Titania Nanotubes

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A step towards commercialization of dye-sensitized solar cells (DSSCs) requires more attention to engineering aspects, such as flexibility, the roll to roll fabrication process, the use of cost effective materials, etc. In this aspect, advantages of flexible DSSCs attracted many researchers to contemplate the transparent conducting oxide coated flexible plastic substrates and the thin metallic foils. In this feature article, the pros and cons of these two kinds of substrates are compared. The flexible dye-sensitized solar cells fabricated using metal substrates are briefly discussed. The working electrodes of DSSCs fabricated on various metal substrates, their fabrication methods, the effect of high temperature calcination and drawbacks of back illumination are reviewed in detail. A few reports on the flexible metal substrate based counter electrodes that could be combined with the plastic substrate based working electrodes are also covered at the end.

Bulk g‐C3N4 is an earth‐abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P‐doping and size quantization are combined to synthesize highly fluorescent P‐doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase‐phase and rutile‐phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight‐driven water‐splitting and as photocatalysts for surface catalytic reactions. Square‐shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD‐STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD‐STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light‐driven transformation of 4‐nitrobenzenethiol (4‐NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.

This project report describes the synthesis of self-organized TiO2 nanotubes via electrochemical anodization of titanium, using the electrolytic solution of 99.7% ethylene glycol (EG), 0.3% deionized water (DI) and 0.3wt% ammonium fluoride (NH4F). The synthesized nanotubes were characterized using X-ray diffraction (XRD) and current-voltage (I-V) behavior. A dip at the high voltages during the I-V analysis indicated the formation of TiO2 nanotubes. The synthesis of amorphous TiO2 nanotubes was also confirmed from the presence of a broad peak between 2θ values of 20° and 30° in the XRD pattern.

Nitrogen-doped TiO2 fibers (N–TiO2 Fs) were successfully and efficiently fabricated using titanium diisopropoxide bis(acetylacetonate) and polyvinylpyrrolidone (PVP) as a carrier polymer and nitrogen source via centrifugal spinning and subsequent calcination methods. XRD analysis confirmed that N–TiO2 Fs contains only anatase and rutile phases. XPS analysis revealed that N-atoms (from PVP) were successfully incorporated into the lattice of TiO2 whereas DTA and FTIR analysis confirmed that calcination at 550 °C for 1 h is appropriate to remove all organic impurities from the N–TiO2 Fs. SEM images showed that the N–TiO2 Fs of diameter (0.65 μm–1.2 μm) were produced and controlled with the amount of Ti-precursor. BET analysis confirmed that the addition of commercial TiO2 nanoparticles increased the specific surface area of the N–TiO2 Fs. UV–Vis diffuse reflectance measurements showed that N–TiO2 Fs exhibited a stronger light absorption in the visible region and a red-shift which is responsible for narrow band gap energy owing to the presence of N-atoms in the TiO2 lattice. This results in enhanced photocatalytic activity of the synthesized N–TiO2 Fs for degradation of methylene blue under visible light irradiation.

Anatase-type TiO 2 nanotube arrays (TiO 2-NTAs) were grown on Ti foil by anodic oxidation in CH 3 COOH/NH 4 F solutions followed by thermal treatment. The surface of TiO 2-NTAs was further decorated by palladium and silver metal clusters through a chemical-reduction method and its photocatalytic activity was tested by investigating the degradation of p-nitrophenol (PNP) in aqueous solution under visible-light irradiation and electrical polarization. The effects of preparation variables both on microstructural properties of samples and photocatalytic activity were examined by using the 3D response surface and the 2D contour plots. The experimental investigations carried out by using XRD, SEM, HRTEM, EDS, XRF, ICP-AES, XPS, DRS, and PL, demonstrated a strong relation between the phase structure and the photocatalytic activity of TiO 2-NTAs. Titania nanotubes grown in acetic acid solution and thermally post-treated have stable anatase crystal structure, to a point that by performing annealing at 800 • C for 3 h, only the 35% of anatase transforms into rutile. Finally, it was shown that the TiO 2-NTAs decorated with Pd(0.72 wt%) and Ag(1.26 wt%) particles show higher photocatalytic activity compared with nanotubes modified with single metal particles. It is believed that the high photoactivity of TiO 2 nanotubes decorated with Pd–Ag heterostructures is due to the prolonged lifetimes of photogenerated electron–hole pairs. The possible mechanism for the enhanced photocatalytic activity is discussed in detail.

