Electrochemical Synthesis Of Silver Nanostructures:Morphological Control And Characterization

Noble metal nanostructures has received widespread attention for their rich plasmonic properties in recent years.Localized surface plasmon(LSP)features greatly enhanced electric fields near the metal nanostructures' surface,which can be employed in various applications,such as chemical sensing and biosensing,photothermal therapy and solar cells.A facile synthesis of shape-controlled silver nanostructures is presenting,and their plasmonic modes are investigated by cathodoluminescence microscopy.The following researches have been carried out.1?The size-controlled silver nanobelts were synthesized by electrochemical deposition at liquid/liquid interface.The width of silver nanobelts could be tuned from a few tens of nanometers to several micrometers with the length up to millimeter level.The influences of growth conditions are investigated systematically.By applying low constant voltage(about 0.3V),nanobelts with very low branching rate were obtained.The width of silver nanobelts depends on the molar ratio of oleic acid to Ag+,and alcohols in the system also show an impact on the width by limiting the interaction between oleic acid and Ag+.The polarization of the incident light decides the mode components of the excited SPPs,and near field intensity imaging by fluorescence of quantum dots shows a pronounced spatial modulation is due to the interference among multiple SPP modes.2?By applying sinusoidal voltage,nanobelts with periodic sawtooth edges were synthesized for the first time,with a spatial period of 25nm to 150nm.Furthermore,encoded nanobelts that possess alternately smooth and sawtooth edges were obtained by applying constant voltage and sinusoidal voltage in a certain sequence.The TEM results indicate that nanobelts are single crystal silver of face-centered cubic phase and the flat faces of the nanobelts are {111} facets.Watched under the epi-illumination microscope,part of encoded nanobelts show distribution feature alternate with brightness and darkness when the incident light polarized transverse to the nanobelts.Morphology characterization combined with numerical simulation suggest that the difference in width is the main cause of this phenomenon,and the angular distribution of scattering light also plays a role in it.The observability makes this structure a nanoscale barcode.The SPP standing wave pattern that are caused by SPP's reflection at the end facets can clearly be distinguished in smooth silver nanobelts and nanobelts with sawtooth edges in the CL-SEM system.Furthermore,enhancement of the CL signal observed at the sawtooth edges is concluded to be caused by LSP.3?By applying low frequency sinusoidal voltage(10Hz),seaweed-like nanostructures were synthesized.AFM images show a thickness of 25nm to 50nm.The TEM results indicate that the complex nanostructures are single crystal.The magnitude of voltage decides the branching rate of nanobelts because it provides the growth-driving force.The nanobelts grow along<110>directions when low voltage is applied and bifurcate heavily along<211>directions,this is the main reason of the formation of this morphology.