Nanoscale heat transfer and phase transformation surrounding intensely heated nanoparticles

NASA Astrophysics Data System (ADS)

Sasikumar, Kiran

Over the last decade there has been significant ongoing research to use nanoparticles for hyperthermia-based destruction of cancer cells. In this regard, the investigation of highly non-equilibrium thermal systems created by ultrafast laser excitation is a particularly challenging and important aspect of nanoscale heat transfer. It has been observed experimentally that noble metal nanoparticles, illuminated by radiation at the plasmon resonance wavelength, can act as localized heat sources at nanometer-length scales. Achieving biological response by delivering heat via nanoscale heat sources has also been demonstrated. However, an understanding of the thermal transport at these scales and associated phase transformations is lacking. A striking observation made in several laser-heating experiments is that embedded metal nanoparticles heated to extreme temperatures may even melt without an associated boiling of the surrounding fluid. This unusual phase stability is not well understood and designing experiments to understand the physics of this phenomenon is a challenging task. In this thesis, we will resort to molecular dynamics (MD) simulations, which offer a powerful tool to investigate this phenomenon, without assumptions underlying continuum-level model formulations. We present the results from a series of steady state and transient non-equilibrium MD simulations performed on an intensely heated nanoparticle immersed in a model liquid. For small nanoparticles (1-10 nm in diameter) we observe a stable liquid phase near the nanoparticle surface, which can be at a temperature well above the boiling point. Furthermore, we report the existence of a critical nanoparticle size (4 nm in diameter) below which we do not observe formation of vapor even when local fluid temperatures exceed the critical temperature. Instead, we report the existence of a stable fluid region with a density much larger than that of the vapor phase. We explain this stability in terms of the

Solid phase monofunctionalization of gold nanoparticles using ionic exchange resin as polymer support.

PubMed

Zou, Jianhua; Dai, Qiu; Wang, Jinhai; Liu, Xiong; Huo, Qun

2007-07-01

A solid phase modification method using anionic exchange resin as polymer support was developed for the synthesis of monofunctional gold nanoparticles. Based on a "catch and release" mechanism to control the number of functional groups attached to the nanoparticle surface, bifunctional thiol ligands with a carboxylic acid end group were first immobilized at a controlled density on anionic exchange resin through electrostatic interactions. Gold nanoparticles were then immobilized to the anionic exchange resin by a one-to-one place exchange reaction between resin-bound thiol ligands and butanethiol-protected gold nanoparticles in solution. After cleaving off from the resin under mild conditions, gold nanoparticles with a single carboxyl group attached to the surface were obtained as the major product. Experimental conditions such as the solvents used for ligand loading and solid phase place exchange reaction, and the loading density of the ligands, were found to play a critical role towards the successful synthesis of monofunctional nanoparticles. Overall, the noncovalent bond-based ligand immobilization technique reported here greatly simplified the process of solid phase monofunctionalization of nanoparticles compared to a previously reported covalent bond-based ligand immobilization technique.

The self-healing of defects induced by the hydriding phase transformation in palladium nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulvestad, A.; Yau, A.

Nanosizing can dramatically alter material properties by enhancing surface thermodynamic contributions, shortening diffusion lengths, and increasing the number of catalytically active sites per unit volume. These mechanisms have been used to explain the improved properties of catalysts, battery materials, plasmonic materials, etc. Here we show that Pd nanoparticles also have the ability to self-heal defects in their crystal structures. Using Bragg coherent diffractive imaging, we image dislocations nucleated deep in a Pd nanoparticle during the forward hydriding phase transformation that heal during the reverse transformation, despite the region surrounding the dislocations remaining in the hydrogen-poor phase. We show that defectivemore » Pd nanoparticles exhibit sloped isotherms, indicating that defects act as additional barriers to the phase transformation. Our results resolve the formation and healing of structural defects during phase transformations at the single nanoparticle level and offer an additional perspective as to how and why nanoparticles differ from their bulk counterparts.« less

Size-dependent structural transformations of hematite nanoparticles. 1. Phase transition.

PubMed

Chernyshova, I V; Hochella, M F; Madden, A S

2007-04-14

Using Fourier Transform InfraRed (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM), we characterize the structure and/or morphology of hematite (alpha-Fe(2)O(3)) particles with sizes of 7, 18, 39 and 120 nm. It is found that these nanoparticles possess maghemite (gamma-Fe(2)O(3))-like defects in the near surface regions, to which a vibrational mode at 690 cm(-1), active both in FTIR and Raman spectra, is assigned. The fraction of the maghemite-like defects and the net lattice disorder are inversely related to the particle size. However, the effect is opposite for nanoparticles grown by sintering of smaller hematite precursors under conditions when the formation of a uniform hematite-like structure throughout the aggregate is restricted by kinetic issues. This means that not only particle size but also the growth kinetics determines the structure of the nanoparticles. The observed structural changes are interpreted as size-induced alpha-Fe(2)O(3)<-->gamma-Fe(2)O(3) phase transitions. We develop a general model that considers spinel defects and absorbed/adsorbed species (in our case, hydroxyls) as dominant controls on structural changes with particle size in hematite nanoparticles, including solid-state phase transitions. These changes are represented by trajectories in a phase diagram built in three phase coordinates-concentrations of spinel defects, absorbed impurities, and adsorbed species. The critical size for the onset of the alpha-->gamma phase transition depends on the particle environment, and for the dry particles used in this study is about 40 nm. The model supports the existence of intermediate phases (protohematite and hydrohematite) during dehydration of goethite. We also demonstrate that the hematite structure is significantly less defective when the nanoparticles are immersed in water or KBr matrix, which is explained by the effects of the electrochemical double layer and increased rigidity of

Gas-liquid chromatography with a volatile "stationary" liquid phase.

PubMed

Wells, P S; Zhou, S; Parcher, J F

2002-05-01

A unique type of gas-liquid chromatography is described in which both mobile and "stationary" phases are composed of synthetic mixtures of helium and carbon dioxide. At temperatures below the critical point of the binary mixture and pressures above the vapor pressure of pure liquid carbon dioxide, helium and carbon dioxide can form two immiscible phases over extended composition ranges. A binary vapor phase enriched in helium can act as the mobile phase for chromatographic separations, whereas a CO2-rich liquid in equilibrium with the vapor phase, but condensed on the column wall, can act as a pseudostationary phase. Several examples of chromatographic separations obtained in "empty" capillary columns with no ordinary stationary liquid phase illustrate the range of conditions that produce such separations. In addition, several experiments are reported that confirm the proposed two-phase hypothesis. The possible consequences of the observed chromatographic phenomenon in the field of supercritical fluid chromatography with helium headspace carbon dioxide are discussed.

A surface phase transition of supported gold nanoparticles.

PubMed

Plech, Anton; Cerna, Roland; Kotaidis, Vassilios; Hudert, Florian; Bartels, Albrecht; Dekorsy, Thomas

2007-04-01

A thermal phase transition has been resolved in gold nanoparticles supported on a surface. By use of asynchronous optical sampling with coupled femtosecond oscillators, the Lamb vibrational modes could be resolved as a function of annealing temperature. At a temperature of 104 degrees C the damping rate and phase changes abruptly, indicating a structural transition in the particle, which is explained as the onset of surface melting.

Genotyping of alpha-thalassemia deletions using multiplex polymerase chain reactions and gold nanoparticle-filled capillary electrophoresis.

PubMed

Chen, Yen-Ling; Shih, Chi-Jen; Ferrance, Jerome; Chang, Ya-Sian; Chang, Jan-Gowth; Wu, Shou-Mei

2009-02-13

A gold nanoparticle-filled capillary electrophoresis method combined with three multiplex polymerase chain reactions (PCRs) was established for simultaneous diagnosis of five common alpha-thalassemia deletions, including the -alpha(3.7) deletion, -alpha(4.2) deletion, Southeast Asian (--(SEA)), Filipino (--(FIL)) and Thai (--(THAI)) deletions. Gold nanoparticles (GNPs) were used as a pseudostationary phase to improve the resolution between DNA fragments in a low-viscosity polymer. To achieve the best CE separation, several parameters were evaluated for optimizing the separation conditions, including the capillary coating, the concentrations of polymer sieving matrix, the sizes and concentrations of GNPs, the buffer concentrations, and the pH. The final CE method for separating a 200-base pair (bp) DNA ladder and alpha-thalassemia deletions used a DB-17 capillary, 0.6% poly(ethylene oxide) (PEO) prepared in a mixture of GNP(32nm) solution and glycine buffer (25mM, pH 9.0) (80:20, v/v) as the sieving matrix with 1microM YO-PRO-1 for fluorescence detection; the applied voltage was -10kV (detector at anode side) and the separation temperature was 25 degrees C. Under these optimal conditions, 15 DNA fragments with sizes ranging from 0.2kb to 3.0kb were resolved within 11.5min. The RSDs of migration times were less than 2.81%. A total of 21 patients with alpha-thalassemia deletions were analyzed using this method, and all results showed good agreement with those obtained by gel electrophoresis.

Gas-Phase Synthesis of Gold- and Silica-Coated Nanoparticles

NASA Astrophysics Data System (ADS)

Boies, Adam Meyer

2011-12-01

Composite nanoparticles consisting of separate core-shell materials are of interest for a variety of biomedical and industrial applications. By combining different materials at the nanoscale, particles can exhibit enhanced or multi-functional behavior such as plasmon resonance combined with superparamagnetism. Gas-phase nanoparticle synthesis processes are promising because they can continuously produce particles with high mass-yield rates. In this dissertation, new methods are investigated for producing gas-phase coatings of nanoparticles in an "assembly-line" fashion. Separate processes are developed to create coatings from silica and gold that can be used with a variety of core-particle chemistries. A photoinduced chemical vapor deposition (photo-CVD) method is used to produce silica coatings from tetraethyl orthosilicate (TEOS) on the surface of nanoparticles (diameter ˜5--70 nm). Tandem differential mobility analysis (TDMA) of the process demonstrates that particle coatings can be produced with controllable thicknesses (˜1--10 nm) by varying system parameters such as precursor flow rate. Electron microscopy and infrared spectroscopy confirm that the photo-CVD films uniformly coat the particles and that the coatings are silica. In order to describe the coating process a chemical mechanism is proposed that includes gas-phase, surface and photochemical reactions. A chemical kinetics model of the mechanism indicates that photo-CVD coating proceeds primarily through the photodecomposition of TEOS which removes ethyl groups, thus creating activated TEOS species. The activated TEOS then adsorbs onto the surface of the particle where a series of subsequent reactions remove the remaining ethyl groups to produce a silica film with an open site for further attachment. The model results show good agreement with the experimentally measured coating trends, where increased TEOS flow increases coating thickness and increased nitrogen flow decreases coating thickness. Gold

Organic Phase Change Nanoparticles for in-Product Labeling of Agrochemicals.

PubMed

Wang, Miao; Duong, Binh; Su, Ming

2015-10-28

There is an urgent need to develop in-product covert barcodes for anti-counterfeiting of agrochemicals. This paper reports a new organic nanoparticle-based in-product barcode system, in which a panel of organic phase change nanoparticles is added as a barcode into in a variety of chemicals (herein agrochemicals). The barcode is readout by detecting melting peaks of organic nanoparticles using differential scanning calorimetry. This method has high labeling capacity due to small sizes of nanoparticles, sharp melting peaks, and large scan range of thermal analysis. The in-product barcode can be effectively used to protect agrochemical products from being counterfeited due to its large coding capacity, technical readiness, covertness, and robustness.

Recent applications of nanomaterials in capillary electrophoresis.

PubMed

González-Curbelo, Miguel Ángel; Varela-Martínez, Diana Angélica; Socas-Rodríguez, Bárbara; Hernández-Borges, Javier

2017-10-01

Nanomaterials have found an important place in Analytical Chemistry and, in particular, in Separation Science. Among them, metal-organic frameworks, magnetic and non-magnetic nanoparticles, carbon nanotubes and graphene, as well as their combinations, are the most important nanomaterials that have been used up to now. Concerning capillary electromigration techniques, these nanomaterials have also been used as both pseudostationary phases in electrokinetic chromatography (EKC) and as stationary phases in microchip capillary electrophoresis (CE) and capillary electrochromatography (CEC), as a result of their interesting and particular properties. This review article pretends to provide a general and critical revision of the most recent applications of nanomaterials in this field (period 2010-2017). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solid-phase synthesis of molecularly imprinted nanoparticles.

PubMed

Canfarotta, Francesco; Poma, Alessandro; Guerreiro, Antonio; Piletsky, Sergey

2016-03-01

Molecularly imprinted polymers (MIPs) are synthetic materials, generally based on acrylic or methacrylic monomers, that are polymerized in the presence of a specific target molecule called the 'template' and capable of rebinding selectively to this target molecule. They have the potential to be low-cost and robust alternatives to biomolecules such as antibodies and receptors. When prepared by traditional synthetic methods (i.e., with free template in solution), their usefulness has been limited by high binding site heterogeneity, the presence of residual template and the fact that the production methods are complex and difficult to standardize. To overcome some of these limitations, we developed a method for the synthesis of MIP nanoparticles (nanoMIPs) using an innovative solid-phase approach, which relies on the covalent immobilization of the template molecules onto the surface of a solid support (glass beads). The obtained nanoMIPs are virtually free of template and demonstrate high affinity for the target molecule (e.g., melamine and trypsin in our published work). Because of an affinity separation step performed on the solid phase after polymerization, poor binders and unproductive polymer are removed, so the final product has more uniform binding characteristics. The overall protocol, starting from the immobilization of the template onto the solid phase and including the purification and characterization of the nanoparticles, takes up to 1 week.

Effect of anisotropic MoS2 nanoparticles on the blue phase range of a chiral liquid crystal.

PubMed

Lavrič, Marta; Cordoyiannis, George; Kralj, Samo; Tzitzios, Vassilios; Nounesis, George; Kutnjak, Zdravko

2013-08-01

Liquid-crystalline blue phases are attracting significant interest due to their potential for applications related to tunable photonic crystals and fast optical displays. In this work a brief theoretical model is presented accounting for the impact of anisotropic nanoparticles on the blue phase stability region. This model is tested by means of high-resolution calorimetric and optical measurements of the effect of anisotropic, surface-functionalized MoS2 nanoparticles on the blue phase range of a chiral liquid crystal. The addition of these nanoparticles effectively increases the temperature range of blue phases and especially the cubic structure of blue phase I.

Synthesis of fullerene-like tantalum disulfide nanoparticles by a gas-phase reaction and laser ablation.

PubMed

Schuffenhauer, Christoph; Parkinson, Bruce A; Jin-Phillipp, Neng Yun; Joly-Pottuz, Lucile; Martin, Jean-Michel; Popovitz-Biro, Ronit; Tenne, Reshef

2005-11-01

Motivated by the discovery of the C(60) molecule (buckminsterfullerene), the search for inorganic counterparts of this closed-cage nanostructure started in 1992 with the discovery of nested fullerene-like nanoparticles of WS(2). Inorganic fullerene-like (IF) materials have since been found in numerous two-dimensional compounds and are available in a variety of shapes that offer major applications such as in lubricants and nanocomposites. Various synthetic methodologies have been employed to achieve the right conditions for the constricted or templated growth needed for the occurrence of this new phase. In this study, IF-TaS(2) is produced from a volatile chloride precursor in the gas phase and in small yield by room temperature laser ablation both in argon and in liquid CS(2). For the gas-phase reaction, a high yield of IF nanoparticles was obtained between 400 and 600 degrees C with a low concentration of the precursor gas. The average size and the yield of the IF-TaS(2) nanoparticles decrease with temperature. Above 600 degrees C, IF nanoparticles were found in low yields and at sizes below 20 nm. The stability of the IF nanoparticles produced by the gas-phase reaction is discussed in the light of two existing theoretical models. Laser ablation in argon leads to IF nanoparticles filled with clusters of TaS(2). Agglomeration of the nanoparticles can be avoided by laser ablation in liquid CS(2).

Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

PubMed Central

Mukundan, Vineetha; Yin, Jun; Joseph, Pharrah; Luo, Jin; Shan, Shiyao; Zakharov, Dmitri N; Zhong, Chuan-Jian; Malis, Oana

2014-01-01

Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2) alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C). The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering. PMID:27877663

Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

NASA Astrophysics Data System (ADS)

Hufschmid, Ryan; Arami, Hamed; Ferguson, R. Matthew; Gonzales, Marcela; Teeman, Eric; Brush, Lucien N.; Browning, Nigel D.; Krishnan, Kannan M.

2015-06-01

Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25 : 1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular

Polarization-independent refractive index tuning using gold nanoparticle-stabilized blue phase liquid crystals.

PubMed

Yabu, Shuhei; Tanaka, Yuma; Tagashira, Kenji; Yoshida, Hiroyuki; Fujii, Akihiko; Kikuchi, Hirotsugu; Ozaki, Masanori

2011-09-15

Polarization-independent refractive index (RI) modulation can be achieved in blue phase (BP) liquid crystals (LCs) by applying an electric field parallel to the direction of light transmission. One of the problems limiting the achievable tuning range is the field-induced phase transition to the cholesteric phase, which is birefringent and chiral. Here we report the RI modulation capabilities of gold nanoparticle-doped BPs I and II, and we show that field-induced BP-cholesteric transition is suppressed in nanoparticle-doped BP II. Because the LC remains optically isotropic even at high applied voltages, a larger RI tuning range can be achieved.

Confined Pattern-Directed Assembly of Polymer-Grafted Nanoparticles in a Phase Separating Blend with a Homopolymer Matrix.

PubMed

Zhang, Ren; Lee, Bongjoon; Bockstaller, Michael R; Douglas, Jack F; Stafford, Christopher M; Kumar, Sanat K; Raghavan, Dharmaraj; Karim, Alamgir

The controlled organization of nanoparticle (NP) constituents into superstructures of well-defined shape, composition and connectivity represents a continuing challenge in the development of novel hybrid materials for many technological applications. We show that the phase separation of polymer-tethered nanoparticles immersed in a chemically different polymer matrix provides an effective and scalable method for fabricating defined submicron-sized amorphous NP domains in melt polymer thin films. We investigate this phenomenon with a view towards understanding and controlling the phase separation process through directed nanoparticle assembly. In particular, we consider isothermally annealed thin films of polystyrene-grafted gold nanoparticles (AuPS) dispersed in a poly(methyl methacrylate) (PMMA) matrix. Classic binary polymer blend phase separation related morphology transitions, from discrete AuPS domains to bicontinuous to inverse domain structure with increasing nanoparticle composition is observed, yet the kinetics of the AuPS/PMMA polymer blends system exhibit unique features compared to the parent PS/PMMA homopolymer blend. We further illustrate how to pattern-align the phase-separated AuPS nanoparticle domain shape, size and location through the imposition of a simple and novel external symmetry-breaking perturbation via soft-lithography. Specifically, submicron-sized topographically patterned elastomer confinement is introduced to direct the nanoparticles into kinetically controlled long-range ordered domains, having a dense yet well-dispersed distribution of non-crystallizing nanoparticles. The simplicity, versatility and roll-to-roll adaptability of this novel method for controlled nanoparticle assembly should make it useful in creating desirable patterned nanoparticle domains for a variety of functional materials and applications.

[Characteristics of electroosmotic flow in open-tubular capillary electrochromatography with magnetic nanoparticle coating as mixed-mode stationary phase].

PubMed

Qin, Sasa; Zhou, Chaoran; Zhu, Yaxian; Ren, Zhiyu; Zhang, Lingyi; Fu, Honggang; Zhang, Weibing

2011-09-01

A novel open-tubular capillary electrochromatography (OT-CEC) column with magnetic nanoparticle coating as mixed-mode stationary phase was prepared. The mixed-mode stationary phases were obtained by mixing C18 and amino modified magnetic nanoparticles with different ratios. The mixed modified magnetic nanoparticles as stationary phase were introduced into the capillary by using external magnetic force. The magnetic nanoparticle coating can be easily regenerated by removing the external magnetic field, and applied to other separation modes. The characteristics of electroosmotic flow (EOF) were theoretically investigated through the effect of physicochemical properties of different stationary phases on EOF. The experiment was conducted under different ratios of mixed-mode stationary phases and coating lengths, and it was verified that the theoretical conclusions accorded with the experimental results. It was shown that the EOF can be easily adjusted by changing the ratio of stationary phases or the number of permanent magnets.

A comparative ecotoxicity analysis of α- and γ-phase aluminium oxide nanoparticles towards a freshwater bacterial isolate Bacillus licheniformis.

PubMed

Pakrashi, Sunandan; Kumar, Deepak; Iswarya, V; Bhuvaneshwari, M; Chandrasekaran, N; Mukherjee, Amitava

2014-12-01

Crystalline structure of nanoparticles may influence their physicochemical behaviour as well as their toxicological impact on biota. The differences in orientation of the atoms result in the variations in chemical stability. Thus, toxicological impacts of different crystalline phases of aluminium oxide nanoparticles are expected to vary. The present study brings out a comparative toxicity analysis of γ-phase and α-phase aluminium oxide nanoparticles of comparable hydrodynamic size range towards a freshwater bacterial isolate Bacillus licheniformis at low exposure concentrations (5, 1, 0.5 and 0.05 µg/mL). Upon 2-h exposure, the α-aluminium oxide particles showed lower toxicity than the γ-phase aluminium oxide. The lower level of oxidative stress generation and cell membrane damage in case of the α-phase aluminium oxide nanoparticles substantiated the toxicity results. The involvement of protein, lipopolysaccharides in nanoparticle-cell surface interaction, was noted in both the cases. To conclude, the crystallinity of aluminium oxide nanoparticles played an important role in the interaction and the toxicity response.

Structure and Interaction in the pH-Dependent Phase Behavior of Nanoparticle-Protein Systems.

PubMed

Yadav, Indresh; Kumar, Sugam; Aswal, Vinod K; Kohlbrecher, Joachim

2017-02-07

The pH-dependent structure and interaction of anionic silica nanoparticles (diameter 18 nm) with two globular model proteins, lysozyme and bovine serum albumin (BSA), have been studied. Cationic lysozyme adsorbs strongly on the nanoparticles, and the adsorption follows exponential growth as a function of lysozyme concentration, where the saturation value increases as pH approaches the isoelectric point (IEP) of lysozyme. By contrast, irrespective of pH, anionic BSA does not show any adsorption. Despite having a different nature of interactions, both proteins render a similar phase behavior where nanoparticle-protein systems transform from being one-phase (clear) to two-phase (turbid) above a critical protein concentration (CPC). The measurements have been carried out for a fixed concentration of silica nanoparticles (1 wt %) with varying protein concentrations (0-5 wt %). The CPC is found to be much higher for BSA than for lysozyme and increases for lysozyme but decreases for BSA as pH approaches their respective IEPs. The structure and interaction in these systems have been examined using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The effective hydrodynamic size of the nanoparticles measured using DLS increases with protein concentration and is related to the aggregation of the nanoparticles above the CPC. The propensity of the nanoparticles to aggregate is suppressed for lysozyme and enhanced for BSA as pH approached their respective IEPs. This behavior is understood from SANS data through the interaction potential determined by the interplay of electrostatic repulsion with a short-range attraction for lysozyme and long-range attraction for BSA. The nanoparticle aggregation is caused by charge neutralization by the oppositely charged lysozyme and through depletion for similarly charged BSA. Lysozyme-mediated attractive interaction decreases as pH approaches the IEP because of a decrease in the charge on the protein. In the case of

Phase study of titanium dioxide nanoparticle prepared via sol-gel process

NASA Astrophysics Data System (ADS)

Oladeji Araoyinbo, Alaba; Bakri Abdullah, Mohd Mustafa Al; Salleh, Mohd Arif Anuar Mohd; Aziz, Nurul Nadia Abdul; Iskandar Azmi, Azwan

2018-03-01

In this study, titanium dioxide nanoparticles have been prepared via sol-gel process using titanium tetraisopropoxide as a precursor with hydrochloric acid as a catalyst, and ethanol with deionized water as solvents. The value of pH used is set to 3, 7 and 8. The sols obtained were dried at 100 °C for 1 hr and calcined at 350, 550, and 750 °C for 3 hrs to observe the phase transformation of titanium dioxide nanoparticle. The samples were characterized by x-ray diffraction and field emission scanning electron microscope. The morphology analysis is obtained from field emission scanning electron microscope. The phase transformation was investigated by x-ray diffraction. It was found that the pH of the solution affect the agglomeration of titanium dioxide particle. The x-ray diffraction pattern of titanium dioxide shows the anatase phase most abundant at temperature of 350 °C. At temperature of 550 °C the anatase and rutile phase were present. At temperature of 750 °C the rutile phase was the most abundant for pH 3, 7 and 8. It was confirmed that at higher temperature the rutile phase which is the stable phase are mostly present.

Time-resolved imaging of gas phase nanoparticle synthesis by laser ablation

NASA Astrophysics Data System (ADS)

Geohegan, David B.; Puretzky, Alex A.; Duscher, Gerd; Pennycook, Stephen J.

1998-06-01

The dynamics of nanoparticle formation, transport, and deposition by pulsed laser ablation of c-Si into 1-10 Torr He and Ar gases are revealed by imaging laser-induced photoluminescence and Rayleigh-scattered light from gas-suspended 1-10 nm SiOx particles. Two sets of dynamic phenomena are presented for times up to 15 s after KrF-laser ablation. Ablation of Si into heavier Ar results in a uniform, stationary plume of nanoparticles, while Si ablation into lighter He results in a turbulent ring of particles which propagates forward at 10 m/s. Nanoparticles unambiguously formed in the gas phase were collected on transmission electron microscope grids for Z-contrast imaging and electron energy loss spectroscopy analysis. The effects of gas flow on nanoparticle formation, photoluminescence, and collection are described.

Chemical phase analysis of seed mediated synthesized anisotropic silver nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bharti, Amardeep, E-mail: abharti@pu.ac.in; Goyal, Navdeep; Singh, Suman

Noble-metal nanoparticles are of great interest because of its broad applications almost in every stream (i.e. biology, chemistry and engineering) due to their unique size/shape dependant properties. In this paper, chemical phase of seed mediated synthesized anisotropic silver nanoparticle (AgNPs) has been investigated via fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). These nanaoparticles were synthesized by seed-growth method controlled by urea and dextrose results to highly stable 12-20 nm particle size revealed by zeta potential and transmission electron microscopy (TEM)

Security authentication using phase-encoded nanoparticle structures and polarized light.

PubMed

Carnicer, Artur; Hassanfiroozi, Amir; Latorre-Carmona, Pedro; Huang, Yi-Pai; Javidi, Bahram

2015-01-15

Phase-encoded nanostructures such as quick response (QR) codes made of metallic nanoparticles are suggested to be used in security and authentication applications. We present a polarimetric optical method able to authenticate random phase-encoded QR codes. The system is illuminated using polarized light, and the QR code is encoded using a phase-only random mask. Using classification algorithms, it is possible to validate the QR code from the examination of the polarimetric signature of the speckle pattern. We used Kolmogorov-Smirnov statistical test and Support Vector Machine algorithms to authenticate the phase-encoded QR codes using polarimetric signatures.

Solid phase extraction of magnetic carbon doped Fe3O4 nanoparticles.

PubMed

Yang, Jing; Li, Jia-yuan; Qiao, Jun-qin; Lian, Hong-zhen; Chen, Hong-yuan

2014-01-17

Carbon decorated Fe3O4 nanoparticles (Fe3O4/C) are promising magnetic solid-phase extraction (MSPE) sorbents in environmental and biological analysis. Fe3O4/C based MSPE method shows advantages of easy operation, rapidness, high sensitivity, and environmental friendliness. In this paper, the MSPE mechanism of Fe3O4/C nanoparticles has been comprehensively investigated, for the first time, through the following three efforts: (1) the comparison of extraction efficiency for polycyclic aromatic hydrocarbons (PAHs) between the Fe3O4/C sorbents and activated carbon; (2) the chromatographic retention behaviors of hydrophobic and hydrophilic compounds on Fe3O4/C nanoparticles as stationary phase; (3) related MSPE experiments for several typical compounds such as pyrene, naphthalene, benzene, phenol, resorcinol, anisole and thioanisole. It can be concluded that there are hybrid hydrophobic interaction and hydrogen bonding interaction or dipole-dipole attraction between Fe3O4/C sorbents and analytes. It is the existence of carbon and oxygen-containing functional groups coated on the surface of Fe3O4/C nanoparticles that is responsible for the effective extraction process. Copyright © 2013 Elsevier B.V. All rights reserved.

High photocatalytic activity of mixed anatase-rutile phases on commercial TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ruu Siah, Wai; Lintang, Hendrik O.; Shamsuddin, Mustaffa; Yuliati, Leny

2016-02-01

Titanium dioxide (TiO2) is well-known as an active photocatalyst for degradation of various organic pollutants. Over the years, a wide range of TiO2 nanoparticles with different phase compositions, crystallinities, and surface areas have been developed. Due to the different methods and conditions used to synthesize these commercial TiO2 nanoparticles, the properties and photocatalytic performance would also be different from each other. In this study, the photocatalytic removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) was investigated on commercial Evonik P25, Evonik P90, Hombikat UV100 and Hombikat N100 TiO2 nanoparticles. Upon photocatalytic tests, it was found that overall, the photocatalytic activities of the P25 and the P90 were higher than the N100 and the UV100 for the removal of both 2,4-D and 2,4,5-T. The high activities of the P25 and the P90 could be attributed to their phase compositions, which are made up of a mixture of anatase and rutile phases of TiO2. Whereas, the UV100 and the N100 are made up of 100% anatase phase of TiO2. The synergistic effect of the anatase/rutile mixture was reported to slow down the recombination rate of photogenerated electron-hole pairs. Consequently, the photocatalytic activity was increased on these TiO2 nanoparticles.

Harmonic phases of the nanoparticle magnetization: An intrinsic temperature probe

NASA Astrophysics Data System (ADS)

Garaio, Eneko; Collantes, Juan-Mari; Garcia, Jose Angel; Plazaola, Fernando; Sandre, Olivier

2015-09-01

Magnetic fluid hyperthermia is a promising cancer therapy in which magnetic nanoparticles act as heat sources activated by an external AC magnetic field. The nanoparticles, located near or inside the tumor, absorb energy from the magnetic field and then heat up the cancerous tissues. During the hyperthermia treatment, it is crucial to control the temperature of different tissues: too high temperature can cause undesired damage in healthy tissues through an uncontrolled necrosis. However, the current thermometry in magnetic hyperthermia presents some important technical problems. The widely used optical fiber thermometers only provide the temperature in a discrete set of spatial points. Moreover, surgery is required to locate these probes in the correct place. In this scope, we propose here a method to measure the temperature of a magnetic sample. The approach relies on the intrinsic properties of the magnetic nanoparticles because it is based on monitoring the thermal dependence of the high order harmonic phases of the nanoparticle dynamic magnetization. The method is non-invasive and it does not need any additional probe or sensor attached to the magnetic nanoparticles. Moreover, this method has the potential to be used together with the magnetic particle imaging technique to map the spatial distribution of the temperature.

Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

NASA Astrophysics Data System (ADS)

Phatak, C.; Petford-Long, A. K.; Beleggia, M.; De Graef, M.

2014-06-01

Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift computation for a uniformly polarized prolate ellipsoid with varying aspect ratio in the absence of screening charges.

Synthesis of TiO2 Nanoparticles from Ilmenite Through the Mechanism of Vapor-Phase Reaction Process by Thermal Plasma Technology

NASA Astrophysics Data System (ADS)

Samal, Sneha

2017-11-01

Synthesis of nanoparticles of TiO2 was carried out by non-transferred arc thermal plasma reactor using ilmenite as the precursor material. The powder ilmenite was vaporized at high temperature in plasma flame and converted to a gaseous state of ions in the metastable phase. On cooling, chamber condensation process takes place on recombination of ions for the formation of nanoparticles. The top-to-bottom approach induces the disintegration of complex ilmenite phases into simpler compounds of iron oxide and titanium dioxide phases. The vapor-phase reaction mechanism was carried out in thermal plasma zone for the synthesis of nanoparticles from ilmenite compound in a plasma reactor. The easy separation of iron particles from TiO2 was taken place in the plasma chamber with deposition of light TiO2 particles at the top of the cooling chamber and iron particles at the bottom. The dissociation and combination process of mechanism and synthesis are studied briefly in this article. The product TiO2 nanoparticle shows the purity with a major phase of rutile content. TiO2 nanoparticles produced in vapor-phase reaction process shows more photo-induced capacity.

Anti-Adhesive Behaviors between Solid Hydrate and Liquid Aqueous Phase Induced by Hydrophobic Silica Nanoparticles.

PubMed

Min, Juwon; Baek, Seungjun; Somasundaran, P; Lee, Jae W

2016-09-20

This study introduces an "anti-adhesive force" at the interface of solid hydrate and liquid solution phases. The force was induced by the presence of hydrophobic silica nanoparticles or one of the common anti-agglomerants (AAs), sorbitan monolaurate (Span 20), at the interface. The anti-adhesive force, which is defined as the maximum pushing force that does not induce the formation of a capillary bridge between the cyclopentane (CP) hydrate particle and the aqueous solution, was measured using a microbalance. Both hydrophobic silica nanoparticles and Span 20 can inhibit adhesion between the CP hydrate probe and the aqueous phase because silica nanoparticles have an aggregative property at the interface, and Span 20 enables the hydrate surface to be wetted with oil. Adding water-soluble sodium dodecyl sulfate (SDS) to the nanoparticle system cannot affect the aggregative property or the distribution of silica nanoparticles at the interface and, thus, cannot change the anti-adhesive effect. However, the combined system of Span 20 and SDS dramatically reduces the interfacial tension: emulsion drops were formed at the interface without any energy input and were adsorbed on the CP hydrate surface, which can cause the growth of hydrate particles. Silica nanoparticles have a good anti-adhesive performance with a relatively smaller dosage and are less influenced by the presence of molecular surfactants; consequently, these nanoparticles may have a good potential for hydrate inhibition as AAs.

Preparation of manganese doped cadmium sulfide nanoparticles in zincblende phase and their magnetic properties.

PubMed

Nakaya, Masafumi; Tanaka, Itaru; Muramatsu, Atsushi

2012-12-01

In this study, the random dope of Mn into CdS nanoparticles in zincblende phase has been carried out under the mild reaction condition. The resulting nanoparticles were characterized by energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), X-ray diffractometer (XRD), UV-Vis spectrometer, PL spectrometer, and SQUID. EDX showed that the compositions of Mn doped CdS nanoparticles were readily controlled. TEM showed the particle sizes were not significantly affected by the compositions, retaining to be ca. 3 nm with a narrow size distribution. UV-Vis and PL spectra of the resulting nanoparticles showed the intra-Mn level may be affected by the quantum size effect. SQUID measurement showed that the resulting nanoparticles showed diamagnetism, paramagnetism and superparamagnetism dependent on Mn content.

Biomimetic Silica Nanoparticles Prepared by a Combination of Solid-Phase Imprinting and Ostwald Ripening.

PubMed

Piletska, Elena; Yawer, Heersh; Canfarotta, Francesco; Moczko, Ewa; Smolinska-Kempisty, Katarzyna; Piletsky, Stanislav S; Guerreiro, Antonio; Whitcombe, Michael J; Piletsky, Sergey A

2017-09-14

Herein we describe the preparation of molecularly imprinted silica nanoparticles by Ostwald ripening in the presence of molecular templates immobilised on glass beads (the solid-phase). To achieve this, a seed material (12 nm diameter silica nanoparticles) was incubated in phosphate buffer in the presence of the solid-phase. Phosphate ions act as a catalyst in the ripening process which is driven by differences in surface energy between particles of different size, leading to the preferential growth of larger particles. Material deposited in the vicinity of template molecules results in the formation of sol-gel molecular imprints after around 2 hours. Selective washing and elution allows the higher affinity nanoparticles to be isolated. Unlike other strategies commonly used to prepare imprinted silica nanoparticles this approach is extremely simple in nature and can be performed under physiological conditions, making it suitable for imprinting whole proteins and other biomacromolecules in their native conformations. We have demonstrated the generic nature of this method by preparing imprinted silica nanoparticles against targets of varying molecular mass (melamine, vancomycin and trypsin). Binding to the imprinted particles was demonstrated in an immunoassay (ELISA) format in buffer and complex media (milk or blood plasma) with sub-nM detection ability.

Phase progression of γ-Al2O3 nanoparticles synthesized in a solvent-deficient environment.

PubMed

Smith, Stacey J; Amin, Samrat; Woodfield, Brian F; Boerio-Goates, Juliana; Campbell, Branton J

2013-04-15

Our simple and uniquely cost-effective solvent-deficient synthetic method produces 3-5 nm Al2O3 nanoparticles which show promise as improved industrial catalyst-supports. While catalytic applications are sensitive to the details of the atomic structure, a diffraction analysis of alumina nanoparticles is challenging because of extreme size/microstrain-related peak broadening and the similarity of the diffraction patterns of various transitional Al2O3 phases. Here, we employ a combination of X-ray pair-distribution function (PDF) and Rietveld methods, together with solid-state NMR and thermogravimetry/differential thermal analysis-mass spectrometry (TG/DTA-MS), to characterize the alumina phase-progression in our nanoparticles as a function of calcination temperature between 300 and 1200 °C. In the solvent-deficient synthetic environment, a boehmite precursor phase forms which transitions to γ-Al2O3 at an extraordinarily low temperature (below 300 °C), but this γ-Al2O3 is initially riddled with boehmite-like stacking-fault defects that steadily disappear during calcination in the range from 300 to 950 °C. The healing of these defects accounts for many of the most interesting and widely reported properties of the γ-phase.

Reactor for tracking catalyst nanoparticles in liquid at high temperature under a high-pressure gas phase with X-ray absorption spectroscopy.

PubMed

Nguyen, Luan; Tao, Franklin Feng

2018-02-01

Structure of catalyst nanoparticles dispersed in liquid phase at high temperature under gas phase of reactant(s) at higher pressure (≥5 bars) is important for fundamental understanding of catalytic reactions performed on these catalyst nanoparticles. Most structural characterizations of a catalyst performing catalysis in liquid at high temperature under gas phase at high pressure were performed in an ex situ condition in terms of characterizations before or after catalysis since, from technical point of view, access to the catalyst nanoparticles during catalysis in liquid phase at high temperature under high pressure reactant gas is challenging. Here we designed a reactor which allows us to perform structural characterization using X-ray absorption spectroscopy including X-ray absorption near edge structure spectroscopy and extended X-ray absorption fine structure spectroscopy to study catalyst nanoparticles under harsh catalysis conditions in terms of liquid up to 350 °C under gas phase with a pressure up to 50 bars. This reactor remains nanoparticles of a catalyst homogeneously dispersed in liquid during catalysis and X-ray absorption spectroscopy characterization.

Nanoparticle growth by particle-phase chemistry

NASA Astrophysics Data System (ADS)

Apsokardu, Michael J.; Johnston, Murray V.

2018-02-01

The ability of particle-phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2-100 nm diameter range is investigated through the use of a kinetic growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound, and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle-phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particles larger than about 20 nm in diameter. The modeling results provide a fundamental basis for understanding recent experimental measurements of the molecular composition of secondary organic aerosol showing that accretion reaction product formation increases linearly with increasing aerosol volume-to-surface-area. They also allow initial estimates of the reaction rate constants for these systems. For secondary aerosol produced by either OH oxidation of the cyclic dimethylsiloxane (D5) or ozonolysis of β-pinene, oligomerization rate constants on the order of 10-3 to 10-1 M-1 s-1 are needed to explain the experimental results. These values are consistent with previously measured rate constants for reactions of hydroperoxides and/or peroxyacids in the condensed phase.

Effects of nanoparticles on melting process with phase-change using the lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Ibrahem, Ahmed M.; El-Amin, Mohamed F.; Sun, Shuyu

In this work, the problem of nanoparticles dispersion effects on coupled heat transfer and solid-liquid phase change has been studied. The lattice Boltzmann method (LBM) enthalpy-based is employed. The collision model of lattice Bhatnagar-Gross-Krook (LBGK) is used to solve the problem of 1D melting by conduction. On the other hand, we use the model of multi-distribution functions (MDF) to calculate the density, the velocity and the temperature for the problem of 2D melting by free convection, associated with different boundary conditions. In these simulations, the volume fractions of copper nanoparticles (0-2%) added to water-base fluid and Rayleigh numbers of 103-105. We use the Chapman-Enskog expansion to derive the governing macroscopic quantities from the mesoscopic lattice Boltzmann equation. The results obtained by these models have been compared to an analytical solution or other numerical methods. The effects of nanoparticles on conduction and natural convection during the melting process have been investigated. Moreover, the influences of nanoparticles on moving of the phase change front, the thermal conductivity and the latent heat of fusion are also studied.

The effect of doping titanium dioxide nanoparticles on phase transformation, photocatalytic activity and anti-bacterial properties

NASA Astrophysics Data System (ADS)

Buzby, Scott Edward

Nanosized titanium dioxide has a variety of important applications in everyday life including a photocatalyst for pollution remediation, photovoltaic devices, sunscreen, etc. This study focuses on the various properties of titanium dioxide nanoparticles doped with various cation and anion species. Samples were produced by various methods including metalorganic chemical vapor deposition (MOCVD), plasma assisted metalorganic chemical vapor deposition (PA-MOCVD) and sol-gel. Numerous techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy both scanning (SEM) and transmission (TEM) were used for physical characterization. Photocatalytic properties were determined by the oxidation of methylene blue dye and 2-chlorophenol in water as well as gaseous formic acid with results analyzed by high performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR) and ultra violet - visible spectroscopy (UV-VIS). For the purpose of enhancement of the photocatalytic activity of titanium dioxide nanoparticles, the effect of anion doping and the anatase-rutile phase ratio were studied. Although anatase, rutile and mixed crystallite phases all show some degree of activity in photocatalytic reactions, these results show that anatase is better suited for the degradation of organic compounds in an aqueous medium any advantage in photocatalytic activity gained through the enhancement in optical response from the smaller band gap by addition of rutile was overcome by the negatives associated with the rutile phase. Furthermore substitutional nitrogen doping showed significant improvement in UV photocatalysis as well as allowing for visible light activation of the catalyst. Further studies on the phase transitions in titanium dioxide nanoparticles were carried out by synthesizing various cation doped samples by sol-gel. Analysis of the phases by XRD showed an inverse relationship between dopant size and rutile percentage

Detection of macrophages in atherosclerotic tissue using magnetic nanoparticles and differential phase optical coherence tomography.

PubMed

Oh, Junghwan; Feldman, Marc D; Kim, Jihoon; Sanghi, Pramod; Do, Dat; Mancuso, J Jacob; Kemp, Nate; Cilingiroglu, Mehmet; Milner, Thomas E

2008-01-01

We demonstrate the detection of iron oxide nanoparticles taken up by macrophages in atherosclerotic plaque with differential phase optical coherence tomography (DP-OCT). Magneto mechanical detection of nanoparticles is demonstrated in hyperlipidemic Watanabe and balloon-injured fat-fed New Zealand white rabbits injected with monocrystalline iron oxide nanoparticles (MIONs) of < 40 nm diam. MIONs taken up by macrophages was excited by an oscillating magnetic flux density and resulting nanometer tissue surface displacement was detected by DP-OCT. Frequency response of tissue surface displacement in response to an externally applied magnetic flux density was twice the stimulus frequency as expected from the equations of motion for the nanoparticle cluster.

Smectite clay--inorganic nanoparticle mixed suspensions: phase behaviour and rheology.

PubMed

Bailey, Louise; Lekkerkerker, Henk N W; Maitland, Geoffrey C

2015-01-14

Smectite clay minerals and their suspensions have long been of both great scientific and applications interest and continue to display a remarkable range of new and interesting behaviour. Recently there has been an increasing interest in the properties of mixed suspensions of such clays with nanoparticles of different size, shape and charge. This review aims to summarize the current status of research in this area focusing on phase behaviour and rheological properties. We will emphasize the rich range of data that has emerged for these systems and the challenges they present for future investigations. The review starts with a brief overview of the behaviour and current understanding of pure smectite clays and their suspensions. We then cover the work on smectite clay-inorganic nanoparticle mixed suspensions according to the shape and charge of the nanoparticles - spheres, rods and plates either positively or negatively charged. We conclude with a summary of the overarching trends that emerge from these studies and indicate where gaps in our understanding need further research for better understanding the underlying chemistry and physics.

Encapsulated Solid-Liquid Phase Change Nanoparticles as Thermal Barcodes for Highly Sensitive Detections of Multiple Lung Cancer Biomarkers

DTIC Science & Technology

2012-10-01

5e. TASK NUMBER LC90061 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT...transduction mechanism based on solid- liquid phase change nanoparticles works for the detection of multiple proteins. A series of metal and alloy...early stage. With the support from DOD-LCRP, we have proved the new signal transduction mechanism based on solid-liquid phase change nanoparticles works

Nanoparticles for Nonaqueous-phase liquids (NAPLs) Remediation

NASA Astrophysics Data System (ADS)

Jiemvarangkul, Pijit

Nanotechnology has gained attention in various fields of science and engineering for more than decades. Many nanotechnologies using nanosorbents, nanosensors, and nanoparticles have been developed, studied, and used to solve environmental problems. This dissertation contributes to the applications of two types of nanoparticles: 1) using zero valent iron nanoparticle technology (nZVI) for treatment of groundwater contaminated by chlorinated hydrocarbons and study effect of polyelectrolyte polymers on enhancing the mobility of nZVI in porous media and 2) testing a new type of nanoparticle, nano-scale calcium peroxide (CaO2) particles (nano-peroxide); particles have been synthesized and preliminarily tests on their chemical properties and oxidizing reactions with petroleum hydrocarbons investigated. Trichloroethylene (TCE) is one of the high toxic, dense, non-aqueous phase liquids (DNAPLs) and it is one of the major problems of groundwater contamination. The direct reaction of nano-scale zerovalent iron (nZVI) particles and TCE liquid phase batch experiments shows that nZVI has capability to remove pure phase TCE and there is the reduction reaction occurred with reaction byproduct. Mass balance of nZVI-TCE reaction demonstrates that 7--9 % TCE mass was trapped in 1 g of nZVI sludge indicating that absorption occurred during the removal process confirming the absorption of TCE into nZVI sludge. The reaction and absorption abilities of nZVI are depended upon its surface areas. Increasing amount of nZVI reduces the space of batch experiment systems, so TCE removal efficiency of nZVI is decreased. These experiments show the practicability of using nZVI to directly remove TCE from contaminated groundwater. The transport of nanoscale zero-valent iron (nZVI) particles stabilized by three polyelectrolytes: polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A), poly(acrylic acid) (PAA) and soy proteins were examined. The study shows the increase in nZVI mobility by

Smart Nanoparticles Undergo Phase Transition for Enhanced Cellular Uptake and Subsequent Intracellular Drug Release in a Tumor Microenvironment.

PubMed

Ye, Guihua; Jiang, Yajun; Yang, Xiaoying; Hu, Hongxiang; Wang, Beibei; Sun, Lu; Yang, Victor C; Sun, Duxin; Gao, Wei

2018-01-10

Inefficient cellular uptake and intracellular drug release at the tumor site are two major obstacles limiting the antitumor efficacy of nanoparticle delivery systems. To overcome both problems, we designed a smart nanoparticle that undergoes phase transition in a tumor microenvironment (TME). The smart nanoparticle is generated using a lipid-polypetide hybrid nanoparticle, which comprises a PEGylated lipid monolayer shell and a pH-sensitive hydrophobic poly-l-histidine core and is loaded with the antitumor drug doxorubicin (DOX). The smart nanoparticle undergoes a two-step phase transition at two different pH values in the TME: (i) At the TME (pH e : 7.0-6.5), the smart nanoparticle swells, and its surface potential turns from negative to neutral, facilitating the cellular uptake; (ii) After internalization, at the acid endolysosome (pH endo : 6.5-4.5), the smart nanoparticle dissociates and induces endolysosome escape to release DOX into the cytoplasm. In addition, a tumor-penetrating peptide iNRG was modified on the surface of the smart nanoparticle as a tumor target moiety. The in vitro studies demonstrated that the iNGR-modified smart nanoparticles promoted cellular uptake in the acidic environment (pH 6.8). The in vivo studies showed that the iNGR-modified smart nanoparticles exerted more potent antitumor efficacy against late-stage aggressive breast carcinoma than free DOX. These data suggest that the smart nanoparticles may serve as a promising delivery system for sequential uptake and intracellular drug release of antitumor agents. The easy preparation of these smart nanoparticles may also have advantages in the future manufacture for clinical trials and clinical use.

Synthesis of bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles

NASA Astrophysics Data System (ADS)

Li, Xue-Mei; Liu, Hong-Ling; Liu, Xiao; Fang, Ning; Wang, Xian-Hong; Wu, Jun-Hua

2015-11-01

Bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO) as the surfactant. The morphology and crystal structure of the nanoparticles were studied by TEM/HRTEM and XRD. The nanoparticles manifest soft ferromagnetic and/or near superparamagnetic behavior with a small coercivity of ~19 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by the modified Langevin equation. The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the nanoparticles. The UV-vis and PL results reveal the well-behaved absorption bands including surface plasmon resonance and multiple visible fingerprint photoluminescent emissions of the nanoparticles dispersed in both hydrophilic and hydrophobic solvents. Moreover, the processes of solvent dispersion-collection of the nanoparticles were demonstrated for application readiness of such core-shell nanostructures.

Synthesis of bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles

PubMed Central

Li, Xue-Mei; Liu, Hong-Ling; Liu, Xiao; Fang, Ning; Wang, Xian-Hong; Wu, Jun-Hua

2015-01-01

Bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO) as the surfactant. The morphology and crystal structure of the nanoparticles were studied by TEM/HRTEM and XRD. The nanoparticles manifest soft ferromagnetic and/or near superparamagnetic behavior with a small coercivity of ~19 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by the modified Langevin equation. The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the nanoparticles. The UV-vis and PL results reveal the well-behaved absorption bands including surface plasmon resonance and multiple visible fingerprint photoluminescent emissions of the nanoparticles dispersed in both hydrophilic and hydrophobic solvents. Moreover, the processes of solvent dispersion-collection of the nanoparticles were demonstrated for application readiness of such core-shell nanostructures. PMID:26548369

Polymerization in the gas phase, in clusters, and on nanoparticle surfaces.

PubMed

El-Shall, M Samy

2008-07-01

on the oligomers formed by gas-phase polymerization can be obtained using the mass-selected ion mobility technique where the measured collision cross-sections of the selected oligomer ions and collision-induced dissociation can provide fairly accurate structural identifications. The identification of the structures of the dimers and trimers formed in the gas-phase thermal polymerization of styrene confirms that the polymerization proceeds according to the Mayo mechanism. Similarly, the ion mobility technique has been utilized to confirm the formation of benzene cations by intracluster polymerization following the ionization of acetylene clusters. Finally, it has been shown that polymerization of styrene vapor on the surface of activated nanoparticles can lead to the incorporation of a variety of metal and metal oxide nanoparticles within polystyrene films. The ability to probe the reactivity and structure of the small growing oligomers in the gas phase can provide fundamental insight into mechanisms of polymerization that are difficult to obtain from condensed-phase studies. These experiments are also important for understanding the growth mechanisms of complex organics in flames, combustion processes, interstellar clouds, and solar nebula where gas-phase reactions, cluster polymerization, and surface catalysis on dust nanoparticles represent the major synthetic pathways. This research can lead to the discovery of novel initiation mechanisms and reaction pathways with applications in the synthesis of oligomers and nanocomposites with unique and improved properties.

Abnormal cubic-tetragonal phase transition of barium strontium titanate nanoparticles studied by in situ Raman spectroscopy and transmission electron microscopy heating experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yin; Chen, Chen; Gao, Ran

2015-11-02

Phase stability of the ferroelectric materials at high temperature is extremely important to their device performance. Ba{sub x}Sr{sub 1−x}TiO{sub 3} (BST) nanoparticles with different Sr contents (x = 1, 0.91, 0.65, 0.4, and 0) are prepared by a facile hydrothermal method. Using Raman spectroscopy and transmission electron microscopy (TEM) analyses under in situ heating conditions (up to 300 °C), the phase transitions of BST nanoparticles between 25 °C and 280 °C are comprehensively investigated. The original Curie temperature of BST nanoparticles decreases abruptly with the increase in Sr content, which is more obvious than in the bulk or film material. Besides, an abnormal phase transitionmore » from cubic to tetragonal structure is observed from BST nanoparticles and the transition temperature rises along with the increase in Sr content. Direct TEM evidences including a slight lattice distortion have been provided. Differently, BaTiO{sub 3} nanoparticles remained in the tetragonal phase during the above temperature ranges.« less

New Approach for Gas Phase Synthesis and Growth Mechanism of MoS2 Fullerene-like Nanoparticles

NASA Astrophysics Data System (ADS)

Zak, Alla; Feldman, Yishay; Alperovich, Vladimir; Rosentsveig, Rita; Tenne, Reshef

2002-10-01

Inorganic fullerene-like (hollow onion-like) nanoparticles (IF) and nanotubes are of significant interest over the past few years due to their unusual crystallographic morphology and their interesting physical properties. The synthesis of inorganic fullerene-like spherical MoS2 nanoparticles (IF-MoS2) of 5-300nm in diameter was studied in the present work. This process is based on the previous formation of suboxide (MoO3-x) 5-300nm nanoparticles and their subsequent sulfidization. During the sulfidization process the overall geometrical parameters of the suboxide nanoparticles are preserved. The oxide nanoparticles were obtained in-situ by the condensation of the evaporated MoO3 powder precursor. The condensation was provoked not by cooling (conventional method for nano-size particle formation), but by a chemical reaction (partial reduction of the MoO3 vapor by hydrogen). In this case the vapor pressure of the product (MoO2) was much lower than that of the precursor (MoO3). Based on the comprehensive understanding of the IF-MoS2 growth mechanism from MoO3 powder, a gas phase reactor, which allowed reproducible preparation of a pure IF-MoS2 phase (up to 100mg/batch) with controllable sizes, is demonstrated. Further scale-up of this production is underway.

Metal matrix-metal nanoparticle composites with tunable melting temperature and high thermal conductivity for phase-change thermal storage.

PubMed

Liu, Minglu; Ma, Yuanyu; Wu, Hsinwei; Wang, Robert Y

2015-02-24

Phase-change materials (PCMs) are of broad interest for thermal storage and management applications. For energy-dense storage with fast thermal charging/discharging rates, a PCM should have a suitable melting temperature, large enthalpy of fusion, and high thermal conductivity. To simultaneously accomplish these traits, we custom design nanocomposites consisting of phase-change Bi nanoparticles embedded in an Ag matrix. We precisely control nanoparticle size, shape, and volume fraction in the composite by separating the nanoparticle synthesis and nanocomposite formation steps. We demonstrate a 50-100% thermal energy density improvement relative to common organic PCMs with equivalent volume fraction. We also tune the melting temperature from 236-252 °C by varying nanoparticle diameter from 8.1-14.9 nm. Importantly, the silver matrix successfully prevents nanoparticle coalescence, and no melting changes are observed during 100 melt-freeze cycles. The nanocomposite's Ag matrix also leads to very high thermal conductivities. For example, the thermal conductivity of a composite with a 10% volume fraction of 13 nm Bi nanoparticles is 128 ± 23 W/m-K, which is several orders of magnitude higher than typical thermal storage materials. We complement these measurements with calculations using a modified effective medium approximation for nanoscale thermal transport. These calculations predict that the thermal conductivity of composites with 13 nm Bi nanoparticles varies from 142 to 47 W/m-K as the nanoparticle volume fraction changes from 10 to 35%. Larger nanoparticle diameters and/or smaller nanoparticle volume fractions lead to larger thermal conductivities.

Facile synthesis and photocatalytic activity of bi-phase dispersible Cu-ZnO hybrid nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Xiao; Liu, HongLing; Zhang, WenXing; Li, XueMei; Fang, Ning; Wang, XianHong; Wu, JunHua

2015-04-01

Bi-phase dispersible Cu-ZnO hybrid nanoparticles were synthesized by one-pot non-aqueous nanoemulsion with the use of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO) as the surfactant. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) show high crystallinity of the Cu-ZnO hybrid nanoparticles and an average particle size of ~19.4 nm. The ultraviolet-visible light absorbance spectrometry (UV-vis) and photoluminescence spectrophotometry (PL) demonstrate well dispersibility and excellent optical performance of Cu-ZnO hybrid nanoparticles both in organic and aqueous solvent. The X-ray photoelectron spectroscopy (XPS) confirms Cu1+ and Cu2+ in ZnO. The observation using Sudan red (III) as probe molecule reveals that the Cu-ZnO hybrid nanoparticles possess enhanced photocatalytic activity and stability which are promising for potential applications in photocatalysis.

