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.

Precursor induced synthesis of hierarchical nanostructured ZnO

As-synthesized ZnO nanostructures with a bladed bundle-like architecture have been fabricated from a flower-like precursor ZnO (.) 0.33ZnBr(2) (.) 1.74H(2)O via a mechanism of dissolution - recrystallization. Experimental conditions, such as initial reactants and reaction time, are examined. The results show that no bladed bundle-like ZnO hierarchical nanostructures can be obtained by using the same molar amount of other zinc salts, such as ZnBr2, instead of the flower-like ZnO (.) 0.33ZnBr(2) (.) 1.74H(2)O precursor, and keeping other conditions unchanged. The products were characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The ZnO nanostructures are mainly composed of nanowires with a diameter around 40 - 50 nm and length up to 1.5 - 2.5 mu m. Meanwhile, ZnO nanoflakes with a thickness of about 4 - 5 nm attached to the surface of ZnO nanowires with a preferred radially aligned orientation. Furthermore, the photoluminescence (PL) measurements exhibited the unique white-light-emitting characteristic of hierarchical ZnO nanostructures. The emission spectra cover the whole visible region from 380 to 700 nm.

Synthesis of Pt/Ag bimetallic nanorattle with Au core

A straightforward combination of the seeding growth method and replacement reaction allowed for the formation of a nanorattle composed of a gold core and Pt/Ag shell. The size, structure, and composition of the Pt/Ag rattle-type nanostructure were confirmed by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectrometry.

Syntheses of Ag, PbSe, and PbTe nanocrystals and their binary self-assembly exploration at low size-ratio

Nanocrystals of Ag, PbSe, and PbTe were prepared via a high-temperature organic solution approach, respectively. Using a size-selection technique, the size-distribution of each set of nanocrystals could be fine-tuned and finally monodisperse products were achieved. Superlattice structure of binary self-assemblies in low size-ratio were also explored and characterized by transmission electron microscopy. It is realized that a success of achieving binary self-assembly pattern is greatly dependent on several key factors including particle size-distributions, relative concentrations of both components, as well as the size-ratios between Ag and PbSe (or PbTe) nanocrystals.

Synthesis, crystal structure, and photoluminescent property of a novel heterobimetallic Zn(II)-Ag(I) cyano-bridged coordination polymer incorporating,a pentameric unit [Ag(CN)(2-)](5) assembled by argentophilic interaction

A new photoluminescent heterobimetallic Zn(II)-Ag(I) cyano-bridged coordination polymer, [Ag5Zn2(tren)(2)(CN)(9)] (tren = tris(2-aminoethyl)amine) (1), has been synthesized and structurally characterized. It features rare linear pentameric unit of dicyanoargentate(I) ions assembled by d(10)-d(10) interaction as building blocks. Solid state emission spectrum of I shows strong ultraviolet luminescence with emission peak in the range of 376 nm.

An approach for fabricating self-assembled monolayer of Ag nanoparticles on gold as the SERS-active substrate

In this paper, an approach for fabricating an active surface-enhanced Raman scattering (SERS) substrate is adopted. This approach is based on the assembling of silver nanoparticles film on gold substrate. Rhodamine 6G (R6G) and p-aminothiophenol (P-ATP) were used as probe molecules for SERS experiments, showing that this new active substrate has sensitivity to SERS response. Tapping-mode atomic force microscopy (AFM) was also used to investigate the surface morphology following the fabricating process of the active SERS substrate, which showed that large quantities of silver nanoparticles were uniformly coated on the substrate.

Electrochemical Metalloimmunoassay Based on Enlargement of Gold Nanoparticle Label Treated with Ag Enhancement System

A novel sensitive electrochemical immunoassay with colloidal gold as the antibody labeling tag and subsequent signal amplification by silver enhancement is described. Colloidal gold was treated by a light-sensitive silver enhancement system which made silver deposit on the surface of colloidal gold(form Au/Ag core-shell structure), followed by the release of the metallic silver atoms anchored on the antibody by oxidative dissolution of them in an acidic solution and the indirect determination of the dissolved Ag+ ions by anodic stripping voltammetry(ASV) at a carbon fiber microelectrode. The electrochemical signal is directly proportional to the amount of analyte(goat IgG) in the standard or a sample. The method was evaluated by means of a noncompetitive heterogeneous immunoassay of immunoglobulin G(IgG) with a concentration as low as 0.2 ng/ mL. The high performance of the method is related to the sensitive ASV determination of silver(I) at a carbon fiber microelectrode and to the release of a large number of Ag+ ions from each silver shell anchored on the analyte(goat IgG).

