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This work aims to investigate the chemical and/or structural modification of Ti and Ti-6Al-4V (TiAlV) alloy surfaces to possess even more favorable properties toward cell growth. These modifications were achieved by (i) growing TiO 2 nanotube layers on these substrates by anodization, (ii) surface coating by ultrathin TiO 2 atomic layer deposition (ALD), or (iii) by the combination of both. In particular, an ultrathin TiO 2 coating, achieved by 1 cycle of TiO 2 ALD, was intended to shade the impurities of F- and V-based species in tested materials while preserving the original structure and morphology. The cell growth on TiO 2 -coated and uncoated TiO 2 nanotube layers, Ti foils, and TiAlV alloy foils were compared after incubation for up to 72 h. For evaluation of the biocompatibility of tested materials, cell lines of different tissue origin, including predominantly MG-63 osteoblastic cells, were used. For all tested nanomaterials, adding an ultrathin TiO 2 coating improved the growth of MG-63 cells and other cell lines compared with the non-TiO 2 -coated counterparts. Here, the presented approach of ultrathin TiO 2 coating could be used potentially for improving implants, especially in terms of shading problematic F- and V-based species in TiO 2 nanotube layers.

In this work, for the first time 3D Ti-Nb meshes of different composition, i.e., Ti, Ti-1Nb, Ti-5Nb, and Ti-10 Nb, were produced by direct ink writing. This additive manufacturing method allows tuning of the mesh composition by simple blending of pure Ti and Nb powders. The 3D meshes are extremely robust with a high compressive strength, giving potential use in photocatalytic flow-through systems. After successful wireless anodization of the 3D meshes toward Nb-doped TiO 2 nanotube (TNT) layers using bipolar electrochemistry, they were employed for the first time for photocatalytic degradation of acetaldehyde in a flow-through reactor built based on ISO standards. Nb-doped TNT layers with low concentrations of Nb show superior photocatalytic performance compared with nondoped TNT layers due to the lower amount of recombination surface centers. High concentrations of Nb lead to an increased number of recombination centers within the TNT layers and reduce the photocatalytic degradation rates.

2-dimensional FeS x nanosheets of different sizes are synthesized by applying different numbers of atomic layer deposition (ALD) cycles on TiO 2 nanotube layers and graphite sheets as supporting materials and used as an electrocatalyst for the hydrogen evolution reaction (HER). The electrochemical results confirm electrocatalytic activity in alkaline media with outstanding long-term stability (>65 h) and enhanced catalytic activity, reflected by a notable drop in the initial HER overpotential value (up to 26 %). By using a range of characterization techniques, the origin of the enhanced catalytic activity was found to be caused by the synergistic interplay between in situ morphological and compositional changes in the 2D FeS x nanosheets during HER. Under the application of a cathodic potential in alkaline media, the as-synthesized 2D FeS x nanosheets transformed into iron oxyhydroxide-iron oxysulfide core-shell nanoparticles, which exhibited a higher active catalytic surface and newly created Fe-based HER catalytic sites., (© 2023 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Detection of visible light is a key component in material characterization techniques and often a key component of quality or purity control analyses for health and safety applications. Here in this work, to enable visible light detection at gigahertz frequencies, a planar microwave resonator is integrated with high aspect ratio TiO 2 nanotube (TNT) layer-sensitized CdS coating using the atomic layer deposition (ALD) technique. This unique method of visible light detection with microwave-based sensing improves integration of the light detection devices with digital technology. The designed planar microwave resonator sensor was implemented and tested with resonant frequency between 8.2 and 8.4 GHz and a resonant amplitude between -15 and -25 dB, depending on the wavelength of the illuminated light illumination on the nanotubes. The ALD CdS coating sensitized the nanotubes in visible light up to ∼650 nm wavelengths, as characterized by visible spectroscopy. Furthermore, CdS-coated TNT layer integration with the planar resonator sensor allowed for development of a robust microwave sensing platform with improved sensitivity to green and red light (60 and 1300%, respectively) compared to the blank TNT layers. Moreover, the CdS coating of the TNT layer enhanced the sensor's response to light exposure and resulted in shorter recovery times once the light source was removed. Despite having a CdS coating, the sensor was capable of detecting blue and UV light; however, refining the sensitizing layer could potentially enhance its sensitivity to specific wavelengths of light in certain applications.

