Ivo Vavra - Academia.edu (original) (raw)

Papers by Ivo Vavra

Nanotoxicology

Abstract Innovative nanotechnology aims to develop particles that are small, monodisperse, smart,... more Abstract Innovative nanotechnology aims to develop particles that are small, monodisperse, smart, and do not cause unintentional side effects. Uniform magnetic Fe3O4 nanoparticles (12 nm in size) were prepared by thermal decomposition of iron(III) oleate. To make them colloidally stable and dispersible in water and cell culture medium, they were modified with phosphonic acid- (PA) and hydroxamic acid (HA)-terminated poly(ethylene glycol) yielding PA-PEG@Fe3O4 and HA-PEG@Fe3O4 nanoparticles; conventional γ-Fe2O3 particles were prepared as a control. Advanced techniques were used to evaluate the properties and safety of the particles. Completeness of the nanoparticle coating was tested by real-time polymerase chain reaction. Interaction of the particles with primary human peripheral blood cells, cellular uptake, cytotoxicity, and immunotoxicity were also investigated. Amount of internalized iron in peripheral blood mononuclear cells was 72, 38, and 25 pg Fe/cell for HA-PEG@Fe3O4, γ-Fe2O3, and PA-PEG@Fe3O4, respectively. Nanoparticles were localized within the cytoplasm and in the extracellular space. No cytotoxic effect of both PEGylated nanoparticles was observed (0.12–75 μg/cm2) after 24 and 72-h incubation. Moreover, no suppressive effect was found on the proliferative activity of T-lymphocytes and T-dependent B-cell response, phagocytic activity of monocytes and granulocytes, and respiratory burst of phagocytes. Similarly, no cytotoxic effect of γ-Fe2O3 particles was observed. However, they suppressed the proliferative activity of T-lymphocytes (75 μg/cm2, 72 h) and also decreased the phagocytic activity of monocytes (15 μg/cm2, 24 h; 3–75 μg/cm2, 72 h). We thus show that newly developed particles have great potential especially in cancer diagnostics and therapy.

Reproductive Toxicology, 2015

Croatian Medical Journal, 2016

Aim To determine cytotoxicity and effect of silica-coated magnetic nanoparticles (MNPs) on immune... more Aim To determine cytotoxicity and effect of silica-coated magnetic nanoparticles (MNPs) on immune response, in particular lymphocyte proliferative activity, phagocytic activity, and leukocyte respiratory burst and in vitro production of interleukin-6 (IL-6) and 8 (IL-8), interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and granulocyte macrophage colony stimulating factor (GM-CSF). Methods Maghemite was prepared by coprecipitation of iron salts with ammonia, oxidation with NaOCl and modified by tetramethyl orthosilicate and aminosilanes. Particles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Cytotoxicity and lymphocyte proliferative activity were assessed using [ 3 H]-thymidine incorporation into DNA of proliferating human peripheral blood cells. Phagocytic activity and leukocyte respiratory burst were measured by flow cytometry; cytokine levels in cell supernatants were determined by ELISA. Results γ-Fe 2 O 3 &SiO 2-NH 2 MNPs were 13 nm in size. According to TEM, they were localized in the cell cytoplasm and extracellular space. Neither cytotoxic effect nor significant differences in T-lymphocyte and T-dependent Bcell proliferative response were found at particle concentrations 0.12-75 μg/cm 2 after 24, 48, and 72 h incubation. Significantly increased production of IL-6 and 8, and GM-CSF cytokines was observed in the cells treated with 3, 15, and 75 µg of particles/cm 2 for 48 h and stimulated with pokeweed mitogen (PHA). No significant changes in TNF-α and IFN-γ production were observed. MNPs did not affect phagocytic activity of monocytes and granulocytes when added to cells for 24 and 48 h. Phagocytic respiratory burst was significantly enhanced in the cultures exposed to 75 µg MNPs/cm 2 for 48 h. Conclusions The cytotoxicity and in vitro immunotoxicity were found to be minimal in the newly developed porous core-shell γ-Fe 2 O 3 &SiO 2-NH 2 magnetic nanoparticles.

physica status solidi (a), 1981

... The direct observation of electromigration in A1-Cu films by transmission electron microscopy... more ... The direct observation of electromigration in A1-Cu films by transmission electron microscopy ... a sensitive tool for studying the role of film structure in electro-migration damage mechanisms. ... at higher substrate temperature (eg 300 “C) are more suitable for IC interconnections. ...

