I am trying to make black TiO2 by sol gel method. In this I am taking a titanium precursor (TTIP) solution in diethylene glycol followed by its hydrolysis and condensation to form a gel. Drying and calcination of this gel is giving me black TiO2 powders. But the powders settle down pretty quickly even after crushing. Whereas, the commercially available amorphous TiO2 (bulk) seems to make a better dispersion in water than the nanoparticles which I have made by sol gel method. I was wondering if there is indeed any benefit of using the as prepared particles? Because the purchased amorphous particles are finer in texture than the ones I have synthesized. Is there anything that I can do to make my final particles really fine? I am aware that even though my particles are aggregated ,their grain sizes are in the nano dimensions. But what is the point if I cant make use of their nano size (high surface area) when they settle quickly?
If the particles in your colloidal solution are getting settled rapidly the it means the dispersion is not stable. The NP' s should remain in the body of liquid when the dispersion is kept on standing. Better you characterize your NP' s and give a fresh look at the method parameters.
Drying your particles has led to irreversible aggregation. You have a collection of fused sub- and post-micron aggregates and agglomerates.A simple Stokes' Law calculation (density of TiO2 is 4.2 g/cm3 and thus it has to be really small to stay in suspension) will demonstrate this. To preserve the nano form (separate, discrete, independent particles < 100 nm), then you need to keep the system in stable (charge or steric) colloidal suspension. Never dry them.
A lot of the potential surface area may be available despite the fused aggregated form. Have you measured the SSA of the materials? Is it greater than 60 m2/g? (Remember to correct for the density of the material)
Yes, but only when the synthesis of these particles can control the size by the molar ratio of organic solvent / aqueous phase and other parameters.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nano