scholarly journals Characterization of anatase TiO2 nanopowder by variable-temperature Raman spectroscopy

2009 ◽  
Vol 41 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Maja Scepanovic ◽  
M. Grujic-Brojcin ◽  
Z.D. Dohcevic-Mitrovic ◽  
Z.V. Popovic
Keyword(s):  
Raman Spectroscopy ◽  
Grain Size ◽  
Variable Temperature ◽  
Anatase Phase ◽  
Great Influence ◽  
Tio2 Powder ◽  
Phonon Confinement ◽  
Anti Stokes ◽  
Nanosized Tio2

Raman spectroscopy has been used for characterization of commercial nanosized TiO2 powder with declared grain size of 5 nm. The Raman spectra measured in Stokes and anti-Stokes regime confirm the anatase phase of TiO2 powder in temperature range 25-1173K. It is shown that phonon-confinement (due to small grain size) and nonstoichiometry (caused by laser irradiation in vacuum) have a great influence on blueshift and broadening of the main Eg Raman mode at low temperatures, while the influence of the strong anharmonic effect becomes dominant at higher temperatures. The phonon confinement effect decreases due to the crystallite growth at temperatures above 673K.

Broadband Coherent Anti-Stokes Raman Spectroscopy Characterization of Polymer Thin Films

2006 ◽  
Vol 60 (10) ◽  
pp. 1097-1102 ◽  
Author(s):  
Zachary D. Schultz ◽  
Marc C. Gurau ◽  
Lee J. Richter
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Polymer Thin Films ◽  
Anti Stokes

Formation and characterization of germanium nanoparticles

2000 ◽  
Vol 15 (11) ◽  
pp. 2400-2407 ◽  
Author(s):  
N. J. Welham
Keyword(s):  
Raman Spectroscopy ◽  
Crystallite Size ◽  
Magnesium Oxide ◽  
Phonon Confinement ◽  
X Ray Diffraction ◽  
Acid Leach ◽  
Crystallite Sizes ◽  
Crystal Core ◽  
Individual Particles

Elemental germanium was mechanically milled with magnesium oxide with the intention of forming disperse nanoparticulate germanium in a soluble matrix. The crystallite size was determined by x-ray diffraction (XRD) and Raman spectroscopy using a phonon confinement model. The crystallite size was found to decrease exponentially with milling time; however, the size determined by XRD was typically five to ten times greater than that by Raman. This was attributed to the presence of two separate crystallite sizes, which were averaged when using the Scherrer equation for the XRD data. Sonication of the powder resulted in the breakup of >20 μm aggregates into individual particles of approximately 40 nm. These particles are thought to compose a single crystal core with a crystallite size of approximately 28 nm surrounded by a layer of smaller crystallites (approximately 5 nm), which showed quantization during Raman spectroscopy. Separation of the germanium from the magnesium oxide was readily achieved using a simple acid leach, although some oxidation of germanium was evident when using an aqueous leach.

Sol-Gel Synthesis and Characterization of TiO2-Based Photocatalyst and its Photoactivity Research

2013 ◽  
Vol 864-867 ◽  
pp. 613-616
Author(s):  
Xue Mei Qi ◽  
Xin Yuan Zhu ◽  
Jiang Wu ◽  
Yu Wu ◽  
Han Cheng Luo
Keyword(s):  
Anatase Phase ◽  
Sol Gel ◽  
Great Influence ◽  
Rutile Phase ◽  
Xrd Diffraction ◽  
Sol Gel Process ◽  
Photocatalytic Activities ◽  
Stirring Time ◽  
Sol Gel Synthesis

The TiO2-based photocatalysts have been synthesized by using sol-gel process and their photocatalytic activities were studied by the degradation of methylene blue (MB). It was shown that the calcination temperature has great influence on the crystalline phase transition of TiO2. For all the samples (Ag-doped and undoped TiO2photocatalysts) calcined at 573K, only anatase phase was observed from XRD diffraction spectra and the intensity of peaks is weak. After the calcined at 773K, a mixture of anatase-rutile phase appeared. The contents of rutile phase were about 85% and77% for undoped and Ag-adopted TiO2photocatalysts.There were only rutile phases for all the TiO2photocatalysts calcined at 973K observed from XRD diffraction spectra. Magnetically stirring time of A solution before added B had no obvious effects on the polymorphs transition of TiO2.

