The AFM characterization of Ni(phen)(3)(2+) fixing effects on DNA

In this paper, the fixing and stretching effect of Ni(phen)(2+)(3) with different concentrations on DNA had been studied by Tapping mode AFM. Under an ambient condition, the high-resolution DNA images were obtained, the average height, width and length of well spread DNA molecules were measured. The results showed that because of the variations of ionic concentration, the density and topography of DNA molecules on substrate had a great difference. The AFM and gel electrophoresis results also showed that, under our experimental condition, DNA molecules kept intact, Ni(phen)(2+)(3) did not catalyze the cleavage activity of EcoRI, therefore, Ni (phen)(2+)(3) would be used to make high-resolution physical mapping of DNA by AFM.

Improved size control of large palladium nanoparticles by a seeding growth method

A new approach to the preparation of large palladium nanoparticles with diameters between 25 and 100 nm is presented. In this approach PdCl42- ions are reduced on the surface of performed 12-nm-diameter gold "seeds'' by the introduction of ascorbic acid. The resultant particles exhibit improved monodispersity relative to previous work. Interestingly, these nanoparticles possess Au-Pd core-shell structures. The method can be scaled up to produce 50-110 mg of large palladium nanoparticles.

An organic-inorganic hybrid ultrathin film: preparation and characterization of copper phthalocyanine derivative-ferric oxide nanoparticles

A nanoparticulate ferric oxide-copper tris(2,4-di-tert-amylphenoxy)-8-quinolinolylphthalocyanine hybrid ultrathin film was constructed from alternate layers by the Langmuir-Blodgett technique. The composition, morphology and structure of the film were studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, atomic force microscopy, small-angle X-ray diffraction, visible spectroscopy and polarized UV-Vis spectroscopy. All the above analyses suggest that the thin film is a kind of one-dimensional superlattice, composed of organic and inorganic components. The XPS data reveal that the nanoparticulate ferric oxide exists as an alpha-Fe2O3 phase in the films. Gas-sensing measurements show that the hybrid LB film has very fast response-recovery characteristics towards 2 ppm C2H5OH vapor.

Seed-mediated growth of large, monodisperse core-shell gold-silver nanoparticles with Ag-like optical properties

Large, monodisperse core-shell Au-Ag nanoparticles with Ag-like optical properties have been prepared by the seeding growth method in micellar media.

Single-crystal X-ray structure and properties of K-10[Ni-4(H2O)(2)(AsW9O34)(2)]center dot 4H(2)O

The rational synthesis and the structural and magnetic characterization of a nickel cluster are presented. The compound comprises a rhomblike Ni4O16 group encapsulated between two-heptadentate tungstoarsenate ligands [AsW9O34](9-). The crystal structure of K-10[Ni-4(H2O)(2)(AsW9O34)(2)](.)4H(2)O was solved in monoclinic, P2(1)/n symmetry, with a = 12.258(3) Angstrom, b = 21.232(4) Angstrom, c = 15.837(3) Angstrom, beta = 92.05(3)degrees, V = 4119.1(14) Angstrom(3), Z = 2, and R = 0.0862. The crystal structure of the Ni(II) derivative was compared with that of the Cu(II), Zn(II), Co(II) and Mn(II) derivatives. The Ni4O14(H2O)(2) unit in the compound shows no Jahn-Teller distortion. On the other hand, the Ni(II) derivative shows ferromagnetic exchange interactions within the Ni4O16 group (J = 7.8 cm(-1), J' = 13.7 cm(-1)) and an S = 4 ground state, the highest spin state reported in a heteropoly complex. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited two steps of one-electron redox waves attributed to redox processes of the tungsten-oxo framework. The new catalyst showed an electrocatalytic effect on the reduction of NO2-.

Alternating LB film of ferric oxide nanoparticles-copper phthalocyanine derivative and its gas sensitivity

Nanoparticulate ferric oxide - tris - (2,4-di-t-amylphenoxy) - (8-quinolinolyl) copper phthalocyanine Langmuir-Blodgett Z-type multilayers were obtained by using monodisperse nanoparticle ferric oxide hydrosol as the subphase. XPS data reveal that the nanoparticle ferric oxide exist as alpha -Fe2O3 phase in the films. Transition electron microscopic (TEM) image of the alternating monolayer shows that the film was highly covered by the copper phthalocyanine derivative and the nanoparticles were arranged rather closely. IR and visible spectra all give the results that the nanoparticles were deposited onto the substrate with the copper phthalocyanine derivative. The gas-sensing measurements show that the alternating LB film had very fast response-recovery characteristic to 2 ppm C2H5OH gas, and also sensitive to larger than 200 ppm NH3.

Sol-gel-derived alpha(2)-K7P2W17VO62/graphite/organoceramic composite as the electrode material for a renewable amperometric hydrogen peroxide sensor

The conductive alpha (2)-K7P2W17VO62/graphite/organoceramic composite was prepared by dispersing alpha (2)-K7P2W17VO62 and graphite powder in a propyltrimethoxysilane-based sol-gel solution; it was used as the electrode material for an amperometric hydrogen peroxide sensor. The modified electrode had a homogeneous mirror-like surface and showed well defined cyclic voltammograms. Square-wave voltammetry was employed to study the pH-dependent electrochemical behavior of c alpha (2)-K7P2W17VO62 doped in the graphite organoceramic matrix, and the experiment showed that both protons and sodium cations participated in the odor process. A hydrodynamic voltammetric experiment was performed to characterize the electrode as an amperometric sensor for the determination of hydrogen peroxide. The sensor can be renewed easily in a repeatable manner by a mechanical polishing step and has a long operational lifetime. (C) 2000 Elsevier Science B.V. All rights reserved.

