217 results found
Roqan IS, Venkatesh S, Zhang Z, et al., 2015, Obtaining strong ferromagnetism in diluted Gd-doped ZnO thin films through controlled Gd-defect complexes, Journal of Applied Physics, Vol: 117, ISSN: 1089-7550
We demonstrate the fabrication of reproducible long-range ferromagnetism (FM) in highly crystalline Gdx Zn 1−xO thin films by controlling the defects. Films are grown on lattice-matched substrates by pulsed laser deposition at low oxygen pressures (≤25 mTorr) and low Gd concentrations (x ≤ 0.009). These films feature strong FM (10 μB per Gd atom) at room temperature. While films deposited at higher oxygen pressure do not exhibit FM, FM is recovered by post-annealing these films under vacuum. These findings reveal the contribution of oxygen deficiency defects to the long-range FM. We demonstrate the possible FM mechanisms, which are confirmed by density functional theory study, and show that Gd dopants are essential for establishing FM that is induced by intrinsic defects in these films.
Marchetti M, Shaffer MSP, Zambianchi M, et al., 2015, Adsorption of surfactant protein D from human respiratory secretions by carbon nanotubes and polystyrene nanoparticles depends on nanomaterial surface modification and size, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 370, ISSN: 0962-8436
Wang T, Costan J, Centeno A, et al., 2015, Broadband enhanced fluorescence using Zinc-Oxide nanoflower arrays, Journal of Materials Chemistry C, Vol: 3, Pages: 2656-2663, ISSN: 2050-7534
ZnO nanostructures were fabricated into flower-like nanoscale arrays by the hydrothermal growth of ZnO nanowires onto a self-assembled monolayer of polystyrene spheres on a glass substrate. Fluorescent molecules conjugated with streptavidin were incubated on glass with 3-(glycidoxypropyl) trimethoxysilane (GPTS) modified and biotinylated bovine serum albumin (bBSA) attached (GPTS–bBSA), aligned ZnO nanorod arrays and ZnO nanoflower arrays, respectively. An enhancement factor of up to 45 was obtained from ZnO nanoflower arrays, compared to less than 10 for the aligned nanorods. More importantly, using the same substrate, we observed a broadband fluorescence enhancement. The level of enhancement obtained from the nanoflower arrays is comparable with that from Metal Enhanced Fluorescence. The broadband nature of this process makes it an attractive alternative for fluorescent based device development.
Chen S, Goode AE, Skepper JN, et al., 2015, Avoiding artefacts during electron microscopy of silver nanomaterials exposed to biological environments, Journal of Microscopy, Vol: 261, Pages: 157-166, ISSN: 1365-2818
Electron microscopy has been applied widely to study the interaction of nanomaterials with proteins, cells and tissues at nanometre scale. Biological material is most commonly embedded in thermoset resins to make it compatible with the high vacuum in the electron microscope. Room temperature sample preparation protocols developed over decades provide contrast by staining cell organelles, and aim to preserve the native cell structure. However, the effect of these complex protocols on the nanomaterials in the system is seldom considered. Any artefacts generated during sample preparation may ultimately interfere with the accurate prediction of the stability and reactivity of the nanomaterials. As a case study, we review steps in the room temperature preparation of cells exposed to silver nanomaterials (AgNMs) for transmission electron microscopy imaging and analysis. In particular, embedding and staining protocols, which can alter the physicochemical properties of AgNMs and introduce artefacts thereby leading to a misinterpretation of silver bioreactivity, are scrutinized. Recommendations are given for the application of cryogenic sample preparation protocols, which simultaneously fix both particles and diffusible ions. By being aware of the advantages and limitations of different sample preparation methods, compromises or selection of different correlative techniques can be made to draw more accurate conclusions about the data. Lay description: With increasing commercialization of silver nanomaterials (AgNMs) comes a concomitant need to understand occupational health, public safety and environmental implications of these materials. Nanoscale studies of the complex bio-nano interface lie at the heart of technical challenges. Despite numerous reports, there is no consensus regarding biological mechanisms enacted by AgNMs. Powerful new electron microscopy techniques can be used to visualize the interaction of the AgNMs with tissues. However, it is extremely difficult to
Venkatesh S, Franklin JB, Ryan MP, et al., 2015, Defect-band mediated ferromagnetism in Gd-doped ZnO thin films, JOURNAL OF APPLIED PHYSICS, Vol: 117, ISSN: 0021-8979
Metze AL, Pishbin F, Ryan MP, et al., 2015, Electrophoretic co-deposition of chitosan and graphene oxide results in antibacterial coatings for medical applications, Pages: 176-182, ISSN: 1013-9826
© (2015) Trans Tech Publications, Switzerland. Chitosan - graphene oxide (GO) composite coatings intended for antibacterial applications were obtained by cathodic electrophoretic deposition (EPD) on stainless steel. The coatings were characterized using SEM, FTIR, contact angle and roughness measurements and by antibacterial studies against E.coli. The coating was observed to consist of a polymer matrix with embedded, agglomerated graphene oxide sheets. A decrease in bacteria cell viability of at least 50 % was measured on the chitosan - GO surface in comparison to uncoated stainless steel.