HRTEM/EELS Analysis, Structural Characterization and Sensor Performances of Hydrothermal Nano-TiO2

2004 ◽  
Vol 828 ◽  
Author(s):  
Ana M. Ruiz ◽  
J. Arbiol ◽  
A. Cornet ◽  
K. Shimanoe ◽  
Joan R. Morante ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Grain Size ◽  
Grain Growth ◽  
Structural Characterization ◽  
Phase Structure ◽  
Anatase Phase ◽  
Sensor Response ◽  
Small Particles ◽  
Nano Tio2 ◽  
Ethanol Response

ABSTRACTPure nanophased TiO2 with controlled microstructure and resistant to thermal induced grain growth has been prepared by hydrothermal treatments. The synthesized nano-TiO2 presents small size and well defined and faceted surface, as shown by Raman spectroscopy, XRD, EELS and HRTEM. Such performances are slightly changed with the posterior temperature treatments up to 700 °C, maintaining anatase phase structure and grain size about 20nm. The extent of stabilization depended on the pH of the treatment, being pH 2 more convenient for stabilizing the size, and pH 3 for the phase. HRTEM and EELS measurements showed the coexistence of rutile big particles (∼100 nm) with anatase small particles (∼40 nm) at pH 3 and calcination at 900°C. Thick-films of precipitated TiO2 and hydrothermally treated TiO2 were tested for the CO and the ethanol response. The hydrothermal treatment allowed obtaining stable sensitive films which exhibited enlarged sensor response and improved transients, specially in the case of the materials treated at pH 3.

Raman Spectroscopy of Ge Nanocrystals Grown by Self-Organization Processes

1996 ◽  
Vol 452 ◽  
Author(s):  
A. Stella ◽  
C. E. Bottani ◽  
P. Cheyssac ◽  
R. Kofman ◽  
P. Milani ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Size Dependence ◽  
Self Organization ◽  
Phonon Confinement ◽  
Amorphous Substrate ◽  
Crystalline Nature ◽  
Size Dispersion ◽  
Ge Nanocrystals ◽  
Confinement Model

AbstractWe report Raman spectroscopy measurements on Ge nanocrystals with average radii ranging from about 65 Å down to 10 Å (with a size dispersion lower than 20 %).Ge has been deposited by UHV evaporation on an amorphous substrate, kept at such a temperature as to produce the Ge nanodroplets nucleation in the liquid phase.A nanocrystalline size dependence of the Raman spectra has been observed and explained in the framework of a phonon confinement model. We have observed the softening of the TO Raman peak predicted by the theory when the dimensions of the particles are decreased. Moreover the observed inhomogeneous broadening of the Raman lines has been correlated with the size distribution of the particles in the samples.Our results provide a characterization of Ge nanoparticles exhibiting a good crystalline nature, down to about 10 Å, and in conditions of substantial absence of perturbations of the environment.

Preparation and characterization of nanosized TiO2 powder as an inorganic adsorbent for aqueous radionuclide Co(II) ions

2012 ◽  
Vol 295 (2) ◽  
pp. 1305-1312 ◽  
Author(s):  
Song Wang ◽  
Liqiang Tan ◽  
Jinlong Jiang ◽  
Jing Chen ◽  
Liangdong Feng
Keyword(s):  
Tio2 Powder ◽  
Nanosized Tio2

Sol-Gel Synthesis and Characterization of Neodymium-Ion Doped Nanostructured Titania Thin Films

2001 ◽  
Vol 703 ◽  
Author(s):  
Andrew Burns ◽  
W. Li ◽  
C. Baker ◽  
S.I. Shah
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Anatase Phase ◽  
Sol Gel ◽  
Ionic Radii ◽  
Si Substrates ◽  
Gel Technique ◽  
The Difference ◽  
Sol Gel Synthesis

ABSTRACTNd doped TiO2 nanostructured thin films were prepared by sol-gel technique on quartz and Si substrates using TiCl4 precursor. As-deposited amorphous films were annealed to form anatase phase in the thin films. The film grain size increased with annealing temperature. Above 800°C, rutile began to segregate and the grain size decreased slightly.The photodegradation of 2-chlorophenol (2-CP) was studied. Doping TiO2 with Nd+3 reduced the photodegradation time. The difference in the ionic radii of Nd+3 and Ti+4 and the oxygen affinities of Nd and Ti were responsible for this effect. These differences help promote electron trapping, thereby increasing the lifetime of the holes which are responsible for the oxidation of 2-CP.

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