Molecular Weight of PVP and weight % of PVP and also the weight of WO3 addition in PVP all matters for the proper dispersion.

The best way to prevent agglomeration of particles is by surface-modification of the particles. In the Table 1.12 of the book Aroon V. Shenoy, Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Netherlands (1999), there are a number of suggested surface modifiers. These would be from the categories of silanes, and titanates and their full forms are given in Table 1.8. Which one would be most effective for WO3 nanoparticles can only be worked out by some mixing experiments, which are discussed in the book. There is an entire chapter (Chapter 5) dedicated to the Preparation of filled polymer systems in the book. Though the contents are specifically meant for polymer melts, some necessary hints can be got on how to go about for the specific case of WO3 nanoparticles in PVP by reading Chapter 5 of the book.

Thanks Sir Aroon, I will study and get back to you if some more help needed....thanks alot

Hi Prof Aroon, This book is not available online or in my library. Could you please share the Pdf version of the book or the specific chapter?

thanks

It is available for purchase from websites such as www.amazon.com, www.booksamillion.com, www.barnesandnoble.com, www.abebooks.com, www.flipkart.com, www.shimply.com, and also available for reference in many libraries. You could request your library to purchase a copy if they do not have one or ask them to borrow from another library.

Good day Muhammad

WO3 IEP is very low (around 1.0). You do not mention suspension or PVP pH but pH is not defined for non aqueous fluids but it still exerts an effect. Nevertheless in ethanol the problem might be the opposite. Once I measured the zeta potential of hidroxyapatite in absolute ethanol and is opposite to the potential in water, I obtained higher stability with the alcohol than water, remember ethyl alcolhol is a surface active agent ( surface tension near 28). You could measure the WO3 zeta potential in ethanol as well as PVPs. It looks like you are putting together stuff with opposite surface electric polarities and they agglomerate. Polymer stabilizing of non hydrophylic dispersion is the most effective way to attain stability. There are gold sols stabilized with gelatine that are over one hundred years old. You can check this under "gold number of collois"

Other aspect you should consider is the size and shape of your PVP molecules. To protect polymers must atract and attach to particles surfaces and surround them to convert their hydrophobicity into hydrophilicity. But But if the molecule is too long or too big they will bond many particles into one huge blob or agglomerate.

Proteins are dipoles and so is PVP but the distance between the charges is different. Have you tried a protein instead?

Other option is the use of a cosolvent.

OK that is enough for now. Tell me how you do.

Edgar Delgado M.

Hi Edgar,

I am preparing WO3 NPs suspension in ethanol thats why i didn't consider the pH of the suspension. Moreover i am using PVP (1300 000 Mw) polymer from Sigma Aldrich.

My main problem is that i am using WO3 NPs (size 90 - 120 nm) bought from Sigma Aldrich which means i didn't prepare them by sol gel or any other method. As per literature, all the techniques of surface coating of NPs are applied during NPs synthesis but as i am using WO3 NPs (powder) bought from Sigma Aldrich. i am confused how to intergrate those techniques with my case. I hope you better understand the situation now.

Thanks

Muhammad

'My main problem is that i am using WO3 NPs (size 90 - 120 nm) bought from Sigma Aldrich' - yes, definitely. Which means you are using a highly agglomerated/aggregated powder. You maybe able to deagglomerate the powder, but you will not be able to disperse the aggregates or do you have a proof that you obtain nanoparticle dispersion before adding PVP?

For the desagglomeration of your WO3 particles, I think a simple US treatment will not be sufficient enough to receive particles in NP scale. Maybe atomization would be a better choice. Depending on your futher application, the particles could be coated in the gas phase which might work better.

I made experiments for studying the stabilization of nanoparticles in aqueous solutions. The used PVP may have to much to high molecular weight for a good surface “coating“ of the particles as the PVP is not surface active. We had better results for low weight PVPs.