Mesoporous TiO2 Nanospheres Research Articles

Sono-Catalytic Tooth Whitening and Oral Health Enhancement with Oxygen Vacancies-Enriched Mesoporous TiO2 Nanospheres: A Nondestructive Approach for Daily Tooth Care.

Tooth discoloration and the breeding of oral microorganisms pose threats to both one's aesthetic appearance and oral health. Clinical whitening agents based on H2O2 with high concentrations are effective in tooth whitening and bacterial elimination but may also cause enamel demineralization, gingival irritation, or cytotoxicity, necessitating professional supervision. Herein, leveraging sono-catalysis effects, a nondestructive and convenient tooth whitening strategy was developed, utilizing oxygen vacancies (OVs)-enriched mesoporous TiO2 nanospheres. The introduction of OVs leads to TiO2 bandgap narrowing, boosting the generation of reactive oxygen species (ROS) by TiO2 under ultrasound treatment. Additionally, through the chemocatalysis effect, the ROS yield can be further augmented by employing OVs-enriched TiO2 in conjunction with an extremely low concentration of H2O2 (1%) during ultrasound treatment. Hence, under ultrasound treatment simulating daily tooth brushing using an electronic toothbrush, the combination of OVs-enriched TiO2 and 1% H2O2 proves to be effective in whitening teeth stained by tea, coffee, and mix juice. Furthermore, the combination of OVs-enriched TiO2 and 1% H2O2 demonstrates potent bacterial-killing and biofilm-eradicating effects under ultrasound treatment within an extremely short duration (5 min). Additionally, given the mesoporous structure, curcumin, serving as an anti-inflammatory agent, can be efficiently loaded into OVs-enriched TiO2 and then controllably released through ultrasound treatment. The curcumin-loaded TiO2 facilitates the transition of macrophages to the anti-inflammatory M2 phenotype, potentially alleviating oral inflammation induced by bacterial infection without showing any biotoxicity. The OVs-enriched TiO2 based sono-catalysis tooth whitening procedure provides the convenience of whitening teeth during daily brushing without requiring professional supervision.

Mesoporous and phase pure anatase TiO2 nanospheres for enhanced photocatalysis

Mesoporous and phase pure anatase TiO2 nanospheres for enhanced photocatalysis

Surface defects induced charge imbalance for boosting charge separation and solar-driven photocatalytic hydrogen evolution

Low charge separation efficiency of semiconductor materials is the main obstacle for high-performance photocatalyst. Herein, we report surface defects engineered uniform mesoporous TiO2 nanospheres (DMTNSs) through surfactant-mediated self-assembly solvothermal approach combined with hydrogenation strategy to promote charge separation. The surface defects induced charge imbalance result in the formation of built-in field, which can promote photogenerated charge separation efficiently and be confirmed by experimental and density functional theory (DFT) calculations. Under AM 1.5G irradiation, the photocatalytic hydrogen evolution of DMTNSs is ~3.34 mmol h−1 g−1, almost 3.5 times higher than that of pristine non-defective TiO2 nanospheres (0.97 mmol h−1 g−1), due to the engineered surface defects narrowing the bandgap (~3.01 eV) and inducing charge imbalance to boost spatial charge separation and extend visible-light response. The defect induced charge imbalance strategy opens a new valuable perspective for fabricating other high-efficient oxide photocatalysts.

Enhanced Photocatalytic CO2 Reduction with Photothermal Effect by Cooperative Effect of Oxygen Vacancy and Au Cocatalyst.

CO2 conversion into chemical fuels is a sustainable approach to the concurrent mitigation of the energy crisis and the greenhouse effect. It is still urgently desirable but quite challenging to explore a promising catalyst for CO2 photoreduction due to the severity in the fast recombination of electron holes and the deficiency of active sites, which have a tremendous influence on the catalytic behavior. In this regard, mesoporous TiO2 nanospheres containing oxygen vacancies (OVs) and metallic Au nanoparticles (NPs) were successfully prepared and showed markedly enhanced CO2 reduction activity and CH4 selectivity by the simple combination of photocatalysis with the simultaneous photothermal effect under full-spectrum irradiation. The dual introduction of OVs and a Au/TiO2 Schottky junction can not only serve as an electron sink to significantly improve the charge separation/transfer efficiency but also show effective photothermal conversion to raise the local temperature of the catalyst, thus resulting in an enhanced shuttle of electrons and desorption of products. This study not only offers new insights into the integrated tuning of charge recombination processes but also demonstrates that the photothermocatalysis has great potential in CO2 reduction.

