Publications
271 results found
Scatigno GG, Ryan MP, Giuliani F, et al., 2016, The effect of prior cold work on the chloride stress corrosion cracking of 304L austenitic stainless steel under atmospheric conditions, Materials Science and Engineering: A, Vol: 668, Pages: 20-29, ISSN: 0921-5093
A systematic study of the effect of cold work (CW) on chloride-induced stress corrosion cracking (SCC) in 304L stainless steel was performed. CW between 0% and 40% was applied prior to corrosion of specimens at 75 °C and 70% relative humidity, for 500 h, using MgCl2 (at atmospheric pressure). Samples cracked most readily between 0.5% and 5% CW; at 20% and above no cracks were present. Additionally, above 5% CW, some specific orientation relationships become evident, with cracks primarily aligned along <111> parallel to the transverse direction. The results suggest that at levels of CW >20%, the synergistic effect of micro-mechanisms may hinder SCC in this system.
Sweeney S, Leo BF, Chen S, et al., 2016, Pulmonary surfactant mitigates silver nanoparticle toxicity in human alveolar type-I-like epithelial cells., Colloids and Surfaces B - Biointerfaces, Vol: 145, Pages: 167-175, ISSN: 1873-4367
Accompanying increased commercial applications and production of silver nanomaterials is an increased probability of human exposure, with inhalation a key route. Nanomaterials that deposit in the pulmonary alveolar region following inhalation will interact firstly with pulmonary surfactant before they interact with the alveolar epithelium. It is therefore critical to understand the effects of human pulmonary surfactant when evaluating the inhalation toxicity of silver nanoparticles. In this study, we evaluated the toxicity of AgNPs on human alveolar type-I-like epithelial (TT1) cells in the absence and presence of Curosurf(®) (a natural pulmonary surfactant substitute), hypothesising that the pulmonary surfactant would act to modify toxicity. We demonstrated that 20nm citrate-capped AgNPs induce toxicity in human alveolar type I-like epithelial cells and, in agreement with our hypothesis, that pulmonary surfactant acts to mitigate this toxicity, possibly through reducing AgNP dissolution into cytotoxic Ag(+) ions. For example, IL-6 and IL-8 release by TT1 cells significantly increased 10.7- and 35-fold, respectively (P<0.01), 24h after treatment with 25μg/ml AgNPs. In contrast, following pre-incubation of AgNPs with Curosurf(®), this effect was almost completely abolished. We further determined that the mechanism of this toxicity is likely associated with Ag(+) ion release and lysosomal disruption, but not with increased reactive oxygen species generation. This study provides a critical understanding of the toxicity of AgNPs in target human alveolar type-I-like epithelial cells and the role of pulmonary surfactant in mitigating this toxicity. The observations reported have important implications for the manufacture and application of AgNPs, in particular for applications involving use of aerosolised AgNPs.
Othman BA, Greenwood C, Abuelela AF, et al., 2016, Correlative light-electron microscopy shows RGD-targeted ZnO nanoparticles dissolve in the intracellular environment of triple negative breast cancer cells and cause apoptosis with intra-tumor heterogeneity, Advanced Healthcare Materials, Vol: 5, Pages: 1310-1325, ISSN: 2192-2640
ZnO nanoparticles (NPs) are reported to show a high degree of cancer cell selectivity with potential use in cancer imaging and therapy. Questions remain about the mode by which the ZnO NPs cause cell death, whether they exert an intra- or extra-35 cellular effect, and the resistance among different cancer cell types to ZnO NP exposure. The present study quantified the variability between the cellular toxicity, dynamics of cellular uptake and dissolution of bare and RGD (Arg-Gly-Asp)-targeted ZnO NPs by MDA-MB-231 cells. Compared to bare ZnO NPs, RGD-targeting of the ZnO NPs to integrin αvβ3 receptors expressed on MDA-MB-231 cells appeared to increase the toxicity of the ZnO NPs to breast cancer cells at lower doses. Confocal microscopy of live MDA-MB-231 cells confirmed uptake of both classes of ZnO NPs with a commensurate rise in intracellular Zn2+ concentration prior to cell death. The response of the cells within the population to intracellular Zn2+ was highly heterogeneous. In addition, the results emphasize the utility of dynamic and quantitative imaging in understanding cell uptake and processing of targeted therapeutic ZnO NPs at the cellular level by heterogeneous cancer cell populations, which could be crucial for the development of optimized treatment strategies.
