Titanate Nanowires Research Articles

How substrate surface area and surface curvature determine kinetics and titanate formation during non-hydrothermal alkali treatment of titanium microspheres

Titanium surface nanostructuring using alkali treatment gains significant attention in a wide range of fields, such as biomaterials, (photo)catalysis, (metal/ion) sorption, CO2 capture, electrochromism and sodium-ion batteries. Even though the physicochemical properties and application potentials of the surface nanostructures are fairly well understood, there is still debate about their exact formation mechanism, limiting knowledge based structural control through altered synthesis conditions. Moreover, this knowledge is largely focused on hydrothermal synthesis conditions, whereas non-hydrothermal conditions might provide benefits towards industrial application. Also the impact of substrate properties, rather than chemical reaction conditions, on the nanostructure formation is only limitedly reported in literature. This work reveals new fundamental knowledge of non-hydrothermal alkali treatment of titanium, using microspheres by implementing, for the first time, in-situ hydrogen measurement during alkali treatment in combination with the ex-situ determination of the sodium and oxygen content in the recovered alkali treated samples, providing critical information on the role of dissolution apart from the precipitation process. The effect of surface area and surface curvature on the dissolution and precipitation process, and the resulting impact on the physicochemical properties of the obtained titanate layer is studied. This shows the much larger impact on dissolution in contrast to precipitation, knowledge that is lacking in literature, but important when implementing alkali surface nanostructuring on complex (e.g. 3D printed) substrates, and considering the prospective shift from lab-scale to industry. The Ti dissolution step was found to be mainly controlled by the total surface area, while the rate determining step was found to be the titanate precipitation, not influenced by either surface area or particle size.The changes in oxygen content in the samples after transformation of titanate into TiO2 provided a novel method for its quantification. The microspheres were analysed chemically (Raman), structurally (XRD) and morphologically (SEM, MIP), screening the effect of surface area, particle size and reaction time on the growth behaviour of the titanate layer. The porous layer structurally corresponds to Na2Ti2O4(OH)2 for all evaluated conditions, with pores in the range of 10–600 nm. Increasing surface area and particle size results in local and non-uniform titanate growth, while titanate nanowire and strut formation between the microspheres were enhanced by reduced microsphere size and prolonged reaction times.

Ce3+/Ce4+–TiO2 Nano‐Octahedra as Active Photocatalysts for Ciprofloxacin Photodegradation Under Solar Light

AbstractCerium‐containing titania nano‐octahedra (CeTNOh) are obtained by ultrasonication‐hydrothermal synthesis of Ce‐containing titanate nanowires (0.35, 0.46, and 0.70 Ce mol %) from commercial TiO2 (Degussa P25). CeTNOh are tested as photocatalysts to degrade a target pollutant (ciprofloxacin) under simulated solar light and at mild conditions. CeTNOh are anatase polymorphs with increasing crystallite size as Ce content increases. Hydrothermal treatments enhance the specific surface area (SSA) compared to P25, although Ce addition slightly reduces SSA while increasing crystallite size. Electron Microscopy confirms the morphology, although higher Ce levels hinder a full transformation. X‐ray photoemission spectroscopy (XPS) shows the presence of Ce3+/Ce4+ redox pair, promoting electron mobility and Ti‐Ce interactions. Optical and electronic spectroscopy reveals that Ce loading reduces the bandgap from 3.20 to 2.74 eV, extending light absorption into the visible range, thus enhancing the photocatalytic activity. The best sample, CeTNOh0.35, achieved 83% degradation of ciprofloxacin after 360 minutes under solar irradiation, with poor adsorption in the dark period. Higher Ce loadings negatively affect photoactivity by partially covering titania active sites. Reusability tests confirm the stability and efficiency of CeTNOh0.35 over three cycles, highlighting the importance of octahedral morphology in Ce‐containing systems to boost the final photoactivity for water remediation.