Theodorou IG, Ryan MP, Tetley TD, et al., 2014, Inhalation of silver nanomaterials - seeing the risks, International Journal of Molecular Sciences, Vol: 15, Pages: 23936-23974, ISSN: 1661-6596
Demand for silver engineered nanomaterials (ENMs) is increasing rapidly in optoelectronic and in health and medical applications due to their antibacterial, thermal, electrical conductive, and other properties. The continued commercial up-scaling of ENM production and application needs to be accompanied by an understanding of the occupational health, public safety and environmental implications of these materials. There have been numerous in vitro studies and some in vivo studies of ENM toxicity but their results are frequently inconclusive. Some of the variability between studies has arisen due to a lack of consistency between experimental models, since small differences between test materials can markedly alter their behaviour. In addition, the propensity for the physicochemistry of silver ENMs to alter, sometimes quite radically, depending on the environment they encounter, can profoundly alter their bioreactivity. Consequently, it is important to accurately characterise the materials before use, at the point of exposure and at the nanomaterial-tissue, or “nanobio”, interface, to be able to appreciate their environmental impact. This paper reviews current literature on the pulmonary effects of silver nanomaterials. We focus our review on describing whether, and by which mechanisms, the chemistry and structure of these materials can be linked to their bioreactivity in the respiratory system. In particular, the mechanisms by which the physicochemical properties (e.g., aggregation state, morphology and chemistry) of silver nanomaterials change in various biological milieu (i.e., relevant proteins, lipids and other molecules, and biofluids, such as lung surfactant) and affect subsequent interactions with and within cells will be discussed, in the context not only of what is measured but also of what can be visualized.
Goode AE, Porter AE, Ryan MP, et al., 2014, Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution, Nanoscale, Vol: 7, Pages: 1534-1548, ISSN: 2040-3372
Two powerful and complementary techniques for chemical characterisation of nanoscale systems are electron energy-loss spectroscopy in the scanning transmission electron microscope, and X-ray absorption spectroscopy in the scanning transmission X-ray microscope. A correlative approach to spectro-microscopy may not only bridge the gaps in spatial and spectral resolution which exist between the two instruments, but also offer unique opportunities for nanoscale characterisation. This review will discuss the similarities of the two spectroscopy techniques and the state of the art for each microscope. Case studies have been selected to illustrate the benefits and limitations of correlative electron and X-ray microscopy techniques. In situ techniques and radiation damage are also discussed.