Gas phase synthesis of core-shell Fe@FeO x magnetic nanoparticles into fluids

NASA Astrophysics Data System (ADS)

Aktas, Sitki; Thornton, Stuart C.; Binns, Chris; Denby, Phil

2016-12-01

Sorbitol, short chain molecules, have been used to stabilise of Fe@FeO x nanoparticles produced in the gas phase under the ultra-high vacuum (UHV) conditions. The sorbitol coated Fe@FeO x nanoparticles produced by our method have a narrow size distribution with a hydrodynamic diameter of 35 nm after NaOH is added to the solution. Magnetisation measurement shows that the magnetic nanoparticles are superparamagnetic at 100 K and demonstrate hysteresis at 5 K with an anisotropy constant of 5.31 × 104 J/m3 (similar to bulk iron). Also, it is shown that sorbitol is only suitable for stabilising the Fe@FeO x suspensions, and it does not prevent further oxidation of the metallic Fe core. According to MRI measurement, the nanoparticles have a high transverse relaxation rate of 425 mM-1 s-1.

Morphology and phase control of iron oxide polymorph nanoparticles

NASA Astrophysics Data System (ADS)

Cui, Hongtao; Wang, Li; Shi, Min; Li, Yanhong

2017-04-01

In this work, lepidocrocite (γ-FeOOH) nanobundles were prepared by a facile NH4F assisted epoxide precipitation route. The reactions between epoxide and [Fe(H2O)6]2+ promoted the hydrolysis and condensation of [Fe(H2O)6]2+, resulting in the formation of iron oxyhydroxide. After calcination of γ-FeOOH nanobundles at 400 °C, the produced α-Fe2O3 still kept the bundle morphology. Due to the unique chemistry of epoxide, the morphology and phase of iron oxide polymorph nanoparticles (goethite, akaganeite, lepidocrocite, magnetite) were well-controlled through controlling reaction conditions such as Fe2+ concentration, NH4F additive and reaction temperature. It is particularly interesting that NH4F working as phase controlling agent is able to control the phase development of iron oxyhydroxides. This phase control effect of NH4F is attributed to the promoted reaction rate of epoxide originating from the higher electronegativity of fluoride ions than chloride ions. Based on the results in this work and our other preliminary works, it is considered that this route can be used as a general strategy for controlling the morphology and phase of transition element compounds.

ENANTIOSEPARATION OF MALATHION, CRUFORMATE, AND FENSULFOTHION ORGANOSPHOSPHORUS PESTICIDES BY MIXED-MODE ELECTROKINETIC CAPILLARY CHROMATOGRAPHY

EPA Science Inventory

Mixed-mode electrokinetic capillary chromatography (mixed-ECC) has been used for the enantioseparation of organophosphorus pesticides. In mixed-ECC, a combination of three pseudostationary phases including surfactants, neutral, and charged cyclodextrins, are used to resolve very ...

Multiscale Aspects of Modeling Gas-Phase Nanoparticle Synthesis

PubMed Central

Buesser, B.; Gröhn, A.J.

2013-01-01

Aerosol reactors are utilized to manufacture nanoparticles in industrially relevant quantities. The development, understanding and scale-up of aerosol reactors can be facilitated with models and computer simulations. This review aims to provide an overview of recent developments of models and simulations and discuss their interconnection in a multiscale approach. A short introduction of the various aerosol reactor types and gas-phase particle dynamics is presented as a background for the later discussion of the models and simulations. Models are presented with decreasing time and length scales in sections on continuum, mesoscale, molecular dynamics and quantum mechanics models. PMID:23729992

Structural and optical characterization of Eu3+ doped beta-Ga2O3 nanoparticles using a liquid-phase precursor method.

PubMed

Kim, Moung-O; Kang, Bongkyun; Yoon, Daeho

2013-08-01

Eu3+ doped beta-Ga2O3 and non-doped beta-Ga2O3 nanoparticles were synthesized at 800 degrees C using a liquid-phase precursor (LPP) method, with different annealing times and Eu3+ ion concentrations. Eu3+ doped beta-Ga2O3 nanoparticles showed broad XRD peaks, revealing a second phase compared with the non-doped beta-Ga2O3 nanoparticles. The cathode luminescence (CL) spectra of beta-Ga2O3 and Eu3+ doped beta-Ga2O3 nanoparticles showed a broad band emission (300-500 nm) of imperfection and two component emissions. The luminescence quenching properties of Eu3+ dopant ion concentration appeared gradually beyond 5 mol% in our investigation.

Micellar electrokinetic chromatography with acid labile surfactant.

PubMed

Stanley, Bob; Lucy, Charles A

2012-02-24

We present a study of a degradable surfactant, sodium 4-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propane sulfonate that is also known as an acid-labile surfactant (ALS). The performance of ALS as a pseudostationary phase is assessed and compared with established pseudostationary phases such as sodium dodecyl sulphate (SDS), volatile surfactants and polymeric micelles. ALS achieves separation efficiency of 100,000-145,000 theoretical plates and relative standard deviation (RSD) of electrophoretic mobility (n=5) of less than 3%. Retention factors with ALS are strongly correlated with those with SDS. This is shown by the R2=0.79 for all eleven analytes and an R2=0.992 for specifically the non-hydrogen bonding (NHB) analytes. However, ALS displays different selectivity than SDS for hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) solutes (R2 of 0.74 and 0.88, respectively). ALS is degraded to less surface active compounds in acidic solution. These less surface-active compounds are more compatible with the electrospray ionization mass spectrometry (ESI-MS). ALS has a half-life of 48 min at pH 4. ALS has the potential to couple micellar electrokinetic chromatography (MEKC) with the ESI-MS. ALS can be used as a pseudostationary phase for a high efficiency separation and later acid hydrolyzed to enable an ESI-MS analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

MesoDyn simulation study on the phase morphologies of Miktoarm PEO-b-PMMA copolymer doped by nanoparticles

NASA Astrophysics Data System (ADS)

Mu, Dan; Li, Jian-Quan; Feng, Sheng-Yu

2013-03-01

The compatibility of six groups of 12 miktoarm poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) copolymers is studied at 270, 298 and 400 K via mesoscopic modeling. The values of the order parameters depend on both the architectures of the block copolymers and the simulation temperature, while the tendency to change of the order parameters at low temperature, such as 270 and 298 K, is nearly the same. However, the values of order parameters of the copolymer in the same group are the same at high temperature, i.e. 400 K. Obviously, temperature has a more obvious effect on long and PEO-rich chains. A study of plain copolymers doped with nanoparticles shows that the microscopic phase is influenced by not only the properties of the nanoparticles, such as the size, number and density, but also the composition and architecture of copolymers. Increasing the size and the number of the nanoparticles used as a dopant plays the most significant role on determining the phase morphologies of the copolymers at lower and higher temperature, respectively. In paricular, the 23141 and 23241-type copolymers, which are both of PEO-rich composition, presents microscopic phase separation as perforated lamallae phase morphologies at 400 K, alternated with PEO and PMMA components.

Phase, microstructure and hydrogen storage properties of Mg-Ni materials synthesized from metal nanoparticles.

PubMed

Shao, Huaiyu; Chen, Chunguang; Liu, Tong; Li, Xingguo

2014-04-04

After Mg and Ni nanoparticles were fabricated by hydrogen plasma metal reaction, Mg-rich MgxNi₁₀₀₋x(75 < x < 90) materials were synthesized from these metal nanoparticles to study the synergistic effects for hydrogen storage in these samples to show both good kinetics and high capacity. These MgxNi₁₀₀₋x materials may absorb hydrogen with a capacity of around 3.3-5.1 wt% in 1 min at 573 K. The Mg₉₀Ni₁₀ sample shows a hydrogen capacity of 6.1 wt%. The significant kinetic enhancement is thought to be due to the unique nanostructure from the special synthesis route, the catalytic effect of the Mg₂Ni nano phase, and the synergistic effects between the Mg₂Ni and Mg phases in the materials. An interesting phenomenon which has never been reported before was observed during pressure composition isotherm (PCT) measurements. One steep step in the absorption process and two obviously separated steps in the desorption process during PCT measurements of Mg₈₀Ni₂₀ and Mg₉₀Ni₁₀ samples were observed and a possible reason from the kinetic performance of the Mg₂Ni and Mg phases in absorption and desorption processes was explained. These MgxNi₁₀₀₋x materials synthesized from Mg and Ni nanoparticles show high capacity and good kinetics, which makes these materials very promising candidates for thermal storage or energy storage and utilization for renewable power.

Synthesis and Properties of Nanoparticle Forms Saponite Clay, Cancrinite Zeolite and Phase Mixtures Thereof.

PubMed

Shao, Hua; Pinnavaia, Thomas J

2010-09-01

The low-temperature synthesis (90°C) of nanoparticle forms of a pure phase smectic clay (saponite) and zeolite (cancrinite) is reported, along with phase mixtures thereof. A synthesis gel corresponding to the Si:Al:Mg unit cell composition of saponite (3.6:0.40:3.0) and a NaOH/Si ratio of 1.39 affords the pure phase clay with disordered nanolayer stacking. Progressive increases in the NaOH/Si ratio up to a value of 8.33 results in the co-crystallization of first garronite and then cancrinite zeolites with nanolath morphology. The resulting phase mixtures exhibit a compound particulate structure of intertwined saponite nanolayers and cancrinite nanolaths that cannot be formed through physical mixing of the pure phase end members. Under magnesium-free conditions, pure phase cancrinite nanocrystals are formed. The Si/Al ratio of the reaction mixture affects the particle morphology as well as the chemical composition of the cancrinite zeolite. Ordinarily, cancrinite crystallizes with a Si/Al ratio of 1.0, but a silicon-rich form of the zeolite (Si/Al=1.25) is crystallized at low temperature from a silica rich synthesis gel, as evidenced by (29)Si NMR spectroscopy and XEDS-TEM. Owing to the exceptionally high external surface areas of the pure phase clay (875 m(2)/g) and zeolite end members (8.9 - 40 m(2)/g), as well as their unique mixed phase composites (124 - 329 m(2)/g), these synthetic derivatives are promising model nanoparticles for studies of the bioavailability of poly-aromatic hydrocarbons immobilized in silicate bearing sediments and soils.

Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

NASA Astrophysics Data System (ADS)

Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

2015-12-01

Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. Our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.

Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

PubMed Central

Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

2015-01-01

Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. Our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments. PMID:26655832

Cross-phase separation of nanowires and nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Fang; Duoss, Eric; Han, Jinkyu

In one embodiment, a process includes creating a mixture of an aqueous component, nanowires and nanoparticles, and a hydrophobic solvent and allowing migration of the nanowires to the hydrophobic solvent, where the nanoparticles remain in the aqueous component. Moreover, the nanowires and nanoparticles are in the aqueous component before the migration.

Phase- and shape-controlled hydrothermal synthesis of CdS nanoparticles, and oriented attachment growth of its hierarchical architectures

NASA Astrophysics Data System (ADS)

Cao, Yali; Hu, Pengfei; Jia, Dianzeng

2013-01-01

Hydrothermal strategies were successfully used to control the phases and morphologies of CdS nanocrystals. In the absence of an external direction-controlling process, the hexagonal and cubic phase well-defined leaf- and flower-like CdS nanocrystals were controlled obtained via adjusting the reaction duration or the concentration of surfactant. Oriented attachment growth modes were suggested for the formation of CdS superstructures, which was clarified through the tracing of temporal evolution of CdS nanoparticles. The CdS superstructures were structured by primary building nanoparticles, and held excellent visible emission with a peak in the green regions. This strategy is very helpful for studying the phase and morphology controlled fabrication of sulfides nanocrystals.

Dendronization-induced phase-transfer, stabilization and self-assembly of large colloidal Au nanoparticles

NASA Astrophysics Data System (ADS)

Malassis, Ludivine; Jishkariani, Davit; Murray, Christopher B.; Donnio, Bertrand

2016-07-01

The phase-transfer of CTAB-coated aqueous, spherical gold nanoparticles, with metallic core diameters ranging from ca. 27 to 54 nm, into organic solvents by exchanging the primitive polar bilayer with lipophilic, disulfide dendritic ligands is reported. The presence of such a thick nonpolar organic shell around these large nanoparticles enhances their stabilization against aggregation, in addition to enabling their transfer into a variety of solvents such as chloroform, toluene or tetrahydrofuran. Upon the slow evaporation of a chloroform suspension deposited on a solid support, the dendronized hybrids were found to self-assemble into ring structures of various diameters. Moreover, their self-assembly at the liquid-air interface affords the formation of fairly long-range ordered monolayers, over large areas, that can then be entirely transferred onto solid substrates.The phase-transfer of CTAB-coated aqueous, spherical gold nanoparticles, with metallic core diameters ranging from ca. 27 to 54 nm, into organic solvents by exchanging the primitive polar bilayer with lipophilic, disulfide dendritic ligands is reported. The presence of such a thick nonpolar organic shell around these large nanoparticles enhances their stabilization against aggregation, in addition to enabling their transfer into a variety of solvents such as chloroform, toluene or tetrahydrofuran. Upon the slow evaporation of a chloroform suspension deposited on a solid support, the dendronized hybrids were found to self-assemble into ring structures of various diameters. Moreover, their self-assembly at the liquid-air interface affords the formation of fairly long-range ordered monolayers, over large areas, that can then be entirely transferred onto solid substrates. Electronic supplementary information (ESI) available: TEM microscope images. See DOI: 10.1039/c6nr03404g

In situ growth of capping-free magnetic iron oxide nanoparticles on liquid-phase exfoliated graphene

NASA Astrophysics Data System (ADS)

Tsoufis, T.; Syrgiannis, Z.; Akhtar, N.; Prato, M.; Katsaros, F.; Sideratou, Z.; Kouloumpis, A.; Gournis, D.; Rudolf, P.

2015-05-01

We report a facile approach for the in situ synthesis of very small iron oxide nanoparticles on the surface of high-quality graphene sheets. Our synthetic strategy involved the direct, liquid-phase exfoliation of highly crystalline graphite (avoiding any oxidation treatment) and the subsequent chemical functionalization of the graphene sheets via the well-established 1,3-dipolar cycloaddition reaction. The resulting graphene derivatives were employed for the immobilization of the nanoparticle precursor (Fe cations) at the introduced organic groups by a modified wet-impregnation method, followed by interaction with acetic acid vapours. The final graphene-iron oxide hybrid material was achieved by heating (calcination) in an inert atmosphere. Characterization by X-ray diffraction, transmission electron and atomic force microscopy, Raman and X-ray photoelectron spectroscopy gave evidence for the formation of rather small (<12 nm), spherical, magnetite-rich nanoparticles which were evenly distributed on the surface of few-layer (<1.2 nm thick) graphene. Due to the presence of the iron oxide nanoparticles, the hybrid material showed a superparamagnetic behaviour at room temperature.We report a facile approach for the in situ synthesis of very small iron oxide nanoparticles on the surface of high-quality graphene sheets. Our synthetic strategy involved the direct, liquid-phase exfoliation of highly crystalline graphite (avoiding any oxidation treatment) and the subsequent chemical functionalization of the graphene sheets via the well-established 1,3-dipolar cycloaddition reaction. The resulting graphene derivatives were employed for the immobilization of the nanoparticle precursor (Fe cations) at the introduced organic groups by a modified wet-impregnation method, followed by interaction with acetic acid vapours. The final graphene-iron oxide hybrid material was achieved by heating (calcination) in an inert atmosphere. Characterization by X-ray diffraction, transmission

Synthesis of erbium,ytterbium-doped hexagonal phase sodium yttrium fluoride nanoparticles and application to ligand exchange and energy transfer studies

NASA Astrophysics Data System (ADS)

Goel, Vishya

Nanoparticles containing rare earth ions have the ability to absorb and convert infrared light into visible light. The purpose of this work is to synthesize rare earth ion-doped NaYF4 nanoparticles in their most efficient form, the hexagonal phase. These nanoparticles are then used in ligand exchange and energy transfer studies. The synthesis procedure produces gram scale quantities of nanoparticles. Such a scale is important for reproducibility and application of these materials. Oleylamine-capped NaYF4 nanoparticles were synthesized and were doped with 2 % Er3+ and 20 % Yb3+ using a thermal decomposition method. The procedure was optimized in terms of precursor concentration and injection rate. The samples were characterized using photoluminescence spectroscopy, transmission electron microscopy, and X-ray diffraction. Photoluminescence spectra were collected using infrared excitation (980 nm). Control of the temperature and injection resulted in 15 nm (diameter) hexagonal phase NaYF4:Er3+,Yb3+ nanoparticles capped with oleylamine. The nanoparticles exhibited bright emission in the red (640 nm) and green (540 nm) portions of the visible spectrum. The surface of the nanoparticles was modified with decanoic acid, dodecanedioic acid, or dodecane sulfonic acid using a ligand exchange reaction. Energy transfer was studied from the oleylamine-capped nanoparticles to the fluorophores Nile Red, 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran, and poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene). Successful surface ligand exchange was achieved and the preliminary exploration of upconverting nanoparticles as an energy transfer donor was performed.

Solid-Phase Synthesis of Molecularly Imprinted Polymer Nanoparticles with a Reusable Template - "Plastic Antibodies".

PubMed

Poma, Alessandro; Guerreiro, Antonio; Whitcombe, Michael J; Piletska, Elena V; Turner, Anthony P F; Piletsky, Sergey A

2013-06-13

Molecularly Imprinted Polymers (MIPs) are generic alternatives to antibodies in sensors, diagnostics and separations. To displace biomolecules without radical changes in infrastructure in device manufacture, MIPs should share their characteristics (solubility, size, specificity and affinity, localized binding domain) whilst maintaining the advantages of MIPs (low-cost, short development time and high stability) hence the interest in MIP nanoparticles. Herein we report a reusable solid-phase template approach (fully compatible with automation) for the synthesis of MIP nanoparticles and their precise manufacture using a prototype automated UV photochemical reactor. Batches of nanoparticles (30-400 nm) with narrow size distributions imprinted with: melamine (d = 60 nm, K d = 6.3 × 10 -8 m), vancomycin (d = 250 nm, K d = 3.4 × 10 -9 m), a peptide (d = 350 nm, K d = 4.8 × 10 -8 m) and proteins have been produced. Our instrument uses a column packed with glass beads, bearing the template. Process parameters are under computer control, requiring minimal manual intervention. For the first time we demonstrate the reliable re-use of molecular templates in the synthesis of MIPs (≥ 30 batches of nanoMIPs without loss of performance). NanoMIPs are produced template-free and the solid-phase acts both as template and affinity separation medium.

Preparation of starch stabilized silver nanoparticles with spatial self-phase modulation properties by laser ablation technique

NASA Astrophysics Data System (ADS)

Zamiri, Reza; Azmi, B. Z.; Darroudi, Majid; Sadrolhosseini, Amir R.; Husin, M. S.; Zaidan, A. W.; Mahdi, M. A.

2011-01-01

Silver nanoparticles inside the starch solution have been successfully fabricated by laser ablation of a silver plate immersed in starch solution. The ablation has been done using a Q-switched Nd:YAG laser at 10 Hz repetition rate. The starch solution allows for the formation of silver nanoparticles with uniform particle diameters and well dispersed. The ablation was performed at different time durations to study the influence of the laser ablation time on efficiency of particle formation and sizes. The Spatial Self-phase modulation phenomena which can determine the nonlinear optical property of the samples were also investigated for starch solutions containing silver nanoparticles.

Graphene nanosheets preparation using magnetic nanoparticle assisted liquid phase exfoliation of graphite: The coupled effect of ultrasound and wedging nanoparticles.

PubMed

Hadi, Alireza; Zahirifar, Jafar; Karimi-Sabet, Javad; Dastbaz, Abolfazl

2018-06-01

This study aims to investigate a novel technique to improve the yield of liquid phase exfoliation of graphite to graphene sheets. The method is based on the utilization of magnetic Fe 3 O 4 nanoparticles as "particle wedge" to facilitate delamination of graphitic layers. Strong shear forces resulted from the collision of Fe 3 O 4 particles with graphite particles, and intense ultrasonic waves lead to enhanced exfoliation of graphite. High quality of graphene sheets along with the ease of Fe 3 O 4 particle separation from graphene solution which arises from the magnetic nature of Fe 3 O 4 nanoparticles are the unique features of this approach. Initial graphite flakes and produced graphene sheets were characterized by various methods including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. Moreover, the effect of process factors comprising initial graphite concentration, Fe 3 O 4 nanoparticles concentration, sonication time, and sonication power were investigated. Results revealed that graphene preparation yield and the number of layers could be manipulated by the presence of magnetic nanoparticles. Copyright © 2018 Elsevier B.V. All rights reserved.

Single step, phase controlled, large scale synthesis of ferrimagnetic iron oxide polymorph nanoparticles by thermal plasma route and their rheological properties

NASA Astrophysics Data System (ADS)

Raut, Suyog A.; Mutadak, Pallavi R.; Kumar, Shiv; Kanhe, Nilesh S.; Huprikar, Sameer; Pol, Harshawardhan V.; Phase, Deodatta M.; Bhoraskar, Sudha V.; Mathe, Vikas L.

2018-03-01

In this paper we report single step large scale synthesis of highly crystalline iron oxide nanoparticles viz. magnetite (Fe3O4) and maghemite (γ-Fe2O3) via gas phase condensation process, where micron sized iron metal powder was used as a precursor. Selective phases of iron oxide were obtained by variation of gas flow rate of oxygen and hence partial pressure of oxygen inside the plasma reactor. Most of the particles were found to possesses average crystallite size of about 20-30 nm. The DC magnetization curves recorded indicate almost super-paramagnetic nature of the iron oxide magnetic nanoparticles. Further, iron oxide nanoparticles were analyzed using Raman spectroscopy, X-ray photoelectron spectroscopy and Mossbauer spectroscopy. In order to explore the feasibility of these nanoparticles for magnetic damper application, rheological studies have been carried out and compared with commercially available Carbonyl Iron (CI) particles. The nanoparticles obtained by thermal plasma route show improved dispersion which is useful for rheological applications.

New immobilisation protocol for the template used in solid-phase synthesis of MIP nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Lu; Muhammad, Turghun; Yakup, Burabiye; Piletsky, Sergey A.

2017-06-01

As a novel imprinting method, solid-phase synthesis has proven to be a promising approach to prepare polymer nanoparticles with specific recognition sites for a template molecule. In this method, imprinted polymer nanoparticles were synthesized using template immobilized on a solid support. Herein, preparation of immobilized templates on quartz chips through homogeneous route was reported as an efficient alternative strategy to heterogeneous one. The template molecule indole-3-butyric acid (IBA) was reacted with 3-aminopropyltriethoxysilane (APTES) to produce silylated template (IBA-APTES), and it was characterized by IR, 1H NMR and GC-MS. Then, the silylated template molecule was grafted onto the activated surfaces of quartz chip to prepare immobilized template (SiO2@IBA-APTES). The immobilization was confirmed by contact angle, XPS, UV and fluorescence measurement. Immobilization protocol has shown good reproducibility and stability of the immobilized template. MIP nanoparticles were prepared with high selectivity toward the molecule immobilized onto the solid surface. This provides a new approach for the development of molecularly imprinted nanoparticles.

Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulvestad, A.; Welland, M. J.; Collins, S. S. E.

2015-12-11

Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/ discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surfacemore » layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. In conclusion, our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.« less

Effect of cobalt doping on the phase transformation of TiO2 nanoparticles.

PubMed

Barakat, M A; Hayes, G; Shah, S Ismat

2005-05-01

Co-doped TiO2 nanoparticles containing 0.0085, 0.017, 0.0255, 0.034, and 0.085 mol % Co(III) ion dopant were synthesized via sol-gel and dip-coating techniques. The effects of metal ion doping on the transformation of anatase to the rutile phase have been investigated. Several analytical tools, such as X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray analysis (EDAX) were used to investigate the nanoparticle structure, size distribution, and composition. Results obtained revealed that the rutile to anatase concentration ratio increases with increase of the cobalt dopant concentration and annealing temperature. The typical composition of Co-doped TiO2 was Ti(1-x)Co(x)O2, where x values ranged from 0.0085 to 0.085. The activation energy for the phase transformation from anatase to rutile was measured to be 229, 222, 211, and 195 kJ/mole for 0.0085, 0.017, 0.0255, and 0.034 mol % Co in TiO2, respectively.

Introducing Students to Surface Modification and Phase Transfer of Nanoparticles with a Laboratory Experiment

ERIC Educational Resources Information Center

Alkilany, Alaaldin M.; Mansour, Sara; Amro, Hamza M.; Pelaz, Beatriz; Soliman, Mahmoud G.; Hinman, Joshua G.; Dennison, Jordan M.; Parak, Wolfgang J.; Murphy, Catherine J.

2017-01-01

A simple, reliable, and cost-effective experiment is presented in which students synthesized citrate-capped gold nanoparticles (GNPs), functionalized them with poly(ethylene glycol) (PEG), and transferred the PEG-GNPs from water to the organic phase dichloromethane. The experiment introduces students to nanotechnology with foci on important…

Synthesis and Characterization of Phase-pure Copper Zinc Tin Sulfide (Cu2ZnSnS4) Nanoparticles

NASA Astrophysics Data System (ADS)

Monahan, Bradley Michael

Semiconductor nanoparticles have been an important area of research in many different disciplines. A substantial amount of this work has been put toward advancing the field of photovoltaics. However, current p-type photovoltaic materials can not sustain the large scale production needed for future energy demands due to their low elemental abundance. Therefore, Earth abundant semiconductor materials have become of great interest to the photovoltaic community especially, the material copper zinc tin sulfide (CZTS), also known by its mineral name kesterite. CZTS exhibits desirable properties for photovoltaics, such as elemental abundance, high absorption coefficient (~104 cm-1 ), high carrier concentration, and optimum direct band gap (1.5 eV). To date, solution based approaches for making CZTS have yielded the most promising conversion efficiencies in solar cells. To that end, the motivation of nanoparticle based inks that can be used in high throughput production are an attractive route for large scale deployment. This has driven the need to make high quality CZTS nanoparticles that possess the properties of the pure kesterite phase with high monodispersity that can be deposited into dense thin films. The inherent challenge of making a quaternary compound of a single phase has made this a difficult task; however, some of those fundamental problems are addressed in this thesis. This had resulted in the synthesis of phase-pure k-CZTS confirmed by powder X-ray diffraction, Raman spectroscopy, UV-visible absorption spectroscopy and energy dispersive x-ray spectroscopy. Furthermore, ultra-fast laser spectroscopy was done on CZTS thin films made from phase-pure kesterite nanoparticles synthesized in this work. This thesis provides new data that directly probes the lifetime of photogenerated free carriers in kesterite CZTS (k-CZTS) thin films.

Systematic investigation of the SERS efficiency and SERS hotspots in gas-phase deposited Ag nanoparticle assemblies.

PubMed

He, L B; Wang, Y L; Xie, X; Han, M; Song, F Q; Wang, B J; Cheng, W L; Xu, H X; Sun, L T

2017-02-15

Gas-phase deposited Ag nanoparticle assemblies are one of the most commonly used plasmonic substrates benefiting from their remarkable advantages such as clean particle surface, tunable particle density, available inter-particle gaps, low-cost and scalable fabrication, and excellent industry compatibility. However, their performance efficiencies are difficult to optimize due to the lack of knowledge of the hotspots inside their structures. We here report a design of delicate rainbow-like Ag nanoparticle assemblies, based on which the hotspots can be revealed through a combinatorial approach. The findings show that the hotspots in gas-phase deposited Ag nanoparticle assemblies are uniquely entangled by the excitation energy and specific inter-particle gaps, differing from the matching conditions in periodic arrays. For Ag nanoparticle assemblies deposited on Formvar-filmed substrates, the mean particle size is maintained around 10 nm, while the particle density can be widely tuned. The one possessing the highest SERS efficiency (under 473 nm excitation) have a particle number density of around 7100 μm -2 . Gaps with an inter-particle spacing of around 3 nm are found to serve as SERS hotspots, and these hotspots contribute to 68% of the overall SERS intensity. For Ag nanoparticle assemblies fabricated on carbon-filmed substrates, the mean particle size can be feasibly tuned. The one possessing the highest SERS efficiency under 473 nm excitation has a particle number density of around 460 μm -2 and a mean particle size of around 42.1 nm. The construction of Ag-analyte-Ag sandwich-like nanoparticle assemblies by a two-step-deposition method slightly improves the SERS efficiency when the particle number density is low, but suppresses the SERS efficiency when the particle number density is high.

Fullerene-like WS2 nanoparticles and nanotubes by the vapor-phase synthesis of WCln and H2S

NASA Astrophysics Data System (ADS)

Margolin, A.; Deepak, F. L.; Popovitz-Biro, R.; Bar-Sadan, M.; Feldman, Y.; Tenne, R.

2008-03-01

Inorganic fullerene-like (IF) nanoparticles and nanotubes of WS2 were synthesized by a gas phase reaction starting from WCln (n = 4, 5, 6) and H2S. The effect of the various metal chloride precursors on the formation of the products was investigated during the course of the study. Various parameters have been studied to understand the growth and formation of the IF-WS2 nanoparticles and nanotubes. The parameters that have been studied include flow rates of the various carrier gases, heating of the precursor metal chlorides and the temperature at which the reactions were carried out. The best set of conditions wherein maximum yields of the high quality pure-phase IF-WS2 nanoparticles and nanotubes are obtained have been identified. A detailed growth mechanism has been outlined to understand the course of formation of the various products of WS2.

Study of phase development and thermal stability in as synthesized TiO2 nanoparticles by laser pyrolysis: ethylene uptake and oxygen enrichment

NASA Astrophysics Data System (ADS)

Ilie, Alina Georgiana; Scarisoreanu, Monica; Dutu, Elena; Dumitrache, Florian; Banici, Ana-Maria; Fleaca, Claudiu Teodor; Vasile, Eugenia; Mihailescu, Ion

2018-01-01

Laser pyrolysis has proven a viable and trustworthy method of TiO2 nanoparticles fabrication, ensuring good quality and wide variety of nanoparticle morphologies and sizes. This work is aimed to phase control, experimentally studied, by parameter modulation, during one step laser pyrolysis synthesis or in combination with thermal annealing. High phase purity anatase and rutile TiO2 nanoparticles, oxygen abundant, are synthesized from TiCl4 and C2H4 gas mixtures, in the presence of air as oxygen donor, under CO2 laser radiation. The nano-titania samples are analyzed by X-ray Diffraction, EDAX, TEM and Raman spectroscopy and reveal good phase stability and distinct morphology. This study extends the method applicability onto rutile majoritarian TiO2 synthesis and generation of thermally stable anatase titania, a well-known catalyst.

Magneto-transport properties of Co3O4 nanoparticles added (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ superconducting phase

NASA Astrophysics Data System (ADS)

Mumtaz, M.; Baig, Mirza Hassan; Waqee-ur-Rehman, M.; Nasir Khan, M.

2018-05-01

Solid-state reaction method was used to synthesize Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase and sol-gel method was used to prepare cobalt oxide (Co3O4) magnetic nanoparticles. These Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223; x = 0-2.00 wt.% nanoparticles-superconductor composites. The effects of Co3O4 nanoparticles on crystal structure, phase formation, phase purity and infield superconducting transport properties of CuTl-1223 phase were investigated at different operating temperatures and external applied magnetic fields. The crystal structure and phase formation of Co3O4 nanoparticles and CuTl-1223 superconductor were determined by X-ray diffraction (XRD) technique. XRD peaks of Co3O4 nanoparticles were well indexed according to FCC crystal structure and the average particle size of 70 nm was calculated by using Debye-Scherer's formula. The unaltered crystal structure of host CuTl-1223 superconducting phase (i.e. Tetragonal) with the addition of Co3O4 nanoparticles indicated the dispersion of nanoparticles at inter-granular sites. Temperature dependent magneto-transport superconducting properties of (Co3O4)x/CuTl-1223 composites were investigated by zero field cooled (ZFC) and field cooled (FC) magnetic moment versus temperature (M-T) measurements. The onset transition temperatures {TcOnset (K)} was decreased along with the suppression of diamagnetic amplitude of CuTl-1223 superconducting phase with the addition of magnetic Co3O4 nanoparticles. Temperature dependent magnetic hysteresis (M-H loops) measurements of (Co3O4)x/CuTl-1223 composites were carried out at different operating temperatures from 5 K to 150 K. Critical current density (Jc) was calculated from M-H loops measurements by using Bean's model. Like the suppression of TcOnset (K) values, Jc was also decreased with the inclusion of Co3O4 nanoparticles. It was also observed that variation of Jc with H followed the power law Jc = �

Antimicrobial activity of spherical silver nanoparticles: evidence for induction of a prolonged bacterial lag phase

USDA-ARS?s Scientific Manuscript database

Background: Recently, there has been a great deal of interest surrounding the discovery that Ag[0] nanoparticles (Np) are more effective antimicrobial agents in terms of the minimum effective concentration than their Ag[+] counterparts. Methods: Both solid and liquid phase experiments were perform...

Synthesis of nanoparticles in a flame aerosol reactor with independent and strict control of their size, crystal phase and morphology

NASA Astrophysics Data System (ADS)

Jiang, Jingkun; Chen, Da-Ren; Biswas, Pratim

2007-07-01

A flame aerosol reactor (FLAR) was developed to synthesize nanoparticles with desired properties (crystal phase and size) that could be independently controlled. The methodology was demonstrated for TiO2 nanoparticles, and this is the first time that large sets of samples with the same size but different crystal phases (six different ratios of anatase to rutile in this work) were synthesized. The degree of TiO2 nanoparticle agglomeration was determined by comparing the primary particle size distribution measured by scanning electron microscopy (SEM) to the mobility-based particle size distribution measured by online scanning mobility particle spectrometry (SMPS). By controlling the flame aerosol reactor conditions, both spherical unagglomerated particles and highly agglomerated particles were produced. To produce monodisperse nanoparticles, a high throughput multi-stage differential mobility analyser (MDMA) was used in series with the flame aerosol reactor. Nearly monodisperse nanoparticles (geometric standard deviation less than 1.05) could be collected in sufficient mass quantities (of the order of 10 mg) in reasonable time (1 h) that could be used in other studies such as determination of functionality or biological effects as a function of size.

Irreversible phase transitions due to laser-based T-jump heating of precursor Eu:ZrO{sub 2}/Tb:Y{sub 2}O{sub 3} core/shell nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunawidjaja, Ray; Diez-y-Riega, Helena; Eilers, Hergen, E-mail: eilers@wsu.edu

2015-09-15

Amorphous precursors of Eu-doped-ZrO{sub 2}/Tb-doped-Y{sub 2}O{sub 3} (p-Eu:ZrO{sub 2}/p-Tb:Y{sub 2}O{sub 3}) core/shell nanoparticles are rapidly heated to temperatures between 200 °C and 950 °C for periods between 2 s and 60 s using a CO{sub 2} laser. During this heating process the nanoparticles undergo irreversible phase changes. The fluorescence spectra due to Eu{sup 3+} dopants in the core and Tb{sup 3+} dopants in the shell are used to identify distinct phases within the material and to generate time/temperature phase diagrams. Such phase diagrams can potentially help to determine unknown time/temperature histories in thermosensor applications. - Graphical abstract: A CO{sub 2}more » laser is used for rapid heating of p-Eu:ZrO{sub 2}/p-Tb:Y{sub 2}O{sub 3} core/shell nanoparticles. Optical spectra are used to identify distinct phases and to determine its thermal history. - Highlights: • Synthesized oxide precursors of lanthanide doped core/shell nanoparticles. • Heated core/shell nanoparticles via laser-based T-jump technique. • Observed time- and temperature-dependent irreversible phase transition.« less

Optical properties of hydrothermally synthesized TGA-capped CdS nanoparticles: controlling crystalline size and phase

NASA Astrophysics Data System (ADS)

Tavakoli Banizi, Zoha; Seifi, Majid

2017-10-01

TGA-capped CdS nanoparticles were obtained in the presence of thioglycolic acid (TGA) as capping agent via a facile hydrothermal method at relatively low temperature and over a short duration. As-synthesized TGA-capped CdS nanoparticles were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, photoluminescence spectroscopy, Ultraviolet-visible spectroscopy and energy-dispersive x-ray spectroscopy. The products had spherical shapes, although their crystalline size and phase was dependent on temperature and time of the reaction. Photoluminescence spectra showed that the fluorescence intensity decreased when increasing the reaction time and temperature.

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

DOE PAGES

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.; ...

2018-01-11

Gadolinium silicide (Gd 5Si 4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd 5Si 4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd 5Si 4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd 5Si 3 impurity. Here as the particle sizes decrease, the volumemore » fraction of Gd 5Si 3 phase increases at the expense of the Gd 5Si 4 phase, and the ferromagnetic transition temperature of Gd 5Si 4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.« less

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.; Gupta, Shalabh; Pecharsky, Vitalij K.; Hadimani, Ravi L.

2018-05-01

Gadolinium silicide (Gd5Si4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd5Si4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd5Si4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd5Si3 impurity. As the particle sizes decrease, the volume fraction of Gd5Si3 phase increases at the expense of the Gd5Si4 phase, and the ferromagnetic transition temperature of Gd5Si4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.

Gadolinium silicide (Gd 5Si 4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd 5Si 4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd 5Si 4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd 5Si 3 impurity. Here as the particle sizes decrease, the volumemore » fraction of Gd 5Si 3 phase increases at the expense of the Gd 5Si 4 phase, and the ferromagnetic transition temperature of Gd 5Si 4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.« less

Fullerene-like WS(2) nanoparticles and nanotubes by the vapor-phase synthesis of WCl(n) and H(2)S.

PubMed

Margolin, A; Deepak, F L; Popovitz-Biro, R; Bar-Sadan, M; Feldman, Y; Tenne, R

2008-03-05

Inorganic fullerene-like (IF) nanoparticles and nanotubes of WS(2) were synthesized by a gas phase reaction starting from WCl(n) (n = 4, 5, 6) and H(2)S. The effect of the various metal chloride precursors on the formation of the products was investigated during the course of the study. Various parameters have been studied to understand the growth and formation of the IF-WS(2) nanoparticles and nanotubes. The parameters that have been studied include flow rates of the various carrier gases, heating of the precursor metal chlorides and the temperature at which the reactions were carried out. The best set of conditions wherein maximum yields of the high quality pure-phase IF-WS(2) nanoparticles and nanotubes are obtained have been identified. A detailed growth mechanism has been outlined to understand the course of formation of the various products of WS(2).

Pressure-Induced Amorphization and a New High Density Amorphous Metallic Phase in Matrix-Free Ge Nanoparticles.

PubMed

Corsini, Niccolo R C; Zhang, Yuanpeng; Little, William R; Karatutlu, Ali; Ersoy, Osman; Haynes, Peter D; Molteni, Carla; Hine, Nicholas D M; Hernandez, Ignacio; Gonzalez, Jesus; Rodriguez, Fernando; Brazhkin, Vadim V; Sapelkin, Andrei

2015-11-11

Over the last two decades, it has been demonstrated that size effects have significant consequences for the atomic arrangements and phase behavior of matter under extreme pressure. Furthermore, it has been shown that an understanding of how size affects critical pressure-temperature conditions provides vital guidance in the search for materials with novel properties. Here, we report on the remarkable behavior of small (under ~5 nm) matrix-free Ge nanoparticles under hydrostatic compression that is drastically different from both larger nanoparticles and bulk Ge. We discover that the application of pressure drives surface-induced amorphization leading to Ge-Ge bond overcompression and eventually to a polyamorphic semiconductor-to-metal transformation. A combination of spectroscopic techniques together with ab initio simulations were employed to reveal the details of the transformation mechanism into a new high density phase-amorphous metallic Ge.

Development of SiC Nanoparticles and Second Phases Synergistically Reinforced Mg-Based Composites Processed by Multi-Pass Forging with Varying Temperatures.

PubMed

Nie, Kaibo; Guo, Yachao; Deng, Kunkun; Wang, Xiaojun; Wu, Kun

2018-01-13

In this study, SiC nanoparticles were added into matrix alloy through a combination of semisolid stirring and ultrasonic vibration while dynamic precipitation of second phases was obtained through multi-pass forging with varying temperatures. During single-pass forging of the present composite, as the deformation temperature increased, the extent of recrystallization increased, and grains were refined due to the inhibition effect of the increasing amount of dispersed SiC nanoparticles. A small amount of twins within the SiC nanoparticle dense zone could be found while the precipitated phases of Mg 17 Al 12 in long strips and deformation bands with high density dislocations were formed in the particle sparse zone after single-pass forging at 350 °C. This indicated that the particle sparse zone was mainly deformed by dislocation slip while the nanoparticle dense zone may have been deformed by twinning. The yield strength and ultimate tensile strength of the composites were gradually enhanced through increasing the single-pass forging temperature from 300 °C to 400 °C, which demonstrated that initial high forging temperature contributed to the improvement of the mechanical properties. During multi-pass forging with varying temperatures, the grain size of the composite was gradually decreased while the grain size distribution tended to be uniform with reducing the deformation temperature and extending the forging passes. In addition, the amount of precipitated second phases was significantly increased compared with that after multi-pass forging under a constant temperature. The improvement in the yield strength of the developed composite was related to grain refinement strengthening and Orowan strengthening resulting from synergistical effect of the externally applied SiC nanoparticles and internally precipitated second phases.

Modulating interactions between ligand-coated nanoparticles and phase-separated lipid bilayers by varying the ligand density and the surface charge.

PubMed

Chen, Xiaojie; Tieleman, D Peter; Liang, Qing

2018-02-01

The interactions between nanoparticles and lipid bilayers are critical in applications of nanoparticles in nanomedicine, cell imaging, toxicology, and elsewhere. Here, we investigate the interactions between nanoparticles coated with neutral and/or charged ligands and phase-separated lipid bilayers using coarse-grained molecular dynamics simulation. Both penetration and adsorption processes as well as the final distribution of the nanoparticles can be readily modulated by varying the ligand density and the surface charge of the nanoparticles. Completely hydrophobic (neutral) nanoparticles with larger size initially preferentially penetrate into the liquid-disordered region of the lipid bilayer and finally transfer into the liquid-ordered region; partially hydrophilic nanoparticles with low or moderate surface charge tend to either distribute in the liquid-disordered region or be adsorbed on the surface of the lipid bilayer, while strongly hydrophilic nanoparticles with high surface charge always reside on the surface of the lipid bilayer. Interactions of the nanoparticles with the lipid bilayers are affected by the surface charge of nanoparticles, hydrophobic mismatch, bending of the ligands, and the packing state of the lipids. Insight in these factors can be used to improve the efficiency of designing nanoparticles for specific applications.

Water adsorbate phases on ZnO and impact of vapor pressure on the equilibrium shape of nanoparticles

NASA Astrophysics Data System (ADS)

Kenmoe, Stephane; Biedermann, P. Ulrich

2018-02-01

ZnO nanoparticles are used as catalysts and have potential applications in gas-sensing and solar energy conversion. A fundamental understanding of the exposed crystal facets, their surface chemistry, and stability as a function of environmental conditions is essential for rational design and improvement of synthesis and properties. We study the stability of water adsorbate phases on the non-polar low-index (10 1 ¯ 0 ) and (11 2 ¯ 0 ) surfaces from low coverage to multilayers using ab initio thermodynamics. We show that phonon contributions and the entropies due to a 2D lattice gas at low coverage and multiple adsorbate configurations at higher coverage have an important impact on the stability range of water adsorbate phases in the (T,p) phase diagram. Based on this insight, we compute and analyze the possible growth mode of water films for pressures ranging from UHV via ambient conditions to high pressures and the impact of water adsorption on the equilibrium shape of nanoparticles in a humid environment. A 2D variant of the Wulff construction shows that the (10 1 ¯ 0 ) and (11 2 ¯ 0 ) surfaces coexist on 12-faceted prismatic ZnO nanoparticles in dry conditions, while in humid environment, the (10 1 ¯ 0 ) surface is selectively stabilized by water adsorption resulting in hexagonal prisms.

Imaging with Second-Harmonic Generation Nanoparticles

NASA Astrophysics Data System (ADS)

Hsieh, Chia-Lung

Second-harmonic generation nanoparticles show promise as imaging probes due to their coherent and stable signal with a broad flexibility in the choice of excitation wavelength. In this thesis, we developed and demonstrated barium titanate nanoparticles as second-harmonic radiation imaging probes. We studied the absolute second-harmonic generation efficiency of the nanoparticles on single-particle level. The polarization dependent second-harmonic signal of single nanoparticles was studied in detail. From the measured polar response, we were able to find the orientation of the nanoparticle. We developed a biochemical interface for using the second-harmonic nanoprobes as biomarkers, including in vitro cellular imaging and in vivo live animal imaging. The nanoparticles were surface functionalized with primary amine groups for stable colloidal dispersion. We achieved specific labeling of the second-harmonic nanoprobes via immunostaining where the antibodies were covalently conjugated onto the nanoparticles. We observed no toxicity of the functionalized nanoparticles to biological cells. The coherent second-harmonic signal radiated from the nanoparticles offers opportunities for new imaging techniques. Using interferometric detection, namely harmonic holography, both amplitude and phase of the second-harmonic field can be captured. Through digital beam propagation, three-dimensional field distribution, reflecting three-dimensional distribution of the nanoparticles, can be reconstructed. We achieved a scan-free three-dimensional imaging of nanoparticles in biological cells with sub-micron spatial resolution by using the harmonic holographic microscope. We further exploited the coherent second-harmonic signal for imaging through scattering media by performing optical phase conjugation of the second-harmonic signal. We demonstrated an all-digital optical phase conjugation of the second-harmonic signal originated from a nanoparticle by combining harmonic holography and

Good Biocompatibility and Sintering Properties of Zirconia Nanoparticles Synthesized via Vapor-phase Hydrolysis

PubMed Central

Wang, Jigang; Yin, Wenyan; He, Xiao; Wang, Qiang; Guo, Ming; Chen, Shaowei

2016-01-01

ZrO2 nanoparticles were synthesized by a vapor-phase hydrolysis process, and characterized in terms of crystalline structures, hardness and microstructures by X-ray diffraction, Vickers hardness test method, and atomic force microscopy (AFM) measurements. Moreover, in vitro cytotoxicity evaluation and hemolysis assay showed that the nanoparticles possessed good biocompatibility. Hardness investigations and AFM measurements indicated that both the sintering temperature and compression force played an important role in determining the physical behaviors (hardness, roughness and density) of flakes of the ZrO2 nanoparticles. When ZrO2 nanoparticles synthesized at 500 °C were pressed into flakes under 6 MPa and sintered at 1400 °C, the resulting flakes exhibited an optimal combination of hardness (534.58 gf·mm−2), roughness (0.07 μm) and density (4.41 g·cm−3). As the Vickers hardness value of human bones is of 315~535 gf·mm−2 and the density of adult femuris about 1.3~1.7 g·cm−3, the experimental results showed that the ZrO2 flakes were comparable to human bones with a higher density. As a result, the synthesized ZrO2 NPs may be useful for biomedical applications, especially for bone repair and replacement in future. PMID:27725744

Effect of metallic silver nanoparticles on the alignment and relaxation behaviour of liquid crystalline material in smectic C* phase

NASA Astrophysics Data System (ADS)

Vimal, Tripti; Kumar Gupta, Swadesh; Katiyar, Rohit; Srivastava, Atul; Czerwinski, Michal; Krup, Katarzyna; Kumar, Sandeep; Manohar, Rajiv

2017-09-01

The influence of silver nanoparticles dispersed in a Ferroelectric Liquid Crystal (FLC) on the properties of the resultant composite system has been investigated by thermal, electro-optical, and dielectric methods. We show that the concentration of thiol capped silver nanoparticles is a critical factor in governing the alignment of nanoparticles (NPs) in the host FLC. The orientation of NPs in composite samples affects the ordering of the LC (Liquid Crystal) phase and consequently changes the various phase transition temperatures of the host LC. Formation of self-assembled 2D (two dimensional) arrays of nanoparticles is observed for high concentration of dopant in the LC, oriented perpendicular to the direction of rubbing. We propose that the molecular interaction between the thiol capped NPs and LC molecules is the key factor behind such an arrangement of NPs. Orientation of NPs has affected the relaxation behaviour and various other material parameters, significantly. A noteworthy change in DC conductivity articulates our proposed idea of the formation of 2D array of NPs perpendicular to the direction of rubbing. This comprehensive study endorses the importance of dopant concentration in modifying the properties of the host LC material.

Gas-Phase Combustion Synthesis of Nonoxide Nanoparticles in Microgravity

NASA Technical Reports Server (NTRS)

Axelbaum, R. L.; Kumfer, B. M.; Sun, Z.; Chao, B. H.

2001-01-01

Gas-phase combustion synthesis is a promising process for creating nanoparticles for the growing nanostructure materials industry. The challenges that must be addressed are controlling particle size, preventing hard agglomerates, maintaining purity, and, if nonoxides are synthesized, protecting the particles from oxidation and/or hydrolysis during post-processing. Sodium-halide Flame Encapsulation (SFE) is a unique methodology for producing nonoxide nanoparticles that addresses these challenges. This flame synthesis process incorporates sodium and metal-halide chemistry, resulting in nanoparticles that are encapsulated in salt during the early stages of their growth in the flame. Salt encapsulation has been shown to allow control of particle size and morphology, while serving as an effective protective coating for preserving the purity of the core particles. Metals and compounds that have been produced using this technology include Al, W, Ti, TiB2, AlN, and composites of W-Ti and Al-AlN. Oxygen content in SFE synthesized nano- AlN has been measured by neutron activation analysis to be as low as 0.54wt.%, as compared to over 5wt.% for unprotected AlN of comparable size. The overall objective of this work is to study the SFE process and nano-encapsulation so that they can be used to produce novel and superior materials. SFE experiments in microgravity allow the study of flame and particle dynamics without the influence of buoyancy forces. Spherical sodium-halide flames are produced in microgravity by ejecting the halide from a spherical porous burner into a quiescent atmosphere of sodium vapor and argon. Experiments are performed in the 2.2 sec Drop Tower at the NASA-Glenn Research Center. Numerical models of the flame and particle dynamics were developed and are compared with the experimental results.

Aqueous-organic phase-transfer of highly stable gold, silver, and platinum nanoparticles and new route for fabrication of gold nanofilms at the oil/water interface and on solid supports.

PubMed

Feng, Xingli; Ma, Houyi; Huang, Shaoxin; Pan, Wei; Zhang, Xiaokai; Tian, Fang; Gao, Caixia; Cheng, Yingwen; Luo, Jingli

2006-06-29

A simple but effective aqueous-organic phase-transfer method for gold, silver, and platinum nanoparticles was developed on the basis of the decrease of the PVP's solubility in water with the temperature increase. The present method is superior in the transfer efficiency of highly stable nanoparticles to the common phase-transfer methods. The gold, silver, and platinum nanoparticles transferred to the 1-butanol phase dispersed well, especially silver and platinum particles almost kept the previous particle size. Electrochemical synthesis of gold nanoparticles in an oil-water system was achieved by controlling the reaction temperature at 80 degrees C, which provides great conveniences for collecting metal particles at the oil/water interface and especially for fabricating dense metal nanoparticle films. A technique to fabricate gold nanofilms on solid supports was also established. The shapes and sizes of gold nanoparticles as the building blocks may be controllable through changing reaction conditions.

Effect of particle size on phase transition among metastable alumina nanoparticles: A view from high resolution 2D solid-state 27Al NMR study

NASA Astrophysics Data System (ADS)

Kim, H.; Lee, S.

2012-12-01

The detailed knowledge of atomic structures of diverse metastable/stable polymorphs in alumina nanoparticles is essential to understand their macroscopic properties. Alumina undergoes successive phase transitions from metastable γ-, δ-, and θ-alumina to stable α-alumina depending on types of precursors, annealing duration, and temperature. As large surface area of nanoparticles plays an important role in controlling their phase transitions, it is also necessary to explore the effect of particle size on nature of phase transition. Solid-state ^{27}Al NMR allows us to determine the atomic structure of Al sites in diverse amorphous/disordered silicates including alumina. However, generally, the crystallographically distinct Al sites among alumina polymorphs were not fully resolved in ^{27}Al magic angle spinning (MAS) NMR spectrum without performing a simulation of overlapped peaks for Al sites of metastable alumina in the spectra. Unfortunately, the simulation of 27Al MAS NMR spectra for alumina nanoparticles cannot be achieved well due to unconfirmed NMR parameters for Al sites of γ- and δ-alumina. The recent progress in triple-quantum (3Q) MAS can provide the much higher resolution for crystallographically distinct Al sites in amorphous alumina (Lee et al., 2009, Phys. Rev. Lett., 103, 095501; Lee et al., 2010, J. Phys. Chem. C, 114, 13890-13894) and aluminosilicate glasses (Lee, 2011, Proc. Natl. Acad. Sci., 108, 6847-6852) as well as crystalline layer silicates (Lee and Weiss, 2008, Am. Mineral. 93, 1066-1071). In this study, we report the ^{27}Al 2D 3QMAS and 1D MAS NMR spectra for alumina nanoparticles with varying particle size (e.g., 15, 19, and 27 nm) and temperature with an aim to explore the atomic structure of alumina polymorphs and nature of their phase transition sequence. The ^{27}Al 2D 3QMAS spectra show the resolved crystallographically distinct ^{[6]}Al and ^{[4]}Al sites in (γ, δ)-, θ-, and α-alumina in nanoparticles consisting of random

Monoclinic to cubic phase transformation and photoluminescence properties in Hf1-xSmxO2 (x = 0-0.12) nanoparticles

NASA Astrophysics Data System (ADS)

Kumar, Sandeep; Rai, S. B.; Rath, Chandana

2018-02-01

Bulk hafnium oxide (HfO2) exhibits the monoclinic phase at room temperature which transforms to tetragonal and cubic phases at 1700 and 2600 °C, respectively, under ambient conditions. For the first time, we observe a monoclinic to stable cubic phase transformation at room temperature in nanoparticles of HfO2 by incorporating Sm3+ ions up to 12 at. %. Although the monoclinic structure is retained at 1 at. % of Sm, a mixed phase of monoclinic and cubic is observed at intermediate Sm concentration (5-11 at. %). Le-Bail profile refinement of X-ray diffraction patterns confirms the monoclinic to cubic phase transformation with increasing Sm3+ ion concentration. While the significant difference in ionic radii of Sm3+ and Hf4+ ion induces strain in the lattice above 9 at. %, a lower valency of Sm produces oxygen vacancy leading to 8-fold coordination with Sm3+ ion and stabilizes the cubic phase at room temperature. Not only the particle size obtained from transmission electron micrograph (TEM) matches well with the size calculated from the Williamson-Hall plot, the lattice spacing estimated from high resolution TEM also confirms the monoclinic and cubic phases in HfO2 and Hf0.88Sm0.12O2, respectively. Apart from phase transformation induced by Sm3+ ions, photoluminescence studies demonstrate an excellent emission in near green and red regions in Hf1-xSmxO2 nanoparticles. A schematic energy band diagram has been proposed based on the excitation and emission processes involved in HfO2 and Hf0.99Sm0.01O2 nanoparticles.

Solid-Phase Synthesis of Molecularly Imprinted Polymer Nanoparticles with a Reusable Template – “Plastic Antibodies”

PubMed Central

Poma, Alessandro; Guerreiro, Antonio; Whitcombe, Michael J.; Piletska, Elena V.; Turner, Anthony P.F.; Piletsky, Sergey A.

