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1

Alcohol dependent production of Fe3O4 and CoFe2O4 nanoparticles.  

PubMed

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

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

2013-06-01

2

Colossal reduction in Curie temperature due to finite-size effects in CoFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

In this talk I will show the tremendous size effect on the ordering transition temperature, TO, in samples of CoFe2O4 nanoparticles with diameters ranging from 1 to 9 nm. Samples were characterized by HRTEM and XRD analyses and show a bimodal particle size distribution centered at 3 nm and around 6 nm for ``small'' and ``large'' particles, respectively. The results and their interpretation are derived from studies of the magnetization dependence of the samples on temperature at low and high magnetic fields and relaxation times using both DC and AC fields. The large particles show a typical superparamagnetic behavior with blocking temperatures, TB, arround 100K and a Curie temperature, TC, above room temperature. The small particles, however, show a colossal reduction of their magnetic ordering temperature and display paramagnetic behavior down to about 10K. At lower temperatures these small particles are blocked and show both exchange and anisotropy field values above 5T. The order of magnitude reduction in TO demonstrates a heretofore unreported magnetic behavior for ultrasmall nanoparticles of CoFe2O4, suggesting its further study as an advanced material.

Tejada, Javier; Lopez-Dominguez, Victor; Hernandez, Joan Manel; Ziolo, Ronald F.

2013-03-01

3

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

PubMed

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

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

2011-01-01

4

Cationic distribution and spin canting in CoFe2O4 nanoparticles.  

PubMed

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

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

2011-10-26

5

Uniaxial anisotropy and novel magnetic behaviors of CoFe2O4 nanoparticles prepared in a magnetic field  

NASA Astrophysics Data System (ADS)

CoFe2O4 nanoparticles prepared by chemical coprecipitation method in a magnetic field exhibit novel magnetic properties. The average particle diameter was about 2 nm and larger depending on the post annealing temperature. Magnetization measurements indicate that smaller nanoparticles are superparamagnetic above their respective blocking temperatures. In the blocked state, these nanoparticles exhibit interesting behaviors in the magnetic hysteresis measurements. Constricted, or wasp waisted with extremely narrow waist, hysteresis curves have been observed in the magnetization versus field sweeps. For larger nanoparticles, the room temperature hysteresis is typical of a ferromagnet with an open loop, but the loop closes at lower temperature. The novel magnetic behavior is attributed to the directional order of Co ions and vacancies in CoFe2O4 established during the coprecipitation of the nanoparticles under an applied field.

Gao, Qian; Hong, Guangyan; Ni, Jiazuan; Wang, Wendong; Tang, Jinke; He, Jibao

2009-04-01

6

Synthesis and characterization of CoFe2O4 magnetic nanoparticles prepared by temperature-controlled coprecipitation method  

Microsoft Academic Search

Magnetic nanoparticles of cobalt ferrite (CoFe2O4) have been synthesized in a homogeneous aqueous solution without any template and subsequent heat treatment. The average particle size could be varied in the range of 2-14nm by controlling coprecipitation temperature of Co2+ and Fe3+ ions in alkaline solution although the size distribution is pretty wide. As the precipitation temperature increased in the range

Yeong Il Kim; Don Kim; Choong Sub Lee

2003-01-01

7

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

NASA Astrophysics Data System (ADS)

Herein, we describe a facile and feasible synthesis method for patterning nanogold particles onto magnetic mesoporous CoFe2O4 nanostructures (Au-MMNs) by using poly(vinyl pyrrolidone) (PVP) as cross-linker. Initially, mesoporous CoFe2O4 nanoparticles were initially synthesized with a thermal decomposition method by using mesoporous silica nanoparticles as templates, and then nanometre-sized gold particles were produced through the in situ reduction of the AuIII on the PVP-functionalized CoFe2O4. The as-prepared Au-MMNs were characterized by transmission electron microscopy (TEM), N2 adsorption-desorption isotherms, UV-visible adsorption spectrometer, vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Furthermore, we also demonstrate the conjugation capacity of the synthesized Au-MMNs toward biomolecules by using quartz crystal microbalance (QCM), and the possible application in the electrochemical immunoassays. Experimental results indicated that the resulting Au-MMNs display good conjugation capability toward the biomolecules, and excellent analytical properties for determination of target molecules.

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

2011-05-01

8

Surface magnetic anisotropy of CoFe2O4 nanoparticles with a giant low-temperature hysteresis  

NASA Astrophysics Data System (ADS)

Ferrimagnetic nanoparticles of CoFe2O4 about 4-16 nm in diameter were synthesized by pyrolysis of a mixture of Fe and Co acetylacetonates. The field dependences of magnetization and hysteresis loops were investigated in magnetic fields up to 4000 kA/m at various temperatures from 4.2 to 500 K. A considerable contribution, positive or negative depending on the temperature, of ``surface'' anisotropy to the effective magnetic anisotropy of the nanoparticles was observed. A correlation was found between the magnetic properties that represent the specificity of small particles, namely, between ``surface'' anisotropy, magnetization, and high-field susceptibility.

Mozul', K. A.; Ol'khovik, L. P.; Sizova, Z. I.; Bludov, A. N.; Pashchenko, V. A.; Baumer, V. N.; Vashchenko, V. V.; Kolosov, M. O.; Kryshtal', A. P.; Prodanov, M. F.

2013-04-01

9

Unusually high coercivity and critical single-domain size of nearly monodispersed CoFe2O4 nanoparticles  

Microsoft Academic Search

Nearly monodispersed CoFe2O4 nanoparticles with average sizes between 8 and 100 nm were synthesized by using seed-mediated growth dominant coprecipitation and modified oxidation methods. X-ray diffraction and Mössbauer spectroscopy analyses confirmed the spinel phase and a stoichiometric composition of (Co0.25Fe0.75)[Co0.75Fe1.25]O4 for powders with different particle diameters. Rotational hysteresis loss (Wr) analysis showed an average switching field (Hp) of 17 kOe

C. N. Chinnasamy; B. Jeyadevan; K. Shinoda; K. Tohji; D. J. Djayaprawira; M. Takahashi; R. Justin Joseyphus; A. Narayanasamy

2003-01-01

10

A study of oleic acid-based hydrothermal preparation of CoFe 2 O 4 nanoparticles  

Microsoft Academic Search

Nearly monodisperse, well crystalline, superparamagnetic CoFe2O4 nanoparticles with diameter of 6 nm were synthesized in oleic acid–water–pentanol system at 180 °C. Hydrothermal procedure,\\u000a as an efficient and environment friendly alternative to organic decomposition methods, was investigated by variation of reaction\\u000a conditions, and the particle formation mechanism was finally proposed (i.e., hydrolysis of metal oleates in organic phase,\\u000a with size of the particles

Anton Repko; Daniel Niž?anský; Jana Poltierová-Vejpravová

11

Immobilization of glucose oxidase using CoFe 2O 4\\/SiO 2 nanoparticles as carrier  

Microsoft Academic Search

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 3h, solution pH of 7.0 and 0.4mg GOD (in 3.0mg carrier). The immobilized GOD showed maximal catalytic activity at pH

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

2011-01-01

12

Surface spin effects in La-doped CoFe2O4 nanoparticles prepared by microemulsion route  

NASA Astrophysics Data System (ADS)

A comparative study of pure CoFe2O4 nanoparticles and La-doped CoFe2O4 nanoparticles, prepared by microemulsion route has been performed. The samples were characterized using x-ray diffraction and transmission electron microscopy in order to obtain average particle size. The doping of small amount of La3+ ions (up to 3 molar %) causes significant reduction of the particle size using the identical preparation route. The samples were investigated by magnetization measurements, which revealed the coercivity values strongly dependent on particle size, but not significantly on level of La3+ doping. Detailed in-field Mössbauer spectroscopy studies were performed in order to determine spin canting angles and cation distribution within the spinel network. The non-negligible canting angles up to 40° in the La-doped samples were observed. The presence of the spin surface effects was also supported by magnetic measurement as the magnetization did not saturate even in considerably high magnetic fields (7 T). Moreover, significantly reduced values of the saturation magnetization were obtained. The observed features originated by the surface spin disorder in nanosized particles are explained in the frame of the core-shell model.

Burianova, Simona; Poltierova Vejpravova, Jana; Holec, Petr; Plocek, Jiri; Niznansky, Daniel

2011-10-01

13

The enhanced microwave absorption property of CoFe2O4 nanoparticles coated with a Co3Fe7-Co nanoshell by thermal reduction  

NASA Astrophysics Data System (ADS)

CoFe2O4 nanoparticles were fabricated by a sol-gel method and then were coated with Co3Fe7-Co by means of a simple reduction process at different temperatures under 2% H2 with the protection of argon to generate the dielectric-core/metallic-shell structure. The optimum reflection loss (RL) calculated from permittivity and permeability of the 80 wt% CoFe2O4/Co3Fe7-Co and 20 wt% epoxy resin composites reached - 34.4 dB, which was much lower than that of unreduced CoFe2O4 and epoxy resin composites, at 2.4 GHz with a matching thickness of 4.0 mm. Moreover the RL exceeding - 10 dB in the maximum frequency range of 2.2-16 GHz was achieved for a thickness of composites of 1.0-4.5 mm with 600 °C thermal reduction process. The improved microwave absorption properties are a consequence of a proper electromagnetic match and the enhanced magnetic loss besides its dielectric loss due to the existence of the core/shell structure in CoFe2O4 composites. Thus, the reductive CoFe2O4 nanoparticles have great potential for being a highly efficient microwave absorber.

Xi, Li; Wang, Zhen; Zuo, Yalu; Shi, Xiaoning

2011-01-01

14

Immobilization of glucose oxidase using CoFe 2O 4/SiO 2 nanoparticles as carrier  

NASA Astrophysics Data System (ADS)

Aminated-CoFe 2O 4/SiO 2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe 2O 4/SiO 2 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.

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

2011-04-01

15

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

Microsoft Academic Search

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.%)

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

2011-01-01

16

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

PubMed

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

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

2013-01-16

17

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

18

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

19

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

PubMed

Here, we report a highly simple and general protocol for functionalization of the CoFe(2)O(4) NPs with chitosan polymers in order to make CoFe(2)O(4) NPs disperse and stable in solution. The functionalized CoFe(2)O(4) NPs (denoted as CF-CoFe(2)O(4) NPs) were characterized by scanning electron microscope (SEM), thermogravimetric (TG), X-ray diffraction (XRD) and FT-IR spectra. It was found that the CoFe(2)O(4) NPs were successfully decorated and uniformly dispersed on the surface of chitosan without agglomeration. The CF-CoFe(2)O(4) NPs were found to increase greatly the radiation emitted during the CL oxidation of luminol by hydrogen peroxide. Results of ESR spin-trapping experiments demonstrated that the CF-CoFe(2)O(4) NPs showed catalytic ability to H(2)O(2) decomposition into ?OH radicals. On this basis, a highly sensitive and rapid chemiluminescent method was developed for hydrogen peroxide in water samples and glucose in blood samples. Under optimum conditions, the proposed method allowed the detection of H(2)O(2) in the range of 1.0 × 10(-9) to 4.0 × 10(-6) M and glucose in the range of 5.0 × 10(-8) to 1.0 × 10(-5) M with detectable H(2)O(2) as low as 500 pM and glucose as low as 10 nM, respectively. This proposed method has been successfully applied to detect H(2)O(2) in environmental water samples and glucose in serum samples with good accuracy and precision. PMID:22258160

Fan, Yingwei; Huang, Yuming

2012-01-19

20

Controlled synthesis of monodisperse CoFe2O4 nanoparticles by the phase transfer method and their catalytic activity on methylene blue discoloration with H2O2  

NASA Astrophysics Data System (ADS)

Monodisperse spinel CoFe2O4 nanoparticles have been synthesized through the solvothermal-assisted phase transfer method using aqueous soluble metal salts as starting materials and sodium oleate (SO) as the phase-transfer agent. The as-synthesized nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, infrared spectroscopy, vibrating sample magnetometry, ultraviolet and visible spectrophotometry and Mössbauer spectrum. The results revealed that the as-obtained nanoparticles have a cubic spinel structure and an average diameter of 2–6 nm. It was found that SO played an important role during the transfer of the hydrophilic inorganic precursor from aqueous phase to the organic phase. On the basis of the experimental results, a possible mechanism for the formation of the nanoparticles was proposed. Surface functionalization of the as-prepared nanoparticles was conducted to render the hydrophobic nanoparticles water-soluble, which makes the nanoparticles suitable for catalytic applications. The nanoparticles showed catalytic activity in the oxidation of methylene blue with H2O2 as an oxidizing agent.

Feng, X.; Mao, G. Y.; Bu, F. X.; Cheng, X. L.; Jiang, D. M.; Jiang, J. S.

2013-10-01

21

The effect of reaction temperature on the particle size, structure and magnetic properties of coprecipitated CoFe 2O 4 nanoparticles  

Microsoft Academic Search

Magnetic nanoparticles of cobalt ferrite have been synthesized at different temperatures without any subsequent heat treatment. The particle size, crystal structure and magnetic properties of as-synthesized particles were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and vibrating sample magnetometer. The nanoparticles are of cubic spinel structure and equiaxial shape. The average size of nanoparticles increases

Yuqiu Qu; Haibin Yang; Nan Yang; Yuzun Fan; Hongyang Zhu; Guangtian Zou

2006-01-01

22

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

NASA Astrophysics Data System (ADS)

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

Sangmanee, Montana; Maensiri, Santi

2009-10-01

23

Hollow glass microspheres coated with CoFe2O4 and its microwave absorption property  

NASA Astrophysics Data System (ADS)

Spinel CoFe2O4 coating on the surface of hollow glass microspheres of low density was synthesized by co-precipitation method. The phase structures, morphologies, particle size, shell thickness, chemical compositions of the composites have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy (EDS). The results show that CoFe2O4 coating on hollow glass microspheres can be achieved, and the coating layers are constituted by CoFe2O4 nanoparticles of mean size ca. 10 nm. The as-synthesized powder materials were uniformly dispersed into the phenolic cement, then the mixture was pasted on metal plate with the area of 200 mm×200 mm as the test plate. The test of microwave absorption was carried out by the radar-absorbing materials (RAM) reflectivity far field radar cross-section (RCS) method. The results indicate that the coated CoFe2O4/hollow glass microspheres composites can be applied in lightweight and strong absorption microwave absorbers.

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

2007-09-01

24

Preparation and Characterization of CoFe2O4\\/Poly Vinyl Acetate Nanocomposite  

Microsoft Academic Search

CoFe2O4 (CFO) nano-particles have been synthesized successfully by a redox chemical reaction in aqueous solution of cobalt chloride and ferric chloride. The synthesized CFO nanoparticles have been used for preparation of CFO\\/Poly vinyl acetate (CFO\\/PVAc) nanocomposite by in situ emulsion polymerization method. The nanocomposite exhibited superparamagnetic behavior at room temperature under an applied magnetic field. The synthesized CFO\\/PVAc nanocomposite has

Mohsen Mohsen-Nia; Fatemeh Seyed Mohammad Doulabi

2012-01-01

25

Magnetic Properties of CoFe2O4 Nanopillars  

Microsoft Academic Search

Ferrimagnetic CoFe2O4 spontaneously forms nanopillars embedded in a BaTiO3 or BiFeO3 matrix during thin film growth by pulsed laser deposition. Such thin film nanostructures show three dimensional heteroepitaxy. All the films have a large uniaxial magnetic anisotropy with an easy axis normal to the film plane. It is calculated that stress anisotropy is the main contribution to the anisotropy field.

Haimei Zheng; F. Zavaliche; D. Schlom

2005-01-01

26

Magnetic Properties of CoFe_2O4 and Fe_3O_4  

NASA Astrophysics Data System (ADS)

In order to optimize the magnetization of magnetic nanoparticles for use as Magnetic Resonance Imaging contrast agents and other in vivo biological applications, we have synthesized CoFe_2O_4(Liu, C.; Bingsuo, Z.; Rondinone, A.J.; Zhang, Z.J. J. Am. Chem. Soc.) 122, 6263 (2000). and Fe_3O_4(Shen, T.; Weissleder, R.; Papisov, M.; Bogdanov, A.; Brady, T. MRM) 29, 599 (1993). magnetic nanoparticles of sizes 5, 8, and 11nm using water-in-oil reverse micelles. Size was determined using Dynamic Light Scattering (DLS), X-Ray Diffraction (XRD), and High Pressure Liquid Chromatography (HPLC). Magnetic properties were measure from 10K-340K using SQUID magnetometry. Magnetization as a function of magnetic field has been performed at approximately body temperature ( ~310K) in order to help us determine the optimal size and composition for in vivo application.

Rodriguez, Robert; Chan, T.; Kenning, G. G.; Huang, L.; Yan, Y.

2002-03-01

27

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

PubMed

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

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

2013-02-26

28

Magnetic and elastic properties of CoFe2O4- polydimethylsiloxane magnetically oriented elastomer nanocomposites  

NASA Astrophysics Data System (ADS)

Magnetic elastic structured composites were prepared by using CoFe2O4 ferromagnetic and superparamagnetic nanoparticles as fillers in polydimethylsiloxane (PDMS) matrixes, which were cured in the presence of a uniform magnetic field. Cobalt-iron oxide nanoparticles of three different average sizes (between 2 and 12 nm) were synthesized and characterized. The smallest nanoparticles presented superparamagnetic behavior, with a blocking temperature of approximately 75 K, while larger particles are already blocked at room temperature. Macroscopically structured-anisotropic PDMS-CoFe2O4 composites were obtained when curing the dispersion of the nanoparticles in the presence of a uniform magnetic field (0.3 T). The formation of the particle's chains (needles) orientated in the direction of the magnetic field was observed only when loading with the larger magnetically blocked nanoparticles. The SEM images show that the needles are formed by groups of nanoparticles which retain their original average size. The Young's moduli of the structured composites are four times larger when measured along the oriented needles than in the perpendicular direction. Magnetization (VSM) and ferromagnetic resonance curves of the structured composites were determined as a function of the relative orientation between the needles and the probe field. The remanence magnetization was 30% higher when measured parallel to the needles, while the coercive field remains isotropic. These observations are discussed in terms of the individual nanoparticle's properties and its aggregation in the composites.

Soledad Antonel, P.; Jorge, Guillermo; Perez, Oscar E.; Butera, Alejandro; Gabriela Leyva, A.; Martín Negri, R.

2011-08-01

29

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

PubMed

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

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

2011-11-01

30

Low temperature measurements by infrared spectroscopy in CoFe2O4 ceramic  

NASA Astrophysics Data System (ADS)

This paper presents results of new far-infrared and middle-infrared measurements (wavenumber range of 4000-100 cm-1) of the CoFe2O4 ceramic in the temperature range from 300 K to 8 K. The band positions and their shapes remain constant across the wide temperature range. The quality of the sample was investigated by X-ray, EDS and EPMA studies. The CoFe2O4 retains the cubic structure ( Fd - 3 m) across the temperature range from 85 K to 360 K without any traces of distortion. Based on current knowledge the polycrystalline CoFe2O4 does not exhibit any phase transitions across the temperature range from 8 K to 300 K.

Bujakiewicz-Koro?ska, Renata; Hetma?czyk, ?ukasz; Garbarz-Glos, Barbara; Budziak, Andrzej; Kalvane, Anna; Bormanis, Karlis; Dru?bicki, Kacper

2012-10-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

32

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

NASA Astrophysics Data System (ADS)

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 ?C?(2.2 ± 0.1)10 - 11 s m - 1, which surpasses those reported previously for similar structures. A change of the sign of the magnetoelectric coefficient observed for an increasing magnetic bias field is related to the non-monotonic field dependence of magnetostriction in polycrystalline CoFe2O4.

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

2011-07-01

33

Anisotropy of the Faraday rotation of CoFe2O4 single crystals  

Microsoft Academic Search

Faraday rotation measurements, performed at 1150 nm wavelength on single-crystal platelets of CoFe2O4 with two different crystallographic orientations [100] and [111], are presented under magnetic fields up to 20 kOe, in the 5–580-K temperature range. A high anisotropy of magnetic origin is observed particularly at low temperatures (T<230 K) where saturation cannot be obtained along the [111] direction in a

J. Ostorero; M. Guillot; M. Leblanc; D. Rouet

1991-01-01

34

Substrate temperature dependent properties of sprayed CoFe 2O 4 ferrite thin films  

Microsoft Academic Search

The CoFe2O4 ferrite thin films have been prepared by spray pyrolysis technique at different substrate temperatures (Ts). The XRD patterns reveal a good (111) texture in the film prepared at Ts=325°C. The slow scan XRD studies show that the grain size is of the order of 150 Å and is not varied much with the substrate temperature. The lattice parameter

S. S Bellad; C. H Bhosale

1998-01-01

35

In situ synthesis of CoFe2O4-Co rods as anode materials for lithium ion batteries  

NASA Astrophysics Data System (ADS)

The CoFe2O4-Co rods with diameters in the range of 300-700 nm and length extending from 1 to 4 ?m were synthesized successfully by a facile in situ method. A transmission electron microscopy image has shown that the as-formed CoFe2O4-Co rods are composed of smaller nanocrystallines. The CoFe2O4-Co rods as anode materials for lithium ion batteries indicate high reversible capacity of 574.3 mAh g-1 at 100 mA g-1 in the first cycle, and good rate capability at various current densities between 100 and 1600 mA g-1. The improved electrochemical performance is ascribed to the presence of the metallic Cobalt and the well-designed rod structure.

Zhang, Mei; Jin, Yuhong; Wen, Qianqian; Chen, Cheng; Jia, Mengqiu

2013-07-01

36

CoFe2O4/buffer layer ultrathin heterostructures on Si(001)  

NASA Astrophysics Data System (ADS)

Epitaxial films of ferromagnetic CoFe2O4 (CFO) were grown by pulsed laser deposition on Si(001) buffered with ultrathin yttria-stabilized zirconia (YSZ) layers in a single process. Reflection high-energy electron diffraction was used to monitor in real time the crystallization of YSZ, allowing the fabrication of epitaxial YSZ buffers with thickness of about 2 nm. CFO films, with thicknesses in the 2-50 nm range were subsequently deposited. The magnetization of the CFO films is close to the bulk value. The ultrathin CFO/YSZ heterostructures have very flat morphology (0.1 nm roughness) and thin interfacial SiOx layer (about 2 nm thick) making them suitable for integration in tunnel (e.g., spin injection) devices.

Bachelet, R.; de Coux, P.; Warot-Fonrose, B.; Skumryev, V.; Fontcuberta, J.; Sánchez, F.

2011-10-01

37

Preparation and characterization of hollow magnetic silica (CoFe2O4 SiO2) microspheres  

NASA Astrophysics Data System (ADS)

Hollow magnetic-silica-bilayered microsphere was prepared by the ionic polymer sphere template. After calcination at 600 °C for 5 h, the hollow cobalt ferrite SiO2 hybrid spheres were formed. The hollow magnetic (CoFe2O4, 73 wt%)/silica (SiO2, 27 wt%) hybrid sphere was uniform and its thickness was about 50 nm. The hollow CoFe2O4/SiO2 spheres exhibit a superparamagnetic behavior at room temperature.

Wang, Cheng-Chien; Chen, I.-Han; Lin, Chun-Rong

2006-09-01

38

Preparation and characterization of hollow magnetic silica (CoFe 2O 4–SiO 2) microspheres  

Microsoft Academic Search

Hollow magnetic-silica-bilayered microsphere was prepared by the ionic polymer sphere template. After calcination at 600°C for 5h, the hollow cobalt ferrite–SiO2 hybrid spheres were formed. The hollow magnetic (CoFe2O4, 73wt%)\\/silica (SiO2, 27wt%) hybrid sphere was uniform and its thickness was about 50nm. The hollow CoFe2O4\\/SiO2 spheres exhibit a superparamagnetic behavior at room temperature.

Cheng-Chien Wang; I-Han Chen; Chun-Rong Lin

2006-01-01

39

Determination of the minimum concentrations of ferrofluid of CoFe2O4 required to orient liquid crystals  

NASA Astrophysics Data System (ADS)

A lyotropic liquid crystal doped with CoFe2O4 ionic ferrofluid with magnetic grains of different sizes is studied by means of optical techniques. The minimum concentrations of grains required to orient liquid crystals are determined. Brochard's and de Gennes' theory of magnetic suspensions is extended to include ellipsoidal grains.

Matuo, C. Y.; Tourinho, F. A.; Neto, A. M. Figueiredo

1993-04-01

40

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

PubMed

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

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

2012-05-16

41

Dielectric response of epitaxially strained CoFe2O4 spinel thin films  

NASA Astrophysics Data System (ADS)

Aiming to explore strain effects on the dielectric permittivity of ultrathin films of oxides with spinel structure, we report here on the thickness (4-160 nm) dependence of the dielectric response of CoFe2O4 (CFO) epitaxial films grown on La2/3Sr1/3MnO3 buffered SrTiO3(001) substrates. It is found that films thicker than ˜30 nm display bulklike permittivity values (?r?14); however, a pronounced and gradual ?r reduction is observed for thinner films when the in-plane compressive strain induced by the substrate increases. First-principle calculations are used to simulate the variation of the permittivity of CFO spinel thin films under epitaxial strain; in agreement with simple bond-length considerations, the out-of-plane permittivity is predicted to increase under in-plane compressive strain due to the resulting out-of-plane lattice expansion, but this enhancement can be overcompensated if this expansion is suppressed, resulting in an effective reduction of permittivity. However, the predicted reduction is substantially smaller than observed experimentally. We discuss possible mechanisms to account for this observation.

Gutiérrez, Diego; Foerster, Michael; Fina, Ignasi; Fontcuberta, Josep; Fritsch, Daniel; Ederer, Claude

2012-09-01

42

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

43

Quantitative determination of anisotropic magnetoelectric coupling in BiFeO3-CoFe2O4 nanostructures  

NASA Astrophysics Data System (ADS)

The transverse and longitudinal magnetoelectric susceptibilities (MES) were quantitatively determined for (001) heteroepitaxial BiFeO3-CoFe2O4 nanostructures. Both of these MES values were sharply enhanced at magnetic fields below 6 kOe and revealed asymmetric line shapes with respect to the dc magnetic field, demonstrating the strain-induced magnetoelectric effect. The maximum transverse MES, which reached as high as ~60 mV/cm Oe, was about five times larger than the longitudinal MES. This observation signifies that transverse magnetostriction of the CoFe2O4 nanopillars is enhanced more than the bulk value due to preferred magnetic domain alignment along the [001] direction coming from compressive, heteroepitaxial strain.

Oh, Yoon Seok; Crane, S.; Zheng, H.; Chu, Y. H.; Ramesh, R.; Kim, Kee Hoon

2010-08-01

44

Preparation of a vast CoFe2O4 magnetic monolayer by Langmuir-Blodgett technique.  

PubMed

The preparation of ultrathin films of CoFe2O4 nanocrystallites is reported. TEM images of them showed 2-dimensional assembly of particles, demonstrating the uniformity of these nanocrystallites. The formation of a Langmuir monolayer of the surface coated CoFe2O4 nanocrystallites with oleate at the air/water interface and its stability were studied with pressure-area isotherm curves and Brewster Angle Microscope (BAM) images. Surface pressure vs surface area isotherms and TEM studies demonstrated that the increasing surface pressure resulted in a transition from a complex with well-separated domains of nanocrystallites to well-compressed, monoparticulate layers, and, ultimately, to multiparticulate layers. PMID:16852892

Lee, Don Keun; Kim, Young Hwan; Kang, Young Soo; Stroeve, Pieter

2005-08-11

45

Preparation and photocatalytic properties of hybrid core-shell reusable CoFe2O4-ZnO nanospheres  

NASA Astrophysics Data System (ADS)

Magnetically separable and reusable core-shell CoFe2O4-ZnO photocatalyst nanospheres were prepared by the hydrothermal synthesis technique using glucose derived carbon nanospheres as the template. The morphology and the phase of core-shell hybrid structure of CoFe2O4-ZnO were assessed via TEM, SEM and XRD. The magnetic composite showed high UV photocatalytic activity for the degradation of methylene blue in water. The photocatalytic activity was found to be ZnO shell thickness dependent. Thicker ZnO shells lead to higher rate of photocatalytic activity. Hybrid nanospheres recovered using an external magnetic field demonstrated good repeatability of photocatalytic activity. These results promise the reusability of the hybrid nanospheres for photocatalytic activity.

Wilson, A.; Mishra, S. R.; Gupta, R.; Ghosh, K.

2012-08-01

46

Driving mechanism for magnetoelectric effect in CoFe2O4 BaTiO3 multiferroic composite  

NASA Astrophysics Data System (ADS)

The magnetoelectric effect in the CoFe2O4 BaTiO3 core shell structure composite prepared by wet chemical method occurs mainly due to a coupling between the magnetostrictive and piezostrictive phases. The driving mechanism is attributed to the mechanical coupling through the magnetostriction of the magnetostrictive constituent. The ME coefficient is found to be proportional to an efficiency factor ko and a coupling coefficient k, defined as k=???/?H, where ? is the linear magnetostriction.

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

2007-03-01

47

Molecular beam epitaxial growth and properties of CoFe2O4 on MgO(001)  

Microsoft Academic Search

We have grown single-crystal Co ferrite (CoFe2O4) on MgO(001) by oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE), and have characterized the composition, structure, surface morphology, and magnetic properties by a number of methods. The as-grown OPA-MBE material forms a perfect inverse spinel, in which all Co is in the 2+ formal oxidation state, and occupies octahedral sites within the cation sublattice. The

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

2002-01-01

48

Molecular beam epitaxial growth and properties of CoFe 2O 4 on MgO(0 0 1)  

Microsoft Academic Search

We have grown single-crystal Co ferrite (CoFe2O4) on MgO(001) by oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE), and have characterized the composition, structure, surface morphology, and magnetic properties by a number of methods. The as-grown OPA-MBE material forms a perfect inverse spinel, in which all Co is in the 2+ formal oxidation state, and occupies octahedral sites within the cation sublattice. The

S. A. Chambers; R. F. C. Farrow; S. Maat; M. F. Toney; L. Folks; J. G. Catalano; T. P. Trainor; G. E. Brown

2002-01-01

49

Temperature Dependence of the Dielectric Permittivity of BaTiO3-CoFe2O4 Ceramic Composites  

Microsoft Academic Search

Two-phase ceramic composites of cobalt ferrite dispersed in a barium titanate matrix were prepared and their dielectric permittivity was characterized. A rounding of their dielectric constant near the ferroelectric transition temperature of the BaTiO3 phase was observed. A generalized brick-wall model, taking into account the BaTiO3 contribution, fitted with the Landau-Devonshire theory, and the CoFe2O4 permittivity, experimentally determined, was used

J. G. Barbosa; B. G. Almeida; C. Araujo; J. A. Mendes

2008-01-01

50

Large Magnetoresistance in Magnetically Coupled SrRuO3 -CoFe2 O4 Self-Assembled Nanostructures.  

PubMed

A new way to induce a large magnetoresistance has been achieved by self-assembled nanostructures consisting of ferromagnetic spinel CoFe2 O4 (CFO) and metallic perovskite SrRuO3 (SRO). The interdiffused Fe(3+) ions in SRO have paved the way to strong magnetic couplings with CFO nanopillars, resulting in the suppression of spin-polarized electron scattering. PMID:23847088

Liu, Heng-Jui; Tra, Vu-Thanh; Chen, Ying-Jiun; Huang, Rong; Duan, Chun-Gang; Hsieh, Ying-Hui; Lin, Hong-Ji; Lin, Jiunn-Yuan; Chen, Chien-Te; Ikuhara, Yuichi; Chu, Ying-Hao

2013-07-12

51

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

52

Magnetic field dependence of piezoelectric resonance frequency in CoFe2O4-BaTiO3 composites  

NASA Astrophysics Data System (ADS)

The particulate and the multilayer CoFe2O4(CFO)-BaTiO3(BT) composites were prepared by the conventional solid state reaction method and the tape casting method, respectively. Both the prepared composites were simultaneously ferroelectric and ferromagnetic at room temperature. For the multilayer composite sample, a piezoelectric resonance frequency remarkably depended on the applied DC magnetic field, while no remarkable magnetic field dependence was observed for the particulate composite samples. An uniform magnetostriction of the CFO phase in the multilayer composite contributes to piezoelectric effect of the BT phases, resulting in the modulation of the piezoelectric resonance frequency.

Kagomiya, Isao; Hayashi, Yusuke; Kakimoto, Ken-ichi; Kobayashi, Kazuyoshi

2012-08-01

53

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

PubMed Central

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

de Brito, Vera Lucia Othero; Cunha, Stephanie Ala; Lemos, Leonardo Violim; Nunes, Cristina Bormio

2012-01-01

54

Nucleation-Induced Self-Assembly of Multiferroic BiFeO3-CoFe2O4 Nanocomposites.  

PubMed

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

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

2013-07-31

55

Chemical tuning of the optical band gap in spinel ferrites: CoFe2O4 vs NiFe2O4  

NASA Astrophysics Data System (ADS)

We measured the optical properties of epitaxial CoFe2O4 thin films and compared our findings with complementary electronic structure calculations and similar studies on the Ni analog. Our work reveals CoFe2O4 to be an indirect band gap material (1.2 eV, X --> ? in the spin-down channel) with a direct gap at 2.7 eV. The latter is robust up to 800 K. Compared to NiFe2O4, the indirect gap is ~0.5 eV lower, a difference we discuss in terms of size and covalency effects in spinel ferrites.

Holinsworth, B. S.; Mazumdar, D.; Sims, H.; Sun, Q.-C.; Yurtisigi, M. K.; Sarker, S. K.; Gupta, A.; Butler, W. H.; Musfeldt, J. L.

2013-08-01

56

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

Microsoft Academic Search

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

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

2011-01-01

57

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

NASA Astrophysics Data System (ADS)

Multiferroic xBi3.15Nd0.85Ti3O12-(1-x)CoFe2O4 composite thin films with x=0.5, 0.6, and 0.7 were fabricated on Pt/Ti/SiO2/Si(100) substrates by a chemical solution deposition technique. X-ray diffraction shows that there are no other phases but bismuth-layered perovskite Bi3.15Nd0.85Ti3O12 and spinel CoFe2O4 phases in the films. Scanning electron microscopy reveals that CoFe2O4 aggregates locally into nanoparticles and embeds in the Bi3.15Nd0.85Ti3O12 matrix. The composite films exhibit both good ferroelectric and magnetic properties at room temperature, as well as distinct magnetoelectric coupling behaviors, which are comparable with those of multiferroic composite films with conventional Pb-based ferroelectric as a ferroelectric component.

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

2007-04-01

58

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

NASA Astrophysics Data System (ADS)

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 ?-phase of poly(vinylidene fluoride), PVDF, by the addition of CoFe2O4 and NiFe2O4 nanoparticles in order to prepare poly(vinylidene fluoride)/ferrite nanocomposite for multiferroic and magnetoelectric applications,. The dispersed ferrite nanofiller particles strongly enhance the nucleation of the ?-phase of the polymer matrix. In this way, magnetoelectric polymer nanocomposites can be processed avoiding the usual ?- to ?-phase transformation by stretching of the polymer matrix.

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

2011-04-01

59

Role of epitaxial strain on the magnetic structure of Fe-doped CoFe2O4  

NASA Astrophysics Data System (ADS)

The magnetic structure of Fe-doped CoFe2O4 (Co1-xFe2+xO4) grown on MgO (0 0 1) and SrTiO3 (0 0 1) substrates is studied with superconducting quantum interference device magnetometry and soft x-ray magnetic spectroscopies. X-ray and electron diffraction show that the choice of substrate has large effects on the strain, crystal structure and surface morphology of Co1-xFe2+xO4 thin films. Samples grown on MgO have small, coherent strains and surfaces that are nearly atomically flat, whereas films grown on SrTiO3 have large tensile strains and surfaces terminated with islands, which indicate the presence of a large density of misfit dislocations. These differences in structural properties correlate with the large differences seen in the magnetic structure; samples grown on SrTiO3 have larger magnetic moments and increased anisotropies compared to those grown on MgO. Most strikingly, the large magnetic spin and orbital moments found in the films grown on SrTiO3 suggest a suppression of anti-phase boundary formation, which we attribute to the large compressive lattice mismatch and the formation of misfit dislocations during the film growth in order to relieve the epitaxial strain. This results in the films grown on SrTiO3 having magnetic properties that are more similar to bulk Co1-xFe2+xO4 than those grown on MgO, demonstrating that epitaxial strain can result in large changes in the magnetic structure of Co1-xFe2+xO4.

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

2013-11-01

60

Magnetoelectric CoFe2O4-Pb(Zr,Ti)O3 composite thin films derived by a sol-gel process  

NASA Astrophysics Data System (ADS)

Magnetoelectric (ME) CoFe2O4-Pb(Zr,Ti)O3 composite thin films have been prepared by a sol-gel process and spin-coating technique. X-ray diffraction and scanning electron microscopy reveal that there exists local aggregation or phase separation of the CoFe2O4 and Pb(Zr,Ti)O3 phases in the films. Vibrating sample magnetometer, ferroelectric test unit, and magnetoelectric measuring device were used to characterize the magnetic and ferroelectric properties, as well as the ME effect of the films. It is shown that the films exhibit both good magnetic and ferroelectric properties, as well as a ME effect. A high initial magnetoelectric voltage coefficient for the film is observed. The ME effect of the film strongly depends on the magnetic bias and magnetic field frequency.

Wan, J. G.; Wang, X. W.; Wu, Y. J.; Zeng, M.; Wang, Y.; Jiang, H.; Zhou, W. Q.; Wang, G. H.; Liu, J.-M.

