| The shape of nanostructure determines the types of crystal planes exposed on its surfaceand thus greatly affects its properties and functions, particularly in catalysis andelectrocatalysis exclusively occurring on the nanostructure surface. Therefore, tailoring theshape of nanostructures is becoming an emerging strategy to innovate functional materials.Based on these, Ag nanospheres, nanorods, nanwires, nanoplates and hollow Ag spheres wereprepared through modified polyol synthesis method and aqueous synthesis method in ourpaper.Ag nanoparticles (NPs) with a size range of6to42nm were synthesized using NaBH4asreducing agent and Tri-sodium citrate (TSC) and poly (vinyl pyrolidone)(PVP) as stabilizersthrough a facile one pot aqueous synthesis. In the presence of PVP, TSC, NaCl, Ag atoms canselectively deposite on special facets of Ag nucleus and finally formed Ag nanospheres. Theselective adsorption role of TSC and PVP on the {111} plane, in addition to the stacking faultof {111} plane, led to silver atoms in the reaction solution deposited on {111} facet in theabsence of NaCl, and then formed triangular Ag nanoplates.Ag rods with two kinds of morphologies were synthesized under ambient atmospherethrough changing the concentration of AgNO3by modified polyol synthesis method. Theeffect of starting materials on the final products were systematically investigated, and theresults indicate that twinned-crystal seeds play an key role on the growth of anisotropic Agrods. The growth rate of different crystalline surfaces can be kinetically controlled throughcontrolling the adsorption and desorption process caused by PVP. Through changing theconcentration of NaCl, the rod which was consisting of twinned crystal was degraded, thusyielding uniform Ag cubes with adjusting size from150to600nm.Ag nanowires with a pentagonal cross-section and zigzag, linear morphologies werefabricated using one-pot polyol synthesis method. Through changing the concentration ofPVP in reaction solutions, the diameters of the nanowires could be adjusted between50nmand200nm. The zigzag Ag nanowires with bending angles were adjusted through changingreaction time and PVP concentration. It is demonstrated that multiply twinned Ag NPs playsimportant role on forming Ag nanowires. However, Clˉ/O2etching played important roles on governing the formation of twinned nanostructures. Therefore, Ag nanowires with pentagontwinned cross section can be tuned by controlling the interplay between the population oftwinned-crystal Ag seeds and the concentration of NaCl.Ag nanoplates are capable of generating maximum electromagnetic-field enhancementand many other potential applications. Therefore, it is necessary to synthesize size controlledAg nanoplates. Through polyol synthesis method was usually used to synthesize NPs withvarious morphologies, it is difficult to synthesize Ag nanoplates with small size when usingethylene glycol (EG) as a solvent because EG with high viscosity. Base on this, Ag nanoplateswith controllable edge length from30nm to100nm were prepared through a one-pot synthesismethod by using TSC and PVP as capping agents, NaBH4as reducing reagent in aqueoussolution. PVP plays an important role on determining the final morphologies and edge length ofresulting nanoplates because PVP was a kind of polymer which can affect the viscosity ofsolutions. Furthermore, the viscosity of solutions can kinetically control the nucleation andgrowth of Ag nanoplates. Therefore, Ag nanoplates were not created in the case of without PVP.We also demonstrated that stacking fault was a key for the growth of triangular nanostructures.Reaction temperature and aging time also affected the formation of Ag nanoplates.In addition to the above morphologies, the fabrication of hollow noble metal spheres hasreceived great attraction in the past few decades owing to their attractive optical and electricalproperties. However, there are few reports on the large scale to synthesize hollow silver spheresat room temperature and without template. Thererfore, A two-step synthesize method was usedand successfully prepared hollow Ag spheres with tunable sizes in a range of74to167nm atroom temperature in this paper. Ag and H2were generated by reducing Ag2O particles whichwere obtained through the reaction between NaOH and AgNO3. During the reduction of theseAg2O particles in situ using NaBH4, the diffusion of H2from inside of Ag2O particles resultedin the formation of a hollow part in Ag spheres. In addition, the effect of the viscosity of solventon the size of hollow Ag sphere was also discussed. Furthermore, the diameter of hollow Agsphere decreased from157to89nm when the temperature increased from0oC to40oC. Thismethod provides an effective approach for synthesizing other hollow metal structures. |
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