When TiO2 nano particles are prepared using Sol-gel method from TTIP it sometimes have different physical appearance. Pls what may be responsible for the difference in color especially after calcination at may be 500oC for 2h.
Dear Mr. Ashiru Abubakar Garba ,
Please, ensure If the samples are polluted with other different metals salts., when metal ions bonded with TiO2 that leads to change the color of it. Mostly loaded of Au caused different degrees of purple color but Pt and Pd lead to grey ....etc.
Regards,
If the colours are due to its physical properties it mean from the optical properties then it relate to the nanoparticles size particularly for the range from 15nm and down. From this size the colour which is due to the energy absorption of light, related to energy gap icreases to a higher energy level or lower light frequency fo smaller particle sizes
there are many published articles in this regard as a nanosize depends of energ gap in nonoscale particles
Please check the pH during the synthesis. Sometimes the differents in pH plays important role. Also maintain a strict clean environment for the synthesis and calcination it might also because of the contamination during these processes
Thank you all, I think even though nano particles are are of nm size, the color of the powder can be observed with bare eyes. pH is also targeted. It was prepared in alkaline medium and later acid was use to control the pH and then water to neutral. Also during preparation, it was done in the lab that is very clean and while calcining it was covered in a cleaned crucible.
According to my knowledge, the color change can be observed due to the the presence of carbon in your sample.
You can confirm the composition by performing Energy-dispersive X-ray spectroscopy (EDX) of your samples.
Ashiru Abubakar Garba , Even I am getting the same problem that you have mentioned. In spite of all precautions to prevent any contamination. Calcination is giving different colours in the final powder. Can anybody explain?
I also observed it and one factor found is temperature, check your sample at different calcination temperatures. And it may also due to Carbon present in the sample as already said by Rohini Singh.
The grey colour is given by the presence of Ti3+. You can check it by XPS
https://pubs.rsc.org/en/content/articlelanding/2022/cy/d1cy01450a
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