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Helmut Münstedt - One of the best experts on this subject based on the ideXlab platform.
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Silver Nanoparticles in Blends of Polyethylene and a Superabsorbent Polymer: Morphology and Silver Ion Release
Macromolecular Materials and Engineering, 2011Co-Authors: Hana Stara, Zdeněk Starý, Helmut MünstedtAbstract:Antimicrobial properties of polymer materials are required in many applicatIons. The poly-ethylene/superabsorbent polymer (PE/SAP) blends containing silver nanoparticles were successfully prepared via thermal reductIon during melt mixing. It was found that in situ formed silver nanoparticles are preferentially located at the interface between PE matrix and SAP particles. The expectatIon was that the low water uptake of the PE will be enhanced by blending with a SAP and thus the silver Ion Release from the material will increase. Surprisingly, the silver Ion Release was markedly suppressed by the additIon of SAP. This finding is explained by the preferential sorptIon of silver Ions by the SAP particles.
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Silver Ion Release from Antimicrobial Acrylate Photopolymer Layers
Polymers & Polymer Composites, 2009Co-Authors: Cornelia Damm, Helmut MünstedtAbstract:Crosslinked silver-filled acrylate photopolymer layers on polyetheretherketone (PEEK) films were prepared by a heterogeneous photocatalytic polymerisatIon initiatIon using silver-coated titanium dioxide as a catalyst material. The silver Ion Release from 5 μm thick acrylate photopolymer layers was studied as a functIon of the chemical structure of the polymer matrix. The silver Ion Release increases with the number of ethoxy groups per monomer unit, although the filler content in all acrylate samples was the same (2.5 wt.% titanium dioxide coated with 1 mol.% elemental Ag). This finding can be explained on the basis of the water uptake of the polymer matrix: silver Ions are generated from elemental silver particles only in the presence of water. The maximum water absorptIon of the photopolymers as well as the diffusIon coefficient of water in the polymers increases with the number of hydrophilic ethoxy groups per monomer unit. The silver Ion Release from the acrylate photopolymer layers is governed by diffusIon. The diffusIon coefficient of silver Ions, however, is at least two orders of magnitude smaller than that of water. This finding suggests that the interactIons between silver Ions and the polymers and/or the titanium dioxide must be stronger than the interactIons between water molecules and the polymers and/or the titanium dioxide because the mobility of a diffusing species decreases if the interactIons with the surrounding matrix become stronger. Acrylate photopolymer layers containing at least 6 ethoxy groups per monomer unit Release an amount of silver Ions of 3 μg * l -1* cm -2 or more per day. This amount is sufficient to eliminate Escherichia coli completely within 24 h.
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kinetic aspects of the silver Ion Release from antimicrobial polyamide silver nanocomposites
Applied Physics A, 2008Co-Authors: Cornelia Damm, Helmut MünstedtAbstract:Spherical silver nanoparticles were grown in situ in different polyamides by a thermal reductIon of silver acetate during melt processing of the polymers. Most of the particles have a diameter of about 20 nm. The absolute amount as well as the kinetics of the silver Ion Release from the various polyamide/silver nanocomposites differ strongly, although the filler content in all materials is the same (1.5 wt. %) and the morphologies of the silver particles are not very different. One result of the investigatIons was that the absolute amount of the long-term silver Ion Release increases exponentially with the maximum water absorptIon of the polymers used as matrix materials, because silver Ions are formed from elemental silver particles in the presence of water, only. Moreover, it was also found that the long-term silver Ion Release increases with a growing diffusIon coefficient of water in the polymer. The water absorptIon properties of the polymers govern the kinetics of the silver Ion Release, too: for strong hydrophilic polyamides like PA6 or PA6.6, which are plasticized by water, the silver Ion Release is a zero-order process. For nanocomposites with less hydrophilic polyamides like a cycloaliphatic polyamide or a P12 modified with polytetrahydrofurane (PA12-poly-THF), the silver Ion Release is governed by diffusIon. As expected from the efficacy of the silver Ion Release, PA6, PA6.6, PA12 and PA12 modified with polytetrahydrofurane and a cycloaliphatic polyamide filled with 1.5 wt. % of silver nanoparticles are active against Escherichia coli. But, only nanocomposites with PA6, PA6.6 and P12-poly-THF as matrix materials are suitable as long-term biocidal materials.