Harnessing Plasmonic Membranes for nanostructured TiO2 Activity Profiling

Titanium dioxide nanoparticles (TiO2 NPs) are widely used semiconductors that pose significant risks to both ecosystems and human health when released into aquatic environments. The primary environmental hazard of TiO2 NPs in surface water stems from their ability to generate reactive oxygen species (ROS) through photocatalytic activity. Addressing these risks is crucial for the safe utilization of TiO2 NPs and environmental protection. Herein, a novel plasmonic membrane, consisting of titanate nanowires (Ti NWs) functionalized with silica‐coated gold nanostars (AuNSts), has been developed to capture and measure the photocatalytic activity of TiO2 NPs in complex media such as seawater. This method provides a precise approach for real‐time monitoring of TiO2 NPs, thereby contributing to the establishment of an environmental risk parameter for these particles.

A Layered Titanate Nanowire Helps Pt/TiO2 Photocatalyst for Solar Hydrogen Evolution from Water with High Quantum Efficiency

Abstract Research into TiO2 photocatalysts for solar H2 evolution from water is still growing for environmentally benign and economically valid H2 production. Herein, in contrast to many researches on the modification of TiO2 toward higher photocatalytic activities, we develop a photocatalytically inactive TiO2-based nanostructure and use it, like graphene, as a booster of a benchmark TiO2. A layered potassium titanate with two-dimensional plate-like particle morphology was converted to the corresponding one-dimensional nanowire form via a hydrothermal reaction, after which the layered potassium titanate nanowire was acid-treated to obtain a layered titanate nanowire. This nanowire was completely inactive toward H2 evolution from water containing methanol under solar simulator irradiation. However, when Pt nanoparticle-loaded P25 TiO2 (Pt/P25) was mixed with a considerably smaller amount of the layered titanate nanowire in water, a durable composite was obtained and the composite showed a good photocatalytic activity three times higher than Pt/P25. The apparent quantum efficiency of the reaction at wavelength of 350 nm was 56%, which was higher than or comparable to those of the state-of-the-art TiO2-based photocatalysts. The possible reason for the enhanced photocatalytic activity of the Pt/P25 and layered titanate nanowire composite involved the transfer of photogenerated holes from Pt/P25 to the nanowire to suppress charge recombination and/or disaggregation (improved dispersion) of Pt/P25 particles on the nanowire.

Preparation and Characterization of Nanofiber Coatings on Bone Implants for Localized Antimicrobial Activity Based on Sustained Ion Release and Shape-Preserving Design.

Titanium (Ti), as a hard tissue implant, is facing a big challenge for rapid and stable osseointegration owing to its intrinsic bio-inertness. Meanwile, surface-related infection is also a serious threat. In this study, large-scale quasi-vertically aligned sodium titanate nanowire (SNW) arrayed coatings incorporated with bioactive Cu2+ ions were fabricated through a compound process involving acid etching, hydrothermal treatment (HT), and ion exchange (IE). A novel coating based on sustained ion release and a shape-preserving design is successfully obtained. Cu2+ substituted Na+ in sodium titanate lattice to generate Cu-doped SNW (CNW), which maintains the micro-structure and phase components of the original SNW, and can be efficiently released from the structure by immersing them in physiological saline (PS) solutions, ensuring superior long-term structural stability. The synergistic effects of the acid etching, bidirectional cogrowth, and solution-strengthening mechanisms endow the coating with higher bonding strengths. In vitro antibacterial tests demonstrated that the CNW coatings exhibited effective good antibacterial properties against both Gram-positive and Gram-negative bacteria based on the continuous slow release of copper ions. This is an exciting attempt to achieve topographic, hydrophilic, and antibacterial activation of metal implants, demonstrating a paradigm for the activation of coatings without dissolution and providing new insights into insoluble ceramic-coated implants with high bonding strengths.

