These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Alcohol dependent production of Fe3O4 and CoFe2O4 nanoparticles.  

PubMed

Commonly available alcohols of varying lengths and degree of branching were used to synthesize iron oxide, Fe3O4, and cobalt iron oxide, CoFe2O4, nanoparticles by means of a simple solvothermal decomposition of iron (III) acetylacetonates and cobalt (II) acetylacetonates. Depending on the solvent employed resulting Fe3O4 and CoFe2O4 nanoparticles ranged in size from approximately 5-16 nm and approximately 4-8 nm, respectively. All alcohols utilized resulted in the formation of nanoparticles with a spinel crystal structure, with the exception of methanol. Use of tert-butanol and phenol resulted in nearly spherical agglomerations of individual nanoparticles ranging between 100-250 nm. The resulting structures and morphologies of all samples were confirmed by X-ray diffraction and electron microscopy. Mass specific moments are reported based on SQUID magnetometry, and ranged from 57.5(5)-76.4(3) emu/g for Fe3O4 and 47.7(7)-67.0(4) emu/g CoFe2O4. PMID:23862521

Yocum, Brandon J; Ekiert, Thomas F; Alexander, Max D; O'Malley, Matthew J

2013-06-01

2

Magnetic properties and morphology of block copolymer templated ferrimagnetic CoFe2O4 nanoparticles  

Microsoft Academic Search

We synthesized the block copolymer of poly(norbornene-dicarboxcylic acid) and poly(norbornene) at room temperature, using ring opening metathesis polymerization. We then templated the CoFe2O4 nanoparticles within the polymer matrix, utilizing the self-assembled nature of the block copolymer. We used transmission electron microscopy, superconducting quantum interference device magnetometry, and X-ray powder diffraction to investigate the morphology and magnetic properties of the nanocomposites.

Sufi R. Ahmed; Satish B. Ogale; Peter Kofinas

2003-01-01

3

Tuning of magnetic properties of CoFe2O4 nanoparticles through charge transfer effect  

NASA Astrophysics Data System (ADS)

Herein, we report the microscopic origin of surfactant modified magnetic properties of nearly monodispersed CoFe2O4 nanoparticles (NPs). Surface modification is carried out with four surfactants having ?-acceptor/?-donor head group along with different chain-length. Upon functionalization, magnetic NPs show a maximum 65.61% increase in coercivity and 78.24% decrease in magnetization as compared to the bare one. Furthermore, ?-donor head group surfactant modified CoFe2O4 NPs show higher coercivity and magnetization with respect to ?-acceptor head group surfactant modified NPs and with the increase in chain-length of the surfactant, coercivity of NPs enhances slightly. These consequences are explained in context of crystal field splitting energy and steric hindrance offered by the surfactant.

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

2014-03-01

4

Size selected synthesis of CoFe2O4 nanoparticles prepared in a chitosan matrix  

NASA Astrophysics Data System (ADS)

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).

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

5

Magnetic properties and energy absorption of CoFe2O4 nanoparticles for magnetic hyperthermia  

E-print Network

We have studied the magnetic and power absorption properties of three samples of CoFe2O4 nanoparticles with sizes from 5 to 12 nm prepared by thermal decomposition of Fe (acac)3 and Co(acac)2 at high temperatures. The blocking temperatures TB estimated from magnetization M(T) curves spanned the range 180 < TB < 320 K, reflecting the large magnetocrystalline anisotropy of these nanoparticles. Accordingly, high coercive fields HC \\approx 1.4 - 1.7 T were observed at low temperatures. Specific Power Absorption (SPA) experiments carried out in ac magnetic fields indicated that, besides particle volume, the effective magnetic anisotropy is a key parameter determining the absorption efficiency. SPA values as high as 98 W/g were obtained for nanoparticles with average size of \\approx12 nm.

Torres, T E; Morales, M P; Ibarra, A; Marquina, C; Ibarra, M R; Goya, G F; 10.1088/1742-6596/200/7/072101

2011-01-01

6

Size-dependent magnetic properties of CoFe2O4 nanoparticles prepared in polyol.  

PubMed

Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe Mössbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles. PMID:22119894

Artus, Mathieu; Tahar, Lotfi Ben; Herbst, Frédéric; Smiri, Leila; Villain, Françoise; Yaacoub, Nader; Grenèche, Jean-Marc; Ammar, Souad; Fiévet, Fernand

2011-12-21

7

A facile synthesis of monodisperse CoFe 2O 4/SiO 2 nanoparticles  

NASA Astrophysics Data System (ADS)

Aminated-CoFe 2O 4/SiO 2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. By optimizing the preparation conditions, monodisperse CoFe 2O 4/SiO 2 NPs with high amino groups' density were obtained, which is necessary for enzyme immobilization. TEM confirm that the sample is a core/shell structure. These aminated-CoFe 2O 4/SiO 2 NPs have narrow size distributions with a mean size of about 60 nm. Moreover, the aminated-CoFe 2O 4/SiO 2 NPs can be easily dispersed in aqueous medium. The experimental results also show that the NPs have superparamagnetism, indicating that the aminated-CoFe 2O 4/SiO 2 NPs can be used as an effective carrier for the enzyme immobilization.

Wang, Hai; Huang, Jun; Ding, Liyun; Li, DaPeng; Han, Yun

2011-06-01

8

CoFe2O4 magnetic nanoparticles as a peroxidase mimic mediated chemiluminescence for hydrogen peroxide and glucose.  

PubMed

This communication presents a new peroxidase mimic of CoFe(2)O(4) nanoparticles evaluated by the luminol-based chemiluminescent (CL) reaction. This offers a new method for evaluation and screening of the nanoparticles-based enzyme mimetics. PMID:21892508

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

2011-10-14

9

Feasibility of TEOS coated CoFe2O4 nanoparticles to a GMR biosensor agent for single molecular detection.  

PubMed

Magnetic properties of 200 nm ferrimagnetic CoFe2O4 nanoparticles before and after coating with TEOS were explored and compared to soft ferrimagnetic MgFe2O4 nanoparticles (200 nm) to evaluate the feasibility as an in-vitro GMR SV (giant magnetoresistance spin-valve) biosensor agent for single molecular detection (SMD). It was found that the magnetic degradation (or variation) of TEOS coated CoFe2O4 and MgFe2O4 nanoparticles are dominantly affected by the chemical dispersion process, which is carried out in the oleic acid (OA), oleylamine (OL), or OA+OL surfactant, before starting major coating process. In addition, the TEOS coating thickness controlled by TEOS concentration and pH level in the buffer solution prominently influenced on the magnetic degradation of TEOS coated nanoparticles. According to the experimental analysis results, the magnetic degradation of TEOS coated nanoparticles is mainly attributed to the variation of particle dipole interaction caused by the degree of particle aggregation depending on TEOS coating process conditions. The TEOS coated CoFe2O4 nanoparticles exhibited a higher magnetic stability for a GMR biosensor agent, e.g., small variation of remnant magnetization, saturation magnetization and magnetic coercivity, than that of MgFe2O4 nanoparticles at the different coating process conditions. The physical and chemical analysis confirmed that this is primarily due to its higher magnetic anisotropy. The experimentally verified high biocompatibility as well as the stably maintained magnetic properties of TEOS coated CoFe2O4 nanoparticles demonstrate that CoFe2O4 nanoparticles can be considered as one of the promising ferrimagnetic nanoparticle sensor agent for an SMD GMR SV biosensor. PMID:21446410

Tang, Shao Qiang; Moon, Seung Je; Park, Ki Ho; Paek, Sun Ha; Chung, Kyung-Won; Bae, Seongtae

2011-01-01

10

Size and surface effects in the magnetic order of CoFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

In this work, we have focused on the size dependence of the magnetic properties and the surface effects of CoFe2O4 nanoparticles synthesized by high-temperature chemical method with diameter d~2, 4.5, and 7 nm, with narrow size distribution. transmission electron microscopy (TEM) images and X-ray diffraction (XRD) profiles indicates that samples with 7 and 4.5 nm present a high crystallinity while the 2 nm sample has a poor one. We have investigated by magnetization measurements and in-field Mössbauer spectroscopy the influence of the surface in the internal magnetic order of the particles. Particles with d=7 nm have almost single domain behavior and the monodomain occupies approximately the whole particle. In the sample with d=4.5 nm the surface anisotropy is large enough to alter the ferrimagnetic order in the particle shell. Then, a surface/volume ratio of ~60% is the crossover between a single domain nanoparticle and a frustrated order in a magnetic core-shell structure, due to the competition between surface anisotropy and exchange interaction+crystalline anisotropy in cobalt ferrite. In the d=2 nm sample the poor crystallinity and the large surface/volume ratio avoid the ferrimagnetic order in the particle down to T=5 K.

Pianciola, Betiana N.; Lima, Enio; Troiani, Horacio E.; Nagamine, Luiz C. C. M.; Cohen, R.; Zysler, Roberto D.

2015-03-01

11

Cationic distribution and spin canting in CoFe2O4 nanoparticles.  

PubMed

CoFe(2)O(4) nanoparticles (D(NPD) ~6 nm), prepared by a thermal decomposition technique, have been investigated through the combined use of dc magnetization measurements, neutron diffraction, and (57)Fe Mössbauer spectrometry under high applied magnetic field. Despite the small particle size, the value of saturation magnetization at 300 K (M(s) ?= 70 A m(2) kg(-1)) and at 5 K (M(s) ?= 100 A m(2) kg(-1)) are rather close to the bulk values, making the samples prepared with this method attractive for biomedical applications. Neutron diffraction measurements indicate the typical ferrimagnetic structure of the ferrites, showing an inversion degree (?(NPD) = 0.74) that is in very good agreement with cationic distribution established from low temperature (10 K) Mössbauer measurements in high magnetic field (?(moss) = 0.76). In addition, the in-field Mössbauer spectrum shows the presence of a non-collinear spin structure in both A and B sublattices. The results allow us to explain the high value of saturation magnetization and provide a better insight into the complex interplay between cationic distribution and magnetic disorder in ferrimagnetic nanoparticles. PMID:21983141

Peddis, D; Yaacoub, N; Ferretti, M; Martinelli, A; Piccaluga, G; Musinu, A; Cannas, C; Navarra, G; Greneche, J M; Fiorani, D

2011-10-26

12

The magnetic and colloidal properties of CoFe2O4 nanoparticles synthesized by co-precipitation.  

PubMed

Magnetic CoFe(2)O(4) nanoparticles were synthesized by co-precipitation at 80 °C. This co-precipitation was achieved by the rapid addition of a strong base to an aqueous solution of cations. The investigation of the samples that were quenched at different times after the addition of the base, using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDXS) and X-ray powder diffractometry, revealed the formation of a Co-deficient amorphous phase and Co(OH)(2), which rapidly reacted to form small CoFe(2)O(4) nanoparticles. The nanoparticles grew with the time of aging at elevated temperature. The colloidal suspensions of the nanoparticles were prepared in both an aqueous medium and in a non-polar organic medium, with the adsorption of citric acid and ricinoleic acid on the nanoparticles, respectively. The measurements of the room-temperature magnetization revealed the ferrimagnetic state of the CoFe(2)O(4) nanoparticles, while their suspensions displayed superparamagnetic behaviour. PMID:25286204

Gyergyek, Sašo; Drofenik, Miha; Makovec, Darko

2014-01-01

13

Influence of particle size and temperature on the dielectric properties of CoFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

The objective of this study was to establish the dielectric properties of CoFe2O4 nanoparticles with particle sizes that varied from 28.6 to 5.8 nm. CoFe2O4 nanoparticles were synthesized using a chemical coprecipitation method. The particle sizes were calculated according to the Scherrer formula using X-ray diffraction (XRD) peaks, and the particle size distribution curves were constructed by using field-emission scanning electron microscopy (FESEM) images. The dielectric permittivity and loss tangents of the samples were determined in the frequency range of 1 kHz to 1 MHz and in the temperature range of 300 to 10 K. Both the dielectric permittivity and the loss tangent were found to decrease with increasing frequency and decreasing temperature. For the smallest CoFe2O4 nanoparticle size, the dielectric permittivity and loss tangent exhibited their highest and lowest values, respectively. This behavior is very useful for materials used in devices that operate in the microwave or radio frequency ranges.

Rathore, Deepshikha; Kurchania, Rajnish; Pandey, R. K.

2014-04-01

14

Synthesis of patterned nanogold and mesoporous CoFe2O4 nanoparticle assemblies and their application in clinical immunoassays.  

PubMed

Herein, we describe a facile and feasible synthesis method for patterning nanogold particles onto magnetic mesoporous CoFe(2)O(4) nanostructures (Au-MMNs) by using poly(vinyl pyrrolidone) (PVP) as cross-linker. Initially, mesoporous CoFe(2)O(4) nanoparticles were initially synthesized with a thermal decomposition method by using mesoporous silica nanoparticles as templates, and then nanometre-sized gold particles were produced through the in situ reduction of the Au(III) on the PVP-functionalized CoFe(2)O(4). The as-prepared Au-MMNs were characterized by transmission electron microscopy (TEM), N(2) adsorption-desorption isotherms, UV-visible adsorption spectrometer, vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Furthermore, we also demonstrate the conjugation capacity of the synthesized Au-MMNs toward biomolecules by using quartz crystal microbalance (QCM), and the possible application in the electrochemical immunoassays. Experimental results indicated that the resulting Au-MMNs display good conjugation capability toward the biomolecules, and excellent analytical properties for determination of target molecules. PMID:21465042

Liu, Bingqian; Li, Qunfang; Zhang, Bing; Cui, Yuling; Chen, Huafeng; Chen, Guonan; Tang, Dianping

2011-05-01

15

Synthesis and characterisation of flexible hybrid magnetoelectric films: cobalt ferrite (CoFe2O4) nanoparticles inside a polyvinylidene fluoride (PVDF) matrix.  

E-print Network

??This project is about the synthesis of new magnetoelectric flexible nanocomposites: PVDF β-phase ferro- and piezoelectric matrices with CoFe2O4 ferromagnetic and magnetostrictive nanoparticles. In order… (more)

Marchesini, Sofia

2014-01-01

16

Reduced graphene oxide anchoring CoFe2O4 nanoparticles as an effective catalyst for non-aqueous lithium-oxygen batteries.  

PubMed

CoFe2O4 nanoparticles were uniformly anchored on reduced graphene oxide by a facile solvothermal method. The obtained CoFe2O4/reduced graphene oxide (CoFe2O4/rGO) hybrid was employed as catalyst for Li-O2 batteries. It could effectively lower the ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) overpotentials of the batteries and deliver a large capacity of 12?235 mA h grGO(-1) (2116 mA h ghybrid(-1)). It also exhibited high cyclic stability. PMID:25427137

Cao, Yong; Cai, Sen-Rong; Fan, Shao-Cong; Hu, Wei-Qiang; Zheng, Ming-Sen; Dong, Quan-Feng

2014-01-01

17

Growth dominant co-precipitation process to achieve high coercivity at room temperature in CoFe2O4 nanoparticles  

Microsoft Academic Search

Applications of CoFe2O4 are limited due to the lack of synthesis technique to produce monodispersed, single domain and high coercivity (Hc) nanoparticles. Here, we describe the growth dominant co-precipitation process to achieve high Hc, with moderate magnetization at room temperature (RT) in CoFe2O4 nanoparticles. It is well known that the particle size is closely related to the relative interdependence between

C. N. Chinnasamy; B. Jeyadevan; O. Perales-Perez; K. Shinoda; K. Tohji; A. Kasuya

2002-01-01

18

Dependence of magnetic properties on crystallite size of CoFe2O4 nanoparticles synthesised by auto-combustion method  

Microsoft Academic Search

Cobalt ferrite (CoFe2O4) nanoparticles were prepared through an auto-combustion method. The results of XRD show that the crystallite size of CoFe2O4 nanoparticles increases from 57 to 105 nm with a slight change in lattice constant as the annealing temperature increases from 300 to 1200°C. The magnetic measurements by vibrating sample magnetometer (VSM) show that Ms increases monotonously by increasing the

Y. Liu; Y. Zhang; J. D. Feng; C. F. Li; J. Shi; R. Xiong

2009-01-01

19

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

PubMed

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. PMID:22810351

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

2012-08-22

20

Synthesis, structural, dielectric, magnetic and optical properties of Cr substituted CoFe2O4 nanoparticles by co-precipitation method  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles of chromium substituted cobalt ferrite (CoFe2-xCrxO4) were prepared by the co-precipitation method for different concentrations (x=0.0, 0.1, 0.2 and 0.3) of chromium (Cr) and were annealed at 600 °C for 3 h. Formation of single phase cubic spinel structure was confirmed by X-ray diffraction analysis and the average crystallite size was in the range of 15-23 nm. Studies on the energy dispersive spectroscopy confirm the presence of Cr in Cr substituted CoFe2O4 nanoparticles. Transmission electron microscopy observations revealed that CoFe2O4 and Cr substituted CoFe2O4 nanoparticles are uniformly distributed and not highly agglomerated. Dielectric properties such as dielectric constant (??) and dielectric loss (??) of prepared nanoparticles were investigated as a function of frequency and temperature. The dielectric study reveals that dielectric constant and dielectric loss are higher for Cr substituted CoFe2O4 than the corresponding value of pure CoFe2O4 nanoparticles. Studies on magnetic properties revealed that the saturation magnetization of samples decreases with increasing Cr concentration and lies in the range of 69.67-42.71 emu/g for the prepared samples. Strong red emission and weak blue and UV emissions are observed from the fluorescence spectral analysis of the prepared pure and Cr substituted CoFe2O4 nanoparticles.

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

2014-08-01

21

Synthesis and characterization of CoFe2O4 ferrite nanoparticles obtained by an electrochemical method.  

PubMed

Uniform size cobalt ferrite nanoparticles have been synthesized in one step using an electrochemical technique. Synthesis parameters such as the current density, temperature and stirring were optimized to produce pure cobalt ferrite. The nanoparticles have been investigated by means of magnetic measurements, Mössbauer spectroscopy, x-ray powder diffraction and transmission electron microscopy. The average size of the electrosynthesized samples was controlled by the synthesis parameters and this showed a rather narrow size distribution. The x-ray analysis shows that the CoFe(2)O(4) obtained presents a totally inverse spinel structure. The magnetic properties of the stoichiometric nanoparticles show ferromagnetic behavior at room temperature with a coercivity up to 6386 Oe and a saturation magnetization of 85 emu g(-1). PMID:22894928

Mazarío, E; Herrasti, P; Morales, M P; Menéndez, N

2012-09-01

22

Adsorption of sulfur dioxide by CoFe2O4 spinel ferrite nanoparticles and corresponding changes in magnetism.  

PubMed

Adsorption of sulfur dioxide on 10 nm CoFe(2)O(4) spinel ferrite nanoparticles was examined. Adsorption loadings of sulfur dioxide at breakthrough conditions were determined to be approximately 0.62 mol/kg, which is significant given the 150 m(2)/g surface area of the nanoparticles. Adsorption proceeds through a chemisorption mechanism with sulfur dioxide forming a sulfate upon adsorption on the particle surface, which leads to a 23% decrease in the remnant magnetization, a 20% decrease in the saturation magnetization, and a 9% decrease in the coercivity of the magnetic nanoparticles. Adsorbent materials that provide a magnetic signal when adsorption occurs could have broad implications on adsorption-based separations. PMID:22400990

Glover, T Grant; Sabo, Daniel; Vaughan, Lisa A; Rossin, Joseph A; Zhang, Z John

2012-04-01

23

Magnetic couplings in CoFe2O4/FeCo-FeO core-shell nanoparticles  

NASA Astrophysics Data System (ADS)

CoFe2O4/FeCo-FeO core-shell nanoparticles with an average particle size of about 4.3 nm were prepared by reducing nanoparticles of superparamagnetic cobalt-ferrite under hydrogen and oxygen atmospheres. The low temperature magnetic hysteresis showed an interesting behavior which has only been observed in thin film multilayer systems. At low magnetic fields H(< 0.2 kOe) the behavior is dominated by the magnetic structure of the magnetically soft shell while for higher values of H the exchange-spring core-shell coupling plays a major role. A particle model which is coherent with the observed magnetic behavior has been also proposed.

Soares, J. M.; Conceição, O. L. A.; Machado, F. L. A.; Prakash, A.; Radha, S.; Nigam, A. K.

2015-01-01

24

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

PubMed

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 2weeks, 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. PMID:25437955

Romih, Tea; Drašler, Barbara; Jemec, Anita; Drobne, Damjana; Novak, Sara; Golobi?, Miha; Makovec, Darko; Susi?, Robert; Kogej, Ksenija

2015-03-01

25

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

NASA Astrophysics Data System (ADS)

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.

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

2010-08-01

26

Temperature dependence of magnetic anisotropy constant in CoFe2O4 nanoparticles examined by Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

The temperature dependence of the effective magnetic anisotropy constant of CoFe2O4 nanoparticles is determined based on the measurements of SQUID magnetometry and Mössbauer spectroscopy. Under an intuitive assumption that the superparamagnetic fraction of the cumulative area in the particle size distribution at a temperature is equal to the doublet fraction in the Mössbauer spectra at that temperature, we are able to get a relation between r and T B, from which the temperature dependence of the effective magnetic anisotropy constant is determined. The resultant magnetic anisotropy constant increases markedly with decreasing temperature from 2.0 ×105 J/m 3 at 300 K to 8.3 ×106 J/m 3 at 125 K.

Yoon, Sunghyun

2015-01-01

27

Controlling phase formation in solids: rational synthesis of phase separated Co@Fe2O3 heteroparticles and CoFe2O4 nanoparticles.  

PubMed

A wet chemical approach from organometallic reactants allowed the targeted synthesis of Co@Fe(2)O(3) heterodimer and CoFe(2)O(4) ferrite nanoparticles. They display magnetic properties that are useful for magnetic MRI detection. PMID:21748171

Nakhjavan, Bahar; Tahir, Muhammad Nawaz; Panthöfer, Martin; Gao, Haitao; Gasi, Teuta; Ksenofontov, Vadim; Branscheid, Robert; Weber, Stefan; Kolb, Ute; Schreiber, Laura Maria; Tremel, Wolfgang

2011-08-21

28

Preparation of chitosan-ethylenediaminetetraacetate-enwrapped magnetic CoFe 2O 4 nanoparticles via zero-length emulsion crosslinking method  

NASA Astrophysics Data System (ADS)

A kind of magnetic multiple functional groups nanocomposites, chitosan-ethylenediaminetetraacetate (EDTA)-enwrapped CoFe 2O 4 nanoparticles, i.e. CoFe 2O 4@chitosan-EDTA nanocomposites were synthesized by a facile zero-length emulsion crosslinking process. In this method, CoFe 2O 4 was used as magnetic core, and 1-ethyl-3-(3-dimethylminopropyl) carbodiimide hydrochloride (EDAC) was used as a crosslinker, integrating amino group of chitosan and carboxyl group of EDTA. Determination of amino groups in chitosan modified by EDAC-activated EDTA was carried out through the trinitrobenzenesulfonic acid (TNBS) method. The as-prepared magnetic nanocomposites were characterized by XRD, FT-IR, XPS, SEM, EDS, TEM, SAED and vibrating sample magnetometer (VSM), and the results showed that the as-prepared CoFe 2O 4@chitosan-EDTA nanocomposites have good dispersibility, spherical shape and enough magnetization. The method proposed can be extended to fabricate other magnetic nanocomposites possessed amino and carboxyl groups.

Qin, Runhua; Li, Fengsheng; Chen, Mingyue; Jiang, Wei

2009-10-01

29

Spectroscopic signature of the superparamagnetic transition and surface spin disorder in CoFe2O4 nanoparticles.  

PubMed

Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials. To investigate confinement in combination with strong magnetoelastic interactions, we measured the infrared vibrational properties of CoFe(2)O(4) nanoparticles and compared our results to trends in the coercivity over the same size range and to the response of the bulk material. Remarkably, the spectroscopic response is sensitive to the size-induced crossover to the superparamagnetic state, which occurs between 7 and 10 nm. A spin-phonon coupling analysis supports the core-shell model. Moreover, it provides an estimate of the magnetically disordered shell thickness, which increases from 0.4 nm in the 14 nm particles to 0.8 nm in the 5 nm particles, demonstrating that the associated local lattice distortions take place on the length scale of the unit cell. These findings are important for understanding finite length scale effects in this and other magnetic oxides where magnetoelastic interactions are important. PMID:22540958

Sun, Qi-C; Birkel, Christina S; Cao, Jinbo; Tremel, Wolfgang; Musfeldt, Janice L

2012-06-26

30

Phase evaluation of Li+ substituted CoFe2O4 nanoparticles, their characterizations and magnetic properties  

NASA Astrophysics Data System (ADS)

Li+ substituted CoFe2O4 with the chemical formula Li3xCoFe2-xO4 were synthesized by sol-gel auto combustion method. The synthesized samples were annealed at 600 °C for 4 h. X-ray diffraction data were used to evaluate the structure of the prepared samples. Spinel ferrite phase of CoFe2O4 changes to ordered like lithium ferrite phase with increase in Li+ substitution. Lattice constant increases whereas particle size found to decrease with Li+ substitution. Infrared spectroscopy also confirmed the phase transition of CoFe2O4 after the incorporation of lithium ions. Substitution of Li+ ions for Fe3+ caused a decrease in the saturation magnetization from 69.59 emu/g to 47.71 emu/g and the coercivity increased from 647 Oe to 802 Oe. Resistivity and dielectric properties shows inverse relation to each other.

Kadam, R. H.; Alone, Suresh T.; Mane, Maheshkumar L.; Biradar, A. R.; Shirsath, Sagar E.

2014-04-01

31

Synthesis of magnetic spinel ferrite CoFe2O4 nanoparticles from ferric salt and characterization of the size-dependent superparamagnetic properties  

Microsoft Academic Search

The CoFe 2 O 4 nanoparticles have been synthesized by using a stable ferric salt of FeCl 3 with a micellar microemulsion method. The normal micelles are formed by sodium dodecyl sulfate (NaDS) in aqueous solutions. The mean size of the nanoparticles can be controlled from less than 4 nm to about 10 nm through controlling the concentrations of the

Chao Liu; Adam J. Rondinone; Z. John

2000-01-01

32

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

PubMed

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. PMID:23289402

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

2013-01-30

33

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

PubMed

Cobalt ferrite (CoFe2O4) nano-particles were synthesized by the hydrothermal method with the addition of a surfactant sodium bis(2-ethylhexyl) sulphosuccinate (AOT). Characterization measurements including X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy showed that all the final products were single-phase CoFe2O4 nano-crystals with AOT molecules bonding to the surfaces, the average crystallite sizes were all near 25 nm, and the lattice constant increased with the increasing mass of AOT. The magnetic hysteresis loops measured at room temperature indicated that the bonding of the AOT to the surfaces led to an increase of the saturation magnetization (Ms), the coercivity (Hc) and the remanence ratio (Mr/Ms). Furthermore, as the concentration of AOT reached the critical micelle concentration (CMC), turning points were observed in the the curves of Hc, Mr/Ms and K(eff) (effective magnetic anisotropy constants) versus. the mass of AOT due to the formation of the AOT micelles. PMID:21137736

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

2010-10-01

34

The effect of annealing on phase evolution, microstructure and magnetic properties of Mn substituted CoFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

Manganese substituted CoFe2O4 nanoparticles has been prepared by a simple evaporation method and auto combustion method. The role of annealing temperature on phase, particle size and morphology of Mn-Co ferrite nanoparticles were determined by X-ray diffraction, and transmission electron microscopy (TEM). The lowest size of particles (~3 nm) is obtained by auto combustion method. The annealing effect creates a vital change in magnetic properties which is studied by using vibrating sample magnetometer (VSM). These spinel ferrites are decomposed to ?-Fe2O3 after annealing above 550 °C in air. However, ?-Fe2O3 phase was slowly vanished after ferrites annealing above 900 °C. The effect of this secondary phase on the structural and magnetic properties of Mn substituted cobalt ferrite nanoparticles is also discussed.

Ranjith Kumar, E.; Jayaprakash, R.; Prakash, T.

2014-05-01

35

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

36

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

PubMed

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. PMID:24334365

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

2014-01-17

37

Size-regulated group separation of CoFe2O4 nanoparticles using centrifuge and their magnetic resonance contrast properties  

PubMed Central

Magnetic nanoparticle (MNP)-based magnetic resonance imaging (MRI) contrast agents (CAs) have been the subject of extensive research over recent decades. The particle size of MNPs varies widely and is known to influence their physicochemical and pharmacokinetic properties. There are two commonly used methods for synthesizing MNPs, organometallic and aqueous solution coprecipitation. The former has the advantage of being able to control the particle size more effectively; however, the resulting particles require a hydrophilic coating in order to be rendered water soluble. The MNPs produced using the latter method are intrinsically water soluble, but they have a relatively wide particle size distribution. Size-controlled water-soluble MNPs have great potential as MRI CAs and in cell sorting and labeling applications. In the present study, we synthesized CoFe2O4 MNPs using an aqueous solution coprecipitation method. The MNPs were subsequently separated into four groups depending on size, by the use of centrifugation at different speeds. The crystal shapes and size distributions of the particles in the four groups were measured and confirmed by transmission electron microscopy and dynamic light scattering. Using X-ray diffraction analysis, the MNPs were found to have an inverse spinel structure. Four MNP groups with well-selected semi-Gaussian-like diameter distributions were obtained, with measured T2 relaxivities (r2) at 4.7 T and room temperature in the range of 60 to 300 mM?1s?1, depending on the particle size. This size regulation method has great promise for applications that require homogeneous-sized MNPs made by an aqueous solution coprecipitation method. Any group of the CoFe2O4 MNPs could be used as initial base cores of MRI T2 CAs, with almost unique T2 relaxivity owing to size regulation. The methodology reported here opens up many possibilities for biosensing applications and disease diagnosis. PACS 75.75.Fk, 78.67.Bf, 61.46.Df PMID:24004536

2013-01-01

38

Size-regulated group separation of CoFe2O4 nanoparticles using centrifuge and their magnetic resonance contrast properties.  

PubMed

Magnetic nanoparticle (MNP)-based magnetic resonance imaging (MRI) contrast agents (CAs) have been the subject of extensive research over recent decades. The particle size of MNPs varies widely and is known to influence their physicochemical and pharmacokinetic properties. There are two commonly used methods for synthesizing MNPs, organometallic and aqueous solution coprecipitation. The former has the advantage of being able to control the particle size more effectively; however, the resulting particles require a hydrophilic coating in order to be rendered water soluble. The MNPs produced using the latter method are intrinsically water soluble, but they have a relatively wide particle size distribution. Size-controlled water-soluble MNPs have great potential as MRI CAs and in cell sorting and labeling applications. In the present study, we synthesized CoFe2O4 MNPs using an aqueous solution coprecipitation method. The MNPs were subsequently separated into four groups depending on size, by the use of centrifugation at different speeds. The crystal shapes and size distributions of the particles in the four groups were measured and confirmed by transmission electron microscopy and dynamic light scattering. Using X-ray diffraction analysis, the MNPs were found to have an inverse spinel structure. Four MNP groups with well-selected semi-Gaussian-like diameter distributions were obtained, with measured T2 relaxivities (r2) at 4.7 T and room temperature in the range of 60 to 300 mM-1s-1, depending on the particle size. This size regulation method has great promise for applications that require homogeneous-sized MNPs made by an aqueous solution coprecipitation method. Any group of the CoFe2O4 MNPs could be used as initial base cores of MRI T2 CAs, with almost unique T2 relaxivity owing to size regulation. The methodology reported here opens up many possibilities for biosensing applications and disease diagnosis. PACS: 75.75.Fk, 78.67.Bf, 61.46.Df. PMID:24004536

Kang, Jongeun; Lee, Hyunseung; Kim, Young-Nam; Yeom, Areum; Jeong, Heejeong; Lim, Yong Taik; Hong, Kwan Soo

2013-01-01

39

Size-regulated group separation of CoFe2O4 nanoparticles using centrifuge and their magnetic resonance contrast properties  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticle (MNP)-based magnetic resonance imaging (MRI) contrast agents (CAs) have been the subject of extensive research over recent decades. The particle size of MNPs varies widely and is known to influence their physicochemical and pharmacokinetic properties. There are two commonly used methods for synthesizing MNPs, organometallic and aqueous solution coprecipitation. The former has the advantage of being able to control the particle size more effectively; however, the resulting particles require a hydrophilic coating in order to be rendered water soluble. The MNPs produced using the latter method are intrinsically water soluble, but they have a relatively wide particle size distribution. Size-controlled water-soluble MNPs have great potential as MRI CAs and in cell sorting and labeling applications. In the present study, we synthesized CoFe2O4 MNPs using an aqueous solution coprecipitation method. The MNPs were subsequently separated into four groups depending on size, by the use of centrifugation at different speeds. The crystal shapes and size distributions of the particles in the four groups were measured and confirmed by transmission electron microscopy and dynamic light scattering. Using X-ray diffraction analysis, the MNPs were found to have an inverse spinel structure. Four MNP groups with well-selected semi-Gaussian-like diameter distributions were obtained, with measured T2 relaxivities ( r 2) at 4.7 T and room temperature in the range of 60 to 300 mM-1s-1, depending on the particle size. This size regulation method has great promise for applications that require homogeneous-sized MNPs made by an aqueous solution coprecipitation method. Any group of the CoFe2O4 MNPs could be used as initial base cores of MRI T2 CAs, with almost unique T2 relaxivity owing to size regulation. The methodology reported here opens up many possibilities for biosensing applications and disease diagnosis.

Kang, Jongeun; Lee, Hyunseung; Kim, Young-Nam; Yeom, Areum; Jeong, Heejeong; Lim, Yong Taik; Hong, Kwan Soo

2013-09-01

40

Synthesis of cobalt ferrite (CoFe2O4) nanoparticles using combustion, coprecipitation, and precipitation methods: A comparison study of size, structural, and magnetic properties  

NASA Astrophysics Data System (ADS)

In this work the cobalt ferrite (CoFe2O4) nanoparticles are synthesized using three different methods; combustion, coprecipitation, and precipitation. Size, structural, and magnetic properties were determined and compared using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). XRD data analysis showed an average size of 69.5 nm for combustion, 49.5 nm for coprecipitation, and 34.7 nm for precipitation samples which concorded with SEM images. XRD data further revealed a reverse cubic spinel structure with the space group Fd-3m in all three samples. VSM data of samples showed a saturation point in the magnetic field of less than 15 kOe. Magnetization saturation (Ms) was 56.7 emu/g for combustion synthestized samples, 55.8 emu/g for coprecipitation samples, and 47.2 emu/g for precipitation samples. Coercivity (Hc) was 2002 Oe for combustion synthestized samples, 850 Oe for coprecipitation samples, and 233 Oe for precipitation samples. These results show that various methods of nanoparticle synthesis can lead to different particle sizes and magnetic properties. Hc and Ms are greatest in the combustion method and least in precipitation method.

Houshiar, Mahboubeh; Zebhi, Fatemeh; Razi, Zahra Jafari; Alidoust, Ali; Askari, Zohreh

2014-12-01

41

Synthesis and magnetic properties of CoFe2O4 spinel ferrite nanoparticles doped with lanthanide ions  

Microsoft Academic Search

Lanthanide ions have been doped into cobalt spinel ferrites using an oil-in-water micellar method to form CoLn0.12Fe1.88O4 nanoparticles with Ln=Ce, Sm, Eu, Gd, Dy, or Er. Doping with lanthanide ions (LnIII) modulates the magnetic properties of cobalt spinel ferrite nanoparticles. In particular cases of Gd3+ or Dy3+ ions, a dramatic increase in the blocking temperature and coercivity is observed. Indeed,

Myrtil L. Kahn; Z. John Zhang

2001-01-01

42

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

PubMed

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. PMID:22258160

Fan, Yingwei; Huang, Yuming

2012-03-01

43

Catalytic decomposition of acetylene over CoFe 2O 4\\/BaFe 12O 19 core shell nanoparticles for the production of carbon nanotubes  

Microsoft Academic Search

In this study, carbon nanotubes were formed by acetylene decomposition on hydrogen-reduced CoFe2O4\\/BaFe12O19 core shell catalysts at 500–800°C. X-ray diffraction (XRD) was used to examine the crystal characteristics of catalysts. The carbon nanotubes were also examined both by transmission electron microscopy (TEM) to define their appearance and structure. Little amount of carbon nanotubes were found on the catalyst surface at

M. H. Khedr; M. Bahgat; S. A. Abdel-Moaty

2009-01-01

44

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

PubMed

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. PMID:24140535

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

2013-11-15

45

Unique magnetic properties and magnetization reversal process of CoFe2O4 nanotubes fabricated by electrospinning.  

PubMed

CoFe(2)O(4) nanotubes have been directly fabricated by single-capillary spinneret electrospinning. The external diameter of the CoFe(2)O(4) nanotubes ranges from 60 nm to 160 nm. The morphology and structure characterizations show that individual CoFe(2)O(4) nanotubes are made of CoFe(2)O(4) nanocrystals stacking along the nanotubes with no preferred growth directions and these individual nanocrystals are single crystal with a cubic spinel structure. Each nanocrystal was shown to be a single magnetic domain. The magnetic measurements show that the coercivity (H(c)) of the CoFe(2)O(4) nanotubes decreases from 10?400 Oe at 5 K to 300 Oe at 360 K. The CoFe(2)O(4) nanotubes have a spin reorientation (SR) at 5 K, which is different from CoFe(2)O(4) nanorods and nanoparticles. Based on the observed morphology and crystal structure, a micromagnetic model, "chain-of-rings", is developed to interpret the magnetic behavior of the CoFe(2)O(4) nanotubes. The theoretical coercivity (534 Oe) is in good agreement with the experimental results (509 Oe). It is believed that our work should open a new route to prepare various magnetic ferrite nanotubes and is significant for expanding the application of CoFe(2)O(4) into the new fields. PMID:22622489

Fu, Jiecai; Zhang, Junli; Peng, Yong; Zhao, Jianguo; Tan, Guoguo; Mellors, Nigel J; Xie, Erqing; Han, Weihua

2012-07-01

46

Low-Temperature Preparation of Superparamagnetic CoFe2O4 Microspheres with High Saturation Magnetization  

Microsoft Academic Search

Based on a low-temperature route, monodispersed CoFe2O4 microspheres (MSs) were fabricated through aggregation of primary nanoparticles. The microstructural and magnetic characteristics of the as-prepared MSs were characterized by X-ray diffraction\\/photoelectron spectroscopy, scanning\\/transmitting electron microscopy, and vibrating sample magnetometer. The results indicate that the diameters of CoFe2O4 MSs with narrow size distribution can be tuned from over 200 to ~330 nm.

Hong Lei Yuan; Yong Qiang Wang; Shao Min Zhou; Li Sheng Liu; Xi Liang Chen; Shi Yun Lou; Rui Jian Yuan; Yao Ming Hao; Ning Li

2010-01-01

47

Magnetic structure of CoFe2O4  

Microsoft Academic Search

Up to now, the cubic spinel CoFe2O4 was assumed to have a collinear ferrimagnetic structure; however a High Field Mössbauer Study (HFMS) recently evidenced for canting angles at both A and B iron sites. In order to have a coherent view on the CoFe2O4 magnetic structure, we performed high field magnetic measurements and neutron diffraction experiments on the same powdered

J. Teillet; F. Bouree; R. Krishnan

1993-01-01

48

Hollow glass microspheres coated with CoFe 2O 4 and its microwave absorption property  

NASA Astrophysics Data System (ADS)

Spinel CoFe 2O 4 coating on the surface of hollow glass microspheres of low density was synthesized by co-precipitation method. The phase structures, morphologies, particle size, shell thickness, chemical compositions of the composites have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy (EDS). The results show that CoFe 2O 4 coating on hollow glass microspheres can be achieved, and the coating layers are constituted by CoFe 2O 4 nanoparticles of mean size ca. 10 nm. The as-synthesized powder materials were uniformly dispersed into the phenolic cement, then the mixture was pasted on metal plate with the area of 200 mm×200 mm as the test plate. The test of microwave absorption was carried out by the radar-absorbing materials (RAM) reflectivity far field radar cross-section (RCS) method. The results indicate that the coated CoFe 2O 4/hollow glass microspheres composites can be applied in lightweight and strong absorption microwave absorbers.

Fu, Wuyou; Liu, Shikai; Fan, Wenhua; Yang, Haibin; Pang, Xiaofen; Xu, Jing; Zou, Guangtian

2007-09-01

49

A facile thermal decomposition route to synthesise CoFe2O4 nanostructures  

NASA Astrophysics Data System (ADS)

The synthesis of CoFe2O4 nanoparticles has been achieved by a simple thermal decomposition method from an inorganic precursor, cobalt ferrous cinnamate hydrazinate (CoFe2(cin)3(N2H4)3) which was obtained by a novel precipitation method from the corresponding metal salts, cinnamic acid and hydrazine hydrate. The precursor was characterized by hydrazine and metal analyses, infrared spectral analysis and thermo gravimetric analysis. Under appropriate annealing, CoFe2(cin)3(N2H4)3 yielded CoFe2O4 nanoparticles, which were characterized for their size and structure using X-Ray diffraction (XRD), high resolution transmission electron microscopic (HRTEM), selected area electron diffraction (SAED) and scanning electron microscopic (SEM) techniques.

Kalpanadevi, K.; Sinduja, C. R.; Manimekalai, R.

2014-01-01

50

Bioinspired Formation of 3D Hierarchical CoFe2O4 Porous Microspheres for Magnetic-Controlled Drug Release.  

PubMed

Bioinspired by the morphology of dandelion pollen grains, we successfully prepared a template-free solution-based method for the large-scale preparation of three-dimensional (3D) hierarchical CoFe2O4 porous microspheres. Besides, on the basis of the effect of the reaction time on the morphology evolution of the precursor, we proposed an in situ dissolution-recrystallization growth mechanism with morphology and phase change to understand the formation of dandelion pollenlike microspheres. Doxorubicin hydrochloride, an anticancer drug, is efficiently loaded into the CoFe2O4 microspheres. The magnetic nanoparticles as field-controlled drug carriers offer a unique power of magnetic guidance and field-triggered drug-release behavior. Therefore, 3D hierarchical CoFe2O4 porous microspheres demonstrate the great potential for drug encapsulation and controlled drug-release applications. PMID:25539822

Cai, Bin; Zhao, Minggang; Ma, Ye; Ye, Zhizhen; Huang, Jingyun

2015-01-21

51

High frequency study of core-shell reusable CoFe2O4-ZnO nanospheres  

NASA Astrophysics Data System (ADS)

Recently, coated nanoshells combined with magnetic nanoparticles and cancer-cell-specific antibodies have been used to develop a multifunctional platform for simultaneously diagnosing and treating cancer, via magnetic resonance imaging and photothermal therapy. For this application, core-shell nano-spheres with a low resonance frequency (low GHz range) in a strong applied field are required. In this aspect, ferromagnetic resonance experiment is an important tool for determining the dynamic properties of nano-materials. Magnetic field dependence of resonance frequency (fr) and linewidths (?ƒ and ?H) for both the ZnO coated and uncoated CoFe2O4 hollow spheres are studied using a vector network analyzer. As compared to uncoated CoFe2O4 hollow sphere, ZnO coated CoFe2O4 showed reduced resonance frequency, larger ?ƒ and ?H, reduced gyromagnetic ratio and effective fields. The experimental results are confirmed with the effective medium theory.

Kuanr, Bijoy K.; Veerakumar, V.; Mishra, S. R.; Wilson, Armstrong M.; Kuanr, Alka V.; Camley, R. E.; Celinski, Z.

2014-05-01

52

Controlled synthesis of CoFe2O4 nano-octahedra Andr Lus Lopes-Moriyamaa,b *  

E-print Network

, fax number: +558432153770 Abstract Nano-octahedral grains of cobalt ferrite (CoFe2O4) with size around powder. The oxidation state of cobalt atoms on the ferrite structure was also influenced by CTAB" DOI : 10.1016/j.powtec.2014.01.080 #12;2 Hydrothermal synthesis; nanoparticles; cobalt ferrite; shape

Boyer, Edmond

53

Controlling role of pH and temperature on CoFe2O4 nanostructures produced by hydrothermal synthesis.  

PubMed

The hydrothermal synthesis (HS) of CoFe2O4 nanoparticles (NPs) has been investigated as a function of reaction temperature and pH, using complementary characterisation techniques of transmission electron microscopy and X-ray diffractometry. The HS of CoFe2O4 NPs (< 25 nm) at pH - 8 proceeded through the formation and dissolution of intermediate Fe(OH)3 and [FeCo3(OH)8]+ x [Cl- x H2O]- phases with increasing reaction temperature. In contrast, HS of CoFe2O4 NPs (< 50 nm) at pH - 12 resulted in the formation of additional intermediate Co(OH)2, CoOOH and alpha-FeOOH phases, with residual alpha-Fe2O3 present in the final reaction product. This research demonstrates the size and phase purity of the CoFe2O4 NPs may be controlled through the formation and dissolution of the intermediate phases at various pH values in the alkaline pH regime. PMID:23421290

Almeida, Trevor P; Fay, Mike; Zhu, Yanqiu; Brown, Paul D

2012-11-01

54

Synthesis and characterization of superparamagnetic CoFe2O4/MWCNT hybrids for tumor-targeted therapy.  

