Properties Of 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.

Effect of potential variation on morphology and photoelectrochemical properties of TiO2 nanotube arrays (TNAs) by two-step anodization method

Effect of potential variation on morphology and photoelectrochemical properties of TiO2 nanotube arrays (TNAs) by two-step anodization method

The Role of Lattice Defects on the Optical Properties of TiO2 Nanotube Arrays for Synergistic Water Splitting.

In this study, we report a facile one-step chemical method to synthesize reduced titanium dioxide (TiO2) nanotube arrays (NTAs) with point defects. Treatment with NaBH4 introduces oxygen vacancies (OVs) in the TiO2 lattice. Chemical analysis and optical studies indicate that the OV density can be significantly increased by changing reduction time treatment, leading to higher optical transmission of the TiO2 NTAs and retarded carrier recombination in the photoelectrochemical process. A cathodoluminescence (CL) study of reduced TiO2 (TiO2-x) NTAs revealed that OVs contribute significantly to the emission bands in the visible range. It was found that the TiO2 NTAs reduced for a longer duration exhibited a higher concentration of OVs. A typical CL spectrum of TiO2 was deconvoluted to four Gaussian components, assigned to F, F+, and Ti3+ centers. X-ray photoelectron spectroscopy measurements were used to support the change in the surface chemical bonding and electronic valence band position in TiO2. Electron paramagnetic resonance spectra confirmed the presence of OVs in the TiO2-x sample. The prepared TiO2-x NTAs show an enhanced photocurrent for water splitting due to pronounced light absorption in the visible region, enhanced electrical conductivity, and improved charge transportation.

Fluoro-Substituted Covalent Organic Framework Particles Anchored on TiO2 Nanotube Arrays for Photoelectrochemical Determination of Dopamine

In this work, the photoelectrochemical (PEC) properties of TiO2 nanotube arrays (NTAs) were enhanced by forming heterostructures with non-substituted covalent organic frameworks (H-COFs) and fluoro...

Anodic Oxidation of TC4 Substrate to Synthesize Ce-Doped TiO2 Nanotube Arrays with Enhanced Photocatalytic Performance

Starting from the urgent need for water pollution treatment, TiO2 nanotube arrays (TNAs) and Ce-doped TNAs have been prepared on TC4 titanium alloy substrate via anodic oxidation. Several properties of TNAs and Ce-doped TNAs were characterized utilizing field emission scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction and ultraviolet-visible spectrophotometer to analyze their morphology, phase structure, distribution of element and optical property respectively. The photocatalytic performance was evaluated by the photo-degradation of methylene blue (MB) under simulated visible light irradiation. The result indicated that the best photodegradation rate of the Ce-doped TNAs on MB reached to 90.4%, which was a huge improvement compared with pristine TNAs.

Photoelectrochemical properties of “increasingly dark” TiO2 nanotube arrays

“Black” TiO2 nanotube arrays (TNTAs) of different darkness are formed by thermal reduction of anodic TiO2 nanotube layers in H2 atmosphere at different temperatures (300–500 °C), and their (photo-)electrochemical properties are studied by IPCE spectroscopy, transient photocurrent measurements, IMPS, PEIS, CV, and Mott-Schottky analysis. Hydrogenation of the TNTAs leads to the enhancement of their IPCE (by up to 1.5 times), despite increased recombination losses at anodic potentials. Reduced TNTAs demonstrate a “metallic” behavior by a characteristic frequency response of their impedance and phase angle, reduced charge transfer resistance at anodic bias, increased double layer capacitance, and remarkably increased donor densities (up to 7.25 × 1023 cm−3). The observed alterations in the properties of TNTAs after hydrogenation are ascribed to the formation of defects and TiHx.

Tuning the density distribution of deep localized states of TiO2 nanotube arrays through decoration with Pt and Pt@DLC

We demonstrate the possibility to tune the distribution of deep localized states and electronic transport properties of TiO2 nanotube arrays (TNA) through decoration its surface with Pt or Pt@DLC (Diamond-like carbon). A quantitative calculation of the position of the deep trap states in the band gap and the amount of accumulated charge in deep traps of Pt/TNA and Pt-DLC/TNA electrodes are presented and compared based on photocurrent-voltage curves. Our findings demonstrate that both Pt NPs and Pt@DLC depositions could decrease the quantity of deep localized states in the band gap by saturating the dangling bonds on the surface of TNA. A decline in photoluminescence intensity in platinized samples confirmed the density of deep trap states acting as recombination centers reduced by these surface modifications. Also, the deep localized states in Pt/TNA and Pt-DLC/TNA electrodes shift down towards valence band, in comparison with pure TNA. The neighborhood of the trapped electrons in deep states to the hole sites (VB) in platinized samples leads to the reduction of the electron- hole life time in these samples. Moreover, higher anodic photocurrent density was observed for pure TNA, revealed that in pure TNA the free photoexcited electrons reached to the conduction band will transport to the external circuit whereas, in Pt/TNAs and Pt-DLC/TNAs some free electrons would transfer to Pt NPs via Schottky junction at the semiconductor/electrolyte interface or via hopping or tunneling of pi-electrons existing in the sp2 nanoregions of DLC. Finally, Pt- and Pt@DLC-modified TNA electrodes absorbing light in the visible range and suppressing photoelectron recombination are worthy photocatalysts. In contrast, the deposition of Pt or Pt@DLC on TiO2 nanotubes resulted in lower PEC response.

