Chitosan/nano-silica hybrid film was prepared according to Yeh
et al. (2007) with minor modification. Chitosan (2.0%, w/v) coating
solution was dispersed in an aqueous solution of glacial acetic acid
(0.5%, v/v). The solution was well stirred with a magnetic stirrer for
48 h at room temperature to form a homogeneous mixture. Required
amount of this solution was taken in a 500 ml bottle, and
measured amount of TEOS was added to it. And then, the solution
was repeatedly stirred with a magnetic stirrer until the mixture
solution became clear and coating formation. Stoichiometric
amount of an equal mixture of ethanol and water was added to
the solution and allowed to stir for 20 h at room temperature.
The water to TEOS ratio was 1:4. The pH of the solution was adjusted
to 5.6 with 1 M NaOH. The 500 ml final volume solution
was vacuumed for 2 h to remove trapped air bubbles during the
mixing.