lux, François; Coll, Jean-Luc; Perriat, Pascal; Roux, Stéphane; Tillement, Olivier

    2016-01-01

    We recently developed the synthesis of ultrasmall gadolinium-based nanoparticles (GBN), (hydrodynamic diameter <5 nm) characterized by a safe behavior after intravenous injection (renal clearance, preferential accumulation in tumors). Owing to the presence of gadolinium ions, GBN can be used as contrast agents for magnetic resonance imaging (MRI) and as radiosensitizers. The attempt to determine the most opportune delay between the intravenous injection of GBN and the irradiation showed that a very low content of radiosensitizing nanoparticles in the tumor area is sufficient (0.1 μg/g of particles, i.e. 15 ppb of gadolinium) for an important increase of the therapeutic effect of irradiation. Such a promising and unexpected result is assigned to a suited distribution of GBN within the tumor, as revealed by the X-ray fluorescence (XRF) maps. PMID:27411781

  19. Nanostructured materials for multifunctional applications under NSF-CREST research at Norfolk State University

    NASA Astrophysics Data System (ADS)

    Pradhan, A. K.; Mundle, R.; Zhang, K.; Holloway, T.; Amponsah, O.; Biswal, D.; Konda, R.; White, C.; Dondapati, H.; Santiago, K.; Birdsong, T.; Arslan, M.; Peeples, B.; Shaw, D.; Smak, J.; Samataray, C.; Bahoura, M.

    2012-04-01

    Magnetic nanoparticles of CoFe2O4 have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles of varying size was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. The anomalous magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe2O4 nanoparticles were synthesized under applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments, which produce Co ions and vacancies disorder. We performed the fabrication of condensed and mesoporous silica coated CoFe2O4 magnetic nanocomposites. The CoFe2O4 magnetic nanoparticles were encapsulated with well-defined silica layer. The mesopores in the shell were fabricated as a consequence of removal of organic group of the precursor through annealing. The NiO nanoparticles were loaded into the mesoporous silica. The mesoporous silica coated magnetic nanostructure loaded with NiO as a final product may have potential use in the field of biomedical applications. Growth mechanism of ZnO nanorod arrays on ZnO seed layer investigated by electric and Kelvin probe force microscopy. Both electric and Kelvin force probe microscopy was used to investigate the surface potentials on the ZnO seed layer, which shows a remarkable dependence on the annealing temperature. The optimum temperature for the growth of nanorod arrays normal to the surface was found to be at 600 °C, which is in the range of right surface potentials and energy measured between 500 °C and 700 °C. We demonstrated from both EFM and Kelvin force probe microscopy studies that surface potential controls the growth of ZnO nanorods. This study will provide important understanding of growth of other nanostructures. Zn

  20. Solvent-like ligand-coated ultrasmall cadmium selenide nanocrystals: strong electronic coupling in a self-organized assembly

    NASA Astrophysics Data System (ADS)

    Lawrence, Katie N.; Johnson, Merrell A.; Dolai, Sukanta; Kumbhar, Amar; Sardar, Rajesh

    2015-07-01

    Strong inter-nanocrystal electronic coupling is a prerequisite for delocalization of exciton wave functions and high conductivity. We report 170 meV electronic coupling energy of short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals (SNCs) in solution. Cryo-transmission electron microscopy analysis showed the formation of a pearl-necklace assembly of nanocrystals in solution with regular inter-nanocrystal spacing. The electronic coupling was studied as a function of CdSe nanocrystal size where the smallest nanocrystals exhibited the largest coupling energy. The electronic coupling in spin-cast thin-film (<200 nm in thickness) of poly(ethylene glycol) thiolate-coated CdSe SNCs was studied as a function of annealing temperature, where an unprecedentedly large, ~400 meV coupling energy was observed for 1.6 nm diameter SNCs, which were coated with a thin layer of poly(ethylene glycol) thiolates. Small-angle X-ray scattering measurements showed that CdSe SNCs maintained an order array inside the films. The strong electronic coupling of SNCs in a self-organized film could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device application.Strong inter-nanocrystal electronic coupling is a prerequisite for delocalization of exciton wave functions and high conductivity. We report 170 meV electronic coupling energy of short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals (SNCs) in solution. Cryo-transmission electron microscopy analysis showed the formation of a pearl-necklace assembly of nanocrystals in solution with regular inter-nanocrystal spacing. The electronic coupling was studied as a function of CdSe nanocrystal size where the smallest nanocrystals exhibited the largest coupling energy. The electronic coupling in spin-cast thin-film (<200 nm in thickness) of poly(ethylene glycol) thiolate

