Solvothermal synthesis and characterization of anatase TiO2 nanocrystals with ultrahigh surface area

ArticleinJournal of Colloid and Interface Science 302(2):530-6 · November 2006with23 Reads
DOI: 10.1016/j.jcis.2006.07.003 · Source: PubMed
Abstract
Phase-pure, ultrafine nanocrystalline anatase with high specific surface area (up to 250 m(2) g(-1)) was obtained upon injection of a titanium alkoxide precursor into ethanol with designed volume of water under mild solvothermal conditions (<200 degrees C, 2 h). Primary particle sizes were tuned by adjusting various reaction parameters, with the smallest grain sizes occurring at low temperatures (140-150 degrees C), low initial alkoxide concentrations, and intermediate hydrolysis ratios (r identical with[H2O]/[Ti(OR)4]=5-10). Additionally, variations in the reaction temperature result in changes in particle morphology and distribution, with high-temperature samples exhibiting bimodal distributions of small spherical and larger cubic particles that suggest grain growth via Ostwald ripening. A crystalline product with high thermal stability and specific surface area up to 5 times that of commercial nano-titania can be obtained at a relatively low temperature of 150 degrees C. The physical properties of the titania samples obtained in this study suggest they might be well suited for catalytic applications.
    • "Pavasupree et al. synthesised anatase TiO 2 nanopowder using TTBT, by keeping the reaction temperature at 130°C for 12 h and the photoconversion efficiency of the anatase TiO 2 -based cell was about 6.30%, higher than 5.82% of P25 [14]. Pure rutile titania nanocrystallites were synthesised using TiCl 4 as starting material and several kinds of acids as reaction media [2, 9,[15][16][17][18]. A mixture of anatase, brookite and rutile TiO 2 nanocrystallites was obtained by hydrothermal treatment using titanium (IV) isopropoxide as starting material [19, 20]. "
    [Show abstract] [Hide abstract] ABSTRACT: Nanocrystalline TiO2 was prepared through hydrothermal synthesis using tetrabutyl titanate as starting material. With a constant reaction time of 12 h, the reaction temperature was changed from 120 to 160°C and the pH value of the reaction medium was ranged from 1 to 9. Every specimen of the as-prepared TiO2 powder was characterised by X-ray diffraction, a scanning electron microscope, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction and was also used to fabricate dye sensitised solar cells (DSSCs). The experimental results showed that the phase of the powder was affected by the pH value, whereas the particle size depended on the reaction temperature. Pure anatase TiO2 was obtained with the pH value of 3. The solar energy conversion efficiency (η) of the DSSC fabricated with the pure anatase TiO2 prepared at 140°C was 3.64%, which was higher than those with the TiO2 prepared under any other conditions. The purchased TiO2 (P25) was used to make a DSSC for comparison. It turned out that the performance of all the DSSCs with TiO2 prepared by hydrothermal synthesis was higher than that with the P25.
    Full-text · Article · May 2013
    • "Based on the solvent used as the reactant in the first step, it can be described as hydrolysis (reaction with water)22232425, alcoholysis (reaction with alcohols)262728, and ammonolysis (reaction with ammonium ions) [29,30]. The synthesis reaction and subsequent treatments are carried out under ambient313233 or solvothermal conditions [11,3435363738. Recently, a novel solution-based method to synthesize nanostructured metal oxides -the direct liquid phase precipitation (DLPP), has been developed by us [39] . In this approach , a great variety of metal oxide NPs can be easily prepared by exchange of anions of a corresponding metal salt (e.g., CuCl, ZnCl 2 , FeCl 3 , and SnCl 4 ) with alkali metal oxides in non-aqueous conditions . "
    [Show abstract] [Hide abstract] ABSTRACT: Highly aqueously dispersible (soluble) TiO2 nanoparticles are usually synthesized by a solution-based sol-gel (solvolysis/condensation) process, and no direct precipitation of titania has been reported. This paper proposes a new approach to synthesize stable TiO2 nanoparticles by a non-solvolytic method - direct liquid phase precipitation at room temperature. Ligand-capped TiO2 nanoparticles are more readily solubilized compared to uncapped TiO2 nanoparticles, and these capped materials show distinct optical absorbance/emission behaviors. The influence of ligands, way of reactant feeding, and post-treatment on the shape, size, crystalline structure, and surface chemistry of the TiO2 nanoparticles has been thoroughly investigated by the combined use of X-ray diffraction, transmission electron microscopy, UV-visible (UV-vis) spectroscopy, and photoluminescence (PL). It is found that all above variables have significant effects on the size, shape, and dispersivity of the final TiO2 nanoparticles. For the first time, real-time UV-vis spectroscopy and PL are used to dynamically detect the formation and growth of TiO2 nanoparticles in solution. These real-time measurements show that the precipitation process begins to nucleate after an initial inhibition period of about 1 h, thereafter a particle growth occurs and reaches the maximum point after 2 h. The synthesis reaction is essentially completed after 4 h.
    Full-text · Article · Jun 2012
    • "Titanium dioxide can exist in several physical forms (anatase, rutile, amorphous, and brookite; see for example Mogyorósi et al., 2003). Irradiation of the anatase form of titanium dioxide with light below 380 nm results in the generation of reactive oxygen species (Hoffman et al., 1995; Blake et al., 1999; Mills and LeHunte, 1997) resulting in photocatalytic killing of bacteria (Gaswami et al., 1997; Stevenson et al., 1997; Sunada et al., 1998; Jacoby et al., 1998; Byrne et al., 1998; Maness et al., 1999), photodecomposition of dyes (Aleboyeh et al., 2003, and Neamtu et al., 2004, Moraes et al., 2004, Wahi et al 2005, 2006), and use as a photocatalyst in dye-sensitized solar cells (Kusama and Arakawa, 2003). This generation of reaction oxygen species can be prevented by physically separating the titanium dioxide crystal from oxygen or water with an inert coating (i.e. "
    [Show abstract] [Hide abstract] ABSTRACT: Topical exposure to nanoscale materials is likely from a variety of sources including sunscreens and cosmetics. Because the in vivo disposition of nanoscale materials is not well understood, we have evaluated the distribution of quantum dots (QDs) following intradermal injection into female SKH-1 hairless mice as a model system for determining tissue localization following intradermal infiltration. The QD (CdSe core, CdS capped, poly[ethylene glycol] coated, 37 nm diameter, 621 nm fluorescence emission) were injected intradermally (ID) on the right dorsal flank. Within minutes following intradermal injection, the highly UV fluorescent QD could be observed moving from the injection sites apparently through the lymphatic duct system to regional lymph nodes. Residual fluorescent QD remained at the site of injection until necropsy at 24 h. Quantification of cadmium and selenium levels after 0, 4, 8, 12, or 24 h in multiple tissues, using inductively coupled plasma mass spectrometry (ICP-MS), showed a time-dependent loss of cadmium from the injection site, and accumulation in the liver, regional draining lymph nodes, kidney, spleen, and hepatic lymph node. Fluorescence microscopy corroborated the ICP-MS results regarding the tissue distribution of QD. The results indicated that (1) ID injected nanoscale QD remained as a deposit in skin and penetrated the surrounding viable subcutis, (2) QD were distributed to draining lymph nodes through the sc lymphatics and to the liver and other organs, and (3) sentinel organs are effective locations for monitoring transdermal penetration of nanoscale materials into animals.
    Full-text · Article · Jul 2007
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