Hydrogen Titanate Nanotubes Research Articles

Zeolitic imidazolate framework@hydrogen titanate nanotubes for efficient adsorption and catalytic oxidation of organic dyes and microplastics

Metal-organic frameworks (MOFs) have significant promise as materials for many environmental applications, namely in the realm of water treatment. In this study, we produced a nanocomposite material by combining zeolitic imidazolate frameworks (ZIF-67) with hydrogen titanate nanotubes (HTNT) at ambient temperature. The materials, namely HTNT, ZIF-67, and HTNT@ZIF-67, were analyzed and employed for the adsorption and catalytic oxidation of water pollutants such as organic dyes (fluorescein acid (FL), Rhodamine B (RhB), direct blue I (DB), and basic fuchsin (BF)) and microplastics extracted from personal care and cosmetics products. The HTNT@ZIF-67 nanocomposite exhibited dye removal efficiencies of 99% and 97% for adsorption and catalytic oxidation by hydrogen peroxide (H2O2), respectively. ZIF-67 exhibits the most rapid disintegration rate among the tested substances, with rates of 517, 439, 1764, 1764, and 1621 mL/min·g for H2O2 and H2O2 in the presence of FL, RhB, DB, and BF, respectively. The catalytic degradation process may be used for up to six cycles, while maintaining an efficiency of 78%. Catalysts based on ZIF-67, such as HTNT@ZIF-67, show great potential for removal targeting organic contaminants such dyes and microplastics.

Structural, linear/nonlinear optical and electrical studies on PVP/CMC blend filled with hydrogen titanate nanotubes and TMAI

Structural, linear/nonlinear optical and electrical studies on PVP/CMC blend filled with hydrogen titanate nanotubes and TMAI

Regeneration and Recycling of Hydrogen Titanate Nanotubes as Methylene Blue Adsorbent via Ozonation-Based Advanced Oxidation Process

Regeneration and Recycling of Hydrogen Titanate Nanotubes as Methylene Blue Adsorbent via Ozonation-Based Advanced Oxidation Process

Reactive species regulation by interlayered Na+/H+ of titanate nanotubes decorated Co(OH)2 hollow microsphere for peroxymonosulfate activation and gatifloxacin degradation

Emerging organic pollutants (EOPs) in water are of great concern due to their high environmental risk, so urgent technologies are needed for effective removal of those pollutants. Herein, a heterogeneous advanced oxidation process (AOP) of peroxymonosulfate (PMS) activation by functional material was developed for degradation of a typical antibiotic, gatifloxacin (GAT). The reactive species including sulfate radical (SO4•−) and singlet oxygen (1O2) in this AOP were regulated by interlayered ions (Na+/H+) of titanate nanotubes that supported on Co(OH)2 hollow microsphere. Both the Na-type (NaTi-CoHS) and H-type (HTi-CoHS) materials achieved efficient PMS activation for GAT degradation, and HTi-CoHS even exhibited a relatively high degradation efficiency of 96.6% within 5 min. Co(OH)2 was considered the key component for generation of SO4•− after PMS activation, while hydrogen titanate nanotubes (H-TNTs) promoted the transformation of peroxysulfate radical (SO5•−) to 1O2 by hydrogen bond interaction. Therefore, when the interlayer ion of TNTs transformed from Na+ to H+, more 1O2 was produced for organic pollutant degradation. H-TNTs with lower symmetry preferred to adsorb PMS molecules to achieve interlayer electron transport through hydrogen bonding, rather than electrostatic interaction of Na+ for Na-TNTs. In addition, the degradation pathway of GAT mainly proceeded by the cleavage of C–N bond at the 8 N site of the piperazine ring, which was confirmed by condensed Fukui index and mass spectrographic analysis. This work gives new sights into the regulation of reactive species in AOPs by the composition of material and promotes the understanding of pollutant degradation mechanisms in water treatment process.

Core–Shell Nanostructures of Tungsten Oxide and Hydrogen Titanate for H2 Gas Adsorption

