Mn-doped ZnS quantum dots for the determination of acetone by phosphorescence attenuation

Quantum dot (QD) nanoparticles (NPs) are increasingly used as highly valuable fluorescent biomarkers and as sensitive (bio)chemical probes. Interestingly, if certain metal impurities are incorporated during the NPs synthesis, phosphorescent QDs with analytical potential can be obtained. We report here the synthesis of colloidal manganese-doped ZnS nanoparticles which have been surface-modified with l-cysteine that exhibit an intense room temperature phosphorescence (RTP) emission in aqueous media even in the presence of dissolved oxygen (i.e. sample deoxygenation is not needed). An exhaustive RTP photoluminescent and morphological characterization of the synthesized QDs and their potential for development of phosphorescent analytical methodologies is described. Application to analytical control of acetone ("model analyte" from the ketones family) in water and urine samples is carried out by measuring the QDs phosphorescence quenching rate. The observed results showed a high selectivity of Mn(2+)-doped ZnS QDs towards acetone. The linear range of the developed methodology turned out to be at least up to 600 mg L(-1) with a detection limit (DL) for acetone dissolved in aqueous medium of 0.2 mg L(-1). The developed methodology was finally applied for acetone determination in different spiked water and urine samples, and the recoveries fall in the range of 93-107%.