Sample records for ultrasmall cofe2o4 nanoparticles

  1. Motility of CoFe2O4 nanoparticle-labelled microtubules in magnetic fields

    E-print Network

    Hancock, William O.

    Motility of CoFe2O4 nanoparticle-labelled microtubules in magnetic fields B.M. Hutchins, M. Platt is investigated both with and without applied magnetic fields. Microtubule gliding speed decreased of a magnetic field, however, the presence of a field did not significantly affect gliding speed or direction

  2. Synthesis and characterization of CoFe2O4 nanoparticles with high coercivity

    NASA Astrophysics Data System (ADS)

    Gandha, Kinjal; Elkins, Kevin; Poudyal, Narayan; Ping Liu, J.

    2015-05-01

    Single crystalline CoFe2O4 nanoparticles with high coercivity were prepared via a one-step hydrothermal method. The shape and size of the nanocrystals (in the range of 20-100 nm) can be controlled by varying synthesis parameters such as the concentration of NaOH and CTAB. X-ray diffraction and Raman spectra analysis confirmed that all the as-synthesized nanoparticles have a face centered cubic spinel crystal structure. HRTEM observation of particles shows interlayer spacing 0.48 nm of (111) lattice planes. A coercive force up to 5.0 kOe and saturation magnetization of 73 emu/g was achieved at room temperature for the 40 nm CoFe2O4 nanoparticles.

  3. Polyethylene glycol coated CoFe2O4 nanoparticles: A potential spinel ferrite for biomedical applications

    NASA Astrophysics Data System (ADS)

    Humbe, Ashok V.; Birajdar, Shankar D.; Bhandari, J. M.; Waghule, N. N.; Bhagwat, V. R.; Jadhav, K. M.

    2015-06-01

    The structural and magnetic properties of the polyethylene glycol (PEG) coated cobalt spinel ferrite (CoFe2O4) nanoparticles have been reported in the present study. CoFe2O4 nanoparticles were prepared by sol-gel auto-combustion method using citric acid + ethylene glycol as a fuel. The prepared powder of cobalt ferrite nanoparticles was annealed at 600°C for 6h and used for further study. The structural characterization of CoFe2O4 nanoparticles were carried out by X-ray diffraction technique. The X-ray analysis confirmed the formation of single phase cubic spinel structure. The crystallite size, Lattice constant and X-ray density of the PEG coated CoFe2O4 nanoparticles were calculated by using XRD data. The presence of PEG on CoFe2O4 nanoparticles and reduced agglomeration in the CoFe2O4 nanoparticles were revealed by SEM studies. The magnetic properties were studied by pulse field hysteresis loop tracer technique at a room temperature. The magnetic parameters such as saturation magnetization, remanence magnetization, coercivity etc have been obtained. These magnetic parameters were get decreased by PEG coating.

  4. Magnetic properties of CoFe2O4 nanoparticles distributed in a multiferroic BiFeO3 matrix

    NASA Astrophysics Data System (ADS)

    Sone, Keita; Sekiguchi, Sho; Naganuma, Hiroshi; Miyazaki, Takamichi; Nakajima, Takashi; Okamura, Soichiro

    2012-06-01

    BiFeO3-CoFe2O4 composite thin films were formed on Pt/Ti/SiO2/Si(100) substrates by chemical solution deposition from a mixed precursor solution. X-ray diffraction and transmission electron microscopy analyses confirmed that CoFe2O4 nanoparticles less than 10 nm were uniformly distributed in the BiFeO3 matrix. The BiFeO3-CoFe2O4 composite films exhibited the same ferroelectric switching charge as BiFeO3 thin films, although a larger applied electric field was necessary. However, the magnetic properties were significantly improved by incorporation of CoFe2O4 nanoparticles into BiFeO3; a saturated magnetization of 80 emu/cm3 and a magnetic coercive field of 450 Oe were attained at 300 K. Furthermore, the composite films did not show superparamagnetic behavior in zero-field-cooling and field-cooling measurements, which suggest that the thermal fluctuation of CoFe2O4 nanoparticles was suppressed by exchange coupling with BiFeO3.

  5. Cationic distribution and spin canting in CoFe2O4 nanoparticles.

    PubMed

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

    2011-10-26

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

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

    PubMed

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

    2012-09-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

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

    PubMed

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

    2015-03-01

    The aim of this study was to determine whether citric acid adsorbed onto cobalt ferrite (CoFe2O4) nanoparticles (NPs) influences the bioavailability of their constituents Co and Fe. Dissolution of Co and Fe was assessed by two measures: (i) in aqueous suspension using chemical analysis, prior to application onto the food of test organisms; and (ii) in vivo, measuring the bioavailability in the model terrestrial invertebrate (Porcellio scaber, Isopoda, Crustacea). The isopods were exposed to citric-acid-adsorbed CoFe2O4 NPs for 2 weeks, and tissue accumulation of Co and Fe was assessed. This was compared to pristine CoFe2O4 NPs, and CoCl2 and Fe(III) salts as positive controls. The combined data shows that citric acid enhances free metal ion concentration from CoFe2O4 NPs in aqueous suspension, although in vivo, very similar amounts of assimilated Co were found in isopods exposed to both types of NPs. Therefore, evaluation of the dissolution in suspension by chemical means is not a good predictor of metal assimilation of this model organism; body assimilation of Co and Fe is rather governed by the physiological capacity of P. scaber for the uptake of these metals. Moreover, we propose that citric acid, due to its chelating properties, may hinder the uptake of Co that dissolves from citric-acid-adsorbed CoFe2O4 NPs, if citric acid is present in sufficient quantity. PMID:25437955

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

    PubMed

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

    2010-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Yoon, Sunghyun

    2015-04-01

    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.

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

    PubMed

    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

    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

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  14. Ethanol Gas Sensing of Mn-Doped CoFe$_{2}$O $_{4}$ Nanoparticles

    Microsoft Academic Search

    P. Indra Devi; N. Rajkumar; B. Renganathan; D. Sastikumar; K. Ramachandran

    2011-01-01

    Undoped and Mn-doped cobalt ferrite (CoFe O ) nanoparticles were synthesized and characterized for thermal conductivity and magnetic properties. Room temperature ferro- magnetism and an increase in saturation magnetization due to Mn doping (65.4 emu\\/g for 3 at.% of Mn and 20.8 emu\\/g for undoped CoFe O nanoparticles) are observed. The ethanol gas sensitivity of undoped and Mn-doped (3 at.%)

  15. Magnetic properties of core-shell CoFe2O4@CoFe-FeO nanoparticles at a high H/T regime

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    The magnetic properties of nanopowders of CoFe2O4 and of core-shell CoFe2O4@CoFe-FeO with 6 nm average particle sizes were investigated in the temperature (T) range 5 - 300 K under applied magnetic fields H up to 350 kOe. The coercive fields HC determined from hysteresis loops were found to be highly enhanced compared to samples with larger particles sizes. For instance, for the CoFe2O4 nanoparticles HC was found to be about 22 kOe for T = 5 K. The broad range of applied fields allowed us to establish of the regime of validity for the law of approach (LA) to saturation which, in turn, allowed the determination of the T-dependence for the saturation magnetization MS and for the uniaxial anisotropy constant K1. The core-shell exchange-coupling was found to nearly double the values of MS (= 400 emu/cm3) when compared to the value for the pure CoFe2O4 particles (= 240 emu/cm3). Moreover, the T-dependence of K1 for the core-shell particles presented a maximum close to 100 K with substantially enhanced values. The results will be discussed in terms of a particle model which takes into account a thin amorphous layer and the core-shell structure. Work supported by CNPq and FACEPE. The NHMFL is supported by NSF through NSF-DMR-0084173 and the State of Florida.

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

    PubMed

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

    2013-01-30

    Recently, the intrinsic enzyme-like activity of nanoparticles (NPs) has become a growing area of interest. However, the analytical applications of the NP-based enzyme mimetic are mainly concentrated on their peroxidase-like activity; no attempts have been made to investigate the analytical applications based on the oxidase mimic activities of NPs. For the first time, we report that CoFe(2)O(4) NPs were found to possess intrinsic oxidase-like activity and could catalyze luminol oxidation by dissolved oxygen to produce intensified chemiluminescence (CL). The effect of sulfite on CoFe(2)O(4) NP oxidase mimic-mediated CL of aqueous luminol was investigated. It is very interesting that when adding sulfite to the luminol-CoFe(2)O(4) system, the role of sulfite in the luminol-CoFe(2)O(4) NP-sulfite system depends on its concentration. At a relatively low concentration level, sulfite presents an inhibition effect on the luminol-CoFe(2)O(4) NP system. However, it does have an enhancement effect at a higher concentration level. Investigations on the effect of the solution pH and luminol and CoFe(2)O(4) NP concentrations on the kinetic characteristics of the studied CL system in the presence of trace sulfite suggested that the enhancement and inhibition of the luminol-CoFe(2)O(4) NP-sulfite CL system also depended on the solution pH. It seems that the concentrations of luminol and CoFe(2)O(4) NPs did not influence the CL pathway. The possible mechanism of the luminol-CoFe(2)O(4) NP-sulfite CL system was also discussed. On this basis, a flow injection chemiluminescence method was established for the determination of trace sulfite in this study. Under the optimal conditions, the proposed system could respond down to 2.0 × 10(-8) M sulfite. The method has been applied to the determination of trace sulfite in white wine samples with satisfactory results. The results given by the proposed method are in good agreement with those given by the standard titration method. PMID:23289402

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

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

    PubMed

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

    2014-01-17

    Metal oxide nanoparticles, hybridized with various polymeric chemicals, represent a novel and breakthrough application in drug delivery, hyperthermia treatment and imaging techniques. Radiolabeling of these nanoformulations can result in new and attractive dual-imaging agents as well as provide accurate in vivo information on their biodistribution profile. In this paper a comparison study has been made between two of the most promising hybrid core-shell nanosystems, bearing either magnetite (Fe3O4) or cobalt ferrite (CoFe2O4) cores, regarding their magnetic, radiolabeling, hyperthermic and biodistribution properties. While hyperthermic properties were found to be affected by the metal-core type, the radiolabeling ability and the in vivo fate of the nanoformulations seem to depend critically on the size and the shell composition. PMID:24334365

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

    PubMed Central

    2013-01-01

    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

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

    PubMed

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

    2013-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

  2. 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)

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

    2014-12-01

    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.

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

    Microsoft Academic Search

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

    2007-01-01

    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

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

    PubMed

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

    2013-11-15

    A magnetic nanoscaled catalyst cobalt ferrite (CoFe2O4) was successfully prepared and used for the activation of oxone to generate sulfate radicals for the degradation of diclofenac. The catalyst was characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The effects of calcination temperature, initial pH, catalyst and oxone dosage on the degradation efficiency were investigated. Results demonstrated that CoFe2O4-300 exhibited the best catalytic performance and almost complete removal of diclofenac was obtained in 15 min. The degradation efficiency increased with initial pH decreasing in the pH range of 5-9. The increase of catalyst and oxone dosage both had the positive effect on the degradation of diclofenac. Moreover, CoFe2O4 could retain high degradation efficiency even after being reused for five cycles. Finally, the major diclofenac degradation intermediates were identified and the primary degradation pathways were proposed. PMID:24140535

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

    PubMed

    Abdolmohammad-Zadeh, Hossein; Rahimpour, Elaheh

    2015-06-30

    A simple dispersive solid-phase micro-extraction method based on CoFe2O4 nano-particles (NPs) functionalized with 8-hydroxyquinoline (8-HQ) with the aid of sodium dodecyl sulfate (SDS) was developed for separation of Al(III) ions from aqueous solutions. Al(III) ions are separated at pH 7 via complex formation with 8-HQ using the functionalized CoFe2O4 nano-particles sol solution as a dispersed solid-phase extractor. The separated analyte is directly quantified by a spectrofluorometric method at 370nm excitation and 506nm emission wavelengths. A comparison of the fluorescence of Al(III)-8-HQ complex in bulk solution and that of Al(III) ion interacted with 8-HQ/SDS/CoFe2O4 NPs revealed a nearly 5-fold improvement in intensity. The experimental factors influencing the separation and in situ monitoring of the analyte were optimized. Under these conditions, the calibration graph was linear in the range of 0.1-300ngmL(-1) with a correlation coefficient of 0.9986. The limit of detection and limit of quantification were 0.03ngmL(-1) and 0.10ngmL(-1), respectively. The inter-day and intra-day relative standard deviations for six replicate determinations of 150ngmL(-1) Al(III) ion were 2.8% and 1.7%, respectively. The method was successfully applied to direct determine Al(III) ion in various human serum and water samples. PMID:26041520

  6. Exchange coupling behavior in bimagnetic CoFe2O4/CoFe2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Leite, G. C. P.; Chagas, E. F.; Pereira, R.; Prado, R. J.; Terezo, A. J.; Alzamora, M.; Baggio-Saitovitch, E.

    2012-09-01

    In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe2O4 and ferrimagnetic oxide/ferromagnetic metal CoFe2O4/CoFe2 nanocomposite. The latter compound is a good system to study hard ferrimagnet/soft ferromagnet exchange coupled. Two steps were followed to synthesize the bimagnetic CoFe2O4/CoFe2 nanocomposite: (i) first, preparation of CoFe2O4 nanoparticles using a simple hydrothermal method, and (ii) second, reduction reaction of cobalt ferrite nanoparticles using activated charcoal in inert atmosphere and high temperature. The phase structures, particle sizes, morphology, and magnetic properties of CoFe2O4 nanoparticles were investigated by X-Ray diffraction (XRD), Mossbauer spectroscopy (MS), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) with applied field up to 3.0 kOe at room temperature and 50 K. The mean diameter of CoFe2O4 particles is about 16 nm. Mossbauer spectra revealed two sites for Fe3+. One site is related to Fe in an octahedral coordination and the other one to the Fe3+ in a tetrahedral coordination, as expected for a spinel crystal structure of CoFe2O4. TEM measurements of nanocomposite showed the formation of a thin shell of CoFe2 on the cobalt ferrite and indicate that the nanoparticles increase to about 100 nm. The magnetization of the nanocomposite showed a hysteresis loop that is characteristic of exchange coupled systems. A maximum energy product (BH)max of 1.22 MGOe was achieved at room temperature for CoFe2O4/CoFe2 nanocomposites, which is about 115% higher than the value obtained for CoFe2O4 precursor. The exchange coupling interaction and the enhancement of product (BH)max in nanocomposite CoFe2O4/CoFe2 are discussed.

  7. Synthesis of Trimagnetic Multishell MnFe2 O4 @CoFe2 O4 @NiFe2 O4 Nanoparticles.

    PubMed

    Gavrilov-Isaac, Véronica; Neveu, Sophie; Dupuis, Vincent; Taverna, Dario; Gloter, Alexandre; Cabuil, Valérie

    2015-06-01

    The synthesis and characterization of original ferrite multishell magnetic nanoparticles made of a soft core (manganese ferrite) covered with two successive shells, a hard one (cobalt ferrite) and then a soft one (nickel ferrite), are described. The results demonstrate the modulation of the coercivity when new magnetic shells are added. PMID:25684735

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    PubMed

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

    2015-04-21

    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

  10. A facile thermal decomposition route to synthesise CoFe2O4 nanostructures

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  11. Preparation of CoFe 2O 4/SiO 2 nanocomposites by sol-gel method

    NASA Astrophysics Data System (ADS)

    Huang, Xianghui; Chen, Zhenhua

    2004-10-01

    Nanocomposites with cobalt ferrite nanoparticles uniformly dispersed in silica have been successfully synthesized. The effects of the thermal treatment temperature and the initial drying temperature on the structural and magnetic properties of the nanocomposites were examined. The crystalline phase, the particle size, and the homogeneity of the resulting nanocomposites were studied by X-ray diffraction, IR spectroscopy, differential scanning calorimetry, transmission electron spectroscopy and vibrating sample magnetometer. The xerogels were amorphous. Heat treatment at 400 °C resulted in CoFe 2O 4 clusters being partially formed and when the heat treatment temperature was increased to 600 °C, CoFe 2O 4 clusters were formed in large quantities. The formation reaction of CoFe 2O 4 clusters was accompanied by a rearrangement of the silica matrix network. On further increasing the heat treatment temperature to 800 °C, materials with CoFe 2O 4 nanocrystals, well crystalline dispersed in the silica matrix, could be obtained. By increasing the annealing temperature, composites with a progressive increase of the coercivity and of the remanent magnetization were produced. The remarkable effect of initial drying temperature on the particle size of cobalt ferrite suggested that a well-established silica network provided an effective confinement to the coarsening and aggregation of CoFe 2O 4 nanoparticles.

  12. A new CoFe2O4-Cr2O3-SiO2 fluorescent magnetic nanocomposite

    NASA Astrophysics Data System (ADS)

    Borgohain, Chandan; Senapati, Kula Kamal; Mishra, Debabrata; Sarma, Kanak Ch.; Phukan, Prodeep

    2010-10-01

    A combined sonochemical co-precipitaion method has been developed for the synthesis of a CoFe2O4-Cr2O3-SiO2 magnetic nanocomposite. The synthesis involved the pre-synthesis of CoFe2O4-Cr2O3 nanoparticles, which were subsequently coated with SiO2 by treatment with tetraethyl orthosilicate. It was observed that the as-prepared CoFe2O4-Cr2O3-SiO2 nanocomposite exhibits photoluminescence properties without the addition of any external fluorescent marker. The fluorescent magnetic nanoparticles (FMNPs) had a typical diameter of 30 +/- 5 nm and a saturation magnetization of 5.1 emu g-1 at room temperature. This as-prepared nanocomposite was used for staining cultured HeLa cells for fluorescence imaging.

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

    E-print Network

    Boyer, Edmond

    for controlling its catalytic, gas-sensing, and magnetic properties [22,23,24,25]. Different synthesis techniques1 Title Controlled synthesis of CoFe2O4 nano-octahedra Authors André Luís Lopes" DOI : 10.1016/j.powtec.2014.01.080 #12;2 Hydrothermal synthesis; nanoparticles; cobalt ferrite; shape

  14. Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres.

    PubMed

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

    2015-05-01

    Magnetoelectric 0-1 composites comprising CoFe2O4 (CFO) nanoparticles in a polyvinylidene fluoride (PVDF) polymer-fibre matrix have been prepared by electrospinning. The average diameter of the electrospun composite fibres is ?325 nm, independent of the nanoparticle content, and the amount of the crystalline polar ? phase is strongly enhanced when compared to pure PVDF polymer fibres. The piezoelectric response of these electroactive nanofibres is modified by an applied magnetic field, thus evidencing the magnetoelectric character of the CFO/PVDF 0-1 composites. PMID:25871851

  15. Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  16. Multiferroic and magnetoelectric properties of core-shell CoFe2O4@BaTiO3 nanocomposites

    Microsoft Academic Search

    Kalyan Raidongia; Angshuman Nag; A. Sundaresan; C. N. R. Rao

    2010-01-01

    Core-shell CoFe2O4@BaTiO3 nanoparticles and nanotubes have been prepared using a combination of solution processing and high temperature calcination. Both the core-shell nanostructures exhibit magnetic and dielectric hysteresis at room temperature and magnetoelectric effect. The dielectric constant of both the nanocomposites decreases upon application of magnetic field. The core-shell nanoparticles exhibit 1.7% change in magnetocapacitance around 134 K at 1 T,

  17. In situ powder X-ray diffraction study of magnetic CoFe2O4 nanocrystallite synthesis

    NASA Astrophysics Data System (ADS)

    Andersen, Henrik L.; Christensen, Mogens

    2015-02-01

    The evolution of size and size distribution during hydrothermal synthesis of nanocrystalline CoFe2O4 has been studied by in situ synchrotron powder X-ray diffraction (PXRD). Varying synthesis temperature or [OH-] concentration in the precursor proves to have no significant effect on the final volume-weighted nanocrystallite sizes (~12 nm) of CoFe2O4. However, analysis by whole powder pattern modeling of the [OH-] concentration series reveals a substantial difference in the number-weighted size distributions when varying the amount of base used. Furthermore, changing the metal ion concentration prior to NaOH addition in the precursor preparation gives a handle to control the nanoparticle sizes (~5-15 nm). All in situ experiments show almost instantaneous formation of the CoFe2O4 nanocrystallites, without significant growth or broadening of the size distribution after 60 s. Magnetic hysteresis curve measurements illustrate, how this facilitates the tailoring of materials with specific magnetic properties, as larger particles (~15 nm) exhibit hard magnetic properties while the smaller particles (~6-7 nm) are superparamagnetic.The evolution of size and size distribution during hydrothermal synthesis of nanocrystalline CoFe2O4 has been studied by in situ synchrotron powder X-ray diffraction (PXRD). Varying synthesis temperature or [OH-] concentration in the precursor proves to have no significant effect on the final volume-weighted nanocrystallite sizes (~12 nm) of CoFe2O4. However, analysis by whole powder pattern modeling of the [OH-] concentration series reveals a substantial difference in the number-weighted size distributions when varying the amount of base used. Furthermore, changing the metal ion concentration prior to NaOH addition in the precursor preparation gives a handle to control the nanoparticle sizes (~5-15 nm). All in situ experiments show almost instantaneous formation of the CoFe2O4 nanocrystallites, without significant growth or broadening of the size distribution after 60 s. Magnetic hysteresis curve measurements illustrate, how this facilitates the tailoring of materials with specific magnetic properties, as larger particles (~15 nm) exhibit hard magnetic properties while the smaller particles (~6-7 nm) are superparamagnetic. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06937d

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

    PubMed

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

    2013-05-15

    In this study, an attempt was made to render both the magnetic and photocatalytic properties in a semiconductor material to enhance the efficiency of degradation and recycling possibility of magnetic nanophotocatalysts. CoFe2O4 and CoFe2O4 loaded ZnO nanoparticles were prepared by a simple co-precipitation method and characterized using various analytical tools and in addition to check its visible light assisted photocatalytic activity. CoFe2O4/ZnO nanocatalyst coupled with acceptor, peroxomonosulphate (PMS) showed 1.69-fold enhancement in Direct Blue 71 (triazo dye; DB71) mineralization within 5h. The accomplished enrichment in decolorization was due to the production of more number of non-selective and active free radicals at the catalyst surface. PMID:23523908

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    PubMed

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

    2014-06-14

    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

  1. Effect of structure on magnetoelectric properties of CoFe 2O 4–BaTiO 3 multiferroic composites

    Microsoft Academic Search

    Giap V. Duong; R. Groessinger; R. Sato Turtelli

    2007-01-01

    The 50%CoFe2O4–50%BaTiO3 (in mass) composites with four different building structures, namely: CoFe2O4–BaTiO3 core–shell structure with CoFe2O4 in core, BaTiO3–CoFe2O4 core–shell structure with BaTiO3 in core, CoFe2O4–BaTiO3 mixed structure, and BaTiO3–CoFe2O4–BaTiO3 layer structure, have been synthesized and studied. The core–shell structures give higher magnetoelectric (ME) coefficients compared to the other structures. When using CoFe2O4 as core, the ME coefficient is highest,

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    PubMed Central

    2013-01-01

    Transition metal ferrites such as CoFe2O4, possessing a large magnetostriction coefficient and high Curie temperature (Tc > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0–3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 ?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

  4. Formation Mechanism and Shape Control of Monodisperse Magnetic CoFe2O4 Nanocrystals

    SciTech Connect

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

    2009-07-28

    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.

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

    PubMed

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

    2013-01-01

    Transition metal ferrites such as CoFe2O4, possessing a large magnetostriction coefficient and high Curie temperature (Tc > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0-3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 ?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

  6. Nanolamellar magnetoelectric BaTiO3–CoFe2O4 bicrystal

    E-print Network

    Ren, Shenqiang; Laver, Mark; Wuttig, Manfred

    2009-10-13

    Nanolamellar magnetoelectric BaTiO3–CoFe2O4 bicrystal Shenqiang Ren,1 Mark Laver,2 and Manfred Wuttig1,a#1; 1Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115, USA 2NIST Center for Neutron... 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...

  7. Converse magnetoelectric effect in CoFe2O4-BaTiO3 composites with a core-shell structure

    Microsoft Academic Search

    V. V. Shvartsman; F. Alawneh; P. Borisov; D. Kozodaev; D. C. Lupascu

    2011-01-01

    Multiferroic composites were prepared by covering CoFe2O4 nanoparticles with a shell of BaTiO3 using a sol-gel technique. Scanning probe microscopy confirmed the formation of a core-shell structure with a magnetic core and a piezoelectric shell. The converse magnetoelectric effect was studied at different temperatures and bias fields. The magnetoelectric coefficient peaks at approximately 270 K and reaches the value alphaC≈(2.2

  8. Magnetism of sol-gel fabricated CoFe2O4/SiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Vejpravová, J.; Sechovský, V.; Plocek, J.; Niž?anský, D.; Hutlová, A.; Rehspringer, J.-L.

    2005-06-01

    Details of synthesis and characterization of sol-gel-produced CoFe2O4 nanoparticles embedded in the amorphous SiO2 matrix are presented together with results of an extended magnetization study of these materials. The particle size was found to increase from 6to15nm by varying the temperature of a subsequent annealing from 800to1100°C. All samples exhibited superparamagnetic behavior with values of the blocking temperature TB increasing with the particle size. At temperatures above TB the magnetization curves follow the expected Langevin scaling of M vs H /T, which is consistent with the formation of the superparamagnetic state. For T

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

    PubMed

    Praveena, K; Srinath, S

    2014-06-01

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

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

    Microsoft Academic Search

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

    2005-01-01

    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)

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

    Microsoft Academic Search

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

    2008-01-01

    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

  12. Multiferroic BaTiO3-CoFe2O4 Nanostructures

    Microsoft Academic Search

    H. Zheng; J. Wang; S. E. Lofland; Z. Ma; L. Mohaddes-Ardabili; T. Zhao; L. Salamanca-Riba; S. R. Shinde; S. B. Ogale; F. Bai; D. Viehland; Y. Jia; D. G. Schlom; M. Wuttig; A. Roytburd; R. Ramesh

    2004-01-01

    We report on the coupling between ferroelectric and magnetic order parameters in a nanostructured BaTiO3-CoFe2O4 ferroelectromagnet. This facilitates the interconversion of energies stored in electric and magnetic fields and plays an important role in many devices, including transducers, field sensors, etc. Such nanostructures were deposited on single-crystal SrTiO3 (001) substrates by pulsed laser deposition from a single Ba-Ti-Co-Fe-oxide target. The

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

    NASA Astrophysics Data System (ADS)

    Wang, W. H.; Ren, X.

    2006-04-01

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

  14. Robust SiO2-modified CoFe2O4 hollow nanofibers with flexible room temperature magnetic performance.

    PubMed

    Jing, Panpan; Pan, Lining; Du, Jinlu; Wang, Jianbo; Liu, Qingfang

    2015-05-01

    A range of robust SiO2-modified CoFe2O4 hollow nanofibers with high uniformity and productivity were successfully prepared via polyvinylpyrrolidone-sol assisted electrospinning followed by annealing at a high temperature of 1000 °C, and they were characterized using scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction and X-ray photoelectron spectroscopy in detail. It was demonstrated that amorphous SiO2 has a significant influence on not only the surface morphology, microstructure and crystalline size but also the room temperature magnetic performance of the inverse spinel CoFe2O4 nanofibers. The pure CoFe2O4 sample shows a particle chain rod-shape appearance but the SiO2-modified CoFe2O4 sample shows a robust hollow fibrous structure. With increasing SiO2 content, an increase at first and then a decrease in coercivity (Hc) and monotonously a decrease in saturation magnetization (Ms) have been determined in the obtained modified CoFe2O4 hollow nanofibers. A maximum Ms of about 80 emu g(-1) and a maximum Hc of about 1477 Oe could be, respectively, acquired from the pure CoFe2O4 nanorods and the modified CoFe2O4 hollow nanofibers with about 14.9% SiO2. The changes in Ms, Hc and the structure evolution mechanism of these SiO2-modified CoFe2O4 hollow nanofibers have been elaborated systematically. Furthermore, it is suggested that amorphous SiO2 enables effectively improving the structure endurance of 1D electrospun inorganic oxide hollow nanostructures being subjected to high temperatures. PMID:25907405

  15. A novel nonenzymatic hydrogen peroxide sensor based on LaNi0.5Ti0.5O3/CoFe2O4 modified electrode.

    PubMed

    Ye, Daixin; Xu, Yanhong; Luo, Liqiang; Ding, Yaping; Wang, Yulong; Liu, Xiaojuan; Xing, Lijun; Peng, Jinwei

    2012-01-01

    A novel nonenzymatic hydrogen peroxide (H(2)O(2)) sensor based on LaNi(0.5)Ti(0.5)O(3)/CoFe(2)O(4) nanoparticles modified glassy carbon electrode (LNT-CFO/GCE) was proposed. Perovskite-type nanocomposite oxide LaNi(0.5)Ti(0.5)O(3)/CoFe(2)O(4) was synthesized by sol-gel method and characterized by X-ray diffraction and transmission electron microscopy. The electrochemical properties of the modified electrode were studied by cyclic voltammetry and amperometry, which showed an excellent electrocatalytic activity for the oxidation of H(2)O(2). Under the optimum conditions, the linear response was obtained in the range of 0.1 ?M to 8.2 mM, with the correlation coefficient of 0.997. The sensitivity of the modified electrode was calculated to be 3.21 ?A ?M(-1) cm(-2) and the detection limit was 23 nM (based on the S/N=3). PMID:21917429

  16. Local dielectric measurements of BaTiO3?CoFe2O4 nanocomposites through microwave microscopy

    Microsoft Academic Search

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

    2007-01-01

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

  17. Nucleation of electroactive beta-phase poly(vinilidene fluoride) with CoFe2O4 and NiFe2O4 nanofillers: a new method for the preparation of multiferroic nanocomposites

    Microsoft Academic Search

    P. Martins; C. M. Costa; S. Lanceros-Mendez

    2011-01-01

    Multiferroic and magnetoelectric materials show enormous potential for technological developments. Multiferroic composites are more attractive for applications due to their enhanced properties with respect to single-phase multiferroic materials. In this paper we report on the nucleation of the electroactive beta-phase of poly(vinylidene fluoride), PVDF, by the addition of CoFe2O4 and NiFe2O4 nanoparticles in order to prepare poly(vinylidene fluoride)\\/ferrite nanocomposite for

  18. CoFe2O4 polypyrrole (PPy) nanocomposites: new multifunctional materials

    NASA Astrophysics Data System (ADS)

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

    2004-04-01

    Spinel ferrites (iron cobalt oxide) were prepared by the microemulsion method at different temperatures and sodium dodecyl sulphate (SDS) surfactant concentrations. Subsequently, a quantity of the different samples were coated with an intrinsically conducting polymer (ICP) shell of polypyrrole. The polymer shell was synthesized by a chemical route after the ferrites particle production. By combining in a single material the electrical conductivity of ICPs and the magnetic properties of nanopowder ferrites, new multifunctional materials have been developed. Different CoFe2O4 grain size particles were obtained ranging from 3 to 30 nm, as determined by x-ray diffraction (XRD). Particles with grain size below a critical size exhibit a superparamagnetic behaviour. These superparamagnetic particles, without and with a conducting polymer shell, were analysed by transmission electron microscopy (TEM) to find the grains' morphology and the growth evolution of the polypyrrole shell in the ferrites grains. The electrical conductivity of the nanocomposite was measured by the four points probe method, showing values of 120 ± 4 S cm-1 at ambient temperature. The behaviour of the magnetization and the coercivity with temperature, from nearly 0 K to the ambient, were measured in a vibrating sample magnetometer (VSM).

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  20. Response surface measurement for BiFeO3-CoFe2O4 multiferroic nanocomposite

    Microsoft Academic Search

    B. E. Piccone; J. E. Blendell; R. E. Garcia

    2008-01-01

    A thin film BiFeO3 - CoFe2O4 multiferroic nanocomposite has been investigated to determine the coupling between the two phases in a constrained film by combining piezoelectric force microscopy and an externally applied magnetic field. In addition, finite element modeling was carried out to fully explain the observed local piezoelectric response. The results of the experiments and modeling show that the

  1. Magnetic annealing effects on multiferroic BiFeO 3\\/CoFe 2O 4 bilayered films

    Microsoft Academic Search

    Xianwu Tang; Jianming Dai; Xuebin Zhu; Wenhai Song; Yuping Sun

    2011-01-01

    In situ magnetic annealing effects on c-axis-preferred multiferroic BiFeO3\\/CoFe2O4 bilayered by chemical solution deposition route are investigated. It is observed that magnetic annealing can enhance the crystallization quality, texture and densification as well as dielectric properties. In addition, the magnetolosses decrease with increasing the magnetic fields. Moreover, both increase of the polarization and decrease of the leakage current due to

  2. Near room temperature giant magnetodielectricity in BiFeO3/CoFe2O4 composite

    NASA Astrophysics Data System (ADS)

    Kuila, S.; Ray, J.; Biswal, A. K.; Vishwakarma, P. N.

    2015-06-01

    Here we report near room temperature giant magnetodielectric observed in BiFeO3/CoFe2O4 composite. This composite is prepared in slightly un-conventional method involving sol-gel auto combustion route. Phase purity has been confirmed by Reitweld refinement of powder x-ray diffraction data. Highest magnetodielectric (in %) of 62% is seen at 320K. Most interesting, in the temperature range (300 - 350K) of measurement, magnetodielectric has not gone below 50%.

  3. Electromagnetic properties of microwave sintered xTiO2 + (1 - x) CoFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Sadhana, K.; Praveena, K.; Raju, P.; Murthy, S. R.

    2012-09-01

    The nanocomposites of xTiO2 + (1 - x) CoFe2O4 (where 0 ? x ? 1) were prepared using microwave-hydrothermal method at 165 °C/45 min. The as-synthesized powders were characterized using X-ray diffraction (XRD), transmission electron microscope and Fourier transform infrared spectroscopy. The particle size was found to be ~18, ~22 and 24 nm for TiO2, CoFe2O4, 50 mol% TiO2 + 50 mol% CoFe2O4 composite powder, respectively. The as-prepared powders were densified at 500 °C/30 min using microwave sintering method. The sintered composite samples were characterized using XRD and field emission scanning electron microscopy. The bulk densities of the present composites were increasing with an addition of TiO2. The saturation magnetization of composites decreased with an increase of TiO2 content. The grain sizes of all the composite lies between 54 and 78 nm. The addition of TiO2 to ferrite increased ?' and ?? and the resonant frequency of all the sintered samples were found to be >1 GHz. The value of ?? found to increase with an increase of TiO2.

  4. Electrical and magnetic properties of BiFeO3-CoFe2O4 nanotube composite

    NASA Astrophysics Data System (ADS)

    Sudakar, Chandran; Dixit, Ambesh; Bheema Sahana, Moodakare; Lawes, Gavin; Naik, Ratna; Naik, Vaman M.

    2009-03-01

    We report the electrical and magnetic properties of BiFeO3 and CoFe2O4 nanotube composite multiferroics. CoFe2O4 nanotubes were prepared on Pt coated Si substrates using a template assisted method, yielding nanotubes with 20-50 nm thick walls and an outer diameter of 200 to 400 nm. These nanotubes were then uniformly coated by a BiFeO3 layer by a metal organic decomposition method to yield the composite multiferroics. We observed ferroelectric switching behavior with saturated hysteresis loops with Pr and Ec values of approximately 0.08 ?C/cm^2 and 15 kV/cm, respectively, for a maximum applied electric field of 50 kV/cm. For pure BiFeO3 thin films the hysteresis curves do not show any saturating trend and the Ec is three times smaller than that of the composite. The magnetic measurements show that the pure BiFeO3 is non-ferrimagnetic, while the composite shows a clear hysteresis with saturation magnetization of ˜12 emu/cm^3. These composite BiFeO3 -- CoFe2O4 structures provide an approach for studying magnetoelectric coupling at the interfaces between different ferroic materials.

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

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

    E-print Network

    Spinu, Leonard

    Articles Magnetoelectric coupling of multilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4 film by piezoresponse forceRole of spinel substrate in the morphology of BiFeO3-CoFe2O4 epitaxial nanocomposite films Ilan microscopy under magnetic field J. Appl. Phys. 112, 074110 (2012) Coexistence of coupled magnetic phases

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

    PubMed

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

    2013-12-15

    In this study, we adopted the chemical co-precipitation (CP) method and sol-gel method followed by calcination at temperatures of 100-900°C for 12h to synthesize CoFe2O4 materials, which were further characterized by TEM, XRD and XPS techniques. The properties of CoFe2O4 materials were evaluated in a microwave (MW) induced catalytic oxidation (MICO) process for the elimination of brilliant green (BG). The results showed that: (1) the removal rates of BG gradually decreased over a series of CoFe2O4 materials prepared by CP method and calcinated with 100-700°C (except 900°C) for 12h within three reuse cycles; for comparison, no removal of BG was obtained over CoFe2O4 synthesized by sol-gel method and CoFe2O4-900 (CP); (2) no hydroxyl radicals were captured with salicylic acid used as molecular probe in the MICO process; (3) MW irradiation enhanced the release of residual NaOH within the microstructure of CoFe2O4 and further discolored BG, because BG is sensitive to pH; (4) granular activated carbon (GAC), an excellent MW-absorbing material possessing higher dielectric loss tangent compared to that of a series of CoFe2O4 materials, could not remove BG in suspensions at a higher efficiency, even if the loading amount was 20 g L(-1). Accordingly, MICO process over CoFe2O4 materials and GAC could not effectively eliminate BG in suspensions. PMID:24220199

  8. Structural and morphological characterization of FeCo 2O 4 and CoFe 2O 4 spinels prepared by a coprecipitation method

    Microsoft Academic Search

    T. A. S. Ferreira; J. C. Waerenborgh; M. H. R. M. Mendonça; M. R. Nunes; F. M. Costa

    2003-01-01

    Due to the importance of cation distribution in the physical properties of spinels, a structural and morphological study of the FeCo2O4 and CoFe2O4 spinels prepared by a low-temperature coprecipitation method has been undertaken. Only spinel phases are observed after annealing at 570 K. However, up to 770 K the sample with global composition CoFe2O4 was chemically heterogeneous. At 1170 K, a single homogeneous

  9. Large magnetoelectric properties in CoFe2O4:BaTiO3 core-shell nanocomposites

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Arka; Mandal, Kalyan

    2015-03-01

    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.

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

    PubMed

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

    2012-05-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    PubMed

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

    2015-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

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

    Microsoft Academic Search

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

    2008-01-01

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

  18. Multiferroic Double-layer BiFeO3-CoFe2O4 Composite Films Prepared by Pulsed-Laser Deposition

    Microsoft Academic Search

    Yanyan Zhu; Jinrong Cheng; Shengwen Yu; Wenbiao Wu; Zhongyan Meng

    2007-01-01

    Multiferroic BiFeO3-CoFe2O4 (BFO-CFO) double-layer thin film has been deposited on platinized silicon substrate by pulsed-laser deposition. The BFO and CFO thin layers are deposited at 450 and 600 degC respectively. The diffraction peaks from spinel CoFe2O4 phases can be observed from the x-ray diffraction patterns of the double-layer BFO-CFO films. Dielectric constant and loss of the BFO-CFO films are of

  19. Pinning of Ferroelectric Domain Walls in Nanostructured CoFe2O4-BiFeO3 Composite

    NASA Astrophysics Data System (ADS)

    Freedy, Keren; Comes, Ryan; Siebein, Kerry; Lu, Jiwei; Wolf, Stuart

    2015-03-01

    Ferroelectric domain walls in BiFeO3(BFO) thin films have attracted interest due to the observation of enhanced electronic transport at the domain walls in an otherwise insulating material. To understand the properties of domain walls in nanostructured thin films having matrix-pillar morphology, thin films of CoFe2O4 (CFO)-BFO were grown epitaxially by pulsed electron deposition on SrTiO3 (STO) substrates. Piezoresponse force microscopy (PFM) measurements indicate that the vertically-oriented CFO nanopillars act as pinning sites for the in-plane domain walls. The pinning effect is most likely due to misfit dislocations at the matrix/pillar interface which have been identified in transmission electron microscopy images. The ability to produce ordered nanocomposites by directed self-assembly offers potential for more extensive investigation of domain wall behavior.

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

    PubMed

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

    2013-08-14

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

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

    PubMed Central

    2014-01-01

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

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

    Microsoft Academic Search

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

    1975-01-01

    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.

  3. Microstructure and properties of well-ordered multiferroic Pb(Zr,Ti)O(3)/CoFe(2)O(4) nanocomposites.

    PubMed

    Gao, Xingsen; Rodriguez, Brian J; Liu, Lifeng; Birajdar, Balaji; Pantel, Daniel; Ziese, Michael; Alexe, Marin; Hesse, Dietrich

    2010-02-23

    A nanofabrication technique combining pulsed laser deposition and a nanoporous anodic aluminum oxide membrane mask is being proposed to prepare various types of multiferroic nanocomposites, viz. periodically ordered CoFe(2)O(4) dots covered by a continuous Pb(Zr,Ti)O(3) layer, Pb(Zr,Ti)O(3) dots covered with CoFe(2)O(4), and Pb(Zr,Ti)O(3)/CoFe(2)O(4) bilayer heterostructure dots. By properly tuning the processing parameters, epitaxial nanodot-matrix composites can be obtained. For the composite consisting of CoFe(2)O(4) nanostructures covered by a Pb(Zr,Ti)O(3) film, an unexpected out-of-plane magnetic easy axis induced by the top Pb(Zr,Ti)O(3) layer and a uniform microdomain structure can be observed. The nanocomposites tested by piezoresponse force microscopy (PFM) exhibit strong piezoelectric signals, and they also display magnetoelectric coupling revealed by magnetic-field dependent capacitance measurement. PMID:20112922

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

    E-print Network

    Rubloff, Gary W.

