Growth Of Rutile TiO2 Nanorods Research Articles

Switching of Electron Transport Direction from the Long Axis to Short Axis in a Radial SnO2(Head)-Rutile TiO2 Nanorod(Tail) Heteromesocrystal Photocatalyst.

Heteroepitaxial growth of rutile TiO2 nanorods from SnO2 seeds yielded radial heteromesocrystals consisting of SnO2(head) and rutile TiO2 nanorod(tail) with the SnO2(head) oriented toward the center (TiO2-NR//SnO2 HEMCs). Iron oxide clusters were formed on the surface by the chemisorption-calcination technique. The FeOx-surface modification gives rise to drastic increases in the photocatalytic activity for aerobic oxidation of 2-naphthol under irradiation of UV and visible light. As a 2D-model for 3D-TiO2-NR//SnO2 HEMC, electrochemical measurements were performed for the rutile TiO2-NR array formed on a fluorine-doped tin oxide (SnO2:F) electrode. The results showed that the FeOx clusters possess electrocatalytic activity for a multielectron oxygen reduction reaction, and the high photocurrent of the electrode is remarkably reduced by the FeOx-surface modification. Consequently, the striking photocatalytic activity of FeOx/TiO2-NR//SnO2 HEMCs was ascribable to the switching of the electron transport direction necessary for the charge separation from the long axis of the TiO2 NR to the short axis.

P.705 European Brain Research Area (EBRA): Promoting and enhancing collaboration in brain research

The mechanism of hydrothermal heteroepitaxial growth of rutile TiO2 nanorods from SnO2 seed nanocrystals under acidic conditions was studied. On the basis of the experimental and density functional theory (DFT) simulation results, we have presented a reaction mechanism that chloride ions are preferentially adsorbed on the oxygen-defect sites on the (1 1 0) plane of TiO2 to suppress the growth, and consequently, TiO2 grows in the [0 0 1] direction to yield the nanorod with the (1 1 0)-faceted side walls. Importantly, the DFT simulations indicated that easy defect formation on the (1 1 0) facet is a key to the preferential adsorption of chloride ions.

Action of chloride ions as a habit modifier in the hydrothermal crystal growth of rutile TiO2 nanorod from SnO2 seed crystal

The mechanism of hydrothermal heteroepitaxial growth of rutile TiO2 nanorods from SnO2 seed nanocrystals under acidic conditions was studied. On the basis of the experimental and density functional theory (DFT) simulation results, we have presented a reaction mechanism that chloride ions are preferentially adsorbed on the oxygen-defect sites on the (110) plane of TiO2 to suppress the growth, and consequently, TiO2 grows in the [001] direction to yield the nanorod with the (110)-faceted side walls. Importantly, the DFT simulations indicated that easy defect formation on the (110) facet is a key to the preferential adsorption of chloride ions.

Vapor-Solid Reaction Growth of Rutile TiO2 Nanorods and Nanowires for Li-Ion-Battery Electrodes.

A new synthetic method to grow O-deficient rutile TiO2(s) nanorods (NRs) and nanowires (NWs) by a vapor–solid reaction growth method is developed. TiCl4(g) was employed to react with commercially supplied CaTiO3(s) (size 2–4 μm) at 973 K under atmospheric pressure to generate TiO2(s) NRs (diameters 80–120 nm, lengths 1–4 μm). The reaction employing TiCl4(g) and CaO(s) at 973 K also generated CaTiO3(s) (size 4–13 μm) as the intermediate which reacted further with TiCl4(g) to produce NWs (diameters 80–120 nm, lengths 4–15 μm). This is the first report of 1D rutile TiO2(s) nanostructure with such a high aspect ratio. Both of the NRs and the NWs, with compositions TiO1.81 and TiO1.65, respectively, were single crystals grown in the [001] direction. Their morphology was affected by the reaction temperature, the concentration of TiCl4(g), and the particle size of CaTiO3(s). The NRs and the NWs were investigated as anode materials for Li+-ion batteries. At constant current rates 1, 2, and 5 C (1 C = 170 mA g–1) for 100 cycles, the cycling (1.0–3.0 V) performance data of the NRs were 146, 123, and 104 mA h g–1, respectively. On the other hand, the cycling performance data of the NWs were 120, 80, and 52 mA h g–1, respectively. This is attributed to the high Li+ ion diffusion rate (DLi+) of the NRs (29.52 × 10–15 cm2 s–1), which exceeds that of the NWs (8.61 × 10–15 cm2 s–1). Although the [001] growth direction of the NR crystals would provide the fastest channels for the diffusion of Li+ ions and enhance the battery capacity, the extremely long channels in the NWs could hamper the diffusion of the Li+ ions. The O-deficiency in the structure would increase the conductivity of the electrode material and improve the stable cycling stability of the batteries also. The long-term cycling test at 2 C for the battery constructed from the NRs retained 121 mA h g–1 after 200 cycles and 99.2 mA h g–1 after 800 cycles. The device has an excellent long-term cycling stability with a loss of only 0.04% per cycle.

