Search Results (61)

In this research, a single composite-type stretchable triboelectric nanogenerator (TENG) is proposed for efficient energy harvesting and handwriting recognition. The composite TENGs were fabricated by blending dielectric barium titanate (BT) and conductive carbon nanotubes (CNTs) in varying amounts into a styrene–butadiene rubber matrix. The energy harvesting efficiency depends on the type and amount of fillers, as well as their dispersion within the matrix. Stearic acid modification of BT enables near-nanoscale filler distribution, resulting in high energy conversion efficiencies. The composite achieved power efficiency, power density, charge efficiency, and charge density values of 1.127 nW/N, 8.258 mW/m³, 0.146 nC/N, and 1.072 mC/m³, respectively, under only 2% cyclic compressive strain at 0.85 Hz. The material performs better at low stress–strain ranges, exhibiting higher charge efficiency. The generated charge in the TENG composite is well correlated with the compressive stress, which provides a minimum activation pressure of 0.144 kPa, making it suitable for low-pressure sensing applications. A flat composite with dimensions of 0.02 × 6 × 5 cm³ can produce a power density of 26.04 W/m³, a charge density of 0.205 mC/m³, and an output voltage of 10 V from a single hand pat. The rubber composite also demonstrates high accuracy in handwriting recognition across different individuals, with clear differences in sensitivity curves. Repeated attempts by the same person show minimal deviation (<5%) in writing time. Additionally, the presence of reinforcing fillers enhances mechanical strength and durability, making the composite suitable for long-term cyclic energy harvesting and wearable sensor applications. Full article

The chemical and microstructural transformation of the surface of a 31.5 vol.% ZrB₂-31.5 vol.% HfB₂-27 vol.% SiC-10 vol.% C_CNT ultrahigh-temperature ceramic sample (where C_CNT refers to carbon nanotubes) was studied under the influence of a subsonic N₂-plasma flow with the addition of 5 mol% methane, simulating aerodynamic heating in the atmosphere of Titan. As in the case of pure nitrogen flow, it was found that silicon carbide is removed from the surface. Zirconium and hafnium diborides are partially transformed into a Zr-Hf-B-C-N solid solution in the experiment conducted. XRD, Raman spectroscopy, and SEM-EDX analysis show that the presence of C₂ in the N₂-CH₄ plasma flow leads to surface carbonization (formation of a graphite- and diamond-like coating with a high proportion of amorphous carbon), resulting in significant changes in the microstructure and emissivity, potentially affecting the catalytic properties of the surface. Full article

Graphene quantum dots (GQDs) show significant promise as antibacterial agents, but their application is hindered by several limitations, including potential cytotoxicity at high concentrations, as well as concerns regarding aggregation and reusability. In this study, sodium titanate (NTO) ultralong nanotubes were utilized as both a photocatalyst and support for GQDs. The NTO/GQDs heterojunction was formed by embedding GQDs nanoplates onto the walls of NTO nanotubes. This integration significantly improved the visible light absorption and enhanced the separation and transfer of electron–hole pairs, leading to an efficient photocatalytic antibacterial process. The NTO/GQD-8 self-supporting membrane composed of these ultralong nanotubes demonstrated outstanding antibacterial efficiency (99.99%) against E. coli and exhibited remarkable cycling stability. Radical scavenging experiments revealed that ∙OH and e⁻ were the primary reactive species driving the photocatalytic antibacterial process. Notably, NTO and NTO/GQDs-8 exhibited distinct antibacterial outcomes. After photocatalytic treatment with NTO/GQDs-8, E. coli cells were completely fragmented, with no intact cell structures remaining due to the synergy effect of GQDs’ physical cutting during photocatalytic treatment. Full article

