Preferential growth of thin rutile TiO2 films upon thermal oxidation of sputtered Ti films

Thin rutile TiO₂ films with (200) preferred orientation were fabricated by thermal oxidation of sputtered Ti metal films on a fused silica substrate. Experimental results indicate that the preferential crystal growth of (200)-oriented TiO₂ is determined by the competition between surface free energy and strain energy. The highly crystalline Ti film with (002) orientation has a greater tendency to promote the growth of (200)-oriented TiO₂. However, for the amorphous and low crystalline Ti films, orientation of the crystallites evolved in the resulting TiO₂ film tends to be randomly distributed. The extent of preferential crystal growth of TiO₂ (200) plane can be enhanced by decreasing the annealing temperature or the thickness of Ti film.     

In situ synthesis of transparent TiO2 nanoparticle/polymer hybrid

Transparent TiO₂ nanoparticle/polymer hybrids were synthesized from titanium isopropoxy methacrylate via hydrolysis and polymerization in 2-methoxymethanol. Crystalline TiO₂ nanoparticles were uniformly dispersed in the polymer matrix. A highly transparent free-standing TiO₂ nanoparticle/polymer hybrid film was synthesized. The refractive index (RI) of the hybrid films on Si substrates could be controlled by varying the concentration of TiO₂ nanoparticles: the RI increased with increase in Ti content. A further increase in the RI was achieved upon irradiation with ultraviolet light. A TiO₂ nanoparticle/PMMA hybrid without the silica component exhibited an RI of 1.717 and an Abbe number of 21.6.     

Electrochemical corrosion behaviors of titanium covered by various TiO<Subscript>2</Subscript> nanotube films in artificial saliva

TiO₂ nanotube films obtained by anodization have shown great promise as biomaterials. In the present work, we report on the corrosion behaviors of titanium (Ti) with various TiO₂ nanotubes prepared by using controlled anodization procedures. Special emphasis is put on the impact of film morphologies on the corrosion resistance of the Ti substrate. The corrosion behaviors of Ti with different nanotube films were studied in artificial saliva using open-circuit potential measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques. Ti covered by TiO₂ nanotube films showed the markedly enhanced corrosion resistance properties compared to bare Ti. The existence of the compact oxide layer formed in a fluoride-free electrolyte was found to be beneficial for improving corrosion resistance properties. Besides, the TiO₂ nanotube films obtained by two-step anodization had better corrosion resistance than those obtained by single-step anodization, though they used the identical anodization parameters.     

Hydrothermal growth of rutile TiO2 nanorod films on titanium substrates

Rutile TiO₂ nanorod films have been successfully prepared on titanium substrate via a hydrothermal method using Tetra-n-butyl titanate as Ti source in the presence of concentrated hydrochloric acid. The effect of Ti substrate annealing treatment and adding of additional alkali metal chlorides in hydrothermal solution on the growth of TiO₂ nanorod films has been studied using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and water contact angle measurement. The growth mechanism of the TiO₂ nanorods on Ti substrate has also been discussed. It has shown that the initial rutile film transformed from anatase promotes the nucleation and epitaxial growth of rutile TiO₂ nanorods. The superior wettabilities of the TiO₂ nanorods resulted from treatments of vacuum and ultraviolet show great potential for applications in orthopaedic, dental implants, and possible photocatalysis.     

Polyimide/silica/titania nanohybrids via a novel non-hydrolytic sol–gel route

Polyimide/silica/titania hybrid films were prepared via a non-hydrolytic sol–gel route. Silicic acid and titanium tetrachloride were used as the precursors of silica and titania, respectively. The absorption band of Si–O–Ti bonds in FTIR spectra of the hybrid films revealed the formation of the hybrid inorganic network between SiO₂ and TiO₂. Scanning electron microscopy results indicated that the nanometer-scaled inorganic domains were homogeneously dispersed in polyimide matrix due to the introduction of silica-stabilized TiO₂ and the interactions between organic and inorganic phases. The studies on the optical properties of the hybrid films indicated the red-shift of the absorption band increased with increasing TiO₂ content, while all the hybrid films maintained their transparencies. The surface resistances of the hybrid samples decreased with increasing TiO₂ content. The thermal decomposition temperature of the ternary hybrid films decreased slightly with increasing TiO₂ content. This kind of hybrid materials may have potential application in the preparation of opto-electronic devices.     

