Mesoporous Titania Microspheres Research Articles

Iron(III) removal from acidic solutions using mesoporous titania microspheres prepared by vibrational droplet coagulation

The removal of contaminants, such as Fe(III) from acidic leachates, is often needed as its presence as a contaminant hinders the recovery of the desired metals. An inorganic adsorbent of interest for the removal of Fe(III) is titania due to its high specific surface area and good chemical stability. However, besides the material properties, also the macroscopic shape of the adsorbent is important for its implementation. In this study we have shaped monodisperse titania microspheres using vibrating nozzle technology. In a first step, a suspension containing titania nanopowder and sodium alginate is broken up into monodisperse droplets. The droplets are then solidified through ionotropic gelation of the alginate binder molecules with the calcium ions used as solidification species. The thermally treated microspheres had an average diameter 518 µm, a specific surface area 97 mm2 g−1 and an average pore size of 19 nm. These titania microspheres were employed as an adsorbent to remove Fe(III) from acidic solutions (pH 2). A maximum adsorption capacity of 13.2 mg g−1 was found. A high selectivity (kD 449 mL g−1) was observed towards Fe(III) removal in an acidic leachate originating from a spend automotive catalyst. The titania microspheres could be easily separated and regenerated using a 0,1 M EDTA solution which was demonstrated for up to 5 cycles.

Stepwise construction of Pt decorated oxygen-deficient mesoporous titania microspheres with core-shell structure and magnetic separability for efficient visible-light photocatalysis

Solid photocatalysts with high specific surface area, superior photoactivity and ease of recycling are highly desired in chemical process, water treatment and so on. In this study, a facile stepwise sol-gel coating approach was utilized to synthesize Pt decorated oxygen-deficient mesoporous titania microspheres with core-shell structure and convenient magnetic separability (denoted as Fe3O4@SiO2@Pt/mTiO2-x). These photocatalysts consist of magnetic Fe3O4 cores, nonporous insulating SiO2 middle layer and mesoporous anatase TiO2-x shell decorated by Pt nanoparticles (∼3.5 nm) through wet impregnation and H2 reduction. As a result of high activity of oxygen-deficiency of black TiO2-x by H2 reduction and efficient inhibition of electron-hole recombination by Pt nanoparticles, the rationally designed core-shell Fe3O4@SiO2@Pt/mTiO2-x photocatalysts exhibit superior photocatalytic performance in rhodamine B (RhB) degradation under visible light irradiation, with more than 98% of RhB degraded within 50 min. These core-shell structured photocatalysts show excellent recyclability under the assistance of magnetic separation with well-retained photocatalytic performance even after running five cycles. This stepwise synthesis method paves the way for the rational design of a high-efficiency recyclable heterogeneous catalyst, including photocatalysts, for various applications.

Scalable synthesis of wrinkled mesoporous titania microspheres with uniform large micron sizes for efficient removal of Cr(vi)

Scalable synthesis of wrinkled mesoporous TiO2 microspheres with uniform large micron sizes is achieved. They show excellent performance for removal of Cr(vi).

Mesoporous Titania Microspheres with Highly Tunable Pores as an Anode Material for Lithium Ion Batteries.

Mesoporous titania microspheres (MTMs) have been employed in many applications, including (photo)catalysis as well as energy conversion and storage. Their morphology offers a hierarchical structural design motif that lends itself to being incorporated into established large-scale fabrication processes. Despite the fact that device performance hinges on the precise morphological characteristics of these materials, control over the detailed mesopore structure and the tunability of the pore size remains a challenge. Especially the accessibility of a wide range of mesopore sizes by the same synthesis method is desirable, as this would allow for a comparative study of the relationship between structural features and performance. Here, we report a method that combines sol-gel chemistry with polymer micro- and macrophase separation to synthesize porous titania spheres with diameters in the micrometer range. The as-prepared MTMs exhibit well-defined, accessible porosities with mesopore sizes adjustable by the choice of the polymers. When applied as an anode material in lithium ion batteries (LIBs), the MTMs demonstrate excellent performance. The influence of the pore size and an in situ carbon coating on charge transport and storage is examined, providing important insights for the optimization of structured titania anodes in LIBs. Our synthesis strategy presents a facile one-pot approach that can be applied to different structure-directing agents and inorganic materials, thus further extending its scope of application.

