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Nanomaterials
Volume 4
Issue 2
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Nanomaterials, Volume 4, Issue 2 (June 2014) – 19 articles , Pages 189-534

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2557 KiB  
Article
Reducing X-Ray Induced Oxidative Damages in Fibroblasts with Graphene Oxide
by Yong Qiao, Peipei Zhang, Chaoming Wang, Liyuan Ma and Ming Su
Nanomaterials 2014, 4(2), 522-534; https://doi.org/10.3390/nano4020522 - 24 Jun 2014
Cited by 41 | Viewed by 7519
Abstract
A major issue of X-ray radiation therapy is that normal cells can be damaged, limiting the amount of X-rays that can be safely delivered to a tumor. This paper describes a new method based on graphene oxide (GO) to protect normal cells from [...] Read more.
A major issue of X-ray radiation therapy is that normal cells can be damaged, limiting the amount of X-rays that can be safely delivered to a tumor. This paper describes a new method based on graphene oxide (GO) to protect normal cells from oxidative damage by removing free radicals generated by X-ray radiation using grapheme oxide (GO). A variety of techniques such as cytotoxicity, genotoxicity, oxidative assay, apoptosis, γ-H2AX expression, and micro-nucleus assay have been used to assess the protective effect of GO in cultured fibroblast cells. It is found that although GO at higher concentration (100 and 500 µg/mL) can cause cell death and DNA damage, it can effectively remove oxygen free radicals at a lower concentration of 10 µg/mL. The level of DNA damage and cell death is reduced by 48%, and 39%, respectively. Thus, low concentration GO can be used as an effective radio-protective agent in occupational and therapeutic settings. Full article
(This article belongs to the Special Issue Nanotoxicology)
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Figure 1

Figure 1
<p>Optical images of cells (<b>A</b>) and cells treated with graphene oxide (GO) for 24 h (<b>B</b>); cytotoxicity of cells treated with different concentrations of GO (<b>C</b>); and exposed to different dose of X-ray (<b>D</b>). “<b>*</b>” (<span class="html-italic">p</span> &lt; 0.05) and “<b>**</b>” (<span class="html-italic">p</span> &lt; 0.01) represent significant difference and extra significant difference, respectively.</p> Full article ">Figure 2
<p>Genotoxicity of cells treated with GO and X-ray irradiation with halo assay. Fluorescent images of arrayed cells (<b>A</b>); cells treated with 10 µg/mL GO (<b>B</b>); cells exposed to 1.25 Gy X-ray (<b>C</b>); and cells treated with GO and then exposed to 1.25 Gy X-ray (<b>D</b>); an enlarged image shows that halo and nucleus (<b>E</b>); the NDF values of cells after different treatment (<b>F</b>); the rNDF values of cells treated with different concentration of GO without (<b>G</b>) and with 1.25 Gy X-ray radiations (<b>H</b>). “<b>*</b>” (<span class="html-italic">p</span> &lt; 0.05) and “<b>**</b>” (<span class="html-italic">p</span> &lt; 0.01) represent significant difference and extra significant difference, respectively.</p> Full article ">Figure 3
<p>Immunostaining images of cells (<b>A</b>); cells treated with GO (<b>B</b>); cells exposed to X-ray (<b>C</b>); and cells treated with GO and then exposed to X-ray (<b>D</b>); flow cytometry results of cells after different treatments (<b>E</b>–<b>H</b>).</p> Full article ">Figure 4
<p>Oxidative stress induced by GO and X-ray. Fluorescent images of cells (<b>A</b>); cells treated with 10 µg/mL GO (<b>B</b>); cells exposed to 1.25 Gy X-ray (<b>C</b>); and cells treated with 10 µg/mL GO and then exposed to 1.25 Gy X-ray (<b>D</b>); Flow cytometry results of cells after different treatment: cells (<b>E</b>); cells treated with GO (<b>F</b>); cells exposed to 1.25 Gy X-ray (<b>G</b>); and cells treated with GO and exposed to X-ray (<b>H</b>).</p> Full article ">Figure 5
<p>Flow cytometry evaluation of cell apoptosis: cells (<b>A</b>); cells treated with GO (<b>B</b>); cells exposed to 1.25 Gy X-ray (<b>C</b>); and cells treated with 10 µg/mL GO and then exposed to 1.25 Gy X-ray (<b>D</b>).</p> Full article ">Figure 6
<p>Fluorescence images of cells exposed to X-ray, where a bi-nucleated fibroblast has no micronucleus (<b>A</b>); one micronucleus (<b>B</b>); two micronuclei (<b>C</b>); a nucleoplasmic bridge (NPB) (<b>D</b>); and a nuclear bud (NBUD) (<b>E</b>); the appearance frequency of micronucleus of four samples (<b>F</b>), where cells are arrested at inter-phase stage. “<b>*</b>” (<span class="html-italic">p</span> &lt; 0.05) and “<b>**</b>” (<span class="html-italic">p</span> &lt; 0.01) represent significant difference and extra significant difference, respectively.</p> Full article ">
206 KiB  
Review
Carbon Nanotubes and Chronic Granulomatous Disease
by Barbara P. Barna, Marc A. Judson and Mary Jane Thomassen
Nanomaterials 2014, 4(2), 508-521; https://doi.org/10.3390/nano4020508 - 23 Jun 2014
Cited by 18 | Viewed by 5712
Abstract
Use of nanomaterials in manufactured consumer products is a rapidly expanding industry and potential toxicities are just beginning to be explored. Combustion-generated multiwall carbon nanotubes (MWCNT) or nanoparticles are ubiquitous in non-manufacturing environments and detectable in vapors from diesel fuel, methane, propane, and [...] Read more.
Use of nanomaterials in manufactured consumer products is a rapidly expanding industry and potential toxicities are just beginning to be explored. Combustion-generated multiwall carbon nanotubes (MWCNT) or nanoparticles are ubiquitous in non-manufacturing environments and detectable in vapors from diesel fuel, methane, propane, and natural gas. In experimental animal models, carbon nanotubes have been shown to induce granulomas or other inflammatory changes. Evidence suggesting potential involvement of carbon nanomaterials in human granulomatous disease, has been gathered from analyses of dusts generated in the World Trade Center disaster combined with epidemiological data showing a subsequent increase in granulomatous disease of first responders. In this review we will discuss evidence for similarities in the pathophysiology of carbon nanotube-induced pulmonary disease in experimental animals with that of the human granulomatous disease, sarcoidosis. Full article
(This article belongs to the Special Issue Nanotoxicology)
136 KiB  
Editorial
Magnetic Nanomaterials and Their Applications
by Yurii K. Gun'ko
Nanomaterials 2014, 4(2), 505-507; https://doi.org/10.3390/nano4020505 - 23 Jun 2014
Cited by 3 | Viewed by 5616
Abstract
This Special Issue of Nanomaterials is dedicated to the development of new magnetic nanomaterials and their applications in biomedicine, catalysis, spintronics and other areas. The publications in this Issue demonstrate that the interest in magnetic nanomaterials is continuously growing and their realm is [...] Read more.
This Special Issue of Nanomaterials is dedicated to the development of new magnetic nanomaterials and their applications in biomedicine, catalysis, spintronics and other areas. The publications in this Issue demonstrate that the interest in magnetic nanomaterials is continuously growing and their realm is expanding rapidly. Some highlights of the publications in this issue are discussed below. [...] Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
4191 KiB  
Article
Biological Effects of Clinically Relevant CoCr Nanoparticles in the Dura Mater: An Organ Culture Study
by Iraklis Papageorgiou, Thomas Abberton, Martin Fuller, Joanne L. Tipper, John Fisher and Eileen Ingham
Nanomaterials 2014, 4(2), 485-504; https://doi.org/10.3390/nano4020485 - 16 Jun 2014
Cited by 10 | Viewed by 6680
Abstract
Medical interventions for the treatment of spinal disc degeneration include total disc replacement and fusion devices. There are, however, concerns regarding the generation of wear particles by these devices, the majority of which are in the nanometre sized range with the potential to [...] Read more.