Goode AE, Porter AE, Kłosowski MM, et al., 2016, Analytical transmission electron microscopy at organic interfaces, Current Opinion in Solid State and Materials Science, Vol: 21, Pages: 55-67, ISSN: 1359-0286
Organic materials are ubiquitous in all aspects of our daily lives. Increasingly there is a need to understand interactions between different organic phases, or between organic and inorganic materials (hybrid interfaces), in order to gain fundamental knowledge about the origin of their structural and functional properties. In order to understand the complex structure–property–processing relationships in (and between) these materials, we need tools that combine high chemical sensitivity with high spatial resolution to allow detailed interfacial characterisation. Analytical transmission electron microscopy (TEM) is a powerful and versatile technique that can fulfil both criteria. However, the application of analytical TEM to organic systems presents some unique challenges, such as low contrast between phases, and electron beam sensitivity. In this review recent analytical TEM approaches to the nanoscale characterisation of two systems will be discussed: the hybrid collagen/mineral interface in bone, and the all-organic donor/acceptor interface in OPV devices.
Zhang X, Wu X, Centeno A, et al., 2016, Significant broadband photocurrent enhancement by Au-CZTS core-shell nanostructured photocathodes, Scientific Reports, Vol: 6, ISSN: 2045-2322
Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap.
Tay SER, Goode AE, Weker JN, et al., 2016, Direct in situ observation of ZnO nucleation and growth via transmission X-ray microscopy, Nanoscale, Vol: 8, Pages: 1849-1853, ISSN: 2040-3364
The nucleation and growth of a nanostructure controls its size and morphology, and ultimately its functional properties. Hence it is crucial to investigate growth mechanisms under relevant growth conditions at the nanometer length scale. Here we image the nucleation and growth of electrodeposited ZnO nanostructures in situ, using a transmission X-ray microscope and specially designed electrochemical cell. We show that this imaging technique leads to new insights into the nucleation and growth mechanisms in electrodeposited ZnO including direct, in situ observations of instantaneous versus delayed nucleation.
Ramadan AJ, Rochford LA, Moffat J, et al., 2016, The morphology and structure of vanadyl phthalocyanine thin films on lithium niobate single crystals, Journal of Materials Chemistry C, Vol: 4, Pages: 348-351, ISSN: 2050-7534
The electric field of ferroelectric materials has been used as a driving force to promote molecular adsorption and control the orientation of small dipolar molecules. This approach has not been investigated on larger polyaromatic molecules, such as those used in organic electronic devices, even though the physical and electronic properties of thin films are strongly dependent on molecular structure and orientation, ultimately affecting device performance. Here we investigate the effects of model ferroelectric surfaces on a dipolar organic semiconducting molecule. Thin films of vanadyl phthalocyanine (VOPc) deposited on to (0001) and (2[1 with combining macron][1 with combining macron]0) lithium niobate were subjected to structural and morphological analysis. Whilst thin films could be grown on these surfaces, no obvious change to their structure or morphology was observed suggesting there was no influence of a surface electrical field or surface chemistry on the film structure, and that the substrate is more complex than previously thought.
Walker RJ, Pougin A, Oropeza FE, et al., 2016, Surface Termination and CO<sub>2</sub> Adsorption onto Bismuth Pyrochlore Oxides, CHEMISTRY OF MATERIALS, Vol: 28, Pages: 90-96, ISSN: 0897-4756
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- Citations: 18
Botelho DJ, Leo BF, Massa CB, et al., 2016, Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity, NANOTOXICOLOGY, Vol: 10, Pages: 118-127, ISSN: 1743-5390
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- Citations: 20
Sarkar S, Leo BF, Carranza C, et al., 2015, Modulation of human macrophage responses to mycobacterium tuberculosis by silver nanoparticles of different size and surface modification, PLOS One, Vol: 10, ISSN: 1932-6203
Exposure to silver nanoparticles (AgNP) used in consumer products carries potential health risks including increased susceptibility to infectious pathogens. Systematic assessments of antimicrobial macrophage immune responses in the context of AgNP exposure are important because uptake of AgNP by macrophages may lead to alterations of innate immune cell functions. In this study we examined the effects of exposure to AgNP with different particle sizes (20 and 110 nm diameters) and surface chemistry (citrate or polyvinlypyrrolidone capping) on cellular toxicity and innate immune responses against Mycobacterium tuberculosis (M.tb) by human monocyte-derived macrophages (MDM). Exposures of MDM to AgNP significantly reduced cellular viability, increased IL8 and decreased IL10 mRNA expression. Exposure of M.tb-infected MDM to AgNP suppressed M.tb-induced expression of IL1B, IL10, and TNFA mRNA. Furthermore, M.tb-induced IL-1β, a cytokine critical for host resistance to M.tb, was inhibited by AgNP but not by carbon black particles indicating that the observed immunosuppressive effects of AgNP are particle specific. Suppressive effects of AgNP on the M.tb-induced host immune responses were in part due to AgNP-mediated interferences with the TLR signaling pathways that culminate in the activation of the transcription factor NF-κB. AgNP exposure suppressed M.tb-induced expression of a subset of NF-κB mediated genes (CSF2, CSF3, IFNG, IL1A, IL1B, IL6, IL10, TNFA, NFKB1A). In addition, AgNP exposure increased the expression of HSPA1A mRNA and the corresponding stress-induced Hsp72 protein. Up-regulation of Hsp72 by AgNP can suppress M.tb-induced NF-κB activation and host immune responses. The observed ability of AgNP to modulate infectious pathogen-induced immune responses has important public health implications.
