L-Cysteine modified luminescence nanomaterials as fluorescence sensor for Co2+: Effects of core nanomaterials in detection selectivity

A selective cobalt ion sensor derived from L-Cysteine modified on fluorescence nanomaterials including silver nanoclusters (L-Cyst-AgNCs) and cadmuim sulfide quantum dots (L-Cyst-CdS QDs) were proposed. In the presence of Co2+, the fluorescence intensity of both nanomaterials were efficiently quenched. However, in the case of L-Cyst-CdS QDs, other metal ions can also quench the fluorescence intensity of L-Cyst-CdS QDs. On the other hand, the fluorescence intensity of L-Cyst-AgNCs can be quenched exclusively in the presence of Co2+ suggested the role of the fluorescence core material towards the detection selectivity. Circular dichroism spectroscopy revealed that only Co2+ could interact with L-Cyst-AgNCs by coordinating with L-Cysteine modified on AgNCs surface. Thus, L-Cyst-AgNCs were used as a sensor to detect Co2+ by measuring the fluorescence quenching. In addition, the degree of fluorescence quenching was linearly increased with the increasing of Co2+ concentration. The proposed L-Cyst-AgNCs sensor can be used to detect Co2+ in a wide working linear concentration range of 14-150 mu M. Furthermore, the proposed sensor can be efficiently used for detection of Co2+ in real water samples with satisfactory results. (C) 2015 Elsevier B.V. All rights reserved.