Akiko Kitajima

Application of Prussian blue nanoparticles for the radioactive Cs decontamination in Fukushima region.

Cs decontamination efficiencies of the composites of iron hexacyanoferrate nanoparticles were investigated in comparison with commercial Prussian blue and natural zeolite. In pure water solution, the adsorption rate varied with sizes. In ash extract, where Cs adsorbing ability of zeolite was sharply dropped due to its poor selectivity, the impact of coexisting ions was negligible for FeHCF. FeHCF-n11, having the finest primary and secondary particle size, resulted the highest distribution coefficient, which was comparable to the high efficiency analogues, CoHCF or NiHCF. This observation suggested the possibility of preparing the high performance FeHCF by particle size and composition adjustment. FeHCF nanoparticle in bead form was tested for the removal of radioactive Cs in pilot scale. Due to larger secondary particle size, pronounced effect of solution temperature on the Cs adsorption kinetics on FeHCF bead was observed. Adjusting the mass of the adsorbent for the given solution temperature is recommended for achieving high decontamination rate.

Label-free and ‘signal-on’ DNA detection using a probe DNA terminated with ferrocene and β-cyclodextrin

A novel oligonucleotide probe was designed to provide a self-reporting ‘signal-on’ DNA detection. The probe was terminated with a ferrocene moiety at one end and a β-cyclodextrin moiety at the other end, as the signal-generating and signal-suppressing parts, respectively. Electrochemical measurement of the probe using a carbon-based interdigitated array microelectrode chip showed a sigmoidal current–potential curve in the absence of the target oligonucleotide complementary to the probe. In the presence of the target, however, the curve shifted towards a more negative potential (62 mV) and the observed current at +0.3 V was increased 5.2-fold, indicating that the probe provided a ‘signal-on’ response upon hybridisation. This probe achieves simple DNA detection without the need to label the target oligonucleotides or to add any other electroactive reagents to the measurement system.

Optical switch array based on microforming process

With increasing data traffics, the importance of the switches is increasing and further cost reduction will be expected. One of the most effective efforts to decrease the cost is introduction of forming technology for micro parts fabrication. The materials of interest are polymer materials for their low cost. In this study, the prototype is presented of the optical switch based on microforming process of polymer materials, and basic characteristics of micro hot embossing are presented. In the present switch, the pop up type micro mirror array on the moving diaphragm fabricated by microforming is actuated by electrostatic force and the optimum electrodes structure of the switch is analyzed by computer simulation to fulfill the large deformation and stable switching. Total system fabrication process including optical fiber alignment and device packaging is also presented. Finally hot embossing of polymer materials are characterized experimentally.

Hydroxyapatite Film Formation on Polylactic Acid Plate by Aerosol Beam Irradiation

A coating technology was developed to form hydroxyapatite (HAp) films on polylactic acid (PLA) plates by aerosol beam irradiation. The aerosol beam was composed of HAp particles of submicron size and helium gas. HAp films were produced at incidence angles of 0, 10, 20, and 30°, but the HAp films did not have good adhesion to the PLA plate when incidence angles were 0, 10, and 20°. To increase the adhesion strength between the HAp film and the PLA plate, the HAp film produced on the plate with an incidence angle of 30° was heated in an electric furnace. In vitro assessments using simulated body fluid (SBF) were performed to investigate the bioactivity of the HAp-coated PLA plate. The heat-treated HAp film did not peel off from the plate throughout the SBF test. The surface morphology and the crystallinity of the film produced in the SBF suggest that the HAp-coated PLA plate is bioactive.

Numerical evaluation of Cs adsorption in PB column by extended Langmuir formula and one-dimensional adsorption model

Adsorption property of granulated Prussian blue adsorbent on radioactive cesium was evaluated for efficient decontamination in Fukushima area. The adsorbent was found to show an inflective adsorption isotherm, which was expressed by extended Langmuir formula with three adsorption sites. Adsorption speeds of each site were evaluated by time-dependent batch experiment. The simulation using derived parameters and one-dimensional adsorption model successfully reproduced the experimental data of cesium decontamination by small and large columns.