The influence of magnetic nanoparticle concentration with dextran polymers in agar gel on heating efficiency in magnetic hyperthermia

The article presents the results of research on the effect of magnetic hyperthermia performed on agar gel samples containing magnetite nanoparticles coated with dextran polymers for different molar weight M (150 kDa, 70 kDa, and 40 kDa). Regardless of the difference in molar dextran weights, these samples differed in a mass concentration of nanoparticles in the ferrogel C 0 (1.602 mg/cm 3, 2.506 mg/cm 3, 3.311 mg/cm 3, and 4.218 mg/cm 3). In the case of the highest magnetic field value H (20 kA·m −1), the specific loss power SPL reaches 70 W·g −1 for nanoparticles with 150 kDa dextran at a concentration of nanoparticles C 0 = 1.602 mg/cm 3. An oscillating magnetic field with an amplitude up to 20 kA·m −1 and a frequency of 357 kHz was used in the study

Effect of Nb doping on structural, optical and photocatalytic properties of flame-made TiO2 nanopowder

TiO2:Nb nanopowders within a dopant concentration in the range of 0.1-15at.% were prepared by one-step flame spray synthesis. Effect of niobium doping on structural, optical and photocatalytic properties of titanium dioxide nanopowders was studied. Morphology and structure were investigated by means of Brunauer-Emmett-Teller isotherm, X-ray diffraction and transmission electron microscopy. Diffuse reflectance and the resulting band gap energy were determined by diffuse reflectance spectroscopy. Photocatalytic activity of the investigated nanopowders was revised for the photodecomposition of methylene blue (MB), methyl orange (MO) and 4-chlorophenol under UVA and VIS light irradiation. Commercial TiO2-P25 nanopowder was used as a reference. The specific surface area of the powders was ranging from 42.9m2/g for TiO2:0.1at.% Nb to 90.0m2/g for TiO2:15at.% Nb. TiO2:Nb particles were nanosized, spherically shaped and polycrystalline. Anatase was the predominant phase in all samples. The anatase-related transition was at 3.31eV and rutile-related one at 3.14eV. TiO2:Nb nanopowders exhibited additional absorption in the visible range. In comparison to TiO2-P25, improved photocatalytic activity of TiO2:Nb was observed for the degradation of MB and MO under both UVA and VIS irradiation, where low doping level (Nb < 1at.%) was the most effective. Niobium doping affected structural, optical and photocatalytic properties of TiO2. Low dopant level enhanced photocatalytic performance under UVA and VIS irradiation. Therefore, TiO2:Nb (Nb < 1at.%) can be proposed as an efficient selective solar light photocatalys

