Nanotube Array Films Research Articles

Remarkable fluorescence enhancement of acridine orange and rhodamine B through immobilization on zirconia nanotube array film and its application on nitrite sensing

Zirconia nanotube array films (ZNAF) prepared by anodic oxidation method were used as immobilization materials for acridine orange (AO), rhodamine B (RB) and AO-RB systems. A comparative study on their fluorescence emission intensity, fluorescence resonance energy transfer (FRET) and fluorescence detection of nitrite in aqueous solutions and on immobilization films with ZNAF as carriers was carried out. Results demonstrate that the solution pH values and immobilization on ZNAF have a great influence on the performance of these fluorescent molecules. Compared with aqueous solutions, the fluorescence emission intensity of AO and RB is considerably increased by immobilization, which is 8.0 and 4.2 times higher than the original, respectively. The energy transfer efficiency (E) of the AO-RB system increases from 40.9 % to 84.8 % by loading it on ZNAF. Moreover, after immobilization onto ZNAF, the fluorescence detection performance of nitrite is also significantly improved. The limit of detection decreases from 0.95 ng/mL to 0.22 ng/mL and the sensitivity increases from 939.18 to 15,031.68 mL/µg through loading AO onto ZNAF.

A comparative study on fluorescent performance of several heterocyclic dyes: In aqueous solution or immobilized on zirconia nanotube arrays

The solution pH values, cosolvent type, and immobilization of the fluorescent dyes affect their dispersion state and fluorescent performance significantly. Zirconia, with abundant resources, low cost and high refractive index, is a commonly used immobilization material for fluorescent dyes. In this paper, zirconia nanotube array films (ZNAF) prepared by anodic oxidation method were used as immobilization materials for common heterocyclic dyes (fluorescein, rhodamine B, acridine, acridine orange). A systematically comparative study on their fluorescent performance of aqueous solutions at different pH values with or without cosolvent sodium benzenesulfonate and of immobilization films with ZNAF as carriers was investigated. Moreover, the performances of acridine orange-rhodamine B fluorescence resonance energy transfer (FRET) system with different dispersion states were studied in detail. Results demonstrate that the solution pH values, immobilization and sodium benzenesulfonate have great influence on the performance of these fluorescent dyes, and the change rules of different fluorescent molecules are obviously different, which is closely related to their molecular structure and dispersion state. Compared with aqueous solutions, the fluorescence emission of acridine orange and rhodamine B is greatly improved by immobilization, which is 8.6 and 5.4 times higher than the original, respectively. Furthermore, energy transfer efficiency (E) and enhancement ratio of the acridine orange-rhodamine B system are significantly increased by loading it on ZNAF, with a maximum E value of 84.8% (pH = 13) and a maximum enhancement ratio of 5.27 (pH = 5).

Photoactivity of amorphous and crystalline TiO2 nanotube arrays (TNA) films in gas phase CO2 reduction to methane with simultaneous H2 production

This study assessed the photoactivity of amorphous and crystalline TiO2 nanotube arrays (TNA) films in gas phase CO2 reduction. The TNA photocatalysts were fabricated by titanium anodization and submitted to an annealing treatment for crystallization and/or cathodic reduction to introduce Ti3+ and oxygen vacancies into the TiO2 structure. The cathodic reduction demonstrated a significant effect on the generated photocurrent. The photoactivity of the four TNA catalysts in CO2 reduction with water vapor was evaluated under UV irradiation for 3 h, where CH4 and H2 were detected as products. The annealed sample exhibited the best performance towards methane with a production rate of 78 μmol gcat−1 h−1, followed by the amorphous film, which also exhibited an impressive formation rate of 64 μmol gcat−1 h−1. The amorphous and reduced-amorphous films exhibited outstanding photoactivity regarding H2 production (142 and 144 μmol gcat−1 h−1, respectively). The annealed catalyst also revealed a good performance for H2 production (132 μmol gcat−1 h−1) and high stability up to five reaction cycles. Molecular dynamic simulations demonstrated the changes in the band structure by introducing oxygen vacancies. The topics covered in this study contribute to the Sustainable Development Goals (SDG), involving affordable and clean energy (SDG#7) and industry, innovation, and infrastructure (SDG#9).