2005-03-01

61

Magnetic properties of isotropic and anisotropic CoFe2O4 -based ferrogels and their application as torsional and rotational actuators  

Microsoft Academic Search

CoFe2O4 -based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles

S. Monz; A. Tschöpe; R. Birringer

2008-01-01

62

Effects of morphology and strain on the dielectric response of multiferroic CoFe2O4-BaTiO3 nanocomposite thin films  

Microsoft Academic Search

The dielectric response (permittivity and losses) of epitaxial CoFe2O4-BaTiO3 thin film nanocomposites deposited under different conditions has been measured. Exhaustive microstructural analyses have allowed tracking the evolution of structure and morphology as a function of thickness, deposition temperature and rate. It is found that the dielectric permittivity of the nanocomposite increases with the grain size of the BaTiO3 matrix and

I. Fina; N. Dix; L. Fàbrega; F. Sánchez; J. Fontcuberta

2010-01-01

63

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

Microsoft Academic Search

Ho-doped CoFe2O4 spinel ferrite has been synthesized by a combination of mechanical alloying and subsequent annealing of the alloyed powder in the temperature range 950 °C <= TAN <= 1200 °C. The grains of the nanocrystalline samples have been found in the single domain\\/pseudo-single domain state for TAN <= 1050 °C and multi-domain state for TAN >= 1100 °C. The

I. Panneer Muthuselvam; R. N. Bhowmik

2010-01-01

64

Reaction kinetic, magnetic and microwave absorption studies of SrFe 12 O 19 \\/CoFe 2 O 4 ferrite nanocrystals  

Microsoft Academic Search

Mixture of cobalt ferrite and strontium hexaferrite nanocrystals i.e. SrFe12O19\\/CoFe2O4 exhibiting super paramagnetic nature were synthesized by modified flux method. The resulting precursors were heat treated\\u000a (HT) at 900 and 1200°C for 4 h in nitrogen atmosphere. During heat treatment, transformation proceeds as instantaneous rate\\u000a of nucleation and three dimensional growth with activation energy of 135.835 kJ\\/mole. The hysteresis loops

Sachin Tyagi; Himanshu B. Baskey; R. C. Agarwala; Vijaya Agarwala; T. C. Shami

2011-01-01

65

Photocatalytic degradation of methylene blue in water using CoFe 2O 4–Cr 2O 3–SiO 2 fluorescent magnetic nanocomposite  

Microsoft Academic Search

A CoFe2O4–Cr2O3–SiO2 fluorescent magnetic nanocomposite (FMNC) has been synthesized by a combined sonochemical co-precipitation method. Remarkable feature of the FMNC is its high band gap energy (3–4eV). Photocatalytic activity of the FMNC has been examined for degradation of methylene blue in aqueous solution under UV irradiation (12mW Hg lamp, major wavelength 400nm). The catalyst could be separated from aqueous media

Kula Kamal Senapati; Chandan Borgohain; Kanak C. Sarma; Prodeep Phukan

2011-01-01

66

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

NASA Astrophysics Data System (ADS)

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.

Narendra Babu, S.; Malkinski, Leszek

2012-04-01

67

Temperature dependent phonon Raman scattering of highly a-axis oriented CoFe2O4 inverse spinel ferromagnetic films grown by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Lattice vibrations of highly a-axis oriented CoFe2O4 (CFO) films have been investigated by Raman scattering in the temperature range of 80-873 K. The five phonon modes T1g(2), T1g(3), Eg, A1g(1), A1g(2), and their evolutions can be uniquely distinguished. It was found that an electron transfer between Co2+ and Fe3+ cations occurs in octahedral sites at about 173 K. The structure disorder in the CFO films appears with increasing the temperature, which indicates the cation migration between tetrahedral and octahedral sites. The phenomena suggest the structural transformation trend from inverse spinel to normal spinel at the elevated temperatures.

Liao, Y. Y.; Li, Y. W.; Hu, Z. G.; Chu, J. H.

2012-02-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

69

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

70

Residual stress and magnetic behavior of multiferroic CoFe2O4/Pb(Zr0.52Ti0.48)O3 thin films  

NASA Astrophysics Data System (ADS)

Multiferroic composite thin films consisting of CoFe2O4 (CFO) and Pb(Zr0.52Ti0.48)O3 (PZT) layers were deposited through a combined route of rf magnetron sputtering and sol gel on Pt(111)/TiO2/SiO2/Si substrates. The coupling effects in the bilayered thin film were studied by looking at the relationships among the crystallite orientation, magnetic behavior, and the in-plane residual stress. Phase selective residual stress analysis conducted by using x-ray method demonstrated a close correlation between the stress imposed on the PZT layer and its texture. A change in the PZT layer orientation from (111) to (010) with the increasing layer thickness was observed in the multiferroic thin film as the system changes from an interface energy minimizing texture to a strain energy density minimizing texture. The CFO phase in the multiferroic thin films was preferably oriented in the (111) orientation. However, there is a change in magnetization as well as coercivity of the multiferroic thin films when the top PZT layer was varied in thickness. A close correlation between the magnetization and the in-plane stress in the CFO bottom layer imposed by the PZT film thickness was observed.

Sim, Chow Hong; Pan, Z. Z.; Wang, John

2009-04-01

71

Magnetic properties of isotropic and anisotropic CoFe2O4 -based ferrogels and their application as torsional and rotational actuators  

NASA Astrophysics Data System (ADS)

CoFe2O4 -based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles and the polymer network exists, which prevents the particles from Brownian relaxation. The contribution of such particles was investigated by field cooling field warming and zero field cooling field warming measurements as well as temperature-dependent magnetization measurements. By application of an external field during gel polymerization, a magnetic texture was induced as confirmed by the angular dependence of mR/mS and HC . The net-magnetic torque, exerted on the magnetic particles in an anisotropic ferrogel in combination with the soft elastic properties of the gel matrix enables the application as torsional soft actuator as demonstrated.

Monz, S.; Tschöpe, A.; Birringer, R.

2008-08-01

72

Magnetic properties of isotropic and anisotropic CoFe2O4-based ferrogels and their application as torsional and rotational actuators.  

PubMed

CoFe2O4-based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles and the polymer network exists, which prevents the particles from Brownian relaxation. The contribution of such particles was investigated by field cooling field warming and zero field cooling field warming measurements as well as temperature-dependent magnetization measurements. By application of an external field during gel polymerization, a magnetic texture was induced as confirmed by the angular dependence of mRmS and HC . The net-magnetic torque, exerted on the magnetic particles in an anisotropic ferrogel in combination with the soft elastic properties of the gel matrix enables the application as torsional soft actuator as demonstrated. PMID:18850833

Monz, S; Tschöpe, A; Birringer, R

2008-08-15

73

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

NASA Astrophysics Data System (ADS)

Self-assembled (0.65)BiFeO3-(0.35)CoFe2O4 (BFO-CFO) nanostructures were deposited on SrTiO3 (001) and (111) substrates by pulsed laser deposition at various temperatures from 500 to 800 °C. The crystal phases and the lattice strain for the two different substrate orientations have been determined and compared. The films grow epitaxial on both substrates but separation of the spinel and perovskite crystallites, without parasitic phases, is only obtained for growth temperatures of around 600-650 °C. The BFO crystallites are out-of-plane expanded on STO(001), whereas they are almost relaxed on (111). In contrast, CFO crystallites grow out-of-plane compressed on both substrates. The asymmetric behavior of the cell parameters of CFO and BFO is discussed on the basis of the role of the epitaxial stress caused by the substrate and the spinel-perovskite interfacial stress. It is concluded that interfacial stress dominates the elastic properties of CFO crystallites and thus it may play a fundamental on the interface magnetoelectric coupling in these nanocomposites.

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

2008-04-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

75

Anomalous Enhancement in Magnetization of BiFeO3 – CoFe2O4 Heterostructure Multilayer Thin Films Deposited on SrTiO3 with Different Orientation  

Microsoft Academic Search

The magnetic properties of BiFeO3(BFO) – CoFe2O4(CFO) heterostructure thin films, grown on (100), (110) and (111) SrTiO3 (STO) substrates by employing pulsed laser deposition (PLD) method, have been studied. The XRD patterns of BFO-CFO multilayer thin films compared with the pure CFO and BFO thin films grown using under identical conditions evidenced that all peaks present correspond to CFO and

Sandra Dussan; Manoj K. Singh; Ram S. Katiyar

2011-01-01

76

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

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

77

Magnetic, dielectric, magnetoelectric, and microstructural studies demonstrating improved magnetoelectric sensitivity in three-phase BaTiO3-CoFe2O4-poly(vinylidene-fluoride) composite  

Microsoft Academic Search

A three-phase BaTiO3-CoFe2O4-poly(vinylidene-fluoride) (BT-CF-PVDF) particulate composite showing a maximum magnetoelectric voltage coefficient alphaE33~26 mV\\/cm Oe, at a small applied magnetic field HDC=263 Oe, has been demonstrated in this work. Large magnetoelectric response in this composite (particulate BT-CF embedded in PVDF matrix) is possibly a result of the effective mechanical interaction between CF and BT through the PVDF matrix. Processing temperatures

Arti Gupta; Ratnamala Chatterjee

2009-01-01

78

Plasmonic nanohybrid with ultrasmall Ag nanoparticles and fluorescent dyes.  

PubMed

We investigate a hybrid nanocomposite combining fluorescent dyes and ultrasmall (<3 nm) silver nanocrystals in a block copolymer micelle. Although the metal nanoparticles are significantly smaller than the electromagnetic skin depth, we observe a modification of the exciton lifetime and the nonradiative energy transfer among the dyes. This behavior is absent in a control experiment with dyes whose energetic levels are far from the plasmonic resonance, establishing the plasmonic nature of the interaction. PMID:21534536

Rainò, Gabriele; Stöferle, Thilo; Park, Chanhee; Kim, Ho-Cheol; Topuria, Teya; Rice, Philip M; Chin, In-Joo; Miller, Robert D; Mahrt, Rainer F

2011-05-02

79

Antibody-functionalized magnetic nanoparticles for electrochemical immunoassay of ?-1-fetoprotein in human serum  

Microsoft Academic Search

A simple and sensitive electrochemical immunoassay protocol for the detection of ?-1-fetoprotein (AFP) has been designed based\\u000a on antibody-functionalized core–shell–shell nanocomposite particles. The core–shell CoFe2O4\\/(3-mercaptopropyl) trimethoxysilane (CoFe2O4–MPS) was initially synthesized by covalent conjugation, then gold nanoparticles were adsorbed onto the surface of CoFe2O4–MPS via an Au–S bond, and then anti-AFP antibodies were immobilized onto the nanogold surface. With the aid

Li Wang; Xianxue Gan

2009-01-01

80

Structural and morphological studies of manganese substituted CoFe2O4 and NiFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

81

Polyvinyl alcohol functionalized cobalt ferrite nanoparticles for biomedical applications  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

82

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

PubMed

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

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

2013-08-30

83

Magnetic, dielectric, magnetoelectric, and microstructural studies demonstrating improved magnetoelectric sensitivity in three-phase BaTiO3-CoFe2O4-poly(vinylidene-fluoride) composite  

NASA Astrophysics Data System (ADS)

A three-phase BaTiO3-CoFe2O4-poly(vinylidene-fluoride) (BT-CF-PVDF) particulate composite showing a maximum magnetoelectric voltage coefficient ?E33~26 mV/cm Oe, at a small applied magnetic field HDC=263 Oe, has been demonstrated in this work. Large magnetoelectric response in this composite (particulate BT-CF embedded in PVDF matrix) is possibly a result of the effective mechanical interaction between CF and BT through the PVDF matrix. Processing temperatures for composite preparation are low, ensuring no chemical reaction or interdiffusion between the atoms of piezoelectric and magnetostrictive phases, leading to large value of magnetoelectric voltage coefficient. Detailed measurements of dielectric, magnetic, and static magnetoelectric data are reported. Peak in the dielectric spectrum is shown to correlate with the buildup of magnetization in the composite. Although the M-H loop gives Ms, Mr, and Hc (=37.2 emu/g, 16.4 emu/g, and 830 Oe, respectively) in accordance with the expected values (wt % of CF in the composite is 52.5%), the overall magnetic behavior of the composite is identified as ``spin glass.''

Gupta, Arti; Chatterjee, Ratnamala

2009-07-01

84

Electric field tunable magnetic properties of lead-free Na0.5Bi0.5TiO3/CoFe2O4 multiferroic composites  

NASA Astrophysics Data System (ADS)

Lead-free multiferroic particulate composites of Na0.5Bi0.5TiO3 (NBT) and CoFe2O4 (CFO) have been synthesized by solid-state sintering method. A systematic study of structural, magnetic and magnetoelectric (ME) properties is undertaken. Structural and morphology studies carried out by x-ray diffraction and field emission scanning electron microscopy indicate formation of single phase for parent phases and presence of both phases in the composites. Magnetic properties are investigated using vibrating sample magnetometer and ferromagnetic resonance (FMR) measurements at room temperature. Strong ME coupling is demonstrated in NBT-CFO 70-30 mol% composite by an electrostatically tunable FMR field shift up to 428 Oe (at E = 3.9 kV/cm), which increases to a large value of 640 Oe at E = 6.8 kV/cm. Furthermore, these lead-free multiferroic composites exhibiting electrostatically induced magnetic resonance field at microwave frequencies provide great opportunities for electric field tunable microwave devices.

Narendra Babu, S.; Gi Min, Seong; Malkinski, Leszek

2011-04-01

85

Mössbauer studies of superparamagnetic ferrite nanoparticles for functional application  

NASA Astrophysics Data System (ADS)

Nanoparticles of CoFe2O4 and MnFe2O4 prepared for functional applications in nanomedicine were studied using Mössbauer spectrometry. Superparamagnetic properties of nanoparticles of different size and composition were compared applying collective excitations and multilevel models for the description of the Mössbauer spectra.

Mažeika, K.; Jagminas, A.; Kurtinaitien?, M.

2013-04-01

86

Magnetic characterization and self-heating of various magnetic nanoparticles for medical applications  

Microsoft Academic Search

Magnetic and self-heating properties of CoFe2O4, MgFe2O4 and NiFe2O4 nanoparticles were evaluated. MgFe2O4 and NiFe2O4, whose coercive forces are lower than that of CoFe2O4, exhibited higher temperature rise in self-heating excited by ac magnetic field of 150 Oe at 10 kHz. The energy efficiency of magnetic field in generating self heating of these ferrite nanoparticles is also analyzed. It was

A. Tomitaka; H. Kobayashi; T. Yamada; Minhong Jeun; Seongtae Bae; Y. Takemura

2010-01-01

87

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

PubMed

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

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

2013-03-25

88

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

PubMed

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

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

2008-08-20

89

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

PubMed Central

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

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

2008-01-01

90

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

Microsoft Academic Search

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

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

2008-01-01

91

Rechargeable Mg batteries with graphene-like MoS? cathode and ultrasmall Mg nanoparticle anode.  

PubMed

The combination of a highly exfoliated, graphene-like MoS? cathode and ultrasmall Mg nanoparticle anode is proposed, for the first time, for rechargeable Mg batteries. Such a configuration exhibits an operating voltage of 1.8 V and a well reversible discharge capacity of ca. 170 mA h g?1, emphasizing the necessity of rational morphological control of electrode materials and opening up new opportunities for rechargeable Mg batteries. PMID:21274912

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

2010-12-06

92

Ultrasmall iron oxide nanoparticles: Synthesis, physicochemical, and magnetic properties  

Microsoft Academic Search

A new synthetic method leading to the formation of polycaprolactone (PCL)\\/iron oxide nanoparticles using polyvinylpyrrolidone (PVP) is described. The unique feature of this method is that the conventional polymerization step can be avoided. A stable colloidal dispersion of the PCL-coated iron oxide nanoparticles (PCLNP) is thus formed in the presence of PVP as a stabilizer. The PCLNP has a mean

Sung-Jin Bae; Ji-Ae Park; Jae-Jun Lee; Gang-Ho Lee; Tae-Jeong Kim; Done-Sik Yoo; Yongmin Chang

2009-01-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

94

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

PubMed

The present work addresses the main bottleneck in the synthesis of magnetic nanoparticles by laser pyrolysis. Since the introduction of laser pyrolysis for the production of nanoparticles nearly three decades ago, this method has been repeatedly presented as a highly promising alternative, on account of two main characteristics: (i) its flexibility, since nanoparticles can be formed from a wide variety of precursors in both gas and liquid phase, and (ii) its continuous nature, avoiding the intrinsic variability of batch processing. However, the results reported to date invariably show considerable aggregation of the obtained nanoparticles, which strongly limits their application in most fields. In this work, we have been able to circumvent this problem by collecting the particles in a polyol liquid medium. This method prevents the formation of aggregates and renders a uniform distribution of well dispersed ultrasmall nanoparticles (<4 nm) in a water-compatible solvent. We consider that the effectiveness of this novel collection method for the production of well-dispersed magnetic nanoparticles will be of high interest to a wide range of scientists working in the nanoparticle synthesis field and may enable new applications wherever there is a strict requirement for non-agglomerated nanoparticles. PMID:23037862

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

2012-10-04

95

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

96

FeCo Nanoparticles by Salt-Matrix Annealing  

NASA Astrophysics Data System (ADS)

Preparation of monodisperse FeCo nanoparticles remains a challenge due to poor chemical stability of the nanoparticles during heat treatments. We report a novel route of preparation of monodisperse FeCo nanoparticles with controllable particle size and size distribution. CoFe2O4 nanoparticles were first prepared by chemical solution method via reduction of iron acetylacetonate and cobalt acetylacetonate. The as-synthesized CoFe2O4 nanoparticles were then mixed with NaCl powder particles and the mixtures were annealed in forming gas to form FeCo nanoparticles. Structural characterization showed that the FeCo nanoparticles obtained by salt-matrix annealing have been transformed to body-centered cubic (bcc) structure without sintering and agglomeration. The particle size can be well controlled by adjusting the synthetic parameters for CoFe2O4 nanoparticles. It is also found that the recovered bcc FeCo nanoparticles are stable under ambient condition. The magnetization of the FeCo nanoparticles is found to be size dependent.

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

2007-03-01

97

Susceptibility of cobalt ferrite nanoparticles dispersed in polylactic acid microspheres  

NASA Astrophysics Data System (ADS)

In this study dynamic susceptibility (DS) was used to investigate cobalt ferrite (CoFe2O4) nanoparticles dispersed in polylactic-based microsized spheres. The peak position of the imaginary component of the DS curve was analyzed as a function of the polarizing external field, using a picture of an asymmetric double-well potential for the relaxation of the magnetization associated to the magnetic nanoparticle.

Silveira, L. B.; Santos, J. G.; Oliveira, A. C.; Tedesco, A. C.; Marchetti, J. M.; Lima, E. C. D.; Morais, P. C.

2004-05-01

98

Ultrasmall gold nanoparticles anchored to graphene and enhanced photothermal effects by laser irradiation of gold nanostructures in graphene oxide solutions.  

PubMed

In this work we demonstrate the coupling of the photothermal effects of gold nanostructures of controlled size and shape with graphene oxide nanosheets dispersed in water. The enhanced photothermal effects can be tuned by controlling the shape and size of the gold nanostructures, which result in a remarkable increase in the heating efficiency of the laser-induced size reduction of gold nanostructures. The Raman spectra of the Au-graphene nanosheets provide direct evidence for the presence of more structural defects in the graphene lattice induced by laser irradiation of graphene oxide nanosheets in the presence of Au nanostructures. The large surface areas of the laser-reduced graphene oxide nanosheets with multiple defect sites and vacancies provide efficient nucleation sites for the ultrasmall gold nanoparticles with diameters of 2-4 nm to be anchored to the graphene surface. This defect filling mechanism decreases the mobility of the ultrasmall gold nanoparticles and, thus, stabilizes the particles against the Ostwald ripening process, which leads to a broad size distribution of the laser-size-reduced gold nanoparticles. The Au nanostructures/graphene oxide solutions and the ultrasmall gold-graphene nanocomposites are proposed as promising materials for photothermal therapy and for the efficient conversion of solar energy into usable heat for a variety of thermal, thermochemical, and thermomechanical applications. PMID:23194145

Zedan, Abdallah F; Moussa, Sherif; Terner, James; Atkinson, Garrett; El-Shall, M Samy

2012-12-10

99

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

PubMed Central

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

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

2007-01-01

100

Synthesis of cobalt ferrite nano-particles and their magnetic characterization  

Microsoft Academic Search

Cobalt ferrite nano-particles (CoFe2O4) were synthesized by the co-precipitation method with ammonium hydroxide as an alkaline solution. The reactions were carried out at different temperatures between 20 and 80°C. The nano-particles have been investigated by magnetic measurements, X-ray powder diffraction and transmission electron microscopy. The average crystallite size of the synthesized samples was between 11 and 45nm, which was found

M. M. El-Okr; M. A. Salem; M. S. Salim; R. M. El-Okr; M. Ashoush; H. M. Talaat

2011-01-01

101

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

Microsoft Academic Search

We have developed a magnetic immunoassay system (MIA) using magnetic nanoparticle markers for biomolecule detection. We have magnetically characterized multi-core magnetic nanoparticles (MNPs) containing single-domain crystals of Fe3O4 and CoFe2O4 with our system using a high temperature superconducting quantum interference device as detector. We use a Helmholtz coil to excite the MNPs and study the AC-susceptibility. The data is fit

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

2010-01-01

102

Highly accessible catalytic sites on recyclable organosilane-functionalized magnetic nanoparticles: An alternative to functionalized porous silica catalysts  

Microsoft Academic Search

Diaminosilane-functionalized cobalt spinel ferrite (CoFe2O4) magnetic nanoparticles are synthesized and used as efficient heterogeneous base catalysts for the Knoevenagel condensation of aromatic and heteroaromatic aldehydes with malononitrile. The magnetic nanoparticle catalyst is characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and nitrogen physisorption measurements. Quantitative conversion of the reactants is achieved

Nam T. S. Phan; Christopher W. Jones

2006-01-01

103

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

104

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

PubMed

Monodispersed core/shell spinel ferrite/carbon nanoparticles are formed by thermolysis of metal (Fe3+, Co2+) oleates followed by carbon coating. The phase and morphology of nanoparticles are characterized by x-ray diffraction and transmission electron microscopy. Pure Fe3O4 and CoFe2O4 nanoparticles are initially prepared through thermal decomposition of metal–oleate precursors at 310 degrees C and they are found to exhibit poor electrochemical performance because of the easy aggregation of nanoparticles and the resulting increase in the interparticle contact resistance. In contrast, uniform carbon coating of Fe3O4 and CoFe2O4 nanoparticles by low-temperature (180 degrees C) decomposition of malic acid allowed each nanoparticle to be electrically wired to a current collector through a conducting percolative path. Core/shell Fe3O4/C and CoFe2O4/C nanocomposite electrodes show a high specific capacity that can exceed 700 mAh g(-1) after 200 cycles, along with enhanced cycling stability. PMID:22414887

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

2012-03-30

105

Thiol-functionalized silica colloids, grains, and membranes for irreversible adsorption of metal(oxide) nanoparticles  

Microsoft Academic Search

Thiol-functionalization is described for silica surfaces from diverging origin, including commercial silica nanoparticles and Stöber silica as well as silica structures provided by porous glasses and novel polymer-templated silica membranes. The functionalization allows in all cases for the irreversible binding of metal(oxide) particles from a solution. Examples are the adsorption of CoFe2 O4 particles for the preparation of magnetizable silica

E. Maria Claesson; Albert P. Philipse

2007-01-01

106

Phase matched magnetooptic planar waveguide elaborated by magnetic nanoparticles embedded in an organic-inorganic sol-gel matrix  

Microsoft Academic Search

This paper presents a magnetooptical way to reduce the modal birefringence of planar waveguides, which is a critical point for applications. Indeed, composite material, made of Cobalt ferrite (CoFe2O4) nanoparticles embedded in a silica\\/zirconia matrix by the sol-gel method, are used to develop a phase matched magnetooptic planar waveguides. Such thin composite films coated on a pyrex slide using the

F. Choueikani; F. Royer; D. Jamon; S. Neveu; J. Charara

2008-01-01

107

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

Microsoft Academic Search

In this work, multi-layered thin film materials comprised of cobalt ferrite (CoFe2O4) magnetic nanoparticles and polystyrene amine-functionalized (PS-NH2) star polymers have been prepared on silicon dioxide surfaces by means of organometallic-driven layer-by-layer (LBL) self-assembly. The films formed were characterized using surface plasmon resonance (SPR) spectroscopy, which indicated the rapid formation (sub-second to second time frames) of reproducible molecular thin layers.

Shimul Shah

2011-01-01

108

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

Microsoft Academic Search

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 (CoFe2O4@oleic acid) magnetic nanoparticles (MNPs) as optimized sorbent for the target analytes. The variables involved in dSPE

Iván P. Román; Alberto Chisvert; Antonio Canals

2011-01-01

109

Morphology of cobalt ferrite nanoparticle-polyelectrolyte multilayered nanocomposites  

NASA Astrophysics Data System (ADS)

Novel magnetic nanocomposite films with controlled morphology were produced via the electrostatic layer-by-layer assembly of cationic CoFe2O4 nanoparticles and anionic poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonic acid) (PEDOT:PSS) complex. The electrostatic interaction between nanoparticle and the polyelectrolyte complex ensured a stepwise growth of the nanocomposite film with virtually identical amounts of materials being adsorbed at each deposition cycle as observed by UV-vis spectroscopy. AFM images acquired under the tapping mode revealed a globular morphology with dense and continuous layers of nanoparticles with voids being filled with polymeric material.

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

2011-05-01

110

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

PubMed Central

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

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

2012-01-01

111

Evaluating the effect of ultrasmall superparamagnetic iron oxide nanoparticles for a long-term magnetic cell labeling  

PubMed Central

In order to evaluate the long-term viability, the iron content stability, and the labeling efficiency of mammalian cells using magnetic cell labeling; dextran-coated ultrasmall superparamagnetic iron oxide (USPIOs) nanoparticles with plain surfaces having a hydrodynamic size of 25 nm were used for this study. Tests were carried out in four groups each containing 5 flasks of 5.5 × 106 AD-293 embryonic kidney cells. The cell lines were incubated for 24 h using four different iron concentrations with and without protamine sulfate (Pro), washed with phosphate-buffered saline (PBS) and centrifuged three times to remove the unbounded USPIOs. Cell viability was also verified using USPIOs. There were no significant differences in the cell viability between the control group of cells and those groups with iron uptake at the specified iron concentrations. The average iron uptake ratio compared to that of the control group was (114 ± 1). The magnetic resonance images (MRI) at post-labeling day 1 and day 21 showed (75 ± 4)% and (22 ± 5)% signal decrements compared to that of the control, respectively. The Perl's Prussian blue test showed that 98% of the cells were labeled, and the iron concentration within the media did not affect the cell iron uptake. Magnetic cellular labeling with the USPIO-Pro complex had no short or medium term (3 weeks) toxic effects on AD-293 embryonic kidney cells.

Shanehsazzadeh, Saeed; Oghabian, Mohammad Ali; Allen, Barry J.; Amanlou, Massoud; Masoudi, Afshin; Daha, Fariba Johari

2013-01-01

112

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

113

Magnoelastic coupling in magnetic oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

114

A highly effective, nontoxic T1 MR contrast agent based on ultrasmall PEGylated iron oxide nanoparticles.  

PubMed

In this study we systematically developed a potential MR T(1) contrast agent based on very small PEGylated iron oxide nanoparticles. We adjusted the size of the crystalline core providing suitable relaxometric properties. In addition, a dense and optimized PEG coating provides high stability under physiological conditions together with low cytotoxicity and low nonspecific phagocytosis into macrophage cells as a part of the reticulo endothelial system at biologically relevant concentrations. The as developed contrast agent has the lowest r(2)/r(1) ratio (2.4) at 1.41 T reported so far for PEGylated iron oxide nanoparticles as well as a r(1) relaxivity (7.3 mM(-1) s(-1)) that is two times higher compared to that of Magnevist as a typical T(1) contrast agent based on gadolinium as a clinical standard. PMID:19799448

Tromsdorf, Ulrich I; Bruns, Oliver T; Salmen, Sunhild C; Beisiegel, Ulrike; Weller, Horst

2009-12-01

115

[Pharmacokinetics, tissue distribution and magnetic resonance's response characterstics of folic acid-O-carboxymethyl chitosan ultrasmall superparamagnetic iron oxide nanoparticles in mice and rats].  

PubMed

Folic acid-O-carboxymethyl chitosan ultrasmall superparamagnetic iron oxide nanoparticles (FA-OCMCS-USPIO-NPs) are a novel molecular targeting MR contrast agent. This paper reperts the pharmacokinetics and magnetic resonance response characteristics of FA-OCMCS-USPIO-NPs in normal rats and mice, and discussed its distributing regularity in animals, providing basis for tumor targeting imaging. O-phenanthroline method was used to determine iron content in rats' plasma and mice's organs following high and low doses of nanoparticles injected through tail vein, and the blood concentration-time curve was drawn, the calculated t1/2 of two groups were greater than 7 h. The results of tissue distribution showed that only a small part of nanoparticles were swallowed by the liver and spleen, while none in the heart, lung and kidney. At the same times, the phagocytosis of nanoparticles did not change with the dose. The results of MRI showed that renal excretion occurred 4 hours after injection, and signal to noise ratio (SNR) of liver and kidney returned to normal levels 24 hours after injection. There were no nanoparticles in the lungs. So a part of nanoparticles escaped from phagocytosis of liver and spleen, and it owned lower toxicity and longer half-life. indicated its use for tumor-targeting imaging. All of these indicated its use for tumor-targeting imaging. PMID:22010356

Gao, Wen-Hui; Liu, Shi-Ting; Fan, Cai-Xia; Qi, Lin-Yan; Chen, Zhi-Liang

2011-07-01

116

Magnetocaloric effect in ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

A comparative study of the magnetocaloric effect (MCE) is reported in two different types of chemically synthesized magnetic nanoparticle systems—cobalt ferrite and manganese zinc ferrite with mean size around 5 and 15 nm, respectively. While CoFe2O4 nanoparticles were synthesized using co-precipitation, the Mn0.68Zn0.25Fe2.07O4 (MZFO) nanoparticles were prepared by reverse micelle technique using AOT as surfactant. Our results indicate that the change in entropy with the change in applied magnetic field (dS/dH) is reasonably large for this class of nanoparticles and has a wide distribution over a broad temperature range covering the region above and below the blocking temperature. The maximum entropy change is influenced by the particle size, overall distribution in anisotropy and magnetic moments.

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

2006-12-01

117

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

PubMed

We report that ultra-small, monodisperse, water-dispersible magnetite (Fe(3)O(4)) nanoparticles can be synthesized by a facile one-pot approach using trisodium citrate as crystal grain growth inhibitor and stabilizer in polyol solution. The resultant Fe(3)O(4) nanoparticles exhibit an excellent long-term colloidal stability in various buffer solutions without any modification. They are also superparamagnetic at room temperature and their magnetic property relies heavily on their size. Due to the low magnetization and good water-dispersibility, the 1.9 nm-sized Fe(3)O(4) nanoparticles reveal a low r(2)/r(1) ratio of 2.03 (r(1) = 1.415 mM(-1) s(-1), r(2) = 2.87 mM(-1) s(-1)), demonstrating that they can be efficient T(1) contrast agents. On the other hand, because of the excellent magnetic responsivity, the 13.8 nm-sized Fe(3)O(4) nanoparticles can be readily modified with nitrilotriacetic acid and used to separate the protein simply with the assistance of a magnet. In addition, these Fe(3)O(4) nanoparticles may be useful in other fields, such as hyperthermia treatment of cancer and targeted drug delivery based on their size-dependent magnetic property and excellent stability. PMID:23385623

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

2013-02-06

118

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

119

Magnetic properties of iron-oxide and (iron, cobalt)-oxide nanoparticles synthesized in polystyrene resin matrix  

Microsoft Academic Search

A sulfonated polystyrene resin matrix was ion exchanged with aqueous solutions of (1) FeCl2, (2) FeCl3, (3) 2FeCl2:FeCl3, (4) 9FeCl2:CoCl2, and (5) 4FeCl2:CoCl2 to prepare magnetic nanoparticles of varying size. The samples were characterized by X-ray diffraction (XRD), 57Fe Mossbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), and identify two major phases: ?-Fe2O3, CoFe2O4, and perhaps a

R. Naik; E. Kroll; D. Rodak; G. M. Tsoi; E. McCullen; L. E. Wenger; R. Suryanarayanan; V. M. Naik; P. P. Vaishnava; Qu Tao; P. Boolchand

2004-01-01

120

Fabrication of superparamagnetic and ferromagnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Monodisperse magnetic nanoparticles with controlled size and geometry have drawn great attention in the last decade for fundamental scientific studies and for their potential applications in advanced materials and devices such as ultra-high-density magnetic recording media, exchange-coupled nanocomposite magnets, biomedicines and nanodevices. This dissertation focuses on the fabrication and characterization of superparamagnetic and ferromagnetic nanoparticles of hard magnetic materials (FePt, SmCo5, Sm2Co 17, and Nd2Fe14B) and soft magnetic materials (CoFe2O4, NiFe2O4, and FeCo). Novel preparation techniques, including salt-matrix annealing, surfactant-assisted ball milling and magnetic field milling have been adopted in this study. The FePt nanocrystals, with a variety of morphologies, including nanowires, nanorods, spherical nanoparticles, nanocubes, and nanosized multi-pods, were synthesized by a polyol reduction process. The size and shape control was achieved by adjusting synthesis parameters. The as-synthesized FePt nanocrystals have chemically disordered fcc structure and are superparamagnetic at room temperature. Upon heat treatment, the nanoparticles were transformed into hard magnetic films with ordered fct structure, and high coercivity up to 25 kOe was achieved. Monodisperse L10 FePt nanoparticles from 3 to 15 nm were prepared by a salt-matrix annealing technique. Size dependent phase transition and chemical ordering of FePt nanoparticles were also systematically investigated. Magnetic properties of L1 0 FePt nanoparticles including magnetization and coercivity are strongly dependent on both the particle size and the chemical ordering and increase with particle diameter. The giant coercivity up to 35 kOe was achieved for 8 nm L10 FePt nanoparticles with faceted shape. Monodisperse CoFe2O4 and NiFe2O 4 nanoparticles of different sizes ranging from 3 to 20 nm were also synthesized by a polyol reduction process. Air-stable FeCo nanoparticles with controllable particle size and narrow size distribution were prepared by reductive salt-matrix annealing of CoFe2O4 nanoparticles. Size and temperature dependent magnetic properties of CoFe2O4, NiFe2O4, and FeCo have been reported. Sm2Co17, SmCo5, and Nd2Fe 14B nanoparticles with narrow size distribution were fabricated by high energy ball milling in the presence of surfactants and followed by subsequent size selection process. Significant room-temperature coercivity up to 3.2 kOe was achieved with the Sm2Co17 nanoparticles of an average size of ˜ 20 nm. Nd2Fe14B and Sm2Co 17 sub-micron particles were also prepared by ball milling in a magnetic field. Particles milled in a magnetic field, consisting of nano-sized grains, exhibit strong magnetic anisotropy compared with the particles milled without a magnetic field.

Poudyal, Narayan

121

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

PubMed

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

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

2012-03-21

122

Silica-dendrimer core-shell microspheres with encapsulated ultrasmall palladium nanoparticles: efficient and easily recyclable heterogeneous nanocatalysts.  

PubMed

We report the synthesis, characterization, and catalytic properties of novel monodisperse SiO(2)@Pd-PAMAM core-shell microspheres containing SiO(2) microsphere cores and PAMAM dendrimer-encapsulated Pd nanoparticle (Pd-PAMAM) shells. First, SiO(2) microspheres, which were prepared by the Stöber method, were functionalized with vinyl groups by grafting their surfaces with vinyltriethoxysilane (VTS). The vinyl groups were then converted into epoxides by using m-chloroperoxybenzoic acid. Upon treatment with amine-terminated G4 poly(amidoamine) (PAMAM) dendrimers, the SiO(2)-supported epoxides underwent ring-opening and gave SiO(2)@PAMAM core-shell microspheres. Pd nanoparticles within the cores of the SiO(2)-supported PAMAM dendrimers were synthesized by letting Pd(II) ions complex with the amine groups in the cores of the dendrimers and then reducing them into Pd(0) with NaBH(4). This produced the SiO(2)@Pd-PAMAM core-shell microspheres. The presence of the different functional groups on the materials was monitored by following the changes in FTIR spectra, elemental analyses, and weight losses on thermogravimetric traces. Transmission electron microscopy (TEM) images showed the presence of Pd nanoparticles with average size of 1.56 ± 0.67 nm on the surface of the monodisperse SiO(2)@Pd-PAMAM core-shell microspheres. The SiO(2)@Pd-PAMAM core-shell microspheres were successfully used as an easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto, and nitro groups, giving ~100% conversion and high turnover numbers (TONs) under 10 bar H(2) pressure, at room temperature and in times ranging from 10 min to 3 h. In addition, the SiO(2)@Pd-PAMAM core-shell microspheres were proven to be recyclable catalysts up to five times with barely any leaching of palladium into the reaction mixture. PMID:21951192

Biradar, Ankush V; Biradar, Archana A; Asefa, Tewodros

2011-11-08

123

Magnetic properties of Co-ferrite-doped hydroxyapatite nanoparticles having a core/shell structure  

NASA Astrophysics Data System (ADS)

The magnetic properties of Co-ferrite-doped hydroxyapatite (HAP) nanoparticles of composition Ca10-3xFe2xCox(PO4)6(OH)2 (where x=0, 0.1, 0.2, 0.3, 0.4 and 0.5% mole) are studied. Transmission electron microscope micrograms show that the 90 nm size nanoparticles annealed at 1250 °C have a core/shell structure. Their electron diffraction patterns show that the shell is composed of the hydroxyapatite and the core is composed of the Co-ferrite, CoFe2O4. Electron spin resonance measurements indicate that the Co2+ ions are being substituted into the Ca(1) sites in HAP lattice. X-ray diffraction studies show the formation of impurity phases as higher amounts of the Fe3+/Co2+ ions which are substituted into the HAP host matrix. The presence of two sextets (one for the A-site Fe3+ and the other for the B-site Fe3+) in the Mössbauer spectrum for all the doped samples clearly indicates that the CoFe2O4.cores are in the ferromagnetic state. Evidence of the impurity phases is seen in the appearance of doublet patterns in the Mössbauer spectrums for the heavier-doped (x=0.4 and 0.5) specimens. The decrease in the saturation magnetizations and other magnetic properties of the nanoparticles at the higher doping levels is consistent with some of the Fe3+ and Co2+ which being used to form the CoO and Fe2O3 impurity phase seen in the XRD patterns.

Petchsang, N.; Pon-On, W.; Hodak, J. H.; Tang, I. M.

2009-07-01

124

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

SciTech Connect

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

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

2011-12-31

125

Fabrication and Electrical Measurements of CoFe2O4 Nanopillars in a BiFeO3 matrix  

Microsoft Academic Search

Coupling between ferromagnetic and ferroelectric ordering has recently stimulated many scientific and technological interests. This ``coupling'', would provide an additional degree of freedom in the design of micro and nano-electronic devices such as actuators, transducers, or memories. Unfortunately, the clamping effect of the substrate negates any such magnetoelectric coupling through elastic interactions which evident in a multilayer structures. Therefore our

Scott Rutherford; Rasmi Das; Xianglin Ke; Dmitry Ruzmetov; Dong-Min Kim; Seung Hyub Baek; Mark Rzchowski; Chang-Beom Eom

2006-01-01

126

On the formation of CoFe 2O 4 when drilling hematite with WC–Co drill bit inserts  

Microsoft Academic Search

It is commonly observed that WC–Co drill bit inserts wear more rapidly when drilling hematite ore than when drilling other ores of comparable hardness, e.g. ores that contain high percentages of SiO2. This investigation was carried out to assess if chemical wear is part of the wear process of these inserts, i.e. if chemical reactions occur between hematite (?-Fe2O3) and

C. Banganayi; A. F. Mulaba-Bafubiandi; S. Luyckx

2006-01-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

128

Magnetic properties of iron-oxide and (iron, cobalt)-oxide nanoparticles synthesized in polystyrene resin matrix  

NASA Astrophysics Data System (ADS)

A sulfonated polystyrene resin matrix was ion exchanged with aqueous solutions of (1) FeCl2, (2) FeCl3, (3) 2FeCl2:FeCl3, (4) 9FeCl2:CoCl2, and (5) 4FeCl2:CoCl2 to prepare magnetic nanoparticles of varying size. The samples were characterized by X-ray diffraction (XRD), 57Fe Mossbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), and identify two major phases: ?-Fe2O3, CoFe2O4, and perhaps a minor Fe3O4 phase. SQUID magnetometry measurements indicate superparamagnetic particles with blocking temperatures (TB) ranging from 20K to room temperature.

