Orientation control of liquid crystals using carbon-nanotube-magnetic particle hybrid materials.

We have developed a simple yet versatile method for aligning liquid crystals (LCs) by using magnetic-field oriented single-walled carbon nanotubes (SWNTs) that were modified with magnetic particles. A high degree of homeotropic/planar LC alignment was achieved by SWNTs being exposed to a very low strength magnetic field, combined with strong π-π interactions between the biphenyl group in the LCs and the wall of the SWNTs.

Effect of the exposure time of hydrazine vapor on the reduction of graphene oxide films.

Preparation of highly uniform graphene with superior electrical properties is one of the key issues in graphene researches. The use of hydrazine vapor for reducing the graphene oxide (GO) has attracted considerable attention in recent year due to the simplicity, reproduciblilty and availibility of one-step procedure. Here, we investigated the effect of the exposure time of hydrazine vapor on the reduction of GO films. Raman spectroscopy, UV-vis spectroscopy, X-ray photoelectron spectrophotometer, and X-ray diffraction results showed that the reduction rate of the GO films by hydrazine vapor was very fast in the initial 10 min, and thereafter the reduction rate slowed down. Upon 12 hours of hydrazine vapor treatment, the reduction came to a level that further hydrazine vapor treatment did not bring about significant improvement of the reduction. We demonstrated that this might be attributed to the slow penetration of hydrazine vapor into the GO films in order to reduce the inner sheets of the GO films.

Vertical alignment of reduced graphene oxide/Fe-oxide hybrids using the magneto-evaporation method.

We developed a new method for fabricating reduced graphene oxide (RGO)/Fe-oxide structures from graphene oxide (GO), and for the simultaneous vertical alignment of the RGOs using a single-step process that involves a magnetic field and the fixation of the aligned structures by means of direct evaporation of the films.

Vertical alignment of carbon nanotubes using the magneto-evaporation method.

We developed a novel method of vertical alignment of SWNTs using a single-step process for the simultaneous vertical alignment of the SWNTs by a magnetic field and the fixation of their alignment by means of the direct evaporation of the films. We fabricated Fe-oxide/SWNT samples that are reacted by iron-oleate complex, oleic acid and cut SWNTs in 1-octadecene. The Fe-oxide/SWNT samples are dispersed in N,N-dimethylformamide and the resulting solution was deposited on an ITO glass substrate using the spraying method with magnetic field. After evaporation of the SWNT solution in the presence of a magnetic field, we transferred the nanotubes to the vacuum-evaporator chamber, and titanium is evaporated by e-beam evaporation to hold the vertical alignment of the SWNTs. The resulting SWNTs exhibit the formation of a high degree of vertically aligned SNWTs over a large area. We showed that the degree of orientation of the SWNTs is strongly influenced by the field strength, film thickness of the evaporating molecules and evaporating rates. This technique takes significant advantages of the alignment of SWNTs with high aspect ratio at room temperature, without any organic binders and without the need for further alignment procedures. Moreover, this method might be applicable to other anisotropic materials with high aspect ratio.