Spyros Yannopoulos - Academia.edu (original) (raw)

Papers by Spyros Yannopoulos

NATO Science for Peace and Security Series B: Physics and Biophysics, 2009

ABSTRACT Amorphous chalcogenide (As—S) thin films can be fabricated by the spin-coating technique... more ABSTRACT Amorphous chalcogenide (As—S) thin films can be fabricated by the spin-coating technique from appropriate solutions of the corresponding glasses. Such films exhibit a grainy texture, which is presumably related to the cluster size in the solution. In this paper we report on a possible relation between the grain size of the surface of spin-coated As33S67 chalcogenide thin films and the cluster size of the glass in butylamine solutions, using atomic force microscopy and dynamic light scattering, respectively. A novel athermal photo-aggregation effect in the liquid state is reported also.

A low-frequency Raman study on the fragile ionic glass-forming system 2BiCl 3-KCl is reported. Ap... more A low-frequency Raman study on the fragile ionic glass-forming system 2BiCl 3-KCl is reported. Approaches that are usually followed for a quantitative interpretation of the frequency and temperature dependence of the spectra have been employed. The inadequacy of satisfactorily fitting the experimental data applying standard models has led to the introduction of an extra contribution having its origin in scattering caused by charge-current fluctuations. The frequency dependence of the depolarization ratio, which is usually overlooked in low-frequency Raman studies, is another fact that reveals the necessity of the approach followed. We put forward a partial depolarization ratio analysis of the individual contributions involved in the lowfrequency Raman spectrum. The characteristic frequency dependence of the depolarization ratio that each component exhibits is discussed alongside the corresponding physical mechanism on which the particular scattering contribution originates. Although applicable only to ionic glass-forming systems this picture stems from a well-grounded physical basis and may aid towards a better comprehension to selected aspects for supercooled liquids.

We report a novel approach for deposition of amorphous chalcogenide glass films inside the cylind... more We report a novel approach for deposition of amorphous chalcogenide glass films inside the cylindrical air channels of photonic crystal fiber (PCF). In particular, we demonstrate the formation of nanocolloidal solution-based As 2 S 3 films inside the air channels of PCFs of different glass-solvent concentrations for two fibers with cladding-hole diameter 3.5 and 1.3µm. Scanning electron microscopy is used to observe the formed chalcogenide layers and Raman scattering is employed to verify the existence and the structural features of the amorphous As 2 S 3 layers. Optical transmission measurements reveal strong photonic bandgaps over a range covering visible and near-infrared wavelengths. The transmittance spectra and the corresponding losses were recorded in the wavelength range 500-1750 nm. The main advantage of the proposed technique is the simplicity of the deposition of amorphous chalcogenide layers inside the holes of PCF and constitutes an efficient route to the development of fiberbased devices combined with sophisticated glasses for supercontinuum generation as well as other non-linear applications.

Vibrational Spectroscopy, 2008

In this work we report on a vibrational spectroscopic study on the structural aspects of the bina... more In this work we report on a vibrational spectroscopic study on the structural aspects of the binary xCaOÁ(100 À x)SiO 2 , xMgOÁ(100 À x)SiO 2 and ternary xCaOÁyMgO (100 À x À y)SiO 2 systems for various x values up to 50%. Raman and IR spectroscopies have revealed the degradation of the silica network with the addition of the oxide modifiers. The main differences in the spectra of the alkaline earth modified sol-gel glasses are located in the region 900-1200 cm À1 where vibrations of SiO 4 tetrahedra with a variable number of non-bridging oxygen atoms are located. A comparison between the structural modifications of bulk (melt-quenched) and porous glasses is also advanced revealing particular differences in the network modification of the two types of glasses. CaO is more drastic than MgO in depolymerizing silica's network and both of them cause more significant structure modifications in the sol-gel glasses. The depolymerization structural units offer the appropriate sites in the glass network that are responsible for the facilitation of Ca/Mg dissolution, which is an important step for bioactivity. Furthermore, to support the conclusions drawn from the experimental data, preliminary molecular structure simulations using semiempirical molecular orbital theory are also presented. #

