Author Topic: Maltodextrin for Stabilizing Colloidal Gold  (Read 12633 times)

RamanShift

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #15 on: January 18, 2012, 03:17:45 AM »
my question is... if it is ok to add the pvp after i make the colloidal gold ( when it is already red ) and stirr it hard enough so the pva dissolves in the water and capp the gold nanoparticles?

I've done exactly that. I used this PVA http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=363162|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC. Simply add the PVA to hot (not boiling) colloidal gold with vigorous stirring. I did this not for stabilization, but to make films and pucks. See the attached image.

Offline mraluma415

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #16 on: May 02, 2012, 05:51:30 AM »
How much PVA did you use in 250mL?

Thats a very nice concept
"The art of healing comes from nature, not from the physician. Therefore the physician must start from nature, with an open mind." - Paracelsus

ShivaDestructor

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #17 on: May 02, 2012, 08:16:23 AM »
I did this not for stabilization, but to make films and pucks. See the attached image.

Looks very interesting. What is the purpose of an AuNP-film/puck?

/J

RamanShift

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #18 on: May 05, 2012, 04:12:01 PM »
How much PVA did you use in 250mL?

I made used around 100mg per 25-30ml. The key is to add it slowly, otherwise you get large globs forming that take forever to dissolve. You can vary the amount of PVA to get thinner or thicker solution. I used thicker for pucks, and thinner for films.

 I did this not for stabilization, but to make films and pucks. See the attached image.

Looks very interesting. What is the purpose of an AuNP-film/puck?
 

I saw it done elsewhere, and it looked interesting. http://www.youtube.com/watch?v=VRMleauyKjQ&feature=plcp This is where I got the idea. I also wanted to do some conductivity tests. One cool thing about the stuff is it redissolves into water. Or at least the PVA does. I haven't tried redistributing the NP with ultrasonics yet, but if I can this would allow dry storage of gold NP.

Offline mraluma415

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #19 on: May 12, 2012, 09:16:43 AM »
when the PVA completely dissolves, you let it cool and it turns into the puck?
"The art of healing comes from nature, not from the physician. Therefore the physician must start from nature, with an open mind." - Paracelsus

RamanShift

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #20 on: May 21, 2012, 06:05:28 PM »
I let the water evaporate. You can speed the process by heating with toaster ovens and the like. The thicker the film, the less even the distribution of particles, so I've found it best to keep them thin. The film will also be thinner when dried than the liquid. So keep that in mind.

Offline mraluma415

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #21 on: May 22, 2012, 11:37:23 AM »
that's interesting. So the nano-particles stay stable while the water evaporated to the point the PVA finally bonds and hardens? I wonder if this works for the silver as well.
"The art of healing comes from nature, not from the physician. Therefore the physician must start from nature, with an open mind." - Paracelsus

RamanShift

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #22 on: May 27, 2012, 01:27:57 AM »
that's interesting. So the nano-particles stay stable while the water evaporated to the point the PVA finally bonds and hardens? I wonder if this works for the silver as well.

When in a liquid PVA acts as a surfactant, "holding apart" the nanoparticles. As the water evaporates, the molecules form a polymer lattice, and the particles get stuck in. I'm not sure when the surfactant properties stop working while dehydrating, but the films look fairly uniform. I haven't bothered to do any tests on them.

Silver works as well. It's not as pretty though :D. Though I've been making some wacky coloured silver nanoparticles. I cant keep them for very long before they crash out. I use polystyrene sulfonate for stabilization in one method of silver np synthesis. I may try PVA next week. Maybe I'll make a concentrated batch and make a few films.

samiam

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #23 on: April 11, 2013, 01:42:13 AM »
kephra,

a question-

ive been using 1/4 tsp-flat malto instead of 1/2tsp for 250.. seems fine and everything..

in your 'how-to' post, you'd said to use 1/2tsp, then added that 'it's in excess to insure no gold chloride left in the solution'..

are there any ways to test to see presence of gold chloride in the colloidal gold solution?

is 1/4 tsp-flat too little in amount in your opinion?

Offline kephra

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #24 on: April 11, 2013, 02:26:26 AM »
The only test I can think of that you can do easily is to add silver nitrate to the gold solution. If gold chloride is present you will get silver chloride which will precipitate as a white cloud. Or add more maltodextrin and look for a deepening of color. The accuracy of either test is limited by your visual accuity.  Since mine is not very good, I prefer to add excessive maltodextrin.
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Offline mraluma415

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #25 on: April 11, 2013, 02:45:31 AM »
It is in your best interest to be sure that all gold ions are reduced, so more is always better with gold chloride method indeed!
"The art of healing comes from nature, not from the physician. Therefore the physician must start from nature, with an open mind." - Paracelsus

Auric

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #26 on: October 25, 2015, 06:19:39 PM »
Quote
If the reduction of the gold chloride is done by the sodium in the sodium carbonate, then:

I would guess the reaction is:
2HAuCl4 +3Na2CO3 --> 2Au + 6NaCl +2 HCl + 2CO2 +O2

If it is done by the maltodextrin, then I can't say because I don't know the formula for maltodextrin.

I think they are both necessary.

The maltodextrin also acts as a stabilizer by adsorbing onto the surface of the gold particles preventing them from aggregating.

Maltodextrin is a 'reducing sugar' with a free aldehyde group. This (http://pubs.rsc.org/en/content/articlehtml/2013/ra/c3ra44842h#fig8) colloidal gold research shows the use of reducing agents with a free ketone group that first catalyses to an aldehyde group and then reduce the chloroauric acid. It further shows a suggested reaction mechanism for the formaton of gold nanoparticles, wich might be what is happening when using this colloidal gold formula.

Handyguy

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Re: Maltodextrin for Stabilizing Colloidal Gold
« Reply #27 on: January 22, 2016, 03:17:31 AM »
I used to make all my colloidal gold with citrate, and it is good for up to 50 ppm or so, but after that it tends to fail.  When I read about Abrams making such high ppm product with maltodextrin, I had to try it.  But maltodextrin is only a reducing agent in an alkaline environment, so I also needed a base.  Thats what the sodium carbonate is for, to raise the ph so that the maltodextrin will work.  It seems to work well, as the first sample I made shows no signs that the gold is falling out.  It looks just like it did the day I made it.

But another base might also work, or it may not need to be basic at all. 

Initially I made twelve 50 ml batches using this process.  I consumed 6 of them so far, and all of the remaining six still look good.

I don't experiment as much with gold as I do with silver because its too expensive to waste so even though this process might be able to be improved, it works well enough that I probably won't try anymore to optimize it.

What did you raise the PH to?