3D printing is an emergent manufacturing technology recently being applied in the medical field for the development of custom bone prostheses and scaffolds. However, successful industry transformation to this new design and manufacturing approach requires technology integration, concurrent multidisciplinary collaboration, and a robust quality management framework. This latter change enabler is the focus of this study. While a number of comprehensive quality frameworks have been developed in recent decades to ensure that the manufacturing of medical devices produces reliable products, they are centred on the traditional context of standardised manufacturing techniques. The advent of 3D printing technologies and the prospects for mass customisation provides significant market opportunities, but also presents a serious challenge to regulatory bodies tasked with managing and assuring product quality and safety. Before 3D printing bone prostheses and scaffolds can gain traction, industry stakeholders, such as regulators, clients, medical practitioners, insurers, lawyers, and manufacturers, would all require a high degree of confidence that customised manufacturing can achieve the same quality outcomes as standardised manufacturing. A Quality by Design (QbD) approach to custom 3D printed prostheses can help to ensure that products are designed and manufactured correctly from the beginning without errors. This paper reports on the adaptation of the QbD approach for the development process of 3D printed custom bone prosthesis and scaffolds. This was achieved through the identification of the Critical Quality Attributes of such products, and an extensive review of different design and fabrication methods for 3D printed bone prostheses. Research outcomes include the development of a comprehensive design and fabrication process flow diagram, and cat-egorised risks associated with the design and fabrication processes of such products. An extensive systematic literature review and post-hoc evaluation survey with experts was completed to evaluate the likely effectiveness of the herein suggested QbD framework.

Titanium (Ti) and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V) is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. 868 TiO2 nanotube (NTs) layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized material. In his study, NTs were grown on a Ti6Al4V alloy by anodic oxidation for 5 min using a super-oxidative aqueous solution, and their in vitro biocompatibility was investigated in pig periosteal osteoblasts and cartilage chondrocytes. Scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDX) and atomic force microscopy (AFM) were used to characterize the materials. Cell morphology was analyzed by SEM and AFM. Cell viability was examined by fluorescence microscopy. Cell adhesion was evaluated by nuclei staining and cell number quantification by fluorescence microscopy. The average diameter of the NTs was 80 nm. The results demonstrate improved cell adhesion and viability at Day 1 and Day 3 of cell growth on the nanostructured material as compared to the non-anodized alloy. In conclusion, this study evidences the suitability of NTs grown on Ti6Al4V alloy using a super-oxidative water and a short anodization process to enhance the adhesion and viability of osteoblasts and chondrocytes. The results warrant further investigation for its use as medical implant materials.

The present work was an attempt to investigate the potentialities of
multi-walled carbon nanotubes (MWCNT) as a carrier for targeting 6
Mercaptopurine to cancer tissues. MWCNTs were carboxy
functionalized and then loaded with 6 Mercaptopurine (6MP) using
the Incipient Wetness impregnation method to produce 6MP loaded
CNTs. The conjugate was characterized for drug loading efficiency,
in vitro drug release and release kinetics. The result indicated that a
maximum of about 65% entrapment was achieved. The loaded
nanotubes were shown to release the drug for more than 20 hours and
thus controlling the release. The release was found to follow the Zero
Order and Hixson Crowell release pattern. Our work established a
novel, easy to prepare formulation of MWCNTs with better drug
loading efficiency and increased dispersibility of CNTs and thus
improved bioavailability at cancer site with reduced systemic
toxicity.

