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1

Spin-canting and magnetic anisotropy in ultrasmall CoFe2O4 nanoparticles.  

PubMed

The magnetic properties of cobalt ferrite nanoparticles dispersed in a silica matrix in samples with different concentrations (5 and 10 wt% CoFe2O 4) and same particle size (3 nm) were studied by magnetization, DC and AC susceptibility, and Mossbauer spectroscopy measurements. The results indicate that the particles are very weakly interacting. The magnetic properties (saturation magnetization, anisotropy constant, and spin-canting) are discussed in relation to the cation distribution. PMID:18590326

Peddis, D; Mansilla, M V; Mørup, S; Cannas, C; Musinu, A; Piccaluga, G; D'Orazio, F; Lucari, F; Fiorani, D

2008-07-24

2

Enhanced hydrogen storage properties of LiAlH4 catalyzed by CoFe2O4 nanoparticles  

E-print Network

Enhanced hydrogen storage properties of LiAlH4 catalyzed by CoFe2O4 nanoparticles Ziliang Li The catalytic effects of CoFe2O4 nanoparticles on the hydrogen storage properties of LiAlH4 prepared by ball of advanced hydrogen storage materials for safely storing it at high gravimetric and volumetric densities.4

Volinsky, Alex A.

3

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

4

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

5

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

NASA Astrophysics Data System (ADS)

Herein, we describe a facile and feasible synthesis method for patterning nanogold particles onto magnetic mesoporous CoFe2O4 nanostructures (Au-MMNs) by using poly(vinyl pyrrolidone) (PVP) as cross-linker. Initially, mesoporous CoFe2O4 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 AuIII on the PVP-functionalized CoFe2O4. The as-prepared Au-MMNs were characterized by transmission electron microscopy (TEM), N2 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.

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

2011-05-01

6

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

7

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

8

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

9

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 2 weeks, and tissue accumulation of Co and Fe was assessed. This was compared to pristine CoFe2O4 NPs, and CoCl2 and Fe(III) salts as positive controls. The combined data shows that citric acid enhances free metal ion concentration from CoFe2O4 NPs in aqueous suspension, although in vivo, very similar amounts of assimilated Co were found in isopods exposed to both types of NPs. Therefore, evaluation of the dissolution in suspension by chemical means is not a good predictor of metal assimilation of this model organism; body assimilation of Co and Fe is rather governed by the physiological capacity of P. scaber for the uptake of these metals. Moreover, we propose that citric acid, due to its chelating properties, may hinder the uptake of Co that dissolves from citric-acid-adsorbed CoFe2O4 NPs, if citric acid is present in sufficient quantity. PMID:25437955

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

2015-03-01

10

Synthesis and Magnetic Properties of Nearly Monodisperse CoFe2O4Nanoparticles Through a Simple Hydrothermal Condition.  

PubMed

Nearly monodisperse cobalt ferrite (CoFe2O4) nanoparticles without any size-selection process have been prepared through an alluring method in an oleylamine/ethanol/water system. Well-defined nanospheres with an average size of 5.5 nm have been synthesized using metal chloride as the law materials and oleic amine as the capping agent, through a general liquid-solid-solution (LSS) process. Magnetic measurement indicates that the particles exhibit a very high coercivity at 10 K and perform superparamagnetism at room temperature which is further illuminated by ZFC/FC curves. These superparamagnetic cobalt ferrite nanomaterials are considered to have potential application in the fields of biomedicine. The synthesis method is possible to be a general approach for the preparation of other pure binary and ternary compounds. PMID:20672131

Li, Xing-Hua; Xu, Cai-Ling; Han, Xiang-Hua; Qiao, Liang; Wang, Tao; Li, Fa-Shen

2010-01-01

11

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

12

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

13

Preparation and characterization of hollow glass microspheres coated by CoFe 2O 4 nanoparticles using urea as precipitator via coprecipitation method  

Microsoft Academic Search

The composite of hollow glass microspheres coated by CoFe2O4 nanoparticles has been successfully prepared using urea as precipitator via coprecipitation method. The resultant composites were characterized by X-ray diffraction, field emission scanning electron microscope and vibrating sample magnetometer. The results showed that the slow decomposition of urea could be beneficial to form uniform and entire cobalt ferrite coating layer on

Xiaofen Pang; Wuyou Fu; Haibin Yang; Hongyang Zhu; Jing Xu; Xiang Li; Guangtian Zou

2009-01-01

14

Exchange bias of MnFe2O4@?Fe2O3 and CoFe2O4@?Fe2O3 core/shell nanoparticles  

NASA Astrophysics Data System (ADS)

We compare here exchange bias (EB) properties of chemically synthesized core-shell nanoparticles (NPs), based either on a core of soft ferrite (MnFe2O4) or hard ferrite (CoFe2O4) protected by a maghemite shell (?-Fe2O3). These NPs dispersed in acidic solutions are electrostatically stabilized, yielding to stable colloidal dispersions with a strong interparticle repulsion and negligible dipolar interactions in the probed range of temperatures. Field cooled (FC) magnetic hysteresis loops of non-textured frozen dispersions (with magnetic anisotropy axis of NPs distributed at random) and those of a powder based on the same NPs present a shift along the H-axis, expressing the coupling between the spin-ordered cores and the disordered surface layer of the NPs. The bias field is found to present a maximum, larger for NPs based on harder ferrite core. It is obtained for a cooling field of the order of one half of the anisotropy field, which is much larger for the CoFe2O4 cores than for MnFe2O4 ones. In powders, particles are in contact leading to an interparticle exchange which is not present in the dilute solutions where exchange bias properties are only due to an intraparticle exchange between core and surface. The thermal dependence of the bias field is well described by a reduced exponential behavior with a characteristic freezing temperature of about 8 K.

Cabreira-Gomes, R.; G. Silva, F.; Aquino, R.; Bonville, P.; Tourinho, F. A.; Perzynski, R.; Depeyrot, J.

2014-11-01

15

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

16

Engineered spin-valve type magnetoresistance in Fe3O4-CoFe2O4 core-shell nanoparticles  

NASA Astrophysics Data System (ADS)

Naturally occurring spin-valve-type magnetoresistance (SVMR), recently observed in Sr2FeMoO6 samples, suggests the possibility of decoupling the maximal resistance from the coercivity of the sample. Here we present the evidence that SVMR can be engineered in specifically designed and fabricated core-shell nanoparticle systems, realized here in terms of soft magnetic Fe3O4 as the core and hard magnetic insulator CoFe2O4 as the shell materials. We show that this provides a magnetically switchable tunnel barrier that controls the magnetoresistance of the system, instead of the magnetic properties of the magnetic grain material, Fe3O4, and thus establishing the feasibility of engineered SVMR structures.

Anil Kumar, P.; Ray, Sugata; Chakraverty, S.; Sarma, D. D.

2013-09-01

17

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

18

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

19

Effect hyperthermia in CoFe2O4@MnFe2O4 nanoparticles studied by using field-induced Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

CoFe2O4@MnFe2O4, with a mixed core-shell structure was fabricated by a high temperature thermal decomposition. From the Rietveld refinement, these nanoparticles were found to be cubic spinel with space group Fd-3 m and with a Bragg factor ( R B ) and a structure factor ( R F ) less than 5%. The size and the shape of the nanoparticles were examined with high-resolution transmission electron microscopy (HR-TEM). The values of the magnetization ( M S ) and the coercivity ( H C ) of these nanoparticles at room temperature were 78.95 emu/g and 21.2 mT, respectively. The effect of hyperthermia, measured with a magneTherm device showed that the self-heating temperature of the nanoparticles could reach 133 °C. To determine the applicability of nanoparticles in hyperthermia therapy, we evaluated the in-vitro cell viability of nanoparticles. Based on the probability distribution of cations, we determined the Mössbauer spectra at 4.2 K with two sets of six lines under various applied fields parallel to the direction of the ?-rays. To separate the A and the B sites, we also obtained the Mössbauer spectra of the nanoparticles under high external field up to 5 T at 4.2 K. From the detailed analysis of the Mössbauer spectra, the spin canting angles and the anisotropy energies at the A and the B sites were determined.

Kim, Minseon; Kim, Chul Sung; Kim, Hyung Joon; Yoo, Kyung-Hwa; Hahn, Eunjoo

2013-12-01

20

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

21

Synthesis and magnetic properties of cobalt ferrite (CoFe 2O 4) nanoparticles prepared by wet chemical route  

Microsoft Academic Search

Magnetic nanoparticles of cobalt ferrite have been synthesized by wet chemical method using stable ferric and cobalt salts with oleic acid as the surfactant. X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) confirmed the formation of single-phase cobalt ferrite nanoparticles in the range 15–48nm depending on the annealing temperature and time. The size of the particles increases with annealing temperature

K. Maaz; Arif Mumtaz; S. K. Hasanain; Abdullah Ceylan

2007-01-01

22

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

23

Magnetic CoFe2O4/carbon nanotubes composites: fabrication, microstructure and magnetic response  

NASA Astrophysics Data System (ADS)

By combining the unique microstructure of carbon nanotubes (CNTs) with the good magnetism of CoFe2O4 ferrites, CoFe2O4/CNTs nanocomposites were prepared by the solvothermal method for the application of targeting therapy and tumor hyperthermia. X-ray diffraction (XRD), thermal gravity analysis (TGA), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) were introduced to study the influence of the solvothermal temperature, time and the CNTs content on the microstructure and magnetic properties of CoFe2O4/CNTs nanocomposites. The diameter of CoFe2O4 nanoparticles coating on the surface of CNTs and the saturation magnetization (Ms) increased with the solvothermal temperature. CoFe2O4/CNTs nanocomposites prepared at 180°C, 200°C and 220°C exhibited superparamagnetism at room temperature, while the samples prepared at 240°C and 260°C presented ferromagnetism. And the solvothermal time and CNTs content slightly affected the microstructure and magnetic properties, Ms and coercivity (Hc) increased slightly with the increasing solvothermal time and the decreasing CNTs content.

Wang, Panfeng; Xu, Jingcai; Han, Yanbing; Hong, Bo; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Li, Jing; Ge, Hongliang; Wang, Xinqing

2014-05-01

24

Nanostructures and magnetic properties of cobalt ferrite (CoFe2O4) fabricated by electrospinning  

NASA Astrophysics Data System (ADS)

This paper describes the fabrication of cobalt ferrite (CoFe2O4) nanostructures (in the form of nanofibers and nanoparticles) by the electrospinning method using a solution that contained poly(vinyl pyrrolidone) (PVP) and cheap Co and Fe nitrates as metal sources. The as-spun and calcined CoFe2O4/PVP composite samples were characterized by TG-DTA, X-ray diffraction, FT-IR, SEM and TEM, respectively. After calcination of the as-spun CoFe2O4/PVP composite nanofibers (fiber size of 320±48 nm in diameter) at 500, 600, and 800°C in air for 3 h with different heating rates of 5 or 20°C/min, either NiFe2O4 nanofibers of ˜10-200 nm in diameter or nanoparticles with particle sizes of ˜50-400 nm having a well-developed spinel structure were successfully obtained. The crystal structure and morphology of the nanofibers were influenced by the calcination temperature and heating rate. A faster heating rate allowed for a rapid removal of the PVP matrix and resulted in a complete change from fibrous structure to particle in the calcined CoFe2O4/PVP composite nanofibers. Room temperature magnetization results showed a ferromagnetic behavior of the calcined CoFe2O4/PVP composite nanofibers, having their hysteresis loops in the field range of ± 4500 and 3000 Oe for the samples calcined respectively with heating rates of 5 and 20°C/min. The values of the specific magnetization ( M s) at 10 kOe, remnant magnetization ( M r), M r/ M s ratio, and coercive forces ( H c) are obtained from hysteresis loops. It was found that the values of M s, M r, M r/ M s, and H c depended strongly on morphology of the CoFe2O4 nanostructures.

Sangmanee, Montana; Maensiri, Santi

2009-10-01

25

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

NASA Astrophysics Data System (ADS)

CoFe2O4 nanotubes have been directly fabricated by single-capillary spinneret electrospinning. The external diameter of the CoFe2O4 nanotubes ranges from 60 nm to 160 nm. The morphology and structure characterizations show that individual CoFe2O4 nanotubes are made of CoFe2O4 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 (Hc) of the CoFe2O4 nanotubes decreases from 10 400 Oe at 5 K to 300 Oe at 360 K. The CoFe2O4 nanotubes have a spin reorientation (SR) at 5 K, which is different from CoFe2O4 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 CoFe2O4 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 CoFe2O4 into the new fields.CoFe2O4 nanotubes have been directly fabricated by single-capillary spinneret electrospinning. The external diameter of the CoFe2O4 nanotubes ranges from 60 nm to 160 nm. The morphology and structure characterizations show that individual CoFe2O4 nanotubes are made of CoFe2O4 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 (Hc) of the CoFe2O4 nanotubes decreases from 10 400 Oe at 5 K to 300 Oe at 360 K. The CoFe2O4 nanotubes have a spin reorientation (SR) at 5 K, which is different from CoFe2O4 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 CoFe2O4 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 CoFe2O4 into the new fields. Electronic supplementary information (ESI) available: EDX spectrum and mappings, statistical analysis of nanoparticle size. See DOI: 10.1039/c2nr30487b

FuThese Authors Contributed Equally To This Work., Jiecai; Zhang, Junli; Peng, Yong; Zhao, Jianguo; Tan, Guoguo; Mellors, Nigel J.; Xie, Erqing; Han, Weihua

2012-06-01

26

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

PubMed

Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23?817 and 15?056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance. PMID:25787852

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

2015-04-01

27

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

28

Realization of highest specific absorption rate near superparamagnetic limit of CoFe2O4 colloids for magnetic hyperthermia applications  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles offer some attractive possibilities in biomedicine with local heat generation abilities. Here we report on the realization of highest specific absorption rate (˜2 kW g-1) and a stable dynamic heat production (42-46 °C) using oleic acid coated CoFe2O4 based ferrofluids which are very promising for hyperthermia applications. CoFe2O4 nanoparticles with different sizes were prepared via co-precipitation method followed by heat treatment in the temperature range 100-600 °C to vary the particle sizes from 12-24 nm. Structural analysis using high resolution transmission electron microscopy (HRTEM) shows well separated oleic acid coated CoFe2O4 nanoparticles with a tapered spherical nature and narrow size (3 nm) distribution. Thermo-gravimetric analysis reveals the strong bonding of oleic acid to the CoFe2O4 nanoparticles. Magnetization studies show oleic acid coated CoFe2O4 nanoparticles have high saturation magnetization and reduced surface spin randomization compared to bare particles. Heat production efficiency was studied near the superparamagnetic limit of CoFe2O4 as a function of magnetic core size and ferrofluid concentration. For a given particle size and concentration, the maximum specific absorption rate varies as the square of the magnetic field applied. Notable increase in the maximum specific absorption rate was found with decrease in particle size and concentration. MTT assay studies with L-929 cells using oleic acid coated CoFe2O4 nanoparticles reveals that the particles with a size of 12 nm are more biocompatible compared to particles with a size of 24 nm.

Krishna Surendra, Muvvala; Dutta, Rajesh; Ramachandra Rao, M. S.

2014-04-01

29

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

30

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

31

Magnetic properties and local configurations of 57Fe atoms in CoFe2O4 powders and CoFe2O4/PVA nanocomposites  

NASA Astrophysics Data System (ADS)

The composition and magnetic properties of the powders extracted from CoFe2O4 aqueous suspensions and the CoFe2O4/PVA (PVA is polyvinyl alcohol) nanocomposites with a cobalt ferrite content of 10-30 wt % have been investigated using Mössbauer spectroscopy, transmission electron microscopy, and vibration magnetometry. The cationic formulas of the cobalt ferrites synthesized have been determined. The differences between samples synthesized at temperatures of 72.5 and 82.5°C have been revealed. The specific features of the observed changes in the agglomeration of CoFe2O4 particles after introducing into the PVA matrix have been studied. It has been shown that the iron ion distribution determined by Mössbauer spectroscopy in octahedral and tetrahedral lattice sites correlates with vibration magnetometry data.

Fedotova, Yu. A.; Baev, V. G.; Lesnikovich, A. I.; Milevich, I. A.; Vorob'eva, S. A.

2011-04-01

32

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

Microsoft Academic Search

Spinel CoFe2O4 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 CoFe2O4 coating on hollow glass microspheres

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

2007-01-01

33

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

34

Hollow CoFe2O4-Co3Fe7 microspheres applied in electromagnetic absorption  

NASA Astrophysics Data System (ADS)

In this work, monodisperse hollow cobalt ferrite (CoFe2O4) microspheres with mean diameter of 150 nm and shell thickness of 50 nm have been successfully prepared via a one-pot solvothermal method. In order to improve the microwave absorption, a thermal reduction process was designed to synthesize hollow CoFe2O4-Co3Fe7 microspheres. Scanning electron microscopy and transmission electron microscopy images showed that the CoFe2O4-Co3Fe7 microspheres retained hollow structure. Microwave absorption results revealed that hollow CoFe2O4-Co3Fe7 microspheres exhibited much stronger electromagnetic absorption than the original hollow CoFe2O4 microspheres. Most importantly, when the sample thickness was 1.3 mm, the reflection loss (RL) less than -10 dB was obtained in the frequency range of 12.5-17.7 GHz, which nearly covered the entire Ku-band. When the sample thickness increased to 2 mm, the minimum RL was as high as -41.6 dB with the effective bandwidth (the bandwidth of RL at -10 dB) of 3 GHz. The enhanced microwave absorption was attributed to efficient complement between dielectric loss and magnetic loss. These results indicated that the hollow CoFe2O4-Co3Fe7 microspheres could be used as a new candidate for microwave absorbents, especially in Ku-band.

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

2015-03-01

35

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

36

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

NASA Astrophysics Data System (ADS)

Transition metal ferrites such as CoFe2O4, possessing a large magnetostriction coefficient and high Curie temperature ( T c > 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 ( M s). 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 M s up to +20.7% was observed at room temperature in the case of the 10 wt.% CoFe2O4-P(VDF-HFP) sample.

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

2013-09-01

37

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

38

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

39

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

40

High accuracy photopyroelectric investigation of dynamic thermal parameters of Fe 3 O 4 and CoFe 2 O 4 magnetic nanofluids  

Microsoft Academic Search

The suitability of the photopyroelectric (PPE) calorimetry in measuring the thermal parameters of nanofluids was demonstrated.\\u000a The main advantages of the method (concerning nanofluids) as compared to classical calorimetric techniques are: high sensitivity\\u000a and small amount of sample required. The thermal diffusivity and effusivity of some nanofluids based on Fe3O4 and CoFe2O4 type of nanoparticles (mean diameter 6.5 nm) were investigated

D. Dadarlat; C. Neamtu; M. Streza; R. Turcu; I. Craciunescu; D. Bica; L. Vekas

2008-01-01

41

Exchange bias effect in CoFe2O4-Cr2O3 nanocomposite embedded in SiO2 matrix  

NASA Astrophysics Data System (ADS)

A nanogranular system composed of CoFe2O4-Cr2O3 core-shell nanoparticles (embedded in SiO2 matrix) having average particle size of 35 ± 5 nm was prepared by chemical synthesis. Structural characterizations by x-ray diffraction, Transmission Electron Microscope (TEM) show highly crystalline phase of these nanocomposites. High resolution TEM images show distorted and modified grain boundary region. CoFe2O4-Cr2O3 nanocomposites show excellent positive exchange bias effect after field cooling at 100 Oe of applied field. Both the exchange bias field and vertical shift in magnetization loop has been observed in this system below 300 K after field cooling. There is a positive loop shift of about 5 kOe along the field axis at 20 K in this system while the vertical shift is nearly 100% owing to the strong exchange bias effect. The exchange bias effect has been explained in terms of the different magnetic exchange interactions and modified grain boundary effect of CoFe2O4-Cr2O3 nanocomposites. The role of spin glass like phase and surface effects of the nanocomposite on the vertical shift of the hysteresis loop and the sharp increase of exchange bias field (HEB) has also been discussed.

Borgohain, Chandan; Mishra, Debabrata; Sarma, K. C.; Phukan, Prodeep

2012-12-01

42

Synthesis and magnetic properties of spinel CoFe 2O 4 nanowire arrays  

NASA Astrophysics Data System (ADS)

Spinel CoFe 2O 4 nanowire arrays were synthesized in nanopores of anodic aluminum oxide (AAO) template using aqueous solution of cobalt and iron nitrates as precursor. The precursor was filled into the nanopores by vacuum impregnation. After heat treatment, it transformed to spinel CoFe 2O 4 nanowires. The structure, morphology and magnetic properties of the sample were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results indicate that the nanowire arrays are compact. And the individual nanowires have a high aspect ratio, which are about 80 nm in diameter and 10 ?m in length. The nanowires are polycrystalline spinel phase. Magnetic measurements indicate that the nanowire arrays are nearly magnetic isotropic. The reason is briefly discussed. Moreover, the temperature dependence of the coercive force of the nanowire arrays was studied.

Yuan, J. J.; Zhao, Q.; Xu, Y. S.; Liu, Z. G.; Du, X. B.; Wen, G. H.

2009-09-01

43

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

44

Fabrication and characterization of cobalt ferrite (CoFe 2O 4) nanofibers by electrospinning  

Microsoft Academic Search

By sol–gel process and electrospinning method, cobalt ferrite\\/polyvinyl acetate (PVAc) composite fiber was obtained. Cobalt ferrite (CoFe2O4) nanofibers were synthesized by calcination of the cobalt ferrite\\/polyvinyl acetate (PVAc) composite fiber with several temperatures. The nanofibers were characterized by SEM, FT-IR, XRD and EXAFS. The diameter of nanofibers was slightly decreased with increasing the calcination temperature. The fibers calcined at 800°C

Young-Wan Ju; Jae-Hyun Park; Hong-Ryun Jung; Sung-June Cho; Wan-Jin Lee

2008-01-01

45

Synthesis of nanocrystalline spinel CoFe 2O 4 via a polymer-pyrolysis route  

Microsoft Academic Search

Nanocrystalline CoFe2O4 spinel ferrites were synthesized via the pyrolysis of polyacrylate salt precursors prepared by in situ polymerization of metal salts and acrylic acid. The pyrolytic behaviors of the polymeric precursors were analyzed by use of simultaneous thermogravimetric and differential thermal analysis (TG-DTA). The structural characteristics of the calcined products were obtained by powder X-ray diffraction (XRD), infrared spectroscopy (IR)

Xian-Ming Liu; Shao-Yun Fu; Hong-Mei Xiao; Chuan-Jun Huang

2005-01-01

46

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

47

Nanolamellar magnetoelectric BaTiO3–CoFe2O4 bicrystal  

E-print Network

Research, Gaithersburg, Maryland 20899-6103, USA #1;Received 30 July 2009; accepted 9 September 2009; published online 13 October 2009#2; Here, we report a spontaneously formed nanolamellar BaTiO3–CoFe2O4 bicrystal. #1;11¯0#2; interfaces join the BaTiO3... with the phase diagram of the quinary system Fe–Co–Ti–Ba–O.12 The corresponding nanometer scale transmission electron micros- copy #1;TEM#2; images #1;Fig. 1#2; display two types of contrast at different length scales. Figure 1#1;a#2; displays the low magnifi...

Ren, Shenqiang; Laver, Mark; Wuttig, Manfred

2009-10-13

48

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

49

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.

50

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

51

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

52

Nanolamellar magnetoelectric BaTiO3CoFe2O4 bicrystal Shenqiang Ren,1  

E-print Network

Nanolamellar magnetoelectric BaTiO3­CoFe2O4 bicrystal Shenqiang Ren,1 Mark Laver,2 and Manfred 2 nm wavelength is magnetoelectric with a frequency dependent coupling coefficient of 20 mV/Oe cm great potential for magnetoelectric devices. © 2009 American Institute of Physics. doi:10

Rubloff, Gary W.

53

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

54

Effect of Strain on Electronic and Magnetic Structure of Fe-doped CoFe2O4  

Microsoft Academic Search

The development of new materials with large room temperature spin polarizations and small conductivity mismatches with semiconductors is key for more complex spintronics devices. CoFe2O4 has a high Curie temperature (TC = 793 K), a large predicted spin polarization, and, when doped with iron, a conductivity similar to semiconductors; however, the magnetic properties of thin films are different from the

Jarrett Moyer; Carlos Vaz; Ezana Negusse; Dario Arena; Victor Henrich

2011-01-01

55

Chemical profiling and defect distribution of the magnetoelectric CoFe2O4/BaTiO3 system using transmission electron microscopy techniques  

E-print Network

Chemical profiling and defect distribution of the magnetoelectric CoFe2O4/BaTiO3 system using of composite magnetoelectric (ME) devices depends primarily on the coupling between the magnetostrictive the interface characteristics of the model magneto-electric CoFe2O4/BaTiO3 system using a range of different

Dunin-Borkowski, Rafal E.

56

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

E-print Network

the optical properties of epitaxial CoFe2O4 thin films and compared our findings with complementary electronic structure calculations and similar studies on the Ni analog. Our work reveals CoFe2O4 to be an indirect band Examples include spin-filters3,4 and spin-transfer torque devices.1 Among the various candidate materials

57

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

58

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

59

Influence of grain size dispersion on the magnetic properties of nanogranular BaTiO3-CoFe2O4 thin films.  

PubMed

Thin film nanogranular composites of cobalt ferrite (CoFe2O4) dispersed in a barium titanate (BaTiO3) matrix were deposited by laser ablation with different cobalt ferrite concentrations (x). Their structural and magnetic properties were characterized. The films were polycrystalline and composed by a mixture of tetragonal-BaTiO3 and CoFe2O4 with the cubic spinel structure. A slight (111) barium titanate phase orientation and (311) CoFe2O4 phase orientation were observed. The lattice parameter of the CoFe2O4 was always smaller than the bulk value indicating that the cobalt ferrite was under compressive stress. From atomic force microscopy a broad distribution of grain sizes was observed in the nanocomposites, with a significant amount of smaller grains (<40 nm) from the CoFe2O4 phase. The magnetic measurements show an increase of the magnetic moment from the low concentration region where the magnetic grains are more isolated and their magnetic interaction is small, towards the bulk value for higher CoFe2O4 content in the films. A corresponding decrease of coercive field with increasing cobalt ferrite concentration was also observed, due to the higher inter-particle magnetic interaction (and reduced stress) of the agglomerated grains. PMID:19504912

Barbosa, J; Almeida, B G; Mendes, J A; Leitão, D; Araújo, J P

2009-06-01

60

Large magnetoelectric properties in CoFe2O4:BaTiO3 core-shell nanocomposites  

NASA Astrophysics Data System (ADS)

Composites of ferroelectric and magnetostrictive materials show more magnetoelectric coupling than single phase materials. Core-shell CoFe2O4:BaTiO3 nanocomposites (1:1 weight ratio) and a mixture of both of them have been synthesized by a combination of hydrothermal and sol gel techniques. X ray diffraction analysis confirms the presence of both the materials in the samples. High Resolution Transmission Electron Microscope images confirm the core shell structure. The magnetoelectric coupling effect is investigated by measuring the magnetoelectric coefficient. It is observed that the coefficient is 35 times larger in the core-shell nanocomposites compared to that of the mixture.

Chaudhuri, Arka; Mandal, Kalyan

2015-03-01

61

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

62

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

63

A novel method to fabricate CoFe2O4/SrFe12O19 composite ferrite nanofibers with enhanced exchange coupling effect.  

PubMed

Nanocomposite of CoFe2O4/SrFe12O19 has been synthesized by the electrospinning and calcination process. A novel method that cobalt powder was used to replace traditional cobalt salt in the precursor sol-gel for electrospinning was proposed. The crystal structures, morphologies, and magnetic properties of these samples have been characterized in detail. Moreover, when the average crystallite size of the hard/soft phases reached up to an optimal value, the CoFe2O4 have an enhanced saturation magnetization of 62.8 emu/g and a coercivity of 2,290 Oe. Significantly, the hysteresis loops for the nanocomposites show a single-phase magnetization behavior, and it has been found that the exchange coupling interaction strongly exists in the CoFe2O4/SrFe12O19 magnetic nanocomposite nanofibers. PMID:25852422

Pan, Lining; Cao, Derang; Jing, Panpan; Wang, Jianbo; Liu, Qingfang

2015-01-01

64

The normal state properties of nano-sized CoFe2O4 added Bi-based superconductors in bipolaron model  

NASA Astrophysics Data System (ADS)

The effect of nano-sized CoFe2O4 particles (10 nm in diameter) addition on the structure and the normal state transport properties of polycrystalline Bi-based superconductors were systematically studied. The additional amount, x wt.%, of CoFe2O4 in this case varied from 0.0 to 1 wt.% of the total mass of the sample. Phase analysis by X-ray diffraction (XRD) and Electrical resistance as a function of temperature, ?(T) were carried out. Nano-sized particles addition modifies the electrical behavior of the normal state with increasing the CoFe2O4 concentration. The bipolaron model can explain properly the normal state resistivity of the samples.

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

2013-12-01

65

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

66

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

67

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

68

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

69

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

70

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

71

Modification of structure and magnetic anisotropy of epitaxial CoFe2O4 films by hydrogen reduction  

NASA Astrophysics Data System (ADS)

Heteroepitaxial CoFe2O4 (CFO) thin films with different thicknesses were deposited on MgO (001) substrates. The as-deposited CFO films show a clear switching of magnetic anisotropy with increasing film thickness. The thinner films (<100 nm) show a perpendicular magnetic anisotropy due to the out-of-plane compressive strain. The thicker films exhibit an in-plane easy axis owing to the dominating shape anisotropy effect. The magnetostriction coefficient of CFO films is estimated to be ?[001] = -188 × 10-6. Metallic CoFe2 films were obtained by annealing the as-deposited CFO films in forming gas (Ar 93% + H2 7%) at 450 °C. XRD shows that CoFe2 films are textured out-of-plane and aligned in-plane, owing to lattice matching between CoFe2 and MgO substrate. TEM results indicate that as-deposited films are continuous while the annealed films exhibit a nanopore mushroom structure. The magnetic anisotropy of CoFe2 films is dominated by the shape effect. The results demonstrate that hydrogen reduction can be effectively used to modify microstructures and physical properties of complex metal oxide materials.

Chen, Aiping; Poudyal, Narayan; Xiong, Jie; Liu, J. Ping; Jia, Quanxi

2015-03-01

72

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

73

Core shell particles consisting of cobalt ferrite and silica as model ferrofluids [CoFe 2O 4–SiO 2 core shell particles  

Microsoft Academic Search

Nearly monodisperse core shell particles consisting of a magnetic core of cobalt ferrite (CoFe2O4) and a shell of silica (SiO2) are prepared via a modified Stöber synthesis. The core shell structure is confirmed by TEM, the size distribution of the whole particles was determined by means of photon correlation spectroscopy and small angle X-ray scattering. Due to charged surface groups

Joachim Wagner; Tina Autenrieth; Rolf Hempelmann

2002-01-01

74

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

NASA Astrophysics Data System (ADS)

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 remains stable to at least 93.6 GPa. The bulk modulus (K0) of the tetragonal and the high-pressure polymorphs were calculated to be 94(12) and 145(16) GPa, respectively, with K'?4. Upon release of pressure the orthorhombic phase persists and appears to be structurally metastable. At zero pressure, laser induced heating leads to a significant transformation back to the tetragonal phase. The high-pressure orthorhombic phase at one atmosphere is 14.7% denser than the tetragonal phase.

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

2003-09-01

75

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

76

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

77

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

78

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

79

Electric in-plane polarization in multiferroic CoFe2O4/BaTiO3 nanocomposite tuned by magnetic fields  

NASA Astrophysics Data System (ADS)

Ferrimagnetic CoFe2O4 nanopillars embedded in a ferroelectric BaTiO3 matrix are an example for a two-phase magnetoelectrically coupled system. They operate at room temperature and are free of any resource-critical rare-earth element, which makes them interesting for potential applications. Prior studies succeeded in showing strain-mediated coupling between the two subsystems. In particular, the electric properties can be tuned by magnetic fields and the magnetic properties by electric fields. Here we take the analysis of the coupling to a new level utilizing soft X-ray absorption spectroscopy and its associated linear dichroism. We demonstrate that an in-plane magnetic field breaks the tetragonal symmetry of the (1,3)-type CoFe2O4/BaTiO3 structures and discuss it in terms of off-diagonal magnetostrictive-piezoelectric coupling. This coupling creates staggered in-plane components of the electric polarization, which are stable even at magnetic remanence due to hysteretic behaviour of structural changes in the BaTiO3 matrix. The competing mechanisms of clamping and relaxation effects are discussed in detail.