In vitro release of cisplatin from sol–gel processed organically modified silica xerogels

SiO₂, SiO₂/PEG and SiO₂/PDMS xerogels were examined as polymeric carriers for the controlled release of cisplatin—an antineoplasmic medicine. Drug/carrier systems were prepared by the sol–gel method. The effect of organic substitution of the silica xerogel matrix and drying conditions on the release of cisplatin was evaluated. Based on the presented results of the study it may be stated that sol–gel method is useful for entrapping a cisplatin in the pores of organically modified silica gels and for releasing cisplatin mainly in the way of diffusion from the pores of the lattice under the in vitro conditions. The use of organic impurities in silica gel increased the release of cisplatin from xerogel (from 62% to 97% within 7 days), and thermal treatment of all xerogels with cisplatin at the temperature of 80 °C resulted in the acceleration of the drug release (2 days) and increase of the released drug (89–98%).     

Conductivity of nanometer TiO2 thin films by magnetron sputtering

The conductivity of nanometer TiO₂ thin films was presented in this paper. The dependence of the conductivity of TiO₂ thin films on the thickness of the film and the substrate material were educed. The TiO₂ films were deposited by reactive magnetron sputtering of a Ti targets in an Ar+O₂ mixture in a conventional sputtering reactor. The thickness of the films deposited on Ti varied in the range from 15 to 225 nm. The resistivity of the films was measured at room temperature in the air. It was found that the conductivity of TiO₂ thin films varies in the range from conductor, semiconductor to nonconductor. This was attributed to electrons transfer at the interface between the TiO₂ and substrates, and the depth of electrons transfer was determined by the difference of work function.     

Preparation and hydrophilicity of TiO2 sol-gel derived nanocomposite films modified with copper loaded TiO2 nanoparticles

In this study, TiO₂ nanocomposite films with 10 g/L of TiO₂ and copper loaded TiO₂ nanoparticles as nanofillers were deposited on the glass substrates using the sol gel dip-coating method. FE-SEM and UV-vis spectrophotometer were used to evaluate morphological and optical properties of copper loaded titania nanoparticles. In addition, XPS and water contact angle techniques were used to study the surface properties and superhydrophilicity of titania nanocomposite films, respectively. The results indicated that copper loaded TiO₂ nanoparticles had a significant effect on the hydrophilicity of nanocomposite film and maintaining it in a dark place for a long time (6.2 degree for titania nanocomposite films with copper loaded nanoparticle and 23.7 degree for nanocomposite film with titania nanoparticles).     

Electrolytic deposition of titania films as interference coatings on biomedical implants: Microstructure,chemistry and nano-mechanical properties