Mesoporous dark brown TiO2 spheres for pollutant removal and energy storage applications

Colored TiO2 has tremendously attained significant interest worldwide due to its fascinating optical properties. Mesoporous dark brown TiO2 nanospheres with extremely high surface area (1246 m2/g) fabricated through the combined approach of thermal annealing with the sol–gel method. FESEM images inferred the creation of the spherical structure of 357 nm which transformed into defected mesoporous TiO2 spheres of 452 nm under annealing at 350 °C. UV-DRS PL and EPR studies confirm the bandgap narrowing due to the creation of oxygen defects sates in the TiO2 sample. Dark brown TiO2 exhibits remarkable sunlight-induced photodegradation activity for methylene blue and oxytetracycline hydrochloride molecules. Mesoporous TiO2 defect rich spheres adsorb the 32% of the MB pollutant molecules in just 30 min. Moreover, it decomposes the rest 67% of 15 µM MB dye solution and 0.5 mg/mL OTC solution in 30 min and 80 min respectively. Existences of high oxygen defect states in TiO2 were responsible for the bandgap narrowing and improve charge carriers separation and superior photocatalytic activity (PCA). Mesoporous dark brown TiO2 sample was also investigated for the energy storage application. Unusual high surface area also facilitated the accumulation of charges and led to the enhancement in charge storage properties.

1T- and 2H-mixed phase MoS2 nanosheets coated on hollow mesoporous TiO2 nanospheres with enhanced photocatalytic activity

Recently, photocatalysts with a hollow mesoporous structure have drawn increasing interest owing to their extensive application in environmental protection. Herein, we prepared hollow mesoporous TiO2 nanospheres decorated with few layer 1T- and 2H- mixed phase MoS2 nanosheets via a template-based method and a hydrothermal reaction. The as-synthesized samples are of hollow mesoporous structure and high specific surface area, providing abundant mass transport and active sites for photocatalytic reaction. 1T-MoS2 in the mixed phase MoS2 mainly play the role as a bridge that transfers photoexcited electrons. Besides, the heterojunction between MoS2 and TiO2 can also efficiently restrain the recombination of photogenerated charge carriers in photocatalysts. As a consequence, under UV–vis light irradiation, the hollow porous TiO2/MoS2 presents a remarkable photocatalytic activity in rhodaming B degradation. Scavenger studies demonstrate that the primary active species in photocatalytic process are hydroxyl radicals. Moreover, a possible photocatalytic reaction mechanism has also been put forward.

Dissolution–precipitation approach for long-term stable low-friction composites consisting of mesoporous TiO2 nanospheres and carbon black in Poly(Vinylidene fluoride) matrix

Low-friction composites with long-term stability based on three-dimensional, mass-producible mesoporous TiO2 nanospheres (MTNs) with a large surface area and carbon black (CB) dispersed in a poly (vinylidene fluoride) (PVDF) matrix were developed via dissolution–precipitation approach. The interaction and miscibility were enhanced by the incorporation of a small amount of CB filler. A long-term test (4 h) indicated that the incorporation of 5% MTN reduced both the friction coefficient (0.480) and the specific wear rate (0.412 × 10−4 mm3 N−1 m−1) compared with neat PVDF. The friction coefficient (0.446) was further reduced by the addition of CB (MTN_15CB with 15% MTN) owing to the increased fraction of the nonpolar α phase in the PVDF and the good adhesion properties of the composites.

Zn and Sr co-doped TiO2 mesoporous nanospheres as photoanodes in dye sensitized solar cell

Mesoporous TiO2 nanospheres that were co-doped with Zn and Sr were synthesized via a simple hydrothermal method. These materials were used as the photoanode in dye-sensitized solar cells (DSSCs). Field-emission electron microscopy showed that the nanospheres were monodisperse and interconnected, while transmission electron microscopy (TEM) showed that the nanospheres were composed of different nanostructures (nanotubes, diamond and sheet-like structures). Scanning TEM showed a homogeneous distribution of Sr, Ti, Zn and O throughout the nanospheres. When the Zn, Sr co-doped mesoporous TiO2 nanospheres were incorporated into DSSCs, a device efficiency of 4.6%, a short circuit photocurrent density of 8.63 mA cm−2 and an open circuit voltage 0.72 V were achieved. The efficiencies of these devices were higher than that of a comparison device (2.9%) that contained TiO2 (P25).

