Nanotubular Arrays Research Articles

Structural, morphological, and optical properties of CuO nanoblade-decorated TiO2 nanotubular photoelectrodes

Titania (TiO2) nanotubular photoelectrodes are a competitive component of titania-based photoelectrochemical water splitting systems. However, TiO2 actively absorbs light in the UV region, which limits its usefulness in solar water splitting, a fast-growing clean energy alternative. In this study, the structural, morphological and optical properties of CuO/TiO2 nanostructures on conductive transparent F-doped SnO2 (FTO) coated glass substrates are engineered for potential application in solar water splitting. The efficacy of a three-step anodization synthesis process to develop free-standing high-fidelity nanotubular TiO2 thin films (∼8μm) is demonstrated. CuO nanoblades were deposited on TiO2/FTO by a successive ionic layer adsorption reaction (SILAR). An increase in the precursor concentration and number of immersion cycles influenced the adsorption of CuO and the resultant red shift in the absorption range. SEM and TEM analyses confirm the formation of a heterostructure, with evidence of CuO nanostructures within the TiO2 nanotubular arrays and on the top of the tubes.

Designing TiO2 Nanotubular Arrays with Au-CoOx Core-Shell Nanoparticles for Enhanced Photoelectrochemical Methanol and Lignin Oxidation.

One-dimensional (1D) ordered TiO2 nanotubes exhibit exceptional charge transfer capabilities, making them suitable candidates for constructing visible-light-active photoanodes in selective PEC oxidation reactions. Herein, we employed a facile and easily scalable electrochemical method to fabricate Au-CoOx-deposited ordered TiO2 nanotubular array photoanodes. The improved visible light absorption capacity of TiO2-Au-CoOx, with unhampered 1D channels and the controlled integration of Au between TiO2 and CoOx, along with their synergistic interaction, have been identified as the most promising strategy for enhanced PEC performance, as evidenced by an IPCE of 3.7% at 450 nm. Furthermore, the robust interfacial charge transfer pathway from CoOx to the TiO2 surface via the Au mediator promotes the migration of photogenerated electrons and enables the accumulation of holes on the surface of CoOx. These holes are then efficiently utilized by oxidants such as methanol or lignin to generate value-added products, highlighting the potential of this system for advanced PEC applications.

Insight into antibacterial effect of titanium nanotubular surfaces with focus on Staphylococcus aureus and Pseudomonas aeruginosa

Materials used for orthopedic implants should not only have physical properties close to those of bones, durability and biocompatibility, but should also exhibit a sufficient degree of antibacterial functionality. Due to its excellent properties, titanium is still a widely used material for production of orthopedic implants, but the unmodified material exhibits poor antibacterial activity. In this work, the physicochemical characteristics, such as chemical composition, crystallinity, wettability, roughness, and release of Ti ions of the titanium surface modified with nanotubular layers were analyzed and its antibacterial activity against two biofilm-forming bacterial strains responsible for prosthetic joint infection (Staphylococcus aureus and Pseudomonas aeruginosa) was investigated. Electrochemical anodization (anodic oxidation) was used to prepare two types of nanotubular arrays with nanotubes differing in dimensions (with diameters of 73 and 118 nm and lengths of 572 and 343 nm, respectively). These two surface types showed similar chemistry, crystallinity, and surface energy. The surface with smaller nanotube diameter (TNT-73) but larger values of roughness parameters was more effective against S. aureus. For P. aeruginosa the sample with a larger nanotube diameter (TNT-118) had better antibacterial effect with proven cell lysis. Antibacterial properties of titanium nanotubular surfaces with potential in implantology, which in our previous work demonstrated a positive effect on the behavior of human gingival fibroblasts, were investigated in terms of surface parameters. The interplay between nanotube diameter and roughness appeared critical for the bacterial fate on nanotubular surfaces. The relationship of nanotube diameter, values of roughness parameters, and other surface properties to bacterial behavior is discussed in detail. The study is believed to shed more light on how nanotubular surface parameters and their interplay affect antibacterial activity.

Surface Topography Steer Soft Tissue Response and Antibacterial Function at the Transmucosal Region of Titanium Implant.