Goode AE, Gonzalez Carter DA, Motskin M, et al., 2015, High resolution and dynamic imaging of biopersistence and bioreactivity of extra and intracellular MWNTs exposed to microglial cells, Biomaterials, Vol: 70, Pages: 57-70, ISSN: 1878-5905
Multi-walled carbon nanotubes (MWNTs) are increasingly being developed both as neuro-therapeutic drug delivery systems to the brain and as neural scaffolds to drive tissue regeneration across lesion sites. MWNTs with different degrees of acid oxidation may have different bioreactivities and propensities to aggregate in the extracellular environment, and both individualised and aggregated MWNTs may be expected to be found in the brain. Before practical application, it is vital to understand how both aggregates and individual MWNTs will interact with local phagocytic immune cells, the microglia, and ultimately to determine their biopersistence in the brain. The processing of extra- and intracellular MWNTs (both pristine and when acid oxidised) by microglia was characterised across multiple length scales by correlating a range of dynamic, quantitative and multi-scale techniques, including: UV-vis spectroscopy, light microscopy, focussed ion beam scanning electron microscopy and transmission electron microscopy. Dynamic, live cell imaging revealed the ability of microglia to break apart and internalise micron-sized extracellular agglomerates of acid oxidised MWNT, but not pristine MWNTs. The total amount of MWNTs internalised by, or strongly bound to, microglia was quantified as a function of time. Neither the significant uptake of oxidised MWNTs, nor the incomplete uptake of pristine MWNTs affected microglial viability, pro-inflammatory cytokine release or nitric oxide production. However, after 24 hrs exposure to pristine MWNTs, a significant increase in the production of reactive oxygen species was observed. Small aggregates and individualised oxidised MWNTs were present in the cytoplasm and vesicles, including within multilaminar bodies, after 72 hours. Some evidence of morphological damage to oxidised MWNT structure was observed including highly disordered graphitic structures, suggesting possible biodegradation. This work demonstrates the utility of dynamic, quant
Ramadan AJ, Rochford LA, Ryan MP, et al., 2015, The influence of polar (0001) zinc oxide (ZnO) on the structure and morphology of vanadyl phthalocyanine (VOPc), RSC Advances, Vol: 5, Pages: 65949-65952, ISSN: 2046-2069
Metal oxide thin films are increasingly utilized in small molecular organic photovoltaic devices to facilitate electron transport and injection. Despite this there is little understanding of the influence these layers have on the structure of adjacent organic semiconductor layers. Here we use both O- and Zn- terminated (0001) single crystal zinc oxide (ZnO) as a model system to investigate the effect of a metal oxide surface on the growth of a molecular semiconductor, vanadyl phthalocyanine (VOPc). The surface reconstructions of these model surfaces are determined and the properties of thin films of VOPc deposited atop are investigated. The nature of the bulk truncation of the surface is found to have pronounced effects on both the morphology and crystal structure of these molecular films. This work highlights the importance of considering the effects of the chemical composition and surface termination of metal oxide films on the structure of adjacent molecular semiconductor films.
