Search Results (25)

We developed dye-sensitized solar cells based on anatase–titanium dioxide (A-TiO₂) nanotubes (TiNTs) and nanocubes (TiNcs) with {001} crystal facets generated using simple and facile electrochemical anodization. We also demonstrated a simple way of developing one-dimensional, two-dimensional, and three-dimensional self-assembled TiO₂ nanostructures via electrochemical anodization, using them as an electron-transporting layer in DSSCs. TiNTs maintain tubular arrays for a limited time before becoming nanocrystals with {001} facets. Using FESEM and TEM, we observed that the TiO₂ nanobundles were transformed into nanocubes with {001} facets and lower fluorine concentrations. Optimizing the reaction approach resulted in better-ordered, crystalline anatase TiNTs/Ncs being formed on the Ti metal foil. The anatase phase of as-grown TiO₂ was confirmed by XRD, with (101) being the predominant intensity and preferred orientation. The nanostructured TiO₂ had lattice values of a = 3.77–3.82 and c = 9.42–9.58. The structure and morphology of these as-grown materials were studied to understand the growth process. The photoconversion efficiency and impedance spectra were explored to analyze the performance of the designed DSSCs, employing N719 dye as a sensitizer and the I⁻/I³⁻ redox pair as electrolytes, sandwiched with a Pt counter-electrode. As a result, we found that self-assembled TiNTs/Ncs presented a more effective photoanode in DSSCs than standard TiO₂ (P25). TiNcs (0.5 and 0.25 NH₄F) and P25 achieved the highest power conversion efficiencies of 3.47, 3.41, and 3.25%, respectively. TiNcs photoanodes have lower charge recombination capability and longer electron lifetimes, leading to higher voltage, photocurrent, and photovoltaic performance. These findings show that electrochemical anodization is an effective method for preparing TiNTs/Ncs and developing low-cost, highly efficient DSSCs by fine-tuning photoanode structures and components. Full article

Titanium (Ti) thin films deposited on insulated substrates were progressively anodized and formed titanium dioxide (TiO₂) nanotube arrays on the surface through a customized anodization tool designed to improve the uniformity and diameters of the nanotubes. With a motorized vertical moving arm attached to the anode, the sample was gradually submerged into the electrolyte at a controlled speed alongside the continuous anodization from the edge to the center to prevent the discontinuation of the conductive Ti layer and its nanotube surface. The effects of Ti deposition rate, anodization voltage, NH₄F concentration, and post-etching conditions on nanotube morphology were also explored. Scanning electron microscopy (SEM) analysis revealed that smaller Ti grain sizes, higher anodization voltages, higher electrolyte concentrations, and optimized post-etching times produce uniform, mature nanotubes with larger diameters, which are crucial for practical applications. This work enhances the applicability of nanotube surfaces with non-conductive substrates, such as Zirconia dental implants, and establishes a foundation for future process optimizations. Full article

The degradation of organic matter using TiO₂ nanotube photocatalytic technology is limited by the short lifetime and diffusion radius of the generated hydroxyl radicals, decreasing the removal efficiency. This study developed a chlorine radical-coupled photoelectrocatalytic system, significantly enhancing the performance of TiO₂ nanotube arrays in removing sulfonamide antibiotics (SAs) from cold-water aquaculture systems. The highest degradation rates were observed at 5 mM NaCl and 15 mM NaNO₃. When SA concentrations were 0.1–10 mg/L, degradation efficiency decreased with higher initial concentrations. The best degradation was achieved at an initial pH of 3 for SA. Humic acid and sodium acetate, natural organic matter in the water column, served as low-concentration promoters and high-concentration inhibitors. In our study, three degradation intermediates were identified, and hydrolysis and nitration reactions are proposed as the primary pathways for SA degradation. We confirmed that oxygen radicals play a major role in this system. Furthermore, toxicology experiments revealed the weakening of the toxicity of the degraded products. This study provides an efficient method for treating organic matter in cold-water fish culture water in chloride-containing saline and alkaline waters. Full article

In this study, we investigated the fabrication, properties, and sensing applications of TiO₂ nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO₂ nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO₂ nanotube was found to be suitable for NO₂ gas sensor applications. With an oxidation time of 15 min, its detection of NO₂ gas showed a good result at 250 °C, especially when exposed to a NO₂ gas flow of 100 ppm, where a maximum NO₂ gas response of 96% was obtained. The NO₂ sensors based on the TiO₂ nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity. Full article