Medical interventions for the treatment of spinal disc degeneration include total disc replacement and fusion devices. There are, however, concerns regarding the generation of wear particles by these devices, the majority of which are in the nanometre sized range with the potential to cause adverse biological effects in the surrounding tissues. The aims of this study were to develop an organ culture model of the porcine dura mater and to investigate the biological effects of CoCr nanoparticles in this model. A range of histological techniques were used to analyse the structure of the tissue in the organ culture. The biological effects of the CoCr wear particles and the subsequent structural changes were assessed using tissue viability assays, cytokine assays, histology, immunohistochemistry, and TEM imaging. The physiological structure of the dura mater remained unchanged during the seven days of in vitro culture. There was no significant loss of cell viability. After exposure of the organ culture to CoCr nanoparticles, there was significant loosening of the epithelial layer, as well as the underlying collagen matrix. TEM imaging confirmed these structural alterations. These structural alterations were attributed to the production of MMP-1, -3, -9, -13, and TIMP-1. ELISA analysis revealed that there was significant release of cytokines including IL-8, IL-6, TNF-α, ECP and also the matrix protein, tenascin-C. This study suggested that CoCr nanoparticles did not cause cytotoxicity in the dura mater but they caused significant alterations to its structural integrity that could lead to significant secondary effects due to nanoparticle penetration, such as inflammation to the local neural tissue. Full article
(This article belongs to the Special Issue Nanotoxicology)
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<p>Images of histological sections of the isolated porcine dura-mater tissue at Day 0 (<b>A</b>) and after seven days in organ culture (<b>B</b>) stained with H&amp;E. Immunohistochemical staining of the porcine dura mater with antibodies to fibronectin (<b>C</b>,<b>D</b>), collagen I (<b>F</b>,<b>G</b>), collagen II (<b>I</b>,<b>J</b>) at Day 0 and Day 7 respectively. Isotypes controls for fibronectin (<b>E</b>), collagen I (<b>H</b>) and collagen II (<b>K</b>) antibodies. Tissue viability over a period of 7 days in organ culture as determined by MTT assay (<b>L</b>). Results are presented as OD at 570 nm per mg of wet weight of tissue. Data is presented as the mean (<span class="html-italic">n</span> = 3) ± 95% confidence limits. Data were analysed by one-way analysis of variance and individual differences between group means determined by the T-method. * indicates significant difference (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 2
<p>(<b>A</b>) Representative image of cobalt-chrome nanoparticles that were generated using a pin-on-plate tribometer. Images were captured by FEGSEM; (<b>B</b>) Size distribution of cobalt-chrome nanoparticles. The size distribution of the cobalt-chrome nanoparticles was determined from SEM images taken from different locations on the filter membrane and analysed using Image Pro-Plus imaging software; (<b>C</b>) Effects of CoCr nanoparticles on the viability of dura-mater at 0 and 7 days of culture. Porcine dura mater tissue was cultured in the absence (control) and presence of CoCr nanoparticles at an estimated dose of 5 and 50 µm<sup>3</sup> per epithelial cell and viability determined by the MTT assay. Data are expressed as the mean (<span class="html-italic">n</span> = 3) ± 95% confidence limits. The data were analysed by ANOVA which revealed no significant variation between control and CoCr-treated tissues at day 0 or day 7. Images of dura mater tissue exposed to cobalt-chrome nanoparticles at an estimated dosage of 0 (<b>D</b>), 5 (<b>E</b>) and 50 (<b>F</b>) µm<sup>3</sup> per epithelial cell for a period of 7 days and stained with H&amp;E. Tissues sections shown are orientated so that the outer epithelial layer is closest to the top of the section.</p> Full article ">Figure 3
<p>TEM images across the dura mater tissue that was exposed to CoCr nanoparticlesfor a period of seven days. (<b>A</b>–<b>C</b>) Images of the control dura mater from the epithelial region (<b>A</b>), inner collagen region (<b>B</b>) and the basal side of the dura mater close to arachnoid mater (<b>C</b>); (<b>D</b>–<b>F</b>) Images of the dura mater exposed to an estimated dose of 5 µm<sup>3</sup> of CoCr particles per epithelial cell, from the epithelial region (<b>D</b>), inner collagen region (<b>E</b>), and the basal side of the dura mater close to arachnoid mater (<b>F</b>); (<b>G</b>–<b>I</b>) Images of the dura mater exposed to an estimated dose of 50 µm<sup>3</sup> of CoCr particles per epithelial cell, from the epithelial region (<b>G</b>), inner collagen region (<b>H</b>), and the basal side of the dura mater close to arachnoid mater (<b>I</b>). Single continuous black arrows indicate the dural epithelial cells. Single dotted black arrow indicated the dural fibroblast cells. Black circles indicated disruption of the collagen layer.</p> Full article ">Figure 4
<p>Pattern of cytokine and other mediator release during the exposure of porcine dura mater to CoCr nanoparticles for a period of 0–7 days. The dura mater organ culture was exposed to estimated doses of 0 (control), 5 and 50 µm<sup>3</sup> of CoCr nanoparticles per epithelial cell. The factors that were investigated were IL-8 (<b>A</b>), IL-1β (<b>B</b>), TNF-α (<b>C</b>), IL-6 (<b>D</b>), LBT-4 (leukotriene B4) (<b>E</b>), IL-33 (<b>F</b>), ECP (eosinophil chemotactic protein, eotaxin, CCL-11) (<b>G</b>), and tenascin C (<b>H</b>). Data is expressed as the mean (<span class="html-italic">n</span> = 3) ±95% confidence limits. Data were analysed by one-way analysis of variance and individual differences between group means determined by the T-method. * indicates significantly difference between control and CoCr-treated tissue (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 5
<p>Images of dura mater exposed for seven days to CoCr nanoparticles and stained for the presence of matrix metalloproteinases and TIMP-1 by immunhistochemistry. Images of section of control dura mater tissue (<b>A</b>,<b>D</b>,<b>G</b>,<b>J</b>,<b>M</b>), dura mater exposed to an estimated dose of 5 µm<sup>3</sup> CoCr nanoparticles per epithelial cell (<b>B</b>,<b>E</b>,<b>H</b>,<b>K</b>,<b>N</b>) and dura mater exposed to an estimated dose of 50 µm<sup>3</sup> CoCr nanoparticles per epithelial cell (<b>C</b>,<b>F</b>,<b>I</b>,<b>L</b>,<b>O</b>). The tissues were stained for MMP-1 (<b>A</b>–<b>C</b>), MMP-3 (<b>D</b>–<b>F</b>), MMP-9 (<b>G</b>–<b>I</b>), MMP-13 (<b>J</b>–<b>L</b>), TIMP-1 (<b>M</b>–<b>O</b>).</p> Full article ">
2369 KiB  
Review
Mechanisms Underlying Cytotoxicity Induced by Engineered Nanomaterials: A Review of In Vitro Studies
by Daniele R. Nogueira, Montserrat Mitjans, Clarice M.B. Rolim and M. Pilar Vinardell
Nanomaterials 2014, 4(2), 454-484; https://doi.org/10.3390/nano4020454 - 12 Jun 2014
Cited by 44 | Viewed by 9242
Abstract
Engineered nanomaterials are emerging functional materials with technologically interesting properties and a wide range of promising applications, such as drug delivery devices, medical imaging and diagnostics, and various other industrial products. However, concerns have been expressed about the risks of such materials and [...] Read more.
Engineered nanomaterials are emerging functional materials with technologically interesting properties and a wide range of promising applications, such as drug delivery devices, medical imaging and diagnostics, and various other industrial products. However, concerns have been expressed about the risks of such materials and whether they can cause adverse effects. Studies of the potential hazards of nanomaterials have been widely performed using cell models and a range of in vitro approaches. In the present review, we provide a comprehensive and critical literature overview on current in vitro toxicity test methods that have been applied to determine the mechanisms underlying the cytotoxic effects induced by the nanostructures. The small size, surface charge, hydrophobicity and high adsorption capacity of nanomaterial allow for specific interactions within cell membrane and subcellular organelles, which in turn could lead to cytotoxicity through a range of different mechanisms. Finally, aggregating the given information on the relationships of nanomaterial cytotoxic responses with an understanding of its structure and physicochemical properties may promote the design of biologically safe nanostructures. Full article
(This article belongs to the Special Issue Nanotoxicology)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Light microscopic morphology and kinetics of macrophage aggregation in 2D and 3D cultures. BMDM were exposed to 0.5 μg/mL (0.38 μg/cm<sup>2</sup>) of particulates. Formation of stable cellular aggregates was evaluated at 3 and 14 days post-exposure. Macrophages were stained with May-Grünwald-Giemsa. Reprinted from [<a href="#B65-nanomaterials-04-00454" class="html-bibr">65</a>]. Open Access article, under the terms of Creative Commons Attribution License. Copyright 2011, Licensee Biomed Central Ltd.</p> Full article ">Figure 2
<p>(<b>A</b>) Morphological changes of nano-chelidonines (NCs) (10 and 20 µg/mL)-treated HepG2 cells observed by phase contrast microscope; (<b>B</b>) nuclear condensation assessment of control and treated cells by DAPI staining were analyzed through fluorescence microscopy; (<b>C</b>) the increased apoptotic cells were determined by AO/EB staining through fluorescence microscopy. The nuclear condensation and transformation of color green to reddish orange with fragmented nuclear membrane represents the induction of apoptosis in the treated cells with respect to control ones; (<b>D</b>) assessment of cellular apoptosis by externalizing phosphatidyl serine through Annexin V/PI assay by flow-cytometric analysis. Reprinted with permission from [<a href="#B34-nanomaterials-04-00454" class="html-bibr">34</a>]. Copyright 2013, Elsevier.</p> Full article ">Figure 3
<p>Measurement of ROS production in A549 cells after 24 h NP exposure. The DCF fluorescence of treated cells was normalized to that of untreated controls and reported as mean ± SD. Reprinted with permission from [<a href="#B45-nanomaterials-04-00454" class="html-bibr">45</a>]. Copyright 2013, Elsevier.</p> Full article ">Figure 4
<p>Assessment of the effects of chitosan NPs encapsulating MTX (MTX-CS-NPs) on lysosomal membrane permeabilization in HeLa cells as visualized via AO staining. In untreated control cells, lysosomes can be seen as red–orange granules and cytoplasm has a diffuse green fluorescence. In cells with lysosomal membrane damage (HeLa cells treated with 50 mg/mL MTX-CS-NPs), lysosomes exhibit a shift from red–orange to a yellow–green fluorescent color. Reprinted with permission from [<a href="#B7-nanomaterials-04-00454" class="html-bibr">7</a>]. Copyright 2013, Elsevier.</p> Full article ">Figure 5
<p>Comet data (% tail DNA) of human lymphocytes treated with different concentrations of titanium dioxide (TiO<sub>2</sub>) nanoparticle; <b>*</b> <span class="html-italic">P</span> &lt; 0.05. Reprinted with permission from [<a href="#B37-nanomaterials-04-00454" class="html-bibr">37</a>]. Copyright 2013, John Wiley and Sons.</p> Full article ">
4197 KiB  
Article
Assessment of the Aerosol Generation and Toxicity of Carbon Nanotubes
by Patrick T. O'Shaughnessy, Andrea Adamcakova-Dodd, Ralph Altmaier and Peter S. Thorne
Nanomaterials 2014, 4(2), 439-453; https://doi.org/10.3390/nano4020439 - 12 Jun 2014
Cited by 9 | Viewed by 6858
Abstract
Current interest in the pulmonary toxicity of carbon nanotubes (CNTs) has resulted in a need for an aerosol generation system that is capable of consistently producing a CNT aerosol at a desired concentration level. This two-part study was designed to: (1) assess the [...] Read more.
