Takuya Nakanishi

Luminescent lanthanide coordination polymers for photonic applications

Luminescent lanthanide coordination polymers composed of lanthanide ions and organic joint ligands exhibit characteristic photophysical and thermostable properties that are different from typical organic dyes, luminescent metal complexes, and semiconductor nanoparticles. Various types of luminescent Eu(III) and Tb(III) coordination polymers have been reported to date. One-, two-, and three-dimensional alternating sequences of lanthanide ions and organic ligands exhibit remarkable characteristics as novel organic materials with various structures, and unique physical properties. In this review, the characteristic structures, photophysical properties, and photonic applications for organic display devices, triboluminescent materials, thermosensors, color and brightness tuning, new type organogels, future magneto-optical materials, luminescent organo-nanoparticles, and energy transfer process of lanthanide coordination polymers are introduced.

Effect of surface charge of magnetite nanoparticles on their internalization into breast cancer and umbilical vein endothelial cells

Internalization of magnetite nanoparticles with diameter of approximately 40 nm into normal and cancer cells was examined by microscopic observation and flow cytometry. Magnetite nanoparticles were synthesized by hydrolysis in an aqueous solution containing ferrous chloride with organic amines as a base. It was demonstrated that the difference in surface charge of magnetite nanoparticles brought about the difference in uptake efficiency. The nanoparticles with positive charge showed higher internalization into human breast cancer cells than the nanoparticles with negative charge, while the degree of internalization of the positively- and negatively-charged nanoparticles into human umbilical vein endothelial cells (HUVEC) was almost the same.

Layer-by-layer self-assembly of composite films of CdS nanoparticle and alkanedithiol on gold: An X-ray photoelectron spectroscopic characterization

Abstract Layer-by-layer self-assembly of composite thin films of cadmium sulfide (CdS) nanoparticle and alkanedithiol was achieved on a gold substrate by an alternate immersion into solutions of dithiols (1,6-hexanedithiol and 1,10-decanedithiol) and solution containing CdS nanoparticles (ca. 3 nm in diameter). The layer-by-layer structure was confirmed by angle-resolved X-ray photoelectron spectroscopy (XPS) at each composite-film preparation step. The proposed structure and mechanism of self-assembly were in agreement with our previous results obtained by Fourier transform infrared reflection-absorption spectroscopy.

Pulsed Electrodeposition of Nanocrystalline CoNiFe Soft Magnetic Thin Films

A pulsed electrodeposition method was applied to the preparation of soft magnetic CoNiFe films in the compositional region corresponding to the phase boundary between face-centered cubic (fcc) and body-centered cubic (bcc) structures. Crystalline grain size was found to be almost the same smaller than 10 nm, and independent of the duty cycle which is the ratio of the pulse-on time to the pulse-on plus pulse-off period. Depending on the operating conditions, the ratio of bcc to fcc varied. Current efficiency decreased with decreasing duty cycle and pulse current density. The intensity ratio of bcc( 110) to fcc( 111) X-ray diffraction peaks showed a maximum at the operating conditions in which the transition from kinetic to mass-transfer controlled deposition occurred with only a slight increase of Fe content (approximately I atom %). Magnetic properties were suggested to be controllable by adjusting the bcc-fcc ratio using pulsed electrodeposition.

Microstructure of electroplated soft magnetic CoNiFe thin films

The microstructural and crystallographic characteristics of electroplated soft magnetic CoNiFe thin films were investigated by transmission electron microscopy. Dark field images showed that the film with fcc-bcc dual crystals has a smaller grain size than the fcc or bcc single phase film. The fcc films were found to have a unique microstructure with twin-like stacking faults with relatively uniform grain size distribution, and such twins were also found in the dual phase films. Some coarse grains were found in the bcc films with a twin-free microstructure. The film prepared from the thiourea bath had a smaller grain size than that of the film from the saccharin bath. It is suggested from the diffraction patterns that the fcc and bcc components of the films are substitutional solid solutions of Co, Ni and Fe. The lattice constants of fcc CoNiFe films are determined by atomic concentrations of the three elements. The crystal structures of bcc films are determined by Fe, and the lattice constants are slightly changed by the incorporation of Co and Ni into the bcc lattice of Fe. The CoNiFe films obtained from saccharin and thiourea baths have different lattice constants, because of different sulfur contents of the films.

