In situ nanoparticle sizing with zeptomole sensitivity

Abstract

We present the basis for an entirely new approach to in situ nanoparticle sizing. Nanoparticles containing just 12 zeptomoles (1 zeptomole = 10(-21) moles) of silver, are detected via in situ particle coulometry. These stochastic charge measurements correspond to the transfer of only 7000-8000 electrons, yielding direct information relating to the individual nanoparticle volumes. The resulting particle size distribution (average equivalent radius 5 nm) obtained via nanoparticle coulometry is in excellent correspondence with that attained from TEM analysis. Moreover, the measurable particle size limit by this electrochemical method is shown to be significantly below that of more common optical nanoparticle tracking techniques, and as such can be viewed as a potential disruptive nano-technology.

Catalytic activity of catalase–silica nanoparticle hybrids: from ensemble to individual entity activity

“…13 Recently and ‘unrelated at first sight’, a new electrochemical method has emerged 14–16 aiming to unravel electrochemical activity at the single entity level. This electrochemical technique provides the opportunity to characterize single nanoparticles 17–19 in situ and large macromolecules in solution. 20–23 Herein, we further extend the applicability of the electrochemical method at a single entity level, and demonstrate that the activity of a single NP/enzyme hybrid can be detected and quantified.…”

Diffusional impacts of nanoparticles on microdisc and microwire electrodes: The limit of detection and first passage statistics

“…As the average number of expected impacts in a given time interval is proportional to a microdisc's electrode radius as well as to a wire-electrode's length, the sensitivity of both systems can be adjusted via one or the other parameter (taking into account that the overall electrode area is proportional to the capacitance background noise [7,8]). However, in the case of the microdisc, the electrode area increases quadratically with the electrode radius, while the electrode area only increases linearly with the length of the microwire electrode.…”

“…In the 'nano-impact' method, nanoparticles diffuse freely in an electrochemical cell, and are detected via their stochastic hits on an electrode, which may also be referred to as an 'impact'. Typically, micrometre sized electrodes are used to avoid large capacitance noise [7,8] or simultaneous impacts. During an impact event, the impacting particle may be involved in an electrochemical reaction at the electrode surface, which may result in a direct oxidation of the nanoparticle itself, while a corresponding current is measured [9][10][11].…”

Femtomolar Detection of Silver Nanoparticles by Flow-Enhanced Direct-Impact Voltammetry at a Microelectrode Array

“…For initial flow cell characterization, an in-house-fabricated 4.15-mm-diameter glassy carbon (GC) electrode was used. Both an Autolab PGSTAT 302N (Metrohm-Autolab, Schiedam, The Netherlands) and an in-house-built low-noise potentiostat 36 (250 Hz sampling rate, 4-pole Bessel filter) were used for all electrochemical experiments.…”