Nanocomposite-based rapid, visual, and selective luminescence turn-on assay for Hg2+ sensing in aqueous media.

Composite nanospheres containing dithizone, luminescent LaVO4:Eu(3+) nanoparticles (NPs), and amphiphilic polymer have been composed for the rapid, selective, and visual luminescence turn-on detection of mercury ions (Hg(2+)) in water. Due to the absorption of dithizone, the strong red luminescence of LaVO4:Eu(3+) NPs encapsulated in nanospheres was quenched noticeably. As a result, these as-prepared nanocomposites (NCs) demonstrate very weak red luminescence. However, in the presence of Hg(2+), the red luminescence of nanocomposites was turned on dramatically, which can be attributed to the strong binding of mercury (II) ions by dithizone and forming a complex without absorption in the red emission range. Meanwhile, other cations have no influence on the detection of Hg(2+), suggesting a good selectivity for Hg(2+) sensing. Due to the high photostability and chemical stability of the nanocomposites, operation simplicity, low cost, and good selectivity, this newly developed method is highly desirable for field assay of Hg(2+) in aqueous media ranging from 40.0 nM to 4.0 µM with a limit of detection of 32.0 nM and a good linearity (r=0.9980). Therefore, a facile, rapid, selective, and visual luminescence turn-on technology has been successfully developed for Hg(2+) detection.

Down-/up-conversion luminescence nanocomposites for dual-modal cell imaging.

Dual-modal luminescence nanocomposites (NCs) were successfully prepared via a facile and versatile strategy by embedding the hydrophobic down-conversion (DC) fluorescence ZnS:Mn2+ quantum dots (QDs) and up-conversion (UC) luminescence NaYF4:Er3+/Yb3+ nanoparticles (NPs) into hydrophilic polymer matrixes through in situ cross-linking polymerization. Due to the enriched carboxylic groups in the polymer matrixes, the as-prepared NCs are highly water-stable and bioconjugatable with chemical and biological moieties. The results of cytotoxicity assay and dual-modal luminescence cell imaging application of DC-UC NCs indicate that the as-prepared NCs are biocompatible and applicable in biomedical fields. The current work paves the way to the fabrication of multifunctional NCs including down- and up-conversion dual-modal luminescence, luminescence-magnetism, magnetic targeted drug vehicles and magnetic recyclable catalyst NCs, and will attract wide attention from the fields of chemistry, materials, catalysis, nanotechnology, nanobiotechnology and nanomedicine.