  1. Erlotinib-Conjugated Iron Oxide Nanoparticles as a Smart Cancer-Targeted Theranostic Probe for MRI

    NASA Astrophysics Data System (ADS)

    Ali, Ahmed Atef Ahmed; Hsu, Fei-Ting; Hsieh, Chia-Ling; Shiau, Chia-Yang; Chiang, Chiao-Hsi; Wei, Zung-Hang; Chen, Cheng-Yu; Huang, Hsu-Shan

    2016-11-01

    We designed and synthesized novel theranostic nanoparticles that showed the considerable potential for clinical use in targeted therapy, and non-invasive real-time monitoring of tumors by MRI. Our nanoparticles were ultra-small with superparamagnetic iron oxide cores, conjugated to erlotinib (FeDC-E NPs). Such smart targeted nanoparticles have the preference to release the drug intracellularly rather than into the bloodstream, and specifically recognize and kill cancer cells that overexpress EGFR while being non-toxic to EGFR-negative cells. MRI, transmission electron microscopy and Prussian blue staining results indicated that cellular uptake and intracellular accumulation of FeDC-E NPs in the EGFR overexpressing cells was significantly higher than those of the non-erlotinib-conjugated nanoparticles. FeDC-E NPs inhibited the EGFR–ERK–NF-κB signaling pathways, and subsequently suppressed the migration and invasion capabilities of the highly invasive and migrative CL1-5-F4 cancer cells. In vivo tumor xenograft experiments using BALB/c nude mice showed that FeDC-E NPs could effectively inhibit the growth of tumors. T2-weighted MRI images of the mice showed significant decrease in the normalized signal within the tumor post-treatment with FeDC-E NPs compared to the non-targeted control iron oxide nanoparticles. This is the first study to use erlotinib as a small-molecule targeting agent for nanoparticles.

  2. Erlotinib-Conjugated Iron Oxide Nanoparticles as a Smart Cancer-Targeted Theranostic Probe for MRI

    PubMed Central

    Ali, Ahmed Atef Ahmed; Hsu, Fei-Ting; Hsieh, Chia-Ling; Shiau, Chia-Yang; Chiang, Chiao-Hsi; Wei, Zung-Hang; Chen, Cheng-Yu; Huang, Hsu-Shan

    2016-01-01

    We designed and synthesized novel theranostic nanoparticles that showed the considerable potential for clinical use in targeted therapy, and non-invasive real-time monitoring of tumors by MRI. Our nanoparticles were ultra-small with superparamagnetic iron oxide cores, conjugated to erlotinib (FeDC-E NPs). Such smart targeted nanoparticles have the preference to release the drug intracellularly rather than into the bloodstream, and specifically recognize and kill cancer cells that overexpress EGFR while being non-toxic to EGFR-negative cells. MRI, transmission electron microscopy and Prussian blue staining results indicated that cellular uptake and intracellular accumulation of FeDC-E NPs in the EGFR overexpressing cells was significantly higher than those of the non-erlotinib-conjugated nanoparticles. FeDC-E NPs inhibited the EGFR–ERK–NF-κB signaling pathways, and subsequently suppressed the migration and invasion capabilities of the highly invasive and migrative CL1-5-F4 cancer cells. In vivo tumor xenograft experiments using BALB/c nude mice showed that FeDC-E NPs could effectively inhibit the growth of tumors. T2-weighted MRI images of the mice showed significant decrease in the normalized signal within the tumor post-treatment with FeDC-E NPs compared to the non-targeted control iron oxide nanoparticles. This is the first study to use erlotinib as a small-molecule targeting agent for nanoparticles. PMID:27833124

  3. One-pot green synthesis of luminescent gold nanoparticles using imidazole derivative of chitosan.

    PubMed

    Nazirov, Alexander; Pestov, Alexander; Privar, Yuliya; Ustinov, Alexander; Modin, Evgeny; Bratskaya, Svetlana

