Nanostructured Titania Films Research Articles

In situ synthesis of nanostructured titania film on NiTi shape memory alloy by Fenton's oxidation method

Fenton's oxidation method was successfully used to synthesize an ideal titania film in situ on NiTi shape memory alloy(SMA) for medical applications. Characterized with scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, inductively coupled plasma mass spectrometry and electrochemical tests, it is found that the titania film produced by Fenton's oxidation method on NiTi SMA is nanostructured and has a Ni-free zone near its top surface, which results in a notable improvement in corrosion resistance and a remarkable decrease in leaching of harmful Ni ions from NiTi SMA in simulated body fluids. The improvement of effectiveness to corrosion resistance and the reduction in Ni release of NiTi SMA by Fenton's oxidation method are comparable to those by oxygen plasma immersion ion implantation reported earlier.

Nanoporous Titania by Embossing with PMMA Nanopoles Made from Nanoporous Alumina Template

We produced highly uniform nanoporous thin films of the dense array of titania (TiO2) pores of 70~80 nm in diameter with nanoimprinting method. Titania in HCl and 2-propanol solution was coated on an indium tin oxide (ITO) surface and embossed with an array of PMMA nanopoles which was produced using a nanoporous alumina (Al2O3) template. Two-step anodization was introduced to produce highly uniform and dense nanopores on the aluminum surface. The polymethyl methacrylate (PMMA) was poured onto and infiltrated into the nanoporous alumina surface which was heated at 150 oC. The alumina nanopores and aluminum plate were removed by wet-etching leaving an array of PMMA nanopoles. These highly uniform nanostructured titania films will be very useful for photovoltaic and photocatalytic applications where nanostructuring of surface with controlled dimensions are essential.

Ultrahigh-Surface-Area Anatase Thin Films by Direct Oxidation of Ti Film with Hydrogen Peroxide

Nanostructured titania films are formed by directly oxidizing titanium with hydrogen peroxide. A low-temperature anneal transforms the films from an amorphous phase to anatase crystal. Surface-area measurements of the annealed nanostructured titania using the Brunauer, Emmett, and Teller method reveal a specific surface area of 535 m 2 /g, the highest ever reported for a nanostructured titania film. The low-temperature anneal is compatible with heat-treated polyimide or polyester substrates for roll-to-roll processing of flexible electronics or solar cells.

Plasma‐controlled nanocrystallinity and phase composition of TiO2: A smart way to enhance biomimetic response

This contribution sheds light on the role of crystal size and phase composition in inducing biomimetic apatite growth on the surface of nanostructured titania films synthesized by reactive magnetron sputtering of Ti targets in Ar+O(2) plasmas. Unlike most existing techniques, this method enables one to deposit highly crystalline titania films with a wide range of phase composition and nanocrystal size, without any substrate heating or postannealing. Moreover, by using this dry plasma-based method one can avoid surface hydroxylation at the deposition stage, almost inevitable in wet chemical processes. Results of this work show that high phase purity and optimum crystal size appear to be the essential requirement for efficient apatite formation on magnetron plasma-fabricated bioactive titania coatings.

Enhanced Ability of Nanostructured Titania Film to Assist Photodegradation of Rhodamine B in Water Through Natural Aging

Gradually but significantly improved abilities of titania films with various nanofeatures and crystal structures to assist photodegradation of trace rhodamine B in water were observed when the films were subjected to natural aging. The so-called natural aging behavior can be attributed to the gradual increase in the surface hydroxyl groups that are beneficial to the photocatalytic reaction.

Titanium fullerenoid oxides

Nanostructured titanium oxide films synthesized by supersonic cluster beam deposition were analyzed by high-resolution transmission electron microscopy. Nanoparticles were produced in a pulsed microplasma cluster source in the presence of He or helium-oxygen mixture as carrier gas. While films grown using He consist only of rutile and anatase TiO2 nanocrystals formed upon exposure to air, films grown with a He∕O mixture also contain isolated TiOx cages that closely resemble carbon fullerenes. The diameter of the cages ranges from about 0.9to2.7nm. A fraction of the cages have irregular shapes, possibly induced by oxygen vacancies. The TiOx fullerenoids grow in the gas phase, in a narrow temperature/pressure range within the cluster source, and are preserved through low-energy deposition.

