G. Kordas | Insitute of Matelials Science, NCSR "Demorktios" (original) (raw)
Papers by G. Kordas
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2016
To survey the preparation of novel hybrid microspheres of quaternary silicate glassy composition ... more To survey the preparation of novel hybrid microspheres of quaternary silicate glassy composition (SiO 2 AP 2 O 5 ACaOANa 2 O) and the prospect of using them as an osteogenic system with enhanced bioactive properties for the development of hydroxyapatite. Method: In line with our previous synthetic procedure a twostep process was followed, wherein polystyrene (PS) microspheres were prepared by the emulsifier free-emulsion polymerization method and constituted the core for the solgel coating of the silicate inorganic shell. The development of the hybrid microspheres was based on silane and phosphate precursors and was assesses at different ratio of ethanol/water (of 9/1, 4/1, and 2/1, in mL) and at varied ammonia concentration of 4.8-1.0 mL. Results: The hybrid microspheres had an average size ranged between 350 and 550 nm according to SEM, depending on the ethanol/water solution rate and ammonia content. The final microspheres probably exhibited a porous-like structure through the formation of diffused voids along with the low carbon content of the EDX analysis, which could be regulated by the catalyst content. The hybrid microspheres exhibited effective in vitro bioactivity assessed in simulated body fluids (SBF). Conclusion: Quaternary hybrid silica microspheres were effectively synthesized. The bioassay evaluation of the final microspheres revealed the rapid in vitro formation of a bone-like apatite layer. The results verify the bioactivity of the microspheres and promote further research of their suitability on regenerative treatment of bone abnormalities. V
Physics and Chemistry of Glasses, Sep 30, 2000
Glasses of composition (100-x) mol% B 2 O 3 . x mol% Li 2 O have been subjected to γ-irradiation ... more Glasses of composition (100-x) mol% B 2 O 3 . x mol% Li 2 O have been subjected to γ-irradiation at room temperature and subsequently studied by cw-EPR, 1D-ESEEM, 2D-HYSCORE and pulsed ENDOR spectroscopies at 20 K. The cw-EPR spectrum of a-B 2 O 3 have been simulated. Pulsed ENDOR revealed a strong coupling for a-B 2 O 3 , A weaker coupling was detected by HYSCORE and pulsed ENDOR spectroscopies. HYSCORE spectroscopy determined two weak hyperfine couplings when recorded with a τ-value of 248 and 168 ns, respectively. The cw-EPR spectra of the (100-x) mol% B 2 O and x mol% Li 2 O glasses revealed a strong dependence of their line shape on x. SCF-HF calculations have been employed to determine the hfs couplings produced by ring structures such as boroxol rings, boron oxygen hole centre (BOHC), pentaborate, diborate, tetraborate and borate network with nonbridging atoms (NBO). Data obtained by cw-EPR, pulsed ENDOR and HYSCORE spectroscopies can be explained assuming only boroxol rings to be present in a-B 2 O 3 . The variation of the cw-EPR signal with the composition, x, can be attributed to the formation of various ring structures.
Journal of Colloid and Interface Science, 2014
Hypothesis: Dual-modality imaging agents, such as radiolabeled iron oxide nanoparticles (IO-NPs),... more Hypothesis: Dual-modality imaging agents, such as radiolabeled iron oxide nanoparticles (IO-NPs), are promising candidates for cancer diagnosis and therapy. We developed and evaluated aminosilane coated Fe 3 O 4 (10 ± 2 nm) as a tumor imaging agent in nuclear medicine through 3-aminopropyltriethoxysilane (APTES) functionalization. We evaluated this multimeric system of targeted 99m Tc-labeled nanoparticles (NPs) conjugated with a new RGD derivate (cRGDfK-Orn 3-CGG), characterized as NPs-RGD as a potential thermal therapy delivery vehicle. Experiments: Transmission Electron Microscopy (TEM) and spectroscopy techniques were used to characterize the IO-NPs indicating their functionalization with peptides. Radiolabeled IO-NPs (targeted, non-targeted) were evaluated with regard to their radiochemical, radiobiological and imaging characteristics. In vivo studies were performed in normal and a m b 3-positive tumor (U87MG glioblastoma) bearing mice. We also demonstrated that this system could reach ablative temperatures in vivo. Findings: Both radiolabeled IO-NPs were obtained in high radiochemical yield (>98%) and proved stable in vitro. The in vivo studies for both IO-NPs have shown significant liver and spleen uptake at all examined time points in normal and U87MG glioblastoma tumor-bearing mice, due to their colloidal nature. We have confirmed through in vivo biodistribution studies that the non-targeted 99m Tc-NPs poorly internalized in the tumor, while the targeted 99m Tc-NPs-RGD, present 9-fold higher tumor accumulation at 1 h p.i. Accumulation of both IO-NPs in other organs was negligible. Blocking experiments indicated target specificity for integrin receptors in U87MG glioblastoma cells. The preliminary in vivo study of applied alternating magnetic field showed that the induced hyperthermia is feasible due to the aid of IO-NPs.
Journal of Nanoparticle Research, 2013
This study is focused on the production of hollow nanospheres that reveal antibacterial action. C... more This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 ± 15 and 221 ± 10 nm, respectively, were synthesized using emulsion polymerization and the sol-gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue-black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.
Journal of Drug Delivery Science and Technology, 2021
Journal of Drug Delivery Science and Technology, 2020
Abstract Polymeric materials are in the epicenter of scientific research the last decade and have... more Abstract Polymeric materials are in the epicenter of scientific research the last decade and have been used in a range of pharmaceutical and biological applications. Multifunctional polymeric materials are capable targeting agents, which can be used as controlled drug release vehicles for the enhancement of therapeutic efficacy, as well as for diagnostic purposes. A newer generation of these smart polymeric entities constitutes of smart nanocontainers (NCs), which can navigate the drug to specific areas by avoiding random distribution, and thus resulting in drug toxicity reduction. The combination of pH, thermo and redox sensitivity of the multi stimuli NCs can help to achieve specific release of the drug in the tumor area, where these sensitivity parameters can be observed. Hollow polymeric multi stimuli fluorescent tNCs based on N-(2-Hydroxypropyl)methacrylamide (HPMA) were successfully functionalized with a specific targeting moiety; folic acid, and then characterized morphologically, by scanning electron and transmission electron microscopy, as well as structurally, by Fourier-transform infrared spectroscopy. Their targeting mechanism was investigated in vitro in cervical cancer cell lines and in vivo in tumor bearing mice. According to our results the folic acid functionalized NCs targeted HeLa cells’ surface within the first 30 min of treatment. Human tumor xenografted mice (nonobese diabetic/severe combined immunodeficient) were injected with folate functionalized NCs and their tumor uptake was estimated by γ-imaging at about 3.5%. The targeting efficiency of the folate functionalized NCs was investigated directly in vivo by γ-imaging and indirectly by a tumor efficacy protocol.
Materials Letters, 1995
Multilayer, wavelength-selective reflective coatings have been prepared by alternating deposition... more Multilayer, wavelength-selective reflective coatings have been prepared by alternating deposition of TiOa and Si02 layers from solutions. Appropriate alkoxide solutions in ethanol were used as starting materials. The thickness of each layer, the profile of the coatings and the diffusion effects between multilayers were examined by the Rutherford back scattering method, using "C ion scattering. The spectral reflectance of multilayer coatings was studied, as a function of both the number and thickness of layers, and the range of maximum reflectance determined.
Please note that technical editing may introduce minor changes to the text and/or graphics contai... more Please note that technical editing may introduce minor changes to the text and/or graphics contained in the manuscript submitted by the author(s) which may alter content, and that the standard Terms & Conditions and the ethical guidelines that apply to the journal are still applicable. In no event shall the RSC be held responsible for any errors or omissions in these Accepted Manuscript manuscripts or any consequences arising from the use of any information contained in them.
Materials Letters, 2012
ABSTRACT Hybrid organically modified xerogels based on silica Si/Ca or Mg (90/10) content have be... more ABSTRACT Hybrid organically modified xerogels based on silica Si/Ca or Mg (90/10) content have been developed via a two step process with a pH sensitive dextran hydrogel. Doxorubicin hydrochloride (DOX) was coupled on the functionalized surface. The textural properties were optimized by ex vitro prediction of bioactivity and evaluation of drug release. The results indicated that the DOX-conjugated xerogels exhibited good apatite deposition properties after being soaked in Simulated Body Fluid (SBF) for 7 days. Furthermore, the DOX release study presented better behavior at pH = 4.5 in relation to neutral pH. The results of the present study are indicative of a promising scaffold for potential application as drug delivery vehicle for dual functionalities in bone cancer and bone repair.