PubMed

Owing to their great potentialities of carbon nanotubes (CNTs)-based magnetic nano-composites, numerous applications of them have been found in nanotechnology, integrated functional system, and in medicine. Herein, nearly monodisperse CoFe2O4 nanoparticles have been deposited on multi-walled carbon nanotubes (MWCNTs) by high-temperature hydrolysis and inorganic polymerization of ionic Co(II) and Fe(III) salts and MWCNTs in a polyol solution. X-ray diffraction, energy-dispersive X-ray spectrometry and transmission electron microscopy were used to characterize the final products. The average size of CoFe2O4 nanoparticles and their coverage density on MWCNTs can be adjusted to some extent by altering the reaction parameters. A proposed formation mechanism of the magnetic hybrids is presented. Magnetic measurements showed that the hybrids were superparamagnetic at room temperature and their saturation magnetization could be fine tuned by changing the loading of CoFe2O4 nanoparticles on the MWCNTs. PMID:23646722

Sun, Chuanyu; Liu, Yong; Ding, Weihong; Gou, Yuancheng; Xu, Ke; Xia, Guowei; Ding, Qiang

2013-01-01

55

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

PubMed

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. PMID:22284478

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

2012-01-30

56

Electrophoretic deposition of BaTiO 3/CoFe 2O 4 multiferroic composite films  

NASA Astrophysics Data System (ADS)

Electrophoretic deposition was utilized for preparation of BaTiO 3/CoFe 2O 4 multiferroic composite thick films on indium-tin oxide substrates. The suspensions for electrophoretic experiments were prepared by dispersing BaTiO 3 and CoFe 2O 4 nanoparticles with different molar ratios into solvents composed of ethanol and acetylacetone. Polyvinyl butyral was added to the suspensions in order to enhance the adhesion and strength of deposit and prevent cracking. The zeta potential values of BaTiO 3/CoFe 2O 4 suspensions were measured to be 26.4-36.9 mV. The experiment results showed that deposited films were obtained only when the applied electric field was larger than a certain critical value. XRD and SEM analysis depicted the presence of constituent phases in composite films. The percolation threshold of composite films was improved through dispersing ferromagnetic phase into ferroelectric phase. Therefore, the ferroelectric properties of composite thick films were maintained when the ferromagnetic properties were enhanced significantly with increasing CFO content.

Zhou, Dongxiang; Jian, Gang; Zheng, Yanan; Gong, Shuping; Shi, Fei

2011-06-01

57

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)

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.

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

2014-11-01

58

Ethanol gas sensor based on CoFe 2O 4 nano-crystallines prepared by hydrothermal method  

Microsoft Academic Search

CoFe2O4 nano-crystallines were prepared by a hydrothermal method at 120–220°C. CoFe2O4 sensors were fabricated from the CoFe2O4 nano-crystallines and their gas sensing properties were investigated. Spinel CoFe2O4 nano-crystallines could be obtained when the pH value was in the range of 8–14, and the morphology of the particles obtained under different conditions was almost spherical. The CoFe2O4 nano-crystallines obtained at a

Chu Xiangfeng; Jiang Dongli; Guo Yu; Zheng Chenmou

2006-01-01

59

Formation Mechanism and Shape Control of Monodisperse Magnetic CoFe2O4 Nanocrystals  

Microsoft Academic Search

The formation mechanism and shape control of monodisperse magnetic cobalt ferrite (CoFe2O4) nanocrystals produced by thermolysis of a stoichiometric Co2+Fe2 3+-oleate complex in organic solution has been investigated. Synthesis of the pure ternary CoFe2O4 inverse spinel phase, without formation of any intermediate binary cobalt and iron oxides, is favored by the close thermal decomposition temperature of the Co2+-oleate and Fe3+-oleate

Ningzhong Bao; Liming Shen; Wei An; Prahallad Padhan; C. Heath Turner; Arunuba Gupta

2009-01-01

60

Strain-induced high coercivity in CoFe2O4 powders  

Microsoft Academic Search

Three cobalt ferrite (CoFe2O4) powders were used as starting materials for mechanical milling. A mechanical milling for a short time resulted in a relatively large residual strain and a high density of defects in the micrometer-sized CoFe2O4 powders. High coercivities (up to 5.1 kOe) were achieved in these samples, probably due to the stress anisotropy and pinning effects. A relatively

B. H. Liu; J. Ding

2006-01-01

61

Deposition of luminescent Y2O3:Eu3+ on ferromagnetic mesoporous CoFe2O4@mSiO2 nanocomposites.  

PubMed

Luminescent Y2O3:Eu(3+) particles have been deposited on the surface of ferromagnetic mesoporous CoFe2O4@mSiO2 nanoparticles by a co-precipitation method, obtaining multifunctional CoFe2O4@mSiO2@Y2O3:Eu(3+) nanocomposites. XRD, SEM, TEM, EDX, XPS, N2-adsorption-desorption, FT-IR, VSM and PL were used to characterized the samples. The results reveal that the nanocomposites display typical mesoporous characteristics with high surface areas (BET), large pore volumes and core-shell structures. The composites show ferromagnetic properties and red luminescence from the (5)D0-(7)F2 transition at 610 nm. The size and the magnetic and luminescence properties of the composites could be tuned by systematically varying the experimental parameters, such as the annealing temperature, the mass ratio of CoFe2O4@mSiO2 to Y2O3:Eu(3+), and the volume of TEOS. A possible quenching mechanism of the luminescent Y2O3:Eu(3+) by the ferromagnetic CoFe2O4 is proposed. The high BET and large pore volume may give the composite potential application in controlled drug release. PMID:24741669

Ren, Xiaozhen; Tong, Lizhu; Chen, Xiaodong; Ding, Hong; Yang, Xuwei; Yang, Hua

2014-06-14

62

Preparation and photocatalytic properties of nanometer-sized magnetic TiO2/SiO2/CoFe2O4 composites.  

PubMed

Magnetic TiO2/SiO2/CoFe2O4 nanoparticles (TiO2/SCFs) were prepared by a sol-gel process in a reverse microemulsion combined with solvent-thermal technique. TiO2/SCFs were characterized by Fourier transform infrared spectrometry, thermogravimetric analysis-differential scanning calorimetry, X-ray diffraction, Raman spectrometry, TEM, BET specific surface area measurement, and magnetic analysis. Structure analyses indicated that TiO2/SCFs presented a core-shell structure with TiO2 uniformly coating on SiO2/CoFe2O4 nanomagnets (SCFs) and typical ferromagnetic hysteresis. TiO2/SCFs showed larger specific surface area and better photocatalytic activities than TiO2 and TiO2/CoFe2O4 photocatalysts prepared by the same method. The doping interaction between TiO2 and CoFe2O4 reduced thanks to the inert SiO2 mesosphere. PMID:22413361

Li, Hansheng; Zhang, Yaping; Wu, Qin; Wang, Xitao; Liu, Changhao

2011-11-01

63

Self-oriented CoFe2O4 composites for non-reciprocal microwave components  

NASA Astrophysics Data System (ADS)

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 (?0Hc) 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.

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

2014-07-01

64

Formation Mechanism and Shape Control of Monodisperse Magnetic CoFe2O4 Nanocrystals  

SciTech Connect

The formation mechanism and shape control of monodisperse magnetic cobalt ferrite (CoFe2O4) nanocrystals produced by thermolysis of a stoichiometric Co2+Fe2 3+-oleate complex in organic solution has been investigated. Synthesis of the pure ternary CoFe2O4 inverse spinel phase, without formation of any intermediate binary cobalt and iron oxides, is favored by the close thermal decomposition temperature of the Co2+-oleate and Fe3+-oleate precursors. For reaction temperatures between 250 and 320 ?C, the nucleation and growth dynamics dictate the size and shape evolution of the nanocrystals. Prenucleation of CoFe2O4 occurs at 250-300 ?C but without any growth of nanocrystals, because the monomer concentration is lower than the critical nucleation concentration. For temperatures in the range of 300-320 ?C,which is above the thermolysis temperature of the mixed Co2+Fe2 3+-oleate complex, the monomer concentration increases rapidly resulting in homogeneous nucleation. Atomic clusters of CoFe2O4 with size<2 nm are initially formed at 314 ?C that then grow rapidly when the temperature is raised to 320 ?C in less than a minute. The shape of the CoFe2O4 nanocrystals can be reproducibly controlled by prolonging the aging time at 320 ?C, evolving from initial spherical, to spherical-to-cubic, cubic, corner-grown cubic, or starlike shapes. Thus, with careful choice of reaction parameters, such as the precursor concentration and the heating rate, it is possible to achieve large-scale synthesis of shape-controlled monodisperse CoFe2O4 nanocrystals with high yield.

Bao, Ningzhong; Shen, Liming; An, Wei; Padhan, Prahallad; Turner, C. H.; Gupta, Arunuba

2009-07-28

65

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

PubMed

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 ?m. 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

Liu, Xiaohua; Liu, Shuangyi; Han, Myung-Geun; Zhao, Lukas; Deng, Haiming; Li, Jackie; Zhu, Yimei; Krusin-Elbaum, Lia; O'Brien, Stephen

2013-01-01

66

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

PubMed Central

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 ?m. 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

2013-01-01

67

Epitaxial CoFe2O4(111)-based multilayers for spin filter applications  

NASA Astrophysics Data System (ADS)

Efficient spin filtering at room temperature has high potential for ultra sensitive detectors and spin injection into semiconductors, leading to the growth of spin-based devices. We investigate the interaction of spin filter CoFe2O4(111) epitaxial tunnel barriers with Co and Fe3O4 electrodes in light of their possible application at room temperature. The question of the exchange coupling that often prohibits the independent switching between a magnetic tunnel barrier and its magnetic electrode is addressed, as is the difference between an oxide/metal and oxide/oxide system. Our study of the magnetic reversal in the CoFe2O4/Co and CoFe2O4/Fe3O4 bilayers, supported by a detailed structural and chemical analysis of the samples and their interfaces, clearly evidences the effect of a metallic or an oxide interface. An unusual exchange spring magnet behavior arises in the case of the CoFe2O4/Fe3O4 samples due to the superexchange interactions found in these ferrimagnetic oxides. This unique exchange phenomenon at the oxide-oxide interface ultimately leads to a barrier/electrode system that switches independently without the necessity of a non-magnetic spacer.

Ramos, Ana; Moussy, Jean-Baptiste; Gautier-Soyer, Martine

2007-03-01

68

Structural and Raman scattering study of Ni-doped CoFe2O4  

NASA Astrophysics Data System (ADS)

Raman scattering measurements were made on polycrystalline CoFe2O4 and Co0.5Ni0.5Fe2O4 ferrites as prepared by solid-state reaction route. Rietveld refined X-ray diffraction pattern confirmed the formation of single-phase and both of the samples perfectly indexed in cubic spinel structure with Fd3m space group. Slight reduction in the lattice parameter of Co0.5Ni0.5Fe2O4 has been observed as compared to CoFe2O4. From Raman scattering spectra, a shoulder like feature has been observed in both of the compounds reveals that octahedral site is occupied by Co, Ni and Fe ions and tetrahedral site is occupied by only Fe ion.

Kumar, Ashwini; Dar, Mashkoor A.; Sharma, Poorva; Varshney, Dinesh

2014-04-01

69

Synthesis and characterization of CoFe2O4/polyaniline nanocomposites for electromagnetic interference applications.  

PubMed

The Cobalt ferrite (CoFe2O4) powders were synthesized by Co-precipitation method. The as prepared ferrite powders were incorporated into a polyaniline matrix at various volumetric ratios. The as prepared composites of ferrite and polyaniline powders were characterized using X-ray diffraction (XRD), transmission electron microscope (TEM). The particle size of CoFe2O4 is found to be 20 nm. The saturation magnetization (M(s)) of all the composites was found to be decreasing with decrease of ferrite content, while coercivity (H(c)) remained at the value corresponding to pure cobalt ferrite nanopowders. The complex permittivity (epsilon' and epsilon") and permeability (mu' and mu") of composite samples were measured in the range of 1 MHz to 1.1 GHz. The value of epsilon' and mu' found to be increased with ferrite volume concentration. PMID:24738398

Praveena, K; Srinath, S

2014-06-01

70

The cooling rate dependence of cation distributions in CoFe2O4  

NASA Technical Reports Server (NTRS)

The room-temperature cation distributions in bulk CoFe2O4 samples, cooled at rates between less than 0.01 and about 1000 C/sec, have been determined using Mossbauer spectroscopy in an 80-kOe magnetic field. With increasing cooling rate, the quenched structure departs increasingly from the mostly ordered cation distribution ordinarily observed at room temperature. However, the cation disorder appears to saturate just short of a random distribution at very high cooling rates. These results are interpreted in terms of a simple relaxation model of cation redistribution kinetics. The disordered cation distributions should lead to increased magnetization and decreased coercivity in CoFe2O4.

De Guire, Mark R.; O'Handley, Robert C.; Kalonji, Gretchen

1989-01-01

71

Tuning of optical bandgap and magnetization of CoFe2O4 thin films  

NASA Astrophysics Data System (ADS)

Single phase CoFe2O4 thin films are deposited on quartz substrates at 400 °C using ultrasonic assisted chemical vapor deposition, and the tuning of optical bandgap and saturation magnetization of films is demonstrated by varying the post deposition annealing temperature. The optical band gap varies from 1.58 to 1.41 eV and saturation magnetization increases from 4 to 46 emu/g as the post deposition annealing temperature is increased from 500 °C to 700 °C. The observed change in optical bandgap and the magnetic properties is attributed of the shifting of Co2+ from the octahedral to the tetrahedral site with the increase in the annealing temperature. Raman studies of the films support the redistribution of Co2+ among the octahedral and tetrahedral sites in CoFe2O4 films with the increase in the annealing temperature.

Sharma, Deepanshu; Khare, Neeraj

2014-07-01

72

Noncollinear magnetic structure of CoFe2O4 small particles  

Microsoft Academic Search

The magnetic structure of small CoFe2O4 particles has been investigated as a function of the particle size. Samples (in the 10–100 nm size range and up) were prepared by chemical precipitation followed by a heat treatment at relatively low temperatures. Mo¨ssbauer spectra of the 57Fe nuclei, obtained with a longitudinal magnetic applied field, unambiguously establish that a noncollinear structure exists

K. Haneda; A. H. Morrish

1988-01-01

73

Coupling interaction in multiferroic BaTiO3 CoFe2O4 nanostructures  

Microsoft Academic Search

Recent experimental results (Zheng et al 2004 Science 303 661) have shown that a 1-3-type BaTiO3-CoFe2O4 composite film exhibited a strong coupling between the ferroelectric and ferromagnetic order parameters. The coupling interaction in the nanostructured multiferroic film could be different from that in a bulk composite because there exists a giant residual stress\\/strain in the film. In this paper, by

Gang Liu; Ce-Wen Nan; Z. K. Xu; Haydn Chen

2005-01-01

74

Magnetoelectric behavior of BaTiO3 films directly grown on CoFe2O4 ceramics  

Microsoft Academic Search

BaTiO3 films were grown on highly dense CoFe2O4 ceramics via pulsed laser deposition. Microstructural characterization showed that polycrystalline BaTiO3 thin films with grain size of about 70 nm were grown on the CoFe2O4 ceramics. BaTiO3 films showed good ferroelectric feature. An obvious magnetoelectric response, which had the same bias-dependent trend as the piezomagnetic coupling coefficient of CoFe2O4 ceramics, was observed

Jing Wang; Yi Zhang; Jing Ma; Yuanhua Lin; C. W. Nan

2008-01-01

75

Preparation and magnetic study of the CoFe2O4-CoFe2 nanocomposite powders  

Microsoft Academic Search

Ferri-ferromagnetic nanocomposites CoFe2O4-CoFe2 were prepared via reduction of the cobalt ferrite CoFe2O4 into a hydrogen atmosphere and by heat treatments. This preparation method yielded powders with relative volume fraction of CoFe2O4 and CoFe2 in the range 0-0.91. The structure and the room temperature magnetization of the samples were analyzed by X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope

F. de Assis Olimpio Cabral; F. L. de Araujo Machado; José Humberto de Araujo; João Maria Soares; Alexandre Ricalde Rodrigues; Armando Araujo

2008-01-01

76

Three-dimensional heteroepitaxy in self-assembled BaTiO3-CoFe2O4 nanostructures  

Microsoft Academic Search

Self-assembled BaTiO3-CoFe2O4 complex oxide nanostructures have been synthesized by pulsed laser deposition. A single ceramic target with a molar ratio of 0.62BaTiO3-0.38CoFe2O4 was used. Spinel CoFe2O4 and perovskite BaTiO3 phases spontaneously separated during heteroepitaxial growth on a single-crystal SrTiO3 (001) substrate. The nanostructures are epitaxial in-plane as well as out-of-plane, with CoFe2O4 nanopillar arrays embedded in a BaTiO3 matrix. The

H. Zheng; J. Wang; L. Mohaddes-Ardabili; M. Wuttig; L. Salamanca-Riba; D. G. Schlom; R. Ramesh

2004-01-01

77

Fabrication, characterization, exchange coupling and magnetic behavior of CoFe2O4/CoFe2 nanocomposite nanofibers  

NASA Astrophysics Data System (ADS)

CoFe2O4/CoFe2 nanocomposite nanofibers (NFs) with superior magnetic performance have been fabricated using electrospinning technique combined with hydrogen-thermal reduction reaction. A detailed study on the evolution of structural, morphological and magnetic properties with reduction temperature is undertaken. It is found that these composite NFs exhibit a good single-phase magnetic behavior, indicating that the magnetically hard CoFe2O4 and soft CoFe2 phases in them are sufficiently exchange coupled. The composition dependence of magnetic properties of CoFe2O4/CoFe2 composite NFs is obviously different from the reported nanopowder and microfiber counterparts. Furthermore, a higher remanence and maximum energy product can be achieved for CoFe2O4/CoFe2 composite NFs.

Xiang, Jun; Zhang, Xionghui; Li, Jiale; Chu, Yanqiu; Shen, Xiangqian

2013-06-01

78

Microstructural evolution and its influence on the magnetic properties of CoFe2O4 powders during mechanical milling  

Microsoft Academic Search

A high coercivity of up to 5.1 kOe was induced in a large-grained CoFe2O4 powder after milling for a short time 1.5 h. It was found that the initial grain particle size played an important role in the microstructural evolution and in the magnetic properties of the milled CoFe2O4 materials. The milling-induced microstructural evolution was analyzed using x-ray diffraction and

B. H. Liu; J. Ding; Z. L. Dong; C. B. Boothroyd; J. H. Yin; J. B. Yi

2006-01-01

79

Magnetic Nanocheckerboards with Tunable Sizes in the Mn-Doped CoFe2O4 Spinel  

Microsoft Academic Search

In the Mn-doped CoFe2O4 spinel, a highly ordered array of two types of rectangular nanorods, ˜300 nm in length and a few nanometer in size, is achieved through chemical phase separation mediated by cooperative Jahn-Teller distortions. At room temperature, the magnetic nanorods with composition close to CoFe2O4 interlace with the paramagnetic counterparts and form a highly organized checkerboard pattern in

Chenglin Zhang; C. M. Tseng; C. H. Chen; S. Yeo; Y. J. Choi; S.-W. Cheong

2008-01-01

80

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)

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.

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

2014-12-01

81

Magnetoelectric CoFe2O4-lead zirconate titanate thick films prepared by a polyvinylpyrrolidone-assisted sol-gel method  

Microsoft Academic Search

Magnetoelectric CoFe2O4-PZT (lead zirconate titanate) films as thick as 1 mum have been prepared by spin coating using a PZT sol-gel solution containing polyvinylpyrrolidone and CoFe2O4 powder. X-ray diffraction result reveals that there exists no chemical reaction or phase diffusion between the CoFe2O4 and PZT phases. The scanning electron microscopy observation confirms that the composite thick film is crack-free and

Jian-Guo Wan; Hao Zhang; Xiuwei Wang; Dengyu Pan; Jun-Ming Liu; Guanghou Wang

2006-01-01

82

High-pressure x-ray diffraction and Raman spectroscopic studies of the tetragonal spinel CoFe2O4 Zhongwu Wang,1,2,  

E-print Network

High-pressure x-ray diffraction and Raman spectroscopic studies of the tetragonal spinel CoFe2O4 to pressures of 93.6 and 63.2 GPa, respectively, to explore the pressure-induced phase transformation of CoFe2O4 spinel. CoFe2O4 adopts a distorted tetragonal spinel structure at one atmosphere. At a pressure

Downs, Robert T.

83

Multiferroic Behavior of Templated BiFeO3-CoFe2O4 Self-Assembled Nanocomposites.  

PubMed

Self-assembled BiFeO3-CoFe2O4 nanocomposites were templated into ordered structures in which the ferrimagnetic CoFe2O4 pillars form square arrays of periods 60-100 nm in a ferroelectric BiFeO3 matrix. The ferroelectricity, magnetism, conductivity, and magnetoelectric coupling of the ordered nanocomposites were characterized by scanning probe microscopy. The insulating BiFeO3 matrix exhibited ferroelectric domains, whereas the resistive CoFe2O4 pillars exhibited single-domain magnetic contrast with high anisotropy due to the magnetoelasticity of the spinel phase. Magnetoelectric coupling was observed in which an applied voltage led to reversal of the magnetic pillars. PMID:25559139

Aimon, Nicolas M; Kim, Dong Hun; Sun, XueYin; Ross, C A

2015-02-01

84

Nonlinear strain dependence of magnetic anisotropy in CoFe2O4 films on MgO(001) substrates  

NASA Astrophysics Data System (ADS)

CoFe2O4 films were deposited on MgO(001) substrates using pulsed laser deposition with various laser energy densities. We found that the CoFe2O4 films were grown in the (001) orientation and that the lattice constant of the CoFe2O4 films was dependent on the laser energy densities. Perpendicular magnetic anisotropy (PMA) was observed, but the lattice strain dependence was not consistent with the phenomenological model in which the PMA is in proportion to the lattice strain. The lattice strain dependence of PMA was compared with an electron theory in which the spin-orbit interaction and the tetragonal crystal field in the electronic state of a single Co ion are considered. The experimental result does not contradict with the calculation, which shows that the magnetic anisotropy is not proportional to the lattice strain and asymmetric in respect to negative and positive lattice strain.

Tanaka, M. A.; Harada, K.; Takemura, M.; Mibu, K.; Inoue, J.

2014-05-01

85

A first-principles study of magnetostrictions of Fe3O4 and CoFe2O4  

NASA Astrophysics Data System (ADS)

Effects of charge ordering in the octahedral sites of Fe3O4 and CoFe2O4 on their magnetostrictions are investigated using the density functional theory plus U approach. Precise description of charge ordering was found to be crucial in determining only band-gaps of Fe3O4 and CoFe2O4, but not other physical properties such as lattice constant, magnetic moment, and magnetostriction. And Co configuration in CoFe2O4 is important in determining its magnetostriction; the most stable configuration results in substantially enhanced magnetostriction (-245 ppm), compared to that (-25 ppm) of Fe3O4, in consistent with experiments.

Odkhuu, Dorj; Taivansaikhan, Purev; Yun, Won Seok; Hong, Soon Cheol

2014-05-01

86

Enhancement in magnetoelectric response in CoFe2O4-BaTiO3 heterostructure  

Microsoft Academic Search

CoFe2O4-BaTiO3 heterostructure was epitaxially grown on the (001)-SrTiO3 substrate via pulsed laser deposition, in which the bottom BaTiO3 layer epitaxially grown on the substrate acts as a buffer layer and effectively reduces the coherent constraint in the magnetic layer arising from the substrate. Microstructure studies from x-ray diffraction and electron microscopies showed good coherent epitaxy thin films of the (001)-CoFe2O4

Yi Zhang; Chaoyong Deng; Jing Ma; Yuanhua Lin; Ce-Wen Nan

2008-01-01

87

Directional solidification and interface structure of BaTiO3-CoFe2O4 eutectic  

Microsoft Academic Search

The directional solidification and the interface structure of BaTiO3-CoFe2O4 eutectic grown by the floating zone melting method were investigated. The microstructure of the eutectic were found to consist grains of lamellar or fibrous morphology. Two types of crystal structures of BaTiO3 were observed for different growth conditions. The orientation relationships between BaTiO3 and CoFe2O4 (the spinel-type crystal structure) are a)

J. Echigoya; S. Hayashi; Y. Obi

2000-01-01

88

Multiferroic nanoparticulate Bi3.15Nd0.85Ti3O12-CoFe2O4 composite thin films prepared by a chemical solution deposition technique  

Microsoft Academic Search

Multiferroic xBi3.15Nd0.85Ti3O12-(1-x)CoFe2O4 composite thin films with x=0.5, 0.6, and 0.7 were fabricated on Pt\\/Ti\\/SiO2\\/Si(100) substrates by a chemical solution deposition technique. X-ray diffraction shows that there are no other phases but bismuth-layered perovskite Bi3.15Nd0.85Ti3O12 and spinel CoFe2O4 phases in the films. Scanning electron microscopy reveals that CoFe2O4 aggregates locally into nanoparticles and embeds in the Bi3.15Nd0.85Ti3O12 matrix. The composite films

X. L. Zhong; J. B. Wang; M. Liao; G. J. Huang; S. H. Xie; Y. C. Zhou; Y. Qiao; J. P. He

2007-01-01

89

FTIR and UV-vis diffuse reflectance spectroscopy studies of the wet chemical (WC) route synthesized nano-structure CoFe2O4 from CoCl2 and FeCl3  

NASA Astrophysics Data System (ADS)

Nano-structure CoFe2O4 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 47 nm. Field emission scanning electron microscopy investigations showed spherical morphology of nanoparticles with average particle size of 46 nm. The FTIR spectra of CoFe2O4 nanoparticles showed absorption bands at about 594 cm-1 and 401 cm-1 due to the stretching vibrations of Co-O and Fe-O respectively. Investigation of the optical properties of the produced nano-structure CoFe2O4 confirmed its semiconducting properties by revealing two optical band gaps at 1.4 and 2.0 eV.

Habibi, Mohammad Hossein; Parhizkar, Hadi Janan

2014-06-01

90

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

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. PMID:24637270

Habibi, Mohammad Hossein; Parhizkar, Hadi Janan

2014-06-01

91

Wintersweet-flower-like CoFe2O4/MWCNTs hybrid material for high-capacity reversible lithium storage.  

PubMed

CoFe(2)O(4)/multiwalled carbon nanotubes (MWCNTs) hybrid materials were synthesized by a hydrothermal method. Field emission scanning electron microscopy and transmission electron microscopy analysis confirmed the morphology of the as-prepared hybrid material resembling wintersweet flower "buds on branches", in which CoFe(2)O(4) nanoclusters, consisting of nanocrystals with a size of 5-10 nm, are anchored along carbon nanotubes. When applied as an anode material in lithium ion batteries, the CoFe(2)O(4)/MWCNTs hybrid material exhibited a high performance for reversible lithium storage. In particular, the hybrid anode material delivered reversible lithium storage capacities of 809, 765, 539, and 359 mA h g(-1) at current densities of 180, 450, 900, and 1800 mA g(-1), respectively. The superior performance of CoFe(2)O(4)/MWCNTs hybrid materials could be ascribed to the synergistic pinning effect of the wintersweet-flower-like nanoarchitecture. This strategy could also be applied to synthesize other metal oxide/CNTs hybrid materials as high-capacity anode materials for lithium ion batteries. PMID:22593078

Wang, Ying; Park, Jinsoo; Sun, Bing; Ahn, Hyojun; Wang, Guoxiu

2012-08-01

92

Effect of nanodisperse ferrite cobalt (CoFe2O4) particles on contractile reactions in guinea pigs airways.  

PubMed

The effect of nanopowder CoFe(2)O(4)on contractile responses of smooth-muscle segments of guinea pigs airways was studied by mechanography. Both in vivo inhalation of nanopowder aerosol or in vitro application of nanopowder to isolated airway segments increased the amplitude of contractile responses to histamine and potentiated the dilatory reaction to adrenergic salbutamol. PMID:21113462

Kapilevich, L V; D'yakova, E Yu; Nosarev, A V; Zaitseva, T N; Petlina, Z R; Ogorodova, L M; Ageev, B G; Magaeva, A A; Itin, V I; Terekhova, O G

2010-07-01

93

Exchange bias in BiFeO3/CoFe2O4 heterostructure  

NASA Astrophysics Data System (ADS)

Room temperature multiferroics BiFeO3 (BFO), both ferroelectric and antiferromagnetic, has been extensively investigated as a part of exchange bias structures since it promises the electrical field control over the exchange bias. This work focuses on the exchange interaction between ferromagnet CoFe2O4 (CFO) and BFO. Bilayer films CFO and BFO were first grown on SrTiO3 (STO) by Pulsed Electron Deposition (PED) and then field cooled in magnetic field. XRD showed single phase CFO and BFO were grown epitaxially on STO single crystal substrates, and the typical thickness was 21nm for BFO and 3.6˜18nm for CFO. In the bilayer structure, we observed that the coercive field increased 100% at 300K and 30 % at 50K, comparing to these of CFO single layer. Also in the bilayer structure, a noticeable exchange bias field (Hex) increased from ˜30 Oe at 300 K to ˜ 60 Oe at 50 K. We will discuss the impact of the film thickness and the roughness of interface on exchange bias.

Pei, Yonghang; Lu, Jiwei; Comes, Ryan; Wolf, Stuart

2012-02-01

94

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

PubMed

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. PMID:23732994

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

95

Pillar shape modulation in epitaxial BiFeO3-CoFe2O4 vertical nanocomposite films  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

96

High-pressure x-ray diffraction and Raman spectroscopic studies of the tetragonal spinel CoFe2O4  

Microsoft Academic Search

In situ x-ray diffraction and Raman spectroscopy have been carried out to pressures of 93.6 and 63.2 GPa, respectively, to explore the pressure-induced phase transformation of CoFe2O4 spinel. CoFe2O4 adopts a distorted tetragonal spinel structure at one atmosphere. At a pressure of ˜32.5 GPa, both x-ray diffraction and Raman spectroscopy indicate that CoFe2O4 transforms to the orthorhombic CaFe2O4 structure, which

Zhongwu Wang; R. T. Downs; V. Pischedda; R. Shetty; S. K. Saxena; C. S. Zha; Y. S. Zhao; D. Schiferl; A. Waskowska

2003-01-01

97

Role of spinel substrate in the morphology of BiFeO3-CoFe2O4 epitaxial nanocomposite films  

Microsoft Academic Search

Epitaxial thin films of BiFeO3-CoFe2O4 composite were grown on spinel MgAl2O4 substrates with a (001) orientation. The composite formed an intriguing nanogrid structure where perovskite BiFeO3 forms linear mounds embedded in a matrix of spinel CoFe2O4. The structure makes a stark distinction with similar composite films on (001) perovskite SrTiO3 substrates where CoFe2O4 forms nanopillars surrounded by a BiFeO3 matrix.

Ilan Stern; Jibao He; Xiaolan Zhou; Punam Silwal; Ludi Miao; Jose Marcelo Vargas; Leonard Spinu; Dae Ho Kim

2011-01-01

98

Role of spinel substrate in the morphology of BiFeO3-CoFe2O4 epitaxial nanocomposite films  

E-print Network

Role of spinel substrate in the morphology of BiFeO3-CoFe2O4 epitaxial nanocomposite films Ilan://apl.aip.org/about/rights_and_permissions #12;Role of spinel substrate in the morphology of BiFeO3-CoFe2O4 epitaxial nanocomposite films Ilan; published online 26 August 2011) Epitaxial thin films of BiFeO3-CoFe2O4 composite were grown on spinel MgAl2

Spinu, Leonard

99

Synthesis and magnetic properties of hard magnetic (CoFe 2O 4)-soft magnetic (Fe 3O 4) nano-composite ceramics by SPS technology  

NASA Astrophysics Data System (ADS)

CoFe2O4/Fe3O4 nano-composite ceramics were synthesized by Spark Plasma Sintering. The X-ray diffraction patterns show that all samples are composed of CoFe2O4 and Fe3O4 phases when the sintering temperature is below 900 °C. It is found that the magnetic properties strongly depend on the sintering temperature. The two-step hysteresis loops for samples sintered below 500 °C are observed, but when sintering temperature reaches 500 °C, the step disappears, which indicates that the CoFe2O4 and Fe3O4 are well exchange coupled. As the sintering temperature increases from 500 to 800 °C, the results of X-ray diffractometer indicate the constriction of crystalline regions due to the ion diffusion at the interfaces of CoFe2O4/Fe3O4 phases, which have great impact on the magnetic properties.

Fei, Chunlong; Zhang, Yue; Yang, Zhi; Liu, Yong; Xiong, Rui; Shi, Jing; Ruan, Xuefeng

2011-07-01

100

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

PubMed

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. PMID:24220199

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

101

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

PubMed

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. PMID:22486737

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

2012-05-01

102

Magnetic Properties of Nanocrystalline CoFe 2 O 4 \\/ZnFe 2 O 4 Bilayers  

Microsoft Academic Search

Nanocrystalline spinel CoFe2O4\\/ZnFe2O4 bilayers were deposited by the pulsed laser deposition technique on amorphous fused quartz substrate at different substrate\\u000a temperatures ranging from room temperature to 750?°C. The magnetic properties of the bilayers and of the single layer films\\u000a deposited in identical conditions were studied at 300 K and at 10 K. Magnetic properties of the bilayers, in general, were\\u000a found to

S. C. Sahoo; N. Venkataramani; Shiva Prasad; Murtaza Bohra; R. Krishnan

103

Local Dielectric Measurements of BaTiO3-CoFe2O4 Nanocomposites Through Microwave Microscopy  

Microsoft Academic Search

We report on linear and non-linear dielectric property measurements of BaTiO3\\u000a- CoFe2O4 (BTO-CFO) ferroelectro-magnetic nano-composites and pure BaTiO3 and\\u000aCoFe2O4 samples with Scanning Near Field Microwave Microscopy. The permittivity\\u000ascanning image with spatial resolution on the micro-meter scale shows that the\\u000anano-composites have very uniform quality with an effective dielectric constant\\u000a\\\\epsilon_r = 140 +\\/- 6.4 at 3.8 GHz

Yi Qi; H. Zheng; R. Ramesh; Steven M. Anlage

2006-01-01

104

Preparation of CoFe2O4 Spin Valves and Improvement of Their Magnetoresistance Property by Postannealing  

Microsoft Academic Search

We have fabricated spin valves which had the simple structure of Si\\/SiO2\\/CoFe2O4 (40 nm)\\/Co (2 nm)\\/Cu (2 nm)\\/Co (4 nm) by rf-magnetron sputtering at room temperature. A hard magnetic and insulating Co-ferrite film was used as a pinning layer. As-deposited films showed a high sheet resistance of 36.3 Omega\\/square and a magnetoresistance (MR) ratio of 4.5%. The MR property of

Hiroshi Naganuma; Soichiro Okamura; Hiroshi Sakakima; Tadashi Shiosaki

2003-01-01

105

Tuning of the magnetostrictive properties of CoFe2O4 by Mn substitution for Co  

Microsoft Academic Search

Marked changes in the magnetostriction of CoFe2O4 in the substitution of\\u000a Mn for Co has been observed. The magnetostriction parallel to the\\u000a applied field direction decreases with increasing Mn content, whereas\\u000a the magnetostriction perpendicular to the field showed a marked increase\\u000a for 10\\\\% of the Mn substitution. The observed magnetostrictive\\u000a properties are correlated with the magnetic properties. The results\\u000a suggest

Shekhar D. Bhame; P. A. Joy

2006-01-01

106

Thickness dependence of the magnetoelastic effect of CoFe2O4 films grown on piezoelectric substrates  

NASA Astrophysics Data System (ADS)

Epitaxial CoFe2O4 (CFO) films of varying thickness were grown on piezoelectric Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrates. The magnetic anisotropy of the CFO films is controlled by the piezoelectric in-plane strain imposed by the substrate constraint during application of an electric field. We find that the strain-induced change of the remanent magnetization is constant at large thickness, but drops significantly below ˜100 nm. This thickness dependence of the magnetoelastic effect is shown not to be caused by a variation of the as-grown strain state.

Rus, S. F.; Herklotz, A.; Roth, R.; Schultz, L.; Dörr, K.

2013-07-01

107

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

PubMed

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. PMID:24829135

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

2014-06-28

108

Band gap hierarchy of single crystal CoFe2O4 thin films from optical absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Thin film materials have a wide variety of applications and also serve as an useful bridge between bulk single crystals and the nanoscale. In this work, we report temperature-dependent optical absorption spectroscopy of single crystal CoFe2O4 thin-films along with complimentary electronic structure analysis. This magnetic insulator has one of the highest Curie temperature among complex oxides and potentially useful in areas such as spintronics. Similar to its Nickel analogue,footnotetextQ.C. Sun, H. Sims, D.Mazumdar, J.X.Ma, B. Holinswoth, K.O'Neal, G.Kim, W.H.Butler, A.Gupta, and J.Musfeldt (accepted to Phys. Rev. B). our work reveals CoFe2O4 to be an indirect band gap material (1.2 eV) with a direct gap much higher (2.8eV) at 300K. These gap values are robust down to 4.2K. Electronically, both chemical tuning and inversion fraction are found to be important factors in lowering of the band gap compared to NiFe2O4.

Holinsworth, Brian; Sims, Hunter; Mazumdar, Dipanjan; Sun, Qi; Yurtisigi, Mehmet; Sarker, Sanjoy; Gupta, Arun; Butler, Bill; Musfeldt, Janice

2013-03-01

109

Synthesis, structure, and magnetic studies on the CoFe2O4-BiFeO3 nanocomposite films with different number of CoFe2O4 layers  

NASA Astrophysics Data System (ADS)

The multiferroic heterostructures consisting of CoFe2O4 (CFO)-BiFeO3 (BFO) layers with increasing the number of CFO layers (2, 4, 6 and 8) have been grown on LaNiO3 buffered Si (1 0 0) substrate by a simple sol-gel spin-coating route. X-ray diffraction (XRD) shows that the CFO and BFO phases have been successfully retained in the heterostructures and the films are polycrystalline. The high resolution transmission electron microscope (HRTEM) images show the clear interplanar distances and the interface between the two phases. The magnetization (M) versus field (H) loops reveal that, with increasing the CFO layers, the magnetization of CFO-BFO films will be enhanced. The Ms, Mr and Hc of the composite film with 8 CFO layers are measured to be the largest values of 1304 emu/cm3, 562 emu/cm3 and 2074 Oe, respectively.

Liu, Y. Q.; Zhang, B.; Wu, Y. H.; Zhang, J.; Li, D.; Liu, Y.; Wei, M. B.; Yang, J. H.

2013-09-01

110

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

111

Room-temperature spin filtering in a CoFe2O4/MgAl2O4/Fe3O4 magnetic tunnel barrier  

NASA Astrophysics Data System (ADS)

By growing ultrathin and high quality CoFe2O4/MgAl2O4/Fe3O4 epitaxial multilayers, we have demonstrated a room temperature spin filter junction, which could open the way for highly polarized spin injection, single-qubit spintronic measurements, magnetic field sensing, and other applications. In these devices the Fe3O4 layer functions as a source of spin polarized electrons while the CoFe2O4/MgAl2O4 double barrier functions as a spin filter. The current-voltage curves depend on the relative orientation of the magnetization of the Fe3O4 and CoFe2O4 layers and display a large magnetoresistive effect. The inferred net spin polarizations produced by the junctions typically exceeded 70%.

Chapline, Michael G.; Wang, Shan X.

2006-07-01

112

Modification of Ferroelectric Properties of BaTiO3-CoFe2O4 Multiferroic Composite Thin Film by Application of Magnetic Field  

Microsoft Academic Search

We prepared BaTiO3-CoFe2O4 composite thin film on (La0.5Sr0.5)CoO3\\/CeO2\\/YSZ\\/Si(100) substrate by pulsed laser deposition. Simultaneous epitaxial growths of BaTiO3 and CoFe2O4 were achieved. Reciprocal space map measurement revealed that the lattice parameters of BaTiO3 parallel and perpendicular to the substrate are 0.4239 and 0.4060 nm, respectively. The fact that both lattice parameters are larger than those of the bulk (a =

Shigeki Sawamura; Naoki Wakiya; Naonori Sakamoto; Kazuo Shinozaki; Hisao Suzuki

2008-01-01

113

Nucleation-induced self-assembly of multiferroic BiFeO3-CoFe2O4 nanocomposites.  

PubMed

Large areas of perfectly ordered magnetic CoFe2O4 nanopillars embedded in a ferroelectric BiFeO3 matrix were successfully fabricated via a novel nucleation-induced self-assembly process. The nucleation centers of the magnetic pillars are induced before the growth of the composite structure using anodic aluminum oxide (AAO) and lithography-defined gold membranes as hard mask. High structural quality and good functional properties were obtained. Magneto-capacitance data revealed extremely low losses and magneto-electric coupling of about 0.9 ?C/cmOe. The present fabrication process might be relevant for inducing ordering in systems based on phase separation, as the nucleation and growth is a rather general feature of these systems. PMID:23902288

Stratulat, Sergiu M; Lu, Xiaoli; Morelli, Alessio; Hesse, Dietrich; Erfurth, Wilfried; Alexe, Marin

2013-08-14

114

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

PubMed Central

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

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

2012-01-01

115

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

PubMed Central

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

2014-01-01

116

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

PubMed

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. PMID:22755080

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

2012-03-01

117

A contribution to the investigation of fine-particle solid solutions between cubic iron sesquioxide ?Fe2O3and cobalt ferrite CoFe2O4  

Microsoft Academic Search

The authors give the chemical, morphological, crystallographic, and magnetic properties of solid solutions between cubic iron sesquioxide ?Fe2O3and cobalt ferrite CoFe2O4obtained as fine particles by a new preparation method. This method gives the whole range of compositions and allows shifting of the magnetic and morphological features in a direction suitable for magnetic recording applications.

PAUL MOLLARD; A. Collomb; J. Devenyi; A. Rousset

1975-01-01

118

Magnetoelectric nano-Fe3O4?CoFe2O4?PbZr0.53Ti0.47O3 composite  

E-print Network

A new magnetoelectric hybrid device composed of a nanoparticulate magnetostrictive iron oxide-cobalt ferritefilm on a piezoelectric lead zirconic titanate crystal serving as both substrate and straining medium is described. Nano-Fe3O4?CoFe2O4...

Ren, Shenqiang; Wuttig, Manfred

2008-02-26

119

Chemical tuning of the optical band gap in spinel ferrites: CoFe2O4 vs B. S. Holinsworth,1  

E-print Network

Chemical tuning of the optical band gap in spinel ferrites: CoFe2O4 vs NiFe2O4 B. S. Holinsworth,1 in terms of size and covalency effects in spinel ferrites. VC 2013 AIP Publishing LLC. [http, the most noteworthy are strongly correlated spinel oxides (general for- mula AB2O4),5 particularly

120

Controlled synthesis and magnetic properties of bimagnetic spinel ferrite CoFe2O4 and MnFe2O4 nanocrystals with core-shell architecture.  

PubMed

A combination of hard phase CoFe(2)O(4) and soft phase MnFe(2)O(4) as the bimagnetic nanocrystals in a core-shell architecture has been synthesized, and their magnetic properties have been systematically studied. Both HRTEM and EDS results confirmed the formation of bimagnetic core-shell structured nanocrystals. On the basis of the systematic and comparative studies of the magnetic properties of a mechanical mixture of pure CoFe(2)O(4) and MnFe(2)O(4) nanocrystals, chemically mixed Co(1-x)Mn(x)Fe(2)O(4) nanocrystals, and bimagnetic core-shell CoFe(2)O(4)@MnFe(2)O(4) and MnFe(2)O(4)@CoFe(2)O(4) nanocrystals, the bimagnetic core-shell nanocrystals show very unique magnetic properties, such as the blocking temperature and coercivity. Our results show that the coercivity correlates with the volume fraction of the soft phase as the theoretical hard-soft phase model has suggested. Furthermore, switching the hard phase CoFe(2)O(4) from the core to the shell shows great changes in the coercivity of the nanocrystals. The bimagnetic core-shell nanocrystals evidently demonstrate the rational design capability to separately control the blocking temperature and the coercivity in magnetic nanocrystals by varying the materials, their combination, and the volume ratio between the core and the shell and by switching hard or soft phase materials between the core and shell. Such controls via a bimagnetic core-shell architecture are highly desirable for magnetic nanocrystals in various applications. PMID:22621435

Song, Qing; Zhang, Z John

2012-06-20

121

Investigation of nanocrystalline CoFe2O4 by positron annihilation lifetime spectroscopy  

Microsoft Academic Search

Nanoparticles of cobalt ferrite prepared by the co-precipitation method with crystallite size varying from 4.7 to 41 nm have been characterized by positron annihilation lifetime spectroscopy. Three lifetime components are fitted to the lifetime data. The shortest lifetime component is attributed to the delocalized positron lifetime shortened by defect trapping. The intermediate lifetime is assigned to the positron annihilation in

S. Bandyopadhyay; A. Roy; D. Das; S. S. Ghugre; J. Ghose

2003-01-01

122

Enhanced magnetostrictive properties of CoFe2O4 synthesized by an autocombustion method  

Microsoft Academic Search

The magnetostrictive properties of sintered cobalt ferrite derived from\\u000a nanocrystalline powders synthesized by three different low-temperature\\u000a methods (citrate, coprecipitation and autocombustion) and the\\u000a high-temperature ceramic method have been compared. A strong dependence\\u000a of the magnetostrictive strain is observed on the initial morphology of\\u000a the ferrite particles and the microstructure of the final sintered\\u000a product. The nanoparticles synthesized by the autocombustion

S. D. Bhame; P. A. Joy

2007-01-01

123

Epitaxial Bi5Ti3FeO15-CoFe2O4 pillar-matrix multiferroic nanostructures.  