Mesoporous TiO2 nanospheres loaded with highly dispersed Pd nanoparticles for pH-universal hydrogen evolution reaction

An effective cation exchange strategy is developed to synthesize highly dispersed palladium (Pd) nanoparticle (NP)–embedded mesoporous TiO2 nanospheres enriched with oxygen vacancies aiming at overcoming the specific service condition and stability limitations of supported metal electrocatalysts. This strategy involves embedding Pd2+ cation into the interlayer of sodium titanate sheets through cation exchange with Na+, followed by annealing to obtain metallic Pd NP–embedded anatase phase TiO2 (Pd–TiO2). The resulting Pd–TiO2 shows excellent electrocatalytic activity toward hydrogen evolution reaction (HER) (i.e., an overpotential of 108 mV at 10 mA cm−2) with good stability in acidic media, along with good activity and excellent stability under basic and neutral conditions. The high HER activity is attributed to the uniform distribution and strong attachment of Pd NPs in the TiO2 nanospheres, the high porosity of mesoporous TiO2 nanostructures, and the creation of oxygen vacancies in TiO2 induced during the cation exchange process. Our findings are supported by the density functional theory calculations, which demonstrate the synergistic effect between Pd and TiO2 and the contribution of oxygen vacancies to the high HER performance.

One-pot synthesis of oleic acid modified monodispersed mesoporous TiO2 nanospheres with enhanced visible light photocatalytic performance

Herein, we report a facile one-pot solvothermal method to prepare unique oleic acid (OA) modified monodispersed mesoporous TiO2 nanospheres with carboxylate ligands from the oleic acid in the bidentate chelating linkage mode. The mesoporous OA-TiO2 nanospheres have a very large specific surface of nearly 510 m2/g. The oleic acid cannot only act as a binding ligand to control the shape of mesoporous TiO2 nanospheres, but also be benefit to enhance the visible-light absorption. The mesoporous OA-TiO2 nanospheres exhibit an excellent photocatalytic performance in the degradation of Rhodamine B and phenol under the visible light irradiation and show almost no attenuation after four cycles.

Ultra-fast photocatalytic and dye-sensitized solar cell performances of mesoporous TiO2 nanospheres

Mesoporous anatase TiO2 nanospheres with good interconnectivity were prepared by solvothermal method using carbon spheres as a template. FESEM and TEM images revealed the formation of mesoporous TiO2 nanospheres with the sizes of 150–200 nm. It was composed of nanoparticles in the range of 5–10 nm. XRD patterns revealed the anatase phase. Raman and X-ray photoelectron spectroscopy analyses ascertained that the carbon spheres acted only as a template to obtain the mesoporous TiO2 nanospheres. The formation mechanism of the mesoporous TiO2 nanospheres was discussed. The photocatalytic performance of the mesoporous TiO2 nanospheres with different dosage on Methylene Blue (MB) as a model pollutant was carried out under visible light irradiation. The mesoporous TiO2 nanospheres exhibited ultra-fast degradation of MB within 1.5 min. It was three times higher than that of commercial P25 TiO2 photocatalyst. TiO2 mesoporous nanospheres were used as a photoanode material for the fabrication of dye sensitized solar cell (DSSC) using N719 dye as a sensitizer and device showed an efficiency of 4.65%.

Enhanced photon collection of high surface area carbonate-doped mesoporous TiO2 nanospheres in dye sensitized solar cells

Carbonate-doped mesoporous TiO2 nanospheres with anatase phase were successfully synthesized by the simple solvothermal method. The synthesized nanospheres were monodispersed and composed of particles having the size of 10–15 nm. Scanning transmission electron microscopy (STEM) analysis showed nanosphere with large number particles. STEM-mapping clearly showed that Ti, O, and C were homogeneously distributed. Incorporation of carbonate in TiO2 was confirmed by XPS analysis. The peak at 284.3 eV was assigned to CO and indicated the formation TiOC structure due to carbonate doping in TiO2 lattice. Dye-sensitized solar cells (DSSCs) containing the nanospheres were fabricated by spray coating technique using N719 dye. Carbonate-doped mesoporous TiO2 showed enhanced DSSC efficiency (5.4%) compared to undoped (3.4%) and commercially available TiO2 (P25) (2.4%). It indicated (1) higher surface area and incident photon conversion efficiency, (2) lower resistance and longer life time compared with undoped TiO2.

Soft-Template Synthesis of Mesoporous Anatase TiO₂ Nanospheres and Its Enhanced Photoactivity.

