TiO2 Nanotube Arrays Research Articles

Synergistic antibacterial activity and inhibition of TiO2 nanotube arrays and loaded antibiotics against gram-positive and gram-negative bacteria

Introduction: Implantable medical devices continue to be vulnerable to bacterial infections. The unrelenting formation of antibiotic resistant bacterial strains not only exacerbates these infections but also renders the current treatment strategies impotent. The need is greater than ever for innovative and effective approaches to counteract drug-resistant bacteria. This study examines the innate antibacterial properties of TiO2 nanotube arrays (TNAs) and their ability to locally deliver antibiotics to inactivate gram-positive and gram-negative bacteria, in vitro.Methods: Using a two-step electrochemical anodization process, TNAs with a diameter of ∼100 nm and a length of ∼5 µm were grown on titanium substrates.Results and Discussion: After 24 h of incubation, as-fabricated TNAs showed 100% clearance of Escherichia coli, and 97% clearance of Staphylococcus aureus growth. The antibiotic-loaded TNAs demonstrated sustained slow-release of cefotaxime and imipenem measured over 14 days. In vitro bacterial studies revealed the capability of cefotaxime- and imipenem-loaded TNAs in completely inhibiting the growth with 100% clearance of Klebsiella pneumoniae after 24 and 48 h of incubation. Bacterial inhibition assay revealed a significantly enlarged inhibition zone difference of 18 mm around the imipenem-loaded TNAs against K. pneumoniae compared to the as-fabricated TNAs which was maintained for 7 days with ∼10 μgmL−1 of antibiotic released from the TNAs which was found to be lower than the dose required to completely eradicate multidrug resistant bacteria when used in conjunction with the antibacterial TNAs. The results of our study highlight the potential of TNAs as a versatile platform for addressing treatment strategies related to bacterial infections and antibiotic resistance in implantable medical devices.

Evaluation of bioactivity and antibacterial properties of Ti6Al4V-based green biocomposite implant encompassing TiO2 nanotube arrays and garlic extract

This study involved the incorporation of an antibacterial garlic extract into titanium oxide nanotubes (TNTs) formed via the anodization of Ti6Al4V implants. The garlic extract, obtained through low-temperature extraction aided by ultrasound waves, was loaded into the nanotubes. The presence of the nanotubes was confirmed through X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) were used to investigate the presence of bioactive compounds, particularly sulfur compounds responsible for garlic's antibacterial effects. The impact of loading two concentrations (0.1 and 0.2 g per milliliter) of garlic extract on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria was examined. Results indicated a decrease in the growth range of S. aureus from 109 to 106 (CFU/ml) and E. coli from 1011 to 109 (CFU/ml) upon treatment. Additionally, cell adhesion and viability tests conducted on MG63 cells revealed an 8% increase in cell viability with the 0.1 g per milliliter concentration and a 35% decrease with the 0.2 g per milliliter concentration of garlic extract after 72 h of incubation (They have been evaluated by Microculture tetrazolium (MTT) assay). GC-MS analysis identified the presence of diethyl phthalate compounds in the garlic extract, suggesting a potential correlation with cellular toxicity observed in the sample with the higher concentration (0.2 g per milliliter) of garlic extract. Overall, the TNTs loaded with 0.1 g per milliliter of garlic extract simultaneously demonstrated antibacterial activity, cell viability, adhesion, and growth enhancement.

Constructing Sequential Type II Heterojunction CQDs/Bi2S3/TiNbO Photoanode with Superior Charge Transfer Capability Toward Stable Photoelectrochemical Water Splitting.

