1. The width can be estimated by the distance between two atoms at edges, and the width can be estimated by the distance between two atoms at two ends of ribbon.
2. The atomic structures of graphene oxide is quite complicated and diversiform. The exact atomic structures of graphene oxides are not known even in experiment. You can construct some atomic structures of the graphene oxide by adding some oxygen-containing functional groups on graphene as you like and according to your study purpose. And then optimize the atomic structures.
3. Currently, such tutorial may be not available.
4. The topic is quite ambiguous. For a simple case of such topic, you may try the simulations of adsorption of some toxic gases.