    2016-10-20

    Water soluble luminescent gold nanoparticles with average size 2.3nm were for the first time synthesized by completely green method of Au(III) reduction using chitosan derivative-biocompatible nontoxic N-(4-imidazolyl)methylchitosan (IMC) as both reducing and stabilizing agent. Reduction of Au(III) to gold nanoparticles in IMC solution is a slow process, in which coordination power of biopolymer controls both reducing species concentration and gold crystal growth rate. Gold nanoparticles formed in IMC solution do not manifest surface plasmon resonance, but exhibit luminescence at 375nm under UV light excitation at 230nm. Due to biological activity of imidazolyl-containing polymers and their ability to bind proteins and drugs, the obtained ultra-small gold nanoparticles can find an application for biomolecules detection, bio-imaging, drug delivery, and catalysis. Very high catalytic activity (as compared to gold nanoparticles obtained by other green methods) was found for Au/IMC nanoparticles in the model reaction of p-nitrophenol reduction providing complete conversion of p-nitrophenol to p-aminophenol within 180-190s under mild conditions.

  4. Facile synthesis of ultrasmall monodisperse ``raisin-bun''-type MoO3/SiO2 nanocomposites with enhanced catalytic properties

    NASA Astrophysics Data System (ADS)

    Wang, Jiasheng; Li, Xin; Zhang, Shufen; Lu, Rongwen

    2013-05-01

    We report the preparation of ultrasmall monodisperse MoO3/SiO2 nanocomposites in reverse microemulsions formed by Brij-58/cyclohexane/water. The nanocomposites are of ``raisin-bun''-type with 1.0 +/- 0.2 nm MoO3 homogeneously dispersed in 23 +/- 2 nm silica spheres. Characterization is carried out based on transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDS), X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 sorption measurement, and NH3 temperature-programmed desorption (NH3-TPD). The as-prepared MoO3/SiO2 nanocomposites are microporous and exhibit enhanced catalytic activities for acetalization of benzaldehyde with ethylene glycol and can be repeatedly used 5 times without obvious deactivation. The catalytic performance improvement is attributed to the unique structure and ultrasmall size of the nanocomposites.We report the preparation of ultrasmall monodisperse MoO3/SiO2 nanocomposites in reverse microemulsions formed by Brij-58/cyclohexane/water. The nanocomposites are of ``raisin-bun''-type with 1.0 +/- 0.2 nm MoO3 homogeneously dispersed in 23 +/- 2 nm silica spheres. Characterization is carried out based on transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDS), X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 sorption measurement, and NH3 temperature-programmed desorption (NH3-TPD). The as-prepared MoO3/SiO2 nanocomposites are microporous and exhibit enhanced catalytic activities for acetalization of benzaldehyde with ethylene glycol and can be repeatedly used 5 times without obvious deactivation. The catalytic performance improvement is attributed to the unique

  5. A Self-Sensing Piezoelectric MicroCantilever Biosensor for Detection of Ultrasmall Adsorbed Masses: Theory and Experiments

    PubMed Central

    Faegh, Samira; Jalili, Nader; Sridhar, Srinivas

    2013-01-01

    Detection of ultrasmall masses such as proteins and pathogens has been made possible as a result of advancements in nanotechnology. Development of label-free and highly sensitive biosensors has enabled the transduction of molecular recognition into detectable physical quantities. Microcantilever (MC)-based systems have played a widespread role in developing such biosensors. One of the most important drawbacks of all of the available biosensors is that they all come at a very high cost. Moreover, there are certain limitations in the measurement equipments attached to the biosensors which are mostly optical measurement systems. A unique self-sensing detection technique is proposed in this paper in order to address most of the limitations of the current measurement systems. A self-sensing bridge is used to excite piezoelectric MC-based sensor functioning in dynamic mode, which simultaneously measures the system's response through the self-induced voltage generated in the piezoelectric material. As a result, the need for bulky, expensive read-out equipment is eliminated. A comprehensive mathematical model is presented for the proposed self-sensing detection platform using distributed-parameters system modeling. An adaptation strategy is then implemented in the second part in order to compensate for the time-variation of piezoelectric properties which dynamically improves the behavior of the system. Finally, results are reported from an extensive experimental investigation carried out to prove the capability of the proposed platform. Experimental results verified the proposed mathematical modeling presented in the first part of the study with accuracy of 97.48%. Implementing the adaptation strategy increased the accuracy to 99.82%. These results proved the measurement capability of the proposed self-sensing strategy. It enables development of a cost-effective, sensitive and miniaturized mass sensing platform. PMID:23666133

