Ultrasensitive electroanalytical tool for detecting, sizing, and evaluating the catalytic activity of platinum nanoparticles

Radhika Dasari, Donald A. Robinson, Keith J. Stevenson

Research output: Contribution to journalArticlepeer-review

117 Citations (Scopus)


Here we describe a very simple, reliable, low-cost electrochemical approach to detect single nanoparticles (NPs) and evaluate NP size distributions and catalytic activity in a fast and reproducible manner. Single NPs are detected through an increase in current caused by electrocatalytic oxidation of N 2H4 at the surface of the NP when it contacts a Hg-modified Pt ultramicroelectrode (Hg/Pt UME). Once the NP contacts the Hg/Pt UME, Hg poisons the Pt NP, deactivating the N2H4 oxidation reaction. Hence, the current response is a "spike" that decays to the background current level rather than a stepwise "staircase" response as previously described for a Au UME. The use of Hg as an electrode material has several quantitative advantages including suppression of the background current by 2 orders of magnitude over a Au UME, increased signal-to-noise ratio for detection of individual collisions, precise integration of current transients to determine charge passed and NP size, reduction of surface-induced NP aggregation and electrode fouling processes, and reproducible and renewable electrodes for routine detection of catalytic NPs. The NP collision frequency was found to scale linearly with the NP concentration (0.016 to 0.024 pM -1s-1). NP size distributions of 4-24 nm as determined from the current-time transients correlated well with theory and TEM-derived size distributions.

Original languageEnglish
Pages (from-to)570-573
Number of pages4
JournalJournal of the American Chemical Society
Issue number2
Publication statusPublished - 16 Jan 2013
Externally publishedYes


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