Detection and Characterization of Single Particles by Electrochemical Impedance Spectroscopy

Abstract

We present an electrochemical impedance spectroscopy (EIS) technique that can detect and characterize single particles as they collide with an electrode in solution. This extension of single-particle electrochemistry offers more information than typical amperometric single-entity measurements, as EIS can isolate concurrent capacitive, resistive, and diffusional processes on the basis of their time scales. Using a simple model system, we show that time-resolved EIS can detect individual polystyrene particles that stochastically collide with an electrode. Discrete changes are observed in various equivalent circuit elements, corresponding to the physical properties of the single particles. The advantages of EIS are leveraged to separate kinetic and diffusional processes, enabling enhanced precision in measurements of the size of the particles. In a broader context, the frequency analysis and single-object resolution afforded by this technique can provide valuable insights into single pseudocapacitive microparticles, electrocatalysts, and other energy-relevant materials.

Recent advances in single liposome electrochemistry

“…In the future, the coupling of electrochemistry and specific imaging techniques such as electrochemiluminescence imaging will be a very promising strategy to study in real time the membrane electroporation mechanism with a high spatial and temporal resolution, especially for observing the release of the liposome content into the extra-vesicular medium after opening. In addition to amperometry measurements, new individual particle detection technique such as electrochemical impedance spectroscopy [55] should also be addressed in the future for single liposome electrochemistry.…”

Estimating Average Velocities of Particle Arrival Using the Time Duration of the Current Signal in Stochastic Blocking Electrochemistry

“…Stochastic collision electrochemistry comprises a series of methods that detect individual micro- and nanoparticles as they collide in real time with a miniaturized electrode. − Depending on the electroactive properties of particle and electrode, particle impacts generate stochastic and discrete signals leading to different detection methods, − for example, particle electrocatalysis, , direct particle electrolysis, change in open-circuit potential, and stochastic blocking electrochemistry. ,− Since the seminal work by Lemay et al in 2004, stochastic blocking electrochemistry has become the ideal technique for studying insulating particles notwithstanding the difficulty of interpreting the only measurable parameters of the technique, namely, current and impact frequency. , So far, a variety of particles have been studied, including polymer microbeads, − , metal nanoparticles, graphene nanoplatelets, , liquid microdroplets, vesicles, viruses, DNA, proteins, bacteria, − and red blood cells …”

Electrochemical Energy Harvesting Using Microbial Active Matter

“…This circuit provided an excellent model for our system, indicating different active and passive impedance sources. As shown in the SI, the equivalent circuit was composed of three resistors ( R s , R ct and R d ), a capacitor ( C dl ), and a constant phase element ( Z d ), which signified nonlinear diffusion of the analytes toward the WE surface . Upon fitting the Nyquist and Bode plots recorded at different concentrations to this model, the magnitude of various circuit elements ( R s , R ct , R d , C dl , and Z d ) were found to change.…”

“…Furthermore, bacterial activity is likely to perturb the diffuse ion layer near the WE, resulting in an increase of the Debye length and, hence, decrease of the double layer capacitance, C dl . The slight decrease in the impedance parameter Z d (constant phase element) with increasing bacterial concentration may be attributed to enhanced transport of redox species toward the WE surface. , The parameter R ct is the charge-transfer resistance associated with Cu 2+ reduction. An increase in the R ct may result from bacterial adsorption on the WE surface, reducing the active surface area for the redox reaction.…”