Efficient charge transfer and light-trapping units are pivotal prerequisites in the realm of Ti-based photoanode photoelectrochemical (PEC) water splitting. In this work, we successfully synthesized a ternary carbon quantum dots/Bi2S3 quantum dots/Nb-doped TiO2 nanotube arrays (CQDs/Bi2S3/TiNbO) composite photoanode for PEC water splitting. CQDs/Bi2S3/TiNbO composite photoanode exhibited a considerably elevated photocurrent density of 8.80 mA cm-2 at 1.23 V vs the reversible hydrogen electrode, which was 20.00 times better than that of TiO2 (0.44 mA cm-2). Furthermore, the CQDs/Bi2S3/TiNbO composite photoanode attested to exceptional stability, maintaining 92.54% of its initial current after 5 h of stability measurement. Nb-doping boosted the electrical conductivity, facilitating charge transfer at the solid-liquid interface. Moderate amounts of Bi2S3 quantum dots (QDs) and CQDs deposited on TiNbO provided abundant active sites for the electrolyte-photoanode interaction. Simultaneously, Bi2S3 QDs and CQDs synergistically functioned as light-trapping units to broaden the light absorption range from 396 to 530 nm, stimulating increased carrier generation within the composite photoanode. In comparison with pristine TiO, CQDs/Bi2S3/TiNbO photoanodes possessed a superior ability to promote interfacial reactions. This study may provide a strategy for developing high-performance Ti-based photoanodes with efficient charge transfer and light trapping units for highly driving solar-to-hydrogen conversion.

Optimization of Photoelectrochemical Response on TiO2 Nanotube Arrays Treated by H3PO4 and Mechanism Analysis of the Slowing Down Effect during Preparation.

The process control of anodization has been a hot topic for a long time. In this study, the addition of phosphoric acid to the traditional electrolyte changed the ion distribution on the reaction interface and the composition of the anion contamination layer so as to achieve the slowing down effect on anodization, the mechanism and theoretical model of which are also given in this paper. TiO2 is a common material in photoelectrocatalysis, but there are few studies on the photoelectrochemical performance of TiO2 nanotube arrays. The stability and rapidity of the photoelectrochemical response of TiO2 nanotube arrays prepared in phosphoric acid containing an electrolyte were effectively optimized in this study.

Synergy of Nd:YAG Picosecond Pulsed Laser Irradiation and Electrochemical Anodization in the Formation of TiO2 Nanostructures for the Photocatalytic Degradation of Pesticide Carbofuran

This study proposes a simple and controlled method for producing TiO2 with phase junction, oxygen vacancies, and Ti3+ by combining picosecond pulsed laser irradiation and electrochemical anodization. Ti mesh was pretreated by irradiating with a picosecond pulsed laser technique using an Nd:YAG laser (1064 nm) at two fluencies, 15 J/cm2 and 30 J/cm2. The samples were then subjected to electrochemical anodization to form TiO2 nanotube arrays on the previously laser-treated surface. This study will investigate the possibility of forming TiO2 nanotube arrays on a pre-laser-treated Ti substrate and determine their physicochemical and photocatalytic properties. The samples were characterized by FESEM, XRD, Raman, XPS, and UV-Vis DRS. UV-Vis spectroscopy was used to observe the progress of photocatalytic degradation for all samples, and degradation products were determined using GC-MS. With the synergistic effects of phase junction, oxygen vacancies, and Ti3+, the laser-treated TiO2 with 30 J/cm2 showed a higher photocatalytic degradation rate (85.1%) of the pesticide carbofuran compared to non-laser-treated TiO2 (54.8%), remaining stable during successive degradation cycles, which has promising practical applications.

Synthesis of P-(NiCo)CO3/TiO2/Ti Self-Supported Electrode with High Catalytic Activity and Stability for Hydrogen Evolution.

Hydrogen is considered an ideal clean energy due to its high mass-energy density, and only water is generated after combustion. Water electrolysis is a sustainable method of obtaining a usable amount of pure hydrogen among the various hydrogen production methods. However, its development is still limited by applying expensive noble metal catalysts. Here, the dissolution-recrystallization process of TiO2 nanotube arrays in water with the hydrothermal reaction of a typical nickel-cobalt hydroxide synthesis process followed by phosphating to prepare a self-supported electrode with (NiCo)CO3/TiO2 heterostructure named P-(NiCo)CO3/TiO2/Ti electrode is combined. The electrode exhibits an ultra-low overpotential of 31mV at 10mA cm-2 with a Tafel slope of 46.2mVdec-1 in 1m KOH and maintained its stability after running for 500h in 1m KOH. The excellent catalytic activity can be attributed to the structure of nanotube arrays with high specific surface area, superhydrophilicity, and super aerophobicity on the electrode surface. In addition, the uniform (NiCo)CO3/TiO2 heterostructure also accelerates the electron transfer on the electrode surface. Finally, DFT calculations demonstrate that phosphating also improves the ΔGH* and ΔGH2O of the electrode. The synthesis strategy also promotes the exploration of catalysts for other necessary electrocatalytic fields.

