Aptamer-based label-free method for hemin recognition and DNA assay by capillary electrophoresis with chemiluminescence detection

An aptamer-based label-free approach to hemin recognition and DNA assay using capillary electrophoresis with chemiluminescence detection is introduced here. Two guanine-rich DNA aptamers were used as the recognition element and target DNA, respectively. In the presence of potassium ions, the two aptamers folded into the G-quartet structures, binding hemin with high specificity and affinity. Based on the G-quartet-hemin interactions, the ligand molecule was specifically recognized with a K (d)approximate to 73 nM, and the target DNA could be detected at 0.1 mu M. In phosphate buffer of pH 11.0, hemin catalyzed the H2O2-mediated oxidation of luminol to generate strong chemiluminescence signal; thus the target molecule itself served as an indicator for the molecule-aptamer interaction, which made the labeling and/or modification of aptamers or target molecules unnecessary. This label-free method for molecular recognition and DNA detection is therefore simple, easy, and effective.

Electrochemical designing of Au/Pt core shell nanoparticles as nanostructured catalyst with tunable activity for oxygen reduction

Au/Pt core shell nanoparticles (NPs) have been prepared via a layer-by-layer growth of Pt layers on An NPs using underpotential deposition (UPD) redox replacement technique. A single UPD Cu monolayer replacement with Pt(11) yielded a uniform Pt film on Au NPs, and the shell thickness can be tuned by controlling the number of UPD redox replacement cycles. Oxygen reduction reaction (ORR) in air-saturated 0.1 M H2SO4 was used to investigate the electrocatalytic behavior of the as-prepared core shell NPs. Cyclic voltammograms of ORR show that the peak potentials shift positively from 0.32 V to 0.48 V with the number of Pt layers increasing from one to five, suggesting the electrocatalytic activity increases with increasing the thickness of Pt shell. The increase in electrocatalytic activity may originate mostly from the large decrease of electronic influence of Au cores on surface Pt atoms. Rotating ring-disk electrode voltammetry and rotating disk electrode voltammetry demonstrate that ORR is mainly a four-electron reduction on the as-prepared modified electrode with 5 Pt layers and first charge transfer is the rate-determining step.

Microarray-based kinase inhibition assay by gold nanoparticle probes

We report on the development of a new class of kinase microarray for the detection of kinase inhibition based on marking peptide phosphorylation/biotinylation events by attachment of gold nanoparticles followed by silver deposition for signal enhancement. The alpha-catalytic subunit of cyclic adenosine 5'-monophosphate-dependent protein kinase (PKA), and its well-known substrate, kemptide, were used for the purpose of monitoring phosphorylation and inhibition. As expected, highly selective inhibition of PKA is demonstrated with the four inhibitors: H89, HA1077, mallotoxin, and KN62. Furthermore, an inhibition assay demonstrates the ability to detect kinase inhibition as well as derive IC50 (half-maximal inhibitory concentration) plots.

Reduction from Eu3+ to Eu2+ in BaAl2O4 : Eu phosphor prepared in an oxidizing atmosphere and luminescent properties of BaAl2O4 : Eu

A reduction phenomenon of Eu3+ -> Eu2+ was observed for the first time when Eu3+ ions were doped into an AlO4-tetrahedron-containing compound BaAl2O4 in an oxidizing atmosphere of air by high-temperature solid-state reaction. X-ray powder diffraction patterns and photoluminescent spectra are used to confirm the compound structure and detect the simultaneous existence of both divalent and trivalent europium ions, respectively. The abnormal Eu3+ -> Eu2+ reduction is explained by a charge compensation model. Spectroscopic properties of BaAl2O4:Eu are discussed and Eu2+ emission spectrum shows consistence with the results reported by Katsumata et a]. [J. Cryst. Growth 198/199 (1999) 869.] and Lin et al. [Mater. Chem. Phys. 70 (2001) 156.].

Single-crystalline nanowires of SiC synthesized by carbothermal reduction of electrospun PVP/TEOS composite fibres

Nanowires of SiC were synthesized by carbothermally reducing PVP/TEOS composite fibres obtained by electrospinning. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) indicated that the SiC nanowires are single crystalline in nature. Both Fourier-transformed infrared spectroscopy and HRTEM indicated that a thin layer of SiO2 was formed on the outer surface of the nanowire as a result of post-heat treatment for the removal of residual carbon. Such SiO2 layer protects the inner SiC fibre from further oxidation. The formation mechanism of single-crystalline SiC nanowires was proposed based on our understanding and characterizations. The growth of the nanowire is believed to be along the ( 111) of its cubic cell.

The real role of carbon in Pt/C catalysts for oxygen reduction reaction

A new electrocatalysis of carbon materials for oxygen reduction reaction (ORR) on Pt/C catalysts was discovered. It was found that there exist two kinds of electroactive sites on these supports of carbon materials, which can effectively electrocatalyze the reduction of peroxide intermediated from oxygen reduction on Pt, as this provides continuous driving force to move the equilibrium toward the production of peroxide from ORR.

