Strong-Field Driven Dynamics of Metal and Dielectric Nanoparticles

NASA Astrophysics Data System (ADS)

Powell, Jeffrey

The motion of electrons in atoms, molecules, and solids in the presence of intense electromagnetic radiation is an important research topic in physics and physical chemistry because of its fundamental nature and numerous practical applications, ranging from precise machining of materials to optical control of chemical reactions and light-driven electronic devices. Mechanisms of light-matter interactions critically depend on the dimensions of the irradiated system and evolve significantly from single atoms or molecules to the macroscopic bulk. Nanoparticles provide the link between these two extremes. In this thesis, I take advantage of this bridge to study light-matter interactions as a function of nanoparticle size, shape, and composition. I present here three discrete, but interconnected, experiments contributing to our knowledge of nanoparticle properties and their response to intense, short-pulsed light fields. First, I investigate how individual nanoparticles interact with each other in solution, studying their temperature-dependent solubility. The interaction potential between 5.5nm gold nanoparticles, ligated by an alkanethiol was found to be -0.165eV, in reasonable agreement with a phenomenological model. The other two experiments explore ultrafast dynamics driven by intense femtosecond lasers in isolated, gas-phase metallic and dielectric nanoparticles. Photoelectron momentum imaging is applied to study the response of gold, silica, and gold-shell/silica-core nanoparticles (ranging from single to several hundred nanometers in size) with near-infrared (NIR), 25 fs laser pulses in the intensity range of 1011 - 1014 W/cm2. These measurements, which constitute the bulk of my graduate work, reveal the complex interplay between the external optical field and the induced near-field of the nanoparticle, resulting in the emission of very energetic electrons that are much faster than those emitted from isolated atoms or molecules exposed to the same light pulses

Hyaluronic acid-modified zirconium phosphate nanoparticles for potential lung cancer therapy.

PubMed

Li, Ranwei; Liu, Tiecheng; Wang, Ke

2017-02-01

Novel tumor-targeting zirconium phosphate (ZP) nanoparticles modified with hyaluronic acid (HA) were developed (HA-ZP), with the aim of combining the drug-loading property of ZP and the tumor-targeting ability of HA to construct a tumor-targeting paclitaxel (PTX) delivery system for potential lung cancer therapy. The experimental results indicated that PTX loading into the HA-ZP nanoparticles was as high as 20.36%±4.37%, which is favorable for cancer therapy. PTX-loaded HA-ZP nanoparticles increased the accumulation of PTX in A549 lung cancer cells via HA-mediated endocytosis and exhibited superior anticancer activity in vitro. In vivo anticancer efficacy assay revealed that HA-ZP nanoparticles possessed preferable anticancer abilities, which exhibited minimized toxic side effects of PTX and strong tumor-suppression potential in clinical application.

Carnauba wax nanoparticles enhance strong systemic and mucosal cellular and humoral immune responses to HIV-gp140 antigen

PubMed Central

Arias, Mauricio A.; Loxley, Andrew; Eatmon, Christy; Van Roey, Griet; Fairhurst, David; Mitchnick, Mark; Dash, Philip; Cole, Tom; Wegmann, Frank; Sattentau, Quentin; Shattock, Robin

2011-01-01

Induction of humoral responses to HIV at mucosal compartments without inflammation is important for vaccine design. We developed charged wax nanoparticles that efficiently adsorb protein antigens and are internalized by DC in the absence of inflammation. HIV-gp140-adsorbed nanoparticles induced stronger in vitro T-cell proliferation responses than antigen alone. Such responses were greatly enhanced when antigen was co-adsorbed with TLR ligands. Immunogenicity studies in mice showed that intradermal vaccination with HIV-gp140 antigen-adsorbed nanoparticles induced high levels of specific IgG. Importantly, intranasal immunization with HIV-gp140-adsorbed nanoparticles greatly enhanced serum and vaginal IgG and IgA responses. Our results show that HIV-gp140-carrying wax nanoparticles can induce strong cellular/humoral immune responses without inflammation and may be of potential use as effective mucosal adjuvants for HIV vaccine candidates. PMID:21145913

Gelatin Nanoparticles with Enhanced Affinity for Calcium Phosphate.

PubMed

Farbod, Kambiz; Diba, Mani; Zinkevich, Tatiana; Schmidt, Stephan; Harrington, Matthew J; Kentgens, Arno P M; Leeuwenburgh, Sander C G

2016-05-01

Gelatin nanoparticles can be tuned with respect to their drug loading efficiency, degradation rate, and release kinetics, which renders these drug carriers highly suitable for a wide variety of biomedical applications. The ease of functionalization has rendered gelatin an interesting candidate material to introduce specific motifs for selective targeting to specific organs, but gelatin nanoparticles have not yet been modified to increase their affinity to mineralized tissue. By means of conjugating bone-targeting alendronate to biocompatible gelatin nanoparticles, a simple method is developed for the preparation of gelatin nanoparticles which exhibit strong affinity to mineralized surfaces. It has been shown that the degree of alendronate functionalization can be tuned by controlling the glutaraldehyde crosslinking density, the molar ratio between alendronate and glutaraldehyde, as well as the pH of the conjugation reaction. Moreover, it has been shown that the affinity of gelatin nanoparticles to calcium phosphate increases considerably upon functionalization with alendronate. In summary, gelatin nanoparticles have been developed, which exhibit great potential for use in bone-specific drug delivery and regenerative medicine. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carnauba wax nanoparticles enhance strong systemic and mucosal cellular and humoral immune responses to HIV-gp140 antigen.

PubMed

Arias, Mauricio A; Loxley, Andrew; Eatmon, Christy; Van Roey, Griet; Fairhurst, David; Mitchnick, Mark; Dash, Philip; Cole, Tom; Wegmann, Frank; Sattentau, Quentin; Shattock, Robin

2011-02-01

Induction of humoral responses to HIV at mucosal compartments without inflammation is important for vaccine design. We developed charged wax nanoparticles that efficiently adsorb protein antigens and are internalized by DC in the absence of inflammation. HIV-gp140-adsorbed nanoparticles induced stronger in vitro T-cell proliferation responses than antigen alone. Such responses were greatly enhanced when antigen was co-adsorbed with TLR ligands. Immunogenicity studies in mice showed that intradermal vaccination with HIV-gp140 antigen-adsorbed nanoparticles induced high levels of specific IgG. Importantly, intranasal immunization with HIV-gp140-adsorbed nanoparticles greatly enhanced serum and vaginal IgG and IgA responses. Our results show that HIV-gp140-carrying wax nanoparticles can induce strong cellular/humoral immune responses without inflammation and may be of potential use as effective mucosal adjuvants for HIV vaccine candidates. Copyright © 2010 Elsevier Ltd. All rights reserved.

Nonlinear Dynamics and Strong Cavity Cooling of Levitated Nanoparticles.

PubMed

Fonseca, P Z G; Aranas, E B; Millen, J; Monteiro, T S; Barker, P F

2016-10-21

Optomechanical systems explore and exploit the coupling between light and the mechanical motion of macroscopic matter. A nonlinear coupling offers rich new physics, in both quantum and classical regimes. We investigate a dynamic, as opposed to the usually studied static, nonlinear optomechanical system, comprising a nanosphere levitated in a hybrid electro-optical trap. The cavity offers readout of both linear-in-position and quadratic-in-position (nonlinear) light-matter coupling, while simultaneously cooling the nanosphere, for indefinite periods of time and in high vacuum. We observe the cooling dynamics via both linear and nonlinear coupling. As the background gas pressure was lowered, we observed a greater than 1000-fold reduction in temperature before temperatures fell below readout sensitivity in the present setup. This Letter opens the way to strongly coupled quantum dynamics between a cavity and a nanoparticle largely decoupled from its environment.

Nonlinear Dynamics and Strong Cavity Cooling of Levitated Nanoparticles

NASA Astrophysics Data System (ADS)

Fonseca, P. Z. G.; Aranas, E. B.; Millen, J.; Monteiro, T. S.; Barker, P. F.

2016-10-01

Optomechanical systems explore and exploit the coupling between light and the mechanical motion of macroscopic matter. A nonlinear coupling offers rich new physics, in both quantum and classical regimes. We investigate a dynamic, as opposed to the usually studied static, nonlinear optomechanical system, comprising a nanosphere levitated in a hybrid electro-optical trap. The cavity offers readout of both linear-in-position and quadratic-in-position (nonlinear) light-matter coupling, while simultaneously cooling the nanosphere, for indefinite periods of time and in high vacuum. We observe the cooling dynamics via both linear and nonlinear coupling. As the background gas pressure was lowered, we observed a greater than 1000-fold reduction in temperature before temperatures fell below readout sensitivity in the present setup. This Letter opens the way to strongly coupled quantum dynamics between a cavity and a nanoparticle largely decoupled from its environment.

Optical nonlinear absorption characteristics of Sb2Se3 nanoparticles

NASA Astrophysics Data System (ADS)

Muralikrishna, Molli; Kiran, Aditha Sai; Ravikanth, B.; Sowmendran, P.; Muthukumar, V. Sai; Venkataramaniah, Kamisetti

2014-04-01

In this work, we report for the first time, the nonlinear optical absorption properties of antimony selenide (Sb2Se3) nanoparticles synthesized through solvothermal route. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies revealed that the nanoparticles are in the range of 10 - 40 nm. Elemental analysis was performed using EDAX. By employing open aperture z-scan technique, we have evaluated the effective two-photon absorption coefficient of Sb2Se3 nanoparticles to be 5e-10 m/W at 532 nm. These nanoparticles exhibit strong intensity dependent nonlinear optical absorption and hence could be considered to have optical power limiting applications in the visible range.

Fabrication, Light Emission, and Magnetism of Silica Nanoparticles Hybridized with AIE Luminogens and Inorganic Nanostructures

NASA Astrophysics Data System (ADS)

Faisal, Mahtab

Much research efforts have been devoted in developing new synthetic approaches for fluorescent silica nanoparticles (FSNPs) due to their potential high-technological applications. However, light emissions from most of the FSNPs prepared so far have been rather weak. This is due to the emission quenching caused by the aggregation of fluorophores in the solid state. We have observed a novel phenomenon of aggregation-induced emission (AIE): a series of propeller-shaped molecules such as tetraphenylethene (TPE) and silole are induced to emit efficiently by aggregate formation. Thus, they are ideal fluorophors for the construction of FSNPs and my thesis work focuses on the synthesis of silica nanoparticles containing these luminogens and magnetic nanostructures. Highly emissive FSNPs with core-shell structures are fabricated by surfactant-free sol-gel reactions of tetraphenylethene- (TPE) and silole-functionalized siloxanes followed by the reactions with tetraethoxysilane. The FSNPs are uniformly sized, surface-charged and colloidally stable. The diameters of the FSNPs are tunable in the range of 45--295 nm by changing the reaction conditions. Whereas their TPE and silole precursors are non-emissive, the FSNPs emit strong visible lights, thanks to the novel aggregation-induced emission characteristics of the TPE and silole aggregates in the hybrid nanoparticles. The FSNPs pose no toxicity to living cells and can be utilized to selectively image cytoplasm of HeLa cells. Applying the same tool in the presence of citrate-coated magnetite nanoparticles, uniform magnetic fluorescent silica nanoparticles (MFSNPs) with smooth surfaces are fabricated. These particles exhibit appreciable surface charges and hence good colloidal stability. They are superparamagnetic, exhibiting no hysteresis at room temperature. UV irradiation of a suspension of MFSNPs in ethanol gives strong blue and green emissions. The MFSNPs can selectively stain the cytoplasmic regions of the living cells

A Discovery of Strong Metal-Support Bonding in Nanoengineered Au-Fe3O4 Dumbbell-like Nanoparticles by in Situ Transmission Electron Microscopy.

PubMed

Han, Chang Wan; Choksi, Tej; Milligan, Cory; Majumdar, Paulami; Manto, Michael; Cui, Yanran; Sang, Xiahan; Unocic, Raymond R; Zemlyanov, Dmitry; Wang, Chao; Ribeiro, Fabio H; Greeley, Jeffrey; Ortalan, Volkan

2017-08-09

The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions. Herein, we report the discovery of an anomalous "strong metal-support bonding" between gold nanoparticles and "nano-engineered" Fe 3 O 4 substrates by in situ microscopy. During in situ vacuum annealing of Au-Fe 3 O 4 dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-Fe 3 O 4 on Au nanoparticles, the gold nanoparticles transform into the gold thin films and wet the surface of nano-Fe 3 O 4 , as the surface reduction of nano-Fe 3 O 4 proceeds. This phenomenon results from a unique coupling of the size-and shape-dependent high surface reducibility of nano-Fe 3 O 4 and the extremely strong adhesion between Au and the reduced Fe 3 O 4 . This strong metal-support bonding reveals the significance of controlling the metal oxide support size and morphology for optimizing metal-support bonding and ultimately for the development of improved catalysts and functional nanostructures.

Rare Earth Oxide Fluoride Nanoparticles And Hydrothermal Method For Forming Nanoparticles

DOEpatents

Fulton, John L.; Hoffmann, Markus M.

2003-12-23

A hydrothermal method for forming nanoparticles of a rare earth element, oxygen and fluorine has been discovered. Nanoparticles comprising a rare earth element, oxygen and fluorine are also described. These nanoparticles can exhibit excellent refractory properties as well as remarkable stability in hydrothermal conditions. The nanoparticles can exhibit excellent properties for numerous applications including fiber reinforcement of ceramic composites, catalyst supports, and corrosion resistant coatings for high-temperature aqueous solutions.

Rare earth oxide fluoride nanoparticles and hydrothermal method for forming nanoparticles

DOEpatents

Fulton, John L [Richland, WA; Hoffmann, Markus M [Richland, WA

2001-11-13

A hydrothermal method for forming nanoparticles of a rare earth element, oxygen and fluorine has been discovered. Nanoparticles comprising a rare earth element, oxygen and fluorine are also described. These nanoparticles can exhibit excellent refractory properties as well as remarkable stability in hydrothermal conditions. The nanoparticles can exhibit excellent properties for numerous applications including fiber reinforcement of ceramic composites, catalyst supports, and corrosion resistant coatings for high-temperature aqueous solutions.

Multifunctional biosynthesized silver nanoparticles exhibiting excellent antimicrobial potential against multi-drug resistant microbes along with remarkable anticancerous properties.

PubMed

Jha, Diksha; Thiruveedula, Prasanna Kumar; Pathak, Rajiv; Kumar, Bipul; Gautam, Hemant K; Agnihotri, Shrish; Sharma, Ashwani Kumar; Kumar, Pradeep

2017-11-01

This study demonstrates the therapeutic potential of silver nanoparticles (AgNPs), which were biosynthesized using the extracts of Citrus maxima plant. Characterization through UV-Vis spectrophotometry, Dynamic Light Scattering (DLS), Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) confirmed the formation of AgNps in nano-size range. These nanoparticles exhibited enhanced antioxidative activity and showed commendable antimicrobial activity against wide range of microbes including multi-drug resistant bacteria that were later confirmed by TEM. These particles exhibited minimal toxicity when cytotoxicity study was performed on normal human lung fibroblast cell line as well as human red blood cells. It was quite noteworthy that these particles showed remarkable cytotoxicity on human fibrosarcoma and mouse melanoma cell line (B16-F10). Additionally, the apoptotic topographies of B16-F10 cells treated with AgNps were confirmed by using acridine orange and ethidium bromide dual dye staining, caspase-3 assay, DNA fragmentation assay followed by cell cycle analysis using fluorescence-activated cell sorting. Taken together, these results advocate promising potential of the biosynthesized AgNps for their use in therapeutic applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Microfluidic magnetic switching valves based on aggregates of magnetic nanoparticles: Effects of aggregate length and nanoparticle sizes

NASA Astrophysics Data System (ADS)

Jiemsakul, Thanakorn; Manakasettharn, Supone; Kanharattanachai, Sivakorn; Wanna, Yongyuth; Wangsuya, Sujint; Pratontep, Sirapat

2017-01-01

We demonstrate microfluidic switching valves using magnetic nanoparticles blended within the working fluid as an alternative microfluidic flow control in microchannels. Y-shaped microchannels have been fabricated by using a CO2 laser cutter to pattern microchannels on transparent poly(methyl methacrylate) (PMMA) sheets covered with thermally bonded transparent polyvinyl chloride (PVC) sheets. To examine the performance of the microfluidic magnetic switching valves, an aqueous magnetic nanoparticle suspension was injected into the microchannels by a syringe pump. Neodymium magnets were then employed to attract magnetic nanoparticles and form an aggregate that blocked the microchannels at a required position. We have found that the maximum volumetric flow rate of the syringe pump that the magnetic nanoparticle aggregate can withstand scales with the square of the external magnetic flux density. The viscosity of the fluid exhibits dependent on the aggregate length and the size of the magnetic nanoparticles. This microfluidic switching valve based on aggregates of magnetic nanoparticles has strong potentials as an on-demand flow control, which may help simplifying microfluidic channel designs.

A Discovery of Strong Metal–Support Bonding in Nanoengineered Au–Fe 3 O 4 Dumbbell-like Nanoparticles by in Situ Transmission Electron Microscopy

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

Han, Chang Wan; Choksi, Tej; Milligan, Cory

The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions. Herein, we report the discovery of an anomalous “strong metal-support bonding” between gold nanoparticles and “nano-engineered” Fe 3O 4 substrates by in-situ microscopy. During in-situ vacuum annealing of Au-Fe 3O 4 dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-Fe 3O 4 on Au nanoparticles, the gold nanoparticles transform into the monolayered gold thinfilms and wet the surface of nano-Fe 3O 4, as the surface reduction of nano-Fe 3O 4 proceeds. This phenomenon results frommore » a unique coupling of the size-and shape-dependent high surface reducibility of nano-Fe 3O 4 and the extremely strong adhesion between Au and the reduced Fe 3O 4. This strong-metal support bonding reveals the significance of controlling the metal oxide support size and morphology for optimizing metal-support bonding and, ultimately, for the development of improved catalysts and functional nanostructures.« less

A Discovery of Strong Metal–Support Bonding in Nanoengineered Au–Fe 3 O 4 Dumbbell-like Nanoparticles by in Situ Transmission Electron Microscopy

DOE PAGES

Han, Chang Wan; Choksi, Tej; Milligan, Cory; ...

2017-06-26

The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions. Herein, we report the discovery of an anomalous “strong metal-support bonding” between gold nanoparticles and “nano-engineered” Fe 3O 4 substrates by in-situ microscopy. During in-situ vacuum annealing of Au-Fe 3O 4 dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-Fe 3O 4 on Au nanoparticles, the gold nanoparticles transform into the monolayered gold thinfilms and wet the surface of nano-Fe 3O 4, as the surface reduction of nano-Fe 3O 4 proceeds. This phenomenon results frommore » a unique coupling of the size-and shape-dependent high surface reducibility of nano-Fe 3O 4 and the extremely strong adhesion between Au and the reduced Fe 3O 4. This strong-metal support bonding reveals the significance of controlling the metal oxide support size and morphology for optimizing metal-support bonding and, ultimately, for the development of improved catalysts and functional nanostructures.« less

Exceptionally strong, stiff and hard hybrid material based on an elastomer and isotropically shaped ceramic nanoparticles.

PubMed

Georgopanos, Prokopios; Schneider, Gerold A; Dreyer, Axel; Handge, Ulrich A; Filiz, Volkan; Feld, Artur; Yilmaz, Ezgi D; Krekeler, Tobias; Ritter, Martin; Weller, Horst; Abetz, Volker

2017-08-04

In this work the fabrication of hard, stiff and strong nanocomposites based on polybutadiene and iron oxide nanoparticles is presented. The nanocomposites are fabricated via a general concept for mechanically superior nanocomposites not based on the brick and mortar structure, thus on globular nanoparticles with nanosized organic shells. For the fabrication of the composites oleic acid functionalized iron oxide nanoparticles are decorated via ligand exchange with an α,ω-polybutadiene dicarboxylic acid. The functionalized particles were processed at 145 °C. Since polybutadiene contains double bonds the nanocomposites obtained a crosslinked structure which was enhanced by the presence of oxygen or sulfur. It was found that the crosslinking and filler percolation yields high elastic moduli of approximately 12-20 GPa and hardness of 15-18 GPa, although the polymer volume fraction is up to 40%. We attribute our results to a catalytically enhanced crosslinking reaction of the polymer chains induced by oxygen or sulfur and to the microstructure of the nanocomposite.

Silver and palladium alloy nanoparticle catalysts: reductive coupling of nitrobenzene through light irradiation.

PubMed

Peiris, Sunari; Sarina, Sarina; Han, Chenhui; Xiao, Qi; Zhu, Huai-Yong

2017-08-15

Silver-palladium (Ag-Pd) alloy nanoparticles strongly absorb visible light and exhibit significantly higher photocatalytic activity compared to both pure palladium (Pd) and silver (Ag) nanoparticles. Photocatalysts of Ag-Pd alloy nanoparticles on ZrO 2 and Al 2 O 3 supports are developed to catalyze the nitroaromatic coupling to the corresponding azo compounds under visible light irradiation. Ag-Pd alloy NP/ZrO 2 exhibited the highest photocatalytic activity for nitrobenzene coupling to azobenzene (yield of ∼80% in 3 hours). The photocatalytic efficiency could be optimized by altering the Ag : Pd ratio of the alloy nanoparticles, irradiation light intensity, temperature and wavelength. The rate of the reaction depends on the population and energy of the excited electrons, which can be improved by increasing the light intensity or by using a shorter wavelength. The knowledge developed in this study may inspire further studies on Ag alloy photocatalysts and organic syntheses using Ag-Pd nanoparticle catalysts driven under visible light Irradiation.

Bifunctional redox tagging of carbon nanoparticles

NASA Astrophysics Data System (ADS)

Poon, Jeffrey; Batchelor-McAuley, Christopher; Tschulik, Kristina; Palgrave, Robert G.; Compton, Richard G.

2015-01-01

Despite extensive work on the controlled surface modification of carbon with redox moieties, to date almost all available methodologies involve complex chemistry and are prone to the formation of polymerized multi-layer surface structures. Herein, the facile bifunctional redox tagging of carbon nanoparticles (diameter 27 nm) and its characterization is undertaken using the industrial dye Reactive Blue 2. The modification route is demonstrated to be via exceptionally strong physisorption. The modified carbon is found to exhibit both well-defined oxidative and reductive voltammetric redox features which are quantitatively interpreted. The method provides a generic approach to monolayer modifications of carbon and carbon nanoparticle surfaces.

Chiromagnetic nanoparticles and gels

NASA Astrophysics Data System (ADS)

Yeom, Jihyeon; Santos, Uallisson S.; Chekini, Mahshid; Cha, Minjeong; de Moura, André F.; Kotov, Nicholas A.

2018-01-01

Chiral inorganic nanostructures have high circular dichroism, but real-time control of their optical activity has so far been achieved only by irreversible chemical changes. Field modulation is a far more desirable path to chiroptical devices. We hypothesized that magnetic field modulation can be attained for chiral nanostructures with large contributions of the magnetic transition dipole moments to polarization rotation. We found that dispersions and gels of paramagnetic Co3O4 nanoparticles with chiral distortions of the crystal lattices exhibited chiroptical activity in the visible range that was 10 times as strong as that of nonparamagnetic nanoparticles of comparable size. Transparency of the nanoparticle gels to circularly polarized light beams in the ultraviolet range was reversibly modulated by magnetic fields. These phenomena were also observed for other nanoscale metal oxides with lattice distortions from imprinted amino acids and other chiral ligands. The large family of chiral ceramic nanostructures and gels can be pivotal for new technologies and knowledge at the nexus of chirality and magnetism.

Overcoming the Coupling Dilemma in DNA-Programmable Nanoparticle Assemblies by "Ag+ Soldering".

PubMed

Wang, Huiqiao; Li, Yulin; Liu, Miao; Gong, Ming; Deng, Zhaoxiang

2015-05-20

Strong coupling between nanoparticles is critical for facilitating charge and energy transfers. Despite the great success of DNA-programmable nanoparticle assemblies, the very weak interparticle coupling represents a key barrier to various applications. Here, an extremely simple, fast, and highly efficient process combining DNA-programming and molecular/ionic bonding is developed to address this challenge, which exhibits a seamless fusion with DNA nanotechnology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermomechanical Response of Self-Assembled Nanoparticle Membranes

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

Wang, Yifan; Chan, Henry; Narayanan, Badri

2017-07-21

Monolayers composed of colloidal nanoparticles, with a thickness of less than 10 nm, have remarkable mechanical moduli and can suspend over micrometer-sized holes to form free-standing membranes. In this paper, we discuss experiment's and coarse-grained molecular dynamics simulations characterizing the thermomechanical properties of these self-assembled nanoparticle membranes. These membranes remain strong and resilient up to temperatures much higher than previous simulation predictions and exhibit an unexpected hysteretic behavior during the first heating cooling cycle. We show this hysteretic behavior can be explained by an asymmetric ligand configuration from the self assembly process and can be controlled by changing the ligandmore » coverage or cross-linking the ligand molecules. Finally, we show the screening effect of water molecules on the ligand interactions can strongly affect the moduli and thermomechanical behavior.« less

Catalase coupled gold nanoparticles: Comparison between carbodiimide and biotin-streptavidin methods

PubMed Central

Chirra, Hariharasudhan D.; Sexton, Travis; Biswal, Dipti; Hersh, Louis B.; Hilt, J. Zach

2011-01-01

The use of proteins for therapeutic applications requires the protein to maintain sufficient activity for the period of in vivo treatment. Many proteins exhibit a short half-life in vivo and, thus, require delivery systems for them to be applied as therapeutics. The relative biocompatibility and the ability to form functionalized bioconjugates via simple chemistry make gold nanoparticles excellent candidates as protein delivery systems. Herein, two protocols for coupling proteins to gold nanoparticles were compared. In the first, the strong biomolecular binding between biotin and streptavidin was used to couple catalase to the surface of gold nanoparticles. In the second protocol, the formation of an amide bond between carboxylic acid coated gold nanoparticles and free surface amines of catalase using carbodiimide chemistry was performed. The stability and kinetics of the different steps involved in these protocols were studied using UV-Visible spectroscopy, dynamic light scattering, and transmission electron microscopy. The addition of mercaptoundecanoic acid in conjugation with (N-(6-(biotinamido)hexyl)-3′-(2′-pyridyldithio)-propionamide increased the stability of biotinylated gold nanoparticles. Although the carbodiimide chemistry based bioconjugation approach exhibited a decrease in catalase activity, the carbodiimide chemistry based bioconjugation approach resulted in more active catalase per gold nanoparticle compared to that of mercaptoundecanoic acid stabilized biotinylated gold nanoparticles. Both coupling protocols resulted in gold nanoparticles loaded with active catalase. Thus, these gold nanoparticle systems and coupling protocols represent promising methods for the application of gold nanoparticles for protein delivery. PMID:21232642

Efficient Second-Harmonic Generation in Nanocrystalline Silicon Nanoparticles.

PubMed

Makarov, Sergey V; Petrov, Mihail I; Zywietz, Urs; Milichko, Valentin; Zuev, Dmitry; Lopanitsyna, Natalia; Kuksin, Alexey; Mukhin, Ivan; Zograf, George; Ubyivovk, Evgeniy; Smirnova, Daria A; Starikov, Sergey; Chichkov, Boris N; Kivshar, Yuri S

2017-05-10

Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

Multicolored redox active upconverter cerium oxide nanoparticle for bio-imaging and therapeutics†

PubMed Central

Babu, Suresh; Cho, Jung-Hyun; Dowding, Janet M.; Heckert, Eric; Komanski, Chris; Das, Soumen; Colon, Jimmie; Baker, Cheryl H.; Bass, Michael; Self, William T.; Seal, Sudipta

2011-01-01

Cytocompatible, co-doped cerium oxide nanoparticles exhibited strong upconversion properties that were found to kill lung cancer cells by inducing apoptosis thereby demonstrating the potential to be used as clinical contrast agents for imaging and as therapeutic agents for treatment of cancer. PMID:20683524

Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies

PubMed Central

Ravishankar, Thammadihalli Nanjundaiah; Ramakrishnappa, Thippeswamy; Nagaraju, Ganganagappa; Rajanaika, Hanumanaika

2015-01-01

CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm−1 due to the Ce−O−Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce CrVI to CrIII and show antibacterial activity against Pseudomonas aeruginosa. PMID:25969812

Polysaccharide-based bioflocculant template of a diazotrophic Bradyrhizobium japonicum 36 for controlled assembly of AgCl nanoparticles.

PubMed

Rasulov, Bakhtiyor A; Pattaeva, Mohichehra A; Yili, Abulimiti; Aisa, Haji Akber

2016-08-01

A simple and green method was developed for the biosynthesis of silver chloride nanoparticles, free from silver nanoparticles, using polysaccharide-based bioflocculant of a diazotrophic rhizobacteria Bradyrhizobium japonicum 36 strain. The synthesized silver chloride nanoparticles were characterized by UV-vis, XRD, FT-IR and TEM. The concentration-dependent and controllable method for silver chloride nanoparticles was developed. The biosynthesized silver chloride nanoparticles exhibited strong antimicrobial activity towards pathogenic microorganisms such as Escherichia coli, Staphylococcus aureus and Candida albicans. The synthesized silver chloride nanoparticles can be exploited as a promising new biocide bionanocomposite against pathogenic microorganisms. Copyright © 2016 Elsevier B.V. All rights reserved.

Poly-ϵ-caprolactone/chitosan nanoparticles provide strong adjuvant effect for hepatitis B antigen.

PubMed

Jesus, Sandra; Soares, Edna; Borchard, Gerrit; Borges, Olga

2017-10-01

This work aims to investigate the adjuvant effect of poly-ϵ-caprolactone/chitosan nanoparticles (NPs) for hepatitis B surface antigen (HBsAg) and the plasmid DNA encoding HBsAg (pRC/CMV-HBs). Both antigens were adsorbed onto preformed NPs. Vaccination studies were performed in C57BL/6 mice. Transfection efficiency was investigated in A549 cell line. HBsAg-adsorbed NPs generated strong anti-HBsAg IgG titers, mainly of IgG1 isotype, and induced antigen-specific IFN-γ and IL-17 secretion by spleen cells. The addition of pRC/CMV-HBs to the HBsAg-adsorbed NPs inhibited IL-17 secretion but had minor effect on IFN-γ levels. Lastly, pRC/CMV-HBs-loaded NPs generated a weak serum antibody response. Poly-ϵ-caprolactone/chitosan NPs provide a strong humoral adjuvant effect for HBsAg and induce a Th1/Th17-mediated cellular immune responses worth explore for hepatitis B virus vaccination.

Preparation of poly(N-vinylpyrrolidone)-stabilized ZnO colloid nanoparticles

PubMed Central

Gutul, Tatyana; Condur, Nadejda; Ursaki, Veaceslav; Goncearenco, Evgenii; Vlazan, Paulina

2014-01-01

Summary We propose a method for the synthesis of a colloidal ZnO solution with poly(N-vinylpyrrolidone) (PVP) as stabilizer. Stable colloidal solutions with good luminescence properties are obtained by using PVP as stabilizer in the synthesis of ZnO nanoparticles by a sol–gel method assisted by ultrasound. Nanoparticles with sizes of 30–40 nm in a PVP matrix are produced as a solid product. The colloidal ZnO/PVP/methanol solution, apart from the most intense PL band at 356 nm coming from the PVP, exhibits a strong PL band at 376 nm (3.30 eV) which corresponds to the emission of the free exciton recombination in ZnO nanoparticles. PMID:24778966

Water soluble (Ln3+) doped nanoparticle: Retention of strong luminescence

NASA Astrophysics Data System (ADS)

Attar, Tarannum Vahid; Khandpekar, Mahendra M.

2018-04-01

This paper deals with the synthesis of hexagonal nanoparticles of LaF3: Nd, Ho (LFNH) in the presence of LaCl3.7H2O and NH4F by precipitation method using deionized water as solvent. The nanoparticles have a nearly hexagonal shape with cell parameters, a = b = 7.0980 AU and c = 7.2300 AU and confirms with the JCPDS standard card (32-0483) of pure LaF3 crystals. The TEM results show that the average sizes of these nanoparticles are 15nm which is consistent with the sizes obtained from XRD measurements. The SEM image shows uniform size distribution of the nanoparticles. Detection of Second harmonic generation (SHG) signal together with the presence of wide transparency window (UV studies) makes LFNH suitable for optoelectronic applications. The Photoluminescence of the nanocrystals has been observed by excitation and emission spectra. The peak at 629nm indicates red up conversion fluorescence useful in applications like bioimaging and biolabelling.

Cellulase immobilization on magnetic nanoparticles encapsulated in polymer nanospheres.

PubMed

Lima, Janaina S; Araújo, Pedro H H; Sayer, Claudia; Souza, Antonio A U; Viegas, Alexandre C; de Oliveira, Débora

2017-04-01

Immobilization of cellulases on magnetic nanoparticles, especially magnetite nanoparticles, has been the main approach studied to make this enzyme, economically and industrially, more attractive. However, magnetite nanoparticles tend to agglomerate, are very reactive and easily oxidized in air, which has strong impact on their useful life. Thus, it is very important to provide proper surface coating to avoid the mentioned problems. This study aimed to investigate the immobilization of cellulase on magnetic nanoparticles encapsulated in polymeric nanospheres. The support was characterized in terms of morphology, average diameter, magnetic behavior and thermal decomposition analyses. The polymer nanospheres containing encapsulated magnetic nanoparticles showed superparamagnetic behavior and intensity average diameter about 150 nm. Immobilized cellulase exhibited broader temperature stability than in the free form and great reusability capacity, 69% of the initial enzyme activity was maintained after eight cycles of use. The magnetic support showed potential for cellulase immobilization and allowed fast and easy biocatalyst recovery through a single magnet.

Palladium and Platinum Nanoparticles Attenuate Aging-Like Skin Atrophy via Antioxidant Activity in Mice

PubMed Central

Shibuya, Shuichi; Ozawa, Yusuke; Watanabe, Kenji; Izuo, Naotaka; Toda, Toshihiko; Yokote, Koutaro; Shimizu, Takahiko

2014-01-01

Cu-Zn superoxide dismutase (Sod1) loss causes a redox imbalance as it leads to excess superoxide generation, which results in the appearance of various aging-related phenotypes, including skin atrophy. Noble metal nanoparticles, such as palladium (Pd) and platinum (Pt) nanoparticles, are considered to function as antioxidants due to their strong catalytic activity. In Japan, a mixture of Pd and Pt nanoparticles called PAPLAL has been used to treat chronic diseases over the past 60 years. In the present study, we investigated the protective effects of PAPLAL against aging-related skin pathologies in mice. Transdermal PAPLAL treatment reversed skin thinning associated with increased lipid peroxidation in Sod1 −/− mice. Furthermore, PAPLAL normalized the gene expression levels of Col1a1, Mmp2, Has2, Tnf-α, Il-6, and p53 in the skin of the Sod1 −/− mice. Pt nanoparticles exhibited marked SOD and catalase activity, while Pd nanoparticles only displayed weak SOD and catalase activity in vitro. Although the SOD and catalase activity of the Pt nanoparticles significantly declined after they had been oxidized in air, a mixture of Pd and Pt nanoparticles continued to exhibit SOD and catalase activity after oxidation. Importantly, a mixture of Pd and Pt nanoparticles with a molar ratio of 3 or 4 to 1 continued to exhibit SOD and catalase activity after oxidation, indicating that Pd nanoparticles prevent the oxidative deterioration of Pt nanoparticles. These findings indicate that PAPLAL stably suppresses intrinsic superoxide generation both in vivo and in vitro via SOD and catalase activity. PAPLAL is a potentially powerful tool for the treatment of aging-related skin diseases caused by oxidative damage. PMID:25333617

Palladium and platinum nanoparticles attenuate aging-like skin atrophy via antioxidant activity in mice.

PubMed

Shibuya, Shuichi; Ozawa, Yusuke; Watanabe, Kenji; Izuo, Naotaka; Toda, Toshihiko; Yokote, Koutaro; Shimizu, Takahiko

2014-01-01

Cu-Zn superoxide dismutase (Sod1) loss causes a redox imbalance as it leads to excess superoxide generation, which results in the appearance of various aging-related phenotypes, including skin atrophy. Noble metal nanoparticles, such as palladium (Pd) and platinum (Pt) nanoparticles, are considered to function as antioxidants due to their strong catalytic activity. In Japan, a mixture of Pd and Pt nanoparticles called PAPLAL has been used to treat chronic diseases over the past 60 years. In the present study, we investigated the protective effects of PAPLAL against aging-related skin pathologies in mice. Transdermal PAPLAL treatment reversed skin thinning associated with increased lipid peroxidation in Sod1-/- mice. Furthermore, PAPLAL normalized the gene expression levels of Col1a1, Mmp2, Has2, Tnf-α, Il-6, and p53 in the skin of the Sod1-/- mice. Pt nanoparticles exhibited marked SOD and catalase activity, while Pd nanoparticles only displayed weak SOD and catalase activity in vitro. Although the SOD and catalase activity of the Pt nanoparticles significantly declined after they had been oxidized in air, a mixture of Pd and Pt nanoparticles continued to exhibit SOD and catalase activity after oxidation. Importantly, a mixture of Pd and Pt nanoparticles with a molar ratio of 3 or 4 to 1 continued to exhibit SOD and catalase activity after oxidation, indicating that Pd nanoparticles prevent the oxidative deterioration of Pt nanoparticles. These findings indicate that PAPLAL stably suppresses intrinsic superoxide generation both in vivo and in vitro via SOD and catalase activity. PAPLAL is a potentially powerful tool for the treatment of aging-related skin diseases caused by oxidative damage.

Factors affecting drug encapsulation and stability of lipid-polymer hybrid nanoparticles.

PubMed

Cheow, Wean Sin; Hadinoto, Kunn

2011-07-01

Lipid-polymer hybrid nanoparticles are polymeric nanoparticles enveloped by lipid layers that combine the highly biocompatible nature of lipids with the structural integrity afforded by polymeric nanoparticles. Recognizing them as attractive drug delivery vehicles, antibiotics are encapsulated in the present work into hybrid nanoparticles intended for lung biofilm infection therapy. Modified emulsification-solvent-evaporation methods using lipid as surfactant are employed to prepare the hybrid nanoparticles. Biodegradable poly (lactic-co-glycolic acid) and phosphatidylcholine are used as the polymer and lipid models, respectively. Three fluoroquinolone antibiotics (i.e. levofloxacin, ciprofloxacin, and ofloxacin), which vary in their ionicity, lipophilicity, and aqueous solubility, are used. The hybrid nanoparticles are examined in terms of their drug encapsulation efficiency, drug loading, stability, and in vitro drug release profile. Compared to polymeric nanoparticles prepared using non-lipid surfactants, hybrid nanoparticles in general are larger and exhibit higher drug loading, except for the ciprofloxacin-encapsulated nanoparticles. Hybrid nanoparticles, however, are unstable in salt solutions, but the stability can be conferred by adding TPGS into the formulation. Drug-lipid ionic interactions and drug lipophilicity play important roles in the hybrid nanoparticle preparation. First, interactions between oppositely charged lipid and antibiotic (i.e. ciprofloxacin) during preparation cause failed nanoparticle formation. Charge reversal of the lipid facilitated by adding counterionic surfactants (e.g. stearylamine) must be performed before drug encapsulation can take place. Second, drug loading and the release profile are strongly influenced by drug lipophilicity, where more lipophilic drug (i.e. levofloxacin) exhibit a higher drug loading and a sustained release profile attributed to the interaction with the lipid coat. Copyright © 2011 Elsevier B.V. All

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.

Microporous Co@C Nanoparticles Prepared by Dealloying CoAl@C Precursors: Achieving Strong Wideband Microwave Absorption via Controlling Carbon Shell Thickness.

PubMed

Li, Da; Liao, Haoyan; Kikuchi, Hiroaki; Liu, Tong

2017-12-27

Excellent magnetic features make Co-based materials promising candidates as high-performance microwave absorbers. However, it is still a significant challenge for Co-based absorbers to possess high-intensity and broadband absorption simultaneously, owing to the lack of dielectric loss and impedance matching. Herein, microporous Co@C nanoparticles (NPs) with carbon shell thicknesses ranging from 1.8-4.9 nm have been successfully synthesized by dealloying CoAl@C precursors. All of the samples exhibit high microwave absorption performance. The microporous Co@C sample possessing a carbon shell of 1.8 nm exhibits the highest absorption intensity among these samples with a minimum reflection loss (RL) of -141.1 dB, whose absorption bandwidth for RL ≤ -10 dB is 7.3 GHz. As the thickness of the carbon shell increases, the absorption bandwidth of the NPs becomes wider. For the sample with the carbon shell thickness of 4.9 nm, the absorption bandwidth for RL ≤ -10 dB reaches a record high of 13.2 GHz. The outstanding microwave attenuation properties are attributed to the dielectric loss of the carbon shell, the magnetic loss of the Co core, and the cooperation of the core-shell structure and microporous morphology. The strong wideband microwave absorption of the carbon-coated microporous Co NPs highlights their potential applications in microwave absorbing systems.

Zein/caseinate/pectin complex nanoparticles: Formation and characterization.

PubMed

Chang, Chao; Wang, Taoran; Hu, Qiaobin; Luo, Yangchao

2017-11-01

In this study, pectin was used as coating material to form zein/caseinate/pectin complex nanoparticles through pH adjustment and heating treatment for potential oral delivery applications. The preparation conditions were studied by applying heating treatment at different pHs, either the isoelectric point of zein (pH 6.2) or caseinate (pH 4.6), or consecutively at both pHs. The particulate characteristics, including particle size, polydispersity index, and zeta potential were monitored for complex nanoparticles formed under different preparation conditions. The complex nanoparticles generally exhibited particle size smaller than 200nm with narrow distribution, spherical shape, and strong negative charge. Fourier transform infrared and fluorescence spectroscopy revealed that hydrophobic interactions and hydrogen bonds were involved in the formation of complex nanoparticles, in addition to electrostatic interactions. Fresh colloidal dispersion and freeze-dried powders varied in their morphology, depending on their preparation conditions. Our results suggested that heating pH and sequence significantly affected the morphology of complex nanoparticles, and pectin coating exerted stabilization effect under simulated gastrointestinal conditions. The present study provides insight into the formation of protein/polysaccharide complex nanoparticles under different preparation conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Rapid preparation process of antiparkinsonian drug Mucuna pruriens silver nanoparticle by bioreduction and their characterization

PubMed Central

Arulkumar, Subramanian; Sabesan, Muthukumaran

2010-01-01

Backgorund: Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving an important branch of nanotechnology. Methods: The bioreduction behavior of plant seed extract of Mucuna pruriens in the synthesis of silver nanoparticles was investigated employing UV/visible spectrophotometry, X-ray diffraction (XRD), and transmission electron microscopy (TEM), Fourier transform – infra red (FT- IR). Result: M. pruriens was found to exhibit strong potential for rapid reduction of silver ions. The formation of nanoparticles by this method is extremely rapid, requires no toxic chemicals, and the nanoparticles are stable for several months. Conclusion: The main conclusion is that the bioreduction method to produce nanoparticles is a good alternative to the electrochemical methods and it is expected to be biocompatible. PMID:21808573

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

PubMed Central

Cantu, Travis; Rodier, Bradley; Iszard, Zachary; Kilian, Alissa; Pattani, Varun; Walsh, Kyle; Weber, Katharina; Tunnell, James; Betancourt, Tania; Irvin, Jennifer

2016-01-01

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT). PMID:26780244

Microfluidic separation of magnetic nanoparticles on an ordered array of magnetized micropillars

NASA Astrophysics Data System (ADS)

Orlandi, G.; Kuzhir, P.; Izmaylov, Y.; Alves Marins, J.; Ezzaier, H.; Robert, L.; Doutre, F.; Noblin, X.; Lomenech, C.; Bossis, G.; Meunier, A.; Sandoz, G.; Zubarev, A.

2016-06-01

Microfluidic separation of magnetic particles is based on their capture by magnetized microcollectors while the suspending fluid flows past the microcollectors inside a microchannel. Separation of nanoparticles is often challenging because of strong Brownian motion. Low capture efficiency of nanoparticles limits their applications in bioanalysis. However, at some conditions, magnetic nanoparticles may undergo field-induced aggregation that amplifies the magnetic attractive force proportionally to the aggregate volume and considerably increases nanoparticle capture efficiency. In this paper, we have demonstrated the role of such aggregation on an efficient capture of magnetic nanoparticles (about 80 nm in diameter) in a microfluidic channel equipped with a nickel micropillar array. This array was magnetized by an external uniform magnetic field, of intensity as low as 6-10 kA/m, and experiments were carried out at flow rates ranging between 0.3 and 30 μ L /min . Nanoparticle capture is shown to be mostly governed by the Mason number Ma, while the dipolar coupling parameter α does not exhibit a clear effect in the studied range, 1.4 < α < 4.5. The capture efficiency Λ shows a strongly decreasing Mason number behavior, Λ ∝M a-1.78 within the range 32 ≤ Ma ≤ 3250. We have proposed a simple theoretical model which considers destructible nanoparticle chains and gives the scaling behavior, Λ ∝M a-1.7 , close to the experimental findings.

Spectral Selectivity of Plasmonic Interactions between Individual Up-Converting Nanocrystals and Spherical Gold Nanoparticles.

PubMed

Piątkowski, Dawid; Schmidt, Mikołaj K; Twardowska, Magdalena; Nyk, Marcin; Aizpurua, Javier; Maćkowski, Sebastian

2017-08-04

We experimentally demonstrate strong spectral selectivity of plasmonic interaction that occurs between α-NaYF₄:Er 3+ /Yb 3+ nanocrystals, which feature two emission bands, and spherical gold nanoparticles, with plasmon frequency resonant with one of the emission bands. Spatially-resolved luminescence intensity maps acquired for individual nanocrystals, together with microsecond luminescence lifetime images, show two qualitatively different effects that result from the coupling between plasmon excitations in metallic nanoparticles and emitting states of the nanocrystals. On the one hand, we observe nanocrystals, whose emission intensity is strongly enhanced for both resonant and non-resonant bands with respect to the plasmon resonance. Importantly, this increase is accompanied with shortening of luminescence decays times. In contrast, a significant number of nanocrystals exhibits almost complete quenching of the emission resonant with the plasmon resonance of gold nanoparticles. Theoretical analysis indicates that such an effect can occur for emitters placed at distances of about 5 nm from gold nanoparticles. While under these conditions, both transitions experience significant increases of the radiative emission rates due to the Purcell effect, the non-radiative energy transfer between resonant bands results in strong quenching, which in that situation nullifies the enhancement.

Sea urchin like shaped cdse nanoparticles grown in aqueous solutions via electron beam irradiation.

PubMed

Singh, Shalini; Guleria, Apurav; Rath, M C; Singh, A K; Adhikari, S; Sarkar, S K

2013-08-01

Cadmium selenide (CdSe) nanoparticles have been grown from an aqueous solutions containing equimolar ammoniated cadmium sulphate and sodium selenosulphate as precursors in presence of citric acid as a capping agent, via electron beam irradiation. The radiolytic processes occurring in the medium result in the formation of CdSe nanoparticles through the reactions mediated by hydrated electrons (e(aq)-). The dynamics of the formation of these nanoparticles was investigated by pulse radiolysis studies. The size of the primary nanoparticles as estimated from the absorption spectra recorded immediately was less than 3 nm. These nanoparticles exhibited strong excitonic absorption pattern and broad photoluminescence at room temperature, which has been attributed to the presence of surface states/defects. This has been confirmed by Raman spectral studies, where CdSe nanoparticles exhibited characteristic surface phonon modes at around 250 cm(-1). The photoluminescence lifetime decay measurements further supported the existence of surface defects on the as-grown CdSe nanoparticles. These nanoparticles were found to exist in the agglomerated form of sea urchin like shapes of uniform size of about 500 nm as revealed from TEM and SEM images. These sea urchin like shaped CdSe nanoparticles grown in this route were found to be very stable under the ambient conditions. We infer that citric acid influences the growth as well as stability of these nanoparticles. It is expected that these nanomaterials could find potential applications in the field of sensors, catalysis and photovoltaics.

Morphologically cryptic Amazonian bird species pairs exhibit strong postzygotic reproductive isolation.

PubMed

Pulido-Santacruz, Paola; Aleixo, Alexandre; Weir, Jason T

2018-03-14

We possess limited understanding of how speciation unfolds in the most species-rich region of the planet-the Amazon basin. Hybrid zones provide valuable information on the evolution of reproductive isolation, but few studies of Amazonian vertebrate hybrid zones have rigorously examined the genome-wide underpinnings of reproductive isolation. We used genome-wide genetic datasets to show that two deeply diverged, but morphologically cryptic sister species of forest understorey birds show little evidence for prezygotic reproductive isolation, but substantial postzygotic isolation. Patterns of heterozygosity and hybrid index revealed that hybrid classes with heavily recombined genomes are rare and closely match simulations with high levels of selection against hybrids. Genomic and geographical clines exhibit a remarkable similarity across loci in cline centres, and have exceptionally narrow cline widths, suggesting that postzygotic isolation is driven by genetic incompatibilities at many loci, rather than a few loci of strong effect. We propose Amazonian understorey forest birds speciate slowly via gradual accumulation of postzygotic genetic incompatibilities, with prezygotic barriers playing a less important role. Our results suggest old, cryptic Amazonian taxa classified as subspecies could have substantial postzygotic isolation deserving species recognition and that species richness is likely to be substantially underestimated in Amazonia. © 2018 The Author(s).

A New Solution Route to Hydrogen Terminated Silicon Nanoparticles: Synthesis, Functionalization, and Water Stability

PubMed Central

Zhang, Xiaoming; Neiner, Doinita; Wang, Shizhong; Louie, Angelique Y.; Kauzlarich, Susan M.

2010-01-01

Hydrogen capped silicon nanoparticles with strong blue photoluminescence were synthesized by the metathesis reaction of sodium silicide, NaSi, with NH4Br. The hydrogen capped Si nanoparticles were further terminated with octyl groups and then coated with a polymer to render them water soluble. The nanoparticles were characterized by TEM, FT-IR, UV-VIS absorption, and photoluminescence. The Si nanoparticles were shown to have an average diameter of 3.9 ±1.3 nm and exhibited room-temperature photoluminescence with a peak maximum at 438 nm with a quantum efficiency of 32% in hexane and 18% in water; the emission was stable in ambient air for up to 2 months. These nanoparticles could hold great potential as a non-heavy element containing quantum dot for applications in biology. PMID:25170189

A New Solution Route to Hydrogen Terminated Silicon Nanoparticles: Synthesis, Functionalization, and Water Stability.

PubMed

Zhang, Xiaoming; Neiner, Doinita; Wang, Shizhong; Louie, Angelique Y; Kauzlarich, Susan M

2007-01-24

Hydrogen capped silicon nanoparticles with strong blue photoluminescence were synthesized by the metathesis reaction of sodium silicide, NaSi, with NH 4 Br. The hydrogen capped Si nanoparticles were further terminated with octyl groups and then coated with a polymer to render them water soluble. The nanoparticles were characterized by TEM, FT-IR, UV-VIS absorption, and photoluminescence. The Si nanoparticles were shown to have an average diameter of 3.9 ±1.3 nm and exhibited room-temperature photoluminescence with a peak maximum at 438 nm with a quantum efficiency of 32% in hexane and 18% in water; the emission was stable in ambient air for up to 2 months. These nanoparticles could hold great potential as a non-heavy element containing quantum dot for applications in biology.

A new solution route to hydrogen-terminated silicon nanoparticles: synthesis, functionalization and water stability

NASA Astrophysics Data System (ADS)

Zhang, Xiaoming; Neiner, Doinita; Wang, Shizhong; Louie, Angelique Y.; Kauzlarich, Susan M.

2007-03-01

Hydrogen-capped silicon nanoparticles with strong blue photoluminescence were synthesized by the metathesis reaction of sodium silicide, NaSi, with NH4Br. The hydrogen-capped Si nanoparticles were further terminated with octyl groups and then coated with a polymer to render them water-soluble. The nanoparticles were characterized by TEM, FT-IR, UV-vis absorption and photoluminescence. The Si nanoparticles were shown to have an average diameter of 3.9 ± 1.3 nm and exhibited room temperature photoluminescence with a peak maximum at 438 nm with a quantum efficiency of 32% in hexane and 18% in water; the emission was stable in ambient air for up to 2 months. These nanoparticles could hold great potential as a non-heavy-element-containing quantum dot for applications in biology.

Self-assembled gemcitabine-gadolinium nanoparticles for magnetic resonance imaging and cancer therapy.

PubMed

Li, Lele; Tong, Rong; Li, Mengyuan; Kohane, Daniel S

2016-03-01

Nanoparticles with combined diagnostic and therapeutic functions are promising tools for cancer diagnosis and treatment. Here, we demonstrate a theranostic nanoparticle that integrates an active gemcitabine metabolite and a gadolinium-based magnetic resonance imaging agent via a facile supramolecular self-assembly synthesis, where the anti-cancer drug gemcitabine-5'-monophosphate (a phosphorylated active metabolite of the anti-cancer drug gemcitabine) was used to coordinate with Gd(III) to self-assemble into theranostic nanoparticles. The formulation exhibits a strong T1 contrast signal for magnetic resonance imaging of tumors in vivo, with enhanced retention time. Furthermore, the nanoparticles did not require other inert nanocarriers or excipients and thus had an exceptionally high drug loading (55 wt%), resulting in the inhibition of MDA-MB-231 tumor growth in mice. Recent advances in nanoparticle-based drug delivery systems have spurred the development of "theranostic" multifunctional nanoparticles, which combine therapeutic and diagnostic functionalities in a single formulation. Developing simple and efficient synthetic strategies for the construction of nanotheranostics with high drug loading remains a challenge. Here, we demonstrate a theranostic nanoparticle that integrates high loadings of an active gemcitabine metabolite and a gadolinium-based magnetic resonance imaging agent via a facile synthesis. The nanoparticles were better T1 contrast agents than currently used Gd-DTPA and had prolonged retention in tumor. Moreover they exhibited enhanced in vivo antitumor activity compared to free drug in a breast cancer xenograft mouse model. The strategy provides a scalable way to fabricate nanoparticles that enables enhancement of both therapeutic and diagnostic capabilities. Published by Elsevier Ltd.

Free energy landscape and localization of nanoparticles at block copolymer model defects.

PubMed

Kim, Yongjoo; Chen, Hsieh; Alexander-Katz, Alfredo

2014-05-14

Nanoparticle localization in block copolymer model defects is studied using self-consistent field theory simulations. In particular we study the nanoparticle free energy landscape for three different model defects: X, T, Y shape defects. Our results indicate that nanoparticles can be strongly bound to certain locations in these defects. The symmetry of the defects affects in a non-trivial fashion the "stiffness of the trap", with the X shape defect displaying the deepest energy well. The T and Y defects exhibit orientations along which the potential energy well is rather shallow. Furthermore, we find that the free energy well is tunable by the size of the nanoparticles. Our results help to explain recent experimental observations in block copolymer templated assembly of nanoparticles. Furthermore, they may open new avenues to assemble arbitrary heterogeneous patterns with precise nanoparticle positions by carefully controlling the morphology of a block copolymer system by using directed self-assembly techniques.

Spectroscopic and photoacoustic characterization of encapsulated iron oxide super-paramagnetic nanoparticles as a new multiplatform contrast agent

NASA Astrophysics Data System (ADS)

Armanetti, Paolo; Flori, Alessandra; Avigo, Cinzia; Conti, Luca; Valtancoli, Barbara; Petroni, Debora; Doumett, Saer; Cappiello, Laura; Ravagli, Costanza; Baldi, Giovanni; Bencini, Andrea; Menichetti, Luca

2018-06-01

Recently, a number of photoacoustic (PA) agents with increased tissue penetration and fine spatial resolution have been developed for molecular imaging and mapping of pathophysiological features at the molecular level. Here, we present bio-conjugated near-infrared light-absorbing magnetic nanoparticles as a new agent for PA imaging. These nanoparticles exhibit suitable absorption in the near-infrared region, with good photoacoustic signal generation efficiency and high photo-stability. Furthermore, these encapsulated iron oxide nanoparticles exhibit strong super-paramagnetic behavior and nuclear relaxivities that make them useful as magnetic resonance imaging (MRI) contrast media as well. Their simple bio-conjugation strategy, optical and chemical stability, and straightforward manipulation could enable the development of a PA probe with magnetic and spectroscopic properties suitable for in vitro and in vivo real-time imaging of relevant biological targets.

Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid

NASA Astrophysics Data System (ADS)

Małolepszy, A.; Błonski, S.; Chrzanowska-Giżyńska, J.; Wojasiński, M.; Płocinski, T.; Stobinski, L.; Szymanski, Z.

2018-04-01

The results of synthesis of the fluorescent carbon dots (CDots) from graphite target and reduced graphene oxide (rGO) nanoparticles performed by the nanosecond laser ablation in polyethylene glycol 200 (PEG200) are shown. Two-step laser irradiation (first graphite target, next achieved suspension) revealed a very effective production of CDots. However, the ablation in PEG appeared to be effective with 1064 nm laser pulse in contrast to the ablation with 355 nm laser pulse. In the case of rGO nanoparticles similar laser irradiation procedure was less efficient. In both cases, received nanoparticles exhibited strong, broadband photoluminescence with a maximum dependent on the excitation wavelength. The size distribution for obtained CDots was evaluated using the DLS technique and HRTEM images. The results from both methods show quite good agreement in nanoparticle size estimation although the DLS method slightly overestimates nanoparticle's diameter.

Electron Dynamics in Nanostructures in Strong Laser Fields

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

Kling, Matthias

2014-09-11

The goal of our research was to gain deeper insight into the collective electron dynamics in nanosystems in strong, ultrashort laser fields. The laser field strengths will be strong enough to extract and accelerate electrons from the nanoparticles and to transiently modify the materials electronic properties. We aimed to observe, with sub-cycle resolution reaching the attosecond time domain, how collective electronic excitations in nanoparticles are formed, how the strong field influences the optical and electrical properties of the nanomaterial, and how the excitations in the presence of strong fields decay.

Protein coated gold nanoparticles as template for the directed synthesis of highly fluorescent gold nanoclusters

NASA Astrophysics Data System (ADS)

Zhang, Lingyan; Han, Fei

2018-04-01

Bovine serum albumin (BSA) modified gold nanoparticles (AuNPs) was selected as template for the synthesis of AuNPs@gold nanoclusters (AuNCs) core/shell nanoparticles, in which BSA not only acted as dual functions agent for both anchoring and reducing Au3+ ions, but also was employed as a bridge between the AuNPs and AuNCs. Optical properties of AuNPs@AuNCs core/shell nanoparticles were studied using UV-visible and fluorescence spectroscopy. The prepared AuNPs@AuNCs core/shell nanoparticles exhibited sphere size uniformity with improved monodispersity, excellent fluorescence and fluorescent stability. Compared with AuNCs, AuNPs@AuNCs core/shell nanoparticles possessed large size and strong fluorescence intensity due to the effect of AuNPs as core. Moreover, the mechanism of the AuNPs induced fluorescence changes of the core/shell nanoparticles was first explored.