Schmitz-Antoniak, Carolin; Schmitz, Detlef; Borisov, Pavel; de Groot, Frank M. F.; Stienen, Sven; Warland, Anne; Krumme, Bernhard; Feyerherm, Ralf; Dudzik, Esther; Kleemann, Wolfgang; Wende, Heiko

2013-06-01

80

Structural and dielectric properties of laser ablated BaTiO3 films deposited over electrophoretically dispersed CoFe2O4 grains  

NASA Astrophysics Data System (ADS)

Thin film nanocomposites with mixed connectivity, composed by CoFe2O4 grains, deposited by electrophoresis on Si|Pt substrates, and subsequently covered by a laser ablation deposited BaTiO3 layer were prepared with different cobalt ferrite concentrations. Their structure presented a combination of BaTiO3, with its tetragonal and the orthorhombic phases coexisting at room temperature, and CoFe2O4 with the cubic spinel structure. The cobalt ferrite nanograins were under in-plane tensile stress, while the BaTiO3 phase was under in-plane compressive stress. The dielectric measurements showed that as the barium titanate grain size decreased, its ferroelectric Curie temperature shifted to lower temperatures relative to the bulk. This grain size dependent TC shift was associated and modeled by a core-shell structure of BaTiO3 grains in the films, with a tetragonal core and cubic shell. Additionally, a diffuse tetragonal-orthorhombic phase transition was observed and, in agreement with Raman spectroscopy results, associated to the coexistence of barium titanate orthorhombic and tetragonal phases in the room temperature region. This led to the formation of polar nanoclusters with random polarization orientations, which induced a frustrated phase transition between the tetragonal and orthorhombic phases of barium titanate in the films.

Barbosa, J. G.; Gomes, I. T.; Pereira, M. R.; Moura, C.; Mendes, J. A.; Almeida, B. G.

2014-10-01

81

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

82

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

83

Three-state resistive switching in CoFe2O4/Pb(Zr0.52Ti0.48)O3/ZnO heterostructure  

NASA Astrophysics Data System (ADS)

The heterostructural film combining multiferroic CoFe2O4/Pb(Zr0.52Ti0.48)O3 bilayer with semiconductor ZnO layer was prepared. Three-state resistive switching was demonstrated by time-dependent current measurements under different stimuli combination of voltage pulse and magnetic bias. The asymmetry diodelike current-voltage, capacitance-voltage, and polarization-voltage loops, which seriously depend on magnetic bias, were observed. We revealed that three-state resistive switching was dominated by the changes in the charge carriers in the heterostructure, which were modulated by the magnetoelectric coupling between ferromagnetic and ferroelectric layers and interface polarization coupling between ferroelectric and semiconductor layers. This work provides promising candidates for developing advanced switchable devices with multifunctional memory.

Li, Ziwei; Zhou, Mingxiu; Ding, Wangfeng; Zhou, Hang; Chen, Bo; Wan, Jian-Guo; Liu, Jun-Ming; Wang, Guanghou

2012-06-01

84

Preparation and characterization of multiferroic CoFe2O4/Bi0.97Ce0.03FeO3 coaxial nanotubes  

NASA Astrophysics Data System (ADS)

Multiferroic CoFe2O4 (CFO)/Bi0.97Ce0.03FeO3 (BCFO) coaxial nanotubes were prepared by a sol-gel template method. Transmission electron microscopy revealed that the coaxial nanotubes featured with inner CFO and outer BCFO nanotubes. Selected area electron diffraction confirmed the coexistence of spinel CFO and perovskite BCFO phases in the coaxial nanotubes. Vibrating sample magnetometer measurements showed that the saturated magnetization of the coaxial nanotubes was 3.3 emu/g, smaller than that of CFO nanotubes. The P- E hysteresis loop of the coaxial nanotubes was of poor shape due to possible high conductivity in the inner CFO nanotubes. Dielectric measurements exhibited that the dielectric constant of the coaxial nanotubes decreased while the dielectric loss increased due probably to the small dielectric constant and high conductivity in the inner CFO nanotube. Ferroelectric and magnetic properties were simultaneously demonstrated in the CFO/BCFO coaxial nanotubes.

Liu, X. L.; Li, M. Y.; Wang, J.; Hu, Z. Q.; Zhu, Y. D.; Zhao, X. Z.

2012-09-01

85

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

86

Magnetic properties of Y-, La-, Nd-, Gd-, and Bi-doped ultrafine CoFe 2O 4 spinel grown by using a sol-gel method  

NASA Astrophysics Data System (ADS)

Y-, La-, Nd-, Gd-, and Bi-doped ultrafine CoFe 2O 4 particles are fabricated by using a sol-gel method. Magnetic and structural properties depending on annealing temperature of powders are investigated with X-ray diffractometer (XRD), Mössbauer spectroscopy, and vibrating sample magnetometer (VSM). Y-, Gd-, and Bi-doped samples fired at and above 923 K have only a single cubic spinel strcture and behave ferrimagnetically, but in La- and Nd-doped samples ?-Fe 2O 3 phase was observed at and above 1123 K. Powders annealed at 823 K have a typical spinel structure and have a paramagnetic and ferrimagnetic nature, simultaneously. The isomer shifts of all samples indicated that the iron ions were ferric at the tetrahedral [A] and the octahedral sites [B], respectively. The magnetic behavior of CoFe 1.9Bi 0.1O 4 and CoFe 1.9Nd 0.1O 4 spinel powders fired at and above 923 K shows that an increase of the annealing temperature yields a decrease of the coercivity and an increase of the saturation magnetization. The highest coercivity of 1368 Oe and saturation magnetization of 76.2 emu/g are observed in CoFe 1.9Bi 0.1O 4 compound.

Kim, Woo Chul; Lee, Seung Wha; Kim, Sam Jin; Yoon, Sung Hyun; Kim, Chul Sung

2000-06-01

87

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

88

Magnetoelectric coupling of multilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4 film by piezoresponse force microscopy under magnetic field  

NASA Astrophysics Data System (ADS)

Multiferroic Pb(Zr0.52Ti0.48)O3-CoFe2O4-Pb(Zr0.52Ti0.48)O3 (PCP) laminated film has been synthesized by sol-gel process and spin coating, with the spinel structure of CoFe2O4 and perovskite structure of Pb(Zr0.52Ti0.48)O3 verified by x-ray diffraction. The good multiferroic properties of PCP film have been confirmed by ferroelectric and magnetic hysteresis loops, with leakage current substantially reduced. The local magnetoelectric coupling has been verified using piezoresponse force microscopy under external magnetic field, showing magnetically induced evolution of piezoresponse and ferroelectric switching characteristics, with piezoresponse amplitude reduced and coercive voltage increased. Such technique will be useful in characterizing local magnetoelectric (ME) couplings for a wide range of multiferroic materials.

Xie, S. H.; Liu, Y. M.; Ou, Y.; Chen, Q. N.; Tan, X. L.; Li, J. Y.

2012-10-01

89

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

90

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

91

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

92

Improving magnetic properties of ultrasmall magnetic nanoparticles by biocompatible coatings  

NASA Astrophysics Data System (ADS)

This paper deals with the effect of a biocompatible surface coating layer on the magnetic properties of ultrasmall iron oxide nanoparticles. Particles were synthesized by laser pyrolysis and fully oxidized to maghemite by acid treatment. The surface of the magnetic nanoparticles was systematically coated with either phosphonate (phosphonoacetic acid or pamidronic acid) or carboxylate-based (carboxymethyl dextran) molecules and the binding to the nanoparticle surface was analyzed. Magnetic properties at low temperature show a decrease in coercivity and an increase in magnetization after the coating process. Hysteresis loop displacement after field cooling is significantly reduced by the coating, in particular, for particles coated with pamidronic acid, which show a 10% reduction of the displacement of the loop. We conclude that the chemical coordination of carboxylates and phosphonates reduces the surface disorder and enhances the magnetic properties of ultrasmall maghemite nanoparticles.

Costo, R.; Morales, M. P.; Veintemillas-Verdaguer, S.

2015-02-01

93

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

94

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

95

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

96

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

97

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

98

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

99

Synthesis of monodisperse FeCo nanoparticles by reductive salt-matrix annealing  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

100

Orientation-Dependent Properties of CoFe2O4-Bi3.15Nd0.85Ti3O12 Bilayer Multiferroic Films Prepared by a Sol-Gel Method  

NASA Astrophysics Data System (ADS)

Lead-free bilayer multiferroic films of CoFe2O4 (CFO) and oriented Bi3.15Nd0.85Ti3O12 (BNT) were deposited on a conventional Pt(111)/Ti/SiO2/Si(100) substrate by use of a sol-gel method. BNT layers with different preferred orientations were grown by use of different spinning and annealing processes. The ferroelectric, ferromagnetic, and magnetoelectric (ME) properties of the CFO-BNT bilayer thin films were investigated at room temperature. a-Axis-oriented bilayer films had larger ME voltage coefficients and larger converse ME response than c-axis-oriented films. This study shows that the orientation of the BNT layer has a stress-mediated interfacial effect which can substantially affect the magnetoelectric coupling behavior of the bilayer structures.

Zhang, Fuwei; Yang, Feng; Dong, Cuifang; Liu, Xiaotong; Nan, Huilin; Wang, Yingying; Zong, Zhihao; Tang, Minghua

2015-03-01

101

Strong magnetoelectric coupling in sol-gel derived multiferroic (Pb0.76Ca0.24)TiO3-CoFe2O4 composite films  

NASA Astrophysics Data System (ADS)

A multilayer heterostructure composite thin films consisting of alternating layers (Pb0.76Ca0.24)TiO3 (PCT) and CoFe2O4 (CFO) were grown on Pt/Ti/SiO2/Si(100) substrate by a sol-gel process. X-ray measurements indicated high quality of crystallization of both PCT and CFO layers. The magnetic and ferroelectric properties of the composite were investigated. Well-defined polarization vs. electric field (P-E) and magnetic hysteresis (M-H) loops were obtained. A strong magnetoelectric (ME) response was observed in the sample which was subjected to an alternating magnetic field, and a high ME voltage coefficient ?E = 870 mV/Oe cm was obtained for the composite thin films when applied magnetic field parallel to the sample plane.

Cheng, T. D.; Tang, X. G.; Wang, Yu; Chan, H. L. W.

2012-10-01

102

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

103

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

104

Magnetic properties of nano-crystalline Gd- or Pr-substituted CoFe 2O 4 synthesized by the citrate precursor technique  

NASA Astrophysics Data System (ADS)

The magnetic properties of nano-crystalline CoM xFe 2- xO 4 (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 6.8 nm and a maximum of 87.5 nm. The materials were characterized by powder X-ray diffraction (XRD) and thermogravimetric (TG) measurements. TG study indicates the formation of the spinel ferrite phase at 220°C. The phase identification of the materials by XRD reveals the single-phase nature of the materials. The room temperature saturation magnetization of the ferrite materials decreases with the reduction of size. This has been attributed to the presence of superparamagnetic fractions in the materials and spin canting at the surface of nano-particles. Insertion of rare-earth atoms in the crystal lattice inhibits the grain growth of the materials in a systematic manner compared with that of the pure cobalt ferrite materials. The improved coercivity compared with those for the pure cobalt ferrites is attributed to the contribution from the single ion anisotropy of the rare-earth ions present in the crystal lattice and the surface effects resulting in alteration of magnetic structures on the surface of nano-particles.

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

2003-02-01

105

On Ultrasmall Nanocrystals  

PubMed Central

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

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

2010-01-01

106

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

107

Magnetostatic Coupling in CoFe2O4/Pb(Zr0.53Ti0.47)O3 Magnetoelectric Composite Thin Films of 2-2 Type Structure  

NASA Astrophysics Data System (ADS)

CoFe2O4/Pb(Zr0.53Ti0.47)O3 (CFO/PZT) magnetoelectric composite thin films of 2-2 type structure had been prepared onto Pt/Ti/SiO2/Si substrate by a sol-gel process and spin coating technique. The structure of the prepared thin film is substrate/PZT/CFO/PZT/CFO. Two CFO ferromagnetic layers are separated from each other by a thin PZT layer. The upper CFO layer is magnetostatically coupled with the lower CFO layer. Subsequent scanning electron microscopy (SEM) investigations show that the prepared thin films exhibit good morphologies and compact structure, and cross-sectional micrographs clearly display a multilayered nanostructure of multilayered thin films. The composite thin films exhibit both good magnetic and ferroelectric properties. The spacing between ferromagnetic layers can be varied by adjusting the thickness of intermediate PZT layer. It is found that the strength of magnetostatic coupling has a great impact on magnetoelectric properties of composite thin films, i.e., the magnetoelectric voltage coefficient of composite thin film tends to increase with the decreasing of pacing between two neighboring CFO ferromagnetic layers as a result of magnetostatic coupling effect.

Xu, Yu-dong; Wang, Lei; Shi, Min; Su, Hai-lin; Wu, Guang

2012-02-01

108

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

109

Anatase TiO 2 nanolayer coating on cobalt ferrite nanoparticles for magnetic photocatalyst  

Microsoft Academic Search

TiO2\\/CoFe2O4 composite nanoparticles with a core–shell structure have been obtained. The core CoFe2O4 nanoparticles were synthesized via co-precipitation method, and the shell TiO2 nanocrystals were derived via sol–gel technology followed by heat-treatment at 450 °C. The morphology and the crystalline structure of composite nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction, respectively. The as-prepared composite particles can

Wuyou Fu; Haibin Yang; Minghua Li; Minghui Li; Nan Yang; Guangtian Zou

2005-01-01

110

Effect of BaTiO3 addition on structural, multiferroic and magneto-dielectric properties of 0.3CoFe2O4?0.7BiFeO3 ceramics  

NASA Astrophysics Data System (ADS)

This study reports the various physical properties of (1 ? x)(0.3CoFe2O4-0.7BiFeO3)-xBaTiO3 composites (equivalently denoted as 0.3CFO-0.7BFO/BT) with the compositions x = 0, 0.30, 0.35, 0.40 and 1.0. The composites are synthesized through a hybrid processing technique in which 0.3CFO–0.7BFO is prepared through a sol-gel process, and BT is processed through a solid state reaction method. Subsequently, the effects of the addition of BT on the structural, dielectric, magnetic and magneto-dielectric properties of 0.3CFO–0.7BFO have been investigated for various BT concentrations. The Rietveld refinement analysis of x-ray diffraction patterns reveals the structural distortion in the BFO phase with the addition of BT, while no such distortion has been observed for the CFO phase. Energy dispersive spectroscopy confirms the presence of two types of grains that correspond to the 0.3CFO–0.7BFO and BT phases in field emission scanning electron micrographs of the composites. Improved dielectric properties have been observed, which are associated with the improved density of composites with the addition of BT. Measurements of the magnetic and ferroelectric hysteresis loops at room temperature indicate that the composites exhibit ferroelectricity and ferromagnetism simultaneously at room temperature. An increase of the electric polarization has been observed due to structural distortion arising with the addition of BT. The significant dependence of the dielectric constant on the magnetic field has been observed in the prepared composites. The highest value of the magneto-dielectric response (3.2%) has been observed for a 40 mol% addition of BT.

Adhlakha, Nidhi; Yadav, K. L.; Singh, Ripandeep

2014-10-01

111

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

112

Confirmation of disordered structure of ultrasmall CdSe nanoparticles from X-ray atomic pair distribution function analysis.  

PubMed

The atomic pair distribution function (PDF) analysis of X-ray powder diffraction data has been used to study the structure of small and ultra-small CdSe nanoparticles. A method is described that uses a wurtzite and zinc-blende mixed phase model to account for stacking faults in CdSe particles. The mixed-phase model successfully describes the structure of nanoparticles larger than 2 nm yielding a stacking fault density of about 30%. However, for ultrasmall nanoparticles smaller than 2 nm, the models cannot fit the experimental PDF showing that the structure is significantly modified from that of larger particles and the bulk. The observation of a significant change in the average structure at ultra-small size is likely to explain the unusual properties of the ultrasmall particles such as their white light emitting ability. PMID:23525376

Yang, Xiaohao; Masadeh, Ahmad S; McBride, James R; Božin, Emil S; Rosenthal, Sandra J; Billinge, Simon J L

2013-06-14

113

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

114

Synthesis and characterization of ultra-small superparamagnetic iron oxide nanoparticles thinly coated with silica  

PubMed Central

Ultra-small superparamagnetic iron oxide nanoparticles (SPIOs) were synthesized by co-precipitation of iron chloride salts with ammonia and then encapsulated with thin (~2nm) layers of silica. The particles have been characterized for size, diffraction pattern, surface charge, and magnetic properties. This rapid and economical synthesis has a number of industrial applications; however, the silica-coated particles have been optimized for use in medical applications as MR contrast agents, biosensors, DNA capturing, bioseparation and enzyme immobilization PMID:19701448

Bumb, A; Brechbiel, M W; Choyke, P L; Fugger, L; Eggeman, A; Prabhakaran, D; Hutchinson, J; Dobson, P J

2008-01-01

115

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

116

Synthesis and characterization of ultra-small superparamagnetic iron oxide nanoparticles thinly coated with silica  

NASA Astrophysics Data System (ADS)

Ultra-small superparamagnetic iron oxide nanoparticles were synthesized by co-precipitation of iron chloride salts with ammonia and then encapsulated with thin (~2 nm) layers of silica. The particles have been characterized for size, diffraction pattern, surface charge, and magnetic properties. This rapid and economical synthesis has a number of industrial applications; however, the silica-coated particles have been optimized for use in medical applications such as magnetic resonance contrast agents and biosensors, and in DNA capturing, bioseparation and enzyme immobilization.

Bumb, A.; Brechbiel, M. W.; Choyke, P. L.; Fugger, L.; Eggeman, A.; Prabhakaran, D.; Hutchinson, J.; Dobson, P. J.

2008-08-01

117

High-performance liquid chromatography coupled with mass spectrometry for analysis of ultrasmall palladium nanoparticles.  

PubMed

Metal nanoparticles (NPs) have recently attracted considerable attention in many areas of research including bioscience, chemistry and material science. Regrettably, most current and past work usually focuses on studies of multi-component NPs mixture where there is a plethora of NPs species co-existing. This work highlights the merits of reverse-phase high-performance liquid chromatography (RP-HPLC) for disclosing the genuine properties of individual palladium nanoparticles (PdNPs) species present in an as-synthesized N,N'-dimethylformamide-stabilized PdNPs product (DMF-PdNPs) which might have been previously hidden or misinterpreted. DMF-PdNPs is successfully separated by RP-HPLC that smaller DMF-PdNPs are approximately eluted first and then follow by the large ones on a C18 column. The separation fractions are further collected and determined their chemical compositions by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results unambiguously reveal that the as-synthesized DMF-PdNPs product is indeed a complex mixture of ultrasmall PdxNPs (x=10-20) stabilized with different numbers of DMF ligands. It is anticipated that the separated fractions afforded by RP-HPLC will offer more accurate determinations of the catalytic, electronic, optical and toxicological properties of metal NPs which might have been previously misinterpreted. PMID:25281151

Zhang, Lei; Li, Zhongping; Zhang, Yan; Paau, Man Chin; Hu, Qin; Gong, Xiaojuan; Shuang, Shaomin; Dong, Chuan; Peng, Xiaoguang; Choi, Martin M F

2015-01-01

118

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

119

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

120

Highly coercive cobalt ferrite nanoparticles-CuTl-1223 superconductor composites  

NASA Astrophysics Data System (ADS)

We explored the effects of highly coercive cobalt ferrite (CoFe2O4) nanoparticles addition on structural, morphological, and superconducting properties of Cu0.5Tl0.5Ba2Ca2Cu3O10-? (CuTl-1223} matrix. Series of (CoFe2O4)x/CuTl-1223 (x=0 2.0 wt%) composites samples were synthesized and were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) absorption spectroscopy, and dc-resistivity versus temperature measurements. The magnetic behavior of CoFe2O4 nanoparticles was determined by MH-loops with the help of superconducting quantum interference device (SQUID). MH-loops analysis showed that these nanoparticles exhibit high saturation magnetization (86 emu/g) and high coercivity (3350 Oe) at 50 K. The tetragonal structure of host CuTl-1223 superconducting matrix was not altered after the addition of CoFe2O4 nanoparticles, which gave us a clue that these nanoparticles had occupied the inter-granular sites (grain-boundaries) and had filled the pores. The increase of mass density with increasing content of these nanoparticles in composites can also be an evidence of filling up the voids in the matrix. The resistivity versus temperature measurements showed an increase in zero resistivity critical {Tc(0)}, which could be most probably due to improvement of weak-links by the addition of these nanoparticles. But the addition of these nanoparticles beyond an optimum level caused the agglomeration and produced additional stresses in material and suppressed the superconductivity.

Jabbar, Abdul; Qasim, Irfan; Khan, Shahid A.; Nadeem, K.; Waqee-ur-Rehman, M.; Mumtaz, M.; Zeb, F.

2015-03-01

121

One-pot fabrication of yolk-shell nanospheres with ultra-small Au nanoparticles for catalysis.  

PubMed

We report a "one-pot" method for the direct synthesis of an organosilica shell/silica core nanoreactor confined with ultra-small metal (Au, Pd, and Ru) nanoparticles. The nano-reactor confined with Au nanoparticles showed high activity towards styrene oxidation using O2 as the oxidant under 1 atm pressure and could be stably recycled without deterioration of both conversion and selectivity. The strategy could be adapted onto other nanostructures with little modification to obtain yolk-shell nanoreactors for catalysis application. PMID:25644426

Yao, Yi; Zhang, Xiaoming; Peng, Juan; Yang, Qihua

2015-02-17

122

In vitro studies on ultrasmall superparamagnetic iron oxide nanoparticles coated with gummic acid for T2 MRI contrast agent  

PubMed Central

Ultrasmall superparamagnetic iron oxide nanoparticles coated with gummic acid have been investigated as possible constituents of aqueous ferrofluids for biomedical applications and especially for MRI contrast agent. The structural characteristics and the size of the nanoparticles have been analyzed as well as the magnetic properties. In order to evaluate any possible capabilities as a contrast agent, the relaxation time, T2, of hydrogen protons in the colloidal solutions of nanoparticles have been measured in order to gain information on the relaxation behavior compared to other MRI contrast agents. The in vitro cytotoxicity of the obtained magnetic nanoparticles of iron oxide coated with gummic acid was investigated by two separate methods (MTT and FACS analysis) and by using three different normal and transformed cell lines. Our results showed that the synthesized nanoparticles had no toxic effect on any of the cell lines used. PMID:19693403

Rabias, I.; Pratsinis, H.; Drossopoulou, G.; Fardis, M.; Maris, T.; Boukos, N.; Tsotakos, N.; Kletsas, D.; Tsilibary, E.; Papavassiliou, G.

2007-01-01

123

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

2015-01-21

124

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

125

[Investigation of the interaction between DNA and cobalt ferrite nanoparticles by FTIR spectroscopy].  

PubMed

The interaction of DNA with nanoparticles of cobalt ferrite powder prepared by the mechano-chemical method was studied. It was shown that CoFe(2)O(4) nanoparticles efficiently bind DNA in aqueous solutions (Tris-HCl), forming a bionanocomposite. The adsorption capacity of CoFe(2)O(4) nanoparticles for DNA was evaluated to be 5.25 x 10(-3) mol/m(2). The desorption of DNA from the surface of the particles was analyzed while changing the pH, the ionic strength, and the chemical content of the medium. The DNA-CoFe(2)O(4) nanocomposite was investigated by FTIR spectroscopy. The block of the data allowed one to consider the mechanism of the interaction between a polynucleotide and CoFe(2)O(4) nanoparticles and to make the assumption that the binding occurred due to the coordination interaction of the phosphate groups and heterocyclic bases of DNA (oxygen atoms of thymine and guanine) with metal ions on the particle surface. The analysis of the IR spectra showed that binding can lead to the partial destabilization of the DNA structure, with the B conformation of a polynucleotide being preserved. PMID:19915646

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

2009-01-01

126

Effect of light on the magnetic properties of cobalt ferrite nanoparticles  

Microsoft Academic Search

We report variations in the coercivity of CoFe2O4 nanoparticles as a function of particle size, temperature and light intensity. For 30 nm particles, this change in was 2300 Oe at 10 K, 120 Oe at 170 K, for a light intensity of under 2 milliwatts. The remanent magnetization was nearly unchanged by illumination. A simple model of optical absorption followed

Anit K. Giri; Kelly Pellerin; Wanida Pongsaksawad; Monica Sorescu; Sara A. Majetich

2000-01-01

127

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

PubMed

Superparamagnetic nanoferrites are prepared by simple and one step refluxing in polyol synthesis. The ferrite nanoparticles prepared by this method exhibit particle sizes below 10 nm and high degree of crystallinity. These ferrite nanoparticles are compared by means of their magnetic properties, induction heating and cell viability studies for its application in magnetic fluid hyperthermia. Out of all studied nanoparticles in present work, only ZnFe2O4 and CoFe2O4 MNPs are able to produce threshold hyperthermia temperature. This rise in temperature is discussed in detail in view of their magneto-structural properties. Therefore ZnFe2O4 and CoFe2O4 MNPs with improved stability, magnetic induction heating and cell viability are suitable candidates for magnetic hyperthermia. PMID:25690622

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

2015-03-01

128

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

129

Ultrasmall Sn nanoparticles embedded in nitrogen-doped porous carbon as high-performance anode for lithium-ion batteries.  

PubMed

In this Letter, we reported on the preparation and Li-ion battery anode application of ultrasmall Sn nanoparticles (?5 nm) embedded in nitrogen-doped porous carbon network (denoted as 5-Sn/C). Pyrolysis of Sn(Salen) at 650 °C under Ar atmosphere was carried out to prepare N-doped porous 5-Sn/C with the BET specific surface area of 286.3 m(2) g(-1). The 5-Sn/C showed an initial discharge capacity of 1014 mAh g(-1) and a capacity retention of 722 mAh g(-1) after 200 cycles at the current density of 0.2 A g(-1). Furthermore, a reversible capacity of ?480 mAh g(-1) was obtained at much higher current density of 5 A g(-1). The remarkable electrochemical performance of 5-Sn/C was attributed to the effective combination of ultrasmall Sn nanoparticles, uniform distribution, and porous carbon network structure, which simultaneously solved the major problems of pulverization, loss of electrical contact, and particle aggregation facing Sn anode. PMID:24328829

Zhu, Zhiqiang; Wang, Shiwen; Du, Jing; Jin, Qi; Zhang, Tianran; Cheng, Fangyi; Chen, Jun

2014-01-01

130

One-step synthesis of water-dispersible ultra-small Fe3O4 nanoparticles as contrast agents for T1 and T2 magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Uniform, highly water-dispersible and ultra-small Fe3O4 nanoparticles were synthesized via a modified one-step coprecipitation approach. The prepared Fe3O4 nanoparticles not only show good magnetic properties, long-term stability in a biological environment, but also exhibit good biocompatibility in cell viability and hemolysis assay. Due to the ultra-small sized and highly water-dispersibility, they exhibit excellent relaxivity properties, the 1.7 nm sized Fe3O4 nanoparticles reveal a low r2/r1 ratio of 2.03 (r1 = 8.20 mM-1 s-1, r2 = 16.67 mM-1 s-1) and the 2.2 nm sized Fe3O4 nanoparticles also appear to have a low r2/r1 ratio of 4.65 (r1 = 6.15 mM-1 s-1, r2 = 28.62 mM-1 s-1). This demonstrates that the proposed ultra-small Fe3O4 nanoparticles have great potential as a new type of T1 magnetic resonance imaging contrast agents. Especially, the 2.2 nm sized Fe3O4 nanoparticles, have a competitive r1 value and r2 value compared to commercial contrasting agents such as Gd-DTPA (r1 = 4.8 mM-1 s -1), and SHU-555C (r2 = 69 mM-1 s-1). In vitro and in vivo imaging experiments, show that the 2.2 nm sized Fe3O4 nanoparticles exhibit great contrast enhancement, long-term circulation, and low toxicity, which enable these ultra-small sized Fe3O4 nanoparticles to be promising as T1 and T2 dual contrast agents in clinical settings.Uniform, highly water-dispersible and ultra-small Fe3O4 nanoparticles were synthesized via a modified one-step coprecipitation approach. The prepared Fe3O4 nanoparticles not only show good magnetic properties, long-term stability in a biological environment, but also exhibit good biocompatibility in cell viability and hemolysis assay. Due to the ultra-small sized and highly water-dispersibility, they exhibit excellent relaxivity properties, the 1.7 nm sized Fe3O4 nanoparticles reveal a low r2/r1 ratio of 2.03 (r1 = 8.20 mM-1 s-1, r2 = 16.67 mM-1 s-1) and the 2.2 nm sized Fe3O4 nanoparticles also appear to have a low r2/r1 ratio of 4.65 (r1 = 6.15 mM-1 s-1, r2 = 28.62 mM-1 s-1). This demonstrates that the proposed ultra-small Fe3O4 nanoparticles have great potential as a new type of T1 magnetic resonance imaging contrast agents. Especially, the 2.2 nm sized Fe3O4 nanoparticles, have a competitive r1 value and r2 value compared to commercial contrasting agents such as Gd-DTPA (r1 = 4.8 mM-1 s -1), and SHU-555C (r2 = 69 mM-1 s-1). In vitro and in vivo imaging experiments, show that the 2.2 nm sized Fe3O4 nanoparticles exhibit great contrast enhancement, long-term circulation, and low toxicity, which enable these ultra-small sized Fe3O4 nanoparticles to be promising as T1 and T2 dual contrast agents in clinical settings. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05550g

Wang, Guannan; Zhang, Xuanjun; Skallberg, Andreas; Liu, Yaxu; Hu, Zhangjun; Mei, Xifan; Uvdal, Kajsa

2014-02-01

131

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

132

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

133

Morphology of cobalt ferrite nanoparticle-polyelectrolyte multilayered nanocomposites  

NASA Astrophysics Data System (ADS)

Novel magnetic nanocomposite films with controlled morphology were produced via the electrostatic layer-by-layer assembly of cationic CoFe 2O 4 nanoparticles and anionic poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonic acid) (PEDOT:PSS) complex. The electrostatic interaction between nanoparticle and the polyelectrolyte complex ensured a stepwise growth of the nanocomposite film with virtually identical amounts of materials being adsorbed at each deposition cycle as observed by UV-vis spectroscopy. AFM images acquired under the tapping mode revealed a globular morphology with dense and continuous layers of nanoparticles with voids being filled with polymeric material.

Alcantara, G. B.; Paterno, L. G.; Fonseca, F. J.; Morais, P. C.; Soler, M. A. G.

2011-05-01

134

Ultrasmall integrin-targeted silica nanoparticles modulate signaling events and cellular processes in a concentration-dependent manner.  

PubMed

Cellular and molecular-level interactions of nanoparticles with biological systems are a rapidly evolving field requiring an improved understanding of endocytic trafficking as the principal driver and regulator of signaling events and cellular responses. An understanding of these processes is vital to nanomedicine applications. Studies investigating the complex interplay of these processes and their relationship to targeted nanoparticles exploiting endocytic pathways are notably lacking. It is known that integrins traffic through the endosomal pathway and participate in diverse roles controlling signal transduction, cell migration, and proliferation. Here, it is shown that ultrasmall, nontoxic, core-shell silica nanoparticles (C-dots), surface-functionalized with cRGDY peptides, modestly activate integrin-signaling pathways, in turn, promoting the enhancement of cellular functions. First, nanomolar concentrations, two orders of magnitude higher than clinical trial doses, internalize within ?v?3 integrin-expressing melanoma and endothelial cells, predominantly through an integrin receptor-dependent endocytic route. Second, integrin-mediated activation of focal adhesion kinase (FAK) and downstream signaling pathways occurs, in turn, upregulating phosphorylated protein expression levels and promoting concentration-dependent cellular migration and proliferative activity. Inhibiting FAK catalytic activity leads to decreased phosphorylation levels and cellular migration rates. These findings may inform the design of more effectively-targeted nanomedicines and provide insights into endocytic regulation of signal transduction. PMID:25471698

Benezra, Miriam; Phillips, Evan; Overholtzer, Michael; Zanzonico, Pat B; Tuominen, Esa; Wiesner, Ulrich; Bradbury, Michelle S

2015-04-01

135

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

136

Evaluation of uptake and transport of cationic and anionic ultrasmall iron oxide nanoparticles by human colon cells  

PubMed Central

Nanoparticles (NPs) are in clinical use or under development for therapeutic imaging and drug delivery. However, relatively little information exists concerning the uptake and transport of NPs across human colon cell layers, or their potential to invade three-dimensional models of human colon cells that better mimic the tissue structures of normal and tumoral colon. In order to gain such information, the interactions of biocompatible ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) (iron oxide core 9–10 nm) coated with either cationic polyvinylamine (aminoPVA) or anionic oleic acid with human HT-29 and Caco-2 colon cells was determined. The uptake of the cationic USPIO NPs was much higher than the uptake of the anionic USPIO NPs. The intracellular localization of aminoPVA USPIO NPs was confirmed in HT-29 cells by transmission electron microscopy that detected the iron oxide core. AminoPVA USPIO NPs invaded three-dimensional spheroids of both HT-29 and Caco-2 cells, whereas oleic acid-coated USPIO NPs could only invade Caco-2 spheroids. Neither cationic aminoPVA USPIO NPs nor anionic oleic acid-coated USPIO NPs were transported at detectable levels across the tight CacoReady™ intestinal barrier model or the more permeable mucus-secreting CacoGoblet™ model. PMID:22419874

Kenzaoui, Blanka Halamoda; Vilà, Maya R; Miquel, Josep M; Cengelli, Feride; Juillerat-Jeanneret, Lucienne

2012-01-01

137

Biological reactivity of nanoparticles: mosaics from optical microscopy videos of giant lipid vesicles  

NASA Astrophysics Data System (ADS)

Emerging fields such as nanomedicine and nanotoxicology, demand new information on the effects of nanoparticles on biological membranes and lipid vesicles are suitable as an experimental model for bio-nano interaction studies. This paper describes image processing algorithms which stitch video sequences into mosaics and recording the shapes of thousands of lipid vesicles, which were used to assess the effect of CoFe2O4 nanoparticles on the population of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine lipid vesicles. The applicability of this methodology for assessing the potential of engineered nanoparticles to affect morphological properties of lipid membranes is discussed.

