Rutile TiO2 Nanostructures Research Articles

Morphology control of rutile TiO2 hierarchical architectures and their excellent field emission properties

Titanium dioxide nanoarchitectures with well-defined morphologies have been successfully synthesized by a hydrothermal process at temperature 180 °C for 4 h using titanium butoxide, oleic acid and hydrochloric acid as precursor materials. Different hierarchical morphologies such as cauliflower, 3D microsphere, densely-packed nanorod array, step edge faceted nanorod, branched structures of the rutile TiO2 nanostructures could be easily controlled by varying the volume fraction of the added hydrochloric acid. The structural, photoluminescence and field emission properties of the as-prepared nanoarchitectures were investigated. Among the different morphologies, dense nanorod arrays and multilevel branched architectures showed good field emission properties. Morphology, surface-related defects and oxygen vacancies were found to be the major responsible factors for the observed variations of field emission properties. Compared to any previously reported TiO2 based field emitter, lower turn-on field at 2.76 V μm−1 and higher field-enhancement factors 7.44 × 103 were observed for the hierarchically dense TiO2 nanorods array. Therefore, these nanoarchitectures can be used in vacuum microelectronic applications.

Continually adjustable oriented 1D TiO2 nanostructure arrays with controlled growth of morphology and their application in dye-sensitized solar cells

Oriented, single-crystalline, one-dimensional (1D) TiO2 nanostructures would be most desirable for providing fascinating properties and features, such as high electron mobility or quantum confinement effects, high specific surface area, and even high mechanical strength, but achieving these structures has been limited by the availability of synthetic techniques. In this study, a concept for precisely controlling the morphology of 1D TiO2 nanostructures by tuning the hydrolysis rate of titanium precursors is proposed. Based on this innovation, oriented 1D rutile TiO2 nanostructure arrays with continually adjustable morphologies, from nanorods (NRODs) to nanoribbons (NRIBs), and then nanowires (NWs), as well as the transient state morphologies, were successfully synthesized. The proposed method is a significant finding in terms of controlling the morphology of the 1D TiO2 nano-architectures, which leads to significant changes in their band structures. It is worth noting that the synthesized rutile NRIBs and NWs have a comparable bandgap and conduction band edge height to those of the anatase phase, which in turn enhances their photochemical activity. In photovoltaic performance tests, the photoanode constructed from the oriented NRIB arrays possesses not only a high surface area for sufficient dye loading and better light scattering in the visible light range than for the other morphologies, but also a wider bandgap and higher conduction band edge, with more than 200% improvement in power conversion efficiency in dye-sensitized solar cells (DSCs) compared with NROD morphology.

A novel technique for tailored surface modification of dental implants – a step wise approach based on plasma immersion ion implantation

A novel technique based on plasma immersion ion implantation (PIII) is presented to modify titanium implant surfaces. Initially, the implants are cleaned with argon to remove contaminants and the nanostructures are created by the bombardment of the surface with a mix of noble gases. Desired crystal structure of the titanium is obtained by the implantation of oxygen on the contaminant-free surface with particular nanostructures. In this study, turned implants modified by PIII revealed a high density of rutile-TiO2 nanostructures. Turned implants used as control revealed mainly microstructures and amorphous crystal structure. Surface roughness values were similar at the microscale for both turned and turned+PIII implants. Bone response was evaluated by removal torque tests of implants placed in the rabbit tibia and femur. After 4weeks of healing, turned+PIII demonstrated higher removal torque values (P=0.001) compared to turned implants. The presence of rutile-TiO2 nanostructures may explain the improved bone formation to turned+PIII implants.

Template-Free Synthesis and Photocatalytic Application of Rutile TiO2 Hierarchical Nanostructures

A simple template-free hydrothermal method was employed to synthesize flower-shaped single-crystal rutile TiO2 hierarchical nanostructures without calcination process. Scanning electron microscope and transmission electron microscope images show that rutile TiO2 nanostructures with diameters of 1–1.5 μm are composed of nanorods with a wimble shape. The band gap of the as-prepared rutile TiO2 is about 3.02 eV by ultraviolet–visible absorption spectrum. The photocatalytic performance of the as-obtained samples as catalysts for Rhodamine B (RhB) degradation under simulated solar light was greatly enhanced with the assistance of a small amount of H2O2. In the H2O2-containing system, the as-prepared rutile TiO2 photocatalyst was more efficient in the photodegradation of RhB than commercial P25. The stability and recycle of the rutile TiO2/H2O2 system were also investigated.

Control synthesis of rutile TiO2 microspheres, nanoflowers, nanotrees and nanobelts via acid-hydrothermal method and their optical properties

Semiconductor rutileTiO2 nanostructures with a diversity of well-defined morphologies, such as microspheres, nanoflowers, nanotrees and nanobelts, are synthesized via an acid-hydrothermal process without any structure-directing agents. Their morphologies, crystal structures and orientation relationship were characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. By controlling hydrochloric acid concentration, anisotropic growth of the rutile TiO2 leads to various morphologies. The synthesis mechanism of rich TiO2 nanostructures was also studied. Finally, the relationship between optical properties and the structural complexity of the rutileTiO2 nanocrystals was characterized.

In Situ Coating of Flame-Made TiO2 Particles with Nanothin SiO2 Films

Rutile TiO2 particles made by flame spray pyrolysis (FSP) were coated in a single step with SiO2 layers in an enclosed flame reactor. This in situ particle coating was accomplished by a hollow ring delivering hexamethyldisiloxane (HMDSO) vapor (precursor to SiO2) through multiple jets in swirl cross-flow to Al-doped nanostructured rutile TiO2 aerosol freshly made by FSP of a solution of titanium tetraisopropoxide and aluminum sec-butoxide in xylene. The as-prepared powders were characterized by (scanning) transmission electron microscopy (STEM and TEM), energy dispersive X-ray analysis, X-ray diffraction, nitrogen adsorption, electrophoretic mobility, DC plasma optical emission (DCP-OES), and Fourier transform infrared (FT-IR) spectroscopy. The coating quality was assessed further by the photocatalytic oxidation of isopropyl alcohol to acetone. The effect of HMDSO injection point and vapor concentration on product particle morphology was investigated. The titania particles were uniformly SiO2-coated with controlled and uniform thickness at a production rate of about 30 g h(-1) and exhibited limited, if any, photoactivity. In contrast, spraying and combusting equivalent mixtures of the above Si/Al/Ti precursors in the above reactor (without delivering HMDSO through the hollow ring) resulted in particles segregated in amorphous (SiO2) and crystalline (TiO2) domains which exhibited high photocatalytic activity.

Synthesis of Arrayed, TiO2 Needlelike Nanostructures via a Polystyrene-block-poly(4-vinylpyridine) Diblock Copolymer Template

Arrayed, needlelike nanostructures of rutile phase crystal TiO2 were grown on a Si substrate containing TiO2 seeds prepared through a thin polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer template. The morphology of the deposited TiO2 nanostructures was characterized by field-emission scanning electron microscopy, X-ray diffraction, and transmission electron microscopy (TEM). By using TiO2 seeds prepared from their diblock copolymer PS-b-P4VP template, we fabricated arrayed, needlelike rutile TiO2 nanostructures with variable spatial positions and densities. The distance between two TiO2 needle bunches (120 and 160 nm) could be controlled using block copolymer templates with different molecular weights.