Scalable synthesis of mesoporous titania microspheres via spray-drying method

Mesoporous TiO2 has several potential applications due to its unique electronic and optical properties, although its structures and morphologies are typically difficult to tune because of its uncontrollable and fast sol-gel reaction. In this study we have coupled the template-directed-sol-gel-chemistry with the low-cost, scalable, and environmentally benign aerosol (spray-drying) one-pot preparation technique for the fabrication of hierarchically mesoporous TiO2 microspheres and Fe3O4@mesoporous TiO2−x microspheres in a large scale. Parameters during the pre-hydrolysis and spray-drying treatment were varied to successfully control the bead diameter, morphology, monodispersity, surface area and pore size for improving their effectiveness for better application. Unlike to the previous aerosol synthetic approaches, where mainly quite a high temperature gradient with the strict control of spray-drying precursor concentration is implied, our strategy is lying on comparatively low drying temperature with an additional post-ultrasonication (further hydrolysis and condensation) route of the pre-calcined TiO2 samples. As-synthesized mesoporous microspheres have a size distribution from 500nm to 5μm, specific surface areas ranging from 150 to 162m2g−1 and mean pore sizes of several nanometers (4–6nm). Further Fe3O4@mesoporous TiO2−x microspheres were observed to show remarkable selective phosphopeptide-enrichment activity which might have significant importance in disease diagnosis and other biomedical applications.

Monodisperse mesoporous TiO2 microspheres for dye sensitized solar cells

Uniform discrete mesoporous titania microspheres have been synthesized via a facile and controllable interface-directed co-assembly approach by using 3-dimensional macroporous carbon (3DOMC) as the nanoreactor for the confined co-assembly of template molecules and titania source. By adjusting the synthesis parameters, hollow mesoporous microspheres and hemi-microspheres can also be synthesized. The obtained mesoporous TiO2 microspheres possess a large pore size (4.7nm), high accessible surface area (145m2/g), large pore volume (0.26cm3/g) and highly crystallized anatase pore walls. The dye-sensitized solar cell based on the mesoporous TiO2 microspheres exhibits high photoconversion efficiencies up to 8.5%, which are largely attributed to their intrinsic high surface area, high porosity and well-connected crystalline framework.

One pot preparation of silver nanoparticles decorated TiO2 mesoporous microspheres with enhanced antibacterial activity

We report a simple “one-pot” solvothermal preparation of silver nanoparticles (Ag NPs) decorated mesoporous titania (TiO2) microspheres as an effective antibacterial agent. TBOT as Ti source was hydrolyzed and crystallized in media composed of acetic acid and ethanol, in which esterification catalyzed by TBOT occurred for in-situ “controlled water release”. AgNO3 as Ag source was reduced by ethanol to form Ag NPs embedded in the TiO2 microspheres. The effect of AgNO3 and HAc on the morphology of Ag/TiO2 was investigated. The Ag/TiO2 with various Ag content showed excellent antibacterial activities with extremely low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Escherichia coli and Staphylococcus aureus when compared with colloidal Ag NPs.

Hollow mesoporous titania microspheres: New technology and enhanced photocatalytic activity

Hollow titania microspheres (HTS) were fabricated via a sol–gel process by coating the hydrolysis product of titanium tetrabutoxide (TBOT) onto the amino (–NH2) modified porous polystyrene cross-linked divinyl benzene (PS-DVB) microspheres under changing atmospheric pressure, followed by calcination in nitrogen and air atmosphere. Particularly, the atmospheric pressure was continuously and regularly changed during the formation process of PS-DVB@TiO2 microspheres. Then the TiO2 particles were absorbed into the pores and onto the surface of PS-DVB as well. The resultant HTS (around 2μm in diameter) featured a high specific surface area (84.37m2/g), anatase crystal and stable hollow microsphere structure, which led to high photocatalysis activity. The photocatalytic degradation of malachite green (MG) organic dye solution was conducted under ultraviolet (UV) light irradiation, which showed a high photocatalytic ability (81% of MG was degraded after UV irradiation for 88min). Therefore, it could be potentially applied for the treatment of wastewater contaminated by organic pollutants.

Titania composite microspheres endowed with a size-exclusive effect toward the highly specific revelation of phosphopeptidome.

The efficient isolation of low-abundance phosphopeptides from complicated biological samples containing a significant quantity of nonphosphopeptides and proteins is essential for phosphopeptidome research but remains a great challenge. In this Article, magnetic composite microspheres comprising a magnetic colloidal nanocrystal cluster core and a mesoporous titania shell with an average pore diameter of 3.4 nm were modified by directly coating an amorphous titania shell onto the magnetite core, followed by converting the amorphous titania shell into a crystalline structure via a hydrothermal process at 80 °C. The as-prepared magnetic mesoporous titania microspheres possess a remarkable specific surface area that is as high as 603.5 m2/g, which is an appropriate pore size with a narrow size distribution and a high magnetic responsiveness. These outstanding features imply that the composite microspheres exhibit extraordinary performance in phosphopeptidome research, including high specificity toward phosphopeptides, an excellent size-exclusion effect against phosphoproteins, exceptional enrichment capacity, and efficient separation from mixtures. Encouraged by the experimental results, we employed this method to investigate the phosphopeptidome of snake venom for the first time. A total of 35 phosphopeptides was identified from the snake venom from the family Viperidae, accounting for 75% of the total identified peptides. This result represents the largest data set of the phosphopeptidome in snake venom from the family Viperidae.

