The two-step electrosynthesis of nanocomposites of Ag, Au, and Pd nanoparticles with iron(ii) oxide-hydroxide

The two-step electrosynthesis of metal nanoparticle (MNP, M = Ag, Pd, and Au) nanocomposites with iron oxide-hydroxide FeO-xFe(OH)2 was investigated.

Structure and catalytic activity of ultrasmall Rh, Pd and (Rh + Pd) nanoparticles obtained by mediated electrosynthesis

Efficient mediated electrosynthesis of catalytically active ultrasmall mono- and bimetallic nanoparticles of Rh, Pd stabilized with CTAC was carried out in water.

Mediated electrochemical synthesis of metal nanoparticles

The review integrates and analyzes data of original studies on the mediated electrosynthesis of metal nanoparticles — a new efficient and environmentally attractive process for obtaining these particles in the solution bulk. The general principles and specific features of electrosynthesis of metal nanoparticles by mediated electroreduction of metal ions and complexes are considered. The discussed issues include the role of cyclic voltammetry in the development of this method, the method efficiency, some aspects of selection of mediators, and aggregation, stabilization and catalytic activity of the metal nanoparticles thus obtained. Analysis of the results of mediated electrosynthesis of Pd, Ag, PdAg, Au, Pt and Cu nanoparticles stabilized by various compounds and mediated electrogeneration of highly active metal particles is used as basic data for discussion.

The bibliography includes 247 references.

Label-free and sensitive detection of microalgae protein using GNRs-based resonance light scattering system

A novel and label-free gold nanorods (GNRs)-based resonance light scattering system assay has been developed on the basis of that the interactions between microalgae proteins and GNRs could emit strong fluorescence signal.

Methylviologen mediated electrosynthesis of gold nanoparticles in the solution bulk

Electrosynthesis of gold nanoparticles (AuNp) was carried out by methylviologen mediated reduction of Au(i) at potentials of the MV²⁺/MV˙⁺redox couple in water/0.1 M NaCl medium, in the absence and in the presence of stabilizers.

Adsorption of ozone and plasmonic properties of gold hydrosol: the effect of the nanoparticle size

The impact of the size of gold nanoparticles on the magnitude of the bathochromic shift of their plasmon resonance peak upon ozone adsorption is revealed and analyzed. Namely, the plasmon band position of 7, 10, 14 and 32 nm nanoparticles shifts toward longer wavelengths by 51, 35, 23 and 9 nm respectively, i.e. the smaller the nanoparticles, the greater the shift of the band. Thus, the sensor efficiency of gold hydrosol increases with a decrease in the nanoparticle size. The shift of the Fermi level is a linear function of the inverse radius of nanoparticles. The observed alterations in the gold nanoparticle plasmonic properties and the Fermi level position are explained by a decrease in the electron density of nanoparticles caused by the electrons' partial binding by adsorbed O3 molecules. The insignificance of oxygen and nitrous oxide effects on plasmonic properties of gold hydrosol is observed.

Statistical and electrical properties of the conduction electrons of a metal nanosphere in the region of metal-insulator transition

Statistical and electrical properties of the conduction electrons of a silver or gold sphere with a radius from 1 to 2 nm are shown to differ drastically from the properties of electrons in a bulk metal sample. If the radius of a noble metal sphere decreases from 10 to 1 nm, its conductivity oscillates around the bulk metal value with increasing amplitude and drops at the 'magic' numbers of electrons. These numbers are equal to 186, 198, 254, 338, 440, 556, 676, 832, 912, 1,284, 1,502, and 1,760, in agreement with various experimental data. We show that the conductivity and capacitance of a metal nanosphere can be changed by several orders of magnitude by adding or removing just a few electrons.

Structural analysis of PdAu dendrimer-encapsulated bimetallic nanoparticles

PdAu dendrimer-encapsulated nanoparticles (DENs) were prepared via sequential reduction of the component metals. When Au is reduced onto 55-atom, preformed Pd DEN cores, analysis by UV-vis spectroscopy, electron microscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy leads to a model consistent with inversion of the two metals. That is, Au migrates into the core and Pd resides on the surface. However, when Pd is reduced onto a 55-atom Au core, the expected Au core-Pd shell structure results. In this latter case, the EXAFS analysis suggests partial oxidation of the relatively thick Pd shell. When the DENs are extracted from their protective dendrimer stabilizers by alkylthiols, the resulting monolayer-protected clusters retain their original Au core-Pd shell structures. The structural analysis is consistent with a study of nanoparticle-catalyzed conversion of resazurin to resorufin. The key conclusion from this work is that correlation of structure to catalytic function for very small, bimetallic nanoparticles requires detailed information about atomic configuration.

Synthesis and agglomeration of gold nanoparticles in reverse micelles

Reverse micelles prepared in the system water, sodium bis-(2-ethylhexyl) sulfoccinate (AOT), and isooctane were investigated as a templating system for the production of gold nanoparticles from Au(III) and the reducing agent sulfite. A core-shell Mie model was used to describe the optical properties of gold nanoparticles in the reverse micelles. Dynamic light scattering of gold colloids in aqueous media and in reverse micelle solution indicated agglomeration of micelles containing particles. This was verified theoretically with an analysis of the total interaction energy between pairs of particles as a function of particle size. The analysis indicated that particles larger than about 8 nm in diameter should reversibly flocculate. Transmission electron microscopy measurements of gold nanoparticles produced in our reverse micelles showed diameters of 8-10 nm. Evidence of cluster formation was also observed. Time-correlated UV-vis absorption measurements showed a red shift for the peak wavelength. This was interpreted as the result of multiple scattering and plasmon interaction between particles due to agglomeration of micelles with particles larger than 8 nm.

Bimetallic Palladium−Gold Dendrimer-Encapsulated Catalysts

The synthesis, characterization, and catalytic properties of 1-3 nm-diameter bimetallic PdAu dendrimer-encapsulated catalysts are reported. Both alloy and core/shell PdAu nanoparticles were prepared. The catalytic hydrogenation of allyl alcohol was significantly enhanced in the presence of the alloy and core/shell PdAu nanoparticles as compared to mixtures of single-metal nanoparticles.