Showing papers by "Jiaguo Yu published in 2009"
TL;DR: In this paper, a visible-light-driven plasmonic photocatalyst was proposed for photocatalytic degradation of methyl orange in water and stability by depositing AgCl nanoparticles (NPs) into the self-organized TiO2 nanotube arrays.
Abstract: Conventional TiO2 photocatalyst possesses excellent activities and stabilities, but requires near-ultraviolet (UV) irradiation (about 4% of the solar spectrum) for effective photocatalysis, thereby severely limiting its practical application. It is highly desirable to develop a photocatalyst that can use visible light in high efficiency under sunlight irradiation. In this work, we prepare new visible-light-driven plasmonic photocatalyst Ag/AgCl/TiO2 nanotube arrays (NTs) by depositing AgCl nanoparticles (NPs) into the self-organized TiO2 NTs, and then reducing partial Ag+ ions in the surface region of the AgCl particles to Ag0 species under xenon lamp irradiation. The prepared metal−semiconductor nanocomposite plasmonic photocatalyst exhibits a highly visible-light photocatalytic activity for photocatalytic degradation of methyl orange in water and stability. A new plasmonic photocatalytic mechanism, which is proposed on the basis of the fact that the Ag NPs are photoexcited due to plasmon resonance and c...
773 citations
TL;DR: In this paper, the photocatalytic activity of mesoporous TiO 2 nanorods has been investigated by using an impregnating-calcination method using the hydrothermally prepared titanate nanotubes.
Abstract: Fe-doped TiO 2 (Fe-TiO 2 ) nanorods were prepared by an impregnating-calcination method using the hydrothermally prepared titanate nanotubes as precursors and Fe(NO 3 ) 3 as dopant. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, N 2 adsorption–desorption isotherms and UV–vis spectroscopy. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air under visible-light irradiation. The results show that Fe-doping greatly enhance the visible-light photocatalytic activity of mesoporous TiO 2 nanorods, and when the atomic ratio of Fe/Ti ( R Fe ) is in the range of 0.1–1.0%, the photocatalytic activity of the samples is higher than that of Degussa P25 and pure TiO 2 nanorods. At R Fe = 0.5%, the photocatalytic activity of Fe-TiO 2 nanorods exceeds that of Degussa P25 by a factor of more than two times. This is ascribed to the fact that the one-dimensional nanostructure can enhance the transfer and transport of charge carrier, the Fe-doping induces the shift of the absorption edge into the visible-light range with the narrowing of the band gap and reduces the recombination of photo-generated electrons and holes. Furthermore, the first-principle density functional theory (DFT) calculation further confirms the red shift of absorption edges and the narrowing of band gap of Fe-TiO 2 nanorods.
709 citations
TL;DR: In this paper, the photocatalytic activity of surface-fluorinated powders of anatase phase with high photocatalysis activity was evaluated by using a photoluminescence (PL) technique with terephthalic acid as a probe molecule.
Abstract: Mesporous surface-fluorinated TiO2 (F−TiO2) powders of anatase phase with high photocatalytic activity are prepared by a one-step hydrothermal strategy in a NH4HF2−H2O−C2H5OH mixed solution with tetrabutylorthotitanate (Ti(OC4H9)4, TBOT) as precursor. The prepared samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption−desorption isotherms, UV−vis absorption spectroscopy, and transmission electron microscopy. The production of hydroxyl radicals (•OH) on the surface of UV-illuminated TiO2 is detected by a photoluminescence (PL) technique with use of terephthalic acid as a probe molecule. The photocatalytic activity is evaluated by photocatalytic oxidation decomposition of acetone in air under UV light illumination. The results show that the photocatalytic activity of F−TiO2 powders is obviously higher than that of pure TiO2 and commercial Degussa P25 (P25) powders due to the fact that the strong electron-withdrawing ability of the surface ≡Ti−F groups reduces the rec...
571 citations
TL;DR: In this paper, a cage-like structure and porous crystalline shells were successfully fabricated by a controlled hydrothermal precipitation reaction using urea as a precipitating agent and carbonaceous polysaccharide spheres as templates in a mixed solvent of water and ethanol, and then calcined at 500 °C for 4 h.
