Hydrogen-assisted fabrication of spherical gold nanoparticles through sonochemical reduction of tetrachloride gold(III) ions in water

Spherical gold nanoparticles (AuNPs) were selectively synthesized through sonochemical reduction of tetrachloride gold(III) ions ([AuCl4](-)) in an aqueous solution of hydrogen tetrachloroaurate(III) tetrahydrate (HAuCl4.H2O) with the aid of hydrogen (H-2) gas in the absence of any additional capping agents. On the other hand, various shaped-AuNPs such as spherical nanoparticles, triangular and hexagonal plates were formed from sonochemical reduction of [AuCl4](-) in argon (Ar)-, nitrogen (N-2)- or oxygen (O-2)-purged aqueous [AuCl4](-) solutions. The selective fabrication of spherical AuNPs assisted by H-2 gas is most likely attributed to the generation of hydrogen radicals (H center dot) promoted by the reaction of H-2 introduced and hydrogen oxide radicals (center dot OH) produced by sonolysis of water.ArticleULTRASONICS SONOCHEMISTRY. 21(3):946-950 (2014)journal articl

Block copolymer-mediated synthesis of silver nanoparticles from silver ions in aqueous media

We report here on the silver (Ag) nanoparticle synthesis in aqueous solutions of poly(ethylene oxide)poly(propylene oxide) (PEO-PPO) block copolymers in the absence of any additional agents. In particular, we examined the effect of reaction temperature, molecular weight of PEO-PPO block copolymer and PEO-PPO block copolymer concentration on the reduction of silver ions (Ag+) and the resulting formation of Ag nanoparticles in aqueous PEO-PPO block copolymer solutions. We found that Ag nanoparticles were formed from aqueous silver nitrate (AgNO3) solutions containing PEO-PPO block copolymer above 100 degrees C. This is most likely due to the dehydration of Ag+ caused by thermal motion of water molecules in higher-temperature aqueous solution at high vapor pressure. We also found that the formation of Ag nanoparticles in aqueous PEO-PPO block copolymer solutions was enhanced with larger molecular weight of PEO-PPO block copolymer and with increase in the concentration of PEO-PPO block copolymer in aqueous solutions. (C) 2015 Elsevier B.V. All rights reserved.ArticleCOLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS. 487:84-91 (2015)journal articl

Spontaneous Resolution of Left Ventricular Outflow Tract Obstruction in the Course of Newly-Developed Mitral Valve Prolapse in a Hypertrophic Cardiomyopathy Patient

A 63-year-old man was diagnosed with hypertrophic obstructive cardiomyopathy. Echocardiography revealed asymmetrical left ventricular hypertrophy, systolic anterior movement (SAM) of mitral leaflets causing an outflow tract pressure gradient of 52 mmHg, and moderate mitral regurgitation (MR) directed posteriorly in the left atrium.Four years later,when the patient was admitted for mild congestive heart failure, SAM and left ventricular outflow obstruction were absent, and prolapse of the posterior mitral leaflet was causing anteriorly-directed severe MR. Rupture of the chordae tendineae was responsible for the mitral prolapse and for the abolition of the outflow obstruction. Shinshu Med J 59 : 259 ―263, 2011Article信州医学雑誌 59(4): 259-263(2011)departmental bulletin pape

Surfactant- and reducer-free synthesis of gold nanoparticles in aqueous solutions

We report here the surfactant- and reducer-free synthesis of gold nanoparticles from an aqueous hydrogen tetrachloroaurate (III) tetrahydrate (HAuCl(4)center dot 4H(2)O) solution using a high-frequency (950 kHz) ultrasound (in the absence of any stabilizing, capping and reducing agents). In particular, size, shape and stability of gold nanoparticles prepared by the 950 kHz ultrasound irradiation (sonication) for 8 min in the surfactant-free aqueous solutions were examined in terms of AuCl(4)(-) concentration (in the range of 0.01-0.1 mM), additional salts (NaCl, HCl and NaOH) and temperature (in the range of 4-60 degrees C). We found that higher AuCl(4)(-) concentration promoted particle growth (size increase) and plate formation. In addition, the plate formation was enhanced with the addition of NaCl or HCl (but not NaOH). This is most likely due to the AuCl(4)(-) reduction on a certain crystal facets (e.g. (1 1 0) facets) caused by the adsorption of Cl(-) ions on specific crystal facets (e.g. (1 1 1) facets). Furthermore, we revealed that the temperature elevated above 50 degrees C led to the formation of spherical gold nanoparticles with the diameter of 20-60 nm from a 0.1 mM AuCl(4)(-) aqueous solution while triangular plates formed coexisting with spherical nanoparticles below 50 degrees C.ArticleCOLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS. 347(1-3):18-26 (2009)journal articl