  6. Ultra-small vanadium nitride quantum dots embedded in porous carbon as high performance electrode materials for capacitive energy storage

    NASA Astrophysics Data System (ADS)

    Yang, Yunlong; Zhao, Lei; Shen, Kuiwen; Liu, Ying; Zhao, Xiaoning; Wu, Yage; Wang, Yanqin; Ran, Fen

    2016-11-01

    Ultra-small vanadium nitride quantum dots embedded in porous carbon (VNQDs/PC) were fabricated by a thermal treatment process of NH4VO3/C3H6N6 under nitrogen atmosphere. The specific capacitance of VNQDs/PC was 1008 mF cm-2 at a current density of 0.004 A cm-2, whereas the VN/carbon hybrid material obtained by a solid-state blending of NH4VO3 and C3H6N6 just exhibited a capacitance of 432 mF cm-2 at the same current density. By mediating the ratio of NH4VO3 and C3H6N6, a maximum specific capacitance of 1124 mF cm-2 was achieved at a current density of 0.002 A cm-2 in aqueous 6 mol/L KOH electrolyte with the potential range from 0 to -1.15 V when it reached 1: 7 (wt./wt.). Additionally, symmetrical supercapacitor fabricated with synthesized VNQDs/PC presented a high specific capacitance of 215 mF cm-2 at 0.002 A cm-2 based on the entire cell, and exhibited a high capacitance retention of 86.6% with current density increased to 5 A g-1. The VNQDs/PC negative electrodes were combined with Ni(OH)2 positive electrodes for the fabrication of hybrid supercapacitors. Remarkably, at a power density of 828.7 W kg-1, the device delivered an ultrahigh energy density of 47.2 Wh kg-1.

  7. Silica nanoparticles separation from water: aggregation by cetyltrimethylammonium bromide (CTAB).

    PubMed

    Liu, Y; Tourbin, M; Lachaize, S; Guiraud, P

    2013-07-01

    Nanoparticles will inevitably be found in industrial and domestic wastes in the near future and as a consequence soon in water resources. Due to their ultra-small size, nanoparticles may not only have new hazards for environment and human health, but also cause low separation efficiency by classical water treatments processes. Thus, it would be an important challenge to develop a specific treatment with suitable additives for recovery of nanoparticles from waters. For this propose, this paper presents aggregation of silica nanoparticles (Klebosol 30R50 (75nm) and 30R25 (30nm)) by cationic surfactant cetyltrimethylammonium bromide (CTAB). Different mechanisms such as charge neutralization, "depletion flocculation" or "volume-restriction", and "hydrophobic effect" between hydrocarbon tails of CTAB have been proposed to explicate aggregation results. One important finding is that for different volume concentrations between 0.05% and 0.51% of 30R50 suspensions, the same critical coagulation concentration was observed at CTAB=0.1mM, suggesting the optimized quantity of CTAB during the separation process for nanoparticles of about 75nm. Furthermore, very small quantities of CTAB (0.01mM) can make 30R25 nanosilica aggregated due to the "hydrophobic effect". It is then possible to minimize the sludge and allow the separation process as "greener" as possible by studying this case. It has also shown that aggregation mechanisms can be different for very small particles so that a special attention has to be paid to the treatment of nanoparticles contained in water and wastewaters.

  8. Unsteady Casson nanofluid flow over a rotating cone in a rotating frame filled with ferrous nanoparticles: A numerical study

    NASA Astrophysics Data System (ADS)

    Raju, C. S. K.; Sandeep, N.

    2017-01-01

    In this study, we investigated the momentum and heat transfer characteristics of Casson nanofluid flow over a rotating cone in a rotating frame filled with water based CoFe2O4 nano particles. Heat flux conditions and wall temperature conditions are very important in controlling of up and down heat transport phenomena's in industrial as well as engineering application. Resulting set of coupled nonlinear governing equations are solved numerically using Runge-Kutta based shooting technique. In graphical results we presented dual solutions for the prescribed wall temperature (PWT) and prescribed heat flux (PHF) cases. The effect of governing parameters on velocity and temperature fields along with the skin friction coefficient and the heat transfer rate are presented with the help of graphs and tables. Results indicate that the rising values of the volume fraction of ferro particles and buoyancy parameter have tendency to improve the skin friction coefficient as well as the heat transfer rate for both the prescribed wall temperature (PWT) and prescribed heat flux (PHF) cases.