Self-organized Titanium dioxide (TiO2) nanotubes grown on Ti grid acting as anode for Li-ion microbatteries were prepared via an electrochemical anodization. By tuning the anodization time, the morphology and length of the nanotubes were investigated by scanning electron microscope. When the anodization time reached 1.5 h, the TiO2 nts/Ti grid anode showed a well-defined nanotubes, which are stable, well-adherent ∼90 nm with a length of 1.9 ± 0.1 µm. Due to their high surface utilization, surface area, and material loading per unit area, TiO2 nts/Ti grid anode using polymer electrolyte exhibited a high areal capacity of 376 µAh cm −2 at C/10 rate and a stable discharge plateau at 1.8 V without using a polymer binder and conductive additive. The storage capacity of the TiO2nts/Ti grid after 10 cycles is 15 times higher compared to previous reports using planar Ti foils.

The electrochemical behavior of fluorine containing electrolytes and its influence in controlling the lateral dimensions of TiO 2 nanotubes is thoroughly investigated. Potentiostatic anodization is carried out in three different electrolytes, viz., aqueous hydrofluoric acid (HF), HF containing dimethyl sulphoxide (DMSO) and HF containing ethylene glycol (EG). The experiments were carried out over a broad voltage range from 2 to 200 V in 0.1-48 wt% HF concentrations and different electrolytic compositions for anodization times ranging from 5 s to 70 h. The chemistry that dictates how the nature of electrolytes influences the morphology of nanotubes is discussed. Electrochemical impedance spectra were recorded for varying compositions of all the electrolytes. It was observed that composition of the electrolyte and its fluorine inhibiting nature has significant impact on nanotube formation as well as in controlling the aspect ratio. The inhibiting nature of EG is helpful in holding fluorine at the titanium anode, thereby allowing controlled etching at appropriate voltages. Thus our study demonstrates that HF containing EG is a promising electrolytic system providing wide tunability in lateral dimensions and aspect ratio of TiO 2 nanotubes by systematically varying the anodization voltage and electrolyte composition.

Objective: The objective of this study was to investigate the reproducibility, mechanical integrity, surface characteristics and corrosion behavior of nanotubular (NT) titanium oxide arrays in comparison with a novel nano-pitted (NP) anodic film. Methods: Surface treatment processes were developed to grow homogenous NT and NP anodic films on the surface of grade 2 titanium discs and dental implants. The effect of process parameters on the surface characteristics and reproducibility of the anodic films was investigated and optimized. The mechanical integrity of the NT and NP anodic films were investigated by scanning electron microscopy, surface roughness measurement, scratch resistance and screwing tests, while the chemical and physicochemical properties were investigated in corrosion tests, contact angle measurement and X-ray photoelectron spectroscopy (XPS). Results and discussion: The growth of NT anodic films was highly affected by process parameters, especially by temperature, and they were apt to corrosion and exfoliation. In contrast, the anodic growth of NP film showed high reproducibility even on the surface of 3-dimensional screw dental implants and they did not show signs of corrosion and exfoliation. The underlying reason of the difference in the tendency for exfoliation of the NT and NP anodic films is unclear; however the XPS analysis revealed fluorine dopants in a magnitude larger concentration on NT anodic film than on NP surface, which was identified as a possible causative. Concerning other surface characteristics that are supposed to affect the biological behavior of titanium implants, surface roughness values were found to be similar, whereas considerable differences were revealed in the wettability of the NT and NP anodic films. Conclusion: Our findings suggest that the applicability of NT anodic films on the surface of titanium bone implants may be limited because of mechanical considerations. In contrast, it is worth to consider the applicability of nano-pitted anodic films over nanotubular arrays for the enhancement of the biological properties of titanium implants.

www.afm-journal.de www.MaterialsViews.com Figure 2. a) Cross-sectional TEM image of annealed ST2 sample and the corresponding diffraction pattern in the inset. b) A magnifi ed region of (a) showing the preferred orientation of the (101) crystallographic planes in FFT. c) HRTEM image and the FFT reconstruction of the crystalline region. d) The TEM image of undoped TiO 2 nanotube and e) the corresponding diffraction pattern of the outer layer.