Synthesis and applications of novel silver nanoparticle structures

NASA Astrophysics Data System (ADS)

Dukes, Kyle

The field of nanotechnology is rapidly expanding across disciplines as each new development is realized. New exciting technologies are being driven by advances in the application of nanotechnology; including biochemical, optical, and semiconductors research. This thesis will focus on the use of silver nanoparticles as optical labels on cells, methods of forming different small structures of silver nanoparticles, as well as the use of silver nanoparticles in the development of a photovoltaic cell. Silver nanoparticles have been modified with self-assembled monolayers of hydroxyl-terminated long chain thiols and encapsulated with a silica shell. The resulting core-shell nanoparticles were used as optical labels for cell analysis using flow cytometry and microscopy. The excitation of plasmon resonances in nanoparticles results in strong depolarized scattering of visible light permitting detection at the single nanoparticle level. The nanoparticles were modified with neutravidin via epoxide-azide coupling chemistry and biotinylated antibodies targeting cell surface receptors were bound to the nanoparticle surface. The nanoparticle labels exhibited long-term stability under physiological conditions without aggregation or silver ion leaching. Labeled cells exhibited two orders of magnitude enhancement of the scattering intensity compared to unlabeled cells. Dimers of silver nanoparticles have been fabricated by first immobilizing a monolayer of single silver nanoparticles onto poly(4-vinylpyridine) covered glass slides. The monolayer was then exposed to adenine, which has two amines which will bind to silver. The nanoparticle monolayer, now modified with adenine, is exposed to a second suspension of nanoparticles which will bind with the amine modified monolayer. Finally, a thin silica shell is formed about the structure via solgel chemistry to prevent dissolution or aggregation upon sonication/striping. Circular arrays of silver nanoparticels are developed using a

Hyaluronan- and heparin-reduced silver nanoparticles with antimicrobial properties

PubMed Central

Kemp, Melissa M; Kumar, Ashavani; Clement, Dylan; Ajayan, Pulickel; Mousa, Shaker

2009-01-01

Aims Silver nanoparticles exhibit unique antibacterial properties that make these ideal candidates for biological and medical applications. We utilized a clean method involving a single synthetic step to prepare silver nanoparticles that exhibit antimicrobial activity. Materials & methods These nanoparticles were prepared by reducing silver nitrate with diaminopyridinylated heparin (DAPHP) and hyaluronan (HA) polysaccharides and tested for their efficacy in inhibiting microbial growth. Results & discussion The resulting silver nanoparticles exhibit potent antimicrobial activity against Staphylococcus aureus and modest activity against Escherichia coli. Silver–HA showed greater antimicrobial activity than silver–DAPHP, while silver–glucose nanoparticles exhibited very weak antimicrobial activity. Neither HA nor DAPHP showed activity against S. aureus or E. coli. Conclusion These results suggest that DAPHP and HA silver nanoparticles have potential in antimicrobial therapeutic applications. PMID:19505245

Green synthesis and characterization of zinc oxide nanoparticle using insulin plant (Costus pictus D. Don) and investigation of its antimicrobial as well as anticancer activities

NASA Astrophysics Data System (ADS)

Suresh, Joghee; Pradheesh, Ganeshan; Alexramani, Vincent; Sundrarajan, Mahalingam; Hong, Sun Ig

2018-03-01

In this work we aim to synthesize biocompatible ZnO nanoparticles from the zinc nitrate via green process using leaf extracts of the Costus pictus D. Don medicinal plant. FTIR studies confirm the presence of biomolecules and metal oxides. X-ray diffraction (XRD) structural analysis reveals the formation of pure hexagonal phase structures of ZnO nanoparticles. The surface morphologies of ZnO nanoparticles observed under a scanning electron microscope (SEM) suggest that most ZnO crystallites are hexagonal. EDX analysis confirms the presence of primarily zinc and oxygen. TEM images show that biosynthesized zinc oxide nanoparticles are hexagonal and spherical. The plausible formation mechanisms of zinc oxide nanoparticles are also predicted. The biosynthesized zinc oxide nanoparticles exhibit strong antimicrobial behavior against bacterial and fungal species when employing the agar diffusion method. Synthesized ZnO nanoparticles exhibit anticancer activity against Daltons lymphoma ascites (DLA) cells as well as antimicrobial activity against some bacterial and fungal strains.

Receptor-Targeted Nanoparticles for In Vivo Imaging of Breast Cancer

PubMed Central

Yang, Lily; Peng, Xiang-Hong; Wang, Y. Andrew; Wang, Xiaoxia; Cao, Zehong; Ni, Chunchun; Karna, Prasanthi; Zhang, Xinjian; Wood, William C.; Gao, Xiaohu; Nie, Shuming; Mao, Hui

2009-01-01

Purpose Cell surface receptor-targeted magnetic iron oxide (IO) nanoparticles provide molecular magnetic resonance imaging (MRI) contrast agents for improving specificity of the detection of human cancer. Experimental design The present study reports the development of a novel targeted IO nanoparticle using a recombinant peptide containing the amino-terminal fragment (ATF) of urokinase plasminogen activator conjugated to IO nanoparticles (ATF-IO). This nanoparticle targets urokinase plasminogen activator receptor (uPAR), which is overexpressed in breast cancer tissues. Results ATF-IO nanoparticles are able to specifically bind to and be internalized by uPAR-expressing tumor cells. Systemic delivery of ATF-IO nanoparticles into mice bearing subcutaneous and intraperitoneal mammary tumors leads to the accumulation of the particles in tumors, generating a strong MRI contrast detectable by a clinical MRI scanner at a field strength of 3 Tesla. Target specificity of ATF-IO nanoparticles demonstrated by in vivo MRI is further confirmed by near infrared (NIR) fluorescence imaging of the mammary tumors using NIR dye-labeled ATF peptides conjugated to IO nanoparticles. Furthermore, mice administered ATF-IO nanoparticles exhibit lower uptake of the particles in the liver and spleen compared to those receiving non-targeted IO nanoparticles. Conclusions Our results suggest that uPAR-targeted ATF-IO nanoparticles have potential as molecularly-targeted, dual modality imaging agents for in vivo imaging of breast cancer. PMID:19584158

Toxic behavior of silver and zinc oxide nanoparticles on environmental microorganisms.

PubMed

Dhas, Sindhu Priya; Shiny, Punalur John; Khan, Sudheer; Mukherjee, Amitava; Chandrasekaran, Natrajan

2014-09-01

Silver and zinc oxide nanoparticles (Ag and ZnO NPs) are widely used as antimicrobial agents. However, their potential toxicological impact on environmental microorganisms is largely unexplored. The aim of this work was to investigate the sensitivity and adaptability of five bacterial species isolated from sewage towards Ag and ZnO NPs. The bacterial species were exposed to increasing concentration of nanoparticles and the growth inhibitory effect, exopolysaccharides (EPSs) and extracellular proteins (ECPs) productions were determined. The involvement of surface charge in nanoparticles toxicity was also determined. The bacterial species were constantly exposed to nanoparticles to determine the adaptation behavior toward nanoparticles. The nanoparticles exhibited remarkable growth inhibitory effect on tested bacterial species. The toxicity of nanoparticles was found to be strongly dependent on surface charge effects. Though, these organisms are highly sensitive to Ag and ZnO NPs, the continuous exposure to these nanoparticles leads to moderate adaptation of bacterial species and the adapted bacterial species convert the highly toxic nano form to less toxic microform. Finally we predict that the continuing applications of nanoparticles in consumer products may lead to the development of nanoparticles resistant bacterial strains in future. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Understanding the physics of magnetic nanoparticles and their applications in the biomedical field

NASA Astrophysics Data System (ADS)

Laha, Suvra Santa

The study of magnetic nanoparticles is of great interest because of their potential uses in magnetic-recording, medical diagnostic and therapeutic applications. Additionally, they also offer an opportunity to understand the physics underlying the complex behavior exhibited by these materials. Two of the most important relaxation phenomena occurring in magnetic nanoparticles are superparamagnetic blocking and spin-glass-like freezing. In addition to features attributed to superparamagnetism, these nanoparticles can also exhibit magnetic relaxation effects at very low temperatures (≤ 50 K). Our studies suggest that all structural defects, and not just surface spins, are responsible for the low-temperature glass-like relaxation observed in many magnetic nanoparticles. The characteristic dipolar interaction energy existing in an ensemble of magnetic nanoparticles does not apparently depend on the average spacing between the nanoparticles but is likely to be strongly influenced by the fluctuations in the nanoparticle distribution. Our findings revealed that incorporating a small percentage of boron can stabilize the spinel structure in Mn 3O4 nanoparticles. We have also demonstrated that the dipolar interactions between the magnetic cores can be tuned by introducing non-magnetic nanoparticles. In particular, we studied the magnetic properties of Gd-doped Fe3O4 nanoparticles, a potential applicant for T1--T2 dual-modal MRI contrast agent. We have explored the interactions of BiFeO3 nanoparticles on live cells and the binding of FITC-conjugated Fe3O 4 nanoparticles with artificial lipid membranes to investigate these materials as candidates in medical imaging. Taken together, these studies have advanced our understanding of the fundamental physical principles that governs magnetism in magnetic materials with a focus on developing these nanoparticles for advanced biomedical applications. The materials developed and studied expand the repertoire of tools available for

Effects of Nanoparticle Size on Cellular Uptake and Liver MRI with PVP-Coated Iron Oxide Nanoparticles

PubMed Central

Huang, Jing; Bu, Lihong; Xie, Jin; Chen, Kai; Cheng, Zhen; Li, Xingguo; Chen, Xiaoyuan

2010-01-01

The effect of nanoparticle size (30–120 nm) on magnetic resonance imaging (MRI) of hepatic lesions in vivo has been systematically examined using polyvinylpyrrolidone (PVP)-coated iron oxide nanoparticles (PVP-IOs). Such biocompatible PVP-IOs with different sizes were synthesized by a simple one-pot pyrolysis method. These PVP-IOs exhibited good crystallinity and high T2 relaxivities, and the relaxivity increased with the size of the magnetic nanoparticles. It was found that cellular uptake changed with both size and surface physiochemical properties, and that PVP-IO-37 with a core size of 37 nm and hydrodynamic particle size of 100 nm exhibited higher cellular uptake rate and greater distribution than other PVP-IOs and Feridex. We systematically investigated the effect of nanoparticle size on MRI of normal liver and hepatic lesions in vivo. The physical and chemical properties of the nanoparticles influenced their pharmacokinetic behavior, which ultimately determined their ability to accumulate in the liver. The contrast enhancement of PVP-IOs within the liver was highly dependent on the overall size of the nanoparticles, and the 100 nm PVP-IO-37 nanoparticles exhibited the greatest enhancement. These results will have implications in designing engineered nanoparticles that are optimized as MR contrast agents or for use in therapeutics. PMID:21043459

Size-dependent magnetic and inductive heating properties of Fe3O4 nanoparticles: scaling laws across the superparamagnetic size.

PubMed

Mohapatra, Jeotikanta; Zeng, Fanhao; Elkins, Kevin; Xing, Meiying; Ghimire, Madhav; Yoon, Sunghyun; Mishra, Sanjay R; Liu, J Ping

2018-05-09

An efficient heat activating mediator with an enhanced specific absorption rate (SAR) value is attained via control of the iron oxide (Fe3O4) nanoparticle size from 3 to 32 nm. Monodispersed Fe3O4 nanoparticles are synthesized via a seed-less thermolysis technique using oleylamine and oleic acid as the multifunctionalizing agents (surfactant, solvent and reducing agent). The inductive heating properties as a function of particle size reveal a strong increase in the SAR values with increasing particle size up to 28 nm. In particular, the SAR values of ferromagnetic nanoparticles (>16 nm) are strongly enhanced with the increase of ac magnetic field amplitude than that for the superparamagnetic (3-16 nm) nanoparticles. The enhanced SAR values in the ferromagnetic regime are attributed to the synergistic contribution from the hysteresis and susceptibility loss. Specifically, the 28 nm Fe3O4 nanoparticles exhibit an enhanced SAR value of 801 W g-1 which is nearly an order higher than that of the commercially available nanoparticles.

Men without a sense of smell exhibit a strongly reduced number of sexual relationships, women exhibit reduced partnership security - a reanalysis of previously published data.

PubMed

Croy, Ilona; Bojanowski, Viola; Hummel, Thomas

2013-02-01

Olfactory function influences social behavior. For instance, olfaction seems to play a key role in mate choice and helps detecting emotions in other people. In a previous study, we showed that people who were born without a sense of smell exhibit enhanced social insecurity. Based on the comments to this article we decided to have a closer look to whether the absence of the sense of smell affects men and women differently. Under this focus questionnaire data of 32 patients, diagnosed with isolated congenital anosmia (10 men, 22 women) and 36 age-matched healthy controls (15 men, 21 women) was reanalyzed. In result, men and women without a sense of smell reported enhanced social insecurity, but with different consequences: Men who were born without a sense of smell exhibit a strongly reduced number of sexual relationships and women are affected such that they feel less secure about their partner. This emphasizes the importance of the sense of smell for intimate relationships. Copyright © 2012 Elsevier B.V. All rights reserved.

Spectroscopic and photoacoustic characterization of encapsulated iron oxide super-paramagnetic nanoparticles as a new multiplatform contrast agent.

PubMed

Armanetti, Paolo; Flori, Alessandra; Avigo, Cinzia; Conti, Luca; Valtancoli, Barbara; Petroni, Debora; Doumett, Saer; Cappiello, Laura; Ravagli, Costanza; Baldi, Giovanni; Bencini, Andrea; Menichetti, Luca

2018-06-15

Recently, a number of photoacoustic (PA) agents with increased tissue penetration and fine spatial resolution have been developed for molecular imaging and mapping of pathophysiological features at the molecular level. Here, we present bio-conjugated near-infrared light-absorbing magnetic nanoparticles as a new agent for PA imaging. These nanoparticles exhibit suitable absorption in the near-infrared region, with good photoacoustic signal generation efficiency and high photo-stability. Furthermore, these encapsulated iron oxide nanoparticles exhibit strong super-paramagnetic behavior and nuclear relaxivities that make them useful as magnetic resonance imaging (MRI) contrast media as well. Their simple bio-conjugation strategy, optical and chemical stability, and straightforward manipulation could enable the development of a PA probe with magnetic and spectroscopic properties suitable for in vitro and in vivo real-time imaging of relevant biological targets. Copyright © 2018 Elsevier B.V. All rights reserved.

Low cytotoxic trace element selenium nanoparticles and their differential antimicrobial properties against S. aureus and E. coli

NASA Astrophysics Data System (ADS)

Tran, Phong A.; O'Brien-Simpson, Neil; Reynolds, Eric C.; Pantarat, Namfon; Biswas, Dhee P.; O'Connor, Andrea J.

2016-01-01

Antimicrobial agents that have no or low cytotoxicity and high specificity are desirable to have no or minimal side effects. We report here the low cytotoxicity of polyvinyl alcohol-stabilized selenium (Se) nanoparticles and their differential effects on growth of S. aureus, a gram-positive bacterium and E. coli, a gram-negative bacterium. The nanoparticles were synthesised through redox reactions in an aqueous environment at room temperature and were characterised using UV visible spectrophotometry, transmission electron microscopy, dynamic light scattering and x-ray photoelectron spectroscopy. The nanoparticles showed low toxicity toward fibroblasts which remained more than 70% viable at Se concentrations as high as 128 ppm. The nanoparticles also exhibited very low haemolysis with only 18% of maximal lysis observed at a Se concentration of 128 ppm. Importantly, the nanoparticles showed strong growth inhibition toward S. aureus at a concentration as low as 1 ppm. Interestingly, growth of E. coli was unaffected at all concentrations tested. This study therefore strongly suggests that these nanoparticles should be investigated further to understand this differential effect as well as for potential advanced antimicrobial applications such as S. aureus infection—resisting, non-cytotoxic coatings for medical devices.

Antioxidant Potential and Antibacterial Efficiency of Caffeic Acid-Functionalized ZnO Nanoparticles

PubMed Central

Choi, Kyong-Hoon; Nam, Ki Chang; Lee, Sang-Yoon; Cho, Guangsup; Jung, Jin-Seung; Kim, Ho-Joong; Park, Bong Joo

2017-01-01

We report a novel zinc oxide (ZnO) nanoparticle with antioxidant properties, prepared by immobilizing the antioxidant 3-(3,4-dihydroxyphenyl)-2-propenoic acid (caffeic acid, CA) on the surfaces of micro-dielectric barrier discharge (DBD) plasma-treated ZnO nanoparticles. The microstructure and physical properties of ZnO@CA nanoparticles were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), infrared spectroscopy, and steady state spectroscopic methods. The antioxidant activity of ZnO@CA nanoparticles was evaluated using an ABTS (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation decolorization assay. ZnO@CA nanoparticles exhibited robust antioxidant activity. Moreover, ZnO@CA nanoparticles showed strong antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) including resistant bacteria such as methicillin-resistant S. aureus and against Gram-negative bacteria (Escherichia coli). Although Gram-negative bacteria appeared to be more resistant to ZnO@CA nanoparticles than Gram-positive bacteria, the antibacterial activity of ZnO@CA nanoparticles was dependent on particle concentration. The antioxidant and antibacterial activity of ZnO@CA may be useful for various biomedical and nanoindustrial applications. PMID:28621707

Development of polymeric-cationic peptide composite nanoparticles, a nanoparticle-in-nanoparticle system for controlled gene delivery.

PubMed

Jain, Arvind K; Massey, Ashley; Yusuf, Helmy; McDonald, Denise M; McCarthy, Helen O; Kett, Vicky L

2015-01-01

We report the formulation of novel composite nanoparticles that combine the high transfection efficiency of cationic peptide-DNA nanoparticles with the biocompatibility and prolonged delivery of polylactic acid-polyethylene glycol (PLA-PEG). The cationic cell-penetrating peptide RALA was used to condense DNA into nanoparticles that were encapsulated within a range of PLA-PEG copolymers. The composite nanoparticles produced exhibited excellent physicochemical properties including size <200 nm and encapsulation efficiency >80%. Images of the composite nanoparticles obtained with a new transmission electron microscopy staining method revealed the peptide-DNA nanoparticles within the PLA-PEG matrix. Varying the copolymers modulated the DNA release rate >6 weeks in vitro. The best formulation was selected and was able to transfect cells while maintaining viability. The effect of transferrin-appended composite nanoparticles was also studied. Thus, we have demonstrated the manufacture of composite nanoparticles for the controlled delivery of DNA.

Development of polymeric–cationic peptide composite nanoparticles, a nanoparticle-in-nanoparticle system for controlled gene delivery

PubMed Central

Jain, Arvind K; Massey, Ashley; Yusuf, Helmy; McDonald, Denise M; McCarthy, Helen O; Kett, Vicky L

2015-01-01

We report the formulation of novel composite nanoparticles that combine the high transfection efficiency of cationic peptide-DNA nanoparticles with the biocompatibility and prolonged delivery of polylactic acid–polyethylene glycol (PLA-PEG). The cationic cell-penetrating peptide RALA was used to condense DNA into nanoparticles that were encapsulated within a range of PLA-PEG copolymers. The composite nanoparticles produced exhibited excellent physicochemical properties including size <200 nm and encapsulation efficiency >80%. Images of the composite nanoparticles obtained with a new transmission electron microscopy staining method revealed the peptide-DNA nanoparticles within the PLA-PEG matrix. Varying the copolymers modulated the DNA release rate >6 weeks in vitro. The best formulation was selected and was able to transfect cells while maintaining viability. The effect of transferrin-appended composite nanoparticles was also studied. Thus, we have demonstrated the manufacture of composite nanoparticles for the controlled delivery of DNA. PMID:26648722

pH- and Temperature-Sensitive Hydrogel Nanoparticles with Dual Photoluminescence for Bioprobes.

PubMed

Zhao, Yue; Shi, Ce; Yang, Xudong; Shen, Bowen; Sun, Yuanqing; Chen, Yang; Xu, Xiaowei; Sun, Hongchen; Yu, Kui; Yang, Bai; Lin, Quan

2016-06-28

This study demonstrates high contrast and sensitivity by designing a dual-emissive hydrogel particle system, whose two emissions respond to pH and temperature strongly and independently. It describes the photoluminescence (PL) response of poly(N-isopropylacrylamide) (PNIPAM)-based core/shell hydrogel nanoparticles with dual emission, which is obtained by emulsion polymerization with potassium persulfate, consisting of the thermo- and pH-responsive copolymers of PNIPAM and poly(acrylic acid) (PAA). A red-emission rare-earth complex and a blue-emission quaternary ammonium tetraphenylethylene derivative (d-TPE) with similar excitation wavelengths are inserted into the core and shell of the hydrogel nanoparticles, respectively. The PL intensities of the nanoparticles exhibit a linear temperature response in the range from 10 to 80 °C with a change as large as a factor of 5. In addition, the blue emission from the shell exhibits a linear pH response between pH 6.5 and 7.6 with a resolution of 0.1 unit, while the red emission from the core is pH-independent. These stimuli-responsive PL nanoparticles have potential applications in biology and chemistry, including bio- and chemosensors, biological imaging, cancer diagnosis, and externally activated release of anticancer drugs.

Green synthesis of silver nanoparticles using Delphinium denudatum root extract exhibits antibacterial and mosquito larvicidal activities

NASA Astrophysics Data System (ADS)

Suresh, Gopal; Gunasekar, Poosali Hariharan; Kokila, Dhanasegaran; Prabhu, Durai; Dinesh, Devadoss; Ravichandran, Nagaiya; Ramesh, Balasubramanian; Koodalingam, Arunagirinathan; Vijaiyan Siva, Ganesan

2014-06-01

Green synthesis of silver nanoparticles (AgNPs) using aqueous root extract of Delphinium denudatum (Dd) by reduction of Ag+ ions from silver nitrate solution has been investigated. The synthesized DdAgNPs were characterized by using UV-Vis spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). The prepared DdAgNPs showed maximum absorbance at 416 nm and particles were polydispersed in nature, spherical in shape and the size of the particle obtained was ⩽85 nm. The DdAgNPs exhibited antibacterial activity against Staphylococcus aureus ATCC 6538, Bacillus cereus NCIM 2106, Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 9027. The DdAgNPs showed potent larvicidal activity against second instar larvae of dengue vector Aedes aegypti with a LC50 value of 9.6 ppm.

The Potential Application of Raw Cadmium Sulfide Nanoparticles as CT Photographic Developer

NASA Astrophysics Data System (ADS)

Wu, Qiang; Huang, Lingxin; Li, Zhan; An, Wenzhen; Liu, Dan; Lin, Jin; Tian, Longlong; Wang, Xinling; Liu, Bo; Qi, Wei; Wu, Wangsuo

2016-04-01

With the development of science and technology, new applications about nanoparticles should be explored to achieve full-scale knowledge. Therefore, in this work, the toxicity and potential application of raw cadmium sulfide nanoparticles (CdS) in vivo were further studied through ICP-OES and CTs. Surprisingly, CdS exhibited an excellent photographic property, except for finding the accumulation of CdS in the lungs, liver, spleen, and kidney with a strong dependence on time; it is also found that there were a significant uptake in the pancreas for an obvious CT imaging. And the following investigations showed that the raw CdS could damage the tissues accumulating nanoparticles. Through this work, it can be seen that the raw CdS being modified might be an excellent photographic developer for detecting cancers or other diseases.

Silicon nanoparticle-functionalized fiberglass pads for sampling

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

Mantey, Kevin; Nayfeh, Munir H.; Al-Hreish, Bahjat

2011-03-15

We used wet treatment to immobilize luminescent silicon nanoparticles on industrial glass fibers to impart optical and chemical functions to the fiber. Carpets or pads consisting of thousands of fibers are processed in parallel, enhancing the sensitivity of detection and the sampled volume. Treated pads exhibit strong luminescence, characteristic of the luminescence of the particles; showing no shift, broadening, or reduction of quantum efficiency. We demonstrate that drawing material by the pad due to physical adsorption can be reversed. We also demonstrate that allylamine can be covalently attached by photoinduced irradiation reactions, which results in imprinting the amine emission spectrum,more » providing spectral recognition. The imprint accompanied with a blue-shifting of the luminescence spectrum of the probe, allowing examination of the effect of termination on the nanoparticle structure. The shift is found to be consistent with an increase in the bandgap of the Si nanoparticle and is consistent with Quantum Monte Carlo calculations. In addition to sampling, the nano probe pad has the potential to enable a variety of biomedical applications through subsequent attachment.« less

Bioluminescent magnetic nanoparticles as potential imaging agents for mammalian spermatozoa.

PubMed

Vasquez, Erick S; Feugang, Jean M; Willard, Scott T; Ryan, Peter L; Walters, Keisha B

2016-03-17

Nanoparticles have emerged as key materials for developing applications in nanomedicine, nanobiotechnology, bioimaging and theranostics. Existing bioimaging technologies include bioluminescent resonance energy transfer-conjugated quantum dots (BRET-QDs). Despite the current use of BRET-QDs for bioimaging, there are strong concerns about QD nanocomposites containing cadmium which exhibits potential cellular toxicity. In this study, bioluminescent composites comprised of magnetic nanoparticles and firefly luciferase (Photinus pyralis) are examined as potential light-emitting agents for imaging, detection, and tracking mammalian spermatozoa. Characterization was carried out using infrared spectroscopy, TEM and cryo-TEM imaging, and ζ-potential measurements to demonstrate the successful preparation of these nanocomposites. Binding interactions between the synthesized nanoparticles and spermatozoon were characterized using confocal and atomic/magnetic force microscopy. Bioluminescence imaging and UV-visible-NIR microscopy results showed light emission from sperm samples incubated with the firefly luciferase-modified nanoparticles. Therefore, these newly synthesized luciferase-modified magnetic nanoparticles show promise as substitutes for QD labeling, and can potentially also be used for in vivo manipulation and tracking, as well as MRI techniques. These preliminary data indicate that luciferase-magnetic nanoparticle composites can potentially be used for spermatozoa detection and imaging. Their magnetic properties add additional functionality to allow for manipulation, sorting, or tracking of cells using magnetic techniques.

Catalytically and biologically active silver nanoparticles synthesized using essential oil

NASA Astrophysics Data System (ADS)

Vilas, Vidya; Philip, Daizy; Mathew, Joseph

2014-11-01

There are numerous reports on phytosynthesis of silver nanoparticles and various phytochemicals are involved in the reduction and stabilization. Pure explicit phytosynthetic protocol for catalytically and biologically active silver nanoparticles is of importance as it is an environmentally benign green method. This paper reports the use of essential oil of Myristica fragrans enriched in terpenes and phenyl propenes in the reduction and stabilization. FTIR spectra of the essential oil and the synthesized biogenic silver nanoparticles are in accordance with the GC-MS spectral analysis reports. Nanosilver is initially characterized by an intense SPR band around 420 nm, followed by XRD and TEM analysis revealing the formation of 12-26 nm sized, highly pure, crystalline silver nanoparticles. Excellent catalytic and bioactive potential of the silver nanoparticles is due to the surface modification. The chemocatalytic potential of nanosilver is exhibited by the rapid reduction of the organic pollutant, para nitro phenol and by the degradation of the thiazine dye, methylene blue. Significant antibacterial activity of the silver colloid against Gram positive, Staphylococcus aureus (inhibition zone - 12 mm) and Gram negative, Escherichia coli (inhibition zone - 14 mm) is demonstrated by Agar-well diffusion method. Strong antioxidant activity of the biogenic silver nanoparticles is depicted through NO scavenging, hydrogen peroxide scavenging, reducing power, DPPH and total antioxidant activity assays.

Cytotoxic and antimicrobial effect of biosynthesized silver nanoparticles using the fruit extract of Ribes nigrum

NASA Astrophysics Data System (ADS)

Dobrucka, Renata; Kaczmarek, Mariusz; Dlugaszewska, Jolanta

2018-06-01

The present study reveals the efficiency of the fruit extract of Ribes nigrum in the green synthesis of silver nanoparticles (Ag-NPs). Biosynthesized Ag-NPs were characterized by UV-vis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The nanoparticles were found to be 5–10 nm. In some places, the particles were agglomerated. The nanoparticles showed strong bactericidal activity and fungicidal activity against dermatophytes Trichophyton rubrum ATCC 28188. Moreover, the A549 and CCD39Lu cells under the influence of the highest concentration of nanoparticles synthesized using the fruit extract of Ribes nigrum showed the maximum mortality. Also, the results indicate that Ag-NPs synthesized using the fruit extract of Ribes nigrum exhibit efficiency in therapy of human non-small cell lung cancer A549.

Influence of Surface Roughness on Strong Light-Matter Interaction of a Quantum Emitter-Metallic Nanoparticle System.

PubMed

Lu, Yu-Wei; Li, Ling-Yan; Liu, Jing-Feng

2018-05-08

We investigate the quantum optical properties of strong light-matter interaction between a quantum emitter and a metallic nanoparticle beyond idealized structures with a smooth surface. Based on the local coupling strength and macroscopic Green's function, we derived an exact quantum optics approach to obtain the field enhancement and light-emission spectrum of a quantum emitter. Numerical simulations show that the surface roughness has a greater effect on the near-field than on the far-field, and slightly increases the vacuum Rabi splitting on average. Further, we verified that the near-field enhancement is mainly determined by the surface features of hot-spot area.

Superhydrophobic silica nanoparticles as ultrasound contrast agents.

PubMed

Jin, Qiaofeng; Lin, Chih-Yu; Kang, Shih-Tsung; Chang, Yuan-Chih; Zheng, Hairong; Yang, Chia-Min; Yeh, Chih-Kuang

2017-05-01

Microbubbles have been widely studied as ultrasound contrast agents for diagnosis and as drug/gene carriers for therapy. However, their size and stability (lifetime of 5-12min) limited their applications. The development of stable nanoscale ultrasound contrast agents would therefore benefit both. Generating bubbles persistently in situ would be one of the promising solutions to the problem of short lifetime. We hypothesized that bubbles could be generated in situ by providing stable air nuclei since it has been found that the interfacial nanobubbles on a hydrophobic surface have a much longer lifetime (orders of days). Mesoporous silica nanoparticles (MSNs) with large surface areas and different levels of hydrophobicity were prepared to test our hypothesis. It is clear that the superhydrophobic and porous nanoparticles exhibited a significant and strong contrast intensity compared with other nanoparticles. The bubbles generated from superhydrophobic nanoparticles sustained for at least 30min at a MI of 1.0, while lipid microbubble lasted for about 5min at the same settings. In summary MSNs have been transformed into reliable bubble precursors by making simple superhydrophobic modification, and made into a promising contrast agent with the potentials to serve as theranostic agents that are sensitive to ultrasound stimulation. Copyright © 2016 Elsevier B.V. All rights reserved.

Strongly bound excitons in anatase TiO 2 single crystals and nanoparticles

DOE PAGES

Baldini, E.; Chiodo, L.; Dominguez, A.; ...

2017-04-13

Anatase TiO 2 is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron-hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved photoemission spectroscopy and spectroscopic ellipsometry with state-of-the-art ab initio calculations, we demonstrate that the direct optical gap of single crystals is dominated by a strongly bound exciton rising over the continuum of indirect interband transitions. This exciton possesses an intermediate character between the Wannier-Mott and Frenkelmore » regimes and displays a peculiar two-dimensional wavefunction in the three-dimensional lattice. The nature of the higher-energy excitations is also identified. Furthermore, the universal validity of our results is confirmed up to room temperature by observing the same elementary excitations in defect-rich samples (doped single crystals and nanoparticles) via ultrafast two-dimensional deep-ultraviolet spectroscopy.« less

Red blood cell membrane-camouflaged melanin nanoparticles for enhanced photothermal therapy.

PubMed

Jiang, Qin; Luo, Zimiao; Men, Yongzhi; Yang, Peng; Peng, Haibao; Guo, Ranran; Tian, Ye; Pang, Zhiqing; Yang, Wuli

2017-10-01

Photothermal therapy (PTT) has represented a promising noninvasive approach for cancer treatment in recent years. However, there still remain challenges in developing non-toxic and biodegradable biomaterials with high photothermal efficiency in vivo. Herein, we explored natural melanin nanoparticles extracted from living cuttlefish as effective photothermal agents and developed red blood cell (RBC) membrane-camouflaged melanin (Melanin@RBC) nanoparticles as a platform for in vivo antitumor PTT. The as-obtained natural melanin nanoparticles demonstrated strong absorption at NIR region, higher photothermal conversion efficiency (∼40%) than synthesized melanin-like polydopamine nanoparticles (∼29%), as well as favorable biocompatibility and biodegradability. It was shown that RBC membrane coating on melanin nanoparticles retained their excellent photothermal property, enhanced their blood retention and effectively improved their accumulation at tumor sites. With the guidance of their inherited photoacoustic imaging capability, optimal accumulation of Melanin@RBC at tumors was achieved around 4 h post intravenous injection. Upon irradiation by an 808-nm laser, the developed Melanin@RBC nanoparticles exhibited significantly higher PTT efficacy than that of bare melanin nanoparticles in A549 tumor-bearing mice. Given that both melanin nanoparticles and RBC membrane are native biomaterials, the developed Melanin@RBC platform could have great potential in clinics for anticancer PTT. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ferrofluids based on Co-Fe-Si-B amorphous nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Tianqi; Bian, Xiufang; Yang, Chuncheng; Zhao, Shuchun; Yu, Mengchun

2017-03-01

Magnetic Co-Fe-Si-B amorphous nanoparticles were successfully synthesized by chemical reduction method. ICP, XRD, DSC, and TEM were used to investigate the composition, structure and morphology of Co-Fe-Si-B samples. The results show that the Co-Fe-Si-B samples are amorphous, which consist of nearly spherical nanoparticles with an average particle size about 23 nm. VSM results manifest that the saturation magnetization (Ms) of Co-Fe-Si-B samples ranges from 46.37 to 62.89 emu/g. Two kinds of ferrofluids (FFs) were prepared by dispersing Co-Fe-Si-B amorphous nanoparticles and CoFe2O4 nanoparticles in kerosene and silicone oil, respectively. The magnetic properties, stability and viscosity of the FFs were investigated. The FFs with Co-Fe-Si-B samples have a higher Ms and lower coercivity (Hc) than FFs with CoFe2O4 sample. Under magnetic field, the silicone oil-based FFs exhibit high stability. The viscosity of FFs under different applied magnetic fields was measured by a rotational viscometer, indicating that FFs with Co-Fe-Si-B particles present relative strong response to an external magnetic field. The metal-boride amorphous alloy nanoparticles have potential applications in the preparation of magnetic fluids with good stability and good magnetoviscous properties.

Interfacial functionalization and engineering of nanoparticles

NASA Astrophysics Data System (ADS)

Song, Yang

nanoparticles in the formation of functional nanocomposites. Part of the dissertation research was also devoted to graphene quantum dots (GQDs)-supported platinum (Pt/G) nanoparticles and their electrocatalytic activity in oxygen reduction reaction. These Pt/G nanocomposites were prepared by a hydrothermal procedure at controlled temperatures. Spectroscopic measurements based on FTIR, Raman and XPS confirmed the formation of various oxygenated structural defects on GQDs and the variation of their concentrations with the hydrothermal conditions. Interestingly, electrocatalytic activity of GQD/Pt composites exhibited a volcano-shaped variation with the GQD structural defects, with the best identified as the samples prepared at 160 °C for 6 h where the mass activity was found to meet the DOE target for 2015. This remarkable performance was accounted for by the deliberate manipulation of the adsorption of oxygen and reaction intermediates on platinum by the GQD structural defects through partial charge transfer. The strategy presented herein may offer a new paradigm in the design and engineering of nanoparticle catalysts for fuel cell electrochemistry. In addition, studies were also carried out to study intervalence charge transfer between ferrocenyl moieties bonded on carbon nanoparticle surfaces by diazonium reaction. Electrochemical studies exhibited two pairs of voltammetric waves with a difference of their formal potentials at about 78 mV, suggesting nanoparticle-mediated intraparticle charge delocalization at mixed valence as a result of the strong core-ligand covalent bonds and the conductive sp 2 carbon matrix of the graphitic cores. Consistent behaviors were observed in near-infrared measurements, indicating that the particles behaved analogously to a Class I/II mixed-valence compound.

Individual and collective modes of surface magnetoplasmon in thiolate-protected silver nanoparticles studied by MCD spectroscopy.

PubMed

Yao, Hiroshi; Shiratsu, Taisuke

2016-06-07

Large magneto-optical (MO) responses at the energy of localized surface plasmon resonance (LSPR), namely, surface magnetoplasmons, are demonstrated for the first time in thiolate-protected silver nanoparticles with magnetic circular dichroism (MCD) spectroscopy. The samples examined are decanethiol (DT)-, azobenzenethiol (ABT)-, and ABT/DT mixed-monolayer-protected Ag nanoparticles. ABT-protected Ag nanoparticles are somewhat aggregated and thus exhibit a broad, collective mode of plasmonic absorption, whereas other samples with highly-dispersed nanoparticles show an individual mode of LSPR absorption. In all Ag nanoparticles, a derivative-like MCD signal is observed under an applied magnetic field of 1.6 T, which can be explained in terms of two circular modes of magnetoplasmon caused by the increase (or decrease) in the Lorentz force imparted on the free electrons that oscillate in the left (or right) circular orbits in the nanosphere. For the Ag nanoparticles exhibiting an individual LSPR mode, in particular, simultaneous deconvolution analysis of UV-vis absorption and MCD spectra reveal that (i) the amplitude of the magnetoplasmonic component with lower frequency (ω-), resulting from the reduction in the confinement strength of collective electrons by the Lorentz force, is stronger than that with a higher frequency (ω+); (ii) the accurate shift or cyclotron frequency between two magnetoplasmonic modes (ωc = ω+-ω-) is size-dependent, and presents a very large value with implications for the apparent enhancement of the local magnetic-field in the Ag nanoparticles. These results strongly suggest that the Ag-thiolate layer or Ag-S bonding on the nanoparticle surface plays a significant role in the MO enhancement.

Synthesis and Luminescence Properties of Core/Shell ZnS:Mn/ZnO Nanoparticles.

PubMed

Jiang, Daixun; Cao, Lixin; Liu, Wei; Su, Ge; Qu, Hua; Sun, Yuanguang; Dong, Bohua

2009-01-01

In this paper the influence of ZnO shell thickness on the luminescence properties of Mn-doped ZnS nanoparticles is studied. Transmission electron microscopy (TEM) images showed that the average diameter of ZnS:Mn nanoparticles is around 14 nm. The formation of ZnO shells on the surface of ZnS:Mn nanoparticles was confirmed by X-ray diffraction (XRD) patterns, high-resolution TEM (HRTEM) images, and X-ray photoelectron spectroscopy (XPS) measurements. A strong increase followed by a gradual decline was observed in the room temperature photoluminescence (PL) spectra with the thickening of the ZnO shell. The photoluminescence excitation (PLE) spectra exhibited a blue shift in ZnO-coated ZnS:Mn nanoparticles compared with the uncoated ones. It is shown that the PL enhancement and the blue shift of optimum excitation wavelength are led by the ZnO-induced surface passivation and compressive stress on the ZnS:Mn cores.

Inorganic Nanoparticles/Metal Organic Framework Hybrid Membrane Reactors for Efficient Photocatalytic Conversion of CO2.

PubMed

Maina, James W; Schütz, Jürg A; Grundy, Luke; Des Ligneris, Elise; Yi, Zhifeng; Kong, Lingxue; Pozo-Gonzalo, Cristina; Ionescu, Mihail; Dumée, Ludovic F

2017-10-11

Photocatalytic conversion of carbon dioxide (CO 2 ) to useful products has potential to address the adverse environmental impact of global warming. However, most photocatalysts used to date exhibit limited catalytic performance, due to poor CO 2 adsorption capacity, inability to efficiently generate photoexcited electrons, and/or poor transfer of the photogenerated electrons to CO 2 molecules adsorbed on the catalyst surface. The integration of inorganic semiconductor nanoparticles across metal organic framework (MOF) materials has potential to yield new hybrid materials, combining the high CO 2 adsorption capacity of MOF and the ability of the semiconductor nanoparticles to generate photoexcited electrons. Herein, controlled encapsulation of TiO 2 and Cu-TiO 2 nanoparticles within zeolitic imidazolate framework (ZIF-8) membranes was successfully accomplished, using rapid thermal deposition (RTD), and their photocatalytic efficiency toward CO 2 conversion was investigated under UV irradiation. Methanol and carbon monoxide (CO) were found to be the only products of the CO 2 reduction, with yields strongly dependent upon the content and composition of the dopant semiconductor particles. CuTiO 2 nanoparticle doped membranes exhibited the best photocatalytic performance, with 7 μg of the semiconductor nanoparticle enhancing CO yield of the pristine ZIF-8 membrane by 233%, and methanol yield by 70%. This work opens new routes for the fabrication of hybrid membranes containing inorganic nanoparticles and MOFs, with potential application not only in catalysis but also in electrochemical, separation, and sensing applications.

Preparation and characterization of biocompatible silver nanoparticles using pomegranate peel extract.

PubMed

Nasiriboroumand, Majid; Montazer, Majid; Barani, Hossein

2018-02-01

The potential application of any nanoparticles, including silver nanoparticles (AgNPs), strongly depends on their stability against aggregation. In the current study, an aqueous extract of pomegranate peel was used as a stabilizer during synthesis of AgNPs. Nanoparticles have been prepared by the chemical reduction method from an aqueous solution of silver nitrate in the presence of sodium borohydride as a reducing agent. The AgNPs were characterized by dynamic light scattering (DLS), zeta-potential measurements, UV-Vis spectroscopy and transmission electron microscopy (TEM). The antibacterial efficiency of AgNPs against Escherichia coli was investigated. The size, polydispersity index, FWHM, and colloidal stability of nanoparticles in dispersion depends on the extract concentrations. In the presence of pomegranate peel extract, the nanoparticles suspension shows colloidal stability at least for a week. Our studies show that synthesized AgNPs with the above described procedure were stable at pH = 3-12 and in the temperature range of 25-85 °C. Additionally, AgNPs exhibit antibacterial properties, especially at the lowest amount of extract to silver ratio (K Extract/Ag ). Copyright © 2018. Published by Elsevier B.V.

On the Role of Specific Interactions in the Diffusion of Nanoparticles in Aqueous Polymer Solutions

PubMed Central

2013-01-01

Understanding nanoparticle diffusion within non-Newtonian biological and synthetic fluids is essential in designing novel formulations (e.g., nanomedicines for drug delivery, shampoos, lotions, coatings, paints, etc.), but is presently poorly defined. This study reports the diffusion of thiolated and PEGylated silica nanoparticles, characterized by small-angle neutron scattering, in solutions of various water-soluble polymers such as poly(acrylic acid) (PAA), poly(N-vinylpyrrolidone) (PVP), poly(ethylene oxide) (PEO), and hydroxyethylcellulose (HEC) probed using NanoSight nanoparticle tracking analysis. Results show that the diffusivity of nanoparticles is affected by their dimensions, medium viscosity, and, in particular, the specific interactions between nanoparticles and the macromolecules in solution; strong attractive interactions such as hydrogen bonding hamper diffusion. The water-soluble polymers retarded the diffusion of thiolated particles in the order PEO > PVP > PAA > HEC whereas for PEGylated silica particles retardation followed the order PAA > PVP = HEC > PEO. In the absence of specific interactions with the medium, PEGylated nanoparticles exhibit enhanced mobility compared to their thiolated counterparts despite some increase in their dimensions. PMID:24354390

On the role of specific interactions in the diffusion of nanoparticles in aqueous polymer solutions.

PubMed

Mun, Ellina A; Hannell, Claire; Rogers, Sarah E; Hole, Patrick; Williams, Adrian C; Khutoryanskiy, Vitaliy V

2014-01-14

Understanding nanoparticle diffusion within non-Newtonian biological and synthetic fluids is essential in designing novel formulations (e.g., nanomedicines for drug delivery, shampoos, lotions, coatings, paints, etc.), but is presently poorly defined. This study reports the diffusion of thiolated and PEGylated silica nanoparticles, characterized by small-angle neutron scattering, in solutions of various water-soluble polymers such as poly(acrylic acid) (PAA), poly(N-vinylpyrrolidone) (PVP), poly(ethylene oxide) (PEO), and hydroxyethylcellulose (HEC) probed using NanoSight nanoparticle tracking analysis. Results show that the diffusivity of nanoparticles is affected by their dimensions, medium viscosity, and, in particular, the specific interactions between nanoparticles and the macromolecules in solution; strong attractive interactions such as hydrogen bonding hamper diffusion. The water-soluble polymers retarded the diffusion of thiolated particles in the order PEO > PVP > PAA > HEC whereas for PEGylated silica particles retardation followed the order PAA > PVP = HEC > PEO. In the absence of specific interactions with the medium, PEGylated nanoparticles exhibit enhanced mobility compared to their thiolated counterparts despite some increase in their dimensions.

Rational design of cancer-targeted selenium nanoparticles to antagonize multidrug resistance in cancer cells.

PubMed

Liu, Ting; Zeng, Lilan; Jiang, Wenting; Fu, Yuanting; Zheng, Wenjie; Chen, Tianfeng

2015-05-01

Multidrug resistance is one of the greatest challenges in cancer therapy. Herein we described the synthesis of folate (FA)-conjugated selenium nanoparticles (SeNPs) as cancer-targeted nano-drug delivery system for ruthenium polypyridyl (RuPOP) exhibits strong fluorescence, which allows the direct imaging of the cellular trafficking of the nanosystem. This nanosystem could effectively antagonize against multidrug resistance in liver cancer. FA surface conjugation significantly enhanced the cellular uptake of SeNPs by FA receptor-mediated endocytosis through nystain-dependent lipid raft-mediated and clathrin-mediated pathways. The nanomaterials overcame the multidrug resistance in R-HepG2 cells through inhibition of ABC family proteins expression. Internalized nanoparticles triggered ROS overproduction and induced apoptosis by activating p53 and MAPKs pathways. Moreover, FA-SeNPs exhibited low in vivo acute toxicity, which verified the safety and application potential of FA-SeNPs as nanodrugs. This study provides an effective strategy for the design of cancer-targeted nanodrugs against multidrug resistant cancers. In the combat against hepatocellular carcinoma, multidrug resistance remains one of the obstacles to be overcome. The authors designed and synthesized folate (FA)-conjugated selenium nanoparticles (SeNPs) with enhanced cancer-targeting capability. This system carried ruthenium polypyridyl (RuPOP), an efficient metal-based anti-cancer drug with strong fluorescence. It was shown that this combination was effective in antagonizing against multidrug resistance in vitro. Copyright © 2015 Elsevier Inc. All rights reserved.

Reactive Capture of Gold Nanoparticles by Strongly Physisorbed Monolayers on Graphite

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

Wei, Xiaoliang; Tong, Wenjun; Fidler, Vlastimil

2012-12-01

Anthracene Diels Alder adducts (DAa) bearing two long side chains (H-(CH2)22O(CH2)6OCH2-) at the 1- and 5-positions form self-assembled monolayers (SAMs) at the phenyloctane - highly oriented pyrolytic graphite (HOPG) interface. The long DAa side chains promote strong physisorption of the monolayer to HOPG and maintain the monolayer morphology upon rinsing or incubation in ethanol and air-drying of the substrate. Incorporating a carboxylic acid group on the DAa core enables capture of 1 - 4 nm diameter gold nanoparticles (AuNP) provided (i) the monolayer containing DAa-carboxylic acids is treated with Cu2+ ions and (ii) the organic coating on the AuNP containsmore » carboxylic acids (11-mercaptoundecanoic acid, MUA-AuNP). AuNP capture by the monolayer proceeds with formation of Cu2+ - carboxylate coordination complexes. The captured AuNP appear as mono- and multi-layered clusters at high coverage on HOPG. The surface density of the captured AuNPs can be adjusted from AuNP multi-layers to isolated AuNPs by varying incubation times, MUA-AuNP concentration, the number density of carboxylic acids in the monolayer, the number of MUA per AuNP, and the post-incubation treatments.« less

Proteasome inhibitory, antioxidant, and synergistic antibacterial and anticandidal activity of green biosynthesized magnetic Fe3O4 nanoparticles using the aqueous extract of corn (Zea mays L.) ear leaves.

PubMed

Patra, Jayanta Kumar; Ali, Md Sarafat; Oh, In-Gyung; Baek, Kwang-Hyun

2017-03-01

Herein, Fe 3 O 4 nanoparticles synthesized using aqueous extract of corn ear leaves were investigated for proteasome inhibitory activity, antioxidant activity, synergistic antibacterial, and anticandidal potential. The UV-Vis spectrum displayed an absorption band at 355 nm that indicated the formation of nano-sized Fe 3 O 4 particles. Vibrating sample magnetometer analysis revealed its superparamagnetic nature. Fe 3 O 4 nanoparticles exhibited strong proteasome inhibitory potential and antioxidant activity and exerted strong synergistic antibacterial and anticandidal activity. Its significant proteasome inhibitory potential could be useful in cancer treatment and drug delivery. Furthermore, strong antioxidant, antibacterial, and anticandidal activity make them a promising candidate for biomedical and pharmaceutical applications.

Structural characterization, antibacterial and catalytic effect of iron oxide nanoparticles synthesised using the leaf extract of Cynometra ramiflora

NASA Astrophysics Data System (ADS)

Groiss, Silvia; Selvaraj, Raja; Varadavenkatesan, Thivaharan; Vinayagam, Ramesh

2017-01-01

In the present investigation, the leaf extract of Cynometra ramiflora was used to synthesize iron oxide nanoparticles. Within minutes of adding iron sulphate to the leaf extract, iron oxide nanoparticles were formed and thus, the method is very simple and fast. UV-VIS spectra showed the strong absorption band in the visible region. SEM images showed discrete spherical shaped particles and EDS spectra confirmed the iron and oxygen presence. The XRD results depicted the crystalline structure of iron oxide nanoparticles. FT-IR spectra portrayed the existence of functional groups of phytochemicals which are probably involved in the formation and stabilization of nanoparticles. The iron oxide nanoparticles exhibited effective inhibition against E. coli and S. epidermidis which may find its applications in the antibacterial drug development. Furthermore, the catalytic activity of the nanoparticles as Fenton-like catalyst was successfully investigated for the degradation of Rhodamine-B dye. This outcome could play a prominent role in the wastewater treatment.

Design and Preparation of Supported Au Catalyst with Enhanced Catalytic Activities by Rationally Positioning Au Nanoparticles on Anatase.

PubMed

Wang, Liang; Wang, Hong; Rice, Andrew E; Zhang, Wei; Li, Xiaokun; Chen, Mingshu; Meng, Xiangju; Lewis, James P; Xiao, Feng-Shou

2015-06-18

A synergistic effect between individual components is crucial for increasing the activity of metal/metal oxide catalysts. The greatest challenge is how to control the synergistic effect to obtain enhanced catalytic performance. Through density functional theory calculations of model Au/TiO2 catalysts, it is suggested that there is strong interaction between Au nanoparticles and Ti species at the edge/corner sites of anatase, which is favorable for the formation of stable oxygen vacancies. Motivated by this theoretical analysis, we have rationally prepared Au nanoparticles attached to edge/corner sites of anatase support (Au/TiO2-EC), confirmed by their HR-TEM images. As expected, this strong interaction is well characterized by Raman, UV-visible, and XPS techniques. Very interestingly, compared with conventional Au catalysts, Au/TiO2-EC exhibits superior catalytic activity in the oxidations using O2. Our approach to controlling Au nanoparticle positioning on anatase to obtain enhanced catalytic activity offers an efficient strategy for developing more novel supported metal catalysts.

Precision control of drying using rhythmic dancing of sessile nanoparticle laden droplets

NASA Astrophysics Data System (ADS)

Sanyal, Apratim; Basu, Saptarshi; Chowdhuri, Subham; Kabi, Prasenjit; Chaudhuri, Swetaprovo

2014-04-01

This work analyses the unique spatio-temporal alteration of the deposition pattern of evaporating nanoparticle laden droplets resting on a hydrophobic surface through targeted low frequency substrate vibrations. External excitation near the lowest resonant mode (n = 2) of the droplet initially de-pins and then subsequently re-pins the droplet edge creating pseudo-hydrophilicity (low contact angle). Vibration subsequently induces droplet shape oscillations (cyclic elongation and flattening) resulting in strong flow recirculation. This strong radially outward liquid flow augments nanoparticle transport, vaporization, and agglomeration near the pinned edge resulting in much reduced drying time under certain characteristic frequency of oscillations. The resultant deposit exhibits a much flatter structure with sharp, defined peripheral wedge topology as compared to natural drying. Such controlled manipulation of transport enables tailoring of structural and topological morphology of the deposits and offers possible routes towards controlling the formation and drying timescales which are crucial for applications ranging from pharmaceutics to surface patterning.

Strong and Long Makes Short: Strong-Pump Strong-Probe Spectroscopy.

PubMed

Gelin, Maxim F; Egorova, Dassia; Domcke, Wolfgang

2011-01-20

We propose a new time-domain spectroscopic technique that is based on strong pump and probe pulses. The strong-pump strong-probe (SPSP) technique provides temporal resolution that is not limited by the durations of the pump and probe pulses. By numerically exact simulations of SPSP signals for a multilevel vibronic model, we show that the SPSP signals exhibit electronic and vibrational beatings on time scales which are significantly shorter than the pulse durations. This suggests the possible application of SPSP spectroscopy for the real-time investigation of molecular processes that cannot be temporally resolved by pump-probe spectroscopy with weak pump and probe pulses.

Individual and collective modes of surface magnetoplasmon in thiolate-protected silver nanoparticles studied by MCD spectroscopy

NASA Astrophysics Data System (ADS)

Yao, Hiroshi; Shiratsu, Taisuke

2016-05-01

Large magneto-optical (MO) responses at the energy of localized surface plasmon resonance (LSPR), namely, surface magnetoplasmons, are demonstrated for the first time in thiolate-protected silver nanoparticles with magnetic circular dichroism (MCD) spectroscopy. The samples examined are decanethiol (DT)-, azobenzenethiol (ABT)-, and ABT/DT mixed-monolayer-protected Ag nanoparticles. ABT-protected Ag nanoparticles are somewhat aggregated and thus exhibit a broad, collective mode of plasmonic absorption, whereas other samples with highly-dispersed nanoparticles show an individual mode of LSPR absorption. In all Ag nanoparticles, a derivative-like MCD signal is observed under an applied magnetic field of 1.6 T, which can be explained in terms of two circular modes of magnetoplasmon caused by the increase (or decrease) in the Lorentz force imparted on the free electrons that oscillate in the left (or right) circular orbits in the nanosphere. For the Ag nanoparticles exhibiting an individual LSPR mode, in particular, simultaneous deconvolution analysis of UV-vis absorption and MCD spectra reveal that (i) the amplitude of the magnetoplasmonic component with lower frequency (ω-), resulting from the reduction in the confinement strength of collective electrons by the Lorentz force, is stronger than that with a higher frequency (ω+) (ii) the accurate shift or cyclotron frequency between two magnetoplasmonic modes (ωc = ω+ - ω-) is size-dependent, and presents a very large value with implications for the apparent enhancement of the local magnetic-field in the Ag nanoparticles. These results strongly suggest that the Ag-thiolate layer or Ag-S bonding on the nanoparticle surface plays a significant role in the MO enhancement.Large magneto-optical (MO) responses at the energy of localized surface plasmon resonance (LSPR), namely, surface magnetoplasmons, are demonstrated for the first time in thiolate-protected silver nanoparticles with magnetic circular dichroism (MCD

Engineered Gold Nanoparticles and Plant Adaptation Potential

NASA Astrophysics Data System (ADS)

Siddiqi, Khwaja Salahuddin; Husen, Azamal

2016-09-01

Use of metal nanoparticles in biological system has recently been recognised although little is known about their possible effects on plant growth and development. Nanoparticles accumulation, translocation, growth response and stress modulation in plant system is not well understood. Plants exposed to gold and gold nanoparticles have been demonstrated to exhibit both positive and negative effects. Their growth and yield vary from species to species. Cytoxicity of engineered gold nanoparticles depends on the concentration, particle size and shape. They exhibit increase in vegetative growth and yield of fruit/seed at lower concentration and decrease them at higher concentration. Studies have shown that the gold nanoparticles exposure has improved free radical scavenging potential and antioxidant enzymatic activities and alter micro RNAs expression that regulate different morphological, physiological and metabolic processes in plants. These modulations lead to improved plant growth and yields. Prior to the use of gold nanoparticles, it has been suggested that its cost may be calculated to see if it is economically feasible.

Nucleation and Growth of Ordered Arrays of Silver Nanoparticles on Peptide Nanofibers: Hybrid Nanostructures with Antimicrobial Properties.

PubMed

Pazos, Elena; Sleep, Eduard; Rubert Pérez, Charles M; Lee, Sungsoo S; Tantakitti, Faifan; Stupp, Samuel I

2016-05-04

Silver nanoparticles have been of great interest as plasmonic substrates for sensing and imaging, catalysts, or antimicrobial systems. Their physical properties are strongly dependent on parameters that remain challenging to control such as size, chemical composition, and spatial distribution. We report here on supramolecular assemblies of a novel peptide amphiphile containing aldehyde functionality in order to reduce silver ions and subsequently nucleate silver metal nanoparticles in water. This system spontaneously generates monodisperse silver particles at fairly regular distances along the length of the filamentous organic assemblies. The metal-organic hybrid structures exhibited antimicrobial activity and significantly less toxicity toward eukaryotic cells. Metallized organic nanofibers of the type described here offer the possibility to create hydrogels, which integrate the useful functions of silver nanoparticles with controllable metallic content.

SERS of semiconducting nanoparticles (TIO{sub 2} hybrid composites).

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

Rajh, T.; Musumeci, A.; Gosztola, D.

Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules thatmore » lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.« less

Gold-magnetite nanoparticle-biomolecule conjugates: Synthesis, properties and toxicity studies

NASA Astrophysics Data System (ADS)

Pariti, Akshay

This thesis study focuses on synthesizing and characterizing gold-magnetite optically active magnetic nanoparticle and its conjugation with biomolecules for biomedical applications, especially magnetic fluid hyperthermia treatment for cancerous tissue. Gold nanoparticles have already displayed their potential in the biomedical field. They exhibit excellent optical properties and possess strong surface chemistry which renders them suitable for various biomolecule attachments. Studies have showed gold nanoparticles to be a perfect biocompatible vector. However, clinical trials for gold mediated drug delivery and treatment studied in rat models identified some problems. Of these problems, the low retention time in bloodstream and inability to maneuver externally has been the consequential. To further enhance their potential applications and overcome the problems faced in using gold nanoparticles alone, many researchers have synthesized multifunctional magnetic materials with gold at one terminal. Magnetite, among the investigated magnetic materials is a promising and reliable candidate because of its high magnetic saturation moment and low toxicity. This thesis showcases a simple and facile one pot synthesis of gold-magnetite nanoparticles with an average particle size of 80 nm through hot injection method. The as-synthesized nanoparticles were characterized by XRD, TEM, Mossbauer spectroscopy, SQUID and MTS toxicity studies. The superparamagnetism of the as-synthesized nanoparticles has an interestingly high saturation magnetization moment and low toxicity than the literature values reported earlier. L-cysteine and (-)-EGCG (epigallacatechin-3-gallate) were attached to this multifunctional nanoparticles through the gold terminal and characterized to show the particles applicability through Raman, FTIR and UV-Vis spectroscopy.

Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe2O3 nanoparticles

PubMed Central

Khurshid, Hafsa; Lampen-Kelley, Paula; Iglesias, Òscar; Alonso, Javier; Phan, Manh-Huong; Sun, Cheng-Jun; Saboungi, Marie-Louise; Srikanth, Hariharan

2015-01-01

Disorder among surface spins is a dominant factor in the magnetic response of magnetic nanoparticle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8 ± 0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and become frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point to highly frustrated surface spins that rearrange much more slowly than interior spins. Monte Carlo simulations of a hollow particle corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures. PMID:26503506

Direct experimental evidence for photoinduced strong-coupling polarons in organolead halide perovskite nanoparticles

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

Zheng, Kaibo; Qatar Univ., Doha; Abdellah, Mohamed

Echoing the roaring success of their bulk coun-terparts, nano-objects built from organolead halide perov-skites (OLHP) present bright prospects for surpassing the performances of their conventional organic and inorganic analogues in photodriven technologies. Unraveling the pho-toinduced charge dynamics is essential for optimizing OLHP optoelectronic functionalities. However, mapping the carri-er-lattice interactions remains challenging, owing to their manifestations on multiple length scales and time scales. By correlating ultrafast time-resolved optical and X-ray absorp-tion measurements, this work reveals the photoinduced formation of strong-coupling polarons in CH 3NH 3PbBr 3 nanoparticles. Such polarons originate from the self-trapping of electrons in the net Coulombic field causedmore » by the dis-placed inorganic nuclei and the oriented organic cations. The transient structural change detected at the Pb L 3 X-ray ab-sorption edge is well captured by a distortion with average bond elongation in the [PbBr 6] 2- motif. As a result, general implications for designing novel OLHP nanomaterials targeting the active utilization of these quasi-particles are outlined.« less

Direct experimental evidence for photoinduced strong-coupling polarons in organolead halide perovskite nanoparticles

DOE PAGES

Zheng, Kaibo; Qatar Univ., Doha; Abdellah, Mohamed; ...