Gas sensitivity of composite Langmuir-Blodgett films of Fe2O3 nanoparticle-copper phthalocyanine

The Langmuir-Blodgett (LB) composite films, ferric oxide nanoparticle composite with tris-(2,3-di-t-amylphenoxy)-(8-quinolinolinolyl) copper phthalocyanine (CuPcA(2)), were obtained by capped type and alternated type and characterized by X-ray photoelectron spectroscopy (XPS) and visible spectra. The gas sensitivity of the composite films and the pure ferric oxide and pure CuPcA(2) LB films to ammonia and ethanol were measured at room temperature. The composite films could be used as the C2H5OH sensors in the range of 2-8 or 100-200 ppm. The XPS data suggested that the adduct complex NH3-CuPcA(2) was formed after the capped film was exposed to the detected gas of ammonia. (C) 2000 Elsevier Science B.V. All rights reserved.

Europium ion labeling anti-HBs

A microsecond time-resolved laser fluorescence spectroscopic analysis set was developed, A chelate-cyclic anhydride of diethylenetrimin pentaacetic acid anhydride (DTPAA) was synthesized. An anti-HBs antibody was purified, A EU3+ -DTPAA-anti-HBs label was prepared by two step procedure. We described the optimal condtion with EU3+ as marker and DTPAA as chelate bounding to antibody molecule. Labeling parameters such as solvent pH, protein and chelate molar ratio, reaction time, separation method were discussed in detail.

Effect of LB monolayers on the mixed crystals of Lead and barium sulfate

The effect of LB monolayers on the mixed crystal was investigated by using X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), and Inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The results show that LB monolayer has selectivity for the different nucleation ions with equal charge numbers and about the same ion radius. The selectivity is dependent on the head groups of monolayer. The monolayer and the doped ions have also an effect on the crystal morphology. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

Self-assembled multilayers of alternating gold nanoparticles and dithiols: approaching to superlattice

The preparation of self-assembled multilayers of alternating gold nanoparticles and dithiols on Si or SiO2 substrates coated with (3-aminopropyl) trimethoxysilane are reported. The superlattice structure of these self-assembled multilayers was demonstrated by the results of UV-Vis spectrometry, AFM and X-ray diffraction measurements. The multilayer assembled by small-size gold particles has good periodic structure. (C) 2000 Elsevier Science B.V. All rights reserved.

Laser-time-resolved fluorescence spectroscopy in immunoassays

This paper described a laser-excited time-resolved fluoroimmunoassay set. It made lanthanide ion to couple the anhydrde of diethylenetriaminepentaacetic acid (DTPAA) for labeling antibodies. The experiment used polystyrene tap coated with HCV antigen as the solid phase and a chelate of the rare earth metal europium as fluorescent label. A nitrogen laser beam was used to excite the Eu3+ chelates and after 60 ys delay time,the emission fluorescence was measured. Background fluorescence of short lifetimes caused by serum components and Raman scattering can be eliminated by set the delay rime. In the system condition, fluorescent spectra and fluorescent lifetimes of Eu3+ beta-naphthoyltrifluroacetone (NTA) chelates were measured. The fluorescent lifetime value is 650 mu s. The maximum emssion wavelength is 613 nm. The linear range of europium ion concentration is 1 x 10(-7)- 1 x 10(-11) g.mL(-1) and the detection limit is 1 x 10(-13) g.mL(-1). The relative standard deviation of determination ( n = 12) for samples at 0.01 ng.mL(-1) magnitude is 6.4%. Laser-TRFIA was also found to be suitable for diagnosis of HCV. The sensitvity and specificity were comparable to enzyme immunoassay. The result was obtained with laser-TRFIA for 29 human correlated well with enzyme immunoassay.

Preparation and properties of conducting polymer of doped polyaniline LB film

Stable monolayer of polyaniline doped with camphor sulfonic acid at the air-water interface has been obtained and has been successfully deposited by Langmuir-Blodgett technique onto CaF2 substrate. IR and UV-Vis-NIR spectra show that the doped molecules dedoped partially from the PANI backbone during the monolayer compression or deposition. Gas-sensing measurement indicates that the doped polyaniline LB film was sensitive to ethanol vapor at room temperature.

Renewable-surface amperometric nitrite sensor based on sol-gel-derived silicomolybdate-methylsilicate-graphite composite material

A new type of silicomolybdate-methylsilicate-graphite composite material was prepared by the sol-gel technique and used for the fabrication of an amperometric nitrite sensor. The silicomolybdic anion acts as a catalyst, the graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. Cyclic voltammetry, square-wave voltammetry and chronoamperometry were employed to characterize the sensor. The amperometric nitrite sensor exhibited a series of good properties: high sensitivity (1.771 mu A mmol(-1) dm(3)), a short response time (7 s), remarkable long-term stability and especially reproducibility of surface renewal in the event of electrode surface fouling.

Study of ferric oxide nanoparticles-tris-(2,4-di-t-amylphenoxy)-(8-quinolinolyl) copper phthalocyanine composite LB film

The ferric oxide nanoparticles-tris-(2,4-di-t-amylphenoxy)-(8-quinolinolyl) copper phthalocyanine (CuPcA(2)) composite ultrathin film was obtained by LB (Langmuir-Blodgett) technique. Structure of the composite LB film was characterized by X-ray photoelectron spectra, transmission electron microscopy, infrared spectra and visible spectra. Gas sensitivity measurements indicate that the composite LB film is sensitive to 100-200 ppm C2H5OH at room temperature. (C) 2000 Elsevier Science S.A. All rights reserved.