A biomimetic calcium phosphate nanowire coating on titanium surface enhances osteoimmunomodulation and osteointegration

The appropriate immune microenvironment plays crucial roles in bone regeneration. Surface structure and chemistry are key factors affecting immune cells behavior and subsequently regulating the activity of bone-related cells. To achieve rapid osteointegration, this study prepared a biomimetic calcium phosphate (CaP) coating on Ti-based substrates (THCaP) with the help of oleic acid under hydrothermal condition. The coating was composed of hydroxyapatite nanowires and further self-assembled into micropores. Also, the effect of the biomimetic CaP coating on the immune response of macrophages and the impact on angiogenesis and osteogenesis were investigated. In vitro cell culture results showed that compared with pristine Ti and similar titanate nanowire structure (TH), THCaP not only stimulated the polarization of macrophages towards a pro-healing M2 phenotype, but also enhanced the angiogenic and osteogenic differentiation of endothelial cells and pre-osteoblastic cells, respectively. Particularly, macrophages on THCaP induced a favorable immune microenvironment that facilitated osteogenic differentiation of pre-osteoblastic cells. In vivo tests confirmed these findings, showing that the implanted THCaP could suppress the inflammatory response and facilitate new bone formation when compared with pristine Ti and TH implants. These results indicate that preparation of biomimetic CaP network structure is a promising approach to surface design of Ti-based substrates, which is beneficial to generate a favorable osteoimmunomodulatory microenvironment for enhancing osteointegration.

Efficient Photocatalytic Core–Shell Synthesis of Titanate Nanowire/rGO

Wide bandgap semiconductor-based photocatalysts are usually limited by their low solar energy conversion efficiency due to their limited absorption solar wavelength, their rapid surface recombination of the photogenerated electron–hole pairs, and their low charge-carrier mobility. Here, we report a novel stepwise solution synthesis for achieving a new photocatalytic core–shell consisting of a titanate nanowire/reduced graphene oxide shell (or titanate/rGO) 1D-nanocomposite. The new core–shell nanocomposite maximized the specific surface area, largely reduced the charge transfer resistance and reaction energy barrier, and significantly improved the absorption of visible light. The core–shell nanocomposites’ large on/off current ratio and rapid photo-responses boosted the photocurrent by 30.0%, the photocatalysis rate by 50.0%, and the specific surface area by 16.4% when compared with the results for the pure titanate nanowire core. Our numerical simulations support the effective charge separation on the new core–shell nanostructure, which can help further advance the novel photocatalysis.

Enhancing Dielectric Properties of (CaCu3Ti4O12 NWs-Graphene)/PVDF Ternary Oriented Composites by Hot Stretching.

Using high-dielectric inorganic ceramics as fillers can effectively increase the dielectric constant of polymer-based composites. However, a high percentage of fillers will inevitably lead to a decrease in the mechanical toughness of the composite materials. By introducing high aspect ratio copper calcium titanate (CaCu3Ti4O12) nanowires (CCTO NWs) and graphene as fillers, the ternary poly(vinylidene fluoride) (PVDF)-based composites (CCTO NWs-graphene)/PVDF with a significant one-dimensional orientation structure were prepared by hot stretching. CCTO NWs and graphene are arranged in a directional manner to form a large number of microcapacitor structures, which significantly improves the dielectric constant of the composites. When the ratio of CCTO NWs and graphene is 0.2 and 0.02, the oriented composites have the highest dielectric constant, which is 19.3% higher than the random composites, respectively. Numerical simulations reveal that the introduction of graphene and the construction of the one-dimensional oriented microstructure have a positive effect on improving the dielectric properties of the composites. This study provides a strategy to improve the dielectric properties of composite materials by structural design without changing the filler content, which has broad application prospects in the field of electronic devices.

Alginate-PVDF piezoelectric hydrogel containing calcium copper titanate- hydroxyapatite as a self-powered scaffold for bone tissue engineering and energy harvesting