ABSTRACT Scientists in engineering and biological fields share common concerns and in recent year... more ABSTRACT Scientists in engineering and biological fields share common concerns and in recent years these concerns have shaped the direction of research in both fields. The inspiration stemming from nature for the development of new technologies and particularly nanotechnology has been very extensive. The development of new analytical and imaging methods allows us to understand structures, functions and solutions used by all living systems. Biosynthesis of nanoparticles (NPs) and nanostructures can profit from the use of natural processes found in cells. The usage of biomolecules, different functional groups or enzymes from the living organisms and cells can lead to significant improvement in the biosynthesis process. In this chapter, we will discuss the fabrication of colloidal solutions and composites containing gold and silver nanoparticles prepared by means of algae with silica based coverings and their potential applications. We summarized existing utilization of diatoms in nanotechnology research and outlined the potential usage of these interesting organisms and their silica frustules. We also performed experiments leading to the formation of gold nanoparticles in the presence of the golden alga Mallomonas kalinae.

Short title: Andreev reflection in Nb/Fe0.5Si0.5/Nb and Nb/Fe0.5Si0.5/Si/Nb junctions PACS: 74.50... more Short title: Andreev reflection in Nb/Fe0.5Si0.5/Nb and Nb/Fe0.5Si0.5/Si/Nb junctions PACS: 74.50+r Abstract Electrical properties of Josephson junctions Nb/Fe0.5Si0.5/Nb with superconductor/ferromagnet (S/F) interfaces are presented. Due to Andreev reflection the nearly exact quadruple enhancement of the tunnel junction differential conductance compared with that of the normal state was achieved. The transparency of the S/F interfaces in our junctions was estimated to be close to unity. This almost ideal value is obtained due to the use of a very smooth amorphous magnetic Fe0.5Si0.5 alloy for the barrier preparation. The real structure of the Nb/Fe0.5Si0.5/Nb tunnel junction is described as a S/F/I/F/S junction. Also Nb/Fe0.5Si0.5/Si/Nb Josephson junctions were investigated and the results found on these junctions confirm the effects observed in Nb/Fe0.5Si0.5/Nb.

Journal of Pharmacology and Experimental Therapeutics

Physical Review B

ABSTRACT

Materials Science Forum, 1996

Solid State Phenomena, 2003

ABSTRACT

The Ninth International Conference on Advanced Semiconductor Devices and Mircosystems, 2012

ABSTRACT GaP/ZnO core-shell nanowires were prepared by Metal Organic Vapour Phase Epitaxy and RF ... more ABSTRACT GaP/ZnO core-shell nanowires were prepared by Metal Organic Vapour Phase Epitaxy and RF sputtering. We studied systematically room temperature photoluminescence of the NWs in the ultraviolet and green regions. Our study revealed that the UV peak position shifted slightly towards longer wavelengths while the green emission with the main transition at 2.25eV was almost unchanged.

