Observation of Single Pt Nanoparticle Collisions: Enhanced Electrocatalytic Activity on a Pd Ultramicroelectrode.

Single Pt nanoparticle (NP) collisions on an electrode surface were detected by using an electrocatalytic amplification method with a Pd ultramicroelectrode (UME). Pd is not a preferred material for UMEs for the detection of single Pt NP collisions, because Pd shows similar electrocatalytic activity compared with Pt for hydrazine oxidation, thus resulting in a high background current level. However, a Pt NP colliding on the Pd UME shows greatly enhanced activity compared with a Pt NP on an inert UME, such as a Au UME, which is usually used for the detection of single Pt NP collisions. The use of an electroactive UME material instead of an inert one facilitated the study of single-NP activity on the various solid supports, which is important in many NP applications.