Preparation and photoluminescence properties of Tb3+ and rhodamine B composite films supported by ZrO2 nanotube arrays

ZrO2 can be used as both the matrix for rare earth ions and the supporting material for organic fluorescent molecules. In this work, using ZrO2 nanotube array films (ZNA) as the supporting material, Tb3+ composite films (Tb-ZrO2/ZNA) were obtained by depositing Tb3+-doped ZrO2 nanoparticles into ZNA through ionic layer adsorption deposition method. Then, rhodamine B (RB) was immobilized on Tb-ZrO2/ZNA to obtain RB@Tb-ZrO2/ZNA composite films. The photoluminescence (PL) properties, fluorescence resonance energy transfer (FRET) and ultraviolet (UV) display performances of the composite films were studied. Results show that the Tb3+ ions in RB@Tb-ZrO2/ZNA can significantly enhance the PL emission of RB with a maximum enhancement multiple of up to 3.93-fold. The composite films can display the UV intensity directly through brightness and color changes, among which RB@Tb-ZrO2/ZNA is the brightest and most sensitive to UV light. This work can provide ideas and methods for the preparation and application of organic-inorganic hybrid fluorescent materials.

Nano selenium-doped TiO2 nanotube arrays on orthopedic implants for suppressing osteosarcoma growth.

Osteosarcoma, the most common primary malignant bone tumor, is characterized by malignant cells producing osteoid or immature bone tissue. Most osteosarcoma patients require reconstructive surgery to restore the functional and structural integrity of the injured bone. Metal orthopedic implants are commonly used to restore the limb integrity in postoperative patients. However, conventional metal implants with a bioinert surface cannot inhibit the growth of any remaining cancer cells, resulting in a higher risk of cancer recurrence. Herein, we fabricate a selenium-doped TiO2 nanotube array (Se-doped TNA) film to modify the surface of medical pure titanium substrate, and evaluate the anti-tumor effect and biocompatibility of Se-doped TNA film. Moreover, we further explore the anti-tumor potential mechanism of Se-doped TNA film by studying the behaviors of human osteosarcoma cells in vitro. We provide a new pathway for achieving the anti-tumor function of orthopedic implants while keeping the biocompatibility, aiming to suppress the recurrence of osteosarcoma.

Preparation and Photoelectrochemical Properties of Mo/N Co-Doped TiO2 Nanotube Array Films

Mo/N co-doped TiO2 nanotube array films were obtained by a combination of magnetron sputtering and anodization. The influences of doping concentration and nanotube morphology on the structure, morphology, elemental composition, light-absorption capacity, and optoelectronic properties of TiO2 nanotubes were studied. The findings revealed that Mo was primarily incorporated into the TiO2 lattice in the Mo6+ valence state, while N was mainly embedded into the lattice as interstitial atoms. It was observed that when the sputtering power was 35 W for TiN target and 150 W for Mo-Ti target, the Mo/N co-doped TiO2 nanotube array films exhibited the best photovoltaic performance with a photogenerated current of 0.50 µA/cm2, which was 5.5 times of that of Mo-doped TiO2. The enhanced photocatalytic efficiency observed in Mo/N co-doped TiO2 nanotube array films can be ascribed to three main factors: an increase in the concentration of photogenerated electrons and holes, a reduction in the band gap width, and intense light absorption within the visible spectrum.