We have developed a piezoelectric hydrogel composite comprising cross-linked polyvinylidene fluoride-sodium alginate (PVDF-SA) and calcium copper titanate nanowires (CCTO) as the piezoelectric filler, and hydroxyapatite nanoparticles (HA) as the mineral filler. A freeze-drying method was used to prepare piezoelectric hydrogel scaffold. The PVDF/SA-CCTOs-HA hydrogel composite with 0.5% CCTO and 0.4% HA content demonstrated significantly improved piezoelectric performance. Specifically, it exhibited the highest piezoelectric performance among all samples, with VOC of 7 V and ISC of 3.5 μA. These values were 5.5 and 4.9 times higher, than those of the pure PVDF-SA hydrogel scaffold. The rheology studies explored the viscoelastic properties of hydrogel and found that the hydrogel's solid characteristics led to a higher elastic modulus in comparison to the viscous modulus. The composite exhibited higher compressive and tensile strengths at 8.2 and 0.8 MPa, respectively, compared to the pure hydrogel, which has strengths of 6.3 and 0.4 MPa. In vitro studies revealed the good cytocompatibility, cell proliferation of MC3T3-E1 cells on piezoelectric composite. The PVDF-SA/CCTO-HA demonstrated significant antibacterial properties, offering further advantages for its practical applications. The hydrogel composite can identify various human activities, such as wrist and elbow movements, finger pressing and releasing, and heel pressure. Furthermore, it demonstrated its energy storage capability by charging a 1 μF capacitor. This work offers a practical approach to fabricate hydrogel scaffolds possessing favorable piezoelectric characteristics, biocompatibility, robust mechanical properties, and enhanced proliferation, thereby enabling their extensive utilization in bone tissue engineering applications, human movement detection, and energy harvesting.

Evaluation of kinetic constants uncertainty for the metrologically sound comparison of photodegradation efficiency using TiO2 catalysts

The comparison of the efficiency of a pair of catalysts for the photodegradation of a compound in the same irradiation conditions is affected by many independent and correlated random and systematic effects. These comparisons become objective and indisputable if the efficiency difference is estimated with uncertainty, producing an interval encompassing the “true” difference value with a known probability. This work presents a tool for the detailed evaluation of the uncertainty of estimated kinetic constant values and differences by the Monte Carlo Method simulation of all relevant uncertainty components. First-order kinetics were quantified from regression of the concentrations of studied compounds over various degradation times. The efficiency of methylene blue (MB) and sulfamethazine (SMZ) photodegradation using various solid-state catalysts was quantified and compared. Synthesised TiO2 nanoparticles are more efficient than the purchased TiO2 for MB degradation. For SMZ degradation, ruthenium-doped titanate nanowires and ruthenium-doped titanate nanotubes are equally efficient and more efficient than pristine titanate nanowires. The efficiency equivalence can be challenged by quantifying larger and/or less uncertain SMZ concentrations. First-order kinetics was tested by taking the simulated confidence limits of the intercept of the linear regression used to describe this kinetic order. Kinetic constants with asymmetric distribution and a relative expanded uncertainty for a 95 % confidence level between 3.6% and 17% were quantified. Three successively more uncertain procedures for preparing calibrators for the quantification of MB by UV/Vis spectroscopy were tested, concluding that since the same calibration curve is used to quantify all MB solutions, kinetic quantification is not proportionally or significantly affected by this uncertainty component.

Na2Ti3O7@RF@Ag Heterostructures as Efficient Substrates for SERS and Photocatalytic Applications.

A multi-step procedure was effectively employed to synthesize innovative three-dimensional (3D) heterostructures encompassing sodium titanate (Na2Ti3O7) nanowire cores, an intermediate resorcinol-formaldehyde (RF) layer, and outer silver (Ag) nanoparticle sheaths, referred to as Na2Ti3O7@RF@Ag heterostructures. Initially, a one-step hydrothermal technique facilitated the direct growth of single-crystal Na2Ti3O7 nanowires onto a flexible Ti foil. Subsequently, a two-step wet chemical process facilitated the sequential deposition of an RF layer and Ag nanoparticles onto the Na2Ti3O7 nanowires at a low reaction temperature. Optimal concentrations of silver nitrate and L-ascorbic acid can lead to the cultivation of Na2Ti3O7@RF@Ag heterostructures exhibiting heightened surface-enhanced Raman scattering (SERS), which is particularly beneficial for the detection of rhodamine B (RhB) molecules. This phenomenon can be ascribed to the distinctive geometry of the Na2Ti3O7@RF@Ag heterostructures, which offer an increased number of hot spots and surface-active sites, thereby showcasing notable SERS enhancement, commendable reproducibility, and enduring stability over the long term. Furthermore, the Na2Ti3O7@RF@Ag heterostructures demonstrate remarkable follow-up as first-order chemical kinetic and recyclable photocatalysts for the photodecomposition of an RhB solution under UV light irradiation. This result can be attributed to the enhanced inhibition of electron-hole pair recombination and increased surface-active sites.