Ceramics Silikaty

In the work we describe the use of Al2O3-Y 2O3 glass microspheres with high alumina contents prep... more In the work we describe the use of Al2O3-Y 2O3 glass microspheres with high alumina contents prepared by flame synthesis as a precursor for materials with binary eutectic microstructure and high hardness. XRD amorphous microspheres with eutectic composition in a pseudobinary system Al2O3-Y 3Al5O12 (YAG) were prepared by feeding a crystalline powder precursor of respective composition into methane-oxygen flame. The microspheres with the mean diameter ≈10 μm were hot-pressed in vacuum under various conditions (temperatures 840-1600°C, pressure 30 or 40 MPa, isothermal dwell 0-120 min). Hot pressing at 1600°C without isothermal dwell yielded fully dense bulk materials with fine two phase microstructure with Al2O3 and YAG phases percolating at submicrometre level and with hardness 15 GPa. Extension of the isothermal dwell resulted in undesirable coarsening of the resulting microstructure.

Electrical properties of Josephson junctions Nb/FeSi/Nb with superconductor/ferromagnet (S/F)inte... more Electrical properties of Josephson junctions Nb/FeSi/Nb with superconductor/ferromagnet (S/F)interfaces are presented. Due to Andreev reflection the nearly exact quadruple enhancement of the tunnel junction differential conductance compared with that of the normal state was achieved. The transparency of the S/F interfaces in our junctions was estimated to be close to unity. This almost ideal value is obtained due to the use of a very smooth amorphous magnetic FeSi alloy for the barrier preparation. The real structure of the Nb/FeSi/Nb tunnel junction is described as a S/F/I/F/S junction. Also Nb/FeSi/Si/Nb Josephson junctions were investigated and the results found on these junctions confirm the effects observed in Nb/FeSi/Nb.

Magnetic rod-like particles have been prepared through two type hydrolysis. The influence of diff... more Magnetic rod-like particles have been prepared through two type hydrolysis. The influence of different conditions during synthesis on the size (length and diameter), structure and magnetic properties of the prepared nanoparticles was studied. The molar ratio of the reactants affects structure, shape and magnetic properties of particles. The prepared samples were characterized by a variety of methods: infrared spectroscopy, magnetization measurements, Transmission electron microscopy and Scanning electron microscopy.

Carbon

Carbon–nickel composite thin films (600 nm thick) were prepared by dc magnetron sputtering of Ni ... more Carbon–nickel composite thin films (600 nm thick) were prepared by dc magnetron sputtering of Ni and C at several temperatures (25–800 °C) on oxidized silicon substrates. By transmission electron microscopy it was found that the composite consisted of Ni (or Ni3C) nanoparticles embedded in a carbon matrix. The metallic nanoparticles were shaped in the form of globular grains or nanowires (of the aspect ratio as high as 1:60 in the sample prepared at 200 °C). The carbon matrix was amorphous, or graphite-like depending on deposition temperature. At low deposition temperatures TS (25–400 °C) the Ni3C nanoparticles were of hcp phase. Samples prepared at TS ⩾ 600 °C contained ferromagnetic fcc Ni nanoparticles. A correlation was found between the structural, electrical and magnetic properties of the composites. To characterise the films, dependences, such as resistivity vs. temperature, current vs. voltage, differential conductivity vs. bias voltage, and magnetoresistivity, were determin...

Magnetite labeled carbon nanotubes were prepared by precipitation method in nitrogen atmosphere a... more Magnetite labeled carbon nanotubes were prepared by precipitation method in nitrogen atmosphere at 60°C. For the preparation were used single-walled carbon nanotubes with diameter from 1 to 2.0 nm and length in the range of 500 – 2000 nm, and multi-walled carbon nanotubes with outer diameter from 20 nm to 30 nm, wall thickness from 1 nm to 2 nm and length from 500–2000 nm. Magnetic properties of the prepared samples investigated by a SQUID magnetometer show significant changes in comparison with non labeled samples. Transmission electron microscopy was employed to obtain structural and size information. Infrared spectroscopy proved the presence of magnetite in the CNT/Fe 3 O 4 product.

