The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)-20% acetonitrile and detected at 1.55 V. The methods were validated over the concentration range 0.05-100 ppm with the overall average recoveries from 83.3 to 102.5% and R.S.D. of less than 10%. The proposed method was further applied to analyse shrimp samples. 相似文献
Rheological and rheo-optical studies are reported for isotropic solutions of the mesogenic rodlike polymer poly(1,4-phenylene-2,6-benzobisthiazole) (PBT). Several PBT samples were used with average contour lengths from 95 to 135 nm. Concentrations were varied over a range just below the concentration Cc for the formation of an ordered (nematic) state. The predictions of a single-integral constitutive equation of the BKZ type utilizing experimental estimates of the distribution of discrete relaxation times is compared with experimental data on the steady-state viscosity ηκ, the recoverable compliance function Rκ, and the steady-state flow birefringence as functions of the shear rate κ, with satisfactory results. The relaxation of the shear stress and the flow birefringence on cessation of steady-state flow at shear rate κ are also compared with the single-integral constitutive equation, and it is found that in the nonlinear response range the data can be superposed over a wide range in κ. The overall behavior is qualitatively similar to that for flexible chains, which can also be fitted by the single-integral constitutive equations over similar ranges of η0R0κ, with η0 and R0 the limiting values of ηk and Rκ for small κ. Of course, the dependence of η0 and R0 on concentration and molecular weight differs markedly for rodlike and flexible-chain polymers. 相似文献
A novel end-capping method of pseudorotaxanes via the hydrosilylation of the alkyne of the axle terminal was developed. RuHCl(CO)(PPh3)3 and RhCl(CO)(PPh3)3 complexes catalyzed the hydrosilylation reactions of the alkyne moiety of several pseudorotaxanes at ambient temperature to give the corresponding [2]- and higher order rotaxanes in high yields with excellent regio- and stereoselectivity. 相似文献
[reaction: see text] Pd-catalyzed monophosphinylation of (R)-2-bromo-2'-iodo-1,1'-binaphthyl with Ph(2)P(O)H afforded (R)-2-bromo-2'-diphenylphosphinyl-1,1'-binaphthyl in good yield with excellent chemoselectivity and no observable racemization. Subsequent lithiation in the presence of excess thiosulfonate furnished an enantiomerically pure sulfenylation product, which was reduced to afford a chiral S-MOP ligand. 相似文献
The study of CO2 electrochemical reduction to useful compounds using bare or modified BDD electrode attracts numerous attentions. Meanwhile, the efficiency of products obtained from CO2 electrochemical reduction is known to be determined by the electrode material and the electrolyte. Formic acid as main product and CO as a minor product, have also been known on the CO2 reduction using BDD electrode. Recently, we reported the successful improvement of CO production from the reduction of CO2 by decorating the surface of BDD electrode with palladium particles. Following this, herein, we present further investigation on electrolyte dependence, including cation and anion dependence and also concentration effect in order to understand deeply the CO2 reduction on surface of palladium modified BDD electrode. The results suggest the use of NaCl and KCl as a catholyte for optimum performance, in addition to the improvement of CO2 reduction product in higher electrolyte concentration. 相似文献
The relationship between the photocatalytic activity and the arrangement of metal cations was investigated with Sr-Al-Nb-O double perovskite (SAN) synthesized at 1400 °C for various calcination times using a solid state reaction. Transmission electron microscopic observation revealed that SAN particles had a domain structure of completely B-site ordered (Sr(2)AlNbO(6)) and disordered (SrAl(0.5)Nb(0.5)O(3)) phases. The ordered phase fraction was determined using a newly proposed mixed-phase model for the Rietveld refinement and a method using the relative intensity of the superlattice line of powder X-ray diffraction. It turned out that the mass fraction of the ordered phase in SAN calcined at 1400 °C could be controlled by the calcination time as 33% (10 h), 37% (20 h), 44% (30 h), and 48% (50 h). Photocatalytic activities of SAN for the evolution of H(2) and O(2) respectively from aqueous solutions of methanol and AgF decreased with increasing the calcination time, that is, with increasing the fraction of the ordered phase. These results suggested that the photocatalytic activity of ordered Sr(2)AlNbO(6) should be lower than that of disordered SrAl(0.5)Nb(0.5)O(3). This is practically the first report to reveal the photocatalytic activity of SAN as well as the effect of cation ordering in oxides on the photocatalytic activity. 相似文献
Getting organized : Assemblies of ferromagnetic FePt nanoparticles were generated with large perpendicular magnetic anisotropy by a magnetic‐field‐assisted layer‐by‐layer method, and subsequently layer‐by‐layer films consisting of L10‐FePt nanoparticles and organic polymers were prepared. These films are phototunable when photochromic molecules are used as polymer layers.
The formation mechanisms of metal particles (platinum (Pt) particles) in an aqueous ethanol solution of poly(N-vinyl-2-pyrrolidone) (PVP) by the photoreduction method have been studied by transmission electron microscopy (TEM) and in situ and ex situ X-ray absorption fine structure (XAFS) analysis. The average diameter of the dilute and concentrated Pt particles in the PVP solution is estimated from TEM to be 2.0 and 2.5 nm, respectively. XAFS analysis was performed for the reduction process of Pt4+ ions to metallic Pt particles for the Pt L3 edge of the colloidal dispersions of the concentrated Pt solutions. The photoreduction process proceeds by the following steps: (1) reduction of PtCl6(2-) to PtCl4(2-), (2) dissociation of Cl from PtCl4(2-), followed by reduction of Pt2+ ionic species to Pt0, (3) formation of a Pt0-Pt0 bond and particle growth by the association of Pt0-Pt0. The reduction of PtCl4(2-) to Pt0 is a slower process, compared with the reduction of PtCl6(2-) to PtCl4(2-). There is a delay between the disappearance of PtCl4(2-) and the formation of Pt0-Pt0 clusters. 相似文献
Three Salen-like gadolinium complexes, namely, mononuclear (4f) complex [{H2L}Gd(NO3)3] (1), heterodinuclear (3d–4f) complex [{LCu}Gd(NO3)3]·0.25H2O (2) and dimeric heterotrinuclear (3d–4f–3d′) complex [{LCu}Gd(H2O)3{Fe(CN)6}]2·6H2O (3) [H2L = N,N′-ethylene-bis(3-methoxysalicylideneimine)] have been synthesized by stepwise reactions. X-ray diffraction analysis reveals that 1 is of a discrete structure in which H2L coordinates to gadolinium ion through O2O2 moiety. Then, addition of Cu(Ac)2·H2O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes [{LCu}Gd(NO3)3]. 3 features a unique 1D ladder-like topology structure through the intermolecular double links of Cu–N bonds. The measurement of variable-temperature magnetic susceptibility reveals that complex 1 exhibits antiferromagnetic interaction while 2 and 3 exhibit ferromagnetic interaction between spin carriers. The correlations between the structure and magnetism are described and discussed. 相似文献
The first preparation of an Fe(II) spin-crossover complex including a 1,3-dithiole ligand is reported. Crystal analyses of both the low- and the high-temperature phases reveal that short S...S contacts play a key role in an abrupt spin transition. 相似文献