A fluorescent probe for the sensitive and selective determination of copper ion (Cu2+) is presented.It is based on the use of tungsten disulfide quantum dots (WS2 QDs) which is independent of the pH of solution and emits strong blue fluorescence.Copper ions could cause aggregation of the WS2 QDs and lead to fluorescence quenching of WS2 QDs.The change of fluorescence intensity is proportional to the concentration of Cu2+,and the limit of detection is 0.4 μM.The fluorescent probe is highly selective for Cu2+ over some potentially interfering ions.These results indicate that WS2 QDs,as a fluorescent sensing platform,can meet the selective requirements for biomedical and environmental application.