Naik, R.; Kroll, E.; Rodak, D.; Tsoi, G. M.; McCullen, E.; Wenger, L. E.; Suryanarayanan, R.; Naik, V. M.; Vaishnava, P. P.; Tao, Qu; Boolchand, P.

2004-05-01

129

Spin-flop transition, magnetic and microwave absorption properties of ?-Fe2O4 spinel type ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

We have prepared NiFe2O4, CoFe2O4, Ni0.6Zn0.4Fe2O4 and ZnFe2O4 spinel type ferrite nanoparticles by surfactant-assisted hydrothermal process using cetyltrimethylammonium bromide (CTAB). The spin-flop transition, magnetic, dielectric and permittivity characterizations have been investigated. The spin-flop transition occurs from antiferromagnetic state to mixed state and then ferromagnetic state for Zn doped samples. The spin-flop transition occurs in the temperature range of 50-250 K. The ionic conduction, dipolar relaxation, atomic polarization and electronic polarization are the main mechanisms that contribute to the permittivity of a dielectric material. The permittivity increases with increasing frequency. This suggests a resonance behavior, which is expected when the ferrite samples are highly conductive and skin effect become significant. These samples will provide great benefits for electromagnetic applications and electromagnetic interference shielding characteristics.

Yalç?n, Orhan; Bayrakdar, Harun; Özüm, Songül

2013-10-01

130

Facile syntheses of monodisperse ultrasmall Au clusters.  

PubMed

During our effort to synthesize the tetrahedral Au20 cluster, we found a facile synthetic route to prepare monodisperse suspensions of ultrasmall Au clusters AuN (N < 12) using diphosphine ligands. In our monophasic and single-pot synthesis, a Au precursor ClAu(I)PPh3 (Ph = phenyl) and a bidentate phosphine ligand P(Ph)2(CH2)(M)P(Ph)2 are dissolved in an organic solvent. Au(I) is reduced slowly by a borane-tert-butylamine complex to form Au clusters coordinated by the diphosphine ligand. The Au clusters are characterized by both high-resolution mass spectrometry and UV-vis absorption spectroscopy. We found that the mean cluster size obtained depends on the chain length M of the ligand. In particular, a single monodispersed Au11 cluster is obtained with the P(Ph)2(CH2)3P(Ph)2 ligand, whereas P(Ph)2(CH2)(M)P(Ph)2 ligands with M = 5 and 6 yield Au10 and Au8 clusters. The simplicity of our synthetic method makes it suitable for large-scale production of nearly monodisperse ultrasmall Au clusters. It is suggested that diphosphines provide a set of flexible ligands to allow size-controlled synthesis of Au nanoparticles. PMID:17064088

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

2006-11-01

131

Enigmatic, ultrasmall, uncultivated Archaea  

PubMed Central

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

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

132

Enigmatic, ultrasmall, uncultivated Archaea  

SciTech Connect

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

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

2010-01-01

133

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

PubMed Central

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

2011-01-01

134

Synthesis and magnetic behavior of silica-coated cobalt ferrite hollow spheres  

NASA Astrophysics Data System (ADS)

We have used functional polymer poly(methyl methacrylate-co-methacrylic acid) latex (500 nm) as a core template to prepare magnetic hollow SiO2/CoFe2O4 spheres. The mean crystallite sizes of coated CoFe2O4 nanoparticles, depending on the calcined temperature, are in the range from 2.2 to 10.1 nm. The thickness of the CoFe2O4/SiO2 composite shell is between 40 and 50 nm and the content of CoFe2O4 in the composites is 73 wt %. The magnetic properties of the hollow spherical particles can go from superparamagnetic to ferromagnetic behavior depending on the sizes of CoFe2O4 nanoparticles.

Lin, Chun-Rong; Wang, Cheng-Chien; Chen, I.-Han

2006-04-01

135

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

NASA Astrophysics Data System (ADS)

Ultra-small gadolinium oxide (Gd2O3) can be used as T1-weighted Magnetic Resonance Imaging (MRI) contrast agent own to its high longitudinal relaxivity (r1) and has attracted intensive attention in these years. In this paper, ultra-small Gd2O3 nanoparticles of 3.8 nm in diameter have been successfully synthesized by a microsecond laser ablating a gadolinium (Gd) target in diethylene glycol (DEG). The growth inhibition effect induced by the large viscosity of DEG makes it possible to synthesize ultra-small Gd2O3 by laser ablation in DEG. The r1 value and T1-weighted MR images are measured by a 3.0 T MRI spectroscope. The results show these nanoparticles with a high r1 value of 9.76 s-1 mM-1 to be good MRI contrast agents. We propose an explanation for the high r1 value of ultra-small Gd2O3 by considering the decreasing factor (surface to volume ratio of the nanoparticles, S/V) and the increasing factor (water hydration number of the Gd3+ on Gd2O3 surface, q), which offer a new look into the relaxivity studies of MRI contrast agents. Our research provides a new approach to preparing ultra-small Gd2O3 of high r1 value by laser ablation in DEG and develops the understanding of high relaxivity of ultra-small Gd2O3 MRI contrast agents.

Luo, Ningqi; Tian, Xiumei; Xiao, Jun; Hu, Wenyong; Yang, Chuan; Li, Li; Chen, Dihu

2013-04-01

136

Pulsed Magneto-motive Ultrasound Imaging Using Ultrasmall Magnetic Nanoprobes  

PubMed Central

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

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

2011-01-01

137

Applications of ultrasmall superparamagnetic iron oxide contrast agents in the MR study of animal models  

Microsoft Academic Search

Ultrasmall superparamagnetic iron oxide nanoparticles have been widely used during the past decade as MR intravascular contrast agents in the study of animal models. Such agents enhance both T1 and T2\\/T2* relaxation, although for animal studies it is the later type of enhancement that is most commonly exploited. Their strong microscopic intravascular susceptibility effect enables the local blood volume distribution

Ed X. Wu; Haiying Tang; Jens H. Jensen

2004-01-01

138

Enhanced Magnetic Properties in Nanoparticle-Filled CNTs  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

139

Giant Magnetioimpedance in Co-Based Amorphous Ribbons Coated in Magnetic Nanoparticles for Biosensing Applications  

NASA Astrophysics Data System (ADS)

Giant magnetoimpedance (GMI) is a large change in the ac impedance of a ferromagnetic conductor subject to a dc magnetic field. It forms the basis for developing highly sensitive magnetic sensors. We report studies aimed at developing GMI as a magnetic biosensing technique. We have investigated the GMI effect and its field sensitivity in Co-based amorphous alloys with and without coated magnetic nanoparticles. Fe3O4 and CoFe2O4 nanoparticles (mean size, 5-10 nm) were patterned onto the ribbon surfaces and the number of particle layers was varied from 10 to 80. The influences of particles size, concentration, and layer thickness on the GMI and field sensitivity have been investigated systematically. The coating of the nanoparticles has been shown to enhance the GMI and field sensitivity, both of which increase with increase of particle concentration and layer thickness. Overall, our studies demonstrate the possibility of using GMI as a magnetic biosensor with high sensitivity for applications in biomolecular detection.

Laurita, N.; Chaturvedi, A.; Stojak, K.; Chandra, S.; Phan, M. H.; Srikanth, H.

2011-03-01

140

Effect of thermal fluctuations in FMR experiments in uniaxial magnetic nanoparticles: Blocked vs. superparamagnetic regimes  

NASA Astrophysics Data System (ADS)

We present ferromagnetic resonance (FMR) experiments on two low-interacting nanoparticle systems: Fe3O4 and CoFe2O4 corresponding to low- and high-anisotropy cases, respectively. The spectra have been interpreted in terms of a phenomenological model which applies to the FMR of nanoparticles. The model includes the effect of thermal fluctuations in the FMR covering the range from the superparamagnetic (low-anisotropy-high-temperature) regime to the high-anisotropy-low-temperature situation. We have been able to explain several simultaneous features observed in the FMR spectra of a system of anisotropic nanoparticles when lowering the temperature that include: a decrease of the resonance field with a simultaneous linewidth increase and intensity reduction. These effects had been previously attributed to the existence of a "blocking-temperature" in the FMR. Our interpretation, however, shows that in a magnetic system with easy axes this FMR response originates in the temperature dependence of the dispersion relation. Also, applying the present model to the FMR within the hysteresis cycle it is possible to reproduce the irreversibilities occurring in the resonance spectra. Comparison of FMR and magnetization measurements show that the characteristic FMR time is not related to the inverse microwave frequency.

De Biasi, E.; Lima, E.; Ramos, C. A.; Butera, A.; Zysler, R. D.

2013-01-01

141

Ultrasmall subwavelength nanorod plasmonic cavity.  

PubMed

We propose an ultrasmall plasmonic cavity consisting of a high-index/low-index dielectric nanorod covered with silver. Full three-dimensional subwavelength confinement of the surface-plasmon polaritons was achieved at the high-index dielectric-silver interface without propagating to the low-index dielectric-silver interface. The numerical simulations showed that the plasmonic mode excited in this cavity has a deep subwavelength mode volume of 0.0038(?/2n)(3) and a quality factor of 1500 at 40 K, and consequently a large Purcell factor of ?2×10(5). Therefore, this plasmonic cavity is expected to be useful for the demonstration of high-efficiency single photon sources or low-threshold lasers in an ultracompact nanophotonic circuit. PMID:21633432

Kang, Ju-Hyung; No, You-Shin; Kwon, Soon-Hong; Park, Hong-Gyu

2011-06-01

142

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

143

Synthesis and magnetic behavior of silica-coated cobalt ferrite hollow spheres  

Microsoft Academic Search

We have used functional polymer poly(methyl methacrylate-co-methacrylic acid) latex (500 nm) as a core template to prepare magnetic hollow SiO2\\/CoFe2O4 spheres. The mean crystallite sizes of coated CoFe2O4 nanoparticles, depending on the calcined temperature, are in the range from 2.2 to 10.1 nm. The thickness of the CoFe2O4\\/SiO2 composite shell is between 40 and 50 nm and the content of

Chun-Rong Lin; Cheng-Chien Wang; I.-Han Chen

2006-01-01

144

Facile Syntheses of Monodisperse Ultra-Small Au Clusters  

SciTech Connect

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

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

2006-11-02

145

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

NASA Astrophysics Data System (ADS)

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

Thomas, Dippong; Zoita, Berinde; Ivan, Pauliuc

2013-05-01

146

Size dependent magnetic and dielectric properties of nano CoFe2O4 prepared by a salt assisted gel-combustion method  

NASA Astrophysics Data System (ADS)

In this communication, we report the preparation and properties of nano-CoFe2O4 by gel combustion in presence of KCl and subsequent heat treatments. The products were characterized by X-ray diffraction, Infrared spectroscopy, and Mössbauer Spectroscopy. Spinel type structure with all Fe in 3+ oxidation states was confirmed from the XRD and Mossbauer spectroscopy. The average crystallite sizes of the studied samples were about 6 and 50 nm. Low temperature magnetic and dielectric properties of the samples were studied by superconducting quantum interference device magnetometry and ac-impedance spectroscopy. The field and temperature dependent magnetization studies indicated superparamagnetic nature for 6 nm sample and ferromagnetic nature for 50 nm sample. The temperature-dependent dielectric properties measured over a wide range of frequencies indicated an increasing trend of dielectric permittivity with the decrease in crystallite size. Variable range polaron hopping conduction was observed in both samples.

Vasundhara, K.; Achary, S. N.; Deshpande, S. K.; Babu, P. D.; Meena, S. S.; Tyagi, A. K.

2013-05-01

147

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

Microsoft Academic Search

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

G. C Sih; Z. F Song

2003-01-01

148

Ultrasmall near-infrared gold nanoclusters for tumor fluorescence imaging in vivo  

NASA Astrophysics Data System (ADS)

In this paper, we explore the possibility of using ultrasmall near-infrared (NIR) gold nanoclusters (AuNCs) as novel contrast imaging agents for tumor fluorescence imaging in vivo. The fluorescence imaging signal of the tail vein administrated AuNCs in living organisms can spectrally be well distinguished from the background with maximum emission wavelength at about 710 nm, and the high photostability of AuNCs promises continuous imaging in vivo. The uptake of AuNCs by the reticuloendothelial system is relatively low in comparison with other nanoparticle-based contrast imaging agents due to their ultrasmall hydrodynamic size (~2.7 nm). Through the body weight change analysis, the results show that the body weight of the mice administrated with AuNCs has not been changed obviously in comparison with that of the control mice injected with PBS. Furthermore, using MDA-MB-45 and Hela tumor xenograft models, in vivo and ex vivo imaging studies show that the ultrasmall NIR AuNCs are able to be highly accumulated in the tumor areas, thanks to the enhanced permeability and retention (EPR) effects. And the tumor-to-background ratio is about 15 for 6 h postinjection. The results indicate that the ultrasmall NIR AuNCs appear as very promising contrast imaging agents for in vivo fluorescence tumor imaging.

Wu, Xu; He, Xiaoxiao; Wang, Kemin; Xie, Can; Zhou, Bing; Qing, Zhihe

2010-10-01

149

Ultrasmall near-infrared gold nanoclusters for tumor fluorescence imaging in vivo.  

PubMed

In this paper, we explore the possibility of using ultrasmall near-infrared (NIR) gold nanoclusters (AuNCs) as novel contrast imaging agents for tumor fluorescence imaging in vivo. The fluorescence imaging signal of the tail vein administrated AuNCs in living organisms can spectrally be well distinguished from the background with maximum emission wavelength at about 710 nm, and the high photostability of AuNCs promises continuous imaging in vivo. The uptake of AuNCs by the reticuloendothelial system is relatively low in comparison with other nanoparticle-based contrast imaging agents due to their ultrasmall hydrodynamic size (?2.7 nm). Through the body weight change analysis, the results show that the body weight of the mice administrated with AuNCs has not been changed obviously in comparison with that of the control mice injected with PBS. Furthermore, using MDA-MB-45 and Hela tumor xenograft models, in vivo and ex vivo imaging studies show that the ultrasmall NIR AuNCs are able to be highly accumulated in the tumor areas, thanks to the enhanced permeability and retention (EPR) effects. And the tumor-to-background ratio is about 15 for 6 h postinjection. The results indicate that the ultrasmall NIR AuNCs appear as very promising contrast imaging agents for in vivo fluorescence tumor imaging. PMID:20835443

Wu, Xu; He, Xiaoxiao; Wang, Kemin; Xie, Can; Zhou, Bing; Qing, Zhihe

2010-09-08

150

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

NASA Astrophysics Data System (ADS)

Dimercaptosuccinic acid (DMSA) modified ultra-small particles of iron oxide (USPIO) were synthesized through a two-step process. The first step: oleic acid (OA) capped Fe3O4 (OA-USPIO) were synthesized by a novel oxidation coprecipitation method in H2O/DMSO mixing system, where DMSO acts as an oxidant simultaneously. The second step: OA was replaced by DMSA to obtain water-soluble nanoparticles. The as-synthesized nanoparticles were characterized by TEM, FTIR, TGA, VSM, DLS, EDS and UV-vis. Hydrodynamic sizes and Peroxidase-like catalytic activity of the nanoparticles were investigated. The hydrodynamic sizes of the nanoparticles (around 24.4 nm) were well suited to developing stable nanoprobes for bio-detection. The kinetic studies were performed to quantitatively evaluate the catalytic ability of the peroxidase-like nanoparticles. The calculated kinetic parameters indicated that the DMSA-USPIO possesses high catalytic activity. Based on the high activity, immunohistochemical experiments were established: using low-cost nanoparticles as the enzyme instead of expensive HRP, Nimotuzumab was conjugated onto the surface of the nanoparticles to construct a kind of ultra-small nanoprobe which was employed to detect epidermal growth factor receptor (EGFR) over-expressed on the membrane of esophageal cancer cell. The proper sizes of the probes and the result of membranous immunohistochemical staining suggest that the probes can be served as a useful diagnostic reagent for bio-detection.

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

2011-06-01

151

Fabrication and microwave absorption of carbon nanotubes/CoFe2O4 spinel nanocomposite  

NASA Astrophysics Data System (ADS)

A large-scale carbon nanotube/CoFe2O4 (CNTs/CoFe2O4) spinel nanocomposite has been fabricated by a chemical vapor deposition method using CoFe2O4 nanoparticles as catalysts. A uniform mixture of CNTs and CoFe2O4 nanoparticles was obtained simultaneously. The structure and chemical composition of the product were investigated using various techniques, such as x-ray diffraction, high-resolution transmission electron microscopy, and electron energy loss spectroscopy. It was found that the particles functionalized on CNTs were cubic phase CoFe2O4. Microwave absorption of the CNT/CoFe2O4 nanocomposites at 2-18 GHz is evidently enhanced, as compared with that of both pure CNTs and CoFe2O4 nanoparticles. The enhancement mechanism is discussed based on magnetization hysteresis loop measurement and electromagnetic theory.

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

2006-01-01

152

DNA base (cytosine) modified/capped ultrasmall Gd2S3:Eu3+ gadofluoroprobes for platelet isolation  

NASA Astrophysics Data System (ADS)

The present letter deals with the synthesis of ultrasmall Gd2S3:Eu3+ nanoparticles and their surface modification with ``cytosine,'' a nucleobase present in DNA/RNA. These nanoparticles show orthorhombic (Pnma) crystal symmetry with excellent magnetic and luminescent characters simultaneously. In contrast to the previous reports, cytosine modified nanoparticles do not show a significant change in their structural and magnetic properties, whereas luminescence is enhanced slightly owing to the surface passivation. The in vitro studies show better accumulation of blood platelets with cytosine modified nanoparticles as compared to unmodified posing them a potential candidate for platelet isolation from the plasma for different applications and studies.

Dutta, Ranu K.; Sharma, Prashant K.; Pandey, Avinash C.

2010-12-01

153

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

PubMed Central

The nanotechnology capable of high-specificity targeted delivery of anti-neoplastic drugs would be a significant breakthrough in Cancer in general and Ovarian Cancer in particular. We addressed this challenge through a new physical concept that exploited (i) the difference in the membrane electric properties between the tumor and healthy cells and (ii) the capability of magneto-electric nanoparticles (MENs) to serve as nanosized converters of remote magnetic field energy into the MENs' intrinsic electric field energy. This capability allows to remotely control the membrane electric fields and consequently trigger high-specificity drug uptake through creation of localized nano-electroporation sites. In in-vitro studies on human ovarian carcinoma cell (SKOV-3) and healthy cell (HOMEC) lines, we applied a 30-Oe d.c. field to trigger high-specificity uptake of paclitaxel loaded on 30-nm CoFe2O4@BaTiO3 MENs. The drug penetrated through the membrane and completely eradicated the tumor within 24 hours without affecting the normal cells.

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

2013-01-01

154

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

PubMed

The nanotechnology capable of high-specificity targeted delivery of anti-neoplastic drugs would be a significant breakthrough in Cancer in general and Ovarian Cancer in particular. We addressed this challenge through a new physical concept that exploited (i) the difference in the membrane electric properties between the tumor and healthy cells and (ii) the capability of magneto-electric nanoparticles (MENs) to serve as nanosized converters of remote magnetic field energy into the MENs' intrinsic electric field energy. This capability allows to remotely control the membrane electric fields and consequently trigger high-specificity drug uptake through creation of localized nano-electroporation sites. In in-vitro studies on human ovarian carcinoma cell (SKOV-3) and healthy cell (HOMEC) lines, we applied a 30-Oe d.c. field to trigger high-specificity uptake of paclitaxel loaded on 30-nm CoFe2O4@BaTiO3 MENs. The drug penetrated through the membrane and completely eradicated the tumor within 24 hours without affecting the normal cells. PMID:24129652

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

2013-10-16

155

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

NASA Astrophysics Data System (ADS)

The nanotechnology capable of high-specificity targeted delivery of anti-neoplastic drugs would be a significant breakthrough in Cancer in general and Ovarian Cancer in particular. We addressed this challenge through a new physical concept that exploited (i) the difference in the membrane electric properties between the tumor and healthy cells and (ii) the capability of magneto-electric nanoparticles (MENs) to serve as nanosized converters of remote magnetic field energy into the MENs' intrinsic electric field energy. This capability allows to remotely control the membrane electric fields and consequently trigger high-specificity drug uptake through creation of localized nano-electroporation sites. In in-vitro studies on human ovarian carcinoma cell (SKOV-3) and healthy cell (HOMEC) lines, we applied a 30-Oe d.c. field to trigger high-specificity uptake of paclitaxel loaded on 30-nm CoFe2O4@BaTiO3 MENs. The drug penetrated through the membrane and completely eradicated the tumor within 24 hours without affecting the normal cells.

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

2013-10-01

156

Magnetic order in two-dimensional nanoparticle assemblies  

NASA Astrophysics Data System (ADS)

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.

Georgescu, M.

2008-12-01

157

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

NASA Astrophysics Data System (ADS)

Ferrofluids are colloidal systems composed of a single domain of magnetic nanoparticles with a mean diameter around 30 nm, dispersed in a liquid carrier. Magnetic Co(1-x)ZnxFe2O4 (x=0.25, 0.50, 0.75) ferrite nanoparticles were prepared via co-precipitation method from aqueous salt solutions in an alkaline medium. The composition and structure of the samples were characterized through Energy Dispersive X-ray Spectroscopy and X-ray diffraction, respectively. Transmission Electron Microscopy (TEM) studies permitted determining nanoparticle size; grain size of nanoparticle conglomerates was established via Atomic Force Microscopy. The magnetic behavior of ferrofluids was characterized by Vibrating Sample Magnetometer (VSM); and finally, a magnetic force microscope was used to visualize the magnetic domains of Co(1-x)ZnxFe2O4 nanoparticles. X-ray diffraction patterns of Co(1-x)ZnxFe2O4 show the presence of the most intense peak corresponding to the (311) crystallographic orientation of the spinel phase of CoFe2O4. Fourier Transform Infrared Spectroscopy confirmed the presence of the bonds associated to the spinel structures; particularly for ferrites. The mean size of the crystallite of nanoparticles determined from the full-width at half maximum of the strongest reflection of the (311) peak by using the Scherrer approximation diminished from (9.5±0.3) nm to (5.4±0.2) nm when the Zn concentration increases from 0.21 to 0.75. The size of the Co-Zn ferrite nanoparticles obtained by TEM is in good agreement with the crystallite size calculated from X-ray diffraction patterns, using Scherer's formula. The magnetic properties investigated with the aid of a VSM at room temperature presented super-paramagnetic behavior, determined by the shape of the hysteresis loop. In this study, we established that the coercive field of Co(1-x)ZnxFe2O4 magnetic nanoparticles, the crystal and nanoparticle sizes determined by X-ray Diffraction and TEM, respectively, decrease with the increase of the Zn at%. Finally, our magnetic nanoparticles are not very hard magnetic materials given that the hysteresis loop is small and for this reason Co(1-x)ZnxFe2O4 nanoparticles are considered as soft magnetic material.

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

2012-02-01

158

Influence of cobalt on structural and magnetic properties of nickel ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

Improving the magnetic response of nanocrystalline nickel ferrites is the key issue in high density recording media. A series of cobalt substituted nickel ferrite nanoparticles with composition Ni(1?x)CoxFe2O4, where 0.0 ? x ? 1.0, are synthesized using co-precipitation method. The XRD spectra revealed the single phase spinel structure and the average sizes of nanoparticles are estimated to be 16–19 nm. These sizes are small enough to achieve the suitable signal to noise ratio in the high density recording media. The lattice parameter and coercivity shows monotonic increment with the increase of Co contents ascribed to the larger ionic radii of the cobalt ion. The specific saturation magnetization (Ms), remanent magnetization (Mr) and the coercivity (Hc) of the spinel ferrites are further improved by the substitutions of Co+2 ions. The values of Ms for NiFe2O4 and CoFe2O4 are found to be 43.92 and 78.59 emu/g, respectively and Hc are in the range of 51–778 Oe. The FTIR spectra of the spinel phase calcinated at 600 °C exhibit two prominent fundamental absorption bands in the range of 350–600 cm?1 assigned to the intrinsic stretching vibrations of the metal at the tetrahedral and octahedral sites. The role played by the Co ions in improving the structural and magnetic properties are analyzed and understood. Our simple, economic and environmental friendly preparation method may contribute towards the controlled growth of high quality ferrite nanopowders, potential candidates for recording.

Ati, Ali A.; Othaman, Zulkafli; Samavati, Alireza

2013-11-01

159

Ultrasmall spot size scanning laser ophthalmoscopy  

PubMed Central

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

Vohnsen, Brian; Rativa, Diego

2011-01-01

160

Ultrasmall spot size scanning laser ophthalmoscopy.  

PubMed

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

Vohnsen, Brian; Rativa, Diego

2011-05-18

161

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

NASA Astrophysics Data System (ADS)

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.

Davis, Lloyd; Orfield, Noah; Rosenthal, Sandra

2013-03-01

162

Thermodynamics and Dynamics of Physically Restricted Ultrasmall  

NASA Astrophysics Data System (ADS)

To understand the thermodynamics and dynamics of physically restricted ultrasmall systems and to discern the relative role of the physical restriction of the sample size from that of the surface-fluid interaction on the structural and thermodynamic properties of the confined fluids, we undertook the specific heat and molecular vibrational measurements of cyclohexane physically restricted in well -defined porous silica glasses and of geometrically confined cyclohexane films. Our specific heat results showed that both solid -to-solid (monoclinic-to-cubic) structural transition and solid melting transition temperatures were depressed. The amount of the temperature depression for the both phase transitions, i.e., solid-to-solid and melting, inversely scaled with the pore radius (R_{rm p}). It is argued that the surface heterogeneity, the presence of hydroxyl groups, and the radius of curvature led to the nucleation of crystalline grains of various sizes rather than a single plug. The observation of the lambda-shaped specific heat anomaly also suggested the multigrain formation model. With our developed lithographic techniques, we have measured ultrathin (20 nm) film via a vibrational (FTIR) approach. For the first time, a new metastable phase was manifested when the system was cooled. The results can be explained with the theoretical predictions. Molecular vibrational investigation of cyclohexane physically restricted in filled and partially filled pores of controlled pore glass showed there are indeed two distinct types of cyclohexane in the porous silica, idle and non -idle cyclohexane molecules. In addition, the temperature dependent linewidth of the cyclohexane in the filled silica pores also suggested the existence of a diffuse layer between the idle and the non-idle layers, which exhibited unique temperature dependent characteristics.

Mu, Rixiang

163

Quantum Transport in Systems of Ultrasmall Tunnel Junctions  

Microsoft Academic Search

We have measured the current-voltage characteristics of a system of two ultrasmall (<100 nm diameter) metallic tunnel junctions connected in series. At low temperatures, the transport of electrons through this system is strongly affected by the electrostatic energy of a single excess electron on the submicron \\

Travis Matthew Eiles

1993-01-01

164

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

PubMed

?This paper reports on the advancement of magnetic ionic liquids (MILs) as stable dispersions of surface-modified ?-Fe(2)O(3), Fe(3)O(4), and CoFe(2)O(4) magnetic nanoparticles (MNPs) in a hydrophobic ionic liquid, 1-n-butyl 3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf(2)). The MNPs were obtained via coprecipitation and were characterized using powder X-ray diffraction, transmission electron microscopy, Raman spectroscopy and Fourier transform near-infrared (FT-NIR) spectroscopy, and magnetic measurements. The surface-modified MNPs (SM-MNPs) were obtained via the silanization of the MNPs with the aid of 1-butyl-3-[3-(trimethoxysilyl)propyl]imidazolium chloride (BMSPI.Cl). The SM-MNPs were characterized by Raman spectroscopy and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and by magnetic measurements. The FTIR-ATR spectra of the SM-MNPs exhibited characteristic absorptions of the imidazolium and those of the Fe-O-Si-C moieties, confirming the presence of BMSPI.Cl on the MNP surface. Thermogravimetric analysis (TGA) showed that the SM-MNPs were modified by at least one BMSPI.Cl monolayer. The MILs were characterized using Raman spectroscopy, differential scanning calorimetry (DSC), and magnetic measurements. The Raman and DSC results indicated an interaction between the SM-MNPs and the IL. This interaction promotes the formation of a supramolecular structure close to the MNP surface that mimics the IL structure and is responsible for the stability of the MIL. Magnetic measurements of the MILs indicated no hysteresis. Superparamagnetic behavior and a saturation magnetization of ~22 emu/g could be inferred from the magnetic measurements of a sample containing 50% w/w ?-Fe(2)O(3) SM-MNP/BMI.NTf(2). PMID:22966984

Medeiros, Anderson M M S; Parize, Alexandre L; Oliveira, Vanda M; Neto, Brenno A D; Bakuzis, Andris F; Sousa, Marcelo H; Rossi, Liane M; Rubim, Joel C

2012-09-24

165

Ultrasmall square-lattice zero-cell photonic crystal laser  

NASA Astrophysics Data System (ADS)

We report optically pumped room-temperature lasing in a square-lattice photonic crystal cavity consisting of two shifted lattice points and heterogeneous lattices with different air hole sizes. Three-dimensional finite-difference time-domain simulation shows that this cavity has an ultrasmall mode volume of 0.017 ?m3 ~1.7 (?/2nslab)3. Photoluminescence spectroscopy exhibits pulsed lasing action at 1511 nm with a low lasing threshold of ~130 ?W. The measured Q factor is ~2400 that is well agreed with the theoretical Q of 4200. In addition, the computational analysis based on the actual fabricated structural parameters unambiguously presents the successful demonstration of this ultrasmall lasing mode.

Ee, Ho-Seok; Jeong, Kwang-Yong; Seo, Min-Kyo; Lee, Yong-Hee; Park, Hong-Gyu

2008-07-01

166

Ultra-small photonic crystal zero-cell laser cavities  

NASA Astrophysics Data System (ADS)

We investigate optical characteristics of the ultra-small zero-cell cavities that consist of two, four and three shifted lattice points in square- and triangular-lattice photonic crystal structures. Mode volumes and Q factors of these cavities are systematically studied using three-dimensional finite-difference-time-domain simulation. In particular, an extremely small mode volume of ~0.015 ?m3 [~1.5 (?/2nslab)3] is obtained in the triangular-lattice three-hole-shifted cavity. In an experiment, we demonstrate optically pumped room-temperature lasing action with a low lasing threshold of ~130 ?W in a square-lattice two-hole-shifted cavity. The operation of this ultra-small laser is unambiguously confirmed by the numerical simulation based on the actual fabricated structures.

Ee, Ho-Seok; Park, Hong-Gyu

2009-02-01

167

Ultrasmall metal nanoclusters for bio-related applications.  

PubMed

The study of ultrasmall metal nanoclusters (NCs, ranging from subnanometer to ca 2?nm) is evidently a quickly evolving field in current nanoscience and nanotechnology research. Metal NCs, typically composed of several to hundreds of metal atoms, have attracted great interest in recent years owing to their unique properties including ultrasmall size and enhanced photoluminescence, together with other properties such as excellent photostability, low toxicity, and good biocompatibility desired for biological applications. This review summarizes recent advances in the field of bio-related applications of metal NCs materials. We highlight the applications of metal NCs for biosensor development, fluorescent biological imaging, and biomedical research, and finally discuss briefly some current challenges and future work. WIREs Nanomed Nanobiotechnol 2013, 5:569-581. doi: 10.1002/wnan.1227 Conflict of interest: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website. PMID:23939885

Tan, Xiaohong; Jin, Rongchao

2013-08-12

168

Mössbauer and magnetic studies of MFe 2 O 4 (M=Co, Ni) nanoparticles  

Microsoft Academic Search

Nanocrystalline MFe2O4 (M=Co, Ni) particles are synthesized by citrate precursor technique. Mössbauer and magnetic studies are carried out with\\u000a the CoFe2O4 samples having particle sizes of 9, 14 and 30 nm and the NiFe2O4 samples having particle sizes of 9, 21 and 30 nm. The intrinsic magnetic parameters are found to vary with the particle size.\\u000a The magnetic interactions and

N. S. Gajbhiye; Sayan Bhattacharyya; G. Balaji; R. S. Ningthoujam; Raj Kumar Das; Susmita Basak; J. Weissmüller

169

Bright White Light Emission from Ultrasmall Cadmium Selenide Nanocrystals  

SciTech Connect

A simple treatment method using formic acid has been found to increase the fluorescence quantum yield of ultrasmall white light-emitting CdSe nanocrystals from 8% to 45%. Brighter white-light emission occurs with other carboxylic acids as well, and the magnitude of the quantum yield enhancement is shown to be dependent on the alkyl chain length. Additionally, the nanocrystal luminescence remains enhanced relative to the untreated nanocrystals over several days. This brightened emission opens the possibility for even further quantum yield improvement and potential for use of these white-light nanocrystals in solid-state lighting applications.

Rosson, Teresa [Vanderbilt University; Claiborne, Sarah [Vanderbilt University; McBride, James [Vanderbilt University; Stratton, Benjamin S [Vanderbilt University; Rosenthal, Sandra [ORNL

2012-01-01

170

Capturing Ultrasmall EMT Zeolite from Template-Free Systems  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

172

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

PubMed

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

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

2012-10-21

173

Uniform ultrasmall graphene oxide nanosheets with low cytotoxicity and high cellular uptake.  

PubMed

Graphene oxide (GO) is an increasingly important nanomaterial, which exhibits great promise in the area of bionanotechnology and nanobiomedicine. In this study, we synthesized uniform ultrasmall graphene oxide nanosheets with high yield by a convenient way of modified Hummers' method. The uniform ultrasmall GO nanosheets, which exhibit fluorescence property and outstanding stability in a wide range of pH values, were less than 50 nm. Furthermore, because of the advantages of its lateral size, the uniform ultrasmall GO nanosheets showed excellent biocompatibility of lower cytotoxicity and higher cellular uptake amount compared to the random large GO nanosheets. Therefore, the as-prepared uniform ultrasmall GO nanosheets could be explored as the ideal nanocarriers for drug delivery and intracellular fluorescent nanoprobe. PMID:23402618

Zhang, Huan; Peng, Cheng; Yang, Jianzhong; Lv, Min; Liu, Rui; He, Dannong; Fan, Chunhai; Huang, Qing

2013-03-01

174

Cooper-pair current through ultrasmall Josephson junctions  

SciTech Connect

The current-voltage characteristics of ultrasmall Josephson junctions sensitively depend on the electromagnetic environment of the junction. When the charging energy exceeds the Josephson coupling energy, the usual supercurrent at zero voltage is completely suppressed. However, for typical environmental impedances, which are small compared to the resistance quantum, stochastic Cooper-pair tunneling leads to a supercurrent peak at a small finite voltage which is proportional to the temperature and the low-frequency resistance of the external circuit. An analytic expression for the form of this universal peak, which is independent of the high-frequency behavior of the environment, is given. With increasing Josephson coupling the peak merges into the usual supercurrent of a Josephson junction. At larger voltages the Cooper-pair current depends on details of the environment. Current peaks are shown to result from resonances in the environmental impedance. Specifically, the case of an [ital LC] transmission line of finite length is discussed.

Ingold, G.; Grabert, H. (Fachbereich Physik, Universitaet Essen, D-45117 Essen (Germany)); Eberhardt, U. (Fachbereich Physik, Universitaet Duisburg, D-47048 Duisburg (Germany))

1994-07-01

175

Magnetic Polymer Nanocomposites with Tunable Microwave Properties  

Microsoft Academic Search

Due to the multifunctionality, polymer nanocomposites (PNCs) have potential applications for electromagnetic interference shielding, tunable electromagnetic devices and flexible electronics. We report on synthesis, magnetic and RF characterization of polymer films loaded with varying concentrations of Fe3O4 and CoFe2O4 nanoparticles. The nanoparticles (5 ± 1 nm) were synthesized by chemical co-precipitation. Structural properties were characterized by XRD and TEM. Nanoparticles

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

2010-01-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

177

Nanoparticles for neuroimaging  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

178

Quantum Transport in Systems of Ultrasmall Tunnel Junctions.  

NASA Astrophysics Data System (ADS)

We have measured the current-voltage characteristics of a system of two ultrasmall (<100 nm diameter) metallic tunnel junctions connected in series. At low temperatures, the transport of electrons through this system is strongly affected by the electrostatic energy of a single excess electron on the submicron "island" between the junctions. This phenomenon, known as Coulomb blockade, enables this device to measure very sensitively the charge polarized on it by a gate electrode. The simplicity of the Coulomb blockade electrometer makes it an ideal system for exploring the fundamental tunneling processes of small tunnel junction circuits. The stochastic semiclassical theory of single-electron tunneling predicts much of the observed current; however, there are several higher-order quantum processes responsible for transport in the electrometer. One of these processes is the two-electron "cotunneling" seen in the normal metal (NNN) electrometer at voltages below the single junction tunneling thresholds. Electrons tunnel simultaneously across the two junctions as the energetically -forbidden charge states in the island are virtually occupied. When the island is superconducting, a new effect arises: the energy gap in the quasiparticle spectrum yields the recently observed symmetry-breaking between the superconducting states consisting of an even or odd number of electrons, causing the ground state to be periodic in the gate charge with a period of 2e. We observed the novel two-electron transport mechanism of Andreev reflection at ultrasmall tunnel junctions was observed in a sample with normal metal leads (NSN). Finally, in the all-superconducting (SSS) electrometer, the Josephson effect allows Cooper pairs to tunnel across the junctions. The Josephson coupling energy reduces the ground state energy of the superconducting island by coherently mixing charge states. We observed the resulting 2e-periodic supercurrent which indicates the coherent transport of Cooper pairs through both junctions simultaneously. The charge dependence of this supercurrent agrees with the theory incorporating a charge-phase commutation relation. Shapiro steps were observed upon microwave radiation, proving that the low-voltage current feature was indeed a supercurrent as expected.