    Multiferroic properties of Pb,,Zr,Ti...O3/CoFe2O4 composite thin films N. Ortega,a P. Bhattacharya multiferroic thin films. It was claimed that since the magnetoelectric coupling is through elastic interaction; published online 26 December 2006 In the present work we report multiferroic behavior in lead zirconate

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

    PubMed

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

    2012-03-01

    A reusable photocatalytic TiO2/CoFe2O4 composite nanofiber was directly formed by using a vertical two-spinneret electrospinning process and sol-gel method, followed by heat treatment at 550 degrees C for 2 h. The high photocatalytic activity of the composite nanofibers depends on the good morphology of the fibers and the appropriate calcination temperature. The crystal structure and magnetic properties of the fibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The photocatalytic activity of the TiO2/CoFe2O4 fibers was investigated through ultraviolet-visible absorbance following the photo-oxidative decomposition of phenol. Meanwhile, the presence of CoFe2O4 not only broadens the response region of visible light, but also enhances the absorbance of UV light. Furthermore, these fibers displayed photocatalytic activity associated with magnetic activity of CoFe2O4 ferrites, allowing easy separated of the photocatalysts after the photo-oxidative process and effectively avoided the secondary pollution of the treated water. PMID:22755080

  6. Coin-like ?-Fe2O3@CoFe2O4 core-shell composites with excellent electromagnetic absorption performance.

    PubMed

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

    2015-03-01

    In this paper, we designed a novel core-shell composite for microwave absorption application in which the ?-Fe2O3 and the porous CoFe2O4 nanospheres served as the core and shell, respectively. Interestingly, during the solvothermal process, the solvent ratio (V) of PEG-200 to distilled water played a key role in the morphology of ?-Fe2O3 for which irregular flake, coin-like, and thinner coin-like forms of ?-Fe2O3 can be produced with the ratios of 1:7, 1:3, and 1:1, respectively. The porous 70 nm diameter CoFe2O4 nanospheres were generated as the shell of ?-Fe2O3. It should be noted that the CoFe2O4 coating layer did not damage the original shape of ?-Fe2O3. As compared with the uncoated ?-Fe2O3, the Fe2O3@CoFe2O4 composites exhibited improved microwave absorption performance over the tested frequency range (2-18 GHz). In particular, the optimal reflection loss value of the flake-like composite can reach -60 dB at 16.5 GHz with a thin coating thickness of 2 mm. Furthermore, the frequency bandwidth corresponding to the RLmin value below -10 dB was up to 5 GHz (13-18 GHz). The enhanced microwave absorption properties of these composites may originate from the strong electron polarization effect (i.e., the electron polarization between Fe and Co) and the electromagnetic wave scattering on this special porous core-shell structure. In addition, the synergy effect between ?-Fe2O3 and CoFe2O4 also favored balancing the electromagnetic parameters. Our results provided a promising approach for preparing an absorbent with good absorption intensity and a broad frequency that was lightweight. PMID:25664491

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  9. Multiferroic behavior and impedance spectroscopy of bilayered BiFeO3/CoFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Wu, Jiagang; Wang, John

    2009-06-01

    Lead-free bilayered multiferroic thin films consisting of BiFeO3 (BFO) and CoFe2O4 (CFO) layers with different thicknesses were grown on SrRuO3-coated Pt/TiO2/SiO2/Si substrates by radio frequency sputtering. The effects of constituent layer thicknesses on the ferroelectric and magnetic behavior have been studied. The physical behaviors are shown to strongly depend on the thicknesses of the constituent layers. BFO (220 nm)/CFO (30 nm) bilayered thin film demonstrated much improved ferroelectric and ferromagnetic behavior (2Pr=144.2 ?C/cm2, 2Ec=778.0 kV/cm, Ms=61.2 emu/cm3, and Hc=200.8 Oe) as compared to those of the single layer BFO thin film. The dielectric behavior and conductivity of BFO (220 nm)/CFO (30 nm) bilayered thin film were investigated as a function of both temperature (in the range of 294-534 K) and frequency (in the range of 10-1-106 Hz), where an activation energy of ˜1.11 eV for dielectric relaxation was demonstrated. From the conductivity behavior, an activation energies of ˜0.98 eV was derived for dc conductivity are, implying that oxygen vacancies are involved in the conduction of the BFO (220 nm)/CFO (30 nm) bilayered film.

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

    NASA Astrophysics Data System (ADS)

    Ren, Shenqiang; Wuttig, Manfred

    2008-02-01

    A new magnetoelectric hybrid device composed of a nanoparticulate magnetostrictive iron oxide-cobalt ferrite film on a piezoelectric lead zirconic titanate crystal serving as both substrate and straining medium is described. Nano-Fe3O4/CoFe2O4 particles, ranging from 5to42nm, were prepared using a variation of the sol-gel method. A small electric field, 5-10kVcm-1, applied at the coercive field of the nano-Fe3O4/CoFe2O4 component modulates the film magnetization up to 10% of the saturation magnetization of ferrite. At the smallest particle size of 5nm, the coercive field is as low as 25Oe and the inverse MEE voltage coefficient is as high as (10.1V/cmOe)-1.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Nguyen, Van Cuong; Huynh, Thi Kim Ngoc

    2014-06-01

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

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

    Microsoft Academic Search

    Joachim Wagner; Tina Autenrieth; Rolf Hempelmann

    2002-01-01

    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

  14. Structural, microstructural and magnetic properties of NiFe 2 O 4 , CoFe 2 O 4 and MnFe 2 O 4 nanoferrite thin films

    Microsoft Academic Search

    Kuldeep Chand Verma; Virender Pratap Singh; Mast Ram; Jyoti Shah; R. K. Kotnala

    2011-01-01

    The structural, microstructural and magnetic properties of nanoferrite NiFe 2 O 4 (NF), CoFe 2 O 4 (CF) and MnFe 2 O 4 (MF) thin films have been studied. The coating solution of these ferrite films was prepared by a chemical synthesis route called sol-gel combined metallo-organic decomposition method. The solution was coated on Si substrate by spin coating and

  15. Structural, microstructural and magnetic properties of NiFe 2O 4, CoFe 2O 4 and MnFe 2O 4 nanoferrite thin films

    Microsoft Academic Search

    Kuldeep Chand Verma; Virender Pratap Singh; Mast Ram; Jyoti Shah; R. K. Kotnala

    2011-01-01

    The structural, microstructural and magnetic properties of nanoferrite NiFe2O4 (NF), CoFe2O4 (CF) and MnFe2O4 (MF) thin films have been studied. The coating solution of these ferrite films was prepared by a chemical synthesis route called sol–gel combined metallo-organic decomposition method. The solution was coated on Si substrate by spin coating and annealed at 700°C for 3h. X-ray diffraction pattern has

  16. Magnetoelectric and multiferroic properties of variously oriented epitaxial BiFeO3-CoFe2O4 nanostructured thin films

    Microsoft Academic Search

    Li Yan; Zhiguang Wang; Zengping Xing; Jiefang Li; D. Viehland

    2010-01-01

    We report the ferroelectric, ferromagnetic, and magnetoelectric (ME) properties of self-assembled epitaxial BiFeO3-CoFe2O4 (BFO-CFO) nanostructure composite thin films deposited on (001), (110), and (111) SrTiO3 (STO) single crystal substrates. These various properties are shown to depend on orientation. The maximum values of the relative dielectric constant, saturation polarization, longitudinal piezoelectric coefficient, saturation magnetization, and ME coefficient at room temperature were

  17. Investigation of Dielectric and Noise Properties of the Multiferoic Composite BaTiO3 with CoFe2O4

    Microsoft Academic Search

    J. Banys; T. Ramoška; J. Matukas; S. Pralgauskait?; F. M. M. Alawneh; V. V. Shvartsman; D. C. Lupascu

    2011-01-01

    Dielectric and noise characteristics of CoFe2O4-BaTiO3 ceramic composites were investigated. The complex dielectric permittivity displays a broad maximum around 300 K, where a phase transition occurs. The dielectric spectra of the complex dielectric permittivity are caused by the conductivity above 300 K. Intensive almost periodic telegraphic noise with relaxation type spectra is observed in the same temperature range (around 300 K).

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  19. Inhomogeneity Induced Conductivity Fluctuation in YBa2Cu3O7-?/BaTiO3-CoFe2O4 Composite

    NASA Astrophysics Data System (ADS)

    Sahoo, Mousumibala; Behera, Dhrubananda

    2013-08-01

    Polycrystalline (1-x)YBa2Cu3O7-y + xBaTiO3-CoFe2O4(x = 0.0, 0.2, 0.4, 0.6 wt.%) superconductors were prepared by solid state route. XRD analysis reveals no significant change in "b" parameter and increase in "a" and "c" parameters. SEM micrographs show no change in grain size of the samples. With the increase of BaTiO3-CoFe2O4 (BTO-CFO) addition it has been analyzed that the superconducting transition temperatures (Tc) determined from standard four-probe method was decreased and dropped sharply with higher wt.% addition. Excess conductivity fluctuation analysis using Aslamazov-Larkin model fitting reveals transition of two dominant regions (2D and 3D) above Tc. The decrease in 2D-3D crossover temperature TLD (Lawerence-Doniach temperature) in the mean field region has been observed as a consequent dominance of 3D region to increase in wt.% in the composite. The increasing value of ?wl and ?0 and the decreasing trend in the value of zero-resistance critical temperature (Tc0) indicates that the connectivity between grains decreases gradually with the addition of magneto-electric composite BTO-CFO.

  20. Multiferroic CoFe2O4-Pb(Zr(0.52)Ti(0.48))O3 core-shell nanofibers and their magnetoelectric coupling.

    PubMed

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

    2011-08-01

    Multiferroic CoFe(2)O(4)-Pb(Zr(0.52)Ti(0.48))O(3) 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 CoFe(2)O(4) and perovskite structure of Pb(Zr(0.52)Ti(0.48))O(3) 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 × 10(4) mV/cmOe, two orders of magnitude higher than multiferroic thin films of similar composition. PMID:21643573

  1. Multiferroic properties of Pb0.90Sr0.10TiO3-CoFe2O4 nanostructured bilayered thin film

    NASA Astrophysics Data System (ADS)

    Bala, Kanchan; Kotnala, R. K.; Negi, N. S.

    2015-05-01

    Pb0.90Sr0.10TiO3-CoFe2O4(PST10-CFO) nanostructured bilayered thin film were grown on Si (100) substrate by using metallo-organic decomposition chemical route and spin coating technique. Results show that PST (pervoskite structure) and CFO (spinel) phase coexist in the bilayered thin films, annealed at 650°C for 2hr and no obvious impurity phase can be detected. The structural, surface morphology and micro structural properties were confirmed by X-Ray diffraction (XRD), atomic force microscope (AFM) respectively. Excellent ferroelectric behavior at different voltage was observed, with two platinum electrodes only at surface of the bilayer thin film. A room temperature ferromagnetic behavior was observed in the bilayered Pb0.90Sr0.10TiO3-CoFe2O4 nanostructured thin film. The saturation magnetization and variation in coercivity value of the bilayer thin film is lower than that of the pure CFO film in the presence of non ferromagnetic PST layer which is the attributed that the significant coupling between the two phases.

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

    E-print Network

    Volinsky, Alex A.

    transition metals [4,6e11], transition metal oxides [12e18], transition metal halides [19e21 transition metal oxides have better catalytic performance with MgH2 [24], such as Cr2O3 and Fe2O3 [7,16]. Li] and intermetallic compounds [22,23]. Since the transition metals have multiple valence states, the corresponding

  3. Synthesis of coaxial CoFe2O4 - K0.5Na0.5NbO3 nanotubes by sol-gel technique using inexpensive templates

    NASA Astrophysics Data System (ADS)

    Chitralekha, C. S.; Rasi, Mohammed; Aravind, P. B.; Anantharaman, M. R.; Nair, Swapna. S.

    2015-06-01

    A modified sol-gel method was introduced by employing a cost effective novel template to synthesize coaxial one dimensional (1-D) composite nanostructures based on CoFe2O4 (CFO) - K0.5Na0.5NbO3 (KNN) and magnetic nanostructures based on CoFe2O4 (CFO). The studies with scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that the composite material is characterized by the 1-D tubular structure. The absorption edge is blue shifted for both KNN and CFO nanotubes due to the lattice strain effect.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  5. Large converse magnetoelectric effect in Na0.5Bi0.5TiO3-CoFe2O4 lead-free multiferroic composites

    NASA Astrophysics Data System (ADS)

    Narendra Babu, S.; Malkinski, Leszek

    2012-04-01

    Lead-free multiferroic composites of ferroelectric, Na0.5Bi0.5TiO3 (NBT) and ferrimagnetic, CoFe2O4 (CFO) were synthesized by the solid-state sintering method and a systematic study of structural, magnetic, and magnetoelectric properties was undertaken. X-ray diffraction and field emission scanning electron microscopy displayed the formation of single phase for parent phases and the presence of both phases in the composites. Magnetic properties were investigated using a vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR) measurements at room temperature. Strong magnetoelectric (ME) coupling was demonstrated by an electric field tunable FMR field shift. A large value of converse ME coefficient 109 Oe-cm kV-1 was observed for NBT/CFO 70/30 composite. Furthermore, these lead-free multiferroic composites exhibiting a large converse magnetoelectric effect at room temperature provide great opportunities for electrostatically tunable devices at microwave frequencies.

  6. Magnetoelectricity of lateral 1-3 type composites with CoFe2O4 ferromagnetic microstrips embedded in (K,Na)NbO3-based piezoceramic substrate

    NASA Astrophysics Data System (ADS)

    Xu, Ying; Li, Jing-Feng; Ma, Jing; Nan, Ce-Wen

    2011-08-01

    Microscale 1-3-type-like magnetoelectric (ME) composites with ferromagnetic microstrips laterally embedded in a piezoelectric ceramic substrate were fabricated by a dice-and-insert method. Mechanically sliced microstrips of Li/Ta-modified (K,Na)NbO3 lead-free ceramics and CoFe2O4 ceramics were used as the piezoelectric and piezomagnetic phases, respectively, which were inserted into each other and bonded together by epoxy. The ME properties of such 1-3-type-like composites with piezoelectric substrates were verified. The maximum ME coefficient was found to vary with the strip size, substrate thickness, and thickness of epoxy bonding layers. A maximum value of 48 mV/(cm.Oe) was achieved. In addition, a special anisotropy was obtained in the present lateral 1-3 type ceramic composites and made it have potential applications in detecting magnetic field directions.

  7. Magnetic and thermoelectric properties of Fe3-xCoxO4 thin films and CoFe2O4/Fe3O4 superlattices

    NASA Astrophysics Data System (ADS)

    Nguyen van, Quang; Christian, Meny; Duong, Anh Tuan; Shin, Yooleemi; S. H, Rhim; Nguyen Thi, Minh Hai; Cho, Sunglae

    2015-03-01

    Microcrystalline ferrites are used as a medium for the magnetic recording and storage of information. Magnetite, Fe3O4, is a ferrimagnet with a cubic inverse spinel structure and exhibits a metal-insulator, Verwey, transition at about 120 K. It is predicted to possess as half-metallic nature, ~ 100% spin polarization, and high TC (850 K). Cobalt ferrite, Co3O4, is one of the most important members of the ferrite family, which is characterized by its high HC, moderate magnetization and very high magnetocrystalline anisotropy. Here we report on the magnetic and thermoelectric properties of Fe3-xCoxO4 (x = 0 to 1) thin films and CoFe2O4/Fe3O4 superlattices grown on MgO (100) by MBE. XRD and RHEED patterns confirmed the inverse spinel structure of the Fe3O4 films. Magnetic properties of the Fe3-xCoxO4 films are markedly sensitive to the Co content. The Verwey transition was disappeared in Co-doped films. A negative MR curve with butterfly shape was observed with low Co content but disappeared for the samples with x = 0.8 and 1. Seebeck coefficients increased with Co concentration; -70 ?V/K for x =0 and -220 ?V/K for x =1. We will also discuss on the relationship between magnetic and thermoelectric characteristics in CoFe2O4/Fe3O4 superlattices with the modulations of 5, 10, and 20 nm.

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

    PubMed

    Shi, Wenbing; Wang, Hui; Huang, Yuming

    2011-01-01

    CoFe(2)O(4) nanoparticles (NPs) could stimulate the weak chemiluminescence (CL) system of luminol and AgNO(3), resulting in a strong CL emission. The UV-visible spectra, X-ray photoelectron spectra and TEM images of the investigated system revealed that AgNO(3) was reduced by luminol to Ag in the presence of CoFe(2)O(4) NPs and the formed Ag covered the surface of CoFe(2)O(4) NPs, resulting in CoFe(2)O(4)-Ag core-shell nanoparticles. Investigation of the CL reaction kinetics demonstrated that the reaction among luminol, AgNO(3) and CoFe(2)O(4) NPs was fast at the beginning and slowed down later. The CL spectra of the luminol - AgNO(3) - CoFe(2)O(4) NPs system indicated that the luminophor was still an electronically excited 3-aminophthalate anion. A CL mechanism has been postulated. When the CoFe(2)O(4) NPs were injected into the mixture of luminol and AgNO(3), they catalyzed the reduction of AgNO(3) by luminol to produce luminol radicals and Ag, which immediately covered the CoFe(2)O(4) NPs to form CoFe(2)O(4)-Ag core-shell nanoparticles, and the luminol radicals reacted with the dissolved oxygen, leading to a strong CL emission. With the continuous deposition of Ag on the surface of CoFe(2)O(4) NPs, the catalytic activity of the core-shell nanoparticles was inhibited and a decrease in CL intensity was observed and also a slow growth of shell on the nanoparticles. PMID:21400653

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

    PubMed

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

    2015-06-01

    To develop CoFe2 O4 as magneto-fluorescent nanoparticles (NPs) for biomedical applications, it would be advantageous to identify any intrinsic fluorescence of this important magnetic material by simply adjusting the surface chemistry of the NPs themselves. Herein, we demonstrate that intrinsic multicolor fluorescence, covering the whole visible region, can be induced by facile functionalization of CoFe2 O4 NPs with Na-tartrate. Moreover, the functionalized CoFe2 O4 NPs also show unprecedented catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, pioneering the potential application of these NPs in therapeutics and wastewater treatment. Detailed investigation through various spectroscopic tools unveils the story behind the emergence of this unique optical property of CoFe2 O4 NPs upon functionalization with tartrate ligands. We believe our developed multifunctional CoFe2 O4 NPs hold great promise for advanced biomedical and technological applications. PMID:25867626

  10. Enhanced coercive and remanence fields for CoFe2O4 and BaFe12O19 bilayers deposited on (111) MgO

    NASA Astrophysics Data System (ADS)

    Yoon, S. D.; Oliver, S. A.; Vittoria, C.

    2002-05-01

    High quality epitaxial bilayer films of spinel CoFe2O4 (CoF) and M-type hexagonal ferrite BaFe12O19 (BaM) were deposited onto (111) magnesium oxide (MgO) substrate by pulsed laser ablation deposition. X-ray diffraction patterns of both BaM/CoF and CoF/BaM films showed only (0001) BaM, (111) CoF, and (111) MgO peaks. The highest coercive field of Hc=1.4 kOe was obtained for a BaM/CoF film where the CoF layer was deposited at 400 °C, which was higher than typical Hc values of ˜0.4 kOe found for single layer BaM films on (111) MgO. This was less than the Hc˜3.0 kOe found for (111) CoF films deposited at 400 °C, probably due to in situ annealing effects during the growth of the overlying BaM film at 900 °C. This Hc enhancement for BaM/CoF bilayers as compared to BaM/MgO films may provide a means to combine large coercive fields with high quality hexaferrite films.

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

    PubMed

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

    2015-01-01

    We report the preparation of (111) preferentially oriented CoFe2O4 thin films on Pt(111)/TiO2/SiO2/Si substrates using a spin-coating process. The post-annealing conditions and film thickness were varied for cobalt ferrite (CFO) thin films, and Pt/CFO/Pt structures were prepared to investigate the resistance switching behaviors. Our results showed that resistance switching without a forming process is preferred to obtain less fluctuation in the set voltage, which can be regulated directly from the preparation conditions of the CFO thin films. Therefore, instead of thicker film, CFO thin films deposited by two times spin-coating with a thickness about 100 nm gave stable resistance switching with the most stable set voltage. Since the forming process and the large variation in set voltage have been considered as serious obstacles for the practical application of resistance switching for non-volatile memory devices, our results could provide meaningful insights in improving the performance of ferrite material-based resistance switching memory devices. PMID:25897310

  12. Magnetic anomalies in self-assembled SrRuO3 -CoFe2O4 nanostructures studied by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Chun; Huang, Yen-Chin; Chien, Chia-Hsien; Liu, Heng-Jui; Chu, Ying-Hao

    2015-03-01

    Self-assembled nanostructures with high interface-to-volume ratio usually possess interesting physical properties through the coupling between neighboring materials. In complex-oxide nanocomposites, the interplay of spin, charge, orbital, and lattice degrees of freedom especially provides various functionalities. Our recent study had shown photo-induced magnetization switching in a self-assembled system, CoFe2O4 (CFO)- SrRuO3(SRO), where the CFO nanopillars were embedded in the SRO matrix. Moreover, this system also has significant magnetoresistance behaviors. In this study, we used Raman spectroscopy to investigate the magnetic coupling mechanisms in CFO-SRO nanostructures. Compared to the pure CFO films, the CFO nano-pillars under out-of-plane compressive strain show a slightly increase of A1g(Co)/A1g(Fe) intensity ratio, which corresponds to a migration of Co ions from O-site (oxygen octahedron) to T-site (oxygen tetrahedron). This behavior can be further tuned by external stimulus, such as magnetic fields and temperatures. A strong increase of A1g(Co)/A1g(Fe) ratio together with a discontinuous A1g frequency shift occur at the SRO magnetic transition temperature. This result indicated that the spin-orbital interaction in CFO can be modulated by the SRO magnetic orderings.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  16. Facile synthesis of ultra-small rhenium nanoparticles.

    PubMed

    Ayval?, Tu?çe; Lecante, Pierre; Fazzini, Pier-Francesco; Gillet, Angélique; Philippot, Karine; Chaudret, Bruno

    2014-09-25

    Ultra-small monodisperse rhenium nanoparticles (Re NPs; ca. 1.0-1.2 nm) were easily prepared by reducing the organometallic complex [Re2(C3H5)4] under a dihydrogen atmosphere under mild reaction conditions (3 bar H2; 120 °C). The particles can be stabilized by a ligand, hexadecylamine, or a polymer, polyvinylpyrrolidone and accommodate surface hydrides. PMID:25087598

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

    PubMed

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

    2011-12-28

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    Pb(Zr0.53Ti0.47)O3/CoFe2O4 (abbreviated as PZT/CFO) multiferroic composite thick films have been prepared on the Pt/Ti/SiO2/Si substrate by using a hybrid sol-gel process. The thick films were finally annealed at 650 °C in air and the ferromagnetic, ferroelectric and dielectric properties of these films were investigated. Both the PZT pervoskite phase and the CFO spinel phase were detected from x-ray diffraction. The thickness of the film was measured to be about 3.55 µm using a surface profiler and was confirmed with scanning electron microscopy. Effective saturated magnetization (Mes) estimated from the measured saturated magnetization (Ms) was defined and the result shows that the Mes of the film fabricated in this work is larger than that of the thickest PZT/CFO film reported so far, so are the coercive magnetic fields (Hc). The properties of the films can be attributed to less constraints from the substrate to the composite thick films. The remanent polarization (Pr) of 12.5 µC cm-2 is comparable to that of the thickest PZT/CFO film reported so far due to the lack of polyvinylpyrrolidone (PVP), while the coercive electric field (Ec) of 252.8 kV cm-1 is much larger than it. In addition, the PZT/CFO thick films exhibit a smaller dielectric permittivity of about 200 within the whole measured frequency range due to the introduction of the low dielectric permittivity CFO phase. Furthermore, dielectric loss decreases to ~0.01 with increasing frequency to 1 MHz, even lower than that of the PZT thick films. Although the ferroelectric properties and the dielectric constant of the PZT/CFO thick film were degraded compared with a pure PZT thick film, the coexistence of a promising ferromagnetic and ferroelectric response with a lower loss indicated that the PZT/CFO film is a good candidate for future applications in a reasonably high frequency range.

  19. Magnetic properties of cobalt ferrite nanoparticles synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

    George, T.; Sunny, A. T.; Varghese, T.

    2015-02-01

    Cobalt ferrite nanoparticles of average size 18 nm are synthesized by sol-gel method and investigated the magnetic properties. The saturation magnetization value calculated from vibration sample magnetometer (VSM) studies for CoFe2O4 is lower than the reported value for the bulk. The magnetization curves demonstrate a trend towards the superparamagnetic behavior of the as-prepared CoFe2O4 nanoparticles. The microwave magnetic parameters show a decreasing trend with the increase of frequency.

  20. Comparative study of the synthesis of CoFe 2 O 4 and NiFe 2 O 4 in silica through the polymerized complex route of the sol–gel method

    Microsoft Academic Search

    Sagrario M. Montemayor; L. A. García-Cerda; J. R. Torres-Lubián; O. S. Rodríguez-Fernández

    2007-01-01

    In this work the synthesis of CoFe2O4-SiO2 and NiFe2O4-SiO2 nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained\\u000a by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride\\u000a were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors,

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

    Microsoft Academic Search

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

    2008-01-01

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

  2. Effect of Ferrite Concentration on Dielectric and Magnetoelectric Properties in (1-x)Pb(Mg1\\/3Nb2\\/3)0.68Ti0.32O3 +(x) CoFe2O4 Particulate Composites

    Microsoft Academic Search

    F. L. Zabotto; A. J. Gualdi; A. J. A. De Oliveira; J. A. Eiras; D. Garcia

    2012-01-01

    In this work the effect of ferrite concentration on dielectric and magnetoelectric properties in (1-x)Pb(Mg1\\/3Nb2\\/3)0.68Ti0.32O3 +(x) CoFe2O4, 0.10 ? x ? 0.50, particulate composites sintered by conventional method was investigated. Optimized sintering conditions, which resulted in samples with relatively high density and resistivity values, allowed an effective poling processing. Moreover, resulting low phase interdiffusion guaranteed a good 0-3 connectivity maintenance

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

    Microsoft Academic Search

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

    2008-01-01

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

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

    Microsoft Academic Search

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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.

  6. Synthesis of Monodisperse FeCo Nanoparticles by Reductive Salt-Matrix Annealing

    SciTech Connect

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

    2013-08-02

    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.

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

    PubMed

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

    2013-08-30

    We report here a novel synthetic method to prepare monodisperse air-stable FeCo nanoparticles with average sizes of 8, 12 and 20 nm. CoFe2O4 nanoparticles of different sizes were first synthesized by a chemical solution method. The as-synthesized CoFe2O4 nanoparticles were then mixed with ball-milled NaCl powders and heated to 400-500?° C in forming gas (Ar 93%+H2 7%). The salt powder worked as a separating medium that prevents the CoFe2O4 nanoparticles from agglomerating during the heat treatment while the forming gas reduces the CoFe2O4 nanoparticles to FeCo nanoparticles. Monodisperse FeCo nanoparticles were recovered by dissolving the NaCl in water and subsequently washing with ethanol and acetone. Structural analyses confirmed that FeCo nanoparticles retained the same size as their oxide precursors. The size of the FeCo nanoparticles can be well tuned by controlling the size of the CoFe2O4 nanoparticles. The saturation magnetization of FeCo nanoparticles is size dependent and increases with size. PMID:23912629

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  10. Ultrasmall lanthanide-doped nanoparticles as multimodal platforms

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    PubMed

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

    2014-06-21

    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

  12. Synthesis and Characterization of Bimagnetic Bricklike Nanoparticles

    E-print Network

    Liu, J. Ping

    Synthesis and Characterization of Bimagnetic Bricklike Nanoparticles Girija S. Chaubey, Vikas Bimagnetic FePt/CoFe2O4 nanoparticles having a bricklike morphology were synthesized by growing a soft magnetic CoFe2O4 phase on FePt cubic nanoparticle seeds. The size of the soft phase could be controlled

  13. Structure and catalytic properties of ultra-small ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Huang, Xing

    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.

  14. On Ultrasmall Nanocrystals

    PubMed Central

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

    2010-01-01

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

  15. Effects of Nd:YAG laser irradiation on structural, morphological, cation distribution and magnetic properties of nanocrystalline CoFe 2O 4

    NASA Astrophysics Data System (ADS)

    Mane, Maheshkumar L.; Dhage, Vinod N.; Sundar, R.; Ranganathan, K.; Oak, S. M.; Shengule, D. R.; Jadhav, K. M.

    2011-08-01

    The cobalt ferrite nanoparticles of 20 nm size were synthesized by sol-gel auto-combustion technique. The samples were irradiated with Nd:YAG laser to understand the effects of irradiation on structural, cation distribution and magnetic properties. The virgin and irradiated samples were characterized by X-ray diffraction technique. The X-ray diffraction studies at room temperature shows that defects were created in the lattice after irradiation which causes effects on structural, cation distribution and magnetic properties. The energy dispersive analysis of X-rays (EDAX) showed the chemical composition is as per the expected stichiometry. The lattice constant observed from XRD data for virgin and irradiated samples shows increasing trend after irradiation. Cation distribution was investigated by using X-ray diffraction method. We observe decrease in magnetization of the samples after irradiation. The observed reduction in the saturation magnetization after irradiation can be understood on the basis of the partial formation of paramagnetic centers and rearrangement of cations in the lattice.

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

    Microsoft Academic Search

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

    2005-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  18. Synthesis and coating of cobalt ferrite nanoparticles: a first step toward the obtainment of new magnetic nanocarriers.

    PubMed

    Baldi, Giovanni; Bonacchi, Daniele; Franchini, Mauro Comes; Gentili, Denis; Lorenzi, Giada; Ricci, Alfredo; Ravagli, Costanza

    2007-03-27

    Monodisperse and stable cobalt ferrite (CoFe2O4) nanoparticles (5.4 nm) have been produced, coated with mono- and difunctional phosphonic and hydroxamic acids, and fully characterized (using thermogravimetric analysis (TGA), dynamic light scattering (DLS), IR spectroscopy, transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) measurements). Cobalt leakage of the coated nanoparticles has been also studied. Magnetic measurements show the possible applications in hyperthermia at low frequencies, and for this reason, water-soluble coated CoFe2O4 can be seen as a first step toward the obtainment of novel systems for biomagnetic applications. PMID:17335257

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

    PubMed

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

    2011-11-30

    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

  20. Millimeter Scale Alignment of Magnetic Nanoparticle Functionalized Microtubules in Magnetic Fields

    E-print Network

    Hancock, William O.

    Millimeter Scale Alignment of Magnetic Nanoparticle Functionalized Microtubules in Magnetic Fields techniques,4 by viscous forces,5 or by strong magnetic or electric fields applied during tubule ferrite nanoparticles (CoFe2O4) and the facile use of an externally applied magnetic field to control

  1. Synthesis of Ag-CoFe2O4 dimer colloidal nanoparticles and enhancement of their magnetic response

    NASA Astrophysics Data System (ADS)

    Sharma, S. K.; Lopes, G.; Vargas, J. M.; Socolovsky, L. M.; Pirota, K. R.; Knobel, M.

    2011-04-01

    This paper reports the structural and magnetic properties of Ag-CoFe2O4 colloidal dimer nanoparticles (NPs) synthesized using a two-step solution-phase route. Ag NPs were used as seeds to grow Ag-CoFe2O4 dimer NPs using thermal decomposition of metallic precursor. By means of temperature and field dependent dc magnetization measurements, it is found that the silver due to its interface with CoFe2O4 particles leads to thermal stabilization of the dimer NPs superior as compared to CoFe2O4 alone. Our results show enhancement of the magnetic anisotropy and a large coercivity at 2 K for dimer NPs, which could be ascribed to interface effect between Ag and CoFe2O4 components and the related structural defects.

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

    PubMed Central

    2015-01-01

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

  3. Various ligand-coated ultrasmall gadolinium-oxide nanoparticles: Water proton relaxivity and in-vivo T1 MR image

    NASA Astrophysics Data System (ADS)

    Park, Ja Young; Kim, Sung June; Lee, Gang Ho; Jin, Seonguk; Chang, Yongmin; Bae, Ji Eun; Chae, Kwon Seok

    2015-04-01

    Surface coating of nanoparticles with ligands is essential in magnetic resonance imaging (MRI) because of solubility in water and biocompatibility. In this study, five organic molecules were used for surface coating of ultrasmall gadolinium-oxide (Gd2O3) nanoparticles (d avg = 2.0 nm). All of the samples showed large longitudinal (r1) and transverse (r2) water proton relaxivities with r2/r1 ratios that were close to one, corresponding to ideal conditions for T1 MRI contrast agents. Finally, in-vivo T1 MR images were acquired to prove the effectiveness of the surface-coated ultrasmall Gd2O3 nanoparticles as a T1 MRI contrast agent.

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

    PubMed

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

    2015-05-26

    Ultrasmall polymer nanoparticles are rapidly gaining importance as nanocarriers for drugs and contrast agents. Here, a straightforward modular approach to efficiently loaded and stable sub-20-nm polymer particles is developed. In order to obtain ultrasmall polymer nanoparticles, we investigated the influence of one to two charged groups per polymer chain on the size of particles obtained by nanoprecipitation. Negatively charged carboxylate and sulfonate or positively charged trimethylammonium groups were introduced into the polymers poly(d,l-lactide-co-glycolide) (PLGA), polycaprolactone (PCL), and poly(methyl methacrylate) (PMMA). According to dynamic light scattering, atomic force and electron microscopy, the presence of one to two charged groups per polymer chain can strongly reduce the size of polymer nanoparticles made by nanoprecipitation. The particle size can be further decreased to less than 15 nm by decreasing the concentration of polymer in the solvent used for nanoprecipitation. We then show that even very small nanocarriers of 15 nm size preserve the capacity to encapsulate large amounts of ionic dyes with bulky counterions at efficiencies >90%, which generates polymer nanoparticles 10-fold brighter than quantum dots of the same size. Postmodification of their surface with the PEG containing amphiphiles Tween 80 and pluronic F-127 led to particles that were stable under physiological conditions and in the presence of 10% fetal bovine serum. This modular route could become a general method for the preparation of ultrasmall polymer nanoparticles as nanocarriers of contrast agents and drugs. PMID:25894117

  5. Size-Dependent Localization and Penetration of Ultrasmall Gold Nanoparticles in Cancer Cells, Multicellular Spheroids, and Tumors in Vivo

    PubMed Central

    Huang, Keyang; Ma, Huili; Liu, Juan; Huo, Shuaidong; Kumar, Anil; Wei, Tuo; Zhang, Xu; Jin, Shubin; Gan, Yaling; Wang, Paul C.; He, Shengtai; Zhang, Xiaoning; Liang, Xing-Jie

    2012-01-01

    This work demonstrated that ultrasmall gold nanoparticles (AuNPs) smaller than 10 nm display unique advantages over nanoparticles larger than 10 nm in terms of localization to, and penetration of, breast cancer cells, multicellular tumor spheroids, and tumors in mice. Au@tiopronin nanoparticles that have tunable sizes from 2 to 15 nm with identical surface coatings of tiopronin and charge were successfully prepared. For monolayer cells, the smaller the Au@tiopronin NPs, the more AuNPs found in each cell. In addition, the accumulation of Au NPs in the ex vivo tumor model was size-dependent: smaller AuNPs were able to penetrate deeply into tumor spheroids, whereas 15 nm nanoparticles were not. Owing to their ultrasmall nanostructure, 2 and 6 nm nanoparticles showed high levels of accumulation in tumor tissue in mice after a single intravenous injection. Surprisingly, both 2 and 6 nm Au@tiopronin nanoparticles were distributed throughout the cytoplasm and nucleus of cancer cells in vitro and in vivo, whereas 15 nm Au@tiopronin nanoparticles were found only in the cytoplasm, where they formed aggregates. The ex vivo multicellular spheroid proved to be a good model to simulate in vivo tumor tissue and evaluate nanoparticle penetration behavior. This work gives important insights into the design and functionalization of nanoparticles to achieve high levels of accumulation in tumors. PMID:22540892

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  7. Development of SM5-1-conjugated ultrasmall superparamagnetic iron oxide nanoparticles for hepatoma detection.

    PubMed

    Kou, Geng; Wang, Shuhui; Cheng, Changming; Gao, Jie; Li, Bohua; Wang, Hao; Qian, Weizhu; Hou, Sheng; Zhang, Dapeng; Dai, Jianxin; Gu, Hongchen; Guo, Yajun

    2008-09-19

    Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are maghemite or magnetite nanoparticles currently used as contrast agent in magnetic resonance imaging (MRI). In this study, a targeted contrast agent (SM-USPIO) was prepared by conjugating coprecipitated USPIO to a humanized SM5-1 antibody which can specifically react with human hepatocellular carcinoma (HCC) cells. The binding and internalization of SM-USPIO to the HCC cell line ch-hep-3 was confirmed by flow cytometry and confocal microscopy. Furthermore, SM-USPIO was demonstrated to be able to selectively accumulate in the tumor cells, resulting in a marked decrease of MRI T2-weighted signal intensity. Biodistribution studies demonstrated the efficient accumulation of SM-USPIO in the ch-hep-3 tumor in nude mice. The in vivo study in the ch-hep-3 tumor-bearing nude mice indicated that MRI using the SM-USPIO as contrast agent possessed good diagnostic ability, suggesting that SM-USPIO had the potential to be a promising targeted contrast agent for diagnosis of HCC. PMID:18621023

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

    PubMed Central

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

    2007-01-01

    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

  9. Effect of light on the magnetic properties of cobalt ferrite nanoparticles

    Microsoft Academic Search

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

    2000-01-01

    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

  10. 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)

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

    2014-12-01

    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

  11. 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)

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

    2014-02-01

    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

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

    PubMed Central

    Liu, Yonghuan; Wang, Rutao; Yan, Xingbin

    2015-01-01

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

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

    PubMed

    Liu, Yonghuan; Wang, Rutao; Yan, Xingbin

    2015-01-01

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

  14. Fabrication and evaluation of tumor-targeted positive MRI contrast agent based on ultrasmall MnO nanoparticles.

    PubMed

    Huang, Haitao; Yue, Tao; Xu, Ke; Golzarian, Jafar; Yu, Jiahui; Huang, Jin

    2015-07-01

    Gd(III) chelate is currently used as positive magnetic resonance imaging (MRI) contrast agent in clinical diagnosis, but generally induces the risk of nephrogenic systemic fibrosis (NSF) due to the dissociated Gd(3+) from Gd(III) chelates. To develop a novel positive MRI contrast agent with low toxicity and high sensitivity, ultrasmall MnO nanoparticles were PEGylated via catechol-Mn chelation and conjugated with cRGD as active targeting function to tumor. Particularly, the MnO nanoparticles with a size of ca. 5nm were modified by ?,?-poly(aspartic acid)-based graft polymer containing PEG and DOPA moieties and, meanwhile, conjugated with cRGD to produce the contrast agent with a size of ca. 100nm and a longitudinal relaxivity (r1) of 10.2mM(-1)S(-1). Such nanoscaled contrast agent integrated passive- and active-targeting function to tumor, and its efficient accumulation behavior in tumor was verified by in vivo distribution study. At the same time, the PEG moiety played a role of hydrophilic coating to improve the biocompatibility and stability under storing and physiological conditions, and especially might guarantee enough circulation time in blood. Moreover, in vivo MRI revealed a good and long-term effect of enhancing MRI signal for as-fabricated contrast agent while cell viability assay proved its acceptable cytotoxicity for MRI application. On the whole, the as-fabricated PEGylated and cRGD-functionalized contrast agent based on ultrasmall MnO nanoparticles showed a great potential to the T1-weighted MRI diagnosis of tumor. PMID:25982318

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

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

    PubMed

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

    2015-04-01

    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

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

    PubMed

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

    2011-09-01

    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

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

    PubMed

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

    2009-12-01

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

  19. Fabrication of Efficient Hydrogenation Nanoreactors by Modifying the Freedom of Ultrasmall Platinum Nanoparticles within Yolk-Shell Nanospheres.

    PubMed

    Peng, Juan; Lan, Guojun; Guo, Miao; Wei, Xuming; Li, Can; Yang, Qihua

    2015-07-13

    The synthesis of silica-based yolk-shell nanospheres confined with ultrasmall platinum nanoparticles (Pt NPs) stabilized with poly(amidoamine), in which the interaction strength between Pt NPs and the support could be facilely tuned, is reported. By ingenious utilization of silica cores with different surface wettability (hydrophilic vs. -phobic) as the adsorbent, Pt NPs could be confined in different locations of the yolk-shell nanoreactor (core vs. hollow shell), and thus, exhibit different interaction strengths with the nanoreactor (strong vs. weak). It is interesting to find that the adsorbed Pt NPs are released from the core to the hollow interiors of the yolk-shell nanospheres when a superhydrophobic inner core material (SiO2 ?Ph) is employed, which results in the preparation of an immobilized catalyst (Pt@SiO2 ?Ph); this possesses the weakest interaction strength with the support and shows the highest catalytic activity (88?500 and 7080?h(-1) for the hydrogenation of cyclohexene and nitrobenzene, respectively), due to its unaffected freedom of Pt NPs for retention of the intrinsic properties. PMID:26094810

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

    PubMed

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

    2014-02-01

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

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

    PubMed

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

    2015-03-01

    We report a synthetic approach for the production of ultra-small (0.6 nm) gold nanoparticles soluble in water with a precise control of the nanoparticle size. Our synthetic approach utilizes a pH-depending Au-cysteine polymer as a quencher for the AuNPs grown. The method extends the synthetic capabilities of nanoparticles with sizes down to 1 nm. In addition to the strict pH control, the existence of free -SH groups present in the mixture of reaction has been observed as a key requirement for the synthesis of small nanoparticles in mild conditions. UV-Vis, SAXS, XANES, EXAFS and HR-TEM, has been used to determinate the particle size, characterization of the gold precursor and gold-cysteine interaction. PMID:25485807

  2. Ultrasmall TiO2 Nanoparticles in Situ Growth on Graphene Hybrid as Superior Anode Material for Sodium/Lithium Ion Batteries.

    PubMed

    Liu, Huiqiao; Cao, Kangzhe; Xu, Xiaohong; Jiao, Lifang; Wang, Yijing; Yuan, Huatang

    2015-06-01

    To inhibit the aggregation of TiO2 nanoparticles and to improve the electrochemical kinetics of TiO2 electrode, a hybrid material of ultrasmall TiO2 nanoparticles in situ grown on rGO nanosheets was obtained by ultraphonic and reflux methods. The size of the TiO2 particles was controlled about 10 nm, and these particles were evenly distributed across the rGO nanosheets. When used for the anode of a sodium ion battery, the electrochemical performance of this hybrid TiO2@rGO was much improved. A capacity of 186.6 mAh g(-1) was obtained after 100 cycles at 0.1 A g(-1), and 112.2 mAh g(-1) could be maintained at 1.0 A g(-1), showing a high capacity and good rate capability. On the basis of the analysis of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the achieved excellent electrochemical performance was mainly attributed to the synergetic effect of well-dispersed ultrasmall TiO2 nanoparticles and conductive graphene network and the improved electrochemical kinetics. The superior electrochemical performance of this hybrid material on lithium storage further confirmed the positive effect of rGO. PMID:25965945

  3. Cobalt and magnesium ferrite nanoparticles: preparation using liquid foams as templates and their magnetic characteristics.

