Selective detection of Zn2+ and Cd2+ ions in water using a host-guest complex between chromone and Q[7]

Abstract In this paper, the host-guest interaction of cucurbit[7]uril (Q[7]) and chromone (CMO) has been developed as a fluorescent probe for the highly selective detection of Zn2+ and Cd2+ in water based on a chelation-enhanced fluorescence (CHEF) mechanism. There was a good linear relationship between the fluorescence intensity of the CMO@Q[7] probe and the concentration of Zn2+ or Cd2+ in the range of 0–3.0 × 10–5 mol/L and the detection limit for Zn2+ and Cd2+ was found to be 2.03 × 10–6 mol/L and 1.89 × 10–6 mol/L, respectively. The X-ray crystal structure indicated that different coordination fashions were triggered by Zn2+ and Cd2+ in the CMO@Q[7] complexes, respectively. However, both metal ions coordinated with the carbonyl oxygen of CMO, which was encapsulated in the cavity of Q[7], thus leading to the enhancement of recognition fluorescence emission of CMO.