Eiles, Travis Matthew

1993-01-01

179

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

PubMed Central

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

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

2012-01-01

180

Magnetic and spectroscopic properties of Polyacrylamide-CoFe2O4 magnetic hydrogel  

NASA Astrophysics Data System (ADS)

This study investigates synthesis and characterization of polyacrylamide (PAAm) hydrogels containing ferromagnetic CoFe2O4 nanoparticles. Structural, electrical, and magnetic characterization of the gels have been performed with X-ray powder diffractometry, Scanning electron microscopy, DC conductivity, magnetization and fluorescence spectroscopy techniques. Fluorescence and electrical measurements show that nanoparticles have trapped in the gel so they cannot move through the gel even if the gel is swollen and the voltage is applied. Pyranine molecules diffuse easily through the gel due to the presence of ferromagnetic nanoparticles. As number of diffused pyranine molecules increases current densities of the magnetic hydrogel increase. Magnetization measurements reveal that CoFe2O4 nanoparticles do not diffuse out of the gel during swelling. As a result, total magnetization of the gel do not change as volume of the gel increases.

Alvero?lu, E.; Sözeri, H.; Kurtan, U.; ?enel, M.; Baykal, A.

2013-03-01

181

Synthesis and characterisation of biologically compatible TiO2 nanoparticles  

PubMed Central

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.

2011-01-01

182

Synthesis and characterisation of biologically compatible TiO2 nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Cheyne, Richard W.; Smith, Tim Ad; Trembleau, Laurent; McLaughlin, Abbie C.

2011-06-01

183

Magnetically Tunable Polymer Nanocomposites for RF and Microwave Device Applications  

Microsoft Academic Search

There has been much interest in polymer nanocomposites (PNC) recently due to potential applications for EMI shielding, tunable electromagnetic devices and flexible electronics. We report synthesis, structural, magnetic and RF characterization on PNCs ranging from 20-80 wt-% loadings of Fe3O4 and CoFe2O4 nanoparticles (˜8nm) in a thermosetting resin from the Rogers Corporation. Nanoparticles were synthesized by thermal decomposition and characterized

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

2011-01-01

184

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

SciTech Connect

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.

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

185

Mössbauer and magnetic studies of MFe 2 O 4 (M?=?Co, Ni) nanoparticles  

Microsoft Academic Search

Nanocrystalline MFe2O4 (M?=?Co, Ni) particles are synthesized by citrate precursor technique. Mssbauer and magnetic studies are carried out with\\u000a the CoFe2O4 samples having particle sizes of 9, 14 and 30 nm and the NiFe2O4 samples having particle sizes of 9, 21 and 30 nm. The intrinsic magnetic parameters are found to vary with the particle size.\\u000a The magnetic interactions and cation distribution

N. S. Gajbhiye; Sayan Bhattacharyya; G. Balaji; R. S. Ningthoujam; Raj Kumar Das; Susmita Basak; J. Weissmüller

2005-01-01

186

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

PubMed Central

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

2011-01-01

187

Comparison of Two Ultrasmall Superparamagnetic Iron Oxides on Cytotoxicity and MR Imaging of Tumors  

PubMed Central

Purpose: This study was performed to compare the cytotoxicity and magnetic resonance (MR) contrast in diverse cultured cells and xenograft tumors models of two ultra-small superparamagnetic iron oxides (USPIOs), thermally cross-linked superparamagnetic iron oxide nanoparticles (TCL-SPION) and monocrystalline iron oxide nanoparticles (MION-47). Materials and methods: Transmission electron microscopy (TEM) images and R2 relaxivity values of the TCL-SPION and MION-47 were obtained and the cell viability and cell growth velocity of treated and untreated human fibroblasts and human umbilical vein endothelial cells (HUVEC) were evaluated. The effect of TCL-SPION and MION-47 on the secretion of interlukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-?), the production of nitric oxides and the mitochondrial membrane potentials in murine macrophage cells (RAW264.7) was compared. Human hepatocellular carcinoma cells (HepG2, 5x105) were subcutaneously injected into nude mice (BALB/c) and in vivo MR imaging of tumors before and after injection with TCL-SPION or MION-47 (12.5 mg Fe/kg) was performed on a 1.5 Tesla MRI scanner. Results: On TEM images, the average core diameter of TCL-SPION was 9 nm whereas that of MION-47 was 5 nm. TCL- SPION (345.0 ± 6.2 mM-1sec-1) had higher relaxivity (R2) than MION-47 (130.7 ± 1.1 mM-1sec-1). Significant changes in cell viability and growth were not found in human fibroblasts and HUVEC exposed to TCL-SPION and MION-47. However, IL-6 and TNF-? secretions increased dose-dependently and significantly in the macrophages treated with MION-47 or TCL-SPION. TCL-SPION had a lower stimulatory effect on IL-6 secretions than did MION-47 (P <0.05) and nitric oxides were produced in the macrophages by MION-47 but not TCL-SPION. A change in the mitochondrial membrane potential of the macrophages was observed 24 hours after the exposure, and MION-47 induced more collapses of the mitochondrial membrane potential than did TCL-SPION. In the in vivo MR imaging, 33.0 ± 1.3% and 7.5 ± 0.4% signal intensity decrease on T2*-weighted images was observed in the tumors injected with TCL-SPION and MION-47, respectively. Conclusion: Due to the modified surface properties and larger core size of its iron oxide nanoparticles, TCL-SPION achieves lower cytotoxicity and better tumor MR contrast than MION-47. Our study suggests that TCL-SPION may be used as a new platform for tumor imaging and therapy monitoring.

Li, Mulan; Kim, Hoe Suk; Tian, Lianji; Yu, Mi Kyung; Jon, Sangyong; Moon, Woo Kyung

2012-01-01

188

Gram-scale synthesis of ultrasmall SnO2 nanocrystals with an excellent electrochemical performance.  

PubMed

The gram-scale synthesis of ultrasmall SnO2 nanocrystals has been successfully realized via a solvothermal process, during which the solvent used plays an important role in inhibiting the growth and aggregation of the nanocrystals. When investigating their electrochemical behaviour, the nanocrystal electrode shows an excellent performance in capacity retention and a better rate capacity. PMID:23483211

Chen, Yuejiao; Ma, Jianmin; Li, Qiuhong; Wang, Taihong

2013-03-13

189

Ultrasmall volume molecular isothermal amplification in microfluidic chip with advanced surface processing  

Microsoft Academic Search

In this paper, we developed a metal micro-fluidic chip with advanced surface processing for ultra-small volume molecular isothermal amplification. This method takes advantages of the nucleic acid amplification with good stability and consistency, high sensitivity about 31 genomic DNA copies and bacteria specific gene identification. Based on the advanced surface processing, the bioreaction assays of nucleic acid amplification was dropped

Guoliang Huang; Li Ma; Xiaoyong Yang; Xu Yang

2011-01-01

190

Electrochemical Oxidation of 5-Hydroxytryptamine and 5-Hydroxyindoleacetic Acid at Ultrasmall Gold Ring Electrodes.  

National Technical Information Service (NTIS)

Ultrasmall gold ring electrodes have been constructed by electrodeposition of gold onto carbon ring electrodes. Electrodes thus formed show similar adsorption/desorption peaks for oxygen in H2SO4 solution compared to those obtained at conventional-sized e...

Y. Y. Lau D. K. Wong G. Luo A. G. Ewing

1991-01-01

191

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

Microsoft Academic Search

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

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

1990-01-01

192

Renormalization-group calculations of ground-state and transport properties of ultrasmall tunnel junctions  

Microsoft Academic Search

We have done a numerical renormalization-group calculation for a Hamiltonian modeling charging effect in ultrasmall tunnel junctions. We find that the conductance is enhanced by the quantum charge fluctuations allowing tunneling below the charging energy gap. However, in all cases the conductance is found to vanish at zero frequency.

H. O. Frota; Karsten Flensberg

1992-01-01

193

Structure and magnetic properties of Co and Ni nano-ferrites prepared by a two step direct microemulsions synthesis  

NASA Astrophysics Data System (ADS)

Nano-particles of CoFe2O4, NiFe2O4 and Co0.5Ni0.5Fe2O4 were synthesized by a two step microemulsion precipitation where inverse micelles of water in hexanol were stabilized using cetyltrimethylammonium bromide. Powder X-ray diffraction analysis and Transmission electron microscopy measurements provided data to clarify the crystal structure and size of the produced nano-particles. Different measurements of magnetic properties at low temperatures of 2 K revealed that nano-particles of NiFe2O4 represent magnetically soft ferrite with a coercivity ˜40 kA/m, whereas nano-particles of CoFe2O4 and Co0.5Ni0.5Fe2O4 were magnetically harder with a coercivity of 815 and 947 kA/m, respectively. Additionally zero field cooling and field cooling measurements provided data for estimating the blocking temperature of the materials produced. For NiFe2O4 this temperature is lower, 23 K. The blocking temperature of CoFe2O4 of 238 K and Co0.5Ni0.5Fe2O4 of 268 K are higher in comparison with NiFe2O4.

Pulišová, P.; Ková?, J.; Voigt, A.; Raschman, P.

2013-09-01

194

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

PubMed

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

Li, Wei; Zhao, Xin; Liu, Shouxin

2013-01-25

195

Comparison of superparamagnetic and ultrasmall superparamagnetic iron oxide cell labeling for tracking green fluorescent protein gene marker with negative and positive contrast magnetic resonance imaging.  

PubMed

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

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

196

Studies on ultrasmall bacteria in relation to the presence of bacteria in the stratosphere  

NASA Astrophysics Data System (ADS)

Recent studies confirm that bacteria exist in the stratosphere. It is generally assumed that these bacteria are exiting from Earth, although it is possible that some are incoming from space. Most stratospheric bacterial isolates belong to the spore-forming genus Bacillus, although non-spore formers have also been isolated. Theoretically, the smaller a bacterium is, the more likely it is to be carried from Earth to the stratosphere. Ultrasmall bacteria have been frequently isolated from Earth environments, but not yet from the stratosphere. This is an anomalous situation, since we would expect such small bacteria to be over represented in the stratosphere-microflora. Here, we show that ultrasmall bacteria are present in the environment on Earth (i.e. in seawater and rainwater) and discuss the paradox of why they have not been isolated from the stratosphere.

Alshammari, Fawaz; Wainwright, Milton; Alabri, Khalid; Alharbi, Sulamain A.

2011-04-01

197

Ultrasmall volume molecular isothermal amplification in microfluidic chip with advanced surface processing  

NASA Astrophysics Data System (ADS)

In this paper, we developed a metal micro-fluidic chip with advanced surface processing for ultra-small volume molecular isothermal amplification. This method takes advantages of the nucleic acid amplification with good stability and consistency, high sensitivity about 31 genomic DNA copies and bacteria specific gene identification. Based on the advanced surface processing, the bioreaction assays of nucleic acid amplification was dropped about 392nl in volume. A high numerical aperture confocal optical detection system was advanced to sensitively monitor the DNA amplification with low noise and high power collecting fluorescence near to the optical diffraction limit. A speedy nucleic acid isothermal amplification was performed in the ultra-small volume microfluidic chip, where the time at the inflexions of second derivative to DNA exponential amplified curves was brought forward and the sensitivity was improved about 65 folds to that of in current 25?l Ep-tube amplified reaction, which indicates a promising clinic molecular diagnostics in the droplet amplification.

Huang, Guoliang; Ma, Li; Yang, Xiaoyong; Yang, Xu

2011-01-01

198

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

PubMed

Ultra-small superparamagnetic particles of iron oxides (USPIO) have been developed as intravenous organ/tissue-targeted contrast agents to improve magnetic resonance imaging (MRI) in vivo. However, their potential toxicity and effects on metabolism have attracted particular attention. In the present study, uncoated and dextran-coated USPIO were investigated by analyzing both rat urine and plasma metabonomes using high-resolution NMR-based metabonomic analysis in combination with multivariate statistical analysis. The wealth of information gathered on the metabolic profiles from rat urine and plasma has revealed subtle metabolic changes in response to USPIO administration. The metabolic changes include the elevation of urinary alpha-hydroxy-n-valerate, o- and p-HPA, PAG, nicotinate and hippurate accompanied by decreases in the levels of urinary alpha-ketoglutarate, succinate, citrate, N-methylnicotinamide, NAG, DMA, allantoin and acetate following USPIO administration. The changes associated with USPIO administration included a gradual increase in plasma glucose, N-acetyl glycoprotein, saturated fatty acid, citrate, succinate, acetate, GPC, ketone bodies (beta-hydroxybutyrate, acetone and acetoacetate) and individual amino acids, such as phenylalanine, lysine, isoleucine, glycine, glutamine and glutamate and a gradual decrease of myo-inositol, unsaturated fatty acid and triacylglycerol. Hence USPIO administration effects are reflected in changes in a number of metabolic pathways including energy, lipid, glucose and amino acid metabolism. The size- and surface chemistry-dependent metabolic responses and possible toxicity were observed using NMR analysis of biofluids. These changes may be attributed to the disturbances of hepatic, renal and cardiac functions following USPIO administrations. The potential biotoxicity can be derived from metabonomic analysis and serum biochemistry analysis. Metabonomic strategy offers a promising approach for the detection of subtle physiological responses on mammalian metabolism, and can be employed to investigate the potential adverse effects of other nanoparticles and nanomaterials on the environment and human health. PMID:20820093

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

2010-09-06

199

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

PubMed Central

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

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

2012-01-01

200

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

NASA Astrophysics Data System (ADS)

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

Ramalingam, Balavinayagam; Mukherjee, Somik; Mathai, Cherian J.; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

2013-05-01

201

Amine-functionalized lanthanide-doped zirconia nanoparticles: optical spectroscopy, time-resolved fluorescence resonance energy transfer biodetection, and targeted imaging.  

PubMed

Ultrasmall inorganic oxide nanoparticles doped with trivalent lanthanide ions (Ln(3+)), a new and huge family of luminescent bioprobes, remain nearly untouched. Currently it is a challenge to synthesize biocompatible ultrasmall oxide bioprobes. Herein, we report a new inorganic oxide bioprobe based on sub-5 nm amine-functionalized tetragonal ZrO(2)-Ln(3+) nanoparticles synthesized via a facile solvothermal method and ligand exchange. By utilizing the long-lived luminescence of Ln(3+), we demonstrate its application as a sensitive time-resolved fluorescence resonance energy transfer (FRET) bioprobe to detect avidin with a record-low detection limit of 3.0 nM. The oxide nanoparticles also exhibit specific recognition of cancer cells overexpressed with urokinase plasminogen activator receptor (uPAR, an important marker of tumor biology and metastasis) and thus may have great potentials in targeted bioimaging. PMID:22913455

Liu, Yongsheng; Zhou, Shanyong; Tu, Datao; Chen, Zhuo; Huang, Mingdong; Zhu, Haomiao; Ma, En; Chen, Xueyuan

2012-08-30

202

Ultrasmall superparamagnetic iron oxides (USPIOs): a future alternative magnetic resonance (MR) contrast agent for patients at risk for nephrogenic systemic fibrosis (NSF)?  

PubMed Central

Gadolinium (Gd) based contrast agents (GBCAs) in magnetic resonance imaging (MRI) are used in daily clinical practice and appear safe in most patients; however, nephrogenic systemic fibrosis (NSF) is a recently recognized severe complication associated with GBCAs. It affects primarily patients with renal disease, such as stage 4 or 5 chronic kidney disease (CKD; glomerular filtration rate <30 ml/min per 1.73 m2), acute kidney injury, or kidney and liver transplant recipients with kidney dysfunction. Contrast-enhanced MRI and computed tomography (CT) scans provide important clinical information and influence patient management. An alternative contrast agent is needed to obtain adequate imaging results while avoiding the risk of NSF in this vulnerable patient group. One potential alternative is ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, which provide enhancement characteristics similar to GBCAs. We review our experience in approximately 150 patients on the potential benefits of the USPIOs ferumoxtran-10 and ferumoxytol. We focus on central nervous system (CNS) MRI but also review imaging of other vascular beds. Safety studies, including USPIO administration (ferumoxytol) as iron supplement therapy in CKD patients on and not on dialysis, suggest that decreased kidney function does not alter the safety profile. We conclude that for both CNS MR imaging and MR angiography, USPIO agents like ferumoxytol are a viable option for patients at risk for NSF.

Neuwelt, Edward A.; Hamilton, Bronwyn E.; Varallyay, Csanad G.; Rooney, William R.; Edelman, Robert D.; Jacobs, Paula M.; Watnick, Suzanne G.

2008-01-01

203

Nanotechnologies of photonic crystals and quantum dots for ultrasmall and ultrafast all-optical switches  

Microsoft Academic Search

We have fabricated several two-dimensional photonic-crystal (2DPC) slab waveguides by using fine EB lithography and dry etching. The 2DPC waveguides include straight, bend and directional coupler on the GaAs\\/AlGaAs substrate as an application to the ultra-small and ultra-fast all-optical switching device (PC-SMZ). Site-controlled InAs quantum dots (QDs) responsible for nonlinear phase shift in the PC-SMZ have been investigated by developing

Kiyoshi Asakawa; Yoshimasa Sugimoto; H. Nakamura; Naoki Ikeda; Y. Tanaka; Y. Nakamura; S. Ohkouchi; Kozyo Kanamoto; Hiroshi Ishikawa; Y. Watanabe; K. Inoue; H. Sasaki; Koji Ishida

2004-01-01

204

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

PubMed

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

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

2013-01-29

205

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

SciTech Connect

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

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

2011-01-01

206

Ultrasmall Peptides Self-Assemble into Diverse Nanostructures: Morphological Evaluation and Potential Implications  

PubMed Central

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.

Lakshmanan, Anupama; Hauser, Charlotte A.E.

2011-01-01

207

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

SciTech Connect

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

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

2010-07-01

208

Simulation of Ultra-Small GaAs MESFET Using Quantum Moment Equations. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Ultra-small MESFET's have characteristic lengths comparable to quantum lengths: wavelength, mean free path, etc. In a first attempt to incorporate these quantum lengths, we develop a model based upon a set of quantum moment equations obtained from the Wig...

J. R. Zhou D. K. Ferry

1992-01-01

209

Nanotechnologies of photonic crystals and quantum dots for ultrasmall and ultrafast all-optical switches  

NASA Astrophysics Data System (ADS)

We have fabricated several two-dimensional photonic-crystal (2DPC) slab waveguides by using fine EB lithography and dry etching. The 2DPC waveguides include straight, bend and directional coupler on the GaAs/AlGaAs substrate as an application to the ultra-small and ultra-fast all-optical switching device (PC-SMZ). Site-controlled InAs quantum dots (QDs) responsible for nonlinear phase shift in the PC-SMZ have been investigated by developing a nano-probe assisted in-situ process. Optical linear and nonlinear properties of stacked QDs were characterized. The result exhibited the ?/2 phase shift required for the SMZ-type optical switching operation. These results are capable of achieving the PC-SMZ.

Asakawa, Kiyoshi; Sugimoto, Yoshimasa; Nakamura, H.; Ikeda, Naoki; Tanaka, Y.; Nakamura, Y.; Ohkouchi, S.; Kanamoto, Kozyo; Ishikawa, Hiroshi; Watanabe, Y.; Inoue, K.; Sasaki, H.; Ishida, Koji

2004-03-01

210

Features of Set Dynamics in Ultrasmall Sns and Nsn Double Junctions  

NASA Astrophysics Data System (ADS)

The aim of this paper is to investigate the behavior of ultrasmall SNS and NSN double junctions at T = 0 in terms of a golden rule ansatz with regard to the normal conducting phase of the superconducting electrodes. The sensitivity of electrometers built from SNS and NSN single electron tunneling (SET) transistors is evaluated for T > 0 including a consideration of the shot noise behavior. Incoherent cotunneling is treated analytically in both SNS and NSN devices and a rough estimation of coherent cotunneling is done numerically in the case of SNS. The influence of a high impedance but ohmic environment is discussed. Emphasis is put on the case ? < e2/[2(C1 + C2)] (with the capacitance C1,2 of the respective junction) and the effects of discrete states of the central electrode are neglected.

Krech, Wolfram; Müller, Heinz-Olaf

211

Förster resonance energy transfer-based biosensing platform with ultrasmall silver nanoclusters as energy acceptors.  

PubMed

We studied the energy transfer (ET) property of ultrasmall Ag nanoclusters (Ag NCs) and exploited its biosensing application for the first time. A hybridized DNA duplex model was designed to study the energy transfer process from fluorescent energy donors to Ag NCs. By changing the DNA duplex model and the number of hybridized pairs, the separation distance between the energy donor and Ag NCs was adjusted to investigate the distance dependence and possible mechanisms involved in the ET process, which was assigned to Förster resonance energy transfer (FRET). Using Ag NCs with different photophysical properties as energy acceptors, FRET-based biosensing platforms with two different energy donors were constructed utilizing either the off-on or ratiometric fluorescence signaling. This study will provide the basis for understanding energy transfer properties of Ag NCs and bring to light the universal application of these properties in bio/chemo sensing. PMID:23981044

Xiao, Yan; Shu, Fan; Wong, Kwok-Yin; Liu, Zhihong

2013-08-29

212

Phase-shifter using submicron silicon waveguide couplers with ultra-small electro-mechanical actuator.  

PubMed

Phase shifter is an important part of optical waveguide circuits as used in interferometer. However, it is not always easy to generate a large phase shift in a small region. Here, a variable phase-shifter operating as delay-line of silicon waveguide was designed and fabricated by silicon micromachining. The proposed phase-shifter consists of a freestanding submicron-wide silicon waveguide with two waveguide couplers and an ultrasmall silicon comb-drive actuator. The position of the freestanding waveguide is moved by the actuator to vary the total optical path. Phase-shift was measured in a Mach-Zehnder interferometer to be 3.0pi at the displacement of 1.0 mum at the voltage of 31 V. The dimension of the fabricated device is 50microm wide and 85microm long. PMID:20389723

Ikeda, Taro; Takahashi, Kazunori; Kanamori, Yoshiaki; Hane, Kazuhiro

2010-03-29

213

Evaluation of an ultrasmall superparamagnetic iron oxide in MRI in a bone tumor model in rabbits.  

PubMed

Ultrasmall superparamagnetic iron oxides (USPIOs) are a class of MRI contrast agents having moderately selective affinity for the reticuloendothelial cells of lymph nodes and bone marrow. This study evaluated a USPIO preparation, Combidex (Code 7227), in MRI of a rabbit bone tumor model. VX2 carcinoma implanted into the tibial marrow of nine subject rabbits was studied. After tumor growth, the subjects underwent MRI of their lesions both before and after intravenous administration of Code 7227. Code 7227 was judged subjectively to conspicuously reduce the signal intensity of normal marrow on some pulse sequences. A hypointense zone outlined the tumor margins on postcontrast imaging, which allowed improved visualization of the soft tissue component of the larger lesions. Accumulation of the contrast agent in a zone of inflammation outside the tumor margin was demonstrated on histologic sections of the lesions. Code 7227 deserves additional study as a potential contrast agent for MRI of bone tumors. PMID:9170045

Bush, C H; Mladinich, C R; Montgomery, W J

214

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor  

PubMed Central

Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the crystallinity and size of CoFe2O4 nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results showed that the well-established silica network provided nucleation locations for CoFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an ideal nucleation environment to disperse CoFe2O4 nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even more versatile.

2011-01-01

215

Quantum Tunneling of Magnetization in Ultrasmall Half-Metallic V3O4 Quantum Dots: Displaying Quantum Superparamagnetic State  

PubMed Central

Quantum tunneling of magnetization (QTMs), stemming from their importance for understanding materials with unconventional properties, has continued to attract widespread theoretical and experimental attention. However, the observation of QTMs in the most promising candidates of molecular magnets and few iron-based compounds is limited to very low temperature. Herein, we first highlight a simple system, ultrasmall half-metallic V3O4 quantum dots, as a promising candidate for the investigation of QTMs at high temperature. The quantum superparamagnetic state (QSP) as a high temperature signature of QTMs is observed at 16?K, which is beyond absolute zero temperature and much higher than that of conventional iron-based compounds due to the stronger spin-orbital coupling of V3+ ions bringing high anisotropy energy. It is undoubtedly that this ultrasmall quantum dots, V3O4, offers not only a promising candidate for theoretical understanding of QTMs but also a very exciting possibility for computers using mesoscopic magnets.

Xiao, Chong; Zhang, Jiajia; Xu, Jie; Tong, Wei; Cao, Boxiao; Li, Kun; Pan, Bicai; Su, Haibin; Xie, Yi

2012-01-01

216

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

Microsoft Academic Search

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

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

2010-01-01

217

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

Microsoft Academic Search

The abundant microbial population in a 3,043-m-deep Greenland glacier ice core was dominated by ultra- small cells (<0.1 m3) that may represent intrinsically small organisms or starved, minute forms of normal- sized microbes. In order to examine their diversity and obtain isolates, we enriched for ultrasmall psychro- philes by filtering melted ice through filters with different pore sizes, inoculating anaerobic

Vanya I. Miteva; Jean E. Brenchley

2005-01-01

218

RHEED studies of nucleation of Ge islands on Si(001) and optical properties of ultra-small Ge quantum dots  

Microsoft Academic Search

The initial stages of Ge growth on the Si(001)-(2×1) surface have been studied by using a RHEED pattern zero-streak profile analysis technique. Thicknesses for {105} and {113} facets formation, corresponding to the nucleation of coherent ‘hut’-clusters and dislocated ‘dome’ three-dimensional (3D) islands respectively, were determined in a growth temperature range of about 200–600°C. Multilayer structures containing ultra-small Ge quantum dots

V. A. Markova; H. H. Chengb; Chih-ta Chiac; A. I. Nikiforovd; V. A. Cherepanov; O. P. Pchelyakov; K. S. Zhuravlev; A. B. Talochkin; E. McGlynn; M. O. Henry

2000-01-01

219

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

NASA Astrophysics Data System (ADS)

We report the synthesis of ultrafine S nanoparticles with diameter 10 ~ 20 nm via a membrane-assisted precipitation technique. The S nanoparticles were then coated with conducting poly (3,4-ethylenedioxythiophene) (PEDOT) to form S/PEDOT core/shell nanoparticles. The ultrasmall size of S nanoparticles facilitates the electrical conduction and improves sulfur utilization. The encapsulation of conducting PEDOT shell restricts the polysulfides diffusion, alleviates self-discharging and the shuttle effect, and thus enhances the cycling stability. The resulting S/PEDOT core/shell nanoparticles show initial discharge capacity of 1117 mAh g-1 and a stable capacity of 930 mAh g-1 after 50 cycles.

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

2013-05-01

220

Ultrafine sulfur nanoparticles in conducting polymer shell as cathode materials for high performance lithium/sulfur batteries.  

PubMed

We report the synthesis of ultrafine S nanoparticles with diameter 10 ~ 20 nm via a membrane-assisted precipitation technique. The S nanoparticles were then coated with conducting poly (3,4-ethylenedioxythiophene) (PEDOT) to form S/PEDOT core/shell nanoparticles. The ultrasmall size of S nanoparticles facilitates the electrical conduction and improves sulfur utilization. The encapsulation of conducting PEDOT shell restricts the polysulfides diffusion, alleviates self-discharging and the shuttle effect, and thus enhances the cycling stability. The resulting S/PEDOT core/shell nanoparticles show initial discharge capacity of 1117 mAh g(-1) and a stable capacity of 930 mAh g(-1) after 50 cycles. PMID:23714786

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

2013-01-01

221

Electron spin resonance investigation of ultra-small double walled carbon nanotubes embedded in zeolite nanochannels.  

PubMed

We report on the low temperature electron spin resonance (ESR) properties of ultra-small (0.45 nm) double walled carbon nanotubes (DWCNTs) embedded in zeolite nanochannels. An isotropic ESR signal is observed at g(c) = 2.002?77 with the spin density (S = 1/2) ? 10(19) g(-1), which is suggested to originate from the carbon related point defects in the DWCNTs. Measurements of the ESR line width and signal intensity as a function of temperature indicate that the spins are of a localized nature as opposed to the conduction type electrons observed in large diameter CNTs. The results are consistent with the suggestion that electrons are trapped at interstitial defects. The observed linear frequency dependence of the ESR line width of embedded DWCNTs points to 'strain' as the prime source of broadening. By contrast, the study of free standing DWCNTs shows the presence of a distinctly superlinear frequency dependence of the signal width at low temperatures. The possible origin of the frequency dependence is discussed. PMID:22037383

Rao, S S; Stesmans, A; Noyen, J V; Jacobs, P; Sels, B

2011-10-28

222

Metabolic profiling of ultrasmall sample volumes with GC/MS: from microliter to nanoliter samples.  

PubMed

Profiling of metabolites is increasingly used to study the functioning of biological systems. For some studies the volume of available samples is limited to only a few microliters or even less, for fluids such as cerebrospinal fluid (CSF) of small animals like mice or the analysis of individual oocytes. Here we present an analytical method using in-liner silylation coupled to gas chromatography/mass spectrometry (GC/MS), that is suitable for metabolic profiling in ultrasmall sample volumes of 2 microL down to 10 nL. Method performance was assessed in various biosamples. Derivatization efficiencies for sugars, organic acids, and amino acids were satisfactory (105-120%), and repeatabilities were generally better than 15%, except for amino acids that had repeatabilities up to about 35-40%. For endogenous sugars and organic acids in fetal bovine serum, the response was linear for aliquots from 10 nL up to at least 1 microL. The developed GC/MS method was applied for the analysis of different sample matrixes, i.e., fetal bovine serum, mouse CSF, and aliquots of the intracellular content of Xenopus laevis oocytes. To the best of our knowledge, we present here the first comprehensive GC/MS metabolite profiles from mouse CSF and from the intracellular content of a single X. laevis oocyte. PMID:19947586

Koek, Maud M; Bakels, Floor; Engel, Willem; van den Maagdenberg, Arn; Ferrari, Michel D; Coulier, Leon; Hankemeier, Thomas

2010-01-01

223

Competing mechanisms of catalytic H2 formation and dissociation on ultrasmall silicate nanocluster dust grains  

NASA Astrophysics Data System (ADS)

Silicate dust grains are thought to be essential in catalysing the formation of H2. Ultrasmall silicates (diameter ?1.5 nm) are fundamental intermediates in silicate dust formation in stellar outflows, and are ubiquitous in the interstellar medium. To investigate the catalytic formation and dissociation of H2 on such nanosilicates, we have performed ab initio quantum chemical calculations of hydrogen interacting with a stable 21 atom nanosilicate cluster having the stoichiometry of forsterite, (MgO)6(SiO2)3. Due to its small size and high percentage of surface atoms, our particle inherently does not exhibit the bulk forsterite crystal structure and possesses a range of chemisorption and physisorption sites, presumably similar to those that larger amorphous silicates would offer. We find a number of exothermic H2 formation routes and pathways for H2 catalytic dissociation on the nanosilicate. In particular, we discover some H2 formation routes that are energetically more favourable than that reported for the forsterite (010) surface. Further, we find a linear correlation between the dissociative chemisorption of two H atoms and the dissociation transition state, suggestive of a general Brønsted-Evans-Polanyi relation for H2 dissociation on bare silicates independent of dust grain size and/or crystallinity.

Kerkeni, Boutheïna; Bromley, Stefan T.

2013-10-01

224

Ultrasmall near-infrared Ag2Se quantum dots with tunable fluorescence for in vivo imaging.  

PubMed

A strategy is presented that involes coupling Na(2)SeO(3) reduction with the binding of silver ions and alanine in a quasi-biosystem to obtain ultrasmall, near-infrared Ag(2)Se quantum dots (QDs) with tunable fluorescence at 90 °C in aqueous solution. This strategy avoids high temperatures, high pressures, and organic solvents so that water-dispersible sub-3 nm Ag(2)Se QDs can be directly obtained. The photoluminescence of the Ag(2)Se QDs was size-dependent over a wavelength range from 700 to 820 nm, corresponding to sizes from 1.5 ± 0.4 to 2.4 ± 0.5 nm, with good monodispersity. The Ag(2)Se QDs are less cytotoxic than other nanomaterials used for similar applications. Furthermore, the NIR fluorescence of the Ag(2)Se QDs could penetrate through the abdominal cavity of a living nude mouse and could be detected on its back side, demonstrating the potential applications of these less toxic NIR Ag(2)Se QDs in bioimaging. PMID:22148738

Gu, Yi-Ping; Cui, Ran; Zhang, Zhi-Ling; Xie, Zhi-Xiong; Pang, Dai-Wen

2011-12-14

225

Monodisperse rutile microspheres with ultrasmall nanorods on surfaces: synthesis, characterization, luminescence, and photocatalysis.  

PubMed

A complex nanostructure of rutile TiO(2) microspheres with ultrasmall nanorods on surfaces was prepared by a simple solvothermal method. This complex nanostructure is different from the hierarchical structure of microspheres composed of nanorods. The obtained complex nanostructure possesses an epitaxy-like interface between the nanorod-shell and the sphere-core, which often provides superior physical and chemical properties. The size and morphology of the obtained rutile TiO(2) complex nanostructure were observed by scanning electron microscopy and transmission electron microscopy (TEM). Their intrinsic crystallography was characterized by X-ray diffraction, high-resolution TEM, and selected area electron diffraction. Controlled experiments were designed using varied temperatures and assistant reagent compositions to study their influences on the crystal phase and morphology of TiO(2). The formation process of this complex nanostructure was determined via time-dependent experiments. Its photoluminescence spectra showed the strongest emission at about 400 nm with a blue-shift. The photocatalytic experiments demonstrated the obtained complex nanostructure had the highest catalytic efficiency in the five TiO(2) samples with different morphologies. PMID:22885113

Tian, Yang; Zhang, Jing; Ma, Ji-Chao; Jia, Xiao

2012-07-20

226

Crossover from bulk to few-electron limit in ultrasmall metallic grains  

NASA Astrophysics Data System (ADS)

We study the properties of ultrasmall metallic grains with sizes in the range 20-400 electrons. Using a particle-hole version of the density-matrix renormalization-group (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 qualitatively 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 projected BCS (PBCS) wave function in order to describe correctly the crossover. Finally we present a recursive method to compute norms and expectation values with the PBCS wave function.

Dukelsky, J.; Sierra, G.

2000-05-01

227

Magnetic and magnetorheological characterization of a polymer liquid crystal ferronematic  

NASA Astrophysics Data System (ADS)

Cobalt ferrite (CoFe2O4) nanoparticles (~12 nm diameter) were suspended in the polymer liquid crystal hydroxypropyl cellulose (HPC)/m-cresol to obtain a new type of ferronematic. Suspension of these particles in 35% wt HPC in m-cresol did not affect the appearance of the liquid crystalline phase as evidenced by small angle x-ray scattering. Magnetic measurements performed on the 35% wt HPC/m-cresol/CoFe2O4 ferronematic showed the appearance of ferromagnetic behavior and magnetic hysteresis. In addition, rheometry of the samples showed magnetorheological effect upon application of a dc magnetic field, with the ferronematic having the largest response.

Santiago-Quiñones, Darlene I.; Acevedo, Aldo; Rinaldi, Carlos

2009-04-01

228

Crystalline Si Nanoparticles as Carriers of the Blue Luminescence in the Red Rectangle Nebula  

NASA Astrophysics Data System (ADS)

The discovery of a band of blue luminescence in the Red Rectangle proto-planetary nebula has been recently reported by Vijh et al. These authors used the hydrogen Balmer lines and the line-depth technique to extract the intensity of the blue luminescence. This luminescence was attributed to fluorescence from small neutral polycyclic aromatic hydrocarbon molecules in the interstellar medium, consisting of three to four aromatic rings such as anthracene and pyrene. We present in this Letter evidence of another potential carrier responsible for the blue luminescence, namely, ultrasmall silicon nanoparticles of 1 nm in diameter.

Nayfeh, Munir H.; Habbal, Shadia Rifai; Rao, Satish

2005-03-01

229

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

Microsoft Academic Search

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

Un-Byoung Kang; Young-Ho Kim

2004-01-01

230

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

PubMed Central

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

Miteva, Vanya I.; Brenchley, Jean E.

2005-01-01

231

Inorganic nanoparticle-based T1 and T1/T2 magnetic resonance contrast probes.  

PubMed

Magnetic resonance imaging (MRI) yields high spatially resolved contrast with anatomical details for diagnosis, deeper penetration depth and rapid 3D scanning. To improve imaging sensitivity, adding contrast agents accelerates the relaxation rate of water molecules, thereby greatly increasing the contrast between specific issues or organs of interest. Currently, the majority of T(1) contrast agents are paramagnetic molecular complexes, typically Gd(iii) chelates. Various nanoparticulate T(1) and T(1)/T(2) contrast agents have recently been investigated as novel agents possessing the advantages of both the T(1) contrast effect and nanostructural characteristics. In this minireview, we describe the recent progress of these inorganic nanoparticle-based MRI contrast agents. Specifically, we mainly report on Gd and Mn-based inorganic nanoparticles and ultrasmall iron oxide/ferrite nanoparticles. PMID:22971876

Hu, Fengqin; Zhao, Yong Sheng

2012-10-21

232

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

Microsoft Academic Search

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

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

2002-01-01

233

Two-in-One Protocol: Simultaneous Small-Pore and Ultrasmall-Pore Peritoneal Transport Quantification  

PubMed Central

? Background: Reduced free water transport (FWT) through ultrasmall pores contributes to net ultrafiltration failure (UFF) and should be seen as a sign of more severe functional deterioration of the peritoneal membrane. The modified peritoneal equilibration test (PET), measuring the dip in dialysate Na concentration, estimates only FWT. Our aim was to simultaneously quantify small-solute transport, FWT, and small-pore ultrafiltration (SPUF) during a single PET procedure. ? Methods: We performed a 4-hour, 3.86% glucose PET, with additional measurement of ultrafiltration (UF) at 60 minutes, in 70 peritoneal dialysis patients (mean age: 50 ± 16 years; 61% women; PD vintage: 26 ± 23 months). We calculated the dialysate-to-plasma ratios (D/P) of creatinine and Na at 0 and 60 minutes, and the Na dip (DipD/PNa60?), the delta dialysate Na 0-60 (?DNa0-60), FWT, and SPUF. ? Results: Sodium sieving (as measured by ?DNa0-60) correlated strongly with the corrected DipD/PNa60? (r = 0.85, p < 0.0001) and the corrected FWT (r = 0.41, p = 0.005). Total UF showed better correlation with FWT than with indirect measurements of Na sieving (r = 0.46, p < 0.0001 for FWT; r = 0.360, p < 0.0001 for DipD/PNa60?). Corrected FWT fraction was 0.45 ± 0.16. A negative correlation was found between time on PD and both total UF and FWT (r = -0.253, p = 0.035 and r = -0.272, p = 0.023 respectively). The 11 patients (15.7%) diagnosed with UFF had lower FWT (89 mL vs 164 mL, p < 0.05) and higher D/P creatinine (0.75 vs 0.70, p < 0.05) than did the group with normal UF. The SPUF correlated positively with FWT in the normal UF group, but negatively in UFF patients (r = -0.709, p = 0.015). Among UFF patients on PD for a longer period, 44.4% had a FWT percentage below 45%. ? Conclusions: Measurement of FWT and SPUF is feasible by simultaneous quantification during a modified 3.86% glucose PET, and FWT is a decisive parameter for detecting causes of UFF in addition to increased effective capillary surface.

