Near-band-gap luminescence from TiO2 nanograss–nanotube hierarchical membranes

2015 ◽  
Vol 93 (1) ◽  
pp. 106-112 ◽  
Author(s):  
Lijia Liu ◽  
Jun Li ◽  
Tsun-Kong Sham
Keyword(s):  
Anatase Phase ◽  
Rutile Phase ◽  
Electrochemical Anodization ◽  
Metal Foil ◽  
Green Luminescence ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Optical Luminescence ◽  
Uv Luminescence ◽  
X Ray Absorption

Freestanding TiO2 nanograss–nanotube hierarchical membranes are synthesized from a Ti metal foil by electrochemical anodization. It is found that the two nanostructures exhibit different luminescence properties, which are also affected by the crystal phases upon phase transformation. An unusual near-UV luminescence is observed from the amorphous nanograss, which is found to be excitation element specific. The amorphous nanotube shows no luminescence. Upon calcination, both nanograss and nanotubes are crystalized into the anatase phase with some rutile phase present, and both structures emit visible green luminescence at slightly different energies. The luminescence mechanism is explored using UV–vis spectroscopy, X-ray absorption near-edge structures (XANES), and X-ray excited optical luminescence (XEOL), and its implications are presented.

Structural, Optical and Magnetic Properties of Nanocrystalline Cobalt Doped TiO2 Prepared by Sol-Gel Route

2013 ◽  
Vol 24 ◽  
pp. 168-175
Author(s):  
Kirit S. Siddhapara ◽  
D.V. Shah
Keyword(s):  
Magnetic Properties ◽  
Anatase Phase ◽  
Sol Gel ◽  
Photo Luminescence ◽  
Rutile Phase ◽  
Gravimetric Analysis ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Drying Treatment

Nanocrystalline Cobalt-doped TiO2was prepared by Sol-Gel technique, followed by freeze-drying treatment at-30°C temperature for 12hrs. The obtained Gel was thermally treated at 200,400,600, 800°C. 1%, 2% and 4% Cobalt doped TiO2nanopowder has been prepared X-ray Powder Diffraction (XRD), Scanning Electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), was used to study its structural properties. The XRD pattern shows the coexistence of anatase phase and rutile phase. Thermal gravimetric analysis shows Cobalt concentration affects thermal decomposition. UV-Vis Spectroscopy, Photo luminescence (PL), was used to study its Optical properties. Optical Bandgap were calculated with the incorporation of different concentration of cobalt. UV-Visible spectroscopy show variation in band gap for the sample treated at different temperature for same concentration. All Cobalt doped TiO2nanostructures shows an appearance of Red shift relative to the bulk TiO2. The determination of magnetic properties was also carried out by Vibrating Sample Magnetometer.

scholarly journals Tm-doped TiO2 and Tm2Ti2O7 pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

2015 ◽  
Vol 6 ◽  
pp. 605-616 ◽  
Author(s):  
Desiré M De los Santos ◽  
Javier Navas ◽  
Teresa Aguilar ◽  
Antonio Sánchez-Coronilla ◽  
Concha Fernández-Lorenzo ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Anatase Phase ◽  
Pyrochlore Phase ◽  
Rutile Phase ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Controlled Hydrolysis

Tm-doped TiO2 nanoparticles were synthesized using a water-controlled hydrolysis reaction. Analysis was performed in order to determine the influence of the dopant concentration and annealing temperature on the phase, crystallinity, and electronic and optical properties of the resulting material. Various characterization techniques were utilized such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and UV–vis spectroscopy. For the samples annealed at 773 and 973 K, anatase phase TiO2 was obtained, predominantly internally doped with Tm3+. ICP–AES showed that a doping concentration of up to 5.8 atom % was obtained without reducing the crystallinity of the samples. The presence of Tm3+ was confirmed by X-ray photoelectron spectroscopy and UV–vis spectroscopy: the incorporation of Tm3+ was confirmed by the generation of new absorption bands that could be assigned to Tm3+ transitions. Furthermore, when the samples were annealed at 1173 K, a pyrochlore phase (Tm2Ti2O7) mixed with TiO2 was obtained with a predominant rutile phase. The photodegradation of methylene blue showed that this pyrochlore phase enhanced the photocatalytic activity of the rutile phase.

scholarly journals Tuning Anatase-Rutile Phase Transition Temperature: TiO2/SiO2 Nanoparticles Applied in Dye-Sensitized Solar Cells

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Billy N. Cardoso ◽  
Emerson C. Kohlrausch ◽  
Marina T. Laranjo ◽  
Edilson V. Benvenutti ◽  
Naira M. Balzaretti ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Surface Area ◽  
Phase Transition Temperature ◽  
Dye Sensitized Solar Cells ◽  
Rutile Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Molar Percent

TiO2/SiO2 nanoparticles with 3, 5, and 10 molar percent of silica, were synthesized by hydrothermal method and characterized by SEM, TEM, N2 adsorption-desorption isotherms, X-ray diffraction, and Raman and UV-Vis spectroscopy. While pristine TiO2 thermally treated at 500°C presents a surface area of 36 m2 g-1 (±10 m2 g-1), TiO2/SiO2 containing 3, 5, and 10 molar percent of silica present surface areas of 93, 124, and 150 m2 g-1 (±10 m2 g-1), respectively. SiO2 is found to form very small amorphous domains well dispersed in the TiO2 matrix. X-ray diffraction and Raman spectroscopy data show that anatase-to-rutile phase transition temperature is delayed by the presence of SiO2, enabling single-anatase phase photoanodes for DSSCs. According to the I×V measurements, photoanodes with 3% of SiO2 result in improved efficiency, which is mainly related to increased surface area and dye loading. In addition, the results suggest a gain in photocurrent related to the passivation of defects by SiO2.

