Oxide Nanoparticles (oxide + nanoparticle)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Oxide Nanoparticles

  • iron oxide nanoparticle
  • superparamagnetic iron oxide nanoparticle
  • zinc oxide nanoparticle


  • Selected Abstracts


    Superparamagnetic Iron Oxide Nanoparticle,Aptamer Bioconjugates for Combined Prostate Cancer Imaging and Therapy

    CHEMMEDCHEM, Issue 9 2008
    Andrew
    Multifunctional superparamagnetic iron oxide nanoparticles: Herein we report a novel, targeted, iron oxide nanoparticle for combined prostate cancer imaging and therapy. By conjugating an aptamer to a thermally stable iron oxide nanoparticle, we have demonstrated that bioconjugates can detect prostate cancer cells with high sensitivity and specificity. Furthermore, the bioconjugates can be used to deliver targeted chemotherapy. [source]


    PEI,PEG,Chitosan-Copolymer-Coated Iron Oxide Nanoparticles for Safe Gene Delivery: Synthesis, Complexation, and Transfection

    ADVANCED FUNCTIONAL MATERIALS, Issue 14 2009
    Forrest M. Kievit
    Abstract Gene therapy offers the potential of mediating disease through modification of specific cellular functions of target cells. However, effective transport of nucleic acids to target cells with minimal side effects remains a challenge despite the use of unique viral and non-viral delivery approaches. Here, a non-viral nanoparticle gene carrier that demonstrates effective gene delivery and transfection both in vitro and in vivo is presented. The nanoparticle system (NP,CP,PEI) is made of a superparamagnetic iron oxide nanoparticle (NP), which enables magnetic resonance imaging, coated with a novel copolymer (CP,PEI) comprised of short chain polyethylenimine (PEI) and poly(ethylene glycol) (PEG) grafted to the natural polysaccharide, chitosan (CP), which allows efficient loading and protection of the nucleic acids. The function of each component material in this nanoparticle system is illustrated by comparative studies of three nanoparticle systems of different surface chemistries, through material property characterization, DNA loading and transfection analyses, and toxicity assessment. Significantly, NP,CP,PEI demonstrates an innocuous toxic profile and a high level of expression of the delivered plasmid DNA in a C6 xenograft mouse model, making it a potential candidate for safe in vivo delivery of DNA for gene therapy. [source]


    Inorganic Nanoparticles for MRI Contrast Agents

    ADVANCED MATERIALS, Issue 21 2009
    Hyon Bin Na
    Abstract Various inorganic nanoparticles have been used as magnetic resonance imaging (MRI) contrast agents due to their unique properties, such as large surface area and efficient contrasting effect. Since the first use of superparamagnetic iron oxide (SPIO) as a liver contrast agent, nanoparticulate MRI contrast agents have attracted a lot of attention. Magnetic iron oxide nanoparticles have been extensively used as MRI contrast agents due to their ability to shorten T2* relaxation times in the liver, spleen, and bone marrow. More recently, uniform ferrite nanoparticles with high crystallinity have been successfully employed as new T2 MRI contrast agents with improved relaxation properties. Iron oxide nanoparticles functionalized with targeting agents have been used for targeted imaging via the site-specific accumulation of nanoparticles at the targets of interest. Recently, extensive research has been conducted to develop nanoparticle-based T1 contrast agents to overcome the drawbacks of iron oxide nanoparticle-based negative T2 contrast agents. In this report, we summarize the recent progress in inorganic nanoparticle-based MRI contrast agents. [source]


    Stabilized Copper(I) Oxide Nanoparticles Catalyze Azide-Alkyne Click Reactions in Water