Currently, titanium and its alloys have emerged as the predominant metallic biomaterials for orthopedic implants. Nonetheless, the relatively high post-operative infection rate (2–5%) exacerbates patient discomfort and imposes significant economic costs on society. Hence, urgent measures are needed to enhance the antibacterial properties of titanium and titanium alloy implants. The titanium dioxide nanotube array (TNTA) is gaining increasing attention due to its topographical and photocatalytic antibacterial properties. Moreover, the pores within TNTA serve as excellent carriers for chemical ion doping and drug loading. The fabrication of TNTA on the surface of titanium and its alloys can be achieved through various methods. Studies have demonstrated that the electrochemical anodization method offers numerous significant advantages, such as simplicity, cost-effectiveness, and controllability. This review presents the development process of the electrochemical anodization method and its applications in synthesizing TNTA. Additionally, this article systematically discusses topographical, chemical, drug delivery, and combined antibacterial strategies. It is widely acknowledged that implants should possess a range of favorable biological characteristics. Clearly, addressing multiple needs with a single antibacterial strategy is challenging. Hence, this review proposes systematic research into combined antibacterial strategies to further mitigate post-operative infection risks and enhance implant success rates in the future. Full article

Electrochemical nitrate reduction (NO₃⁻RR) has been recognized as a promising strategy for sustainable ammonia (NH₃) production due to its environmental friendliness and economical nature. However, the NO₃⁻RR reaction involves an eight-electron coupled proton transfer process with many by-products and low Faraday efficiency. In this work, a molybdenum oxide (MoO_x)-decorated titanium dioxide nanotube on Ti foil (Mo/TiO₂) was prepared by means of an electrodeposition and calcination process. The structure of MoO_x can be controlled by regulating the concentration of molybdate during the electrodeposition process, which can further influence the electron transfer from Ti to Mo atoms, and enhance the binding energy of intermediate species in NO₃⁻RR. The optimized Mo/TiO₂-M with more Mo(IV) sites exhibited a better activity for NO₃⁻RR. The Mo/TiO₂-M electrode delivered a NH₃ yield of 5.18 mg h⁻¹ cm⁻² at −1.7 V vs. Ag/AgCl, and exhibited a Faraday efficiency of 88.05% at −1.4 V vs. Ag/AgCl. In addition, the cycling test demonstrated that the Mo/TiO₂-M electrode possessed a good stability. This work not only provides an attractive electrode material, but also offers new insights into the rational design of catalysts for NO₃⁻RR. Full article

Electrochemical anodization is already a well-established process, owing to its multiple benefits for creating high-grade titanium dioxide nanotubes with suitable characteristics and tunable shapes. Nevertheless, more research is necessary to fully comprehend the basic phenomena at the anode-electrolyte interface during anodization. In a recent paper, we proposed the use of sawtooth-shaped voltage pulses for Ti anodization, which controls the pivoting point of the balance between the two processes that compete to create nanotubes during a self-organization process: oxide etching and oxidation. Under these conditions, pulsed anodization clearly reveals the history of nanotube growth as recorded in the nanotube morphology. We show that by selecting the suitable electrolyte and electrical discharge settings, a nanoporous structure may be generated as a repeating pattern along the nanotube wall axis. We report the findings in terms of nanotube morphology, crystallinity, surface chemistry, photocatalytic activity, and surface hydrophilicity as they relate to the electrical parameters of electrochemical anodization. Aside from their fundamental relevance, our findings could lead to the development of a novel form of TiO₂ nanotube array layer. Full article

This study explores an ultrarapid electrochemical self-doping procedure applied to anodic titanium dioxide (TiO₂) nanotube arrays in an alkaline solution to boost their performance for electroanalytical and photocatalytic applications. The electrochemical self-doping process (i.e., the creation of surface Ti³⁺ states by applying a negative potential) is recently emerging as a simpler and cleaner way to improve the electronic properties of TiO₂ compared to traditional chemical and high-temperature doping strategies. Here, self-doping was carried out through varying voltages and treatment times to identify the most performing materials without compromising their structural stability. Interestingly, cyclic voltammetry characterization revealed that undoped TiO₂ shows negligible activity, whereas all self-doped materials demonstrate their suitability as electrode materials: an outstandingly short 10 s self-doping treatment leads to the highest electrochemical activity. The electrochemical detection of hydrogen peroxide was assessed as well, demonstrating a good sensitivity and a linear detection range of 3–200 µM. Additionally, the self-doped TiO₂ nanotubes exhibited an enhanced photocatalytic activity compared to the untreated substrate: the degradation potential of methylene blue under UV light exposure increased by 25% in comparison to undoped materials. Overall, this study highlights the potential of ultrafast electrochemical self-doping to unleash and improve TiO₂ nanotubes performances for electroanalytical and photocatalytic applications. Full article