Advanced scanning probe lithography using anatase-to-rutile transition to create localized TiO2 nanorods.

In this article, we demonstrate the position-controlled hydrothermal growth of rutile TiO2 nanorods using a new scanning probe lithography method in which a silicon tip, commonly used for atomic force microscopy, was pulled across an anatase TiO2 film. This process scratches the film causing tiny anatase TiO2 nanoparticles to form on the surface. According to previous reports, these anatase particles convert into rutile nanocrystals and provide the growth of rutile TiO2 nanorods in well-defined areas. Due to the small tip radius, the resolution of this method is excellent and the method is quite inexpensive compared to electron-beam lithography and similar methods providing a position-controlled growth of semiconducting TiO2 nanostructures.

An economical approach combining vacuum assisted soft imprinting and hydrothermal treatments to fabricate lotus leaf-like biomimetic hierarchical TiO2 structures

Here we report an low-cost method for fabricating 3D hierarchical TiO2 films with lotus-leaf-like micro/nano structures. With some low pressure provided by two middle-sized binder clips, the microscale pillar arrays of lotus leaf could be easily imprinted into the TiO2 sol film. In addition, if a low vacuum was introduced into the imprinting process, the complex laminar sub-microstructure on the micro pillars could also be duplicated with high fidelity. Hierarchical TiO2 micro/nano-structures were subsequently fabricated by the hydrothermal growth of TiO2 nanorods on the micro-structured TiO2 film. SEM observation and XRD analysis revealed that the micro-structured TiO2 film was anatase phase, which served as a nucleation layer for the growth of rutile TiO2 nanorods. This hierarchical surface exhibited a WCA of 155° after surface fluoroalkylsilane modification.

Influence of substrates and rutile seed layers on the assembly of hydrothermally grown rutile TiO2 nanorod arrays

Rutile TiO2 nanorod arrays (NRAs) are applicable in various prospective technologies. Hydrothermal methods present a simple technique to fabricate such NRAs. In this report, we present the fabrication of seed layers for the hydrothermal growth of rutile TiO2 nanorods via sputter deposition, electron-beam evaporation, and sol-gel method and study the influence of each on the growth behavior. To satisfy the requirements of numerous applications, p-type silicon, platinum, levitating carbon membranes, a template made of polystyrene spheres, and commercial fluorine tin oxide (FTO) were employed as substrates. We document the structural properties of the TiO2 seed layers and describe the relationship between the characteristics of the seed crystals, the growth evolution, and the appearance of as-grown nanorods. Various growth stages of rutile TiO2 nanorods are compared depending on whether they are grown on polycrystalline TiO2 or FTO seed layers. In both cases, a homogenous TiO2 bottom layer is formed at the seed layer/substrate interface, which is essential for electronic applications such as hybrid solar cells. Detached NRAs illustrate the effect of rutile FTO and TiO2 on the porosity of this bottom layer. Further details about the formation process of this layer are obtained from the growth on confined seed layers fabricated by electron-beam lithography.

Growth of rutile TiO2 nanorods in Ti and Cu ion sequentially implanted SiO2 and the involved mechanisms

TiO2 in nanoscale exhibits unique physicochemical and optoelectronic properties and has attracted much more interest of the researchers. In this work, TiO2 nanostructures are synthesized in amorphous SiO2 slices by implanting Ti ions, or sequentially implanting Ti and Cu ions combined with annealing at high temperature. The morphology, structure, spatial distribution and optical properties of the formed nanostructures have been investigated in detail. Our results clearly show that the thermal growth of TiO2 nanostructures in SiO2 substrate is significantly enhanced by presence of post Cu ion implantation, which depends strongly on the applied Cu ion fluence, as well as the annealing atmosphere. Due to the formation of Cu2O in the substrate, rutile TiO2 nanorods of large size have been well fabricated in the Ti and Cu sequentially implanted SiO2 after annealing in N2 atmosphere, in which Cu2O plays a role as a catalyst. Moreover, the sample with well-fabricated TiO2 nanorods exhibits a narrowed band gap, an enhanced optical absorption in visible region, and catalase-/peroxidase-like catalytic characteristics. Our findings provide an effective route to fabricate functional TiO2 nanorods in SiO2 via ion implantation.

