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 (λem = 605 nm) with MOF (Fe-MIL-88NH2,λem = 425 nm). Under an UV lamp (λex = 365 nm), orange-red CdTe QDs is gradually quenched with increasing levels of Hg2+ or Cu2+, while blue MOF is unchanged, accompanying with a visual change from bright pink to blue fluorescence. Hence, a new method for determining Hg2+ and Cu2+ by MOF/CdTe QDs sensor is established, whose detection limits are 0.22 ng mL-1 for Hg2+ (2.1% RSD) and 0.26 ng mL-1 for Cu2+ (1.1% RSD), respectively. In addition, on-site, rapid and visual determination of Hg2+/Cu2+ in red wine without any pretreatment is realized by using a MOF/CdTe QDs paper-based sensor. For Hg2+ and Cu2+, 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 Hg2+ and Cu2+ in liquid samples.