Nitrogen ion implanted nanostructured titania films used in dye-sensitised solar cells and photocatalyst

Nanostructured titania films were implanted with N at energies between 10 and 40 keV and ion dose range 10 14 to 5 × 10 16 cm −2 and the films were characterized using various techniques. The surface morphology of the nanostructured films has been modified with ion implantation as observed using scanning electron microscopy (SEM). From SIMS depth profile analysis the amount of nitrogen was found to increase with increasing ion energy. The profile of N appeared to have a skewed Gaussian curve and the results have been explained using SRIM theoretical simulations. A maximum nitrogen concentration of about 6.08 at% has been quantified by X-ray photoelectron spectrometer (XPS). Transmittance of the films decreases with increasing implantation energy and ion dose due to defects created by the ion implantation. Annealing can remove defects and thereby increase the transmittance of the films.

Synthesis and characterization of nanostructured titania film for photocatalysis

Nanostructured titania film was synthesized using nonionic triblock copolymer P123 as surfactant template removed by ethanol extraction followed by calcination at different temperatures. The results of SAXRD indicate that the mesostructures of the films are not damaged until the calcination temperature as high to 450 °C. The results of TG/DSC, UV–visible and Raman spectra analyses provide the evidences for anatase phase to occur at 400 °C and above. The results of TEM and N 2 adsorption and desorption measures indicate that, with temperature increasing from 350 to 500 °C, anatase nanocrystal sizes and pore diameter increase, while the calculated BET surface area decreases. The photocatalytic activity of the films was characterized by the degradation test of methylene blue, and the results show that it depends on both the specific surface area and the crystallinity of nanostructured titania film.

Deposition of nanostructured titania films by particle-assisted MOCVD

Nanostructured TiO 2 films and particles were prepared in a tubular flow reactor at atmospheric pressure using titanium tetraisopropoxide (TTIP) as precursor. The morphology of the films and particles was characterised with scanning and transmission electron microscopy. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy analysis of the deposits were also performed. Depending on the location of the substrate in the reactor, i.e., the film forming species (vapour, monomers, particles), the morphology of the deposits was very different. In this paper, a qualitative explanation is given for the different film morphologies. The formation and growth of the particles are also explained. Close to the inlet, diffusion-controlled chemical vapour deposition (CVD) took place resulting in a dendritic (leaf-like) structure. Once particles are formed in the gas phase, they deposit together with vapour resulting in granular, nanostructured films with incorporated particles. After the point where all the vapour is consumed, separate, nearly monodisperse, 15-nm-sized particles deposited due to a competition between diffusion and thermophoresis. Downstream of the reactor, porous deposits consisting of agglomerated nanosized particles formed. The influence of the reactor temperature and the inlet precursor concentration on the morphology of the deposits was also investigated and is explained.

Factors that Affect Protein Adsorption on Nanostructured Titania Films. A Novel Spectroelectrochemical Application to Sensing

Nanoporous, thick (8 μm) films of titania (TiO2) were prepared and used for the immobilization of proteins. A detailed study has been made into the factors influencing protein adsorption on TiO2. Among these, we investigated pH, ionic strength of solution, protein surface charge, protein size, and immobilization time. Protein immobilization is found to be remarkably stable, attributed to secondary binding processes occurring after the initial immobilization. We also investigated the electrochemical properties of these films using cyclic voltammetry and spectroelectrochemistry and found that not only was direct reduction of the FeIII−heme to FeII−heme of both cytochrome-c and hemoglobin possible but that all the protein in the film is electroactive. We further demonstrate the use of a hemoglobin/TiO2 film as an aerobic sensor for nitric oxide. Optical sensing is demonstrated, with a limit of detection of 1 μM.

Vacuum-Plasma Sprayed Nanostructured Titanium Oxide Films

Nanostructured titanium oxide films were fabricated by vacuum-plasma spraying. The microstructure of the films was characterized with SEM, TEM, and XRD. The chemical state of the titanium oxide of the films was analyzed using XPS. The results indicated that the vacuum-plasma sprayed nanostructured titanium oxide films possessed a corallike structure with small pores and agglomerated grains, which was composed of nanosized particles. The main phases of the films were anatase and rutile, and their relative content was determined by the plasma parameters. Low-valence titanium cations were also found in the films.