Bernardo, Ana Paula; Bajo, M. Auxiliadora; Santos, Olivia; del Peso, Gloria; Carvalho, Maria Joao; Cabrita, Antonio; Selgas, Rafael; Rodrigues, Anabela

2012-01-01

234

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

SciTech Connect

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

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

2009-12-01

235

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

236

Overview of nanoparticle use in cancer imaging.  

PubMed

Current cross-sectional imaging modalities are inaccurate in characterizing nodal metastatic disease because of their use of size and/or morphology as differentiating factors. PET has overcome some of these limitations but it is constrained by its spacial resolution particularly for detecting small nodal metastases. These challenges have led to the development of lymphotropic contrast agents. Ferumoxtran-10 is one such MRI lymphotropic contrast agent that consists of ultrasmall superparamagnetic iron-oxide based nanoparticles targeted at the reticuloendothelial system. After intravenous administration ferumoxtran-10 is phagocytosed by macrophages which then accumulate within benign lymph nodes. Disturbances in lymph flow or in nodal architecture caused by metastases lead to abnormal patterns of accumulation of the particles, which are detectable by MRI. On postcontrast T2- and T2*-weighted MRI benign lymph nodes show a drop in signal intensity and homogenous darkening whereas areas of malignant infiltration show lack of nanoparticle uptake and remain signal-intense. Summary ROC curve analysis for per-lymph-node data showed an overall sensitivity of 88% and overall specificity of 96% for ferumoxtran-10-enhanced MRI. Ferumoxtran-10-enhanced MRI offers higher diagnostic precision than unenhanced MRI and is sensitive and specific for the detection of lymph-node metastases, especially in malignant diseases of the abdomen and pelvis. PMID:19414922

Islam, Tina; Harisinghani, Mukesh G

2009-01-01

237

Protein fibrillation and nanoparticle interactions: opportunities and challenges  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

238

Protein fibrillation and nanoparticle interactions: opportunities and challenges.  

PubMed

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. PMID:23463168

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

2013-04-01

239

Highly biocompatible and water-dispersible, amine functionalized magnetite nanoparticles, prepared by a low temperature, air-assisted polyol process: a new platform for bio-separation and diagnostics.  

PubMed

A low temperature polyol process, based on glycolaldehyde mediated partial reduction of FeCl(3).6H(2)O at 120 degrees C in the presence of sodium acetate as an alkali source and 2, 2(')-(ethylenedioxy)-bis-(ethylamine) as an electrostatic stabilizer has been used for the gram-scale preparation of biocompatible, water-dispersible, amine functionalized magnetite nanoparticles (MNPs) with an average diameter of 6 +/- 0.75 nm. With a reasonably high magnetization (37.8 e.m.u.) and amine groups on the outer surface of the nanoparticles, we demonstrated the magnetic separation and concentration implications of these ultrasmall particles in immunoassay. MRI studies indicated that these nanoparticles had the desired relaxivity for T(2) contrast enhancement in vivo. In vitro biocompatibility, cell uptake and MR imaging studies established that these nanoparticles were safe in clinical dosages and by virtue of their ultrasmall sizes and positively charged surfaces could be easily internalized by cancer cells. All these positive attributes make these functional nanoparticles a promising platform for further in vitro and in vivo evaluations. PMID:20195015

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

2010-03-02

240

Highly biocompatible and water-dispersible, amine functionalized magnetite nanoparticles, prepared by a low temperature, air-assisted polyol process: a new platform for bio-separation and diagnostics  

NASA Astrophysics Data System (ADS)

A low temperature polyol process, based on glycolaldehyde mediated partial reduction of FeCl3·6H2O at 120 °C in the presence of sodium acetate as an alkali source and 2, 2'-(ethylenedioxy)-bis-(ethylamine) as an electrostatic stabilizer has been used for the gram-scale preparation of biocompatible, water-dispersible, amine functionalized magnetite nanoparticles (MNPs) with an average diameter of 6 ± 0.75 nm. With a reasonably high magnetization (37.8 e.m.u.) and amine groups on the outer surface of the nanoparticles, we demonstrated the magnetic separation and concentration implications of these ultrasmall particles in immunoassay. MRI studies indicated that these nanoparticles had the desired relaxivity for T2 contrast enhancement in vivo. In vitro biocompatibility, cell uptake and MR imaging studies established that these nanoparticles were safe in clinical dosages and by virtue of their ultrasmall sizes and positively charged surfaces could be easily internalized by cancer cells. All these positive attributes make these functional nanoparticles a promising platform for further in vitro and in vivo evaluations.

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

2010-03-01

241

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

NASA Astrophysics Data System (ADS)

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

Mirzaei, Mahmoud

2013-05-01

242

The Combined Ultra-Small- and Small-Angle Neutron Scattering (USANS/SANS) Technique for Earth Sciences  

NASA Astrophysics Data System (ADS)

The extension of the well-known Small-Angle Neutron Scattering (SANS) technique to Ultra-Small Angles (USANS) provides a unique tool for studying hierarchical structures ranging in size from nanometers to micrometers. Hierarchical structures are common for many natural and man-made materials, which show multi-level morphology (atoms-molecules-aggregates-agglomerates), in other words, are made up of structural units encompassing the atomic, molecular, micro- and macroscopic length scales. Combining USANS and SANS data can provide complete structural information for complicated polydisperse systems, allowing the determination of their complex morphology and hence has been successfully applied to structural studies in geology, petrology, and archeology. This chapter briefly outlines the technique and provides detailed examples of the applications in the Earth Sciences.

Triolo, Roberto; Agamalian, Michael

243

Colloidal synthesis and characterization of ultrasmall perovskite GdFeO3 nanocrystals  

NASA Astrophysics Data System (ADS)

Synthesis of very small (about 4 nm) perovskite structured gadolinium orthoferrite nanoparticles (GdFeO3) was performed by the polyol method. The material shows promising relaxivity properties and potential as a contrast agent in magnetic resonance imaging. The perovskite nanoparticles were characterized by x-ray diffraction, transmission electron microscopy, energy dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, magnetic resonance, and magnetization measurements. Upon heating in air at 800 °C for 3 h the size of the crystals increased to about 40 nm. The crystalline structure of the heat treated compound is in good agreement with perovskite GdFeO3 as the primary product. Contributions from various secondary phases were also identified, including one hitherto unknown phase with the suggested composition 'Gd3FeO6' and isostructural with Gd3GaO6. The novel 'Gd3FeO6' phase appears to be kinetically stabilized in the nano state.

Söderlind, Fredrik; Fortin, Marc A.; Petoral, Rodrigo M., Jr.; Klasson, Anna; Veres, Teodor; Engström, Maria; Uvdal, Kajsa; Käll, Per-Olov

2008-02-01

244

Packaging Technology for Ultra-Small Variable Optical Attenuator Multiplexer (V-AWG) With Multichip PLC Integration Structure Using Chip-Scale-Package PD Array  

Microsoft Academic Search

We have developed an ultra-small 16-channel variable optical attenuator (VOA) multiplexer (V-AWG) with excellent optical performance by using multichip planar lightwave circuit (PLC) integration technology. The insertion loss is 3.2 dB, and the polarization-dependent loss (PDL) at 25 dB attenuation is less than 0.3 dB. The module size is 90 mmtimes55 mmtimes14 mm. We describe our concept and developed techniques

Ikuo Ogawa; Yoshiyuki Doi; Yasuaki Hashizume; Shin Kamei; Yasuaki Tamura; M. Ishii; T. Kominato; H. Yamazaki; A. Kaneko

2006-01-01

245

Silica nanoparticles separation from water: aggregation by cetyltrimethylammonium bromide (CTAB).  

PubMed

Nanoparticles will inevitably be found in industrial and domestic wastes in the near future and as a consequence soon in water resources. Due to their ultra-small size, nanoparticles may not only have new hazards for environment and human health, but also cause low separation efficiency by classical water treatments processes. Thus, it would be an important challenge to develop a specific treatment with suitable additives for recovery of nanoparticles from waters. For this propose, this paper presents aggregation of silica nanoparticles (Klebosol 30R50 (75nm) and 30R25 (30nm)) by cationic surfactant cetyltrimethylammonium bromide (CTAB). Different mechanisms such as charge neutralization, "depletion flocculation" or "volume-restriction", and "hydrophobic effect" between hydrocarbon tails of CTAB have been proposed to explicate aggregation results. One important finding is that for different volume concentrations between 0.05% and 0.51% of 30R50 suspensions, the same critical coagulation concentration was observed at CTAB=0.1mM, suggesting the optimized quantity of CTAB during the separation process for nanoparticles of about 75nm. Furthermore, very small quantities of CTAB (0.01mM) can make 30R25 nanosilica aggregated due to the "hydrophobic effect". It is then possible to minimize the sludge and allow the separation process as "greener" as possible by studying this case. It has also shown that aggregation mechanisms can be different for very small particles so that a special attention has to be paid to the treatment of nanoparticles contained in water and wastewaters. PMID:23618346

Liu, Y; Tourbin, M; Lachaize, S; Guiraud, P

2013-04-22

246

New Nanoparticles Dispersing Beads Mill with Ultra Small Beads and its Application  

NASA Astrophysics Data System (ADS)

Two of the major problems related to nanoparticle dispersion with a conventional beads mill are re-agglomeration and damage to the crystalline structure of the particles. The Ultra Apex Mill was developed to solve these problems by enabling the use of ultra-small beads with a diameter of less than 0.1mm. The core of this breakthrough development is centrifugation technology which allows the use of beads as small as 0.015mm. When dispersing agglomerated nanoparticles the impulse of the small beads is very low which means there is little influence on the particles. The surface energy of the nanoparticles remains low so the properties are not likely to change. As a result, stable nanoparticle dispersions can be achieved without re-cohesion. The Ultra Apex Mill is superior to conventional beads mills that are limited to much larger bead sizes. The technology of the Ultra Apex Mill has pioneered practical applications for nanoparticles in various fields: composition materials for LCD screens, ink-jet printing, ceramic condensers and cosmetics.

Inkyo, M.; Tahara, T.; Imajyo, Y.

2011-10-01

247

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

PubMed

Human skin not only functions as a permeation barrier (mainly because of 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 especially chitosan, followed by those made of synthetic, degradable (aliphatic polyesters), and nondegradable (polyacrylates) 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 nanosized drug carriers and the topical approach, and are promising for the treatment of skin diseases. For the perspectives, the penetration of ultra-small nanoparticles (size smaller than 40 nm) into skin strata, the targeted delivery of the encapsulated drugs to hair follicle stem cells, and the combination of nanoparticles and microneedle array technologies for special applications such as vaccine delivery are discussed. PMID:23386536

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

2013-02-05

248

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

PubMed

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

Landsmann, Steve; Luka, Martin; Polarz, Sebastian

2012-01-01

249

Two-dimensional pattern reverse Monte Carlo method for modelling the structures of nano-particles in uniaxial elongated rubbers  

NASA Astrophysics Data System (ADS)

Two-dimensional pattern reverse Monte Carlo (2D pattern RMC) analysis is performed to model the structures of nano-particles in uniaxially elongated rubbers using two-dimensional patterns of structure factor of the nano-particles obtained by time-resolved two-dimensional ultra-small angle x-ray scattering. Four spot patterns are observed for a large elongation ratio and the shapes change with increasing elongation ratio. We performed the 2D pattern RMC method for the uniaxial system in order to make a model of the structures from the two-dimensional structure factors. The preliminary results of the 2D pattern RMC analysis of the two-dimensional structure factors of silica particles in a uniaxially elongated styrene-butadiene rubber are presented.

Hagita, K.; Arai, T.; Kishimoto, H.; Umesaki, N.; Shinohara, Y.; Amemiya, Y.

2007-08-01

250

Two-dimensional pattern reverse Monte Carlo method for modelling the structures of nano-particles in uniaxial elongated rubbers.  

PubMed

Two-dimensional pattern reverse Monte Carlo (2D pattern RMC) analysis is performed to model the structures of nano-particles in uniaxially elongated rubbers using two-dimensional patterns of structure factor of the nano-particles obtained by time-resolved two-dimensional ultra-small angle x-ray scattering. Four spot patterns are observed for a large elongation ratio and the shapes change with increasing elongation ratio. We performed the 2D pattern RMC method for the uniaxial system in order to make a model of the structures from the two-dimensional structure factors. The preliminary results of the 2D pattern RMC analysis of the two-dimensional structure factors of silica particles in a uniaxially elongated styrene-butadiene rubber are presented. PMID:21694140

Hagita, K; Arai, T; Kishimoto, H; Umesaki, N; Shinohara, Y; Amemiya, Y

2007-07-05

251

Electroless deposition of platinum nanoparticles in room-temperature ionic liquids.  

PubMed

The electroless deposition of Pt nanoparticles (Pt-NPs) could be carried out by dissolving potassium tetrachloroplatinate(II) (K2[PtCl4]) in 1-ethyl-3-methylimidazolium (EMI(+)) room-temperature ionic liquids (RTILs) containing bis(trifluoromethylsulfonyl) imide (NTf2(-)) or tetrafluoroborate (BF4(-)) anion and small cations, such as H(+), K(+), and Li(+). In this case, no deposition of Pt-NPs occurred in RTILs without such small cations. The formation of Pt-NPs was only observed in RTILs containing trifluoromethanesulfonimide (HNTf2) and protons at high temperature (?80 °C) when potassium hexachloroplatinate(IV) (K2[PtCl6]) was dissolved in the RTILs. The obtained Pt-NPs gave a characteristic absorption spectrum of ultrasmall Pt-NPs. The ultrasmall and uniform Pt-NPs of ca. 1-4 nm in diameter were produced and the Pt-NPs/EMI(+)NTf2(-) dispersion was kept stably for several months without adding any additional stabilizers or capping molecules. The identified Fourier-transform patterns along the [0 1 1] zone axis were observed for the TEM images of Pt-NPs. On the basis of the results obtained, a probable mechanism of the electroless formation of Pt-NPs is discussed. PMID:23985068

Zhang, Da; Okajima, Takeyoshi; Lu, Dalin; Ohsaka, Takeo

2013-09-13

252

Mycobacteriophages BPs, Angel and Halo: comparative genomics reveals a novel class of ultra-small mobile genetic elements  

PubMed Central

Mycobacteriophages BPs, Angel and Halo are closely related viruses isolated from Mycobacterium smegmatis, and possess the smallest known mycobacteriophage genomes, 41?901?bp, 42?289?bp and 41?441?bp, respectively. Comparative genome analysis reveals a novel class of ultra-small mobile genetic elements; BPs and Halo each contain an insertion of the proposed mobile elements MPME1 and MPME2, respectively, at different locations, while Angel contains neither. The close similarity of the genomes provides a comparison of the pre- and post-integration sequences, revealing an unusual 6?bp insertion at one end of the element and no target duplication. Nine additional copies of these mobile elements are identified in a variety of different contexts in other mycobacteriophage genomes. In addition, BPs, Angel and Halo have an unusual lysogeny module in which the repressor and integrase genes are closely linked. The attP site is located within the repressor-coding region, such that prophage formation results in expression of a C-terminally truncated, but active, form of the repressor.

Sampson, Timothy; Broussard, Gregory W.; Marinelli, Laura J.; Jacobs-Sera, Deborah; Ray, Mondira; Ko, Ching-Chung; Russell, Daniel; Hendrix, Roger W.; Hatfull, Graham F.

2009-01-01

253

MR assessment of iodinated contrast-medium-induced nephropathy in rats using ultrasmall particles of iron oxide.  

PubMed

The purpose of this study was to determine the diagnostic value of ultrasmall particles of iron oxide (USPIO)-enhanced MR imaging at different concentrations to evaluate experimental nephropathy. This study was conducted in 23 uninephrectomized rats using a model of iodinated contrast media-induced renal failure. Eleven rats received selective intra-arterial renal administration of diatrizoate (370 mg I/ml) and were compared to two control groups, including five animals injected with isotonic saline and seven noninjected animals. MR imaging was performed 28 hours after the procedure, including T1- and T2-weighted images before and after intravenous administration of successively 5 mumol Fe/kg and 60 mumol/kg of USPIO. Results were interpreted qualitatively and quantitatively with respect to pathologic data, and differences were studied statistically. The maximal signal intensity decrease was noted in normal kidneys in cortex (-65 +/- 4%) and medulla (-84 +/- 5%) on T2-weighted images after injection of 60 mumol/kg of USPIO. At this dose, diseased kidneys displayed less signal intensity decrease than normal kidneys on T2-weighted images (p = .05). Moreover, qualitative analysis showed that the highest sensitivity and specificity to diagnose kidney involvement were obtained with T2-weighted MR images (75% and 91%, respectively) when 60 mumol/kg of USPIO were used (p < .01). USPIO should be useful for in vivo evaluation of the severity of experimentally induced iodinated contrast media renal impairment in animals. PMID:9039610

Laissy, J P; Benderbous, S; Idée, J M; Chillon, S; Beaufils, H; Schouman-Claeys, E

254

MR imaging of pelvic lymph nodes in primary pelvic carcinoma with ultrasmall superparamagnetic iron oxide (Combidex): preliminary observations.  

PubMed

The potential of ultrasmall superparamagnetic iron oxide (Combidex)-enhanced MRI of pelvic lymph nodes in patients with primary pelvic carcinoma is evaluated. Fifteen histologically classified lymph nodes in six patients with known primary pelvic cancer (four prostate; one rectum; one uterus) were evaluated with T2-weighted fast spin-echo (FSE) and T2*-weighted gradient-echo (GRE) MRI at 1.5T 12 to 48 hours after intravenous administration of Combidex at a dose of 1.7 mg Fe/kg. Quantitative image evaluation was performed by comparing signal intensity of individual nodes on pre- and postcontrast images. All patients proceeded to pelvic lymph-node biopsy or surgical dissection, where six were found to be benign and nine were malignant. Of the 15 lymph nodes, four nodes showed a decrease in signal intensity. Of these, three, in which signal loss was homogenous were benign, and one, in which the signal-intensity decrease was heterogeneous, was malignant (micrometastases). No signal change was noted in 11 of 15 lymph nodes of which three were benign (inflammatory) and eight were malignant. Combidex is a promising MR contrast agent for evaluating pelvic lymph nodes. Our preliminary observations suggest that the agent is most useful for classifying normal lymph nodes. PMID:9039609

Harisinghani, M G; Saini, S; Slater, G J; Schnall, M D; Rifkin, M D

255

Fluorescent Nanoparticles  

NSDL National Science Digital Library

This site from Clemson University shows how fluorescence enables the tracking of nanoparticles in living cells. Illustrations include the fluorescence of different kinds of nanoparticles, close-up views of the fluorescent particles, and the fluorescent particles as seen within cells.

Mcneill, Jason

2008-04-16

256

Synthesis of nanoparticles of CoxFe(3-x)O4 by combustion reaction method  

NASA Astrophysics Data System (ADS)

Nanocrystalline magnetic particles of CoxFe(3-x)O4, with x ranging from 0.79 to 1.15, has been synthesised by combustion reaction method using iron nitrate Fe(NO3)3.9H2O, cobalt nitrate Co(NO3)2·6H2O, and urea CO(NH2)2 as fuel without template and subsequent heat treatment. The process is quite simple and inexpensive since it does not involve intermediate decomposition and/or calcining steps. The maximum reaction temperature ranged from 850 to 1010 °C and combustion lasted less then 30 s for all systems. X-ray diffraction patterns of all systems showed broad peaks consistent with cubic inverse spinel structure of CoFe2O4. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures phase purity. The average crystallite sizes determined from the prominent (3 1 1) peak of the diffraction using Scherre's equation and TEM micrographs consisted of ca. 27 nm in spherical morphology. FTIR spectra of the as-prepared material showed traces of organic and metallic salts byproducts. However, when the same material was washed with deionised water the byproducts were rinsed off, resulting in pure materials. Magnetic properties such as saturation magnetisation, remanence magnetisation and coercivity field measured at room temperature were 48 emu/g, 15 emu/g and 900 Oe, respectively.

Franco, Adolfo; Celma de Oliveira Lima, Emília; Novak, Miguel A.; Wells, Paulo R.

2007-01-01

257

Magnetically Tunable Polymer Nanocomposites for RF and Microwave Device Applications  

NASA Astrophysics Data System (ADS)

There has been much interest in polymer nanocomposites (PNC) recently due to potential applications for EMI shielding, tunable electromagnetic devices and flexible electronics. We report synthesis, structural, magnetic and RF characterization on PNCs ranging from 20-80 wt-% loadings of Fe3O4 and CoFe2O4 nanoparticles (˜8nm) in a thermosetting resin from the Rogers Corporation. Nanoparticles were synthesized by thermal decomposition and characterized by XRD and TEM. Magnetic properties were studied using a Quantum Design PPMS. PNCs displayed characteristic features of superparamagnetism at room temperature and blocking at low temperature. Microwave transmission/reflection studies were done using a microstrip resonator. Strong tunability in the microwave absorption was observed. We extend our study to include nanoparticle-filled multi-walled carbon nanotubes synthesized by CVD. These high-aspect ratio magnetic nanostructures, with tunable anisotropy, are of particular interest in enhancing magnetic and microwave responses in existing PNCs.

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

2011-03-01

258

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

PubMed Central

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

2013-01-01

259

Ultrasmall superparamagnetic iron oxide particles (AMI 227) as a blood pool contrast agent for MR angiography: experimental study in rabbits.  

PubMed

The purpose of this study was to evaluate the contribution of an ultrasmall superparamagnetic iron oxide particles (USPIOs) based contrast agent (AMI 227), in a transverse three-dimensional time-of-flight TONE MR angiography sequence of abdominal aorta in rabbits. The main goal was to assess improvement in the visualization of small arteries such as renal arteries, when using such a sequence. Imaging experiments were performed on a 1.5 T magnet, using a transverse 3D time-of-flight (TOF) tilted optimized nonsaturating excitation (TONE) sequence with magnetization transfer suppression. The contrast media used were composed of a USPIO core surrounded by a dextran-surfactant (AMI 227). Different concentrations of AMI 227 were evaluated in 12 rabbits. Concentrations varied within the range 8.5-34 micromol Fe/kg - bw: 8.5 micromol Fe/kg (three rabbits); 17 micromol Fe/kg (three rabbits); 25.5 micromol Fe/kg (three rabbits); 34 micromol Fe/kg (three rabbits). A visual analysis based on the improvement of visualization of small arteries (renal arteries) on MIP images and a quantitative analysis based on the percentage of contrast enhancement of the aorta plotted against distance in the slab from the top edge of the acquisition volume were obtained. A signal-to-noise ratio enhancement of the distal part of the aorta and only improvement in the delineation of the renal arteries were noted when using low concentrations of the contrast media. A loss of signal-to-noise ratio of the aorta and a decrease in arterial visualization were respectively noted with higher concentration of contrast media. In this experimental study, using a transverse three-dimensional TOF TONE MR angiography sequence of renal arteries, in which sequence the saturation effect is minimized, the use of AMI 227 allows only improvement in the delineation of small arteries when using low concentrations of contrast media. PMID:9400837

Loubeyre, P; Zhao, S; Canet, E; Abidi, H; Benderbous, S; Revel, D

260

Efficient synthesis of single gold nanoparticle hybrid amphiphilic triblock copolymers and their controlled self-assembly.  

PubMed

We report on a robust approach to the size-selective and template-free synthesis of asymmetrically functionalized ultrasmall (<4 nm) gold nanoparticles (AuNPs) stably anchored with a single amphiphilic triblock copolymer chain per NP. Directed NP self-assembly in aqueous solution can be facilely accomplished to afford organic/inorganic hybrid micelles, vesicles, rods, and large compound micelles by taking advantage of the rich microphase separation behavior of the as-synthesized AuNP hybrid amphiphilic triblock copolymers, PEO-AuNP-PS, which act as the polymer-metal-polymer analogue of conventional amphiphilic triblock copolymers. Factors affecting the size-selective fabrication and self-assembly characteristics and the time-dependent morphological evolution of NP assemblies were thoroughly explored. PMID:22524544

Hu, Jinming; Wu, Tao; Zhang, Guoying; Liu, Shiyong

2012-04-30

261

Superparamagnetic Nanoparticles  

Microsoft Academic Search

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

Boon Hoong Ong; Nisha Kumari Devaraj

262

Characterizing nanoparticles  

NASA Astrophysics Data System (ADS)

The properties of nanoscale materials have been shown to deviate from those expected of bulk materials. In order to better understand the causes of these observations, a fundamental understanding of the structure of nanoparticles and nanostructured materials is necessary. This work focuses on the characterization of such materials using techniques of electron microscopy. Structures composed of nanoparticles and mechanically deformed, lithographically created silicon towers were analyzed using a combination of focused ion beam milling, scanning electron microscopy, and transmission electron microscopy. The nanostructured films were found to be not fully dense and composed of chemically heterogeneous areas; such specimens could not be produced using traditional methods of sample preparation. The mechanically indented towers exhibited an increased defect structure that was consistent with the increase in applied load. Additional studies focusing on individual nanoparticles produced by different plasma processes have been analyzed in terms of morphology, chemistry, and defect structure. It was found that nanoparticle morphology can be a direct indicator of the particle formation processes occurring in the plasma. Spherical particles can be formed by rapidly solidifying a liquid sphere, with a convex solid-liquid interface. Highly-oriented cubic particles are the result of a slower vapor condensation process on energetically favorable crystallographic planes. Intermediate nanoparticle shapes were encountered and indicate a transition in solidification mechanisms is possible. Using aberration-corrected high-resolution transmission electron microscopy, silicon nanoparticles as small as 1.25 nm in diameter were discovered in hydrogenated nanocrystalline silicon (a/nc-Si:H) films. Some of these nanoparticles contained twin defects and stacking faults; the structure of these planar defects indicate that the nanoparticles were formed in the plasma and not by solid-state nucleation in the film.

Perrey, Christopher Robert

263

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

PubMed

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

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

2013-04-24

264

Bi-photon imaging and diagnostics using ultra-small diagnostic probes engineered from semiconductor nanocrystals and single-domain antibodies  

NASA Astrophysics Data System (ADS)

Semiconductor fluorescent quantum dots (QDs) have just demonstrated their numerous advantages over organic dyes in bioimaging and diagnostics. One of characteristics of QDs is a very large cross section of their twophoton absorption. A common approach to biodetection by means of QDs is to use monoclonal antibodies (mAbs) for targeting. Recently, we have engineered ultrasmall diagnostic nanoprobes (sdAb-QD) based on highly oriented conjugates of QDs with the single-domain antibodies (sdAbs) against cancer biomarkers. With a molecular weight of only 13 kDa (12-fold smaller than full-size mAbs) and extreme stability and capacity to refolding, sdAbs are the smallest functional Ab fragments capable of binding antigens with affinities comparable to those of conventional Abs. Ultrasmall diagnostic sdAb-QD nanoprobes were engineered through oriented conjugation of QDs with sdAbs. This study is the first to demonstrate the possibility of immunohistochemical imaging of colon carcinoma biomarkers with sdAb-QD conjugates by means of two-photon excitation. The optimal excitation conditions for imaging of the markers in clinical samples with sdAb-QD nanoprobes have been determined. The absence of sample autofluorescence significantly improves the sensitivity of biomarker detection with the use of the two-photon excitation diagnostic setup.

Hafian, Hilal; Sukhanova, Alyona; Chames, Patrick; Baty, Daniel; Pluot, Michel; Cohen, Jacques H. M.; Nabiev, Igor R.; Millot, Jean-Marc

2012-10-01

265

OxLDL-targeted iron oxide nanoparticles for in vivo MRI detection of perivascular carotid collar induced atherosclerotic lesions in ApoE-deficient mice  

PubMed Central

Atherosclerotic disease is a leading cause of morbidity and mortality in developed countries, and oxidized LDL (OxLDL) plays a key role in the formation, rupture, and subsequent thrombus formation in atherosclerotic plaques. In the current study, anti-mouse OxLDL polyclonal antibody and nonspecific IgG antibody were conjugated to polyethylene glycol-coated ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, and a carotid perivascular collar model in apolipoprotein E-deficient mice was imaged at 7.0 Tesla MRI before contrast administration and at 8 h and 24 h after injection of 30 mg Fe/kg. The results showed MRI signal loss in the carotid atherosclerotic lesions after administration of targeted anti-OxLDL-USPIO at 8 h and 24 h, which is consistent with the presence of the nanoparticles in the lesions. Immunohistochemistry confirmed the colocalization of the OxLDL/macrophages and iron oxide nanoparticles. The nonspecific IgG-USPIO, unconjugated USPIO nanoparticles, and competitive inhibition groups had limited signal changes (p < 0.05). This report shows that anti-OxLDL-USPIO nanoparticles can be used to directly detect OxLDL and image atherosclerotic lesions within 24 h of nanoparticle administration and suggests a strategy for the therapeutic evaluation of atherosclerotic plaques in vivo.

Wen, Song; Liu, Dong-Fang; Liu, Zhen; Harris, Steven; Yao, Yu-Yu; Ding, Qi; Nie, Fang; Lu, Tong; Chen, Hua-Jun; An, Yan-Li; Zang, Feng-Chao; Teng, Gao-Jun

2012-01-01

266

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

SciTech Connect

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.

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

267

Electroluminescence with micro-watt output from ultra-small sized Si quantum dots/amorphous SiO 2 multilayers prepared by laser crystallization method  

NASA Astrophysics Data System (ADS)

We report the fabrication of Si quantum dots (QDs)/SiO 2 multilayers by using KrF excimer laser (248 nm) crystallization of amorphous Si/SiO 2 multilayered structures on ITO coated glass substrates. Raman spectra and transmission electron microscopy demonstrate the formation of Si QDs and the size can be controlled as small as 1.8 nm. After laser crystallization, Al electrode is evaporated to obtain light emitting devices and the room temperature electroluminescence (EL) can be detected with applying the DC voltage above 8 V on the top gate electrode. The luminescent intensity increases with increasing the applied voltage and the micro-watt light output is achieved. The EL behaviors for samples with different Si dot sizes are studied and it is found that the corresponding external quantum efficiency is significantly enhanced in sample with ultra-small sized Si QDs.

Xu, W.; Sun, H. C.; Xu, J.; Li, W.; Mu, W. W.; Liu, Y.; Yan, M. Y.; Huang, X. F.; Chen, K. J.

2011-10-01

268

Quantum phase transition from superparamagnetic to quantum superparamagnetic state in ultrasmall Cd(1-x)Cr(II)(x)Se quantum dots?  

PubMed

Despite a long history of success in formation of transition-metal-doped quantum dots (QDs), the origin of magnetism in diluted magnetic semiconductors (DMSs) is yet a controversial issue. Cr(II)-doped II-VI DMSs are half-metallic, resulting in high-temperature ferromagnetism. The magnetic properties reflect a strong p-d exchange interaction between the spin-up Cr(II) t(2g) level and the Se 4p. In this study, ultrasmall (~3.1 nm) Cr(II)-doped CdSe DMSQDs are shown to exhibit room-temperature ferromagnetism, as expected from theoretical arguments. Surprisingly, a low-temperature phase transition is observed at 20 K that is believed to reflect the onset of long-range ordering of the single-domain DMSQD. PMID:22074220

Zheng, Weiwei; Kumar, Pushpendra; Washington, Aaron; Wang, Zhenxing; Dalal, Naresh S; Strouse, Geoffrey F; Singh, Kedar

2011-12-28

269

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

270

Certain types of iron oxide nanoparticles are not suited to passively target inflammatory cells that infiltrate the brain in response to stroke.  

PubMed

Intravenous administration of iron oxide nanoparticles during the acute stage of experimental stroke can produce signal intensity changes in the ischemic region. This has been attributed, albeit controversially, to the infiltration of iron-laden blood-borne macrophages. The properties of nanoparticles that render them most suitable for phagocytosis is a matter of debate, as is the most relevant timepoint for administration. Both of these questions are examined in the present study. Imaging experiments were performed in mice with 30?minutes of middle cerebral artery occlusion (MCAO). Iron oxide nanoparticles with different charges and sizes were used, and mice received 300 ?mol Fe/kg intravenously: either superparamagnetic iron oxide nanoparticles (SPIOs), ultrasmall SPIOs, or very small SPIOs. The particles were administered 7 days before MCAO, at the time of reperfusion, or 72 hours after MCAO. Interestingly, there was no observable signal change in the ischemic brains that could be attributed to iron. Furthermore, no Prussian blue-positive cells were found in the brains or blood leukocytes, despite intense staining in the livers and spleens. This implies that the nanoparticles selected for this study are not phagocytosed by blood-borne leukocytes and do not enter the ischemic mouse brain. PMID:23443176

Harms, Christoph; Datwyler, Anna Lena; Wiekhorst, Frank; Trahms, Lutz; Lindquist, Randall; Schellenberger, Eyk; Mueller, Susanne; Schütz, Gunnar; Roohi, Farnoosh; Ide, Andreas; Füchtemeier, Martina; Gertz, Karen; Kronenberg, Golo; Harms, Ulrike; Endres, Matthias; Dirnagl, Ulrich; Farr, Tracy D

2013-02-27

271

Multiferroism and Magnetoelectric Coupling in Nano-Microscale Lead-Free Composite by 0.3Co-FERRITE and 0.7(K0.5Na0.5)NbO3-BASED Ferroelectric Matrix  

NASA Astrophysics Data System (ADS)

Nontoxic lead-free multiferroic composites are synthesized by incorporating the dispersed 0.3CoFe2O4 (CFO) ferromagnetic nanoparticles into 0.7(K0.5Na0.5) NbO3-LiSbO3 (KNN-LS5.2) ferroelectric micromatrix. The multiferroicity of the composite can be verified by polarization-electric field hysteresis loop and magnetic hysteresis loop. The composite exhibits excellent magnetic properties. A dilution effect is observed in magnetic hysteresis loops. The field dependence of ME voltage coefficient is given as a function of magnetic field from -4 kOe to 4 kOe with a maximum magnetoelectric voltage coefficient of 10.7 mV?cm-1?Oe-1 at the frequency of 1 kHz. It is a very high value in the lead-free magnetoelectric composites system for the potential use on multifunctional devices.

Zhou, Yun; Wang, Xinyan; Li, Li; Su, Yuling; Zhang, Jincang; Cao, Shixun

272

[Nanoparticles: the industrial viewpoint. Applications in diagnostic imaging].  

PubMed

Iron oxide particles can be divided into two categories: small superparamagnetic iron oxide (SPIO) and ultrasmall superparamagnetic iron oxide (USPIO). Both describe nanoparticles most often formulated with dextran or dextran derivatives. For magnetic resonance imaging, these agents are of major importance because of their superparamagnetic effect, that is the magnetic field generated locally by their presence. Clinical applications have been well differentiated: 1) SPIO (larger than 50nm) are mainly used via intravenous infusion to detect and characterize small focal lesions in the liver. SPIO can also be given orally to visualize the digestive tract; 2) USPIO (smaller than 50nm) have a longer plasmatic half-life (>36hours) and exhibit slower uptake by liver and spleen after intravenous administration. This allows the product to access macrophages in normal (lymph nodes) or diseased tissue (multiple sclerosis, graft rejection, atheroma plaques, stroke, rhumatoid arthritis). They can also be used as biomarkers to evaluate the efficacy of treatments. In addition to routine clinical applications, these agents are also under investigation to improve diagnoses in oncological, inflammatory and degenerative as well as cardiovascular diseases (risk of atheroma plaques). PMID:19061725

Bonnemain, B

2008-09-17

273

Synthesis and characterization of PEGylated Gd2O3 nanoparticles for MRI contrast enhancement.  

PubMed

Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study, we report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in MRI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3-5 nm) gadolinium oxide (DEG-Gd(2)O(3)) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd(2)O(3) nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd(2)O(3) nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r(1) and r(2) values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd(2)O(3). Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is, an extremely high MR signal at the cellular and molecular level. PMID:20334417

Ahrén, Maria; Selegård, Linnéa; Klasson, Anna; Söderlind, Fredrik; Abrikossova, Natalia; Skoglund, Caroline; Bengtsson, Torbjörn; Engström, Maria; Käll, Per-Olov; Uvdal, Kajsa

2010-04-20

274

Polymer nanoparticles and nanoparticle arrays  

NASA Astrophysics Data System (ADS)

The manufacturing of polymeric nanoparticles by intramolecular crosslinking is studied by molecular dynamics simulation. Firstly an overview of the intramolecular crosslinking process is obtained by the simulations of benzocyclobutene(BCB)/styrene copolymers using an atomistic model. Then various coarse grained models, including Freely Jointed Chain (FJC). Freely Rotating Chain (FRC) and stiff chain models, are adopted for studying general properties of intramolecular crosslinking of polymers. A temperature series simulation on the FJC model reveals that the change of ambient temperature results in the formation of nanoparticles with distinct morphologies. To describe their structures, a quantity referred to as chemical distance density is introduced, with a quantitative relation between it and the radius of gyration being found. The subsequent study of rigidity effects adopts FRC and stiff chain models. It is found that in the rigid regime, the crosslinking process leaves a substantial number of crosslinkers unlinked, and forms nanoparticles that are significantly larger than their non-rigid counterparts. The Maxwell constraint counting method is used to determine the rigidity thresholds, which yields good agreements with the simulation data. In the last chapter, the atomistic model for polystyrene in the previous crosslinking simulations is employed for a study of polystyrene chains on attractive substrates. The phase diagram and a rough overview of chain dynamics on substrates are obtained.

Liu, Jiwu

275

Particle size distribution analysis for nano-SiO2 powder by ultra-small angle X-ray scattering (USAXS) using synchrotron radiation  

NASA Astrophysics Data System (ADS)

Ultra-small angle X-ray scattering (USAXS) experiments were conducted with the BL15XU beamline (SPring-8) to perform a particle size distribution analysis of nano-powder, i.e. aggregations of particles with dimensions on the order of nanometers. The samples measured were amorphous nano-SiO2 powders of varying specific surface areas. Since a highly collimated and high-intensity X-ray beam is available, it is possible to obtain USAXS spectra that are only slightly affected by background noise. The USAXS spectra obtained from nano-SiO2 powders were analyzed by a modified Fankuchen technique, a method for particle size distribution analysis adapted by the authors. Using this technique, particle size distribution measurements can be performed over a wide range of particle diameters from 1 to 200 nm. Since this method enables the particle size distribution of nano-powder to be accurately and easily determined, it is expected to be useful in a wide variety of fields.