Electrocatalytic reduction of 1,2-diiodoethane by anions of supramolecular complex of (beta-CD)(2)/C-60 in DMF solution

The homogeneous electrocatalytic reduction of 1,2-diiodoethane by anions of the supramolecular complex of (beta-CD)(2)/C-60 in DMF solution is reported. The results show that the trianion of (beta-CD)(2)/C-60 exhibits electrocatalytic behavior towards the reduction of 1,2-diiodoethane, whereas the diani on is unable to reduce the diiodoethane. The second-order catalytic rate constant in DMF solution was determined to be 3.1 x 10(5) M-1 s(-1) by analysis of voltammetric responses under pseudo-first-order conditions with respect to (beta-CD)(2)/C-60. The results suggest that the host beta-cyclodextrin molecules have little effect on the electrocatalytic ability of the encapsulated C-60 toward organic halides.

Preparation of hybrid thin film modified carbon nanotubes on glassy carbon electrode and its electrocatalysis for oxygen reduction

A hybrid thin film containing Pt nanoparticles and [tetrakis(N-methylpyridyl)porphyrinato] cobalt (CoTMPyP) modified multi-walled carbon nanotubes (MWNTs) on a glassy carbon (GC) electrode surface was fabricated. This hybrid film electrode exhibited remarkable electrocatalytic activity for oxygen reduction and high stability with promising applications in fuel cells.

Synthesis of gold nanoplates by aspartate reduction of gold chloride

Single crystal nanoplates with thickness less than 30 nm, characterized by hexagonal and truncated triangular shapes bounded mainly by {111} facets, were obtained in large quantities by aspartate reduction of gold chloride.

Electrochemical design of ultrathin platinum-coated gold nanoparticle monolayer films as a novel nanostructured electrocatalyst for oxygen reduction

The deliberate tailoring of nanostructured metallic catalysts at the monolayer-level is an ongoing challenge and could lead to new electronic and catalytic properties, since surface-catalyzed reactions are extremely sensitive to the atomic-level details of the catalytic surface. In this article, we present a novel electrochemical strategy to nanoparticle-based catalyst design using the recently developed underpotential deposition (UPD) redox replacement technique. A single UPD Cu replacement with Pt2+ yielded a uniform Pt layer on colloid gold surfaces. The ultrathin (nominally monolayer-level) Pt coating of the novel nanostructured particles was confirmed by cyclic voltammetry and X-ray photoelectron spectra (XPS). The present results demonstrate that ultrathin Pt coating effects efficiently and behaves as the nanostructured monometallic Pt for electrocatalytic oxygen reduction, and also shows size-dependent, tunable electrocatalytic ability. The as-prepared ultrathin Pt-coated Au nanoparticle monolayer electrodes reduce O-2 predominantly by four electrons to H2O, as confirmed by the rotating ring-disk electrode (RRDE) technique.

Electrocatalytic reduction of oxygen at multi-walled carbon nanotubes and cobalt porphyrin modified glassy carbon electrode

The multi-walled carbon nanotubes (MWNTs) modified glassy carbon electrode exhibited electrocatalytic activity to the reduction of oxygen in 0.1 M HAc-NaAc (pH 3.8) buffer solution. Further modification with cobalt porphyrin film on the MWNTs by adsorption, the resulted modified electrode showed more efficient catalytic activity to O-2 reduction. The reduction peak potential of O-2 is shifted much more positively to 0.12 V (vs. Ag/AgCl), and the peak current is increased greatly. Cyclic voltammetry (CV), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), were used to characterize the material and the modified film on electrode surface. Electrochemical experiments gave the total number of electron transfer for oxygen reduction as about 3, which indicated a co-exist process of 2 electrons and 4 electrons for reduction of oxygen at this modified electrode. Meanwhile, the catalytic activities of the multilayer film (MVVNTs/CoTMPyP)(n) prepared by layer-by-layer method were investigated, and the results showed that the peak current of O-2 reduction increased and the peak potential shifted to a positive direction with the increase of layer numbers.

Hydrothermal synthesis and crystal structure of a sulfur-bridged binuclear copper(II) coordination polymer generated by a spontaneous reduction

A simultaneous reduction SO42- to S2- by 2,5-pyridinedicarboxylate under hydrothermal conditions produced a new binuclear copper(II) coordination polymer [CuS(4,4'-bipy)](n) (4,4-bipy = 4,4'-bipyridine) (1). Single crystal X-ray analysis revealed that compound I consisted of sulfur-bridged binuclear copper(II) units with Cu-Cu bonding which were combined with 4,4-bipy to generate a three-dimensional network constructed from mutual interpenetration of two-dimensional (6,3) nets. Crystal data for 1:C10H8CuN2S, tetragonal 14(1)/acd, a = 14.0686(5) Angstrom, b = 14.0686(5) Angstrom, c = 38.759(2) Angstrom, Z = 32. Other characterizations by elemental analysis, IR, EPR and TGA analysis were also described in this paper.