Scientists in engineering and biological fields share common concerns and in recent years these c... more Scientists in engineering and biological fields share common concerns and in recent years these concerns have shaped the direction of research in both fields. The inspiration stemming from nature for the development of new technologies and particularly nanotechnology has been very extensive. The development of new analytical and imaging methods allows us to understand structures, functions and solutions used by all living systems. Biosynthesis of nanoparticles (NPs) and nanostructures can profit from the use of natural processes found in cells. The usage of biomolecules, different functional groups or enzymes from the living organisms and cells can lead to significant improvement in the biosynthesis process. In this chapter, we will discuss the fabrication of colloidal solutions and composites containing gold and silver nanoparticles prepared by means of algae with silica based coverings and their potential applications. We summarized existing utilization of diatoms in nanotechnolog...

The Eighth International Conference on Advanced Semiconductor Devices and Microsystems, 2010

Great advances in the development of III-V diluted magnetic semiconductors materials (DMS) allow ... more Great advances in the development of III-V diluted magnetic semiconductors materials (DMS) allow for the incorporation of ferromagnetic epitaxial layers into advanced structures. In this contribution, we report on the growth of GaAs/InMnAs layers by metalorganic vapour phase epitaxy (MOVPE) over an AlGaAs/GaAs MQW light-emitting diode structure. In particular, results of electrical and structural characterization of structures are presented. We prepared a single-phase ferromagnetic In 1-x Mn x As ternary with x close to 0.075 on (100) GaAs substrates using MOVPE. The material exhibited room temperature ferromagnetic behavior with a Curie temperature close to 330K. In addition, all InMnAs ternary samples showed p-type conductivity. The ferromagnetic material was incorporated into four different AlGaAs/GaAs LED structure.

2006 International Conference on Advanced Semiconductor Devices and Microsystems, 2006

A 400mum times 400mum sized square quantum-well infrared photodetector with 30 periods of the GaA... more A 400mum times 400mum sized square quantum-well infrared photodetector with 30 periods of the GaAs/Al0.3Ga0.7 As multiple quantum well has been prepared on patterned (001) GaAs substrate. The absorption spectrum at room temperature with normal incidence geometry is peaked at 9mum with a full width at half maximum (FWHM) of 3.7 mum. Dark current with influence of 300K background was

Nanotoxicology

Abstract Innovative nanotechnology aims to develop particles that are small, monodisperse, smart,... more Abstract Innovative nanotechnology aims to develop particles that are small, monodisperse, smart, and do not cause unintentional side effects. Uniform magnetic Fe3O4 nanoparticles (12 nm in size) were prepared by thermal decomposition of iron(III) oleate. To make them colloidally stable and dispersible in water and cell culture medium, they were modified with phosphonic acid- (PA) and hydroxamic acid (HA)-terminated poly(ethylene glycol) yielding PA-PEG@Fe3O4 and HA-PEG@Fe3O4 nanoparticles; conventional γ-Fe2O3 particles were prepared as a control. Advanced techniques were used to evaluate the properties and safety of the particles. Completeness of the nanoparticle coating was tested by real-time polymerase chain reaction. Interaction of the particles with primary human peripheral blood cells, cellular uptake, cytotoxicity, and immunotoxicity were also investigated. Amount of internalized iron in peripheral blood mononuclear cells was 72, 38, and 25 pg Fe/cell for HA-PEG@Fe3O4, γ-Fe2O3, and PA-PEG@Fe3O4, respectively. Nanoparticles were localized within the cytoplasm and in the extracellular space. No cytotoxic effect of both PEGylated nanoparticles was observed (0.12–75 μg/cm2) after 24 and 72-h incubation. Moreover, no suppressive effect was found on the proliferative activity of T-lymphocytes and T-dependent B-cell response, phagocytic activity of monocytes and granulocytes, and respiratory burst of phagocytes. Similarly, no cytotoxic effect of γ-Fe2O3 particles was observed. However, they suppressed the proliferative activity of T-lymphocytes (75 μg/cm2, 72 h) and also decreased the phagocytic activity of monocytes (15 μg/cm2, 24 h; 3–75 μg/cm2, 72 h). We thus show that newly developed particles have great potential especially in cancer diagnostics and therapy.

