Investigation of Relative Stability of Different Facets of Ag2O Nanocrystals through Face-Selective Etching

Ag2O nanocubes, rhombicuboctahedra, octahedra, and extended hexapods were employed for the examination of the relative stability of different crystal planes to chemical etching through careful face-selective etching. Precise control of the amount of NH3 solution injected into a mixture of Ag2O nanocrystals and NaOH enables this face-selective etching. Ag(NH3)(2)(+) formed from dissolved silver ions should drive the etching process while NaOH tunes the reaction equilibrium to control morphology of the etched nanocrystals. The order of facet stability in this reaction was found to be {111} > {110} > {100}. The {100} faces are most easily etched. By carefully adjusting the volume of NH3 solution introduced, novel Ag2O cubic nanoframes and rhombicuboctahedra with square depressions on all the {100} faces can be fabricated. The {111} facets contain significant terminal silver atoms, so hydroxide ions should interact strongly to maintain these surfaces. Hydroxide ions are less effective at adsorbing on the {100} faces with terminal oxygen atoms, so these faces are more susceptible to etching. zeta potential measurements support the argument of hydroxide ion adsorption. Interestingly, the {100} facets of Ag2O were found to be most stable in a weakly acidic HNO3 solution; octahedral nanocrystals can transform into particles consisted of {100} square terraces.