Hollow α-Bi2O3/TiO2 nanotube arrays hierarchical heterojunction with strong interface interaction for efficient photocatalytic ciprofloxacin degradation

Interfacial regulation for photocatalyst is considered as an effective strategy to enhance visible-light utilization and charges transfer. But it is still a great challenge for the conscious design of interfacial engineering. Herein, hollow α-Bi2O3/TiO2 nanotube arrays (α-Bi2O3/TNAs) hierarchical heterojunction was constructed to modulate the interface structure for efficient photocatalytic degradation of ciprofloxacin (CIP). The systematic characterization analysis, density functional theory (DFT) calculations and electron paramagnetic resonance spectra revealed that the Z-scheme charges transfer mechanism was affirmed between α-Bi2O3 and TNAs. The hierarchical tubular heterostructure was contributed to enhancing light absorption, and the strong interfacial interaction could promote the separation and transfer of photogenerated charges. The optimal α-Bi2O3/TNAs exhibited higher photocatalytic activity for CIP (73.9 %) than TNAs (25.3 %) under visible-light irradiation. The anions and natural organic matters could decline CIP removal owing to competing active sites or aggravating radicals consumption. The theoretical calculations further demonstrated that the staggered energy levels produced an internal electric field at heterojunction interface to promote charges transfer. Three degradation pathways of CIP were proposed based on DFT calculations and LC-MS. The photocatalytic degradation of CIP by α-Bi2O3/TNAs could effectively reduce its toxicity, and eventually alleviate the environmental hazards of antibiotics.

Binary junctions enhance electron storage and potential difference for photo-assisted electrocatalytic CO2 reduction to HCOOH

Photo-assisted electrocatalytic (PAEC) CO2 conversion is a crucial approach for achieving sustainable carbon neutrality. Here, we have developed a binary-junctions photoanode by integrating SrTiO3 and anatase-rutile TiO2 nanotube arrays (STO/A-R TNTAs), which exhibits exceptional activity and selectivity in converting CO2 to HCOOH. The synergetic effects of the SrTiO3/TiO2 heterogeneous junction and the anatase-rutile TiO2 heterophase junction effectively facilitate photoelectron separation and storage, leading to a potential difference between anode and cathode. The establishment of the electron storage strategy, triggered by hetero- junction/phase interfaces, serves as remarkably efficient electron trapping regions with dam-like characteristics. As a result, the STO/A-R TNTAs achieves a generation rate of 68.24 μmol cm−2 h−1 with 92.25% selectivity and 90.70% Faradic efficiency. This performance is approximately 8 times higher compared to the pristine TiO2 nanotube arrays photoanode. The implementation of the electron storage mechanism presents a promising approach to improve CO2 reduction activity and selectivity.

Photoelectrocatalytic activation of sulfate for sulfamethoxazole degradation and simultaneous H2 production by bifunctional N,P co-doped black-blue TiO2 nanotube array electrode

In recent years, sulfate radical (SO4•−)-based advanced oxidation processes and hybrid water electrolysis for hydrogen production have attracted widespread attention. However, the conventional electrochemical persulfate activation requires mass/expensive persulfate reagent, limiting its practical application due to high operation cost. In this work, using bifunctional N, P co-doped black-blue TiO2 nanotube arrays (N,P-BTNAs) as a wide-spectrum absorptive photoanode, we report the synergistic PEC sulfate activation for effective degrading sulfamethoxazole (SMX) antibiotic and simultaneous generating H2 at N,P-BTNAs cathode. With sulfate as h+ scavenger and SO4•− precursor, HO•, SO4•−, 1O2 and h+ are generated during PEC activation process. Detailed physicochemical characterization and density functional theory (DFT) calculations revealed that the Ti3+, P5+, N triple-doping induced a narrowed band gap (2.78 eV), a rapid separation/transfer of photo-induced carriers, an accelerated h+ extraction/utilization, and an optimized H binding/releasing ability, resulting in an outstanding PEC sulfate activation for SMX degradation (0.05368 min−1) and H2 evolution efficiency (132.3 μmol/cm2/h) under optimal conditions. This study provides a novel strategy for efficient contaminants removal and stable H2 production simultaneously, via the synergistic PEC activation of the coexisted sulfate using the bifunctional N,P-BTNAs electrode.