Hu S, Chen S, Menzel R, et al., 2014, Aqueous dispersions of oligomer-grafted carbon nanomaterials with controlled surface charge and minimal framework damage, FARADAY DISCUSSIONS, Vol: 173, Pages: 273-285, ISSN: 1359-6640
Illy BN, Ingham B, Toney MF, et al., 2014, Understanding the Selective Etching of Electrodeposited ZnO Nanorods, LANGMUIR, Vol: 30, Pages: 14079-14085, ISSN: 0743-7463
Ramadan AJ, Rochford LA, Keeble DS, et al., 2014, Exploring High Temperature Templating in Non-planar Phthalocyanine / Copper Iodide (111) Bilayers, Journal of Materials Chemistry C, ISSN: 2050-7526
Elevated substrate temperature growth of phthalocyanine thin films is known to influence film morphology and increase crystallinity. Structural templating offers another method through which the structure of phthalocyanine films can be controlled. Here we combine the use of copper iodide (CuI) and elevated substrate temperatures and investigate their effect on the growth of a non-planar phthalocyanine system. Employing x-ray diffraction and atomic force microscopy we present detailed surface and crystal structure information. Vanadyl phthalocyanine (VOPc) is shown to adopt an edge-on orientation on CuI at ambient substrate temperatures, a behavior in stark contrast to that of previously studied planar phthalocyanine molecules. Elevated substrate temperature is shown to result in changes in the surface morphology and structure demonstrating the versatility of the system. The crystal structure of VOPc was redetermined and used to infer the molecular orientation of the various VOPc/CuI bilayer structures.
Mukherjee D, Royce SG, Sarkar S, et al., 2014, Modeling in vitro cellular responses to silver nanoparticles, Journal of Toxicology, Vol: 2014, ISSN: 1687-8205
Engineered nanoparticles (NPs) have been widely demonstrated to induce toxic effects to various cell types. In vitro cell exposure systems have high potential for reliable, high throughput screening of nanoparticle toxicity, allowing focusing on particular pathways while excluding unwanted effects due to other cells or tissue dosimetry. The work presented here involves a detailed biologically based computational model of cellular interactions with NPs; it utilizes measurements performed in human cell culture systems in vitro, to develop a mechanistic mathematical model that can support analysis and prediction of in vivo effects of NPs. The model considers basic cellular mechanisms including proliferation, apoptosis, and production of cytokines in response to NPs. This new model is implemented for macrophages and parameterized using in vitro measurements of changes in cellular viability and mRNA levels of cytokines: TNF, IL-1b, IL-6, IL-8, and IL-10. The model includes in vitro cellular dosimetry due to nanoparticle transport and transformation. Furthermore, the model developed here optimizes the essential cellular parameters based on in vitro measurements, and provides a "stepping stone" for the development of more advanced in vivo models that will incorporate additional cellular and NP interactions.
Teo GY, Ryan MP, Riley DJ, 2014, A mechanistic study on templated electrodeposition of one-dimensional TiO2 nanorods and nanotubes using TiOSO4 as a precursor, ELECTROCHEMISTRY COMMUNICATIONS, Vol: 47, Pages: 13-16, ISSN: 1388-2481
van Veelen A, Preedy O, Qi J, et al., 2014, Uranium and technetium interactions with wustite [Fe1-xO] and portlandite [Ca(OH)(2)] surfaces under geological disposal facility conditions, MINERALOGICAL MAGAZINE, Vol: 78, Pages: 1097-1113, ISSN: 0026-461X
Mukherjee D, Leo BF, Royce SG, et al., 2014, Modeling physicochemical interactions affecting in vitro cellular dosimetry of engineered nanomaterials: application to nanosilver, JOURNAL OF NANOPARTICLE RESEARCH, Vol: 16, ISSN: 1388-0764
Baer DR, Munusamy P, Smith JN, et al., 2014, Time dependent transformations of ceria and silver nanoparticles during synthesis, storage, and in biological media, 248th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Dunlop IE, Ryan MP, Goode AE, et al., 2014, Direct synthesis of PEG-encapsulated gold nanoparticles using branched copolymer nanoreactors, RSC Advances, Vol: 4, Pages: 27702-27707
Pishbin F, Mourino V, Flor S, et al., 2014, Electrophoretic Deposition of Gentamicin-Loaded Bioactive Glass/Chitosan Composite Coatings for Orthopaedic Implants, ACS APPLIED MATERIALS & INTERFACES, Vol: 6, Pages: 8796-8806, ISSN: 1944-8244