Optical and Electrical Properties of TiO2 Nanotubes Grown by Titanium Anodization

2009 ◽  
Vol 1178 ◽  
Author(s):  
Yahya Alivov ◽  
Vladimir Kuryatkov ◽  
Mahesh Pandikunta ◽  
Gautam Rajanna ◽  
Daniel Johnstone ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electrical Properties ◽  
Tio2 Nanotubes ◽  
Anatase Phase ◽  
Rutile Phase ◽  
Electrochemical Anodization ◽  
Voltage Range ◽  
Wide Range ◽  
Transient Spectroscopy ◽  
Tio2 Nts

AbstractIn this work we investigated the structural, electrical, and optical properties of titanium dioxide (TiO2) nanotubes (NTs) formed by electrochemical anodization of Ti metal sheets in NH4F+glycerol electrolyte at different anodization voltages (Va) and acid concentrations. Our results revealed that TiO2 NTs can be grown in a wide range of anodization voltages from 10 V to 240 V. The maximum NH4F acid concentration, at which NTs can be formed, decreases with the anodization voltage, which is 0.7% for Va<60V, and decreases to 0.1% at Va =240 V. Glancing angle X-ray diffraction (GAXRD) experiments show that as-grown amorphous TiO2 transforms to anatase phase after annealing at 400 oC, and further transforms to rutile phase at annealing temperatures above 500 oC. Samples grown in 30-120 voltage range have higher crystal quality as seen from anatase (101) peak intensity and reduced linewidth. The electrical resistivity of the NTs varies with Va concentration and increases by eight orders of magnitude when Va increases from 10 V to 240 V. This is consistent with cathodoluminescense studies which showed improved optical properties for samples grown in this voltage range. Optical properties of samples were also studied by low temperature photoluminescence. Temperature dependent I-V and photo-induced current transient spectroscopy were employed to analyze electrical properties and defect structure on NT samples.

VUV- and Soft X-Ray-Induced Optical Luminescence and X-Ray Absorption Fine Structures of Porous Silicon

1992 ◽  
Vol 281 ◽  
Author(s):  
T. K. Sham ◽  
D. T. Jiang ◽  
I. Coulthard ◽  
J. W. Lorimer ◽  
X. H. Feng ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Total Electron Yield ◽  
Total Electron ◽  
X Ray ◽  
Absorption Fine ◽  
Electron Yield ◽  
Optical Luminescence ◽  
Fine Structures ◽  
X Ray Absorption ◽  
Uv Excitation

ABSTRACTOptical luminescence in porous silicon induced by soft X-ray and vacuum UV excitation with energies in the vicinity of the Si K-edge (1838 eV) and the Si L-edge (99 eV) has been observed. The luminescence has been used, together with total electron yield, to record X-ray absorption fine structure (XAFS) in the near-edge region of both Si edges. The near- edge spectra recorded simultaneously with either luminescence or total electron yield were compared, and the implications of these measurements for the structure of porous silicon are discussed.

scholarly journals Niobium Uptake and Release by Bacterial Ferric Ion Binding Protein

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
Yanbo Shi ◽  
Ian Harvey ◽  
Dominic Campopiano ◽  
Peter J. Sadler
Keyword(s):  
Iron Uptake ◽  
Pathogenic Bacteria ◽  
Ion Binding ◽  
Ferric Ion ◽  
Gram Negative Bacteria ◽  
Icp Oes ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Binding Cleft ◽  
X Ray Absorption

Ferric ion binding proteins (Fbps) transportFeIIIacross the periplasm and are vital for the virulence of many Gram negative bacteria. Iron(III) is tightly bound in a hinged binding cleft with octahedral coordination geometry involving binding to protein side chains (including tyrosinate residues) together with a synergistic anion such as phosphate. Niobium compounds are of interest for their potential biological activity, which has been little explored. We have studied the binding of cyclopentadienyl and nitrilotriacetatoNbVcomplexes to the Fbp fromNeisseria gonorrhoeaeby UV-vis spectroscopy, chromatography, ICP-OES, mass spectrometry, and Nb K-edge X-ray absorption spectroscopy. These data suggest thatNbVbinds strongly to Fbp and that a dinuclearNbVcentre can be readily accommodated in the interdomain binding cleft. The possibility of designing niobium-based antibiotics which block iron uptake by pathogenic bacteria is discussed.

Optical Luminescence Yield X-ray Absorption Fine Structures at the Sulphur and Silicon K-edge

1993 ◽  
Vol 32 (S2) ◽  
pp. 223 ◽  
Author(s):  
T. K. Sham ◽  
X.-H. Feng ◽  
D.-T. Jiang ◽  
K. H. Tan ◽  
S. P. Frigo ◽  
...  
Keyword(s):  
X Ray ◽  
Absorption Fine ◽  
Optical Luminescence ◽  
Luminescence Yield ◽  
Fine Structures ◽  
X Ray Absorption
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