▎ 摘　　要

Using the Z-scan method, the nonlinear optical absorption property of carboxyl-functionalized graphene oxide (GO) was researched for the first time. The strong optical limiting (OL) effect was found in carboxyl-GO, which can be attributed to the two-photon absorption (2PA). At 532-nm excitation condition, the threshold of OL behavior is only 8% of that at 1064 nm excitation, and the saturable intensity I-s as well as the 2PA coefficient beta(2) are 1.31 GW/cm(2) and 0.17 cm/GW, respectively. It indicates that carboxyl-GO is an excellent nanomaterial for OL application, especially in short wavelength scope.