    PubMed

    Bala, Tanushree; Sankar, C Raj; Baidakova, Marina; Osipov, Vladimir; Enoki, Toshiaki; Joy, P A; Prasad, B L V; Sastry, Murali

    2005-11-01

    An easy and convenient method for the synthesis of cobalt and magnesium ferrite nanoparticles is demonstrated using liquid foams as templates. The foam is formed from an aqueous mixture of an anionic surfactant and the desired metal ions, where the metal ions are electrostatically entrapped by the surfactant at the thin borders between the foam bubbles and their junctions. The hydrolysis is carried out using alkali resulting in the formation of desired nanoparticles, with the foam playing the role of a template. However, in the formation of ferrites with the formula MFe(2)O(4), where the metal ion and iron possess oxidation states of +2 and +3, respectively, forming a foam from a 1:2 mixture of the desired ionic solutions would lead to a foam composition at variance with the original solution mixture because of greater electrostatic binding of ions possessing a greater charge with the surfactant. In our procedure, we circumvent this problem by preparing the foam from a 1:2 mixture of M(2+) and Fe(2+) ions and then utilizing the in situ conversion of Fe(2+) to Fe(3+) under basic conditions inside the foam matrix to get the desired composition of the metal ions with the required oxidation states. The fact that we could prepare both CoFe(2)O(4) and MgFe(2)O(4) particles shows the vast scope of this method for making even multicomponent oxides. The magnetic nanoparticles thus obtained exhibit a good crystalline nature and are characterized by superparamagnetic properties. The magnetic features observed for CoFe(2)O(4) and MgFe(2)O(4) nanoparticles are well in accordance with the expected behaviors, with CoFe(2)O(4) particles showing higher blocking temperatures and larger coercivities. These features can easily be explained by the contribution of Co(2+) sites to the magnetocrystalline anisotropy and the absence of the same from the Mg(2+) ions. PMID:16262331

  4. Synthesis and magnetic behavior of ultra-small bimetallic FeCo/graphite nanoparticles.

    PubMed

    Castrillón, M; Mayoral, A; Urtizberea, A; Marquina, C; Irusta, S; Meier, J G; Santamaría, J

    2013-12-20

    FeCo-alloy graphite-coated nanoparticles with mean particle diameter under 8 nm have been synthesized following a CVD carbon-deficient method. The superior magnetic properties of FeCo-alloy nanoparticles makes them good candidates to be used as magnetic filler in magneto-polymer composites. Thanks to the protective effect of the graphite shell, FeCo nanoparticles are stable under oxygen atmosphere up to 200 ° C. The as-prepared nanoparticles presented a highly long range chemically ordered core being ferromagnetic at room temperature with a saturation magnetization at room temperature close to the bulk value. After annealing at 750 K the saturation magnetization and the coercive field increase. To investigate the processes involved in the thermal treatment, the temperature dependence of the magnetization and the particle composition, size and structure have been characterized before and after annealing. Besides powder x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS), a detailed study by means of advanced transmission electron microscopy (TEM) techniques has been carried out. In particular, aberration corrected scanning transmission electron microscopy (STEM), has shown that nanoparticles became faceted after the thermal treatment, as a mechanism to reach the thermodynamic equilibrium within the metastable phase. This outstanding feature, not previously reported, leads to an increase of the shape anisotropy, which in turn might be the origin of the observed increase of the coercive field after annealing. PMID:24270853

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

    PubMed Central

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

    2014-01-01

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

  6. Optical Characterization of Ultrasmall Si Nanoparticles Prepared through Electrochemical Dispersion of Bulk Si

    E-print Network

    Braun, Paul

    , and H2O2. The observed population is divided into two types of material: bright species consisting dots (CQDs) such as ZnS, CdSe, GaAs, and InP nanoparticles.26-35 Progress with the core-shell synthesis

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

    PubMed

    Loukanov, Alexandre R; Gagov, Hristo

    2012-09-01

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

  8. Hybrid melittin cytolytic Peptide-driven ultrasmall lipid nanoparticles block melanoma growth in vivo.

    PubMed

    Huang, Chuan; Jin, Honglin; Qian, Yuan; Qi, Shuhong; Luo, Haiming; Luo, Qingming; Zhang, Zhihong

    2013-07-23

    The cytolytic peptide melittin is a potential anticancer candidate that may be able to overcome tumor drug resistance due to its lytic properties. However, in vivo applications of melittin are limited due to its main side effect, hemolysis, which is especially pronounced following intravenous administration. Here, we designed a hybrid cytolytic peptide, ?-melittin, in which the N-terminus of melittin is linked to the C-terminus of an amphipathic ?-helical peptide (?-peptide) via a GSG linker. The strong ?-helical configuration allows ?-melittin to interact with phospholipids and self-assemble into lipid nanoparticles, with a high efficiency for ?-melittin encapsulation (>80%) and a strong ability to control the structure of the nanoparticle (~20 nm). This ?-melittin-based lipid nanoparticle (?-melittin-NP) efficiently shields the positive charge of melittin (18.70 ± 0.90 mV) within the phospholipid monolayer, resulting in the generation of a neutral nanoparticle (2.45 ± 0.56 mV) with reduced cytotoxicity and a widened safe dosage range. Confocal imaging data confirmed that ?-melittin peptides were efficiently released from the nanoparticles and were cytotoxic to the melanoma cells. Finally, ?-melittin-NPs were administered to melanoma-bearing mice via intravenous injection. The growth of the melanoma cells was blocked by the ?-melittin-NPs, with an 82.8% inhibition rate relative to the PBS-treated control group. No side effects of treatment were found in this study. Thus, the excellent properties of ?-melittin-NP give it potential clinical applications in solid tumor therapeutics through intravenous administration. PMID:23790040

  9. Ultrasmall iron nanoparticles: Effect of size reduction on anisotropy and magnetization

    SciTech Connect

    Lacroix, L.-M.; Lachaize, S.; Falqui, A.; Blon, T.; Carrey, J.; Respaud, M.; Dumestre, F.; Amiens, C.; Margeat, O.; Chaudret, B.; Lecante, P.; Snoeck, E. [Laboratoire de Physique et Chimie des Nano-Objets, 31077 Toulouse Cedex 4 (France); NANOMEPS, 135 avenue de Rangueil, 31400 Toulouse (France); Laboratoire de Chimie de Coordination, 31077 Toulouse Cedex 4 (France); Centre d'Elaboration des Materiaux et d'Etudes Structurales, 31055 Toulouse Cedex 4 (France)

    2008-04-01

    Stable iron nanoparticles have been synthesised by the decomposition of (Fe(N[Si(CH{sub 3}){sub 3}]{sub 2}){sub 2}){sub 2} under dihydrogen pressure. Those conditions lead to a system of monodisperse and metallic nanoparticles which diameter is less than 2 nm and stabilized by HN[Si(CH{sub 3}){sub 3}]{sub 2}. The magnetization is found to be M{sub S}=1.92{mu}{sub B}/at., i.e., 10% lower than the bulk value. The Moessbauer spectrum is fitted by two contributions of metallic iron. The magnetic anisotropy energy constant increases up to 5.2x10{sup 5} J/m{sup 3}, i.e., ten times the bulk one.

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Li, Wei; Chen, Minfang

    2014-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Shen, Li-Hua; Bao, Jian-Feng; Wang, Dong; Wang, Yi-Xiao; Chen, Zhi-Wei; Ren, Lei; Zhou, Xi; Ke, Xue-Bin; Chen, Min; Yang, An-Qi

    2013-02-01

    We report that ultra-small, monodisperse, water-dispersible magnetite (Fe3O4) nanoparticles can be synthesized by a facile one-pot approach using trisodium citrate as crystal grain growth inhibitor and stabilizer in polyol solution. The resultant Fe3O4 nanoparticles exhibit an excellent long-term colloidal stability in various buffer solutions without any modification. They are also superparamagnetic at room temperature and their magnetic property relies heavily on their size. Due to the low magnetization and good water-dispersibility, the 1.9 nm-sized Fe3O4 nanoparticles reveal a low r2/r1 ratio of 2.03 (r1 = 1.415 mM-1 s-1, r2 = 2.87 mM-1 s-1), demonstrating that they can be efficient T1 contrast agents. On the other hand, because of the excellent magnetic responsivity, the 13.8 nm-sized Fe3O4 nanoparticles can be readily modified with nitrilotriacetic acid and used to separate the protein simply with the assistance of a magnet. In addition, these Fe3O4 nanoparticles may be useful in other fields, such as hyperthermia treatment of cancer and targeted drug delivery based on their size-dependent magnetic property and excellent stability.

  14. Facile Synthesis of Ultrasmall CoS2 Nanoparticles within Thin N-Doped Porous Carbon Shell for High Performance Lithium-Ion Batteries.

    PubMed

    Wang, Qingfei; Zou, Ruqiang; Xia, Wei; Ma, Jin; Qiu, Bin; Mahmood, Asif; Zhao, Ruo; Yang, Yangyuchen; Xia, Dingguo; Xu, Qiang

    2015-06-01

    Cobalt sulfide (CoS2 ) is considered one of the most promising alternative anode materials for high-performance lithium-ion batteries (LIBs) by virtue of its remarkable electrical conductivity, high theoretical capacity, and low cost. However, it suffers from a poor cycling stability and low rate capability because of its volume expansion and dissolution of the polysulfide intermediates in the organic electrolytes during the battery charge/discharge process. In this study, a novel porous carbon/CoS2 composite is prepared by using nano metal-organic framework (MOF) templates for high-preformance LIBs. The as-made ultrasmall CoS2 (15 nm) nanoparticles in N-rich carbon exhibit promising lithium storage properties with negligible loss of capacity at high charge/discharge rate. At a current density of 100 mA g(-1) , a capacity of 560 mA h g(-1) is maintained after 50 cycles. Even at a current density as high as 2500 mA g(-1) , a reversible capacity of 410 mA h g(-1) is obtained. The excellent and highly stable battery performance should be attributed to the synergism of the ultrasmall CoS2 particles and the thin N-rich porous carbon shells derieved from nanosized MOF precusors. PMID:25688868

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    Nanomanipulation of matter to create responsive, ordered materials still remains extremely challenging. Supramolecular chemistry has inspired new strategies by which such nanomaterials can be synthesized step by step by exploiting the self-recognition properties of molecules. In this work, the ring-shaped architecture of the 2-Cys peroxiredoxin I protein from Schistosoma mansoni, engineered to have metal ion-binding sites, is used as a template to build up 1D nanoscopic structures through metal-induced self-assembly. Chromatographic and microscopic analyses demonstrate the ability of the protein rings to stack directionally upon interaction with divalent metal ions and form well-defined nanotubes by exploiting the intrinsic recognition properties of the ring surfaces. Taking advantage of such behavior, the rings are then used to capture colloidal Ni2+-functionalized ultrasmall gold nanoparticles and arrange them into 1D arrays through stacking into peapod-like complexes. Finally, as the formation of such nano-peapods strictly depends on nanoparticle dimensions, the peroxiredoxin template is used as a colloidal cut-off device to sort by size the encapsulated nanoparticles. These results open up possibilities in developing Prx-based methods to synthesize new advanced functional materials.Nanomanipulation of matter to create responsive, ordered materials still remains extremely challenging. Supramolecular chemistry has inspired new strategies by which such nanomaterials can be synthesized step by step by exploiting the self-recognition properties of molecules. In this work, the ring-shaped architecture of the 2-Cys peroxiredoxin I protein from Schistosoma mansoni, engineered to have metal ion-binding sites, is used as a template to build up 1D nanoscopic structures through metal-induced self-assembly. Chromatographic and microscopic analyses demonstrate the ability of the protein rings to stack directionally upon interaction with divalent metal ions and form well-defined nanotubes by exploiting the intrinsic recognition properties of the ring surfaces. Taking advantage of such behavior, the rings are then used to capture colloidal Ni2+-functionalized ultrasmall gold nanoparticles and arrange them into 1D arrays through stacking into peapod-like complexes. Finally, as the formation of such nano-peapods strictly depends on nanoparticle dimensions, the peroxiredoxin template is used as a colloidal cut-off device to sort by size the encapsulated nanoparticles. These results open up possibilities in developing Prx-based methods to synthesize new advanced functional materials. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr01526f

  16. Facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrast T1- and T2-weighted magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Hu, Fengqin; Jia, Qiaojuan; Li, Yilin; Gao, Mingyuan

    2011-06-01

    The development of new types of high-performance nanoparticulate MR contrast agents with either positive (T1) or dual-contrast (both positive and negative, T1 + T2) ability is of great importance. Here we report a facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrast T1- and T2-weighted MRI. The produced superparamagnetic iron oxide nanoparticles (SPIONs) are of high crystallinity and size uniformity with an average diameter of 5.4 nm, and can be individually dispersed in the physiological buffer with high stability. The SPIONs reveal an impressive saturation magnetization of 94 emu g - 1 Fe3O4, the highest r1 of 19.7 mM - 1 s - 1 and the lowest r2/r1 ratio of 2.0 at 1.5 T reported so far for PEGylated iron oxide nanoparticles. T1- and T2-weighted MR images showed that the SPIONs could not only improve surrounding water proton signals in the T1-weighted image, but induce significant signal reduction in the T2-weighted image. The good contrast effect of the SPIONs as T1 + T2 dual-contrast agents might be due to its high magnetization, optimal nanoparticle size for T1 + T2 dual-contrast agents, high size monodispersity and excellent colloidal stability. In vitro cell experiments showed that the SPIONs have little effect on HeLa cell viability.

  17. 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

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

    2012-08-01

    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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2011-06-01

    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

  20. Giant enhancement of upconversion in ultra-small Er³?/Yb³?:NaYF? nanoparticles via laser annealing.

    PubMed

    Bednarkiewicz, A; Wawrzynczyk, D; Gagor, A; Kepinski, L; Kurnatowska, M; Krajczyk, L; Nyk, M; Samoc, M; Strek, W

    2012-04-13

    Most of the synthesis routes of lanthanide-doped phosphors involve thermal processing which results in nanocrystallite growth, stabilization of the crystal structure and augmentation of luminescence intensity. It is of great interest to be able to transform the sample in a spatially localized manner, which may lead to many applications like 2D and 3D data storage, anti-counterfeiting protection, novel design bio-sensors and, potentially, to fabrication of metamaterials, 3D photonic crystals or plasmonic devices. Here we demonstrate irreversible spatially confined infrared-laser-induced annealing (LIA) achieved in a thin layer of dried colloidal solution of ultra-small ?8 nm NaYF? nanocrystals (NCs) co-doped with 2% Er³? and 20% Yb³? ions under a localized tightly focused beam from a continuous wave 976 nm medium power laser diode excitation. The LIA results from self-heating due to non-radiative relaxation accompanying the NIR laser energy upconversion in lanthanide ions. We notice that localized LIA appears at optical power densities as low as 15.5 kW cm?² (?354 ± 29 mW) threshold in spots of 54 ± 3 µm diameter obtained with a 10 × microscope objective. In the course of detailed studies, a complete recrystallization to different phases and giant 2-3 order enhancement in luminescence yield is found. Our results are highly encouraging and let us conclude that the upconverting ultra-small lanthanide-doped nanophosphors are particularly promising for direct laser writing applications. PMID:22433162

  1. Giant enhancement of upconversion in ultra-small Er3+/Yb3+:NaYF4 nanoparticles via laser annealing

    NASA Astrophysics Data System (ADS)

    Bednarkiewicz, A.; Wawrzynczyk, D.; Gagor, A.; Kepinski, L.; Kurnatowska, M.; Krajczyk, L.; Nyk, M.; Samoc, M.; Strek, W.

    2012-04-01

    Most of the synthesis routes of lanthanide-doped phosphors involve thermal processing which results in nanocrystallite growth, stabilization of the crystal structure and augmentation of luminescence intensity. It is of great interest to be able to transform the sample in a spatially localized manner, which may lead to many applications like 2D and 3D data storage, anti-counterfeiting protection, novel design bio-sensors and, potentially, to fabrication of metamaterials, 3D photonic crystals or plasmonic devices. Here we demonstrate irreversible spatially confined infrared-laser-induced annealing (LIA) achieved in a thin layer of dried colloidal solution of ultra-small ˜8 nm NaYF4 nanocrystals (NCs) co-doped with 2% Er3+ and 20% Yb3+ ions under a localized tightly focused beam from a continuous wave 976 nm medium power laser diode excitation. The LIA results from self-heating due to non-radiative relaxation accompanying the NIR laser energy upconversion in lanthanide ions. We notice that localized LIA appears at optical power densities as low as 15.5 kW cm-2 (˜354 ± 29 mW) threshold in spots of 54 ± 3 µm diameter obtained with a 10 × microscope objective. In the course of detailed studies, a complete recrystallization to different phases and giant 2-3 order enhancement in luminescence yield is found. Our results are highly encouraging and let us conclude that the upconverting ultra-small lanthanide-doped nanophosphors are particularly promising for direct laser writing applications.

  2. Vascular toxicity of ultra-small TiO2 nanoparticles and single walled carbon nanotubes in vitro and in vivo.

    PubMed

    Bayat, Narges; Lopes, Viviana R; Schölermann, Julia; Jensen, Lasse Dahl; Cristobal, Susana

    2015-09-01

    Ultra-small nanoparticles (USNPs) at 1-3 nm are a subset of nanoparticles (NPs) that exhibit intermediate physicochemical properties between molecular dispersions and larger NPs. Despite interest in their utilization in applications such as theranostics, limited data about their toxicity exist. Here the effect of TiO2-USNPs on endothelial cells in vitro, and zebrafish embryos in vivo, was studied and compared to larger TiO2-NPs (30 nm) and to single walled carbon nanotubes (SWCNTs). In vitro exposure showed that TiO2-USNPs were neither cytotoxic, nor had oxidative ability, nevertheless were genotoxic. In vivo experiment in early developing zebrafish embryos in water at high concentrations of TiO2-USNPs caused mortality possibly by acidifying the water and caused malformations in the form of pericardial edema when injected. Myo1C involved in glomerular development of zebrafish embryos was upregulated in embryos exposed to TiO2-USNPs. They also exhibited anti-angiogenic effects both in vitro and in vivo plus decreased nitric oxide concentration. The larger TiO2-NPs were genotoxic but not cytotoxic. SWCNTs were cytotoxic in vitro and had the highest oxidative ability. Neither of these NPs had significant effects in vivo. To our knowledge this is the first study evaluating the effects of TiO2-USNPs on vascular toxicity in vitro and in vivo and this strategy could unravel USNPs potential applications. PMID:26066004

  3. CoFe2O4 polypyrrole (PPy) nanocomposites: new multifunctional materials

    Microsoft Academic Search

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

    2004-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  5. Magnetic chessboard-type nanodomains in Mn-doped CoFe2O4

    NASA Astrophysics Data System (ADS)

    Ohno, M.; Mori, S.; Togawa, Y.; Horibe, Y.

    2011-10-01

    We examined formation processes of ordered array of two types of rectangular nanorods, characterized as chessboard-type (CB-type) nanodomain structures, by changing the isothermal annealing time at 648 K. Highly organized CB-type nanodomain structures developed through the isothermal annealing treatment from 10 to 730 hours and consequently the CB-type nanodomain structures with ~50 nm2 in size are formed in samples annealed for 730 hours. From the chemical composition analysis, it is revealed that the two types of rectangular nanorods comprise the coexisting state of one nanorod with composition close to CoFe1.4MnO4 with the cubic structure and another nanorod with composition close to CoFe0.4Mn2O4 with the orthorhombic structure.

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

    PubMed

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

    2004-09-01

    Stable CoFe(2)O(4) nanoparticles have been obtained by co-precipitation using a microwave heating system. Transmission electron microscopy images analysis shows an agglomeration of particles with an average size of about 5 nm, and X-ray diffraction reveals the presence of a pure ferrite nanocrystalline phase. X-ray photoelectron spectroscopy and thermal gravimetric analysis show the presence of organic matter in the range of about 16 wt%. The magnetic response in DC fields is typical for an assembly of single-domain particles. The measured saturation magnetization is slightly larger than the bulk value, probably due to the presence of small amounts of Co and Fe. AC magnetization data indicate the presence of magnetic interactions between the nanoparticles. PMID:15276045

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

    NASA Astrophysics Data System (ADS)

    Nadeau, Jay; Poon, Wilson; Zhang, Xuan

    2015-03-01

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

  8. Synthesis of cobalt ferrite nanoparticles using combustion waves

    NASA Astrophysics Data System (ADS)

    de Biasi, R. S.; Figueiredo, A. B. S.; Fernandes, A. A. R.; Larica, C.

    2007-10-01

    Nanocrystalline particles of cobalt ferrite (CoFe 2O 4) were prepared by a combustion wave method, based on the Self-propagating High temperature Synthesis technique (SHS), using iron nitrate, Fe(NO 3) 3?9H 2O, cobalt nitrate, Co(NO 3) 2?6H 2O, and glycine, C 2H 5NO 2. The average particle size, determined by means of X-ray diffraction, was found to depend on the glycine-nitrate ratio and varied between 2.7 and 17 nm. By measuring at several temperatures the relative intensity of the Mössbauer spectra due to superparamagnetic particles and to ferrimagnetic particles, we determined the size distribution of the nanoparticles in one of the samples. It was found to be a log-normal distribution with a most probable diameter Dm=1.8 nm and a full width at half-height ?D=2.6 nm.

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-01-01

    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

  11. Cobalt ferrite thin films as anode material for lithium ion batteries

    Microsoft Academic Search

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

    2004-01-01

    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

  12. Magnetocaloric effect in ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Rebar, D.

    2005-03-01

    Miniaturization of the electronic devices for space, military and consumer applications requires cooling devices to be fabricated on a chip for power efficient, noise-free operations. Refrigeration based on the adiabatic-demagnetization has been used for several decades for cooling down to sub-kelvin temperatures. Superparamagnetic particles also hold tremendous potential towards this application. We have studied magnetocaloric effect (MCE) properties in chemically synthesized ferrite nanoparticles over a broad range in temperature and magnetic fields. Nanoparticles investigated include Fe3O4 (average size = 8 nm, synthesized using co-precipitation method), MnZnFe2O4 (average size = 15 nm, synthesized using reverse-micelle technique) and CoFe2O4 (average size 8 nm, synthesized using pyrolectic technique). The magnetic entropy change was calculated by applying Maxwell's relations to magnetization vs magnetic field curves at various temperatures. Our results indicate that the single-domain particles in their superparamagnetic state show a considerable entropy change near the blocking temperature. The influence of interactions on MCE effect will also be discussed. Work supported by NSF through Grant No. CTS-0408933

  13. Ultrasmall silicon quantum dots

    NASA Astrophysics Data System (ADS)

    Zwanenburg, F. A.; van Loon, A. A.; Steele, G. A.; van Rijmenam, C. E. W. M.; Balder, T.; Fang, Y.; Lieber, C. M.; Kouwenhoven, L. P.

    2009-06-01

    We report the realization of extremely small single quantum dots in p-type silicon nanowires, defined by Schottky tunnel barriers with Ni and NiSi contacts. Despite their ultrasmall size the NiSi-Si-NiSi nanowire quantum dots readily allow spectroscopy of at least ten consecutive holes, and additionally they display a pronounced excited-state spectrum. The Si channel lengths are visible in scanning electron microscopy images and match the dimensions predicted by a model based on the Poisson equation. The smallest dots (<12 nm) allow identification of the last charge and thus the creation of a single-charge quantum dot.

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

    PubMed

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

    2014-02-01

    The aim of this work is to investigate the effect of electrostatic interactions between the nanoparticles and the membrane lipids on altering the physical properties of the liposomal membrane such as fluidity and bending elasticity. For this purpose, we have used nanoparticles and lipids with different surface charges. Positively charged iron oxide (?-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

  15. Magnetic and structural properties of CoFe2O4 thin films synthesized via a sol-gel process

    Microsoft Academic Search

    J. G. dos S. Duque; M. A. Macêdo; N. O. Moreno; J. L. Lopez; H.-D. Pfanes

    2001-01-01

    Using a sol-gel process having the coconut water as a precursor of organic chain, we synthesized thin films of cobalt ferrite. The films were characterized by using a SQUID magnetometer, an X-ray diffractometer, an X-ray spectrophotometer, Mössbauer spectroscopy and atomic force microscope. Co ferrite films annealed at 500°C for 2h show grain sizes between 10 and 20nm, grown as single-phase

  16. Magnetic and structural properties of CoFe 2O 4 thin films synthesized via a sol–gel process

    Microsoft Academic Search

    J. G dos S. Duque; M. A Macêdo; N. O Moreno; J. L Lopez; H.-D Pfanes

    2001-01-01

    Using a sol–gel process having the coconut water as a precursor of organic chain, we synthesized thin films of cobalt ferrite. The films were characterized by using a SQUID magnetometer, an X-ray diffractometer, an X-ray spectrophotometer, Mössbauer spectroscopy and atomic force microscope. Co ferrite films annealed at 500°C for 2h show grain sizes between 10 and 20nm, grown as single-phase

  17. Magnetic and structural properties of CoFe 2O 4 thin films synthesized via a sol-gel process

    NASA Astrophysics Data System (ADS)

    dos S. Duque, J. G.; Macêdo, M. A.; Moreno, N. O.; Lopez, J. L.; Pfanes, H.-D.

    2001-05-01

    Using a sol-gel process having the coconut water as a precursor of organic chain, we synthesized thin films of cobalt ferrite. The films were characterized by using a SQUID magnetometer, an X-ray diffractometer, an X-ray spectrophotometer, Mössbauer spectroscopy and atomic force microscope. Co ferrite films annealed at 500°C for 2 h show grain sizes between 10 and 20 nm, grown as single-phase spinel structure and exhibit high coercivity and a moderate saturation magnetization (above 30 kOe).

  18. Ferromagnetism in lead graphite-pencils and magnetic composite with CoFe2O4 particles

    Microsoft Academic Search

    R. N. Bhowmik

    2011-01-01

    This work has been initiated with a curiosity to investigate the elemental composition and magnetic response of different grades of lead pencils (6B, 2B, HB, 2H, 5H) that people use in daily life. Interestingly, experimental results landed with a great achievement of observing soft magnetism in lead pencils, indicating a wide scope of magnetic tuning for room temperature applications. A

  19. Ferromagnetism in lead graphite-pencils and magnetic composite with CoFe 2O 4 particles

    Microsoft Academic Search

    R. N. Bhowmik

    This work has been initiated with a curiosity to investigate the elemental composition and magnetic response of different grades of lead pencils (6B, 2B, HB, 2H, 5H) that people use in daily life. Interestingly, experimental results landed with a great achievement of observing soft magnetism in lead pencils, indicating a wide scope of magnetic tuning for room temperature applications. A

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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).

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

    PubMed Central

    2011-01-01

    The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications. PMID:21774807

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

    PubMed Central

    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

    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

  3. Enigmatic, ultrasmall, uncultivated Archaea

    SciTech Connect

    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

    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.

  4. Enigmatic, ultrasmall, uncultivated Archaea

    PubMed Central

    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

    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

  5. Enigmatic, ultrasmall, uncultivated Archaea

    SciTech Connect

    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

    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.

  6. Exchange bias mediated by interfacial nanoparticles (invited)

    NASA Astrophysics Data System (ADS)

    Berkowitz, A. E.; Sinha, S. K.; Fullerton, E. E.; Smith, D. J.

    2015-05-01

    The objective of this study on the iconic exchange-bias bilayer Permalloy/CoO has been to identify those elements of the interfacial microstructure and accompanying magnetic properties that are responsible for the exchange-bias and hysteretic properties of this bilayer. Both epitaxial and polycrystalline samples were examined. X-ray and neutron reflectometry established that there existed an interfacial region, of width ˜1 nm, whose magnetic properties differed from those of Py or CoO. A model was developed for the interfacial microstructure that predicts all the relevant properties of this system; namely; the temperature and Permalloy thickness dependence of the exchange-bias, HEX, and coercivity, HC; the much smaller measured values of HEX from what was nominally expected; the different behavior of HEX and HC in epitaxial and polycrystalline bilayers. A surprising result is that the exchange-bias does not involve direct exchange-coupling between Permalloy and CoO, but rather is mediated by CoFe2O4 nanoparticles in the interfacial region.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    In this study, a simple, efficient and reproducible microemulsion method was applied for the successful decoration of carbon nanotubes (CNTs) with magnetic MIIFe2O4 (M = Co, Ni, Cu, Zn) nanoparticles. The structure, composition and morphology of the prepared nanocomposite materials were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The magnetic properties were investigated by the vibrating sample magnetometer (VSM). The SEM results illustrated that large quantity of MIIFe2O4 nanoparticles were uniformly decorated around the circumference of CNTs and the sizes of the nanoparticles ranged from 15 to 20 nm. Magnetic hysteresis loop measurements revealed that all the MIIFe2O4/CNTs nanocomposites displayed ferromagnetic behavior at 300 K and can be manipulated using an external magnetic field. The CoFe2O4/CNTs nanocomposite showed maximum value of saturation magnetization which was 37.47 emu g-1. The as prepared MIIFe2O4/CNTs nanocomposites have many potential application in magnetically guided targeted drug delivery, clinical diagnosis, electrochemical biosensing, magnetic data storage and magnetic resonance imaging.

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

    PubMed

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

    2012-08-01

    Magnetic nanoparticles have become important tools for imaging a wide range of diseases, improving drug delivery and applying hyperthermic treatment. Iron oxide based nanoparticles have been widely examined, unlike cobalt ferrite based ones. Herein, monodisperse and stable CoFe2O4 nanoparticles have been produced, coated and further stabilized using ethyl 12-(hydroxyamino)-12-oxododecanoate, poly(lactic-co-glycolic acid) and bovine serum albumin. The final product, NBRh1, was fully characterized and has been directly radiolabeled with 99mTc using SnCl1 as the reducing agent in high yields. In vitro stability and hyperthermic properties of 99mTC-NBRh1 were encouraging for further application in low frequencies hyperthermia and biomagnetic applications. In vivo evaluation followed after injection in healthy mice. The planar and SPECT imaging data as well as the biodistribution results were in accordance, showing high liver and spleen uptake as expected starting almost immediately after administration. In conclusion the preliminary results for nanoparticles bearing a cobalt ferrite core justify further investigations towards potential hyperthermic applications, drug transportation and liver or spleen imaging. PMID:22852467

  9. Ultrasmall Carbide Nanospheres - Formation and Electronic Properties

    NASA Astrophysics Data System (ADS)

    Reinke, Petra; Monazami, Ehsan; McClimon, John

    2015-03-01

    Metallic nanoparticles are highly coveted but are subject to rapid Ostwald ripening even at moderate temperatures limiting study of their properties. Ultrasmall transition metal carbide ``nanospheres'' are synthesized by a solid-state reaction between fullerene as carbon scaffold, and a W surface. This produces nanospheres with a narrow size distribution below 2.5 nm diameter. The nanosphere shape is defined by the scaffold and densely packed arrays can be achieved. The metal-fullerene reaction is temperature driven and progresses through an intermediate semiconducting phase until the fully metallic nanospheres are created at about 350 C. The reaction sequence is observed with STM, and STS maps yield the local density of states. The reaction presumably progresses by stepwise introduction of W-atoms in the carbon scaffold. The results of high resolution STM/STS in combination with DFT calculations are used to unravel the reaction mechanism. We will discuss the transfer of this specific reaction mechanism to other transition metal carbides. The nanospheres are an excellent testbed for the physics and chemistry of highly curved surfaces.

  10. Fabrication of Porous Anodic Alumina with Ultrasmall Nanopores

    PubMed Central

    2010-01-01

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

  11. Arrays of ultrasmall metal rings.

    PubMed

    Singh, Deepak K; Krotkov, Robert V; Xiang, Hongqi; Xu, Ting; Russell, Thomas P; Tuominen, Mark T

    2008-06-18

    In this paper, we present a simple method to fabricate ultra-high-density hexagonal arrays of ferromagnetic nanorings having 13 nm outer diameter, 5 nm inner diameter and 5 nm thickness. Cobalt magnetic nanorings were fabricated using a self-assembled diblock copolymer template with an angular evaporation of metal followed by an ion-beam etching. Magnetic measurements and theoretical calculations suggest that, at low fields, only the single domain and vortex states are important for rings of this size. The measured magnetization as a function of applied field shows a hysteresis that is consistent. These ultrasmall ferromagnetic rings have potential use in magnetic memory devices due to the simplicity of the preparation coupled with the ultra-high-density and geometry-controlled switching. This fabrication technique can be extended to other materials for applications in optics, sensing and nanoscale research. PMID:21825810

  12. Arrays of ultrasmall metal rings

    NASA Astrophysics Data System (ADS)

    Singh, Deepak K.; Krotkov, Robert V.; Xiang, Hongqi; Xu, Ting; Russell, Thomas P.; Tuominen, Mark T.

    2008-06-01

    In this paper, we present a simple method to fabricate ultra-high-density hexagonal arrays of ferromagnetic nanorings having 13 nm outer diameter, 5 nm inner diameter and 5 nm thickness. Cobalt magnetic nanorings were fabricated using a self-assembled diblock copolymer template with an angular evaporation of metal followed by an ion-beam etching. Magnetic measurements and theoretical calculations suggest that, at low fields, only the single domain and vortex states are important for rings of this size. The measured magnetization as a function of applied field shows a hysteresis that is consistent. These ultrasmall ferromagnetic rings have potential use in magnetic memory devices due to the simplicity of the preparation coupled with the ultra-high-density and geometry-controlled switching. This fabrication technique can be extended to other materials for applications in optics, sensing and nanoscale research.

  13. Impact of larger rare earth Pr3+ ions on the physical properties of chemically derived PrxCoFe2-xO4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Pachpinde, A. M.; Langade, M. M.; Lohar, K. S.; Patange, S. M.; Shirsath, Sagar E.

    2014-01-01

    Rare earth Pr3+ ions with its larger ionic radii substituted CoFe2O4 nanoparticles with x ranging from 0.0 to 0.1 were synthesized by sol-gel auto-combustion chemical method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR) and vibrating sample magnetometer (VSM) were employed to characterize the physical properties of these ferrite nanoparticles. XRD pattern reveals the formation of cubic spinel ferrite with the signature of PrFeO3 phases for x ? 0.05. SEM images show that the synthesized samples are in good homogeneity with uniformly distributed grain. The results of IR spectroscopy analysis indicated that the functional groups of cobalt spinel ferrite were formed during the sol-gel process. The cations distribution between the tetrahedral (A-site) and octahedral sites (B-site) has been estimated by XRD analysis. Room temperature magnetic measurement shows saturation magnetization and coercivity increased from 54.7 to 64.2 emu/g and 644 to 1013 Oe, respectively with the increasing Pr3+ substitution.

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

    NASA Astrophysics Data System (ADS)

    Thomas, Dippong; Zoita, Berinde; Ivan, Pauliuc

    2013-05-01

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

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

    E-print Network

    Ren, Shenqiang; Wuttig, Manfred

    2008-02-26

    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. ...

  16. Dielectric, magnetic, and magnetoelectric properties of laminated PbZr0.52Ti0.48O3\\/CoFe2O4 composite ceramics

    Microsoft Academic Search

    Jian-Ping Zhou; Hong-Cai He; Zhan Shi; Gang Liu; Ce-Wen Nan

    2006-01-01

    Multiferroic laminated composites of PbZr0.52Ti0.48O3(PZT)\\/CoFe2O4(CFO)\\/PbZr0.52Ti0.48O3 were prepared by conventional ceramic processing. The interdiffusion of the elements between different layers occurred, altering material properties. The dielectric behavior of such a sandwiched ceramic was dominated by the relative thickness of the different layers because of the high dielectric constant of the PZT layer and the low dielectric constant of the CFO layer.

  17. Microstructure and magnetic properties of CoFe 2 O 4 thin films deposited on Si substrates with an Fe 3 O 4 under-layer

    Microsoft Academic Search

    Zhiyong Zhong; Huaiwu Zhang; Xiaoli Tang; Yulan Jing; Feiming Bai; Shuang Liu

    2011-01-01

    The microstructure and magnetic properties of cobalt ferrite thin films deposited by the sputtering method on an Fe3O4 under-layer were investigated at different post-annealing temperatures. Results show that the Fe3O4 under-layer can accelerate the grain growth of cobalt ferrite films due to the phase transformation of the Fe3O4 under-layer at about 400°C–500°C. By introducing the Fe3O4 under-layer, cobalt ferrite nanocrystalline

  18. Microstructure and magnetic properties of CoFe2O4 thin films deposited on Si substrates with an Fe3O4 under-layer

    NASA Astrophysics Data System (ADS)

    Zhong, Zhiyong; Zhang, Huaiwu; Tang, Xiaoli; Jing, Yulan; Bai, Feiming; Liu, Shuang

    2011-07-01

    The microstructure and magnetic properties of cobalt ferrite thin films deposited by the sputtering method on an Fe3O4 under-layer were investigated at different post-annealing temperatures. Results show that the Fe3O4 under-layer can accelerate the grain growth of cobalt ferrite films due to the phase transformation of the Fe3O4 under-layer at about 400°C-500°C. By introducing the Fe3O4 under-layer, cobalt ferrite nanocrystalline thin films with high coercivity can be obtained at lower post-annealing temperatures.

  19. Magnetic order in two-dimensional nanoparticle assemblies

    NASA Astrophysics Data System (ADS)

    Georgescu, M.

    2008-12-01

    This thesis involves a fundamental study of two-dimensional arrays of magnetic nanoparticles using non-contact Atomic Force Microscopy, Magnetic Force Microscopy, and Atomic Force Spectroscopy. The goal is to acquire a better understanding of the interactions between magnetic nanoparticles and the resulting configuration of their magnetic moments. We have studied two systems: 20-nm magnetite (Fe3O4) and 21-nm cobalt ferrite (CoFe2O4) nanoparticles, capped with oleic acid and oleylamine, deposited using drop-casting technique on HOPG (Highly Oriented Pyrolytic Graphite). We present an analytical model to interpret the experimental spectroscopy curves (frequency shift as a function of the tip-sample distance) in terms of force, to enable a quantitative interpretation of the experimental results. In addition, a numerical model based on the Metropolis Monte Carlo method has been developed to calculate the configuration of magnetic moments with minimum energy. The energy consists of dipolar energy and anisotropy energy. The simulations have shown that local energy minima are present that correspond to different configurations of magnetic moments. Because of the thermal energy, the system may jump in between these energy minima. Considering a specific configuration of moments, MFM images were simulated taking the dipolar interactions between the nanoparticles and the tip into account. Spectroscopy curves were calculated for two cases: namely with and without the influence of the tip. The magnetite nanoparticles present a relatively large magnetic moment and exhibit strong dipole-dipole interactions and small, negligible, anisotropy. The observed repulsion between the tip and the nanoparticles at the side of the nanoparticle islands shows that dipolar coupling between the particles causes blocking of their magnetic moments. The experimental observations agree well with the numerical calculations, which show that the magnetic moments arrange themselves in flux-closure structures. However, the magnetite nanoparticle 2D systems can be considered soft-magnetic: their moments are strongly influenced by the field of the tip. This has been observed experimentally and confirmed by simulations for the considered magnetic moment of the tip. The cobalt-ferrite nanoparticles present a similar magnetic moment as the magnetite nanoparticles. The anisotropy, however, increases significantly with decreasing temperature, which leads to blocking of the moments even in the strong field of the tip. As a consequence, attractive and repulsive areas were observed in the MFM image above the islands of nanoparticles at low temperatures. In our simulation we have assumed arbitrary orientations of the easy axes of the particles. Simulation results reveal short-range order of the magnetic moments, consistent with the experimental results.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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

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

    E-print Network

    McHenry, Michael E.

    . Fe­Co core-shell MNPs have protective CoFe2O4 shell which prevents oxidation. The oxide coating also SLP for FeCo SLP 450 W/g at biocompatible fields to be significantly larger in comparision to oxide materials. The anisotropy of Fe-Co MNPs may be tuned by composition and/or shape variation to achieve

  3. Atomic scale dynamics of ultrasmall germanium clusters.

    PubMed

    Bals, S; Van Aert, S; Romero, C P; Lauwaet, K; Van Bael, M J; Schoeters, B; Partoens, B; Yücelen, E; Lievens, P; Van Tendeloo, G

    2012-01-01

    Starting from the gas phase, small clusters can be produced and deposited with huge flexibility with regard to composition, materials choice and cluster size. Despite many advances in experimental characterization, a detailed morphology of such clusters is still lacking. Here we present an atomic scale observation as well as the dynamical behaviour of ultrasmall germanium clusters. Using quantitative scanning transmission electron microscopy in combination with ab initio calculations, we are able to characterize the transition between different equilibrium geometries of a germanium cluster consisting of less than 25 atoms. Seven-membered rings, trigonal prisms and some smaller subunits are identified as possible building blocks that stabilize the structure. PMID:22692540

  4. Lithium Ion Batteries: Facile Synthesis of Ultrasmall CoS2 Nanoparticles within Thin N-Doped Porous Carbon Shell for High Performance Lithium-Ion Batteries (Small 21/2015).

