Hi,
Am working on Biosensors, for that i had used the new gold electrode which comes polished and cleaned. Once am done with an experiment i have to use the same electrode, so i need to remove the SAM layer and other residues to perform another trail of experiments.
Some literature suggests that Piranha solution oxidizes the gold.
As per the literature, i had followed to treat with H202 + 50mM KOH for few minutes then CV in 50mM KOH, i used to get a lot of noise even though after the electrodes has been polished and sonicated.
Later, i used 50% HNO3 for Gold electrodes, there was a drastic change in the noise, which actually reduced.
But still i could find a peak at 0.4 V.
Parameter as follows.
Technique: CV
Low V : -1.0
High V : +1.0
Scan rate - 0.05v/s
Cycles : 20 (10 cycles)
Should i have to get the peaks for Bare Gold electrode ?.
All these trails were carried out with Au as gold electrode/ Ag-Agcl as Reference and Pt as Counter electrode in 0.1M PBS, pH 7.0
Hi Manohar,
I guess you performed a control CV for your new, polished and cleaned gold electrode? Was there any peak there? If not, then your surface is very likely not clean if you still see some peaks after your attempted cleaning. I'm not used to gold nor SAM, but maybe mechanical (but smooth) polishing or electrocleaning at high potential (check the following: Canaria et al., Formation and removal of alkylthiolate self-assembled monolayers on gold in aqueous solutions, 2006).
Cheers and good luck,
Antonin
Using nitric acid is not a good option for cleaning gold electrode because it solubilize the metal, and make it very porous. A usual procedure, after polishing, I usually cycle the gold electrode in 0.5 M H2SO4 from -0.2 to 1.6/1.7 V at 1 Vs-1 for 100 cycles, after that if the profile is good I repeat the same cycling for 10 cycles at 0.1 Vs-1.
Thanks Antonin Prévoteau , will go through the article you had mentioned.
How does the graph of the CV look like ? Linear ?
Please check with the file attached.
Dear Manohar, you clearly have some faradaic peaks there. However, as a general recommendation, you should avoid performing CV on such big interval of potential (- 1.6 to + 1.6 V!). You are clearly oxidizing and reducing your solvent (water). As such, if you perform CV under stagnant conditions, you may re-oxidize H2 or reduced O2 you've been producing during your scan. By the way, do you work under anaerobic conditions?
No, as of now am not working under anaerobic. I thought to purge the Cell with nitrogen. Is that fine, or any other ways to do that .
From where do i learn more about these stuff ?
Yeah, but O2 will certainly be reduced on your gold. And actually your peak current at + 0.4V seems to increase of 1 order of magnitude when you record CV over a longer ranger, with more solvent reactions. I therefore guess it's O2 reduction. If you mix your solvent you'll see something more like a plateau rather than a peak for you continuously replenish your O2 at the electrode surface. Yes, you could bubble N2 and keep only a small part of the cell open to avoid air to go back. And for learning, I guess a course of electrochemistry would be the best! Good luck!
THE "Bard and Faulkner" book is often very well consider in the field. But maybe start with something a bit more basic. I am sure you can find plenty of electrochemistry courses and basic and the Internet. Cheers.
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