Nanostructured tungsten oxide is a promising material for sensing reducing gases such as hydrogen. However, this material exhibits limitations due to a poor response toward sensing at room temperature, incomplete recovery to the initial state, long response time, and a low response factor, which is not desired for explosive gases like hydrogen. In this work, we, for the first time, demonstrate that these limitations can be significantly overcome using the core–shell structure of tungsten oxide (WO3) nanorods and hydrogen titanate (H2Ti3O7) nanotubes developed and suitably defect-engineered by low-energy ion irradiation. The sensor based on the pristine core–shell heterostructure of tungsten oxide nanorods and hydrogen titanate nanotubes exhibits excellent response and selectivity to different concentrations of H2 ranging from 10 to 500 ppm. However, it requires a quite high temperature of 300 °C with response and recovery times of about 38 and 99.8 s, respectively. After irradiation, the hybrid form shows a similar level of response and selectivity, however, at a much lower temperature of about 120 °C with significantly faster response and recovery times of about 16 and 18 s, respectively. Such an ion beam-modified structure addresses critical issues of developing a gas-sensing device, such as the effects of moisture and power consumption. The experimental observations are very well in agreement with the predictions of the state-of-the-art Monte Carlo-based TRI3DYN ion-solid interaction simulation, and the gas-sensing mechanism was explained using first principles-based calculation. The study reveals that low-energy ion-induced defect engineering yields better charge transport, better binding of the gas with the surface, as well as the superior moisture-repelling ability of the surface, leading to better sensing performance than the pristine core-shell structure. This heterostructure between two nanomaterials carries complementary advantages in various aspects, such as the surface area, conductivity, and sensitivity toward a wide range and mixture of gases. Additionally, the wrapping yields good mechanical strength and flexibility, making it possible to use as a flexible sensing device made through a bottom-up fabrication technique.

Removal of methylene blue and azo reactive dyes from aqueous solution and textile effluent via modified pulsed low-frequency ultrasound cavitation process.

Organic dyes in the aqueous solutions and textile effluents cause severe environmental pollution due to their carcinogenic and mutagenic nature. Ultrasound (US) cavitation is one of the promising advanced oxidation processes (AOP) to remove the organic dyes from the aqueous solutions and textile effluents. Nevertheless, the conventional low-frequency US cavitation process exhibits very low efficiency in the dye removal process and demands effective modification to improve its performance. In this investigation, a conventional pulsed low-frequency (22 ± 2kHz) US cavitation process has been modified by varying the US power (50-150W), initial solution pH (2-10), and O2 flow rate (1-4 L min-1) to enhance the decomposition of cationic methylene blue (MB) dye in an aqueous solution. The operation of the classic Haber-Weiss reaction, both in the forward and backward directions, and the ozone effect have been observed, for the first time, under the modified US cavitation process, as confirmed via the radical trapping experiments. Moreover, the hydrothermally synthesized hydrogen titanate (H2Ti3O7) nanotubes (HTN) have been utilized as sonocatalyst, for the first time, for 100% dye removal, with effective regeneration obtained via an in-situ thermal activation of persulfate (PS, S2O82-). The most optimum values of US power, initial solution pH, O2 flow rate, HTN, and PS concentrations for 100% MB decomposition are observed to be 150W, 2, 2 L min-1, 0.3g L-1, and 10mM, respectively. The decomposition of industrial azo reactive dyes in an aqueous solution as well as in a textile effluent has also been demonstrated using a modified pulsed low-frequency US cavitation process involving the thermal activation of PS without the use of HTN, which justifies its suitability for a commercial application.

Behavior of the Energy Levels of Hydrogen Titanate Nanotubes Decorated with Au, Ag, Mn, and Ni and Their Effect on the H2 Evolution

Behavior of the Energy Levels of Hydrogen Titanate Nanotubes Decorated with Au, Ag, Mn, and Ni and Their Effect on the H2 Evolution

Removal of Methyl Violet Dye by Adsorption Process on Hydrogen Titanate Nanotubes: Experimental-Theoretical Study

Removal of Methyl Violet Dye by Adsorption Process on Hydrogen Titanate Nanotubes: Experimental-Theoretical Study

Autoclave and pulsed ultrasound cavitation based thermal activation of persulfate for regeneration of hydrogen titanate nanotubes as recyclable dye adsorbent.

In the dye removal application, regeneration of hydrogen titanate nanotubes (HTN, H2Ti3O7) has been achieved via thermal activation of persulfate anion (PS, S2O82-) by using the conventional hot plate technique which has limitations from the commercial perspective since it does not provide any precise control over the thermal generation process typically during the scale-up operation. To overcome this drawback, HTN have been synthesized via hydrothermal process which exhibit the methylene blue (MB) adsorption of 93% at the initial dye concentration and solution pH of 90µM and 10 respectively. HTN have been regenerated via the thermal activation of PS by varying its initial concentration and regeneration temperature, within the range of 0.27-1 wt% and 40-80°C, under the thermal conditions set by the autoclave and pulsed ultrasound (US) cavitation process. The results of recycling experiments suggest that the optimum values of initial PS concentration and temperature, for the regeneration of HTN under the autoclave conditions, are 1 wt% and 70°C with the maximum MB adsorption of 92%, while, the corresponding values for the pulsed US cavitation process are 1 wt%, 80°C, and 91% respectively. Thus, the regeneration and recycling of HTN have been successfully demonstrated by using the autoclave and pulsed US cavitation process. Under the optimum conditions, MB degradation involves the generation and attack of SO4•- for both the thermal generation techniques. The regeneration techniques developed here may be utilized in future during the scale-up operation and also for the regeneration of adsorbents besides HTN.

