We conducted continuous-wave photoluminescence (PL) measurements to study optical properties of graphene oxide (GO) before and after a centrifugation treatment. The pristine GOs show a PL peak around near-infrared (NIR) region (similar to 1.7 eV). In contrast, the centrifuged GOs exhibit PL peaks at blue (similar to 2.8 eV) and UV (similar to 4.1 eV) region. The difference among the emission features in the pristine and centrifuged GOs originates from the change of major structure from the sp(2) clusters to the quasi-molecular structure. Our findings indicate tunability of PL from GOs in the range from NIR to UV region by the centrifugation treatment. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim