I have prepared 2wt% Chitosan in 0.5% Acetic acid aqueous solution. To form Hydrogel sheets with ionic cross linking with silver nitrate, i have immersed the drop casted solution on Glass slide in 0.3M AgNo3. But failed to get the sheets. I tried freeze thawing process but with in 24 hours hydrogel sheet becoming black and the sheets are not of uniform thickness.

Can you give any suggestions or any reference related.

Thank you in advance.