2016-01-01

Molecularly Imprinted Polymers (MIPs) are generic alternatives to antibodies in sensors, diagnostics and separations. To displace biomolecules without radical changes in infrastructure in device manufacture, MIPs should share their characteristics (solubility, size, specificity and affinity, localized binding domain) whilst maintaining the advantages of MIPs (low-cost, short development time and high stability) hence the interest in MIP nanoparticles. Herein we report a reusable solid-phase template approach (fully compatible with automation) for the synthesis of MIP nanoparticles and their precise manufacture using a prototype automated UV photochemical reactor. Batches of nanoparticles (30-400 nm) with narrow size distributions imprinted with: melamine (d = 60 nm, Kd = 6.3 × 10−8 m), vancomycin (d = 250 nm, Kd = 3.4 × 10−9 m), a peptide (d = 350 nm, Kd = 4.8 × 10−8 m) and proteins have been produced. Our instrument uses a column packed with glass beads, bearing the template. Process parameters are under computer control, requiring minimal manual intervention. For the first time we demonstrate the reliable re-use of molecular templates in the synthesis of MIPs (≥ 30 batches of nanoMIPs without loss of performance). NanoMIPs are produced template-free and the solid-phase acts both as template and affinity separation medium. PMID:26869870

Development of SiC Nanoparticles and Second Phases Synergistically Reinforced Mg-Based Composites Processed by Multi-Pass Forging with Varying Temperatures

PubMed Central

Nie, Kaibo; Guo, Yachao; Deng, Kunkun; Wang, Xiaojun; Wu, Kun

2018-01-01

In this study, SiC nanoparticles were added into matrix alloy through a combination of semisolid stirring and ultrasonic vibration while dynamic precipitation of second phases was obtained through multi-pass forging with varying temperatures. During single-pass forging of the present composite, as the deformation temperature increased, the extent of recrystallization increased, and grains were refined due to the inhibition effect of the increasing amount of dispersed SiC nanoparticles. A small amount of twins within the SiC nanoparticle dense zone could be found while the precipitated phases of Mg17Al12 in long strips and deformation bands with high density dislocations were formed in the particle sparse zone after single-pass forging at 350 °C. This indicated that the particle sparse zone was mainly deformed by dislocation slip while the nanoparticle dense zone may have been deformed by twinning. The yield strength and ultimate tensile strength of the composites were gradually enhanced through increasing the single-pass forging temperature from 300 °C to 400 °C, which demonstrated that initial high forging temperature contributed to the improvement of the mechanical properties. During multi-pass forging with varying temperatures, the grain size of the composite was gradually decreased while the grain size distribution tended to be uniform with reducing the deformation temperature and extending the forging passes. In addition, the amount of precipitated second phases was significantly increased compared with that after multi-pass forging under a constant temperature. The improvement in the yield strength of the developed composite was related to grain refinement strengthening and Orowan strengthening resulting from synergistical effect of the externally applied SiC nanoparticles and internally precipitated second phases. PMID:29342883

Magnetic nanoparticles stimulation to enhance liquid-liquid two-phase mass transfer under static and rotating magnetic fields

NASA Astrophysics Data System (ADS)

Azimi, Neda; Rahimi, Masoud

2017-01-01

Rotating magnetic field (RMF) was applied on a micromixer to break the laminar flow and induce chaotic flow to enhance mass transfer between two-immiscible organic and aqueous phases. The results of RMF were compared to those of static magnetic field (SMF). For this purpose, experiments were carried out in a T-micromixer at equal volumetric flow rates of organic and aqueous phases. Fe3O4 nanoparticles were synthesized by co-precipitation technique and they were dissolved in organic phase. Results obtained from RMF and SMF were compared in terms of overall volumetric mass transfer coefficient (KLa) and extraction efficiency (E) at various Reynolds numbers. Generally, RMF showed higher effect in mass transfer characteristics enhancement compared with SMF. The influence of rotational speeds of magnets (ω) in RMF was investigated, and measurable enhancements of KLa and E were observed. In RMF, the effect of magnetic field induction (B) was investigated. The results reveal that at constant concentration of nanoparticles, by increasing of B, mass transfer characteristics will be enhanced. The effect of various nanoparticles concentrations (ϕ) within 0.002-0.01 (w/v) on KLa and E at maximum induction of RMF (B=76 mT) was evaluated. Maximum values of KLa (2.1±0.001) and E (0.884±0.001) were achieved for the layout of RMF (B=76 mT), ω=16 rad/s and MNPs concentration of 0.008-0.01 (w/v).

One-step large scale gas phase synthesis of Mn2 + doped ZnS nanoparticles in reducing flames

NASA Astrophysics Data System (ADS)

Athanassiou, E. K.; Grass, R. N.; Stark, W. J.

2010-05-01

Metal sulfide nanoparticles have attracted considerable interest because of their unique semiconducting and electronic properties. In order to prepare these fascinating materials at an industrial scale, however, solvent-free, dry processes would be most advantageous. In the present work, we demonstrate how traditional oxide nanoparticle synthesis in flames can be extended to sulfides if we apply a careful control on flame gas composition and sulfur content. The ultra-fast (<1 ms) gas phase kinetics at elevated temperatures allow direct sulfidization of metals in flames (\\mathrm {MO}_{x} \\Rightarrow \\mathrm {MS}_{x} ). As a representative example, we prepared air-stable Mn2 + doped zinc sulfide nanoparticles. Post-sintering of the initially polycrystalline nanopowder resulted in a material of high crystallinity and improved photoluminescence. An analysis of the thermodynamics, gas composition, and kinetics in these reducing flames indicates that the here-presented extension of flame synthesis provides access to a broad range of metal sulfide nanoparticles and offers an alternative to non-oxide phosphor preparation.

Stable tetragonal phase and magnetic properties of Fe-doped HfO2 nanoparticles

NASA Astrophysics Data System (ADS)

Sales, T. S. N.; Cavalcante, F. H. M.; Bosch-Santos, B.; Pereira, L. F. D.; Cabrera-Pasca, G. A.; Freitas, R. S.; Saxena, R. N.; Carbonari, A. W.

2017-05-01

In this paper, the effect in structural and magnetic properties of iron doping with concentration of 20% in hafnium dioxide (HfO2) nanoparticles is investigated. HfO2 is a wide band gap oxide with great potential to be used as high-permittivity gate dielectrics, which can be improved by doping. Nanoparticle samples were prepared by sol-gel chemical method and had their structure, morphology, and magnetic properties, respectively, investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with electron back scattering diffraction (EBSD), and magnetization measurements. TEM and SEM results show size distribution of particles in the range from 30 nm to 40 nm with small dispersion. Magnetization measurements show the blocking temperature at around 90 K with a strong paramagnetic contribution. XRD results show a major tetragonal phase (94%).

Contact Forces between Single Metal Oxide Nanoparticles in Gas-Phase Applications and Processes.

PubMed

Salameh, Samir; van der Veen, Monique A; Kappl, Michael; van Ommen, J Ruud

2017-03-14

In this work we present a comprehensive experimental study to determine the contact forces between individual metal oxide nanoparticles in the gas-phase using atomic force microscopy. In addition, we determined the amount of physisorbed water for each type of particle surface. By comparing our results with mathematical models of the interaction forces, we could demonstrate that classical continuum models of van der Waals and capillary forces alone cannot sufficiently describe the experimental findings. Rather, the discrete nature of the molecules has to be considered, which leads to ordering at the interface and the occurrence of solvation forces. We demonstrate that inclusion of solvation forces in the model leads to quantitative agreement with experimental data and that tuning of the molecular order by addition of isopropanol vapor allows us to control the interaction forces between the nanoparticles.

Contact Forces between Single Metal Oxide Nanoparticles in Gas-Phase Applications and Processes

PubMed Central

2017-01-01

In this work we present a comprehensive experimental study to determine the contact forces between individual metal oxide nanoparticles in the gas-phase using atomic force microscopy. In addition, we determined the amount of physisorbed water for each type of particle surface. By comparing our results with mathematical models of the interaction forces, we could demonstrate that classical continuum models of van der Waals and capillary forces alone cannot sufficiently describe the experimental findings. Rather, the discrete nature of the molecules has to be considered, which leads to ordering at the interface and the occurrence of solvation forces. We demonstrate that inclusion of solvation forces in the model leads to quantitative agreement with experimental data and that tuning of the molecular order by addition of isopropanol vapor allows us to control the interaction forces between the nanoparticles. PMID:28186771

Multi-phase structures of boron-doped copper tin sulfide nanoparticles synthesized by chemical bath deposition for optoelectronic devices

NASA Astrophysics Data System (ADS)

Rakspun, Jariya; Kantip, Nathakan; Vailikhit, Veeramol; Choopun, Supab; Tubtimtae, Auttasit

2018-04-01

We investigated the influence of boron doping on the structural, optical, and electrical properties of copper tin sulfide (CTS) nanoparticles coated on a WO3 surface and synthesized using chemical bath deposition. Boron doping at concentrations of 0.5, 1.0, 1.5, and 2.0 wt% was investigated. The X-ray diffraction pattern of CTS showed the presence of monoclinic Cu2Sn3S7, cubic Cu2SnS3, and orthorhombic Cu4SnS4. Boron doping influenced the preferred orientation of the nanoparticles for all phase structures and produced a lattice strain effect and changes in the dislocation density. Increasing the concentration of boron in CTS from 0.5 wt% to 2.0 wt% reduced the band gap for all phases of CTS from 1.46 to 1.29 eV and reduced the optical transmittance. Optical constants, such as the refractive index, extinction coefficient, and dissipation factor, were also obtained for B-doped CTS. The dispersion behavior of the refractive index was investigated in terms of a single oscillator model and the physical parameters were determined. Fourier transform infrared spectroscopy confirmed the successful synthesis of CTS nanoparticles. Cyclic voltammetry indicated that optimum boron doping (<1.5 wt% for all phases) resulted in desirable p-n junction behavior for optoelectronic applications.

Phase stability and dynamics of entangled polymer-nanoparticle composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mangal, Rahul; Srivastava, Samanvaya; Archer, Lynden A.

Nanoparticle–polymer composites, or polymer–nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales,more » where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.« less

Edge states and topological phase transitions in chains of dielectric nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruk, Sergey; Slobozhanyuk, Alexey; Denkova, Denitza

Recently introduced field of topological photonics aims to explore the concepts of topological insulators for novel phenomena in optics. Here polymeric chains of subwavelength silicon nanodisks are studied and it is demonstrated that these chains can support two types of topological edge modes based on magnetic and electric Mie resonances, and their topological properties are fully dictated by the spatial arrangement of the nanoparticles in the chain. Here, it is observed experimentally and described how theoretically topological phase transitions at the nanoscale define a change from trivial to nontrivial topological states when the edge mode is excited.

Edge states and topological phase transitions in chains of dielectric nanoparticles

DOE PAGES

Kruk, Sergey; Slobozhanyuk, Alexey; Denkova, Denitza; ...

2017-01-12

Recently introduced field of topological photonics aims to explore the concepts of topological insulators for novel phenomena in optics. Here polymeric chains of subwavelength silicon nanodisks are studied and it is demonstrated that these chains can support two types of topological edge modes based on magnetic and electric Mie resonances, and their topological properties are fully dictated by the spatial arrangement of the nanoparticles in the chain. Here, it is observed experimentally and described how theoretically topological phase transitions at the nanoscale define a change from trivial to nontrivial topological states when the edge mode is excited.

Solid-phase synthesis of Cu2MoS4 nanoparticles for degradation of methyl blue under a halogen-tungsten lamp

NASA Astrophysics Data System (ADS)

Li, Shi-na; Ma, Rui-xin; Wang, Cheng-yan

2018-03-01

The Cu2MoS4 nanoparticles were prepared using a relatively simple and convenient solid-phase process, which was applied for the first time. The crystalline structure, morphology, and optical properties of Cu2MoS4 nanoparticles were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and UV-vis spectrophotometry. Cu2MoS4 nanoparticles having a band gap of 1.66 eV exhibits good photocatalytic activity in the degradation of methylene blue, which indicates that this simple process may be critical to facilitate the cheap production of photocatalysts.

Effect of Cr-N codoping on structural phase transition, Raman modes, and optical properties of TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Hassnain Jaffari, G.; Tahir, Adnan; Ali, Naveed Zafar; Ali, Awais; Qurashi, Umar S.

2018-04-01

Noncompensated cation-anion codoping in TiO2 nanoparticles has been achieved by a chemical synthesis route. Significant reduction in the optical bandgap and enhancement in the absorption of visible light have been observed. Structural phase transformation has been tracked in detail as a function of doping and heat treatment temperature. Anatase to rutile phase transition temperature for doped samples was higher in comparison to the pure TiO2 nanoparticles. Nitrogen and chromium addition increases the phase transformation barrier, where the effect of the former dopant is of more significance. The Raman results showed an increase in the oxygen content with higher post annealing temperatures. With Cr incorporation, the peak associated with the Eg mode has been found to shift towards a higher wave number, while with nitrogen incorporation, the shift was towards a lower wave number. A decrease in reflectance with N co-doping for all samples, irrespective of phase and annealing temperatures, has been observed. In compositions with nitrogen of the same content, bandgap reduction was higher in the rutile phase in comparison to the anatase phase. In general, overall results revealed that with a higher loading fraction of ammonia, the N content increases, while Cr addition prevents nitrogen loss even up to high post annealing temperatures, i.e., 850 °C.

Structural characterization of multimetallic nanoparticles

NASA Astrophysics Data System (ADS)

Mukundan, Vineetha

Bimetallic and trimetallic alloy nanoparticles have enhanced catalytic activities due to their unique structural properties. Using in situ time-resolved synchrotron based x-ray diffraction, we investigated the structural properties of nanoscale catalysts undergoing various heat treatments. Thermal treatment brings about changes in particle size, morphology, dispersion of metals on support, alloying, surface electronic properties, etc. First, the mechanisms of coalescence and grain growth in PtNiCo nanoparticles supported on planar silica on silicon were examined in detail in the temperature range 400-900°C. The sintering process in PtNiCo nanoparticles was found to be accompanied by lattice contraction and L10 chemical ordering. The mass transport involved in sintering is attributed to grain boundary diffusion and its corresponding activation energy is estimated from the data analysis. Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles were also investigated in real time with in situ synchrotron based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. PdCu nanoparticles are interesting because they are found to be more efficient as catalysts in ethanol oxidation reaction (EOR) than monometallic Pd catalysts. The combination of metal support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. The composition of the as prepared Pd:Cu mixture in this study was 34% Pd and 66% Cu. At 300°C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2) alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (>450°C). The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals

Photothermal quantitative phase imaging of living cells with nanoparticles utilizing a cost-efficient setup

NASA Astrophysics Data System (ADS)

Turko, Nir A.; Isbach, Michael; Ketelhut, Steffi; Greve, Burkhard; Schnekenburger, Jürgen; Shaked, Natan T.; Kemper, Björn

2017-02-01

We explored photothermal quantitative phase imaging (PTQPI) of living cells with functionalized nanoparticles (NPs) utilizing a cost-efficient setup based on a cell culture microscope. The excitation light was modulated by a mechanical chopper wheel with low frequencies. Quantitative phase imaging (QPI) was performed with Michelson interferometer-based off-axis digital holographic microscopy and a standard industrial camera. We present results from PTQPI observations on breast cancer cells that were incubated with functionalized gold NPs binding to the epidermal growth factor receptor. Moreover, QPI was used to quantify the impact of the NPs and the low frequency light excitation on cell morphology and viability.

Gold Nanoparticle Monolayers from Sequential Interfacial Ligand Exchange and Migration in a Three-Phase System

PubMed Central

Yang, Guang; Hallinan, Daniel T.

2016-01-01

Using a three-phase system, centimeter-scale monolayer gold nanoparticle (Au NP) films have been prepared that have long-range order and hydrophobic ligands. The system contains an interface between an aqueous phase containing Au NPs and an oil phase containing one of various types of amine ligands, and a water/air interface. As the Au NPs diffuse to the water/oil interface, ligand exchange takes place which temporarily traps them at the water/oil interface. The ligand-exchanged particles then spontaneously migrate to the air/water interface, where they self-assemble, forming a monolayer under certain conditions. The spontaneous formation of the NP film at the air/water interface was due to the minimization of the system Helmholtz free energy. However, the extent of surface functionalization was dictated by kinetics. This decouples interfacial ligand exchange from interfacial self-assembly, while maintaining the simplicity of a single system. The interparticle center-to-center distance was dictated by the amine ligand length. The Au NP monolayers exhibit tunable surface plasma resonance and excellent spatial homogeneity, which is useful for surface-enhanced Raman scattering. The “air/water/oil” self-assembly method developed here not only benefits the fundamental understanding of NP ligand conformations, but is also applicable to the manufacture of plasmonic nanoparticle devices with precisely designed optical properties. PMID:27762394

Numerical Analysis of Dusty-Gas Flows

NASA Astrophysics Data System (ADS)

Saito, T.

2002-02-01

This paper presents the development of a numerical code for simulating unsteady dusty-gas flows including shock and rarefaction waves. The numerical results obtained for a shock tube problem are used for validating the accuracy and performance of the code. The code is then extended for simulating two-dimensional problems. Since the interactions between the gas and particle phases are calculated with the operator splitting technique, we can choose numerical schemes independently for the different phases. A semi-analytical method is developed for the dust phase, while the TVD scheme of Harten and Yee is chosen for the gas phase. Throughout this study, computations are carried out on SGI Origin2000, a parallel computer with multiple of RISC based processors. The efficient use of the parallel computer system is an important issue and the code implementation on Origin2000 is also described. Flow profiles of both the gas and solid particles behind the steady shock wave are calculated by integrating the steady conservation equations. The good agreement between the pseudo-stationary solutions and those from the current numerical code validates the numerical approach and the actual coding. The pseudo-stationary shock profiles can also be used as initial conditions of unsteady multidimensional simulations.

Size-dependent phase diagrams of metallic alloys: A Monte Carlo simulation study on order–disorder transitions in Pt–Rh nanoparticles

PubMed Central

Stahl, Christian; Albe, Karsten

2012-01-01

Summary Nanoparticles of Pt–Rh were studied by means of lattice-based Monte Carlo simulations with respect to the stability of ordered D022- and 40-phases as a function of particle size and composition. By thermodynamic integration in the semi-grand canonical ensemble, phase diagrams for particles with a diameter of 7.8 nm, 4.3 nm and 3.1 nm were obtained. Size-dependent trends such as the lowering of the critical ordering temperature, the broadening of the compositional stability range of the ordered phases, and the narrowing of the two-phase regions were observed and discussed in the context of complete size-dependent nanoparticle phase diagrams. In addition, an ordered surface phase emerges at low temperatures and low platinum concentration. A decrease of platinum surface segregation with increasing global platinum concentration was observed, when a second, ordered phase is formed inside the core of the particle. The order–disorder transitions were analyzed in terms of the Warren–Cowley short-range order parameters. Concentration-averaged short-range order parameters were used to remove the surface segregation bias of the conventional short-range order parameters. Using this procedure, it was shown that the short-range order in the particles at high temperatures is bulk-like. PMID:22428091

Size-dependent and tunable crystallization of GeSbTe phase-change nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Bin; Ten Brink, Gert H.; Palasantzas, George; Kooi, Bart J.

2016-12-01

Chalcogenide-based nanostructured phase-change materials (PCMs) are considered promising building blocks for non-volatile memory due to their high write and read speeds, high data-storage density, and low power consumption. Top-down fabrication of PCM nanoparticles (NPs), however, often results in damage and deterioration of their useful properties. Gas-phase condensation based on magnetron sputtering offers an attractive and straightforward solution to continuously down-scale the PCMs into sub-lithographic sizes. Here we unprecedentedly present the size dependence of crystallization for Ge2Sb2Te5 (GST) NPs, whose production is currently highly challenging for chemical synthesis or top-down fabrication. Both amorphous and crystalline NPs have been produced with excellent size and composition control with average diameters varying between 8 and 17 nm. The size-dependent crystallization of these NPs was carefully analyzed through in-situ heating in a transmission electron microscope, where the crystallization temperatures (Tc) decrease when the NPs become smaller. Moreover, methane incorporation has been observed as an effective method to enhance the amorphous phase stability of the NPs. This work therefore elucidates that GST NPs synthesized by gas-phase condensation with tailored properties are promising alternatives in designing phase-change memories constrained by optical lithography limitations.

Phase and electrical properties of PZT thin films embedded with CuO nano-particles by a hybrid sol-gel route

NASA Astrophysics Data System (ADS)

Sreesattabud, Tharathip; Gibbons, Brady J.; Watcharapasorn, Anucha; Jiansirisomboon, Sukanda

2013-07-01

Pb(Zr0.52Ti0.48)O3 or PZT thin films embedded with CuO nano-particles were successfully prepared by a hybrid sol-gel process. In this process, CuO (0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1 wt. %) nanopowder was suspended in an organometallic solution of PZT, and then coated on platinised silicon substrate using a spin-coating technique. The influence of CuO nano-particles' dispersion on the phase of PZT thin films was investigated. XRD results showed a perovskite phase in all films. At the CuO concentration of 0.4-1 wt. %, a second phase was observed. The addition of CuO nano-particles affected the orientation of PZT thin films. The addition was also found to reduce the ferroelectric properties of PZT thin films. However, at 0.2 wt. % CuO concentration, the film exhibited good ferroelectric properties similar to those of PZT films. In addition, the fatigue retention properties of the PZT/CuO system was observed, and it showed 14% fatigue at 108 switching bipolar pulse cycles while the fatigue in PZT thin films was found to be 17% at the same switching bipolar pulse cycles.

One-pot solvothermal synthesis of dual-phase titanate/titania Nanoparticles and their adsorption and photocatalytic Performances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Yu Hua; Gong, Dangguo; Tang, Yuxin

2014-06-01

Dual phase titanate/titania nanoparticles undergo phase transformation gradually with the increase of solvothermal synthesis temperature from 100 °C to 200 °C, and eventually are fully transformed into anatase TiO{sub 2}. The crystal structure change results in the changes of optical absorption, sensitizer/dopant formation and surface area of the materials which finally affect the overall dye removal ability. Reactions under dark and light have been conducted to distinguish the contributions of surface adsorption from photocatalytic degradation. The sample synthesized at 160 °C (S160) shows the best performances for both adsorption under dark and photocatalytic degradation of methylene blue (MB) under visiblemore » light irradiation. The adsorption mechanism for S160 is determined as monolayer adsorption based on the adsorption isotherm test under dark condition, and an impressive adsorption capacity of 162.19 mg/g is achieved. For the photocatalytic application, this sample at 0.1 g/L loading is also able to degrade 20 ppm MB within 6 hours under the visible light (>420 nm) condition. - Graphical abstract: The effect of solvothermal synthesis temperature on the formation and dye removal performance of dual phase titanate/titania nanoparticles was unveiled and optimized. - Highlights: • Low temperature one-pot solvothermal synthesis of dual-phase photocatalysts. • Correlation of the synthesis temperature is made with the phase composition. • Adsorption isotherm, kinetics, photocatalytic degradation were studied. • Synthesis at 160 °C yields the best material for adsorption of MB in dark. • The same sample also shows the best visible light degradation of MB.« less

Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herz, A., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.

2015-08-17

Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observedmore » phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.« less

Barium Titanate Nanoparticles for Biomarker Applications

NASA Astrophysics Data System (ADS)

Matar, O.; Posada, O. M.; Hondow, N. S.; Wälti, C.; Saunders, M.; Murray, C. A.; Brydson, R. M. D.; Milne, S. J.; Brown, A. P.

2015-10-01

A tetragonal crystal structure is required for barium titanate nanoparticles to exhibit the nonlinear optical effect of second harmonic light generation (SHG) for use as a biomarker when illuminated by a near-infrared source. Here we use synchrotron XRD to elucidate the tetragonal phase of commercially purchased tetragonal, cubic and hydrothermally prepared barium titanate (BaTiO3) nanoparticles by peak fitting with reference patterns. The local phase of individual nanoparticles is determined by STEM electron energy loss spectroscopy (EELS), measuring the core-loss O K-edge and the Ti L3-edge energy separation of the t2g, eg peaks. The results show a change in energy separation between the t2g and eg peak from the surface and core of the particles, suggesting an intraparticle phase mixture of the barium titanate nanoparticles. HAADF-STEM and bright field TEM-EDX show cellular uptake of the hydrothermally prepared BaTiO3 nanoparticles, highlighting the potential for application as biomarkers.

Role of Co3O4 Nanoparticles in Dielectric Properties of Cu0.5Tl0.5Ba2Ca2Cu3O10-δ Superconducting Phase

NASA Astrophysics Data System (ADS)

Imran, M.; Mumtaz, M.; Naveed, M.; Khan, M. Nasir

2018-04-01

Cobalt oxide (Co3O4) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase were prepared by sol-gel and solid-state reaction methods, respectively. Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223, x = 0-2.0 wt.%, nanoparticles-superconductor composites. The unchanged crystal structure of the host CuTl-1223 superconducting phase (i.e. tetragonal) revealed that Co3O4 nanoparticles were settled at the grain boundaries. Superconducting properties of the CuTl-1223 phase were overall suppressed due to hole-charge carriers interaction at the grain boundaries. The dielectric properties of (Co3O4)x/CuTl-1223 composites were investigated by varying the test frequencies from 40 Hz to 100 MHz and operating temperatures from 77 to 298 K. The values of dielectric properties were found maximal at lower frequencies and started to decrease at higher frequencies. So, the dielectric properties of the CuTl-1223 superconducting phase can be tuned by varying the contents of (Co3O4) nanoparticles, test frequencies as well as operating temperatures.

Combined synthesis and in situ coating of nanoparticles in the gas phase

NASA Astrophysics Data System (ADS)

Lähde, Anna; Raula, Janne; Kauppinen, Esko I.

2008-12-01

Combined gas phase synthesis and coating of sodium chloride (NaCl) and lactose nanoparticles has been developed using an aerosol flow reactor. Nano-sized core particles were produced by the droplet-to-particle method and coated in situ by the physical vapour deposition of L-leucine vapour. The saturation of L-leucine in the reactor determined the resulting particle size and size distribution. In general, particle size increased with the addition of L-leucine and notable narrowing of the core particle size distribution was observed. In addition, homogeneous nucleation of the vapour, i.e. formation of pure L-leucine particles, was observed depending on the saturation conditions of L-leucine as well as the core particle characteristics. The effects of core particle properties, i.e. size and solid-state characteristics, on the coating process were studied by comparing the results for coated NaCl and lactose particles. During deposition, L-leucine formed a uniform coating on the surface of the core particles. The coating stabilised the nanoparticles and prevented the sintering of particles during storage.

Stabilizing liquid drops of arbitrary shape by the interfacial jamming of nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, Thomas P.; Cui, Mengmeng; Emrick, Todd

A stabilized assembly including a first liquid phase of non-spherical droplets in a second liquid phase, wherein the second liquid phase is immiscible with the first phase, and nanoparticle surfactants assembled at an interface of the non-spherical droplets and the second phase is disclosed. The nanoparticle surfactants include nanoparticles and end-functionalized polymers that can interact through ligand type interactions, and the first phase is stabilized by a disordered, jammed layer of nanoparticle surfactants. A method of preparing a stabilized assembly is also disclosed.

Comparison of magnetic properties and high-temperature phase stability of phosphate- and oleic acid-capped iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Muthukumaran, T.; Pati, S. S.; Singh, L. H.; de Oliveira, A. C.; Garg, V. K.; Philip, John

2018-03-01

We study the influence of dynamic capping of Fe3O4 nanoparticles with phosphate and oleic acid, on their structure, magnetic properties and thermal stability of magnetic nanoparticles. It is observed that the phosphate coating on iron oxide lowers the dipole-dipole interaction significantly, as compared to oleic acid capping. The Mössbauer results show that the spin canting order of oxidized shell and the mean hyperfine field values follow the order Fe0 (uncoated) > FeOA (oleic acid capped) > FP1 (phosphate capped). The uncoated Fe3O4 nanoparticle is non-stoichiometric in nature due to oxidation, whereas FP1 and FeOA are of the correct stoichiometry. Mössbauer and photoacoustic spectroscopic studies on air-annealed phosphate-coated magnetite nanoparticles confirm that the magnetic iron oxide phase is preserved up to 833 K and a complete conversion of Fe3O4 into the non-magnetic hematite phase occurs at 1173 K. The iron oxide air annealed at 833 K is found to have a shell of orthorhombic α-Fe2O3 over the magnetite core. However, in oleic acid-coated nanoparticles, the magnetic to non-magnetic phase transformation commences at 623 K and the conversion was complete at 823 K. The photoacoustic spectra of the air-annealed phosphate-coated Fe3O4 particles showed a flipping of the absorption intensity between 500-700 nm and 800-1000 nm, due to the conversion of Fe3O4 to γ-Fe2O3 at 923 and γ-Fe2O3 to α-Fe2O3 at 1173 K, respectively. The γ-Fe2O3 showed an intense absorption peak above 750 nm, whereas the α-Fe2O3 showed a peak broadening in the wavelength range of 600-700 nm, in addition to the strong peaks at a wavelength above 750 nm. This study suggests that the photoacoustic spectroscopy can distinguish clearly the three polymorphs of iron oxide i.e., Fe3O4, γ-Fe2O3 and α-Fe2O3. Our results confirm the ability of phosphate-capped iron oxide particles to retard the oxidation of Fe2+ contents during the crystal growth process.

Phase transitions and kinetic properties of gold nanoparticles confined between two-layer graphene nanosheets

NASA Astrophysics Data System (ADS)

Wang, Gang; Wu, Nanhua; Chen, Jionghua; Wang, Jinjian; Shao, Jingling; Zhu, Xiaolei; Lu, Xiaohua; Guo, Lucun

2016-11-01

The thermodynamic and kinetic behaviors of gold nanoparticles confined between two-layer graphene nanosheets (two-layer-GNSs) are examined and investigated during heating and cooling processes via molecular dynamics (MD) simulation technique. An EAM potential is applied to represent the gold-gold interactions while a Lennard-Jones (L-J) potential is used to describe the gold-GNS interactions. The MD melting temperature of 1345 K for bulk gold is close to the experimental value (1337 K), confirming that the EAM potential used to describe gold-gold interactions is reliable. On the other hand, the melting temperatures of gold clusters supported on graphite bilayer are corrected to the corresponding experimental values by adjusting the εAu-C value. Therefore, the subsequent results from current work are reliable. The gold nanoparticles confined within two-layer GNSs exhibit face center cubic structures, which is similar to those of free gold clusters and bulk gold. The melting points, heats of fusion, and heat capacities of the confined gold nanoparticles are predicted based on the plots of total energies against temperature. The density distribution perpendicular to GNS suggests that the freezing of confined gold nanoparticles starts from outermost layers. The confined gold clusters exhibit layering phenomenon even in liquid state. The transition of order-disorder in each layer is an essential characteristic in structure for the freezing phase transition of the confined gold clusters. Additionally, some vital kinetic data are obtained in terms of classical nucleation theory.

Fabrication and analysis of Cr-doped ZnO nanoparticles from the gas phase.

PubMed

Schneider, L; Zaitsev, S V; Jin, W; Kompch, A; Winterer, M; Acet, M; Bacher, G

2009-04-01

High quality Cr-doped ZnO nanoparticles from the gas phase were prepared and investigated with respect to their structural, optical and magnetic properties. The extended x-ray absorption fine structure and the x-ray absorption near edge structure of the particles verify that after nanoparticle preparation Cr is incorporated as Cr3+ ) at least partially on sites with a 4-fold oxygen configuration, most likely on a Zn site, into the wurtzite lattice. Despite the fact that Cr is known to act as an efficient non-radiative loss centre for near band gap emission (NBE), a pronounced NBE is obtained up to room temperature even for a nominal Cr concentration of 10 at.%. Annealing at 1000 degrees C results in a significant improvement of the photoluminescence efficiency and a reduced PL linewidth down to 2.9 meV at low temperatures while the structural and magnetic data indicate the formation of ZnCr2O4 clusters.

Crystal Analysis of Multi Phase Calcium Phosphate Nanoparticles Containing Different amount of Magnesium

NASA Astrophysics Data System (ADS)

Gozalian, Afsaneh; Behnamghader, Ali Asghar; Moshkforoush, Arash

In this study, Mg doped hydroxyapatite [(Ca, Mg)10(PO4)6(OH)2] and β-tricalcium phosphate nanoparticles were synthesized via sol gel method. Triethyl phosphite, calcium nitrate tetrahydrate and magnesium nitrate hexahydrate were used as P, Ca and Mg precursors. The ratio of (Ca+Mg)/P and the amount of magnesium (x) were kept constant at 1.67 and ranging x = 0 up to 3 in molecular formula of Ca10-xMgx (PO4)6(OH)2, respectively. Phase composition and chemical structure were performed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Phase percentages, crystallite size, degree of crystallinity and lattice parameters were investigated. The presence of magnesium led to form the Mg doped tricalcium phosphate (β-TCMP) and Mg doped hydroxyapatite (Mg-HA). Based on the results of this study, lattice parameters, degree of crystallinity and crystallite size decreased with magnesium content. In addition, with increasing magnesium content, the amount of CaO phase decreased whereas the amount of MgO phase increased significantly. Obtained results can be used for new biomaterials design.

Magnetic phase diagram and critical behavior of electron-doped LaxCa1-xMnO3(0⩽x⩽0.25) nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Yang; Fan, Hong Jin

2011-06-01

A comparative study of electron-doped perovskite manganites LaxCa1-xMnO3 (0 ⩽ x ⩽ 0.25) in nanoparticle and bulk form is reported. The bulks and nanoparticles exhibit different magnetic evolutions. Overall with increasing x, the bulks have a phase-separated ground state with ferromagnetic (FM) clusters and antiferromagnetic (AFM) matrix coexisting. The FM clusters gradually grow, and the magnetization M peaks at x= 0.1. Subsequently, charge-ordering (CO) or local CO occurs, which suppresses the increase in FM clusters but favors the development of antiferromagnetism so M starts to decrease. Finally the system becomes a homogeneous AFM state at x > 0.18. For the nanoparticles in the range of 0 ⩽ x ⩽ 0.1, the ground state is similar to that of the bulks, but M is slightly increased because of a surface ferromagnetism. Nevertheless because of the structure distortion induced by surface pressure and the size effect, CO does not occur in the nanoparticles. Consequently, the ferromagnetism still gradually develops at x > 0.1 and thus M monotonously rises. M reaches a maximum at x= 0.18, after which the competition between ferromagnetism and antiferromagnetism induces a cluster-glass (CG) state. On the basis of these observations the phase diagrams for both bulks and nanoparticles are established. For the nanoparticles that display enhanced ferromagnetism the critical behavior analysis indicates that they fall into a three-dimensional (3D) Heisenberg ferromagnet class.

Small-Angle Neutron Scattering Study of Interplay of Attractive and Repulsive Interactions in Nanoparticle-Polymer System.

PubMed

Kumar, Sugam; Aswal, Vinod K; Kohlbrecher, Joachim

2016-02-16

The phase behavior of nanoparticle (silica)-polymer (polyethylene glycol) system without and with an electrolyte (NaCl) has been studied. It is observed that nanoparticle-polymer system behaves very differently in the presence of electrolyte. In the absence of electrolyte, the nanoparticle-polymer system remains in one-phase even at very high polymer concentrations. On the other hand, a re-entrant phase behavior is found in the presence of electrolyte, where one-phase (individual) system undergoes two-phase (nanoparticle aggregation) and then back to one-phase with increasing polymer concentration. The regime of two-phase system has been tuned by varying the electrolyte concentration. The polymer concentration range over which the two-phase system exists is significantly enhanced with the increase in the electrolyte concentration. These systems have been characterized by small-angle neutron scattering (SANS) experiments of contrast-marching the polymer to the solvent. The data are modeled using a two-Yukawa potential accounting for both attractive and repulsive parts of the interaction between nanoparticles. The phase behavior of nanoparticle-polymer system is explained by interplay of attractive (polymer-induced attractive depletion between nanoparticles) and repulsive (nanoparticle-nanoparticle electrostatic repulsion and polymer-polymer repulsion) interactions present in the system. In the absence of electrolyte, the strong electrostatic repulsion between nanoparticles dominates over the polymer-induced depletion attraction and the nanoparticle system remains in one-phase. With addition of electrolyte, depletion attraction overcomes electrostatic repulsion at some polymer concentration, resulting into nanoparticle aggregation and two-phase system. Further addition of polymer increases the polymer-polymer repulsion which eventually reduces the strength of depletion and hence re-entrant phase behavior. The effects of varying electrolyte concentration on the phase

Cytotoxicity of iron oxide nanoparticles made from the thermal decomposition of organometallics and aqueous phase transfer with Pluronic F127

PubMed Central

Gonzales, Marcela; Mitsumori, Lee M.; Kushleika, John V.; Rosenfeld, Michael E.; Krishnan, Kannan M.

2010-01-01

Magnetic nanoparticles are promising molecular imaging agents due to their relative high relaxivity and the potential to modify surface functionality to tailor biodistribution. In this work we describe the synthesis of magnetic nanoparticles using organic solvents with organometallic precursors. This method results in nanoparticles that are highly crystalline, and have uniform size and shape. The ability to create a monodispersion of particles of the same size and shape results in unique magnetic properties that can be useful for biomedical applications with MR imaging. Before these nanoparticles can be used in biological applications, however, means are needed to make the nanoparticles soluble in aqueous solutions and the toxicity of these nanoparticles needs to be studied. We have developed two methods to surface modify and transfer these nanoparticles to the aqueous phase using the biocompatible co-polymer, Pluronic F127. Cytotoxicity was found to be dependent on the coating procedure used. Nanoparticle effects on a cell-culture model was quantified using concurrent assaying; a LDH assay to determine cytotoxicity and an MTS assay to determine viability for a 24 hour incubation period. Concurrent assaying was done to insure that nanoparticles did not interfere with the colorimetric assay results. This report demonstrates that a monodispersion of nanoparticles of uniform size and shape can be manufactured. Initial cytotoxicity testing of new molecular imaging agents need to be carefully constructed to avoid interference and erroneous results. PMID:20623517

Phase behaviour in complementary DNA-coated gold nanoparticles and fd-viruses mixtures: a numerical study.

PubMed

Chiappini, Massimiliano; Eiser, Erika; Sciortino, Francesco

2017-01-01

A new gel-forming colloidal system based on a binary mixture of fd-viruses and gold nanoparticles functionalized with complementary DNA single strands has been recently introduced. Upon quenching below the DNA melt temperature, such a system results in a highly porous gel state, that may be developed in a new functional material of tunable porosity. In order to shed light on the gelation mechanism, we introduce a model closely mimicking the experimental one and we explore via Monte Carlo simulations its equilibrium phase diagram. Specifically, we model the system as a binary mixture of hard rods and hard spheres mutually interacting via a short-range square-well attractive potential. In the experimental conditions, we find evidence of a phase separation occurring either via nucleation-and-growth or via spinodal decomposition. The spinodal decomposition leads to the formation of small clusters of bonded rods and spheres whose further diffusion and aggregation leads to the formation of a percolating network in the system. Our results are consistent with the hypothesis that the mixture of DNA-coated fd-viruses and gold nanoparticles undergoes a non-equilibrium gelation via an arrested spinodal decomposition mechanism.

Comparative study of alkylthiols and alkylamines for the phase transfer of gold nanoparticles from an aqueous phase to n-hexane.

PubMed

Li, Lingxiangyu; Leopold, Kerstin; Schuster, Michael

2013-05-01

An efficient ligand-assisted phase transfer method has been developed to transfer gold nanoparticles (Au-NPs, d: 5-25 nm) from an aqueous solution to n-hexane. Four different ligands, namely 1-dodecanethiol (DDT), 1-octadecanethiol (ODT), dodecylamine (DDA), and octadecylamine (ODA) were investigated, and DDT was found to be the most efficient ligand. It appears that the molar ratio of DDT to Au-NPs is a critical factor affecting the transfer efficiency, and 270-310 is found to be the optimum range, under which the transfer efficiency is >96%. Moreover, the DDT-assisted phase transfer can preserve the shape and size of the Au-NPs, which was confirmed by UV-vis spectra and transmission electron microscopy (TEM). Additionally, the transferred Au-NPs still can be well dispersed in the n-hexane phase and remain stable for at least 2 weeks. On the other hand, the ODT-, DDA-, and ODA-assisted phase transfer is fraught with problems either related to transfer efficiency or NPs aggregation. Overall, the DDT-assisted phase transfer of Au-NPs provides a rapid and efficient method to recover Au-NPs from an aqueous solution to n-hexane. Copyright © 2013 Elsevier Inc. All rights reserved.

3D map of theranostic nanoparticles distribution in mice brain and liver by means of X-ray Phase Contrast Tomography

NASA Astrophysics Data System (ADS)

Longo, E.; Bravin, A.; Brun, F.; Bukreeva, I.; Cedola, A.; Fratini, M.; Le Guevel, X.; Massimi, L.; Sancey, L.; Tillement, O.; Zeitoun, P.; de La Rochefoucauld, O.

2018-01-01

The word "theranostic" derives from the fusion of two terms: therapeutic and diagnostic. It is a promising research field that aims to develop innovative therapies with high target specificity by exploiting the therapeutic and diagnostic properties, in particular for metal-based nanoparticles (NPs) developed to erase cancer. In the framework of a combined research program on low dose X-ray imaging and theranostic nanoparticles (NPs), high resolution Phase-Contrast Tomography images of mice organs injected with gadolinium and gold-NPs were acquired at the European Synchrotron Radiation Facility (ESRF). Both compounds are good X-ray contrast agents due to their high attenuation coefficient with respect to biological tissues, especially immediately above K-edge energy. X-ray tomography is a powerful non-invasive technique to image the 3D vasculature network in order to detect abnormalities. Phase contrast methods provide more detailed anatomical information with higher discrimination among soft tissues. We present the images of mice liver and brain injected with gold and gadolinium NPs, respectively. We discuss different image processing methods used aiming at enhancing the accuracy on localizing nanoparticles.

Preparation and characterization of copper oxide nanoparticles decorated carbon nanoparticles using laser ablation in liquid

NASA Astrophysics Data System (ADS)

Khashan, K. S.; Jabir, M. S.; Abdulameer, F. A.

2018-05-01

Carbon nanoparticles CNPs ecorated by copper oxide nano-sized particles would be successfully equipped using technique named pulsed laser ablation in liquid. The XRD pattern proved the presence of phases assigned to carbon and different phases of copper oxide. The chemical structure of the as-prepared nanoparticles samples was decided by Energy Dispersive Spectrum (EDS) measurement. EDS analysis results show the contents of Carbon, Oxygen and Copper in the final product. These nanoparticles were spherical shaped with a size distribution 10 to 80 nm or carbon nanoparticles and 5 to 50 nm for carbon decorated copper oxide nanoparticles, according to Transmission Electron Microscopy (TEM) images and particle-size distribution histogram. It was found that after doping with copper oxide, nanoparticles become smaller and more regular in shape. Optical absorption spectra of prepared nanoparticles were measured using UV–VIS spectroscopy. The absorption spectrum of carbon nanoparticles without doping indicates absorption peak at about 228 nm. After doping with copper oxide, absorption shows appearance of new absorption peak at about (254-264) nm, which is referred to the movement of the charge between 2p and 4s band of Cu2+ ions.

Effect of phase transformation on optical and dielectric properties of zirconium oxide nanoparticles

NASA Astrophysics Data System (ADS)

Chintaparty, Rajababu; Palagiri, Bhavani; Reddy Nagireddy, Ramamanohar; subbha Reddy Imma Reddy, Venkata

2015-09-01

Zirconium oxide nanoparticle (ZrO2) is synthesized by the hydrothermal method at different calcination temperatures. The structural analysis is carried out by X-ray diffraction and Raman spectra. The sample prepared at 400 °C and 1100 °C showed the cubic and monoclinic phase, respectively, and the sample calcined at 600 °C and 800 °C showed the mixed phase with co-existence of cubic and monoclinic phases. Furthermore, the morphology and particle size of these samples were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis. The band gap estimated from UV-Vis spectra of ZrO2 (zirconia) nanocrystalline materials calcined at different temperatures from 400 °C to 1100 °C was in the range of 2.6-4.2 eV. The frequency dependence of dielectric constant and dielectric loss was investigated at room temperature. The low frequency region of dielectric constant is attributed to space charge effects.

Stable cavitation using acoustic phase-change dodecafluoropentane nanoparticles for coronary micro-circulation thrombolysis.

PubMed

Hu, Bo; Jiang, Nan; Zhou, Qing; Cao, Sheng; Gao, Shunji; Zhang, Binghong; Chen, Jinling; Guo, Ruiqiang

2018-06-11

The thrombolysis in micro-circulation after acute myocardial infarction has been an unsolved issue, as elimination effect of acute thrombolysis and primary intervention were unsatisfied. Stable cavitation using acoustic phase-change nanoparticles may have potential for thrombolysis. Therefore, we sought to investigate a novel treatment method with dodecafluoropentane (DDFP) nanoparticles for rapid and effective thrombolysis in an in-vitro artificial vascular system, as a mimicking preparation of coronary circulation. To simulate thrombus embolism in coronary circulation, an in-vitro artificial vascular system was established with cavitation effect using DDFP nanoparticles. For PBS blank control (group A), SonoVue microbubbles (group B) and DDFP nanoparticles (group C), the durations for cavitation effect were recorded and the thrombolysis efficiency with low intensity focused ultrasound irradiation in the in-vitro vascular system were analyzed with weight loss and pathological changes of thrombus before and after thrombolysis. The optimal conditions for acoustic cavitation effect were power of 6 W for 20 min by ultrasound irradiation at 37 °C. The weight loss and weight loss rates of thrombus in group C (189.4 ± 30.2 mg and 34.2 ± 5.7%) were higher than those in group A (30.2 ± 16.0 mg and 5.2 ± 2.1%) and group B (84.0 ± 20.4 mg and 14.6 ± 1.5%) (P < 0.01, all). The duration for cavitation effect in group C (32.8 ± 3.9 min) was also longer than those in group A (0.0 ± 0.0 min) and group B (5.3 ± 0.3 min) (P < 0.01, all). By stable and sustaining cavitation in targeted area, DDFP nanoparticles with ultrasound irradiation have significantly increased the thrombolysis efficiency, which has provided a powerful experimental foundation for potential coronary thrombolysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Growth and analysis of gallium arsenide-gallium antimonide single and two-phase nanoparticles

NASA Astrophysics Data System (ADS)

Schamp, Crispin T.

When evaluating the path of phase transformations in systems with nanoscopic dimensions one often relies on bulk phase diagrams for guidance because of the lack of phase diagrams that show the effect of particle size. The GaAs-GaSb pseudo-binary alloy is chosen for study to gain insight into the size dependence of solid-solubility in a two-phase system. To this end, a study is performed using independent laser ablation of high purity targets of GaAs and GaSb. The resultant samples are analyzed by transmission electron microscopy. Experimental results indicate that GaAs-GaSb nanoparticles have been formed with compositions that lie within the miscibility gap of bulk GaAs-GaSb. An unusual nanoparticle morpohology resembling the appearance of ice cream cones has been observed in single component experiments. These particles are composed of a spherical cap of Ga in contact with a crystalline cone of either GaAs or GaSb. The cones take the projected 2-D shape of a triangle or a faceted gem. The liquid Ga is found to consistently be of spherical shape and wets to the widest corners of the cone, suggesting an energy minimum exists at that wetting condition. To explore this observation a liquid sphere is modeled as being penetrated by a solid gem. The surface energies of the solid and liquid, and interfacial energy are summed as a function of penetration depth, with the sum showing a cusped minimum at the penetration depth corresponding to the waist of the gem. The angle of contact of the liquid wetting the cone is also calculated, and Young's contact angle is found to occur when the derivative of the total energy with respect to penetration depth is zero, which can be a maximum or a minimum depending on the geometrical details. The spill-over of the meniscus across the gem corners is found to be energetically favorable when the contact angle achieves the value of the equilibrium angle; otherwise the meniscus is pinned at the corners.

Interaction of fibrinogen and albumin with titanium dioxide nanoparticles of different crystalline phases

NASA Astrophysics Data System (ADS)

Marucco, Arianna; Fenoglio, Ivana; Turci, Francesco; Fubini, Bice

2013-04-01

TiO2 nanoparticles (NPs) are contained in different kinds of industrial products including paints, self-cleaning glasses, sunscreens. TiO2 is also employed in photocatalysis and it has been proposed for waste water treatment. Micrometric TiO2 is generally considered a safe material, while there is concern on the possible health effects of nanometric titania. Due to their small size NPs may migrate within the human body possibly entering in the blood stream. Therefore studies on the interaction of NPs with plasma proteins are needed. In fact, the interaction with proteins is believed to ultimately influences the NPs biological fate. Fibrinogen and albumin are two of the most abundant plasma proteins. They are involved in several important physiological functions. Furthermore, fibrinogen is known to trigger platelet adhesion and inflammation. For these reasons the study of the interaction between these protein and nanoparticles is an important step toward the understanding of the behavior of NPs in the body. In this study we investigated the interaction of albumin and fibrinogen with TiO2 nanoparticles of different crystal phases (rutile and anatase) using an integrated set of techniques. The amount of adsorbed fibrinogen and albumin for each TiO2 surface was investigated by using the bicinchoninic acid assay (BCA). The variation of the surface charge of the NP-protein conjugates respect to the naked NPs was used to indirectly estimate both surface coverage and reversibility of the adsorption upon dilution. Surface charge was monitored by measuring the ζ potential with a conventional electrophoretic light scattering (ELS) system. The extent of protein deformation was evaluated by Raman Spectroscopy. We found that both proteins adsorb irreversibly against electrostatic repulsion, likely undergoing conformational changes or selective orientation upon adsorption. The size of primary particles and the particles aggregation rather than the crystal phase modulate the

Nanoparticle engineering of colloidal suspension behavior

NASA Astrophysics Data System (ADS)

Chan, Angel Thanda

We investigate the effects of highly charged nanoparticles on the phase behavior, structure, and assembly of colloidal microsphere suspensions. Specifically, by selectively tuning the electrostatic interactions between silica microspheres and polystyrene nanoparticles, we study the behavior of four key systems: (i) strongly repulsive, (ii) haloing, (iii) weakly attractive, and (iv) strongly attractive systems. In each system, a combination of nanoparticle adsorption, zeta potential, and confocal microscopy measurements are carried out to systematically study the effects of nanoparticle volume fraction, microsphere/nanoparticle size ratios, and interparticle interactions on their behavior. Our observations indicate that minimal adsorption of highly charged nanoparticles occurs on like-charged and negligibly-charged microspheres, whereas their extent of association increases dramatically with increasing microsphere-nanoparticle attraction. A rich phase behavior emerges in these systems based on whether the nanoparticle species serve as depletants, haloing, or bridging species. The phase transitions in the haloing system occur at constant nanoparticle volume fractions, φnano, over a broad range of microsphere volume fractions, φmicro . By contrast, the observed transitions in the weakly and strongly attractive mixtures occur at a constant number ratio of nanoparticles per microsphere, Nnano/Nmicro. Important structural differences emerge, which can be exploited in the assembly of colloidal gels for direct ink writing and colloidal crystals on epitaxially patterned substrates. Finally, for the first time, we explore nanoparticle haloing as a new route for stabilizing hydrophobic colloidal drugs in aqueous suspensions media for preparation of injectable pharmaceuticals. These microsphere suspensions exhibit improved stability relative to their surfactant-stabilized counterparts after autoclaving, a critical processing step for this target applications. This research

Interaction of lysozyme protein with different sized silica nanoparticles and their resultant structures

NASA Astrophysics Data System (ADS)

Yadav, Indresh; Aswal, V. K.; Kohlbrecher, J.

2016-05-01

The interaction of model protein-lysozyme with three different sized anionic silica nanoparticles has been studied by UV-vis spectroscopy, dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The surface area and curvature of the nanoparticles change with size, which significantly influence their interaction with protein. The lysozyme adsorbs on the surface of the nanoparticles due to electrostatic attraction and leads to the phase transformation from one phase (clear) to two-phase (turbid) of the nanoparticle-protein system. The dominance of lysozyme induced short-range attraction over long-range electrostatic repulsion between nanoparticles is responsible for phase transformation and modeled by the two-Yukawa potential. The magnitude of the attractive interaction increases with the size of the nanoparticles as a result the phase transformation commences relatively at lower concentration of lysozyme. The structure of the nanoparticle-protein system in two-phase is characterized by the diffusion limited aggregate type of mass fractal morphology.

Interaction of lysozyme protein with different sized silica nanoparticles and their resultant structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Indresh, E-mail: iykumarindresh288@gmail.com; Aswal, V. K.; Kohlbrecher, J.

The interaction of model protein-lysozyme with three different sized anionic silica nanoparticles has been studied by UV-vis spectroscopy, dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The surface area and curvature of the nanoparticles change with size, which significantly influence their interaction with protein. The lysozyme adsorbs on the surface of the nanoparticles due to electrostatic attraction and leads to the phase transformation from one phase (clear) to two-phase (turbid) of the nanoparticle-protein system. The dominance of lysozyme induced short-range attraction over long-range electrostatic repulsion between nanoparticles is responsible for phase transformation and modeled by the two-Yukawa potential. Themore » magnitude of the attractive interaction increases with the size of the nanoparticles as a result the phase transformation commences relatively at lower concentration of lysozyme. The structure of the nanoparticle-protein system in two-phase is characterized by the diffusion limited aggregate type of mass fractal morphology.« less

In Situ Observation of Single-Phase Lithium Intercalation in Sub-25-nm Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Li; Liu, Yang; Han, Wei-Qiang

Although a non-equilibrium single-phase reaction, with the absence of nucleation and growth of a second phase, is believed to be a key factor for high-rate performance of lithium-ion batteries, it is thermodynamically unfavorable and usually proceeds in electrode materials with small particle sizes (tens of nanometers). Unfortunately, the phase evolutions inside such small particles are often shrouded by the macroscopic inhomogeneous reactions of electrodes containing millions of particles, leading to intensive debate over the size-dependent microscopic reaction mechanisms. Here, we provide a generally applicable methodology based on in-situ electron diffraction study on a multi-particle system to track the lithiation pathwaysmore » in individual nanoparticles, and unambiguously reveal that lithiation of anatase TiO 2, previously long believed to be biphasic, converts to a single-phase reaction when the particle size is below ~25 nm. Our results imply the prevalence of such a size-dependent transition in lithiation mechanism among intercalation compounds whose lithium miscibility gaps are associated with a prominent size effect, and therefore provide important guidelines for designing high-power electrodes, especially cathodes.« less

In Situ Observation of Single-Phase Lithium Intercalation in Sub-25-nm Nanoparticles

DOE PAGES

Zhong, Li; Liu, Yang; Han, Wei-Qiang; ...

2017-05-05

Although a non-equilibrium single-phase reaction, with the absence of nucleation and growth of a second phase, is believed to be a key factor for high-rate performance of lithium-ion batteries, it is thermodynamically unfavorable and usually proceeds in electrode materials with small particle sizes (tens of nanometers). Unfortunately, the phase evolutions inside such small particles are often shrouded by the macroscopic inhomogeneous reactions of electrodes containing millions of particles, leading to intensive debate over the size-dependent microscopic reaction mechanisms. Here, we provide a generally applicable methodology based on in-situ electron diffraction study on a multi-particle system to track the lithiation pathwaysmore » in individual nanoparticles, and unambiguously reveal that lithiation of anatase TiO 2, previously long believed to be biphasic, converts to a single-phase reaction when the particle size is below ~25 nm. Our results imply the prevalence of such a size-dependent transition in lithiation mechanism among intercalation compounds whose lithium miscibility gaps are associated with a prominent size effect, and therefore provide important guidelines for designing high-power electrodes, especially cathodes.« less

Enzymatically Controlled Vacancies in Nanoparticle Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnaby, Stacey N.; Ross, Michael B.; Thaner, Ryan V.

In atomic systems, the mixing of metals results in distinct phase behavior that depends on the identity and bonding characteristics of the atoms. In nanoscale systems, the use of oligonucleotides as programmable “bonds” that link nanoparticle “atoms” into superlattices allows for the decoupling of atom identity and bonding. While much research in atomic systems is dedicated to understanding different phase behavior of mixed metals, it is not well understood on the nanoscale how changes in the nanoscale “bond” affect the phase behavior of nanoparticle crystals. In this work, the identity of the atom is kept the same but the chemicalmore » nature of the bond is altered, which is not possible in atomic systems, through the use of DNA and RNA bonding elements. These building blocks assemble into single crystal nanoparticle superlattices with mixed DNA and RNA bonding elements throughout. The nanoparticle crystals can be dynamically changed through the selective and enzymatic hydrolysis of the RNA bonding elements, resulting in superlattices that retain their crystalline structure and habit, while incorporating up to 35% random vacancies generated from the nanoparticles removed. Therefore, the bonding elements of nanoparticle crystals can be enzymatically and selectively addressed without affecting the nature of the atom.« less

Toward industrial scale synthesis of ultrapure singlet nanoparticles with controllable sizes in a continuous gas-phase process

NASA Astrophysics Data System (ADS)

Feng, Jicheng; Biskos, George; Schmidt-Ott, Andreas

2015-10-01

Continuous gas-phase synthesis of nanoparticles is associated with rapid agglomeration, which can be a limiting factor for numerous applications. In this report, we challenge this paradigm by providing experimental evidence to support that gas-phase methods can be used to produce ultrapure non-agglomerated “singlet” nanoparticles having tunable sizes at room temperature. By controlling the temperature in the particle growth zone to guarantee complete coalescence of colliding entities, the size of singlets in principle can be regulated from that of single atoms to any desired value. We assess our results in the context of a simple analytical model to explore the dependence of singlet size on the operating conditions. Agreement of the model with experimental measurements shows that these methods can be effectively used for producing singlets that can be processed further by many alternative approaches. Combined with the capabilities of up-scaling and unlimited mixing that spark ablation enables, this study provides an easy-to-use concept for producing the key building blocks for low-cost industrial-scale nanofabrication of advanced materials.

Preparation of α-alumina nanoparticles with various shapes via hydrothermal phase transformation under supercritical water conditions

NASA Astrophysics Data System (ADS)

Hakuta, Y.; Nagai, N.; Suzuki, Y.-H.; Kodaira, T.; Bando, K. K.; Takashima, H.; Mizukami, F.