    PubMed

    Wang, Qingfei; Zou, Ruqiang; Xia, Wei; Ma, Jin; Qiu, Bin; Mahmood, Asif; Zhao, Ruo; Yang, Yangyuchen; Xia, Dingguo; Xu, Qiang

    2015-06-01

    Small MOFs Make Our Big Earth Greener: This rhombic dodecahedron stands for the big green Earth and the small particle of the MOF material described by R. Zou and co-workers. The application of this material is indicated by the electrical vehicle and battery on the green land at the bottom of the picture. The fruit-bearing tree represents the structure of the material, where the canopy, branches, and fruits of the tree represent the porous carbon substrate, inner pores, and CoS2 nanoparticles, respectively. Find out more on page 2511. PMID:26033960

  5. Ultrasmall Cu2-x S Nanodots for Highly Efficient Photoacoustic Imaging-Guided Photothermal Therapy.

    PubMed

    Mou, Juan; Li, Pei; Liu, Chengbo; Xu, Huixiong; Song, Liang; Wang, Jin; Zhang, Kun; Chen, Yu; Shi, Jianlin; Chen, Hangrong

    2015-05-01

    Monodisperse, ultrasmall (<5 nm) Cu2-x S nanodots (u-Cu2-x S NDs) with significantly strong near-infrared absorption and conversion are successfully demonstrated for effective deep-tissue photoacoustic imaging-guided photothermal therapy both in vitro and in vivo. Owing to ultrasmall nanoparticle size and high water dispersibility as well as long stability, such nanodots possess a prolonged circulation in blood and good passive accumulation within tumors through the enhanced permeability and retention effect. These u-Cu2-x S NDs have negligible side effects to both blood and normal tissues according to in vivo toxicity evaluations for up to 3 months, showing excellent hemo/histocompatibility. Furthermore, these u-Cu2-x S NDs can be thoroughly cleared through feces and urine within 5 days, showing high biosafety for further potential clinical translation. This novel photoacoustic imaging-guided photothermal therapy based on u-Cu2-x S NDs composed of a single component shows great prospects as a multifunctional nanoplatform with integration and multifunction for cancer diagnosis and therapy. PMID:25641784

  6. Ultrasensitive spectroscopy of ultrasmall quantum dots for energy conversion and lighting applications

    NASA Astrophysics Data System (ADS)

    Davis, Lloyd; Orfield, Noah; Rosenthal, Sandra

    2013-03-01

    Quantum dots typically have narrow spectra with a peak that tunes with their size but ultrasmall semiconductor nanocrystals of diameters less than a few nanometers have size-independent spectra and many other strikingly different properties. One especially interesting feature is that ultrasmall CdSe nanocrystals emit an almost pure white-light spectrum, which has great potential for solid-state lighting that yields excellent color rendering. To gain understanding of the photophysical properties and mechanisms for broadband emission, we have constructed a modular fluorescence microscope for ultrasensitive spectroscopy of individual nanoparticles. Using 400-nm wide-field excitation from a frequency-doubled Ti-Sapphire laser and a high-efficiency electron-multiplying CCD, we observe that single CdSe nanocrystals exhibit blinking and abrupt photobleaching, often after detection of only a few hundred photons. Moreover, spectrally dispersed imaging shows that each particle emits the entire broadband spectrum. We discuss mechanisms for homogeneous broadband emission and ongoing experiments in which the instrument is configured for scanning, confocal, two-channel, time-resolved single photon counting for studies of photon antibunching, emission lifetimes, and correlations between spectral regions.

  7. Cobalt ferrite nanocrystals: out-performing magnetotactic bacteria.

    PubMed

    Prozorov, Tanya; Palo, Pierre; Wang, Lijun; Nilsen-Hamilton, Marit; Jones, DeAnna; Orr, Daniel; Mallapragada, Surya K; Narasimhan, Balaji; Canfield, Paul C; Prozorov, Ruslan

    2007-10-01

    Magnetotactic bacteria produce exquisitely ordered chains of uniform magnetite (Fe(3)O(4)) nanocrystals, and the use of the bacterial mms6 protein allows for the shape-selective synthesis of Fe(3)O(4) nanocrystals. Cobalt ferrite (CoFe(2)O(4)) nanoparticles, on the other hand, are not known to occur in living organisms. Here we report on the use of the recombinant mms6 protein in a templated synthesis of CoFe(2)O(4) nanocrystals in vitro. We have covalently attached the full-length mms6 protein and a synthetic C-terminal domain of mms6 protein to self-assembling polymers in order to template hierarchical CoFe(2)O(4) nanostructures. This new synthesis pathway enables facile room-temperature shape-specific synthesis of complex magnetic crystalline nanomaterials with particle sizes in the range of 40-100 nm that are difficult to produce using conventional techniques. PMID:19206653

  8. 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

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

    2011-05-01

    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

  9. 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

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

    2014-10-01

    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

  10. 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

    Microsoft Academic Search

    Brinkman

    2009-01-01

    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-} (CGO)-CoFeO (CFO) use gadolinium

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

    PubMed

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

    2014-07-14

    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

  12. The ferroelectric and ferromagnetic characterization of CoFe 2O 4/Pb(Mg 1/3Nb 2/3)O 3-PbTiO 3 multilayered thin films

    NASA Astrophysics Data System (ADS)

    Guo, Hong-li; Liu, Guo; Li, Xue-dong; Li, Hai-min; Zhang, Wan-li; Zhu, Jian-guo; Xiao, Ding-quan

    2011-05-01

    The multiferroic (PMN-PT/CFO) n ( n = 1,2) multilayered thin films have been prepared on SiO 2/Si(1 0 0) substrate with LNO as buffer layer via a rf magnetron sputtering method. The structure and surface morphology of multilayered thin films were determined by X-ray diffraction (XRD) and atom force microscopy (AFM), respectively. The smooth, dense and crack-free surface shows the excellent crystal quality with root-mean-square (RMS) roughness only 2.9 nm, and average grain size of CFO thin films on the surface is about 44 nm. The influence of the thin films thickness size, periodicity n and crystallite orientation on their properties including ferroelectric, ferromagnetic properties in the (PMN-PT/CFO) n multilayered thin films were investigated. For multilayered thin films with n = 1 and n = 2, the remanent polarization Pr are 17.9 ?C/cm 2 and 9.9 ?C/cm 2; the coercivity Hc are 1044 Oe and 660 Oe, respectively. In addition, the relative mechanism are also discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  14. Measuring and controlling the transport of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Stephens, Jason R.

    Despite the large body of literature describing the synthesis of magnetic nanoparticles, few analytical tools are commonly used for their purification and analysis. Due to their unique physical and chemical properties, magnetic nanoparticles are appealing candidates for biomedical applications and analytical separations. Yet in the absence of methods for assessing and assuring their purity, the ultimate use of magnetic particles and heterostructures is likely to be limited. For magnetic nanoparticles, it is the use of an applied magnetic flux or field gradient that enables separations. Flow based techniques are combined with applied magnetic fields to give methods such as magnetic field flow fractionation and high gradient magnetic separation. Additional techniques have been explored for manipulating particles in microfluidic channels and in mesoporous membranes. This thesis further describes development of these and new analytical tools for separation and analysis of colloidal particles is critically important to enable the practical use of these, particularly for medicinal purposes. Measurement of transport of nanometer scale particles through porous media is important to begin to understand the potential environmental impacts of nanomaterials. Using a diffusion cell with two compartments separated by either a porous alumina or polycarbonate membrane as a model system, diffusive flux through mesoporous materials is examined. Experiments are performed as a function of particle size, pore diameter, and solvent, and the particle fluxes are monitored by the change in absorbance of the solution in the receiving cell. Using the measured extinction coefficient and change in absorbance of the solution as a function of time, the fluxes of 3, 8, and 14 nm diameter CoFe2O4 particles are determined as they are translocated across pores with diameters 30, 50, 100, and 200 nm in hexane and aqueous solutions. In general, flux decreases with increasing particle size and 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

  15. Engineering ultrasmall water-soluble gold and silver nanoclusters for biomedical applications.

    PubMed

    Luo, Zhentao; Zheng, Kaiyuan; Xie, Jianping

    2014-05-25

    Gold and silver nanoclusters or Au/Ag NCs with core sizes smaller than 2 nm have been an attractive frontier of nanoparticle research because of their unique physicochemical properties such as well-defined molecular structure, discrete electronic transitions, quantized charging, and strong luminescence. As a result of these unique properties, ultrasmall size, and good biocompatibility, Au/Ag NCs have great potential for a variety of biomedical applications, such as bioimaging, biosensing, antimicrobial agents, and cancer therapy. In this feature article, we will first discuss some critical biological considerations, such as biocompatibility and renal clearance, of Au/Ag NCs that are applied for biomedical applications, leading to some design criteria for functional Au/Ag NCs in the biological settings. According to these biological considerations, we will then survey some efficient synthetic strategies for the preparation of protein- and peptide-protected Au/Ag NCs with an emphasis on our recent contributions in this fast-growing field. In the last part, we will highlight some potential biomedical applications of these protein- and peptide-protected Au/Ag NCs. It is believed that with continued efforts to understand the interactions of biomolecule-protected Au/Ag NCs with the biological systems, scientists can largely realize the great potential of Au/Ag NCs for biomedical applications, which could finally pave their way towards clinical use. PMID:24266029

  16. Thermal Signatures of Pairing Correlations in Nuclei and Nanoparticles

    E-print Network

    Y. Alhassid

    2007-02-15

    The Bardeen-Cooper-Schrieffer (BCS) mean-field theory of the pairing interaction breaks down for nuclei and ultra-small metallic grains (nanoparticles). Finite-temperature pairing correlations in such finite-size systems can be calculated beyond the BCS theory in an auxiliary-field Monte Carlo approach. We identify thermal signatures of pairing correlations in both nuclei and nanoparticles that depend on the particle-number parity.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

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

    PubMed

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

    2012-10-21

    In this work, ultra-small Cu(2)O nanoparticles have been loaded on TiO(2) nanosheets with {001} facets exposed through a one-pot hydrothermal reaction. These Cu(2)O nanoparticles are well-dispersed on TiO(2) nanosheets with narrow size distributions and controllable sizes from 1.5 to 3.0 nm. Through XRD, TEM, N(2) absorption-desorption isotherms and UV-vis diffuse reflectance spectra, the Cu(2)O/TiO(2) nanosheets show similar phase structures, morphologies, pore structures as compared to pure TiO(2) nanosheets. Due to the loading of ultra-small Cu(2)O nanoparticles, heterojunctions are formed between Cu(2)O and TiO(2), which favors the efficient separation of photo-generated electrons and holes. Caused by the electron transfer from Cu(2)O to TiO(2), Cu(2)O/TiO(2) nanosheets show excellent visible-light activity, about 3 times that of N-doped TiO(2) nanosheets with {001} facets exposed. Furthermore, charge transfer rate across the interface of Cu(2)O and TiO(2) shows great dependence on the size of Cu(2)O particles. The charge transfer across the interface may be more efficient between TiO(2) nanosheets and smaller Cu(2)O nanoparticles. Therefore, the Ti : Cu = 30 : 1(atomic ratio) sample shows the best activity due to its balance in light harvest and electron transfer rate in the degradation of phenol under visible light. PMID:22945479

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  20. Surface-Stress-Driven Lattice Contraction Effects on the Extinction Spectra of Ultrasmall Silver Nanowires

    E-print Network

    Lin, Xi

    Surface-Stress-Driven Lattice Contraction Effects on the Extinction Spectra of Ultrasmall Silver-driven lattice contraction on the extinction spectra of silver nanowires with a square cross section of length 2

  1. Nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  2. Nanoparticle-DNA-polymer composites for hepatocellular carcinoma cell labeling, sensing, and magnetic resonance imaging.

    PubMed

    Leung, Ken Cham-Fai; Lee, Siu-Fung; Wong, Chi-Hin; Chak, Chun-Pong; Lai, Josie M Y; Zhu, Xiao-Ming; Wang, Yi-Xiang J; Sham, Kathy W Y; Cheng, Christopher H K

    2013-12-15

    This paper describes comparative studies and protocols in (1) self-assembling of ultrasmall superparamagnetic iron oxide nanoparticle (NP), circular plasmid DNA, and branched polyethylenimine (PEI) composites; (2) magnetofection; (3) gene delivery, (4) magnetic resonance imaging (MRI), and (5) cytotoxicity of the composites toward hepatocellular carcinoma HepG2 cells. PMID:23811300

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

    Microsoft Academic Search

    V. Pillai; D. O. Shah

    1996-01-01

    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

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

    PubMed

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

    2010-07-01

    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

  5. Synthesis and characterisation of biologically compatible TiO2 nanoparticles

    PubMed Central

    2011-01-01

    We describe for the first time the synthesis of biocompatible TiO2 nanoparticles containing a functional NH2 group which are easily dispersible in water. The synthesis of water dispersible TiO2 nanoparticles coated with mercaptosuccinic acid is also reported. We show that it is possible to exchange the stearic acid from pre-synthesised fatty acid-coated anatase 5-nm nanoparticles with a range of organic ligands with no change in the size or morphology. With further organic functionalisation, these nanoparticles could be used for medical imaging or to carry cytotoxic radionuclides for radioimmunotherapy where ultrasmall nanoparticles will be essential for rapid renal clearance. PMID:21711954

  6. Influence of pH on the structural and magnetic behavior of cobalt ferrite synthesized by sol-gel auto-combustion

    NASA Astrophysics Data System (ADS)

    Kakade, S. G.; Kambale, R. C.; Kolekar, Y. D.

    2015-06-01

    Cobalt ferrite (CoFe2O4) shown to be promising candidate for applications such as high-density magnetic recording, enhanced memory storage, magnetic fluids and catalysts. Utility of ferrite nanoparticles depends on its size, dispersibility in solutions, and magnetic properties. We have investigated the structural properties of synthesized cobalt ferrite nanoparticles synthesized by sol gel auto combustion for uncontrolled, acidic, neutral and basic pH values. X-ray diffraction (XRD) study confirms the cubic spinel phase formation with lattice constant 8.38 Å. In this study, we have optimized the pH value to synthesize homogenous cobalt ferrite nanoparticles with enhanced magnetic behavior. The surface morphology has been investigated by employing SEM images and the confirmation of spinel ferrite was also supported by using IR spectroscopy. Magnetic measurements for CoFe2O4 compositions (with pH <1, pH = 3, 7, 10) were investigated using VSM measurements.

  7. Electrochemical Activity of Dendrimer-Stabilized Tin Nanoparticles for Lithium Alloying Reactions.

    PubMed

    Bhandari, Rohit; Anderson, Rachel M; Stauffer, Shannon; Dylla, Anthony G; Henkelman, Graeme; Stevenson, Keith J; Crooks, Richard M

    2015-06-16

    The synthesis and characterization of Sn nanoparticles in organic solvents using sixth-generation dendrimers modified on their periphery with hydrophobic groups as stabilizers are reported. Sn(2+):dendrimer ratios of 147 and 225 were employed for the synthesis, corresponding to formation of Sn147 and Sn225 dendrimer-stabilized nanoparticles (DSNs). Transmission electron microscopy analysis indicated the presence of ultrasmall Sn nanoparticles having an average size of 3.0-5.0 nm. X-ray absorption spectroscopy suggested the presence of Sn nanoparticles with only partially oxidized surfaces. Cyclic voltammetry studies of the Sn DSNs for Li alloying/dealloying reactions demonstrated good reversibility. Control experiments carried out in the absence of DSNs clearly indicated that these ultrasmall Sn DSNs react directly with Li to form SnLi alloys. PMID:26039456

  8. Hydrogen gas sensing with networks of ultra-small palladium nanowires formed on filtration membranes.

    SciTech Connect

    Zeng, X. Q.; Latimer, M. L.; Xiao, Z. L.; Panuganti, S.; Welp, U.; Kwok, W. K.; Xu, T. (Materials Science Division); (Northern Illinois Univ.)

    2010-11-29

    Hydrogen sensors based on single Pd nanowires show promising results in speed, sensitivity, and ultralow power consumption. The utilization of single Pd nanowires, however, face challenges in nanofabrication, manipulation, and achieving ultrasmall transverse dimensions. We report on hydrogen sensors that take advantage of single palladium nanowires in high speed and sensitivity and that can be fabricated conveniently. The sensors are based on networks of ultrasmall (<10 nm) palladium nanowires deposited onto commercially available filtration membranes. We investigated the sensitivities and response times of these sensors as a function of the thickness of the nanowires and also compared them with a continuous reference film. The superior performance of the ultrasmall Pd nanowire network based sensors demonstrates the novelty of our fabrication approach, which can be directly applied to palladium alloy and other hydrogen sensing materials.

  9. Hydrogen gas sensing with networks of ultrasmall palladium nanowires formed on filtration membranes.

    PubMed

    Zeng, X Q; Latimer, M L; Xiao, Z L; Panuganti, S; Welp, U; Kwok, W K; Xu, T

    2011-01-12

    Hydrogen sensors based on single Pd nanowires show promising results in speed, sensitivity, and ultralow power consumption. The utilization of single Pd nanowires, however, face challenges in nanofabrication, manipulation, and achieving ultrasmall transverse dimensions. We report on hydrogen sensors that take advantage of single palladium nanowires in high speed and sensitivity and that can be fabricated conveniently. The sensors are based on networks of ultrasmall (<10 nm) palladium nanowires deposited onto commercially available filtration membranes. We investigated the sensitivities and response times of these sensors as a function of the thickness of the nanowires and also compared them with a continuous reference film. The superior performance of the ultrasmall Pd nanowire network based sensors demonstrates the novelty of our fabrication approach, which can be directly applied to palladium alloy and other hydrogen sensing materials. PMID:21114299

  10. Ultrasmall biocompatible nanocomposites: a new approach using seeded emulsion polymerization for the encapsulation of nanocrystals.

    PubMed

    Kloust, Hauke; Pöselt, Elmar; Kappen, Sascha; Schmidtke, Christian; Kornowski, Andreas; Pauer, Werner; Moritz, Hans-Ulrich; Weller, Horst

    2012-05-01

    We report a novel approach of seeded emulsion polymerization in which nanocrystals are used as seeds. Ultrasmall biocompatible polymer-coated nanocrystal with sizes between 15 and 110 nm could be prepared in a process that avoids any treatment with high shear forces or ultrasonication. The number of nanocrystals per seed, the size of the seeds, and the shell thickness can be independently adjusted. Single encapsulated nanocrystals in ultrasmall nanobeads as well as clusters of nanocrystals can be obtained. Polysorbat-80 was used as surfactant. It consists of poly(ethylene glycol) (PEG) chains, giving the particles outstanding biofunctional characteristics such as a minimization of unspecific interactions. PMID:22497455

  11. Characterization of sol–gel-prepared nanoferrites

    Microsoft Academic Search

    M. K. Shobana; S. Sankar

    2009-01-01

    Spinel Co1?xMnxFe2O4 nanoparticles were prepared by the sol–gel combustion technique. X-ray diffraction (XRD), atomic force microscopy (AFM) and vibration sample magnetometer (VSM) studies have been carried out in order to understand the temperature dependence of their properties. It is observed that the high concentration of Mn2+ substituted into CoFe2O4 tends to reduce the particle size. Furthermore, the influence of Mn

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

    PubMed Central

    2011-01-01

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

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

    Microsoft Academic Search

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

    2011-01-01

    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

  14. One-dimensional arrays of ultrasmall tunnel junctions with alternating superconducting and normal metal islands

    Microsoft Academic Search

    M. Matters; J. E. Mooij

    1994-01-01

    We have fabricated and performed measurements on one-dimensional arrays of ultrasmall tunnel junctions. These arrays consist of alternating superconducting and normal metal islands. With two gate electrodes, capacitively coupled to the aluminum islands, the array is irradiated with microwaves of frequency f; with an adjustable phase difference between the two microwave signals. In the normal state the I-V characteristics show

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  16. Microwave absorption properties of cobalt ferrite-modified carbonized bacterial cellulose

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    Ultra-small superparamagnetic particles of iron oxides (USPIO) have been developed as intravenous organ/tissue-targeted contrast agents to improve magnetic resonance imaging (MRI) in vivo. However, their potential toxicity and effects on metabolism have attracted particular attention. In the present study, uncoated and dextran-coated USPIO were investigated by analyzing both rat urine and plasma metabonomes using high-resolution NMR-based metabonomic analysis in combination with multivariate statistical analysis. The wealth of information gathered on the metabolic profiles from rat urine and plasma has revealed subtle metabolic changes in response to USPIO administration. The metabolic changes include the elevation of urinary ?-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.

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

    PubMed

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

    2012-01-01

    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 (r(2)) and decreases longitudinal (r(1)) magnetic resonance (MR) relaxivities of water proton in micelle solution, leading to a notably high r(2)/r(1) ratio up to 78, which makes the PEG-PCL-SPIONs a highly sensitive MR imaging (MRI) T(2) 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 T(2)-weighted MR images of the tumor, indicating the efficient accumulation of Fa-PEG-PCL-SPIONs in the tumor tissue. PMID:22745549

  19. Improved multiphoton ultraviolet upconversion photoluminescence in ultrasmall core-shell nanocrystals.

    PubMed

    Tao, Lili; Zhou, Bo; Jin, Wei; Chai, Yang; Tang, Chun-Yin; Tsang, Yuen H

    2014-11-01

    Near-infrared to ultraviolet multiphoton upconversion photoluminescence in ultrasmall Tm3+/Yb3+-codoped CaF2 nanocrystals (?6.7??nm in size) was observed and further significantly enhanced by growing an active shell of NaYF4:Yb3+. Owing to the active shell, the lanthanide emitters inside the core are effectively prevented from the surface quenchers, and the excitation energy is absorbed more efficiently via the additional luminescence sensitizer Yb3+ embedded in the shell. The details of underlying physics were investigated and discussed. The results present a good ultrasmall luminescent material system for achieving efficient multiphoton upconversion, which shows great potential in versatile industrial and biological applications. PMID:25361330

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

    Microsoft Academic Search

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

    2009-01-01

    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

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

    Microsoft Academic Search

    Shann S Yu; Randy L Scherer; Ryan A Ortega; Charleson S Bell; Conlin P O’Neil; Jeffrey A Hubbell; Todd D Giorgio

    2011-01-01

    Background  Drug and contrast agent delivery systems that achieve controlled release in the presence of enzymatic activity are becoming\\u000a increasingly important, as enzymatic activity is a hallmark of a wide array of diseases, including cancer and atherosclerosis.\\u000a Here, we have synthesized clusters of ultrasmall superparamagnetic iron oxides (USPIOs) that sense enzymatic activity for\\u000a applications in magnetic resonance imaging (MRI). To achieve

  2. A high-temperature Bonse-Hart ultrasmall-angle x-ray scattering instrument

    Microsoft Academic Search

    Benjamin Chu; Yingjie Li; Paul J. Harney; Fengji Yeh

    1993-01-01

    A Bonse–Hart ultrasmall-angle x-ray scattering (USAXS) instrument has been designed, constructed, and tested employing a synchrotron x-ray source. The instrument permits experiments ranging from below 0 °C up to about 400 °C, as well as temperature scanning, jumping, quenching, and annealing experiments. The mechanical elements used Super Invar as the basic building material in order to minimize the thermal expansion

  3. Transport spectroscopy of the ultrasmall silicon quantum dot in a single-electron transistor

    Microsoft Academic Search

    Masumi Saitoh; Toshiki Saito; Takashi Inukai; Toshiro Hiramoto

    2001-01-01

    We investigate electron transport through the ultrasmall silicon quantum dot in a single-electron transistor. The device is fabricated in the form of a silicon point-contact channel metal-oxide-semiconductor field-effect transistor. The size of the formed dot is estimated to be as small as 5.3 nm. Negative differential conductance is clearly observed up to 25 K. It turns out that this is

  4. Clinical applications of iron oxide nanoparticles for magnetic resonance imaging of brain tumors.

    PubMed

    Iv, Michael; Telischak, Nicholas; Feng, Dan; Holdsworth, Samantha J; Yeom, Kristen W; Daldrup-Link, Heike E

    2015-01-01

    Current neuroimaging provides detailed anatomic and functional evaluation of brain tumors, allowing for improved diagnostic and prognostic capabilities. Some challenges persist even with today's advanced imaging techniques, including accurate delineation of tumor margins and distinguishing treatment effects from residual or recurrent tumor. Ultrasmall superparamagnetic iron oxide nanoparticles are an emerging tool that can add clinically useful information due to their distinct physiochemical features and biodistribution, while having a good safety profile. Nanoparticles can be used as a platform for theranostic drugs, which have shown great promise for the treatment of CNS malignancies. This review will provide an overview of clinical ultrasmall superparamagnetic iron oxides and how they can be applied to the diagnostic and therapeutic neuro-oncologic setting. PMID:25867862

  5. Effect of surface reconstruction on the structural prototypes of ultrasmall ultrabright Si29 nanoparticles

    E-print Network

    Mitas, Lubos

    a hydrogen terminated reconstructed Si surface. The surface is a highly wrinkled or puckered system, absorption edge, and polarizability for several sur- face reconstruction models. One interesting structure constitute a hydrogen terminated reconstructed Si surface Si29H24, with six reconstructed sur- face dimers

  6. Ultrasmall particle detection using a submicron Hall sensor

    SciTech Connect

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

    2010-05-15

    We demonstrate detection of a single FePt nanoparticle (diameter 150 nm, moment {approx}10{sup 7} {mu}{sub B}) using an ultrasensitive InSb Hall sensor with the bar lateral width of 600 nm. The white noise of a typical nanodevice, S{sub V}{sup 1/2{approx_equal}}28 nV/{radical}Hz, is limited only by two-terminal resistance of the voltage leads which results in a minimum field sensitivity of the device B{sub min}=0.87 {mu}T/{radical}Hz. To detect a single FePt bead, we employed a phase-sensitive method based on measuring the ac susceptibility change in a bead when exposed to a switched dc magnetic field. Such nano-Hall devices, enabling detection of potentially even smaller moments, are of considerable significance both for nanomagnetic metrology and high sensitivity biological and environmental detectors.

  7. Exact Study of the Effect of Level Statistics in Ultrasmall Superconducting Grains

    E-print Network

    G. Sierra; J. Dukelsky; G. G. Dussel; Jan von Delft; Fabian Braun

    1999-09-01

    The reduced BCS model that is commonly used for ultrasmall superconducting grains has an exact solution worked out long ago by Richardson in the context of nuclear physics. We use it to check the quality of previous treatments of this model, and to investigate the effect of level statistics on pairing correlations. We find that the ground state energies are on average somewhat lower for systems with non-uniform than uniform level spacings, but both have an equally smooth crossover from the bulk to the few-electron regime. In the latter, statistical fluctuations in ground state energies strongly depend on the grain's electron number parity.

  8. Fabrication and characterization of well-aligned plasmonic nanopillars with ultrasmall separations

    PubMed Central

    2014-01-01

    We show the fabrication of well-aligned gold and silver nanopillars with various array parameters via interference lithography followed by ion beam milling and compare the etching rates of these two metallic materials. Silver is suitable for fabricating ultrafine arrays with ultrasmall separations due to high milling rates. The optical properties of the fabricated nanopillars are specifically characterized from both normal incidence and oblique incident angles. Tunable surface plasmon resonances are achieved with varying structural parameters. Strong coupling effects are enabled when the separation between adjacent nanopillars is dramatically reduced, leading to useful applications in sensing and waveguiding. PMID:24959111

  9. Magnetic colloidal superparticles of Co, Mn and Ni ferrite featured with comb-type and/or linear amphiphilic polyelectrolytes; NMR and MRI relaxometry.

    PubMed

    Menelaou, Melita; Iatridi, Zacharoula; Tsougos, Ioannis; Vasiou, Katerina; Dendrinou-Samara, Catherine; Bokias, Georgios

    2015-06-28

    The ability to encapsulate hydrophobic ferrites in colloidal superparticle structures of an a-telechelic hexadecyl-functionalized poly(methacrylic acid) (C16H33-PMAA) polymer with a linear architecture was investigated and compared with that of two amphiphilic comb-type water-soluble copolymers, namely, P(ANa-co-DAAm) and P(MANa-co-DMA), which are comprised of a poly(sodium acrylate) or poly(sodium methacrylate) backbone and pendent dodecyl acrylamide or dodecyl methacrylate chains, respectively. In the case of C16H33-PMAA, the pH-sensitive self-assembly behavior, which was studied through Nile Red probing and TEM, was related to its encapsulation properties. Hydrophobic MFe2O4 nanoparticles coated with oleylamine (MFe2O4@OAm MNPs, where M = Co, Mn, Ni) with a similar shape and size (?9 nm) and magnetization values of 87.4, 63.1 and 55.0 emu g(-1) for CoFe2O4@OAm, MnFe2O4@OAm and NiFe2O4@OAm, respectively, were successfully encapsulated into the hydrophobic cores of spherical micellar structures formed by the copolymers in an aqueous solution through a solvent mixing procedure. The synthesized magnetic colloidal superparticles fell in the static dephasing regime (SDR). NMR relaxivity measurements of MFe2O4@P(ANa-co-DAAm), MFe2O4@P(MANa-co-DMA) and MFe2O4@C16H33-PMAA at pH = 4.5 and pH = 7 (where M = Co, Mn, Ni) at 11.7 T were recorded and the transverse relaxivity (r2) (mM(-1) s(-1)) was determined. Among all, the CoFe2O4@polymers demonstrated the highest r2 relaxivity values, ranging from 61.6 for CoFe2O4@C16H33-PMAA (pH = 7) to 316.0 mM(-1) s(-1) for CoFe2O4@P(ANa-co-DAAm). The relaxation efficiency (r1 and r2) of CoFe2O4@P(ANa-co-DAAm) was investigated further by magnetic resonance imaging (MRI) at 1.5 T and 3 T and the r2/r1 ratios were found to be 16.5 and 18.2, respectively, indicating its potential use as a T2 contrast agent. PMID:25986081

  10. Giant electric field controlled magnetic anisotropy in epitaxial BiFeO3-CoFe2O4 thin film heterostructures on single crystal Pb(Mg1\\/3Nb2\\/3)0.7Ti0.3O3 substrate

    Microsoft Academic Search

    Zhiguang Wang; Yaodong Yang; Ravindranath Viswan; Jiefang Li; D. Viehland

    2011-01-01

    We have deposited self-assembled BiFeO3 (BFO)-CoFe2O4 (CFO) thin films on Pb(Mg1\\/3Nb2\\/3)0.7Ti0.3O3 (PMN-PT) substrates and studied the change in magnetic anisotropy under different strain conditions induced by an applied electric field. After electric field poling, we observed (i) giant magnetization change: magnetization of original CFO phase is three times larger than that of strained one and (ii) magnetic force microscopy line

  11. Networks of ultrasmall Pd/Cr bilayer nanowires as high performance hydrogen sensors.

    SciTech Connect

    Zeng, X.-Q.; Wang, Y.-L.; Deng, H.; Latimer, M. L.; Xiao, Z.-L.; Pearson, J.; Xu, T.; Wang, H.-H.; Welp, U.; Crabtree, G. W.; Kwok, W.-K. (Center for Nanoscale Materials); ( MSD); (Northern Illinois Univ.); (Illinois Math and Science Academy); (Univ. of Illinois at Chicago)

    2011-01-01

    The newly developed hydrogen sensor, based on a network of ultrasmall pure palladium nanowires sputter-deposited on a filtration membrane, takes advantage of single palladium nanowires' characteristics of high speed and sensitivity while eliminating their nanofabrication obstacles. However, this new type of sensor, like the single palladium nanowires, cannot distinguish hydrogen concentrations above 3%, thus limiting the potential applications of the sensor. This study reports hydrogen sensors based on a network of ultrasmall Cr-buffered Pd (Pd/Cr) nanowires on a filtration membrane. These sensors not only are able to outperform their pure Pd counterparts in speed and durability but also allow hydrogen detection at concentrations up to 100%. The new networks consist of a thin layer of palladium deposited on top of a Cr adhesion layer 1-3 nm thick. Although the Cr layer is insensitive to hydrogen, it enables the formation of a network of continuous Pd/Cr nanowires with thicknesses of the Pd layer as thin as 2 nm. The improved performance of the Pd/Cr sensors can be attributed to the increased surface area to volume ratio and to the confinement-induced suppression of the phase transition from Pd/H solid solution ({alpha}-phase) to Pd hydride ({beta}-phase).

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

    PubMed

    Lakshmanan, Anupama; Hauser, Charlotte A E

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Salehpour, Mehran; Håkansson, Karl; Possnert, Göran

    2013-01-01

    An overview is presented covering the biological accelerator mass spectrometry activities at Uppsala University. The research utilizes the Uppsala University Tandem laboratory facilities, including a 5 MV Pelletron tandem accelerator and two stable isotope ratio mass spectrometers. In addition, a dedicated sample preparation laboratory for biological samples with natural activity is in use, as well as another laboratory specifically for 14C-labeled samples. A variety of ongoing projects are described and presented. Examples are: (1) Ultra-small sample AMS. We routinely analyze samples with masses in the 5-10 ?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.

  14. Statics and dynamics of single-electron solitons in two-dimensional arrays of ultrasmall tunnel junctions

    Microsoft Academic Search

    N. S. Bakhvalov; G. S. Kazacha; K. K. Likharev; S. I. Serdyukova

    1991-01-01

    We have analyzed the distribution and transfer of electric charge in a uniform two-dimensional array of ultrasmall tunnel junctions. The effects can be most adequately described in terms of topological solitons with charge +\\/-e. Field distribution in the soliton, its intrinsic energy, and the energy of interaction between the solitons and array edges have been calculated and compared with those

  15. Demonstration of an air-slot mode-gap confined photonic crystal slab nanocavity with ultrasmall mode volumes

    E-print Network

    Hone, James

    Demonstration of an air-slot mode-gap confined photonic crystal slab nanocavity with ultrasmall; accepted 23 December 2009; published online 5 February 2010 We demonstrate experimentally an air-slot mode on the design of an air-slot in a width-modulated line-defect in a photonic crystal slab. The origin of the high

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

    NASA Astrophysics Data System (ADS)

    Pillai, V.; Shah, D. O.

    1996-10-01

    Magnetic nanoparticles of cobalt ferrite (CoFe 2O 4) 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 were less than 50 nm in size and had a high intrinsic coercivity (1440 Oe) and saturation magnetization (65 emu/g).

  17. Correction: Facile synthesis of phosphine free ultra-small PbSe nanocrystals and their light harvesting studies in ETA solar cells.

    PubMed

    Akhtar, Javeed; Banski, Mateusz; Malik, Mohammad Azad; Revaprasadu, Neerish; Podhorodecki, Artur; Misiewicz, Jan

    2015-07-01

    Correction for 'Facile synthesis of phosphine free ultra-small PbSe nanocrystals and their light harvesting studies in ETA solar cells' by Javeed Akhtar, et al., Dalton Trans., 2014, 43, 16424-16430. PMID:26101182

  18. Manipulating superconducting fluctuations by the Little-Parks-de Gennes effect in ultrasmall Al loops.

    PubMed

    Staley, Neal E; Liu, Ying

    2012-09-11

    The destruction of superconducting phase coherence by quantum fluctuations and the control of these fluctuations are a problem of long-standing interest, with recent impetus provided by the relevance of these issues to the pursuit of high temperature superconductivity. Building on the work of Little and Parks, de Gennes predicted more than three decades ago that superconductivity could be destroyed near half-integer-flux quanta in ultrasmall loops, resulting in a destructive regime, and restored by adding a superconducting side branch, which does not affect the flux quantization condition. We report the experimental observation of this Little-Parks-de Gennes effect in Al loops prepared by advanced e-beam lithography. We show that the effect can be used to restore the lost phase coherence by employing side branches. PMID:22927386

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

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

    SciTech Connect

    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

    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.

  1. Multiferroic composites in nano–microscale with non-solid solution by Co-ferrite and (K 0.5Na 0.5)NbO 3-based ferroelectric matrix

    Microsoft Academic Search

    Yun Zhou; Jincang Zhang; Li Li; Yuling Su; Jinrong Cheng; Shixun Cao

    2009-01-01

    A new kind of lead-free multiferroic magnetoelectric composites was successfully prepared by incorporating the dispersed CoFe2O4 (CFO) ferromagnetic nanoparticles into (K0.5Na0.5)NbO3–LiSbO3 (KNN-LS5.2) ferroelectric micromatrix. The dependence of dielectric properties and DC magnetization on CFO phase content was systemically studied. The results show that the dielectric constant decreases with increasing CFO phase content at higher frequencies while the loss tangent and

  2. Nucleation of electroactive ? -phase poly(vinilidene fluoride) with CoFe 2 O 4 and NiFe 2 O 4 nanofillers: a new method for the preparation of multiferroic nanocomposites

    Microsoft Academic Search

    P. Martins; C. M. Costa; S. Lanceros-Mendez

    2011-01-01

    Multiferroic and magnetoelectric materials show enormous potential for technological developments. Multiferroic composites\\u000a are more attractive for applications due to their enhanced properties with respect to single-phase multiferroic materials.\\u000a In this paper we report on the nucleation of the electroactive ?-phase of poly(vinylidene fluoride), PVDF, by the addition of CoFe2O4 and NiFe2O4 nanoparticles in order to prepare poly(vinylidene fluoride)\\/ferrite nanocomposite for

  3. Toward an image-guided microbeam radiation therapy using gadolinium-based nanoparticles.

    PubMed

    Le Duc, Géraldine; Miladi, Imen; Alric, Christophe; Mowat, Pierre; Bräuer-Krisch, Elke; Bouchet, Audrey; Khalil, Enam; Billotey, Claire; Janier, Marc; Lux, François; Epicier, Thierry; Perriat, Pascal; Roux, Stéphane; Tillement, Olivier

    2011-12-27

    Ultrasmall gadolinium-based nanoparticles (GBNs) induce both a positive contrast for magnetic resonance imaging and a radiosentizing effect. The exploitation of these characteristics leads to a greater increase in lifespan of rats bearing brain tumors since the radiosensitizing effect of GBNs can be activated by X-ray microbeams when the gadolinium content is, at the same time, sufficiently high in the tumor and low in the surrounding healthy tissue. GBNs exhibit therefore an interesting potential for image-guided radiotherapy. PMID:22040385

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

    PubMed Central

    Li, Shengliang; Cao, Weipeng; Kumar, Anil; Jin, Shubin; Zhao, Yuanyuan; Zhang, Chunqiu; Zou, Guozhang; Wang, Paul C.

    2014-01-01

    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 Hg2+ and Cu2+ based on fluorescence quenching of ultrasmall DNA-Ag NCs. The fluorescence intensity of DNA-Ag NCs was selectively quenched by Hg2+ and Cu2+, 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 Hg2+ and Cu2+ 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 Hg2+ and Cu2+ and monitoring water quality in a wide range of samples regulated under the Environmental Protection Agency. PMID:24839391

  5. A high-temperature Bonse--Hart ultrasmall-angle x-ray scattering instrument

    SciTech Connect

    Chu, B.; Li, Y.; Harney, P.J.; Yeh, F. (Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400 (United States))

    1993-06-01

    A Bonse--Hart ultrasmall-angle x-ray scattering (USAXS) instrument has been designed, constructed, and tested employing a synchrotron x-ray source. The instrument permits experiments ranging from below 0 [degree]C up to about 400 [degree]C, as well as temperature scanning, jumping, quenching, and annealing experiments. The mechanical elements used Super Invar as the basic building material in order to minimize the thermal expansion effect. As the synchrotron beam after the beamline optics is already somewhat collimated and monochromatized, a very fine tuning of the first crystal was necessary. The high-temperature Bonse--Hart instrument increased the performance by a factor of about 10 when compared with our earlier room-temperature Bonse--Hart instrument using the same set of channel-cut germanium crystals. The instrument was tested by using a suspension of polystyrene latex spheres and by combining the USAXS measurement, for the first time, with measurements of the same latex suspension by means of laser light scattering.

  6. A high-temperature Bonse-Hart ultrasmall-angle x-ray scattering instrument

    NASA Astrophysics Data System (ADS)

    Chu, Benjamin; Li, Yingjie; Harney, Paul J.; Yeh, Fengji

    1993-06-01

    A Bonse-Hart ultrasmall-angle x-ray scattering (USAXS) instrument has been designed, constructed, and tested employing a synchrotron x-ray source. The instrument permits experiments ranging from below 0 °C up to about 400 °C, as well as temperature scanning, jumping, quenching, and annealing experiments. The mechanical elements used Super Invar as the basic building material in order to minimize the thermal expansion effect. As the synchrotron beam after the beamline optics is already somewhat collimated and monochromatized, a very fine tuning of the first crystal was necessary. The high-temperature Bonse-Hart instrument increased the performance by a factor of about 10 when compared with our earlier room-temperature Bonse-Hart instrument using the same set of channel-cut germanium crystals. The instrument was tested by using a suspension of polystyrene latex spheres and by combining the USAXS measurement, for the first time, with measurements of the same latex suspension by means of laser light scattering.

  7. Further analysis of focusing performance of an ultra-small gradient-index fiber probe

    NASA Astrophysics Data System (ADS)

    Wang, Chi; Bi, Shubo; Xia, Xueqin; Yu, Yingjie

    2014-01-01

    In order to optimize ultra-small gradient-index (GRIN) fiber probes and provide a theoretical prediction for the fabrication of such probes with high performance, focusing performance of the GRIN fiber probe is further analyzed based on the optical characteristic parameters. According to the optical model of the GRIN fiber probe and its mathematical expressions of characteristic parameters, the three-dimensional (3-D) function diagram is used for analyzing the impact of the lengths of probe components on the characteristic parameters. Partial derivatives of the mathematical expressions of characteristics are derived to analyze the mutation of focusing performance caused by the different lengths of probe components. According to the analytical results, our predictions suggest that focusing performance could be reflected through the 3-D function diagram between the characteristic parameters and the continuous change of the lengths of probe components. In addition, mutation occurs in the focusing performance of the GRIN fiber probe when the length of probe components changes. The research results are of practical guiding significance for the fabrication of GRIN fiber probes requiring specific optical focusing performance.

  8. The Crossover from the Bulk to the Few-Electron limit in Ultrasmall Metallic Grains

    E-print Network

    J. Dukelsky; G. Sierra

    1999-11-24

    We study the properties of ultrasmall metallic grains with sizes in the range of 20 up to 400 electrons. Using a particle-hole version of the DMRG method we compute condensation energies, spectroscopic gaps, pairing parameters and particle-hole probabilities of the ground state wave function. The results presented in this paper confirm that the bulk superconducting regime (large grains) and the fluctuation dominated regime (small grains) are qualitative different, but show that the crossover between them is very smooth with no signs of critical level spacings separating them. We compare our DMRG results with the exact ones obtained with the Richardson solution finding complete agreement. We also propose a simplified version of the DMRG wave function, called the Particle-Hole BCS ansatz, which agrees qualitatively with the DMRG solution and illustrates what is lacking in the PBCS wave function in order to describe correctly the crossover. Finally we present a new recursive method to compute norms and expectation values with the PBCS wave function.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  10. Effects of Ultrasmall Orifices on the Electro-generation of Femtoliter-Volume Aqueous Droplets

    PubMed Central

    He, Mingyan; Kuo, Jason S.; Chiu, Daniel T.