Vesicle formation in mixture of a PEO-PPO-PEO block copolymer (Pluronic P123) and a nonionic surfactant (Span 65) in water

Fabrication of vesicles with the diameter of 4-30 mu m was achieved by mixing hydrophobic nonionic surfactant (Span 65) with a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (Pluronic P123) in aqueous solutions at room temperature. Ring-shaped structure of the Plutonic P123/Span 65 mixture assemblies was confirmed by fluorescence microscopy. The presence of internal aqueous phase in the Pluronic P123/Span 65 mixture assemblies was determined by measuring the entrapment efficiency of calcein using fluorescence spectroscopy. On the other hand, Pluronic P123/Span 60 mixture system formed wire-like assemblies but not vesicles.ArticleCOLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS. 389(1-3):82-89 (2011)journal articl

Titania/C-n TAB Nanoskeleton as adsorbent and photocatalyst for removal of alkylphenols dissolved in water

We report here on the removal of alkylphenols (phenol, 4-n-propylphenol, 4-n-heptylphenol and 4-nonylphenol) dissolved in water using the composite particles of nanocrystalline titania and alkyltrimethylammonium bromide (CnH2n+1N(CH3)(3)Br, C(n)TAB; n = 12, 14, 16 and 18) (named as TiO2/C(n)TAB Nanoskeleton) as adsorbents and photocatalysts. In particular, the adsorption of alkylphenols onto TiO2/C(n)TAB Nanoskeleton in water was investigated in terms of hydrophobic interaction between alkylphenols and C(n)TAB, surface area, pore structure and crystal size of TiO2/C(n)TAB Nanoskeleton. We revealed that C(n)TAB incorporated in the TiO2/C(n)TAB Nanoskeleton promotes the adsorption of alkylphenols onto TiO2/C(n)TAB Nanoskeleton due to the hydrophobic interaction between alkylphenols and C(n)TAB. On the other hand, the surface area, pore structure and crystal size of TiO2/C(n)TAB Nanoskeleton did not affect the adsorption of allcylphenols onto TiO2/C(n)TAB Nanoskeleton. We also found that the alkylphenols dissolved in water were completely removed by the combination of adsorption and photocatalytic degradation by the TiO2/C(n)TAB Nanoskeleton under UV irradiation. These results prove that the TiO2/C(n)TAB Nanoskeleton acts as in tandem an adsorbent and a photocatalyst for removal of alkylphenols dissolved in water.ArticleJOURNAL OF HAZARDOUS MATERIALS. 248:487-495 (2013)journal articl

Block copolymer-mediated synthesis of gold nanoparticles in aqueous solutions: Segment effect on gold ion reduction, stabilization, and particle morphology

We report here on the segment effects of poly(ethylene oxide)-containing block copolymers (PEO-BCP) on the reduction activity for tetrachloride gold(III) ([AuCl4](-)), interfacial activity for gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions. In particular, the effects of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), polyethylene (PE) segments and amino group (NH2) on the rate of [AuCl4](-) reduction, adsorption of PEO-BCP onto gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions were examined using a poly(ethylene oxide)-poly(propylene oxide) triblock copolymer (PEO-PPO-PEO, Pluronic L44), an amino-terminated poly(ethylene oxide)-poly(propylene oxide) block copolymer (PEO-PPO-NH2, SURFONAMINE(R) L-207), a poly(ethylene oxide) homopolymer (PEO, poly(ethylene glycol)2000), and a polyethylene-poly(ethylene oxide) block copolymer (PE-PEO). We found that the reduction activity of PEO-BCP for [AuCl4](-) became higher with the order of PEO-PPO-NH2 < PE-PEO < PEO < PEO-PPO-PEO. The interfacial activity (affinity) of PEO-BCP for gold surface increased with the order of PEO < PE-PEO < PEO-PPO-PEO < PEO-PPO-NH2. Consequently, the colloidal stability of gold nanoparticles formed in aqueous PEO-PPO-NH2 solutions was extremely high compared with that in PEO, PEO-PPO-PEO, and PE-PEO solutions. In addition, the size of gold nanoparticles formed in aqueous PEO-PPO-NH2 solutions was much smaller than that in aqueous solutions of PEO-PPO-PEO, PEO or PE-PEO.ArticleJOURNAL OF COLLOID AND INTERFACE SCIENCE. 394:124-131 (2013)journal articl