PubMed

Epitaxial self-assembled ferro(i)magnetic spinel (CoFe2O4 (CFO)) and ferroelectric bismuth layered perovskite (Bi5Ti3FeO15 (BTFO)) pillar-matrix nanostructures are demonstrated on (001) single-crystalline strontium titanate substrates. The CFO remains embedded in the BTFO matrix as vertical pillars (?50 nm in diameter) up to a volume fraction of 50%. Piezoresponse force microscopy experiments evidence a weak out-of-plane and a strong in-plane ferroelectricity in the BTFO phase, despite previously reported paraelectricity along the c-axis in a pure BTFO film. Phenomenological Landau-Ginzburg-Devonshire-based thermodynamic computations show that the radial stress induced by the CFO nanopillars can influence these ferroelectric phases, thus signifying the importance of the nanopillars. The CFO pillars demonstrate robust ferromagnetic hysteresis loops with little degradation in the saturation magnetization (ca. 4 ?B/f.u.). Thus BTFO-CFO nanocomposites show significant promise as a lead-free magnetoelectric materials system. PMID:24215598

Imai, Akira; Cheng, Xuan; Xin, Huolin L; Eliseev, Eugene A; Morozovska, Anna N; Kalinin, Sergei V; Takahashi, Ryota; Lippmaa, Mikk; Matsumoto, Yuji; Nagarajan, Valanoor

2013-12-23

124

Molecular Beam Epitaxial Growth and Properties of CoFe2O4 on MgO(001)  

SciTech Connect

We have grown single-crystal Co ferrite (CoFe2O4) on MgO(001) by oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE), and have characterized the composition, structure, surface morphology, and magnetic properties by a number of methods The as-grown OPA-MBE material forms a perfect inverse spinel, in which all Co is in the? formal oxidation state, and occupies octahedral sites within the cation sublattice. The OPA-MBE film surfaces are very flat, with mean roughnesses of only a few A, and exhibit large, stable magnetic domains. The measured moment per unit volume is 250 emu/cm3, and the saturation magnetization for films in the 1000A film thickness range is {approx}60% of that of bulk Co ferrite. The material also exhibits strain-dependent magnetic anisotropy that can be understood by considering the various contributions to the total magnetic energy. The overall quality of epitaxial Co ferrite grown on MgO by OPA-MBE is superior in every respect to that obtained using pulsed laser deposition as the growth method.

Chambers, Scott A.; Farrow, Robin F.; Maat, S.; Toney, M.; Folks, L.; Catalano, J.G.; Trainor, T.P.; Brown, G.E. Jr.

2002-04-01

125

Fully spin-polarized two-dimensional electron gas at the CoFe2O4/MgAl2O4(001) polar interface  

NASA Astrophysics Data System (ADS)

We performed first-principles calculations to show that a fully spin-polarized two-dimensional electron gas can be created at the interface between the polar and insulating spinel oxides CoFe2O4 and MgAl2O4. We give a clear description of the physical parameters (in particular the atomic termination of the interfaces), which favor the formation of this electron gas that is due either to an electric field induced in stoichiometric oxide layers because of their polar character or to a charge reorganization that preserves the global electric neutrality in nonstoichiometric layers. We show that the electric field-induced spin-polarized two-dimensional electron gas can only exist if the thickness of the CoFe2O4 layer is large enough and that it may be destroyed by intermixing at the interfaces.

Arras, R.; Calmels, L.

2014-07-01

126

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

NASA Astrophysics Data System (ADS)

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).

Nguyen, Van Cuong; Huynh, Thi Kim Ngoc

2014-06-01

127

Impedance spectroscopy of multiferroic PbZrxTi1-xO3\\/CoFe2O4 layered thin films  

Microsoft Academic Search

The electrical properties of ferroelectric Pb(Zr,Ti)O3 (PZT) and ferromagnetic CoFe2O4 (CFO) thin film multilayers (MLs) fabricated by pulsed laser deposition technique has been studied by impedance and modulus spectroscopy. The effect of various PZT\\/CFO configurations having three, five, and nine layers has been systematically investigated. The transmission electron microscopy images revealed that the ML structures were at least partially diffused

N. Ortega; Ashok Kumar; P. Bhattacharya; S. B. Majumder; R. S. Katiyar

2008-01-01

128

LETTER TO THE EDITOR: Cation migration and magnetic ordering in spinel CoFe2O4 powder: micro-Raman scattering study  

Microsoft Academic Search

Micro-Raman scattering was used to characterize spinel CoFe2O4 at high temperature up to 870 K and under an external magnetic field up to 6.0 kOe. It was found that the rapid increase in the linewidth of the Raman modes was related to the inter-site cation migration starting at ~390 K. A red-shift of the Raman peaks induced by the magnetic

T. Yu; Z. X. Shen; Y. Shi; J. Ding

2002-01-01

129

Evidence for first-order nature of the ferromagnetic transition in Ni, Fe, Co, and CoFe2O4  

Microsoft Academic Search

Nearly all ferromagnetic transitions have been considered to be continuous or second order, and the most typical examples are the ferromagnetic transitions in Ni, Fe, Co, and CoFe2O4 . However, by precise measurement with electrical resistivity or impedance and differential scanning calorimetry, we show clear evidence for the first-order nature of these ``second-order transitions''---a small thermal hysteresis and latent heat.

Sen Yang; Xiaobing Ren; Xiaoping Song

2008-01-01

130

Thickness and coupling effects in bilayered multiferroic CoFe2O4\\/Pb(Zr0.52Ti0.48)O3 thin films  

Microsoft Academic Search

Four CoFe2O4\\/Pb(Zr0.52Ti0.48)O3 (CFO\\/PZT) bilayered thin films with increasing PZT constituent layer thicknesses have been fabricated in order to investigate the optimized PZT layer thickness and the thickness effect on the magnetic and ferroelectric behaviors of the heterolayered multiferroic thin films. These heterostructured thin films were fabricated via a combined route of spin coating and rf sputtering. Both magnetic CFO and

C. H. Sim; A. Z. Z. Pan; J. Wang

2008-01-01

131

Controllable phase connectivity and magnetoelectric coupling behavior in CoFe2O4 Pb(Zr,Ti)O3 nanostructured films  

Microsoft Academic Search

Magnetoelectric CoFe2O4-Pb(Zr,Ti)O3 nanostructured films with various phase connectivity patterns were prepared by a pulsed laser deposition method. It was found that the microstructure as well as the phase connectivity pattern of the film varied remarkably with the variation of phase content ratio. All composite nanofilms exhibit evident ferromagnetic and ferroelectric characteristics, as well as distinct magnetoelectric coupling behavior upon increasing

Jian-guo Wan; Yuyan Weng; Yujie Wu; Zhengyu Li; Jun-ming Liu; Guanghou Wang

2007-01-01

132

Influence of a metallic or oxide top layer in epitaxial magnetic bilayers containing CoFe2O4(111) tunnel barriers  

Microsoft Academic Search

We investigate the interaction of CoFe2O4(111) tunnel barriers with Co and Fe3O4 electrodes in light of their potential as room temperature spin filters. The question of the exchange coupling that often prohibits the independent switching between a magnetic tunnel barrier and its magnetic electrode is addressed, as is the difference between an oxide\\/metal and oxide\\/oxide system. Our study of the

A. V. Ramos; J.-B. Moussy; M.-J. Guittet; M. Gautier-Soyer; C. Gatel; P. Bayle-Guillemaud; B. Warot-Fonrose; E. Snoeck

2007-01-01

133

A large low field colossal magnetoresistance in the La0.7Sr0.3MnO3 and CoFe2O4 combined system  

Microsoft Academic Search

La0.7Sr0.3MnO3 and CoFe2O4 samples have been prepared by a sol-gel process. A mixture of the two samples was annealed at 800 °C and the scanning electron micrograph shows large CoFe2O4 grains well surrounded by La0.7Sr0.3MnO3 grains. The powder x-ray diffraction patterns indicate no evidence of reaction between the La0.7Sr0.3MnO3 and CoFe2O4. The resistivity of the combined sample (with 20 wt%

Chun-Hua Yan; Zhi-Gang Xu; Tao Zhu; Zhe-Ming Wang; Fu-Xiang Cheng; Yun-Hui Huang; Chun-Sheng Liao

2000-01-01

134

Ascorbic acid-assisted synthesis of cobalt ferrite (CoFe2O4) hierarchical flower-like microspheres with enhanced lithium storage properties  

NASA Astrophysics Data System (ADS)

CoFe2O4 flower-like microspheres are prepared via a surfactant- and template-free method, involving the controlled hytrothermal synthesis firstly and a subsequent thermal decomposition treatment. The microspheres with diameters of 3-4 ?m are characterized by the assembly of numerous porous and inter-connected lamella structures. Lithium-ion batteries electrodes based on the as-prepared CoFe2O4 microspheres show a high specific capacity of 733.5 mAh g-1 after 50 cycles at a current density of 200 mA g-1 and a good cyclic stability, as well as excellent rate capability. The enhanced electrochemical performance can be attributed to the hierarchical microsphere structure with high sufficient interfacial contact area between the microspheres and electrolyte, the short diffusion distance of Li+, better accommodation of structural stress and volume change with the lithiation/delithiation process. It is suggested that the CoFe2O4 microsphere is one of the most promising candidates for high-performance lithium-ion batteries.

Xiong, Q. Q.; Tu, J. P.; Shi, S. J.; Liu, X. Y.; Wang, X. L.; Gu, C. D.

2014-06-01

135

Local probing of magnetoelectric coupling and magnetoelastic control of switching in BiFeO3-CoFe2O4 thin-film nanocomposite  

NASA Astrophysics Data System (ADS)

We report on the combination of piezoresponse force microscopy (PFM), magnetic force microscopy, and local ferroelectric switching with magnetic field for the study of a thin-film magnetoelectric (ME) nanocomposite. The collection of PFM under an applied variable magnetic field within a polycrystalline perovskite-spinel BiFeO3-CoFe2O4 (BFO-CFO) 0-3 type thin-film nanocomposite enables quantitative and proximal measurement of magnetoelastic strain-driven ME response. Combination of measurement of the as-grown strain state with local measurements of microstructure and macroscopic magnetization permits local mapping of ME coupling.

Yan, Feng; Chen, Guannan; Lu, Li; Finkel, Peter; Spanier, Jonathan E.

2013-07-01

136

Synthesis, structure, and magnetic studies on self-assembled BiFeO3-CoFe2O4 nanocomposite thin films  

Microsoft Academic Search

Self-assembled (0.65)BiFeO3-(0.35)CoFe2O4 (BFO-CFO) nanostructures were deposited on SrTiO3 (001) and (111) substrates by pulsed laser deposition at various temperatures from 500 to 800 °C. The crystal phases and the lattice strain for the two different substrate orientations have been determined and compared. The films grow epitaxial on both substrates but separation of the spinel and perovskite crystallites, without parasitic phases,

R. Muralidharan; N. Dix; V. Skumryev; M. Varela; F. Sánchez; J. Fontcuberta

2008-01-01

137

Dielectric and Magnetoelectric Characterization of CoFe2O4\\/Sr0.5Ba0.5Nb2O6 Composites  

Microsoft Academic Search

Magnetoelectric composites were created through incorporating dispersed CoFe2O4 ferromagnetic grains into a Sr0.5Ba0.5Nb2O6 relaxor ferroelectric matrix. The two phases are chemically compatible and coexist in the dense, sintered composites. Unlike other relaxors, the Sr0.5Ba0.5Nb2O6-containing composites can be electrically poled. The apparent dielectric constant is enhanced by the conductivity in the ferrite phase and the space charge at the phase interface.

X. M. Chen; Y. H. Tang; I.-W. Chen; Z. C. Xu; S. Y. Wu

2004-01-01

138

Strain relaxation and enhanced perpendicular magnetic anisotropy in BiFeO3:CoFe2O4 vertically aligned nanocomposite thin films  

NASA Astrophysics Data System (ADS)

Self-assembled BiFeO3:CoFe2O4 (BFO:CFO) vertically aligned nanocomposite thin films have been fabricated on SrTiO3 (001) substrates using pulsed laser deposition. The strain relaxation mechanism between BFO and CFO with a large lattice mismatch has been studied by X-ray diffraction and transmission electron microscopy. The as-prepared nanocomposite films exhibit enhanced perpendicular magnetic anisotropy as the BFO composition increases. Different anisotropy sources have been investigated, suggesting that spin-flop coupling between antiferromagnetic BFO and ferrimagnetic CFO plays a dominant role in enhancing the uniaxial magnetic anisotropy.

Zhang, Wenrui; Jian, Jie; Chen, Aiping; Jiao, Liang; Khatkhatay, Fauzia; Li, Leigang; Chu, Frank; Jia, Quanxi; MacManus-Driscoll, Judith L.; Wang, Haiyan

2014-02-01

139

Ferromagnetic, ferroelectric and dielectric properties of Pb(Zr0.53Ti0.47)O3\\/CoFe2O4 multiferroic composite thick films  

Microsoft Academic Search

Pb(Zr0.53Ti0.47)O3\\/CoFe2O4 (abbreviated as PZT\\/CFO) multiferroic composite thick films have been prepared on the Pt\\/Ti\\/SiO2\\/Si substrate by using a hybrid sol-gel process. The thick films were finally annealed at 650 °C in air and the ferromagnetic, ferroelectric and dielectric properties of these films were investigated. Both the PZT pervoskite phase and the CFO spinel phase were detected from x-ray diffraction. The

W. Chen; Z. H. Wang; W. Zhu; O. K. Tan

2009-01-01

140

Multiferroic Properties of CoFe2O4\\/PbZr0.52Ti0.48O3 Composite Ceramics  

Microsoft Academic Search

The xCoFe2O4-(1?x)PbZr0.52Ti0.48O3 (PZT) composite ceramics with x = 0.1, 0.2 and 0.3 have been prepared by solid state reaction method. X-ray diffraction result reveals that no chemical reaction or phase diffusion between the CoFe2O4 and PZT phases exists in the composites. The composites exhibited ferroelectric as well as magnetic characteristics at room temperature. The distribution of the ferroelectric and magnetic

Xiaobo Wu; Wei Cai; Yi Kan; Pan Yang; Yunfei Liu; Huifeng Bo; Xiaomei Lu; Jinsong Zhu

2009-01-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

142

The role of magnetoelastic strain on orbital control and transport properties in an LaTiO(3)-CoFe(2)O(4) heterostructure.  

PubMed

Epitaxial heterostructures of CoFe(2)O(4)/LaTiO(3)/LaAlO(3) have been successfully prepared by using the pulsed laser deposition technique. The magnetoresistance (MR) of the samples is negative and linear with field at H?2 T, exhibiting no dependence on field directions. Nevertheless, when H<2 T, the MR is negative in a field parallel to the sample plane, but positive in that along the film normal. This novel observed anisotropic MR is explained in terms of the magnetic anisotropy in the ferrimagnetic layer, as well as the magnetoelastic coupling between the two. In fields of different directions, the top CoFe(2)O(4) layer contracts or expands in the sample plane due to the significant magnetostriction effect, changing its resistance accordingly and exerting compressive or tensile strains on the bottom LaTiO(3) layer. Apparently the orbital status and the one-electron bandwidth in the LaTiO(3) layer are altered, which leads to a change in resistance. PMID:21828504

Li, J; Chu, H F; Zhang, Y; Wang, J; Zheng, D N; Song, Q; Wang, P; Ma, Y G; Ong, C K; Wang, S J

2009-07-01

143

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

PubMed

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. PMID:25406863

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

2015-01-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

145

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)

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.

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

2015-02-01

146

Observation of abnormal magnetoelectric behavior in 0-3 type CoFe2O4-BaTiO3 nanocomposites  

NASA Astrophysics Data System (ADS)

Herein we report an example of xCoFe2O4/(1 - x)BaTiO3 composites formed in 0-3 type structure, which exhibit abnormal magnetic field-dependent magnetoelectric behaviors different from those reported previously. The magnetoelectric response of the composites with x ? 0.4 is found to undergo a minor change upon the dc bias magnetic field. However, when the BaTiO3 content is decreased to the extent x = 0.5, the magnetoelectric response exhibits a staircase-like dependence on the dc magnetic field with a sudden decrease at around 2.5 kOe. We propose another possible mechanism to explain the field-dependent magnetoelectric behaviors of our CoFe2O4/BaTiO3 composites.

Wang, W. P.; Yang, H.; Xian, T.; Yu, R. C.

2015-01-01

147

Spin and phonon anomalies in epitaxial self-assembled CoFe2O4-BaTiO3 multiferroic nanostructures  

NASA Astrophysics Data System (ADS)

Temperature dependent magnetic and phonon anomalies in epitaxial self-assembled CoFe2O4 (CFO) rods embedded in BaTiO3 (BTO) matrix nanostructures were investigated. The temperature dependence of A1(2TO) phonon frequency of BTO indicates that the BTO matrix experiences structural transformations. The lattice strain produced during the structural transformations drives spin reorientation in CFO rods, resulting in anomalous changes of magnetization. Through correlating the phonon anomalies with the increase of in-plane spin ordering, we show the spin-phonon coupling induces the softening of A1g and A1(2TO) phonons. It suggests that spin strongly couples with lattice strain and phonons in this nanostructure.

Tsai, C. Y.; Cheng, H. M.; Chen, H. R.; Huang, K. F.; Tsai, L. N.; Chu, Y. H.; Lai, C. H.; Hsieh, W. F.

2014-06-01

148

Anisotropic strain, magnetic properties, and lattice dynamics in self-assembled multiferroic CoFe2O4-PbTiO3 nanostructures  

NASA Astrophysics Data System (ADS)

We investigate the anisotropic stress dependent magnetic and phonon behaviors in self-assembled CoFe2O4-PbTiO3 (CFO-PTO) nanostructures deposited on SrRuO3 buffered SrTiO3 substrates of various thickness. The increased vertical compressed stress with increasing thickness enhances the vertical magnetic anisotropy of CFO while gradually reducing the vertical polarization of PTO. By applying the magnetic-field dependent Raman scattering, the CFO-A1g and T2g(1) phonon frequencies shift oppositely because of the magnetostriction. Moreover, the PTO-A1 mode intensities anomalously enhance and the A1 and E mode frequencies, respectively, increase and decrease, which prove the existence of the stress-mediated magnetoelectric (ME) effect. This study shows that the ME transmission process is dominated by interfacial stress, which is critical for enhancing the ME efficiency.

Tsai, C. Y.; Chen, H. R.; Chang, F. C.; Kuo, H. H.; Cheng, H. M.; Tsai, W. C.; Chu, Y. H.; Lai, C. H.; Hsieh, W. F.

2014-04-01

149

Ti diffusion in (001) SrTiO3-CoFe2O4 epitaxial heterostructures: blocking role of a MgAl2O4 buffer.  

PubMed

Titanium diffusion from (001) SrTiO3 (STO) substrates into CoFe2O4 (CFO) films grown using pulsed laser deposition is reported. To elucidate the reasons for Ti interdiffusion, a comparative study of CFO films grown on MgAl2O4 (MAO) and STO substrates, buffered by thin STO and MAO layers, has been made. It is shown that whereas bottom STO layers always result in Ti migration, a thin MAO layer, only 8 nm thick, is effective in blocking it. We argue that this success relies on the lower mobility of Ti ions in the MAO lattice compared to that of CFO. This result should contribute to the development of high quality epitaxial heterostructures of dissimilar complex oxides. PMID:24068072

Rebled, J M; Foerster, M; Estradé, S; Rigato, F; Kanamadi, C; Sánchez, F; Peiró, F; Fontcuberta, J

2013-11-01

150

Hierarchical templating of a BiFeO3-CoFe2O4 multiferroic nanocomposite by a triblock terpolymer film.  

PubMed

A process route to fabricate templated BiFeO3/CoFe2O4 (BFO/CFO) vertical nanocomposites is presented in which the self-assembly of the BFO/CFO is guided using a self-assembled triblock terpolymer. A linear triblock terpolymer was selected instead of a diblock copolymer in order to produce a square-symmetry template, which had a period of 44 nm. The triblock terpolymer pattern was transferred to a (001) Nb:SrTiO3 substrate to produce pits that formed preferential sites for the nucleation of CFO crystals, in contrast to the BFO, which wetted the flat regions of the substrate. The crystallographic orientation and magnetic properties of the templated BFO/CFO were characterized. PMID:25184546

Choi, Hong Kyoon; Aimon, Nicolas M; Kim, Dong Hun; Sun, Xue Yin; Gwyther, Jessica; Manners, Ian; Ross, Caroline A

2014-09-23

151

Epitaxial strain-induced changes in the cation distribution and resistivity of Fe-doped CoFe2O4  

NASA Astrophysics Data System (ADS)

The distribution of cations in Fe-doped cobalt ferrite (Co1-xFe2+xO4) is investigated as a function of epitaxial strain through x-ray absorption measurements of samples grown on SrTiO3, MgO, and CoCr2O4-buffered MgAl2O4 (001). In agreement with recent theoretical calculations, compressive (tensile) strain results in the films having a larger (smaller) degree of cation inversion for iron doping levels up to x = 0.62. Measurements of the resistivity further conclude that the degree of cation inversion has a direct effect on the size of the bandgap for stoichiometric CoFe2O4, an effect that is reduced as the iron doping level is increased.

Moyer, J. A.; Kumah, D. P.; Vaz, C. A. F.; Arena, D. A.; Henrich, V. E.

2012-07-01

152

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

PubMed

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. PMID:21400653

Shi, Wenbing; Wang, Hui; Huang, Yuming

2011-01-01

153

Engineered magnetic shape anisotropy in BiFeO3-CoFe2O4 self-assembled thin films.  

PubMed

We report growth of various phase architectures of self-assembled BiFeO3-CoFe2O4 (BFO-CFO) thin films on differently oriented SrTiO3 (STO) substrates. CFO forms segregated square, stripe, and triangular nanopillars embedded in a coherent BFO matrix on (001)-, (110)-, and (111)-oriented STO substrates, respectively. Nanostructures with an aspect ratio of up to 5:1 with a prominent magnetic anisotropy were obtained on both (001) and (110) STO along out-of-plane and in-plane directions. Magnetic easy axis rotation from in-plane to out-of-plane directions was realized through aspect ratio control. An intractable in-plane anisotropy was fixed in CFO on (111) STO due to the triangular shape of the ferromagnetic phase nanopillars. These studies established a detailed relationship of magnetic anisotropy with specific shape and dimensions of ordered magnetic arrays. The results suggest a way to effectively control the magnetic anisotropy in patterned ferromagnetic oxide arrays with tunable shape, aspect ratio, and elastic strain conditions of the nanostructures. PMID:23473343

Wang, Zhiguang; Li, Yanxi; Viswan, Ravindranath; Hu, Bolin; Harris, Vincent G; Li, Jiefang; Viehland, Dwight

2013-04-23

154

Magnetic nanocomposites: Preparation and characterization of Co-ferrite nanoparticles  

Microsoft Academic Search

Cobalt ferrite nanoparticles, CoFe2O4, are one of the important spinel ferrites because of their high cubic magnetocrystalline anisotropy, high coercivity and moderate saturation magnetization. CoFe2O4 nanoparticles have been known to be a photomagnetic material which shows an interesting light induced coercivity change. In this study, various preparation techniques were used to produce cobalt ferrite nanoparticles: (i) ball milling of a

M. H. Khedr; A. A. Omar; S. A. Abdel-Moaty

155

Magnetic nanocomposites: Preparation and characterization of Co-ferrite nanoparticles  

Microsoft Academic Search

Cobalt ferrite nanoparticles, CoFe2O4, are one of the important spinel ferrites due to their high cubic magnetocrystalline anisotropy, high coercivity and moderate saturation magnetization. CoFe2O4 nanoparticles have been known to be a photomagnetic material which shows an interesting light induced coercivity change. In this study, various preparation techniques were used to produce cobalt ferrite nanoparticles namely, (i) ball milling of

M. H. Khedr; A. A. Omar; S. A. Abdel-Moaty

2006-01-01

156

Preparation of magnetic spinel ferrite core\\/shell nanoparticles: Soft ferrites on hard ferrites and vice versa  

Microsoft Academic Search

Hard\\/soft CoFe2O4\\/ZnFe2O4 and soft\\/hard ZnFe2O4\\/CoFe2O4 core\\/shell nanoparticles were prepared by combining high-temperature thermolysis of metal oxide precursors with seed-mediated growth. Magnetic properties of the core\\/shell nanoparticles were compared to those of individual CoFe2O4 and ZnFe2O4 nanoparticles of similar size prepared by the same method. The structure of the core\\/shell materials was established using a combination of X-ray and neutron powder

Ombretta Masala; Darin Hoffman; Nalini Sundaram; Katharine Page; Thomas Proffen; Gavin Lawes; Ram Seshadri

2006-01-01

157

Magnetic properties of (CoFe2O4)x:(CeO2)1-x vertically aligned nanocomposites and their pinning properties in YBa2Cu3O7-? thin films  

NASA Astrophysics Data System (ADS)

Vertically aligned nanocomposites (VAN) combined ferrimagnetic CoFe2O4 with non-magnetic CeO2 ((CoFe2O4)x:(CeO2)1-x) in different phase ratios (x = 10%, 30% to 50%) have been grown by a pulsed laser deposition technique. Various unique magnetic domain structures form based on the VAN compositions and growth conditions. Anisotropic and tunable ferrimagnetic properties have been demonstrated. These ordered ferrimagnetic nanostructures have been incorporated into YBa2Cu3O7-? thin films as both cap and buffer layers to enhance the flux pinning properties of the superconducting thin films. The results suggest that the ordered magnetic VAN provides effective pinning centers by both defect and magnetic nanoinclusions.

Huang, Jijie; Tsai, Chen-Fong; Chen, Li; Jian, Jie; Khatkhatay, Fauzia; Yu, Kaiyuan; Wang, Haiyan

2014-03-01

158

Synthesis and magnetic properties of polycrystalline films of Co x Fe y Cr3 - x - y O4 and Cr2O3/CoFe2O4 multiferroics  

NASA Astrophysics Data System (ADS)

Magnetic properties of first obtained polycrystalline films of FeCr2O4, CoCr2O4, and CoFe0.5Cr1.5O4 multiferroics and films of a Cr2O3/CoFe2O4 composite multiferroic have been studied. In particular, magnetization curves and temperature dependences of the magnetic moment of the samples were measured in the temperature range 4.2-300 K in fields of up to 10 kOe. It was shown that the Curie point of a multiferroic depends on its cation composition. It was found that an exchange bias of the hysteresis loop exists in films of the Cr2O3/CoFe2O4 composite multiferroic at temperatures below the Néel point of Cr2O3 (330 K).

Polyakova, K. P.; Polyakov, V. V.; Velikanov, D. A.; Yurkin, G. Yu.; Patrin, G. S.

2014-08-01

159

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

160

Submitted for publication Sept. 2007 Magnetoelectric nano-Fe3O4/CoFe2O4//PbZr0.53Ti0.47O3 Composite 1/11  

E-print Network

composites as these are predominantly fabricated by thin film technologies, e.g.,3 and the oxide featuring. The composite was manufactured by spinning a CFO sol-gel11 onto a mirror polished PZT single crystal substrate ______________________________________________________________________________________ Magnetoelectric nano-Fe3O4/CoFe2O4//PbZr0.53Ti0.47O3 Composite 1/11 Shenqiang Ren and Manfred Wuttig

Rubloff, Gary W.

161

Dependence of Site Occupancy and Structural and Electrical Properties on Successive Replacement of Co by Zn in CoFe2O4  

NASA Astrophysics Data System (ADS)

The crystal structure and cation distribution at particular sites in the crystal lattice play the primary role in determining the properties of nanocrystalline transition-metal oxide materials. Nanocrystalline ferrite particles of Co1- x Zn x Fe2O4 with x varying from 0.0 to 1.0 were synthesized by a coprecipitation method. Samples synthesized at the reaction temperature of 70°C were sintered at 600°C for 3 h. The face-centered cubic (FCC) spinel structure of the synthesized particles was confirmed by x-ray diffraction patterns. The grain sizes calculated from the most intense peak (311) using the Scherrer equation were found to be in the range from 10 nm to 35 nm. Extended x-ray absorption fine-structure and x-ray absorption near-edge structure spectroscopy is a powerful tool for structural study of metal oxide materials. These techniques are element specific and sensitive to the local structure. These techniques were used at Fe, Co, and Zn K-edges to investigate the cation distribution in the crystal structure. The dependence of the electrical transport properties on the shift in the crystal structure due to successive replacement of Co by Zn in CoFe2O4 was examined. Direct-current (dc) electrical conduction measurements were carried out as a function of temperature from 313 K to 700 K. Activation energy values indicated the polaron hopping conduction mechanism. The alternating-current (ac) electrical transport properties were studied by measuring the dielectric constant as a function of frequency. A regular shift?in the electrical properties was observed depending upon the cation distribution.

Akram, M.; Anis-ur-Rehman, M.

2014-02-01

162

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

PubMed

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 thickness increasing from about 20 to 120 nm while shifting from 3 to 10 CoFe(2)O(4)/PSS bilayers, using the 8.9 × 10(-6) (moles of cobalt ferrite per litre) suspension. PMID:22025281

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

163

Millimeter Scale Alignment of Magnetic Nanoparticle Functionalized Microtubules in Magnetic Fields  

E-print Network

polymerization.6 In this communication, we report the first instance of microtubule functionalization with cobalt ferrite nanoparticles (CoFe2O4) and the facile use of an externally applied magnetic field to control

Hancock, William O.

164

Formation of nanostructured magnetic films using layer-by-layer self-assembly of star polymers and magnetic nanoparticles.  

E-print Network

?? In this work, multi-layered thin film materials comprised of cobalt ferrite (CoFe2O4) magnetic nanoparticles and polystyrene amine-functionalized (PS-NH2) star polymers have been prepared on… (more)

Shah, Shimul

2011-01-01

165

A novel nanostructure and multiferroic properties in Pb(Zr0.52Ti0.48)O3\\/CoFe2O4 nanocomposite films grown by pulsed-laser deposition  

Microsoft Academic Search

Multiferroic nanocomposite thin films containing Pb(Zr0.52Ti0.48)O3 (PZT) and CoFe2O4(CFO) with a novel nanostructure are deposited on (1 0 0)-oriented Nb-doped SrTiO3 (STO) substrates by pulsed-laser deposition. Structural characterizations show that only PZT and CFO phases exist in the composite films, and the perovskite-structured PZT nano-pyramids with diameters of 50-100 nm are randomly embedded in the spinel-structured polycrystalline CFO matrix. Ferroelectric

J. X. Zhang; J. Y. Dai; W. Lu; H. L. W. Chan; B. Wu; D. X. Li

2008-01-01

166

Influence of relative thickness on multiferroic properties of bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4 thin films  

Microsoft Academic Search

Multiferroic bilayered thin films consisting of Pb(Zr0.52Ti0.48)O3 (PZT) and CoFe2O4 (CFO) layers of different relative thicknesses were prepared on a general Pt\\/Ti\\/SiO2\\/Si substrate via a simple solution processing. The influence of the thickness fraction on their properties including ferroelectric, ferromagnetic, and magnetoelectric properties in the PZT-CFO bilayered thin films was investigated. Our results showed that the thickness fractions (or relative

Hong-Cai He; Jing Ma; Yuanhua Lin; C. W. Nan

2008-01-01

167

Orientation-dependent multiferroic properties in Pb(Zr0.52Ti0.48)O3-CoFe2O4 nanocomposite thin films derived by a sol-gel processing  

Microsoft Academic Search

Bilayered multiferroic nanocomposite films of preferentially oriented Pb(Zr0.52Ti0.48)O3 (PZT) and CoFe2O4 (CFO) were prepared on general Pt\\/Ti\\/SiO2\\/Si substrate via a simple solution processing. Different annealing processings resulted in different preferential orientations for the PZT layers in the bilayered thin films, on which the dependence of properties, including ferroelectric, ferromagnetic, and magnetoelectric properties, in the PZT-CFO nanocomposite thin films was investigated.

Hong-Cai He; Jing Ma; Jing Wang; Ce-Wen Nan

2008-01-01

168

Magnetoelectric CoFe2O4\\/Pb(Zr0.52Ti0.48)O3 double-layer thin film prepared by pulsed-laser deposition  

Microsoft Academic Search

Double-layer magnetoelectric CoFe2O4 (CFO)\\/Pb(Zr0.52Ti0.48)O3 (PZT) nanocomposite thin film was prepared via a pulsed-laser deposition. X-ray diffraction showed that there are no other phases but PZT and CFO phases in the film. The smooth film surface was obtained after depositing the CFO and PZT layers. The double-layer thin film exhibits both good ferromagnetic and electric properties, as well as a magnetoelectric

Jian-Ping Zhou; Hongcai He; Zhan Shi; Ce-Wen Nan

2006-01-01

169

Effect of sample shape on the zero-field-cooled magnetization behavior: comparative studies on NiFe2O4, CoFe2O4 and SrFe12O19  

Microsoft Academic Search

The zero-held-cooled (ZFC) magnetization behavior of powders and\\u000a sintered solid pieces having arbitrary shapes and sizes of three\\u000a different ferrimagnetic oxides, NiFe2O4, CoFe2O4 and SrFe12O19, has been\\u000a compared to distinguish the contribution from magnetocrystalline and\\u000a shape anisotropies on the general characteristics of the ZFC\\u000a magnetization curves. It is observed that the general shape of the ZFC\\u000a magnetization curve is mainly

PA Joy; S. K Date

2000-01-01

170

Enhanced magnetoelectric properties in Pb(Zr,Ti)O3-CoFe2O4 layered thin films with LaNiO3 as a buffer layer  

Microsoft Academic Search

Conductive LaNiO3 thin films were prepared via a simple solution method to be used as both a buffer layer and a bottom electrode layer, on which Pb(Zr,Ti)O3-CoFe2O4 bi-layered films were also deposited by a similar solution method. The results showed that the LaNiO3 buffer layer could induce a different preferential orientation for the Pb(Zr,Ti)O3 layer in the composite films and

H. C. He; J. Ma; Y. H. Lin; C. W. Nan

2009-01-01

171

Synthesis of ultrasmall platinum nanoparticles and structural relaxation.  

PubMed

We report the synthesis of ligand-protected, ultrasmall Pt nanoparticles of ?1 nm size via a one-phase wet chemical method. Using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), we determined the mass of the nanoparticles to be ?8 kDa. Characterization of the Pt nanoparticles was further carried out by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), optical absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS). Interestingly, we observed a large structural relaxation in the 8kDa nanoparticles (i.e. lattice parameter elongation by +10%) compared to bulk platinum. XPS analysis revealed a positive shift of Pt 4f core level energy by approximately +1 eV compared with bulk Pt, indicating charge transfer from Pt to S atom of the thiolate ligand on the particle. Compared to bulk Pt, the 5d band of Pt nanoparticles is narrower and shifts to higher binding energy. Overall, the ?1 nm ultrasmall Pt nanoparticles exhibit quite distinct differences in electronic and structural properties compared to their larger counterparts and bulk Pt. PMID:24703677

Liu, Chao; Li, Gao; Kauffman, Douglas R; Pang, Guangsheng; Jin, Rongchao

2014-06-01

172

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

PubMed Central

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

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

2014-01-01

173

Polyvinyl alcohol functionalized cobalt ferrite nanoparticles for biomedical applications  

NASA Astrophysics Data System (ADS)

In the present work, cobalt ferrite nanoparticles (CoFe2O4 NPs) have been synthesized by combustion method. The surface of the CoFe2O4 NPs was modified with biocompatible polyvinyl alcohol (PVA). To investigate effect and nature of coating on the surface of CoFe2O4 NPs, the NPs were characterized X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The transmission electron microscopy (TEM) and dynamic light scattering (DLS) results demonstrate the monodispersed characteristics of CoFe2O4 NPs after surface modification with PVA. The decrease in contact angle from 162° to 50° with PVA coating on NPs indicates the transition from hydrophobic nature to hydrophilic. The Magnetic properties measurement system (MPMS) results show that the NPs have ferromagnetic behavior with high magnetization of 75.04 and 71.02 emu/g of uncoated and coated CoFe2O4 NPs respectively. These PVA coated NPs exhibit less toxicity over uncoated CoFe2O4 NPs up to 1.8 mg mL-1 when tested with mouse fibroblast L929 cell line.

Salunkhe, A. B.; Khot, V. M.; Thorat, N. D.; Phadatare, M. R.; Sathish, C. I.; Dhawale, D. S.; Pawar, S. H.

2013-01-01

174

Si{endash}N linkage in ultrabright, ultrasmall Si nanoparticles  

SciTech Connect

Ultrabright ultrasmall ({similar_to}1 nm) blue luminescent Si{sub 29} nanoparticles are chlorinated by reaction with Cl{sub 2} gas. A Si{endash}N linkage is formed by the reaction of the chlorinated particles with the functional amine group in butylamine. Fourier transform infrared spectroscopy and x-ray photospectroscopy measurements confirm the N linkage and the presence of the butyl group, while emission, excitation, and autocorrelation femtosecond optical spectroscopy show that, after the linkage formation, the particles with the ultrabright blue luminescent remain, but with a redshift of 40 nm. {copyright} 2001 American Institute of Physics.

Rogozhina, E.; Belomoin, G.; Smith, A.; Abuhassan, L.; Barry, N.; Akcakir, O.; Braun, P. V.; Nayfeh, M. H.

2001-06-04

175

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

PubMed

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. PMID:23912629

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

2013-08-30

176

Synthesis of Monodisperse FeCo Nanoparticles by Reductive Salt-Matrix Annealing  

SciTech Connect

We report here a novel synthetic method to prepare monodisperse air-stable FeCo nanoparticles. CoFe2O4 nanoparticles with 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 400–500oC 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.

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

2013-08-02

177

Ultrasmall lanthanide-doped nanoparticles as multimodal platforms  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

178

Effect of annealing temperature on the magnetoelectric properties of CoFe2O4/Pt/Pb(Zr0.52Ti0.48)O3 multilayer films  

NASA Astrophysics Data System (ADS)

CoFe2O4(CoFO)/Pt/Pb(Zr0.52Ti0.48)O3 (PZT) multilayer films were grown on Pt/Ti/SiO2/Si substrates. A thin Pt layer was inserted between the ferrimagnetic and the ferroelectric layers in order to suppress diffusion at high temperatures and thereby to prevent possible interfacial reactions. The effect of annealing on the film's microstructure and multiferroic properties was then investigated using thin film stacks heat-treated at temperatures ranging from 550 to 650 °C. The magnetoelectric coefficients were calculated from the magnetoelectric voltages measured using a magnetoelectric measurement system. The effect of annealing temperature on the magnetoelectric coupling in the CoFO/Pt/PZT multilayer thin film is discussed in detail.

Eum, You Jeong; Hwang, Sung-Ok; Koo, Chang Young; Lee, Jai-Yeoul; Lee, Hee Young; Ryu, Jungho; Park, Jung Min

2014-08-01

179

Controlled growth of epitaxial BiFeO3 films using self-assembled BiFeO3-CoFe2O4 multiferroic heterostructures as a template  

NASA Astrophysics Data System (ADS)

The growth mechanism of a BiFeO3 layer deposited on self assembled (0.65) BiFeO3-(0.35) CoFe2O4 (BFO-CFO) composite thin films was studied. Epitaxial and self-assembled BFO-CFO thin films were deposited on SrTiO3 (111) substrates by pulsed laser deposition and were subsequently used as a seed layer for the deposition of an additional BFO layer. x-ray line scans showed the heterostructures were highly epitaxial. Cross-sectional scanning electron microscopy and focused ion beam images revealed the top BFO layer grew preferentially from BFO nanopillars in the BFO-CFO thin films, thus, demonstrating controlled growth. The multiferroic properties of this new nanostructure were then studied.

Li, Yanxi; Yang, Yaodong; Yao, Jianjun; Viswan, Ravindranath; Wang, Zhiguang; Li, Jiefang; Viehland, D.

2012-07-01

180

Structural and morphological studies of manganese substituted CoFe2O4 and NiFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

Nanocrystalline manganese substituted cobalt and nickel ferrites have been synthesized through the evaporation method by using egg white. These powders were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The XRD pattern of manganese substituted spinel ferrites contains some impurity peaks, which are the decomposition of the ferrites to ?-Fe2O3 phase at higher annealing temperature. The microstructure and particle size of the annealed sample analyzed by TEM, which gives the particle size well with XRD. The magnetic properties were measured using Vibrating Sample Magnetometer (VSM). The surface/near-surface chemical states of the nanocrystalline manganese substituted cobalt and nickel ferrites are analyzed by XPS within a range of binding energies of 0-1000 eV.

Ranjith kumar, E.; Jayaprakash, R.; Patel, Rajesh

2013-10-01

181

Application of hydrophobically modified water-soluble polymers for the dispersion of hydrophobic magnetic nanoparticles in aqueous media.  

PubMed

Hydrophobically modified water-soluble polymers (HMWSPs), comprised of a poly(sodium methacrylate) (PMANa) or poly(sodium acrylate) (PANa) backbone and pendent dodecyl methacrylate (DMA) or dodecyl acrylamide (DAAm) chains, respectively, were synthesized. The hydrophobic content of the copolymers, P(MANa-co-DMA) and P(ANa-co-DAAm), is in the range of 0 to 25 mol%, while their weight-average molar mass varies from ~10?000 up to ~75?000. Their self-assembly behavior in dilute aqueous solution was followed through Nile Red probing, DLS and TEM measurements. The critical micelle concentration (CMC) is mainly controlled by the hydrophobic content and not the molar mass of the copolymers. Above CMC, spherical and large-compound micelles are identified by DLS and TEM. Moreover, oleylamine coated CoFe2O4 nanoparticles (CoFe2O4@OAm MNPs) of 9.4 nm with a saturation magnetization Ms = 85 emu g(-1) were solvothermally prepared. The hydrophobic CoFe2O4@OAm MNPs were successfully encapsulated into the hydrophobic cores of the structures formed by the copolymers above CMC through a solvent mixing procedure, and in that way hydrophilic CoFe2O4@HMWSP nanohybrids resulted. For comparison purposes, two alternate phase transfer approaches were also used to convert CoFe2O4@OAm MNPs to hydrophilic ones: (a) addition of a coating layer by cetyltrimethyl ammonium bromide (CTAB) and (b) by the ligand exchange procedure with 2,3-dimercaptosuccinic acid (DMSA). NMR transverse relaxivity measurements of the aqueous suspensions of CoFe2O4@P(ANa-co-DAAm), CoFe2O4@CTAB and CoFe2O4@DMSA were recorded and the r2 relaxivity was determined. CoFe2O4@CTAB demonstrated the highest r2 relaxivity of 554.0 mM(-1) s(-1), while CoFe2O4@P(ANa-co-DAAm) and CoFe2O4@DMSA showed lower values of 313.6 mM(-1) s(-1) and 76.3 mM(-1) s(-1), respectively. PMID:24759871

Iatridi, Zacharoula; Georgiadou, Violetta; Menelaou, Melita; Dendrinou-Samara, Catherine; Bokias, Georgios

2014-06-21

182

Molecularly stabilised ultrasmall gold nanoparticles: synthesis, characterization and bioactivity  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

183

Structure and catalytic properties of ultra-small ceria nanoparticles  

NASA Astrophysics Data System (ADS)

Cerium dioxide (ceria) is an excellent catalytic material due to its ability to both facilitate oxidation/reduction reactions as well as store/release oxygen as an oxygen buffer. The traditional approach to assess and improve ceria's catalytic behavior focuses on how efficiently O-vacancies can be generated and/or annihilated within the material, and how to extend established understandings of "bulk" ceria to further explain the greatly enhanced catalytic behavior of ultra-small ceria nanoparticles (uCNPs) with sizes less than 10 nm. Here, using density functional theory (DFT) calculations, we reexamine the atomic and electronic structures of uCNPs, especially their surface configurations. A unique picture dissimilar to the traditional point of view emerges from these calculations for the surface structure of uCNPs. uCNPs similar to those obtained by experimental synthesis and applied in catalytic environments exhibit core-shell like structures overall, with under-stoichiometric, reduced CNP "cores" and over-stoichiometric, oxidized surface "shells" constituted by various surface functional groups, e.g., Ox and/or OH surface groups. Therefore, their catalytic behavior is dominated by surface chemistry rather than O-vacancies. Based on this finding, reaction pathways of two prevalent catalytic reactions, namely CO oxidation and the water-gas shift reaction over uCNPs are systematically investigated. Combined, these results demonstrate an alternative understanding of the surface structure of uCNPs, and provide new avenues to explore and enhance their catalytic behavior, which is likely applicable to other transition metal oxide nanoparticles with multivalent ions and very small sizes. KEYWORDS: density functional theory, ceria nanoparticles, surface, catalysis, thermodynamics.

Huang, Xing

184

Crafting the strain state in epitaxial thin films: A case study of CoFe2O4 films on Pb(Mg,Nb)O3-PbTiO3  

NASA Astrophysics Data System (ADS)

The strain dependence of electric and magnetic properties has been widely investigated, both from a fundamental science perspective and an applications point of view. Electromechanical coupling through field-induced polarization rotation (PRO) and polarization reorientation (PRE) in piezoelectric single crystals can provide an effective strain in film/substrate epitaxial heterostructures. However, the specific pathway of PRO and PRE is a complex thermodynamic process, depending on chemical composition, temperature, electric field, and mechanical load. Here, systematic studies of the temperature-dependent field-induced phase transitions in Pb(Mg,Nb)O3-PbTiO3 single crystals with different initial phase and orientation configurations have been performed. Different types of strains, volatile/nonvolatile and biaxial/uniaxial, have been measured by both macroscopic and in situ x-ray diffraction techniques. In addition, the strain state of epitaxial Mn-doped CoFe2O4 thin films was examined by magnetic anisotropy measurements, where a giant magnetoelectric coupling has been demonstrated.

Wang, Zhiguang; Wang, Yaojin; Luo, Haosu; Li, Jiefang; Viehland, D.

