Takuya Kinoshita

Magnetic evaluation of nanostructure of gold-iron composite particles synthesized by a reverse micelle method

Abstract Iron–gold nanocomposite powder was synthesized by sequential reduction of Fe 2+ and Au 3+ in reversed micelles. The UV–Vis absorption spectrometry and magnetic separation experiment indicated that the powder is composed of composite nanoparticle containing both iron and gold. XRD indicated that gold exists as metal, and X-ray absorption near edge structure showed that the magnetic phase was Fe 3 O 4 . TEM observation indicated that the nanocomposite was single-nanosized and has a sharp size distribution. The magnetization was measured with a SQUID magnetometer and found to be superparamagnetic. The magnetic moment size was evaluated by fitting the lognormal distribution function and the Langevin function to the magnetization data. These results were discussed taking account of the core–shell structure.

Influence of size distribution on the magnetocaloric effect of superparamagnetic gold-magnetite nanocomposite

Abstract The magnetocaloric effect of the superparamagnetic nanocomposite composed of magnetite grains isolated by gold was investigated as a function of the size distribution width. The magnetic entropy change Δ S was evaluated by applying Maxwell’s relation to the magnetization data sets measured at various temperature and applied field. The size distribution was evaluated by the TEM observation, showing that the average sizes were from 4.6 to 7.4 nm and the geometric standard deviations σ g from 1.32 to 1.59. Thus evaluated Δ S was found to increase with decreasing σ g , demonstrating our previous anticipation that the narrow size distribution would much enhance the magnetocaloric effect of the superparamagnetic nanocomposite material. The Δ S was several times larger than that of our previous nanocomposite composed of γ-Fe 2 O 3 and silver.

Synthesis of gold/magnetic iron oxide composite nanoparticles for biomedical applications with good dispersibility

Composite nanoparticles consisting of gold and magnetic iron oxide were synthesized in an aqueous solution system by sonochemical and radiochemical processes. Small Au nanoparticles were immobilized on the surface of the iron oxide nanoparticles. Removal of the excess polymers in the solution leads to the good dispersibility of the composite nanoparticles. The composite nanoparticles are expected as a type of nanocarrier for biomedical applications.Composite nanoparticles consisting of gold and magnetic iron oxide were synthesized in an aqueous solution system by sonochemical and radiochemical processes. Small Au nanoparticles were immobilized on the surface of the iron oxide nanoparticles. Removal of the excess polymers in the solution leads to the good dispersibility of the composite nanoparticles. The composite nanoparticles are expected as a type of nanocarrier for biomedical applications.

A Strategy to Control the Reactivation of Frustrated Lewis Pairs from Shelf-Stable Carbene Borane Complexes

N-Phosphine oxide substituted imidazolylidenes (PoxIms) have been synthesized and fully characterized. These species can undergo significant changes to the spatial environment surrounding their carbene center through rotation of the phosphine oxide moiety. Either classical Lewis adducts (CLAs) or frustrated Lewis pairs (FLPs) are thus formed with B(C6F5)3 depending on the orientation of the phosphine oxide group. A strategy to reactivate FLPs from CLAs by exploiting molecular motions that are responsive to external stimuli has therefore been developed. The reactivation conditions were successfully controlled by tuning the strain in the PoxIm–B(C6F5)3 complexes so that reactivation only occurred above ambient temperature.

Synthesis of La0.75Sr0.25MnO3 fine particles for self-controlled magnetic heating hyperthermia by ultrasonic spray pyrolysis

La0.75Sr0.25MnO3 particles were synthesized by ultrasonic spray pyrolysis at synthesis temperatures of 1173, 1273, and 1473 K, a reaction time of 9.4 S, and a source solution concentration of 0.5 mol L−1. The particles produced generated heat in the AC magnetic field, and particle temperature increased quickly with time, attaining constant Thmax values of 312, 327, and 353 K. These Thmax values enclosed the temperature range for hyperthermia (316–318 K). Their Curie temperatures Tc evaluated were 314, 329, and 358 K. Thmax increased linearly with increasing Tc and the values obtained were almost similar to Tc.