Visible and near-infrared luminescent mesoporous titania microspheres functionalized with lanthanide complexes: microstructure and luminescence with visible excitation

A new type of monodisperse mesoporous titania microspheres possessing visible (Eu3+, Sm3+) and near-infrared (Sm3+, Yb3+, Nd3+) luminescence were synthesized with covalent linking to Ln(dbm)3bpdc complexes (Ln = Eu, Sm, Yb, Nd, dbm = dibenzoylmethanate, bpdc = 2,2′-bipyridine-4,4′-dicarboxylic acid). These lanthanide complex-functionalized titania microspheres can be excited with visible light to extend the practical application in lighting devices and biomedical analysis. The materials were characterized using Fourier-transform infrared (FT-IR) spectroscopy, wide-angle X-ray powder diffraction (WAXD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), nitrogen adsorption/desorption, diffuse reflectance (DR) spectroscopy, fluorescence spectroscopy, and thermogravimetric analysis. The results show that the microsphere morphology composed of single anatase crystallites and mesoporous structure is retained after linking to the lanthanide complexes. To the best of our knowledge, this is the first successful attempt to graft lanthanide complexes onto mesoporous anatase titania microspheres with high crystallinity. The novel combination of lanthanide complexes with NIR luminescence under visible light excitation and mesoporous titania microspheres with high thermal and chemical stabilities as well as anatase crystallinity affords potential applications in the fields of energy conversion, photocatalysis, and biomaterials.

Mesoporous titania microspheres composed of exposed active faceted nanosheets and their catalytic activities for solvent-free synthesis of azoxybenzenes

Mesoporous titania microspheres composed of nanosheets with exposed active facets were prepared by hydrothermal synthesis in the presence of hexafluorosilicic acid. They exhibited superior catalytic activity in the solvent-free synthesis of azoxybenzene by oxidation of aniline and could be used for 7 cycles with slight loss of activity.

Facile one-pot synthesis of Eu, N-codoped mesoporous titania microspheres with yolk-shell structure and high visible-light induced photocatalytic performance

A new type of Eu, N-codoped mesoporous TiO2 microspheres with yolk–shell structure (TiO2@void@TiO2) was successfully synthesized by a facile one-pot hydrothermal method at low temperature (180°C). The physical and chemical properties of as-synthesized samples, such as morphology, crystal phase, surface elements composition, porous structure, specific surface area and optical response, were characterized in detail. The resultant samples were porous microspheres with a diameter of about 1–3μm, and were composed of a large number of smaller nanoparticles. An interior circular cavity in each microsphere was formed between core and shell to construct a special yolk–shell structure, and a large number of pores were produced in shell and yolk by CO2 gas bubbles resulting from hydrothermal decomposition of the urea molecules, which tremendously increased the specific surface area and the pore volume of as-obtained samples. The absorption edges of Eu, N-codoped TiO2 were extended to longer wavelength, which led to notable absorption in the visible-light region. The photocatalytic performances of all samples were evaluated by photocatalytic decoloration of rhodamine B and methyl orange under visible light irradiation (λ>420nm). Eu, N-codoped TiO2 with 0.1at.% Eu dopant showed the highest photocatalytic activity, the efficiency of which was 5 times higher than that of Degussa P25. The enhanced photocatalytic performance could be attributed to the synergic effects of many factors, such as high specific surface area, large pore volume and strong absorption to visible light, which were created by the Eu, N-codoping and the unique yolk–shell structure. Based on the above results, the mechanism of enhanced photocatalysis on Eu, N-codoped TiO2 under visible light was proposed.

Synthesis and characterization of mesoporous titania microspheres and their applications

Mesoporous titanium dioxide microspheres were synthesized by the sol–gel templating method, using calcium alginate as a sacrificial template, and subjecting to different temperatures, under various atmospheres. The gradual changes in composition, crystallinity, phase and surface morphology, due to variation in calcination atmosphere and temperature, were monitored by TGA, XRD, SEM and EDX techniques. The effect of polymeric content on the surface area and the pore size of the titania beads was evaluated by BET analysis. The results show that N2 atmosphere and high temperature influence the phase content and morphology of the microsphere significantly. Anatase to rutile phase transformation and formation of calcium titanate take place under nitrogen atmosphere at lower temperature, as compared to that under air atmosphere. To examine the applications of these synthesized microspheres, photo-catalytic activity and sorption efficiency of the microspheres were evaluated, by carrying out photo-degradation of methylene blue (MB) dye, and removal of arsenic ions from ammoniacal solution. The microspheres showed good photo catalytic activity towards MB dye. Tracer experiments with 76As showed ∼98% sorption of arsenic ions from aqueous solution onto the titania microspheres.

