Three　different　graphene　nanostructure　suspensions　of　graphene　oxide　nanosheets　(GONSs),　graphene　oxide　nanoribbons　(GONRs),　and　graphene　oxide　quantum　dots　(GOQDs)　are　prepared　and　characterized.　Using　a　typical　two-step　method,　the　GONSs,　GONRs,　and　GOQDs　are　incorporated　into　a　polyimide　(PI)　matrix　to　synthesize　graphene/PI　composite　films,　whose　nonlinear　optical　(NLO)　and　optical　limiting　(OL)　properties　are　investigated　at　532　nm　in　the　nanosecond　regime.　The　GONR　suspension　exhibits　superior　NLO　and　OL　effects　compared　with　those　of　GONSs　and　GOQDs　because　of　its　stronger　nonlinear　scattering　and　excited-state　absorption.　The　graphene/PI　composite　films　exhibit　NLO　and　OL　performance　superior　to　that　of　their　corresponding　suspensions,　which　is　attributed　primarily　to　a　combination　of　nonlinear　mechanisms,　charge　transfer　between　graphene　materials　and　PI,　and　the　matrix　effect.　(C)　2014　AIP　Publishing　LLC.