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Nanostructured Anodic Oxides: Fabrication & Applications
摘要： The special issue of Current Nanoscience entitled “Nanostructured Anodic Oxides: Fabrication & Applications” comprises review papers focused on various aspects of these nanostructures. Nanostructured anodic oxides are awaking high hopes in the research community due to the solutions of emerging problems they offer. Classically, the anodic oxides on aluminum and its alloys are a protective coating, providing improved corrosion resistance [1-5], adhesion of primer to metallic substrate [6] and hardness of the anodized surface [7-10]. However, since two-step self-organized anodization was invented in 1995, allowing to form highly-ordered honey-comb ordering of the nanopores (Fig. 1a), numerous researches have been triggered. On one hand, still new electrolytes, operating conditions and electrolyte additives are being researched, providing new ranges of the applied voltages and consequently new ranges of oxides pore diameter and interpore distance [11-17]. On the other hand, research on anodic aluminum oxide is so mature, that already significant achievements in nanofabrication [18-22] (Figs. 1b-1c), surfaces with tunable wetting angle [23-27], cells culturing platforms [28, 29], biomaterials performance [29], sensing [30, 31], structural color generation [31, 32], photocatalysis [33], renewable energy harvesting [34-36], photonic crystals [37] and plasmonic materials [38] have been reported. Moreover, also other metals are being researched. Numerous achievements in anodization of Ti [39-45] W [46], Zr [47, 48], Cu [49-51], Fe [52], Sn [53], Zn [54] and stainless steel [55] allowed to make progress in renewable energy harvesting [43, 44, 51] (especially in the assembly of dye-sensitized solar cells [44] and photoelectrochemical water splitting [43, 51]), CO2 reduction to hydrocarbons [45], drug delivery systems [41], improvement in biomaterials performance [40] and photocatalysis [46]. Moreover, also intermetallic alloys, like FeAl [56, 57] and bimetallic, layered systems like Al-Ti [58] were anodized in order to form nanoporous oxides with tunable band gap and to ease the nanofabrication, respectively.
关键词： Nanostructured Anodic Oxides,Biomaterials,Anodization,Renewable Energy Harvesting,Photocatalysis,Sensing,Fabrication,Applications,Nanofabrication
更新于2025-09-04 15:30:14
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Enhanced Visible Light Sensitization of N-doped TiO2 Nanotubes Containing Ti-Oxynitride Species Fabricated via Electrochemical Anodization of Titanium Nitride
摘要： The concentration and chemical state of nitrogen represent critical factors to control the band-gap narrowing and the enhancement of visible light harvesting in nitrogen-doped titanium dioxide. In this study, photocatalytic TiO2-N nanoporous structures were fabricated by the electrochemical anodization of titanium nitride sputtered films. Doping was straightforwardly obtained by oxidizing as-sputtered titanium nitride films containing N-metal bonds varying from 7.3 to 18.5 % in the Ti matrix. Severe morphological variations into the as-anodized substrates were registered at different nitrogen concentration and studied by Small-Angle X-ray Scattering. Titanium nitride films with minimum N content of 6.2 at% N led to a quasi-nanotubular geometry, whilst an increase in N concentration up to 23.8 at% determined an inhomogeneous, polydispersed distribution of nanotube apertures. The chemical state of nitrogen in the TiO2 matrix was investigated by X-ray Photoelectron Spectroscopy depth profile analysis and correlated to the photocatalytic performance. The presence of Ti-N and β-Ti substitutional bonds, as well as Ti-oxynitride species was revealed by the analysis of N 1s X-ray Photoelectron Spectroscopy High Resolution spectra. The minimum N content of 4.1 at% in the TiO2-N corresponded to the lowest Ti-oxynitride ratio of 13.5 %. The relative variation of N-metal bonds was correlated to the visible light sensitization and the highest Ti-N/Ti oxynitride ratio of 3.3 was attributed to the lowest band-gap of 2.7 eV and associated to a threefold increase in the degradation of organic dye. Further increase of N doping led to a dramatic drop of Ti-N/Ti oxynitride ratio, from 3.3 to 0.4, which resulted in a loss photocatalytic activity. The impact of the chemical state of nitrogen towards efficient doping of TiO2 nanotubes is demonstrated with a direct correlation to the N loading and a strategy to optimise these factors based on a simple, rapid synthesis from titanium nitride.
关键词： visible light sensitization,photocatalytic performance,titanium nitride,nitrogen-doped titanium dioxide,electrochemical anodization
更新于2025-09-04 15:30:14