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Kinetic aspects of the silver Ion Release from antimicrobial polyamide/silver nanocomposites
Applied Physics A, 2008Co-Authors: Cornelia Damm, Helmut MünstedtAbstract:Spherical silver nanoparticles were grown in situ in different polyamides by a thermal reductIon of silver acetate during melt processing of the polymers. Most of the particles have a diameter of about 20 nm. The absolute amount as well as the kinetics of the silver Ion Release from the various polyamide/silver nanocomposites differ strongly, although the filler content in all materials is the same (1.5 wt. %) and the morphologies of the silver particles are not very different. One result of the investigatIons was that the absolute amount of the long-term silver Ion Release increases exponentially with the maximum water absorptIon of the polymers used as matrix materials, because silver Ions are formed from elemental silver particles in the presence of water, only. Moreover, it was also found that the long-term silver Ion Release increases with a growing diffusIon coefficient of water in the polymer. The water absorptIon properties of the polymers govern the kinetics of the silver Ion Release, too: for strong hydrophilic polyamides like PA6 or PA6.6, which are plasticized by water, the silver Ion Release is a zero-order process. For nanocomposites with less hydrophilic polyamides like a cycloaliphatic polyamide or a P12 modified with polytetrahydrofurane (PA12-poly-THF), the silver Ion Release is governed by diffusIon. As expected from the efficacy of the silver Ion Release, PA6, PA6.6, PA12 and PA12 modified with polytetrahydrofurane and a cycloaliphatic polyamide filled with 1.5 wt. % of silver nanoparticles are active against Escherichia coli. But, only nanocomposites with PA6, PA6.6 and P12-poly-THF as matrix materials are suitable as long-term biocidal materials.
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Kinetic aspects of the silver Ion Release from antimicrobial polyamide/silver nanocomposites
Applied Physics A, 2008Co-Authors: Cornelia Damm, Helmut MünstedtAbstract:Spherical silver nanoparticles were grown in situ in different polyamides by a thermal reductIon of silver acetate during melt processing of the polymers. Most of the particles have a diameter of about 20 nm. The absolute amount as well as the kinetics of the silver Ion Release from the various polyamide/silver nanocomposites differ strongly, although the filler content in all materials is the same (1.5 wt. %) and the morphologies of the silver particles are not very different. One result of the investigatIons was that the absolute amount of the long-term silver Ion Release increases exponentially with the maximum water absorptIon of the polymers used as matrix materials, because silver Ions are formed from elemental silver particles in the presence of water, only. Moreover, it was also found that the long-term silver Ion Release increases with a growing diffusIon coefficient of water in the polymer. The water absorptIon properties of the polymers govern the kinetics of the silver Ion Release, too: for strong hydrophilic polyamides like PA6 or PA6.6, which are plasticized by water, the silver Ion Release is a zero-order process. For nanocomposites with less hydrophilic polyamides like a cycloaliphatic polyamide or a P12 modified with polytetrahydrofurane (PA12-poly-THF), the silver Ion Release is governed by diffusIon. As expected from the efficacy of the silver Ion Release, PA6, PA6.6, PA12 and PA12 modified with polytetrahydrofurane and a cycloaliphatic polyamide filled with 1.5 wt. % of silver nanoparticles are active against Escherichia coli. But, only nanocomposites with PA6, PA6.6 and P12-poly-THF as matrix materials are suitable as long-term biocidal materials.
Nisreen Alissawi - One of the best experts on this subject based on the ideXlab platform.
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Plasma-polymerized HMDSO coatings to adjust the silver Ion Release properties of Ag/polymer nanocomposites
Journal of Nanoparticle Research, 2013Co-Authors: Nisreen Alissawi, Christoph Ebbert, Guido Grundmeier, T. Peter, Thomas Strunskus, Franz FaupelAbstract:In the current work, we study the silver Ion Release potential and the water uptake through a SiO x C y H z -polymer which is grown from the precursor hexamethyldisiloxane (HMDSO) in radiofrequency (RF) plasma. These layers were deposited on top of two dimensIonal (2D) ensembles of silver nanoparticles (AgNPs) with nominal thickness of 2 nm on a 20 nm RF-sputtered polytetrafluoroethylene (PTFE) thin film. The compositIon of the plasma-polymerized HMDSO barriers was varied by changing the oxygen flow during the polymerizatIon process and their thickness was varied as well. Morphology and optical properties of the nanocomposites were investigated using transmissIon electron microscopy (TEM) and UV–Visible spectroscopy (UV–Vis), respectively. The concentratIon of the silver Ions Released from the nanocomposites after immersIon in water for several time intervals was measured using inductively coupled plasma mass spectrometry (ICP-MS). Contact angle analysis and electrochemical impedance spectroscopy (EIS) measurements were also performed and results show a strong dependence of the coatings properties and their water uptake on the oxygen content in the coating films and their thickness. Plasma polymerizatIon with increasing the oxygen flow leads to the formatIon of more hydrophilic thin films with a higher Ag Ion Release potential. Increasing the thickness of the coatings reduced the amount of the Released Ions and the rate of the Release process was slowed down. This indicates that by tailoring the structure and the thickness of the plasma-polymerized coating films, one can tune the silver Ion Release properties of Ag/polymer nanocomposites.