Photoelectrochemical performance of BiOI/TiO 2 nanotube arrays (TNAs) p-n heterojunction synthesized by SILAR-ultrasonication-assisted methods

In order to extend the visible region activity of titania nanotube array (TNAs) films, the successive ionic layer adsorption and reaction (SILAR)-ultrasonication-assisted method has been used to prepare BiOI-modified TiO 2 nanotube arrays (BiOI/TNAs). The band gap of BiOI/TNAs for all the variations reveals absorption in the visible absorption. The surface morphology of BiOI/TNAs is shown in the nanoplate, nanoflake and nanosheet forms with a vertical orientation perpendicular to TiO 2 . The crystalline structure of BiOI did not change the structure of the anatase TNAs, with the band gap energy of the BiOI/TNAs semiconductor in the visible region. The photocurrent density of the BiOI/TNAs extends to the visible-light range. BiOI/TNAs prepared with 1 mM Bi and 1 mM KI on TNAs 40 V 1 h, 50 V 30 min show the optimum photocurrent density. A tandem dye-sensitized solar cell (DSSC)-photoelectrochemical (PEC) was used for hydrogen production in salty water. BiOI/TNAs optimum was used as the photoanode of the PEC cell. The solar to hydrogen conversion efficiency (STH) of tandem DSSC-PEC reaches 1.34% in salty water.

Highly sensitive and selective fluorescence sensor based on zirconia nanotube array films for Cu2+ detection

ZrO2 nanotube array films (ZNA) were prepared by anodisation method, and ZNA was modified with γ-aminopropyltriethoxysilane (APTES) to prepare amino-functionalized ZNA (ZNA-NH2). Through immobilizing Cu2+ ions and RB on ZNA and ZNA-NH2, the detection of Cu2+ ions could be realized by measuring the change of fluorescence intensity of RB, and the effects of APTES and RB concentrations on the detection performances were studied. The results show that the fluorescence detection performances of ZNA-NH2 carrier are significantly better than those of ZNA. The best detection performances for Cu2+ ions are achieved with the RB concentration of 10 mg/L and the APTES concentration of 0.4 M. The minimum detection limit is 0.68 nM (S/N = 3), and the linear range is from 1 × 10−3 to 3 × 102 μM under the optimal experimental conditions. The carriers can be regenerated and reused after being soaked in acetic acid solution. This work can be applied to the detection of Cu2+ ions in real seawater.

Synergistic effects of charge transport and trapping in tribomaterials for boosted triboelectric nanogenerators

Improving output performance is a key to develop triboelectric nanogenerator (TENG) applications. Herein, an improved melamine foam (MF) /MXene/Ecoflex@TiO2-TENG (FME@TiO2-TENG) based on the composite dielectric MF/MXene/Ecoflex@TiO2 (FME@TiO2) is developed after comprehensively considering charge generation, transport, trapping, and dissipation. A 3D MF framework with evenly dispersed MXene exhibits strong electronegativity, electrical conductivity, and a formation of a large number of micro-capacitances, which are advantageous for surface charge generation, transfer, and retention in the composite dielectric FME@TiO2. More importantly, dual functions of a TiO2 nanotube array film, i.e., its high dielectric property and electron-trapping ability, are beneficial for output of electrical properties. A cathodic protection system powered by the FME@TiO2-TENG was designed to demonstrate its application potential in electrochemistry. Furthermore, a novel in-situ micro-electrolytic cell observation system using K3[Fe (CN)6] as an indicator was designed to evaluate the cathodic protection effect. The results showed that the FME@TiO2-TENG could be used as an independent power source to provide electrochemical cathodic protection. This study provides a useful guidance for a development of the high-performance TENG composite dielectrics and promotes their practical application in the field of the electrochemical cathodic protection.

Stabilized Brookite Nanotube Array Films Grown on Transparent Substrates for Photoelectrochemical Water Splitting

