Porous TiO2 Microspheres Research Articles

Porous TiO2 microspheres containing MgO nanoparticles/epoxy composite with superior thermal conductivity, EMI shielding, and electrical insulation

With the continuous advancement of electronic devices, the amounts of heat as well as electromagnetic (EM) waves generated have increased. Materials with high thermal conductivity and excellent EM interference shielding effectiveness (EMI SE) can be utilized to address this issue. In this work, we synthesized hollow anatase TiO2 microspheres. Through a reaction, MgO nanoparticles were incorporated into the interior of TiO2 microspheres. (H-TiO2/MgO). The heterostructure of the fillers contributed to performance enhancement. TiO2 and MgO particles formed a dual thermal-conduction pathway. H-TiO2/MgO effectively weakened the energy of EM waves upon contact. Additionally, TiO2, MgO, and epoxy all exhibited hydrophilicity. Consequently, the interfacial compatibility between H-TiO2/MgO and epoxy was excellent. They formed strong interfacial interactions by hydrogen bonding. Because of the excellent electrical insulation properties of H-TiO2 and MgO, the composites exhibited superior insulation performance (over 1010 Ω·cm). Our H-TiO2/MgO/Epoxy composites exhibited a maximum thermal conductivity of 7.52 W/m·K, an EMI SE of 64.92 dB, and a tensile strength of 79.10 MPa. Our composites are expected to effectively manage heat and EM waves generated by electronic devices.

Double nonmetal elements modified porous TiO2 homogeneous junction for efficient photocatalytic oxidation of cyclohexane

The nitrogen-doped TiO2 with mesoporous structure, anatase/rutile homogeneous junction and surface carbon species were successfully synthesized by facile hydrolysis of tetrabutyl titanate and preheating under the sealed condition, followed by a urea-aided calcination process. Interestingly, the as-obtained carbon modified TiO2 intermediates prepared by pretreating at different temperatures showed a certain photocatalytic activity for cyclohexane oxidation, and the carbon species were deposited to the surfaces of TiO2 via the Ti-O-C bond. The microstructure and photocatalytic activity of the double nonmetal elements modified porous mixed-phase TiO2 microspheres were found to depend on the preheating conditions, and nitrogen was doped into TiO2 lattice, the co-modification of nitrogen and carbon jointly improved the light absorption capacity and reduced the band gap of TiO2. The construction of a mixed-phase junction further improved the photocatalytic performance of the co-modified TiO2 compared with pure anatase or rutile TiO2. The optimal catalyst (N-TiO2-3 b) displayed efficient and stable photocatalytic performance for three cycles. When the reaction was conducted in real outdoor circumstances, the high ketone yield (206.22 μmol) and selectivity (99.92 %) were achieved. The synthetic method was simple and cheap, thus this work showed great potential for green production of fine chemicals under moderate conditions.

Accelerated Charge Transfer through Interface Chemical Bonds in MoS2/TiO2 for Photocatalytic Conversion of Lignocellulosic Biomass to H2.

Solar photocatalytic H2 production from lignocellulosic biomass has attracted great interest, but it suffers from low photocatalytic efficiency owing to the absence of highly efficient photocatalysts. Herein, we designed and constructed ultrathin MoS2-modified porous TiO2 microspheres (MT) with abundant interface Ti-S bonds as photocatalysts for photocatalytic H2 generation from lignocellulosic biomass. Owing to the accelerated charge transfer related to Ti-S bonds, as well as the abundant active sites for both H2 and ●OH generation, respectively, related to the high exposed edge of MoS2 and the large specific surface area of TiO2, MT photocatalysts demonstrate good performance in the photocatalytic conversion of α-cellulose and lignocellulosic biomass to H2. The highest H2 generation rate of 849 μmol·g-1·h-1 and apparent quantum yield of 4.45% at 380 nm was achieved in α-cellulose aqueous solution for the optimized MT photocatalyst. More importantly, lignocellulosic biomass of corncob, rice hull, bamboo, polar wood chip, and wheat straw were successfully converted to H2 over MT photocatalysts with H2 generation rate of 10, 19, 36, 29, and 8 μmol·g-1·h-1, respectively. This work provides a guiding design approach to develop highly active photocatalysts via interface engineering for solar H2 production from lignocellulosic biomass.

Boosted charge transfer in Pt cluster anchored TiO2 microspheres with rich oxygen vacancies for solar driven H2 production from lignocellulosic biomass

Pt nanoclusters anchored porous TiO2 microspheres with abundant oxygen vacancy was developed as a highly-efficient photocatalyst for solar driven photocatalytic lignocellulosic biomass-to-H2 conversion.