Current interest in the pulmonary toxicity of carbon nanotubes (CNTs) has resulted in a need for an aerosol generation system that is capable of consistently producing a CNT aerosol at a desired concentration level. This two-part study was designed to: (1) assess the properties of a commercially-available aerosol generator when producing an aerosol from a purchased powder supply of double-walled carbon nanotubes (DWCNTs); and (2) assess the pulmonary sub-acute toxicity of DWCNTs in a murine model during a 5-day (4 h/day) whole-body exposure. The aerosol generator, consisting of a novel dustfeed mechanism and venturi ejector was determined to be capable of producing a DWCNT consistently over a 4 h exposure period at an average level of 10.8 mg/m3. The count median diameter was 121 nm with a geometric standard deviation of 2.04. The estimated deposited dose was 32 µg/mouse. The total number of cells in bronchoalveolar lavage (BAL) fluid was significantly (p < 0.01) increased in exposed mice compared to controls. Similarly, macrophages in BAL fluid were significantly elevated in exposed mice, but not neutrophils. All animals exposed to CNT and euthanized immediately after exposure had changes in the lung tissues showing acute inflammation and injury; however these pathological changes resolved two weeks after the exposure. Full article
(This article belongs to the Special Issue Nanotoxicology)
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Graphical abstract
Full article ">Figure 1
<p>Dust generator schematic diagram (not to scale).</p> Full article ">Figure 2
<p>Aerosol delivery system consisting of the (<b>a</b>) aerosol generator in an acrylic plastic enclosure; (<b>b</b>) charge neutralizer; (<b>c</b>) whole body exposure chamber; (<b>d</b>) aerosol photometer; and (<b>e</b>) scanning mobility particle sizer.</p> Full article ">Figure 3
<p>Changes in chamber concentration with step changes in ring speed when using the 0.3 mm ring.</p> Full article ">Figure 4
<p>Aerosol concentration time series during mouse exposure days (excluding Day 3).</p> Full article ">Figure 5
<p>Linear relationship between photometer readings and associated aerosol concentrations measured gravimetrically.</p> Full article ">Figure 6
<p>Average of aerosol size distributions measured during 4 h exposure periods (counts normalized to the maximum count), with inset of transmission electron micrograph of double-walled carbon nanotubes (DWCNT) fibers emanating from a fiber bundle.</p> Full article ">Figure 7
<p>Number of macrophages, neutrophils and lymphocytes in bronchoalveolar lavage (BAL) fluid in controls (sentinels), animals exposed to carbon nanotube (CNT) euthanized immediately (0 week) or 2 weeks post exposure (2 weeks).</p> Full article ">Figure 8
<p>BAL macrophages from mice necropsied (<b>a</b>) immediately; or (<b>b</b>) 2 weeks after last exposure to CNTs; and (<b>c</b>) from control mice without exposure; (<b>d</b>) Pie charts represent percentage of macrophages population with and without CNTs.</p> Full article ">Figure 9
<p>Mice exposed to CNT and necropsied at 0 week post exposure developed acute inflammation/injury. Lungs were partially atelectatic with coalescing vascular congestion. Overt fibrosis characterized by fibroplasia and collagen deposition was not detected in these mice.</p> Full article ">
2135 KiB  
Review
Superparamagnetic Nanoparticles for Atherosclerosis Imaging
by Fernando Herranz, Beatriz Salinas, Hugo Groult, Juan Pellico, Ana V. Lechuga-Vieco, Riju Bhavesh and J. Ruiz-Cabello
Nanomaterials 2014, 4(2), 408-438; https://doi.org/10.3390/nano4020408 - 5 Jun 2014
Cited by 25 | Viewed by 14639
Abstract
The production of magnetic nanoparticles of utmost quality for biomedical imaging requires several steps, from the synthesis of highly crystalline magnetic cores to the attachment of the different molecules on the surface. This last step probably plays the key role in the production [...] Read more.
The production of magnetic nanoparticles of utmost quality for biomedical imaging requires several steps, from the synthesis of highly crystalline magnetic cores to the attachment of the different molecules on the surface. This last step probably plays the key role in the production of clinically useful nanomaterials. The attachment of the different biomolecules should be performed in a defined and controlled fashion, avoiding the random adsorption of the components that could lead to undesirable byproducts and ill-characterized surface composition. In this work, we review the process of creating new magnetic nanomaterials for imaging, particularly for the detection of atherosclerotic plaque, in vivo. Our focus will be in the different biofunctionalization techniques that we and several other groups have recently developed. Magnetic nanomaterial functionalization should be performed by chemoselective techniques. This approach will facilitate the application of these nanomaterials in the clinic, not as an exception, but as any other pharmacological compound. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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Figure 1
<p>Steps in the synthesis of iron oxide nanoparticles (IONP) for preclinical atherosclerosis imaging. (<b>A</b>) Mixture of iron precursors and different surfactants in organic solvents; (<b>B</b>) Iron oxide nanoparticles in organic solvent; (<b>C</b>) Phase transfer to a water-based solution, in two steps or in a one-step phase transfer and functionalization (red arrow); (<b>D</b>) Functionalization of the nanoparticles for selective and/or multifunctional imaging; (<b>E</b>) Imaging of atherosclerotic plaque with iron oxide nanoparticles. EPR, enhanced permeability and retention.</p> Full article ">Figure 2
<p>TEM images of 16-nm IONPs synthesized by the decomposition of organic precursors:  (<b>A</b>) a monolayer assembly; (<b>B</b>) a multilayer assembly; (<b>C</b>) High Resolution Transmission Electron Microscopy (HRTEM) image of a single Fe<sub>3</sub>O<sub>4</sub> nanoparticle. Reproduced with permission from [<a href="#B13-nanomaterials-04-00408" class="html-bibr">13</a>]. Copyright 2002, American Chemical Society.</p> Full article ">Figure 3
<p>Structure of common silane-based molecules for the ligand exchange approach.</p> Full article ">Figure 4
<p>Micelle approach for PAMAM-C12 coating of the oleic acid-capped iron oxide nanoparticles. Reproduced with permission from [<a href="#B142-nanomaterials-04-00408" class="html-bibr">142</a>]. Copyright 2013, American Chemical Society.</p> Full article ">Figure 5
<p>Schematic structure and TEM imaging of HDL-iron oxide nanoparticles. Adapted with permission from [<a href="#B149-nanomaterials-04-00408" class="html-bibr">149</a>]. Copyright 2008, American Chemical Society.</p> Full article ">Figure 6
<p>Direct chemical modification of the surfactant for oleic acid-coated IONPs, by (<b>A</b>) oxidation of the double bond and (<b>B</b>) olefin metathesis by the use of Hoveyda-Grubbs 2nd generation catalyst.</p> Full article ">Figure 7
<p>Synthesis of multifunctional IONPs by the direct chemical modification of oleic acid. The attachment of allergen Phl p5a and a fluorophore, via biotin-streptavidin interaction, was done by amide formation with the carboxylic groups generated. TEM image of the final IONPs (<b>bottom</b> <b>left</b>). Immunogenicity of the synthesized nanoparticles compared to non-functionalized particles, grass pollen extract and pure protein (<b>bottom</b> <b>right</b>). Reproduced from [<a href="#B87-nanomaterials-04-00408" class="html-bibr">87</a>]. Copyright 2012, John Wiley &amp; Sons, Ltd.</p> Full article ">Figure 8
<p>Evolution of atherosclerosis disease and the main targets at each step, according to the American Heart Assocciation (AHA). Reproduced with permission from [<a href="#B158-nanomaterials-04-00408" class="html-bibr">158</a>]. Copyright 2008, Nature Publishing Group.</p> Full article ">Figure 9
<p>Fibrin-specific IONPs for the T1-weighted imaging of fibrin in atherosclerotic plaque. Reproduced with permission from [<a href="#B178-nanomaterials-04-00408" class="html-bibr">178</a>]. Copyright 2009, American Chemical Society.</p> Full article ">
1033 KiB  
Review
Emergent Properties and Toxicological Considerations for Nanohybrid Materials in Aquatic Systems
by Navid B. Saleh, A. R. M. Nabiul Afrooz, Joseph H. Bisesi,, Jr., Nirupam Aich, Jaime Plazas-Tuttle and Tara Sabo-Attwood
Nanomaterials 2014, 4(2), 372-407; https://doi.org/10.3390/nano4020372 - 3 Jun 2014
Cited by 41 | Viewed by 12612
Abstract
Conjugation of multiple nanomaterials has become the focus of recent materials development. This new material class is commonly known as nanohybrids or “horizon nanomaterials”. Conjugation of metal/metal oxides with carbonaceous nanomaterials and overcoating or doping of one metal with another have been pursued [...] Read more.
Conjugation of multiple nanomaterials has become the focus of recent materials development. This new material class is commonly known as nanohybrids or “horizon nanomaterials”. Conjugation of metal/metal oxides with carbonaceous nanomaterials and overcoating or doping of one metal with another have been pursued to enhance material performance and/or incorporate multifunctionality into nano-enabled devices and processes. Nanohybrids are already at use in commercialized energy, electronics and medical products, which warrant immediate attention for their safety evaluation. These conjugated ensembles likely present a new set of physicochemical properties that are unique to their individual component attributes, hence increasing uncertainty in their risk evaluation. Established toxicological testing strategies and enumerated underlying mechanisms will thus need to be re-evaluated for the assessment of these horizon materials. This review will present a critical discussion on the altered physicochemical properties of nanohybrids and analyze the validity of existing nanotoxicology data against these unique properties. The article will also propose strategies to evaluate the conjugate materials’ safety to help undertake future toxicological research on the nanohybrid material class. Full article
(This article belongs to the Special Issue Nanotoxicology)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Bandgap energetics diagram of (<b>a</b>) ZnO and (<b>b</b>) ZnO-graphene or ZnO-CNT NH. The diagrams also show the relative energetic positions of the cellular redox potential (−4.12 to −4.84 eV) and relevant oxygen species (superoxides and hydroxy radicals).</p> Full article ">Figure 2
<p>Diagram showing the relevant properties of carbonaceous and metal NMs that are associated with toxicity (<b>right panels</b>, <b>a.1</b>–<b>e.1</b>). How these properties might be altered for nanohybrid materials is displayed in the corresponding left panels (<b>a.2</b>–<b>e.2</b>).</p> Full article ">
1015 KiB  
Article
The Impact of Surface Ligands and Synthesis Method on the Toxicity of Glutathione-Coated Gold Nanoparticles
by Bryan Harper, Federico Sinche, Rosina Ho Wu, Meenambika Gowrishankar, Grant Marquart, Marilyn Mackiewicz and Stacey L. Harper
Nanomaterials 2014, 4(2), 355-371; https://doi.org/10.3390/nano4020355 - 12 May 2014
Cited by 43 | Viewed by 12041
Abstract
Gold nanoparticles (AuNPs) are increasingly used in biomedical applications, hence understanding the processes that affect their biocompatibility and stability are of significant interest. In this study, we assessed the stability of peptide-capped AuNPs and used the embryonic zebrafish (Danio rerio) as [...] Read more.