Eurogel '91, 1992
Yttrium methoxyethoxide, barium methoxyethoxide and various copper(II) alkoxide groups were used ... more Yttrium methoxyethoxide, barium methoxyethoxide and various copper(II) alkoxide groups were used as precursors for the formation of YBa 2 Cu 3 O 7-δ stable sols in a 2-methoxyethanol / methyl ethyl ketone / toluene / diisopropyl ketone solvent system. Sol fractal dimensions were varied with the sol concentration and with the addition of pyridine. Strong correlation was found between the wettability and the fractal dimensions of the various precursors as determined by contact angle measurements. TI 2Ca 1 Ba 2 Cu 2 O 8+x and Tl 2 Ca 2 Ba 2 Cu 3 O 10+x superconductors were produced using a modified alkoxide sol-gel technique. TI-butoxide, Ca- and Ba- methoxyethoxide, and Cu(II) ethoxide were used as precursors. Complete solubility of the Cu component was accomplished by using the additive 2-dimethylethanolamine in a solvent system of 1-butanol, 2-methoxyethanol, methyl ethyl ketone, and toluene. Samples were produced by heating the sols under vacuum, prefiring the resulting gels to 525°C, pelletizing, and firing at 885°C in closed containers. T c (zero) values for these phases were 105 and 115 K with increases in these transitions occurring with firing times. Microstructural analysis revealed that a large degree of directional plate like crystal growth occurred on the surface of the pellets.
MRS Proceedings, 1987
ABSTRACTWe have synthesized orthorhombic phase YBa2Cu3O7−x superconductors by using metal alkoxid... more ABSTRACTWe have synthesized orthorhombic phase YBa2Cu3O7−x superconductors by using metal alkoxides. Cu (II) ethoxide was first partially dissolved in toluene, followed by the addition of Ba-methoxyethoxide and Y-methoxyethoxide in methoxyethanol to further enhance the solution solubility. A homogeneous gel-like paste was obtained both by adding water to the stock solution and by exposing it to the atmosphere. The gels were then vacuum dried and fired at 800 and 850°C in flowing O2. The superconducting transition temperature was 90 +K.
Thin Solid Films, 2004
... The simultaneous fitting of measured parameters of Δ and Ψ of SE between 400 ... Fig. 4. The ... more ... The simultaneous fitting of measured parameters of Δ and Ψ of SE between 400 ... Fig. 4. The models used in the ellipsometric fit for the TiO 2 (Cu) films deposited on glass (a,b,c) and for films deposited on SiO 2 /glass (d,e,f); (MSD-mean square differences). View Within Article. ...
Thin Solid Films, 1998
Ž. Very thin TiO films-100 nm were prepared by a sol-gel dip-coating process on glass substrates.... more Ž. Very thin TiO films-100 nm were prepared by a sol-gel dip-coating process on glass substrates. The films were characterized 2 with optical transmission measurements and atomic force microscopy. The optical properties of these films were analyzed within the w Ž. x Forouhi-Bloomer model, A. Forouhi, I. Bloomer, Phys. Rev., B34 1986 7018 , describing the optical dispersion in disordered dielectrics. Theoretical spectra were generated and fitted, using standard regression analysis techniques, to the experimental ones having as adjustable parameters, the five Forouhi-Bloomer physical model constants and the film thickness. It was found that the model describes satisfactorily the optical properties of very thin sol-gel TiO films within the range of 200-2500 nm. The energy difference 2 Ž between bonding-antibonding states was found to be approximately 4.3 eV, while the energy gap values as defined by the physical. model obtained, ranged between 2.8 and 3.2 eV. The energy gap values using Tauc's formula have also been estimated and found to be approximately 3.6 eV, slightly higher than other corresponding values found in the literature.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002
ABSTRACT N-type float zone (FZ) silicon doped with tin (2–10×1018cm−3) was irradiated by neutrons... more ABSTRACT N-type float zone (FZ) silicon doped with tin (2–10×1018cm−3) was irradiated by neutrons in a nuclear reactor (fluence of 1×1017cm−2 for 2 h). The irradiation-induced paramagnetic defects were studied by continuous wave (cw) and pulsed electron paramagnetic resonance (EPR) spectroscopy. The EPR measurements were carried out between liquid helium and room temperature. The two- and three-pulse electron spin echo envelope modulation (ESEEM) experiments were performed in order to inspect the hyperfine couplings between the electron spin and its surrounding nuclei. This study also revealed the existence of a weak coupling between the paramagnetic centre and nearby protons.
