Raman scattering study on anatase TiO2 nanocrystals
TL;DR: In this article, the evolution of the anatase phase in TiO2 nanocrystals during annealing was investigated using x-ray diffraction and the influence of interfacial vibrations on the Raman linewidth was also discussed.
Abstract: Titanium dioxide (TiO2 ) nanocrystals are prepared by a hydrolysis process of tetrabutyl titanate. Nanocrystal samples with various sizes of 6.8-27.9 nm are obtained after annealing from 100 to 650 °C. The crystal structures and the average particle sizes are examined using x-ray diffraction. Raman scattering was employed to investigate the evolution of the anatase phase in the nanocrystals during annealing. Phonon confinement and non-stoichiometry effects are responsible for the blueshift and broadening of the lowest-frequency Eg Raman mode. The influence of interfacial vibrations on the Raman linewidth is also discussed.
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TL;DR: The present review tries to give a comprehensive and most up to date view to the field, with an emphasis on the currently most investigated anodic TiO2 nanotube arrays.
Abstract: In the present review we try to give a comprehensive and most up to date view to the field, with an emphasis on the currently most investigated anodic TiO2 nanotube arrays. We will first give an overview of different synthesis approaches to produce TiO2 nanotubes and TiO2 nanotube arrays, and then deal with physical and chemical properties of TiO2 nanotubes and techniques to modify them. Finally, we will provide an overview of the most explored and prospective applications of nanotubular TiO2.
984 citations
TL;DR: In this article, the authors provide a basic understanding of the information micro-Raman Spectroscopy (mRS) may yield when applied to nanomaterials, a generic term for describing nano-sized crystals and bulk homogeneous materials with a structural disorder at the nanoscale.
905 citations
Cites background or methods from "Raman scattering study on anatase T..."
...0 C(k ,k) =0 for r= /2)[181,184,186,198,201]....
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...It is nothing but a coherence length which can correspond to a grain size [180,192,203-206], defects/impurities interspacing [186,197,201,207,208], the extension of cation-ordered domains in incommensurate phases [92], that of undamaged crystalline domains in ion-implanted GaAs [199], the size of polytypic domains [182,209,210] or clusters in semiconducting alloys [183,184,211] and ferroelectrics [12]....
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...22 One should not forget that peak altering effects like internal stress [9,185,187,216,217,219,292], growth directionality [81], non-stoichiometry [186], local heating [190,222,293], couplings or defect-induced diffusions [293] may add to the size effect on Raman spectra of nanomaterials....
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...The stress will act on the position of the peaks [187], defects (non-stoichiometry for instance) will widen them [186,187,190] and temperature will act on both position and width....
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...This is the equation to which most authors refer when using the PCM [180-187]....
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892 citations
TL;DR: In this paper, the photocatalytic performance of the reduced graphene oxide (hGO)-TNT composites was evaluated for the photodegradation of malachite green using X-ray diffraction (XRD), Raman, FTIR, and XPS analysis.
Abstract: In this study, TiO2 nanotube (TNT)/reduced graphene oxide (hGO) composites were prepared by an alkaline hydrothermal process. This was achieved by decorating graphene oxide (GO) layers with commercially available TiO2 nanoparticles (P90) followed by hydrothermal synthesis, which converts the TiO2 nanoparticles to small diameter (∼9 nm) TNTs on the hGO surface. The alkaline medium used to synthesize the TNTs simultaneously converts GO to deoxygenated graphene oxide (hGO). Compared to GO, the hGO has a ∼70% reduction of oxygenated species after alkaline hydrothermal treatment. The graphene nature of hGO in the composites was confirmed by X-ray diffraction (XRD), Raman, FTIR, and X-ray photoelectron spectroscopy (XPS) analysis. The photocatalytic performance of the hGO-TNT composites was evaluated for the photodegradation of malachite green. It was found that the ratio of hGO to TNT in the composites significantly affects the photocatalytic activity. Higher amounts of hGO in hGO-TNT composites showed lower p...
868 citations
References
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TL;DR: In this article, the effect of the exact shape of the microcrystal and the relationship between the width, shift and asymmetry of the Raman line is calculated and is in good agreement with available experimental data.
1,957 citations
TL;DR: In this paper, the anatase and rutile phases of polycrystalline titanium dioxide using an argon ion laser as exciter were recorded at room temperature for the first-order Raman spectra.
784 citations
TL;DR: In this paper, the Raman spectrum of nanophase TiO2 was used to determine the oxygen-titanium ratio, and the thermogravimetric analysis studies used to calculate the ratio were discussed.
Abstract: Calibration curves of the Raman spectrum of nanophase TiO2 to the material’s oxygen stoichiometry are presented. The thermogravimetric analysis studies used to determine the oxygen‐titanium ratio are also discussed.
594 citations
TL;DR: A size effect on the ferroelectric phase transition in ultrafine particles is reported, when the particle size is less than 50 nm, and the transition temperature decreases from its bulk value as the size decreases.
Abstract: We report a size effect on the ferroelectric phase transition in ${\mathrm{PbTiO}}_{3}$ ultrafine particles. The samples were synthesized by an alkoxide method. The size was determined by x-ray analysis with the aid of Scherrer's equation. When the particle size is less than 50 nm, the transition temperature ${T}_{c}$, determined by Raman scattering, decreases from its bulk value (500 \ifmmode^\circ\else\textdegree\fi{}C) as the size decreases. The temperature ${T}_{c}$ is described by an empirical expression, ${T}_{c}$=500-588.5/(D-12.6) (\ifmmode^\circ\else\textdegree\fi{}C), where D is the average particle size (nm).
577 citations
TL;DR: In this article, the authors used Raman scattering and x-ray diffraction measurements to correlate finite-size effects on the Raman spectra of nonpolar vibrational modes in BN.
Abstract: Raman scattering and x-ray diffraction measurements are used to correlate finite-size effects on the Raman spectra of nonpolar vibrational modes in BN. The BN microcrystalline samples used exhibited domain sizes varying from 4.4 to 78.5 nm in the plane and 1.5 and 47.5 nm perpendicular to the planes. The Raman measurements indicated that the high-frequency ${E}_{2g}$ mode shifted to higher frequency and broadened as the crystallite size decreased. A formulation of the Raman cross section for scattering from nonpolar microcrystals is presented. The development includes evaluation of the susceptibility correlation function over a limited spatial extent. The results indicate that spectral changes are related to the phonon dispersion, and the wave-vector uncertainty is accounted for. The formulation is applied to describe the BN light scattering results, and good agreement was obtained to describe the observed shift in frequency.
520 citations