Gold nanoparticles (AuNPs) are increasingly used in biomedical applications, hence understanding the processes that affect their biocompatibility and stability are of significant interest. In this study, we assessed the stability of peptide-capped AuNPs and used the embryonic zebrafish (Danio rerio) as a vertebrate system to investigate the impact of synthesis method and purity on their biocompatibility. Using glutathione (GSH) as a stabilizer, Au-GSH nanoparticles with identical core sizes were terminally modified with Tryptophan (Trp), Histidine (His) or Methionine (Met) amino acids and purified by either dialysis or ultracentrifugation. Au-GSH-(Trp)2 purified by dialysis elicited significant morbidity and mortality at 200 µg/mL, Au-GSH-(His)2 induced morbidity and mortality after purification by either method at 20 and 200 µg/mL, and Au-GSH-(Met)2 caused only sublethal responses at 200 µg/mL. Overall, toxicity was significantly reduced and ligand structure was improved by implementing ultracentrifugation purifications at several stages during the multi-step synthesis and surface modification of Au-GSH nanoparticles. When carefully synthesized at high purity, peptide-functionalized AuNPs showed high biocompatibility in biological systems. Full article
(This article belongs to the Special Issue Nanotoxicology)
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<p>Thin layer chromatography (TLC) determination of Au-GSH-(Met)<sub>2</sub>-U2 purity after ultracentrifugation. (<b>A</b>) R<sub>f</sub> values for compounds listed on the TLC; (<b>B</b>) TLC plate of Au-GSH-(Met)<sub>2</sub>-U2: <span class="html-italic">Lane A</span> before purification, <span class="html-italic">Lane B</span> after purification by ultracentrifugation, and <span class="html-italic">Lane C</span> of free Met ligand in butanol/acetic acid/H<sub>2</sub>O (12:3:5) solvent system.</p> Full article ">Figure 2
<p>Representative <sup>1</sup>H NMR spectra of (<b>A</b>) unpurified and (<b>B</b>) purified Au-GSH-(Trp)<sub>2</sub>-U2 nanoparticles in H<sub>2</sub>O at 25 °C.</p> Full article ">Figure 3
<p>Survival rates for embryonic zebrafish exposed to varying concentrations of Au-GSH-(X)<sub>2</sub> (X = Trp, His, and Met) nanoparticles. Survival measured at 120 hpf for AuNPs with (<b>A</b>) His; (<b>B</b>) Trp; (<b>C</b>) Met. Results are presented as mean ± SEM. Asterisks indicate significant differences from control (untreated, concentration = 0) embryos (<span class="html-italic">p</span> ≤ 0.05, <span class="html-italic">n</span> = 48).</p> Full article ">Figure 4
<p>Incidence of sublethal effects in zebrafish embryos after 5 days of exposure to 200 µg/mL Au-GSH nanoparticles conjugated with (<b>A</b>) His; (<b>B</b>) Trp; or (<b>C</b>) Met. Data on malformations are presented as mean ± SEM (<span class="html-italic">n</span> = 48). Asterisk indicates significant difference exists in the percent incidence <span class="html-italic">vs</span><span class="html-italic">.</span> control (untreated) embryos (<span class="html-italic">p</span> ≤ 0.05, <span class="html-italic">n</span> = 48).</p> Full article ">Figure 5
<p>Uptake of AuNPs containing (<b>A</b>) Au-GSH-(His)<sub>2</sub>-U1 or (<b>B</b>) Au-GSH-(Trp)<sub>2</sub>-U1, both purified by ultracentrifugation as measured by INAA in zebrafish at 24 and 120 hpf. Data are presented as mean ± STDV of three independent samples (<span class="html-italic">n</span> = 3). Asterisk indicates significant difference exists in gold content compared to untreated embryos (<span class="html-italic">p</span> ≤ 0.05, <span class="html-italic">n</span> = 48).</p> Full article ">
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Article
Directed Kinetic Self-Assembly of Mounds on Patterned GaAs (001): Tunable Arrangement, Pattern Amplification and Self-Limiting Growth
by Chuan-Fu Lin, Hung-Chih Kan, Subramaniam Kanakaraju, Christopher Richardson and Raymond Phaneuf
Nanomaterials 2014, 4(2), 344-354; https://doi.org/10.3390/nano4020344 - 12 May 2014
Cited by 2 | Viewed by 5958
Abstract
We present results demonstrating directed self-assembly of nanometer-scale mounds during molecular beam epitaxial growth on patterned GaAs (001) surfaces. The mound arrangement is tunable via the growth temperature, with an inverse spacing or spatial frequency which can exceed that of the features of [...] Read more.
We present results demonstrating directed self-assembly of nanometer-scale mounds during molecular beam epitaxial growth on patterned GaAs (001) surfaces. The mound arrangement is tunable via the growth temperature, with an inverse spacing or spatial frequency which can exceed that of the features of the template. We find that the range of film thickness over which particular mound arrangements persist is finite, due to an evolution of the shape of the mounds which causes their growth to self-limit. A difference in the film thickness at which mounds at different sites self-limit provides a means by which different arrangements can be produced. Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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Graphical abstract

Graphical abstract
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<p>AFM images of nanopatterned GaAs (001) topography before and after homoepitaxial growth: (<b>a</b>) before growth; (<b>b</b>) after growth of 60 nm; (<b>c</b>) after growth of 100 nm; (<b>d</b>) after growth of 150 nm. Initial nanopit widths w =140 nm; center-center spacing between nanopits λ = 280 nm; growth temperature = 460 °C; growth rate = 0.28 nm/s; (<b>e</b>) Measured height profiles from <a href="#nanomaterials-04-00344-f001" class="html-fig">Figure 1</a><b>a</b>–<b>d</b>, taken along [<span class="html-overline">1</span>10] across bridge sites, as shown by green dashed line in (<b>b</b>); profiles are offset vertically for visibility. Blue squares show a pattern unit cell. The horizontal dashed lines indicate the height of the non-templated (“unpatterned”) regions of the surface.</p> Full article ">Figure 2
<p>Temperature and lateral spatial periodicity (λ) dependence of directing self-assembly of mound structures (<b>a</b>) growth at 525 °C, λ = 120 nm; (<b>b</b>) growth at 460 °C, λ = 200 nm; (<b>c</b>,<b>d</b>) growth at 300 °C on nanopit-patterned surface with lateral spatial periodicities of 160 nm, and 120 nm, respectively. The dashed line in 2d marks the edge of the patterned region.</p> Full article ">Figure 3
<p>AFM images of nanopatterned GaAs (001) topography after homoepitaxial growth of 100 nm layer on nanopit arrays with different center to center spacings, λ; (<b>a</b>) λ = 200 nm; (<b>b</b>) λ = 280 nm; (<b>c</b>) λ = 400 nm; (<b>d</b>) λ = 560 nm; (<b>e</b>) λ = 800 nm; (<b>f</b>) Measured height profiles from <a href="#nanomaterials-04-00344-f003" class="html-fig">Figure 3</a><b>a</b>–<b>e</b>, taken along [<span class="html-overline">1</span>10], across bridge sites, as shown by green dashed line in (<b>c</b>); profiles are offset vertically for visibility; the horizontal axes are each normalized to the individual λ. Growth conditions as in <a href="#nanomaterials-04-00344-f001" class="html-fig">Figure 1</a>, <span class="html-italic">i.e</span>., growth temperature = 460 °C; growth rate = 0.28 nm/s.</p> Full article ">Figure 4
<p>Growth rates and characteristics of pit array with λ = 280 nm (<b>a</b>) (top) Schematic showing positions referred to in growth rate analysis; (bottom) Growth rate, relative to level of unpatterned region of surface of mounds at 2-fold bridge sites (dashed line), mounds at 4-fold bridge sites (double dot-dashed line), nanopit bottoms (dotted line); markers show measured average rates, continuous curves are smooth interpolations, intended as a guide to the eye; (<b>b</b>) Measured widths of topmost terrace width for mounds at 2-fold bridge sites, measured along [110]; (<b>c</b>) Histogram of measured topmost terrace widths for a range of pattern periods measured at the growth thicknesses corresponding to the minimum.</p> Full article ">
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Article
Synthesis Characterization and Photocatalytic Studies of Cobalt Ferrite-Silica-Titania Nanocomposites
by David Greene, Raquel Serrano-Garcia, Joseph Govan and Yurii K. Gun'ko
Nanomaterials 2014, 4(2), 331-343; https://doi.org/10.3390/nano4020331 - 23 Apr 2014
Cited by 56 | Viewed by 11693
Abstract
In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating of cobalt ferrite nanoparticles with the double SiO2/TiO2 layer using metallorganic precursors. The Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis [...] Read more.
In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating of cobalt ferrite nanoparticles with the double SiO2/TiO2 layer using metallorganic precursors. The Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis (EDX), Vibrational Sample Magnetometer (VSM) measurements and Raman spectroscopy results confirm the presence both of the silica and very thin TiO2 layers. The core-shell nanoparticles have been sintered at 600 °C and used as a catalyst in photo-oxidation reactions of methylene blue under UV light. Despite the additional non-magnetic coatings result in a lower value of the magnetic moment, the particles can still easily be retrieved from reaction mixtures by magnetic separation. This retention of magnetism was of particular importance allowing magnetic recovery and re-use of the catalyst. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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<p>Transmission Electron Microscopy (TEM) image of uncoated CoFe<sub>2</sub>O<sub>4</sub> nanoparticles.</p> Full article ">Figure 2
<p>X-ray powder diffraction (XRD) pattern of initial CoFe<sub>2</sub>O<sub>4</sub> nanoparticles.</p> Full article ">Figure 3
<p>TEM images of the SiO<sub>2</sub> coated CoFe<sub>2</sub>O<sub>4</sub> nanoparticles.</p> Full article ">Figure 4
<p>XRD pattern of SiO<sub>2</sub> coated CoFe<sub>2</sub>O<sub>4</sub> nanoparticles before and after sintering at 600 °C.</p> Full article ">Figure 5
<p>Reaction scheme for the coating of SiO<sub>2</sub> coated cobalt ferrite nanoparticles with a second TiO<sub>2</sub> coating.</p> Full article ">Figure 6
<p>Vibrational Sample Magnetometer (VSM) curves of CoFe<sub>2</sub>O<sub>4</sub>, CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub> and CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub>@TiO<sub>2</sub> coated nanostructures.</p> Full article ">Figure 7
<p>TEM images of the two types of coating around the CoFe<sub>2</sub>O<sub>4</sub> core, forming the double coated core-shell nanostructures.</p> Full article ">Figure 8
<p>Energy Dispersive X-Ray (EDX) analysis of the TiO<sub>2</sub>/SiO<sub>2</sub> coated CoFe<sub>2</sub>O<sub>4</sub> nanostructures.</p> Full article ">Figure 9
<p>Raman spectrum of CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub>@TiO<sub>2</sub> core-shell nanostructures.</p> Full article ">Figure 10
<p>Graphs showing the absorption of methylene blue dye with the catalytic CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub>@TiO<sub>2</sub> nanoparticles present over time (<b>Top Left</b>) for catalytic testing and also showing just the dye without the nanoparticles present (<b>Top Right</b>), the dye in the presence of CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub> nanoparticles (<b>Bottom Left</b>) and in the presence of CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub>@TiO<sub>2</sub> without UV illumination (<b>Bottom Right</b>) all as controls.</p> Full article ">Figure 11
<p>Graph of the changes in the maximum of dye absorbance plotted against time for catalytic CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub>@TiO<sub>2</sub> nanoparticles sintered at 600 °C (<b>Left</b>). Graph of Log (1/Max Abs) <span class="html-italic">versus</span> time for the catalytic CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub>@TiO<sub>2</sub> nanoparticles sintered at 600 °C (<b>Right</b>).</p> Full article ">Figure 12
<p>Images of suspended CoFe<sub>2</sub>O<sub>4</sub>@SiO<sub>2</sub>@TiO<sub>2</sub> in methylene blue solution in water (<b>Left</b>) and in the presence of a permanent magnet (<b>Right</b>).</p> Full article ">
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Article
Hyperthermia Using Antibody-Conjugated Magnetic Nanoparticles and Its Enhanced Effect with Cryptotanshinone
by Satoshi Ota, Naoya Yamazaki, Asahi Tomitaka, Tsutomu Yamada and Yasushi Takemura
Nanomaterials 2014, 4(2), 319-330; https://doi.org/10.3390/nano4020319 - 23 Apr 2014
Cited by 20 | Viewed by 6665
Abstract
Heat dissipation by magnetic nanoparticles (MNPs) under an alternating magnetic field can be used to selectively treat cancer tissues. Antibodies conjugated to MNPs can enhance the therapeutic effects of hyperthermia by altering antibody-antigen interactions. Fe3O4 nanoparticles (primary diameter, 20–30 nm) [...] Read more.