Zupanc, Jernej; Dobnikar, Andrej; Drobne, Damjana; Valant, Janez; Erdogmus, Deniz; Bas, Erhan

2011-02-01

138

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

139

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

PubMed

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

140

Strong stokes and upconversion luminescence from ultrasmall Ln(3+)-doped BiF3 (Ln=Eu3+, Yb3+/Er3+) nanoparticles confined in a polymer matrix.  

PubMed

Heavy metal fluorides like BiF3 as a host for lanthanide ions are of interest as bismuth is the only heavy metal that is nontoxic. In this work, we report the synthesis of highly water-dispersible ultrasmall BiF3 nanoparticles about 6?nm in size within a poly(vinyl pyrrolidone) matrix by a hydrothermal method. Microscopy analysis reveals that the nanoparticles are well separated and confined within the polymer network. These nanoparticles were found to be excellent hosts for lanthanide (Ln(3+)) ions. Through suitable Ln(3+) doping, BiF3 exhibits strong emissions in the visible region upon both UV and near infrared (NIR) excitations. The non-toxicity of both bismuth and PVP can be advantageous for the potential use of BiF3 nanoparticles in drug delivery and bioimaging. PMID:24259494

Sarkar, Shyam; Dash, Armita; Mahalingam, Venkataramanan

2014-02-01

141

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

142

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

143

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

144

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

PubMed

UV irradiation leads to the formation of reactive oxygen species (ROS). An imbalance between the antioxidant system and ROS can lead to cell damage, premature skin aging or skin cancer. To counteract these processes, antioxidants such as coenzyme Q10 (CoQ10) are contained in many cosmetics. To improve and optimize cell/tissue penetration properties of the lipophilic CoQ10, ultra-small lipid nanoparticles (usNLC) were developed. The antioxidant effectiveness of CoQ10-loaded usNLC compared to conventional nanocarriers was investigated in the human keratinocyte cell line HaCaT. Using confocal laser scanning microscopy investigations of the carriers additionally loaded with nile red showed a clear uptake into cells and their distribution within the cytoplasm. By use of the XTT cell viability test, CoQ10 concentrations of 10-50?g/ml were shown to be non-toxic, and the antioxidant potential of 10?g/ml CoQ10 loaded usNLC in the HaCaT cells was analyzed via electron paramagnetic resonance spectroscopy after cellular exposure to UVA (1J/cm(2)) and UVB (18mJ/cm(2)) irradiation. In comparison with the CoQ10-loaded conventional carriers, usNLC-CoQ10 demonstrated the strongest reduction of the radical formation; reaching up to 23% compared to control cells without nanocarrier treatment. Therefore, usNLC-CoQ10 are very suitable to increase the antioxidant potential of skin. PMID:25500282

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

2015-01-01

145

Structure investigation of ultra-small CdSe nanoparticles using the atomic PDF  

Microsoft Academic Search

The size-dependent structure of CdSe nanoparticles, with diameter ranging from 1.5 to 3.6 nm, has been studied using the atomic pair distribution function (PDF) method. The samples are prepared by the methods of Peng et al [1], with modifications. The structure of the smallest stable size, (˜1.5 nm), have been found to posses locally distorted wurtzite structure, with no clear

Ahmad S. Masadeh; Simon J. L. Billinge; Emil S. Bozin; James R. McBride; Sandra J. Rosenthal

2011-01-01

146

Structure investigation of ultra-small CdSe nanoparticles using the atomic PDF  

NASA Astrophysics Data System (ADS)

The size-dependent structure of CdSe nanoparticles, with diameter ranging from 1.5 to 3.6 nm, has been studied using the atomic pair distribution function (PDF) method. The samples are prepared by the methods of Peng et al [1], with modifications. The structure of the smallest stable size, (˜1.5 nm), have been found to posses locally distorted wurtzite structure, with no clear evidence of a heavily disordered surface region [2]. The PDF data of the smallest particle show an extra structural peak appears around r = 3.5 A indicates there is structure modification happened in this sample. This peak start appearing the nanoparticles PDF data gradually as nanoparticle size decreases. The structural parameters are reported quantitatively. We measure a size-dependent strain on the Cd-Se bond which reaches 1.0% at the smallest particle size [3]. The size of the well-ordered core extracted directly from the data agrees with the size determined from other methods. [0pt] [1] Peng, et al, JACS., 120, 5343-5344 (1998). [2] Gilbert et al, Science, 305, 651-654 (2004). [3] Masadeh et al. PRB 76, 115413 (2007).

Masadeh, Ahmad S.; Billinge, Simon J. L.; Bozin, Emil S.; McBride, James R.; Rosenthal, Sandra J.

2011-03-01

147

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

PubMed

Reducing the particle size of active component in electrode material could significantly improve the electrochemical performance of lithium-ion batteries. Herein, we report a facile method for preparing cobalt oxide nanoparticles-reduced graphene oxide (Co3O4-RGO) nanocomposite, which was composed of ultra-small Co3O4 nanoparticles (?12.5 nm in size) anchored on RGO nanosheets, as anode material for lithium-ion batteries. Both of the Co3O4-RGO nanocomposite and Co3O4 nanoparticles showed very high specific surface areas of ?149.5 m(2) g(-1) and ?107.4 m(2) g(-1). The Co3O4-RGO nanocomposite showed excellent coulombic efficiency, high lithium storage capacity and good rate capability. With an optimum weight percentage of RGO (?40 wt%), the nanocomposite displayed a high reversible discharge capacity of 830.7 mA h g(-1) after 75 cycles at 200 mA g(-1), and a reversible capacity of 680.9 mA h g(-1) after 30 cycles at 200 mA g(-1) and 100 consecutive cycles at 500 mA g(-1). After each eight cycles at 50, 100, 200, and 500 mA g(-1), the nanocomposite showed high reversible specific capacities of about 1153.2, 961.0, 851.4 and 736.4 mA h g(-1), respectively. These results show the importance of anchoring ultra-small nanoparticles on graphene nanosheets for maximum utilization of electrochemically active Co3O4 nanoparticles and graphene for energy storage applications in high-performance lithium-ion batteries. PMID:25742903

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

2015-04-14

148

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

149

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

150

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

151

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

152

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

153

Creation of high-density and low-defect single-layer film of magnetic nanoparticles by the method of interfacial molecular films.  

PubMed

A technique to solubilize fine magnetic inorganic particles in general organic solvents is proposed via surfaces modification by long-chain carboxylic acids. This organic modification should overcome the relatively weak van der Waals interactions between the nanoparticles, allowing the formation of ordered arrangements of the modified Fe3O4 and CoFe2O4 materials. Using nanodispersions of these organo-modified magnetic nanoparticles as "spreading solutions", Langmuir monolayers of these particles were formed. Multiparticle layered structures were constructed by the Langmuir-Blodgett (LB) technique. The fabrication of single- and multiparticle layers of organo-modified magnetic nanoparticles was investigated using surface pressure-area (?-A) isotherms, out-of-plane X-ray diffraction (XRD), in-plane XRD, and atomic force microscopy (AFM). The out-of-plane XRD profile of a single-particle layer of organo-modified Fe3O4 clearly showed a sharp peak which was attributed to the distance between Fe3O4 layers along the c-axis. The AFM image of single-particle layer of organo-modified CoFe2O4 revealed integrated particle organization with a uniform height; these aggregated particles formed large two-dimensional crystals. For both nanoparticle species, regular periodic structures along the c-axis and high-density single-particle layers were produced via the Langmuir and LB techniques. PMID:25727135

Fujimori, Atsuhiro; Ohmura, Kyohei; Honda, Nanami; Kakizaki, Koichi

2015-03-17

154

Mössbauer and magnetic study of Co x Fe3--x O4 nanoparticles  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles of cobalt ferrites Co x Fe3-x O4 (x = 1 or 2) have been obtained either by mechanical milling or thermal treatment of pre-prepared layered double hydroxide carbonate x-LDH CO3. Mechanical milling of the 1-LDH CO3 leads to the large-scale preparation of nearly spherical nanoparticles of CoFe2O4, the size of which (5 to 20 nm) is controlled by the treatment time. Core-shell structure with surface spin-canting has been considered for the nanoparticles formed to explain the observed hysteresis loop shift (from ZFC FC) in the magnetic properties. Annealing treatment of the 2-LDH CO3 below 673 K results in the formation of nearly spherical pure Co2FeO4 nanoparticles. At 673 K and above, the LDH decomposition leads to the formation of a mixture of both spinels phases Co2FeO4 and CoFe2O4, the amount of the latter increases with annealing temperature. Unusually high magnetic hardness characterized by a 22 kOe coercive field at 1.8 K has been observed, which reflects the high intrinsic anisotropy for Co2FeO4.

Estournès, C.; D'Orléans, C.; Rehspringer, J.-L.; Manova, E.; Kunev, B.; Paneva, D.; Mitov, I.; Petrov, L.; Kurmoo, M.

2005-09-01

155

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

156

Optimal Labeling Dose, Labeling Time, and Magnetic Resonance Imaging Detection Limits of Ultrasmall Superparamagnetic Iron-Oxide Nanoparticle Labeled Mesenchymal Stromal Cells  

PubMed Central

Background. Regenerative therapy is an emerging treatment modality. To determine migration and retention of implanted cells, it is crucial to develop noninvasive tracking methods. The aim was to determine ex vivo magnetic resonance imaging (MRI) detection limits of ultrasmall superparamagnetic iron-oxide (USPIO) labeled mesenchymal stromal cells (MSCs). Materials and Methods. 248 gel-phantoms were constructed and scanned on a 1.5T MRI-scanner. Phantoms contained human MSCs preincubated with USPIO nanoparticles for 2, 6, or 21 hours using 5 or 10??g?USPIO/105 MSCs. In addition, porcine hearts were scanned after injection of USPIO labeled MSCs. Results. Using 21?h incubation time and 10??g?USPIO/105 MSCs, labeled cells were clearly separated from unlabeled cells on MRI using 250.000 (P < 0.001), 500.000 (P = 0.007), and 1.000.000 MSCs (P = 0.008). At lower incubation times and doses, neither labeled nor unlabeled cells could be separated. In porcine hearts labeled, but not unlabeled, MSCs were identified on MRI. Conclusions. As few as 250.000 MSCs can be detected on MRI using 21?h incubation time and 10??g?USPIO/105 MSCs. At lower incubation times and doses, several million cells are needed for MRI detection. USPIO labeled cells can be visualized by MRI in porcine myocardial tissue. PMID:23577035

Mathiasen, Anders Bruun; Hansen, Louise; Friis, Tina; Thomsen, Carsten; Bhakoo, Kishore; Kastrup, Jens

2013-01-01

157

Magnetic properties of CoFe2O4-BaTiO3 composites  

NASA Astrophysics Data System (ADS)

The aim of the present work is to study how the volume (lattice parameters) changes of barium titanate, induced by a phase transition, which occurs by temperature sweeps, influence magnetic behavior of cobalt ferrite in their composites via inverse magnetostrictive (Villari) effect. Structure, phase composition, and magnetic properties were investigated using X-ray diffraction, Mössbauer spectroscopy, and temperature dependence of magnetization. The tetragonal-to-orthorhombic phase transition in barium titanate occurring at ˜280 K on cooling can be observed in the zero-field cooled magnetization curve. The other phase transitions, i.e., tetragonal-to-cubic transition at ˜390 K and orthorhombic-to-rhombohedral transition at ˜178 K, were detected neither by magnetic nor by Mössbauer measurements.

?uda, J.; Mousa, I.; David, B.; Pizúrová, N.; Tu?ek, J.; Žák, T.; MašláÅ, M.; Schneeweiss, O.

2012-10-01

158

Magnetic properties of CoFe2O4-BaTiO3 composites  

NASA Astrophysics Data System (ADS)

The aim of the present work is to study how the volume (lattice parameters) changes of barium titanate, induced by a phase transition, which occurs by temperature sweeps, influence magnetic behavior of cobalt ferrite in their composites via inverse magnetostrictive (Villari) effect. Structure, phase composition, and magnetic properties were investigated using X-ray diffraction, Mössbauer spectroscopy, and temperature dependence of magnetization. The tetragonal-to-orthorhombic phase transition in barium titanate occurring at ~280 K on cooling can be observed in the zero-field cooled magnetization curve. The other phase transitions, i.e., tetragonal-to-cubic transition at ~390 K and orthorhombic-to-rhombohedral transition at ~178 K, were detected neither by magnetic nor by Mössbauer measurements.

?uda, J.; Mousa, I.; David, B.; Pizúrová, N.; Tu?ek, J.; Žák, T.; Mašlá?, M.; Schneeweiss, O.

2012-10-01

159

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

160

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

161

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

PubMed

Cystic fibrosis (CF) is a genetic disease mainly manifested in the respiratory tract. Pseudomonas aeruginosa (P. aeruginosa) is the most common pathogen identified in cultures of the CF airways, however, its eradication with antibiotics remains challenging as it grows in biofilms that counterwork human immune response and dramatically decrease susceptibility to antibiotics. P. aeruginosa regulates pathogenicity via a cell-to-cell communication system known as quorum sensing (QS) involving the virulence factor (pyocyanin), thus representing an attractive target for coping with bacterial pathogenicity. The first in vivo potent QS inhibitor (QSI) was recently developed. Nevertheless, its lipophilic nature might hamper its penetration of non-cellular barriers such as mucus and bacterial biofilms, which limits its biomedical application. Successful anti-infective inhalation therapy necessitates proper design of a biodegradable nanocarrier allowing: 1) high loading and prolonged release, 2) mucus penetration, 3) effective pulmonary delivery, and 4) maintenance of the anti-virulence activity of the QSI. In this context, various pharmaceutical lipids were used to prepare ultra-small solid lipid nanoparticles (us-SLNs) by hot melt homogenization. Plain and QSI-loaded SLNs were characterized in terms of colloidal properties, drug loading, in vitro release and acute toxicity on Calu-3 cells. Mucus penetration was studied using a newly-developed confocal microscopy technique based on 3D-time-lapse imaging. For pulmonary application, nebulization efficiency of SLNs and lung deposition using next generation impactor (NGI) were performed. The anti-virulence efficacy was investigated by pyocyanin formation in P. aeruginosa cultures. Ultra-small SLNs (<100nm diameter) provided high encapsulation efficiency (68-95%) according to SLN composition, high burst in phosphate buffer saline compared to prolonged release of the payload over >8h in simulated lung fluid with minor burst. All types and concentrations of plain and QSI-loaded SLNs maintained the viability of Calu-3 cells. 3D time-lapse confocal imaging proved the ability of SLNs to penetrate into artificial sputum model. SLNs were efficiently nebulized; NGI experiments revealed their deposition in the bronchial region. Overall, nanoencapsulated QSI showed up to sevenfold superior anti-virulence activity to the free compound. Most interestingly, the plain SLNs exhibited anti-virulence properties themselves, which was shown to be related to anti-virulence effects of the emulsifiers used. These startling findings represent a new perspective of ultimate significance in the area of nano-based delivery of novel anti-infectives. PMID:24997276

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

2014-10-28

162

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

163

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

PubMed

Today, by injecting iron oxide based nanoparticles (USPIO) as MRI contrast agents, it is possible to study lymphatic system and some specific tumors and their metastasis. The type of surface coating, and coating characteristics of the nanoparticles are important factors for the biological properties of nanoparticles and their destination target. On the other hand, these properties contribute to different signal intensities. This may confine application of all types of USPIO based contrast agents in routine daily experiments. In this study, the ability of detecting these particles having various sizes and coating properties was evaluated for MRI applications. Signal intensity changes after administration of these particles into tissues have been studied and their detection sensitivity was evaluated using a liver phantom and animal model (rat). IO based nanoparticles of various sizes (8-30 nm) functionalized and coated with various surface polymers such as dextran and starch, amine and hydroxide groups, and bear IO particles were used to investigate the signal changes. The optimized pulse sequences for proper demonstration of lymph nodes using these contrast agents were found (T2* FSPGR protocol with fat suppressions). A detection sensitivity of 98% was achieved in most experiments during applying a proper MR protocol. However, the type of surface coating, and coating characteristics such as thickness were shown to be essential factors for MRI signal intensity in both T1 and T2 protocols. PMID:17945909

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

2006-01-01

164

A betaine adduct of N-heterocyclic carbene and carbodiimide, an efficient ligand to produce ultra-small ruthenium nanoparticles.  

PubMed

The betaine adduct of N-heterocyclic carbene and carbodiimide (ICy·((p-tol))NCN) was found to be a very efficient ligand to prepare very small (1-1.3 nm) ruthenium nanoparticles (RuNPs). The coordination of the ligand on the metal surface takes place through the carbodiimide moiety. The resulting RuNPs led to decarbonylation of THF and showed size selectivity for styrene hydrogenation. PMID:25690829

Martínez-Prieto, L M; Urbaneja, C; Palma, P; Cámpora, J; Philippot, K; Chaudret, B

2015-03-01

165

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

166

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

167

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

168

Acid-functionalized nanoparticles for biomass hydrolysis  

NASA Astrophysics Data System (ADS)

Cellulosic ethanol is a renewable source of energy. Lignocellulosic biomass is a complex material composed mainly of cellulose, hemicellulose, and lignin. Biomass pretreatment is a required step to make sugar polymers liable to hydrolysis. Mineral acids are commonly used for biomass pretreatment. Using acid catalysts that can be recovered and reused could make the process economically more attractive. The overall goal of this dissertation is the development of a recyclable nanocatalyst for the hydrolysis of biomass sugars. Cobalt iron oxide nanoparticles (CoFe2O4) were synthesized to provide a magnetic core that could be separated from reaction using a magnetic field and modified to carry acid functional groups. X-ray diffraction (XRD) confirmed the crystal structure was that of cobalt spinel ferrite. CoFe2O4 were covered with silica which served as linker for the acid functions. Silica-coated nanoparticles were functionalized with three different acid functions: perfluoropropyl-sulfonic acid, carboxylic acid, and propyl-sulfonic acid. Transmission electron microscope (TEM) images were analyzed to obtain particle size distributions of the nanoparticles. Total carbon, nitrogen, and sulfur were quantified using an elemental analyzer. Fourier transform infra-red spectra confirmed the presence of sulfonic and carboxylic acid functions and ion-exchange titrations accounted for the total amount of catalytic acid sites per nanoparticle mass. These nanoparticles were evaluated for their performance to hydrolyze the beta-1,4 glycosidic bond of the cellobiose molecule. Propyl-sulfonic (PS) and perfluoropropyl-sulfonic (PFS) acid functionalized nanoparticles catalyzed the hydrolysis of cellobiose significantly better than the control. PS and PFS were also evaluated for their capacity to solubilize wheat straw hemicelluloses and performed better than the control. Although PFS nanoparticles were stronger acid catalysts, the acid functions leached out of the nanoparticle during the catalytic reactions. PS nanoparticles were further evaluated for the pretreatment of corn stover in order to increase digestibility of the biomass. The pretreatment was carried out at three different catalyst load and temperature levels. At 180°C, the total glucose yield was linearly correlated to the catalyst load. A maximum glucose yield of 90% and 58% of the hemicellulose sugars were obtained at this temperature.

Pena Duque, Leidy Eugenia

169

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

170

Incorporation of cobalt-ferrite nanoparticles into a conducting polymer in aqueous micellar medium: strategy to get photocatalytic composites.  

PubMed

In this study an easy strategy for conducting polymer based nanocomposite formation is presented through the deposition of cobalt-ferrite (CoFe(2)O(4)) containing poly(3,4-ethylenedioxythiophene) (PEDOT) thin layers. The electrochemical polymerization has been performed galvanostatically in an aqueous micellar medium in the presence of the nanoparticles and the surface active Triton X-100. The nanoparticles have been characterized by Transmission electron microscopy (TEM), the thin layers has been studied by applying Scanning electron microscopy (SEM), and X-ray diffraction (XRD), and the basic electrochemical properties have been also determined. Moreover, electrocatalytic activity of the composite was demonstrated in the electrooxidation reaction of dopamine (DA). The enhanced sensitivity - related to the cobalt-ferrite content - and the experienced photocatalyitic activity are promising for future application. PMID:25125121

Endr?di, Balázs; Hursán, Dorottya; Petrilla, Liliána; Bencsik, Gábor; Visy, Csaba; Chams, Amani; Maslah, Nabiha; Perruchot, Christian; Jouini, Mohamed

2014-01-01

171

Cold plasma treatment of magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

This thesis investigates the application of cold plasma to remove the oleic acid bonded on magnetic nanoparticles: SmCo5 nanoflakes prepared via surfactant assisted high energy ball milling and CoFe2O 4 nanoparticles prepared via chemical synthesis. Oleic acid molecules bonded on nanoparticles are in the carboxylate form which could not be washed away by organic solvents in ultrasonic bath; only free oleic acid molecules left on the nanoparticle surface after ball milling can be washed away through ultrasonic bath. High temperature annealing method works for removing oleic acid but nanoparticles would be damaged because of oxidation and decomposition. The RF cold plasma has advantages over above methods as the plasma temperature is typically around room temperature, and the energetic ions could strike away carboxylate molecules bonded on the surface of nanoparticles without changing the surface chemistry. Powder X-ray diffraction (XRD) was performed to see if there was phase transformation, decomposition during plasma treatment. The content change of oleic acid molecules on the nanoparticles surface was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR).

Wang, Ke

172

Cobalt ferrite thin films as anode material for lithium ion batteries  

Microsoft Academic Search

Spinel cobalt ferrite (CoFe2O4) thin films have been fabricated by 355nm reactive pulsed laser deposition on stainless steel substrates. XRD and SEM analyses showed that the CoFe2O4 films exhibited a polycrystalline structure and were composed of nanoparticles with an average size of 80nm. At 1C rate, the initial irreversible capacity of polycrystalline CoFe2O4 film electrode cycled between 0.01 and 3.0V

Yan-Qiu Chu; Zheng-Wen Fu; Qi-Zong Qin

2004-01-01

173

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

174

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

175

Optimization of sol-gel synthesis of CoFe2O4 nanowires using template assisted vacuum suction method  

NASA Astrophysics Data System (ADS)

In this study, cobalt ferrite nanowires were synthesized by a sol-gel route using anodized aluminum oxide (AAO) template by applying mechanical vacuum suction. The parameters of calcination temperature and pH value were optimized subsequently. The single phase cobalt ferrite was obtained at 600 °C. The results showed that pH=1 is appropriate for synthesis of uniform nanowires because at the higher pH values the autocombustion of the gel, with making cracks in nanowires, will be happened. Furthermore, the nanowires showed higher coercivity in the direction parallel to the axis of the nanowires (Hc?=1050 Oe) rather than that in the perpendicular direction (Hc?=772 Oe).

Pirouzfar, A.; Seyyed Ebrahimi, S. A.

2014-12-01

176

Magnetic Structure of Fe-doped CoFe(2)O(4) Probed by X-ray Magnetic Spectroscopies  

SciTech Connect

The magnetic properties of iron-doped cobalt ferrite (Co{sub 1-x}Fe{sub 2+x}O{sub 4}) (001) thin films grown epitaxially on MgO (001) substrates are investigated by superconducting quantum interference device magnetometry and soft x-ray magnetic linear and circular dichroisms. All Co{sub 1-x}Fe{sub 2+x}O{sub 4} (0.01 {le} x {le} 0.63) samples have out-of-plane magnetic easy axes and large coercive fields, unlike Fe{sub 3}O{sub 4}, due to a large Co{sup 2+} orbital moment. The magnetic moments for those samples are significantly reduced from their bulk values; however, as x increases, the magnetic moments tend nearer to their bulk values and increase more rapidly as x approaches 1. This reduction in magnetic moment is attributed to spin canting among the Co{sup 2+} cations, owing to a small in-plane tensile strain in the film and to an increased antiferromagnetic alignment among all the cations caused by a partially inverse spinel cubic structure and the likely presence of antiphase boundaries. Our results show that small changes in stoichiometry can lead to significant changes in the magnetic moment of Co{sub 1-x}Fe{sub 2+x}O{sub 4}, especially at large values of x.

J Moyer; C Vaz; D Arena; D Kumah; E Negusse; V Henrich

2011-12-31

177

Magnetic Structure of Fe-doped CoFe(2)O(4) Probed by X-ray Magnetic Spectroscopies  

Microsoft Academic Search

The magnetic properties of iron-doped cobalt ferrite (Co{sub 1-x}Fe{sub 2+x}Oâ) (001) thin films grown epitaxially on MgO (001) substrates are investigated by superconducting quantum interference device magnetometry and soft x-ray magnetic linear and circular dichroisms. All Co{sub 1-x}Fe{sub 2+x}Oâ (0.01 ⤠x ⤠0.63) samples have out-of-plane magnetic easy axes and large coercive fields, unlike FeâOâ, due to a large

J Moyer; C Vaz; D Arena; D Kumah; E Negusse; V Henrich

2011-01-01

178

Magnetic structure of Fe-doped CoFe2O4 probed by x-ray magnetic spectroscopies  

Microsoft Academic Search

The magnetic properties of iron-doped cobalt ferrite (Co1-xFe2+xO4) (001) thin films grown epitaxially on MgO (001) substrates are investigated by superconducting quantum interference device magnetometry and soft x-ray magnetic linear and circular dichroisms. All Co1-xFe2+xO4 (0.01 <= x <= 0.63) samples have out-of-plane magnetic easy axes and large coercive fields, unlike Fe3O4, due to a large Co2+ orbital moment. The

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

2011-01-01

179

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

180

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

181

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

182

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

183

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

184

Enigmatic, ultrasmall, uncultivated Archaea  

PubMed Central

Metagenomics has provided access to genomes of as yet uncultivated microorganisms in natural environments, yet there are gaps in our knowledge—particularly for Archaea—that occur at relatively low abundance and in extreme environments. Ultrasmall cells (<500 nm in diameter) from lineages without cultivated representatives that branch near the crenarchaeal/euryarchaeal divide have been detected in a variety of acidic ecosystems. We reconstructed composite, near-complete ~1-Mb genomes for three lineages, referred to as ARMAN (archaeal Richmond Mine acidophilic nanoorganisms), from environmental samples and a biofilm filtrate. Genes of two lineages are among the smallest yet described, enabling a 10% higher coding density than found genomes of the same size, and there are noncontiguous genes. No biological function could be inferred for up to 45% of genes and no more than 63% of the predicted proteins could be assigned to a revised set of archaeal clusters of orthologous groups. Some core metabolic genes are more common in Crenarchaeota than Euryarchaeota, up to 21% of genes have the highest sequence identity to bacterial genes, and 12 belong to clusters of orthologous groups that were previously exclusive to bacteria. A small subset of 3D cryo-electron tomographic reconstructions clearly show penetration of the ARMAN cell wall and cytoplasmic membranes by protuberances extended from cells of the archaeal order Thermoplasmatales. Interspecies interactions, the presence of a unique internal tubular organelle [Comolli, et al. (2009) ISME J 3:159–167], and many genes previously only affiliated with Crenarchaea or Bacteria indicate extensive unique physiology in organisms that branched close to the time that Cren- and Euryarchaeotal lineages diverged. PMID:20421484

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

2010-01-01

185

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 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

186

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

187

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

2014-01-01

188

Pulsed Magneto-motive Ultrasound Imaging Using Ultrasmall Magnetic Nanoprobes  

PubMed Central

Nano-sized particles are widely regarded as a tool to study biologic events at the cellular and molecular levels. However, only some imaging modalities can visualize interaction between nanoparticles and living cells. We present a new technique, pulsed magneto-motive ultrasound imaging, which is capable of in vivo imaging of magnetic nanoparticles in real time and at sufficient depth. In pulsed magneto-motive ultrasound imaging, an external high-strength pulsed magnetic field is applied to induce the motion within the magnetically labeled tissue and ultrasound is used to detect the induced internal tissue motion. Our experiments demonstrated a sufficient contrast between normal and iron-laden cells labeled with ultrasmall magnetic nanoparticles. Therefore, pulsed magneto-motive ultrasound imaging could become an imaging tool capable of detecting magnetic nanoparticles and characterizing the cellular and molecular composition of deep-lying structures. PMID:21439255

Mehrmohammadi, Mohammad; Oh, Junghwan; Mallidi, Srivalleesha; Emelianov, Stanislav Y.

2011-01-01

189

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

190

Enhanced Magnetic Properties in Nanoparticle-Filled CNTs  

NASA Astrophysics Data System (ADS)

There has been much interest in magnetic polymer nanocomposites (MPNCs) recently due to potential applications for EMI shielding, tunable EM devices and flexible electronics. In past studies, using ferrite fillers, we have shown MPNCs to be magnetically tunable when passing a microwave signal through films under the influence of an external magnetic field. We extend this study to include nanoparticle-filled multi-walled carbon nanotubes (CNTs) synthesized by CVD. These high-aspect ratio magnetic nanostructures, with tunable anisotropy, are of particular interest in enhancing magnetic and microwave responses in existing MPNCs. CNTs have an average diameter and length of 300nm and 6 ?m, respectively and are partially filled with CoFe2O4 and NiFe2O4 nanoparticles (NPs) (˜ 7nm). When comparing NPs to NP-filled CNTs, TB increases by ˜ 40K and relaxation time, ?0, increases several orders of magnitude, indicating that enclosing NPs in CNTs enhances interparticle interactions. Structural and magnetic characterization were completed using XRD, TEM and Quantum Design PPMS, using VSM and ACMS options.

Stojak, K.; Chandra, S.; Khurshid, H.; Phan, M. H.; Srikanth, H.

2013-03-01

191

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

192

Fabrication of Porous Anodic Alumina with Ultrasmall Nanopores  

PubMed Central

Anodization of Al foil under low voltages of 1–10 V was conducted to obtain porous anodic aluminas (PAAs) with ultrasmall nanopores. Regular nanopore arrays with pore diameter 6–10 nm were realized in four different electrolytes under 0–30°C according to the AFM, FESEM, TEM images and current evolution curves. It is found that the pore diameter and interpore distance, as well as the barrier layer thickness, are not sensitive to the applied potentials and electrolytes, which is totally different from the rules of general PAA fabrication. The brand-new formation mechanism has been revealed by the AFM study on the samples anodized for very short durations of 2–60 s. It is discovered for the first time that the regular nanoparticles come into being under 1–10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultrasmall nanopores. Under higher potentials from 10 to 40 V, the surface nanoparticles will be less and less and nanopores transform into general PAAs. PMID:20676199

2010-01-01

193

Fabrication of porous anodic alumina with ultrasmall nanopores.  