Controllable preparation and photocatalytic performance of hollow hierarchical porous TiO2/Ag composite microspheres

Mesoporous titania-based composites have attracted much attention in the world due to their large specific surface area, high material transport efficiency, and photocatalytic efficiency. The hollow and hierarchical porous structure is rarely involved in a binary photocatalytic material. In the present work, a novel type of hollow hierarchical porous TiO2/Ag composite microsphere with tunable microstructure was successfully prepared by simple solution methods, including sol-gel method, template method and impregnation method. Hollow hierarchical porous TiO2 microspheres were prepared by a sol-gel process with P123 as a hierarchical pore structure guide agent and template method with polystyrene microspheres as a hollow hard template. Further, hollow hierarchical porous TiO2/Ag composite microspheres were obtained by modifying Ag in the hollow hierarchical porous TiO2 microspheres by the impregnation method. The different hollow hierarchical porous TiO2/Ag composite microspheres are obtained by changing the molar ratio R of Ti/Ag. The optimal addition amount of Ti and Ag in sample HHPA6 (10:0.5) is the molar ratio of 10:0.5, and the experimental value of XPS is the molar ratio of 10:0. 91. Compared with the hollow hierarchical porous TiO2 microspheres, the excitation wavelength of composite microspheres is shifted to the visible light direction by 24 nm, and their response range and their light utilization rate were improved. When the molar ratio R of Ti/Ag is 10:0.5, hollow hierarchical porous TiO2/Ag composite microspheres have a specific surface area of 177 m2/g, the pore volume of 0.37 cm3/g, and the primary and secondary pore size of 4.04 nm and 7.74 nm, respectively. It shows the highest photocatalytic activity in the ultraviolet band of 365 nm and 395 nm, and the degradation rate of methyl orange solution is 96.84% and 98.65%, respectively. Their excellent photocatalytic performance is attributed to their special structure combining hierarchical pores and hollow structures as well as the synergistic effect of Ag and TiO2.

Programmable Y-Shaped Probes with Proximity Bivalent Recognition for Rapid Electrochemiluminescence Response of Acute Myocardial Infarction.

Herein, an exogenous luminophore-free and disposable electrochemiluminescence (ECL) biosensor was established for rapid response of acute myocardial infarction (AMI) using programmable Y-shaped probes (Y-probes) with proximity bivalent recognition. Specifically, the indium tin oxide thin film coated glass electrode (ITO) was modified with urchin-like porous TiO2 microspheres (pTiO2 MSs), which could achieve strong and stable ECL in S2O82- solution due to the dual promoting effect of the coreaction accelerator pTiO2 MSs, exhibiting 2.7-fold higher ECL intensity in comparison with that of bare ITO. Moreover, the Y-probes as bivalent recognition elements containing two kinds of cardiac troponin I (cTnI, a biomarker of AMI) aptamers and a linker labeled with ferrocene (L-Fc) were designed to export a "signal off" mode. When the target cTnI was in the proximity of the Y-probes, the L-Fc was separated from the electrode surface due to the proximity recognition of cTnI and its aptamers, achieving the highly effective recovery of ECL, which allowed for a much more rapid detection of cTnI than the sandwich-type immunoassay. As a proof of concept, an exogenous luminophore-free and disposable ECL platform for rapid and sensitive monitoring of cTnI was obtained and displayed a desired linear range from 100 fg mL-1 to 100 ng mL-1 with a limit of detection (LOD) of 30.1 fg mL-1, which can be ingeniously expanded as a portable home tester with ECL biosensors developments.

Synthesis, characterization, and photocatalytic antibacterial activities of porous Ce-doped TiO2 microspheres using pine pollen as novel biotemplates

Synthesis, characterization, and photocatalytic antibacterial activities of porous Ce-doped TiO2 microspheres using pine pollen as novel biotemplates

Synthesis of TiO2 microspheres by ultrasonic spray pyrolysis and photocatalytic activity evaluation

This work presents and discusses TiO2 microspheres synthesized by ultrasonic spray pyrolysis. A simple setup allowed for the continuous production of TiO2 nanocrystals. During the process, the particles experienced a short residence time (ca. 40 s) at the set temperature (700 °C), promoting phase stability and limited particle coarsening. As a result, porous anatase TiO2 microspheres with crystallite size ∼8 nm and specific surface area ∼27 m2 g-1 were produced as soft spherical agglomerates of ∼0.6 μm. Samples were analyzed using X-ray diffraction, BET specific surface area, SEM, TEM, XPS, and UV/Vis diffuse reflectance spectra, as well as in their photocatalytic activities. Photoactivity was evaluated through the degradation of the model contaminant acetaminophen under UV irradiation, and the results confirmed the superior performance of the synthesized TiO2 microspheres, exceeding the commercial standard TiO2 P25 by ca. 60% in terms of reactivity.