Boosting strong metal-support interactions between Ru and sodium titanate nanowire for hydrogenolysis of polyolefins under mild conditions

Catalytic hydrogenolysis provides promising opportunities for the chemical recycling of polyolefins. In this study, we have successfully developed a novel catalyst consisting of ruthenium (Ru) nanoparticles supported on sodium titanate nanowires (Ru@NTO-NH) for the hydrogenolysis of low-density polyethylene (LDPE) into high-value long-chain alkanes under mild reaction conditions (180 °C, 1–2 MPa H2), achieving yields of up to 91%. Control experiments and thorough characterizations have elucidated that the exceptional catalytic performance of Ru@NTO-NH in the hydrogenolysis of polyolefins can be attributed to strong metal-support interactions (SMSI). NTO-NH exhibits stronger SMSI with Ru species than TiO2, leading to the formation of smaller Ru nanoparticles that are more positively charged and NaTiOx-overlayered. This unique configuration facilitates the adsorption and activation of H2 as well as the desorption of alkanes, thereby enhancing catalytic efficiency and selectivity towards liquid alkanes. Moreover, the Ru@NTO-NH catalyst demonstrates remarkable stability throughout recycling experiments (10 runs). Notably, apart from LDPE, high-density polyethylene (HDPE) and polypropylene (PP) can also be effectively converted into liquid alkanes through hydrogenolysis using this catalyst.

Synergistic Improvement of Dielectric and Thermal Conductivity Properties for Polymers Filled with Multifunctional Modified Nanowires.

Dielectric composites are widely used in power electronics, power systems, aerospace, and other fields due to their extremely high power density. However, if their energy density can be further increased, the application range will be greatly improved. Improving the dielectric constant of composites is one of the most effective ways to increase the energy density. In this study, a preparation method for copper calcium titanate nanowires (CCTO-NWs) with adjustable aspect ratio was investigated. Upon incorporation of these CCTO-NWs into the polymer matrix, the nanocomposites exhibit a significantly higher dielectric constant and a lower dielectric loss. In addition, a thin layer of Al2O3 with excellent thermal conductivity is coated on the surface of the CCTO-NWs to form a core-shell structure nanowire CCTO-NW@Al2O3. The introduction of the thermal conductive layer of Al2O3 not only creates a continuous heat transfer path within the dielectric composite, increasing the thermal conductivity of the composite from 0.11 W/(m·K) of pure HIPS to 1.12 W/(m·K), but also serves as a buffer layer between HIPS and CCTO-NWs, effectively alleviating the electric field distortion caused by the large difference in the dielectric constant between them, thereby optimizing the dielectric properties of the composite and reducing the dielectric permeability threshold from 30 to 20 vol %. This work provides an effective strategy for synergistically improving the dielectric constant and thermal conductivity of dielectric composites while also taking into account the good flexibility of polymer/ceramic nanocomposites.

Transport properties investigations of nanocomposite membranes incorporating titanate nanowires for water desalination

AbstractImprovement of membrane properties is an important issue to enhance the efficiency of water permeation processes. Nanocomposite membranes are gaining prominence in this field due to the particular properties of these materials. In the present study, incorporating titanate nanowires (TNW) into the cellulose acetate (CA) matrix allowed getting a nanocomposite membrane with modified characteristics. Morphologic and physical–chemical properties of the synthesized membranes were characterized by Fourier transform infrared spectrometry and scanning electron microscopy analysis, presenting a dense, uniform membrane formation with a highly dispersed inorganic phase when low amounts of particles were added. The membranes were tested by measuring water flux and salt rejection. The results showed that the incorporation of inorganic nanostructures into polymer membranes affects their transport properties. It was observed an increase of three times in water flux, reaching from 1.33 to 4.0 L/h m2, with NaCl rejection over 65%. Membranes with such characteristics could be specially designed for nanofiltration or forward osmosis processes as a promising application for water desalination or energy generation.