Photoelectrochemical water splitting is a promising route to realizing a clean energy economy. Herein, we report on the ability to selectively fabricate optimized Ni-doped brookite nanotube array films on fluorine-doped tin oxide (FTO) substrate using ultrarapid radio frequency sputtering followed by electrochemical anodization and thermal annealing under ambient air. Ni doping promotes photocatalytic performance by introducing impurity bands within the TiO2 bandgap. Further, annealing at various temperatures helps to tune the photoactivity of the fabricated photoelectrodes, which is in agreement with the nature of the trap states. The nanotubes enjoy high crystallinity and enhanced photoresponse with a noticeable bandgap of 2.7 eV. The Mott–Schottky analysis reveals the variation in the charge carriers density of the fabricated nanotubes. Most importantly, the electrochemical impedance spectroscopy (EIS) analysis unravels the involved kinetics and helps to determine the charge transfer properties of the annealed nanotubular films under open-circuit voltage (OCV) and with applied potential under dark and illumination conditions. EIS analysis reveals decreased charge transfer resistance under illumination, in agreement with the obtained photocurrent, electron lifetime, and density of trap states.

Enhanced Supercapacitive Properties of Mixed Oxide Nanotubes Grown by Anodization of Ti–Fe Alloys

Like titanium metal, nanotube array films can be grown on Ti alloys by anodization in fluoride‐containing electrolytes. Further, the anodization of Ti alloys provide a unique pathway to dope TiO2 nanotubes with the alloying element. However, the details of anodization behaviors of Ti alloys and the obtained nanotubes for application in supercapacitors remain poorly understood. Herein, three Ti–Fe alloys containing different amounts of Fe element (10, 15, and 20 wt%) are fabricated by using a vacuum arc melting furnace. Their anodization behaviors are systematically investigated. The nanotube array films can be achieved on these alloys, which are composed of TiO2, Fe2O3, and Fe‐doped TiO2. Their electrochemical behaviors are completely different from both the pure TiO2 and the pure Fe2O3. The mixed oxide nanotubes on Ti–15 wt%Fe have the maximum capacitance among the three Ti–Fe alloys, which is 3.75 times higher than that of pure TiO2. Moreover, the mixed oxide electrode exhibits high rate capability and excellent cycling stability with only 5.7% loss in capacitance over 10 000 cycles. The presented results suggest that the alloy anodization is an efficient strategy for enhancing the performance of TiO2 electrode materials for supercapacitors.

INFLUENCE OF ANATASE TITANIUM DIOXIDE NANOTUBE ARRAYS ON HUMIDITY SENSOR SYNTHESIZED BY ELECTROCHEMICAL ANODIZATION

Humidity sensors have become increasingly important and widely used to improve the quality of life and industrial processes. Over the past decades, titanium dioxide (TiO2) has received wide attention in many promising areas such as sensors, solar cells, and photocatalytic. However, TiO2 required high operating conditions such as high temperatures to examine the crystalline stability phase. This study focuses on highly ordered titanium dioxide nanotube arrays (TiO2 NTAs) film synthesized using the electrochemical anodization method. Annealing temperature effect on the fabricated TiO2 NTAs was investigated. An electrolyte solution was prepared by mixing ammonium fluoride (0.3 wt%) and ethylene glycol (25 ml) with deionized water (2 vol%). Titanium (Ti) sheet was anodized at 35 V for 120 minutes. The films were annealed from 350 °C to 550 °C. FESEM images showed the diameter size of TiO2 NTAs film decreases as the annealing temperatures increases. Results had also shown that the average diameter annealed at 450 °C was around ~50.82 nm while the XRD pattern demonstrated TiO2 NTAs exhibiting an anatase phase with a prominent (101) peak recorded for the sample prepared at 450 °C with a high crystallite size of 29.17 nm. The calculated optical band gap annealed at 450 °C (3.24 eV) is comparable with other literature. The current-voltage characteristic of TiO2 NTAs film reported a high current for 450 °C (1.12 x 10-5 A) with a conductivity of 0.048 S.cm-1 and high sensitivity (287.72).