Effects of synthesis conditions on Curie temperature of La0.75Sr0.25MnO3 fine particles formed by ultrasonic spray pyrolysis

Manganese perovskite La0.75Sr0.25MnO3 (LSM) fine particles were synthesized by an ultrasonic spray pyrolysis method at various synthesis temperatures (Ts), reaction times (tr), and source solution concentrations (Ctotal) to clarify the effects of these synthesis conditions on their Curie temperature Tc and maximum particle temperature attained by magnetic heating at Thmax. At constant Ctotal, the Tc of synthesized LSM particles was increased from 288.6 to 363.5 K (15.6 to 90.5 ?C) by increasing Ts from 1073 to 1627 K (800 to 1400 ?C), and was increased from 281.8 to 339 K (8.89 to 66 ?C) by increasing tr from 2.4 to 19 s. When the AC magnetic field was applied, the particles generated heat, and the particle temperature Th increased with time for t < about 2 min, and then attained constant Thmax near Tc. Thmax increased with increasing Tc. The LSM particles produced at Ts = 1213 K, Ctotal = 0.5 mol L?1, and tr = 9.4 s had Thmax = 316.6 K (43.6 ?C), which is within the temperature range of 316?318 K (43?45 ?C) for hyperthermia therapy for cancer.

SONOCHEMICAL PREPARATION OF GOLD/IRON OXIDE COMPOSITE MAGNETIC NANOPARTICLES AND SELECTIVE MAGNETIC SEPARATION OF BIOMOLECULES

We have successfully prepared Au nanoparticles by the sonochemically reducing Au(III) ions and immobilized them on the surface of magnetic γ-Fe2O3 nanoparticles. Au particles with average diameter of about 10 nm were homogeneously dispersed on the surface of γ-Fe2O3 (average diameter : 26 nm) without aggregation. Au nanoparticles are known to selectively adsorb the molecules having sulfur. Aiming at the uses for magnetic carriers of specific biomolecules, we employed prepared composite nanoparticles for selective separation of biomolecules and estimated their adsorption properties. The composite nanoparticles exhibited a high affinity with glutathione, a tripeptide with mercapto group, so that separation and manipulation of glutathione in aqueous solutions could be performed by applying an external magnetic field. Magnetic separations of amino acids were also investigated. Composite nanoparticles were mixed with amino acid standard solution containing 17 kinds of amino acids and their magnetic separations...

Patterning and Formation of SiO2 Nanoparticles on a Substrate by Electrically Attracting of Cluster Ions

The cluster-ion deposition method was newly developed here based on the ionization chemical vapor deposition (ionization CVD) method. In this new method, reactant gases are first ionized and then form cluster ions that deposit directly onto a substrate. Experimental results revealed that (1) SiO2 nanoparticles can be deposited on Si wafers at temperatures lower than the particle generation temperature in tetraethylorthosilicate (TEOS)/oxygen reaction system, (2) the Si wafer (1.4 ×1.4 cm2) can be uniformly covered with nanoparticles at high density (1010 cm-2), and (3) nanoparticles can be selectively deposited and arranged onto a charged line pattern on the Si wafer.

DNA Separation Using Gold/Magnetic Iron-oxide Composite Nanoparticles

Amounts of oligonucleotides adsorbed onto the Au/γ-Fe 2 O 3 composite nanoparticles synthesized by gamma-ray irradiation and picked up by a magnet were evaluated using fluorescence technique. The adsorbing capacity of the oligonucleotides on our nanoparticles are larger than a commercial magnetic beads for a separation of biomolecules.

Synthesis of Porous Submicron Gd0.1Ce0.9O1.95 Particles by Carbon Nanoparticle-Addition Ultrasonic Spray Pyrolysis (CNA-USP) and Nanoparticle Preparation by Ball Milling

A new ultrasonic spray pyrolysis method, called carbon nanoparticle-addition ultrasonic spray pyrolysis (CNA-USP), is developed to synthesize nanoparticles of electrolyte material for solid oxide fuel cell applications. In CNA-USP, carbon nanoparticles are added in a precursor solution. First, Gd0.1Ce0.9O1.95 (GDC) particles were synthesized from an aqueous solution of Ce(NO3)3 6H2O and Gd(NO3)3 6H2O by using the CNA-USP method. The resulting synthesized GDC particles were agglomerated, porous, primary particles on the order of 10 nm in diameter. EDX images revealed uniform distributions of Ce, Gd, and O in these porous particles. Then, these agglomerated, porous submicron GDC particles were ground into primary nanoparticles by ball milling for 24 h. The average diameter of the ground GDC nanoparticles was about double of their average crystallite size. Copyright 2014 American Association for Aerosol Research