TiO₂ films with uniform thickness were electrolytically deposited on AISI 316L stainless steel and Ti6Al4V substrates for potential use as color coded biocompatible coatings on biomedical implants. Deposition occurred via a peroxoprecursor method from solutions containing TiCl₄ and H₂O₂. By optimizing electrolyte formulation and deposition parameters, thin stoichiometric titania films with almost uniform thickness-dependent interference colors, similar as known from the color anodization processes of Ti-alloys, were obtained. Crack-free films were found up to 140 nm on AISI 316L and up to 190 nm on Ti6Al4V substrates. After thermal annealing at 450 °C of as-deposited amorphous peroxotitanium hydrate films, Raman and transmission electron microscopy showed highly stoichiometric, nanocrystalline anatase films. Chemical depth profiling was performed by glow-discharge optical emission spectrometry (GD-OES), showing clearly a densification and loss of water during annealing. On AISI 316L, GD-OES revealed stoichiometric TiO₂ films containing a small Fe (3–4 at.%) and Cr (1 at.%) contamination due to thermal diffusion from the substrate. On Ti6Al4V, the comparison between electrolytic TiO₂ films and color-anodization in different sulfuric and phosphoric acid containing electrolytes showed significant higher purity of electrolytic films, absent of V, Al, S, P contaminations as they were found in anodic oxides (4–6 at.% Al, 1–2 at.% V), especially V and S being problematic in biomedical applications. Annealing greatly increased the mechanical properties of the green films. A nano-hardness of 5.5–6.6 GPa, elastic modules close to substrate modules, excellent adhesion and very ductile behavior were found from nanoindentation and scratch tests. Based on thickness uniformity, high purity and good mechanical properties, electrolytic TiO₂ films are not only attractive as biocompatible colored coatings on non-anodizable biomedical alloys such as AISI 316L and CoCrMo, but also for Ti-alloys that are anodized for protective as well as coding reasons prior to implantation.     

Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO₂). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N₂ adsorption–desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV–vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO₂ tubes than in mesoporous silica matrix.     

High-temperature anomalies of dielectric constant in TiO2 thin films

Anatase and rutile TiO₂ thin films were prepared by chemical vapor deposition with precursors Ti(OPrⁱ)₄ and Ti(dpm)₂(OPrⁱ)₂ (dpm = 2,2,6,6-tetramethylheptane-3,5-dione and Prⁱ = isopropyl), respectively. The dielectric properties of TiO₂ thin films have been studied in 20-1100 K temperature range in air, in controlled Ar/O₂ atmospheres, and in vacuum with silicon-based metal-insulator-semiconductor Au/TiO₂/Si capacitors. High-temperature (T_c ∼ 980 K) anomalous behavior of dielectric constant was observed in both anatase and rutile TiO₂ thin films.     

Chemical–hydrothermal combined surface modification of titanium for improvement of osteointegration

The chemical–hydrothermal combined synthesis of TiO₂ and CaTiO₃ films on pure Ti substrates was examined with a focus on crystallinity and surface morphology of the films. Pure Ti disks were chemically treated with H₂O₂/HNO₃ solutions at 353 K for 5–60 min in order to introduce a TiO₂ layer with low crystallinity on the surface. The samples were then hydrothermally treated in an autoclave at 453 K for 12 h. Anatase-type TiO₂ and perovskite-type CaTiO₃ films with high crystallinity were obtained upon treatment with distilled water and an aqueous solution of Ca(OH)₂, respectively. Cracks in the TiO₂ precursor films disappeared after hydrothermal treatment. Uniform and crack-free films could be obtained by the present process. In addition, in vitro formation of hydroxyapatite (HAp) on the films was investigated. Obtained samples were immersed in SBF (Simulated Body Fluid), adjusted to 310 K. A light HAp precipitate could be observed on non-surface modified Ti after 6 days of immersion. In contrast, precipitate formed after only 2 days on the present oxide films. The present surface modification was confirmed to drastically promote deposition of HAp on the surface of Ti.     

The role of Ag particles deposited on TiO2 or Al2O3 self-organized nanoporous layers in their behavior as SERS-active and biomedical substrates

In this paper, we present recent results of investigations of hybrid materials consisting of nanoporous oxides layers loaded with Ag nanoparticles: Ag/TiO₂-n/Ti and Ag/Al₂O₃-n/Al (where “n-“stands for nanotubes), which could be used as active SERS substrates or as bioactive materials in medicine (implants). Simple electrochemical, chemical and physical methods appear suitable for fabricating such hybrid materials having different functional properties.     