Explaining the Enhanced Photoelectrochemical Behavior of Highly Ordered TiO2 Nanotube Arrays: Anatase/Rutile Phase Junction

The effect of calcination temperature on the photoelectrochemical properties of TiO2 nanotube arrays (TNTAs) has been investigated in many studies. Most work focused on improving the photoelectroch...

Formation and photoelectrochemical properties of TiO2 nanotube arrays in fluorinated organic electrolyte

Formation and photoelectrochemical properties of TiO2 nanotube arrays in fluorinated organic electrolyte

Polydopamine-assisted decoration of TiO2 nanotube arrays with enzyme to construct a novel photoelectrochemical sensing platform

A novel photoelectrochemical (PEC) biosensing platform coupling with enzyme-induced biocatalytic precipitation (BCP) for H2O2 was successfully constructed. TiO2 nanotube arrays (TNs) were coated with polydopamine (PDA) and horseradish peroxidase (HRP) as the PEC electrode through a facile method. PDA was incorporated into the sensor system not only as a sensitizing agent to alter the optical properties of TiO2 nanotube arrays and enhance the visible light (λ>400nm) absorption, but also as a bonding resin to HRP via Michael addition or Schiff base reaction. The immobilized HRP on the PEC electrodes could induce BCP reaction as the signal amplifier by oxidizing the 4-chloro-1-naphthol (4-CN) into insoluble products in the presence of H2O2. The quantitative monitoring of H2O2 could be realized thanks to the photocurrent decrease caused by the BCP generated insoluble products deposited on the PEC electrode surface. The fabricated TNs@HRP/PDA PEC electrode for biosensing of H2O2 exhibited a good sensitivity as well as selectivity in a detection range from 1nM to 50μM, with a detection limit of 0.7nM.

Electrochemical Reductive Doping and Interfacial Impedance of TiO2 Nanotube Arrays in Aqueous and Aprotic Solvents

Electrochemical reductive doping is considered to be a simple and effective method to improve the electric properties of TiO2 nanotube arrays (NTAs). We report on electrochemical tests of the reductive reaction of anatase TiO2 NTAs in aqueous and aprotic solvents. It is confirmed that hydrogen is not necessary for the electrochemical reduction of TiO2, and the reaction can be performed in either aqueous or aprotic solvents, where the former is more effective. Three equivalent circuit models were also built to understand the electrochemical behavior, via electrochemical impedance, of pristine, reduced, and post-oxidized TiO2 NTAs in contact with electrolyte. Ti4+ is reduced to Ti3+ by electrochemical treatment to form self-doped TiO2 with metallic properties at the initial stages, and the reduced TiO2 NTAs can be easily re-oxidized to form a stable semiconductor when exposed in air. Two different reaction mechanisms performed in aqueous and aprotic solvents are discussed. These findings help to understand the complexity of the processes involved in the electrochemical reductive doping of TiO2 NTAs and suggest a way to improve the electronic properties of TiO2 nanomaterials.

Enhancement of photoelectrochemical and photocathodic protection properties of TiO2 nanotube arrays by simple surface UV treatment

A simple and efficient surface treatment method toward practical applications to enhance photo response of TiO2 nanotube arrays (NTs) photoelectrode was reported. TiO2 NTs were prepared by two-step electrochemical anodization methods, following by surface ultra violet light (UV) illumination treatment, which can produce amounts of hydroxyl groups on the surface of TiO2 NTs photoelectrode. The photoelectrochemical measurements demonstrate that the photocurrent density of the UV treated TiO2 NTs photoelectrode enhances by 50% than that of the pristine TiO2 NTs photoelectrode. More interestingly, the decayed photocurrent density of TiO2 NTs can recover the high value by illumination treatment again after using/storing for several days. Additionally, open circuit potential, tafel curves and electrochemical impedance spectroscopy measurements exhibit that the UV illumination treatment for TiO2 NTs photoelectrode is an easy and effective strategy to protect 304 stainless steel from corrosion by photogenerated cathode protection.