The possibility of in situ doping during electrochemical anodization of titania
nanotube arrays is demonstrated and the mechanism and variations in structural
and electronic characteristics of the nanotube arrays as after doping
is systematically explored. In the presence of strontium as the dopant, bulk
analysis shows strontium mainly incorporated into the lattice of TiO 2 . Surface
analysis, however, reveals phase segregation of SrO in the TiO 2 matrix at high
Sr doping levels. The near edge X-ray absorption fi ne structure (NEXAFS)
spectroscopy analysis reveals that Sr 2+ doping only alters the Ti and O ions
interaction in the TiO 2 lattice on the surface with no effect on their individual
charge states. An in-depth understanding of the dopant incorporation mechanism
and distribution into TiO 2 nanotube arrays is achieved using high resolution
transmission electron microscopy (HRTEM) and the high angle annular
dark-fi eld scanning transmission electron microscopy (HAADF-STEM) coupled
with the electron energy loss spectroscopy (EELS) measurements on the
surface and bulk of the nanotubes. Upon their use to photoelectrochemically split water, the Sr-doped TiO 2 nanotube fi lm shows incident photon conversion
effi ciencies (IPCE) as high as 65%. The enhanced light activity in conjunction with the ordered one-dimensional morphology makes the fabricated fi lms promising candidates for water photoelectrolysis.

The synthesized titanium dioxide nanoparticles (TiO 2 -NPs) were used as adsorbent to remove reactive black 5 (RB 5) in aqueous solution. Various factors affecting adsorption of RB 5 aqueous solutions such as pH, initial concentration, contact time, dose of nanoparticles, and temperature were analyzed at fixed solid/solution ratio. Langmuir and Freundlich isotherms were used as model adsorption equilibrium data. Langmuir isotherm was found to be the most adequate model. The pseudo-first-order, pseudo-secondorder, and intraparticle diffusion models were used to describe the adsorption kinetics. The experimental data was fitted to pseudosecond-order kinetics. The thermodynamic parameters such as Gibbs-free energy, enthalpy, and entropy changes were determined. These parameters indicated the endothermic and spontaneity nature of the adsorption. The results demonstrated the fact that the TiO 2 -NPs are promising adsorbent for the removal of RB 5 from aqueous solutions.

RESUMEN En este trabajo se evaluó el efecto de la electrodeposición de fosfato de calcio sobre nanoestructuras de TiO 2. Para ello, se desarrollaron nanoestructuras de TiO 2 sobre sustratos de Ti6Al4V en una solución de NH 4 F y NH 4 H 2 PO 4 y posteriormente se realizó electrodeposición catódica empleando una solución compuesta de Ca(NO 3) 2 y (NH 4) 2 HPO 4 como electrolito. La morfología de las superficies se observó mediante microscopia electrónica de barrido y la capacidad de las superficies para formar apatitas se evaluó a través de absorción atómica tras inmersión de las muestras en fluido corporal simulado (SBF) durante 7 días. Finalmente se eva-luó la respuesta electroquímica de las superficies biofuncionalizadas mediante pruebas de resistencia a la polarización y curvas potenciodinámicas. Estos ensayos permitieron observar un incremento en la resistencia a la degradación de las superficies biofuncionalizadas respecto al sustrato. ABSTRACT In this work the effect of the electrodeposition of calcium phosphate on TiO2 nanostructures was evaluated. For that, TiO2 nanostructures were developed in a solution of NH4F and NH4H2PO4 on Ti6Al4V substrates and subsequent cathodic electrodeposition was performed using Ca(NO3)2 and (NH4)2HPO4 as electrolyte. The surface morphology was observed by scanning electron microscopy and the surface capacity to form apatites was evaluated by Atomic absorption spectroscopy after immersion of samples in simulated body fluid (SBF) for 7 days. Finally, the electrochemical response of biofunctionalized surfaces was evaluated by polarization resistance tests and potentiodynamic curves. These tests allowed to observe an increase in the resistance to degradation of biofunctionalized surfaces respect to the substrate.