Metallic dental implants have been extensively used in clinical practice due to their superior mechanical properties, biocompatibility, and aesthetic outcomes. However, their integration with the surrounding soft tissue at the mucosal region remains challenging and can cause implant failure due to the peri-implant immune microenvironment. The soft tissue integration of dental implants can be ameliorated through different surface modifications. This review discussed and summarized the current knowledge of topography-mediated immune response and topography-mediated antibacterial activity in Ti dental implants which enhance soft tissue integration and their clinical performance. For example, nanopillar-like topographies such as spinules, and spikes showed effective antibacterial activity in human salivary biofilm which was due to the lethal stretching of bacterial membrane between the nanopillars. The key findings of this review were (I) cross-talk between surface nanotopography and soft tissue integration in which the surface nanotopography can guide the perpendicular orientation of collagen fibers into connective tissue which leads to the stability of soft tissue, (II) nanotubular array could shift the macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) and manipulate the balance of osteogenesis/osteoclasia, and (III) surface nanotopography can provide specific sites for the loading of antibacterial agents and metallic nanoparticles of clinical interest functionalizing the implant surface. Silver-containing nanotubular topography significantly decreased the formation of fibrous encapsulation in per-implant soft tissue and showed synergistic antifungal and antibacterial properties. Although the Ti implants with surface nanotopography have shown promising in targeting soft tissue healing in vitro and in vivo through their immunomodulatory and antibacterial properties, however, long-term in vivo studies need to be conducted particularly in osteoporotic, and diabetic patients to ensure their desired performance with immunomodulatory and antibacterial properties. The optimization of product development is another challenging issue for its clinical translation, as the dental implant with surface nanotopography must endure implantation and operation inside the dental microenvironment. Finally, the sustainable release of metallic nanoparticles could be challenging to reduce cytotoxicity while augmenting the therapeutic effects.

Dual Optical Response Strategy for the Detection of Cytochrome c Using Highly Luminescent Lanthanide-Based Nanotubular Sensor Arrays.

Here, we demonstrate a label-free dual optical response strategy for the detection of cytochrome c (Cyt c) with ultrahigh sensitivity using highly luminescent lanthanides containing inorganic-organic hybrid nanotubular sensor arrays. These sensor arrays are formed by the sequential incorporation of the photosensitizers 2,3-dihydroxynaphthalene (DHN) or 1,10-phenanthroline (Phen), and trivalent lanthanide terbium ions (Tb3+) into sodium lithocholate (NaLC) nanotube templates. Our sensing platform relies on the detection and quantification of Cyt c in solution by providing dual photoluminescence quenching responses from the nanotubular hybrid arrays in the presence of Cyt c. The large quenching of the sensitized Tb3+ emission within the DHN/Phen-Tb3+-NaLC nanotubular sensor arrays caused by the strong binding of the photosensitizers to Cyt c provides an important signal response for the selective detection of Cyt c. This long-lived lanthanide emission response-based sensing strategy can be highly advantageous for the detection of Cyt c in a cellular environment eliminating background fluorescence and scattering signals through time-gated measurements. The DHN containing nanotubular sensor arrays (DHN-NaLC and DHN-Tb3+-NaLC) provide an additional quenching response characterized by a unique spectral valley splitting with quantized quenching dip on the DHN fluorescence emission. This spectral quenching dip resulting from efficient FRET between the protein bound DHN photosensitizer and the heme group of Cyt c serves as an important means for specific detection and quantification of Cyt c in the concentration range of 0-30 μM with a low detection limit of around 20 nM.

Structural and corrosion analysis of copper/chitosan coating on nanotubular TiO2/Ti6Al4V implant surface

