How can I choose the right redox probe in EIS measurement?

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Dimitrios V. Stergiou

Dear Li Zeng,

it seems like you have two semicircle regions or a small semicircle region (charge transfer controlled) and a large diffusion controlled region. The recorded Nyquist plots vary in every experiment according to what are you planning to do (see attached file EIS primer impedance). In your case I suppose that you are trying to develop a faradic impedimetric sensor.

Regarding the redox probe choice please take a look at the attached review. It is very helpful.

Best regards

li Zeng

Thank you very much for Mr Stergiou' answer. I will take a look at the references in detail soon.

Chaker Tlili

You may try to increase a little bit the redox couple (5mM for example the charge transfer resistance Rct was related to the concentration of the redox couple) and check the protocol for the modified-electrode. Maybe you shall to characterize your modified-electrode to see if you have a monolayer or multi-layers (it is related to what you are doing exactly). You can use [Ru(NH3)]2+/3+ to characterize your modified electrode. What's your goal for this modification?

Dear Chaker Tlili,

I was trying to prepare the hybrid phospholipid bilayer by fusing the vesicle on DT-modified Au electrode and characterize the formation of bilayer by EIS. The figure was the impedance result of the hybrid phospholipid bilayer. I don't know what's the problem in my experiment.

It is normal now to see two semi-circles since you have two layers different DT (Dithiol, How long the chain?) and the phospholipid bilayers. If you are planning to use this structure for electrochemical impedance spectroscopy you may reduce the long of your DT and decrease the time of your incubation of your gold electrode in DT solution. You need some ''pinhole'' in your modified-electrode to get .

Dear Chaker Thili,

I don't understand that the some pinhole has to get for EIS measurement. By the way, the gold electrode was prepared by electroless deposition and it was in polycrystalline state. DT is short for 1-dodecanethiol. So the DT layer may have pinhole.