Prussian blue (PB) modified titanate nanotubes (PB-TiNT) have been synthesized by the reaction of Fe 2 + -modified TiNT with hexacyanoferrate(III) ions. The rate constant for heterogeneous catalytic reaction between PB-TiNT and H 2 O 2 was found to be k = 2 10 4 dm 3 mol À1 s À1 , which is an order of magnitude higher than the values of k reported for conventionally prepared, electrochemically deposited PB films. On the PB-TiNT modified electrode with subnanomolar surface concentration of PB (G(PB) = 2.8 10 À11 mol/cm 2 ), a stable, reproducible and linear response towards H 2 O 2 was obtained in the concentration range 0.02-4 mM, with the sensitivity of 0.10 AM À1 cm À2 at À150 mV.

The synthesized titanium dioxide nanoparticles (TiO2-NPs) were used as adsorbent to remove reactive black 5 (RB 5) in aqueous
solution. Various factors affecting adsorption of RB 5 aqueous solutions such as pH, initial concentration, contact time, dose of
nanoparticles, and temperature were analyzed at fixed solid/solution ratio. Langmuir and Freundlich isotherms were used as model
adsorption equilibriumdata. Langmuir isothermwas found to be themost adequatemodel.The pseudo-first-order, pseudo-secondorder,
and intraparticle diffusionmodels were used to describe the adsorption kinetics.The experimental data was fitted to pseudosecond-
order kinetics.The thermodynamic parameters such as Gibbs-free energy, enthalpy, and entropy changes were determined.
These parameters indicated the endothermic and spontaneity nature of the adsorption. The results demonstrated the fact that theTiO2-NPs are promising adsorbent for the removal of RB 5 from aqueous solutions.

Highly oriented titania nanotube arrays are formed by self-organizing anodization of Ti foil in organic electrolytes in the presence of fluoride ions. The effects of tube length and the tube wall stratified layer on the electrochemical capacitance of these bamboo-type nanotubes are investigated. Field emission scanning electron microscopy (FESEM) is used to characterize the surface morphology, while cyclic voltammetry is used to investigate the pseudocapacitive properties of these nanostructured electrodes. The bamboo-type titania nanotube array with a higher aspect ratio shows a higher specific capacitance value of 52μFcm-2 in 1M Na2SO4 with excellent reversibility characteristics. The introduction of surface defects by annealing in NH3 increased the specific capacitance value to 118μFcm-2. This simple and cost-saving binder-free electrode is considered a promising candidate for supercapacitor applications.

http://www.sciencedirect.com/science/article/pii/S0257897212011024

Titanate nanotubes were synthesized by hydrothermally treating the TiO2 powder with NaOH solution and their formation and thermal stability was discussed in the view of different TiO2 precursors and Na+ content. The starting precursors for nanotube synthesis were either anatase or the mixture of anatase, rutile and high-pressure TiO2 II phase (TiO2 II) as a major component. The samples with various Na/Ti ratios were prepared by ion exchange of interlayer Na+ cations with H+ ions under controlled pH conditions. The thermal stability and the structural changes of nanotubes were studied in situ at high temperatures using Raman spectroscopy (RS) and transmission electron microscopy (TEM).

We found that hydrothermal treatment of mixture of TiO2 phases (anatase, rutile and TiO2 II) leads to the formation of titanate nanotubes with structure and morphology similar to these obtained from pure anatase. However, their temperature stability was reduced, so transform to anatase at temperatures around 80 °C. In the case of nanotubes obtained from anatase precursor, Raman bands characteristic for titanate nanotubes were visible up to 300 °C. At 500 °C titanate nanotubes in H-form, H2Ti3O7, were completely transformed to anatase, while Na-form, Na2Ti3O7, showed phase transition to hexatitanate, Na2Ti6O13, nanowires.

Nanostructured palladium particles (nanorods, icosahedra, cubes) were synthesized in aqueous solution using a seeding-mediated approach with a structure-directing agent. These nanostructured Pd particles were then impregnated onto hydrogenotitanate nanotubes using two different impregnation procedures. The as-prepared catalysts were then tested in the selective hydrogenation of cinnamaldehyde at 323 K under 10 bars of H 2. The selectivity is influenced by the morphology of the Pd nanostructured particles with a higher selectivity into saturated alcohols when the proportion of (111) Pd sites increases.