2013-12-01

Alumina (Al2O3) fine particles are widely used as industrial materials including fillers for metal or plastics, paints, polisher, cosmetics and electric substrates, due to its high hardness, chemical stability, and high thermal conductivity. The performance of those industrial products is closely related to the particle size or shape of the alumina particles used, and thus a new synthetic method to control size, shape, and crystal structure of the aluminum oxide is desired for the improvement of the performance. Hydrothermal phase transformation using various aluminum compounds such as oxide, hydroxide, and salt as a staring material, is known as one of the synthetic methods for producing alumina fine particles; however, the influence about the size and shape of the starting aluminum compounds has been little mentioned, although they strongly affect the size and shape of the final products. In this study, we investigated the influence of the shape, size and crystal structure of the starting aluminum compounds on those of the products, and newly succeeded in the production of rod-like α-Al2O3 nanoparticles from fibrous boehmite nanoparticles using hydrothermal phase transformation under supercritical water conditions.

Nanoparticle titanium dioxide aqueous interfacial energy can be modified to control phase stability, coarsening, and morphology

NASA Astrophysics Data System (ADS)

Finnegan, Michael Patrick

The effect of solution chemistry on the phase stability, coarsening kinetics and morphology of titanium dioxide (TiO2) nanoparticles is investigated in order to attain efficient production pathways to desired nano-structures with optimal properties. To obtain sample, TiO2 was synthesized via hydrolysis of titanium isopropoxide producing an 85% anatase/15% brookite mixture. The titania was hydrothermally heated in an array of temperatures and pH values for various times. There are distinct phase stability fields for nanoscale titania based on pH alone due to slight interface charging behavior differences among the polymorphs. The mixture transforms to rutile below the pH of zero point of charge (ZPC) and remains anatase above the ZPC. This phenomenon is partially reversible. The solution chemistry also dictates the hydrothermal coarsening mechanism of the anatase polymorph. Ostwald ripening (OR) takes place in basic pH where titania solubility is elevated relative to neutral pH where lower solubility prevents rapid OR but allows for coarsening via oriented attachment (OA) of nanoparticles. This OA event can alter the symmetry of anatase causing unexpected and perhaps technically useful morphologies such as straight and curved nanorods during coarsening.

Phase-Change Nanoparticles Using Highly Volatile Perfluorocarbons: Toward a Platform for Extravascular Ultrasound Imaging

PubMed Central

Matsunaga, Terry O.; Sheeran, Paul S.; Luois, Samantha; Streeter, Jason E.; Mullin, Lee B.; Banerjee, Bhaskar; Dayton, Paul A.

2012-01-01

Recent efforts using perfluorocarbon (PFC) nanoparticles in conjunction with acoustic droplet vaporization has introduced the possibility of expanding the diagnostic and therapeutic capability of ultrasound contrast agents to beyond the vascular space. Our laboratories have developed phase-change nanoparticles (PCNs) from the highly volatile PFCs decafluorobutane (DFB, bp =-2 °C) and octafluoropropane (OFP, bp =-37 °C ) for acoustic droplet vaporization. Studies with commonly used clinical ultrasound scanners have demonstrated the ability to vaporize PCN emulsions with frequencies and mechanical indices that may significantly decrease tissue bioeffects. In addition, these contrast agents can be formulated to be stable at physiological temperatures and the perfluorocarbons can be mixed to modulate the balance between sensitivity to ultrasound and general stability. We herein discuss our recent efforts to develop finely-tuned diagnostic/molecular imaging agents for tissue interrogation. We discuss studies currently under investigation as well as potential diagnostic and therapeutic paradigms that may emerge as a result of formulating PCNs with low boiling point PFCs. PMID:23382775

Extremely asymmetric phase diagram of homopolymer-monotethered nanoparticles: Competition between chain conformational entropy and particle steric interaction.

PubMed

Zhang, Tiancai; Fu, Chao; Yang, Yingzi; Qiu, Feng

2017-02-07

The phase behaviors of homopolymer-monotethered nanoparticles (HMNs) in melt are investigated via a theoretical method combining self-consistent field theory for polymers and density functional theory for hard spheres. An extremely asymmetric phase diagram is observed: (i) microphases are only possible for the volume fraction of the tethered polymer f A > 0.35; (ii) in addition to lamellar phase, the system can only self-assemble into various morphologies with a polymer-rich matrix, including gyroid phase, cylindrical phase, and spherical phase. In the frame of this theory, the critical point for HMNs' microphase separation is significantly lower than that of linear diblock copolymers. Furthermore, the characteristic length of microphase-separated structures of HMNs is much smaller than that of linear diblock copolymers with the same molecular weight. Our calculation results on morphologies and characteristic length agree well with recent simulations and experimental observations.

D-sorbitol-induced phase control of TiO2 nanoparticles and its application for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Shaikh, Shoyebmohamad F.; Mane, Rajaram S.; Min, Byoung Koun; Hwang, Yun Jeong; Joo, Oh-Shim

2016-02-01

Using a simple hydrothermal synthesis, the crystal structure of TiO2 nanoparticles was controlled from rutile to anatase using a sugar alcohol, D-sorbitol. Adding small amounts of D-sorbitol to an aqueous TiCl4 solution resulted in changes in the crystal phase, particle size, and surface area by affecting the hydrolysis rate of TiCl4. These changes led to improvements of the solar-to-electrical power conversion efficiency (η) of dye-sensitized solar cells (DSSC) fabricated using these nanoparticles. A postulated reaction mechanism concerning the role of D-sorbitol in the formation of rutile and anatase was proposed. Fourier-transform infrared spectroscopy, 13C NMR spectroscopy, and dynamic light scattering analyses were used to better understand the interaction between the Ti precursor and D-sorbitol. The crystal phase and size of the synthesized TiO2 nanocrystallites as well as photovoltaic performance of the DSSC were examined using X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and photocurrent density-applied voltage spectroscopy measurement techniques. The DSSC fabricated using the anatase TiO2 nanoparticles synthesized in the presence of D-sorbitol, exhibited an enhanced η (6%, 1.5-fold improvement) compared with the device fabricated using the rutile TiO2 synthesized without D-sorbitol.

Nanoparticle guests in lyotropic liquid crystals

NASA Astrophysics Data System (ADS)

Dölle, Sarah; Park, Ji Hyun; Schymura, Stefan; Jo, Hyeran; Scalia, Giusy; Lagerwall, Jan P. F.

In this chapter we discuss the benefits, peculiarities and main challenges related to nanoparticle templating in lyotropic liquid crystals. We first give a brief bird's-eye view of the field, discussing different nanoparticles as well as different lyotropic hosts that have been explored, but then quickly focus on the dispersion of carbon nanotubes in surfactant-based lyotropic nematic phases. We discuss in some detail how the transfer of orientational order from liquid crystal host to nanoparticle guest can be verified and which degree of ordering can be expected, as well as the importance of choosing the right surfactant and its concentration for the stability of the nanoparticle suspension. We introduce a method for dispersing nanoparticles with an absolute minimum of stabilizing surfactant, based on dispersion below the Krafft temperature, and we discuss the peculiar phenomenon of filament formation in lyotropic nematic phases with a sufficient concentration of well-dispersed carbon nanotubes. Finally, we describe how the total surfactant concentration in micellar nematics can be greatly reduced by combining cat- and anionic surfactants, and we discuss how nanotubes can help in inducing the liquid crystal phase close to the isotropic-nematic boundary.

Upward shift of the vortex solid phase in high-temperature-superconducting wires through high density nanoparticle addition

DOE PAGES

Miura, Masashi; Maiorov, Boris; Balakirev, Fedor F.; ...

2016-02-08

Here, we show a simple and effective way to improve the vortex irreversibility line up to very high magnetic fields (60T) by increasing the density of second phase BaZrO 3 nanoparticles. (Y 0.77,Gd 0.23)Ba 2Cu 3O y films were grown on metal substrates with different concentration of BaZrO 3 nanoparticles by the metal organic deposition method. We find that upon increase of the BaZrO 3 concentration, the nanoparticle size remains constant but the twin-boundary density increases. Up to the highest nanoparticle concentration (n ~ 1.3 × 10 22/m 3), the irreversibility field (H irr) continues to increase with no signmore » of saturation up to 60 T, although the vortices vastly outnumber pinning centers. We find extremely high H irr, namely H irr = 30 T (H||45°) and 24 T (H||c) at 65 K and 58 T (H||45°) and 45 T (H||c) at 50K. The difference in pinning landscape shifts the vortex solid-liquid transition upwards, increasing the vortex region useful for power applications, while keeping the upper critical field, critical temperature and electronic mass anisotropy unchanged.« less

Thermodynamically equilibrium roton states of nanoparticles in molten and vapour phases

NASA Astrophysics Data System (ADS)

Karasevskii, A. I.

2015-05-01

We show a possibility for a thermodynamically equilibrium nanocrystalline structure consisting of nanosized solid inclusions to appear in a melt just beyond the melting curve. Thermodynamic stability of the nanocrystalline structure in the melt results from the free energy lowering due to rotational motion of nanoparticles. The main contribution to the reduction of the free energy of the system is due to an increase in the rotational entropy and change in formation energy of nanocrystals, i.e. the nanocrystalline structure in the melt, like vacancies in a crystal, is an equilibrium defect structure of the melt. It is demonstrated that similar nanocrystalline structures can also appear in the vapour phase in the form of liquid nanodrops and in liquid solutions, e.g. in He II.

Enhancement of β-phase in PVDF films embedded with ferromagnetic Gd 5Si 4 nanoparticles for piezoelectric energy harvesting

DOE PAGES

Harstad, Shane; D’Souza, Noel; Soin, Navneet; ...

2017-01-04

Self-polarized Gd5Si4-polyvinylidene fluoride (PVDF) nanocomposite films have been synthesized via a facile phase-inversion technique. For the 5 wt% Gd 5Si 4-PVDF films, the enhancement of the piezoelectric β-phase and crystallinity are confirmed using Fourier transform infrared (FTIR) spectroscopy (phase fraction, FβFβ, of 81% as compared to 49% for pristine PVDF) and differential scanning calorimetry (crystallinity, ΔXcΔXc, of 58% as compared to 46% for pristine PVDF), respectively. The Gd5Si4 magnetic nanoparticles, prepared using high-energy ball milling were characterized using Dynamic Light Scattering and Vibrating Sample Magnetometry (VSM) to reveal a particle size of ~470 nm with a high magnetization of 11more » emu/g. The VSM analysis of free-standing Gd5Si4-PVDF films revealed that while the pristine PVDF membrane shows weak diamagnetic behavior, the Gd5Si4-PVDF films loaded at 2.5 wt% and 5 wt% Gd 5Si 4 show enhanced ferromagnetic behavior with paramagnetic contribution from Gd5Si3 phase. The interfacial interactions between Gd5Si4 and PVDF results in the preferential crystallization of the β-phase as confirmed via the shift in the CH 2 asymmetric and symmetric stretching vibrations in the FTIR. These results confirm the magnetic Gd 5Si 4 nanoparticles embedded in the PVDF membrane lead to an increased β-phase fraction, which paves the way for future efficient energy harvesting applications using a combination of magnetic and piezoelectric effects.« less

Enhancement of 𝜷-phase in PVDF films embedded with ferromagnetic Gd5Si4 nanoparticles for piezoelectric energy harvesting

NASA Astrophysics Data System (ADS)

Harstad, Shane; D'Souza, Noel; Soin, Navneet; El-Gendy, Ahmed A.; Gupta, Shalabh; Pecharsky, Vitalij K.; Shah, Tahir; Siores, Elias; Hadimani, Ravi L.

2017-05-01

Self-polarized Gd5Si4-polyvinylidene fluoride (PVDF) nanocomposite films have been synthesized via a facile phase-inversion technique. For the 5 wt% Gd5Si4-PVDF films, the enhancement of the piezoelectric β-phase and crystallinity are confirmed using Fourier transform infrared (FTIR) spectroscopy (phase fraction, Fβ, of 81% as compared to 49% for pristine PVDF) and differential scanning calorimetry (crystallinity, Δ Xc , of 58% as compared to 46% for pristine PVDF), respectively. The Gd5Si4 magnetic nanoparticles, prepared using high-energy ball milling were characterized using Dynamic Light Scattering and Vibrating Sample Magnetometry (VSM) to reveal a particle size of ˜470 nm with a high magnetization of 11 emu/g. The VSM analysis of free-standing Gd5Si4-PVDF films revealed that while the pristine PVDF membrane shows weak diamagnetic behavior, the Gd5Si4-PVDF films loaded at 2.5 wt% and 5 wt% Gd5Si4 show enhanced ferromagnetic behavior with paramagnetic contribution from Gd5Si3 phase. The interfacial interactions between Gd5Si4 and PVDF results in the preferential crystallization of the β-phase as confirmed via the shift in the CH2 asymmetric and symmetric stretching vibrations in the FTIR. These results confirm the magnetic Gd5Si4 nanoparticles embedded in the PVDF membrane lead to an increased β-phase fraction, which paves the way for future efficient energy harvesting applications using a combination of magnetic and piezoelectric effects.

Enhancement of β-phase in PVDF films embedded with ferromagnetic Gd 5Si 4 nanoparticles for piezoelectric energy harvesting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harstad, Shane; D’Souza, Noel; Soin, Navneet

Self-polarized Gd5Si4-polyvinylidene fluoride (PVDF) nanocomposite films have been synthesized via a facile phase-inversion technique. For the 5 wt% Gd 5Si 4-PVDF films, the enhancement of the piezoelectric β-phase and crystallinity are confirmed using Fourier transform infrared (FTIR) spectroscopy (phase fraction, FβFβ, of 81% as compared to 49% for pristine PVDF) and differential scanning calorimetry (crystallinity, ΔXcΔXc, of 58% as compared to 46% for pristine PVDF), respectively. The Gd5Si4 magnetic nanoparticles, prepared using high-energy ball milling were characterized using Dynamic Light Scattering and Vibrating Sample Magnetometry (VSM) to reveal a particle size of ~470 nm with a high magnetization of 11more » emu/g. The VSM analysis of free-standing Gd5Si4-PVDF films revealed that while the pristine PVDF membrane shows weak diamagnetic behavior, the Gd5Si4-PVDF films loaded at 2.5 wt% and 5 wt% Gd 5Si 4 show enhanced ferromagnetic behavior with paramagnetic contribution from Gd5Si3 phase. The interfacial interactions between Gd5Si4 and PVDF results in the preferential crystallization of the β-phase as confirmed via the shift in the CH 2 asymmetric and symmetric stretching vibrations in the FTIR. These results confirm the magnetic Gd 5Si 4 nanoparticles embedded in the PVDF membrane lead to an increased β-phase fraction, which paves the way for future efficient energy harvesting applications using a combination of magnetic and piezoelectric effects.« less

Carbothermal shock synthesis of high-entropy-alloy nanoparticles

NASA Astrophysics Data System (ADS)

Yao, Yonggang; Huang, Zhennan; Xie, Pengfei; Lacey, Steven D.; Jacob, Rohit Jiji; Xie, Hua; Chen, Fengjuan; Nie, Anmin; Pu, Tiancheng; Rehwoldt, Miles; Yu, Daiwei; Zachariah, Michael R.; Wang, Chao; Shahbazian-Yassar, Reza; Li, Ju; Hu, Liangbing

2018-03-01

The controllable incorporation of multiple immiscible elements into a single nanoparticle merits untold scientific and technological potential, yet remains a challenge using conventional synthetic techniques. We present a general route for alloying up to eight dissimilar elements into single-phase solid-solution nanoparticles, referred to as high-entropy-alloy nanoparticles (HEA-NPs), by thermally shocking precursor metal salt mixtures loaded onto carbon supports [temperature ~2000 kelvin (K), 55-millisecond duration, rate of ~105 K per second]. We synthesized a wide range of multicomponent nanoparticles with a desired chemistry (composition), size, and phase (solid solution, phase-separated) by controlling the carbothermal shock (CTS) parameters (substrate, temperature, shock duration, and heating/cooling rate). To prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with ~100% conversion and >99% nitrogen oxide selectivity over prolonged operations.

Green synthesis of bacterial mediated anti-proliferative gold nanoparticles: inducing mitotic arrest (G2/M phase) and apoptosis (intrinsic pathway)

NASA Astrophysics Data System (ADS)

Ganesh Kumar, C.; Poornachandra, Y.; Chandrasekhar, Cheemalamarri

2015-11-01

The physiochemical and biological properties of microbial derived gold nanoparticles have potential applications in various biomedical domains as well as in cancer therapy. We have fabricated anti-proliferative bacterial mediated gold nanoparticles (b-Au NPs) using a culture supernatant of Streptomyces clavuligerus and later characterized them by UV-visible, TEM, DLS, XRD and FT-IR spectroscopic techniques. The capping agent responsible for the nanoparticle formation was characterized based on SDS-PAGE and MALDI-TOF-MS analyses. They were tested for anticancer activity in A549, HeLa and DU145 cell lines. The biocompatibility and non-toxic nature of the nanoparticles were tested on normal human lung cell line (MRC-5). The b-Au NPs induced the cell cycle arrest in G2/M phase and also inhibited the microtubule assembly in DU145 cells. Mechanistic studies, such as ROS, MMP, Cyt-c, GSH, caspases 9, 8 and 3 activation and the Annexin V-FITC staining, along with the above parameters tested provided sufficient evidence that the b-Au NPs induced apoptosis through the intrinsic pathway. The results supported the use of b-Au NPs for future therapeutic application in cancer therapy and other biomedical applications.The physiochemical and biological properties of microbial derived gold nanoparticles have potential applications in various biomedical domains as well as in cancer therapy. We have fabricated anti-proliferative bacterial mediated gold nanoparticles (b-Au NPs) using a culture supernatant of Streptomyces clavuligerus and later characterized them by UV-visible, TEM, DLS, XRD and FT-IR spectroscopic techniques. The capping agent responsible for the nanoparticle formation was characterized based on SDS-PAGE and MALDI-TOF-MS analyses. They were tested for anticancer activity in A549, HeLa and DU145 cell lines. The biocompatibility and non-toxic nature of the nanoparticles were tested on normal human lung cell line (MRC-5). The b-Au NPs induced the cell cycle arrest in G2

A novel superparamagnetic surface molecularly imprinted nanoparticle adopting dummy template: an efficient solid-phase extraction adsorbent for bisphenol A.

PubMed

Lin, Zhenkun; Cheng, Wenjing; Li, Yanyan; Liu, Zhiren; Chen, Xiangping; Huang, Changjiang

2012-03-30

Leakage of the residual template molecules is one of the biggest challenges for application of molecularly imprinted polymer (MIP) in solid-phase extraction (SPE). In this study, bisphenol F (BPF) was adopted as a dummy template to prepare MIP of bisphenol A (BPA) with a superparamagnetic core-shell nanoparticle as the supporter, aiming to avoid residual template leakage and to increase the efficiency of SPE. Characterization and test of the obtained products (called mag-DMIP beads) revealed that these novel nanoparticles not only had excellent magnetic property but also displayed high selectivity to the target molecule BPA. As mag-DMIP beads were adopted as the adsorbents of solid-phase extraction for detecting BPA in real water samples, the recoveries of spiked samples ranged from 84.7% to 93.8% with the limit of detection of 2.50 pg mL(-1), revealing that mag-DMIP beads were efficient SPE adsorbents. Copyright © 2012 Elsevier B.V. All rights reserved.

Size-dependent interaction of silica nanoparticles with lysozyme and bovine serum albumin proteins

NASA Astrophysics Data System (ADS)

Yadav, Indresh; Aswal, Vinod K.; Kohlbrecher, Joachim

2016-05-01

The interaction of three different sized (diameter 10, 18, and 28 nm) anionic silica nanoparticles with two model proteins—cationic lysozyme [molecular weight (MW) 14.7 kDa)] and anionic bovine serum albumin (BSA) (MW 66.4 kDa) has been studied by UV-vis spectroscopy, dynamic light scattering (DLS), and small-angle neutron scattering (SANS). The adsorption behavior of proteins on the nanoparticles, measured by UV-vis spectroscopy, is found to be very different for lysozyme and BSA. Lysozyme adsorbs strongly on the nanoparticles and shows exponential behavior as a function of lysozyme concentration irrespective of the nanoparticle size. The total amount of adsorbed lysozyme, as governed by the surface-to-volume ratio, increases on lowering the size of the nanoparticles for a fixed volume fraction of the nanoparticles. On the other hand, BSA does not show any adsorption for all the different sizes of the nanoparticles. Despite having different interactions, both proteins induce similar phase behavior where the nanoparticle-protein system transforms from one phase (clear) to two phase (turbid) as a function of protein concentration. The phase behavior is modified towards the lower concentrations for both proteins with increasing the nanoparticle size. DLS suggests that the phase behavior arises as a result of the nanoparticles' aggregation on the addition of proteins. The size-dependent modifications in the interaction potential, responsible for the phase behavior, have been determined by SANS data as modeled using the two-Yukawa potential accounting for the repulsive and attractive interactions in the systems. The protein-induced interaction between the nanoparticles is found to be short-range attraction for lysozyme and long-range attraction for BSA. The magnitude of attractive interaction irrespective of protein type is enhanced with increase in the size of the nanoparticles. The total (attractive+repulsive) potential leading to two-phase formation is found to be

Stimuli-Responsive Polymeric Nanoparticles.

PubMed

Liu, Xiaolin; Yang, Ying; Urban, Marek W

2017-07-01

There is increasing evidence that stimuli-responsive nanomaterials have become significantly critical components of modern materials design and technological developments. Recent advances in synthesis and fabrication of stimuli-responsive polymeric nanoparticles with built-in stimuli-responsive components (Part A) and surface modifications of functional nanoparticles that facilitate responsiveness (Part B) are outlined here. The synthesis and construction of stimuli-responsive spherical, core-shell, concentric, hollow, Janus, gibbous/inverse gibbous, and cocklebur morphologies are discussed in Part A, with the focus on shape, color, or size changes resulting from external stimuli. Although inorganic/metallic nanoparticles exhibit many useful properties, including thermal or electrical conductivity, catalytic activity, or magnetic properties, their assemblies and formation of higher order constructs are often enhanced by surface modifications. Section B focuses on selected surface reactions that lead to responsiveness achieved by decorating nanoparticles with stimuli-responsive polymers. Although grafting-to and grafting-from dominate these synthetic efforts, there are opportunities for developing novel synthetic approaches facilitating controllable recognition, signaling, or sequential responses. Many nanotechnologies utilize a combination of organic and inorganic phases to produce ceramic or metallic nanoparticles. One can envision the development of new properties by combining inorganic (metals, metal oxides) and organic (polymer) phases into one nanoparticle designated as "ceramers" (inorganics) and "metamers" (metallic). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tailoring gas-phase CO2 electroreduction selectivity to hydrocarbons at Cu nanoparticles

NASA Astrophysics Data System (ADS)

Merino-Garcia, I.; Albo, J.; Irabien, A.

2018-01-01

Copper-based surfaces appear as the most active catalysts for CO2 electroreduction to hydrocarbons, even though formation rates and efficiencies still need to be improved. The aim of the present work is to evaluate the continuous gas-phase CO2 electroreduction to hydrocarbons (i.e. ethylene and methane) at copper nanoparticulated-based surfaces, paying attention to particle size influence (ranging from 25-80 nm) on reaction productivity, selectivity, and Faraday efficiency (FE) for CO2 conversion. The effect of the current density and the presence of a microporous layer within the working electrode are then evaluated. Copper-based gas diffusion electrodes are prepared by airbrushing the catalytic ink onto carbon supports, which are then coupled to a cation exchange membrane (Nafion) in a membrane electrode assembly. The results show that the use of smaller copper nanoparticles (25 nm) leads to a higher ethylene production (1148 μmol m-2 s-1) with a remarkable high FE (92.8%), at the same time, diminishing the competitive hydrogen evolution reaction in terms of FE. This work demonstrates the importance of nanoparticle size on reaction selectivity, which may be of help to design enhanced electrocatalytic materials for CO2 valorization to hydrocarbons.

Porous polymer monolithic columns with gold nanoparticles as an intermediate ligand for the separation of proteins in reverse phase-ion exchange mixed mode

DOE PAGES

Terborg, Lydia; Masini, Jorge C.; Lin, Michelle; ...

2014-11-04

A new approach has been developed for the preparation of mixed-mode stationary phases to separate proteins. The pore surface of monolithic poly(glycidyl methacrylate- co-ethylene dimethacrylate) capillary columns was functionalized with thiols and coated with gold nanoparticles. The final mixed mode surface chemistry was formed by attaching, in a single step, alkanethiols, mercaptoalkanoic acids, and their mixtures on the free surface of attached gold nanoparticles. Use of these mixtures allowed fine tuning of the hydrophobic/hydrophilic balance. The amount of attached gold nanoparticles according to thermal gravimetric analysis was 44.8 wt.%. This value together with results of frontal elution enabled calculation ofmore » surface coverage with the alkanethiol and mercaptoalkanoic acid ligands. Interestingly, alkanethiols coverage in a range of 4.46–4.51 molecules/nm 2 significantly exceeded that of mercaptoalkanoic acids with 2.39–2.45 molecules/nm 2. The mixed mode character of these monolithic stationary phases was for the first time demonstrated in the separations of proteins that could be achieved in the same column using gradient elution conditions typical of reverse phase (using gradient of acetonitrile in water) and ion exchange chromatographic modes (applying gradient of salt in water), respectively.« less

Non-rare earth magnetic nanoparticles

DOEpatents

Carpenter, Everett E.; Huba, Zachary J.; Carroll, Kyler J.; Farghaly, Ahmed; Khanna, Shiv N.; Qian, Meichun; Bertino, Massimo

2017-09-26

Continuous flow synthetic methods are used to make single phase magnetic metal alloy nanoparticles that do not contain rare earth metals. Soft and hard magnets made from the magnetic nanoparticles are used for a variety of purposes, e.g. in electric motors, communication devices, etc.

Aptamer-functionalized Fe3 O4 magnetic nanoparticles as a solid-phase extraction adsorbent for the selective extraction of berberine from Cortex phellodendri.

PubMed

Jiang, Ling-Feng; Chen, Bo-Cheng; Chen, Ben; Li, Xue-Jian; Liao, Hai-Lin; Zhang, Wen-Yan; Wu, Lin

2017-07-01

The extraction adsorbent was fabricated by immobilizing the highly specific recognition and binding of aptamer onto the surface of Fe 3 O 4 magnetic nanoparticles, which not only acted as recognition elements to recognize and capture the target molecule berberine from the extract of Cortex phellodendri, but also could favor the rapid separation and purification of the bound berberine by using an external magnet. The developed solid-phase extraction method in this work was useful for the selective extraction and determination of berberine in Cortex phellodendri extracts. Various conditions such as the amount of aptamer-functionalized Fe 3 O 4 magnetic nanoparticles, extraction time, temperature, pH value, Mg 2+ concentration, elution time and solvent were optimized for the solid-phase extraction of berberine. Under optimal conditions, the purity of berberine extracted from Cortex phellodendri was as high as 98.7% compared with that of 4.85% in the extract, indicating that aptamer-functionalized Fe 3 O 4 magnetic nanoparticles-based solid-phase extraction method was very effective for berberine enrichment and separation from a complex herb extract. The applicability and reliability of the developed solid-phase extraction method were demonstrated by separating berberine from nine different concentrations of one Cortex phellodendri extract. The relative recoveries of the spiked solutions of all the samples were between 95.4 and 111.3%, with relative standard deviations ranging between 0.57 and 1.85%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Versatile Methodology to Encapsulate Gold Nanoparticles in PLGA Nanoparticles Obtained by Nano-Emulsion Templating.

PubMed

Fornaguera, Cristina; Feiner-Gracia, Natàlia; Dols-Perez, Aurora; García-Celma, Maria José; Solans, Conxita

2017-05-01

Gold nanoparticles have been proved useful for many biomedical applications, specifically, for their use as advanced imaging systems. However, they usually present problems related with stability and toxicity. In the present work, gold-nanoparticles have been encapsulated in polymeric nanoparticles using a novel methodology based on nano-emulsion templating. Firstly, gold nanoparticles have been transferred from water to ethyl acetate, a solvent classified as class III by the NIH guidelines (low toxic potential). Next, the formation of nano-emulsions loaded with gold nanoparticles has been performed using a low-energy, the phase inversion composition (PIC) emulsification method, followed by solvent evaporation giving rise to polymeric nanoparticles. Using this methodology, high concentrations of gold nanoparticles (>100 pM) have been encapsulated. Increasing gold nanoparticle concentration, nano-emulsion and nanoparticle sizes increase, resulting in a decrease on the stability. It is noteworthy that the designed nanoparticles did not produce cytotoxicity neither hemolysis at the required concentration. Therefore, it can be concluded that a novel and very versatile methodology has been developed for the production of polymeric nanoparticles loaded with gold nanoparticles. Graphical Abstract Schematic representation of AuNP-loaded polymeric nanoparticles preparation from nano-emulsion templating.

Influence of Capping Ligand and Synthesis Method on Structure and Morphology of Aqueous Phase Synthesized CuInSe2 Nanoparticles

NASA Astrophysics Data System (ADS)

Ram Kumar, J.; Ananthakumar, S.; Moorthy Babu, S.

2017-01-01

A facile route to synthesize copper indium diselenide (CuInSe2) nanoparticles in aqueous medium was developed using mercaptoacetic acid (MAA) as capping agent. Two different mole ratios (5 and 10) of MAA were used to synthesize CuInSe2 nanoparticles at room temperature, as well as hydrothermal (high temperature) method. Powder x-ray diffraction analysis reveals that the nanoparticles exhibit chalcopyrite phase and the crystallinity increases with increasing the capping ratio. Raman analysis shows a strong band at 233 cm-1 due to the combination of B2 (E) modes. Broad absorption spectra were observed for the synthesized CuInSe2 nanoparticles. The effective surface capping by MAA on the nanoparticles surface was confirmed through attenuated total reflection-Fourier transform infrared spectral analysis. The thermal stability of the synthesized samples was analyzed through thermogravimetric analysis-differential scanning calorimetry. The change in morphology of the synthesized samples was analyzed through scanning electron microscope and it shows that the samples prepared at room temperature are spherical in shape, whereas hydrothermally synthesized samples were found to have nanorod- and nanoflake-like structures. Transmission electron microscope analysis further indicates larger grains for the hydrothermally prepared samples with 10 mol ratio of MAA. Comparative analyses were made for synthesizing CuInSe2 nanoparticles by two different methods to explore the role of ligand and influence of temperature.

Computational studies of adsorption in metal organic frameworks and interaction of nanoparticles in condensed phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annapureddy, HVR; Motkuri, RK; Nguyen, PTM

In this review, we describe recent efforts to systematically study nano-structured metal organic frameworks (MOFs), also known as metal organic heat carriers, with particular emphasis on their application in heating and cooling processes. We used both molecular dynamics and grand canonical Monte Carlo simulation techniques to gain a molecular-level understanding of the adsorption mechanism of gases in these porous materials. We investigated the uptake of various gases such as refrigerants R12 and R143a. We also evaluated the effects of temperature and pressure on the uptake mechanism. Our computed results compared reasonably well with available measurements from experiments, thus validating ourmore » potential models and approaches. In addition, we investigated the structural, diffusive and adsorption properties of different hydrocarbons in Ni-2(dhtp). Finally, to elucidate the mechanism of nanoparticle dispersion in condensed phases, we studied the interactions among nanoparticles in various liquids, such as n-hexane, water and methanol.« less

Nanoparticles of conjugated polymers prepared from phase-separated films of phospholipids and polymers for biomedical applications.

PubMed

Yoon, Jungju; Kwag, Jungheon; Shin, Tae Joo; Park, Joonhyuck; Lee, Yong Man; Lee, Yebin; Park, Jonghyup; Heo, Jung; Joo, Chulmin; Park, Tae Jung; Yoo, Pil J; Kim, Sungjee; Park, Juhyun

2014-07-09

Phase separation in films of phospholipids and conjugated polymers results in nanoassemblies because of a difference in the physicochemical properties between the hydrophobic polymers and the polar lipid heads, together with the comparable polymer side-chain lengths to lipid tail lengths, thus producing nanoparticles of conjugated polymers upon disassembly in aqueous media by the penetration of water into polar regions of the lipid heads. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase separation of comb polymer nanocomposite melts.

PubMed

Xu, Qinzhi; Feng, Yancong; Chen, Lan

2016-02-07

In this work, the spinodal phase demixing of branched comb polymer nanocomposite (PNC) melts is systematically investigated using the polymer reference interaction site model (PRISM) theory. To verify the reliability of the present method in characterizing the phase behavior of comb PNCs, the intermolecular correlation functions of the system for nonzero particle volume fractions are compared with our molecular dynamics simulation data. After verifying the model and discussing the structure of the comb PNCs in the dilute nanoparticle limit, the interference among the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions between the comb polymer and nanoparticles in spinodal demixing curves is analyzed and discussed in detail. The results predict two kinds of distinct phase separation behaviors. One is called classic fluid phase boundary, which is mediated by the entropic depletion attraction and contact aggregation of nanoparticles at relatively low nanoparticle-monomer attraction strength. The second demixing transition occurs at relatively high attraction strength and involves the formation of an equilibrium physical network phase with local bridging of nanoparticles. The phase boundaries are found to be sensitive to the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions. As the side chain length is fixed, the side chain number has a large effect on the phase behavior of comb PNCs; with increasing side chain number, the miscibility window first widens and then shrinks. When the side chain number is lower than a threshold value, the phase boundaries undergo a process from enlarging the miscibility window to narrowing as side chain length increases. Once the side chain number overtakes this threshold value, the phase boundary shifts towards less miscibility. With increasing nanoparticle-monomer size ratio, a crossover of particle size occurs, above which the phase separation

Kinetics of laser irradiated nanoparticles cloud

NASA Astrophysics Data System (ADS)

Mishra, S. K.; Upadhyay Kahaly, M.; Misra, Shikha

2018-02-01

A comprehensive kinetic model describing the complex kinetics of a laser irradiated nanoparticle ensemble has been developed. The absorbed laser radiation here serves dual purpose, viz., photoenhanced thermionic emission via rise in its temperature and direct photoemission of electrons. On the basis of mean charge theory along with the equations for particle (electron) and energy flux balance over the nanoparticles, the transient processes of charge/temperature evolution over its surface and mass diminution on account of the sublimation (phase change) process have been elucidated. Using this formulation phenomenon of nanoparticle charging, its temperature rise to the sublimation point, mass ablation, and cloud disintegration have been investigated; afterwards, typical timescales of disintegration, sublimation and complete evaporation in reference to a graphite nanoparticle cloud (as an illustrative case) have been parametrically investigated. Based on a numerical analysis, an adequate parameter space describing the nanoparticle operation below the sublimation temperature, in terms of laser intensity, wavelength and nanoparticle material work function, has been identified. The cloud disintegration is found to be sensitive to the nanoparticle charging through photoemission; as a consequence, it illustrates that radiation operating below the photoemission threshold causes disintegration in the phase change state, while above the threshold, it occurs with the onset of surface heating.

Optical diffraction in ordered VO2 nanoparticle arrays

NASA Astrophysics Data System (ADS)

Lopez, Rene; Feldman, Leonard; Haglund, Richard

2006-03-01

The potential of oxide electronic materials as multifunctional building blocks is one of the driving concepts of the field. In this presentation, we show how nanostructured particle arrays with long-range order can be used to modulate an optical response through exploiting the metal-insulator transition of vanadium dioxide. Arrays of VO2 nanoparticles with long-range order were fabricated by pulsed laser deposition in an arbitrary pattern defined by focused ion-beam lithography. The interaction of light with the nanoparticles is controlled by the nanoparticle size, spacing and geometrical arrangement and by switching between the metallic and semiconducting phases of VO2. In addition to the near-infrared surface plasmon response observed in previous VO2 studies, the VO2 nanoparticle arrays exhibit size-dependent optical resonances in the visible region that likewise show an enhanced optical contrast between the semiconducting and metallic phases. The collective optical response as a function of temperature gives rise to an enhanced scattering state during the evolving phase transition, while the incoherent coupling between the nanoparticles produces an order-disorder-order transition.

Structural phase analysis and photoluminescence properties of Mg-doped TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ali, T.; Ashraf, M. Anas; Ali, S. Asad; Ahmed, Ateeq; Tripathi, P.

2018-05-01

In this paper, we report the synthesis, characterization and photoluminescence properties of Mg-doped TiO2 nanoparticles (NPs). The samples were synthesized by sol-gel method and characterized using the standard analytical techniques such as X-ray diffraction (XRD), Transmission electron microscope (TEM), Energy dispersive X-ray spectroscopy (EDX), UV-visible and photoluminescence spectroscopy. The powder XRD spectra revealed that the synthesized samples are pure and crystalline in nature and showing tetragonal anatase phase of TiO2 NPs. UV-visible spectrum illustrates that an absorption edge shifts toward the visible region. This study may provide a new insight for making the nanomaterials which can be used in photocatalytic applications.

Molecular Dynamics Simulations of Cubic Phases in Pluronics Systems and Their Role in Templating Nanoparticles

NASA Astrophysics Data System (ADS)

Anderson, Joshua; Travesset, Alex; Lorenz, Chris

2007-03-01

We discuss molecular dynamics simulations aimed at predicting phase diagrams in Pluronic systems. Crystalline phases with cubic symmetries are particularly challenging to simulate. A general method that is able to obtain these phases is presented. As an example, we show our results for a system of ABA triblock polymers where each hydrophilic A block contains 10 beads and the hydrophobic block B contains 7 beads. These values match the ratio of PEO to PPO in Pluronic F127. Numerous simulation runs are carried out with differing initial conditions, which consistently produce textbook bcc and fcc lattices of micelles along with two other distorted bcc lattices. We find that the formation of a lattice is sensitive to the system's preparation and depends mainly on the kinetic temperature and equilibration time. Examination of the distorted lattices shows that they are related to the finite size of the simulation box. We conclude with some discussion on using these crystals as a template for nanoparticles or biomineralization.

Double-phase-functionalized magnetic Janus polymer microparticles containing TiO2 and Fe2O3 nanoparticles encapsulated in mussel-inspired amphiphilic polymers.

PubMed

Yabu, Hiroshi; Ohshima, Hiroyuki; Saito, Yuta

2014-10-22

Recently, anisotropic colloidal polymeric materials including Janus microparticles, which have two distinct aspects on their surfaces or interiors, have garnered much interest due to their anisotropic alignment and rotational orientation with respect to external electric or magnetic fields. Janus microparticles are also good candidates for pigments in "twisting ball type" electronic paper, which is considered promising for next-generation flexible display devices. We demonstrate here a universal strategy to encapsulate inorganic nanoparticles and to introduce different such inorganic nanoparticles into distinct polymer phases in Janus microparticles. TiO2 and Fe2O3 nanoparticles were separately encapsulated in two different mussel-inspired amphiphilic copolymers, and then organic-inorganic composite Janus microparticles were prepared by simple evaporation of solvent from the dispersion containing the polymer and nanoparticle. These Janus microparticles were observed to rotate quickly in response to applied magnetic fields.

Multifunctional silver nanoparticle-doped silica for solid-phase extraction and surface-enhanced Raman scattering detection

NASA Astrophysics Data System (ADS)

Markina, Natalia E.; Markin, Alexey V.; Zakharevich, Andrey M.; Gorin, Dmitry A.; Rusanova, Tatiana Yu.; Goryacheva, Irina Yu.

2016-12-01

Multifunctional silica gel with embedded silver nanoparticles (SiO2-AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO2-AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO2 bulk. Synthesis of AgNP directly to the SiO2 matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO3 concentration used during the SiO2-AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO2-AgNP with optimal composition was around 105. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations.

Partitioning of Nanoparticles into Organic Phases and Model Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Posner, J.D.; Westerhoff, P.; Hou, W-C.

2011-08-25

There is a recognized need to understand and predict the fate, transport and bioavailability of engineered nanoparticles (ENPs) in aquatic and soil ecosystems. Recent research focuses on either collection of empirical data (e.g., removal of a specific NP through water or soil matrices under variable experimental conditions) or precise NP characterization (e.g. size, degree of aggregation, morphology, zeta potential, purity, surface chemistry, and stability). However, it is almost impossible to transition from these precise measurements to models suitable to assess the NP behavior in the environment with complex and heterogeneous matrices. For decades, the USEPA has developed and applies basicmore » partitioning parameters (e.g., octanol-water partition coefficients) and models (e.g., EPI Suite, ECOSAR) to predict the environmental fate, bioavailability, and toxicity of organic pollutants (e.g., pesticides, hydrocarbons, etc.). In this project we have investigated the hypothesis that NP partition coefficients between water and organic phases (octanol or lipid bilayer) is highly dependent on their physiochemical properties, aggregation, and presence of natural constituents in aquatic environments (salts, natural organic matter), which may impact their partitioning into biological matrices (bioaccumulation) and human exposure (bioavailability) as well as the eventual usage in modeling the fate and bioavailability of ENPs. In this report, we use the terminology "partitioning" to operationally define the fraction of ENPs distributed among different phases. The mechanisms leading to this partitioning probably involve both chemical force interactions (hydrophobic association, hydrogen bonding, ligand exchange, etc.) and physical forces that bring the ENPs in close contact with the phase interfaces (diffusion, electrostatic interactions, mixing turbulence, etc.). Our work focuses on partitioning, but also provides insight into the relative behavior of ENPs as either

Thermodynamic analysis of a thermal storage unit under the influence of nano-particles added to the phase change material and/or the working fluid

NASA Astrophysics Data System (ADS)

Abolghasemi, Mehran; Keshavarz, Ali; Mehrabian, Mozaffar Ali

2012-11-01

The thermal storage unit consists of two concentric cylinders where the working fluid flows through the internal cylinder and the annulus is filled with a phase change material. The system carries out a cyclic operation; each cycle consists of two processes. In the charging process the hot working fluid enters the internal cylinder and transfers heat to the phase change material. In the discharging process the cold working fluid enters the internal cylinder and absorbs heat from the phase change material. The differential equations governing the heat transfer between the two media are solved numerically. The numerical results are compared with the experimental results available in the literature. The performance of an energy storage unit is directly related to the thermal conductivity of nano-particles. The energy consumption of a residential unit whose energy is supplied by a thermal storage system can be reduced by 43 % when using nano-particles.

Preparation of DPPE-Stabilized Gold Nanoparticles

ERIC Educational Resources Information Center

Dungey, Keenan E.; Muller, David P.; Gunter, Tammy

2005-01-01

An experiment is presented that introduces students to nanotechnology through the preparation of nanoparticles and their visualization using transmission electron microscopy (TEM). The experiment familiarizes the students with nonaqueous solvents, biphasic reactions, phase-transfer agents, ligands to stabilize growing nanoparticles, and bidentate…

Layered Lithium-Rich Oxide Nanoparticles Doped with Spinel Phase: Acidic Sucrose-Assistant Synthesis and Excellent Performance as Cathode of Lithium Ion Battery.

PubMed

Chen, Min; Chen, Dongrui; Liao, Youhao; Zhong, Xiaoxin; Li, Weishan; Zhang, Yuegang

2016-02-01

Nanolayered lithium-rich oxide doped with spinel phase is synthesized by acidic sucrose-assistant sol-gel combustion and evaluated as the cathode of a high-energy-density lithium ion battery. Physical characterizations indicate that the as-synthesized oxide (LR-SN) is composed of uniform and separated nanoparticles of about 200 nm, which are doped with about 7% spinel phase, compared to the large aggregated ones of the product (LR) synthesized under the same condition but without any assistance. Charge/discharge demonstrates that LR-SN exhibits excellent rate capability and cyclic stability: delivering an average discharge capacity of 246 mAh g(-1) at 0.2 C (1C = 250 mA g(-1)) and earning a capacity retention of 92% after 100 cycles at 4 C in the lithium anode-based half cell, compared to the 227 mA g(-1) and the 63% of LR, respectively. Even in the graphite anode-based full cell, LR-SN still delivers a capacity of as high as 253 mAh g(-1) at 0.1 C, corresponding to a specific energy density of 801 Wh kg(-1), which are the best among those that have been reported in the literature. The separated nanoparticles of the LR-SN provide large sites for charge transfer, while the spinel phase doped in the nanoparticles facilitates lithium ion diffusion and maintains the stability of the layered structure during cycling.

Aqueous-Phase Hydrogenolysis of Glycerol over Re Promoted Ru Catalysts Encapuslated in Porous Silica Nanoparticles

PubMed Central

Li, Kuo-Tseng; Yen, Ruey-Hsiang

2018-01-01

Activity improvement of Ru-based catalysts is needed for efficient production of valuable chemicals from glycerol hydrogenolysis. In this work, a series of Re promoted Ru catalysts encapuslated in porous silica nanoparticles (denoted as Re-Ru@SiO2) were prepared by coating silica onto the surface of chemically reduced Ru-polyvinylpyrrolidone colloids, and were used to catalyze the conversion of glycerol to diols and alcohols in water. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) were used to characterize these nanoparticles. Effects of Ru/Si atomic ratio, Re addition, glycerol and catalyst concentrations, reaction time, temperature, and hydrogen pressure were investigated. Re addition retarded the reduction of ruthenium oxide, but increased the catalyst reactivity for glycerol hydrogenolysis. Due to its greater Ru content, Re-Ru@ SiO2 showed much better activity (reacted at much lower temperature) and more yields of 1,2-propanediol and overall liquid-phase products than Re-Ru/SiO2 (prepared by conventional impregnation method) reported before. The rate of glycerol disappearance exhibited first-order dependence on glycerol concentration and hydrogen pressure, with an activation energy of 107.8 kJ/mol. The rate constant increased linearly with increasing Ru/Si atomic ratio and catalyst amount. The yield of overall liquid-phase products correlated well with glycerol conversion. PMID:29522432

Rapid microwave-assisted synthesis of sub-30nm lipid nanoparticles.

PubMed

Dunn, Stuart S; Beckford Vera, Denis R; Benhabbour, S Rahima; Parrott, Matthew C

2017-02-15

Accessing the phase inversion temperature by microwave heating may enable the rapid synthesis of small lipid nanoparticles. Nanoparticle formulations consisted of surfactants Brij 78 and Vitamin E TPGS, and trilaurin, trimyristin, or miglyol 812 as nanoparticle lipid cores. Each formulation was placed in water and heated by microwave irradiation at temperatures ranging from 65°C to 245°C. We observed a phase inversion temperature (PIT) for these formulations based on a dramatic decrease in particle Z-average diameters. Subsequently, nanoparticles were manufactured above and below the PIT and studied for (a) stability toward dilution, (b) stability over time, (c) fabrication as a function of reaction time, and (d) transmittance of lipid nanoparticle dispersions. Lipid-based nanoparticles with distinct sizes down to 20-30nm and low polydispersity could be attained by a simple, one-pot microwave synthesis. This was carried out by accessing the phase inversion temperature using microwave heating. Nanoparticles could be synthesized in just one minute and select compositions demonstrated high stability. The notable stability of these particles may be explained by the combination of van der Waals interactions and steric repulsion. 20-30nm nanoparticles were found to be optically transparent. Published by Elsevier Inc.

Laser printing of silicon nanoparticles with resonant optical electric and magnetic responses.

PubMed

Zywietz, Urs; Evlyukhin, Andrey B; Reinhardt, Carsten; Chichkov, Boris N

2014-03-04

Silicon nanoparticles with sizes of a few hundred nanometres exhibit unique optical properties due to their strong electric and magnetic dipole responses in the visible range. Here we demonstrate a novel laser printing technique for the controlled fabrication and precise deposition of silicon nanoparticles. Using femtosecond laser pulses it is possible to vary the size of Si nanoparticles and their crystallographic phase. Si nanoparticles produced by femtosecond laser printing are initially in an amorphous phase (a-Si). They can be converted into the crystalline phase (c-Si) by irradiating them with a second femtosecond laser pulse. The resonance-scattering spectrum of c-Si nanoparticles, compared with that of a-Si nanoparticles, is blue shifted and its peak intensity is about three times higher. Resonant optical responses of dielectric nanoparticles are characterized by accumulation of electromagnetic energy in the excited modes, which can be used for the realization of nanoantennas, nanolasers and metamaterials.

Formation and Stability of Pb-Sn Embedded Multiphase Alloy Nanoparticles via Mechanical Alloying

NASA Astrophysics Data System (ADS)

Khan, Patan Yousaf; Devi, M. Manolata; Biswas, Krishanu

2015-08-01

The present paper describes the preparation, characterization, and stability of Pb-Sn multiphase alloy nanoparticles embedded in Al matrix via mechanical alloying (MA). MA is a solid-state processing route, which can produce nanocrystalline phases by severely deforming the materials at high strain rate. Therefore, in order to understand the effect of the increasing interface as well as defects on the phase transformation behavior of Pb-Sn nanoparticles, Pb-Sn multiphase nanoparticles have been embedded in Al by MA. The nanoparticles have extensively been characterized using X-ray diffraction and transmission electron microscope. The characterization reveals the formation of biphasic as well as single-phase solid solution nanoparticles embedded in the matrix. The detailed microstructural and differential scanning calorimetry studies indicate that the formation of biphasic nanoparticles is due to size effect, mechanical attrition, and ballistic diffusion of Pb and Sn nanoparticles embedded in Al grains. Thermal characterization data reveal that the heating event consists of the melting peaks due to the multiphase nanoparticles and the peak positions shift to lower temperature with the increase in milling time. The role of interface structure is believed to play a prominent role in determining the phase stability of the nanoparticle. The results are discussed in the light of the existing literature.

Passive membrane penetration by ZnO nanoparticles is driven by the interplay of electrostatic and phase boundary conditions.

PubMed

Tiwari, Anuj; Prince, Ashutosh; Arakha, Manoranjan; Jha, Suman; Saleem, Mohammed

2018-02-15

The internalization of nanoparticles through the biological membrane is of immense importance for biomedical applications. A fundamental understanding of the lipid specificity and the role of the membrane biochemical and physical forces at play in modulating penetration are lacking. The current understanding of nanoparticle-membrane interaction is drawn mostly from computational studies and lacks sufficient experimental evidence. Herein, using confocal fluorescence imaging and potentiometric dye-based fluorimetry, we first investigated the interaction of ZnONP in both multi-component and individual lipid membranes using cell-like giant unilamellar vesicles to dissect the lipid specificity; also, we investigated the changes in membrane order, anisotropy and hydrophobicity. ZnONP was found to interact with phosphatidylinositol and phosphatidylcholine head-group-containing lipids specifically. We further investigated the interaction of ZnONP with three physiologically relevant membrane conditions varying in composition and dipole potential. We found that ZnONP interaction leads to a photoinduced enhancement of the partial-to-complete phase separation depending upon the membrane composition and cholesterol content. Interestingly, while the lipid order of a partially-phase-separated membrane remained unchanged upon ZnONP crowding, a fully-phase-separated membrane showed an increase in the lipid order. Strikingly, ZnONP crowding induced a contrasting effect on the fluorescence anisotropy of the membrane upon binding to the two membrane conditions, in line with the measured diffusion coefficient. ZnONP seems to preferentially penetrate through the liquid disordered areas of the membrane and the boundaries of the phase-separated regions driven by the interplay between the electrostatics and phase boundary conditions, which are collectively dictated by the composition and ZnONP-induced lipid reorganization. The results may lead to a greater understanding of the interplay of

Surface and finite size effects impact on the phase diagrams, polar, and dielectric properties of (Sr,Bi)Ta{sub 2}O{sub 9} ferroelectric nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eliseev, E. A.; Fomichov, Y. M.; Glinchuk, M. D.

2016-05-28

In the framework of the thermodynamic approach Landau-Ginzburg-Devonshire (LGD) combined with the equations of electrostatics, we investigated the effect of polarization surface screening on finite size effects of the phase diagrams, polar, and dielectric properties of ferroelectric nanoparticles of different shapes. We obtained and analyzed the analytical results for the dependences of the ferroelectric phase transition temperature, critical size, spontaneous polarization, and thermodynamic coercive field on the shape and size of the nanoparticles. The pronounced size effect of these characteristics on the scaling parameter, the ratio of the particle characteristic size to the length of the surface screening, was revealed.more » Also our modeling predicts a significant impact of the flexo-chemical effect (that is a joint action of flexoelectric effect and chemical pressure) on the temperature of phase transition, polar, and dielectric properties of nanoparticles when their chemical composition deviates from the stoichiometric one. We showed on the example of the stoichiometric nanosized SrBi{sub 2}Ta{sub 2}O{sub 9} particles that except the vicinity of the critical size, where the system splitting into domains has an important role, results of analytical calculation of the spontaneous polarization have a little difference from the numerical ones. We revealed a strong impact of the flexo-chemical effect on the phase transition temperature, polar, and dielectric properties of Sr{sub y}Bi{sub 2+x}Ta{sub 2}O{sub 9} nanoparticles when the ratio Sr/Bi deviates from the stoichiometric value of 0.5 within the range from 0.35 to 0.65. From the analysis of experimental data, we derived the parameters of the theory, namely, the coefficients of expansion of the LGD functional, the contribution of flexo-chemical effect, and the length of the surface screening.« less

Interaction of Inorganic Nanoparticles With Cell Membranes

DTIC Science & Technology

2008-10-20

the field of colloidal and biological behaviour of nanoparticles. Questions regarding the colloidal behavior of particles in biological liquids...better the behaviour of nanoparticles in living systems. 2. Research work During the preparation phase of this project we have defined following...unique knowledge of the participating researgroups in the field of colloidal and biological behaviour of nanoparticles. Questions regarding the

Structural and spectroscopic characterization of irreversible phase changes in rapidly heated precursors of europium-doped titania nanoparticles

NASA Astrophysics Data System (ADS)

Gunawidjaja, Ray; Anderson, Benjamin R.; Eilers, Hergen

2018-02-01

We observe temperature-dependent phase changes in a precursor of europium-doped titania (p-Eu:TiO2) that is prepared via precipitation and is laser-heated to temperatures between 473 K and 1246 K within sub-second heating durations. The phase changes are characterized using X-ray diffraction and site-selective photoluminescence spectroscopy. We find that upon heating, the initially amorphous p-Eu:TiO2 first transforms into the anatase phase and then into a mixed anatase/rutile phase. These phase transformations change the local environment of the dopant Eu3+ ions resulting in modifications to the Eu3+ ions spectroscopic properties, with the modifications occurring for calcination temperatures above approximately 573 K following sub-second durations. These results demonstrate the temperature sensing ability of p-Eu:TiO2 nanoparticles for use in sub-second heating events. Moreover, at 573 K this temperature is lower than other host materials that we have evaluated (i.e., La2O3, ZrO2 and Y2O3).

Prediction of binary nanoparticle superlattices from soft potentials

NASA Astrophysics Data System (ADS)

Horst, Nathan; Travesset, Alex

2016-01-01

Driven by the hypothesis that a sufficiently continuous short-ranged potential is able to account for shell flexibility and phonon modes and therefore provides a more realistic description of nanoparticle interactions than a hard sphere model, we compute the solid phase diagram of particles of different radii interacting with an inverse power law potential. From a pool of 24 candidate lattices, the free energy is optimized with respect to additional internal parameters and the p-exponent, determining the short-range properties of the potential, is varied between p = 12 and p = 6. The phase diagrams contain the phases found in ongoing self-assembly experiments, including DNA programmable self-assembly and nanoparticles with capping ligands assembled by evaporation from an organic solvent. The resulting phase diagrams can be mapped quantitatively to existing experiments as a function of only two parameters: Nanoparticle radius ratio (γ) and softness asymmetry.

Vanadium Dioxide Nanoparticle-based Thermochromic Smart Coating: High Luminous Transmittance, Excellent Solar Regulation Efficiency, and Near Room Temperature Phase Transition.

PubMed

Zhu, Jingting; Zhou, Yijie; Wang, Bingbing; Zheng, Jianyun; Ji, Shidong; Yao, Heliang; Luo, Hongjie; Jin, Ping

2015-12-23

An annealing-assisted preparation method of well-crystallized VxW1-xO2(M)@SiO2 core-shell nanoparticles for VO2-based thermochromic smart coatings (VTSC) is presented. The additional annealing process reduces the defect density of the initial hydrothermally prepared VxW1-xO2(M) nanoparticles and enhances their crystallinity so that the thermochromic film based on VxW1-xO2(M)@SiO2 nanoparticles can exhibit outstanding thermochromic performance with balanced solar regulation efficiency (ΔTsol) of 17.3%, luminous transmittance (Tlum) up to 52.2%, and critical phase transition temperature (Tc) around 40.4 °C, which is very promising for practical application. Furthermore, it makes great progress in reducing Tc of VTSC to near room temperature (25.2 °C) and simutaneously maintaining excellent optical properties (ΔTsol = 14.7% and Tlum = 50.6%). Such thermochromic performance is good enough to make VTSC applicable to practical architecture.

