I am using Ni (nano particles) on SiC as a catalyst for Glycerol oxidation. i am doing CV studies. and I modify my GCE (WE) with a droplet of this suspension. I put 4 mg of Ni-SiC and 70ul of Nafion (5wt%) along with 1mL of water:isopropanol mixture (1:1). after sonicating for 1 hour, i get a a turbid suspension with Ni-SiC particles (mostly) suspended in the solution but with the passage of time the solution gets clear and Ni-SiC particles settle down the bottom?
what should i do to get a thoroughly suspended suspension of Ni-SiC?
It could be that your Ni-SiC aren't highly water soluble. From the looks of it, the particle stability in the solution isn't high. Have you tried using different compositions of your solution mixture, or different solvents to suspend these particles ? Additionally, you could try and do Zeta Potential studies to measure your particle stability.
thanks for your reply Priyanka,
Yes I have varied the proportion of water: Isopropanol from 1:3, 1;1, 3:1.
Visually the best suspension resulted in 1:1 water: Isopropanol mixture. I am now thinking of using just ethanol for suspension. can you suggest any preferred solvent for Ni-SiC?
Hi Asad,
You should check your particles isoelectric point and adjust your solution pH with this information. Moreover, surfactants are widely used for stability of nanoparticle solutions. Which surfactant is suitable for your study? You can check your particles surface charge with DLS and then you can decide surfactant type.
maybe there is another problem - reacting Ni nanoparticles with water during sonication?
Very likely both the Ni and the SiC particles have isoelectric point in the acidic range, around pH 2-3. SiC exposed to air has a thin layer of SiO2 on its surface, so no wonder SiC has similar IEP to SiO2. Surface chemistry of Ni in an aqueous medium is quite complex. It may depend on its synthetic route, i.e. industrial processes such as hydrothermal synthesis, decomposition from nickel tetracarbonyl, or some other lab scale wet chemistry methods. I had done concentrated aqueous nickel slurry involving the use of some micron sized spherical nickel particles from hydrothermal synthesis, cationic polyelectrolyte polyethylenimine (PEI) worked pretty well for dispersing Ni in water. PEI should work pretty well for SiC too.
As Ayse had suggested, check the zeta potential curve of Ni to confirm the above information. If you cannot use polymeric additives in your process, try adjusting the pH to higher pH range where zeta potential
Yes, I think the secret must be that your particles are aggregating. You have to stabilize using an adequate surfactant. pH may also have an influence. If you do not want to change pH it is possible to stabilize them based on steric effect. Of course you may be careful not to decrease the reactivity of the particles making sure that your surfactant does not cover all the reactive sites.
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