Effect of magnetite nanoparticles on living rate of MCF-7 human breast cancer cells

Superparamagnetic and ferromagnetic magnetite nanoparticles, with diameters of approximately 13 and 44 nm, respectively, were synthesized and their uptake amount and heating efficiency were evaluated for application to magnetic hyperthermia. Both nanoparticles had almost the same zeta-potential (+10.2 mV) and hydrodynamic size (∼1 μm) and there was no significant difference in their uptake amount 18 h after they were added to the medium. After internalization, the ferromagnetic nanoparticles incorporated in human breast cancer cells (MCF-7) showed a higher heating efficiency than the superparamagnetic nanoparticles when an external magnetic field (4 kW, 250 kHz) high enough to produce heat by hysteresis loss was applied, followed by cellular death of MCF-7 with high ferromagnetic nanoparticle content.

Increasing the resistivity of electrodeposited high B/sub S/ CoNiFe thin film

In order to increase the resistivity of electrodeposited high B/sub S/ CoNiFe thin film, the effect of an organic additive such as diethylenetriamine (DET) added to the plating bath was investigated. The values of /spl rho/ and H/sub C/ were gradually increased as a function of DET concentration. The desirable soft magnetic CoNiFe thin film with /spl rho/=25-90 /spl mu//spl Omega/-cm under the conditions of B/sub S/>1.9 T and H/sub C/<2.5 Oe was developed as function of carbon in the deposited films. Additionally, the high resistivity CoNiFe thin film with /spl rho/=130 /spl mu//spl Omega/-cm was established under the conditions of B/sub S/=1.7 T and H/sub C/<6 0e.

Cytotoxicity evaluation of magnetite (Fe3O4) nanoparticles in mouse embryonic stem cells.

Magnetite nanoparticles are expected to be applied in the medical field because of their biocompatibility and high saturated magnetization. In this paper, magnetite nanoparticles with a diameter of approximately 40 nm were evaluated for their safety by using mouse embryonic stem (mES) cells. First, various doses of magnetite nanoparticles were added to mES cells to find an optimal dose and to evaluate viability and keeping undifferentiated states of mES. The uptake of nanoparticles by mES cells was confirmed by using cytospin and transmission electron microscopy. Next, mES cells containing magnetite nanoparticles were collected by a magnet column 24h after the addition of magnetite nanoparticles, and the change in the ratio of those mES cells to the total mES cells was assayed by FACS 0, 4, 8, 12, 16, 24, 48 and 72 h after incubation. The result showed that the ratio decreased with time, indicating that the mES cells excreted the nanoparticles, for there was no change in the total number of cells. Based on these results, it was concluded that magnetite nanoparticles were safe to mES cells.

Biosensing by optical waveguide spectroscopy based on localized surface plasmon resonance of gold nanoparticles used as a probe or as a label

The application of localized surface plasmon resonance (LSPR) of gold nanoparticles for the detection of biotin-streptavidin binding, as a typical biological reaction, was investigated by using optical waveguide spectroscopy, and two different modes for the use of gold nanoparticles, one as a probe and the other as a label were compared with each other. The combination with optical waveguide spectroscopy was found to bring about a high sensitivity for the biomolecular detection system using LSPR of gold nanoparticles in both modes. In particular, the mode using gold nanoparticles as a label was demonstrated to be of advantage to devising proper procedures for using nanoparticles and evaluating actual response relevant to the phenomenon concerned, and thus to sensitive detection.

Construction of Semiconductor Nanoparticle Layers on Gold by Self-Assembly Technique

Cadmium sulfide (CdS) nanoparticles were prepared using the Aerosol-OT (AOT)/heptane inverse-micelle method. The particle size was controlled by changing the [H 2 O]/[AOT] ratio in the preparation process to be ca. 3 nm, which was estimated from their absorption maximum (ca. 385 nm) and absorption edge (ca. 450 nm) in heptane solutions. Self-assembled monolayers (SAMs) of α,ω-dithiols were prepared on (111)-oriented gold substrates. They were highly stable in aqueous solutions and showed a blocking effect toward electron exchange between the gold substrate and the electroactive species in the solution. Mono- and multi-layers of CdS nanoparticles were prepared by immersing the SAM-covered gold substrates in a heptane solution containing CdS particles. Infrared reflection-absorption spectra revealed that CdS particles on SAMs were surrounded by AOT and that a sequential immersion procedure led to the alternately layered structure of CdS particles and dithiol molecules.