PubMed

Anodization of Al foil under low voltages of 1-10 V was conducted to obtain porous anodic aluminas (PAAs) with ultrasmall nanopores. Regular nanopore arrays with pore diameter 6-10 nm were realized in four different electrolytes under 0-30°C according to the AFM, FESEM, TEM images and current evolution curves. It is found that the pore diameter and interpore distance, as well as the barrier layer thickness, are not sensitive to the applied potentials and electrolytes, which is totally different from the rules of general PAA fabrication. The brand-new formation mechanism has been revealed by the AFM study on the samples anodized for very short durations of 2-60 s. It is discovered for the first time that the regular nanoparticles come into being under 1-10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultrasmall nanopores. Under higher potentials from 10 to 40 V, the surface nanoparticles will be less and less and nanopores transform into general PAAs. PMID:20676199

Ding, Guqiao; Yang, Rong; Ding, Jianning; Yuan, Ningyi; Zhu, Yuanyuan

2010-01-01

194

Fabrication of Porous Anodic Alumina with Ultrasmall Nanopores  

NASA Astrophysics Data System (ADS)

Anodization of Al foil under low voltages of 1-10 V was conducted to obtain porous anodic aluminas (PAAs) with ultrasmall nanopores. Regular nanopore arrays with pore diameter 6-10 nm were realized in four different electrolytes under 0-30°C according to the AFM, FESEM, TEM images and current evolution curves. It is found that the pore diameter and interpore distance, as well as the barrier layer thickness, are not sensitive to the applied potentials and electrolytes, which is totally different from the rules of general PAA fabrication. The brand-new formation mechanism has been revealed by the AFM study on the samples anodized for very short durations of 2-60 s. It is discovered for the first time that the regular nanoparticles come into being under 1-10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultrasmall nanopores. Under higher potentials from 10 to 40 V, the surface nanoparticles will be less and less and nanopores transform into general PAAs.

Ding, Gu Qiao; Yang, Rong; Ding, Jian Ning; Yuan, Ning Yi; Zhu, Yuan Yuan

2010-08-01

195

Micrometric periodic assembly of magnetotactic bacteria and magnetic nanoparticles using audio tapes  

NASA Astrophysics Data System (ADS)

We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum magneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and of superparamagnetic Fe3O4 and ferromagnetic CoFe2O4 nanoparticles in aqueous suspensions using periodically magnetized audio tapes. The distribution of the stray magnetic field at the surface of the tapes was determined analytically and experimentally by magneto-optic imaging. Calculations showed that the magnetic field close to the tape surface was of the order of 100 mT, and the magnetic field gradient was larger than 1 T mm-1. Drops of aqueous solutions were deposited on the tapes, and bacteria and particles were trapped at locations where magnetic energy is minimized, as observed using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treated with formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated that magnetic forces dominate over self-propelling forces in these experiments, in accordance with calculated values. The behavior of the different types of samples is discussed.

Godoy, M.; Moreno, A. J.; Jorge, G. A.; Ferrari, H. J.; Antonel, P. S.; Mietta, J. L.; Ruiz, M.; Negri, R. M.; Pettinari, M. J.; Bekeris, V.

2012-02-01

196

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

197

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

198

Developing a millifluidic platform for the synthesis of ultrasmall nanoclusters: ultrasmall copper nanoclusters as a case study.  

PubMed

The future of lab-on-a-chip devices for the synthesis of nanomaterials hinges on the successful development of high-throughput methods with better control over their size. While significant effort in this direction mainly focuses on developing "difficult to fabricate" complex microfluidic reactors, scant attention has been paid to the "easy to fabricate" and simple millifluidic systems that could provide the required control as well as high throughput. By utilizing numerical simulation of fluids within the millifluidic space at different flow rates, the results presented here show velocity profiles and residence time distributions similar to the case of microfluidics. By significantly reducing the residence time and residence time distribution, a continuous flow synthesis of ultrasmall copper nanoclusters (UCNCs) with exceptional colloidal stability is achieved. In-situ synchrotron-radiation-based X-ray absorption spectroscopy (XAS) reveal that the as-prepared clusters are about 1 nm, which is further supported by transmission electron microscopy and UV-vis spectroscopy studies. The clusters reported here are the smallest ever produced using a lab-on-a-chip platform. When supported on silica, they are found to efficiently catalyze C-H oxidation reactions, hitherto unknown to be catalyzed by Cu. This work suggests that a millifluidic platform can be an inexpensive, versatile, easy-to-use, and powerful tool for nanoparticle synthesis in general, and more specifically for ultrasmall nanoclusters (UNCs). PMID:22298499

Biswas, Sanchita; Miller, Jeffrey T; Li, Yuehao; Nandakumar, Krishnaswamy; Kumar, Challa S S R

2012-03-12

199

Uptake and distribution of ultra-small anatase TiO2 Alizarin red S nanoconjugates in Arabidopsis thaliana  

PubMed Central

While few publications have documented the uptake of nanoparticles in plants, this is the first study describing uptake and distribution of the ultra-small anatase TiO2 in the plant model system Arabidopsis. We modified the nanoparticle surface with Alizarin red S and sucrose, and demonstrated that nanoconjugates traversed cell walls, entered into plant cells, and accumulated in specific subcellular locations. Optical and X-ray fluorescence microscopy co-registered the nanoconjugates in cell vacuoles and nuclei. PMID:20218662

Kurepa, Jasmina; Paunesku, Tatjana; Vogt, Stefan; Arora, Hans; Rabatic, Bryan M.; Lu, Jinju; Wanzer, M. Beau; Woloschak, Gayle E.; Smalle, Jan A.

2010-01-01

200

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

201

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

202

Magnetic and electric poling effects associated with crack growth in BaTiO 3–CoFe 2O 4 composite  

Microsoft Academic Search

Magnetoelectroelastic composite possesses the dual feature that the application of magnetic field induces electric polarization and electric field induces magnetization. The poling directions introduced magnetically and electrically can be different in addition to those for the applied magnetic and electric field. Their choices can influence the character of crack growth which could be enhanced or retarded. The details of how

G. C Sih; Z. F Song

2003-01-01

203

Formation and evolution of crystalline magnetic phases of CoFe2O4 with temperature depending on the nature of the diol used  

NASA Astrophysics Data System (ADS)

An organic precursor was obtained from cobalt nitrate and iron nitrate with different diols (etilendiol, 1,2-propanediol and 1,3-propanediol). The precursor was observed through thermal analysis and FT-IR spectrometry, techniques aimed at tracking the formation of carboxylate type complex combinations and establishing the optimal synthesis temperature. The formation of magnetic crystalline phases is observed through advanced heat treatments.

Thomas, Dippong; Zoita, Berinde; Ivan, Pauliuc

2013-05-01

204

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

205

Multiferroic properties of Pb,,Zr,Ti...O3/CoFe2O4 composite thin films N. Ortega,a  

E-print Network

structures are intermixed at least partially, and CFO is phase separated into PZT matrix to form a composite profiling of the constituent elements in conjunction with dielectric spectroscopy measurements the reduction of ferroelectric polarization when measured under an applied magnetic field. © 2006 American

Rubloff, Gary W.

206

dc and high frequency magnetic properties of nanopatterned CoFe2O4 arrays fabricated using sol-gel precursors  

E-print Network

fabricated on insulating oxidized silicon substrates and on epitaxial thin films of ferroelectric BiFeO3. We-dimensional magnetic structures of elemental magnets like cobalt,1,2 nickel,3,4 alloys like permalloy,5,6 and metal-oxides of ferromagnetic oxides having Curie temperatures above room temperature have potential for applications in memory

Chandrasekhar, Venkat

207

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

208

The synthesis of Co1-xDyxFe2O4 nanoparticles and thin films as well as investigating their magnetic and magneto-optical properties  

NASA Astrophysics Data System (ADS)

The modification and optimization of the magnetic and magneto-optical properties of cobalt ferrite are of great importance due to their various applications in well-known scientific and industrial categories. In order to observe the effect of adding Dy3+ to the cobalt ferrite composition, Co1-xDyxFe2O4 (0?x?0.1) ceramic nanoparticles were synthesized by the co-precipitation chemical method and then their microstructure and magnetism were investigated through x-ray diffractometry, TEM micrography, IR spectroscopy and VSM magnetometry. The polar magneto-optical Kerr effect of the thin film specimens was also studied. The results reveal that the doping of Dy3+ ions could effectively alter the inversion degree of the spinel structure and the following magnetic and magneto-optical features. The ferrite coercivity was enhanced by 150% after adding Dy. The perceptible shifts of peak rotations were observed in the Kerr spectra for the Dy-doped CoFe2O4 films. Furthermore, TC had a descending trend with the addition of Dy from 440 °C to 420 °C for Co0.95Dy0.05Fe2O4.

Mohammadifar, Y.; Shokrollahi, H.; Karimi, Z.; Karimi, L.

2014-10-01

209

Controlling transport and chemical functionality of magnetic nanoparticles.  

PubMed

A wide range of metal, magnetic, semiconductor, and polymer nanoparticles with tunable sizes and properties can be synthesized by wet-chemical techniques. Magnetic nanoparticles are particularly attractive because their inherent superparamagnetic properties make them desirable for medical imaging, magnetic field assisted transport, and separations and analyses. With such applications on the horizon, synthetic routes for quickly and reliably rendering magnetic nanoparticle surfaces chemically functional have become an increasingly important focus. This Account describes common synthetic routes for making and functionalizing magnetic nanoparticles and discusses initial applications in magnetic field induced separations. The most widely studied magnetic nanoparticles are iron oxide (Fe2O3 and Fe3O4), cobalt ferrite (CoFe 2O4), iron platinum (FePt), and manganese ferrite (MnFe 2O4), although others have been investigated. Magnetic nanoparticles are typically prepared under either high-temperature organic phase or aqueous conditions, producing particles with surfaces that are stabilized by attached surfactants or associated ions. Although it requires more specialized glassware, high-temperature routes are generally preferred when a high degree of stability and low particle size dispersity is desired. Particles can be further modified with a secondary metal or polymer to create core-shell structures. The outer shells function as protective layers for the inner metal cores and alter the surface chemistry to enable postsynthetic modification of the surfactant chemistry. Efforts by our group as well as others have centered on pathways to yield nanoparticles with surfaces that are both easily functionalized and tunable in terms of the number and variety of attached species. Ligand place-exchange reactions have been shown quite successful for exchanging silanes, acids, thiols, and dopamine ligands onto the surfaces of some magnetic particles. Poly(ethylene oxide)-modified phospholipids can be inserted into nonpolar surface monolayers of as-prepared nanoparticles as a method for modifying the surface chemistry that induces water solubility. In general, reactive termini can subsequently be used to append a range of chemical groups. For example, surfactants with trifluoroethylester or azide termini have been used to attach a range of amine- or alkyne-containing species, respectively. Chemically functionalized magnetic nanoparticles are promising as advanced materials for analytical separations and analysis. Magnetic field flow fractionation leverages the size-dependent magnetic moments to purify and separate the components of a complex mixture of particles. Similarly, magnetic field gradients are useful for manipulating transport and separation in simple microfluidic devices. By either approach, magnet-induced transport of the particles is a simple method in which an attached reagent, catalyst, or bioanalytical tag can be moved between flow streams within a lab on a chip device. PMID:18251514

Latham, Andrew H; Williams, Mary Elizabeth

2008-03-01

210

Ultrasmall fluorescent ion-exchanging nanospheres containing selective ionophores.  

PubMed

We present a convenient precipitation procedure to fabricate ultrasmall fluorescent ion-selective nanosensors that operate on the basis of bulk ion-exchange sensing principles. The nanosphere matrix is composed of bis(2-ethylhexyl) sebacate (DOS) and a triblock copolymer Pluronic(®) F-127, which also functions as a surfactant to stabilize the nanoparticle. The particles can be prepared easily in large quantity without resorting to further complicated purification. Dynamic light scattering shows that these particles have a monodisperse size distribution with an average diameter of ?40 nm, suggesting that the nanoparticles are among the smallest ionophore-based ion-selective nanosensors reported to date. A newly reported oxazinoindoline (Ox) as well as a Nile blue derivative (chromoionophore I) was used as a chromoionophore. Na(+)- and H(+)-selective nanospheres were characterized by absorbance and fluorescence spectroscopy. Owing to the very small size of the nanospheres, the suspension containing the particles is transparent. In the additional presence of the pH indicator HPTS, spectroscopic interrogation of pH and Na(+) in the same sample was demonstrated. As an example, the nanospheres were used to measure the Na(+) level in commercial mineral waters, and the results showed good agreement with atomic absorption spectroscopy (AAS). PMID:24020858

Xie, Xiaojiang; Mistlberger, Günter; Bakker, Eric

2013-10-15

211

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

212

Photovoltaic performance of ultrasmall PbSe quantum dots.  

PubMed

We investigated the effect of PbSe quantum dot size on the performance of Schottky solar cells made in an ITO/PEDOT/PbSe/aluminum structure, varying the PbSe nanoparticle diameter from 1 to 3 nm. In this highly confined regime, we find that the larger particle bandgap can lead to higher open-circuit voltages (?0.6 V), and thus an increase in overall efficiency compared to previously reported devices of this structure. To carry out this study, we modified existing synthesis methods to obtain ultrasmall PbSe nanocrystals with diameters as small as 1 nm, where the nanocrystal size is controlled by adjusting the growth temperature. As expected, we find that photocurrent decreases with size due to reduced absorption and increased recombination, but we also find that the open-circuit voltage begins to decrease for particles with diameters smaller than 2 nm, most likely due to reduced collection efficiency. Owing to this effect, we find peak performance for devices made with PbSe dots with a first exciton energy of ?1.6 eV (2.3 nm diameter), with a typical efficiency of 3.5%, and a champion device efficiency of 4.57%. Comparing the external quantum efficiency of our devices to an optical model reveals that the photocurrent is also strongly affected by the coherent interference in the thin film due to Fabry-Pérot cavity modes within the PbSe layer. Our results demonstrate that even in this simple device architecture, fine-tuning of the nanoparticle size can lead to substantial improvements in efficiency. PMID:21939281

Ma, Wanli; Swisher, Sarah L; Ewers, Trevor; Engel, Jesse; Ferry, Vivian E; Atwater, Harry A; Alivisatos, A Paul

2011-10-25

213

Ultrasmall mode volume plasmonic nanodisk resonators.  

PubMed

We study the resonant modes of nanoscale disk resonators sustaining metal-insulator-metal (MIM) plasmons and demonstrate the versatility of these cavities to achieve ultrasmall cavity mode volume. Ag/SiO2/Ag MIM structures were made by thin-film deposition and focused ion beam milling with cavity diameters that ranged from d = 65-2000 nm. High-resolution two-dimensional cavity-mode field distributions were determined using cathodoluminescence imaging spectroscopy and are in good agreement with boundary element calculations. For the smallest cavities (d = 65-140 nm), the lowest order mode (m = 1, n = 1) is observed in the visible spectral range. This mode is of similar nature as the one in plasmonic particle dimers, establishing a natural connection between localized and traveling plasmon cavities. A cavity quality factor of Q = 16 is observed for the 105 nm diameter cavity, accompanied by a mode volume as small as 0.00033lamda(0)(3). The corresponding Purcell factor is 900, making these ultrasmall disk resonators ideal candidates for studies of enhanced spontaneous emission and lasing. PMID:19813755

Kuttge, Martin; García de Abajo, F Javier; Polman, Albert

2010-05-12

214

Design of an ultrasmall aspect ratio concentrator  

NASA Astrophysics Data System (ADS)

The concentrated photovoltaic (CPV) can be employed to improve the efficiency of solar cells and reduce the system cost of power generation, which is the primary part of the CPV system. Based on the demands for the concentrators to have an ultrathin and ultralight design, a design of ultrasmall aspect ratio concentrators is proposed. The concentrator is formed by a lens array and a freeform reflector to precisely control the light. The solar cell is placed at the side of the concentrator, which greatly reduces the overall thickness of the concentrator. The design can reduce the aspect ratio of concentrator by a considerable amount. The freeform reflector can shape the light beam and achieve a uniform distribution of light energy.

Cheng, Ying; Fang, Fengzhou; Zhang, Xiaodong

2014-11-01

215

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

216

Highly fluorescent, photostable, and ultrasmall silicon drug nanocarriers for long-term tumor cell tracking and in-vivo cancer therapy.  

PubMed

Silicon nanoparticle (SiNP) nanocarriers feature strong fluorescence, ultrasmall size, robust photostability, and tunable drug-loading capacity. Using SiNP nanocarriers, the first example of long-term cancer cell tracking is successfully demonstrated. Furthermore, in vivo experiments show that tumor-bearing mice treated with SiNP nanocarriers survive over 20 d without observable tumor growth, demonstrating the high-efficacy chemotherapy of the Si nanocarriers. PMID:25377423

Ji, Xiaoyuan; Peng, Fei; Zhong, Yiling; Su, Yuanyuan; Jiang, Xiangxu; Song, Chongxi; Yang, Liu; Chu, Binbin; Lee, Shuit-Tong; He, Yao

2015-02-01

217

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

218

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

219

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

220

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

221

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

222

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

E-print Network

magnetoelectric hybrid device composed of a nano-particulate magnetostrictive iron oxide-cobalt ferrite film the film magnetization up to 10% of the saturation magnetization of ferrite. At the smallest particle size. Ferromagnetic bulk Co- ferrite is a good choice due to its high magnetostriction. But, because of its high

Rubloff, Gary W.

223

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

224

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

225

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

226

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

227

Synthesis of structurally ordered Pt3Ti and Pt3V nanoparticles as methanol oxidation catalysts.  

PubMed

Structurally ordered Pt3Ti or Pt3V intermetallic nanoparticle catalysts with ultrasmall particle sizes have never been successfully synthesized. Herein, we present a KCl-nanoparticle method to successfully provide such compounds. These two catalysts show enhanced catalytic activity and stability for methanol oxidation compared to pure Pt. PMID:25000137

Cui, Zhiming; Chen, Hao; Zhao, Mengtian; Marshall, Daniel; Yu, Yingchao; Abruña, Héctor; DiSalvo, Francis J

2014-07-23

228

Measuring and controlling the transport of magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Despite the large body of literature describing the synthesis of magnetic nanoparticles, few analytical tools are commonly used for their purification and analysis. Due to their unique physical and chemical properties, magnetic nanoparticles are appealing candidates for biomedical applications and analytical separations. Yet in the absence of methods for assessing and assuring their purity, the ultimate use of magnetic particles and heterostructures is likely to be limited. For magnetic nanoparticles, it is the use of an applied magnetic flux or field gradient that enables separations. Flow based techniques are combined with applied magnetic fields to give methods such as magnetic field flow fractionation and high gradient magnetic separation. Additional techniques have been explored for manipulating particles in microfluidic channels and in mesoporous membranes. This thesis further describes development of these and new analytical tools for separation and analysis of colloidal particles is critically important to enable the practical use of these, particularly for medicinal purposes. Measurement of transport of nanometer scale particles through porous media is important to begin to understand the potential environmental impacts of nanomaterials. Using a diffusion cell with two compartments separated by either a porous alumina or polycarbonate membrane as a model system, diffusive flux through mesoporous materials is examined. Experiments are performed as a function of particle size, pore diameter, and solvent, and the particle fluxes are monitored by the change in absorbance of the solution in the receiving cell. Using the measured extinction coefficient and change in absorbance of the solution as a function of time, the fluxes of 3, 8, and 14 nm diameter CoFe2O4 particles are determined as they are translocated across pores with diameters 30, 50, 100, and 200 nm in hexane and aqueous solutions. In general, flux decreases with increasing particle size and increases with pore diameter. We find that fluxes are faster in aqueous solutions than in hexane, which is attributed to the hydrophilic nature of the porous membranes and differences in wettability. The impact of an applied magnetic flux gradient, which induces magnetization and motion, on permeation is also examined. Surface chemistry plays an important role in determining flux through porous media such as in the environment. Diffusive flux of nanoparticles through alkylsilane modified porous alumina is measured as a model for understanding transport in porous media of differing surface chemistries. Experiments are performed as a function of particle size, pore diameter, attached hydrocarbon chain length and chain terminus, and solvent. Particle fluxes are monitored by the change in absorbance of the solution in the receiving side of a diffusion cell. In general, flux increases when the membranes are modified with alkylsilanes compared to untreated membranes, which is attributed to the hydrophobic nature of the porous membranes and differences in wettability. We find that flux decreases, in both hexane and aqueous solutions, when the hydrocarbon chain lining the interior pore wall increases in length. The rate and selectivity of transport across these membranes is related to the partition coefficient (Kp) and the diffusion coefficient (D) of the permeating species. By conducting experiments as a function of initial particle concentration, we find that KpD increases with increasing particle size, is greater in alkylsilane--modified pores, and larger in hexane solution than water. The impact of the alkylsilane terminus (--CH3, --Br, --NH2, --COOH) on permeation in water is also examined. In water, the highest KpD is observed when the membranes are modified with carboxylic acid terminated silanes and lowest with amine terminated silanes as a result of electrostatic effects during translocation. Finally, the manipulation of magnetic nanoparticles for the controlled formation of linked nanoparticle assemblies between microfluidic channels by the application of an external

Stephens, Jason R.

229

Nanoparticles  

NASA Astrophysics Data System (ADS)

MnFe2O4 nanoparticles of various particle sizes were prepared by co-precipitation, in which different hydroxide concentrations were employed to control particle growth. X-ray diffraction and scanning electron microscopy were used to investigate the nanoparticle structure and morphology (shape and size). The particle size increased with increasing hydroxide concentration. The magnetization and coercivity field were measured by vibrating sample magnetometry. Changes in magnetic behavior were observed in the magnetic hysteresis loop curves of nanoparticles with increasing hydroxide concentration. In the absence of hydroxide, nanoparticles exhibited paramagnetic behavior. Increasing the hydroxide concentration caused a gradual conversion to ferrimagnetic behavior. An increased Néel temperature was observed with increasing hydroxide concentration, and the saturation magnetization exhibited a sharp decrease. Nonuniform hysteresis was observed in the magnetization curve for the sample prepared from hydroxide and ammonium.

Vaez-Zadeh, Mehdi; Mohammadi, Ali

2014-07-01

230

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

231

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

232

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

233

Pauli Spin Blockade and the Ultrasmall Magnetic Field Effect  

NASA Astrophysics Data System (ADS)

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.

Danon, Jeroen; Wang, Xuhui; Manchon, Aurélien

2013-08-01

234

Capturing Ultrasmall EMT Zeolite from Template-Free Systems  

NASA Astrophysics Data System (ADS)

Small differences between the lattice energies of different zeolites suggest that kinetic factors are of major importance in controlling zeolite nucleation. Thus, it is critical to control the nucleation kinetics in order to obtain a desired microporous material. Here, we demonstrate how careful investigation of the very early stages of zeolite crystallization in colloidal systems can provide access to important nanoscale zeolite phases while avoiding the use of expensive organic templates. We report the effective synthesis of ultrasmall (6- to 15-nanometer) crystals of the large-pore zeolite EMT from template-free colloidal precursors at low temperature (30°C) and very high yield.

Ng, Eng-Poh; Chateigner, Daniel; Bein, Thomas; Valtchev, Valentin; Mintova, Svetlana

2012-01-01

235

Ultrasmall hollow gold-silver nanoshells with extinctions strongly red-shifted to the near-infrared.  

PubMed

Hollow gold-silver nanoshells having systematically varying sizes between 40 and 100 nm were prepared. These particles consist of a hollow spherical silver shell surrounded by a thin gold layer. By varying the volume of the gold stock solution added to suspensions of small silver-core templates, we tailored the hollow gold-silver nanoshells to possess strong tunable optical extinctions that range from the visible to the near-IR spectral regions, with extinctions routinely centered at ?950 nm. The size and morphology of these core/shell nanoparticles were characterized by dynamic light scattering (DLS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Separately, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used for measuring their elemental composition; UV-vis spectroscopy was used to evaluate their optical properties. Given their relatively small size compared to other nanoparticles that absorb strongly at near IR wavelengths, these easy-to-synthesize particles should find use in applications that require ultrasmall nanoparticles with extinctions comfortably beyond visible wavelengths (e.g., medicinal therapies, diagnostic imaging, nanofluidics, and display technologies). PMID:21761855

Vongsavat, Varadee; Vittur, Brandon M; Bryan, William W; Kim, Jun-Hyun; Lee, T Randall

2011-09-01

236

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

237

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

238

Gold Nanoparticles for Neural Prosthetics Devices  

PubMed Central

Treatments of neurological diseases and the realization of brain-computer interfaces require ultrasmall electrodes which are “invisible” to resident immune cells. Functional electrodes smaller than 50?m are impossible to produce with traditional materials due to high interfacial impedance at the characteristic frequency of neural activity and insufficient charge storage capacity. The problem can be resolved by using gold nanoparticle nanocomposites. Careful comparison indicates that layer-by-layer assembled films from Au NPs provide more than threefold improvement in interfacial impedance and one order of magnitude increase in charge storage capacity. Prototypes of microelectrodes could be made using traditional photolithography. Integration of unique nanocomposite materials with microfabrication techniques opens the door for practical realization of the ultrasmall implantable electrodes. Further improvement of electrical properties is expected when using special shapes of gold nanoparticles. PMID:22734673

Zhang, Huanan; Shih, Jimmy; Zhu, Jian; Kotov, Nicholas A.

2012-01-01

239

Synthesis of binary polyelectrolyte\\/inorganic composite capsules of micron size  

Microsoft Academic Search

Different approaches for the synthesis of binary polyelectrolyte\\/inorganic layered composite capsules of micron size are described. As the polyelectrolyte part of the composite, a poly(styrene sulfonate)\\/poly(allylamine hydrochloride) complex was taken; the inorganic component was composed of magnetic nanoparticles (Fe 3O 4, CoFe 2O 4, MnFe 2O 4, ZnFe 2O 4), insulator nanoparticles (rare-earth fluorides) or metal nanoparticles (Ag). An inner

Dmitry G. Shchukin; Gleb B. Sukhorukov

2003-01-01

240

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

241

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

242

Synthesis of high-coercivity cobalt ferrite particles using water-in-oil microemulsions  

Microsoft Academic Search

Magnetic nanoparticles of cobalt ferrite (CoFe2O4) have been synthesized using water-in-oil microemulsions consisting of water, cetyl trimethyl ammonium bromide (surfactant), n-butanol (cosurfactant), and n-octane (oil). Precursor hydroxides were precipitated in the aqueous cores of water-in-oil microemulsions and these were then separated and calcined to give the magnetic oxide. X-ray diffraction confirmed the formation of phase pure cobalt ferrite. These nanoparticles

V. Pillai; D. O. Shah

1996-01-01

243

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

244

²?¹Tl?-labelled Prussian blue nanoparticles as contrast agents for SPECT scintigraphy.  

PubMed

Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive (201)Tl(+) to obtain new nanoprobes as radiotracers for 201-thallium-based imaging. PMID:25283238

Perrier, M; Busson, M; Massasso, G; Long, J; Boudousq, V; Pouget, J-P; Peyrottes, S; Perigaud, Ch; Porredon-Guarch, C; de Lapuente, J; Borras, M; Larionova, J; Guari, Y

2014-11-21

245

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

246

Ultrasmall superparamagnetic iron oxide (USPIO)-based liposomes as magnetic resonance imaging probes  

PubMed Central

Background Magnetic liposomes (MLs) are phospholipid vesicles that encapsulate magnetic and/or paramagnetic nanoparticles. They are applied as contrast agents for magnetic resonance imaging (MRI). MLs have an advantage over free magnetic nanocores, in that various functional groups can be attached to the surface of liposomes for ligand-specific targeting. We have synthesized PEG-coated sterically-stabilized magnetic liposomes (sMLs) containing ultrasmall superparamagnetic iron oxides (USPIOs) with the aim of generating stable liposomal carriers equipped with a high payload of USPIOs for enhanced MRI contrast. Methods Regarding iron oxide nanoparticles, we have applied two different commercially available surface-coated USPIOs; sMLs synthesized and loaded with USPIOs were compared in terms of magnetization and colloidal stability. The average diameter size, morphology, phospholipid membrane fluidity, and the iron content of the sMLs were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence polarization, and absorption spectroscopy, respectively. A colorimetric assay using potassium thiocyanate (KSCN) was performed to evaluate the encapsulation efficiency (EE%) to express the amount of iron enclosed into a liposome. Subsequently, MRI measurements were carried out in vitro in agarose gel phantoms to evaluate the signal enhancement on T1- and T2-weighted sequences of sMLs. To monitor the biodistribution and the clearance of the particles over time in vivo, sMLs were injected in wild type mice. Results DLS revealed a mean particle diameter of sMLs in the range between 100 and 200 nm, as confirmed by TEM. An effective iron oxide loading was achieved just for one type of USPIO, with an EE% between 74% and 92%, depending on the initial Fe concentration (being higher for lower amounts of Fe). MRI measurements demonstrated the applicability of these nanostructures as MRI probes. Conclusion Our results show that the development of sMLs is strictly dependent on the physicochemical characteristics of the nanocores. Once established, sMLs can be further modified to enable noninvasive targeted molecular imaging. PMID:22661890

Frascione, Daniela; Diwoky, Clemens; Almer, Gunter; Opriessnig, Peter; Vonach, Caroline; Gradauer, Kerstin; Leitinger, Gerd; Mangge, Harald; Stollberger, Rudolf; Prassl, Ruth

2012-01-01

247

nanoparticles  

NASA Astrophysics Data System (ADS)

In this work, we present the role of vanadium ions (V+5 and V+3), oxygen vacancies (VO), and interstitial zinc (Zni) to the contribution of specific magnetization for a mixture of ZnO-V2O5 nanoparticles (NPs). Samples were obtained by mechanical milling of dry powders and ethanol-assisted milling for 1 h with a fixed atomic ratio V/Zn?=?5% at. For comparison, pure ZnO samples were also prepared. All samples exhibit a room temperature magnetization ranging from 1.18?×?10-3 to 3.5?×?10-3 emu/gr. Pure ZnO powders (1.34?×?10-3 emu/gr) milled with ethanol exhibit slight increase in magnetization attributed to formation of Zni, while dry milled ZnO powders exhibit a decrease of magnetization due to a reduction of VO concentration. For the ZnO-V2O5 system, dry milled and thermally treated samples under reducing atmosphere exhibit a large paramagnetic component associated to the formation of V2O3 and secondary phases containing V+3 ions; at the same time, an increase of VO is observed with an abrupt fall of magnetization to ??~?0.7?×?10-3 emu/gr due to segregation of V oxides and formation of secondary phases. As mechanical milling is an aggressive synthesis method, high disorder is induced at the surface of the ZnO NPs, including VO and Zni depending on the chemical environment. Thermal treatment restores partially structural order at the surface of the NPs, thus reducing the amount of Zni at the same time that V2O5 NPs segregate reducing the direct contact with the surface of ZnO NPs. Additional samples were milled for longer time up to 24 h to study the effect of milling on the magnetization; 1-h milled samples have the highest magnetizations. Structural characterization was carried out using X-ray diffraction and transmission electron microscopy. Identification of VO and Zni was carried out with Raman spectra, and energy-dispersive X-ray spectroscopy was used to verify that V did not diffuse into ZnO NPs as well to quantify O/Zn ratios.

Olive-Méndez, Sion F.; Santillán-Rodríguez, Carlos R.; González-Valenzuela, Ricardo A.; Espinosa-Magaña, Francisco; Matutes-Aquino, José A.

2014-04-01

248

Enzymatic- and temperature-sensitive controlled release of ultrasmall superparamagnetic iron oxides (USPIOs)  

PubMed Central

Background Drug and contrast agent delivery systems that achieve controlled release in the presence of enzymatic activity are becoming increasingly important, as enzymatic activity is a hallmark of a wide array of diseases, including cancer and atherosclerosis. Here, we have synthesized clusters of ultrasmall superparamagnetic iron oxides (USPIOs) that sense enzymatic activity for applications in magnetic resonance imaging (MRI). To achieve this goal, we utilize amphiphilic poly(propylene sulfide)-bl-poly(ethylene glycol) (PPS-b-PEG) copolymers, which are known to have excellent properties for smart delivery of drug and siRNA. Results Monodisperse PPS polymers were synthesized by anionic ring opening polymerization of propylene sulfide, and were sequentially reacted with commercially available heterobifunctional PEG reagents and then ssDNA sequences to fashion biofunctional PPS-bl-PEG copolymers. They were then combined with hydrophobic 12 nm USPIO cores in the thin-film hydration method to produce ssDNA-displaying USPIO micelles. Micelle populations displaying complementary ssDNA sequences were mixed to induce crosslinking of the USPIO micelles. By design, these crosslinking sequences contained an EcoRV cleavage site. Treatment of the clusters with EcoRV results in a loss of R2 negative contrast in the system. Further, the USPIO clusters demonstrate temperature sensitivity as evidenced by their reversible dispersion at ~75°C and re-clustering following return to room temperature. Conclusions This work demonstrates proof of concept of an enzymatically-actuatable and thermoresponsive system for dynamic biosensing applications. The platform exhibits controlled release of nanoparticles leading to changes in magnetic relaxation, enabling detection of enzymatic activity. Further, the presented functionalization scheme extends the scope of potential applications for PPS-b-PEG. Combined with previous findings using this polymer platform that demonstrate controlled drug release in oxidative environments, smart theranostic applications combining drug delivery with imaging of platform localization are within reach. The modular design of these USPIO nanoclusters enables future development of platforms for imaging and drug delivery targeted towards proteolytic activity in tumors and in advanced atherosclerotic plaques. PMID:21352596

2011-01-01

249

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

250

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

251

The ultrasmall green alga Ostreococcus unveils a unique regulation of the Calvin cycle  

E-print Network

The ultrasmall green alga Ostreococcus unveils a unique regulation of the Calvin cycle Steven: nuclear encoded GapA: cyanobacterial (plastid) ancestor transition from green algae to land plants Origin:1109-1118, (2006)) Ostreococcus tauri is a unicellular green alga, belonging to the Prasinophyceae. With a size

Gent, Universiteit

252

Submicrometer diameter micropillar cavities with high quality factor and ultrasmall mode volume  

E-print Network

Submicrometer diameter micropillar cavities with high quality factor and ultrasmall mode volume 105451); published March 17, 2009 We theoretically demonstrate high quality factor Q 3 106 micropillar.3948, 270.0270, 140.7260. Micropillar optical cavities, typically used in low- threshold vertical

Loncar, Marko

253

Ultra-Small Reader/Writer with Multiple Contactless Interfaces on a Flexible Circuit Board  

NASA Astrophysics Data System (ADS)

In order to incorporate the reader/writers (RWs) into mobile electronic devices, miniaturization and flexibility are required. To meet these requirements, we fabricate an ultra-small RW with multiple contactless interfaces by mounting main unit circuits inside the antenna coil and using flexible multi-layer circuit board.

