Mn(II)-monosubstituted polyoxometalates as candidates for contrast agents in magnetic resonance imaging

Two mono-substituted manganese polyoxometalates, K6MnSiW11O39 (MnSiW11) and K8MnP2W17O61 (MnP2W17), have been evaluated by in vivo and in vitro experiments as the candidates of potential tissue-specific contrast agents for magnetic resonance imaging (MRI). T-1-relaxivities of 12.1 mM(-1) s(-1) for MnSiW11 and 4.7 mM(-1) s(-1) for MnP2W17 (400 MHz, 25 degrees C) were higher than or similar to that of the commercial MRI contrast agent (GdDTPA). Their relaxivities in BSA and hTf solutions were also reported. After administration of MnSiW11 and MnP2W17 to Wistar rats, MR imaging showed longer and remarkable enhancement in rat liver and favorable renal excretion capability. The signal intensity increased by 74.0 +/- 4.9% for the liver during the whole imaging period (90 min) and by 67.2 +/- 5.3% for kidney within 20-70 min after injection at 40 +/- 3 mu mol kg(-1) dose for MnSiW11. MnP2W17 induced 71.5 +/- 15.1%. enhancement for the liver in 10-45 min range and 73.1 +/- 3.2% enhancement for kidney within 5-40 min after injection at 39 +/- 3 mu mol kg(-1) dose. In vitro and in vivo study showed MnSiW11 and MnP2W17 being favorable candidates as the tissue-specific contrast agents for MRI.

Synthesis and electrical properties of new solid state. Electrolyte materials Ce5.2RE0.8MoO15-delta

A series of solid state electrolytes, Ce-5.2 RE0.8 MoO15-delta (RE = Y, La, Sm, Gd, Dy, Ho, Er), were synthesized by sol-gel method. Their structures and electrical conductivities were characterized by X-ray Diffraction (XRD), Raman and X-ray Photoelectron Spectroscopy (XPS) and AC impedance spectroscopy, respectively. The results show that the concentrations of oxygen vacancy increased with increasing x and their conductivity were improved. And the cell parameters increase as the radius of RE3+ increases. Because the ionic radius of doped Dy3+ (0.0908 nm) is closed to that of Ce4+ (0.0920 nm), their oxide has minimal cell elastic straining between RE3+ and oxygen vacancy, and the system has the least association enthalpy, thus the oxide Ce-5.2 Dy-0.8 MoO15-delta exhibits a higher conductivity (7.02 x 10(-3) S/cm) and lower activation energy (1.056 eV) compared to the other doped compounds.

Synthesis, characterization and electrical properties of solid state electrolyte materials La2-xCaxMo1.7W0.3O9-delta (0 <= x <= 0.2)

The new compounds La2-xCaxMo1.7W0.3O9-delta (0 <= x <= 0.2) in which La3+ substituted with Ca2+ were synthesized by dry-chemistry techniques based on the oxygen Ionic conductor La2Mo1.7W0.3O9. The new series were characterized by X-ray Diffraction (XRD), Raman and X-ray Photoelectron Spectroscopy (XPS) and the electrical conductivity of samples were investigated by AC impedance spectroscopy. The lattice parameters were reduced due to the smaller atomic radius of the Ca2+ compared with that of the La3+. Furthermore, Additional oxygen vacancies were introduced into La2Mo1.7W0.3O9 lattice by substitution, and then the oxygen ionic conductivity was increased. At 550 degrees C, the conductivity increased 89.9%, that is, from 0.79 x 10(-4) S center dot cm(-1) (x=0) to 1.5 X 10(-4)S center dot cm(-1) (x=0.16, 0.2).

Coating Gd2O3 : Eu phosphors with silica by solid-state reaction at room temperature

Silica coating on Gd2O3:Eu particles was obtained by a simple method, e.g. solid-state reaction at room temperature. The urea homogeneous precipitation method was used to synthesize the Gd2O3:Eu cores. Transmission electron microscopy (TEM) shows that the core particles are spherical with submicrometer size which is the soft agglomerates with nanometer crystallites. The TEM morphology of coated particles shows that a thin film is coated on the surface of Gd2O3:Eu cores. Scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) analysis indicate that the coating of silica can be used to avoid agglomeration of Gd2O3:Eu particles to obtain smaller particles. X-ray photoelectron spectra (XPS) show that silica is coated on the surface of core particles by forming the chemical bond. Photoluminescence (PL) spectra conform that Gd2O3:Eu phosphors remain well-luminescent properties by the silica coating.

Pt nanoparticles: Heat treatment-based preparation and Ru(bpy)(3)(2+)-mediated formation of aggregates that can form stable films on bare solid electrode surfaces for solid-state electrochemiluminescence detection

A simple thermal process for the preparation of small Pt nanoparticles is presented, carried out by heating a H-2-PtCl6/3- thiophenemalonic acid aqueous solution. The following treatment of such colloidal Pt solution with Ru( bpy)(3)(2+) causes the assembly of Pt nanoparticles into aggregates. Most importantly, directly placing such aggregates on bare solid electrode surfaces can produce very stable films exhibiting excellent electrochemiluminescence behaviors.