Formation of core-shell nanostructure through wrapping of cuprous oxide nanowires by hydrogen titanate nanotubes

Recent developments of heterojunction-based devices through bottom-up approach such as sensors, light-emitters, energy generation and storage have emerged with great interest due to their wide range of operation and application related flexibilities. This work demonstrates how as-grown hydrogen titanate nanotubes (HTNT) bend and wrap on pristine curpous oxide nanowires (CONW) when mixed together. The unique architecture of wrapping followed by junction formation enhances the active surface area and reduces the contact resistance between the adjacent CONW and HTNT. Such a film upon further ion beam irradiation produces a large-scale network of hetero- and homo-junctions. This newly formed thin film surface upon irradiation shows strong water repelling properties and higher electrical conductivity. The wrapping mechanism, bond formation and the change of conductivity are explained using first principles calculations. The ion beam modifications and large-scale joining are predicted by state-of-the-art TRI3DYN simulation, which is based on binary collision approximation and simulated in a Monte Carlo approach. The observed wrapping and heterojunction are expected to provide excellent mechanical strength and flexibility, which are suitable for fabrication of flexible electronic devices.

Correction: Selective oxidation of alcohols on hydrogen titanate nanotubes under visible light irradiation: relationship between nanostructure and catalytic activity

Correction for ‘Selective oxidation of alcohols on hydrogen titanate nanotubes under visible light irradiation: relationship between nanostructure and catalytic activity’ by Juan Yang et al., Catal. Sci. Technol., 2016, 6, 7604–7614, DOI: https://doi.org/10.1039/C6CY01345G

Effect of hydrothermal time and acid-washing on the antibacterial activity of Sodium titanate nanotubes

Bacterial resistance to antibiotics has been a major concern globally. In this work, sodium and hydrogen titanate nanotubes were successfully synthesised using a facile hydrothermal technique. The prepared samples were characterized by XRD, FTIR, HRTEM surface area analyser, hydrodynamic size analyser and zeta potential. Minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) measurements besides agar well diffusion method showed good antimicrobial activity of both nanotubes. The antimicrobial activity of sodium titanate nanotubes prepared at 6 and 23 hr., and their hydrogen exchanged forms; (HTNT) and (HTNS) explored good antimicrobial activity against both Gram positive and Gram negative bacteria besides their antifungal activity which reflects their importance in treatment of bacterial infections causing serious diseases in both animal and human.

Ion beam engineered hydrogen titanate nanotubes for superior energy storage application

Nanotube or nanowire-based supercapacitors are having huge potentials as they offer large device-level energy density and they can withstand significant stress, which is important for building flexible and high-performance storage devices. The present work shows how we can exploit ion beam as a tool to create surface defects and porous structure besides enhancing charge-transfer property and surface area through large-scale joining among hydrogen titanate nanotubes and achieve enhancement of charge storage capacity and energy density. Self-assembled hydrogen titanate nanotubes have been hydrothermally synthesized on oxidized titanium foil and exposed to low energy (5 keV) Ar+ ion-beam at different ion fluences, before detailed electrochemical analyses to validate their charge storage performance. Irradiated hydrogen titanate nanotubes showed exceptional charge storage performance in terms of specific capacitance, which is about 1572 F/g, at a very high mass-normalized-current of 10 A/g. The charge storage performance of irradiated hydrogen titanate nanotubes was found to be superior to the performance recorded for the pristine/unmodified nanotubes. The detailed experimental findings, further corroborated by first-principles calculations, provide clear insights regarding the enhanced charge storage performance in the case of irradiated nanotubes. We have also computed the work function of the material before and after O vacancy. Reduction in work function due to O vacancy supports improved charge storage performance due to irradiation. Factors like the induced oxygen vacancy, pore formation, improved surface area, and enhanced charge-transfer property play significant roles in the high charge storage performance of the irradiated samples. This study further demonstrates the potential of using the ion beam irradiation technique to tune the surface area, conductivity, and storage capacity of the supercapacitor electrode.

