| 1. |
- Ergeneman, O., et al.
(author)
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Morphology, structure and magnetic properties of cobalt-nickel films obtained from acidic electrolytes containing glycine
- 2011
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In: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 56:3, s. 1399-1408
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Journal article (peer-reviewed)abstract
- This paper focuses on the development and optimization of electroplated cobalt-nickel (CoNi) alloys for use in biomedical microdevices. CoNi films were electrodeposited from glycine-containing electrolyte solutions at acidic pH. The influence of pH (2.5-5), temperature (55 and 80 degrees C). current density (from -5 to -40 mA cm(-2)), glycine concentration (0.5 and 1 mol dm(-3)) and the nature of the metal salts (chlorides or sulphates) on the composition and the magnetic properties of the films were systematically analyzed. The cobalt content varied between 50 and 83 wt% depending on the applied conditions. As a result, deposits showed variable morphologies, different structures (either hexagonal close-packed (hcp) or mixed hcp and face-centered cubic phases) and tunable magnetic properties, ranging from semi-hard (18.51 kA m(-1). i.e. 233 Oe) to very soft (1.43 kA m(-1), i.e. 18 Oe). To understand the role of glycine in this system, a comparison of the electrochemical processes, and the structural and magnetic properties is made for samples produced in glycine-containing and glycine-free baths. (C) 2010 Elsevier Ltd. All rights reserved.
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| 2. |
- Sotiriou, Georgios A., et al.
(author)
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Thermal Energy Dissipation by SiO2-Coated Plasmonic-Superpararnagnetic Nanoparticles in Alternating Magnetic Fields
- 2013
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 25:22, s. 4603-4612
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Journal article (peer-reviewed)abstract
- Multifunctional nanoparticles show great potential in the biomedical field and may help the diagnosis and therapy of diseases. Superparamagnetic nanoparticles are especially attractive because of their ability to dissipate thermal energy in an alternating magnetic field. Furthermore, plasmonic nanoparticles can be effectively used in non- or minimally invasive therapy of tumors exploiting their plasmonic photothermal effect. Here, hybrid plasmonicmagnetic Ag/Fe2O3 nanoparticles are made by flame aerosol technology. These nanoparticles can be in situ encapsulated with an amorphous nanothin SiO2 film to facilitate their dispersion and block any toxicity from Ag/Fe2O3. Detailed physicochemical characterization, including electron microscopy, electron dispersive X-ray spectroscopy, and X-ray diffraction, is performed. Furthermore, their magnetic properties are characterized in detail by monitoring their hysteresis, first-order-reversal-curves, and isothermal remanent magnetization. Finally, the effect of SiO2 and Agcontent on the specific absorption rate (SAR) of the hybrid Ag/Fe2O3 nanoparticles is investigated. The obtained understanding will help the rational design and engineering of multifunctional hybrid nanoprobes targeting specific biomedical applications.
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| 3. |
- Hirt, Ann M., et al.
(author)
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Effect of size, composition, and morphology on magnetic performance : First-order reversal curves evaluation of iron oxide nanoparticles
- 2014
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:4
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Journal article (peer-reviewed)abstract
- Superparamagnetic nanoparticles are employed in a broad range of applications that demand detailed magnetic characterization for superior performance, e. g., in drug delivery or cancer treatment. Magnetic hysteresis measurements provide information on saturation magnetization and coercive force for bulk material but can be equivocal for particles having a broad size distribution. Here, first-order reversal curves (FORCs) are used to evaluate the effective magnetic particle size and interaction between equally sized magnetic iron oxide (Fe2O3) nanoparticles with three different morphologies: (i) pure Fe2O3, (ii) Janus-like, and (iii) core/shell Fe2O3/SiO2 synthesized using flame technology. By characterizing the distribution in coercive force and interaction field from the FORC diagrams, we find that the presence of SiO2 in the core/shell structures significantly reduces the average coercive force in comparison to the Janus-like Fe2O3/SiO2 and pure Fe2O3 particles. This is attributed to the reduction in the dipolar interaction between particles, which in turn reduces the effective magnetic particle size. Hence, FORC analysis allows for a finer distinction between equally sized Fe2O3 particles with similar magnetic hysteresis curves that can significantly influence the final nanoparticle performance. (C) 2014 AIP Publishing LLC.
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| 4. |
- Sotiriou, Georgios A., et al.