Antibacterial activities of titanium dioxide (TiO2) nanotube with planar titanium silver (TiAg) to prevent orthopedic implant infection

BackgroundOrthopedic implant infection has become a common catastrophic complication after various orthopedic implants, which can lead to prolonged use of antibiotics and even surgical failure. The quality of care (QoC) of orthopedic implant infection is very important.MethodsTitanium dioxide (TiO2) nanotube array with planar TiAg was prepared, and their antibacterial rates were tested. 400 patients hospitalized in the Department of Orthopedics of Wuhan Fourth Hospital from May 2019 to May 2020 were selected as controls (before QoC evaluation system of orthopedics), and 400 patients hospitalized from June 2020 to June 2021 were selected as observation group (after QoC evaluation system of orthopedics).ResultsRegardless of Staphylococcus aureus or Escherichia coli, the antibacterial rate of TiO2 nanotube array with planar TiAg was clearly higher than that of pure iron film on the 10th and 20th days (P < 0.05). The accuracy of hospitalization assessment, disease assessment, adverse event intervention, nursing record filing and nursing satisfaction in observation group were higher as against controls (P < 0.05).ConclusionThe TiO2 nanotube array with planar TiAg has good antibacterial property, which can effectively prevent orthopedic implant infection. The construction of QoC evaluation system for orthopedic specialists can effectively improve the QoC of orthopedic specialists.

Customizing Wettability of Defect-Rich CeO2/TiO2 Nanotube Arrays for Humidity-Resistant, Ultrafast, and Sensitive Ammonia Response.

In all their applications, gas sensors should satisfy several requirements, including low cost, reduced energy consumption, fast response/recovery, high sensitivity, and reliability in a broad humidity range. Unfortunately, the fast response/recovery and sensing reliability under high humidity conditions are often still missing, especially those working at room temperature. In this study, a humidity-resistant gas sensor with an ultrafast response/recovery rate was designed by integrating a defect-rich semiconducting sensing interface and a self-assembled monolayer (SAM) with controllable wettability. As a proof-of-concept application, ammonia (NH3), one of the atmospheric and indoor pollutants, was selected as the target gas. The decoration of interconnected defective CeO2 nanowires on spaced TiO2 nanotube arrays (NTAs) provided superior NH3 sensing performances. Moreover, we showed that manipulating the functional end group of SAMs is an efficient and simple method to adjust the wettability, by which 86% sensitivity retention with an ultrafast response (within 5 s) and a low limit of detection (45 ppb) were achieved even at 75% relative humidity and room temperature. This work provides a new route toward the comprehensive design and application of metal oxide semiconductors for trace gas monitoring under harsh conditions, such as those of agricultural, environmental, and industrial fields.

Enhanced photoelectrocatalytic performance of ZnIn2S4 modified TiO2 nanotube array toward methylene blue

Enhanced photoelectrocatalytic performance of ZnIn2S4 modified TiO2 nanotube array toward methylene blue

Enhanced Photoelectrochemical Property of TiO2 Nanotube Array Photoanode Deposited with Al,Cr-Codoped SrTiO3 Nanocubes.

There is a demand for the effective utilization of solar energy with highly functional photoelectrodes for photoelectrochemical (PEC) applications, such as water splitting and CO2 reduction. TiO2 nanotube arrays (TNTA) with a large surface area have been studied as potential photoelectrodes mainly due to their strong oxidation potential. However, it has disadvantages of fast charge recombination and little responsivity to visible light. In this study, we prepared TNTA by anodizing a Ti plate and decorated the TNTA with Al,Cr-codoped SrTiO3 (STO) nanocubes through a hydrothermal treatment to enhance the PEC properties. We also prepared pristine and undoped STO-decorated TNTA for comparison. The hydrothermal treatment duration was optimized for the TNTA-STO:Al,Cr sample to achieve the best PEC performance. Finally, the possible PEC reaction mechanism was proposed based on the obtained experimental results.