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010
    Zhenfang Zhang
    Abstract A novel form of polyvinylpyrrolidone (PVP) coated copper(I) oxide nanoparticle (Cu2O-NP) was prepared and used to catalyze azide-alkyne click reactions in water under aerobic conditions. The nanoparticles were well dispersed in aqueous solutions and have a size of 2010,nm, as determined by transmission electron microscope (TEM). Inductively coupled plasma (ICP), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses demonstrated that the main content of Cu2O-NP is copper(I). The cytotoxicity of it was evaluated by an in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and its catalytic efficiency for azide-alkyne click reactions was studied in water and organic solvents at physiological temperatures. Our results indicate that Cu2O-NP is more efficient in catalytic reactions in water for both aliphatic and aromatic azides and alkynes and less toxic than the commonly used CuSO4/reductant catalyst systems. [source]


    Superparamagnetic Iron Oxide Nanoparticle,Aptamer Bioconjugates for Combined Prostate Cancer Imaging and Therapy

    CHEMMEDCHEM, Issue 9 2008
    Andrew
    Multifunctional superparamagnetic iron oxide nanoparticles: Herein we report a novel, targeted, iron oxide nanoparticle for combined prostate cancer imaging and therapy. By conjugating an aptamer to a thermally stable iron oxide nanoparticle, we have demonstrated that bioconjugates can detect prostate cancer cells with high sensitivity and specificity. Furthermore, the bioconjugates can be used to deliver targeted chemotherapy. [source]


    Assessing cytotoxicity of (iron oxide-based) nanoparticles: an overview of different methods exemplified with cationic magnetoliposomes

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2009
    Stefaan J. H. Soenen
    Abstract Iron oxide nanoparticles are the most widely used T2/T2* contrast agents and for biomedical research purposes, one of the main applications is the in vitro labeling of stem or therapeutic cells, allowing them to be subsequently tracked in vivo upon transplantation. To allow this, the nanoparticles used should not show any sign of cytotoxicity and not affect cellular physiology as this could impede normal cell functionality in vivo or lead to undesired side-effects. Assessing the biocompatibility of the nanoparticles has proven to be quite a difficult task. In the present work, a small overview of commonly used assays is presented in order to assess several aspects, such as cell viability, induction of reactive oxygen species, nanoparticle uptake, cellular morphology, cellular proliferation, actin cytoskeleton architecture and differentiation of stem cells. The main focus is on comparing the advantages and disadvantages of the different assays, highlighting several common problems and presenting possible solutions to these problems as well as pointing out the high importance of the relationship between intracellular nanoparticle concentration and cytotoxicity. Copyright 2009 John Wiley & Sons, Ltd. [source]


    A new method for the aqueous functionalization of superparamagnetic Fe2O3 nanoparticles

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2008
    Fernando Herranz
    Abstract A new methodology for the synthesis of hydrophilic iron oxide nanoparticles has been developed. This new method is based on the direct chemical modification of the nanoparticles' surfactant molecules. Using this methodology both USPIO (ultrasmall super paramagnetic iron oxide) (hydrodynamic size smaller than 50,nm) and SPIO (super paramagnetic iron oxide) (hydrodynamic size bigger than 50,nm) were obtained. In addition, we also show that it is possible to further functionalize the hydrophilic nanoparticles via covalent chemistry in water. The magnetic properties of these nanoparticles were also studied, showing their potential as MRI contrast agents. Copyright 2008 John Wiley & Sons, Ltd. [source]


    Single-cell detection by gradient echo 9.4 T MRI: a parametric study

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 4 2006
    P. Smirnov
    Abstract Recent studies have shown that cell migration can be monitored in vivo by magnetic resonance imaging after intracellular contrast agent incorporation. This is due to the dephasing effect on proton magnetization of the local magnetic field created by a labelled cell. Anionic iron oxide nanoparticles (AMNP) are among the most efficient and non-toxic contrast agents to be spontaneously taken up by a wide variety of cells. Here we measured the iron load and magnetization of HeLa tumour cells labelled with AMNP, as a function of the external magnetic field. High-resolution gradient echo 9.4,T MRI detected individual labelled cells, whereas spin echo sequences were poorly sensitive. We then conducted a systematic study in order to determine the gradient echo sequence parameters (echo time, cell magnetization and resolution) most suitable for in vivo identification of single cells. Copyright 2006 John Wiley & Sons, Ltd. [source]