  9. Synthesis and structural characterization of magnetic cadmium sulfide-cobalt ferrite nanocomposite, and study of its activity for dyes degradation under ultrasound

    NASA Astrophysics Data System (ADS)

    Farhadi, Saeed; Siadatnasab, Firouzeh

    2016-11-01

    Cadmium sulfide-cobalt ferrite (CdS/CFO) nanocomposite was easily synthesized by one-step hydrothermal decomposition of cadmium diethyldithiocarbamate complex on the CoFe2O4 nanoparticles at 200 °C. Spectroscopic techniques of powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-visible spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and magnetic measurements were applied for characterizing the structure and morphology of the product. The results of FT-IR, XRD and EDX indicated that the CdS/CFO was highly pure. SEM and TEM results revealed that the CdS/CFO nanocomposite was formed from nearly uniform and sphere-like nanoparticles with the size of approximately 20 nm. The UV-vis absorption spectrum of the CdS/CFO nanocomposite showed the band gap of 2.21 eV, which made it suitable for sono-/photo catalytic purposes. By using the obtained CdS/CFO nanocomposite, an ultrasound-assisted advanced oxidation process (AOP) has been developed for catalytic degradation of methylene blue (MB), Rhodamine B (RhB), and methyl orange (MO)) in the presence of H2O2 as a green oxidant. CdS/CFO nanocomposite exhibited excellent sonocatalytic activity, so that, dyes were completely degraded in less than 10 min. The influences of crucial factors such as the H2O2 amount and catalyst dosage on the degradation efficiency were evaluated. The as-prepared CdS/CFO nanocomposite exhibited higher catalytic activity than pure CdS nanoparticles. Moreover, the magnetic property of CoFe2O4 made the nanocomposite recyclable.

  10. Bi-photon imaging and diagnostics using ultra-small diagnostic probes engineered from semiconductor nanocrystals and single-domain antibodies

    NASA Astrophysics Data System (ADS)

    Hafian, Hilal; Sukhanova, Alyona; Chames, Patrick; Baty, Daniel; Pluot, Michel; Cohen, Jacques H. M.; Nabiev, Igor R.; Millot, Jean-Marc

    2012-10-01

    Semiconductor fluorescent quantum dots (QDs) have just demonstrated their numerous advantages over organic dyes in bioimaging and diagnostics. One of characteristics of QDs is a very large cross section of their twophoton absorption. A common approach to biodetection by means of QDs is to use monoclonal antibodies (mAbs) for targeting. Recently, we have engineered ultrasmall diagnostic nanoprobes (sdAb-QD) based on highly oriented conjugates of QDs with the single-domain antibodies (sdAbs) against cancer biomarkers. With a molecular weight of only 13 kDa (12-fold smaller than full-size mAbs) and extreme stability and capacity to refolding, sdAbs are the smallest functional Ab fragments capable of binding antigens with affinities comparable to those of conventional Abs. Ultrasmall diagnostic sdAb-QD nanoprobes were engineered through oriented conjugation of QDs with sdAbs. This study is the first to demonstrate the possibility of immunohistochemical imaging of colon carcinoma biomarkers with sdAb-QD conjugates by means of two-photon excitation. The optimal excitation conditions for imaging of the markers in clinical samples with sdAb-QD nanoprobes have been determined. The absence of sample autofluorescence significantly improves the sensitivity of biomarker detection with the use of the two-photon excitation diagnostic setup.

  11. Magnetic superlattices and their nanoscale phase transition effects.

    PubMed

    Cheon, Jinwoo; Park, Jong-Il; Choi, Jin-sil; Jun, Young-wook; Kim, Sehun; Kim, Min Gyu; Kim, Young-Min; Kim, Youn Joong

    2006-02-28

    The systematic assembly of nanoscale constituents into highly ordered superlattices is of significant interest because of the potential of their multifunctionalities and the discovery of new collective properties. However, successful observations of such superlattice-associated nanoscale phenomena are still elusive. Here, we present magnetic superlattices of Co and Fe(3)O(4) nanoparticles with multidimensional symmetry of either AB (NaCl) or AB(2) (AlB(2)). The discovery of significant enhancement (approximately 25 times) of ferrimagnetism is further revealed by forming previously undescribed superlattices of magnetically soft-hard Fe(3)O(4)@CoFe(2)O(4) through the confined geometrical effect of thermally driven intrasuperlattice phase transition between the nanoparticulate components.