Experimental Study on the Plant Dye Sensitized TiO<sub>2</sub> Electrode

In this paper, Ti sheets were anodized to obtain TiO2 nanotube arrays electrodes. The impact of different oxidation conditions on photoelectric properties of TiO2 nanotube arrays were discussed by the photocurrent density, and the optimal oxidation conditions of TiO2 which had good photoelectric properties were found. Pigments were extracted from fresh spinach leaves, tomatoes and carrots, and to be used as plant dye to sensitize TiO2 electrodes. The photocurrent density and the Incident Photon to Current Efficiency (IPCE) of the plant dye sensitized TiO2 electrodes were examined.

Effect of acid solution, fluoride ions, anodic potential and time on the microstructure and electronic properties of self-ordered TiO2 nanotube arrays

Self-ordered TiO2 nanotube arrays were fabricated by the anodization of Ti foil in acid solution containing fluoride ions in the present work. The influences of the acid solution, fluoride ions, anodic potential and time on the microstructure and electronic properties of TiO2 nanotube arrays (TNTs) were also systematically investigated by SEM, Raman spectroscopy, EIS and Mott-Schottky analysis. The SEM results show that TNTs are formed in a double-layer structure, i.e., as the upper TNTs and a lower barrier film. The lengths of TNTs and the thickness of the barrier film increased with increasing potential and time, reached maximum value in phosphoric acid solution containing NH4F, and reached minimum value in oxalic acid solution containing NaF. The crystallinity of TNTs was enhanced with increasing anodic potential and time, and TNTs fabricated in NH4F solution had the best crystallinity. The influences of the acid solution, fluoride salt, anodic potential and time on the electronic properties of TNTs were similar to those on the crystallinity.

Anodic formation of highly ordered TiO2 nanotube arrays on conducting glass substrate: Effect of titanium film thickness

Highly ordered TiO2 nanotube arrays were successfully fabricated using ammonium fluoride electrolyte by galvanostatic anodization technique. The nanotube arrays were grown perpendicular to the titanium film deposited onto conducting glass substrate. The effect of the different titanium film thicknesses on the morphology, optical, and electrical properties of TiO2 nanotube arrays is investigated. It is found that the titanium film thickness is a crucial parameter for achieving highly ordered TiO2 nanotube arrays. Morphological investigations on the nanotube arrays reveal that anodization of 1.5 μm thick titanium films leads to formation of pores at the upper layer of the film with nonuniform pore size distribution and poor interconnectivity. Instead, anodization of 2.5 and 2.0 μm thick titanium films with the same conditions leads to formation of highly ordered TiO2 nanotube arrays with uniform size and sharp clear tubular structures, which are well connected to each other. The absorbance and optical band gap of the TiO2 nanotube arrays are also inferred from the diffuse reflectance spectra.Highly ordered TiO2 nanotube arrays were successfully fabricated using ammonium fluoride electrolyte by galvanostatic anodization technique. The nanotube arrays were grown perpendicular to the titanium film deposited onto conducting glass substrate. The effect of the different titanium film thicknesses on the morphology, optical, and electrical properties of TiO2 nanotube arrays is investigated. It is found that the titanium film thickness is a crucial parameter for achieving highly ordered TiO2 nanotube arrays. Morphological investigations on the nanotube arrays reveal that anodization of 1.5 μm thick titanium films leads to formation of pores at the upper layer of the film with nonuniform pore size distribution and poor interconnectivity. Instead, anodization of 2.5 and 2.0 μm thick titanium films with the same conditions leads to formation of highly ordered TiO2 nanotube arrays with uniform size and sharp clear tubular structures, which are well connected to each other. The absorbance and optical band ...

Photovoltaic properties of dye sensitised solar cells using TiO2 nanotube arrays for photoanodes: Role of hydrochloric acid treatment

A hydrochloric acid treatment was performed to modify the surface of TiO2 nanotube arrays for improving the photovoltaic performance of dye-sensitized solar cells. The microstructural, optical and photovoltaic properties of TiO2 nanotube arrays and the assembled cells were investigated in detail. It was found that HCl treatment does not change the morphology and crystallographic structure of the nanotube arrays, but it results in more hydroxyl groups on the TiO2 surface for dye adsorption and a surface protonation for both an improved dye adsorption and a higher quantum yield of electron injection. A major performance enhancement was found which originated from the remarkable increase in the dye adsorption. A power conversion efficiency of 8.4%, JSC of ∼16.8mAcm−2 and VOC of 0.7V was observed when the photoanode was treated with a 0.1M HCl solution.