    2008-01-01

    The ability to generate individual picoliter- and femtoliter-volume aqueous droplets on-demand is useful for encapsulating and chemically manipulating discrete chemical and biological samples. This paper characterizes the effects of orifice dimensions and material choices on generating such droplets in an immiscible oil phase using single high-voltage pulses with various amplitudes and durations. We have examined microfluidic orifices as small as 1.7 ?m in equivalent radii, and found that the electrohydrodynamic jet lengths and the subsequent formation of droplets are affected by the axial aspect ratios of the orifices (length of an orifice divided by its equivalent radius). As higher voltages were used to compensate for the increased capillary pressure and hydrodynamic resistance in ultrasmall orifices, we observed secondary jet protrusions and droplet formations that were not of classical electrohydrodynamic origin. The droplets generated from secondary jets traveled at relatively lower velocities as compared to those of electrohydrodynamic origin, and these slow individual droplets are potentially more useful for applications in microscale chemical reactions. PMID:16800707

  11. Ultra-small plutonium oxide nanocrystals: an innovative material in plutonium science.

    PubMed

    Hudry, Damien; Apostolidis, Christos; Walter, Olaf; Janssen, Arne; Manara, Dario; Griveau, Jean-Christophe; Colineau, Eric; Vitova, Tonya; Prüssmann, Tim; Wang, Di; Kübel, Christian; Meyer, Daniel

    2014-08-11

    Apart from its technological importance, plutonium (Pu) is also one of the most intriguing elements because of its non-conventional physical properties and fascinating chemistry. Those fundamental aspects are particularly interesting when dealing with the challenging study of plutonium-based nanomaterials. Here we show that ultra-small (3.2±0.9?nm) and highly crystalline plutonium oxide (PuO2 ) nanocrystals (NCs) can be synthesized by the thermal decomposition of plutonyl nitrate ([PuO2 (NO3 )2 ]?3?H2 O) in a highly coordinating organic medium. This is the first example reporting on the preparation of significant quantities (several tens of milligrams) of PuO2 NCs, in a controllable and reproducible manner. The structure and magnetic properties of PuO2 NCs have been characterized by a wide variety of techniques (powder X-ray diffraction (PXRD), X-ray absorption fine structure (XAFS), X-ray absorption near edge structure (XANES), TEM, IR, Raman, UV/Vis spectroscopies, and superconducting quantum interference device (SQUID) magnetometry). The current PuO2 NCs constitute an innovative material for the study of challenging problems as diverse as the transport behavior of plutonium in the environment or size and shape effects on the physics of transuranium elements. PMID:25042621

  12. Multipole plasmons and their disappearance in few-nanometer silver nanoparticles

    E-print Network

    Raza, Søren; Christensen, Thomas; Di Vece, Marcel; Wubs, Martijn; Mortensen, N Asger; Stenger, Nicolas

    2015-01-01

    In electron energy-loss spectroscopy (EELS) of individual silver nanoparticles encapsulated in silicon nitride, we observe besides the usual dipole resonance an additional surface plasmon (SP) resonance corresponding to higher angular momenta. We even observe both resonances for nanoparticle radii as small as 4 nm, where previously only the dipole resonance was assumed to play a role. Electron beams positioned outside of the particles mostly excite the dipole mode, but the higher-order resonance can even dominate the dipole peak when exciting at the particle surface, the usual choice for maximal EELS signal. This allows us to study the radius dependence of both resonances separately. For particles smaller than 4 nm, the higher-order SP mode disappears, in agreement with generalized nonlocal optical response (GNOR) theory, while the dipole resonance blueshift exceeds GNOR predictions. Unlike in optical spectra, multipole surface plasmons are important in EELS spectra even of ultra-small metallic nanoparticles.

  13. Glutathione-Coated Luminescent Gold Nanoparticles: A Surface Ligand for Minimizing Serum Protein Adsorption

    PubMed Central

    2015-01-01

    Ultrasmall glutathione-coated luminescent gold nanoparticles (GS-AuNPs) are known for their high resistance to serum protein adsorption. Our studies show that these NPs can serve as surface ligands to significantly enhance the physiological stability and lower the serum protein adsorption of superparamagnetic iron oxide nanoparticles (SPIONs), in addition to rendering the NPs the luminescence property. After the incorporation of GS-AuNPs onto the surface of SPIONs to form the hybrid nanoparticles (HBNPs), these SPIONs’ protein adsorption was about 10-fold lower than those of the pure glutathione-coated SPIONs suggesting that GS-AuNPs are capable of providing a stealth effect against serum proteins. PMID:25029478

  14. Bifunctional non-noble metal oxide nanoparticle electrocatalysts through lithium-induced conversion for overall water splitting.

    PubMed

    Wang, Haotian; Lee, Hyun-Wook; Deng, Yong; Lu, Zhiyi; Hsu, Po-Chun; Liu, Yayuan; Lin, Dingchang; Cui, Yi

    2015-01-01

    Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, including oxygen evolution reaction and hydrogen evolution reaction, is important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanoparticles (?20?nm) are electrochemically transformed into ultra-small diameter (2-5?nm) nanoparticles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanoparticles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10?mA?cm(-2) water-splitting current at only 1.51?V for over 200?h without degradation in a two-electrode configuration and 1?M KOH, better than the combination of iridium and platinum as benchmark catalysts. PMID:26099250

  15. Cerebral blood volume MRI with intravascular superparamagnetic iron oxide nanoparticles.

    PubMed

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

    2013-08-01

    The cerebral blood volume (CBV) is a crucial physiological indicator of tissue viability and vascular reactivity. Thus, noninvasive CBV mapping has been of great interest. For this, ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, including monocrystalline iron oxide nanoparticles, can be used as long-half-life, intravascular susceptibility agents of CBV MRI measurements. Moreover, CBV-weighted functional MRI (fMRI) with USPIO nanoparticles provides enhanced sensitivity, reduced large vessel contribution and improved spatial specificity relative to conventional blood oxygenation level-dependent fMRI, and measures a single physiological parameter that is easily interpretable. We review the physiochemical and magnetic properties, and pharmacokinetics, of USPIO nanoparticles 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 the application of CBV measurements to functional and pharmacological studies in animals. Overall, the use of USPIO nanoparticles can determine baseline CBV and its changes induced by functional activity and pharmacological interventions. PMID:23208650

  16. Detection and Isolation of Ultrasmall Microorganisms from a 120,000-Year-Old Greenland Glacier Ice Core

    PubMed Central

    Miteva, Vanya I.; Brenchley, Jean E.

    2005-01-01

    The abundant microbial population in a 3,043-m-deep Greenland glacier ice core was dominated by ultrasmall cells (<0.1 ?m3) that may represent intrinsically small organisms or starved, minute forms of normal-sized microbes. In order to examine their diversity and obtain isolates, we enriched for ultrasmall psychrophiles by filtering melted ice through filters with different pore sizes, inoculating anaerobic low-nutrient liquid media, and performing successive rounds of filtrations and recultivations at 5°C. Melted ice filtrates, cultures, and isolates were analyzed by scanning electron microscopy, flow cytometry, cultivation, and molecular methods. The results confirmed that numerous cells passed through 0.4-?m, 0.2-?m, and even 0.1-?m filters. Interestingly, filtration increased cell culturability from the melted ice, yielding many isolates related to high-G+C gram-positive bacteria. Comparisons between parallel filtered and nonfiltered cultures showed that (i) the proportion of 0.2-?m-filterable cells was higher in the filtered cultures after short incubations but this difference diminished after several months, (ii) more isolates were obtained from filtered (1,290 isolates) than from nonfiltered (447 isolates) cultures, and (iii) the filtration and liquid medium cultivation increased isolate diversity (Proteobacteria; Cytophaga-Flavobacteria-Bacteroides; high-G+C gram-positive; and spore-forming, low-G+C gram-positive bacteria). Many isolates maintained their small cell sizes after recultivation and were phylogenetically novel or related to other ultramicrobacteria. Our filtration-cultivation procedure, combined with long incubations, enriched for novel ultrasmall-cell isolates, which is useful for studies of their metabolic properties and mechanisms for long-term survival under extreme conditions. PMID:16332755

  17. Enhanced sensitivity and contrast with bimodal atomic force microscopy with small and ultra-small amplitudes in ambient conditions

    SciTech Connect

    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

    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.

  18. Giant enhancement of upconversion in ultra-small Er3+\\/Yb3+:NaYF4 nanoparticles via laser annealing

    Microsoft Academic Search

    A Bednarkiewicz; D Wawrzynczyk; A Gagor; L Kepinski; M Kurnatowska; L Krajczyk; M Nyk; M Samoc; W Strek

    2012-01-01

    Most of the synthesis routes of lanthanide-doped phosphors involve thermal processing which results in nanocrystallite growth, stabilization of the crystal structure and augmentation of luminescence intensity. It is of great interest to be able to transform the sample in a spatially localized manner, which may lead to many applications like 2D and 3D data storage, anti-counterfeiting protection, novel design bio-sensors

  19. Wedge hybrid plasmonic THz waveguide with long propagation length and ultra-small deep-subwavelength mode area

    PubMed Central

    Gui, Chengcheng; Wang, Jian

    2015-01-01

    We present a novel design of wedge hybrid plasmonic terahertz (THz) waveguide consisting of a silicon (Si) nanowire cylinder above a triangular gold wedge with surrounded high-density polyethylene as cladding. It features long propagation length and ultra-small deep-subwavelength mode confinement. The mode properties of wedge hybrid plasmonic THz waveguide are comprehensively characterized in terms of propagation length (L), normalized mode area (Aeff /A0), figure of merit (FoM), and chromatic dispersion (D). The designed wedge hybrid plasmonic THz waveguide enables an ultra-small deep-subwavelength mode area which is more than one-order of magnitude smaller compared to previous rectangular one. When choosing the diameter of Si nanowire cylinder, a smaller diameter (e.g. 10??m) is preferred to achieve longer L and higher FoM, while a larger diameter (e.g. 60??m) is favorable to obtain smaller Aeff /A0 and higher FoM. We further study the impacts of possible practical fabrication errors on the mode properties. The simulated results of propagation length and normalized mode area show that the proposed wedge hybrid plasmonic THz waveguide is tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, variation of wedge tip angle, and variation of wedge tip curvature radius. PMID:26155782

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

    E-print Network

    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

    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 ...

  1. Nano-photonic-device technologies for ultra-small and ultra-fast all-optical devices - Fusion of photonic crystals and quantum dots -

    Microsoft Academic Search

    K. Asakawa; H. Nakamura; Y. Sugimoto; Y. Watanabe; S. Lan; N. Ikeda; T. Yang; Y. Tanaka; Y. Nakamura; S. Ohkouchi; N. Yamamoto; K. Kanamoto; H. Ishikawa; K. Inoue

    2002-01-01

    Simulation, fabrication, characterization of two-dimensional photonic crystals and fabrication of nanoprobe-assisted site-controlled quantum dots for large optical non-linearity are presented for photonic crystal and quantum dot-based ultra-small and ultra-fast all optical switches

  2. Protein fibrillation and nanoparticle interactions: opportunities and challenges

    NASA Astrophysics Data System (ADS)

    Mahmoudi, Morteza; Kalhor, Hamid R.; Laurent, Sophie; Lynch, Iseult

    2013-03-01

    Due to their ultra-small size, nanoparticles (NPs) have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. NPs are recognized as promising and powerful tools to fight against the human brain diseases such as multiple sclerosis or Alzheimer's disease. In this review, after an introductory part on the nature of protein fibrillation and the existing approaches for its investigations, the effects of NPs on the fibrillation process have been considered. More specifically, the role of biophysicochemical properties of NPs, which define their affinity for protein monomers, unfolded monomers, oligomers, critical nuclei, and other prefibrillar states, together with their influence on protein fibrillation kinetics has been described in detail. In addition, current and possible-future strategies for controlling the desired effect of NPs and their corresponding effects on the conformational changes of the proteins, which have significant roles in the fibrillation process, have been presented.

  3. A new approach to quantification of metamorphism using ultra-small and small angle neutron scattering.

    SciTech Connect

    Anovitz, Lawrence {Larry} M [ORNL; Lynn, Gary W [ORNL; Cole, David R [ORNL

    2009-12-01

    In this paper we report the results of a study using small angle and ultra-small angle neutron scattering techniques (SANS and USANS) to examine the evolution of carbonates during contact metamorphism. Data were obtained from samples collected along two transects in the metamorphosed Hueco limestone at the Marble Canyon, Texas, contact aureole. These samples were collected from the igneous contact out to {approx}1700 m. Scattering curves obtained from these samples show mass fractal behavior at low scattering vectors, and surface fractal behavior at high scattering vectors. Significant changes are observed in the surface and mass fractal dimensions as well as the correlation lengths (pore and grain sizes), surface area to volume ratio and surface Gibbs Free energy as a function of distance, including regions of the aureole outside the range of classic metamorphic petrology. A change from mass-fractal to non-fractal behavior is observed at larger scales near the outer boundary of the aureole that implies significant reorganization of pore distributions early in the metamorphic history. Surface fractal results suggest significant smoothing of grain boundaries, coupled with changes in pore sizes. A section of the scattering curve with a slope less than -4 appears at low-Q in metamorphosed samples, which is not present in unmetamorphosed samples. A strong spike in the surface area to volume ratio is observed in rocks near the mapped metamorphic limit, which is associated with reaction of small amounts of organic material to graphite. It may also represent an increase in pore volume or permeability, suggesting that a high permeability zone forms at the boundary of the aureole and moves outwards as metamorphism progresses. Neutron scattering data also correlate well with transmission electron microscopic (TEM) observations, which show formation of micro- and nanopores and microfractures during metamorphism. The scattering data are, however, quantifiable for a bulk rock 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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

  5. Targeting of peptide conjugated magnetic nanoparticles to urokinase plasminogen activator receptor (uPAR) expressing cells.

    PubMed

    Hansen, Line; Larsen, Esben Kjær Unmack; Nielsen, Erik Holm; Iversen, Frank; Liu, Zhuo; Thomsen, Karen; Pedersen, Michael; Skrydstrup, Troels; Nielsen, Niels Chr; Ploug, Michael; Kjems, Jørgen

    2013-09-01

    Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are currently being used as a magnetic resonance imaging (MRI) contrast agent in vivo, mainly by their passive accumulation in tissues of interest. However, a higher specificity can ideally be achieved when the nanoparticles are targeted towards cell specific receptors and this may also facilitate specific drug delivery by an enhanced target-mediated endocytosis. We report efficient peptide-mediated targeting of magnetic nanoparticles to cells expressing the urokinase plasminogen activator receptor (uPAR), a surface biomarker for poor patient prognosis shared by several cancers including breast, colorectal, and gastric cancers. Conjugation of a uPAR specific targeting peptide onto polyethylene glycol (PEG) coated USPIO nanoparticles by click chemistry resulted in a five times higher uptake in vitro in a uPAR positive cell line compared to nanoparticles carrying a non-binding control peptide. In accordance with specific receptor-mediated recognition, a low uptake was observed in the presence of an excess of ATF, a natural ligand for uPAR. The uPAR specific magnetic nanoparticles can potentially provide a useful supplement for tumor patient management when combined with MRI and drug delivery. PMID:23835641

  6. Development of carbon nanotubes/CoFe2O4 magnetic hybrid material for removal of tetrabromobisphenol A and Pb(II).

    PubMed

    Zhou, Lincheng; Ji, Liqin; Ma, Peng-Cheng; Shao, Yanming; Zhang, He; Gao, Weijie; Li, Yanfeng

    2014-01-30

    Multi-walled carbon nanotubes (MWCNTs) coated with magnetic amino-modified CoFe2O4 (CoFe2O4-NH2) nanoparticles (denoted as MNP) were prepared via a simple one-pot polyol method. The MNP composite was further modified with chitosan (CTS) to obtain a chitosan-functionalized MWCNT/CoFe2O4-NH2 hybrid material (MNP-CTS). The obtained hybrid materials were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectrogram (FT-IR) Analysis and X-ray Photoelectron Spectroscopy (XPS) Analysis, Vibrating Sample Magnetometer (VSM) Analysis and the Brunauer-Emmett-Teller (BET) surface area method, respectively. The composites were tested as adsorbents for tetrabromobisphenol A (TBBPA) and Pb(II), and were investigated using a pseudo-second-order model. The adsorption of TBBPA was well represented by the Freundlich isotherm; the Langmuir model better described Pb(II) absorption. MNP-CTS adsorbed both TBBPA and Pb(II) (maximum adsorption capacities of 42.48 and 140.1mgg(-1), respectively) better than did MNP without CTS. Magnetic composite particles with adsorbed TBBPA and Pb(II) could be regenerated using 0.2M NaOH solution and were separable from liquid media using a magnetic field. PMID:24342050

  7. Biotemplated Synthesis of Anatase Titanium Dioxide Nanoparticles via Lignocellulosic Waste Material

    PubMed Central

    Bagheri, Samira; Abd Hamid, Sharifah Bee

    2014-01-01

    Anatase titanium dioxide nanoparticles (TiO2-NPs) were synthesized by sol-gel method using rice straw as a soft biotemplate. Rice straw, as a lignocellulosic waste material, is a biomass feedstock which is globally produced in high rate and could be utilized in an innovative approach to manufacture a value-added product. Rice straw as a reliable biotemplate has been used in the sol-gel method to synthesize ultrasmall sizes of TiO2-NPs with high potential application in photocatalysis. The physicochemical properties of titanium dioxide nanoparticles were investigated by a number of techniques such as X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), ultraviolet visible spectra (UV-Vis), and surface area and pore size analysis. All results consensually confirmed that particle sizes of synthesized titanium dioxide were template-dependent, representing decrease in the nanoparticles sizes with increase of biotemplate concentration. Titanium dioxide nanoparticles as small as 13.0 ± 3.3?nm were obtained under our experimental conditions. Additionally, surface area and porosity of synthesized TiO2-NPs have been enhanced by increasing rice straw amount which results in surface modification of nanoparticles and potential application in photocatalysis. PMID:25126547

  8. Polymeric nanoparticles-based topical delivery systems for the treatment of dermatological diseases

    PubMed Central

    Zhang, Zheng; Tsai, Pei-Chin; Ramezanli, Tannaz; Michniak-Kohn, Bozena B.

    2013-01-01

    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

  9. Ultra-dispersed Pt nanoparticles on SAPO-34/?-Al2O3 support for efficient propane dehydrogenation.

    PubMed

    Chu, Yue; Zhang, Qiang; Wu, Tongwei; Nawaz, Zeeshan; Wang, Yao; Wei, Fei

    2014-09-01

    Ultra-dispersed precious metal nanoparticles with good thermal stability are highly required for heterogeneous catalysis. However, the efficient and effective strategy to disperse ultra-fine precious metal nanoparticles at high reaction temperature is still not fully understood yet. In this contribution, a family of catalysts with ultra-small Pt nanoparticles were prepared using impregnation method by adjusting the zeolite content in the SAPO-34 and ?-Al2O3 mixed support. The effect of Pt nanoparticle size on the catalytic activity, selectivity, and stability was investigated in the propane dehydrogenation reaction. Catalyst with smaller Pt particles exhibits better catalytic performance. Both the highest Pt dispersion and the best catalytic activity can be achieved by using SAPO-34 and ?-Al2O3 mixed support with 70 wt.% of SAPO-34. The size and structure of the Pt nanoparticles on the optimal catalyst were characterized by transmission electron microscopy. Pt nanoparticles with an average size of 1.32 nm were observed. There were stronger metal-support interactions between the oxidized tin species and Pt particles on SAPO-34 support compared to that on ?-Al2O3 catalyst. These lead to high Pt dispersion and consequently good catalytic performance. PMID:25924347

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    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.

  11. Copper nanoparticles exert size and concentration dependent toxicity on somatosensory neurons of rat

    PubMed Central

    PRABHU, BADANAVALU M.; ALI, SYED F.; MURDOCK, RICHARD C.; HUSSAIN, SABER M.; SRIVATSAN, MALATHI

    2010-01-01

    Metal nanoparticles, due to their unique properties and important applications in optical, magnetic, thermal, electrical, sensor devices and cosmetics, are beginning to be widely manufactured and used. This new and rapidly growing field of technology warrants a thorough examination of the material’s bio-compatibility and safety. Ultra-small particles may adversely affect living cells and organisms since they can easily penetrate the body through skin contact, inhalation and ingestion. Retrograde transport of copper nanoparticles from nerve endings on the skin can reach the somatosensory neurons in dorsal root ganglion (DRG). Since copper nanoparticles have industrial and healthcare applications, we determined the concentration and size-dependant effects of their exposure on survival of DRG neurons of rat in cell culture. The neurons were exposed to copper nanoparticles of increasing concentrations (10–100 ?M) and sizes (40, 60 and 80 nm) for 24 h. Light microscopy, histochemical staining for copper, lactate dehydrogenase (LDH) assay for cell death, and MTS [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay for cell viability were performed to measure the resultant toxicity and cell survival. DRG neurons exposed to copper nanoparticles displayed vacuoles and detachment of some neurons from the substratum. Neurons also exhibited disrupted neurite network. LDH and MTS assays revealed that exposure to copper nanoparticles had significant toxic effect with all the sizes tested when compared to unexposed control cultures. Further analysis of the results showed that copper nanoparticles of smaller size and higher concentration exerted the maximum toxic effects. Rubeanic acid staining showed intracellular deposition of copper. These results demonstrate that copper nanoparticles are toxic in a size- and concentration-dependent manner to DRG neurons. PMID:20543894

  12. Bolaform surfactants with polyoxometalate head groups and their assembly into ultra-small monolayer membrane vesicles

    PubMed Central

    Landsmann, Steve; Luka, Martin; Polarz, Sebastian

    2012-01-01

    Surfactants are indispensable in established technologies as detergents or emulsification agents, and also in recent studies for controlling the growth of nanoparticles or for creating nanocarriers. Although the properties of conventional, organic surfactants are thoroughly explored, strong interest persists in surfactants that possess unique features inaccessible for ordinary systems. Here we present dipolar, bolaform surfactants with a head group comprising of 11 tungsten atoms. These novel compounds are characterized by an exceptionally low critical self-organization concentration, which leads to monolayer vesicles with a diameter of only 15?nm, that is, substantially smaller than for any other system. The membrane of the vesicles is impermeable for water-soluble and oil-soluble guests. Control over release kinetics, which can be followed via the quantitative fluorescence quenching of confined fluorophores, is gained by means of pH adjustments. PMID:23250429

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

    PubMed Central

    2013-01-01

    Background The Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored. In this paper, the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ?? 2H2O (1a) is elucidated, including the topotactic dehydration, valence and spins exchange mechanisms suggestion and the formation of a mixture of CoFe2O4-Co3O4 (3:1) as final products of thermal degradation. Results The course of thermal decomposition of 1a in air atmosphere up to 600°C was monitored by TG/DSC techniques, 57Fe Mössbauer and IR spectroscopy. As first, the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ?? 1/2H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-ray diffraction analysis. The consequent thermal decomposition proceeded in further four stages including intermediates varying in valence and spin states of both transition metal ions in their structures, i.e. [FeII(en)2(?-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

  14. Oxidation kinetics of ultrasmall colloidal chalcopyrite (CuFeS{sub 2}) with one-electron oxidants

    SciTech Connect

    Silvester, E.J.; Grieser, F.; Healy, T.W. [Univ. of Melbourne, Victoria (Australia)] [and others

    1992-05-28

    The stopped flow technique has been used to study the oxidation of ultrasmall colloidal chalcopyrite (CuFeS{sub 2}) particles (diameter 50-90 {angstrom}) by the one-electron oxidants hexacyanoferrate(III) (Fe(CN){sub 6}{sup 3{minus}}) and hexachloroiridate(IV) (IrCl{sub 6}{sup 2{minus}}) in aqueous solution. The stoichiometry of the initial oxidation step corresponds to the reaction CuFeS{sub 2(s)} + 5H{sub 2}O {yields} Cu(OH){sub 2(s)} + Fe(OH){sub 3(s)} + 2S{sub (s)}{sup 0} + 5H{sup +} + 5e{sup {minus}}. Further oxidation of the elemental sulfur results in the formation of S{sub 2}O{sub 3}{sup 2{minus}} and SO{sub 4}{sup 2{minus}} in solution, as determined by ion chromatography. Time-resolved measurement of both the oxidant and chalcopyrite concentrations has provided a detailed understanding of the mechanism involved in the oxidation of colloidal chalcopyrite. 88 refs., 11 figs., 2 tabs.

  15. Solvent-like ligand-coated ultrasmall cadmium selenide nanocrystals: strong electronic coupling in a self-organized assembly.

    PubMed

    Lawrence, Katie N; Johnson, Merrell A; Dolai, Sukanta; Kumbhar, Amar; Sardar, Rajesh

    2015-07-21

    Strong inter-nanocrystal electronic coupling is a prerequisite for delocalization of exciton wave functions and high conductivity. We report 170 meV electronic coupling energy of short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals (SNCs) in solution. Cryo-transmission electron microscopy analysis showed the formation of a pearl-necklace assembly of nanocrystals in solution with regular inter-nanocrystal spacing. The electronic coupling was studied as a function of CdSe nanocrystal size where the smallest nanocrystals exhibited the largest coupling energy. The electronic coupling in spin-cast thin-film (<200 nm in thickness) of poly(ethylene glycol) thiolate-coated CdSe SNCs was studied as a function of annealing temperature, where an unprecedentedly large, ?400 meV coupling energy was observed for 1.6 nm diameter SNCs, which were coated with a thin layer of poly(ethylene glycol) thiolates. Small-angle X-ray scattering measurements showed that CdSe SNCs maintained an order array inside the films. The strong electronic coupling of SNCs in a self-organized film could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device application. PMID:26098759

  16. Polymeric nanoparticles

    PubMed Central

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

    2014-01-01

    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

  17. Precision Nanoparticles

    SciTech Connect

    John Hemminger

    2009-07-21

    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

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

    PubMed Central

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

    2015-01-01

    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

  19. DNA base pair resolution measurements using resonance energy transfer efficiency in lanthanide doped nanoparticles.

    PubMed

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

    2015-01-01

    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

  20. Fluorescent nanoparticle interactions with biological systems: What have we learned so far?

    NASA Astrophysics Data System (ADS)

    Shang, Li; Nienhaus, Gerd Ulrich

    2015-03-01

    Fluorescent nanoparticles (NPs) are promising optical probes for biological and biomedical applications, thanks to their excellent photophysical properties, color tunability and facile bioconjugation. It still remains unclear, however, how fluorescent NPs behave in the complex biological environment. Our group has quantified interactions of different fluorescent NPs (i.e., semiconductor quantum dots and metal nanoclusters) with serum proteins and living cells by the combined use of different spectroscopic and microscopic techniques. Our studies show that (1) interactions with proteins may significantly alter the photophysical properties of the NPs as well as the responses of cells internalizing them; (2) protein surface charge distributions play an important role in the interactions of NPs with proteins and cells; (3) ultrasmall NPs (diameter less than 10 nm) show a cellular internalization behavior that is distinctly different from the one observed with larger particles (diameter ~100 nm).

  1. Mesoporous silica nanoparticles applied as a support for Pd and Au nanocatalysts in cycloisomerization reactions

    NASA Astrophysics Data System (ADS)

    Verho, Oscar; Gao, Feifei; Johnston, Eric V.; Wan, Wei; Nagendiran, Anuja; Zheng, Haoquan; Bäckvall, Jan-Erling; Zou, Xiaodong

    2014-11-01

    Ultra-small mesoporous silica nanoparticles (MSNs) have been synthesized at room temperature with particle sizes ranging from 28 to 45 nm. These MSNs have been employed as heterogeneous supports for palladium and gold nanocatalysts. The colloidal nature of the MSNs is highly useful for catalytic applications as it allows for better mass transfer properties and a more uniform distribution of the nanocatalysts in solution. The two nanocatalysts were evaluated in the cycloisomerization of alkynoic acids and demonstrated to produce the corresponding alkylidene lactones in good to excellent yields under mild conditions. In addition to their high activity, the catalysts exhibit low degree of metal leaching and straight-forward recycling, which highlight the practical utility of MSNs as supports for nanocatalysts.

  2. Facile synthesis of ultrasmall monodisperse ``raisin-bun''-type MoO3/SiO2 nanocomposites with enhanced catalytic properties

    NASA Astrophysics Data System (ADS)

    Wang, Jiasheng; Li, Xin; Zhang, Shufen; Lu, Rongwen

    2013-05-01

    We report the preparation of ultrasmall monodisperse MoO3/SiO2 nanocomposites in reverse microemulsions formed by Brij-58/cyclohexane/water. The nanocomposites are of ``raisin-bun''-type with 1.0 +/- 0.2 nm MoO3 homogeneously dispersed in 23 +/- 2 nm silica spheres. Characterization is carried out based on transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDS), X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 sorption measurement, and NH3 temperature-programmed desorption (NH3-TPD). The as-prepared MoO3/SiO2 nanocomposites are microporous and exhibit enhanced catalytic activities for acetalization of benzaldehyde with ethylene glycol and can be repeatedly used 5 times without obvious deactivation. The catalytic performance improvement is attributed to the unique structure and ultrasmall size of the nanocomposites.We report the preparation of ultrasmall monodisperse MoO3/SiO2 nanocomposites in reverse microemulsions formed by Brij-58/cyclohexane/water. The nanocomposites are of ``raisin-bun''-type with 1.0 +/- 0.2 nm MoO3 homogeneously dispersed in 23 +/- 2 nm silica spheres. Characterization is carried out based on transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDS), X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 sorption measurement, and NH3 temperature-programmed desorption (NH3-TPD). The as-prepared MoO3/SiO2 nanocomposites are microporous and exhibit enhanced catalytic activities for acetalization of benzaldehyde with ethylene glycol and can be repeatedly used 5 times without obvious deactivation. The catalytic performance improvement is attributed to the unique structure and ultrasmall size of the nanocomposites. Electronic supplementary information (ESI) available: N2 sorption isotherm, HK curve, and NH3-TPD curve of R-MoO3/SiO2, mass spectrometry of the acetalization product, and TEM images of I-MoO3/SiO2. See DOI: 10.1039/c3nr01097j

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

    PubMed Central

    Faegh, Samira; Jalili, Nader; Sridhar, Srinivas

    2013-01-01

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

  4. Ultrasmall superparamagnetic iron oxide to enhance MRA of the renal and coronary arteries: Studies in human patients

    SciTech Connect

    Stillman, A.E.; Wilke, N. [Univ. of Minnesota, Minneapolis, MN (United States)] [Univ. of Minnesota, Minneapolis, MN (United States); Li, D.; Haacke, E.M. [Washington Univ., St. Louis, MO (United States)] [Washington Univ., St. Louis, MO (United States); McLachlan, S. [Advanced Magnetics, Inc., Princeton, NJ (United States)] [Advanced Magnetics, Inc., Princeton, NJ (United States)

    1996-01-01

    Our goal was to determine the feasibility of using an intravascular MR contrast agent to improve 3D MRA. Three-dimensional TOF MRA was performed in nine patients both prior to and following the administration of an ultrasmall particle superparamagnetic iron oxide contrast agent (AMI 227). The lengths of both renal arteries were measured from the maximum intensity projection (MIP) images as well as the individual partitions. Seven of these patients also were studied by a 3D coronary artery MRA sequence. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements of the right coronary artery were determined both prior to and following the administration of AMI 227. Statistical analysis of both renal artery lengths and right coronary SNR and CNR was performed using a one tailed paired t test comparing pre- and postcontrast images. The renal artery lengths significantly increased (right renal artery: 30%, p = 0.001; left renal artery: 25%, p < 0.008) when measured from the individual axial slice partitions. No significant increase in length was observed on the MIP images following contrast. In the right coronary artery, the SNR increased by an average of 80% (p = 0.008) and CNR increased by an average of 109% (p = 0.007). Increased background signal and superimposed venous structures reduced the measurable lengths of the renal arteries from the MIP images. These studies support the hypothesis that 3D MRA in the body will benefit from the use of intravascular contrast agents. Nevertheless, conventional MIP processing is unable to reveal the full advantage of the contrast improvement. 14 refs., 6 figs., 2 tabs.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Magnetic nanoparticles of CoFe2O4 have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles of varying size was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. The anomalous magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe2O4 nanoparticles were synthesized under applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments, which produce Co ions and vacancies disorder. We performed the fabrication of condensed and mesoporous silica coated CoFe2O4 magnetic nanocomposites. The CoFe2O4 magnetic nanoparticles were encapsulated with well-defined silica layer. The mesopores in the shell were fabricated as a consequence of removal of organic group of the precursor through annealing. The NiO nanoparticles were loaded into the mesoporous silica. The mesoporous silica coated magnetic nanostructure loaded with NiO as a final product may have potential use in the field of biomedical applications. Growth mechanism of ZnO nanorod arrays on ZnO seed layer investigated by electric and Kelvin probe force microscopy. Both electric and Kelvin force probe microscopy was used to investigate the surface potentials on the ZnO seed layer, which shows a remarkable dependence on the annealing temperature. The optimum temperature for the growth of nanorod arrays normal to the surface was found to be at 600 °C, which is in the range of right surface potentials and energy measured between 500 °C and 700 °C. We demonstrated from both EFM and Kelvin force probe microscopy studies that surface potential controls the growth of ZnO nanorods. This study will provide important understanding of growth of other nanostructures. 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.

  6. Silver confined within zeolite EMT nanoparticles: preparation and antibacterial properties

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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

  7. Facile synthesis of ultrasmall monodisperse "raisin-bun"-type MoO3/SiO2 nanocomposites with enhanced catalytic properties.

    PubMed

    Wang, Jiasheng; Li, Xin; Zhang, Shufen; Lu, Rongwen

    2013-06-01

    We report the preparation of ultrasmall monodisperse MoO3/SiO2 nanocomposites in reverse microemulsions formed by Brij-58/cyclohexane/water. The nanocomposites are of "raisin-bun"-type with 1.0 ± 0.2 nm MoO3 homogeneously dispersed in 23 ± 2 nm silica spheres. Characterization is carried out based on transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDS), X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 sorption measurement, and NH3 temperature-programmed desorption (NH3-TPD). The as-prepared MoO3/SiO2 nanocomposites are microporous and exhibit enhanced catalytic activities for acetalization of benzaldehyde with ethylene glycol and can be repeatedly used 5 times without obvious deactivation. The catalytic performance improvement is attributed to the unique structure and ultrasmall size of the nanocomposites. PMID:23613166

  8. Kondo-like zero-bias anomaly in electronic transport through an ultrasmall Si quantum dot L. P. Rokhinson, L. J. Guo, S. Y. Chou, and D. C. Tsui

    E-print Network

    Kondo-like zero-bias anomaly in electronic transport through an ultrasmall Si quantum dot L. P bias. The magnetic field dependence of this zero-bias anomaly is different from that of the Kondo peaks smaller, collective phenomena, such as the Kondo effect, were recently reported.2,3 To further reduce

  9. Sub-10 nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production.

    PubMed

    Li, Landong; Yan, Junqing; Wang, Tuo; Zhao, Zhi-Jian; Zhang, Jian; Gong, Jinlong; Guan, Naijia

    2015-01-01

    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

  10. Magnetic and ultrasonic studies on stable cobalt ferrite magnetic nanofluid.

    PubMed

    Nabeel Rashin, M; Hemalatha, J

    2014-03-01

    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

  11. Magnetic nanoparticles

    Microsoft Academic Search

    R. H Kodama

    1999-01-01

    Intrinsic properties of magnetic nanoparticles are reviewed, with special emphasis on the effects of finite size on zero-temperature spin ordering, magnetic excitations, and relaxation. Effects on zero-temperature spin ordering include moment enhancement due to band narrowing in 3d transition metal particles, surface spin disorder in ferrite particles, and multi-sublattice states in antiferromagnetic oxide particles. Magnetic excitations include discretized spin wave

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

    E-print Network

    Frenkel, Anatoly

    ,* Jason R. Croy,** Simon Mostafa,** Beatriz Roldan Cuenya,** Anatoly I. Frenkel,*** and Judith C. Yang. Valden, X. Lai, and D. W. Goodman, Science 281 (5383), 1647 (1998). [2] We acknowledge the Department

  13. The structure and dynamics of polymer nanocomposites containing anisotropic nanoparticles

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Chun; Ohno, Kohji; Clarke, Nigel; Winey, Karen; Composto, Russell; Hore, Michael

    2014-03-01

    The tracer diffusion of deuterated polystyrene (dPS; 49-532 kg/mol) is measured in polystyrene (PS: 270 kg/mol) nanocomposites containing PS-grafted (132 kg/mol) anisotropic nanoparticles (NP). The NP's are small aggregates containing iron oxide spheres (5nm). These NP's uniformly disperse in PS up to 100% loading. The structure of the polymer nanocomposites is probed using (ultra)small angle x-ray scattering (USAXS,SAXS). Peaks shift to high Q region with increasing NP loadings, indicating a decrease in spacing between particles. The interparticle distance for the pure NP case is 30nm, consistent with TEM, and a brush thickness of 15nm. The brush profile is also measured using SANS. The reduced tracer diffusion coefficient initially decreases as NP loadings increase and then reaches a minimum (35% reduction) near 0.25 vol% (core) for all dPS. With a further increase in NP loading, diffusion recovers to 90% of the unfilled case. Penetration of the tracer (i.e., wetting) into the brush will affect the effective interparticle distance. Diffusion of dPS (1866 kg/mol) will be examined to determine if the dry brush case influences the recovery at high loading. These experiments demonstrate that polymer brushes grafted to anisotropic nano particles can affect the tracer diffusion pathway and indicate that diffusion models should incorporate the interfacial structure between brush and matrix.

  14. Nonvolatile memories of Ge nanodots self-assembled by depositing ultrasmall amount Ge on SiO{sub 2} at room temperature

    SciTech Connect

    Hong, Seung Hui; Kim, Min Choul; Jeong, Pil Seong; Choi, Suk-Ho [Department of Physics and Applied Physics, College of Electronics and Information, Kyung Hee University, Yongin 449-701 (Korea, Republic of); Kim, Yong-Sung; Kim, Kyung Joong [Advanced Industrial Technology Group, Korea Research Institute of Standards and Science, P.O. Box 102, Yusong, Taejon 305-340 (Korea, Republic of)

    2008-03-03

    Ge nanodots (NDs) for nonvolatile memories (NVMs) have been self-assembled at room temperature (RT) by ion beam sputtering deposition of ultrasmall amount Ge (<72 ML) on SiO{sub 2} without postannealing. High-resolution transmission electron microscopy demonstrates the existence of well-defined Ge ND layers with respect to the SiO{sub 2}/Si interface. As Ge amount increases, the size of NDs increases, while their density decreases. A possible mechanism is proposed to explain the formation of Ge NDs at RT based on simple model calculations. The memory window that is estimated by capacitance-voltage hysteresis increases up to 18.7 V with increasing Ge amount up to 54 ML. The program speed is enhanced by increasing Ge amount and the charge-loss speed in the programed state is slower for larger Ge amount. These NVM properties are very promising in view of device application.

  15. High-efficiency single photon detector combined with an ultra-small APD module and a self-training discriminator for high-speed quantum cryptosystems

    E-print Network

    Seigo Takahashi; Akio Tajima; Akihisa Tomita

    2007-12-27

    A single-photon avalanche detector (SPAD) for high-speed quantum-key generation has successfully been developed. It has the highest photon detection repetition frequency and the lowest dark count rate in the world, as a board-mountable sub-system. The SPAD consists of an ultra-small dual-avalanche photodiode (APD) module and a novel discriminator. The APD module design is consistent with cooling capability and high-frequency characteristics. The new module has a 3 GHz bandwidth enabling 1 GHz gate-pulse repetition. The bandwidth is extended 15-fold relative to the most wideband peltier cooled APD module. The discriminator has a self-training mechanism to compensate charge pulse. Dark count rare of the SPAD is reduced 1/10th relative to the lowest dark count single photon detector. The SPAD allows 3.2-fold multiplying the quantum key generation rate in theoretical estimation.

  16. Gadolinium nanoparticles and contrast agent as radiation sensitizers.

    PubMed

    Taupin, Florence; Flaender, Mélanie; Delorme, Rachel; Brochard, Thierry; Mayol, Jean-François; Arnaud, Josiane; Perriat, Pascal; Sancey, Lucie; Lux, François; Barth, Rolf F; Carrière, Marie; Ravanat, Jean-Luc; Elleaume, Hélène

    2015-06-01

    The goal of the present study was to evaluate and compare the radiosensitizing properties of gadolinium nanoparticles (NPs) with the gadolinium contrast agent (GdCA) Magnevist(®) in order to better understand the mechanisms by which they act as radiation sensitizers. This was determined following either low energy synchrotron irradiation or high energy gamma irradiation of F98 rat glioma cells exposed to ultrasmall gadolinium NPs (GdNPs, hydrodynamic diameter of 3?nm) or GdCA. Clonogenic assays were used to quantify cell survival after irradiation in the presence of Gd using monochromatic x-rays with energies in the 25?keV-80?keV range from a synchrotron and 1.25 MeV gamma photons from a cobalt-60 source. Radiosensitization was demonstrated with both agents in combination with X-irradiation. At the same concentration (2.1?mg?mL(-1)), GdNPS had a greater effect than GdCA. The maximum sensitization-enhancement ratio at 4?Gy (SER4Gy) was observed at an energy of 65?keV for both the nanoparticles and the contrast agent (2.44???±???0.33 and 1.50???±???0.20, for GdNPs and GdCA, respectively). At a higher energy (1.25?MeV), radiosensitization only was observed with GdNPs (1.66???±???0.17 and 1.01???±???0.11, for GdNPs and GdCA, respectively). The radiation dose enhancements were highly 'energy dependent' for both agents. Secondary-electron-emission generated after photoelectric events appeared to be the primary mechanism by which Gd contrast agents functioned as radiosensitizers. On the other hand, other biological mechanisms, such as alterations in the cell cycle may explain the enhanced radiosensitizing properties of GdNPs. PMID:25988839

  17. Gadolinium nanoparticles and contrast agent as radiation sensitizers

    NASA Astrophysics Data System (ADS)

    Taupin, Florence; Flaender, Mélanie; Delorme, Rachel; Brochard, Thierry; Mayol, Jean-François; Arnaud, Josiane; Perriat, Pascal; Sancey, Lucie; Lux, François; Barth, Rolf F.; Carrière, Marie; Ravanat, Jean-Luc; Elleaume, Hélène

    2015-06-01

    The goal of the present study was to evaluate and compare the radiosensitizing properties of gadolinium nanoparticles (NPs) with the gadolinium contrast agent (GdCA) Magnevist® in order to better understand the mechanisms by which they act as radiation sensitizers. This was determined following either low energy synchrotron irradiation or high energy gamma irradiation of F98 rat glioma cells exposed to ultrasmall gadolinium NPs (GdNPs, hydrodynamic diameter of 3?nm) or GdCA. Clonogenic assays were used to quantify cell survival after irradiation in the presence of Gd using monochromatic x-rays with energies in the 25?keV–80?keV range from a synchrotron and 1.25 MeV gamma photons from a cobalt-60 source. Radiosensitization was demonstrated with both agents in combination with X-irradiation. At the same concentration (2.1?mg?mL?1), GdNPS had a greater effect than GdCA. The maximum sensitization-enhancement ratio at 4?Gy (SER4Gy) was observed at an energy of 65?keV for both the nanoparticles and the contrast agent (2.44???±???0.33 and 1.50???±???0.20, for GdNPs and GdCA, respectively). At a higher energy (1.25?MeV), radiosensitization only was observed with GdNPs (1.66???±???0.17 and 1.01???±???0.11, for GdNPs and GdCA, respectively). The radiation dose enhancements were highly ‘energy dependent’ for both agents. Secondary-electron-emission generated after photoelectric events appeared to be the primary mechanism by which Gd contrast agents functioned as radiosensitizers. On the other hand, other biological mechanisms, such as alterations in the cell cycle may explain the enhanced radiosensitizing properties of GdNPs.

