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Titanium dioxide (TiO2 ), tin dioxide (SnO2 ), and heterostructured TiO2 /SnO2 nanotube (NT) arrays have been fabricated by template-assisted atomic-layer deposition (ALD) for use as anodes in a lithium-ion battery (LIB). TiO2 NT arrays with 8 nm thick walls showed higher capacity (≈250 mA h g(-1) after the 50th cycle at a rate of C/10) than the typical theoretical capacity of bulk TiO2 and a radically improved capacity retention property upon cycling. SnO2 NT arrays with different wall thicknesses (8, 10, 13, and 20 nm) were also fabricated and their electrochemical performances were measured. All of the SnO2 NT arrays showed substantially higher initial irreversible capacity and higher reversible capacity than those of bulk TiO2 . Thinner walls of the SnO2 NTs result in better capacity retention. Heterotubular structures of TiO2 (5 nm)/SnO2 (10 nm)/TiO2 (5 nm) were successfully fabricated, and displayed a sufficiently high capacity (≈300 mA h g(-1) after 50 cycles) with exceptionally improved cycling performance up to the 50th cycle., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Surface decoration strategy for one-dimensional nanostructures will improve their electrical, optical, mechanical, and electrochemical performances dramatically. Heterogeneous growth/deposition on surfaces, however, may create undesired junction interfaces in the system. Here we report a procedure during which amorphous titania nanotubes are readily self-branched with crystalline titanate nanorods at room temperature. The starting amorphous titania nanotubes were prepared by low-temperature atomic layer deposition combined with the template-directed approach. We routinely observed the self-branching phenomenon of crystalline titanate nanorods with a few nanometers in diameter onto the surfaces of the amorphous titania nanotubes in mild alkali solutions. The resulting structures were analyzed by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and electron energy loss spectroscopy. The reactivity of the hierarchical titania nanotube arrays was observed to be improved as a Li secondary battery electrode. Upon complete consumption of the amorphous body of titania nanotubes, in addition, titanate nanosheets/layers consisting of single TiO(2) layers with unit-cell thickness were obtained, elucidating the formation mechanism of layered titanate materials by alkali treatment.

We report, for the first time, a novel procedure for fabricating multiwall anatase TiO2nanotubes by utilizing templated atomic layer deposition synthesis in conjunction with alternating TiO2/Al2O3nanolaminate structures. [ABSTRACT FROM AUTHOR]

Nanostructured electrodes and their flexible integrated systems have great potential for many applications, including electrochemical energy storage, electrocatalysis and solid-state memory devices, given their ability to improve faradaic reaction sites by large surface area. Although many processing techniques have been employed to fabricate nanostructured electrodes onto flexible substrates, these present limitations in terms of achieving flexible electrodes with high mechanical stability. In this study, the adhesion, mechanical properties and flexibility of TiN nanotube arrays on a Pt substrate were improved using a Ti interlayer. Highly ordered and well-aligned TiN nanotube arrays were fabricated on a Pt substrate using a template-assisted method with an anodic aluminum oxide (AAO) template and atomic layer deposition (ALD) system. We show that with the use of a Ti interlayer between the TiN nanotube arrays and Pt substrate, the TiN nanotube arrays could perfectly attach to the Pt substrate without delamination and faceted phenomena. Furthermore, the I-V curve measurements confirmed that the electric contact between the TiN nanotube arrays and substrate for use as an electrode was excellent, and its flexibility was also good for use in flexible electronic devices. Future efforts will be directed toward the fabrication of embedded electrodes in flexible plastic substrates by employing the concepts demonstrated in this study. [ABSTRACT FROM AUTHOR]

We report visualization of three-dimensional domain structures in ferroelectric PbTiO3 (PTO) nanotubes (NTs) using piezoresponse force microscopy (PFM). The domain distributions of the x, y, and z-axes in PTO NTs were separately measured out-of and in-planes at angles of 0° and 90° by vertical and lateral PFM. The separately obtained PFM images were combined to reconstruct the complex domain structures based on some basic assumptions and finite element modeling. The cross-sectional domain configurations of the PTO NTs were visualized by the proposed approach. The results can provide insight into complex domain configurations of ferroelectric nanostructures. [ABSTRACT FROM AUTHOR]