In this research, we focused on the investigation of the structural, surface, and corrosion behavior properties of copper-loaded TiO2 nanotubular array surfaces that were further deposited with a chitosan biopolymer. This composite material was fabricated on Ti6Al4V alloy substrates using a combination of anodic oxidation (AO), electro-cathodic deposition (ECD), and electrophoretic deposition (EPD) techniques, primarily to apply it in medical implant contexts. Initially, the TiO2 nanotubes were prepared via anodization (AO). Subsequently, copper was introduced into the TiO2 nanotubes through electro-cathodic deposition (ECD), followed by the coating of chitosan over the copper-loaded TiO2 nanotubes using electrophoretic deposition (EPD). To comprehensively assess the characteristics of these surfaces, a series of analytical techniques were employed, including SEM, EDX mapping, XRD, and wettability measurements. Furthermore, the electrochemical properties of these surfaces, namely the OCP, PDP, and EIS, were extensively scrutinized.The outcomes of this investigation directed a notable development in the electrochemical corrosion resistance of the chitosan-deposited copper-loaded TiO2 nanotubular array surfaces in comparison to uncoated Ti6Al4V alloy, particularly under conditions simulating a physiological environment (simulated body fluid, SBF). Corrosion rates, assessed through PDP (Potentiodynamic Polarization) curves, were determined to be 0.3023 mm/y for polished Ti6Al4V, 0.1476 mm/y for TiO2 30 V 4 h, 0.1235 mm/y for TNT-Cu2/30/Ch, 0.0733 mm/y for TNT-Cu2/60/Ch, and 0.0611 mm/y for TNT-Cu2/90/Ch. Additionally, corrosion protection efficiencies were calculated as 51.16 % for TiO2 30 V 4 h, 59.15 % for TNT-Cu2/30/Ch, 75.76 % for TNT-Cu2/60/Ch, and 79.81 % for TNT-Cu2/90/Ch. Notably, the TNT-Cu2/90/Ch sample demonstrated a significantly low corrosion rate of 0.0611 mm/year and a high corrosion protection efficiency of 79.81 %. This enhancement can happen due to the chitosan coating, which acts as a protective layer, hindering the ingress of the physical solution into the original metal surfaces. Notably, TNT-Cu2/90/Ch coated sample exhibited a corrosion rate (icorr) approximately 5 times lower than that of the uncoated alloy. In conclusion, this study presents a novel chitosan-coated composite material consisting of copper-loaded TiO2 nanotubular surfaces that effectively enhances corrosion resistance compared to polished Ti6Al4V substrates.

Tuning charge transfer and ion diffusion in 3D nanotubular arrays by engineering vacancy and implanting sodiophilic seeds for dendrite-free sodium metal anodes

Sodium metal anode (SMA) stands out as a compelling choice for future high-energy Na batteries due to its high theoretical capacity and low redox potential. However, its widespread application is severely impeded by dendrite-related hazards. Designing a host for “hostless” SMA has emerged as a promising strategy to address its harmful dendrite growth. Recent studies highlight the effectiveness of low-tortuosity arrays in SMA for guiding rapid ion transport and achieving uniform Na deposition. Herein, a pioneering 3D host, Ag@H-TNTA, characterized by low-tortuosity hydrogenated TiO2-x nanotubular arrays decorated with silver nanocrystals, are unveiled for constructing fast, stable, and dendrite-free SMA. The strategic introduction of oxygen vacancies and the implantation of sodiophilic seeds enable the achievement of rapid and coordinated electronic/ion transport as well as uniform electric-field/ion flux distribution in the Ag@H-TNTA, ultimately facilitating uniform Na deposition. Consequently, Ag@H-TNTA electrode exhibits a dendrite-free plating morphology and maintains an impressive Coulombic efficiency of ≈ 98% over 600 cycles at 1 mA cm−2 with a capacity of 1 mAh cm−2. Outstanding cycling performances and high rate capabilities of Ag@H-TNTA-Na anode are also demonstrated in both symmetric and full cells, underscoring the potential of Ag@H-TNTA as a robust host for stable and dendrite-free SMA.

Controlled assembly of novel Fe2O3/MgFe2O4 nanotubular array structures for rapid detection of dibutylamine

The development of an efficient, fast, and real-time sensor for detecting dibutylamine (C8H19N) gas remains challenging. In this study, a simple controllable and environmentally friendly solvothermal method was used to construct novel Fe2O3/MgFe2O4 nanotube array structures with heterointerfaces. The array structure exhibits a relatively large specific surface area and high-activity heterointerfaces. These features greatly promote the diffusion and adsorption of gas molecules onto the sensitive layer, effectively increasing the surface-adsorbed oxygen species and active sites of the sensing material. The sensing performance of the Fe2O3/MgFe2O4 array structure for C8H19N gas is greatly improved due to the synergistic effect of these multiple factors. The sensor showed a high response of 92.6 to 100 ppm C8H19N at 170 °C, with a short response time of 3.6 s and an ultra-low detection limit of 10 ppb. The sensitization mechanism of Fe2O3/MgFe2O4 to C8H19N was investigated by combining theoretical calculations and experimental techniques. This study broadens the application of gas sensors for the detection of volatile organic compounds (VOCs).