Synthesis of PtNPs/AQ/Ru(bpy)(3)(2+) colloid and its application as a sensitive solid-state electrochemiluminescence sensor material

The facile synthesis of the novel platinum nanoparticles/Eastman AQ55D/ruthenium(II) tris( bipyridine) (PtNPs/ AQ/Ru(bpy)(3)(2+)) colloidal material for ultrasensitive ECL solid-state sensors was reported for the first time. The cation ion-exchanger AQ was used not only to immobilize ECL active species Ru(bpy)(3)(2+) but also as the dispersant of PtNPs. Colloidal characterization was accomplished by transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), and UV-vis spectroscopy. Directly coating the as-prepared colloid on the surface of a glassy carbon electrode produces an electrochemiluminescence (ECL) sensor. The electronic conductivity and electroactivity of PtNPs in composite film made the sensor exhibit faster electron transfer, higher ECL intensity of Ru(bpy)(3)(2+), and a shorter equilibration time than Ru(bpy)(3)(2+) immobilized in pure AQ film. Furthermore, it was demonstrated that the combination of PtNPs and permselective cation exchanger made the sensor exhibite excellent ECL behavior and stability and a very low limit of detection (1 x 10(-15) M) of tripropylamine with application prospects in bioanalysis. This method was very simple, effective, and low cost.

Crystallization and characterization of substoichiometric compound (W0.5Al0.5)C-0..5 obtained by solid-state reaction

(W0.5Al0.5)C-0.5 substoichiometric compound is synthesized by a combination of mechanical milling and high-pressure reactive sintering. X-ray diffraction is used to monitor the phase changes and crystallization of (W0.5Al0.5) C-0.5 during the whole reaction process. As a result, (W0.5Al0.5) C-0.5 is identified as the hexagonal WC-type belonging to the P-6m2 space group (No. 187), and the lattice parameters of (W0.5Al0.5)C-0.5 are calculated to be a = 2.907 (1) angstrom, c = 2.838 (1) angstrom, which are very similar to those of WC even if there are approximately 50 pct carbon vacancies in the cell of (W0.5Al0.5)C-0.5 as compared with WC. The substoichiometric (W0.5Al0.5)C-0.5 compound has a Vickers microhardness of 2385 +/- 70 kg mm(-2), which is as high as that of WC, while its density is far lower than that of WC.

Synthesis and catalytic kinetics of tellurium-modified hyaluronic acid with glutathione peroxidase activity

A novel mimic TeHA was synthesized by modifying hyaluronic acid (HA) with tellurium, whose function is similar to that of glutathione peroxidase (GPX). The structure of TeHA was characterized by means of infrared spectroscopy and nuclear magnetic resonance spectroscopy, showing that the target Te is located at -CH2OH of the N-acetyl-D-glucosamine of HA. The activity of TeHA is 163.6 U/mu mol according to Wilson's method. In contrast to other mimics, TeHA displays a high activity. Moreover, TeHA can use many hydroperoxides as substrates, such as H2O2, cumenyl hydroperoxide, and tert-butyl hydroperoxide, and cumenyl hydroperoxide is the optimal substrate. A ping-pong mechanism was deduced for the reduction reactions catalyzed by TeHA according to the steady-state kinetic studies.

Capillary electrophoresis with solid-state electrochemiluminescence detector

We report capillary electrophoresis coupling to a solid-state electrochemiluminescence (ECL) detector for the first time. The solid-state ECL detector was fabricated by immobilizing the ECL reagent tris(2,2'-bipyridyf)ruthenium (TBR) in poly-(p-styrenesulfonate)-silica-poly(vinyl alcohol) grafting 4-vinylpyridine copolymer films. The excellent stability of the solid-state ECL detector in the phosphate solution satisfied application in CE. The CE with solid-state ECL detector system was characterized using tripropylamine (TPA) and proline. The influences of detection potential, the concentration of TBR in the film, and pH value of ECL buffer were investigated. The linear range for TPA and proline was 0.005-10 muM and 5-10 mM with correlation coefficients of 0.997 and 0.998, respectively. The detection limit (signal-to-noise ratio S/N = 3) was estimated to be 0.002 and 2.0 muM for TPA and proline, respectively. The relative standard deviations for 1.0 pm TPA and 1.0 mm proline were 8.7% and 7.5% with theoretical plate numbers of 70 000 and 16 000, respectively. Compared with the CE-ECL of TBR in aqueous solution, the CE coupling with solid-state ECL detector system gave the same sensitivity of analysis.