Yamamoto, Hideaki; Ikeda, Minoru; Hosoda, Yasuhiro

254

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

255

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

256

Fabrication, structure, and magnetic properties of electrospun carbon/cobalt ferrite (C/CoFe2O4) composite nanofibers  

NASA Astrophysics Data System (ADS)

This work reports the fabrication and properties of carbon/cobalt ferrite (C/CoFe2O4) composite nanofibers by using electrospinning technique followed by carbonization process under mixed air and argon atmosphere. The as-prepared samples were characterized by means of thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray absorption spectroscopy, and vibrating sample magnetometry. It was found that the structure of CoFe2O4 was cubic spinel with the variation of crystallite size between 22 and 54 nm depending on the magnetic source content. X-ray absorption near-edge spectra at the Fe (7,112 eV) and Co (7,709 eV) absorption K-edge were used to confirm the Fe3+ and Co2+ oxidation states of CoFe2O4 nanoparticles. The X-ray absorption fine structure analysis indicated that CoFe2O4 nanoparticles had a structure analogous to bulk-inverted spinel structure. All composite nanofibers exhibited ferromagnetic behavior related to the distribution of cations over tetrahedral and octahedral sites, whereas diamagnetic behavior was observed in pure carbon nanofibers. The magnetization was clearly enhanced with respect to the increase of magnetic source content, whereas the coercivity and the squareness ( M r/ M s) were dependent of crystallite size.

Nilmoung, S.; Kidkhunthod, P.; Pinitsoontorn, S.; Rujirawat, S.; Yimnirun, R.; Maensiri, S.

2015-04-01

257

Fabrication, structure, and magnetic properties of electrospun carbon/cobalt ferrite (C/CoFe2O4) composite nanofibers  

NASA Astrophysics Data System (ADS)

This work reports the fabrication and properties of carbon/cobalt ferrite (C/CoFe2O4) composite nanofibers by using electrospinning technique followed by carbonization process under mixed air and argon atmosphere. The as-prepared samples were characterized by means of thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray absorption spectroscopy, and vibrating sample magnetometry. It was found that the structure of CoFe2O4 was cubic spinel with the variation of crystallite size between 22 and 54 nm depending on the magnetic source content. X-ray absorption near-edge spectra at the Fe (7,112 eV) and Co (7,709 eV) absorption K-edge were used to confirm the Fe3+ and Co2+ oxidation states of CoFe2O4 nanoparticles. The X-ray absorption fine structure analysis indicated that CoFe2O4 nanoparticles had a structure analogous to bulk-inverted spinel structure. All composite nanofibers exhibited ferromagnetic behavior related to the distribution of cations over tetrahedral and octahedral sites, whereas diamagnetic behavior was observed in pure carbon nanofibers. The magnetization was clearly enhanced with respect to the increase of magnetic source content, whereas the coercivity and the squareness (M r/M s) were dependent of crystallite size.

Nilmoung, S.; Kidkhunthod, P.; Pinitsoontorn, S.; Rujirawat, S.; Yimnirun, R.; Maensiri, S.

2015-02-01

258

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

NASA Astrophysics Data System (ADS)

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 ?-hydroxy-n-valerate, o- and p-HPA, PAG, nicotinate and hippurate accompanied by decreases in the levels of urinary ?-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 (?-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.

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

2010-10-01

259

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

260

Magnetic Resonance Imaging of Atherosclerotic Plaque With Ultrasmall Superparamagnetic Particles of Iron Oxide in Hyperlipidemic Rabbits  

Microsoft Academic Search

Background—Based on the observation that ultrasmall superparamagnetic particles of iron oxides (USPIOs) are phagocytosed by cells of the mononuclear phagocytic system, the purpose of this study was to evaluate their use as a marker of atherosclerosis-associated inflammatory changes in the vessel wall before luminal narrowing is present. Methods and Results—Experiments were conducted on 6 heritable hyperlipidemic and 3 New Zealand

Stefan G. Ruehm; Claire Corot; Peter Vogt; Stefan Kolb; Jörg F. Debatin

2009-01-01

261

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

262

Manipulating superconducting fluctuations in ultrasmall loops and quasi one-dimensional wires of Al  

NASA Astrophysics Data System (ADS)

Superconducting fluctuations and the control of these fluctuations have been a problem of long-standing interest, with recent impetus provided by its relevance to the pursuit of very high temperature superconductivity through the engineering of global phase coherence. In quasi one-dimensional superconductors, fluctuations due to thermal or quantum processes lead to phase slips, and the appearance of a finite electrical resistance. We found that the critical current in mesoscopic quasi one-dimensional wires of Al is influenced by the bulk measurement electrodes, and in fact increases with magnetic field at low fields, suggesting that the phase slips are suppressed by the loss of superconductivity in the bulk electrodes. Manipulation of superconducting fluctuations is also possible in ultrasmall loops, where the strength of the fluctuations is controlled by the loop's size in comparison with ? and the enclosed flux. For ultrasmall loops with a circumference ˜ ??(0), de Gennes predicted more than three decades ago that superconductivity could be completely destroyed near half-integer-flux quanta even to zero temperature. Furthermore, the resulting destructive regime, likely dominated by quantum fluctuations at low temperatures, was predicted to be suppressed with the addition of a superconducting side branch. We observed this Little-Parks-de Gennes effect in ultrasmall Al loops prepared by e-beam lithography and we found that the addition of a superconducting side branch restores the lost phase coherence. We will present our most recent data and discuss the implications of our experimental observations.

Staley, Neal

2012-02-01

263

201Tl+-labelled Prussian blue nanoparticles as contrast agents for SPECT scintigraphy  

NASA Astrophysics Data System (ADS)

Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive 201Tl+ to obtain new nanoprobes as radiotracers for 201-thallium-based imaging.Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive 201Tl+ to obtain new nanoprobes as radiotracers for 201-thallium-based imaging. Electronic supplementary information (ESI) available: Experimental details and procedures, toxicological data, PXRD, TEM images, kinetics and adsorption isotherms, SPECT/CT images, Tl+ captation profiles. See DOI: 10.1039/c4nr03044c

Perrier, M.; Busson, M.; Massasso, G.; Long, J.; Boudousq, V.; Pouget, J.-P.; Peyrottes, S.; Perigaud, Ch.; Porredon-Guarch, C.; de Lapuente, J.; Borras, M.; Larionova, J.; Guari, Y.

2014-10-01

264

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

265

Magnetoconductance response in unipolar and bipolar organic diodes at ultrasmall fields.  

PubMed

We measured magnetoconductance (MC) response in a number of unipolar and bipolar organic diodes based on ?-conjugated polymers and small molecules at fields |B|<100??mT and various bias voltages and temperatures. Similar to magneto-electroluminescence, the MC(B) response in bipolar diodes shows a sign reversal at ultrasmall |B|<1-2??mT due to interplay of hyperfine and Zeeman interactions in opposite-charge polaron pairs. Surprisingly, similar MC(B) response was also measured in unipolar devices, indicating the existence of like-charge polaron pairs, however, with a clear difference between the hyperfine interaction constants of electron polaron and hole polaron. PMID:21230995

Nguyen, T D; Gautam, B R; Ehrenfreund, E; Vardeny, Z V

2010-10-15

266

White light-emitting diodes based on ultrasmall CdSe nanocrystal electroluminescence.  

PubMed

We report white light-emitting diodes fabricated with ultrasmall CdSe nanocrystals, which demonstrate electroluminescence from a size of nanocrystals (<2 nm) previously thought to be unattainable. These LEDs have excellent color characteristics, defined by their pure white CIE color coordinates (0.333, 0.333), correlated color temperatures of 5461-6007 K, and color rendering indexes as high as 96.6. The effect of high voltage on the trap states responsible for the white emission is also described. PMID:20063863

Schreuder, Michael A; Xiao, Kai; Ivanov, Ilia N; Weiss, Sharon M; Rosenthal, Sandra J

2010-02-10

267

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

268

Ultrasmall peptides self-assemble into diverse nanostructures: morphological evaluation and potential implications.  

PubMed

In this study, we perform a morphological evaluation of the diverse nanostructures formed by varying concentration and amino acid sequence of a unique class of ultrasmall self-assembling peptides. We modified these peptides by replacing the aliphatic amino acid at the C-aliphatic terminus with different aromatic amino acids. We tracked the effect of introducing aromatic residues on self-assembly and morphology of resulting nanostructures. Whereas aliphatic peptides formed long, helical fibers that entangle into meshes and entrap >99.9% water, the modified peptides contrastingly formed short, straight fibers with a flat morphology. No helical fibers were observed for the modified peptides. For the aliphatic peptides at low concentrations, different supramolecular assemblies such as hollow nanospheres and membrane blebs were found. Since the ultrasmall peptides are made of simple, aliphatic amino acids, considered to have existed in the primordial soup, study of these supramolecular assemblies could be relevant to understanding chemical evolution leading to the origin of life on Earth. In particular, we propose a variety of potential applications in bioengineering and nanotechnology for the diverse self-assembled nanostructures. PMID:22016623

Lakshmanan, Anupama; Hauser, Charlotte A E

2011-01-01

269

Accelerator mass spectrometry of ultra-small samples with applications in the biosciences  

NASA Astrophysics Data System (ADS)

An overview is presented covering the biological accelerator mass spectrometry activities at Uppsala University. The research utilizes the Uppsala University Tandem laboratory facilities, including a 5 MV Pelletron tandem accelerator and two stable isotope ratio mass spectrometers. In addition, a dedicated sample preparation laboratory for biological samples with natural activity is in use, as well as another laboratory specifically for 14C-labeled samples. A variety of ongoing projects are described and presented. Examples are: (1) Ultra-small sample AMS. We routinely analyze samples with masses in the 5-10 ?g C range. Data is presented regarding the sample preparation method, (2) bomb peak biological dating of ultra-small samples. A long term project is presented where purified and cell-specific DNA from various part of the human body including the heart and the brain are analyzed with the aim of extracting regeneration rate of the various human cells, (3) biological dating of various human biopsies, including atherosclerosis related plaques is presented. The average built up time of the surgically removed human carotid plaques have been measured and correlated to various data including the level of insulin in the human blood, and (4) In addition to standard microdosing type measurements using small pharmaceutical drugs, pre-clinical pharmacokinetic data from a macromolecular drug candidate are discussed.

Salehpour, Mehran; Håkansson, Karl; Possnert, Göran

2013-01-01

270

Morphological characterization of carbon-nanofiber-reinforced epoxy nanocomposites using ultra-small angle scattering  

SciTech Connect

Studies of the properties of nanocomposites reinforced with vapor-grown carbon nanofibers (VGCFs) can be found throughout the literature. Electrical, mechanical, viscoelastic, and rheological properties are just a few of the characteristics that have been well discussed. Although these properties depend on morphology, morphological characterization is rare. Due to its 2-dimensional nature, microscopy is of limited value when analyzing network morphologies. This work will show how the characterization of the three-dimensional geometry and network formation of VGCFs can be determined using ultra-small angle scattering techniques. Ultra-small angle x-ray and neutron scattering (USAXS and USANS) were used to characterize the morphology of carbon nanofibers suspended in epoxy. Using a simplified tube model, we estimate the dimensions of suspended fibers. The assumption of tubular fibers accounts for the increased surface area observed with USAXS that is not accounted for using a solid rod model. Furthermore, USANS was used to search for a structural signature associated with the electrical percolation threshold. USANS extends to longer dimensional scales than USAXS, which measures a smaller range of momentum transfer. To determine the electrical percolation threshold, AC impedance spectroscopy was employed to verify that an electrically conductive, percolated network forms at VGCNF loadings of 0.8% < CNF wt% < 1.2%. These values correlate with the USANS data, where a morphological transition is seen at {approx}1.2% loading.

Justice, R.S.; Anderson, D.P.; Brown, J.M.; Arlen, M.J.; Colleary, A.J.; Lafdi, K.; Schaefer, D.W. (UCIN); (AFRL)

2010-07-01

271

Post-detection analysis for grating-based ultra-small angle X-ray scattering.  

PubMed

Until recently, the hard X-ray, phase-sensitive imaging technique called grating interferometry was thought to provide information only in real space. However, by utilizing an alternative approach to data analysis we demonstrated that the angular resolved ultra-small angle X-ray scattering distribution can be retrieved from experimental data. Thus, reciprocal space information is accessible by grating interferometry in addition to real space. Naturally, the quality of the retrieved data strongly depends on the performance of the employed analysis procedure, which involves deconvolution of periodic and noisy data in this context. The aim of this article is to compare several deconvolution algorithms to retrieve the ultra-small angle X-ray scattering distribution in grating interferometry. We quantitatively compare the performance of three deconvolution procedures (i.e., Wiener, iterative Wiener and Lucy-Richardson) in case of realistically modeled, noisy and periodic input data. The simulations showed that the algorithm of Lucy-Richardson is the more reliable and more efficient as a function of the characteristics of the signals in the given context. The availability of a reliable data analysis procedure is essential for future developments in grating interferometry. PMID:23375790

Scattarella, F; Tangaro, S; Modregger, P; Stampanoni, M; De Caro, L; Bellotti, R

2013-09-01

272

Unique Regulation of the Calvin Cycle in the Ultrasmall Green Alga Ostreococcus Steven Robbens,1,2  

E-print Network

Unique Regulation of the Calvin Cycle in the Ultrasmall Green Alga Ostreococcus Steven Robbens,1 to be generally present in the Plantae (glaucophytes, red and green algae, and plants), up to now GapB was exclusively found in Streptophyta, including the enigmatic green alga Mesostigma viride. However, here we show

Gent, Universiteit

273

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

274

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

275

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

276

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

277

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

278

Facile synthesis of ultra-small PbSe nanorods for photovoltaic application  

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05707d

Han, Lu; Liu, Jie; Yu, Ningning; Liu, Zeke; Gu, Jinan; Lu, Jialing; Ma, Wanli

2015-01-01

279

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

280

Sugar and pH dual-responsive snap-top nanocarriers based on mesoporous silica-coated Fe3O4 magnetic nanoparticles for cargo delivery.  

PubMed

A facile strategy to prepare snap-top magnetic nanocarriers has been developed where ultrasmall superparamagnetic Fe3O4 nanoparticles were used as the core with mesoporous silica as the shell followed by the covalent installation of a layer of ?-cyclodextrins on the outer surfaces. The smart hybrid nanomaterials showed remarkable pH- and sugar-responsive cargo release property and low cytotoxicity as proved by an MTT assay with HEK293T cell lines. PMID:25670321

Qiu, Xi-Long; Li, Qing-Lan; Zhou, Yue; Jin, Xiao-Yu; Qi, Ai-Di; Yang, Ying-Wei

2015-02-24

281

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

282

Biofunctional polymer nanoparticles for intra-articular targeting and retention in cartilage  

NASA Astrophysics Data System (ADS)

The extracellular matrix of dense, avascular tissues presents a barrier to entry for polymer-based therapeutics, such as drugs encapsulated within polymeric particles. Here, we present an approach by which polymer nanoparticles, sufficiently small to enter the matrix of the targeted tissue, here articular cartilage, are further modified with a biomolecular ligand for matrix binding. This combination of ultrasmall size and biomolecular binding converts the matrix from a barrier into a reservoir, resisting rapid release of the nanoparticles and clearance from the tissue site. Phage display of a peptide library was used to discover appropriate targeting ligands by biopanning on denuded cartilage. The ligand WYRGRL was selected in 94 of 96 clones sequenced after five rounds of biopanning and was demonstrated to bind to collagen II ?1. Peptide-functionalized nanoparticles targeted articular cartilage up to 72-fold more than nanoparticles displaying a scrambled peptide sequence following intra-articular injection in the mouse.

Rothenfluh, Dominique A.; Bermudez, Harry; O'Neil, Conlin P.; Hubbell, Jeffrey A.

2008-03-01

283

Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe{sub 3}O{sub 4} nanoparticle rings  

SciTech Connect

This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe{sub 3}O{sub 4} nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25?nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

Takeno, Yumu [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Murakami, Yasukazu, E-mail: murakami@tagen.tohoku.ac.jp, E-mail: kannanmk@uw.edu; Shindo, Daisuke [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Center for Emergent Matter Science, RIKEN, Wako 351-0198 (Japan); Sato, Takeshi [Hitachi High-Technologies Corporation, 1040 Ichige, Hitachinaka-shi, Ibaraki 312-0033 (Japan); Tanigaki, Toshiaki [Center for Emergent Matter Science, RIKEN, Wako 351-0198 (Japan); Central Research Laboratory, Hitachi, Ltd., Hatoyama 350-0395 (Japan); Park, Hyun Soon [Center for Emergent Matter Science, RIKEN, Wako 351-0198 (Japan); Department of Materials Science and Engineering, Dong-A University, Busan 604-714, Republic of South Korea (Korea, Republic of); Ferguson, R. Matthew [LodeSpin Labs, P.O. Box 95632, Seattle, Washington 91845 (United States); Krishnan, Kannan M., E-mail: murakami@tagen.tohoku.ac.jp, E-mail: kannanmk@uw.edu [Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195-2120 (United States)

2014-11-03

284

Ultrafine Sulfur Nanoparticles in Conducting Polymer Shell as Cathode Materials for High Performance Lithium/Sulfur Batteries  

PubMed Central

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. PMID:23714786

Chen, Hongwei; Dong, Weiling; Ge, Jun; Wang, Changhong; Wu, Xiaodong; Lu, Wei; Chen, Liwei

2013-01-01

285

Detection and Isolation of Ultrasmall Microorganisms from a 120,000YearOld Greenland Glacier Ice Core  

Microsoft Academic Search

The abundant microbial population in a 3,043-m-deep Greenland glacier ice core was dominated by ultra- small 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 psychro- philes by filtering melted ice through filters with different pore sizes, inoculating anaerobic

Vanya I. Miteva; Jean E. Brenchley

2005-01-01

286

Ultrasmall Glutathione-Protected Gold Nanoclusters as Next Generation Radiotherapy Sensitizers with High Tumor Uptake and High Renal Clearance  

PubMed Central

Radiotherapy is often the most straightforward first line cancer treatment for solid tumors. While it is highly effective against tumors, there is also collateral damage to healthy proximal tissues especially with high doses. The use of radiosensitizers is an effective way to boost the killing efficacy of radiotherapy against the tumor while drastically limiting the received dose and reducing the possible damage to normal tissues. Here, we report the design and application of a good radiosensitizer by using ultrasmall Au29–43(SG)27–37 nanoclusters (<2?nm) with a naturally-occurring peptide (e.g., glutathione or GSH) as the protecting shell. The GSH-coated Au29–43(SG)27–37 nanoclusters can escape the RES absorption, leading to a good tumor uptake (~8.1% ID/g at 24?h post injection). As a result, the as-designed Au nanoclusters led to a strong enhancement for radiotherapy, as well as a negligible damage to normal tissues. After the treatment, the ultrasmall Au29–43(SG)27–37 nanoclusters can be efficiently cleared by the kidney, thereby avoiding potential long-term side-effects caused by the accumulation of gold atoms in the body. Our data suggest that the ultrasmall peptide-protected Au nanoclusters are a promising radiosensitizer for cancer radiotherapy. PMID:25727895

Zhang, Xiao-Dong; Luo, Zhentao; Chen, Jie; Song, Shasha; Yuan, Xun; Shen, Xiu; Wang, Hao; Sun, Yuanming; Gao, Kai; Zhang, Lianfeng; Fan, Saijun; Leong, David Tai; Guo, Meili; Xie, Jianping

2015-01-01

287

Ultrasmall Glutathione-Protected Gold Nanoclusters as Next Generation Radiotherapy Sensitizers with High Tumor Uptake and High Renal Clearance  

NASA Astrophysics Data System (ADS)

Radiotherapy is often the most straightforward first line cancer treatment for solid tumors. While it is highly effective against tumors, there is also collateral damage to healthy proximal tissues especially with high doses. The use of radiosensitizers is an effective way to boost the killing efficacy of radiotherapy against the tumor while drastically limiting the received dose and reducing the possible damage to normal tissues. Here, we report the design and application of a good radiosensitizer by using ultrasmall Au29-43(SG)27-37 nanoclusters (<2 nm) with a naturally-occurring peptide (e.g., glutathione or GSH) as the protecting shell. The GSH-coated Au29-43(SG)27-37 nanoclusters can escape the RES absorption, leading to a good tumor uptake (~8.1% ID/g at 24 h post injection). As a result, the as-designed Au nanoclusters led to a strong enhancement for radiotherapy, as well as a negligible damage to normal tissues. After the treatment, the ultrasmall Au29-43(SG)27-37 nanoclusters can be efficiently cleared by the kidney, thereby avoiding potential long-term side-effects caused by the accumulation of gold atoms in the body. Our data suggest that the ultrasmall peptide-protected Au nanoclusters are a promising radiosensitizer for cancer radiotherapy.

Zhang, Xiao-Dong; Luo, Zhentao; Chen, Jie; Song, Shasha; Yuan, Xun; Shen, Xiu; Wang, Hao; Sun, Yuanming; Gao, Kai; Zhang, Lianfeng; Fan, Saijun; Leong, David Tai; Guo, Meili; Xie, Jianping

2015-03-01

288

Ultrasmall glutathione-protected gold nanoclusters as next generation radiotherapy sensitizers with high tumor uptake and high renal clearance.  

PubMed

Radiotherapy is often the most straightforward first line cancer treatment for solid tumors. While it is highly effective against tumors, there is also collateral damage to healthy proximal tissues especially with high doses. The use of radiosensitizers is an effective way to boost the killing efficacy of radiotherapy against the tumor while drastically limiting the received dose and reducing the possible damage to normal tissues. Here, we report the design and application of a good radiosensitizer by using ultrasmall Au29-43(SG)27-37 nanoclusters (<2?nm) with a naturally-occurring peptide (e.g., glutathione or GSH) as the protecting shell. The GSH-coated Au29-43(SG)27-37 nanoclusters can escape the RES absorption, leading to a good tumor uptake (~8.1% ID/g at 24?h post injection). As a result, the as-designed Au nanoclusters led to a strong enhancement for radiotherapy, as well as a negligible damage to normal tissues. After the treatment, the ultrasmall Au29-43(SG)27-37 nanoclusters can be efficiently cleared by the kidney, thereby avoiding potential long-term side-effects caused by the accumulation of gold atoms in the body. Our data suggest that the ultrasmall peptide-protected Au nanoclusters are a promising radiosensitizer for cancer radiotherapy. PMID:25727895

Zhang, Xiao-Dong; Luo, Zhentao; Chen, Jie; Song, Shasha; Yuan, Xun; Shen, Xiu; Wang, Hao; Sun, Yuanming; Gao, Kai; Zhang, Lianfeng; Fan, Saijun; Leong, David Tai; Guo, Meili; Xie, Jianping

2015-01-01

289

Highly Sensitive Simultaneous Detection of Mercury and Copper Ions by Ultrasmall Fluorescent DNA-Ag Nanoclusters.  

PubMed

Fluorescent metal nanoclusters (NCs) have given rise to a new class of fluorescent nanomaterials for the detection of heavy metals. Here, we design a simple, rapid and highly sensitive sensing nanosystem for the detection of Hg(2+) and Cu(2+) based on fluorescence quenching of ultrasmall DNA-Ag NCs. The fluorescence intensity of DNA-Ag NCs was selectively quenched by Hg(2+) and Cu(2+), and the limit of detection (LOD) was found to be 5 nM and 10 nM, respectively. The technique was renewable employment by EDTA addition and successfully applied to detection of Hg(2+) and Cu(2+) in domestic water samples. The quantum yield (QY) of DNA-Ag NCs was significantly higher to ~30% compared to traditional water-soluble fluorescent metal NCs. The DNA-Ag NC detection system make it potentially suitable for detecting Hg(2+) and Cu(2+) and monitoring water quality in a wide range of samples regulated under the Environmental Protection Agency. PMID:24839391

Li, Shengliang; Cao, Weipeng; Kumar, Anil; Jin, Shubin; Zhao, Yuanyuan; Zhang, Chunqiu; Zou, Guozhang; Wang, Paul C; Li, Feng; Liang, Xing-Jie

2014-04-01

290

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

291

Reactive molecular dynamics simulations on SiO2-coated ultra-small Si-nanowires  

NASA Astrophysics Data System (ADS)

The application of core-shell Si-SiO2 nanowires as nanoelectronic devices strongly depends on their structure, which is difficult to tune precisely. In this work, we investigate the formation of the core-shell nanowires at the atomic scale, by reactive molecular dynamics simulations. The occurrence of two temperature-dependent oxidation mechanisms of ultra-small diameter Si-NWs is demonstrated. We found that control over the Si-core radius and the SiOx (x <= 2) oxide shell is possible by tuning the growth temperature and the initial Si-NW diameter. Two different structures were obtained, i.e., ultrathin SiO2 silica nanowires at high temperature and Si core|ultrathin SiO2 silica nanowires at low temperature. The transition temperature is found to linearly decrease with the nanowire curvature. Finally, the interfacial stress is found to be responsible for self-limiting oxidation, depending on both the initial Si-NW radius and the oxide growth temperature. These novel insights allow us to gain control over the exact morphology and structure of the wires, as is needed for their application in nanoelectronics.

Khalilov, Umedjon; Pourtois, Geoffrey; Bogaerts, Annemie; van Duin, Adri C. T.; Neyts, Erik C.

2012-12-01

292

Fabrication of Si Thermoelectric Nanomaterials Containing Ultrasmall Epitaxial Ge Nanodots with an Ultrahigh Density  

NASA Astrophysics Data System (ADS)

A Si-based nanomaterial is proposed for use as a thermoelectric material. Ultrasmall epitaxial Ge nanodots (NDs) with an ultrahigh density are introduced into Si films as phonon scatterers using an ultrathin SiO2 film technique. The nanomaterial has the stacked structure Si/Ge NDs/Si on Si substrates. Reflection high-energy electron diffraction reveals epitaxial growth of the Ge NDs and Si layers in all of the stacking stages. Sharp interfaces of the Ge NDs/Si in the stacked structures were observed by high-angle annular field scanning transmission electron microscopy. The Ge NDs were controlled in terms of their composition and strain: main parts of the NDs did not alloy with Si, and the elastic strain was relaxed. These features were confirmed by Raman scattering and x-ray diffraction measurements. The fabrication techniques used to make the simple Si-based stacked structure with strain-relaxed almost pure Ge NDs are useful to develop thermoelectric nanomaterials.

Yamasaka, Shuto; Nakamura, Yoshiaki; Ueda, Tomohiro; Takeuchi, Shotaro; Yamamoto, Yuta; Arai, Shigeo; Tanji, Takayoshi; Tanaka, Nobuo; Sakai, Akira

2015-03-01

293

The microstructure characterization of ultrasmall eutectic Bi-Sn solder bumps on Au\\/Cu\\/Ti and Au\\/Ni\\/Ti under-bump metallization  

Microsoft Academic Search

The microstructure of the ultrasmall eutectic Bi-Sn solder bumps on Au\\/Cu\\/Ti and Au\\/Ni\\/Ti under-bump metallizations (UBMs)\\u000a was investigated as a function of cooling rate. The ultrasmall eutectic Bi-Sn solder bump, about 50 ?m in diameter, was fabricated\\u000a by using the lift-off method and reflowed at various cooling rates using the rapid thermal annealing system. The microstructure\\u000a of the solder bump

Un-Byoung Kang; Young-Ho Kim

2004-01-01

294

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

295

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

296

A self-sensing piezoelectric microcantilever biosensor for detection of ultrasmall adsorbed masses: theory and experiments.  

PubMed

Detection of ultrasmall masses such as proteins and pathogens has been made possible as a result of advancements in nanotechnology. Development of label-free and highly sensitive biosensors has enabled the transduction of molecular recognition into detectable physical quantities. Microcantilever (MC)-based systems have played a widespread role in developing such biosensors. One of the most important drawbacks of all of the available biosensors is that they all come at a very high cost. Moreover, there are certain limitations in the measurement equipments attached to the biosensors which are mostly optical measurement systems. A unique self-sensing detection technique is proposed in this paper in order to address most of the limitations of the current measurement systems. A self-sensing bridge is used to excite piezoelectric MC-based sensor functioning in dynamic mode, which simultaneously measures the system's response through the self-induced voltage generated in the piezoelectric material. As a result, the need for bulky, expensive read-out equipment is eliminated. A comprehensive mathematical model is presented for the proposed self-sensing detection platform using distributed-parameters system modeling. An adaptation strategy is then implemented in the second part in order to compensate for the time-variation of piezoelectric properties which dynamically improves the behavior of the system. Finally, results are reported from an extensive experimental investigation carried out to prove the capability of the proposed platform. Experimental results verified the proposed mathematical modeling presented in the first part of the study with accuracy of 97.48%. Implementing the adaptation strategy increased the accuracy to 99.82%. These results proved the measurement capability of the proposed self-sensing strategy. It enables development of a cost-effective, sensitive and miniaturized mass sensing platform. PMID:23666133

Faegh, Samira; Jalili, Nader; Sridhar, Srinivas

2013-01-01

297

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

298

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

299

Ultrasmall Glutathione-Protected Gold Nanoclusters as Next Generation Radiotherapy Sensitizers with High Tumor Uptake and High Renal Clearance  

E-print Network

Radiotherapy is often the most straightforward first line cancer treatment for solid tumors. While it is highly effective against tumors, there is also collateral damage to healthy proximal tissues especially with high doses. The use of radiosensitizers is an effective way to boost the killing efficacy of radiotherapy against the tumor while drastically limiting the received dose and reducing the possible damage to normal tissues. Here, we report the design and application of a good radiosensitizer by using ultrasmall gold nanoclusters with a naturally occurring peptide (e.g., glutathione or GSH) as the protecting shell. The GSH coated gold nanoclusters can escape the RES absorption, leading to a good tumor uptake (8.1% ID/g at 24 h post injection). As a result, the as-designed Au nanoclusters led to a strong enhancement for radiotherapy, as well as a negligible damage to normal tissues. After the treatment, the ultrasmall gold nanoclusters can be efficiently cleared by the kidney, thereby avoiding potential ...

Zhang, Xiao-Dong; Chen, Jie; Song, Shasha; Yuan, Xun; Shen, Xiu; Wang, Hao; Sun, Yuanming; Gao, Kai; Zhang, Lianfeng; Fan, Saijun; Leong, David Tai; Guo, Meili; Xie, Jianping

2015-01-01

300

Ultrasmall particles for Gd-MRI and (68) Ga-PET dual imaging.  