Journal of Non-Crystalline Solids, 2000
Journal of Non-Crystalline Solids, 2008
45S5 Bioglasses of the composition 46.1 SiO 2-2.6 P 2 O 5-26.9 CaO-(24.4 À x) Na 2 O-xMe 2 O (Me ... more 45S5 Bioglasses of the composition 46.1 SiO 2-2.6 P 2 O 5-26.9 CaO-(24.4 À x) Na 2 O-xMe 2 O (Me = Li or K) have been investigated using MAS NMR and MQ-MAS NMR methods. The analysis of the 29 Si MAS NMR spectrum revealed two lineshapes whose chemical shift is consistent with two silica Q n=2,3 species. The 31 P MAS NMR spectrum reveals the effect of both Na and Ca ions. The chemical shift of the observed 31 P signal is intermediate between those of Na 3 PO 4 (near 10 ppm) and Ca 3 (PO 4) 2 (near 3-0 ppm) species. The 23 Na MAS NMR spectra were observed in the alkali oxide composition: 24.4 Na 2 O, 12.2 Na 2 O-12.2 K 2 O and 12.2 Na 2 O-12.2 Li 2 O. The substitution of Na with Li or K was done to determine the extend of alteration of the glass structure. This goal was best accomplished by 23 Na MQ-MAS NMR. The two-dimensional spectra revealed three sites in the 24.4 mol% Na 2 O glass. These sites were not resolved in the 1D MAS NMR spectroscopy. In the mixed glasses, only two sites were obtained.
Journal of Non-Crystalline Solids, 1996
Gels in the system xMgO. (1-x)B20 3 (0.42 <x_< 0.80) have been prepared by hydrolytic polycondens... more Gels in the system xMgO. (1-x)B20 3 (0.42 <x_< 0.80) have been prepared by hydrolytic polycondensation of boron-butoxide with magnesium methoxide in alcoholic medium. The gels were heated at 400°C in order to obtain organic-free amorphous materials. The infrared spectra of these gels reveal the progressive modification of the borate network with increasing magnesium percentage. The X-ray diffraction patterns of the gels show that calcination at temperatures higher than 400°C leads to crystallization of the amorphous network. For the very high magnesium content glass (x = 0.80), evidence for magnesium carbonate formation is detected.
Journal of Non-Crystalline Solids, 1985
ABSTRACT Electron-spin-resonance(ESR)-spectra of unirradiated and 60Co γ-ray irradiated GeO2SiO2... more ABSTRACT Electron-spin-resonance(ESR)-spectra of unirradiated and 60Co γ-ray irradiated GeO2SiO2-fiber optic preform materials, densified (sintered) at 1550°C and 1625°C in air and in vacuum (10−6 Torr) for 75 min., were measured at 9.5 and 35 GHz and room temperature. The spectra of unirradiated preforms, densified in vacuum exhibit an asymmetric line due to the GeO2-E1′-center, [Ge(3)]. After irradiation the Ge(0)- and Ge(2)-germanium E1′ centers were observed with concentrations which depend upon the densification conditions. The Ge(0) center was observed in air as well as in vacuum sintered preform material. The Ge(2) center was observed only in vacuum densified preform material. Saturation of the defect center concentration is obtained at about 6 × 105 R. The total defect center concentration at constant irradiation dose increases with increasing temperature of densification [c(1625°C,air) = 724 × 1015 spins/g, c(1550 °C, air) = 330 × 1015 spins/g]. The defect center concentrations obtained in materials densified at 1550°C in air and in vacuum are equal within experimental errors.
Journal of Materials Chemistry, 1991
An alkoxide sol-gel route has been developed for producing YBa,Cu,O,_ ... Keywords: Oxide superco... more An alkoxide sol-gel route has been developed for producing YBa,Cu,O,_ ... Keywords: Oxide superconductor; Fractal; Sol-gel processing; Thin film ... 1. Introduction Processing of single-phase YBa,Cu,O, - x superconducting powder and oriented thin films has been a ...
Journal of Materials Chemistry, 1991
Bi-Sr-Ca-Cu-0 High-T, Superconductors produced by using a Rapid Thermal Melt Processing Technique... more Bi-Sr-Ca-Cu-0 High-T, Superconductors produced by using a Rapid Thermal Melt Processing Technique ... Byung M. Moon and George Kordas Science and Technology Center for Superconductivity, Materials Research Laboratory, Department of Materials Science and ...
