Re: pirahna solution

andrea_gazze@xxxxxxxx wrote:
>
> well, i have silicon wafers with gold areas. yes, i know the O2 dry
> plasma, but my company hasn't the needed instrumentation. what do you
> think of aqua regia? Is it less dangerous than piranha solution? I know
> that aqua regia destroy gold, but for short time contact it could be
> used to clean gold.
> thank you for your reply

Plasma ashing is much to be preferred - fast, effective, no chemical
waste, no residuals. Cells are very happy with plasma ashed metal
surfaces.

Piranha solution can spontaneously explode just sitting there. 30%
hydrogen peroxide is death on skin contact - it rapidly diffuses in
through surface callous then explodes into oxygen on contact with
catalase in living tissue. Its mixing with H2SO4(conc) is exothermic
and can explode. I would feel uncomfortable with the reagent.

Aqua regia goes through gold very rapidly indeed. Newly warmed
freshly made hot aqueous persulfate in a sonicator ought to be very
aggressive. Hot nitric acid by itself is very aggressive.

Do the work in a fume hood. Wear substantial gloves.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
.

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