  18. Engineered magnetic hybrid nanoparticles with enhanced relaxivity for tumor imaging.

    PubMed

    Aryal, Santosh; Key, Jaehong; Stigliano, Cinzia; Ananta, Jeyarama S; Zhong, Meng; Decuzzi, Paolo

    2013-10-01

    Clinically used contrast agents for magnetic resonance imaging (MRI) suffer by the lack of specificity; short circulation time; and insufficient relaxivity. Here, a one-step combinatorial approach is described for the synthesis of magnetic lipid-polymer (hybrid) nanoparticles (MHNPs) encapsulating 5 nm ultra-small super-paramagnetic iron oxide particles (USPIOs) and decorated with Gd(3+) ions. The MHNPs comprise a hydrophobic poly(lactic acid-co-glycolic acid) (PLGA) core, containing up to ~5% USPIOs (w/w), stabilized by lipid and polyethylene glycol (PEG). Gd(3+) ions are directly chelated to the external lipid monolayer. Three different nanoparticle configurations are presented including Gd(3+) chelates only (Gd-MHNPs); USPIOs only (Fe-MHNPs); and the combination thereof (MHNPs). All three MHNPs exhibit a hydrodynamic diameter of about 150 nm. The Gd-MHNPs present a longitudinal relaxivity (r1 = 12.95 ± 0.53 (mM s)(-1)) about four times larger than conventional Gd-based contrast agents (r1 = 3.4 (mM s)(-1)); MHNPs have a transversal relaxivity of r2 = 164.07 ± 7.0 (mM s)(-1), which is three to four times larger than most conventional systems (r2 ~ 50 (mM s)(-1)). In melanoma bearing mice, elemental analysis for Gd shows about 3% of the injected MHNPs accumulating in the tumor and 2% still circulating in the blood, at 24 h post-injection. In a clinical 3T MRI scanner, MHNPs provide significant contrast confirming the observed tumor deposition. This approach can also accommodate the co-loading of hydrophobic therapeutic compounds in the MHNP core, paving the way for theranostic systems. PMID:23871540

  19. Magnetic resonance imaging of folic acid-coated magnetite nanoparticles reflects tissue biodistribution of long-acting antiretroviral therapy

    PubMed Central

    Li, Tianyuzi; Gendelman, Howard E; Zhang, Gang; Puligujja, Pavan; McMillan, JoEllyn M; Bronich, Tatiana K; Edagwa, Benson; Liu, Xin-Ming; Boska, Michael D

    2015-01-01

    Regimen adherence, systemic toxicities, and limited drug penetrance to viral reservoirs are obstacles limiting the effectiveness of antiretroviral therapy (ART). Our laboratory’s development of the monocyte-macrophage-targeted long-acting nanoformulated ART (nanoART) carriage provides a novel opportunity to simplify drug-dosing regimens. Progress has nonetheless been slowed by cumbersome, but required, pharmacokinetic (PK), pharmacodynamics, and biodistribution testing. To this end, we developed a small magnetite ART (SMART) nanoparticle platform to assess antiretroviral drug tissue biodistribution and PK using magnetic resonance imaging (MRI) scans. Herein, we have taken this technique a significant step further by determining nanoART PK with folic acid (FA) decorated magnetite (ultrasmall superparamagnetic iron oxide [USPIO]) particles and by using SMART particles. FA nanoparticles enhanced the entry and particle retention to the reticuloendothelial system over nondecorated polymers after systemic administration into mice. These data were seen by MRI testing and validated by comparison with SMART particles and direct evaluation of tissue drug levels after nanoART. The development of alendronate (ALN)-coated magnetite thus serves as a rapid initial screen for the ability of targeting ligands to enhance nanoparticle-antiretroviral drug biodistribution, underscoring the value of decorated magnetite particles as a theranostic tool for improved drug delivery.

  20. Targeting B16 tumors in vivo with peptide-conjugated gold nanoparticles.

    PubMed

    Poon, Wilson; Zhang, Xuan; Bekah, Devesh; Teodoro, Jose G; Nadeau, Jay L

    2015-07-17

    This study examines the effects of polyethylene glycol (PEG) and peptide conjugation on the biodistribution of ultrasmall (2.7 nm) gold nanoparticles in mice bearing B16 melanoma allografts. Nanoparticles were delivered intravenously, and biodistribution was measured at specific timepoints by organ digestion and inductively coupled plasma mass spectrometry. All major organs were examined. Two peptides were tested: the cyclic RGD peptide (cRGD, which targets integrins); and a recently described peptide derived from the myxoma virus. We found the greatest specific tumor delivery using the myxoma peptide, with or without PEGylation. Un-PEGylated cRGD performed poorly, but PEGylated RGD showed a significant transient collection in the tumor. Liver and kidney were the primary targets of all constructs. None of the particles were able to cross the blood-brain barrier. Although it was able to deliver Au to B16 cells, the myxoma peptide did not show any cytotoxic activity against these cells, in contrast to previous reports. These results indicate that the effect of passive targeting by PEGylation and active targeting by peptides can be independent or combined, and that they should be evaluated on a case-by-case basis when designing new nanosystems for targeted therapies. Both myxoma peptide and cRGD should be considered for specific targeting to melanoma, but a thorough investigation of the cytotoxicity of the myxoma peptide to different cell lines remains to be performed. PMID:26111959

  1. Targeting B16 tumors in vivo with peptide-conjugated gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Poon, Wilson; Zhang, Xuan; Bekah, Devesh; Teodoro, Jose G.; Nadeau, Jay L.

    2015-07-01

    This study examines the effects of polyethylene glycol (PEG) and peptide conjugation on the biodistribution of ultrasmall (2.7 nm) gold nanoparticles in mice bearing B16 melanoma allografts. Nanoparticles were delivered intravenously, and biodistribution was measured at specific timepoints by organ digestion and inductively coupled plasma mass spectrometry. All major organs were examined. Two peptides were tested: the cyclic RGD peptide (cRGD, which targets integrins); and a recently described peptide derived from the myxoma virus. We found the greatest specific tumor delivery using the myxoma peptide, with or without PEGylation. Un-PEGylated cRGD performed poorly, but PEGylated RGD showed a significant transient collection in the tumor. Liver and kidney were the primary targets of all constructs. None of the particles were able to cross the blood–brain barrier. Although it was able to deliver Au to B16 cells, the myxoma peptide did not show any cytotoxic activity against these cells, in contrast to previous reports. These results indicate that the effect of passive targeting by PEGylation and active targeting by peptides can be independent or combined, and that they should be evaluated on a case-by-case basis when designing new nanosystems for targeted therapies. Both myxoma peptide and cRGD should be considered for specific targeting to melanoma, but a thorough investigation of the cytotoxicity of the myxoma peptide to different cell lines remains to be performed.

  2. Nanoparticles for Biomedical Imaging

    Microsoft Academic Search

    Satish K. Nune; Padmaja Gunda; Praveen K. Thallapally; Ying-Ying Lin; Laird M. Forrest; Cory J. Berkland

    2009-01-01

    Background: Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 to 100 nm in diameter possess dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for

  3. Nanoparticles by Laser Ablation

    Microsoft Academic Search

    N. G. Semaltianos

    2010-01-01

    This review concerns nanoparticles collected in the form of nanopowder or a colloidal solution by laser ablating a solid target that lies in a gaseous or a liquid environment. The paper discusses the advantages of the method as compared with other methods for nanoparticle synthesis, outlines the factors on which the properties of the produced nanoparticles depend, explains the mechanisms

  4. CCMR: Bimetallic Nanoparticle Catalysis

    NSDL National Science Digital Library

    Chong, Hahn

    2010-08-15

    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.

  5. De-alloyed platinum nanoparticles

    DOEpatents

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

    2011-08-09

    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.

  6. Cd{sub 1?x}Mn{sub x}Te ultrasmall quantum dots growth in a silicate glass matrix by the fusion method

    SciTech Connect

    Dantas, Noelio Oliveira; Lima Fernandes, Guilherme de; Almeida Silva, Anielle Christine [Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Física, Universidade Federal de Uberlândia, 38408-100 Uberlândia, MG (Brazil); Baffa, Oswaldo; Gómez, Jorge Antônio [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto, SP (Brazil)

    2014-09-29

    In this study, we synthesized Cd{sub 1?x}Mn{sub x}Te ultrasmall quantum dots (USQDs) in SiO{sub 2}-Na{sub 2}CO{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass system using the fusion method. Growth of these Cd{sub 1?x}Mn{sub x}Te USQDs was confirmed by optical absorption, atomic force microscopy (AFM), magnetic force microscopy (MFM), scanning transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR) measurements. The blueshift of absorption transition with increasing manganese concentration gives evidence of incorporation of manganese ions (Mn{sup 2+}) in CdTe USQDs. AFM, TEM, and MFM confirmed, respectively, the formation of high quality Cd{sub 1?x}Mn{sub x}Te USQDs with uniformly distributed size and magnetic phases. Furthermore, EPR spectra showed six lines associated to the S?=?5/2 spin half-filled d-state, characteristic of Mn{sup 2+}, and confirmed that Mn{sup 2+} are located in the sites core and surface of the CdTe USQD. Therefore, synthesis of high quality Cd{sub 1?x}Mn{sub x}Te USQDs may allow the control of optical and magnetic properties.

  7. Ultra-small, uniform, and single bcc-phased Fe(x)Co(1-x)/graphitic shell nanocrystals for T1 magnetic resonance imaging contrast agents.

    PubMed

    Choi, In Ae; Li, Yan; Kim, Da Jeong; Pal, Mou; Cho, Jee-Hyun; Lee, Kyujoon; Jung, Myung-Hwa; Lee, Chulhyun; Seo, Won Seok

    2013-01-01

    We have synthesized ultra-small and uniform Fe(x)Co(1-x)/graphitic carbon shell (Fe(x)Co(1-x)/GC) nanocrystals (x=0.13, 0.36, 0.42, 0.50, 0.56, and 0.62, respectively) with average diameters of <4 nm by thermal decomposition of metal precursors in approximately 60 nm MCM-41 and methane CVD. The composition of the Fe(x)Co(1-x)/GC nanocrystals can be tuned by changing the Fe:Co ratios of the metal precursors. The Fe(x)Co(1-x)/GC nanocrystals show superparamagnetic properties at room temperature. The Fe(0.50)Co(0.50)/GC, Fe(0.56)Co(0.44)/GC, and Fe(0.62)Co(0.38)/GC nanocrystals have a single bcc FeCo structure, whereas the Fe(0.13)Co(0.87)/GC, Fe(0.36)Co(0.64)/GC, and Fe(0.42)Co(0.58)/GC nanocrystals have a mixed structure of bcc FeCo and fcc Co. The single bcc-phased Fe(x)Co(1-x)/GC nanocrystals functionalized with phospholipid-poly(ethylene glycol) (PL-PEG) in phosphate buffered saline (PBS) are demonstrated to be excellent T(1) MRI contrast agents. PMID:23161874

  8. Nanoparticles for Biomedical Imaging

    SciTech Connect

    Nune, Satish K.; Gunda, Padmaja; Thallapally, Praveen K.; Lin, Ying-Ying; Forrest, Laird M.; Berkland, Cory J.

    2009-11-01

    Background: Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 to 100 nm in diameter possess dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for early detection of diseases such as cancer. Surface functionalization has further expanded the potential of nanoparticles as probes for molecular imaging. Objective: To summarize emerging research of nanoparticles for biomedical imaging with increased selectivity and reduced non-specific uptake with increased spatial resolution containing stabilizers conjugated with targeting ligands. Methods: This review summarizes recent technological advances in the synthesis of various nanoparticle probes, and surveys methods to improve the targeting of nanoparticles for their applications in biomedical imaging. Conclusion: Structural design of nanomaterials for biomedical imaging continues to expand and diversify. Synthetic methods have aimed to control the size and surface characteristics of nanoparticles to control distribution, half-life and elimination. Although molecular imaging applications using nanoparticles are advancing into clinical applications, challenges such as storage stability and long-term toxicology should continue to be addressed. Keywords: nanoparticle synthesis, surface modification, targeting, molecular imaging, and biomedical imaging.

  9. J-aggregates of organic dye molecules complexed with iron oxide nanoparticles for imaging-guided photothermal therapy under 915-nm light.

    PubMed

    Song, Xuejiao; Gong, Hua; Liu, Teng; Cheng, Liang; Wang, Chao; Sun, Xiaoqi; Liang, Chao; Liu, Zhuang

    2014-11-12

    Recently, the development of nano-theranostic agents aiming at imaging guided therapy has received great attention. In this work, a near-infrared (NIR) heptamethine indocyanine dye, IR825, in the presence of cationic polymer, polyallylamine hydrochloride (PAH), forms J-aggregates with red-shifted and significantly enhanced absorbance. After further complexing with ultra-small iron oxide nanoparticles (IONPs) and the followed functionalization with polyethylene glycol (PEG), the obtained IR825@PAH-IONP-PEG composite nanoparticles are highly stable in different physiological media. With a sharp absorbance peak, IR825@PAH-IONP-PEG can serve as an effective photothermal agent under laser irradiation at 915 nm, which appears to be optimal in photothermal therapy application considering its improved tissue penetration compared with 808-nm light and much lower water heating in comparison to 980-nm light. As revealed by magnetic resonance (MR) imaging, those nanoparticles after intravenous injection exhibit high tumor accumulation, which is then harnessed for in vivo photothermal ablation of tumors, achieving excellent therapeutic efficacy in a mouse tumor model. This study demonstrates for the first time that J-aggregates of organic dye molecules are an interesting class of photothermal material, which when combined with other imageable nanoprobes could serve as a theranostic agent for imaging-guided photothermal therapy of cancer. PMID:24976309

  10. Nanoparticle agglomerates in magnetoliposomes

    NASA Astrophysics Data System (ADS)

    Cintra, E. R.; Ferreira, F. S.; Santos Junior, J. L.; Campello, J. C.; Socolovsky, L. M.; Lima, E. M.; Bakuzis, A. F.

    2009-01-01

    Magnetoliposomes consist of vesicles composed of a phospholipid membrane encapsulating magnetic nanoparticles. These systems have several important applications, such as in MRI contrast agents, drug and gene carriers, and cancer treatment devices. For all of these applications, controlling the number of encapsulated magnetic nanoparticles is a key issue. In this work, we used a magneto-optical technique to obtain information about the efficiency of encapsulation, the number of nanoparticles encapsulated per liposome and also about the formation of the nanoparticle structures. The parameters studied included the effect of the duration of sonication, the presence of cholesterol in the liposome membrane, as well as time-related stability. For the liposomal vesicles prepared in this work, we found between 35 and 300 nanoparticles encapsulated per liposome, depending on the experimental conditions, consisting of small linear chains of nanoparticles, basically trimers and tetramers. The methodology developed might be useful for the investigation and improvement of the properties of several magnetic nanocarrier systems.

  11. Nanoparticle agglomerates in magnetoliposomes.

    PubMed

    Cintra, E R; Ferreira, F S; Santos Junior, J L; Campello, J C; Socolovsky, L M; Lima, E M; Bakuzis, A F

    2009-01-28

    Magnetoliposomes consist of vesicles composed of a phospholipid membrane encapsulating magnetic nanoparticles. These systems have several important applications, such as in MRI contrast agents, drug and gene carriers, and cancer treatment devices. For all of these applications, controlling the number of encapsulated magnetic nanoparticles is a key issue. In this work, we used a magneto-optical technique to obtain information about the efficiency of encapsulation, the number of nanoparticles encapsulated per liposome and also about the formation of the nanoparticle structures. The parameters studied included the effect of the duration of sonication, the presence of cholesterol in the liposome membrane, as well as time-related stability. For the liposomal vesicles prepared in this work, we found between 35 and 300 nanoparticles encapsulated per liposome, depending on the experimental conditions, consisting of small linear chains of nanoparticles, basically trimers and tetramers. The methodology developed might be useful for the investigation and improvement of the properties of several magnetic nanocarrier systems. PMID:19417311

  12. Stimulus Responsive Nanoparticles

    NASA Technical Reports Server (NTRS)

    Cairns, Darran Robert (Inventor); Huebsch, Wade W. (Inventor); Sierros, Konstantinos A. (Inventor); Shafran, Matthew S. (Inventor)

    2015-01-01

    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.

  13. Functional Magnetic Nanoparticles

    Microsoft Academic Search

    James Gass

    2012-01-01

    Nanoparticle system research and characterization is the focal point of this research and dissertation. In the research presented here, magnetite, cobalt, and ferrite nanoparticle systems have been explored in regard to their magnetocaloric effect (MCE) properties, as well as for use in polymer composites. Both areas of study have potential applications across a wide variety of interdisciplinary fields.\\u000aMagnetite nanoparticles

  14. Stimulus responsive nanoparticles

    NASA Technical Reports Server (NTRS)

    Cairns, Darren Robert (Inventor); Huebsch, Wade W. (Inventor); Sierros, Konstantinos A. (Inventor); Shafran, Matthew S. (Inventor)

    2013-01-01

    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.

  15. Nanoparticles for biomedical imaging

    PubMed Central

    Nune, Satish K; Gunda, Padmaja; Thallapally, Praveen K; Lin, Ying-Ying; Forrest, M Laird; Berkland, Cory J

    2011-01-01

    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

  16. DOCTORAL THESIS UNIVERSITE PIERRE ET MARIE CURIE

    E-print Network

    Paris-Sud XI, Université de

    reversal behavior of the CoFe2O4 spin-filter barrier and its magnetic counter-electrode (Co or Fe3O4-polarized tunneling experiments involving either the Meservey-Tedrow technique or tunneling magnetoresistance (TMR

  17. OPTICAL PROPERTIES OFOPTICAL PROPERTIES OF METALLIC NANOPARTICLES,METALLIC NANOPARTICLES,

    E-print Network

    Grujicic, Mica

    OPTICAL PROPERTIES OFOPTICAL PROPERTIES OF METALLIC NANOPARTICLES,METALLIC NANOPARTICLES, MOLECULESImaginary Part of Dielectric Function of Particles ppp i += Dielectric Function of the NanoparticlesDielectric Function of the Nanoparticles #12;Complex Dielectric FunctionComplex Dielectric Function For Bulk Material

  18. 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)

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

    2014-12-01

    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.

  19. Nanoparticles for bioimaging

    Microsoft Academic Search

    Parvesh Sharma; Scott Brown; Glenn Walter; Swadeshmukul Santra; Brij Moudgil

    2006-01-01

    The emergence of synthesis strategies for the fabrication of nanosized contrast agents is anticipated to lead to advancements in understanding biological processes at the molecular level in addition to progress in the development of diagnostic tools and innovative therapies. Imaging agents such as fluorescent dye-doped silica nanoparticles, quantum dots and gold nanoparticles have overcome many of the limitations of conventional

  20. Nanoparticles in Ophthalmic Medicine

    Microsoft Academic Search

    Yureeda Qazi; Brian Stagg; Balamurali Ambati

    2009-01-01

    Over the past decade, nanoparticles have risen to the forefront of biotechnology, promising diverse applications in the fields of gene therapy, drug delivery, and imaging. Nanoparticles can be engineered to create optimal features that are tissue-specific or target-orientated to promote their uptake, clearance, biodegradability, reduced immunogenicity, and detection. Nanomedicine offers potentially safe and successful treatment regimens for ocular disorders. In

  1. Targeting nanoparticles to cancer.

    PubMed

    Wang, M; Thanou, M

    2010-08-01

    Nanotechnology applications in medicine, termed as nanomedicine, have introduced a number of nanoparticles of variable chemistry and architecture for cancer imaging and treatment. Nanotechnology involves engineering multifunctional devices with dimensions at the nanoscale, similar dimensions as those of large biological vesicles or molecules in our body. These devices typically have features just tens to hundred nanometers across and they can carry one or two detection signals and/or therapeutic cargo(s). One unique class of nanoparticles is designed to do both, providing this way the theragnostic nanoparticles (therapy and diagnosis). Being inspired by physiologically existing nanomachines, nanoparticles are designed to safely reach their target and specifically release their cargo at the site of the disease, this way increasing the drug's tissue bioavailability. Nanoparticles have the advantage of targeting cancer by simply being accumulated and entrapped in tumours (passive targeting). The phenomenon is called the enhanced permeation and retention effect, caused by leaky angiogenetic vessels and poor lymphatic drainage and has been used to explain why macromolecules and nanoparticles are found at higher ratios in tumours compared to normal tissues. Although accumulation in tumours is observed cell uptake and intracellular drug release have been questioned. Polyethyleneglycol (PEG) is used to protect the nanoparticles from the Reticulo-Endothelial System (RES), however, it prevents cell uptake and the required intracellular drug release. Grafting biorecognition molecules (ligands) onto the nanoparticles refers to active targeting and aims to increase specific cell uptake. Nanoparticles bearing these ligands are recognised by cell surface receptors and this leads to receptor-mediated endocytosis. Several materials are suggested for the design of nanoparticles for cancer. Polymers, linear and dendrimers, are associated with the drug in a covalent or non-covalent way and have been used with or without a targeting ligand. Stealth liposomes are suggested to carry the drug in the aqueous core, and they are usually decorated by recognition molecules, being widely studied and applied. Inorganic nanoparticles such as gold and iron oxide are usually coupled to the drug, PEG and the targeting ligand. It appears that the PEG coating and ligand decoration are common constituents in most types of nanoparticles for cancer. There are several examples of successful cancer diagnostic and therapeutic nanoparticles and many of them have rapidly moved to clinical trials. Nevertheless there is still a room for optimisation in the area of the nanoparticle kinetics such as improving their plasma circulation and tumour bioavailability and understanding the effect of targeting ligands on their efficiency to treat cancer. The need to develop novel and efficient ligands has never been greater, and the use of proper conjugation chemistry is mandatory. PMID:20380880

  2. Nanoscale x-ray magnetic circular dichroism probing of electric-field-induced magnetic switching in multiferroic nanostructures

    Microsoft Academic Search

    T. Zhao; A. Scholl; F. Zavaliche; H. Zheng; M. Barry; A. Doran; K. Lee; M. P. Cruz; R. Ramesh

    2007-01-01

    The magnetic structure as well as its response to an external electric field were studied in ferrimagnetic CoFe2O4 nanopillars embedded in an epitaxial ferroelectric BiFeO3 film using photoemission electron microscopy and x-ray magnetic circular dichroism. Magnetic switching was observed in both Co and Fe magnetic sublattices after application of an electric field. About 50% of the CoFe2O4 nanopillars were measured

  3. Shaped gold and silver nanoparticles

    Microsoft Academic Search

    Yugang Sun; Changhua An

    2011-01-01

    Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with\\u000a a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline\\u000a structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories:\\u000a nanoparticles with single crystallinity, nanoparticles

  4. Gas Phase Nanoparticle Synthesis

    NASA Astrophysics Data System (ADS)

    Granqvist, Claes; Kish, Laszlo; Marlow, William

    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.

  5. Nanoparticle Stained Glass

    NSDL National Science Digital Library

    2014-06-18

    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."

  6. Synthesis of Silver Nanoparticles

    NSDL National Science Digital Library

    Johnson, Chris

    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.

  7. Theranostic Upconversion Nanoparticles (I)

    PubMed Central

    Chen, Guanying; Han, Gang

    2013-01-01

    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

  8. Engines and nanoparticles

    Microsoft Academic Search

    David B. Kittelson

    1998-01-01

    Most of the particle number emitted by engines is in the nanoparticle range, Dp<50 nm, while most of the mass is in the accumulation mode, 50nmNanoparticles are typically hydrocarbons or sulfate and form by nucleation during dilution and cooling of the exhaust, while accumulation mode particles are mainly carbonaceous soot agglomerates formed directly by combustion. Emission standards

  9. Engineering Pharmaceutical Nanoparticles

    E-print Network

    Berkland, Cory

    2006-10-26

    Engineering Pharmaceutical Nanoparticles Cory Berkland Assistant Professor Department of Pharmaceutical Chemistry Assistant Professor Department of Chemical and Petroleum Engineering The University of Kansas 2 Acknowledgements Postdocs: David Shi....retsch.de 8 For example, the bioavailability of poorly soluble drugs can be enhanced. Spironalactone is a synthetic 17-lactone steroid. Nanoparticle suspensions of this drug dramatically enhance the drug dissolution. 9 For example, tumor accumulation via...

  10. Phonon-assisted energy back transfer-induced multicolor upconversion emission of Gd2O3:Yb(3+)/Er(3+) nanoparticles under near-infrared excitation.

    PubMed

    Liu, Jun; Deng, Huawei; Huang, Zhanyun; Zhang, Yueli; Chen, Dihu; Shao, Yuanzhi

    2015-06-01

    Manipulation of upconversion (UC) emission is of particular importance for multiplexed bioimaging. Here, we precisely manipulate the UC color output by utilizing the phonon-assisted energy back transfer (EBT) process in ultra-small (sub-10 nm) Gd2O3:Yb(3+)/Er(3+) UC nanoparticles (UCNPs). We synthesized the Gd2O3:Yb(3+)/Er(3+) UCNPs by adopting the laser ablation in liquid (LAL) technique. The synthesized Gd2O3:Yb(3+)/Er(3+) UCNPs are small spherical and monoclinic structures. Continuous color-tunable (from green to red) UC fluorescence emission is achieved by increasing the concentration of Yb(3+) ions from 0 to 15 mol%. A phonon-assisted energy back transfer (EBT) process from Er(3+) ((4)S3/2 ? (4)I13/2) to nearby Yb(3+) ((2)F7/2 ? (2)F5/2), which can significantly enhance red emission at 672 nm and decrease green emission, is responsible for the color-tunable UC emission by increasing the Yb(3+) concentration in Gd2O3:Yb(3+)/Er(3+) UC nanoparticles. PMID:26006337

  11. The effect of carboxydextran-coated superparamagnetic iron oxide nanoparticles on c-Jun N-terminal kinase-mediated apoptosis in human macrophages.

    PubMed

    Lunov, Oleg; Syrovets, Tatiana; Büchele, Berthold; Jiang, Xiue; Röcker, Carlheinz; Tron, Kyrylo; Nienhaus, G Ulrich; Walther, Paul; Mailänder, Volker; Landfester, Katharina; Simmet, Thomas

    2010-07-01

    Superparamagnetic iron oxide nanoparticles are frequently used for cell labeling or as diagnostic contrast media, yet studies analyzing their effects on immune cells remain scarce. Here we investigated how nanosized carboxydextran-coated superparamagnetic iron oxide (SPIO) and ultrasmall superparamagnetic iron oxide (USPIO) might affect human macrophages. Within 1 h, both SPIO and USPIO were rapidly taken up by macrophages. Confocal microscopy revealed that after 24 h the particles were almost exclusively localized within the lysosomal compartment. Continued cultivation of the macrophages for several days was associated with apoptosis induction caused by a long-lasting activation of the c-Jun N-terminal kinase (JNK) pathway. JNK activation was due to significantly elevated levels of reactive oxygen species, whereas no TNF-alpha was produced by the macrophages treated with nanoparticles. Compared to SPIO, USPIO induced more pronounced biochemical alterations and cytotoxicity, which could be antagonized by the JNK inhibitor V. Alternatively, treatment of macrophages with Trolox or N-acetyl-L-cysteine, two functionally different scavengers of reactive oxygen species, abolished both the JNK activation and the subsequent cytotoxic effects. These data indicate that nanosized superparamagnetic iron oxide-based contrast media exert cytotoxicity in human macrophages that can be functionally antagonized with radical scavengers. PMID:20381862

  12. Detection of Target Biomolecules by Magnetic Reporting Using Rod-Like Nanosensors

    NASA Astrophysics Data System (ADS)

    Guertin, R. P.; Goldberg, E.; Harrah, T. P.; Sonkusale, S.; Park, K.; Sun, S.; Oh, J. I.; Naughton, M.

    2008-03-01

    We describe the ongoing development of a device to assay a variety of cellular, viral and molecular targets by measuring the increase of the Brownian relaxation time, ?, in solution of magnetically-tagged nanoscale detectors. The shift shows as a frequency reduction of the peak of the complex magnetic susceptibility, ?(?)''. Measurements of ?(?)'' with 12 nm monodisperse nanoparticles of CoFe2O4 coated with polyethelyne glycol reveal spectra with the narrowest lines yet reported. Thin avidin coating of these particles reveals small shifts in ?(?)''. Bacteriophage T4 tail fibers, engineered to specific lengths (30-150 nm), were employed as the platform for magnetic nanoparticle attachment and at the other end for an inserted target peptide epitope. Attachment of the nanoparticles to bacteriophage T4 tail fibers was successful, though no detectable shifts in ?(?)'' were detected due to weak attachment. The advantages associated with non-spherical geometry detectors will be discussed, as will preliminary measurements with rare earth oxide magnetic nanoparticles. Progress on miniaturization and low power requirements of the electronic detection system will be reported. Supported by NERCE/BEID (NIAID).

  13. 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...

  14. Direct hierarchical assembly of nanoparticles

    DOEpatents

    Xu, Ting; Zhao, Yue; Thorkelsson, Kari

    2014-07-22

    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.

  15. Automated Morphology Analysis of Nanoparticles

    E-print Network

    Park, Chiwoo

    2012-10-19

    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...

  16. Nanoparticles for Targeted Drug Delivery

    E-print Network

    Chow, Gan-Moog

    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) ...

  17. Automated Morphology Analysis of Nanoparticles 

    E-print Network

    Park, Chiwoo

    2012-10-19

    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...

  18. Nanoparticles for molecular imaging.

    PubMed

    Sheng, Yang; Liao, Lun De; Thakor, Nitish V; Tan, Mei Chee

    2014-10-01

    Imaging techniques have been instrumental in the visualization of fundamental biological processes, identification and diagnosis of diseased states and the development of structure-function relationships at the cellular, tissue and anatomical levels. Together with the advancements made in imaging techniques, complementary chemical compounds, also known as imaging probes or contrast agents, are developed to improve the visibility of the image by enhancing sensitivity, and for the identification and quantitation of specific molecular species or structures. Extensive studies have been conducted to explore the use of inorganic nanoparticles which exhibit magnetic and optical properties unique to the nano regime so as to enhance the signals sensitivity for magnetic resonance and fluorescent imaging. These physical properties are tailored by controlling the size, shape and surface properties of nanoparticles. In addition, surface modification of nanoparticles is often required to improve its stability, compatibility and functionality. Surfactants, surface-active agents, have been used to engineer the surface characteristics of nanoparticles to improved particle stability and functionality. Surfactants enhance nanoparticle stability through the reduction of surface energy, and by acting as a barrier to agglomeration through either steric hindrance or repulsive electrostatic forces. Coupling of nanoparticles with biomolecules such as antibodies or tumor targeting peptides are enabled by the presence of functional groups (e.g., carboxyl or amine groups) on surfactants. This paper provides an overview of the chemistry underlying the synthesis and surface modification of nanomaterials together with a discussion on how the physical properties (e.g., magnetic, absorption and luminescent) can be controlled. The applications of these nanoparticles for magnetic resonance, fluorescent and photoacoustic imaging techniques that do not rely on ionizing radiation are also covered in this review. PMID:25992413

  19. SYNTHESIS AND CHARACTERIZATION OF NANOPARTICLES

    E-print Network

    Ding, Yu

    SYNTHESIS AND CHARACTERIZATION OF NANOPARTICLES Lokesh Kulkarni Dept. of Industrial and Systems of gold nanoparticles: - Chemicals: Auric salt (source of Au ions), sodium citrate (reducing agent - Process: See figure - Capable of producing spherical gold nanoparticles of around 10-20 nm in diameter

  20. Antimicrobial effects of silver nanoparticles

    Microsoft Academic Search

    Jun Sung Kim; Eunye Kuk; Kyeong Nam Yu; Jong-Ho Kim; Sung Jin Park; Hu Jang Lee; So Hyun Kim; Young Kyung Park; Yong Ho Park; Cheol-Yong Hwang; Yong-Kwon Kim; Yoon-Sik Lee; Dae Hong Jeong; Myung-Haing Cho

    2007-01-01

    The antimicrobial effects of silver (Ag) ion or salts are well known, but the effects of Ag nanoparticles on microorganisms and antimicrobial mechanism have not been revealed clearly. Stable Ag nanoparticles were prepared and their shape and size distribution characterized by particle characterizer and transmission electron microscopic study. The antimicrobial activity of Ag nanoparticles was investigated against yeast, Escherichia coli,

  1. Paper surfaces functionalized by nanoparticles.

    PubMed

    Ngo, Ying Hui; Li, Dan; Simon, George P; Garnier, Gil

    2011-03-15

    Nanomaterials with unique electronic, optical and catalytic properties have recently been at the forefront of research due to their tremendous range of applications. Taking gold, silver and titania nanoparticles as examples, we have reviewed the current research works on paper functionalized by these nanoparticles. The functionalization of paper with only a very small concentration of nanoparticles is able to produce devices with excellent photocatalytic, antibacterial, anti-counterfeiting, Surface Enhanced Raman Scattering (SERS) and Surface Plasmon Resonance (SPR) performances. This review presents a brief overview of the properties of gold, silver and titania nanoparticles which contribute to the major applications of nanoparticles-functionalized paper. Different preparation methods of the nanoparticles-functionalized paper are reviewed, focusing on their ability to control the morphology and structure of paper as well as the spatial location and adsorption state of nanoparticles which are critical in achieving their optimum applications. In addition, main applications of the nanoparticles-functionalized papers are highlighted and their critical challenges are discussed, followed by perspectives on the future direction in this research field. Whilst a few studies to date have characterized the distribution of nanoparticles on paper substrates, none have yet optimized paper as a nanoparticles' substrate. There remains a strong need to improve understanding on the optimum adsorption state of nanoparticles on paper and the heterogeneity effects of paper on the properties of these nanoparticles. PMID:21324427

  2. Ordered mesoporous silica nanoparticles with and without embedded iron oxide nanoparticles: structure evolution during synthesis

    E-print Network

    Gruner, Sol M.

    Ordered mesoporous silica nanoparticles with and without embedded iron oxide nanoparticles of hexagonally ordered mesoporous silica nanoparticles with and without embedded iron oxide particles. Oleic acid surfactant, hexadecyltrimethylammonium bromide (CTAB). MCM-41 type silica and composite nanoparticles

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

    PubMed Central

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

    2014-01-01

    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

  4. Intracellular antioxidants dissolve man-made antioxidant nanoparticles: using redox vulnerability of nanoceria to develop a responsive drug delivery system.

    PubMed

    Muhammad, Faheem; Wang, Aifei; Qi, Wenxiu; Zhang, Shixing; Zhu, Guangshan

    2014-11-12

    Regeneratable antioxidant property of nanoceria has widely been explored to minimize the deleterious influences of reactive oxygen species. Limited information is, however, available regarding the biological interactions and subsequent fate of nanoceria in body fluids. This study demonstrates a surprising dissolution of stable and ultrasmall (4 nm) cerium oxide nanoparticles (CeO2 NPs) in response to biologically prevalent antioxidant molecules (glutathione, vitamin C). Such a redox sensitive behavior of CeO2 NPs is subsequently exploited to design a redox responsive drug delivery system for transporting anticancer drug (camptothecin). Upon exposing the CeO2 capped and drug loaded nanoconstruct to vitamin c or glutathione, dissolution-accompanied aggregation of CeO2 nanolids unleashes the drug molecules from porous silica to achieve a significant anticancer activity. Besides stimuli responsive drug delivery, immobilization of nanoceria onto the surface of mesoporous silica also facilitates us to gain a basic insight into the biotransformation of CeO2 in physiological mediums. PMID:25312332

  5. Edible oil structures at low and intermediate concentrations. II. Ultra-small angle X-ray scattering of in situ tristearin solids in triolein

    SciTech Connect

    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

    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.

  6. Superbackscattering nanoparticle dimers

    NASA Astrophysics Data System (ADS)

    Liberal, Iñigo; Ederra, Iñigo; Gonzalo, Ramón; Ziolkowski, Richard W.

    2015-07-01

    The theory and design of superbackscattering nanoparticle dimers are presented. We analytically derive the optimal configurations and the upper bound of their backscattering cross-sections. In particular, it is demonstrated that electrically small nanoparticle dimers can enhance the backscattering by a factor of 6.25 with respect to single dipolar particles. We demonstrate that optimal designs approaching this theoretical limit can be found by using a simple circuit model. The study of practical implementations based on plasmonic and high-permittivity particles has been also addressed. Moreover, the numerical examples reveal that the dimers can attain close to a fourfold enhancement of the single nanoparticle response even in the presence of high losses.

  7. Superbackscattering nanoparticle dimers.

    PubMed

    Liberal, Iñigo; Ederra, Iñigo; Gonzalo, Ramón; Ziolkowski, Richard W

    2015-07-10

    The theory and design of superbackscattering nanoparticle dimers are presented. We analytically derive the optimal configurations and the upper bound of their backscattering cross-sections. In particular, it is demonstrated that electrically small nanoparticle dimers can enhance the backscattering by a factor of 6.25 with respect to single dipolar particles. We demonstrate that optimal designs approaching this theoretical limit can be found by using a simple circuit model. The study of practical implementations based on plasmonic and high-permittivity particles has been also addressed. Moreover, the numerical examples reveal that the dimers can attain close to a fourfold enhancement of the single nanoparticle response even in the presence of high losses. PMID:26081943

  8. X-ray absorption spectroscopy on magnetic nanoscale systems for modern applications

    NASA Astrophysics Data System (ADS)

    Schmitz-Antoniak, Carolin

    2015-06-01

    X-ray absorption spectroscopy facilitated by state-of-the-art synchrotron radiation technology is presented as a powerful tool to study nanoscale systems, in particular revealing their static element-specific magnetic and electronic properties on a microscopic level. A survey is given on the properties of nanoparticles, nanocomposites and thin films covering a broad range of possible applications. It ranges from the ageing effects of iron oxide nanoparticles in dispersion for biomedical applications to the characterisation on a microscopic level of nanoscale systems for data storage devices. In this respect, new concepts for electrically addressable magnetic data storage devices are highlighted by characterising the coupling in a BaTiO3/CoFe2O4 nanocomposite as prototypical model system. But classical magnetically addressable devices are also discussed on the basis of tailoring the magnetic properties of self-assembled ensembles of FePt nanoparticles for data storage and the high-moment material Fe/Cr/Gd for write heads. For the latter cases, the importance is emphasised of combining experimental approaches in x-ray absorption spectroscopy with density functional theory to gain a more fundamental understanding.

  9. Long-term doxorubicin release from multiple stimuli-responsive hydrogels based on ?-amino-acid residues.

    PubMed

    Casolaro, Mario; Casolaro, Ilaria; Bottari, Severino; Del Bello, Barbara; Maellaro, Emilia; Demadis, Konstantinos D

    2014-10-01

    We have developed a series of pH- and temperature-stimuli-sensitive vinyl hydrogels, bearing ?-amino acid residues (L-phenylalanine, L-valine) and incorporating magnetic nanoparticles of different chemical compositions (CoFe2O4 and Fe3O4). The goal was to study the potential applications of these nanocomposites in the controlled release of doxorubicin (DOXO), a potent anticancer drug. The strength of the electrostatic interaction between the protonated nitrogen of the DOXO molecule and the ionized carboxylic groups of the hydrogel allowed effective control of the drug release rate in saline solutions. The embedded magnetic nanoparticles were an additional remote control of the drug release under the stimulus of an appropriate external alternating magnetic field (AMF). Data showed that the controlled release of DOXO proceeded for months and followed a diffusion-controlled release mechanism, while maintaining the amount of released drug within acceptable therapeutic windows. The amount of the released DOXO was found in all cases substantially higher than the "control" because the application of the AMF augments in stimulating the nanoparticles within the DOXO-loaded hydrogel. In vitro experiments have shown that the released DOXO is able to induce cell death to cervix adenocarcinoma cells (HeLa cells). PMID:24931342

  10. Chemical Transformations in Individual Ultrasmall

    E-print Network

    Zare, Richard N.

    Gaggar,1 Biren P. Modi,1 Alexander Moscho,1 Roberto A. Garza-Lo´pez,3 Owe Orwar,2 Richard N. Zare1. The diffusive mixing time of dye molecules is about 8 ms for a 2- m vesicle and 20 s for a 0.1- m vesicle

  11. PEGylated Inorganic Nanoparticles

    SciTech Connect

    Karakoti, Ajay S.; Das, Soumya; Thevuthasan, Suntharampillai; Seal, Sudipta

    2011-02-25

    Application of inorganic nanoparticles in diagnosis and therapy has become a critical component in targeted treatment of diseases. The surface modification of inorganic oxides is important for providing diversity in size, shape, solubility, long term stability and attachment of selective functional groups. PEGylation of surfaces is a key strategic approach for providing stealth characteristics to nanomaterials otherwise identified as foreign materials by human body. The current review describes the role of surface modification of oxides by polyethylene glycol (PEG) in providing versatile characteristics to inorganic oxide nanoparticles with a focus on their biomedical applications. The role of PEG as structure directing agent in synthesis of oxides is also captured in this short review.