Macroporous-mesoporous C-, S-, N-doped titania microspheres via the polyHIPE microspheres templates

Doping and increasing specific surface area by forming highly porous structures are two effective ways to enhance the photocatalytic performances of TiO2 particles. Here for the first time, we report a new facile method to prepare the macroporous-mesoporous C-, S-, N-doped TiO2 (C/S/N-TiO2) microspheres via polyHIPE microspheres as templates. The chemical and crystalline structures of these hierarchical porous TiO2 microspheres are analyzed with FTIR, XPS, EDS, and XRD. The macroporous-mesoporous structures are confirmed with SEM observation and BET analysis. UV–vis DRS spectra analysis shows that the band gaps of C doped TiO2, C/N doped TiO2, C/S doped TiO2 and C/S/N doped TiO2 are estimated to be 3.07, 3.01, 2.94 and 2.81 eV, respectively, which are significantly narrower than that of TiO2 nanoparticles (3.23 eV). Photoluminescence spectra demonstrate that the recombination of electrons and holes in these macroporous-mesoporous TiO2 microspheres is also suppressed. The hierarchical porous C/S/N-TiO2 microspheres show high visible-light catalytic efficiency and excellent cycling stability to degrade RhB dye.

High-humidity tolerance of porous TiO2(B) microspheres in photothermal catalytic removal of NOx

Semiconductor oxides are widely used to achieve photocatalytic removal of NOx (NO and NO2) species. These materials also exhibit enhanced oxidation ability in thermally assisted photocatalysis; however, many of them tend to be deactivated at high relative humidity (RH) levels. In the case of the benchmark P25 TiO2 photocatalyst, we observe a significant decrease in non-NO2 selectivity from 95.02% to 58.33% when RH increases from 20% to 80%. Interestingly, the porous TiO2(B) microspheres synthesized in this work exhibit 99% selectivity at 20% RH; the selectivity remains as high as 96.18% at 80% RH. The high humidity tolerance of the TiO2(B) sample can be ascribed to its strong water desorption capacity and easy O2 adsorption at elevated temperatures, which reflects the fact that the superoxide radical is the main active species for the deep oxidation of NOx. This work may inspire the design of efficient photothermal catalysts with application in NOx removal in hot and humid environments.

Hierarchical Porous Anatase TiO2 Microspheres with High-Rate and Long-Term Cycling Stability for Sodium Storage in Ether-Based Electrolyte

Hierarchical architecture of porous anatase TiO2 microspheres are obtained by a universal solvothermal reaction, which can improve the cycling stability and ionic/electronic transport properties in...

In vitro evaluation of doxorubicin-eluting porous titania microspheres for transcatheter arterial chemoembolization

ABSTRACTPreparing drug-eluting beads (DEBs) from radiopaque materials such as titania (TiO2) can meet clinical need for directly visualizing DEBs during drug-eluting bead transcatheter arterial chemoembolization (DEB-TACE). Porous anatase-type TiO2 microspheres with mean volume diameters of approximately 30 µm were obtained when silica nanoparticles (SiNPs) were introduced into the TiO2 matrix by a sol–gel process involving a water-in-oil emulsion, and the SiNPs were then dissolved by subsequent treatment with NaOH solution. Of special note, microspheres prepared using SiNPs of approximately 20 – 25 nm in diameter had a high specific surface area of ~120 m2·g−1 and a high doxorubicin (DOX)-adsorption capacity of ~150 mg·mL−1, and they gradually released ~10% of the adsorbed DOX within 5 days. The DOX-loaded microspheres were non-cytotoxic, moreover, and exerted anticancer effects on HeLa cells. We propose that the present TiO2 microspheres are potentially useful as novel radiopaque embolic materials for DEB-TACE.

Controlled and sustained drug release performance of calcium sulfate cement porous TiO2 microsphere composites.