Effect of Voltage on Gas Sensor Performance of Anodization Synthesized TiO2 Nanotubes Arrays

Serious gases have been highly related to being prejudiced against human life within the environment. The evolution of a trustworthy gas sensor with an elevated response is of major importance for detecting various hazardous gases. Titanium dioxide (TiO2) nanotubes (TNTs) are favorable candidates with considerable potential and stellar performance in gas sensor applications. In this work, we have studied the effect of voltage on preparing TiO2 nanotubular arrays via the anodization technique for gas sensor applications. A simple electrochemical anodization approach was used to synthesize titanium dioxide nanotubes. Diverse techniques of characterization were used to evaluate TNTs. The results gained from field emission scanning electron microscopy (FESEM), energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD) indicate that TiO2 was formed. Gas sensors were created, and the gas detection characteristics were directed towards hydrogen sulfide (H2S), which is not a healthy gas. The sensor made from these nanotubes responds well to this gas at different temperatures and has high sensitivity. The H2S-detecting characteristics were evaluated at values ranging from room temperature up to 300 oC. Results show that the gas sensor TNTs that was prepared at 30 volt for H2S gas sensing has the highest sensitivity and shortest response time at room temperature.

Anodization and nonstructural surface characterizations of fabricated Ti–29Nb–13Ta–7.1Zr alloy for biomedical applications and its mechanical, wettability, tribological, and corrosion properties

Implants subjected to tribocorrosion release metallic ions and solid wear debris, which can cause a peri-implant disease, bone loss, and eventually implant loosening. TiO2 coatings have a wide application range owing to their biocompatibility. In this study, the Ti–29Nb–13Ta–7.1 Zr alloy was fabricated using powder metallurgy technique. The samples were electrochemically oxidized to produce self-standing TiO2 nanotubular arrays followed by annealing for 1 h at 450 °C to improve their crystallinity. The prepared TiO2 coatings were characterized by SEM, X-ray diffraction, and EDX, and the wettability, tribomechanical characteristics, and corrosion behavior of bio-functionalized TiO2 nanotubes were investigated. Atomic force microscopy observations were conducted to examine wear scars, and the wear volume was measured via 2D profilometry. Microhardness and nanoindentation tests were performed to evaluate the mechanical characteristics of TiO2 nanotubes such as microhardness, nanohardness, and modulus of elasticity. The thickness and diameter of the observed TiO2 nanotubes are 2 μm and 90.94 nm, respectively. The obtained results revealed that the deposition of a biofunctionalized Ti/TiO2 nanotube layer enhanced the hydrophilicity, tribomechanical properties, and corrosion resistance of the Ti–29Nb–13Ta–7.1Zr alloy. The COF of Ti alloy was 0.51 and it decreased to 0.28 after anodization and annealing at 450 °C. The contact angle of the Ti sample was 79.9° and it decreased to 45.6° after annealing at 850 °C. However, after the anodic oxidation and annealing at 450 °C, the contact angle decreased to 45.6°.

Structural, cell culture, antibacterial and in vitro bioactivity analysis of highly-ordered Al2O3 nanotube coating with decorated Ag2O nanoparticles on Ti-6Al-4V

The alumina nanotubular arrays (Al2O3 NTs) are a promising candidate for application in bone and dental implants for their better mechanical and chemical behavior in the human body compared to titanium. Nevertheless, the biocompatibility and antibacterial activity of Al2O3 NTs still need further improvement to meet the requirements of safe implants. In this research, Al2O3 NTs coating was proposed on Ti-6Al-4 V via magnetron sputtering pure aluminum followed by an anodization and sealing process, then heat treated for 1 h at 450 °C. After that, Ag2O nanoparticles (NPs) were decorated on the nanotubular walls under controlled conditions using magnetron sputtering. The findings demonstrated that the proposed Al2O3 NTs-Ag2O NPs promoted in-vitro bioactivity alongside excellent antibacterial activity against E.coli and S.aureus bacteria within 4 h and 6 h, respectively. Additionally, the cell-culture showed healthy growth of the human osteoblast cells (HOb) on the Al2O3 NTs-Ag2O NPs. The new design of coating also shows that the total cumulative Ag+released after 14 days is significantly low which is safe and provides the long-term antibacterial activity. It is illustrated that Al2O3 NTs-Ag2O NPs have promising biomedical properties to enhance the biofunctionality of biomedical-grade Ti-6Al-4 V implants.

