▎ 摘　　要

An easy bottom-up method for the preparation of photoluminescent (PL) graphene quantum dots (GODs) and graphene oxide (GO) has been developed by tuning the carbonization degree of citric acid and dispersing the carbonized products into alkaline solutions. The GQDs are nanosheets similar to 15 nm in width, and 0.5-2.0 nm in thickness. They show a relatively strong (9.0%) PL quantum yield and an excitation-independent PL emission activity. In contrast, the GO nanostructures consist of sheets that are hundreds of nanometers in width and similar to 1 nm in height. They exhibit a relatively weak (2.2%) PL quantum yield and an excitation-dependent PL emission activity. (C) 2012 Elsevier Ltd. All rights reserved.