PubMed

Nanoparticles made of a polysiloxane matrix and surrounded by 1,4,7,10-tetraazacyclododecane-1-glutaric anhydride-4,7,10-triacetic acid (DOTAGA)[Gd(3+) ] and 2,2'-(7-(1-carboxy-4-((2,5-dioxopyrrolidin-1-yl)oxy)-4-oxobutyl)-1,4,7-triazonane-1,4-diyl)diacetic acid) NODAGA[(68) Ga(3+) ] have been synthesized for positron emission tomography/magnetic resonance (PET/MRI) dual imaging. Characterizations were carried out in order to determine the nature of the ligands available for radiolabelling and to quantify them. High radiolabelling purity (>95%) after (68) Ga labelling was obtained. The MR and PET images demonstrate the possibility of using the nanoparticles for a combined PET/MR imaging scanner. The images show fast renal elimination of the nanoparticles after intravenous injection.Copyright © 2014 John Wiley & Sons, Ltd. PMID:25483609

Truillet, Charles; Bouziotis, Penelope; Tsoukalas, Charalambos; Brugière, Jérémy; Martini, Matteo; Sancey, Lucie; Brichart, Thomas; Denat, Franck; Boschetti, Frédéric; Darbost, Ulrich; Bonnamour, Isabelle; Stellas, Dimitris; Anagnostopoulos, Constantinos D; Koutoulidis, Vassilis; Moulopoulos, Lia A; Perriat, Pascal; Lux, François; Tillement, Olivier

2014-12-01

301

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

302

Highly bright multicolor tunable ultrasmall ?-Na(Y,Gd)F4:Ce,Tb,Eu/?-NaYF4 core/shell nanocrystals  

NASA Astrophysics Data System (ADS)

Herein, we report highly bright multicolor-emitting ?-Na(Y,Gd)F4:Ce,Tb,Eu/?-NaYF4 nanoparticles (NPs) with precise color tunability. First, highly bright sub-20 nm ?-Na(Y,Gd)F4:Ce,Tb,Eu NPs were synthesized via a heating-up method. By controlling the ratio of Eu3+ to Tb3+, we generated green, yellow-green, greenish yellow, yellow, orange, reddish orange, and red emissions from the NP solutions via energy transfer of Ce3+ --> Gd3+ --> Tb3+ (green) and Ce3+ --> Gd3+ --> Tb3+ --> Eu3+ (red) ions under ultraviolet light illumination (254 nm). Because of Ce3+ and Gd3+ sensitization, Tb3+ ions exhibited strong green emission. The decay time of Tb3+ emission decreased from 4.0 to 1.4 ms as the Eu3+ concentration was increased, suggesting that energy was transferred from Tb3+ to Eu3+. As a result, Eu3+ emission peaks were generated and the emission color was transformed from green to red. Monodisperse sub-6 nm ?-Na(Y,Gd)F4:Ce,Tb,Eu NPs were synthesized through a simple reduction of the reaction temperature. Although fine color tunability was retained, their brightness was considerably decreased owing to an increase in the surface-to-volume ratio. The formation of a ?-NaYF4 shell on top of the sub-6 nm NP core to produce ?-Na(Y,Gd)F4:Ce,Tb,Eu/?-NaYF4 significantly increased the emission intensity, while maintaining the sub-10 nm sizes (8.7-9.5 nm). Quantum yields of the ultrasmall NPs increased from 1.1-6.9% for the core NPs to 6.7-44.4% for the core/shell NPs. Moreover, highly transparent core/shell NP-polydimethylsiloxane (PDMS) composites featuring a variety of colors, excellent color tunability, and high brightness were also prepared.Herein, we report highly bright multicolor-emitting ?-Na(Y,Gd)F4:Ce,Tb,Eu/?-NaYF4 nanoparticles (NPs) with precise color tunability. First, highly bright sub-20 nm ?-Na(Y,Gd)F4:Ce,Tb,Eu NPs were synthesized via a heating-up method. By controlling the ratio of Eu3+ to Tb3+, we generated green, yellow-green, greenish yellow, yellow, orange, reddish orange, and red emissions from the NP solutions via energy transfer of Ce3+ --> Gd3+ --> Tb3+ (green) and Ce3+ --> Gd3+ --> Tb3+ --> Eu3+ (red) ions under ultraviolet light illumination (254 nm). Because of Ce3+ and Gd3+ sensitization, Tb3+ ions exhibited strong green emission. The decay time of Tb3+ emission decreased from 4.0 to 1.4 ms as the Eu3+ concentration was increased, suggesting that energy was transferred from Tb3+ to Eu3+. As a result, Eu3+ emission peaks were generated and the emission color was transformed from green to red. Monodisperse sub-6 nm ?-Na(Y,Gd)F4:Ce,Tb,Eu NPs were synthesized through a simple reduction of the reaction temperature. Although fine color tunability was retained, their brightness was considerably decreased owing to an increase in the surface-to-volume ratio. The formation of a ?-NaYF4 shell on top of the sub-6 nm NP core to produce ?-Na(Y,Gd)F4:Ce,Tb,Eu/?-NaYF4 significantly increased the emission intensity, while maintaining the sub-10 nm sizes (8.7-9.5 nm). Quantum yields of the ultrasmall NPs increased from 1.1-6.9% for the core NPs to 6.7-44.4% for the core/shell NPs. Moreover, highly transparent core/shell NP-polydimethylsiloxane (PDMS) composites featuring a variety of colors, excellent color tunability, and high brightness were also prepared. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02591h

Kim, Su Yeon; Woo, Kyoungja; Lim, Kipil; Lee, Kwangyeol; Jang, Ho Seong

2013-09-01

303

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

304

Uracil-functionalized ultra-small (n, 0) boron nitride nanotubes (n = 3-6): Computational studies  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) calculations were performed to investigate properties of uracil-functionalized ultra-small (n, 0; n = 3-6) boron nitride nanotubes (BNNTs). The constructed structures through B-C (BC model) or N-C (NC model) bonds to the sidewall of BNNTs were optimized and their molecular and atomic scale properties were then evaluated. The mentioned properties are linking bond lengths, dipole moments, energy gaps, binding energies, and quadrupole coupling constants. The results indicated that the properties are different for the n = 3-6 nanotubes in both BC and NC models. The effects of functionalization on the original properties of BNNTs were many more significant in the NC model than the BC model. For each model, the effects of atomic scale properties of the counterparts were significant for those atoms close to the functionalization regions.

Mirzaei, Mahmoud

2013-05-01

305

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

306

Silver Nanoparticles  

NASA Astrophysics Data System (ADS)

The bactericidal effect of silver nanoparticles obtained by a novel electrochemical method on Escherichia coli, Staphylococcus aureus, Aspergillus niger and Penicillium phoeniceum cultures has been studied. The tests conducted have demonstrated that synthesized silver nanoparticles — when added to water paints or cotton fabrics — show a pronounced antibacterial/antifungal effect. It was shown that smaller silver nanoparticles have a greater antibacterial/antifungal efficacy. The paper also provides a review of scientific literature with regard to recent developments in the field of toxicity of silver nanoparticles and its effect on environment and human health.

Khaydarov, R. R.; Khaydarov, R. A.; Estrin, Y.; Evgrafova, S.; Scheper, T.; Endres, C.; Cho, S. Y.

307

Liposomal nanoreactors for the synthesis of monodisperse palladium nanoparticles using glycerol.  

PubMed

The synthesis of highly stable ultrasmall monodisperse populations of palladium nanoparticles in the range of 1-3 nm in size was achieved via polyol reduction within 1,2-dioleoyl-sn-glycero-3-phosphor-rac-(1-glycerol) liposomal nanoreactors exploiting glycerol as both reducing and stabilizing agent. The liposome-based green method was compared with synthesis in solution, and the reducing agent concentration and the lipidic composition of the liposomal nanoreactors were demonstrated to have a strong effect on the final size and homogeneity of the palladium nanoparticles. Glycerol molecules acting as capping agent demonstrated the ability to stabilize the palladium nanoparticles over a long period of time, maintaining their homogeneity in size and shape. The obtained palladium nanoparticles were characterized using transmission electron microscopy, selected area electron diffraction, Fourier transform infrared and Raman spectroscopies, X-ray diffraction, and dynamic light scattering to determine their morphology, size, charge, surface chemistry, and crystal structure. The catalytic activity of the palladium nanoparticles was also tested for a reduction reaction. PMID:24246054

Clergeaud, Gael; Genç, Rükan; Ortiz, Mayreli; O'Sullivan, Ciara K

2013-12-10

308

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

309

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

310

Simulation of Ultra-Small MOSFETs Using a 2-D Quantum-Corrected Drift-Diffusion Model  

NASA Technical Reports Server (NTRS)

The continued down-scaling of electronic devices, in particular the commercially dominant MOSFET, will force a fundamental change in the process of new electronics technology development in the next five to ten years. The cost of developing new technology generations is soaring along with the price of new fabrication facilities, even as competitive pressure intensifies to bring this new technology to market faster than ever before. To reduce cost and time to market, device simulation must become a more fundamental, indeed dominant, part of the technology development cycle. In order to produce these benefits, simulation accuracy must improve markedly. At the same time, device physics will become more complex, with the rapid increase in various small-geometry and quantum effects. This work describes both an approach to device simulator development and a physical model which advance the effort to meet the tremendous electronic device simulation challenge described above. The device simulation approach is to specify the physical model at a high level to a general-purpose (but highly efficient) partial differential equation solver (in this case PROPHET, developed by Lucent Technologies), which then simulates the model in 1-D, 2-D, or 3-D for a specified device and test regime. This approach allows for the rapid investigation of a wide range of device models and effects, which is certainly essential for device simulation to catch up with, and then stay ahead of, electronic device technology of the present and future. The physical device model used in this work is the density-gradient (DG) quantum correction to the drift-diffusion model [Ancona, Phys. Rev. B 35(5), 7959 (1987)]. This model adds tunneling and quantum smoothing of carrier density profiles to the drift-diffusion model. We used the DG model in 1-D and 2-D (for the first time) to simulate both bipolar and unipolar devices. Simulations of heavily-doped, short-base diodes indicated that the DG quantum corrections do not have a large effect on the IN characteristics of electronic devices without heteroj unction s. On the other hand, ultra-small MOSFETs certainly exhibit important quantum effects that the DG model will include: quantum repulsion of the inversion and gate charges from the oxide interfaces, and quantum tunneling through thin gate oxides. We present initial results of 2-D DG simulations of ultra-small MOSFETs. Subtle but important issues involving the specification of the model, boundary conditions, and interface constraints for DG simulation of MOSFETs will also be illuminated.

Biegal, Bryan A.; Rafferty, Connor S.; Yu, Zhiping; Ancona, Mario G.; Dutton, Robert W.; Saini, Subhash (Technical Monitor)

1998-01-01

311

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

312

Thermal decomposition of [Co(en)3][Fe(CN)6]? 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation  

PubMed Central

Background The Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored. In this paper, the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ?? 2H2O (1a) is elucidated, including the topotactic dehydration, valence and spins exchange mechanisms suggestion and the formation of a mixture of CoFe2O4-Co3O4 (3:1) as final products of thermal degradation. Results The course of thermal decomposition of 1a in air atmosphere up to 600°C was monitored by TG/DSC techniques, 57Fe Mössbauer and IR spectroscopy. As first, the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ?? 1/2H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-ray diffraction analysis. The consequent thermal decomposition proceeded in further four stages including intermediates varying in valence and spin states of both transition metal ions in their structures, i.e. [FeII(en)2(?-NC)CoIII(CN)4], FeIII(NH2CH2CH3)2(?-NC)2CoII(CN)3] and FeIII[CoII(CN)5], which were suggested mainly from 57Fe Mössbauer, IR spectral and elemental analyses data. Thermal decomposition was completed at 400°C when superparamagnetic phases of CoFe2O4 and Co3O4 in the molar ratio of 3:1 were formed. During further temperature increase (450 and 600°C), the ongoing crystallization process gave a new ferromagnetic phase attributed to the CoFe2O4-Co3O4 nanocomposite particles. Their formation was confirmed by XRD and TEM analyses. In-field (5 K / 5 T) Mössbauer spectrum revealed canting of Fe(III) spin in almost fully inverse spinel structure of CoFe2O4. Conclusions It has been found that the thermal decomposition of [Co(en)3][Fe(CN)6] ?? 2H2O in air atmosphere is a gradual multiple process accompanied by the formation of intermediates with different composition, stereochemistry, oxidation as well as spin states of both the central transition metals. The decomposition is finished above 400°C and the ongoing heating to 600°C results in the formation of CoFe2O4-Co3O4 nanocomposite particles as the final decomposition product. PMID:23391378

2013-01-01

313

On the feasibility of visualizing ultrasmall gold labels in biological specimens by STEM tomography.  

PubMed

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

2007-09-01

314

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

315

Polymeric nanoparticles  

PubMed Central

Nanocarriers with various compositions and biological properties have been extensively applied for in vitro/in vivo drug and gene delivery. The family of nanocarriers includes polymeric nanoparticles, lipid-based carriers (liposomes/micelles), dendrimers, carbon nanotubes, and gold nanoparticles (nanoshells/nanocages). Among different delivery systems, polymeric carriers have several properties such as: easy to synthesize, inexpensive, biocompatible, biodegradable, non-immunogenic, non-toxic, and water soluble. In addition, cationic polymers seem to produce more stable complexes led to a more protection during cellular trafficking than cationic lipids. Nanoparticles often show significant adjuvant effects in vaccine delivery since they may be easily taken up by antigen presenting cells (APCs). Natural polymers such as polysaccharides and synthetic polymers have demonstrated great potential to form vaccine nanoparticles. The development of new adjuvants or delivery systems for DNA and protein immunization is an expanding research field. This review describes polymeric carriers especially PLGA, chitosan, and PEI as vaccine delivery systems. PMID:24128651

Bolhassani, Azam; Javanzad, Shabnam; Saleh, Tayebeh; Hashemi, Mehrdad; Aghasadeghi, Mohammad Reza; Sadat, Seyed Mehdi

2014-01-01

316

Precision Nanoparticles  

ScienceCinema

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

2010-01-08

317

Cerebral Blood Volume MRI with Intravascular Superparamagentic Iron Oxide Nanoparticles  

PubMed Central

Cerebral blood volume (CBV) is a crucial physiological indicator of tissue viability and vascular reactivity. Thus, non-invasive CBV mapping has been of great interest. For this, ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) including monocrystalline iron oxide nanoparticles (MION) can be used as long half-life, intravascular susceptibility agents of CBV MRI measurements. Also, CBV-weighted fMRI with USPIO provides enhanced sensitivity, reduced large vessel contribution, and improved spatial specificity compared to conventional blood oxygenation-level dependent (BOLD) fMRI, and measures a single physiological parameter that is easily interpretable. We review physiochemical and magnetic properties as well as pharmacokinetics of USPIO in brief. We then extensively discuss quantifications of baseline CBV, vessel size index, and functional CBV change. We also provide reviews of dose-dependent sensitivity, vascular filter function, specificity, characteristics, and impulse response function of CBV fMRI. Examples of CBV fMRI specificity at the laminar and columnar resolution are provided. Finally, we briefly review application of CBV measurements to functional and pharmacological studies in animals. Overall, the use of USPIO can determine baseline CBV and its changes induced by functional activity and pharmacological interventions. PMID:23208650

Kim, Seong-Gi; Harel, Noam; Jin, Tao; Kim, Tae; Lee, Phil; Zhao, Fuqiang

2013-01-01

318

Superparamagnetic Nanoparticles  

Microsoft Academic Search

\\u000a Nanoscaled magnetic materials are great candidates for fundamental and applied research. 0D, 1D and 2D magnetic nanostructures\\u000a have been extensively studied previously. One of the unique phenomena that only exists in nanoscaled magnetic structure (below\\u000a a certain critical size) is superparamagnetism. In this chapter, various chemical synthesis methods to obtain superparamagnetic\\u000a nanoparticles are compared. Strategies to prevent agglomeration of nanoparticles

Boon Hoong Ong; Nisha Kumari Devaraj

319

DNA Base Pair Resolution Measurements Using Resonance Energy Transfer Efficiency in Lanthanide Doped Nanoparticles  

PubMed Central

Lanthanide-doped nanoparticles are of considerable interest for biodetection and bioimaging techniques thanks to their unique chemical and optical properties. As a sensitive luminescence material, they can be used as (bio) probes in Förster Resonance Energy Transfer (FRET) where trivalent lanthanide ions (La3+) act as energy donors. In this paper we present an efficient method to transfer ultrasmall (ca. 8 nm) NaYF4 nanoparticles dispersed in organic solvent to an aqueous solution via oxidation of the oleic acid ligand. Nanoparticles were then functionalized with single strand DNA oligomers (ssDNA) by inducing covalent bonds between surface carboxylic groups and a 5’ amine modified-ssDNA. Hybridization with the 5’ fluorophore (Cy5) modified complementary ssDNA strand demonstrated the specificity of binding and allowed the fine control over the distance between Eu3+ ions doped nanoparticle and the fluorophore by varying the number of the dsDNA base pairs. First, our results confirmed nonradiative resonance energy transfer and demonstrate the dependence of its efficiency on the distance between the donor (Eu3+) and the acceptor (Cy5) with sensitivity at a nanometre scale. PMID:25748446

Delplanque, Aleksandra; Wawrzynczyk, Dominika; Jaworski, Pawel; Matczyszyn, Katarzyna; Pawlik, Krzysztof; Buckle, Malcolm; Nyk, Marcin; Nogues, Claude; Samoc, Marek

2015-01-01

320

A Self-Sensing Piezoelectric MicroCantilever Biosensor for Detection of Ultrasmall Adsorbed Masses: Theory and Experiments  

PubMed Central

Detection of ultrasmall masses such as proteins and pathogens has been made possible as a result of advancements in nanotechnology. Development of label-free and highly sensitive biosensors has enabled the transduction of molecular recognition into detectable physical quantities. Microcantilever (MC)-based systems have played a widespread role in developing such biosensors. One of the most important drawbacks of all of the available biosensors is that they all come at a very high cost. Moreover, there are certain limitations in the measurement equipments attached to the biosensors which are mostly optical measurement systems. A unique self-sensing detection technique is proposed in this paper in order to address most of the limitations of the current measurement systems. A self-sensing bridge is used to excite piezoelectric MC-based sensor functioning in dynamic mode, which simultaneously measures the system's response through the self-induced voltage generated in the piezoelectric material. As a result, the need for bulky, expensive read-out equipment is eliminated. A comprehensive mathematical model is presented for the proposed self-sensing detection platform using distributed-parameters system modeling. An adaptation strategy is then implemented in the second part in order to compensate for the time-variation of piezoelectric properties which dynamically improves the behavior of the system. Finally, results are reported from an extensive experimental investigation carried out to prove the capability of the proposed platform. Experimental results verified the proposed mathematical modeling presented in the first part of the study with accuracy of 97.48%. Implementing the adaptation strategy increased the accuracy to 99.82%. These results proved the measurement capability of the proposed self-sensing strategy. It enables development of a cost-effective, sensitive and miniaturized mass sensing platform. PMID:23666133

Faegh, Samira; Jalili, Nader; Sridhar, Srinivas

2013-01-01

321

Polymer nanocomposites exhibiting magnetically tunable microwave properties  

NASA Astrophysics Data System (ADS)

Polymer nanocomposites (PNCs) have been synthesized using Rogers polymer and CoFe2O4 nanoparticles (CFO NPs). X-ray diffraction (XRD) confirms the inverse spinel crystal structure of CFO NPs and transmission electron microscopy (TEM) images show the uniform dispersion of nanoparticles (10 nm ± 1) into the polymer matrix. Magnetic measurements indicate superparamagnetic response near room temperature for all PNCs. A blocking temperature TB ~ 298 K was observed and does not vary for different loading fractions of CFO NPs for the PNCs. The saturation magnetization (Ms) was found to be 11 emu g - 1 for 30 wt% CFO, increasing to 32 emu g - 1 for the 80 wt% CFO loaded PNC. A large value of coercivity (Hc = 19 kOe) is also observed at 10 K and is not affected by varying CFO loading. Microwave measurements show significant absorption in the 80 wt% CFO loading PNC and the quality factor shows a strong enhancement with applied magnetic field.

Stojak, K.; Pal, S.; Srikanth, H.; Morales, C.; Dewdney, J.; Weller, T.; Wang, J.

2011-04-01

322

CdTe quantum dots induce activation of human platelets: implications for nanoparticle hemocompatibility  

PubMed Central

New nanomaterials intended for systemic administration have raised concerns regarding their biocompatibility and hemocompatibility. Quantum dots (QD) nanoparticles have been used for diagnostics, and recent work suggests their use for in vivo molecular and cellular imaging. However, the hemocompatibility of QDs and their constituent components has not been fully elucidated. In the present study, comprehensive investigation of QD–platelet interactions is presented. These interactions were shown using transmission electron microscopy. The effects of QDs on platelet function were investigated using light aggregometry, quartz crystal microbalance with dissipation, flow cytometry, and gelatin zymography. Platelet morphology was also analyzed by phase-contrast, immunofluorescence, atomic-force and transmission electron microscopy. We show that the QDs bind to platelet plasma membrane with the resultant upregulation of glycoprotein IIb/IIIa and P-selectin receptors, and release of matrix metalloproteinase-2. These findings unravel for the first time the mechanism of functional response of platelets to ultrasmall QDs in vitro.

Samuel, Stephen P; Santos-Martinez, Maria J; Medina, Carlos; Jain, Namrata; Radomski, Marek W; Prina-Mello, Adriele; Volkov, Yuri

2015-01-01

323

Nanostructured materials for multifunctional applications under NSF-CREST research at Norfolk State University  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles of CoFe2O4 have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles of varying size was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. The anomalous magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe2O4 nanoparticles were synthesized under applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments, which produce Co ions and vacancies disorder. We performed the fabrication of condensed and mesoporous silica coated CoFe2O4 magnetic nanocomposites. The CoFe2O4 magnetic nanoparticles were encapsulated with well-defined silica layer. The mesopores in the shell were fabricated as a consequence of removal of organic group of the precursor through annealing. The NiO nanoparticles were loaded into the mesoporous silica. The mesoporous silica coated magnetic nanostructure loaded with NiO as a final product may have potential use in the field of biomedical applications. Growth mechanism of ZnO nanorod arrays on ZnO seed layer investigated by electric and Kelvin probe force microscopy. Both electric and Kelvin force probe microscopy was used to investigate the surface potentials on the ZnO seed layer, which shows a remarkable dependence on the annealing temperature. The optimum temperature for the growth of nanorod arrays normal to the surface was found to be at 600 °C, which is in the range of right surface potentials and energy measured between 500 °C and 700 °C. We demonstrated from both EFM and Kelvin force probe microscopy studies that surface potential controls the growth of ZnO nanorods. This study will provide important understanding of growth of other nanostructures. ZnO nanolayers were also grown by atomic layer deposition techniques. These nanolayers of ZnO demonstrate remarkable optical and electrical properties. These nanolayers were patterned by the Electron Beam Lithography (EBL) technique. A major goal of nanotechnology is to couple the self-assembly of molecular nanostructures with conventional lithography, using either or both bottom-up and top-down fabrication methods, that would enable us to register individual molecular nanostructures onto the functional devices. However, combining the nanofabrication technique with high resolution Electron Beam Lithography, we can achieve 3D bimolecular or/and DNA origami that will be able to identify nucleic acid sequences, antigen targets, and other molecules, as for a perfect nano-biosensor. We have explored some of the nanopatterning using EBL in order to fabricate biomolecule sensing on a single chip with sub nm pitch. The applications are not limited for the bioactivity, but for enhancing immunoreactions, cell culture dishes, and tissue engineering applications.

Pradhan, A. K.; Mundle, R.; Zhang, K.; Holloway, T.; Amponsah, O.; Biswal, D.; Konda, R.; White, C.; Dondapati, H.; Santiago, K.; Birdsong, T.; Arslan, M.; Peeples, B.; Shaw, D.; Smak, J.; Samataray, C.; Bahoura, M.

2012-04-01

324

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

325

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

326

Silver confined within zeolite EMT nanoparticles: preparation and antibacterial properties  

NASA Astrophysics Data System (ADS)

The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag+-EMT) and reduced silver (Ag0-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps.The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag+-EMT) and reduced silver (Ag0-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps. Electronic supplementary information (ESI) available: Zeta potential data of Ag-EMT suspensions, pore-size distributions and antibacterial data for Ag-EMT 2 h samples. See DOI: 10.1039/c4nr03169e

Dong, B.; Belkhair, S.; Zaarour, M.; Fisher, L.; Verran, J.; Tosheva, L.; Retoux, R.; Gilson, J.-P.; Mintova, S.

2014-08-01

327

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

328

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

329

Multimodal silica nanoparticles are effective cancer-targeted probes in a model of human melanoma  

PubMed Central

Nanoparticle-based materials, such as drug delivery vehicles and diagnostic probes, currently under evaluation in oncology clinical trials are largely not tumor selective. To be clinically successful, the next generation of nanoparticle agents should be tumor selective, nontoxic, and exhibit favorable targeting and clearance profiles. Developing probes meeting these criteria is challenging, requiring comprehensive in vivo evaluations. Here, we describe our full characterization of an approximately 7-nm diameter multimodal silica nanoparticle, exhibiting what we believe to be a unique combination of structural, optical, and biological properties. This ultrasmall cancer-selective silica particle was recently approved for a first-in-human clinical trial. Optimized for efficient renal clearance, it concurrently achieved specific tumor targeting. Dye-encapsulating particles, surface functionalized with cyclic arginine–glycine–aspartic acid peptide ligands and radioiodine, exhibited high-affinity/avidity binding, favorable tumor-to-blood residence time ratios, and enhanced tumor-selective accumulation in ?v?3 integrin–expressing melanoma xenografts in mice. Further, the sensitive, real-time detection and imaging of lymphatic drainage patterns, particle clearance rates, nodal metastases, and differential tumor burden in a large-animal model of melanoma highlighted the distinct potential advantage of this multimodal platform for staging metastatic disease in the clinical setting. PMID:21670497

Benezra, Miriam; Penate-Medina, Oula; Zanzonico, Pat B.; Schaer, David; Ow, Hooisweng; Burns, Andrew; DeStanchina, Elisa; Longo, Valerie; Herz, Erik; Iyer, Srikant; Wolchok, Jedd; Larson, Steven M.; Wiesner, Ulrich; Bradbury, Michelle S.

2011-01-01

330

Water-soluble superparamagnetic magnetite nanoparticles with biocompatible coating for enhanced magnetic resonance imaging.  

PubMed

Ultrasmall superparamagnetic Fe(3)O(4) nanoparticles (USIRONs) were synthesized by a novel, easily scalable chemical reduction of colloidal iron hydroxide under hydrothermal conditions. The average crystallite size (5.1 ± 0.5 nm) and good crystallinity of the samples were supported by HR-TEM analysis and the saturation magnetization value (47 emu g(-1)). Vitamin C, used as a chemical reducing agent, also served as a capping agent in the oxidized form (dehydroascorbic acid, DHAA) to impart nanoparticles with exceptional solubility and stability in water, PBS buffer, and cell culture medium. Detailed physicochemical analysis of the USIRON suspensions provided insight into the magnetic ordering phenomena within the colloid, arising from the formation of uniform clusters displaying a hydrodynamic size of 41 nm. Phantom experiments on the contrast agent (clinical 3 T MRI scanner) revealed an enhanced r(2)/r(1) ratio of 36.4 (r(1)= 5 s(-1) mM(-1) and r(2)= 182 s(-1) mM(-1)) when compared to the clinically approved agents. The potential of the DHAA-Fe(3)O(4) nanoparticles as negative contrast agents for MRI with optimal hydrodynamic size for extended blood circulation times was confirmed by strong contrast observed in T(2)- and T(2)*-weighted images. The cell tests performed with primary human immune-competent cells confirmed the excellent biocompatibility of USIRONs. PMID:21790153

Xiao, Lisong; Li, Jiangtian; Brougham, Dermot F; Fox, Eoin K; Feliu, Neus; Bushmelev, Alexey; Schmidt, Annette; Mertens, Natascha; Kiessling, Fabian; Valldor, Martin; Fadeel, Bengt; Mathur, Sanjay

2011-08-23

331

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

332

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

333

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

334

Shrunk to femtolitre: Tuning high-throughput monodisperse water-in-oil droplet arrays for ultra-small micro-reactors  

NASA Astrophysics Data System (ADS)

We report a facile, low-cost, and high-yielding microfluidic technology for in situ generating and arraying water-in-oil droplets by shrinking them to the order of femtolitres (fLs) as scalable batch micro-reactors. Instead of generating ultra-small droplets by the direct atomization, which requires dedicate control and high energy input, we shrink droplets to stable smaller ones by utilizing the controlled water diffusion in oil. This "shrunk to fL" method is combined with a three-dimensional microwell design to create high-density addressable droplet arrays. As the result, scalable, high-throughput, and well-aligned W/O arrays with excellent long-term stability and predicable droplet sizes have been achieved.

Wu, Tianzhun; Hirata, Katsuki; Suzuki, Hiroaki; Xiang, Rong; Tang, Zikang; Yomo, Tetsuya

2012-08-01

335

Conjugation of Iron Oxide Nanoparticles with RGD-Modified Dendrimers for Targeted Tumor MR Imaging.  

PubMed

This article reports a new approach for the synthesis of ultrasmall iron oxide nanoparticles (NPs) conjugated with Arg-Gly-Asp (RGD)-modified dendrimers (G5.NHAc-RGD-Fe3O4 NPs) as a platform for targeted magnetic resonance (MR) imaging of C6 glioma cells. Ultrasmall Fe3O4 NPs synthesized via a solvothermal route were conjugated with RGD peptide-modified generation-5 poly(amidoamine) dendrimers (G5.NH2-RGD). The final G5.NHAc-RGD-Fe3O4 NPs were formed following the acetylation of the remaining dendrimer terminal amines. The as-prepared multifunctional Fe3O4 NPs were characterized using various techniques. The results of a cell viability assay, cell morphological observation, and hemolysis assay indicated that the G5.NHAc-RGD-Fe3O4 NPs exhibit excellent cytocompatibility and hemocompatibility over the studied concentration range. In addition, RGD conjugated onto the Fe3O4 NPs allows for the efficient targeting of the particles to C6 cells that overexpress ?v?3 receptors, which was confirmed via in vitro cell MR imaging and cellular uptake. Finally, the G5.NHAc-RGD-Fe3O4 NPs were used in the targeted MR imaging of C6 glioma cells in mice. The results obtained from the current study indicate that the developed G5.NHAc-RGD-Fe3O4 NPs offer significant potential for use as contrast agents in the targeted MR imaging of different types of tumors. PMID:25695661

Yang, Jia; Luo, Yu; Xu, Yanhong; Li, Jingchao; Zhang, Zaixian; Wang, Han; Shen, Mingwu; Shi, Xiangyang; Zhang, Guixiang

2015-03-11

336

Comparison of Ultrasmall Particles of Iron Oxide (USPIO)Enhanced T2Weighted, Conventional T2- Weighted, and GadoliniumEnhanced T1Weighted MR Images in Rats with Experimental Autoimmune Encephalomyelitis  

Microsoft Academic Search

BACKGROUND AND PURPOSE:Ultrasmall particles of iron oxide (USPIO) constitute a con- trast agent that accumulates in cells from the mononuclear phagocytic system. In the CNS they may accumulate in phagocytic cells such as macrophages. The goal of this study was to compare USPIO-enhanced MR images with conventional T2-weighted images and gadolinium-enhanced T1-weighted images in a model of experimental autoimmune encephalomyelitis

Vincent Dousset; Lucrecia Ballarino; Christophe Delalande; Monique Coussemacq; Paul Canioni; Klaus G. Petry

337

Ultrathin InAs nanowire growth by spontaneous Au nanoparticle spreading on indium-rich surfaces.  

PubMed

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. PMID:25383665

Jung, Kyooho; Mohseni, Parsian K; Li, Xiuling

2014-12-21

338

CCMR: Bimetallic Nanoparticle Catalysis  

NSDL National Science Digital Library

Bimetallic nanoparticles are of great interest in scientific research due to their large surface to volume ratios and surface restructuring that may occur during catalysis. Our goals were to synthesize different bimetallic nanoparticles and test their catalytic abilities for use in future experiments. The nanoparticles we concentrated on were Au/Ag alloy, Au/Cu alloy, and Au/Pd core-shell.

Chong, Hahn

2010-08-15

339

Oil-enriched, ultra-small nanostructured lipid carriers (usNLC): a novel delivery system based on flip-flop structure.  

