Nanostructured Oxide Surfaces Research Articles

Tape of the truth: Ta2O5 nanopore array formed under broad potential range and SERS potential after silver sputtering

The deposition of a plasmonic metal layer on a nanostructured oxide surface is one of the important methods of preparing a platform for surface-enhanced Raman scattering (SERS) measurements. In this contribution, we describe the formation of SERS substrates by the deposition of a silver layer on ordered a Ta2O5 nanopore array. The influence of various experimental anodization process parameters on the morphology of a Ta2O5 nanopore array was carefully studied. It was found that the formation of a Ta2O5 nanopore array is possible under a broad potential range (15–50 V) in a highly acidic solution containing F− ions. In some cases, the nanopore array structures were covered by an outer layer rich in F− and SO42− ions, which could easily be removed using adhesive tape or by sonication. The deposition of an Ag layer led to SERS activity. The optimal Ag layer thickness was specified based on SEM and DRS measurements. The SERS substrates formed exhibited high point-to-point, sample-to-sample and time durability.

Zirconia nanotube coatings - UV-resistant superhydrophobic surfaces

Surface modifications influence material interactions such as wettability, imparting hydrophobicity or hydrophilicity. Mainstream research focused on enhancing product shelf-life directs attention towards superhydrophobic surfaces (SHS). SHS offer several benefits for out-door applications such as self-cleaning, anti-soiling, anti-mist etc. Recently, such surfaces were created by hydrophobization of anodized titania, which although effective lacked a long-term stability of their hydrophobic modifications due to it being susceptible to UV-mitigated degradation. In light of this situation, ZrO2-nanotubes are evaluated with regard to their application as transparent UV-stable superhydrophobic coatings. Nanostructured oxide surfaces are created via single-step electrochemical anodization. The absence of HF acid-based pre-etching steps offer a safe and alternatively a green synthesis route. Anodized oxides are modified using octadecylphosphonic acid (OPA) self-assembled monolayers, demonstrate superhydrophobicity and are at par with conventionally employed coatings such as PTFE, PFDPA and PTES. The OPA-coatings are evaluated for their mechanical stability under a jet of water, chemical stability under indirect sunlight irradiation in air/water and direct UV exposure. Zirconia nanotubular films were evaluated for optical transparency using light microscopy and surface wettability of the different zirconia-composites was compared to the model system - titania. Structural and compositional differences of the SAM layer upon time dependent decay were analyzed with X-ray photoelectron spectroscopy.

Nanorods grown by copper anodizing in sodium carbonate

Self-organized anodization of copper in 0.1 M Na2CO3 electrolyte was studied in order to obtain nanostructured oxide surface on the metal substrate. Linear sweep voltammetry (LSV) revealed that the most suitable voltage range for anodic film formation is from 3 to 31 V. In this range (except between 3 and 7 V), the oxide is formed as nanorods, with the diameter of the anodically grown nanostructures increasing with the applied voltage. The smallest diameter of the nanorods was found to be 28 ± 9 nm (15 V), while the greatest diameter was 109 ± 15 nm (30 V). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy pointed out that the nanorods consist of crystalline CuO (tenorite) and Cu2O (cuprite), and amorphous Cu(OH)2. Moreover, the greater the anodizing voltage, the greater the CuO content versus Cu2O. The formed nanostructured materials may find applications in photocatalysis and catalytic electrochemical reduction of carbon dioxide into light hydrocarbons.

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

Phthalocyanines (Pc) are well-known light-harvesting compounds. However, despite the tremendous efforts on phthalocyanine synthesis, the achieved energy conversion efficiencies for Pc-based dye-sensitized solar cells are moderate. To cast light on the factors reducing the conversion efficiency, we have undertaken a time-resolved spectroscopy study of the primary photoinduced reactions at a semiconductor-Pc interface. ZnO nanorods were chosen as a model semiconductor substrate with enhanced specific surface area. The use of a nanostructured oxide surface allows to extend the semiconductor-dye interface with a hole transporting layer (spiro-MeOTAD) in a controlled way, making the studied system closer to a solid-state dye-sensitized solar cell. Four zinc phthalocyanines are compared in this study. The compounds are equipped with bulky peripheral groups designed to reduce the self-aggregation of the Pcs. Almost no signs of aggregation can be observed from the absorption spectra of the Pcs assembled on a ZnO ...

Oxygen Vacancy Structure Associated Photocatalytic Water Oxidation of BiOCl

A central issue in understanding photocatalytic water splitting on a stoichiometric or defective nanostructured oxide surface is its adsorption mode and related reactivity. More than just improving the adsorption of water on oxide surfaces, we demonstrate in this work that surface oxygen vacancies (OVs) also offer a possibility of activating water toward thermodynamically enhanced photocatalytic water oxidation, while the water activation state, as reflected by its capability to trap holes, strongly depends on the structures of OVs. Utilizing well-ordered BiOCl single-crystalline surfaces, we reveal that dissociatively adsorbed water on the OV of the (010) surface exhibits higher tendency to be oxidized than the molecularly adsorbed water on the OV of the (001) surface. Analysis of the geometric atom arrangement shows that the OV of the BiOCl (010) surface can facilitate barrierless O–H bond breaking in the first proton removal reaction, which is sterically hindered on the OV of the BiOCl (001) surface, a...