Abstract: Fe2O3 hollow spheres with novel cage-like architectures and porous crystalline shells were successfully fabricated by a controlled hydrothermal precipitation reaction using urea as a precipitating agent and carbonaceous polysaccharide spheres as templates in a mixed solvent of water and ethanol, and then calcined at 500 °C for 4 h. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption−desorption isotherms, and UV−visible diffuse reflectance spectroscopy. The visible-light photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution at ambient temperature under visible-light illumination in the presence of H2O2. The results indicated that the diameter, shell thickness, average crystallite size, specific surface areas, pore structures, and photocatalytic activity of Fe2O3 hollow spheres could be easily controlled...
286 citations
TL;DR: The results show that all the prepared nanospheres have hexagonal wurtzite structures and exhibit good size uniformity and regularity and are of great interest for use in flat displays, sensors, lasers, catalysis, separation technology, biomedical engineering, and nanotechnology.
Abstract: Monodisperse wurtzite ZnS hollow spheres with diameters of about 200 nm and shells composed of nanoparticles have been successfully synthesized in high yield by a one-pot template-free hydrothermal route. The reaction duration, reactant species, and reaction temperature have been shown to play important roles in the formation of ZnS hollow spheres. X-ray diffraction, scanning and transmission electron microscopy, nitrogen adsorption/desorption, UV/Vis diffuse reflectance spectroscopy, and photoluminescence were used to characterize the products. The results show that all the prepared nanospheres have hexagonal wurtzite structures and exhibit good size uniformity and regularity. A mechanism for the formation of the ZnS hollow spherical structure by localized Ostwald ripening has been proposed based on experimental observations. In addition, studies of the photocatalytic properties of the ZnS hollow spheres by exposure to UV irradiation have demonstrated that they have potential photocatalytic applications. Hydroxyl radicals (*OH) were not detected on the surface of UV-illuminated ZnS by the photoluminescence technique, which suggests that *OH is not the dominant photo-oxidant and a photogenerated hole could instead directly participate in the photocatalytic reaction. The prepared ZnS hollow spheres are also of great interest for use in flat displays, sensors, lasers, catalysis, separation technology, biomedical engineering, and nanotechnology.
225 citations
TL;DR: In this paper, a variety of boehmite hollow core/shell and hollow microspheres with high adsorption affinity toward organic pollutants in water were prepared via a facile one-pot hydrothermal method using aluminum sulfate as a precursor and urea and sodium tartrate as precipitating and mediating agents, respectively.
Abstract: A variety of boehmite hollow core/shell and hollow microspheres with high adsorption affinity toward organic pollutants in water were prepared via a facile one-pot hydrothermal method using aluminum sulfate as a precursor and urea and sodium tartrate as precipitating and mediating agents, respectively. These microspheres were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. In addition, the aforementioned microspheres were examined as potential adsorbents for Congo red and phenol from aqueous solutions. This study shows that the crystallinity, specific surface area, and pore structure of the resulting microspheres can be controlled by varying the concentration of sodium tartrate and reaction time. The reported experiments allowed us to propose the mechanism of formation of hollow core/shell and hollow microspheres, which involves sodium tartrate-mediated phase transformation, followed by a subsequent self-assembly process. ...
202 citations
TL;DR: In this paper, hierarchical boehmite superstructures (HFBS) composed of intermeshed nanoflakes were synthesized by hydrothermal treatment from as-formed aluminum hydroxide microspheres, which were prepared by adding aluminum spheres into a sodium metaaluminate solution.
Abstract: Hierarchical flower-like boehmite superstructures (HFBS) composed of intermeshed nanoflakes were synthesized by hydrothermal treatment from as-formed aluminum hydroxide microspheres, which were prepared by adding aluminum spheres into a sodium metaaluminate solution. A two-step mechanism for the formation of HFBS is proposed, which involves initial formation of Al(OH)3 microspheres followed by their transformation to AlOOH. The as-prepared HFBS superstructures can be easily transformed into γ-Al2O3 superstructures without morphology change by calcination at 500 °C for 2 h. Furthermore, the TiO2 nanoparticles can homogeneously deposited on the surface of HFBS by the vapor-thermal method. The TiO2 nanoparticles coated on HFBS showed higher photocatalytic activity for photocatalytic decolorization of rhodamine B (RhB) aqueous solution than Degussa P25 (P25) and TiO2 powders prepared at the same experimental conditions. A significant enhancement of the photocatalytic activity can be related to several factors...
