Hi Neelesh

Most sol-gel syntheses of TiO2 nanoparticles use an alkoxide Ti(OR)4 precursor such as Ti(IV) ethoxide, Ti(IV) isopropoxide, Ti(IV) propoxide or Ti(IV) butoxide. Hydrolysis of these alkoxides with water yields Ti(OH)4 + 4ROH. The Ti(OH)4 subsequently transforms to amorphous TiO2 + 2H2O with mild heating. Calcination at temperature up to 500 oC yields nanocrystalline TiO2 (typically anatase), which slowly transforms to rutile TiO2 at higher calcination temperatures.

The calcination step thus serves multiple purposes

1) it removes and residual organic species from the Ti(IV) alkoxide precursor to yield pure TiO2

2) it transforms amorphous TiO2 into nanocrystalline TiO2. TiO2 crystallite and particle sizes increase with calcination temperature.

3) it allows a degree of control over the polymorphic composition of the TiO2 product

For photocatalytic applications, nanocrystalline TiO2 (especially nanocrystalline anatase-rutile mixtures) is much more active than amorphous TiO2 even though the amorphous TiO2 will have a much higher specific surface area. The calcination step is therefore very important for synthesizing TiO2 photocatalysts with good activities.

Best regards

Geoff

It will affect the morphology and size of the nanoparticles.

Hi Neelesh

Most sol-gel syntheses of TiO2 nanoparticles use an alkoxide Ti(OR)4 precursor such as Ti(IV) ethoxide, Ti(IV) isopropoxide, Ti(IV) propoxide or Ti(IV) butoxide. Hydrolysis of these alkoxides with water yields Ti(OH)4 + 4ROH. The Ti(OH)4 subsequently transforms to amorphous TiO2 + 2H2O with mild heating. Calcination at temperature up to 500 oC yields nanocrystalline TiO2 (typically anatase), which slowly transforms to rutile TiO2 at higher calcination temperatures.

The calcination step thus serves multiple purposes

1) it removes and residual organic species from the Ti(IV) alkoxide precursor to yield pure TiO2

2) it transforms amorphous TiO2 into nanocrystalline TiO2. TiO2 crystallite and particle sizes increase with calcination temperature.

3) it allows a degree of control over the polymorphic composition of the TiO2 product

For photocatalytic applications, nanocrystalline TiO2 (especially nanocrystalline anatase-rutile mixtures) is much more active than amorphous TiO2 even though the amorphous TiO2 will have a much higher specific surface area. The calcination step is therefore very important for synthesizing TiO2 photocatalysts with good activities.

Best regards

Geoff

thanx to both of you