2016-10-28

Echoing the roaring success of their bulk coun-terparts, nano-objects built from organolead halide perov-skites (OLHP) present bright prospects for surpassing the performances of their conventional organic and inorganic analogues in photodriven technologies. Unraveling the pho-toinduced charge dynamics is essential for optimizing OLHP optoelectronic functionalities. However, mapping the carri-er-lattice interactions remains challenging, owing to their manifestations on multiple length scales and time scales. By correlating ultrafast time-resolved optical and X-ray absorp-tion measurements, this work reveals the photoinduced formation of strong-coupling polarons in CH 3NH 3PbBr 3 nanoparticles. Such polarons originate from the self-trapping of electrons in the net Coulombic field causedmore » by the dis-placed inorganic nuclei and the oriented organic cations. The transient structural change detected at the Pb L 3 X-ray ab-sorption edge is well captured by a distortion with average bond elongation in the [PbBr 6] 2- motif. As a result, general implications for designing novel OLHP nanomaterials targeting the active utilization of these quasi-particles are outlined.« less

The effects of plasma inhomogeneity on the nanoparticle coating in a low pressure plasma reactor

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

Pourali, N.; Foroutan, G.

2015-10-15

A self-consistent model is used to study the surface coating of a collection of charged nanoparticles trapped in the sheath region of a low pressure plasma reactor. The model consists of multi-fluid plasma sheath module, including nanoparticle dynamics, as well as the surface deposition and particle heating modules. The simulation results show that the mean particle radius increases with time and the nanoparticle size distribution is broadened. The mean radius is a linear function of time, while the variance exhibits a quadratic dependence. The broadening in size distribution is attributed to the spatial inhomogeneity of the deposition rate which inmore » turn depends on the plasma inhomogeneity. The spatial inhomogeneity of the ions has strong impact on the broadening of the size distribution, as the ions contribute both in the nanoparticle charging and in direct film deposition. The distribution width also increases with increasing of the pressure, gas temperature, and the ambient temperature gradient.« less

Molecular dynamics simulation of the local concentration and structure in multicomponent aerosol nanoparticles under atmospheric conditions.

PubMed

Karadima, Katerina S; Mavrantzas, Vlasis G; Pandis, Spyros N

2017-06-28

Molecular dynamics (MD) simulations were employed to investigate the local structure and local concentration in atmospheric nanoparticles consisting of an organic compound (cis-pinonic acid or n-C 30 H 62 ), sulfate and ammonium ions, and water. Simulations in the isothermal-isobaric (NPT) statistical ensemble under atmospheric conditions with a prespecified number of molecules of the abovementioned compounds led to the formation of a nanoparticle. Calculations of the density profiles of all the chemical species in the nanoparticle, the corresponding radial pair distribution functions, and their mobility inside the nanoparticle revealed strong interactions developing between sulfate and ammonium ions. However, sulfate and ammonium ions prefer to populate the central part of the nanoparticle under the simulated conditions, whereas organic molecules like to reside at its outer surface. Sulfate and ammonium ions were practically immobile; in contrast, the organic molecules exhibited appreciable mobility at the outer surface of the nanoparticle. When the organic compound was a normal alkane (e.g. n-C 30 H 62 ), a well-organized (crystalline-like) phase was rapidly formed at the free surface of the nanoparticle and remained separate from the rest of the species.

Biosynthesis, Antimicrobial and Cytotoxic Effect of Silver Nanoparticles Using a Novel Nocardiopsis sp. MBRC-1

PubMed Central

Manivasagan, Panchanathan; Senthilkumar, Kalimuthu; Sivakumar, Kannan; Kim, Se-Kwon

2013-01-01

The biosynthesis of nanoparticles has been proposed as a cost effective environmental friendly alternative to chemical and physical methods. Microbial synthesis of nanoparticles is under exploration due to wide biomedical applications, research interest in nanotechnology and microbial biotechnology. In the present study, an ecofriendly process for the synthesis of nanoparticles using a novel Nocardiopsis sp. MBRC-1 has been attempted. We used culture supernatant of Nocardiopsis sp. MBRC-1 for the simple and cost effective green synthesis of silver nanoparticles. The reduction of silver ions occurred when silver nitrate solution was treated with the Nocardiopsis sp. MBRC-1 culture supernatant at room temperature. The nanoparticles were characterized by UV-visible, TEM, FE-SEM, EDX, FTIR, and XRD spectroscopy. The nanoparticles exhibited an absorption peak around 420 nm, a characteristic surface plasmon resonance band of silver nanoparticles. They were spherical in shape with an average particle size of 45 ± 0.15 nm. The EDX analysis showed the presence of elemental silver signal in the synthesized nanoparticles. The FTIR analysis revealed that the protein component in the form of enzyme nitrate reductase produced by the isolate in the culture supernatant may be responsible for reduction and as capping agents. The XRD spectrum showed the characteristic Bragg peaks of 1 2 3, 2 0 4, 0 4 3, 1 4 4, and 3 1 1 facets of the face centered cubic silver nanoparticles and confirms that these nanoparticles are crystalline in nature. The prepared silver nanoparticles exhibited strong antimicrobial activity against bacteria and fungi. Cytotoxicity of biosynthesized AgNPs against in vitro human cervical cancer cell line (HeLa) showed a dose-response activity. IC50 value was found to be 200 μg/mL of AgNPs against HeLa cancer cells. Further studies are needed to elucidate the toxicity and the mechanism involved with antimicrobial and anticancer activity of the synthesized Ag

Biosynthesis, antimicrobial and cytotoxic effect of silver nanoparticles using a novel Nocardiopsis sp. MBRC-1.

PubMed

Manivasagan, Panchanathan; Venkatesan, Jayachandran; Senthilkumar, Kalimuthu; Sivakumar, Kannan; Kim, Se-Kwon

2013-01-01

The biosynthesis of nanoparticles has been proposed as a cost effective environmental friendly alternative to chemical and physical methods. Microbial synthesis of nanoparticles is under exploration due to wide biomedical applications, research interest in nanotechnology and microbial biotechnology. In the present study, an ecofriendly process for the synthesis of nanoparticles using a novel Nocardiopsis sp. MBRC-1 has been attempted. We used culture supernatant of Nocardiopsis sp. MBRC-1 for the simple and cost effective green synthesis of silver nanoparticles. The reduction of silver ions occurred when silver nitrate solution was treated with the Nocardiopsis sp. MBRC-1 culture supernatant at room temperature. The nanoparticles were characterized by UV-visible, TEM, FE-SEM, EDX, FTIR, and XRD spectroscopy. The nanoparticles exhibited an absorption peak around 420 nm, a characteristic surface plasmon resonance band of silver nanoparticles. They were spherical in shape with an average particle size of 45 ± 0.15 nm. The EDX analysis showed the presence of elemental silver signal in the synthesized nanoparticles. The FTIR analysis revealed that the protein component in the form of enzyme nitrate reductase produced by the isolate in the culture supernatant may be responsible for reduction and as capping agents. The XRD spectrum showed the characteristic Bragg peaks of 1 2 3, 2 0 4, 0 4 3, 1 4 4, and 3 1 1 facets of the face centered cubic silver nanoparticles and confirms that these nanoparticles are crystalline in nature. The prepared silver nanoparticles exhibited strong antimicrobial activity against bacteria and fungi. Cytotoxicity of biosynthesized AgNPs against in vitro human cervical cancer cell line (HeLa) showed a dose-response activity. IC50 value was found to be 200 μg/mL of AgNPs against HeLa cancer cells. Further studies are needed to elucidate the toxicity and the mechanism involved with antimicrobial and anticancer activity of the synthesized AgNPs as

High potential of Mn-doped ZnS nanoparticles with different dopant concentrations as novel MRI contrast agents: synthesis and in vitro relaxivity studies

NASA Astrophysics Data System (ADS)

Jahanbin, Tania; Gaceur, Meriem; Gros-Dagnac, Hélène; Benderbous, Soraya; Merah, Souad Ammar

2015-06-01

Over several decades, metal-doped quantum dots (QDs) with core-shell structure have been studied as dual probes: fluorescence and magnetic resonance imaging (MRI) probes (Dixit et al., Mater Lett 63(30):2669-2671, 2009). However, metal-doped nanoparticles, in which the majority of metal ions are close to the surface, can affect their efficacy as MRI contrast agents (CAs). In this context, herein the high potential of synthesized Mn-doped ZnS QDs via polyol method as imaging probe is demonstrated. The mean diameters of QDs were measured via transmission electron microscopy (TEM) and X-ray diffraction (XRD). Optical and magnetic properties of MnZnS nanoparticles were characterized using fluorescence spectroscopy and super quanducting interference devices magnetometer and electron paramagnetic resonance system, respectively. T1- and T2-weighted images of nanoparticles in aqueous solution were acquired from spin-echo sequences at 3 T. From TEM images and XRD spectra of the prepared nanoparticles, it is observed that the average diameter of particles does not significantly change with Mn dopant content ( 1.6-1.9 nm). All three samples exhibit broad blue emission under UV light excitation. According to the MRI studies, MnZnS nanoparticles generate strong T1 contrast enhancement (bright T1-weighted images) at the low concentration (<0.1 mM). The MnZnS nanoparticles exhibit the high longitudinal ( r 1) relaxivity that increases from 20.34 to 75.5 mM-1 s-1 with the Mn dopant contents varying between 10 and 30 %. Strong signal intensity on T1-weighted images and high r 1 with {r2 }/{r_{1 }} ≈ 1 can demonstrate the high potential of the synthesized Mn:ZnS nanoparticles, which can serve as an effective T1 CA.

Pullulan-coated phospholipid and Pluronic F68 complex nanoparticles for carrying IR780 and paclitaxel to treat hepatocellular carcinoma by combining photothermal therapy/photodynamic therapy and chemotherapy

PubMed Central

Zhang, Tao; Wan, Guoyun; Chen, Bowei; Xiong, Qingqing; Zhang, Jie; Zhang, Wenxue; Wang, Yinsong

2017-01-01

IR780, a near-infrared dye, can also be used as a photosensitizer both for photothermal therapy (PTT) and photodynamic therapy (PDT). In this study, we designed a simple but effective nanoparticle system for carrying IR780 and paclitaxel, thus hoping to combine PTT/PDT and chemotherapy to treat hepatocellular carcinoma (HCC). This nanosystem, named PDF nanoparticles, consisted of phospholipid/Pluronic F68 complex nanocores and pullulan shells. IR780 and paclitaxel were loaded separately into PDF nanoparticles to form PDFI and PDFP nanoparticles, which had regular sphere shapes and relatively small sizes. Upon near-infrared laser irradiation at 808 nm, PDFI nanoparticles showed strong PTT/PDT efficacy both in vitro and in vivo. In MHCC-97H cells, the combined treatment of PDFI nanoparticles/laser irradiation and PDFP nanoparticles exhibited significant synergistic effects on inhibiting cell proliferation and inducing cell apoptosis and cell cycle arrest at G2/M phase. In MHCC-97H tumor-bearing mice, PDFI nanoparticles exhibited excellent HCC-targeting and accumulating capability after intravenous injection. Furthermore, the combined treatment of PDFI nanoparticles/laser irradiation and PDFP nanoparticles also effectively inhibited the tumor growth and the tumor angiogenesis in MHCC-97H tumor-bearing mice. In summary, we put forward a therapeutic strategy for HCC treatment by combining PTT/PDT and chemotherapy. PMID:29255359

Pullulan-coated phospholipid and Pluronic F68 complex nanoparticles for carrying IR780 and paclitaxel to treat hepatocellular carcinoma by combining photothermal therapy/photodynamic therapy and chemotherapy.

PubMed

Wang, Dan; Zhang, Sipei; Zhang, Tao; Wan, Guoyun; Chen, Bowei; Xiong, Qingqing; Zhang, Jie; Zhang, Wenxue; Wang, Yinsong

2017-01-01

IR780, a near-infrared dye, can also be used as a photosensitizer both for photothermal therapy (PTT) and photodynamic therapy (PDT). In this study, we designed a simple but effective nanoparticle system for carrying IR780 and paclitaxel, thus hoping to combine PTT/PDT and chemotherapy to treat hepatocellular carcinoma (HCC). This nanosystem, named PDF nanoparticles, consisted of phospholipid/Pluronic F68 complex nanocores and pullulan shells. IR780 and paclitaxel were loaded separately into PDF nanoparticles to form PDFI and PDFP nanoparticles, which had regular sphere shapes and relatively small sizes. Upon near-infrared laser irradiation at 808 nm, PDFI nanoparticles showed strong PTT/PDT efficacy both in vitro and in vivo. In MHCC-97H cells, the combined treatment of PDFI nanoparticles/laser irradiation and PDFP nanoparticles exhibited significant synergistic effects on inhibiting cell proliferation and inducing cell apoptosis and cell cycle arrest at G2/M phase. In MHCC-97H tumor-bearing mice, PDFI nanoparticles exhibited excellent HCC-targeting and accumulating capability after intravenous injection. Furthermore, the combined treatment of PDFI nanoparticles/laser irradiation and PDFP nanoparticles also effectively inhibited the tumor growth and the tumor angiogenesis in MHCC-97H tumor-bearing mice. In summary, we put forward a therapeutic strategy for HCC treatment by combining PTT/PDT and chemotherapy.

Fluorescence-Guided Probes of Aptamer-Targeted Gold Nanoparticles with Computed Tomography Imaging Accesses for in Vivo Tumor Resection.

PubMed

Li, Cheng-Hung; Kuo, Tsung-Rong; Su, Hsin-Jan; Lai, Wei-Yun; Yang, Pan-Chyr; Chen, Jinn-Shiun; Wang, Di-Yan; Wu, Yi-Chun; Chen, Chia-Chun

2015-10-28

Recent development of molecular imaging probes for fluorescence-guided surgery has shown great progresses for determining tumor margin to execute the tissue resection. Here we synthesize the fluorescent gold nanoparticles conjugated with diatrizoic acid and nucleolin-targeted AS1411 aptamer. The nanoparticle conjugates exhibit high water-solubility, good biocompatibility, visible fluorescence and strong X-ray attenuation for computed tomography (CT) contrast enhancement. The fluorescent nanoparticle conjugates are applied as a molecular contrast agent to reveal the tumor location in CL1-5 tumor-bearing mice by CT imaging. Furthermore, the orange-red fluorescence emitting from the conjugates in the CL1-5 tumor can be easily visualized by the naked eyes. After the resection, the IVIS measurements show that the fluorescence signal of the nanoparticle conjugates in the tumor is greatly enhanced in comparison to that in the controlled experiment. Our work has shown potential application of functionalized nanoparticles as a dual-function imaging agent in clinical fluorescence-guided surgery.

Fluorescence-Guided Probes of Aptamer-Targeted Gold Nanoparticles with Computed Tomography Imaging Accesses for in Vivo Tumor Resection

PubMed Central

Li, Cheng-Hung; Kuo, Tsung-Rong; Su, Hsin-Jan; Lai, Wei-Yun; Yang, Pan-Chyr; Chen, Jinn-Shiun; Wang, Di-Yan; Wu, Yi-Chun; Chen, Chia-Chun

2015-01-01

Recent development of molecular imaging probes for fluorescence-guided surgery has shown great progresses for determining tumor margin to execute the tissue resection. Here we synthesize the fluorescent gold nanoparticles conjugated with diatrizoic acid and nucleolin-targeted AS1411 aptamer. The nanoparticle conjugates exhibit high water-solubility, good biocompatibility, visible fluorescence and strong X-ray attenuation for computed tomography (CT) contrast enhancement. The fluorescent nanoparticle conjugates are applied as a molecular contrast agent to reveal the tumor location in CL1-5 tumor-bearing mice by CT imaging. Furthermore, the orange-red fluorescence emitting from the conjugates in the CL1-5 tumor can be easily visualized by the naked eyes. After the resection, the IVIS measurements show that the fluorescence signal of the nanoparticle conjugates in the tumor is greatly enhanced in comparison to that in the controlled experiment. Our work has shown potential application of functionalized nanoparticles as a dual-function imaging agent in clinical fluorescence-guided surgery. PMID:26507179

Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

NASA Astrophysics Data System (ADS)

Siegel, Jakub; Lyutakov, Oleksiy; Polívková, Markéta; Staszek, Marek; Hubáček, Tomáš; Švorčík, Václav

2017-10-01

Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV-vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

Antibacterial effects of laser ablated Ni nanoparticles

NASA Astrophysics Data System (ADS)

Shamaila, S.; Wali, H.; Sharif, R.; Nazir, J.; Zafar, N.; Rafique, M. S.

2013-10-01

The interaction of nickel nanoparticles with Escherichia coli (E. coli) bacteria has been studied. The nickel nanoparticles have been fabricated by continuous wave laser ablation of nickel target and their properties are studied using different characterization techniques. The antibacterial activity of nickel nanoparticles was checked against E. coli bacteria. Escherichia coli were cultured in nutrients broth and different concentrations of nickel nanoparticles were added to bacterial culture solution to investigate the interaction of nickel nanoparticles with bacteria and to check toxicity of the nickel nanoparticles against E. coli. The fabricated Ni nanoparticles have exhibited considerable antimicrobial activity against E. coli.

Amino acid mediated synthesis of silver nanoparticles and preparation of antimicrobial agar/silver nanoparticles composite films.

PubMed

Shankar, Shiv; Rhim, Jong-Whan

2015-10-05

Silver nanoparticles (AgNPs) were synthesized using amino acids (tyrosine and tryptophan) as reducing and capping agents, and they were incorporated into the agar to prepare antimicrobial composite films. The AgNPs solutions exhibited characteristic absorption peak at 420 nm that showed a red shift to ∼434 nm after forming composite with agar. XRD data demonstrated the crystalline structure of AgNPs with dominant (111) facet. Apparent surface color and transmittance of agar films were greatly influenced by the AgNPs. The incorporation of AgNPs into agar did not exhibit any change in chemical structure, thermal stability, moisture content, and water vapor permeability. The water contact angle, tensile strength, and modulus decreased slightly, but elongation at break increased after AgNPs incorporation. The agar/AgNPs nanocomposite films possessed strong antibacterial activity against Listeria monocytogenes and Escherichia coli. The agar/AgNPs film could be applied to the active food packaging by controlling the food-borne pathogens. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis of new liquid crystals embedded gold nanoparticles for photoswitching properties.

PubMed

Rahman, Md Lutfor; Biswas, Tapan Kumar; Sarkar, Shaheen M; Yusoff, Mashitah Mohd; Yuvaraj, A R; Kumar, Sandeep

2016-09-15

A new series of liquid crystals decorated gold nanoparticles is synthesized whose molecular architecture has azobenzenes moieties as the peripheral units connected to gold nanoparticles (Au NPs) via alkyl groups. The morphology and mesomorphic properties were investigated by field emission scanning electron microscope, high-resolution transmission electron microscopy, differential scanning calorimetry and polarizing optical microscopy. The thiolated ligand molecules (3a-c) showed enantiotropic smectic A phase, whereas gold nanoparticles (5a-c) exhibit nematic and smectic A phase with monotropic nature. HR-TEM measurement showed that the functionalized Au NPs are of the average size of 2nm and they are well dispersed without any aggregation. The trans-form of azo compounds showed a strong band in the UV region at ∼378nm for the π-π(∗) transition, and a weak band in the visible region at ∼472nm due to the n-π(∗) transition. These molecules exhibit attractive photoisomerization behaviour in which trans-cis transition takes about 15s whereas the cis-trans transition requires about 45min for compound 5c. The extent of reversible isomerization did not decay after 10 cycles, which proved that the photo-responsive properties of 5c were stable and repeatable. Therefore, these materials may be suitably exploited in the field of molecular switches and the optical storage devices. Copyright © 2016 Elsevier Inc. All rights reserved.

On the defect origin of the room-temperature magnetism universally exhibited by metal-oxide nanoparticles.

PubMed

Panchakarla, L S; Sundarayya, Y; Manjunatha, S; Sundaresan, A; Rao, C N R

2010-06-07

The occurrence of ferromagnetism in nanoparticles of otherwise non-magnetic oxides seems to be well established. It is, however, necessary to understand the origin of ferromagnetism in these materials. Herein, we present a combined study of the magnetic properties and photoluminescence (PL) behavior of nanoparticles of ZnO, ZrO(2), and MgO annealed at different temperatures (and therefore of different sizes). We find that the magnetization and the intensity of the bands due to defects vary parallel in all these materials. The adsorption of ethanol leads to a decrease in the magnetization and to a reduced intensity of the defect PL band of ZnO nanoparticles whereas UV irradiation has the opposite effect. We have also examined the effect of the morphology of the ZnO on the properties.

A polysaccharide from Armillaria mellea exhibits strong in vitro anticancer activity via apoptosis-involved mechanisms.

PubMed

Wu, Jun; Zhou, Jinxu; Lang, Yaoguo; Yao, Lei; Xu, Hai; Shi, Hubo; Xu, Shidong

2012-11-01

Armillaria mellea is a famous traditional Chinese medicinal and edible fungus. In this study, we purified a water-soluble polysaccharide (AMP) from the fruiting bodies of this fungus. AMP contained 94.8% carbohydrate, 2.3% uronic acid and 0.5% protein. Its molecular weight was determined as 4.6 × 10⁵ Da, as determined by high-performance gel-permeation chromatography (HPGPC). Gas chromatography (GC) analysis indicated that AMP was mainly composed of d-glucose. In vitro assay, AMP exhibited a potent tumor growth inhibitory effect on A549 cells, and induced cell cycle disruption in the G0/G1 phase, accompanied by an increment of apoptotic cells. Furthermore, AMP induced the disruption of mitochondrial membrane potential, thus leading to cytochrome c release from mitochondria and activation of caspase-3 and -9. Taken together, our results demonstrate that AMP possesses strong antitumor activities through the mitochondria dependent pathway and activation of caspase cascade through cytochrome c release. Copyright © 2012 Elsevier B.V. All rights reserved.

Ultrasmall lanthanide-doped nanoparticles as multimodal platforms

NASA Astrophysics Data System (ADS)

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

2014-03-01

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

Facile synthesis of ferromagnetic Ni doped CeO2 nanoparticles with enhanced anticancer activity

NASA Astrophysics Data System (ADS)

Abbas, Fazal; Jan, Tariq; Iqbal, Javed; Ahmad, Ishaq; Naqvi, M. Sajjad H.; Malik, Maaza

2015-12-01

NixCe1-xO2 (where x = 0, 0.01, 0.03, 0.05 and 0.07) nanoparticles were synthesized by soft chemical method and were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, UV-vis absorption spectroscopy and vibrating sample magnetometer (VSM). XRD and Raman results indicated the formation of single phase cubic fluorite structure for the synthesized nanoparticles. Ni dopant induced excessive structural changes such as decrease in crystallite size as well as lattice constants and enhancement in oxygen vacancies in CeO2 crystal structure. These structural variations significantly influenced the optical and magnetic properties of CeO2 nanoparticles. The synthesized NixCe1-xO2 nanoparticles exhibited room temperature ferromagnetic behavior. Ni doping induced effects on the cytotoxicity of CeO2 nanoparticles were examined against HEK-293 healthy cell line and SH-SY5Y neuroblastoma cancer cell line. The prepared NixCe1-xO2 nanoparticles demonstrated differential cytotoxicity. Furthermore, anticancer activity of CeO2 nanoparticles observed to be significantly enhanced with Ni doping which was found to be strongly correlated with the level of reactive oxygen species (ROS) production. The prepared ferromagnetic NixCe1-xO2 nanoparticles with differential cytotoxic nature may be potential for future targeted cancer therapy.

SERS of semiconducting nanoparticles (TiO{sub 2} hybrid composites).

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

Musumeci, A.; Gosztola, D.; Schiller, T.

Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules thatmore » lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.« less

Visualization of upconverting nanoparticles in strongly scattering media

PubMed Central

Khaydukov, E. V.; Semchishen, V. A.; Seminogov, V. N.; Nechaev, A. V.; Zvyagin, A. V.; Sokolov, V. I.; Akhmanov, A. S.; Panchenko, V. Ya.

2014-01-01

Optical visualization systems are needed in medical applications for determining the localization of deep-seated luminescent markers in biotissues. The spatial resolution of such systems is limited by the scattering of the tissues. We present a novel epi-luminescent technique, which allows a 1.8-fold increase in the lateral spatial resolution in determining the localization of markers lying deep in a scattering medium compared to the traditional visualization techniques. This goal is attained by using NaYF4:Yb3+Tm3+@NaYF4 core/shell nanoparticles and special optical fiber probe with combined channels for the excitation and detection of anti-Stokes luminescence signals. PMID:24940552

Nucleation and Growth of Ordered Arrays of Silver Nanoparticles on Peptide Nanofibers: Hybrid Nanostructures with Antimicrobial Properties

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

Pazos, Elena; Sleep, Eduard; Rubert Perez, Charles M.

Here, silver nanoparticles have been of great interest as plasmonic substrates for sensing and imaging, catalysts, or antimicrobial systems. Their physical properties are strongly dependent on parameters that remain challenging to control such as size, chemical composition, and spatial distribution. We report here on supramolecular assemblies of a novel peptide amphiphile containing aldehyde functionality in order to reduce silver ions and subsequently nucleate silver metal nanoparticles in water. This system spontaneously generates monodisperse silver particles at fairly regular distances along the length of the filamentous organic assemblies. The metal–organic hybrid structures exhibited antimicrobial activity and significantly less toxicity toward eukaryoticmore » cells. Metallized organic nanofibers of the type described here offer the possibility to create hydrogels, which integrate the useful functions of silver nanoparticles with controllable metallic content.« less

Nucleation and Growth of Ordered Arrays of Silver Nanoparticles on Peptide Nanofibers: Hybrid Nanostructures with Antimicrobial Properties

DOE PAGES

Pazos, Elena; Sleep, Eduard; Rubert Perez, Charles M.; ...

2016-04-22

Here, silver nanoparticles have been of great interest as plasmonic substrates for sensing and imaging, catalysts, or antimicrobial systems. Their physical properties are strongly dependent on parameters that remain challenging to control such as size, chemical composition, and spatial distribution. We report here on supramolecular assemblies of a novel peptide amphiphile containing aldehyde functionality in order to reduce silver ions and subsequently nucleate silver metal nanoparticles in water. This system spontaneously generates monodisperse silver particles at fairly regular distances along the length of the filamentous organic assemblies. The metal–organic hybrid structures exhibited antimicrobial activity and significantly less toxicity toward eukaryoticmore » cells. Metallized organic nanofibers of the type described here offer the possibility to create hydrogels, which integrate the useful functions of silver nanoparticles with controllable metallic content.« less

Impact of spherical nanoparticles on nematic order parameters

NASA Astrophysics Data System (ADS)

Kyrou, C.; Kralj, S.; Panagopoulou, M.; Raptis, Y.; Nounesis, G.; Lelidis, I.

2018-04-01

We study experimentally the impact of spherical nanoparticles on the orientational order parameters of a host nematic liquid crystal. We use spherical core-shell quantum dots that are surface functionalized to promote homeotropic anchoring on their interface with the liquid crystal host. We show experimentally that the orientational order may be strongly affected by the presence of spherical nanoparticles even at low concentrations. The orientational order of the composite system is probed by means of polarized micro-Raman spectroscopy and by optical birefringence measurements as function of temperature and concentration. Our data show that the orientational order depends on the concentration in a nonlinear way, and the existence of a crossover concentration χc≈0.004 pw . It separates two different regimes exhibiting pure-liquid crystal like (χ <χc ) and distorted-nematic ordering (χ >χc ), respectively. In the latter phase the degree of ordering is lower with respect to the pure-liquid crystal nematic phase.

Gold core@silver semishell Janus nanoparticles prepared by interfacial etching

NASA Astrophysics Data System (ADS)

Chen, Limei; Deming, Christopher P.; Peng, Yi; Hu, Peiguang; Stofan, Jake; Chen, Shaowei

2016-07-01

Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold cores, as manifested in transmission electron microscopy, UV-vis absorption, and X-ray photoelectron spectroscopy measurements. Interestingly, the Au@Ag semishell Janus nanoparticles exhibited enhanced electrocatalytic activity in oxygen reduction reactions, as compared to their Au@Ag and Ag@Au core-shell counterparts, likely due to a synergistic effect between the gold cores and silver semishells that optimized oxygen binding to the nanoparticle surface.Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold

Experimental verification of nanoparticle jet minimum quantity lubrication effectiveness in grinding

NASA Astrophysics Data System (ADS)

Jia, Dongzhou; Li, Changhe; Zhang, Dongkun; Zhang, Yanbin; Zhang, Xiaowei

2014-12-01

In our experiment, K-P36 precision numerical control surface grinder was used for dry grinding, minimum quantity lubrication (MQL) grinding, nanoparticle jet MQL grinding, and traditional flood grinding of hardened 45 steel. A three-dimensional dynamometer was used to measure grinding force in the experiment. In this research, experiments were conducted to measure and calculate specific tangential grinding force, frictional coefficient, and specific grinding energy, thus verifying the lubrication performance of nanoparticles in surface grinding. Findings present that compared with dry grinding, the specific tangential grinding force of MQL grinding, nanoparticle jet MQL grinding, and flood grinding decreased by 45.88, 62.34, and 69.33 %, respectively. Their frictional coefficient was reduced by 11.22, 29.21, and 32.18 %, and the specific grinding energy declined by 45.89, 62.34, and 69.45 %, respectively. Nanoparticle jet MQL presented ideal lubrication effectiveness, which was attributed to the friction oil film with strong antifriction and anti-wear features formed by nanoparticles on the grinding wheel/workpiece interface. Moreover, lubricating properties of nanoparticles of the same size (50 nm) but different types were verified through experimentation. In our experiment, ZrO2 nanoparticles, polycrystal diamond (PCD) nanoparticles, and MoS2 nanoparticles were used in the comparison of nanoparticle jet MQL grinding. The experimental results manifest that MoS2 nanoparticles exhibited the optimal lubricating effectiveness, followed by PCD nanoparticles. Our research also integrated the properties of different nanoparticles to analyze the lubrication mechanisms of different nanoparticles. The experiment further verified the impact of nanoparticle concentration on the effectiveness of nanoparticle jet MQL in grinding. The experimental results demonstrate that when the nanoparticle mass fraction was 6 %, the minimum specific tangential grinding force, frictional

Responsive Block Copolymer and Gold Nanoparticle Hybrid Nanotubes.

NASA Astrophysics Data System (ADS)

Chang, Sehoon; Singamaneni, Srikanth; Young, Seth; Tsukruk, Vladimir

2009-03-01

We demonstrate the facile fabrication of responsive polymer and metal nanoparticle composite nanotube structures. The nanotubes are comprised of responsive block copolymer, polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP), and gold nanoparticles. PS-b-P2VP nanotubes were fabricated using porous alumina template and in situ reduction of the gold nanoparticles in P2VP domains. Owing to the pH sensitive nature of P2VP (anionic polymer with a pKa of 3.8), the nanotubes exhibit a dramatic change in topology in response to the changes in the external pH. Furthermore, the gold nanoparticles in the responsive block exhibit a reversible aggregation, causing a reversible change in optical properties such as absorption.

Cell type-dependent uptake, localization, and cytotoxicity of 1.9 nm gold nanoparticles

PubMed Central

Coulter, Jonathan A; Jain, Suneil; Butterworth, Karl T; Taggart, Laura E; Dickson, Glenn R; McMahon, Stephen J; Hyland, Wendy B; Muir, Mark F; Trainor, Coleman; Hounsell, Alan R; O’Sullivan, Joe M; Schettino, Giuseppe; Currell, Fred J; Hirst, David G; Prise, Kevin M

2012-01-01

Background This follow-up study aims to determine the physical parameters which govern the differential radiosensitization capacity of two tumor cell lines and one immortalized normal cell line to 1.9 nm gold nanoparticles. In addition to comparing the uptake potential, localization, and cytotoxicity of 1.9 nm gold nanoparticles, the current study also draws on comparisons between nanoparticle size and total nanoparticle uptake based on previously published data. Methods We quantified gold nanoparticle uptake using atomic emission spectroscopy and imaged intracellular localization by transmission electron microscopy. Cell growth delay and clonogenic assays were used to determine cytotoxicity and radiosensitization potential, respectively. Mechanistic data were obtained by Western blot, flow cytometry, and assays for reactive oxygen species. Results Gold nanoparticle uptake was preferentially observed in tumor cells, resulting in an increased expression of cleaved caspase proteins and an accumulation of cells in sub G1 phase. Despite this, gold nanoparticle cytotoxicity remained low, with immortalized normal cells exhibiting an LD50 concentration approximately 14 times higher than tumor cells. The surviving fraction for gold nanoparticle-treated cells at 3 Gy compared with that of untreated control cells indicated a strong dependence on cell type in respect to radiosensitization potential. Conclusion Gold nanoparticles were most avidly endocytosed and localized within cytoplasmic vesicles during the first 6 hours of exposure. The lack of significant cytotoxicity in the absence of radiation, and the generation of gold nanoparticle-induced reactive oxygen species provide a potential mechanism for previously reported radiosensitization at megavoltage energies. PMID:22701316

Biofabricated Silver Nanoparticles Act as a Strong Fungicide against Bipolaris sorokiniana Causing Spot Blotch Disease in Wheat

PubMed Central

Singh, Akanksha; Keswani, Chetan; Naqvi, Alim H.; Singh, H. B.

2014-01-01

The present study is focused on the extracellular synthesis of silver nanoparticles (AgNPs) using culture supernatant of an agriculturally important bacterium, Serratia sp. BHU-S4 and demonstrates its effective application for the management of spot blotch disease in wheat. The biosynthesis of AgNPs by Serratia sp. BHU-S4 (denoted as bsAgNPs) was monitored by UV–visible spectrum that showed the surface plasmon resonance (SPR) peak at 410 nm, an important characteristic of AgNPs. Furthermore, the structural, morphological, elemental, functional and thermal characterization of bsAgNPs was carried out using the X-ray diffraction (XRD), electron and atomic microscopies, energy dispersive X-ray (EDAX) spectrometer, FTIR spectroscopy and thermogravimetric analyzer (TGA), respectively. The bsAgNPs were spherical in shape with size range of ∼10 to 20 nm. The XRD and EDAX analysis confirmed successful biosynthesis and crystalline nature of AgNPs. The bsAgNPs exhibited strong antifungal activity against Bipolaris sorokiniana, the spot blotch pathogen of wheat. Interestingly, 2, 4 and 10 µg/ml concentrations of bsAgNPs accounted for complete inhibition of conidial germination, whereas in the absence of bsAgNPs, conidial germination was 100%. A detached leaf bioassay revealed prominent conidial germination on wheat leaves infected with B. sorokiniana conidial suspension alone, while the germination of conidia was totally inhibited when the leaves were treated with bsAgNPs. The results were further authenticated under green house conditions, where application of bsAgNPs significantly reduced B. sorokiniana infection in wheat plants. Histochemical staining revealed a significant role of bsAgNPs treatment in inducing lignin deposition in vascular bundles. In summary, our findings represent the efficient application of bsAgNPs in plant disease management, indicating the exciting possibilities of nanofungicide employing agriculturally important bacteria. PMID:24840186

Synthesis and characterization of phytochemical fabricated zinc oxide nanoparticles with enhanced antibacterial and catalytic applications.

PubMed

Ali, Jawad; Irshad, Rabia; Li, Baoshan; Tahir, Kamran; Ahmad, Aftab; Shakeel, Muhammad; Khan, Naeem Ullah; Khan, Zia Ul Haq

2018-06-01

A "green route" to fabricate nanoparticles has emerged as a revolutionary approach. The reported work presents a green approach to synthesize ZnO nanoparticles using Conyza canadensis plant leaves extract. The synthesis of ZnO was conducted at two different temperatures i.e. 30 °C and 80 °C. ZnO nanoparticles prepared at 80 °C were smaller in size and exhibited spherical morphology. The prepared nanomaterials were examined for the reduction of organic dyes i.e. methylene blue and methyl orange. The fabricated ZnO nanoparticles synthesized at 80 °C were found to be highly active for the reduction of aforementioned dyes with 94.5% reduction of MO and 85.3% reduction of MB in 45 min and 20 min respectively. The rate constant (k) for this reduction of MO was found to be 5.781 × 10 -3  s -1 in the absence of a catalyst and 5.843 × 10 -2  s -1 in the presence of ZnO NPs catalyst. The rate constant (k) for the reduction of MB was found to be 4.7 × 10 -3  s -1 in the absence of a catalyst and 9.936 × 10 -3  s -1 in the presence of ZnO NPs catalyst. ZnO nanoparticles synthesized at 80 °C were examined for their antibacterial activity. The biogenic ZnO nanoparticles exhibited strong antibacterial activity against E. coli and S. aureus with a zone of inhibition (16 mm) and (14 mm) respectively. This high antibacterial and catalytic activity of biogenic ZnO nanoparticles can be attributed to its small size, good dispersion, and well-defined morphology. Copyright © 2018 Elsevier B.V. All rights reserved.

Cryochemistry of Metal Nanoparticles

NASA Astrophysics Data System (ADS)

Sergeev, Gleb B.

2003-12-01

The interaction of metal atoms, clusters and nanoparticles with different organic and inorganic substances were studied at low temperature (10-40K). Combination of matrix isolation technique and preparative cryochemistry was applied for the investigation of activity and selectivity of metal particles of different size. Encapsulation of metal nanoparticles in polymers was studied. The metal-polymer films thus obtained exhibited satisfactory sensitivity to ammonia.

Optimally designed gold nanorattles with strong built-in hotspots and weak polarization dependence

NASA Astrophysics Data System (ADS)

Zhang, Xuemin; Wang, Tieqiang; Li, Yunong; Fu, Yu; Guo, Lei

2017-12-01

Localized electromagnetic fields generated by interparticle plasmon coupling suffer greatly from nonreproducibility because they are extremely sensitive to the nanoparticle aggregation status and the incident polarization. Here, we synthesize gold nanorattles that exhibit inherent aggregation-insensitive hotspots due to the intraparticle core-shell plasmon coupling, and investigate the structural effect on the intraparticle coupling strength and its polarization dependence. Through optimizing the structural parameters, we successfully synthesize gold nanorattles with strong built-in hotspots and weak polarization dependence. These aggregation-insensitive and weakly polarization-dependent hotspots make the Raman enhancement from nanorattle aggregates show an unusual weak dependence on the particle aggregation status, which therefore affords the opportunity to fabricate uniform and reproducible surface enhanced Raman scattering substrates.

Tetanus toxoid-loaded cationic non-aggregated nanostructured lipid particles triggered strong humoral and cellular immune responses.

PubMed

Kaur, Amandeep; Jyoti, Kiran; Rai, Shweta; Sidhu, Rupinder; Pandey, Ravi Shankar; Jain, Upendra Kumar; Katyal, Anju; Madan, Jitender

2016-05-01

In the present investigation, non-aggregated cationic and unmodified nanoparticles (TT-C-NLPs4 and TT-NLPs1) were prepared of about 49.2 ± 6.8-nm and 40.8 ± 8.3-nm, respectively. In addition, spherical shape, crystalline architecture and cationic charge were also noticed. Furthermore, integrity and conformational stability of TT were maintained in both TT-C-NLPs4 and TT-NLPs1, as evidenced by symmetrical position of bands and superimposed spectra, respectively in SDS-PAGE and circular dichroism. Cellular uptake in RAW264.7 cells indicating the concentration-dependent internalisation of nanoparticles. Qualitatively, CLSM exhibited enhanced cellular uptake of non-aggregated TT-C-NLPs4 owing to interaction with negatively charged plasma membrane and clevaloe mediated/independent endocytosis. In last, in vivo immunisation with non-aggregated TT-C-NLPs4 elicited strong humoral (anti-TT IgG) and cellular (IFN-γ) immune responses at day 42, as compared to non-aggregated TT-NLPs1 and TT-Alum following booster immunisation at day 14 and 28. Thus, non-aggregated cationic lipid nanoparticles may be a potent immune-adjuvant for parenteral delivery of weak antigens.

A Herbivore Knows Its Patch: Luderick, Girella tricuspidata, Exhibit Strong Site Fidelity on Shallow Subtidal Reefs in a Temperate Marine Park

PubMed Central

Ferguson, Adrian M.; Harvey, Euan S.; Taylor, Matthew D.; Knott, Nathan A.

2013-01-01

Understanding movement patterns, habitat use and behaviour of fish is critical to determining how targeted species may respond to protection provided by “no-take” sanctuary zones within marine parks. We assessed the fine and broad scale movement patterns of an exploited herbivore, luderick (Girella tricuspidata), using acoustic telemetry to evaluate how this species may respond to protection within Jervis Bay (New South Wales, Australia). We surgically implanted fourteen fish with acoustic transmitters and actively and passively tracked individuals to determine fine and broad scale movement patterns respectively. Eight fish were actively tracked for 24 h d¯1 for 6 d (May 2011), and then intermittently over the following 30 d. Six fish were passively tracked from December 2011 to March 2012, using a fixed array of receivers deployed across rocky reefs around the perimeter of the bay. Luderick exhibited strong site fidelity on shallow subtidal reefs, tending to remain on or return consistently to the reef where they were caught and released. All eight fish actively tracked used core areas solely on their release reef, with the exception of one fish that used multiple core areas, and four of the six fish passively tracked spent between 75 to 96% of days on release reefs over the entire tracking period. Luderick did move frequently to adjacent reefs, and occasionally to more distant reefs, however consistently returned to their release reef. Luderick also exhibited predictable patterns in movement between spatially distinct daytime and night-time core use areas. Night-time core use areas were generally located in sheltered areas behind the edge of reefs. Overall, our data indicate luderick exhibit strong site fidelity on shallow subtidal reefs in Jervis Bay and suggests that this important herbivore may be likely to show a positive response to protection within the marine park. PMID:23741515

A herbivore knows its patch: luderick, Girella tricuspidata, exhibit strong site fidelity on shallow subtidal reefs in a temperate marine park.

PubMed

Ferguson, Adrian M; Harvey, Euan S; Taylor, Matthew D; Knott, Nathan A

2013-01-01

Understanding movement patterns, habitat use and behaviour of fish is critical to determining how targeted species may respond to protection provided by "no-take" sanctuary zones within marine parks. We assessed the fine and broad scale movement patterns of an exploited herbivore, luderick (Girella tricuspidata), using acoustic telemetry to evaluate how this species may respond to protection within Jervis Bay (New South Wales, Australia). We surgically implanted fourteen fish with acoustic transmitters and actively and passively tracked individuals to determine fine and broad scale movement patterns respectively. Eight fish were actively tracked for 24 h d¯(1) for 6 d (May 2011), and then intermittently over the following 30 d. Six fish were passively tracked from December 2011 to March 2012, using a fixed array of receivers deployed across rocky reefs around the perimeter of the bay. Luderick exhibited strong site fidelity on shallow subtidal reefs, tending to remain on or return consistently to the reef where they were caught and released. All eight fish actively tracked used core areas solely on their release reef, with the exception of one fish that used multiple core areas, and four of the six fish passively tracked spent between 75 to 96% of days on release reefs over the entire tracking period. Luderick did move frequently to adjacent reefs, and occasionally to more distant reefs, however consistently returned to their release reef. Luderick also exhibited predictable patterns in movement between spatially distinct daytime and night-time core use areas. Night-time core use areas were generally located in sheltered areas behind the edge of reefs. Overall, our data indicate luderick exhibit strong site fidelity on shallow subtidal reefs in Jervis Bay and suggests that this important herbivore may be likely to show a positive response to protection within the marine park.

Magnolol Nanoparticles Exhibit Improved Water Solubility and Suppress TNF-α-Induced VCAM-1 Expression in Endothelial Cells.

PubMed

Lee, Chiang-Wen; Hu, Stephen Chu-Sung; Yen, Feng-Lin; Hsu, Lee-Fen; Lee, I-Ta; Lin, Zih-Chan; Tsai, Ming-Horng; Huang, Chieh-Liang; Liang, Chan-Jung; Chiang, Yao-Chang

2017-03-01

The expression of the adhesion molecule vascular cell adhesion molecule-1 (VCAM-1) on endothelial cells enables the attachment of leukocytes to the endothelium, which may lead to inflammation and the development of atherosclerosis. Magnolol is a major bioactive compound derived from the plant species Magnolia officinalis. In this study, we synthesized a novel nanoparticle formulation of magnolol to improve its water solubility and physicochemical properties, evaluated its effects on TNF-α-induced VCAM-1 expression in endothelial cells, and determined the signal transduction pathways involved. Our findings demonstrated that the magnolol nanoparticle system showed great improvements in physicochemical properties and water solubility owing to a reduction in particle size, transformation from a crystalline to amorphous structure, and the formation of hydrogen bonds with the nanoparticle carriers. In terms of its biological actions, magnolol nanoparticles attenuated TNF-α-induced VCAM-1 protein expression, promoter activity, and mRNA expression in endothelial cells in vitro. This was found to be mediated by the ERK, AKT, and NF-κB signaling pathways. In addition, magnolol nanoparticles inhibited TNF-α-induced leukocyte adhesion to endothelial cells, and suppressed TNF-α-induced VCAM-1 expression in the aortic endothelium of mice. In summary, since magnolol nanoparticles inhibit endothelial VCAM-1 expression and leukocyte adhesion to endothelial cells, this novel drug formulation may be a potentially useful therapeutic formulation to prevent the development of atherosclerosis and inflammatory diseases.

Nanoparticles for biomedical imaging, therapy, and quantitative diagnostics

NASA Astrophysics Data System (ADS)

Yust, Brian G.

Nanoparticles and nanomaterials are known to exhibit extraordinary characteristics and have a wide range of application which utilizes their unique properties. In particular, nanoparticles have shown great promise towards advancing the state of biological and biomedical techniques such as in vivo and in vitro imaging modalities, biosensing, and disease detection and therapy. Nanocrystalline hosts: NaYF4, KYF4, KGdF4, NaMF3, and KMF3 (M=Mg, Ba, Mn, Fe, Co, Ni, Cr) doped with rare earth ions have been synthesized by thermolysis, solvothermal, and hydrothermal methods. The morphology and spectroscopic properties have been thoroughly characterized. These nanoparticles (NP) are particularly useful for biomedical purposes since both the exciting and emitting wavelengths are in the near-infrared, where most tissues do not strongly absorb or scatter light. In vivo and in vitro imaging was performed with a 980 nm excitation source. Finally, NPs were conjugated with zinc phthalocyanine, a photosensitizer with a large absorption coefficient in the red and NIR regions, to illustrate the efficacy of these NPs as a platform for dual-mode infrared-activated imaging and photodynamic platforms. In addition, nonlinear optical nanomaterials, such as BaTiO3 and Ag@BaTiO3, were also synthesized and characterized. The nonlinear optical properties were investigated, and it is demonstrated that these nanoparticles can produce phase conjugate waves when used in a counterpropagating four wave mixing setup. The third order susceptibility is quantified using the z-scan technique, and the toxicity of these nanoparticles is also explored.

Temperature and size-dependent Hamaker constants for metal nanoparticles

NASA Astrophysics Data System (ADS)

Jiang, K.; Pinchuk, P.

2016-08-01

Theoretical values of the Hamaker constant have been calculated for metal nanoparticles using Lifshitz theory. The theory describes the Hamaker constant in terms of the permittivity of the interacting bodies. Metal nanoparticles exhibit an internal size effect that alters the dielectric permittivity of the particle when its size falls below the mean free path of the conducting electrons. This size dependence of the permittivity leads to size-dependence of the Hamaker constant for metal nanoparticles. Additionally, the electron damping and the plasma frequency used to model the permittivity of the particle exhibit temperature-dependence, which lead to temperature dependence of the Hamaker constant. In this work, both the size and temperature dependence for gold, silver, copper, and aluminum nanoparticles is demonstrated. The results of this study might be of interest for studying the colloidal stability of nanoparticles in solution.

Temperature and size-dependent Hamaker constants for metal nanoparticles.

PubMed

Jiang, K; Pinchuk, P

2016-08-26

Theoretical values of the Hamaker constant have been calculated for metal nanoparticles using Lifshitz theory. The theory describes the Hamaker constant in terms of the permittivity of the interacting bodies. Metal nanoparticles exhibit an internal size effect that alters the dielectric permittivity of the particle when its size falls below the mean free path of the conducting electrons. This size dependence of the permittivity leads to size-dependence of the Hamaker constant for metal nanoparticles. Additionally, the electron damping and the plasma frequency used to model the permittivity of the particle exhibit temperature-dependence, which lead to temperature dependence of the Hamaker constant. In this work, both the size and temperature dependence for gold, silver, copper, and aluminum nanoparticles is demonstrated. The results of this study might be of interest for studying the colloidal stability of nanoparticles in solution.

Electron transport in gold colloidal nanoparticle-based strain gauges.

PubMed

Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen, Ke; Viau, Guillaume; Ressier, Laurence

2013-03-08

A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the 'regular island array model' that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy E(C). This reveals that the Au@CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au@BSPP, Au@TDSP, Au@MPA and Au@MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the E(C) values of these 14 nm NPs cannot be neglected in determining the β values.

Electron transport in gold colloidal nanoparticle-based strain gauges

NASA Astrophysics Data System (ADS)

Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M.; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen, Ke; Viau, Guillaume; Ressier, Laurence

2013-03-01

A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the ‘regular island array model’ that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy EC. This reveals that the Au@CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au@BSPP, Au@TDSP, Au@MPA and Au@MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the EC values of these 14 nm NPs cannot be neglected in determining the β values.

Increased transverse relaxivity in ultrasmall superparamagnetic iron oxide nanoparticles used as MRI contrast agent for biomedical imaging.

PubMed

Mishra, Sushanta Kumar; Kumar, B S Hemanth; Khushu, Subash; Tripathi, Rajendra P; Gangenahalli, Gurudutta

2016-09-01

Synthesis of a contrast agent for biomedical imaging is of great interest where magnetic nanoparticles are concerned, because of the strong influence of particle size on transverse relaxivity. In the present study, biocompatible magnetic iron oxide nanoparticles were synthesized by co-precipitation of Fe 2+ and Fe 3+ salts, followed by surface adsorption with reduced dextran. The synthesized nanoparticles were spherical in shape, and 12 ± 2 nm in size as measured using transmission electron microscopy; this was corroborated with results from X-ray diffraction and dynamic light scattering studies. The nanoparticles exhibited superparamagnetic behavior, superior T 2 relaxation rate and high relaxivities (r 1  = 18.4 ± 0.3, r 2  = 90.5 ± 0.8 s -1 mM -1 , at 7 T). MR image analysis of animals before and after magnetic nanoparticle administration revealed that the signal intensity of tumor imaging, specific organ imaging and whole body imaging can be clearly distinguished, due to the strong relaxation properties of these nanoparticles. Very low concentrations (3.0 mg Fe/kg body weight) of iron oxides are sufficient for early detection of tumors, and also have a clear distinction in pre- and post-enhancement of contrast in organs and body imaging. Many investigators have demonstrated high relaxivities of magnetic nanoparticles at superparamagnetic iron oxide level above 50 nm, but this investigation presents a satisfactory, ultrasmall, superparamagnetic and high transverse relaxivity negative contrast agent for diagnosis in pre-clinical studies. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

When Anatase Nanoparticles Become Bulklike: Properties of Realistic TiO2 Nanoparticles in the 1-6 nm Size Range from All Electron Relativistic Density Functional Theory Based Calculations.

PubMed

Lamiel-Garcia, Oriol; Ko, Kyoung Chul; Lee, Jin Yong; Bromley, Stefan T; Illas, Francesc

2017-04-11

All electron relativistic density functional theory (DFT) based calculations using numerical atom-centered orbitals have been carried out to explore the relative stability, atomic, and electronic structure of a series of stoichiometric TiO 2 anatase nanoparticles explicitly containing up to 1365 atoms as a function of size and morphology. The nanoparticles under scrutiny exhibit octahedral or truncated octahedral structures and span the 1-6 nm diameter size range. Initial structures were obtained using the Wulff construction, thus exhibiting the most stable (101) and (001) anatase surfaces. Final structures were obtained from geometry optimization with full relaxation of all structural parameters using both generalized gradient approximation (GGA) and hybrid density functionals. Results show that, for nanoparticles of a similar size, octahedral and truncated octahedral morphologies have comparable energetic stabilities. The electronic structure properties exhibit a clear trend converging to the bulk values as the size of the nanoparticles increases but with a marked influence of the density functional employed. Our results suggest that electronic structure properties, and hence reactivity, for the largest anatase nanoparticles considered in this study will be similar to those exhibited by even larger mesoscale particles or by bulk systems. Finally, we present compelling evidence that anatase nanoparticles become effectively bulklike when reaching a size of ∼20 nm diameter.

Graphene-bonded and -encapsulated si nanoparticles for lithium ion battery anodes.

PubMed

Wen, Yang; Zhu, Yujie; Langrock, Alex; Manivannan, Ayyakkannu; Ehrman, Sheryl H; Wang, Chunsheng

2013-08-26

Silicon (Si) has been considered a very promising anode material for lithium ion batteries due to its high theoretical capacity. However, high-capacity Si nanoparticles usually suffer from low electronic conductivity, large volume change, and severe aggregation problems during lithiation and delithiation. In this paper, a unique nanostructured anode with Si nanoparticles bonded and wrapped by graphene is synthesized by a one-step aerosol spraying of surface-modified Si nanoparticles and graphene oxide suspension. The functional groups on the surface of Si nanoparticles (50-100 nm) not only react with graphene oxide and bind Si nanoparticles to the graphene oxide shell, but also prevent Si nanoparticles from aggregation, thus contributing to a uniform Si suspension. A homogeneous graphene-encapsulated Si nanoparticle morphology forms during the aerosol spraying process. The open-ended graphene shell with defects allows fast electrochemical lithiation/delithiation, and the void space inside the graphene shell accompanied by its strong mechanical strength can effectively accommodate the volume expansion of Si upon lithiation. The graphene shell provides good electronic conductivity for Si nanoparticles and prevents them from aggregating during charge/discharge cycles. The functionalized Si encapsulated by graphene sample exhibits a capacity of 2250 mAh g⁻¹ (based on the total mass of graphene and Si) at 0.1C and 1000 mAh g⁻¹ at 10C, and retains 85% of its initial capacity even after 120 charge/discharge cycles. The exceptional performance of graphene-encapsulated Si anodes combined with the scalable and one-step aerosol synthesis technique makes this material very promising for lithium ion batteries. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced antitumor activity of surface-modified iron oxide nanoparticles and an α-tocopherol derivative in a rat model of mammary gland carcinosarcoma.

PubMed

Horák, Daniel; Pustovyy, Vitaliy Igorovych; Babinskyi, Andrii Valeriyovich; Palyvoda, Olga Mikhailovna; Chekhun, Vasyl Fedorovich; Todor, Igor Nikolaevich; Kuzmenko, Oleksandr Ivanovich

2017-01-01

Maghemite (γ-Fe 2 O 3 ) nanoparticles were obtained by coprecipitation of ferrous and ferric salts in an alkaline medium followed by oxidation; the nanoparticles were coated with poly( N,N -dimethylacrylamide) (PDMA) and characterized by transmission electron microscopy, attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering, thermogravimetric and elemental analyses, and magnetic measurements in terms of particle morphology, size, polydispersity, amount of coating, and magnetization, respectively. The effects of α-tocopherol (Toc) and its phenolic (Toc-6-OH) and acetate (Toc-6-Ac) derivatives on Fe 2+ release from γ-Fe 2 O 3 @PDMA, as well as from γ-Fe 2 O 3 and CuFe 2 O 4 nanoparticles (controls), were examined in vitro using 1,10-phenanthroline. The presence of tocopherols enhanced spontaneous Fe 2+ release from nanoparticles, with Toc-6-OH exhibiting more activity than neat Toc. All of the nanoparticles tested were found to initiate blood lipid oxidation in a concentration-dependent manner, as determined by analysis of 2-thiobarbituric acid reactive species. Wistar rats with Walker-256 carcinosarcoma (a model of mammary gland carcinosarcoma) received Toc-6-Ac, magnetic nanoparticles, or their combination per os, and the antitumor activity of each treatment was determined in vivo. γ-Fe 2 O 3 @PDMA nanoparticles exhibited increased antitumor activity compared to both commercial CuFe 2 O 4 particles and the antitumor drug doxorubicin. Moreover, increased antitumor activity was observed after combined administration of γ-Fe 2 O 3 @PDMA nanoparticles and Toc-6-Ac; however, levels of bilirubin, aspartate aminotransferase, and white bloods normalized and did not differ from those of the intact controls. The antitumor activity of the γ-Fe 2 O 3 nanoparticles strongly correlated with Fe 2+ release from the nanoparticles but not with nanoparticle-initiated lipid peroxidation in vitro.

Enhanced antitumor activity of surface-modified iron oxide nanoparticles and an α-tocopherol derivative in a rat model of mammary gland carcinosarcoma

PubMed Central

Horák, Daniel; Pustovyy, Vitaliy Igorovych; Babinskyi, Andrii Valeriyovich; Palyvoda, Olga Mikhailovna; Chekhun, Vasyl Fedorovich; Todor, Igor Nikolaevich; Kuzmenko, Oleksandr Ivanovich

2017-01-01

Maghemite (γ-Fe2O3) nanoparticles were obtained by coprecipitation of ferrous and ferric salts in an alkaline medium followed by oxidation; the nanoparticles were coated with poly(N,N-dimethylacrylamide) (PDMA) and characterized by transmission electron microscopy, attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering, thermogravimetric and elemental analyses, and magnetic measurements in terms of particle morphology, size, polydispersity, amount of coating, and magnetization, respectively. The effects of α-tocopherol (Toc) and its phenolic (Toc-6-OH) and acetate (Toc-6-Ac) derivatives on Fe2+ release from γ-Fe2O3@PDMA, as well as from γ-Fe2O3 and CuFe2O4 nanoparticles (controls), were examined in vitro using 1,10-phenanthroline. The presence of tocopherols enhanced spontaneous Fe2+ release from nanoparticles, with Toc-6-OH exhibiting more activity than neat Toc. All of the nanoparticles tested were found to initiate blood lipid oxidation in a concentration-dependent manner, as determined by analysis of 2-thiobarbituric acid reactive species. Wistar rats with Walker-256 carcinosarcoma (a model of mammary gland carcinosarcoma) received Toc-6-Ac, magnetic nanoparticles, or their combination per os, and the antitumor activity of each treatment was determined in vivo. γ-Fe2O3@PDMA nanoparticles exhibited increased antitumor activity compared to both commercial CuFe2O4 particles and the antitumor drug doxorubicin. Moreover, increased antitumor activity was observed after combined administration of γ-Fe2O3@PDMA nanoparticles and Toc-6-Ac; however, levels of bilirubin, aspartate aminotransferase, and white bloods normalized and did not differ from those of the intact controls. The antitumor activity of the γ-Fe2O3 nanoparticles strongly correlated with Fe2+ release from the nanoparticles but not with nanoparticle-initiated lipid peroxidation in vitro. PMID:28652731

Gold core@silver semishell Janus nanoparticles prepared by interfacial etching.