Preparation and characterization of a supported system of Ni2P/Ni12P5 nanoparticles and their use as the active phase in chemoselective hydrogenation of acetophenone

NASA Astrophysics Data System (ADS)

Costa, Dolly C.; Soldati, Analía L.; Pecchi, Gina; Bengoa, José Fernando; Marchetti, Sergio Gustavo; Vetere, Virginia

2018-05-01

Ni2P/Ni12P5 nanoparticles were obtained by thermal decomposition of nickel organometallic salt at low temperature. The use of different characterization techniques allowed us to determine that this process produced a mixture of two nickel phosphide phases: Ni2P and Ni12P5. These nickel phosphides nanoparticles, supported on mesoporous silica, showed activity and high selectivity for producing the hydrogenation of the acetophenone carbonyl group to obtain 1-phenylethanol. This is a first report that demonstrates the ability of supported Ni2P/Ni12P5 nanoparticles to produce the chemoselective hydrogenation of acetophenone. We attribute these special catalytic properties to the particular geometry of the Ni–P sites on the surface of the nanoparticles. This is an interesting result because the nickel phosphides have a wide composition range (from Ni3P to NiP3), with different crystallographic structures, therefore we think that different phases could be active and selective to hydrogenate many important molecules with more than one functional group.

Cobalt ferrite nanoparticles with improved aqueous colloidal stability and electrophoretic mobility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munjal, Sandeep, E-mail: drsandeepmunjal@gmail.com; Khare, Neeraj, E-mail: nkhare@physics.iitd.ernet.in

We have synthesized CoFe{sub 2}O{sub 4} (CFO) nanoparticles of size ∼ 12.2 nm by hydrothermal synthesis method. To control the size of these CFO nanoparticles, oleic acid was used as a surfactant. The inverse spinel phase of the synthesized nanoparticles was confirmed by X-ray diffraction method. As synthesized oleic acid coated CFO (OA@CFO) nanoparticles has very less electrophoretic mobility in the water and are not water dispersible. These OA@CFO nanoparticles were successfully turned into water soluble phase with a better colloidal aqueous stability, through a chemical treatment using citric acid. The modified citric acid coated CFO (CA@CFO) nanoparticles were dispersible inmore » water and form a stable aqueous solution with high electrophoretic mobility.« less

Fluorescence imaging of the nanoparticles modified with indocyanine green

NASA Astrophysics Data System (ADS)

Gareev, K. G.; Babikova, K. Y.; Postnov, V. N.; Naumisheva, E. B.; Korolev, D. V.

2017-11-01

The comparative research of silica, the magnetite and magnetite-silica nanoparticles modified with fluorescent dyes using gas-phase and liquid-phase methods was conducted. At the content of fluorescent dye comparable in size a particular spectrophotometric method, nanoparticles with fluorescein have up to 1000 times larger overall luminous efficiency. It is revealed that magnetic nanoparticles are characterized by a smaller light efficiency in comparison with silica particles, at the same time particles of a magnetite are most effective at modification with fluorescein, and magnetite-silica particles - at modification with indocyanine green.

Nanoparticle flotation collectors: mechanisms behind a new technology.

PubMed

Yang, Songtao; Pelton, Robert; Raegen, Adam; Montgomery, Miles; Dalnoki-Veress, Kari

2011-09-06

This is the first report describing a new technology where hydrophobic nanoparticles adsorb onto much larger, hydrophilic mineral particle surfaces to facilitate attachment to air bubbles in flotation. The adsorption of 46 nm cationic polystyrene nanoparticles onto 43 μm diameter glass beads, a mineral model, facilitates virtually complete removal of the beads by flotation. As little as 5% coverage of the bead surfaces with nanoparticles promotes high flotation efficiencies. The maximum force required to pull a glass bead from an air bubble interface into the aqueous phase was measured by micromechanics. The pull-off force was 1.9 μN for glass beads coated with nanoparticles, compared to 0.0086 μN for clean beads. The pull-off forces were modeled using Scheludko's classical expression. We propose that the bubble/bead contact area may not be dry (completely dewetted). Instead, for hydrophobic nanoparticles sitting on a hydrophilic surface, it is possible that only the nanoparticles penetrate the air/water interface to form a three-phase contact line. We present a new model for pull-off forces for such a wet contact patch between the bead and the air bubble. Contact angle measurements of both nanoparticle coated glass and smooth films from dissolved nanoparticles were performed to support the modeling. © 2011 American Chemical Society

Controlled functionalization of nanoparticles & practical applications

NASA Astrophysics Data System (ADS)

Rashwan, Khaled

With the increasing use of nanoparticles in both science and industry, their chemical modification became a significant part of nanotechnology. Unfortunately, most commonly used procedures provide just randomly functionalized materials. The long-term objective of our work is site- and stoichiometrically-controlled functionalization of nanoparticles with the utilization of solid supports and other nanostructures. On the examples of silica nanoparticles and titanium dioxide nanorods, we have obtained results on the solid-phase chemistry, method development, and modeling, which advanced us toward this goal. At the same time, we explored several applications of nanoparticles that will benefit from the controlled functionalization: imaging of titanium-dioxide-based photocatalysts, bioimaging by fluorescent nanoparticles, drug delivery, assembling of bone implants, and dental compositions. Titanium dioxide-based catalysts are known for their catalytic activity and their application in solar energy utilization such as photosplitting of water. Functionalization of titanium dioxide is essential for enhancing bone-titanium dioxide nanotube adhesion, and, therefore, for its application as an interface between titanium implants and bones. Controlled functionalization of nanoparticles should enhance sensitivity and selectivity of nanoassemblies for imaging and drug delivery applications. Along those lines, we studied the relationship between morphology and surface chemistry of nanoparticles, and their affinity to organic molecules (salicylic and caffeic acid) using Langmuir adsorption isotherms, and toward material surfaces using SEM- and TEM-imaging. We focused on commercial samples of titanium dioxide, titanium dioxide nanorods with and without oleic acid ligands, and differently functionalized silica nanoparticles. My work included synthesis, functionalization, and characterization of several types of nanoparticles, exploring their application in imaging, dentistry, and bone

Green synthesis of platinum nanoparticles that induce cell death and G2/M-phase cell cycle arrest in human cervical cancer cells.

PubMed

Alshatwi, Ali A; Athinarayanan, Jegan; Vaiyapuri Subbarayan, Periasamy

2015-01-01

Platinum-based chemotherapeutic drugs, including cisplatin, carboplatin, and oxaliplatin, have been used to manage cancer in spite of dose-dependent side effects, including nephrotoxicity, neurotoxicity and ototoxicity. These disadvantages have prompted the development of new strategies for cancer therapy that utilize functionalized nanoparticles as nanomedicines. In the present investigation, we have synthesized platinum nanoparticles using tea polyphenol (TPP) as both a reducing and surface modifying agent. The crystalline nature and morphology of the prepared TPP-functionalized platinum nanoparticles (TPP@Pt) were analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD results revealed that the TPP@Pt had a crystalline nature with a face-centered cubic structure. TEM imaging suggested that the TTP@Pt are flower shaped with a well-dispersed 30-60 nm-sized TPP@Pt formation. Cervical cancer cells (SiHa) were then treated with different concentrations of TPP@Pt. The effects of TPP@Pt on cell viability, nuclear morphology and cell cycle distribution were investigated. A cell viability assay revealed that the proliferation of SiHa cells was inhibited by TPP@Pt. Propidium iodide nuclear staining indicated that TPP@Pt induced nuclear fragmentation and chromatin condensation. Treatment with TPP@Pt significantly increased the percentage of cells in the G2/M phase, which indicates induced cell cycle arrest in the G2/M phase and an increased number of cells in the subG0 cell death phase. These findings highlight a potential use of TPP@Pt in cervical cancer treatment.

Micelle depletion-induced vs. micelle-mediated aggregation in nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ray, D., E-mail: debes.phys@gmail.com; Aswal, V. K.

2015-06-24

The phase behavior anionic silica nanoparticle (Ludox LS30) with non-ionic surfactants decaethylene glycol monododecylether (C12E10) and cationic dodecyltrimethyl ammonium bromide (DTAB) in aqueous electrolyte solution has been studied by small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations of nanoparticle (1 wt%), surfactants (1 wt%) and electrolyte (0.1 M NaCl). Each of these nanoparticle–surfactant systems has been examined for different contrast conditions where individual components (nanoparticle or surfactant) are made visible. It is observed that the nanoparticle-micelle system in both the cases lead to the aggregation of nanoparticles. The aggregation is found to be micelle depletion-inducedmore » for C12E10 whereas micelle-mediated aggregation for DTAB. Interestingly, it is also found that phase behavior of mixed surfactant (C12E10 + DTAB) system is similar to that of C12E10 (unlike DTAB) micelles with nanoparticles.« less

Inorganic fullerene-like nanoparticles of TiS 2

NASA Astrophysics Data System (ADS)

Margolin, Alexander; Popovitz-Biro, Ronit; Albu-Yaron, Ana; Rapoport, Lev; Tenne, Reshef

2005-08-01

Inorganic closed-cage nanoparticles of TiS 2 were synthesized using gas-phase synthesis. The reported nanoparticles are perfectly spherical with diameters centered between 60 and 80 nm, consisting from up to 80-100 concentric layers. The nucleation and growth mechanism was proposed for the formation of these nanoparticles. Tribological experiments emphasized the important role played by the spherical shape of the nanoparticles in providing rolling friction with a reduced friction coefficient and wear.

Prediction of binary nanoparticle superlattices from soft potentials

DOE PAGES

Horst, Nathan; Travesset, Alex

2016-01-07

Driven by the hypothesis that a sufficiently continuous short-ranged potential is able to account for shell flexibility and phonon modes and therefore provides a more realistic description of nanoparticle interactions than a hard sphere model, we compute the solid phase diagram of particles of different radii interacting with an inverse power law potential. From a pool of 24 candidate lattices, the free energy is optimized with respect to additional internal parameters and the p-exponent, determining the short-range properties of the potential, is varied between p = 12 and p = 6. The phase diagrams contain the phases found in ongoingmore » self-assembly experiments, including DNA programmable self-assembly and nanoparticles with capping ligands assembled by evaporation from an organic solvent. Thus, the resulting phase diagrams can be mapped quantitatively to existing experiments as a function of only two parameters: Nanoparticle radius ratio (γ) and softness asymmetry.« less

Prediction of Binary Nanoparticle Superlattices from Soft Potentials

NASA Astrophysics Data System (ADS)

Horst, Nathan; Travesset, Alex

Driven by the hypothesis that a sufficiently continuous short-ranged potential is able to account for shell flexibility and phonon modes and therefore provides a more realistic description of nanoparticle interactions than a hard sphere model, we compute the solid phase diagram of particles of different radii interacting with an inverse power law potential. We explore 24 candidate lattices where the p-exponent, determining the short-range properties of the potential, is varied between p=12 and p=6, and optimize the free energy with respect to additional internal parameters. The phase diagrams contain the phases found in ongoing self-assembly experiments, including DNA programmable self-assembly and nanoparticles with capping ligands assembled by evaporation from an organic solvent. The resulting phase diagrams can be mapped quantitatively to existing experiments as a function of only two parameters: nanoparticle radius ratio (γ) and softness asymmetry (SA). Supported by DOE under Contract Number DE-AC02-07CH11358.

Estimation of mutagenic effect and modifications of mitosis by silver nanoparticles.

PubMed

Prokhorova, I M; Kibrik, B S; Pavlov, A V; Pesnya, D S

2013-12-01

We analyzed mutagenic and mitosis-modifying effects of silver nanoparticles (Allium test). Chromosome aberrations and laggings and micronuclei were simultaneously registered in the same sample. Mitotic and phase indexes were calculated. No mutagenic effects were detected after treatment with silver nanoparticles in doses of 1.0, 2.5, 5.0, and 50 mg/liter. Silver nanoparticles in a concentration of 50 mg/liter significantly increased the mitotic index. Nanoparticles in a dose of 5 mg/liter induced slight, but significant increase in mitotic index, but did not affect the ratio of phase indexes. Exposure to silver nanoparticles in concentrations of 1.0 and 2.5 mg/liter was not followed by modification of mitosis.

Synthesis and structural characterization of CdS nanoparticles

NASA Astrophysics Data System (ADS)

Kotkata, M. F.; Masoud, A. E.; Mohamed, M. B.; Mahmoud, E. A.

2009-08-01

Amorphous CdS nanoparticles capped with cetyltrimethyl ammonium bromide (CTAB) were synthesised under various conditions using a coprecipitation method. A blue shift in the band gap was observed in the UV-visible absorption spectra indicating the formation of nanoparticles of an approximate size of 8 nm. The recorded transmission electron micrographs confirmed this result. The phase-nature, phase transformation as well as the structure of the synthesised CdS nanoparticles have been extensively characterized using X-ray diffraction (XRD), radial distribution function (RDF), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), Raman scattering (RS) and/or heat stage X-ray diffraction (HSXRD). Analysis of the obtained results revealed that the synthesised amorphous CdS nanoparticles could be transformed into CdS nanocrystals having a zinc blende or a wurtzite structure, relying on the applied heat treatment scheme. The rate of nanocrystal growth depends on the aging period, prior filtering the reacted materials, and its relation to the quality of the capping process. Five days aging period tends to enhance the stability of the grown phase with a remarkable surface stability.

Controlled assembly of nanoparticle structures: spherical and toroidal superlattices and nanoparticle-coated polymeric beads.

PubMed

Isojima, Tatsushi; Suh, Su Kyung; Vander Sande, John B; Hatton, T Alan

2009-07-21

The emulsion droplet solvent evaporation method has been used to prepare nanoclusters of monodisperse magnetite nanoparticles of varying morphologies depending on the temperature and rate of solvent evaporation and on the composition (solvent, presence of polymer, nanoparticle concentration, etc.) of the emulsion droplets. In the absence of a polymer, and with increasing solvent evaporation temperatures, the nanoparticles formed single- or multidomain crystalline superlattices, amorphous spherical aggregates, or toroidal clusters, as determined by the energetics and dynamics of the solvent evaporation process. When polymers that are incompatible with the nanoparticle coatings were included in the emulsion formulation, monolayer- and multilayer-coated polymer beads and partially coated Janus beads were prepared; the nanoparticles were expelled by the polymer as its concentration increased on evaporation of the solvent and accumulated on the surfaces of the beads in a well-ordered structure. The precise number of nanoparticle layers depended on the polymer/magnetic nanoparticle ratio in the oil droplet phase parent emulsion. The magnetic nanoparticle superstructures responded to the application of a modest magnetic field by forming regular chains with alignment of nonuniform structures (e.g., toroids and Janus beads) that are in accord with theoretical predictions and with observations in other systems.

Graphene oxide decorated with silver nanoparticles as a coating on a stainless-steel fiber for solid-phase microextraction.

PubMed

Wang, Licheng; Hou, Xiudan; Li, Jubai; Liu, Shujuan; Guo, Yong

2015-07-01

A novel graphene oxide decorated with silver nanoparticles coating on a stainless-steel fiber for solid-phase microextraction was prepared. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the coating surface and showed that silver nanoparticles were dispersed on the wrinkled graphene oxide surface. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined in the headspace solid-phase microextraction mode. The extraction parameters including adsorption time, adsorption temperature, salt concentration, desorption time and desorption temperature were investigated. Under the optimized condition, wide linearity with low limits of detection from 2 to 10 ng/L was obtained. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 10.6 and 17.5%, respectively. The enrichment factors were from 1712.5 to 4503.7, showing the fiber has good extraction abilities. Moreover, the fiber exhibited a good stability and could be reused for more than 120 times. The established method was also applied for determination of polycyclic aromatic hydrocarbons in two real water samples and the recoveries of analytes ranged from 84.4-116.3% with relative standard deviations less than 16.2%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermally stable silica-coated hydrophobic gold nanoparticles.

PubMed

Kanehara, Masayuki; Watanabe, Yuka; Teranishi, Toshiharu

2009-01-01

We have successfully developed a method for silica coating on hydrophobic dodecanethiol-protected Au nanoparticles with coating thickness ranging from 10 to 40 nm. The formation of silica-coated Au nanoparticles could be accomplished via the preparation of hydrophilic Au nanoparticle micelles by cationic surfactant encapsulation in aqueous phase, followed by hydrolysis of tetraethylorthosilicate on the hydrophilic surface of gold nanoparticle micelles. Silica-coated Au nanoparticles exhibited quite high thermal stability, that is, no agglomeration of the Au cores could be observed after annealing at 600 degrees C for 30 min. Silica-coated Au nanoparticles could serve as a template to derive hollow nanoparticles. An addition of NaCN solution to silica-coated Au nanoparticles led the formation of hollow silica nanoparticles, which were redispersible in deionized water. The formation of the hollow silica nanoparticles results from the mesoporous structures of the silica shell and such a mesoporous structure is applicable to both catalyst support and drug delivery.

Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles

NASA Astrophysics Data System (ADS)

Kazemzadeh, Farnoud; Wong, Alexander

2016-12-01

Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles.

PubMed

Kazemzadeh, Farnoud; Wong, Alexander

2016-12-13

Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm 2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

Using the Binary Phase-Field Crystal Model to Describe Non-Classical Nucleation Pathways in Gold Nanoparticles

NASA Astrophysics Data System (ADS)

Smith, Nathan; Provatas, Nikolas

Recent experimental work has shown that gold nanoparticles can precipitate from an aqueous solution through a non-classical, multi-step nucleation process. This multi-step process begins with spinodal decomposition into solute-rich and solute-poor liquid domains followed by nucleation from within the solute-rich domains. We present a binary phase-field crystal theory that shows the same phenomology and examine various cross-over regimes in the growth and coarsening of liquid and solid domains. We'd like to the thank Canada Research Chairs (CRC) program for funding this work.

Sustainable steric stabilization of colloidal titania nanoparticles

NASA Astrophysics Data System (ADS)

Elbasuney, Sherif

2017-07-01

A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180-240 °C to ensure DDSA ring opening and binding to titania nanoparticles. Organic-modified titania demonstrated complete change in surface properties from hydrophilic to hydrophobic and exhibited phase transfer from the aqueous phase to the organic phase. Exclusive surface modification in the reactor was found to be an effective approach; it demonstrated surfactant loading level 2.2 times that of post synthesis surface modification. Titania was also stabilized in aqueous media using poly acrylic acid (PAA) as polar polymeric dispersant. PAA-titania nanoparticles demonstrated a durable amorphous polymeric layer of 2 nm thickness. This

Phase behavior of confined polymer blends and nanoparticle composites

NASA Astrophysics Data System (ADS)

Chung, Hyun-Joong

We have investigated phase behavior in polymer blend films of poly(methyl methacrylate) (PMMA) and poly(styrene-ran-acrylonitrile) (SAN) with 33wt% AN content and their nanoparticle (NP) composites by using the combination of imaging techniques, including atomic force microscopy (AFM), focused-ion beam (FIB), transmission and scanning electron microscopy (TEM and SEM), as well as depth profiling techniques of Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD). For neat PMMA:SAN films, we present a novel morphology map based on pattern development mechanisms. Six distinct mechanisms are found for thickness values (d) and bulk compositions between 50-1000 nm and φPMMA = 0.3 to 0.8, respectively. When PMMA is depleted from the mid-layer by preferential wetting at φ PMMA = 0.3 (A), stable PMMA/SAN/PMMA trilayer structure is obtained. With increasing φPMMA (0.4 to 0.7), pattern development is driven by phase separation in the mid-layer, which produces circular domains (B), irregular domains (C), and bicontinuous patterns (D). Here, the growth of circular domains can be explained by the coalescence mechanism, which predicts ξ˜(sigma/eta) 1/3d2/3t1/3 , where ξ, sigma, and eta are correlation length between domains, interfacial tension between phases, and viscosity, respectively. In bicontinuous patterns, hydrodynamic pumping mechanism is suppressed with thickness confinement. When SAN composition is lean, φPMMA = 0.8 (E), the SAN phase is minority component in the mid-layer and breaks up into droplets in smooth PMMA film. When film thickness is less than 80 nm at φPMMA = 0.4 or 0.5 (F), films initially display trilayer structure, which then ruptures upon dewetting of the SAN mid-layer. Building upon the understanding of the neat PMMA:SAN blend films, we have performed the first systematic on the effect of NPs in morphology evolution and stability of polymer blend films. Whereas the location of NP impacts morphology evolution, silica

Micelle-induced depletion interaction and resultant structure in charged colloidal nanoparticle system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ray, D.; Aswal, V. K., E-mail: vkaswal@barc.gov.in; Kohlbrecher, J.

2015-04-28

The evolution of the interaction and the resultant structure in the mixed system of anionic silica nanoparticles (Ludox LS30) and non-ionic surfactant decaethylene glycol monododecylether (C12E10), undergoing phase separation, have been studied using small-angle neutron scattering and dynamic light scattering. The measurements have been carried out for a fixed concentration of nanoparticle (1 wt. %) with varying concentration of surfactant (0 to 1 wt. %), in the absence and presence of an electrolyte. It is found that the micelles of non-ionic surfactant adsorb on the nanoparticle in the absence of electrolyte (form stable system), whereas these micelles become non-adsorbing in the presence of electrolytemore » (show phase separation). The phase separation arises because of C12E10 micelles, causing depletion interaction between nanoparticles and leading to their aggregation. The interaction is modeled by double Yukawa potential accounting for attractive depletion as well as repulsive electrostatic forces. Both the interactions (attraction and repulsion) are found to be of long-range. The nanoparticle aggregation (phase separation) is governed by the increase in the magnitude and the range of the depletion attraction with the increase in the surfactant concentration. The nanoparticle aggregates formed are quite large in size (order of micron) and are characterized by the surface fractal having simple cubic packing of nanoparticles within the aggregates.« less

Enhancing heat capacity of colloidal suspension using nanoscale encapsulated phase-change materials for heat transfer.

PubMed

Hong, Yan; Ding, Shujiang; Wu, Wei; Hu, Jianjun; Voevodin, Andrey A; Gschwender, Lois; Snyder, Ed; Chow, Louis; Su, Ming

2010-06-01

This paper describes a new method to enhance the heat-transfer property of a single-phase liquid by adding encapsulated phase-change nanoparticles (nano-PCMs), which absorb thermal energy during solid-liquid phase changes. Silica-encapsulated indium nanoparticles and polymer-encapsulated paraffin (wax) nanoparticles have been made using colloid method, and suspended into poly-alpha-olefin (PAO) and water for potential high- and low-temperature applications, respectively. The shells prevent leakage and agglomeration of molten phase-change materials, and enhance the dielectric properties of indium nanoparticles. The heat-transfer coefficients of PAO containing indium nanoparticles (30% by mass) and water containing paraffin nanoparticles (10% by mass) are 1.6 and 1.75 times higher than those of corresponding single-phase fluids. The structural integrity of encapsulation allows repeated use of such nanoparticles for many cycles in high heat generating devices.

Hybrid carbon nanoparticles modified core-shell silica: a high efficiency carbon-based phase for hydrophilic interaction liquid chromatography.

PubMed

Ibrahim, Mohammed E A; Wahab, M Farooq; Lucy, Charles A

2014-04-11

Hydrophilic interaction liquid chromatography (HILIC) is a fast growing separation technique for hydrophilic and polar analytes. In this work, we combine the unique selectivity of carbon surfaces with the high efficiency of core-shell silica. First, 5 μm core-shell silica is electrostatically coated with 105 nm cationic latex bearing quaternary ammonium groups. Then 50 nm anionic carbon nanoparticles are anchored onto the surface of the latex coated core-shell silica particles to produce a hybrid carbon-silica phase. The hybrid phase shows different selectivity than ten previously classified HILIC column chemistries and 36 stationary phases. The hybrid HILIC phase has shape selectivity for positional isomeric pairs (phthalic/isophthalic and 1-naphthoic/2-naphthoic acids). Fast and high efficiency HILIC separations of biologically important carboxylates, phenols and pharmaceuticals are reported with efficiencies up to 85,000 plates m(-1). Reduced plate height of 1.9 (95,000 plates m(-1)) can be achieved. The hybrid phase is stable for at least 3 months of usage and storage under typical HILIC eluents. Copyright © 2014 Elsevier B.V. All rights reserved.

Macroscopic and tunable nanoparticle superlattices

DOE PAGES

Zhang, Honghu; Wang, Wenjie; Mallapragada, Surya; ...

2016-10-24

In this paper, we describe a robust method to assemble nanoparticles into highly ordered superlattices by inducing aqueous phase separation of neutral capping polymers. Here we demonstrate the approach with thiolated polyethylene-glycol-functionalized gold nanoparticles (PEG-AuNPs) in the presence of salts (for example, K 2CO 3) in solutions that spontaneously migrate to the liquid–vapor interface to form a Gibbs monolayer. We show that by increasing salt concentration, PEG-AuNP monolayers transform from two-dimensional (2D) gas-like to liquid-like phase and eventually, beyond a threshold concentration, to a highly ordered hexagonal structure, as characterized by surface sensitive synchrotron X-ray reflectivity and grazing incidence X-raymore » diffraction. Furthermore, the method allows control of the inplane packing in the crystalline phase by varying the K 2CO 3 and PEG-AuNPs concentrations and the length of PEG. Using polymer-brush theory, we argue that the assembly and crystallization is driven by the need to reduce surface tension between PEG and the salt solution. Our approach of taking advantage of the phase separation of PEG in salt solutions is general (i.e., can be used with any nanoparticles) leads to high-quality macroscopic and tunable crystals. In conclusion, we discuss how the method can also be applied to the design of orderly 3D structures.« less

PLGA nanoparticles from nano-emulsion templating as imaging agents: Versatile technology to obtain nanoparticles loaded with fluorescent dyes.

PubMed

Fornaguera, C; Feiner-Gracia, N; Calderó, G; García-Celma, M J; Solans, C

2016-11-01

The interest in polymeric nanoparticles as imaging systems for biomedical applications has increased notably in the last decades. In this work, PLGA nanoparticles, prepared from nano-emulsion templating, have been used to prepare novel fluorescent imaging agents. Two model fluorescent dyes were chosen and dissolved in the oil phase of the nano-emulsions together with PLGA. Nano-emulsions were prepared by the phase inversion composition (PIC) low-energy method. Fluorescent dye-loaded nanoparticles were obtained by solvent evaporation of nano-emulsion templates. PLGA nanoparticles loaded with the fluorescent dyes showed hydrodynamic radii lower than 40nm; markedly lower than those reported in previous studies. The small nanoparticle size was attributed to the nano-emulsification strategy used. PLGA nanoparticles showed negative surface charge and enough stability to be used for biomedical imaging purposes. Encapsulation efficiencies were higher than 99%, which was also attributed to the nano-emulsification approach as well as to the low solubility of the dyes in the aqueous component. Release kinetics of both fluorescent dyes from the nanoparticle dispersions was pH-independent and sustained. These results indicate that the dyes could remain encapsulated enough time to reach any organ and that the decrease of the pH produced during cell internalization by the endocytic route would not affect their release. Therefore, it can be assumed that these nanoparticles are appropriate as systemic imaging agents. In addition, in vitro toxicity tests showed that nanoparticles are non-cytotoxic. Consequently, it can be concluded that the preparation of PLGA nanoparticles from nano-emulsion templating represents a very versatile technology that enables obtaining biocompatible, biodegradable and safe imaging agents suitable for biomedical purposes. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanoparticles in Mesostructured Polymers: Stabilizations and Morphology Selection

NASA Astrophysics Data System (ADS)

Kim, Jaeup; O'Shaughnessy, Ben

2002-03-01

A major challenge in the rapidly developing field of nano-materials is finding ways to create delicate spatial arrangements of nano-sized particles. Nanostructured polymer phases and ultrathin polymer films offer potential templates to spontaneously generate this spatial organization. Here we present theory of such systems. Our conclusions are as follows. (1) Nanoparticles tending to aggregate into clusters under van der Waals attractions may be stabilized in a stretched polymer environment as offered by tethered thin film brushes or lamellar diblock phases. By extending the hydrodynamic analogy of Williams and Pincus to the real case of the end-annealed Semenov brush, we show cluster formation is strongly influenced: disc-shaped clusters are suppressed in favor of extended cylindrical forms. (2) The final morphology of extended nanoparticle aggregates depends on the polymer environment. If the nanoparticle/air/polymer surface tensions and the degree of chain stretching satisfy certain conditions, the polymer media selects the length scale of nanoparticle clusters. This offers the possibility of tuning nanoparticle aggregate morphology by suitable choice of polymeric media. Our predictions are consistent with experiments at Columbia by Levicky, Durning, Cerise and Liu demonstrating nanoparticle stabilization and morphology selection in ultrathin end-tethered polymer films.

Preparation of PbS Nanoparticles by Phase-Transfer Method and Application to Pb2+-Selective Electrode Based on PVC Membrane

PubMed Central

Song, Weihong; Wu, Chunhui; Yin, Hongzong; Liu, Xiaoyan; Sa, Panpan; Hu, Jinyang

2008-01-01

A novel approach to prepare homogeneous PbS nanoparticles by phase-transfer method was developed. The preparatory conditions were studied in detail, and the nanoparticles were characterized by transmission electron microscopy (TEM) and UV-vis spectroscopy. Then a novel lead ion-selective electrode of polyvinyl chloride (PVC) membrane based on these lead sulfide nanoparticles was prepared, and the optimum ratio of components in the membrane was determined. The results indicated that the sensor exhibited a wide concentration range of 1.0×10−5 to 1.0×10−2 mol.L−1. The response time of the electrode was about 10 s, and the optimal pH in which the electrode could be used was from 3.0 to 7.0. Selectivity coefficients indicated that the electrode was selective to the primary ion over the interfering ion. The electrode can be used for at least 3 months without any divergence in potential. It was successfully applied to directly determine lead ions in solution and used as an indicator electrode in potentiometric titration of lead ions with EDTA. PMID:19112518

Forces between functionalized silica nanoparticles in solution

NASA Astrophysics Data System (ADS)

Lane, J. Matthew D.; Ismail, Ahmed E.; Chandross, Michael; Lorenz, Christian D.; Grest, Gary S.

2009-05-01

To prevent the flocculation and phase separation of nanoparticles in solution, nanoparticles are often functionalized with short chain surfactants. Here we present fully atomistic molecular dynamics simulations which characterize how these functional coatings affect the interactions between nanoparticles and with the surrounding solvent. For 5-nm-diameter silica nanoparticles coated with poly(ethylene oxide) (PEO) oligomers in water, we determined the hydrodynamic drag on two approaching nanoparticles moving through solvent and on a single nanoparticle as it approaches a planar surface. In most circumstances, macroscale fluid theory accurately predicts the drag on these nanoscale particles. Good agreement is seen with Brenner’s analytical solutions for wall separations larger than the soft nanoparticle radius. For two approaching coated nanoparticles, the solvent-mediated (velocity independent) and lubrication (velocity-dependent) forces are purely repulsive and do not exhibit force oscillations that are typical of uncoated rigid spheres.

Phase gradient imaging for positive contrast generation to superparamagnetic iron oxide nanoparticle-labeled targets in magnetic resonance imaging.

PubMed

Zhu, Haitao; Demachi, Kazuyuki; Sekino, Masaki

2011-09-01

Positive contrast imaging methods produce enhanced signal at large magnetic field gradient in magnetic resonance imaging. Several postprocessing algorithms, such as susceptibility gradient mapping and phase gradient mapping methods, have been applied for positive contrast generation to detect the cells targeted by superparamagnetic iron oxide nanoparticles. In the phase gradient mapping methods, smoothness condition has to be satisfied to keep the phase gradient unwrapped. Moreover, there has been no discussion about the truncation artifact associated with the algorithm of differentiation that is performed in k-space by the multiplication with frequency value. In this work, phase gradient methods are discussed by considering the wrapping problem when the smoothness condition is not satisfied. A region-growing unwrapping algorithm is used in the phase gradient image to solve the problem. In order to reduce the truncation artifact, a cosine function is multiplied in the k-space to eliminate the abrupt change at the boundaries. Simulation, phantom and in vivo experimental results demonstrate that the modified phase gradient mapping methods may produce improved positive contrast effects by reducing truncation or wrapping artifacts. Copyright © 2011 Elsevier Inc. All rights reserved.

The unusual magnetism of nanoparticle LaCoO3.

PubMed

Durand, A M; Belanger, D P; Hamil, T J; Ye, F; Chi, S; Fernandez-Baca, J A; Booth, C H; Abdollahian, Y; Bhat, M

2015-05-08

Bulk and nanoparticle powders of LaCoO3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co3O4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.

The unusual magnetism of nanoparticle LaCoO 3

DOE PAGES

Durand, A. M.; Belanger, D. P.; Hamil, T. J.; ...

2015-04-15

Bulk and nanoparticle powders of LaCoO 3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T≈85K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To ≈ 40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co 3O 4 impurity phase, which induces tensile strain on the LCO lattice. A core-interfacemore » model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.« less

The unusual magnetism of nanoparticle LaCoO3

NASA Astrophysics Data System (ADS)

Durand, A. M.; Belanger, D. P.; Hamil, T. J.; Ye, F.; Chi, S.; Fernandez-Baca, J. A.; Booth, C. H.; Abdollahian, Y.; Bhat, M.

2015-05-01

Bulk and nanoparticle powders of LaCoO3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co3O4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.

Silver nanoparticle-induced degranulation observed with quantitative phase microscopy

NASA Astrophysics Data System (ADS)

Yang, Wenzhong; Lee, Seungrag; Lee, Jiyong; Bae, Yoonsung; Kim, Dugyoung

2010-07-01

Monitoring a degranulation process in a live mast cell is a quite important issue in immunology and pharmacology. Because the size of a granule is normally much smaller than the resolution limit of an optical microscope system, there is no direct real-time live cell imaging technique for observing degranulation processes except for fluorescence imaging techniques. In this research, we propose optical quantitative phase microscopy (QPM) as a new observation tool to study degranulation processes in a live mast cell without any fluorescence labeling. We measure the cell volumes and the cross sectional profiles (x-z plane) of an RBL-2H3 cell and a HeLa cell, before and after they are exposed to calcium ionophore A23187 and silver nanoparticles (AgNPs). We verify that the volume and the cross sectional line profile of the RBL-2H3 cell were changed significantly when it was exposed to A23187. When 50 μg/mL of AgNP is used instead of A23187, the measurements of cell volume and cross sectional profiles indicate that RBL-2H3 cells also follow degranulation processes. Degranulation processes for these cells are verified by monitoring the increase of intracellular calcium ([Ca2+]i) and histamine with fluorescent methods.

Dewetting-mediated pattern formation in nanoparticle assemblies

NASA Astrophysics Data System (ADS)

Stannard, Andrew

2011-03-01

The deposition of nanoparticles from solution onto solid substrates is a diverse subfield of current nanoscience research. Complex physical and chemical processes underpin the self-assembly and self-organization of colloidal nanoparticles at two-phase (solid-liquid, liquid-air) interfaces and three-phase (solid-liquid-air) contact lines. This review discusses key recent advances made in the understanding of nonequilibrium dewetting processes of nanoparticle-containing solutions, detailing how such an apparently simple experimental system can give rise to such a strikingly varied palette of two-dimensional self-organized nanoparticle array morphologies. Patterns discussed include worm-like domains, cellular networks, microscale rings, and fractal-like fingering structures. There remain many unresolved issues regarding the role of the solvent dewetting dynamics in assembly processes of this type, with a significant focus on how dewetting can be coerced to produce nanoparticle arrays with desirable characteristics such as long-range order. In addition to these topics, methods developed to control nanofluid dewetting through routes such as confining the geometries of drying solutions, depositing onto pre-patterned heterogeneous substrates, and post-dewetting pattern evolution via local or global manipulation are covered.

Dewetting-mediated pattern formation in nanoparticle assemblies.

PubMed

Stannard, Andrew

2011-03-02

The deposition of nanoparticles from solution onto solid substrates is a diverse subfield of current nanoscience research. Complex physical and chemical processes underpin the self-assembly and self-organization of colloidal nanoparticles at two-phase (solid-liquid, liquid-air) interfaces and three-phase (solid-liquid-air) contact lines. This review discusses key recent advances made in the understanding of nonequilibrium dewetting processes of nanoparticle-containing solutions, detailing how such an apparently simple experimental system can give rise to such a strikingly varied palette of two-dimensional self-organized nanoparticle array morphologies. Patterns discussed include worm-like domains, cellular networks, microscale rings, and fractal-like fingering structures. There remain many unresolved issues regarding the role of the solvent dewetting dynamics in assembly processes of this type, with a significant focus on how dewetting can be coerced to produce nanoparticle arrays with desirable characteristics such as long-range order. In addition to these topics, methods developed to control nanofluid dewetting through routes such as confining the geometries of drying solutions, depositing onto pre-patterned heterogeneous substrates, and post-dewetting pattern evolution via local or global manipulation are covered.

Nanocomposite capsules with directional, pulsed nanoparticle release.

PubMed

Udoh, Christiana E; Cabral, João T; Garbin, Valeria

2017-12-01

The precise spatiotemporal delivery of nanoparticles from polymeric capsules is required for applications ranging from medicine to materials science. These capsules derive key performance aspects from their overall shape and dimensions, porosity, and internal microstructure. To this effect, microfluidics provide an exceptional platform for emulsification and subsequent capsule formation. However, facile and robust approaches for nanocomposite capsule fabrication, exhibiting triggered nanoparticle release, remain elusive because of the complex coupling of polymer-nanoparticle phase behavior, diffusion, phase inversion, and directional solidification. We investigate a model system of polyelectrolyte sodium poly(styrene sulfonate) and 22-nm colloidal silica and demonstrate a robust capsule morphology diagram, achieving a range of internal morphologies, including nucleated and bicontinuous microstructures, as well as isotropic and non-isotropic external shapes. Upon dissolution in water, we find that capsules formed with either neat polymers or neat nanoparticles dissolve rapidly and isotropically, whereas bicontinuous, hierarchical, composite capsules dissolve via directional pulses of nanoparticle clusters without disrupting the scaffold, with time scales tunable from seconds to hours. The versatility, facile assembly, and response of these nanocomposite capsules thus show great promise in precision delivery.

The synthesis and characterization of iron nanoparticles

NASA Astrophysics Data System (ADS)

Bennett, Tyler

Nanoparticle synthesis has garnered attention for technological applications for catalysts, industrial processing, and medical applications. The size ranges for these is in the particles nanostructural domain. Pure iron nanoparticles have been of particular interest for their reactivity and relative biological inertness. Applications include cancer treatment and carrying medicine to a relevant site. Unfortunately, because of their reactivity, pure iron nanoparticles have been difficult to study. This is because of their accelerated tendency to form oxides in air, due to the increased surface area to volume ratio. Using synthesis processes with polyphenols or long chain amines, air stable iron nanoparticles have been produced with a diameter size range of ~ 2 to about ~10 nm, but apparently have transformed due to internal pressure and crystallographic defects to the FCC phase. The FCC crystals have been seen to form icosahedral and decahedral shapes. This size is within the range for use as a catalyst for the growth of both carbon nanotubes and boron nitride nanotubes as well for biomedical applications. The advantages of these kinds of catalysts are that nanotube growth can be for the first time separated from the catalyst formation. Additionally, the catalyst size can be preselected for a certain size nanotube to grow. In summary: (1) we found the size distributions of nanoparticles for various synthesis processes, (2) we discovered the right size range for growth of nanotubes from the iron nanoparticles, (3) the nanoparticles are under a very high internal pressure, (4) the nanoparticles are in the FCC phase, (5) they appear to be in icosahedral and decahedral structures, (6) they undergo room temperature twinning, (7) the FCC crystals are distorted due to carbon in octahedral sites, (8) the iron nanoparticles are stable in air, (9) adding small amounts of copper make the iron nanoparticles smaller.

In-situ high-pressure x-ray diffraction study of zinc ferrite nanoparticles

DOE PAGES

Ferrari, S.; Kumar, R. S.; Grinblat, F.; ...

2016-04-23

We have studied the high-pressure structural behavior of zinc ferrite (ZnFe 2O 4) nanoparticles by powder X-ray diffraction measurements up to 47 GPa. We found that the cubic spinel structure of ZnFe 2O 4 remains up to 33 GPa and a phase transition is induced beyond this pressure. The high-pressure phase is indexed to an orthorhombic CaMn 2O 4-type structure. Upon decompression the low- and high-pressure phases coexist. The compressibility of both structures was also investigated. We have observed that the lattice parameters of the high-pressure phase behave anisotropically upon compression. Further, we predict possible phase transition around 55 GPa.more » For comparison, we also studied the compression behavior of magnetite (Fe 3O 4) nanoparticles by X-ray diffraction up to 23 GPa. Spinel-type ZnFe 2O 4 and Fe 3O 4 nanoparticles have a bulk modulus of 172 (20) GPa and 152 (9) GPa, respectively. Lastly, this indicates that in both cases the nanoparticles do not undergo a Hall-Petch strengthening.« less

In-situ high-pressure x-ray diffraction study of zinc ferrite nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrari, S.; Kumar, R. S.; Grinblat, F.

We have studied the high-pressure structural behavior of zinc ferrite (ZnFe 2O 4) nanoparticles by powder X-ray diffraction measurements up to 47 GPa. We found that the cubic spinel structure of ZnFe 2O 4 remains up to 33 GPa and a phase transition is induced beyond this pressure. The high-pressure phase is indexed to an orthorhombic CaMn 2O 4-type structure. Upon decompression the low- and high-pressure phases coexist. The compressibility of both structures was also investigated. We have observed that the lattice parameters of the high-pressure phase behave anisotropically upon compression. Further, we predict possible phase transition around 55 GPa.more » For comparison, we also studied the compression behavior of magnetite (Fe 3O 4) nanoparticles by X-ray diffraction up to 23 GPa. Spinel-type ZnFe 2O 4 and Fe 3O 4 nanoparticles have a bulk modulus of 172 (20) GPa and 152 (9) GPa, respectively. Lastly, this indicates that in both cases the nanoparticles do not undergo a Hall-Petch strengthening.« less

Synthesis, characterization and application of noble-metal nanoparticles and their Langmuir films

NASA Astrophysics Data System (ADS)

Sun, Yuan

Noble-metal nanoparticles and their Langmuir films have attracted remarkable research interest due to their unique properties and potential applications in catalysis, hydrogen storage materials, and optical, magnetic and electronic devices. The properties of nanoparticles are affected not only by the size, but also by the shape. In this dissertation, highly crystalline rectangular palladium nanoparticles have been successfully synthesized via the reduction of K2PdCl 4 by ascorbic acid in the presence of a surfactant cetyltrimethylammonium bromide under room temperature. Trisodium citrate is a key factor for high yield of nanocubes and nanorods. The average length and aspect ratio of the nanorods can be tuned by varying the concentration of trisodium citrate. These rectangular nanoparticles were stable for months as colloids. However, after being exposed to air for about 100 days, the dry nanoparticles on TEM grids were oxidized to form shells of 1.6--3.8 nm thick covering the nanoparticle surfaces. This procedure is conducted under room temperature and requires no seed-mediated growth or nanoporous rigid template so that it is easier and more practical for large-scale synthesis. Alkanethiolate palladium nanoparticles can be synthesized by two routes: a one-phase method and a two-phase method. In order to understand the electronic and chemical properties of dodecanethiolate palladium nanoparticles, a systematic comparison between the particles obtained by these two synthetic techniques was conducted. From transmission electron microscopy (TEM) we determined that the particle sizes were 46 +/- 10 A and 20 +/- 5 A for the 1- and 2-phase particles, respectively. Electron diffraction confirmed that their structure was face-centered cubic (FCC). High-resolution TEM (HRTEM) showed that the 1-phase particles had an ordered core surrounded by a disordered shell structure while the 2-phase particles appeared to be crystalline throughout. The particles were also analyzed with

Solar light-driven photocatalysis using mixed-phase bismuth ferrite (BiFeO3/Bi25FeO40) nanoparticles for remediation of dye-contaminated water: kinetics and comparison with artificial UV and visible light-mediated photocatalysis.

PubMed

Kalikeri, Shankramma; Shetty Kodialbail, Vidya

2018-05-01

Mixed-phase bismuth ferrite (BFO) nanoparticles were prepared by co-precipitation method using potassium hydroxide as the precipitant. X-ray diffractogram (XRD) of the particles showed the formation of mixed-phase BFO nanoparticles containing BiFeO 3 /Bi 25 FeO 40 phases with the crystallite size of 70 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the formation of quasi-spherical particles. The BFO nanoparticles were uniform sized with narrow size range and with the average hydrodynamic diameter of 76 nm. The band gap energy of 2.2 eV showed its ability to absorb light even in the visible range. Water contaminated with Acid Yellow (AY-17) and Reactive Blue (RB-19) dye was treated by photocatalysis under UV, visible, and solar light irradiation using the BFO nanoparticles. The BFO nanoparticles showed maximum photocatalytical activity under solar light as compared to UV and visible irradiations, and photocatalysis was favored under acidic pH. Complete degradation of AY-17 dyes and around 95% degradation of RB-19 could be achieved under solar light at pH 5. The kinetics of degradation followed the Langmuir-Hinshelhood kinetic model showing that the heterogeneous photocatalysis is adsorption controlled. The findings of this work prove the synthesized BFO nanoparticles as promising photocatalysts for the treatment of dye-contaminated industrial wastewater.

Block copolymer directed one-pot simple synthesis of L10-phase FePt nanoparticles inside ordered mesoporous aluminosilicate/carbon composites.

PubMed

Kang, Eunae; Jung, Hyunok; Park, Je-Geun; Kwon, Seungchul; Shim, Jongmin; Sai, Hiroaki; Wiesner, Ulich; Kim, Jin Kon; Lee, Jinwoo

2011-02-22

A "one-pot" synthetic method was developed to produce L1(0)-phase FePt nanoparticles in ordered mesostructured aluminosilicate/carbon composites using polyisoprene-block-poly(ethylene oxide) (PI-b-PEO) as a structure-directing agent. PI-b-PEO block copolymers with aluminosilicate sols are self-assembled with a hydrophobic iron precursor (dimethylaminomethyl-ferrocene) and a hydrophobic platinum precursor (dimethyl(1,5-cyclooctadiene)platinum(II)) to obtain mesostructured composites. The as-synthesized material was heat-treated to 800 °C under an Ar/H(2) mixture (5% v/v), resulting in the formation of fct FePt nanocrystals encapsulated in ordered mesopores. By changing the quantities of the Fe and Pt precursors in the composite materials, the average particle size of the resulting fct FePt, estimated using the Debye-Scherer equation with X-ray diffraction patterns, can be easily controlled to be 2.6-10.4 nm. Using this simple synthetic method, we can extend the size of directly synthesized fct FePt up to ∼10 nm, which cannot be achieved directly in the colloidal synthetic method. All fct FePt nanoparticles show hysteresis behavior at room temperature, which indicates that ferromagnetic particles are obtained inside mesostructued channels. Well-isolated, ∼10 nm fct FePt have a coercivity of 1100 Oe at 300 K. This coercivity value is higher than values of fct FePt nanoparticles synthesized through the tedious hard template method by employing SBA-15 as a host material. The coercivity value for FePt-1 (2.6 nm) at 5 K is as high as 11 900 Oe, which is one of the largest values reported for FePt nanoparticles, or any other magnetic nanoparticles. The fct FePt nanoparticles also showed exchange-bias behavior.

Phase retrieval and 3D imaging in gold nanoparticles based fluorescence microscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ilovitsh, Tali; Ilovitsh, Asaf; Weiss, Aryeh M.; Meir, Rinat; Zalevsky, Zeev

2017-02-01

Optical sectioning microscopy can provide highly detailed three dimensional (3D) images of biological samples. However, it requires acquisition of many images per volume, and is therefore time consuming, and may not be suitable for live cell 3D imaging. We propose the use of the modified Gerchberg-Saxton phase retrieval algorithm to enable full 3D imaging of gold nanoparticles tagged sample using only two images. The reconstructed field is free space propagated to all other focus planes using post processing, and the 2D z-stack is merged to create a 3D image of the sample with high fidelity. Because we propose to apply the phase retrieving on nano particles, the regular ambiguities typical to the Gerchberg-Saxton algorithm, are eliminated. The proposed concept is then further enhanced also for tracking of single fluorescent particles within a three dimensional (3D) cellular environment based on image processing algorithms that can significantly increases localization accuracy of the 3D point spread function in respect to regular Gaussian fitting. All proposed concepts are validated both on simulated data as well as experimentally.

The poly-gamma-glutamate of Bacillus subtilis interacts specifically with silver nanoparticles

PubMed Central

Eymard-Vernain, Elise; Coute, Yohann; Adrait, Annie; Rabilloud, Thierry; Sarret, Géraldine

2018-01-01

For many years, silver nanoparticles, as with other antibacterial nanoparticles, have been extensively used in manufactured products. However, their fate in the environment is unclear and raises questions. We studied the fate of silver nanoparticles in the presence of bacteria under growth conditions that are similar to those found naturally in the environment (that is, bacteria in a stationary phase with low nutrient concentrations). We demonstrated that the viability and the metabolism of a gram-positive bacteria, Bacillus subtilis, exposed during the stationary phase is unaffected by 1 mg/L of silver nanoparticles. These results can be partly explained by a physical interaction of the poly-gamma-glutamate (PGA) secreted by Bacillus subtilis with the silver nanoparticles. The coating of the silver nanoparticles by the secreted PGA likely results in a loss of the bioavailability of nanoparticles and, consequently, a decrease of their biocidal effect. PMID:29813090

Characterization of exposure to silver nanoparticles in a manufacturing facility

NASA Astrophysics Data System (ADS)

Park, Junsu; Kwak, Byoung Kyu; Bae, Eunjoo; Lee, Jeongjin; Kim, Younghun; Choi, Kyunghee; Yi, Jongheop

2009-10-01

An assessment of the extent of exposure to nanomaterials in the workplace will be helpful in improving the occupational safety of workers. It is essential that the exposure data in the workplace are concerned with risk management to evaluate and reduce worker exposure. In a manufacturing facility dealing with nanomaterials, some exposure data for gas-phase reactions are available, but much less information is available regarding liquid-phase reactions. Although the potential for inhaling nanomaterials in a liquid-phase process is less than that for gas-phase, the risks of exposure during wet-chemistry processes are not negligible. In this study, we monitored and analyzed the exposure characteristics of silver nanoparticles during a liquid-phase process in a commercial production facility. Based on the measured exposure data, the source of Ag nanoparticles emitted during the production processes was indentified and a mechanism for the growth of Ag nanoparticle released is proposed. The data reported in this study could be used to establish occupational safety guidelines in the nanotechnology workplace, especially in a liquid-phase production facility.

Direct synthesis of ultrafine tetragonal BaTiO3 nanoparticles at room temperature

PubMed Central

2011-01-01

A large quantity of ultrafine tetragonal barium titanate (BaTiO3) nanoparticles is directly synthesized at room temperature. The crystalline form and grain size are checked by both X-ray diffraction and transmission electron microscopy. The results revealed that the perovskite nanoparticles as fine as 7 nm have been synthesized. The phase transition of the as-prepared nanoparticles is investigated by the temperature-dependent Raman spectrum and shows the similar tendency to that of bulk BaTiO3 materials. It is confirmed that the nanoparticles have tetragonal phase at room temperature. PMID:21781339

Tuning structural motifs and alloying of bulk immiscible Mo-Cu bimetallic nanoparticles by gas-phase synthesis

NASA Astrophysics Data System (ADS)

Krishnan, Gopi; Verheijen, Marcel A.; Ten Brink, Gert H.; Palasantzas, George; Kooi, Bart J.

2013-05-01

Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still remains a formidable challenge. Hence, we present here a general methodology for gas phase synthesis of bimetallic NPs with distinctively different structural motifs ranging at a single particle level from a fully mixed alloy to core-shell, to onion (multi-shell), and finally to a Janus/dumbbell, with the same overall particle composition. These concepts are illustrated for Mo-Cu NPs, where the precise control of the bimetallic NPs with various degrees of chemical ordering, including different shapes from spherical to cube, is achieved by tailoring the energy and thermal environment that the NPs experience during their production. The initial state of NP growth, either in the liquid or in the solid state phase, has important implications for the different structural motifs and shapes of synthesized NPs. Finally we demonstrate that we are able to tune the alloying regime, for the otherwise bulk immiscible Mo-Cu, by achieving an increase of the critical size, below which alloying occurs, closely up to an order of magnitude. It is discovered that the critical size of the NP alloy is not only affected by controlled tuning of the alloying temperature but also by the particle shape.Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still

Phase stability, ordering tendencies, and magnetism in single-phase fcc Au-Fe nanoalloys

DOE PAGES

Zhuravlev, I. A.; Barabash, S. V.; An, J. M.; ...

2017-10-01

Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but L1 0 and L1 2 orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and the configuration-dependent lattice deformation model. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phases observed in nanoparticles is reproduced, but the fully ordered L1 0 AuFe, L1 2 Au 3Fe,more » and L1 2 AuFe 3 structures are unstable in DFT. But, a tendency to form concentration waves at the corresponding [001] ordering vector is revealed in nearly-random alloys in a certain range of concentrations. Furthermore, this incipient ordering requires enrichment by Fe relative to the equiatomic composition, which may occur in the core of a nanoparticle due to the segregation of Au to the surface. Effects of magnetism on the chemical ordering are also discussed.« less

Phase stability, ordering tendencies, and magnetism in single-phase fcc Au-Fe nanoalloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuravlev, I. A.; Barabash, S. V.; An, J. M.

Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but L1 0 and L1 2 orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and the configuration-dependent lattice deformation model. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phases observed in nanoparticles is reproduced, but the fully ordered L1 0 AuFe, L1 2 Au 3Fe,more » and L1 2 AuFe 3 structures are unstable in DFT. But, a tendency to form concentration waves at the corresponding [001] ordering vector is revealed in nearly-random alloys in a certain range of concentrations. Furthermore, this incipient ordering requires enrichment by Fe relative to the equiatomic composition, which may occur in the core of a nanoparticle due to the segregation of Au to the surface. Effects of magnetism on the chemical ordering are also discussed.« less

Coercivity and Exchange Bias Study of Polycrystalline Hollow Nanoparticles

NASA Astrophysics Data System (ADS)

Bah, Mohamed Alpha

Magnetic nanoparticles (NPs) have the potential to be useful in a variety of applications such as biomedical instruments, catalysis, sensing, recording information, etc. These nanoparticles exhibit remarkably different properties compared to their bulk counter parts. Synthesis of magnetic NPs with the right morphology, phase, size and surface functionality, as well as their usage for specific applications are challenging in terms of efficiency and safety. Morphology wise, there have been numerous reports on magnetic nanoparticles where morphologies such as core/shell, hollow, solid, etc., have been explored. It has been shown that morphology affects the magnetic response. Achieving the right crystal structure with required morphology and the magnetic behavior of the nanoparticle phases determines the magnetic response of the structure. For example, in the case of core/shell NPs various ferromagnetic (FM), ferrimagnetic (FiM), and antiferromagnetic (AFM) core and shell combinations have been reported. In these cases, interesting and strikingly different features, such as unusually high spin glass transition temperature, large exchange bias, finite size effects, magnetic proximity effects, unusual trend of blocking temperature as function of average crystal size, etc., have been reported. More specifically, the morphology of core/shell nanoparticles provides added degrees of freedom compared to conventional solid magnetic nanoparticles, including variations in the size, phase and material of the core and shell of the particle, etc. which helps enhance their magnetic properties. Similar to traditional core/shell nanoparticles, inverted core/shell having a FiM or FM order above the Curie temperature (TC) of the shell has been reported where the Neel temperature (TN) is comparable with the bulk value and there is nonmonotonic dependence of the coercive field (HC) and exchange bias (HEB) on the core diameter. In addition to the core/shell morphology, nanoparticles with

Prevention of nanoparticle coalescence under high-temperature annealing.

PubMed

Mizuno, Mikihisa; Sasaki, Yuichi; Yu, Andrew C C; Inoue, Makoto

2004-12-21

An effective method of employing 3-aminopropyldimethylethoxysilane linker molecules to stabilize 4.4 nm FePt nanoparticle monolayer films on a SiO2 substrate as well as to prevent coalescence of the particles under 800 degrees C annealing is reported. As-deposited FePt nanoparticle films in chemically disordered face-centered-cubic phase transform to mostly chemically ordered L1 0 structure after annealing, while the nanoparticles are free from serious coalescence. The method may fulfill the pressing need to prevent nanoparticle coalescence under high-temperature annealing for the development of FePt nanoparticle based products, such as ultrahigh-density magnetic recording media and novel memory devices.

Integral equation theory study on the phase separation in star polymer nanocomposite melts.

PubMed

Zhao, Lei; Li, Yi-Gui; Zhong, Chongli

2007-10-21

The polymer reference interaction site model theory is used to investigate phase separation in star polymer nanocomposite melts. Two kinds of spinodal curves were obtained: classic fluid phase boundary for relatively low nanoparticle-monomer attraction strength and network phase boundary for relatively high nanoparticle-monomer attraction strength. The network phase boundaries are much more sensitive with nanoparticle-monomer attraction strength than the fluid phase boundaries. The interference among the arm number, arm length, and nanoparticle-monomer attraction strength was systematically investigated. When the arm lengths are short, the network phase boundary shows a marked shift toward less miscibility with increasing arm number. When the arm lengths are long enough, the network phase boundaries show opposite trends. There exists a crossover arm number value for star polymer nanocomposite melts, below which the network phase separation is consistent with that of chain polymer nanocomposite melts. However, the network phase separation shows qualitatively different behaviors when the arm number is larger than this value.