Optimisation of a Ce–Mn co-doped SnO2–Sb anode based on a nanotubular TiO2 array for electrochemical decolourisation of wastewater

ABSTRACT In this study, Ce and Mn co-doped SnO2–Sb electrode was prepared onto a Ti/TiO2 nanotubes surface. The nanostructure of the novel electrode was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), and specific techniques were used to study the electrochemical characteristics of the electrode. SEM analysis results showed that TiO2 nanotubes could reduce the crack morphology and provide a larger surface area for loading the electrochemically active material. EDS analysis showed that Ce and Mn were doped into the electrode successfully. Under optimised conditions, the electrode prepared with Sn:Sb:Ce:Mn mole ratio of 100:10:3:3 has the best electrocatalytic performance. Ethylene glycol was used as the solvent in cerium-manganese co-doped Ti/TiO2–NTs/TiO2–SnO2–Sb electrode. Ce–Mn co-doped TiO2NTs/SnO2–Sb electrode has a high oxygen evolution potential of 1.79 V (vs. SCE) and a lower charge transfer resistance. The decolourisation extent of 30 mg L−1 methylene blue wastewater reaches 98.5% within 30 min. Finally, the main intermediates were identified by gas chromatography-mass spectrometer (GC-MS), and possible pathways for dye degradation were proposed. This study opens a door to the rapid electrochemical decoloursation treatment of wastewater by using an easily obtainable multi-metal co-doped electrode.

Corrosion behavior of self-organized TiO2 nanotubular arrays grown on Ti6Al4V for biomedical applications

The electrochemical interactions between a biomaterial and a human fluid are important to understand when developing surfaces on titanium biomedical composites to improve bone regeneration, healing times, and longevity. Electrochemical corrosion is a major problem in implant-tissue interaction in that environment. The purpose of this research is to use different electrochemical methods such as open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) to examine the effect of self-organized TiO2 nanotubular surfaces on the corrosion resistance of Ti6Al4V surface. The electrochemical behavior of polished Ti6Al4V (control), and anodized samples at a constant voltage of 30V and various time-periods of anodization, such as 3hr, 4hr, and 5hrs respectively is the main focus of our study. All the anodized samples were annealed at 500 °C for 3hr with preheating rate of 5 °C per minute. The resistance of the nanotubular structure is improved after annealing because the anatase phase is stabilised, and the fluoride ions are removed. The electrochemical behavior of the nanotubular surfaces were investigated by using the simulated body fluid (SBF, 7.4 pH) solution. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), and a Drop Shape Analyzer were all used to investigate the nanotubular morphology, chemical compositions, and structure. According to the findings, the anodic oxidation process results in a nanotubular structure that improves the surface area and influences the surface's chemical composition. Surfaces with self-organized TiO2 nanotubular structures had greater corrosion resistance than polished Ti6Al4V because the passive film had a larger surface area and a more dispersed amorphous crystal structure. Finally, the physical condition of the post-electrochemical treated sample was evaluated by the SEM images and compositional analysis by the EDS and XRD. The PDP curves showed the corrosion rate of the samples polished Ti6Al4V, TiO2 30V 3hr, TiO2 30V 4hr, and TiO2 30V 5hrs are 0.39, 0.35, 0.09, and 0.24 mm per year respectively. Similarly, the efficiencies of the anodized samples TiO2 30V 3hr, 4hr, and 5hrs are 9.96, 76.44, and 38.30% respectively. When comparing all of the anodized samples, the overall corrosion resistance is improved by 2 times.

The synthesis, surface analysis, and cellular response of titania and titanium oxynitride nanotube arrays prepared on TiAl6V4 for potential biomedical applications

Titania nanotubes are gaining prominence in the biomedical field as implant materials due to their mechanical durability, nano-rough properties, and positive influence on cellular response. This work aimed to synthesize titania and titanium oxynitride (Ti–O–N) nanotubular arrays on TiAl6V4 substrates using an anodic oxidation process followed by annealing in air or by additional nitridation in NH3 atmosphere. Different nanotubular layers of unique morphology and structure were fabricated and investigated using advanced surface analysis and biocompatibility tests. In-depth surface analysis was performed by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), 3D profilometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Cell testing using adipose-derived mesenchymal stem cells and human fetal osteoblasts demonstrated good cell viability, high proliferative capacity, and a favorable overall effect on cell morphology for the Ti–O–N nanotubes.