The key component of electrochemical advanced oxidation technology are high-efficiency anodes, and highly efficient and simple-to-prepare materials have generated a lot of interest. In this study, novel self-supported Ti³⁺-doped titanium dioxide nanotube arrays (R-TNTs) anodes were successfully prepared by a two-step anodic oxidation and straightforward electrochemical reduction technique. The electrochemical reduction self-doping treatment produced more Ti³⁺ sites with stronger absorption in the UV-vis region, a band gap reduction from 2.86 to 2.48 ev, and a significant increase in electron transport rate. The electrochemical degradation effect of R-TNTs electrode on chloramphenicol (CAP) simulated wastewater was investigated. At pH = 5, current density of 8 mA cm⁻², electrolyte concentration of 0.1 M sodium sulfate (Na₂SO₄), initial CAP concentration of 10 mg L⁻¹, CAP degradation efficiency exceeded 95% after 40 min. In addition, molecular probe experiments and electron paramagnetic resonance (EPR) tests revealed that the active species were mainly •OH and SO₄⁻, among which •OH played a major role. The CAP degradation intermediates were discovered using high-performance liquid chromatography-mass spectrometry (HPLC-MS), and three possible degradation mechanisms were postulated. In cycling experiments, the R-TNTs anode demonstrated good stability. The R-TNTs prepared in this paper were an anode electrocatalytic material with high catalytic activity and stability, which could provide a new approach for the preparation of electrochemical anode materials for difficult-to-degrade organic compounds. Full article

The aim of this study was to investigate the photoactivity of dioxide titanium (TiO₂) nanotube films depending on different structure factors including pore size, tube length, tube wall thickness and crystallinity. Aqueous p-nitroaniline was used as a probe to assess the photocatalytic activity of titanium dioxide nanotube layers under UV irradiations. Self-organized titanium dioxide nanotube thin films were prepared by electrochemical anodization of titanium (Ti) foils and Ti thin films sputtered onto silicon (Si). The amorphous as-formed titanium nanotube layers were then annealed at different temperatures ranging from 450 to 900 °C in order to form crystalline phases. The structure and the morphology of the films were characterized by surface analysis techniques and scanning electron microscopy, respectively. The photocatalytic activity of the resulting TiO₂ thin films was evaluated by monitoring the UV degradation of p-nitroaniline by UV spectrophotometry and by determining nitrification yields of by ion chromatography. The highest photocatalytic activity was exhibited for titanium nanotubes annealed at 450 °C. The presence of rutile -obtained for an annealing temperature of 900 °C—appeared to reduce the photodegradation yield of p-nitroaniline. Finally, the TiO₂ nanotubes obtained from Ti foils revealed the most efficient photocatalytic properties. Full article

In this work, a new photovoltaic device was prepared. The device uses titanium (Ti) foil/TiO₂ nanotubes as the photoanode and multi-walled carbon nanotubes (MWCNTs) as a photosensitizer. Titanium dioxide nanotube arrays (TiO₂-NTs) were prepared by one-step anodic oxidation. Cut-MWCNTs with a length of less than 100 nm were obtained by the mixed-acid oxidation of MWCNTs. The two materials were combined to form a TiO₂-NTs@cut-MWCNT heterostructure by electrophoresis. TiO₂-NTs@cut-MWCNTs were characterized by field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), which showed that the two materials were effectively combined. We fabricated the heterostructure into a photovoltaic device, showing an enhanced photocurrent response and an efficiency of 0.0138%, and explained this phenomenon by performing UV-vis absorption spectroscopy and electrochemical tests. It is hoped that this work can provide a reference value for the application of carbon nanotubes in photovoltaic devices. Full article

Titanium dioxide (TiO₂) nanotubes are emerging as a provocative target for oral implant research. The aim of this study was to evaluate the effect of UV on the wettability behavior, bacterial colonization, and fibroblast proliferation rate of TiO₂ nanotube surfaces prepared using different anodization voltages and aimed for use as implant abutment materials. Four different experimental materials were prepared: (1) TiO₂ nanotube 10 V; (2) TiO₂ nanotube 15 V; (3) TiO₂ nanotube 20 V; and (4) commercial pure titanium as a control group. TiO₂ nanotube arrays were prepared in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 vol.%). Different anodization voltages were used to modify the morphology of the TiO₂ nanotubes. Equilibrium contact angles were measured using the sessile drop method with a contact angle meter. The investigated surfaces (n = 3) were incubated at 37 °C in a suspension of Streptococcus mutans (S. mutans) for 30 min for bacterial adhesion and 3 days for biofilm formation. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 7 days and the cell proliferation rate was assessed using the AlamarBlue assay^TM (BioSource International, Camarillo, CA, USA). The data were analyzed using one-way ANOVA followed by Tukey’s post-hoc test. Water contact angle measurements on the TiO₂ after UV treatment showed an overall hydrophilic behavior regardless of the anodization voltage. The ranking of the UV-treated surfaces of experimental groups from lowest to highest for bacterial adhesion was: TiO₂ nanotube 20 V < Ti and TiO₂ nanotube 15 V < TiO₂ nanotube 10 V (p < 0.05), and for bacterial biofilm formation was: TiO₂ nanotube 20 V-TiO₂ nanotube 10 V < Ti-TiO₂ nanotube 15 V (p < 0.05). Fibroblast cell proliferation was lower on TiO₂ nanotube surfaces throughout the incubation period and UV light treatment showed no enhancement in cellular response. UV treatment enhances the wettability behavior of TiO₂ nanotube surfaces and could result in lower bacterial adhesion and biofilm formation. Full article