Controllable synthesis of iron oxide nanoparticles in porous NaCl matrix

NASA Astrophysics Data System (ADS)

Kurapov, Yury A.; E Litvin, Stanislav; Romanenko, Sergey M.; Didikin, Gennadii G.; Oranskaya, Elena I.

2017-03-01

The paper gives the results of studying the structure of porous condensates of Fe + NaCl composition, chemical and phase compositions and dimensions of nanoparticles produced from the vapor phase by EB-PVD. Iron nanoparticles at fast removal from the vacuum oxidize in air and possess significant sorption capacity relative to oxygen and moisture. At heating in air, reduction of porous condensate weight occurs right to the temperature of 650 °C, primarily, due to desorption of physically sorbed moisture. Final oxidation of Fe3O4 to Fe2O3 proceeds in the range of 380 °C-650 °C, due to the remaining fraction of physically adsorbed oxygen. At iron concentrations of up to 10-15 at%, condensate sorption capacity is markedly increased with increase of iron concentration, i.e. of the quantity of fine particles. Increase of condensation temperature is accompanied by increase of nanoparticle size, resulting in a considerable reduction of the total area of nanoparticle surface, and, hence of their sorption capacity. In addition to condensation temperature, the size and phase composition of nanoparticles can also be controlled by heat treatment of initial condensate, produced at low condensation temperatures. Magnetite nanoparticles can be transferred into stable colloid systems.

Photocatalytic characteristics of single phase Fe-doped anatase TiO{sub 2} nanoparticles sensitized with vitamin B{sub 12}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gharagozlou, Mehrnaz, E-mail: gharagozlou@icrc.ac.ir; Bayati, R.

Highlights: • Anatase TiO{sub 2}/B{sub 12} hybrid nanostructured catalyst was successfully synthesized by sol–gel technique. • The nanoparticle catalyst was doped with iron at several concentrations. • Nanoparticles were characterized in detail by XRD, Raman, TEM, EDS, and spectroscopy techniques. • The formation mechanism and role of point defects on photocatalytic properties were discussed. • A structure-property-processing correlation was established. - Abstract: We report a processing-structure-property correlation in B{sub 12}-anatase titania hybrid catalysts doped with several concentrations of iron. Our results clearly show that low-level iron doping alters structure, defect content, and photocatalytic characteristics of TiO{sub 2}. XRD and Ramanmore » studies revealed formation of a single-phase anatase TiO{sub 2} where no iron based segregation in particular iron oxide, was detected. FT-IR spectra clearly confirmed sensitization of TiO{sub 2} nanoparticles with vitamin B{sub 12}. TEM micrographs and diffraction patterns confirmed crystallization of anatase nanoparticles with a radius of 15–20 nm. Both XRD and Raman signals showed a peak shift and a peak broadening which are surmised to originate from creation of point defects, namely oxygen vacancy and titanium interstitial. The doped samples revealed a narrower band gap as compared to undoped samples. Photocatalytic activity of the samples was assessed through measuring the decomposition rate of rhodamine B. It was found that sensitization with vitamin B{sub 12} and Fe-doping significantly enhances the photocatalytic efficiency of the anatase nanoparticles. We also showed that there is an optimum Fe-doping level where the maximum photocatalytic activity is achieved. The boost of photocatalytic activity was qualitatively understood to originate from a more effective use of the light photons, formation of point defects, which enhance the charge separation, higher carrier mobility.« less

Oxygen and indocyanine green loaded phase-transition nanoparticle-mediated photo-sonodynamic cytotoxic effects on rheumatoid arthritis fibroblast-like synoviocytes.

PubMed

Tang, Qin; Cui, Jianyu; Tian, Zhonghua; Sun, Jiangchuan; Wang, Zhigang; Chang, Shufang; Zhu, Shenyin

2017-01-01

Photodynamic therapy and sonodynamic therapy are developing, minimally invasive, and site-specific modalities for cancer therapy. A combined strategy PSDT (photodynamic therapy followed by sonodynamic therapy) has been proposed in this study. Here, we aimed to develop novel biodegradable poly(DL-lactide- co -glycolic acid) phase-transition nanoparticles simultaneously loaded with oxygen and indocyanine green (OI-NPs) and to investigate the cytotoxic effects and the potential mechanisms of OI-NP-mediated PSDT on MH7A synoviocytes. The OI-NPs were prepared using a modified double emulsion method and the physicochemical properties were determined. The cellular uptake of OI-NPs was detected by confocal microscopy and flow cytometry. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assay, flow cytometry, and Hoechst 33342/propidium iodide double staining were used to determine the cytotoxic effect of OI-NP-mediated PSDT on MH7A cells. Fluorescence microscope and fluorescence microplate reader were used to detect reactive oxygen species (ROS) generation. The OI-NPs were a stable and efficient carrier to deliver oxygen and indocyanine green, and enhanced cellular uptake was observed in MH7A cells with the nanoparticles. OI-NP-mediated PSDT caused more serious cell damage and more evident cell apoptosis, compared with other groups. Furthermore, increased generation of intracellular ROS was detected in MH7A cells treated with PSDT. Interestingly, the OI-NP-mediated PSDT-induced cell viability loss was effectively rescued by pretreatment with the ROS scavenger N -acetylcysteine. Multifunctional OI-NPs were successfully developed and characterized for the combined delivery of oxygen and indocyanine green, and OI-NP-mediated PSDT would be a potential cytotoxic treatment for MH7A cells. This study may provide a novel strategy for the treatment of RA and develop a model of theranostic application through phase-transition nanoparticle-mediated PSDT in the future.

Oxygen and indocyanine green loaded phase-transition nanoparticle-mediated photo-sonodynamic cytotoxic effects on rheumatoid arthritis fibroblast-like synoviocytes

PubMed Central

Tang, Qin; Cui, Jianyu; Tian, Zhonghua; Sun, Jiangchuan; Wang, Zhigang; Chang, Shufang; Zhu, Shenyin

2017-01-01

Background Photodynamic therapy and sonodynamic therapy are developing, minimally invasive, and site-specific modalities for cancer therapy. A combined strategy PSDT (photodynamic therapy followed by sonodynamic therapy) has been proposed in this study. Here, we aimed to develop novel biodegradable poly(DL-lactide-co-glycolic acid) phase-transition nanoparticles simultaneously loaded with oxygen and indocyanine green (OI-NPs) and to investigate the cytotoxic effects and the potential mechanisms of OI-NP–mediated PSDT on MH7A synoviocytes. Methods The OI-NPs were prepared using a modified double emulsion method and the physicochemical properties were determined. The cellular uptake of OI-NPs was detected by confocal microscopy and flow cytometry. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assay, flow cytometry, and Hoechst 33342/propidium iodide double staining were used to determine the cytotoxic effect of OI-NP–mediated PSDT on MH7A cells. Fluorescence microscope and fluorescence microplate reader were used to detect reactive oxygen species (ROS) generation. Results The OI-NPs were a stable and efficient carrier to deliver oxygen and indocyanine green, and enhanced cellular uptake was observed in MH7A cells with the nanoparticles. OI-NP–mediated PSDT caused more serious cell damage and more evident cell apoptosis, compared with other groups. Furthermore, increased generation of intracellular ROS was detected in MH7A cells treated with PSDT. Interestingly, the OI-NP–mediated PSDT-induced cell viability loss was effectively rescued by pretreatment with the ROS scavenger N-acetylcysteine. Conclusion Multifunctional OI-NPs were successfully developed and characterized for the combined delivery of oxygen and indocyanine green, and OI-NP–mediated PSDT would be a potential cytotoxic treatment for MH7A cells. This study may provide a novel strategy for the treatment of RA and develop a model of theranostic application through phase

Gold nanoparticles as novel agents for cancer therapy

PubMed Central

Jain, S; Hirst, D G; O'Sullivan, J M

2012-01-01

Gold nanoparticles are emerging as promising agents for cancer therapy and are being investigated as drug carriers, photothermal agents, contrast agents and radiosensitisers. This review introduces the field of nanotechnology with a focus on recent gold nanoparticle research which has led to early-phase clinical trials. In particular, the pre-clinical evidence for gold nanoparticles as sensitisers with ionising radiation in vitro and in vivo at kilovoltage and megavoltage energies is discussed. PMID:22010024

Lipid nanoparticle interactions and assemblies

NASA Astrophysics Data System (ADS)

Preiss, Matthew Ryan

oxide nanoparticles encapsulated in the lipid bilayer, the local temperature and membrane fluidity could be observed. DLNAs were encapsulated with different sized nanoparticles and concentrations in order to observe the effect of the bilayer nanoparticles on the lipid bilayer's phase behavior and leakage. Two different sized nanoparticles were used, a 2 nm gold nanoparticle (GNP) much smaller than the thickness of the bilayer and a 4 nm GNP near the thickness of the lipid bilayer. The 2 nm GNPs were shown to affect the lipid bilayer differently than the 4 nm GNP. Specifically, the two nanoparticles altered the phase behavior and leakage differently in a temperature dependent fashion, demonstrating that embedded nanoparticle size can be used induce or inhibit bilayer leakage. A dual solvent exchange method was used to control the lipid surface composition of an iron oxide nanoparticle with a cationic lipid and a polyethylene glycol (PEG) lipid to produce lipid coated magnetic nanoparticles (LMNPs). PEG is well known for its ability to enhance the pharmacokinetics of nanostructures by preventing uptake by the immune system. By controlling the lipid surface composition, the surface charge and PEG conformation can be controlled which allowed the LMNPs to be used as an MRI contrast agent and a delivery system for siRNA that could be triggered with temperature.

Development and validation of a rapid reversed-phase HPLC method for the determination of the non-nucleoside reverse transcriptase inhibitor dapivirine from polymeric nanoparticles.

PubMed

das Neves, José; Sarmento, Bruno; Amiji, Mansoor M; Bahia, Maria Fernanda

2010-06-05

The objective of this work was to develop and validate a rapid reversed-phase (RP) high-performance liquid chromatography (HPLC) method for the in vitro pharmaceutical characterization of dapivirine-loaded polymeric nanoparticles. Chromatographic runs were performed on a RP C18 column with a mobile phase comprising acetonitrile-0.5% (w/v) triethanolamine solution in isocratic mode (80:20, v/v) at a flow rate of 1 ml/min. Dapivirine was detected at a wavelength of 290 nm. The method was shown to be specific, linear in the range of 1-50 microg/ml (R(2)=0.9998), precise at the intra-day and inter-day levels as reflected by the relative standard deviation values (less than 0.85%), accurate (recovery rate of 100.17+/-0.35%), and robust to changes in the mobile phase and column brand. The detection and quantitation limits were 0.08 and 0.24 microg/ml, respectively. The method was successfully used to determine the loading capacity and association efficiency of dapivirine in poly(lactic-co-glycolic acid)-based nanoparticles and its in vitro release. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Synthesis of Lead Sulfide Nanoparticles by Chemical Precipitation Method

NASA Astrophysics Data System (ADS)

Chongad, L. S.; Sharma, A.; Banerjee, M.; Jain, A.

2016-10-01

Lead sulfide (PbS) nanoparticles were prepared by chemical precipitation method (CPM) with the assistance of H2S gas. The microstructure and morphology of the synthesized nanoparticles have been investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns of the PbS nanoparticles reveal formation of cubic phase. To investigate the quality of prepared nanoparticles, the particles size, lattice constant, strain, dislocation density etc. have been determined using XRD. TEM images reveal formation of cubic nanoparticles and the particle size determined from TEM images agree well with those from XRD.

Two phase microstructure for Ag-Ni nanowires

NASA Astrophysics Data System (ADS)

Srivastava, Chandan; Rai, Rajesh Kumar

2013-03-01

In the present study, electrodeposition technique was used to produce Ag-Ni nanowires. Ag-Ni system shows extremely high bulk immiscibility. Nanowire morphology was achieved by employing an anodic alumina membrane having pores of ˜200 nm diameter. Microstructure of as-deposited wire was composed of nano-sized solid solution structured Ag-Ni nanoparticles embedded in a matrix of pure Ag phase. It is proposed that the two phase microstructure resulted from an initial formation of solid solution structured nanoparticles in the alumina template pore followed by nucleation of pure Ag phase over the particles which eventually grew to form the matrix phase.

Binary nanoparticle superlattices of soft-particle systems

DOE PAGES

Travesset, Alex

2015-08-04

The solid-phase diagram of binary systems consisting of particles of diameter σ A=σ and σ B=γσ (γ≤1) interacting with an inverse p = 12 power law is investigated as a paradigm of a soft potential. In addition to the diameter ratio γ that characterizes hard-sphere models, the phase diagram is a function of an additional parameter that controls the relative interaction strength between the different particle types. Phase diagrams are determined from extremes of thermodynamic functions by considering 15 candidate lattices. In general, it is shown that the phase diagram of a soft repulsive potential leads to the morphological diversitymore » observed in experiments with binary nanoparticles, thus providing a general framework to understand their phase diagrams. In addition, particular emphasis is shown to the two most successful crystallization strategies so far: evaporation of solvent from nanoparticles with grafted hydrocarbon ligands and DNA programmable self-assembly.« less

PVP capped CdS nanoparticles for UV-LED applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivaram, H.; Selvakumar, D.; Jayavel, R., E-mail: rjvel@annauniv.edu

Polyvinlypyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles are synthesized by wet chemical method. The powder X-ray diffraction (XRD) result indicates that the nanoparticles are crystallized in cubic phase. The optical properties are characterized by UV-Vis absorption. The morphology of CdS nanoparticles are studied using Scanning electron microscope (SEM). The thermal behavior of the as prepared nanoparticles has been examined by Thermo gravimetric analysis (TGA). The optical absorption study of pvp capped CdS reveal a red shift confirms the UV-LED applications.

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

NASA Astrophysics Data System (ADS)

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

2014-11-01

A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g-1 at current densities of 1, 2, 5, 10 A g-1, respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials.

Phase-controlled synthesis of α-NiS nanoparticles confined in carbon nanorods for high performance supercapacitors.

PubMed

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

2014-11-14

A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g(-1) at current densities of 1, 2, 5, 10 A g(-1), respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials.

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

PubMed Central

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

2014-01-01

A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g−1 at current densities of 1, 2, 5, 10 A g−1, respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials. PMID:25394517

Band Alignment-Driven Oxidative Injury to the Skin by Anatase/Rutile Mixed-Phase Titanium Dioxide Nanoparticles under Sunlight Exposure.

PubMed

Sun, Xiujuan; Chang, Yun; Cheng, Yan; Feng, Yanlin; Zhang, Haiyuan

2018-04-12

Anatase/rutile mixed-phase titanium dioxide (TiO2) nanoparticles (NPs) have been found in cosmetics and cotton textiles. Once exposed to sunlight, mixed-phase TiO2 NPs are even more toxic to cells than pure phase NPs, however, the underlying mechanism remains unclear. Considering the unique anatase/rutile heterojunction structure existing in mixed-phase NPs, the potent toxicity of mixed-phase TiO2 NPs probably originates from the high reactive oxygen species (ROS) production because the anatase/rutile heterojunction is constituted by the staggered energy bands that facilitate the electron-hole separation at the interface due to the band alignment. In the present study, a library of mixed-phase TiO2 NPs with different anatase/rutile ratios was established to investigate the potential property-activity relationship and further clarify the underlying molecular mechanism. Under sunlight exposure, these mixed-phase TiO2 NPs could produce significant abiotic ROS and induce hierarchical oxidative stress to HaCaT skin cells and mice skin. The ROS magnitude and toxicity potential of these NPs were found to be proportional to their energy band bending (BB) levels. This means that the toxicity of mixed-phase TiO2 NPs can be correlated to their heterojunction density, and the toxicity potential of mixed-phase TiO2 NPs can be weighed by their BB levels.

Temperature-Triggered Protein Adsorption on Polymer-Coated Nanoparticles in Serum.

PubMed

Koshkina, Olga; Lang, Thomas; Thiermann, Raphael; Docter, Dominic; Stauber, Roland H; Secker, Christian; Schlaad, Helmut; Weidner, Steffen; Mohr, Benjamin; Maskos, Michael; Bertin, Annabelle

2015-08-18

The protein corona, which forms on the nanoparticle's surface in most biological media, determines the nanoparticle's physicochemical characteristics. The formation of the protein corona has a significant impact on the biodistribution and clearance of nanoparticles in vivo. Therefore, the ability to influence the formation of the protein corona is essential to most biomedical applications, including drug delivery and imaging. In this study, we investigate the protein adsorption on nanoparticles with a hydrodynamic radius of 30 nm and a coating of thermoresponsive poly(2-isopropyl-2-oxazoline) in serum. Using multiangle dynamic light scattering (DLS) we demonstrate that heating of the nanoparticles above their phase separation temperature induces the formation of agglomerates, with a hydrodynamic radius of 1 μm. In serum, noticeably stronger agglomeration occurs at lower temperatures compared to serum-free conditions. Cryogenic transmission electron microscopy (cryo-TEM) revealed a high packing density of agglomerates when serum was not present. In contrast, in the presence of serum, agglomerated nanoparticles were loosely packed, indicating that proteins are intercalated between them. Moreover, an increase in protein content is observed upon heating, confirming that protein adsorption is induced by the alteration of the surface during phase separation. After cooling and switching the surface back, most of the agglomerates were dissolved and the main fraction returned to the original size of approximately 30 nm as shown by asymmetrical flow-field flow fractionation (AF-FFF) and DLS. Furthermore, the amounts of adsorbed proteins are similar before and after heating the nanoparticles to above their phase-separation temperature. Overall, our results demonstrate that the thermoresponsivity of the polymer coating enables turning the corona formation on nanoparticles on and off in situ. As the local heating of body areas can be easily done in vivo, the thermoresponsive

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

PubMed Central

2013-01-01

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed. PMID:24004518

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles.

PubMed

Labunov, Vladimir; Prudnikava, Alena; Bushuk, Serguei; Filatov, Serguei; Shulitski, Boris; Tay, Beng Kang; Shaman, Yury; Basaev, Alexander

2013-09-03

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed.

Curvature induced phase stability of an intensely heated liquid

NASA Astrophysics Data System (ADS)

Sasikumar, Kiran; Liang, Zhi; Cahill, David G.; Keblinski, Pawel

2014-06-01

We use non-equilibrium molecular dynamics simulations to study the heat transfer around intensely heated solid nanoparticles immersed in a model Lennard-Jones fluid. We focus our studies on the role of the nanoparticle curvature on the liquid phase stability under steady-state heating. For small nanoparticles we observe a stable liquid phase near the nanoparticle surface, which can be at a temperature well above the boiling point. Furthermore, for particles with radius smaller than a critical radius of 2 nm we do not observe formation of vapor even above the critical temperature. Instead, we report the existence of a stable fluid region with a density much larger than that of the vapor phase. We explain the stability in terms of the Laplace pressure associated with the formation of a vapor nanocavity and the associated effect on the Gibbs free energy.

Tunable photonic crystals with partial bandgaps from blue phase colloidal crystals and dielectric-doped blue phases.

PubMed

Stimulak, Mitja; Ravnik, Miha

2014-09-07

Blue phase colloidal crystals and dielectric nanoparticle/polymer doped blue phases are demonstrated to combine multiple components with different symmetries in one photonic material, creating a photonic crystal with variable and micro-controllable photonic band structure. In this composite photonic material, one contribution to the band structure is determined by the 3D periodic birefringent orientational profile of the blue phases, whereas the second contribution emerges from the regular array of the colloidal particles or from the dielectric/nanoparticle-doped defect network. Using the planewave expansion method, optical photonic bands of the blue phase I and II colloidal crystals and related nanoparticle/polymer doped blue phases are calculated, and then compared to blue phases with no particles and to face-centred-cubic and body-centred-cubic colloidal crystals in isotropic background. We find opening of local band gaps at particular points of Brillouin zone for blue phase colloidal crystals, where there were none in blue phases without particles or dopants. Particle size and filling fraction of the blue phase defect network are demonstrated as parameters that can directly tune the optical bands and local band gaps. In the blue phase I colloidal crystal with an additionally doped defect network, interestingly, we find an indirect total band gap (with the exception of one point) at the entire edge of SC irreducible zone. Finally, this work demonstrates the role of combining multiple - by symmetry - differently organised components in one photonic crystal material, which offers a novel approach towards tunable soft matter photonic materials.

Transport characteristics and colossal dielectric response of cadmium sulfide nanoparticles

NASA Astrophysics Data System (ADS)

Ahmad, Mushtaq; Rafiq, M. A.; Hasan, M. M.

2013-10-01

We report here the synthesis of ˜20 nm sized cadmium sulfide (CdS) nanoparticles via conventional solid state reaction at low temperature ˜200 °C and ambient pressure. X-ray diffraction and high resolution transmission electron microscopy analysis confirmed the synthesis of hexagonal phased nanoparticles. Impedance and electrical modulus investigations were carried out in the frequency range 20 Hz to 2 MHz and at temperature from 300 K to 400 K, which show the presence of bulk, grain boundary, and sub-grain boundary phases in CdS nanoparticles. Overlapped large polaron tunneling was the observed mechanism of charge carriers in used temperature range. The presence of colossal dielectric constant in the system is attributed to the Maxwell-Wagner type polarization. High and temperature dependent dielectric constants make the CdS nanoparticles efficient material to be used in capacitive energy storage devices.

Microwave Absorption Properties of Iron Nanoparticles Prepared by Ball-Milling

NASA Astrophysics Data System (ADS)

Chu, Xuan T. A.; Ta, Bach N.; Ngo, Le T. H.; Do, Manh H.; Nguyen, Phuc X.; Nam, Dao N. H.

2016-05-01

A nanopowder of iron was prepared using a high-energy ball milling method, which is capable of producing nanoparticles at a reasonably larger scale compared to conventional chemical methods. Analyses using x-ray diffraction and magnetic measurements indicate that the iron nanoparticles are a single phase of a body-centered cubic structure and have quite stable magnetic characteristics in the air. The iron nanoparticles were then mixed with paraffin and pressed into flat square plates for free-space microwave transmission and reflection measurements in the 4-8 GHz range. Without an Al backing plate, the Fe nanoparticles seem to only weakly absorb microwave radiation. The reflected signal S 11 drops to zero and a very large negative value of reflection loss ( RL) are observed for Al-backed samples, suggesting the existence of a phase matching resonance near frequency f ˜ 6 GHz.

Influence of chronobiology on the nanoparticle-mediated drug uptake into the brain.

PubMed

Kreuter, Jörg

2015-02-03

Little attention so-far has been paid to the influence of chronobiology on the processes of nanoparticle uptake and transport into the brain, even though this transport appears to be chronobiologically controlled to a significant degree. Nanoparticles with specific surface properties enable the transport across the blood-brain barrier of many drugs that normally cannot cross this barrier. A clear dependence of the central antinociceptive (analgesic) effects of a nanoparticle-bound model drug, i.e., the hexapeptide dalargin, on the time of day was observable after intravenous injection in mice. In addition to the strongly enhanced antinociceptive effect due to the binding to the nanoparticles, the minima and maxima of the pain reaction with the nanoparticle-bound drug were shifted by almost half a day compared to the normal circadian nociception: The maximum in the pain reaction after i.v. injection of the nanoparticle-bound dalargin occurred during the later rest phase of the animals whereas the normal pain reaction and that of a dalargin solution was highest during the active phase of the mice in the night. This important shift could be caused by an enhanced endo- and exocytotic particulates transport activity of the brain capillary endothelial cells or within the brain during the rest phase.

Modifications in structure and interaction of nanoparticle-protein-surfactant complexes in electrolyte solution

NASA Astrophysics Data System (ADS)

Mehan, Sumit; Kumar, S.; Aswal, V. K.; Schweins, R.

2016-05-01

SANS experiments of three-component system of anionic silica nanoparticles, anionic BSA protein and anionic SDS surfactants have been carried out without and with electrolyte in aqueous solution. In both the cases, the interaction of surfactant with protein results in formation of bead-necklace structure of protein-surfactant complexes in solution. These protein-surfactant complexes interact very differently with nanoparticles in absence and presence of electrolyte. In absence of electrolyte, nanoparticles remain in dispersed phase in solution, whereas with the addition of electrolyte the nanoparticles fractal aggregates are formed. SANS describes the phase behavior to be governed by competition of electrostatic and depletion interactions among the components solution.

Monitoring Nanoparticle Synthesis in a Carbon Arc Discharge Environment, In Situ

NASA Astrophysics Data System (ADS)

Mitrani, James

This work presents experimental and theoretical studies of gas-phase synthesis of fullerenes and carbon nanoparticles in the presence of an atmospheric-pressure, arc discharge plasma. Carbon arc discharges have been used for synthesizing carbon nanotubes for over 25 years, and have the potential for economically synthesizing industrial-scale quantities of fullerenes. However, the efficiency and selectivity of fullerene synthesis with carbon arc discharges are quite low. Optimizing carbon arc discharges for fullerene synthesis requires a thorough understanding of the dynamics behind gas-phase nanoparticle synthesis in the presence of an arc discharge plasma. We built a carbon arc discharge setup to study nanoparticle and fullerene synthesis. The laser-induced incandescence (LII) diagnostic was applied for monitoring nanoparticle synthesis, in situ. The LII diagnostic had previously been applied as a combustion diagnostic for in situ measurements of concentrations and sizes of soot particles in flame environments. Prior to the present study, it had never been applied for studying fullerenes, nor had it been applied to study nanoparticles in the presence of an atmospheric-pressure plasma. Therefore, experiments were designed that allowed for the calibration of the LII diagnostic with research-grade, arc-synthesized soot particles and carbon nanotubes. Additionally, the theory and models underpinning the LII diagnostic were adapted to include the presence of an atmospheric-pressure, arc-discharge plasma. Results presented in this work confirm the ability of the LII diagnostic to measure sizes of arc-synthesized nanoparticles in situ, and show the spatial location of high densities of arc-synthesized nanoparticles with respect to the arc discharge plasma. Determining the spatial location of nanoparticle synthesis and growth is crucial for understanding the background conditions (e.g. background gas temperature, electron densities ...) in which nanoparticles nucleate and

Green synthesis of NiO nanoparticles using Moringa oleifera extract and their biomedical applications: Cytotoxicity effect of nanoparticles against HT-29 cancer cells.

PubMed

Ezhilarasi, A Angel; Vijaya, J Judith; Kaviyarasu, K; Maaza, M; Ayeshamariam, A; Kennedy, L John

2016-11-01

Green protocols for the synthesis of nickel oxide nanoparticles using Moringa oleifera plant extract has been reported in the present study as they are cost effective and ecofriendly, moreover this paper records that the nickel oxide (NiO) nanoparticles prepared from green method shows better cytotoxicity and antibacterial activity. The NiO nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray analysis (EDX), and Photoluminescence spectroscopy (PL). The formation of a pure nickel oxide phase was confirmed by XRD and FTIR. The synthesized NiO nanoparticles was single crystalline having face centered cubic phase and has two intense photoluminescence emissions at 305.46nm and 410nm. The formation of nano- and micro-structures was confirmed by HRTEM. The in-vitro cytotoxicity and cell viability of human cancer cell HT-29 (Colon Carcinoma cell lines) and antibacterial studies against various bacterial strains were studied with various concentrations of nickel oxide nanoparticles prepared from Moringa oleifera plant extract. MTT assay measurements on cell viability and morphological studies proved that the synthesized NiO nanoparticles posses cytotoxic activity against human cancer cells and the various zones of inhibition (mm), obtained revealed the effective antibacterial activity of NiO nanoparticles against various Gram positive and Gram negative bacterial pathogens. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface plasmon resonances in liquid metal nanoparticles

NASA Astrophysics Data System (ADS)

Ershov, A. E.; Gerasimov, V. S.; Gavrilyuk, A. P.; Karpov, S. V.

2017-06-01

We have shown significant suppression of resonant properties of metallic nanoparticles at the surface plasmon frequency during the phase transition "solid-liquid" in the basic materials of nanoplasmonics (Ag, Au). Using experimental values of the optical constants of liquid and solid metals, we have calculated nanoparticle plasmonic absorption spectra. The effect was demonstrated for single particles, dimers and trimers, as well as for the large multiparticle colloidal aggregates. Experimental verification was performed for single Au nanoparticles heated to the melting temperature and above up to full suppression of the surface plasmon resonance. It is emphasized that this effect may underlie the nonlinear optical response of composite materials containing plasmonic nanoparticles and their aggregates.

Liquid Phase Plasma Synthesis of Iron Oxide Nanoparticles on Nitrogen-Doped Activated Carbon Resulting in Nanocomposite for Supercapacitor Applications.

PubMed

Lee, Heon; Lee, Won-June; Park, Young-Kwon; Ki, Seo Jin; Kim, Byung-Joo; Jung, Sang-Chul

2018-03-25

Iron oxide nanoparticles supported on nitrogen-doped activated carbon powder were synthesized using an innovative plasma-in-liquid method, called the liquid phase plasma (LPP) method. Nitrogen-doped carbon (NC) was prepared by a primary LPP reaction using an ammonium chloride reactant solution, and an iron oxide/NC composite (IONCC) was prepared by a secondary LPP reaction using an iron chloride reactant solution. The nitrogen component at 3.77 at. % formed uniformly over the activated carbon (AC) surface after a 1 h LPP reaction. Iron oxide nanoparticles, 40~100 nm in size, were impregnated homogeneously over the NC surface after the LPP reaction, and were identified as Fe₃O₄ by X-ray photoelectron spectroscopy and X-ray diffraction. NC and IONCCs exhibited pseudo-capacitive characteristics, and their specific capacitance and cycling stability were superior to those of bare AC. The nitrogen content on the NC surface increased the compatibility and charge transfer rate, and the composites containing iron oxide exhibited a lower equivalent series resistance.

Ni3Si(Al)/a-SiOx core shell nanoparticles: characterization, shell formation, and stability

NASA Astrophysics Data System (ADS)

Pigozzi, G.; Mukherji, D.; Gilles, R.; Barbier, B.; Kostorz, G.

2006-08-01

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni3Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni3Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiOx). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

Lattice-patterned LC-polymer composites containing various nanoparticles as additives

PubMed Central

2012-01-01

In this study, we show the effect of various nanoparticle additives on phase separation behavior of a lattice-patterned liquid crystal [LC]-polymer composite system and on interfacial properties between the LC and polymer. Lattice-patterned LC-polymer composites were fabricated by exposing to UV light a mixture of a prepolymer, an LC, and SiO2 nanoparticles positioned under a patterned photomask. This resulted in the formation of an LC and prepolymer region through phase separation. We found that the incorporation of SiO2 nanoparticles significantly affected the electro-optical properties of the lattice-patterned LC-polymer composites. This effect is a fundamental characteristic of flexible displays. The electro-optical properties depend on the size and surface functional groups of the SiO2 nanoparticles. Compared with untreated pristine SiO2 nanoparticles, which adversely affect the performance of LC molecules surrounded by polymer walls, SiO2 nanoparticles with surface functional groups were found to improve the electro-optical properties of the lattice-patterned LC-polymer composites by increasing the quantity of SiO2 nanoparticles. The surface functional groups of the SiO2 nanoparticles were closely related to the distribution of SiO2 nanoparticles in the LC-polymer composites, and they influenced the electro-optical properties of the LC molecules. It is clear from our work that the introduction of nanoparticles into a lattice-patterned LC-polymer composite provides a method for controlling and improving the composite's electro-optical properties. This technique can be used to produce flexible substrates for various flexible electronic devices. PMID:22222011

Functionalized nanoparticles based solid-phase membrane micro-tip extraction and high-performance liquid chromatography analyses of vitamin B complex in human plasma.

PubMed

Ali, Imran; Kulsum, Umma; Al-Othman, Zeid A; Alwarthan, Abdulrahman; Saleem, Kishwar

2016-07-01

Iron nanoparticles were prepared by a green method following functionalization using 1-butyl-3-methylimidazolium bromide. 1-Butyl-3-methylimidazole iron nanoparticles were characterized using FTIR spectroscopy, energy dispersive X-ray fluorescence, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The nanoparticles were used in solid-phase membrane micro-tip extraction to separate vitamin B complex from plasma before high-performance liquid chromatography. The optimum conditions obtained were sorbent (15 mg), agitation time (30 min), pH (9.0), desorbing solvent [water (5 mL) + methanol (5 mL) + sodium hydroxide (0.1 N) + acetic acid (d = 1.05 kg/L, pH 5.5), desorbing volume (10 mL) and desorption time (30 min). The percentage recoveries of all the eight vitamin B complex were from 60 to 83%. A high-performance liquid chromatography method was developed using a PhE column (250 × 4.6 mm, 5.0 μm) and water/acetonitrile (95:5, v/v; pH 4.0 with 0.1% formic acid) mobile phase. The flow rate was 1.0 mL/min with detection at 270 and 210 nm. The values of the capacity, separation and resolution factor were 0.57-39.47, 1.12-6.00 and 1.84-26.26, respectively. The developed sample preparation and chromatographic methods were fast, selective, inexpensive, economic and reproducible. The developed method can be applied for analyzing these drugs in biological and environmental matrices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-Phase Bactericidal Mechanism of Silver Nanoparticles against Burkholderia pseudomallei

PubMed Central

Hongsing, Nuttaya; Thammawithan, Saengrawee; Daduang, Sakda; Klaynongsruang, Sompong; Tuanyok, Apichai; Patramanon, Rina

2016-01-01

Silver nanoparticles (AgNPs) have a strong antimicrobial activity against a variety of pathogenic bacteria. The killing mechanism of AgNPs involves direct physical membrane destruction and subsequent molecular damage from both AgNPs and released Ag+. Burkholderia pseudomallei is the causative agent of melioidosis, an endemic infectious disease primarily found in northern Australia and Southeast Asia. B. pseudomallei is intrinsically resistant to most common antibiotics. In this study, the antimicrobial activity and mechanism of AgNPs (10–20 nm) against B. pseudomallei were investigated. The MIC and MBC for nine B. pseudomallei strains ranged from 32–48 μg/mL and 96–128 μg/mL, respectively. Concentrations of AgNPs less than 256 μg/mL were not toxic to human red blood cells. AgNPs exhibited a two-phase mechanism: cell death induction and ROS induction. The first phase was a rapid killing step within 5 min, causing the direct damage of the cytoplasmic membrane of the bacterial cells, as observed by a time-kill assay and fluorescence microscopy. During the period of 5–30 min, the cell surface charge was rapidly neutralized from -8.73 and -7.74 to 2.85 and 2.94 mV in two isolates of B. pseudomallei, as revealed by zeta potential measurement. Energy-dispersive X-ray (EDX) spectroscopy showed the silver element deposited on the bacterial membrane, and TEM micrographs of the AgNP-treated B. pseudomallei cells showed severe membrane damage and cytosolic leakage at 1/5 MIC and cell bursting at MBC. During the killing effect the released Ag+ from AgNPs was only 3.9% from the starting AgNPs concentration as observed with ICP-OES experiment. In the second phase, the ROS induction occurred 1–4 hr after the AgNP treatment. Altogether, we provide direct kinetic evidence of the AgNPs killing mechanism, by which cell death is separable from the ROS induction and AgNPs mainly contributes in the killing action. AgNPs may be considered a potential candidate to develop a

Self-assembled Lyotropic Liquid Crystalline Phase Behavior of Monoolein-Capric Acid-Phospholipid Nanoparticulate Systems.

PubMed

Zhai, Jiali; Tran, Nhiem; Sarkar, Sampa; Fong, Celesta; Mulet, Xavier; Drummond, Calum J

2017-03-14

We report here the lyotropic liquid crystalline phase behavior of two lipid nanoparticulate systems containing mixtures of monoolein, capric acid, and saturated diacyl phosphatidylcholines dispersed by the Pluronic F127 block copolymer. Synchrotron small-angle X-ray scattering (SAXS) was used to screen the phase behavior of a library of lipid nanoparticles in a high-throughput manner. It was found that adding capric acid and phosphatidylcholines had opposing effects on the spontaneous membrane curvature of the monoolein lipid layer and hence the internal mesophase of the final nanoparticles. By varying the relative concentration of the three lipid components, we were able to establish a library of nanoparticles with a wide range of mesophases including at least the inverse bicontinuous primitive and double diamond cubic phases, the inverse hexagonal phase, the fluid lamellar phase, and possibly other phases. Furthermore, the in vitro cytotoxicity assay showed that the endogenous phospholipid-containing nanoparticles were less toxic to cultured cell lines compared to monoolein-based counterparts, improving the potential of the nonlamellar lipid nanoparticles for biomedical applications.

Magnetic Properties of Nanoparticle Matrix Composites

DTIC Science & Technology

2015-06-02

recording materials with large value of Ku are SmCo5 with Ku = 11-20 x 10 7 erg/cm 3 for the minimum stable particle size of 2.45 nm, FePt with Ku...nanoparticles and the matrix compared with the bulk behavior of the soft and hard phases and ferromagnetic coupling. 15. SUBJECT TERMS...Magnetic materials , Ab initio methods, nanoparticles, Nanocomposites, Ferromagnetics 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT

Re-creation of single phase, and improvement of magnetic property of CoFe2O4 nanoparticles versus heat treatment

NASA Astrophysics Data System (ADS)

Tran, N.; Kim, D. H.; Phan, T. L.; Dang, N. T.; Bach, T. N.; Manh, D. H.; Lee, B. W.

2018-03-01

Our studies on the crystal characterization and magnetic property of CoFe2O4 nanoparticles (NPs) point out their instability in a specific temperature range. While as-prepared NPs exhibit single phase in a cubic spinel structure, annealing at temperatures T=673-1273 K leads to the development of an impurity phase of Fe2O3. Interestingly, annealing at higher temperatures re-creates the single phase of NPs. This strongly influences their magnetic property. The magnetic inhomogeneity and/or multiple phase exist in as-prepared NPs and in those annealed below 1273 K, better magnetic property is found in the samples with annealing temperature (Tan) higher than 1273 K. Ferromagnetic-paramagnetic phase transition temperatures of these samples are located around 815-850 K, and are less dependent on Tan. At room temperature, their saturation magnetization is located in the range of 41-55 emu/g, while the coercivity can be changed from 600 to 3200 Oe. These results are related to microstructures, structural phases, and exchange interactions between Fe and Co ions situated in the A and B sites of the spinel structure, which are modified by heat treatment.

Structure and magnetic properties of L10-MnGa nanoparticles prepared using direct reactions between Mn nanoparticles and Ga

NASA Astrophysics Data System (ADS)

Si, P. Z.; Qian, H. D.; Park, J.; Ge, H. L.; Shinde, K. P.; Chung, K. C.; Choi, C. J.

2018-05-01

The tetragonal L10-Mn1+xGa (x<0.8) nanoparticles and bcc-Mn23Ga77 nanoparticles with large coercivity were prepared using direct reactions between Mn nanoparticles and Ga at elevated temperatures. The Mn23Ga77 phase was formed at ˜573 K while the L10-structured Mn1+xGa was formed at ˜850 K. After ball-milling, the L10-Mn1+xGa nanoparticles transformed into nano-flakes with enhanced coercivity. The size of the as-prepared Mn23Ga77 nanoparticles is comparable to that of the precursor Mn nanoparticles. An aggregation of the nanoparticles and thus a larger particle size were observed in the L10-Mn1+xGa nanoparticles obtained at 850 K. The size of the L10-Mn1+xGa nano-flakes is reduced to about 200-400 nm with a thickness of ˜20 nm. The coercivity of the Mn23Ga77 nanoparticles and the L10-Mn1+xGa nanoparticles at 300 K reached up to 0.2 T and 0.43 T, respectively. The coercivity of L10-Mn1+xGa ball-milled nano-flakes is 0.59 T at 300 K.

Dynamics of nanoparticle-protein corona complex formation: analytical results from population balance equations.

PubMed

Darabi Sahneh, Faryad; Scoglio, Caterina; Riviere, Jim

2013-01-01

Nanoparticle-protein corona complex formation involves absorption of protein molecules onto nanoparticle surfaces in a physiological environment. Understanding the corona formation process is crucial in predicting nanoparticle behavior in biological systems, including applications of nanotoxicology and development of nano drug delivery platforms. This paper extends the modeling work in to derive a mathematical model describing the dynamics of nanoparticle corona complex formation from population balance equations. We apply nonlinear dynamics techniques to derive analytical results for the composition of nanoparticle-protein corona complex, and validate our results through numerical simulations. The model presented in this paper exhibits two phases of corona complex dynamics. In the first phase, proteins rapidly bind to the free surface of nanoparticles, leading to a metastable composition. During the second phase, continuous association and dissociation of protein molecules with nanoparticles slowly changes the composition of the corona complex. Given sufficient time, composition of the corona complex reaches an equilibrium state of stable composition. We find analytical approximate formulae for metastable and stable compositions of corona complex. Our formulae are very well-structured to clearly identify important parameters determining corona composition. The dynamics of biocorona formation constitute vital aspect of interactions between nanoparticles and living organisms. Our results further understanding of these dynamics through quantitation of experimental conditions, modeling results for in vitro systems to better predict behavior for in vivo systems. One potential application would involve a single cell culture medium related to a complex protein medium, such as blood or tissue fluid.

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications

NASA Astrophysics Data System (ADS)

Lasfargues, Mathieu; Bell, Andrew; Ding, Yulong

2016-06-01

In this study, TiO2 nanoparticles (average particle size 16 nm) were successfully produced in molten salt phase and were showed to significantly enhance the specific heat capacity of a binary eutectic mixture of sodium and potassium nitrate (60/40) by 5.4 % at 390 °C and 7.5 % at 445 °C for 3.0 wt% of precursors used. The objective of this research was to develop a cost-effective alternate method of production which is potentially scalable, as current techniques utilized are not economically viable for large quantities. Enhancing the specific heat capacity of molten salt would promote more competitive pricing for electricity production by concentrating solar power plant. Here, a simple precursor (TiOSO4) was added to a binary eutectic mixture of potassium and sodium nitrate, heated to 450 °C, and cooled to witness the production of nanoparticles.

Influence of surface-imprinted nanoparticles on trypsin activity.

PubMed

Guerreiro, António; Poma, Alessandro; Karim, Kal; Moczko, Ewa; Takarada, Jessica; de Vargas-Sansalvador, Isabel Perez; Turner, Nicholas; Piletska, Elena; de Magalhães, Cristiana Schmidt; Glazova, Natalia; Serkova, Anastasia; Omelianova, Aleksandra; Piletsky, Sergey

2014-09-01

Here, the modulation of enzyme activity is presented by protein-imprinted nanoparticles produced using a solid-phase approach. Using trypsin as target, binding of the nanoparticles to the enzyme results in its inhibition or in stabilization, depending on the orientation of the immobilized enzyme used during imprinting. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gas phase condensation of superparamagnetic iron oxide-silica nanoparticles - control of the intraparticle phase distribution

NASA Astrophysics Data System (ADS)

Stötzel, C.; Kurland, H.-D.; Grabow, J.; Müller, F. A.

2015-04-01

Spherical, softly agglomerated and superparamagnetic nanoparticles (NPs) consisting of maghemite (γ-Fe2O3) and amorphous silica (SiO2) were prepared by CO2 laser co-vaporization (CoLAVA) of hematite powder (α-Fe2O3) and quartz sand (SiO2). The α-Fe2O3 portion of the homogeneous starting mixtures was gradually increased (15 mass%-95 mass%). It was found that (i) with increasing iron oxide content the NPs' morphology changes from a nanoscale SiO2 matrix with multiple γ-Fe2O3 inclusions to Janus NPs consisting of a γ-Fe2O3 and a SiO2 hemisphere to γ-Fe2O3 NPs each carrying one small SiO2 lens on its surface, (ii) the multiple γ-Fe2O3 inclusions accumulate at the NPs' inner surfaces, and (iii) all composite NPs are covered by a thin layer of amorphous SiO2. These morphological characteristics are attributed to (i) the phase segregation of iron oxide and silica within the condensed Fe2O3-SiO2 droplets, (ii) the temperature gradient within these droplets which arises during rapid cooling in the CoLAVA process, and (iii) the significantly lower surface energy of silica when compared to iron oxide. The proposed growth mechanism of these Fe2O3-SiO2 composite NPs during gas phase condensation can be transferred to other systems comprising a glass-network former and another component that is insoluble in the regarding glass. Thus, our model will facilitate the development of novel functional composite NPs for applications in biomedicine, optics, electronics, or catalysis.Spherical, softly agglomerated and superparamagnetic nanoparticles (NPs) consisting of maghemite (γ-Fe2O3) and amorphous silica (SiO2) were prepared by CO2 laser co-vaporization (CoLAVA) of hematite powder (α-Fe2O3) and quartz sand (SiO2). The α-Fe2O3 portion of the homogeneous starting mixtures was gradually increased (15 mass%-95 mass%). It was found that (i) with increasing iron oxide content the NPs' morphology changes from a nanoscale SiO2 matrix with multiple γ-Fe2O3 inclusions to Janus NPs

Nanoparticle-Delivered Chemotherapy: Old Drugs in New Packages.

PubMed

Lee, Michael S; Dees, E Claire; Wang, Andrew Z

2017-03-15

Cytotoxic chemotherapies have a narrow therapeutic window, with high peaks and troughs of plasma concentration. Novel nanoparticle formulations of cytotoxic chemotherapy drugs can enhance pharmacokinetic characteristics and facilitate passive targeting of drugs to tumors via the enhanced permeability and retention effect, thus mitigating toxicity. Nanoparticle vehicles currently in clinical use or undergoing clinical investigation for anticancer therapies include liposomes, polymeric micelles, protein-drug nanoparticles, and dendrimers. Multiple nanoparticle formulations of existing cytotoxic chemotherapies are approved for use in several indications, with clinical data indeed showing optimization of pharmacokinetics and different toxicity profiles compared with their parent drugs. There are also many new nanoparticle drug formulations in development and undergoing early- and late-phase clinical trials, including several that utilize active targeting or triggered release based on environmental stimuli. Here, we review the rationale for nanoparticle formulations of existing or previously investigated cytotoxic drugs, describe currently approved nanoparticle formulations of drugs, and discuss some of the most promising clinical trials currently underway.

Highly bacterial resistant silver nanoparticles: synthesis and antibacterial activities

NASA Astrophysics Data System (ADS)

Chudasama, Bhupendra; Vala, Anjana K.; Andhariya, Nidhi; Mehta, R. V.; Upadhyay, R. V.

2010-06-01

In this article, we describe a simple one-pot rapid synthesis route to produce uniform silver nanoparticles by thermal reduction of AgNO3 using oleylamine as reducing and capping agent. To enhance the dispersal ability of as-synthesized hydrophobic silver nanoparticles in water, while maintaining their unique properties, a facile phase transfer mechanism has been developed using biocompatible block co-polymer pluronic F-127. Formation of silver nanoparticles is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis spectroscopy. Hydrodynamic size and its distribution are obtained from dynamic light scattering (DLS). Hydrodynamic size and size distribution of as-synthesized and phase transferred silver nanoparticles are 8.2 ± 1.5 nm (σ = 18.3%) and 31.1 ± 4.5 nm (σ = 14.5%), respectively. Antimicrobial activities of hydrophilic silver nanoparticles is tested against two Gram positive ( Bacillus megaterium and Staphylococcus aureus), and three Gram negative ( Escherichia coli, Proteus vulgaris and Shigella sonnei) bacteria. Minimum inhibitory concentration (MIC) values obtained in the present study for the tested microorganisms are found much better than those reported for commercially available antibacterial agents.

Nanoparticle formation after nanosecond-laser irradiation of thin gold films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ratautas, Karolis; Gedvilas, Mindaugas; Raciukaitis, Gediminas

2012-07-01

Evolution in nanoparticle formation was observed after nanosecond-laser irradiation of thin gold films on a silicon substrate and physical phenomena leading to the formation of nanoparticles were studied. Gold films of different thickness (3, 5, 10, 15, 20, and 25 nm) were evaporated on the silicon (110) substrate and irradiated with the pulsed nanosecond laser using different pulse energies and the number of pulses in a burst. Experimentally morphological changes appeared in the films only when the pulse energy was high enough to initiate the phase transition. The threshold energy density for phase transitions in the films was estimated frommore » the thermal model of the laser beam and sample interaction. With the pulse energy just above the threshold, it was possible to observe evolution of nanoparticle formation from a plane metal film by changing the number of pulses applied, as duration of the pulse burst represented the time how long the liquid phase existed. The final size of nanoparticles was a function of the film thickness and was found to be independent of the pulse energy and the number of pulses.« less

Memory effects in annealed hybrid gold nanoparticles/block copolymer bilayers

PubMed Central

2011-01-01

We report on the use of the self-organization process of sputtered gold nanoparticles on a self-assembled block copolymer film deposited by horizontal precipitation Langmuir-Blodgett (HP-LB) method. The morphology and the phase-separation of a film of poly-n-butylacrylate-block-polyacrylic acid (PnBuA-b-PAA) were studied at the nanometric scale by using atomic force microscopy (AFM) and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The templating capability of the PnBuA-b-PAA phase-separated film was studied by sputtering gold nanoparticles (NPs), forming a film of nanometric thickness. The effect of the polymer chain mobility onto the organization of gold nanoparticle layer was assessed by heating the obtained hybrid PnBuA-b-PAA/Au NPs bilayer at T >Tg. The nanoparticles' distribution onto the different copolymer domains was found strongly affected by the annealing treatment, showing a peculiar memory effect, which modifies the AFM phase response of the Au NPs layer onto the polar domains, without affecting their surfacial composition. The effect is discussed in terms of the peculiar morphological features induced by enhanced mobility of polymer chains on the Au NPs layer. PMID:21711674

Selective transformations between nanoparticle superlattices via the reprogramming of DNA-mediated interactions

DOE PAGES

Zhang, Yugang; Pal, Suchetan; Srinivasan, Babji; ...

2015-05-25

The rapid development of self-assembly approaches has enabled the creation of materials with desired organization of nanoscale components. However, achieving dynamic control, wherein the system can be transformed on demand into multiple entirely different states, is typically absent in atomic and molecular systems and has remained elusive in designed nanoparticle systems. Here, we demonstrate with in situ small-angle x-ray scattering that, by using DNA strands as inputs, the structure of a three-dimensional lattice of DNA-coated nanoparticles can be switched from an initial 'mother' phase into one of multiple 'daughter' phases. The introduction of different types of re-programming DNA strands modifiesmore » the DNA shells of the nanoparticles within the superlattice, thereby shifting interparticle interactions to drive the transformation into a particular daughter phase. We mapped quantitatively with free-energy calculations the selective re-programming of interactions onto the observed daughter phases.« less

Gas chromatographic detection of some nitro explosive compounds in soil samples after solid-phase microextraction with carbon ceramic copper nanoparticle fibers.

PubMed

Farhadi, Khalil; Bochani, Shayesteh; Hatami, Mehdi; Molaei, Rahim; Pirkharrati, Hossein

2014-07-01

In this research, a new solid-phase microextraction fiber based on carbon ceramic composites with copper nanoparticles followed by gas chromatography with flame ionization detection was applied for the extraction and determination of some nitro explosive compounds in soil samples. The proposed method provides an overview of trends related to synthesis of solid-phase microextraction sorbents and their applications in preconcentration and determination of nitro explosives. The sorbents were prepared by mixing of copper nanoparticles with a ceramic composite produced by mixture of methyltrimethoxysilane, graphite, methanol, and hydrochloric acid. The prepared sorbents were coated on copper wires by dip-coating method. The prepared nanocomposites were evaluated statistically and provided better limits of detection than the pure carbon ceramic. The limit of detection of the proposed method was 0.6 μg/g with a linear response over the concentration range of 2-160 μg/g and square of correlation coefficient >0.992. The new proposed fiber has been demonstrated to be a suitable, inexpensive, and sensitive candidate for extraction of nitro explosive compounds in contaminated soil samples. The constructed fiber can be used more than 100 times without the need for surface generation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Haloing in bimodal magnetic colloids: The role of field-induced phase separation

NASA Astrophysics Data System (ADS)

Magnet, C.; Kuzhir, P.; Bossis, G.; Meunier, A.; Suloeva, L.; Zubarev, A.

2012-07-01

If a suspension of magnetic micrometer-sized and nanosized particles is subjected to a homogeneous magnetic field, the nanoparticles are attracted to the microparticles and form thick anisotropic halos (clouds) around them. Such clouds can hinder the approach of microparticles and result in effective repulsion between them [M. T. López-López, A. Yu. Zubarev, and G. Bossis, Soft Matter10.1039/c0sm00261e 6, 4346 (2010)]. In this paper, we present detailed experimental and theoretical studies of nanoparticle concentration profiles and of the equilibrium shapes of nanoparticle clouds around a single magnetized microsphere, taking into account interactions between nanoparticles. We show that at a strong enough magnetic field, the ensemble of nanoparticles experiences a gas-liquid phase transition such that a dense liquid phase is condensed around the magnetic poles of a microsphere while a dilute gas phase occupies the rest of the suspension volume. Nanoparticle accumulation around a microsphere is governed by two dimensionless parameters—the initial nanoparticle concentration (φ0) and the magnetic-to-thermal energy ratio (α)—and the three accumulation regimes are mapped onto a α-φ0 phase diagram. Our local thermodynamic equilibrium approach gives a semiquantitative agreement with the experiments on the equilibrium shapes of nanoparticle clouds. The results of this work could be useful for the development of the bimodal magnetorheological fluids and of the magnetic separation technologies used in bioanalysis and water purification systems.

Switchable Pickering Emulsions Stabilized by Awakened TiO2 Nanoparticle Emulsifiers Using UV/Dark Actuation.

PubMed

Zhang, Qing; Bai, Rui-Xue; Guo, Ting; Meng, Tao

2015-08-26

In this work, switchable Pickering emulsions that utilize UV/dark manipulation employ a type of smart TiO2 nanoparticle as emulsifiers. The emulsifiers can be awakened when needed via UV-induced degradation of grafted silanes on TiO2 nanoparticles. By tuning the surface wettability of TiO2 nanoparticles in situ via UV/dark actuation, emulsions stabilized by the nanoparticles can be reversibly switched between the water-in-oil (W/O) type and oil-in-water (O/W) type for several cycles. Due to the convertible wettability, the smart nanoparticle emulsifiers can be settled in either the oil phase or the water phase as desired during phase separation, making it convenient for recycling. The present work provides a facile and noninvasive method to freely manipulate the formation, breakage, and switching of the emulsion; this method has promising potential as a powerful technique for use in energy-efficient and environmentally friendly industries.

Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Jaspal, E-mail: jaspal0314@gmail.com; Vashihth, A.; Gill, Pritampal Singh

Zn{sub 1-x}Mg{sub x}O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could bemore » attributed to decrease of oxygen vacancies present in host nanoparticles.« less

Ni(3)Si(Al)/a-SiO(x) core-shell nanoparticles: characterization, shell formation, and stability.

PubMed

Pigozzi, G; Mukherji, D; Gilles, R; Barbier, B; Kostorz, G

2006-08-28

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni(3)Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni(3)Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiO(x)). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

Interferometric detection of nanoparticles

NASA Astrophysics Data System (ADS)

Hayrapetyan, Karen

Interferometric surfaces enhance light scattering from nanoparticles through constructive interference of partial scattered waves. By placing the nanoparticles on interferometric surfaces tuned to a special surface phase interferometric condition, the particles are detectable in the dilute limit through interferometric image contrast in a heterodyne light scattering configuration, or through diffraction in a homodyne scattering configuration. The interferometric enhancement has applications for imaging and diffractive biosensors. We present a modified model based on Double Interaction (DI) to explore bead-based detection mechanisms using imaging, scanning and diffraction. The application goal of this work is to explore the trade-offs between the sensitivity and throughput among various detection methods. Experimentally we use thermal oxide on silicon to establish and control surface interferometric conditions. Surface-captured gold beads are detected using Molecular Interferometric Imaging (MI2) and Spinning-Disc Interferometry (SDI). Double-resonant enhancement of light scattering leads to high-contrast detection of 100 nm radius gold nanoparticles on an interferometric surface. The double-resonance condition is achieved when resonance (or anti-resonance) from an asymmetric Fabry-Perot substrate coincides with the Mie resonance of the gold nanoparticle. The double-resonance condition is observed experimentally using molecular interferometric imaging (MI2). An invisibility condition is identified for which the gold nanoparticles are optically cloaked by the interferometric surface.

Nanoparticles with photoinduced precipitation for the extraction of pollutants from water and soil

NASA Astrophysics Data System (ADS)

Brandl, Ferdinand; Bertrand, Nicolas; Lima, Eliana Martins; Langer, Robert

2015-07-01

Nanotechnology may offer fast and effective solutions for environmental clean-up. Herein, amphiphilic diblock copolymers are used to develop a platform of photosensitive core-shell nanoparticles. Irradiation with ultraviolet light removes the protective layer responsible for colloidal stability; as a result, the nanoparticles are rapidly and irreversibly converted to macroscopic aggregates. The associated phase separation allows measuring the partitioning of small molecules between the aqueous phase and nanoparticles; data suggests that interactions are enhanced by decreasing the particle size. Adsorption onto nanoparticles can be exploited to efficiently remove hydrophobic pollutants from water and contaminated soil. Preliminary in vivo experiments suggest that treatment with photocleavable nanoparticles can significantly reduce the teratogenicity of bisphenol A, triclosan and 17α-ethinyl estradiol without generating obviously toxic byproducts. Small-scale pilot experiments on wastewater, thermal printing paper and contaminated soil demonstrate the applicability of the approach.