199 citations
TL;DR: The results showed that the presence of nanosized Au particles slightly depressed the grain growth of anatase, resulting in smaller crystallite size and greater specific surface areas, and the photocatalytic activity of Au-TiO2 nanocomposite microspheres was obviously higher than that of pure TiO2microspheres and Degussa P25.
195 citations
TL;DR: It was found that the three-dimensional tungsten trioxide assemblies were constructed from two-dimensional layers, which were further composed of a large number of interconnected lathy nanoplates with different sizes that exhibited hierarchically porous structure and higher visible-light photocatalytic activity than the samples without such hierarchical structures.
133 citations
TL;DR: Hierarchically organized γ-AlOOH hollow spheres with nanoflake-like porous surface textures were fabricated by chemically induced self-transformation of metastable solid particles of amorphous aluminium oxyhydroxide produced in situ within hydrothermal reaction mixtures containing aluminium sulfate and urea.
104 citations
TL;DR: In this paper, a review of the recent progress in the synthesis of hierarchically porous materials, targeted through templating methods, is reviewed, which involves a supermolecular assembly of amphiphilic polymers or surfactants combined with second surfactant systems or macrotemplates such as solid particles, liquid drops, and air bubbles.
Abstract: Hierarchically porous materials displaying multimodal pore sizes are desirable for their improved flow performance coupled with high surface areas. In the last five years, a tremendous amount of research has focused upon the synthesis and applications of hierarchically porous materials. This review aims to open up a new avenue of research in this exciting field. At first, recent progress in the synthesis of hierarchically porous materials, targeted through templating methods, is reviewed. These synthesis methods involve a supermolecular assembly of amphiphilic polymers or surfactants combined with second surfactant systems or with macrotemplates such as solid particles, liquid drops, and air bubbles. The preparation procedures using surfactants combined with other chemical or physical methods, controlled phase-separation, or template replication will also be discussed. Subsequently, an innovative procedure concerning the self-formation of hierarchically porous materials is thoroughly examined. This self-formation procedure is based on a self-generated porogen mechanism. Porogens such as alcohol molecules can be precisely controlled at the molecular level to design new hierarchically porous materials. Most of these synthesis methods allow an easy and independent adjustment to the multiporosity of a material, i.e., its micro-, meso-, and macroporosity.
TL;DR: Dye-sensitized solar cells (DSSCs) are fabricated based on ordered titanate nanotube (TNT) films obtained by electrophoretic deposition (EPD) method.
TL;DR: In this article, the synergetic effects of codoped Zr4+ and F− ions within anatase hollow microspheres produced by a fluoride-mediated self-transformation strategy are investigated and discussed.
Abstract: The synergetic effects of codoped Zr4+ and F− ions within anatase hollow microspheres produced by a fluoride-mediated self-transformation strategy are investigated and discussed. The concomitant participation of F− promotes lattice substitution of Ti4+ ions by Zr4+ and facilitates the transformation of surface-segregated amorphous ZrOx clusters into Zr−F species. Codoping is associated with electron transfer-mediated charge compensation between the Zr/F impurities, which reduces the number of both bulk and surface defects and provides a stabilizing effect on the local structure. Moreover, these synergetic interactions influence the textural characteristics and surface states of the TiO2 host, such that the photocatalytic activity with regard to the decomposition of gaseous toluene is enhanced. Synergetic codoping of heterogeneous impurities within the host lattice or near-surface regions provides a general and effective alternative strategy for higher level doping and surface modification, which may be cr...
TL;DR: The high surface area, bimodal mesoporosity of the shell walls, and increased band gap of the hollow TiO(2) microspheres give rise to increases in photocatalytic activity when compared with anatase nanoparticles and aggregates prepared in the absence of urea.
Abstract: Discrete and chain-like aggregates of well-defined hollow TiO2 microspheres are reproducibly synthesized in high yield by a modified fluoride-mediated self-transformation strategy using urea as a base catalyst. The shell walls are composed of agglomerated polyhedral anatase nanocrystals, and exhibit hierarchical porosity. The addition of urea tunes the nucleation dynamics and surface states of the elementary TiO2 building blocks, which together promote the formation of metastable solid microparticles of uniform size that subsequently transform into morphologically invariant hollow microspheres and chain-like aggregates. The high surface area, bimodal mesoporosity of the shell walls, and increased band gap of the hollow TiO2 microspheres give rise to increases in photocatalytic activity when compared with anatase nanoparticles and aggregates prepared in the absence of urea.