One of the challenging problems in the research and development of vibration sensors relates to the formation of Ohmic contacts for the removal of an electrical signal. In some cases, it is proposed to use arrays of carbon nanotubes (CNTs), which can serve as highly elastic electrode materials for vibration sensors. The purpose of this work is to study the effect of a current-collecting layer of CNTs grown over silicon on the properties of a lead zirconate titanate (PZT) film, which is frequently employed in mechanical vibration sensors or energy harvesters. For the experiments, a vibration sensor mock-up was created with the PZT-CNT-Ni-V-SiO₂-Si and PZT-CNT-Ni-V-Si structures where an array of vertically oriented CNTs was grown over an oxidized or high-alloyed silicon substrates by plasma chemical deposition from a gas phase. Then, a thin film of PZT was applied to the CNT layer with a high-frequency reactive plasma spraying. For comparison, the PZT film was applied to silicon without a CNT layer (PZT-Si structure). The calculated average value of the piezoelectric module is 112 pm/V for the Ni-PZT-PT-Ni-Si-SiO₂ sample, and 35 pm/V for PZT-Ni-SiO₂-Si. It can be seen that the contact realized with the help of CNT ensures more than three times the best efficiency in terms of the piezoelectric module. The value of the piezoelectric module of the vibration sensor with the PZT-CNT-Ni-V-Si structure was 186 pm/V, and the value of the residual polarization was 23.2 µC/cm², which is more than eight and three times, respectively, higher than the values of these properties for the vibration sensor with the PZT-Si structure. It is shown that the vibration sensor can operate in the frequency range of 0.1–10 kHz. Full article

Background: Nanotechnology has been the main area of focus for research in different disciplines, such as medicine, engineering, and applied sciences. Therefore, enormous efforts have been made to insert the use of nanoparticles into the daily routines of different platforms due to their impressive performance and the huge potential they could offer. Among numerous types of nanomaterials, titanate nanotubes have been widely recognised as some of the most promising nanocarriers due to their outstanding profile and brilliant design. Their implementation in pharmaceutical applications is of huge interest nowadays as it could be of fundamental importance in the development of the pharmaceutical industry and therapeutic systems. Methods: In the present work, a risk assessment-based procedure was developed and completed using ANN-based modeling to enable the design and fabrication of titanate nanotube-based drug delivery systems with desired properties, based on the critical analysis and evaluation of data collected from published articles regarding titanate nanotube preparation using the hydrothermal treatment method. Results: This analysis is presented as an integrated pathway for titanate nanotube preparation and utilization in a proper way that meets the strict requirements of pharmaceutical systems (quality, safety, and efficacy). Furthermore, a reasonable estimation of the factors affecting titanate nanotube preparation and transformation from traditional uses to novel pharmaceutical ones was established with the aid of a quality by design approach and risk assessment tools, mainly an Ishikawa diagram, a risk estimation matrix, and Pareto analysis. Conclusions: To the best of our knowledge, this is the first article using the QbD approach to suggest a systematic method for the purpose of upgrading TNT use to the pharmaceutical domain. Full article

Two ranges of dielectric permittivity (k) increase in polymer composites upon the modification of BaTiO₃ filler with multiwalled carbon nanotubes (MWCNTs) are shown for the first time. The first increase in permittivity is observed at low MWCNT content in the composite (approximately 0.07 vol.%) without a considerable increase in dielectric loss tangent and electrical conductivity. This effect is determined by the intensification of filler–polymer interactions caused by the nanotubes, which introduce Brønsted acidic centers on the modified filler surface and thus promote interactions with the cyanoethyl ester of polyvinyl alcohol (CEPVA) polymer binder. Consequently, the structure of the composites becomes more uniform: the permittivity increase is accompanied by a decrease in the lacunarity (nonuniformity) of the structure and an increase in scale invariance, which characterizes the self-similarity of the composite structure. The permittivity of the composites in the first range follows a modified Lichtenecker equation, including the content of Brønsted acidic centers as a parameter. The second permittivity growth range features a drastic increase in the dielectric loss tangent and conductivity corresponding to the percolation effect with the threshold at 0.3 vol.% of MWCNTs. Full article

