Influence of Oxidative Etching of Au Nanostructures by KMnO4 on its Surface Morphology, Electro-kinetic Properties and Improved Catalytic Activity

Influence of Oxidative Etching of Au Nanostructures by KMnO4 on its Surface Morphology, Electro-kinetic Properties and Improved Catalytic Activity

This paper reports the impact of oxidative etching of Au nanospheres and nanorods by KMnO4 on theirsurface morphology, electro-kinetic properties and catalytic activity. A significant blue-shift of thesurface plasmon bands for Au nanospheres (536 to 527 nm) and Au nanorods (679 to 532 nm) wereobserved, due to their size and shape alterations after oxidative dissolution. TEM analysis also revealedthe formation of various irregular Au nano-morphologies such as spheres ( 4-7 nm), low aspect ratiorods (2.6) and spheroids ( 13 nm) of narrow size distribution after KMnO4 etching. As a result, thehydrodynamic diameter of Au nanospheres ( 41 nm) and Au nanorods ( 109 nm) were reduced to4 nm and 34 nm, respectively. The oxidative dissolution of Au0 by KMnO4 occurred via its oxidation toAu3+ ions as confirmed by the measured electrode potential, E0(Au0/Au3+) = -0.90 V by cyclic voltammetrywith significant increase in the zeta potential and conductance values. The etched Au nanoparticlesbeing smaller in size and of higher surface to volume ratio resulted in 2 fold higher catalytic activitiesfor the reduction of p-nitrophenol and p-nitrobenzoic acid as compared to bare unetched Aunanostructures.

This paper reports the impact of oxidative etching of Au nanospheres and nanorods by KMnO4 on theirsurface morphology, electro-kinetic properties and catalytic activity. A significant blue-shift of thesurface plasmon bands for Au nanospheres (536 to 527 nm) and Au nanorods (679 to 532 nm) wereobserved, due to their size and shape alterations after oxidative dissolution. TEM analysis also revealedthe formation of various irregular Au nano-morphologies such as spheres ( 4-7 nm), low aspect ratiorods (2.6) and spheroids ( 13 nm) of narrow size distribution after KMnO4 etching. As a result, thehydrodynamic diameter of Au nanospheres ( 41 nm) and Au nanorods ( 109 nm) were reduced to4 nm and 34 nm, respectively. The oxidative dissolution of Au0 by KMnO4 occurred via its oxidation toAu3+ ions as confirmed by the measured electrode potential, E0(Au0/Au3+) = -0.90 V by cyclic voltammetrywith significant increase in the zeta potential and conductance values. The etched Au nanoparticlesbeing smaller in size and of higher surface to volume ratio resulted in 2 fold higher catalytic activitiesfor the reduction of p-nitrophenol and p-nitrobenzoic acid as compared to bare unetched Aunanostructures.