Chen S, Hu S, Smith EF, et al., 2014, Aqueous cationic, anionic and non-ionic multi-walled carbon nanotubes, functionalised with minimal framework damage, for biomedical application, Biomaterials, Vol: 35, Pages: 4729-4738
Sarkar S, Zhang L, Subramaniam P, et al., 2014, Variability in Bioreactivity Linked to Changes in Size and Zeta Potential of Diesel Exhaust Particles in Human Immune Cells, PLOS One, Vol: 9, ISSN: 1932-6203
Acting as fuel combustion catalysts to increase fuel economy, cerium dioxide (ceria, CeO2) nanoparticles have been used inEurope as diesel fuel additives (EnviroxTM). We attempted to examine the effects of particles emitted from a diesel engineburning either diesel (diesel exhaust particles, DEP) or diesel doped with various concentrations of CeO2 (DEP-Env) on innateimmune responses in THP-1 and primary human peripheral blood mononuclear cells (PBMC). Batches of DEP and DEP-Envwere obtained on three separate occasions using identical collection and extraction protocols with the aim of determiningthe reproducibility of particles generated at different times. However, we observed significant differences in size and surfacecharge (zeta potential) of the DEP and DEP-Env across the three batches. We also observed that exposure of THP-1 cells andPBMC to identical concentrations of DEP and DEP-Env from the three batches resulted in statistically significant differencesin bioreactivity as determined by IL-1b, TNF-a, IL-6, IFN-c, and IL-12p40 mRNA (by qRT-PCR) and protein expression (byELISPOT assays). Importantly, bioreactivity was noted in very tight ranges of DEP size (60 to 120 nm) and zeta potential (237to 241 mV). Thus, these physical properties of DEP and DEP-Env were found to be the primary determinants of thebioreactivity measured in this study. Our findings also point to the potential risk of over- or under- estimation of expectedbioreactivity effects (and by inference of public health risks) from bulk DEP use without taking into account potential batchto-batchvariations in physical (and possibly chemical) properties.
Goode AE, Hine NDM, Chen S, et al., Mapping functional groups on oxidised multi-walled carbon nanotubes at the nanometre scale, Chemical Communications, ISSN: 1364-548X
Diba M, Garcia-Gallastegui A, Taylor RNK, et al., 2014, Quantitative evaluation of electrophoretic deposition kinetics of graphene oxide, CARBON, Vol: 67, Pages: 656-661, ISSN: 0008-6223
Goode AE, Hine NDM, Chen S, et al., 2014, Electron microscopic characterization of functionalized multi-walled carbon nanotubes and their interactions with the blood brain barrier, Pages: 1744-1745, ISSN: 1431-9276
Simoes TA, Goode AE, Porter AE, et al., 2014, Microstructural characterization of low and high carbon CoCrMo alloy nanoparticles produced by mechanical milling, Conference of the Electron-Microscopy-and-Analysis-Group (EMAG), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Goode AE, Hine NDM, Chen S, et al., 2014, Mapping functional groups on oxidised multiwalled carbon nanotubes at the nanometre scale, CHEMICAL COMMUNICATIONS, Vol: 50, Pages: 6744-6747, ISSN: 1359-7345
Burriel M, Wilkins S, Hill JP, et al., 2014, Absence of Ni on the outer surface of Sr doped La2NiO4 single crystals, Energy Environ. Sci.
Fajardo S, Bastidas DM, Ryan MP, et al., 2014, Low energy SIMS characterization of passive oxide films formed on a low-nickel stainless steel in alkaline media., APPLIED SURFACE SCIENCE, Vol: 288, Pages: 423-429, ISSN: 0169-4332
Chen S, Theodorou IG, Goode AE, et al., 2013, High-Resolution Analytical Electron Microscopy Reveals Cell Culture Media-Induced Changes to the Chemistry of Silver Nanowires, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 47, Pages: 13813-13821, ISSN: 0013-936X
Woolley RJ, Ryan MP, Skinner SJ, 2013, In Situ Measurements on Solid Oxide Fuel Cell Cathodes - Simultaneous X-Ray Absorption and AC Impedance Spectroscopy on Symmetrical Cells, FUEL CELLS, Vol: 13, Pages: 1080-1087, ISSN: 1615-6846
Zhang J, Nazarenko Y, Zhang L, et al., 2013, Impacts of a Nanosized Ceria Additive on Diesel Engine Emissions of Particulate and Gaseous Pollutants, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 47, Pages: 13077-13085, ISSN: 0013-936X
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