Heat dissipation by magnetic nanoparticles (MNPs) under an alternating magnetic field can be used to selectively treat cancer tissues. Antibodies conjugated to MNPs can enhance the therapeutic effects of hyperthermia by altering antibody-antigen interactions. Fe3O4 nanoparticles (primary diameter, 20–30 nm) coated with polyethylenimine (PEI) were prepared and conjugated with CH11, an anti-Fas monoclonal antibody. HeLa cell growth was then evaluated as a function of antibody and MNP/antibody complex doses. HeLa cell growth decreased with increased doses of the antibody and complexes. However, MNPs alone did not affect cell growth; thus, only the antibody affected cell growth. In hyperthermia experiments conducted using an alternating magnetic field frequency of 210 kHz, cell viability varied with the intensity of the applied alternating magnetic field, because the temperature increase of the culture medium with added complexes was dependent on magnetic field intensity. The HeLa cell death rate with added complexes was significantly greater as compared with that with MNPs alone. Cryptotanshinone, an anti-apoptotic factor blocker, was also added to cell cultures, which provided an additional anti-cancer cell effect. Thus, an anti-cancer cell effect using a combination of magnetic hyperthermia, an anti-Fas antibody and cryptotanshinone was established. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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<p>HeLa cell growth in the presence of a CH11 antibody added at 0.2, 0.5 and 1.0 μg/mL. The control did not include this antibody. Cell numbers were normalized by the number of control cells. Cell numbers decreased with increased antibody dose.</p> Full article ">Figure 2
<p>Images of HeLa cells without (<b>a</b>) and with (<b>b</b>) a CH11 antibody at 1.0 μg/mL. There were fewer cells after adding this antibody compared with those without this antibody.</p> Full article ">Figure 3
<p>HeLa cell growth in the presence of polyethylenimine (PEI)-coated magnetic nanoparticles (MNPs) at 300 μg/mL and with MNP/antibody complexes added at 100, 200 and 300 μg/mL. The control did not include these treatments. Cell numbers were normalized by the number of control cells. Cell numbers decreased with increasing complex doses.</p> Full article ">Figure 4
<p>Images of HeLa cells with (<b>b</b>) PEI-coated MNPs added at 300 μg/mL or (<b>c</b>) MNP/antibody complexes added at 300 μg/mL. The image in (<b>a</b>) is of the control cells in <a href="#nanomaterials-04-00319-f001" class="html-fig">Figure 1</a>. There were fewer cells after adding PEI-coated MNPs and complexes compared to without these treatments.</p> Full article ">Figure 5
<p>TIG-1 cell growth in the presence of PEI-coated MNPs at 300 μg/mL and with MNP/antibody complexes at 100, 200 and 300 μg/mL. The control did not include these treatments. Cell numbers were normalized to the number of control cells.</p> Full article ">Figure 6
<p>The temperature rise of culture medium added with PEI-coated MNPs of 200 μg/mL in the case of applying an AC magnetic field for 30 min. The magnetic field intensity was 210, 230 and 250 Oe. The frequency of magnetic field was 210 kHz. The control indicates the sample added with nothing in the case of applying the AC magnetic field of 250 Oe. MNPs were effective in hyperthermia. The temperature rise depended on AC magnetic field intensity.</p> Full article ">Figure 7
<p>HeLa cell viability with added PEI-coated MNPs or MNP/antibody complexes and the application of an AC magnetic field for 1 h. The magnetic field intensities were 210, 230 and 250 Oe. The AC magnetic field frequency was 210 kHz. The control did not include MNPs or complexes while applying an AC magnetic field of 250 Oe. Cell viability decreased with increased magnetic field intensity. The complexes decreased cell viability compared with PEI-coated MNPs. The confirmation of cell viability decrease by adding the complexes in each magnetic field is marked with an asterisk (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 8
<p>Images of HeLa cells in the presence of PEI-coated MNPs or MNP/antibody complexes and the application of an AC magnetic field for 1 h. Cell conditions and magnetic field intensities were: (<b>b</b>) PEI-coated MNPs and 210 Oe; (<b>c</b>) PEI-coated MNPs and 250 Oe; (<b>d</b>) complexes and 210 Oe; and (<b>e</b>) complexes and 250 Oe. The image in (<b>a</b>) is of the control cells in <a href="#nanomaterials-04-00319-f007" class="html-fig">Figure 7</a>. The AC magnetic field frequency was 210 kHz. The clusters in (<b>c</b>) and (<b>e</b>) are cell colonies. Cells had adhered and formed large colonies in (<b>a</b>), (<b>b</b>) and (<b>d</b>). However, cells were divided into a number of small colonies in (<b>c</b>) and (<b>e</b>).</p> Full article ">Figure 9
<p>HeLa cell viability in the presence of PEI-coated MNPs, MNP/antibody complexes or MNP/antibody complexes and cryptotanshinone (CP) and when applying an AC magnetic field for 1 h. The magnetic field intensities were 230 and 250 Oe. The AC magnetic field frequency was 210 kHz. Cryptotanshinone effectively reduced cell viability.</p> Full article ">Figure 10
<p>The size distribution of PEI-coated Fe<sub>3</sub>O<sub>4</sub> nanoparticles and the complexes in phosphate-buffered saline (PBS). The size of PEI-coated Fe<sub>3</sub>O<sub>4</sub> nanoparticles and the complexes were 318 ± 57 nm and 349 ± 70 nm, respectively.</p> Full article ">
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Article
Reproductive Toxicity and Life History Study of Silver Nanoparticle Effect, Uptake and Transport in Arabidopsis thaliana
by Jane Geisler-Lee, Marjorie Brooks, Jacob R. Gerfen, Qiang Wang, Christin Fotis, Anthony Sparer, Xingmao Ma, R. Howard Berg and Matt Geisler
Nanomaterials 2014, 4(2), 301-318; https://doi.org/10.3390/nano4020301 - 22 Apr 2014
Cited by 107 | Viewed by 11122
Abstract
Concerns about nanotechnology have prompted studies on how the release of these engineered nanoparticles impact our environment. Herein, the impact of 20 nm silver nanoparticles (AgNPs) on the life history traits of Arabidopsis thaliana was studied in both above- and below-ground parts, at [...] Read more.
Concerns about nanotechnology have prompted studies on how the release of these engineered nanoparticles impact our environment. Herein, the impact of 20 nm silver nanoparticles (AgNPs) on the life history traits of Arabidopsis thaliana was studied in both above- and below-ground parts, at macroscopic and microscopic scales. Both gross phenotypes (in contrast to microscopic phenotypes) and routes of transport and accumulation were investigated from roots to shoots. Wild type Arabidopsis growing in soil, regularly irrigated with 75 μg/L of AgNPs, did not show any obvious morphological change. However, their vegetative development was prolonged by two to three days and their reproductive growth shortened by three to four days. In addition, the germination rates of offspring decreased drastically over three generations. These findings confirmed that AgNPs induce abiotic stress and cause reproductive toxicity in Arabidopsis. To trace transport of AgNPs, this study also included an Arabidopsis reporter line genetically transformed with a green fluorescent protein and grown in an optical transparent medium with 75 μg/L AgNPs. AgNPs followed three routes: (1) At seven days after planting (DAP) at S1.0 (stages defined by Boyes et al. 2001 [41]), AgNPs attached to the surface of primary roots and then entered their root tips; (2) At 14 DAP at S1.04, as primary roots grew longer, AgNPs gradually moved into roots and entered new lateral root primordia and root hairs; (3) At 17 DAP at S1.06 when the Arabidopsis root system had developed multiple lateral roots, AgNPs were present in vascular tissue and throughout the whole plant from root to shoot. In some cases, if cotyledons of the Arabidopsis seedlings were immersed in melted transparent medium, then AgNPs were taken up by and accumulated in stomatal guard cells. These findings in Arabidopsis are the first to document specific routes and rates of AgNP uptake in vivo and in situ. Full article
(This article belongs to the Special Issue Nanotoxicology)
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<p>Study of life history traits of Arabidopsis plants irrigated with ddH<sub>2</sub>O or with AgNPs. (<b>A</b>,<b>B</b>) Morphology of Arabidopsis rosette leaves growing in potted soil. (<b>A</b>) Control plants irrigated with ddH<sub>2</sub>O; (<b>B</b>) treated plants with 75 μg/L of 20 nm AgNPs. (<b>A</b>) and (<b>B</b>) were at S3.50. (<b>A</b>) and (<b>B</b>) showed no distinct and visual differences. (<b>C</b>) Growth of aboveground vegetative parts of control and AgNP-treated within 42 days after planting (DAP). (<b>D</b>) Chronological progression of control, AgNPs-treated (both 75 and 300 μg/L) and AgNO<sub>3</sub>-treated (4.25 and 17 μg/L) plants from sowing to S6.90.</p> Full article ">Figure 2
<p>Reproductive nanotoxicity of AgNP and AgNO<sub>3</sub> in Arabidopsis. This showed 20 nm AgNPs affected seed germination; it also showed stronger toxicity of AgNPs than that of AgNO<sub>3</sub> on germination in E1 generation. Different letters indicate significantly different.</p> Full article ">Figure 3
<p>Transport of AgNPs in Arabidopsis ER::GFP plants. Seedlings of 14 (<b>B</b>,<b>E</b>) and 17 (<b>A</b>,<b>C</b>,<b>D</b>,<b>F</b>) days after planting (DAP) were examined under a Zeiss LSM 510 confocal microscope. (<b>A,C</b>) came from root sections of maturation region; (<b>D</b>–<b>F</b>) came from cotyledon. (<b>A</b>) and (<b>D</b>) are control; (<b>B</b>,<b>C</b>) and (<b>E</b>,<b>F</b>) are AgNPs-treated. Green color was intrinsic GFP; red color was Ag<sup>0</sup> light scattering. At 14 DAP, AgNPs accumulated mainly in root hair cells and surface of roots (<b>B</b>). By 17 DAP, AgNPs already entered vascular tissue, both phloem (white arrowhead) and xylem (black arrowhead), of the roots and could be bulk transported through vascular tissue. Upon germination, some condensed media might have touched cotyledons. At 14 DAP, AgNPs could be observed in the pores of stomata (yellow arrows in <b>E</b>). By 17 DAP, not only the pores of stomata but also the stomata themselves (yellow arrows in <b>F</b>) showed AgNP accumulation. The uneven surface of pavement cells [<a href="#B56-nanomaterials-04-00301" class="html-bibr">56</a>] showed AgNP accumulated on the grooves (white arrowhead) between pavement cells (orange arrow). Scale bar = 0.2 μm.</p> Full article ">Figure 4
<p>Measurements of silver contents in plant tissues and soil matter. (<b>A</b>) Silver accumulation in aboveground parts (shoots) and belowground parts (roots) at the growth stages of S6.0 and S9.0. (<b>B</b>) Silver accumulation in AgNP exposed soil after plants were harvested at S6.0 and S9.0 in terms of μg per g of dry weight of soil sediment with μg of AgNP relative to the fraction of organic and inorganic matter. The presence of AgNPs in control samples might have been due to human errors, <span class="html-italic">i.e.</span>, misirrigation of AgNP suspension instead of ddH<sub>2</sub>O. See the Materials and Methods for the definition of dry weight, organic and inorganic matter. Different letters indicate significantly different soil or tissue concentrations (<span class="html-italic">t</span>-tests, <span class="html-italic">p</span> = 0.05). Abbreviations: dw, dry weight; inorg, inorganic; org, organic; original soil, potting soil from Fafard<sup>R</sup> 4M Mix.</p> Full article ">Figure 5
<p>Inorganic nitrogen nutrients in soil. Inorganic nitrate/nitrite contents of soil were measured after plant tissues were harvested at S6.0 and S9.0. At S6.0, there was no significant difference between control and treated soil. However by S9.0, more nitrate/nitrite remained in the AgNP-treated soil than control soil.</p> Full article ">
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Review
Work Function Engineering of Graphene
by Rajni Garg, Naba K. Dutta and Namita Roy Choudhury
Nanomaterials 2014, 4(2), 267-300; https://doi.org/10.3390/nano4020267 - 3 Apr 2014
Cited by 250 | Viewed by 42108
Abstract
Graphene is a two dimensional one atom thick allotrope of carbon that displays unusual crystal structure, electronic characteristics, charge transport behavior, optical clarity, physical & mechanical properties, thermal conductivity and much more that is yet to be discovered. Consequently, it has generated unprecedented [...] Read more.