Urinary-based infections affect millions of people worldwide. Such bacterial infections are mainly caused by Escherichia coli (E. coli) biofilm formation in the bladder and/or urinary catheters. Herein, the authors present a hybrid enzyme/photocatalytic microrobot, based on urease-immobilized TiO 2 /CdS nanotube bundles, that can swim in urea as a biocompatible fuel and respond to visible light. Upon illumination for 2 h, these microrobots are able to remove almost 90% of bacterial biofilm, due to the generation of reactive radicals, while bare TiO 2 /CdS photocatalysts (non-motile) or urease-coated microrobots in the dark do not show any toxic effect. These results indicate a synergistic effect between the self-propulsion provided by the enzyme and the photocatalytic activity induced under light stimuli. This work provides a photo-biocatalytic approach for the design of efficient light-driven microrobots with promising applications in microbiology and biomedicine., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

In this work, large 3D Ti meshes fabricated by direct ink writing were wirelessly anodized for the first time to prepare highly photocatalytically active TiO 2 nanotube (TNT) layers. The use of bipolar electrochemistry enabled the fabrication of TNT layers within the 3D Ti meshes without the establishment of an electrical contact between Ti meshes and the potentiostat, confirming its unique ability and advantage for the synthesis of anodic structures on metallic substrates with a complex geometry. TNT layers with nanotube diameters of up to 110 nm and thicknesses of up to 3.3 μm were formed. The TNT-layer-modified 3D Ti meshes showed a superior performance for the photocatalytic degradation of methylene blue in comparison to TiO 2 -nanoparticle-decorated and nonanodized Ti meshes (with a thermal oxide layer), resulting in multiple increases in the dye degradation rate. The results presented here open new horizons for the employment of anodized 3D Ti meshes in various flow-through (photo)catalytic reactors.

The present work exploits Ti sheets and TiO 2 nanotube (TNT) layers and their surface modifications for the proliferation of different cells. Ti sheets with a native oxide layer, Ti sheets with a crystalline thermal oxide layer, and two kinds of TNT layers (prepared via electrochemical anodization) with a defined inner diameter of 12 and 15 nm were used as substrates. A part of the Ti sheets and the TNT layers was additionally coated by thin TiO 2 coatings using atomic layer deposition (ALD). An increase in cell growth of WI-38 fibroblasts (>50%), MG-63 osteoblasts (>30%), and SH-SY5Y neuroblasts (>30%) was observed for all materials coated by five cycles ALD compared to their uncoated counterparts. The additional ALD TiO 2 coatings changed the surface composition of all materials but preserved their original structure and protected them from unwanted crystallization and shape changes. The presented approach of mild surface modification by ALD has a significant effect on the materials' biocompatibility and is promising toward application in implant materials.

The continuous emission of nitrous oxides contributes to the overall air pollution and deterioration of air quality. In particular, an effective NO 2 sensor capable of low concentration detection for continuous monitoring is demanded for safety, health, and wellbeing. The sensing performance of a metal oxide-based sensor is predominantly influenced by the availability of surface area for O 2 adsorption and desorption, efficient charge transport, and size or thickness of the sensing layer. In this study, we utilized anodic one-dimensional (1D) TiO 2 nanotube layers of 5 μm thick which offer large surface area and unidirectional electron transport pathway as a platform to accommodate thin SnO 2 coatings as a sensing layer. Conformal and homogeneous SnO 2 coatings across the entire inner and outer TiO 2 nanotubes were achieved by atomic layer deposition with a controlled thickness of 4, 8, and 16 nm. The SnO 2 -coated TiO 2 nanotube layers attained a higher sensing response than a reference Figaro SnO 2 sensor. Specifically, the 8 nm SnO 2 -coated TiO 2 nanotube layer has recorded up to ten-fold enhancement in response as compared to the blank nanotubes for the detection of 1 ppm NO 2 at an operating temperature of 300 °C with 0.5 V applied bias. This is attributed to the SnO 2 /TiO 2 heterojunction effect and controlled SnO 2 thickness within the range of the Debye length. We demonstrated in this work, a tailored large surface area platform based on 1D nanotubes with thin active coatings as an efficient approach for sensing applications and beyond.

In this study, crystallization of amorphous TiO 2 nanotube (TNT) layers upon optimized laser annealing is shown. The resulting anatase TNT layers do not show any signs of deformation or melting. The crystallinity of the laser annealed TNT layers was investigated using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM). The study of the (photo-)electrochemical properties showed that the laser annealed TNT layers were more defective than conventional TNT layers annealed in a muffle oven at 400 °C, resulting in a higher charge recombination rate and lower photocurrent response. However, a lower overpotential for hydrogen evolution reaction was observed for the laser annealed TNT layer compared to the oven annealed TNT layer., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

One-dimensional TiO 2 nanotube layers with different dimensions were homogeneously decorated with 2D MoS 2 nanosheets via atomic layer deposition and employed for liquid and gas phase photocatalysis. The 2D MoS 2 nanosheets revealed a high amount of exposed active edge sites and strongly enhanced the photocatalytic performance of TiO 2 nanotube layers.