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Ion Release from silver / polymer nanocomposites
2013Co-Authors: Nisreen AlissawiAbstract:The tuning of silver Ion Release is very important for biomedical applicatIons of silver nanocomposite materials to reduce the potential toxicity effects towards human cells and the environment. The present work is based on developing different metal/polymer nanocomposites using several physical vapor depositIon (PVD) techniques. Since the properties of the nanoparticles strongly depend on their size, distributIon and shape, the determinatIon of their exact morphology is important in order to understand and control their physical properties. Thus, in this work the metal nanoparticles are deposited on the surface of the polymer films or buried under a polymer barrier instead of being embedded into the polymer matrix. The model system consists of ensembles of silver nanoparticles (AgNPs) on sputtered polytetrafluoroethylene (PTFE) thin films. Sputtered PTFE films are suitable to host the AgNPs due to the high crosslinking and since PTFE is a hydrophobic polymer so the quick depletIon of the AgNPs could be avoided. Besides, PTFE is known for its high resistance to chemicals, transparency, good dielectric properties and biocompatibility. We examined the morphology, the compositIon and the optical properties of these nanocomposites using various analytical methods to characterize them and to study the potential of the silver Ion Release of the samples after immersIon in water for several periods of time. Inductively coupled plasma mass spectroscopy (ICP-MS) is used to measure the concentratIon of silver Ions in water. Changes in the microstructure and the optical properties of the nanocomposite films upon immersIon in water allow demonstrating the kinetics of the silver Ion Release. Different approaches to tune the silver Ion Release process are studied and demonstrated in this work. Adjusting the Release of silver Ions through variatIon of the initial amount of silver nanoparticles, particle size control and through barrier thickness control is presented. Tuning the silver Ion Release by alloying with gold is also discussed. Furthermore, we study the Release of silver Ions from Ag/PTFE nanocomposites covered by thin films of plasma polymerized hexamethyldisiloxane (HMDSO) and we show how varying the oxygen flow during the plasma polymerizatIon process can adjust the silver Ion Release potential of the nanocomposites due to changes in the properties of the formed plasma polymerized HMDSO thin films.
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Tuning of the Ion Release properties of silver nanoparticles buried under a hydrophobic polymer barrier
Journal of Nanoparticle Research, 2012Co-Authors: Nisreen Alissawi, Lothar Kienle, Vladimir Zaporojtchenko, Guido Grundmeier, Ibrahim Kocabaş, Venkata Sai Kiran Chakravadhanula, Tomislav Hrkac, Burak Erkartal, Thomas Strunskus, D. Garbe-schönbergAbstract:Tuning of Ag Ion Release from silver-polymer nanocomposites is very important for biomedical applicatIons of nanocomposite materials to reduce the potential toxicity effects toward human cells. In this work a well defined model system consisting of nearly two dimensIonal silver nanoparticle arrangements which are either directly accessible or covered by polymer barrier was used. The Ag nanoparticles (AgNPs) with nominal thickness ranging from 1.3 to 8.3 nm and the polytetrafluoroethylene polymer layers were synthesized by physical vapor depositIon techniques. Study of the Ag Ion Release was accompanied with a control of the composite morphology (Ag nanoparticle size, concentratIon, and distributIon) to understand the mechanism and the kinetics of the interfacial Ion transfer reactIons of the AgNPs. The surface plasmon resonance of the AgNPs and the composite morphology variatIon as well as the time-dependent Release of silver Ions after immersIon in water were examined by UV-visible spectroscopy, transmissIon electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry. A correlatIon between changes in the surface plasmon resonance, composite morphology, and the kinetics of Ag Ion Release was found. It is shown that the strong dependence of the silver Ion Release on the particles' size leads to significant redistributIon of the composite morphology and suppressIon of the Ag ? Release with time. It is also observed that a polymer barrier stabilizes the morphology of the composites and can be applied to control the Ag Ion Release rate.
Franz Faupel - One of the best experts on this subject based on the ideXlab platform.
