Currently, i'm preparing my nanosilica via sol-gel method, but the nanoparticle's size obtained is >100nm. I'm using TEOS as a precursor, acetic acid as catalyst and water as hydrolyzing agent. But i did not add alcohol to my TEOS. Do i need to add alcohol(ex: ethanol) to my TEOS? Because i'm thinking that could be the reason. Does anyone know?
The idea behind addition of alcohol is to improve the miscibility of the system as water and alkoxides are immiscible. (Aelion 1950). The majority of the work done on sol-gel processing has employed methanol or ethanol as solvent. However, any family of organic liquid capable of hydrogen bonding with water can be employed, such as amines, amides or ketones.
The solvent was commonly chosen to have the same carbon chain as the ligands of the alkoxide, so as to prevent the possibility of ligand exchange as discussed by Bradly (Bradly et al 1978). If one uses ethyl alcohol as solvent with a methyl alkoxide, it is possible for the ethyl group to replace the methyl group
So in your case ethanol will be suitable.
An added solvent is not necessary if the volume of generated alcohol is sufficient to bring all the components into solution. Severe agitation, through ultrasonic vibration, facilities the initial hydrolysis needed to result in miscibility (Tarasevich 1984).
You used water to hydrolyze TEOS for growing silica particles, which is very faster process than particle nucleation resulting large size particles. If you want to get relatively smaller particles, you have to control the hydrolysis reaction of TEOS as well as growth process of silica using only quantitative amount of water and ethanol as medium.
Of course you can use ethanol but for the smaller nanoparticles and better distribution you have to use glycerol or polyethylene glycol.
Thank you for your answers.
Md. Abdur Rahman does it mean that i dont need to use catalyst at all?
Of course, you would use catalyst, which enhance hydrolysis and polycondensation to form SiO2.
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