Titanate nanosheets (TiNS), titanate nanotubes (TiNT), and scrolled titanate nanosheets (STiNS) were used to synthesise polymer nanocomposites by solution processing. The hardness was found to increase by 90% on addition of 2% TiNS while the modulus (Er) increased by 103% compared to the pure polymer. Small angle X-ray scattering (SAXS) measurements of composite films were used to study alignment of nanostructures within the polymer. The obtained data on mechanical properties of composites have been tested against theoretical values and it was established that both nanostructures alignment as well as their mechanical properties affect the hardness and modulus of the polymer composites. At a low content of TiNS, the reinforcement behaviour matched well with Halpin-Tsai theory which assumes the filler has unidirectional orientation. After addition of 2 wt% TiNT, the hardness and modulus of the polyamic acid salt composites increased by 91% and 165%, respectively, and were higher than theoretical predictions, indicating that both TiNT and STiNS, prepared by hydrothermal synthesis, may have higher mechanical properties than bulk TiO 2. At a high filler loading (>2 wt%), the mechanical properties of composites do not fit established theories due to agglomeration of titanate nanostructures.

The objective of this study was to investigate the reproducibility, mechanical integrity, surface characteristics and corrosion behavior of nanotubular (NT) titanium oxide arrays in comparison with a novel nano-pitted (NP) anodic film. Surface treatment processes were developed to grow homogenous NT and NP anodic films on the surface of grade 2 titanium discs and dental implants. The effect of process parameters on the surface characteristics and reproducibility of the anodic films was investigated and optimized. The mechanical integrity of the NT and NP anodic films were investigated by scanning electron microscopy, surface roughness measurement, scratch resistance and screwing tests, while the chemical and physicochemical properties were investigated in corrosion tests, contact angle measurement and X-ray photoelectron spectroscopy (XPS). The growth of NT anodic films was highly affected by process parameters, especially by temperature, and they were apt to corrosion and exfoliati...

The purpose of the present study was to synthetize 80 nm diameter TiO2 nanotubes (NTs) on Ti6Al4V alloy using a commercially superoxidized water (SOW) enriched with fluoride to reduce anodization time and promote the antibacterial efficacy againstStaphylococcus aureus(S. aureus). The alloy discs were anodized for 5 min and as a result, NTs of approximately 80 nm diameters were obtained with similar morphology as reported in previous studies using longer anodization times (1-2 h). Filed emission-scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the materials surfaces. The NTs showed significantly decreasedS. aureusviability after 1, 3, and 5 days of culture in comparison to nonanodized alloy. Likewise, SEM analysis also suggested lower bacterial adhesion on the NTs surface. No differences in bacterial morphology and topography were observed on both materials, as analyzed by SEM and atomic force microscopy (AFM). In conclusi...

The synthesis technique of composite based on nanotubular titania (TiO 2-NT) and carbon nanotubes (CNT) was presented. Anodization of titanium to form TiO 2-NT layer, magnetron sputtering to deposit Ni-catalyst and chemical vapor deposition to grow CNT were main stages of fabrication the CNT@TiO 2-NT structures. Nano-cables consisted of double-walled TiO 2-NT shells (outer diameters of 80 and 250 nm) and multi-walled CNT cores (diameter of 20 nm) were synthesized and characterized by scanning electron microscopy.