Thin Solid Films, 2007

A new method to produce zinc oxide nanocrystals is presented. The method is based on the thermal ... more A new method to produce zinc oxide nanocrystals is presented. The method is based on the thermal decomposition of zinc alginate gels. The gels were produced in the form of beads by ionic gelation between a zinc solution and sodium alginate. The wet beads were heated at 800 and 450°C for 24 h and the products were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission electron microscopy (TEM) and micro-Raman spectroscopy. XRD analysis showed that all obtained samples are of wurtzite structure. TEM analysis combined with electron diffraction also showed the presence of single crystals indexed as ZnO hexagonal phase. Crystal size was determined by measuring individual crystals from SEM pictures. It was found that heating temperature and the kind of zinc agent influence the crystal size. Raman scattering revealed the existence of defects in the structure of nanoparticles whose cringing was discussed in the context of recent studies in this field.

Thin Solid Films, 2007

We report on the formation of ZnO/carbon nanotubes heterostructures achieved by means of a therma... more We report on the formation of ZnO/carbon nanotubes heterostructures achieved by means of a thermal evaporation method. Scanning electron microscopy revealed that the main building block of the observed morphologies was the nanorod whose self-assembling resulted in ...

The Journal of Physical Chemistry C, 2012

In this study, we aimed to use physicochemical and theoretical tools to understand fundamental pr... more In this study, we aimed to use physicochemical and theoretical tools to understand fundamental problems of the interaction between lipid bilayers (Egg-PC liposomes) and unmodified C 60 fullerenes. The morphology, the size, and the electrokinetic properties of plain and C 60 -loaded liposomes were investigated by means of atomic force microscopy, dynamic light scattering, and ζ-potential studies, respectively. The incorporation of C 60 molecules into the liposomes increases their size; however, there was no effect on their electrokinetic properties. Visualization studies revealed that the presence of C 60 in the membranes induced distortion in vesicle morphology, resulting in nonspherical vesicles. To elucidate further the impact of C 60 molecules on lipid bilayers, we assessed their miscibility by fluorescence spectroscopy measurements. Fluorescence measurements showed that the presence of C 60 in liposomes causes a pronounced effect on the Nile red emission spectrum due to alterations to the packing of the lipid membrane. The release of vesicle-encapsulated calcein was used as a measure of the integrity of the liposomes. Plain liposomes were found to be more stable compared with C 60 -loaded (PC) liposomes, suggesting that C 60 ruptures the liposome membrane. Toxicity studies of C 60 in liposomes were carried out on cultured cells [rodent fibroblasts (3T3)] to assess further their toxicity. The results suggest that fullerene cytotoxic effect was reduced significantly after its incorporation into the liposomal bilayer after 24 h of incubation with the rodent fibroblasts (3T3). Finally, energy minimization studies were employed to underpin the experimental observations. The theoretical calculations show that low concentration of fullerene molecules present in the membrane had no effect on the membrane integrity; however, at high concentrations of fullerenes significant enlargement of the surface area is observed, supporting the experimental findings.

Solid State Communications, 2002

Unexpected structural and dynamical features of non-crystalline As 2 O 3 , revealed through vario... more Unexpected structural and dynamical features of non-crystalline As 2 O 3 , revealed through various light scattering techniques, indicate that this glass is distinctively different form other common oxide glasses. In view of its structural similarity with other chalcogenide glasses, i.e. As 2 S 3 and As 2 Se 3 , it is suggested that the peculiar spectral properties of As 2 O 3 may originate from structural con®gurations like those usually employed to account for photoinduced phenomena in chalcogenide glasses. The lone-pair electrons of oxygen atoms and the structural¯exibility characterizing As 2 O 3 compared to other tetrahedrally coordinated oxide glasses seems to be the key factor for the observed unique properties of this glass.