Reproductive Toxicology, 2015

Croatian Medical Journal, 2016

Aim To determine cytotoxicity and effect of silica-coated magnetic nanoparticles (MNPs) on immune... more Aim To determine cytotoxicity and effect of silica-coated magnetic nanoparticles (MNPs) on immune response, in particular lymphocyte proliferative activity, phagocytic activity, and leukocyte respiratory burst and in vitro production of interleukin-6 (IL-6) and 8 (IL-8), interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and granulocyte macrophage colony stimulating factor (GM-CSF). Methods Maghemite was prepared by coprecipitation of iron salts with ammonia, oxidation with NaOCl and modified by tetramethyl orthosilicate and aminosilanes. Particles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Cytotoxicity and lymphocyte proliferative activity were assessed using [ 3 H]-thymidine incorporation into DNA of proliferating human peripheral blood cells. Phagocytic activity and leukocyte respiratory burst were measured by flow cytometry; cytokine levels in cell supernatants were determined by ELISA. Results γ-Fe 2 O 3 &SiO 2-NH 2 MNPs were 13 nm in size. According to TEM, they were localized in the cell cytoplasm and extracellular space. Neither cytotoxic effect nor significant differences in T-lymphocyte and T-dependent Bcell proliferative response were found at particle concentrations 0.12-75 μg/cm 2 after 24, 48, and 72 h incubation. Significantly increased production of IL-6 and 8, and GM-CSF cytokines was observed in the cells treated with 3, 15, and 75 µg of particles/cm 2 for 48 h and stimulated with pokeweed mitogen (PHA). No significant changes in TNF-α and IFN-γ production were observed. MNPs did not affect phagocytic activity of monocytes and granulocytes when added to cells for 24 and 48 h. Phagocytic respiratory burst was significantly enhanced in the cultures exposed to 75 µg MNPs/cm 2 for 48 h. Conclusions The cytotoxicity and in vitro immunotoxicity were found to be minimal in the newly developed porous core-shell γ-Fe 2 O 3 &SiO 2-NH 2 magnetic nanoparticles.

physica status solidi (a), 1981

... The direct observation of electromigration in A1-Cu films by transmission electron microscopy... more ... The direct observation of electromigration in A1-Cu films by transmission electron microscopy ... a sensitive tool for studying the role of film structure in electro-migration damage mechanisms. ... at higher substrate temperature (eg 300 “C) are more suitable for IC interconnections. ...

ABSTRACT Scientists in engineering and biological fields share common concerns and in recent year... more ABSTRACT Scientists in engineering and biological fields share common concerns and in recent years these concerns have shaped the direction of research in both fields. The inspiration stemming from nature for the development of new technologies and particularly nanotechnology has been very extensive. The development of new analytical and imaging methods allows us to understand structures, functions and solutions used by all living systems. Biosynthesis of nanoparticles (NPs) and nanostructures can profit from the use of natural processes found in cells. The usage of biomolecules, different functional groups or enzymes from the living organisms and cells can lead to significant improvement in the biosynthesis process. In this chapter, we will discuss the fabrication of colloidal solutions and composites containing gold and silver nanoparticles prepared by means of algae with silica based coverings and their potential applications. We summarized existing utilization of diatoms in nanotechnology research and outlined the potential usage of these interesting organisms and their silica frustules. We also performed experiments leading to the formation of gold nanoparticles in the presence of the golden alga Mallomonas kalinae.