  12. Nanoparticles from renewable polymers.

    PubMed

    Wurm, Frederik R; Weiss, Clemens K

    2014-01-01

    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

  13. Nanoparticles from Renewable Polymers

    NASA Astrophysics Data System (ADS)

    Wurm, Frederik; Weiss, Clemens

    2014-07-01

    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.

  14. Nanoparticle shuttle memory

    DOEpatents

    Zettl, Alex Karlwalter (Kensington, CA)

    2012-03-06

    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.

  15. Thermally stable nanoparticles on supports

    SciTech Connect

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

    2012-11-13

    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.

  16. Mesoscale spatial distribution of electron spins studied by time-resolved small-angle and ultrasmall-angle neutron scattering with dynamic nuclear polarization: A case of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) doped in high-density polyethylene

    Microsoft Academic Search

    Takayuki Kumada; Yohei Noda; Satoshi Koizumi; Takeji Hashimoto

    2010-01-01

    We carried out time-resolved small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) studies of dynamically polarized high-density polyethylene (HDPE) doped with 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) persistent free radicals. We observed a remarkable enhancement of the scattering intensity shortly after a switching of microwave frequency from positive (negative) to negative (positive) dynamic nuclear polarization (DNP). The enhancement was found to be

  17. Nanoparticle assemblies as memristors.

    PubMed

    Kim, Tae Hee; Jang, Eun Young; Lee, Nyun Jong; Choi, Deung Jang; Lee, Kyung-Jin; Jang, Jung-tak; Choi, Jin-sil; Moon, Seung Ho; Cheon, Jinwoo

    2009-06-01

    Recently a memristor ( Chua, L. O. IEEE Trans. Circuit Theory 1971 , 18 , 507 ), the fourth fundamental passive circuit element, has been demonstrated as thin film device operations ( Strukov, D. B.; Snider, G. S.; Stewart, D. R.; Williams, R. S. Nature (London) 2008 , 453 , 80 ; Yang, J. J.; Pickett. M. D.; Li, X.; Ohlberg, D. A. A.; Stewart, D. R.; Williams, R. S. Nat. Nanotechnol. 2008 , 3 , 429 ). A new addition to the memristor family can be nanoparticle assemblies consisting of an infinite number of monodispersed, crystalline magnetite (Fe(3)O(4)) particles. Assembly of nanoparticles that have sizes below 10 nm, exhibits at room temperature a voltage-current hysteresis with an abrupt and large bipolar resistance switching (R(OFF)/R(ON) approximately 20). Interestingly, observed behavior could be interpreted by adopting an extended memristor model that combines both a time-dependent resistance and a time-dependent capacitance. We also observed that such behavior is not restricted to magnetites; it is a general property of nanoparticle assemblies as it was consistently observed in different types of spinel structured nanoparticles with different sizes and compositions. Further investigation into this new nanoassembly system will be of importance to the realization of the next generation nanodevices with potential advantages of simpler and inexpensive device fabrications. PMID:19408928

  18. Solid Lipid Nanoparticles

    Microsoft Academic Search

    Anne Saupe; Thomas Rades

    In the last decade of the last century, solid lipid nanoparticles (SLN) have been introduced to the literature as a novel carrier system for cosmetic active ingredients and pharmaceutical drugs. SLN consist of biodegradable physiological lipids or lipidic substances and stabilisers which are generally recognised as safe (GRAS) or have a regulatory accepted status. Compared to other delivery systems such

  19. Nanoparticles in forensic science

    NASA Astrophysics Data System (ADS)

    Cantu, Antonio A.

    2008-10-01

    Nanoparticles appear in several areas of forensic science including security documents, paints, inks, and reagents that develop latent prints. One reagent (known as the silver physical developer) that visualizes the water insoluble components of latent print residue is based on the formation of highly charged silver nanoparticles. These attach to and grow on the residue and generate a silver image. Another such reagent involves highly charged gold nanoparticles. These attach to the residue forming a weak gold image which can be amplified with a silver physical developer. Nanoparaticles are also used in items such as paints, printing inks, and writing inks. Paints and most printing inks consist of nano-sized pigments in a vehicle. However, certain modern ink jet printing inks now contain nano-sized pigments to improve their light fastness and most gel inks are also based on nano scale pigments. These nanoparticlecontaining materials often appear as evidence and are thus subject to forensic characterization. Both luminescent (quantum dots), up-converting nano scale phosphors, and non luminescent nanoparticles are used as security tags to label product, add security to documents, and as anti counterfeiting measures. These assist in determining if an item is fraudulently made.

  20. Nanoparticles & Quantum Dots

    E-print Network

    Strathclyde, University of

    Nanoparticles & Quantum Dots in the SEM Paul Edwards & Robert Martin #12;Outline & Acknowledgments, David Flint & Nial Wheate (SIPBS); David Stirling (UWS) · Gold nanorods Yinan Zhang & Yu Chen (Physics Society: S.Brown, P.Nativo, J.-A.Smith, D.Stirling, P.R.Edwards, D.J.Flint, D.Graham & N

  1. Nanoparticles as biochemical sensors

    PubMed Central

    El-Ansary, Afaf; Faddah, Layla M

    2010-01-01

    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

  2. Traveling Nanoparticles Model

    NSDL National Science Digital Library

    Dr. Neil Forbes

    2008-01-01

    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.

  3. Targeting nanoparticles to cancer

    Microsoft Academic Search

    M. Wang; M. Thanou

    2010-01-01

    Nanotechnology applications in medicine, termed as nanomedicine, have introduced a number of nanoparticles of variable chemistry and architecture for cancer imaging and treatment. Nanotechnology involves engineering multifunctional devices with dimensions at the nanoscale, similar dimensions as those of large biological vesicles or molecules in our body. These devices typically have features just tens to hundred nanometers across and they can

  4. Ultrastable silver nanoparticles.

    PubMed

    Desireddy, Anil; Conn, Brian E; Guo, Jingshu; Yoon, Bokwon; Barnett, Robert N; Monahan, Bradley M; Kirschbaum, Kristin; Griffith, Wendell P; Whetten, Robert L; Landman, Uzi; Bigioni, Terry P

    2013-09-19

    Noble-metal nanoparticles have had a substantial impact across a diverse range of fields, including catalysis, sensing, photochemistry, optoelectronics, energy conversion and medicine. Although silver has very desirable physical properties, good relative abundance and low cost, gold nanoparticles have been widely favoured owing to their proved stability and ease of use. Unlike gold, silver is notorious for its susceptibility to oxidation (tarnishing), which has limited the development of important silver-based nanomaterials. Despite two decades of synthetic efforts, silver nanoparticles that are inert or have long-term stability remain unrealized. Here we report a simple synthetic protocol for producing ultrastable silver nanoparticles, yielding a single-sized molecular product in very large quantities with quantitative yield and without the need for size sorting. The stability, purity and yield are substantially better than those for other metal nanoparticles, including gold, owing to an effective stabilization mechanism. The particular size and stoichiometry of the product were found to be insensitive to variations in synthesis parameters. The chemical stability and structural, electronic and optical properties can be understood using first-principles electronic structure theory based on an experimental single-crystal X-ray structure. Although several structures have been determined for protected gold nanoclusters, none has been reported so far for silver nanoparticles. The total structure of a thiolate-protected silver nanocluster reported here uncovers the unique structure of the silver thiolate protecting layer, consisting of Ag2S5 capping structures. The outstanding stability of the nanoparticle is attributed to a closed-shell 18-electron configuration with a large energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, an ultrastable 32-silver-atom excavated-dodecahedral core consisting of a hollow 12-silver-atom icosahedron encapsulated by a 20-silver-atom dodecahedron, and the choice of protective coordinating ligands. The straightforward synthesis of large quantities of pure molecular product promises to make this class of materials widely available for further research and technology development. PMID:24005327

  5. Nanoparticle adhesion on soft substrates

    NASA Astrophysics Data System (ADS)

    Cao, Zhen; Dobrynin, Andrey; Oyer, Andrew; Stevens, Mark

    2014-03-01

    Using combination of the molecular dynamics simulations and theoretical calculations we study adhesion of spherical and cylindrical nanoparticles on soft substrates. The nanoparticle and substrate deformations are obtained as a function of the nanoparticle and substrate crosslinking density, nanoparticle size and substrate thickness, surface energy of nanoparticles and substrate, and work of adhesion. We have showed that the classical JKR model can be applied to describe nanoparticle adhesion when deformation of both substrate and nanoparticle are small. In this so-called JKR-regime the deformations of substrates and nanoparticles are determined by balancing the elastic energy of deformed objects and work of adhesion between nanoparticle and substrate. However, in the case of soft substrates and nanoparticles when both objects undergo large deformations their equilibrium shapes are determined by balancing the surface energy and work of adhesion (the so-called wetting regime). We present a simple scaling model describing crossover between JKR and wetting regimes. The model predictions are in a very good agreement with simulation results. NSF # DMR-1004576.

  6. DNA templated magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kinsella, Joseph M.

    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.

  7. Facile Surface Functionalization of Hydrophobic Magnetic Nanoparticles

    E-print Network

    Tan, Weihong

    Facile Surface Functionalization of Hydrophobic Magnetic Nanoparticles Yuan Liu,,§ Tao Chen hydrophobic magnetic nanoparticles (MNPs) to an aqueous phase using tetrahydrofuran, NaOH and 3 to other types of hydrophobic nanoparticles to facilitate biomedical appli- cations of nanomaterials

  8. POLYMER PROGRAM SEMINAR "Targeted polymeric nanoparticles

    E-print Network

    Alpay, S. Pamir

    POLYMER PROGRAM SEMINAR "Targeted polymeric nanoparticles: From discovery to clinical trials" Dr, IMS Room 20 A variety of organic and inorganic materials have been utilized to generate nanoparticles for drug delivery applications, including polymeric nanoparticles, dendrimers, nanoshells, liposomes

  9. Solvothermal Synthesis and Supported Catalysis of Polyanion-derived Metal Oxide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Soultanidis, Nikolaos

    Supported metal oxides (SMOs) are important catalytic materials that find numerous applications in important industrial processes. Improving the structural properties of SMOs is a challenging objective due to material synthesis and characterization limitations. Recent developments in the characterization of SMOs, specifically tungstated zirconia (WOx/ZrO2), have revealed structural information that renewed scientific interest in developing more sophisticated synthetic protocols for SMOs. The current work aims to provide a robust characterization of WO x/ZrO2 by using different characterization techniques and probe reactions. Conventional and non-conventional synthetic methods are investigated to cover the whole spectrum of published methods in order to understand the properties and limitations of these techniques. In the second part of this work, a new synthetic approach is presented that successfully produces ultrasmall (smaller than 2 nm) tungsten oxide nanoparticles (WOx NPs). By using conventional tungsten precursors and oleylamine, WOx NPs are synthesized, characterized, and finally supported to test their propene metathesis activity. Conventional WOx/ZrO2 catalysts were prepared and extensively studied by probing their n-pentane isomerization activity and methanol dehydration activity. WOx/ZrO2 prepared via incipient wetness impregnation shows maximum n-pentane isomerization turnover rates (TOR) at intermediate surface densities (rhosurf). This method delivers the most active n-pentane isomerization WOx/ZrO 2 catalysts since it maximizes the number density of the active sub-nm slightly distorted Zr-WOx sites at rhosurf between 5.2-6.2 W/nm2. By comparing the n-pentane isomerization activity with the methanol dehydration activity of WOx /ZrO2, n-pentane isomerization is shown to be an excellent probe reaction for qualitatively identifying the relative (to the other species) population density of Zr-WOx clusters. Bimolecular n-pentane isomerization is the prevailing mechanism and requires a higher population density of Zr-WOx clusters than methanol dehydration. In the second part of this work, a new solvothermal synthesis route for the preparation of ultrasmall tungsten oxide nanoparticles (WOx NPs) is introduced. By using ammonium polyanionic salts and oleylamine, high yields (92+/-5%) of oleylaminecoated WOx NPs were consistently synthesized. The co-addition of an organic oxidant during the synthesis led to smaller WOx NPs thereby providing insight into the NP synthesis mechanism. Deposition and activation of the NPs on SiO2 support by removal of oleylamine allows better control over the WOx domain size than conventional methods. Oleylamine suppresses WOx NP sintering during calcination and prevents the formation of larger polytungstates present in conventional catalysts. The supported WOx NPs were found to be up to 3 times more selective for metathesis products than conventionally prepared tungstated silica likely due to their controlled structure.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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

  11. Gold nanoparticle - modified zinc oxide nanoparticles as novel photocatalytic materials

    Microsoft Academic Search

    Nayane Udawatte

    2010-01-01

    The current study entails the construction of a novel nano-composite catalyst based on ZnO and Au nanoparticles and demonstrates its distinctive photocatalytic characteristics. Monodisperse gold nanoparticles (GNPs) passivated with monolayers of tiopronin or glutathione were synthesized via facile methods, and they were assembled on ZnO nanoparticles to form the nano-catalyst. Steady state and time resolved photoluminescent studies on the nano-composite

  12. Chemical synthesis of magnetic nanoparticles.

    PubMed

    Hyeon, Taeghwan

    2003-04-21

    Recent advances in the synthesis of various magnetic nanoparticles using colloidal chemical approaches are reviewed. Typically, these approaches involve either rapid injection of reagents into hot surfactant solution followed by aging at high temperature, or the mixing of reagents at a low temperature and slow heating under controlled conditions. Spherical cobalt nanoparticles with various crystal structures have been synthesized by thermally decomposing dicobalt octacarbonyl or by reducing cobalt salts. Nanoparticles of Fe-Pt and other related iron or cobalt containing alloys have been made by simultaneously reacting their constituent precursors. Many different ferrite nanoparticles have been synthesized by the thermal decomposition of organometallic precursors followed by oxidation or by low-temperature reactions inside reverse micelles. Rod-shaped iron nanoparticles have been synthesized from the oriented growth of spherical nanoparticles, and cobalt nanodisks were synthesized from the thermal decomposition of dicobalt octacarbonyl in the presence of a mixture of two surfactants. PMID:12744306

  13. Composite nanoparticles for gene delivery.

    PubMed

    Wang, Yuhua; Huang, Leaf

    2014-01-01

    Nanoparticle-mediated gene and siRNA delivery has been an appealing area to gene therapists when they attempt to treat the diseases by manipulating the genetic information in the target cells. However, the advances in materials science could not keep up with the demand for multifunctional nanomaterials to achieve desired delivery efficiency. Researchers have thus taken an alternative approach to incorporate various materials into single composite nanoparticle using different fabrication methods. This approach allows nanoparticles to possess defined nanostructures as well as multiple functionalities to overcome the critical extracellular and intracellular barriers to successful gene delivery. This chapter will highlight the advances of fabrication methods that have the most potential to translate nanoparticles from bench to bedside. Furthermore, a major class of composite nanoparticle-lipid-based composite nanoparticles will be classified based on the components and reviewed in details. PMID:25409605

  14. Harnessing nanoparticles for immune modulation.

    PubMed

    Getts, Daniel R; Shea, Lonnie D; Miller, Stephen D; King, Nicholas J C

    2015-07-01

    Recent approaches using nanoparticles engineered for immune regulation have yielded promising results in preclinical models of disease. The number of nanoparticle therapies is growing, fueled by innovations in nanotechnology and advances in understanding of the underlying pathogenesis of immune-mediated diseases. In particular, recent mechanistic insight into the ways in which nanoparticles interact with the mononuclear phagocyte system and impact its function during homeostasis and inflammation have highlighted the potential of nanoparticle-based therapies for controlling severe inflammation while concurrently restoring peripheral immune tolerance in autoimmune disease. Here we review recent advances in nanoparticle-based approaches aimed at immune-modulation, and discuss these in the context of concepts in polymeric nanoparticle development, including particle modification, delivery and the factors associated with successful clinical deployment. PMID:26088391

  15. Photoacoustic signal amplification through plasmonic nanoparticle aggregation

    PubMed Central

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

    2013-01-01

    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

  16. Evaluation of monolayer protected metal nanoparticle technology

    E-print Network

    Wu, Diana J

    2005-01-01

    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 ...

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

    PubMed

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

    2014-02-21

    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

  18. Nanoparticles for Detection and Diagnosis

    PubMed Central

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

    2009-01-01

    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

  19. Theranostic magnetic nanoparticles.

    PubMed

    Yoo, Dongwon; Lee, Jae-Hyun; Shin, Tae-Hyun; Cheon, Jinwoo

    2011-10-18

    Early detection and treatment of disease is the most important component of a favorable prognosis. Biomedical researchers have thus invested tremendous effort in improving imaging techniques and treatment methods. Over the past decade, concepts and tools derived from nanotechnology have been applied to overcome the problems of conventional techniques for advanced diagnosis and therapy. In particular, advances in nanoparticle technology have created new paradigms for theranostics, which is defined as the combination of therapeutic and diagnostic agents within a single platform. In this Account, we examine the potential advantages and opportunities afforded by magnetic nanoparticles as platform materials for theranostics. We begin with a brief overview of relevant magnetic parameters, such as saturation magnetization, coercivity, and magnetocrystalline anisotropy. Understanding the interplay of these parameters is critical for optimizing magnetic characteristics needed for effective imaging and therapeutics, which include magnetic resonance imaging (MRI) relaxivity, heat emission, and attractive forces. We then discuss approaches to constructing an MRI nanoparticle contrast agent with high sensitivity. We further introduce a new design concept for a fault-free contrast agent, which is a T1 and T2 dual mode hybrid. Important capabilities of magnetic nanoparticles are the external controllability of magnetic heat generation and magnetic attractive forces for the transportation and movement of biological objects. We show that these functions can be utilized not only for therapeutic hyperthermia of cancer but also for controlled release of cancer drugs through the application of an external magnetic field. Additionally, the use of magnetic nanoparticles to drive mechanical forces is demonstrated to be useful for molecular-level cell signaling and for controlling the ultimate fate of the cell. Finally, we show that targeted imaging and therapy are made possible by attaching a variety of imaging and therapeutic components. These added components include therapeutic genes (small interfering RNA, or siRNA), cancer-specific ligands, and optical reporting dyes. The wide range of accessible features of magnetic nanoparticles underscores their potential as the most promising platform material available for theranostics. PMID:21823593

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

    PubMed

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

    2012-01-01

    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

  1. Flow and heat transfer of ferrofluids over a flat plate with uniform heat flux

    NASA Astrophysics Data System (ADS)

    Khan, W. A.; Khan, Z. H.; Haq, R. U.

    2015-04-01

    The present work is dedicated to analyze the flow and heat transport of ferrofluids along a flat plate subjected to uniform heat flux and slip velocity. A magnetic field is applied in the transverse direction to the plate. Moreover, three different kinds of magnetic nanoparticles (Fe3O4, CoFe2O4, Mn-ZnFe2O4 are incorporated within the base fluid. We have considered two different kinds of base fluids (kerosene and water) having poor thermal conductivity as compared to solid magnetic nanoparticles. Self-similar solutions are obtained and are compared with the available data for special cases. A simulation is performed for each ferrofluid mixture by considering the dominant effects of slip and uniform heat flux. It is found that the present results are in an excellent agreement with the existing literature. The variation of skin friction and heat transfer is also performed at the surface of the plate and then the better heat transfer and of each mixture is analyzed. Kerosene-based magnetite Fe3O4 provides the higher heat transfer rate at the wall as compared to the kerosene-based cobalt ferrite and Mn-Zn ferrite. It is also concluded that the primary effect of the magnetic field is to accelerate the dimensionless velocity and to reduce the dimensionless surface temperature as compared to the hydrodynamic case, thereby increasing the skin friction and the heat transfer rate of ferrofluids.

  2. Silver Nanoparticles in Dental Biomaterials

    PubMed Central

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

    2015-01-01

    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

  3. Multicomponent periodic nanoparticle superlattices.

    SciTech Connect

    Podsiadlo, P.; Krylova, G. V.; Demortiere, A.; Shevchenko, E. V. (Center for Nanoscale Materials)

    2011-01-01

    In this article, we review the state-of-the-art in the preparation and characterization of multicomponent self-assembled superlattices of colloidal nanoparticles with core sizes in the range of 2-20 nm and interparticle spacing less than 2 nm down to intimate contact stemming from sintering. Several aspects of the field are discussed, including: structural organization, the role of particle size distribution, key interparticle forces at play, and methods of investigation of the structures. Contrary to the extensively studied colloidal crystals composed of microscale particles, the nanoparticles possess unique size-dependent properties, such as electronic, optical, or magnetic, which when combined into periodic structures can potentially lead to new collective states stemming from precise positioning of the nanocolloids. As such, we examine a number of emerging applications of this new class of metamaterials. Finally, we speculate on the potential impact of these materials, the new directions, and the challenges for the researchers.

  4. Nanoparticle Reactions on Chip

    NASA Astrophysics Data System (ADS)

    Köhler, J. M.; Kirner, Th.; Wagner, J.; Csáki, A.; Möller, R.; Fritzsche, W.

    The handling of heterogenous systems in micro reactors is difficult due to their adhesion and transport behaviour. Therefore, the formation of precipitates and gas bubbles has to be avoided in micro reaction technology, in most cases. But, micro channels and other micro reactors offer interesting possibilities for the control of reaction conditions and transport by diffusion and convection due to the laminar flow caused by small Reynolds numbers. This can be used for the preparation and modification of objects, which are much smaller than the cross section of microchannels. The formation of colloidal solutions and the change of surface states of nano particles are two important tasks for the application of chip reactors in nanoparticle technology. Some concepts for the preparation and reaction of nanoparticles in modular chip reactor arrangements will be discussed.

  5. Metallic nanoparticles meet Metadynamics

    E-print Network

    Pavan, Luca; Baletto, Francesca

    2015-01-01

    We show how standard Metadynamics coupled with classical Molecular Dynamics can be successfully ap- plied to sample the configurational and free energy space of metallic and bimetallic nanopclusters via the implementation of collective variables related to the pair distance distribution function of the nanoparticle itself. As paradigmatic examples we show an application of our methodology to Ag147, Pt147 and their alloy AgshellPtcore at 1:1 and 2:1 chemical compositions. The proposed scheme is not only able to reproduce known structural transformation pathways, as the five and the six square-diamond mechanisms both in pure and core-shell nanoparticles but also to predict a new route connecting icosahedron to anti-cuboctahedron.

  6. Photoluminescence by Interstellar Nanoparticles

    SciTech Connect

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

    2004-04-21

    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.

  7. Magnetic Nanoparticle Sensors

    PubMed Central

    Koh, Isaac; Josephson, Lee

    2009-01-01

    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

  8. Nanoparticles in dermatology

    Microsoft Academic Search

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

    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

  9. Characterization of starch nanoparticles

    NASA Astrophysics Data System (ADS)

    Szymo?ska, J.; Targosz-Korecka, M.; Krok, F.

    2009-01-01

    Nanomaterials already attract great interest because of their potential applications in technology, food science and medicine. Biomaterials are biodegradable and quite abundant in nature, so they are favoured over synthetic polymer based materials. Starch as a nontoxic, cheap and renewable raw material is particularly suitable for preparation of nanoparticles. In the paper, the structure and some physicochemical properties of potato and cassava starch particles of the size between 50 to 100 nm, obtained by mechanical treatment of native starch, were presented. We demonstrated, with the aim of the Scanning Electron Microscopy (SEM) and the non-contact Atomic Force Microscopy (nc-AFM), that the shape and dimensions of the obtained nanoparticles both potato and cassava starch fit the blocklets - previously proposed as basic structural features of native starch granules. This observation was supported by aqueous solubility and swelling power of the particles as well as their iodine binding capacity similar to those for amylopectin-type short branched polysaccharide species. Obtained results indicated that glycosidic bonds of the branch linkage points in the granule amorphous lamellae might be broken during the applied mechanical treatment. Thus the released amylopectin clusters could escape out of the granules. The starch nanoparticles, for their properties qualitatively different from those of native starch granules, could be utilized in new applications.

  10. Thermal treatment of magnetite nanoparticles

    PubMed Central

    Wykowska, Urszula; Satula, Dariusz; Nordblad, Per

    2015-01-01

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

  11. Antimicrobial Properties of Silver Nanoparticles

    NSDL National Science Digital Library

    Kouadio, Carrie

    This module provides students the opportunity to "explore silver nanoparticles and their effectiveness against bacterial growth in hands-on laboratory activities." Students first make silver nanoparticles and then use them in an experiment they design. This lesson will require two or more class periods and is aimed at secondary students.The document is available to download in PDF file format.

  12. Resveratrol in Solid Lipid Nanoparticles

    Microsoft Academic Search

    Maria Eugenia Carlotti; Simona Sapino; Elena Ugazio; Marina Gallarate; Silvia Morel

    2011-01-01

    This report investigates the possibility of producing solid lipid nanoparticles as protective vehicle of resveratrol, an antioxidant characterised by a fast trans-cis isomerisation. SLN aqueous dispersions were produced by hot melt homogenisation technique and characterised. It was found that the presence of tetradecyl-?-cyclodextrin in SLN formulation induced an improvement of nanoparticle characteristics. Moreover a significant reduction in resveratrol photodegradation was

  13. Role of Nanoparticles in Photocatalysis

    Microsoft Academic Search

    D. Beydoun; R. Amal; G. Low; S. McEvoy

    1999-01-01

    The aim of this review paper is to give an overview of the development and implications of nanotechnology in photocatalysis. The topics covered include a detailed look at the unique properties of nanoparticles and their relation to photocatalytic properties. Current applications of and research into the use of nanoparticles as photocatalysts has also been reviewed. Also covered is the utilization

  14. Gold-Nanoparticle-Enhanced Cancer Photothermal Therapy

    Microsoft Academic Search

    Jing-Liang Li; Min Gu

    2010-01-01

    In this paper, progress on the gold-nanoparticle-enhanced photothermal therapy is reviewed. Size- and shape-dependent optical absorption of gold nanoparticles, the effects of various parameters on the therapeutic efficiency, and the mechanisms of gold-nanoparticle-assisted cancer therapy are discussed. Future research directions of gold-nanoparticle-assisted cancer photothermal therapy are also suggested.

  15. A simple way to prepare bismuth nanoparticles

    Microsoft Academic Search

    Yanbao Zhao; Zhijun Zhang; Hongxin Dang

    2004-01-01

    In this paper, we report a simple method to prepare bismuth nanoparticles from bulk bismuth. Bismuth nanoparticles of near spherical shape have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and other techniques. Bismuth nanoparticles have mean diameter of 40–50 nm and exhibit the same crystal structure as the bulk bismuth. The surface of bismuth nanoparticle has been

  16. Green nanoparticle production using micro reactor technology

    Microsoft Academic Search

    A. Kück; M. Steinfeldt; K. Prenzel; P. Swiderek; A. v. Gleich; J. Thöming

    2011-01-01

    The importance and potential of nanoparticles in daily life as well as in various industrial processes is becoming more predominant. Specifically, silver nanoparticles are increasingly applied, e.g. in clothes and wipes, due to their antibacterial properties. For applications in liquid phase it is advantageous to produce the nanoparticles directly in suspension. This article describes a green production of silver nanoparticles

  17. Fluorescent Magnetic Nanoparticles for Biomedical Applications

    E-print Network

    Candea, George

    Fluorescent Magnetic Nanoparticles for Biomedical Applications V.M.Dao, Dr. G. Coullerez, Dr. L, the main goal was to synthesize and to characterize novel fluorescent magnetic nanoparticles. These nanoparticles (NPs) involve superparamagnetic iron oxide nanoparticles (SPIONs), a fluorescently-labeled polymer

  18. Solventless synthesis of ruthenium nanoparticles

    NASA Astrophysics Data System (ADS)

    García-Peña, Nidia G.; Redón, Rocío; Herrera-Gomez, Alberto; Fernández-Osorio, Ana Leticia; Bravo-Sanchez, Mariela; Gomez-Sosa, Gustavo

    2015-06-01

    This paper presents a novel solventless method for the synthesis of zero-valent ruthenium nanoparticles Ru(0). The proposed method, although not entirely new in the nanomaterials world, was used for the first time to synthesize zero-valent ruthenium nanoparticles. This new approach has proved to be an environmentally friendly, clean, cheap, fast, and reproducible technique which employs low amounts of solvent. It was optimized through varying amounts of reducing salt on a determined quantity of precursor and measuring the effect of this variation on the average particle size obtained. The resulting products were fully characterized by powder XRD, TEM, HR-TEM, and XPS studies, all of which corroborated the purity of the nanoparticles achieved. In order to verify the advantages of our method over other techniques, we compared our nanoparticles with two common colloidal-synthesized ruthenium nanoparticles.

  19. Stress-Induced Nanoparticle Crystallization

    PubMed Central

    2015-01-01

    We demonstrate for the first time a new mechanical annealing method that can significantly improve the structural quality of self-assembled nanoparticle arrays by eliminating defects at room temperature. Using in situ high-pressure small-angle X-ray scattering, we show that deformation of nanoparticle assembly in the presence of gigapascal level stress rebalances interparticle forces within nanoparticle arrays and transforms the nanoparticle film from an amorphous assembly with defects into a quasi-single crystalline superstructure. Our results show that the existence of the hydrostatic pressure field makes the transformation both thermodynamically and kinetically possible/favorable, thus providing new insight for nanoparticle self-assembly and integration with enhanced mechanical performance. PMID:24829089

  20. Galactosylated Albumin Nanoparticles of Simvastatin

    PubMed Central

    Ganesh, Kumar; Archana, Dhyani; Preeti, Kothiyal

    2015-01-01

    The present study was an attempt to develop galactosylated albumin nanoparticles of Simvastatin for treatment of hypercholesterolemia. By developing the galactosylated nanoparticulated delivery, the required action of the drug at the target site at the liver can be provided. The advantage of targeting helps to reduce the systemic side effects that may occur due to the distribution of the drug to the other organs and thus helps in maintaining the required concentration of drug at the desired site. The galacotsylated albumin nanoparticles were prepared for the selective delivery of a Simvastatin to the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) the rate-limiting enzyme in the pathway of cholesterol biosynthesis that is particularly presents on hepatocytes. The asialoglycoprotein receptor (ASGP-R) which is particularly presents on mammalian hepatocytes can be utilize for active targeting by using its natural and synthetic ligands. By utilizing this receptors can provides a unique means for the development of liver-specific carriers, such as liposomes, recombinant lipoproteins, and polymers for drug or gene delivery to the liver, especially to hepatocytes. These receptors recognize the ligands with terminal galactose or N-acetylgalactosamine residues, and endocytose the ligands for an intracellular degradation process. The albumin nanoparticles (NPs) were prepared by using desolvation method and efficiently conjugated with galactose. Various parameters such as particle size, zeta potential, percentage entrapment efficiency and drug loading efficiency, percentage yield, in-vitro drug release were determined. The size of nanoparticles (both plain and coated NPs) was 200 and 250 nm. The zeta potential of plain nanoparticles was -3.61 and that of galactose-coated nanoparticles was 64.1. The maximum drug content was in between 79.98% to 79.8 % respectively in plain, and galactose coated nanoparticles while the maximum entrapment efficiency was 70.10% and 71.03% in plain and coated nanoparticles. It was found that coating of nanoparticles increases the size of nanoparticles. PMID:25901147

  1. Control Large Nanoparticle Assemblies in Suparmolecular Nanoparticle Thin Films

    NASA Astrophysics Data System (ADS)

    Huang, Jingyu; Xu, Ting

    2015-03-01

    Nanocomposites can generate new properties beyond those offered by organic and inorganic building blocks to meet the demands in functional materials. The collective properties of nanocomposite materials depend on both the nature of individual building block and their spatial arrangements. With the recent development, colloidal synthesis and surface modification methods provide inorganic nanoparticles (NPs) with various sizes, shapes, compositions and properties in a facile manner. Block copolymer-based supramolecules further provide more versatile routes to control spatial arrangement of the nanoparticles over multiple length scales. Nanoparticle size is a critical parameter determining the optical and electronic properties. However, most of studies to date focused on nanoparticle smaller than 10 nm in size. Here, our recent studies showed that the assembly of nanoparticles with size larger than 10 nm can be achieved in the supramolecular nanocomposite thin films by finely tuning the ligand-polymer interactions and the sample treatment conditions. Both the overall morphology of the nanoparticle assemblies and inter-particle distances can be readily tailored. These new results opened a viable approach to construct functional materials using nanoparticles with different quantum confinement effects.

  2. Biological nanoparticles and their influence on organisms.

    PubMed

    Stanley, Sarah

    2014-08-01

    Over millions of years, biological systems have evolved wide varieties of nanoparticles. Naturally occurring nanoparticles show great diversity: they may be intracellular or extracellular, formed of organic or inorganic materials and have wide-ranging biological roles. Despite this diversity, nanoparticles found in nature possess several characteristics that make them attractive for biomedical purposes. This review presents an overview of the most common biological nanoparticles and outlines the potential applications of natural and modified biological nanoparticles. PMID:24832077

  3. Nanoparticle enhanced ionic liquid heat transfer fluids

    DOEpatents

    Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.

    2014-08-12

    A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.

  4. Triggered Nanoparticles as Therapeutics

    PubMed Central

    Kim, Chang Soo; Duncan, Bradley; Creran, Brian; Rotello, Vincent M.

    2013-01-01

    Summary Drug delivery systems (DDSs) face several challenges including site-specific delivery, stability, and the programmed release of drugs. Engineered nanoparticle (NP) surfaces with responsive moieties can enhance the efficacy of DDSs for in vitro and in vivo systems. This triggering process can be achieved through both endogenous (biologically controlled release) and exogenous (external stimuli controlled release) activation. In this review, we will highlight recent examples of the use of triggered release strategies of engineered nanomaterials for in vitro and in vivo applications. PMID:24159362

  5. Antibacterial properties of nanoparticles.

    PubMed

    Hajipour, Mohammad J; Fromm, Katharina M; Ashkarran, Ali Akbar; Jimenez de Aberasturi, Dorleta; de Larramendi, Idoia Ruiz; Rojo, Teofilo; Serpooshan, Vahid; Parak, Wolfgang J; Mahmoudi, Morteza

    2012-10-01

    Antibacterial agents are very important in the textile industry, water disinfection, medicine, and food packaging. Organic compounds used for disinfection have some disadvantages, including toxicity to the human body, therefore, the interest in inorganic disinfectants such as metal oxide nanoparticles (NPs) is increasing. This review focuses on the properties and applications of inorganic nanostructured materials and their surface modifications, with good antimicrobial activity. Such improved antibacterial agents locally destroy bacteria, without being toxic to the surrounding tissue. We also provide an overview of opportunities and risks of using NPs as antibacterial agents. In particular, we discuss the role of different NP materials. PMID:22884769

  6. Influence of organic solvent on optical and structural properties of ultra-small silicon dots synthesized by UV laser ablation in liquid.

    PubMed

    Intartaglia, Romuald; Bagga, Komal; Genovese, Alessandro; Athanassiou, Athanassia; Cingolani, Roberto; Diaspro, Alberto; Brandi, Fernando

    2012-11-28

    Ultra small silicon nanoparticles (Si-NPs) with narrow size distribution are prepared in a one step process by UV picosecond laser ablation of silicon bulk in liquid. Characterization by electron microscopy and absorption spectroscopy proves Si-NPs generation with an average size of 2 nm resulting from an in situ photofragmentation effect. In this context, the current work aims to explore the liquid medium (water and toluene) effect on the Si-NPs structure and on the optical properties of the colloidal solution. Si-NPs with high pressure structure (s.g. Fm3m) and diamond-like structure (s.g. Fd3m), in water, and SiC moissanite 3C phase (s.g. F4[combining macron]3m) in toluene are revealed by the means of High-Resolution TEM and HAADF-STEM measurements. Optical investigations show that water-synthesized Si-NPs have blue-green photoluminescence emission characterized by signal modulation at a frequency of 673 cm(-1) related to electron-phonon coupling. The synthesis in toluene leads to generation of Si-NPs embedded in the graphitic carbon-polymer composite which has intrinsic optical properties at the origin of the optical absorption and luminescence of the obtained colloidal solution. PMID:23059971

  7. Precise Quantification of Nanoparticle Internalization

    PubMed Central

    Gottstein, Claudia; Wu, Guohui; Wong, Benjamin J.; Zasadzinski, Joseph Anthony

    2013-01-01

    Nanoparticles have opened new exciting avenues for both diagnostic and therapeutic applications in human disease, and targeted nanoparticles are increasingly used as specific drug delivery vehicles. The precise quantification of nanoparticle internalization is of importance to measure the impact of physical and chemical properties on the uptake of nanoparticles into target cells or into cells responsible for rapid clearance. Internalization of nanoparticles has been measured by various techniques, but comparability of data between different labs is impeded by lack of a generally accepted standardized assay. Furthermore, the distinction between associated and internalized particles has been a challenge for many years, although this distinction is critical for most research questions. Previously used methods to verify intracellular location are typically not quantitative and do not lend themselves to high throughput analysis. Here we developed a mathematical model which integrates the data from high throughput flow cytometry measurements with data from quantitative confocal microscopy. The generic method described here will be a useful tool in biomedical nanotechnology studies. The method was then applied to measure the impact of surface coatings of vesosomes on their internalization by cells of the reticuloendothelial system (RES). RES cells are responsible for rapid clearance of nanoparticles, and the resulting fast blood clearance is one of the major challenges in biomedical applications of nanoparticles. Coating of vesosomes with long chain polyethylene glycol showed a trend for lower internalization by RES cells. PMID:23706031

  8. Nanoparticle optical notch filters

    NASA Astrophysics Data System (ADS)

    Kasinadhuni, Pradeep Kumar

    Developing novel light blocking products involves the design of a nanoparticle optical notch filter, working on the principle of localized surface plasmon resonance (LSPR). These light blocking products can be used in many applications. One such application is to naturally reduce migraine headaches and light sensitivity. Melanopsin ganglion cells present in the retina of the human eye, connect to the suprachiasmatic nucleus (SCN-the body's clock) in the brain, where they participate in the entrainment of the circadian rhythms. As the Melanopsin ganglion cells are involved in triggering the migraine headaches in photophobic patients, it is necessary to block the part of visible spectrum that activates these cells. It is observed from the action potential spectrum of the ganglion cells that they absorb light ranging from 450-500nm (blue-green part) of the visible spectrum with a ?max (peak sensitivity) of around 480nm (blue line). Currently prescribed for migraine patients is the FL-41 coating, which blocks a broad range of wavelengths, including wavelengths associated with melanopsin absorption. The nanoparticle optical notch filter is designed to block light only at 480nm, hence offering an effective prescription for the treatment of migraine headaches.

  9. Nanoparticles in dermatology.

    PubMed

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

    2011-10-01

    Recent advances in the field of nanotechnology have allowed the manufacturing of elaborated nanometer-sized particles for various biomedical applications. A broad spectrum of particles, extending from various lipid nanostructures such as liposomes and solid lipid nanoparticles, to metal, nanocrystalline and polymer particles have already been tested as drug delivery systems in different animal models with remarkable results, promising an extensive commercialization in the coming years. Controlled drug release to skin and skin appendages, targeting of hair follicle-specific cell populations, transcutaneous vaccination and transdermal gene therapy are only a few of these new applications. Carrier systems of the new generation take advantage of improved skin penetration properties, depot effect with sustained drug release and of surface functionalization (e.g., the binding to specific ligands) allowing specific cellular and subcellular targeting. Drug delivery to skin by means of microparticles and nanocarriers could revolutionize the treatment of several skin disorders. However, the toxicological and environmental safety of micro- and nanoparticles has to be evaluated using specific toxicological studies prior to a wider implementation of the new technology. This review aims to give an overview of the most investigated applications of transcutaneously applied particle-based formulations in the fields of cosmetics and dermatology. PMID:21837474

  10. Structural Characterization of Ceria Nanoparticles

    NASA Astrophysics Data System (ADS)

    Srinivasan, R.; Bose, A. Chandra

    2011-07-01

    Cerium oxide (Ceria) nanoparticles were successfully synthesized by hydrolysis assisted co-precipitation method. As-synthesized samples are annealed at 500 °C and 800 °C respectively. Crystalline nature of the sample is analyzed by X-ray diffraction (XRD). The morphology of all the samples is investigated by transmission electron microscope (TEM) and scanning electron microscope (SEM). The average size of the nanoparticles varies between the 8 and 20 nm. Poly crystalline natures of the nanoparticles proved by selected are electron diffraction pattern (SAED). The grain size dependent absorption is demonstrated with UV-vis spectra.

  11. Method of synthesizing tungsten nanoparticles

    DOEpatents

    Thoma, Steven G; Anderson, Travis M

    2013-02-12

    A method to synthesize tungsten nanoparticles has been developed that enables synthesis of nanometer-scale, monodisperse particles that can be stabilized only by tetrahydrofuran. The method can be used at room temperature, is scalable, and the product concentrated by standard means. Since no additives or stabilizing surfactants are required, this method is particularly well suited for producing tungsten nanoparticles for dispersion in polymers. If complete dispersion is achieved due to the size of the nanoparticles, then the optical properties of the polymer can be largely maintained.

  12. Fluorescent Property of Gold Nanoparticles with Different Surface Structures

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-juan; Wang, Chun-xia; Wang, Yong; Niu, Shu-hua; Lü, Chang-gui; Fu, De-gang

    2007-12-01

    Fluorescence spectra of naked gold nanoparticles, triphenylphosphine stabled gold nanoparticles, and 3-mercaptopropionic acid substituted gold nanoparticles were studied. It was found that fluorescence intensities of gold nanoparticles were highly sensitive to surface molecules. The fluorescence quenching effect of these gold nanoparticles on CdSe nanoparticles was also investigated. This quenching effect was related to the overlap degree between the absorption spectra of gold nanoparticles and the emission spectrum of CdSe nanoparticles, and was surface-dependent as well.

