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Andreu J.S.,CSIC - Institute of Materials Science | Andreu J.S.,Autonomous University of Barcelona | Camacho J.,Autonomous University of Barcelona | Faraudo J.,CSIC - Institute of Materials Science | And 3 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

Magnetophoresis-the motion of magnetic particles under applied magnetic gradient-is a process of great interest in novel applications of magnetic nanoparticles and colloids. In general, there are two main different types of magnetophoresis processes: cooperative magnetophoresis (a fast process enhanced by particle-particle interactions) and noncooperative magnetophoresis (driven by the motion of individual particles in magnetic fields). In the case of noncooperative magnetophoresis, we have obtained a simple analytical solution which allows the prediction of the magnetophoresis kinetics from particle characterization data (size and magnetization). Our comparison with new experimental results shows good quantitative agreement. In addition, we show the existence of a universal curve onto which all experimental results should collapse after proper rescaling. The range of applicability of the analytical solution is discussed in light of the predictions of a magnetic aggregation model. © 2011 American Physical Society.


Benelmekki M.,University of Minho | Caparros C.,University of Minho | Montras A.,Sepmag Tecnologies | Goncalves R.,University of Minho | And 2 more authors.
AIP Conference Proceedings | Year: 2010

In this work we investigate the possibilities of the use of Horizontal Low Gradient Magnetic Field (HLGMF) (<100T/m) for filtration, control and separation of the synthesized magnetic particles, considering, the characteristics of the suspension, the size and the type of nanoparticles (NPs) and focusing on the process scale up. Reversible aggregation is considered in the different steps of magnetic nanobeads synthesis. For these purpose, we synthesized Fe2O3-silica core-shell nanobeads by co-precipitation, monodispersion and silica coating. SQUID, TEM, XRD, and Zeta potential techniques were used to characterize the synthesized nanobeads. An extensive magnetophoresis study was performed at different magnetophoretic conditions. Different reversible aggregation times were observed at different HLGMF, at each step of the synthesis route: Several orders of magnitude differences where observed when comparing citric acid (CA) suspension with silicon coated beads. Reversible aggregation times are correlated with the properties of the NPs at different steps of synthesis. © 2010 American Institute of Physics.


Caparros C.,University of Minho | Benelmekki M.,University of Minho | Montras A.,Sepmag Tecnologies | Lanceros-Mendez S.,University of Minho | Martinez L.,SEPMAG Technologies
Journal of Nanoscience and Nanotechnology | Year: 2012

Magnetic nanoclusters are widely used as carriers for biomedical and bioindustrial applications. The chemical resistance of the nanoclusters is a key factor for the recycling the magnetic beads for a repetitive use in the industrial bioprocesses. In this work, a study of the chemical resistance of Fe 2o 3 silica-coated nanoclusters at different pH is presented. The use of Horizontal Low Gradient Magnetic Field (HLGMF) for the control and separation of the magnetic nanoclusters at diferent magnetic field gradients is also investigated. For these purposes Fe 2o 3 silica-coated nanoclusters are synthesised and characreized by SQUID, TEM, Zeta potential techniques. The magnetophoresis study was performed at 15 T/m and 30 T/m magnetic field gradients. Recycling aspects of the nanoclusters were estimated by evaluating their resistance to pH variation from acid to basic solutions of about pH 2.5 and 10. Copyright © 2012 American Scientific Publishers.


Benelmekki M.,University of Minho | Caparros C.,University of Minho | Montras A.,SEPMAG Technologies | Goncalves R.,University of Minho | And 2 more authors.
Journal of Nanoparticle Research | Year: 2011

In this study, the use of horizontal low gradient magnetic field (HLGMF) (<100 T/m) for filtration, control and separation of synthesized magnetic nanoparticles (NPs) is investigated. The characteristics of the suspension, size and type of the NPs are considered and discussed. For these purposes, Fe 2O3 silica-coated nanoclusters of about 150 nm are synthesized by co-precipitation, monodispersion and silica coating. Superconducting quantum interference device, TEM, XRD and ζ potential techniques were used to characterize the synthesized nanoclusters. An extensive magnetophoresis study was performed at different magnetophoretical conditions. Different reversible aggregation times were observed at different HLGMF, at each step of the synthesis route. In particular, differences of several orders of magnitude were observed when comparing citric acid-modified NPs with silica-coated nanoclusters. Reversible aggregation times are correlated to the properties of the NPs at different steps of synthesis route. © 2011 Springer Science+Business Media B.V.