Physical Review E, 2008

We present a detailed dynamic light scattering study on the phase separation in the ocular lens e... more We present a detailed dynamic light scattering study on the phase separation in the ocular lens emerging during cold cataract development. Cold cataract is a phase separation effect that proceeds via spinodal decomposition of the lens cytoplasm with cooling. Intensity auto-correlation functions of the lens protein content are analyzed with the aid of two methods providing information on the populations and dynamics of the scattering elements associated with cold cataract. It is found that the temperature dependence of many measurable parameters changes appreciably at the characteristic temperature ~16+1 o C which is associated with the onset of cold cataract. Extending the temperature range of this work to previously inaccessible regimes, i.e. well below the phase separation or coexistence curve at T cc , we have been able to accurately determine the temperature dependence of the collective and self-diffusion coefficient of proteins near the spinodal. The analysis showed that the dynamics of proteins bears some resemblance to the dynamics of structural glasses where the apparent activation energy for particle diffusion increases below T cc indicating a highly cooperative motion. Application of ideas developed for studying the critical dynamics of binary protein/solvent mixtures, as well as the use of a modified Arrhenius equation, enabled us to estimate the spinodal temperature T sp of the lens nucleus. The applicability of dynamic light scattering as a non-invasive, earlydiagnostic tool for ocular diseases is also demonstrated in the light of the findings of the present paper.

Journal of the Optical Society of America B, 2011

chalcogenide glasses have been recorded and the corresponding Raman gain coefficients have been c... more chalcogenide glasses have been recorded and the corresponding Raman gain coefficients have been calculated in order to evaluate the role of Ge, Ga, Sb, and As on a novel Ge 17 Ga 4 Sb 10 S 69 glass proposed for highly nonlinear microstructured optical fibers. We calculated the Raman response functions of As 2 S 3 n 2 ¼ 2:3 × 10 −17 m 2 =W, G ∼ 2:78 × 10 −11 m=W; and Ge 17 Ga 4 Sb 10 S 69 n 2 ¼ 1:8 × 10 −17 m 2 =W, G ∼ 1:57 × 10 −11 m=W glasses. The supercontinuum generation of a three-air-hole Ge 17 Ga 4 Sb 10 S 69 fiber was simulated, challenging the properties of a similar fiber design made of As 2 S 3 chalcogenide glass. We calculated the zero dispersion wavelengths of Ge 17 Ga 4 Sb 10 S 69 fibers with the core diameters of 1.2, 1.5, and 2:0 μm at λ ¼ 1:48, 1.66, and 1:75 μm in comparison with λ ¼ 1:60, 1.87, and 1:98 μm obtained for As 2 S 3 fibers.

Nanoscale, 2011

We have previously demonstrated that chitosan derivative N-octyl-O-sulfate chitosan (NOSC), which... more We have previously demonstrated that chitosan derivative N-octyl-O-sulfate chitosan (NOSC), which presents important pharmacological properties, can suspend single walled carbon nanotubes (SWNTs) up to 20 times more effectively than other chitosan derivatives in an aqueous environment. In an attempt to further investigate the impact of different molecular weights of chitosan to the solubilization and anticoagulant properties of these hybrids an array of NOSC derivatives varying their molecular weight (low, medium and high respectively) was synthesised and characterised by means of FT-IR spectroscopy, NMR spectroscopy and thermal gravimetric analysis (TGA). Microwave and nitric acid purified SWNTs, characterised by FT-IR spectroscopy, transmission electron microscopy (TEM) and Raman spectroscopy, were colloidally stabilised by these polymers and their anticoagulant activity was assessed. The results revealed that the low molecular weight NOSC coated SWNTs exhibit the highest activity when 0.5 mg mL À1 NOSC solutions are used, activity which is similar to that of the free polymer. Preliminary studies by exposure of these hybrids to Brine Shrimp (Artemia) cysts revealed no effect on the viability of sub-adult Artemia. Our findings suggest the possibility of tailoring these nanomaterials to bear the required properties for application as biocompatible building blocks for nanodevices including biosensors and biomaterials. † Electronic supplementary information (ESI) available: Synthesis of NOC and NOSC; SWNT purification methods; MTT assay; mechanism of sulfation; ATR and NMR data; and further Raman analysis, in vivo biomodification assay. See

Macromolecules, 2005

... 23) Tsitsilianis, C.; Stavrouli, N.; Gorodyska, A.; Kiriy, A.; Minko, S.; Stamm, M., to be pu... more ... 23) Tsitsilianis, C.; Stavrouli, N.; Gorodyska, A.; Kiriy, A.; Minko, S.; Stamm, M., to be published. (24) Silberberg, A.; Eliassaf, J.; Katsalski, A. J. Polym. Sci.1957, 23, 259. ... 25) Minko, S.; Kiriy, A.; Gorodyska, G.; Stamm, M. J. Am. Chem. Soc.2002, 124, 3218. ...

