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Non-equilibrium fractal growth of MoS2 was induced by establishing an extremely Mo rich chemical vapor deposition (CVD) environment using a rapid heating rate in a confined reaction space. In addition, a detailed shape evolution mechanism was suggested based on the results of thermodynamics and kinetics studies. The extremely Mo rich CVD condition allowed various MoS2 flakes to be synthesized with triangular, star-like, and dendrite-like shapes in series, owing to the thermodynamic preference to increase the number of growth directions. Moreover, numerous small triangular crystals led to the formation of MoS2 flakes with jagged edges, probably as a result of the aggressive nucleation triggered by a fast and abundant supply of MoO3−x vapors. Lastly, using the MoS2 flakes with various fractal shapes, a systematic improvement of the hydrogen evolution reaction performance was demonstrated in accordance with the increase in the surrounding edge length. [ABSTRACT FROM AUTHOR]

Nanotubes of TiO2 (anatase) and their ordered arrays are emerging, promising candidates as efficient host materials in many applications such as photovoltaic cells, batteries, sensors and catalysts/catalytic supports, but the interplay between these structures and their transport properties has been reported only rarely. Monodisperse, stoichiometric TiO2 nanotubes with smooth morphology and controlled wall thickness were fabricated by template-directed low-temperature atomic layer deposition (ALD), followed by annealing at elevated temperatures. We present a study on the wall thickness-dependent crystallization behaviors due to physical and/or self-confinement, as well as on the corresponding electrical properties. Over certain wall thicknesses, unexpectedly, our TiO2 nanotubes were found to be a new type of mesoporous wide gap semiconductor in which they possess similar porosity, but in terms of conductivity differ from previously known mesoporous photoanodes (i.e., anodized surfaces of Ti films and sintered films consisting of TiO2 nanoparticles). These results were ascribed to the large, elongated anatase domains (by a factor of up to 15–40 wall thicknesses) that developed via boosted crystal growth on porous alumina templates (physical confinement) as well as to the highly curved tubular shape (self-confinement). Indeed, nanotube arrays with walls thicker than 10 nm exhibited an enhancement in conductivity, by more than three orders of magnitude, compared to sintered, mesoporous TiO2 (anatase) particles, approaching the bulk value. The nearly single-crystalline TiO2 nanotubes presented here should allow for a good model system to study TiO2-based surface chemistry and have potential for many applications in photovoltaic and/or catalytic systems. [ABSTRACT FROM AUTHOR]

We describe a procedure for one-step patterning and transfer of self-assembled organic monolayers (SAMs) on SiO2/Si substrates. This procedure was inspired from an idea of pattern formation at contact area, which realizes high patterning fidelity, and enables a universal approach for the micro/nanometre scale patterning of SAMs. [ABSTRACT FROM AUTHOR]