A new alpha-Keggin type polyoxometalate coordinated to four silver complex moieties: {PW9V3O40[Ag(2,2 '-bipy)](2)[Ag-2(2,2 '-bipy)(3)](2)}

A new polyoxometalate derivative {PW9V3O40[Ag(2,2'-bipy)](2)[Ag-2(2,2'-bipy)(3)](2)} 1 has been hydrothermally synthesized and structurally characterized by the single crystal X-ray diffraction. X-Ray analysis showed that both [Ag(2,2'-bipy)](+) and [Ag-2(2,2'-bipy)(3)](2+) units are supported on the alpha-Keggin polyoxoanion [PW9V3O40](6-) via the surface bridging oxygen atoms. 1 represents the first alpha-Keggin type polyoxoanion coordinated with four transition metal complex moieties, which further acts as a neutral molecular units for the construction of an interesting three-dimensional supramolecular framework.

Nanometer scale mechanical study on well defined nanostructured chain aggregation of polyethylene

Two kinds of polyethylene chain aggregation with chain axis perpendicular and parallel to the supported substrate were designed and successfully obtained from melt under an electric field and by melt-drawn method

Encapsulation and luminescence of the nanostructured supramolecular material [Eu(Phen)(4)](NO3)(3)/(CH3)(3)Si-MCM-41

The nanostructured material (NSM) of pure silica MCM-41 molecular sieve was synthesized with tetraethyl orthosilicate (TEOS) as the source of silica and cetyltrimethylammonium bromide (CTMABr) as the template under supersonic wave condition. Then NSM of (CH3)(3)Si-MCM-41 was obtained by introducing trimethylsilyl to MCM-41. (CH3)(3)Si-MCM-41 showed the similar TEM and XRD photographs with the normal crystal of MCM-41 and the diameter of the NSM crystallites with a hexagon shape is of about 10-40 nm. The dispersivity of (CH3)(3)Si-MCM-41 prevails over the NSM of MCM-41 as its hydrophobicity. The fluorescent intensity of (CH3)(3)Si-MCM-41 is 3.4 times as that of the MCM-41. The luminescent functional supramolecular nanostructured material was prepared in EtOH, and characterized by TEM, HRTEM, XRD, TG, IR, and elemental analysis. The results showed that the [Eu(Phen)(4)](NO3)(3) had entered into the channels of nanosized mesoporous sieve of (CH3)(3)Si-MCM-41, forming discrete centers of luminescence. The energy transferring of the host to guest, superficial effect of NSM, quanta tunnel effect, and discrete luminescent center result in the fluorescent intensity of the supramolecule enhancement.

Electrochemical and electrocatalytic properties of microperoxidase-11 adsorbed on the poly-L-lysine modified Ag electrode

It is found that Ply adsorbed roughed silver electrode, it is easy to immobilize MP-11 with the electrostatic interaction and to prepare the MP-11/Ply/Ag modified electrode. The preparation method of the modified electrode is simple. In addition, the modified electrode obtained shows the high and stable electrocatalytic activity for O-2 reduction. It is also found that when the sixth coordination of heme in MP-11 is replaced with other coordination species with stronger coordination ability, such as imidazole, its formal redox potential shifts to the negative direction and the electrocatalytic activity for O-2 reduction is reduced.

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.

Nanostructured hybrid organic-inorganic lanthanide complex films produced in situ via a sol-gel approach

Communication: Nanostructural hybrid organic-inorganic lanthanide complex films were prepared in situ by use of a novel sol-gel precursor containing pendant triethoxy-silyl and carboxyl groups (see Figure). The resulting transparent and crack-free films gave rise to strong red or green emission, even at low lanthanide ion concentration. Phase separation and lanthanide ion aggregation were controlled at the nanoscale.