The Mechanistic Details for the Growth of Palladium Nanoparticles on Graphene Oxide Support

Effect of the Synthetic Approach on the Formation and Magnetic Properties of Iron-Based Nanophase in Branched Polyester Polyol Matrix

This article shows the success of using the chemical reduction method, the polyol thermolytic process, the sonochemistry method, and the hybrid sonochemistry/polyol process method to design iron-based magnetically active composite nanomaterials in a hyperbranched polyester polyol matrix. Four samples were obtained and characterized by transmission and scanning electron microscopy, infrared spectroscopy and thermogravimetry. In all cases, the hyperbranched polymer is an excellent stabilizer of the iron and iron oxides nanophase. In addition, during the thermolytic process and hybrid method, the branched polyol exhibits the properties of a good reducing agent. The use of various approaches to the synthesis of iron nanoparticles in a branched polyester polyol matrix makes it possible to control the composition, geometry, dispersity, and size of the iron-based nanophase and to create new promising materials with colloidal stability, low hemolytic activity, and good magnetic properties. The NMR relaxation method proved the possibility of using the obtained composites as tomographic probes.

Counterion Concentration Profiles at the Graphene Oxide/Water Interface

Despite enormous interest toward graphene oxide (GO) from the research community, surprisingly, little is known about its solutions. In particular, the questions related to the structure of the GO/liquid interface have not been yet properly addressed. In this report, we use a simple but efficient experimental approach to investigate the distribution of the four metal cations Na⁺, Cs⁺, Ni²⁺, and Gd³⁺ at the GO/water interface. We demonstrate that the concentration of the cations decreases exponentially with the distance from the GO surface. Such distribution for colloid systems was theoretically predicted and commonly accepted for a century but, to the best of our knowledge, has been never proved experimentally. We further demonstrate that the shape of the counterion distribution profiles depends on the pH of solution and on the fine chemical structure of GO. In particular, organic sulfates and vinylogous acids that are ionizable at different pH levels are responsible for the difference in the shapes of the concentration profiles. Unlike classical colloid systems, the diffuse layer in the GO solutions is rather broad (30-55 nm), and the concentration gradient is registered even at distances of >55 nm from the GO surface, which is typically considered as the bulk solution. The latter observation is explained by the immobilized character of the GO flakes in the nematic phase, impeding the flow of liquid and the migration of hydrated metal cations. This helps to establish and maintain the long-range concentration gradient in the space between the two parallel neighboring GO flakes. Based on the new findings and on the previously reported data, we formulate some basic principles of GO solutions.

Catalytic properties of graphene oxide/palladium composites as a function of the fabrication method

In this work, we used a two-step synthetic procedure to prepare palladium nanoparticles (Pd-NP) on a graphenic support by impregnating graphene oxide (GO) with Pd(ii) ions with subsequent thermal or chemical reduction of palladium.

Growth of invar nanoparticles on a graphene oxide support

Alloyed binary invar-like FeNi nanocrystals are synthesized on the surface of graphene oxide in a two-step impregnation–annealing procedure.

Direct growth of oriented nanocrystals of gamma-iron on graphene oxide substrates. Detailed analysis of the factors affecting unexpected formation of the gamma-iron phase

Substrate-oriented nanocrystals of room-temperature-stable gamma-iron have been synthesized by a two-step impregnation/annealing method on a graphene oxide surface.