2014-10-01

185

Probing optical band gaps at the nanoscale in NiFe2O4 and CoFe2O4 epitaxial films by high resolution electron energy loss spectroscopy  

NASA Astrophysics Data System (ADS)

Nanoscale optical band gap variations in epitaxial thin films of two different spinel ferrites, i.e., NiFe2O4 (NFO) and CoFe2O4 (CFO), have been investigated by spatially resolved high resolution electron energy loss spectroscopy. Experimentally, both NFO and CFO show indirect/direct band gaps around 1.52 eV/2.74 and 2.3 eV, and 1.3 eV/2.31 eV, respectively, for the ideal inverse spinel configuration with considerable standard deviation in the band gap values for CFO due to various levels of deviation from the ideal inverse spinel structure. Direct probing of the regions in both the systems with tetrahedral A site cation vacancy, which is distinct from the ideal inverse spinel configuration, shows significantly smaller band gap values. The experimental results are supported by the density functional theory based modified Becke-Johnson exchange correlation potential calculated band gap values for the different cation configurations.

Dileep, K.; Loukya, B.; Pachauri, N.; Gupta, A.; Datta, R.

2014-09-01

186

Effect of thickness on the stress and magnetoelectric coupling in bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4 films  

NASA Astrophysics Data System (ADS)

Magnetoelectric bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4(PZT-CFO) films with different PZT thicknesses were grown on (111)Pt/Ti/SiO2/Si substrates using chemical solution spin-coating. Structural characterization by X-ray diffraction and electron microscopy shows pure phases and well-defined interfaces between the PZT and CFO films. The CFO-PZT-substrate structure effectively alleviates the substrate clamping effect for the CFO layer, showing appreciable magnetoelectric responses in the composite films. Both the direct magnetoelectric effect and the magnetic field-induced Raman shifts in the A1(TO1) soft mode of PZT demonstrate the magnetic-mechanical-electric coupling in the films. The results also indicate that with a constant CFO layer thickness, the thickness of the PZT layer plays an important role in the stress relaxation and strong magnetoelectric coupling. The coupling could be further enhanced by increasing the CFO thickness, optimizing the volume (thickness) fraction of the PZT thickness, and releasing the clamping effect from the substrate.

Wang, Jing; Li, Zheng; Wang, Jianjun; He, Hongcai; Nan, Cewen

2015-01-01

187

Cellular distribution and degradation of cobalt ferrite nanoparticles in Balb/3T3 mouse fibroblasts.  

PubMed

The effect of the concentration of cobalt ferrite (CoFe(2)O(4)) nanoparticles (NPs) on their intracellular location and distribution has been explored by synchrotron radiation X-ray and fluorescence microscopy (SR-XRF) monitoring the evolution of NPs elemental composition as well. In cells exposed to low concentrations of CoFe(2)O(4) NPs, the NPs preferentially segregate in the perinuclear region preserving their initial chemical content. At concentrations exceeding 500 ?M the XRF spectra indicate the presence of Co and Fe also in the nuclear region, accompanied by sensible changes in the cellular morphology. The increase of the Co/Fe ratio measured in the nuclear compartment indicates that above certain concentrations the CoFe(2)O(4) NPs intracellular distribution could be accompanied by biodegradation resulting in Co accumulation in the nucleus. PMID:21925252

Marmorato, Patrick; Ceccone, Giacomo; Gianoncelli, Alessandra; Pascolo, Lorella; Ponti, Jessica; Rossi, François; Salomé, Murielle; Kaulich, Burkhard; Kiskinova, Maya

2011-11-30

188

Ultra-small platinum and gold nanoparticles by arc plasma deposition  

NASA Astrophysics Data System (ADS)

Ultra-small (<2 nm) nanoparticles of platinum and gold were produced by arc plasma deposition (APD) in a systematic way and the deposition behavior was studied. Nanoparticles were deposited on two dimensional amorphous carbon and amorphous titania thin films and characterized by transmission electron microscopy (TEM). Deposition behavior of nanoparticles by APD was studied with discharge voltage (V), discharge condenser capacitance (C), and the number of plasma pulse shots (n) as controllable parameters. The average size of intrinsic nanoparticles generated by APD process was as small as 0.9 nm and deposited nanoparticles began to have crystal structures from the particle size of about 2 nm. V was the most sensitive parameter to control the size and coverage of generated nanoparticles compared to C and n. Size of APD deposited nanoparticles was also influenced by the nature of evaporating materials and substrates.

Kim, Sang Hoon; Jeong, Young Eun; Ha, Heonphil; Byun, Ji Young; Kim, Young Dok

2014-04-01

189

Magnetocaloric effect in ferrite nanoparticles  

Microsoft Academic Search

A comparative study of the magnetocaloric effect (MCE) is reported in two different types of chemically synthesized magnetic nanoparticle systems—cobalt ferrite and manganese zinc ferrite with mean size around 5 and 15nm, respectively. While CoFe2O4 nanoparticles were synthesized using co-precipitation, the Mn0.68Zn0.25Fe2.07O4 (MZFO) nanoparticles were prepared by reverse micelle technique using AOT as surfactant. Our results indicate that the change

P. Poddar; J. Gass; D. J. Rebar; S. Srinath; H. Srikanth; S. A. Morrison; E. E. Carpenter

2006-01-01

190

Structural and magnetic properties of pulsed laser deposited SrRuO3/CoFe2O4/La2/3Sr1/3MnO3 magnetic oxide heterostructures on SrTiO3(001) and MgO(001)  

NASA Astrophysics Data System (ADS)

We report on the growth of all-oxide SrRuO3/CoFe2O4/La2/3Sr1/3MnO3 and La2/3Sr1/3MnO3/CoFe2O4/SrRuO3 heterostuctures on SrTiO3(001) and MgO(001) substrates by pulsed laser deposition. Structural analyses by X-ray diffraction and transmission electron microscopy clearly indicate the preservation of epitaxial relations when the La2/3Sr1/3MnO3 layer is grown first, whereas trilayers with SrRuO3 at the bottom are more disordered. Both the substrate material and the deposition sequence strongly influence the formation of various structural defects such as interfacial dislocations and sub-grain structures, and this is clearly reflected by a reduction of the saturation magnetization in the top electrode. When the substrate material and the deposition sequence are correctly chosen, however, the magnetic moments of the La2/3Sr1/3MnO3 and SrRuO3 layers reverse independently, and the La2/3Sr1/3MnO3 layer retains bulk-like magnetic properties.

Äkäslompolo, Laura; Sánchez, Ana M.; Qin, Qi Hang; Hakola, Antti; Kajava, Timo; van Dijken, Sebastiaan

2013-03-01

191

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

PubMed Central

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

Altinok, Mahmut; Urfels, Stephan; Bauer, Johann

2014-01-01

192

Synthesis of carboxyl superparamagnetic ultrasmall iron oxide (USPIO) nanoparticles by a novel flocculation-redispersion process  

NASA Astrophysics Data System (ADS)

We report a novel flocculation-redispersion method to synthesize and purify the biocompatible superparamagnetic ultrasmall iron oxide (USPIO) nanoparticles coated with carboxyl dextran derivative. First, USPIO nanoparticles were synthesized and flocculated to form the large clusters through bridging effect of polyvinyl alcohol (PVA) during coprecipitation process. Then the flocculated USPIO was separated and purified from the solution conveniently through magnetic sedimentation. Finally, USPIO in the clusters were released again and well dispersed through electrostatic repelling effect of citric acid with the aid of ultrasonic. The dispersed carboxyl-functionalized USPIO was conjugated with the monoclonal antibodies. And it has been proved that the antibodies anchored on USPIO still retained their bioactivity after the conjugation. These results implied that the USPIO synthesized have good potential as active targeting molecular probe in biomedical application.

Cheng, Chang-Ming; Kou, Geng; Wang, Xiao-Liang; Wang, Shu-Hui; Gu, Hong-Chen; Guo, Ya-Jun

2009-09-01

193

Differential hERG ion channel activity of ultrasmall gold nanoparticles  

PubMed Central

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

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

194

Large-Pore Ultrasmall Mesoporous Organosilica Nanoparticles: Micelle/Precursor Co-templating Assembly and Nuclear-Targeted Gene Delivery.  

PubMed

A novel micelle/precursor co-templating assembly strategy is successfully developed to synthesize large-pore ultrasmall mesoporous organosilica nanoparticles (MONs). Furthermore, elaborately designed MONs with a cell-penetrating peptide (TAT) (MONs-PTAT) are constructed for highly efficient intranuclear gene delivery. They exhibit a high loading capacity, improved protection for the loaded gene, and enhanced transfection efficiencies of EGFP plasmid (pEGFP). PMID:25423915

Wu, Meiying; Meng, Qingshuo; Chen, Yu; Du, Yanyan; Zhang, Lingxia; Li, Yaping; Zhang, Linlin; Shi, Jianlin

2015-01-01

195

Oleylamine as a beneficial agent for the synthesis of CoFe?O? nanoparticles with potential biomedical uses.  

PubMed

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. PMID:24604256

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

2014-05-01

196

Influence of the morphology of ferrite nanoparticles on the directed assembly into magnetically anisotropic hierarchical structures.  

PubMed

The effect of the morphology of ferrite nanoparticles on their assembly in a magnetic field was studied. Thin BaFe12O19 nanoplatelets were compared with isotropic, spherical or octahedral, CoFe2O4 nanoparticles, all of which were synthesized hydrothermally. The nanoplatelets and nanoparticles assembled into a variety of hierarchical structures from stable suspensions during the "drop deposition" and drying in a magnetic field. The alignment of the nanoparticles in the magnetic field was observed in situ with an optical microscope. The morphologies of the nanoparticles and the subsequent assemblies were observed with transmission and scanning electron microscopes, respectively. The magnetic properties of the nanoparticles and the assemblies were measured with a vibrating-sample magnetometer. The BaFe12O19 nanoplatelets aligned in the plane of the substrate and formed several-micrometers-thick, ordered films with a magnetic alignment of approximately 90%. The CoFe2O4 nanoparticles assembled into thick, dense columns with a height of several hundreds of micrometers and showed a magnetic alignment of up to 60%. The differences in the morphologies and the magnetic alignments between the BaFe12O19 and CoFe2O4 hierarchical structures could be explained in terms of the differences in the shape and magnetocrystalline structure of the specific nanoparticles. PMID:24841592

Lisjak, Darja; Jenuš, Petra; Mertelj, Alenka

2014-06-10

197

Ultrasmall superparamagnetic iron oxide nanoparticles with titanium-N,N-dialkylcarbamato coating  

NASA Astrophysics Data System (ADS)

This work deals with the preparation and physical-chemical characterization of new ultrasmall iron oxide superparamagnetic nanoparticles (USPIONs) functionalized with titanium-N,N-dialkylcarbamato. The preparation was performed starting with monodispersed USPIONs covered with oleic acid, synthesized by thermal-decomposition, and subsequently functionalized with metal-carbamato by a ligand-exchange reaction. The surface and coating structure was characterized by infrared (FT-IR) spectroscopy on the solid powders and thermogravimetry (TG) coupled with an FT-IR detector in order to better investigate the self-assembling properties of the coating. A detailed dimensional and morphological study was carried out by transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis. Zero-field-cooled (ZFC) and field-cooled (FC) magnetic susceptibility curves as well as the magnetization behavior as a function of temperature were investigated on both the starting oleic-USPIONs and those covered by titanium-N,N-dialkylcarbamato. These results confirmed the superparamagnetic properties of the new nanoparticles (NPs), highlighting the quite high saturation value of the magnetization. Based on the results obtained by combining different experimental techniques, a model of the coating structure and ligand organization around the magnetic core is proposed for both NPs, i.e. the starting USPIONs covered by oleic acid and the new USPIONs functionalized by titanium-N,N-dialkylcarbamato.

Dolci, S.; Domenici, V.; Duce, C.; Tiné, M. R.; Ierardi, V.; Valbusa, U.; Jaglicic, Z.; Boni, A.; Gemmi, M.; Pampaloni, G.

2014-09-01

198

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

PubMed

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 (124)I for positron emission tomography (PET) imaging and modified with cRGDY peptides for molecular targeting. (124)I-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 (124)I-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

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

2014-10-29

199

Enhanced magnetism and ferroelectricity in epitaxial Pb(Zr0.52Ti0.48)O3/CoFe2O4/La0.7Sr0.3MnO3 multiferroic heterostructures grown using dual-laser ablation technique  

NASA Astrophysics Data System (ADS)

PbZr0.52Ti0.48O3/CoFe2O4/La0.7Sr0.3MnO3 (PZT/CFO/LSMO) and PZT/LSMO heterostructures were grown on single-crystal MgO (100) substrates using the dual-laser ablation technique. X-ray diffraction confirmed the epitaxial relationship between the layers in the heterostructures. Magnetization measurements showed in-plane uniaxial magnetic anisotropy in PZT/CFO/LSMO with enhanced saturation magnetization of 288 emu/cm3 as compared to 244 emu/cm3 for PZT/LSMO. With the introduction of the hard magnetic CFO, the low coercivity of PZT/LSMO increased from 0.1 kOe to 1.4 kOe. Polarization measurements showed well-saturated square hysteresis loops for PZT/CFO/LSMO with enhanced remanent polarization (Pr) values of 69 ?C/cm2 at a coercive field (Ec) of 88 kV/cm as compared to Pr = 51 ?C/cm2 at Ec = 39 kV/cm for PZT/LSMO. The improved hard ferromagnetic and ferroelectric properties in PZT/CFO/LSMO as compared to PZT/LSMO make it desirable for multiferroic device applications.

Mukherjee, Devajyoti; Hordagoda, Mahesh; Lampen, Paula; Phan, Manh-Huong; Srikanth, Hariharan; Witanachchi, Sarath; Mukherjee, Pritish

2014-05-01

200

A simple method for the preparation of ultra-small palladium nanoparticles and their utilization for the hydrogenation of terminal alkyne groups to alkanes.  

PubMed

A simple and convenient method for the preparation of ultra-small palladium nanoparticles (Pd-NPs) by a modified digestive ripening method is described. These nanoparticles catalyse the hydrogenation of the terminal alkyne groups to alkanes selectively, and show no effect on other labile protecting and internal alkyne or internal/external alkene groups present in the molecule. PMID:25489764

Seth, Jhumur; Kona, Chandrababu Naidu; Das, Shyamsundar; Prasad, B L V

2014-12-18

201

Ultrasmall superparamagnetic iron oxide nanoparticles coated with fucoidan for molecular MRI of intraluminal thrombus.  

PubMed

Aim: We have designed ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles associated with fucoidan (USPOI-FUCO), a natural sulfated polysaccharide with high affinity for activated platelets, to visualize by MRI arterial thrombi. Materials & methods: USPIOs were prepared and sizes, zeta-potentials and relaxivities were measured. Elastase perfusion in the infrarenal aorta of Wistar rats induced intraluminal thrombus. They were scanned on 4.7 T MRI before and after injection of USPIO-FUCO or USPIO coated with anionic dextran. Results: Surface plasmon resonance evidenced that fucoidan and USPIO-FUCO bind in vitro to immobilized P-selectin. All intraluminal hyposignals detected by MRI after injection of USPIO-FUCO on animals (13 out of 13) were correlated by histology with thrombi, whereas none could be identified with control USPIOs (0 out of 7). No signal was seen in absence of thrombus. Thrombi by MRI were correlated with P-selectin immunostaining and USPIO detection by electron microscopy. Conclusion: In vivo thrombi can thus be evidenced by MRI with USPIO-FUCO. Original submitted 8 July 2013; Revised submitted 4 March 2014. PMID:24960075

Suzuki, Michimasa; Bachelet-Violette, Laure; Rouzet, François; Beilvert, Anne; Autret, Gwennhael; Maire, Murielle; Menager, Christine; Louedec, Liliane; Choqueux, Christine; Saboural, Pierre; Haddad, Oualid; Chauvierre, Cédric; Chaubet, Frédéric; Michel, Jean-Baptiste; Serfaty, Jean-Michel; Letourneur, Didier

2014-06-24

202

Chemisorption of cyanogen chloride by spinel ferrite magnetic nanoparticles.  

PubMed

Spinel ferrite magnetic nanoparticles, MnFe2O4, NiFe2O4, and CoFe2O4, were synthesized and used as gas-phase adsorbents for the removal of cyanogen chloride from dry air. Fixed-bed adsorption breakthrough experiments show adsorption wave behavior at the leading edge of the breakthrough curve that is not typical of physically adsorbed species. Fourier transform infrared spectroscopy (FTIR) results indicate that CK is reacting with the spinel ferrite surface and forming a carbamate species. The reaction is shown to be a function of the hydroxyl groups and adsorbed water on the surface of the particles as well as the metallic composition of the particles. The surface reaction decreases the remnant and saturation magnetism of the MnFe2O4 and CoFe2O4 particles by approximately 25%. PMID:23540752

Glover, T Grant; DeCoste, Jared B; Sabo, Daniel; Zhang, Z John

2013-05-01

203

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

PubMed

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 degrees 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 degrees 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. PMID:22414887

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

2012-03-30

204

Finite size and surface effects on the magnetic properties of cobalt ferrite nanoparticles  

Microsoft Academic Search

Cobalt ferrite, CoFe2O4, nanoparticles in the size range 2–15 nm have been prepared using a non-aqueous solvothermal method. The magnetic studies\\u000a indicate a superparamagnetic behavior, showing an increase in the blocking temperatures (ranging from 215 to more than 340 K)\\u000a with the particle size, D\\u000a TEM. Fitting M versus H isotherms to the saturation approach law, the anisotropy constant, K, and the

C. Vázquez-Vázquez; M. A. López-Quintela; M. C. Buján-Núñez; J. Rivas

2011-01-01

205

Re-appearance of cooperativity in ultra-small spin-crossover [Fe(pz){Ni(CN)?}] nanoparticles.  

PubMed

A reverse nanoemulsion technique was used for the elaboration of [Fe(pz){Ni(CN)4}] nanoparticles. Low-temperature micellar exchange made it possible to elaborate ultra-small nanoparticles with sizes down to 2?nm. When decreasing the size of the particles from 110 to 12?nm the spin transition shifts to lower temperatures, becomes gradual, and the hysteresis shrinks. On the other hand, a re-opening of the hysteresis was observed for smaller (2?nm) particles. A detailed (57)Fe?Mössbauer spectroscopy analysis was used to correlate this unusual phenomenon to the modification of the stiffness of the nanoparticles thanks to the determination of their Debye temperature. PMID:25160504

Peng, Haonan; Tricard, Simon; Félix, Gautier; Molnár, Gábor; Nicolazzi, William; Salmon, Lionel; Bousseksou, Azzedine

2014-10-01

206

A simple method for the preparation of ultra-small palladium nanoparticles and their utilization for the hydrogenation of terminal alkyne groups to alkanes  

NASA Astrophysics Data System (ADS)

A simple and convenient method for the preparation of ultra-small palladium nanoparticles (Pd-NPs) by a modified digestive ripening method is described. These nanoparticles catalyse the hydrogenation of the terminal alkyne groups to alkanes selectively, and show no effect on other labile protecting and internal alkyne or internal/external alkene groups present in the molecule.A simple and convenient method for the preparation of ultra-small palladium nanoparticles (Pd-NPs) by a modified digestive ripening method is described. These nanoparticles catalyse the hydrogenation of the terminal alkyne groups to alkanes selectively, and show no effect on other labile protecting and internal alkyne or internal/external alkene groups present in the molecule. Electronic supplementary information (ESI) available: Details of nanoparticle synthesis, characterization techniques, sample preparation, catalysis reactions and the spectral characterization of substrates and products listed in Tables 1-4. See DOI: 10.1039/c4nr04239e

Seth, Jhumur; Kona, Chandrababu Naidu; Das, Shyamsundar; Prasad, B. L. V.

2014-12-01

207

Ultra-Small and Monodisperse Pt Nanoparticles Supported on Gamma-Al2O3 Long Li,* Zhongfan Zhang,* Jason R. Croy,** Simon Mostafa,** Beatriz Roldan Cuenya,**  

E-print Network

Ultra-Small and Monodisperse Pt Nanoparticles Supported on Gamma-Al2O3 Long Li,* Zhongfan Zhang to P2VP concentration ratio. The TEM samples were prepared by spreading a drop of Pt/-Al2O3 suspension images from two samples of 1 nm or less Pt NPs supported on -Al2O3 with different loadings. The size

Frenkel, Anatoly

208

Characterization and magnetism of Co-modified ?-Fe2O3 core-shell nanoparticles by enhancement using NaOH  

NASA Astrophysics Data System (ADS)

During synthesis of ?-Fe2O3 nanoparticles by chemically-induced transition in FeCl2 solution, Co-modification of the particles has been attempted by adding Co(NO3)2 (sample (1)) or Co(NO3)2/NaOH (samples (2) and (3)). Using VSM, TEM, XRD, EDS, and XPS, the specific magnetization, morphology, crystal structure, and bulk and surface chemical compositions have been characterized. Particles in sample (1) are composed of ?-Fe2O3 and CoCl2·6H2O, and particles in samples (2) and (3) have CoFe2O4 in addition to ?-Fe2O3 and CoCl2·6H2O. Detailed analysis shows that the Co-modification can be enhanced by additional NaOH to form ?-Fe2O3/CoFe2O4 core-shell nanoparticles coated by CoCl2·6H2O. The molar, mass, and volume ratios of each phase have been estimated for each sample, and the average density and saturation magnetization are derived. Accordingly, it is revealed that for these nanoparticle systems, the magnetization and coercivity depend on the grain size of the spinel structure crystallites based on ?-Fe2O3 or ?-Fe2O3/CoFe2O4, but the anisotropy constant remains at 1.48×10-1 J/cm3.

Li, Junming; Li, Jian; Chen, Longlong; Lin, Yueqiang; Liu, Xiaodong; Gong, Xiaomin; Li, Decai

2015-01-01

209

Ultrasmall NHC-coated gold nanoparticles obtained through solvent free thermolysis of organometallic Au(i) complexes.  

PubMed

Ultrasmall gold nanoparticles (Au UNPs) represent a unique class of nanomaterials making them very attractive for certain applications. Herein, we developed an organometallic approach to the synthesis of Au UNPs stabilized with the C18H37-NHC ligand by the solvent free thermolysis of [RMIM][Au(C6F5)2] () or [Au(C6F5)(RNHC)] () (with R = C18H37-), by controlling the reactivity of pentafluorophenyl ligands as deprotonating or reductive elimination agents; Au UNPs can be achieved by solvent free thermolysis. Pentafluorophenyl Au(i) complexes and are synthesized from the corresponding ionic and neutral precursors. The presence of long alkyl chain imidazolium or carbene species in the complexes makes them to behave as isotropic liquids at moderate temperatures. The use of multinuclear NMR allows the description of the mechanism of formation of the UNPs as well as the surface state of the UNPs. PMID:25245422

Crespo, Julián; Guari, Yannick; Ibarra, Alfonso; Larionova, Joulia; Lasanta, Tania; Laurencin, Danielle; López-de-Luzuriaga, José M; Monge, Miguel; Olmos, M Elena; Richeter, Sébastien

2014-11-14

210

ZrO2-SiO2 nanosheets with ultrasmall WO3 nanoparticles and their enhanced pseudocapacitance and stability.  

PubMed

We report on the first synthesis of porous ZrO2-SiO2 sheets with well-defined ultrasmall WO3 nanoparticles for energy storage performance. In our system, for improving the surface deterioration of electrode, we use the ZrO2-SiO2 sheets using graphene oxide as a template to access electrode substrate. The synthesized electrode with about 20 nm thickness and about 10 nm pores, has a maximum value of 313 F/g at current density of 1 A/g and a minimum value of 160 F/g at current density of 30 A/g in the specific capacitance. In addition, over 90% of its initial specific capacitance is retained when they are cycled up to 2500 cycles. PMID:25347202

Jeong, Gyoung Hwa; Lee, Hae-Min; Kang, Ji-goo; Lee, Heewoong; Kim, Chang-Koo; Lee, Jae-Hyeok; Kim, Jae-Ho; Kim, Sang-Wook

2014-11-26

211

Solvothermal synthesis of cobalt ferrite nanoparticles loaded on multiwalled carbon nanotubes for magnetic resonance imaging and drug delivery.  

PubMed

Multiwalled carbon nanotube (MWCNT)/cobalt ferrite (CoFe(2)O(4)) magnetic hybrids were synthesized by a solvothermal method. The reaction temperature significantly affected the structure of the resultant MWCNT/CoFe(2)O(4) hybrids, which varied from 6nm CoFe(2)O(4) nanoparticles uniformly coated on the nanotubes at 180°C to agglomerated CoFe(2)O(4) spherical particles threaded by MWCNTs and forming necklace-like nanostructures at 240°C. Based on the superparamagnetic property at room temperature and high hydrophilicity, the MWCNT/CoFe(2)O(4) hybrids prepared at 180°C (MWCNT/CoFe(2)O(4)-180) were further investigated for biomedical applications, which showed a high T(2) relaxivity of 152.8 Fe mM(-1)s(-1) in aqueous solutions, a significant negative contrast enhancement effect on cancer cells and, more importantly, low cytotoxicity and negligible hemolytic activity. The anticancer drug doxorubicin (DOX) can be loaded onto the hybrids and subsequently released in a sustained and pH-responsive way. The DOX-loaded hybrids exhibited notable cytotoxicity to HeLa cancer cells due to the intracellular release of DOX. These results suggest that MWCNT/CoFe(2)O(4)-180 hybrids may be used as both effective magnetic resonance imaging contrast agents and anticancer drug delivery systems for simultaneous cancer diagnosis and chemotherapy. PMID:21664499

Wu, Huixia; Liu, Gang; Wang, Xue; Zhang, Jiamin; Chen, Yu; Shi, Jianlin; Yang, Hong; Hu, He; Yang, Shiping

2011-09-01

212

Ultrasmall superparamagnetic iron oxide nanoparticles for magnetic resonance imaging contrast agent.  

PubMed

Nanotechnology has given scientists new tools for the development of advanced materials for the detection and diagnosis of various types of diseases. In particular, ultrasmall superparamagnetic iron oxides (USPIOs) have been investigated in many biological applications, both in vitro and in vivo. Due to their small size (diameter < 20 nm), these particles are not immediately removed from the circulation by the reticuloendothelial system (RES), have a longer blood half-life, a wider biodistribution and allow potential targeting with appropriate bioconjugates to specific tissues both normal and tumorous. This review will mainly discuss the synthesis of USPIOs and their applications as MRI contrast agent for disease detection. PMID:24730260

Zhao, Xueling; Zhao, Hongli; Chen, Zongyan; Lan, Minbo

2014-01-01

213

Ultra-small nanoparticles of MgTi2O5 embedded in carbon rods with superior rate performance for sodium ion batteries.  

PubMed

Confinement of ultra-small MgTi2O5 nanoparticles in carbon is demonstrated to be an efficient method for fabricating long cycle-life anode material for sodium ion batteries. Superior rate and excellent cyclic capabilities as well as high Coulombic efficiency of the MgTi2O5-C nanocomposite, obtained from pyrolysis of a single molecule precursor, are shown. PMID:25627279

Xie, Fangxi; Deng, Yuanfu; Xie, Ye; Xu, Hongjie; Chen, Guohua

2015-02-12

214

Biofunctionalized, phosphonate-grafted, ultrasmall iron oxide nanoparticles for combined targeted cancer therapy and multimodal imaging.  

PubMed

A novel, inexpensive biofunctionalization approach is adopted to develop a multimodal and theranostic nanoagent, which combines cancer-targeted magnetic resonance/optical imaging and pH-sensitive drug release into one system. This multifunctional nanosystem, based on an ultrasmall superparamagnetic iron oxide (USPIO) nanocore, is modified with a hydrophilic, biocompatible, and biodegradable coating of N-phosphonomethyl iminodiacetic acid (PMIDA). Using appropriate spacers, functional molecules, such as rhodamine B isothiocyanate, folic acid, and methotrexate, are coupled to the amine-derivatized USPIO-PMIDA support with the aim of endowing simultaneous targeting, imaging, and intracellular drug-delivering capability. For the first time, phosphonic acid chemistry is successfully exploited to develop a stealth, multifunctional nanoprobe that can selectively target, detect, and kill cancer cells overexpressing the folate receptor, while allowing real-time monitoring of tumor response to drug treatment through dual-modal fluorescence and magnetic resonance imaging. PMID:19856326

Das, Manasmita; Mishra, Debasish; Dhak, Prasanta; Gupta, Satyajit; Maiti, Tapas Kumar; Basak, Amit; Pramanik, Panchanan

2009-12-01

215

PEG-nanolized ultrasmall selenium nanoparticles overcome drug resistance in hepatocellular carcinoma HepG2 cells through induction of mitochondria dysfunction  

PubMed Central

Gray selenium (Se) is one of the most widely used Se sources with very limited biocompatibility and bioactivity. In the present study, a simple method for the preparation of ultrasmall selenium nanoparticles (SeNPs) through direct nanolization of gray selenium by polyethylene glycol (PEG) was demonstrated. Monodisperse and homogeneous PEG-SeNPs with ultrasmall diameters were successfully prepared under optimized conditions. The products were characterized using various microscopic and spectroscopic methods, and the results suggest that the amphoteric properties of PEG and the coordination between oxygen and selenium atoms contributed to the formation of ultrasmall nanoparticles. PEG-SeNPs exhibited stronger growth inhibition on drug-resistant hepatocellular carcinoma (R-HepG2) cells than on normal HepG2 cells. Dose-dependent apoptosis was induced by PEG-SeNPs in R-HepG2 cells, as evidenced by an increase in the sub-G1 cell population. Further investigation on the underlying molecular mechanisms revealed that depletion of mitochondrial membrane potential and generation of superoxide anions contributed to PEG-SeNPs-induced apoptotic cell death in R-HepG2 cells. Our results suggest that PEG-SeNPs may be a candidate for further evaluation as a chemotherapeutic agent for drug-resistant liver cancer, and the strategy to use PEG200 as a surface decorator could be a highly efficient way to enhance the anticancer efficacy of nanomaterials. PMID:22915845

Zheng, Shanyuan; Li, Xiaoling; Zhang, Yibo; Xie, Qiang; Wong, Yum-Shing; Zheng, Wenjie; Chen, Tianfeng

2012-01-01

216

Ultra-small BaGdF5-based upconversion nanoparticles as drug carriers and multimodal imaging probes.  

PubMed

A new type of drug-delivery system (DDS) was constructed, in which the anti-cancer drug doxorubicin (DOX) was conjugated to the ultra-small sized (sub-10 nm) BaGdF5:Yb(3+)/Tm(3+) based upconversion nanoparticles (UCNPs). This multifunctional DDS simultaneously possesses drug delivery and optical/magnetic/X-ray computed tomography imaging capabilities. The DOX can be selectively released by cleavage of hydrazone bonds in acidic environment, which shows a pH-triggered drug release behavior. The MTT assay shows these DOX-conjugated UCNPs exhibit obvious cytotoxic effect on HeLa cells. Moreover, to improve the upconversion luminescence intensity, core-shell structured UCNPs were constructed. The in vitro upconversion luminescence images of these UCNPs uptaken by HeLa cells show bright emission with high contrast. In addition, these UCNPs were further explored for T1-weighted magnetic resonance (MR) and X-ray computed tomography (CT) imaging in vitro. Long-term in vivo toxicity studies indicated that mice intravenously injected with 10 mg/kg of UCNPs survived for 40 days without any apparent adverse effects to their health. The results indicate that this multifunctional drug-delivery system with optimized size, excellent optical/MR/CT trimodal imaging capabilities, and pH-triggered drug release property is expected to be a promising platform for simultaneous cancer therapy and bioimaging. PMID:24314558

Yang, Dongmei; Dai, Yunlu; Liu, Jianhua; Zhou, Ying; Chen, Yinyin; Li, Chunxia; Ma, Ping'an; Lin, Jun

2014-02-01

217

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

PubMed

We report a synthetic approach for the production of ultra-small (0.6nm) 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 1nm. 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. PMID:25485807

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

218

Silica SBA-15 template assisted synthesis of ultrasmall and homogeneously sized copper nanoparticles.  

PubMed

The synthesis of spherical copper nanoparticles with extremely narrow size distribution by electroless copper deposition on mesoporous silica support is described. The materials were characterized by nitrogen sorption, transmission electron microscopy, x-ray diffractometry and Fourier transform infrared spectroscopy. The copper nanoparticles have a cubic crystalline structure and an average particle size of 5.5 +/- 0.8 nm. The copper nanoparticles are stable, without detectable oxidation or further agglomeration under ambient conditions even after months. These results demonstrate that electroless copper reduction can be conducted and constrained within the mesoporous silica framework, which pave the way for engineered mesoreactors. PMID:21776729

Tsai, H T; Córdoba, J M; Johansson, E M; Ballem, M A; Odén, M

2011-04-01

219

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

PubMed Central

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

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

2013-01-01

220

Magnoelastic coupling in magnetic oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials. To investigate confinement in combination with strong magnetoelastic interactions, we measured the infrared vibrational properties of MnO and CoFe2O4 nanoparticles and their parent compounds. For MnO, a charge and bonding analysis reveals that Born effective charge, local effective charge, total polarizability, and the force constant are overall lower in the nanoparticles compared to the bulk. We find that the spin-lattice coupling drops from ˜7 cm-1 in the single crystal to <1 cm-1 in the nanoparticles. For CoFe2O4, the spectroscopic response is sensitive to the size-induced crossover to the superparamagnetic state, which occurs between 7 and 10 nm, and a spin-phonon coupling analysis supports the core-shell model. Moreover, it provides an estimate of the thickness of the magnetically disordered shell, increasing from 0.4 nm in the 14 nm particles to 0.8 nm in the 5 nm particles, demonstrating that the associated local lattice distortions take place on the length scale of the unit cell. These findings are important for understanding finite length scale effects in magnetic oxides and other more complex functional oxides.

Sun, Qi; Baker, Sheila; Birkel, Christina; Seshadri, Ram; Tremel, Wolfgang; Christianson, Andrew; Musfeldt, Janice

2012-02-01

221

Silicon phthalocyanine covalently functionalized N-doped ultrasmall reduced graphene oxide decorated with pt nanoparticles for hydrogen evolution from water.  

PubMed

To improve the photocatalytic activity of graphene-based catalysts, silicon phthalocyanine (SiPc) covalently functionalized N-doped ultrasmall reduced graphene oxide (N-usRGO) has been synthesized through 1,3-dipolar cycloaddition of azomethine ylides. The obtained product (N-usRGO/SiPc) was characterized by transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, Raman spectra, X-ray photoelectron spectroscopy, fluorescence, and UV-vis spectroscopy. The results demonstrate that SiPc has been successfully grafted on the surface of N-usRGO. The N-usRGO/SiPc nanocomposite exhibits high light-harvesting efficiency covering a range of wavelengths from the ultraviolet to visible light. The efficient fluorescence quenching and the enhanced photocurrent response confirm that the photoinduced electron transfers from the SiPc moiety to the N-usRGO sheet. Moreover, we chose Pt nanoparticles as cocatalyst to load on N-usRGO/SiPc sheets to obtain the optimal H2 production effect. The platinized N-usRGO/SiPc (N-usRGO/SiPc/Pt) demonstrates good hydrogen evolution performance under both UV-vis and visible light (?>400 nm) irradiation. The apparent quantum yields are 1.3% and 0.56% at 365 and 420 nm, respectively. These results reveal that N-usRGO/SiPc/Pt nanocomposite, consolidating the advantages of SiPc, N-usRGO, and Pt NPs, can be a potential candidate for hydrogen evolution from water under UV-vis or visible light irradiation. PMID:25616022

Huang, Jie; Wu, Yijie; Wang, Dandan; Ma, Yufei; Yue, Zongkuan; Lu, Yongtao; Zhang, Mengxin; Zhang, Zhijun; Yang, Ping

2015-02-18

222

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

PubMed Central

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

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

223

High-resolution subunit detection of glutamate receptor by ultrasmall gold nanoparticles.  

PubMed

In this study, we aimed to increase the sensitivity of protein labeling using 1.4 nm gold nanoparticles and glutamate ?2 receptor (GluD2) from the postsynaptic membrane of the Purkinje cells. The very small marker size of the particles reduces the steric hindrance between antibodies leading to a higher labeling efficiency of more than one subunit per single receptor molecule. The nanoparticles are visible in 200 kV dark-field scanning transmission electron microscope on freeze-fractured carbon replica of nervous tissue after plasma cleaning treatment. The different elemental composition of nanoparticles as Au nanogold or CdS quantum dot can be distinguished by energy dispersive X-ray spectroscopy. This method ensures detection of an average of three subunits per GluD2 and often labels all four of them with 1.4 nm Au nanoparticles. It is concluded that this high-resolution microscopic method is useful for exploring the quaternary structure of membrane proteins. PMID:22461110

Loukanov, Alexandre R; Gagov, Hristo

2012-09-01

224

Microwave characterization of magnetically hard and soft ferrite nanoparticles in K-band  

NASA Astrophysics Data System (ADS)

Nano-sized magnetic particles show great promise in improving the performance of microwave absorbers with respect to the corresponding bulk materials. In this paper, magnetically hard and soft ferrite nanoparticles (CoFe2O4 and Fe3O4) having an average size of 14 and 11 nm were prepared by co-precipitation method and characterized in terms of morphology, structure, and magnetic properties. Their permeability and permittivity were measured by a waveguide technique, embedding each sample in a host medium. Their parameters at microwave frequencies were retrieved by comparing different effective medium equations.

Della Pina, C.; Falletta, E.; Ferretti, A. M.; Ponti, A.; Gentili, G. G.; Verri, V.; Nesti, R.

2014-10-01

225

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

NASA Astrophysics Data System (ADS)

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 ?? 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.

Li, Wei; Chen, Minfang

2014-01-01

226

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

NASA Astrophysics Data System (ADS)

We report that ultra-small, monodisperse, water-dispersible magnetite (Fe3O4) 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 Fe3O4 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 Fe3O4 nanoparticles reveal a low r2/r1 ratio of 2.03 (r1 = 1.415 mM-1 s-1, r2 = 2.87 mM-1 s-1), demonstrating that they can be efficient T1 contrast agents. On the other hand, because of the excellent magnetic responsivity, the 13.8 nm-sized Fe3O4 nanoparticles can be readily modified with nitrilotriacetic acid and used to separate the protein simply with the assistance of a magnet. In addition, these Fe3O4 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.

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

2013-02-01

227

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

PubMed

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. PMID:23385623

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

2013-03-01

228

Hollow magnetic microspheres obtained by nanoparticle adsorption on surfactant stabilized microbubbles.  

PubMed

We report on the stabilization of nanoparticle-decorated microbubbles for long periods of time using a synergism between a soluble surfactant and nanoparticles. The soluble surfactant is the perfluoroalkyl phosphate C8F17(CH2)2OP(O)(OH)2 (labeled F8H2Phos) and the nanoparticles (NPs) are 20-25 nm cobalt ferrite (CoFe2O4). The NP-F8H2Phos system has been studied by dynamic light scattering, dynamic magnetic susceptibility measurements and thermal gravimetric analysis. Microbubbles with diameters in the 1-20 ?m range have been stabilized in 0.1 M NaCl brine. Its presence is crucial for the long-term stabilization. The surfactant adsorbs rapidly on bubbles and slows down the bubble shrinkage. Thus, the NPs can attach to the bubble and form a hollow sphere with a rigid shell. The charge screening by NaCl favors the attachment of NPs to the bubble surface. The coverage of the bubbles by the CoFe2O4 nanoparticle layer is confirmed by thermally induced inflation-deflation experiments and the control of bubbles with a magnetic field. PMID:24909785

Kovalenko, Artem; Jouhannaud, Julien; Polavarapu, Prasad; Krafft, Marie Pierre; Waton, Gilles; Pourroy, Geneviève

2014-07-28

229

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

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

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

2013-01-01

230

Copper(0) nanoparticles supported on silica-coated cobalt ferrite magnetic particles: cost effective catalyst in the hydrolysis of ammonia-borane with an exceptional reusability performance.  

PubMed

Herein we report the development of a new and cost-effective nanocomposite catalyst for the hydrolysis of ammonia-borane (NH(3)BH(3)), which is considered to be one of the most promising solid hydrogen carriers because of its high gravimetric hydrogen storage capacity (19.6% wt) and low molecular weight. The new catalyst system consisting of copper nanoparticles supported on magnetic SiO(2)/CoFe(2)O(4) particles was reproducibly prepared by wet-impregnation of Cu(II) ions on SiO(2)/CoFe(2)O(4) followed by in situ reduction of the Cu(II) ions on the surface of magnetic support during the hydrolysis of NH(3)BH(3) and characterized by ICP-MS, XRD, XPS, TEM, HR-TEM and N(2) adsorption-desorption technique. Copper nanoparticles supported on silica coated cobalt(II) ferrite SiO(2)/CoFe(2)O(4) (CuNPs@SCF) act as highly active catalyst in the hydrolysis of ammonia-borane, providing an initial turnover frequency of TOF = 2400 h(-1) at room temperature, which is not only higher than all the non-noble metal catalysts but also higher than the majority of the noble metal based homogeneous and heterogeneous catalysts employed in the same reaction. More importantly, they were easily recovered by using a permanent magnet in the reactor wall and reused for up to 10 recycles without losing their inherent catalytic activity significantly, which demonstrates the exceptional reusability of the CuNPs@SCF catalyst. PMID:22856878

Kaya, Murat; Zahmakiran, Mehmet; Ozkar, Saim; Volkan, Mürvet

2012-08-01

231

Influence of ferrite nanoparticle type and content on the crystallization kinetics and electroactive phase nucleation of poly(vinylidene fluoride).  

PubMed

This work reports on the nucleation of the ?-phase of poly(vinylidene fluoride) (PVDF) by incorporating CoFe(2)O(4) and NiFe(2)O(4) nanoparticles, leading in this way to the preparation of magnetoelectric composites. The fraction of filler nanoparticles needed to produce the same ?- to ?-phase ratio in crystallized PVDF is 1 order of magnitude lower in the cobalt ferrite nanoparticles. The interaction between nanoparticles and PVDF chains induce the all-trans conformation in PVDF segments, and this structure then propagates in crystal growth. The nucleation kinetics is enhanced by the presence of nanoparticles, as corroborated by the increasing number of spherulites with increasing nanoparticle content and by the variations of the Avrami's exponent. Further, the decrease of the crystalline fraction of PVDF with increasing nanoparticle content indicates that an important fraction of polymer chains are confined in interphases with the filler particle. PMID:21545124

Sencadas, Vitor; Martins, Pedro; Pitães, Alexandre; Benelmekki, Maria; Gómez Ribelles, José Luis; Lanceros-Mendez, Senentxu

2011-06-01

232

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

NASA Astrophysics Data System (ADS)

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 in samples with narrowed size distributions. Differential magnetic catch and release has been used as a method for the purification and separation of magnetic nanoparticles. In Chapter 3 the separation metrics are reported. DMCR separates nanoparticles in the mobile phase by magnetic trapping of magnetic nanoparticles against the wall of an open tubular capillary wrapped between two narrowly spaced electromagnetic poles. Using Au and CoFe2O4 nanoparticles as model systems, the loading capacity of the 250 microm diameter capillary is determined to be ˜130 microg, and is scalable to higher quantities with larger bore capillary. Peak resolution in DMCR is externally controlled by selection of the release time (Rt) at which the magnetic flux density is removed, however longer capture times are shown to reduce the capture yield. In addition, the magnetic nanoparticle capture yields are observed to depend on the nanoparticle diameter, mobile phase viscosity and velocity, and applied magnetic flux. Using these optimized parameters, three samples of CoFe 2O4 nanoparticles whose diameters are different by less than 10 nm are separated with excellent resolution and capture yield, demonstrating the capability of DMCR for separation and purification of magnetic nanoparticles. Individual hybrid nanocrystals possess multiple structural units with solid state interfaces, giving them a wide range of possible applications. Synthesis of truly monodisperse nanoparticles and hybrid nanocrystals is a formidable task, which has led us to apply our analytical technique, differential magnetic catch and release, to separate and purify magnetic nanoparticles. Using an open tubular capillary column and electromagnet, DMCR separates magnetic nanoparticles based on a balance of their magnetic moment and hydrodynamic size. Chapter 4 focuses on the purification of real world samples of hybrid nanocrystals including Au-Fe3O4 heterostructures and FePt-Fe3O4 dimers. Samples are characterized with transmission electron microscopy, UV-Vis, X-ray diffraction spectroscopy, selected area electro

Beveridge, Jacob S.

233

CoFe2O4 polypyrrole (PPy) nanocomposites: new multifunctional materials  

Microsoft Academic Search

Spinel ferrites (iron cobalt oxide) were prepared by the microemulsion method at different temperatures and sodium dodecyl sulphate (SDS) surfactant concentrations. Subsequently, a quantity of the different samples were coated with an intrinsically conducting polymer (ICP) shell of polypyrrole. The polymer shell was synthesized by a chemical route after the ferrites particle production. By combining in a single material the

N. Murillo; E. Ochoteco; Y. Alesanco; J. A. Pomposo; J. Rodriguez; J. González; J. J. del Val; M. R. Britel; F. M. Varela-Feria; A. R. de Arellano-López

2004-01-01

234

Thermal conductivity of Zn doped CoFe2O4 ferrites  

Microsoft Academic Search

A series of samples of the type Co1-xZnxFe2O4 (x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0) was prepared as ceramics. The existence of a single phase was confirmed by x-ray studies. The thermal conductivity and specific heat were measured at temperatures ranging from 100°C to 200°C. The thermal conductivity had a minimum value at x = 0.4,

M. I. Abd El-Ati

1994-01-01

235

Signature of ferroelectricity in magnetically ordered Mo-doped CoFe2O4  

Microsoft Academic Search

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

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

2010-01-01

236

A LOW TEMPERATURE PATH TO THE PREPARATION OF CoFe2O4 FERRITE  

Microsoft Academic Search

Ultrafine cobalt ferrite has been prepared by the decomposition of cobalt oxalate-hydrazinate complex, which is used as precursor. The preparation and thermal decomposition of the precursor have been studied using chemical, thermal, and infrared techniques. The precursor decomposes at low temperatures with the effusion of large amounts of gases. The coordination compounds used as chemical precursors have to include, ligands,

E. Chirtop; I. Mitova; R. M. Ion; M. Iliescu

237

Neutron diffraction study of multiferroic Mo-doped CoFe2O4  

NASA Astrophysics Data System (ADS)

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.

