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.

Studies of Gd-diethylenetriamine pentaacetic acid in boving serum albumin solution by nuclear magnetic resonance spectroscopy

In this paper, the water relaxation enhancement behavior of Gd-diethylenetriamine pentaacetic acid(DTPA) in water and in aqueous solution of bovine serum albumine(BSA) has been studied. The T-1 relaxivity of Gd-DTPA in BSA solution is higher than that in aqueous solution. The results indicate that Gd-DTPA can integrate non-covalently with BSA mainly in forms of (Gd-DTPA) . BSA, (Gd-DTPA)(2) . BSA, for which the apparent equilibrium constant is 0.026 mmol(-1).L,0.0018 mmol(-2).L-2 respectively. This method would be used to study the interactivities between protein and contrast agent.

Electric field-induced conformational transition of bovine serum albumin from alpha-helix to beta-sheet

The irreversible conformational transition of bovine serum albumin (BSA) from alpha-helix to beta-sheet, induced by electric field near the electrode surface, was monitored by circular dichroism (CD) with a long optical path thin layer cell (LOPTLC).

Separation of zinc(II) from europium(III) by using hollow fiber membrane

Extraction and separation of Eu3+ and Zn2+ in sulfuric acid solution was investigated by hollow fiber membrane with cyanex 302 (bis (2,4,4-trimethylpentyl) monothiophosphinic acid) in counter-currently circulating operation. Reaction mechanism of membrane extraction and effect of extractant concentration and H+ concentration in aqueous phase on the mass transfer coefficient were discussed. It can be concluded that Zn2+ can be extracted completely from Eu3+ sulfate solution according to the kinetics competing difference. In one extractor process, extraction percentage of Zn2+ was not completely and Eu3+ was not extracted. Extraction percentage of Zn2+ reached 94.92%, but Eu3+ only reached 8.59% after 100 minutes extraction in two series connectors and that of Zn2+ and Eu3+ reached 99.9% and 6.53% respectively after 40 minutes extraction in three series connectors.

Simultaneous spectrophotometric determination of zinc, cadmium and mercury with hybrid linear analysis

A new method for simultaneous spectrophotometric determination of Zn, Cd and Hg using 2-(5-Br-2-pyridylazo)-5-diethylaminophenol as the color developing reagent was proposed. The absorption spectra of these three complexes have similar features with severe overlap in visible spectral range. For resolving these spectra, hybrid linear analysis was used, and the pure spectrum of each component was obtained from the calibration mixtures by least squares method. The effects of reaction condition, selection of wavelengths, determination of pure spectrum and additivity of absorbances etc. on the determination were discussed. The proposed method offers the advantages of simple, rapid, and accuracy. It has been successfully applied to the simultaneous determination of Zn, Cd and Hg in synthetic sample. A comparison was also made with the partial least squares method.

The electrochemically induced conformational transition of disulfides in bovine serum albumin studied by thin layer circular dichroism spectroelectrochemistry

The conformational transition of disulfides in bovine serum albumin (BSA) induced by electrochemical redox reaction of disulfides were monitored by in-situ circular dichroism (CD) spectroelectrochemistry, with a long optical path thin layer cell and analyzed by a singular value decomposition least square (SVDLS) method. Electrochemical reduction of disulfides drives the left-handed conformation of disulfides changed into the right-handed. At open circuit, eight of the 17 disulfides were of left-handed conformation. Four of the 17 disulfides took part in the electrochemical reduction with an EC mechanism. Only one-fourth of the reduced disulfides returned to left-handed conformation in the re-oxidation process. Some parameters of the electrochemical reduction process, i.e. the number of electrons transferred and electron transfer coefficient, n=8, alphan=0.15, apparent formal potential, E-1(0') = -0.65(+/-0.01) V, standard heterogeneous electron transfer rate constant, k(1)(0) = (2.84 +/- 0.14)x 10(-5) cm s(-1) and chemical reaction equilibrium constant, K-c=(5.13 +/- 0.12) x 10(-2), were also obtained by double logarithmic analysis based on the near-UV absorption spectra with applied potentials. (C) 2001 Elsevier Science B.V. All rights reserved.

Synthesis and characterization of a new layered zinc phosphate: (C3H4N2)(3)Zn-4(HPO4)(PO4)(2) with imidazole coordinating to Zn atoms

A new two-dimensional hybrid zinc phosphate with electro-neutral open-framework has been hydrothermally synthesized by using imidazole as a structure-directing agent, whose structure is characterized with 3-, 4-, 5, and 12-ring layers and coordination bonds between imidazole groups and zinc atoms, resulting in primary building units of ZnO2N2 and ZnO3N.

Langmuir-Blodgett film formation from surfactant-capped zinc sulfide nanoparticles spread on water surface

The surfactant-capped ZnS nanoparticulate multilayer film has been fabricated by Langmuir-Blodgett(LB) technique. ZnS LB firm was investigated by the small-angle x-ray diffraction(XRD), atomic force microscopy(AFM) and transmission electron microscopy(TEM). The results indicate that ZnS nanoparticulate LB film is one-dimensional superlattice.

NMR relaxation studies of GdDTPA in human serum albumin solution

The water relaxation enhancement behavior of GdDTPA in human serum albumin (HSA) solution has been studied. The results indicate that GdDTPA can integrate noncovalently with HSA, mainly in forms of (GdDTPA)HSA and (GdDTPA),HSA, for which the apparent equilibrium constants are 0.05 mM(-1) and 0.02 mM(-2), respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.