Lepidocrocite-type layered sodium titanate (Na_xH_2−xTi₂O₅) is widely used in environmental remediation because of its large specific surface area, formed by anisotropic crystal growth, and its ability to store and exchange cations between layers. Additionally, peroxo-titanate nanotubes (PTNTs), which are tubular titanates with peroxy groups, exhibit visible-light absorption capabilities, rendering them suitable for photocatalytic applications under visible light irradiation. However, because of cation exchange reactions, the Na⁺ concentration and pH of the solution can fluctuate under aqueous conditions, affecting the photocatalytic performance of the PTNTs. Herein, we evaluated the impact of cation exchange reactions on the photocatalytic degradation of Rhodamine B (Rh B) by PTNTs at controlled Na⁺ ratios. The observed pH of Rh B solutions increases due to the cation exchange reaction with Na⁺ and H₃O⁺, leading to the formation of zwitter-ionic Rh B molecules, eventually weakening their adsorption and photodegradation performance. Moreover, the results indicate that inhibiting the pH increase of the Rh B solution can prevent the weakening of both the adsorption and photodegradation performance of PTNTs. This study highlights the significance of regulating the sodium ion content in layered titanate materials, emphasizing their importance in optimizing these materials’ photocatalytic efficacy for environmental purification applications. Full article

Recently, titanate nanotubes (TNTs) have been receiving more attention and becoming an attractive candidate for use in several disciplines. With their promising results and outstanding performance, they bring added value to any field using them, such as green chemistry, engineering, and medicine. Their good biocompatibility, high resistance, and special physicochemical properties also provide a wide spectrum of advantages that could be of crucial importance for investment in different platforms, especially medical and pharmaceutical ones. Hydrothermal treatment is one of the most popular methods for TNT preparation because it is a simple, cost-effective, and environmentally friendly water-based procedure. It is also considered as a strong candidate for large-scale production intended for biomedical application because of its high yield and the special properties of the resulting nanotubes, especially their small diameters, which are more appropriate for drug delivery and long circulation. TNTs’ properties highly differ according to the preparation conditions, which would later affect their subsequent application field. The aim of this review is to discuss the factors that could possibly affect their synthesis and determine the transformations that could happen according to the variation of factors. To fulfil this aim, relevant scientific databases (Web of Science, Scopus, PubMed, etc.) were searched using the keywords titanate nanotubes, hydrothermal treatment, synthesis, temperature, time, alkaline medium, post treatment, acid washing, calcination, pharmaceutical applications, drug delivery, etc. The articles discussing TNTs preparation by hydrothermal synthesis were selected, and papers discussing other preparation methods were excluded; then, the results were evaluated based on a careful reading of the selected articles. This investigation and comprehensive review of different parameters could be the answer to several problems concerning establishing a producible method of TNTs production, and it might also help to optimize their characteristics and then extend their application limits to further domains that are not yet totally revealed, especially the pharmaceutical industry and drug delivery. Full article

Manganese oxide-cerium oxide supported on titanate nanotubes (i.e., MnCe/TiNTs) were prepared and their catalytic activities towards NH₃-SCR of NO were tested. The results indicated that the MnCe/TiNT catalyst can achieve a high NO removal efficiency above 95% within the temperature range of 150–350 °C. Even after exposure to a HCl-containing atmosphere for 2 h, the NO removal efficiency of the MnCe/TiNT catalyst maintains at approximately 90% at 150 °C. This is attributed to the large specific surface area as well as the unique hollow tubular structure of TiNTs that exposes more Ce atoms, which preferentially react with HCl and thus protect the active Mn atoms. Moreover, the abundant OH groups on TiNTs serve as Brønsted acid sites and provide H protons to expel Cl atom from the catalyst surface. The irreversible deactivation caused by HCl can be alleviated by H₂O. That is because the dissociated adsorption of H₂O on TiNTs forms additional OH groups and relieves HCl poisoning. Full article