Application of synthesized mesoporous titania microspheres for arsenic [(III) and (V)] uptake studies

The present work describes the application of radiotracer technique for studying uptake of arsenic on titanium hydroxide, commercial titanium dioxide (TiO2) powder (anatase) and synthesized mesoporous titania beads in acidic, neutral, and alkaline conditions. Sol–gel templating method was used to prepare titania–polysaccharide composites, with different polymer contents. Mesoporous titania was obtained by heat treatment of the composite beads in a controlled environment. The synthesis process was optimized, using thermogravimetry analysis. X-ray diffraction patterns confirmed the formation of anatase pure phase titania (TiO2) at 700 °C in different environments, and scanning electron microscopy studies confirmed uniform pore size distribution. The effect of surface area, polymer content and pH on uptake of arsenic(III) and (V) on the synthesized titania beads was also investigated. Arsenic(V) was found to be retained quantitatively on the titania beads synthesized from 0.8% polymer content titania–polymer composite precursor in neutral to alkaline conditions. Details of the results obtained are discussed.

Aerosol-Assisted Production of Mesoporous Titania Microspheres with Enhanced Photocatalytic Activity: The Basis of an Improved Process

An aerosol-based process was used to prepare mesoporous TiO(2) microspheres (MTM) with an average diameter in the range of 0.5-1 microm. The structural characteristics and photocatalytic properties of the synthesized materials were determined. As-prepared MTM materials and those heated in air from 400 to 600 degrees C exhibited mesoporous texture with a narrow size distribution and an inorganic framework that consisted of 4-13 nm anatase crystallites. Pore volumes for the MTM materials were in the range of 0.17-0.34 cm(3) g(-1). Microspheres heated to 400 degrees C presented a locally ordered mesopore structure and possessed X-ray diffraction d spacings between 9.8 and 17.3 nm. Heating above 400 degrees C resulted in a loss of the mesoscopic order, a decrease of the surface area, retention of the porosity, and an increase of the anatase nanoparticle size to 13 nm. The accessibility of the pore volume was measured by monitoring the uptake of gallic acid (GA) using Fourier transform IR. The MTM materials made excellent catalysts for the photodegradation of GA, with the performance being higher than that of an equivalent sample of Degussa P25. The present MTM materials are advantageous in terms of their ease of separation from the aqueous phase, and hence a novel photocatalytic process is proposed based on separate adsorption and photocatalytic decomposition steps with an improved and more rational use of both catalyst and sunlight.

Effects of urea on the microstructure and photocatalytic activity of bimodal mesoporous titania microspheres

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.

Facile Fabrication of Hollow Silica and Titania Microspheres Using Plasma-Treated Polystyrene Spheres as Sacrificial Templates

By means of a plasma technique, the surfaces of monodisperse polystyrene (PS) colloids have been modified with hydroxyl groups. Using these surface-modified PS colloids as sacrificial templates, we have fabricated silica-coated PS colloids (PS@silica) and titania-coated PS colloids (PS@titania) composite microspheres as well as hollow and mesoporous silica and titania microspheres. This process not only demonstrated a facile, low-cost, environmentally benign way to fabricate hollow oxides structures but also offered a feasible alternative to the preparation of polymer/inorganic oxide composites by templating against the polymer substrate with hydrophobic surfaces.

Novel core-shell structured mesoporous titania microspheres: Preparation, characterization and excellent photocatalytic activity in phenol abatement

Thermally stable mesoporous core-shell structured nanocrystallite titanium dioxide (TiO 2) microspheres were prepared by a novel hydro-alcohol thermal method. Anatase powders were synthesized under hydrothermal condition at 368 K from aqueous titania tetrachloride solution with the presence of urea and ammonium sulfate, then the samples were annealed at various temperatures before testing their photocatalytic activity. The morphology and microstructure characteristics of TiO 2 microspheres series were characterized by means of the specific surface area (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential thermal analysis (DTA), photoluminescence spectra (PLS), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD). The specific microsphere structures were maintained after a heat treatment at 973 K for 3 h, exhibiting a significant thermal stability. The photocatalytic activity was measured in a reactor with ultraviolet lamps. The catalysts show considerably high catalytic activity and recyclability during the photodegradation of phenol in aqueous suspension, the microsphere titania sample calcinated under 733 K for 3 h shows the best photocatalytic activity. The results obtained with this novel photocatalyst are compared with the behavior of the well-studied and widely used Degussa P25 TiO 2 under the same conditions.