From my research on development of electrochemical sensor using self-assembled monolayer, the resulted voltammogram from cyclic voltammetry shows that when the number of layer on the electrode increases the voltammogram shifted to the left. What does it mean?
Hi
You are depositing SAMs on the electrode right? your SAMs are creating a selectivity or sensitivity towards a specific thing you are measuring but at the same time they are covering the electrode surface. The electron transfer you are measuring is between your redox active species and the electrode surface (they pass throw pin-holes, defects etc. ) if your SAMs are too long they will block completely the electron transfer, if they are short but you are depositing too much you still see the CV (or electron transfer) but it is harder so you see a shift because it is harder to oxidize or reduce them.
Hi
Yeah it seems that your electrode kinetics are changing while you deposit, also your current is telling you that, you can see how the current is decreasing with your deposits have you noticed that? Maybe you are looking to increase the current which then current is proportional of concentration of species in your cell. The area as Tomer said it seems to be blocked.
Hi all,
I am afraid kinetics effects would not induce changes in voltammograms as those shown in the attached documents. Partially or totally block electrodes would significantly decrease the faradaic current, but the formal redox potential (roughly the mid-point between cathodic and anodic peaks) will stay put. One could argue that there are some minor kinetic effects on the green trace, but this has little to do with the significant shift in the potential scale.
My guess is that your SAM is behaving as a membrane creating a Donnan potential. The redox probe appears to be able to penetrate the membrane with relative ease (one would have to see the effect of potential scan rate for the various modifications - impedance even better). The membrane is generating a different ionic environment, shifting the effective potential at the electrode surface. Remember that the potential scale refers to as the potential difference between the electrode and the reference electrode. If you introduce a membrane between them, then the whole voltammogram will appear shifted in the x-scale (effectively a different reference electrode).
We have some papers on kinetics of electron transfer affected by SAMs. Ernesto J. Calvo published an excellent paper on Donnan potential induced by polyelectrolyte multilayers in JACS some 10 years ago.
Hey..I do not know whether you have already found answer to your question..From your Cv figure it is clear that the potential of the redox active species is shifting to lower potential indicating that the species is getting hard to reduce. if the role would be just related to electron transfer then their would be an increase in peak splitting. But in your case it is not. I think the only factor is the growth of SAM and to be correct it is not a monolayer but a multilayer.
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