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In the present work we grow self-organized Ta 2 O 5 nanotube layers in a H 2 SO 4 /NH 4 F electrolyte at various elevated temperatures. Under optimized conditions we obtain 4 μm long nanotubes that are well adherent to the substrate and can be grown very homogenous over large surface areas. Moreover, the key advantage of this approach is that an open top morphology (initiation layer free) is obtained. After a suitable conversion treatment in NH 3 atmosphere Ta 3 N 5 nanotubes are obtained, that after (Co-Pi+Co(OH) x ) modification provide, under AM 1.5G illumination conditions, a photoelectrochemical current response of 4.7 mA cm −2 at +1.23 V vs RHE.

In the present work we report the fabrication of non-thickness-limited 1D nanostructures with nanochannelar structure by anodization of Ti50Zr alloy in hot glycerol-phosphate electrolyte. These nanochannelar structures show high and adjustable aspect ratios and provide as-formed already partial crystallinity for nanochannels. In vitro studies were performed to assess the inflammatory response to nanochannel coated surfaces using RAW 264.7 macrophages. The results show that these nanochannels yield a reduced amount of metabolically-active macrophages, low potential to induce macrophage fusion into FBGC, and low concentration of pro-inflammatory cytokines in the culture medium. Moreover, higher hydrophilicity and lower corrosion rates were registered, compared to compact oxide. Collectively, the results indicate a more favorable cellular response on such nanoscale topography as compared to compact oxide control substrate, and suggest that surface architecture design of nanochannel type on implant materials holds promise for biomedical applications.The use of titanium and its alloys in biomedical devices has been extensively investigated, especially for alloys possessing inherent antibacterial properties such as TiZr alloys. We report for the first time the growth of mesoporous structures, aligned oxide nanochannels, on Ti50Zr alloy. The advantages of these nanochannelar surfaces are a high surface area, a long range ordered nanoscale topology and already partial crystallinity in the as-grown state. In vitro studies performed on RAW 264.7 macrophages demonstrate the potential of nanochannels to lower the inflammatory response, thus reducing the foreign body reaction against Ti50Zr biomedical implants and promoting the successful integration of the implant.

Ordered W-doped Ta2O5 nanotube arrays were grown by self-organizing electrochemical anodization of TaW alloys with different tungsten concentrations and by a suitable high temperature ammonia treatment, fully converted to W:Ta3N5 tubular structures. A main effect found is that W doping can decrease the band gap from 2 eV (bare Ta3N5) down to 1.75 eV. Ta3N5 nanotubes grown on 0.5 at.% W alloy and modified with Co(OH)x as co-catalyst show ~33% higher photocurrents in photoelectrochemical (PEC) water splitting than pure Ta3N5. Keywords: W doping, Ta3N5 nanotubes, Anodization, Band gap tailoring, Photoelectrochemical water splitting

This work shows that highly ordered and mechanically stable micrometer-long Ta2O5 nanotube arrays can be fabricated by galvanostatic anodization in a few seconds. Typically, ~7.7 μm long nanotubes can be grown at 1.2 A cm−2 in only 2 s. Such nanotubes can be converted to Ta3N5 nanotube arrays by nitridation. Photoelectrochemical (PEC) water splitting using AM 1.5G illumination yields for the Ta3N5 nanotube photoanode modified with cobalt phosphate (Co–Pi) remarkable photocurrents of 5.9 mA cm−2 at 1.23 VRHE and 12.9 mA cm−2 at 1.59 VRHE and after Ba-doping a value of 7.5 mA cm−2 at 1.23 VRHE is obtained. Keywords: Ta2O5 nanotubes, Ta3N5 nanotubes, Photoelectrochemical water splitting

We grow vertically aligned single crystalline Ta2O5 nanorod arrays that can be converted to Ta3N5 nanorod arrays by nitridation. Combined with cobalt phosphate (Co-Pi) as a co-catalyst, such Ta3N5 nanorod photoanodes can yield photocurrent densities of ∼3.6 mA cm(-2) at 1.23 VRHE and ∼8.2 mA cm(-2) at 1.59 VRHE under AM 1.5G (100 mW cm(-2)) irradiation.

A two-step anodization of a Ti50Zr alloy results in a various sized nanotube oxide structures, which show an improved antibacterial activity. The nanotubes were formed in glycol with 15 vol.% H 2 O and 0.2 M NH 4 F by two-step anodization. The oxide layer grown during 2 h was removed by sonication in deionized water and anodized again for 1 h at the same conditions as in the first step. The removed layer acts as a nano-prepatterned surface, where higher ordered and open nanotubes can be achieved. The surface morphologies were analyzed by SEM and AFM, the surface wettability by contact angle measurements. The diameter and the length of the grown nanotubes are potential dependent between 20 and 100 nm in diameter and 2.3 and 5.7 μm in length, respectively. The antibacterial properties were evaluated in vitro on the formed nanotubes on the TiZr alloy against gram negative Escherichia coli bacteria. The E. coli (ATCC 8738) were cultured in a tube containing Luria Bertani medium at 37 °C. The optical density was determined after 18 h of incubation. In comparison, the smallest nanotubes exhibited the most efficient antibacterial behavior against E. coli bacterium. This suggests the use of small diameter nanotubes on TiZr for antimicrobial surface applications, which are susceptible for biofilms and microbial cultures.

Different iron oxide structures were formed by annealing of iron foils in air at temperatures between 500 °C to 800 °C. Depending on temperature, a significant variation in the hematite/magnetite ratio and a strongly temperature dependent morphology is obtained. While over a wide range of conditions more or less compact Fe3O4/Fe2O3 layers are obtained, at 600 °C rapid growth (several micrometer per hour) of highly crystalline hematite nanowires can be observed. Visible light photocurrent measurements in 1 M NaOH under AM 1.5 100 mW/cm2 conditions show that photocurrent density and the onset potential for water oxidation strongly shifted in the cathodic direction for the nanowire morphology. The results indicate that a simple air oxidation of iron can provide a rapid path to form hematite nanowires. Obtained layers are considerably active as photoanodes for solar water splitting. Keywords: Iron oxide, Thermal annealing, Water splitting, Photoanode

A NiFe layered double hydroxide (LDH) co-catalyst coated Ta3N5 nanorod electrode is fabricated by vapor deposition of Al on a Ta foil followed by anodizing the Al layer in oxalic acid, (40 V, 0.5 h), pore widening of the as-prepared porous Al2O3 by immersion in 5% aq.

Various TiO 2 nanotubes on Ti50Zr alloy have been fabricated via a two step anodization method in glycol with 15 vol.% H 2 O and 0.2 M NH 4 F under anodization controlled voltages of 15, 30 and 45 V. A new sonication treatment in deionized water with three steps and total sonication time as 1 min was performed after the first anodization step in order to remove the oxide layer grown during 2 h. The second step of anodization was for 1 h and took place at the same conditions. The role of removed layer as a nano-prepatterned surface was evidenced in the formation of highly ordered nanotubular structures and morphological features were analyzed by SEM, AFM and surface wettability. The voltage-controlled anodization leads to various nanoarhitectures, with diameters in between 20 and 80 nm. As biological assay, cell culture tests with MG63 cell line originally derived from a human osteosarcoma were performed. A correlation between nanostructure morphological properties as a result of voltage-controlled anodization and cell response was established.