Graphene is a two dimensional one atom thick allotrope of carbon that displays unusual crystal structure, electronic characteristics, charge transport behavior, optical clarity, physical & mechanical properties, thermal conductivity and much more that is yet to be discovered. Consequently, it has generated unprecedented excitement in the scientific community; and is of great interest to wide ranging industries including semiconductor, optoelectronics and printed electronics. Graphene is considered to be a next-generation conducting material with a remarkable band-gap structure, and has the potential to replace traditional electrode materials in optoelectronic devices. It has also been identified as one of the most promising materials for post-silicon electronics. For many such applications, modulation of the electrical and optical properties, together with tuning the band gap and the resulting work function of zero band gap graphene are critical in achieving the desired properties and outcome. In understanding the importance, a number of strategies including various functionalization, doping and hybridization have recently been identified and explored to successfully alter the work function of graphene. In this review we primarily highlight the different ways of surface modification, which have been used to specifically modify the band gap of graphene and its work function. This article focuses on the most recent perspectives, current trends and gives some indication of future challenges and possibilities. Full article
(This article belongs to the Special Issue Nanomaterials in Energy Conversion and Storage)
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<p>History of scientific publications on carbon-based materials: (<b>a</b>) Total annual number of publications for each carbon allotrope based on Scopus; (<b>b</b>) History of the number of publications in graphene from different countries; (<b>c</b>) History of the number of publications on grapheme based on different subject areas.</p> Full article ">Figure 2
<p>The common naturally-occurring sp<sup>2</sup> and sp<sup>3</sup> allotropes of carbon occur in different crystallographic forms. <b>Graphite</b>: Hexagonal; stacked flat layers of 3-coordinated sp<sup>2</sup> C. <b>Diamond</b>: Cubic; framework of 4-coordinated sp<sup>3</sup> C. <b>Lonsdaleite</b>: Hexagonal; framework of 4-coordinated sp<sup>3</sup> C. <b>Fullerenes</b>: Closed cage molecules sp<sup>2</sup> C: C60, C70, C76, <span class="html-italic">etc.</span> Nanotubes cylindrical fibers of sp<sup>2</sup> C, single tubes or nested. <b>Graphene</b>: one-atom-thick graphitic layers with sp<sup>2</sup> bonding. Reprinted with permission from [<a href="#B3-nanomaterials-04-00267" class="html-bibr">3</a>]. Copyright 2013 Mineralogical Society of America.</p> Full article ">Figure 3
<p>Schematic representation of the hexagonal arrangement of the carbon atoms in graphene. It can be reduced into two interpenetrating sub-lattices of carbon atoms with inversion symmetry between them. Atoms from different sub-lattices (<b>A</b> and <b>B</b>) are marked by different colors. Reprinted with permission from [<a href="#B6-nanomaterials-04-00267" class="html-bibr">6</a>]<span class="html-italic">.</span> Copyright 2007 Elsevier.</p> Full article ">Figure 4
<p>(<b>a</b>) Energy bands near the Fermi level in graphene. The first Brillouin zone of graphene is illustrated in the horizontal plane and labelled with some points of interest. The conduction and valence bands cross at points K and K'—the two non-equivalent corners of the zone, also known as the Dirac points; (<b>b</b>) Conic energy bands in the vicinity of the K and K' points; (<b>c</b>) Density of states near the Fermi level with Fermi energy <span class="html-italic">E</span><sub>F</sub>. Reprinted with permission from [<a href="#B7-nanomaterials-04-00267" class="html-bibr">7</a>]. Copyright 2009 Nature publishing group.</p> Full article ">Figure 5
<p>Schematic representation of the synthesis of single/few layer graphene from graphite: An oxidative treatment is initially performed to generate graphite oxide; which is followed by exfoliation to produce graphene oxide. Finally, (<b>i</b>) Thermal reduction; (<b>ii</b>) Chemical reduction or (<b>iii</b>) Electrochemical reduction of graphene oxide produces reduced graphene (r-GO).</p> Full article ">Figure 6
<p>Work function tunability in rGO structures. (<b>a</b>) Calculated work function of carbonyl-rich and hydroxyl-rich rGO structures with different oxygen content; (<b>b</b>) The effect of individual functional groups on the work function of rGO, for two different total oxygen concentrations of 1.5% (for validation purpose) and of 20%. Change in Work function in rGO structures with respect to its functional groups. Reprinted with permission from [<a href="#B118-nanomaterials-04-00267" class="html-bibr">118</a>]. Copyright 2013 American Chemical Society.</p> Full article ">Figure 7
<p>(<b>a</b>) Bar graph of contact surface potential difference (CPD) as a function of oxygen content at different stages in graphene synthesis; and (<b>b</b>) Linear fitting of CPD variation during decreasing oxygen content at different stages from graphite oxide to graphene. Reprinted with permission from [<a href="#B119-nanomaterials-04-00267" class="html-bibr">119</a>]. Copyright 2013 American Chemical Society.</p> Full article ">Figure 8
<p>GO reduction mechanism. Routes1–3 and 2’represents the mechanism for hydrazine de-epoxidation of GO. Routes 4–5 represent the mechanism for thermal dehydroxylation for GO. Routes 6 and 7 represent the mechanism for thermal decarbonylation and thermal decarboxylation of GO. Reprinted with permission from [<a href="#B128-nanomaterials-04-00267" class="html-bibr">128</a>]. Copyright 2009 American Chemical Society.</p> Full article ">Figure 9
<p>Effect of GO treatment on the properties of GO. (<b>a</b>) Shows increase in transmittance with respect to wavelength and (<b>b</b>) Shows decrease in sheet resistance with respect to hydrazine treatment, whereas (<b>c</b>) Shows percentage of N-doping and work function modulation with no hydrazine pre-treatment, and (<b>d</b>) With hydrazine pre-treatment plotted again H<sub>2</sub>/NH<sub>3</sub> ratio. Reprinted with permission from [<a href="#B129-nanomaterials-04-00267" class="html-bibr">129</a>]. Copyright 2011 American Chemical Society.</p> Full article ">Figure 10
<p>Formation of GO–OSO<sub>3</sub>H. Reprinted with permission from [<a href="#B132-nanomaterials-04-00267" class="html-bibr">132</a>]. Copyright 2012 American Chemical Society.</p> Full article ">Figure 11
<p>Work functions of graphene can be widely tuned using direct surface functionalization, which is demonstrated by self-assembled monolayers anchored onto the surfaces of the r-GO. Charge-transport characteristics of r-GO field-effect transistors (FETs) functionalized with the various self-assembled monolayers (SAMs). The inset of (<b>a</b>) shows the device configuration, where r-GO was used as an active layer. (<b>a</b>) Output characteristics of pristine r-GO FETs; (<b>b</b>) Transfer characteristics (<span class="html-italic">V</span> D = −1 V) of various r-GO FETs: APTS-rGO (<b>left</b>), pr-GO (<b>middle</b>), and FTS-r-GO (<b>right</b>). The insets show schematic band diagrams of SAM-functionalized r-GOs; (<b>c</b>) Comparative plots of Dirac voltages of the r-GO FETs. Reprinted with permission from [<a href="#B138-nanomaterials-04-00267" class="html-bibr">138</a>]. Copyright 2013 Wiley-VCH.</p> Full article ">Figure 12
<p>Change in WF with respect to doping time. Reprinted with permission from [<a href="#B60-nanomaterials-04-00267" class="html-bibr">60</a>]. Copyright 2010 American Chemical Society.</p> Full article ">Figure 13
<p>Schematic diagrams of near-ultraviolet light-emitting diodes (NUV-LEDs) with (<b>a</b>) multi-layer graphene (MLG) and (<b>b</b>) Au-doped MLG TCLs; (<b>c</b>) SEM images of MLG and (<b>d</b>) Au-doped MLG. Reprinted with permission from [<a href="#B155-nanomaterials-04-00267" class="html-bibr">155</a>]. Copyright 2013 AIP Publishing.</p> Full article ">Figure 14
<p>Schematic representation of the Dirac point state and morphological state of graphene according to sample treatment condition. Schematic representation of morphological state of graphene, before treatment, after treatment and after annealing are shown (left to right). Reprinted with permission from [<a href="#B156-nanomaterials-04-00267" class="html-bibr">156</a>]. Copyright 2013 Royal Society of Chemistry.</p> Full article ">Figure 15
<p>Schematic diagram showing the electron transfer mechanism from different energy levels of the Graphene-ZnO-Au heterostructure for the photo-reduction of nitrobenzene. Reprinted with permission from [<a href="#B146-nanomaterials-04-00267" class="html-bibr">146</a>]. Copyright 2013 American Chemical Society.</p> Full article ">
10924 KiB  
Article
NiO Nanofibers as a Candidate for a Nanophotocathode
by Thomas J. Macdonald, Jie Xu, Sait Elmas, Yatin J. Mange, William M. Skinner, Haolan Xu and Thomas Nann
Nanomaterials 2014, 4(2), 256-266; https://doi.org/10.3390/nano4020256 - 3 Apr 2014
Cited by 51 | Viewed by 10482
Abstract
p-type NiO nanofibers have been synthesized from a simple electrospinning and sintering procedure. For the first time, p-type nanofibers have been electrospun onto a conductive fluorine doped tin oxide (FTO) surface. The properties of the NiO nanofibers have been directly compared [...] Read more.