Journal of Physics and Chemistry of Solids, 2006

Journal of Physics and Chemistry of Solids, 2007

Raman spectra of xNa 2 OÀ(1Àx)TeO 2 glasses were measured and analyzed over a broad composition r... more Raman spectra of xNa 2 OÀ(1Àx)TeO 2 glasses were measured and analyzed over a broad composition range. The network structure of the glass consists of a mixture of TeO 4 trigonal bipyramids and TeO 3 trigonal pyramidal units. Increase of alkali content results in conversion of the TeO 4 units into TeO 3 units with a varying number of non-bridging oxygen atoms. This local structure transformation becomes more evident at x ¼ 0.2, where rigidity percolation theory predicts a threshold for the rigid-to-floppy transition. However, other spectral features such as the composition dependence of the energy of the Boson peak do not support the occurrence of the stiffness transition. The controversial dependence of dynamical parameters such as the fragility index as a function of Na 2 O concentration is also discussed.

The Journal of Chemical Physics, 2002

Journal of Applied Physics, 2008

Amorphous chalcogenide thin film deposition can be achieved by a spin-coating technique from prop... more Amorphous chalcogenide thin film deposition can be achieved by a spin-coating technique from proper solutions of the corresponding glass. Films produced in this way exhibit certain grain texture, which is presumably related to the cluster size in solution. This paper deals with the search of such a correlation between grain size of surface morphology of as-deposited spin-coated As 33 S 67 chalcogenide thin films and cluster size of the glass in butylamine solutions. Optical absorption spectroscopy and dynamic light scattering were employed to study optical properties and cluster size distributions in the solutions at various glass concentrations. Atomic force microscopy is used to study the surface morphology of the surface of as-deposited and thermally stabilized spin-coated films. Dynamic light scattering revealed a concentration dependence of cluster size in solution.

NATO Science for Peace and Security Series B: Physics and Biophysics, 2009

ABSTRACT Amorphous chalcogenide (As—S) thin films can be fabricated by the spin-coating technique... more ABSTRACT Amorphous chalcogenide (As—S) thin films can be fabricated by the spin-coating technique from appropriate solutions of the corresponding glasses. Such films exhibit a grainy texture, which is presumably related to the cluster size in the solution. In this paper we report on a possible relation between the grain size of the surface of spin-coated As33S67 chalcogenide thin films and the cluster size of the glass in butylamine solutions, using atomic force microscopy and dynamic light scattering, respectively. A novel athermal photo-aggregation effect in the liquid state is reported also.

A low-frequency Raman study on the fragile ionic glass-forming system 2BiCl 3-KCl is reported. Ap... more A low-frequency Raman study on the fragile ionic glass-forming system 2BiCl 3-KCl is reported. Approaches that are usually followed for a quantitative interpretation of the frequency and temperature dependence of the spectra have been employed. The inadequacy of satisfactorily fitting the experimental data applying standard models has led to the introduction of an extra contribution having its origin in scattering caused by charge-current fluctuations. The frequency dependence of the depolarization ratio, which is usually overlooked in low-frequency Raman studies, is another fact that reveals the necessity of the approach followed. We put forward a partial depolarization ratio analysis of the individual contributions involved in the lowfrequency Raman spectrum. The characteristic frequency dependence of the depolarization ratio that each component exhibits is discussed alongside the corresponding physical mechanism on which the particular scattering contribution originates. Although applicable only to ionic glass-forming systems this picture stems from a well-grounded physical basis and may aid towards a better comprehension to selected aspects for supercooled liquids.