PubMed

For the development of ultra-small NLC (usNLC) the determination of the required HLB (hydrophilic lipophilic balance) was found to be a suitable method, i.e., usNLC with a size below 50 nm were obtained by this method. Loading with 5% (w/w) coenzyme Q10 (Q10) led to usNLC with a size of about 85 nm. In comparison to classical NLC with a size of 230 nm and a nanoemulsion with similar size, the Q10 loaded usNLC show a higher release, a higher antioxidant capacity, and a better skin penetration for Q10. The reason for this is a flip-flop core-shell structure of the lipid matrix, i.e., the oil with dissolved active is surrounding the solid lipid based core. As the flip-flop structure was probably achieved by admixing high contents of liquid lipid, oil enriched usNLC might represent a novel and promising carrier system for the improved delivery of lipophilic actives. PMID:25455773

Keck, Cornelia M; Baisaeng, Nuttakorn; Durand, Philippe; Prost, Michel; Meinke, Martina C; Müller, Rainer H

2014-12-30

340

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

341

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

342

De-alloyed platinum nanoparticles  

DOEpatents

A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

Strasser, Peter (Houston, TX); Koh, Shirlaine (Houston, TX); Mani, Prasanna (Houston, TX); Ratndeep, Srivastava (Houston, TX)

2011-08-09

343

Nanoparticle mediated micromotor motion  

NASA Astrophysics Data System (ADS)

In this paper, we report the utilization of nanoparticles to mediate the motion of a polymer single crystal catalytic micromotor. Micromotors have been fabricated by directly self-assembling functional nanoparticles (platinum and iron oxide nanoparticles) onto one or both sides of two-dimensional polymer single crystals. We show that the moving velocity of these micromotors in fluids can be readily tuned by controlling the nanoparticles' surface wettability and catalytic activity. A 3 times velocity increase has been achieved for a hydrophobic micromotor as opposed to the hydrophilic ones. Furthermore, we demonstrate that the catalytic activity of platinum nanoparticles inside the micromotor can be enhanced by their synergetic interactions with iron oxide nanoparticles and an electric field. Both strategies lead to dramatically increased moving velocities, with the highest value reaching ~200 ?m s-1. By decreasing the nanoparticles' surface wettability and increasing their catalytic activity, a maximum of a ~10-fold increase in the moving speed of the nanoparticle based micromotor can be achieved. Our results demonstrate the advantages of using nanoparticles in micromotor systems.In this paper, we report the utilization of nanoparticles to mediate the motion of a polymer single crystal catalytic micromotor. Micromotors have been fabricated by directly self-assembling functional nanoparticles (platinum and iron oxide nanoparticles) onto one or both sides of two-dimensional polymer single crystals. We show that the moving velocity of these micromotors in fluids can be readily tuned by controlling the nanoparticles' surface wettability and catalytic activity. A 3 times velocity increase has been achieved for a hydrophobic micromotor as opposed to the hydrophilic ones. Furthermore, we demonstrate that the catalytic activity of platinum nanoparticles inside the micromotor can be enhanced by their synergetic interactions with iron oxide nanoparticles and an electric field. Both strategies lead to dramatically increased moving velocities, with the highest value reaching ~200 ?m s-1. By decreasing the nanoparticles' surface wettability and increasing their catalytic activity, a maximum of a ~10-fold increase in the moving speed of the nanoparticle based micromotor can be achieved. Our results demonstrate the advantages of using nanoparticles in micromotor systems. Electronic supplementary information (ESI) available: Fig. S1-S5 and Video S1-S3. See DOI: 10.1039/c4nr07558g

Liu, Mei; Liu, Limei; Gao, Wenlong; Su, Miaoda; Ge, Ya; Shi, Lili; Zhang, Hui; Dong, Bin; Li, Christopher Y.

2015-03-01

344

A nanoparticle in plasma  

SciTech Connect

Charge and energy fluxes onto a nanoparticle under conditions typical of laboratory plasmas are investigated theoretically. Here, by a nanoparticle is meant a grain the size of which is much smaller than both the electron Larmor radius and Debye length and the thermionic emission from which is not limited by the space charge. Under conditions at which thermionic emission plays an important role, the electric potential and temperature T{sub p} of a nanoparticle are determined by solving a self-consistent set of equations describing the balance of energy and charge fluxes onto the nanoparticle. It is shown that, when the degree of plasma ionization exceeds a critical level, the potential of the nanoparticle and the energy flux onto it increase with increasing nanoparticle temperature, so that, starting from a certain temperature, the nanoparticle potential becomes positive. The critical degree of ionization starting from which the potential of a nanoparticle is always positive is determined as a function of the plasma density and electron temperature. The nanoparticle temperature T{sub p} corresponding to the equilibrium state of a positively charged nanoparticle is found as a function of the electron density for different electron temperatures.

Martynenko, Yu. V.; Nagel', M. Yu.; Orlov, M. A. [Russian Research Centre Kurchatov Institute (Russian Federation)

2009-06-15

345

Nanoparticle ? -potentials.  

PubMed

For over half a century, alternating electric fields have been used to induce particle transport, furnishing the ?-potential of analytes with sizes ranging from a few nanometers to several micrometers. Concurrent advances in nanotechnology have provided new materials for catalysis, self-assembly, and biomedical applications, all of which benefit from a thorough understanding of particle surface charge. Therefore, the measurement of the ?-potential via electrophoretic light scattering (ELS) has become essential for nanoparticle (NP) research. However, the interpretation of NP electrophoretic mobility, especially that of ligand-coated NPs, can be a complex undertaking. Despite the inherent intricacy of these data, key concepts from colloidal science can help to distill valuable information from ELS. In this Account, we adopt PEGylated Au NPs as an illustrative example to explore extensions of the classical theories of Smoluchowski, Hückel, and Henry to more contemporary theories for ligand-coated NP systems such as those from Ohshima, and Hill, Saville, and Russel. First, we review the basic experimental considerations necessary to understand NP electrophoretic mobility, identifying when O'Brien and White's numerical solution of the standard electrokinetic model should be adopted over Henry's closed-form analytical approximation. Next, we explore recent developments in the theory of ligand-coated particle electrophoresis, and how one can furnish accurate and meaningful relationships between measured NP mobility, ?-potential, and surface charge. By identifying key ligand-coated NP parameters (e.g., coating thickness, permeability, molecular mass, and hydrodynamic segment size), we present a systematic method for quantitatively interpreting NP electrophoretic mobility. In addition to reviewing theoretical foundations, we describe our recent results that examine how the unique surface curvature of NPs alters and controls their properties. These data provide guidelines that can expedite the rational design of NPs for advanced uses, such as heterogeneous catalysis and in vivo drug delivery. As a practical demonstration of these concepts, we apply the ligand-coated theory to a recently developed noncovalent PEGylated Au NP drug-delivery system. Our analysis suggests that anion adsorption on the Au NP core may enhance the stability of these NP-drug conjugates in solution. In addition to providing useful nanochemistry insights, the information in this Account will be useful to biomedical and materials engineers, who use ELS and ?-potentials for understanding NP dynamics. PMID:22074988

Doane, Tennyson L; Chuang, Chi-Hung; Hill, Reghan J; Burda, Clemens

2012-03-20

346

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

347

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

348

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

349

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

350

Nanoparticle mediated micromotor motion.  

PubMed

In this paper, we report the utilization of nanoparticles to mediate the motion of a polymer single crystal catalytic micromotor. Micromotors have been fabricated by directly self-assembling functional nanoparticles (platinum and iron oxide nanoparticles) onto one or both sides of two-dimensional polymer single crystals. We show that the moving velocity of these micromotors in fluids can be readily tuned by controlling the nanoparticles' surface wettability and catalytic activity. A 3 times velocity increase has been achieved for a hydrophobic micromotor as opposed to the hydrophilic ones. Furthermore, we demonstrate that the catalytic activity of platinum nanoparticles inside the micromotor can be enhanced by their synergetic interactions with iron oxide nanoparticles and an electric field. Both strategies lead to dramatically increased moving velocities, with the highest value reaching ?200 ?m s(-1). By decreasing the nanoparticles' surface wettability and increasing their catalytic activity, a maximum of a ?10-fold increase in the moving speed of the nanoparticle based micromotor can be achieved. Our results demonstrate the advantages of using nanoparticles in micromotor systems. PMID:25689965

Liu, Mei; Liu, Limei; Gao, Wenlong; Su, Miaoda; Ge, Ya; Shi, Lili; Zhang, Hui; Dong, Bin; Li, Christopher Y

2015-03-01

351

Harnessing the extracellular bacterial production of nanoscale cobalt ferrite with exploitable magnetic properties.  

PubMed

Nanoscale ferrimagnetic particles have a diverse range of uses from directed cancer therapy and drug delivery systems to magnetic recording media and transducers. Such applications require the production of monodisperse nanoparticles with well-controlled size, composition, and magnetic properties. To fabricate these materials purely using synthetic methods is costly in both environmental and economical terms. However, metal-reducing microorganisms offer an untapped resource to produce these materials. Here, the Fe(III)-reducing bacterium Geobacter sulfurreducens is used to synthesize magnetic iron oxide nanoparticles. A combination of electron microscopy, soft X-ray spectroscopy, and magnetometry techniques was employed to show that this method of biosynthesis results in high yields of crystalline nanoparticles with a narrow size distribution and magnetic properties equal to the best chemically synthesized materials. In particular, it is demonstrated here that cobalt ferrite (CoFe(2)O(4)) nanoparticles with low temperature coercivity approaching 8 kOe and an effective anisotropy constant of ?10(6) erg cm(-3) can be manufactured through this biotechnological route. The dramatic enhancement in the magnetic properties of the nanoparticles by the introduction of high quantities of Co into the spinel structure represents a significant advance over previous biomineralization studies in this area using magnetotactic bacteria. The successful production of nanoparticulate ferrites achieved in this study at high yields could open up the way for the scaled-up industrial manufacture of nanoparticles using environmentally benign methodologies. PMID:19507866

Coker, Victoria S; Telling, Neil D; van der Laan, Gerrit; Pattrick, Richard A D; Pearce, Carolyn I; Arenholz, Elke; Tuna, Floriana; Winpenny, Richard E P; Lloyd, Jonathan R

2009-07-28

352

An experimental and theoretical study on the structure and photoactivity of XFe2O4 (X = Mn, Fe, Ni, Co, and Zn) structures  

NASA Astrophysics Data System (ADS)

XFe2O4 magnetic nanoparticles (X = Mn, Fe, Co, Ni, and Zn) were prepared by using two methods: coprecipitation and hydrothermal. The synthesized nanoparticles were compared according to the separation in an external magnetic field and finally, the hydrothermal method was specified as a better synthesis method. The magnetic nanoparticles were characterized by physico-chemical analysis methods such as Vibrating Sample Magnetometer (VSM), X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), nitrogen adsorption-adsorption isotherm and Transmission Electron Microscopy (TEM). Magnetic properties of synthesized nanoparticles were studied by ab-initio theoretical methods to confirm and compare with the experimental results. According to the VSM analysis, all of magnetic nanoparticles had good magnetization while CoFe2O4 nanoparticles showed the ferromagnetic behavior. The magnetic properties of XFe2O4 configurations were studied using Density Functional Theory ab-initio method. The theoretical results were consistent with experimental magnetizations in the absence of external field. Finally, the photocatalytic behavior of prepared samples was investigated in the presence of oxone as an accelerated agent for degradation of an azo dye.

Padervand, M.; Vossoughi, M.; Yousefi, H.; Salari, H.; Gholami, M. R.

2014-12-01

353

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

354

Transferring biomarker into molecular probe: melanin nanoparticle as a naturally active platform for multimodality imaging.  

PubMed

Developing multifunctional and easily prepared nanoplatforms with integrated different modalities is highly challenging for molecular imaging. Here, we report the successful transfer of an important molecular target, melanin, into a novel multimodality imaging nanoplatform. Melanin is abundantly expressed in melanotic melanomas and thus has been actively studied as a target for melanoma imaging. In our work, the multifunctional biopolymer nanoplatform based on ultrasmall (<10 nm) water-soluble melanin nanoparticle (MNP) was developed and showed unique photoacoustic property and natural binding ability with metal ions (for example, (64)Cu(2+), Fe(3+)). Therefore, MNP can serve not only as a photoacoustic contrast agent, but also as a nanoplatform for positron emission tomography (PET) and magnetic resonance imaging (MRI). Traditional passive nanoplatforms require complicated and time-consuming processes for prebuilding reporting moieties or chemical modifications using active groups to integrate different contrast properties into one entity. In comparison, utilizing functional biomarker melanin can greatly simplify the building process. We further conjugated ?v?3 integrins, cyclic c(RGDfC) peptide, to MNPs to allow for U87MG tumor accumulation due to its targeting property combined with the enhanced permeability and retention (EPR) effect. The multimodal properties of MNPs demonstrate the high potential of endogenous materials with multifunctions as nanoplatforms for molecular theranostics and clinical translation. PMID:25292385

Fan, Quli; Cheng, Kai; Hu, Xiang; Ma, Xiaowei; Zhang, Ruiping; Yang, Min; Lu, Xiaomei; Xing, Lei; Huang, Wei; Gambhir, Sanjiv Sam; Cheng, Zhen

2014-10-29

355

Nanoparticles in drinking water  

Microsoft Academic Search

Synthetic nanoparticles are increasingly being used in everyday products, but little is known about environmental releases of these materials. Our knowledge of how many natural nanoparticles occur in drinking water is also inadequate. An initial assessment is presented here. Drinking water is clear, and yet it contains millions of particles. Substances are described as particulate - as opposed to dissolved

Ralf Kaegi

356

Nanoparticle approaches against bacterial infections.  

PubMed

Despite the wide success of antibiotics, the treatment of bacterial infections still faces significant challenges, particularly the emergence of antibiotic resistance. As a result, nanoparticle drug delivery platforms including liposomes, polymeric nanoparticles, dendrimers, and various inorganic nanoparticles have been increasingly exploited to enhance the therapeutic effectiveness of existing antibiotics. This review focuses on areas where nanoparticle approaches hold significant potential to advance the treatment of bacterial infections. These areas include targeted antibiotic delivery, environmentally responsive antibiotic delivery, combinatorial antibiotic delivery, nanoparticle-enabled antibacterial vaccination, and nanoparticle-based bacterial detection. In each area we highlight the innovative antimicrobial nanoparticle platforms and review their progress made against bacterial infections. PMID:25044325

Gao, Weiwei; Thamphiwatana, Soracha; Angsantikul, Pavimol; Zhang, Liangfang

2014-01-01

357

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

358

Effect of Flip Angle on the Correlation Between Signal Intensity and Different Concentrations of Iron Oxide Nanoparticles Using T1-Weighted Turbo-FLASH Inversion Recovery Sequence  

PubMed Central

Background: Ultrasmall superparamagnetic iron oxide nanoparticles have been used as a blood pool contrast agent for magnetic resonance angiography and perfusion studies. Linear relationship between signal intensity (SI) and nanoparticle concentration is essential for perfusion measurement. Objectives: The aim of this study was to investigate the effect of different flip angles on maximum SI and the linear relationship between SI and different concentrations of iron oxide nanoparticles using T1-weighted Turbo-FLASH (fast low angle shot) inversion recovery sequence to find the optimum flip angle for perfusion measurement. Materials and Methods: This in vitro study was performed using carboxydextran coated iron oxide nanoparticles with 20 nm hydrodynamic size. Different concentrations of nanoparticles between 0 and 500 µmol Fe/L were prepared. MR imaging was performed using T1-weighted Turbo-FLASH inversion recovery sequence. Applied flip angles were 10-45º (interval of 5º). Then the maximum SI resulted by each concentration of nanoparticles was measured. Linear relationship between SI and nanoparticle concentration was evaluated regarding square correlations of 0.95 and 0.99. Coil non-uniformity was considered to obtain accurate SI of each image. Results: The maximum SI was obtained at the highest applied flip angle (45°). The linear relationship between SI and nanoparticle concentration was seen up to 112.21 and 98.83 ?mol Fe/L for the short (10°) and the long (45°) flip angles, respectively (R2 = 0.95). These values were reduced up to 48.54 and 42.73 ?mol Fe/L for these flip angles with R2 of 0.99. Conclusions: The maximum SI will be increased at higher flip angles with non-linear relationship between SI and nanoparticle concentration. The result shows that an increase in the flip angle leads to a decrease in the range of the linearity. The optimum flip angle which is suitable for perfusion measurement was obtained at 10º for our imaging parameters and sequence. The results of this study may be used in in vivo perfusion measurements. PMID:25901260

Gharehaghaji, Nahideh; Nazarpoor, Mahmood; Saharkhiz, Hodaiseh

2015-01-01

359

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

360

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

361

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

362

Nanoparticle Stained Glass  

NSDL National Science Digital Library

In this activity/demo, learners are introduced to the connection between medieval stained glass artisans and nanotechnology. Learners discover that the red and yellow colors in stained glass windows come from nanoparticles of gold and silver embedded in the glass. This activity/demo consists of two hands-on activities: making a collaborative stained glass window with pre-made nanoparticle solutions containing silver or gold and making a take-away card that contains a small piece of nanoparticle stained “glass."

2014-06-18

363

Gas Phase Nanoparticle Synthesis  

NASA Astrophysics Data System (ADS)

This book deals with gas-phase nanoparticle synthesis and is intended for researchers and research students in nanomaterials science and engineering, condensed matter physics and chemistry, and aerosol science. Gas-phase nanoparticle synthesis is instrumental to nanotechnology - a field in current focus that raises hopes for environmentally benign, resource-lean manufacturing. Nanoparticles can be produced by many physical, chemical, and even biological routes. Gas-phase synthesis is particularly interesting since one can achieve accurate manufacturing control and hence industrial viability.

Granqvist, Claes; Kish, Laszlo; Marlow, William

364

Shear thinning of nanoparticle suspensions  

NASA Astrophysics Data System (ADS)

Results of large scale nonequilibrium molecular dynamics 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. We present results for the shear rheology of spherical nanoparticles of diameter 10 times that of the solvent for a range of nanoparticle volume fractions. By varying the strength of the interactions between nanoparticles and with the solvent, this system can be used to model colloidal gels and glasses as well as hard spherelike nanoparticles. Effect of including the solvent explictly is demonstrated by comparing the pair correlation function of nanoparticles to that in an implicit solvent. The shear rheology for dumbbell nanoparticles made of two fused spheres is similar to that of single nanoparticle.

in 'T Veld, Pieter J.; Petersen, Matt K.; Grest, Gary S.

2009-02-01

365

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

366

Thermally Polymerized Rylene Nanoparticles  

E-print Network

Rylene dyes functionalized with varying numbers of phenyl trifluorovinyl ether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene ...

Andrew, Trisha Lionel

367

Theranostic Upconversion Nanoparticles (I)  

PubMed Central

This theme issue provides a comprehensive collection of original research articles on the creation of diverse types of theranostic upconversion nanoparticles, their fundamental interactions in biology, as well as their biophotonic applications in noninvasive diagnostics and therapy. PMID:23606916

Chen, Guanying; Han, Gang

2013-01-01

368

Magnetic nanoparticle temperature estimation.  

PubMed

The authors present a method of measuring the temperature of magnetic nanoparticles that can be adapted to provide in vivo temperature maps. Many of the minimally invasive therapies that promise to reduce health care costs and improve patient outcomes heat tissue to very specific temperatures to be effective. Measurements are required because physiological cooling, primarily blood flow, makes the temperature difficult to predict a priori. The ratio of the fifth and third harmonics of the magnetization generated by magnetic nanoparticles in a sinusoidal field is used to generate a calibration curve and to subsequently estimate the temperature. The calibration curve is obtained by varying the amplitude of the sinusoidal field. The temperature can then be estimated from any subsequent measurement of the ratio. The accuracy was 0.3 degree K between 20 and 50 degrees C using the current apparatus and half-second measurements. The method is independent of nanoparticle concentration and nanoparticle size distribution. PMID:19544801

Weaver, John B; Rauwerdink, Adam M; Hansen, Eric W

2009-05-01

369

Magnetic nanoparticle temperature estimation  

PubMed Central

The authors present a method of measuring the temperature of magnetic nanoparticles that can be adapted to provide in vivo temperature maps. Many of the minimally invasive therapies that promise to reduce health care costs and improve patient outcomes heat tissue to very specific temperatures to be effective. Measurements are required because physiological cooling, primarily blood flow, makes the temperature difficult to predict a priori. The ratio of the fifth and third harmonics of the magnetization generated by magnetic nanoparticles in a sinusoidal field is used to generate a calibration curve and to subsequently estimate the temperature. The calibration curve is obtained by varying the amplitude of the sinusoidal field. The temperature can then be estimated from any subsequent measurement of the ratio. The accuracy was 0.3 °K between 20 and 50?°C using the current apparatus and half-second measurements. The method is independent of nanoparticle concentration and nanoparticle size distribution. PMID:19544801

Weaver, John B.; Rauwerdink, Adam M.; Hansen, Eric W.

2009-01-01

370

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

371

Antifungal nanoparticles and surfaces.  

PubMed

Nosocomial fungal infections, an increasing healthcare concern worldwide, are often associated with medical devices. We have developed antifungal nanoparticle conjugates that can act in suspension or attach to a surface, efficiently killing fungi. For that purpose, we immobilized covalently amphotericin B (AmB), a potent antifungal agent approved by the FDA, widely used in clinical practice and effective against a large spectrum of fungi, into silica nanoparticles. These antifungal nanoparticle conjugates are fungicidal against several strains of Candida sp., mainly by contact. In addition, they can be reused up to 5 cycles without losing their activity. Our results show that the antifungal nanoparticle conjugates are more fungistatic and fungicidal than 10 nm colloidal silver. The antifungal activity of the antifungal nanoparticle conjugates is maintained when they are immobilized on a surface using a chemical adhesive formed by polydopamine. The antifungal nanocoatings have no hemolytic or cytotoxic effect against red blood cells and blood mononuclear cells, respectively. Surfaces coated with these antifungal nanoparticle conjugates can be very useful to render medical devices with antifungal properties. PMID:20845938

Paulo, Cristiana S O; Vidal, Maria; Ferreira, Lino S

2010-10-11

372

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

373

Introduction to metallic nanoparticles.  

PubMed

Metallic nanoparticles have fascinated scientist for over a century and are now heavily utilized in biomedical sciences and engineering. They are a focus of interest because of their huge potential in nanotechnology. Today these materials can be synthesized and modified with various chemical functional groups which allow them to be conjugated with antibodies, ligands, and drugs of interest and thus opening a wide range of potential applications in biotechnology, magnetic separation, and preconcentration of target analytes, targeted drug delivery, and vehicles for gene and drug delivery and more importantly diagnostic imaging. Moreover, various imaging modalities have been developed over the period of time such as MRI, CT, PET, ultrasound, SERS, and optical imaging as an aid to image various disease states. These imaging modalities differ in both techniques and instrumentation and more importantly require a contrast agent with unique physiochemical properties. This led to the invention of various nanoparticulated contrast agent such as magnetic nanoparticles (Fe(3)O(4)), gold, and silver nanoparticles for their application in these imaging modalities. In addition, to use various imaging techniques in tandem newer multifunctional nanoshells and nanocages have been developed. Thus in this review article, we aim to provide an introduction to magnetic nanoparticles (Fe(3)O(4)), gold nanoparticles, nanoshells and nanocages, and silver nanoparticles followed by their synthesis, physiochemical properties, and citing some recent applications in the diagnostic imaging and therapy of cancer. PMID:21180459

Mody, Vicky V; Siwale, Rodney; Singh, Ajay; Mody, Hardik R

2010-10-01

374

Introduction to metallic nanoparticles  

PubMed Central

Metallic nanoparticles have fascinated scientist for over a century and are now heavily utilized in biomedical sciences and engineering. They are a focus of interest because of their huge potential in nanotechnology. Today these materials can be synthesized and modified with various chemical functional groups which allow them to be conjugated with antibodies, ligands, and drugs of interest and thus opening a wide range of potential applications in biotechnology, magnetic separation, and preconcentration of target analytes, targeted drug delivery, and vehicles for gene and drug delivery and more importantly diagnostic imaging. Moreover, various imaging modalities have been developed over the period of time such as MRI, CT, PET, ultrasound, SERS, and optical imaging as an aid to image various disease states. These imaging modalities differ in both techniques and instrumentation and more importantly require a contrast agent with unique physiochemical properties. This led to the invention of various nanoparticulated contrast agent such as magnetic nanoparticles (Fe3O4), gold, and silver nanoparticles for their application in these imaging modalities. In addition, to use various imaging techniques in tandem newer multifunctional nanoshells and nanocages have been developed. Thus in this review article, we aim to provide an introduction to magnetic nanoparticles (Fe3O4), gold nanoparticles, nanoshells and nanocages, and silver nanoparticles followed by their synthesis, physiochemical properties, and citing some recent applications in the diagnostic imaging and therapy of cancer. PMID:21180459

Mody, Vicky V.; Siwale, Rodney; Singh, Ajay; Mody, Hardik R.

2010-01-01

375

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

376

OPTICAL PROPERTIES OFOPTICAL PROPERTIES OF METALLIC NANOPARTICLES,METALLIC NANOPARTICLES,  

E-print Network

OPTICAL PROPERTIES OFOPTICAL PROPERTIES OF METALLIC NANOPARTICLES,METALLIC NANOPARTICLES, MOLECULES,and Scattering of Light by Small Particles, Wiley: New York, 1983Wiley: New York, 1983.. #12;Extinction CrossDielectric Function of the Nanoparticles #12;Complex Dielectric FunctionComplex Dielectric Function For Bulk Material

Grujicic, Mica

377

Nanoparticles for Targeted Drug Delivery  

E-print Network

Nanoparticles were synthesized and modified for target drug delivery. The research involved the aqueous synthesis of near infrared (NIR) sensitive Au-Au2S nanoparticles. An anti-cancer drug (cis-platin) ...

Chow, Gan-Moog

378

Direct hierarchical assembly of nanoparticles  

DOEpatents

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

379

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

380

MICROBIAL IMPACTS OF ENGINEERED NANOPARTICLES  

EPA Science Inventory

Reactivity at the nanometric scale is intimately linked to nanoparticle mobility and microbial sensitivity. Thus, first-order factors increasing nanoparticle reactivity should increase the rate of redox reactions with second-order effects on particle mobility and ecot...

381

Nanoparticle–polymer photovoltaic cells  

Microsoft Academic Search

The need to develop and deploy large-scale, cost-effective, renewable energy is becoming increasingly important. In recent years photovoltaic (PV) cells based on nanoparticles blended with semiconducting polymers have achieved good power conversion efficiencies (PCE). All the nanoparticle types used in these PV cells can be considered as colloids. These include spherical, rod-like or branched organic or inorganic nanoparticles. Nanoparticle–polymer PV

Brian R. Saunders; Michael L. Turner

2008-01-01

382

Carbon nanoparticles from laser pyrolysis  

Microsoft Academic Search

Carbon nanoparticles synthesised by laser pyrolysis of hydrocarbons in a flow reactor have been investigated as a function of laser power. Samples are cross-characterised by high resolution transmission electron microscopy (HRTEM) and infrared (IR) spectroscopy. Nanoparticles appear highly aromatic in character in all the experimental conditions explored here. As the flame temperature in the interaction zone increases, the nanoparticles evolve

Aymeric Galvez; Nathalie Herlin-Boime; Cécile Reynaud; Christian Clinard; Jean-Noël Rouzaud

2002-01-01

383

Phase-controlled synthesis of ?-NiS nanoparticles confined in carbon nanorods for High Performance Supercapacitors  

NASA Astrophysics Data System (ADS)

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.

Sun, Chencheng; Ma, Mingze; Yang, Jun; Zhang, Yufei; Chen, Peng; Huang, Wei; Dong, Xiaochen

2014-11-01

384

Phase-controlled synthesis of ?-NiS nanoparticles confined in carbon nanorods for High Performance Supercapacitors  

PubMed Central

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

385

Nanoparticle delivery of an SN38 conjugate is more effective than irinotecan in a mouse model of neuroblastoma.  

PubMed

Neuroblastoma (NB) is the most common and deadly solid tumor in children. The majority of NB patients have advanced stage disease with poor prognosis, so more effective, less toxic therapy is needed. We developed a novel nanocarrier-based strategy for tumor-targeted delivery of a prodrug of SN38, the active metabolite of irinotecan. We formulated ultrasmall-sized (<100?nm) biodegradable poly(lactide)-poly(ethylene glycol) based nanoparticles (NPs) containing SN38 conjugated to tocopherol succinate (SN38-TS). Alternative dosing schedules of SN38-TS NPs were compared to irinotecan. Comparison of SN38-TS NPs (2 doses) with irinotecan (20 doses) showed equivalent efficacy but no cures. Comparison of SN38-TS NPs (8, 8, and 16 doses, respectively) to irinotecan (40 doses) showed that all SN38-TS NP regimens were far superior to irinotecan, and "cures" were obtained in all NP arms. SN38-TS NP delivery resulted in 200× the amount of SN38 in NB tumors at 4?hr post-treatment, compared to SN38 detected for the irinotecan arm; no toxicity was seen with NPs. We conclude that this SN38-TS NP formulation improved delivery, retention, and efficacy, without causing systemic toxicity. PMID:25684664

Iyer, Radhika; Croucher, Jamie L; Chorny, Michael; Mangino, Jennifer L; Alferiev, Ivan S; Levy, Robert J; Kolla, Venkatadri; Brodeur, Garrett M

2015-05-01

386

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

387

Facile synthesis of ultrafine carbon-coated SnO2 nanoparticles for high-performance reversible lithium storage  

NASA Astrophysics Data System (ADS)

Ultrafine carbon-coated SnO2 nanoparticles (NPs) with diameters of 3-6 nm are prepared by a hydrothermal method in the presence of ascorbic acid and subsequent thermal treatment. The ascorbic acid, on the one hand, serves as a ligand to control the growth of the ultrafine SnO2 NPs during the hydrothermal process and on the other hand it acts as carbon precursor to form carbon shell surrounding the ultrafine SnO2 NPs in the thermal treatment process. When evaluated as an anode material for lithium-ion batteries (LIBs), the as-synthesized ultrafine carbon-coated SnO2 NPs exhibit a high reversible capacity of 688.6 mAh g-1 at a rate of 1 C after 50 cycles. Even charging at the rate of as high as 5 C, they still deliver a reversible capacity of 414 mAh g-1, which is about 50% of the theoretical capacity of SnO2. The perfect electrochemical performance can be ascribed to the synergic effects of the conductive carbon shell surrounding the SnO2 NPs and the ultra-small size of the SnO2 NPs.

Liu, Bing; Cao, Minhua; Zhao, Xinyu; Tian, Yuan; Hu, Changwen

2013-12-01

388

Enhanced electrode performance of Fe2O3 nanoparticle-decorated nanomesh graphene as anodes for lithium-ion batteries.  

PubMed

Nanostructured Fe2O3-nanomesh graphene (NMG) composites containing ?3 nm Fe2O3 nanoparticles (NPs) uniformly distributed in the nanopores of NMG are synthesized by an adsorption-precipitation process. As anodes for Li ion batteries (LIBs), the 10%Fe2O3-NMG composite exhibits an upward trend in the capacity and delivers a reversible specific capacity of 1567 mA h g(-1) after 50 cycles at 150 mA g(-1), and 883 mA h g(-1) after 100 cycles at 1000 mA g(-1), much higher than the corresponding values for the NMG electrode. The significant capacity enhancement of the 10%Fe-NMG composite is attributed to the positive synergistic effect between NMG and Fe2O3 NPs due to the catalytic activity of Fe2O3 NPs for decomposition of the solid electrolyte interface film. Our results indicate that decoration of ultrasmall Fe2O3 NPs can significantly change the surface condition of graphene. This synthesis strategy is simple, effective, and broadly applicable for constructing other electrode materials for LIBs. PMID:24786919

Zhu, Xiao; Song, Xinyu; Ma, Xinlong; Ning, Guoqing

2014-05-28

389

Gold Nanoparticles Cytotoxicity  

NASA Astrophysics Data System (ADS)

Over the last two decades gold nanoparticles (AuNPs) have been used for many scientific applications and have attracted attention due to the specific chemical, electronic and optical size dependent properties that make them very promising agents in many fields such as medicine, imagine techniques and electronics. More specifically, biocompatible gold nanoparticles have a huge potential for use as the contrast augmentation agent in X-ray Computed Tomography and Photo Acoustic Tomography for early tumor diagnostic as well these nanoparticles are extensively researched for enhancing the targeted cancer treatment effectiveness such as photo-thermal and radiotherapy. In most biomedical applications biocompatible gold nanoparticles are labeled with specific tumor or other pathology targeting antibodies and used for site specific drug delivery. However, even though gold nanoparticles poses very high level of anti cancer properties, the question of their cytotoxicity ones they are released in normal tissue has to be researched. Moreover, the huge amount of industrially produced gold nanoparticles raises the question of these particles being a health hazard, since the penetration is fairly easy for the "nano" size substances. This study focuses on the effect of AuNPs on a human skin tissue, since it is fall in both categories -- the side effects for biomedical applications and industrial workers and users' exposure during production and handling. Therefore, in the present project, gold nanoparticles stabilized with the biocompatible agent citric acid were generated and characterized by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The cytotoxic effect of AuNPs release to healthy skin tissue was modeled on 3 different cell types: human keratinocytes, human dermal fibroblasts, and human adipose derived stromal (ADS) cells. The AuNPs localization inside the cell was found to be cell type dependent. Overall cytotoxicity was found to be dependent on time, concentration and nanoparticle size. Additionally, the question of cell recovery once the source of AuNPs is removed was investigated in the present work. It was found that full cell functions recovery is possible after removing the source of nanoparticles.

