Size tailoring of TiO2 anatase nanoparticles in aqueous medium and synthesis of nanocomposites. Characterization by Raman spectroscopy

Abstract

Nanoparticles of anatase with mean size in the range 5-10 nm were prepared by precipitation of TiCl 4 in aqueous medium in the range 2 ¡ pH ¡ 6. Hydroxylation of TiCl 4 at room temperature leads instantaneously to an amorphous titanium oxyhydroxide phase which crystallizes as anatase upon aging at 60 uC in suspension. Small amounts of brookite or rutile are concurrently obtained depending on the acidity. The size of anatase particles was characterized by X-ray diffraction, electron microscopy and Raman spectroscopy. The latter was also used to determine the particle size and to characterize the crystallinity of particles through the phonon confinement effect. The particle size, dependent on the acidity, is closely related to the electrostatic surface charge density of particles. The size variation was interpreted as resulting from a lowering of the interfacial tension due to the protonation of particle surface groups. Composite materials were synthesized by polymerisation of silica in aqueous sols of anatase. The dispersed anatase nanoparticles are stable against the transformation to rutile up to 1000 uC.

Solvothermal synthesis of N-doped TiO2 nanotubes for visible-light-responsive photocatalysis

“…It was reported that TiO 2 nanocrystals were ready to form by hydrothermal treatment of titanium hydrogel with the existence of Cl À in the solution. 26,27 In the present work, Cl À probably results in formation of TiO 2 anatase nanotubes, while NH 3 absorbed on the walls of the nanotubes and partially formed ammonia titanates, then visible-light-responsive N-TDNTs are formed upon annealing them. It appears that the N-TDNTs are uniform in composition because the walls of TDNTs are extremely thin.…”

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

“…[66][67][68][69][70][71][72][73] Much less is known about the ternary Ti-Fe-O diagram when dealing with nanoparticle synthesis in water. [74][75][76] In the 2-6 pH range, both metal ions first form an amorphous or very poorly organized hydroxide precipitate.…”

Communication: Three-dimensional model for phonon confinement in small particles: Quantitative bandshape analysis of size-dependent Raman spectra of nanodiamonds

“…18 As of the natural bandwidth ( 0 in formula (3)), it was shown in several works that the experimental 0 cannot be simply described by the inverse dependence on the particle size, as one should expect only from the size-dependent phonon lifetime. [19][20][21] The physical model of this phenomenon is quite complex, hence for the fitting purposes we have chosen the function with three fitting parameters (A, B, n) allowing for certain flexibility (Eq. (6)):…”