PubMed

Chen, Limei; Deming, Christopher P; Peng, Yi; Hu, Peiguang; Stofan, Jake; Chen, Shaowei

2016-08-14

Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold cores, as manifested in transmission electron microscopy, UV-vis absorption, and X-ray photoelectron spectroscopy measurements. Interestingly, the Au@Ag semishell Janus nanoparticles exhibited enhanced electrocatalytic activity in oxygen reduction reactions, as compared to their Au@Ag and Ag@Au core-shell counterparts, likely due to a synergistic effect between the gold cores and silver semishells that optimized oxygen binding to the nanoparticle surface.

Effects of laser fluence and liquid media on preparation of small Ag nanoparticles by laser ablation in liquid

NASA Astrophysics Data System (ADS)

Moura, Caroline Gomes; Pereira, Rafael Santiago Floriani; Andritschky, Martin; Lopes, Augusto Luís Barros; Grilo, João Paulo de Freitas; Nascimento, Rubens Maribondo do; Silva, Filipe Samuel

2017-12-01

This study aims to assess a method for preparation of small and highly stable Ag nanoparticles by nanosecond laser ablation in liquid. Effect of liquid medium and laser fluence on the size, morphology and structure of produced nanoparticles has been studied experimentally. Pulses of a Nd:YAG laser of 1064 nm wavelength at 35 ns pulse width at different fluences were employed to irradiate the silver target in different environments (water, ethanol and acetone). The UV-Visible absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the UV region. STEM and TEM micrographs were used to evaluate the size and shape of nanoparticles. The stability of silver colloids in terms of oxidation at different liquid media was analyzed by SAED patterns. The results showed that characteristics of Ag nanoparticles and their production rate were strongly influenced by varying laser fluence and liquid medium. Particles from 2 to 80 nm of diameter were produced using different conditions and no oxidation was found in ethanol and acetone media. This work puts in evidence a promising approach to produce small nanoparticles by using high laser fluence energy.

Global gene response in Saccharomyces cerevisiae exposed to silver nanoparticles.

PubMed

Niazi, Javed H; Sang, Byoung-In; Kim, Yeon Seok; Gu, Man Bock

2011-08-01

Silver nanoparticles (AgNPs), exhibiting a broad size range and morphologies with highly reactive facets, which are widely applicable in real-life but not fully verified for biosafety and ecotoxicity, were subjected to report transcriptome profile in yeast Saccharomyces cerevisiae. A large number of genes accounted for ∼3% and ∼5% of the genome affected by AgNPs and Ag-ions, respectively. Principal component and cluster analysis suggest that the different physical forms of Ag were the major cause in differential expression profile. Among 90 genes affected by both AgNPs and Ag-ions, metalloprotein mediating high resistance to copper (CUP1-1 and CUP1-2) were strongly induced by AgNPs (∼45-folds) and Ag-ions (∼22-folds), respectively. A total of 17 genes, responsive to chemical stimuli, stress, and transport processes, were differentially induced by AgNPs. The differential expression was also seen with Ag-ions that affected 73 up- and 161 down-regulating genes, and most of these were involved in ion transport and homeostasis. This study provides new information on the knowledge for impact of nanoparticles on living microorganisms that can be extended to other nanoparticles.

Synthesis and structural characterization of CZTS nanoparticles

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

Lydia, R.; Reddy, P. Sreedhara

2013-06-03

The CZTS nanoparticles were successfully synthesized by Chemical co-precipitation method with different pH values in the range of 6 to 8. The synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. XRD studies revealed that the CZTS nanoparticles exhibited Kesterite Structure with preferential orientation along the (112) direction. Sample at pH value of 7 reached the nearly stoichiometric ratio.

Development of active biofilms of quinoa (Chenopodium quinoa W.) starch containing gold nanoparticles and evaluation of antimicrobial activity.

PubMed

Pagno, Carlos H; Costa, Tania M H; de Menezes, Eliana W; Benvenutti, Edilson V; Hertz, Plinho F; Matte, Carla R; Tosati, Juliano V; Monteiro, Alcilene R; Rios, Alessandro O; Flôres, Simone H

2015-04-15

Active biofilms of quinoa (Chenopodium quinoa, W.) starch were prepared by incorporating gold nanoparticles stabilised by an ionic silsesquioxane that contains the 1,4-diazoniabicyclo[2.2.2]octane chloride group. The biofilms were characterised and their antimicrobial activity was evaluated against Escherichiacoli and Staphylococcusaureus. The presence of gold nanoparticles produces an improvement in the mechanical, optical and morphological properties, maintaining the thermal and barrier properties unchanged when compared to the standard biofilm. The active biofilms exhibited strong antibacterial activity against food-borne pathogens with inhibition percentages of 99% against E. coli and 98% against S. aureus. These quinoa starch biofilms containing gold nanoparticles are very promising to be used as active food packaging for the maintenance of food safety and extension of the shelf life of packaged foods. Copyright © 2014 Elsevier Ltd. All rights reserved.

Memory and Mourning: An Exhibit History

ERIC Educational Resources Information Center

Eberle, Scott G.

2005-01-01

Mounted by the Strong Museum in Rochester, New York, in 1993, and traveling nationally thereafter, the exhibit Memory and Mourning provided historical and contemporary perspectives to help museum guests explore their own reactions to loss and grief. In the process the exhibit's development team encountered a range of philosophical, historical,…

Controlled green synthesis of silver nanoparticles by Allium cepa and Musa acuminata with strong antimicrobial activity

NASA Astrophysics Data System (ADS)

Sahni, Geetika; Panwar, Amit; Kaur, Balpreet

2015-02-01

A controlled "green synthesis" approach to synthesize silver nanoparticles by Allium cepa and Musa acuminata plant extract has been reported. The effect of different process parameters, such as pH, temperature and time, on synthesis of Ag nanoparticles from plant extracts has been highlighted. The work reports an easy approach to control the kinetics of interaction of metal ions with reducing agents, stabilized by ammonia to achieve sub-10 nm particles with narrow size distribution. The nanoparticles have been characterized by UV-Visible spectra and TEM analysis. Excellent antimicrobial activity at extremely low concentration of the nanoparticles was observed against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Fusarium oxysporum which may allow their exploitation as a new generation nanoproduct in biomedical and agricultural applications.

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst.

PubMed

Wu, Chien-Chen; Chen, Dong-Hwang

2012-06-19

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe3O4 nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe3O4 nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles.

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst

PubMed Central

2012-01-01

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe3O4 nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe3O4 nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles. PMID:22713480

Drug Synergy of Tenofovir and Nanoparticle-Based Antiretrovirals for HIV Prophylaxis

PubMed Central

Chaowanachan, Thanyanan; Krogstad, Emily; Ball, Cameron; Woodrow, Kim A.

2013-01-01

Background The use of drug combinations has revolutionized the treatment of HIV but there is no equivalent combination product that exists for prevention, particularly for topical HIV prevention. Strategies to combine chemically incompatible agents may facilitate the discovery of unique drug-drug activities, particularly unexplored combination drug synergy. We fabricated two types of nanoparticles, each loaded with a single antiretroviral (ARV) that acts on a specific step of the viral replication cycle. Here we show unique combination drug activities mediated by our polymeric delivery systems when combined with free tenofovir (TFV). Methodology/Principal Findings Biodegradable poly(lactide-co-glycolide) nanoparticles loaded with efavirenz (NP-EFV) or saquinavir (NP-SQV) were individually prepared by emulsion or nanoprecipitation techniques. Nanoparticles had reproducible size (d ∼200 nm) and zeta potential (-25 mV). The drug loading of the nanoparticles was approximately 7% (w/w). NP-EFV and NP-SQV were nontoxic to TZM-bl cells and ectocervical explants. Both NP-EFV and NP-SQV exhibited potent protection against HIV-1 BaL infection in vitro. The HIV inhibitory effect of nanoparticle formulated ARVs showed up to a 50-fold reduction in the 50% inhibitory concentration (IC50) compared to free drug. To quantify the activity arising from delivery of drug combinations, we calculated combination indices (CI) according to the median-effect principle. NP-EFV combined with free TFV demonstrated strong synergistic effects (CI50 = 0.07) at a 1∶50 ratio of IC50 values and additive effects (CI50 = 1.05) at a 1∶1 ratio of IC50 values. TFV combined with NP-SQV at a 1∶1 ratio of IC50 values also showed strong synergy (CI50 = 0.07). Conclusions ARVs with different physicochemical properties can be encapsulated individually into nanoparticles to potently inhibit HIV. Our findings demonstrate for the first time that combining TFV with either NP-EFV or NP

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.

Symmetry Breaking by Surface Blocking: Synthesis of Bimorphic Silver Nanoparticles, Nanoscale Fishes and Apples.

PubMed

Cathcart, Nicole; Kitaev, Vladimir

2016-09-08

A powerful approach to augment the diversity of well-defined metal nanoparticle (MNP) morphologies, essential for MNP advanced applications, is symmetry breaking combined with seeded growth. Utilizing this approach enabled the formation of bimorphic silver nanoparticles (bi-AgNPs) consisting of two shapes linked by one regrowth point. Bi-AgNPs were formed by using an adsorbing polymer, poly(acrylic acid), PAA, to block the surface of a decahedral AgNP seed and restricting growth of new silver to a single nucleation point. First, we have realized 2-D growth of platelets attached to decahedra producing nanoscale shapes reminiscent of apples, fishes, mushrooms and kites. 1-D bimorphic growth of rods (with chloride) and 3-D bimorphic growth of cubes and bipyramids (with bromide) were achieved by using halides to induce preferential (100) stabilization over (111) of platelets. Furthermore, the universality of the formation of bimorphic nanoparticles was demonstrated by using different seeds. Bi-AgNPs exhibit strong SERS enhancement due to regular cavities at the necks. Overall, the reported approach to symmetry breaking and bimorphic nanoparticle growth offers a powerful methodology for nanoscale shape design.

Symmetry Breaking by Surface Blocking: Synthesis of Bimorphic Silver Nanoparticles, Nanoscale Fishes and Apples

NASA Astrophysics Data System (ADS)

Cathcart, Nicole; Kitaev, Vladimir

2016-09-01

A powerful approach to augment the diversity of well-defined metal nanoparticle (MNP) morphologies, essential for MNP advanced applications, is symmetry breaking combined with seeded growth. Utilizing this approach enabled the formation of bimorphic silver nanoparticles (bi-AgNPs) consisting of two shapes linked by one regrowth point. Bi-AgNPs were formed by using an adsorbing polymer, poly(acrylic acid), PAA, to block the surface of a decahedral AgNP seed and restricting growth of new silver to a single nucleation point. First, we have realized 2-D growth of platelets attached to decahedra producing nanoscale shapes reminiscent of apples, fishes, mushrooms and kites. 1-D bimorphic growth of rods (with chloride) and 3-D bimorphic growth of cubes and bipyramids (with bromide) were achieved by using halides to induce preferential (100) stabilization over (111) of platelets. Furthermore, the universality of the formation of bimorphic nanoparticles was demonstrated by using different seeds. Bi-AgNPs exhibit strong SERS enhancement due to regular cavities at the necks. Overall, the reported approach to symmetry breaking and bimorphic nanoparticle growth offers a powerful methodology for nanoscale shape design.

Vitis vinifera peel and seed gold nanoparticles exhibit chemopreventive potential, antioxidant activity and induce apoptosis through mutant p53, Bcl-2 and pan cytokeratin down-regulation in experimental animals.

PubMed

Nirmala, J Grace; Narendhirakannan, R T

2017-05-01

Several studies suggest surface modifications of gold nanoparticles (AuNPs) by capping agents or surface coatings could play an important role in biological systems, and site directed delivery. The present study was carried out to assess the antioxidant and apoptotic activities of the Vitis vinifera peel and seed gold nanoparticles in experimentally induced cancer in Swiss albino mice. 12-dimethylbenz [a] anthracene (DMBA) (single application) and 12-O-tetradecanoylphorbol 13-acetate (TPA) (thrice a week) were applied on the dorsal area of the skin to induce skin papillomagenesis in Swiss albino mice for 16 weeks. Gold nanoparticles were synthesized using Vitis vinifera peel and seed aqueous extracts and characterized by Transmission electron microscopic (TEM) analyses. On topical application, peel and seed gold nanoparticles demonstrated chemopreventive potential by significantly (p<0.05) reducing the cumulative number of tumors while increasing the antioxidant enzyme activities in the gold nanoparticles treated mice. The down-regulated expression of mutant p53, Bcl-2 and the levels of pan-cytokeratins might have facilitated the process of apoptosis in the chemical carcinogenesis process. The results were supported by the histopathological evaluation which exhibited mild dysplasia and acanthosis in the skin tissues of Vitis vinifera peel and seed AuNPs treated mice. Based on the present study, the chemopreventive action of Vitis vinifera peel and seed AuNPs is probably due to its ability to stimulate the antioxidant enzymes within the cells and suppressed abnormal skin cell proliferation that occurred during DMBA-induced skin papillomagenesis. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

High Ultraviolet Absorption in Colloidal Gallium Nanoparticles Prepared from Thermal Evaporation

PubMed Central

Bravo, Iria; Catalan-Gomez, Sergio; Vázquez, Luis; Lorenzo, Encarnación; Pau, Jose Luis

2017-01-01

New methods for the production of colloidal Ga nanoparticles (GaNPs) are introduced based on the evaporation of gallium on expendable aluminum zinc oxide (AZO) layer. The nanoparticles can be prepared in aqueous or organic solvents such as tetrahydrofuran in order to be used in different sensing applications. The particles had a quasi mono-modal distribution with diameters ranging from 10 nm to 80 nm, and their aggregation status depended on the solvent nature. Compared to common chemical synthesis, our method assures higher yield with the possibility of tailoring particles size by adjusting the deposition time. The GaNPs have been studied by spectrophotometry to obtain the absorption spectra. The colloidal solutions exhibit strong plasmonic absorption in the ultra violet (UV) region around 280 nm, whose width and intensity mainly depend on the nanoparticles dimensions and their aggregation state. With regard to the colloidal GaNPs flocculate behavior, the water solvent case has been investigated for different pH values, showing UV-visible absorption because of the formation of NPs clusters. Using discrete dipole approximation (DDA) method simulations, a close connection between the UV absorption and NPs with a diameter smaller than ~40 nm was observed. PMID:28684687

Shape-dependent dispersion and alignment of nonaggregating plasmonic gold nanoparticles in lyotropic and thermotropic liquid crystals.

PubMed

Liu, Qingkun; Tang, Jianwei; Zhang, Yuan; Martinez, Angel; Wang, Shaowei; He, Sailing; White, Timothy J; Smalyukh, Ivan I

2014-05-01

We use both lyotropic liquid crystals composed of prolate micelles and thermotropic liquid crystals made of rod-like molecules to uniformly disperse and unidirectionally align relatively large gold nanorods and other complex-shaped nanoparticles at high concentrations. We show that some of these ensuing self-assembled orientationally ordered soft matter systems exhibit polarization-dependent plasmonic properties with strongly pronounced molar extinction exceeding that previously achieved in self-assembled composites. The long-range unidirectional alignment of gold nanorods is mediated mainly by anisotropic surface anchoring interactions at the surfaces of gold nanoparticles. Polarization-sensitive absorption, scattering, and extinction are used to characterize orientations of nanorods and other nanoparticles. The experimentally measured unique optical properties of these composites, which stem from the collective plasmonic effect of the gold nanorods with long-range order in a liquid crystal matrix, are reproduced in computer simulations. A simple phenomenological model based on anisotropic surface interaction explains the alignment of gold nanorods dispersed in liquid crystals and the physical underpinnings behind our observations.

Ordering nanoparticles with polymer brushes

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

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

Ordering nanoparticles with polymer brushes

NASA Astrophysics Data System (ADS)

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

2017-12-01

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a single layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. An interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.

Ordering nanoparticles with polymer brushes

DOE PAGES

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

2017-12-08

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

Strong damping of the localized surface plasmon resonance of Ag nanoparticles by Ag2O.

PubMed

Wu, Qingmen; Si, Mengting; Zhang, Bing; Zhang, Kang; Li, Huanhuan; Mi, Longfei; Jiang, Yang; Rong, Yan; Chen, Junling; Fang, Yingcui

2018-07-20

By studying oxidation of AgNPs (Ag nanoparticles) and decomposition of the produced silver oxide, we demonstrate that the localized surface plasmon resonance (LSPR) of AgNPs was damped by Ag 2 O produced during oxygen plasma irradiation (OPI). The AgNPs were fabricated by evaporation of high pure silver under high vacuum. The oxidation was conducted in oxygen plasma generated by radio frequency glow discharging in vacuum, and the decomposition was performed by annealing the silver oxide in nitrogen ambient at temperatures ranging from room temperature to 450 °C. Samples were characterized by color, absorption spectra, surface enhanced Raman scattering, x-ray photoelectron spectroscopy, and field emission scanning electron microscopy. The bandgap of the silver oxide was calculated. We propose that AgNPs are only partially oxidized into silver oxide during OPI, and the LSPR of the AgNPs left without being oxidation is strongly damped by the produced silver oxide. This LSPR damping is responsible for the transparency of the sample after OPI for 2 s.

Strong damping of the localized surface plasmon resonance of Ag nanoparticles by Ag2O

NASA Astrophysics Data System (ADS)

Wu, Qingmen; Si, Mengting; Zhang, Bing; Zhang, Kang; Li, Huanhuan; Mi, Longfei; Jiang, Yang; Rong, Yan; Chen, Junling; Fang, Yingcui

2018-07-01

By studying oxidation of AgNPs (Ag nanoparticles) and decomposition of the produced silver oxide, we demonstrate that the localized surface plasmon resonance (LSPR) of AgNPs was damped by Ag2O produced during oxygen plasma irradiation (OPI). The AgNPs were fabricated by evaporation of high pure silver under high vacuum. The oxidation was conducted in oxygen plasma generated by radio frequency glow discharging in vacuum, and the decomposition was performed by annealing the silver oxide in nitrogen ambient at temperatures ranging from room temperature to 450 °C. Samples were characterized by color, absorption spectra, surface enhanced Raman scattering, x-ray photoelectron spectroscopy, and field emission scanning electron microscopy. The bandgap of the silver oxide was calculated. We propose that AgNPs are only partially oxidized into silver oxide during OPI, and the LSPR of the AgNPs left without being oxidation is strongly damped by the produced silver oxide. This LSPR damping is responsible for the transparency of the sample after OPI for 2 s.

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.

Morphology and Structural Properties of Novel Short Linear Glucan/Protein Hybrid Nanoparticles and Their Influence on the Rheological Properties of Starch Gel.

PubMed

Li, Xiaojing; Ji, Na; Li, Man; Zhang, Shuangling; Xiong, Liu; Sun, Qingjie

2017-09-13

Starch nanoparticles were potential texture modifiers. However, they have strong tendency to aggregate and poor water dispersibility, which limited their application. The interaction between glucan (prepared from starch by enzymatic modification) and protein could significantly improve the dispersity of starch nanoparticles and, thus, enhance the rheological properties of food gels. In this work, glucan/protein hybrid nanoparticles were successfully developed for the first time using short linear glucan (SLG) and edible proteins [soy protein isolate (SPI), rice protein (RP), and whey protein isolate (WPI)]. The results showed that the SLG/SPI hybrid nanoparticles exhibited hollow structures, of which the smallest size was approximately 10-20 nm when the SLG/SPI ratio was 10:5. In contrast, SLG/RP nanoparticles displayed flower-like superstructures, and SLG/WPI nanoparticles presented stacked lamellar nanostructures with a width of 5-10 nm and a length of 50-70 nm. In comparison to bare SLG nanoparticles, SLG/SPI and SLG/WPI hybrid nanoparticles had higher melting temperatures. The addition of all nanoparticles greatly increased the storage modulus of corn starch gels and decreased loss tangent values. Importantly, the G' value of starch gels increased by 567% with the addition of flower-like SLG/RP superstructures.

Melanin nanoparticles derived from a homology of medicine and food for sentinel lymph node mapping and photothermal in vivo cancer therapy.

PubMed

Chu, Maoquan; Hai, Wangxi; Zhang, Zheyu; Wo, Fangjie; Wu, Qiang; Zhang, Zefei; Shao, Yuxiang; Zhang, Ding; Jin, Lu; Shi, Donglu

2016-06-01

The use of non-toxic or low toxicity materials exhibiting dual functionality for use in sentinel lymph node (SLN) mapping and cancer therapy has attracted considerable attention during the past two decades. Herein, we report that the natural black sesame melanin (BSM) extracted from black sesame seeds (Sesamum indicum L.) shows exciting potential for SLN mapping and cancer photothermal therapy. Aqueous solutions of BSM under neutral and alkaline conditions can assemble into sheet-like nanoparticles ranging from 20 to 200 nm in size. The BSM nanoparticles were encapsulated by liposomes to improve their water solubility and the encapsulated and bare BSM nanoparticles were both non-toxic to cells. Furthermore, the liposome-encapsulated BSM nanoparticles (liposome-BSM) did not exhibit any long-term toxicity in mice. The liposome-BSM nanoparticles were subsequently used to passively target healthy and tumor-bearing mice SLNs, which were identified by the black color of the nanoparticles. BSM also strongly absorbed light in the near-infrared (NIR) range, which was rapidly converted to heat energy. Human esophagus carcinoma cells (Eca-109) were killed efficiently by liposome-BSM nanocomposites upon NIR laser irradiation. Furthermore, mouse tumor tissues grown from Eca-109 cells were seriously damaged by the photothermal effects of the liposome-BSM nanocomposites, with significant tumor growth suppression compared with controls. Given that BSM is a safe and nutritious biomaterial that can be easily obtained from black sesame seed, the results presented herein represent an important development in the use of natural biomaterials for clinical SLN mapping and cancer therapy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Facile solid-state synthesis of oxidation-resistant metal nanoparticles at ambient conditions

NASA Astrophysics Data System (ADS)

Lee, Kyu Hyung; Jung, Hyuk Joon; Lee, Ju Hee; Kim, Kyungtae; Lee, Byeongno; Nam, Dohyun; Kim, Chung Man; Jung, Myung-Hwa; Hur, Nam Hwi

2018-05-01

A simple and scalable method for the synthesis of metal nanoparticles in the solid-state was developed, which can produce nanoparticles in the absence of solvents. Nanoparticles of coinage metals were synthesized by grinding solid hydrazine and the metal precursors in their acetates and oxides at 25 °C. The silver and gold acetates converted completely within 6 min into Ag and Au nanoparticles, respectively, while complete conversion of the copper acetate to the Cu sub-micrometer particles took about 2 h. Metal oxide precursors were also converted into metal nanoparticles by grinding alone. The resulting particles exhibit distinctive crystalline lattice fringes, indicating the formation of highly crystalline phases. The Cu sub-micrometer particles are better resistant to oxidation and exhibit higher conductivity compared to conventional Cu nanoparticles. This solid-state method was also applied for the synthesis of platinum group metals and intermetallic Cu3Au, which can be further extended to synthesize other metal nanoparticles.

Determination of 2-methoxyestradiol in serum samples and pharmaceutical preparations by silver nanoparticles-enhanced chemiluminescence.

PubMed

Zhang, Min; Xiao, Xiangqin; Zeng, Wenyuan; Zeng, Xiaoying; Yao, Hanchun

2014-03-01

Silver nanoparticles (AgNPs) exhibited better chemiluminescence (CL) catalysis activity and smaller nanoparticles have stronger catalysis ability in luminol-K3Fe(CN)6 system among the synthesized AgNPs of different size. 10±2 nm nanoparticles was used as catalysts to enhance the reaction sensitivity. It was found that the CL intensity of AgNPs-luminol-K3Fe(CN)6 was strongly inhibited in the presence of 2-methoxyestradiol (2-ME) and the relative CL intensity was in linear correlation with the concentration of 2-ME. Thus, the silver nanoparticles-enhanced CL method for the determination of 2-ME was developed. The proposed method has a detection limit (3 Sb/K) of 5.0×10(-10) mol L(-1) with a relative standard deviation of 0.75% for 5.0×10(-8) mol L(-1) 2-ME. The method was successfully applied for determination of 2-ME in human serum and pharmaceutical preparations. The possible CL reaction mechanism was also discussed briefly. Oxygen radicals played an important role in the catalytic process. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis and characterization of bactericidal silver nanoparticles using cultural filtrate of simulated microgravity grown Klebsiella pneumoniae.

PubMed

Kalpana, Duraisamy; Lee, Yang Soo

2013-03-05

Silver nanoparticles were synthesized by biological method using cultural filtrate of Klebsiella pneumoniae cultured under simulated microgravity and silver nitrate solution as precursor. The nanoparticles exhibited typical plasmon absorption maximum of silver nanoparticles between 405 and 407 nm. Spherical silver nanoparticles were found to have size between 15 and 37 nm by TEM analysis. XRD pattern corresponding to planes (111), (200), (220) (311) revealed the crystalline nature of the biosynthesized silver nanoparticles. FTIR spectrum proposed stabilization of silver nanoparticles by the protein molecules present in the cultural filtrate. The silver nanoparticles exhibited high bactericidal activity against Salmonella enterica, Escherichia coli and moderate bactericidal activity against Streptococcus pyogenes. Copyright © 2012 Elsevier Inc. All rights reserved.

Green Synthesized Silver Nanoparticles Exhibit Reduced Toxicity to Mammalian Cells and Retain Antimicrobial Activity

EPA Science Inventory

The interest in silver nanoparticles (AgNPs) and silver nanomaterial stems from their antimicrobial properties. AgNPs are being added to clothing, paint, refrigerators, washing machines and a variety of other commercially available items. Recent in vitro and in vivo studies, howe...

Directing self-assembly of gold nanoparticles in diblock copolymer scaffold

NASA Astrophysics Data System (ADS)

Li, Qifang; He, Jinbo; Glogowski, Elizabeth; Emrick, Todd; Russell, Thomas

2007-03-01

A versatile hierarchical approach for directing self -assembly of gold nanostructures with size 2-3nm in diblock copolymer scaffolds is found. Diblock copolymer polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) is used to form a regular scaffold of highly anisotropic, stripe-like domains, and controlled differential wetting by dichloromethane and thermal annealing guides gold nanoparticles with half hydrophilic ligand to aggregate selectively along the scaffold, producing highly organized metal nanostructures. In as-cast block-copolymer and gold nanoparticles thin films, micelle structure and gold nanoparticles random distribution on scaffold are typically observed. However, samples annealed in dichloromethane exhibit well-defined short-range ordered nanostructure with gold nanoparticles located at the interface of PS and P2VP nanoscale domain. After annealing at 170 C, the gold nanoparticles at interface migrated into the middle of P2VP phase and exhibited long-range ordered hierarchical structures. Synergistic interactions between the gold nanoparticles and the PS-b-P2VP caused an orientation of the microdomains normal to the film surface.

Rationally engineered polymeric cisplatin nanoparticle for improved antitumor efficacy

PubMed Central

Paraskar, Abhimanyu; Soni, Shivani; Basu, Sudipta; Chitra, J; Amarasiriwardena; Lupoli, Nicola; Srivats, Shyam; Roy, Rituparna Sinha; Sengupta, Shiladitya

2011-01-01

The use of cisplatin, a first line chemotherapy for most cancers, is dose-limited due to nephrotoxicity. While, this toxicity can be addressed through nanotechnology, previous attempts at engineering cisplatin nanoparticles have been limited by the impact on the potency of cisplatin. Here we report the rational engineering of a novel cisplatin nanoparticle by harnessing a novel polyethylene glycol-functionalized poly-isobutylene-maleic acid (PEG-PIMA) co-polymer, which can complex with cis-platinum (II) through a monocarboxylato and a coordinate bond. We show that this complex self-assembles into a nanoparticle, and exhibit an IC50 = 0.77 ± 0.11μM comparable to that of free cisplatin (IC50 = 0.44 ± 0.09 μM). The nanoparticles are internalized into the endolysosomal compartment of cancer cells, and releases cisplatin in a pH-dependent manner. Furthermore, the nanoparticles exhibited significantly improved antitumor efficacy in a 4T1 breast cancer model in vivo with limited nephrotoxicity, which can be explained by preferential biodistribution in the tumor with reduced kidney concentrations. Our results suggest that the PEG-PIMA-cisplatin nanoparticle can emerge as an attractive solution to the challenges in cisplatin chemotherapy. PMID:21576779

Tunable Semiconducting Polymer Nanoparticles with INDT-Based Conjugated Polymers for Photoacoustic Molecular Imaging.

PubMed

Stahl, Thomas; Bofinger, Robin; Lam, Ivan; Fallon, Kealan J; Johnson, Peter; Ogunlade, Olumide; Vassileva, Vessela; Pedley, R Barbara; Beard, Paul C; Hailes, Helen C; Bronstein, Hugo; Tabor, Alethea B

2017-06-21

Photoacoustic imaging combines both excellent spatial resolution with high contrast and specificity, without the need for patients to be exposed to ionizing radiation. This makes it ideal for the study of physiological changes occurring during tumorigenesis and cardiovascular disease. In order to fully exploit the potential of this technique, new exogenous contrast agents with strong absorbance in the near-infrared range, good stability and biocompatibility, are required. In this paper, we report the formulation and characterization of a novel series of endogenous contrast agents for photoacoustic imaging in vivo. These contrast agents are based on a recently reported series of indigoid π-conjugated organic semiconductors, coformulated with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, to give semiconducting polymer nanoparticles of about 150 nm diameter. These nanoparticles exhibited excellent absorption in the near-infrared region, with good photoacoustic signal generation efficiencies, high photostability, and extinction coefficients of up to three times higher than those previously reported. The absorption maximum is conveniently located in the spectral region of low absorption of chromophores within human tissue. Using the most promising semiconducting polymer nanoparticle, we have demonstrated wavelength-dependent differential contrast between vasculature and the nanoparticles, which can be used to unambiguously discriminate the presence of the contrast agent in vivo.

Biogenic silver and gold nanoparticles synthesized using red ginseng root extract, and their applications.

PubMed

Singh, Priyanka; Kim, Yeon Ju; Wang, Chao; Mathiyalagan, Ramya; El-Agamy Farh, Mohamed; Yang, Deok Chun

2016-05-01

In the present study, we report a green methodology for the synthesis of silver and gold nanoparticles, using the root extract of the herbal medicinal plant Korean red ginseng. The silver and gold nanoparticles were synthesized within 1 h and 10 min respectively. The nanoparticles generated were not aggregated, and remained stable for a long time, which suggests the nature of nanoparticles. The phytochemicals and ginsenosides present in the root extract assist in reducing and stabilizing the synthesized nanoparticles. The red ginseng root extract-generated silver nanoparticles exhibit antimicrobial activity against pathogenic microorganisms including Vibrio parahaemolyticus, Staphylococcus aureus, Bacillus cereus, and Candida albicans. In addition, the silver nanoparticles exhibit biofilm degrading activity against S. aureus and Pseudomonas aeruginosa. Thus, the present study opens up a new possibility of synthesizing silver and gold nanoparticles in a green and rapid manner using Korean red ginseng root extract, and explores their biomedical applications.

Modeling of interactions between nanoparticles and cell membranes

NASA Astrophysics Data System (ADS)

Ban, Young-Min

Rapid development of nanotechnology and ability to manufacture materials and devices with nanometer feature size leads to exciting innovations in many areas including the medical and electronic fields. However, the possible health and environmental impacts of manufactured nanomaterials are not fully known. Recent experimental reports suggest that some of the manufactured nanomaterials, such as fullerenes and carbon nanotubes, are highly toxic even in small concentrations. The goal of the current work is to understand the mechanisms responsible for the toxicity of nanomaterials. In the current study coarse-grained molecular dynamics simulations are employed to investigate the interactions between NPs and cellular membranes at a molecular level. One of the possible toxicity mechanisms of the nanomaterials is membrane disruption. Possibility of membrane disruption exposed to the manufactured nanomaterials are examined by considering chemical reactions and non-reactive physical interactions as chemical as well as physical mechanisms. Mechanisms of transport of carbon-based nanoparticles (fullerene and its derivative) across a phospholipid bilayer are investigated. The free energy profile is obtained using constrained simulations. It is shown that the considered nanoparticles are hydrophobic and therefore they tend to reside in the interior of the lipid bilayer. In addition, the dynamics of the membrane fluctuations is significantly affected by the nanoparticles at the bilayer-water interface. The hydrophobic interaction between the particles and membrane core induces the strong coupling between the nanoparticle motion and membrane deformation. It is observed that the considered nanoparticles affect several physical properties of the membrane. The nanoparticles embedded into the membrane interior lead to the membrane softening, which becomes more significant with increase in CNT length and concentration. The lateral pressure profile and membrane energy in the membrane

Cost-effective alternative to nano-encapsulation: Amorphous curcumin-chitosan nanoparticle complex exhibiting high payload and supersaturation generation.

PubMed

Nguyen, Minh Hiep; Yu, Hong; Kiew, Tie Yi; Hadinoto, Kunn

2015-10-01

While the wide-ranging therapeutic activities of curcumin have been well established, its successful delivery to realize its true therapeutic potentials faces a major challenge due to its low oral bioavailability. Even though nano-encapsulation has been widely demonstrated to be effective in enhancing the bioavailability of curcumin, it is not without drawbacks (i.e. low payload and costly preparation). Herein we present a cost-effective bioavailability enhancement strategy of curcumin in the form of amorphous curcumin-chitosan nanoparticle complex (or curcumin nanoplex in short) exhibiting a high payload (>80%). The curcumin nanoplex was prepared by a simple yet highly efficient drug-polysaccharide complexation method that required only mixing of the curcumin and chitosan solutions under ambient condition. The effects of (1) pH and (2) charge ratio of chitosan to curcumin on the (i) physical characteristics of the nanoplex (i.e. size, colloidal stability and payload), (ii) complexation efficiency, and (iii) production yield were investigated from which the optimal preparation condition was determined. The nanoplex formation was found to favor low acidic pH and charge ratio below unity. At the optimal condition (i.e. pH 4.4. and charge ratio=0.8), stable curcumin nanoplex (≈260nm) was prepared at >90% complexation efficiency and ≈50% production yield. The amorphous state stability, colloidal stability, and in vitro non-cytotoxicity of the nanoplex were successfully established. The curcumin nanoplex produced prolonged supersaturation (3h) in the presence of hydroxypropyl methylcellulose (HPMC) at five times of the saturation solubility of curcumin. In addition, curcumin released from the nanoplex exhibited improved chemical stability owed to the presence of chitosan. Both results (i.e. high supersaturation and improved chemical stability) bode well for the ability of the curcumin nanoplex to enhance the bioavailability of curcumin clinically. Copyright © 2015

Calcium oxide-modified mesoporous silica loaded onto ferriferrous oxide core: Magnetically responsive mesoporous solid strong base.

PubMed

Li, Tian-Tian; Liu, Yu; Qi, Shi-Chao; Liu, Xiao-Qin; Huang, Li; Sun, Lin-Bing

2018-05-03

The design of new type of solid strong base with ideal activity, stability, and reusability is strongly urged by the growing demand of green chemistry and sustainable development. In this study, a new type of mesoporous solid strong base, denoted as CaO/mSiO 2 /Fe 3 O 4 , is successfully fabricated by successively coating SiO 2 onto Fe 3 O 4 magnetic nanoparticles and loading CaO into the mesoporous SiO 2 . Compared with a series of other typical solid bases, the CaO/mSiO 2 /Fe 3 O 4 exhibits higher activity towards the synthesis of dimethyl carbonate by the transesterification of ethylene carbonate and methanol. The activity of the CaO/mSiO 2 /Fe 3 O 4 is not observed to decrease obviously even after sextic catalyst recirculation, and in particular, the recovery of the catalyst without quality loss is very convenient due to the good magnetic responsiveness of the Fe 3 O 4 cores. Copyright © 2018. Published by Elsevier Inc.

Nanoparticle Superlattices: The Roles of Soft Ligands

PubMed Central

Si, Kae Jye; Chen, Yi; Shi, Qianqian

2017-01-01

Abstract Nanoparticle superlattices are periodic arrays of nanoscale inorganic building blocks including metal nanoparticles, quantum dots and magnetic nanoparticles. Such assemblies can exhibit exciting new collective properties different from those of individual nanoparticle or corresponding bulk materials. However, fabrication of nanoparticle superlattices is nontrivial because nanoparticles are notoriously difficult to manipulate due to complex nanoscale forces among them. An effective way to manipulate these nanoscale forces is to use soft ligands, which can prevent nanoparticles from disordered aggregation, fine‐tune the interparticle potential as well as program lattice structures and interparticle distances – the two key parameters governing superlattice properties. This article aims to review the up‐to‐date advances of superlattices from the viewpoint of soft ligands. We first describe the theories and design principles of soft‐ligand‐based approach and then thoroughly cover experimental techniques developed from soft ligands such as molecules, polymer and DNA. Finally, we discuss the remaining challenges and future perspectives in nanoparticle superlattices. PMID:29375958

Structural, optical and dielectric investigation of CdFe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Sagadevan, Suresh; Pal, Kaushik; Zaman Chowdhury, Zaira; Enamul Hoque, Md

2017-07-01

A simple thermal decomposition technique has been executed for the synthesis of cadmium ferrite (CdFe2O4) nanoparticles. With the help of x-ray diffraction; scanning electron microscopy, energy-dispersive x-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy the prepared nanoparticles were identified. The crystal size of the average particles aggregated and was found approximately to be 10-14 nm by means of XRD studies. However, the results of high-resolution transmission electron microscopy (HR-TEM) investigation ensured distinguished nanoparticles, and also the polycrystalline nature of those nanoparticles was confirmed by selected area diffraction (SAED) patterns. The scanning electron microscopy (SEM) images explored a random distribution of grains within the sample. Thin film surface topology of roughness and surface current measurement were studied by atomic force microscopy (TP-AFM, C-AFM). Hence, from the ultraviolet-visible (UV) spectroscopic absorption illustrated significant optical properties. Moreover, the optical energy band gap (E g) of CdFe2O4 nanoparticle was determined to be 1.74 eV. By studying the variation of dielectric constant and dielectric loss with respect to frequency, the CdFe2O4 nanoparticles electrical properties were analyzed. Analysis in the real and imaginary part of impedance explained their frequency and temperature dependence of the CdFe2O4 nanoparticles. The traditional solution-phase organometallic approach provides an effective way to synthesize high quality hydrophobic semiconductor-CdFe2O4 nanoparticles. Our simple, cost-effective approach is quite general, which is applicable to other nanomaterials, and it utilizes the currently mature in Nano-chemistry. The nanocomposite assemblies’ exhibit strong anisotropic optical and electrical properties are open up new possibilities in remarkable applications for optoelectronics in the near future.

pH-activated Nanoparticles for Controlled Topical Delivery of Farnesol to Disrupt Oral Biofilm Virulence

PubMed Central

Horev, Benjamin; Klein, Marlise I.; Hwang, Geelsu; Li, Yong; Kim, Dongyeop; Koo, Hyun; Benoit, Danielle S.W.

2015-01-01

Development of effective therapies to control oral biofilms is challenging, as topically introduced agents must avoid rapid clearance from biofilm-tooth interfaces while targeting biofilm microenvironments. Additionally, exopolysaccharide matrix and acidification of biofilm microenvironments are associated with cariogenic (caries-producing) biofilm virulence. Thus, nanoparticle carriers capable of binding to hydroxyapatite (HA), saliva-coated HA (sHA), and exopolysaccharides with enhanced drug-release at acidic pH were developed. Nanoparticles are formed from diblock copolymers composed of 2-(dimethylamino)ethyl methacrylate (DMAEMA), butyl methacrylate (BMA), and 2-propylacrylic acid (PAA) (p(DMAEMA)-b-p(DMAEMA-co-BMA-co-PAA)) that self-assemble into ~21 nm cationic nanoparticles. Nanoparticles exhibit outstanding adsorption affinities (~244 L-mmol−1) to negatively-charged HA, sHA, and exopolysaccharide-coated sHA due to strong electrostatic interactions via multivalent tertiary amines of p(DMAEMA). Owing to hydrophobic cores, Nanoparticles load farnesol, a hydrophobic antibacterial drug, at ~22 wt%. Farnesol release is pH-dependent with t1/2=7 and 15 h for release at pH 4.5 and 7.2, as Nanoparticles undergo core destabilization at acidic pH, characteristic of cariogenic biofilm microenvironments. Importantly, topical applications of farnesol-loaded nanoparticles disrupted Streptococcus mutans biofilms 4-fold more effectively than free farnesol. Mechanical stability of biofilms treated with drug-loaded nanoparticles was compromised, resulting in >2-fold enhancement in biofilm removal under shear stress compared to free farnesol and controls. Farnesol-loaded nanoparticles effectively attenuated biofilm virulence in vivo using a clinically-relevant topical treatment regimen (2×/day) in a rodent dental caries disease model. Treatment with farnesol-loaded nanoparticles reduced both the number and severity of carious lesions, while free-farnesol had no effect

Step-reduced synthesis of starch-silver nanoparticles.

PubMed

Raghavendra, Gownolla Malegowd; Jung, Jeyoung; Kim, Dowan; Seo, Jongchul

2016-05-01

In the present process, silver nanoparticles were directly synthesized in a single step by microwave irradiation of a mixture of starch, silver nitrate, and deionized water. This is different from the commonly adopted procedure for starch-silver nanoparticle synthesis in which silver nanoparticles are synthesized by preparing a starch solution as a reaction medium first. Thus, the additional step associated with the preparation of the starch solution was eliminated. In addition, no additional reducing agent was utilized. The adopted method was facile and straight forward, affording spherical silver nanoparticles with diameter below 10nm that exhibited good antibacterial activity. Further, influence of starch on the size of the silver nanoparticles was noticed. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of a PSMA-targeted BNF nanoparticle construct

NASA Astrophysics Data System (ADS)

Behnam Azad, Babak; Banerjee, Sangeeta R.; Pullambhatla, Mrudula; Lacerda, Silvia; Foss, Catherine A.; Wang, Yuchuan; Ivkov, Robert; Pomper, Martin G.

2015-02-01

Early detection enables improved prognosis for prostate cancer (PCa). A promising target for imaging and therapy of PCa is the prostate-specific membrane antigen (PSMA), which exhibits both expression within the epithelium of PCa cells, and becomes internalized upon ligand binding. Here we report the synthesis of a PSMA-targeted bionized nanoferrite (BNF) nanoparticle and its biological evaluation in an experimental model of PCa. The BNF nanoparticle formulation exhibits properties conducive to targeted imaging such as stealth, prolonged circulation time and enhanced clearance from non-target sites. Optical imaging of the targeted BNF in vivo indicates preferential accumulation in PSMA+ tumors 4 h post-injection, suggesting target specificity. On the other hand, non-targeted nanoparticles exhibit lower uptake with similar accumulation in both PSMA+ and PSMA- tumors indicating tumor access without preferential accumulation. Imaging with single photon emission computed tomography (SPECT) and biodistribution studies of a modified construct indicate highest tumor accumulation at 48 h post-injection [4.3 +/- 0.4 percentage injected dose per gram of tissue (%ID g-1)], with tumor/blood and tumor/muscle ratios of 7.5 +/- 2.4 and 11.6 +/- 1.2 %ID g-1, respectively. Ex vivo fluorescence microscopy, Prussian blue staining, immunohistochemistry and biodistribution studies confirm enhanced nanoparticle uptake in PSMA+ tumors compared to those not expressing PSMA. The BNF nano-formulation described is promising for PSMA-targeted imaging applications in vivo.Early detection enables improved prognosis for prostate cancer (PCa). A promising target for imaging and therapy of PCa is the prostate-specific membrane antigen (PSMA), which exhibits both expression within the epithelium of PCa cells, and becomes internalized upon ligand binding. Here we report the synthesis of a PSMA-targeted bionized nanoferrite (BNF) nanoparticle and its biological evaluation in an experimental model of

Ordered quasi-two-dimensional structure of nanoparticles in semiflexible ring polymer brushes under compression

NASA Astrophysics Data System (ADS)

Hua, Yunfeng; Deng, Zhenyu; Jiang, Yangwei; Zhang, Linxi

2017-06-01

Molecular dynamics simulations of a coarse-grained bead-spring model of ring polymer brushes under compression are presented. Flexible polymer brushes are always disordered during compression, whereas semiflexible polymer brushes tend to be ordered under sufficiently strong compression. Further, the polymer monomer density of the semiflexible polymer brush is very high near the brush surface, inducing a peak value of the free energy near the surface. Therefore, when nanoparticles are compressed in semiflexible ring polymer brushes, they tend to exhibit a closely packed single-layer structure between the brush surface and the impenetrable wall, and a quasi-two-dimensional ordered structure near the brush surface is formed under strong compression. These findings provide a new approach to designing responsive applications.

Polymer Crosslinked 3-D Assemblies of Nanoparticles: Mechanically Strong Lightweight Porous Materials

NASA Technical Reports Server (NTRS)

Leventis, Nicholas

2005-01-01

In analogy to supramolecular assemblies, which are pursued because of properties above and beyond those of the individual molecules, self-standing monolithic three-dimensional assemblies of nanoparticles also have unique properties attributed to their structure. For example, ultra low-density 3-D assemblies of silica nanoparticles, known as silica aerogels, are characterized by large internal void space, high surface area and very low thermal conductivity. Aerogels, however, are also extremely fragile materials, limiting their application to a few specialized environments, e.g., in nuclear reactors as Cerenkov radiation detectors, in space (refer to NASA's Stardust Program) and aboard certain planetary vehicles (thermal insulators on Mars Rovers in 1997 and 2004). The fragility problem is traced to well-defined weak points in the aerogel skeletal framework, the interparticle necks. Using the surface functionality of the nanoparticle building blocks as a focal point, we have directed attachment of a conformal polymer coating over the entire framework, rendering all necks wider. Thus, although the bulk density may increase only by 3x, the mesoporosity (pores in the range 2-50 nm) remains unchanged, while the strength of the material increases by up to 300... Having addressed the fragility problem, aerogels are now robust materials, and a variety of applications, ranging from thermal/acoustic insulators to catalyst supports, to platform for sensors, and dielectrics are all within reach. Our approach employs molecular science to manipulate nanoscopic matter for achieving useful macroscopic properties, and in our view it resides at the core of what defines nanotechnology. In that spirit, this technology is expandable in three directions. Thus, we have already crosslinked successfully amine-modified silica, and we anticipate that more rich chemistry will be realized by been creative with the nanoparticle surface modifiers. On the other hand, although we do not expect

Green synthesis of silver nanoparticles: characterization and determination of antibacterial potency

NASA Astrophysics Data System (ADS)

Annamalai, Jayshree; Nallamuthu, Thangaraju

2016-02-01

Silver ions (Ag+) and its compounds are highly toxic to microorganisms, exhibiting strong biocidal effects on many species of bacteria but have a low toxicity toward animal cells. In the present study, silver nanoparticles (SNPs) were biosynthesized using aqueous extract of Chlorella vulgaris as reducing agent and size of SNPs synthesized ranged between 15 and 47 nm. SNPs were characterized by UV-visible spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier infrared spectroscopy, and analyzed for its antibacterial property against human pathogens. This approach of SNPs synthesis involving green chemistry process can be considered for the large-scale production of SNPs and in the development of biomedicines.

Synthesis, characterization and assembly of metal pnictide nanoparticles, and evaluation of their physicochemical (catalytic, magnetic, and semiconducting) properties

NASA Astrophysics Data System (ADS)

Senevirathne, Keerthisinghe

Synthesis of transition metal phosphide (Ni2P) and arsenide (MnAs) discrete nanoparticles was conducted by following a solution-phase arrested precipitation route and the size- and structure-dependent physicochemical properties of these materials were explored. Furthermore, the assembly of metal phosphide nanoparticles into a network structure via a sol-gel process and the evaluation of their structure related properties also was conducted. The surface ligation chemistry of unsupported Ni2P nanoparticles prepared by arrested precipitation was found to strongly impact the structural integrity and the hydrodesulfurization (HDS) catalytic activity of Ni 2P nanoparticles. The HDS activity of unsupported surface modified Ni2P nanoparticles is higher than that of unsupported Ni2P prepared by temperature programmed reduction (TPR) but considerably lower than silica-supported Ni2P prepared by TPR. However, by supporting the pre-formed Ni 2P nanoparticles on silica, activity comparable to that of silica-supported Ni2P prepared by TPR can be achieved. The synthetic control offered by the Ni2P nanoparticle preparation, not achieved by TPR methods, is expected to enable a systematic study of particle size and shape effects on HDS activity. By using arrested precipitation reactions, for the first time, discrete and dispersible MnAs nanoparticles have been prepared and their magnetic properties evaluated. Syntheses were developed to target both the thermodynamically stable alpha-type (hexagonal) and the metastable beta-type (orthorhombic) MnAs nanoparticles. Surprisingly, both types of ˜25 nm particles exhibit nearly identical ferromagnetic behavior with blocking temperatures, T B, in the region ˜275-310 K, TC's of 315 K and room temperature coercivities of HC ˜ 190-320 Oe. No evidence of the expected structural transition from alpha to beta-MnAs at TC is observed. Oxidative sol-gel assembly of nanoparticles to make nanoparticulate gels was successfully employed to Ni2P

Rapid extra-/intracellular biosynthesis of gold nanoparticles by the fungus Penicillium sp.

NASA Astrophysics Data System (ADS)

Du, Liangwei; Xian, Liang; Feng, Jia-Xun

2011-03-01

In this work, the fungus Penicillium was used for rapid extra-/intracellular biosynthesis of gold nanoparticles. AuCl4 - ions reacted with the cell filtrate of Penicillium sp. resulting in extracellular biosynthesis of gold nanoparticles within 1 min. Intracellular biosynthesis of gold nanoparticles was obtained by incubating AuCl4 - solution with fungal biomass for 8 h. The gold nanoparticles were characterized by means of visual observation, UV-Vis absorption spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The extracellular nanoparticles exhibited maximum absorbance at 545 nm in UV-Vis spectroscopy. The XRD spectrum showed Bragg reflections corresponding to the gold nanocrystals. TEM exhibited the formed spherical gold nanoparticles in the size range from 30 to 50 nm with an average size of 45 nm. SEM and TEM revealed that the intracellular gold nanoparticles were well dispersed on the cell wall and within the cell, and they are mostly spherical in shape with an average diameter of 50 nm. The presence of gold was confirmed by EDX analysis.

Nonenzymatic glucose sensor based on renewable electrospun Ni nanoparticle-loaded carbon nanofiber paste electrode.

PubMed

Liu, Yang; Teng, Hong; Hou, Haoqing; You, Tianyan

2009-07-15

A novel nonenzymatic glucose sensor was developed based on the renewable Ni nanoparticle-loaded carbon nanofiber paste (NiCFP) electrode. The NiCF nanocomposite was prepared by combination of electrospinning technique with thermal treatment method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that large amounts of spherical nanoparticles were well dispersed on the surface or embedded in the carbon nanofibers. And the nanoparticles were composed of Ni and NiO, as revealed by energy dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD). In application to nonenzymatic glucose determination, the renewable NiCFP electrodes, which were constructed by simply mixing the electrospun nanocomposite with mineral oil, exhibited strong and fast amperometric response without being poisoned by chloride ions. Low detection limit of 1 microM with wide linear range from 2 microM to 2.5 mM (R=0.9997) could be obtained. The current response of the proposed glucose sensor was highly sensitive and stable, attributing to the electrocatalytic performance of the firmly embedded Ni nanoparticles as well as the chemical inertness of the carbon-based electrode. The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of effective glucose sensor.

Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

NASA Astrophysics Data System (ADS)

de Julián Fernández, C.; Mattei, G.; Paz, E.; Novak, R. L.; Cavigli, L.; Bogani, L.; Palomares, F. J.; Mazzoldi, P.; Caneschi, A.

2010-04-01

Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO2 matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles.

PubMed

de Julián Fernández, C; Mattei, G; Paz, E; Novak, R L; Cavigli, L; Bogani, L; Palomares, F J; Mazzoldi, P; Caneschi, A

2010-04-23

Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO(2) matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe 2O 3 nanoparticles

DOE PAGES

Khurshid, Hafsa; Lampen-Kelley, Paula; Iglesias, Òscar; ...

2015-10-27

Disorder among surface spins largely dominates the magnetic response of ultrafine magnetic particle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8±0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and becomes frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point tomore » highly frustrated surface spins that rearrange much more slowly than interior spins with bulk coordination. Monte Carlo simulations of a hollow particle reproducing the experimental morphology corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Lastly, our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures.« less

Functionalized rare earth-doped nanoparticles for breast cancer nanodiagnostic using fluorescence and CT imaging.

PubMed

Jain, Akhil; Fournier, Pierrick G J; Mendoza-Lavaniegos, Vladimir; Sengar, Prakhar; Guerra-Olvera, Fernando M; Iñiguez, Enrique; Kretzschmar, Thomas G; Hirata, Gustavo A; Juárez, Patricia

2018-03-22

Breast cancer is the second leading cause of cancer death among women and represents 14% of death in women around the world. The standard diagnosis method for breast tumor is mammography, which is often related with false-negative results leading to therapeutic delays and contributing indirectly to the development of metastasis. Therefore, the development of new tools that can detect breast cancer is an urgent need to reduce mortality in women. Here, we have developed Gd 2 O 3 :Eu 3+ nanoparticles functionalized with folic acid (FA), for breast cancer detection. Gd 2 O 3 :Eu 3+ nanoparticles were synthesized by sucrose assisted combustion synthesis and functionalized with FA using EDC-NHS coupling. The FA-conjugated Gd 2 O 3 :Eu 3+ nanoparticles exhibit strong red emission at 613 nm with a quantum yield of ~ 35%. In vitro cytotoxicity studies demonstrated that the nanoparticles had a negligible cytotoxic effect on normal 293T and T-47D breast cancer cells. Cellular uptake analysis showed significantly higher internalization of FA-conjugated RE nanoparticles into T-47D cells (Folr hi ) compared to MDA-MB-231 breast cancer cells (Folr lo ). In vivo confocal and CT imaging studies indicated that FA-conjugated Gd 2 O 3 :Eu 3+ nanoparticles accumulated more efficiently in T-47D tumor xenograft compared to the MDA-MB-231 tumor. Moreover, we found that FA-conjugated Gd 2 O 3 :Eu 3+ nanoparticles were well tolerated at high doses (300 mg/kg) in CD1 mice after an intravenous injection. Thus, FA-conjugated Gd 2 O 3 :Eu 3+ nanoparticles have great potential to detect breast cancer. Our findings provide significant evidence that could permit the future clinical application of FA-conjugated Gd 2 O 3 :Eu 3+ nanoparticles alone or in combination with the current detection methods to increase its sensitivity and precision.

The type of adjuvant strongly influences the T-cell response during nanoparticle-based immunization

PubMed Central

Knuschke, Torben; Epple, Matthias; Westendorf, Astrid M

2014-01-01

Potent vaccines require the ability to effectively induce immune responses. Especially for the control of infectious diseases with intracellular pathogens, like viruses or bacteria, potent T-cell responses are indispensable. Several delivery systems such as nanoparticles have been considered to boost the immunogenicity of pathogen derived peptides or subunits for the induction of potent T-cell responses. Since they can be further functionalized with immunostimulants, like Toll-like receptor (TLR) agonists, they improve the response by enhanced activation of the innate immune system. Currently, TLR agonists like unmethylated CpG oligonucleotides and the synthetic dsRNA derivate polyriboinosinic acid-polyribocytidylic acid (poly[I:C]) are widely used as vaccine adjuvants. CpG and poly(I:C) trigger different TLRs and therefore show differential signal transduction. Recently, we established biodegradable calcium phosphate (CaP) nanoparticles as potent T cell inducing vaccination vehicles. In this commentary we discuss the role of CpG and poly(I:C) for the effective induction of virus-specific T cells during immunization with CaP nanoparticles. The presented results underline the importance of the right formulation of vaccines for specific immunization purpose. PMID:23982325

Development and evaluation of co-formulated docetaxel and curcumin biodegradable nanoparticles for parenteral administration.

PubMed

Pawar, Harish; Wankhade, Shrikant Rameshrao; Yadav, Dharmendra K; Suresh, Sarasija

2016-09-01

Technology for development of biodegradable nanoparticles encapsulating combinations for enhanced efficacy. To develop docetaxel (DTX) and curcumin (CRM) co-encapsulated biodegradable nanoparticles for parenteral administration with potential for prolonged release and decreased toxicity. Modified emulsion solvent-evaporation technique was employed in the preparation of the nanoparticles optimized by the face centered-central composite design (FC-CCD). The uptake potential was studied in MCF-7 cells, while the toxicity was evaluated by in vitro hemolysis test. In vivo pharmacokinetic was evaluated in male Wistar rats. Co-encapsulated nanoparticles were developed of 219 nm size, 0.154 PDI, -13.74 mV zeta potential and 67.02% entrapment efficiency. Efficient uptake was observed by the nanoparticles in MCF-7 cells with decreased toxicity in comparison with the commercial DTX intravenous injection, Taxotere®. The nanoparticles exhibited biphasic release with initial burst release followed by sustained release for 5 days. The nanoparticles displayed a 4.3-fold increase in AUC (391.10 ± 32.94 versus 89.77 ± 10.58 μg/ml min) in comparison to Taxotere® with a 6.2-fold increase in MRT (24.78 ± 2.36 versus 3.58 ± 0.21 h). The nanoparticles exhibited increased uptake, prolonged in vitro and in vivo release, with decreased toxicity thus exhibiting potential for enhanced efficacy.

Silver nanoparticles toxicity against airborne strains of Staphylococcus spp.

PubMed

Wolny-Koładka, Katarzyna A; Malina, Dagmara K

2017-11-10

The aim of this study was to explore the toxicity of silver nanoparticles (AgNPs) synthesized by chemical reduction method assessment with regard to airborne strains of Staphylococcus spp. The first step of the experiment was the preparation of silver nanoparticle suspension. The suspension was obtained by a fast and simple chemical method involving the reduction of silver ions through a reducing factor in the presence of the suitable stabilizer required to prevent the aggregation. In the second stage, varied instrumental techniques were used for the analysis and characterization of the obtained nanostructures. Third, the bacteria of the Staphylococcus genus were isolated from the air under stable conditions with 47 sports and recreational horses, relatively. Next, isolated strains were identified using biochemical and spectrophotometric methods. The final step was the evaluation of the Staphylococcus genus sensitivity to nanosilver using the disk diffusion test. It has been proven that prepared silver nanoparticles exhibit strong antibacterial properties. The minimum inhibitory concentration for tested isolates was 30 μg/mL. It has been found that the sensitivity of Staphylococcus spp. isolated from six identified species differs considerably. The size distribution of bacterial growth inhibition zones indicates that resistance to various nanosilver concentrations is an individual strain feature, and has no connection with belonging to a specific species.

Photoinduced electron transfer from semiconductor quantum dots to metal oxide nanoparticles.

PubMed

Tvrdy, Kevin; Frantsuzov, Pavel A; Kamat, Prashant V

2011-01-04

Quantum dot-metal oxide junctions are an integral part of next-generation solar cells, light emitting diodes, and nanostructured electronic arrays. Here we present a comprehensive examination of electron transfer at these junctions, using a series of CdSe quantum dot donors (sizes 2.8, 3.3, 4.0, and 4.2 nm in diameter) and metal oxide nanoparticle acceptors (SnO(2), TiO(2), and ZnO). Apparent electron transfer rate constants showed strong dependence on change in system free energy, exhibiting a sharp rise at small driving forces followed by a modest rise further away from the characteristic reorganization energy. The observed trend mimics the predicted behavior of electron transfer from a single quantum state to a continuum of electron accepting states, such as those present in the conduction band of a metal oxide nanoparticle. In contrast with dye-sensitized metal oxide electron transfer studies, our systems did not exhibit unthermalized hot-electron injection due to relatively large ratios of electron cooling rate to electron transfer rate. To investigate the implications of these findings in photovoltaic cells, quantum dot-metal oxide working electrodes were constructed in an identical fashion to the films used for the electron transfer portion of the study. Interestingly, the films which exhibited the fastest electron transfer rates (SnO(2)) were not the same as those which showed the highest photocurrent (TiO(2)). These findings suggest that, in addition to electron transfer at the quantum dot-metal oxide interface, other electron transfer reactions play key roles in the determination of overall device efficiency.

pH-controlled gas-generating mineralized nanoparticles: a theranostic agent for ultrasound imaging and therapy of cancers.