A novel titanium dioxide nanotube (TiO₂NTS) coated fiber for solid-phase microextraction (SPME) was prepared by in situ anodization of titanium wire in electrolyte containing ethylene glycol and ammonium fluoride (NH₄F). The effects of different electrolyte solutions (NH₄F and ethylene glycol) and oxidation voltages on the formation and size of TiO₂NTs was studied. It was obtained from the experiment that TiO₂NTs arrays were arranged with a wall thickness of 25 nm and the diameter of 100 nm pores in ethylene glycol and water (v/v, 1:1) containing NH₄F of 0.5% (w/v) with a voltage of 20 V at 25 °C for 30 min. The TiO₂NTs were used as solid-phase microextraction fiber coatings coupled with high-performance liquid chromatography (HPLC) in sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in spiked real samples water. Under the optimized SPME conditions, the calibration curve has good linearity in the range of 0.20–500 μg·L⁻¹, and the correlation coefficient (R²) is between 0.9980 and 0.9991. Relative standard deviations (RSDs) of 3.5–4.7% (n = 5) for single fiber repeatability and of 5.2% to 7.9% for fiber-to-fiber reproducibility (n = 3) was obtained. The limits of detection (LOD) (S/N = 3) and limits of quantification (LOQ) (S/N = 10) of PAHs were 0.03–0.05 µg·L⁻¹ and 0.12–0.18 µg·L⁻¹. The developed method was applied to the preconcentration and determination of trace PAHs in spiked real samples of water with good recoveries from 78.6% to 119% and RSDs from 4.3 to 8.9%, respectively. Full article

Bioanalytical methods, in particular electrochemical biosensors, are increasingly used in different industrial sectors due to their simplicity, low cost, and fast response. However, to be able to reliably use this type of device, it is necessary to undertake in-depth evaluation of their fundamental analytical parameters. In this work, analytical parameters of an amperometric biosensor based on covalent immobilization of glucose oxidase (GOx) were evaluated. GOx was immobilized using plasma-grafted pentafluorophenyl methacrylate (pgPFM) as an anchor onto a tailored HEMA-co-EGDA hydrogel that coats a titanium dioxide nanotubes array (TiO₂NTAs). Finally, chitosan was used to protect the enzyme molecules. The biosensor offered outstanding analytical parameters: repeatability (RSD = 1.7%), reproducibility (RSD = 1.3%), accuracy (deviation = 4.8%), and robustness (RSD = 2.4%). In addition, the Ti/TiO₂NTAs/ppHEMA-co-EGDA/pgPFM/GOx/Chitosan biosensor showed good long-term stability; after 20 days, it retained 89% of its initial sensitivity. Finally, glucose concentrations of different food samples were measured and compared using an official standard method (HPLC). Deviation was lower than 10% in all measured samples. Therefore, the developed biosensor can be considered to be a reliable analytical tool for quantification measurements. Full article

Triclosan (TCS) is being detected in breast milk and in infants of puerperal women. The harmful effects caused by this compound on living beings are now critical and thus it is pivotal find new tools to TCS monitoring. In the present study, an electronic tongue (e-tongue) device comprising an array of sputtered thin films based on Multi-Walled Carbon Nanotubes and titanium dioxide was developed to identify TCS concentrations, from 10⁻¹⁵ to 10⁻⁵ M, in both water and milk-based solutions. Impedance spectroscopy was used for device signal transducing and data was analyzed by principal component analysis (PCA). The e-tongue revealed to be able to distinguish water from milk-based matrices through the two Principal Components (PC1 and PC2), which represented 67.3% of the total variance. The PC1 values of infant formula milk powder prepared with tap water (MT) or mineral water (MMW) follows a similar exponential decay curve when plotted with the logarithm of concentration. Therefore, considering the TCS concentration range between 10⁻¹⁵ and 10⁻⁹ M, the PC1 values are fitted by a straight line and values of −1.9 ± 0.2 and of 7.6 × 10⁻¹⁶ M were calculated for the sensor sensitivity and sensor resolution, respectively. Additionally, a strong correlation (R = 0.96) between MT and MMW PC1 data was found. These results have shown that the proposed device corresponds to a promisor method for the detection of TCS in milk-based solutions. Full article