Removal of contaminants of emerging concern by photocatalysis with a highly ordered TiO2 nanotubular array catalyst

In this work, the treatment of wastewater polluted with contaminants of emerging concern is evaluated by heterogeneous photocatalysis with TiO2. Titanium plates are anodized by different experimental conditions, and the influence of these conditions on the catalytic performance is evaluated by factorial design of experiments. The formation of TiO2 nanotubes in the anatase form is sought for photocatalysts with high active surface. Thus, electrolyte used in the anodization process (NH4F/H2O in ethylene glycol or H2SO4 in water), potential ramp (2 – 4 V min−1), maximal applied potential (20 – 60 V) and heat treatment are evaluated as influencing factors of the experimental design. The activity of these catalysts is tested by ofloxacin (pharmaceutical compound used as model of contaminant of emerging concern) degradation in wastewater treatment, obtaining the kinetic constant of the process, parameter chosen as response variable of the experimental design. Results show that NH4F/H2O as electrolyte, 2 V min−1, 40 V and a heat treatment are the optimum conditions for the formation of TiO2–anatase nanotubes with a good disposition and arrangement, observing the higher efficiency in the wastewater treatment process. In addition, wastewater treatment conditions are evaluated (UV wavelength, irradiance and initial concentration of ofloxacin), and it is found that UV-B, maximal irradiance and minimal initial concentration of the pollutant are the optimal factors for a higher process efficiency. This is a work that opens the door to the removal of contaminants of emerging concern from wastewater with a technology of low cost, with easy implantation and environmental compatibility, making possible to use only sunlight as a reagent.

Thermally stimulated luminescence of oxygen-deficient zirconia nanotubes

ZrO2 nanotubular arrays with intrinsic defects are a promising solid-state basis for the development of devices for detecting, storing, and converting energy. Layers of the self-ordered zirconia nanotubes of 5 μm length and 30 nm diameter, containing oxygen vacancies and their complexes, have been synthesized by anodic oxidation. The spectrally resolved TSL (thermally stimulated luminescence) above room temperature for the samples exposed by UV-irradiation with an energy of 4.1 eV have been studied. Two emission bands with maxima near 2.5 and 2.8 eV, associated with radiative relaxation of T and F+ centers, respectively, have been found. An analysis of the measured glow curves within the framework of general order kinetics established the presence of four TSL peaks caused by charge carriers traps with activation energies of 0.7–0.8 eV. A band diagram is proposed to explain the role of optically active centers based on electron (vacancies in positions of three- and four-coordinated oxygen) and hole (interstitial oxygen ions) traps in observed TSL processes during the irradiation and the followed heating of anion-deficient ZrO2 nanotubes.

Docked ions: Vertical-aligned tubular arrays for highly efficient capacitive deionization

Capacitive deionization (CDI) is an effective method for desalination of brackish water to alleviate the global freshwater crisis. Obtaining high desalination capacity is the primary focus of this field. Based on capacitive and pseudocapacitive behavior of the electrodes, current research is mainly devoted to increasing the specific surface area of electrode materials, however, the NaCl adsorption capacity is typically limited to the range of 10–20 mg g−1. In this work, we propose a new design paradigm of using a vertical-aligned nanotubular structure for CDI. This design allows ions to be temporarily held inside the electrodes like ships docked in a harbor (ion-docking effect, IDE) due to the greatly diminished water flow inside the tubes, thus enhancing the desalination capacity. As a result, the obtained CDI device based on vertical-aligned nanotubular P-TiO2 arrays shows an ultra-high NaCl adsorption capacity of ~60 mg g−1 within 30 min in 0.01 mol L−1 NaCl solution under 1.2 V, corresponding to a rapid average adsorption rate of 2 mg g−1 min−1. Moreover, the adsorption capacity could be further increased up to 121 and 136 mg g−1 under 1.2 and 1.5 V for 2.5 h adsorption, respectively, but still far from its equilibrium value. Finally, experiments and theoretical simulations are combined to further understand the IDE in CDI. This work highlights the discovery and the utilization of IDE in CDI, and provides new guidance for the design of CDI electrodes and can facilitate the development of CDI technology.

TiO2 nanotubular arrays decorated with ultrafine Ag nanoseeds enabling a stable and dendrite-free lithium metal anode.