TL;DR: In this article, mesoporous titania nanospheres with high specific surface area and good photocatalytic activity were fabricated on a large scale by a simple spray-hydrolytic method at 90°C.
Abstract: Mesoporous titania nanospheres with high specific surface area and good photocatalytic activity were fabricated on a large scale by a simple spray-hydrolytic method at 90 °C. The as-prepared TiO2 spherical powders were characterized by X-ray diffraction, N2 adsorption–desorption measurements, field emission scanning electron microscope, transmission electron microscopy, UV–visible diffuse reflectance spectra and photocurrent measurements. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air. The effects of calcination temperatures on the microstructures and photocatalytic activity of the TiO2 powders were investigated and discussed. The results revealed that a large amount of mesoporous titania nanospheres could spontaneously form by self-assembly of countless tiny TiO2 primary nanoparticle during the spray hydrolysis at 90 °C. The calcination temperature exhibited a strong effect on the microstructures and photocatalytic activity of the prepared titania. The 400 °C-calcined sample showed the highest photocatalytic activity and was about two times higher than that of Degussa P25. At 600 °C, the photocatalytic activity decreased because of the destruction of bimodal mesoporous structure of the titania and the drastic decrease of specific surface areas.
TL;DR: In this article, two dandelion-like heads built up from rod-like subunits were synthesized via a facile precipitation reaction between Na{sub 2}CO{sub 3} and CaCl{sub2} at ambient temperature in the presence of magnesium ions and ethanol solvent.
TL;DR: In this article, a nano-sized particles of anatase and rutile phases of titanium dioxide were synthesized by reactive plasma processing and the photocatalytic activity of the powder was evaluated by studying the degradation of methylene blue dye solution under direct sunlight as well as UV irradiation.
TL;DR: In this paper, a hierarchical disorder sponge-like macro/mesoporous titania was prepared by adding distilled water dropwise to a coating of tetrabutyl titanate, and the results reveal that the un-calcined samples show obvious photocatalytic activity and multi-modal pore-size distribution.
Abstract: Hierarchically disorder sponge-like macro/mesoporous titania was prepared by adding distilled water dropwise to a coating of tetrabutyl titanate. The results reveal that the un-calcined samples show obvious photocatalytic activity and multi-modal pore-size distribution. With increasing calcination temperatures, the photocatalytic activity and crystallinity increase. At 400°C, the calcined sample shows the highest photocatalytic activity. Further increasing the calcination temperatures results in the decrease of photocatalytic activity due to the drastic decrease of specific surface areas. However, the 600°C-calcined sample exhibits the highest specific photocatalytic activity due to high anatase crystallinity.
TL;DR: In this paper, the photocatalytic activity of bimodal mesoporous TiO 2 microspheres was investigated using a hydrothermal method using titanium sulfate as a precursor in the presence of urea.
Abstract: Bimodal mesoporous TiO 2 microspheres with high photocatalytic activity were prepared by a hydrothermal method using titanium sulfate as precursor in the presence of urea. The results indicate that all prepared samples show bimodal pore-size distributions in the mesoporous region: smaller intra-aggregated pores with peak pore diameter of ca. 2 nm and larger inter-aggregated pores with peak pore diameter of ca. 12.5 nm. The molar ratio of urea to Ti(SO 4 ) 2 ( R u ) has an obvious influence on the morphology, microstructure and photocatalytic activity of TiO 2 . With increasing R u , specific surface areas and porosity increase, contrarily, the crystallite size and relative anatase crystallinity decrease. The photocatalytic activity first increases with R u . At R u = 2.0, the photocatalytic activity reaches the highest and is obviously higher than that of Degussa P25. With further increasing R u , the photocatalytic activity decreases. The formation rate of hydroxyl radicals during photocatalysis has a positive correlation with the photocatalytic activity.
01 May 2009
TL;DR: In this paper, the Hidden-Valley scenario is used for exploring the challenges posed by long-lived particles with long decay paths to the trigger and the reconstruction capabilities of the ATLAS apparatus.
Abstract: Neutral particles with long decay paths that decay to many-particle final states represent, from an experimental point of view, a challenge both for the trigger and for the reconstruction capabilities of the ATLAS apparatus. The Hidden Valley scenario serves as an excellent setting for the purpose of exploring the challenges to the trigger posed by long-lived particles.