Synthesis of visible-light-responsive Fe(III)-doped TiO2 films using graphene oxide-based composite sheets as sacrificial building blocks

Graphene oxide sheets have been utilized as both carriers and sacrificial building blocks to prepare freestanding Fe(III)-doped TiO₂ composite films. First, graphene oxide sheets are decorated by TiO₂ particles, and the as-obtained products are further modified by Fe(III) precursors, forming relatively uniform composite sheets. Assembling of these composite sheets enables different substances (Ti and Fe) to be distributed uniformly in the as-formed bulk films, which results in the formation of homogeneous freestanding Fe(III)-doped TiO₂ composite films under calcinations. Furthermore, the contents of Fe(III) in TiO₂ films can be controlled easily by adjusting deposition amount of Fe(III) precursors in graphene oxide-TiO₂ composite sheets. UV–vis diffuse reflectance results and photocurrent tests indicate that addition of Fe can enhance visible light responses of TiO₂ films. At certain doping amount of Fe(III), the as-prepared TiO₂ films display the strongest photocurrent signals under visible light irradiation.     

The microstructure and wettability of the TiOx films synthesized by reactive DC magnetron sputtering

Different chemical state of titanium oxide films were deposited on commercially pure Ti (CP Ti) by reactive DC magnetron sputtering under different oxygen flow rates to examine a possibility of their applications to endovascular stents. The chemical composition and crystal structure of the obtained films were analyzed by XPS and XRD, respectively. In dependence on the deposition parameters employed, the obtained films demonstrated different mixture of anatase TiO₂, Ti₂O₃, TiO and Ti. The wettability of the films was measured by the water contact angle variation. By formation of titanium oxide film on CP Ti, contact angle was decreased. In order to modify and control the surface wettability, the resultant TiO_x films were etched subsequently by different plasma. The wettability was influenced by etched process according to the decreased contact angle values of etched TiO_x film. Furthermore, TiO_x films became highly hydrophilic by ultraviolet (UV) irradiation, and returned to the initial relatively hydrophobic state by visible-light (VIS) irradiation. The wettability of the TiO_x film was enabled to convert between hydrophilic and hydrophobic reversibly by alternative UV and VIS irradiation. By adjusting deposition parameter and further modification process, the wettability of the TiO_x films can be changed freely in the range of 0–90°.     

Sol–gel preparation and properties of Ag–TiO2 films on surface roughened Ti–6Al–4V alloy

Ag–TiO₂ films (Ag/Ti?=?3·3, 9·1 at-%) were sol–gel coated on Ti–6Al–4V alloy that had been surface roughened by the NaOH–HCl treatment for antibacterial applications. Scanning electron microscopy observation showed that pore size of the surface layer of NaOH–HCl treated Ti–6Al–4V alloy increased with the NaOH concentration. Ag–TiO₂ films on the surface roughened substrate were adherent and crack-free. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses indicated that Ag existed in metallic state, and the films completely covered the roughened substrate. X-ray diffraction peaks of the substrate and anatase TiO₂ were detected. The Ag–TiO₂ films on the roughened substrate exhibited good adhesion quality and high cohesion strength in the indentation test. The potentiodynamic polarisation test showed that the TiO₂ and Ag–TiO₂ films improved corrosion resistance of the substrate.     

Synthesis and characterization of TiO<Subscript>2</Subscript>-incorporated silica foams

Titania-incorporated silica (TiO₂–SiO₂) porous materials have great applications in diverse areas. In this work, TiO₂–SiO₂ porous materials with tunable Si/Ti molar ratio (R) have been successfully prepared through a one-pot method under a near-neutral condition. With decreasing Si/Ti R, a phase transition from a macroporous foam-like structure to mesostructure is observed. The resultant TiO₂–SiO₂ porous materials possess large surface areas and high pore volumes. In addition, the titania species are homogenously dispersed in silica matrix when Si/Ti R ≥ 10. Our contribution provides a convenient method to synthesize TiO₂/SiO₂ porous materials with very large pore size, high pore volume, and relatively high titania content well dispersed in the silica wall framework.     