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

2015-04-01

238

Nanolamellar magnetoelectric BaTiO3–CoFe2O4 bicrystal  

E-print Network

susceptibility, #7;i, will then be determined by the balance of the magnetic and effective anisotropy energy densities of CFO, #7;i= #1;Is CFO #2; 2 / #3;2#1;Ku CFO+Umel#2;#4;. The quantities Is and Ku designate the saturation magnetization FIG. 1. #1;Color... of eutectic BTO-CFO leads to lamellar micro- structures. Phase separated self-assembled BTO/CFO three- dimensional nanostructures are also formed in pulsed laser deposited films.12 Despite the elegance of this method, eco- nomically motivated efforts...

Ren, Shenqiang; Laver, Mark; Wuttig, Manfred

2009-10-13

239

Multiferroic BaTiO3-CoFe2O4 Nanostructures  

E-print Network

. Schlom,5 M. Wuttig,1 A. Roytburd,1 R. Ramesh1,2 We report on the coupling between ferroelectric is manifested as a change in magnetization at the ferroelectric Curie temperature. Thermodynamic analyses show an additional degree of freedom in the design of actuators, transducers, and storage devices. However

Ramesh, R.

240

Sonochemical Preparation and Size-Dependent Properties of Nanostructured CoFe2O4 Particles  

E-print Network

by a sonochemical approach, first by preparation of the amorphous precursor powders, followed by heat treatment. In the sonochemical process, the mechanism is the cavitation phenomenon, and the reaction occurs inside a microbubble

Prozorov, Ruslan

241

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)

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+-?-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+-?-Fe2O3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeLn)3/4+-?-Fe2O3 NPs enabled to exploit both rHSA (protein functionalities) and (CeLn)3/4+-?-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.

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

2015-01-01

242

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

PubMed

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+)-?-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+)-?-Fe2O3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeLn)(3/4+)-?-Fe2O3 NPs enabled to exploit both rHSA (protein functionalities) and (CeLn)(3/4+)-?-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. PMID:25556693

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

2015-01-30

243

Role of oxygen defects on the magnetic properties of ultra-small Sn1-xFexO2 nanoparticles  

NASA Astrophysics Data System (ADS)

Although the role of oxygen defects in the magnetism of metal oxide semiconductors has been widely discussed, it is been difficult to directly measure the oxygen defect concentration of samples to verify this. This work demonstrates a direct correlation between the photocatalytic activity of Sn1-xFexO2 nanoparticles and their magnetic properties. For this, a series of ˜2.6 nm sized, well characterized, single-phase Sn1-xFexO2 crystallites with x = 0-0.20 were synthesized using tin acetate, urea, and appropriate amounts of iron acetate. X-ray photoelectron spectroscopy confirmed the concentration and 3+ oxidation state of the doped Fe ions. The maximum magnetic moment/Fe ion, ?, of 1.6 × 10-4 ?B observed for the 0.1% Fe doped sample is smaller than the expected spin-only contribution from either high or low spin Fe3+ ions, and ? decreases with increasing Fe concentration. This behavior cannot be explained by the existing models of magnetic exchange. Photocatalytic studies of pure and Fe-doped SnO2 were used to understand the roles of doped Fe3+ ions and of the oxygen vacancies and defects. The photocatalytic rate constant k also showed an increase when SnO2 nanoparticles were doped with low concentrations of Fe3+, reaching a maximum at 0.1% Fe, followed by a rapid decrease of k for further increase in Fe%. Fe doping presumably increases the concentration of oxygen vacancies, and both Fe3+ ions and oxygen vacancies act as electron acceptors to reduce e--h+ recombination and promote transfer of electrons (and/or holes) to the nanoparticle surface, where they participate in redox reactions. This electron transfer from the Fe3+ ions to local defect density of states at the nanoparticle surface could develop a magnetic moment at the surface states and leads to spontaneous ferromagnetic ordering of the surface shell under favorable conditions. However, at higher doping levels, the same Fe3+ ions might act as recombination centers causing a decrease of both k and magnetic moment ?.

Dodge, Kelsey; Chess, Jordan; Eixenberger, Josh; Alanko, Gordon; Hanna, Charles B.; Punnoose, Alex

2013-05-01

244

Grain Size Control of the Magnetic Nanoparticles by Solid State Route Modification  

NASA Astrophysics Data System (ADS)

The CoFe2O4 and NiFe2O4 nanoparticles were synthesized exploiting a co-precipitation method and afterward calcinated at 400 °C through two different experimental apparatus: a conventional muffle and rotatory oven. X-ray diffraction (XRD) analysis revealed that nanocrystalline ferrites grew with a face center cubic structure (fcc) and Fd3 m symmetry space group. XRD, transmission electron microscopy, and magnetic measurements confirmed the compositional homogeneity and the narrow size particle distribution (6-8 nm) of the sample thermally treated in a rotary oven, in all likelihood due to the sample's constant turning movement. The size of the magnetic particles is extremely important and influences the choice of a potential technological application. For this reason, our study emerges as a new and simple innovating procedure to control the size of magnetic nanoparticles.

Barreto, A. C. H.; Santiago, V. R.; Freire, R. M.; Mazzetto, S. E.; Sasaki, J. M.; Vasconcelos, I. F.; Denardin, J. C.; Mele, Giuseppe; Carbone, Luigi; Fechine, P. B. A.

2013-07-01

245

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

PubMed Central

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

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

2014-01-01

246

Annealing relaxation of ultrasmall gold nanostructures  

NASA Astrophysics Data System (ADS)

Except serving as an excellent gift on proper occasions, gold finds applications in life sciences, particularly in diagnostics and therapeutics. These applications were made possible by gold nanoparticles, which differ drastically from macroscopic gold. Versatile surface chemistry of gold nanoparticles allows coating with small molecules, polymers, biological recognition molecules. Theoretical investigation of nanoscale gold is not trivial, because of numerous metastable states in these systems. Unlike elsewhere, this work obtains equilibrium structures using annealing simulations within the recently introduced PM7-MD method. Geometries of the ultrasmall gold nanostructures with chalcogen coverage are described at finite temperature, for the first time.

Chaban, Vitaly

2015-01-01

247

The need for stable, mono-dispersed, and biofunctional magnetic nanoparticles for one-step magnetic immunoassays  

NASA Astrophysics Data System (ADS)

We have developed a magnetic immunoassay system (MIA) using magnetic nanoparticle markers for biomolecule detection. We have magnetically characterized multi-core magnetic nanoparticles (MNPs) containing single-domain crystals of Fe3O4 and CoFe2O4 with our system using a high temperature superconducting quantum interference device as detector. We use a Helmholtz coil to excite the MNPs and study the AC-susceptibility. The data is fit to a model and information about the particle size distribution of the MNP system is extracted. We observe high stability of the unfunctionalized MNPs. However, our MIA measurements require stable functionalized MNPs. We have found a significant increase in hydrodynamic size of the functionalized MNP systems in the course of just a few days caused by agglomeration behaviour. Separate measurements performed at Imego AB with their AC-Susceptometer, DynoMAG®, confirm these findings. Without stable, functionalized MNPs MIAs of this kind are impossible.

Öisjöen, F.; Schneiderman, J. F.; Astalan, A. P.; Kalabukhov, A.; Johansson, C.; Winkler, D.

2010-01-01

248

Evaluation of iron-cobalt/ferrite core-shell nanoparticles for cancer thermotherapy  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles (MNPs) offer promise for local hyperthermia or thermoablative cancer therapy. Magnetic hyperthermia uses MNPs to heat cancerous regions in an rf field. Metallic MNPs have larger magnetic moments than iron oxides, allowing similar heating at lower concentrations. By tuning the magnetic anisotropy in alloys, the heating rate at a particular particle size can be optimized. Fe-Co core-shell MNPs have protective CoFe2O4 shell which prevents oxidation. The oxide coating also aids in functionalization and improves biocompatibility of the MNPs. We predict the specific loss power (SLP) for FeCo (SLP ˜450W /g) at biocompatible fields to be significantly larger in comparision to oxide materials. The anisotropy of Fe-Co MNPs may be tuned by composition and/or shape variation to achieve the maximum SLP at a desired particle size.

Habib, A. H.; Ondeck, C. L.; Chaudhary, P.; Bockstaller, M. R.; McHenry, M. E.

2008-04-01

249

2014 Drasler et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution Non Commercial (unported, v3.0) License. The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3  

E-print Network

Full Text article http://dx.doi.org/10.2147/IJN.S57671 effects of magnetic cobalt ferrite nanoparticles cobalt ferrite (CoFe2 O4 ) or citric acid (CA)-adsorbed CoFe2 O4 nanoparticles dispersed in phosphate

Iglic, Ales

250

Ferrite nanoparticles for future heart diagnostics  

NASA Astrophysics Data System (ADS)

Normally, CoFe2O4 has been known as ferromagnetic ferrite with a quite large magnetic moment. However, since we aim to inject the particles into the human body, we are also interested in ZnFe2O4 because in the human body, Fe and Zn exist, so that adding ZnFe2O4 is safer. In both cases, the nanoparticles are coated by silica in order to get rid of toxicity. Our main purpose is to test whether these nanoparticles affect the contractile function of heart cells. Our results on rat's heart cells have shown that both Zn and Co ferrites improved the contractility of heart cells. Notably, although both nanoparticles increased contraction and delayed relaxation, Co ferrites induced a greater contraction but with a slower relaxation. We can theoretically argue that the magnetization effects of the quantum dots have a considerable effect on the pulsating properties of the heart cells. Through this effect, the locally applied magnetic field is able to induce as well as turn on/off various regular beating patterns, thus, resetting the heart beatings.

Hong, Nguyen Hoa; Raghavender, A. T.; Ciftja, O.; Phan, M.-H.; Stojak, K.; Srikanth, H.; Zhang, Yin Hua

2013-08-01

251

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

PubMed

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 (?-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. PMID:24309194

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

2014-02-01

252

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

Microsoft Academic Search

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

I. Panneer Muthuselvam; R. N. Bhowmik

2010-01-01

253

Magnetic properties of CoFe2O4 thin films prepared by a sol-gel method  

Microsoft Academic Search

Thin films with cobalt ferrite layers on thermally oxidized silicon wafers were fabricated by a sol-gel method. Magnetic and structural properties of the films were investigated with an x-ray diffractometer, a vibrating sample magnetometer and atomic force microscopy. The crystallization temperature for Co ferrite thin films was determined by using Mössbauer spectroscopy. Co ferrite films annealed at and above 450

Jae-Gwang Lee; Jae Yun Park; Young-Jei Oh; Chul Sung Kim

1998-01-01

254

Multiferroic properties of Pb(Zr,Ti)O3\\/CoFe2O4 composite thin films  

Microsoft Academic Search

In the present work we report multiferroic behavior in lead zirconate titanate (PZT)-cobalt iron oxide (CFO) composite thin films. It is found that upon annealing, the multilayered structures are intermixed at least partially, and CFO is phase separated into PZT matrix to form a composite film. The phase separation behavior has been characterized by x-ray photoelectron spectroscopy depth profiling of

N. Ortega; P. Bhattacharya; R. S. Katiyar; P. Dutta; A. Manivannan; M. S. Seehra; I. Takeuchi; S. B. Majumder

2006-01-01

255

Effect of non-magnetic ion substitution on the magnetoelastic properties of CoFe2O4 films  

NASA Astrophysics Data System (ADS)

We report on the structural and magnetic properties of CoFe1.9Zr0.1O4 films under epitaxial strain. The films are grown with high structural quality on MgO, SrTiO3, and piezoelectric Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrates by pulsed laser deposition. The substrate-induced strain is found effective to alter the magnetic anisotropy of the films. Reversible strain measurements using the piezoelectric substrates are providing evidence that nearly bulk-like magnetoelastic properties are maintained for films of down to at least 25 nm thickness. This is in contrast to unsubstituted cobalt ferrite films and suggests that a chemical control of the spinel lattice provides a promising route to optimize the tunability of the magnetic properties of thin ferrite films.

Rus, S. F.; Vlazan, P.; Herklotz, A.

2014-07-01

256

Nanolamellar magnetoelectric BaTiO3CoFe2O4 bicrystal Shenqiang Ren,1  

E-print Network

, Maryland 20742-2115, USA 2 NIST Center for Neutron Research, Gaithersburg, Maryland 20899-6103, USA in which ferroelectricity and ferromagnetism coexist in a single crystal at room temperature would present/CFO nanostructure that persists throughout entire crystal grains. We have discovered that the quinary system Fe

Rubloff, Gary W.

257

Electrical manipulation of interface conduction in BiFeO3-CoFe2O4 columnar heterostructures  

NASA Astrophysics Data System (ADS)

Complex oxide interfaces emerge as one of the most exciting subjects in the condensed-matter field due to its unique physical properties and new possibilities for next-generation electronic devices. Recently, we found local conduction at the tubular interfaces of self-assembled BiFeO3 (BFO)-CoFe2O4 (CFO) heterostructures. In this study, to further investigate the electrical properties of the tubular oxide interface, conductive atomic force microscopy (CAFM) at different temperatures was performed to examine the sample. The origin of local conduction at the BFO-CFO vertical interface is identified as a result of the accumulation of oxygen vacancies. In addition, the interface conduction can be modulated with non-volatile and reversible behaviors via an external electric field. This memritor-like phenomenon can be understood owing to the movement of oxygen vacancies driven by the applied bias. The bias causes the oxygen vacancies either accumulate or deplete to the metal contact tip, which in turn affect the resistance at the tubular interface. Our results provide the control of the conduction at complex oxide interfaces and suggest the possibility for new devices based on complex oxide interfaces.

Chen, Yi-Chun; Hsieh, Ying-Hui; Liou, Jia-Ming; Shen, Chia-Ying; Chu, Ying-Hao

2013-03-01

258

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

PubMed

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). PMID:20566333

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

2010-09-01

259

Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles.  

PubMed

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

Girgis, Emad; Wahsh, Mohamed Ms; Othman, Atef Gm; Bandhu, Lokeshwar; Rao, Kv

2011-01-01

260

Synthesis, magnetic and optical properties of core/shell Co1- x Zn x Fe2O4/SiO2 nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Girgis, Emad; Wahsh, Mohamed Ms; Othman, Atef Gm; Bandhu, Lokeshwar; Rao, Kv

2011-07-01

261

Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles  

PubMed Central

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

2011-01-01

262

Passing through the renal clearance barrier: toward ultrasmall sizes with stable ligands for potential clinical applications  

PubMed Central

The use of nanoparticles holds promise for medical applications, such as X-ray imaging, photothermal therapy and radiotherapy. However, the in vivo toxicity of inorganic nanoparticles raises some concern regarding undesirable side effects which prevent their further medical application. Ultrasmall sub-5.5 nm particles can pass through the barrier for renal clearance, minimizing their toxicity. In this letter we address some recent interesting work regarding in vivo toxicity and renal clearance, and discuss the possible strategy of utilizing ultrasmall nanomaterials. We propose that small hydrodynamic sized nanoclusters can achieve both nontoxic and therapeutic clinical features. PMID:24812507

Zhang, Xiao-Dong; Yang, Jiang; Song, Sha-Sha; Long, Wei; Chen, Jie; Shen, Xiu; Wang, Hao; Sun, Yuan-Ming; Liu, Pei-Xun; Fan, Saijun

2014-01-01

263

Enigmatic, ultrasmall, uncultivated Archaea  

SciTech Connect

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.

Baker, Brett J. [University of California, Berkeley; Comolli, Luis [Lawrence Berkeley National Laboratory (LBNL); Dick, Gregory J. [University of California, Berkeley; Hauser, Loren John [ORNL; Hyatt, Philip Douglas [ORNL; Dill, Brian [ORNL; Land, Miriam L [ORNL; Verberkmoes, Nathan C [ORNL; Hettich, Robert {Bob} L [ORNL; Banfield, Jillian F. [University of California, Berkeley

2010-01-01

264

Chemistry and Physics of Lipids 178 (2014) 5262 Contents lists available at ScienceDirect  

E-print Network

( -Fe2O3) nanoparticles, neutral and negatively charged cobalt ferrite (CoFe2O4) nanoparticles were elasticity modulus was observed for cobalt ferrite nanoparticles. The experimental results were supported

Iglic, Ales

265

Gene Delivery: Large-Pore Ultrasmall Mesoporous Organosilica Nanoparticles: Micelle/Precursor Co-templating Assembly and Nuclear-Targeted Gene Delivery (Adv. Mater. 2/2015).  

PubMed

Mesoporous organosilica nanoparticles (MONs) with concurrent well-defined large pores, small particle sizes, and unique molecularly organic-inorganic hybrid compositions are successfully synthesized by Y. Chen, Y. Li, J. Shi, and co-workers on page 215, via a novel micelle/precursor co-templating assembly (M/P-CA) strategy. Furthermore, a MONs-PTAT conjugated system is constructed for nuclear-targeted direct transportation of plasmids. PMID:25572845

Wu, Meiying; Meng, Qingshuo; Chen, Yu; Du, Yanyan; Zhang, Lingxia; Li, Yaping; Zhang, Linlin; Shi, Jianlin

2015-01-01

266

Strong and moldable cellulose magnets with high ferrite nanoparticle content.  

PubMed

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. PMID:25331121

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

2014-11-26

267

Synthesis, characterization and magnetic properties of carbon nanotubes decorated with magnetic MIIFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Ali, Syed Danish; Hussain, Syed Tajammul; Gilani, Syeda Rubina

2013-04-01

268

Preliminary evaluation of a 99mTc labeled hybrid nanoparticle bearing a cobalt ferrite core: in vivo biodistribution.  

PubMed

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. PMID:22852467

Psimadas, Dimitrios; Baldi, Giovanni; Ravagli, Costanza; Bouziotis, Penelope; Xanthopoulos, Stavros; Franchini, Mauro Comes; Georgoulias, Panagiotis; Loudos, George

2012-08-01

269

Externally controlled on-demand release of anti-HIV drug using magneto-electric nanoparticles as carriers.  

PubMed

Although highly active anti-retroviral therapy has resulted in remarkable decline in the morbidity and mortality in AIDS patients, inadequately low delivery of anti-retroviral drugs across the blood-brain barrier results in virus persistence. The capability of high-efficacy-targeted drug delivery and on-demand release remains a formidable task. Here we report an in vitro study to demonstrate the on-demand release of azidothymidine 5'-triphosphate, an anti-human immunodeficiency virus drug, from 30 nm CoFe2O4@BaTiO3 magneto-electric nanoparticles by applying a low alternating current magnetic field. Magneto-electric nanoparticles as field-controlled drug carriers offer a unique capability of field-triggered release after crossing the blood-brain barrier. Owing to the intrinsic magnetoelectricity, these nanoparticles can couple external magnetic fields with the electric forces in drug-carrier bonds to enable remotely controlled delivery without exploiting heat. Functional and structural integrity of the drug after the release was confirmed in in vitro experiments with human immunodeficiency virus-infected cells and through atomic force microscopy, spectrophotometry, Fourier transform infrared and mass spectrometry studies. PMID:23591874

Nair, Madhavan; Guduru, Rakesh; Liang, Ping; Hong, Jeongmin; Sagar, Vidya; Khizroev, Sakhrat

2013-01-01

270

One-step synthesis of stoichiometrically defined metal oxide nanoparticles at room temperature.  

PubMed

A great variety of metal oxide nanoparticles have been readily synthesized by using alkali metal oxides, M(2)O (M is Na or Li) and soluble metal salts (metal chlorides) in polar organic solutions, for example, methanol and ethanol, at room temperature. The oxidation states of the metals in the resulting metal oxides (Cu(2)O, CuO, ZnO, Al(2)O(3), Fe(2)O(3), Bi(2)O(3), TiO(2), SnO(2), CeO(2), Nb(2)O(5), WO(3), and CoFe(2)O(4)) range from 1 to 6 and remain invariable through the reactions where good control of stoichiometry is achieved. Metal oxide nanoparticles are 1-30 nm and have good monodispersivity and displayed comparable optical spectra. These syntheses are based on a general ion reaction pathway during which the precipitate occurs when O(2-) ions meet metal cations (M(n+)) in anhydrous solution and the reaction equation is M(n+) + n/2 O(2-) --> MO(n/2) (n=1-6). PMID:18991306

Chen, Lan; Xu, Ju; Tanner, David A; Phelan, Richard; Van der Meulen, Machteld; Holmes, Justin D; Morris, Michael A

2009-01-01

271

High longitudinal relaxivity of ultra-small gadolinium oxide prepared by microsecond laser ablation in diethylene glycol  

SciTech Connect

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.

Luo Ningqi; Xiao Jun; Hu Wenyong; Chen Dihu [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Tian Xiumei [State Key Laboratory of Oncology in South China, Imaging Diagnosis and Interventional Center, Sun Yat-sen University, Cancer Center, Guangzhou 510060 (China); Department of Biomedical Engineering, Guangzhou Medical University, Guangzhou 510182 (China); Yang Chuan; Li Li [State Key Laboratory of Oncology in South China, Imaging Diagnosis and Interventional Center, Sun Yat-sen University, Cancer Center, Guangzhou 510060 (China)

2013-04-28

272

Facile Syntheses of Monodisperse Ultra-Small Au Clusters  

SciTech Connect

During our effort to synthesize the tetrahedral Au20 cluster, we found a facile synthetic route to prepare monodisperse suspensions of ultra-small Au clusters AuN (N<12) using diphosphine ligands. In our monophasic and single-pot synthesis, a Au precursor ClAu(I)PPh3 and a bidentate phosphine ligand P(Ph)2(CH2)MP(Ph)2 (Ph = phenyl) are dissolved in an organic solvent. Au(I) is reduced slowly by a borane-tert-butylamine complex to form Au clusters coordinated by the diphosphine ligand. The Au clusters are characterized by both high resolution mass spectrometry and UV-Vis absorption spectroscopy. We found that the mean cluster size obtained depends on the chain length M of the ligand. In particular, a single monodispersed Au11 cluster is obtained with the P(Ph)2(CH2)3P(Ph)2 ligand, whereas P(Ph)2(CH2)MP(Ph)2 ligands with M = 5 and 6 yield Au10 and Au8 clusters. The simplicity of our synthetic method makes it suitable for large-scale production of nearly monodisperse ultrasmall Au clusters. It is suggested that diphosphines provide a set of flexible ligands to allow size-controlled synthesis of Au nanoparticles.

Bertino, Massimo F.; Sun, Zhong-Ming; Zhang, Rui; Wang, Lai S.

2006-11-02

273

Ultra-small particles of iron oxide as peroxidase for immunohistochemical detection  

NASA Astrophysics Data System (ADS)

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.

Wu, Yihang; Song, Mengjie; Xin, Zhuang; Zhang, Xiaoqing; Zhang, Yu; Wang, Chunyu; Li, Suyi; Gu, Ning

2011-06-01

274

The role of annealing temperature and bio template (egg white) on the structural, morphological and magnetic properties of manganese substituted MFe2O4 (M=Zn, Cu, Ni, Co) nanoparticles  

NASA Astrophysics Data System (ADS)

Manganese substituted ferrites (ZnFe2O4, CuFe2O4, NiFe2O4 and CoFe2O4) have been prepared in the bio template medium by using a simple evaporation method. The annealing temperature plays an important position on changing particle size and morphology of the mixed ferrite nanoparticles were found out by X-ray diffraction, transmission electron microscopy and scanning electron microscopy methods. The role of manganese substitution in the mixed ferrite nanoparticles were also analyzed for different annealing temperature. The substitution of Mn also creates a vital change in magnetic properties which is studied by using vibrating sample magnetometer (VSM). These spinel ferrites are decomposed to ?-Fe2O3 after annealing above 550 °C in air. However, ?-Fe2O3 phase was slowly vanished after ferrites annealing above 900 °C. The effect of this secondary phase on the structural change and magnetic properties of the mixed ferrite nanoparticles is discussed.

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

2014-02-01

275

Synthesis, size and magnetic properties of controllable MnFe2O4 nanoparticles with versatile surface functionalities.  

PubMed

Size controllable MnFe2O4 superparamagnetic nanoparticles (NPs) were prepared by a solvothermal method using low-cost metal oleate as the source. The particle size, chemical composition and magnetic properties were investigated. The MnFe2O4 nanomaterials exhibit high colloidal stabilities and superparamagnetic properties, with an average particle size in the range of 2 to 10 nm by modifying the reaction condition, such as surfactant, reaction temperature and reaction time. By changing Mn(2+) to different cations, CoFe2O4, NiFe2O4, and ZnFe2O4 with different magnetic properties could be obtained. The hydrophobic MnFe2O4 NPs could also be modified with many surfactants, such as cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl benzene sulfonate (SDBS) and sodium dodecylsulfate (SDS), with the aim of achieving high zeta-potential hydrophilic bilayer-coated MnFe2O4 NPs. In addition, the water soluble MnFe2O4 magnetic NPs can be applied to the removal of Pb(ii) from waste water with good recovery under external magnetic field. PMID:24847889

Bateer, Buhe; Tian, Chungui; Qu, Yang; Du, Shichao; Yang, Ying; Ren, Zhiyu; Pan, Kai; Fu, Honggang

2014-07-14

276

Magneto-electric Nanoparticles to Enable Field-controlled High-Specificity Drug Delivery to Eradicate Ovarian Cancer Cells  

NASA Astrophysics Data System (ADS)

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.

Guduru, Rakesh; Liang, Ping; Runowicz, Carolyn; Nair, Madhavan; Atluri, Venkata; Khizroev, Sakhrat

2013-10-01

277

Magneto-electric Nanoparticles to Enable Field-controlled High-Specificity Drug Delivery to Eradicate Ovarian Cancer Cells  

PubMed Central

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. PMID:24129652

Guduru, Rakesh; Liang, Ping; Runowicz, Carolyn; Nair, Madhavan; Atluri, Venkata; Khizroev, Sakhrat

2013-01-01

278

Multiferroic CoFe2O4-Pb(Zr0.53Ti0.47)O3 thick films for magnetoelectric application.  

E-print Network

??Recent theoretical breakthroughs in understanding the concurrence of magnetic and electrical ordering, combined with advances in thin film growth techniques and experimental methods for observing… (more)

Chen, Wei.

2012-01-01

279

ENGINEERING OF SELF-ASSEMBLED MULTIFERROIC NANOSTRUCTURES IN PbTiO3-CoFe2O4 THIN FILMS .  

E-print Network

??Multiferroic materials which display a coexistence of ferroelectric and ferromagnetic properties attract considerable interest for their potential for novel device applications as well as for… (more)

Li, jianhua

2006-01-01

280

Influence of thermal annealing on the dielectric properties and electrical relaxation behaviour in nanostructured CoFe2O4 ferrite  

Microsoft Academic Search

Nanocrystalline cobalt ferrite particles with the grain size of 8 nm were synthesized by using the co-precipitation technique and subsequently heat treated to obtain larger grain sizes. The effect of grain size, cation distribution, frequency and temperature on their dielectric properties has been studied. The dielectric constant (?') of 8 nm grains is found to be an order of magnitude

N. Sivakumar; A. Narayanasamy; C. N. Chinnasamy; B. Jeyadevan

2007-01-01

281

Sum Rules in X-Ray Resonant Raman Scattering: Recovering the Co Ground State Information in CoFe2O4 as a Test Case  

Microsoft Academic Search

We present an approach to x-ray resonant Raman scattering suitable for sum-rule analysis. In magnetic systems it gives ground state information as represented by an expansion in coupled multipoles of orbital and spin moments. The experiment is based on the angular dependence of the integrated peak intensities. In 3d transition elements one obtains information up to order 4 from the

L. Braicovich; A. Tagliaferri; G. van der Laan; G. Ghiringhelli; N. B. Brookes

2003-01-01

282

Síntese botton up de nanopartículas magnéticas core-shell do tipo ?-Fe2O3@CoFe2O4 visando aplicações em magneto-hipertermia.  

E-print Network

??Dissertação (mestrado)—Universidade de Brasília, Faculdade UnB Planaltina, Programa de Pós-Graduação em Ciência de Materiais, 2013. O interesse pelos nanomateriais ocorre da possibilidade de manipulação de… (more)

Cruz, Carlos José Domingos da

2013-01-01

283

Magnetic properties of nano-crystalline Gd or Pr-substituted CoFe2O4 synthesized by the citrate precursor technique  

Microsoft Academic Search

The magnetic properties of nano-crystalline CoMxFe2-xO4 (where M=Gd and Pr and \\/x=0, 0.1 and 0.2) powders prepared by a citrate precursor technique have been studied by using vibrating sample magnetometer (VSM). The crystallite sizes of the materials were varied by altering the synthetic conditions and are within the range of a minimum of 6.8nm and a maximum of 87.5nm. The

R. N. Panda; J. C. Shih; T. S. Chin

2003-01-01

284

Maxwell-Wagner space charge effects on the Pb(Zr,Ti)O3-CoFe2O4 multilayers  

Microsoft Academic Search

Electrical properties of Pb(Zr0.53Ti0.47)O3\\/CoFe3O4 (PZT\\/CFO) multilayers (MLs) were investigated in the light of Maxwell-Wagner space charge effects and the data differ from those of BiFeO3\\/CoFe3O4 nanocomposites. These MLs are of special interest as weak field sensors of magnetism. These data fit the Maxwell-Wagner space charge model of Catalan et al. [Appl. Phys. Lett. 77, 3078 (2000)]. Very large temperature shifts

N. Ortega; Ashok Kumar; R. S. Katiyar; J. F. Scott

2007-01-01

285

The crystallographic, magnetic properties of Al, Ti doped CoFe2O4 powders grown by sol-gel method  

Microsoft Academic Search

The Al and Ti doped cobalt ferrite powders, Al0.2CoFe1.8O4 and Ti0.2Co1.2Fe1.6O4, have been fabricated by the sol-gel method, and the powders' crystallographic and magnetic properties related to the annealing temperature are being studied. Using X-ray diffraction and Mössbauer spectroscopy, the formation of crystallized particles has been confirmed in Al0.2CoFe1.8O4 and Ti0.2Co1.2Fe1.6O4 ferrite powders. The Al doped cobalt ferrite, Al0.2CoFe1.8O4, has

Kwang Pyo Chae; Jae-Gwang Lee; Hyzzuck Su Kweon; Young Bae Lee

2004-01-01

286

Effects of In3+ substitution on structural properties, cation distribution and Mössbauer spectra of CoFe2O4 ferrite  

NASA Astrophysics Data System (ADS)

The use of non-destructive, high resolution technique namely Mössbauer spectroscopy is discussed in detail for the investigation of structural and magnetic properties of Fe based indium substituted cobalt ferrites. The polycrystalline samples of CoFe2-xInxO4 (x = 0.2, 0.6) were prepared by double sintering solid state reaction method. To ensure a single phase formation of the as prepared samples the X-ray diffraction (XRD) data of the powdered samples was Rietveld refined using Fd3m space group. An excellent agreement is obtained between the integrated intensity ratios of 57 Fe spectra at A- and B-sites and those calculated on the basis of cation distribution the cation distribution obtained data analysis. The results of Mössbauer spectra and cation distribution are also correlated well with magnetization versus applied field (M-H) study.

Kumar, Ravi; Pandit, Rabia; Sharma, K. K.; Kaur, Pawanpreet

2014-04-01

287

On the correlation between nanoscale structure and magnetic properties in ordered mesoporous cobalt ferrite (CoFe2O4) thin films.  

PubMed

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. PMID:20698611

Quickel, Thomas E; Le, Van H; Brezesinski, Torsten; Tolbert, Sarah H

2010-08-11

288

Raman scattering spectra, magnetic and ferroelectric properties of BiFeO3-CoFe2O4 nanocomposite thin films structure  

NASA Astrophysics Data System (ADS)

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.

Tyagi, Mintu; Kumari, Mukesh; Chatterjee, Ratnamala; Sharma, Puneet

2014-09-01

289

Structural, electrical, magnetic and dielectric properties of rare-earth substituted cobalt ferrites nanoparticles synthesized by the co-precipitation method  

NASA Astrophysics Data System (ADS)

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.

Nikumbh, A. K.; Pawar, R. A.; Nighot, D. V.; Gugale, G. S.; Sangale, M. D.; Khanvilkar, M. B.; Nagawade, A. V.

2014-04-01

290

RGD-conjugated iron oxide magnetic nanoparticles for magnetic resonance imaging contrast enhancement and hyperthermia.  

PubMed

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 ?(v)?? 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. PMID:23796630

Zheng, S W; Huang, M; Hong, R Y; Deng, S M; Cheng, L F; Gao, B; Badami, D

2014-03-01

291

Interrogation of CoxZnyNizFe2O4 ferrite nanoparticles for insight into specific power loss for medical hyperthermia  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles (MNPs) have shown to be viable candidates as heat sources for magnetic hyperthermia under an alternating magnetic field. The present work investigates heating characteristics of sol-gel processed ferro-magnetic CoxZnyNizFe2O4 (ferrite) nanoparticles with different magnetic properties. The nanoparticles were irradiated by a radio-frequency magnetic field through a 5-turns coil using a 1.2 kW heating system with variable frequency in the 295-315 kHz range and a maximum current output of 100 A. Higher specific power losses were measured for nanoparticles that had lower coercivities. The advantage of having a high specific power loss for clinical applications is that a minute amount of nanoparticle has to be introduced in the body to adequately destroy malignant tumor cells.[4pt] |c|c|c|c|c|c| Name & Grain Size & Mr & Ms & Hc & SPL100A&(nm) & (emu/g) & (emu/g) & (Oe) & (W/g^2)Ni0.5Zn0.5Fe2O4 & 48.7 & 2.85 & 47.5 & 42.2 & 84 ± 2Co0.4Ni0.4Zn0.2Fe2O4 & 46 & 3.29 & 26.2 & 75.3 & 28 ± 3NiFe2O4 & 42.9 & 3.47 & 14.8 & 146 & 17.0 ± 0.5CoFe2O4 & 34.5 & 7.01 & 22.2 & 626 & 0.64 ± 0.05

Jagoo, Zafrullah; Kozlowski, Gregory; Turgut, Zafer; Rebrov, Evgeny

2012-04-01

292

Study of magnetic and structural properties of ferrofluids based on cobalt-zinc ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

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 increase of the Zn at%. Finally, our magnetic nanoparticles are not very hard magnetic materials given that the hysteresis loop is small and for this reason Co(1-x)ZnxFe2O4 nanoparticles are considered as soft magnetic material.

López, J.; González-Bahamón, L. F.; Prado, J.; Caicedo, J. C.; Zambrano, G.; Gómez, M. E.; Esteve, J.; Prieto, P.

2012-02-01

293

Atomic scale dynamics of ultrasmall germanium clusters  

PubMed Central

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. PMID:22692540

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.

2012-01-01

294

Atomic scale dynamics of ultrasmall germanium clusters.  

PubMed

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. PMID:22692540

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

2012-01-01

295

Nickel-doped cobalt ferrite nanoparticles: efficient catalysts for the reduction of nitroaromatic compounds and photo-oxidative degradation of toxic dyes  

NASA Astrophysics Data System (ADS)

This study deals with the exploration of NixCo1-xFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) ferrite nanoparticles as catalysts for reduction of 4-nitrophenol and photo-oxidative degradation of Rhodamine B. The ferrite samples with uniform size distribution were synthesized using the reverse micelle technique. The structural investigation was performed using powder X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive X-ray and scanning tunneling microscopy. The spherical particles with ordered cubic spinel structure were found to have the crystallite size of 4-6 nm. Diffused UV-visible reflectance spectroscopy was employed to investigate the optical properties of the synthesized ferrite nanoparticles. The surface area calculated using BET method was found to be highest for Co0.4Ni0.6Fe2O4 (154.02 m2 g-1). Co0.4Ni0.6Fe2O4 showed the best catalytic activity for reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4 as reducing agent, whereas CoFe2O4 was found to be catalytically inactive. The reduction reaction followed pseudo-first order kinetics. The effect of varying the concentration of catalyst and NaBH4 on the reaction rates was also scrutinized. The photo-oxidative degradation of Rhodamine B, enhanced oxidation efficacy was observed with the introduction of Ni2+ in to the cobalt ferrite lattice due to octahedral site preference of Ni2+. Almost 99% degradation was achieved in 20 min using NiFe2O4 nanoparticles as catalyst.

Singh, Charanjit; Goyal, Ankita; Singhal, Sonal

2014-06-01

296

Ultrasmall spot size scanning laser ophthalmoscopy  

PubMed Central

An ultrasmall spot size scanning laser ophthalmoscope has been developed that employs an annular aberration-corrected incident beam to increase the effective numerical aperture of the eye thereby reducing the width of the probing light spot. Parafovea and foveal cone photoreceptor visibility determined from small area retinal image scans are discussed from the perspective of mode matching between the focused incident beam and the waveguide modes of individual cones. The cone visibility near the fovea centralis can be increased with the annular illumination scheme whereas the visibility of larger parafovea cones drops significantly as a consequence of poorer mode match. With further improvements of the implemented wavefront correction technology it holds promise for individual cone-photoreceptor imaging at the fovea centralis and for optical targeting of the retina with increased resolution. PMID:21698022

Vohnsen, Brian; Rativa, Diego

2011-01-01

297

Brine Assemblages of Ultrasmall Microbial Cells within the Ice Cover of Lake Vida, Antarctica  

PubMed Central

The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (?0.2-?m) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 ?m 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 ?m, 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 ?m among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-?m-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-?m-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-?m-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-?m-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

Kuhn, Emanuele; Ichimura, Andrew S.; Peng, Vivian; Fritsen, Christian H.; Trubl, Gareth; Doran, Peter T.

2014-01-01

298

Brine assemblages of ultrasmall microbial cells within the ice cover of Lake Vida, Antarctica.  

PubMed

The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (?0.2-?m) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 ?m 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 ?m, 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 ?m among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-?m-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-?m-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-?m-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-?m-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

Kuhn, Emanuele; Ichimura, Andrew S; Peng, Vivian; Fritsen, Christian H; Trubl, Gareth; Doran, Peter T; Murray, Alison E

2014-06-01

299

Fabrication and microwave absorption of carbon nanotubes\\/CoFe2O4 spinel nanocomposite  

Microsoft Academic Search

A large-scale carbon nanotube\\/CoFe2O4 (CNTs\\/CoFe2O4) spinel nanocomposite has been fabricated by a chemical vapor deposition method using CoFe2O4 nanoparticles as catalysts. A uniform mixture of CNTs and CoFe2O4 nanoparticles was obtained simultaneously. The structure and chemical composition of the product were investigated using various techniques, such as x-ray diffraction, high-resolution transmission electron microscopy, and electron energy loss spectroscopy. It was

R. C. Che; C. Y. Zhi; C. Y. Liang; X. G. Zhou

2006-01-01

300

Ultrasmall PtSn alloy catalyst for ethanol electro-oxidation reaction  

NASA Astrophysics Data System (ADS)

To improve the electrocatalytic properties for an ethanol electro-oxidation reaction, modifications of Pt nanocrystallites have been used by alloying with other elements such as Ru, Sn, and Au. Here we demonstrate carbon supported Pt3Sn alloy electrocatalyst (Pt3Sn/C) synthesized using a thermal-decomposition method. The PtSn/C prepared by the present synthetic process shows a homogeneous distribution of ultrasmall alloy nanoparticles (?2.5 nm) in the presence of Pt and Sn metallic states. At 0.45 V, the Pt3Sn/C (0.35 mA cm-2) exhibits much higher current density as compared with Pt/C (0.13 mA cm-2). In an electrochemical stability test, the Pt3Sn/C supported quite high current density and thus showed 3% current reduction after the stability test.

Kwak, Da-Hee; Lee, Young-Woo; Han, Sang-Beom; Hwang, Eui-Tak; Park, Han-Chul; Kim, Min-Cheol; Park, Kyung-Won

2015-02-01

301

High-flux characterization of ultrasmall multijunction concentrator solar cells  

NASA Astrophysics Data System (ADS)

A characterization study of ultrasmall ultraefficient multijunction concentrator solar cells is presented, with emphasis on performance sensitivity to light intensity and distribution. Information of this type is essential in the design and optimization of the latest generations of high-flux photovoltaic systems. Cell miniaturization allows increasing the concentration at which efficiency peaks, facilitates passive heat rejection, and permits the use of all-glass optics. However, few device measurements have been published on ultrasmall cells. Extensive measurements, up to ˜5000 suns, on the 1.0mm2 active region within the busbars are reported and analyzed.

Korech, Omer; Hirsch, Baruch; Katz, Eugene A.; Gordon, Jeffrey M.

2007-08-01

302

Ultra-small droplet generation via volatile component evaporation.  

PubMed

In this paper, we present a novel method to generate ultra-small droplets via volatile component evaporation. By regulating the composition of the binary solvent, the volume ratio of the high saturated vapor pressure component, and the flow rate ratio of the two phases, monodisperse ultra-small water or nonvolatile organic droplets can be formed. This method is flexible, versatile, and compatible with tip-streaming or nanofluidics, and may have potential applications in single molecule assay, colloid synthesis, and block copolymer assembly. PMID:24584363

Zhang, Qingquan; Liu, Xiaojun; Liu, Dayu; Gai, Hongwei

2014-04-21

303

Development of stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles and its analytical application to the determination of hydrophobic organic compounds in aqueous media.  

PubMed

A novel microextraction technique combining the principles of stir bar sorptive extraction (SBSE) and dispersive micro-solid phase extraction (D?SPE) is presented. The main feature of the method is the use of a neodymium-core stirring bar physically coated with a hydrophobic magnetic nanosorbent. Depending on stirring speed, the magnetic sorbent either acts as a coating material to the stir bar, thus affording extraction alike SBSE, or as a dispersed nanosorbent medium for the collection and extraction of the target analytes, in close analogy to D?SPE. Once the stirring process is finished, the strong magnetic field of the stir bar prevails again and rapidly retrieves the dispersed MNPs. Alike SBSE, the stir bar is collected and the analytes are back-extracted by liquid desorption into an appropriate organic solvent, which is used for analysis. This enrichment technique is easy to prepare since it does not require special surface modification procedures, uses low volumes of non-toxic organic solvents and most importantly imbues SBSE with additional functionalities against a wide range of analytes (since nanosorbents with various coatings can be employed) while it affords additional merits to D?SPE in terms of extraction and post-extraction treatment. As proof-of-concept this new approach was applied to the determination of organic UV filters in seawater samples using oleic acid-coated cobalt ferrite (CoFe2O4@oleic acid) magnetic nanoparticles as sorbent material. The method showed good analytical features in terms of linearity, enrichment factors (11-148), limits of detection (low ngmL(-1)), intra- and inter-day repeatability (RSD<11%) and relative recoveries (87-120%). PMID:25173996

Benedé, Juan L; Chisvert, Alberto; Giokas, Dimosthenis L; Salvador, Amparo

2014-10-01

304

Magnetic ionic liquids produced by the dispersion of magnetic nanoparticles in 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf2).  

PubMed

?This paper reports on the advancement of magnetic ionic liquids (MILs) as stable dispersions of surface-modified ?-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 ?-Fe(2)O(3) SM-MNP/BMI.NTf(2). PMID:22966984

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

305

Dispersive solid-phase extraction based on oleic acid-coated magnetic nanoparticles followed by gas chromatography-mass spectrometry for UV-filter determination in water samples.  

PubMed

A sensitive analytical method to concentrate and determine extensively used UV filters in cosmetic products at (ultra)trace levels in water samples is presented. The method is based on a sample treatment using dispersive solid-phase extraction (dSPE) with laboratory-made chemisorbed oleic acid-coated cobalt ferrite (CoFe(2)O(4)@oleic acid) magnetic nanoparticles (MNPs) as optimized sorbent for the target analytes. The variables involved in dSPE were studied and optimized in terms of sensitivity, and the optimum conditions were: mass of sorbent, 100mg; donor phase volume, 75 mL; pH, 3; and sodium chloride concentration, 30% (w/v). After dSPE, the MNPs were eluted twice with 1.5 mL of hexane, and then the eluates were evaporated to dryness and reconstituted with 50 ?L of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) for the injection into the gas chromatography-mass spectrometry (GC-MS). Under the optimized experimental conditions the method provided good levels of repeatability with relative standard deviations below 16% (n=5, at 100 ng L(-1) level). Limit of detection values ranged between 0.2 and 6.0 ng L(-1), due to the high enrichment factors achieved (i.e., 453-748). Finally, the proposed method was applied to the analysis of water samples of different origin (tap, river and sea). Recovery values showed that the matrices under consideration do not significantly affect the extraction process. PMID:21411104

Román, Iván P; Chisvert, Alberto; Canals, Antonio

2011-05-01

306

Investigation of phase formation of (Zn, Mg)0.5Co0.5Fe2O4 nanoferrites  

NASA Astrophysics Data System (ADS)

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.

Msomi, J. Z.; Dlamini, W. B.; Moyo, T.; Ezekiel, P.