    Quantized Double-Layer Charging of Iron Oxide Nanoparticles on a-Si:H Controlled by Charged Defects in a-Si:H

    ELECTROANALYSIS, Issue 12 2007
    Martin Weis
    Abstract Sequential single-electron charging of iron oxide nanoparticles encapsulated in oleic acid/oleyl amine envelope and deposited by the Langmuir-Blodgett technique onto Pt electrode covered with undoped hydrogenated amorphous silicon film (a-Si:H) is reported. Quantized double-layer charging of nanoparticles is detected by cyclic voltammetry as current peaks and the charging effect can be switched on/off by the excess of negative/positive charged defect states in the a-Si:H layer. The particular charge states in a-Si:H are created by the simultaneous application of a suitable bias voltage and illumination before the measurement. [source]


    Erratum: Developmental phytotoxicity of metal oxide nanoparticles to Arabidopsis thaliana

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2010
    Chang Woo Lee
    No abstract is available for this article. [source]


    Toxicity of manufactured zinc oxide nanoparticles in the nematode Caenorhabditis elegans

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2009
    Hongbo Ma
    Abstract Information describing the possible impacts of manufactured nanoparticles on human health and ecological receptors is limited. The objective of the present study was to evaluate the potential toxicological effects of manufactured zinc oxide nanoparticles (ZnO-NPs; 1.5 nm) compared to aqueous zinc chloride (ZnCl2) in the free-living nematode Caenorhabditis elegans. Toxicity of both types of Zn was investigated using the ecologically relevant endpoints of lethality, behavior, reproduction, and transgene expression in a mtl-2::GFP (gene encoding green fluorescence protein fused onto the metallothionein-2 gene promoter) transgenic strain of C. elegans. Zinc oxide nanoparticles showed no significant difference from ZnCl2 regarding either lethality or reproduction in C. elegans, as indicated by their median lethal concentrations (LC50s; p = 0.29, n = 3) and median effective concentrations (EC50s; Z = 0.835, p = 0.797). Also, no significant difference was found in EC50s for behavioral change between ZnO-NPs (635 mg Zn/L; 95% confidence interval [CI], 477,844 mg Zn/L) and ZnCl2 (546 mg Zn/L; 95% CI, 447,666 mg Zn/L) (Z = 0.907, p = 0.834). Zinc oxide nanoparticles induced transgene expression in the mtl-2::GFP transgenic C. elegans in a manner similar to that of ZnCl2, suggesting that intracellular biotransformation of the nanoparticles might have occurred or the nanoparticles have dissolved to Zn2+ to enact toxicity. These findings demonstrate that manufactured ZnO-NPs have toxicity to the nematode C. elegans similar to that of aqueous ZnCl2. [source]


    The Effect of Surface Area and Crystal Structure on the Catalytic Efficiency of Iron(III) Oxide Nanoparticles in Hydrogen Peroxide Decomposition

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2010
    Cenek Gregor
    Abstract Iron(II) oxalate dihydrate has been used as a readily decomposable substance for the controlled synthesis of nanosized iron(III) oxides. The polymorphous composition, particle size and surface area of these iron oxide nanoparticles were controlled by varying the reaction temperature between 185 and 500 C. As-prepared samples were characterized by XRD, low-temperature and in-field Mssbauer spectroscopy, BET surface area and the TEM technique. They were also tested as heterogeneous catalysts in hydrogen peroxide decomposition. At the selected temperatures, the formed nanomaterials did not contain any traces of amorphous phase, which is known to considerably reduce the catalytic efficiency of iron(III) oxide catalysts. As the thickness of the sample (, 2 mm) was above the critical value, a temporary temperature increase ("exo effect") was observed during all quasi-isothermal decompositions studied, irrespective of the reaction temperature. Increasing the reaction temperature resulted in a shift of the exo effect towards shorter times and an increased content of maghemite phase. The maghemite content decreases above 350 C as a result of a thermally induced polymorphous transition into hematite. The catalytic data demonstrate that the crystal structure of iron(III) oxide (i.e. the relative contents of maghemite and hematite) does not influence the rate of hydrogen peroxide decomposition. However, the rate constant increases monotonously with increasing sample surface area (and decreasing thermolysis temperature), reaching a maximum of 27,,10,3 min,1(g/L),1 for the sample with a surface area of 285 m2,g,1. This rate constant is currently the highest reported value of all known iron oxide catalytic systems and is even slightly higher than that observed for the most efficient catalyst reported to date, which has a significantly larger surface area of 337 m2,g,1. This surprisingly high catalytic activity at relatively low surface area can be ascribed to the absence of a amorphous phase in the samples prepared in this study. Taking into account these new findings, the contributions of the key factors highlighted above (surface area, particle size, crystal structure, crystallinity) to the overall activity of iron oxides forhydrogen peroxide decomposition are discussed. [source]