Anomalous Diffusion in Supported Lipid Bilayers Induced by Oxide Surface Nanostructures

Hierarchic structure and anomalous diffusion on submicrometer scale were introduced into an artificial cell membrane, and the spatiotemporal dependence of lipid diffusion was visualized on nanostructured oxide surfaces. We observed the lipid diffusion in supported lipid bilayers (SLBs) on step-and-terrace TiO(2)(100) and amorphous SiO(2)/Si surfaces by single molecule tracking (SMT) method. The SMT at the time resolution of 500 μs to 30 ms achieved observation of the lipid diffusion over the spatial and temporal ranges of 100 nm/millisecond to 1 μm/second. The temporal dependence of the diffusion coefficient in the SLB on TiO(2)(100) showed that the crossover from anomalous diffusion to random diffusion occurred around 10 ms. The surface fine architecture on substrates will be applicable to induce hierarchic structures on the order of 100 nm or less, which correspond to the microcompartment size in vivo.

Biocompatibility of metal carbides on Fe–Al–Mn-based alloys

The biocompatibility and microstructural variation of Fe–Al–Mn (FAM)-based alloys have been investigated clearly. The ((Fe,Mn) 3AlC x ) carbide (κ′-carbide) and Fe 0.6Mn 5.4C 2 carbide (κ-carbide) as well as Cr 7C 3 (Cr-carbide) were formed on FAM alloy, following phase transformation by heat treatment and surface functionalization. These carbides have important role in forming nanostructure and oxidation layer. Moreover, it was found that the albumin adsorbed onto the surface increased with increasing nano-metal carbides. Therefore, heat treatment and surface functionalization such as electro-discharging and anodization not only generates a nanostructural precipitates, but also converts the alloy surface into a nanostructured oxide surface, then increasing the alloy biocompatibility.

C60 on Nanostructured Nb-Doped SrTiO3(001) Surfaces

Nanostructured Nb-doped SrTiO3(001) surfaces were investigated with STM, and the surface patterns for observed nanostructures were assigned. Sequential C60 deposition onto these nanostructured templates reveals distinct growth modes, including discrete small C60 islands on the c(4 × 2) reconstruction surface, parallel one-dimensional C60 chains on (6 × 2) dilines, C60 double chains on (8 × 2) trilines, epitaxial C60 close packed adlayers over (11 × 2) tetralines, and two-dimensional ordered C60 dimer arrays on (7 × 6) waffles. These structural diversities mainly stem from the relatively strong adsorbate−substrate interactions as well as the surface topography demands. The nanostructured oxide surfaces as templates thus have great potential in molecular nanoarchitecture.

Effect of electrical-discharging on formation of nanoporous biocompatible layer on titanium

Abstract In this study, we performed an electrical discharge machining (EDM), by which a recast layer was formed on a titanium surface. Subsequently, an α-phase and a γ-TiH-(γ-hydride)-phase were formed on the recast layer by electrical-discharging. Nano-(δ + γ) hydrides play important roles in the formation of nanostructural oxide layers. Electrical-discharging not only generates a nanostructural recast layer but also converts the alloy surface into a nanostructured oxide surface, which increases the alloy biocompatibility. A γ-hydride microstructure was also formed on the recast layer following electrical-discharging. The microstructure had a tetragonal structure with lattice constant a = 0.421 nm. In the recast layer, a transition, α → (α + δ) → (δ + γ) → γ, occurred during electrical-discharging. This result has never been previously reported. The recast layer that contains nanophases was dissolved during electrical-discharging; by this process, electrical-discharging for a short duration yields nanoporous TiO2. Hence, electric discharging for a short duration leads to the production of nanostructures as well as bioactive titanium.

Preparation of bioactive amorphous-like titanium oxide layer on titanium by plasma oxidation treatment

The effectiveness of titanium plates with Ar and oxygen plasma treatment in producing a biocompatible layer between the plate and bone tissue has been investigated. An amorphous-like oxide layer was found to form on the surface of the titanium bone plate after oxygen plasma treatment. Oxygen and titanium bonding states were observed for the titanium surface following plasma oxidation. Furthermore, nano-(α + rutile-TiO 2) were formed on the amorphous-like oxide layer following glow-discharging. Surface cleaning and oxidation modification by plasma treatments thus are believed to improve the biocompatibility and tissue healing. Furthermore, glow-discharging not only generates a nanostructural oxide layer, but also converts the alloy microstructure into a nanostructured oxide surface, increasing the alloy biocompatibility.

Effect of electro-discharging on formation of biocompatible layer on implant surface

This investigation elucidates the biocompatibility and microstructural variation of Fe–Al–Mn and electro-discharged Fe–Al–Mn alloys. A recast layer was formed on the alloy surface, following electro-discharged machining. γ-Phase and Fe 0.6Mn 5.4C 2 carbide (κ-carbide) were formed on the recast layer following electro-discharging. The γ-phase and κ-carbide are nanostructures. The nano-(γ-phase + κ-carbide) has important roles in forming nanostructured oxide layer. Furthermore, electro-discharging not only generates a nanostructural recast layer, but also converts the alloy surface into a nanostructured oxide surface, increasing the alloy biocompatibility.