Rational Synthesis of Cylindrical Silver Single-crystalline Nanowires via Poly(vinyl pyrrolidone) Reduction of AgCl

We presented a simple yet convenient hydrothermal approach for the large-scale synthesis of uniform cylindrical silver (Ag) single-crystalline nanowires with diameters of about 25 nm and lengths of 1-4 μm. Poly(vinyl pyrrolidone) (PVP) was used as a reducing agent, and AgCl was used as a precursor to deliberately control [Ag^+] at a low degree in the overall reaction process through its dynamic equilibrium by directly reducing AgCl with PVP at a quasi-equilibrium growth condition. The as-obtained products were characterized by powder X-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), infrared spectra (IR) and Raman spectra. Factors such as [PVP], reaction temperature, time, and species of reducing agents and precursors were investigated to have strong influences on the morphologies and structures of the resultant Ag nanostructures. The wire diameter can conveniently be adjusted between 25 and 50 nm by simply adjusting [PVP], reaction temperature and reducing agent species. The as-synthesized silver nanowires can be self-assembled into perfect order arrays after being dried on tin foil due to the PVP coating on the surface, the circular cross-section and the uniform diameter of the Ag nanowires. These special silver nanowires with a core-shell structure as well as their spontaneous self-assembly of order arrays are expected to provide potential applications in flexible conductors, dielectric materials, electromagnetic shielding materials and nano-devices.

Synthesis and Structure of Azacalix[2]pyrimidine[2]triazines and Their Self-assembly in the Solid State

A number of azacalix[2]pyrimidine[2]triazines were synthesized in moderate to good yields from both a step-wise fragment coupling approach and a one-pot reaction strategy starting from 4,6-diaminopyrimidines and cyanuric chloride.Nucleophilic aromatic substitution reaction of resulting dichloro-substituted azacalix[2]-pyrimidine[2]triazines with NH_(4)Cl led to the formation of NH_(2)-bearing azacalix[2]pyrimidine[2]triazine analogs.Azacalix[2]pyrimidine[2]triazines adopted symmetric 1,3-alternate conformations in solution while twisted 1,3-alternate conformations were observed in the solid state.In the presence of different additives during the growth of single crystals,azacalix[2]pyrimidine[2]triazines containing amino(-NH_(2))groups gave varied self-assembled structures due to the formation of different intermolecular hydrogen bond motifs.

Co_(a)Sm_(b)O_(x) Catalyst with Excellent Catalytic Performance for NH3 Decomposition

Transition metal-rare earth oxide catalysts had the ability to catalyze ammonia decomposition according to recent years'scientific reports.However,most of those catalysts had their own limitations:the catalytic activity was poor,and/or the active species could not clearly be iden tified.Here we report the Co_(a)Sm_(b)O_(x) catalysts with good dispersi on,con trollable content,and excelle nt catalytic performs nee for amm onia decomposition.The various content catalysts were syn thesized by aerosol-assisted self-assembly approach.These catalysts had high dispersion and great morphology according to the images of the transmission electron microscope(TEM)and the seanning electron microscope(SEM).The temperature-programmed reduction by hydrogen(Hq-TPR)and in-situ X-ray diffraction(XRD)results indicated that the interaction between cobalt oxide and samarium oxide influenced the redox properties of cobalt oxide.Combined with in-situ Raman,we found that Co0 was an active species of the Co_(a)Sm_(b)O_(x) catalysts in ammonia decomposition.Moreover,the temperature-programmed desorption of NH_(3)(NH_(3)-TPD)data illustrated that the addition of Sm was beneficial to the adsorption of NH3.In general,we successfully obtained the Co_(a)Sm_(b)O_(x) catalyst with high activity and good stability.More im-porta ntly,we have identified the structure-function relation ship of catalysts by exploring the active species in the reaction process.