Pore-size expansion of hexagonal-structured nanocrystalline titania/CTAB Nanoskeleton using cosolvent organic molecules

Pore-size expansion of hexagonal-structured assembly of nanocrystalline titania (anatase) combined with cetyltrimethyammonium bromide (CH(3)(CH(2))(15)N(+)(CH(3))(3)Br(-), CTAB) (named as Hex-ncTiO(2)/CTAB Nanoskeleton) was achieved with the aid of cosolvent organic molecules (COMs). The pore-size expanded Hex-ncTiO(2)/CTAB Nanoskeleton was prepared through the sot-gel reaction of titanium oxysulfate sulfuric acid hydrate (TiOSO(4)center dot xH(2)SO(4)center dot xH(2)O, TiOSAH) in an aqueous solution initiated by CAB swollen micelles pre-prepared with the addition of COMs into aqueous CTAB micellar solutions at 60 degrees C (the product was named as Hex-ncTiO(2)/CTAB/COM Nanoskeleton). Long-chain alcohol (1-hexadecanol. C16OH), normal alkane (n-decane, C10) and benzene derivatives (benzene. Bz; 1,3,5-trimethylbenzene, TMB; 1,3,5-triethylbenzene, TEB; 1,3,5-triisopropylbenzene, TiPB) were used as COMs to evaluate the effects of COM solubilization site in CTAB micelles and COM molecular size on the pore-size expansion of the Hex-ncTiO(2)/CTAB/COM Nanoskeleton. We found that 1,3,5-trimethylbenzene (TMB) and 1,3,5-triethylbenzene (TEB) act as effective COMs for pore-size expansion of the Hex-ncTiO(2)/CTAB/COM Nanoskeleton in aqueous media. Pore sizes (average diameters) of the Hex-ncTiO(2)/CTAB/TMB Nanoskeleton and Hex-ncTiO(2)/CTAB/TEB Nanoskeleton were enlarged up to 4.2 nm and 4.3 nm, respectively, while pore size (average diameter) of the Hex-ncTiO(2)/CTAB Nanoskeleton prepared in the absence of any COMs was 2.9 nm. We also revealed that thermal stability of the Hex-ncTiO(2)/CTAB/TMB Nanoskeleton became higher than that of Hex-ncTiO(2)/CTAB Nanoskeleton. The hexagonally pore-structure of the Hex-ncTiO(2)/CTAB/TMB Nanoskeleton was retained up to 400 degrees C, while the hexagonally pore-structure of the Hex-ncTiO(2)/CTAB Nanoskeleton was kept up to 300 degrees C.ArticleCOLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS. 371(1-3):29-39 (2010)journal articl

Thermodynamic properties of quantum sine-Gordon spin chain system KCuGaF6

We investigated the thermodynamic properties of the spin-1/2 one-dimensional Heisenberg antiferromagnet KCuGaF6 by measuring the specific heat in magnetic fields. When this compound is subjected to a uniform magnetic field H a transverse staggered magnetic field h is induced in this compound owing to the staggered component of the g tensor and the Dzyaloshinskii-Moriya interaction with an alternating D vector. Consequently, the quantum sine-Gordon (SG) model is an effective model of this compound in a uniform magnetic field. In three different field directions, we observed a magnetic-field-induced gap, which increases with H. We analyzed experimental results using specific heat theory based on quantum SG theory. The thermodynamic property for H // c is very well described in terms of the elementary excitations characteristic of the quantum SG model, while for the other field directions, significant contributions from other excitation modes beyond the framework of the quantum SG model were observed. For H // b, a quantum phase transition between gapless and gapped ground states was observed.Comment: 10 pages, 14 figure