Electrocatalytic Amplification of Nanoparticle Collisions at Electrodes Modified with Polyelectrolyte Multilayer Films

Abstract

We report electrochemical catalytic amplification of individual collisions between ∼57 nm diameter Pt nanoparticles (Pt NPs) and 12.5 μm diameter Au ultramicroelectrodes modified with passivating, electrostatically assembled polyelectrolyte multilayer (PEM) films prepared by the layer-by-layer deposition method. Two key findings are reported. First, despite the thicknesses of the insulating PEM films, which range up to 5 nm, electrons are able to tunnel from the Pt NPs to the electrode resulting in electrocatalytic N2H4 oxidation at the PEM film-solution interface. These single-particle measurements are in accord with prior reports showing that the electrochemical activity of passive PEM films can be reactivated by adsorption of metallic NPs. Second, it is possible to control the frequency of the collisions by manipulating the net electrostatic charge present on the outer surface of the PEM thin film. These results, which demonstrate that chemistry can be used to control electrocatalytic amplification, set the stage for future sensing applications.

Electrocatalytic amplification of DNA-modified nanoparticle collisions via enzymatic digestion

“…This observation is consistent with previous findings for collisions of naked PtNPs at Au UMEs. 20 Here, we also found that the collision frequency is higher for PtNP@ssDNA post-Exo I than for naked PtNPs. For example, at a concentration of 11.7 pM, the frequency for PtNP@ssDNA post-Exo I was 0.190 ± 0.033 Hz, compared to 0.048 ± 0.006 Hz for naked PtNPs.…”

“…In a previous study involving larger (57 nm) PtNPs, the predicted current was also larger than the experimental average. 20 In this case the calculated collision current was 613 pA, but the average measured current was only 185 ± 177 pA. We do not know why this calculation does not agree well with the experimental results for PtNPs larger than 3–4 nm, but one possibility is that the majority of collision signals arise from a relatively small subset of PtNPs residing at the low end of the size distribution. This in turn could be a consequence of the lower diffusion coefficients of larger PtNP aggregates.…”

Monitoring the Dynamic Process of Formation of Plasmonic Molecular Junctions during Single Nanoparticle Collisions

“…The dynamic collision events of individual nanoparticles (NPs) at an ultrasmall electrode (ultramicroelectrode (UME) or nanoelectrode (NE)) have been extensively studied by electrochemical methods . This is motivated by the fundamental research in nanoscale electrochemistry and applications in NP analysis, catalysis, and chemical/biological sensing . In one type of single NP collision experiments, a thin layer of insulator is coated on the UME to suppress direct electron transfer from redox molecules in electrolyte to the UME.…”

Direct electrochemical detection of individual collisions between magnetic microbead/silver nanoparticle conjugates and a magnetized ultramicroelectrode

“…These include the groups of Alpuche-Aviles,14 Bard,15–23 Crooks,24–26 Koper,27 Macpherson,28 Stevenson,29 Unwin,30 and Zhang 31…”