Comparison of morphology and phase composition of hydroxyapatite nanoparticles sonochemically synthesized with dual- or single-frequency ultrasonic reactor

NASA Astrophysics Data System (ADS)

Deng, Shi-ting; Yu, Hong; Liu, Di; Bi, Yong-guang

2017-10-01

To investigate how a dual- or single-frequency ultrasonic reactor changes the morphology and phase composition of hydroxyapatite nanoparticles (nHAPs), we designed and constructed the preparation of nHAPs using dual- or single-frequency ultrasonic devices, i.e., the single frequency ultrasonic generator with ultrasonic horn (25 kHz), the ultrasonic bath (40 kHz) and the dual-frequency sonochemical systems combined with the ultrasonic horn and the ultrasonic bath simultaneously (25 + 40 kHz). The results showed that the sonicated samples displayed a more uniform shape with less agglomeration than non-sonicated sample. The rod-shaped particles with 1.66 stoichiometry and without a second phase were synthesized successfully in the ultrasonic bath or horn systems. The nHAPs obtained from the dual-frequency ultrasonic systems exhibited a regular rod-shaped structure with better dispersion and more uniform shapes than those of obtained in either ultrasonic bath or horn systems. Additionally, the size of rod-shaped particles obtained in the dual-frequency ultrasound with a mean width of 35 nm and a mean length of 64 nm was smaller than other samples. A possible mechanism is that the dual-frequency ultrasound significantly enhances the cavitation yield over single frequency ultrasound and thus improves the dispersion of particles and reduces the size of the crystals. In addition, irregular holes can be observed in the nanoparticles obtained in the dual-frequency ultrasound. Therefore, the dual-frequency ultrasonic systems are expected to become a convenient, efficient and environmentally friendly synthetic technology to obtain well-defined nHAPs for specific biomedical applications.

An accessible protocol for solid-phase extraction of N-linked glycopeptides through reductive amination by amine-functionalized magnetic nanoparticles.

PubMed

Zhang, Ying; Kuang, Min; Zhang, Lijuan; Yang, Pengyuan; Lu, Haojie

2013-06-04

In light of the significance of glycosylation for wealthy biological events, it is important to prefractionate glycoproteins/glycopeptides from complex biological samples. Herein, we reported a novel protocol of solid-phase extraction of glycopeptides through a reductive amination reaction by employing the easily accessible 3-aminopropyltriethoxysilane (APTES)-functionalized magnetic nanoparticles. The amino groups from APTES, which were assembled onto the surface of the nanoparticles through a one-step silanization reaction, could conjugate with the aldehydes from oxidized glycopeptides and, therefore, completed the extraction. To the best of our knowledge, this is the first example of applying the reductive amination reaction into the isolation of glycopeptides. Due to the elimination of the desalting step, the detection limit of glycopeptides was improved by 2 orders of magnitude, compared to the traditional hydrazide chemistry-based solid phase extraction, while the extraction time was shortened to 4 h, suggesting the high sensitivity, specificity, and efficiency for the extraction of N-linked glycopeptides by this method. In the meantime, high selectivity toward glycoproteins was also observed in the separation of Ribonuclease B from the mixtures contaminated with bovine serum albumin. What's more, this technique required significantly less sample volume, as demonstrated in the successful mapping of glycosylation of human colorectal cancer serum with the sample volume as little as 5 μL. Because of all these attractive features, we believe that the innovative protocol proposed here will shed new light on the research of glycosylation profiling.

Optimizing single-nanoparticle two-photon microscopy by in situ adaptive control of femtosecond pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Donghai; Deng, Yongkai; Chu, Saisai

2016-07-11

Single-nanoparticle two-photon microscopy shows great application potential in super-resolution cell imaging. Here, we report in situ adaptive optimization of single-nanoparticle two-photon luminescence signals by phase and polarization modulations of broadband laser pulses. For polarization-independent quantum dots, phase-only optimization was carried out to compensate the phase dispersion at the focus of the objective. Enhancement of the two-photon excitation fluorescence intensity under dispersion-compensated femtosecond pulses was achieved. For polarization-dependent single gold nanorod, in situ polarization optimization resulted in further enhancement of two-photon photoluminescence intensity than phase-only optimization. The application of in situ adaptive control of femtosecond pulse provides a way for object-orientedmore » optimization of single-nanoparticle two-photon microscopy for its future applications.« less

Preparation & characterization of high purity Cu2 ZnSn(SxSe1-x)4 nanoparticles

NASA Astrophysics Data System (ADS)

Negash, Bethlehem G.

Research in thin film solar cells applies novel techniques to synthesize cost effective and highly efficient absorber materials in order to generate electricity directly from solar energy. Of these materials, copper zinc tin sulfoselenide (Cu2ZnSn(SxSe1-x) 4) nanoparticles have shown great promise in solar cell applications due to optimal material properties as well as low cost & relative abundance of materials.1,2 Sulfoselenide nanoparticles have also a broader impact in other industries including electronics3, LED 4, and biomedical research5. Of the many routes of manufacturing these class of semiconductors, colloidal synthesis of Cu 2ZnSn(SxSe1-x)4 offers a scalable, low cost and high-throughput route for manufacturing high efficiency thin-film solar cells. Hydrazine processed Cu2ZnSn(SxSe1-x )4 devices have reached a record power conversion efficiency (PCE) of 12.6%, much higher than the 9.6% reported for physical vapor deposition (PVD) systems.6,7. Despite high efficiencies, wet synthesis of nanoparticles, however, is made more complicated in multi-element, quaternary and quinary systems such as copper zinc tin sulfoselenide (CZTSSe) and copper indium gallium diselenide (CIGSe). One major disadvantage in these systems is growth of the desired quaternary or quinary phase in competition with unwanted binary and ternary phases with low energy of formation.8,9 Moreover, various reaction parameters such as reaction time, temperature, and choice of ligand also affect, chemical as well as physical properties of resulting nanoparticles. Understanding of the formation mechanisms of the particles is necessary in order to address some of these challenges in wet synthesis of CZTSSe nanoparticles. In this study, we investigate synthesis conditions & reaction parameters which yield high purity Cu2ZnSn(SxSe1-x) 4 nanoparticles as well as attempt to understand the growth mechanism of these nanoparticles. This was achieved by manipulating anion precursor preparation routes as

Nanoparticle Phosphors Manufactured Using the Bicontinuous Cubic Phase Process

DTIC Science & Technology

1997-11-18

due to the recent interest in developing emissive 13 flat panel displays, e.g. full-color low-voltage field eminer displays (FEDs), large area plasma...it was determined that the nanoparticles were 5 monocrystalline with a zinc-blende cubic lattice. 6 7 Example 2 - Photoluminescence studies 8

Soft X-ray spectroscopy of nanoparticles by velocity map imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostko, O.; Xu, B.; Jacobs, M. I.

Velocity map imaging (VMI), a technique traditionally used to study chemical dynamics in the gas phase, is applied to study X-ray photoemission from aerosol nanoparticles. Soft X-rays from the Advanced Light Source synchrotron, probe a beam of nanoparticles, and the resulting photoelectrons are velocity mapped to obtain their kinetic energy distributions. A new design of the VMI spectrometer is described. The spectrometer is benchmarked by measuring vacuum ultraviolet photoemission from gas phase xenon and squalene nanoparticles followed by measurements using soft X-rays. It is demonstrated that the photoelectron distribution from X-ray irradiated squalene nanoparticles is dominated by secondary electrons. Bymore » scanning the photon energies and measuring the intensities of these secondary electrons, a near edge X-ray absorption fine structure (NEXAFS) spectrum is obtained. The NEXAFS technique is used to obtain spectra of aqueous nanoparticles at the oxygen K edge. By varying the position of the aqueous nanoparticle beam relative to the incident X-ray beam, evidence is presented such that the VMI technique allows for NEXAFS spectroscopy of water in different physical states. Finally, we discuss the possibility of applying VMI methods to probe liquids and solids via X-ray spectroscopy.« less

Soft X-ray spectroscopy of nanoparticles by velocity map imaging

DOE PAGES

Kostko, O.; Xu, B.; Jacobs, M. I.; ...

2017-05-05

Velocity map imaging (VMI), a technique traditionally used to study chemical dynamics in the gas phase, is applied to study X-ray photoemission from aerosol nanoparticles. Soft X-rays from the Advanced Light Source synchrotron, probe a beam of nanoparticles, and the resulting photoelectrons are velocity mapped to obtain their kinetic energy distributions. A new design of the VMI spectrometer is described. The spectrometer is benchmarked by measuring vacuum ultraviolet photoemission from gas phase xenon and squalene nanoparticles followed by measurements using soft X-rays. It is demonstrated that the photoelectron distribution from X-ray irradiated squalene nanoparticles is dominated by secondary electrons. Bymore » scanning the photon energies and measuring the intensities of these secondary electrons, a near edge X-ray absorption fine structure (NEXAFS) spectrum is obtained. The NEXAFS technique is used to obtain spectra of aqueous nanoparticles at the oxygen K edge. By varying the position of the aqueous nanoparticle beam relative to the incident X-ray beam, evidence is presented such that the VMI technique allows for NEXAFS spectroscopy of water in different physical states. Finally, we discuss the possibility of applying VMI methods to probe liquids and solids via X-ray spectroscopy.« less

Synthesis and Characterization of BSA Conjugated Silver Nanoparticles (Ag/BSA Nanoparticles) and Evaluation of Biological Properties of Ag/BSA Nanoparticles and Ag/BSA Nanoparticles Loaded Poly(hydroxy butyrate valerate) PHBV Films

NASA Astrophysics Data System (ADS)

Ambaye, Almaz

Ag/BSA nanoparticles was found to be in a range of 9-13 nm. X-ray photo electron spectroscopy measurements of argon sputtered Ag/BSA nanoparticles provided evidence that the outer and inner region of nanoparticles are mainly composed of BSA and silver, respectively. Having characterized the nanoparticles, the next phase of the study was to evaluate the antibacterial activity and cytotoxicity level of BSA stabilized silver nanoparticles. The antibacterial efficacy of Ag/BSA nanoparticles against E. coli and S. aureus was evaluated, and minimum lethal concentration was found to be 2ppm and 7ppm, respectively. E. coli showed a higher susceptibility to silver nanoparticles than S. aureus, which could be attributed to the difference in the cell wall structure. We have also investigated the cytotoxicity level of Ag/BSA nanoparticles towards MC3T3-E1 osteoblast cells. The minimum bactericidal concentration found for both strains is lower than the silver nanoparticles concentration that was toxic to the osteoblast cells. Preliminary studies of Ag/BSA nanoparticles loaded collagen immobilized PHBV film showed that the Ag/BSA nanoparticles loaded PHBV film inhibit bacterial growth. The findings of our study can be extremely useful in the design of novel scaffold to address the critical needs of bone tissue engineering community.

Nanoscale Phase-Separated Structure in Core-Shell Nanoparticles of SiO2-Si1-xGexO2 Glass Revealed by Electron Microscopy.

PubMed

Kubo, Yugo; Yonezawa, Kazuhiro

2017-09-05

SiO 2 -based optical fibers are indispensable components of modern information communication technologies. It has recently become increasingly important to establish a technique for visualizing the nanoscale phase-separated structure inside SiO 2 -GeO 2 glass nanoparticles during the manufacturing of SiO 2 -GeO 2 fibers. This is because the rapidly increasing price of Ge has made it necessary to improve the Ge yield by clarifying the detailed mechanism of Ge diffusion into SiO 2 . However, direct observation of the internal nanostructure of glass particles has been extremely difficult, mainly due to electrostatic charging and the damage induced by electron and X-ray irradiation. In the present study, we used state-of-the-art scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and energy dispersive X-ray spectroscopy (EDX) to examine cross-sectional samples of SiO 2 -GeO 2 particles embedded in an epoxy resin, which were fabricated using a broad Ar ion beam and a focused Ga ion beam. These advanced techniques enabled us to observe the internal phase-separated structure of the nanoparticles. We have for the first time clearly determined the SiO 2 -Si 1-x Ge x O 2 core-shell structure of such particles, the element distribution, the degree of crystallinity, and the quantitative chemical composition of microscopic regions, and we discuss the formation mechanism for the observed structure. The proposed imaging protocol is highly promising for studying the internal structure of various core-shell nanoparticles, which affects their catalytic, optical, and electronic properties.

Dynamics of Nanoparticle-Protein Corona Complex Formation: Analytical Results from Population Balance Equations

PubMed Central

Darabi Sahneh, Faryad; Scoglio, Caterina; Riviere, Jim

2013-01-01

Background Nanoparticle-protein corona complex formation involves absorption of protein molecules onto nanoparticle surfaces in a physiological environment. Understanding the corona formation process is crucial in predicting nanoparticle behavior in biological systems, including applications of nanotoxicology and development of nano drug delivery platforms. Method This paper extends the modeling work in to derive a mathematical model describing the dynamics of nanoparticle corona complex formation from population balance equations. We apply nonlinear dynamics techniques to derive analytical results for the composition of nanoparticle-protein corona complex, and validate our results through numerical simulations. Results The model presented in this paper exhibits two phases of corona complex dynamics. In the first phase, proteins rapidly bind to the free surface of nanoparticles, leading to a metastable composition. During the second phase, continuous association and dissociation of protein molecules with nanoparticles slowly changes the composition of the corona complex. Given sufficient time, composition of the corona complex reaches an equilibrium state of stable composition. We find analytical approximate formulae for metastable and stable compositions of corona complex. Our formulae are very well-structured to clearly identify important parameters determining corona composition. Conclusion The dynamics of biocorona formation constitute vital aspect of interactions between nanoparticles and living organisms. Our results further understanding of these dynamics through quantitation of experimental conditions, modeling results for in vitro systems to better predict behavior for in vivo systems. One potential application would involve a single cell culture medium related to a complex protein medium, such as blood or tissue fluid. PMID:23741371

Fluorescence quenching near small metal nanoparticles.

PubMed

Pustovit, V N; Shahbazyan, T V

2012-05-28

We develop a microscopic model for fluorescence of a molecule (or semiconductor quantum dot) near a small metal nanoparticle. When a molecule is situated close to metal surface, its fluorescence is quenched due to energy transfer to the metal. We perform quantum-mechanical calculations of energy transfer rates for nanometer-sized Au nanoparticles and find that nonlocal and quantum-size effects significantly enhance dissipation in metal as compared to those predicted by semiclassical electromagnetic models. However, the dependence of transfer rates on molecule's distance to metal nanoparticle surface, d, is significantly weaker than the d(-4) behavior for flat metal surface with a sharp boundary predicted by previous calculations within random phase approximation.

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications.

PubMed

Lasfargues, Mathieu; Bell, Andrew; Ding, Yulong

In this study, TiO 2 nanoparticles (average particle size 16 nm) were successfully produced in molten salt phase and were showed to significantly enhance the specific heat capacity of a binary eutectic mixture of sodium and potassium nitrate (60/40) by 5.4 % at 390 °C and 7.5 % at 445 °C for 3.0 wt% of precursors used. The objective of this research was to develop a cost-effective alternate method of production which is potentially scalable, as current techniques utilized are not economically viable for large quantities. Enhancing the specific heat capacity of molten salt would promote more competitive pricing for electricity production by concentrating solar power plant. Here, a simple precursor (TiOSO 4 ) was added to a binary eutectic mixture of potassium and sodium nitrate, heated to 450 °C, and cooled to witness the production of nanoparticles.

In situ investigations of the phase change behaviour of tungsten oxide nanostructures

NASA Astrophysics Data System (ADS)

Thummavichai, Kunyapat; Wang, Nannan; Xu, Fang; Rance, Graham; Xia, Yongda; Zhu, Yanqiu

2018-04-01

This study uses two in situ techniques to investigate the geometry and phase change behaviour of bundled ultrathin W18O49 nanowires and WO3 nanoparticles. The in situ X-ray diffraction (XRD) results have shown that the phase transition of WO3 nanoparticles occurs in sequence from monoclinic (room temperature) → orthorhombic (350°C) → tetragonal (800°C), akin to bulk WO3; however, W18O49 nanowires remain stable as the monoclinic phase up to 500°C, after which a complete oxidation to WO3 and transformation to the orthorhombic β-phase at 550°C is observed. The in situ Raman spectroscopy investigations have revealed the Raman peak downshifts as the temperature increases, and have identified the 187.6 cm-1 as the fingerprint band for the phase transition from γ- to β-phase of the WO3 nanoparticle. Furthermore, WO3 nanoparticles exhibit the γ- to β-phase conversion at 275°C, which is about 75°C lower than the relaxation temperature of 350°C for the monoclinic γ-W18O49 nanowires. These new fundamental understandings on the phase transition behaviour offer important guidance for the design and development of tungsten oxide-based nanodevices by defining their allowed operating conditions.

Effect of zinc oxide nanoparticles on dielectric behavior of nematic liquid crystal

NASA Astrophysics Data System (ADS)

Sharma, Amit; Kumar, Pankaj; Malik, Praveen

2018-05-01

In this work, phase transition and dielectric behavior of nematic liquid crystal (NLC), E7 and zinc oxide (ZnO) nanoparticles (NPs) doped nematic liquid crystals are investigated. Effect of nano-particles dispersion is analyzed and compared with the dielectric behavior of E7 and E7-ZnO. Frequency dependent dielectric permittivity at various temperatures in nematic phase for E7 and E7-ZnO sample is also studied.

Temperature, Crystalline Phase and Influence of Substrate Properties in Intense Pulsed Light Sintering of Copper Sulfide Nanoparticle Thin Films.

PubMed

Dexter, Michael; Gao, Zhongwei; Bansal, Shalu; Chang, Chih-Hung; Malhotra, Rajiv

2018-02-02

Intense Pulsed Light sintering (IPL) uses pulsed, visible light to sinter nanoparticles (NPs) into films used in functional devices. While IPL of chalcogenide NPs is demonstrated, there is limited work on prediction of crystalline phase of the film and the impact of optical properties of the substrate. Here we characterize and model the evolution of film temperature and crystalline phase during IPL of chalcogenide copper sulfide NP films on glass. Recrystallization of the film to crystalline covellite and digenite phases occurs at 126 °C and 155 °C respectively within 2-7 seconds. Post-IPL films exhibit p-type behavior, lower resistivity (~10 -3 -10 -4  Ω-cm), similar visible transmission and lower near-infrared transmission as compared to the as-deposited film. A thermal model is experimentally validated, and extended by combining it with a thermodynamic approach for crystal phase prediction and via incorporating the influence of film transmittivity and optical properties of the substrate on heating during IPL. The model is used to show the need to a-priori control IPL parameters to concurrently account for both the thermal and optical properties of the film and substrate in order to obtain a desired crystalline phase during IPL of such thin films on paper and polycarbonate substrates.

Nanoparticle coagulation in fractionally charged and charge fluctuating dusty plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nunomura, Shota; Kondo, Michio; Shiratani, Masaharu

2008-08-15

The kinetics of nanoparticle coagulation has been studied in fractionally charged and charge fluctuating dusty plasmas. The coagulation occurs when the mutual collision frequency among nanoparticles exceeds their charging and decharging/neutralization frequency. Interestingly, the coagulation is suppressed while a fraction (several percent) of nanoparticles are negatively charged in a plasma, in which stochastic charging plays an important role. A model is developed to predict a phase diagram of the coagulation and its suppression.

Formation of supported lipid bilayers containing phase-segregated domains and their interaction with gold nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melby, Eric S.; Mensch, Arielle C.; Lohse, Samuel E.

2016-01-01

The cell membrane represents an important biological interface that nanoparticles may encounter after being released into the environment. Interaction of nanoparticles with cellular membranes may alter membrane structure and function, lead to their uptake into cells, and elicit adverse biological responses. Supported lipid bilayers have proven to be valuable ex vivo models for biological membranes, allowing investigation of their mechanisms of interaction with nanoparticles with a degree of control impossible in living cells. To date, the majority of research on nanoparticle interaction with supported lipid bilayers has employed membranes composed of single or binary mixtures of phospholipids. Cellular membranes containmore » a wide variety of lipids and exhibit lateral organization. Ordered membrane domains enriched in specific membrane components are referred to as lipid rafts and have not been explored with respect to their interaction with nanoparticles. Here we develop model lipid raft-containing membranes amenable to investigation by a variety of surface-sensitive analytical techniques and demonstrate that lipid rafts influence the extent of nanoparticle attachment to model membranes. We determined conditions that allow reliable formation of bilayers containing rafts enriched in sphingomyelin and cholesterol and confirmed their morphology by structured illumination and atomic force microscopies. We demonstrate that lipid rafts increase attachment of cationic gold nanoparticles to model membranes under near physiological ionic strength conditions (0.1 M NaCl) at pH 7.4. We anticipate that these results will serve as the foundation for and motivate further study of nanoparticle interaction with compositionally varied lipid rafts.« less

A 106-fold enhancement in the conductivity of a discotic liquid crystal doped with only 1% (w/w) gold nanoparticles

NASA Astrophysics Data System (ADS)

Holt, Lucy A.; Bushby, Richard J.; Evans, Stephen D.; Burgess, Andrew; Seeley, Gordon

2008-03-01

The presence of 1% (w/w) of methylbenzene thiol coated gold nanoparticles increases the conductivity of the discotic liquid crystal 2,3,6,7,10,11-hexakis(hexyloxy)triphenylene (HAT6) by about two orders of magnitude in all three phases (crystal, columnar liquid crystal, and isotropic liquid). However, when a field (above a certain critical value) is applied to the isotropic phase, the conductivity rapidly increases by another three or four orders of magnitude after which the higher conductivity is maintained regardless of phase, field, or temperature. This increase in conductivity is attributed to the formation of chains of gold nanoparticles. A similar phenomenon is observed for 1% (w/w) gold nanoparticles in the isotropic phase of hexadecane. However, the liquid crystal/nanoparticle mixture preserves its high conductivity when it is cooled into the crystalline phase whereas that of the hexadecane/nanoparticle mixture is lost. In hexadecane, crystal grain boundaries are expected to form in a random fashion and this disrupts the conductive pathways. However, if HAT6 crystallizes via the homeotropically aligned columnar phase, the grain boundaries form predominantly surface to surface (electrode to electrode) so that the conductive nanoparticle chains are trapped in a stabilizing solid matrix.

Charge storage in β-FeSi2 nanoparticles

NASA Astrophysics Data System (ADS)

Theis, Jens; Bywalez, Robert; Küpper, Sebastian; Lorke, Axel; Wiggers, Hartmut

2015-02-01

We report on the observation of a surprisingly high specific capacitance of β-FeSi2 nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on thermally grown silicon dioxide and covered with β-FeSi2 particles by drop or spin casting. The β-FeSi2-nanoparticles, with crystallite sizes in the range of 10-30 nm, were fabricated by gas phase synthesis in a hot wall reactor. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3-4 orders of magnitude increased capacitance. Time-resolved current voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are robust and exhibit long-term stability under ambient conditions. The specific capacitance is highest for a saturated relative humidity, while for a relative humidity below 40% the capacitance is almost indistinguishable from a nanoparticle-free reference sample. The devices work without the need of a fluid phase, the charge storing material is abundant and cost effective, and the sample design is easy to fabricate.

Exchange bias effect in Au-Fe 3O 4 dumbbell nanoparticles induced by the charge transfer from gold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feygenson, Mikhail; Bauer, John C; Gai, Zheng

2015-08-10

We have studied the origin of the exchange bias effect in the Au-Fe 3O 4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe 3O 4 nanoparticles (9.8 nm). The magnetization, small-angle neutron scattering, synchrotron x-ray diffraction and scanning transmission electron microscope measurements determined the antiferromagnetic FeO wüstite phase within Fe 3O 4 nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe 3O 4 is giving rise to the exchange bias effect. The strength of the exchange bias fieldsmore » depends on the interfacial area and lattice mismatch between both phases. We propose that the charge transfer from the Au nanoparticles is responsible for a partial reduction of the Fe 3O 4 into FeO phase at the interface with Au nanoparticles. The Au-O bonds are formed across the interface to accommodate an excess of oxygen released during the reduction of magnetite.« less

Exchange bias effect in Au-Fe3O4 dumbbell nanoparticles induced by the charge transfer from gold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feygenson, Mikhail; Bauer, John C.; Gai, Zheng

2015-08-10

We have studied the origin of the exchange bias effect in the Au-Fe3O4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe3O4 nanoparticles (9.8 nm). The magnetization, small-angle neutron-scattering, synchrotron x-ray diffraction, and scanning transmission electron microscope measurements determined the antiferromagnetic FeO wustite phase within Fe3O4 nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe3O4 is giving rise to the exchange bias effect. The strength of the exchange bias fields depends on the interfacial area and lattice mismatch betweenmore » both phases. We propose that the charge transfer from the Au nanoparticles is responsible for a partial reduction of the Fe3O4 into the FeO phase at the interface with Au nanoparticles. The Au-O bonds are formed, presumably across the interface to accommodate an excess of oxygen released during the reduction of magnetite« less

Synthesis and Characterization of Some Alkaline-Earth-Oxide Nanoparticles

NASA Astrophysics Data System (ADS)

Singh, Jitendra Pal; Lim, Weon Cheol; Won, Sung Ok; Song, Jonghan; Chae, Keun Hwa

2018-04-01

The present work reports the synthesis of MgO and CaO nanoparticles by using the sol-gel autocombustion method. The annealing of the precursor at 1200 °C was observed to lead the formation of MgO nanoparticles having average crystallite size of 31 nm. Annealing the precursor at same temperature produced materials having a CaO phase with a minor impure phase of calcium carbonate ( 3%). The crystallite size corresponding to the CaO phase was 38 nm. A change of thermal history in the precursor was observed not to result in an improvement of the CaO phase. The change of thermal history in the precursor gave rise to mixed phases of CaCO3 and Ca(OH)2 rather than the phase of CaO. Further, annealing at 1200 °C for 12 h resulted in the formation of the CaO phase along with almost 1 - 5% of calcium hydroxide as an impurity phase. X-ray absorption spectroscopic measurements carried out on these materials revealed that the local electronic/atomic structure of these oxides was not only affected by the impurity phases but also influenced by the carbaneous impurities attached to the crystallites.

Nanoparticles with photoinduced precipitation for the extraction of pollutants from water and soil

PubMed Central

Brandl, Ferdinand; Bertrand, Nicolas; Lima, Eliana Martins; Langer, Robert

2015-01-01

Nanotechnology may offer fast and effective solutions for environmental clean-up. Herein, amphiphilic diblock copolymers are used to develop a platform of photosensitive core-shell nanoparticles. Irradiation with ultraviolet light removes the protective layer responsible for colloidal stability; as a result, the nanoparticles are rapidly and irreversibly converted to macroscopic aggregates. The associated phase separation allows measuring the partitioning of small molecules between the aqueous phase and nanoparticles; data suggests that interactions are enhanced by decreasing the particle size. Adsorption onto nanoparticles can be exploited to efficiently remove hydrophobic pollutants from water and contaminated soil. Preliminary in vivo experiments suggest that treatment with photocleavable nanoparticles can significantly reduce the teratogenicity of bisphenol A, triclosan and 17α-ethinyl estradiol without generating obviously toxic byproducts. Small-scale pilot experiments on wastewater, thermal printing paper and contaminated soil demonstrate the applicability of the approach. PMID:26196119

Martensitic and austenitic transformations in core-surface cubic nanoparticles

NASA Astrophysics Data System (ADS)

Özüm, S.; Yalçın, O.; Erdem, R.; Bayrakdar, H.; Eker, H. N.

2015-01-01

As a continuation of our recently published work, we have used the pair approximation in Kikuchi version to investigate martensitic and austenitic transformations in homogeneous (HM) and composite (CM) cubic nanoparticles (CNPs) based on the Blume-Emery-Griffiths model. A single cubic nanoparticle made of a core surrounded by a surface is considered as shaped in two dimensional (2D) square arrays instead of hexagonal array. From the phase diagrams of HM and CM-CNPs it has been observed that the martensitic-austenitic transformations (MT-AT) occurred. The influence of the exchange coupling and single-ion anisotropy parameters in the model Hamiltonian on the MT-AT is studied and analyzed in comparison with the results for hexagonal nanoparticles. Significant changes of the phase transition points and hysteresis behaviours depending upon the particle structure have been discussed.

Surface-modified multifunctional MIP nanoparticles

NASA Astrophysics Data System (ADS)

Moczko, Ewa; Poma, Alessandro; Guerreiro, Antonio; Perez de Vargas Sansalvador, Isabel; Caygill, Sarah; Canfarotta, Francesco; Whitcombe, Michael J.; Piletsky, Sergey

2013-04-01

The synthesis of core-shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as a protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity (PEG methacrylate); electro-activity (vinylferrocene); fluorescence (eosin acrylate); thiol groups (pentaerythritol tetrakis(3-mercaptopropionate)). The method has broad applicability and can be used to produce multifunctional imprinted nanoparticles with potential for further application in the biosensors, diagnostics and biomedical fields and as an alternative to natural receptors.The synthesis of core-shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as a protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity

Direct observation of two-step crystallization in nanoparticle superlattice formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jungwon; Zheng, Haimei; Lee, Won Chul

2011-10-06

Direct imaging of nanoparticle solutions by liquid phase transmission electron microscopy has enabled unique in-situ studies of nanoparticle motion and growth. In the present work, we report on real-time formation of two-dimensional nanoparticle arrays in the very low diffusive limit, where nanoparticles are mainly driven by capillary forces and solvent fluctuations. We find that superlattice formation appears to be segregated into multiple regimes. Initially, the solvent front drags the nanoparticles, condensing them into an amorphous agglomerate. Subsequently, the nanoparticle crystallization into an array is driven by local fluctuations. Following the crystallization event, superlattice growth can also occur via the additionmore » of individual nanoparticles drawn from outlying regions by different solvent fronts. The dragging mechanism is consistent with simulations based on a coarse-grained lattice gas model at the same limit.« less

Monte Carlo simulation of dynamic phase transitions and frequency dispersions of hysteresis curves in core/shell ferrimagnetic cubic nanoparticle

NASA Astrophysics Data System (ADS)

Vatansever, Erol

2017-05-01

By means of Monte Carlo simulation method with Metropolis algorithm, we elucidate the thermal and magnetic phase transition behaviors of a ferrimagnetic core/shell nanocubic system driven by a time dependent magnetic field. The particle core is composed of ferromagnetic spins, and it is surrounded by an antiferromagnetic shell. At the interface of the core/shell particle, we use antiferromagnetic spin-spin coupling. We simulate the nanoparticle using classical Heisenberg spins. After a detailed analysis, our Monte Carlo simulation results suggest that present system exhibits unusual and interesting magnetic behaviors. For example, at the relatively lower temperature regions, an increment in the amplitude of the external field destroys the antiferromagnetism in the shell part of the nanoparticle, leading to a ground state with ferromagnetic character. Moreover, particular attention has been dedicated to the hysteresis behaviors of the system. For the first time, we show that frequency dispersions can be categorized into three groups for a fixed temperature for finite core/shell systems, as in the case of the conventional bulk systems under the influence of an oscillating magnetic field.

Localized, plasmon-mediated heating from embedded nanoparticles in nanocomposites

NASA Astrophysics Data System (ADS)

Maity, Somsubhra; Downen, Lori; Bochinski, Jason; Clarke, Laura

2010-03-01

Metallic nanoparticles exhibit a surface plasmon resonance which, when excited with visible light, results in a dramatic increase in the nanoparticle temperature. Previously such localized heating has been primarily employed in biomedical research and other experiments involving aqueous environments. In this work, we investigated use of the nanoparticles in solid phase to re-shape, bond, melt, and otherwise process nanofibrous mats of ˜200 nm diameter nanofibers doped with ˜80 nm spherical gold nanoparticles. Under low light intensities (100 mW/cm^2 @ 532 nm) and dilute nanoparticle loading (˜0.15% volume fraction), irradiation of a few minutes melted nanofibrous mats of poly (ethylene oxide) (Tm = 65 degree C). Control samples without gold nanoparticles displayed no melting. Because the heat is generated from within the material and only at the nanoparticle locations, this technique enables true nanoprocessing -- the non-contact, controlled application of heat at specific nano-sized locations within a material to effect desired local changes. Funded by CMMI-0829379.

Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

NASA Astrophysics Data System (ADS)

Wang, S. F.; Li, Q.; Zu, X. T.; Xiang, X.; Liu, W.; Li, S.

2016-12-01

(Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M2+ ion active sites were coordinated by -OH of the water molecules except for EDTA anions. The MFe2O4 magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe2O4 of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly.

Computational studies of adsorption in metal organic frameworks and interaction of nanoparticles in condensed phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annapureddy, Harsha V.; Motkuri, Radha K.; Nguyen, Phuong T.

In this review, we describe recent efforts in which computer simulations were used to systematically study nano-structured metal organic frameworks, with particular emphasis on their application in heating and cooling processes. These materials also are known as metal organic heat carriers. We used both molecular dynamics and Grand Canonical Monte Carlo simulation techniques to gain a molecular-level understanding of the adsorption mechanism of gases in these porous materials. We investigated the uptake of various gases such as refrigerants R12 and R143a and also the elemental gases Xe and Rn by the metal organic framework (i.e., Ni2(dhtp)). We also evaluated themore » effects of temperature and pressure on the uptake mechanism. Our computed results compared reasonably well with available experimental measurements, thus validating our potential models and approaches. In addition, we also investigated the structural, diffusive, and adsorption properties of different hydrocarbons in Ni2(dhtp). To elucidate the mechanism of nanoparticle dispersion in condensed phases, we also studied the interactions among nanoparticles in various liquids, such as n-hexane, water and methanol. This work was performed at Pacific Northwest National Laboratory (PNNL) and was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). PNNL is operated by Battelle for the DOE. The authors also gratefully acknowledge support received from the National Energy Technology Laboratory of DOE's Office of Fossil Energy.« less

Carbon Nanoparticles decorated with cupric oxide Nanoparticles prepared by laser ablation in liquid as an antibacterial therapeutic agent

NASA Astrophysics Data System (ADS)

Khashan, Khawla S.; Jabir, Majid S.; Abdulameer, Farah A.

2018-03-01

Carbon nanoparticles (CNPs) decorated with cupric oxide nanoparticles (CuO NPs) were prepared by laser ablation in water, and their antibacterial activity was examined. X-ray diffraction measurements demonstrated the presence of carbon phases and different CuO phases, and results were confirmed by Fourier transform infrared analysis. Energy- Dispersive spectra showed the presence of C, O, and Cu in the final product. Transmission electron micrographs revealed that the CNPs were 10-80 nm in size and spherical; after being decorated with CuO NPs, particles became 5-50 nm in size and uniform in shape. The absorption spectrum of decorated Nanoparticles indicated the appearance of a new peak at 254-264 nm in addition to the fundamental peak at 228 nm. We then examined the antibacterial activity of the decorated CNPs for both gram-negative and -positive bacteria using the agar-well-diffusion method. The mode of action was determined using acridine orange-ethidium bromide staining to detect reactive oxygen species, and bacterial morphological change was studied by scanning electron microscopy. Results showed that CNPs decorated with 43% CuO NPs had the highest antibacterial activity for gram-positive bacteria. The CNPs acted on the cytoplasmic membrane and nucleic acid of bacteria, which led to a loss of cell-wall integrity, increased cell-wall permeability, and nucleic acid damage. The results offer a novel way to synthesis Carbon nanoparticles decorated with cupric oxide nanoparticles and could use them as novel antibacterial agent in future for pharmaceutical and biomedical applications.

Maghemite nanoparticles with enhanced magnetic properties: one-pot preparation and ultrastable dextran shell.

PubMed

Di Corato, Riccardo; Aloisi, Alessandra; Rella, Simona; Greneche, Jean-Marc; Pugliese, Giammarino; Pellegrino, Teresa; Malitesta, Cosimino; Rinaldi, Rosaria

2018-05-10

In the field on nanomedicine, superparamagnetic nanoparticles are one of the most studied nanomaterials for theranostics. In this paper, a one-pot synthesis of magnetic nanoparticles is presented, with elevated control on particles size from 10 to 40 nm. The monitoring of vacuum level is here introduced as a crucial parameter for achieving a fine particle morphology. Magnetic properties of these nanoparticles are highly affected by disorders or mismatches in crystal structure. A prolonged oxidation step is applied to the obtained nanoparticles to transform the magnetic phases into a pure maghemite one, confirmed by a high resolution XPS analysis, by Mössbauer spectrometry and, indirectly, by increased performances in magnetization curves and in relaxation times. Afterward, the attained nanoparticles are transferred in water by a non-derivatized dextran coating. The thermogravimetric analysis confirms that the polysaccharide molecules replace the oleic acid on the surface by stabilizing the particles in aqueous phase and culture media. Preliminary in vitro test reveals as the dextran coated nanoparticles are not passively internalized from the cells. As proof of concept, a secondary layer of chitosan assures a positive charge to the nanoparticle surface, thus enhancing the cellular internalization.

Mössbauer Studies of Core-Shell FeO/Fe3O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Kamzin, A. S.; Valiullin, A. A.; Khurshid, H.; Nemati, Z.; Srikanth, H.; Phan, M. H.

2018-02-01

FeO/Fe3O4 nanoparticles were synthesized by thermal decomposition. Electron microscopy revealed that these nanoparticles were of the core-shell type and had a spherical shape with an average size of 20 nm. It was found that the obtained FeO/Fe3O4 nanoparticles had exchange coupling. The effect of anisotropy on the efficiency of heating (hyperthermic effect) of FeO/Fe3O4 nanoparticles by an external alternating magnetic field was examined. The specific absorption rate (SAR) of the studied nanoparticles was 135 W/g in the experiment with an external alternating magnetic field with a strength of 600 Oe and a frequency of 310 kHz. These data led to an important insight: the saturation magnetization is not the only factor governing the SAR, and the efficiency of heating of magnetic FeO/Fe3O4 nanoparticles may be increased by enhancing the effective anisotropy. Mössbauer spectroscopy of the phase composition of the synthesized nanoparticles clearly revealed the simultaneous presence of three phases: magnetite Fe3O4, maghemite γ-Fe2O3, and wustite FeO.

Effect of solvent on the synthesis of SnO{sub 2} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Virender; Singh, Karamjit; Singh, Kulwinder

Tin oxide (SnO{sub 2}) nanoparticles have been synthesized by co-precipitation method. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD) and Ultraviolet-Visible spectroscopy (UV-VIS). XRD analysis confirmed the formation of single phase of SnO{sub 2} nanoparticles. It has been found that solvents played important role in controlling the crystallite size of SnO{sub 2} nanoparticles. The XRD analysis showed well crystallized tetragonal SnO{sub 2} nanoparticles. The crystallite size of SnO{sub 2} nanoparticles varies with the solvent. Tauc plot showed that optical band gap was also tailored by controlling the solvent during synthesis.

Monitoring nanoparticle synthesis in a carbon arc discharge environment, in situ

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitrani, James

This work presents experimental and theoretical studies of gas-phase synthesis of fullerenes and carbon nanoparticles in the presence of an atmospheric-pressure, arc discharge plasma. Carbon arc discharges have been used for synthesizing carbon nanotubes for over 25 years, and have the potential for economically synthesizing industrial-scale quantities of fullerenes. However, the efficiency and selectivity of fullerene synthesis with carbon arc discharges are quite low. Optimizing carbon arc discharges for fullerene synthesis requires a thorough understanding of the dynamics behind gas-phase nanoparticle synthesis in the presence of an arc discharge plasma. We built a carbon arc discharge setup to study nanoparticlemore » and fullerene synthesis. The laser-induced incandescence (LII) diagnostic was applied for monitoring nanoparticle synthesis, in situ. The LII diagnostic had previously been applied as a combustion diagnostic for in situ measurements of concentrations and sizes of soot particles in flame environments. Prior to the present study, it had never been applied for studying fullerenes, nor had it been applied to study nanoparticles in the presence of an atmospheric-pressure plasma. Therefore, experiments were designed that allowed for the calibration of the LII diagnostic with research-grade, arc-synthesized soot particles and carbon nanotubes. Additionally, the theory and models underpinning the LII diagnostic were adapted to include the presence of an atmospheric-pressure, arc-discharge plasma. Results presented in this work confirm the ability of the LII diagnostic to measure sizes of arc-synthesized nanoparticles in situ, and show the spatial location of high densities of arc-synthesized nanoparticles with respect to the arc discharge plasma. Determining the spatial location of nanoparticle synthesis and growth is crucial for understanding the background conditions (e.g. background gas temperature, electron densities ...) in which nanoparticles

Cubic liquid crystalline nanoparticles: optimization and evaluation for ocular delivery of tropicamide.

PubMed

Verma, Purnima; Ahuja, Munish

2016-10-01

The purpose of this study was to investigate the potential of cubic liquid crystalline nanoparticles for ocular delivery of tropicamide. Ultrasound-assisted fragmentation of cubic liquid crystalline bulk phases resulted in cubic liquid crystalline nanoparticles employing Pluronic F127 as dispersant. The effects of process variables such as sonication time, sonication amplitude, sonication depth, and pre-mixing time on particle size and polydispersity index was investigated using central composite design. The morphology of tropicamide-loaded nanoparticles was found to be nearly cubical in shape by transmission electron microscopy observation. Further, small angle X-ray scattering experiment confirmed the presence of D and P phase cubic structures in coexistence. The optimized tropicamide-loaded cubic nanoparticles showed in vitro corneal permeation of tropicamide across isolated porcine cornea comparable to its commercial preparation, Tropicacyl®. Ocular tolerance was evaluated by Hen's egg-chorioallantoic membrane test and histological studies. The results of in vivo mydriatic response study demonstrated a remarkably higher area under mydriatic response curve (AUC 0→1440 min ) values of cubic nanoparticles over Tropicacyl® indicating better therapeutic value of cubic nanoparticles. Furthermore, tropicamide-loaded cubic nanoparticles exhibited prolonged mydriatic effect on rabbits as compared to commercial conventional aqueous ophthalmic solution.

Spectral Properties of Gas-phase Condensed Fullerene-like Carbon Nanoparticles from Far-ultraviolet to Infrared Wavelengths

NASA Astrophysics Data System (ADS)

Jäger, C.; Mutschke, H.; Henning, Th.; Huisken, F.

2008-12-01

Carbon solids are ubiquitous material in interstellar space. However, the formation pathway of carbonaceous matter in astrophysical environments, as well as in terrestrial gas-phase condensation reactions, is not yet understood. Laser ablation of graphite in different quenching gas atmospheres, such as pure He, He/H2, and He/H2O at varying pressures, is used to synthesize very small, fullerene-like carbon nanoparticles. The particles are characterized by very small diameters between 1 and 4 nm and a disturbed onion-like structure. The soot particles extracted from the condensation zone obviously represent a very early stage of particle condensation. The spectral properties have been measured from the far-ultraviolet (FUV; λ = 120 nm) to the mid-infrared (MIR; λ = 15 μm). The seedlike soot particles show strong absorption bands in the 3.4 μm range. The profile and the intensity pattern of the 3.4 μm band of the diffuse interstellar medium can be well reproduced by the measured 3.4 μm profile of the condensed particles; however, all the carbon which is left to form solids is needed to fit the intensity of the interstellar bands. In contrast to the assumption that onion-like soot particles could be the carriers of the interstellar ultraviolet (UV) bump, our very small onion-like carbon nanoparticles do not show distinct UV bands due to (π-π*) transitions.

Anisotropic Shape Changes of Silica Nanoparticles Induced in Liquid with Scanning Transmission Electron Microscopy.

PubMed

Zečević, Jovana; Hermannsdörfer, Justus; Schuh, Tobias; de Jong, Krijn P; de Jonge, Niels

2017-01-01

Liquid-phase transmission electron microscopy (TEM) is used for in-situ imaging of nanoscale processes taking place in liquid, such as the evolution of nanoparticles during synthesis or structural changes of nanomaterials in liquid environment. Here, it is shown that the focused electron beam of scanning TEM (STEM) brings about the dissolution of silica nanoparticles in water by a gradual reduction of their sizes, and that silica redeposites at the sides of the nanoparticles in the scanning direction of the electron beam, such that elongated nanoparticles are formed. Nanoparticles with an elongation in a different direction are obtained simply by changing the scan direction. Material is expelled from the center of the nanoparticles at higher electron dose, leading to the formation of doughnut-shaped objects. Nanoparticles assembled in an aggregate gradually fuse, and the electron beam exposed section of the aggregate reduces in size and is elongated. Under TEM conditions with a stationary electron beam, the nanoparticles dissolve but do not elongate. The observed phenomena are important to consider when conducting liquid-phase STEM experiments on silica-based materials and may find future application for controlled anisotropic manipulation of the size and the shape of nanoparticles in liquid. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Arsenic Mobilization Through Microbial Bioreduction of Ferrihydrite Nanoparticles

NASA Astrophysics Data System (ADS)

Tadanier, C. J.; Roller, J.; Schreiber, M. E.

2004-12-01

Under anaerobic conditions Fe(III)-reducing microorganisms can couple the reduction of solid phase Fe(III) (hydr)oxides with the oxidation of organic carbon. Nutrients and trace metals, such as arsenic, associated with Fe(III) hydroxides may be mobilized through microbially-mediated surface reduction. Although arsenic mobilization has been attributed to mineral surface reduction in a variety of pristine and contaminated environments, minimal information exists on the mechanisms causing this arsenic mobilization. Understanding of the fundamental biochemical and physicochemical processes involved in these mobilization mechanisms is still limited, and has been complicated by the often contradictory and interchangeable terminology used in the literature to describe them. We studied arsenic mobilization mechanisms using a series of controlled microcosm experiments containing aggregated arsenic-bearing ferrihydrite nanoparticles and an Fe(III)-reducing microorganism, Geobacter metallireducens. The phase distribution of iron and arsenic was determined through filtration and ultracentrifugation techniques. Experimental results showed that in the biotic trials, approximately 10 percent of the Fe(III) was reduced to Fe(II) by microbial activity, which remained associated with ferrihydrite surfaces. Biotic activity resulted in changes in nanoparticle surface potential and caused deflocculation of nanoparticle aggregates. Deflocculated nanoparticles were able to pass through a 0.2 micron filter and could only be removed from solution by ultracentrifugation. Arsenic mobilized over time in the biotic trials was found to be exclusively associated with the nanoparticles; 98 percent of arsenic that passed through a 0.2 micron filter was removed from solution by ultracentrifugation. None of these changes were observed in abiotic controls. Because arsenic contamination of natural waters due to mobilization from mineral surfaces is a significant route of human arsenic exposure

Laser synthesis and spectroscopy of acetonitrile/silver nanoparticles

NASA Astrophysics Data System (ADS)

Akin, S. T.; Liu, X.; Duncan, M. A.

2015-11-01

Silver nanoparticles with acetonitrile ligands are produced in a laser ablation flow reactor. Excimer laser ablation produces gas phase metal clusters which are thermalized with helium or argon collisions in the flowtube, and reactions with acetonitrile vapor coordinate this ligand to the particle surface. The gaseous mixture is captured in a cryogenic trap; warming produces a solution of excess ligand and coated particles. TEM images reveal particle sizes of 10-30 nm diameter. UV-vis absorption and fluorescence spectra are compared to those of standard silver nanoparticles with surfactant coatings. Deep-UV ligand absorption is strongly enhanced by nanoparticle adsorption.

Interfacial functionalization and engineering of nanoparticles

NASA Astrophysics Data System (ADS)

Song, Yang

also of the metal elements in the nanoparticle cores, in contrast to the bulk-exchange counterparts where these distributions were homogeneous within the nanoparticles, as manifested in contact angle, UV--vis, XPS, and TEM measurements. More interestingly, the electrocatalytic performance of the Janus nanoparticles was markedly better than the bulk-exchange ones, suggesting that the segregated distribution of the polar ligands from the apolar ones might further facilitate charge transfer from Ag to Au in the nanoparticle cores, leading to additional improvement of the adsorption and reduction of oxygen. This interfacial protocol was then adopted to prepare trimetallic Ag AuPt Neapolitan nanoparticles by two sequential galvanic exchange reactions of 1-hexanethiolate-capped silver nanoparticles with gold(I)-thiomalic acid and platinum(II)-hexanethiolate complexes. As both reactions were confined to an interface, the Au and Pt elements were situated on two opposite poles of the original Ag nanoparticles, which was clearly manifested in elemental mapping of the nanoparticles, and consistent with the damping and red-shift of the nanoparticle surface plasmon resonance. As nanoscale analogs to conventional amphiphilic molecules, the resulting Janus nanoparticles were found to form oil-in-water micelle-like or water-in-oil reverse micelle-like superparticulate structures depending on the solvent media. These unique characteristics were exploited for the effective transfer of diverse guest nanoparticles between organic and water phase. The transfer of hydrophobic nanoparticles from organic to water media or water-soluble nanoparticles to the organic phase was evidenced by TEM, DLS, UV-Vis, and PL measurements. In particular, line scans based on EDS analysis showed that the vesicle-like structures consisted of multiple layers of the Janus nanoparticles, which encapsulated the guest nanoparticles in the cores. The results highlight the unique effectiveness of using Janus

Dramatically different kinetics and mechanism at solid/liquid and solid/gas interfaces for catalytic isopropanol oxidation over size-controlled platinum nanoparticles.

PubMed

Wang, Hailiang; Sapi, Andras; Thompson, Christopher M; Liu, Fudong; Zherebetskyy, Danylo; Krier, James M; Carl, Lindsay M; Cai, Xiaojun; Wang, Lin-Wang; Somorjai, Gabor A

2014-07-23

We synthesize platinum nanoparticles with controlled average sizes of 2, 4, 6, and 8 nm and use them as model catalysts to study isopropanol oxidation to acetone in both the liquid and gas phases at 60 °C. The reaction at the solid/liquid interface is 2 orders of magnitude slower than that at the solid/gas interface, while catalytic activity increases with the size of platinum nanoparticles for both the liquid-phase and gas-phase reactions. The activation energy of the gas-phase reaction decreases with the platinum nanoparticle size and is in general much higher than that of the liquid-phase reaction which is largely insensitive to the size of catalyst nanoparticles. Water substantially promotes isopropanol oxidation in the liquid phase. However, it inhibits the reaction in the gas phase. The kinetic results suggest different mechanisms between the liquid-phase and gas-phase reactions, correlating well with different orientations of IPA species at the solid/liquid interface vs the solid/gas interface as probed by sum frequency generation vibrational spectroscopy under reaction conditions and simulated by computational calculations.

In situ investigations of the phase change behaviour of tungsten oxide nanostructures.

PubMed

Thummavichai, Kunyapat; Wang, Nannan; Xu, Fang; Rance, Graham; Xia, Yongda; Zhu, Yanqiu

2018-04-01

This study uses two in situ techniques to investigate the geometry and phase change behaviour of bundled ultrathin W 18 O 49 nanowires and WO 3 nanoparticles. The in situ X-ray diffraction (XRD) results have shown that the phase transition of WO 3 nanoparticles occurs in sequence from monoclinic (room temperature) → orthorhombic (350°C) → tetragonal (800°C), akin to bulk WO 3 ; however, W 18 O 49 nanowires remain stable as the monoclinic phase up to 500°C, after which a complete oxidation to WO 3 and transformation to the orthorhombic β-phase at 550°C is observed. The in situ Raman spectroscopy investigations have revealed the Raman peak downshifts as the temperature increases, and have identified the 187.6 cm -1 as the fingerprint band for the phase transition from γ- to β-phase of the WO 3 nanoparticle. Furthermore, WO 3 nanoparticles exhibit the γ- to β-phase conversion at 275°C, which is about 75°C lower than the relaxation temperature of 350°C for the monoclinic γ-W 18 O 49 nanowires. These new fundamental understandings on the phase transition behaviour offer important guidance for the design and development of tungsten oxide-based nanodevices by defining their allowed operating conditions.

Green nanoparticle production using micro reactor technology

NASA Astrophysics Data System (ADS)

Kück, A.; Steinfeldt, M.; Prenzel, K.; Swiderek, P.; Gleich, A. v.; Thöming, J.

2011-07-01

The importance and potential of nanoparticles in daily life as well as in various industrial processes is becoming more predominant. Specifically, silver nanoparticles are increasingly applied, e.g. in clothes and wipes, due to their antibacterial properties. For applications in liquid phase it is advantageous to produce the nanoparticles directly in suspension. This article describes a green production of silver nanoparticles using micro reactor technology considering principles of green chemistry. The aim is to reveal the potential and constraints of this approach and to show, how economic and environmental costs vary depending on process conditions. For this purpose our research compares the proposed process with water-based batch synthesis and demonstrates improvements in terms of product quality. Because of the lower energy consumption and lower demand of cleaning agents, micro reactor is the best ecological choice.

Effect of Zn-doping on structural and magnetic properties of copper ferrite nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gautam, Nisha; Thirupathi, Gadipelly; Singh, Rajender

2016-05-23

The nanoparticles of CuFe{sub 2}O{sub 4} (CF) and Cu{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (CZF) were synthesized using co-precipitation method to study the effect of Zn doping in Cu-ferrite. The X-ray diffraction (XRD) patterns were well fitted with two-phase structure using Rietveld analysis as Fd-3 m space group (spinel system) and C12/c1 space group (monoclinic system CuO-phase). The average crystallite size of the CF and CZF nanoparticles for spinel structure are 6 and 7 nm respectively. The spinel phase fraction is increased from 56% to 71% with Zn-doping of 20% in CF. The transmission electron micrograph analysis showed the narrow size distribution formore » CZF nanoparticles. The magnetization plots as a function of magnetic field (M (H)) of CF and CZF nanoparticles indicate superparamagnetic behavior. The magnetization is increased with Zn-doping in CF. The stable spinel Cu-ferrite can be obtained with Zn-doping in CF.« less

Adsorption of bovine serum albumin on silicon dioxide nanoparticles: Impact of pH on nanoparticle-protein interactions.

PubMed

Givens, Brittany E; Diklich, Nina D; Fiegel, Jennifer; Grassian, Vicki H

2017-05-03

Bovine serum albumin (BSA) adsorbed on amorphous silicon dioxide (SiO 2 ) nanoparticles was studied as a function of pH across the range of 2 to 8. Aggregation, surface charge, surface coverage, and protein structure were investigated over this entire pH range. SiO 2 nanoparticle aggregation is found to depend upon pH and differs in the presence of adsorbed BSA. For SiO 2 nanoparticles truncated with hydroxyl groups, the largest aggregates were observed at pH 3, close to the isoelectric point of SiO 2 nanoparticles, whereas for SiO 2 nanoparticles with adsorbed BSA, the aggregate size was the greatest at pH 3.7, close to the isoelectric point of the BSA-SiO 2 complex. Surface coverage of BSA was also the greatest at the isoelectric point of the BSA-SiO 2 complex with a value of ca. 3 ±   1 × 10 11 molecules cm -2 . Furthermore, the secondary protein structure was modified when compared to the solution phase at all pH values, but the most significant differences were seen at pH 7.4 and below. It is concluded that protein-nanoparticle interactions vary with solution pH, which may have implications for nanoparticles in different biological fluids (e.g., blood, stomach, and lungs).

A single-step aerosol process for in-situ surface modification of nanoparticles: Preparation of stable aqueous nanoparticle suspensions.

PubMed

Sapra, Mahak; Pawar, Amol Ashok; Venkataraman, Chandra

2016-02-15

Surface modification of nanoparticles during aerosol or gas-phase synthesis, followed by direct transfer into liquid media can be used to produce stable water-dispersed nanoparticle suspensions. This work investigates a single-step, aerosol process for in-situ surface-modification of nanoparticles. Previous studies have used a two-step sublimation-condensation mechanism following droplet drying, for surface modification, while the present process uses a liquid precursor containing two solutes, a matrix lipid and a surface modifying agent. A precursor solution in chloroform, of stearic acid lipid, with 4 %w/w of surface-active, physiological molecules [1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol)-sodium salt (DPPG) or 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol) 2000]-ammonium salt (DPPE-PEG)] was processed in an aerosol reactor at a low gas temperatures. The surface modified nanoparticles were characterized for morphology, surface composition and suspension properties. Spherical, surface-modified lipid nanoparticles with median mobility diameters in the range of 105-150nm and unimodal size distributions were obtained. Fourier transform infra-red spectroscopy (FTIR) measurements confirmed the presence of surface-active molecules on external surfaces of modified lipid nanoparticles. Surface modified nanoparticles exhibited improved suspension stability, compared to that of pure lipid nanoparticles for a period of 30days. Lowest aggregation was observed in DPPE-PEG modified nanoparticles from combined electrostatic and steric effects. The study provides a single-step aerosol method for in-situ surface modification of nanoparticles, using minimal amounts of surface active agents, to make stable, aqueous nanoparticle suspensions. Copyright © 2015 Elsevier Inc. All rights reserved.

