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Author: Subject: Metallic and insoluble salt Nanoparticles
Ramiel
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[*] posted on 14-10-2005 at 07:31
Metallic and insoluble salt Nanoparticles


<html>
I thought about deleting this post forever, but here we go! I'm not going to suggest the uses of nanoparticles, the special properties of these extra-specially small particles are astounding in their multitude (anyone ever heard of OH<sup>o</sup> [free radicals] being created from n-ZnO and UV?).

I'm sure each member could think of a way to use n-particles. It also bears mentioning that although they may be easy to produce, even inocuous little metal n-particles can be dangerous in new and interesting ways.

Without furthur ado:
<b>Au Nanoparticles</b>
Gold particles are a bit of a special case - not all metals will form up like gold, but one can reliably create colloidal Au nanoparticles by reducing Au<sup>3+</sup> to Au<sub>(s)</sub>...
This is a very small scale procedure, but scaling shouldn't be an issue.
<ul>20mL of 1mM Au<sup>3+</sup> was brought to the boil with stirring (stirring is very important - magnetic stirring probably ideal here)<br>
To the solution was added 2mL of 1%w/w trisodium-citrate-dihydrate [Na<sub>3</sub>C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>.2H<sub>2</sub>O] The solution rapidly turns a deep red colour (via blue)<br>
Shining polarised light through this baby will let you know if you have actual n-particles.<br>
Adding 1M NaCl dropwise to the solution will disrupt the citrussy ions hanging around the gold particles, this will cause them to agglomerate into larger particles.</ul><br>

<b>Insoluble salt n-particle synthesis in inverted micelles</b>
Another (still less expedient, but very consistent) method of nanoparticle "synthesis" involves using inverted micelles to provide crucibles in which aqueous reactions can take place. The sizes of these 'polar-reaction crucibles' can range from 1nm to 1mm, it would be interesting to invent a messy, large scale method for producing micelles for things like pyrophoric metal powders.
The method described <a href="http://www.uaf.edu/chem/467Sp05/manuals.pdf">here</a> produces particles with exceeding consistent in terms of size. Unfortunately, some of the chemicals used are fairly exotic. I'm sure substitutes could be used where accuracy isn't a problem!</html>

This probably isn't very interesting to most of you, but I find it fascinating :P I was privileged enough to perform both of these experiments in a very nice lab, so I can attest to their ease.

Personally, I think the whole field of amateur-nano-chemistry is worth touching on. :)




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[*] posted on 14-10-2005 at 11:57


A good method of creating very fine particles is reacting two soluble precursors in a solvent which is suspended in another solvent which doesn't mix with the first one and in which your reagents and product are insoluble.

A classic example is small water droplets in pentane or hexane by vigorous stirring. The reaction will only occur in the water droplets hence particles will be small. The particle size can then be controlled by the rate of stirring and the concentration of the solvents.

[Edited on 14-10-2005 by vulture]




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[*] posted on 23-10-2005 at 11:59


This is a very interesting topic! Thanks for the link to the lab instructions.

The other method I've seen mentioned to form nanoparticles uses a colloid, aerogel, or similar method for keeping the newly created crystals small. That is:

(solution 1) FeSO4 + something that gels at high pH in H2O
(solution 2) NaOH in H2O
mix rapidly producing Fe(OH)2, which becomes FexOx in air.

How does one recover the product? Filtering it out is difficult! One could add something to destroy the gel,
but how to keep the product particles from coalescing? Dessicate the gel in vacuum, then somehow wash the gel from the product?
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[*] posted on 23-10-2005 at 21:38


Quote:
Originally posted by densest
How does one recover the product?


Duh, you simply add a supercritical fluid then evaporate it out... :D

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[*] posted on 7-11-2005 at 20:46


>>>> Duh, you simply add a supercritical fluid then evaporate it out...



Hey 12AX7, can I borrow your 300bar 300C kettle for a little supercritical concocting? It seems that the kitchen pressure cooker won't do! :mad:
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12AX7
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[*] posted on 8-11-2005 at 13:24


Heh heh.. okay, so steam at least sucks...(wait isn't critical pressure only 80 bar or so?)

CO2 however is critical around room temp IIRC, so that's a possibility. :) I mean, in as much as 80+ bar is a possibility at home, but still...

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[*] posted on 8-11-2005 at 20:24


Actually, it's a little over room temperature and more like 40 bar.
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[*] posted on 9-11-2005 at 14:35


>>Actually, it's a little over room temperature and more like 40 bar.

That isn't totally impossible at home. In English units & US standard part sizes, Schedule 160 seamless steel pipe is rated for 3000 psi and steam (100+ C), if I read the charts correctly. Using nominal pipe size 2 (inch) the pieces are about US$20 each for fittings or short lengths of pipe. Instant mini-pressure-system? :D

Unfortunately the prices go up exponentially for larger pieces.

A blast shield made of 1/4" (1.2 cm) scrap steel and a 2" (10 cm) laminated polycarbonate - acrylic - glass - acrylic - polycarbonate window would also be useful, and also under US$200 to make.
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[*] posted on 30-11-2015 at 09:08


Gold Aerogel
http://phys.org/news/2015-11-real-gold-air.html

Related paper
http://courses.chem.psu.edu/chem500/Past%20Chem%20500%20pdf%...




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