To exploit next-generation high-energy Li metal batteries, it is vitally important to settle the issue of dendrite growth accompanied by interfacial instability of the Li anode. Applying 3D current collectors as hosts for Li deposition emerges as a prospective strategy to achieve uniform Li nucleation and suppress Li dendrites. Herein, well-aligned and spaced TiO2 nanotube arrays grown on Ti foil and surface decorated with dispersed Ag nanocrystals (Ag@TNTAs/Ti) were constructed and employed as a 3D host for regulating Li stripping/plating behaviors and suppressing Li dendrites, and also relieving volume fluctuation during repetitive Li plating/stripping. Uniform TiO2 nanotubular structures with a large surface allow fast electron/ion transport and uniform local current density distribution, leading to homogeneous Li growth on the nanotube surface. Moreover, Ag nanocrystals and TiO2 nanotubes have good Li affinity, which facilitates Li+ capture and reduces the Li nucleation barrier, achieving uniform nucleation and growth of Li metal over the 3D Ag@TNTAs/Ti host. As a result, the as-fabricated Ag@TNTAs/Ti electrode exhibits dendrite-free plating morphology and long-term cycle stability with coulombic efficiency maintained over 98.5% even after 1000 cycles at a current density of 1 mA cm-2 and cycling capacity of 1 mA h cm-2. In symmetric cells, the Ag@TNTAs/Ti-Li electrode shows a much lower hysteresis of 40 mV over an ultralong cycle period of 2600 h at a current density of 1 mA cm-2 and cycling capacity of 1 mA h cm-2. Moreover, the full cell with the Ag@TNTAs/Ti-Li anode and LiFePO4 cathode achieves a high capacity of 155.2 mA h g-1 at 0.5C and retains 77.9% capacity with an average CE of ≈99.7% over 200 cycles.

First-order phase transition in nanotubular titanium dioxide

Titanium dioxide (TiO2) nanotubes array with the length of 16 μm and the outer diameter of 100 nm were synthesized by anodic oxidation of titanium foil in an electrolyte solution containing a fluorine-containing solution of ethylene glycol. The selected synthesis conditions make it possible to separate the nanotubular array from the titanium foil and study it as a homogeneous functional material. The performed scanning electron microscopy study and Brunauer--Emmett--Teller analysis allowed to get data on the morphology of the samples. X-ray diffraction, thermogravimetric, and differential scanning calorimetry analysis made it possible to determine the temperature of the phase transition of the amorphous state into crystalline anatase (sp.gr. I4/amd). Observed phase transition of first order takes place at temperature about 350oC. Keywords: nanotubular titanium dioxide films, anodic oxidation, phase transition, anatase, TG, DSC.

Development of a novel smart carrier for drug delivery: Ciprofloxacin loaded vaterite/reduced graphene oxide/PCL composite coating on TiO2 nanotube coated titanium

In the field of orthopaedic implants, post-surgery infections and biocompatibility are the most challenging obstacles. Sustained and controlled antibiotic release is a key factor in novel drug delivery systems. A novel drug delivery system combined with vaterite microsphere, graphite oxide (GO), reduced graphene oxide (rGO) incorporated in a polycaprolactone (PCL) matrix on TiO2 nanotube coated Ti (TNT-Ti) is established. Anodization was employed to develop TiO2 nanotubular arrays on Ti. Ciprofloxacin hydrochloride (CPF–HCl) loaded vaterite microspheres were synthesized by in situ precipitation method. Deposition of vaterite/PCL, vaterite-GO/PCL and vaterite-rGO/PCL composite coating on TNT-Ti was carried out by dip coating method. The composite coatings were characterized for their phase content, morphological features and functional groups. Among the three types of composite coatings, vaterite-rGO/PCL composite coating is found to be capable of encapsulating CPF-HCl to a level of 75.14 μg. The drug release profile of CPF-HCl from the vaterite-rGO/PCL composite coating exhibits a controlled release amounting to only 35.02 % of release at the end of 120 h. The vaterite-rGO/PCL composite coating exhibits a low dissolution rate and possesses adequate bioactivity in HBSS and SBF solutions at 37 °C for 14 and 10 days, respectively. The in situ loaded CPF-HCL drug on vaterite microspheres, PCL polymer matrix and GO/rGO nanofillers does not affect the cytocompatibility and all the composite coatings supported cell viability and proliferation. The ability of vaterite-rGO/PCL composite coating to provide a slow and steady release of antibiotics with sufficient bioactivity and biocompatibility at the tissue implant interface makes it a promising for osteomyelitis infection of bone tissue implant materials.