Mukherjee D, Porter A, Ryan M, et al., 2015, Modeling in vivo interactions of engineered nanoparticles in the pulmonary alveolar lining fluid, Nanomaterials, Vol: 5, Pages: 1223-1249, ISSN: 2079-4991
Increasing use of engineered nanomaterials (ENMs) in consumer products may result in widespread human inhalation exposures. Due to their high surface area per unit mass, inhaled ENMs interact with multiple components of the pulmonary system, and these interactions affect their ultimate fate in the body. Modeling of ENM transport and clearance in vivo has traditionally treated tissues as well-mixed compartments, without consideration of nanoscale interaction and transformation mechanisms. ENM agglomeration, dissolution and transport, along with adsorption of biomolecules, such as surfactant lipids and proteins, cause irreversible changes to ENM morphology and surface properties. The model presented in this article quantifies ENM transformation and transport in the alveolar air to liquid interface and estimates eventual alveolar cell dosimetry. This formulation brings together established concepts from colloidal and surface science, physics, and biochemistry to provide a stochastic framework capable of capturing essential in vivo processes in the pulmonary alveolar lining layer. The model has been implemented for in vitro solutions with parameters estimated from relevant published in vitro measurements and has been extended here to in vivo systems simulating human inhalation exposures. Applications are presented for four different ENMs, and relevant kinetic rates are estimated, demonstrating an approach for improving human in vivo pulmonary dosimetry.
Munusamy P, Wang C, Engelhard MH, et al., 2015, Comparison of 20nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages, Biointerphases, Vol: 10, ISSN: 1934-8630
Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies.
Theodorou IG, Botelho D, Schwander S, et al., 2015, Static and Dynamic Microscopy of the Chemical Stability and Aggregation State of Silver Nanowires in Components of <i>Murine</i> Pulmonary Surfactant, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 49, Pages: 8048-8056, ISSN: 0013-936X
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- Citations: 19
Theodorou I, Porter AE, Ryan M, et al., 2015, Towards understanding the antibacterial activity of Ag nanoparticles: electron microscopy in the analysis of the materials-biology interface in the lung, Environmental Science: Nano, Vol: 2, Pages: 312-326, ISSN: 2051-8161
Bacterial infections of the pulmonary system are increasing. With almost half of today's infections beingcaused by strains of bacteria that are resistant to existing conventional antibiotics, there is an urgent needfor the development of novel therapeutic platforms. Silver nanoparticles (AgNPs) have been receivingincreasing attention due to their unique antibacterial properties, and whilst the biological efficacy of silveris well known, the mechanisms by which AgNPs degrade within cells and how these processes correlate totheir bioreactivity are poorly understood. This review summarises the current knowledge on thebactericidal pathways of AgNPs and discusses the challenges to be faced before we are able to developefficient and safe antibacterial agents for the treatment of bacterial infections in the lung.
Sweeney S, Theodorou IG, Zambianchi M, et al., 2015, Silver nanowire interactions with primary human alveolar type-II epithelial cell secretions: contrasting bioreactivity with human alveolar type-I and type-II epithelial cells., Nanoscale, Vol: 7, Pages: 10398-10409, ISSN: 2040-3372
Inhaled nanoparticles have a high deposition rate in the alveolar units of the deep lung. The alveolar epithelium is composed of type-I and type-II epithelial cells (ATI and ATII respectively) and is bathed in pulmonary surfactant. The effect of native human ATII cell secretions on nanoparticle toxicity is not known. We investigated the cellular uptake and toxicity of silver nanowires (AgNWs; 70 nm diameter, 1.5 μm length) with human ATI-like cells (TT1), in the absence or presence of Curosurf® (a natural porcine pulmonary surfactant with a low amount of protein) or harvested primary human ATII cell secretions (HAS; containing both the complete lipid as well as the full protein complement of human pulmonary surfactant i.e. SP-A, SP-B, SP-C and SP-D). We hypothesised that Curosurf® or HAS would confer improved protection for TT1 cells, limiting the toxicity of AgNWs. In agreement with our hypothesis, HAS reduced the inflammatory and reactive oxygen species (ROS)-generating potential of AgNWs with exposed TT1 cells. For example, IL-8 release and ROS generation was reduced by 38% and 29%, respectively, resulting in similar levels to that of the non-treated controls. However in contrast to our hypothesis, Curosurf® had no effect. We found a significant reduction in AgNW uptake by TT1 cells in the presence of HAS but not Curosurf. Furthermore, we show that the SP-A and SP-D are likely to be involved in this process as they were found to be specifically bound to the AgNWs. While ATI cells appear to be protected by HAS, evidence suggested that ATII cells, despite no uptake, were vulnerable to AgNW exposure (indicated by increased IL-8 release and ROS generation and decreased intracellular SP-A levels one day post-exposure). This study provides unique findings that may be important for the study of lung epithelial-endothelial translocation of nanoparticles in general and associated toxicity within the alveolar unit.
