Facile and Scalable Fabrication of Flexible Reattachable Ionomer Nanopatterns by Continuous Multidimensional Nanoinscribing and Low-temperature Roll Imprinting.

We develop a facile route to the scalable fabrication of flexible reattachable ionomer nanopatterns (RAINs) by continuous nanoinscribing and low-temperature roll imprinting, which are repeatedly attachable to and detachable from arbitrarily shaped surfaces. First, by sequentially performing continuous nanoinscribing over a polymer substrate along the multiple directions, we readily create the multidimensional nanopattern, which otherwise demands complex nanofabrication. After its transfer to an elastomer pad for use as a soft nanoimprinting stamp, we then conduct a low-temperature roll imprinting of the ionomer film to fabricate a flexible and highly transparent RAIN. Reversible loosening of ionic units in the ionomer material at the mild temperature as low as ∼60-70 °C enables the faithful nanopatterning over thermosensitive organic compounds and fragile materials under a slight pressure. The excellent adhesion purely emerging from ionic interactions uniquely realizes the conformal attachability and clean detachability of RAINs for universal targets in ambient conditions, particularly beneficial for individual wearable and mobile devices requiring the user-specific "on/off" of the nanopattern-driven functionalities. As one vivid example, we demonstrate that a single light-emitting device can be switched from the focused pointer to the widespread flashlight depending on the RAIN application upon user's purpose.

Simple fabrication of carbon/TiO2 composite nanotubes showing dual functions with adsorption and photocatalytic decomposition of Rhodamine B.

Carbon/TiO2 composite nanotubes were fabricated via a very simple electrospinning process and their dual functionalities of adsorptivity and photocatalytic activity were evaluated using Rhodamine B (RhB) as a model organic pollutant. A poly(vinyl alcohol) (PVA) aqueous solution was directly electrospun into a coagulation bath containing titanium (IV) tetraisopropoxide (TTIP) solution so that PVA-core/TiO2-shell composite nanofibers were formed through the in situ sol-gel reaction of TTIP. The carbon/TiO2 composite nanotubes were then fabricated by heat treatment of composite nanofibers under nitrogen atmosphere. By using several characterization methods, we confirmed that the resultant nanotubes consisted of anatase TiO2 nanocrystallites embedded in a carbonaceous matrix. The prepared nanotubes exhibited fast adsorption of RhB with high capacity compared with a commercial porous carbon, and they also showed the photocatalytic decomposition activity for the dye molecules under UV irradiation comparable to the degradation by P-25 and ST-01 (commercial TiO2). Finally, the carbon/TiO2 composite nanotubes exhibited several cycle performances of adsorption-photodegradation for RhB. This indicates that the composite nanotubes can adsorb and photodecompose organic pollutants repeatedly without additional activating processes.

Comparative study of carbon dioxide and nitrogen atmospheric effects on the chemical structure changes during pyrolysis of phenol-formaldehyde spheres.

The effect of CO(2) atmosphere on the chemical structure changes of resol-type phenol-formaldehyde spheres during pyrolysis was investigated, in comparison with that of N(2) atmosphere, using FT-IR, TGA, and elemental analysis techniques. It was found that, in contrast to the expectation that CO(2) may act as an oxidizing agent at high temperature, it behaves very similar to N(2) during pyrolysis of PF spheres up to 700 degree C, but results in a somewhat different extent of some specific reactions. That is, although the reactions occurring up to 700 degree C were dominated by crosslinking and/or polyaromatization under both CO(2) and N(2) atmospheres, fewer alkyl-phenolic ether bonds were formed under CO(2) than under N(2). As a consequence, the samples carbonized under CO(2) at 700 degree C were found to have more pendant groups on the edge carbon atoms of carbon in the carbonized samples than those prepared under N(2) atmosphere.