Precise Electrochemical Sizing of Individual Electro-Inactive Particles

Our protocol increases measurement precision associated with particle sizing using common analytical chemistry techniques. This provides better characterization of nanomaterials one at a time in situ using electrochemistry. The main advantage of this technique is that it utilizes common lab reagents in order to address the edge effect phenomenon, which is a longstanding problem in the field of nanoelectrochemistry.

Due to electrocatalytic interruption's modular nature, the electrode, the redox probe, and the substrate can all be swapped out to better meet detection needs. After preparing the required solutions and electrodes, select macroelectrode as the working electrode. To prepare the control cell, prepare five milliliters of a solution containing one millimolar TEMPO and five millimolar sodium perchlorate in carbonate buffer at pH 12.

To prepare a test cell, prepare five milliliters of a solution containing one millimolar TEMPO, five millimolar sodium perchlorate, and 120 millimolar maltose in carbonate buffer. Before an experimental run, use a polishing pad with aluminum slurry to polish the electrode and move the electrode in a figure eight pattern to ensure an even polish. Liberally rinse it with deionized water.

Then dry the electrode using a laboratory wipe without touching its tip. For electrochemical measurements, use a three-electrode setup by employing a macroelectrode for cyclic voltammograms or an 11 micron ultra microelectrode for chronoamperograms, a platinum wire counter electrode, and a saturated calomel reference electrode or SCE. Set the control cell in the Faraday cage and connect the electrodes to the appropriate cables.

Collect the cyclic voltammetry data using a potential window from 0.2 to 0.8 volts at a scan rate of 10, followed by 20, 30, 40, and 50 millivolts per second. To collect chronoamperomtery data, select an ultra microelectrode. With the control cell in the potentiostat, apply 0.8 volts versus SCE for 10 minutes and start recording at a sample rate of 10 hertz.

Using the same parameters, obtain data for the test cell. Next, spike the solution with polystyrene beads to a final concentration of 0.66 picomolar into each electrochemical cell and collect the chronoamperomtery data of each cell as previously demonstrated. Select the sample size of approximately 200 individual impact events to detect differences between the multiple sizing methods.

The polystyrene beads addition showed stepwise changes in the chronoamperogram current of electrochemical cells as individual particles impacted and absorbed. The histogram demonstrated the size distribution determined by scanning electron microscopy, electrocatalytic interruption, and conventional nano-impact electrochemistry. Cyclic voltammogram fitting software demonstrated the model fitting of the yielded parameters from the electrode and solution phase chemical reactions.

The increased addition of maltose concentration compressed the diffusion layer and depressed the heterogeneous flux at the electrode edges. It's critical to have well-established controls. When collecting data at the micro or nanoscale, you have to ensure that the observations are real and not the result of noise or contaminants.

This technique is non-destructive to the sample and can be followed by other characterization methods such as dynamic light scattering. In addition, this technique is amenable for computational modeling and simulations.