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2016
To survey the preparation of novel hybrid microspheres of quaternary silicate glassy composition ... more To survey the preparation of novel hybrid microspheres of quaternary silicate glassy composition (SiO 2 AP 2 O 5 ACaOANa 2 O) and the prospect of using them as an osteogenic system with enhanced bioactive properties for the development of hydroxyapatite. Method: In line with our previous synthetic procedure a twostep process was followed, wherein polystyrene (PS) microspheres were prepared by the emulsifier free-emulsion polymerization method and constituted the core for the solgel coating of the silicate inorganic shell. The development of the hybrid microspheres was based on silane and phosphate precursors and was assesses at different ratio of ethanol/water (of 9/1, 4/1, and 2/1, in mL) and at varied ammonia concentration of 4.8-1.0 mL. Results: The hybrid microspheres had an average size ranged between 350 and 550 nm according to SEM, depending on the ethanol/water solution rate and ammonia content. The final microspheres probably exhibited a porous-like structure through the formation of diffused voids along with the low carbon content of the EDX analysis, which could be regulated by the catalyst content. The hybrid microspheres exhibited effective in vitro bioactivity assessed in simulated body fluids (SBF). Conclusion: Quaternary hybrid silica microspheres were effectively synthesized. The bioassay evaluation of the final microspheres revealed the rapid in vitro formation of a bone-like apatite layer. The results verify the bioactivity of the microspheres and promote further research of their suitability on regenerative treatment of bone abnormalities. V
Physics and Chemistry of Glasses, Sep 30, 2000
Glasses of composition (100-x) mol% B 2 O 3 . x mol% Li 2 O have been subjected to γ-irradiation ... more Glasses of composition (100-x) mol% B 2 O 3 . x mol% Li 2 O have been subjected to γ-irradiation at room temperature and subsequently studied by cw-EPR, 1D-ESEEM, 2D-HYSCORE and pulsed ENDOR spectroscopies at 20 K. The cw-EPR spectrum of a-B 2 O 3 have been simulated. Pulsed ENDOR revealed a strong coupling for a-B 2 O 3 , A weaker coupling was detected by HYSCORE and pulsed ENDOR spectroscopies. HYSCORE spectroscopy determined two weak hyperfine couplings when recorded with a τ-value of 248 and 168 ns, respectively. The cw-EPR spectra of the (100-x) mol% B 2 O and x mol% Li 2 O glasses revealed a strong dependence of their line shape on x. SCF-HF calculations have been employed to determine the hfs couplings produced by ring structures such as boroxol rings, boron oxygen hole centre (BOHC), pentaborate, diborate, tetraborate and borate network with nonbridging atoms (NBO). Data obtained by cw-EPR, pulsed ENDOR and HYSCORE spectroscopies can be explained assuming only boroxol rings to be present in a-B 2 O 3 . The variation of the cw-EPR signal with the composition, x, can be attributed to the formation of various ring structures.
Journal of Colloid and Interface Science, 2014
Hypothesis: Dual-modality imaging agents, such as radiolabeled iron oxide nanoparticles (IO-NPs),... more Hypothesis: Dual-modality imaging agents, such as radiolabeled iron oxide nanoparticles (IO-NPs), are promising candidates for cancer diagnosis and therapy. We developed and evaluated aminosilane coated Fe 3 O 4 (10 ± 2 nm) as a tumor imaging agent in nuclear medicine through 3-aminopropyltriethoxysilane (APTES) functionalization. We evaluated this multimeric system of targeted 99m Tc-labeled nanoparticles (NPs) conjugated with a new RGD derivate (cRGDfK-Orn 3-CGG), characterized as NPs-RGD as a potential thermal therapy delivery vehicle. Experiments: Transmission Electron Microscopy (TEM) and spectroscopy techniques were used to characterize the IO-NPs indicating their functionalization with peptides. Radiolabeled IO-NPs (targeted, non-targeted) were evaluated with regard to their radiochemical, radiobiological and imaging characteristics. In vivo studies were performed in normal and a m b 3-positive tumor (U87MG glioblastoma) bearing mice. We also demonstrated that this system could reach ablative temperatures in vivo. Findings: Both radiolabeled IO-NPs were obtained in high radiochemical yield (>98%) and proved stable in vitro. The in vivo studies for both IO-NPs have shown significant liver and spleen uptake at all examined time points in normal and U87MG glioblastoma tumor-bearing mice, due to their colloidal nature. We have confirmed through in vivo biodistribution studies that the non-targeted 99m Tc-NPs poorly internalized in the tumor, while the targeted 99m Tc-NPs-RGD, present 9-fold higher tumor accumulation at 1 h p.i. Accumulation of both IO-NPs in other organs was negligible. Blocking experiments indicated target specificity for integrin receptors in U87MG glioblastoma cells. The preliminary in vivo study of applied alternating magnetic field showed that the induced hyperthermia is feasible due to the aid of IO-NPs.
