On-site, rapid and visual determination of Hg2+ and Cu2+ in red wine by ratiometric fluorescence sensor of metal-organic frameworks and CdTe QDs

A ratiometric sensor of MOF/ CdTe QDs was constructed by physically mixing CdTe QDs ( λ em  = 605 nm) with MOF (Fe-MIL-88NH 2, λ em  = 425 nm). Under an UV lamp ( λ ex  = 365 nm), orange-red CdTe QDs is gradually quenched with increasing levels of Hg 2+ or Cu 2+ , while blue MOF is unchanged, accompanying with a visual change from bright pink to blue fluorescence. Hence, a new method for determining Hg 2+ and Cu 2+ by MOF/CdTe QDs sensor is established, whose detection limits are 0.22 ng mL −1 for Hg 2+ (2.1% RSD) and 0.26 ng mL −1 for Cu 2+ (1.1% RSD), respectively. In addition, on-site, rapid and visual determination of Hg 2+ /Cu 2+ in red wine without any pretreatment is realized by using a MOF/CdTe QDs paper-based sensor. For Hg 2+ and Cu 2+ , the semi-quantitative detection ranges of the paper-based sensor are both 10 ~ 5000 ng mL −1 , implying that it has great application value in analyzing Hg 2+ and Cu 2+ in liquid samples.