This thesis investigates various carbon nanomaterials from the basic synthesis to the characterizations and applications in fibers, photonics and composites. The carbon nanomaterials we studied include graphene, graphene oxide, graphene nanoribbons, functionalized graphene nanoribbons, graphene oxide nanoribbons, graphene quantum dots and carbon nanotubes. With all these chemical approaches, these carbon nanomaterials’ mechanical, electrical, photonic and gas barrier properties were carefully studied and demonstrated.