  13. Fluorescent Property of Gold Nanoparticles with Different Surface Structures

    Microsoft Academic Search

    Zhi-Juan Zhang; Chun-Xia Wang; Yong Wang; Shu-Hua Niu; Chang-Gui Lü; De-Gang Fu

    2007-01-01

    Fluorescence spectra of naked gold nanoparticles, triphenylphosphine stabled gold nanoparticles, and 3-mercaptopropionic acid substituted gold nanoparticles were studied. It was found that fluorescence intensities of gold nanoparticles were highly sensitive to surface molecules. The fluorescence quenching effect of these gold nanoparticles on CdSe nanoparticles was also investigated. This quenching effect was related to the overlap degree between the absorption spectra

  14. Nanoparticles containing insoluble drug for cancer therapy.

    PubMed

    Guo, Shutao; Huang, Leaf

    2014-01-01

    Nanoparticle drug formulations have been extensively researched and developed in the field of drug delivery as a means to efficiently deliver insoluble drugs to tumor cells. By mechanisms of the enhanced permeability and retention effect, nanoparticle drug formulations are capable of greatly enhancing the safety, pharmacokinetic profiles and bioavailability of the administered treatment. Here, the progress of various nanoparticle formulations in both research and clinical applications is detailed with a focus on the development of drug/gene delivery systems. Specifically, the unique advantages and disadvantages of polymeric nanoparticles, liposomes, solid lipid nanoparticles, nanocrystals and lipid-coated nanoparticles for targeted drug delivery will be investigated in detail. PMID:24113214

  15. Non-Engineered Nanoparticles of C60

    PubMed Central

    Deguchi, Shigeru; Mukai, Sada-atsu; Sakaguchi, Hide; Nonomura, Yoshimune

    2013-01-01

    We discovered that rubbing bulk solids of C60 between fingertips generates nanoparticles including the ones smaller than 20?nm. Considering the difficulties usually associated with nanoparticle production by pulverisation, formation of nanoparticles by such a mundane method is unprecedented and noteworthy. We also found that nanoparticles of C60 could be generated from bulk solids incidentally without deliberate engineering of any sort. Our findings imply that there exist highly unusual human exposure routes to nanoparticles of C60, and elucidating formation mechanisms of nanoparticles is crucial in assessing their environmental impacts. PMID:23807024

  16. Nanoparticles Containing Insoluble Drug for Cancer Therapy

    PubMed Central

    Guo, Shutao; Huang, Leaf

    2014-01-01

    Nanoparticle drug formulations have been extensively researched and developed in the field of drug delivery as a means to efficiently deliver insoluble drugs to tumor cells. By mechanisms of the enhanced permeability and retention effect, nanoparticle drug formulations are capable of greatly enhancing the safety, pharmacokinetic profiles and bioavailability of the administered treatment. Here, the progress of various nanoparticle formulations in both research and clinical applications is detailed with a focus on the development of drug/gene delivery systems. Specifically, the unique advantages and disadvanges of polymeric nanoparticles, liposomes, solid lipid nanoparticles, nanocrystals and lipid-coated nanoparticles for targeted drug delivery will be investigated in detail. PMID:24113214

  17. Zinc oxide nanoparticles on silicon

    NASA Astrophysics Data System (ADS)

    Giannakopoulos, K.; Boukos, N.; Travlos, A.

    2006-01-01

    Self-assembled ZnO nanoparticles are grown by electron beam evaporation of Zn on silicon oxide and silicon substrates and subsequent annealing in oxygen. Characterization by TEM and EELS shows that the nanoparticles can be zinc oxide single crystals grown with their c-axis perpendicular to the substrate; their distribution, size and crystallinity depend on the deposition parameters of zinc and the growth substrate. We discuss the effect of these parameters on the morphology of the resulting material.

  18. Diamond Synthesis Employing Nanoparticle Seeds

    NASA Technical Reports Server (NTRS)

    Uppireddi, Kishore (Inventor); Morell, Gerardo (Inventor); Weiner, Brad R. (Inventor)

    2014-01-01

    Iron nanoparticles were employed to induce the synthesis of diamond on molybdenum, silicon, and quartz substrates. Diamond films were grown using conventional conditions for diamond synthesis by hot filament chemical vapor deposition, except that dispersed iron oxide nanoparticles replaced the seeding. This approach to diamond induction can be combined with dip pen nanolithography for the selective deposition of diamond and diamond patterning while avoiding surface damage associated to diamond-seeding methods.

  19. Citrate Synthesis of Gold 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 gold nanoparticles. The experiment allows students to view the formation of gold nanoparticles that can be detected by the reflection of a laser beam. 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.

  20. Functionalized magnetic nanoparticle analyte sensor

    DOEpatents

    Yantasee, Wassana; Warner, Maryin G; Warner, Cynthia L; Addleman, Raymond S; Fryxell, Glen E; Timchalk, Charles; Toloczko, Mychailo B

    2014-03-25

    A method and system for simply and efficiently determining quantities of a preselected material in a particular solution by the placement of at least one superparamagnetic nanoparticle having a specified functionalized organic material connected thereto into a particular sample solution, wherein preselected analytes attach to the functionalized organic groups, these superparamagnetic nanoparticles are then collected at a collection site and analyzed for the presence of a particular analyte.

  1. Extrinsic magnetoresistance in magnetite nanoparticles

    Microsoft Academic Search

    Kai Liu; L. Zhao; P. Klavins; Frank E. Osterloh; H. Hiramatsu

    2003-01-01

    Magnetite (Fe3O4) nanoparticles, 8 to 9 nm in size, have been synthesized using an aqueous precipitation technique. X-ray diffraction and chemical titration confirm a single cubic spinel phase with expected stoichiometry. Superparamagnetic behavior has been observed in pressed pellets of the nanoparticles above 200 K. Spin-dependent tunneling through adjacent particles has led to a negative magnetoresistance, -8.6% at 200 K

  2. Method for producing metallic nanoparticles

    DOEpatents

    Phillips, Jonathan; Perry, William L.; Kroenke, William J.

    2004-02-10

    Method for producing metallic nanoparticles. The method includes generating an aerosol of solid metallic microparticles, generating non-oxidizing plasma with a plasma hot zone at a temperature sufficiently high to vaporize the microparticles into metal vapor, and directing the aerosol into the hot zone of the plasma. The microparticles vaporize in the hot zone to metal vapor. The metal vapor is directed away from the hot zone and to the plasma afterglow where it cools and condenses to form solid metallic nanoparticles.

  3. Gold nanoparticles enhancing protontherapy efficiency.

    PubMed

    Torrisi, Lorenzo

    2015-03-11

    The insertion of gold nanoparticles in biological liquids, tissues and organs permits to increase the equivalent atomic number of the medium that, if used as target to be irradiated by ionizing radiation, permits an increment of the absorbed dose. No toxic nanoparticles, such as the Au, can be injected in the cancer tissues at different concentrations before using a localized treatment that uses energetic proton beams for radiotherapy. Due to the high density and atomic number of the used gold nanoparticles, the absorbed radiation dose can be increased to about a factor six per cent using relatively low concentration of nanoparticles injectable as solution in the tumor tissue. This means to reduce the exposition to ionizing radiation or to increase the dose to the tumor site. Simulation programs of proton energy loss in tissues, using SRIM Code, are employed to evaluate the Bragg peak enhancing in presence of Au nanoparticles, so it will be presented and discussed. Some research findings and patents in the gold nanoparticle preparation and application to Medicine are reviewed in the present paper. PMID:25986229

  4. Exposure to Nanoparticles and Hormesis

    PubMed Central

    Iavicoli, Ivo; Calabrese, Edward J.; Nascarella, Marc A.

    2010-01-01

    Nanoparticles are particles with lengths that range from 1 to 100 nm. They are increasingly being manufactured and used for commercial purpose because of their novel and unique physicochemical properties. Although nanotechnology-based products are generally thought to be at a pre-competitive stage, an increasing number of products and materials are becoming commercially available. Human exposure to nanoparticles is therefore inevitable as they become more widely used and, as a result, nanotoxicology research is now gaining attention. However, there are many uncertainties as to whether the unique properties of nanoparticles also pose occupational health risks. These uncertainties arise because of gaps in knowledge about the factors that are essential for predicting health risks such as routes of exposure, distribution, accumulation, excretion and dose-response relationship of the nanoparticles. In particular, uncertainty remains with regard to the nature of the dose-response curve at low level exposures below the toxic threshold. In fact, in the literature, some studies that investigated the biological effects of nanoparticles, observed a hormetic dose-response. However, currently available data regarding this topic are extremely limited and fragmentary. It therefore seems clear that future studies need to focus on this issue by studying the potential adverse health effects caused by low-level exposures to nanoparticles. PMID:21191487

  5. Nanoparticles and Neurotoxicity

    PubMed Central

    Win-Shwe, Tin-Tin; Fujimaki, Hidekazu

    2011-01-01

    Humans are exposed to nanoparticles (NPs; diameter < 100 nm) from ambient air and certain workplaces. There are two main types of NPs; combustion-derived NPs (e.g., particulate matters, diesel exhaust particles, welding fumes) and manufactured or engineered NPs (e.g., titanium dioxide, carbon black, carbon nanotubes, silver, zinc oxide, copper oxide). Recently, there have been increasing reports indicating that inhaled NPs can reach the brain and may be associated with neurodegeneration. It is necessary to evaluate the potential toxic effects of NPs on brain because most of the neurobehavioral disorders may be of environmental origin. This review highlights studies on both combustion-derived NP- and manufactured or engineered NP-induced neuroinflammation, oxidative stress, and gene expression, as well as the possible mechanism of these effects in animal models and in humans. PMID:22016657

  6. Nanoparticles and neurotoxicity.

    PubMed

    Win-Shwe, Tin-Tin; Fujimaki, Hidekazu

    2011-01-01

    Humans are exposed to nanoparticles (NPs; diameter < 100 nm) from ambient air and certain workplaces. There are two main types of NPs; combustion-derived NPs (e.g., particulate matters, diesel exhaust particles, welding fumes) and manufactured or engineered NPs (e.g., titanium dioxide, carbon black, carbon nanotubes, silver, zinc oxide, copper oxide). Recently, there have been increasing reports indicating that inhaled NPs can reach the brain and may be associated with neurodegeneration. It is necessary to evaluate the potential toxic effects of NPs on brain because most of the neurobehavioral disorders may be of environmental origin. This review highlights studies on both combustion-derived NP- and manufactured or engineered NP-induced neuroinflammation, oxidative stress, and gene expression, as well as the possible mechanism of these effects in animal models and in humans. PMID:22016657

  7. Structural Properties and Microstructure of Cobalt Ferrite Particles Synthesized by a Sol-Gel Auto Combustion Method

    NASA Astrophysics Data System (ADS)

    Raval, Anand; Panchal, Nital; Jotania, Rajshree

    Synthesis and characterization of Cobalt ferrite powders by a sol gel combustion process is focused in the present work. The prepared precursors was calcined at 950° C for 4 hours in order to get cobalt ferrite powder. The effect of metal nitrates/citric acid ratio (referred as x) of CoFe2O4 on structural and micro-structural properties was investigated. The structural characterization on CoFe2O4 ferrite samples were carried out using the X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. Phase identification and crystallite size of calcined powder were determined using XRD analysis. The formation of the ferrite is confirmed by FTIR results. The morphology of prepared CoFe2O4 ferrite samples (with x = 0.5, 1.0, 1.5 and 2.0, where x is metal to citrate ratio) was studied using a scanning electron microscopy.

  8. In vitro and in vivo characterization of several functionalized ultrasmall particles of iron oxide, vectorized against amyloid plaques and potentially able to cross the blood-brain barrier: toward earlier diagnosis of Alzheimer's disease by molecular imaging.

    PubMed

    Ansciaux, Emilie; Burtea, Carmen; Laurent, Sophie; Crombez, Deborah; Nonclercq, Denis; Vander Elst, Luce; Muller, Robert N

    2015-05-01

    Alzheimer's disease (AD) is a neurodegenerative disorder most often diagnosed 10?years after its onset and development. It is characterized by the accumulation of amyloid-? peptide (ABP) into amyloid plaques between nerve cells, which produces a massive local neurodegeneration. Molecular magnetic resonance imaging allows diagnosis of AD by showing ABP accumulation in the brain. The ultrasmall particles of iron oxide (USPIO) derivatives proposed in the present work were functionalized with peptides that present an affinity for ABP, independently of its state of aggregation. Their nanomolar Kd * confirms the high affinity of our vectorized contrast agents (VCA) for ABP and therefore their high labeling potential, specificity and sensitivity. Their lack of toxicity has been demonstrated, both by in vitro studies using the MTT method on several cell types, and by in vivo investigations with assessment of renal and hepatic biomarkers and by histopathology evaluation. The results of biodistribution studies corroborated by MRI demonstrate that USPIO-PHO (USPIO coupled to peptide C-IPLPFYN-C) are able to cross the blood-brain barrier without any facilitating strategy, and accumulates in the brain 90?min after its injection in NMRI mice. None of the USPIO derivatives were found in any organs one week after administration. To conclude, USPIO-PHO seems to have a genuine potential for labeling amyloid plaques in the brain; it has a nanomolar binding affinity, no toxic effects, and its elimination half-life is about 3?h. Further tests will be made on transgenic mice, aimed at confirming the potential of early AD diagnosis using our VCA. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25284012

  9. Aerodynamic Focusing of Nanoparticles: I. Guidelines for Designing Aerodynamic Lenses for Nanoparticles

    Microsoft Academic Search

    Xiaoliang Wang; Frank Einar Kruis; Peter H. McMurry

    2005-01-01

    This article describes the challenges in focusing nanoparticles (< 30 nm) into tightly collimated beams, and provide guidelines for designing aerodynamic lens systems for nanoparticles. The major difficulties of focusing nanoparticles arise from their low inertia and high diffusivity. Because of their low inertia, nanoparticles tend to closely follow gas streamlines; their high diffusivities lead to beam broadening and diffusional

  10. A molecular dynamics simulation study of nanoparticle interactions in a model polymer-nanoparticle composite

    E-print Network

    Utah, University of

    A molecular dynamics simulation study of nanoparticle interactions in a model polymer-nanoparticle 15 December 2002 Abstract Molecular dynamics (MD) simulations were performed on a model polymer­nanoparticle composite (PNPC) consisting of spherical nanoparticles in a bead-spring polymer melt. The polymer

  11. Molecular Imaging with Theranostic Nanoparticles

    PubMed Central

    Jokerst, Jesse V.; Gambhir, Sanjiv S.

    2011-01-01

    Conspectus Nanoparticles offer diagnostic and therapeutic capabilities impossible with small molecules or micro-scale tools. As molecular biology merges with medical imaging to form the field of molecular imaging, nanoparticle imaging is increasingly common with both therapeutic and diagnostic applications. The term theranostic indicates technology with concurrent and complementary diagnostic and therapeutic capabilities. When performed with sub-micron materials, the field may be termed theranostic nanomedicine. Although nanoparticles have been FDA-approved for clinical use as transport vehicles for nearly 15 years, full translation of their theranostic potential is incomplete. Still, remarkable successes with nanoparticles have been realized in the areas of drug delivery and magnetic resonance imaging. Emerging applications include image-guided resection, optical/photoacoustic imaging in vivo, contrast-enhanced ultrasound, and thermoablative therapy. Diagnosis with nanoparticles in molecular imaging involves correlating signal to a phenotype. The disease’s size, stage, and biochemical signature can be gleaned from the location and intensity of nanoparticle signal emanating from a living subject. Therapy with NP uses the image for resection or delivery of small molecule or RNA thererapeutic. Ablation of the affected area is also possible via heat or radioactivity. The ideal theranostic NP: (1) selectively and rapidly accumulates in diseased tissue, (2) reports biochemical and morphological characteristics of the area, (3) delivers a non-invasive therapeutic, and (4) is safe and biodegrades with non-toxic byproducts. Above is a schematic of such a system which contains a central imaging core (yellow) surrounded by small molecule therapeutics (red). The system targets via ligands such as IgG (pink) and is protected from immune scavengers by a cloak of protective polymer (green). While no nanoparticle has achieved all of the above features, many NPs do fulfill one or more. While the most clinically translatable nanoparticles have been used in the field of magnetic resonance imaging, other types are quickly becoming more biocompatible by overcoming toxicity and biodistribution concerns. The document details diagnostic imaging and therapeutic uses of nanoparticles. We propose five main types of nanoparticles with concurrent diagnostic and thereapeutic uses and offer examples of each. PMID:21919457

  12. Ultrasound mediated nanoparticle drug delivery

    NASA Astrophysics Data System (ADS)

    Mullin, Lee B.

    Ultrasound is not only a powerful diagnostic tool, but also a promising therapeutic technology that can be used to improve localized drug delivery. Microbubble contrast agents are micron sized encapsulated gas filled bubbles that are administered intravenously. Originally developed to enhance ultrasound images, microbubbles are highly echogenic due to the gas core that provides a detectable impedance difference from the surrounding medium. The core also allows for controlled response of the microbubbles to ultrasound pulses. Microbubbles can be pushed using acoustic radiation force and ruptured using high pressures. Destruction of microbubbles can increase permeability at the cellular and vascular level, which can be advantageous for drug delivery. Advances in drug delivery methods have been seen with the introduction of nanoparticles, nanometer sized objects often carrying a drug payload. In chemotherapy, nanoparticles can deliver drugs to tumors while limiting systemic exposure due to abnormalities in tumor vasculature such large gaps between endothelial cells that allow nanoparticles to enter into the interstitial space; this is referred to as the enhanced permeability and retention (EPR) effect. However, this effect may be overestimated in many tumors. Additionally, only a small percentage of the injected dose accumulates in the tumor, which most the nanoparticles accumulating in the liver and spleen. It is hypothesized that combining the acoustic activity of an ultrasound contrast agent with the high payload and extravasation ability of a nanoparticle, localized delivery to the tumor with reduced systemic toxicity can be achieved. This method can be accomplished by either loading nanoparticles onto the shell of the microbubble or through a coadministration method of both nanoparticles and microbubbles. The work presented in this dissertation utilizes novel and commercial nanoparticle formulations, combined with microbubbles and a variety of ultrasound systems. Ultrasound parameters are optimized to achieve maximum cell internalization of molecules and increased nanoparticle delivery to a cell layer on a coverslip. In-vivo studies demonstrate the possibility of using a lower dose of paclitaxel to slow tumor growth rates, increase doxorubicin concentration in tumor tissue, and enhance tumor delivery of fluorescent molecules through treatments that combine nanoparticles with ultrasound and microbubbles.

  13. Sweet plasmonics: Sucrose macrocrystals of metal nanoparticles

    E-print Network

    Demir, Hilmi Volkan

    Sweet plasmonics: Sucrose macrocrystals of metal nanoparticles Talha Erdem1 , Zeliha Soran-Erdem1-Verlag Berlin Heidelberg 2014 KEYWORDS plasmonics, macrocrystals, metal nanoparticles, metal enhanced fluorescence, colloidal quantum dots ABSTRACT The realization of plasmonic structures generally necessitates

  14. Targeted Nanoparticle Tested in Patients with Cancer

    Cancer.gov

    By packaging molecules of the chemotherapy drug docetaxel in nanoparticles, researchers aim to deliver a high dose directly to tumors and reduce the drug's toxicity. A trial to test the targeted nanoparticle is underway in humans.

  15. Surface Functionalization of Monodisperse Magnetic Nanoparticles

    E-print Network

    Lattuada, Marco

    We present a systematic methodology to functionalize magnetic nanoparticles through surface-initiated atom-transfer radical polymerization (ATRP). The magnetite nanoparticles are prepared according to the method proposed ...

  16. Surface modification of metallic Co nanoparticles

    Microsoft Academic Search

    Nina Matoussevitch; Angelika Gorschinski; Wilhelm Habicht; Jens Bolle; Eckhard Dinjus; Helmut Bönnemann; Silke Behrens

    2007-01-01

    Monodisperse Co nanoparticles were synthesized by thermal decomposition in the presence of aluminium alkyls yielding air-stable Co nanoparticles after surface passivation. Several procedures for surface modification of these pre-stabilized, metallic Co nanoparticles are presented, including direct anchoring of surface-active functional groups and biocompatible dextran layers as well as silica and polymer coatings. As a result, individually coated nanoparticles as well

  17. Alloy nanoparticle synthesis using ionizing radiation

    DOEpatents

    Nenoff, Tina M. (Sandia Park, NM); Powers, Dana A. (Albuquerque, NM); Zhang, Zhenyuan (Durham, NC)

    2011-08-16

    A method of forming stable nanoparticles comprising substantially uniform alloys of metals. A high dose of ionizing radiation is used to generate high concentrations of solvated electrons and optionally radical reducing species that rapidly reduce a mixture of metal ion source species to form alloy nanoparticles. The method can make uniform alloy nanoparticles from normally immiscible metals by overcoming the thermodynamic limitations that would preferentially produce core-shell nanoparticles.

  18. Nanoparticle bridge DNA biosensor

    NASA Astrophysics Data System (ADS)

    Huang, Hong-Wen

    A new DNA sensing method is demonstrated in which DNA hybridization events lead to the formation of nanoparticle satellites that bridge two electrodes and are detected electrically. The hybridization events are exclusively carried out only on specific locations, the surfaces of C-ssDNA modified 50 nm GNPs. The uniqueness of this work is that only a small number of T-ccDNA molecules (<10) is required to form the nanoparticle satellites, allowing ultra-sensitive DNA sensing. The principle of this new DNA sensing technique has been demonstrated using target DNA and three-base-pair-mismatched DNA in 20nM concentrations. Three single-stranded DNA (ssDNA) system is used in our experiment which includes Capture-ssDNA (C-ssDNA), Target-ssDNA (T-ssDNA) and Probe-ssDNA (P-ssDNA). Both C-ssDNA and P-ssDNA are modified by a thiol group and can hybridize with different portions of T-ssDNA. T-ssDNA requires no modification in three ssDNA system, which is beneficial in many applications. C-ssDNA modified 50nm gold nanoparticle (C-50au) and P-ssDNA modified 30nm gold nanoparticle (P-30au) are prepared through the reaction of thiol-gold chemical bonding between thiolated ssDNA and gold nanoparticle (GNP) (C-ssDNA with 50nm GNP, P-ssDNA with 30nm GNP). We controllably place the C-50au only on the SiO2 band surface (˜ 90nm width) between two gold electrodes (source and drain electrodes) by forming positively- and negatively-charged self-assembled monolayers (SAMs) on SiO2 and gold surface, respectively. DNA modified GNP is negatively charged due to ionization of phosphate group on DNA back bone. C-50au therefore is negatively charged and can only be attracted toward SiO2 area (repelled by negatively charged gold electrode surface). The amine group of positively-charged SAMs on SiO2 surface is then passivated by converting to non-polar methyl functional group after C-50au placement. P-30au is first hybridized with T-ssDNA in the solution phase (T-P- 30au formed) and is introduced into DNA detection device in which C-50au are immobilized on ˜90nm width SiO2 band (between two gold electrodes). The passivation step ensures every TP-30au are attached only to C-50au through hybridization (T-P-30au will not be attracted toward SiO2 surface or gold electrodes). GNP bridges are formed across the electrodes and provide an electrical path between two gold electrodes. We ensure that every T-P-30au only hybridizes on the surface of C-50au by (1) accurately controlling C-50au placement between two gold electrodes, (2) passivating positively-charged SAMs on SiO2 surface after C-50au immobilization. When T-P-30au hybridize with C-50au on ˜90nm wide SiO 2 surface, GNP bridges form and provide an electrical path between two gold electrodes even with only a few hybridization events. Experimental results show that even a few GNP bridges formed on SiO2 band can provide a significant conductance change from an open circuit to a conductive circuit (current = 0.5 uA at voltage = 0.1 V with four GNP bridge). We also used 3-base-pair-mismatched ssDNA (3mm-ssDNA) as a control experiment, which always resulted in an open circuit (no GNP bridge formed). Our detection device is compatible with current CMOS fabrication technology and can be manufactured on a wafer scale. The direct electrical output of this DNA detection technique provides a promising basis for high-throughput screening (can be fabricated on a wafer scale) with no expensive equipment required.

  19. Modelling Nanoparticle Diffusion into Cancer Tumors

    Microsoft Academic Search

    Vishwa Priya Podduturi; Pedro Derosa

    2011-01-01

    Cancer is one of the major, potentially deadly diseases and has been for years. Non-specific delivery of the drug can damage healthy tissue seriously affecting in many cases the patient's living condition. Nanoparticles are being used for a targeted drug delivery thereby reducing the dose. In addition, metallic nanoparticles are being used in thermal treatment of cancer cells where nanoparticles

  20. The Stability of Cerium Oxide Nanoparticles

    Microsoft Academic Search

    K. Buettner; S. E. Mylon

    2007-01-01

    Interest has been shown in cerium oxide nanoparticles due to their potential use catalysts, gas sensors, and more. Unchecked use of these nano-materials could have profound environmental impacts, however, little is known about the fate and transport of these nanoparticles in aquatic systems. In this work, small (d ~ 15 nm) mostly spherical cerium oxide nanoparticles were synthesized in house

  1. Optical properties of zinc phthalocyanine nanoparticle dispersions

    NASA Astrophysics Data System (ADS)

    Nitschke, Christian; O'Flaherty, Seán M.; Kröll, Michael; Doyle, James J.; Blau, Werner J.

    2004-01-01

    We report a study of the fabrication of aqueous nanoparticle dispersions from metallo-phthalocyanine solutions. Furthermore, we examine these nanoparticles using transmission electron and atomic force microscopy (TEM and AFM, respectively). Linear absorption and fluorescence spectroscopy are employed to characterise the novel nanoparticles. Finally, we demonstrate a significant improvement in their nonlinear optical dissipative response compared to dissolved solutions of the same phthalocyanines.

  2. Nanoparticles for Imaging: Top or Flop?

    PubMed Central

    Kiessling, Fabian; Mertens, Marianne E.; Grimm, Jan; Lammers, Twan

    2014-01-01

    Nanoparticles are frequently suggested as diagnostic agents. However, except for iron oxide nanoparticles, diagnostic nanoparticles have been barely incorporated into clinical use so far. This is predominantly due to difficulties in achieving acceptable pharmacokinetic properties and reproducible particle uniformity as well as to concerns about toxicity, biodegradation, and elimination. Reasonable indications for the clinical utilization of nanoparticles should consider their biologic behavior. For example, many nanoparticles are taken up by macrophages and accumulate in macrophage-rich tissues. Thus, they can be used to provide contrast in liver, spleen, lymph nodes, and inflammatory lesions (eg, atherosclerotic plaques). Furthermore, cells can be efficiently labeled with nanoparticles, enabling the localization of implanted (stem) cells and tissue-engineered grafts as well as in vivo migration studies of cells. The potential of using nanoparticles for molecular imaging is compromised because their pharmacokinetic properties are difficult to control. Ideal targets for nanoparticles are localized on the endothelial luminal surface, whereas targeted nanoparticle delivery to extravascular structures is often limited and difficult to separate from an underlying enhanced permeability and retention (EPR) effect. The majority of clinically used nanoparticle-based drug delivery systems are based on the EPR effect, and, for their more personalized use, imaging markers can be incorporated to monitor biodistribution, target site accumulation, drug release, and treatment efficacy. In conclusion, although nanoparticles are not always the right choice for molecular imaging (because smaller or larger molecules might provide more specific information), there are other diagnostic and theranostic applications for which nanoparticles hold substantial clinical potential. PMID:25247562

  3. Phase Transfer Properties of Silver Nanoparticles

    Microsoft Academic Search

    Michiel Dokter

    2005-01-01

    Silver nanoparticles are synthesized by reduction of silver nitrate in a toluene solution of tetra-n-octyl ammonium bromide (TAB) and dodecanethiol (DDT). The nanoparticles consist of a silver core with DDT chemically bound at the particle surface. TAB remains associated with the particles and provides them extra stability. These passivated silver nanoparticles are dissolved in dry chloroform and various phase transfer

  4. Polymer Diffusion in the Presence of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Winey, Karen

    2014-03-01

    The center-of-mass diffusion of polymers within a polymer melt proceeds by the mechanism of reptation wherein the polymer is confined to a tube that is defined by neighboring entanglements and moves along its contour. Polymer diffusion is perturbed when the melt contains nanoparticles that are comparable in size to the radius of gyration (Rg) of the polymers. Within this talk, we will present tracer diffusion coefficients (D) results for three types of nanocomposite: spherical nanoparticles with surface functionalization, spherical nanoparticles with brushes, and cylindrical nanoparticles (aspect ratio = 5 to 50). When functionalized spherical nanoparticles have neutral or attractive interactions with the polymer matrix, a monotonic decrease in the diffusion coefficient is observed across a wide range of polymer molecular weight, nanoparticle size, and nanoparticle concentration. These data collapse onto a master curve when plotted as D normalized by the diffusion coefficient into a neat homopolymer (D/Do) versus our confinement parameter defined as the interparticle distance divided by 2Rg (ID/2Rg). Polymer diffusion in systems with grafted spherical nanoparticles exhibit the same D/Do versus ID/2Rg, when ID accounts for the extent to which the tracer polymer penetrates the polymer brush. For various cylindrical nanoparticles D/Do versus nanoparticle concentration exhibits a minimum when 2Rg is both larger than the nanoparticle diameter and smaller than the nanoparticle length. Complimentary molecular dynamics simulations and neutron scattering results will also be presented.

  5. Nanoparticles as image enhancing agents for ultrasonography

    Microsoft Academic Search

    Jun Liu; Andrea L. Levine; John S. Mattoon; Mamoru Yamaguchi; Robert J. Lee; Xueliang Pan; Thomas J. Rosol

    2006-01-01

    Nanoparticles have drawn great attention as targeted imaging and\\/or therapeutic agents. The small size of the nanoparticles allows them to target cells that are beyond capillary vasculature, such as cancer cells. We investigated the effect of solid nanoparticles for enhancing ultrasonic grey scale images in tissue phantoms and mouse livers in vivo. Silica nanospheres (100 nm) were dispersed in agarose

  6. Platinum attachments on iron oxide nanoparticle surfaces

    Microsoft Academic Search

    Soubantika Palchoudhury; Yaolin Xu; Wei An; C. Heath Turner; Yuping Bao

    2010-01-01

    Platinum nanoparticles supported on metal oxide surfaces have shown great potential as heterogeneous catalysts to accelerate electrochemical processes, such as the oxygen reduction reaction in fuel cells. Recently, the use of magnetic supports has become a promising research topic for easy separation and recovery of catalysts using magnets, such as Pt nanoparticles supported on iron oxide nanoparticles. The attachment of

  7. Friction mechanism of individual multilayered nanoparticles

    PubMed Central

    Tevet, Ofer; Von-Huth, Palle; Popovitz-Biro, Ronit; Rosentsveig, Rita; Wagner, H. Daniel; Tenne, Reshef

    2011-01-01

    Inorganic nanoparticles of layered [two-dimensional (2D)] compounds with hollow polyhedral structure, known as fullerene-like nanoparticles (IF), were found to have excellent lubricating properties. This behavior can be explained by superposition of three main mechanisms: rolling, sliding, and exfoliation-material transfer (third body). In order to elucidate the tribological mechanism of individual nanoparticles in different regimes, in situ axial nanocompression and shearing forces were applied to individual nanoparticles using a high resolution scanning electron microscope. Gold nanoparticles deposited onto the IF nanoparticles surface served as markers, delineating the motion of individual IF nanoparticle. It can be concluded from these experiments that rolling is an important lubrication mechanism for IF-WS2 in the relatively low range of normal stress (0.96±0.38 GPa). Sliding is shown to be relevant under slightly higher normal stress, where the spacing between the two mating surfaces does not permit free rolling of the nanoparticles. Exfoliation of the IF nanoparticles becomes the dominant mechanism at the high end of normal stress; above 1.2 GPa and (slow) shear; i.e., boundary lubrication conditions. It is argued that the modus operandi of the nanoparticles depends on their degree of crystallinity (defects); sizes; shape, and their mechanical characteristics. This study suggests that the rolling mechanism, which leads to low friction and wear, could be attained by improving the sphericity of the IF nanoparticle, the dispersion (deagglomeration) of the nanoparticles, and the smoothness of the mating surfaces. PMID:22084073

  8. Perfluorocarbon Nanoparticles for Molecular Imaging and

    E-print Network

    McCarthy, John E.

    INVITED P A P E R Perfluorocarbon Nanoparticles for Molecular Imaging and Targeted Therapeutics and drug delivery (see [1] and references cited therein). Perfluorocarbon (PFC) nanoparticles are a unique nanoparticles (250 nm nominal diameter) have inherent physicochemical properties that provide acoustic contrast

  9. Environmental Monitoring Plan for Unbound Engineered Nanoparticles

    E-print Network

    Eisen, Michael

    Environmental Monitoring Plan for Unbound Engineered Nanoparticles Prepared by Gary Casuccio ..................................................................................................................................... 15 APPENDIX A Worker and Environmental Assessment of Potential Unbound Engineered Nanoparticle Nanoparticles #12;vi This page is intentionally blank. #12;1 1.0 INTRODUCTION The Department of Energy (DOE

  10. Sorption of Organic Pollutants by Carbon Nanoparticles

    E-print Network

    Fischlin, Andreas

    Sorption of Organic Pollutants by Carbon Nanoparticles Term Paper by Daniele Vergari Bodenmatte 14c . . . . . . . . . . . . . . . . . . . . . . 3 2.2 Approaches to Determine Sorption Phenomenons on Nanoparticles . . . . . . . 4 3 Methods 5 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 Abstract Nanoparticles are widely distributed in different applications and also released

  11. Imaging the electrocatalytic activity of single nanoparticles

    E-print Network

    Reisslein, Martin

    Imaging the electrocatalytic activity of single nanoparticles Xiaonan Shan1,2 , Ismael Di, Qihuang Gong4, Jinghong Li5 * and Nongjian Tao1,2 * 1 The electrocatalytic properties of nanoparticles the total electrocatalytic 4 reaction current of a large number of nanoparticles, but this 5 approach

  12. Magnetic properties of biosynthesized magnetite nanoparticles

    Microsoft Academic Search

    Lucas W. Yeary; Ji-Won Moon; L. J. Love; J. R. Thompson; C. J. Rawn; T. J. Phelps

    2005-01-01

    Magnetic nanoparticles, which are unique because of both structural and functional elements, have various novel applications. The popularity and practicality of nanoparticle materials create a need for a synthesis method that produces quality particles in sizable quantities. This paper describes such a method, one that uses bacterial synthesis to create nanoparticles of magnetite. The thermophilic bacterial strain Thermoanaerobacter ethanolicus TOR-39

  13. Subchronic oral toxicity of silver nanoparticles

    Microsoft Academic Search

    Yong Soon Kim; Moon Yong Song; Jung Duck Park; Kyung Seuk Song; Hyeon Ryol Ryu; Yong Hyun Chung; Hee Kyung Chang; Ji Hyun Lee; Kyung Hui Oh; Bruce J Kelman; In Koo Hwang; Il Je Yu

    2010-01-01

    BACKGROUND: The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronic, consumer, medicinal, pesticide, and home products; however, silver nanoparticles remain a controversial area of research with respect to their toxicity in biological and ecological systems. RESULTS: This study tested the oral toxicity of silver nanoparticles (56 nm) over a period of 13 weeks (90

  14. Brain uptake of thiamine-coated nanoparticles.

    PubMed

    Lockman, Paul R; Oyewumi, Moses O; Koziara, Joanna M; Roder, Karen E; Mumper, Russell J; Allen, David D

    2003-12-12

    Recently, a novel nanoparticle (NP) comprised of emulsifying wax and Brij 78 was shown to have significant brain uptake using the in-situ rat brain perfusion technique. To further these studies and to specifically target brain, we have incorporated thiamine as a surface ligand on the nanoparticles. Solid nanoparticles were prepared from oil-in-water microemulsion precursors. Nanoparticles were radiolabeled and a thiamine ligand (thiamine linked to distearoylphosphatidylethanolamine via a polyethylene glycol spacer) was coated on the surface of the nanoparticles. Initial experiments focused on assessing uptake of [3H]nanoparticles with and without thiamine surface ligands. Biodistribution nanoparticle studies were also carried out in BALB/c mice. The results showed: (1) the effectiveness of using microemulsions as precursors to engineer nanoparticles, (2) kinetic modeling for brain uptake of nanoparticles with and without the thiamine surface ligands, and (3) initial data suggesting mechanisms for nanoparticle brain entry. Comparison of NP brain uptake demonstrated that the thiamine-coated nanoparticle associated with the blood-brain barrier (BBB) thiamine transporter and had an increased K(in) between 45 and 120 s (thiamine coated NP 9.8 +/- 1.1 x 10(-3) ml/s/g versus uncoated NPs; 7.0 +/- 0.3 x 10(-3) ml/s/g). It was concluded that the thiamine ligand facilitated binding and/or association with blood-brain barrier thiamine transporters, which may be a viable mechanism for nanoparticle mediated brain drug delivery. PMID:14644577

  15. Optical Trapping of Nanoparticles

    PubMed Central

    Bergeron, Jarrah; Zehtabi-Oskuie, Ana; Ghaffari, Saeedeh; Pang, Yuanjie; Gordon, Reuven

    2013-01-01

    Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3. A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure. The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres. PMID:23354173

  16. Nanoparticle Superlattice Engineering with DNA

    NASA Astrophysics Data System (ADS)

    Macfarlane, Robert John

    In this thesis, we describe a set of design rules for using programmable oligonucleotide interactions, elements of both thermodynamic and kinetic control, and an understanding of the dominant forces that are responsible for particle assembly to design and deliberately make a wide variety of nanoparticle-based superlattices. Like the rules for ionic solids developed by Linus Pauling, these rules are guidelines for determining relative nanoparticle superlattice stability, rather than rigorous mathematical descriptions. However, unlike Pauling's rules, the set of rules developed herein allow one to not just predict crystal stability, but also to deliberately and independently control the nanoparticle sizes, interparticle spacings, and crystallographic symmetries of a superlattice. In the first chapter of this thesis, a general background is given for using DNA as a tool in programmable materials synthesis. Chapter 2 demonstrates how altering oligonucleotide length and nanoparticle size can be used to control nanoparticle superlattice lattice parameters with nanometer-scale precision. In the third chapter, the kinetics of crystallization are examined, and a method to selectively stabilize kinetic products is presented. The data in chapter 4 prove that it is the overall hydrodynamic radius of a DNA-functionalized particle, rather than the sizes of the inorganic nanoparticles being assembled, that dictates particle packing behavior. Chapter 5 demonstrates how particles that exhibit non-equivalent packing behavior can be used to control superlattice symmetry, and chapter 6 utilizes these data to develop a phase diagram that predicts lattice stability a priori to synthesis. In chapter 7, the ability to functionalize a particle with multiple types of oligonucleotides is used to synthesize complex lattices, including ternary superlattices that are capable of dynamic symmetry conversion between a binary and a ternary state. The final chapter provides an outlook on other developments in DNA-programmed nanoparticle assembly not covered in this thesis, as well as future challenges for this field. Supplementary information to support the conclusions of the thesis, as well as provide technical details on how these materials are synthesized, are provided in appendices at the end of the thesis. As a whole, this methodology presents a major advance towards nanoparticle superlattice engineering, as it effectively separates the identity of a particle core (and thereby its physical properties) from the variables that control its assembly, enabling the synthesis of designer nanoparticle-based materials.

  17. Upconverting nanoparticles: assessing the toxicity.

    PubMed

    Gnach, Anna; Lipinski, Tomasz; Bednarkiewicz, Artur; Rybka, Jacek; Capobianco, John A

    2015-03-21

    Lanthanide doped nanoparticles (Ln:NPs) hold promise as novel luminescent probes for numerous applications in nanobiophotonics. Despite excellent photostability, narrowband photoluminescence, efficient anti-Stokes emission and long luminescence lifetimes, which are needed to meet the requirements of multiplexed and background free detection at prolonged observation times, concern about their toxicity is still an issue for both in vivo and in vitro applications. Similar to other chemicals or pharmaceuticals, the very same properties that are desirable and potentially useful from a biomedical perspective can also give rise to unexpected and hazardous toxicities. In engineered bionanomaterials, the potentially harmful effects may originate not only from their chemical composition but also from their small size. The latter property enables the nanoparticles to bypass the biological barriers, thus allowing deep tissue penetration and the accumulation of the nanoparticles in a number of organs. In addition, nanoparticles are known to possess high surface chemical reactivity as well as a large surface-to-volume ratio, which may seriously affect their biocompatibility. Herein we survey the underlying mechanisms of nanotoxicity and provide an overview on the nanotoxicity of lanthanides and of upconverting nanoparticles. PMID:25176037

  18. Silicon nanoparticles and interstellar extinction

    E-print Network

    Victor G. Zubko; Tracy L. Smith; Adolf N. Witt

    1998-11-22

    To examine a recently proposed hypothesis that silicon nanoparticles are the source of extended red emission (ERE) in the interstellar medium, we performed a detailed modeling of the mean Galactic extinction in the presence of silicon nanoparticles. For this goal we used the appropriate optical constants of nanosized Si, essentially different from those of bulk Si due to quantum confinement. It was found that a dust mixture of silicon nanoparticles, bare graphite grains, silicate core-organic refractory mantle grains and three-layer silicate-water ice-organic refractory grains works well in explaining the extinction and, in addition, results in the acceptable fractions of UV/visible photons absorbed by silicon nanoparticles: 0.071-0.081. Since these fractions barely agree with the fraction of UV/visible photons needed to excite the observed ERE, we conclude that the intrinsic photon conversion efficiency of the photoluminescence by silicon nanoparticles must be near 100%, if they are the source of the ERE.

  19. Reduction kinetics and microstructures of Al 3+ -containing cobalt ferrites

    Microsoft Academic Search

    Michael C. Ray; LUTGARD C. DE JONGHE

    1980-01-01

    Dense, polycrystalline CoFe2O4, CoAl0.02Fe1.98O4, and CoAl0.1Fe1.9O4 were reduced in flowing H2\\/0.01% H2O at temperatures between 500 and 800° C. The reactions proceeded in a topochemical fashion. The rate of advance of the reaction interface was determined by direct measurement and by thermogravimetric analysis. An anomalous decrease in the reduction kinetics was observed for CoFe2O4 around 650° C and for CoAl0.02Fe1.98O4

  20. [Influence of nanosize particles of cobalt ferrite on contractile responses of smooth muscle segment of airways].

    PubMed

    Kapilevich, L V; Za?tseva, T N; Nosarev, A V; D'iakova, E Iu; Petlina, Z R; Ogorodova, L M; Ageev, B G; Magaeva, A A; Itin, V I; Terekhova, O G; Medvedev, M A

    2012-02-01

    Contractile responses of airways segments of porpoises inhaling nanopowder CoFe2O4 were stidued by means of a mechanographic method. Inhalation of the nanosize particles of CoFe2O4 in vivo and in vitro testing the nanomaterial on isolated smooth muscles led to potentiation histaminergic, cholinergic contractile activity in airways of porpoises and to strengthening of adrenergic relaxing answers. Nanosize particles vary amplitude of hyperpotassium reductions in smooth muscle segments of airways similarly to the effect of depolymerizing drug colchicine. PMID:22650066