PubMed

Min, Kyung Hyun; Min, Hyun Su; Lee, Hong Jae; Park, Dong Jin; Yhee, Ji Young; Kim, Kwangmeyung; Kwon, Ick Chan; Jeong, Seo Young; Silvestre, Oscar F; Chen, Xiaoyuan; Hwang, Yu-Shik; Kim, Eun-Cheol; Lee, Sang Cheon

2015-01-27

We report a theranostic nanoparticle that can express ultrasound (US) imaging and simultaneous therapeutic functions for cancer treatment. We developed doxorubicin-loaded calcium carbonate (CaCO3) hybrid nanoparticles (DOX-CaCO3-MNPs) through a block copolymer templated in situ mineralization approach. The nanoparticles exhibited strong echogenic signals at tumoral acid pH by producing carbon dioxide (CO2) bubbles and showed excellent echo persistence. In vivo results demonstrated that the DOX-CaCO3-MNPs generated CO2 bubbles at tumor tissues sufficient for echogenic reflectivity under a US field. In contrast, the DOX-CaCO3-MNPs located in the liver or tumor-free subcutaneous area did not generate the CO2 bubbles necessary for US contrast. The DOX-CaCO3-MNPs could also trigger the DOX release simultaneously with CO2 bubble generation at the acidic tumoral environment. The DOX-CaCO3-MNPs displayed effective antitumor therapeutic activity in tumor-bearing mice. The concept described in this work may serve as a useful guide for development of various theranostic nanoparticles for US imaging and therapy of various cancers.

Room-Temperature and Aqueous-Phase Synthesis of Plasmonic Molybdenum Oxide Nanoparticles for Visible-Light-Enhanced Hydrogen Generation.

PubMed

Shi, Jiayuan; Kuwahara, Yasutaka; Wen, Meicheng; Navlani-García, Miriam; Mori, Kohsuke; An, Taicheng; Yamashita, Hiromi

2016-09-06

A straightforward aqueous synthesis of MoO3-x nanoparticles at room temperature was developed by using (NH4 )6 Mo7 O24 ⋅4 H2 O and MoCl5 as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as-prepared products are nanoparticles with diameters of 90-180 nm. The diffuse reflectance UV-visible-near-IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible-light and near-infrared region, such nanostructures exhibit an enhancement of activity toward visible-light catalytic hydrogen generation. MoO3-x nanoparticles synthesized with a molar ratio of Mo(VI) /Mo(V) 1:1 show the highest yield of H2 evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as-prepared plasmonic MoO3-x nanoparticles, which reveals its potential application in visible-light catalytic hydrogen production. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toxicity of CeO2 nanoparticles - the effect of nanoparticle properties.

PubMed

Leung, Yu Hang; Yung, Mana M N; Ng, Alan M C; Ma, Angel P Y; Wong, Stella W Y; Chan, Charis M N; Ng, Yip Hang; Djurišić, Aleksandra B; Guo, Muyao; Wong, Mabel Ting; Leung, Frederick C C; Chan, Wai Kin; Leung, Kenneth M Y; Lee, Hung Kay

2015-04-01

Conflicting reports on the toxicity of CeO2 nanomaterials have been published in recent years, with some studies finding CeO2 nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO2 from three different suppliers as well as CeO2 synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO2 nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO2 nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results. Copyright © 2015 Elsevier B.V. All rights reserved.

Tailor-made Au@Ag core-shell nanoparticle 2D arrays on protein-coated graphene oxide with assembly enhanced antibacterial activity

NASA Astrophysics Data System (ADS)

Wang, Huiqiao; Liu, Jinbin; Wu, Xuan; Tong, Zhonghua; Deng, Zhaoxiang

2013-05-01

Water-dispersible two-dimensional (2D) assemblies of Au@Ag core-shell nanoparticles are obtained through a highly selective electroless silver deposition on pre-assembled gold nanoparticles on bovine serum albumin (BSA)-coated graphene oxide (BSA-GO). While neither BSA-GO nor AuNP-decorated BSA-GO shows any antibacterial ability, the silver-coated GO@Au nanosheets (namely GO@Au@Ag) exhibit an enhanced antibacterial activity against Gram-negative Escherichia coli (E. coli) bacteria, superior to unassembled Au@Ag nanoparticles and even ionic Ag. Such an improvement may be attributed to the increased local concentration of silver nanoparticles around a bacterium and a polyvalent interaction with the bacterial surface. In addition, the colloidal stability of this novel nano-antimicrobial against the formation of random nanoparticle aggregates guarantees a minimized activity loss of the Au@Ag nanoparticles. The antibacterial efficacy of GO@Au@Ag is less sensitive to the existence of Cl-, in comparison with silver ions, providing another advantage for wound dressing applications. Our research unambiguously reveals a strong and very specific interaction between the GO@Au@Ag nanoassembly and E. coli, which could be an important clue toward a rational design, synthesis and assembly of innovative and highly active antibacterial nanomaterials.

Antimicrobial property of zinc based nanoparticles

NASA Astrophysics Data System (ADS)

Chiriac, V.; Stratulat, D. N.; Calin, G.; Nichitus, S.; Burlui, V.; Stadoleanu, C.; Popa, M.; Popa, I. M.

2016-06-01

Pathogen bacteria strains with wide spectrum can cause serious infections with drastic damages on humans. There are studies reflecting antibacterial effect of nanoparticles type metal or metal oxides as an alternative or concurrent treatment to the diseases caused by infectious agents. Synthesised nanoparticles using different methods like sol-gel, hydrothermal or plant extraction were tested following well-established protocols with the regard to their antimicrobial activity. It was found that zinc based nanoparticles possess strong synergistic effect with commonly used antibiotics on infection tratment.

Green synthesis of silver nanoparticles using cell extracts of Anabaena doliolum and screening of its antibacterial and antitumor activity.

PubMed

Singh, Garvita; Babele, Piyoosh K; Shahi, Shailesh K; Sinha, Rajeshwar P; Tyagi, Madhu B; Kumar, Ashok

2014-10-01

In the present work, we describe a simple, cheap, and unexplored method for "green" synthesis of silver nanoparticles using cell extracts of the cyanobacterium Anabaena doliolum. An attempt was also made to test the antimicrobial and antitumor activities of the synthesized nanoparticles. Analytical techniques, namely UV-vis spectroscopy, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and TEMselected area electron diffraction, were used to elucidate the formation and characterization of silver-cyanobacterial nanoparticles (Ag-CNPs). Results showed that the original color of the cell extract changed from reddish blue to dark brown after addition of silver nitrate solution (1 mM) within 1 h, suggesting the synthesis of Ag-CNPs. That the formation Ag-CNPs indeed occurred was also evident from the spectroscopic analysis of the reaction mixture, wherein a prominent peak at 420 nm was noted. TEM images revealed well-dispersed, spherical Ag- CNPs with a particle size in the range of 10-50 nm. The X-ray diffraction spectrum suggested a crystalline nature of the Ag-CNPs. FTIR analysis indicated the utilization of a hydroxyl (-OH) group in the formation of Ag-CNPs. Ag-CNPs exhibited strong antibacterial activity against three multidrug-resistant bacteria. Additionally, Ag-CNPs strongly affected the survival of Dalton's lymphoma and human carcinoma colo205 cells at a very low concentration. The Ag-CNPs-induced loss of survival of both cell types may be due to the induction of reactive oxygen species generation and DNA fragmentation, resulting in apoptosis. Properties exhibited by the Ag-CNP suggest that it may be used as a potential antibacterial and antitumor agent.

All-boron fullerene exhibits a strong affinity to inorganic anions

NASA Astrophysics Data System (ADS)

Colherinhas, Guilherme; Fileti, Eudes Eterno; Chaban, Vitaly V.

2017-03-01

Experimentally observed all-boron fullerene, B-80, inspires systematic investigation of its physical chemical properties and search for possible applications. We hereby report density functional theory calculations to characterize interactions of B-80 with the selected imidazolium room-temperature ionic liquids (RTILs), dimethylimidazolium nitrate and dimethylimidazolium hexafluorophosphate. Whereas the imidazolium cation exhibits a rather poor affinity to B-80, the inorganic anions form polar covalent bonds with the boron atom occupying a central position within a B-6 hexagon. Attachment of the RTIL ion pairs leads to a significant alteration of the electronic spectra, charge density distribution, valence and conduction molecular orbitals. The total binding energies keeping the RTIL@B80 complexes together range 200-250 kcal mol-1, being higher than the energies of many interactions in chemistry. The observed phenomenon predicts an excellent solubility of B-80 in the considered RTILs, but may also reveal a poor stability of B-80 in the polar media. Our results motivate further efforts in studying the behavior of the all-boron fullerene in polar environments.

Multifunctional platinum-based nanoparticles for biomedical applications.

PubMed

Cheng, Qinqin; Liu, Yangzhong

2017-03-01

Platinum-based anticancer drugs play a central role in current cancer therapy. However, their applicability and efficacy are limited by drug resistance and adverse effects. Nanocarrier-based platinum drug delivery systems are promising alternatives to circumvent the disadvantages of bare platinum drugs. The various properties of nanoparticle chemistry allow for the trend toward multiple functionality. Nanoparticles preferentially accumulate at the tumor site through passive targeting, and the attachment of tumor targeting moieties further enhances their tumor-specific localization as well as tumor cell uptake. The introduction of stimuli-responsive groups into drug delivery systems can further achieve spatially and temporally controlled drug release in response to specific stimuli. Combination therapy strategies have been used to promote synergetic efficacy and overcome the resistance of platinum drugs. The tumor-localized drug delivery strategies exhibit benefits for preventing local tumor recurrence. In addition, the combination of platinum drugs and imaging agents in one unity allows the cancer diagnostics for real-time monitoring the distribution of drug-loaded nanoparticles inside the body and tumor. This review discusses recent scientific advances in multifunctional nanoparticle formulations of platinum drugs, and these designs exhibit new potential of multifunctional nanoparticles for delivering platinum-based anticancer drugs. WIREs Nanomed Nanobiotechnol 2017, 9:e1410. doi: 10.1002/wnan.1410 For further resources related to this article, please visit the WIREs website. © 2016 Wiley Periodicals, Inc.

A nano-bio interfacial protein corona on silica nanoparticle.

PubMed

Zhang, Hongyan; Peng, Jiaxi; Li, Xin; Liu, Shengju; Hu, Zhengyan; Xu, Guiju; Wu, Ren'an

2018-07-01

Nano-bio interaction takes the crucial role in bio-application of nanoparticles. The systematic mapping of interfacial proteins remains the big challenge as low level of proteins within interface regions and lack of appropriate technology. Here, a facile proteomic strategy was developed to characterize the interfacial protein corona (noted as IPC) that has strong interactions with silica nanoparticle, via the combination of the vigorous elution with high concentration sodium dodecyl sulfate (SDS) and the pre-isolation of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The trace level IPCs for silica nanoparticle were thus qualitatively and quantitatively identified. Bioinformatics analyses revealed the intrinsic compositions, relevance and potential regularity addressing the strong interactions between IPC and nanoparticle. This strategy in determining IPCs is opening an avenue to give a deep insight to understand the interaction between proteins and not only nanoparticles but also other bulk materials. Copyright © 2018 Elsevier B.V. All rights reserved.

Hepatoprotective effect of engineered silver nanoparticles coated bioactive compounds against diethylnitrosamine induced hepatocarcinogenesis in experimental mice.

PubMed

Prasannaraj, Govindaraj; Venkatachalam, Perumal

2017-02-01

Nanoparticle based drug delivery can rapidly improves the therapeutic potential of anti-cancer agents. The present study focused to evaluate the hepatoprotective activity of silver nanoparticles (AgNPs) synthesized using aqueous extracts of Andrographis paniculata leaves (ApAgNPs) and Semecarpus anacardium nuts (SaAgNPs) against diethylnitrosamine (DEN) induced liver cancer in mice model. The physico-chemical properties of synthesized AgNPs were characterized by Fourier transform infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), X-ray Diffraction (XRD), Energy Dispersive X-ray (EDX) spectrum, Zeta potential and Dynamic Light Scattering (DLS) analysis. The surface plasmon resonance (SPR) absorption spectrum revealed a strong peak at 420nm for both SaAgNPs and ApAgNPs. FTIR results exhibited the presence of possible functional groups in the synthesized AgNPs. TEM analysis determined the hexagonal, and spherical shape of the synthesized silver nanoparticles. The XRD and SAED pattern confirmed the crystalline nature and crystalline size of the AgNPs. EDX result clearly showed strong silver signals in the range between 2 and 4keV. Zeta potential measurements indicated a sharp peak at -3.93 and -13.8mV for ApAgNPs and SaAgNPs, respectively. DLS measurement expressed the particle size distribution was 70 and 60nm for ApAgNPs and SaAgNPs, respectively. DEN (20mg/kg b.wt.) was subjected to induce liver cancer in mice for 8weeks and treated with biosynthesized silver nanoparticles. Interestingly, ApAgNPs and SaAgNPs treated DEN induced animal groups show a decreased level of aspartate amino transferase (AST), alanine amino transferase (ALT), serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT) activity and elevated level of catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and superoxide dismutase (SOD) activity over untreated DEN control

Field-assisted organization, substrate effects and magnetic behavior of Ag 30Co 70 core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Crisan, A. D.; Angelakeris, M.; Simeonidis, K.; Tsiaoussis, I.; Crisan, O.

2010-11-01

In core-shell systems with non-magnetic core and magnetic shell, the electron transport and magnetic properties are expected to show enhanced behavior due to the particular morpho-structural features of the conductive and magnetic regions. This may lead to novel advanced GMR materials and spin valves. This is the case of core-shell Ag-Co colloidal nanoscale particles that organize into regular arrays. An insight on the structure and morphology of the newly synthesized Ag-Co nanoparticles deposited on different substrates will be presented. The influence of the substrate on different morphologies and organization dynamics is discussed. It is shown that the magnetic behavior of the Ag-Co nanoparticles is highly influenced by the corona-like morphology of Co shell, chemical environment of the magnetic atoms and by the fact that they exhibit strongly reduced coordination due to the surface states.

Enhanced Formation of Oxidants from Bimetallic Nickel-Iron Nanoparticles in the Presence of Oxygen

PubMed Central

Lee, Changha; Sedlak, David L.

2009-01-01

Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants, capable of transforming organic contaminants in water. However, the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not enhance the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4 – 9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values. PMID:19068843

Dynamic protein coronas revealed as a modulator of silver nanoparticle sulphidation in vitro

NASA Astrophysics Data System (ADS)

Miclăuş, Teodora; Beer, Christiane; Chevallier, Jacques; Scavenius, Carsten; Bochenkov, Vladimir E.; Enghild, Jan J.; Sutherland, Duncan S.

2016-06-01

Proteins adsorbing at nanoparticles have been proposed as critical toxicity mediators and are included in ongoing efforts to develop predictive tools for safety assessment. Strongly attached proteins can be isolated, identified and correlated to changes in nanoparticle state, cellular association or toxicity. Weakly attached, rapidly exchanging proteins are also present at nanoparticles, but are difficult to isolate and have hardly been examined. Here we study rapidly exchanging proteins and show for the first time that they have a strong modulatory effect on the biotransformation of silver nanoparticles. Released silver ions, known for their role in particle toxicity, are found to be trapped as silver sulphide nanocrystals within the protein corona at silver nanoparticles in serum-containing cell culture media. The strongly attached corona acts as a site for sulphidation, while the weakly attached proteins reduce nanocrystal formation in a serum-concentration-dependent manner. Sulphidation results in decreased toxicity of Ag NPs.

Optical, structural and nonlinear optical properties of laser ablation synthesized Ag nanoparticles and photopolymer nanocomposites based on them

NASA Astrophysics Data System (ADS)

Zulina, Natalia A.; Pavlovetc, Ilia M.; Baranov, Mikhail A.; Denisyuk, Igor Yu.

2017-03-01

In this work Ag nanoparticles (NPs) stable colloid solution were prepared by laser ablation of chemically pure silver rod in liquid monomer isodecyl acrylate (IDA). Sizes of obtained nanoparticles were determined by scanning electron microscope and vary from 27 to 120 nm. Nanocomposites films were prepared from obtained stable colloid solution of AgNPs by photocuring. For aliphatic polymer IDA long molecules cross-linking Diurethane dimethacrylate, 1,6-Hexandiol diacrylate and Tetra (ethylene glycol) diacrylate were used. Prepared nanomaterials exhibit strong third-order nonlinear optical responses, which was estimated by using z-scan technique. The third-order nonlinear optical coefficients of the studied nanocomposites were found to be up to Reχ(3)=1.31×10-5 (esu) and Imχ(3)=7.64×10-5 (esu).

Ionic liquid and nanoparticle hybrid systems: Emerging applications.

PubMed

He, Zhiqi; Alexandridis, Paschalis

2017-06-01

Having novel electronic and optical properties that emanate from their nano-scale dimensions, nanoparticles are central to numerous applications. Ionic liquids can confer to nanoparticle chemical protection and physicochemical property enhancement through intermolecular interactions and can consequently improve the stability and reusability of nanoparticle for various operations. With an aim to combine the novel properties of nanoparticles and ionic liquids, different structures have been generated, based on a balance of several intermolecular interactions. Such ionic liquid and nanoparticle hybrids are showing great potential in diverse applications. In this review, we first introduce various types of ionic liquid and nanoparticle hybrids, including nanoparticle colloidal dispersions in ionic liquids, ionic liquid-grafted nanoparticles, and nanoparticle-stabilized ionic liquid-based emulsions. Such hybrid materials exhibit interesting synergisms. We then highlight representative applications of ionic liquid and nanoparticle hybrids in the catalysis, electrochemistry and separations fields. Such hybrids can attain better stability and higher efficiency under a broad range of conditions. Novel and enhanced performance can be achieved in these applications by combining desired properties of ionic liquids and of nanoparticles within an appropriate hybrid nanostructure. Copyright © 2016 Elsevier B.V. All rights reserved.

Morphology-Controlled Synthesis and Metalation of Porphyrin Nanoparticles with Enhanced Photocatalytic Performance

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

Wang, Jiefei; Zhong, Yong; Wang, Liang

The design and engineering of the size, shape, and chemistry of photoactive building blocks enables the fabrication of functional nanoparticles for applications in light harvesting, photocatalytic synthesis, water splitting, phototherapy, and photodegradation. Here, we report the synthesis of such nanoparticles through a surfactant-assisted interfacial self-assembly process using optically active porphyrin as a functional building block. The self-assembly process relies on specific interactions such as π–π stacking and metalation (metal atoms and ligand coordination) between individual porphyrin building blocks. Depending on the kinetic conditions and type of surfactants, resulting structures exhibit well-defined one- to three-dimensional morphologies such as nanowires, nanooctahedra, andmore » hierarchically ordered internal architectures. Specifically, electron microscopy and X-ray diffraction results indicate that these nanoparticles exhibit stable single-crystalline and nanoporous frameworks. In conclusion, due to the hierarchical ordering of the porphyrins, the nanoparticles exhibit collective optical properties resulted from coupling of molecular porphyrins and photocatalytic activities such as photodegradation of methyl orange (MO) pollutants and hydrogen production.« less

Morphology-Controlled Synthesis and Metalation of Porphyrin Nanoparticles with Enhanced Photocatalytic Performance

DOE PAGES

Wang, Jiefei; Zhong, Yong; Wang, Liang; ...

2016-09-12

The design and engineering of the size, shape, and chemistry of photoactive building blocks enables the fabrication of functional nanoparticles for applications in light harvesting, photocatalytic synthesis, water splitting, phototherapy, and photodegradation. Here, we report the synthesis of such nanoparticles through a surfactant-assisted interfacial self-assembly process using optically active porphyrin as a functional building block. The self-assembly process relies on specific interactions such as π–π stacking and metalation (metal atoms and ligand coordination) between individual porphyrin building blocks. Depending on the kinetic conditions and type of surfactants, resulting structures exhibit well-defined one- to three-dimensional morphologies such as nanowires, nanooctahedra, andmore » hierarchically ordered internal architectures. Specifically, electron microscopy and X-ray diffraction results indicate that these nanoparticles exhibit stable single-crystalline and nanoporous frameworks. In conclusion, due to the hierarchical ordering of the porphyrins, the nanoparticles exhibit collective optical properties resulted from coupling of molecular porphyrins and photocatalytic activities such as photodegradation of methyl orange (MO) pollutants and hydrogen production.« less

Plasmonic nanoparticles for bioanalytics and therapy at the limit

NASA Astrophysics Data System (ADS)

Schneider, T.; Wirth, J.; Garwe, F.; Csáki, A.; Fritzsche, W.

2011-12-01

Noble metal nanoparticles interacting with electromagnetic waves exhibit the effect of localized surface plasmon resonance (LSPR) based on the collective oscillation of their conduction electrons. Local refractive index changes by a (bio) molecular layer surrounding the nanoparticle are important for a variety of research areas like optics and life sciences. In this work we demonstrate the potential of two applications in the field of molecular plasmonics, single nanoparticle sensors and nanoantennas, situated between plasmonics effects and the molecular world.

Effect of magnetic nanoparticles size on rheumatoid arthritis targeting and photothermal therapy.

PubMed

Zhang, Shengchang; Wu, Lin; Cao, Jin; Wang, Kaili; Ge, Yanru; Ma, Wanjun; Qi, Xueyong; Shen, Song

2018-06-13

Nanoparticles based multifunctional system exhibits great potential in diagnosis and therapy of rheumatoid arthritis (RA). The size of nanoparticles plays an essential role in biodistribution and cellular uptake, in turn affects the drug delivery efficiency and therapeutic effect. To investigate the optimal size for RA targeting, Fe 3 O 4 nanoparticles with well-defined particle sizes (70-350 nm) and identical surface properties were developed as model nanoparticles. The synthesized Fe 3 O 4 nanoparticles exhibited excellent biocompatibility and showed higher temperature response under irradiation of near infrared light. Size-dependent internalization was observed when incubated with inflammatory cells. Compared with large ones, small nanoparticles were more readily be phagocytized, leading to higher cytotoxicity in vitro. However, the in vivo experiment in CIA mice demonstrated a quite different result that nanoparticles with size of 220 nm exerted better accessibility to inflamed joint and resulted in higher temperature and better therapeutic effect under laser irradiation. This study not only offered a novel method for RA therapy but also a guideline for RA targeted drug carrier design. Copyright © 2018 Elsevier B.V. All rights reserved.

Platinum nanoparticles on gallium nitride surfaces: effect of semiconductor doping on nanoparticle reactivity.

PubMed

Schäfer, Susanne; Wyrzgol, Sonja A; Caterino, Roberta; Jentys, Andreas; Schoell, Sebastian J; Hävecker, Michael; Knop-Gericke, Axel; Lercher, Johannes A; Sharp, Ian D; Stutzmann, Martin

2012-08-01

Platinum nanoparticles supported on n- and p-type gallium nitride (GaN) are investigated as novel hybrid systems for the electronic control of catalytic activity via electronic interactions with the semiconductor support. In situ oxidation and reduction were studied with high pressure photoemission spectroscopy. The experiments revealed that the underlying wide-band-gap semiconductor has a large influence on the chemical composition and oxygen affinity of supported nanoparticles under X-ray irradiation. For as-deposited Pt cuboctahedra supported on n-type GaN, a higher fraction of oxidized surface atoms was observed compared to cuboctahedral particles supported on p-type GaN. Under an oxygen atmosphere, immediate oxidation was recorded for nanoparticles on n-type GaN, whereas little oxidation was observed for nanoparticles on p-type GaN. Together, these results indicate that changes in the Pt chemical state under X-ray irradiation depend on the type of GaN doping. The strong interaction between the nanoparticles and the support is consistent with charge transfer of X-ray photogenerated free carriers at the semiconductor-nanoparticle interface and suggests that GaN is a promising wide-band-gap support material for photocatalysis and electronic control of catalysis.

``The Princess and the Pea'' at the Nanoscale: Wrinkling and Delamination of Graphene on Nanoparticles

NASA Astrophysics Data System (ADS)

Yamamoto, Mahito; Pierre-Louis, Olivier; Huang, Jia; Fuhrer, Michael S.; Einstein, Theodore L.; Cullen, William G.

2012-10-01

Thin membranes exhibit complex responses to external forces or geometrical constraints. A familiar example is the wrinkling, exhibited by human skin, plant leaves, and fabrics, that results from the relative ease of bending versus stretching. Here, we study the wrinkling of graphene, the thinnest and stiffest known membrane, deposited on a silica substrate decorated with silica nanoparticles. At small nanoparticle density, monolayer graphene adheres to the substrate, detached only in small regions around the nanoparticles. With increasing nanoparticle density, we observe the formation of wrinkles which connect nanoparticles. Above a critical nanoparticle density, the wrinkles form a percolating network through the sample. As the graphene membrane is made thicker, global delamination from the substrate is observed. The observations can be well understood within a continuum-elastic model and have important implications for strain-engineering the electronic properties of graphene.

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.

The effects of bacteria-nanoparticles interface on the antibacterial activity of green synthesized silver nanoparticles.

PubMed

Ahmad, Aftab; Wei, Yun; Syed, Fatima; Tahir, Kamran; Rehman, Aziz Ur; Khan, Arifullah; Ullah, Sadeeq; Yuan, Qipeng

2017-01-01

Neutralization of bacterial cell surface potential using nanoscale materials is an effective strategy to alter membrane permeability, cytoplasmic leakage, and ultimate cell death. In the present study, an attempt was made to prepare biogenic silver nanoparticles using biomolecules from the aqueous rhizome extract of Coptis Chinensis. The biosynthesized silver nanoparticles were surface modified with chitosan biopolymer. The prepared silver nanoparticles and chitosan modified silver nanoparticles were cubic crystalline structures (XRD) with an average particle size of 15 and 20 nm respectively (TEM, DLS). The biosynthesized silver nanoparticles were surface stabilized by polyphenolic compounds (FTIR). Coptis Chinensis mediated silver nanoparticles displayed significant activity against E. coli and Bacillus subtilus with a zone of inhibition 12 ± 1.2 (MIC = 25 μg/mL) and 18 ± 1.6 mm (MIC = 12.50 μg/mL) respectively. The bactericidal efficacy of these nanoparticles was considerably increased upon surface modification with chitosan biopolymer. The chitosan modified biogenic silver nanoparticles exhibited promising activity against E. coli (MIC = 6.25 μg/mL) and Bacillus subtilus (MIC = 12.50 μg/mL). Our results indicated that the chitosan modified silver nanoparticles were promising agents in damaging bacterial membrane potential and induction of high level of intracellular reactive oxygen species (ROS). In addition, these nanoparticles were observed to induce the release of the high level of cytoplasmic materials especially protein and nucleic acids into the media. All these findings suggest that the chitosan functionalized silver nanoparticles are efficient agents in disrupting bacterial membrane and induction of ROS leading to cytoplasmic leakage and cell death. These findings further conclude that the bacterial-nanoparticles surface potential modulation is an effective strategy in enhancing the antibacterial potency of silver nanoparticles

Dynamic shear rheology of colloidal suspensions of surface-modified silica nanoparticles in PEG

NASA Astrophysics Data System (ADS)

Swarna; Pattanayek, Sudip Kumar; Ghosh, Anup Kumar

2018-03-01

The present work illustrates the effect of surface modification of silica nanoparticles (500 nm) with 3-(glycidoxypropyl)trimethoxy silane which was carried out at different reaction times. The suspensions prepared from modified and unmodified silica nanoparticles were evaluated for their shear rate-dependent viscosity and strain-frequency-dependent modulus. The linear viscoelastic moduli, viz., storage modulus and loss modulus, were compared with those of nonlinear moduli. The shear-thickened suspensions displayed strain thinning at low-frequency smaller strains and a strong strain overshoot at higher strains, characteristics of a continuous shear thickening fluids. The shear-thinned suspension, conversely, exhibited a strong elastic dominance at smaller strains, but at higher strains, its strain softened observed in the steady shear viscosity plot indicating characteristics of yielding material. Considering higher order harmonic components, the decomposed elastic and viscous stress revealed a pronounced elastic response up to 10% strain and a high viscous damping at larger strains. The current work is one of a kind in demonstrating the effect of silica surface functionalization on the linear and nonlinear viscoelasticity of suspensions showing a unique rheological fingerprint. The suspensions can thus be predicted through rheological studies for their applicability in energy absorbing and damping materials with respect to their mechanical properties.

In vitro cell imaging using multifunctional small sized KGdF4:Yb3+,Er3+ upconverting nanoparticles synthesized by a one-pot solvothermal process

NASA Astrophysics Data System (ADS)

Wong, Hon-Tung; Tsang, Ming-Kiu; Chan, Chi-Fai; Wong, Ka-Leung; Fei, Bin; Hao, Jianhua

2013-03-01

Multifunctional KGdF4:18%Yb3+,2%Er3+ nanoparticles with upconversion fluorescence and paramagnetism are synthesized. The average sizes of the nanoparticles capped with branched polyethyleneimine (PEI) and 6-aminocaproic acid (6AA) are ~14 and ~13 nm, respectively. Our KGdF4 host does not exhibit any phase change with the decrease of particle size, which can prevent the detrimental significant decrease in upconversion luminescence caused by this effect observed in the well-known NaYF4 host. The branched PEI and 6AA capping ligands endow our nanoparticles with water-dispersibility and biocompatibility, which can favor internalization of our nanoparticles into the cytoplasm of HeLa cells and relatively high cell viability. The strong upconversion luminescence detected at the cytoplasm of HeLa cells incubated with the branched PEI-capped nanoparticles is probably attributed to the reported high efficiency of cellular uptake. The magnetic mass susceptibility of our nanoparticle is 8.62 × 10-5 emu g-1 Oe-1. This is the highest value ever reported in trivalent rare-earth ion-doped KGdF4 nanoparticles of small size (<=14 nm), and is very close to that of nanoparticles used as T1 contrast agents in magnetic resonance imaging. These suggest the potential of our KGdF4:Yb3+,Er3+ nanoparticles as small-sized multifunctional bioprobes.

Chromium nanoparticle exhibits higher absorption efficiency than chromium picolinate and chromium chloride in Caco-2 cell monolayers.

PubMed

Zha, L-Y; Xu, Z-R; Wang, M-Q; Gu, L-Y

2008-04-01

This study was conducted to determine whether chromium nanoparticle (CrNano) exhibited higher absorption efficiency and possessed unique absorption mechanism in comparison to chromium picolinate (CrPic) and chromium chloride (CrCl(3)), as was postulated by previous reports. Twenty-one-day-old Caco-2 cell monolayers grown on semipermeable membranes in Snapwell tissue culture bichambers were incubated with CrNano, CrPic or CrCl(3) to examine their transport and uptake respectively. In the concentration range of 0.2-20 micromol/l, transport of CrNano, CrPic and CrCl(3) across Caco-2 monolayers both in apical-to-basolateral and basolateral-to-apical direction was concentration-, and time-dependent, and temperature independent. The apparent permeability coefficient (P(app)) of CrNano was between 5.89 and 7.92 x 10(-6) cm/s and that of CrPic and CrCl(3) was between 3.52 and 5.31 x 10(-6) cm/s and between 0.97 and 1.37 x 10(-6) cm/s respectively. Uptake of CrNano, CrPic and CrCl(3) by both apical and basolateral membranes was concentration- and time-dependent. Uptake of CrNano by apical membrane was significantly (p < 0.05) decreased when the incubation temperature was reduced from 37 degrees C to 4 degrees C. The transport efficiency of CrNano, CrPic and CrCl(3) after incubation for 120 min at 37 degrees C was 15.83% +/- 0.76%, 9.08% +/- 0.25% and 2.11% +/- 0.53% respectively. The uptake efficiency of CrNano, CrPic and CrCl(3) was 10.08% +/- 0.76%, 4.73% +/- 0.60% and 0.88% +/- 0.08% respectively. It was concluded that the epithelial transport of CrNano, CrPic and CrCl(3) across the Caco-2 cell monolayers was mainly via passive transport pathways. In addition, CrNano exhibited considerably higher absorption efficiency than both CrPic and CrCl(3) in Caco-2 cell monolayers.

Functionalization of gold nanoparticles as antidiabetic nanomaterial

NASA Astrophysics Data System (ADS)

Venkatachalam, M.; Govindaraju, K.; Mohamed Sadiq, A.; Tamilselvan, S.; Ganesh Kumar, V.; Singaravelu, G.

2013-12-01

In the present investigation, functionalization of gold nanoparticles synthesized using propanoic acid 2-(3-acetoxy-4,4,14-trimethylandrost-8-en-17-yl) (PAT) an active biocomponent isolated from Cassia auriculata is studied in detail. On reaction of PAT with aqueous HAuCl4, rapid formation of stable gold nanoparticles was achieved. Formation of gold nanoparticles was confirmed by UV-vis spectroscopy, XRD, GC-MS, FTIR, TEM and SEM with EDAX. Gold nanoparticles mostly were monodisperse, spherical in shape and ranged in size 12-41 nm. Gold nanoparticles synthesised using PAT was administered to alloxan (150 mg/kg body weight) induced diabetic male albino rats at different doses (0.25, 0.5, 0.75 and 1.0 mg/kg body weight) for 28 days. Plasma glucose level, cholesterol and triglyceride were significantly (p < 0.001) reduced in experimental animals treated with gold nanoparticles at dosage of 0.5 mg/kg body weight and plasma insulin increased significantly. The newly genre green gold nanoparticles exhibit remarkable protein tyrosine phosphatase 1B inhibitory activity.

Electronic and magnetic properties of Ni nanoparticles embedded in various organic semiconductor matrices.

PubMed

Bräuer, Björn; Vaynzof, Yana; Zhao, Wei; Kahn, Antoine; Li, Wen; Zahn, Dietrich R T; Fernández, César de Julián; Sangregorio, Claudio; Salvan, Georgeta

2009-04-09

Ni nanoparticles with a size distribution from 2 to 6 nm, embedded in various organic matrices, were fabricated in ultrahigh vacuum. For this purpose metal free and Ni phthalocyanine, fullerene C(60), and pentacene were coevaporated with Ni. When coevaporated, Ni and H(2)Pc react, leading to the formation of NiPc and Ni nanoparticles. The molecular structure of the matrix was found to have negligible effect on the size of the nanoparticles but to influence the magnetic anisotropy of the nanoparticles: Ni nanoparticles formed in the buckyball matrix have a cubic symmetry, while nanoparticles formed in matrices consisting of planar molecules exhibit a uniaxial symmetry. After exposure to atmosphere, photoelectron spectroscopy investigations demonstrate the presence of metallic Ni nanoparticles accompanied by Ni oxide and the existence of a charge transfer from the organic matrix to the particles in all investigated systems. The oxidized Ni nanoparticles exhibit a larger magnetic anisotropy compared to the freshly prepared particles which show superparamagnetic properties above 17 K. Moreover, photoelectron spectroscopy was used to probe the oxidation process of the Ni nanoparticles in different organic matrices. It could thus be shown that a matrix consisting of spherical molecules like C(60) prevent the particles much better from oxidation compared to matrices of flat molecules.

Antiproliferative effect of Antrodia camphorata polysaccharides encapsulated in chitosan-silica nanoparticles strongly depends on the metabolic activity type of the cell line

NASA Astrophysics Data System (ADS)

Kong, Zwe-Ling; Chang, Jenq-Sheng; Chang, Ke Liang B.

2013-09-01

Chitosan molecules interact with silica and encapsulate the Antrodia camphorata extract (ACE) polysaccharides to form composite nanoparticles. The nanoparticle suspensions of ACE polysaccharides encapsulated in silica-chitosan and silica nanoparticles approach an average particle size of 210 and 294 nm in solution, respectively. The encapsulation efficiencies of ACE polysaccharides are 66 and 63.5 %, respectively. Scanning electron micrographs confirm the formation of near-spherical nanoparticles. ACE polysaccharides solution had better antioxidative capability than ACE polysaccharides encapsulated in silica or silica-chitosan nanoparticles suspensions. The antioxidant capacity of nanoparticles increases with increasing dissolution time. The antitumor effects of ACE polysaccharides, ACE polysaccharides encapsulated in silica, or silica-chitosan nanoparticles increased with increasing concentration of nanoparticles. This is the first report demonstrating the potential of ACE polysaccharides encapsulated in chitosan-silica nanoparticles for cancer chemoprevention. Furthermore, this study suggests that antiproliferative effect of nanoparticle-encapsulated bioactive could significantly depend on the metabolic activity type of the cell line.

Nanoparticle halos: A new colloid stabilization mechanism

PubMed Central

Tohver, Valeria; Smay, James E.; Braem, Alan; Braun, Paul V.; Lewis, Jennifer A.

2001-01-01

A new mechanism for regulating the stability of colloidal particles has been discovered. Negligibly charged colloidal microspheres, which flocculate when suspended alone in aqueous solution, undergo a remarkable stabilizing transition upon the addition of a critical volume fraction of highly charged nanoparticle species. Zeta potential analysis revealed that these microspheres exhibited an effective charge buildup in the presence of such species. Scanning angle reflectometry measurements indicated, however, that these nanoparticle species did not adsorb on the microspheres under the experimental conditions of interest. It is therefore proposed that highly charged nanoparticles segregate to regions near negligibly charged microspheres because of their repulsive Coulombic interactions in solution. This type of nanoparticle haloing provides a previously unreported method for tailoring the behavior of complex fluids. PMID:11447264

Preparation of silver nanoparticles at low temperature

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

Mishra, Mini, E-mail: mishramini5@gmail.com; Chauhan, Pratima, E-mail: mangu167@yahoo.co.in

Silver from ancient time is used as antimicrobial agent in the bulk form but now with the advancement in nanotechnology silver in the form of nanoparticles shown potential effect against microbes which make us easy to fight with many diseases plants and animals. In this work silver nanoparticles were synthesized by chemical routes using sodium borohydride as reducing agent at low temperature. The particles were characterized through UV-Visible spectroscopy as well as X-Ray Diffraction. The UV-visible spectra of silver nanoparticles exhibited absorption at 425 cm; the crystallite size of the particles is between 19nm to 39nm. EDAX graph shows two peaksmore » of silver and oxygen. Water absorbed by silver nanoparticles was removed by the calcinations.« less

Heat transfer fluids containing nanoparticles

DOEpatents

Singh, Dileep; Routbort, Jules; Routbort, A.J.; Yu, Wenhua; Timofeeva, Elena; Smith, David S.; France, David M.

2016-05-17

A nanofluid of a base heat transfer fluid and a plurality of ceramic nanoparticles suspended throughout the base heat transfer fluid applicable to commercial and industrial heat transfer applications. The nanofluid is stable, non-reactive and exhibits enhanced heat transfer properties relative to the base heat transfer fluid, with only minimal increases in pumping power required relative to the base heat transfer fluid. In a particular embodiment, the plurality of ceramic nanoparticles comprise silicon carbide and the base heat transfer fluid comprises water and water and ethylene glycol mixtures.

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.

Direct observation of a single nanoparticle-ubiquitin corona formation

NASA Astrophysics Data System (ADS)

Ding, Feng; Radic, Slaven; Chen, Ran; Chen, Pengyu; Geitner, Nicholas K.; Brown, Jared M.; Ke, Pu Chun

2013-09-01

The advancement of nanomedicine and the increasing applications of nanoparticles in consumer products have led to administered biological exposure and unintentional environmental accumulation of nanoparticles, causing concerns over the biocompatibility and sustainability of nanotechnology. Upon entering physiological environments, nanoparticles readily assume the form of a nanoparticle-protein corona that dictates their biological identity. Consequently, understanding the structure and dynamics of a nanoparticle-protein corona is essential for predicting the fate, transport, and toxicity of nanomaterials in living systems and for enabling the vast applications of nanomedicine. Here we combined multiscale molecular dynamics simulations and complementary experiments to characterize the silver nanoparticle-ubiquitin corona formation. Notably, ubiquitins competed with citrates for the nanoparticle surface, governed by specific electrostatic interactions. Under a high protein/nanoparticle stoichiometry, ubiquitins formed a multi-layer corona on the particle surface. The binding exhibited an unusual stretched-exponential behavior, suggesting a rich binding kinetics. Furthermore, the binding destabilized the α-helices while increasing the β-sheet content of the proteins. This study revealed the atomic and molecular details of the structural and dynamic characteristics of nanoparticle-protein corona formation.The advancement of nanomedicine and the increasing applications of nanoparticles in consumer products have led to administered biological exposure and unintentional environmental accumulation of nanoparticles, causing concerns over the biocompatibility and sustainability of nanotechnology. Upon entering physiological environments, nanoparticles readily assume the form of a nanoparticle-protein corona that dictates their biological identity. Consequently, understanding the structure and dynamics of a nanoparticle-protein corona is essential for predicting the fate

Methods and apparatus for transparent display using up-converting nanoparticles

DOEpatents

Hsu, Chia Wei; Qiu, Wenjun; Zhen, Bo; Shapira, Ofer; Soljacic, Marin

2016-10-04

Disclosed herein are transparent color displays with nanoparticles made with nonlinear materials and/or designed to exhibit optical resonances. These nanoparticles are embedded in or hosted on a transparent substrate, such as a flexible piece of clear plastic or acrylic. Illuminating the nanoparticles with invisible light (e.g., infrared or ultraviolet light) causes them to emit visible light. For example, a rare-earth doped nanoparticle may emit visible light when illuminated simultaneoulsy with a first infrared beam at a first wavelength .lamda..sub.1 and a second infrared beam at a second wavelength .lamda..sub.2. And a frequency-doubling nanoparticle may emit visible light when illuminated with a single infrared beam at the nanoparticle's resonant frequency. Selectively addressing these nanoparticles with appropiately selected pump beams yields visible light emitted from the nanoparticles hosted by the transparent substrate in a desired pattern.

Characterization, antibacterial, antioxidant, antidiabetic, anti-inflammatory and antityrosinase activity of green synthesized silver nanoparticles using Calophyllum tomentosum leaves extract

NASA Astrophysics Data System (ADS)

Govindappa, M.; Hemashekhar, B.; Arthikala, Manoj-Kumar; Ravishankar Rai, V.; Ramachandra, Y. L.

2018-06-01

The current research study is to develop an easy and eco-friendly method for the synthesis of AgNPs using aqueous leaf extract of Calophyllum tomentosum (CtAgNPs) and evaluated the extract to know the effects of anti-bacterial, antioxidant, anti-diabetic, anti-inflammatory and anti-tyrosinase activity. Using UV-vis spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) characterized the Calophyllum tomentosum mediated silver nanoparticles. The leaf extract of C. tomentosum yielded flavonoids, saponins, tannins, alkaloids, glycosides, phenols, terpenoids and coumarins. AgNPs formation was confirmed by UV-vis spectra at 438 nm. Crystalline structure with a face centered cubic (fcc) of AgNPs was observed in XRD. FTIR had shown that the phytochemicals were responsible for the reduction and capping material of silver nanoparticles. The size and shape of the AgNPs were determined using SEM. From EDX study analysed the strong absorption property of AgNPs. The CtAgNPs have showed significant antibacterial activity on multi drug resistance bacteria. The CtAgNPs had shown strong antioxidant (DPPH, H2O2 scavenging, nitric oxide scavenging power, reducing power) activities. The CtAgNPs had strongly inhibited the α-glucosidase and DPPIV compared to α-amylase. The CtAgNPs exhibited strong anti-inflammatory activity (albumin denaturation, membrane stabilization, heat haemolytic, protein inhibitory, lipoxygenase, xanthine oxidase) and tyrosinase inhibitory activity. To our best knowledge, this is the first attempt on the synthesis of silver nanoparticles using Calophyllum tomentosum leaves extract. Hence, to validate our results the in vivo studies at molecular level are needed to develop an antioxidant, anti-diabetic and anti-inflammatory agent.

Relating Structure to Efficiency in Surfactant-Free Polymer/Fullerene Nanoparticle-Based Organic Solar Cells.

PubMed

Gärtner, Stefan; Clulow, Andrew J; Howard, Ian A; Gilbert, Elliot P; Burn, Paul L; Gentle, Ian R; Colsmann, Alexander

2017-12-13

Nanoparticle dispersions open up an ecofriendly route toward printable organic solar cells. They can be formed from a variety of organic semiconductors by using miniemulsions that employ surfactants to stabilize the nanoparticles in dispersion and to prevent aggregation. However, whenever surfactant-based nanoparticle dispersions have been used to fabricate solar cells, the reported performances remain moderate. In contrast, solar cells from nanoparticle dispersions formed by precipitation (without surfactants) can exhibit power conversion efficiencies close to those of state-of-the-art solar cells processed from blend solutions using chlorinated solvents. In this work, we use small-angle neutron scattering measurements and transient absorption spectroscopy to investigate why surfactant-free nanoparticles give rise to efficient organic solar cells. We show that surfactant-free nanoparticles comprise a uniform distribution of small semiconductor domains, similar to that of bulk-heterojunction films formed using traditional solvent processing. This observation differs from surfactant-based miniemulsion nanoparticles that typically exhibit core-shell structures. Hence, the surfactant-free nanoparticles already possess the optimum morphology for efficient energy conversion before they are assembled into the photoactive layer of a solar cell. This structural property underpins the superior performance of the solar cells containing surfactant-free nanoparticles and is an important design criterion for future nanoparticle inks.

Vertical plasmonic nanowires for 3D nanoparticle trapping

NASA Astrophysics Data System (ADS)

Wu, Jingzhi; Gan, Xiaosong

2011-12-01

Nanoparticle trapping is considered to be more challenging than trapping micron-sized objects because of the diffraction limit of light and the severe Brownian motion of the nanoparticles. We introduce a nanoparticle trapping approach based on plasmonic nanostructures, which consist of nanopillars with high aspect ratio. The plasmonic nanopillars behave as plasmonic resonators that rely on paired nano-pillars supporting gap plasmon modes. The localized surface plasmon resonance effect provides strong electromagnetic field enhancement and enables confinement of nanoparticles in three dimensional space. Numerical simulations indicate that the plasmonic structure provides stronger optical forces for trapping nanoparticles. The study of thermal effect of the plasmonic structure shows that the impact of the thermal force is significant, which may determine the outcome of the nanoparticle trapping.

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.

Synthesis of Multifunctional Nanoparticles for Cancer Diagnostics and Therapeutics

NASA Astrophysics Data System (ADS)

Fang, Chen

2011-12-01

Magnetic nanoparticles (MNPs) have attracted enormous research attention due to their unique magnetic properties that enable the detection by the non-invasive medical imaging modality---magnetic resonance imaging (MRI). By incorporating advanced features, such as specific targeting, multimodality, therapeutic delivery, the detectability and applicability of MNPs have been dramatically expanded. Smart and rational design on structure, composition and surface chemistry is essential to achieving desired properties in MNP systems, such as high sensitivity and colloidal stability, target specificity and/or multimodality. The goal of this research is to develop MNP-based platforms for the detection, diagnosis and treatment of cancer. MNPs with high contrast enhancement were coated with poly(ethylene glycol) (PEG)-based polymers to render aqueous stability and confer therapeutic-loading capability. Tumor-specific MNPs were developed by functionalization of nanoparticles with chlorotoxin (CTX) or arginine-glycine-aspartic acid (RGD) that targets, respectively, MMP-2 receptor or alphavbeta3 integrin overexpressed on a variety of cancer cells. The effects of ligands' molecular targets on the temporal and spatial distribution of MNPs within tumors were also investigated both in vitro and in vivo. All MNPs exhibited excellent long-term stability in cell culture media. CTX-labeled MNP exhibited sustained accumulation, penetration and distribution in the tumor mass. These findings revealed the influence of the targeting ligands on the intratumoral distribution of the ligand-enabled nanoprobes. To demonstrate the ability of nanoparticles as drug carrier, anthracyline chemotherapeutic drugs doxorubicin and mitoxantrone were attached to iron oxide nanoparticles. The theragnostic nanoparticles showed sufficient contrast enhancement and comparable anti-neoplastic efficacy in vitro. With flexible surface chemistry, our nanoparticle platform can be used in a modular fashion to

Synthesis and Characterization of Composite Hydroxyapatite-Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Charlena; Nuzulia, N. A.; Handika

2017-03-01

Hydroxyapatite (HAp) is commonly used as bone implant coating recently; however, the material has disadvantage such as lack of antibacterial properties, that can cause an bacterial infection. Addition of silver nanoparticles is expected to be able to provide antibacterial properties. Silver nanoparticles was obtained by reduction of AgNO3 using glucose monohydrate with microwave heating at 100p for 4 minutes. The composite of hydroxyapatite-silver nanoparticles was synthesized using chemical methods by coprecipitation suspension of Ca(OH)2 with (NH4)HPO4, followed by adding silver nanoparticles solution. The size of the synthesized silver nanoparticles was 30-50 nm and exhibited good antibacterial activity. Nevertheless, when it was composited with HAp to form HAp-AgNPs, there was no antibacterial activity due to very low concentration of silver nanoparticles. This was indicated by the absence of silver nanoparticles diffraction patterns. Infrared spectra indicated the presence of chemical shift and the results of scanning electron microscope showed size of the HAp-AgNPs composite was smaller than that of the HAp. This showed the interaction between HAp and the silver nanoparticles.

A multi-target therapeutic potential of Prunus domestica gum stabilized nanoparticles exhibited prospective anticancer, antibacterial, urease-inhibition, anti-inflammatory and analgesic properties.

PubMed

Islam, Nazar Ul; Amin, Raza; Shahid, Muhammad; Amin, Muhammad; Zaib, Sumera; Iqbal, Jamshed

2017-05-23

Phytotherapeutics exhibit diverse pharmacological effects that are based on the combined action of a mixture of phytoconstituents. In this study, Prunus domestica gum-loaded, stabilized gold and silver nanoparticles (Au/Ag-NPs) were evaluated for their prospective anticancer, antibacterial, urease-inhibition, anti-inflammatory, and analgesic properties. Au/Ag-NPs were biosynthesized and characterized with UV-Vis, FTIR, SEM, EDX, and XRD techniques. The effect of gum and metal ion concentration, reaction temperature, and time on the synthetic stability of nanoparticles was studied along with their post-synthetic stability against varying pH and salt concentrations, long-term storage and extremes of temperature. Nanoparticles were tested for anticancer (HeLa cervical cancer cells), antibacterial (Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa), urease inhibition (jack-bean urease), anti-inflammatory (carrageenan-induced paw edema), and antinociceptive (abdominal constriction response) activities. The nanoparticles were mostly spherical with an average particle size between 7 and 30 nm (Au-NPs) and 5-30 nm (Ag-NPs). Au/Ag-NPs maintained their colloidal stability and nanoscale characteristics against variations in physicochemical factors. Au/Ag-NPs have potent anticancer potential (IC 50  = 2.14 ± 0.15 μg/mL and 3.45 ± 0.23 μg/mL). Au/Ag-NPs selectively suppressed the growth of S. aureus (10.5 ± 0.6 mm, 19.7 ± 0.4 mm), E. coli (10 ± 0.4 mm, 14.4 ± 0.7 mm), and P. aeruginosa (8.2 ± 0.3 mm, 13.1 ± 0.2 mm), as well as showed preferential inhibition against jack-bean urease (19.2 ± 0.86%, 21.5 ± 1.17%). At doses of 40 and 80 mg/kg, Au-NPs significantly ameliorated the increase in paw edema during the 1st h (P < 0.05, P < 0.01) and 2-5 h (P < 0.001) of carrageenan-induced inflammation compared to the 200 and 400 mg/kg doses of P. domestica gum (P < 0.05, P < 0.001). At similar doses, Au-NPs also

Synthesis, optimization, and characterization of molecularly imprinted nanoparticles

NASA Astrophysics Data System (ADS)

Rostamizadeh, Kobra; Abdollahi, Hamid; Parsajoo, Cobra

2013-04-01

Nanoparticles of molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization method. Glucose was used as a template molecule. The impact of different process parameters on the preparation of nanoparticles was investigated in order to reach the maximum binding capacity of MIPs. Experimental data based on uniform design were analyzed using artificial neural network to find the optimal condition. The results showed that the binding ability of nanoparticles of MIPs prepared under optimum condition was much higher than that of the corresponding non-imprinted nanoparticles (NIPs). The findings also demonstrated high glucose selectivity of imprinted nanoparticles. The results exhibited that the particle size for MIP nanoparticles was about 557.6 nm, and the Brunauer-Emmett-Teller analysis also confirmed that the particle pores were mesopores and macropores around 40 nm and possessed higher volume, surface area, and uniform size compared to the corresponding NIPs.

Alternating stacking of ferromagnetic nanosheet and nanoparticle films: heteroassembly and magneto-optical Kerr effect

NASA Astrophysics Data System (ADS)

Jia, Baoping; Zhang, Wei; Liu, Hui; Lin, Bencai; Ding, Jianning

2016-09-01

Heterostructured multilayer films of two different nanocrystals have been successfully fabricated by layer-by-layer stacking of Ti0.8Co0.2O2 nanosheet and Fe3O4 nanoparticle films. UV-Vis spectroscopy and AFM observation confirmed the successful alternating deposition in the multilayer buildup process. The average thickness of both Ti0.8Co0.2O2 nanosheet and Fe3O4 nanoparticle layers was determined to be about 1.4-1.7 and 5 nm, which was in good agreement with TEM results. Magneto-optical Kerr effect measurements demonstrated that the heteroassemblies exhibit gigantic magnetic circular dichroism (MCD) (2 × 104 deg/cm) at 320-360 nm, deriving from strong interlayer [Co2+]t2g-[Fe3+]eg d-d charge transfer which was further confirmed by X-ray photoelectron spectroscopy. Their structure-dependent MCD showed high potential in rational design and construction of high-efficiency magneto-optical devices.

Extracellular biosynthesis of silver nanoparticles using Bacillus sp. GP-23 and evaluation of their antifungal activity towards Fusarium oxysporum

NASA Astrophysics Data System (ADS)

Gopinath, V.; Velusamy, P.

2013-04-01

In last few decades nanoparticles have attracted and emerged as a field in biomedical research due to their incredible applications. The current research was focused on extracellular synthesis of silver nanoparticles (AgNPs) using cell free culture supernatant of strain GP-23. It was found that the strain GP-23 belonged to Bacillus species by 16S rRNA sequence analysis. Biosynthesis of AgNPs was achieved by addition of culture supernatant with aqueous silver nitrate solution, after 24 h it turned to brown color solution with a peak at 420 nm corresponding to the Plasmon absorbance of AgNPs by UV-Vis Spectroscopy. The nanoparticles were characterized by FTIR, XRD, HRTEM, EDX and AFM. The synthesized nanoparticles were found to be spherical in shape with size in the range of 7-21 nm. It was stable in aqueous solution for five months period of storage at room temperature under dark condition. The biosynthesized AgNPs exhibited strong antifungal activity against plant pathogenic fungus, Fusarium oxysporum at the concentration of 8 μg ml-1. The results suggest that the synthesized AgNPs act as an effective antifungal agent/fungicide.

Control of dynamical self-assembly of strongly Brownian nanoparticles through convective forces induced by ultrafast laser

NASA Astrophysics Data System (ADS)

Ilday, Serim; Akguc, Gursoy B.; Tokel, Onur; Makey, Ghaith; Yavuz, Ozgun; Yavuz, Koray; Pavlov, Ihor; Ilday, F. Omer; Gulseren, Oguz

We report a new dynamical self-assembly mechanism, where judicious use of convective and strong Brownian forces enables effective patterning of colloidal nanoparticles that are almost two orders of magnitude smaller than the laser beam. Optical trapping or tweezing effects are not involved, but the laser is used to create steep thermal gradients through multi-photon absorption, and thereby guide the colloids through convective forces. Convective forces can be thought as a positive feedback mechanism that helps to form and reinforce pattern, while Brownian motion act as a competing negative feedback mechanism to limit the growth of the pattern, as well as to increase the possibilities of bifurcation into different patterns, analogous to the competition observed in reaction-diffusion systems. By steering stochastic processes through these forces, we are able to gain control over the emergent pattern such as to form-deform-reform of a pattern, to change its shape and transport it spatially within seconds. This enables us to dynamically initiate and control large patterns comprised of hundreds of colloids. Further, by not relying on any specific chemical, optical or magnetic interaction, this new method is, in principle, completely independent of the material type being assembled.

Chloride (Cl-) ion-mediated shape control of palladium nanoparticles

NASA Astrophysics Data System (ADS)

Nalajala, Naresh; Chakraborty, Arup; Bera, Bapi; Neergat, Manoj

2016-02-01

The shape control of Pd nanoparticles is investigated using chloride (Cl-) ions as capping agents in an aqueous medium in the temperature range of 60-100 °C. With weakly adsorbing and strongly etching Cl- ions, oxygen plays a crucial role in shape control. The experimental factors considered are the concentration of the capping agents, reaction time and reaction atmosphere. Thus, Pd nanoparticles of various shapes with high selectivity can be synthesized. Moreover, the removal of Cl- ions from the nanoparticle surface is easier than that of Br- ions (moderately adsorbing and etching) and I- ions (strongly adsorbing and weakly etching). The cleaned Cl- ion-mediated shape-controlled Pd nanoparticles are electrochemically characterized and the order of the half-wave potential of the oxygen reduction reaction in oxygen-saturated 0.1 M HClO4 solution is of the same order as that observed with single-crystal Pd surfaces.

Experimental and computational study of the effect of 1 atm background gas on nanoparticle generation in femtosecond laser ablation of metals

NASA Astrophysics Data System (ADS)

Wu, Han; Wu, Chengping; Zhang, Nan; Zhu, Xiaonong; Ma, Xiuquan; Zhigilei, Leonid V.

2018-03-01

Laser ablation of metal targets is actively used for generation of chemically clean nanoparticles for a broad range of practical applications. The processes involved in the nanoparticle formation at all relevant spatial and temporal scales are still not fully understood, making the precise control of the size and shape of the nanoparticles challenging. In this paper, a combination of molecular dynamics simulations and experiments is applied to investigate femtosecond laser ablation of aluminum targets in vacuum and in 1 atm argon background gas. The results of the simulations reveal a strong effect of the background gas environment on the initial plume expansion and evolution of the nanoparticle size distribution. The suppression of the generation of small/medium-size Al clusters and formation of a dense layer at the front of the expanding ablation plume, observed during the first nanosecond of the plume expansion in a simulation performed in the gas environment, have important implications on the characteristics of the nanoparticles deposited on a substrate and characterized in the experiments. The nanoparticles deposited in the gas environment are found to be more round-shaped and less flattened as compared to those deposited in vacuum. The nanoparticle size distributions exhibit power-law dependences with similar values of exponents obtained from fitting experimental and simulated data. Taken together, the results of this study suggest that the gas environment may be effectively used to control size and shape of nanoparticles generated by laser ablation.

Calcium-silicate mesoporous nanoparticles loaded with chlorhexidine for both anti- Enterococcus faecalis and mineralization properties.