Highly crystalline anatase TiO2 nanotubes array films enhanced with Bi2S3 for photoelectrochemical applications

Highly crystalline anatase TiO2 nanotubes array films enhanced with Bi2S3 for photoelectrochemical applications

Charge reaction kinetics on TiO2 nanotubes under photoelectrochemical water oxidation condition

Artificial photosynthesis relies on the photoreactions between the chemical molecules and photogenerated charges. The oxygen evolution reactions are regarded as the most difficult procedure, because they are multiple-step reactions with multiple charges transfer. Notwithstanding the extensive study on photoelectrochemical and photochemical water oxidation, understanding how the surface charge reacts with the chemical molecules is limited, especially the reaction kinetics of the surface charges. We prepared anatase TiO2 nanotubes array and dense polycrystalline TiO2 films on Ti substrates, where the photocurrent increased about 4–4.5 times on nanotubes compared with the dense films. Moreover, the surface charge reaction rate and the accumulated charge densities were analyzed by transient surface photovoltage and transient photocurrent techniques. It was found a 2nd-order charge reaction behavior could be found when the charge density was high, differently, a 1st-order charge reaction could be observed when the charge density was low. The nanotubes structures would in situ grow from the Ti substrates, which simultaneously enhanced charge separation and transfer kinetics to improve the PEC performance.

A strategy to improve the performance of TiO2 nanotube array film photocatalysts by magnetron-sputtered amorphous BiFeO3

Amorphous BiFeO3/TiO2 nanotube array thin films were prepared on indium tin oxide glass using an anodic oxidation technique coupled with magnetron sputtering. The morphology, structure, optical properties, photoelectrochemical properties, and photocatalytic activity of heterostructured nanotube array thin films with different morphologies of BiFeO3 were studied. HRTEM observations show the interface between amorphous BiFeO3 and anatase TiO2. The amorphous BiFeO3/TiO2 nanotube array thin films show enhanced visible-light absorption and outstanding separation and transfer of photoinduced charges. The BFO3-TNA sample shows excellent photocatalytic activity. By using it, 97.6% of chromium (VI) can be removed in 60 min under visible-light illumination. This work will provide a feasible route to further enhance the photocatalytic activities of visible-light responsive TiO2 nanotube array thin films as photocatalysts for rapidly removing chromium (VI) from water.

High-quality CdS quantum dots sensitized ZnO nanotube array films for superior photoelectrochemical performance

The surface characteristics of ZnO were synthetically optimized by a self-designed simultaneous etching and W-doping hydrothermal method utilizing as-prepared ZnO nanorod (NR) array films as the template. Benefiting from the etching and regrowth process and the different structural stabilities of the various faces of ZnO NRs, the uniquely etched and W-doped ZnO (EWZ) nanotube (NT) array films with larger surface area, more active sites and better energy band structure were used to improve the photoelectrochemical (PEC) performance and the loading quality of CdS quantum dots (QDs). On the basis of their better surface characteristics, the CdS QDs were uniformly loaded on EWZ NT array film with a good coverage ratio and interface connection; this effectively improved the light-harvesting ability, charge transportation and separation as well as charge injection efficiency during the PEC reaction. Therefore, all the CdS QD-sensitized EWZ NT array films exhibited significantly enhanced PEC performance. The CdS/EWZ-7 composite films exhibited the optimal photocurrent density with a value of 12 mA⋅cm−2, 2.5 times higher than that of conventional CdS/ZnO-7 composite films under the same sensitization times with CdS QDs. The corresponding etching and optimizing mechanisms were also discussed.

Preparation and Properties of Nano ZnO Dye Sensitized Solar Cells on (Titanium) Substrates