Ramadan AJ, Rochford LA, Keeble DS, et al., 2015, Structural templating in a non-planar phthalocyanine using single crystal copper iodide, Advanced Materials Interfaces, ISSN: 2196-7350
Solution-grown copper iodide crystals are used as substrates for the templated growth of the nonplanar vanadyl phthalocyanine using organic molecular beam deposition. Structural characterization reveals a single molecular orientation produced by the (111) Miller plane of the copper iodide crystals. These fundamental measurements show the importance of morphology and structure in templating interactions for organic electronics applications.
Wu X, Zhang X, Price D, et al., 2015, Broadband plasmon photocurrent generation from Au nanoparticles/ mesoporous TiO2 nanotube electrodes, Solar Energy Materials and Solar Cells, Vol: 138, Pages: 80-85, ISSN: 0927-0248
There has been an increasing interest in plasmon-induced enhancement of solar cells and more recently in the direct generation of photocurrent using noble metal nanoparticles with their Localised Surface Plasmon Resonance (LSPR) in the visual part of the spectrum. In this paper we report broadband plasmon photocurrent generation using novel Au nanoparticle incorporated mesoporous TiO2 nanotube electrodes. Plasmonic induced photocurrent due to hot electrons is observed over a broad wavelength range (~500 to 1000 nm). Incident photon-to-electron conversion efficiency (IPCE) measurements undertaken showed a maximum photocurrent enhancement of 200 fold around 700–730 nm wavelength.
Seiffert J, Hussain F, Wiegman C, et al., 2015, Pulmonary Toxicity of Instilled Silver Nanoparticles: Influence of Size, Coating and Rat Strain, PLOS ONE, Vol: 10, ISSN: 1932-6203
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- Citations: 79
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
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- Citations: 11
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
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- Citations: 39
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
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.
Donchev E, Pang JS, Gammon PM, et al., 2014, Erratum to: The rectenna device: From theory to practice (a review) — CORRIGENDUM (10.1007/10.1557/mre.2014.6), MRS Energy and Sustainability, Vol: 1
The article contains the following errors: Page 23, left column, line 19. The sentence should read: Another requirement for the insulator is a small dielectric constant since for small area devices the capacitance is reduced, however due to the requirements for tunneling the ultra-thin thicknesses in turn increase capacitance, which has to be kept to a minimum as per Eq. (2). Page 25, left column, line 1. The sentence should read: If the thickness of the higher electron affinity insulator is increased relative to the other insulator, then the QW will be wide enough to form resonant energy levels. The author regrets these errors.
Donchev E, Pang JS, Gammon PM, et al., 2014, The rectenna device: From theory to practice (a review), MRS Energy and Sustainability, Vol: 1
This review article provides the state-of-art research and developments of the rectenna device and its two main components–the antenna and the rectifier. Furthermore, the history, efficiency trends, and socioeconomic impact of its research are also featured. The rectenna (RECTifying antENNA), which was first demonstrated by William C. Brown in 1964 as a receiver for microwave power transmission, is now increasingly researched as a means of harvesting solar radiation. Tapping into the growing photovoltaic market, the attraction of the rectenna concept is the potential for devices that, in theory, are not limited in efficiency by the Shockley–Queisser limit. In this review, the history and operation of this 40-year old device concept are explored in the context of power transmission and the ever increasing interest in its potential applications at terahertz frequencies, through the infrared and visible spectra. Recent modeling approaches that have predicted controversially high efficiency values at these frequencies are critically examined. It is proposed that to unlock any of the promised potential in the solar rectenna concept, there is a need for each constituent part to be improved beyond the current best performance, with the existing nanometer scale antennas, the rectification and the impedance matching solutions all falling short of the necessary efficiencies at terahertz frequencies. Advances in the fabrication, characterization, and understanding of the antenna and the rectifier are reviewed, and common solar rectenna design approaches are summarized. Finally, the socioeconomic impact of success in this field is discussed and future work is proposed.
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