BackgroundCalcium sulphate cement (CSC) is widely used as an osteoconductive biomaterial in bone repair and regeneration.PurposeIn this study, porous TiO2 microspheres were added to CSC to achieve a controlled and sustained drug (gentamicin) release.MethodsScanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analysis were conducted to analyse the morphology, phase composition, and surface area of the TiO2 micro-spheres and composite cements. In addition, the injection time, compressive strength, degradation behaviour, and antibacterial ability of the composite cements were examined during in vitro degradation. Gentamicin release profile was recorded using an ultraviolet spectrophotometer.ResultsThe results revealed the excellent drug loading ability of the TiO2 microspheres. The addition of TiO2 microspheres improved the injectability and compressive strength of the composite cements, the maximum value of which was achieved at a TiO2 loading of 5 wt.%. When immersed in simulated body fluid (SBF), the composite cements doped with TiO2 microspheres were observed to release gentamicin in a stable and sustained manner, especially in the latter stages of in vitro degradation. During degradation, CSC doped with TiO2 microspheres exhibited a typical apatite-like behaviour. Further, antibacterial analysis showed that CSC doped with TiO2 microspheres exhibited long-term antibiotic activity.ConclusionThus, as an effective sustained-release formulation material, TiO2 microspheres show a great potential for application in bone cements.

Morphology dependent resonance modes in highly porous TiO2 microspheres

Micro and nano structures of titanium dioxide (TiO2) are well-known for their photocatalytic application. High surface area and high light scattering efficiency in such structures enhance their photocatalytic activity. The present work explores the possibility of enhancing photocatalytic activity through mesoporous TiO2 spheres by exploiting the coexistence of high porosity and morphology dependent resonance (MDR) modes. A controlled synthesis of TiO2 spheres with nano-crystalline grains of anatase phase and high surface area of about 96 m2/g has been successfully accomplished leading to mesoporous particles with uniformly distributed pores of small diameters much less than the wavelength of incident light. Despite the high porosity, MDR modes are observed in the photoluminescence spectrum of a single sphere. As inclusion of pores may produce significant changes in the refractive index (RI) of the resonator, and as the quality and density of the modes depend on the RI of the resonator, it is important to have a procedure to determine the RI of the resonator as well as to characterize the MDR modes. An iterative procedure that is quite general is presented for mode identification and for the determination of the porosity-induced reduction in the RI and for ascertaining the presence of chromatic dispersion. The presence of high surface area as well as of MDR modes of reasonably high Q-factor makes these particles promising for photo electrochemical applications.

Aerosol Spray Pyrolysis Synthesis of Porous Anatase TiO2 Microspheres with Tailored Photocatalytic Activity

Porous titanium dioxide (TiO2) microspheres (MS) were prepared by a facile ultrasonic spray pyrolysis process with commercial colloidal silica as a sacrificial template. The morphology structure, Brunauer–Emmett–Teller surface areas and pore size distribution of TiO2 microspheres were studied by changing the content and diameter of the silica template in detail. These porous micro-sized MS are composed of anatase TiO2 nanocrystallites of 5–10 nm and have unique bimodal mesopores. The largest specific surface area of 112.3 m2/g has been achieved using 60 wt% 20 nm silica as a template. When used as photocatalysts, the best photocatalytic activity of the as-prepared porous MS is comparable to commercial P25 nanopowders. Moreover, the micro-size and tailored properties from the design that appear during the ultrasonic spray pyrolysis process give these porous MS a promising application in photocatalytic reaction.

Hierarchically nanostructured porous TiO2(B) with superior photocatalytic CO2 reduction activity

Hierarchically nanostructured, porous TiO2(B) microspheres were synthesized by a microwave-assisted solvothermal method combined with subsequent heat treatment in air. The materials were carefully characterized by scanning and transmission electron microscopy, X-ray diffraction, CO2 adsorption, and a range of spectroscopies, including Raman, infrared, X-ray photoelectron and UV-Vis spectroscopy. The hierarchical TiO2(B) particles are constructed by ultrathin nanosheets and possess large specific surface area, which provided many active sites for CO2 adsorption as well as CO2 conversion. The TiO2(B) nanostructures exhibited marked photocatalytic activity for CO2 reduction to methane and methanol. Anatase TiO2 and P25 were used as the reference photocatalysts. Transient photocurrent measurement also proved the higher photoactivity of TiO2(B) than that of anatase TiO2. In-situ infrared spectrum was measured to identify the intermediates and deduce the conversion process of CO2 under illumination over TiO2(B) photocatalyst.