p-type NiO nanofibers have been synthesized from a simple electrospinning and sintering procedure. For the first time, p-type nanofibers have been electrospun onto a conductive fluorine doped tin oxide (FTO) surface. The properties of the NiO nanofibers have been directly compared to that of bulk NiO nanopowder. We have observed a p-type photocurrent for a NiO photocathode fabricated on an FTO substrate. Full article
(This article belongs to the Special Issue Nanomaterials in Energy Conversion and Storage)
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<p>SEM for NiO nanofibers: (<b>a</b>,<b>b</b>) polyactonitrile (PAN) Ni(AcAc)<sub>2</sub> nanofibers; (<b>c</b>) NiO nanofibers after calcinations; (<b>d</b>) NiO nanofibers on fluorine doped tin oxide (FTO) after calcinations.</p> Full article ">Figure 2
<p>XRD for nickel oxide nanofibers (NiONF) and commercial nickel oxide nanoparticles (NiONP) [<a href="#B23-nanomaterials-04-00256" class="html-bibr">23</a>].</p> Full article ">Figure 3
<p>TEM for NiO nanofibers: (<b>a</b>) series of NiO nanofibers; (<b>b</b>) isolated pair of NiO nanofibers at (<b>c</b>) individual nanofiber; (<b>d</b>) selected area electron diffraction (SAED) pattern of nanofibers.</p> Full article ">Figure 4
<p>X-ray photoelectron spectroscopy (XPS) Ni 2p spectra for NiO nanofibers and nanoparticles.</p> Full article ">Figure 5
<p>Ni valence spectra for NiO nanofibers and nanoparticles.</p> Full article ">Figure 6
<p>Chronoamperogram for the photocurrent as a function of time for NiO nanoparticles on FTO.</p> Full article ">
532 KiB  
Article
Evaluation of Superparamagnetic Silica Nanoparticles for Extraction of Triazines in Magnetic in-Tube Solid Phase Microextraction Coupled to Capillary Liquid Chromatography
by R. A. González-Fuenzalida, Y. Moliner-Martínez, Helena Prima-Garcia, Antonio Ribera, P. Campins-Falcó and Ramon J. Zaragozá
Nanomaterials 2014, 4(2), 242-255; https://doi.org/10.3390/nano4020242 - 2 Apr 2014
Cited by 26 | Viewed by 7148
Abstract
The use of magnetic nanomaterials for analytical applications has increased in the recent years. In particular, magnetic nanomaterials have shown great potential as adsorbent phase in several extraction procedures due to the significant advantages over the conventional methods. In the present work, the [...] Read more.
The use of magnetic nanomaterials for analytical applications has increased in the recent years. In particular, magnetic nanomaterials have shown great potential as adsorbent phase in several extraction procedures due to the significant advantages over the conventional methods. In the present work, the influence of magnetic forces over the extraction efficiency of triazines using superparamagnetic silica nanoparticles (NPs) in magnetic in tube solid phase microextraction (Magnetic-IT-SPME) coupled to CapLC has been evaluated. Atrazine, terbutylazine and simazine has been selected as target analytes. The superparamagnetic silica nanomaterial (SiO2-Fe3O4) deposited onto the surface of a capillary column gave rise to a magnetic extraction phase for IT-SPME that provided a enhancemment of the extraction efficiency for triazines. This improvement is based on two phenomena, the superparamegnetic behavior of Fe3O4 NPs and the diamagnetic repulsions that take place in a microfluidic device such a capillary column. A systematic study of analytes adsorption and desorption was conducted as function of the magnetic field and the relationship with triazines magnetic susceptibility. The positive influence of magnetism on the extraction procedure was demonstrated. The analytical characteristics of the optimized procedure were established and the method was applied to the determination of the target analytes in water samples with satisfactory results. When coupling Magnetic-IT-SPME with CapLC, improved adsorption efficiencies (60%–63%) were achieved compared with conventional adsorption materials (0.8%–3%). Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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<p>(<b>a</b>) Frequency dependence of AC susceptibility of the NPs <span class="html-italic">vs.</span> Temperature with amplitude of 17 Oe; (<b>b</b>) Arrhenius law fit for the nanoparticles.</p> Full article ">Figure 2
<p>Variation of the extraction efficiency as function of the magnetic field for (<b>1</b>) simazine; (<b>2</b>) atrazine; and (<b>3</b>) terbutylazine. Injection 100 μL of a mixture of the target analytes (30 μg L<sup>−1</sup>). Mobile phase: methanol:water 85:15, flow 6 μL min<sup>−1</sup>. <span class="html-italic">B</span><sub>adsorption</sub> = <span class="html-italic">B</span><sub>desorption</sub> (reverse polarity).</p> Full article ">Figure 3
<p>Chromatogram obtained with the magnetic capillary column in the Magnetic-IT-SPME device coupled with Cap-LC-DAD (230 nm); (<b>1</b>) simazine; (<b>2</b>) atrazine; and (<b>3</b>) terbutylazine. (<b>a</b>) Applying magnetic field <span class="html-italic">B</span><sub>adsoprtion</sub> = 150 G (<span class="html-italic">B</span><sub>desorption</sub> = 150 G, reverse polarity); (<b>b</b>) Without magnetic field (<span class="html-italic">B</span> = 0 G). Injection 100 μL of a mixture of the target analytes (30 μg L<sup>−1</sup>). Mobile phase: methanol:water 85:15, flow 6 μL min<sup>−1</sup>.</p> Full article ">Figure 4
<p>Comparison of the extraction efficiency (%) for simazine, atrazine and terbutylazine with a TRB-5 commercial capillary column, SiO<sub>2</sub> supported Fe<sub>3</sub>O<sub>4</sub> capillary column without magnetic field (<span class="html-italic">B</span> = 0 G) and with the SiO<sub>2</sub> supported Fe<sub>3</sub>O<sub>4</sub> capillary column applying magnetic field (<span class="html-italic">B</span><sub>adsorption</sub> = 150 G, <span class="html-italic">B</span><sub>desorption</sub> = 150 G, reverse polarity).</p> Full article ">Figure 5
<p>Schematic diagram of the Magnetic-IT-SPME-Cap-LC system. (---) adsorption (load position of the injection valve); and ( <span class="html-fig-inline" id="nanomaterials-04-00242-i002"> <img alt="Nanomaterials 04 00242 i002" src="/nanomaterials/nanomaterials-04-00242/article_deploy/html/images/nanomaterials-04-00242-i002.png"/></span>) desorption (injection position of the injection valve).</p> Full article ">
1022 KiB  
Review
Recent Advances in the Application of Magnetic Nanoparticles as a Support for Homogeneous Catalysts
by Joseph Govan and Yurii K. Gun'ko
Nanomaterials 2014, 4(2), 222-241; https://doi.org/10.3390/nano4020222 - 2 Apr 2014
Cited by 272 | Viewed by 16890
Abstract
Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We [...] Read more.
Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We discuss magnetic core shell nanostructures (e.g., silica or polymer coated magnetic nanoparticles) as substrates for catalyst immobilisation. Then we consider magnetic nanoparticles bound to inorganic catalytic mesoporous structures as well as metal organic frameworks. Binding of catalytically active small organic molecules and polymers are also reviewed. After that we briefly deliberate on the binding of enzymes to magnetic nanocomposites and the corresponding enzymatic catalysis. Finally, we draw conclusions and present a future outlook for the further development of new catalytic systems which are immobilised onto magnetic nanoparticles. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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<p>General scheme for the synthesis of silica coating and further acid functionalisation of magnetic Fe<sub>3</sub>O<sub>4</sub> nanoparticles. Reproduced from Nazifi <span class="html-italic">et al.</span> [<a href="#B42-nanomaterials-04-00222" class="html-bibr">42</a>]. Copyright 2013 with permission from Spinger.</p> Full article ">Figure 2
<p>Synthesis of Fe<sub>3</sub>O<sub>4</sub> nanoparticles bound with aminocellulose. Reproduced from Heinze <span class="html-italic">et al.</span> [<a href="#B49-nanomaterials-04-00222" class="html-bibr">49</a>]. Copyright 2013 with permission of Elsevier.</p> Full article ">Figure 3
<p>Schematic presentation of the preparation of Fe<sub>3</sub>O<sub>4</sub>@ZIF-8 core-shell microspheres and their use as catalysts in a magnetic capillary reactor. Reproduced from [<a href="#B53-nanomaterials-04-00222" class="html-bibr">53</a>]. Copyright 2013 with permission of Elsevier.</p> Full article ">Figure 4
<p>Structures of dendritic phosphine ligands. Reproduced from M. Keller <span class="html-italic">et al.</span> [<a href="#B55-nanomaterials-04-00222" class="html-bibr">55</a>]. Copyright © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.</p> Full article ">Figure 5
<p>Sequence of the synthesis of Fe<sub>3</sub>O<sub>4</sub>/Dipyridine showing the original magnetic nanoparticle (<b>A</b>), the nanoparticle after attachment of a silica shell with TEOS (<b>B</b>), after the attachment of 3-chloropropyltriethoxysilane to form the organic linker (<b>C</b>), and the addition of methylene di-pyridine catalyst species (<b>D</b>). Reproduced from Nasseri <span class="html-italic">et al.</span> [<a href="#B60-nanomaterials-04-00222" class="html-bibr">60</a>]. Copyright 2013 with permission of Elsevier.</p> Full article ">Figure 6
<p>Method for attachment of proline based catalyst to silica coated magnetic nanoparticles. Reproduced from Kong <span class="html-italic">et al.</span> [<a href="#B62-nanomaterials-04-00222" class="html-bibr">62</a>], with permission of the Royal Society of Chemistry.</p> Full article ">Figure 7
<p>Synthesis of Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>/diazoniabicyclco[2,2,2]octane catalyst (DABCO) for the creation of a silica matrix. Reproduced from Kiasat <span class="html-italic">et al.</span> [<a href="#B66-nanomaterials-04-00222" class="html-bibr">66</a>]. Copyright 2013 with permission of Elsevier.</p> Full article ">Figure 8
<p>Scheme for the immobilisation of first generation Macmillan catalysts on the surface of magnetic nanoparticles and polystyrene microspheres. Reproduced from Pericàs <span class="html-italic">et al.</span> [<a href="#B67-nanomaterials-04-00222" class="html-bibr">67</a>]. Copyright 2012 American Chemical Society.</p> Full article ">Figure 9
<p>Synthesis of piperidine carboxylic acid stabilised magnetite particles. Reproduced from Toprak <span class="html-italic">et al.</span> [<a href="#B72-nanomaterials-04-00222" class="html-bibr">72</a>]. Copyright 2012 with permission of Elsevier.</p> Full article ">Figure 10
<p>Bifunctional catalysts directly immobilised on magnetite nanoparticles. Reproduced from Gleeson <span class="html-italic">et al.</span> [<a href="#B75-nanomaterials-04-00222" class="html-bibr">75</a>] with permission of the Royal Society of Chemistry.</p> Full article ">Figure 11
<p>Change in enzymatic activity with changing pH (<b>Left</b>) and temperature (<b>Right</b>) to compare enzymes immobilized on nanoparticles with the free enzyme. Reproduced from Duan <span class="html-italic">et al.</span> [<a href="#B82-nanomaterials-04-00222" class="html-bibr">82</a>]. Copyright 2013 with permission of Elsevier.</p> Full article ">Figure 12
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0 pages, 1876 KiB  
Article
RETRACTED: Potential Impact of Multi-Walled Carbon Nanotubes Exposure to the Seedling Stage of Selected Plant Species
by Parvin Begum, Refi Ikhtiari and Bunshi Fugetsu
Nanomaterials 2014, 4(2), 203-221; https://doi.org/10.3390/nano4020203 - 31 Mar 2014
Cited by 80 | Viewed by 11707 | Retraction
Abstract
Phytotoxicity is a significant consideration in understanding the potential environmental impact of nanoparticles. Abundant experimental data have shown that multi-walled carbon nanotubes (MWNTs) are toxic to plants, but the potential impacts of exposure remain unclear. The objective of the present study was to [...] Read more.