  12. Magnetic superlattices and their nanoscale phase transition effects

    PubMed Central

    Cheon, Jinwoo; Park, Jong-Il; Choi, Jin-sil; Jun, Young-wook; Kim, Sehun; Kim, Min Gyu; Kim, Young-Min; Kim, Youn Joong

    2006-01-01

    The systematic assembly of nanoscale constituents into highly ordered superlattices is of significant interest because of the potential of their multifunctionalities and the discovery of new collective properties. However, successful observations of such superlattice-associated nanoscale phenomena are still elusive. Here, we present magnetic superlattices of Co and Fe3O4 nanoparticles with multidimensional symmetry of either AB (NaCl) or AB2 (AlB2). The discovery of significant enhancement (≈25 times) of ferrimagnetism is further revealed by forming previously undescribed superlattices of magnetically soft–hard Fe3O4@CoFe2O4 through the confined geometrical effect of thermally driven intrasuperlattice phase transition between the nanoparticulate components. PMID:16492783

  13. Designing new ferrite/manganite nanocomposites.

    PubMed

    Muscas, G; Anil Kumar, P; Barucca, G; Concas, G; Varvaro, G; Mathieu, R; Peddis, D

    2016-01-28

    Two kinds of nanocomposites of transition metal oxides were synthesized and investigated. Each nanocomposite comprises nanoparticles of La0.67Ca0.33MnO3 and CoFe2O4 in similar volume fractions, however arranged with different morphologies. The temperature-dependent magnetic and electrical properties of the two systems are found to greatly differ, suggesting different degrees of interaction and coupling of their constituents. This is confirmed by magnetic field-dependent experiments, which reveal contrasted magnetization reversal and magnetoresistance in the systems. We discuss this morphology-physical property relationship, and the possibility to further tune the magnetism and magneto-transport in such nanocomposites.

  14. Electroless deposition of platinum nanoparticles in room-temperature ionic liquids.

    PubMed

    Zhang, Da; Okajima, Takeyoshi; Lu, Dalin; Ohsaka, Takeo

    2013-09-24

    The electroless deposition of Pt nanoparticles (Pt-NPs) could be carried out by dissolving potassium tetrachloroplatinate(II) (K2[PtCl4]) in 1-ethyl-3-methylimidazolium (EMI(+)) room-temperature ionic liquids (RTILs) containing bis(trifluoromethylsulfonyl) imide (NTf2(-)) or tetrafluoroborate (BF4(-)) anion and small cations, such as H(+), K(+), and Li(+). In this case, no deposition of Pt-NPs occurred in RTILs without such small cations. The formation of Pt-NPs was only observed in RTILs containing trifluoromethanesulfonimide (HNTf2) and protons at high temperature (≥80 °C) when potassium hexachloroplatinate(IV) (K2[PtCl6]) was dissolved in the RTILs. The obtained Pt-NPs gave a characteristic absorption spectrum of ultrasmall Pt-NPs. The ultrasmall and uniform Pt-NPs of ca. 1-4 nm in diameter were produced and the Pt-NPs/EMI(+)NTf2(-) dispersion was kept stably for several months without adding any additional stabilizers or capping molecules. The identified Fourier-transform patterns along the [0 1 1] zone axis were observed for the TEM images of Pt-NPs. On the basis of the results obtained, a probable mechanism of the electroless formation of Pt-NPs is discussed.

  15. Aliidiomarina minuta sp. nov., a haloalkaliphilic bacterium that forms ultra-small cells under non-optimal conditions.