MoS2 thin film decorated TiO2 nanotube arrays on flexible Ti foil for solar water splitting application

MoS2/TiO2 nanostructure provides a lot of advantages in photoelectrochemical (PEC) applications due to the absorption of the wide spectrum solar radiation, more catalytically active sites, proper band alignment, and better separation of photogenerated charge carriers. Here we report PEC water splitting studies of MoS2 thin film grown by chemical vapor deposition on TiO2 nanotubes fabricated on flexible thin Ti foil. Raman and x-ray diffraction analysis confirmed the polycrystalline growth of a few layers MoS2 on TiO2/Ti through their characteristic peaks. Field emission scanning electron microscopy revealed the nanotube surface morphology of TiO2 having a diameter in the range of 200–300 nm. The chemical and electronic composition of MoS2 and TiO2 were investigated by x-ray photoelectron spectroscopy. PEC measurements performed in 0.5 M Na2SO4 aqueous electrolyte solution under 100 mW cm−2 (AM 1.5G) simulated sunlight revealed 2-fold improved photocurrent density for MoS2/TiO2 heterostructure (∼135.7 μA cm−2) compared to that of bare TiO2 (∼70 μA cm−2). This is attributed to extended light absorption and more catalytically active surface area resulting from MoS2 functionalization of the TiO2 nanotubes, which results in better PEC activity. This study provides a new insight to explore the performance of thin metal foil-based photoelectrode in PEC applications that can be beneficial to develop roll-to-roll device fabrication to advance futuristic flexible electronics.

Construction of Photothermo-Electro Coupling Field Based on Surface Modification of Hydrogenated TiO2 Nanotube Array Photoanode and Its Improved Photoelectrochemical Water Splitting.

Solar water splitting has gained increasing attention in converting solar energy into green hydrogen energy. However, the construction of a photothermo-electro coupling field by harnessing light-induced heat and its enhancement on solar water splitting were seldom studied. Herein, we developed a full-spectrum responsive photoanode by depositing CdxZn1-xS onto the surface of hydrogenated TiO2 nanotube array (H-TNA), followed by modification with Ni2P. The resulting ternary photoanode exhibits a photocurrent density of 4.99 mA·cm-2 at 1.23 V vs. RHE with photoinduced heating, which is 11.9-fold higher than that of pristine TNA, with an optimal ABPE of 2.47%. The characterization results demonstrate that the ternary photoanode possesses superior full-spectrum absorption and efficient photogenerated carrier separation driven by the interface electric fields. Additionally, Ni2P reduces the hole injection barrier and increases surface active sites, accelerating the consumption of holes accumulating on the relatively unstable CdxZn1-xS to simultaneously improve the activity and stability of water splitting. Moreover, temperature-dependent measurements reveal that H-TNA and Ni2P significantly motivate the photothermal conversion to construct a photothermo-electro coupling field, optimizing photoelectric conversion and charge carrier-induced surface reactions. This work contributes to understanding the synergistic effect of the photothermo-electro coupling field on the photoelectrochemical water splitting.

Crystallization of amorphous anodized TiO2 nanotube arrays.

Anodized TiO2 nanotube arrays (TNTAs) prepared by anodization have garnered widespread attention due to their unique structure and properties. In this study, we prepared TNTAs of varying lengths by controlling the anodization time. Among them, the nanotubes anodized for 2 h have an inner diameter of approximately 92 nm and a wall thickness of approximately 12 nm. Then we subjected amorphous TNTAs prepared by the anodization method to annealing treatments, systematically analyzing the evolution of morphology and structure with varying annealing temperatures. As the annealing temperature increases, the amorphous successively undergoes transitions to the anatase phase and then to the rutile phase. During the transition to the anatase phase, the structure of the nanotube array remains intact, with the complete preservation of the tubular array structure. However, during the transition to the rutile phase, the tubular array structure is destroyed. To address why the tubular array remains undamaged during the amorphous-to-anatase transition, we subjected amorphous TNTAs to annealing at 300 °C for different durations. Raman spectroscopy was employed for fit analysis, providing insights into the evolution of the molecular structure during the anatase phase transition. Finally, TNTAs annealed at different temperatures were incorporated into lithium-ion batteries. By combining XRD for semi-quantitative phase content and anatase particle size calculations, we established a correlation between structure and electrochemical performance. The results indicate a significant improvement in electrochemical performance for an amorphous-anatase structure obtained through annealing at 300 °C, providing insights for the design of high-performance energy storage materials.