Short title: Andreev reflection in Nb/Fe0.5Si0.5/Nb and Nb/Fe0.5Si0.5/Si/Nb junctions PACS: 74.50... more Short title: Andreev reflection in Nb/Fe0.5Si0.5/Nb and Nb/Fe0.5Si0.5/Si/Nb junctions PACS: 74.50+r Abstract Electrical properties of Josephson junctions Nb/Fe0.5Si0.5/Nb with superconductor/ferromagnet (S/F) interfaces are presented. Due to Andreev reflection the nearly exact quadruple enhancement of the tunnel junction differential conductance compared with that of the normal state was achieved. The transparency of the S/F interfaces in our junctions was estimated to be close to unity. This almost ideal value is obtained due to the use of a very smooth amorphous magnetic Fe0.5Si0.5 alloy for the barrier preparation. The real structure of the Nb/Fe0.5Si0.5/Nb tunnel junction is described as a S/F/I/F/S junction. Also Nb/Fe0.5Si0.5/Si/Nb Josephson junctions were investigated and the results found on these junctions confirm the effects observed in Nb/Fe0.5Si0.5/Nb.

Journal of Pharmacology and Experimental Therapeutics

Physical Review B

ABSTRACT

Materials Science Forum, 1996

Solid State Phenomena, 2003

ABSTRACT

The Ninth International Conference on Advanced Semiconductor Devices and Mircosystems, 2012

ABSTRACT GaP/ZnO core-shell nanowires were prepared by Metal Organic Vapour Phase Epitaxy and RF ... more ABSTRACT GaP/ZnO core-shell nanowires were prepared by Metal Organic Vapour Phase Epitaxy and RF sputtering. We studied systematically room temperature photoluminescence of the NWs in the ultraviolet and green regions. Our study revealed that the UV peak position shifted slightly towards longer wavelengths while the green emission with the main transition at 2.25eV was almost unchanged.

Ceramics Silikaty

In the work we describe the use of Al2O3-Y 2O3 glass microspheres with high alumina contents prep... more In the work we describe the use of Al2O3-Y 2O3 glass microspheres with high alumina contents prepared by flame synthesis as a precursor for materials with binary eutectic microstructure and high hardness. XRD amorphous microspheres with eutectic composition in a pseudobinary system Al2O3-Y 3Al5O12 (YAG) were prepared by feeding a crystalline powder precursor of respective composition into methane-oxygen flame. The microspheres with the mean diameter ≈10 μm were hot-pressed in vacuum under various conditions (temperatures 840-1600°C, pressure 30 or 40 MPa, isothermal dwell 0-120 min). Hot pressing at 1600°C without isothermal dwell yielded fully dense bulk materials with fine two phase microstructure with Al2O3 and YAG phases percolating at submicrometre level and with hardness 15 GPa. Extension of the isothermal dwell resulted in undesirable coarsening of the resulting microstructure.

Electrical properties of Josephson junctions Nb/FeSi/Nb with superconductor/ferromagnet (S/F)inte... more Electrical properties of Josephson junctions Nb/FeSi/Nb with superconductor/ferromagnet (S/F)interfaces are presented. Due to Andreev reflection the nearly exact quadruple enhancement of the tunnel junction differential conductance compared with that of the normal state was achieved. The transparency of the S/F interfaces in our junctions was estimated to be close to unity. This almost ideal value is obtained due to the use of a very smooth amorphous magnetic FeSi alloy for the barrier preparation. The real structure of the Nb/FeSi/Nb tunnel junction is described as a S/F/I/F/S junction. Also Nb/FeSi/Si/Nb Josephson junctions were investigated and the results found on these junctions confirm the effects observed in Nb/FeSi/Nb.

Magnetic rod-like particles have been prepared through two type hydrolysis. The influence of diff... more Magnetic rod-like particles have been prepared through two type hydrolysis. The influence of different conditions during synthesis on the size (length and diameter), structure and magnetic properties of the prepared nanoparticles was studied. The molar ratio of the reactants affects structure, shape and magnetic properties of particles. The prepared samples were characterized by a variety of methods: infrared spectroscopy, magnetization measurements, Transmission electron microscopy and Scanning electron microscopy.