We report a novel approach for deposition of amorphous chalcogenide glass films inside the cylind... more We report a novel approach for deposition of amorphous chalcogenide glass films inside the cylindrical air channels of photonic crystal fiber (PCF). In particular, we demonstrate the formation of nanocolloidal solution-based As 2 S 3 films inside the air channels of PCFs of different glass-solvent concentrations for two fibers with cladding-hole diameter 3.5 and 1.3µm. Scanning electron microscopy is used to observe the formed chalcogenide layers and Raman scattering is employed to verify the existence and the structural features of the amorphous As 2 S 3 layers. Optical transmission measurements reveal strong photonic bandgaps over a range covering visible and near-infrared wavelengths. The transmittance spectra and the corresponding losses were recorded in the wavelength range 500-1750 nm. The main advantage of the proposed technique is the simplicity of the deposition of amorphous chalcogenide layers inside the holes of PCF and constitutes an efficient route to the development of fiberbased devices combined with sophisticated glasses for supercontinuum generation as well as other non-linear applications.

Vibrational Spectroscopy, 2008

In this work we report on a vibrational spectroscopic study on the structural aspects of the bina... more In this work we report on a vibrational spectroscopic study on the structural aspects of the binary xCaOÁ(100 À x)SiO 2 , xMgOÁ(100 À x)SiO 2 and ternary xCaOÁyMgO (100 À x À y)SiO 2 systems for various x values up to 50%. Raman and IR spectroscopies have revealed the degradation of the silica network with the addition of the oxide modifiers. The main differences in the spectra of the alkaline earth modified sol-gel glasses are located in the region 900-1200 cm À1 where vibrations of SiO 4 tetrahedra with a variable number of non-bridging oxygen atoms are located. A comparison between the structural modifications of bulk (melt-quenched) and porous glasses is also advanced revealing particular differences in the network modification of the two types of glasses. CaO is more drastic than MgO in depolymerizing silica's network and both of them cause more significant structure modifications in the sol-gel glasses. The depolymerization structural units offer the appropriate sites in the glass network that are responsible for the facilitation of Ca/Mg dissolution, which is an important step for bioactivity. Furthermore, to support the conclusions drawn from the experimental data, preliminary molecular structure simulations using semiempirical molecular orbital theory are also presented. #

Thin Solid Films, 2007

A new method to produce zinc oxide nanocrystals is presented. The method is based on the thermal ... more A new method to produce zinc oxide nanocrystals is presented. The method is based on the thermal decomposition of zinc alginate gels. The gels were produced in the form of beads by ionic gelation between a zinc solution and sodium alginate. The wet beads were heated at 800 and 450°C for 24 h and the products were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission electron microscopy (TEM) and micro-Raman spectroscopy. XRD analysis showed that all obtained samples are of wurtzite structure. TEM analysis combined with electron diffraction also showed the presence of single crystals indexed as ZnO hexagonal phase. Crystal size was determined by measuring individual crystals from SEM pictures. It was found that heating temperature and the kind of zinc agent influence the crystal size. Raman scattering revealed the existence of defects in the structure of nanoparticles whose cringing was discussed in the context of recent studies in this field.

Thin Solid Films, 2007

We report on the formation of ZnO/carbon nanotubes heterostructures achieved by means of a therma... more We report on the formation of ZnO/carbon nanotubes heterostructures achieved by means of a thermal evaporation method. Scanning electron microscopy revealed that the main building block of the observed morphologies was the nanorod whose self-assembling resulted in ...

The Journal of Physical Chemistry C, 2012

In this study, we aimed to use physicochemical and theoretical tools to understand fundamental pr... more In this study, we aimed to use physicochemical and theoretical tools to understand fundamental problems of the interaction between lipid bilayers (Egg-PC liposomes) and unmodified C 60 fullerenes. The morphology, the size, and the electrokinetic properties of plain and C 60 -loaded liposomes were investigated by means of atomic force microscopy, dynamic light scattering, and ζ-potential studies, respectively. The incorporation of C 60 molecules into the liposomes increases their size; however, there was no effect on their electrokinetic properties. Visualization studies revealed that the presence of C 60 in the membranes induced distortion in vesicle morphology, resulting in nonspherical vesicles. To elucidate further the impact of C 60 molecules on lipid bilayers, we assessed their miscibility by fluorescence spectroscopy measurements. Fluorescence measurements showed that the presence of C 60 in liposomes causes a pronounced effect on the Nile red emission spectrum due to alterations to the packing of the lipid membrane. The release of vesicle-encapsulated calcein was used as a measure of the integrity of the liposomes. Plain liposomes were found to be more stable compared with C 60 -loaded (PC) liposomes, suggesting that C 60 ruptures the liposome membrane. Toxicity studies of C 60 in liposomes were carried out on cultured cells [rodent fibroblasts (3T3)] to assess further their toxicity. The results suggest that fullerene cytotoxic effect was reduced significantly after its incorporation into the liposomal bilayer after 24 h of incubation with the rodent fibroblasts (3T3). Finally, energy minimization studies were employed to underpin the experimental observations. The theoretical calculations show that low concentration of fullerene molecules present in the membrane had no effect on the membrane integrity; however, at high concentrations of fullerenes significant enlargement of the surface area is observed, supporting the experimental findings.