Journal of Nanoparticle Research, 2013
This study is focused on the production of hollow nanospheres that reveal antibacterial action. C... more This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 ± 15 and 221 ± 10 nm, respectively, were synthesized using emulsion polymerization and the sol-gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue-black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.
Journal of Drug Delivery Science and Technology, 2021
Journal of Drug Delivery Science and Technology, 2020
Abstract Polymeric materials are in the epicenter of scientific research the last decade and have... more Abstract Polymeric materials are in the epicenter of scientific research the last decade and have been used in a range of pharmaceutical and biological applications. Multifunctional polymeric materials are capable targeting agents, which can be used as controlled drug release vehicles for the enhancement of therapeutic efficacy, as well as for diagnostic purposes. A newer generation of these smart polymeric entities constitutes of smart nanocontainers (NCs), which can navigate the drug to specific areas by avoiding random distribution, and thus resulting in drug toxicity reduction. The combination of pH, thermo and redox sensitivity of the multi stimuli NCs can help to achieve specific release of the drug in the tumor area, where these sensitivity parameters can be observed. Hollow polymeric multi stimuli fluorescent tNCs based on N-(2-Hydroxypropyl)methacrylamide (HPMA) were successfully functionalized with a specific targeting moiety; folic acid, and then characterized morphologically, by scanning electron and transmission electron microscopy, as well as structurally, by Fourier-transform infrared spectroscopy. Their targeting mechanism was investigated in vitro in cervical cancer cell lines and in vivo in tumor bearing mice. According to our results the folic acid functionalized NCs targeted HeLa cells’ surface within the first 30 min of treatment. Human tumor xenografted mice (nonobese diabetic/severe combined immunodeficient) were injected with folate functionalized NCs and their tumor uptake was estimated by γ-imaging at about 3.5%. The targeting efficiency of the folate functionalized NCs was investigated directly in vivo by γ-imaging and indirectly by a tumor efficacy protocol.
Materials Letters, 1995
Multilayer, wavelength-selective reflective coatings have been prepared by alternating deposition... more Multilayer, wavelength-selective reflective coatings have been prepared by alternating deposition of TiOa and Si02 layers from solutions. Appropriate alkoxide solutions in ethanol were used as starting materials. The thickness of each layer, the profile of the coatings and the diffusion effects between multilayers were examined by the Rutherford back scattering method, using "C ion scattering. The spectral reflectance of multilayer coatings was studied, as a function of both the number and thickness of layers, and the range of maximum reflectance determined.
Please note that technical editing may introduce minor changes to the text and/or graphics contai... more Please note that technical editing may introduce minor changes to the text and/or graphics contained in the manuscript submitted by the author(s) which may alter content, and that the standard Terms & Conditions and the ethical guidelines that apply to the journal are still applicable. In no event shall the RSC be held responsible for any errors or omissions in these Accepted Manuscript manuscripts or any consequences arising from the use of any information contained in them.
Materials Letters, 2012
ABSTRACT Hybrid organically modified xerogels based on silica Si/Ca or Mg (90/10) content have be... more ABSTRACT Hybrid organically modified xerogels based on silica Si/Ca or Mg (90/10) content have been developed via a two step process with a pH sensitive dextran hydrogel. Doxorubicin hydrochloride (DOX) was coupled on the functionalized surface. The textural properties were optimized by ex vitro prediction of bioactivity and evaluation of drug release. The results indicated that the DOX-conjugated xerogels exhibited good apatite deposition properties after being soaked in Simulated Body Fluid (SBF) for 7 days. Furthermore, the DOX release study presented better behavior at pH = 4.5 in relation to neutral pH. The results of the present study are indicative of a promising scaffold for potential application as drug delivery vehicle for dual functionalities in bone cancer and bone repair.