Impact of asymmetric martensite and austenite nucleation and growth behavior on the phase stability and hysteresis of freestanding shape-memory nanoparticles

NASA Astrophysics Data System (ADS)

Ko, Won-Seok; Grabowski, Blazej; Neugebauer, Jörg

2018-03-01

Martensitic transformations in nanoscaled shape-memory alloys exhibit characteristic features absent for the bulk counterparts. Detailed understanding is required for applications in micro- and nanoelectromechanical systems, and experimental limitations render atomistic simulation an important complementary approach. Using a recently developed, accurate potential we investigate the phase transformation in freestanding Ni-Ti shape-memory nanoparticles with molecular-dynamics simulations. The results confirm that the decrease in the transformation temperature with decreasing particle size is correlated with an overstabilization of the austenitic surface energy over the martensitic surface energy. However, a detailed atomistic analysis of the nucleation and growth behavior reveals an unexpected difference in the mechanisms determining the austenite finish and martensite start temperature. While the austenite finish temperature is directly affected by a contribution of the surface energy difference, the martensite start temperature is mostly affected by the transformation strain, contrary to general expectations. This insight not only explains the reduced transformation temperature but also the reduced thermal hysteresis in freestanding nanoparticles.

Tuning the dielectric properties of polystyrene/poly(vinylidene fluoride) blends by selectively localizing carbon black nanoparticles.

PubMed

Zhao, Xiaodong; Zhao, Jun; Cao, Jian-Ping; Wang, Xiaoyan; Chen, Min; Dang, Zhi-Min

2013-02-28

In this work, the dielectric properties of immiscible polystyrene (PS)/poly(vinylidene fluoride) (PVDF) blends are tuned by selectively localizing carbon black (CB) nanoparticles in different phases. The PS/PVDF blends have a wide window of cocontinuity (ca. 30-80 vol % in terms of the volume fraction of PS component (v(PS))). The selective localization of CB nanoparticles is achieved by using the masterbatch process during melt mixing. For the volume ratio PS/PVDF 1/1 and the volume fraction of CB nanoparticles (v(CB)) below but close to the percolation threshold (v(c)(CB)), the selective localization of CB nanoparticles in PVDF phase produces higher dielectric constant (ε) than that in PS phase, whereas the ε of the ternary mixtures without selective localization of fillers is in the middle. For the volume ratios PS/PVDF 1/2 and 2/1, the selective location of CB nanoparticles in different phases can be used to easily tune the system from conductive to insulating or inverse, which might have potential applications in industry. The fillers are found to be "fixed" in the masterbatch of PS or PVDF component and there is no migration of the fillers to another phase occurring during the further mixing process for the mixing time up to 30 min. Furthermore, the addition of CB nanoparticles to the polymer matrix is found to induce the brittle-ductile transition in the system and increase the compatibility between the immiscible PS and PVDF components, which should benefit the mechanical properties.

Revealing nanoparticle assembly under high pressure.

NASA Astrophysics Data System (ADS)

Fan, Hongyou

Precise control of structural parameters through nanoscale engineering to improve optical and electronic properties of functional nanoparticles continuously remains an outstanding challenge. Previous work on nanoparticle assembly has been conducted largely at ambient pressure. Here I will present a new Stress-Induced Fabrication method in which we applied high pressure or stress to nanoparticle arrays to induce structural phase transition and to consolidate new nanomaterials with precisely controlled structures and tunable properties. By manipulating nanoparticle coupling through external pressure, a reversible change in their assemblies and properties can be achieved and demonstrated. In addition, over a certain threshold, the external pressure will force these nanoparticles into contact, thereby allowing the formation and consolidation of one- to three-dimensional nanostructures. Through stress induced nanoparticle assembly, materials engineering and synthesis become remarkably flexible without relying on traditional crystallization process where atoms/ions are locked in a specific crystal structure. Therefore, morphology or architecture can be readily tuned to produce desirable properties for practical applications. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

High-yield synthesis of brookite TiO.sub.2 nanoparticles

DOEpatents

Huber, Dale L [Albuquerque, NM; Monson, Todd C [Albuquerque, NM

2011-05-17

A method for forming non-agglomerated brookite TiO.sub.2 nanoparticles without the use of expensive organic surfactants or high temperature processing. Embodiments of this invention use titanium isopropoxide as the titanium precursor and isopropanol as both the solvent and ligand for ligand-stabilized brookite-phase titania. Isopropanol molecules serve as the ligands interacting with the titania surfaces that stabilize the titania nanoparticles. The isopropanol ligands can be exchanged with other alcohols and other ligands during or after the nanoparticle formation reaction.

[Properties of synthesized CdS nanoparticles by reverse micelle method].

PubMed

Li, Heng-Da; Wang, Qing-Wei; Zhai, Hong-Ju; Li, Wen-Lian

2008-07-01

Micelle system with reverse phase (water/CTAB/n-hexyl alcohol/n-heptane) is a weenie liquid-globelet of surface active agent molecule which can be stably and uniformly dispersed in continuous oil medium. The micelle system with reverse phase can work as a "micro-reactor" to synthesize CdS nano-particle with excellent performance. In the present article considering the effects of W value (W= [water]/[surface agent]) of the micelle system with reverse phase, we observed that the ratio of [Cd2+] and [S2-] ions to the original concentrations of the Cd2+ and S2- ions can affect the luminescent properties of CdS nano-particle. Using regurgitant treatment process the surface of CdS nano-particle can be modified, and as a result the defect emission was reduced and even disappeared, but exciton emissions markedly increased. On the other hand, a red-shift of the exciton emission peak with the increase in the particle size was observed, indicating considerable quantum confinement effect. A maximum quantum efficiency of 11% for the synthesized CdS nano-material was achieved.

Nanoparticle Superlattice Engineering with DNA

NASA Astrophysics Data System (ADS)

Mirkin, Chad

2012-02-01

Recent developments in strategies for assembling nanomaterials have allowed us to draw a direct analogy between the assembly of solid state atomic lattices and the construction of nanoparticle superlattices. Herein, we present a set of six design rules for using DNA as a programmable linker to deliberately stabilize nine distinct colloidal crystal structures, with lattice parameters that are tailorable over the 25-150 nm size regime. These rules are analogous to those put forth by Pauling decades ago to explain the relative stability of lattices composed of atoms and small molecules. It is ideal to use DNA as a nanoscale bond to connect nanoparticles to achieve colloidal superlattice structures in this system, since its programmable nature allows for facile control over nanoparticle bond length and strength, and nanoparticle bond selectivity. This assembly method affords simultaneous and independent control over nanoparticle structure, crystallographic symmetry, and lattice parameters with nanometer scale precision. Further, we have developed a phase diagram that predicts the design parameters necessary to achieve a lattice with a given symmetry and lattice parameters a priori. The rules developed in this work present a major advance towards true materials by design, as they effectively separate the identity of a particle core (and thereby its physical properties) from the variables that control its assembly.

Electronic structure, magnetic and structural properties of Ni doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Shalendra, E-mail: shailuphy@gmail.com; Vats, Prashant; Gautam, S.

Highlights: • XRD, and HR-TEM results show the single phase nature of Ni doped ZnO nanoparticles. • dc magnetization results indicate the RT-FM in Ni doped ZnO nanoparticles. • Ni L{sub 3,2} edge NEXAFS spectra infer that Ni ions are in +2 valence state. • O K edge NEXAFS spectra show that O vacancy increases with Ni doping in ZnO. - Abstract: We report structural, magnetic and electronic structural properties of Ni doped ZnO nanoparticles prepared by auto-combustion method. The prepared nanoparticles were characterized by using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), near edge X-ray absorption finemore » structure (NEXAFS) spectroscopy, and dc magnetization measurements. The XRD and HR-TEM results indicate that Ni doped ZnO nanoparticles have single phase nature with wurtzite lattice and exclude the presence of secondary phase. NEXAFS measurements performed at Ni L{sub 3,2}-edges indicates that Ni ions are in +2 valence state and exclude the presence of Ni metal clusters. O K-edge NEXAFS spectra indicate an increase in oxygen vacancies with Ni-doping, while Zn L{sub 3,2}-edge show the absence of Zn-vacancies. The magnetization measurements performed at room temperature shows that pure and Ni doped ZnO exhibits ferromagnetic behavior.« less

Role of Polymer-grafted Nanoparticle Interactions in Supercrystal Self-Assembly

NASA Astrophysics Data System (ADS)

Horst, Nathan; Waltmann, Curt; Travesset, Alex

Many successful strategies are available for the programmable self-assembly of nanoparticle superlattices. In this talk, we discuss the the case of nanoparticles with grafted polymer ligands. For very short polymers, the phase diagram is rationalized by borrowing results from hard-sphere packing models. Although a clear correlation exists between the maximum of the packing fraction of hard spheres and supercrystal equilibrium phases found experimentally, these systems are flexible, which leads to clear deviations from the sphere packing model. Using theoretical and computational models, we present an investigation of the interactions of polymer-grafted nanoparticles, focusing on the role of the rigidity of the chain, and how it affects the resulting two and three-dimensional superlattice structures. Comparison with an experimental system of gold nanoparticles grafted with polyethylene glycol is also presented. Supported by the U.S. Department of Energy (U.S. DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering. Ames Laboratory is operated for the U.S. DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

Polyethylene Nanocomposites for the Next Generation of Ultralow-Transmission-Loss HVDC Cables: Insulation Containing Moisture-Resistant MgO Nanoparticles.

PubMed

Pourrahimi, Amir Masoud; Pallon, Love K H; Liu, Dongming; Hoang, Tuan Anh; Gubanski, Stanislaw; Hedenqvist, Mikael S; Olsson, Richard T; Gedde, Ulf W

2016-06-15

The use of MgO nanoparticles in polyethylene for cable insulation has attracted considerable interest, although in humid media the surface regions of the nanoparticles undergo a conversion to a hydroxide phase. A facile method to obtain MgO nanoparticles with a large surface area and remarkable inertness to humidity is presented. The method involves (a) low temperature (400 °C) thermal decomposition of Mg(OH)2, (b) a silicone oxide coating to conceal the nanoparticles and prevent interparticle sintering upon exposure to high temperatures, and (c) heat treatment at 1000 °C. The formation of the hydroxide phase on these silicone oxide-coated MgO nanoparticles after extended exposure to humid air was assessed by thermogravimetry, infrared spectroscopy, and X-ray diffraction. The nanoparticles showed essentially no sign of any hydroxide phase compared to particles prepared by the conventional single-step thermal decomposition of Mg(OH)2. The moisture-resistant MgO nanoparticles showed improved dispersion and interfacial adhesion in the LDPE matrix with smaller nanosized particle clusters compared with conventionally prepared MgO. The addition of 1 wt % moisture-resistant MgO nanoparticles was sufficient to decrease the conductivity of polyethylene 30 times. The reduction in conductivity is discussed in terms of defect concentration on the surface of the moisture-resistant MgO nanoparticles at the polymer/nanoparticle interface.

Optimization of nanoparticles for cardiovascular tissue engineering.

PubMed

Izadifar, Mohammad; Kelly, Michael E; Haddadi, Azita; Chen, Xiongbiao

2015-06-12

Nano-particulate delivery systems have increasingly been playing important roles in cardiovascular tissue engineering. Properties of nanoparticles (e.g. size, polydispersity, loading capacity, zeta potential, morphology) are essential to system functions. Notably, these characteristics are regulated by fabrication variables, but in a complicated manner. This raises a great need to optimize fabrication process variables to ensure the desired nanoparticle characteristics. This paper presents a comprehensive experimental study on this matter, along with a novel method, the so-called Geno-Neural approach, to analyze, predict and optimize fabrication variables for desired nanoparticle characteristics. Specifically, ovalbumin was used as a protein model of growth factors used in cardiovascular tissue regeneration, and six fabrication variables were examined with regard to their influence on the characteristics of nanoparticles made from high molecular weight poly(lactide-co-glycolide). The six-factor five-level central composite rotatable design was applied to the conduction of experiments, and based on the experimental results, a geno-neural model was developed to determine the optimum fabrication conditions. For desired particle sizes of 150, 200, 250 and 300 nm, respectively, the optimum conditions to achieve the low polydispersity index, higher negative zeta potential and higher loading capacity were identified based on the developed geno-neural model and then evaluated experimentally. The experimental results revealed that the polymer and the external aqueous phase concentrations and their interactions with other fabrication variables were the most significant variables to affect the size, polydispersity index, zeta potential, loading capacity and initial burst release of the nanoparticles, while the electron microscopy images of the nanoparticles showed their spherical geometries with no sign of large pores or cracks on their surfaces. The release study revealed

Surface-modified multifunctional MIP nanoparticles

PubMed Central

Moczko, Ewa; Poma, Alessandro; Guerreiro, Antonio; de Vargas Sansalvador, Isabel Perez; Caygill, Sarah; Canfarotta, Francesco; Whitcombe, Michael J.; Piletsky, Sergey

2015-01-01

The synthesis of core-shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly-sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity (PEG methacrylate); electro-activity (vinyl ferrocene); fluorescence (eosin acrylate); thiol groups (pentaerythritol tetrakis(3-mercaptopropionate)). The method has broad applicability and can be used to produce multifunctional imprinted nanoparticles with potential for further application in the biosensors, diagnostics and biomedical fields and as an alternative to natural receptors. PMID:23503559

Surface-modified multifunctional MIP nanoparticles.

PubMed

Moczko, Ewa; Poma, Alessandro; Guerreiro, Antonio; Perez de Vargas Sansalvador, Isabel; Caygill, Sarah; Canfarotta, Francesco; Whitcombe, Michael J; Piletsky, Sergey

2013-05-07

The synthesis of core-shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as a protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity (PEG methacrylate); electro-activity (vinylferrocene); fluorescence (eosin acrylate); thiol groups (pentaerythritol tetrakis(3-mercaptopropionate)). The method has broad applicability and can be used to produce multifunctional imprinted nanoparticles with potential for further application in the biosensors, diagnostics and biomedical fields and as an alternative to natural receptors.

Formation of Multiple-Phase Catalysts for the Hydrogen Storage of Mg Nanoparticles by Adding Flowerlike NiS.

PubMed

Xie, Xiubo; Ma, Xiujuan; Liu, Peng; Shang, Jiaxiang; Li, Xingguo; Liu, Tong

2017-02-22

In order to enhance the hydrogen storage properties of Mg, flowerlike NiS particles have been successfully prepared by solvothermal reaction method, and are subsequently ball milled with Mg nanoparticles (NPs) to fabricate Mg-5 wt % NiS nanocomposite. The nanocomposite displays Mg/NiS core/shell structure. The NiS shell decomposes into Ni, MgS and Mg 2 Ni multiple-phases, decorating on the surface of the Mg NPs after the first hydrogen absorption and desorption cycle at 673 K. The Mg-MgS-Mg 2 Ni-Ni nanocomposite shows enhanced hydrogenation and dehydrogenation rates: it can quickly uptake 3.5 wt % H 2 within 10 min at 423 K and release 3.1 wt % H 2 within 10 min at 573 K. The apparent hydrogen absorption and desorption activation energies are decreased to 45.45 and 64.71 kJ mol -1 . The enhanced sorption kinetics of the nanocomposite is attributed to the synergistic catalytic effects of the in situ formed MgS, Ni and Mg 2 Ni multiple-phase catalysts during the hydrogenation/dehydrogenation process, the porthole effects for the volume expansion and microstrain of the phase transformation of Mg 2 Ni and Mg 2 NiH 4 and the reduced hydrogen diffusion distance caused by nanosized Mg. This novel method of in situ producing multiple-phase catalysts gives a new horizon for designing high performance hydrogen storage material.

Gas phase 1H NMR studies and kinetic modeling of dihydrogen isotope equilibration catalyzed by Ru-nanoparticles under normal conditions: dissociative vs. associative exchange.

PubMed

Limbach, Hans-Heinrich; Pery, Tal; Rothermel, Niels; Chaudret, Bruno; Gutmann, Torsten; Buntkowsky, Gerd

2018-04-25

The equilibration of H2, HD and D2 between the gas phase and surface hydrides of solid organic-ligand-stabilized Ru metal nanoparticles has been studied by gas phase 1H NMR spectroscopy using closed NMR tubes as batch reactors at room temperature and 800 mbar. When two different nanoparticle systems, Ru/PVP (PVP ≡ polyvinylpyrrolidone) and Ru/HDA (HDA ≡ hexadecylamine) were exposed to D2 gas, only the release of HD from the hydride containing surface could be detected in the initial stages of the reaction, but no H2. In the case of Ru/HDA also the reverse experiment was performed where surface deuterated nanoparticles were exposed to H2. In that case, the conversion of H2 into gaseous HD was detected. In order to analyze the experimental kinetic and spectroscopic data, we explored two different mechanisms taking into account potential kinetic and equilibrium H/D isotope effects. Firstly, we explored the dissociative exchange mechanism consisting of dissociative adsorption of dihydrogen, fast hydride surface diffusion and associative desorption of dihydrogen. It is shown that if D2 is the reaction partner, only H2 will be released in the beginning of the reaction, and HD only in later reaction stages. The second mechanism, dubbed here associative exchange consists of the binding of dihydrogen to Ru surface atoms, followed by a H-transfer to or by H-exchange with an adjacent hydride site, and finally of the associative desorption of dihydrogen. In that case, in the exchange with D2, only HD will be released in the beginning of the reaction. Our experimental results are not compatible with the dissociative exchange but can be explained in terms of the associative exchange. Whereas the former will dominate at low temperatures and pressures, the latter will prevail around room temperature and normal pressures where transition metal nanoparticles are generally used as reaction catalysts.

Ag–Pt compositional intermetallics made from alloy nanoparticles

DOE PAGES

Pan, Yung -Tin; Yan, Yuqi; Shao, Yu -Tsun; ...

2016-09-07

Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag–Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material thatmore » has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). Finally, this Ag–Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.« less

Ag–Pt compositional intermetallics made from alloy nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Yung -Tin; Yan, Yuqi; Shao, Yu -Tsun

Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag–Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material thatmore » has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). Finally, this Ag–Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.« less

Magnetic dispersive solid-phase extraction based on modified magnetic nanoparticles for the detection of cocaine and cocaine metabolites in human urine by high-performance liquid chromatography-mass spectrometry.

PubMed

Yang, Feiyu; Zou, Yun; Ni, Chunfang; Wang, Rong; Wu, Min; Liang, Chen; Zhang, Jiabin; Yuan, Xiaoliang; Liu, Wenbin

2017-11-01

An easy-to-handle magnetic dispersive solid-phase extraction procedure was developed for preconcentration and extraction of cocaine and cocaine metabolites in human urine. Divinyl benzene and vinyl pyrrolidone functionalized silanized Fe 3 O 4 nanoparticles were synthesized and used as adsorbents in this procedure. Scanning electron microscopy, vibrating sample magnetometry, and infrared spectroscopy were employed to characterize the modified adsorbents. A high-performance liquid chromatography with mass spectrometry method for determination of cocaine and its metabolites in human urine sample has been developed with pretreatment of the samples by magnetic dispersive solid-phase extraction. The obtained results demonstrated the higher extraction capacity of the prepared nanoparticles with recoveries between 75.1 to 105.7% and correlation coefficients higher than 0.9971. The limits of detection for the cocaine and cocaine metabolites were 0.09-1.10 ng/mL. The proposed magnetic dispersive solid-phase extraction method provided a rapid, environmentally friendly and magnetic stuff recyclable approach and it was confirmed that the prepared adsorbents material was a kind of highly effective extraction materials for the trace cocaine and cocaine metabolites analyses in human urine. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Directed Self-Organization of Polymer-Grafted Nanoparticles in Polymer Thin Films

NASA Astrophysics Data System (ADS)

Zhang, Ren

The controlled organization of nanoparticle (NP) constituents into superstructures of well-defined shape, composition and connectivity represents a continuing challenge in the development of novel hybrid materials for many technological applications. Surface modification of NPs with grafted polymer ligands has emerged as a versatile means to control the interaction and organization of particle constituents in polymer-matrix composite materials. In this study, by incorporating polymer-grafted nanoparticles (PGNPs) into polymeric thin films, we aim to understand and control the spatial organization of PGNPs through the interactions between polymer brush layer and matrix chains. As model systems, we investigate thermodynamic behaviors of polystyrene-tethered gold nanoparticles (denoted as AuPS) dispersed in polymer thin film matrices with identical and different chemical compositions (PS and PMMA, respectively), and evaluate the influence of external perturbation fields on directed organization of nanofillers. With the presence of unfavorable enthalpic interactions between grafted and free polymer chains (i.e. AuPS/ PMMA blend thin films), phase-separated structures are generated upon thermal annealing, characterized with morphologies ranging from discrete droplets to spinodal structures, which is consistent with composition-dependent classic binary polymer blends phase separation. The phase separation kinetics of AuPS/ PMMA blends exhibit distinct features compared to the parent PS/ PMMA homopolymer blends. We further illustrate phase-separated AuPS-rich domains can be directed into unidirectionally aligned anisotropic structures through soft-shear dynamic zone annealing (DZA-SS) process with tunable domain aspect ratios. To exert exquisite control over the shape, size and location of phase-separated PGNP domains, topographically patterned elastomer confinement is introduced to PGNP/ polymer blend thin films during thermal annealing. When the phase

Influence of hydrothermal synthesis parameters on the properties of hydroxyapatite nanoparticles.

PubMed

Kuśnieruk, Sylwia; Wojnarowicz, Jacek; Chodara, Agnieszka; Chudoba, Tadeusz; Gierlotka, Stanislaw; Lojkowski, Witold

2016-01-01

Hydroxyapatite (HAp) nanoparticles of tunable diameter were obtained by the precipitation method at room temperature and by microwave hydrothermal synthesis (MHS). The following parameters of the obtained nanostructured HAp were determined: pycnometric density, specific surface area, phase purity, lattice parameters, particle size, particle size distribution, water content, and structure. HAp nanoparticle morphology and structure were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction measurements confirmed crystalline HAp was synthesized, which was pure in terms of phase. It was shown that by changing the synthesis parameters, the diameter of HAp nanoparticles could be controlled. The average diameter of the HAp nanoparticles was determined by Scherrer's equation via the Nanopowder XRD Processor Demo web application, which interprets the results of specific surface area and TEM measurements using the dark-field technique. The obtained nanoparticles with average particle diameter ranging from 8-39 nm were characterized by having homogeneous morphology with a needle shape and a narrow particle size distribution. Strong similarities were found when comparing the properties of some types of nanostructured hydroxyapatite with natural occurring apatite found in animal bones and teeth.

Structural, magnetic and electronic structure properties of Co doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Shalendra, E-mail: shailuphy@gmail.com; School of Materials Science and Engineering, Changwon National University, Changwon, Gyeongnam 641-773; Song, T.K., E-mail: tksong@changwon.ac.kr

Highlights: • XRD and HR-TEM results show the single phase nature of Co doped ZnO nanoparticles. • XMCD and dc magnetization results indicate the RT-FM in Co doped ZnO nanoparticles. • Co L{sub 3,2} NEXAFS spectra infer that Co ions are in 2+ valence state. • O K edge NEXAFS spectra show that O vacancy increases with Co doping in ZnO. - Abstract: We reported structural, magnetic and electronic structure studies of Co doped ZnO nanoparticles. Doping of Co ions in ZnO host matrix has been studied and confirmed using various methods; such as X-ray diffraction (XRD), field emission scanningmore » electron microscopy (FE-SEM), energy dispersed X-ray (EDX), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, magnetic hysteresis loop measurements and X-ray magnetic circular dichroism (XMCD). From the XRD and HR-TEM results, it is observed that Co doped ZnO nanoparticles have single phase nature with wurtzite structure and exclude the possibility of secondary phase formation. FE-SEM and TEM micrographs show that pure and Co doped nanoparticles are nearly spherical in shape. O K edge NEXAFS spectra indicate that O vacancies increase with Co doping. The Co L{sub 3,2} edge NEXAFS spectra revealed that Co ions are in 2+ valence state. DC magnetization hysteresis loops and XMCD results clearly showed the intrinsic origin of temperature ferromagnetism in Co doped ZnO nanoparticles.« less

Supercooled smectic nanoparticles: a potential novel carrier system for poorly water soluble drugs.

PubMed

Kuntsche, J; Westesen, K; Drechsler, M; Koch, M H J; Bunjes, H

2004-10-01

The possibility of preparing nanoparticles in the supercooled thermotropic liquid crystalline state from cholesterol esters with saturated acyl chains as well as the incorporation of model drugs into the dispersions was investigated using cholesteryl myristate (CM) as a model cholesterol ester. Nanoparticles were prepared by high-pressure melt homogenization or solvent evaporation using phospholipids, phospholipid/ bile salt, or polyvinyl alcohol as emulsifiers. The physicochemical state and phase behavior of the particles was characterized by particle size measurements (photon correlation spectroscopy, laser diffraction with polarization intensity differential scattering), differential scanning calorimetry, X-ray diffraction, and electron and polarizing light microscopy. The viscosity of the isotropic and liquid crystalline phases of CM in the bulk was investigated in dependence on temperature and shear rate by rotational viscometry. CM nanoparticies can be obtained in the smectic phase and retained in this state for at least 12 months when stored at 230C in optimized systems. The recrystallization tendency of CM in the dispersions strongly depends on the stabilizer system and the particle size. Stable drug-loaded smectic nanoparticles were obtained after incorporation of 10% (related to CM) ibuprofen, miconazole, etomidate, and 1% progesterone. Due to their liquid crystalline state, colloidal smectic nanoparticles offer interesting possibilities as carrier system for lipophilic drugs. CM nanoparticles are suitable model systems for studying the crystallization behavior and investigating the influence of various parameters for the development of smectic nanoparticles resistant against recrystallization upon storage.

Aerosolized antimicrobial agents based on degradable dextran nanoparticles loaded with silver carbene complexes.

PubMed

Ornelas-Megiatto, Cátia; Shah, Parth N; Wich, Peter R; Cohen, Jessica L; Tagaev, Jasur A; Smolen, Justin A; Wright, Brian D; Panzner, Matthew J; Youngs, Wiley J; Fréchet, Jean M J; Cannon, Carolyn L

2012-11-05

Degradable acetalated dextran (Ac-DEX) nanoparticles were prepared and loaded with a hydrophobic silver carbene complex (SCC) by a single-emulsion process. The resulting particles were characterized for morphology and size distribution using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The average particle size and particle size distribution were found to be a function of the ratio of the organic phase to the surfactant containing aqueous phase with a 1:5 volume ratio of Ac-DEX CH(2)Cl(2) (organic):PBS (aqueous) being optimal for the formulation of nanoparticles with an average size of 100 ± 40 nm and a low polydispersity. The SCC loading was found to increase with an increase in the SCC quantity in the initial feed used during particle formulation up to 30% (w/w); however, the encapsulation efficiency was observed to be the best at a feed ratio of 20% (w/w). In vitro efficacy testing of the SCC loaded Ac-DEX nanoparticles demonstrated their activity against both Gram-negative and Gram-positive bacteria; the nanoparticles inhibited the growth of every bacterial species tested. As expected, a higher concentration of drug was required to inhibit bacterial growth when the drug was encapsulated within the nanoparticle formulations compared with the free drug illustrating the desired depot release. Compared with free drug, the Ac-DEX nanoparticles were much more readily suspended in an aqueous phase and subsequently aerosolized, thus providing an effective method of pulmonary drug delivery.

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity

PubMed Central

Harper-Leatherman, Amanda S.; Pacer, Elizabeth R.; Kosciuszek, Nina D.

2016-01-01

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol–gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development. PMID:26967257

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity.

PubMed

Harper-Leatherman, Amanda S; Pacer, Elizabeth R; Kosciuszek, Nina D

2016-03-01

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol-gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development.

Magnetic solid phase extraction of brominated flame retardants and pentachlorophenol from environmental waters with carbon doped Fe3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Yang, Jing; Li, Jia-yuan; Qiao, Jun-qin; Cui, Shi-hai; Lian, Hong-zhen; Chen, Hong-yuan

2014-12-01

Carbon doped Fe3O4 nanoparticles (Fe3O4/C) prepared by a facile hydrothermal reaction of glucose with iron resource have been applied as magnetic solid-phase extraction (MSPE) sorbent, for the first time, to extract trace brominated flame retardants (BFRs) and pentachlorophenol (PCP) from environmental waters. Various MSPE parameters were optimized including amount of Fe3O4/C nanoparticles, pH of sample solution, enrichment factor of analytes and reusability of Fe3O4/C sorbent. The reliability of the MSPE method was evaluated by the recoveries of BFRs and PCP in spiked water samples. Good recoveries (80.0-110.0%) were achieved with the relative standard deviations range from 0.3% to 6.8%. In this paper, the extraction characteristics of Fe3O4/C sorbent were further elucidated. It is found that the adsorption process of Fe3O4/C to analytes predominates the MSPE efficiency. There is hybrid hydrophobic interaction and hydrogen bonding or dipole-dipole attraction between Fe3O4/C and analytes. Notably, the chemical components of carbon layer on the surface of Fe3O4 nanoparticles were identified by X-ray photoelectron spectroscopy and thermogravimetry-mass spectrometry, and in consequence the covalent bonds between Fe3O4 and the coated carbon have been observed. In addition, the straight influence of synthesis condition of Fe3O4/C nanoparticles including glucose concentration and hydrothermal reaction time on extraction performance for BFRs and PCP has been investigated. It is confirmed that the existence of organic carbon containing functional groups over Fe3O4/C sorbent is responsible for the MSPE extraction.

Structure and stability of charged colloid-nanoparticle mixtures

NASA Astrophysics Data System (ADS)

Weight, Braden M.; Denton, Alan R.

2018-03-01

Physical properties of colloidal materials can be modified by addition of nanoparticles. Within a model of like-charged mixtures of particles governed by effective electrostatic interactions, we explore the influence of charged nanoparticles on the structure and thermodynamic phase stability of charge-stabilized colloidal suspensions. Focusing on salt-free mixtures of particles of high size and charge asymmetry, interacting via repulsive Yukawa effective pair potentials, we perform molecular dynamics simulations and compute radial distribution functions and static structure factors. Analysis of these structural properties indicates that increasing the charge and concentration of nanoparticles progressively weakens correlations between charged colloids. We show that addition of charged nanoparticles to a suspension of like-charged colloids can induce a colloidal crystal to melt and can facilitate aggregation of a fluid suspension due to attractive van der Waals interactions. We attribute the destabilizing influence of charged nanoparticles to enhanced screening of electrostatic interactions, which weakens repulsion between charged colloids. This interpretation is consistent with recent predictions of an effective interaction theory of charged colloid-nanoparticle mixtures.

Rapid synthesis of flower shaped Cu{sub 2}ZnSnS{sub 4} nanoparticles by microwave irradiation for solar cell application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ansari, Mohd Zubair, E-mail: mhd.zubair1@gmail.com; Khare, Neeraj

Single phase Cu{sub 2}ZnSnS{sub 4} (CZTS) nanoparticles have been synthesized by the microwave-assisted solution method in a one step process. Structural, morphological and optical characterizations of the CZTS nanoparticles have been carried out. X-ray diffraction confirms the single phase formation of CZTS nanoparticles with kesterite structure. SEM confirms the homogenous distribution of CZTS nanoparticles flower like assemblies. High resolution TEM image confirms the good crystallinity of the CZTS nanoparticles with the average grain size ~20 nm. The CZTS nanoparticles have strong optical absorption in the visible region with direct band gap as ~1.6 eV which is optimal for photovoltaic application.

Mechanistic approach to study conjugation of nanoparticles for biomedical applications.

PubMed

Uddin, Imran

2018-05-16

Interaction of nanoparticles with biological systems turns out to be vibrant for their efficient application in biomedical field. Here, we have shown antibiotic amakicin loaded nanoparticles are responsible for the dual role as reducing and stabilizing the silver nanoparticles without the use of any undesired chemicals. Synthesized nanoparticles are well-dispersed having quasi spherical morphology with an average particle size around 10-11 nm. Crystallinity of nanoparticles was measured using selected area electron diffraction (SAED) and powder XRD analysis which show that particles are perfectly crystalline with cubic phase of geometry. UV-Vis, FTIR and circular dichroism (CD) analysis explained the presence and interaction of antibiotic on the nanoparticle's surface. Amakicin functionalized Ag nanoparticles used in this study have shown enhanced antibacterial activity against E. coli. These studies will help in designing an in-depth understanding that how nanostructures can possibly interact with biological systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Magnetic nanoparticles: synthesis, functionalization, and applications in bioimaging and magnetic energy storage.

PubMed

Frey, Natalie A; Peng, Sheng; Cheng, Kai; Sun, Shouheng

2009-09-01

This tutorial review summarizes the recent advances in the chemical synthesis and potential applications of monodisperse magnetic nanoparticles. After a brief introduction to nanomagnetism, the review focuses on recent developments in solution phase syntheses of monodisperse MFe(2)O(4), Co, Fe, CoFe, FePt and SmCo(5) nanoparticles. The review further outlines the surface, structural, and magnetic properties of these nanoparticles for biomedicine and magnetic energy storage applications.

Manipulating the Ordered Nanostructure of Self-Assembled Monoolein and Phytantriol Nanoparticles with Unsaturated Fatty Acids.

PubMed

Tran, Nhiem; Mulet, Xavier; Hawley, Adrian M; Fong, Celesta; Zhai, Jiali; Le, Tu C; Ratcliffe, Julian; Drummond, Calum J

2018-02-27

Mesophase structures of self-assembled lyotropic liquid crystalline nanoparticles are important factors that directly influence their ability to encapsulate and release drugs and their biological activities. However, it is difficult to predict and precisely control the mesophase behavior of these materials, especially in complex systems with several components. In this study, we report the controlled manipulation of mesophase structures of monoolein (MO) and phytantriol (PHYT) nanoparticles by adding unsaturated fatty acids (FAs). By using high throughput formulation and small-angle X-ray scattering characterization methods, the effects of FAs chain length, cis-trans isomerism, double bond location, and level of chain unsaturation on self-assembled systems are determined. Additionally, the influence of temperature on the phase behavior of these nanoparticles is analyzed. We found that in general, the addition of unsaturated FAs to MO and PHYT induces the formation of mesophases with higher Gaussian surface curvatures. As a result, a rich variety of lipid polymorphs are found to correspond with the increasing amounts of FAs. These phases include inverse bicontinuous cubic, inverse hexagonal, and discrete micellar cubic phases and microemulsion. However, there are substantial differences between the phase behavior of nanoparticles with trans FA, cis FAs with one double bond, and cis FAs with multiple double bonds. Therefore, the material library produced in this study will assist the selection and development of nanoparticle-based drug delivery systems with desired mesophase.

Optical Properties and Microstructure of Silver-Copper Nanoparticles Synthesized by Pulsed Laser Deposition

NASA Astrophysics Data System (ADS)

Hirai, Makoto; Kumar, Ashok

2007-12-01

Utilizing a pulsed laser deposition (PLD) method, silver-copper (Ag-Cu) nanoparticles have been synthesized by changing the surface area ratio of the target ( S R = S Cu/( S Ag + S Cu)) from 0 to 30%. The peak absorption attributed to surface plasmon resonance (SPR) increased when increasing S R up to 15%, above which it decreased. The peak shifts seem to be induced by the changes in the conductivity and morphology of the Ag-Cu nanoparticles. Additionally, the interplanar spacings of the Ag-Cu nanoparticles prepared at S R = 15% corresponded to the Ag {111}, {200}, {220}, and Cu {111} planes. However, since the interplanar spacings attributed to the Cu {200} and {220} planes were not detected, the Ag-Cu nanoparticles were believed to possess a lattice constant ( a) close not to the Cu phase ( a = 3.615 Å) but to the Ag phase ( a = 4.086 Å). Moreover, confirming the presence of Cu atoms in the nanoparticles using energy dispersive X-ray (EDX) spectra, Ag-Cu nanoparticles may be a solid solution in which Cu atoms partially replace Ag atoms in the fcc structure.

Nucleation of Iron Oxide Nanoparticles Mediated by Mms6 Protein in Situ

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashyap, Sanjay; Woehl, Taylor J; Liu, Xunpei

2014-09-23

Biomineralization proteins are widely used as templating agents in biomimetic synthesis of a variety of organic–inorganic nanostructures. However, the role of the protein in controlling the nucleation and growth of biomimetic particles is not well understood, because the mechanism of the bioinspired reaction is often deduced from ex situ analysis of the resultant nanoscale mineral phase. Here we report the direct visualization of biomimetic iron oxide nanoparticle nucleation mediated by an acidic bacterial recombinant protein, Mms6, during an in situ reaction induced by the controlled addition of sodium hydroxide to solution-phase Mms6 protein micelles incubated with ferric chloride. Using inmore » situ liquid cell scanning transmission electron microscopy we observe the liquid iron prenucleation phase and nascent amorphous nanoparticles forming preferentially on the surface of protein micelles. Our results provide insight into the early steps of protein-mediated biomimetic nucleation of iron oxide and point to the importance of an extended protein surface during nanoparticle formation.« less

Synthesis and characterization of magnetically hard Fe-Pt alloy nanoparticles and nano-islands

NASA Astrophysics Data System (ADS)

Hu, Xiaocao

In this dissertation, we explored the fabrication of FePt nanoparticles and nano-islands with the face-centered tetragonal (fct, L10) phase prepared by both chemical synthesis routes and physical vapor deposition. Microstructure and magnetic properties characterizations were used to gain a fundamental understanding of the nano-structure formation and atomic ordering behavior and determine the possible applications in the next generation ultra-high density magnetic storage media. FePt nanoparticles prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)5] have been widely investigated and by tuning the processing procedure monodispersed FePt nanoparticles with good assembly can be obtained. The as-made FePt nanoparticles are usually in the magnetically soft face-centered cubic (fcc) phase. To transformation to the fct phase, post-annealing at above 600°C is needed which, however, introduces undesirable agglomeration and sintering. To address this problem, we used three different fabrication processes which are discussed below. In the first fabrication experiment, the FePt nanoparticles were fabricated by a novel environmental friendly method involving crystalline saline complex hexaaquairon (II) hexachloroplatinate ([Fe(H2O)6]PtCl 6) with a special layered structure. Then the precursor was ball milled with NaCl and annealed at temperatures above 400°C under a reducing atmosphere of forming gas (95% Ar and 5% H2) FePt nanoparticles were obtained after washing away NaCl with deionized water. This method avoids the use of the very poisonous Fe(CO)5 and other organic solvents such as oleylamine and oleic acid. Instead, environmentally friendly NaCl and water were used. The size of FePt nanoparticles was controlled by varying the proportion of precursor and NaCl (from 10mg/20g to 50mg/20g). Particles with size in the range of 6.2--13.2 nm were obtained. All the nanoparticles annealed above 400°C are in the highly ordered fct phase with a coercivity range of 4

Synthesis and Cs-Corrected Scanning Transmission Electron Microscopy Characterization of Multimetallic Nanoparticles

NASA Astrophysics Data System (ADS)

Khanal, Subarna; Bhattarai, Nabraj; Velázquez-Salazar, Jesus; Jose-Yacaman, Miguel; Subarna Khanal Team

2014-03-01

Multimetallic nanoparticles have been attracted greater attention both in materials science and nanotechnology due to its unique electronic, optical, biological, and catalytic properties lead by physiochemical interactions among different atoms and phases. The distinct features of multimetallic nanoparticles enhanced synergetic properties, large surface to volume ratio and quantum size effects ultimately lead to novel and wide range of possibilities for different applications than monometallic counterparts. For instance, PtPd, Pt/Cu, Au-Au3Cu, AgPd/Pt, AuCu/Pt and many other multimetallic nanoparticles have raised interest for their various applications in fuel cells, ethanol and methanol oxidation reactions, hydrogen storage, and so on. The nanostructures were analyzed by transmission electron microscopy (TEM) and by aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in combination with high angle annular dark field (HAADF), bright field (BF), energy dispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) detectors. These techniques allowed us to probe the structure at the atomic level of the nanoparticles revealing new structural information and elemental composition of the nanoparticles. The authors would like to acknowledge NSF grants DMR-1103730, ``Alloys at the Nanoscale: The Case of Nanoparticles Second Phase'' and NSF PREM Grant # DMR 0934218.

Nanoparticles of CdCl2 with closed cage structures

NASA Astrophysics Data System (ADS)

Popovitz-Biro, R.; Twersky, A.; Hacohen, Y. Rosenfeld; Tenne, R.

2000-11-01

Nanoparticles of various layered compounds having a closed cage or nanotubular structure, designated also inorganic fullerene-like (IF) materials, have been reported in the past. In this work IF-CdCl2 nanoparticles were synthesized by electron beam irradiation of the source powder leading to its recrystallization into closed nanoparticles with a nonhollow core. This process created polyhedral nanoparticles with hexagonal or elongated rectangular characters. The analysis also shows that, while the source (dried) powder is orthorhombic cadmium chloride monohydrate, the crystallized IF cage consists of the anhydrous 3R polytype which is not stable as bulk material in ambient atmosphere. Consistent with previous observations, this study shows that the seamless structure of the IF materials can stabilize phases, which are otherwise unstable in ambient conditions.

Electric-Field-Induced Alignment of Block Copolymer/Nanoparticle Blends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liedel, Clemens; Schindler, Kerstin; Pavan, Mariela J.

External electric fi elds readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-fi eld-induced alignment of a lamellae-forming polystyrene- block -poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-fi eldassisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such fi lms under benign experimental conditions.

Non-hazardous anticancerous and antibacterial colloidal 'green' silver nanoparticles.

PubMed

Barua, Shaswat; Konwarh, Rocktotpal; Bhattacharya, Satya Sundar; Das, Pallabi; Devi, K Sanjana P; Maiti, Tapas K; Mandal, Manabendra; Karak, Niranjan

2013-05-01

Poly(ethylene glycol) stabilized colloidal silver nanoparticles were prepared using the reductive potency of the aqueous extract of Thuja occidentalis leaves under ambient conditions. The nanoparticles were well dispersed within a narrow size spectrum (7-14 nm) and displayed characteristic surface plasmon resonance peak at around 420 nm and Bragg's reflection planes of fcc structure. MTT assay revealed the dose-dependent cytocompatibility and toxicity of the nanoparticles with the L929 normal cell line. On the other hand, the antiproliferative action of the nanoparticles was evaluated on HeLa cell (cancerous cells) line. Fluorescence and phase contrast microscopic imaging indicated the appearance of multinucleate stages with aggregation and nuclear membrane disruption of the HeLa cells post treatment with the nanoparticles. The interaction at the prokaryotic level was also assessed via differential antibacterial efficacy against Staphylococcus aureus (MTCC 3160) and Escherichia coli (MTCC 40). Under these perspectives, it is also necessary to observe the environmental impact of the prepared silver nanoparticles. Hence, the dose dependent toxicity of silver nanoparticles was evaluated upon the earthworm species Eisenia fetida. Neither the survival nor the reproduction was affected by the addition of silver nanoparticles up to 1000 ppm. Thus these 'green' silver nanoparticles have promising potential as future materials. Copyright © 2012 Elsevier B.V. All rights reserved.

Evidence for the Formation of Nitrogen-Rich Platinum and Palladium Nitride Nanoparticles

DOE PAGES

Veith, Gabriel M.; Lupini, Andrew R.; Baggetto, Loïc; ...

2013-12-03

Here, we report evidence for the formation of nitrogen-rich precious metal nanoparticles (Pt, Pd) prepared by reactive sputtering of the pure metal in a N 2 plasma. The composition of the nanoparticles varies as a function of particle size and growth conditions. For the smallest particles the nitrogen content appears to be as high as 6.7 N atoms for each Pd atom or 5.9 N atoms for each Pt atom whereas bulk films have nominal compositions of Pt 7.3N and Pd 2.5N. The nanoparticles are metastable in air and moisture, slowly decomposing over several years. This paper describes the synthesismore » of these materials along with experimental evidence of the composition, oxidation state, and growth modes. Moreover, the catalytic properties of these N-rich nanoparticles were accessed by rotating disk electrode electrochemical studies, the liquid phase oxidation of benzyl alcohol and gas phase CO oxidation and support the experimental evidence for the materials composition.« less

Decoration of vertical graphene with aerosol nanoparticles for gas sensing

NASA Astrophysics Data System (ADS)

Cui, Shumao; Guo, Xiaoru; Ren, Ren; Zhou, Guihua; Chen, Junhong

2015-08-01

A facile method was demonstrated to decorate aerosol Ag nanoparticles onto vertical graphene surfaces using a mini-arc plasma reactor. The vertical graphene was directly grown on a sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method. The aerosol Ag nanoparticles were synthesized by a simple vapor condensation process using a mini-arc plasma source. Then, the nanoparticles were assembled on the surface of vertical graphene through the assistance of an electric field. Based on our observation, nonagglomerated Ag nanoparticles formed in the gas phase and were assembled onto vertical graphene sheets. Nanohybrids of Ag nanoparticle-decorated vertical graphene were characterized for ammonia gas detection at room temperature. The vertical graphene served as the conductance channel, and the conductance change upon exposure to ammonia was used as the sensing signal. The sensing results show that Ag nanoparticles significantly improve the sensitivity, response time, and recovery time of the sensor.

Perspective on nanoparticle technology for biomedical use

PubMed Central

Raliya, Ramesh; Chadha, Tandeep Singh; Hadad, Kelsey; Biswas, Pratim

2016-01-01

This review gives a short overview on the widespread use of nanostructured and nanocomposite materials for disease diagnostics, drug delivery, imaging and biomedical sensing applications. Nanoparticle interaction with a biological matrix/entity is greatly influenced by its morphology, crystal phase, surface chemistry, functionalization, physicochemical and electronic properties of the particle. Various nanoparticle synthesis routes, characteristization, and functionalization methodologies to be used for biomedical applications ranging from drug delivery to molecular probing of underlying mechanisms and concepts are described with several examples (150 references). PMID:26951098

High-throughput multipesticides residue analysis in earthworms by the improvement of purification method: Development and application of magnetic Fe3 O4 -SiO2 nanoparticles based dispersive solid-phase extraction.

PubMed

Sun, Yuhan; Qi, Peipei; Cang, Tao; Wang, Zhiwei; Wang, Xiangyun; Yang, Xuewei; Wang, Lidong; Xu, Xiahong; Wang, Qiang; Wang, Xinquan; Zhao, Changshan

2018-06-01

As a key representative organism, earthworms can directly illustrate the influence of pesticides on environmental organisms in soil ecosystems. The present work aimed to develop a high-throughput multipesticides residue analytical method for earthworms using solid-liquid extraction with acetonitrile as the solvent and magnetic material-based dispersive solid-phase extraction for purification. Magnetic Fe 3 O 4 nanoparticles were modified with a thin silica layer to form Fe 3 O 4 -SiO 2 nanoparticles, which were fully characterized by field-emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry, and vibrating sample magnetometry. The Fe 3 O 4 -SiO 2 nanoparticles were used as the separation media in dispersive solid-phase extraction with primary secondary amine and ZrO 2 as the cleanup adsorbents to eliminate matrix interferences. The amounts of nanoparticles and adsorbents were optimized for the simultaneous determination of 44 pesticides and six metabolites in earthworms by liquid chromatography with tandem mass spectrometry. The method performance was systematically validated with satisfactory results. The limits of quantification were 20 μg/kg for all analytes studied, while the recoveries of the target analytes ranged from 65.1 to 127% with relative standard deviation values lower than 15.0%. The developed method was subsequently utilized to explore the bioaccumulation of bitertanol in earthworms exposed to contaminated soil, verifying its feasibility for real sample analysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface patterning of nanoparticles with polymer patches

NASA Astrophysics Data System (ADS)

Choueiri, Rachelle M.; Galati, Elizabeth; Thérien-Aubin, Héloïse; Klinkova, Anna; Larin, Egor M.; Querejeta-Fernández, Ana; Han, Lili; Xin, Huolin L.; Gang, Oleg; Zhulina, Ekaterina B.; Rubinstein, Michael; Kumacheva, Eugenia

2016-10-01

Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest. Surface-patterned particles act as colloidal analogues of atoms and molecules, serve as model systems in studies of phase transitions in liquid systems, behave as ‘colloidal surfactants’ and function as templates for the synthesis of hybrid particles. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient, but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties. At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles, and nanoparticles with surface ripples or a ‘raspberry’ surface morphology. Here we demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. These patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization.

Determination of trace labile copper in environmental waters by magnetic nanoparticle solid phase extraction and high-performance chelation ion chromatography.

PubMed

Wei, Z; Sandron, S; Townsend, A T; Nesterenko, P N; Paull, B

2015-04-01

Cobalt magnetic nanoparticles surface functionalised with iminodiacetic acid were evaluated as a nano-particulate solid phase extraction absorbent for copper ions (Cu(2+)) from environmental water samples. Using an external magnetic field, the collector nanoparticles could be separated from the aqueous phase, and adsorbed ions simply decomplexed using dilute HNO3. Effects of pH, buffer concentration, sample and sorbent volume, extraction equilibrium time, and interfering ion concentration on extraction efficiency were investigated. Optimal conditions were then applied to the extraction of Cu(2+) ions from natural water samples, prior to their quantitation using high-performance chelation ion chromatography. The limits of detection (LOD) of the combined extraction and chromatographic method were ~0.1 ng ml(-1), based upon a 100-fold preconcentration factor (chromatographic performance; LOD=9.2 ng ml(-1) Cu(2+)), analytical linear range from 20 to 5000 ng mL(-1), and relative standard deviations=4.9% (c=1000 ng ml(-1), n=7). Accuracy and precision of the combined approach was verified using a certified reference standard estuarine water sample (SLEW-2) and comparison of sample determinations with sector field inductively coupled plasma mass spectrometry. Recoveries from the addition of Cu(2+) to impacted estuarine and rain water samples were 103.5% and 108.5%, respectively. Coastal seawater samples, both with and without prior UV irradiation and dissolved organic matter removal were also investigated using the new methodology. The effect of DOM concentration on copper availability was demonstrated. Copyright © 2015. Published by Elsevier B.V.

Cubic phase stabilization in nanoparticles of hafnia-zirconia oxides: Particle-size and annealing environment effects

NASA Astrophysics Data System (ADS)

Lu, Chih-Hsin; Raitano, Joan M.; Khalid, Syed; Zhang, Lihua; Chan, Siu-Wai

2008-06-01

Amorphous hafnia (HfO2-y), zirconia (ZrO2-y), and hafnia-zirconia (xHfO2-y-(1-x)(ZrO2-y)) nanoparticles were prepared by combining aqueous solutions of hexamethylenetetramine (HMT) with hafnium dichloride oxide (HfOCl2ṡ8H2O), zirconium dichloride oxide (ZrOCl2ṡ8H2O), or a mixture of these two salts at room temperature. For pure hafnia, transmission electron microscopy showed that the lower cation concentration (0.01M) resulted in the precipitation of smaller amorphous nanoparticles relative to higher concentrations (0.015M-0.04M). Consequently, the lower concentration preparation route coupled with a reducing environment (H2:N2=9:91) during annealing at temperatures between 650 and 850°C allowed for nanoparticles with a cubic structure to be prepared as determined by x-ray diffraction. The structurally cubic hafnia nanoparticles were 6nm or less in diameter and equiaxed. Using the same method (0.01M total metal cation concentration and reducing environment during annealing), nanoparticles of cubic structure were prepared across the entire hafnia-zirconia compositional spectrum, with a critical particle size for the cubic structure of about 6nm. Nanoparticles of tetragonal and monoclinic structure were prepared by increasing the annealing temperature and/or using a less reducing environment. The unique role of HMT in sample preparation is discussed as well.

The phase diagrams of a spin 1/2 core and a spin 1 shell nanoparticle with a disordered interface

NASA Astrophysics Data System (ADS)

Zaim, N.; Zaim, A.; Kerouad, M.

2016-12-01

The critical and compensation behaviors, of a spherical ferrimagnetic nanoparticle, consisting of a ferromagnetic core of spin-1/2 A atoms, a ferromagnetic shell of spin-1 B atoms and a disordered interface in between that is characterized by a random arrangement of A and B atoms of ApB1-p type and a negative A - B coupling, are studied. The ground state phase diagrams of the system have been determined in the (JAB, D/jA) and (JB, D/jA) planes. Monte Carlo simulation based on Metropolis algorithm has been used to study the effects of the concentration parameter p, the crystal field, the coupling between B - B atoms jB and the antiferromagnetic interface coupling jAB on the phase diagrams and the magnetic properties of the system. It has been found that one, two or even three compensation point(s) can appear for appropriate values of the system parameters.

Nanoparticles Stabilize Thin Polymer Films: A Fundamental Study to Understand the Phenomenon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael E. Mackay

2009-03-04

A new understanding of thermodynamics at the nanoscale resulted in a recently discovered first order phase transition that nanoparticles in a polymer film will all segregate to the supporting substrate. This is an unusual phase transition that was predicted using a modeling technique developed at Sandia National Laboratories and required the equivalent of many computational years on one computer. This project is a collaboration between Prof. Michael Mackay's group and Dr. Amalie Frischknecht (Sandia National Laboratories) where experimental observation and theoretical rationalization and prediction are brought together. Other discoveries were that this phase transition could be avoided by changing themore » nanoparticle properties yielding control of the assembly process at the nanoscale. In fact, the nanoparticles could be made to assemble to the supporting substrate, to the air interface or not assemble at all within a thin polymer film of order 100 nm in thickness. However, when the assembly process is present it is so robust that it is possible to make rough liquid films at the nanoscale due to nanoparticles assembling around three-dimensional objects. From this knowledge we are able to design and manufacture new coatings with particular emphasis on polymer-based solar cells. Careful control of the morphology at the nanoscale is expected to provide more efficient devices since the physics of these systems is dictated at this length scale and assembly of nanoparticles to various interfaces is critical to operation.« less

Magnetic solid phase extraction with CoFe2O4/oleic acid nanoparticles coupled to gas chromatography-mass spectrometry for the determination of alkylphenols in baby foods.

PubMed

Pastor-Belda, Marta; Viñas, Pilar; Campillo, Natalia; Hernández-Córdoba, Manuel

2017-04-15

Magnetic solid phase extraction (MSPE) with cobalt ferrite nanoparticles coated with oleic acid is described for the determination of alkylphenols (APs), 4-tert-butylphenol (TBP), 4-pentylphenol (PP), 4-hexylphenol (HP), 4-tert-octylphenol (TOP), 4-n-octylphenol (OP) and 4-nonylphenol (NP) in baby foods using gas chromatography with mass spectrometry (GC-MS). Prior to MSPE, the sample was treated with trichloroacetic acid, and the APs derivatized with acetic anhydride. Parameters affecting the extraction efficiency: amount of magnetic nanoparticles, extraction time and desorption conditions, were optimized. The enriched phase obtained was evaporated to dryness and the residue reconstituted in 50μL of methanol, 1μL of which was injected into the GC-MS. Samples were quantified applying matrix-matched calibration and using 2-chloro-5-bromoanisole as surrogate standard. The analysis of 0.5g of sample provided detection limits in the 0.4-1.7ngg -1 range. Some samples contained APs at levels of between 3ngg -1 for HP and 122ngg -1 for TOP. Copyright © 2016 Elsevier Ltd. All rights reserved.

Aerosolized Antimicrobial Agents Based on Degradable Dextran Nanoparticles Loaded with Silver Carbene Complexes

PubMed Central

Ornelas-Megiatto, Cátia; Shah, Parth N.; Wich, Peter R.; Cohen, Jessica L.; Tagaev, Jasur A.; Smolen, Justin A.; Wright, Brian D.; Panzner, Matthew J.; Youngs, Wiley J.; Fréchet, Jean M. J.; Cannon, Carolyn L.

2012-01-01

Degradable acetalated dextran (Ac-DEX) nanoparticles were prepared and loaded with a hydrophobic silver carbene complex (SCC) by a single-emulsion process. The resulting particles were characterized for morphology and size distribution using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The average particle size and particle size distribution were found to be a function of the ratio of the organic phase to the surfactant containing aqueous phase with a 1:5 volume ratio of Ac-DEX CH2Cl2 (organic): PBS (aqueous) being optimal for the formulation of nanoparticles with an average size of 100 ± 40 nm and a low polydispersity. The SCC loading was found to increase with an increase in the SCC quantity in the initial feed used during particle formulation up to 30% (w/w); however, the encapsulation efficiency was observed to be the best at a feed ratio of 20% (w/w). In vitro efficacy testing of the SCC loaded Ac-DEX nanoparticles demonstrated their activity against both Gram-negative and Gram-positive bacteria; the nanoparticles inhibited the growth of every bacterial species tested. As expected, a higher concentration of drug was required to inhibit bacterial growth when the drug was encapsulated within the nanoparticle formulations compared with the free drug illustrating the desired depot release. Compared with free drug, the Ac-DEX nanoparticles were much more readily suspended in an aqueous phase and subsequently aerosolized, thus providing an effective method of pulmonary drug delivery. PMID:23025592