New metal oxide nanoparticles for gas sensors

Tyt. z ekranu tytułowego.Promotor: Mieczysław Rękas, Artur Braun.Niepublikowana praca doktorska.Praca doktorska. Akademia Górniczo-Hutnicza im. Stanisława Staszica (Kraków), 2013.Zawiera bibliogr.Dostępna także w wersji drukowanej.Tryb dostępu: Internet.Semiconductor metal oxide, MOx, based gas sensors, review of research on metal oxide based gas sensors, gas sensing semiconductor metal oxide nanoparticles, technology from the perspective of nanotechnology, metal oxide nanoparticles for gas sensing application, electronic structure, optical properties of semiconductor metal oxides, non-stoichiometry, surface properties of MOx vs. electrical properties, gas sensing behavior, defect chemistry of Fe2O3, general model, basic principles of the interaction of gas molecules with the semiconductor metal oxides, electronic band structure of n-type and p-type semiconductor MOx upon oxidizing, acceptor type, reducing, donor type, gas molecules, interaction of oxygen gas molecules with n-type semiconductor metal oxides, interaction of reducing gas molecules with n-type semiconductor metal oxides, interaction of ammonia gas molecules with n-type semiconductor metal oxides, influence of the crystallite/grain size on the sensing mechanism, effect of the water vapor molecules on the conductivity of semiconductor metal oxides, flame spray synthesis of metal oxide nanoparticles, experimental methods, determination of the crystal structure, morphology, XRD, BET, TEM, characterization of the surface chemical composition and stoichiometry, XPS, resonant EBS, investigation of the electronic structure, NEXAFS, in-situ observation of the chemical interaction of the oxygen and hydrogen molecules at the surface and the electronic structure of the metal oxides, AP-XPS, AP-NEXAFS, determination of the optical band gap, DRS, investigation of the nature of the electrical transport properties, EIS, evaluation of the gas sensing performance towards hydrogen and ammonia detection, DC measurements, un-modified and Ti-modified Fe2O3 nanoparticles, crystal structure, morphology, band gap, DRS optical measurements, chemical composition, electronic structure, XPS, resonant EBS, effect of oxidizing, reducing processing conditions on the chemical composition, electronic structure of Fe2O3 nanoparticles, effect of Ti-modification on the chemical composition, electronic structure of Fe2O3 nanoparticles, electronic structure under UHV conditions - NEXAFS, in-situ observations of the surface chemistry, electronic structure of Fe2O3 nanoparticles -AP-XPS, in-situ observations of the surface chemistry and electronic structure of Fe2O3 nanoparticles - AP-NEXAFS, electrical properties - EIS, gas sensing performance, TiO2, ZnO, SnO2 nanoparticles, crystal structure, morphology, band gap - DRS optical measurements, chemical composition, electronic structure - XPS, resonant EBS, effect of oxidizing, reducing processing conditions on the chemical composition, electronic structure of MOx nanoparticles, tungsten trioxide WO3, crystal structure, morphology, band gap - DRS optical measurements, chemical composition and electronic structure - XPS, resonant EBS, effect of oxidizing and reducing processing conditions on the chemical composition, electronic structure of WO3 nanoparticles, electronic structure under UHV conditions - NEXAFS, impedance behavior under H2, NH3, effect of temperatur

New metal oxide nanoparticles for gas sensors ph.d. thesis /

Tyt. z ekranu tytułowego.Praca doktorska. Akademia Górniczo-Hutnicza im. Stanisława Staszica (Kraków), 2013.Zawiera bibliogr.Dostępna także w wersji drukowanej.Tryb dostępu: Internet.Semiconductor metal oxide, MOx, based gas sensors, review of research on metal oxide based gas sensors, gas sensing semiconductor metal oxide nanoparticles, technology from the perspective of nanotechnology, metal oxide nanoparticles for gas sensing application, electronic structure, optical properties of semiconductor metal oxides, non-stoichiometry, surface properties of MOx vs. electrical properties, gas sensing behavior, defect chemistry of Fe2O3, general model, basic principles of the interaction of gas molecules with the semiconductor metal oxides, electronic band structure of n-type and p-type semiconductor MOx upon oxidizing, acceptor type, reducing, donor type, gas molecules, interaction of oxygen gas molecules with n-type semiconductor metal oxides, interaction of reducing gas molecules with n-type semiconductor metal oxides, interaction of ammonia gas molecules with n-type semiconductor metal oxides, influence of the crystallite/grain size on the sensing mechanism, effect of the water vapor molecules on the conductivity of semiconductor metal oxides, flame spray synthesis of metal oxide nanoparticles, experimental methods, determination of the crystal structure, morphology, XRD, BET, TEM, characterization of the surface chemical composition and stoichiometry, XPS, resonant EBS, investigation of the electronic structure, NEXAFS, in-situ observation of the chemical interaction of the oxygen and hydrogen molecules at the surface and the electronic structure of the metal oxides, AP-XPS, AP-NEXAFS, determination of the optical band gap, DRS, investigation of the nature of the electrical transport properties, EIS, evaluation of the gas sensing performance towards hydrogen and ammonia detection, DC measurements, un-modified and Ti-modified Fe2O3 nanoparticles, crystal structure, morphology, band gap, DRS optical measurements, chemical composition, electronic structure, XPS, resonant EBS, effect of oxidizing, reducing processing conditions on the chemical composition, electronic structure of Fe2O3 nanoparticles, effect of Ti-modification on the chemical composition, electronic structure of Fe2O3 nanoparticles, electronic structure under UHV conditions - NEXAFS, in-situ observations of the surface chemistry, electronic structure of Fe2O3 nanoparticles -AP-XPS, in-situ observations of the surface chemistry and electronic structure of Fe2O3 nanoparticles - AP-NEXAFS, electrical properties - EIS, gas sensing performance, TiO2, ZnO, SnO2 nanoparticles, crystal structure, morphology, band gap - DRS optical measurements, chemical composition, electronic structure - XPS, resonant EBS, effect of oxidizing, reducing processing conditions on the chemical composition, electronic structure of MOx nanoparticles, tungsten trioxide WO3, crystal structure, morphology, band gap - DRS optical measurements, chemical composition and electronic structure - XPS, resonant EBS, effect of oxidizing and reducing processing conditions on the chemical composition, electronic structure of WO3 nanoparticles, electronic structure under UHV conditions - NEXAFS, impedance behavior under H2, NH3, effect of temperatur