Eurogel '91, 1992
Yttrium methoxyethoxide, barium methoxyethoxide and various copper(II) alkoxide groups were used ... more Yttrium methoxyethoxide, barium methoxyethoxide and various copper(II) alkoxide groups were used as precursors for the formation of YBa 2 Cu 3 O 7-δ stable sols in a 2-methoxyethanol / methyl ethyl ketone / toluene / diisopropyl ketone solvent system. Sol fractal dimensions were varied with the sol concentration and with the addition of pyridine. Strong correlation was found between the wettability and the fractal dimensions of the various precursors as determined by contact angle measurements. TI 2Ca 1 Ba 2 Cu 2 O 8+x and Tl 2 Ca 2 Ba 2 Cu 3 O 10+x superconductors were produced using a modified alkoxide sol-gel technique. TI-butoxide, Ca- and Ba- methoxyethoxide, and Cu(II) ethoxide were used as precursors. Complete solubility of the Cu component was accomplished by using the additive 2-dimethylethanolamine in a solvent system of 1-butanol, 2-methoxyethanol, methyl ethyl ketone, and toluene. Samples were produced by heating the sols under vacuum, prefiring the resulting gels to 525°C, pelletizing, and firing at 885°C in closed containers. T c (zero) values for these phases were 105 and 115 K with increases in these transitions occurring with firing times. Microstructural analysis revealed that a large degree of directional plate like crystal growth occurred on the surface of the pellets.
MRS Proceedings, 1987
ABSTRACTWe have synthesized orthorhombic phase YBa2Cu3O7−x superconductors by using metal alkoxid... more ABSTRACTWe have synthesized orthorhombic phase YBa2Cu3O7−x superconductors by using metal alkoxides. Cu (II) ethoxide was first partially dissolved in toluene, followed by the addition of Ba-methoxyethoxide and Y-methoxyethoxide in methoxyethanol to further enhance the solution solubility. A homogeneous gel-like paste was obtained both by adding water to the stock solution and by exposing it to the atmosphere. The gels were then vacuum dried and fired at 800 and 850°C in flowing O2. The superconducting transition temperature was 90 +K.
Thin Solid Films, 2004
... The simultaneous fitting of measured parameters of Δ and Ψ of SE between 400 ... Fig. 4. The ... more ... The simultaneous fitting of measured parameters of Δ and Ψ of SE between 400 ... Fig. 4. The models used in the ellipsometric fit for the TiO 2 (Cu) films deposited on glass (a,b,c) and for films deposited on SiO 2 /glass (d,e,f); (MSD-mean square differences). View Within Article. ...
Thin Solid Films, 1998
Ž. Very thin TiO films-100 nm were prepared by a sol-gel dip-coating process on glass substrates.... more Ž. Very thin TiO films-100 nm were prepared by a sol-gel dip-coating process on glass substrates. The films were characterized 2 with optical transmission measurements and atomic force microscopy. The optical properties of these films were analyzed within the w Ž. x Forouhi-Bloomer model, A. Forouhi, I. Bloomer, Phys. Rev., B34 1986 7018 , describing the optical dispersion in disordered dielectrics. Theoretical spectra were generated and fitted, using standard regression analysis techniques, to the experimental ones having as adjustable parameters, the five Forouhi-Bloomer physical model constants and the film thickness. It was found that the model describes satisfactorily the optical properties of very thin sol-gel TiO films within the range of 200-2500 nm. The energy difference 2 Ž between bonding-antibonding states was found to be approximately 4.3 eV, while the energy gap values as defined by the physical. model obtained, ranged between 2.8 and 3.2 eV. The energy gap values using Tauc's formula have also been estimated and found to be approximately 3.6 eV, slightly higher than other corresponding values found in the literature.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002
ABSTRACT N-type float zone (FZ) silicon doped with tin (2–10×1018cm−3) was irradiated by neutrons... more ABSTRACT N-type float zone (FZ) silicon doped with tin (2–10×1018cm−3) was irradiated by neutrons in a nuclear reactor (fluence of 1×1017cm−2 for 2 h). The irradiation-induced paramagnetic defects were studied by continuous wave (cw) and pulsed electron paramagnetic resonance (EPR) spectroscopy. The EPR measurements were carried out between liquid helium and room temperature. The two- and three-pulse electron spin echo envelope modulation (ESEEM) experiments were performed in order to inspect the hyperfine couplings between the electron spin and its surrounding nuclei. This study also revealed the existence of a weak coupling between the paramagnetic centre and nearby protons.