Highly crystalline mesoporous anatase TiO2 nanospheres with high surface area (higher than P25 and anatase TiO2) are prepared by a soft-template method. Despite the high specific surface area, these samples have three times lower equilibrium adsorption (<2%) than Degussa P25. The rate constant of the mesoporous anatase TiO2 (0.024 min−1) reported here is 364% higher than that of P25 (0.0066 min−1), for the same catalytic loading. The results of oxidation-extraction photometry using several reactive oxygen species (ROS) scavengers indicated that mesoporous anatase TiO2 generates more ROS than P25 under UV-light irradiation. This significant improvement in the photocatalytic performance of mesoporous spherical TiO2 arises from the following synergistic effects in the reported sample: (i) high surface area; (ii) improved crystallinity; (iii) narrow pore wall thicknesses (ensuring the rapid migration of photogenerated carriers to the surface of the material); and (iv) greater ROS generation under UV-light.

Activation effect of silver nanoparticles on the photoelectrochemical performance of mesoporous TiO2 nanospheres photoanodes for water oxidation reaction

This work reports the photodeposition of Ag nanoparticles onto mesoporous TiO2 (m-TiO2) pre-formed by the evaporation-induced self-assembly method. Photoanodes of Ag/m-TiO2 assembled by electrophoretic disclose a superior photoelectrochemical (PEC) performance for water oxidation reaction related to m-TiO2. The photoanodes physicochemical investigations witness the even arrangement of m-TiO2 nanospheres particles over the substrates. The PEC study displays a steady photocurrent density of 1 mAcm−2 at −1.0 V vs SCE was attained for Ag/m-TiO2 photoanodes in visible light illumination and it is nearly twofold enhancements in comparison with m-TiO2 photoanodes. The observed superior PEC nature was attributed to the reduced band-gap energy and charge recombination that caused from the incorporation of plasmonic photodeposited Ag nanoparticles on m-TiO2 nanospheres photoanodes.

Mesoporous TiO2@N-doped carbon composite nanospheres synthesized by the direct carbonization of surfactants after sol-gel process for superior lithium storage.

Here, we report mesoporous TiO2@N-doped carbon composite nanospheres synthesized via a double-surfactant-assisted assembly sol-gel process followed by sequential carbonization of surfactants under a N2 atmosphere. The resulting TiO2@N-doped C composite nanospheres are composed of uniformly distributed TiO2 nanocrystals with a diameter of ∼8 nm coated by a N-doped carbon layer that was formed by surfactants. Moreover, a large number of connected mesopores were observed in the nanospheres after high-temperature carbonization treatment. The synthesized nanospheres possess a large specific surface area (∼120 m2 g-1) and a large pore size (4-40 nm), with a well-defined spherical structure and a diameter in the nanoscale range. As an anode material for lithium-ion batteries (LIB), the mesoporous composite nanospheres delivered a reversible capacity of ∼117 mA h g-1 after 2000 cycles at a current rate as high as 10 C, as well as superior rate capability. The N-doped carbon layers greatly improved the overall electrical conductivity of the mesoporous TiO2 nanospheres. This study provides a remarkable synthetic route for the preparation of mesoporous TiO2-based N-doped carbon composite materials as high-performance anode materials in LIBs.

Synthesis of Monodisperse Mesoporous TiO2 Nanospheres from a Simple Double-Surfactant Assembly-Directed Method for Lithium Storage

Exploring facile and reproducible methods to prepare mesoporous TiO2 nanospheres is crucial for improving the performance of TiO2 materials for energy conversion and storage. Herein, we report a simple and reproducible double-surfactant assembly-directed method to prepare monodisperse mesoporous TiO2 nanospheres. A double-surfactant system of n-dodecylamine (DDA) and Pluronic F127 was adopted to control the hydrolysis and condensation rates of tetrabutyl titanate in a mixture of water and alcohol at room temperature. In this process, the diameter size of mesoporous TiO2 nanospheres can be simply tuned from ∼50 to 250 nm by varying the concentration of H2O and surfactants. The double-surfactant system of DDA and F127 plays an effective role in determining the size, morphology, and monodispersity of mesoporous TiO2 nanospheres to reduce agglomeration during the sol-gel process. The resultant mesoporous anatase TiO2 nanospheres after solvothermal treatment at 160 °C are built of interpenetrating nanocrystals with a size of ∼10 nm, which are arranged to obtain a large number of connecting mesopores. Mesoporous TiO2 nanospheres with a small diameter size of around 50 nm possess a high surface area (∼160 m(2)/g) and mesopores with sizes of 4-30 nm. The small diameter size, high crystallinity, and mesoporous structure of TiO2 nanospheres lead to excellent performance in cycling stability and rate capability for lithium-ion batteries. After 500 cycles, the monodisperse mesoporous TiO2 nanospheres exhibit a charge capacity as high as 156 mAhg(-1) without obvious fade, and the Coulombic efficiency can reach up to 100%.