Effects of Annealing Temperature on the Crystal Structure, Morphology, and Optical Properties of Peroxo-Titanate Nanotubes Prepared by Peroxo-Titanium Complex Ion.

This study addresses the effects of annealing temperatures (up to 500 °C) on the crystal structure, morphology, and optical properties of peroxo groups (–O–O–) containing titanate nanotubes (PTNTs). PTNTs, which possess a unique tubular morphology of layered-compound-like hydrogen titanate structure (approximately 10 nm in diameter), were synthesized using peroxo-titanium (Ti–O–O) complex ions as a precursor under very mild conditions—temperature of 100 °C and alkali concentration of 1.5 M—in the precursor solution. The nanotubular structure was dismantled by annealing and a nanoplate-like structure within the range of 20–50 nm in width and 100–300 nm in length was formed at 500 °C via a nanosheet structure by decreasing the specific surface area. Hydrogen titanate-based structures of the as-synthesized PTNTs transformed directly into anatase-type TiO2 at a temperature above 360 °C due to dehydration and phase transition. The final product, anatase-based titania nanoplate, was partially hydrogen titanate crystal in nature, in which hydroxyl (–OH) bonds exist in their interlayers. Therefore, the use of Ti–O–O complex ions contributes to the improved thermal stability of hydrogen titanate nanotubes. These results show a simple and environmentally friendly method that is useful for the synthesis of functional nanomaterials for applications in various fields.

Fe(III) and Zr(IV) surface functionalized 1-D hydrogen titanate nanotubes for remediating fluoride from water at neutral pH

The current study deals with Fe(III) and Zr(IV) incorporated Titanate Nanotubes (FZTNT) for efficient removal of fluoride from potable water. The surface modification of hydrogen titanate nanotubes (HTNT) with Fe and Zr ions, not only transformed the adsorbent surface suitable for fluoride adsorption at neutral pH, but also enhanced its fluoride adsorption capacity. The surface charge of the adsorbent was estimated by zeta potential measurements. The other physical and chemical properties of the FZTNT were examined using BET, FTIR and XPS. FZTNT had specific surface area of 245 m2/g. The crystal structure, morphology and chemical characterizations were carried out using the XRD, TEM, and SEM-EDX respectively. The fluoride adsorption data followed the Langmuir isotherm and the Langmuir adsorption capacity was estimated to be 229.3 mg/g at neutral pH, contact time of 2 h and adsorbent dosage of 1 g/L. FZTNT exhibited superior adsorption properties, compared to HTNT which had negligible adsorption at pH 7 (±0.01). Adsorption of fluoride followed ion exchange mechanism. In addition, FZTNT possessed good adsorption kinetics and could be reused for three cycles without significant drop in its adsorption capacity which allowed FZTNT to be used for defluoridating groundwater to WHO limits (≤1.5 mg/L).

Exotic Nanostructured Titania Supports for Deep Hydrodesulfurization Catalysts: Are They Better Than the Conventional Ones?

In the present work, we compared the hydrodesulfurization (HDS) behavior of NiMo catalysts supported on titania-based nanomaterials (hydrogen titanate nanotubes and nanotubes decorated with anatase nanocrystals), with that of the reference NiMo/γ-alumina and NiMo/TiO2 samples. Supports and calcined catalysts were characterized by nitrogen physisorption, powder XRD, UV–Vis diffuse reflectance spectroscopy, Raman spectroscopy, temperature-programmed reduction, scanning electron microscopy and high resolution transmission electron microscopy (HRTEM). The sulfided catalysts were characterized by HRTEM and evaluated in the HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). In the hydrodesulfurization of DBT, all catalysts supported on nanostructured titania materials showed similar activity as the NiMo/Al2O3 reference. However, their selectivity towards the hydrogenation pathway of the reaction was significantly higher than that of the alumina-supported reference. In the hydrodesulfurization of 4,6-DMDBT, activities of the synthesized NiMo catalysts supported on titania-based nanomaterials were about 50% superior to that of the NiMo/Al2O3 reference. This is an interesting result, since the majority of the conventional NiMo or CoMo catalysts are significantly more active for the elimination of DBT than of the sterically-hindered 4,6-DMDBT. The presence of small titania anatase crystallites in the nanostructured supports had a slight positive effect on the catalytic activity of the NiMo catalysts in HDS of 4,6-DMDBT, and a more noticeable effect on an increase in their hydrogenation ability (production of larger amounts of methylcyclohexyltoluene in the products).

3D Hydrogen Titanate Nanotubes on Ti Foil: A Carrier for Enzymatic Glucose Biosensor.