Vibrational spectra and structure of zinc phthalocyanine

Semi-empirical molecular orbital calculations using PM3 Hamiltonian were employed to determine qualitative assignments of the vibrational spectrum of zinc phthalocyanine (ZnPc). The assignments are from the potential energy distribution calculations in the normal coordinate analysis and optimized geometry in the PM3 calculations. The structure of the ZnPc molecule is also deduced. (C) 1999 Elsevier Science B.V. All rights reserved.

Compatibilization of blends of polystyrene and zinc salt of sulfonated polystyrene by poly(styrene-b-4-vinylpyridine) diblock copolymer

The compatibilizing effect and mechanism of poly(styrene-b-4-vinylpyridine) diblock copolymer, P(S-b-4VPy), on the immiscible blend of polystyrene (PS)/zinc salt of sulphonated polystyrene (Zn-SPS) were studied. SEM results show that the domains of the dispersed phase in the blend become finer. DSC experiments reveal that the difference between the two T-g's corresponding to the phases in the blends becomes larger on addition of P(S-b-4VPy), mainly resulting from dissolving of the poly(4-vinylpyridine (P4VPy) block in the Zn-SPS phase. FTIR analysis shows that compatibility of P4VPy and Zn-SPS arises from the stoichiometric coordination of the zinc ions of Zn-SPS and pyridine nitrogens of P4VPy. SAXS analysis indicates the effect of the P(S-b-4VPy) content on the structure of the compatibilized blends. When the content of the block copolymer is lower than 4.1 wt%, the number of ion pairs in an aggregate in the Zn-SPS becomes smaller, and aggregates in ionomer in the blend become less organized with increasing P(S-b-4VPy). When the P(S-b-4VPy) content in the blend is up to 7.4 wt%, a fraction of P(S-b-4VPy) form a separate domain in the blend. (C) 1999 Elsevier Science Ltd. All rights reserved.

NMR studies of Gd(DTPA-BIN) in human serum albumin solution

Stable gadolinium complexes, such as Gd(DTPA) and Gd(DOTA), are usually used as the contrast agents for magnetic resonance imaging(MRI). Reported here are the enhanced relaxation properties of a novel gadolinium complex, diethylene-triaminopentaacetate Lis (isoniazid) [Gd(DTPA-BIN)], in aqueous and in human serum albumin(HSA) solution, which indicates that (1) two Gd(DTPA-BIN) can integrate non-covalently with one HSA with an equilibrium constant of 0. 02 mmol(-2) . L-2 ; (2) the relaxivities are 3. 28 and 4. 92 mmol(-1) . L . s(-1) for the free Gd(DTPA-BIN) and the [Gd(DTPA-BIN)](2), HSA conjugator, respectively; (3) the rotational correlation time of protein conjugator is notably higher than that of the free complex, The above results may imply that Gd(DTPA-BIN) has a higher tissue selectivity than that of its parent Gd(DTPA).

Dependence of linear electro-optic coefficient on difference in the atomic sizes in zinc blende crystals

Covalent radii of the bonding elements have strong effects on the linear electro-optic coefficients of zinc blende crystals; these effects can be quantitatively determined by investigating the relation between the difference in the atomic sizes rho and the magnitude of the linear electro-optic tensor coefficient r(41). It is interesting to note that for the same cation Zn2+, Ga3+, or In3+ the magnitude of r(41) increases with increased covalent radius of the bonded anion r(beta). Especially with the increasing tendency of the parameter rho, the magnitude of r(41) of crystals that have a same cation will increase suddenly when the value of r(beta) becomes larger. (C) 1997 Academic Press.

The fabrication and performance of an Ag/AgCl reference electrode in human serum

A simple set of electric circuits was used to assemble a pulse generator. With pulse potentials and under galvanostatical control, a clean silver wire was anodized electrochemically for 0.2-0.5 min in 1.0 moll(-1) HCl with a pulse current density of 20 mA cm(-2), and the pulse wave parameters of t(a)/t(c) = 1 and a cycle of 4 s forming an Ag/AgCl reference electrode. Even though the AgCl layer was consumed during the working period when the Ag/AgCl electrode was used as a cathode, the AgCl layer could be in situ recovered electrochemically in serum used when a reversed potential was applied to the electrode system immediately after the measuring program was finished. The current response curve of the anode indicated that an AgCl layer in high density was basically accomplished during the first 6 pulse cycles in human serum. In order to keep a stable and uniform AgCl layer on the reference electrode after each measuring cycle, the ratio of the recovery time (t(r)) to the working time (t(w)) was measured and the smallest value was obtained at 0.03. The open-circuit potential of the Ag/AgCl electrode with respect to a SCE in 0.1 moll(-1) KCl was monitored over a period of 14 days and the mean value was 40.09 mV vs SCE with a standard deviation of 2.55 mV. The potential of the Ag/AgCl reference electrode did remain constant when the measurements were repeated more than 600 times in undiluted human serum with a standard deviation of 1.89 mV. This study indicated that the Ag/AgCl reference electrode could been rapidly fabricated with a pulse potential and could be used as a reference electrode with long-term stable properties in human serum samples.

Fluorescence spectroscopy studies on the action of rare earths with bovine serum albumin in multimolecular system

In this paper. the interaction of tripositive terbium ions (Tb3+) with bovine serum albumin (BSA) has been investigated in the presence of some alkaline earth metals and citric acid (Cit) by using fluorescence spectroscopy. The results show that Tb-31. BSA and Cit can form ternary complex BSA . Tb-2. Cit(4) in mu =0.1 mol/l NaCl. pH6.3 hexamethylenetetramine buffer. Other tare earths are able to compete for the same binding site in BSA with Tb3+-. The sequence of con,petition is Eu3+>Pr3+>Yb3+>Gd3+>La3+>Ca2+ and Mg2+ cannot replace Tb bound to BSA.