This work reports highly selective phosphopeptide enrichment using amorphous TiO 2 nanotubes (TiO 2 NTs) and the same material decorated with superparamagnetic Fe 3 O 4 nanoparticles (TiO 2 NTs@Fe 3 O 4 NPs). TiO 2 NTs and TiO 2 NTs@Fe 3 O 4 NPs materials were applied for phosphopeptide enrichment both from a simple peptide mixture (tryptic digest of bovine serum albumin and α-casein) and from a complex peptide mixture (tryptic digest of Jurkat T cell lysate). The obtained enrichment efficiency and selectivity for phosphopeptides of TiO 2 NTs and TiO 2 NTs@Fe 3 O 4 NPs were increased to 28.7 and 25.3%, respectively, as compared to those of the well-established TiO 2 microspheres. The enrichment protocol was extended for a second elution step facilitating the identification of additional phosphopeptides. It further turned out that both types of amorphous TiO 2 nanotubes provide qualitatively new physicochemical features that are clearly advantageous for highly selective phosphopeptide enrichment. This has been confirmed experimentally resulting in substantial reduction of non-phosphorylated peptides in the enriched samples. In addition, TiO 2 NTs@Fe 3 O 4 NPs combine high selectivity and ease of handling due to the superparamagnetic character of the material. The presented materials and performances are further promising for applications toward a whole range of other types of biomolecules to be treated in a similar fashion., Competing Interests: The authors declare no competing financial interest.

The present work presents a strategy to stabilize amorphous anodic self-organized TiO 2 nanotube layers against morphological changes and crystallization upon extensive water soaking. The growth of needle-like nanoparticles was observed on the outer and inner walls of amorphous nanotube layers after extensive water soakings, in line with the literature on water annealing. In contrary, when TiO 2 nanotube layers uniformly coated by thin TiO 2 using atomic layer deposition (ALD) were soaked in water, the growth rates of needle-like nanoparticles were substantially reduced. We investigated the soaking effects of ALD TiO 2 coatings with different thicknesses and deposition temperatures. Sufficiently thick TiO 2 coatings (≈8.4 nm) deposited at different ALD process temperatures efficiently hamper the reactions between water and F - ions, maintain the amorphous state, and preserve the original tubular morphology. This work demonstrates the possibility of having robust amorphous 1D TiO 2 nanotube layers that are very stable in water. This is very practical for diverse biomedical applications that are accompanied by extensive contact with an aqueous environment.

In this work, a high surface area interface, based on anodic one-dimensional (1D) TiO 2 nanotubes homogeneously decorated by Fe 3 O 4 nanoparticles (TiO 2 NTs@Fe 3 O 4 NPs) is reported for the first time for an unprecedented purification of His-tagged recombinant proteins. Excellent purification results were achieved from the model protein mixture, as well as from the whole cell lysate (with His-tagged ubiquitin). Compared to a conventional immobilized-metal affinity chromatography (IMAC) system, specific isolation of selected His-tagged proteins on behalf of other proteins was significantly enhanced on TiO 2 NTs@Fe 3 O 4 NPs interface under optimized binding and elution conditions. The combination of specific isolation properties, magnetic features, biocompatibility, and ease of preparation of this material consisting of two basic metal oxides makes it a suitable candidate for future purification of recombinant proteins in biotechnology. The principally new material bears a large potential to open new pathways for discoveries in nanobiotechnology and nanomedicine.

The utilization of the anodic TiO 2 nanotube layers, with uniform Al 2 O 3 coatings of different thicknesses (prepared by atomic layer deposition, ALD), as the new electrode material for lithium-ion batteries (LIBs), is reported herein. Electrodes with very thin Al 2 O 3 coatings (∼1 nm) show a superior electrochemical performance for use in LIBs compared to that of the uncoated TiO 2 nanotube layers. A more than 2 times higher areal capacity is received on these coated TiO 2 nanotube layers (∼75 vs 200 μAh/cm 2 ) as well as higher rate capability and coulombic efficiency of the charging and discharging reactions. Reasons for this can be attributed to an increased mechanical stability of the TiO 2 nanotube layers upon Al 2 O 3 coating, as well as to an enhanced diffusion of the Li + ions within the coated nanotube layers. In contrast, thicker ALD Al 2 O 3 coatings result in a blocking of the electrode surface and therefore an areal capacity decrease.

Anodic self-organized TiO 2 nanotube layers (with different aspect ratios) were electrochemically infilled with CuInSe 2 nanocrystals with the aim to prepare heterostructures with a photoelectrochemical response in the visible light. The resulting heterostructure assembly was confirmed by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). High incident photon-to-electron conversion efficiency values exceeding 55% were obtained in the visible-light region. The resulting heterostructures show promise as a candidate for solid-state solar cells.

In this work, we report for the first time on the use of melt spun glass-forming alloys - Ti 75 Zr 10 Si 15 (TZS) and Ti 60 Zr 10 Si 15 Nb 15 (TZSN) - as substrates for the growth of anodic oxide nanotube layers. Upon their anodization in ethylene glycol based electrolytes, highly ordered nanotube layers were achieved. In comparison to TiO 2 nanotube layers grown on Ti foils, under the same conditions for reference, smaller diameter nanotubes (~116nm for TZS and ~90nm for TZSN) and shorter nanotubes (~11.5μm and ~6.5μm for TZS and TZSN, respectively) were obtained for both amorphous alloys. Furthermore, TEM and STEM studies, coupled with EDX analysis, revealed a double-wall structure of the as-grown amorphous oxide nanotubes with Ti species being enriched in the inner wall, and Si species in the outer wall, whereby Zr and Nb species were homogeneously distributed., (Copyright © 2016 Elsevier B.V. All rights reserved.)