    PubMed

    Farooqui, Saad M; Wright, Mitchell H; Greene, Anthony C

    2016-01-01

    An aerobic haloalkaliphilic bacterium, designated strain MLST1(T), was isolated from filtered (0.22 µm) Mono Lake (USA) waters. The isolate was observed to grow primarily on yeast extract, peptone and tryptone. Optimal growth occurred in media at pH 9.5 containing 5-11 g/l yeast extract, and 70-100 g/l NaCl. When in log phase of growth, cells were found to be mostly curved motile rods (1-3 µm length by 0.4-1 µm diameter). Phylogenetic analysis of the 16S rRNA gene and chemotaxonomic data revealed that the isolate belonged to the family Idiomarinaceae, and is closely related to Aliidiomarina maris (96.67 % sequence similarity). The major fatty acids were identified to be iso-C17:1 ω9c (27.1 %), iso-C17:0 (21.3 %) and iso-C15:0 (12.2 %). Predominant polar lipids included phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, and the major respiratory quinone was identified as Q8. The DNA base composition was 46.3 mol% G+C. Survival studies indicated that strain MLST1(T) remains viable after exposure to adverse conditions, particularly in the prolonged absence of a carbon source, at low temperatures and with no NaCl. Under these conditions, the cells shrunk to around 0.2 µm in length by 0.1 µm in diameter and passed through 0.22 µm filters. The ultra-small cells could only be resuscitated in media with low levels of yeast extract, up to 0.6 g/l. Once resuscitated, cells were able to grow to full size. Strain MLST1(T) is clearly a unique bacterium in the waters of Mono Lake and the name Aliidiomarina minuta sp. nov. is proposed. The type strain is MLST1(T) (=JCM 17425(T) = KCTC 23357(T)).

  16. Liposomal nanoreactors for the synthesis of monodisperse palladium nanoparticles using glycerol.

    PubMed

    Clergeaud, Gael; Genç, Rükan; Ortiz, Mayreli; O'Sullivan, Ciara K

    2013-12-10

    The synthesis of highly stable ultrasmall monodisperse populations of palladium nanoparticles in the range of 1-3 nm in size was achieved via polyol reduction within 1,2-dioleoyl-sn-glycero-3-phosphor-rac-(1-glycerol) liposomal nanoreactors exploiting glycerol as both reducing and stabilizing agent. The liposome-based green method was compared with synthesis in solution, and the reducing agent concentration and the lipidic composition of the liposomal nanoreactors were demonstrated to have a strong effect on the final size and homogeneity of the palladium nanoparticles. Glycerol molecules acting as capping agent demonstrated the ability to stabilize the palladium nanoparticles over a long period of time, maintaining their homogeneity in size and shape. The obtained palladium nanoparticles were characterized using transmission electron microscopy, selected area electron diffraction, Fourier transform infrared and Raman spectroscopies, X-ray diffraction, and dynamic light scattering to determine their morphology, size, charge, surface chemistry, and crystal structure. The catalytic activity of the palladium nanoparticles was also tested for a reduction reaction.

  17. Biotemplated synthesis of anatase titanium dioxide nanoparticles via lignocellulosic waste material.

    PubMed

    Ramimoghadam, Donya; Bagheri, Samira; Abd Hamid, Sharifah Bee

    2014-01-01

    Anatase titanium dioxide nanoparticles (TiO2-NPs) were synthesized by sol-gel method using rice straw as a soft biotemplate. Rice straw, as a lignocellulosic waste material, is a biomass feedstock which is globally produced in high rate and could be utilized in an innovative approach to manufacture a value-added product. Rice straw as a reliable biotemplate has been used in the sol-gel method to synthesize ultrasmall sizes of TiO2-NPs with high potential application in photocatalysis. The physicochemical properties of titanium dioxide nanoparticles were investigated by a number of techniques such as X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), ultraviolet visible spectra (UV-Vis), and surface area and pore size analysis. All results consensually confirmed that particle sizes of synthesized titanium dioxide were template-dependent, representing decrease in the nanoparticles sizes with increase of biotemplate concentration. Titanium dioxide nanoparticles as small as 13.0 ± 3.3 nm were obtained under our experimental conditions. Additionally, surface area and porosity of synthesized TiO2-NPs have been enhanced by increasing rice straw amount which results in surface modification of nanoparticles and potential application in photocatalysis.