2015-01-01

307

Quantum dynamics of ultrasmall tunnel junctions: Real-time analysis  

Microsoft Academic Search

We present a real-time path-integral analysis of the quantum dynamics of an ultrasmall tunnel junction interacting with an arbitrary external impedance. For a normal junction, we derive a quasiclassical Langevin equation for the phase variable and calculate the I-V curve beyond perturbation theory for the junction conductance. In the superconducting case, we develop a nonperturbative calculation of the time-dependent expectation

D. S. Golubev; A. D. Zaikin

1992-01-01

308

Controlling bubbles using bubbles--microfluidic synthesis of ultra-small gold nanocrystals with gas-evolving reducing agents.  

PubMed

Microfluidic wet-chemical synthesis of nanoparticles is a growing area of research in chemical microfluidics, enabling the development of continuous manufacturing processes that overcome the drawbacks of conventional batch-based synthesis methods. The synthesis of ultra-small (<5 nm) metallic nanocrystals is an interesting area with many applications in diverse fields, but is typically very challenging to accomplish in a microfluidics-based system due to the use of a strong gas-evolving reducing agent, aqueous sodium borohydride (NaBH(4)), which causes uncontrolled out-gassing and bubble formation, flow disruption and ultimately reactor failure. Here we present a simple method, rooted in the concepts of multiphase mass transfer that completely overcomes this challenge-we simply inject a stream of inert gas bubbles into our channels that essentially capture the evolving gas from the reactive aqueous solution, thereby preventing aqueous dissolved gas concentration from reaching the solubility threshold for bubble nucleation. We present a simple model for coupled mass transfer and chemical reaction that adequately captures device behaviour. We demonstrate the applicability of our method by synthesizing ultra-small gold nanocrystals (<5 nm); the quality of nanocrystals thus synthesized is further demonstrated by their use in an off-chip synthesis of high-quality gold nanorods. This is a general approach that can be extended to a variety of metallic nanomaterials. PMID:22456754

Khan, Saif A; Duraiswamy, Suhanya

2012-04-24

309

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

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}).

Brinkman, K

2009-01-08

310

Finite size effects on the electrical properties of sol-gel synthesized CoFe2O4 powders: deviation from Maxwell-Wagner theory and evidence of surface polarization effects  

Microsoft Academic Search

Fine particles of cobalt ferrite were synthesized by the sol-gel method.\\u000a Subsequent heat treatment at different temperatures yielded cobalt\\u000a ferrites having different grain sizes. X-ray diffraction studies were\\u000a carried out to elucidate the structure of all the samples. Dielectric\\u000a permittivity and ac conductivity of all the samples were evaluated as a\\u000a function of frequency, temperature and grain size. The variation

Mathew George; Swapna S. Nair; K. A. Malini; P. A. Joy; M. R. Anantharaman

2007-01-01

311

Self-biased large magnetoelectric coupling in co-sintered Bi0.5Na0.5TiO3 based piezoelectric and CoFe2O4 based magnetostrictive bilayered composite  

NASA Astrophysics Data System (ADS)

In this work, magnetoelectric properties of a co-sintered bilayered composite of non-lead based piezoelectric 0.97(Bi0.5Na0.5TiO3)-0.03(K0.47Na0.47Li0.06Nb0.74Sb0.06Ta0.2O3) and magnetostrictive Co0.6Zn0.4Fe1.7Mn0.3O4 are presented. Similar optimal sintering conditions of the individual components lead to a very clean interface as evidenced in the scanning electron microscopy, angle dispersive X-ray diffraction, and energy-dispersive X-ray (EDX) results. Clean interface results in strong intimate mechanical coupling between both components and causes a maximum transfer of induced strain, leading to a large magnetoelectric coupling ˜142 mV/cm.Oe measured in longitudinally magnetized-transversely polarized configuration (L-T mode). Remnant polarization ˜32 ?C/cm2, remnant magnetization ˜0.50 emu/g, and sufficiently high self biased magnetoelectricity ˜135 mV/cm Oe (L-T mode) were observed for this composite.

Kumari, Mukesh; Singh, Amrita; Gupta, Arti; Prakash, Chandra; Chatterjee, Ratnamala

2014-12-01

312

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)

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.

Agú, Ulises A.; Oliva, Marcos I.; Marchetti, Sergio G.; Heredia, Angélica C.; Casuscelli, Sandra G.; Crivello, Mónica E.

2014-11-01

313

Observation of magnetoelectric coupling and local piezoresponse in modified (Na0.5Bi0.5)TiO3-BaTiO3-CoFe2O4 lead-free composites.  

PubMed

Lead-free particulate multiferroic composites of [0.94(Na0.5Bi0.5)TiO3-0.06 BaTiO3]:(Co0.6Zn0.4)(Fe1.7Mn0.3)O4 were synthesized and magnetoelectric (ME) properties were studied. X-ray diffraction and microstructural studies indicated the formation of a two-phase composite system without any impurities. The shift of Raman modes corresponding to ferroelectric and ferrite phases was assigned to the induced strain amid the formation of a two-phase system, in relation to the fraction of each phase in the samples. A strong local piezoresponse and hysteresis loops observed for composites established the ferroelectric properties at a nanoscale. Magnetostriction measurements revealed values of ?11 = -10.4 and ?12 = 5.3 ppm and piezomagnetic coefficient d?11/dH = -0.0087 ppm Oe(-1) at 0.45 kOe for a composite with a ferrite concentration of 35 mol%. A maximum change of 18.5% in magnetization after electrical poling indicates a strong magnetoelectric response of the present composites followed by a direct ME coefficient of 8.2 mV cm(-1) Oe(-1). Our studies point to the fact that the present multiferroic composites having strong ME coupling are useful for lead-free electronic applications. PMID:24849499

Ramana, E Venkata; Figueiras, F; Graça, M P F; Valente, M A

2014-07-14

314

Synthesis and Characterization of CoFe2O4\\/Ni0.5Zn0.5Fe2O4 Core\\/shell Magnetic Nanocomposite by the Wet Chemical Route  

Microsoft Academic Search

A cobalt ferrite\\/nickel-zinc ferrite core\\/shell nanocomposite was synthesized by a polymerized complex method using iron citrate, cobalt nitrate, nickel nitrate, zinc nitrate, citric acid, ethylene glycol, benzoic acid and sodium citrate as starting materials. The XRD, TEM and VSM techniques were employed to evaluate the phase composition, morphology and magnetic properties of the samples. The XRD results indicated the coexistence

A. Honarbakhsh-Raouf; H. R. Emamian; A. Yourdkhani; A. Ataie

2010-01-01

315

Mesoscopic superconductivity in ultrasmall metallic grains  

E-print Network

A nano-scale metallic grain (nanoparticle) with irregular boundaries in which the single-particle dynamics are chaotic is a zero-dimensional system described by the so-called universal Hamiltonian in the limit of a large number of electrons. The interaction part of this Hamiltonian includes a superconducting pairing term and a ferromagnetic exchange term. Spin-orbit scattering breaks spin symmetry and suppresses the exchange interaction term. Of particular interest is the fluctuation-dominated regime, typical of the smallest grains in the experiments, in which the bulk pairing gap is comparable to or smaller than the single-particle mean-level spacing, and the Bardeen-Cooper-Schrieffer (BCS) mean-field theory of superconductivity is no longer valid. Here we study the crossover between the BCS and fluctuation-dominated regimes in two limits. In the absence of spin-orbit scattering, the pairing and exchange interaction terms compete with each other. We describe the signatures of this competition in thermodynamic observables, the heat capacity and spin susceptibility. In the presence of strong spin-orbit scattering, the exchange interaction term can be ignored. We discuss how the magnetic-field response of discrete energy levels in such a nanoparticle is affected by pairing correlations. We identify signatures of pairing correlations in this response, which are detectable even in the fluctuation-dominated regime.

Y. Alhassid; K. N. Nesterov

2014-07-31

316

Physicochemical characterization of ultrasmall superparamagnetic iron oxide particles (USPIO) for biomedical application as MRI contrast agents  

PubMed Central

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. PMID:18203428

Di Marco, Mariagrazia; Sadun, Claudia; Port, Marc; Guilbert, Irene; Couvreur, Patrick; Dubernet, Catherine

2007-01-01

317

Ultra-small, highly stable, and membrane-impermeable fluorescent nanosensors for oxygen  

NASA Astrophysics Data System (ADS)

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 ?s, which—in turn—enables lifetime imaging and additional background separation via time-gated methods.

Wang, Xu-dong; Stolwijk, Judith A.; Sperber, Michaela; Meier, Robert J.; Wegener, Joachim; Wolfbeis, Otto S.

2013-09-01

318

Pauli spin blockade and the ultrasmall magnetic field effect.  

PubMed

Based on the spin-blockade model for organic magnetoresistance, we present an analytic expression for the polaron-bipolaron transition rate, taking into account the effective nuclear fields on the two sites. We reveal the physics behind the qualitatively different magnetoconductance line shapes observed in experiment, as well as the ultrasmall magnetic field effect (USFE). Since our findings agree in detail with recent experiments, they also indirectly provide support for the spin-blockade interpretation of organic magnetoresistance. In addition, we predict the existence of a similar USFE in semiconductor double quantum dots tuned to the spin-blockade regime. PMID:23971599

Danon, Jeroen; Wang, Xuhui; Manchon, Aurélien

2013-08-01

319

nanoparticles  

NASA Astrophysics Data System (ADS)

Evenly separated crystalline CuIn0.8Ga0.2Se2 (CIGS) nanoparticles are deposited on ITO-glass substrate by pulsed laser deposition. Such CIGS layers are introduced between conjugated polymer layers and ITO-glass substrates for enhancing light absorbance of polymer solar cells. The P3HT:PCBM absorbance between 300 and 650 nm is enhanced obviously due to the introduction of CIGS nanoparticles. The current density-voltage curves of a P3HT:PCBM/CIGS solar cell demonstrate that the short-circuit current density is improved from 0.77 to 1.20 mA/cm2. The photoluminescence spectra show that the excitons in the polymer are obviously quenched, suggesting that the charge transfer between the P3HT:PCBM and CIGS occurred. The results reveal that the CIGS nanoparticles may exhibit the localized surface plasmon resonance effect just as metallic nanostructures.

Zhao, Yu; Li, Hui; Liu, Xu-Jun; Guan, Lei-Lei; Li, Yan-Li; Sun, Jian; Ying, Zhi-Feng; Wu, Jia-Da; Xu, Ning

2014-06-01

320

Ultrasmall SnO2 Nanocrystals: Hot-bubbling Synthesis, Encapsulation in Carbon Layers and Applications in High Capacity Li-Ion Storage  

PubMed Central

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

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

321

In situ loading of ultra-small Cu2O particles on TiO2 nanosheets to enhance the visible-light photoactivity  

NASA Astrophysics Data System (ADS)

In this work, ultra-small Cu2O nanoparticles have been loaded on TiO2 nanosheets with {001} facets exposed through a one-pot hydrothermal reaction. These Cu2O nanoparticles are well-dispersed on TiO2 nanosheets with narrow size distributions and controllable sizes from 1.5 to 3.0 nm. Through XRD, TEM, N2 absorption-desorption isotherms and UV-vis diffuse reflectance spectra, the Cu2O/TiO2 nanosheets show similar phase structures, morphologies, pore structures as compared to pure TiO2 nanosheets. Due to the loading of ultra-small Cu2O nanoparticles, heterojunctions are formed between Cu2O and TiO2, which favors the efficient separation of photo-generated electrons and holes. Caused by the electron transfer from Cu2O to TiO2, Cu2O/TiO2 nanosheets show excellent visible-light activity, about 3 times that of N-doped TiO2 nanosheets with {001} facets exposed. Furthermore, charge transfer rate across the interface of Cu2O and TiO2 shows great dependence on the size of Cu2O particles. The charge transfer across the interface may be more efficient between TiO2 nanosheets and smaller Cu2O nanoparticles. Therefore, the Ti : Cu = 30 : 1(atomic ratio) sample shows the best activity due to its balance in light harvest and electron transfer rate in the degradation of phenol under visible light.In this work, ultra-small Cu2O nanoparticles have been loaded on TiO2 nanosheets with {001} facets exposed through a one-pot hydrothermal reaction. These Cu2O nanoparticles are well-dispersed on TiO2 nanosheets with narrow size distributions and controllable sizes from 1.5 to 3.0 nm. Through XRD, TEM, N2 absorption-desorption isotherms and UV-vis diffuse reflectance spectra, the Cu2O/TiO2 nanosheets show similar phase structures, morphologies, pore structures as compared to pure TiO2 nanosheets. Due to the loading of ultra-small Cu2O nanoparticles, heterojunctions are formed between Cu2O and TiO2, which favors the efficient separation of photo-generated electrons and holes. Caused by the electron transfer from Cu2O to TiO2, Cu2O/TiO2 nanosheets show excellent visible-light activity, about 3 times that of N-doped TiO2 nanosheets with {001} facets exposed. Furthermore, charge transfer rate across the interface of Cu2O and TiO2 shows great dependence on the size of Cu2O particles. The charge transfer across the interface may be more efficient between TiO2 nanosheets and smaller Cu2O nanoparticles. Therefore, the Ti : Cu = 30 : 1(atomic ratio) sample shows the best activity due to its balance in light harvest and electron transfer rate in the degradation of phenol under visible light. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr31859h

Liu, Lichen; Gu, Xianrui; Sun, Chuanzhi; Li, Hao; Deng, Yu; Gao, Fei; Dong, Lin

2012-09-01

322

nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Andreu-Cabedo, Patricia; Mondragon, Rosa; Hernandez, Leonor; Martinez-Cuenca, Raul; Cabedo, Luis; Julia, J. Enrique

2014-10-01

323

Dynamic Fluctuations in Ultrasmall Nanocrystals Induce White Light Timothy J. Pennycook,*,,,  

E-print Network

at which the surface structure changes. These motions are clear in the movies available online (see Supporting Information, movies si_002.qt, si_003.qt, and si_004.qt). Moving into the ultrasmall regime

Pennycook, Steve

324

Tuning of magnetic properties in cobalt ferrite by varying Fe+2 and Co+2 molar ratios  

NASA Astrophysics Data System (ADS)

Different grades of magnetic cobalt ferrite (CoFe2O4) nanoparticles were synthesized with various molar ratios of Fe+2 to Co+2 ions in the initial salt solutions by the co-precipitation method. The crystal structure and morphology of the nanoparticles are obtained from X-ray diffraction and transmission electron microscopy studies. Fourier transform infrared spectroscopy analysis exhibited the Fe-O stretching vibration ~540 cm-1, confirming the formation of metal oxide. The magnetic studies demonstrate that all of the nanoparticles are superparamagnetic at 300 K. The saturation magnetization and coercivity of the CoFe2O4 nanoparticles are affected by the molar ratios of Fe+2 to Co+2 ions. Among all the synthesized nanoparticles, the system with 75:25 molar ratio of Fe+2 to Co+2 ions with a particle size of 13 nm showed a high magnetization of 90 emu/g.

Biswal, Dipti; Peeples, Brianna N.; Peeples, Caryn; Pradhan, Aswini K.

2013-11-01

325

Complex swept source optical coherence tomography with ultra-small fiber probe for biomedical imaging  

Microsoft Academic Search

We demonstrate a catheter-based complex swept-source optical coherence tomography (SS-OCT) system using a 3x3 Mach-Zehnder quadrature interferometer and an ultra-small optic probe. Design and fabrication of fiber lens for ultrasmall optic probes are presented first. We compare in detail measured performance with expected theoretical performance. Then, we present a 3x3 Mach-Zehnder quadrature interferometer to acquire a complex interferometric signal for

Youxin Mao; Shoude Chang; Costel Flueraru

2009-01-01

326

Quantum dynamics of ultrasmall tunnel junctions: Real-time analysis  

NASA Astrophysics Data System (ADS)

We present a real-time path-integral analysis of the quantum dynamics of an ultrasmall tunnel junction interacting with an arbitrary external impedance. For a normal junction, we derive a quasiclassical Langevin equation for the phase variable and calculate the I-V curve beyond perturbation theory for the junction conductance. In the superconducting case, we develop a nonperturbative calculation of the time-dependent expectation value of the voltage operator and voltage-voltage correlation functions. Provided that dissipation is small enough, both of these quantities show damped oscillations and a power-law decay in the low-temperature limit. We also analyze the effect of resonant voltage steps on the I-V curve of an ac-driven tunnel junction and evaluate the linewidth of Bloch oscillations in the quantum limit.

Golubev, D. S.; Zaikin, A. D.

1992-11-01

327

Evaluation of the resistance of DNA immobilized on ferrimagnetic particles of cobalt ferrite nanopowder against nuclease cleavage.  

PubMed

DNA was immobilized on ferrimagnetic particles of cobalt ferrite nanopowder (CoFe(2)O(4)) and its resistance to endonuclease (DNase I) hydrolysis was studied. Immobilization on cobalt ferrite nanoparticles prevented enzymatic cleavage of DNA. This process was not associated with enzyme inactivation under the effect of nanosize cobalt ferrite and was presumably determined by lesser availability of the DNA molecule as a result of its interaction with nanoparticles. PMID:21113461

Pershina, A G; Sazonov, A E; Ogorodova, L M

2010-07-01

328

Nanoparticles for neuroimaging  

NASA Astrophysics Data System (ADS)

The advent of nanotechnology has introduced a variety of novel exciting possibilities into the medical and clinical field. Nanoparticles, ultra-small object sized between 100 and 1 nm, are promising diagnostic tools for various diseases among other devices, thanks to the possibility of their functionalization allowing the selective targeting of organs, tissues and cells and to facilitate their transport to primary target organs. However, brain targeting represents a still unresolved challenge due to the presence of the blood-brain barrier, a tightly packed layer of endothelial cells that prevents unwanted substances entering the central nervous system. We review a range of nanoparticles suitable for in vivo diagnostic imaging of neurodegenerative diseases and brain disorders, highlighting the possibility to potentially increase their efficiency and kinetics of brain-targeting. We also review a range of imaging techniques with an emphasis on most recently introduced molecular imaging modalities, their current status and future potential.

Re, F.; Moresco, R.; Masserini, M.

2012-02-01

329

Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings  

NASA Astrophysics Data System (ADS)

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.

Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew; Krishnan, Kannan M.

2014-11-01

330

Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings.  

PubMed

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

Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R Matthew; Krishnan, Kannan M

2014-11-01

331

Nanoparticles  

NASA Astrophysics Data System (ADS)

Nanostructured bulk materials are regarded as a means of enhancing the performance of thermoelectric (TE) materials and devices. Powder metallurgy has the distinct advantage over conventional synthesis that it can start directly from nanosized particles. However, further processing, for example extrusion, usually requires elevated temperatures, which lead to grain growth. We have found that introduction of semiconductor nanoparticles of molybdenum disulfide (MoS2), a well-known solid lubricant, suppresses grain growth in bismuth telluride-based alloys, thus improving the extrusion process. Scanning electron microscope images show that adding MoS2 particles at concentrations of 0.2, 0.4, and 0.8 wt% to p-type (Bi0.2Sb0.8)2Te3, under otherwise identical extrusion conditions, reduces average grain size by a factor of four. Scherer's formula applied to x-ray diffraction data indicates that average crystallite sizes (˜17 nm) of powders are not significantly different from those of alloys extruded with MoS2 (˜18 nm), which is in stark contrast with those for conventional alloy (Bi0.2Sb0.8)2Te3 extruded under the same conditions (˜80 nm). Harman measurements of TE properties reveal a decrease of the thermal conductivity accompanied by reduction of the room-temperature figure of merit ( ZT) from 0.9 to 0.7, because of a lower power factor. Above 370 K, however, the performance of alloys containing MoS2 surpasses that of (Bi0.2Sb0.8)2Te3, with reduction of the thermal conductivity which is more significant at temperatures above the cross point of the ZT values.

Keshavarz, Mohsen K.; Vasilevskiy, Dimitri; Masut, Remo A.; Turenne, Sylvain

2014-06-01

332

Magnetic and dielectric properties of sulfonated (S) poly[(styrene)-(ethylene-co-butylene)]-styrene (SEBS) block copolymer\\/magnetic metal oxide nanocomposites synthesized via an in-situ precipitation method  

Microsoft Academic Search

Block copolymer\\/magnetic metal oxide nanocomposites were synthesized by growing metal oxide nanoparticles (cobalt ferrite, CoFe2O 4 and iron oxide, alpha-Fe2O3) in sulfonated (s) poly (styrene) (PS) block domains of sulfonated poly [(styrene)-(ethylene-co-butylene)-(styrene)] (SEBS) BCP preformed films via an in-situ precipitation method by dissolving the salts of respective metal chloride (s) in a suitable solvent that selectively swells the sPS regions.

Sateesh Kumar Peddini

2009-01-01

333

Tunable Ultrasmall Visible-to-Extended Near-Infrared Emitting Silver Sulfide Quantum Dots for Integrin-Targeted Cancer Imaging.  

PubMed

The large size of many near-infrared (NIR) fluorescent nanoparticles prevents rapid extravasation from blood vessels and subsequent diffusion to tumors. This confines in vivo uptake to the peritumoral space and results in high liver retention. In this study, we developed a viscosity modulated approach to synthesize ultrasmall silver sulfide quantum dots (QDs) with distinct tunable light emission from 500 to 1200 nm and a QD core diameter between 1.5 and 9 nm. Conjugation of a tumor-avid cyclic pentapeptide (Arg-Gly-Asp-DPhe-Lys) resulted in monodisperse, water-soluble QDs (hydrodynamic diameter < 10 nm) without loss of the peptide's high binding affinity to tumor-associated integrins (KI = 1.8 nM/peptide). Fluorescence and electron microscopy showed that selective integrin-mediated internalization was observed only in cancer cells treated with the peptide-labeled QDs, demonstrating that the unlabeled hydrophilic nanoparticles exhibit characteristics of negatively charged fluorescent dye molecules, which typically do not internalize in cells. The biodistribution profiles of intravenously administered QDs in different mouse models of cancer reveal an exceptionally high tumor-to-liver uptake ratio, suggesting that the small sized QDs evaded conventional opsonization and subsequent high uptake in the liver and spleen. The seamless tunability of the QDs over a wide spectral range with only a small increase in size, as well as the ease of labeling the bright and noncytotoxic QDs with biomolecules, provides a platform for multiplexing information, tracking the trafficking of single molecules in cells, and selectively targeting disease biomarkers in living organisms without premature QD opsonization in circulating blood. PMID:25560768

Tang, Rui; Xue, Jianpeng; Xu, Baogang; Shen, Duanwen; Sudlow, Gail P; Achilefu, Samuel

2015-01-27

334

Effect of the electromagnetic environment on the Coulomb blockade in ultrasmall tunnel junctions  

Microsoft Academic Search

The current-voltage characteristic of an ultrasmall tunnel junction is calculated for arbitrary frequency dependence of the impedance presented to the junction by its electromagnetic environment. It is shown that the Coulomb blockade of tunneling is washed out by quantum fluctuations of the charge on the junction capacitor except for ultrahigh impedance environments. Two simple cases where the environment can be

M. H. Devoret; D. Esteve; H. Grabert; G.-L. Ingold; H. Pothier; C. Urbina

1990-01-01

335

Nature-Inspired Optimization of High-Impedance Metasurfaces With Ultrasmall Interwoven Unit Cells  

Microsoft Academic Search

This letter introduces a set of novel designs for high-impedance metasurfaces with ultrasmall interwoven unit cells that achieve increased miniaturization compared to existing literature, yet still provide identical bandwidth performance and excellent field of view. This development makes possible more compact designs for artificial magnetic conducting (AMC) ground planes and electromagnetic band-gap (EBG) surfaces as well as providing the ability

Zikri Bayraktar; Jeremiah P. Turpin; Douglas H. Werner

2011-01-01

336

Templated synthesis of highly ordered mesoporous cobalt ferrite and its microwave absorption properties  

NASA Astrophysics Data System (ADS)

Based on the nanocasting strategy, highly ordered mesoporous CoFe2O4 is synthesized via the ‘two-solvent’ impregnation method using a mesoporous SBA-15 template. An ordered two-dimensional (P6mm) structure is preserved for the CoFe2O4/SBA-15 composite after the nanocasting. After the SBA-15 template is dissolved by NaOH solution, a mesoporous structure composed of aligned nanoparticles can be obtained, and the P6mm structure of the parent SBA-15 is preserved. With a high specific surface area (above 90 m2/g) and ferromagnetic behavior, the obtained material shows potential in light weight microwave absorption application. The minimum reflection loss (RL) can reach -18 dB at about 16 GHz with a thickness of 2 mm and the corresponding absorption bandwidth is 4.5 GHz.

Li, Guo-Min; Wang, Lian-Cheng; Xu, Yao

2014-08-01

337

Microwave absorption properties of cobalt ferrite-modified carbonized bacterial cellulose  

NASA Astrophysics Data System (ADS)

A novel magnetic nanocomposite of carbonized bacterial cellulose (CBC) modified by CoFe2O4 nanocrystals with different contents were synthesized successfully using an effective solvothermal method. Scanning electron microscopy and transmission electron microscopy revealed that the CBC fibers were intertwined and networks were loaded with well-distributed CoFe2O4 nanoparticles. With a CBC/CoFe2O4 ratio of 10 wt%, the optimal reflection loss (RL) of -45 dB at 8.6 GHz with a thickness of 2.0 mm because of the enhanced interfacial polarization related to the developed ??. This novel electromagnetic nanocomposite material is believed to have potential applications in terms of microwave-absorbing performance.

Ren, Yong; Li, Shirong; Dai, Bo; Huang, Xiaohu

2014-08-01

338

Preparation of entangled nanocellulose fibers from APMP and its magnetic functional property as matrix.  

PubMed

Nanocellulose fibers (NCFs) aerogels were prepared from poplar alkaline peroxide mechanical pulp (APMP) using physical ultrasonication method. As raw materials, the unique mechanical effects of APMP cause the fiber folding and loose during the pulping process, which was beneficial to further chemical purification and subsequent treatment for long and entangled NCFs. The obtained NCFs exhibited higher crystallinity (77.8%) compared with that of APMP (72.6%) together with diameters range from 20 to 90 nm and self-assembled to network. The primary thermal degradation of NCFs occurred at 331.5°C. The prepared NCFs network aerogels acted as matrix which can prevent the growth and aggregation of ferromagnetic CoFe2O4 nanoparticles. The ratio of the CoFe2O4 of magnetic composites increased from 34 wt% to 75 wt%, and the magnetic properties were all increased with increasing the reaction concentration of FeSO4/CoCl2 salt. PMID:23544539

Li, Wei; Zhao, Xin; Liu, Shouxin

2013-04-15

339

Highly reversible and large lithium storage in mesoporous si/c nanocomposite anodes with silicon nanoparticles embedded in a carbon framework.  

PubMed

A magnesiothermic reduction approach is designed to synthesize mesoporous Si/C nanocomposites with ultrasmall, uniform silicon nanoparticles (ca. 3 nm) embedded in a rigid mesoporous carbon framework. The resultant mesoporous Si/C nanocomposites present excellent performance with high reversible capacity, good Coulombic efficiency and rate capability, and outstanding cycling stability in lithium-ion battery applications. PMID:25164312

Zhang, Renyuan; Du, Yuanjin; Li, Dan; Shen, Dengke; Yang, Jianping; Guo, Zaiping; Liu, Hua Kun; Elzatahry, Ahmed A; Zhao, Dongyuan

2014-10-22

340

Comparison of Superparamagnetic and Ultrasmall Superparamagnetic Iron Oxide Cell Labeling for Tracking Green Fluorescent Protein Gene Marker with Negative and Positive Contrast Magnetic Resonance Imaging  

PubMed Central

The objectives of this study were to investigate the feasibility of imaging green fluorescent protein (GFP)-expressing cells labeled with iron oxide nanoparticles with the fast low-angle positive contrast steady-state free precession (FLAPS) method and to compare them with the traditional negative contrast technique. The GFP-R3230Ac cell line (GFP cell) was incubated for 24 hours using 20 ?g Fe/mL concentration of superparamagnetic iron oxide (SPIO) and ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles. Cell samples were prepared for iron content analysis and cell function evaluation. The labeled cells were imaged using positive contrast with FLAPS imaging, and FLAPS images were compared with negative contrast T2*-weighted images. The results demonstrated that SPIO and USPIO labeling of GFP cells had no effect on cell function or GFP expression. Labeled cells were successfully imaged with both positive and negative contrast magnetic resonance imaging (MRI). The labeled cells were observed as a narrow band of signal enhancement surrounding signal voids in FLAPS images and were visible as signal voids in T2*-weighted images. Positive contrast and negative contrast imaging were both valuable for visualizing labeled GFP cells. MRI of labeled cells with GFP expression holds potential promise for monitoring the temporal and spatial migration of gene markers and cells, thereby enhancing the understanding of cell- and gene-based therapeutic strategies. PMID:19723472

Zhang, Zhuoli; Dharmakumar, Rohan; Mascheri, Nicole; Fan, Zhaoyang; Wu, Shengyong; Li, Debiao

2010-01-01

341

An insight into the metabolic responses of ultra-small superparamagnetic particles of iron oxide using metabonomic analysis of biofluids.  

PubMed

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 alpha-hydroxy-n-valerate, o- and p-HPA, PAG, nicotinate and hippurate accompanied by decreases in the levels of urinary alpha-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 (beta-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 physiological responses on mammalian metabolism, and can be employed to investigate the potential adverse effects of other nanoparticles and nanomaterials on the environment and human health. PMID:20820093

Feng, Jianghua; Liu, Huili; Zhang, Limin; Bhakoo, Kishore; Lu, Lehui

2010-10-01

342

Folate-targeted polymeric micelles loaded with ultrasmall superparamagnetic iron oxide: combined small size and high MRI sensitivity  

PubMed Central

Targeted delivery of contrast agents is a highly desirable strategy for enhancing diagnostic efficiency and reducing side effects and toxicity. Water-soluble and tumor-targeting superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized by loading hydrophobic SPIONs into micelles assembled from an amphiphilic block copolymer poly(ethylene glycol)- poly(?-caprolactone) (PEG-PCL) bearing folate in the distal ends of PEG chains. Compared to the water-soluble SPIONs obtained by small molecular surfactant coating, ultrasmall SPION encapsulation with PEG-PCL micelles (PEG-PCL-SPIONs) simultaneously increases transverse (r2) and decreases longitudinal (r1) magnetic resonance (MR) relaxivities of water proton in micelle solution, leading to a notably high r2/r1 ratio up to 78, which makes the PEG-PCL-SPIONs a highly sensitive MR imaging (MRI) T2 contrast agent. The mean size of folate-attached SPION micelles (Fa-PEG-PCL-SPIONs) is 44 ± 3 nm on average, ideal for in vivo MRI applications in which long circulation is greatly determined by small particle size and is highly desirable. Prussian blue staining of BEL-7402 cells over-expressing folate receptors, after incubation with micelle-containing medium, demonstrated that folate functionalization of the magnetic particles significantly enhanced their cell uptake. The potential of Fa-PEG-PCL-SPIONs as a potent MRI probe for in vivo tumor detection was assessed. At 3 hours after intravenous injection of the Fa-PEG-PCL-SPION solution into mice bearing subcutaneous xenografts of human BEL-7402 hepatoma, a 41.2% signal intensity decrease was detected in the T2-weighted MR images of the tumor, indicating the efficient accumulation of Fa-PEG-PCL-SPIONs in the tumor tissue. PMID:22745549

Hong, Guo-bin; Zhou, Jing-xing; Yuan, Ren-xu

2012-01-01

343

Genome sequence of the ultrasmall unicellular red alga Cyanidioschyzon merolae 10D  

Microsoft Academic Search

Small, compact genomes of ultrasmall unicellular algae provide information on the basic and essential genes that support the lives of photosynthetic eukaryotes, including higher plants. Here we report the 16,520,305-base-pair sequence of the 20 chromosomes of the unicellular red alga Cyanidioschyzon merolae 10D as the first complete algal genome. We identified 5,331 genes in total, of which at least 86.3%

Motomichi Matsuzaki; Osami Misumi; Tadasu Shin-i; Shinichiro Maruyama; Manabu Takahara; Shin-ya Miyagishima; Toshiyuki Mori; Keiji Nishida; Fumi Yagisawa; Keishin Nishida; Yamato Yoshida; Yoshiki Nishimura; Shunsuke Nakao; Tamaki Kobayashi; Yu Momoyama; Tetsuya Higashiyama; Ayumi Minoda; Masako Sano; Hisayo Nomoto; Kazuko Oishi; Hiroko Hayashi; Fumiko Ohta; Satoko Nishizaka; Shinobu Haga; Sachiko Miura; Tomomi Morishita; Yukihiro Kabeya; Kimihiro Terasawa; Yutaka Suzuki; Yasuyuki Ishii; Shuichi Asakawa; Hiroyoshi Takano; Niji Ohta; Haruko Kuroiwa; Kan Tanaka; Nobuyoshi Shimizu; Sumio Sugano; Naoki Sato; Hisayoshi Nozaki; Naotake Ogasawara; Yuji Kohara; Tsuneyoshi Kuroiwa

2004-01-01

344

Ultra-small MMIC mixers for K- and Ka-band communications  

Microsoft Academic Search

We present the design and performance of two ultra-small MMIC double balanced mixers covering the 14 to 26 GHz band and the 18 to 32 GHz band, respectively. These passive mixers have a conversion loss of better than 8 dB with an LO to RF isolation of better than 30 dB. Both mixers are 0.48 mm2 in die size, which

Charles J. Trantanella

2000-01-01

345

A method for synthesis and functionalization of ultrasmall superparamagnetic covalent carriers based on maghemite and dextran  

NASA Astrophysics Data System (ADS)

A new generation of susceptibility contrast agents for MRI and based on maghemite cores covalently bonded to dextran stabilizing macromolecules was investigated. The multistep preparation of these versatile ultrasmall superparamagnetic iron oxides (VUSPIO) consisted of colloidal maghemite synthesis, surface modification by aminopropylsilane groups, and coupling of partially oxidized dextran via Schiff's bases and secondary amine bonds. The dextran corona might be easily derivatized, e.g. by PEGylation.

Mornet, Stéphane; Portier, Josik; Duguet, Etienne

2005-05-01

346

Design and synthesis of ternary cobalt ferrite/graphene/polyaniline hierarchical nanocomposites for high-performance supercapacitors  

NASA Astrophysics Data System (ADS)

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.

Xiong, Pan; Huang, Huajie; Wang, Xin

2014-01-01

347

SiN linkage in ultrabright, ultrasmall Si nanoparticles E. Rogozhina  

E-print Network

with the functional amine group in butylamine. Fourier transform infrared spectroscopy and x-ray photospectroscopy shell due to the attachment of butylamine while still maintaining the optical activity of the particle group in butylamine to form a Si­N linkage. The linkage facilitates the attachment of organic functional

Braun, Paul

348

Ultrasmall particle detection using a submicron Hall sensor  

SciTech Connect

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.

Kazakova, O.; Gallop, J. [National Physical Laboratory, Teddington TW11 0LW (United Kingdom); Panchal, V. [National Physical Laboratory, Teddington TW11 0LW (United Kingdom); Royal Holloway, University of London, Egham TW20 0EX (United Kingdom); See, P. [National Physical Laboratory, Teddington TW11 0LW (United Kingdom); University of Cambridge, Cambridge CB3 0HE (United Kingdom); Cox, D. C. [National Physical Laboratory, Teddington TW11 0LW (United Kingdom); University of Surrey, Guildford GU2 7XH (United Kingdom); Spasova, M. [Center for Nanointegration, University of Duisburg-Essen, Duisburg 47048 (Germany); Cohen, L. F. [Imperial College London, London SW7 2BW (United Kingdom)

2010-05-15

349

Sub-2 nm size and density tunable platinum nanoparticles using room temperature tilted-target sputtering  

NASA Astrophysics Data System (ADS)

This paper describes a tilted-target RF magnetron sputter deposition system to grow nanoparticles in a controlled way. With detailed characterization of ultra-high density (up to 1.1 × 1013 cm-2) and ultra-small size Pt nanoparticles (0.5-2 nm), it explains their growth and crystalline properties on amorphous Al2O3 thin films. It is shown that Pt nanoparticle size and number density can be precisely engineered by varying selected experimental parameters such as target angle, sputtering power and time of deposition to control the energy of the metal atoms in the deposition flux. Based on rate equation modelling of nanoparticle growth, three distinct growth regimes, namely nucleation dependent, coalescence dependent and agglomeration dependent regimes, were observed. The correlation between different nanoparticle growth regimes and the consequent crystal structure transformation, non-crystalline clusters ? single crystalline nanoparticles ? polycrystalline islands, is also discussed.

Ramalingam, Balavinayagam; Mukherjee, Somik; Mathai, Cherian J.; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

2013-05-01

350

Reentrant paramagnetism induced by drastic reduction of magnetic couplings at surfaces of superparamagnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Superparamagnetism appears when the Néel-Brown relaxation time of magnetic nanoparticles is shorter than the measurement time. Recent experimental studies of different types of magnetic nanoparticles revealed the existence of another paramagnetic region below the standard blocking temperatures. Here we elucidate the microscopic origin of this reentrant paramagnetism using a phenomenological model, which exploits the effects of weaker magnetic coupling strengths at the surfaces of ultrasmall nanoparticles. Within this picture, we have calculated the total magnetization of various nanoparticle arrays upon both finite-field and zero-field cooling processes via detailed classical Monte Carlo simulations, and found that the appearance of the reentrant phenomena necessarily invokes a drastic reduction of the magnetic coupling strengths at the surfaces of the nanoparticles. Our predictions can be readily tested experimentally using a micro-SQUID, and is expected to be beneficial in further applications of superparamagnetic nanoparticles.

Qin, Wei; Li, Xiaoguang; Xie, Yi; Zhang, Zhenyu

2014-12-01

351

Generation of ultrasmall nanostructures in oxide layers assisted by self-organization  

NASA Astrophysics Data System (ADS)

We explored the structural limits of unconventional electron-beam lithography by directly writing with an electron beam into ultrathin SiO2 films. The obtained structures were analyzed by tunneling microscopy. The Auger excitation process (Knotek-Feibelman mechanism) necessary for electron-stimulated oxygen desorption allows generation of ultrasmall structures. The subsequent processing step combines thermal desorption of the remaining monoxide and simultaneous etching promoted by thermally activated silicon atoms, which turns out to be a strongly anisotropic process close to step edges. Applying this combination of processes to a regularly stepped Si(557) sample, linewidths close to the resolution of the electron microscope of 5 nm were obtained.

Block, T.; Pfnür, H.

2008-03-01

352

Holographic interferometry of ultrasmall-pressure-induced curvature changes of bilayer lipid membranes  

SciTech Connect

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.

Picard, G.; Schneider-Henriquez, J.E.; Fendler, J.H. (Universite de Montreal, Quebec (Canada))

1990-01-25

353

Networks of ultrasmall Pd/Cr bilayer nanowires as high performance hydrogen sensors.  

SciTech Connect

The newly developed hydrogen sensor, based on a network of ultrasmall pure palladium nanowires sputter-deposited on a filtration membrane, takes advantage of single palladium nanowires' characteristics of high speed and sensitivity while eliminating their nanofabrication obstacles. However, this new type of sensor, like the single palladium nanowires, cannot distinguish hydrogen concentrations above 3%, thus limiting the potential applications of the sensor. This study reports hydrogen sensors based on a network of ultrasmall Cr-buffered Pd (Pd/Cr) nanowires on a filtration membrane. These sensors not only are able to outperform their pure Pd counterparts in speed and durability but also allow hydrogen detection at concentrations up to 100%. The new networks consist of a thin layer of palladium deposited on top of a Cr adhesion layer 1-3 nm thick. Although the Cr layer is insensitive to hydrogen, it enables the formation of a network of continuous Pd/Cr nanowires with thicknesses of the Pd layer as thin as 2 nm. The improved performance of the Pd/Cr sensors can be attributed to the increased surface area to volume ratio and to the confinement-induced suppression of the phase transition from Pd/H solid solution ({alpha}-phase) to Pd hydride ({beta}-phase).

Zeng, X.-Q.; Wang, Y.-L.; Deng, H.; Latimer, M. L.; Xiao, Z.-L.; Pearson, J.; Xu, T.; Wang, H.-H.; Welp, U.; Crabtree, G. W.; Kwok, W.-K. (Center for Nanoscale Materials); ( MSD); (Northern Illinois Univ.); (Illinois Math and Science Academy); (Univ. of Illinois at Chicago)

2011-01-01

354

Convenient synthesis of heterobifunctional poly(ethylene glycol) suitable for the functionalization of iron oxide nanoparticles for biomedical applications.  

PubMed

A straightforward route is proposed for the multi-gram scale synthesis of heterobifunctional poly(ethylene glycol) (PEG) oligomers containing combination of triethyloxysilane extremity for surface modification of metal oxides and amino or azido active end groups for further functionalization. The suitability of these PEG derivatives to be conjugated to nanomaterials was shown by pegylation of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles (NPs), followed by functionalization with small peptide ligands for biomedical applications. PMID:23860589

Passemard, Solène; Staedler, Davide; U??ová, Lucia; Schneiter, Guillaume Stéphane; Kong, Phally; Bonacina, Luigi; Juillerat-Jeanneret, Lucienne; Gerber-Lemaire, Sandrine

2013-09-01

355

Giant electric field controlled magnetic anisotropy in epitaxial BiFeO3-CoFe2O4 thin film heterostructures on single crystal Pb(Mg1/3Nb2/3)0.7Ti0.3O3 substrate  

NASA Astrophysics Data System (ADS)

We have deposited self-assembled BiFeO3 (BFO)-CoFe2O4 (CFO) thin films on Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrates and studied the change in magnetic anisotropy under different strain conditions induced by an applied electric field. After electric field poling, we observed (i) giant magnetization change: magnetization of original CFO phase is three times larger than that of strained one and (ii) magnetic force microscopy line profiles that exhibited significant change in the CFO magnetic domain response in accordance to magnetization-field (M-H) loops. Together, these results demonstrate good control of the magnetic properties of CFO via an electric field induced strain.

Wang, Zhiguang; Yang, Yaodong; Viswan, Ravindranath; Li, Jiefang; Viehland, D.

2011-07-01

356

Interaction of stable colloidal nanoparticles with cellular membranes.  

PubMed

Due to their ultra-small size, inorganic nanoparticles (NPs) have distinct properties compared to the bulk form. The unique characteristics of NPs are broadly exploited in biomedical sciences in order to develop various methods of targeted drug delivery, novel biosensors and new therapeutic pathways. However, relatively little is known in the negotiation of NPs with complex biological environments. Cell membranes (CMs) in eukaryotes have dynamic structures, which is a key property for cellular responses to NPs. In this review, we discuss the current knowledge of various interactions between advanced types of NPs and CMs. PMID:24361955

Mahmoudi, Morteza; Meng, Jie; Xue, Xue; Liang, Xing Jie; Rahman, Masoud; Pfeiffer, Christian; Hartmann, Raimo; Gil, Pilar Rivera; Pelaz, Beatriz; Parak, Wolfgang J; Del Pino, Pablo; Carregal-Romero, Susana; Kanaras, Antonios G; Tamil Selvan, Subramanian

2014-01-01

357

Quantitative measurement of nanoparticle halo formation around colloidal microspheres in binary mixtures.  

SciTech Connect

A new colloidal stabilization mechanism, known as nanoparticle 'haloing' (Tohver, V.; Smay, J. E.; Braem, A.; Braun, P. V.; Lewis, J. A. Proc. Natl. Acad. Sci. U.S.A. 2001, 98, (16), 8950-8954), has been predicted theoretically and inferred experimentally in microsphere--nanoparticle mixtures that possess high charge and size asymmetry. The term 'halo' implies the existence of a nonzero separation distance between the highly charged nanoparticles and the negligibly charged microspheres that they surround. By means of ultrasmall-angle X-ray scattering, we have quantified the microsphere--nanoparticle separation distance as well as the number of nanoparticles and their lateral separation distance within the self-organized halos that form in these binary mixtures.

Zhang, F.; Long, G. G.; Jemian, P. R.; Ilavsky, J.; Milam, V. T.; Lewis, J. A.

2008-07-01

358

Mixed lanthanide oxide nanoparticles as dual imaging agent in biomedicine  

NASA Astrophysics Data System (ADS)

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.

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

359

Mixed lanthanide oxide nanoparticles as dual imaging agent in biomedicine  

PubMed Central

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. PMID:24220641

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

2013-01-01

360

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

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

2011-01-01

361

Manipulating superconducting fluctuations by the Little–Parks–de Gennes effect in ultrasmall Al loops  

PubMed Central

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. PMID:22927386

Staley, Neal E.; Liu, Ying

2012-01-01

362

Quantum theory of the dc Josephson effect: Static tunneling characteristics of ultrasmall Josephson junctions  

NASA Astrophysics Data System (ADS)

We examine the static tunneling characteristics of ultrasmall Josephson junctions that are current biased on the zero-voltage dc step. Novel scaling, magnetic, and thermal characteristics are exhibited by the supercurrent as the device is scaled down from the 1.0 to the 0.01 ?m2 regime. Furthermore, the noise voltage is found to peak for devices in which the electrostatic energy required to transfer a pair is equal to the interaction energy between the two superconductors. For such junctions, noise voltages are on the order of several mV, and the magnitude of the supercurrent is found to be a very sensitive function of device area and operating temperature. Finally, these features of the junction's dynamics have technological implications regarding digital applications of such devices.

Rogovin, D.; Nagel, J.

1982-10-01

363

Facile synthesis of ultra-small PbSe nanorods for photovoltaic application.  