Effect of Nb doping on structural, optical and photocatalytic properties of flame-made TiO2 nanopowder

TiO2:Nb nanopowders within a dopant concentration in the range of 0.1-15 at.% were prepared by one-step flame spray synthesis. Effect of niobium doping on structural, optical and photocatalytic properties of titanium dioxide nanopowders was studied. Morphology and structure were investigated by means of Brunauer–Emmett–Teller isotherm, X-ray diffraction and transmission electron microscopy. Diffuse reflectance and the resulting band gap energy were determined by diffuse reflectance spectroscopy. Photocatalytic activity of the investigated nanopowders was revised for the photodecomposition of methylene blue (MB), methyl orange (MO) and 4-chlorophenol under UVA and VIS light irradiation. Commercial TiO2-P25 nanopowder was used as a reference. The specific surface area of the powders was ranging from 42.9 m2/g for TiO2:0.1 at.% Nb to 90.0 m2/g for TiO2:15 at.% Nb. TiO2:Nb particles were nanosized, spherically shaped and polycrystalline. Anatase was the predominant phase in all samples. The anatase-related transition was at 3.31 eV and rutile-related one at 3.14 eV. TiO2:Nb nanopowders exhibited additional absorption in the visible range. In comparison to TiO2-P25, improved photocatalytic activity of TiO2:Nb was observed for the degradation of MB and MO under both UVA and VIS irradiation, where low doping level (Nb < 1 at.%) was the most effective. Niobium doping affected structural, optical and photocatalytic properties of TiO2. Low dopant level enhanced photocatalytic performance under UVA and VIS irradiation. Therefore, TiO2:Nb (Nb < 1 at.%) can be proposed as an efficient selective solar light photocatalyst

Iron Resonant Photoemission Spectroscopy on Anodized Hematite Points to Electron Hole Doping during Anodization

Anodization of a-Fe2O3 (hematite) electrodes in alkaline electrolyte under constant potential conditions the electrode surface in a way that an additional current wave occurs in the cyclic voltammogram. The energy position of this current wave is closely below the potential of the anodization treatment. Continued cycling or exchanging of the electrolyte causes depletion of this new feature. The O 1s and Fe 2p core-level X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra of such conditioned hematite exhibit a chemical shift towards higher binding energies, in line with the general perception that anodization generates oxide species with dielectric properties. The valence band XPS and particularly the iron resonant valence band photoemission spectra, however, are shifted towards the opposite direction, that is, towards the Fermi energy, suggesting that hole doping on hematite has taken place during anodization. Quantitative analysis of the Fe 2p resonant valence band photoemission spectra shows that the spectra obtained at the Fe 2p absorption threshold are shifted by virtually the same energy as the anodization potential towards the Fermi energy. The tentative interpretation of this observation is that anodization forms a surface film on the hematite that is specific to the anodization potential