Hashimoto, Hisayuki; Nagumo, Toshiaki; Inaba, Tohru; Furukawa, Yoichiro; Okui, Masato; Fukushima, Sei

2005-02-01

276

Multicenter clinical trial of ultrasmall superparamagnetic iron oxide in the evaluation of mediastinal lymph nodes in patients with primary lung carcinoma.  

PubMed

The purpose of this study was to evaluate the clinical efficacy of ultrasmall superparamagnetic iron oxide particles as a magnetic resonance (MR) contrast agent in differentiating metastatic from benign lymph nodes. Eighteen patients with primary lung malignancy and suspected regional lymph node metastases underwent MR imaging before and after Combidex(R) infusion in a multi-institutional study. All MR sequences were interpreted by one or more board-certified radiologists experienced in imaging thoracic malignancy. Each patient was evaluated for the number and location of lymph nodes, homogeneity of nodal signal, and possible change of MR signal post contrast. All patients underwent resection or sampling of the MR-identified lymph node(s) 1-35 day(s) post contrast MR imaging. In all, 27 lymph nodes or nodal groups were available for histopathologic correlation. Combidex had a sensitivity of 92% and a specificity of 80% in identifying pathologically confirmed metastatic mediastinal lymph nodes. Based on our preliminary data, Combidex MR imaging may provide additional functional information useful in the staging of mediastinal lymph nodes. PMID:10508310

Nguyen, B C; Stanford, W; Thompson, B H; Rossi, N P; Kernstine, K H; Kern, J A; Robinson, R A; Amorosa, J K; Mammone, J F; Outwater, E K

1999-09-01

277

Nanoparticles by Laser Ablation  

Microsoft Academic Search

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

N. G. Semaltianos

2010-01-01

278

Development of Inhalable Nanoparticles  

Microsoft Academic Search

The aim of this study was to develop nanoparticles for lung delivery. Nanoparticles were incorporated into carrier particles using spray drying and a new spray-freeze drying technology. The carrier particles were manufactured with the appropriate size for pulmonary delivery. The new technology has important implications for local drug targeting and drug delivery of nanoparticle based delivery systems to the lungs.

Leticia Ely; Raimar Löbenberg; Zhaolin Wang; Yu Zhang; Warren H. Finlay; Wilson H.-Y. Roa; Jeffrey O. H. Sham

2004-01-01

279

Cell tracking using nanoparticles.  

PubMed

Tracking cells in regenerative medicine is becoming increasingly important for basic cell therapy science, for cell delivery optimization and for accurate biodistribution studies. This report describes nanoparticles that utilize stable-isotope metal labels for multiple detection technologies in preclinical studies. Cells labeled with nanoparticles can be imaged by electron microscopy, fluorescence, and magnetic resonance. The nanoparticle-labeled cells can be quantified by neutron activation, thereby allowing, with the use of standard curves, the determination of the number of labeled cells in tissue samples from in vivo sources. This report describes the characteristics of these nanoparticles and methods for using these nanoparticles to label and track cells. PMID:20559922

Vaccaro, Dennis E; Yang, Meiheng; Weinberg, James S; Reinhardt, Christopher P; Groman, Ernest V

2008-07-08

280

Assessing nanoparticle toxicity.  

PubMed

Nanoparticle toxicology, an emergent field, works toward establishing the hazard of nanoparticles, and therefore their potential risk, in light of the increased use and likelihood of exposure. Analytical chemists can provide an essential tool kit for the advancement of this field by exploiting expertise in sample complexity and preparation as well as method and technology development. Herein, we discuss experimental considerations for performing in vitro nanoparticle toxicity studies, with a focus on nanoparticle characterization, relevant model cell systems, and toxicity assay choices. Additionally, we present three case studies (of silver, titanium dioxide, and carbon nanotube toxicity) to highlight the important toxicological considerations of these commonly used nanoparticles. PMID:22524221

Love, Sara A; Maurer-Jones, Melissa A; Thompson, John W; Lin, Yu-Shen; Haynes, Christy L

2012-04-09

281

Dynamics of Nanoparticle Adhesion  

NASA Astrophysics Data System (ADS)

We have performed molecular dynamics simulations of peeling of nanoparticles from substrate to understand the dynamics of nanoparticle adhesion. In our simulations we have calculated the potential of mean force characterizing the strength of the nanoparticle interaction with the substrate as a function of the particle-substrate separation. These simulations have shown that the detachment of the nanoparticle from substrate occurs through neck formation. The neck height decreases with increasing nanoparticle shear modulus (crosslinking density). Furthermore our simulations have established that the detachment time tR scales with the applied force as f-5. This strong force dependence is a result of the fine interplay between nanoparticle surface energy, elastic energy and its adhesion to the substrate that controls the shape of the nanoparticle.

Dobrynin, Andrey; Carrillo, Jan-Michael; Raphael, Elie

2012-02-01

282

High Resolution Ultra High Field Magnetic Resonance Imaging of Glioma Microvascularity and Hypoxia Using Ultra-Small Particles of Iron Oxide  

PubMed Central

Objectives This study assessed whether ultra-small particles of iron oxide (USPIO) intravascular contrast agent could enhance visualization of tumor microvascularity in F98 glioma bearing rats by means of ultra high field (UHF) high-resolution gradient echo (GRE) magnetic resonance imaging (MRI). In an effort to explain differences in visualization of microvascularity before and after USPIO administration, hypoxia and vessel diameters were assessed on corresponding histopathologic sections. Materials and Methods F98 glioma cells were implanted stereotactically into the brains of syngeneic Fischer rats. Based on clinical criteria, rats were imaged 1 to 2 days before their death with and without USPIO contrast on an 8 Tesla MRI. To identify hypoxic regions of the brain tumor by immunohistochemical, a subset of animals also received a nitroimidazole-based hypoxia marker, EF5, before euthanasia. These sections then were compared with noncontrast enhanced MR images. The relative caliber of tumor microvasculature, compared with that of normal brain, was analyzed in a third group of animals. Results After USPIO administration, UHF high-resolution GRE MRI consistently predicted increased microvascular density relative to normal gray matter when correlated with histopathology. The in-plane visibility of glioma microvascularity in 22 rats increased by an average of 115% and signal intensity within the tumor decreased by 13% relative to normal brain. Tumor microvascularity identified on noncontrast MR images matched hypoxic regions identified by immunohistochemical staining with a sensitivity of 83% and specificity of 89%. UHF GRE MRI was able to resolve microvessels less than 20 ? in diameter, although differences in tumor vessel size did not consistently account for differences in visualization of microvascularity. Conclusions USPIO administration significantly enhanced visualization of tumor microvascularity on gradient echo 8 T MRI and significantly improved visualization of tumor microvascularity. Microvascularity identified on pre-contrast images is suspected to be partly associated with hypoxia.

Christoforidis, Gregory A.; Yang, Ming; Kontzialis, Marinos S.; Larson, Douglas G.; Abduljalil, Amir; Basso, Michelle; Yang, Weilian; Ray-Chaudhury, Abhik; Heverhagen, Johannes; Knopp, Michael V.; Barth, Rolf F.

2010-01-01

283

Detection of lymph node metastases with ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging in oesophageal cancer: a feasibility study  

PubMed Central

Abstract Aim: In this feasibility study we investigated whether magnetic resonance imaging (MRI) with ultrasmall superparamagnetic iron oxide (USPIO) can be used to identify regional and distant lymph nodes, including mediastinal and celiac lymph node metastases in patients with oesophageal cancer. Patients and methods: Ten patients with a potentially curative resectable cancer of the oesophagus were eligible for this study. All patients included in the study had positive lymph nodes on conventional staging (including endoscopic ultrasound, computed tomography and fluorodeoxyglucose-positron emission tomography). Nine patients underwent MRI?+?USPIO before surgery. Results were restricted to those patients who had both MRI?+?USPIO and histological examination. Results were compared with conventional staging and histopathologic findings. Results: One patient was excluded due to expired study time. Five out of 9 patients underwent an exploration; in 1 patient prior to surgery MRI?+?USPIO diagnosed liver metastases and in 3 patients an oesophageal resection was performed. USPIO uptake in mediastinal lymph nodes was seen in 6 out of 9 patients; in 3 patients non-malignant nodes were not visible. In total, 9 lymph node stations (of 6 patients) were separately analysed; 7 lymph node stations were assessed as positive (N1) on MRI+USPIO compared with 9 by conventional staging. According to histology findings, there was one false-positive and one false-negative result in MRI?+?USPIO. Also, conventional staging modalities had one false-positive and one false-negative result. MRI?+?USPIO had surplus value in one patient. Not all lymph node stations could be compared due to unforeseen explorations. No adverse effects occurred after USPIO infusion. Conclusion: MRI+USPIO identified the majority of mediastinal and celiac (suspect) lymph nodes in 9 patients with oesophageal cancer. MRI+USPIO could have an additional value in loco-regional staging; however, more supplementary research is needed.

van der Jagt, E.J.; van Westreenen, H.L.; van Dullemen, H.M.; Kappert, P.; Groen, H.; Sietsma, J.; Oudkerk, M.; Plukker, J.Th.M.; van Dam, G.M.

2009-01-01

284

In-Situ Monitoring of the Microstructure of TATB-based Explosive Formulations During Temperature Cycling using Ultra-small Angle X-ray Scattering  

SciTech Connect

TATB (1,3,5 triamino-2,4,6-trinitrobenzene), an extremely insensitive explosive, is used both in plastic-bonded explosives (PBXs) and as an ultra-fine pressed powder (UFTATB). With both PBXs and UFTATB, an irreversible expansion occurs with temperature cycling known as ratchet growth. In TATB-based explosives using Kel-F 800 as binder (LX-17 and PBX-9502), additional voids, sizes hundreds of nanometers to a few microns account for much of the volume expansion caused by temperature cycling. These voids are in the predicted size regime for hot-spot formation during ignition and detonation, and thus an experimental measure of these voids is important feedback for hot-spot theory and for determining the relationship between void size distributions and detonation properties. Also, understanding the mechanism of ratchet growth allows future choice of explosive/binder mixtures to minimize these types of changes to explosives, further extending PBX shelf life. This paper presents the void size distributions of LX-17, UFTATB, and PBXs using commercially available Cytop M, Cytop A, and Hyflon AD60 binders during temperature cycling between -55 C and 70 C. These void size distributions are derived from ultra-small angle x-ray scattering (USAXS), a technique sensitive to structures from about 10 nm to about 2 mm. Structures with these sizes do not appreciably change in UFTATB, indicating voids or cracks larger than a few microns appear in UFTATB during temperature cycling. Compared to Kel-F 800 binders, Cytop M and Cytop A show relatively small increases in void volume from 0.9% to 1.3% and 0.6% to 1.1%, respectively, while Hyflon fails to prevent irreversible volume expansion (1.2% to 4.6%). Computational mesoscale models of ratchet growth and binder wetting and adhesion properties point to mechanisms of ratchet growth, and are discussed in combination with the experimental results.

Willey, T M; Hoffman, D M; van Buuren, T; Lauderbach, L; Ilavsky, J; Gee, R H; Maiti, A; Overturf, G; Fried, L

2008-02-06

285

Contact Mechanics of Nanoparticles  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulations of the detachment of nanoparticles from a substrate. The critical detachment force, f*, is obtained as a function of the nanoparticle radius, Rp, shear modulus, G, surface energy, ?p, and work of adhesion, W. The magnitude of the detachment force is shown to increase from ?WRp to 2.2?WRp with increasing nanoparticle shear modulus and nanoparticle size. This variation of the detachment force is a manifestation of a neck formation upon nanoparticle detachment. Using scaling analysis, we show that the magnitude of the detachment force is controlled by the balance of the nanoparticle elastic energy, surface energy of the neck, and nanoparticle adhesion energy to a substrate. It is a function of the dimensionless parameter ??p(GRp)-1/3W-2/3which is proportional to the ratio of the surface energy of a neck and the elastic energy of deformed nanoparticle. In the case of small values of the parameter ? 1, the critical detachment force approaches a critical Johnson, Kendall and Roberts force, f* 1.5?WRp, as is usually the case for strongly crosslinked large nanoparticles. However, in the opposite limit, corresponding to soft small nanoparticles, for which ?1, the critical detachment force, f*, scales as f*?p^3/2 Rp^1/2 G-1/2. Simulation data are described by a scaling function f*?p^3/2 Rp^1/2 G-1/2&-1.89circ; .

Carrillo, J.-M. Y.; Dobrynin, A. V.

2013-03-01

286

A nanoparticle in plasma  

SciTech Connect

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

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

2009-06-15

287

Adhesion of Nanoparticles  

Microsoft Academic Search

We have developed a new model of nanoparticle adhesion which explicitly takes into account the change in the nanoparticle surface energy. Using combination of the molecular dynamics simulations and theoretical calculations we have showed that the deformation of the adsorbed nanoparticles is a function of the dimensionless parameter betagamma( GR )-2\\/3W-1\\/3, where G is the particle shear modulus, R is

Jan-Michael Carrillo; Elie Raphael; Andrey Dobrynin

2011-01-01

288

Nanoparticles for Pulmonary Delivery  

Microsoft Academic Search

\\u000a This chapter aims to provide a rational for the use of nanoparticles in pulmonary delivery as well as an overview of strategies\\u000a and physiological implications of nanoparticle delivery to the lungs. Formulation aspects of nanoparticle systems in the form\\u000a of liquid dispersions and inhaled dry powders are also reviewed. The chapter also addresses the expanse of lung toxicology\\u000a research surrounding

Alan B. Watts; Robert O. Williams

289

Photosynthesis of nanoparticles  

Microsoft Academic Search

This work is devoted to an overview of the physical processes that underlie a recently developed method for the photosynthesis\\u000a of nanoparticles. The results of nanoparticle synthesis under the condensation of supersaturated atomic vapor produced by\\u000a the photodissociation of carbon- and metal-bearing compounds are demonstrated. The different factors affecting the formation\\u000a kinetics of carbon and metal nanoparticles are analyzed. The

E. V. Gurentsov; A. V. Eremin

2009-01-01

290

Functional Magnetic Nanoparticles  

Microsoft Academic Search

Nanoparticle system research and characterization is the focal point of this research and dissertation. In the research presented here, magnetite, cobalt, and ferrite nanoparticle systems have been explored in regard to their magnetocaloric effect (MCE) properties, as well as for use in polymer composites. Both areas of study have potential applications across a wide variety of interdisciplinary fields.\\u000aMagnetite nanoparticles

James Gass

2012-01-01

291

Adhesion of Nanoparticles  

NASA Astrophysics Data System (ADS)

We have developed a new model of nanoparticle adhesion which explicitly takes into account the change in the nanoparticle surface energy. Using combination of the molecular dynamics simulations and theoretical calculations we have showed that the deformation of the adsorbed nanoparticles is a function of the dimensionless parameter ??( GR )-2/3W-1/3, where G is the particle shear modulus, R is the initial particle radius, ? is the polymer interfacial energy, and W is the particle work of adhesion. In the case of small values of the parameter ?<0.1, which is usually the case for strongly cross-linked large nanoparticles, the particle deformation can be described in the framework of the classical Johnson, Kendall, and Roberts (JKR) theory. However, we observed a significant deviation from the classical JKR theory in the case of the weakly cross-linked nanoparticles that experience large shape deformations upon particle adhesion. In this case the interfacial energy of the nanoparticle plays an important role controlling nanoparticle deformation. Our model of the nanoparticle adhesion is in a very good agreement with the simulation results and provides a new universal scaling relationship for nanoparticle deformation as a function of the system parameters.

Carrillo, Jan-Michael; Raphael, Elie; Dobrynin, Andrey

2011-03-01

292

Nanoparticles for biomedical imaging  

PubMed Central

Background Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 – 100 nm in diameter have dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for early detection of diseases such as cancer. Surface functionalization has expanded further the potential of nanoparticles as probes for molecular imaging. Objective To summarize emerging research of nanoparticles for biomedical imaging with increased selectivity and reduced nonspecific uptake with increased spatial resolution containing stabilizers conjugated with targeting ligands. Methods This review summarizes recent technological advances in the synthesis of various nanoparticle probes, and surveys methods to improve the targeting of nanoparticles for their application in biomedical imaging. Conclusion Structural design of nanomaterials for biomedical imaging continues to expand and diversify. Synthetic methods have aimed to control the size and surface characteristics of nanoparticles to control distribution, half-life and elimination. Although molecular imaging applications using nanoparticles are advancing into clinical applications, challenges such as storage stability and long-term toxicology should continue to be addressed.

Nune, Satish K; Gunda, Padmaja; Thallapally, Praveen K; Lin, Ying-Ying; Forrest, M Laird; Berkland, Cory J

2011-01-01

293

Self-assembled perovskite-spinel heterostructure on a highly distorted substrate  

NASA Astrophysics Data System (ADS)

The pattern configuration and interface structure in epitaxial BiFeO3-CoFe2O4 heterostructures grown on (010)pc NdGaO3 substrates have been investigated systematically by transmission electron microscopy and chemical analysis. The crystal orientation of CoFe2O4 variants was tuned to [111]CFO, while BiFeO3 kept [010]pc matching the substrate. Triangular prism-shaped CoFe2O4 embedded in the BiFeO3 matrix grew as an equilibrium island mode with {111}CFO as its surfaces and interfaces. Two types of BiFeO3-CoFe2O4 orientation relationships were determined as (001)[010]BFO//(0-22)[111]CFO and (101)[010]BFO//(-220)[111]CFO. The results reveal that the dominant factors controlling the growth orientation of the present vertical heterostructures are surface energy anisotropy and atomic structure continuity.

Zhu, Y. M.; Ke, D.; Yu, R.; Hsieh, Y. H.; Liu, H. J.; Liu, P. P.; Chu, Y. H.; Zhan, Q.

2013-03-01

294

Targeting nanoparticles to cancer.  

PubMed

Nanotechnology applications in medicine, termed as nanomedicine, have introduced a number of nanoparticles of variable chemistry and architecture for cancer imaging and treatment. Nanotechnology involves engineering multifunctional devices with dimensions at the nanoscale, similar dimensions as those of large biological vesicles or molecules in our body. These devices typically have features just tens to hundred nanometers across and they can carry one or two detection signals and/or therapeutic cargo(s). One unique class of nanoparticles is designed to do both, providing this way the theragnostic nanoparticles (therapy and diagnosis). Being inspired by physiologically existing nanomachines, nanoparticles are designed to safely reach their target and specifically release their cargo at the site of the disease, this way increasing the drug's tissue bioavailability. Nanoparticles have the advantage of targeting cancer by simply being accumulated and entrapped in tumours (passive targeting). The phenomenon is called the enhanced permeation and retention effect, caused by leaky angiogenetic vessels and poor lymphatic drainage and has been used to explain why macromolecules and nanoparticles are found at higher ratios in tumours compared to normal tissues. Although accumulation in tumours is observed cell uptake and intracellular drug release have been questioned. Polyethyleneglycol (PEG) is used to protect the nanoparticles from the Reticulo-Endothelial System (RES), however, it prevents cell uptake and the required intracellular drug release. Grafting biorecognition molecules (ligands) onto the nanoparticles refers to active targeting and aims to increase specific cell uptake. Nanoparticles bearing these ligands are recognised by cell surface receptors and this leads to receptor-mediated endocytosis. Several materials are suggested for the design of nanoparticles for cancer. Polymers, linear and dendrimers, are associated with the drug in a covalent or non-covalent way and have been used with or without a targeting ligand. Stealth liposomes are suggested to carry the drug in the aqueous core, and they are usually decorated by recognition molecules, being widely studied and applied. Inorganic nanoparticles such as gold and iron oxide are usually coupled to the drug, PEG and the targeting ligand. It appears that the PEG coating and ligand decoration are common constituents in most types of nanoparticles for cancer. There are several examples of successful cancer diagnostic and therapeutic nanoparticles and many of them have rapidly moved to clinical trials. Nevertheless there is still a room for optimisation in the area of the nanoparticle kinetics such as improving their plasma circulation and tumour bioavailability and understanding the effect of targeting ligands on their efficiency to treat cancer. The need to develop novel and efficient ligands has never been greater, and the use of proper conjugation chemistry is mandatory. PMID:20380880

Wang, M; Thanou, M

2010-04-07

295

Toxicology of nanoparticles.  

PubMed

While nanotechnology and the production of nanoparticles are growing exponentially, research into the toxicological impact and possible hazard of nanoparticles to human health and the environment is still in its infancy. This review aims to give a comprehensive summary of what is known today about nanoparticle toxicology, the mechanisms at the cellular level, entry routes into the body and possible impacts to public health. Proper characterisation of the nanomaterial, as well as understanding processes happening on the nanoparticle surface when in contact with living systems, is crucial to understand possible toxicological effects. Dose as a key parameter is essential in hazard identification and risk assessment of nanotechnologies. Understanding nanoparticle pathways and entry routes into the body requires further research in order to inform policy makers and regulatory bodies about the nanotoxicological potential of certain nanomaterials. PMID:21925220

Elsaesser, Andreas; Howard, C Vyvyan

2011-09-08

296

Magnetic interactions between nanoparticles  

PubMed Central

Summary We present a short overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles. Strong magnetic dipole interactions between ferromagnetic or ferrimagnetic particles, that would be superparamagnetic if isolated, can result in a collective state of nanoparticles. This collective state has many similarities to spin-glasses. In samples of aggregated magnetic nanoparticles, exchange interactions are often important and this can also lead to a strong suppression of superparamagnetic relaxation. The temperature dependence of the order parameter in samples of strongly interacting hematite nanoparticles or goethite grains is well described by a simple mean field model. Exchange interactions between nanoparticles with different orientations of the easy axes can also result in a rotation of the sub-lattice magnetization directions.

Hansen, Mikkel Fougt; Frandsen, Cathrine

2010-01-01

297

Shear thinning of nanoparticle suspensions.  

SciTech Connect

Results of large scale non-equilibrium molecular dynamics (NEMD) simulations are presented for nanoparticles in an explicit solvent. The nanoparticles are modeled as a uniform distribution of Lennard-Jones particles, while the solvent is represented by standard Lennard-Jones particles. Here we present results for the shear rheology of spherical nanoparticles of size 5 to 20 times that of the solvent for a range of nanoparticle volume fractions and interactions. Results from NEMD simulations suggest that for strongly interacting nanoparticle that form a colloidal gel, the shear rheology of the suspension depends only weakly on the size of the nanoparticle, even for nanoparticles as small as 5 times that of the solvent. However for hard sphere-like colloids the size of the nanoparticles strongly affects the shear rheology. The shear rheology for dumbbell nanoparticles made of two fused spheres is also compared to spherical nanoparticles and found to be similar except at very high volume fractions.

Grest, Gary Stephen; Petersen, Matthew K.; in't Veld, Pieter J. (Polymer Research, Ludwigshafen, Germany)

2008-08-01

298

Functional Magnetic Nanoparticles  

NASA Astrophysics Data System (ADS)

Nanoparticle system research and characterization is the focal point of this research and dissertation. In the research presented here, magnetite, cobalt, and ferrite nanoparticle systems have been explored in regard to their magnetocaloric effect (MCE) properties, as well as for use in polymer composites. Both areas of study have potential applications across a wide variety of interdisciplinary fields. Magnetite nanoparticles have been successfully dispersed in a polymer. The surface chemistry of the magnetic nanoparticle proves critical to obtaining a homogenous and well separated high density dispersion in PMMA. Theoretical studies found in the literature have indicated that surface interface energy is a critical component in dispersion. Oleic acid is used to alter the surface of magnetite nanoparticles and successfully achieve good dispersion in a PMMA thin film. Polypyrrole is then coated onto the PMMA composite layer. The bilayer is characterized using cross-sectional TEM, cross-sectional SEM, magnetic characterization, and low frequency conductivity. The results show that the superparmagnetic properties of the as synthesized particles are maintained in the composite. With further study of the properties of these nanoparticles for real and functional uses, MCE is studied on a variety of magnetic nanoparticle systems. Magnetite, manganese zinc ferrite, and cobalt ferrite systems show significant broadening of the MCE and the ability to tune the peak temperature of MCE by varying the size of the nanoparticles. Four distinct systems are studied including cobalt, cobalt core silver shell nanoparticles, nickel ferrite, and ball milled zinc ferrite. The results demonstrate the importance of surface characteristics on MCE. Surface spin disorder appears to have a large influence on the low temperature magnetic and magnetocalorie characteristics of these nanoparticle systems.

Gass, James

299

Shaped gold and silver nanoparticles  

Microsoft Academic Search

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

Yugang Sun; Changhua An

2011-01-01

300

Dynamics of nanoparticle adhesion  

NASA Astrophysics Data System (ADS)

We performed molecular dynamics simulations and theoretical analysis of nanoparticle pulling off from adhesive substrates. Our theoretical model of nanoparticle detachment is based on the Kramers' solution of the stochastic barrier crossing in effective one-dimensional potential well. The activation energy, ?E, for nanoparticle detachment first decreases linearly with increasing the magnitude of the applied force, f, then it follows a power law ?E ~ (f* - f)3/2 as magnitude of the pulling force f approaches a critical detachment force value, f*. These two different regimes in activation energy dependence on magnitude of the applied force are confirmed by analyzing nanoparticle detachment in effective one-dimensional potential obtained by weighted histogram analysis method. Simulations show that detachment of nanoparticle proceeds through neck formation such that magnitude of the activation energy is determined by balancing surface energy of the neck connecting particle to a substrate with elastic energy of nanoparticle deformation. In this regime the activation energy at zero applied force, ?E0, for nanoparticle with radius, Rp, shear modulus, G, surface energy, ?p, and work of adhesion, W, is a universal function of the dimensionless parameter ? ~?pW-2/3(GRp)-1/3. Simulation data are described by a scaling function ?E0~?p5/2Rp1/2G-3/2?-3.75. Molecular dynamics simulations of nanoparticle detachment show that the Kramers' approach fails in the vicinity of the critical detachment force f* where activation energy barrier becomes smaller than the thermal energy kBT. In the interval of the pulling forces f > f* nanoparticle detachment becomes a deterministic process.

Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.

2012-12-01

301

Dynamics of nanoparticle adhesion.  

PubMed

We performed molecular dynamics simulations and theoretical analysis of nanoparticle pulling off from adhesive substrates. Our theoretical model of nanoparticle detachment is based on the Kramers' solution of the stochastic barrier crossing in effective one-dimensional potential well. The activation energy, ?E, for nanoparticle detachment first decreases linearly with increasing the magnitude of the applied force, f, then it follows a power law ?E [proportionality] (f* - f)(3/2) as magnitude of the pulling force f approaches a critical detachment force value, f*. These two different regimes in activation energy dependence on magnitude of the applied force are confirmed by analyzing nanoparticle detachment in effective one-dimensional potential obtained by weighted histogram analysis method. Simulations show that detachment of nanoparticle proceeds through neck formation such that magnitude of the activation energy is determined by balancing surface energy of the neck connecting particle to a substrate with elastic energy of nanoparticle deformation. In this regime the activation energy at zero applied force, ?E(0), for nanoparticle with radius, R(p), shear modulus, G, surface energy, ?(p), and work of adhesion, W, is a universal function of the dimensionless parameter ? [proportionality] ?(p)W(-2/3)(GR(p))(-1/3). Simulation data are described by a scaling function ?E(0) [proportionality] ?(p) (5/2)R(p)(1/2)G(-3/2)?(-3.75). Molecular dynamics simulations of nanoparticle detachment show that the Kramers' approach fails in the vicinity of the critical detachment force f* where activation energy barrier becomes smaller than the thermal energy k(B)T. In the interval of the pulling forces f > f* nanoparticle detachment becomes a deterministic process. PMID:23231258

Carrillo, Jan-Michael Y; Dobrynin, Andrey V

2012-12-01

302

Toxicity of therapeutic nanoparticles.  

PubMed

A total of six nanotherapeutic formulations are already approved for medical use and more are in the approval pipeline currently. Despite the massive research effort in nanotherapeutic materials, there is relatively little information about the toxicity of these materials or the tools needed to assess this toxicity. Recently, the scientific community has begun to respond to the paucity of information by investing in the field of nanoparticle toxicology. This review is intended to provide an overview of the techniques needed to assess toxicity of these therapeutic nanoparticles and to summarize the current state of the field. We begin with background on the toxicological assessment techniques used currently as well as considerations in nanoparticle dosing. The toxicological research overview is divided into the most common applications of therapeutic nanoparticles: drug delivery, photodynamic therapy and bioimaging. We end with a perspective section discussing the current technological gaps and promising research aimed at addressing those gaps. PMID:19193187

Maurer-Jones, Melissa A; Bantz, Kyle C; Love, Sara A; Marquis, Bryce J; Haynes, Christy L

2009-02-01

303

Engines and nanoparticles  

Microsoft Academic Search

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

David B. Kittelson

1998-01-01

304

Fluid flow in ultrasmall structures  

NASA Astrophysics Data System (ADS)

We describe studies of the pressure driven flow of several classical fluids through lithographically produced channels in which one dimension, the channel height h, is in the micron or nanometer size range. The measured flow rates are compared with theoretical predictions assuming no-slip boundary conditions at the walls of the channel. The results for water agree well with this prediction for h as small as 40 nm (our smallest channels). However, for hexane, decane, hexadecane, and silicone oil we find deviations from this theory when h is reduced below about 100 nm. The observed flow rates for small h are larger than theoretical expectations, implying significant slip at the walls, and values of the slip length are estimated. The results are compared with previous experimental and theoretical work. We have also developed an improved method of making micro-models for the study of multiphase flow in porous media. A central theme of our work is to use model systems to gain new insights into the geometrical aspects of multiphase flow. We would like to better understand how the geometry of the open pore space affects the geometry (fractal or otherwise) of the wetting and non-wetting phases, and how these geometries vary during a drainage/imbibition cycle. In addition to flow rate measurements at various levels of saturation, we have used photographic studies of the geometries of the wetting and non-wetting phases, in our case decane and nitrogen gas, to measure the interfacial area per unit "volume" (IAV) separating these phases. While the relation between saturation (S) and capillary pressure (Pcap) during these cycles is hysteretic, the IAV appears to be a single valued function of S and Pcap. This observation confirms, at least qualitatively, theoretical predictions of Gray and coworkers concerning the importance of IAV as a fundamental quantity necessary for understanding and characterizing multiphase flow. We believe this to be the first experimental measurement of the IAV for multiphase flow.

Cheng, Jiangtao

305

Origin of magnetic anomalies and relaxation mechanisms in ferrofluids  

NASA Astrophysics Data System (ADS)

From a fundamental physics perspective, it is proposed that blocking of magnetic nanoparticles and freezing of a carrier fluid would affect the magnetization and relaxation processes in ferrofluids. To verify this hypothesis, we have conducted systematic DC magnetization and AC susceptibility studies in different ferrofluids composed of Fe3O4 and CoFe2O4 nanoparticles suspended in hexane and dodecane, which respectively have freezing temperatures below (178K) and above (264K) the blocking temperature of magnetic nanoparticles (˜200K). Experimental results reveal that the particle blocking and carrier fluid freezing effects play key roles in the formation of glass-like relaxation peaks in ferrofluids, which remained largely unexplained in previous studies. It is also shown that the nature of these peaks is strongly affected by varying particle size and carrier fluid medium. Quantitative fits of the frequency dependent AC susceptibility to the Vogel-Fulcher model, ?=?oexp[Ea/k(T-To)], clearly indicate that the blocking of magnetic nanoparticles in the frozen state significantly affects the interparticle dipole-dipole interaction, causing characteristic spin-glass-like dynamics. A clear correlation between the blocking and freezing temperatures emerges from our studies for the first time.

Morales, M. B.; Phan, M. H.; Frey, N. A.; Pal, S.; Srikanth, H.

2009-03-01

306

Introduction to metallic nanoparticles  

PubMed Central

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

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

2010-01-01

307

Magnetic Nanoparticle Compositions and Methods.  

National Technical Information Service (NTIS)

A nanoparticle having a core comprising a magnetic material and surface to which are covalently coupled a plurality of silane moieties, wherein each silane moiety comprises a polyalkylene oxide moiety. The nanoparticle can further include a targeting agen...

J. W. Gunn M. Zhang N. Kohler

2006-01-01

308

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...

309

Fluorescence from Coated Oxide Nanoparticles.  

National Technical Information Service (NTIS)

In many cases, coated nanoparticles behave like isolated ones. Using the microwave plasma process, it is possible to produce oxide nanoparticles with ceramic or polymer coating. Coating the particles has the additional advantage that by proper selection o...

D. Vollath D. V. Szabo I. Lamparth

2001-01-01

310

Transport measurements across single nanoparticles  

NASA Astrophysics Data System (ADS)

During this last decade, numerous progresses have been obtained in the chemical synthesis of nanoparticle. Various materials (oxides, chalcogenides) known for their peculiar electronic or magnetic properties -- superconductivity, Mott localization, topological protection -- can now be obtained as nanoparticles through chemical synthesis. These new nano-materials are offering a unique opportunity to study the effect of quantum confinement on unconventional electronic orders. To improve the preparation of samples with single nanoparticles trapped within a nanogap, we developed a new method where nanoparticles are projected in-vacuum on chip circuits covered by nanogap spaced electrodes. Continuous current measurements during the projection allow identifying the trapping of a single nanoparticle within the nanogap. We apply the method for trapping single gold nanoparticles, which led to the observation of Coulomb blockade. We also applied the method to magnetite (Fe3O4) nanoparticles, which allows to study the electric field induced insulator to metal transition in only a few nanoparticles.

Yu, Qian; Cui, Limin; Ulysse, Christian; Mottaghizadeh, Alireza; Zimmers, Alexandre; Aubin, Hervé.

2013-03-01

311

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

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

Takayuki Kumada; Yohei Noda; Satoshi Koizumi; Takeji Hashimoto

2010-01-01

312

Nanoparticle–polymer photovoltaic cells  

Microsoft Academic Search

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

Brian R. Saunders; Michael L. Turner

2008-01-01

313

Paper surfaces functionalized by nanoparticles  

Microsoft Academic Search

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

Ying Hui Ngo; Dan Li; George P. Simon; Gil Garnier

2011-01-01

314

Paper surfaces functionalized by nanoparticles.  

PubMed

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

Ngo, Ying Hui; Li, Dan; Simon, George P; Garnier, Gil

2011-01-22

315

Lactobacillusassisted synthesis of titanium nanoparticles  

PubMed Central

An eco-friendlylactobacillussp. (microbe) assisted synthesis of titanium nanoparticles is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ti nanoparticles. Individual nanoparticles as well as a number of aggregates almost spherical in shape having a size of 40–60 nm are found.

2007-01-01

316

Multi-scale Size Distributions of Colloidal Gold Clusters Measured by Ultrasmall Angle X-ray Scattering (USAXS) and Dynamic Light Scattering (DLS)  

NASA Astrophysics Data System (ADS)

Gold colloids are of interest as: (1) catalysts for energy conversion and (2) absorption agents for laser photothermal therapy. This research examines the agglomerate sizes (using DLS) and primary particle sizes (using USAXS) for gold nanoparticles synthesized by trisodium citrate reduction of gold chloroauric acid (HAuCl4). USAXS data was collected at the Advanced Photon Source, beamline 15ID-D. Model fitting of the data show primary particle sizes of 7nm to 14nm formed. DLS results show these particles to aggregate into a bimodal set of clusters centered on approximately 20nm and approximately 200nm. Preliminary results aimed at effectively breaking apart these aggregates are presented.

Nieves, Ashli; Ilavsky, Jan; Dobbins, Tabbetha

2013-03-01

317

Gold Nanoparticles Cytotoxicity  

NASA Astrophysics Data System (ADS)

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

Mironava, Tatsiana

318

Engineered Nanoparticles and Their Identification Among Natural Nanoparticles  

NASA Astrophysics Data System (ADS)

The more nanotechnology develops, the more likely the release of engineered nanoparticles into the environment becomes. Due to a huge excess of natural nanoparticles, the identification and quantification of engineered nanoparticles pose a big challenge to analysts. Moreover, identification in a qualitative sense and quantification by mass concentration alone are not sufficient, because the potential environmental hazard arising from engineered nanoparticles is controlled by many other properties of the particles. We discuss the most important methods of fractionation and detection of both natural and engineered nanoparticles, with a focus on the chemical nature of the particles, particle concentration, and particle size. Analyses should not rely on only one method; instead, several complementary methods should, if possible, be used. Coupled techniques should be further developed and increasingly applied. Dedicated techniques that are tailored to the search for a particular sort of engineered nanoparticles are more promising than universal approaches that search for any engineered nanoparticles.

Zänker, H.; Schierz, A.

2012-07-01

319

Engineered nanoparticles and their identification among natural nanoparticles.  

PubMed

The more nanotechnology develops, the more likely the release of engineered nanoparticles into the environment becomes. Due to a huge excess of natural nanoparticles, the identification and quantification of engineered nanoparticles pose a big challenge to analysts. Moreover, identification in a qualitative sense and quantification by mass concentration alone are not sufficient, because the potential environmental hazard arising from engineered nanoparticles is controlled by many other properties of the particles. We discuss the most important methods of fractionation and detection of both natural and engineered nanoparticles, with a focus on the chemical nature of the particles, particle concentration, and particle size. Analyses should not rely on only one method; instead, several complementary methods should, if possible, be used. Coupled techniques should be further developed and increasingly applied. Dedicated techniques that are tailored to the search for a particular sort of engineered nanoparticles are more promising than universal approaches that search for any engineered nanoparticles. PMID:22482788

Zänker, H; Schierz, A

2012-04-15

320

Semiconducting nanoparticles with surface modification  

US Patent & Trademark Office Database

The invention relates to semiconducting nanoparticles. The nanoparticles of the invention comprise a single element or a compound of elements in one or more of groups II, III, IV, V, VI. The nanoparticles have a size in the range of 1 nm to 500 nm, and comprise from 0.1 to 20 atomic percent of oxygen or hydrogen. The nanoparticles are typically formed by comminution of bulk high purity silicon. One application of the nanoparticles is in the preparation of inks which can be used to define active layers or structures of semiconductor devices by simple printing methods.

Britton; David Thomas (Cape Town, ZA); Harting; Margit (Cape Town, ZA)

2013-01-15

321

TOPICAL REVIEW: Biopolymeric nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

322

Nanoparticle-Based Biosensors and Bioassays  

SciTech Connect

In this book chapter, we review the recent advances in nanoparticles based bioassay. The nanoparticles include quantum dots, silica nanoparticles and apoferritin nanoparticles. The new nanoparticles-based labels hold great promise for multiplex protein and DNA detection and for enhancing the sensitivity of other bioassays.

Liu, Guodong; Wang, Jun; Lin, Yuehe; Wang, Joseph

2007-10-11

323

In vitro biomedical applications of functionalized iron oxide nanoparticles, including those not related to magnetic properties.  