Glucose oxidase (GOx) based biosensors are commercialized and marketed for the high selectivity of GOx. Incorporation nanomaterials with GOx can increase the sensitivity performance. In this work, an enzyme glucose biosensor based on nanotubes was fabricated. By using Ti foil as a carrier, hydrogen titanate nanotubes (HTNTs), which present fine 3D structure with vast pores, were fabricated in-situ by the hydrothermal treatment. The multilayer nanotubes are open-ended with a diameter of 10 nm. Then glucose oxidase (GOx) was loaded on the nanotubes by cross-linking to form an electrode of the amperometric glucose biosensor (GOx/HTNTs/Ti electrode). The fabricated GOx/HTNTs/Ti electrode had a linear response to 1–10 mM glucose, and the response time was 1.5 s. The sensitivity of the biosensor was 1.541 μA·mM−1·cm−2, and the detection limit (S/N = 3) was 59 μM. Obtained results indicate that the in-situ fabrication and unique 3D structure of GOx/HTNTs/Ti electrode are beneficial for its sensitivity.

H2Ti3O7 titanate nanotubes for highly effective adsorption of basic fuchsin dye for water purification

Abstract Hydrogen titanate nanotubes with different Ti/NaOH ratios were synthesized using the hydrothermal method. The obtained materials were characterized by X-ray diffraction, UV–vis DRS spectroscopy, N2 physisorption, transmission electron microscopy and zeta potential. According to the characterization results, all the synthesized materials presented tubular morphology and the crystalline phase corresponding to H2Ti3O7. The synthesis parameters were optimized in order to increase as much as possible the specific surface area and minimize the sodium ion concentration as well. Afterward, the produced nanotubes were used as adsorbent materials to remove basic fuchsin dye from water solutions. The best adsorption performance, up to 90% in the first 5 min of testing using a load of 0.05 mgNT L−1BF, was achieved for the sample that showed the highest specific surface area (393.3 m2 g−1); the results for the other samples were around 60% under the same experimental conditions. As expected, the adsorption values were correlated to the specific surface area and point of zero charge values; in this case, at optimal pH (2.4), negatively charged NTs could capture the BF dye (pKa of 3.9) via electrostatic attraction and then ion-exchange or complexation. Through UV–vis DRS and FTIR spectroscopies, a strong interaction of the amino group in the H2Ti3O7 surface was elucidated. The results presented in this work make possible the use of this kind of materials as adsorbents of certain types of contaminants in water purification processes due to their adsorptive properties in continuous cycles.

Synthesis, characterization and simulation of lithium titanate nanotubes for dye sensitized solar cells

In this work we present the comprehensive design of lithium titanate nanotubes (LiTNT) as semiconductors for DSSC photoanodes. The synthesis and characterization of Li1.82Na0.18Ti3O7.nH2O nanotubes was performed and a prototype of cell using this material was assembled. The cell exhibited a 7.7% efficiency and a relatively high open circuit voltage, Voc = 0.72 V. In comparison with previously obtained hydrogen titanate nanotubes (HTNT), improvements have been achieved, like better charge carriers’ lifetime and lower series resistance. In order to study this system, we carried out previous DFT simulations for this lithium titanate nanotubes through different model's complexity levels which were able to correctly predict its properties. Due to the improvements achieved this system would encourage further studies with the aim to explore its potential for solar cells applications.

MoS2 Domains on TiO2-Based Nanostructures: Role of Titanate/TiO2 Transformation and Sulfur Doping on the Interaction with the Support

MoS2/TiO2-based hybrid structures have been synthesized, via a bottom-up approach, by sulfidation, with CS2 as sulfiding molecule, of molybdenum oxide precursor supported on high surface area hydrogen titanate nanotubes (HTNTs). The evolution of morphology and structure of the support, moving from titanates to TiO2 phases together with the simultaneous formation of MoS2 nanosheets have been imaged by means of AFM, HRTEM microscopies, while the vibrational and the optical properties have been investigated by FTIR and UV–visible techniques after each step of the process. More in detail, the different stacking degrees, the size distribution of the MoS2 nanosheets, decorating the heterogeneous supports, have been carefully obtained by means of HRTEM. In order to explore the nature of the surface sites on the exposed faces, in situ FTIR spectra of adsorbed CO as probe molecule have been carried out. It was shown that the sulfidation steps are affecting not only the structure of MoS2 nanosheets, including their curvature, surface defects, and stacking order, but are involving the support, too, and then in turn the MoS2/support interaction, so helping to control and preserve the size of the particles. Lastly, to elucidate the nature of the hybrid composites, a simple scheme summarizing the reaction pathways has been proposed.