PubMed

Fan, Wei; Li, Yanyun; Sun, Qing; Ma, Tengjiao; Fan, Bing

2016-10-21

In infected periapical tissues, Enterococcus faecalis is one of the most common dominant bacteria. Chlorhexidine has been proved to show strong antibacterial ability against E. faecalis but is ineffective in promoting mineralization for tissues around root apex. Mesoporous calcium-silicate nanoparticles are newly synthesized biomaterials with excellent ability to promote mineralization and carry-release bioactive molecules in a controlled manner. In this study, mesoporous calcium-silicate nanoparticles were functionalized with chlorhexidine and their releasing profile, antibacterial ability, effect on cell proliferation and in vitro mineralization property were evaluated. The chlorhexidine was successfully incorporated into mesoporous calcium-silicate nanoparticles by a mixing-coupling method. The new material could release chlorhexidine as well as Ca 2+ and SiO 3 2- in a sustained manner with an alkaline pH value under different conditions. The antimicrobial ability against planktonic E. faecalis was dramatically improved after chlorhexidine incorporation. The nanoparticles with chlorhexidine showed no negative effect on cell proliferation with low concentrations. On dentin slices, the new synthesized material demonstrated a similar inhibitory effect on E. faecalis as the chlorhexidine. After being immersed in SBF for 9 days, numerous apatite crystals could be observed on surfaces of the material tablets. Mesoporous calcium-silicate nanoparticles loaded with chlorhexidine exhibited release of ions and chlorhexidine, low cytotoxicity, excellent antibacterial ability and in vitro mineralization. This material could be developed into a new effective intra-canal medication in dentistry or a new bone defect filling material for infected bone defects.

Mechanochemical activation and patterning of an adhesive surface toward nanoparticle deposition.

PubMed

Baytekin, H Tarik; Baytekin, Bilge; Huda, Sabil; Yavuz, Zelal; Grzybowski, Bartosz A

2015-02-11

Mechanical pulling of adhesive tape creates radicals on the tape's surface. These radicals are capable of reducing metal salts to the corresponding metal nanoparticles. In this way, the mechanically activated tape can be decorated with various types of nanoparticles, including Au, Ag, Pd, or Cu. While retaining their mechanical properties and remaining "sticky," the tapes can exhibit new properties derived from the presence of metal nanoparticles (e.g., bacteriostaticity, increased electrical conductivity). They can also be patterned with nanoparticles only at selective locations of mechanical activation.

Photoinduced electron transfer from semiconductor quantum dots to metal oxide nanoparticles

PubMed Central

Tvrdy, Kevin; Frantsuzov, Pavel A.; Kamat, Prashant V.

2011-01-01

Quantum dot-metal oxide junctions are an integral part of next-generation solar cells, light emitting diodes, and nanostructured electronic arrays. Here we present a comprehensive examination of electron transfer at these junctions, using a series of CdSe quantum dot donors (sizes 2.8, 3.3, 4.0, and 4.2 nm in diameter) and metal oxide nanoparticle acceptors (SnO2, TiO2, and ZnO). Apparent electron transfer rate constants showed strong dependence on change in system free energy, exhibiting a sharp rise at small driving forces followed by a modest rise further away from the characteristic reorganization energy. The observed trend mimics the predicted behavior of electron transfer from a single quantum state to a continuum of electron accepting states, such as those present in the conduction band of a metal oxide nanoparticle. In contrast with dye-sensitized metal oxide electron transfer studies, our systems did not exhibit unthermalized hot-electron injection due to relatively large ratios of electron cooling rate to electron transfer rate. To investigate the implications of these findings in photovoltaic cells, quantum dot-metal oxide working electrodes were constructed in an identical fashion to the films used for the electron transfer portion of the study. Interestingly, the films which exhibited the fastest electron transfer rates (SnO2) were not the same as those which showed the highest photocurrent (TiO2). These findings suggest that, in addition to electron transfer at the quantum dot-metal oxide interface, other electron transfer reactions play key roles in the determination of overall device efficiency. PMID:21149685

Biomedical potential of silver nanoparticles synthesized from calli cells of Citrullus colocynthis (L.) Schrad.

PubMed

Satyavani, K; Gurudeeban, S; Ramanathan, T; Balasubramanian, T

2011-09-26

An increasingly common application is the use of silver nanoparticles for antimicrobial coatings, wound dressings, and biomedical devices. In this present investigation, we report, biomedical potential of silver nanopaticles synthesized from calli extract of Citrullus colocynthis on Human epidermoid larynx carcinoma (HEp -2) cell line. The callus extract react with silver nitrate solution confirmed silver nanoparticles synthesis through the steady change of greenish colour to reddish brown and characterized by using FT-IR, AFM. Toxicity on HEp 2 cell line assessed using MTT assay, caspase -3 assay, Lactate dehydrogenase leakage assay and DNA fragmentation assay. The synthesized silver nanoparticles were generally found to be spherical in shape with size 31 nm by AFM. The molar concentration of the silver nanoparticles solution in our present study is 1100 nM/10 mL. The results exhibit that silver nanoparticles mediate a dose-dependent toxicity for the cell tested, and the silver nanoparticles at 500 nM decreased the viability of HEp 2 cells to 50% of the initial level. LDH activities found to be significantly elevated after 48 h of exposure in the medium containing silver nanoparticles when compared to the control and Caspase 3 activation suggested that silver nanoparticles caused cell death through apoptosis, which was further supported by cellular DNA fragmentation, showed that the silver nanoparticles treated HEp2 cells exhibited extensive double strand breaks, thereby yielding a ladder appearance (Lane 2), while the DNA of control HEp2 cells supplemented with 10% serum exhibited minimum breakage (Lane 1). This study revealed completely would eliminate the use of expensive drug for cancer treatment.

Synthesis and characterization of polymer-coated manganese ferrite nanoparticles as controlled drug delivery

NASA Astrophysics Data System (ADS)

Wang, Guangshuo; Zhao, Dexing; Ma, Yingying; Zhang, Zhixiao; Che, Hongwei; Mu, Jingbo; Zhang, Xiaoliang; Zhang, Zheng

2018-01-01

In this study, monodisperse and superparamagnetic manganese ferrite (MnFe2O4) nanoparticles have been synthesized by a one-pot sonochemical method using polyvinylpyrrolidone (PVP) as stabilizer. The as-prepared MnFe2O4 nanoparticles were investigated systematically by TEM, XRD, FTIR, XPS, SQUID and MTT. The TEM observation showed that the PVP-coated MnFe2O4 nanoparticles had uniform dispersion with narrow particle size distribution. The magnetization curves demonstrated superparamagnetic properties of the coated MnFe2O4 nanoparticles with good hydrophilicity at room temperature. The in vitro cytotoxicity experiments exhibited negligible cytotoxicity of the obtained PVP-coated MnFe2O4 nanoparticles even at the high concentration of 150 μg/mL after 24 h treatment. More importantly, anti-cancer model drug of doxorubicin hydrochloride (DOX) was loaded on the surface of MnFe2O4 nanoparticles. The drug loading capacity of the developed nanocarrier reached 0.45 mg/mg and the loaded DOX exhibited interesting pH-dependent release behavior. In conclusion, the as-prepared PVP-coated MnFe2O4 nanoparticles were proposed as a potential candidate for controlled drug delivery.

Microbial eukaryote plankton communities of high-mountain lakes from three continents exhibit strong biogeographic patterns.

PubMed

Filker, Sabine; Sommaruga, Ruben; Vila, Irma; Stoeck, Thorsten

2016-05-01

Microbial eukaryotes hold a key role in aquatic ecosystem functioning. Yet, their diversity in freshwater lakes, particularly in high-mountain lakes, is relatively unknown compared with the marine environment. Low nutrient availability, low water temperature and high ultraviolet radiation make most high-mountain lakes extremely challenging habitats for life and require specific molecular and physiological adaptations. We therefore expected that these ecosystems support a plankton diversity that differs notably from other freshwater lakes. In addition, we hypothesized that the communities under study exhibit geographic structuring. Our rationale was that geographic dispersal of small-sized eukaryotes in high-mountain lakes over continental distances seems difficult. We analysed hypervariable V4 fragments of the SSU rRNA gene to compare the genetic microbial eukaryote diversity in high-mountain lakes located in the European Alps, the Chilean Altiplano and the Ethiopian Bale Mountains. Microbial eukaryotes were not globally distributed corroborating patterns found for bacteria, multicellular animals and plants. Instead, the plankton community composition emerged as a highly specific fingerprint of a geographic region even on higher taxonomic levels. The intraregional heterogeneity of the investigated lakes was mirrored in shifts in microbial eukaryote community structure, which, however, was much less pronounced compared with interregional beta-diversity. Statistical analyses revealed that on a regional scale, environmental factors are strong predictors for plankton community structures in high-mountain lakes. While on long-distance scales (>10 000 km), isolation by distance is the most plausible scenario, on intermediate scales (up to 6000 km), both contemporary environmental factors and historical contingencies interact to shift plankton community structures. © 2016 John Wiley & Sons Ltd.

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.

Size dependence of magneto-optical activity in silver nanoparticles with dimensions between 10 and 60 nm studied by MCD spectroscopy.

PubMed

Shiratsu, Taisuke; Yao, Hiroshi

2018-02-07

Size-dependent magneto-optical activity in Ag nanoparticles with dimensions from 10 to 60 nm is demonstrated with magnetic circular dichroism (MCD) spectroscopy. The Ag nanoparticles are prepared on the basis of a seeded-growth strategy using sodium citrate and/or tannic acid as reducing agents in aqueous solution. The obtained nanoparticles are roughly spherical, but those larger than ∼28 nm have a slight diversity of shapes with quasi-spherical polyhedrons. They exhibit a derivative-like MCD response in the localized surface plasmon resonance (LSPR) region, which originates from two circular modes of surface magnetoplasmons. With an increase in the nanoparticle diameter, the bisignated MCD signal is strongly distorted and weakened. Such a distortion for large-sized Ag nanoparticles can be phenomenologically simulated on the basis of both spectral inhomogeneity and MCD signal lobe asymmetry. Then the maximum value of MCD amplitude (MCD max ), which is obtained by normalization of the amplitude to the LSPR peak absorbance, first increases with increasing particle diameter and then decreases with a maximum for the 23 nm nanoparticle. Interestingly, the MCD max values are inversely correlated with the spectral bandwidth of LSPR extinction. This behaviour is discussed from a viewpoint of inhomogeneous effects of both spectral and size/shape distributions. We believe the present results will advance the design and application of optical devices based on magnetoplasmonics.

Dry powder inhaler formulation of lipid-polymer hybrid nanoparticles via electrostatically-driven nanoparticle assembly onto microscale carrier particles.

PubMed

Yang, Yue; Cheow, Wean Sin; Hadinoto, Kunn

2012-09-15

Lipid-polymer hybrid nanoparticles have emerged as promising nanoscale carriers of therapeutics as they combine the attractive characteristics of liposomes and polymers. Herein we develop dry powder inhaler (DPI) formulation of hybrid nanoparticles composed of poly(lactic-co-glycolic acid) and soybean lecithin as the polymer and lipid constituents, respectively. The hybrid nanoparticles are transformed into inhalable microscale nanocomposite structures by a novel technique based on electrostatically-driven adsorption of nanoparticles onto polysaccharide carrier particles, which eliminates the drawbacks of conventional techniques based on controlled drying (e.g. nanoparticle-specific formulation, low yield). First, we engineer polysaccharide carrier particles made up of chitosan cross-linked with tripolyphosphate and dextran sulphate to exhibit the desired aerosolization characteristics and physical robustness. Second, we investigate the effects of nanoparticle to carrier mass ratio and salt inclusion on the adsorption efficiency, in terms of the nanoparticle loading and yield, from which the optimal formulation is determined. Desorption of the nanoparticles from the carrier particles in phosphate buffer saline is also examined. Lastly, we characterize aerosolization efficiency of the nanocomposite product in vitro, where the emitted dose and respirable fraction are found to be comparable to the values of conventional DPI formulations. Copyright © 2012 Elsevier B.V. All rights reserved.

Optical properties and antimicrobial effects of silver nanoparticles synthesized by femtosecond laser photoreduction

NASA Astrophysics Data System (ADS)

dos Santos Courrol, Daniella; Regina Borges Lopes, Carla; da Silva Cordeiro, Thiago; Regina Franzolin, Marcia; Dias Vieira Junior, Nilson; Elgul Samad, Ricardo; Coronato Courrol, Lilia

2018-07-01

Silver nanoparticles exhibit a powerful antimicrobial action showing a pronounced potential to be widely used against drug resistance bacteria. The present work describes the optical properties and antimicrobial effect of silver nanoparticles produced by femtosecond laser photoreduction of AgNO3 in the presence of tryptophan water solution. The advantages of this method are the absence of hazardous chemical reducing agents in the solution, and the versatile dimensional control achieved. The synthesized silver nanoparticles were characterized by absorption and fluorescence spectroscopy and their antibacterial activity were determined by monitoring the cell viability of Escherichia coli. The effects of the silver nanoparticles concentration and laser parameters (exposure time and pulse energy), on the formation of the nanoparticles, and its influence on the bacteria growth inhibition were studied. The prepared silver nanoparticles exhibited suitable antimicrobial properties. The results demonstrated that the nanoparticles concentration plays an important role in their bactericidal efficacy. The increase in the laser energy caused an increase in E. coli growth inhibition. Irradiations with energies around 300 μJ for 60 min presented high antimicrobial activity due to the presence of kynurenine, sub product of tryptophan photolysis. The first-time formation mechanism of tryptophan silver nanoparticles in high optical intensities was also discussed.

Modeling of DNA-Mediated Self-Assembly from Anisotropic Nanoparticles: A Molecular Dynamics Study

NASA Astrophysics Data System (ADS)

Millan, Jaime; Girard, Martin; Brodin, Jeffrey; O'Brien, Matt; Mirkin, Chad; Olvera de La Cruz, Monica

The programmable selectivity of DNA recognition constitutes an elegant scheme to self-assemble a rich variety of superlattices from versatile nanoscale building blocks, where the natural interactions between building blocks are traded by complementary DNA hybridization interactions. Recently, we introduced and validated a scale-accurate coarse-grained model for a molecular dynamics approach that captures the dynamic nature of DNA hybridization events and reproduces the experimentally-observed crystallization behavior of various mixtures of spherical DNA-modified nanoparticles. Here, we have extended this model to robustly reproduce the assembly of nanoparticles with the anisotropic shapes observed experimentally. In particular, we are interested in two different particle types: (i) regular shapes, namely the cubic and octahedral polyhedra shapes commonly observed in gold nanoparticles, and (ii) irregular shapes akin to those exhibited by enzymes. Anisotropy in shape can provide an analog to the atomic orbitals exhibited by conventional atomic crystals. We present results for the assembly of enzymes or anisotropic nanoparticles and the co-assembly of enzymes and nanoparticles.

Multidentate zwitterionic chitosan oligosaccharide modified gold nanoparticles: stability, biocompatibility and cell interactions

NASA Astrophysics Data System (ADS)

Liu, Xiangsheng; Huang, Haoyuan; Liu, Gongyan; Zhou, Wenbo; Chen, Yangjun; Jin, Qiao; Ji, Jian

2013-04-01

Surface engineering of nanoparticles plays an essential role in their colloidal stability, biocompatibility and interaction with biosystems. In this study, a novel multidentate zwitterionic biopolymer derivative is obtained from conjugating dithiolane lipoic acid and zwitterionic acryloyloxyethyl phosphorylcholine to the chitosan oligosaccharide backbone. Gold nanoparticles (AuNPs) modified by this polymer exhibit remarkable colloidal stabilities under extreme conditions including high salt conditions, wide pH range and serum or plasma containing media. The AuNPs also show strong resistance to competition from dithiothreitol (as high as 1.5 M). Moreover, the modified AuNPs demonstrate low cytotoxicity investigated by both MTT and LDH assays, and good hemocompatibility evaluated by hemolysis of human red blood cells. In addition, the intracellular fate of AuNPs was investigated by ICP-MS and TEM. It showed that the AuNPs are uptaken by cells in a concentration dependent manner, and they can escape from endosomes/lysosomes to cytosol and tend to accumulate around the nucleus after 24 h incubation but few of them are excreted out of the cells. Gold nanorods are also stabilized by this ligand, which demonstrates robust dispersion stability and excellent hemocompatibility. This kind of multidentate zwitterionic chitosan derivative could be widely used for stabilizing other inorganic nanoparticles, which will greatly improve their performance in a variety of bio-related applications.Surface engineering of nanoparticles plays an essential role in their colloidal stability, biocompatibility and interaction with biosystems. In this study, a novel multidentate zwitterionic biopolymer derivative is obtained from conjugating dithiolane lipoic acid and zwitterionic acryloyloxyethyl phosphorylcholine to the chitosan oligosaccharide backbone. Gold nanoparticles (AuNPs) modified by this polymer exhibit remarkable colloidal stabilities under extreme conditions including high salt

Mycosynthesis of silver nanoparticles using Lingzhi or Reishi medicinal mushroom, Ganoderma lucidum (W. Curt.:Fr.) P. Karst. and their role as antimicrobials and antibiotic activity enhancers.

PubMed

Karwa, A; Gaikwad, Swapnil; Rai, Mahendra K

2011-01-01

Lingzhi or Reishi medicinal mushroom, Ganoderma lucidum, has been used over the ages as highly medicinal herb in the Orient. Many useful properties of this fungus are still being studied; we report here a new facet of this "elixir of life" as a mycosource for synthesis of metal nanoparticles. Treating the extracellular suspension filtrate of the mycelia of G. lucidum with silver nitrate reduces the metal ions to nanoparticles. Optical detection followed by confirmation through spectroscopic analysis suggests that this fungus can be used for the purpose of safe and sure synthesis of silver nanoparticles, demand for which is growing day by day in all fields of human life. LM-20 analysis of these G. lucidum-synthesised nanoparticles reveals the polydispersity and distribution of silver nanoparticles in the range of 10-70 nm with an average size of 45 nm and a concentration of 0.37 x 108 particles/mL. FT-IR spectrum confirms the stability of these nanoparticles due to presence of amide linkages and protein capping. These nanoparticles have shown strong bactericidal activity against test pathogens Staphylococcus aureus and Escherichia coli, and also exhibited their efficiency in enhancing the activity of the synthetic antibiotic tetracycline. The method of synthesising silver nanoparticles and its bactericidal effect discussed here can be used for environment-friendly and economically feasible production for different applications where chemically synthesized nanoparticles cause undesirable effects.

Malva parviflora extract assisted green synthesis of silver nanoparticles

NASA Astrophysics Data System (ADS)

Zayed, Mervat F.; Eisa, Wael H.; Shabaka, A. A.

2012-12-01

Five plant leaf extracts (Malva parviflora, Beta vulgaris subsp. Vulgaris, Anethum graveolens, Allium kurrat and Capsicum frutescens) were screened for their bioreduction behavior for synthesis of silver nanoparticles. M. parviflora (Malvaceae) was found to exhibit the best reducing and protecting action in terms of synthesis rate and monodispersity of the prepared silver nanoparticles. Our measurements indicate that biosynthesis of Ag nanoparticles by M. parviflora produces Ag nanoparticles with the diameters in the range of 19-25 nm. XRD studies reveal a high degree of crystallinity and monophasic Ag nanoparticles of face-centered cubic structure. FTIR analysis proved that particles are reduced and stabilized in solution by the capping agent that is likely to be proteins secreted by the biomass. The present process is an excellent candidate for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive.

Preparation of folate-modified pullulan acetate nanoparticles for tumor-targeted drug delivery.

PubMed

Zhang, Hui-zhu; Li, Xue-min; Gao, Fu-ping; Liu, Ling-rong; Zhou, Zhi-min; Zhang, Qi-qing

2010-01-01

The purpose of this work was to develop a novel nano-carrier with targeting property to tumor. In this study, pullulan acetate (PA) was synthesized by the acetylation of pullulan to simplify the preparation technique of nanoparticles. Folic acid (FA) was conjugated to PA in order to improve the cancer-targeting activity. The products were characterized by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Epirubicin-loaded nanoparticles were prepared by a solvent diffusion method. The loading efficiencies and EPI content increased with the amount of triethylamine (TEA) increasing in some degree. FPA nanoparticles could incorporate more epirubicin than PA nanoparticles. The folate-modified PA nanoparticles (FPA/EPI NPs) exhibited faster drug release than PA nanoparticles (PA/EPI NPs) in vitro. Confocal image analysis and flow cytometry test revealed that FPA/EPI NPs exhibited a greater extent of cellular uptake than PA/EPI NPs against KB cells over-expressing folate receptors on the surface. FPA/EPI NPs also showed higher cytotoxicity than PA/EPI NPs. The cytotoxic effect of FPA/EPI NPs to KB cells was inhibited by an excess amount of folic acid, suggesting that the binding and/or uptake were mediated by the folate receptor.

Fabrication and Cytotoxicity of Fucoidan-Cisplatin Nanoparticles for Macrophage and Tumor Cells.

PubMed

Hwang, Pai-An; Lin, Xiao-Zhen; Kuo, Ko-Liang; Hsu, Fu-Yin

2017-03-14

Fucoidan, an anionic, sulfated polysaccharide from brown seaweed, is known to exhibit antitumor and immunomodulatory functions. To develop an immune protection and chemotherapeutic agent, fucoidan-cisplatin nanoparticles (FCNPs) were designed. FCNPs were prepared by mixing cisplatin with fucoidan solution or fucoidan with cisplatin solution, followed by dialysis to remove trace elements. The nanoparticles, comprising 10 mg of fucoidan and 2 mg of cisplatin, which exhibited the highest cisplatin content and loading efficiency during the production process, were named as Fu100Cis20. The cisplatin content, cisplatin loading efficiency, nanoparticle size, and zeta potential of Fu100Cis20 were 18.9% ± 2.7%, 93.3% ± 7.8%, 181.2 ± 21.0 nm, and -67.4 ± 2.3 mV, respectively. Immune protection assay revealed that Fu100Cis20-treated RAW264.7 cells were protected from the cytotoxicity of cisplatin. Furthermore, antitumor assay indicated that Fu100Cis20-treated HCT-8 cells showed stronger cytotoxicity than those treated with cisplatin alone. These results suggested that fucoidan-based nanoparticles exhibited suitable particle size and high drug encapsulation, and that Fu100Cis20 has potential application in both immunotherapy and chemotherapy.

Multi-functional Magnetic Nanoparticles for Magnetic Resonance Imaging and Cancer Therapy

PubMed Central

Yallapu, Murali M.; Othman, Shadi F.; Curtis, Evan T.; Gupta, Brij K.; Jaggi, Meena; Chauhan, Subhash C.

2010-01-01

We have developed a multi-layer approach for the synthesis of water-dispersible superparamagnetic iron oxide nanoparticles for hyperthermia, magnetic resonance imaging (MRI) and drug delivery applications. In this approach, iron oxide core nanoparticles were obtained by precipitation of iron salts in the presence of ammonia and provided β-cyclodextrin and pluronic polymer (F127) coatings. This formulation (F127250) was highly water dispersible which allowed encapsulation of the anti-cancer drug(s) in β-cyclodextrin and pluronic polymer for sustained drug release. The F127250 formulation has exhibited superior hyperthermia effects over time under alternating magnetic field compared to pure magnetic nanoparticles (MNP) and β-cyclodextrin coated nanoparticles (CD200). Additionally, the improved MRI characteristics were also observed for the F127250 formulation in agar gel and in cisplatin resistant ovarian cancer cells (A12780CP) compared to MNP and CD200 formulations. Furthermore, the drug loaded formulation of F127250 exhibited many folds of imaging contrast properties. Due to the internalization capacity of the F127250 formulation, its curcumin loaded formulation (F127250-CUR) exhibited almost equivalent inhibition effects on A2780CP (ovarian), MDA-MB-231 (breast), and PC3 (prostate) cancer cells even though curcumin release was only 40%. The improved therapeutic effects were verified by examining molecular effects using Western blotting and transmission electron microscopic (TEM) studies. F127250-CUR also exhibited haemocompatibility, suggesting a nanochemo-therapuetic agent for cancer therapy. PMID:21167595

Multi-functional magnetic nanoparticles for magnetic resonance imaging and cancer therapy.

PubMed

Yallapu, Murali M; Othman, Shadi F; Curtis, Evan T; Gupta, Brij K; Jaggi, Meena; Chauhan, Subhash C

2011-03-01

We have developed a multi-layer approach for the synthesis of water-dispersible superparamagnetic iron oxide nanoparticles for hyperthermia, magnetic resonance imaging (MRI) and drug delivery applications. In this approach, iron oxide core nanoparticles were obtained by precipitation of iron salts in the presence of ammonia and provided β-cyclodextrin and pluronic polymer (F127) coatings. This formulation (F127250) was highly water dispersible which allowed encapsulation of the anti-cancer drug(s) in β-cyclodextrin and pluronic polymer for sustained drug release. The F127250 formulation has exhibited superior hyperthermia effects over time under alternating magnetic field compared to pure magnetic nanoparticles (MNP) and β-cyclodextrin coated nanoparticles (CD200). Additionally, the improved MRI characteristics were also observed for the F127250 formulation in agar gel and in cisplatin resistant ovarian cancer cells (A12780CP) compared to MNP and CD200 formulations. Furthermore, the drug-loaded formulation of F127250 exhibited many folds of imaging contrast properties. Due to the internalization capacity of the F127250 formulation, its curcumin-loaded formulation (F127250-CUR) exhibited almost equivalent inhibition effects on A2780CP (ovarian), MDA-MB-231 (breast), and PC-3 (prostate) cancer cells even though curcumin release was only 40%. The improved therapeutic effects were verified by examining molecular effects using Western blotting and transmission electron microscopic (TEM) studies. F127250-CUR also exhibited haemocompatibility, suggesting a nanochemo-therapeutic agent for cancer therapy. Copyright © 2010 Elsevier Ltd. All rights reserved.

Can disc diffusion susceptibility tests assess the antimicrobial activity of engineered nanoparticles?

NASA Astrophysics Data System (ADS)

Kourmouli, Angeliki; Valenti, Marco; van Rijn, Erwin; Beaumont, Hubertus J. E.; Kalantzi, Olga-Ioanna; Schmidt-Ott, Andreas; Biskos, George

2018-03-01

The use of disc diffusion susceptibility tests to determine the antibacterial activity of engineered nanoparticles (ENPs) is questionable because their low diffusivity practically prevents them from penetrating through the culture media. In this study, we investigate the ability of such a test, namely the Kirby-Bauer disc diffusion test, to determine the antimicrobial activity of Au and Ag ENPs having diameters from 10 to 40 nm on Escherichia coli cultures. As anticipated, the tests did not show any antibacterial effects of Au nanoparticles (NPs) as a result of their negligible diffusivity through the culture media. Ag NPs on the other hand exhibited a strong antimicrobial activity that was independent of their size. Considering that Ag, in contrast to Au, dissolves upon oxidation and dilution in aqueous solutions, the apparent antibacterial behavior of Ag NPs is attributed to the ions they release. The Kirby-Bauer method, and other similar tests, can therefore be employed to probe the antimicrobial activity of ENPs related to their ability to release ions rather than to their unique size-dependent properties. [Figure not available: see fulltext.

Photoluminescence study of Mn doped ZnS nanoparticles prepared by co-precipitation method

NASA Astrophysics Data System (ADS)

Deshpande, M. P.; Patel, Kamakshi; Gujarati, Vivek P.; Chaki, S. H.

2016-05-01

ZnS nanoparticles co-doped with different concentration (5,10,15%) of Mn were synthesized using polyvinylpyrrolidone (PVP) as a capping agent under microwave irradiation. We confirmed doping of Mn in the host ZnS by EDAX whereas powder X-ray diffractogram showed the cubic zinc blende structure of all these samples. TEM images did showed agglomeration of particles and SAED pattern obtained indicated polycrystalline nature. From SAED pattern we calculated lattice parameter of the samples which have close resemblance from that obtained from XRD pattern. The band gap values of pure and doped ZnS nanoparticles were calculated from UV-Visible absorption spectra. ZnS itself is a luminescence material but when we dope it with transition metal ion such as Mn, Co, and Cu they exhibits strong and intense luminescence in the particular region. The photoluminescence spectra of pure ZnS nanoparticles showed an emission at 421 and 485nm which is blue emission which was originated from the defect sites of ZnS itself and also sulfur deficiency and when doped with Mn2+ an extra peak with high intensity was observed at 530nm which is nearly yellow-orange emission which isrelated to the presence of Mn in the host lattice.

Stabilization of antimicrobial silver nanoparticles by a polyhydroxyalkanoate obtained from mixed bacterial culture.

PubMed

Castro-Mayorga, J L; Martínez-Abad, A; Fabra, M J; Olivera, Catarina; Reis, M; Lagarón, J M

2014-11-01

The incorporation of antimicrobials into polymer matrices is a promising technology in the food packaging and biomedical areas. Among the most widely used antimicrobials, silver nanoparticles (AgNPs) have emerged as one of the most researched technologies to prevent microbial outbreaks. However, it is known that AgNPs are rather unstable and present patterns of agglomeration that might limit their application. In this work, AgNPs were produced by chemical reduction in suspensions of an unpurified poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) which was previously obtained from a mixed culture fermentation using a synthetic medium mimicking fermented cheese whey. The synthesis of AgNPs was carried out within the unpurified PHBV suspension (in situ) and by physical mixing (mix). The stability of crystalline and spherical nanoparticles (7±3nm) obtained in situ was found to be stable during at least 40 days. The results suggest that the unpurified PHBV appears to be a very efficient capping agent, preventing agglomeration and, thereby, stabilizing successfully the silver nanoparticles. The in situ obtained AgNP-PHBV materials were also found to exhibit a strong antibacterial activity against Salmonella enterica at low concentration (0.1-1ppm). Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and Characterization of Graphene/ITO Nanoparticle Hybrid Transparent Conducting Electrode

NASA Astrophysics Data System (ADS)

Hemasiri, Bastian Waduge Naveen Harindu; Kim, Jae-Kwan; Lee, Ji-Myon

2018-03-01

The combination of graphene with conductive nanoparticles, forming graphene-nanoparticle hybrid materials, offers a number of excellent properties for advanced engineering applications. A novel and simple method was developed to deposit 10 wt% tin-doped indium tin oxide (ITO) nanoparticles on graphene. The method involved a combination of a solution-based environmentally friendly electroless deposition approach and subsequent vacuum annealing. A stable organic-free solution of ITO was prepared from economical salts of In(NO3) 3 · H2O and SnCl4. The obtained ITO nanostructure exhibited a unique architecture, with uniformly dispersed 25-35 nm size ITO nanoparticles, containing only the crystallized In2O3 phase. The synthesized ITO nanoparticles-graphene hybrid exhibited very good and reproducible optical transparency in the visible range (more than 85%) and a 28.2% improvement in electrical conductivity relative to graphene synthesized by chemical vapor deposition. It was observed that the ITO nanoparticles affect the position of the Raman signal of graphene, in which the D, G, and 2D peaks were redshifted by 5.65, 5.69, and 9.74 cm-1, respectively, and the annealing conditions had no significant effect on the Raman signatures of graphene. [Figure not available: see fulltext.

Effects of para-substituents of styrene derivatives on their chemical reactivity on platinum nanoparticle surfaces

NASA Astrophysics Data System (ADS)

Hu, Peiguang; Chen, Limei; Deming, Christopher P.; Lu, Jia-En; Bonny, Lewis W.; Chen, Shaowei

2016-06-01

Stable platinum nanoparticles were successfully prepared by the self-assembly of para-substituted styrene derivatives onto the platinum surfaces as a result of platinum-catalyzed dehydrogenation and transformation of the vinyl groups to the acetylene ones, forming platinum-vinylidene/-acetylide interfacial bonds. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent aggregation, suggesting sufficient protection of the nanoparticles by the organic capping ligands, and the average core diameter was estimated to be 2.0 +/- 0.3 nm, 1.3 +/- 0.2 nm, and 1.1 +/- 0.2 nm for the nanoparticles capped with 4-tert-butylstyrene, 4-methoxystyrene, and 4-(trifluoromethyl)styrene, respectively, as a result of the decreasing rate of dehydrogenation with the increasing Taft (polar) constant of the para-substituents. Importantly, the resulting nanoparticles exhibited unique photoluminescence, where an increase of the Hammett constant of the para-substituents corresponded to a blue-shift of the photoluminescence emission, suggesting an enlargement of the HOMO-LUMO band gap of the nanoparticle-bound acetylene moieties. Furthermore, the resulting nanoparticles exhibited apparent electrocatalytic activity towards oxygen reduction in acidic media, with the best performance among the series of samples observed with the 4-tert-butylstyrene-capped nanoparticles due to an optimal combination of the nanoparticle core size and ligand effects on the bonding interactions between platinum and oxygen species.Stable platinum nanoparticles were successfully prepared by the self-assembly of para-substituted styrene derivatives onto the platinum surfaces as a result of platinum-catalyzed dehydrogenation and transformation of the vinyl groups to the acetylene ones, forming platinum-vinylidene/-acetylide interfacial bonds. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent

Reflectivity and transmissivity of a cavity coupled to a nanoparticle

NASA Astrophysics Data System (ADS)

Khan, M. A.; Farooq, K.; Hou, S. C.; Niaz, Shanawer; Yi, X. X.

2014-07-01

Any dielectric nanoparticle moving inside an optical cavity generates an optomechanical interaction. In this paper, we theoretically analyze the light scattering of an optomechanical cavity which strongly interacts with a dielectric nanoparticle. The cavity is driven by an external laser field. This interaction gives rise to different dynamics that can be used to cool, trap and levitate nanoparticle. We analytically calculate reflection and transmission rate of the cavity field, and study the time evolution of the intracavity field, momentum and position of the nanoparticle. We find the nanoparticle occupies a discrete position inside the cavity. This effect can be exploited to separate nanoparticle and couplings between classical particles and quantized fields.

Facile synthesis and luminescent properties of TiO{sub 2}:Eu{sup 3+} nanorods and spindle-shaped nanoparticles from titanate nanotubes precursors

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

Li, Hongbo; Sheng, Ye; Zhao, Huan

2012-12-15

Graphical abstract: This picture illustration for the formation process of TiO{sub 2}:Eu{sup 3+} nanorods and spindle-shaped nanoparticles. Display Omitted Highlights: ► TiO{sub 2}:Eu{sup 3+} nanorods and spindle-shaped nanoparticles were prepared. ► The nanotubes could transform to nanorods and spindle-shaped nanoparticles. ► The luminescence properties are dependent on the increases of the bandgap. -- Abstract: TiO{sub 2}:Eu{sup 3+} nanorods and spindle-shaped nanoparticles have been successfully prepared through simple calcination and hydrothermal process respectively using titanate as the precursors. On the basis of X-ray diffraction results, the as-obtained precursors are titanate (H{sub 2}Ti{sub 2}O{sub 5}·H{sub 2}O), while nanorods and spindle-shaped nanoparticles aremore » pure anatase phase of TiO{sub 2}. TEM and SEM images show that the as-formed precursor could be transformed from nanotubes into nanorods and spindle-shaped nanoparticles by the calcination and hydrothermal process respectively. Under UV light excitation, both the TiO{sub 2}:Eu{sup 3+} nanorods and spindle-shaped nanoparticles exhibit the strong red emission. In addition, the luminescence intensity of TiO{sub 2}:Eu{sup 3+} nanorods is higher than that of TiO{sub 2}:Eu{sup 3+} spindle-shaped nanoparticles due to the increases of the bandgap of the TiO{sub 2} nanorods.« less

Kinetics and pathogenesis of intracellular magnetic nanoparticle cytotoxicity

NASA Astrophysics Data System (ADS)

Giustini, Andrew J.; Gottesman, Rachel E.; Petryk, A. A.; Rauwerdink, A. M.; Hoopes, P. Jack

2011-03-01

Magnetic nanoparticles excited by alternating magnetic fields (AMF) have demonstrated effective tumor-specific hyperthermia. This treatment is effective as a monotherapy as well as a therapeutic adjuvant to chemotherapy and radiation. Iron oxide nanoparticles have been shown, so far, to be non-toxic, as are the exciting AMF fields when used at moderate levels. Although higher levels of AMF can be more effective, depending on the type of iron oxide nanoparticles use, these higher field strengths and/or frequencies can induce normal tissue heating and toxicity. Thus, the use of nanoparticles exhibiting significant heating at low AMF strengths and frequencies is desirable. Our preliminary experiments have shown that the aggregation of magnetic nanoparticles within tumor cells improves their heating effect and cytotoxicity per nanoparticle. We have used transmission electron microscopy to track the endocytosis of nanoparticles into tumor cells (both breast adenocarcinoma (MTG-B) and acute monocytic leukemia (THP-1) cells). Our preliminary results suggest that nanoparticles internalized into tumor cells demonstrate greater cytotoxicity when excited with AMF than an equivalent heat dose from excited external nanoparticles or cells exposed to a hot water bath. We have also demonstrated that this increase in SAR caused by aggregation improves the cytotoxicity of nanoparticle hyperthermia therapy in vitro.

Aluminosilicate nanoparticles for catalytic hydrocarbon cracking.

PubMed

Liu, Yu; Pinnavaia, Thomas J

2003-03-05

Aluminosilicate nanoparticles containing 9.0-20 nm mesopores were prepared through the use of protozeolitic nanoclusters as the inorganic precursor and starch as a porogen. The calcined, porogen-free composition containing 2 mol % aluminum exhibited the porosity, hydrothermal stability, and acidity needed for the cracking of very large hydrocarbons. In fact, the hydrothermal stability of the nanoparticles to pure steam at 800 degrees C, along with the cumene cracking activity, surpassed the analogous performance properties of ultrastable Y zeolite, the main catalyst component of commercial cracking catalysts. The remarkable hydrothermal stability and catalytic reactivity of the new nanoparticles are attributable to a unique combination of two factors, the presence of protozeolitic nanoclusters in the pore walls and the unprecedented pore wall thickness (7-15 nm). In addition, the excellent catalytic longevity of the nanoparticles is most likely facilitated by the small domain size of the nanoparticles that greatly improves access to the acid sites on the pore walls and minimizes the diffusion length of coke precursors out of the pores.

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.

Antituberculous effect of silver nanoparticles

NASA Astrophysics Data System (ADS)

Kreytsberg, G. N.; Gracheva, I. E.; Kibrik, B. S.; Golikov, I. V.

2011-04-01

The in vitro experiment, involving 1164 strains of the tuberculosis mycobacteria, exhibited a potentiating effect of silver nanoparticles on known antituberculous preparations in respect of overcoming drug-resistance of the causative agent. The in vitro experiment, based on the model of resistant tuberculosis, was performed on 65 white mice. An evident antituberculous effect of the nanocomposite on the basis of silver nanoparticles and isoniazid was proved. Toxicological assessment of the of nanopreparations was carried out. The performed research scientifically establishes efficacy and safety of the nanocomposite application in combination therapy of patients suffering from drug-resistant tuberculosis.

Spectroscopic studies of nanoparticle-sensitised photorefractive polymers

NASA Astrophysics Data System (ADS)

Aslam, Farzana; Binks, David J.; Daniels, Steve; Pickett, Nigel; O'Brien, Paul

2005-09-01

We report on the absorbance and photoluminescence spectra of photorefractive polymer composites sensitized by three different types of nanoparticles. Each nanoparticle is passivated by 1-hexadecylamine (HDA) and the composites also consist of the charge transporting matrix poly( N-vinylcarbazole) and the dye 1-(2'-ethylhexyloxy)-2,5-dimethyl-4-(4-nitrophenylazo) benzene. A strong spectral feature is observed that is attributed to a complex formed between the dye and HDA; elemental analysis indicates that the formation of this complex is determined by the metal content of the nanoparticle surface. The photoluminescence quantum yield for the complex is greatly reduced when the HDA is attached to the nanoparticle, indicating that a charge transfer occurs.

Enhanced bioavailability of tripterine through lipid nanoparticles using broccoli-derived lipids as a carrier material.

PubMed

Li, Wan; Zhang, Tianpeng; Ye, Yanghuan; Zhang, Xingwang; Wu, Baojian

2015-11-30

Chemotherapy via the oral route remains a considerable challenge due to poor water-solubility and permeability of anticancer agents. This study aimed to construct lipid nanoparticles using broccoli-derived lipids for oral delivery of tripterine (Tri), a natural anticancer candidate, and to enhance its oral bioavailability. Tri-loaded broccoli lipid nanoparticles (Tri-BLNs) were prepared by a solvent-diffusion method. The resulting Tri-BLNs were 75±10 nm in particle size with entrapment efficiency over 98%. In vitro release study indicated that Tri was almost not released from Tri-BLNs (<2%), whereas the lipolytic experiment showed that Tri-BLNs possessed a relatively strong anti-enzymatic degradation ability to Tri-CLNs (Tri-loaded common lipid nanoparticles). In situ single-pass intestinal perfusion manifested that the effective permeability of Tri-BLNs were significantly higher than that of Tri-CLNs. Further, Tri-BLNs exhibited more efficient cellular uptake in MDCK-II cells as evidenced by flow cytometry and confocal microscopy. The relative bioavailability of Tri-BLNs and Tri-CLNs was 494.13% and 281.95% compared with Tri suspensions, respectively. Depending on the ability in enhancement of biomembrane permeability, broccoli-derived lipids as an alternative source should be useful to construct lipid nanoparticles for bettering oral delivery of drugs with low bioavailability. Copyright © 2015 Elsevier B.V. All rights reserved.

Novel platinum–palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities

PubMed Central

Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

2015-01-01

Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum–palladium bimetallic nanoparticles (Pt–PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2–5 nm, while PdNPs and Pt–PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88%±1.73% elemental Pt and 68.96%±1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm−1, attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm−1, associated with C–H stretching, N–H bending in primary amines, N–O stretching in nitro group, and C–C stretch, respectively. Anticancer activity against HeLa cells showed that Pt–PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt–PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals. PMID:26719690

Novel platinum-palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities.

PubMed

Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

2015-01-01

Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum-palladium bimetallic nanoparticles (Pt-PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2-5 nm, while PdNPs and Pt-PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88% ± 1.73% elemental Pt and 68.96% ± 1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm(-1), attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm(-1), associated with C-H stretching, N-H bending in primary amines, N-O stretching in nitro group, and C-C stretch, respectively. Anticancer activity against HeLa cells showed that Pt-PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt-PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals.

Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

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

Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C.S.

We report for the first time a rapid preparation of Zn{sub 1−2x}Co{sub x}Ni{sub x}O nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green–orange–red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemicalmore » experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO. - Graphical abstract: Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: optical and electrochemical properties. Co, Ni co-doped ZnO hexagonal nanoparticles with optical and electrocatalytic properties were successfully prepared for the first time using a microwave hydrothermal method at mild conditions. - Highlights: • Co{sup 2+} and Ni{sup 2+} into ZnO lattice obtained a mild and environmentally friendly process. • The heating method strongly influences in the growth and shape of the particles. • Short-range defects generated by the ions insertion affects the photoluminescence. • Doped ZnO nanoparticles improve the electrocatalytic properties of pure oxide.« less

Improving colorimetric assays through protein enzyme-assisted gold nanoparticle amplification.

PubMed

Xie, Xiaoji; Xu, Wei; Liu, Xiaogang

2012-09-18

The discovery of the DNA-mediated assembly of gold nanoparticles was a great moment in the history of science; this understanding and chemical control enabled the rational design of functional nanomaterials as novel probes in biodetection. In contrast with conventional probes such as organic dyes, gold nanoparticles exhibit high photostability and unique size-dependent optical properties. Because of their high extinction coefficients and strong distance dependent optical properties, these nanoparticles have emerged over the past decade as a promising platform for rapid, highly sensitive colorimetric assays that allow for the visual detection of low concentrations of metal ions, small molecules, and biomacromolecules. These discoveries have deepened our knowledge of biological phenomena and facilitated the development of many new diagnostic and therapeutic tools. Despite these many advances and continued research efforts, current nanoparticle-based colorimetric detection systems still suffer from several drawbacks, such as limited sensitivity and selectivity. This Account describes the recent development of colorimetric assays based on protein enzyme-assisted gold nanoparticle amplification. The benefits of such detection systems include significantly improved detection sensitivity and selectivity. First, we discuss the general design of enzyme-modified nanoparticle systems in colorimetric assays. We show that a quantitative understanding of the unique properties of different enzymes is paramount for effective biological assays. We then examine the assays for nucleic acid detection based on different types of enzymes, including endonucleases, ligases, and polymerases. For each of these assays, we identify the underlying principles that contribute to the enhanced detection capability of nanoparticle systems and illustrate them with selected examples. Furthermore, we demonstrate that the combination of gold nanoparticles and specific enzymes can probe enzyme dynamics

Diffusive dynamics of nanoparticles in ultra-confined media

DOE PAGES

Jacob, Jack Deodato; Conrad, Jacinta; Krishnamoorti, Ramanan; ...

2015-08-10

Differential dynamic microscopy (DDM) was used to investigate the diffusive dynamics of nanoparticles of diameter 200 400 nm that were strongly confined in a periodic square array of cylindrical nanoposts. The minimum distance between posts was 1.3 5 times the diameter of the nanoparticles. The image structure functions obtained from the DDM analysis were isotropic and could be fit by a stretched exponential function. The relaxation time scaled diffusively across the range of wave vectors studied, and the corresponding scalar diffusivities decreased monotonically with increased confinement. The decrease in diffusivity could be described by models for hindered diffusion that accountedmore » for steric restrictions and hydrodynamic interactions. The stretching exponent decreased linearly as the nanoparticles were increasingly confined by the posts. Altogether, these results are consistent with a picture in which strongly confined nanoparticles experience a heterogeneous spatial environment arising from hydrodynamics and volume exclusion on time scales comparable to cage escape, leading to multiple relaxation processes and Fickian but non-Gaussian diffusive dynamics.« less

Optical trapping of metal-dielectric nanoparticle clusters near photonic crystal microcavities.

PubMed

Mejia, Camilo A; Huang, Ningfeng; Povinelli, Michelle L

2012-09-01

We predict the formation of optically trapped, metal-dielectric nanoparticle clusters above photonic crystal microcavities. We determine the conditions on particle size and position for a gold particle to be trapped above the microcavity. We then show that strong field redistribution and enhancement near the trapped gold nanoparticle results in secondary trapping sites for a pair of dielectric nanoparticles.

pH dependent conjugation of Ibuprofen to PEGylated nanoparticles

NASA Astrophysics Data System (ADS)

Bharti, Shivani; Jain, Shikshita; Kaur, Gurvir; Gupta, Shikha; Tripathi, S. K.

2018-04-01

In this paper, Ibuprofen, a water insoluble drug was covalently attached to PEGylated nanoparticles. Firstly, Surface functionalization of water dispersed core/shell nanoparticles had been done using hydrophilic polymer PEG-diamine. Therefore, PEGylated nanoparticles contain NH2 groups over the surface of nanoparticles and can be used for the further attachment of biomolecules. Ibuprofen was covalently loaded on the PEGylated core/shell nanoparticles using carbodiimide reaction. The synthesis had been carried out under two different pH environments, as the solubility of Ibuprofen is pH dependent. The resultant samples were characterized using UV-Vis absorption and FT-IR spectroscopy. The results strongly suggest the successful chemical conjugation of Ibuprofen to PEGylated nanoparticles in aqueous media and they could be further used for drug delivery applications.

Nanoporous TiO2 nanoparticle assemblies with mesoscale morphologies: nano-cabbage versus sea-anemone

NASA Astrophysics Data System (ADS)

Darbandi, Masih; Gebre, Tesfaye; Mitchell, Lucas; Erwin, William; Bardhan, Rizia; Levan, M. Douglas; Mochena, Mogus D.; Dickerson, James H.

2014-05-01

We report the novel synthesis of nanoporous TiO2 nanoparticle ensembles with unique mesoscale morphologies. Constituent nanoparticles evolved into multifaceted assemblies, exhibiting excellent crystallinity and enhanced photocatalytic activity compared with commercial TiO2. Such materials could be exploited for applications, like organic pollutant degradation.We report the novel synthesis of nanoporous TiO2 nanoparticle ensembles with unique mesoscale morphologies. Constituent nanoparticles evolved into multifaceted assemblies, exhibiting excellent crystallinity and enhanced photocatalytic activity compared with commercial TiO2. Such materials could be exploited for applications, like organic pollutant degradation. Electronic supplementary information (ESI) available: Synthesis and characterization procedures, TEM/XRD of samples prepared at different temperature and water content, table of nitrogen adsorption-desorption values of different samples. See DOI: 10.1039/c3nr06154j

Magnetite pollution nanoparticles in the human brain

NASA Astrophysics Data System (ADS)

Maher, Barbara A.; Ahmed, Imad A. M.; Karloukovski, Vassil; MacLaren, Donald A.; Foulds, Penelope G.; Allsop, David; Mann, David M. A.; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

2016-09-01

Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <˜200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

Magnetite pollution nanoparticles in the human brain.

PubMed

Maher, Barbara A; Ahmed, Imad A M; Karloukovski, Vassil; MacLaren, Donald A; Foulds, Penelope G; Allsop, David; Mann, David M A; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

2016-09-27

Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

Magnetite pollution nanoparticles in the human brain

PubMed Central

Maher, Barbara A.; Karloukovski, Vassil; MacLaren, Donald A.; Foulds, Penelope G.; Allsop, David; Mann, David M. A.; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

2016-01-01

Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683–7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health. PMID:27601646

Extracellular facile biosynthesis, characterization and stability of gold nanoparticles by Bacillus licheniformis.

PubMed

Singh, Sneha; Vidyarthi, Ambarish Sharan; Nigam, Vinod Kumar; Dev, Abhimanyu

2014-02-01

The development of a reliable, eco-friendly process for synthesis of gold nanoparticles (AuNPs) has gained impetus in recent years to counter the drawbacks of chemical and physical methods. This study illustrates simple, green synthesis of AuNPs in vitro using cell lysate supernatant (CLS) of non-pathogenic bacteria and to investigate its potential antimicrobial activity. Gold nanoparticles were synthesized by the reduction of precursor AuCl4- ions using the CLS of Bacillus licheniformis at 37°C upon 24 h of incubation. The nanoparticles were characterized for their morphology, particle size, optical absorption, zeta potential, and stability. Further the antimicrobial activity was assayed using cup-plate method. The process of biosynthesis was extracellular and the gold ions were reduced to stable nanogold of average size 38 nm. However, upon storage of AuNPs for longer duration at room temperature stability was influenced in terms of increase in particle size and decrease in zeta potential with respect to as synthesized nanoparticles. SEM micrographs revealed the spherical shape of AuNPs and EDX analysis confirmed the presence of gold in the sample. Also clear zone of inhibition was observed against Bacilllus subtilis MTCC 8364, Pseudomonas aeruginosa MTCC 7925, and Escherichia coli MTCC 1698 confirming the antimicrobial activity of AuNPs. The bioprocess under study was simple and less time consuming as compared to other methods as the need for harvesting AuNPs from within the microbial cells via downstream process will be eliminated. Nanoparticles exhibited good stability even in absence of external stabilizing agents. AuNPs showed good antimicrobial activity against several Gram-negative and Gram-positive pathogenic bacteria. The extracellular biosynthesis from CLS may serve as a suitable alternative for large scale synthesis of gold nanoparticles in vitro. The synthesis from lysed bacterial cell strongly suggests that exposure of microbial whole cells to the

Labeling of HeLa cells using ZrO2:Yb3+-Er3+ nanoparticles with upconversion emission

NASA Astrophysics Data System (ADS)

Ceja-Fdez, Andrea; López-Luke, Tzarara; Oliva, Jorge; Vivero-Escoto, Juan; Gonzalez-Yebra, Ana Lilia; Rojas, Ruben A. Rodriguez; Martínez-Pérez, Andrea; de la Rosa, Elder

2015-04-01

This work reports the synthesis, structural characterization, and optical properties of ZrO2:Yb3+-Er3+ (2-1 mol%) nanocrystals. The nanoparticles were coated with 3-aminopropyl triethoxysilane (APTES) and further modified with biomolecules, such as Biotin-Anti-rabbit (mouse IgG) and rabbit antibody-AntiKi-67, through a conjugation method. The conjugation was successfully confirmed by Fourier transform infrared, zeta potential, and dynamic light scattering. The internalization of the conjugated nanoparticles in human cervical cancer (HeLa) cells was followed by two-photon confocal microscopy. The ZrO2:Yb3+-Er3+ nanocrystals exhibited strong red emission under 970-nm excitation. Moreover, the luminescence change due to the addition of APTES molecules and biomolecules on the nanocrystals was also studied. These results demonstrate that ZrO2:Yb3+-Er3+ nanocrystals can be successfully functionalized with biomolecules to develop platforms for biolabeling and bioimaging.

Morphology Tuning of Strontium Tungstate Nanoparticles

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

Joseph, S.; George, T.; George, K. C.

2007-08-22

Strontium tungstate nanocrystals in two different morphologies are successfully synthesized by controlled precipitation in aqueous and in poly vinyl alcohol (PVA) medium. Structural characterizations are carried out by XRD and SEM. The average particle size calculated for the SrWO4 prepared in the two different solvents ranges 20-24 nm. The SEM pictures show that the surface morphologies of the SrWO4 nanoparticles in aqueous medium resemble mushroom and the SrWO4 nanoparticles in PVA medium resemble cauliflower. Investigations on the room temperature luminescent properties of the strontium tungstate nanoparticles prepared in aqueous and PVA medium shows strong emissions around 425 nm.

Citrate- and Succinate-Modified Carbonate Apatite Nanoparticles with Loaded Doxorubicin Exhibit Potent Anticancer Activity against Breast Cancer Cells

PubMed Central

Mehbuba Hossain, Sultana; Chowdhury, Ezharul Hoque

2018-01-01

Biodegradable inorganic apatite-based particle complex is popular for its pH-sensitivity at the endosomal acidic environment to facilitate drug release following cellular uptake. Despite being a powerful anticancer drug, doxorubicin shows severe off-target effects and therefore would need a carrier for the highest effectiveness. We aimed to chemically modify carbonate apatite (CA) with Krebs cycle intermediates, such as citrate and succinate in order to control the growth of the resultant particles to more efficiently carry and transport the anticancer drug into the cancer cells. Citrate- or succinate-modified CA particles were synthesized with different concentrations of sodium citrate or sodium succinate, respectively, in the absence or presence of doxorubicin. The drug loading efficiency of the particles and their cellular uptake were observed by quantifying fluorescence intensity. The average diameter and surface charge of the particles were determined using Zetasizer. Cell viability was assessed by MTT assay. Citrate-modified carbonate apatite (CMCA) exhibited the highest (31.38%) binding affinity for doxorubicin and promoted rapid cellular uptake of the drug, leading to the half-maximal inhibitory concentration 1000 times less than that of the free drug in MCF-7 cells. Hence, CMCA nanoparticles with greater surface area enhance cytotoxicity in different breast cancer cells by enabling higher loading and more efficient cellular uptake of the drug. PMID:29534497

Effect of Nanoparticle Core Size on Polymer-Coated Gold Nanoparticle Location in Block Copolymers

NASA Astrophysics Data System (ADS)

Petrie, J. D.; Fredrickson, G. H.; Kramer, E. J.

2009-03-01

Gold nanoparticles modified by short chain polymer thiols [Au-PS] can be designed to strongly localize either in the PS domains of a polystyrene-b-poly(2-vinylpyridine) [PS-PVP] block copolymer or at the interface. The P2VP block has a stronger attractive interaction with bare gold than the PS block. Thus, when the areal chain density σ of end-attached PS chains falls below a critical areal chain density σc the Au-PS nanoparticles adsorb to the PS-b-P2VP interface. The effect of the polymer ligand molecular weight on the σc has been shown to scale as σc˜ ((R + Rg)/(R*Rg))̂2, where R is the curvature of the Au nanoparticle core radius. To test this scaling relation for σc further we are synthesizing gold nanoparticles with different core radii and will present preliminary results on σc as a function of R.

From tunable core-shell nanoparticles to plasmonic drawbridges: Active control of nanoparticle optical properties

PubMed Central

Byers, Chad P.; Zhang, Hui; Swearer, Dayne F.; Yorulmaz, Mustafa; Hoener, Benjamin S.; Huang, Da; Hoggard, Anneli; Chang, Wei-Shun; Mulvaney, Paul; Ringe, Emilie; Halas, Naomi J.; Nordlander, Peter; Link, Stephan; Landes, Christy F.

2015-01-01

The optical properties of metallic nanoparticles are highly sensitive to interparticle distance, giving rise to dramatic but frequently irreversible color changes. By electrochemical modification of individual nanoparticles and nanoparticle pairs, we induced equally dramatic, yet reversible, changes in their optical properties. We achieved plasmon tuning by oxidation-reduction chemistry of Ag-AgCl shells on the surfaces of both individual and strongly coupled Au nanoparticle pairs, resulting in extreme but reversible changes in scattering line shape. We demonstrated reversible formation of the charge transfer plasmon mode by switching between capacitive and conductive electronic coupling mechanisms. Dynamic single-particle spectroelectrochemistry also gave an insight into the reaction kinetics and evolution of the charge transfer plasmon mode in an electrochemically tunable structure. Our study represents a highly useful approach to the precise tuning of the morphology of narrow interparticle gaps and will be of value for controlling and activating a range of properties such as extreme plasmon modulation, nanoscopic plasmon switching, and subnanometer tunable gap applications. PMID:26665175

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

Phase behavior and orientational ordering in block copolymers doped with anisotropic nanoparticles

NASA Astrophysics Data System (ADS)

Osipov, M. A.; Gorkunov, M. V.; Berezkin, A. V.; Kudryavtsev, Y. V.

2018-04-01

A molecular field theory and coarse-grained computer simulations with dissipative particle dynamics have been used to study the spontaneous orientational ordering of anisotropic nanoparticles in the lamellar and hexagonal phases of diblock copolymers and the effect of nanoparticles on the phase behavior of these systems. Both the molecular theory and computer simulations indicate that strongly anisotropic nanoparticles are ordered orientationally mainly in the boundary region between the domains and the nematic order parameter possesses opposite signs in adjacent domains. The orientational order is induced by the boundary and by the interaction between nanoparticles and the monomer units in different domains. In simulations, sufficiently long and strongly selective nanoparticles are ordered also inside the domains. The nematic order parameter and local concentration profiles of nanoparticles have been calculated numerically using the model of a nanoparticle with two interaction centers and also determined using the results of computer simulations. A number of phase diagrams have been obtained which illustrate the effect of nanoparticle selectivity and molar fraction of the stability ranges of various phases. Different morphologies have been identified by analyzing the static structure factor and a phase diagram has been constructed in coordinates' nanoparticle concentration-copolymer composition. Orientational ordering of even a small fraction of nanoparticles may result in a significant increase of the dielectric anisotropy of a polymer nanocomposite, which is important for various applications.

Diatomite silica nanoparticles for drug delivery

NASA Astrophysics Data System (ADS)

Ruggiero, Immacolata; Terracciano, Monica; Martucci, Nicola M.; De Stefano, Luca; Migliaccio, Nunzia; Tatè, Rosarita; Rendina, Ivo; Arcari, Paolo; Lamberti, Annalisa; Rea, Ilaria

2014-07-01

Diatomite is a natural fossil material of sedimentary origin, constituted by fragments of diatom siliceous skeletons. In this preliminary work, the properties of diatomite nanoparticles as potential system for the delivery of drugs in cancer cells were exploited. A purification procedure, based on thermal treatments in strong acid solutions, was used to remove inorganic and organic impurities from diatomite and to make them a safe material for medical applications. The micrometric diatomite powder was reduced in nanoparticles by mechanical crushing, sonication, and filtering. Morphological analysis performed by dynamic light scattering and transmission electron microscopy reveals a particles size included between 100 and 300 nm. Diatomite nanoparticles were functionalized by 3-aminopropyltriethoxysilane and labeled by tetramethylrhodamine isothiocyanate. Different concentrations of chemically modified nanoparticles were incubated with cancer cells and confocal microscopy was performed. Imaging analysis showed an efficient cellular uptake and homogeneous distribution of nanoparticles in cytoplasm and nucleus, thus suggesting their potentiality as nanocarriers for drug delivery.

Diatomite silica nanoparticles for drug delivery.