PubMed

Superparamagnetic iron oxide nanoparticles (SPION) are very promising contrast media, especially for molecular imaging, due to their superior NMR efficacy. They even have wider biomedical applications such as in drug and gene delivery, tissue engineering and bioseparation, or as sensitive biological nanosensors. By coupling them to affinity ligands, SPION can bind to drugs, proteins, enzymes, antibodies or nucleotides. For in vitro biomedical applications, the detection of molecular interaction is possible by using a diversity of systems capable of sensing the magnetic properties of these materials. The goal of the present work was to develop and validate various in vitro biomedical applications of ultrasmall superparamagnetic particles of iron oxide (USPIO), including some that are not related to their magnetic properties. USPIO coated with dextran, starch or bisphosphonate exposing carboxylate groups were synthesized and some of them were functionalized by conjugating various biomolecules, such as biotin, streptavidin and apoptosis, or VCAM-1 specific peptides. The in vitro biomedical applications assessed in the present work included: (1) the relaxometric measurement of antibody concentration, cell receptor expression, molecular interaction, and enzymatic activity in aqueous suspensions; (2) MRI visualization of cells and detection of molecular interaction in an ELISA system; (3) ELISA applications of USPIO derivatives; and (4) detection of specific biomolecules by histochemistry. Our results confirm that rapid and simple in vitro detection of a diversity of functionalized SPION with relevance in medicine is possible by the existing NMR techniques and by chemical staining reactions. The protocols can be applied to minimally prepared biological samples (e.g. whole blood, blood plasma or serum, cell suspensions, biopsies, histological preparations, etc.), and often do not need complicated systems of signal amplification. The use of SPION labeled compounds could furthermore contribute to cost reductions in the diagnosis and in patient care. PMID:21861284

Burtea, Carmen; Laurent, Sophie; Mahieu, Isabelle; Larbanoix, Lionel; Roch, Alain; Port, Marc; Rousseaux, Olivier; Ballet, Sébastien; Murariu, Oltea; Toubeau, Gérard; Corot, Claire; Vander Elst, Luce; Muller, Robert N

2010-12-29

324

Health implications of nanoparticles  

Microsoft Academic Search

Nanoparticles are increasingly used in a wide range of applications in science, technology and medicine. Since they are produced for specific purposes which cannot be met by larger particles and bulk material they are likely to be highly reactive, in particular, with biological systems. On the other hand a large body of know-how in environmental sciences is available from toxicological

Wolfgang G. Kreyling; Manuela Semmler-Behnke; Winfried Möller

2006-01-01

325

Adhesion between nanoparticles  

Microsoft Academic Search

A study of the contact and adhesion between panicles with clean surfaces (free from oxide and other contamination) is important but increasingly more difficult to perform as the particle size is reduced to a nanoscale. A reproducible way of finding such contacts between a large number of nanoparticles has been developed. Cobalt particles within the size range 5–200 nm have

Y. Yao; A. R. Thölén

1999-01-01

326

Magnetic nanoparticles for theragnostics  

Microsoft Academic Search

Engineered magnetic nanoparticles (MNPs) represent a cutting-edge tool in medicine because they can be simultaneously functionalized and guided by a magnetic field. Use of MNPs has advanced magnetic resonance imaging (MRI), guided drug and gene delivery, magnetic hyperthermia cancer therapy, tissue engineering, cell tracking and bioseparation. Integrative therapeutic and diagnostic (i.e., theragnostic) applications have emerged with MNP use, such as

Veronica I. Shubayev; Thomas R. Pisanic II; Sungho Jin

2009-01-01

327

Nanoparticles in forensic science  

NASA Astrophysics Data System (ADS)

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.

Cantu, Antonio A.

2008-10-01

328

Nanoparticle assemblies as memristors.  

PubMed

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

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

329

Agglomeration of magnetic nanoparticles.  

PubMed

The formation of agglomerates by salt-induced double layer compression of magnetic nanoparticles in the absence and presence of an external magnetic field was investigated experimentally as well as computationally in this study. The structures of the agglomerates were analyzed through scanning electron microscopy and proved to be highly porous and composed of large spaces among the branches of a convoluted network. In the absence of an external magnetic field, the branches of such a network were observed to be oriented in no particular direction. In contrast, when the agglomeration process was allowed to occur in the presence of an external magnetic field, these branches appeared to be oriented predominantly in one direction. A modified Discrete Element Method was applied to simulate the agglomeration process of magnetic nanoparticles both in the absence and presence of an external magnetic field. The simulations show that agglomeration occurred by the formation of random clusters of nanoparticles which then joined to form a network. In the presence of anisotropic magnetic forces, these clusters were rotated to align along the direction of the magnetic field and the final network formed consisted largely of elongated branches of magnetic nanoparticles. PMID:22462837

Lim, Eldin Wee Chuan; Feng, Ruili

2012-03-28

330

Polyoxometalate-decorated nanoparticles.  

PubMed

Polyoxometalate cluster anions (POMs) control formation and morphology, and serve as protecting ligands, for structurally and compositionally diverse nanostructures. While numerous examples of POM-protected metal(0) nanoparticle syntheses and reactions can now be found in the literature, the use of POMs to prepare nano-scale analogs of binary inorganic materials, such as metal-oxides, sulfides and halides, is a relatively recent development. The first part of this critical review summarizes the use of POMs as protecting ligands for metal(0) nanoparticles, as well as their use as templates for the preparation of new inorganic materials. Here, key findings that reveal general trends are given additional emphasis. In the second part of the review, new information concerning the structure of POM-protected metal(0) nanoparticles is systematically developed. This information, obtained by the combined use of cryogenic transmission microscopy (cryo-TEM) and UV-vis spectroscopy, provides a new perspective on the formation and structure of POM-decorated nanoparticles, and on the rational design of catalytic and other functional POM-based nano-assemblies. PMID:22814638

Wang, Yifeng; Weinstock, Ira A

2012-07-20

331

Targeting nanoparticles to cancer  

Microsoft Academic Search

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

M. Wang; M. Thanou

2010-01-01

332

Photoacoustic signal amplification through plasmonic nanoparticle aggregation  

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

333

Photoacoustic signal amplification through plasmonic nanoparticle aggregation.  

PubMed

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

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

2013-01-01

334

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

335

Vacancy Clusters at Nanoparticle Surfaces  

SciTech Connect

The authors detect vacancy clusters at Au nanoparticle surfaces using a combination of positron lifetime spectroscopy, 1- detector, and 2-detector measurements of Doppler broadening of annihilation radiation. Gold nanoparticles are formed by MeV implantation of gold ions into MgO (100) followed by annealing. Clusters of two Mg and two O vacancies (v{sub 4}) are attached to the gold nanoparticle surfaces within the projected range (R{sub p}).

Xu, J.; Moxom, J.; Somieski, B.; White, C.W.; Mills, A.P.; Suzuki, R.; Ishibashi, S.; Ueda, A.; Henderson, D.

2000-08-06

336

Glucose biosensor enhanced by nanoparticles  

Microsoft Academic Search

Glucose biosensors have been formed with glucose oxidase (GOD) immobilized in composite immobilization membrane matrix, which\\u000a is composed of hydrophobic gold, or hydrophilic gold, or hydrophobic silica nanoparticles, or the combination of gold and\\u000a silica nanoparticles, and polyvinyl butyral (PVB) by a sol-gel method. The experiments show that nanoparticles can significantly\\u000a enhance the catalytic activity of the immobilization enzyme. The

Fangqiong Tang; Xianwei Meng; Dong Chen; Junguo Ran; Changqiong Zheng

2000-01-01

337

Inorganic Nanoparticles in Cancer Therapy  

PubMed Central

Nanotechnology is an evolving field with enormous potential for biomedical applications. The growing interest to use inorganic nanoparticles in medicine is due to the unique size and shape-dependent optoelectronic properties. Herein, we will focus on gold, silver and platinum nanoparticles, discussing recent developments for therapeutic applications with regard to cancer in terms of nanoparticles being used as a delivery vehicle as well as therapeutic agents. We will also discuss some of the key challenges to be addressed in future studies.

Bhattacharyya, Sanjib; Kudgus, Rachel A.; Bhattacharya, Resham; Mukherjee, Priyabrata

2011-01-01

338

Nanobiotechnology today: focus on nanoparticles  

PubMed Central

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

Soloviev, Mikhail

2007-01-01

339

Nanobiotechnology today: focus on nanoparticles  

Microsoft Academic Search

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

Mikhail Soloviev

2007-01-01

340

Prospects for Organic Dye Nanoparticles  

Microsoft Academic Search

\\u000a \\u000a Abstract  A review of organic nanoparticles consisting of small functional dye molecules is presented in this chapter. The study of\\u000a organic dye nanoparticles does not have a lengthy history, but there is growing scientific and technological interest owing\\u000a to their special characteristics: physicochemical properties of organic dye nanoparticles considerably differ not only from\\u000a those of individual molecules due to the presence

Hiroshi Yao

341

Nanoparticles as 'smart' pharmaceutical delivery.  

PubMed

Pharmaceuticals in conjunction with nanoparticle delivery systems are growing towards new heights. The aim of this review is to gain a thorough understanding of different types and characteristics of nanoparticle based delivery systems, important properties of delivery systems, pharmaceutical ingredient loading and release in the nanoparticle delivery systems. In this review, we have also highlighted about the promising pharmaceutical deliveries like brain targeted delivery, ocular delivery, oral delivery, dermal and transdermal delivery, cancer chemotherapy, vaccine delivery, nucleic acids delivery and delivery system coupling to implants. A snapshot of the nanoparticle mediated drug deliveries which are commercially available and ongoing clinical trials have been provided. PMID:23747865

Chakraborty, Chiranjib; Pal, Soumen; Doss, George Priya C; Wen, Zhi-Hong; Lin, Chan-Shing

2013-06-01

342

Nanoparticle Reactions on Chip  

NASA Astrophysics Data System (ADS)

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.

Köhler, J. M.; Kirner, Th.; Wagner, J.; Csáki, A.; Möller, R.; Fritzsche, W.

343

Photoluminescence by Interstellar Nanoparticles  

SciTech Connect

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

Witt, Adolf N. (University of Toledo)

2004-04-21

344

Nanoparticles via nanoprecipitation process.  

PubMed

Various encapsulation approaches have been explored during the last years in order to encapsulate classical active molecules and new synthesized molecules principally for the in vivo therapy as drug delivery nanocarriers and also for the in vivo biomedical diagnostic. These approaches lead to new and versatile systems exhibiting high encapsulation yields of small molecules mainly. Due to the use of biodegradable polymers, the final particles and dispersions exhibit low cytotoxicity and in some cases total biocompatibility. To enhance local targeting efficiency, nanoparticles are chemically grafted using specific antibody for a specific disease. One of the easiest processes leading to rapid particles formation is the nanoprecipitation. Such process is mainly based on polymer transfer from good solvent to poor solvent condition, leading consequently to nanoparticles formation via self-assembly of precipitated polymer chains. The article discussed some of patents associated with Nanoprecipitation Process. PMID:22845041

Minost, Audrey; Delaveau, Jean; Bolzinger, Marie-Alexandrine; Fessi, Hatem; Elaissari, Abdelhamid

2012-12-01

345

Nanoparticles in dermatology  

Microsoft Academic Search

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

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

346

Nanoparticle Toxicity Mechanisms: Genotoxicity  

NASA Astrophysics Data System (ADS)

Despite the relatively small amount of convincing experimental data, the potentially genotoxic nature of certain nanoparticles seems plausible, owing in particular to the presence of reactive oxygen species (ROS) such as the superoxide anion O2 • - , the hydroxyl radical • OH, and singlet oxygen 1O2, and reactive nitrogen species (RNS) such as nitrogen monoxide NO, the peroxynitrite anion ONOO - , the peroxynitrite radical ONOO • , and dinitrogen trioxide N2O3, a powerful nitration agent.

Botta, Alain; Benameur, La??la

347

Targeted Nanoparticle Subpopulation  

Microsoft Academic Search

The Filmix® nanoemulsion (including its self-assembling mixed-lipid nanoparticle subpopulations) is easily produced using a relatively mild dispersing technique. The small energy input needed for production of the Filmix® nanoemulsion (at room temperature) resembles the generally mild conditions under which SNEDDS (self-nanoemulsifying drug-delivery system(s)) are formed. Moreover, medium-chain and long-chain glycerides, which are employed for producing various SNEDDS reported in the

Joseph D'Arrigo

2011-01-01

348

Nanoparticle bridge DNA biosensor  

Microsoft Academic Search

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

Hong-Wen Huang

2010-01-01

349

Electrodynamics of Noble Metal Nanoparticles and Nanoparticle Clusters  

Microsoft Academic Search

In this paper we examine the electrodynamics of silver nanoparticles and of clusters of nanoparticles, with an emphasis on extinction spectra and of electric fields near the particle surfaces that are important in determining surface-enhanced Raman (SER) intensities. The particles and clusters are chosen to be representative of what has been studied in recent work on colloids and with lithographically

Traci Jensen; Lance Kelly; Anne Lazarides; George C. Schatz

1999-01-01

350

Sensing with fluorescent nanoparticles  

NASA Astrophysics Data System (ADS)

Fluorescent chemosensors are chemical systems that can detect and signal the presence of selected analytes through variations in their fluorescence emission. Their peculiar properties make them arguably one of the most useful tools that chemistry has provided to biomedical research, enabling the intracellular monitoring of many different species for medical and biological purposes. In its simplest design, a fluorescent chemosensor is composed of a fluorescent dye and a receptor, with a built-in transduction mechanism that converts recognition events into variations of the emission properties of the fluorescent dye. As soon as fluorescent nanoparticles became available, several applications in the field of sensing were explored. Nanoparticles have been used not only as better-performing substitutes of traditional dyes but also as multivalent scaffolds for the realization of supramolecular assemblies, while their high surface to volume ratio allows for distinct spatial domains (bulk, external surface, pores and shells) to be functionalized to a comparable extent with different organic species. Over the last few years, nanoparticles proved to be versatile synthetic platforms for the implementation of new sensing schemes.

Baù, Luca; Tecilla, Paolo; Mancin, Fabrizio

2011-01-01

351

Gold nanoparticles in cancer therapy  

Microsoft Academic Search

The rapid advancement of nanotechnology in recent years has fuelled a burgeoning interest in the field of nanoparticle research, in particular, its application in the medical arena. A constantly expanding knowledge based on a better understanding of the properties of gold nanoparticles (AuNPs) coupled with relentless experimentation means that the frontiers of nanotechnology are constantly being challenged. At present, there

Zhao-Zhin Joanna Lim; Jia-En Jasmine Li; Cheng-Teng Ng; Lin-Yue Lanry Yung; Boon-Huat Bay

2011-01-01

352

Resveratrol in Solid Lipid Nanoparticles  

Microsoft Academic Search

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

Maria Eugenia Carlotti; Simona Sapino; Elena Ugazio; Marina Gallarate; Silvia Morel

2011-01-01

353

DNA-scaffolded nanoparticle structures  

Microsoft Academic Search

DNA self-assembly is a powerful route to the production of very small, complex structures. When used in combination with nanoparticles it is likely to become a key technology in the production of nanoelectronics in the future. Previously, demonstrated nanoparticle assemblies have mainly been periodic and highly symmetric arrays, unsuited as building blocks for any complex circuits. With the invention of

Björn Högberg; Håkan Olin

2007-01-01

354

Equilibrium Shape of Gold Nanoparticles  

NASA Astrophysics Data System (ADS)

Gold nanoparticles are essential components of various nanomaterials; examples include colloidal gold, used in biomedical applications, and gold-based catalysts that can oxidise CO at room temperatures. The performance of gold nanoparticles in these materials depends critically on both their size and their shape. We present a first-principles study for the equilibrium shape of Au nanoparticles of given size in various environments. We consider nanoparticles in a weakly interacting environment and nanoparticles in CO gas. We use well-converged Density-Functional Theory simulations to calculate the surface tension and CO adsorption energy for all low-index Au(hkl) surfaces (h,k,l <= 4). These results are used to estimate the interfacial tensions between Au(hkl) surfaces and CO gas, which in turn determine the shape through a Wulff construction. We calculate key parameters for Au nanoparticles such as the number of active sites as a function of their size. We find variations in the equilibrium shape at small nanoparticle sizes, where edge effects are important. Finally, we observe a dramatic change in the shape of gold nanoparticles upon exposure to CO gas, in very good agreement with recent experiments.

Barmparis, Georgios; Remediakis, Ioannis

2010-03-01

355

Nanoparticle superlattice engineering with DNA  

Microsoft Academic Search

A current limitation in nanoparticle superlattice engineering is that the identities of the particles being assembled often determine the structures that can be synthesized. Therefore, specific crystallographic symmetries or lattice parameters can only be achieved using specific nanoparticles as building blocks (and vice versa). We present six design rules that can be used to deliberately prepare nine distinct colloidal crystal

R. J. MacFarlane; B. Lee; M. R. Jones; N. Harris; G. C. Shatz; C. A. Mirkin

2011-01-01

356

Credible intervals for nanoparticle characteristics  

NASA Astrophysics Data System (ADS)

Solving the inverse problem of nanoparticle characterization has the potential to advance science and benefit society. While considerable progress has been made within a framework based on the scattering of surface plasmon-polaritons, an aspect not heretofore considered is the quantification of uncertainty in the estimation of a nanoparticle characteristic. Therefore, the present article offers a technique by which an investigator may augment an estimate of a nanoparticle characteristic with a companion “credible interval”. Analogous to the familiar confidence interval but arising from within the Bayesian statistical paradigm, a credible interval allows the investigator to make a statement such as “the nanoparticle diameter lies between 36 and 48 nm with 95% probability” instead of merely “the nanoparticle diameter is estimated to be 42 nm”. Our technique may even be applied outside of the surface plasmon-polariton scattering framework, as long as the investigator specifies his/her prior beliefs about the nanoparticle characteristic and indicates which potential outcomes are likely or unlikely in whatever experiment he/she designs to estimate the nanoparticle characteristic. Two numerical studies illustrate the implementation and performance of our technique in constructing ranges of likely values for nanoparticle diameters and agglomeration levels, respectively.

Charnigo, Richard; Francoeur, Mathieu; Kenkel, Patrick; Mengüç, M. Pinar; Hall, Benjamin; Srinivasan, Cidambi

2012-01-01

357

Hydrogel nanoparticles in drug delivery  

Microsoft Academic Search

Hydrogel nanoparticles have gained considerable attention in recent years as one of the most promising nanoparticulate drug delivery systems owing to their unique potentials via combining the characteristics of a hydrogel system (e.g., hydrophilicity and extremely high water content) with a nanoparticle (e.g., very small size). Several polymeric hydrogel nanoparticulate systems have been prepared and characterized in recent years, based

Mehrdad Hamidi; Amir Azadi; Pedram Rafiei

2008-01-01

358

Role of Nanoparticles in Photocatalysis  

Microsoft Academic Search

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

D. Beydoun; R. Amal; G. Low; S. McEvoy

1999-01-01

359

Acoustic vibrations of anisotropic nanoparticles  

Microsoft Academic Search

Acoustic vibrations of nanoparticles made of materials with anisotropic elasticity and nanoparticles with nonspherical shapes are theoretically investigated using a homogeneous continuum model. Cubic, hexagonal, and tetragonal symmetries of the elasticity are discussed, as are spheroidal, cuboctahedral, and truncated cuboctahedral shapes. Tools are described to classify the different vibrations and, for example, help identify the modes having a significant low-frequency

Lucien Saviot; Daniel B. Murray

2009-01-01

360

Gold-Nanoparticle-Enhanced Cancer Photothermal Therapy  

Microsoft Academic Search

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.

Jing-Liang Li; Min Gu

2010-01-01

361

Gold nanoparticles for tumour detection and treatment  

Microsoft Academic Search

The use of nanoparticles in biomedical applications is emerging rapidly. Recent developments have led to numerous studies of noble metal nanoparticles, down to the level of single molecule detection in living cells. The application of noble metal nanoparticles in diagnostics and treatment of early stage carcinomas is the subject of many present studies. Gold nanoparticles are particularly interesting for optical

L. Hartsuiker; W. Petersen; J. Jose; P. van Es; A. Lenferink; A. A. Poot; L. W. M. M. Terstappen; T. G. van Leeuwen; S. Manohar; C. Otto

2011-01-01

362

Size-Dependent Cytotoxicity of Gold Nanoparticles  

Microsoft Academic Search

Gold nanoparticles are widely used in biomedical imaging and diagnos- tic tests. Based on their established use in the laboratory and the chemical stability of Au0, gold nanoparticles were expected to be safe. The recent literature, however, contains conflictingdata reg ardingthe cytotoxicity of gold nanoparticles. Against this background a systematic study of water- soluble gold nanoparticles stabilized by triphenylphosphine derivatives

Yu Pan; Sabine Neuss; Annika Leifert; Monika Fischler; Fei Wen; Ulrich Simon; Günter Schmid; Wolfgang Brandau; Willi Jahnen-Dechent

2007-01-01

363

Preparation and antibacterial activity of chitosan nanoparticles  

Microsoft Academic Search

Chitosan nanoparticles, such as those prepared in this study, may exhibit potential antibacterial activity as their unique character. The purpose of this study was to evaluate the in vitro antibacterial activity of chitosan nanoparticles and copper-loaded nanoparticles against various microorganisms. Chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions. Copper ions were adsorbed onto the

Lifeng Qi; Zirong Xu; Xia Jiang; Caihong Hu; Xiangfei Zou

2004-01-01

364

Compressibility of zinc sulfide nanoparticles  

SciTech Connect

We describe a high-pressure x-ray diffraction (XRD) study of the compressibility of several samples of ZnS nanoparticles. The nanoparticles were synthesized with a range of sizes and surface chemical treatments in order to identify the factors that determine nanoparticle compressibility. Refinement of the XRD data revealed that all ZnS nanoparticles in the nominally cubic (sphalerite) phase exhibited a previously unobserved structural distortion under ambient conditions that exhibited, in addition, a dependence on pressure. Our results show that the compressibility of ZnS nanoparticles increases substantially as the particle size decreases, and we propose an interpretation based upon the available mechanisms of structural compliance in nanoscale vs bulk materials.

Gilbert, B. [Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Zhang, H.; Chen, B.; Banfield, J. F. [Department of Earth and Planetary Sciences, University of California-Berkeley, Berkeley, California 94720 (United States); Kunz, M. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Huang, F. [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China (China)

2006-09-15

365

Functionalized nanoparticles for sensor applications.  

SciTech Connect

We will describe our work on functionalized arrays of nanoparticles crosslinked with short conducting molecules that contain sensing functionalities. These bridging ligands modulate their conductivity based on their interaction with analytes. This functionalized nanoparticles organic ligand composite material once it is assembled between nanogaps electrodes will provide nanosized sensors that can be easily interrogated. These nanogap sensors will be engineered so that they can be fabricated into arrays of different sensor elements. This project consists of a number of different requirements that must be met in order to enable the use of functionalized nanoparticles for sensor applications. The first requirement is the appropriately functionalized nanoparticle. The second is a method to assemble the particles. The third requirement is the generation of a nanogap to contain the nanoparticles. The successes in each of these areas will be discussed as will the sensing behavior of the final films.

Simonson, Robert Joseph; Childs, Kenton David; Howell, Stephen Wayne; Dirk, Shawn M.; Wheeler, David Roger

2005-09-01

366

Antibacterial effects of laser ablated Ni nanoparticles  

NASA Astrophysics Data System (ADS)

The interaction of nickel nanoparticles with Escherichia coli (E. coli) bacteria has been studied. The nickel nanoparticles have been fabricated by continuous wave laser ablation of nickel target and their properties are studied using different characterization techniques. The antibacterial activity of nickel nanoparticles was checked against E. coli bacteria. Escherichia coli were cultured in nutrients broth and different concentrations of nickel nanoparticles were added to bacterial culture solution to investigate the interaction of nickel nanoparticles with bacteria and to check toxicity of the nickel nanoparticles against E. coli. The fabricated Ni nanoparticles have exhibited considerable antimicrobial activity against E. coli.

Shamaila, S.; Wali, H.; Sharif, R.; Nazir, J.; Zafar, N.; Rafique, M. S.

2013-10-01

367

Peptides and metallic nanoparticles for biomedical applications.  

PubMed

In this review, we describe the contribution of peptides to the biomedical applications of metallic nanoparticles. We also discuss strategies for the preparation of peptide-nanoparticle conjugates and the synthesis of the peptides and metallic nanoparticles. An overview of the techniques used for the characterization of the conjugates is also provided. Mainly for biomedical purposes, metallic nanoparticles conjugated to peptides have been prepared from Au and iron oxide (magnetic nanoparticles). Peptides with the capacity to penetrate the plasma membrane are used to deliver nanoparticles to the cell. In addition, peptides that recognize specific cell receptors are used for targeting nanoparticles. The potential application of peptide-nanoparticle conjugates in cancer and Alzheimer's disease therapy is discussed. Several peptide-nanoparticle conjugates show biocompatibility and present a low degree of cytotoxicity. Furthermore, several peptide-metallic nanoparticle conjugates are used for in vitro diagnosis. PMID:17716175

Kogan, Marcelo J; Olmedo, Ivonne; Hosta, Leticia; Guerrero, Ariel R; Cruz, Luis Javier; Albericio, Fernando

2007-06-01

368

Maskless Nanoscale Writing of Nanoparticle-Polymer Composites and Nanoparticle Assemblies using Thermal Nanoprobes.  

National Technical Information Service (NTIS)

Nanoparticle polymer composites containing metal, semiconductor, magnetic, and optically active nanoparticles were deposited onto multiple substrates from a heatable atomic force microscope tip. The nanoparticle nanostructures were functional as deposited...

P. E. Sheehan W. K. Lee W. P. King Z. Dai

2009-01-01

369

Enhanced cellular uptake and long-term retention of chitosan-modified iron-oxide nanoparticles for MRI-based cell tracking  

PubMed Central

Tracking cells after therapeutic transplantation is imperative for evaluation of implanted cell fate and function. In this study, ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) were surface functionalized with water-soluble chitosan, a cationic polysaccharide that mediates enhanced endocytic uptake, endosomal escape into the cytosol, and subsequent long-term retention of nanoparticles. NP surface and chitosan were independently fluorescently labeled. Our NPs enable NP trafficking studies and determination of fate beyond uptake by fluorescence microscopy as well as tracking of labeled cells as localized regions of hypointensity in T2*-weighted magnetic resonance imaging (MRI) images. Adult rat neural stem cells (NSCs) were labeled with NPs, and assessment of NSC proliferation rates and differentiation potential revealed no significant differences between labeled and unlabeled NSCs. Significantly enhanced uptake of chitosan NPs in comparison to native NPs was confirmed by transmission electron microscopy, nuclear magnetic resonance (NMR) spectroscopy and in vitro cellular MRI at 11.7 Tesla. While only negligible fractions of native NPs enter cells, chitosan NPs appear within membranous vesicles within 2 hours of exposure. Additionally, chitosan-functionalized NPs escaped from membrane-bound vesicles within days, circumventing NP endo-lysosomal trafficking and exocytosis and hence enabling long-term tracking of labeled cells. Finally, our labeling strategy does not contain any NSC-specific reagents. To demonstrate general applicability across a variety of primary and immortalized cell types, embryonic mouse NSCs, mouse embryonic stem cells, HEK 293 kidney cells, and HeLa cervical cancer cells were additionally exposed to chitosan-USPIO NPs and exhibited similarly efficient loading as verified by NMR relaxometry. Our efficient and versatile labeling technology can support cell tracking with close to single cell resolution by MRI in vitro, for example, in complex tissue models not optically accessible by confocal or multi-photon fluorescence microscopy, and potentially in vivo, for example, in animal models of human disease or injury.

Bakhru, Sasha H; Altiok, Eda; Highley, Christopher; Delubac, Daniel; Suhan, Joseph; Hitchens, T Kevin; Ho, Chien; Zappe, Stefan

2012-01-01

370

Cancer hyperthermia using magnetic nanoparticles.  

PubMed

Magnetic-nanoparticle-mediated intracellular hyperthermia has the potential to achieve localized tumor heating without any side effects. The technique consists of targeting magnetic nanoparticles to tumor tissue followed by application of an external alternating magnetic field that induces heat through Néel relaxation loss of the magnetic nanoparticles. The temperature in tumor tissue is increased to above 43°C, which causes necrosis of cancer cells, but does not damage surrounding normal tissue. Among magnetic nanoparticles available, magnetite has been extensively studied. Recent years have seen remarkable advances in magnetite-nanoparticle-mediated hyperthermia; both functional magnetite nanoparticles and alternating-magnetic-field generators have been developed. In addition to the expected tumor cell death, hyperthermia treatment has also induced unexpected biological responses, such as tumor-specific immune responses as a result of heat-shock protein expression. These results suggest that hyperthermia is able to kill not only local tumors exposed to heat treatment, but also tumors at distant sites, including metastatic cancer cells. Currently, several research centers have begun clinical trials with promising results, suggesting that the time may have come for clinical applications. This review describes recent advances in magnetite nanoparticle-mediated hyperthermia. PMID:22069094

Kobayashi, Takeshi

2011-08-26

371

The investigation of the compression and tension behavior of the cobalt ferrite magnetorheological fluids synthesized by co-precipitation  

NASA Astrophysics Data System (ADS)

This paper aims at studying the effect of the particle size on the compression and tension behavior of the cobalt ferrite-based magnetorheological fluid (MRF). To achieve this goal, Co-ferrite nano-particles (CoFe2O4) with three different sizes, were synthesized by the chemical co-precipitation method and then two of them were mixed together. The X-Ray Diffraction (XRD) analysis, Scattering Electron Microscope (SEM), Laser Particle Size Analysis (LPSA) and Vibrating Sample Magnetometer (VSM) were carried out to study the phase analysis, particles morphology, particle distribution and magnetic properties, respectively. Then the compression and tension tests were conducted on MRFs containing silicon oil as a carrier. The results showed that the highest values of the compression and tension strengths of fluids correspond to the larger particle sizes (550 nm) with 1.241 and 0.594 MPa, respectively. Furthermore, the compression and tension strengths of the mixed one (1.153 and 0.388 MPa) containing 60 and 300 nm samples are higher than its components with 0.431 and 0.249 MPa, as well as 0.694 and 0.367 MPa, respectively.

Molazemi, M.; Shokrollahi, H.; Hashemi, B.

2013-11-01

372

High coercivity induced by mechanical milling in cobalt ferrite powders  

NASA Astrophysics Data System (ADS)

In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe2O4 treated by mechanical milling with different grinding balls. The cobalt ferrite nanoparticles were prepared using a simple hydrothermal method and annealed at 500 °C. The non-milled sample presented coercivity of about 1.9 kOe, saturation magnetization of 69.5 emu/g, and a remanence ratio of 0.42. After milling, two samples attained coercivity of 4.2 and 4.1 kOe, and saturation magnetization of 67.0 and 71.4 emu/g respectively. The remanence ratio MR/MS for these samples increase to 0.49 and 0.51, respectively. To investigate the influence of the microstructure on the magnetic behavior of these samples, we used X-ray powder diffraction (XPD), transmission electron microscopy, and vibrating sample magnetometry. The XPD analysis by the Williamson-Hall plot was used to estimate the average crystallite size and strain induced by mechanical milling in the samples.

Ponce, A. S.; Chagas, E. F.; Prado, R. J.; Fernandes, C. H. M.; Terezo, A. J.; Baggio-Saitovitch, E.

2013-10-01

373

Biomagnetic of Apatite-Coated Cobalt Ferrite: A Core-Shell Particle for Protein Adsorption and pH-Controlled Release  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticle composite with a cobalt ferrite (CoFe2O4, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core-shell structure formed after the citric acid-stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.

Tang, I.-Ming; Krishnamra, Nateetip; Charoenphandhu, Narattaphol; Hoonsawat, Rassmidara; Pon-On, Weeraphat

2010-12-01

374

Biomagnetic of Apatite-Coated Cobalt Ferrite: A Core-Shell Particle for Protein Adsorption and pH-Controlled Release  

PubMed Central

Magnetic nanoparticle composite with a cobalt ferrite (CoFe2O4, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core–shell structure formed after the citric acid–stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.

2011-01-01

375

Multifunctional Free-Standing Membrane from the Self-assembly of Ultralong MnO2 Nanowires.  

PubMed

In this work, we report the preparation of a free-standing membrane with strong mechanical stability and flexibility through a facile vacuum filtration approach. A field-emission scanning electron microscopy image demonstrates that the membrane composed of MnO2 nanowires is 50 nm in width and up to 100 ?m long and the nanowires are assembled in parallel into bundles. A possible formation mechanism for the ultralong nanowires and the free-standing membrane has been proposed. Meanwhile, the properties of the membrane could be controlled by incorporating different materials to achieve composite membranes. In order to demonstrate the broad applicability of the MnO2 membrane, we fabricate a variety of composite membranes exhibiting various novel properties including magnetism and reversibly switchable wettability between hydrophilicity and hydrophobicity through various material modification, including CoFe2O4 nanoparticles and organic triethoxy(octyl)silane. Furthermore, the free-standing membrane could also simultaneously be functionalized with two materials, which reveal multiple properties. The synthesis method of a free-standing MnO2 membrane is simple and environmentally friendly, and it is easily scalable for industry. These composite membranes constitute a significant contribution to advanced technology. PMID:23815464

Lan, Bang; Yu, Lin; Lin, Ting; Cheng, Gao; Sun, Ming; Ye, Fei; Sun, Qingfeng; He, Jun

2013-07-16

376

Different Sized Luminescent Gold Nanoparticles  

PubMed Central

After one-decade’s efforts, a large amount of highly luminescent metal nanoparticles with different sizes and surface chemistries have been developed. While the luminescence is often attributed to particle size effect, other structural parameters such as surface ligands, valence states of metal atoms and crystallinity of nanoparticles also have significant influence on emission properties and mechanisms. In this minireview, we summarized the strategies used to create luminescent gold nanoparticles with size from few to millions of atoms and discussed how these structural factors affect their photoluminescence.

Zhou, Chen; Yu, Mengxiao; Liu, Jinbin

2012-01-01

377

Single Nanoparticle Surface Enhanced Fluorescence  

NASA Astrophysics Data System (ADS)

It is well established that when in close proximity to gold nanoparticles the optical properties of local fluorescent molecules are dramatically altered. When the localised surface plasmon resonance (LSPR), tuned to the fluorophore absorption band is excited a strong optical enhancement is observed near the nanoparticle due to enhancement in the excitation rate. Both the radiative and non-radiative decay rates undergo significant modification, resulting in either quantum efficiency enhancement, or fluorophore quenching, and a corresponding reduction in the fluorescence lifetime. These effects depend on fluorophore and nanoparticle separation, the fluorophore quantum efficiency, and the alignment of fluorophore excitation and emission wavelength with the LSPR.

Webster, Linden R.; Suhling, K.; Richards, D.

378

Dialysis nanoprecipitation of polystyrene nanoparticles.  

PubMed

Using a facile dialysis nanoprecipitation method, nanoparticles of several hundred nanometers have been successfully generated from a "traditional," non-biodegradable polymer, that is, polystyrene. The effect of initial polymer concentration inside the dialysis membrane, as well as the polymer/solvent system and the ionic strength (electrolyte concentration) of the dialysis solution, on nanoparticle size is examined. A nucleation-aggregation mechanism has been provided to explain the observed trends. Furthermore, we determine the zeta potential as a function of ionic strength for the generated nanoparticles and show that anionic charging may be present in the system. PMID:22836901

Zhang, Chuan; Chung, Jae Woo; Priestley, Rodney D

2012-07-26

379

Fluorescent Property of Gold Nanoparticles with Different Surface Structures  

NASA Astrophysics Data System (ADS)

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.

Zhang, Zhi-juan; Wang, Chun-xia; Wang, Yong; Niu, Shu-hua; Lü, Chang-gui; Fu, De-gang

2007-12-01

380

Magnetic nanoparticles for theragnostics  

PubMed Central

Engineered magnetic nanoparticles (MNPs) represent a cutting-edge tool in medicine because they can be simultaneously functionalized and guided by a magnetic field. Use of MNPs has advanced magnetic resonance imaging (MRI), guided drug and gene delivery, magnetic hyperthermia cancer therapy, tissue engineering, cell tracking and bioseparation. Integrative therapeutic and diagnostic (i.e., theragnostic) applications have emerged with MNP use, such as MRI-guided cell replacement therapy or MRI-based imaging of cancer-specific gene delivery. However, mounting evidence suggests that certain properties of nanoparticles (e.g., enhanced reactive area, ability to cross cell and tissue barriers, resistance to biodegradation) amplify their cytotoxic potential relative to molecular or bulk counterparts. Oxidative stress, a 3-tier paradigm of nanotoxicity, manifests in activation of reactive oxygen species (ROS) (tier I), followed by a pro-inflammatory response (tier II) and DNA damage leading to cellular apoptosis and mutagenesis (tier III). In vivo administered MNPs are quickly challenged by macrophages of the reticuloendothelial system (RES), resulting in not only neutralization of potential MNP toxicity but also reduced circulation time necessary for MNP efficacy. We discuss the role of MNP size, composition and surface chemistry in their intracellular uptake, biodistribution, macrophage recognition and cytotoxicity, and review current studies on MNP toxicity, caveats of nanotoxicity assessments and engineering strategies to optimize MNPs for biomedical use.

Shubayev, Veronica I.; Pisanic, Thomas R.; Jin, Sungho

2009-01-01

381

Magnetic nanoparticles for theragnostics.  

PubMed

Engineered magnetic nanoparticles (MNPs) represent a cutting-edge tool in medicine because they can be simultaneously functionalized and guided by a magnetic field. Use of MNPs has advanced magnetic resonance imaging (MRI), guided drug and gene delivery, magnetic hyperthermia cancer therapy, tissue engineering, cell tracking and bioseparation. Integrative therapeutic and diagnostic (i.e., theragnostic) applications have emerged with MNP use, such as MRI-guided cell replacement therapy or MRI-based imaging of cancer-specific gene delivery. However, mounting evidence suggests that certain properties of nanoparticles (e.g., enhanced reactive area, ability to cross cell and tissue barriers, resistance to biodegradation) amplify their cytotoxic potential relative to molecular or bulk counterparts. Oxidative stress, a 3-tier paradigm of nanotoxicity, manifests in activation of reactive oxygen species (ROS) (tier I), followed by a proinflammatory response (tier II) and DNA damage leading to cellular apoptosis and mutagenesis (tier III). Invivo administered MNPs are quickly challenged by macrophages of the reticuloendothelial system (RES), resulting in not only neutralization of potential MNP toxicity but also reduced circulation time necessary for MNP efficacy. We discuss the role of MNP size, composition and surface chemistry in their intracellular uptake, biodistribution, macrophage recognition and cytotoxicity, and review current studies on MNP toxicity, caveats of nanotoxicity assessments and engineering strategies to optimize MNPs for biomedical use. PMID:19389434

Shubayev, Veronica I; Pisanic, Thomas R; Jin, Sungho

2009-04-20

382

Ionizing radiation increases systemic nanoparticle tumor accumulation  

PubMed Central

Nanoparticle-based therapies are currently being explored for both the imaging and treatment of primary and metastatic cancers. Effective nanoparticle cancer therapy requires significant accumulations of nanoparticles within the tumor environment. Various techniques have been used to improve tumor nanoparticle uptake and biodistribution. Most notable of these techniques are the use of tumor-specific-peptide-conjugated nanoparticles and chemical modification of the nanoparticles with immune-evading polymers. Another strategy for improving the tumor uptake of the nanoparticles is modification of the tumor microenvironment with a goal of enhancing the enhanced permeability and retention effect inherent to solid tumors. We demonstrate a two-fold increase in the tumor accumulation of systemically delivered iron oxide nanoparticles following a single, 15 Gy radiation dose in a syngeneic mouse breast tumor model. This increase in nanoparticle tumor accumulation correlates with a radiation-induced decrease in tumor interstitial pressure and a subsequent increase in vascular permeability.