Carbon

Carbon–nickel composite thin films (600 nm thick) were prepared by dc magnetron sputtering of Ni ... more Carbon–nickel composite thin films (600 nm thick) were prepared by dc magnetron sputtering of Ni and C at several temperatures (25–800 °C) on oxidized silicon substrates. By transmission electron microscopy it was found that the composite consisted of Ni (or Ni3C) nanoparticles embedded in a carbon matrix. The metallic nanoparticles were shaped in the form of globular grains or nanowires (of the aspect ratio as high as 1:60 in the sample prepared at 200 °C). The carbon matrix was amorphous, or graphite-like depending on deposition temperature. At low deposition temperatures TS (25–400 °C) the Ni3C nanoparticles were of hcp phase. Samples prepared at TS ⩾ 600 °C contained ferromagnetic fcc Ni nanoparticles. A correlation was found between the structural, electrical and magnetic properties of the composites. To characterise the films, dependences, such as resistivity vs. temperature, current vs. voltage, differential conductivity vs. bias voltage, and magnetoresistivity, were determin...

Magnetite labeled carbon nanotubes were prepared by precipitation method in nitrogen atmosphere a... more Magnetite labeled carbon nanotubes were prepared by precipitation method in nitrogen atmosphere at 60°C. For the preparation were used single-walled carbon nanotubes with diameter from 1 to 2.0 nm and length in the range of 500 – 2000 nm, and multi-walled carbon nanotubes with outer diameter from 20 nm to 30 nm, wall thickness from 1 nm to 2 nm and length from 500–2000 nm. Magnetic properties of the prepared samples investigated by a SQUID magnetometer show significant changes in comparison with non labeled samples. Transmission electron microscopy was employed to obtain structural and size information. Infrared spectroscopy proved the presence of magnetite in the CNT/Fe 3 O 4 product.

Scientists in engineering and biological fields share common concerns and in recent years these c... more Scientists in engineering and biological fields share common concerns and in recent years these concerns have shaped the direction of research in both fields. The inspiration stemming from nature for the development of new technologies and particularly nanotechnology has been very extensive. The development of new analytical and imaging methods allows us to understand structures, functions and solutions used by all living systems. Biosynthesis of nanoparticles (NPs) and nanostructures can profit from the use of natural processes found in cells. The usage of biomolecules, different functional groups or enzymes from the living organisms and cells can lead to significant improvement in the biosynthesis process. In this chapter, we will discuss the fabrication of colloidal solutions and composites containing gold and silver nanoparticles prepared by means of algae with silica based coverings and their potential applications. We summarized existing utilization of diatoms in nanotechnolog...

The Eighth International Conference on Advanced Semiconductor Devices and Microsystems, 2010

Great advances in the development of III-V diluted magnetic semiconductors materials (DMS) allow ... more Great advances in the development of III-V diluted magnetic semiconductors materials (DMS) allow for the incorporation of ferromagnetic epitaxial layers into advanced structures. In this contribution, we report on the growth of GaAs/InMnAs layers by metalorganic vapour phase epitaxy (MOVPE) over an AlGaAs/GaAs MQW light-emitting diode structure. In particular, results of electrical and structural characterization of structures are presented. We prepared a single-phase ferromagnetic In 1-x Mn x As ternary with x close to 0.075 on (100) GaAs substrates using MOVPE. The material exhibited room temperature ferromagnetic behavior with a Curie temperature close to 330K. In addition, all InMnAs ternary samples showed p-type conductivity. The ferromagnetic material was incorporated into four different AlGaAs/GaAs LED structure.

2006 International Conference on Advanced Semiconductor Devices and Microsystems, 2006

A 400mum times 400mum sized square quantum-well infrared photodetector with 30 periods of the GaA... more A 400mum times 400mum sized square quantum-well infrared photodetector with 30 periods of the GaAs/Al0.3Ga0.7 As multiple quantum well has been prepared on patterned (001) GaAs substrate. The absorption spectrum at room temperature with normal incidence geometry is peaked at 9mum with a full width at half maximum (FWHM) of 3.7 mum. Dark current with influence of 300K background was