    Cytotoxicity and Cell Cycle Effects of Bare and Poly(vinyl alcohol)-Coated Iron Oxide Nanoparticles in Mouse Fibroblasts

    ADVANCED ENGINEERING MATERIALS, Issue 12 2009
    Morteza Mahmoudi
    Super-paramagnetic iron oxide nanoparticles (SPIONs) are recognized as powerful biocompatible materials for use in various biomedical applications, such as drug delivery, magnetic-resonance imaging, cell/protein separation, hyperthermia and transfection. This study investigates the impact of high concentrations of SPIONs on cytotoxicity and cell-cycle effects. The interactions of surface-saturated (via interactions with cell medium) bare SPIONs and those coated with poly(vinyl alcohol) (PVA) with adhesive mouse fibroblast cells (L929) are investigated using an MTT assay. The two SPION formulations are synthesized using a co-precipitation method. The bare and coated magnetic nanoparticles with passivated surfaces both result in changes in cell morphology, possibly due to clustering through their magnetostatic effect. At concentrations ranging up to 80,,10,3,M, cells exposed to the PVA-coated nanoparticles demonstrate high cell viability without necrosis and apoptosis. In contrast, significant apoptosis is observed in cells exposed to bare SPIONs at a concentration of 80,,10,3,M. Nanoparticle exposure (20,80,,10,3,M) leads to variations in both apoptosis and cell cycle, possibly due to irreversible DNA damage and repair of oxidative DNA lesions, respectively. Additionally, the formation of vacuoles within the cells and granular cells indicates autophagy cell death rather than either apoptosis or necrosis. [source]


    Copper Azide Confined Inside Templated Carbon Nanotubes

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
    Valarie Pelletier
    Abstract The currently used primary explosives, such as lead azide and lead styphnate, present serious health hazards due to the toxicity of lead. There is a need to replace them with equally energetic but safer-to-handle and more environmentally friendly materials. Copper azide is more environmentally acceptable, but very sensitive and detonates easily from electrostatic charges during handling. If the highly sensitive copper azide is encapsulated within conducting containers, such as anodic aluminum oxide (AAO)-templated carbon nanotubes (CNTs), its sensitivity can be tamed. This work describes a technique for confining energetic copper azide within CNTs. ,5 nm colloidal copper oxide nanoparticles are synthesized and filled into the 200 nm diameter CNTs, produced by template synthesis. The Cu-O inside the CNTs is reduced in hydrogen to copper, and reacted with hydrazoic acid gas to produce copper azide. Upon initiation, the 60 ,m long straight, open-ended CNTs guide decomposition gases along the tube channel without fracturing the nanotube walls. These novel materials have potential for applications as nano-detonators and green primary explosives; they also offer new opportunities for understanding the physics of detonation at the nanoscale. [source]


    Silica-Coated Manganese Oxide Nanoparticles as a Platform for Targeted Magnetic Resonance and Fluorescence Imaging of Cancer Cells

    ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
    Hong Yang
    Abstract Monodisperse silica-coated manganese oxide nanoparticles (NPs) with a diameter of ,35,nm are synthesized and are aminated through silanization. The amine-functionalized core,shell NPs enable the covalent conjugation of a fluorescent dye, Rhodamine B isothiocyanate (RBITC), and folate (FA) onto their surface. The formed Mn3O4@SiO2(RBITC),FA core,shell nanocomposites are water-dispersible, stable, and biocompatible when the Mn concentration is below 50,g mL,1 as confirmed by a cytotoxicity assay. Relaxivity measurements show that the core,shell NPs have a T1 relaxivity (r1) of 0.50,mM,1,s,1 on the 0.5 T scanner and 0.47,mM,1,s,1 on the 3.0 T scanner, suggesting the possibility of using the particles as a T1 contrast agent. Combined flow cytometry, confocal microscopy, and magnetic resonance imaging studies show that the Mn3O4@SiO2(RBITC),FA nanocomposites can specifically target cancer cells overexpressing FA receptors (FARs). Findings from this study suggest that the silica-coated Mn3O4 core,shell NPs could be used as a platform for bimodal imaging (both magnetic resonance and fluorescence) in various biological systems. [source]


    Pathogen-Mimicking MnO Nanoparticles for Selective Activation of the TLR9 Pathway and Imaging of Cancer Cells,

    ADVANCED FUNCTIONAL MATERIALS, Issue 23 2009
    Mohammed Ibrahim Shukoor
    Abstract Here, design of the first pathogen-mimicking metal oxide nanoparticles with the ability to enter cancer cells and to selectively target and activate the TLR9 pathway, and with optical and MR imaging capabilities, is reported. The immobilization of ssDNA (CpG ODN 2006) on MnO nanoparticles is performed via the phosphoramidite route using a multifunctional polymer. The multifunctional polymer used for the nanoparticle surface modification not only affords a protective organic biocompatible shell but also provides an efficient and convenient means for loading immunostimulatory oligonucleotides. Since fluorescent molecules are amenable to photodetection, a chromophore (Rhodamine) is introduced into the polymer chain to trace the nanoparticles in Caki-1 (human kidney cancer) cells. The ssDNA coupled nanoparticles are used to target Toll-like receptors 9 (TLR9) receptors inside the cells and to activate the classical TLR cascade. The presence of TLR9 is demonstrated independently in the Caki-1 cell line by western blotting and immunostaining techniques. The magnetic properties of the MnO core make functionalized MnO nanoparticles potential diagnostic agents for magnetic resonance imaging (MRI) thereby enabling multimodal detection by a combination of MR and optical imaging methods. The trimodal nanoparticles allow the imaging of cellular trafficking by different means and simultaneously are an effective drug carrier system. [source]


    Size Effect on Properties of Varistors Made From Zinc Oxide Nanoparticles Through Low Temperature Spark Plasma Sintering

    ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009
    Lna Saint Macary
    Abstract Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8-nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at room temperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as-prepared ceramics are based on scanning electron microscopy and X-ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current,voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600,C. [source]


    Densification of Oxide Nanoparticle Thin Films by Irradiation with Visible Light

    ADVANCED FUNCTIONAL MATERIALS, Issue 8 2009
    Massimo F. Bertino
    Abstract A technique is presented that allows for altering of the physical characteristics of films of TiO2 nanoparticles by exposure to visible light. In this technique, dye-sensitized oxide nanoparticles are deposited on a substrate by dip-coating. Photodissociation of the organic ligand layer leads to cross-linking of the nanoparticles. Consequently, irradiated films have a decreased porosity, an increased index of refraction and an increased hydrophobicity. Films irradiated with green light are compared to films irradiated with UV light. Within experimental error, visible- and UV-illumination induces the same changes in the films. The mechanism of surfactant elimination in dye-sensitized oxide particles is discussed, patterning is demonstrated, and prospective applications of the technique are considered. [source]


    Temperature-Sensitive Nanocapsules for Controlled Drug Release Caused by Magnetically Triggered Structural Disruption

    ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
    Ting-Yu Liu
    Abstract Self-assembled nanocapsules containing a hydrophilic core and a crosslinked yet thermosensitive shell are successfully prepared using poly(ethylene-oxide)-poly(propylene-oxide)-poly(ethylene-oxide) block copolymers, 4-nitrophenyl chloroformate, gelatin, and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The core is further rendered magnetic by incorporating iron oxide nanoparticles via internal precipitation to enable externally controlled actuation under magnetic induction. The spherical nanocapsules exhibit a hydrophilic-to-hydrophobic transition at a characteristic but tunable temperature reaching 40,C, triggering a size contraction and shrinkage of the core. The core content experiences very little leakage at 25,C, has a half life about 5,h at 45,C, but bursts out within a few minutes under magnetic heating due to iron oxide coarsening and core/shell disruption. Such burst-like response may be utilized for controlled drug release as illustrated here using a model drug Vitamin B12. [source]


    A Delivery System for Self-Healing Inorganic Films,

    ADVANCED FUNCTIONAL MATERIALS, Issue 22 2008
    Harvey A. Liu
    Abstract Multilayer composites that utilize polymeric and brittle inorganic films are essential components for extending the lifetimes and exploiting the flexibility of many electronic devices. However, crack formation within the brittle inorganic layers that arise from defects as well as the flexing of these multilayer composite materials allows the influx of atmospheric water, a major source of device degradation. Thus, a composite material that can initiate self-healing upon the influx of environmental water through defects or stress-induced cracks would find potential applications in multilayer composite materials for permeation barriers. In the present study, the reactive metal oxide precursor TiCl4 is encapsulated within the pores of a degradable polymer, poly(lactic acid) (PLA). Electrospun PLA fibers are found to be reactive to atmospheric water leading to the hydrolysis of the degradable polymer shell and subsequent release of the reactive metal oxide precursor. Release of the reactive TiCl4 from the pores results in hydrolysis of the metal oxide precursor, forming solid titanium oxides at the surface of the fibers. The efficacy of this self-healing delivery system is also demonstrated by the integration of these reactive fibers in the polymer planarization layer, poly(methyl methacrylate), of a multilayer film, upon which an alumina barrier layer is deposited. The introduction of nanocracks in the alumina barrier layer lead to the release of the metal oxide precursor from the pores of the fibers and the formation of titanium dioxide nanoparticles within the crack and upon the thin film surface. In this study the first delivery system that may find utility for the self-healing of multilayer barrier films through the site-specific delivery of metal oxide nanoparticles through smart reactive composite fibers is established. [source]


    Hybrid Solar Cells from Regioregular Polythiophene and ZnO Nanoparticles,

    ADVANCED FUNCTIONAL MATERIALS, Issue 8 2006

    Abstract Blends of nanocrystalline zinc oxide nanoparticles (nc-ZnO) and regioregular poly(3-hexylthiophene) (P3HT) processed from solution have been used to construct hybrid polymer,metal oxide bulk-heterojunction solar cells. Thermal annealing of the spin-cast films significantly improves the solar-energy conversion efficiency of these hybrid solar cells to ,,0.9,%. Photoluminescence and photoinduced absorption spectroscopy demonstrate that charge-carrier generation is not quantitative, because a fraction of P3HT appears not to be in contact with or in close proximity to ZnO. The coarse morphology of the films, also identified by tapping-mode atomic force microscopy, likely limits the device performance. [source]


    Inorganic Nanoparticles for MRI Contrast Agents

    ADVANCED MATERIALS, Issue 21 2009
    Hyon Bin Na
    Abstract Various inorganic nanoparticles have been used as magnetic resonance imaging (MRI) contrast agents due to their unique properties, such as large surface area and efficient contrasting effect. Since the first use of superparamagnetic iron oxide (SPIO) as a liver contrast agent, nanoparticulate MRI contrast agents have attracted a lot of attention. Magnetic iron oxide nanoparticles have been extensively used as MRI contrast agents due to their ability to shorten T2* relaxation times in the liver, spleen, and bone marrow. More recently, uniform ferrite nanoparticles with high crystallinity have been successfully employed as new T2 MRI contrast agents with improved relaxation properties. Iron oxide nanoparticles functionalized with targeting agents have been used for targeted imaging via the site-specific accumulation of nanoparticles at the targets of interest. Recently, extensive research has been conducted to develop nanoparticle-based T1 contrast agents to overcome the drawbacks of iron oxide nanoparticle-based negative T2 contrast agents. In this report, we summarize the recent progress in inorganic nanoparticle-based MRI contrast agents. [source]