(author)
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Hybrid, Silica-Coated, Janus-Like Plasmonic-Magnetic Nanoparticles
- 2011
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 23:7, s. 1985-1992
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Journal article (peer-reviewed)abstract
- Hybrid plasmonic-magnetic nanoparticles possess properties that are attractive in bioimaging, targeted drug delivery, in vivo diagnosis, and therapy. The stability and toxicity, however, of such nanoparticles challenge their safe use today. Here, biocompatible, SiO(2)-coated, Janus-like Ag/Fe(2)O(3) nanoparticles are prepared by one-step, scalable flame aerosol technology. A nanothin SiO(2) shell around these multifunctional nanoparticles leaves intact their morphology and magnetic and plasmonic properties but minimizes the release of toxic Ag(+) ions from the nanosilver surface and its direct contact with live cells. Furthermore, this silica shell hinders flocculation and allows for easy dispersion of such nanoparticles in aqueous and biological buffer (PBS) solutions without any extra fiinctionalization step. As a result, these hybrid particles exhibited no cytotoxicity during bioimaging and remained stable in suspension with no signs of agglomeration and sedimentation or settling. Their performance as biomarkers was explored by selectively binding them with live tagged Raji and HeLa cells enabling their detection under dark-field illumination. Therefore, these SiO(2)-coated Ag/Fe(2)O(3) nanoparticles do not exhibit the limiting physical properties of each individual component but retain their desired functionalities facilitating thus, the safe use of such hybrid nanoparticles in bioapplications.
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| 5. |
- Sotiriou, Georgios A., et al.
(author)
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Nanosilver on nanostructured silica : Antibacterial activity and Ag surface area
- 2011
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 170:2-3, s. 547-554
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Journal article (peer-reviewed)abstract
- Nanosilver is one of the first nanomaterials to be closely monitored by regulatory agencies worldwide motivating research to better understand the relationship between Ag characteristics and antibacterial activity. Nanosilver immobilized on nanostructured silica facilitates such investigations as the SiO2 support hinders the growth of nanosilver during its synthesis and, most importantly, its flocculation in bacterial suspensions. Here, such composite Ag/silica nanoparticles were made by flame spray pyrolysis of appropriate solutions of Ag-acetate or Ag-nitrate and hexamethyldisiloxane or tetraethylorthosilicate in ethanol, propanol, diethylene glucolmonobutyl ether, acetonitrile or ethylhexanoic acid. The effect of solution composition on nanosilver characteristics and antibacterial activity against the Gram negative Escherichia coli was investigated by monitoring their recombinantly synthesized green fluorescent protein. Suspensions with identical Ag mass concentration exhibited drastically different antibacterial activity pointing out that the nanosilver surface area concentration rather than its mass or molar or number concentration determine best its antibacterial activity. Nanosilver made from Ag-acetate showed a unimodal size distribution, while that made from inexpensive Ag-nitrate exhibited a bimodal one. Regardless of precursor composition or nanosilver size distribution, the antibacterial activity of nanosilver was correlated best with its surface area concentration in solution. (C) 2011 Elsevier B.V. All rights reserved.
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| 6. |
- Sotiriou, Georgios A., et al.
(author)
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Non-Toxic Dry-Coated Nanosilver for Plasmonic Biosensors
- 2010
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In: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 20:24, s. 4250-4257
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Journal article (peer-reviewed)abstract
- The plasmonic properties of noble metals facilitate their use for in vivo bio-applications such as targeted drug delivery and cancer cell therapy. Nanosilver is best suited for such applications as it has the lowest plasmonic losses among all such materials in the UV-visible spectrum. Its toxicity, however, can destroy surrounding healthy tissues and thus, hinders its safe use. Here, that toxicity against a model biological system (Escherichia coli) is "cured" or blocked by coating nanosilver hermetically with a about 2 nm thin SiO(2) layer in one-step by a scalable flame aerosol method followed by swirl injection of a silica precursor vapor (hexamethyldisiloxane) without reducing the plasmonic performance of the enclosed or encapsulated silver nanoparticles (20-40 nm in diameter as determined by X-ray diffraction and microscopy). This creates the opportunity to safely use powerful nanosilver for intracellular bio-applications. The label-free biosensing and surface biofunctionalization of these ready-to-use, non-toxic (benign) Ag nanoparticles is presented by measuring the adsorption of bovine serum albumin (BSA) in a model sensing experiment. Furthermore, the silica coating around nanosilver prevents its agglomeration or flocculation (as determined by thermal annealing, optical absorption spectroscopy and microscopy) and thus, enhances its biosensitivity, including bioimaging as determined by dark field illumination.
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