Many thanks for the suggestions. We'll check them.
We thought about using spin coating, but our solution is extremely non-viscous, so we think it wouldn't help so much.
Jordi Riu Dept. Analytical and Organic Chemistry University Rovira i Virgili of Tarragona Catalonia - Spain
First you need to disperse your particles better. With metal nanoparticles, using aqueous solutions is very difficult even with some of the best ammonium polymethacyrlate type dispersants or electrostatic methods. Your organic solvents should work well though. If you want to stick with methanol try some of the traditional powder processing dispersants (ie menhaden fish oil or hypermer KD1 (made by ICI surfactants)). You should only need less than a weight % to make a significant improvement. Disolve your dispersant (polymer) in solution, add your nanoparticles and disperse with an ultrasonic probe. I have had good success dispersing carbon nanotubes in toluene, etoh, and MEK with the fish oil in this manner. Remember if you have good dispersion, you will not be able to see particles or colloids with the eye. The solubility of the fish oil is improved with about 20-40%xylene in meoh or etoh allowing the polymer chains to stretch out and improve the steric barrier.
To thicken your solution for spin casting add some ethyl cellulose (49% + ethoxyl content) until desired consistency is achieved (approximately 10wieght% yields the viscosity of maple syrup). Polyvinylbutyral works well too, but you might need a bit more to reach equivalent viscosity of the ethyl cellulose. Further, if absolutely clean burnout is required, use polypropylene carbonate (trade name QPAC-40), this is the absolutely cleanest binder for burnout which decomposes in air, vacuum, or inert. Of course you will need to work with acetone or MEK solutions for decent solubility which should also disperse your particles with the fish oil.
Yet one more final option is too use a higher viscosity solvent. Alpha terineol is wonderful with a little oleic acid for the dispersant. The alpha terpineol dries very slow, but levels beautifully, and is quite non-toxic compared to other solvents. If you need more body for spin coating, a % or so of ethyl cellulose will do the trick.
Good luck
Bon dia Jordi:
One possible hi-tech solution is to induce photofragmentation though a high-power visible light laser. It really works !
Milton ( snipped-for-privacy@yahoo.com.br).
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