Electrochemically synthesized silver nanostructures having dimensions
200-1000 Angstrom in diameter and 20-50 Angstrom high were prepared on
graphite surfaces using the scanning tunneling microscope (STM). Thes
e nanostructures were stable while immersed in aqueous solutions conta
ining small(0.5 mM) concentrations of Ag+ during repeated STM imaging
at small sample-negative biases for at least Ih. Upon exchange of the
silver plating-solution for pure water, dissolution of the nanostructu
re occurred within 30 min, irrespective of the applied imaging bias up
to +/-200 mV. The anodic dissolution of silver nanostructures in pure
water was strongly inhibited following the formation of an n-alkaneth
iolate self-assembled monolayer (SAM) on the silver surface, demonstra
ting that molecular self-assembly provides a method for the protective
, and chemically selective, encapsulation of reactive nanometer-scale
structures on solid surfaces. In contrast, self-assembly was not obser
ved following the exposure of silver nanostructures to long-chain n-al
kylamines or carboxylic acids and these prospective ligands provided n
o protection from dissolution of the nanostructure in pure water.