# Oxidized gold

1. Oct 31, 2004

### devious_

What are the benefits of oxidizing gold? I suppose that prevents it from rusting, but are there any other benefits?

2. Oct 31, 2004

### imabug

I thought one of the reasons gold was so useful was because it didn't oxidize.

then again i'm not a chemist, so maybe someone's discovered that gold really dose oxidize.

3. Oct 31, 2004

### chem_tr

Gold oxidization is mainly used for refining purposes, as it is sometimes not sufficiently pure, especially for conductors. Gold amalgams (alloys with mercury) can be broken down by oxidization.

In addition, gold ores are processed with oxidization with "King's water" ($\displaystyle 3HCl + HNO_3$) and treated with cyanide, afterwards reduced with zinc rods; so very pure (up to 99.99%) quality gold can be prepared.

As imabug said, gold isn't oxidized, since it is an inert metal; you hardly prepare a $[AuCl_4]^-$ complex and can easily reduce it to the metal with elemental potassium, etc.

4. Mar 16, 2010

### FiberOptix

I'm quite late to this discussion but actually it's very relevant to some recent issues that have come up in my lab:

I'm looking to oxidize a 50nm gold layer on the back of a BK-7 glass prism. Despite being quite familiar with the use of Aqua Regia, I want to oxidize gold and not remove it from the back of the prism.

Our UV cleaner isn't powerful enough to oxidize it, so I've been thinking of using Nitric acid. Can anybody give me an idea of how long this should take, how much gold will be oxidized, etc.? I'm trying to get an idea of how this should go before I actually proceed.

Thanks

5. Mar 16, 2010

### chemisttree

Any liquid capable of oxidizing gold will certainly remove it from the glass. Think low pressure air plasma for your application.

6. Mar 16, 2010

### Staff: Mentor

Last edited by a moderator: Aug 13, 2013
7. Mar 16, 2010

### Mapes

Seconding this; gold oxide is soluble in aqueous solutions.

8. Mar 17, 2010

### FiberOptix

This is a bit of a problem then, and my complete lack of Chemistry knowledge compounds this.

My ultimate goal is the deposition of DPPC (a membrane protein) on to gold by vesicle fusion. The paper that I've been referencing claims they used a gold substrate that was oxidized by UV lamp... As I said, apparently our UV cleaner isn't powerful enough to do this, and as was pointed out, oxidation by acqueous solution is not an option....

Perhaps you can expand on this low pressure air plasma? I'm not familiar with it.

Thank you

9. Mar 17, 2010

### chemisttree

Last edited by a moderator: May 4, 2017
10. Mar 17, 2010

### Mapes

Almost surely they meant that the gold was exposed to UV-generated ozone and oxygen radicals, and that it was the organic contaminants that were oxidized (and volatalized) to leave the gold as clean as possible before deposition. This is a common procedure.