PubMed

Nanocrystal array solar cells based on lead chalcogenide quantum dots (QDs) have recently achieved a high power conversion efficiency of over 8%. The device performance is expected to further increase by using 1-dimensional nanorods (NRs), due to their improved carrier transport over zero-dimensional quantum dots. However, previously reported PbSe NRs have not been used in solar cells mainly because of their large diameters, resulting in a small bandgap unsuitable for photovoltaic application. In this work, we have demonstrated a new method for synthesizing monodisperse ultra-small PbSe NRs with the diameter approaching 2 nm (Eg > 1.2 eV), which can be attributed to the use of diphenylphosphine (DPP) and trans-2-octenoic acid (t-2-OA). The introduction of trace DPP can greatly lower the reaction temperature, leading to reduced diameters for the obtained PbSe NRs as well as largely increased yield. The use of short-chain t-2-OA together with oleic acid as capping ligands results in high monomer reactivity, fast nucleus diffusion and high growth rate, which realize the anisotropic growth of ultra-small PbSe NRs at low reaction temperatures. The PbSe NRs show n-type properties and high electron mobility as measured using field-effect transistors. The PbSe NRs with narrow diameters also demonstrate a suitable bandgap for photovoltaic application. They are used for the first time in solar cells and their improved efficiency is demonstrated when used together with QDs. PMID:25564767

Han, Lu; Liu, Jie; Yu, Ningning; Liu, Zeke; Gu, Jinan; Lu, Jialing; Ma, Wanli

2015-01-28

364

Self-assembled ferrimagnet--polymer composites for magnetic recording media.  

PubMed

A self-assembled magnetic recording medium was created using colloidal ferrimagnetic building blocks. Monodisperse cobalt ferrite nanoparticles (CoFe(2)O(4)) were synthesized using solution-based methods and then stabilized in solution using the amphiphilic diblock copolymer, poly(acrylic acid)-b-poly(styrene) (PAA-PS). The acid groups of the acrylate block bound the polymer to the nanoparticle surface via multivalent interactions, while the styrene block afforded the magnetic nanoparticle--polymer complex solubility in organic solvents. Moreover, the diblock copolymer improved the colloidal stability of the ferrimagnetic CoFe(2)O(4) nanoparticles by reducing the strong interparticle magnetic interactions, which typically caused the ferrimagnetic nanoparticles to irreversibly aggregate. The nanoparticle--polymer complex was spin-coated onto a silicon substrate to afford self-organized thin film arrays, with the interparticle spacing determined by the molecular weight of the diblock copolymer. The thin film composite was also exposed to an external magnetic field while simultaneously heated above the glass transition temperature of poly(styrene) to allow the nanoparticles to physically rotate to align their easy axes with the direction of the magnetic field. In order to demonstrate that this self-assembled ferrimagnet--polymer composite was suitable as a magnetic recording media, read/write cycles were demonstrated using a contact magnetic tester. This work provides a simple route to synthesizing stabilized ferrimagnetic nanocrystals that are suitable for developing magnetic recording media. PMID:20698640

Dai, Qiu; Berman, David; Virwani, Kumar; Frommer, Jane; Jubert, Pierre-Olivier; Lam, Michelle; Topuria, Teya; Imaino, Wayne; Nelson, Alshakim

2010-08-11

365

From capacitive to tunnelling conduction through annealing in metal-insulating granular films: the role of ultra-small particles  

NASA Astrophysics Data System (ADS)

In situ transmission electron microscopy (TEM) during annealing of metal-insulating granular thin films reveals significant microstructural changes: nucleation of ultra-small particles and growth of those already existing. Radio frequency impedance spectroscopy shows that by subsequent annealing, tunnelling conductance becomes more important at the expense of the decrease of capacitive contributions, giving place to an almost frequency-independent conduction, although being very far from physical percolation. These results are simulated assuming a random resistor-capacitor network, which represents the competing conduction channels between particles through thermally assisted tunnelling and capacitive conductance. The physical parameters derived from this simple model agree well with the microstructural changes observed by TEM through annealing, and evidence the increase of tunnelling conduction paths mediated by segregated ultra-small glue particles in between bigger ones. Those glue particles grow with further annealing and account for the correlation of the microstructural changes to the ac transport properties.

García del Muro, Montserrat; Konstantinovi?, Zorica; Batlle, Xavier; Labarta, Amílcar

2013-12-01

366

Ultrafine Sulfur Nanoparticles in Conducting Polymer Shell as Cathode Materials for High Performance Lithium/Sulfur Batteries  

NASA Astrophysics Data System (ADS)

We report the synthesis of ultrafine S nanoparticles with diameter 10 ~ 20 nm via a membrane-assisted precipitation technique. The S nanoparticles were then coated with conducting poly (3,4-ethylenedioxythiophene) (PEDOT) to form S/PEDOT core/shell nanoparticles. The ultrasmall size of S nanoparticles facilitates the electrical conduction and improves sulfur utilization. The encapsulation of conducting PEDOT shell restricts the polysulfides diffusion, alleviates self-discharging and the shuttle effect, and thus enhances the cycling stability. The resulting S/PEDOT core/shell nanoparticles show initial discharge capacity of 1117 mAh g-1 and a stable capacity of 930 mAh g-1 after 50 cycles.

Chen, Hongwei; Dong, Weiling; Ge, Jun; Wang, Changhong; Wu, Xiaodong; Lu, Wei; Chen, Liwei

2013-05-01

367

Bio-NCs - the marriage of ultrasmall metal nanoclusters with biomolecules  

NASA Astrophysics Data System (ADS)

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.

Goswami, Nirmal; Zheng, Kaiyuan; Xie, Jianping

2014-10-01

368

Ultra-small plutonium oxide nanocrystals: an innovative material in plutonium science.  

PubMed

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. PMID:25042621

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

369

Competing mechanisms of catalytic H2 formation and dissociation on ultrasmall silicate nanocluster dust grains  

NASA Astrophysics Data System (ADS)

Silicate dust grains are thought to be essential in catalysing the formation of H2. Ultrasmall silicates (diameter ?1.5 nm) are fundamental intermediates in silicate dust formation in stellar outflows, and are ubiquitous in the interstellar medium. To investigate the catalytic formation and dissociation of H2 on such nanosilicates, we have performed ab initio quantum chemical calculations of hydrogen interacting with a stable 21 atom nanosilicate cluster having the stoichiometry of forsterite, (MgO)6(SiO2)3. Due to its small size and high percentage of surface atoms, our particle inherently does not exhibit the bulk forsterite crystal structure and possesses a range of chemisorption and physisorption sites, presumably similar to those that larger amorphous silicates would offer. We find a number of exothermic H2 formation routes and pathways for H2 catalytic dissociation on the nanosilicate. In particular, we discover some H2 formation routes that are energetically more favourable than that reported for the forsterite (010) surface. Further, we find a linear correlation between the dissociative chemisorption of two H atoms and the dissociation transition state, suggestive of a general Brønsted-Evans-Polanyi relation for H2 dissociation on bare silicates independent of dust grain size and/or crystallinity.

Kerkeni, Boutheïna; Bromley, Stefan T.

2013-10-01

370

Further analysis of focusing performance of an ultra-small gradient-index fiber probe  

NASA Astrophysics Data System (ADS)

In order to optimize ultra-small gradient-index (GRIN) fiber probes and provide a theoretical prediction for the fabrication of such probes with high performance, focusing performance of the GRIN fiber probe is further analyzed based on the optical characteristic parameters. According to the optical model of the GRIN fiber probe and its mathematical expressions of characteristic parameters, the three-dimensional (3-D) function diagram is used for analyzing the impact of the lengths of probe components on the characteristic parameters. Partial derivatives of the mathematical expressions of characteristics are derived to analyze the mutation of focusing performance caused by the different lengths of probe components. According to the analytical results, our predictions suggest that focusing performance could be reflected through the 3-D function diagram between the characteristic parameters and the continuous change of the lengths of probe components. In addition, mutation occurs in the focusing performance of the GRIN fiber probe when the length of probe components changes. The research results are of practical guiding significance for the fabrication of GRIN fiber probes requiring specific optical focusing performance.

Wang, Chi; Bi, Shubo; Xia, Xueqin; Yu, Yingjie

2014-01-01

371

Production of ultra-small ink jet drops using drop-on-demand (DOD) drop formation  

NASA Astrophysics Data System (ADS)

The formation of drops having radii that are smaller than the radii of the nozzle from which they are ejected is an active area of research in drop-on-demand (DOD) ink jet printing. In the last decade, Chen and Basaran (Phys Fluids, 2002; US patent, 2003) showed experimentally and computationally that several fold reduction in drop radius R (an order of magnitude reduction in drop volume V) is possible by judicious use of waveform modulation in which one or more intrinsic time scales such as capillary time, time for vorticity diffusion, and time for piezo actuation are varied. In this paper, we report the results of a computational study through which we have uncovered a novel method for achieving a factor of 5-10 reduction in R (about two to three orders of magnitude reduction in V). Scaling arguments are also developed which yield a simple expression for the size of the ultra-small drops formed as a function of the governing dimensionless groups. Formation of such small drops using DOD technology may prove especially attractive in applications involving direct printing of flexible electronics and solar cells.

Gao, Haijing; Xu, Qi; Harris, Michael; Basaran, Osman

2009-11-01

372

Toward an image-guided microbeam radiation therapy using gadolinium-based nanoparticles.  

PubMed

Ultrasmall gadolinium-based nanoparticles (GBNs) induce both a positive contrast for magnetic resonance imaging and a radiosentizing effect. The exploitation of these characteristics leads to a greater increase in lifespan of rats bearing brain tumors since the radiosensitizing effect of GBNs can be activated by X-ray microbeams when the gadolinium content is, at the same time, sufficiently high in the tumor and low in the surrounding healthy tissue. GBNs exhibit therefore an interesting potential for image-guided radiotherapy. PMID:22040385

Le Duc, Géraldine; Miladi, Imen; Alric, Christophe; Mowat, Pierre; Bräuer-Krisch, Elke; Bouchet, Audrey; Khalil, Enam; Billotey, Claire; Janier, Marc; Lux, François; Epicier, Thierry; Perriat, Pascal; Roux, Stéphane; Tillement, Olivier

2011-12-27

373

Detection and Isolation of Ultrasmall Microorganisms from a 120,000-Year-Old Greenland Glacier Ice Core  

PubMed Central

The abundant microbial population in a 3,043-m-deep Greenland glacier ice core was dominated by ultrasmall cells (<0.1 ?m3) that may represent intrinsically small organisms or starved, minute forms of normal-sized microbes. In order to examine their diversity and obtain isolates, we enriched for ultrasmall psychrophiles by filtering melted ice through filters with different pore sizes, inoculating anaerobic low-nutrient liquid media, and performing successive rounds of filtrations and recultivations at 5°C. Melted ice filtrates, cultures, and isolates were analyzed by scanning electron microscopy, flow cytometry, cultivation, and molecular methods. The results confirmed that numerous cells passed through 0.4-?m, 0.2-?m, and even 0.1-?m filters. Interestingly, filtration increased cell culturability from the melted ice, yielding many isolates related to high-G+C gram-positive bacteria. Comparisons between parallel filtered and nonfiltered cultures showed that (i) the proportion of 0.2-?m-filterable cells was higher in the filtered cultures after short incubations but this difference diminished after several months, (ii) more isolates were obtained from filtered (1,290 isolates) than from nonfiltered (447 isolates) cultures, and (iii) the filtration and liquid medium cultivation increased isolate diversity (Proteobacteria; Cytophaga-Flavobacteria-Bacteroides; high-G+C gram-positive; and spore-forming, low-G+C gram-positive bacteria). Many isolates maintained their small cell sizes after recultivation and were phylogenetically novel or related to other ultramicrobacteria. Our filtration-cultivation procedure, combined with long incubations, enriched for novel ultrasmall-cell isolates, which is useful for studies of their metabolic properties and mechanisms for long-term survival under extreme conditions. PMID:16332755

Miteva, Vanya I.; Brenchley, Jean E.

2005-01-01

374

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

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.Molecular Psychiatry advance online publication, 23 September 2014; doi:10.1038/mp.2014.110. PMID:25245499

Girardi, G; Fraser, J; Lennen, R; Vontell, R; Jansen, M; Hutchison, G

2014-09-23

375

Enhanced sensitivity and contrast with bimodal atomic force microscopy with small and ultra-small amplitudes in ambient conditions  

SciTech Connect

Here, we introduce bimodal atomic force microscopy operated with sub-nm and ultra-small, i.e., sub-angstrom, first and second mode amplitudes in ambient conditions. We show how the tip can be made to oscillate in the proximity of the surface and in perpetual contact with the adsorbed water layers while the second mode amplitude and phase provide enhanced contrast and sensitivity. Nonlinear and nonmonotonic behavior of the experimental observables is discussed theoretically with a view to high resolution, enhanced contrast, and minimally invasive mapping. Fractions of meV of energy dissipation are shown to provide contrast above the noise level.

Santos, Sergio [Departament de Disseny i Programació de Sistemes Electrònics, UPC-Universitat Politècnica de Catalunya Av. Bases, 61, 08242 Manresa (Barcelona) (Spain)] [Departament de Disseny i Programació de Sistemes Electrònics, UPC-Universitat Politècnica de Catalunya Av. Bases, 61, 08242 Manresa (Barcelona) (Spain)

2013-12-02

376

How size evaluation of lymph node is protocol dependent in MRI when using ultrasmall superparamagnetic iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Gharehaghaji, Nahideh; Oghabian, Mohammad Ali; Sarkar, Saeed; Darki, Fahimeh; Beitollahi, Ali

2009-05-01

377

Targeting of peptide conjugated magnetic nanoparticles to urokinase plasminogen activator receptor (uPAR) expressing cells  

NASA Astrophysics Data System (ADS)

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 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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr32922d

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

378

Quantum Tunneling of Magnetization in Ultrasmall Half-Metallic V3O4 Quantum Dots: Displaying Quantum Superparamagnetic State  

PubMed Central

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. PMID:23091695

Xiao, Chong; Zhang, Jiajia; Xu, Jie; Tong, Wei; Cao, Boxiao; Li, Kun; Pan, Bicai; Su, Haibin; Xie, Yi

2012-01-01

379

Nano-photonic-device technologies for ultra-small and ultra-fast all-optical devices - Fusion of photonic crystals and quantum dots -  

Microsoft Academic Search

Simulation, fabrication, characterization of two-dimensional photonic crystals and fabrication of nanoprobe-assisted site-controlled quantum dots for large optical non-linearity are presented for photonic crystal and quantum dot-based ultra-small and ultra-fast all optical switches

K. Asakawa; H. Nakamura; Y. Sugimoto; Y. Watanabe; S. Lan; N. Ikeda; T. Yang; Y. Tanaka; Y. Nakamura; S. Ohkouchi; N. Yamamoto; K. Kanamoto; H. Ishikawa; K. Inoue

2002-01-01

380

Early-Stage Investigations of Ultrasmall Superparamagnetic Iron Oxide-Induced Signal Change After Permanent Middle Cerebral Artery Occlusion in Mice  

Microsoft Academic Search

Background and Purpose—MR signal changes after intravenous ultrasmall superparamagnetic iron oxide (USPIO) injection are related to inflammatory cells at the subacute stages after focal cerebral injury. However, at the early stages, the interpretation of USPIO-related MR signal alterations remains controversial. Here, we compared MR signal changes after intravenous USPIO injection with the histological iron and macrophage distribution during the first

Virginie Desestret; Jean-Christophe Brisset; Samir Moucharrafie; Emilie Devillard; Serge Nataf; Jerome Honnorat; Norbert Nighoghossian; Yves Berthezène; Marlene Wiart

2010-01-01

381

A new approach to quantification of metamorphism using ultra-small and small angle neutron scattering.  

SciTech Connect

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 in a manner that is difficult to achieve using high-resolution imaging (e.g. TEM). Thus, neutron scattering techniques provide a new approach to the analysis and study of metamorphism.

Anovitz, Lawrence {Larry} M [ORNL; Lynn, Gary W [ORNL; Cole, David R [ORNL

2009-12-01

382

Electrical detection of surface plasmon resonance phenomena by a photoelectronic device integrated with gold nanoparticle plasmon antenna  

NASA Astrophysics Data System (ADS)

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.

Hashimoto, Tatsuya; Fukunishi, Yurie; Zheng, Bin; Uraoka, Yukiharu; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

2013-02-01

383

Protein fibrillation and nanoparticle interactions: opportunities and challenges  

NASA Astrophysics Data System (ADS)

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.

Mahmoudi, Morteza; Kalhor, Hamid R.; Laurent, Sophie; Lynch, Iseult

2013-03-01

384

Manipulation of high-order scattering processes in ultrasmall optical resonators to control far-field emission.  

PubMed

By imposing a set of harmonic perturbations to a microcavity boundary, we induce conversion and mixing of orbital angular momentum of light via surface scattering. Multiple scattering paths are available due to high-order scattering, which can be greatly enhanced by quasidegenerate resonances. By manipulating the relative strengths of these scattering processes, we theoretically synthesize the angular momentum spectra of individual modes so as to control their far-field patterns. We demonstrate experimentally that in wavelength-scale cavities of a fixed shape, the neighboring modes can have dramatically different emission directionality. This phenomenon is robust against slight shape deviation and surface roughness, and provides a general mechanism to control the emission direction of ultrasmall resonators. PMID:24815650

Redding, Brandon; Ge, Li; Song, Qinghai; Solomon, Glenn S; Cao, Hui

2014-04-25

385

Polarity determination by electron energy-loss spectroscopy: application to ultra-small III-nitride semiconductor nanocolumns.  

PubMed

Channeling-enhanced electron energy-loss spectroscopy is applied to determine the polarity of ultra-small nitride semiconductor nanocolumns in transmission electron microscopy. The technique demonstrates some practical advantages in the nanostructure analysis, especially for feature sizes of less than 50 nm. We have studied GaN and (Al, Ga)N nanocolumns grown in a self-assembled way by molecular beam epitaxy directly on bare Si(111) substrates and on AlN buffer layers, respectively. The GaN nanocolumns on Si show an N polarity, while the (Al, Ga)N nanocolumns on an AlN buffer exhibit a Ga polarity. The different polarities of nanocolumns grown in a similar procedure are interpreted in terms of the specific interface bonding configurations. Our investigation contributes to the understanding of polarity control in III-nitride nanocolumn growth. PMID:21914935

Kong, X; Risti?, J; Sanchez-Garcia, M A; Calleja, E; Trampert, A

2011-10-14

386

Development of carbon nanotubes/CoFe2O4 magnetic hybrid material for removal of tetrabromobisphenol A and Pb(II).  

PubMed

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. PMID:24342050

Zhou, Lincheng; Ji, Liqin; Ma, Peng-Cheng; Shao, Yanming; Zhang, He; Gao, Weijie; Li, Yanfeng

2014-01-30

387

Highly flexible magnetic composite aerogels prepared by using cellulose nanofibril networks as templates.  

PubMed

Nanostructured cellulose nanofibrils can form ductile or tough networks that are suitable templates for the creation of materials with functional properties. In this work, a facile method has been developed for the preparation of magnetic hybrid cellulose aerogels. The preparation processes followed by two steps, firstly, preparation of cellulose hydrogel films from LiOH/urea solvent, then CoFe2O4 nanoparticles were synthesized in the porous structured cellulose scaffolds. After being freeze-dried, CoFe2O4/cellulose magnetic aerogels were obtained. The porosity of the composite aerogels ranged from 78 to 52% with pore size distribution in a few tens of nanometers. The internal specific surface areas were around 300-320 m2/g, and the densities were in the range of 0.25-0.39 g/cm3. The hybrid aerogels showed improved mechanical strength, superparamagnetic properties. Unlike solvent-swollen gels and ferrogels, the magnetic composite aerogels were lightweight, flexibility, high porosity and with large specific surface area and could be expected to be used in many fields. PMID:24750757

Liu, Shilin; Yan, Qiufang; Tao, Dandan; Yu, Tengfei; Liu, Xiaoya

2012-06-20

388

Facile synthesis of phosphine free ultra-small PbSe nanocrystals and their light harvesting studies in ETA solar cells.  

PubMed

Ultra-small PbSe nanocrystals (NCs) were synthesized via a 'one-pot' approach in olive oil as the reaction medium and capping agent. The optical spectra showed discernible blue shifts in the absorption band edges (570-780 nm) due to strong quantum confinement effects and photoluminescence (PL) spectra showed significant strong emission peaks in the range of 780-850 nm. The broad peaks in the powder X-ray diffraction (p-XRD) pattern indicate the ultra-small size of the as-prepared NCs. These NCs were used to construct an extremely thin absorber (ETA) solar device after surface modification. The preliminary results indicate their potential as light harvesting entities in nanostructure based solar cells. PMID:25247625

Akhtar, Javeed; Banski, Mateusz; Malik, Mohammad Azad; Revaprasadu, Neerish; Podhorodecki, Artur; Misiewicz, Jan

2014-11-21

389

Ultrasmall biomolecule-anchored hybrid GdVO4 nanophosphors as a metabolizable multimodal bioimaging contrast agent  

NASA Astrophysics Data System (ADS)

Multimodal molecular imaging has recently attracted much attention on disease diagnostics by taking advantage of individual imaging modalities. Herein, we have demonstrated a new paradigm for multimodal bioimaging based on amino acids-anchored ultrasmall lanthanide-doped GdVO4 nanoprobes. On the merit of special metal-cation complexation and abundant functional groups, these amino acids-anchored nanoprobes showed high colloidal stability and excellent dispersibility. Additionally, due to typical paramagnetic behaviour, high X-ray mass absorption coefficient and strong fluorescence, these nanoprobes would provide a unique opportunity to develop multifunctional probes for MRI, CT and luminescence imaging. More importantly, the small size and biomolecular coatings endow the nanoprobes with effective metabolisability and high biocompatibility. With the superior stability, high biocompatibility, effective metabolisability and excellent contrast performance, amino acids-capped GdVO4:Eu3+ nanocastings are a promising candidate as multimodal contrast agents and would bring more opportunities for biological and medical applications with further modifications.Multimodal molecular imaging has recently attracted much attention on disease diagnostics by taking advantage of individual imaging modalities. Herein, we have demonstrated a new paradigm for multimodal bioimaging based on amino acids-anchored ultrasmall lanthanide-doped GdVO4 nanoprobes. On the merit of special metal-cation complexation and abundant functional groups, these amino acids-anchored nanoprobes showed high colloidal stability and excellent dispersibility. Additionally, due to typical paramagnetic behaviour, high X-ray mass absorption coefficient and strong fluorescence, these nanoprobes would provide a unique opportunity to develop multifunctional probes for MRI, CT and luminescence imaging. More importantly, the small size and biomolecular coatings endow the nanoprobes with effective metabolisability and high biocompatibility. With the superior stability, high biocompatibility, effective metabolisability and excellent contrast performance, amino acids-capped GdVO4:Eu3+ nanocastings are a promising candidate as multimodal contrast agents and would bring more opportunities for biological and medical applications with further modifications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03819c

Dong, Kai; Ju, Enguo; Liu, Jianhua; Han, Xueli; Ren, Jinsong; Qu, Xiaogang

2014-09-01

390

Polymeric nanoparticles-based topical delivery systems for the treatment of dermatological diseases  

PubMed Central

Human skin not only functions as a permeation barrier (mainly due to the stratum corneum layer), but also provides a unique delivery pathway for therapeutic and other active agents. These compounds penetrate via intercellular, intracellular and transappendageal routes, resulting in topical delivery (into skin strata) and transdermal delivery (to subcutaneous tissues and into the systemic circulation). Passive and active permeation enhancement methods have been widely applied to increase the cutaneous penetration. The pathology, pathogenesis and topical treatment approaches of dermatological diseases, such as psoriasis, contact dermatitis, and skin cancer, are then discussed. Recent literature has demonstrated that nanoparticles-based topical delivery systems can be successful in treating these skin conditions. The studies are reviewed starting with the nanoparticles based on natural polymers specially chitosan, followed by those made of synthetic, degradable (aliphatic polyesters) and non-degradable (polyarylates) polymers; emphasis is given to nanospheres made of polymers derived from naturally occurring metabolites, the tyrosine-derived nanospheres (TyroSpheres™). In summary, the nanoparticles-based topical delivery systems combine the advantages of both the nano-sized drug carriers and the topical approach, and are promising for the treatment of skin diseases. For the perspectives, the penetration of ultra-small nanoparticles (size smaller than 40 nm) into skin strata, the targeted delivery of the encapsulated drugs to hair follicle stem cells, and the combination of nanoparticles and microneedle array technologies for special applications such as vaccine delivery are discussed. PMID:23386536

Zhang, Zheng; Tsai, Pei-Chin; Ramezanli, Tannaz; Michniak-Kohn, Bozena B.

2013-01-01

391

Biotemplated Synthesis of Anatase Titanium Dioxide Nanoparticles via Lignocellulosic Waste Material  

PubMed Central

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

Bagheri, Samira; Abd Hamid, Sharifah Bee

2014-01-01

392

Bolaform surfactants with polyoxometalate head groups and their assembly into ultra-small monolayer membrane vesicles  

PubMed Central

Surfactants are indispensable in established technologies as detergents or emulsification agents, and also in recent studies for controlling the growth of nanoparticles or for creating nanocarriers. Although the properties of conventional, organic surfactants are thoroughly explored, strong interest persists in surfactants that possess unique features inaccessible for ordinary systems. Here we present dipolar, bolaform surfactants with a head group comprising of 11 tungsten atoms. These novel compounds are characterized by an exceptionally low critical self-organization concentration, which leads to monolayer vesicles with a diameter of only 15?nm, that is, substantially smaller than for any other system. The membrane of the vesicles is impermeable for water-soluble and oil-soluble guests. Control over release kinetics, which can be followed via the quantitative fluorescence quenching of confined fluorophores, is gained by means of pH adjustments. PMID:23250429

Landsmann, Steve; Luka, Martin; Polarz, Sebastian

2012-01-01

393

One-dimensional magnetopolymeric nanostructures with tailored sizes.  

PubMed

Ultra-high aspect ratio nanofibers composed of poly(vinyl alcohol) and CoFe(2)O(4) nanoparticles (PVA/CoFe(2)O(4)) and moderate aspect ratio nanofibers composed of poly(vinyl chloride) and Fe(3)O(4) nanoparticles (PVC/Fe(3)O(4)) have been prepared. Magnetopolymeric one-dimensional (1D) nanostructures with any diameter and length can be prepared by template synthesis using anodic aluminum oxide (AAO) followed by the replication methods presented in this work. These replication methods are very effective, and allow the nanomoulding of any polymer-nanoparticle 1D composite. A first magnetic characterization of the nanostructured composites reveals a modest magnetic anisotropy. The development of magnetopolymeric nanofibers with adjusted length and diameter opens new opportunities in a wide range of applications. PMID:21825668

Martín, J; Vázquez, M; Hernández-Vélez, M; Mijangos, C

2008-04-30

394

Cd1-xMnxTe ultrasmall quantum dots growth in a silicate glass matrix by the fusion method  

NASA Astrophysics Data System (ADS)

In this study, we synthesized Cd1-xMnxTe ultrasmall quantum dots (USQDs) in SiO2-Na2CO3-Al2O3-B2O3 glass system using the fusion method. Growth of these Cd1-xMnxTe USQDs was confirmed by optical absorption, atomic force microscopy (AFM), magnetic force microscopy (MFM), scanning transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR) measurements. The blueshift of absorption transition with increasing manganese concentration gives evidence of incorporation of manganese ions (Mn2+) in CdTe USQDs. AFM, TEM, and MFM confirmed, respectively, the formation of high quality Cd1-xMnxTe USQDs with uniformly distributed size and magnetic phases. Furthermore, EPR spectra showed six lines associated to the S = 5/2 spin half-filled d-state, characteristic of Mn2+, and confirmed that Mn2+ are located in the sites core and surface of the CdTe USQD. Therefore, synthesis of high quality Cd1-xMnxTe USQDs may allow the control of optical and magnetic properties.

Dantas, Noelio Oliveira; de Lima Fernandes, Guilherme; Baffa, Oswaldo; Gómez, Jorge Antônio; Almeida Silva, Anielle Christine

2014-09-01

395

Construction of a high-energy Bonse-Hart ultrasmall-angle x-ray scattering instrument  

NASA Astrophysics Data System (ADS)

A Bonse-Hart ultrasmall-angle x-ray scattering (USAXS) instrument, employing a synchrotron x-ray source at an energy of 18.86 keV (wavelength ?=0.06573 nm), has been designed, constructed, and tested. Solid as well as suspensions of polystyrene and poly(chlorostyrene) latex spheres were used as reference standards in order to demonstrate the range of this instrument. The USAXS results measured at ?=0.06573 nm were also compared with those from a calibrated Bonse-Hart instrument operating at ?=0.154 nm, i.e., the standard Cu K? radiation. The higher-energy synchrotron x rays permit us to study absorbing and/or opaque materials having long range inhomogeneities in the order of microns. Furthermore, for many polymer systems, the optimal sample thickness at ??0.066 nm is increased to ˜10 mm and thin-walled glass windows become acceptable. Thus, a cylindrical light-scattering cell with a wall thickness of 0.3 mm could be used for both USAXS and laser light scattering measurements. The main hurdle for performing simultaneous static and dynamic light scattering as well as USAXS experiments on polymer solutions and gels with the same sample has been resolved. This capability should open up new frontiers in structural and dynamical studies of systems involving a large range of length scales from angstroms to microns.

Chu, Benjamin; Yeh, Fengji; Li, Yingjie; Harney, Paul J.; Rousseau, Jean; Darovsky, Alex; Siddons, D. P.

1994-10-01

396

On the feasibility of visualizing ultrasmall gold labels in biological specimens by STEM tomography  

PubMed Central

Labeling with heavy atom clusters attached to antibody fragments is an attractive technique for determining the 3D distribution of specific proteins in cells using electron tomography. However, the small size of the labels makes them very difficult to detect by conventional bright-field electron tomography. Here we evaluate quantitative scanning transmission electron microscopy (STEM) at a beam voltage of 300 kV for detecting 11-gold atom clusters (Undecagold) and 1.4 nm-diameter nanoparticles (Nanogold) for a variety of specimens and imaging conditions. STEM images as well as tomographic tilt series are simulated by means of the NIST Elastic Scattering Cross-Section Database for gold clusters embedded in carbon. The simulations indicate that the visibility in 2D of Undecagold clusters in a homogeneous matrix is maximized for low inner collection semi-angles of the STEM annular dark-field detector (15–20 mrad). Furthermore, our calculations show that the visibility of Undecagold in 3D reconstructions is significantly higher than in 2D images for an inhomogeneous matrix corresponding to fluctuations in local density. The measurements demonstrate that it is possible to detect Nanogold particles in plastic sections of tissue freeze-substituted in the presence of osmium. STEM tomography has the potential to localize specific proteins in permeabilized cells using antibody fragments tagged with small heavy atom clusters. Our quantitative analysis provides a framework for determining the detection limits and optimal experimental conditions for localizing these small clusters. PMID:17689263

Sousa, A. A.; Aronova, M. A.; Kim, Y. C.; Dorward, L. M.; Zhang, G.; Leapman, R. D.

2009-01-01

397

Thermal signatures of pairing correlations in nuclei and nanoparticles  

NASA Astrophysics Data System (ADS)

Pairing correlations in nuclei at zero temperature are well documented but much less is known about their thermal signatures. Nuclei are in the crossover regime between the bulk BCS limit and the fluctuation-dominated regime. We have used the shell model Monte Carlo approach to study pairing correlations at finite temperature beyond the BCS limit. We identify signatures of pairing correlations in both the heat capacity and moment of inertia [1]. These signatures depend on the particle- number parity of protons and neutrons. Ultra-small metallic grains (nanoparticles) whose linear size is below a few nanometers are also close to the fluctuation-dominated regime. We use auxiliary-field Monte Carlo methods to study pairing correlations in such nanoparticles and find odd-even effects in their heat capacity and spin susceptibility, in analogy to the signatures found in nuclei. This work was supported in part by the U.S. DOE grant No. DE-FG-0291-ER-40608. [1] Y. Alhassid, G.F. Bertsch, L. Fang, and S. Liu, Phys. Rev. C 72, 064326 (2005).

Fang, L.; Schmidt, S.; Alhassid, Y.

2006-10-01

398

Immobilization of selenite on Fe3O4 and Fe/Fe3C ultrasmall particles.  

PubMed

The sorption of selenite ions onto Fe3O4 and Fe/Fe3C nanoparticles (NPs) was studied in aqueous solutions under anoxic conditions using gamma spectrometry and X-ray absorption spectrometry (XAS) techniques. This is the first study related to the remedial applications of Fe/Fe3C NPs. FesO4 NPs have been prepared by conventional coprecipitation of Fe(II) and Fe(III) in basic solutions. Stable Fe/Fe3C NPs have been prepared by Fe(CO)5 sonicating in diphenylmethane solutions and subsequently annealing the as-prepared product. Kinetic study demonstrated that Se(IV) sorption is extremely rapid: the equilibrium is reached in approximately 10 and 30 min for Fe3O4 and Fe/Fe3C NPs, respectively, at pH = 4.9-5.1 in solutions of 0.1 M NaCl. The distribution coefficients are also very high for both kinds of NPs (Kd > 3000). Increasing the pH to 10.3 or adsorption of organic ligands, like L-lysine or dodecanoate, at the surface of NPs causes the decrease in Kd values. However, even in these cases Kd values exceed 150. Magnetic NPs loaded with selenium can be easily and completely removed from solution with a 0.4 T permanent magnet. XAS study revealed the absence of Se(IV) reduction during the sorption onto Fe3O4 NPs in the pH range of 4.8-8.0. By contrast, the removal of Se(IV) with Fe/Fe3C NPs in anaerobic conditions occurs via Se(IV) reduction to Se(-II) and subsequent formation of iron selenide at the particle surface. Thus, the Fe/Fe3C NPs are superior to Fe3O4 NPs due to their ability to immobilize rapidly and irreversibly Se(IV) via reductive mechanism. Presumably these particles could be also effective for the removal of other contaminants such as hexavalent chromium, actinides, technetium, and toxic organic compounds. PMID:18504980

Loyo, Raquel López de Arroyabe; Nikitenko, Sergei I; Scheinost, Andreas C; Simonoff, Monique

2008-04-01

399

Precision Nanoparticles  

SciTech Connect

A revolutionary technology that efficiently produces nanoparticles in uniform and prescribed sizes (1-100 nanometers) using supercritical fluids. INL researcher Robert Fox was joined by Idaho State University researchers Rene Rodriquez and Joshua Pak in d

John Hemminger

2009-07-21

400

Bi-photon imaging and diagnostics using ultra-small diagnostic probes engineered from semiconductor nanocrystals and single-domain antibodies  

NASA Astrophysics Data System (ADS)

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.

Hafian, Hilal; Sukhanova, Alyona; Chames, Patrick; Baty, Daniel; Pluot, Michel; Cohen, Jacques H. M.; Nabiev, Igor R.; Millot, Jean-Marc

2012-10-01

401

Magnetic PEGylated Pt3Co nanoparticles as a novel MR contrast agent: in vivo MR imaging and long-term toxicity study  

NASA Astrophysics Data System (ADS)

Magnetic resonance (MR) imaging using magnetic nanoparticles as the contrast agent has been extensively explored in biomedical imaging and disease diagnosis. Herein, we develop biocompatible polymer coated ultra-small Pt3Co magnetic nanoparticles as a new T2-weighted MR imaging contrast agent. A unique class of alloy Pt3Co nanoparticles is synthesized through a thermal decomposition method. After being modified with polyethylene glycol (PEG), the obtained Pt3Co-PEG nanoparticles exhibit an extremely high T2-weighted relaxivity rate (r2) up to 451.2 mM s-1, which is much higher than that of Resovist®, a commercial T2-MR contrast agent used in the clinic. In vitro experiments indicate no obvious cytotoxicity of Pt3Co-PEG nanoparticles to various cell lines. After intravenous injection of Pt3Co-PEG nanoparticles, in vivo T2-weighted MR imaging of tumor-bearing mice reveals strong tumor contrast, which is much higher than that offered by injecting Resovist®. We further study the long-term biodistribution and toxicology of this new type of MR contrast nanoparticles after intravenous injection into healthy mice. Despite the significant retention of Pt3Co-PEG nanoparticles in the mouse liver and spleen, no appreciable toxicity of these nanoparticles to the treated animals has been noted in our detailed histological and hematological analysis over a course of 60 days. Our work demonstrates that functionalized Pt3Co nanoparticles may be a promising new type of T2-weighted MR contrast agent potentially useful in biomedical imaging and diagnosis.Magnetic resonance (MR) imaging using magnetic nanoparticles as the contrast agent has been extensively explored in biomedical imaging and disease diagnosis. Herein, we develop biocompatible polymer coated ultra-small Pt3Co magnetic nanoparticles as a new T2-weighted MR imaging contrast agent. A unique class of alloy Pt3Co nanoparticles is synthesized through a thermal decomposition method. After being modified with polyethylene glycol (PEG), the obtained Pt3Co-PEG nanoparticles exhibit an extremely high T2-weighted relaxivity rate (r2) up to 451.2 mM s-1, which is much higher than that of Resovist®, a commercial T2-MR contrast agent used in the clinic. In vitro experiments indicate no obvious cytotoxicity of Pt3Co-PEG nanoparticles to various cell lines. After intravenous injection of Pt3Co-PEG nanoparticles, in vivo T2-weighted MR imaging of tumor-bearing mice reveals strong tumor contrast, which is much higher than that offered by injecting Resovist®. We further study the long-term biodistribution and toxicology of this new type of MR contrast nanoparticles after intravenous injection into healthy mice. Despite the significant retention of Pt3Co-PEG nanoparticles in the mouse liver and spleen, no appreciable toxicity of these nanoparticles to the treated animals has been noted in our detailed histological and hematological analysis over a course of 60 days. Our work demonstrates that functionalized Pt3Co nanoparticles may be a promising new type of T2-weighted MR contrast agent potentially useful in biomedical imaging and diagnosis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04212j

Yin, Shengnan; Li, Zhiwei; Cheng, Liang; Wang, Chao; Liu, Yumeng; Chen, Qian; Gong, Hua; Guo, Liang; Li, Yonggang; Liu, Zhuang

2013-11-01

402

Superparamagnetic iron oxide nanoparticles as radiosensitizer via enhanced reactive oxygen species formation  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Ultrasmall citrate-coated SPIONs with {gamma}Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} structure were prepared. Black-Right-Pointing-Pointer SPIONs uptaken by MCF-7 cells increase the ROS production for about 240%. Black-Right-Pointing-Pointer The SPION induced ROS production is due to released iron ions and catalytically active surfaces. Black-Right-Pointing-Pointer Released iron ions and SPION surfaces initiate the Fenton and Haber-Weiss reaction. Black-Right-Pointing-Pointer X-ray irradiation of internalized SPIONs leads to an increase of catalytically active surfaces. -- Abstract: Internalization of citrate-coated and uncoated superparamagnetic iron oxide nanoparticles by human breast cancer (MCF-7) cells was verified by transmission electron microscopy imaging. Cytotoxicity studies employing metabolic and trypan blue assays manifested their excellent biocompatibility. The production of reactive oxygen species in iron oxide nanoparticle loaded MCF-7 cells was explained to originate from both, the release of iron ions and their catalytically active surfaces. Both initiate the Fenton and Haber-Weiss reaction. Additional oxidative stress caused by X-ray irradiation of MCF-7 cells was attributed to the increase of catalytically active iron oxide nanoparticle surfaces.

Klein, Stefanie; Sommer, Anja [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)] [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany); Distel, Luitpold V.R. [Department of Radiation Oncology, Friedrich Alexander University Erlangen-Nuremberg, Universitaetsstrasse 27, D-91054 Erlangen (Germany)] [Department of Radiation Oncology, Friedrich Alexander University Erlangen-Nuremberg, Universitaetsstrasse 27, D-91054 Erlangen (Germany); Neuhuber, Winfried [Department of Anatomy, Chair of Anatomy I, Friedrich Alexander University Erlangen-Nuremberg, Krankenhausstr. 9, D-91054 Erlangen (Germany)] [Department of Anatomy, Chair of Anatomy I, Friedrich Alexander University Erlangen-Nuremberg, Krankenhausstr. 9, D-91054 Erlangen (Germany); Kryschi, Carola, E-mail: kryschi@chemie.uni-erlangen.de [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)] [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)

2012-08-24

403

Sub-10?nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production  

NASA Astrophysics Data System (ADS)

Titanium dioxide is a promising photocatalyst for water splitting, but it suffers from low visible light activity due to its wide band gap. Doping can narrow the band gap of titanium dioxide; however, new charge-carrier recombination centres may be introduced. Here we report the design of sub-10?nm rutile titanium dioxide nanoparticles, with an increased amount of surface/sub-surface defects to overcome the negative effects from bulk defects. Abundant defects can not only shift the top of the valence band of rutile titanium dioxide upwards for band-gap narrowing but also promote charge-carrier separation. The role of titanium(III) is to enhance, rather than initiate, the visible-light-driven water splitting. The sub-10?nm rutile nanoparticles exhibit the state-of-the-art activity among titanium dioxide-based semiconductors for visible-light-driven water splitting and the concept of ultra-small nanoparticles with abundant defects may be extended to the design of other robust semiconductor photocatalysts.

Li, Landong; Yan, Junqing; Wang, Tuo; Zhao, Zhi-Jian; Zhang, Jian; Gong, Jinlong; Guan, Naijia

2015-01-01

404

Sub-10?nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production.  

PubMed

Titanium dioxide is a promising photocatalyst for water splitting, but it suffers from low visible light activity due to its wide band gap. Doping can narrow the band gap of titanium dioxide; however, new charge-carrier recombination centres may be introduced. Here we report the design of sub-10?nm rutile titanium dioxide nanoparticles, with an increased amount of surface/sub-surface defects to overcome the negative effects from bulk defects. Abundant defects can not only shift the top of the valence band of rutile titanium dioxide upwards for band-gap narrowing but also promote charge-carrier separation. The role of titanium(III) is to enhance, rather than initiate, the visible-light-driven water splitting. The sub-10?nm rutile nanoparticles exhibit the state-of-the-art activity among titanium dioxide-based semiconductors for visible-light-driven water splitting and the concept of ultra-small nanoparticles with abundant defects may be extended to the design of other robust semiconductor photocatalysts. PMID:25562287

Li, Landong; Yan, Junqing; Wang, Tuo; Zhao, Zhi-Jian; Zhang, Jian; Gong, Jinlong; Guan, Naijia

2015-01-01

405

Self-biased cobalt ferrite nanocomposites for microwave applications  

NASA Astrophysics Data System (ADS)

Oriented CoFe2O4 nanoparticles, dispersed in polymethyl methacrylate (PMMA) matrix, were fabricated by magnetophoretic deposition of functionalized nanocolloidal cobalt ferrite particles into porous alumina membrane. Their magnetic behavior exhibits an out-of-plane easy axis with a large remanent magnetization and coercitivity. This orientation allows high effective internal magnetic anisotropy that contributes to the permanent bias along the wire axis. The microwave studies reveal a ferromagnetic resonance at 46.5 and 49.5 GHz, depending on the filling ratio of the membrane. Ansoft High Frequency Structure Simulator (Ansoft HFSS) simulations are in good agreement with experimental results. Such nanocomposite is presented as one of the promising candidates for microwave devices (circulators, isolators, noise suppressors etc.).

Hannour, Abdelkrim; Vincent, Didier; Kahlouche, Faouzi; Tchangoulian, Ardaches; Neveu, Sophie; Dupuis, Vincent

2014-03-01

406

Magnetic and ultrasonic studies on stable cobalt ferrite magnetic nanofluid.  

PubMed

Stable cobalt ferrite nanofluids of various concentrations have been prepared through co-precipitation method. Structural and morphological studies of nanoparticles are made with the help of X-ray diffraction technique and Transmission Electron Microscope respectively and it is found that the particles exhibit face centered cubic structure with an average size of 14 nm. The magnetic properties of the nanofluids have been analyzed at room temperature which revealed ferromagnetic behavior and also the very low value of coupling constant which ensures the negligible interparticle interaction in the absence of magnetic field. Ultrasonic investigations have been made for the nanofluids at different temperatures and magnetic fields. The temperature effects are explained with the help of open and close-packed water structure. The inter particle interactions of surface modified CoFe2O4 particles and the cluster formation at higher concentrations are realized through the variations in ultrasonic parameters. PMID:24188514

Nabeel Rashin, M; Hemalatha, J

2014-03-01

407

Synthesis of mesoporous metal oxide by the thermal decomposition of oxalate precursor.  

PubMed

A synthesis method was newly developed to prepare mesoporous transition metal oxides by thermal decomposition of transition metal oxalates, and the method was advantageous in its versatility, low cost, and environmental friendliness. Various mesoporous transition metal oxides were successfully synthesized by the newly developed method, such as magnetic ?-Fe2O3, CoFe2O4, and NiFe2O4, MnxOy, Co3O4, and NiO. Morphology, structure, and magnetic property of the synthesized mesoporous transition metal oxides were characterized by XRD, TG-DTA, SEM, TEM, quantum design SQUID, and N2 sorption techniques. From the dependency of the heating rate, calcination time, and calcination temperature on the metal oxide structures, it was revealed that the calcination temperature was the major factor to determine the final mesoporous structure of the metal oxides. The mesoporous structures were well constructed by their corresponding metal oxide nanoparticles resulting from oxalate thermal decomposition. PMID:23480232

Guo, Limin; Arafune, Hiroyuki; Teramae, Norio

2013-04-01

408

Sub-10 nm Fe3O4@Cu(2-x)S core-shell nanoparticles for dual-modal imaging and photothermal therapy.  