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Tuning silver Ion Release properties in reactively sputtered Ag/TiO x nanocomposites
Applied Physics A, 2017Co-Authors: J. Xiong, Thomas Strunskus, Muhammed Zubair Ghori, Bodo Henkel, Ulrich Schürmann, Mao Deng, Lorenz Kienle, Franz FaupelAbstract:Silver/titania nanocomposites with strong bactericidal effects and good biocompatibility/environmental safety show a high potential for antibacterial applicatIons. Tailoring the silver Ion Release is thus highly promising to optimize the antibacterial properties of such coatings and to preserve biocompatibility. Reactive sputtering is a fast and versatile method for the preparatIon of such Ag/TiOx nanocomposites coatings. The present work is concerned with the influence of sputter parameters on the surface morphology and silver Ion Release properties of reactively sputtered Ag/TiOx nanocomposites coatings showing a silver nanoparticle size distributIon in the range from 1 to 20 nm. It is shown that the silver Ion Release rate strongly depends on the total pressure: the coatings prepared at lower pressure present a lower but long-lasting Release behavior. The much denser structure produced under these conditIons reduces the transport of water molecules into the coating. In additIon, the influence of microstructure and thickness of titanium oxide barriers on the silver Ion Release were investigated intensively. Moreover, for the coatings prepared at high total pressure, it was demonstrated that stable and long-lasting silver Release can be achieved by depositing a barrier with a high rate. Nanocomposites produced under these conditIons show well controllable silver Ion Release properties for applicatIons as antibacterial coatings.
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Plasma-polymerized HMDSO coatings to adjust the silver Ion Release properties of Ag/polymer nanocomposites
Journal of Nanoparticle Research, 2013Co-Authors: Nisreen Alissawi, Christoph Ebbert, Guido Grundmeier, T. Peter, Thomas Strunskus, Franz FaupelAbstract:In the current work, we study the silver Ion Release potential and the water uptake through a SiO x C y H z -polymer which is grown from the precursor hexamethyldisiloxane (HMDSO) in radiofrequency (RF) plasma. These layers were deposited on top of two dimensIonal (2D) ensembles of silver nanoparticles (AgNPs) with nominal thickness of 2 nm on a 20 nm RF-sputtered polytetrafluoroethylene (PTFE) thin film. The compositIon of the plasma-polymerized HMDSO barriers was varied by changing the oxygen flow during the polymerizatIon process and their thickness was varied as well. Morphology and optical properties of the nanocomposites were investigated using transmissIon electron microscopy (TEM) and UV–Visible spectroscopy (UV–Vis), respectively. The concentratIon of the silver Ions Released from the nanocomposites after immersIon in water for several time intervals was measured using inductively coupled plasma mass spectrometry (ICP-MS). Contact angle analysis and electrochemical impedance spectroscopy (EIS) measurements were also performed and results show a strong dependence of the coatings properties and their water uptake on the oxygen content in the coating films and their thickness. Plasma polymerizatIon with increasing the oxygen flow leads to the formatIon of more hydrophilic thin films with a higher Ag Ion Release potential. Increasing the thickness of the coatings reduced the amount of the Released Ions and the rate of the Release process was slowed down. This indicates that by tailoring the structure and the thickness of the plasma-polymerized coating films, one can tune the silver Ion Release properties of Ag/polymer nanocomposites.
Thomas Strunskus - One of the best experts on this subject based on the ideXlab platform.
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Tuning silver Ion Release properties in reactively sputtered Ag/TiO x nanocomposites
Applied Physics A, 2017Co-Authors: J. Xiong, Thomas Strunskus, Muhammed Zubair Ghori, Bodo Henkel, Ulrich Schürmann, Mao Deng, Lorenz Kienle, Franz FaupelAbstract:Silver/titania nanocomposites with strong bactericidal effects and good biocompatibility/environmental safety show a high potential for antibacterial applicatIons. Tailoring the silver Ion Release is thus highly promising to optimize the antibacterial properties of such coatings and to preserve biocompatibility. Reactive sputtering is a fast and versatile method for the preparatIon of such Ag/TiOx nanocomposites coatings. The present work is concerned with the influence of sputter parameters on the surface morphology and silver Ion Release properties of reactively sputtered Ag/TiOx nanocomposites coatings showing a silver nanoparticle size distributIon in the range from 1 to 20 nm. It is shown that the silver Ion Release rate strongly depends on the total pressure: the coatings prepared at lower pressure present a lower but long-lasting Release behavior. The much denser structure produced under these conditIons reduces the transport of water molecules into the coating. In additIon, the influence of microstructure and thickness of titanium oxide barriers on the silver Ion Release were investigated intensively. Moreover, for the coatings prepared at high total pressure, it was demonstrated that stable and long-lasting silver Release can be achieved by depositing a barrier with a high rate. Nanocomposites produced under these conditIons show well controllable silver Ion Release properties for applicatIons as antibacterial coatings.
