HOPG seeing electrodeposited metal nano- and microparticles

2 HOPG seeing electrodeposited metal nano- and microparticles 

Some of the first in situ STM images of electrodes published by Sonnenfeld and Schardt in 1986 (22) showed silver electrodeposits on HOPG. The conclusion of that paper, reinforced by subsequent work (23-25), was that the electrodeposition of silver proceeded by a Vohner-Weber mechanism characterized by prompt 3D growth of silver islands. It was also concluded (23,24) that the nucleation of silver islands occurred at defects present on the HOPG surface. This was an entirely reasonable conclusion that was supported by the in situ STM data. 

Our efforts in this area were initiated in 1995 with investigations of the electrodeposition of silver (26, 27) and, soon thereafter, platinum (28) nanoparticles on HOPG surfaces. The primary characterization tool employed in these experiments was ex situ non-contact atomic force microscopy (NC-AFM). In the silver work, HOPG electrode surfaces were examined by NC-AFM after the application of large amplitude potentiostatic pulses with amphmdes of —100 to —500 mV (vs. Ag/Ag+) and durations of 10-50 msec in dilute silver-plating solutions. These images looked dramatically different from the 

Since coulometry showed that much less than one atomic layer of silver or platinum was present on these surfaces, these NC-AFM images were consistent with a Volmer-Weber mechanism of deposition, but they contradicted the prior STM work because they showed that the nucleation of these metals occurred readily on defect-free terraces. Why were these nanoparticles not observed in the earlier STM experiments  

These experiments proved the value of NC-AFM for characterizing electrodeposits on HOPG and other surfaces. Beyond this, the NC-AFM data demonstrated that a high density of size-similar of 30% (26,28)) metal nanoparticles could be prepared by 

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