Titania (TiO2) nanotube surfaces doped with zinc and strontium for improved cell compatibility.

Titanium-based orthopedic implants are gaining popularity in recent years due to their excellent biocompatibility, superior corrosion resistance and lightweight properties. However, these implants often fail to perform effectively due to poor osseointegration. Nanosurface modification approaches may help to resolve this problem. In this work, TiO2 nanotube (NT) arrays were fabricated on commercially available pure titanium (Ti) surfaces by anodization and annealing. Then, zinc (Zn) and strontium (Sr), important for cell signaling, were doped on the NT surface by hydrothermal treatment. This very simple method of Zn and Sr doping takes less time and energy compared to other complicated techniques. Different surface characterization tools such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), static water contact angle, X-ray diffraction (XRD) and nanoindentation techniques were used to evaluate the modified surfaces. Then, adipose derived stem cells (ADSCs) were cultured with the surfaces to evaluate cell adhesion, proliferation, and growth on the surfaces. After that, the cells were differentiated towards osteogenic lineage to evaluate alkaline phosphatase (ALP) activity, osteocalcin expression, and calcium phosphate mineralization. Results indicate that NT surfaces doped with Zn and Sr had significantly enhanced ADSC adhesion, proliferation, growth, and osteogenic differentiation compared to an unmodified surface, thus confirming the enhanced performance of these surfaces.

A MoS2 quantum dot functionalized TiO2 nanotube array for selective detection of xylene at low temperature

Electrochemically synthesized TiO2 nanotube array was functionalized with MoS2 quantum dots and transformed into metal–insulator–metal type sensor which exhibited xylene selectivity with high response magnitude at low operating temperature.

The role of solution temperature in characteristics of TiO2 nanotube arrays prepared on Ti foil in acid solution.

The characteristics of TiO2 nanotube arrays (TNTs) prepared on Ti foil in sulfuric acid solution that contains Cl- under different temperatures are investigated by field emission scanning electron microscopy (FESEM), electrochemical impedance spectroscopy (EIS), Mott-Schottky measurement and Raman spectra. The solution temperature significantly affects the morphologies of TNTs, i.e., when solution temperature rises from -10 °C to 90 °C, the inner diameter of the nanotube increases and the barrier layer thickness decreases, and, as TNTs display n-type semiconductive properties, the donor density (ND) and corrosion protection decrease. Two types (types I and II) of pulse temperature are used to fabricate TNTs, in which type I is firstly anodized at a low temperature for time t, and then increases to a high temperature. While for type II, the solution temperature order is opposite to that of type I. The ND of TNTs in the case of type I is lower than ND of TNTs in the case of type II. ND decreases with the increased pulse step time for type I, while ND increases with the increased pulse step time for type II.

Structure-regulated enhanced Raman scattering on a semiconductor to study temperature-influenced enantioselective identification.

Surface-enhanced Raman scattering (SERS) spectroscopy is an effective technique that can reveal molecular structure and molecular interaction details. Semiconductor-based SERS platforms exhibit multifaceted tunability and unique selectivity to target molecules as well as high spectral reproducibility. However, the detection sensitivity of semiconductors is impeded by inferior SERS enhancement. Herein, a surface and interference co-enhanced Raman scattering (SICERS) platform based on corrugated TiO2 nanotube arrays (c-TiO2 NTs) was developed, and the coupling of structural regulation and photo-induced charge transfer (PICT) effectively optimized the SERS performance of the semiconductor substrate. Due to the regularly oscillating optical properties of the c-TiO2 NTs, well-defined interference patterns were generated and the local electric field was significantly increased, which greatly promoted both the electromagnetic mechanism and PICT processes. The c-TiO2 NTs were subsequently applied as a highly sensitive SICERS substrate to investigate the mechanism of temperature influence on enantioselective identification. This identification process is related to the existence of temperature-sensitive hydrogen bonds and π-π interaction. This work demonstrates a simply prepared, low-cost, and sensitive SERS substrate that enables better investigation into molecular identification.