Solid State Communications, 2002

Unexpected structural and dynamical features of non-crystalline As 2 O 3 , revealed through vario... more Unexpected structural and dynamical features of non-crystalline As 2 O 3 , revealed through various light scattering techniques, indicate that this glass is distinctively different form other common oxide glasses. In view of its structural similarity with other chalcogenide glasses, i.e. As 2 S 3 and As 2 Se 3 , it is suggested that the peculiar spectral properties of As 2 O 3 may originate from structural con®gurations like those usually employed to account for photoinduced phenomena in chalcogenide glasses. The lone-pair electrons of oxygen atoms and the structural¯exibility characterizing As 2 O 3 compared to other tetrahedrally coordinated oxide glasses seems to be the key factor for the observed unique properties of this glass.

Physical Review E, 2008

We present a detailed dynamic light scattering study on the phase separation in the ocular lens e... more We present a detailed dynamic light scattering study on the phase separation in the ocular lens emerging during cold cataract development. Cold cataract is a phase separation effect that proceeds via spinodal decomposition of the lens cytoplasm with cooling. Intensity auto-correlation functions of the lens protein content are analyzed with the aid of two methods providing information on the populations and dynamics of the scattering elements associated with cold cataract. It is found that the temperature dependence of many measurable parameters changes appreciably at the characteristic temperature ~16+1 o C which is associated with the onset of cold cataract. Extending the temperature range of this work to previously inaccessible regimes, i.e. well below the phase separation or coexistence curve at T cc , we have been able to accurately determine the temperature dependence of the collective and self-diffusion coefficient of proteins near the spinodal. The analysis showed that the dynamics of proteins bears some resemblance to the dynamics of structural glasses where the apparent activation energy for particle diffusion increases below T cc indicating a highly cooperative motion. Application of ideas developed for studying the critical dynamics of binary protein/solvent mixtures, as well as the use of a modified Arrhenius equation, enabled us to estimate the spinodal temperature T sp of the lens nucleus. The applicability of dynamic light scattering as a non-invasive, earlydiagnostic tool for ocular diseases is also demonstrated in the light of the findings of the present paper.

Journal of the Optical Society of America B, 2011

chalcogenide glasses have been recorded and the corresponding Raman gain coefficients have been c... more chalcogenide glasses have been recorded and the corresponding Raman gain coefficients have been calculated in order to evaluate the role of Ge, Ga, Sb, and As on a novel Ge 17 Ga 4 Sb 10 S 69 glass proposed for highly nonlinear microstructured optical fibers. We calculated the Raman response functions of As 2 S 3 n 2 ¼ 2:3 × 10 −17 m 2 =W, G ∼ 2:78 × 10 −11 m=W; and Ge 17 Ga 4 Sb 10 S 69 n 2 ¼ 1:8 × 10 −17 m 2 =W, G ∼ 1:57 × 10 −11 m=W glasses. The supercontinuum generation of a three-air-hole Ge 17 Ga 4 Sb 10 S 69 fiber was simulated, challenging the properties of a similar fiber design made of As 2 S 3 chalcogenide glass. We calculated the zero dispersion wavelengths of Ge 17 Ga 4 Sb 10 S 69 fibers with the core diameters of 1.2, 1.5, and 2:0 μm at λ ¼ 1:48, 1.66, and 1:75 μm in comparison with λ ¼ 1:60, 1.87, and 1:98 μm obtained for As 2 S 3 fibers.

