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

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Editorial

Jump to: Research, Review

Open AccessEditorial Magnetic Nanomaterials and Their Applications
Nanomaterials 2014, 4(2), 505-507; doi:10.3390/nano4020505
Received: 16 June 2014 / Accepted: 17 June 2014 / Published: 23 June 2014
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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 [...] 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)

Research

Jump to: Editorial, Review

Open AccessArticle Electrochemical Synthesis of Mesoporous CoPt Nanowires for Methanol Oxidation
Nanomaterials 2014, 4(2), 189-202; doi:10.3390/nano4020189
Received: 11 March 2014 / Revised: 22 March 2014 / Accepted: 23 March 2014 / Published: 28 March 2014
Cited by 3 | PDF Full-text (2470 KB) | HTML Full-text | XML Full-text
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 [...] 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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Open AccessArticle Potential Impact of Multi-Walled Carbon Nanotubes Exposure to the Seedling Stage of Selected Plant Species
Nanomaterials 2014, 4(2), 203-221; doi:10.3390/nano4020203
Received: 7 February 2014 / Revised: 22 March 2014 / Accepted: 22 March 2014 / Published: 31 March 2014
Cited by 6 | PDF Full-text (2618 KB) | HTML Full-text | XML Full-textRetraction
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 [...] 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)
Open AccessArticle Evaluation of Superparamagnetic Silica Nanoparticles for Extraction of Triazines in Magnetic in-Tube Solid Phase Microextraction Coupled to Capillary Liquid Chromatography
Nanomaterials 2014, 4(2), 242-255; doi:10.3390/nano4020242
Received: 24 February 2014 / Revised: 24 March 2014 / Accepted: 25 March 2014 / Published: 2 April 2014
Cited by 6 | PDF Full-text (532 KB) | HTML Full-text | XML Full-text
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, [...] 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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Open AccessArticle NiO Nanofibers as a Candidate for a Nanophotocathode
Nanomaterials 2014, 4(2), 256-266; doi:10.3390/nano4020256
Received: 28 February 2014 / Revised: 21 March 2014 / Accepted: 28 March 2014 / Published: 3 April 2014
Cited by 18 | PDF Full-text (10924 KB) | HTML Full-text | XML Full-text | Supplementary Files
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 [...] 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)
Open AccessArticle Reproductive Toxicity and Life History Study of Silver Nanoparticle Effect, Uptake and Transport in Arabidopsis thaliana
Nanomaterials 2014, 4(2), 301-318; doi:10.3390/nano4020301
Received: 10 March 2014 / Revised: 15 April 2014 / Accepted: 15 April 2014 / Published: 22 April 2014
Cited by 10 | PDF Full-text (1079 KB) | HTML Full-text | XML Full-text | Supplementary Files
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, [...] 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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Open AccessArticle Hyperthermia Using Antibody-Conjugated Magnetic Nanoparticles and Its Enhanced Effect with Cryptotanshinone
Nanomaterials 2014, 4(2), 319-330; doi:10.3390/nano4020319
Received: 17 February 2014 / Revised: 9 April 2014 / Accepted: 17 April 2014 / Published: 23 April 2014
Cited by 5 | PDF Full-text (1063 KB) | HTML Full-text | XML Full-text
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 [...] 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)
Open AccessArticle Synthesis Characterization and Photocatalytic Studies of Cobalt Ferrite-Silica-Titania Nanocomposites
Nanomaterials 2014, 4(2), 331-343; doi:10.3390/nano4020331
Received: 23 February 2014 / Revised: 11 April 2014 / Accepted: 11 April 2014 / Published: 23 April 2014
Cited by 4 | PDF Full-text (2618 KB) | HTML Full-text | XML Full-text
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 [...] 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)
Open AccessArticle Directed Kinetic Self-Assembly of Mounds on Patterned GaAs (001): Tunable Arrangement, Pattern Amplification and Self-Limiting Growth
Nanomaterials 2014, 4(2), 344-354; doi:10.3390/nano4020344
Received: 18 March 2014 / Revised: 5 April 2014 / Accepted: 23 April 2014 / Published: 12 May 2014
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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 [...] 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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Open AccessArticle The Impact of Surface Ligands and Synthesis Method on the Toxicity of Glutathione-Coated Gold Nanoparticles
Nanomaterials 2014, 4(2), 355-371; doi:10.3390/nano4020355
Received: 20 March 2014 / Revised: 16 April 2014 / Accepted: 30 April 2014 / Published: 12 May 2014
Cited by 6 | PDF Full-text (1015 KB) | HTML Full-text | XML Full-text | Supplementary Files
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) [...] 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)
Open AccessArticle Assessment of the Aerosol Generation and Toxicity of Carbon Nanotubes
Nanomaterials 2014, 4(2), 439-453; doi:10.3390/nano4020439
Received: 31 March 2014 / Revised: 27 May 2014 / Accepted: 29 May 2014 / Published: 12 June 2014
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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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Open AccessArticle Biological Effects of Clinically Relevant CoCr Nanoparticles in the Dura Mater: An Organ Culture Study
Nanomaterials 2014, 4(2), 485-504; doi:10.3390/nano4020485
Received: 29 March 2014 / Revised: 9 May 2014 / Accepted: 26 May 2014 / Published: 16 June 2014
Cited by 2 | PDF Full-text (4191 KB) | HTML Full-text | XML Full-text
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 [...] 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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Open AccessArticle Reducing X-Ray Induced Oxidative Damages in Fibroblasts with Graphene Oxide
Nanomaterials 2014, 4(2), 522-534; doi:10.3390/nano4020522
Received: 1 April 2014 / Revised: 17 June 2014 / Accepted: 19 June 2014 / Published: 24 June 2014
Cited by 4 | PDF Full-text (2557 KB) | HTML Full-text | XML Full-text
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 [...] 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)