  18. Biotemplated Synthesis of Anatase Titanium Dioxide Nanoparticles via Lignocellulosic Waste Material

    PubMed Central

    Bagheri, Samira; Abd Hamid, Sharifah Bee

    2014-01-01

    Anatase titanium dioxide nanoparticles (TiO2-NPs) were synthesized by sol-gel method using rice straw as a soft biotemplate. Rice straw, as a lignocellulosic waste material, is a biomass feedstock which is globally produced in high rate and could be utilized in an innovative approach to manufacture a value-added product. Rice straw as a reliable biotemplate has been used in the sol-gel method to synthesize ultrasmall sizes of TiO2-NPs with high potential application in photocatalysis. The physicochemical properties of titanium dioxide nanoparticles were investigated by a number of techniques such as X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), ultraviolet visible spectra (UV-Vis), and surface area and pore size analysis. All results consensually confirmed that particle sizes of synthesized titanium dioxide were template-dependent, representing decrease in the nanoparticles sizes with increase of biotemplate concentration. Titanium dioxide nanoparticles as small as 13.0 ± 3.3 nm were obtained under our experimental conditions. Additionally, surface area and porosity of synthesized TiO2-NPs have been enhanced by increasing rice straw amount which results in surface modification of nanoparticles and potential application in photocatalysis. PMID:25126547

  19. Multipole plasmons and their disappearance in few-nanometre silver nanoparticles

    PubMed Central

    Raza, Søren; Kadkhodazadeh, Shima; Christensen, Thomas; Di Vece, Marcel; Wubs, Martijn; Mortensen, N. Asger; Stenger, Nicolas

    2015-01-01

    Electron energy-loss spectroscopy can be used for detailed spatial and spectral characterization of optical excitations in metal nanoparticles. In previous electron energy-loss experiments on silver nanoparticles with radii smaller than 20 nm, only the dipolar surface plasmon resonance was assumed to play a role. Here, applying electron energy-loss spectroscopy to individual silver nanoparticles encapsulated in silicon nitride, we observe besides the usual dipole resonance an additional surface plasmon resonance corresponding to higher angular momenta for nanoparticle radii as small as 4 nm. We study the radius and electron beam impact position dependence of both resonances separately. For particles smaller than 4 nm in radius the higher-order surface plasmon mode disappears, in agreement with generalized non-local optical response theory, while the dipole resonance blueshift exceeds our theoretical predictions. Unlike in optical spectra, multipole surface plasmons are important in electron energy-loss spectra even of ultrasmall metallic nanoparticles. PMID:26537568

  20. Imaging C-Fos Gene Expression in Burns Using Lipid Coated Spion Nanoparticles.

    PubMed

    Papagiannaros, Aristarchos; Righi, Valeria; Day, George G; Rahme, Laurence G; Liu, Philip K; Fischman, Alan J; Tompkins, Ronald G; Tzika, A Aria

    2012-10-01

    MR imaging of gene transcription is important as it should enable the non-invasive detection of mRNA alterations in disease. A range of MRI methods have been proposed for in vivo molecular imaging of cells based on the use of ultra-small super-paramagnetic iron oxide (USPIO) nanoparticles and related susceptibility weighted imaging methods. Although immunohistochemistry can robustly differentiate the expression of protein variants, there is currently no direct gene assay technique that is capable of differentiating established to differentiate the induction profiles of c-Fos mRNA in vivo. To visualize the differential FosB gene expression profile in vivo after burn trauma, we developed MR probes that link the T2* contrast agent [superparamagnetic iron oxide nanoparticles (SPION)] with an oligodeoxynucleotide (ODN) sequence complementary to FosB mRNA to visualize endogenous mRNA targets via in vivo hybridization. The presence of this SPION-ODN probe in cells results in localized signal reduction in T2*-weighted MR images, in which the rate of signal reduction (R2*) reflects the regional iron concentration at different stages of amphetamine (AMPH) exposure in living mouse tissue. Our aim was to produce a superior contrast agent that can be administered using systemic as opposed to local administration and which will target and accumulate at sites of burn injury. Specifically, we developed and evaluated a PEGylated lipid coated MR probe with ultra-small super-paramagnetic iron oxide nanoparticles (USPION, a T2 susceptibility agent) coated with cationic fusogenic lipids, used for cell transfection and gene delivery and covalently linked to a phosphorothioate modified oligodeoxynucleotide (sODN) complementary to c-Fos mRNA (SPION-cFos) and used the agent to image mice with leg burns. Our study demonstrated the feasibility of monitoring burn injury using MR imaging of c-Fos transcription in vivo, in a clinically relevant mouse model of burn injury for the first time.