Superhydrophilic TiO2 nanorod films with variable morphology grown on different substrates

Rutile TiO2 nanorods were allowed to grow on FTO or glass substrate under the assistance of an anatase TiO2 nanoparticle/SiO2 primary film through a hydrothermal process. The component of TiO2 nanoparticle was expected to be dissolved and then to induce the growth of rutile TiO2 nanorods during the hydrothermal process and the component of SiO2 was designed to play two roles in providing landing site for rutile TiO2 nucleuses and improving the wettability of the nanorod films. The morphology of the nanorod films could also be varied with the primary film. The nanorod films derived from the primary film performed an enhanced superhydrophilicity as compared with that directly formed on the FTO surface, and showed superhydrophobicity after surface modification.

Effects of variations in precursor concentration on the growth of rutile TiO2 nanorods on Si substrate with fabricated fast-response metal–semiconductor–metal UV detector

This study aimed to investigate the effects of variations in precursor concentration (TiCl3 solution) on the structural, morphological, and optical properties of rutile titanium dioxide (TiO2) nanorods and fabricated metal–semiconductor–metal UV detector depending on the optimal sample. The nanorods were prepared from an aqueous solution of titanium (III) chloride (TiCl3) on p-type, (111)-oriented Si substrates at different concentrations of TiCl3 solutions (2, 3, 4, and 5mM). The experimental results showed that the TiO2 nanorods grown at 4mM concentration exhibited optimal structural properties. A fast-response metal–semiconductor–metal UV detector was fabricated by depositing Pt contacts on the front of the optimal sample via RF reactive magnetron sputtering. Upon exposure to 365nm light (2.3mW/cm2) at 5V bias voltage, the device showed 44.4 sensitivity. In addition, the internal gain was 1.45, and the photoresponse peak was 70mA/W. The response and the recovery times were calculated to be 7.8ms upon illumination to a pulse UV light (365 nm) at 5V bias voltage.

Growth of Rutile TiO<sub>2</sub> Nanorods by Chemical Bath Deposition Method on Silicon Substrate at Different Annealing Temperature

Effects of annealing treatment on growth of rutile TiO2nanorods on structural, morphological and optical properties of TiO2nanorods were investigated. The nanorods were fabricated on p-type (111)-oriented silicon substrates and, all substrates were seeded with a TiO2seed layer synthesized by radio-frequency reactive magnetron sputtering system. Chemical bath deposition (CBD) was carried out to grow rutile TiO2nanorods on Si substrate at different annealing temperatures (350, 550, 750, and 950 °C). Raman spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analyses showed the tetragonal rutile structure of the synthesized TiO2nanorods. Optical properties were examined by photoluminescence spectroscopy. The spectra exhibit one strong UV emission peak which can be seen at around 390 nm for all of the samples. In the visible region, TiO2demonstrated two dominant PL emissions centered at around 519 and 705 nm. The experimental results showed that the TiO2nanorods annealed at 550 °C exhibited the optimal structural properties. Moreover, the CBD method enabled the formation of photosensitive, high-quality rutile TiO2nanorods with few defects for future optoelectronic nanodevice applications.

Growth of TiO2 nanorod arrays on reduced graphene oxide with enhanced lithium-ion storage

We demonstrate the synthesis of a sandwich-like nanocomposite by planting rutile TiO2 nanorods onto reduced graphene oxide (RGO) via a modified seed-assisted hydrothermal growth method. The synthetic process consists of functionalization of graphene oxide (GO), followed by hydrolytic deposition of TiO2 nanoparticles on GO and reduction, and finally hydrothermal growth of rutile TiO2 nanorods on RGO. The resultant nanocomposite, i.e. rutile TiO2 nanorod arrays on RGO (TONRAs–RGO), exhibits largely enhanced reversible charge–discharge capacity and rate capability compared to bare TiO2 nanorods (TONRs) due to its unique structure and superior conductivity. The rate performance of the nanocomposite is also better than that of anatase TiO2 nanoparticles. This study will inspire better design of RGO-based nanocomposites for high energy density lithium-ion battery applications.

Growth of rutile TiO2 nanorods on anatase TiO2 thin films on Si-based substrates

Abstract