Nanoscale, 2011

We have previously demonstrated that chitosan derivative N-octyl-O-sulfate chitosan (NOSC), which... more We have previously demonstrated that chitosan derivative N-octyl-O-sulfate chitosan (NOSC), which presents important pharmacological properties, can suspend single walled carbon nanotubes (SWNTs) up to 20 times more effectively than other chitosan derivatives in an aqueous environment. In an attempt to further investigate the impact of different molecular weights of chitosan to the solubilization and anticoagulant properties of these hybrids an array of NOSC derivatives varying their molecular weight (low, medium and high respectively) was synthesised and characterised by means of FT-IR spectroscopy, NMR spectroscopy and thermal gravimetric analysis (TGA). Microwave and nitric acid purified SWNTs, characterised by FT-IR spectroscopy, transmission electron microscopy (TEM) and Raman spectroscopy, were colloidally stabilised by these polymers and their anticoagulant activity was assessed. The results revealed that the low molecular weight NOSC coated SWNTs exhibit the highest activity when 0.5 mg mL À1 NOSC solutions are used, activity which is similar to that of the free polymer. Preliminary studies by exposure of these hybrids to Brine Shrimp (Artemia) cysts revealed no effect on the viability of sub-adult Artemia. Our findings suggest the possibility of tailoring these nanomaterials to bear the required properties for application as biocompatible building blocks for nanodevices including biosensors and biomaterials. † Electronic supplementary information (ESI) available: Synthesis of NOC and NOSC; SWNT purification methods; MTT assay; mechanism of sulfation; ATR and NMR data; and further Raman analysis, in vivo biomodification assay. See

Macromolecules, 2005

... 23) Tsitsilianis, C.; Stavrouli, N.; Gorodyska, A.; Kiriy, A.; Minko, S.; Stamm, M., to be pu... more ... 23) Tsitsilianis, C.; Stavrouli, N.; Gorodyska, A.; Kiriy, A.; Minko, S.; Stamm, M., to be published. (24) Silberberg, A.; Eliassaf, J.; Katsalski, A. J. Polym. Sci.1957, 23, 259. ... 25) Minko, S.; Kiriy, A.; Gorodyska, G.; Stamm, M. J. Am. Chem. Soc.2002, 124, 3218. ...

Journal of Physics and Chemistry of Solids, 2006

Journal of Physics and Chemistry of Solids, 2007

Raman spectra of xNa 2 OÀ(1Àx)TeO 2 glasses were measured and analyzed over a broad composition r... more Raman spectra of xNa 2 OÀ(1Àx)TeO 2 glasses were measured and analyzed over a broad composition range. The network structure of the glass consists of a mixture of TeO 4 trigonal bipyramids and TeO 3 trigonal pyramidal units. Increase of alkali content results in conversion of the TeO 4 units into TeO 3 units with a varying number of non-bridging oxygen atoms. This local structure transformation becomes more evident at x ¼ 0.2, where rigidity percolation theory predicts a threshold for the rigid-to-floppy transition. However, other spectral features such as the composition dependence of the energy of the Boson peak do not support the occurrence of the stiffness transition. The controversial dependence of dynamical parameters such as the fragility index as a function of Na 2 O concentration is also discussed.

The Journal of Chemical Physics, 2002

Journal of Applied Physics, 2008

Amorphous chalcogenide thin film deposition can be achieved by a spin-coating technique from prop... more Amorphous chalcogenide thin film deposition can be achieved by a spin-coating technique from proper solutions of the corresponding glass. Films produced in this way exhibit certain grain texture, which is presumably related to the cluster size in solution. This paper deals with the search of such a correlation between grain size of surface morphology of as-deposited spin-coated As 33 S 67 chalcogenide thin films and cluster size of the glass in butylamine solutions. Optical absorption spectroscopy and dynamic light scattering were employed to study optical properties and cluster size distributions in the solutions at various glass concentrations. Atomic force microscopy is used to study the surface morphology of the surface of as-deposited and thermally stabilized spin-coated films. Dynamic light scattering revealed a concentration dependence of cluster size in solution.