Tomoya Takada

Proton transfer rates in ionized water clusters (H2O)n (n = 2–4)

A proton transfer process is usually dominant in several biological phenomena such as the energy relaxation of photo-excited DNA base pairs and a charge relay process in Ser-His-Glu. In the present study, the rates of proton transfer along a hydrogen bond in a water cluster cation have been investigated by means of a direct ab initio molecular dynamics (AIMD) method. Three basic clusters, water dimer, trimer and tetramer, (H2O)n (n = 2–4), were examined as the hydrogen bonded system. It was found that the rate of the first proton transfer is strongly dependent on the cluster sizes: average time scales of proton transfer for n = 2, 3, and 4 were 28, 15, and 10 fs, respectively, (MP2/6-311++G(d,p) level) suggesting that proton transfer reactions are very fast processes in the three clusters. The second proton transfer was found in n = 3 and 4 (the average time scales for n = 3 and 4 were 120 fs and 40 fs, respectively, after the ionization). The reaction mechanism was discussed on the basis of theoretical results.

Scanning Electron Microscope Observation of Nano Carbon Materials with Imidazolium-Type Room Temperature Ionic Liquids

A novel pre-treatment method for scanning electron microscopy (SEM) observation using room temperature ionic liquids (ILs) was used for several carbon nano materials. After the ILs pre-treatment, the quality of the SEM images obtained was almost the same as that obtained with conventional platinum/palladium (Pt/Pd) spattering pre-treatment. The highest resolution in this study was under 30 nm. This result means that the pre-treatment with IL can form ultrathin layer on the sample surface at several molecules level. Therefore, the ILs pre-treatment is a simple and easy tool for SEM observation of nano materials on insulating substrates.

A DFT and MD Study on the Interaction of Carbon Nano-Materials with Metal Ions

The interaction of manganese (II) ion (Mn2+) with graphene surfaces have been investigated by means of density functional theory (DFT). Also, the molecular dynamics (MD) calculations using molecular mechanics-2 (MM2) potential functions have been applied to the diffusion dynamics of Mn2+ on the graphene surface. Two graphene sheets (n = 19 and 52, where n means numbers of rings in each carbon cluster) were considered as models of graphene surface in the present study. The B3LYP/LANL2MB calculations showed that the Mn2+ ion is located in the ranges 2.28–2.46 Å from the graphene surface. Also, classical MD calculation was applied to diffusion processes of the Mn2+ on the graphene surface (n = 52). The classical MD calculations showed that the Mn2+ ion diffuses from bulk to edge region at 300–600 K and is trapped in the edge region. The nature of the interaction between the Mn2+ ion and the graphene sheet was discussed on the basis of theoretical results.

Formaldehyde reduction with scallop shell powders fired at high temperatures: Identification of the effective ingredient

The volatile organic compound (VOC) reduction activity of scallop shell powders fired at 300, 600 and 900 degrees C was examined using formaldehyde (HCHO). Raw shells as well as fired shells immediately after firing at several temperatures, except for 600 degrees C, were found to gradually remove HCHO from the air. In the case of shell powders stored for 3 months after firing, the HCHO reduction activity of the powder fired at 900 degrees C was obviously improved, with the HCHO concentrations rapidly reaching zero within 20 min. It has been found by X-ray diffraction measurements that shell powder stored for 3 months after firing at 900 degrees C contains a small amount of calcium hydroxide (Ca(OH)2) generated from calcium oxide (CaO). Our results suggest that Ca(OH)2 may be the effective ingredient in the HCHO reduction.

Amide Bond Formation between Carboxylated Multi-Walled Carbon Nanotubes and Glass Surface by Using Carbodiimide Condensing Agent and Triazole Derivatives

Amide bond formation between carboxylated multi-walled carbon nanotubes (MWCNT-COOHs) and aminated glass surface has been studied to make transparent conductive device. Examining the condensation reaction between MWCNT-COOHs and glass surface under various conditions, it has been found that MWCNT-COOHs are immobilized on the surface by reaction using a carbodiimide and a triazole. The MWCNT layers formed are not easily detached; the interaction between MWCNTs and glass surface is quite strong, implying formation of chemical bonding. Immobilization of MWCNTs on the surface is confirmed also by scanning electron microscopy. Electric conductivity of MWCNT-coated glass has been preliminarily measured.

Density Functional Theory Study on the Reaction of Finite-Sized Graphene with Methyne

We studied the reactivity of finite-sized graphene with methyne (CH radical) theoretically by means of density functional theory (DFT) calculations. We identified a favorable reaction site for model graphene by comparing the total energies of the adducts corresponding to the inequivalent reaction sites. The addition of methyne to an edge site of the graphene was energetically favorable rather than an inner site. The potential energy barrier for the methyne addition became lower as the model size became larger. We also discuss the reactivity of methyne with graphene discussed on the basis of our calculation results.