Fluorescence cadmium sulfide nanosensor for selective recognition of chromium ions in aqueous solution at wide pH range

•Luminescent CdS QDs were prepared with naturally occurring biopolymer, pectin.•CdS QDs are stable at wide pH range.•Chromium ions selectively quenched the QDs fluorescence at nanomolar range.•CdS QDs recognizes chromium ions in blood plasma and in real water samples. Chromium is recognized as a serious environmental pollutant because of high toxicity and carcinogenic properties. In this paper, we have developed cadmium sulfide quantum dots (CdS QDs) based fluorescence sensor for sensitive and selective detection of chromium ions. CdS QDs were synthesized by wet chemical method using pectin biopolymer as capping agent and taurine as an antioxidant. The fluorescence emission intensity of CdS QDs at 450nm was selectively quenched by chromium ions, whereas other cations and anions showed negligible changes. The fluorescence intensity of CdS QDs is linearly proportional to the chromium concentration from 0.016 to 0.260μM with a detection limit of 16×10−9M. The proposed sensor recognizes chromium ion at a wide range of pH from 4 to 10. In addition, CdS QDs were also used to detect chromium ions in biological fluid, sewage water, pond water and tap water samples, with low interference.