We are exploring magnetic materials including hydrogen bond networks in them, named “H-bonded magnets”, whose magnetic properties can be controlled by external stimuli such as heat, pressure, or electric field and so on via their hydrogen bonding units. We introduce structure and magnetic properties of coordination polymers, bis(glycolato)copper(II) [Cu(HOCH2CO2)2] and its deuterium substituted derivatives, which teach us a hint for construction of H-bonded magnets.
We developed the synthesis technique of highly crystalline graphene thin films from the defective graphene oxide using thermal treatment in a reactive ethanol environment at high temperature above 1000°C. The electrical transport property of the reduced graphene oxide (rGO) thin films shows a band-like transport with small thermal activation energy (Ea ~10 meV) that occurs during high carrier mobility (~210 cm2/Vs). Electrical and structural analysis using X-ray absorption fine structure, the valence band photo-electron, and Raman spectra indicate that a high temperature process above 1000°C in the ethanol environment leads to an extraordinary expansion of the conjugated π-electron system in rGO due to the efficient restoration of the graphitic structure. We reveal that Ea decreases with the increasing density of states near the Fermi level due to the expansion of the conjugated π-electron system in the rGO. This means that Ea corresponds to the energy gap between the top of the valence band and the bottom of the conduction band. The origin of the band-like transport can be explained by the carriers, which are more easily excited into the conduction band due to the decreasing energy gap with the expansion of the conjugated π-electron system in the rGO.
Graphene is one of the most exciting two-dimensional (2D) materials due to its linear band dispersion at the Fermi level. The bonding and anti-bonding states originating from the hybridization of π orbitals of two sublattices of graphene, meet at six corners of the Brillouin zone, making it semimetal. The lack of a band gap limits graphene’s application in optical and electronic devices. In order to open a gap in graphene, its inherent symmetry has to be broken. In this review, we present various theoretical and experimental studies employed to open a gap in graphene. Cutting the graphene into nanoribbons or rolling up into a nanotube breaks the translation symmetry leading to band gap opening. The chemical functionalization opens a band gap by destroying the π cloud of graphene. Application of a strain or electric field and the presence of substrate make two sublattices of graphene inequivalent leading to opening of a band gap. With the help of a generic tight binding model, the effect of symmetry breaking on the opening of band gap has been discussed. We present the underlying mechanism of band gap opening in graphene through a review of various techniques, which could be employed to obtain a certain range of band gap for a particular application.
Single layer graphene nanoribbon (sGNR) is a good conductor in nature and it is promising material to be used as nanowiring in next era computers. Here, we have investigated a new fabrication method of sGNR using sonochemical method via longitudinal unzipping of double-walled carbon nanotubes. The electric properties of sGNR as well as the approach of controlling its electric properties was discussed by detail using molecular adsorption technique. The development of general electric properties of sGNR cross structure for utilization in circuit wiring was also performed. The obtained electric results will contribute for downscaling of integrated circuits from the aspect of the combined wiring-device structure.
Iron-based nanomaterials have been successfully prepared at extremely low temperatures by using CaH2. Because of the ability to act as a very strong solid reductant, CaH2 has recently received much attention in the field of solid state chemistry. The reaction temperatures can be lowered by several hundred degrees Celsius by using CaH2 instead of H2 which is the conventional and most widely used reductant. This drastic decrease in the reaction temperatures enables the structures of the nanomaterials to be precisely controlled and the development of new functionalization techniques.