Nanotechnology is playing a significant role in modern life with tremendous potential and promising results in almost every domain, especially the pharmaceutical one. The impressive performance of nanomaterials is shaping the future of science and revolutionizing the traditional concepts of industry and research. Titanate nanotubes (TNTs) are one of these novel entities that became an appropriate choice to apply in several platforms due to their remarkable properties such as preparation simplicity, high stability, good biocompatibility, affordability and low toxicity. Surface modification of these nanotubes is also promoting their superior characters and contributing more to the enhancement of their performance. In this research work, an attempt was made to functionalize the surface of titanate nanotubes with carboxylic groups to increase their surface reactivity and widen the possibility of bonding different molecules that could not be bonded directly. Three carboxylic acids were investigated (trichloroacetic acid, citric acid and acrylic acid), and the prepared composites were examined using FT-IR and Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The toxicity of these functionalized TNTs was also investigated using adherent cancer cell lines and fibroblasts to determine their safety profile and to draw the basic lines for their intended future application. Based on the experimental results, acrylic acid could be the suitable choice for permanent surface modification with multiple carboxylic groups due to its possibility to be polymerized, thus presenting the opportunity to link additional molecules of interest such as polyethylene glycol (PEG) and/or other molecules at the same time. Full article

Anodic titania nanotubes (TiO₂-NT) are very promising for use in photocatalysis and photovoltaics due to their developed surface, symmetrical structure and conductive properties, which, moreover, makes them a convenient matrix for creating various nanocomposites. Herein we propose a new facile way of synthesizing symmetrical TiO₂-NT followed by a modification with barium titanate (BaTiO₃) nanoparticles, combining the advantages of electrochemical oxidation and hydrothermal synthesis. The electrophysical and optoelectronic properties of the formed nanocomposites have been studied. An asymmetry of the current–voltage characteristics was revealed. It is shown that during the barium titanate deposition, a symmetry-breaking nanoheterojunction TiO₂/BaTiO₃ is formed. Using EPR spectroscopy, paramagnetic defects (titanium, barium and oxygen vacancies) in the samples were determined. It was observed for the first time that upon illumination of titania nanotubes modified with BaTiO₃, the asymmetrical separation of photoexcited charge carriers (electrons and holes) between TiO₂-NT and BaTiO₃ occurs, followed by the capture of electrons and holes by defects. As a result, the photoinduced charge accumulates on the defects. Full article

The ion exchange of Na⁺ cations was used to photosensitise titanates nanotubes (Ti-NTs) with tris(2,2’-bipyridine)ruthenium(II) cations (Ru(bpy)₃²⁺); this yielded a light-sensitised Ti-NTs composite denoted as (Ru(bpy)₃)Ti-NTs, exhibiting the characteristic absorption of Ru(bpy)₃²⁺ in visible light. Incident photon-to-current efficiency (IPCE) measurements and the photocatalytic reduction of methyl viologen reaction confirmed that in the photosensitisation of the (Ru(bpy)₃)Ti-NTs composite, charge transfer and charge separation occur upon excitation by ultraviolet and visible light irradiation. The photocatalytic potential of titanate nanotubes was tested in the water-splitting reaction and the H₂ evolution reaction using a sacrificial agent and showed photocatalytic activity under various light sources, including xenon–mercury lamp, simulated sunlight, and visible light. Notably, in the conditions of the H₂ evolution reaction when (Ru(bpy)₃)Ti-NTs were submitted to simulated sunlight, they exceeded the photocatalytic activity of pristine Ti-NTs and TiO₂ by a factor of 3 and 3.5 times, respectively. Also, (Ru(bpy)₃)Ti-NTs achieved the photocatalytic water-splitting reaction under simulated sunlight and visible light, producing, after 4 h, 199 and 282 μmol×H_2×g_cat⁻¹. These results confirm the effective electron transfer of Ru(bpy)₃ to titanate nanotubes. The stability of the photocatalyst was evaluated by a reuse test of four cycles of 24 h reactions without considerable loss of catalytic activity and crystallinity. Full article