PubMed

Ruggiero, Immacolata; Terracciano, Monica; Martucci, Nicola M; De Stefano, Luca; Migliaccio, Nunzia; Tatè, Rosarita; Rendina, Ivo; Arcari, Paolo; Lamberti, Annalisa; Rea, Ilaria

2014-01-01

Diatomite is a natural fossil material of sedimentary origin, constituted by fragments of diatom siliceous skeletons. In this preliminary work, the properties of diatomite nanoparticles as potential system for the delivery of drugs in cancer cells were exploited. A purification procedure, based on thermal treatments in strong acid solutions, was used to remove inorganic and organic impurities from diatomite and to make them a safe material for medical applications. The micrometric diatomite powder was reduced in nanoparticles by mechanical crushing, sonication, and filtering. Morphological analysis performed by dynamic light scattering and transmission electron microscopy reveals a particles size included between 100 and 300 nm. Diatomite nanoparticles were functionalized by 3-aminopropyltriethoxysilane and labeled by tetramethylrhodamine isothiocyanate. Different concentrations of chemically modified nanoparticles were incubated with cancer cells and confocal microscopy was performed. Imaging analysis showed an efficient cellular uptake and homogeneous distribution of nanoparticles in cytoplasm and nucleus, thus suggesting their potentiality as nanocarriers for drug delivery. 87.85.J81.05.Rm; 61.46. + w.

Selenium nanoparticles inhibit Staphylococcus aureus growth

PubMed Central

Tran, Phong A; Webster, Thomas J

2011-01-01

Staphylococcus aureus is a key bacterium commonly found in numerous infections. S. aureus infections are difficult to treat due to their biofilm formation and documented antibiotic resistance. While selenium has been used for a wide range of applications including anticancer applications, the effects of selenium nanoparticles on microorganisms remain largely unknown to date. The objective of this in vitro study was thus to examine the growth of S. aureus in the presence of selenium nanoparticles. Results of this study provided the first evidence of strongly inhibited growth of S. aureus in the presence of selenium nanoparticles after 3, 4, and 5 hours at 7.8, 15.5, and 31 μg/mL. The percentage of live bacteria also decreased in the presence of selenium nanoparticles. Therefore, this study suggests that selenium nanoparticles may be used to effectively prevent and treat S. aureus infections and thus should be further studied for such applications. PMID:21845045

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

Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa are the etiological agents of several infectious diseases. Antibiotic resistance by these three microbes has emerged as a prevalent problem due in part to the misuse of existing antibiotics and the lack of novel antibiotics. Nanoparticles have emerged as an alternative antibacterial agents to conventional antibiotics owing to their high surface area to volume ratio and their unique chemical and physical properties. Among the nanoparticles, silver nanoparticles have gained increasing attention because silver nanoparticles exhibit antibacterial activity against a range of gram positive and gram negative bacteria. Nanoparticles of well-defined chemistry and morphology can be used in broad biomedical applications, especially in bone tissue engineering applications, where bone infection by bacteria can be acute and lethal. It is commonly noted in the literature that the activity of nanoparticles against microorganisms is dependent upon the size and concentration of the nanoparticles as well as the chemistry of stabilizing agent. To the best of our knowledge, a comprehensive study that evaluates the antibacterial activity of well characterized silver nanoparticles in particular Bovine Serum Albumin (BSA) stabilized against S. aureus and E. coli and cytotoxicity level of BSA stabilized silver nanoparticles towards osteoblast cells (MC3T3-E1) is currently lacking. Therefore, the primary objective of this study was to characterize protein conjugated silver nanoparticles prepared by chemical reduction of AgNO3 and BSA mixture. The formation of Ag/BSA nanoparticles was studied by UV-Vis spectroscopy. The molar ratio of silver to BSA in the Ag/BSA nanoparticles was established to be 27+/- 3: 1, based on Thermogravimetric Analysis and Atomic Absorption Spectroscopy. Based on atomic force microscopy, dynamic light scattering,and transmission electron microscopy(TEM) measurements, the particle size (diameter) of

A novel on-line gold nanoparticle-catalyzed luminol chemiluminescence detector for high-performance liquid chromatography.

PubMed

Zhang, Qun Lin; Wu, Liang; Lv, Chen; Zhang, Xiao Yue

2012-06-15

A novel on-line gold nanoparticle-catalyzed luminol-H(2)O(2) chemiluminescence (CL) detector for high-performance liquid chromatography (HPLC) was established, in which gold nanoparticles were produced by the on-line reaction of H(2)O(2), NaHCO(3)-Na(2)CO(3) (buffer solution of luminol), and HAuCl(4). Eight phenolic compounds (gallic acid, protocatechuic acid, protocatechuic aldehyde, 2,5-dihydroxybenzoic acid, caffeic acid, 2,3-dihydroxybenzoic acid, (+)-catechin, and (-)-epicatechin) were chosen as the model compounds. Every separated phenolic compound in the column eluent strongly enhanced the CL signal of on-line gold nanoparticle-catalyzed luminol system. The CL and UV-visible absorption spectra and transmission electron microscopy studies were carried out, and the CL enhancement mechanism was ascribed to that the presence of phenolic compound promoted the on-line formation of 38-nm-diameter gold nanoparticles, which better catalyzed the luminol-H(2)O(2) CL reaction. The effects of methanol and phosphoric acid in the proposed HPLC configuration were performed by two gradient elution programs, and the baseline profile revealed that on-line gold nanoparticle-catalyzed luminol-H(2)O(2) CL detector had better compatibility than 38 nm gold colloids-luminol-H(2)O(2) CL detector. The proposed CL detector exhibits excellent analytical performance with the low detection limit (S/N=3) of 0.53-0.97 ng/mL (10.6-19.4 pg) phenolic compounds, and offers a new strategy for developing on-line nanoparticle-catalyzed CL detector for HPLC with sensitive analysis. Copyright © 2012 Elsevier B.V. All rights reserved.

Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

NASA Astrophysics Data System (ADS)

Rahimi, M.; Ng, E.-P.; Bakhtiari, K.; Vinciguerra, M.; Ahmad, H. Ali; Awala, H.; Mintova, S.; Daghighi, M.; Bakhshandeh Rostami, F.; de Vries, M.; Motazacker, M. M.; Peppelenbosch, M. P.; Mahmoudi, M.; Rezaee, F.

2015-11-01

The affinity of zeolite nanoparticles (diameter of 8-12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy.

Zeolite Nanoparticles for Selective Sorption of Plasma Proteins.

PubMed

Rahimi, M; Ng, E-P; Bakhtiari, K; Vinciguerra, M; Ali Ahmad, H; Awala, H; Mintova, S; Daghighi, M; Bakhshandeh Rostami, F; de Vries, M; Motazacker, M M; Peppelenbosch, M P; Mahmoudi, M; Rezaee, F

2015-11-30

The affinity of zeolite nanoparticles (diameter of 8-12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy.

Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

PubMed Central

Rahimi, M.; Ng, E.-P.; Bakhtiari, K.; Vinciguerra, M.; Ahmad, H. Ali; Awala, H.; Mintova, S.; Daghighi, M.; Bakhshandeh Rostami, F.; de Vries, M.; Motazacker, M. M.; Peppelenbosch, M. P.; Mahmoudi, M.; Rezaee, F.

2015-01-01

The affinity of zeolite nanoparticles (diameter of 8–12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy. PMID:26616161

Fabrication and Luminescence Characterization of a Silica Nanomatrix Embedded with NaYF4:Yb:Er:Tm@NaGdF4/Fe3O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Thangaraju, Dheivasigamani; Santhana, Vedi; Matsuda, Satoshi; Hayakawa, Yasuhiro

2018-05-01

Hexagonal NaYF4:Yb:Er:Tm@NaGdF4 core-shell nanocrystals were synthesized using a seed mediated hot injection method, and monodispersed Fe3O4 (4 nm) nanoparticles were prepared from iron(II) actylacetonate by a precursor thermal decomposition method. Structural and morphology verified NaYF4:Yb:Er:Tm@NaGdF4 and Fe3O4 nanoparticles were utilized for the preparation of NaYF4:Yb:Er:Tm@NaGdF4/Fe3O4@SiO2 nanocomposite using a micro-emulsion method. Existence of Fe3O4 in NaYF4:Yb:Er:Tm@NaGdF4 in SiO2 nano-spheres were confirmed with transmission electron microscopy. Luminescence measurement revealed that NaYF4:Yb:Er:Tm@NaGdF4 exhibited strong emissions at green and red regions, in addition to a weak blue emission also observed under 980 nm excitation. Up-conversion emission of the nanoparticle-embedded silica nanocomposite showed that the up-conversion emission was not affected by Fe3O4 nanoparticles.

Novel ionically crosslinked casein nanoparticles for flutamide delivery: formulation, characterization, and in vivo pharmacokinetics

PubMed Central

Elzoghby, Ahmed O; Helmy, Maged W; Samy, Wael M; Elgindy, Nazik A

2013-01-01

A novel particulate delivery matrix based on ionically crosslinked casein (CAS) nanoparticles was developed for controlled release of the poorly soluble anticancer drug flutamide (FLT). Nanoparticles were fabricated via oil-in-water emulsification then stabilized by ionic crosslinking of the positively charged CAS molecules below their isoelectric point, with the polyanionic crosslinker sodium tripolyphosphate. With the optimal preparation conditions, the drug loading and incorporation efficiency achieved were 8.73% and 64.55%, respectively. The nanoparticles exhibited a spherical shape with a size below 100 nm and a positive zeta potential (+7.54 to +17.3 mV). FLT was molecularly dispersed inside the nanoparticle protein matrix, as revealed by thermal analysis. The biodegradability of CAS nanoparticles in trypsin solution could be easily modulated by varying the sodium tripolyphosphate crosslinking density. A sustained release of FLT from CAS nanoparticles for up to 4 days was observed, depending on the crosslinking density. After intravenous administration of FLT-CAS nanoparticles into rats, CAS nanoparticles exhibited a longer circulation time and a markedly delayed blood clearance of FLT, with the half-life of FLT extended from 0.88 hours to 14.64 hours, compared with drug cosolvent. The results offer a promising method for tailoring biodegradable, drug-loaded CAS nanoparticles as controlled, long-circulating drug delivery systems of hydrophobic anticancer drugs in aqueous vehicles. PMID:23658490

Synthesis, structural and paramagnetic properties of SnO{sub 2} doped NiO nanoparticles

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

Islam, I., E-mail: ishtihadahislam@gmail.com; Dwivedi, Sonam; Dar, Hilal A.

2016-05-06

In this work, Sn doped NiO nanoparticles were synthesized by co-precipitation route to explore the impact of doping on lattice structure, dielectric constant and magnetization. X-ray diffraction analysis confirmed cubic (Fd-3m) structure of Sn doped NiO. Average crystallite size decreases from 78.2 nm (Ni{sub 0.95}Sn{sub 0.05}O) to 64.23 nm (Ni{sub 0.8}Sn{sub 0.2}O). Scanning electron microscopy images confirm that nanocrystals have agglomerated spherical morphology. The Raman spectrum exhibits a strong, broad peak at 410 cm{sup -1} and is attributed to the Ni-O stretching mode and doped samples show a blue shift. The dielectric constants at about 1 Hz are measured to be about 1.795,more » 1.030, 0.442, and 0.302 × 10{sup 3} Ni{sub 1-x}Sn{sub x}O (x = 0.05, 0.1, 0.15, 0.2), respectively. The dielectric constant in nanoparticles of doped Ni{sub 1-x}Sn{sub x}O is three orders of magnitude higher as compared to pure NiO ceramics. The nature of magnetization - applied field (M-H) infers paramagnetic behaviour for Sn doped NiO nanoparticles.« less

Evaluating mononuclear cells as nanoparticle delivery vehicles for the treatment of breast tumors

NASA Astrophysics Data System (ADS)

Murton, Jaclyn K.; Hu, Chelin; Ahmed, Mona M.; Hathaway, Helen J.; Nysus, Monique; Anderson Daniels, Tamara; Norenberg, Jeffrey P.; Adolphi, Natalie L.

2015-08-01

In breast cancer, certain types of circulating immune cells respond to long-range chemical signals from tumors by leaving the blood stream to actively infiltrate tumor tissue. The aim of this study was to evaluate whether immune cells could be used to deliver therapeutic nanoparticles into breast tumors in mice. Mononuclear splenocytes (MS) were harvested from donor mice, labeled with Indium-111, injected intravenously into immune-competent recipient mice (3 tumor-bearing and 3 control), and imaged longitudinally by SPECT/CT. For comparison, the biodistribution of bonemarrow derived macrophages (BMDM) in one pair of mice was also imaged. Quantitative analysis of the SPECT images demonstrates that, after 24 hours, the concentration of MS detected in mammary tumors is more than 3-fold higher than the concentration detected in normal mammary glands. The ratio of MS concentration in mammary tissue to MS concentration in non-target tissues (muscle, lung, heart, liver, spleen, and kidney) was enhanced in tumor-bearing mice (compared to controls), with statistical significance achieved for mammary/muscle (p<0.01), mammary/lung (p<0.05), and mammary/kidney (p<0.05). By contrast, BMDM did not show a different affinity for tumors relative to normal mammary tissue. MS were incubated with 100 nm red fluorescent nanoparticles, and flow cytometry demonstrated that ~35% of the MS population exhibited strong phagocytic uptake of the nanoparticles. After intravenous injection into tumor-bearing mice, fluorescence microscopy images of tumor sections show qualitatively that nanoparticle-loaded MS retain the ability to infiltrate mammary tumors. Taken together, these results suggest that MS carriers are capable of actively targeting therapeutic nanoparticles to breast tumors.

Planktonic and biofilm-grown nitrogen-cycling bacteria exhibit different susceptibilities to copper nanoparticles.

PubMed

Reyes, Vincent C; Opot, Stephen O; Mahendra, Shaily

2015-04-01

Proper characterization of nanoparticle (NP) interactions with environmentally relevant bacteria under representative conditions is necessary to enable their sustainable manufacture, use, and disposal. Previous nanotoxicology research based on planktonic growth has not adequately explored biofilms, which serve as the predominant mode of bacterial growth in natural and engineered environments. Copper nanoparticle (Cu-NP) impacts on biofilms were compared with respective planktonic cultures of the ammonium-oxidizing Nitrosomonas europaea, nitrogen-fixing Azotobacter vinelandii, and denitrifying Paracoccus denitrificans using a suite of independent toxicity diagnostics. Median inhibitory concentration (IC50) values derived from adenosine triphosphate (ATP) for Cu-NPs were lower in N. europaea biofilms (19.6 ± 15.3 mg/L) than in planktonic cells (49.0 ± 8.0 mg/L). However, in absorbance-based growth assays, compared with unexposed controls, N. europaea growth rates in biofilms were twice as resilient to inhibition than those in planktonic cultures. Similarly, relative to unexposed controls, growth rates and yields of P. denitrificans in biofilms exposed to Cu-NPs were 40-fold to 50-fold less inhibited than those in planktonic cells. Physiological evaluation of ammonium oxidation and nitrate reduction suggested that biofilms were also less inhibited by Cu-NPs than planktonic cells. Furthermore, functional gene expression for ammonium oxidation (amoA) and nitrite reduction (nirK) showed lower inhibition by NPs in biofilms relative to planktonic-grown cells. These results suggest that biofilms mitigate NP impacts, and that nitrogen-cycling bacteria in wastewater, wetlands, and soils might be more resilient to NPs than planktonic-based assessments suggest. © 2014 SETAC.

Preparation and near-infrared photothermal conversion property of cesium tungsten oxide nanoparticles

PubMed Central

2013-01-01

Cs0.33WO3 nanoparticles have been prepared successfully by a stirred bead milling process. By grinding micro-sized coarse powder with grinding beads of 50 μm in diameter, the mean hydrodynamic diameter of Cs0.33WO3 powder could be reduced to about 50 nm in 3 h, and a stable aqueous dispersion could be obtained at pH 8 via electrostatic repulsion mechanism. After grinding, the resulting Cs0.33WO3 nanoparticles retained the hexagonal structure and had no significant contaminants from grinding beads. Furthermore, they exhibited a strong characteristic absorption and an excellent photothermal conversion property in the near-infrared (NIR) region, owing to the free electrons or polarons. Also, the NIR absorption and photothermal conversion property became more significant with decreasing particle size or increasing particle concentration. When the concentration of Cs0.33WO3 nanoparticles was 0.08 wt.%, the solution temperature had a significant increase of above 30°C in 10 min under NIR irradiation (808 nm, 2.47 W/cm2). In addition, they had a photothermal conversion efficiency of about 73% and possessed excellent photothermal stability. Such an effective NIR absorption and photothermal conversion nanomaterial not only was useful in the NIR shielding, but also might find great potential in biomedical application. PMID:23379652

Pharmacokinetics study of Zr-89-labeled melanin nanoparticle in iron-overload mice.

PubMed

Zhang, Pengjun; Yue, Yuanyuan; Pan, Donghui; Yang, Runlin; Xu, Yuping; Wang, Lizhen; Yan, Junjie; Li, Xiaotian; Yang, Min

2016-09-01

Melanin, a natural biological pigment present in many organisms, has been found to exhibit multiple functions. An important property of melanin is its ability to chelate metal ions strongly, which might be developed as an iron chelator for iron overload therapy. Herein, we prepared the ultrasmall water-soluble melanin nanoparticle (MP) and firstly evaluate the pharmacokinetics of MP in iron-overload mice to provide scientific basis for treating iron-overload. To study the circulation time and biodistribution, MP was labeled with (89)Zr, a long half-life (78.4h) positron-emitting metal which is suited for the labeling of nanoparticles and large bioactive molecule. MP was chelated with (89)Zr directly at pH5, resulting in non-decay-corrected yield of 89.6% and a radiochemical purity of more than 98%. The specific activity was at least190 MBq/μmol. The (89)Zr-MP was stable in human plasma and PBS for at least 48h. The half-life of (89)Zr-MP was about 15.70±1.74h in iron-overload mice. Biodistribution studies and MicroPET imaging showed that (89)Zr-MP mainly accumulated in liver and spleen, which are the target organ of iron-overload. The results indicate that the melanin nanoparticle is promising for further iron overload therapy. Copyright © 2016 Elsevier Inc. All rights reserved.

Biologically active nanocomposite of DNA-PbS nanoparticles: A new material for non-volatile memory devices

NASA Astrophysics Data System (ADS)

Murgunde, B. K.; Rabinal, M. K.; Kalasad, M. N.

2018-01-01

Composite films of deoxyribonucleic acid (DNA) and lead sulfide (PbS) nanoparticles are prepared to fabricate biological memory devices. A simple solution based electrografting is developed to deposit large (few cm2) uniform films of DNA:PbS on conducting substrates. The films are studied by X-ray photoelectron spectroscopy, field emission SEM, FTIR and optical spectroscopy to understand their properties. Charge transport measurements are carried out on ITO-DNA:PbS-metal junctions by cyclic voltage scans, electrical bi-stability is observed with ON/OFF ratio more than ∼104 times with good stability and endurance, such performance being rarely reported. The observed results are interpreted in the light of strong electrostatic binding of nanoparticles and DNA stands, which leads doping of Pb atoms into DNA. As a result, these devices exhibit negative differential resistance (NDR) effect due to oxidation of doped metal atoms. These composites can be the potential materials in the development of new generation non-volatile memory devices.

Green synthesis of gold and silver nanoparticles using gallic acid: catalytic activity and conversion yield toward the 4-nitrophenol reduction reaction

NASA Astrophysics Data System (ADS)

Park, Jisu; Cha, Song-Hyun; Cho, Seonho; Park, Youmie

2016-06-01

In the present report, gallic acid was used as both a reducing and stabilizing agent to synthesize gold and silver nanoparticles. The synthesized gold and silver nanoparticles exhibited characteristic surface plasmon resonance bands at 536 and 392 nm, respectively. Nanoparticles that were approximately spherical in shape were observed in high-resolution transmission electron microscopy and atomic force microscopy images. The hydrodynamic radius was determined to be 54.4 nm for gold nanoparticles and 33.7 nm for silver nanoparticles in aqueous medium. X-ray diffraction analyses confirmed that the synthesized nanoparticles possessed a face-centered cubic structure. FT-IR spectra demonstrated that the carboxylic acid functional groups of gallic acid contributed to the electrostatic binding onto the surface of the nanoparticles. Zeta potential values of -41.98 mV for the gold nanoparticles and -53.47 mV for the silver nanoparticles indicated that the synthesized nanoparticles possess excellent stability. On-the-shelf stability for 4 weeks also confirmed that the synthesized nanoparticles were quite stable without significant changes in their UV-visible spectra. The synthesized nanoparticles exhibited catalytic activity toward the reduction reaction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride. The rate constant of the silver nanoparticles was higher than that of the gold nanoparticles in the catalytic reaction. Furthermore, the conversion yield (%) of 4-nitrophenol to 4-aminophenol was determined using reversed-phase high-performance liquid chromatography with UV detection at 254 nm. The silver nanoparticles exhibited an excellent conversion yield (96.7-99.9 %), suggesting that the synthesized silver nanoparticles are highly efficient catalysts for the 4-nitrophenol reduction reaction.

Biomedical applications of green synthesized Nobel metal nanoparticles.

PubMed

Khan, Zia Ul Haq; Khan, Amjad; Chen, Yongmei; Shah, Noor S; Muhammad, Nawshad; Khan, Arif Ullah; Tahir, Kamran; Khan, Faheem Ullah; Murtaza, Behzad; Hassan, Sadaf Ul; Qaisrani, Saeed Ahmad; Wan, Pingyu

2017-08-01

Synthesis of Nobel metal nanoparticles, play a key role in the field of medicine. Plants contain a substantial number of organic constituents, like phenolic compounds and various types of glycosides that help in synthesis of metal nanoparticles. Synthesis of metal nanoparticles by green method is one of the best and environment friendly methods. The major significance of the green synthesis is lack of toxic by-products produced during metal nanoparticle synthesis. The nanoparticles, synthesized by green method show various significant biological activities. Most of the research articles report the synthesized nanoparticles to be active against gram positive and gram negative bacteria. Some of these bacteria include Escherichia coli, Bacillus subtilis, Klebsiella pneumonia and Pseudomonas fluorescens. The synthesized nanoparticles also show significant antifungal activity against Trichophyton simii, Trichophyton mentagrophytes and Trichophyton rubrum as well as different types of cancer cells such as breast cancer cell line. They also exhibit significant antioxidant activity. The activities of these Nobel metal nano-particles mainly depend on the size and shape. The particles of small size with large surface area show good activity in the field of medicine. The synthesized nanoparticles are also active against leishmanial diseases. This research article explores in detail the green synthesis of the nanoparticles and their uses thereof. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetocapacitance effect in core/shell NiO nanoparticles

NASA Astrophysics Data System (ADS)

Roy, Subir; Kambhala, Nagaiah; Angappane, S.

2018-04-01

The exchange bias and magnetocapacitance properties of nickel oxide nanoparticles of average particle size 50 nm have been studied. NiO nanoparticles of uniform size distribution were synthesized by a sol-gel method using nickel acetate and polyvinyl acetate. The magnetic measurements show the ferromagnetic like behavior exhibiting exchange bias effect indicative of the formation of core/shell structure of NiO with a antiferromagnetic core and ferromagnetic shell. An electrical double layer capacitance behavior was observed for NiO nanoparticles in the cyclic voltammetry measurement, and it was found that the value of capacitance decreased by about 26 % under the application of magnetic field of 0.1 T.

Study on the mechanism of antibacterial action of magnesium oxide nanoparticles against foodborne pathogens

USDA-ARS?s Scientific Manuscript database

Magnesium oxide nanoparticles (MgO nanoparticles, with average size of 20 nm) have strong antibacterial activities against several important foodborne pathogens. Resazurin (a redox sensitive dye) microplate assay was used for measuring growth inhibition of bacteria treated with MgO nanoparticles. Th...

Nanoparticle Immobilization for Controllable Experiments in Liquid-Cell Transmission Electron Microscopy.

PubMed

Robertson, Alex W; Zhu, Guomin; Mehdi, B Layla; Jacobs, Robert M J; De Yoreo, James; Browning, Nigel D

2018-06-22

We demonstrate that silanization can control the adhesion of nanostructures to the SiN windows compatible with liquid-cell transmission electron microscopy (LC-TEM). Formation of an (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayer on a SiN window, producing a surface decorated with amino groups, permits strong adhesion of Au nanoparticles to the window. Many of these nanoparticles remain static, undergoing minimal translation or rotation during LC-TEM up to high electron beam current densities due to the strong interaction between the APTES amino group and Au. We then use this technique to perform a direct comparative LC-TEM study on the behavior of ligand and nonligand-coated Au nanoparticles in a Au growth solution. While the ligand coated nanoparticles remain consistent even under high electron beam current densities, the naked nanoparticles acted as sites for secondary Au nucleation. These nucleated particles decorated the parent nanoparticle surface, forming consecutive monolayer assemblies of ∼2 nm diameter nanoparticles, which sinter into the parent particle when the electron beam was shut off. This method for facile immobilization of nanostructures for LC-TEM study will permit more sophisticated and controlled in situ experiments into the properties of solid-liquid interfaces in the future.

Structural and magnetic characterization of Fe2CrSi Heusler alloy nanoparticles as spin injectors and spin based sensors

NASA Astrophysics Data System (ADS)

Saravanan, G.; Asvini, V.; Kalaiezhily, R. K.; Parveen, I. Mubeena; Ravichandran, K.

2018-05-01

Half-metallic ferromagnetic [HMF] nanoparticles are of considerable interest in spintronics applications due to their potential use as a highly spin polarized current source. HMF exhibits a semiconductor in one spin band at the Fermi level Ef and at the other spin band they poses strong metallic nature which shows 100 % spin polarization at Ef. Fe based full Heusler alloys are primary interest due to high Curie temperature. Fe2CrSi Heusler alloys are synthesized using metallic powders of Fe, Cr and Si by mechanical alloying method. X-Ray diffractions studies were performed to analyze the structural details of Fe2CrSi nanoparticles with High resolution scanning electron microscope (HRSEM) studies for the morphological details of nanoparticles and magnetic properties were studied using Vibrating sample magnetometer (VSM). XRD Data analysis conforms the Heusler alloy phase showing the existence of L21 structure. Magnetic properties are measured for synthesized samples exhibiting a soft magnetic property possessing low coercivity (HC = 60.5 Oe) and saturation magnetic moment of Fe2CrSi is 3.16 µB, which is significantly higher than the ideal value of 2 µB from the Slater-Pauling rule due to room temperature measurement. The change in magnetic properties are half-metallic nature of Fe2CrSi is due to the shift of the Fermi level with respect to the gap were can be used as spin sensors and spin injectors in magnetic random access memories and other spin dependent devices.

Sonochemical Synthesis of Silver Nanoparticles Using Starch: A Comparison

PubMed Central

Smita, Kumari; Cumbal, Luis; Debut, Alexis; Pathak, Ravinandan Nath

2014-01-01

A novel approach was applied to synthesize silver nanoparticles using starch under sonication. Colloidal silver nanoparticles solution exhibited an increase of absorption from 420 to 440 nm with increase starch quantity. Transmission electron microscopy followed by selected area electron diffraction pattern analysis indicated the formation of spherical, polydispersed, amorphous, silver nanoparticles of diameter ranging from 23 to 97 nm with mean particle size of 45.6 nm. Selected area electron diffraction (SAED) confirmed partial crystalline and amorphous nature of silver nanoparticles. Silver nanoparticles synthesized in this manner can be used for synthesis of 2-aryl substituted benzimidazoles which have numerous biomedical applications. The optimized reaction conditions include 10 ml of 1 mM AgNO3, 25 mg starch, 11 pH range, and sonication for 20 min at room temperature. PMID:24587771

Biosynthesis of Gold and Silver Nanoparticles Using Extracts of Callus Cultures of Pumpkin (Cucurbita maxima).

PubMed

Iyer, R Indira; Panda, Tapobrata

2018-08-01

The potential of callus cultures and field-grown organs of pumpkin (Cucurbita maxima) for the biosynthesis of nanoparticles of the noble metals gold and silver has been investigated. Biosynthesis of AuNPs (gold nanoparticles) and AgNPs (silver nanoparticles) was obtained with flowers of C. maxima but not with pulp and seeds. With callus cultures established in MS-based medium the biogenesis of both AuNPs and AgNPs could be obtained. At 65 °C the biogenesis of AuNPs and AgNPs by callus extracts was enhanced. The AuNPs and AgNPs have been characterized by UV-visible spectroscopy, TEM, DLS and XRD. Well-dispersed nanoparticles, which exhibited a remarkable diversity in size and shape, could be visualized by TEM. Gold nanoparticles were found to be of various shapes, viz., rods, triangles, star-shaped particles, spheres, hexagons, bipyramids, discoid particles, nanotrapezoids, prisms, cuboids. Silver nanoparticles were also of diverse shapes, viz., discoid, spherical, elliptical, triangle-like, belt-like, rod-shaped forms and cuboids. EDX analysis indicated that the AuNPs and AgNPs had a high degree of purity. The surface charges of the generated AuNPs and AgNPs were highly negative as indicated by zeta potential measurements. The AuNPs and AgNPs exhibited remarkable stability in solution for more than four months. FTIR studies indicated that biomolecules in the callus extracts were associated with the biosynthesis and stabilisation of the nanoparticles. The synthesized AgNPs could catalyse degradation of methylene blue and exhibited anti-bacterial activity against E. coli DH5α. There is no earlier report of the biosynthesis of nanoparticles by this plant species. Callus cultures of Cucurbita maxima are effective alternative resources of biomass for synthesis of nanoparticles.

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

HDL-mimetic PLGA nanoparticle to target atherosclerosis plaque macrophages.

PubMed

Sanchez-Gaytan, Brenda L; Fay, Francois; Lobatto, Mark E; Tang, Jun; Ouimet, Mireille; Kim, YongTae; van der Staay, Susanne E M; van Rijs, Sarian M; Priem, Bram; Zhang, Liangfang; Fisher, Edward A; Moore, Kathryn J; Langer, Robert; Fayad, Zahi A; Mulder, Willem J M

2015-03-18

High-density lipoprotein (HDL) is a natural nanoparticle that exhibits an intrinsic affinity for atherosclerotic plaque macrophages. Its natural targeting capability as well as the option to incorporate lipophilic payloads, e.g., imaging or therapeutic components, in both the hydrophobic core and the phospholipid corona make the HDL platform an attractive nanocarrier. To realize controlled release properties, we developed a hybrid polymer/HDL nanoparticle composed of a lipid/apolipoprotein coating that encapsulates a poly(lactic-co-glycolic acid) (PLGA) core. This novel HDL-like nanoparticle (PLGA-HDL) displayed natural HDL characteristics, including preferential uptake by macrophages and a good cholesterol efflux capacity, combined with a typical PLGA nanoparticle slow release profile. In vivo studies carried out with an ApoE knockout mouse model of atherosclerosis showed clear accumulation of PLGA-HDL nanoparticles in atherosclerotic plaques, which colocalized with plaque macrophages. This biomimetic platform integrates the targeting capacity of HDL biomimetic nanoparticles with the characteristic versatility of PLGA-based nanocarriers.

HDL-Mimetic PLGA Nanoparticle To Target Atherosclerosis Plaque Macrophages

PubMed Central

Sanchez-Gaytan, Brenda L.; Fay, Francois; Lobatto, Mark E.; Tang, Jun; Ouimet, Mireille; Kim, YongTae; van der Staay, Susanne E. M.; van Rijs, Sarian M.; Priem, Bram; Zhang, Liangfang; Fisher, Edward A; Moore, Kathryn J.; Langer, Robert; Fayad, Zahi A.; Mulder, Willem J M

2015-01-01

High-density lipoprotein (HDL) is a natural nanoparticle that exhibits an intrinsic affinity for atherosclerotic plaque macrophages. Its natural targeting capability as well as the option to incorporate lipophilic payloads, e.g., imaging or therapeutic components, in both the hydrophobic core and the phospholipid corona make the HDL platform an attractive nanocarrier. To realize controlled release properties, we developed a hybrid polymer/HDL nanoparticle composed of a lipid/apolipoprotein coating that encapsulates a poly(lactic-co-glycolic acid) (PLGA) core. This novel HDL-like nanoparticle (PLGA–HDL) displayed natural HDL characteristics, including preferential uptake by macrophages and a good cholesterol efflux capacity, combined with a typical PLGA nanoparticle slow release profile. In vivo studies carried out with an ApoE knockout mouse model of atherosclerosis showed clear accumulation of PLGA–HDL nanoparticles in atherosclerotic plaques, which colocalized with plaque macrophages. This biomimetic platform integrates the targeting capacity of HDL biomimetic nanoparticles with the characteristic versatility of PLGA-based nanocarriers. PMID:25650634

Nanoscale Motion of Soft Nanoparticles in Unentangled and Entangled Polymer Matrices

NASA Astrophysics Data System (ADS)

Lungova, M.; Krutyeva, M.; Pyckhout-Hintzen, W.; Wischnewski, A.; Monkenbusch, M.; Allgaier, J.; Ohl, M.; Sharp, M.; Richter, D.

2016-09-01

We have studied the motion of polyhedral oligomeric silsesquioxane (POSS) nanoparticles modified with poly(ethylene glycol) (PEG) arms immersed in PEG matrices of different molecular weight. Employing neutron spin echo spectroscopy in combination with pulsed field gradient (PFG) NMR we found the following. (i) For entangled matrices the center of mass mean square displacement (MSD) of the PEG-POSS particles is subdiffusive following a t0.56 power law. (ii) The diffusion coefficient as well as the crossover to Fickian diffusion is independent of the matrix molecular weight and takes place as soon as the center of mass has moved a distance corresponding to the particle radius—this holds also for unentangled hosts. (iii) For the entangled matrices Rubinstein's scaling theory is validated; however, the numbers indicate that beyond Rouse friction the entanglement constraints appear to strongly increase the effective friction even on the nanoparticle length scale imposing a caveat on the interpretation of microrheological experiments. (iv) The oligomer decorated PEG-POSS particles exhibit the dynamics of a Gaussian star with an internal viscosity that rises with an increase of the host molecular weight.

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.

Critical material attributes (CMAs) of strip films loaded with poorly water-soluble drug nanoparticles: III. Impact of drug nanoparticle loading.

PubMed

Krull, Scott M; Moreno, Jacqueline; Li, Meng; Bilgili, Ecevit; Davé, Rajesh N

2017-05-15

Polymer strip films have emerged as a robust platform for poorly water-soluble drug delivery. However, the common conception is that films cannot exceed low drug loadings, mainly due to poor drug stability, slow release, and film brittleness. This study explores the ability to achieve high loadings of poorly water-soluble drug nanoparticles in strip films while retaining good mechanical properties and enhanced dissolution rate. Aqueous suspensions containing up to 30wt% griseofulvin nanoparticles were prepared via wet stirred media milling and incorporated into hydroxypropyl methylcellulose (HPMC) films. Griseofulvin loading in films was adjusted to be between 9 and 49wt% in HPMC-E15 films and 30 and 73wt% in HPMC-E4M films by varying the mixing ratio of HPMC solution-to-griseofulvin suspension. All films exhibited good content uniformity and nanoparticle redispersibility up to 50wt% griseofulvin, while E4M films above 50wt% griseofulvin had slightly worse content uniformity and poor nanoparticle redispersibility. Increasing drug loading in films generally required more time to achieve 100% release during dissolution, although polymer-drug clusters dispersed from E4M films above 50wt% griseofulvin, resulting in similar dissolution profiles. While all films exhibited good tensile strength, a significant decrease in percent elongation was observed above 40-50wt% GF, resulting in brittle films. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanomaterials and nanoparticles: sources and toxicity.

PubMed

Buzea, Cristina; Pacheco, Ivan I; Robbie, Kevin

2007-12-01

This review is presented as a common foundation for scientists interested in nanoparticles, their origin,activity, and biological toxicity. It is written with the goal of rationalizing and informing public health concerns related to this sometimes-strange new science of "nano," while raising awareness of nanomaterials' toxicity among scientists and manufacturers handling them.We show that humans have always been exposed to tiny particles via dust storms, volcanic ash, and other natural processes, and that our bodily systems are well adapted to protect us from these potentially harmful intruders. There ticuloendothelial system, in particular, actively neutralizes and eliminates foreign matter in the body,including viruses and nonbiological particles. Particles originating from human activities have existed for millennia, e.g., smoke from combustion and lint from garments, but the recent development of industry and combustion-based engine transportation has profoundly increased an thropogenic particulate pollution. Significantly, technological advancement has also changed the character of particulate pollution, increasing the proportion of nanometer-sized particles--"nanoparticles"--and expanding the variety of chemical compositions. Recent epidemiological studies have shown a strong correlation between particulate air pollution levels, respiratory and cardiovascular diseases, various cancers, and mortality. Adverse effects of nanoparticles on human health depend on individual factors such as genetics and existing disease, as well as exposure, and nanoparticle chemistry, size, shape,agglomeration state, and electromagnetic properties. Animal and human studies show that inhaled nanoparticles are less efficiently removed than larger particles by the macrophage clearance mechanisms in the lungs, causing lung damage, and that nanoparticles can translocate through the circulatory, lymphatic, and nervous systems to many tissues and organs, including the brain. The key to

c-Type Cytochrome-Dependent Formation of U(IV) Nanoparticles by Shewanella oneidensis

PubMed Central

Marshall, Matthew J; Dohnalkova, Alice C; Kennedy, David W; Shi, Liang; Wang, Zheming; Boyanov, Maxim I; Lai, Barry; Kemner, Kenneth M; McLean, Jeffrey S; Reed, Samantha B; Culley, David E; Bailey, Vanessa L; Simonson, Cody J; Saffarini, Daad A; Romine, Margaret F; Zachara, John M

2006-01-01

Modern approaches for bioremediation of radionuclide contaminated environments are based on the ability of microorganisms to effectively catalyze changes in the oxidation states of metals that in turn influence their solubility. Although microbial metal reduction has been identified as an effective means for immobilizing highly-soluble uranium(VI) complexes in situ, the biomolecular mechanisms of U(VI) reduction are not well understood. Here, we show that c-type cytochromes of a dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1, are essential for the reduction of U(VI) and formation of extracelluar UO 2 nanoparticles. In particular, the outer membrane (OM) decaheme cytochrome MtrC (metal reduction), previously implicated in Mn(IV) and Fe(III) reduction, directly transferred electrons to U(VI). Additionally, deletions of mtrC and/or omcA significantly affected the in vivo U(VI) reduction rate relative to wild-type MR-1. Similar to the wild-type, the mutants accumulated UO 2 nanoparticles extracellularly to high densities in association with an extracellular polymeric substance (EPS). In wild-type cells, this UO 2-EPS matrix exhibited glycocalyx-like properties and contained multiple elements of the OM, polysaccharide, and heme-containing proteins. Using a novel combination of methods including synchrotron-based X-ray fluorescence microscopy and high-resolution immune-electron microscopy, we demonstrate a close association of the extracellular UO 2 nanoparticles with MtrC and OmcA (outer membrane cytochrome). This is the first study to our knowledge to directly localize the OM-associated cytochromes with EPS, which contains biogenic UO 2 nanoparticles. In the environment, such association of UO 2 nanoparticles with biopolymers may exert a strong influence on subsequent behavior including susceptibility to oxidation by O 2 or transport in soils and sediments. PMID:16875436

Nanoscaling laws of magnetic nanoparticles and their applicabilities in biomedical sciences.

PubMed

Jun, Young-Wook; Seo, Jung-Wook; Cheon, Jinwoo

2008-02-01

Magnetic nanoparticles, which exhibit a variety of unique magnetic phenomena that are drastically different from those of their bulk counterparts, are garnering significant interest since these properties can be advantageous for utilization in a variety of applications ranging from storage media for magnetic memory devices to probes and vectors in the biomedical sciences. In this Account, we discuss the nanoscaling laws of magnetic nanoparticles including metals, metal ferrites, and metal alloys, while focusing on their size, shape, and composition effects. Their fundamental magnetic properties such as blocking temperature (Tb), spin life time (tau), coercivity (Hc), and susceptibility (chi) are strongly influenced by the nanoscaling laws, and as a result, these scaling relationships can be leveraged to control magnetism from the ferromagnetic to the superparamagnetic regimes. At the same time, they can be used in order to tune magnetic values including Hc, chi, and remanence (Mr). For example, life time of magnetic spin is directly related to the magnetic anisotropy energy (KuV) and also the size and volume of nanoparticles. The blocking temperature (Tb) changes from room temperature to 10 K as the size of cobalt nanoparticles is reduced from 13 to 2 nm. Similarly, H c is highly susceptible to the anisotropy of nanoparticles, while saturation magnetization is directly related to the canting effects of the disordered surface magnetic spins and follows a linear relationship upon plotting of ms (1/3) vs r(-1). Therefore, the nanoscaling laws of magnetic nanoparticles are important not only for understanding the behavior of existing materials but also for developing novel nanomaterials with superior properties. Since magnetic nanoparticles can be easily conjugated with biologically important constituents such as DNA, peptides, and antibodies, it is possible to construct versatile nano-bio hybrid particles, which simultaneously possess magnetic and biological functions

Characterization of Magnetic NiFe Nanoparticles with Controlled Bimetallic Composition

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

Liu, Yan; Chi, Yanxiu; Shan, Shiyao

2014-02-25

The exploration of the magnetic properties of bimetallic alloy nanoparticles for various technological applications requires the ability to control the morphology, composition, and surface properties. In this report, we describe new findings of an investigation of the morphology and composition of NiFe alloy nanoparticles synthesized under controlled conditions. The controllability over the bimetallic composition has been demonstrated by the observation of an approximate linear relationship between the composition in the nanoparticles and in the synthetic feeding. The morphology of the NiFe nanoparticles is consistent with an fcc-type alloy, with the lattice strain increasing linearly with the iron content in themore » nanoparticles. The alloy nanoparticles exhibit remarkable resistance to air oxidation in comparison with Ni or Fe particles. The thermal stability and the magnetic properties of the as-synthesized alloy nanoparticles are shown to depend on the composition. The alloy nanoparticles have also be sown to display low saturation magnetization and coercivity values in comparison with the Ni nanoparticles, in line with the superparamagnetic characteristic. These findings have important implications for the design of stable and controllable magnetic nanoparticles for various technological applications.« less

Percolation Magnetism in Ferroelectric Nanoparticles

NASA Astrophysics Data System (ADS)

Golovina, Iryna S.; Lemishko, Serhii V.; Morozovska, Anna N.

2017-06-01

Nanoparticles of potassium tantalate (KTaO3) and potassium niobate (KNbO3) were synthesized by oxidation of metallic tantalum in molten potassium nitrate with the addition of potassium hydroxide. Magnetization curves obtained on these ferroelectric nanoparticles exhibit a weak ferromagnetism, while these compounds are nonmagnetic in a bulk. The experimental data are used as a start point for theoretical calculations. We consider a microscopic mechanism that leads to the emerging of a ferromagnetic ordering in ferroelectric nanoparticles. Our approach is based on the percolation of magnetic polarons assuming the dominant role of the oxygen vacancies. It describes the formation of surface magnetic polarons, in which an exchange interaction between electrons trapped in oxygen vacancies is mediated by magnetic impurity Fe3+ ions. The dependences of percolation radius on concentration of the oxygen vacancies and magnetic defects are determined in the framework of percolation theory.

Green chemistry focus on optimization of silver nanoparticles using response surface methodology (RSM) and mosquitocidal activity: Anopheles stephensi (Diptera: Culicidae).

PubMed

Ondari Nyakundi, Erick; Padmanabhan, M Nalini

2015-01-01

There is an exigent necessity for development of environmental friendly bio-control agent(s) for elimination of mosquito due to increased resistance resurgence against synthetic control agents. Mosquito control strategy will lay a strong foundation to malaria exclusion or it can be curbed to certain level especially in the developing nations. In this study, silver nanoparticles were synthesized by green chemistry approach using Tridax procumbens leaf extract as a reducing agent. The reaction medium involved in the synthesis process was optimized by statistical experimental design using response surface methodology to obtain better yield, uniform size, shape and stability. Further, these synthesized nanoparticles were confirmed through UV-Visible, FT-IR spectroscopy, PSA and SEM Subsequently, the bioefficacy of these particles were investigated on Anopheles stephensi for larvicidal and pupicidal activity. Interestingly, time period of 90 min, temperature of 76±2 °C, pH 7.2±2, 2 mM silver nitrate (AgNO3), 3mM PEG and 2mM PVP showed excellent parameters for bioprocess design for large scale production of stabilized nanoparticles. A concentration of 5 ppm of PVP stabilized nanoparticles exhibited 100% mortality. Thus, the obtained results clearly suggest that silver nanoparticles stabilized by PEG and PVP may have important function as stabilizers, dispersants as well as larvicides for mosquito control. Copyright © 2015 Elsevier B.V. All rights reserved.

The impact of vehicles on the mucoadhesive properties of orally administrated nanoparticles: a case study with chitosan-4-thiobutylamidine conjugate.

PubMed

Sakloetsakun, Duangkamon; Perera, Glen; Hombach, Juliane; Millotti, Gioconda; Bernkop-Schnürch, Andreas

2010-09-01

The aim of this study was to evaluate the impact of various vehicles on mucoadhesive properties of thiolated chitosan nanoparticles both in vitro and in vivo. Nanoparticles (NPs) were prepared by in situ gelation technique followed by labeling with fluorescein diacetate. Comparative studies on mucoadhesion were done with these thiolated chitosan NPs and unmodified chitosan NPs (control). The obtained nanoparticles displayed a mean diameter of 164.2 ± 6.9 nm and a zeta potential of 21.5 ± 5 mV. In an in vitro adhesion study, unhydrated thiolated NPs adhered strongly to freshly excised porcine small intestine, which was more than threefold increase compared to the control. In contrast, in the presence of various vehicles (PEG 300, miglyol 840, PEG 6000, cremophor EL, and caprylic triglyceride), the mucoadhesive properties of thiolated NPs were comparatively weak. Thiolated NPs suspended in caprylic triglyceride, for example, had a percent mucoadhesion of 22.50 ± 5.35% on the mucosa. Furthermore, results from in vivo mucoadhesion studies revealed that the dry form of nanoparticles exhibits the strongest mucoadhesion, followed by nanoparticles suspended in PEG 300, miglyol, and 100 mM phosphate buffer, in that order. Three hours after administration, the gastrointestinal residence time of the dry form of thiolated NPs was up to 3.6-fold prolonged. These findings should contribute to the design of highly effective oral mucoadhesive nanoparticulate drug delivery systems.

Chemical synthesis of narrowly dispersed SmCo5 nanoparticles

NASA Astrophysics Data System (ADS)

Gu, Hongwei; Xu, Bing; Rao, Jiancun; Zheng, R. K.; Zhang, X. X.; Fung, K. K.; Wong, Catherine Y. C.

2003-05-01

In this article we report a chemical synthetic means for generating a high Ku magnetic material—narrowly dispersed nanoparticles of SmCo5. Using Co2(CO)8 and Sm(acac)3 as the precursors under air-free conditions, we produced SmCo5 nanoparticles according to the procedure reported by Sun et al. [Science 287, 1981 (2000)] but with some modifications. The nanoparticles, with diameters of 6-8 nm, have a SmCo5 composition, as indicated by transmission electron microscopy, electron diffraction, and x-ray photoelectron spectroscopy. The magnetization measurement of the nanoparticles, exhibits superparamagnetism, which is blocked for temperatures below ˜110 K, suggesting Ku to be ˜2.1×106 erg/cm3 for the as-prepared particles.

Vault Nanoparticles Packaged with Enzymes as an Efficient Pollutant Biodegradation Technology.

PubMed

Wang, Meng; Abad, Danny; Kickhoefer, Valerie A; Rome, Leonard H; Mahendra, Shaily

2015-11-24

Vault nanoparticles packaged with enzymes were synthesized as agents for efficiently degrading environmental contaminants. Enzymatic biodegradation is an attractive technology for in situ cleanup of contaminated environments because enzyme-catalyzed reactions are not constrained by nutrient requirements for microbial growth and often have higher biodegradation rates. However, the limited stability of extracellular enzymes remains a major challenge for practical applications. Encapsulation is a recognized method to enhance enzymatic stability, but it can increase substrate diffusion resistance, lower catalytic rates, and increase the apparent half-saturation constants. Here, we report an effective approach for boosting enzymatic stability by single-step packaging into vault nanoparticles. With hollow core structures, assembled vault nanoparticles can simultaneously contain multiple enzymes. Manganese peroxidase (MnP), which is widely used in biodegradation of organic contaminants, was chosen as a model enzyme in the present study. MnP was incorporated into vaults via fusion to a packaging domain called INT, which strongly interacts with vaults' interior surface. MnP fused to INT and vaults packaged with the MnP-INT fusion protein maintained peroxidase activity. Furthermore, MnP-INT packaged in vaults displayed stability significantly higher than that of free MnP-INT, with slightly increased Km value. Additionally, vault-packaged MnP-INT exhibited 3 times higher phenol biodegradation in 24 h than did unpackaged MnP-INT. These results indicate that the packaging of MnP enzymes in vault nanoparticles extends their stability without compromising catalytic activity. This research will serve as the foundation for the development of efficient and sustainable vault-based bioremediation approaches for removing multiple contaminants from drinking water and groundwater.

Protein-only, antimicrobial peptide-containing recombinant nanoparticles with inherent built-in antibacterial activity.

PubMed

Serna, Naroa; Sánchez-García, Laura; Sánchez-Chardi, Alejandro; Unzueta, Ugutz; Roldán, Mónica; Mangues, Ramón; Vázquez, Esther; Villaverde, Antonio

2017-09-15

The emergence of bacterial antibiotic resistances is a serious concern in human and animal health. In this context, naturally occurring cationic antimicrobial peptides (AMPs) might play a main role in a next generation of drugs against bacterial infections. Taking an innovative approach to design self-organizing functional proteins, we have generated here protein-only nanoparticles with intrinsic AMP microbicide activity. Using a recombinant version of the GWH1 antimicrobial peptide as building block, these materials show a wide antibacterial activity spectrum in absence of detectable toxicity on mammalian cells. The GWH1-based nanoparticles combine clinically appealing properties of nanoscale materials with full biocompatibility, structural and functional plasticity and biological efficacy exhibited by proteins. Because of the largely implemented biological fabrication of recombinant protein drugs, the protein-based platform presented here represents a novel and scalable strategy in antimicrobial drug design, that by solving some of the limitations of AMPs offers a promising alternative to conventional antibiotics. The low molecular weight antimicrobial peptide GWH1 has been engineered to oligomerize as self-assembling protein-only nanoparticles of around 50nm. In this form, the peptide exhibits potent and broad antibacterial activities against both Gram-positive and Gram-negative bacteria, without any harmful effect over mammalian cells. As a solid proof-of-concept, this finding strongly supports the design and biofabrication of nanoscale antimicrobial materials with in-built functionalities. The protein-based homogeneous composition offer advantages over alternative materials explored as antimicrobial agents, regarding biocompatibility, biodegradability and environmental suitability. Beyond the described prototype, this transversal engineering concept has wide applicability in the design of novel nanomedicines for advanced treatments of bacterial infections

Sintering-Resistant Nanoparticles in Wide-Mouthed Compartments for Sustained Catalytic Performance

NASA Astrophysics Data System (ADS)

Liu, Jia; Ji, Qingmin; Imai, Tsubasa; Ariga, Katsuhiko; Abe, Hideki

2017-02-01

Particle sintering is one of the most significant impediments to functional nanoparticles in many valuable applications especially catalysis. Herein, we report that sintering-resistant nanoparticle systems can be realized through a simple materials-design which maximizes the particle-to-particle traveling distance of neighbouring nanoparticles. As a demonstration, Pt nanoparticles were placed apart from each other in wide-mouthed compartments tailored on the surface of self-assembled silica nanosheets. These Pt nanoparticles retained their particle size after calcination at elevated temperatures because the compartment wall elongates the particle-to-particle traveling distance to preclude the possibility of sintering. Moreover, these Pt nanoparticles in wide-mouthed compartments were fully accessible to the environment and exhibited much higher catalytic activity for CO oxidation than the nanoparticles confined in the nanochannels of mesoporous silica. The proposed materials-design strategy is applicable not only to industrial catalysts operating in harsh conditions, but also opens up possibilities in developing advanced nanoparticle-based materials with sustained performance.

Radiofrequency Heating Pathways for Gold Nanoparticles

PubMed Central

Collins, C. B.; McCoy, R. S.; Ackerson, B. J.; Collins, G. J.

2015-01-01

This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry and physics, including the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell may all strongly influence to what extent a nanoparticle heats in an RF field. Aspects of RF include: power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields, and also influence the extent to which a gold nanoparticle heats in RF. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments. PMID:24962620

Prospects for graphene–nanoparticle-based hybrid sensors

PubMed Central

Yin, Perry T.; Kim, Tae-Hyung; Choi, Jeong-Woo; Lee, Ki-Bum

2014-01-01

Graphene is a single-atom thick, two-dimensional sheet of carbon that is characterized by exceptional chemical, electrical, material, optical, and physical properties. As a result, graphene and related materials, such as graphene oxide and reduced graphene oxide, have been brought to the forefront in the field of sensing. Recently, a number of reports have demonstrated that graphene–nanoparticle hybrid structures can act synergistically to offer a number of unique physicochemical properties that are desirable and advantageous for sensing applications. These graphene–nanoparticle hybrid structures are particularly interesting because not only do they display the individual properties of the nanoparticles and of graphene, but they can also exhibit additional synergistic properties thereby enhancing the achievable sensitivity and selectivity using a variety of sensing mechanisms. As such, in this perspective, we will discuss the progress that has been made in the development and application of graphene–nanoparticle hybrid sensors and their future prospects. In particular, we will focus on the preparation of graphene–nanoparticle hybrid structures as well as their application in electronic, electrochemical, and optical sensors. PMID:23828095

Facile method for the synthesis of gold nanoparticles using an ion coater

NASA Astrophysics Data System (ADS)

Lee, Seung Han; Jung, Hyun Kyu; Kim, Tae Cheol; Kim, Chang Hee; Shin, Chang Hwan; Yoon, Tae-Sik; Hong, A.-Ra; Jang, Ho Seong; Kim, Dong Hun

2018-03-01

Herein we report a metal nanoparticle synthesis method based on a physical vapor deposition process instead of the conventional wet process of chemical reactions in liquids. A narrow size distribution of synthesized gold nanoparticles was obtained using an ion coater on glycerin at low vapor pressure. The nanoparticle size could be modulated by controlling the sputtering conditions especially the discharge current. Due to the formation of gold nanoparticles, a surface plasmon resonance peak appeared at ∼530 nm in the absorption spectrum. The surface plasmon resonance peak exhibited red-shift with increasing size of the gold nanoparticles. Our results provide a simple, environmental friendly method for the synthesis of metal nanoparticles by combine low-cost deposition apparatus and a liquid medium, which is free from toxic reagents.

Bubble template synthesis of hollow gold nanoparticles and their applications as theranostic agents

NASA Astrophysics Data System (ADS)

Huang, Chienwen

Hollow gold nanoparticle with a sub-30nm polycrystalline shell and a 50 nm hollow core has been successfully synthesized through the reduction of sodium gold sulfite by electrochemically evolved hydrogen. Such hollow gold nanoparticles exhibit unique plasmonic properties. They strongly scatter and absorb near infrared light. In this thesis we seek to understand the formation mechanism of hollow gold nanoparticles in this new synthesis process and their plasmonic properties. Also, we explore their biomedical applications as theranostic agents (therapeutic and diagnostic imaging). A lithographically patterned electrode consisting of Ag stripes on a glass substrate was used to investigate the formation process of hollow gold nanoparticles. Ag stripes served as working electrode for electrochemically evolution of hydrogen, and adjacent glass areas provided supporting surface for hydrogen nanobubbles nucleation and growth. Hydrogen nanobubbles served as both templates and reducing agents to trigger the autocatalytic disproportionation reaction of sodium gold sulfite. The effects of applied potential and the additives in the electrolyte have been studied. It has been found that the size and size distribution of hollow gold nanoparticle are directly relative to the applied potential, i.e. the hydrogen evolution rate. It has also been found the addition of Ni2+ ions can greatly improve the size distribution of hollow gold nanoparticles that can be contributed to that the newly electrodeposited nickel metal can enhance the hydrogen evolution efficiency. Another additive, ethylenediamine (EDA) can suppress the autocatalytic reaction of gold sulfite to increase the stability of sodium gold sulfite electrolyte. To capture such electrochemically evolved hydrogen nanobubbles, and subsequently to generate hollow gold nanoparticles in large numbers, alumina membranes were placed on the top of the working electrode. Anodic alumina membrane consists of ~200 nm pores, which provides

Heating efficiency in magnetic nanoparticle hyperthermia

NASA Astrophysics Data System (ADS)

Deatsch, Alison E.; Evans, Benjamin A.

2014-03-01

Magnetic nanoparticles for hyperthermic treatment of cancers have gained significant attention in recent years. In magnetic hyperthermia, three independent mechanisms result in thermal energy upon stimulation: Néel relaxation, Brownian relaxation, and hysteresis loss. The relative contribution of each is strongly dependent on size, shape, crystalline anisotropy, and degree of aggregation or agglomeration of the nanoparticles. We review the effects of each of these physical mechanisms in light of recent experimental studies and suggest routes for progress in the field.

Tunable-Porosity Membranes From Discrete Nanoparticles

PubMed Central

Marchetti, Patrizia; Mechelhoff, Martin; Livingston, Andrew G.

2015-01-01

Thin film composite membranes were prepared through a facile single-step wire-wound rod coating procedure in which internally crosslinked poly(styrene-co-butadiene) polymer nanoparticles self-assembled to form a thin film on a hydrophilic ultrafiltration support. This nanoparticle film provided a defect-free separation layer 130–150 nm thick, which was highly permeable and able to withstand aggressive pH conditions beyond the range of available commercial membranes. The nanoparticles were found to coalesce to form a rubbery film when heated above their glass transition temperature (Tg). The retention properties of the novel membrane were strongly affected by charge repulsion, due to the negative charge of the hydroxyl functionalized nanoparticles. Porosity was tuned by annealing the membranes at different temperatures, below and above the nanoparticle Tg. This enabled fabrication of membranes with varying performance. Nanofiltration properties were achieved with a molecular weight cut-off below 500 g mol−1 and a low fouling tendency. Interestingly, after annealing above Tg, memory of the interstitial spaces between the nanoparticles persisted. This memory led to significant water permeance, in marked contrast to the almost impermeable films cast from a solution of the same polymer. PMID:26626565

Metal-coated magnetic nanoparticles in an optically active medium: A nonreciprocal metamaterial

NASA Astrophysics Data System (ADS)

Christofi, Aristi; Stefanou, Nikolaos

2018-03-01

We report on the optical response of a nonreciprocal bianisotropic metamaterial, consisting of spherical, metal-coated magnetic nanoparticles embedded in an optically active medium, thus combining gyrotropy, plasmonic resonances, and chirality in a versatile design. The corresponding effective medium is deduced by an appropriate two-step generalized Maxwell-Garnett homogenization scheme. The associated photonic band structure and transmission spectra are obtained through a six-vector formulation of Maxwell equations, which provides an efficient framework for general bianisotropic structures going beyond existing approaches that involve cumbersome nonlinear eigenvalue problems. Our results, analyzed and discussed in the light of group theory, provide evidence that the proposed metamaterial exhibits some remarkable frequency-tunable properties, such as strong, plasmon-enhanced nonreciprocal polarization azimuth rotation and magnetochiral dichroism.

Effects of para-substituents of styrene derivatives on their chemical reactivity on platinum nanoparticle surfaces.