Phytotoxicity is a significant consideration in understanding the potential environmental impact of nanoparticles. Abundant experimental data have shown that multi-walled carbon nanotubes (MWNTs) are toxic to plants, but the potential impacts of exposure remain unclear. The objective of the present study was to evaluate possible phytotoxicity of MWNTs at 0, 20, 200, 1000, and 2000 mg/L with red spinach, lettuce, rice, cucumber, chili, lady’s finger, and soybean, based on root and shoot growth, cell death, and electrolyte leakage at the seedling stage. After 15 days of hydroponic culture, the root and shoot lengths of red spinach, lettuce, and cucumber were significantly reduced following exposure to 1000 mg/L and 2000 mg/L MWNTs. Similar toxic effects occurred regarding cell death and electrolyte leakage. Red spinach and lettuce were most sensitive to MWNTs, followed by rice and cucumber. Very little or no toxic effects were observed for chili, lady’s finger, and soybean. Full article
(This article belongs to the Special Issue Nanotoxicology)
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<p>(<b>a</b>) SEM (Bar: 500 nm); (<b>b</b>) TEM (Bar: 200 nm) micrographs of MWNTs before and after suspended in a modified Hoagland medium; and (<b>c</b>) AFM image of MWNTs before suspended in a modified Hoagland medium, depicts the morphology of MWNTs. Reproduced with permission from reference [<a href="#B17-nanomaterials-04-00203" class="html-bibr">17</a>], Copyright 2012, Elsevier.</p> Full article ">Figure 2
<p>Morphological observations of red spinach, lettuce, rice, and cucumber exposed to MWNTs at 0, 20, 200, 1000, or 2000 mg/L for 15 days. Reproduced with permission from reference [<a href="#B16-nanomaterials-04-00203" class="html-bibr">16</a>], Copyright 2012, Elsevier.</p> Full article ">Figure 3
<p>Growth reduction of red spinach, lettuce, rice, and cucumber after 15 days of exposure to MWNTs. (<b>a</b>,<b>d</b>) Shoot and root weights, respectively, of red spinach, lettuce, and rice. (<b>b</b>,<b>e</b>) Shoot and root weights, respectively, of cucumber. (<b>c</b>,<b>f</b>) Shoot and root lengths, respectively, of red spinach, lettuce, rice, and cucumber. Error bars represent standard deviation of the mean (<span class="html-italic">n</span> = 3). The cucumber data are presented separately because the shoot and root fresh weights were larger than for the other tested plants. Reproduced with permission from reference [<a href="#B16-nanomaterials-04-00203" class="html-bibr">16</a>], Copyright 2012, Elsevier.</p> Full article ">Figure 4
<p>Dose dependency of (<b>a</b>) cell death and (<b>b</b>) membrane integrity caused by 15-day exposure to MWNTs at 0, 20, 200, 1000, or 2000 mg/L in red spinach, lettuce, rice, and cucumber roots. Error bars represent standard deviation of the mean (<span class="html-italic">n</span> = 3). Reproduced with permission from reference [<a href="#B16-nanomaterials-04-00203" class="html-bibr">16</a>], Copyright 2012, Elsevier.</p> Full article ">Figure 5
<p>Detection of ROS in red spinach leaves. 15 day-old fresh leaves treated with or without MWNTs (0 and 1000 mg/L) were used for all measurements. (<b>a</b>,<b>b</b>) Staining using the 3–3'-diaminobenzidine (DAB) (Image obtained with a magnification of 4×). The brown staining indicates the formation of a brown polymerization product when H<sub>2</sub>O<sub>2</sub> reacts with DAB, and viewed with light microscopy. (<b>c</b>,<b>d</b>) Staining using the NBT (Image obtained with a magnification of 4×). The blue staining indicates the formation of a blue formazon product when superoxide reacts with NBT, and viewed with light microscopy. (<b>e</b>,<b>f</b>) Staining with DCFH-DA (Image obtained with a magnification of 4×). The green signal indicates the presence of hydroperoxides inside the cells. Leaves were observed with fluorescence microscopy.</p> Full article ">Figure 6
<p>SEM observation of the red spinach leaf grown <span class="html-italic">in vivo</span> for 15 days in a medium containing Hoagland media only (control) and supplemented with 1000 mg/L MWNTs (treated). Image showing the morphology of control leaf (<b>a</b>,<b>c</b>) epidermis and MWNTs treated leaf (<b>b</b>,<b>d</b>) epidermis showing swelling epidermis. SEM observation of red spinach roots grown <span class="html-italic">in vivo</span> for 15 days in a medium containing Hoagland media only (control, <b>e</b>) and supplemented with 1000 mg L<sup>−1</sup> MWNTs (treated, <b>f</b>) showing deformed root cap and elongation zone and deformed epidermis. Bar: <b>a</b> and <b>b</b>, 60 µm; <b>c</b> and <b>d</b>, 15 µm; <b>e</b>, 150 µm; <b>f</b>, 429 µm.</p> Full article ">
2470 KiB  
Article
Electrochemical Synthesis of Mesoporous CoPt Nanowires for Methanol Oxidation
by Albert Serrà, Manuel Montiel, Elvira Gómez and Elisa Vallés
Nanomaterials 2014, 4(2), 189-202; https://doi.org/10.3390/nano4020189 - 28 Mar 2014
Cited by 15 | Viewed by 6844
Abstract
A new electrochemical method to synthesize mesoporous nanowires of alloys has been developed. Electrochemical deposition in ionic liquid-in-water (IL/W) microemulsion has been successful to grow mesoporous CoPt nanowires in the interior of polycarbonate membranes. The viscosity of the medium was high, but it [...] Read more.
A new electrochemical method to synthesize mesoporous nanowires of alloys has been developed. Electrochemical deposition in ionic liquid-in-water (IL/W) microemulsion has been successful to grow mesoporous CoPt nanowires in the interior of polycarbonate membranes. The viscosity of the medium was high, but it did not avoid the entrance of the microemulsion in the interior of the membrane’s channels. The structure of the IL/W microemulsions, with droplets of ionic liquid (4 nm average diameter) dispersed in CoPt aqueous solution, defined the structure of the nanowires, with pores of a few nanometers, because CoPt alloy deposited only from the aqueous component of the microemulsion. The electrodeposition in IL/W microemulsion allows obtaining mesoporous structures in which the small pores must correspond to the size of the droplets of the electrolytic aqueous component of the microemulsion. The IL main phase is like a template for the confined electrodeposition. The comparison of the electrocatalytic behaviours towards methanol oxidation of mesoporous and compact CoPt nanowires of the same composition, demonstrated the porosity of the material. For the same material mass, the CoPt mesoporous nanowires present a surface area 16 times greater than compact ones, and comparable to that observed for commercial carbon-supported platinum nanoparticles. Full article
(This article belongs to the Special Issue Ordered Mesoporous Nanomaterials)
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<p>Schematic representation of electrochemical synthesis of mesoporous and non-mesoporous CoPt nanowires on polycarbonate membranes coated with gold layer.</p> Full article ">Figure 2
<p>Cyclic voltammetry at 25 °C and stationary conditions on Si/Ti (15 nm)/Au (100 nm) of (<b>A</b>) CoPt solution (W) and (<b>B</b>) CoPt solution (W), aqueous solution–surfactant system (79W:21S) and IL/W microemulsion.</p> Full article ">Figure 3
<p>(<b>A</b>) Cyclic voltammetrie sand (<b>B</b>) chronoamperometric curves at 25 °C on Au sputtered 20 µm-thick polycarbonate membranes with 200 nm pore diameters size. Geometrical area has been used to calculate current density.</p> Full article ">Figure 4
<p>TEM micrographs of CoPt nanowires prepared in (<b>A</b>) aqueous solution (W), (<b>B</b>) aqueous solution–surfactant system (79W:21S) and (<b>C</b>) IL/W microemulsion systems at 25 °C on Au sputtered 20 µm-thick polycarbonate membranes with 200 nm pore diameters size after circulating the same charge. The first micrographs in each series correspond to a general overview of CoPt nanowires; the second one corresponds to a magnification of a central part of nanowire. In addition, the latter corresponds to a magnification of the edge of a nanowire.</p> Full article ">Figure 5
<p>Cyclic voltammograms for methanol oxidation on CoPt nanowires obtained from W and IL/W systems. Scans were recorded in Ar saturated 1.0 M CH<sub>3</sub>OH/0.5 M H<sub>2</sub>SO<sub>4</sub> at 100 mVs<sup>−1</sup>. Current density calculated using (<b>A</b>) catalyst’s mass, and (<b>B</b>) electrochemically active area. Inset shows the region used to calculate electrochemically active area (in red) from a cyclic voltammogram in 0.5 M H<sub>2</sub>SO<sub>4</sub> at 100 mV s<sup>−1</sup>.</p> Full article ">
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