Silicon dioxide coating of CeO2 nanoparticles by solid state reaction at room temperature

The synthesis Of SiO2 coated CeO2 nanoparticles by humid solid state reaction at room. temperature is described. Transmission electron microscope results show that CeO2 Particles were coated with a layer Of SiO2. Binding energy of Ce 3d(5/2) was shifted from 883.8 to 882.8 eV after coating in the XPS Ce 3d spectra. This confirms the chemical bond formation between SiO32- and Ce4+. Because the surface photovoltage property of CeO2 nanoparticles that were used as core materials in the experiment approaches to that of CeO2 macroparticles, peak P2 (electron transition from 0 2p on surface to Ce 4f) disappeared in the surface photovoltage spectrum of CeO2 nanoparticles. Also, the effect Of SiO2 on the electron transition from 0 2p to Ce 4f results in the lowering of surface photovoltage response intensity of P1 peak (electron transition from 0 2p in bulk to Ce 4f).

Arabinogalactan as a carrier for contrast agent in magnetic resonance imaging

Arabinogalactan-Gd-DTPA was synthesized by the reaction of diethylenetriaminepenta-acetic acid (DTPA) bisanhydride with polysaccharide in dry DMSO and characterized by FTIR, elemental analysis and ICP-AES. Its stability was investigated by competition with Ca2+, EDTA, DTPA. The t(1)-relaxivity is 8.06 mmol(-1) . L . s(-1) in D2O, 8.48 mmol(-1) . L . s(-1) in 0.725 mmol . L-1 BSA, respectively. t(1)-weighted MR imaging of rat kidney and liver showed a remarkable enhancement post injection of Arabinogalactan-Gd-DTPA. The results indicate that the arabinogalactan-Gd-DTPA is a potential contrast agent for MRI.

Coating of Y2O3 : Eu3+ particles with alumina by a humid solid state reaction at room temperature

Humid solid state reaction at room temperature was utilized for the first time to coat Y2O3 : Eu3+ particles with alumina. The particles were studied with an X-ray photoelectron spectrometer (XPS), a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS). XPS results show that the yttrium and europium contents are decreased and that the aluminum content is the highest except for that of oxygen after coating. SEM and EDS results show that particles are coated with a thin shell of alumina.

A new preparation of zinc sulfide nanoparticles by solid-state method at low temperature

A novel solid-state method of the preparation of zinc sulfide nanoparticles is reported. By solid-state reaction of zinc acetate and thioacetamide at low temperature, zinc sulfide nanoparticles of different sizes were prepared. The temperature of preparation varied from room temperature to 300 degrees C. The particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and photoluminescence spectrum. X-ray diffraction patterns revealed that the particles exhibited pure zinc-blende crystal structure and that particle size increased with increasing temperature. The TEM micrograph showed that the mean particle size was about 40 nm for the sample heated at 100 degrees C. A blue shift was observed in the photoluminescence emission spectrum. A possible mechanism of the reaction corresponding to our observation is proposed, (C) 2000 Elsevier Science Ltd. All rights reserved.

The FeCl3-doped poly(3-alkyithiophenes) in solid state

The FeCl3-doped three poly(3-alkylthiophenes) (P3ATs) in solid state, i.e. poly( 3-octylthiophenl) (P3OT), poly(3-dodecylthiophene) (P3ODT) and poly( 3-octadecylthiophene) (P3ODT), were investigated in this paper. In X-ray diffraction results, there are obvious variations of the interlayer and interlayer spacings in the layered structures of P3ATs. In addition, it is found that some orientations of the side-chain groups occur after the doping process. The infrared spectra have also shown the microstructural changes arising from the readjustments of the polymer chains due to the intervention of the dopant. The presence of dopant leads to the formation of bipolarons and polarons at the same time. The conductivity measurements reveal that the conductivity decreases with the increase of the length of sidechain group. We have also observed the relaxation behaviors in the conductivities of the doped polymers. (C) 2001 Elsevier Science B.V. All rights reserved.

High resolution solid-state NMR and DSC study of poly(ethylene glycol) silicate hybrid materials via sol-gel process

Hybrid materials incorporating poly(ethylene glycol) (PEG) with tetraethoxysilane (TEOS) via a sol-gel process were studied for a wide range of compositions of PEG by DSC and high resolution solid-state C-13- and Si-29-NMR spectroscopy. The results indicate that the microstructure of the hybrid materials and the crystallization behavior of PEG in hybrids strongly depend on the relative content of PEG. With an increasing content of PEG, the microstructure of hybrid materials changes a lot, from intimate mixing to macrophase separation. It is found that the glass transition temperatures (T-g) (around 373 K) of PEG homogeneously embedded in a silica network are much higher than that (about 223 K) of pure PEG and also much higher in melting temperatures T-m (around 323 K) than PEG crystallites in heterogeneous hybrids. Meanwhile, the lower the PEG content, the more perfect the silica network, and the higher the T-g of PEG embedded in hybrids. An extended-chain structure of PEG was supposed to be responsible for the unusually high T-g of PEG. Homogeneous PEG-TEOS hybrids on a molecular level can be obtained provided that the PEG. content in the hybrids is less than 30% by weight. (C) 1998 John Wiley & Sons, Inc.