Review

Jump to: Editorial, Research

Open AccessReview Recent Advances in the Application of Magnetic Nanoparticles as a Support for Homogeneous Catalysts
Nanomaterials 2014, 4(2), 222-241; doi:10.3390/nano4020222
Received: 16 February 2014 / Revised: 17 March 2014 / Accepted: 20 March 2014 / Published: 2 April 2014
Cited by 46 | PDF Full-text (1022 KB) | HTML Full-text | XML Full-text
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. [...] 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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Open AccessReview Work Function Engineering of Graphene
Nanomaterials 2014, 4(2), 267-300; doi:10.3390/nano4020267
Received: 16 December 2013 / Revised: 6 March 2014 / Accepted: 18 March 2014 / Published: 3 April 2014
Cited by 27 | PDF Full-text (2316 KB) | HTML Full-text | XML Full-text
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 [...] 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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Open AccessReview Emergent Properties and Toxicological Considerations for Nanohybrid Materials in Aquatic Systems
Nanomaterials 2014, 4(2), 372-407; doi:10.3390/nano4020372
Received: 11 April 2014 / Revised: 21 May 2014 / Accepted: 21 May 2014 / Published: 3 June 2014
Cited by 10 | PDF Full-text (1033 KB) | HTML Full-text | XML Full-text
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 [...] 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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Open AccessReview Superparamagnetic Nanoparticles for Atherosclerosis Imaging
Nanomaterials 2014, 4(2), 408-438; doi:10.3390/nano4020408
Received: 25 March 2014 / Revised: 15 May 2014 / Accepted: 16 May 2014 / Published: 5 June 2014
Cited by 2 | PDF Full-text (2135 KB) | HTML Full-text | XML Full-text
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 [...] 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)
Open AccessReview Mechanisms Underlying Cytotoxicity Induced by Engineered Nanomaterials: A Review of In Vitro Studies
Nanomaterials 2014, 4(2), 454-484; doi:10.3390/nano4020454
Received: 8 May 2014 / Revised: 28 May 2014 / Accepted: 3 June 2014 / Published: 12 June 2014
Cited by 5 | PDF Full-text (2369 KB) | HTML Full-text | XML Full-text
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 [...] 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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Open AccessReview Carbon Nanotubes and Chronic Granulomatous Disease
Nanomaterials 2014, 4(2), 508-521; doi:10.3390/nano4020508
Received: 4 April 2014 / Revised: 15 May 2014 / Accepted: 12 June 2014 / Published: 23 June 2014
Cited by 4 | PDF Full-text (206 KB) | HTML Full-text | XML Full-text
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, [...] 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)

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