Making Cavity Microelectrodes: Overcoming Setbacks

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Discussion Overview

The discussion revolves around the challenges faced in creating a cavity microelectrode for testing the electrochemistry of polyaniline powder. Participants share their experiences and suggestions regarding materials and methods for establishing electrical contact between the gold wire and the voltameter, as well as considerations for electrode design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant, Ryan, discusses the need for reliable contact between a gold wire and a voltameter, mentioning previous attempts with mercury that were unsuccessful due to gold dissolution.
  • Ryan proposes three alternatives: using graphite powder, soldering the gold wire to a copper wire, or finding another low melting point metal.
  • Another participant questions the necessity of soldering copper to gold, suggesting that a 4-point probe might be a better choice for the intended application.
  • A different participant shares their positive results using a platinum wire with a mercury contact, noting the importance of avoiding redox potentials on the surface.
  • This participant mentions their decision to use solder for contact, citing a melting point lower than that of the glass tube, and considers switching to platinum if gold proves ineffective.
  • They also mention using an iron wire instead of copper for connection to the voltameter, emphasizing the need to avoid excessive use of platinum or gold.
  • Another participant reflects on their past experience with liquid crystal conducting organic compounds and the 4-point probe, but indicates they are not currently up to date with the latest methods.

Areas of Agreement / Disagreement

Participants express various approaches and materials for achieving contact in cavity microelectrodes, with no clear consensus on the best method. Some suggest alternatives while others share their experiences, indicating a range of opinions and practices.

Contextual Notes

Participants reference different electrode configurations, such as 3-point and 4-point probes, without resolving which is definitively superior for the application at hand. There are also mentions of specific materials and their properties, but no agreement on the optimal choice.

rloughlin03
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I am attempting to make a cavity microelectrode in which i will test the electro chemistry of polyaniline powder before moving on to other chemicals. I have read numerous papers on the subject. I am having a major setback in my aim: i need contact between my gold wire and the voltameter (as shown in the diagram). I originally tried mercury, but forgot that it would dissolve the gold. I am thinking of either one of three things: a graphite powder, soldering the Gold wire and copper wire together, or finding another low m.p. metal to use. I would really appreciate any ideas or feedback, especially from those who have made cavity electrodes before.

Thanks

Ryan

P.S. apologies for the crude diagram, done in a rush. Just trying to help "paint the picture"
 

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rloughlin03 said:
I am attempting to make a cavity microelectrode in which i will test the electro chemistry of polyaniline powder before moving on to other chemicals. I have read numerous papers on the subject. I am having a major setback in my aim: i need contact between my gold wire and the voltameter (as shown in the diagram). I originally tried mercury, but forgot that it would dissolve the gold. I am thinking of either one of three things: a graphite powder,
Not so good...

...soldering the Gold wire and copper wire together,
solder - yes
Copper to Gold - why?

... or finding another low m.p. metal to use. I would really appreciate any ideas or feedback, especially from those who have made cavity electrodes before.

Thanks

Ryan

P.S. apologies for the crude diagram, done in a rush. Just trying to help "paint the picture"

For what you are intending, isn't a 4-point probe a better choice?
 
Got good results using a platinum wire, with a mercury contact. Obviously any redox potentials on the surface arent desireable, but results are looking to be fine in comparison to previous works in the field. I was able to integrate the curve and get a value for Q, which following on i was able to find the mass of PAN in the cavity and various other info about the cavity.

I have decided to use solder, The M.P. of the solder i am using is around 200-300°C less than the glass, so we've decided to cut up some of the solder, and will heat up the tube to melt the solder for a contact between the wire and Au.If the results don't work, I think i may just go forward with platinum and not gold.The gold would be handy as there is not redox chemistry at the cavity, but needs must...

decided on an iron wire,instead of copper. its just some sort of metal which we can use to connect to the voltameter, no need to use loads of Pt or Au.

We decided just to use a 3 point probe as it was used in a few of the papers we researched. Since then the 4-point probe has popped up a fair bit, but as the results we go were good we are goin to try and continue with what we've got.

Have you done much research in the area? Any advice on what you tried, or even any paticular research papers you used would be appreciated greatly.
 
I did some synthetic work on liquid crystal conducting organic compounds based on n-hexylsexithienyl compounds. Others in my lab were studying thin films (grown on QCM). I also did some brief synthetic work with soluble polyphenylene polymer precursors. Back then the 4-point probe was the state of the art. Been away from it too long to be of much more help to you, though.
 

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