    Injectable Superparamagnetic Ferrogels for Controlled Release of Hydrophobic Drugs

    ADVANCED MATERIALS, Issue 13 2009
    Jian Qin
    A ferrogel for magnetically controlled release of drugs is prepared by integration of superparamagnetic iron oxide nanoparticles and Pluronic F127 gels. The hydrophobic drug indomethacin is loaded in the ferrogel owing to the oil-in-water micellar structure. The characteristic sol,gel transition property renders the ferrogel an injectable drug carrier that will be, in principle, free from surgical implant procedure. [source]


    Low-Temperature Synthesis of Zinc Oxide Nanoparticles

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2006
    Po-Yi Wu
    Crystalline zinc oxide nanoparticles have been prepared by mixing aqueous solutions of zinc nitrate and hexamethylenetetramine (HMT) at 60C and 80C. Transmission electron microscopy and X-ray diffraction show that the ZnO nanoparticles of diameters ranging from 15,33 nm and 25,43 nm long are formed. Aspect ratio is observed to range from 1.18 to 1.74 at 60C and 1.22 to 1.70 at 80C as the HMT to zinc nitrate concentration ratio increases from 10 to 150. Nanoparticle size decreases as the concentration of HMT increases. Much larger ZnO particles are formed with ammonium hydroxide as a hydrolysis agent without HMT. In summary, HMT is an ammonium-hydroxide source in the reaction, a surfactant for retaining nanosize, and not necessarily a template for ZnO nucleation. [source]


    Energetics of oxide nanoparticles

    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 12 2009
    Alexandra Navrotsky
    Abstract New calorimetric techniques enable the measurement of surface enthalpies and phase transformation enthalpies of oxide nanoparticles. These experimental values can benchmark theoretical calculations. A complex and delicate balance of energies of phase transformation, surfaces, and hydration leads to crossovers in thermodynamic stability of polymorphs at the nanoscale. ZnO and TiO2 are discussed in detail as examples. 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source]


    Local dynamics in epoxy coatings containing iron oxide nanoparticles by dielectric relaxation spectroscopy

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008
    G. Kortaberria
    Abstract Nanocomposites of photocurable epoxy resin and epoxy-modified iron oxide magnetic nanoparticles were analyzed by dielectric relaxation spectroscopy to study the local dynamics at temperatures well below the glass-transition temperature. Two secondary processes were detected, , and , processes, but the second one was just detected at lower temperatures in the high-frequency part of the spectra and moved out of the frequency range at higher temperatures. Data were fitted to the Havriliak,Negami and Arrhenius models, and the obtained parameters were analyzed. Relaxation times of the , secondary relaxation did not change with the nanoparticle content, but the relaxation strength increased. The increase could not be explained when we took into account the molecular origin of the relaxation. The presence of ferromagnetic nanoparticles enhanced the internal field and increased the relaxation strengths. Transmission electron microscopy images showed that the nanoparticles were well dispersed in the matrix, without magnetic agglomerates. 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source]