PubMed

Photothermal nanomaterials have recently attracted significant research interest due to their potential applications in biological imaging and therapeutics. However, the development of small-sized photothermal nanomaterials with high thermal stability remains a formidable challenge. Here, we report the rational design and synthesis of ultrasmall (<10 nm) Fe3O4@Cu2-xS core-shell nanoparticles, which offer both high photothermal stability and superparamagnetic properties. Specifically, these core-shell nanoparticles have proven effective as probes for T2-weighted magnetic resonance imaging and infrared thermal imaging because of their strong absorption at the near-infrared region centered around 960 nm. Importantly, the photothermal effect of the nanoparticles can be precisely controlled by varying the Cu content in the core-shell structure. Furthermore, we demonstrate in vitro and in vivo photothermal ablation of cancer cells using these multifunctional nanoparticles. The results should provide improved understanding of synergistic effect resulting from the integration of magnetism with photothermal phenomenon, important for developing multimode nanoparticle probes for biomedical applications. PMID:23687972

Tian, Qiwei; Hu, Junqing; Zhu, Yihan; Zou, Rujia; Chen, Zhigang; Yang, Shiping; Li, Runwei; Su, Qianqian; Han, Yu; Liu, Xiaogang

2013-06-12

409

Polymer nanoparticles and nanoparticle arrays  

NASA Astrophysics Data System (ADS)

The manufacturing of polymeric nanoparticles by intramolecular crosslinking is studied by molecular dynamics simulation. Firstly an overview of the intramolecular crosslinking process is obtained by the simulations of benzocyclobutene(BCB)/styrene copolymers using an atomistic model. Then various coarse grained models, including Freely Jointed Chain (FJC). Freely Rotating Chain (FRC) and stiff chain models, are adopted for studying general properties of intramolecular crosslinking of polymers. A temperature series simulation on the FJC model reveals that the change of ambient temperature results in the formation of nanoparticles with distinct morphologies. To describe their structures, a quantity referred to as chemical distance density is introduced, with a quantitative relation between it and the radius of gyration being found. The subsequent study of rigidity effects adopts FRC and stiff chain models. It is found that in the rigid regime, the crosslinking process leaves a substantial number of crosslinkers unlinked, and forms nanoparticles that are significantly larger than their non-rigid counterparts. The Maxwell constraint counting method is used to determine the rigidity thresholds, which yields good agreements with the simulation data. In the last chapter, the atomistic model for polystyrene in the previous crosslinking simulations is employed for a study of polystyrene chains on attractive substrates. The phase diagram and a rough overview of chain dynamics on substrates are obtained.

Liu, Jiwu

410

Enhanced performance of p-type dye-sensitized solar cells based on ultrasmall Mg-doped CuCrO2 nanocrystals.  

PubMed

Herein, we present ultrasmall delafossite-type Mg-doped CuCrO2 nanocrystals prepared by using hydrothermal synthesis and their first application as photocathodes in efficient p-type dye-sensitized solar cells. The short-circuit current density (Jsc ) is notably increased by approximately 27% owing to the decreased crystallite size and the enhanced optical transmittance associated with Mg doping of the CuCrO2 nanocrystalline sample. An open-circuit voltage (Voc ) of 201 mV, Jsc of 1.51 mA cm(-2) , fill factor of 0.449, and overall photoconversion efficiency of 0.132% have been achieved with the CuCr0.9 Mg 0.1 O2 dye photocathode sensitized with the P1 dye under optimized conditions. This efficiency is nearly three times higher than that of the NiO-based reference device, which is attributed to the largely improved Voc and Jsc . The augmentation of Voc and Jsc can be attributed to the lower valance band position and the faster hole diffusion coefficient of CuCr0.9 Mg 0.1 O2 compared to those of the NiO reference, respectively, which leads to a higher hole collection efficiency. PMID:23794483

Xiong, Dehua; Zhang, Wenjun; Zeng, Xianwei; Xu, Zhen; Chen, Wei; Cui, Jin; Wang, Mingkui; Sun, Licheng; Cheng, Yi-Bing

2013-08-01

411

Nano electrochemical reactors of Fe2O3 nanoparticles embedded in shells of nitrogen-doped hollow carbon spheres as high-performance anodes for lithium-ion batteries.  

PubMed

Iron oxides are extensively investigated as anode materials for lithium-ion batteries (LIBs) because of their large specific capacities. However, they undergo huge volume changes during cycling that result in anode pulverization and loss of electrical connectivity. As a result, the capacity retention of the iron oxide anodes is poor and should be improved for commercial applications. Herein, we report the preparation of ultrasmall Fe2O3 nanoparticles embedded in nitrogen-doped hollow carbon sphere shells (Fe2O3@N-C) by the direct pyrolysis of Fe-based zeolitic imidazolate frameworks (Fe-ZIF) at 620 °C in air. As an anode material for LIBs, the capacity retained was 1573 mA h g(-1) after 50 cycles at a current density of 0.1 C (1 C = 1000 mA g(-1)). Even undergoing the high-rate capability test twice, it can still deliver a remarkably reversible and stable capacity of 1142 mA h g(-1) after 100 cycles at a current density of 1 C. The excellent electrochemical performance is attributed to the unique structure of ultrasmall Fe2O3 nanoparticles uniformly distributed in the shell of nitrogen-doped carbon spheres, which simultaneously solve the major problems of pulverization, facilitate rapid electrochemical kinetics, and effectively avoid the aggregation of Fe2O3 nanoparticles during de/lithiation. The novel method developed in this work for the synthesis of functional hybrid materials can be extended to the preparation of various MOFs-derived functional nanocomposites owing to the versatility of links and metal centers in MOFs. PMID:25631451

Zheng, Fangcai; He, Mengni; Yang, Yang; Chen, Qianwang

2015-02-12

412

Nuclear uptake of ultrasmall gold-doxorubicin conjugates imaged by fluorescence lifetime imaging microscopy (FLIM) and electron microscopy  

NASA Astrophysics Data System (ADS)

Fluorescence lifetime imaging microscopy (FLIM) has been used to image free and encapsulated doxorubicin (Dox) uptake into cells, since interaction of Dox with DNA leads to a characteristic lifetime change. However, none of the reported Dox conjugates were able to enter cell nuclei. In this work, we use FLIM to show nuclear uptake of 2.7 nm mean diameter Au nanoparticles conjugated to Dox. The pattern of labelling differed substantially from what was seen with free Dox, with slower nuclear entry and stronger cytoplasmic labelling at all time points. As the cells died, the pattern of labelling changed further as intracellular structures disintegrated, consistent with association of Au-Dox to membranes. The patterns of Au distribution and intracellular structure changes were confirmed using electron microscopy, and indicate different mechanisms of cytotoxicity with stable Au-Dox conjugates compared to Dox alone. Such conjugates are promising tools for overcoming resistance in Dox-resistant cancers.Fluorescence lifetime imaging microscopy (FLIM) has been used to image free and encapsulated doxorubicin (Dox) uptake into cells, since interaction of Dox with DNA leads to a characteristic lifetime change. However, none of the reported Dox conjugates were able to enter cell nuclei. In this work, we use FLIM to show nuclear uptake of 2.7 nm mean diameter Au nanoparticles conjugated to Dox. The pattern of labelling differed substantially from what was seen with free Dox, with slower nuclear entry and stronger cytoplasmic labelling at all time points. As the cells died, the pattern of labelling changed further as intracellular structures disintegrated, consistent with association of Au-Dox to membranes. The patterns of Au distribution and intracellular structure changes were confirmed using electron microscopy, and indicate different mechanisms of cytotoxicity with stable Au-Dox conjugates compared to Dox alone. Such conjugates are promising tools for overcoming resistance in Dox-resistant cancers. Electronic supplementary information (ESI) available: Histograms of pixel-by-pixel fits; FLIM image of cells incubated with unconjugated Au and Dox; control TEM images. See DOI: 10.1039/c4nr04707a

Zhang, Xuan; Shastry, Sathvik; Bradforth, Stephen E.; Nadeau, Jay L.

2014-11-01

413

Assessing Nanoparticle Toxicity  

NASA Astrophysics Data System (ADS)

Nanoparticle toxicology, an emergent field, works toward establishing the hazard of nanoparticles, and therefore their potential risk, in light of the increased use and likelihood of exposure. Analytical chemists can provide an essential tool kit for the advancement of this field by exploiting expertise in sample complexity and preparation as well as method and technology development. Herein, we discuss experimental considerations for performing in vitro nanoparticle toxicity studies, with a focus on nanoparticle characterization, relevant model cell systems, and toxicity assay choices. Additionally, we present three case studies (of silver, titanium dioxide, and carbon nanotube toxicity) to highlight the important toxicological considerations of these commonly used nanoparticles.

Love, Sara A.; Maurer-Jones, Melissa A.; Thompson, John W.; Lin, Yu-Shen; Haynes, Christy L.

2012-07-01

414

J-aggregates of organic dye molecules complexed with iron oxide nanoparticles for imaging-guided photothermal therapy under 915-nm light.  

PubMed

Recently, the development of nano-theranostic agents aiming at imaging guided therapy has received great attention. In this work, a near-infrared (NIR) heptamethine indocyanine dye, IR825, in the presence of cationic polymer, polyallylamine hydrochloride (PAH), forms J-aggregates with red-shifted and significantly enhanced absorbance. After further complexing with ultra-small iron oxide nanoparticles (IONPs) and the followed functionalization with polyethylene glycol (PEG), the obtained IR825@PAH-IONP-PEG composite nanoparticles are highly stable in different physiological media. With a sharp absorbance peak, IR825@PAH-IONP-PEG can serve as an effective photothermal agent under laser irradiation at 915 nm, which appears to be optimal in photothermal therapy application considering its improved tissue penetration compared with 808-nm light and much lower water heating in comparison to 980-nm light. As revealed by magnetic resonance (MR) imaging, those nanoparticles after intravenous injection exhibit high tumor accumulation, which is then harnessed for in vivo photothermal ablation of tumors, achieving excellent therapeutic efficacy in a mouse tumor model. This study demonstrates for the first time that J-aggregates of organic dye molecules are an interesting class of photothermal material, which when combined with other imageable nanoprobes could serve as a theranostic agent for imaging-guided photothermal therapy of cancer. PMID:24976309

Song, Xuejiao; Gong, Hua; Liu, Teng; Cheng, Liang; Wang, Chao; Sun, Xiaoqi; Liang, Chao; Liu, Zhuang

2014-11-12

415

In-Situ Monitoring of the Microstructure of TATB-based Explosive Formulations During Temperature Cycling using Ultra-small Angle X-ray Scattering  

SciTech Connect

TATB (1,3,5 triamino-2,4,6-trinitrobenzene), an extremely insensitive explosive, is used both in plastic-bonded explosives (PBXs) and as an ultra-fine pressed powder (UFTATB). With both PBXs and UFTATB, an irreversible expansion occurs with temperature cycling known as ratchet growth. In TATB-based explosives using Kel-F 800 as binder (LX-17 and PBX-9502), additional voids, sizes hundreds of nanometers to a few microns account for much of the volume expansion caused by temperature cycling. These voids are in the predicted size regime for hot-spot formation during ignition and detonation, and thus an experimental measure of these voids is important feedback for hot-spot theory and for determining the relationship between void size distributions and detonation properties. Also, understanding the mechanism of ratchet growth allows future choice of explosive/binder mixtures to minimize these types of changes to explosives, further extending PBX shelf life. This paper presents the void size distributions of LX-17, UFTATB, and PBXs using commercially available Cytop M, Cytop A, and Hyflon AD60 binders during temperature cycling between -55 C and 70 C. These void size distributions are derived from ultra-small angle x-ray scattering (USAXS), a technique sensitive to structures from about 10 nm to about 2 mm. Structures with these sizes do not appreciably change in UFTATB, indicating voids or cracks larger than a few microns appear in UFTATB during temperature cycling. Compared to Kel-F 800 binders, Cytop M and Cytop A show relatively small increases in void volume from 0.9% to 1.3% and 0.6% to 1.1%, respectively, while Hyflon fails to prevent irreversible volume expansion (1.2% to 4.6%). Computational mesoscale models of ratchet growth and binder wetting and adhesion properties point to mechanisms of ratchet growth, and are discussed in combination with the experimental results.

Willey, T M; Hoffman, D M; van Buuren, T; Lauderbach, L; Ilavsky, J; Gee, R H; Maiti, A; Overturf, G; Fried, L

2008-02-06

416

Cytotoxic activities of chitosan nanoparticles and copper-loaded nanoparticles  

Microsoft Academic Search

Chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions and copper ion sorption. In this study, the cytotoxic activities of the chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles was investigated and a relationship between physiochemical properties and activity is suggested. The chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles elicited dose-dependent inhibitory effects on

Lifeng Qi; Zirong Xu; Xia Jiang; Yan Li; Minqi Wang

2005-01-01

417

Nanoparticles for Biomedical Imaging  

SciTech Connect

Background: Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 to 100 nm in diameter possess dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for early detection of diseases such as cancer. Surface functionalization has further expanded the potential of nanoparticles as probes for molecular imaging. Objective: To summarize emerging research of nanoparticles for biomedical imaging with increased selectivity and reduced non-specific uptake with increased spatial resolution containing stabilizers conjugated with targeting ligands. Methods: This review summarizes recent technological advances in the synthesis of various nanoparticle probes, and surveys methods to improve the targeting of nanoparticles for their applications in biomedical imaging. Conclusion: Structural design of nanomaterials for biomedical imaging continues to expand and diversify. Synthetic methods have aimed to control the size and surface characteristics of nanoparticles to control distribution, half-life and elimination. Although molecular imaging applications using nanoparticles are advancing into clinical applications, challenges such as storage stability and long-term toxicology should continue to be addressed. Keywords: nanoparticle synthesis, surface modification, targeting, molecular imaging, and biomedical imaging.

Nune, Satish K.; Gunda, Padmaja; Thallapally, Praveen K.; Lin, Ying-Ying; Forrest, Laird M.; Berkland, Cory J.

2009-11-01

418

Self-assembled perovskite-spinel heterostructure on a highly distorted substrate  

NASA Astrophysics Data System (ADS)

The pattern configuration and interface structure in epitaxial BiFeO3-CoFe2O4 heterostructures grown on (010)pc NdGaO3 substrates have been investigated systematically by transmission electron microscopy and chemical analysis. The crystal orientation of CoFe2O4 variants was tuned to [111]CFO, while BiFeO3 kept [010]pc matching the substrate. Triangular prism-shaped CoFe2O4 embedded in the BiFeO3 matrix grew as an equilibrium island mode with {111}CFO as its surfaces and interfaces. Two types of BiFeO3-CoFe2O4 orientation relationships were determined as (001)[010]BFO//(0-22)[111]CFO and (101)[010]BFO//(-220)[111]CFO. The results reveal that the dominant factors controlling the growth orientation of the present vertical heterostructures are surface energy anisotropy and atomic structure continuity.

Zhu, Y. M.; Ke, D.; Yu, R.; Hsieh, Y. H.; Liu, H. J.; Liu, P. P.; Chu, Y. H.; Zhan, Q.

2013-03-01

419

Thermosensitive Gold Nanoparticles  

SciTech Connect

Nanotechnology has experienced a rapid growth recently because nanoparticles exhibit physical and chemical properties that are quite different from those of the bulk solid. Typically, an organic layer comprised of a surfactant or a polymer is anchored at the interface to both localize the nanoparticle and stabilize its properties. Of particular interest is the conjugation of gold nanoparticles with functional macromolecules such as saccharide and oligo deoxyribonucleic acid (DNA). The combination of organic functionality coupled with the dielectric properties of gold nanoparticles has resulted in a new material that provides for sensitive colorimetric detection of polynucleotides. We report here the introduction of thermosensitive polymers onto Au nanoparticles so that the polymer-bound gold nanoparticles now become responsive to temperature.

Zhu, Ming-Qiang; Wang, Li Q.; Exarhos, Gregory J.; Li, Alexander D.

2004-03-10

420

Gold Nanoparticles and Drug Delivery.  

E-print Network

??Nanoparticles are important tools in biotechnology and biomedical research. Gold nanoparticles (AuNPs) have emerged as a particularly important class of nanobiotechnological tools as a result… (more)

Solfiell, David J

2014-01-01

421

Nanoparticles for Pulmonary Delivery  

Microsoft Academic Search

\\u000a This chapter aims to provide a rational for the use of nanoparticles in pulmonary delivery as well as an overview of strategies\\u000a and physiological implications of nanoparticle delivery to the lungs. Formulation aspects of nanoparticle systems in the form\\u000a of liquid dispersions and inhaled dry powders are also reviewed. The chapter also addresses the expanse of lung toxicology\\u000a research surrounding

Alan B. Watts; Robert O. Williams

422

Stimulus responsive nanoparticles  

NASA Technical Reports Server (NTRS)

Disclosed are various embodiments of methods and systems related to stimulus responsive nanoparticles. In one embodiment includes a stimulus responsive nanoparticle system, the system includes a first electrode, a second electrode, and a plurality of elongated electro-responsive nanoparticles dispersed between the first and second electrodes, the plurality of electro-responsive nanorods configured to respond to an electric field established between the first and second electrodes.

Cairns, Darren Robert (Inventor); Huebsch, Wade W. (Inventor); Sierros, Konstantinos A. (Inventor); Shafran, Matthew S. (Inventor)

2013-01-01

423

Functional Magnetic Nanoparticles  

Microsoft Academic Search

Nanoparticle system research and characterization is the focal point of this research and dissertation. In the research presented here, magnetite, cobalt, and ferrite nanoparticle systems have been explored in regard to their magnetocaloric effect (MCE) properties, as well as for use in polymer composites. Both areas of study have potential applications across a wide variety of interdisciplinary fields.\\u000aMagnetite nanoparticles

James Gass

2012-01-01

424

Magnetic properties of Ga doped cobalt ferrite: Compton scattering study  

NASA Astrophysics Data System (ADS)

We present the spin momentum density of Ga doped CoFe2O4 at 100 K using magnetic Compton scattering. The measurement has been performed using circularly polarized synchrotron radiations of 182.65 keV at SPring8, Japan. The experimental profile is decomposed into its constituent profile to determine the spin moment at individual sites. Co atom has the maximum contribution (about 58%) in the total spin moment of the doped CoFe2O4.

Sharma, Arvind; Sahariya, Jagrati; Mund, H. S.; Itou, M.; Sakurai, Y.; Ahuja, B. L.

2014-04-01

425

DOCTORAL THESIS UNIVERSITE PIERRE ET MARIE CURIE  

E-print Network

Cobalt-Ferrite Thin Films for Room Temperature Spin Filtering Defended on September 12, 2008 Before-polarized tunneling. In this thesis, we present a complete study of the material cobalt ferrite (CoFe2O4), whose in cette th`ese, nous pr´esentons une ´etude approfondie du mat´eriau ferrite de cobalt (CoFe2O4), dont le

Paris-Sud XI, Université de

426

Nanoparticles for biomedical imaging  

PubMed Central

Background Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 – 100 nm in diameter have dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for early detection of diseases such as cancer. Surface functionalization has expanded further the potential of nanoparticles as probes for molecular imaging. Objective To summarize emerging research of nanoparticles for biomedical imaging with increased selectivity and reduced nonspecific uptake with increased spatial resolution containing stabilizers conjugated with targeting ligands. Methods This review summarizes recent technological advances in the synthesis of various nanoparticle probes, and surveys methods to improve the targeting of nanoparticles for their application in biomedical imaging. Conclusion Structural design of nanomaterials for biomedical imaging continues to expand and diversify. Synthetic methods have aimed to control the size and surface characteristics of nanoparticles to control distribution, half-life and elimination. Although molecular imaging applications using nanoparticles are advancing into clinical applications, challenges such as storage stability and long-term toxicology should continue to be addressed. PMID:19743894

Nune, Satish K; Gunda, Padmaja; Thallapally, Praveen K; Lin, Ying-Ying; Forrest, M Laird; Berkland, Cory J

2011-01-01

427

Nanoparticles and stem cells - has targeted therapy for aneurysms finally arrived?  

PubMed

Until recently, endovascular management of intracranial aneurysms has focused on mechanical and hemodynamic aspects: characterizing aneurysm morphology by angiogram, mechanical obstruction by detachable coils, and flow diversion with endovascular stents. Although now common practice, these interventions only ward off aneurysm rupture. The source of the problem, disease of the vessel wall itself, remains. New imaging technology and treatment modalities, however, are offering great promise to the field. In this review, we outline several new developments in the recent literature and pose potential adaptations toward cerebral aneurysms using them. The incidence, presentation, and contemporary endovascular treatment for aneurysms are first reviewed to lay the groundwork for new adaptations. Nanoparticles, including ultrasmall supraparagmenetic iron oxide particles (USPIOs), are next explored as a novel mechanism of predicting aneurysm wall instability and as an agent themselves for aneurysm occlusion. Cellular transplant grafts, bone marrow-derived stem cells (BM-MSCs), and endothelial progenitor cells (EPCs) are then investigated, with the role of cellular differentiation, chemokine secretion, and integration into the injured vascular wall receiving particular emphasis. Several promising translational papers are next discussed, with review of multiple studies that show benefit in aneurysm treatment and endovascular stenting using these agents as adjuncts. We next adapt these research findings into several potential applications we feel may be promising directions for the aspiring researcher. These new treatments may one day strengthen the arsenal of the endovascular neurosurgeon. PMID:25082670

Esfahani, Darian R; Viswanathan, Vyas; Alaraj, Ali

2015-03-01

428

Edible oil structures at low and intermediate concentrations. II. Ultra-small angle X-ray scattering of in situ tristearin solids in triolein  

NASA Astrophysics Data System (ADS)

Ultra-small angle X-ray scattering has been used for the first time to elucidate, in situ, the aggregation structure of a model edible oil system. The three-dimensional nano- to micro-structure of tristearin solid particles in triolein solvent was investigated using 5, 10, 15, and 20% solids. Three different sample preparation procedures were investigated: two slow cooling rates of 0.5°/min, case 1 (22 days of storage at room temperature) and case 2 (no storage), and one fast cooling of 30°/min, case 3 (no storage). The length scale investigated, by using the Bonse-Hart camera at beamline ID-15D at the Advanced Photon Source, Argonne National Laboratory, covered the range from 300 Å to 10 ?m. The unified fit and the Guinier-Porod models in the Irena software were used to fit the data. The former was used to fit 3 structural levels. Level 1 structures showed that the primary scatterers were essentially 2-dimensional objects for the three cases. The scatterers possessed lateral dimensions between 1000 and 4300 Å. This is consistent with the sizes of crystalline nanoplatelets present which were observed using cryo-TEM. Level 2 structures were aggregates possessing radii of gyration, Rg2 between 1800 Å and 12000 Å and fractal dimensions of either D2=1 for case 3 or 1.8?D2?2.1 for case 1 and case 2. D2 = 1 is consistent with unaggregated 1-dimensional objects. 1.8 ? D2 ? 2.1 is consistent with these 1-dimensional objects (below) forming structures characteristic of diffusion or reaction limited cluster-cluster aggregation. Level 3 structures showed that the spatial distribution of the level 2 structures was uniform, on the average, for case 1, with fractal dimension D3?3 while for case 2 and case 3 the fractal dimension was D3?2.2, which suggested that the large-scale distribution had not come to equilibrium. The Guinier-Porod model showed that the structures giving rise to the aggregates with a fractal dimension given by D2 in the unified fit level 2 model were cylinders described by the parameter s ?1 in the Guinier-Porod model. The size of the base of these cylinders was in agreement with the cryo-TEM observations as well as with the results of the level 1 unified fit model. By estimating the size of the nanoplatelets and understanding the structures formed via their aggregation, it will be possible to engineer novel lipids systems that embody desired functional characteristics.

Peyronel, Fernanda; Ilavsky, Jan; Mazzanti, Gianfranco; Marangoni, Alejandro G.; Pink, David A.

2013-12-01

429

Biocompatible nanoparticles and biopolyelectrolytes  

NASA Astrophysics Data System (ADS)

The research presented in this manuscript encompasses a merger of two research directions: a study of aqueous nanoparticle colloids and a study of biological polyelectrolytes. The majority of biomedical applications of nanoparticles require stable aqueous colloids of nanoparticles as a starting point. A new one-step method of preparation of aqueous solutions of ultra-fine ferroelectric barium titanate nanoparticles was developed and generalized to the preparation of stable aqueous colloids of semiconductor nanoparticles. This high-energy ball milling technique is low cost, environmentally friendly, and allows for control of nanoparticle size by changing milling time. Aqueous colloids of BaTiO3 nanoparticles are stable over time, maintain ferroelectricity and can be used as second harmonic generating nanoprobes for biomedical imaging. Biopolyelectrolytes exhibit a variety of novel liquid-crystalline phases in aqueous solutions where their electrolytic nature is a driving force behind phase formation. We study medically relevant mixtures of F-actin, DNA and oppositely charged ions (such as multivalent salts and antibiotic drugs) and map out phase diagrams and laws that govern phase transitions. We combine these research directions in studies of the condensation behavior in aqueous solutions of biocompatible nanoparticles and biopolyelectrolytes.

Zribi, Olena

430

Gas Phase Nanoparticle Integration  

Microsoft Academic Search

We report on two gas phase nanoparticle integration processes to assemble nanomaterials onto desired areas on a substrate. We expect these processes to work with any material that can be charged. The processes offer self- aligned integration and could be applied to any nanomaterial device requiring site specific assembly. The Coulomb force process directs the assembly of nanoparticles onto charged

Chad R. Barry; Heiko O. Jacobs

2007-01-01

431

Optical sensor for nanoparticles  

Microsoft Academic Search

In this paper we investigate a method for the detection of nanoparticles in order to reduce the risk associated with their toxicity, by taking into account the electromagnetic characteristics and the chemical analysis of the surface of a hybrid silicon photonic microresonator. Device sensing capabilities, both optical and chemical, are optimized in order to detect and size the nanoparticle. Thus,

Caterina Ciminelli; Clarissa M. Campanella; Rosa Pilolli; Nicola Cioffi; Mario N. Armenise

2011-01-01

432

Targeting nanoparticles to cancer.  

PubMed

Nanotechnology applications in medicine, termed as nanomedicine, have introduced a number of nanoparticles of variable chemistry and architecture for cancer imaging and treatment. Nanotechnology involves engineering multifunctional devices with dimensions at the nanoscale, similar dimensions as those of large biological vesicles or molecules in our body. These devices typically have features just tens to hundred nanometers across and they can carry one or two detection signals and/or therapeutic cargo(s). One unique class of nanoparticles is designed to do both, providing this way the theragnostic nanoparticles (therapy and diagnosis). Being inspired by physiologically existing nanomachines, nanoparticles are designed to safely reach their target and specifically release their cargo at the site of the disease, this way increasing the drug's tissue bioavailability. Nanoparticles have the advantage of targeting cancer by simply being accumulated and entrapped in tumours (passive targeting). The phenomenon is called the enhanced permeation and retention effect, caused by leaky angiogenetic vessels and poor lymphatic drainage and has been used to explain why macromolecules and nanoparticles are found at higher ratios in tumours compared to normal tissues. Although accumulation in tumours is observed cell uptake and intracellular drug release have been questioned. Polyethyleneglycol (PEG) is used to protect the nanoparticles from the Reticulo-Endothelial System (RES), however, it prevents cell uptake and the required intracellular drug release. Grafting biorecognition molecules (ligands) onto the nanoparticles refers to active targeting and aims to increase specific cell uptake. Nanoparticles bearing these ligands are recognised by cell surface receptors and this leads to receptor-mediated endocytosis. Several materials are suggested for the design of nanoparticles for cancer. Polymers, linear and dendrimers, are associated with the drug in a covalent or non-covalent way and have been used with or without a targeting ligand. Stealth liposomes are suggested to carry the drug in the aqueous core, and they are usually decorated by recognition molecules, being widely studied and applied. Inorganic nanoparticles such as gold and iron oxide are usually coupled to the drug, PEG and the targeting ligand. It appears that the PEG coating and ligand decoration are common constituents in most types of nanoparticles for cancer. There are several examples of successful cancer diagnostic and therapeutic nanoparticles and many of them have rapidly moved to clinical trials. Nevertheless there is still a room for optimisation in the area of the nanoparticle kinetics such as improving their plasma circulation and tumour bioavailability and understanding the effect of targeting ligands on their efficiency to treat cancer. The need to develop novel and efficient ligands has never been greater, and the use of proper conjugation chemistry is mandatory. PMID:20380880

Wang, M; Thanou, M

2010-08-01

433

Ultrathin InAs nanowire growth by spontaneous Au nanoparticle spreading on indium-rich surfaces  

NASA Astrophysics Data System (ADS)

Ultrathin InAs nanowires (NWs) can enable true one-dimensional electronics. We report a growth phenomenon where a bimodal size distribution (~? nm and ~5 nm in diameter) of InAs NWs can be achieved from gold (Au) nanoparticles of a single size, ? (? = 50-250 nm). We determine that ultrathin InAs NW growth is seeded by ultra-small Au nanoparticles shed from the large Au seeds upon indium (In) introduction into the growth system and formed prior to the supersaturation of In in Au. The Au spreading phenomenon is explained by the balancing of Gibbs free energy lowering from In-Au mixing and the surface tension increase. Ultrathin InAs NWs formed in this way exhibit a perfect wurtzite structure with no stacking faults. We have observed InAs NWs with diameters down to ~2 nm using our growth method. Passivating the ultrathin InAs NWs with an AlAs shell, subsequently oxidized in air, results in physical deformation of the InAs core, demonstrating the mechanical pliability of these ultrathin NWs.Ultrathin InAs nanowires (NWs) can enable true one-dimensional electronics. We report a growth phenomenon where a bimodal size distribution (~? nm and ~5 nm in diameter) of InAs NWs can be achieved from gold (Au) nanoparticles of a single size, ? (? = 50-250 nm). We determine that ultrathin InAs NW growth is seeded by ultra-small Au nanoparticles shed from the large Au seeds upon indium (In) introduction into the growth system and formed prior to the supersaturation of In in Au. The Au spreading phenomenon is explained by the balancing of Gibbs free energy lowering from In-Au mixing and the surface tension increase. Ultrathin InAs NWs formed in this way exhibit a perfect wurtzite structure with no stacking faults. We have observed InAs NWs with diameters down to ~2 nm using our growth method. Passivating the ultrathin InAs NWs with an AlAs shell, subsequently oxidized in air, results in physical deformation of the InAs core, demonstrating the mechanical pliability of these ultrathin NWs. Electronic supplementary information (ESI) available: SEM images of bimodal NW growth using variously sized Au colloids, SEM image of 3 ?m long ultrathin InAs NW, SEM image showing the proximity effect, EDX composition analysis of the tip of an ultrathin InAs NW, SEM image showing the effect of temperature hold prior to NW growth, SEM image showing the NW tip after extended growth, HRTEM image showing the NW sidewall of 50 nm InAs NW, and SEM image showing the early stage of the Au atom spreading process.

Jung, Kyooho; Mohseni, Parsian K.; Li, Xiuling

2014-11-01

434

Functional Magnetic Nanoparticles  

NASA Astrophysics Data System (ADS)

Nanoparticle system research and characterization is the focal point of this research and dissertation. In the research presented here, magnetite, cobalt, and ferrite nanoparticle systems have been explored in regard to their magnetocaloric effect (MCE) properties, as well as for use in polymer composites. Both areas of study have potential applications across a wide variety of interdisciplinary fields. Magnetite nanoparticles have been successfully dispersed in a polymer. The surface chemistry of the magnetic nanoparticle proves critical to obtaining a homogenous and well separated high density dispersion in PMMA. Theoretical studies found in the literature have indicated that surface interface energy is a critical component in dispersion. Oleic acid is used to alter the surface of magnetite nanoparticles and successfully achieve good dispersion in a PMMA thin film. Polypyrrole is then coated onto the PMMA composite layer. The bilayer is characterized using cross-sectional TEM, cross-sectional SEM, magnetic characterization, and low frequency conductivity. The results show that the superparmagnetic properties of the as synthesized particles are maintained in the composite. With further study of the properties of these nanoparticles for real and functional uses, MCE is studied on a variety of magnetic nanoparticle systems. Magnetite, manganese zinc ferrite, and cobalt ferrite systems show significant broadening of the MCE and the ability to tune the peak temperature of MCE by varying the size of the nanoparticles. Four distinct systems are studied including cobalt, cobalt core silver shell nanoparticles, nickel ferrite, and ball milled zinc ferrite. The results demonstrate the importance of surface characteristics on MCE. Surface spin disorder appears to have a large influence on the low temperature magnetic and magnetocalorie characteristics of these nanoparticle systems.

Gass, James

435

Shear thinning of nanoparticle suspensions.  

SciTech Connect

Results of large scale non-equilibrium molecular dynamics (NEMD) simulations are presented for nanoparticles in an explicit solvent. The nanoparticles are modeled as a uniform distribution of Lennard-Jones particles, while the solvent is represented by standard Lennard-Jones particles. Here we present results for the shear rheology of spherical nanoparticles of size 5 to 20 times that of the solvent for a range of nanoparticle volume fractions and interactions. Results from NEMD simulations suggest that for strongly interacting nanoparticle that form a colloidal gel, the shear rheology of the suspension depends only weakly on the size of the nanoparticle, even for nanoparticles as small as 5 times that of the solvent. However for hard sphere-like colloids the size of the nanoparticles strongly affects the shear rheology. The shear rheology for dumbbell nanoparticles made of two fused spheres is also compared to spherical nanoparticles and found to be similar except at very high volume fractions.

Grest, Gary Stephen; Petersen, Matthew K.; in't Veld, Pieter J. (Polymer Research, Ludwigshafen, Germany)

2008-08-01

436

Nanoparticle flotation collectors II: the role of nanoparticle hydrophobicity.  

PubMed

The ability of polystyrene nanoparticles to facilitate the froth flotation of glass beads was correlated to the hydrophobicity of the nanoparticles. Contact angle measurements were used to probe the hydrophobicity of hydrophilic glass surfaces decorated with hydrophobic nanoparticles. Both sessile water drop advancing angles, ?(a), and attached air bubble receding angle measurements, ?(r), were performed. For glass surfaces saturated with adsorbed nanoparticles, flotation recovery, a measure of flotation efficiency, increased with increasing values of each type of contact angle. As expected, the advancing water contact angle on nanoparticle-decorated, dry glass surfaces increased with surface coverage, the area fraction of glass covered with nanoparticles. However, the nanoparticles were far more effective at raising the contact angle than the Cassie-Baxter prediction, suggesting that with higher nanoparticle coverages the water did not completely wet the glass surfaces between the nanoparticles. A series of polystyrene nanoparticles was prepared to cover a range of surface energies. Water contact angle measurements, ?(np), on smooth polymer films formed from organic solutions of dissolved nanoparticles were used to rank the nanoparticles in terms of hydrophobicity. Glass spheres were saturated with adsorbed nanoparticles and were isolated by flotation. The minimum nanoparticle water contact angle to give high flotation recovery was in the range of 51° < ?(np(min)) ? 85°. PMID:21830818

Yang, Songtao; Pelton, Robert

2011-09-20

437

Synthesis of Silver Nanoparticles  

NSDL National Science Digital Library

This series of videos, presented by the Materials Research Science and Engineering Center at the University of Wisconsin-Madison, deals with the synthesis of silver nanoparticles. The experiment allows students to view the formation of silver nanoparticles that can be detected by the reflection of a laser beam. Silver nanoparticles are used in the creation of yellow stained glass in churches around the country, an interesting, but little known fact. This is a fairly inexpensive activity as it involves stock solutions, and equipment present in any science laboratory. Overall, students will enjoy this basic, but still challenging, experiment.

Johnson, Chris

438

GADOLINIUM(Gd)-BASED and Ion Oxide Nanoparticle Contrast Agents for Pre-Clinical and Clinical Magnetic Resonance Imaging (mri) Research  

NASA Astrophysics Data System (ADS)

It is known that one strength of MRI is its excellent soft tissue discrimination. It naturally provides sufficient contrast between the structural differences of normal and pathological tissues, their spatial extent and progression. However, to further extend its applications and enhance even more contrast for clinical studies, various Gadolinium (Gd)-based contrast agents have been developed for different organs (brain strokes, cancer, cardio-MRI, etc). These Gd-based contrast agents are paramagnetic compounds that have strong T1-effect for enhancing the contrast between tissue types. Gd-contrast can also enhance magnetic resonance angiography (CE-MRA) for studying stenosis and for measuring perfusion, vascular susceptibility, interstitial space, etc. Another class of contrast agents makes use of ferrite iron oxide nanoparticles (including Superparamagnetic Ion Oxide (SPIO) and Ultrasmall Superparamagnetic Iron Oxide (USPIO)). These nanoparticles have superior magnetic susceptibility effect and produce a drop in signal, namely in T2*-weighted images, useful for the determination of lymph nodes metastases, angiogenesis and arteriosclerosis plaques.

Ng, Thian C.

2012-06-01

439

Divalent metal nanoparticles  

E-print Network

Metal nanoparticles hold promise for many scientific and technological applications, such as chemical and biological sensors, vehicles for drug delivery, and subdiffraction limit waveguides. To fabricate such devices, a ...

DeVries, Gretchen Anne

2008-01-01

440

Nanoparticles Flat Precipitates  

E-print Network

20 nm Nanorods Nanoparticles Flat Precipitates 10 nm To improve the performance of superconducting precipitates (red arrows). Artificial and Self-assembled Vortex-pinning Centers in Superconducting Ba(Fe1-x

Weston, Ken

441

Edible oil structures at low and intermediate concentrations. II. Ultra-small angle X-ray scattering of in situ tristearin solids in triolein  

SciTech Connect

Ultra-small angle X-ray scattering has been used for the first time to elucidate, in situ, the aggregation structure of a model edible oil system. The three-dimensional nano- to micro-structure of tristearin solid particles in triolein solvent was investigated using 5, 10, 15, and 20% solids. Three different sample preparation procedures were investigated: two slow cooling rates of 0.5°/min, case 1 (22 days of storage at room temperature) and case 2 (no storage), and one fast cooling of 30°/min, case 3 (no storage). The length scale investigated, by using the Bonse-Hart camera at beamline ID-15D at the Advanced Photon Source, Argonne National Laboratory, covered the range from 300?Å to 10??m. The unified fit and the Guinier-Porod models in the Irena software were used to fit the data. The former was used to fit 3 structural levels. Level 1 structures showed that the primary scatterers were essentially 2-dimensional objects for the three cases. The scatterers possessed lateral dimensions between 1000 and 4300?Å. This is consistent with the sizes of crystalline nanoplatelets present which were observed using cryo-TEM. Level 2 structures were aggregates possessing radii of gyration, R{sub g2} between 1800?Å and 12000?Å and fractal dimensions of either D{sub 2}=1 for case 3 or 1.8?D{sub 2}?2.1 for case 1 and case 2. D{sub 2}?=?1 is consistent with unaggregated 1-dimensional objects. 1.8???D{sub 2}???2.1 is consistent with these 1-dimensional objects (below) forming structures characteristic of diffusion or reaction limited cluster-cluster aggregation. Level 3 structures showed that the spatial distribution of the level 2 structures was uniform, on the average, for case 1, with fractal dimension D{sub 3}?3 while for case 2 and case 3 the fractal dimension was D{sub 3}?2.2, which suggested that the large-scale distribution had not come to equilibrium. The Guinier-Porod model showed that the structures giving rise to the aggregates with a fractal dimension given by D{sub 2} in the unified fit level 2 model were cylinders described by the parameter s?1 in the Guinier-Porod model. The size of the base of these cylinders was in agreement with the cryo-TEM observations as well as with the results of the level 1 unified fit model. By estimating the size of the nanoplatelets and understanding the structures formed via their aggregation, it will be possible to engineer novel lipids systems that embody desired functional characteristics.

Peyronel, Fernanda; Marangoni, Alejandro G. [Food Science Department, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Ilavsky, Jan [Advanced Photon Source, Argonne National Laboratory, 9700S Cass Ave., Bldg. 434D, Argonne, Illinois 60439 (United States); Mazzanti, Gianfranco [Department of Process Engineering and Applied Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2 (Canada); Pink, David A. [Food Science Department, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Physics Department, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5 (Canada)

2013-12-21

442

Cytotoxicity of Photoactive Nanoparticles  

Microsoft Academic Search

\\u000a This chapter describes the cytotoxicity of photoactive materials (specifically, quantum dots, noble metal nanoparticles (including\\u000a gold and silver), and fluorescent silica nanoparticles). A thorough representation of in vitro and in vivo toxicity studies\\u000a is presented. Since the toxicity on photoactive nanomaterials described in this chapter has developed rapidly and has attracted\\u000a a great amount of interest, it is expected that

Yuhui Jin; Xiaojun Zhao

443

Externally modulated theranostic nanoparticles  

PubMed Central

Externally modulated nanoparticles comprise a rapidly advancing class of cancer nanotherapeutics, which combine the favorable tumor accumulation of nanoparticles, with external spatio-temporal control on therapy delivery via optical, magnetic, or ultrasound modalities. The local control on therapy enables higher tumor treatment efficacy, while simultaneously reducing off-target effects. The nanoparticle interactions with external fields have an additional advantage of frequently generating an imaging signal, and thus such agents provide theranostic (both diagnostic and therapeutic) capabilities. In this review, we classify the emerging externally modulated theranostic nanoparticles according to the mode of external control and describe the physiochemical mechanisms underlying the external control of therapy, and illustrate the major embodiments of nanoparticles in each class with proven biological efficacy: (I) electromagnetic radiation in visible and near-infrared range is being exploited for gold based and carbon nanostructures with tunable surface plasmon resonance (SPR) for imaging and photothermal therapy (PTT) of cancer, photochemistry based manipulations are employed for light sensitive liposomes and porphyrin based nanoparticles; (II) Magnetic field based manipulations are being developed for iron-oxide based nanostructures for magnetic resonance imaging (MRI) and magnetothermal therapy; (III) ultrasound based methods are primarily being employed to increase delivery of conventional drugs and nanotherapeutics to tumor sites. PMID:24834381

Urban, Cordula; Urban, Alexander S.; Charron, Heather; Joshi, Amit

2013-01-01

444

Direct hierarchical assembly of nanoparticles  

SciTech Connect

The present invention provides hierarchical assemblies of a block copolymer, a bifunctional linking compound and a nanoparticle. The block copolymers form one micro-domain and the nanoparticles another micro-domain.

Xu, Ting; Zhao, Yue; Thorkelsson, Kari

2014-07-22

445

Automated Morphology Analysis of Nanoparticles  

E-print Network

The functional properties of nanoparticles highly depend on the surface morphology of the particles, so precise measurements of a particle's morphology enable reliable characterizing of the nanoparticle's properties. Obtaining the measurements...

Park, Chiwoo

2012-10-19

446

Efficient magneto-optical mode converter on glass  

NASA Astrophysics Data System (ADS)

The integration of magneto-optical materials to realize non-reciprocal functions is still a difficult problem, because classical magneto-optical materials require an annealing temperature as high as 700°C. In this framework, this study shows how it is possible to realize efficient magneto-optical mode converter using the association of a magnetic nanoparticles silica/zirconia composite with an ion-exchanged glass waveguide. Using a sol gel process, a silica/zirconia matrix is doped by magnetic nanoparticles (CoFe2O4) and coated on a glass substrate containing straight channel waveguides made by a silver/sodium ion exchange. The extremities of the guides were previously buried using electric field-assisted burial in order to facilitate light injection. Soft annealing (90°C) and UV treatment, both compatible with the ion exchange process, have been implemented to finalize the magneto-optical film. Depending on the amount of nanoparticles in the composite, on the spatial distribution of the field in the guide and on the modal birefringence of the hybrid structure, the TE-TM conversion varies from several degrees to several tens of degrees.

Garayt, Jean Philippe; Parsy, François; Jamon, Damien; Neveu, Sophie; Royer, François; Ghibaudo, Elise; Broquin, Jean-Emmanuel

2014-03-01

447

Phase-controlled synthesis of ?-NiS nanoparticles confined in carbon nanorods for high performance supercapacitors.  

PubMed

A facile and phase-controlled synthesis of ?-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of ?-NiS and preventing its transition to ?-phase, which is in strong contrast to large aggregated ?-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall ?-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740?F g(-1) at current densities of 1, 2, 5, 10?A g(-1), respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials. PMID:25394517

Sun, Chencheng; Ma, Mingze; Yang, Jun; Zhang, Yufei; Chen, Peng; Huang, Wei; Dong, Xiaochen

2014-01-01

448

Imaging of oxidation-specific epitopes with targeted nanoparticles to detect high-risk atherosclerotic lesions: progress and future directions.  

PubMed

Oxidation-specific epitopes (OSE) within developing atherosclerotic lesions are key antigens that drive innate and adaptive immune responses in atherosclerosis, leading to chronic inflammation. Oxidized phospholipids and malondialdehyde-lysine epitopes are well-characterized OSE present in human atherosclerotic lesions, particularly in pathologically defined vulnerable plaques. Using murine and human OSE-specific antibodies as targeting agents, we have developed radionuclide and magnetic resonance based nanoparticles, containing gadolinium, manganese or lipid-coated ultrasmall superparamagnetic iron oxide, to non-invasively image OSE within experimental atherosclerotic lesions. These methods quantitate plaque burden, allow detection of lesion progression and regression, plaque stabilization, and accumulation of OSE within macrophage-rich areas of the artery wall, suggesting they detect the most active lesions. Future studies will focus on using "natural" antibodies, lipopeptides, and mimotopes for imaging applications. These approaches should enhance the clinical translation of this technique to image, monitor, evaluate efficacy of novel therapeutic agents, and guide optimal therapy of high-risk atherosclerotic lesions. PMID:25297940

Briley-Saebo, Karen; Yeang, Calvin; Witztum, Joseph L; Tsimikas, Sotirios

2014-11-01

449