The present work investigates the formation of nanotubes by anodizing titanium at 20 V in glycerol containing either 0.175 M or 0.35 M NH 4 F. A photoresist-masking method of thin Ti films allows to use SEM cross-sections to directly obtain information on oxide morphology, layer thickness and metal substrate loss. Therefore not only features of the initial growth stages but also oxide expansion factors can accurately be determined. The expansion factors were found to be ∼2.4 for the initial formation of a barrier layer, ∼1.7-1.9 during pore initiation and ∼2.7-3.1 as the main nanotubes develop. These values (>2.6) suggest substantial contribution to steady state tube growth by a plastic oxide flow mechanism. Combined with RBS efficiency measurements the method presented here allows facile and direct investigation of the mechanism of pore/tube formation.

www.afm-journal.de www.MaterialsViews.com Figure 2. a) Cross-sectional TEM image of annealed ST2 sample and the corresponding diffraction pattern in the inset. b) A magnifi ed region of (a) showing the preferred orientation of the (101) crystallographic planes in FFT. c) HRTEM image and the FFT reconstruction of the crystalline region. d) The TEM image of undoped TiO 2 nanotube and e) the corresponding diffraction pattern of the outer layer.

MoS2/TNT composites have been obtained by impregnation of titanate nanotubes (TNTs) with a centrifuged solution of nanosized MoS2 particles in isopropyl alcohol (IPA). The characterization has been performed by combining UV-Vis-NIR, Raman, AFM and HRTEM analyses, before and after impregnation. HRTEM images show that the contact between single layer MoS2 nanoparticles and the support is efficient, so justifying the decoration concept. The volatility of IPA solvent allows the preparation of composites at low temperature and free of carbonaceous impurities. MoS2 nanoparticles have strong excitonic transitions, which are only slightly shifted with respect to the bulk because of quantum size effects. Concentrations of MoS2, less than 0.1 wt%, are enough to induce strong absorption in the visible. Photodegradation of methylene blue (MB) has been performed on TNTs and MoS2/TNTs to verify the effect of the presence of MoS2. The first layer of adsorbed MB is consumed first, followed by clustered MB in the second and more external layers. The presence of low concentrated MoS2 nanoparticles does not substantially alter the photocatalytic properties of TNTs. This result is due to poor overlapping between the high frequency of MoS2 C, D excitonic transitions and the TNTs band gap transition.

The effect of water additions, from , to an ammonium fluoride/ethylene glycol electrolyte on the composition and morphology of titania-based nanotubes was investigated by scanning and transmission electron microscopy, Rutherford backscattering spectroscopy, and nuclear reaction ...

The present work investigates the formation of nanotubes by anodizing titanium at 20 V in glycerol containing either 0.175 M or 0.35 M NH 4 F. A photoresist-masking method of thin Ti films allows to use SEM cross-sections to directly obtain information on oxide morphology, layer thickness and metal substrate loss. Therefore not only features of the initial growth stages but also oxide expansion factors can accurately be determined. The expansion factors were found to be ∼2.4 for the initial formation of a barrier layer, ∼1.7-1.9 during pore initiation and ∼2.7-3.1 as the main nanotubes develop. These values (>2.6) suggest substantial contribution to steady state tube growth by a plastic oxide flow mechanism. Combined with RBS efficiency measurements the method presented here allows facile and direct investigation of the mechanism of pore/tube formation.

We demonstrate, for the first time, the synthesis of titania nanotubes
with ultrathin (3–5 nm) wall thickness. As revealed by the incident
photon-to-current collection efficiency (IPCE) and electrochemical
impedance spectroscopy measurements, the ultrathin walls, less than
the charge carrier diffusion length, were essential to ensure fast and
efficient charge carrier collection.

En este trabajo se presenta un método alternativo basado en microscopia de modulación de fuerza (FMM), para la identificación de nanogotas producidas en el plasma generado por los spots catódicos de los arcos en vacío. La técnica FMM esta habilitada para la detección de variaciones en las propiedades mecánicas de una superficie, con alta sensibilidad. Se han analizado recubrimientos de nitruro de titanio (TiN) depositados sobre Silicio orientado por el proceso de arco en vacío pulsado. Se han obtenido simultáneamente imágenes de microscopia de fuerza atómica (AFM) y de microscopia FMM mediante las cuales se ha podido identificar la presencia de nanogotas. Adicionalmente se han tomado espectros de difracción de rayos X (XRD) de las muestras recubiertas. Se ha reportado la existencia de partículas contaminantes de 47 nanómetros de diámetro sobre los recubrimientos.

PACS: 42.79.Wc, 68.35.Gy