Mironava, Tatsiana

390

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

391

Enhanced flux-pinning properties in superconducting YBa2Cu3O(7-delta) thin films with nanoengineering  

NASA Astrophysics Data System (ADS)

Since the discovery of the high temperature superconductor YBa2Cu3O7-delta (YBCO), with transition temperature (Tc = 77 K), above liquid nitrogen point in 1987 many research projects have been dedicated to enhancing the high field performance of this material for practical applications. The 2 nd generation YBCO-based coated conductors are believed to be the most promising approach for commercial applications including power transmission, motors, generators, and high field magnets. With the advances of nanotechnologies, different nanoengineering methods have been demonstrated to enhance the performance of YBCO thin films, include doping with 0-dimensional (0-D) self-assembled nanoparticles, 1-dimensional (1-D) nanorods, and 2-dimensional (2-D) nanolayers. Furthermore, dopants with ferromagnetic properties are also reported to provide enhanced pinning effects by Lorentz force, especially under high-applied magnetic fields. The principle of these methods is to generate high-density defects at the heterogeneous interfaces as artificial pinning centers in an effort to improve the flux-pinning properties. The morphology and dimensions of the nanoinclusions play an important role in pining enhancement. Optimized pinning structures are likely to be located at energetically favorable vortex cores, which form a triangular lattice with dimensions close to the YBCO coherence length xi (xiab ~ 4 nm; xic ~ 0.5 nm at 77 K.) However, it is challenging to achieve small dimensional nanodopants in the vapor deposited YBCO thin films. The purpose of this research is to utilize nanoengineering methods to produce optimized pinning structure in YBCO thin films. In this thesis, we systematically study the effects of different nanoinclusions on the flux-pinning properties of YBCO thin films. The 0-D ferromagnetic Fe 2O3 and CoFe2O4 nanoparticles, 2-D CeO2 multilayers, and tunable vertically aligned nanocomposites (VAN) of (Fe2O3)x:(CeO2) 1-x and (CoFe2O4)x:(CeO2) 1-x systems are introduced into the YBCO matrix as artificial pinning centers. Results suggest that all nanoinclusions showed significant enhancement in the superconducting properties of YBCO. The ferromagnetic pinning centers dominate at high field and low temperature regimes, however, the defect pinning centers dominate at low field and high temperature regimes. The uniquely arranged VAN structure of alternating magnetic and non-magnetic nanophases, which incorporates both high defect density and tunable distribution of magnetic dopants, is believed to be an ideal solution for flux-pinning enhancement.

Tsai, Chen-Fong

392

Nanoparticle shuttle memory  

DOEpatents

A device for storing data using nanoparticle shuttle memory having a nanotube. The nanotube has a first end and a second end. A first electrode is electrically connected to the first end of the nanotube. A second electrode is electrically connected to the second end of the nanotube. The nanotube has an enclosed nanoparticle shuttle. A switched voltage source is electrically connected to the first electrode and the second electrode, whereby a voltage may be controllably applied across the nanotube. A resistance meter is also connected to the first electrode and the second electrode, whereby the electrical resistance across the nanotube can be determined.

Zettl, Alex Karlwalter (Kensington, CA)

2012-03-06

393

TOPICAL REVIEW: Biopolymeric nanoparticles  

NASA Astrophysics Data System (ADS)

This review on nanoparticles highlights the various biopolymers (proteins and polysaccharides) which have recently revolutionized the world of biocompatible and degradable natural biological materials. The methods of their fabrication, including emulsification, desolvation, coacervation and electrospray drying are described. The characterization of different parameters for a given nanoparticle, such as particle size, surface charge, morphology, stability, structure, cellular uptake, cytotoxicity, drug loading and drug release, is outlined together with the relevant measurement techniques. Applications in the fields of medicine and biotechnology are discussed along with a promising future scope.

Sundar, Sushmitha; Kundu, Joydip; Kundu, Subhas C.

2010-02-01

394

Nanoparticles from renewable polymers  

PubMed Central

The use of polymers from natural resources can bring many benefits for novel polymeric nanoparticle systems. Such polymers have a variety of beneficial properties such as biodegradability and biocompatibility, they are readily available on large scale and at low cost. As the amount of fossil fuels decrease, their application becomes more interesting even if characterization is in many cases more challenging due to structural complexity, either by broad distribution of their molecular weights (polysaccharides, polyesters, lignin) or by complex structure (proteins, lignin). This review summarizes different sources and methods for the preparation of biopolymer-based nanoparticle systems for various applications. PMID:25101259

Wurm, Frederik R.; Weiss, Clemens K.

2014-01-01

395

Thermally stable nanoparticles on supports  

DOEpatents

An inverse micelle-based method for forming nanoparticles on supports includes dissolving a polymeric material in a solvent to provide a micelle solution. A nanoparticle source is dissolved in the micelle solution. A plurality of micelles having a nanoparticle in their core and an outer polymeric coating layer are formed in the micelle solution. The micelles are applied to a support. The polymeric coating layer is then removed from the micelles to expose the nanoparticles. A supported catalyst includes a nanocrystalline powder, thin film, or single crystal support. Metal nanoparticles having a median size from 0.5 nm to 25 nm, a size distribution having a standard deviation .ltoreq.0.1 of their median size are on or embedded in the support. The plurality of metal nanoparticles are dispersed and in a periodic arrangement. The metal nanoparticles maintain their periodic arrangement and size distribution following heat treatments of at least 1,000.degree. C.

Roldan Cuenya, Beatriz; Naitabdi, Ahmed R.; Behafarid, Farzad

2012-11-13

396

In situ assembly of well-dispersed Ni nanoparticles on silica nanotubes and excellent catalytic activity in 4-nitrophenol reduction  

NASA Astrophysics Data System (ADS)

The easy aggregation nature of ferromagnetic nanoparticles (NPs) prepared by conventional routes usually leads to a large particle size and low loading, which greatly limits their applications to the reduction of 4-nitrophenol (4-NP). Herein, we developed a novel in situ thermal decomposition and reduction strategy to prepare Ni nanoparticles/silica nanotubes (Ni/SNTs), which can markedly prevent the aggregation and growth of Ni NPs, resulting in an ultra-small particle size (about 6 nm), good dispersion and especially high loading of Ni NPs. It was found that Ni/SNTs, which have a high specific surface area (416 m2 g-1), exhibit ultra-high catalytic activity in the 4-NP reduction (complete reduction of 4-NP within only 60 s at room temperature), which is superior to most noble metal (Au, Pt, and Pd) supported catalysts. Ni/SNTs still showed high activity even after re-use for several cycles, suggesting good stability. In particular, the magnetic property of Ni/SNTs makes it easy to recycle for reuse.The easy aggregation nature of ferromagnetic nanoparticles (NPs) prepared by conventional routes usually leads to a large particle size and low loading, which greatly limits their applications to the reduction of 4-nitrophenol (4-NP). Herein, we developed a novel in situ thermal decomposition and reduction strategy to prepare Ni nanoparticles/silica nanotubes (Ni/SNTs), which can markedly prevent the aggregation and growth of Ni NPs, resulting in an ultra-small particle size (about 6 nm), good dispersion and especially high loading of Ni NPs. It was found that Ni/SNTs, which have a high specific surface area (416 m2 g-1), exhibit ultra-high catalytic activity in the 4-NP reduction (complete reduction of 4-NP within only 60 s at room temperature), which is superior to most noble metal (Au, Pt, and Pd) supported catalysts. Ni/SNTs still showed high activity even after re-use for several cycles, suggesting good stability. In particular, the magnetic property of Ni/SNTs makes it easy to recycle for reuse. Electronic supplementary information (ESI) available: XRD pattern and TEM image of SNTs after calcination, XRD pattern and EDS of NiSNTs, SEM images of a single SNT, NiSNTs and Ni/SNTs, enlarged HRTEM of Ni/SNTs, XRD pattern of NiO/SNTs, UV-vis spectra of the catalytic reduction of 4-NP to 4-AP over Ni/SNTs with different loading amounts, Ni/SNTs synthesized by wet impregnation and Ni/CNTs, TEM images of Ni/SNTs synthesized by wet impregnation and Ni/CNTs. See DOI: 10.1039/c4nr02096k

Zhang, Shenghuan; Gai, Shili; He, Fei; Ding, Shujiang; Li, Lei; Yang, Piaoping

2014-09-01

397

Monoclonal antibody conjugated magnetic nanoparticles could target MUC-1-positive cells in vitro but not in vivo.  

PubMed

MUC1 antigen is recognized as a high-molecular-weight glycoprotein that is unexpectedly over-expressed in human breast and other carcinomas. In contrast, C595 a monoclonal antibody (mAb) against the protein core of the human urinary epithelial machine, is commonly expressed in breast carcinomas. The aim of this study was to conjugate ultra-small super paramagnetic iron oxide nanoparticles (USPIO) with C595 mAb, in order to detect in vivo MUC1 expression. A dual contrast agent (the C595 antibody-conjugated USPIO labeled with 99mTc) was prepared for targeted imaging and therapy of anti-MUC1-expressing cancers. The C595 antibody-conjugated USPIO had good stability and reactivity in the presence of blood plasma at 37?°C. No significant differences were observed in immunoreactivity results between conjugated and nonconjugated nanoparticles. The T1 and T2 measurements show >79 and 29% increments (for 0.02?mg/ml iron concentrations) in T1 and T2 values for USPIO-C595 in comparison with USPIO, respectively. The nanoprobes showed the interesting targeting capability of finding the MUC1-positive cell line in vitro. However, we found disappointing in vivo results (i.e. very low accumulation of nanoprobes in the targeted site while >80% of the injected dose per gram was taken up by the liver and spleen), not only due to the coverage of targeting site by protein corona but also because of absorption of opsonin-based proteins at the surface of nanoprobes. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25327822

Shanehsazzadeh, Saeed; Gruettner, Cordula; Lahooti, Afsaneh; Mahmoudi, Morteza; Allen, Barry J; Ghavami, Mahdi; Daha, Fariba Johari; Oghabian, Mohammad Ali

2014-10-18

398

Nanoparticles as biochemical sensors  

PubMed Central

There is little doubt that nanoparticles offer real and new opportunities in many fields, such as biomedicine and materials science. Such particles are small enough to enter almost all areas of the body, including cells and organelles, potentially leading to new approaches in nanomedicine. Sensors for small molecules of biochemical interest are of critical importance. This review is an attempt to trace the use of nanomaterials in biochemical sensor design. The possibility of using nanoparticles functionalized with antibodies as markers for proteins will be elucidated. Moreover, capabilities and applications for nanoparticles based on gold, silver, magnetic, and semiconductor materials (quantum dots), used in optical (absorbance, luminescence, surface enhanced Raman spectroscopy, surface plasmon resonance), electrochemical, and mass-sensitive sensors will be highlighted. The unique ability of nanosensors to improve the analysis of biochemical fluids is discussed either through considering the use of nanoparticles for in vitro molecular diagnosis, or in the biological/biochemical analysis for in vivo interaction with the human body. PMID:24198472

El-Ansary, Afaf; Faddah, Layla M

2010-01-01

399

Traveling Nanoparticles Model  

NSDL National Science Digital Library

This is an activity (located on page 3 of the PDF) about diffusion of small molecules across cell membranes. Learners will use gelatin to represent a cell and dye to represent molecules to model how small molecules such as nanoparticles can penetrate living environments. Relates to linked video, DragonflyTV: Nanosilver.

2012-06-26

400

Highly lattice-mismatched semiconductor-metal hybrid nanostructures: gold nanoparticle encapsulated luminescent silicon quantum dots  

NASA Astrophysics Data System (ADS)

Synthesis of hybrid core-shell nanostructures requires moderate lattice mismatch (<5%) between the materials of the core and the shell and usually results in the formation of structures with an atomically larger entity comprising the core. A reverse situation, where an atomically larger entity encapsulates a smaller atomic radius component having substantial lattice mismatch is unachievable by conventional growth techniques. Here, we report successful synthesis of ultra-small, light-emitting Si quantum dots (QDs) encapsulated by Au nanoparticles (NPs) forming a hybrid nanocomposite that exhibits intense room temperature photoluminescence (PL) and intriguing plasmon-exciton coupling. A facile strategy was adopted to utilize the active surface of oxide etched Si QDs as preferential sites for Au NP nucleation and growth which resulted in the formation of core-shell nanostructures consisting of an atomically smaller Si QD core surrounded by a substantially lattice-mismatched Au NP shell. The PL characteristics of the luminescent Si QDs (quantum yield ~28%) are dramatically altered following Au NP encapsulation. Au coverage of the bare Si QDs effectively stabilizes the emission spectrum and leads to a red-shift of the PL maxima by ~37 nm. The oxide related PL peaks observed in Si QDs are absent in the Au treated sample suggesting the disappearance of oxide states and the appearance of Au NP associated Stark shifted interface states within the widened band-gap of the Si QDs. Emission kinetics of the hybrid system show accelerated decay due to non-radiative energy transfer between the Si QDs and the Au NPs and associated quenching in PL efficiency. Nevertheless, the quantum yield of the hybrid remains high (~20%) which renders these hetero-nanostructures exciting candidates for multifarious applications.Synthesis of hybrid core-shell nanostructures requires moderate lattice mismatch (<5%) between the materials of the core and the shell and usually results in the formation of structures with an atomically larger entity comprising the core. A reverse situation, where an atomically larger entity encapsulates a smaller atomic radius component having substantial lattice mismatch is unachievable by conventional growth techniques. Here, we report successful synthesis of ultra-small, light-emitting Si quantum dots (QDs) encapsulated by Au nanoparticles (NPs) forming a hybrid nanocomposite that exhibits intense room temperature photoluminescence (PL) and intriguing plasmon-exciton coupling. A facile strategy was adopted to utilize the active surface of oxide etched Si QDs as preferential sites for Au NP nucleation and growth which resulted in the formation of core-shell nanostructures consisting of an atomically smaller Si QD core surrounded by a substantially lattice-mismatched Au NP shell. The PL characteristics of the luminescent Si QDs (quantum yield ~28%) are dramatically altered following Au NP encapsulation. Au coverage of the bare Si QDs effectively stabilizes the emission spectrum and leads to a red-shift of the PL maxima by ~37 nm. The oxide related PL peaks observed in Si QDs are absent in the Au treated sample suggesting the disappearance of oxide states and the appearance of Au NP associated Stark shifted interface states within the widened band-gap of the Si QDs. Emission kinetics of the hybrid system show accelerated decay due to non-radiative energy transfer between the Si QDs and the Au NPs and associated quenching in PL efficiency. Nevertheless, the quantum yield of the hybrid remains high (~20%) which renders these hetero-nanostructures exciting candidates for multifarious applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05960j

Ray, Mallar; Basu, Tuhin Shuvra; Bandyopadhyay, Nil Ratan; Klie, Robert F.; Ghosh, Siddhartha; Raja, Sufi Oasim; Dasgupta, Anjan K.

2014-01-01

401

DNA templated magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Recent discoveries in nanoscience are predicted to potentially revolutionize future technologies in an extensive number of fields. These developments are contingent upon discovering new and often unconventional methods to synthesize and control nanoscale components. Nature provides several examples of working nanotechnology such as the use of programmed self assembly to build and deconstruct complex molecular systems. We have adopted a method to control the one dimensional assembly of magnetic nanoparticles using DNA as a scaffold molecule. With this method we have demonstrated the ability to organize 5 nm particles into chains that stretch up to ˜20 mum in length. One advantage of using DNA compared is the ability of the molecule to interact with other biomolecules. After assembling particles onto DNA we have been able to cleave the molecule into smaller fragments using restriction enzymes. Using ligase enzymes we have re-connected these fragments, coated with either gold or iron oxide, to form long one-dimensional arrangements of the two different types of nanoparticles on a single molecular guide. We have also created a sensitive magnetic field sensor by incorporating magnetic nanoparticle coated DNA strands with microfabricated electrodes. The IV characteristics of the aligned nanoparticles are dependant on the magnitude of an externally applied magnetic field. This transport phenomenon known as tunneling magnetoresistance (TMR) shows room temperature resistance of our devices over 80% for cobalt ferrite coated DNA when a field of 20 kOe is applied. In comparison, studies using two dimensional nanoparticle films of irox oxides xii only exhibit a 35% MR effect. Confinement into one dimension using the DNA guide produces a TMR mechanism which produces significant increases in magnetoresistance. This property can be utilized for applications in magnetic field sensing, data storage, and logic elements.

Kinsella, Joseph M.

402

Nanoparticle Measurements and Standards for Biomedical and  

E-print Network

for physical and biological characterization of nanoparticles for imaging, diagnosis and therapy. · New consensus standards for characterization of biomedical nanoparticles are currently under development within a nanoparticle measurement infrastructure. Standards In 2008 NIST issued its first "nano" reference materials

Magee, Joseph W.

403

Thermosensitive/magnetic poly(organophosphazene) hydrogel as a long-term magnetic resonance contrast platform.  

PubMed

A thermosensitive/magnetic poly(organophosphazene) hydrogel (a magnetic hydrogel) was designed and synthesized for long-term magnetic resonance (MR) imaging. To turn a thermosensitive poly(organophosphazene) hydrogel (an original hydrogel) into a long-term MR contrast platform, cobalt ferrite (CoFe(2)O(4)) nanoparticles, which have hydrophobic surfaces, were bound to the original hydrogel via interactions between the hydrophobic surfaces of the nanoparticles and the (L)-isoleucine ethyl esters of the polymer. The magnetic hydrogel showed extremely low cytotoxicity and adequate magnetic properties for use in long-term MR imaging, in addition to possessing the same properties of the original hydrogel, such as viscosity, thermosensitivity, biodegradability, biocompatibility, a reversible sol-to-gel phase transition near body temperature, and injectability. The magnetic hydrogel was injected into a rat brain using stereotactic surgery. After the injection, the applicable potentiality as a long-term MR contrast platform was successfully estimated over 4-5 weeks. Consequently, it was shown that a magnetic hydrogel as a long-term MR contrast platform has the potential to be applied in a long-term theranostic hydrogel system. Furthermore, it is expected that this platform can be useful in the clinical field of incurable diseases due to either surgical difficulties or lethality, such as with brain tumors, when the platform is combined with therapeutic drugs for long-term MR theragnosis in further studies. PMID:21975461

Kim, Jang Il; Chun, ChangJu; Kim, Bora; Hong, Ji Min; Cho, Jung-Kyo; Lee, Seung Hoon; Song, Soo-Chang

2012-01-01

404

Effect of different doping on the structural, morphological and magnetic properties for Cu doped nanoscale spinel type ferrites  

NASA Astrophysics Data System (ADS)

CuxM1-xFe2O4 (M=Co, Mn and Ni; x=0.0, 0.6 and 1.0) spinel type ferrite nanoparticles have been synthesized by cetyltrimethylammonium bromide (CTAB) assisted hydrothermal route using NaOH solution. The purity, structural characterization and magnetic properties have been investigated using the scanning electron microscopy, x-ray diffraction analysis and a quantum design vibrating sample magnetometer depending on the temperature. The scanning electron microscopy imaging exhibits very powerful aspect. The average size of composite nanoparticles for all samples was determined. Diameter of the samples is synthesized in nanoscale. The x-ray diffraction results have indicated that these samples are high phase purity, crystalline and inverse spinel ferrites. The temperature evolution of the magnetic properties and different doping effects for the samples have been observed. The pseudo spin-valve behavior has been showed for Cu0.6Co0.4Fe2O4 and CoFe2O4 samples. These samples can be considered as promising materials for magnetic recording media and electromagnetic absorbing technologies applications.

Bayrakdar, H.; Yalç?n, O.; Vural, S.; Esmer, K.

2013-10-01

405

Highly lattice-mismatched semiconductor-metal hybrid nanostructures: gold nanoparticle encapsulated luminescent silicon quantum dots.  

PubMed

Synthesis of hybrid core-shell nanostructures requires moderate lattice mismatch (<5%) between the materials of the core and the shell and usually results in the formation of structures with an atomically larger entity comprising the core. A reverse situation, where an atomically larger entity encapsulates a smaller atomic radius component having substantial lattice mismatch is unachievable by conventional growth techniques. Here, we report successful synthesis of ultra-small, light-emitting Si quantum dots (QDs) encapsulated by Au nanoparticles (NPs) forming a hybrid nanocomposite that exhibits intense room temperature photoluminescence (PL) and intriguing plasmon-exciton coupling. A facile strategy was adopted to utilize the active surface of oxide etched Si QDs as preferential sites for Au NP nucleation and growth which resulted in the formation of core-shell nanostructures consisting of an atomically smaller Si QD core surrounded by a substantially lattice-mismatched Au NP shell. The PL characteristics of the luminescent Si QDs (quantum yield ?28%) are dramatically altered following Au NP encapsulation. Au coverage of the bare Si QDs effectively stabilizes the emission spectrum and leads to a red-shift of the PL maxima by ?37 nm. The oxide related PL peaks observed in Si QDs are absent in the Au treated sample suggesting the disappearance of oxide states and the appearance of Au NP associated Stark shifted interface states within the widened band-gap of the Si QDs. Emission kinetics of the hybrid system show accelerated decay due to non-radiative energy transfer between the Si QDs and the Au NPs and associated quenching in PL efficiency. Nevertheless, the quantum yield of the hybrid remains high (?20%) which renders these hetero-nanostructures exciting candidates for multifarious applications. PMID:24382635

Ray, Mallar; Basu, Tuhin Shuvra; Bandyopadhyay, Nil Ratan; Klie, Robert F; Ghosh, Siddhartha; Raja, Sufi Oasim; Dasgupta, Anjan K

2014-02-21

406

Evaluation of monolayer protected metal nanoparticle technology  

E-print Network

Self assembling nanostructured nanoparticles represent a new class of synthesized materials with unique functionality. Such monolayer protected metal nanoparticles are capable of resisting protein adsorption, and if utilized ...

Wu, Diana J

2005-01-01

407

Photoacoustic signal amplification through plasmonic nanoparticle aggregation  

PubMed Central

Abstract. Photoacoustic imaging, using targeted plasmonic metallic nanoparticles, is a promising noninvasive molecular imaging method. Analysis of the photoacoustic signal generated by plasmonic metallic nanoparticles is complex because of the dependence upon physical properties of both the nanoparticle and the surrounding environment. We studied the effect of the aggregation of gold nanoparticles on the photoacoustic signal amplitude. We found that the photoacoustic signal from aggregated silica-coated gold nanoparticles is greatly enhanced in comparison to disperse silica-coated gold nanoparticles. Because cellular uptake and endocytosis of nanoparticles results in their aggregation, these results have important implications for the application of plasmonic metallic nanoparticles towards quantitative molecular imaging. PMID:23288414

Bayer, Carolyn L.; Nam, Seung Yun; Chen, Yun-Sheng; Emelianov, Stanislav Y.

2013-01-01

408

Nanoparticles for Detection and Diagnosis  

PubMed Central

Nanoparticle-based platforms for identification of chemical and biological agents offer substantial benefits to biomedical and environmental science. These platforms benefit from the availability of a wide variety of core materials as well as the unique physical and chemical properties of these nanoscale materials. This review surveys some of the emerging approaches in the field of nanoparticle based detection systems, highlighting the nanoparticle based screening methods for metal ions, proteins, nucleic acids, and biologically relevant small molecules. PMID:19913581

Agasti, Sarit S.; Rana, Subinoy; Park, Myoung-Hwan; Kim, Chae Kyu; You, Chang-Cheng; Rotello, Vincent M.

2009-01-01

409

Nanobiotechnology today: focus on nanoparticles  

PubMed Central

In the recent years the nanobiotechnology field and the Journal of Nanobiotechnology readership have witnessed an increase in interest towards the nanoparticles and their biological effects and applications. These include bottom-up and molecular self-assembly, biological effects of naked nanoparticles and nano-safety, drug encapsulation and nanotherapeutics, and novel nanoparticles for use in microscopy, imaging and diagnostics. This review highlights recent Journal of Nanobiotechnology publications in some of these areas . PMID:18163916

Soloviev, Mikhail

2007-01-01

410

Safety of Nanoparticles in Medicine.  

PubMed

Nanomedicine involves the use of nanoparticles for therapeutic and diagnostic purposes. During the past two decades, a growing number of nanomedicines have received regulatory approval and many more show promise for future clinical translation. In this context, it is important to evaluate the safety of nanoparticles in order to achieve biocompatibility and desired activity. However, it is unwarranted to make generalized statements regarding the safety of nanoparticles, since the field of nanomedicine comprises a multitude of different manufactured nanoparticles made from various materials. Indeed, several nanotherapeutics that are currently approved, such as Doxil and Abraxane, exhibit fewer side effects than their small molecule counterparts, while other nanoparticles (e.g. metallic and carbon-based particles) tend to display toxicity. However, the hazardous nature of certain nanomedicines could be exploited for the ablation of diseased tissue, if selective targeting can be achieved. This review discusses the mechanisms for molecular, cellular, organ, and immune system toxicity, which can be observed with a subset of nanoparticles. Strategies for improving the safety of nanoparticles by surface modification and pretreatment with immunomodulators are also discussed. Additionally, important considerations for nanoparticle safety assessment are reviewed. In regards to clinical application, stricter regulations for the approval of nanomedicines might not be required. Rather, safety evaluation assays should be adjusted to be more appropriate for engineered nanoparticles. PMID:25090989

Wolfram, Joy; Zhu, Motao; Yang, Yong; Shen, Jianliang; Gentile, Emanuela; Paolino, Donatella; Fresta, Massimo; Nie, Guangjun; Chen, Chunying; Shen, Haifa; Ferrari, Mauro; Zhao, Yuliang

2014-08-01

411

Silver Nanoparticles in Dental Biomaterials  

PubMed Central

Silver has been used in medicine for centuries because of its antimicrobial properties. More recently, silver nanoparticles have been synthesized and incorporated into several biomaterials, since their small size provides great antimicrobial effect, at low filler level. Hence, these nanoparticles have been applied in dentistry, in order to prevent or reduce biofilm formation over dental materials surfaces. This review aims to discuss the current progress in this field, highlighting aspects regarding silver nanoparticles incorporation, such as antimicrobial potential, mechanical properties, cytotoxicity, and long-term effectiveness. We also emphasize the need for more studies to determine the optimal concentration of silver nanoparticle and its release over time. PMID:25667594

Corrêa, Juliana Mattos; Mori, Matsuyoshi; Sanches, Heloísa Lajas; da Cruz, Adriana Dibo; Poiate, Isis Andréa Venturini Pola

2015-01-01

412

Magnetic Nanoparticle Sensors  

PubMed Central

Many types of biosensors employ magnetic nanoparticles (diameter = 5–300 nm) or magnetic particles (diameter = 300–5,000 nm) which have been surface functionalized to recognize specific molecular targets. Here we cover three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation. The first type consists of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates. The second type consists of magnetic particle relaxation sensors, which determine the relaxation of the magnetic moment within the magnetic particle. The third type is magnetoresistive sensors, which detect the presence of magnetic particles on the surface of electronic devices that are sensitive to changes in magnetic fields on their surface. Recent improvements in the design of magnetic nanoparticles (and magnetic particles), together with improvements in instrumentation, suggest that magnetic material-based biosensors may become widely used in the future. PMID:22408498

Koh, Isaac; Josephson, Lee

2009-01-01

413

Photoluminescence by Interstellar Nanoparticles  

SciTech Connect

Dust grains in interstellar space are an all-pervasive component of the Universe that affect our perception of virtually every cosmic phenomenon. They play important roles in processes like star formation, formation of molecules and formation of terrestrial planets, to name just a few. Yet, their nature, size, structure, and composition are only poorly understood. I shall report on new investigations of optical luminescence emanating from dust grains that reveal the presence of nanoparticle components of dust, most likely polycyclic aromatic hydrocarbons and tiny semiconductor nanocrystals, e.g. silicon nanoparticles. Coordinated laboratory studies of such small particles would greatly aid our efforts of arriving at definitive identifications of the luminescent astronomical dust sources.

Witt, Adolf N. (University of Toledo) [University of Toledo

2004-04-21

414

Nanoparticles in dermatology  

Microsoft Academic Search

Recent advances in the field of nanotechnology have allowed the manufacturing of elaborated nanometer-sized particles for\\u000a various biomedical applications. A broad spectrum of particles, extending from various lipid nanostructures such as liposomes\\u000a and solid lipid nanoparticles, to metal, nanocrystalline and polymer particles have already been tested as drug delivery systems\\u000a in different animal models with remarkable results, promising an extensive

Dimitrios Papakostas; Fiorenza Rancan; Wolfram Sterry; Ulrike Blume-Peytavi; Annika Vogt

415

Effect of chemical structure on the volume-phase transition in neutral and weakly charged poly(N-alkyl(meth)acrylamide) hydrogels studied by ultrasmall-angle x-ray scattering  

NASA Astrophysics Data System (ADS)

Neutral poly(N-isopropylacrylamide) (PIPAAm), poly(N,N-diethylacrylamide) (PDEAAm), and poly(N-isopropylmethacrylamide) (PIPMAm) hydrogels and their weakly charged counterparts prepared by copolymerizing with sodium methacrylate (xMNa=0,0.025,0.05) were studied using ultrasmall-angle x-ray scattering. The volume-phase transition in hydrogels was observed as an increase in the inhomogeneity correlation length of the networks. The change in inhomogeneity correlation length was abrupt in neutral PIPAAm and PIPMAm gels with increase in temperature but was continuous in neutral PDEAAm gels. Addition of ionic comonomer to the network backbone suppressed the volume-phase transition in poly(N-alkylacrylamide)s but not in PIPMAm. The observed differences in temperature-induced volume change of these three polymers in water cannot be rationalized based on their relative hydrophobicity and are instead explained by considering the hydrogen-bonding constraints on their thermal fluctuations. Both PIPAAm and PDEAAm undergo volume collapse since their thermal fluctuations are constrained by hydrogen bonding with water to an extent that beyond a critical temperature they seek entropic compensation. Although thermal fluctuations in both PIPAAm and PIPMAm are equally constrained, thermal energy of the latter can be relaxed via the rotation of ?-methyl groups allowing it greater flexibility. Compared to N-alkylacrylamides, N-alkylmethacrylamide can thus sustain hydrogen bonding to relatively higher temperatures before seeking entropic compensation by undergoing volume collapse.

Tirumala, Vijay R.; Ilavsky, Jan; Ilavsky, Michal

2006-06-01

416

Nanoparticles forNanoparticles for Pharmaceutical ApplicationsPharmaceutical Applications  

E-print Network

1 Nanoparticles forNanoparticles for Pharmaceutical ApplicationsPharmaceutical Applications Robert--soluble drugssoluble drugs 40% of pharmaceutical drugs in development40% of pharmaceutical drugs in development engineering 4 Solution: delivery system for PWS drugsSolution: delivery system for PWS drugs Melt extrusion

Lightsey, Glenn

417

Shockwave Spectroscopy of Nanoparticles  

NASA Astrophysics Data System (ADS)

This dissertation examines the effects of laser-generated shockwaves on colloidally prepared nanocrystals. Their microscopic structure is first examined utilizing gold nanoparticles. The properties under scrutiny in the first study are used to then initiate a polymorphic phase transition in CdSe quantum dots. In the final study, hollow CdS particles are used to show the utility of nanoparticles as possible energy attenuation materials. In gold nanoparticles it is shown, for the first time, a direct observation of the effect of density increase on the optical properties of gold nanoparticles. The splitting of the plasmon resonance into two distinct peaks illustrates the result of a uniaxial compression characteristic of a shock wave. The behavior of CdSe nanocrystals shocked to stresses of 2--3.75 GPa has been studied. Above 3 GPa a near-complete disappearance of the first excitonic feature and broadening of the low-energy absorption edge were observed, consistent with a wurtzite to rocksalt structural transformation. The transformation pressure is reduced relative to hydrostatic compression in a diamond anvil cell. Also, the rate of the phase transition increases. These effects are attributed to shock induced shear stress along the reaction coordinate. The especially rapid rate observed for a 3.75 GPa shock suggests multiple nucleation events per particle. Hollow CdS nanospheres have been fractured under the action of laser-induced shock waves. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been used to image the recovered fragmented particles. Additionally, time-resolved measurements of the transmission of the shock wave through a polymer layer containing hollow nanospheres have been carried out. The hollow nanospheres can attenuate the transmitted shock above a threshold stress. At the highest shock stresses measured, the shock attenuation layer acts as a composite shocked above its elastic limit. To these ends we show that nanoparticles are useful in studying and altering the properties of shockwaves. Shockwaves are also shown to be useful in high time-resolution studies of the morphological processes in solids, using nanocrystals as the archetypical, single-domain sample.

Merkle, Maxwell Graham

418