Soft-Templated Self-Assembly of Mesoporous Anatase TiO2/Carbon Composite Nanospheres for High-Performance Lithium Ion Batteries.

Mesoporous anatase TiO2/carbon composite nanospheres (designated as meso-ATCCNs) were successfully synthesized via a facile soft-templated self-assembly followed by thermal treatment. Structural and morphological analyses reveal that the as-synthesized meso-ATCCNs are composed of primary TiO2 nanoparticles (∼5 nm), combined with in situ deposited carbon either on the surface or between the primary TiO2 nanoparticles. When cycled in an extended voltage window from 0.01 to 3.0 V, meso-ATCCNs exhibit excellent rate capabilities (413.7, 289.7, and 206.8 mAh g(-1) at 200, 1000, and 3000 mA g(-1), respectively) as well as stable cyclability (90% capacity retention over 500 cycles at 1000 mA g(-1)). Compared with both mesoporous TiO2 nanospheres and bulk TiO2, the superior electrochemical performance of the meso-ATCCNs electrode could be ascribed to a synergetic effect induced by hierarchical structure that includes uniform TiO2 nanoparticles, the presence of hydrothermal carbon derived from phenolic resols, a high surface area, and open mesoporosity.

Hierarchical mesoporous rutile TiO2/C composite nanospheres as lithium-ion battery anode materials

Hierarchical mesoporous rutile TiO2 nanospheres were successfully synthesized via a simple low-temperature template-free method. The rutile TiO2 electrode showed poor electrochemical anodic performance in a lithium-ion battery. In order to improve the performance, conductive polyaniline was synthesized and coated on rutile TiO2 nanospheres via in-situ polymerization and chemical etching. After carbonization, the TiO2/C composite electrode showed more stable cyclability and a higher rate performance. Additionally, the amorphous carbon layer provided an effective pathway for charge transport, leading to a lower charge-transfer resistance and a higher lithium-ion diffusion coefficient compared to those of untreated rutile.

Smart Decoration of Mesoporous TiO2 Nanospheres with Noble Metal Alloy Nanoparticles into Core–Shell, Yolk–Core–Shell, and Surface‐Dispersion Morphologies

AbstractNoble metal alloy‐decorated spherical mesoporous TiO2 nanoparticles were synthesized by the one‐pot, single‐step reaction of Ti(OiPr)4, Au3+, Pt4+, and Pd2+ or by the one‐pot reaction of hollow mesoporous TiO2 nanospheres with Au3+, Pt4+, and Pd2+ by means of a solvothermal method in methanol. Au–Pt–Pd@TiO2, Au–Pt@TiO2, and Au@TiO2 mesoporous nanoparticles with core–shell, yolk–core–shell, and surface‐dispersion morphologies were easily constructed. The noble metal alloy cores of the Au–Pt–Pd@TiO2 and Au–Pt@TiO2 yolk–core–shell nanoparticles have Au@Pt–Pd and Au@Pt embedded sub‐core–shell structures, respectively.

Low temperature synthesis and photocatalytic properties of mesoporous TiO2 nanospheres

Facile one-step synthetic method for the fabrication of uniform mesoporous TiO2 nanospheres was reported on the basis of template-directed deposition and in situ template-sacrificial dissolution, in which SiO2 nanospheres was employed as the template and (NH4)2TiF6 was used as the precursor. The deposition of TiO2 nanoparticles on the surface of template is accompanied with the dissolution of SiO2 spherical cores by HF generated during the hydrolysis of (NH4)2TiF6 in the reaction. The obtained products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption–desorption analysis, and UV–visible diffuse reflectance spectroscopy. Furthermore, the photocatalytic activity of samples was evaluated by photocatalytic decolorization of three typical dyes (methyl orange, methylene blue, and rhodamine B) at ambient temperature under UV illumination. The results indicate mesoporous TiO2 nanospheres exhibited good photocatalytic activity for the degradation of different dyes. These monodisperse mesoporous TiO2 nanospheres should find various potential applications in photocatalysis, catalysis, solar cell, separation and purification processes.