Journal of Non-Crystalline Solids, 2000
Journal of Non-Crystalline Solids, 2008
45S5 Bioglasses of the composition 46.1 SiO 2-2.6 P 2 O 5-26.9 CaO-(24.4 À x) Na 2 O-xMe 2 O (Me ... more 45S5 Bioglasses of the composition 46.1 SiO 2-2.6 P 2 O 5-26.9 CaO-(24.4 À x) Na 2 O-xMe 2 O (Me = Li or K) have been investigated using MAS NMR and MQ-MAS NMR methods. The analysis of the 29 Si MAS NMR spectrum revealed two lineshapes whose chemical shift is consistent with two silica Q n=2,3 species. The 31 P MAS NMR spectrum reveals the effect of both Na and Ca ions. The chemical shift of the observed 31 P signal is intermediate between those of Na 3 PO 4 (near 10 ppm) and Ca 3 (PO 4) 2 (near 3-0 ppm) species. The 23 Na MAS NMR spectra were observed in the alkali oxide composition: 24.4 Na 2 O, 12.2 Na 2 O-12.2 K 2 O and 12.2 Na 2 O-12.2 Li 2 O. The substitution of Na with Li or K was done to determine the extend of alteration of the glass structure. This goal was best accomplished by 23 Na MQ-MAS NMR. The two-dimensional spectra revealed three sites in the 24.4 mol% Na 2 O glass. These sites were not resolved in the 1D MAS NMR spectroscopy. In the mixed glasses, only two sites were obtained.
Journal of Non-Crystalline Solids, 1996
Gels in the system xMgO. (1-x)B20 3 (0.42 <x_< 0.80) have been prepared by hydrolytic polycondens... more Gels in the system xMgO. (1-x)B20 3 (0.42 <x_< 0.80) have been prepared by hydrolytic polycondensation of boron-butoxide with magnesium methoxide in alcoholic medium. The gels were heated at 400°C in order to obtain organic-free amorphous materials. The infrared spectra of these gels reveal the progressive modification of the borate network with increasing magnesium percentage. The X-ray diffraction patterns of the gels show that calcination at temperatures higher than 400°C leads to crystallization of the amorphous network. For the very high magnesium content glass (x = 0.80), evidence for magnesium carbonate formation is detected.
Journal of Non-Crystalline Solids, 1985
ABSTRACT Electron-spin-resonance(ESR)-spectra of unirradiated and 60Co γ-ray irradiated GeO2SiO2... more ABSTRACT Electron-spin-resonance(ESR)-spectra of unirradiated and 60Co γ-ray irradiated GeO2SiO2-fiber optic preform materials, densified (sintered) at 1550°C and 1625°C in air and in vacuum (10−6 Torr) for 75 min., were measured at 9.5 and 35 GHz and room temperature. The spectra of unirradiated preforms, densified in vacuum exhibit an asymmetric line due to the GeO2-E1′-center, [Ge(3)]. After irradiation the Ge(0)- and Ge(2)-germanium E1′ centers were observed with concentrations which depend upon the densification conditions. The Ge(0) center was observed in air as well as in vacuum sintered preform material. The Ge(2) center was observed only in vacuum densified preform material. Saturation of the defect center concentration is obtained at about 6 × 105 R. The total defect center concentration at constant irradiation dose increases with increasing temperature of densification [c(1625°C,air) = 724 × 1015 spins/g, c(1550 °C, air) = 330 × 1015 spins/g]. The defect center concentrations obtained in materials densified at 1550°C in air and in vacuum are equal within experimental errors.
Journal of Materials Chemistry, 1991
An alkoxide sol-gel route has been developed for producing YBa,Cu,O,_ ... Keywords: Oxide superco... more An alkoxide sol-gel route has been developed for producing YBa,Cu,O,_ ... Keywords: Oxide superconductor; Fractal; Sol-gel processing; Thin film ... 1. Introduction Processing of single-phase YBa,Cu,O, - x superconducting powder and oriented thin films has been a ...
Journal of Materials Chemistry, 1991
Bi-Sr-Ca-Cu-0 High-T, Superconductors produced by using a Rapid Thermal Melt Processing Technique... more Bi-Sr-Ca-Cu-0 High-T, Superconductors produced by using a Rapid Thermal Melt Processing Technique ... Byung M. Moon and George Kordas Science and Technology Center for Superconductivity, Materials Research Laboratory, Department of Materials Science and ...