Nowadays, the development of science and technology has been increasing demand for energy. Energy problem has become a bottleneck to restrict the development of international social economy. People pay more and more attention to the development and research of renewable resources. Solar energy is a kind of renewable resource with great potential and no pollution. The commercialized solar cells are mainly silicon solar cells, among which the conversion efficiency of single silicon solar cells is the highest, but the cost of silicon solar cells is high. Therefore, people have been exploring new materials, among which titanium based nano ZnO dye sensitized solar cells have been paid more and more attention by scientists at home and abroad. Based on this, the preparation and performance of nano ZnO dye sensitized solar cells based on titanium are studied. In this paper, the optical anode materials of DSSC are used as the research objects. Three-dimensional ZnO nanoband, one-dimensional graded ZnO nanotube array and one-dimensional sub grade ZnO nanowire array are prepared by anodizing and hydrothermal synthesis. The photovoltaic properties of the three materials are studied. One dimensional graded ZnO, nanotube array films were prepared by two-step hydrothermal synthesis. One dimensional hierarchical ZnO nanowire array is obtained by two-step hydrothermal synthesis. The results show that DSSC is assembled by one-dimensional graded ZnO nanotube array film, and the photoelectric conversion efficiency is 5.1%. Compared with one-dimensional ZnO nanowire array, the efficiency is improved by nearly 90%. The ZnO nanowire of the sub grade is used instead of DSSC The efficiency of photoelectric conversion is only 4% in the photoanode, which is higher than that of the smooth ZnO nanowire photocell.

Fabrication of Ag electrodeposited-iron doped TiO2 nanotube composites for photoelectrochemical cathodic protection applications

• Ag/FeTNTs were prepared to investigate photocathodic protection of 403SS. • Ag/FeTNTs exhibited better photocathodic protection performance than FeTNTs. • Ag/FeTNTs has charge storage ability to maintain photocathodic protection in dark. Iron doped TiO 2 nanotube array (FeTNTs) films were first synthesized through facile one step titanium anodization in an appropriate solution, followed by electrodeposition of Ag on the prepared film to obtain Ag/FeTNTs composite films with improved photocathodic protection performance. The effects of variations of electrodeposition time on the morphology, optical and photoelectrochemical properties of the samples prepared have been investigated. Photocurrent density, open circuit potential and Tafel polarization curves were used to confirm the photocathodic protection performance of 403 stainless steel (403SS). Ag/FeTNTs composites were capable of providing effective protection of 403SS under light irradiation and even in the dark in comparison with the uncoated FeTNTs. The corrosion potential of 403SS was shifted to −700 under light irradiation by the optimal composite film (sample t6 obtained by 6 min of silver electrodeposition), which indicates efficient photoelectrochemical cathodic protection.

Preparation of FeS2/TiO2 nanocomposite films and study on the performance of photoelectrochemistry cathodic protection

FeS2/TiO2 nanotube array composite films with clean, high efficiency, low cost and low consumption were prepared by electrochemical anodization and hydrothermal methods. The modification of FeS2 nanoparticles on the surface of TiO2 nanotube array film not only broadens the light absorption range of TiO2, but also improves the utilization ratio of visible light and the separation rate of photogenerated electron–hole pairs, which greatly improves the photoelectrochemical cathodic protection performance of TiO2 for 304 stainless steel (304SS). Under visible light irradiation, the open circuit potential of 304SS coupled with the FeS2/TiO2 nanocomposite films decreased from − 170 to − 700 mV, and the electrode potential can still maintained at − 400 mV after the light was turned off. Compared with pure TiO2 nanotube array film, FeS2/TiO2 nanocomposite film has better photoelectrochemical cathodic protection effect on 304SS in 3.5 wt% NaCl corrosion medium.

Biodegradable Polymer/TiO2 Nanotubes Loaded Roxithromycin as Nanoarray Capsules for Long-Lasting Antibacterial Properties of Titanium Implant

Bacterial infection is one of the main reasons for the clinical failure of oral titanium restorations. In this study, biodegradable polymer/TiO2 nanotube nanoarray capsules were constructed on a titanium substrate surface to locally deliver drugs for long-lasting antibacterial properties. Anodization was applied to prepreparation TiO2 nanotube array film on titanium substrate, and then, the upward opening TiO2 nanotubes were sealed with biodegradable polymer (chitosan and polyethylene glycol) through electrochemical deposition. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the characterization of this system. The drug release characteristics and the antibacterial activity demonstrated that the polymer coating significantly reduced burst release and enhanced lasting antibacterial properties. The nanoarray capsules still preserved integrity with a little degradation after 2 days. The strategy described herein provides a versatile route for designing targeted drug delivery systems in orthopaedical and other biomedical fields.