PubMed

Hu, Peiguang; Chen, Limei; Deming, Christopher P; Lu, Jia-En; Bonny, Lewis W; Chen, Shaowei

2016-06-09

Stable platinum nanoparticles were successfully prepared by the self-assembly of para-substituted styrene derivatives onto the platinum surfaces as a result of platinum-catalyzed dehydrogenation and transformation of the vinyl groups to the acetylene ones, forming platinum-vinylidene/-acetylide interfacial bonds. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent aggregation, suggesting sufficient protection of the nanoparticles by the organic capping ligands, and the average core diameter was estimated to be 2.0 ± 0.3 nm, 1.3 ± 0.2 nm, and 1.1 ± 0.2 nm for the nanoparticles capped with 4-tert-butylstyrene, 4-methoxystyrene, and 4-(trifluoromethyl)styrene, respectively, as a result of the decreasing rate of dehydrogenation with the increasing Taft (polar) constant of the para-substituents. Importantly, the resulting nanoparticles exhibited unique photoluminescence, where an increase of the Hammett constant of the para-substituents corresponded to a blue-shift of the photoluminescence emission, suggesting an enlargement of the HOMO-LUMO band gap of the nanoparticle-bound acetylene moieties. Furthermore, the resulting nanoparticles exhibited apparent electrocatalytic activity towards oxygen reduction in acidic media, with the best performance among the series of samples observed with the 4-tert-butylstyrene-capped nanoparticles due to an optimal combination of the nanoparticle core size and ligand effects on the bonding interactions between platinum and oxygen species.

Microwave-assisted synthesis of iron oxide nanoparticles in biocompatible organic environment

NASA Astrophysics Data System (ADS)

Aivazoglou, E.; Metaxa, E.; Hristoforou, E.

2018-04-01

The development of magnetite and maghemite particles in uniform nanometer size has triggered the interest of the research community due to their many interesting properties leading to a wide range of applications, such as catalysis, nanomedicine-nanobiology and other engineering applications. In this study, a simple, time-saving and low energy-consuming, microwave-assisted synthesis of iron oxide nanoparticles, is presented. The nanoparticles were prepared by microwave-assisted synthesis using polyethylene glycol (PEG) or PEG and β-cyclodextrin (β-CD)/water solutions of chloride salts of iron in the presence of ammonia solution. The prepared nano-powders were characterized using X-Ray Diffraction (XRD), Transition Electron Microscopy (TEM), Fourier-transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Vibrating Sample Magnetometer (VSM), X-Ray Photoelectron Spectroscopy (XPS) and Thermal analysis (TG/DSC). The produced nanoparticles are crystallized mostly in the magnetite and maghemite lattice exhibiting very similar shape and size, with indications of partial PEG coating. Heating time, microwave power and presence of PEG, are the key factors shaping the size properties of nanoparticles. The average size of particles ranges from 10.3 to 19.2 nm. The nanoparticles exhibit a faceted morphology, with zero contamination levels. The magnetic measurements indicate that the powders are soft magnetic materials with negligible coercivity and remanence, illustrating super-paramagnetic behavior.

Hydroxylapatite nanoparticles: fabrication methods and medical applications

NASA Astrophysics Data System (ADS)

Okada, Masahiro; Furuzono, Tsutomu

2012-12-01

Hydroxylapatite (or hydroxyapatite, HAp) exhibits excellent biocompatibility with various kinds of cells and tissues, making it an ideal candidate for tissue engineering, orthopedic and dental applications. Nanosized materials offer improved performances compared with conventional materials due to their large surface-to-volume ratios. This review summarizes existing knowledge and recent progress in fabrication methods of nanosized (or nanostructured) HAp particles, as well as their recent applications in medical and dental fields. In section 1, we provide a brief overview of HAp and nanoparticles. In section 2, fabrication methods of HAp nanoparticles are described based on the particle formation mechanisms. Recent applications of HAp nanoparticles are summarized in section 3. The future perspectives in this active research area are given in section 4.

Synthesis and cytotoxicity study of magnesium ferrite-gold core-shell nanoparticles.

PubMed

Nonkumwong, Jeeranan; Pakawanit, Phakkhananan; Wipatanawin, Angkana; Jantaratana, Pongsakorn; Ananta, Supon; Srisombat, Laongnuan

2016-04-01

In this work, the core-magnesium ferrite (MgFe2O4) nanoparticles were prepared by hydrothermal technique. Completed gold (Au) shell coating on the surfaces of MgFe2O4 nanoparticles was obtained by varying core/shell ratios via a reduction method. Phase identification, morphological evolution, optical properties, magnetic properties and cytotoxicity to mammalian cells of these MgFe2O4 core coated with Au nanoparticles were examined by using a combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, UV-visible spectroscopy (UV-vis), vibrating sample magnetometry and resazurin microplate assay techniques. In general, TEM images revealed different sizes of the core-shell nanoparticles generated from various core/shell ratios and confirmed the completed Au shell coating on MgFe2O4 core nanoparticles via suitable core/shell ratio with particle size less than 100 nm. The core-shell nanoparticle size and the quality of coating influence the optical properties of the products. The UV-vis spectra of complete coated MgFe2O4-Au core-shell nanoparticles exhibit the absorption bands in the near-Infrared (NIR) region indicating high potential for therapeutic applications. Based on the magnetic property measurement, it was found that the obtained MgFe2O4-Au core-shell nanoparticles still exhibit superparamagnetism with lower saturation magnetization value, compared with MgFe2O4 core. Both of MgFe2O4 and MgFe2O4-Au core-shell also showed in vitro non-cytotoxicity to mouse areola fibroblast (L-929) cell line. Copyright © 2015 Elsevier B.V. All rights reserved.

The Dutch-Flemish PROMIS Physical Function item bank exhibited strong psychometric properties in patients with chronic pain.

PubMed

Crins, Martine H P; Terwee, Caroline B; Klausch, Thomas; Smits, Niels; de Vet, Henrica C W; Westhovens, Rene; Cella, David; Cook, Karon F; Revicki, Dennis A; van Leeuwen, Jaap; Boers, Maarten; Dekker, Joost; Roorda, Leo D

2017-07-01

The objective of this study was to assess the psychometric properties of the Dutch-Flemish Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function item bank in Dutch patients with chronic pain. A bank of 121 items was administered to 1,247 Dutch patients with chronic pain. Unidimensionality was assessed by fitting a one-factor confirmatory factor analysis and evaluating resulting fit statistics. Items were calibrated with the graded response model and its fit was evaluated. Cross-cultural validity was assessed by testing items for differential item functioning (DIF) based on language (Dutch vs. English). Construct validity was evaluated by calculation correlations between scores on the Dutch-Flemish PROMIS Physical Function measure and scores on generic and disease-specific measures. Results supported the Dutch-Flemish PROMIS Physical Function item bank's unidimensionality (Comparative Fit Index = 0.976, Tucker Lewis Index = 0.976) and model fit. Item thresholds targeted a wide range of physical function construct (threshold-parameters range: -4.2 to 5.6). Cross-cultural validity was good as four items only showed DIF for language and their impact on item scores was minimal. Physical Function scores were strongly associated with scores on all other measures (all correlations ≤ -0.60 as expected). The Dutch-Flemish PROMIS Physical Function item bank exhibited good psychometric properties. Development of a computer adaptive test based on the large bank is warranted. Copyright © 2017 Elsevier Inc. All rights reserved.

Impact of protein modification on the protein corona on nanoparticles and nanoparticle-cell interactions.

PubMed

Treuel, Lennart; Brandholt, Stefan; Maffre, Pauline; Wiegele, Sarah; Shang, Li; Nienhaus, G Ulrich

2014-01-28

Recent studies have firmly established that cellular uptake of nanoparticles is strongly affected by the presence and the physicochemical properties of a protein adsorption layer around these nanoparticles. Here, we have modified human serum albumin (HSA), a serum protein often used in model studies of protein adsorption onto nanoparticles, to alter its surface charge distribution and investigated the consequences for protein corona formation around small (radius ∼5 nm), dihydrolipoic acid-coated quantum dots (DHLA-QDs) by using fluorescence correlation spectroscopy. HSA modified by succinic anhydride (HSAsuc) to generate additional carboxyl groups on the protein surface showed a 3-fold decreased binding affinity toward the nanoparticles. A 1000-fold enhanced affinity was observed for HSA modified by ethylenediamine (HSAam) to increase the number of amino functions on the protein surface. Remarkably, HSAsuc formed a much thicker protein adsorption layer (8.1 nm) than native HSA (3.3 nm), indicating that it binds in a distinctly different orientation on the nanoparticle, whereas the HSAam corona (4.6 nm) is only slightly thicker. Notably, protein binding to DHLA-QDs was found to be entirely reversible, independent of the modification. We have also measured the extent and kinetics of internalization of these nanoparticles without and with adsorbed native and modified HSA by HeLa cells. Pronounced variations were observed, indicating that even small physicochemical changes of the protein corona may affect biological responses.

Characterization of Platinum Nanoparticles Deposited on Functionalized Graphene Sheets

PubMed Central

Chiang, Yu-Chun; Liang, Chia-Chun; Chung, Chun-Ping

2015-01-01

Due to its special electronic and ballistic transport properties, graphene has attracted much interest from researchers. In this study, platinum (Pt) nanoparticles were deposited on oxidized graphene sheets (cG). The graphene sheets were applied to overcome the corrosion problems of carbon black at operating conditions of proton exchange membrane fuel cells. To enhance the interfacial interactions between the graphene sheets and the Pt nanoparticles, the oxygen-containing functional groups were introduced onto the surface of graphene sheets. The results showed the Pt nanoparticles were uniformly dispersed on the surface of graphene sheets with a mean Pt particle size of 2.08 nm. The Pt nanoparticles deposited on graphene sheets exhibited better crystallinity and higher oxygen resistance. The metal Pt was the predominant Pt chemical state on Pt/cG (60.4%). The results from the cyclic voltammetry analysis showed the value of the electrochemical surface area (ECSA) was 88 m2/g (Pt/cG), much higher than that of Pt/C (46 m2/g). The long-term test illustrated the degradation in ECSA exhibited the order of Pt/C (33%) > Pt/cG (7%). The values of the utilization efficiency were calculated to be 64% for Pt/cG and 32% for Pt/C. PMID:28793577

Strongly luminescent InP/ZnS core-shell nanoparticles.

PubMed

Haubold, S; Haase, M; Kornowski, A; Weller, H

2001-05-18

The wide-bandgap semiconducting material, zinc sulfide, has been coated on indium phosphide nanoclusters to a 1-2-Å thickness. The resulting InP-ZnS core-shell particle (as shown in the TEM image; scale 1 cm=5 nm) exhibits bright luminescence at room temperature with quantum efficiencies as high as 23 %. © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Ultrasmall cationic superparamagnetic iron oxide nanoparticles as nontoxic and efficient MRI contrast agent and magnetic-targeting tool

PubMed Central

Uchiyama, Mayara Klimuk; Toma, Sergio Hiroshi; Rodrigues, Stephen Fernandes; Shimada, Ana Lucia Borges; Loiola, Rodrigo Azevedo; Cervantes Rodríguez, Hernán Joel; Oliveira, Pedro Vitoriano; Luz, Maciel Santos; Rabbani, Said Rahnamaye; Toma, Henrique Eisi; Poliselli Farsky, Sandra Helena; Araki, Koiti

2015-01-01

Fully dispersible, cationic ultrasmall (7 nm diameter) superparamagnetic iron oxide nanoparticles, exhibiting high relaxivity (178 mM−1s−1 in 0.47 T) and no acute or subchronic toxicity in Wistar rats, were studied and their suitability as contrast agents for magnetic resonance imaging and material for development of new diagnostic and treatment tools demonstrated. After intravenous injection (10 mg/kg body weight), they circulated throughout the vascular system causing no microhemorrhage or thrombus, neither inflammatory processes at the mesentery vascular bed and hepatic sinusoids (leukocyte rolling, adhesion, or migration as evaluated by intravital microscopy), but having been spontaneously concentrated in the liver, spleen, and kidneys, they caused strong negative contrast. The nanoparticles are cleared from kidneys and bladder in few days, whereas the complete elimination from liver and spleen occurred only after 4 weeks. Ex vivo studies demonstrated that cationic ultrasmall superparamagnetic iron oxide nanoparticles caused no effects on hepatic and renal enzymes dosage as well as on leukocyte count. In addition, they were readily concentrated in rat thigh by a magnet showing its potential as magnetically targeted carriers of therapeutic and diagnostic agents. Summarizing, cationic ultrasmall superparamagnetic iron oxide nanoparticles are nontoxic and efficient magnetic resonance imaging contrast agents useful as platform for the development of new materials for application in theranostics. PMID:26251595

Size- and pressure-controlled ferromagnetism in LaCoO3 nanoparticles

NASA Astrophysics Data System (ADS)

Fita, I.; Markovich, V.; Mogilyansky, D.; Puzniak, R.; Wisniewski, A.; Titelman, L.; Vradman, L.; Herskowitz, M.; Varyukhin, V. N.; Gorodetsky, G.

2008-06-01

Magnetic properties of nanocrystalline LaCoO3 with particle size of 25, 30, 32, and 38 nm, prepared by the citrate method, were investigated in temperature range 2-320 K, magnetic field up to 50 kOe, and under hydrostatic pressure up to 11 kbar. All nanoparticles exhibit weak ferromagnetism below TC≈85K , in agreement with recent observation on LaCoO3 particles and tensile thin films. It was found that with decreasing particle size, i.e., with increasing the surface to volume ratio, the unit-cell volume increases monotonically due to the surface effect. The ferromagnetic moment increases as well, simultaneously with lattice expansion, whereas TC remains nearly unchanged. On the other hand, an applied hydrostatic pressure suppresses strongly the ferromagnetic phase leading to its full disappearance at 10 kbar, while the TC does not change visibly under pressure. It appears that the ferromagnetism in LaCoO3 nanoparticles is controlled by the unit-cell volume. This clear correlation suggests that the nature of ferromagnetic ground state of LaCoO3 is likely related to orbitally ordered Jahn-Teller active Co3+ ions with intermediate-spin (IS) state, which may persist in the expanded lattice at low temperatures. A robust orbital order presumed among the IS Co3+ species can explain the very stable TC observed for LaCoO3 samples prepared under different conditions: single crystal powders, nanoparticles, and thin films.

Photocatalytic activity of Ag3PO4 nanoparticle/TiO2 nanobelt heterostructures

NASA Astrophysics Data System (ADS)

Liu, Ruoyu; Hu, Peiguang; Chen, Shaowei

2012-10-01

Heterostructures based on Ag3PO4 nanoparticles and TiO2 nanobelts were prepared by a coprecipitation method. The crystalline structures were characterized by X-ray diffraction measurements. Electron microscopic studies showed that the Ag3PO4 nanoparticles and TiO2 nanobelts were in intimate contact which might be exploited to facilitate charge transfer between the two semiconductor materials. In fact, the heterostructures exhibited markedly enhanced photocatalytic activity as compared with unmodified TiO2 nanobelts or commercial TiO2 colloids in the photodegradation of methyl orange under UV irradiation. This was accounted for by the improved efficiency of interfacial charge separation thanks to the unique alignments of their band structures. Remarkably, whereas the photocatalytic activity of the heterostructure was comparable to that of Ag3PO4 nanoparticles alone, the heterostructures exhibited significantly better stability and reusability in repeated tests than the Ag3PO4 nanoparticles.

Synthesis of three-dimensional AgI@TiO2 nanoparticles with improved photocatalytic performance.

PubMed

An, Changhua; Jiang, Wen; Wang, Jizhuang; Wang, Shutao; Ma, Zhanhua; Li, Yanpeng

2013-06-28

Three-dimensional (3D) TiO2 with an acanthosphere-like morphology composed of nanothorns has been used as a suitable support to fabricate a visible-light-induced 3D AgI@TiO2 nanophotocatalyst. The structural characterization revealed that the size of the obtained AgI@TiO2 nanocomposite was close to that of pristine TiO2 particles, where AgI nanoparticles were evenly dispersed on the surfaces of "thorns" of TiO2. The as-achieved 3D AgI@TiO2 nanophotocatalyst exhibited enhanced photocatalytic performance towards photodegradation of organic pollutants, e.g., rhodamine B (RhB), in comparison with TiO2, P25, AgI and AgI@P25 with the same quantity. The enhanced photocatalytic performance is attributed to the strong visible light absorption and the defined interfaces between AgI nanoparticles and TiO2 nanothorns with efficient separation of photogenerated carriers. The excellent performance of the 3D AgI@TiO2 nanophotocatalyst suggests its promising applications in water treatment and environmental remediation.

Tuning structure of oppositely charged nanoparticle and protein complexes

NASA Astrophysics Data System (ADS)

Kumar, Sugam; Aswal, V. K.; Callow, P.

2014-04-01

Small-angle neutron scattering (SANS) has been used to probe the structures of anionic silica nanoparticles (LS30) and cationic lyszyme protein (M.W. 14.7kD, I.P. ˜ 11.4) by tuning their interaction through the pH variation. The protein adsorption on nanoparticles is found to be increasing with pH and determined by the electrostatic attraction between two components as well as repulsion between protein molecules. We show the strong electrostatic attraction between nanoparticles and protein molecules leads to protein-mediated aggregation of nanoparticles which are characterized by fractal structures. At pH 5, the protein adsorption gives rise to nanoparticle aggregation having surface fractal morphology with close packing of nanoparticles. The surface fractals transform to open structures of mass fractal morphology at higher pH (7 and 9) on approaching isoelectric point (I.P.).

Spin morphologies and heat dissipation in spherical assemblies of magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Anand, Manish; Carrey, Julian; Banerjee, Varsha

2016-09-01

Aggregates of magnetic nanoparticles (MNPs) exhibit unusual properties due to the interplay of small system size and long-range dipole-dipole interactions. Using the micromagnetic simulation software oommf, we study the spin morphologies and heat dissipation in micron-size spherical assemblies of MNPs. In particular, we examine the sensitivity of these properties to the dipolar strength, manipulated by the interparticle separation. As oommf is not designed for such a study, we have incorporated a novel scaling protocol for this purpose. We believe that it is essential for all studies where volume fractions are varied. Our main results are as follows: (i) Dense assemblies exhibit strong dipolar effects which yield local magnetic order in the core but not on the surface, where moments are randomly oriented. (ii) The probability distribution of ground-state energy exhibits a long high-energy tail for surface spins in contrast to small tails for the core spins. Consequently, there is a wide variation in the energy of surface spins but not the core spins. (iii) There is strong correlation between ground-state energy and heating properties on application of an oscillating magnetic field h (t ) =hocos2 π f t : the particles in the core heat uniformly, while those on the surface exhibit a wide range from cold to intensely hot. (iv) Specific choices of ho and f yield characteristic spatial heat distributions, e.g., hot surface and cold core, or vice versa. (iv) For all values of ho and f that we consider, heating was maximum at a specific volume fraction. These results are especially relevant in the context of contemporary applications such as hyperthermia and chemotherapy, and also for novel materials such as smart polymer beads and superspin glasses.

Mulberry leaf extract mediated synthesis of gold nanoparticles and its anti-bacterial activity against human pathogens

NASA Astrophysics Data System (ADS)

Adavallan, K.; Krishnakumar, N.

2014-06-01

Gold nanoparticles (Au-NPs) were synthesized at room temperature using Morus alba (mulberry) leaf extract as reducing and stabilizing agent. The development of plant mediated synthesis of nanoparticles is gaining importance due to its simplicity, low cost, non-toxicity, eco-friendliness, long term stability and reproducible aqueous synthesis method to obtain a self-assembly of nearly monodispersed Au-NPs. The formation and morphology of biosynthesized nanoparticles are investigated with the help of UV-Vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) techniques. Au-NPs formation was screened by UV-Vis spectroscopy through color conversion due to surface plasmon resonance band at 538 nm for Au-NPs. DLS studies revealed that the average size of Au-NPs was 50 nm. TEM studies showed the particles to be nearly spherical with few irregular shapes and particle size ranges 15-53 nm. The AFM image clearly shows the surface morphology of the well-dispersed Au-NPs with less than 50 nm. The high crystallinity of nanoparticles is evident from bright circular spots in the selected area electron diffraction (SAED) pattern. X-ray diffraction pattern showed high purity and face-centered cubic structure of Au-NPs. The FT-IR results indicate the presence of different functional groups present in the biomolecule capping the nanoparticles. Further, biosynthesized Au-NPs show strong zone of inhibition against Vibrio cholera (gram-negative) and Staphylococcus aureus (gram-positive) whereas, chemically synthesized Au-NPs and mulberry leaf extract exhibit a fair zone of inhibition.

Ionic liquid functionalized synthesis of gold nanoparticles in response to Elaise Guineensis (oil palm) leaves amount

NASA Astrophysics Data System (ADS)

Irfan, Muhammad; Ahmad, Tausif; Moniruzzaman, Muhammad; Abdullah, Bawadi

2018-05-01

A modified bio-synthesis method was developed to synthesize gold nanoparticles (AuNPs) using Elaeis Guineensis (oil palm) leaves (OPL) extract prepared in aqueous solution of IL, [EMIM][OAc]. The strong interaction and capping ability of IL at surface of AuNPs was examined through XPS analysis. The effect of OPL powder to liquid (P/L) ratio on absorbance, maximum wavelength (λmax) and size variation of AuNPs was observed through UV-vis. TEM analysis indicated predominantly spherical shape AuNPs with mean diameter of 15.76 nm. This study exhibits a rapid, cheap and efficient method to achieve stable AuNPs using bio-waste material.

Extracellular synthesis of mycogenic silver nanoparticles by Cylindrocladium floridanum and its homogeneous catalytic degradation of 4-nitrophenol.

PubMed

Narayanan, Kannan Badri; Park, Hyun Ho; Sakthivel, Natarajan

2013-12-01

Green synthesis of extracellular mycogenic silver nanoparticles using the fungus, Cylindrocladium floridanum is reported. The synthesized mycogenic silver nanoparticles were characterized using UV-Vis absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. The nanoparticles exhibit fcc structure with Bragg's reflections of (111), (200), (220) and (311) was evidenced by XRD pattern, high-resolution TEM lattice fringes and circular rings in selected-area electron diffraction (SAED) pattern. The morphology of nanoparticles was roughly spherical in shape with an average size of ca. 25 nm. From FTIR spectrum, it was found that the biomolecules with amide I and II band were involved in the stabilization of nanoparticles. These mycogenic silver nanoparticles exhibited the homogeneous catalytic potential in the reduction of pollutant, 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using sodium borohydride, which followed a pseudo-first-order kinetic model. Thus, the synthesis of metal nanoparticles using sustainable microbial approach opens up possibilities in the usage of mycogenic metal nanoparticles as catalysts in various chemical reactions. Copyright © 2013 Elsevier B.V. All rights reserved.

Polysaccharide-Coated Magnetic Nanoparticles for Imaging and Gene Therapy

PubMed Central

Uthaman, Saji; Cherukula, Kondareddy; Cho, Chong-Su; Park, In-Kyu

2015-01-01

Today, nanotechnology plays a vital role in biomedical applications, especially for the diagnosis and treatment of various diseases. Among the many different types of fabricated nanoparticles, magnetic metal oxide nanoparticles stand out as unique and useful tools for biomedical applications, because of their imaging characteristics and therapeutic properties such as drug and gene carriers. Polymer-coated magnetic particles are currently of particular interest to investigators in the fields of nanobiomedicine and fundamental biomaterials. Theranostic magnetic nanoparticles that are encapsulated or coated with polymers not only exhibit imaging properties in response to stimuli, but also can efficiently deliver various drugs and therapeutic genes. Even though a large number of polymer-coated magnetic nanoparticles have been fabricated over the last decade, most of these have only been used for imaging purposes. The focus of this review is on polysaccharide-coated magnetic nanoparticles used for imaging and gene delivery. PMID:26078971

Diatomite silica nanoparticles for drug delivery

PubMed Central

2014-01-01

Diatomite is a natural fossil material of sedimentary origin, constituted by fragments of diatom siliceous skeletons. In this preliminary work, the properties of diatomite nanoparticles as potential system for the delivery of drugs in cancer cells were exploited. A purification procedure, based on thermal treatments in strong acid solutions, was used to remove inorganic and organic impurities from diatomite and to make them a safe material for medical applications. The micrometric diatomite powder was reduced in nanoparticles by mechanical crushing, sonication, and filtering. Morphological analysis performed by dynamic light scattering and transmission electron microscopy reveals a particles size included between 100 and 300 nm. Diatomite nanoparticles were functionalized by 3-aminopropyltriethoxysilane and labeled by tetramethylrhodamine isothiocyanate. Different concentrations of chemically modified nanoparticles were incubated with cancer cells and confocal microscopy was performed. Imaging analysis showed an efficient cellular uptake and homogeneous distribution of nanoparticles in cytoplasm and nucleus, thus suggesting their potentiality as nanocarriers for drug delivery. PACS 87.85.J81.05.Rm; 61.46. + w PMID:25024689

Preparation of Bioactive Polysaccharide Nanoparticles with Enhanced Radical Scavenging Activity and Antimicrobial Activity.

PubMed

Qin, Yang; Xiong, Liu; Li, Man; Liu, Jing; Wu, Hao; Qiu, Hongwei; Mu, Hongyan; Xu, Xingfeng; Sun, Qingjie

2018-05-02

Because of their biocompatibility and biodegradability in vivo, natural polysaccharides are effective nanocarriers for delivery of active ingredients or drugs. Moreover, bioactive polysaccharides, such as tea, Ganoderma lucidum, and Momordica charantia polysaccharides (TP, GLP, and MCP), have antibacterial, antioxidant, antitumor, and antiviral properties. In this study, tea, Ganoderma lucidum, and Momordica charantia polysaccharide nanoparticles (TP-NPs, GLP-NPs, and MCP-NPs) were prepared via the nanoprecipitation approach. When the ethanol to water ratio was 10:1, the diameter of the spherical polysaccharide nanoparticles was the smallest, and the mean particle size of the TP-NPs, GLP-NPs, and MCP-NPs was 99 ± 15, 95 ± 7, and 141 ± 9 nm, respectively. When exposed to heat, increased ionic strength and pH levels, the nanoparticles exhibited superior stability and higher activity than the corresponding polysaccharides. In physiological conditions (pH 7.4), the nanoparticles underwent different protein adsorption capacities in the following order: MCP-NPs> TP-NPs> GLP-NPs. Moreover, the 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radical, and superoxide anion radical scavenging rates of the nanoparticles were increased by 9-25% as compared to the corresponding polysaccharides. Compared to the bioactive polysaccharides, the nanoparticles enhanced antimicrobial efficacy markedly and exhibited long-acting antibacterial activity.

Defect tolerance and the effect of structural inhomogeneity in plasmonic DNA-nanoparticle superlattices

DOE PAGES

Ross, Michael B.; Ku, Jessie C.; Blaber, Martin G.; ...

2015-08-03

Bottom-up assemblies of plasmonic nanoparticles exhibit unique optical effects such as tunable reflection, optical cavity modes, and tunable photonic resonances. In this paper, we compare detailed simulations with experiment to explore the effect of structural inhomogeneity on the optical response in DNA-gold nanoparticle superlattices. In particular, we explore the effect of background environment, nanoparticle polydispersity (>10%), and variation in nanoparticle placement (~5%). At volume fractions less than 20% Au, the optical response is insensitive to particle size, defects, and inhomogeneity in the superlattice. At elevated volume fractions (20% and 25%), structures incorporating different sized nanoparticles (10-, 20-, and 40-nm diameter)more » each exhibit distinct far-field extinction and near-field properties. These optical properties are most pronounced in lattices with larger particles, which at fixed volume fraction have greater plasmonic coupling than those with smaller particles. Moreover, the incorporation of experimentally informed inhomogeneity leads to variation in far-field extinction and inconsistent electric-field intensities throughout the lattice, demonstrating that volume fraction is not sufficient to describe the optical properties of such structures. Finally, these data have important implications for understanding the role of particle and lattice inhomogeneity in determining the properties of plasmonic nanoparticle lattices with deliberately designed optical properties.« less

Biomimetic, Strong, Tough, and Self-Healing Composites Using Universal Sealant-Loaded, Porous Building Blocks.

PubMed

Hwang, Sung Hoon; Miller, Joseph B; Shahsavari, Rouzbeh

2017-10-25

Many natural materials, such as nacre and dentin, exhibit multifunctional mechanical properties via structural interplay between compliant and stiff constituents arranged in a particular architecture. Herein, we present, for the first time, the bottom-up synthesis and design of strong, tough, and self-healing composite using simple but universal spherical building blocks. Our composite system is composed of calcium silicate porous nanoparticles with unprecedented monodispersity over particle size, particle shape, and pore size, which facilitate effective loading and unloading with organic sealants, resulting in 258% and 307% increases in the indentation hardness and elastic modulus of the compacted composite. Furthermore, heating the damaged composite triggers the controlled release of the nanoconfined sealant into the surrounding area, enabling moderate recovery in strength and toughness. This work paves the path towards fabricating a novel class of biomimetic composites using low-cost spherical building blocks, potentially impacting bone-tissue engineering, insulation, refractory and constructions materials, and ceramic matrix composites.

Magnetic and luminescent properties of multifunctional GdF3:Eu3+ nanoparticles

NASA Astrophysics Data System (ADS)

Wong, Hon-Tung; Chan, H. L. W.; Hao, J. H.

2009-07-01

Multifunctional GdF3:Eu3+ nanoparticles were synthesized using a hydrothermal method. Photoluminescent excitation and emission spectra, and lifetime were measured. The average lifetime of the nanoparticles is about 11 ms. The nanoparticle exhibits paramagnetism at both 293 and 77 K, ascribing to noninteracting localized nature of the magnetic moment in the compound. The magnetic properties of GdF3:Eu3+ is intrinsic to the Gd3+ ions, which is unaffected by the doping concentration of the Eu3+ luminescent centers. A measured magnetization of approximately 2 emu/g is close to reported values of other nanoparticles for bioseparation.

Magnetic mesoporous silica nanoparticles for potential delivery of chemotherapeutic drugs and hyperthermia.

PubMed

Tao, Cuilian; Zhu, Yufang

2014-11-07

Magnetic mesoporous silica (MMS) nanoparticles with controllable magnetization have been synthesized by encapsulating Fe3O4 nanoparticles in a mesoporous silica matrix. The structure, magnetic heating capacity and drug delivery ability of MMS nanoparticles were evaluated. The results showed that MMS nanoparticles had an average particle size of 150 nm and showed low cytotoxicity and efficient cell uptake ability. MMS nanoparticles exhibited a sustained drug release in the medium of pH 5.0, but a very slow release in the medium of pH 7.4. On the other hand, MMS nanoparticles could controllably generate heat to reach the hyperthermia temperature within a short time upon exposure to an alternating magnetic field due to the superparamagnetic behavior and controllable magnetization. Therefore, MMS nanoparticles could provide a promising multifunctional platform for the combination of chemotherapy and hyperthermia for cancer therapy.

Eco-friendly approach for nanoparticles synthesis and mechanism behind antibacterial activity of silver and anticancer activity of gold nanoparticles.

PubMed

Patil, Maheshkumar Prakash; Kim, Gun-Do

2017-01-01

This review covers general information about the eco-friendly process for the synthesis of silver nanoparticles (AgNP) and gold nanoparticles (AuNP) and focuses on mechanism of the antibacterial activity of AgNPs and the anticancer activity of AuNPs. Biomolecules in the plant extract are involved in reduction of metal ions to nanoparticle in a one-step and eco-friendly synthesis process. Natural plant extracts contain wide range of metabolites including carbohydrates, alkaloids, terpenoids, phenolic compounds, and enzymes. A variety of plant species and plant parts have been successfully extracted and utilized for AgNP and AuNP syntheses. Green-synthesized nanoparticles eliminate the need for a stabilizing and capping agent and show shape and size-dependent biological activities. Here, we describe some of the plant extracts involved in nanoparticle synthesis, characterization methods, and biological applications. Nanoparticles are important in the field of pharmaceuticals for their strong antibacterial and anticancer activity. Considering the importance and uniqueness of this concept, the synthesis, characterization, and application of AgNPs and AuNPs are discussed in this review.

Synthesis and photoluminescence of ultra-pure germanium nanoparticles

NASA Astrophysics Data System (ADS)

Chivas, R.; Yerci, S.; Li, R.; Dal Negro, L.; Morse, T. F.

2011-09-01

We have used aerosol deposition to synthesize defect and micro-strain free, ultra-pure germanium nanoparticles. Transmission electron microscopy images show a core-shell configuration with highly crystalline core material. Powder X-ray diffraction measurements verify the presence of highly pure, nano-scale germanium with average crystallite size of 30 nm and micro-strain of 0.058%. X-ray photoelectron spectroscopy demonstrates that GeO x ( x ⩽ 2) shells cover the surfaces of the nanoparticles. Under optical excitation, these nanoparticles exhibit two separate emission bands at room temperature: a visible emission at 500 nm with 0.5-1 ns decay times and an intense near-infrared emission at 1575 nm with up to ˜20 μs lifetime.

Superparamagnetic iron oxide nanoparticles incorporated into silica nanoparticles by inelastic collision via ultrasonic field: Role of colloidal stability

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

Sodipo, Bashiru Kayode; Azlan, Abdul Aziz; Innovation

2015-04-24

Superparamagnetic iron oxide nanoparticles (SPION)/Silica composite nanoparticles were prepared by ultrasonically irradiating colloidal suspension of silica and SPION mixture. Both silica and SPION were synthesized independently via co-precipitation and sol-gel method, respectively. Their mixtures were sonicated at different pH between 3 and 5. Electrophoresis measurement and other physicochemical analyses of the products demonstrate that at lower pH SPION was found incorporated into the silica. However, at pH greater than 4, SPION was unstable and unable to withstand the turbulence flow and shock wave from the ultrasonic field. Results suggest that the formation of the SPION/silica composite nanoparticles is strongly relatedmore » to the inelastic collision induced by ultrasonic irradiation. More so, the formation the composite nanoparticles via the ultrasonic field are dependent on the zeta potential and colloidal stability of the particles.« less

Biological Fate of Fe3O4 Core-Shell Mesoporous Silica Nanoparticles Depending on Particle Surface Chemistry

PubMed Central

Rascol, Estelle; Daurat, Morgane; Da Silva, Afitz; Maynadier, Marie; Dorandeu, Christophe; Charnay, Clarence; Garcia, Marcel; Lai-Kee-Him, Joséphine; Bron, Patrick; Auffan, Mélanie; Angeletti, Bernard; Devoisselle, Jean-Marie; Guari, Yannick; Gary-Bobo, Magali; Chopineau, Joël

2017-01-01

The biological fate of nanoparticles (NPs) for biomedical applications is highly dependent of their size and charge, their aggregation state and their surface chemistry. The chemical composition of the NPs surface influences their stability in biological fluids, their interaction with proteins, and their attraction to the cell membranes. In this work, core-shell magnetic mesoporous silica nanoparticles (Fe3O4@MSN), that are considered as potential theranostic candidates, are coated with polyethylene glycol (PEG) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayer. Their biological fate is studied in comparison to the native NPs. The physicochemical properties of these three types of NPs and their suspension behavior in different media are investigated. The attraction to a membrane model is also evaluated using a supported lipid bilayer. The surface composition of NPs strongly influences their dispersion in biological fluids mimics, protein binding and their interaction with cell membrane. While none of these types of NPs is found to be toxic on mice four days after intravenous injection of a dose of 40 mg kg−1 of NPs, their surface coating nature influences the in vivo biodistribution. Importantly, NP coated with DMPC exhibit a strong accumulation in liver and a very low accumulation in lung in comparison with nude or PEG ones. PMID:28665317

Resveratrol-loaded glycyrrhizic acid-conjugated human serum albumin nanoparticles wrapping resveratrol nanoparticles: Preparation, characterization, and targeting effect on liver tumors.

PubMed

Wu, Mingfang; Lian, Bolin; Deng, Yiping; Feng, Ziqi; Zhong, Chen; Wu, Weiwei; Huang, Yannian; Wang, Lingling; Zu, Chang; Zhao, Xiuhua

2017-08-01

for HepG2 cells was evaluated using fluorescence-modified albumin techniques. The uptake rate of glycyrrhizic acid-conjugated human serum albumin nanoparticles wrapping resveratrol nanoparticles was higher than that of pure resveratrol and increased with increased nanoparticles concentration. The in vivo body distribution of glycyrrhizic acid-conjugated human serum albumin nanoparticles wrapping resveratrol nanoparticles labeled with the near-infrared fluorophore Cy5 was monitored in H22 tumor-bearing mice through near-infrared fluorescence imaging systems. Glycyrrhizic acid-conjugated human serum albumin nanoparticles wrapping resveratrol nanoparticles exhibited effective target orientation to liver tumor and sustained-release property.

Generation of metal nanoparticles from silver and copper objects: nanoparticle dynamics on surfaces and potential sources of nanoparticles in the environment.

PubMed

Glover, Richard D; Miller, John M; Hutchison, James E

2011-11-22

The use of silver nanoparticles (AgNPs) in antimicrobial applications, including a wide range of consumer goods and apparel, has attracted attention because of the unknown health and environmental risks associated with these emerging materials. Of particular concern is whether there are new risks that are a direct consequence of their nanoscale size. Identifying those risks associated with nanoscale structure has been difficult due to the fundamental challenge of detecting and monitoring nanoparticles in products or the environment. Here, we introduce a new strategy to directly monitor nanoparticles and their transformations under a variety of environmental conditions. These studies reveal unprecedented dynamic behavior of AgNPs on surfaces. Most notably, under ambient conditions at relative humidities greater than 50%, new silver nanoparticles form in the vicinity of the parent particles. This humidity-dependent formation of new particles was broadly observed for a variety of AgNPs and substrate surface coatings. We hypothesize that nanoparticle production occurs through a process involving three stages: (i) oxidation and dissolution of silver from the surface of the particle, (ii) diffusion of silver ion across the surface in an adsorbed water layer, and (iii) formation of new, smaller particles by chemical and/or photoreduction. Guided by these findings, we investigated non-nanoscale sources of silver such as wire, jewelry, and eating utensils that are placed in contact with surfaces and found that they also formed new nanoparticles. Copper objects display similar reactivity, suggesting that this phenomenon may be more general. These findings challenge conventional thinking about nanoparticle reactivity and imply that the production of new nanoparticles is an intrinsic property of the material that is not strongly size dependent. The discovery that AgNPs and CuNPs are generated spontaneously from manmade objects implies that humans have long been in direct

Merely Measuring the UV-Visible Spectrum of Gold Nanoparticles Can Change Their Charge State.

PubMed

Navarrete, Jose; Siefe, Chris; Alcantar, Samuel; Belt, Michael; Stucky, Galen D; Moskovits, Martin

2018-02-14

Metallic nanostructures exhibit a strong plasmon resonance at a wavelength whose value is sensitive to the charge density in the nanostructure, its size, shape, interparticle coupling, and the dielectric properties of its surrounding medium. Here we use UV-visible transmission and reflectance spectroscopy to track the shifts of the plasmon resonance in an array of gold nanoparticles buried under metal-oxide layers of varying thickness produced using atomic layer deposition (ALD) and then coated with bulk layers of one of three metals: aluminum, silver, or gold. A significant shift in the plasmon resonance was observed and a precise value of ω p , the plasmon frequency of the gold comprising the nanoparticles, was determined by modeling the composite of gold nanoparticles and metal-oxide layer as an optically homogeneous film of core-shell particles bounded by two substrates: one of quartz and the other being one of the aforementioned metals, then using a Maxwell-Garnett effective medium expression to extract ω p for the gold nanoparticles before and after coating with the bulk metals. Under illumination, the change in the charge density of the gold nanoparticles per particle determined from the change in the values of ω p is found to be some 50-fold greater than what traditional electrostatic contact electrification models compute based on the work function difference of the two conductive materials. Moreover, when using bulk gold as the capping layer, which should have resulted in a negligible charge exchange between the gold nanoparticles and the bulk gold, a significant charge transfer from the bulk gold layer to the nanoparticles was observed as with the other metals. We explain these observations in terms of the "plasmoelectric effect", recently described by Atwater and co-workers, in which the gold nanoparticles modify their charge density to allow their resonant wavelength to match that of the incident light, thereby achieving, a lower value of the

Synthesis of High Valence Silver-Loaded Mesoporous Silica with Strong Antibacterial Properties

PubMed Central

Chen, Chun-Chi; Wu, Hsin-Hsien; Huang, Hsin-Yi; Liu, Chen-Wei; Chen, Yi-Ning

2016-01-01

A simple chemical method was developed for preparing high valence silver (Ag)-loaded mesoporous silica (Ag-ethylenediaminetetraacetic acid (EDTA)-SBA-15), which showed strong antibacterial activity. Ag-EDTA-SBA-15 exhibited stronger and more effective antibacterial activity than commercial Ag nanoparticles did, and it offered high stability of high valence silver in the porous matrix and long-lasting antibacterial activity. The synthesized materials were characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, and transmission electron microscopy (TEM). Ag existed in both surface complexation and Ag particles. EDTA anchored within a porous structure chelated Ag ions in higher oxidation states and prevented their agglomeration and oxidation reduction. The XRD results showed that most Ag in the Ag-EDTA-SBA-15 existed in higher oxidation states such as Ag(II) and Ag(III). However, the XPS and TEM results showed that Ag easily reduced in lower oxidation states and agglomerated as Ag particles on the exterior layer of the SBA-15. PMID:26742050

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.

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.

Microwave-assisted synthesis of highly fluorescent nanoparticles of a melamine-based porous covalent organic framework for trace-level detection of nitroaromatic explosives.

PubMed

Zhang, Wang; Qiu, Ling-Guang; Yuan, Yu-Peng; Xie, An-Jian; Shen, Yu-Hua; Zhu, Jun-Fa

2012-06-30

Covalent organic frameworks (COFs) are a new generation of porous materials constructed from light elements linked by strong covalent bonds. Herein we present rapid preparation of highly fluorescent nanoparticles of a new type of COF, i.e. melamine-based porous polymeric network SNW-1, by a microwave-assisted synthesis route. Although the synthesis of SNW-1 has to be carried out at 180°C for 3d under conventional reflux conditions, SNW-1 nanoparticles could be obtained in 6h by using such a microwave-assisted method. The results obtained have clearly demonstrated that microwave-assisted synthesis is a simple yet highly efficient approach to nanoscale COFs or other porous polymeric materials. Remarkably, the as-synthesized SNW-1 nanoparticles exhibit extremely high sensitivity and selectivity, as well as fast response to nitroaromatic explosives such as 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (Tetryl) and picric acid (PA) without interference by common organic solvents, which is due to the nanoscaled size and unique hierarchical porosity of such fluorescence-based sensing material. Copyright © 2012 Elsevier B.V. All rights reserved.

Growing Platinum-Ruthenium-Tin ternary alloy nanoparticles on reduced graphene oxide for strong ligand effect toward enhanced ethanol oxidation reaction.

PubMed

Xia, Qing Qing; Zhang, Lian Ying; Zhao, Zhi Liang; Li, Chang Ming

2017-11-15

Uniform Pt 1 Ru 0.5 Sn 0.5 ternary alloy nanoparticles are in situ deposited on reduced graphene oxide (Pt 1 Ru 0.5 Sn 0.5 -RGO) through its functional groups and defects as nucleation sites to greatly electrocatalyze ethanol oxidation reaction for much higher mass current densities, larger apparent specific current densities and better stability than commercial Pt-C catalyst (Pt-C(commer)). Mechanistic studies indicate that the excellent electrocatalytic activity and anti-poisoning are resulted from a strong ligand effect of the ternary alloy components, in which the charge transfer is boosted while decreasing the density of states close to the Fermi level of Pt to reduce bond energy between Pt and CO-like adsorbates for greatly improved anti-poisoning ability. This work holds a great promise to fabricate a high performance anode catalyst with a low Pt loading for direct ethanol fuel cells. Copyright © 2017. Published by Elsevier Inc.

High-Z Nanoparticle/Polymer Nanocomposites for Gamma-Ray Scintillation Detectors

NASA Astrophysics Data System (ADS)

Liu, Chao

An affordable and reliable solution for spectroscopic gamma-ray detection has long been sought after due to the needs from research, defense, and medical applications. Scintillators resolve gamma energy by proportionally converting a single high-energy photon into a number of photomultiplier-tube-detectable low-energy photons, which is considered a more affordable solution for general purposes compared to the delicate semiconductor detectors. An ideal scintillator should simultaneously exhibit the following characteristics: 1) high atomic number (Z) for high gamma stopping power and photoelectron production; 2) high light yield since the energy resolution is inversely proportional to the square root of light yield; 3) short emission decay lifetime; and 4) low cost and scalable production. However, commercial scintillators made from either inorganic single crystals or plastics fail to satisfy all requirements due to their intrinsic material properties and fabrication limitations. The concept of adding high-Z constituents into plastic scintillators to harness high Z, low cost, and fast emission in the resulting nanocomposite scintillators is not new in and of itself. Attempts have been made by adding organometallics, quantum dots, and scintillation nanocrystals into the plastic matrix. High-Z organometallics have long been used to improve the Z of plastic scintillators; however, their strong spin-orbit coupling effect entails careful triplet energy matching using expensive triplet emitters to avoid severe quenching of the light yield. On the other hand, reported quantum dot- and nanocrystal-polymer nanocomposites suffer from moderate Z and high optical loss due to aggregation and self-absorption at loadings higher than 10 wt%, limiting their potential for practical application. This dissertation strives to improve the performance of nanoparticle-based nanocomposite scintillators. One focus is to synthesize transparent nanocomposites with higher loadings of high

Gold nanoparticles prepared by electro-exploding wire technique in aqueous solutions

NASA Astrophysics Data System (ADS)

Kumar, Lalit; Kapoor, Akanksha; Meghwal, Mayank; Annapoorni, S.

2016-05-01

This article presents an effective approach for the synthesis of Au nanoparticles via an environmentally benevolent electro-exploding wire (EEW) technique. In this process, Au nanoparticles evolve through the plasma generated from the parent Au metal. Compared to other typical chemical methods, electro-exploding wire technique is a simple and economical technique which normally operates in water or organic liquids under ambient conditions. Efficient size control was achieved using different aqueous medium like (1mM) NaCl, deionized water and aqueous solution of sodium hydroxide (NaOH, pH 9.5) using identical electro-exploding conditions. The gold nanoparticles exhibited the UV-vis absorption spectrum with a maximum absorption band at 530 nm, similar to that of gold nanoparticles chemically prepared in a solution. The mechanism of size variation of Au nanoparticles is also proposed. The results obtained help to develop methodologies for the control of EEW based nanoparticle growth and the functionalization of nanoparticle surfaces by specific interactions.

Multifunctional superparamagnetic nanoparticles for enhanced drug transport in cystic fibrosis

NASA Astrophysics Data System (ADS)

Armijo, Leisha M.; Brandt, Yekaterina I.; Rivera, Antonio C.; Cook, Nathaniel C.; Plumley, John B.; Withers, Nathan J.; Kopciuch, Michael; Smolyakov, Gennady A.; Huber, Dale L.; Smyth, Hugh D.; Osinski, Marek

2012-10-01

Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the treatment of cystic fibrosis lung infections, the leading cause of mortality in cystic fibrosis patients. We investigate the use of iron oxide nanoparticles to increase the effectiveness of administering antibiotics through aerosol inhalation using two mechanisms: directed particle movement in the presence of an inhomogeneous static external magnetic field and magnetic hyperthermia. Magnetic hyperthermia is an effective method for decreasing the viscosity of the mucus and biofilm, thereby enhancing drug, immune cell, and antibody penetration to the affected area. Iron oxide nanoparticles of various sizes and morphologies were synthesized and tested for specific losses (heating power). Nanoparticles in the superparamagnetic to ferromagnetic size range exhibited excellent heating power. Additionally, iron oxide / zinc selenide core/shell nanoparticles were prepared, in order to enable imaging of the iron oxide nanoparticles. We also report on synthesis and characterization of MnSe/ZnSeS alloyed quantum dots.

Magnetic Nanoparticles: Surface Effects and Properties Related to Biomedicine Applications

PubMed Central

Issa, Bashar; Obaidat, Ihab M.; Albiss, Borhan A.; Haik, Yousef

2013-01-01

Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10–100 μm), viruses, genes, down to proteins (3–50 nm). The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents. PMID:24232575

Effect of organic fuels on surface area and photocatalytic activity of scheelite CaWO4 nanoparticles

NASA Astrophysics Data System (ADS)

Manjunath, Kusuma; Gujjarahalli Thimmanna, Chandrappa

2018-03-01

Discrete nanoscale calcium tungstate (CaWO4) nanoparticles with exquisite photocatalytic activities were synthesized through ultra-rapid solution combustion route. Here, we aim to study the effect of different fuels on the synthesis of CaWO4 nanoparticles which lead to improve the characteristic properties and morphological evolution of the powders. From BET surface area measurement, it is observed that CaWO4 nanoparticles synthesized by using citric acid as fuel exhibits relatively large surface area (31.78 m2 g‑1) as compared to other fuels. The powder x-ray diffraction (PXRD) studies reveal that CaWO4 nanoparticles belong to scheelite type tetragonal system. The morphology of CaWO4 nanoparticles investigated using scanning electron microscopy (SEM) reveals that the powders are highly porous and agglomerated. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the CaWO4 nanoparticles show that a well-dispersed nearly oval-shaped nanoparticles with variable dimensions and lattice spacing that depends on the type of fuels used in the synthesis. The selected area electron diffraction (SAED) patterns of CaWO4 nanoparticles exhibit several concentric rings with bright spots indicating the polycrystalline nature of the powders. Investigation on photocatalytic activity of CaWO4 nanoparticles synthesized using citric acid shows highest (∼93%) degradation of methylene blue (MB).

Molecules coating magnetic nanoparticles for oil-field applications

NASA Astrophysics Data System (ADS)

Zuluaga, Sebastian; Manchanda, Priyanka; Pantelides, Sokrates

Magnetic nanoparticles have recently attracted significant attention in scientific and industrial communities due to their use in the fields of catalysis, spintronics, biomedical applications, and oil recovery and reservoir characterization. However, these nanoparticles have to be protected with a coating layer of molecules that prevents the nanoparticles from oxidation, which is known to occur in air, and from agglomeration into larger nanoparticles. Therefore, the binding of the molecules to the nanoparticles is critical before a large scale implementation can be done. Here we report results of density functional theory calculations on several molecules (methylamine, acetic acid, boronic acid, ethyl phosphate, and ethyl trihydroxysilane) and magnetic nanoparticles (Fe3O4, NiFe2O4, and Fe3C). We focus on two main points: 1) the bond strength between the organic molecule and the nano particle, and 2) how, H2O and H+ in the oil well may facilitate the desorption of the molecules. The results show that H+ and H2O molecules facilitate the desorption of molecules reducing the bond strength by several eV. On the other hand, the results allow us to identify and design molecules that exhibit the best performance in protecting each nanoparticle. Supported by a Grant from the Petroleum Institute, Abu Dhabi.

Dextran sulfate nanoparticles as a theranostic nanomedicine for rheumatoid arthritis.

PubMed

Heo, Roun; You, Dong Gil; Um, Wooram; Choi, Ki Young; Jeon, Sangmin; Park, Jong-Sung; Choi, Yuri; Kwon, Seunglee; Kim, Kwangmeyung; Kwon, Ick Chan; Jo, Dong-Gyu; Kang, Young Mo; Park, Jae Hyung

2017-07-01

With the aim of developing nanoparticles for targeted delivery of methotrexate (MTX) to inflamed joints in rheumatoid arthritis (RA), an amphiphilic polysaccharide was synthesized by conjugating 5β-cholanic acid to a dextran sulfate (DS) backbone. Due to its amphiphilic nature, the DS derivative self-assembled into spherical nanoparticles (220 nm in diameter) in aqueous conditions. The MTX was effectively loaded into the DS nanoparticles (loading efficiency: 73.0%) by a simple dialysis method. Interestingly, the DS nanoparticles were selectively taken up by activated macrophages, which are responsible for inflammation and joint destruction, via scavenger receptor class A-mediated endocytosis. When systemically administrated into mice with experimental collagen-induced arthritis (CIA), the DS nanoparticles effectively accumulated in inflamed joints (12-fold more than wild type mice (WT)), implying their high targetability to RA tissues. Moreover, the MTX-loaded DS nanoparticles exhibited significantly improved therapeutic efficacy against CIA in mice compared to free MTX alone. Overall, the data presented here indicate that DS nanoparticles are potentially useful nanomedicines for RA imaging and therapy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nanoparticle-based Therapies for Wound Biofilm Infection: Opportunities and Challenges

PubMed Central

Kim, Min-Ho

2016-01-01

Clinical data from human chronic wounds implicates biofilm formation with the onset of wound chronicity. Despite the development of novel antimicrobial agents, the cost and complexity of treating chronic wound infections associated with biofilms remain a serious challenge, which necessitates the development of new and alternative approaches for effective anti-biofilm treatment. Recent advancement in nanotechnology for developing a new class of nanoparticles that exhibit unique chemical and physical properties holds promise for the treatment of biofilm infections. Over the last decade, nanoparticle-based approaches against wound biofilm infection have been directed toward developing nanoparticles with intrinsic antimicrobial properties, utilizing nanoparticles for controlled antimicrobials delivery, and applying nanoparticles for antibacterial hyperthermia therapy. In addition, a strategy to functionalize nanoparticles towards enhanced penetration through the biofilm matrix has been receiving considerable interest recently by means of achieving an efficient targeting to the bacterial cells within biofilm matrix. This review summarizes and highlights the recent development of these nanoparticle-based approaches as potential therapeutics for controlling wound biofilm infection, along with current challenges that need to be overcome for their successful clinical translation. PMID:26955044

Deposition of Nanostructured Thin Film from Size-Classified Nanoparticles

NASA Technical Reports Server (NTRS)

Camata, Renato P.; Cunningham, Nicholas C.; Seol, Kwang Soo; Okada, Yoshiki; Takeuchi, Kazuo

2003-01-01

Materials comprising nanometer-sized grains (approximately 1_50 nm) exhibit properties dramatically different from those of their homogeneous and uniform counterparts. These properties vary with size, shape, and composition of nanoscale grains. Thus, nanoparticles may be used as building blocks to engineer tailor-made artificial materials with desired properties, such as non-linear optical absorption, tunable light emission, charge-storage behavior, selective catalytic activity, and countless other characteristics. This bottom-up engineering approach requires exquisite control over nanoparticle size, shape, and composition. We describe the design and characterization of an aerosol system conceived for the deposition of size classified nanoparticles whose performance is consistent with these strict demands. A nanoparticle aerosol is generated by laser ablation and sorted according to size using a differential mobility analyzer. Nanoparticles within a chosen window of sizes (e.g., (8.0 plus or minus 0.6) nm) are deposited electrostatically on a surface forming a film of the desired material. The system allows the assembly and engineering of thin films using size-classified nanoparticles as building blocks.

In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

NASA Astrophysics Data System (ADS)

Wang, Yongliang; Li, Baoqiang; Zhou, Yu; Jia, Dechang

2009-09-01

Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS-Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4 and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3 and hydroxyapatite.

Translocation of polymers into crowded media with dynamic attractive nanoparticles.

PubMed

Cao, Wei-Ping; Ren, Qing-Bao; Luo, Meng-Bo

2015-07-01

The translocation of polymers through a small pore into crowded media with dynamic attractive nanoparticles is simulated. Results show that the nanoparticles at the trans side can affect the translocation by influencing the free-energy landscape and the diffusion of polymers. Thus the translocation time τ is dependent on the polymer-nanoparticle attraction strength ɛ and the mobility of nanoparticles V. We observe a power-law relation of τ with V, but the exponent is dependent on ɛ and nanoparticle concentration. In addition, we find that the effect of attractive dynamic nanoparticles on the dynamics of polymers is dependent on the time scale. At a short time scale, subnormal diffusion is observed at strong attraction and the diffusion is slowed down by the dynamic nanoparticles. However, the diffusion of polymers is normal at a long time scale and the diffusion constant increases with the increase in V.

Modifications in nanoparticle-protein interactions by varying the protein conformation

NASA Astrophysics Data System (ADS)

Kumar, Sugam; Yadav, I.; Aswal, V. K.; Kohlbrecher, J.

2017-05-01

Small-angle neutron scattering has been used to study the interaction of silica nanoparticle with Bovine Serum Albumin (BSA) protein without and with a protein denaturing agent urea. The measurements have been carried out at pH 7 where both the components (nanoparticle and protein) are similarly charged. We show that the interactions in nanoparticle-protein system can be modified by changing the conformation of protein through the presence of urea. In the absence of urea, the strong electrostatic repulsion between the nanoparticle and protein prevents protein adsorption on nanoparticle surface. This non-adsorption, in turn gives rise to depletion attraction between nanoparticles. However, with addition of urea the depletion attraction is completely suppressed. Urea driven denaturation of protein is utilized to expose the positively charged patched of the BSA molecules which eventually leads to adsorption of BSA on nanoparticles eliminating the depletion interaction.

Anticancer drug-based multifunctional nanogels through self-assembly of dextran-curcumin conjugates toward cancer theranostics.

PubMed

Nagahama, Koji; Sano, Yoshinori; Kumano, Takayuki

2015-06-15

Curcumin (CCM) has been received much attention in cancer theranostics because CCM exhibits both anticancer activity and strong fluorescence available for bio-imaging. However, CCM has never been utilized in clinical mainly due to its extremely low water solubility and its low cellular uptake into cancer cells. We fabricated novel CCM-based biodegradable nanoparticles through self-assembly of amphiphilic dextran-CCM conjugates. Significantly high CCM loading contents in the nanoparticles and the high water solubility were achieved. Importantly, the dextran-CCMs nanoparticles were effectively delivered into HeLa cells and exhibited strong fluorescence available for live-cell imaging, although the nanoparticles were not delivered into normal cells. Thus, the dextran-CCMs nanoparticles could be a promising for creation of novel CCM-based cancer theranostics with high efficacy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fluorescent Lead(IV) Sulfide Nanoparticles Synthesized by Idiomarina sp. Strain PR58-8 for Bioimaging Applications.

PubMed

Srivastava, Pallavee; Kowshik, Meenal

2017-04-01

The fabrication of nanoparticles by microorganisms presents a "green" method for generating biocompatible nanomaterials. We discovered the intracellular biosynthesis of fluorescent lead(IV) sulfide nanoparticles by the moderate halophile, Idiomarina sp. strain PR58-8. The bacterium tolerated up to 8 mM Pb(NO 3 ) 2 during growth. Non-protein thiols dose-dependently increased in response to metal exposure, which suggests they are involved in the growth of PbS 2 crystals and lead detoxification. Using X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and energy dispersive analysis of X-rays, the nanoparticles were characterized as spherical β-PbS 2 nanoparticles (PbS 2 NPs) with a tetragonal crystal lattice, a crystallite domain size of 2.38 nm, and an interplanar distance of 0.318 nm. A narrow symmetric emission spectrum with a Gaussian distribution and an emission maximum at 386 nm was obtained when the particles were excited at 570 nm. The PbS 2 NPs exhibited a large Stokes' shift (8,362 cm -1 ) and a relatively high quantum yield (67%). These properties, along with fluorescence that was maintained in various microenvironments and their biocompatibility, make these nanoparticles excellent candidates for bioimaging. The particles were internalized by HeLa cells and evenly distributed within the cytoplasm, exhibiting their potential for in situ bioimaging applications. The "as-synthesized" lead(IV) sulfide nanoparticles may provide expanded opportunities for targeted bioimaging via modifying the surface of the particles. IMPORTANCE This article reports the intracellular synthesis of fluorescent lead(IV) sulfide nanoparticles (PbS 2 NPs) by a microorganism. All previous reports on the microbial synthesis of lead-based nanoparticles are on lead(II) sulfide that exhibits near-infrared fluorescence, requiring expensive instrumentation for bioimaging. Bioimaging using PbS 2 NPs can be achieved using routine epifluorescence microscopes, as it