A self-cleaning coating material of TiO2 porous microspheres/cement composite with high-efficient photocatalytic depollution performance

In this letter, we developed a self-cleaning coating material through simply blending the TiO2 porous microspheres (PMS) with the commercial cement. The TiO2 PMS with the diameters around 500nm were synthesized by an ultrasonic spray pyrolysis method. During the photocatalytic depollution tests, the as-prepared TiO2 PMS/cement composite was processed into a hardened micro-film coated on the glass substrate via a doctor blade method. Upon UV–Vis light irradiation, the TiO2 PMS/cement composite film exhibited the higher photocatalytic activity as compared to the conventional P25/cement composite film. This can be attributed to the fact that the unique micro-nano hierarchical porous structure of TiO2 PMS not only boosts the light harvesting ability, but also provides more active sites for the photocatalytic reaction.

Noble metal modified TiO2 microspheres: Surface properties and photocatalytic activity under UV–vis and visible light

Composite photocatalysts that consist of TiO2 and noble metal nanostructures have been considered to be the promising and pivotal material for accessible enhancement of the efficiency in the photocatalytic process carried out in the aqueous and gas phases. In this work we fabricated porous TiO2 microspheres through a hydrothermal process followed by photochemical reduction of noble metal nanoparticles at the TiO2 surface. The morphology and structure of M-TiO2 spheres (M=Ag, Au, Pt and Pd) were studied with the use of various techniques, including transmission electron microscopy (TEM), X-ray powder diffraction analysis (XRD), photoluminescence (PL) and UV–vis diffuse-reflectance spectroscopy (DRS). The effect of metal amount (from 0.1 to 1wt.%.) on the photocatalytic activity during toluene degradation in gas phase and phenol degradation in aqueous phase was investigated. Additionally, the photocatalytic activity of the M-TiO2 samples was evaluated by measuring the formation rate of photo-induced hydroxyl radicals (OH) under UV–vis light irradiation using coumarin as a probe. The obtained results indicated that toluene could be mostly removed from the air over TiO2 microspheres modified with Ag, Au, Pt, and Pd nanoparticles. UV-mediated photoreactivity was almost similar for all samples obtained by loading metals from solutions consisting of 0.1 and 1wt.% of metal precursors. Under visible light, except for Au, in gas phase toluene oxidation, the optimized loading of the metals was 0.1wt.-% (photoreactivity changed in order: Ag-TiO2≈Pd-TiO2>Pt-TiO2>>Au-TiO2). In case of phenol degradation in the aqueous phase, in the presence of UV irradiation the highest amount of metal (1.5wt.%) was profitable, while under the Vis light reaction the medium amount of metal (0.5wt.%) was beneficial. Additionally, it was noticed that phenol was degraded not only via oxidation by OH radicals but probably also in direct reaction with the photogenerated carriers (e−/h+), particulary in the presence of TiO2 spheres loaded with Au and Ag nanoparticles.

A Facile Synthesis of Hierarchically Porous TiO2 Microspheres with Carbonaceous Species for Visible-light Photocatalysis

Hierarchically porous anatase TiO2 microspheres composited with carbonaceous species (TCS) have been successfully fabricated by a one-step template-free solvothermal method, combined with subsequent low temperature dried process. In this configuration, the TCS microspheres are constructed by the interconnected porous nanosheets, which are further assembled with abundant nanoparticles and carbonaceous species. Such composite microspheres possess a large specific surface area of 337 m2 g–1, uniform mesopores of 3.37 nm and high total pore volumes of 0.275 cm3 g–1. The materials exhibit the enhanced photocatalytic properties and stability for degradation of rhodamine B (RhB) under visible-light irradiation. The enhanced photocatalytic degradation performance may be ascribed to their abundant porous structure, large specific surface area and the unique assist-function of the carbonaceous species.

Synthesis and room-temperature ferromagnetism of porous V-doped rutile TiO2 microspheres

Porous V-doped TiO2 microspheres were synthesized by simply co-precipitating V and Ti precursors. Vanadium could be homogenously inserted into TiO2 lattice, and promotes the phase transition of TiO2 from anatase to rutile. V-doped TiO2 demonstrates ferromagnetism at room temperature of around 15 memu/g, which is highly associated with structure defects. Both surface defects and bulk oxygen vacancy contribute to the introduction of ferromagnetism in V-doped TiO2. It provides some experimental facts and is helpful for further understanding on the room-temperature ferromagnetism in DMSs.