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Plasma-polymerized HMDSO coatings to adjust the silver Ion Release properties of Ag/polymer nanocomposites
Journal of Nanoparticle Research, 2013Co-Authors: Nisreen Alissawi, Christoph Ebbert, Guido Grundmeier, T. Peter, Thomas Strunskus, Franz FaupelAbstract:In the current work, we study the silver Ion Release potential and the water uptake through a SiO x C y H z -polymer which is grown from the precursor hexamethyldisiloxane (HMDSO) in radiofrequency (RF) plasma. These layers were deposited on top of two dimensIonal (2D) ensembles of silver nanoparticles (AgNPs) with nominal thickness of 2 nm on a 20 nm RF-sputtered polytetrafluoroethylene (PTFE) thin film. The compositIon of the plasma-polymerized HMDSO barriers was varied by changing the oxygen flow during the polymerizatIon process and their thickness was varied as well. Morphology and optical properties of the nanocomposites were investigated using transmissIon electron microscopy (TEM) and UV–Visible spectroscopy (UV–Vis), respectively. The concentratIon of the silver Ions Released from the nanocomposites after immersIon in water for several time intervals was measured using inductively coupled plasma mass spectrometry (ICP-MS). Contact angle analysis and electrochemical impedance spectroscopy (EIS) measurements were also performed and results show a strong dependence of the coatings properties and their water uptake on the oxygen content in the coating films and their thickness. Plasma polymerizatIon with increasing the oxygen flow leads to the formatIon of more hydrophilic thin films with a higher Ag Ion Release potential. Increasing the thickness of the coatings reduced the amount of the Released Ions and the rate of the Release process was slowed down. This indicates that by tailoring the structure and the thickness of the plasma-polymerized coating films, one can tune the silver Ion Release properties of Ag/polymer nanocomposites.
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Tuning of the Ion Release properties of silver nanoparticles buried under a hydrophobic polymer barrier
Journal of Nanoparticle Research, 2012Co-Authors: Nisreen Alissawi, Lothar Kienle, Vladimir Zaporojtchenko, Guido Grundmeier, Ibrahim Kocabaş, Venkata Sai Kiran Chakravadhanula, Tomislav Hrkac, Burak Erkartal, Thomas Strunskus, D. Garbe-schönbergAbstract:Tuning of Ag Ion Release from silver-polymer nanocomposites is very important for biomedical applicatIons of nanocomposite materials to reduce the potential toxicity effects toward human cells. In this work a well defined model system consisting of nearly two dimensIonal silver nanoparticle arrangements which are either directly accessible or covered by polymer barrier was used. The Ag nanoparticles (AgNPs) with nominal thickness ranging from 1.3 to 8.3 nm and the polytetrafluoroethylene polymer layers were synthesized by physical vapor depositIon techniques. Study of the Ag Ion Release was accompanied with a control of the composite morphology (Ag nanoparticle size, concentratIon, and distributIon) to understand the mechanism and the kinetics of the interfacial Ion transfer reactIons of the AgNPs. The surface plasmon resonance of the AgNPs and the composite morphology variatIon as well as the time-dependent Release of silver Ions after immersIon in water were examined by UV-visible spectroscopy, transmissIon electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry. A correlatIon between changes in the surface plasmon resonance, composite morphology, and the kinetics of Ag Ion Release was found. It is shown that the strong dependence of the silver Ion Release on the particles' size leads to significant redistributIon of the composite morphology and suppressIon of the Ag ? Release with time. It is also observed that a polymer barrier stabilizes the morphology of the composites and can be applied to control the Ag Ion Release rate.
Lajos Keszthelyi - One of the best experts on this subject based on the ideXlab platform.
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Non-proton Ion Release in purple membrane
Biophysical Journal, 1994Co-Authors: R. Tóth-boconádi, Svetla G Taneva, Lajos KeszthelyiAbstract:Large conductivity changes have been measured during the photocycle of bacteriorhodopsin in purple membrane. These phenomena were explained as being due to the occurrence of large-scale non-proton Ion Release. Here we show that these conductivity changes do not appear if the purple membrane is immobilized. We propose an alternative hypothesis that explains the presence of conductivity change in suspensIons and their absence in gels, as well as several related effects suggesting that the observed conductivity changes are due to alteratIon of the polarizability of purple membrane during the photocycle.