Aminated lignin (AL) was obtained by modifying technical lignin (TL) with the Mannich reaction, and aminated lignin-based titanate nanotubes (AL-TiNTs) were successfully prepared based on the AL by a facile hydrothermal synthesis method. The characterization of AL-TiNTs showed that a Ti–O bond was introduced into the AL, and the layered and nanotubular structure was formed in the fabrication of the nanotubes. Results showed that the specific surface area increased significantly from 5.9 m²/g (TL) to 188.51 m²/g (AL-TiNTs), indicating the successful modification of TL. The AL-TiNTs quickly adsorbed 86.22% of Cr(VI) in 10 min, with 99.80% removal efficiency after equilibration. Under visible light, AL-TiNTs adsorbed and reduced Cr(VI) in one step, the Cr(III) production rate was 29.76%, and the amount of total chromium (Cr) removal by AL-TiNTs was 90.0 mg/g. AL-TiNTs showed excellent adsorption capacities of Zn²⁺ (63.78 mg/g), Cd²⁺ (59.20 mg/g), and Cu²⁺ (66.35 mg/g). After four cycles, the adsorption capacity of AL-TiNTs still exceeded 40 mg/g. AL-TiNTs showed a high Cr(VI) removal efficiency of 95.86% in simulated wastewater, suggesting a promising practical application in heavy metal removal from wastewater. Full article

The majority of bone and joint infections are caused by Gram-positive organisms, specifically staphylococci. Additionally, gram-negative organisms such as E. coli can infect various organs through infected wounds. Fungal arthritis is a rare condition, with examples including Mucormycosis (Mucor rhizopus). These infections are difficult to treat, making the use of novel antibacterial materials for bone diseases crucial. Sodium titanate nanotubes (NaTNTs) were synthesized using the hydrothermal method and characterized using a Field Emission Scanning Electron Microscope (FESEM), High-Resolution Transmission Electron Microscope (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and Zeta sizer. The antibacterial and antifungal activity of the NaTNT framework nanostructure was evaluated using Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Disc Diffusion assays for bacterial activity, and Minimum Fungicidal Concentration (MFC) for antifungal investigation. In addition to examining in vivo antibacterial activity in rats through wound induction and infection, pathogen counts and histological examinations were also conducted. In vitro and in vivo tests revealed that NaTNT has substantial antifungal and antibacterial effects on various bone-infected pathogens. In conclusion, current research indicates that NaTNT is an efficient antibacterial agent against a variety of microbial pathogenic bone diseases. Full article

Although titanium (Ti) alloys have been widely employed as biomedical materials, they cannot achieve satisfactory osseointegration when implanted in the human body due to their biologically inert nature. Surface modification can enhance both their bioactivity and corrosion resistance. The present study employed a Ti–5Nb–5Mo alloy with a metastable α″ phase. This alloy may undergo phase changes after conventional high-temperature heat treatment, which can deteriorate its properties. This study heat-treated the anodized Ti–5Nb–5Mo alloy by using a low-temperature hydrothermal or vapor thermal method to analyze the effects of heat treatment on its apatite induction. The results revealed that the porous nanotube structure on the surface of the alloy was transformed into anatase nanoparticles after hydrothermal or vapor thermal treatment at 150 °C for 6 h. After immersion in simulated body fluid (SBF) for 7 days, the amount of apatite deposited on the surface of the vapor thermal-treated alloy exceeded that on the hydrothermal-treated alloy. Therefore, post-heat treatment of anodized Ti–5Nb–5Mo by using the vapor thermal method can enhance its apatite inductivity without altering its structure. Full article