Design of Sodium Titanate Nanowires as Anodes for Dual Li,Na Ion Batteries

The bottleneck in the implementation of hybrid lithium-sodium-ion batteries is the lack of anode materials with a desired rate capability. Herein, we provide an in-depth examination of the Li-storage performance of sodium titanate nanowires as negative electrodes in hybrid Li,Na-ion batteries. Titanate nanowires were prepared by a simple and reproducible hydrothermal method. At a low reaction pressure, the well-isolated nanowires are formed, while by increasing the reaction pressure from 2 to 30 bar, the isolated nanowires tend to bundle. In nanowires, the local coordinations of Na and Ti atoms deviate from those in Na2Ti3O7 and Na2Ti6O13 and slightly depend on the reaction pressure. During the annealing at 350 °C, both Na and Ti coordinations undergo further changes. The nanowires are highly defective, and they easily crystallize into Na2Ti6O13 and Na2Ti3O7 phases. The lithium storage properties are evaluated in lithium-ion cells vs. lithium metal anode and titanate electrodes fabricated with PVDF and carboxymethyl cellulose (CMC) binders. The Li-storage by nanowires proceeds by a hybrid capacitive-diffusive mechanism between 0.1 and 2.5 V, which enables to achieve a high specific capacity. Sodium titanates accommodate Li+ by formation of mixed lithium-sodium-phase Na2−xLixTi6O13, which is decomposed to the distinct lithium phases Li0.54Ti2.86O6 and Li0.5TiO2. Contrary to lithium, the sodium storage is accomplished mainly by the capacitive reactions, and thus the phase composition is preserved during cycling in sodium ion cells. The isolated nanowires outperform bundled nanowires with respect to rate capability.

High-Capacitance γ-rGO/MXene Cathode and Rapid Na+-Transfer Dynamics Sodium Titanate Anode for a Quasi-Solid-State Sodium-Ion Capacitor

Sodium-ion capacitors (SICs) bear the advantages of secondary batteries and supercapacitors and are regarded as promising energy-storage devices. However, the matching of the respective Na+-transfer kinetics of the anode and the cathode and the low energy density are still a challenge. Herein, to achieve a high-capacity cathode, 2D V2C MXene nanosheets were introduced into γ-ray-reduced graphene oxide (γ-rGO), and the γ-rGO/V2C MXene foam (GMF) was fabricated. The GMF provides a high specific capacitance of 391.4 mF cm–2 (130.5 F g–1) at a high current density of 60 mA cm–2 (20 A g–1). Meanwhile, the structure-directing strategy combining multiple nanocarbon composites accelerates the Na+-transfer kinetics of sodium titanate (NTO). The as-fabricated CNT film-supported sodium titanate nanowires encapsulated by the graphene (CNTF@NTO-G) anode deliver a specific capacity of 109 mA h g–1 at a high current density of 10 A g–1. As a result, the assembled quasi-solid-state SIC displays an energy density of 5.61 mW h cm–3 (56.1 W h kg–1) at a power density of 1 W cm–3 (10 kW kg–1) with excellent cycle stability (87.3% capacitance retention after 10,000 cycles).

Enhancing Removal of Pollutants by Combining Photocatalysis and Photo-Fenton Using Co, Fe-Doped Titanate Nanowires

Aiming to improve their photocatalytic performance, titanate nanowires (TNW) were modified by Fe and Co (co)-doping, FeTNW, CoTNW and CoFeTNW samples, using a hydrothermal methodology. XRD characterization agrees with the existence of Fe and Co in the lattice structure.and the existence of Co2+ together with the presence of Fe2+ and Fe3+ in the structure was confirmed by XPS. The optical characterization of the modified powders shows the impact of the d-d transitions of both metals in the absorption properties of TNW, mainly in the creation of additional 3d energetic levels within the prohibited zone. The effect of the doping metal(s) in the recombination rate of photo-generated charge carriers suggests a higher impact of Fe presence when compared to Co. The photocatalytic characterization of the prepared samples was evaluated via the removal of acetaminophen. Furthermore, a mixture containing both acetaminophen and caffeine, a well-known commercial combination, was also tested. CoFeTNW sample was the best photocatalyst for the degradation of acetaminophen in both situations. A mechanism for the photo-activation of the modified semiconductor is discussed and a model proposed. It was concluded that both Co and Fe are essential, within the TNW structure, for the successful removal of acetaminophen and caffeine.