    Antibacterial activity of dental composites containing zinc oxide nanoparticles,

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2010
    Berdan Aydin Sevin
    Abstract The resin-based dental composites commonly used in restorations result in more plaque accumulation than other materials. Bacterial biofilm growth contributes to secondary caries and failure of resin-based dental composites. Methods to inhibit biofilm growth on dental composites have been sought for several decades. It is demonstrated here that zinc oxide nanoparticles (ZnO-NPs) blended at 10% (w/w) fraction into dental composites display antimicrobial activity and reduce growth of bacterial biofilms by roughly 80% for a single-species model dental biofilm. Antibacterial effectiveness of ZnO-NPs was assessed against Streptococcus sobrinus ATCC 27352 grown both planktonically and as biofilms on composites. Direct contact inhibition was observed by scanning electron microscopy and confocal laser scanning microscopy while biofilm formation was quantified by viable counts. An 80% reduction in bacterial counts was observed with 10% ZnO-NP-containing composites compared with their unmodified counterpart, indicating a statistically significant suppression of biofilm growth. Although, 20% of the bacterial population survived and could form a biofilm layer again, 10% ZnO-NP-containing composites maintained at least some inhibitory activity even after the third generation of biofilm growth. Microscopy demonstrated continuous biofilm formation for unmodified composites after 1-day growth, but only sparsely distributed biofilms formed on 10% ZnO-NP-containing composites. The minimum inhibitory concentration of ZnO-NPs suspended in S. sobrinus planktonic culture was 50 ,g mL,1. ZnO-NP-containing composites (10%) qualitatively showed less biofilm after 1-day-anaerobic growth of a three-species initial colonizer biofilm after being compared with unmodified composites, but did not significantly reduce growth after 3 days. 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. [source]


    Raman spectroscopy of optical phonon confinement in nanostructured materials

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2007
    Akhilesh K. Arora
    Abstract If the medium surrounding a nano-grain does not support the vibrational wavenumbers of a material, the optical and acoustic phonons get confined within the grain of the nanostructured material. This leads to interesting changes in the vibrational spectrum of the nanostructured material as compared to that of the bulk. Absence of periodicity beyond the particle dimension relaxes the zone-centre optical phonon selection rule, causing the Raman spectrum to have contributions also from phonons away from the Brillouin-zone centre. Theoretical models and calculations suggest that the confinement results in asymmetric broadening and shift of the optical phonon Raman line, the magnitude of which depends on the widths of the corresponding phonon dispersion curves. This has been confirmed for zinc oxide nanoparticles. Microscopic lattice dynamical calculations of the phonon amplitude and Raman spectra using the bond-polarizability model suggest a power-law dependence of the peak-shift on the particle size. This article reviews recent results on the Raman spectroscopic investigations of optical phonon confinement in several nanocrystalline semiconductor and ceramic/dielectric materials, including those in selenium, cadmium sulphide, zinc oxide, thorium oxide, and nano-diamond. Resonance Raman scattering from confined optical phonons is also discussed. Copyright 2007 John Wiley & Sons, Ltd. [source]


    XANES study on the valence transitions in cerium oxide nanoparticles

    JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001
    Jing Zhang
    The aim of this work is the determination of Ce environment and valence state in cerium oxide nanoparticles prepared by the microemulsion method. X-ray absorption near-edge structure measurements at Ce L3 edge were performed on the nanoparticles as a function of annealing temperature, ranging from 298K to 873K under air condition. The experimental results support the conclusion that Ce ion, in the investigated systems, is in trivalence state when the annealing temperature is below 473K. As the temperature increases up to 623K, the XANES spectrum shows the coexistence of Ce3+ and Ce4+states. When the temperature is higher than 623K, the spectra become identical to that of CeO2 with a distinct double-peak structure, corresponding to the Ce4+ state. [source]


    Role of Structural Fe(III) and Iron Oxide Nanophases in Mullite Coloration

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2001
    Amde Djemai
    Six mullite samples, derived from heat-treated natural kaolinites with various iron content, were investigated and compared to synthetic monophasic mullite. They were analyzed by X-ray diffraction, diffuse reflectance spectroscopy, and electron paramagnetic resonance. To quantify mullite coloration, the CIE colorimetric system was used. In contrast to synthetic mullite, samples showed charge transfer bands involving O2, and Fe3+ ions as well as ferric crystal-field transitions due to Fe3+ ions in iron oxide nanoparticles. Absorption edges showed red shifts. The resulting yellowness, saturation of which increased with the content of iron oxide nanoparticles, is direct evidence for the coloring effect of Fe3+ ions. [source]