An improved method is described for the production of graphene oxide nanoribbons (GONRs) via longitudinal unzipping of multiwalled carbon nanotubes. The method produces GONRs with fewer defects and/or holes on the basal plane, maintains narrow ribbons <100 nm wide, and maximizes the high aspect ratio. Changes in the reaction conditions such as acid content, time, and temperature were investigated. The new, optimized method which introduces a second, weaker acid into the system, improves the selectivity of the oxidative unzipping presumably by in situ protection of the vicinal diols formed on the basal plane of graphene during the oxidation, and thereby prevents their overoxidation and subsequent hole generation. The optimized GONRs exhibit increased electrical conductivity over those chemically reduced nanoribbons produced by previously reported procedures.