Benelmekki M.,University of Minho | Montras A.,Sepmag Tecnologies | Martins A.J.,University of Minho | Coutinho P.J.G.,University of Minho | Martinez L.M.,SEPMAG Technologies
Journal of Magnetism and Magnetic Materials | Year: 2011

Magnetic separation of organic compounds, proteins, nucleic acids and other biomolecules, and cells from complex reaction mixtures is becoming the most suitable solution for large production in bioindustrial purification and extraction processes. Optimal magnetic properties can be achieved by the use of metals. However, they are extremely sensitive to oxidation and degradation under atmospheric conditions. In this work Ni nanoparticles are synthesised by conventional solution reduction process with the addition of a non-ionic surfactant as a surface agent. The nanoparticles were surfacted in citric acid and then coated with silica to form single core Ni nanobeads. A magnetophoresis study at different magnetic field gradients and at the different steps of synthesis route was performed using Horizontal Low Gradient Magnetic Field (HLGMF) systems. The reversible aggregation times are reduced to a few seconds, allowing a very fast separation process. © 2011 Elsevier B.V. All rights reserved.


Caparros C.,University of Minho | Benelmekki M.,University of Minho | Martins P.M.,University of Minho | Xuriguera E.,University of Barcelona | And 3 more authors.
Materials Chemistry and Physics | Year: 2012

Porous Magnetic Silica (PMS) spheres of about 400 nm diameter were synthesised by one-pot process using the classical Stber method combined with hydrothermal treatment. Maghemite nanoparticles (γ-Fe 2O 3) were used as fillers and cetyltrimethylammonium bromide (CTAB) was used as templating agent. The application of the hydrothermal process (120°C during 48 h) before the calcination leads to the formation of homogeneous and narrow size distribution PMS spheres. X-ray diffraction patterns (XRD), Infrared measurements (FTIR) and Transmission Electron microscopy (TEM) methods were used to determine the composition and morphology of the obtained PMS spheres. The results show a homogeneous distribution of the γ-Fe 2O 3 nanoparticles in the silica matrix with a "hollow-like" morphology. Magnetophoresis measurements at 60 T m -1 show a total separation time of the PMS spheres suspension of about 16 min. By using this synthesis method, the limitation of the formation of silica spheres without incorporation of magnetic nanoparticles is overcome. These achievements make this procedure interesting for industrial up scaling. The obtained PMS spheres were evaluated as adsorbents for Ni 2+ in aqueous solution. Their adsorption capacity was compared with the adsorption capacity of magnetic silica spheres obtained without hydrothermal treatment before calcination process. PMS spheres show an increase of the adsorption capacity of about 15% of the initial dissolution of Ni 2+ without the need to functionalize the silica surface. © 2012 Elsevier B.V. All rights reserved.


Safarik I.,Academy of Sciences of the Czech Republic | Safarik I.,Palacky University | Horska K.,Academy of Sciences of the Czech Republic | Martinez L.M.,SEPMAG Technologies | Safarikova M.,Academy of Sciences of the Czech Republic
AIP Conference Proceedings | Year: 2010

A simple procedure for large scale isolation of Solanum tuberosum tuber lectin from potato starch industry waste water has been developed. The procedure employed magnetic chitosan microparticles as an affinity adsorbent. Magnetic separation was performed in a flow-through magnetic separation system. The adsorbed lectin was eluted with glycine/HCl buffer, pH 2.2. The specific activity of separated lectin increased approximately 27 times during the isolation process. © 2010 American Institute of Physics.


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