Roles of Pt seeds and chloride anions in the preparation of silver nanorods and nanowires by microwave-polyol method

Silver (Ag) nanomaterials with well-defined crystal structures have been rapidly synthesized in three minutes by a microwave (MW)-polyol method. Various precursors such as H2PtCl6 and Pt(acac)2 have been used to detect real roles of Pt seeds and anions for the formation of the Ag nanomaterials. Furthermore, effect of Cl- anions to final morphologies of the Ag nanostructures has also been explored by pre-adding Cl- precursor such as NaCl or KCl in the ethylene glycol (EG) solutions only including AgNO3 and poly(vinylpyrrolidone) (PVP). The experimental results show that pre-formed metallic Pt seeds are probably not responsible for nucleation and subsequent evolution of 1D Ag products, but Cl- ions indeed influence the formation of the 1D Ag nanostructures as well as perfect crystallization of other Ag nanoparticles with well-defined crystal structures including single- and twinned-FCC crystals. It has been further evidenced that the presence of Cl- ions can accelerate re-dissolution of formed spherical Ag particles and is favorable to the growth of the 1D Ag and other Ag nanostructures with well-defined crystal structures such as single-crystal cubes and twinned bi-pyramids in the MW-assisted polyol reduction process. At the same time, it also indicates that H2PtCl6 probably does not act as a nucleation agent for the 1D Ag products but as a precursor of Cl- ions to affect final morphologies of the Ag products. Possible factors affecting shape-selected process of the Ag nanostructures have been discussed in detail

The role of adsorption species in the formation of Ag nanostructures by a microwave-polyol route

The role of adsorption species in reaction solutions has been studied in microwave-polyol synthesis of silver (Ag) nanostructures. When Ag+ ions from AgNO3 were reduced in ethylene glycol by the addition of H2[PtCl6] and poly-(vinylpyrrolidone) (PVP), a mixture of one-dimensional (1-D) nanorods and nanowires and 3-D spherical, cubic, and triangular-bipyramidal nanoparticles was obtained within three minutes. It has been previously believed that PVP acts as a surfactant and its selective adsorption on {100} facets results in pentagonal 1-D nanorods or nanowires and cubic and triangular-bipyramidal nanocrystals. We found here that these Ag products could also be formed without the addition of PVP in the presence of Cl- ions, though their yields were lower than those in the presence of PVP by a factor of ˜300. These results indicate that Cl- anions can also act as adsorption species to assist the formation of these Ag nanostructures. It is concluded that the difference in the adsorption ability of different species in solution on Ag nanostructures determines final shapes, sizes, and yields of formed Ag nanostructures

Fast Preparation and Shape Control of Metallic Nanostructures by Using Microwave Heating

Microwave (MW) heating has received a considerable attention as a new promising method for the synthesis of metallic nanostructures in solutions. In this review, advantageous application of this method has been demonstrated by using typical examples for the preparation of Au, Ag, Au@Ag, and Pt/C nanostructures. No only spherical nanoparticles, but also single crystalline polygonal sheets, plates, rods, wires, and core-shell structures were prepared within a few minutes under MW heating. Morphologies and sizes of nanostructures could be controlled by changing various experimental parameters, such as concentrations of metallic salt and surfactant polymer, chain length of the surfactant polymer, and solvent. In general, nanostructures with smaller sizes, narrower size distributions, and higher degree of crystallization were obtained under MW heating than those in conventional oil-bath heating

マイクロ波加熱を用いた金属ナノ材料の迅速合成と形態制御

Microwave (MW) heating has received a considerable attention as a new promising method for the synthesis of metallic nanostructures in solutions. In this review, advantageous application of this method has been demonstrated by using typical examples for the preparation of Au, Ag, Au@Ag, and Pt/C nanostructures. No only spherical nanoparticles, but also single crystalline polygonal sheets, plates, rods, wires, and core-shell structures were prepared within a few minutes under MW heating. Morphologies and sizes of nanostructures could be controlled by changing various experimental parameters, such as concentrations of metallic salt and surfactant polymer, chain length of the surfactant polymer, and solvent. In general, nanostructures with smaller sizes, narrower size distributions, and higher degree of crystallization were obtained under MW heating than those in conventional oil-bath heating