Effect of Anodization Parameters on Morphology and Photocatalysis Properties of TiO2 Nanotube Arrays

Highly ordered TiO2 nanotube arrays were fabricated via electrochemical anodization of high purity Ti foil in fluoride-containing electrolyte. The effects of applied anodization potential, anodization time on the formation of TiO2 nanotube arrays and the photocatalytic degradation of methylene blue (MB) were discussed. The TiO2 nanotube arrays calcined at 500 °C for 2 h show pure anatase phase. The pore diameters of TiO2 nanotube arrays can be adjusted from 30 to 90 nm using a different anodization voltage. Anodization time mainly influenced TiO2 tube length, and by increasing the anodization time, the nanotube length became longer gradually. When the anodization potential was 40 V, the average growth rate of TiO2 nanotube was about 4.17 µm/h. Both anodization potential and time had important effects on the photocatalytic efficiency. The TiO2 nanotube arrays obtained at anodization potential of 40 V for 1 h showed the best photocatalytic degradation ratio of MB.

TiO2 nanotube coating on stainless steel 304 for biomedical applications

The present study describes the anodic growth of TiO2 nanotube thin layer on stainless steel 304 in ethylene glycol/water/ammonium fluoride electrolyte. In this regard, pure titanium was coated on stainless steel 304 substrates by a physical vapor deposition magnetron sputtering (PVDMS) technique. The adhesion strength of the coating to the substrate was investigated. TiO2 nanotubes were generated on the top of the Ti coated substrates by means of anodization technique at a 25V potential and times of 20, 40, and 60min in an ammonium fluoride electrolyte solution. The anodized Ti-coated samples were heat-treated at 280°C, 430°C and 620°C in a N2 gas furnace to attain diverse phases. The mechanical properties of TiO2 nanotube arrays coated substrate were explored by a nanoindentation apparatus. The results illustrate that the Young׳s modulus and surface hardness of TiO2 nanotube-coated substrates are increased with increasing annealing temperatures (280°C, 430°C and 620°C). The scratch test results show that heat treatment at 430°C and 620°C can improve the adhesion strength of Ti/TiO2 coated samples by up to 2860 and 3140mN, respectively.

Low-temperature ammonia annealed TiO2 nanotube arrays: Synergy of morphology improvement and nitrogen doping for enhanced field emission

The field emission (FE) properties of TiO2 nanotube arrays (TNAs) fabricated by anodization are dramatically enhanced by ammonia annealing at a low temperature of 90°C with various annealing durations of 5–15h, which can spontaneously tailor the as-anodized amorphous TNAs to be an anatase hierarchical structure of worm-like TiO2 decorated TNAs, and simultaneously implant nitrogen into the hierarchical structure. Compared to the as-anodized TNAs, the turn-on field of ammonia annealed TNAs are significantly dropped from 23.11 to 2.94V/μm, and related to the annealing time. Importantly, the optimized sample of ammonia annealed TNAs treated for 10h exhibits excellent FE properties involving both a low turn-on field of 2.94V/μm, a high FE current density of about 3.35mA/cm2 at 7.35V/μm, and a remarkable FE stability. The substantially enhanced FE properties can be attributed to the combination of the optimized morphology, the improved conductivity, and the presence of localized oxygen vacancy states and N 2p states created by N-doping of ammonia annealed TNAs.

Enhanced photoelectrochemical properties of TiO2 nanotube arrays sensitized with energy-band tunable (Cu2Sn)x/3Zn1−xS nanoparticles

In this paper, TiO2 nanotube (TNT) arrays and (Cu2Sn)x/3Zn1−xS (x = 0.75, 0.24, and 0.09) nanocrystals were prepared, and TiO2 nanotubes (TNTs) were sensitized with (Cu2Sn)x/3Zn1−xS nanocrystals. Compared with the plain TNTs, (Cu2Sn)x/3Zn1−xS sensitized TNTs present an enhanced photoelectrochemical response. The photocurrent enhancement was characterized with the photocurrent ratio of (Cu2Sn)x/3Zn1−xS sensitized TNTs to plain TNTs, which were 1.50, 1.63, and 2.13 for (Cu2Sn)x/3Zn1−xS with the composition of x = 0.75, 0.24, and 0.09, respectively. To understand this phenomenon, the energy band alignments of TNTs and (Cu2Sn)x/3Zn1−xS were investigated, based on which the conduction band offsets (CBO) between TNTs and (Cu2Sn)x/3Zn1−xS were determined, which were 0.31, 0.47, and 0.63 eV for (Cu2Sn)x/3Zn1−xS with the composition of x = 0.75, 0.24, and 0.09, respectively. These results display that the photocurrent enhancement becomes large with the increase of CBO, which indicates that the enhanced photoelectrochemical response is mainly due to the energy level matching between TNTs and (Cu2Sn)x/3Zn1−xS, and the variation of enhancement is resulting from the change of CBO.