Giustini, A.J.; Petryk, A.A.; Hoopes, P.J.

2012-01-01

383

Ionizing radiation increases systemic nanoparticle tumor accumulation.  

PubMed

Nanoparticle-based therapies are currently being explored for both the imaging and treatment of primary and metastatic cancers. Effective nanoparticle cancer therapy requires significant accumulations of nanoparticles within the tumor environment. Various techniques have been used to improve tumor nanoparticle uptake and biodistribution. Most notable of these techniques is the use of tumor-specific peptide-conjugated nanoparticles and chemical modification of the nanoparticles with immune-evading polymers. Another strategy for improving the tumor uptake of the nanoparticles is modification of the tumor microenvironment with a goal of intensifying the enhanced permeability and retention effect inherent to solid tumors. We demonstrate a twofold increase in the tumor accumulation of systemically delivered iron oxide nanoparticles following a single 15-Gy radiation dose in a syngeneic mouse breast tumor model. This increase in nanoparticle tumor accumulation correlates with a radiation-induced decrease in tumor interstitial pressure and a subsequent increase in vascular permeability. PMID:22633900

Giustini, Andrew J; Petryk, Alicia A; Hoopes, P Jack

2012-05-23

384

Adsorption of nanoparticles and nanoparticle aggregates on membrane under gravity  

NASA Astrophysics Data System (ADS)

Particle adsorption on lipid membrane is critical to biomedical applications. Gravity effect on the process has long been ignored. A combination of the upright and inverted configuration measurements was developed to exhibit that gravity causes a particle adsorption disparity on membrane between the different heights of medium. The more homogeneous adsorption tendency of nanoparticle aggregate compared to nanoparticle under the same gravitational motive force is attributed to the larger hydrodynamic diameter induced lower concentration disparity.

Zhu, Tao; Jiang, Zhongying; Ma, Yuqiang

2013-04-01

385

High Throughput Single Nanoparticle Spectroscopy  

PubMed Central

Progress in the development and application of nanoengineered systems is limited by the availability of quantitative measurement techniques. For the engineering of nanoparticle (NP)-based systems, single NP characterization is essential, but existing methods are slow and low thoughput. We demonstrate a flow spectroscopy technique capable of analyzing hundreds of nanoparticles per second and use this technique for the high throughput analysis of nanoparticle surface-enhanced resonant Raman scattering (SERRS) tags. By measuring Rayleigh and Raman scattering from thousands of individual tags, tag preparations can be characterized based on their brightness and uniformity. The rapid analysis of individual nanoparticles using high spectral resolution flow spectroscopy will be useful in many areas of nanoengineering.

Sebba, David S.; Watson, Dakota A.; Nolan, John P.

2009-01-01

386

Nanoparticle delivery in infant lungs  

PubMed Central

The lung surface is an ideal pathway to the bloodstream for nanoparticle-based drug delivery. Thus far, research has focused on the lungs of adults, and little is known about nanoparticle behavior in the immature lungs of infants. Here, using nonlinear dynamical systems analysis and in vivo experimentation in developing animals, we show that nanoparticle deposition in postnatally developing lungs peaks at the end of bulk alveolation. This finding suggests a unique paradigm, consistent with the emerging theory that as alveoli form through secondary septation, alveolar flow becomes chaotic and chaotic mixing kicks in, significantly enhancing particle deposition. This finding has significant implications for the application of nanoparticle-based inhalation therapeutics in young children with immature lungs from birth to ˜2 y of age.

Semmler-Behnke, Manuela; Kreyling, Wolfgang G.; Schulz, Holger; Takenaka, Shinji; Butler, James P.; Henry, Frank S.; Tsuda, Akira

2012-01-01

387

Radiation synthesis of seroalbumin nanoparticles  

NASA Astrophysics Data System (ADS)

Synthesis of small polymeric particles can be achieved by ionizing radiation technology via intramolecular crosslinking by gamma rays onto soluble polymer molecules in random coil conformation. Differently soluble globular proteins are naturally densely packed structures. Fragmentation and aggregation processes have been reported for irradiated globular proteins solutions with ionizing radiations.In this work we describe protein-based nanoparticles prepared by gamma irradiation of a soluble and globular protein, such as seroalbumin, as the basic building blocks keeping its original conformational shape. Protein nanoparticles in the range 20-40 nm were detected after gamma irradiation of the aqueous protein solution in the presence of polar organic solvents. Nanoparticles were characterized by DLS, fluorescence, and UV and CD spectroscopy, showing that the protein molecules keep their general three-dimensional structure into the created nanoparticle.

Soto Espinoza, Silvia L.; Sánchez, Mirna L.; Risso, Valeria; Smolko, Eduardo E.; Grasselli, Mariano

2012-09-01

388

Interaction of Silver Nanoparticles with Plasma Proteins  

NASA Astrophysics Data System (ADS)

Bio-functionalization or surface modification is an important technique to obtain biocompatibility in metal nanoparticles for biomedical applications. In this study, colloidal silver nanoparticles have been prepared by chemical reduction method and characterized by TEM & UV- Vis spectroscopy. We have studied binding of plasma proteins with colloidal silver nanoparticles. Particle characterization, effect on particle size and surface charge has been investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). DLS measurements revealed that average particle hydrodynamic diameter (z-average) increased after incubation of silver nanoparticles with plasma. TEM Images after binding of plasma proteins to the Ag nanoparticles showed protein coating over these nanoparticles.

Kaur, Harmandeep; Tripathi, S. K.

2011-12-01

389

Non-Engineered Nanoparticles of C60  

NASA Astrophysics Data System (ADS)

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.

Deguchi, Shigeru; Mukai, Sada-Atsu; Sakaguchi, Hide; Nonomura, Yoshimune

2013-06-01

390

Multiscaffold DNA origami nanoparticle waveguides.  

PubMed

DNA origami templated self-assembly has shown its potential in creating rationally designed nanophotonic devices in a parallel and repeatable manner. In this investigation, we employ a multiscaffold DNA origami approach to fabricate linear waveguides of 10 nm diameter gold nanoparticles. This approach provides independent control over nanoparticle separation and spatial arrangement. The waveguides were characterized using atomic force microscopy and far-field polarization spectroscopy. This work provides a path toward large-scale plasmonic circuitry. PMID:23841957

Klein, William P; Schmidt, Charles N; Rapp, Blake; Takabayashi, Sadao; Knowlton, William B; Lee, Jeunghoon; Yurke, Bernard; Hughes, William L; Graugnard, Elton; Kuang, Wan

2013-07-10

391

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.

2009-01-22

392

Controlling self-assembled perovskite-spinel nanostructures.  

PubMed

We report a discovery that self-assembled perovskite-spinel nanostructures can be controlled simply by selecting single-crystal substrates with different orientations. In a model BiFeO(3)-CoFe(2)O(4) system, a (001) substrate results in rectangular-shaped CoFe(2)O(4) nanopillars in a BiFeO(3) matrix; in contrast, a (111) substrate leads to triangular-shaped BiFeO(3) nanopillars in a CoFe(2)O(4) matrix, irrespective of the volume fraction of the two phases. This dramatic reversal is attributed to the surface energy anisotropy as an intrinsic property of a crystal. PMID:16834419

Zheng, Haimei; Zhan, Qian; Zavaliche, Florin; Sherburne, Matt; Straub, Florian; Cruz, Maria P; Chen, Long-Qing; Dahmen, Uli; Ramesh, R

2006-07-01

393

Effective magnetoelectric effect in multicoated circular fibrous multiferroic composites  

NASA Astrophysics Data System (ADS)

Rayleigh's formalism is generalized for the evaluation of the effective material properties in multicoated circular fibrous multiferroic composites. The derived solution is applied to the special three-phase composite in which coated fibers are embedded in a matrix. For composites made of piezoelectric (BaTiO3) and piezomagnetic (CoFe2O4 or Terfenol-D) phases, we find that the magnetoelectric effect in the composite made of CoFe2O4 coated BaTiO3 in matrix Terfenol-D is five times larger than that in the composite made of BaTiO3 coated Terfenol-D in matrix CoFe2O4. Furthermore, in each case, with appropriate coating to the circular fiber, the magnetoelectric effect in the coated composites can be enhanced by more than one order of magnitude as compared to the corresponding noncoating composite.

Kuo, Hsin-Yi; Pan, Ernian

2011-05-01

394

Structural Properties and Microstructure of Cobalt Ferrite Particles Synthesized by a Sol-Gel Auto Combustion Method  

NASA Astrophysics Data System (ADS)

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.

Raval, Anand; Panchal, Nital; Jotania, Rajshree

395

Tape casting of cobalt ferrite from nonaqueous slurry  

NASA Astrophysics Data System (ADS)

This paper describes the fabrication of CoFe2O4 thick films using the tape casting method from nonaqueous slurry. CoFe2O4 particles with average size of ˜800 nm were prepared by the solid-state reaction method. Sediment volumes and viscosity were tested to study the effects of dispersant in reducing aggregations in slurry. Slurry with 0.25 wt% dispersant amounts and 41.3 wt% solid content showed the optimal stability and rheological properties. A tape velocity of 8 cm/s was used in this study considering the non-Newtonian flow behavior at low shear rate. CoFe2O4 ceramic films sintered at 1150 °C for 2 h have dense structure (relative density of 94%) and exhibited ferromagnetic properties with in-plane saturation magnetization of ˜324 emu/cm3.

Jian, Gang; Zhou, Dongxiang; Yang, Junyou; Fu, Qiuyun

2012-12-01

396

Plasma Crystallization of Silicon Nanoparticles  

NASA Astrophysics Data System (ADS)

Using nonthermal plasmas for synthesis of silicon nanocrystals is well-established. However, nanoparticle heating in the plasma, which leads to particle crystallinity, is poorly understood. The mechanism behind heating of these particles has only been studied through modeling. In-situ measurement of particle temperature during plasma processes is difficult, but particles themselves can serve as thermometers, as their crystallinity will change depending on heating in the plasma. Here we investigate the heating and crystallization of nanoparticles using a double-plasma configuration, examining both the particles and the plasma. Amorphous silicon nanoparticles are formed in a low-power plasma, then injected into a separate plasma which is operated with variable power. Nanoparticle characterization confirms that crystallization of the particles occurs at a threshold power to the secondary plasma, around 30W (nominal) for 5nm particles. Optical emission spectroscopy on the plasma provides estimates of the electron temperature during nanoparticle crystallization, and capacitive probe measurements reveal ion densities at varying plasma powers. We will compare our outcomes to previous modeling results to build a complete picture of nanoparticle heating in plasmas.

Anthony, Rebecca; Kramer, Nicolaas; Aydil, Eray; Kortshagen, Uwe

2012-10-01

397

Respiratory effects of manufactured nanoparticles.  

PubMed

Nanotechnology is the set of techniques used to engineer, characterize, and produce materials that have at least one dimension within the nanoscale. These nanomaterials, or nanoobjects, include nanoparticles and nanotubes. As dictated by the laws of quantum physics, a size within the nanoscale results in unique physicochemical properties and distinctive behaviors. Nanotechnology has a host of applications in fields ranging from cosmetology to the industry and medicine. The production and use of nanomaterials are expanding at a brisk pace. However, concerns are emerging about the potential health effects of nanoparticles in the short and long terms. These concerns are rooted in data on the harmful health effects of micrometric airborne particulate matter. Conceivably, these adverse effects might be amplified when the particles are within the nanoscale. This article is a nonexhaustive overview of current data on the penetration, deposition, translocation, and elimination of inhaled nanoparticles and on the respiratory effects of metallic nanoparticles (with special attention to titanium dioxide) and carbon nanotubes. Both in vivo and in vitro studies consistently found biological effects of nanoparticles on the respiratory system, including oxidative stress generation, proinflammatory and prothrombotic effects, pulmonary fibrosis and emphysema, and DNA damage. Improved knowledge of the potential biological effects of nanoparticles is needed to guide preventive strategies for the workplace and/or general population if needed. PMID:22099416

Andujar, P; Lanone, S; Brochard, P; Boczkowski, J

2011-10-20

398

Exposure to Nanoparticles and Hormesis  

PubMed Central

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.

Iavicoli, Ivo; Calabrese, Edward J.; Nascarella, Marc A.

2010-01-01

399

Hydrogen Adsorption in Carbon nanoparticles  

NASA Astrophysics Data System (ADS)

We have studied hydrogen adsorption in carbon nanoparticles using a quartz crystal microbalance. The carbon nanoparticles were synthesized from a thermal plasma jet at different pressure (15 -- 263 torr) of the reactants and different current (50 -- 250 A) to generate the plasma. The as-prepared carbon nanoparticles were directly deposited on top of the gold electrode of a quartz crystal and we monitored in-situ the changes in resonance frequency while the chamber was pressurized at different hydrogen pressures. These changes enabled determination of absorbed hydrogen mass in order to get H/C mass ratio curves as a function of H2 pressure. Adsorption curves obtained in some carbon nanoparticles indicated the formation of hydrogen monolayer inside the pores of the carbon nanoparticles. Using the value of the jump due to the formation of a H2monolayer, a surface area was estimated between 40-60 m^2/g for hydrogen adsorption. In other carbon samples, hydrogen uptake curves indicated that H2 was filling the sample's pores when pore volume was large. These observations will be discussed in detail for several carbon nanoparticles samples.

Cabrera, A. L.; Rojas, S.; Dias-Droguett, D. E.; Bhuyan, H.; Aomoa, N.; Kakati, M.

2013-03-01

400

Separating nanoparticles from microemulsions.  

PubMed

Water-in-oil microemulsions (w/o ?Es) stabilized by the cationic surfactant cetyltrimethylammonium chloride (CTACl) have been used as reaction media to generate Au nanoparticles (Au-NPs). In addition the pure ?Es have been used as media to disperse Au and Pd-NPs, which have been pre-synthesised in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, and also commercially available SiO(2)-NPs. A general method for recovery and separation of the nanoparticles from these mixed NP-?E systems has been demonstrated by tuning phase behavior of the background microemulsions. Addition of appropriate aliquots of water drives a clean liquid-liquid phase transition, resulting in two macroscopic layers, the NPs preferentially partition into an upper oil-rich phase and are separated from excess surfactant which resides in a lower aqueous portion. UV-vis and (1)H NMR spectroscopy have been used to follow these separation processes and quantify the recovery and recycle efficiencies for the different NPs. For example, ?90% of the microemulsion-prepared Au-NPs can be recovered; with even greater separation efficiencies attainable for pre-synthesised MES-stabilized Au-MES-NPs (?98%) and Pd-MES-NPs (92%). For the silica NP-?E dispersions gravimetry indicates ?84% recovery of the NPs. TEM images of all systems showed that NP shapes and size distributions were generally preserved after these phase transfer processes. This low-energy and cost-effective purification route appears to be a quite general approach for processing different inorganic NPs, having advantages of being isothermal, using only commercially available inexpensive components and requiring no additional organic solvents. PMID:21134683

Nazar, Muhammad Faizan; Myakonkaya, Olesya; Shah, Syed Sakhawat; Eastoe, Julian

2010-12-04

401

Interaction of nanoparticles with proteins: relation to bio-reactivity of the nanoparticle  

PubMed Central

Interaction of nanoparticles with proteins is the basis of nanoparticle bio-reactivity. This interaction gives rise to the formation of a dynamic nanoparticle-protein corona. The protein corona may influence cellular uptake, inflammation, accumulation, degradation and clearance of the nanoparticles. Furthermore, the nanoparticle surface can induce conformational changes in adsorbed protein molecules which may affect the overall bio-reactivity of the nanoparticle. In depth understanding of such interactions can be directed towards generating bio-compatible nanomaterials with controlled surface characteristics in a biological environment. The main aim of this review is to summarise current knowledge on factors that influence nanoparticle-protein interactions and their implications on cellular uptake.

2013-01-01

402

[Nanoparticles (part 2)--advantages and health risk].  

PubMed

Over the recent years, nanotechnologies and their products--nanoparticles--have become extremely popular among scientists. Nanoparticles find numerous applications in many fields, starting with biomedical sciences, through optics, textile, construction, motorization industries, and ending with electricity and electronics. New possibilities of nanoproducts application emerge almost every day. However, it should be remembered that nanoparticles carry both advantages and risks. Small-size-particles enable overcoming the systemic barriers unnoticeably to humans. Exposure to nanoparticles is a serious threat; it may take all possible routes, of which inhalation is the most important one. Toxicity of nanoparticles is manifested by inflammation resulting probably from oxidative stress. Nanosceptics even find certain similarities between nanoparticles and carbon nanotubes, one of the most popular nanoparticles, and asbestos fibers. In view of a rapid development of nanotechnologies it is essential to establish adequate criteria for risk assessment that could protect against potential harmful effects arising from specific properties of substances occurring in the form of nanoparticles. PMID:17926516

Swidwi?ska-Gajewska, Anna Maria

2007-01-01

403

Synthesis and Characterization of Environmentally Benign Nanoparticles  

EPA Science Inventory

There has been a growing interest in replacing current non-biodegradable and toxic nanosystems with environmentally benign biopolymer based ones to minimize post-utilization hazards due to uncontrolled accumulation of nanoparticles in the environment. Lignin based nanoparticles (...

404

Mycogenic metal nanoparticles: progress and applications  

Microsoft Academic Search

Nanotechnology is relevant to diverse fields of science and technology. Due to the many advantages over non-biological systems,\\u000a several research groups have exploited the use of biological systems for the synthesis of nanoparticles. Among the different\\u000a microbes used for the synthesis of nanoparticles, fungi are efficient candidates for fabrication of metal nanoparticles both\\u000a intra- and extracellulary. The nanoparticles synthesized using

Aniket Gade; Avinash Ingle; Chris Whiteley; Mahendra Rai

2010-01-01

405

Facile Gold-Coated Maghemite Nanoparticles Fabrication  

Microsoft Academic Search

The maghemite (?-Fe2O3) nanoparticles were obtained via high temperature pyrolysis with the precursor of magnetite that was synthesized via chemical coprecipitation. Then the (3-aminopropyl) triethoxysilane (APTES) was used for the surface functionalization of ?-Fe2O3 nanoparticles. Finally the gold-coated maghemite (?-Fe2O3\\/Au) nanoparticles are prepared via sonochemical synthesis of a solution mixture of hydrochloroauric acid (HAuCl4) and APTES-coated ?-Fe2O3 nanoparticles with further

Quanguo He; Jingke Huang; Rong Hu; Lei Zeng

2010-01-01

406

Two-dimensional synthesis of anisotropic nanoparticles  

Microsoft Academic Search

A novel approach for the synthesis of nanoparticles has been introduced in which nanoparticles are fabricated via decomposition of an insoluble precursor compound in a monolayer at the gas\\/liquid interface, and nanoparticle growth is an example of a two-dimensional (2-D) process where true 2-D diffusion of precursor molecules, active intermediates, metal atoms and its complexes, nucleus and growing nanoparticles, surfactants

Gennady B Khomutov

2002-01-01

407

Plasmonic Nanoparticles-Liquid Crystal Composites †  

Microsoft Academic Search

We report on the plasmonic properties of 6 nm gold nanoparticles that form highly stable solutions in the nematic liquid crystal 4-cyano-4-n-pentylbiphenyl (5CB). The nanoparticles were covalently functionalized with 4-sulfanylphenyl-4-(4-(octyloxy)phenyl)benzoate, which resembles the structure of the 5CB molecules. The solubility of these nanoparticles in 5CB was significantly higher than that of conventional alkanethiol- terminated nanoparticles. An 8 nm shift of

Saumyakanti Khatua; Pramit Manna; Wei-Shun Chang; Alexei Tcherniak; Eric Friedlander; Eugene R. Zubarev; Stephan Link

2010-01-01

408

Toughening of Epoxy Adhesives by Nanoparticles  

Microsoft Academic Search

With the emergence and commercialization of nanoparticles, new opportunities have emerged for toughening of epoxy adhesives using nanoparticles without sacrificing strength, rigidity and glass transition temperature, as is the case with conventional elastomeric tougheners. Inorganic Fullerene-like tungsten disulfide (IF-WS2) nanoparticles and functionalized nano-POSS (Polyhedral-Oligomeric-Sil-Sesquioxane) were used to study the effects of nanoparticles on the toughening and mechanical properties of low

A. Buchman; H. Dodiuk-Kenig; A. Dotan; R. Tenne; S. Kenig

2009-01-01

409

Nanoparticle bridge DNA biosensor  

NASA Astrophysics Data System (ADS)

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.

Huang, Hong-Wen

410

Anti-proliferative activity of silver nanoparticles  

Microsoft Academic Search

BACKGROUND: Nanoparticles possess exceptional physical and chemical properties which led to rapid commercialisation. Silver nanoparticles (Ag-np) are among the most commercialised nanoparticles due to their antimicrobial potential. Ag-np based cosmetics, therapeutic agents and household products are in wide use, which raised a public concern regarding their safety associated with human and environmental use. No safety regulations are in practice for

PV AshaRani; M Prakash Hande; Suresh Valiyaveettil

2009-01-01

411

In vitro diagnostic prospects of nanoparticles  

Microsoft Academic Search

There is a constant need to improve the performance of current diagnostic assays as well as develop innovative testing strategies to meet new testing challenges. The use of nanoparticles promises to help promote invitro diagnostics to the next level of performance. Quantum dots (QDs), gold nanoparticles (AuNPs), and superparamagnetic nanoparticles are the most promising nanostructures for in vitro diagnostic applications.

Hassan M. E. Azzazy; Mai M. H. Mansour

2009-01-01

412

Inorganic nanoparticles for cancer imaging and therapy  

Microsoft Academic Search

Inorganic nanoparticles have received increased attention in the recent past as potential diagnostic and therapeutic systems in the field of oncology. Inorganic nanoparticles have demonstrated successes in imaging and treatment of tumors both ex vivo and in vivo, with some promise towards clinical trials. This review primarily discusses progress in applications of inorganic nanoparticles for cancer imaging and treatment, with

Huang-Chiao Huang; Sutapa Barua; Gaurav Sharma; Sandwip K. Dey; Kaushal Rege

2011-01-01

413

Inorganic nanoparticles for cancer imaging and therapy  

Microsoft Academic Search

Inorganic nanoparticles have received increased attention in the recent past as potential diagnostic and therapeutic systems in the field of oncology. Inorganic nanoparticles have demonstrated successes in imaging and treatment of tumors both ex vivo and in vivo, with some promise towards clinical trials. This review primarily discusses progress in applications of inorganic nanoparticles for cancer imaging and treatment, with

Huang-Chiao Huang; Sutapa Barua; Gaurav Sharma; Sandwip K. Dey; Kaushal Rege

414

Platinum attachments on iron oxide nanoparticle surfaces  

Microsoft Academic Search

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

Soubantika Palchoudhury; Yaolin Xu; Wei An; C. Heath Turner; Yuping Bao

2010-01-01

415

Lactobacillus assisted synthesis of titanium nanoparticles  

NASA Astrophysics Data System (ADS)

An eco-friendly lactobacillus sp. (microbe) assisted synthesis of titanium nanoparticles is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ti nanoparticles. Individual nanoparticles as well as a number of aggregates almost spherical in shape having a size of 40 60 nm are found.

Prasad, K.; Jha, Anal K.; Kulkarni, A. R.

2007-05-01

416

Control of nanoparticle aggregation in aerogel hosts  

Microsoft Academic Search

Plasmonic aerogel containing 50nm gold nanoparticles is made using a modified 2-step method that maintains control over the gel time while preventing nanoparticle aggregation. Strong narrow surface plasmon resonances verify that the nanoparticles are well dispersed within the silica matrix, and enable applications in sensing, SERS, nonlinear optics or plasmonic gain. Discrepancies between measured and simulated resonance wavelengths are attributed

M. D. W. Grogan; S. C. Heck; L. M. Xiao; R. England; S. A. Maier; T. A. Birks

417

Subchronic oral toxicity of silver nanoparticles  

Microsoft Academic Search

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

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

418

Tannin biosynthesis of iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

In this work, iron oxide nanoparticles synthesized with gallic acid and tannic acid are characterized using High-Resolution Transmission Electron Microscopy (HRTEM). Its size, form, and structure are compared with nanoparticles obtained previously using alfalfa biomass in order to find a simpler, consistent, and environmentally friendly method in the production of iron oxide nanoparticles.

Herrera-Becerra, R.; Rius, J. L.; Zorrilla, C.

2010-08-01

419

Optical control of gallium nanoparticle growth  

NASA Astrophysics Data System (ADS)

We report that low-intensity light can dramatically influence and regulate the nanoparticle self-assembly process: Illumination of a substrate exposed to a beam of gallium atoms results in the formation of gallium nanoparticles with a relatively narrow size distribution. Very low light intensities, below the threshold for thermally induced evaporation, exert considerable control over nanoparticle formation.

MacDonald, K. F.; Fedotov, V. A.; Pochon, S.; Ross, K. J.; Stevens, G. C.; Zheludev, N. I.; Brocklesby, W. S.; Emel'Yanov, V. I.

2002-03-01

420

Engineering biofunctional magnetic nanoparticles for biotechnological applications  

Microsoft Academic Search

Synthesis and characterization of magnetic nanoparticles with excellent size control are showed here. Their functionalization using an amphiphilic polymer is also described. This strategy allows the stabilization of magnetic nanoparticles in aqueous solvents and in addition, the polymer shell serves as a platform to incorporate relevant biomolecules, such as poly(ethylene glycol) and a number of carbohydrates. Nanoparticles functionalized with carbohydrates

Maria Moros; Beatriz Pelaz; Pilar López-Larrubia; Maria L. García-Martin; Valeria Grazú; Jesus M. de La Fuente

2010-01-01

421

Adsorption of gum Arabic on bioceramic nanoparticles  

Microsoft Academic Search

Surface modification agents can be used to tailor the surface chemistry and biological activity of bioceramic nanoparticles in very intriguing ways. However, the specific modes of interactions between macromolecules and nanoparticles can be difficult to characterize. The aim of this study was to investigate the adsorption of gum Arabic on hydroxyapatite (HAp) and magnetic nanoparticles (MNP) using the bicinchoninic acid

A. C. A. Roque; O WILSONJR

2008-01-01

422

Borosilicate nanoparticles prepared by exothermic phase separation  

Microsoft Academic Search

Nanoparticles play an important role in chemical and biological sciences due to their ability to bind and concentrate many molecules on their surface. Polymers and silica are widely used to make nanoparticles, but efforts to make nanoparticles from borosilicate glass—which exhibits high tolerance to chemicals and solvents, combined with excellent mechanical and thermal stability—have proved unsuccessful. Here we show that

Virendra K. Parashar; Jean-Baptiste Orhan; Abdeljalil Sayah; Marco Cantoni; Martin A. M. Gijs

2008-01-01

423

Synthesis and characterizations of ultra-small ZnS and Zn (1? x) Fe x S quantum dots in aqueous media and spectroscopic study of their interactions with bovine serum albumin  

Microsoft Academic Search

This work reports a new experimental methodology for the synthesis of ultra small zinc sulfide and iron doped zinc sulfide quantum dots in aqueous media. The nanoparticles were obtained using a simple procedure based on the precipitation of ZnS in aqueous solution in the presence of 2-mercaptoethanol as a capping agent, at room temperature. The effect of Fe3+ ion concentration

Omid Khani; Hamid Reza Rajabi; Mohammad Hasan Yousefi; Ali Azam Khosravi; Mohammad Jannesari; Mojtaba Shamsipur

2011-01-01

424

Studies on CO 2 decomposition over H 2-reduced MFe 2O 4 (M = Ni, Cu, Co, Zn)  

Microsoft Academic Search

Decomposition of CO2 over reduced MFe2O4 (M = Ni, Co, Cu, Zn) was studied by H2–TPR, H2–TG, and CO2–TG. XRD Rietveld analysis was used for determining phase composition and crystallite size of reduced and oxidized samples. The results indicate that spinel CoFe2O4 and CuFe2O4 are reduced to metals by H2, while ZnFe2O4 and NiFe2O4 only partly reduced at 350 °C. The CoFe2O4 spinel

Lingjuan Ma; Rui Wu; Huadong Liu; Wenju Xu; Linshen Chen; Songying Chen

425

Optical trapping of nanoparticles.  

PubMed

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 beam. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles. 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 sec, which has serious implications for biological matter. A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime. 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 enhancement. 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 spheres and 3.4 nm hydrodynamic radius bovine serum albumin proteins. 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

Bergeron, Jarrah; Zehtabi-Oskuie, Ana; Ghaffari, Saeedeh; Pang, Yuanjie; Gordon, Reuven

2013-01-15

426

Photoinduced heating of nanoparticle arrays.  

PubMed

The temperature distribution throughout arrays of illuminated metal nanoparticles is investigated numerically and experimentally. The two cases of continuous and femtosecond-pulsed illumination are addressed. In the case of continuous illumination, two distinct regimes are evidenced: a temperature confinement regime, where the temperature increase remains confined at the vicinity of each nanosource of heat, and a temperature delocalization regime, where the temperature is uniform throughout the whole nanoparticle assembly despite the heat sources' nanometric size. We show that the occurrence of one regime or another simply depends on the geometry of the nanoparticle distribution. In particular, we derived (i) simple expressions of dimensionless parameters aimed at predicting the degree of temperature confinement and (ii) analytical expressions aimed at estimating the actual temperature increase at the center of an assembly of nanoparticles under illumination, preventing heavy numerical simulations. All these theoretical results are supported by experimental measurements of the temperature distribution on regular arrays of gold nanoparticles under illumination. In the case of femtosecond-pulsed illumination, we explain the two conditions that must be fulfilled to observe a further enhanced temperature spatial confinement. PMID:23895209

Baffou, Guillaume; Berto, Pascal; Bermúdez Ureña, Esteban; Quidant, Romain; Monneret, Serge; Polleux, Julien; Rigneault, Hervé

2013-08-08

427

Timed-release polymer nanoparticles.  

PubMed

Triggered-release of encapsulated therapeutics from nanoparticles without remote or environmental triggers was demonstrated in this work. Disassembly of the polymer nanoparticles to unimers at precise times allowed the controlled release of oligo DNA. The polymers used in this study consisted of a hydrophilic block for stabilization and second thermoresponsive block for self-assembly and disassembly. At temperatures below the second block's LCST (i.e., below 37 °C for in vitro assays), the diblock copolymer was fully water-soluble, and when heated to 37 °C, the polymer self-assembled into a narrow size distribution of nanoparticles with an average diameter of approximately 25 nm. The thermoresponsive nature of the second block could be manipulated in situ by the self-catalyzed degradation of cationic 2-(dimethylamino)ethyl acrylate (DMAEA) units to negatively charged acrylic acid groups and when the amount of acid groups was sufficiently high to increase the LCST of the second block above 37 °C. The disassembly of the nanoparticles could be controlled from 10 to 70 h. The use of these nanoparticles as a combined therapy, in which one or more agents can be released in a predetermined way, has the potential to improve the personal point of care treatment of patients. PMID:23298322

Tran, Nguyen T D; Truong, Nghia P; Gu, Wenyi; Jia, Zhongfan; Cooper, Matthew A; Monteiro, Michael J

2013-01-16

428

Nanoepitaxy using micellar nanoparticles.  

PubMed

The shape of platinum and gold nanoparticles (NPs) synthesized via inverse micelle encapsulation and supported on TiO2(110) has been resolved by scanning tunneling microscopy. Annealing these systems at high temperature (?1000 °C) and subsequent cooling to room temperature produced ordered arrays of well-separated three-dimensional faceted NPs in their equilibrium state. The observed shapes differ from the kinetically limited shapes of conventional physical vapor deposited NPs, which normally form two-dimensional flat islands upon annealing at elevated temperatures. The initial NP volume was found to provide a means to control the final NP shape. Despite the liquid-phase ex situ synthesis of the micellar particles, the in situ removal of the encapsulating ligands and subsequent annealing consistently lead to the development of a well-defined epitaxial relationship of the metal NPs with the oxide support. The observed epitaxial relationships could be explained in terms of the best overlap between the interfacial Pt (or Au) and TiO2 lattices. In most cases, the ratio of {100}/{111} facets obtained for the NP shapes resolved clearly deviates from that of conventional bulklike Wulff structures. PMID:22026561

Behafarid, F; Cuenya, B Roldan

2011-10-31

429

Ecotoxicity of nanoparticles.  

PubMed

Nanotechnology is a science of producing and utilizing nanosized particles that are measured in nanometers. The unique size-dependent properties make the nanoparticles superior and indispensable as they show unusual physical, chemical, and properties such as conductivity, heat transfer, melting temperature, optical properties, and magnetization. Taking the advantages of these singular properties in order to develop new products is the main purpose of nanotechnology, and that is why it is regarded as "the next industrial revolution." Although nanotechnology is quite a recent discipline, there have already high number of publications which discuss this topic. However, the safety of nanomaterials is of high priority. Whereas toxicity focuses on human beings and aims at protecting individuals, ecotoxicity looks at various trophic organism levels and intend to protect populations and ecosystems. Ecotoxicity includes natural uptake mechanisms and the influence of environmental factors on bioavailability (and thereby on toxicity). The present paper focuses on the ecotoxic effects and mechanisms of nanomaterials on microorganisms, plants, and other organisms including humans. PMID:23724300

Rana, Sachindri; Kalaichelvan, P T

2013-03-24

430

Ecotoxicity of Nanoparticles  

PubMed Central

Nanotechnology is a science of producing and utilizing nanosized particles that are measured in nanometers. The unique size-dependent properties make the nanoparticles superior and indispensable as they show unusual physical, chemical, and properties such as conductivity, heat transfer, melting temperature, optical properties, and magnetization. Taking the advantages of these singular properties in order to develop new products is the main purpose of nanotechnology, and that is why it is regarded as “the next industrial revolution.” Although nanotechnology is quite a recent discipline, there have already high number of publications which discuss this topic. However, the safety of nanomaterials is of high priority. Whereas toxicity focuses on human beings and aims at protecting individuals, ecotoxicity looks at various trophic organism levels and intend to protect populations and ecosystems. Ecotoxicity includes natural uptake mechanisms and the influence of environmental factors on bioavailability (and thereby on toxicity). The present paper focuses on the ecotoxic effects and mechanisms of nanomaterials on microorganisms, plants, and other organisms including humans.

Rana, Sachindri; Kalaichelvan, P. T.

2013-01-01

431

Theranostic applications of nanoparticles in cancer.  

PubMed

Nanoparticles are the moieties that have undergone the most investigation in recent years for biomedical applications. They are applied in the field of oncology in the same way as in other branches of biomedical nanotechnology. Regarding cancer, nanoparticles, and especially magnetic nanoparticles, are studied for diagnosis, drug delivery, gene delivery, bioseparation, hyperthermia, phototherapy, chemotherapy, imaging mechanisms, among other uses. Different techniques are used to prepare multifunctional nanoparticles and modify nanoparticle surfaces required for different applications. This review focuses on the basic theranostic approach, the different materials used in theranostics, theranostic applications and future directions based on recent developments in these areas. PMID:22484464

Ahmed, Naveed; Fessi, Hatem; Elaissari, Abdelhamid

2012-03-30

432

Cytotoxic Effects of Fucoidan Nanoparticles against Osteosarcoma.  

PubMed

In this study, we analyzed the size-dependent bioactivities of fucoidan by comparing the cytotoxic effects of native fucoidan and fucoidan lipid nanoparticles on osteosarcoma in vitro and in vivo. In vitro experiments indicated that nanoparticle fucoidan induced apoptosis of an osteosarcoma cell line more efficiently than native fucoidan. The more potent effects of nanoparticle fucoidan, relative to native fucoidan, were confirmed in vivo using a xenograft osteosarcoma model. Caco-2 cell transport studies showed that permeation of nanoparticle fucoidan was higher than native fucoidan. The higher bioactivity and superior bioavailability of nanoparticle fucoidan could potentially be utilized to develop novel therapies for osteosarcoma. PMID:24177673

Kimura, Ryuichiro; Rokkaku, Takayoshi; Takeda, Shinji; Senba, Masachika; Mori, Naoki

2013-10-30

433

Scintillation of rare earth doped fluoride nanoparticles  

SciTech Connect

The scintillation response of rare earth (RE) doped core/undoped (multi-)shell fluoride nanoparticles was investigated under x-ray and alpha particle irradiation. A significant enhancement of the scintillation response was observed with increasing shells due: (i) to the passivation of surface quenching defects together with the activation of the REs on the surface of the core nanoparticle after the growth of a shell, and (ii) to the increase of the volume of the nanoparticles. These results are expected to reflect a general aspect of the scintillation process in nanoparticles, and to impact radiation sensing technologies that make use of nanoparticles.

Jacobsohn, L. G.; McPherson, C. L.; Sprinkle, K. B.; Ballato, J. [Center for Optical Materials Science and Engineering Technologies (COMSET), and School of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 (United States); Yukihara, E. G. [Physics Department, Oklahoma State University, Stillwater, Oklahoma 74078-3072 (United States); DeVol, T. A. [Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, South Carolina 29634-0905 (United States)

2011-09-12

434

SANS Study of Protein Adsorption on Nanoparticles  

NASA Astrophysics Data System (ADS)

Adsorption of lysozyme protein on silica nanoparticle has been studied using small-angle neutron scattering (SANS) at pH 7. The measurements were carried out on fixed concentration (1 wt %) of nanoparticles and varying concentration of protein in the range 0 to 2 wt%. It has been found that the protein is adsorbed on the nanoparticle surface at very low protein concentrations whereas strong electrostatic interaction of lysozyme with silica nanoparticles at higher protein concentrations leads to the aggregation of nanoparticles. The adsorption is found to be increased with increase in the particle size and the aggregation is determined to be fractal structure.