Hydrothermal growth of biomimetic calcium phosphate network structure on titanium surface for biomedical application

Calcium phosphate (CaP) coating-modified titanium (Ti) surfaces have been developed to improve the biological activity and osseointegration of Ti-based implants. However, these coatings always lack three-dimensional micro/nanostructures mimicking bone tissue. To fabricate hierarchical CaP coating structures and enhance the bioactivity of Ti implants, this study developed a novel hydrothermal method for preparing biomimetic three-dimensional CaP network structures on alkali-treated Ti surface with the assistance of oleic acid. Moreover, the growth mechanism of the CaP network structure was investigated, and its biocompatibility was evaluated by co-culture with preosteoblasts. The coatings were mainly composed of HA nanowires, which grew vertically along the titanate nanowires and further self-assembled into macropores. Compared to the pristine Ti surface, this hierarchical network structure showed superior hydrophilicity, elevated roughness, and improved cell attachment, proliferation, and osteogenic differentiation. Furthermore, this CaP structure demonstrated significantly higher alkaline phosphatase (ALP) activity and upregulated the expression of osteopontin (OPN) and osteocalcin (OCN) in comparison with similar titanate structures, suggesting improved bioactivity of the hierarchical CaP network structure. These improvements were probably attributed to hierarchical micro/nanostructure and CaP chemistry. The above findings indicate that this method effectively fabricates hierarchical CaP network structures on Ti-based substrates, which construct a favorable microenvironment for inducing osteogenic differentiation.

Surface-functionalization of hydrogen titanate nanowires for efficiently selective adsorption of methylene blue

Polydopamine coated hydrogen titanate nanowires (PDA-HTN) are prepared via dopamine self-polymerization. The obtained PDA-HTN is a cheap adsorbent for selective adsorption of methylene blue (MB). The adsorption characteristics of PDA-HTN are studied from three aspects: isotherm, kinetics and thermodynamics. Date show that PDA-HTN adsorbs MB spontaneously, and the adsorption process is agreement with the fitting results of Langmuir and pseudo-second-order model. PDA-HTN is used to selectively adsorb MB from dye mixtures, the removal rate of MB can reach as high as 99.8% and adsorption capacity can reach 241.3 mg g−1. PDA-HTN can be used to adsorb MB in 0.5 mol L−1 NaCl solution, and the increase of ionic concentration in NaCl solution will improve the adsorption performance of PDA-HTN for MB, because salt ions will induce the dimerization of MB. PDA-HTN exhibits excellent cyclic adsorption property, the removal rate of MB remains above 97.7% after 12 cycles of adsorption-desorption. The adsorption is explained by cooperative effects of π–π stacking, electrostatic interaction, 1,4–Michael addition reaction and hydrogen bonding. Compared to the pristine HTN, the adsorption capacity of PDA-HTN for MB is greatly increased. In addition, PDA-HTN can also be used to remove other cationic dyes, and its adsorption capacity for basic yellow 1 (BY1) and crystal violet (CV) is 586.7 mg g−1 and 865.1 mg g−1, respectively.

TiOx-supported Na-Mn-W oxides for the oxidative coupling of methane

Supported Na-Mn-W oxides are among the most studied catalysts for the oxidative coupling of methane (OCM) because of their superior thermal stability and relatively high C2+ product yields. However, because of the structural complexity, the roles of each component in these catalysts have been controversial. In this work, WOx and MnOx sites were supported on titanate nanowires and employed in OCM studies. Compared to the commonly studied silica support, which is subject to severe restructuring due to the Na-induced crystallization, titanate support not only serves as a reservoir for alkali metals (e.g., Na), but also stabilizes isolated MnOx species. The catalytic performance of the titanate-based catalyst is similar to that of reference catalyst, MnOx/Na2WO4/SiO2, with a synergistic effect between MnOx and WOx sites. Advanced electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray absorption near edge structure spectroscopy suggest that the basic NaOx and MnOx species have strong interactions with the acidic WOx and TiOx species, which might contribute to the high selectivity toward C2+ products and suppressed COx formation.