Delivery of a Therapeutic Protein for Bone Regeneration from a Substrate Coated with Graphene Oxide

The therapeutic efficacy of drugs often depends on the drug delivery carrier. For efficient delivery of therapeutic proteins, delivery carriers should enable the loading of large doses, sustained release, and retention of the bioactivity of the therapeutic proteins. Here, it is demonstrated that graphene oxide (GO) is an efficient carrier for delivery of therapeutic proteins. Titanium (Ti) substrates are coated with GO through layer‐by‐layer assembly of positively (GO‐NH₃⁺) and negatively (GO‐COO^?) charged GO sheets. Subsequently, a therapeutic protein (bone morphogenetic protein‐2, BMP‐2) is loaded on the GO‐coated Ti substrate with the outermost coating layer of GO‐COO^?(Ti/GO‐). The GO coating on Ti substrate enables loading of large doses and the sustained release of BMP‐2 with preservation of the structure and bioactivity of the drug. The extent of in vitro osteogenic differentiation of human bone marrow‐derived mesenchymal stem cells is higher when they are cultured on Ti/GO‐ carrying BMP‐2 than when they are cultured on Ti with BMP‐2. Eight weeks after implantation in mouse models of calvarial defects, the Ti/GO‐/BMP‐2 implants show more robust new bone formation compared with Ti, Ti/GO‐, or Ti/BMP‐2 implants. Therefore, GO is an effective carrier for the controlled delivery of therapeutic proteins, such as BMP‐2, which promotes osteointegration of orthopedic or dental Ti implants.     

Influence of metal plasma ion implantation on photo-sensitivity of anatase TiO2 thin films

Nano-scale TiO₂ thin films were synthesized by using sol-gel and spin-coating techniques on glass substrates for photo-catalytic applications. The Ti(IV) butoxide-based TiO₂ thin films were optimized for transforming into the high-purity crystalline anatase phase when calcined at 500 °C. To further enhance the photo-catalysis sensitivity of TiO₂ thin films for use in visible light environments, a metal plasma ion implantation process was implemented to modify the band gap electron configuration of Ti. Various transition metal atoms such as Ni, Cu, V, and Fe were ionized and accelerated at 20 keV to impinge on the surface of TiO₂ substrates at a dosage of 5 × 10¹⁵ ions/cm². ESCA analysis confirmed the binding energy shift of Ti by 0.8-1.2 eV, which accounted for the increased effective positive charge of Ti, resulting in more effective electron trapping capability and, thus, the electron-hole pair separation. In addition, the absorption spectroscopy demonstrated that optical absorption in the visible light regime occurred in specimens implanted with transition metal ions, likely due to the formation of extra impurity energy levels within the original TiO₂ band gap energy structure. Among all tested implant materials, the band gap energy of TiO₂ was effectively reduced by Cu and Fe ion implantation by 0.9-1.0 eV, which was sufficient enough to excite valence electrons over the band gap in visible light environments. The feasibility of the metal-doped TiO₂ thin films for effective applications under visible light irradiation was further confirmed by using super-hydrophilicity contact-angle measurement.     

Investigation of superhydrophilic mechanism of titania nano layer thin film—Silica and indium oxide dopant effect

In this paper, TiO₂?CSiO₂?CIn₂O₃ nano layer thin films were deposited on glass substrate using sol?Cgel dip coating method. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements were used to evaluate chemical structure, surface composition, hydroxyl group contents and superhydrophilicity of titania films. FTIR result indicated that Si?CO?CSi, Si?CO?CTi and Ti?CO?CTi bands formed in TiO₂?CSiO₂?CIn₂O₃ sample. According to XPS, the hydroxyl content for TiO₂, TiO₂?CSiO₂ and TiO₂?CSiO₂?CIn₂O₃ films was calculated as 11·6, 17·1 and 20·7%, respectively. The water contact angle measurements indicated that silica and indium oxide dopant improved the superhydrophilicity of titania nano film surface especially in a dark place. The enhanced superhydrophilicity can be related to the generation of surface acidity on the titania nano film surfaces. In the present state, superhydrophilicity is induced by the simultaneous presence of both Lewis and Bronsted sites.