Narrow Results

The oleate capped NaYF₄:Yb/Er upconversion nanoparticles (OA-UCNPs) were firstly synthesized by the thermal decomposition method and subsequently converted to water-dispersible, ligand-free UCNPs (LF-UCNPs) via an easy acid treatment process. The interaction of LF-UCNPs with bovine serum albumin (BSA) was then investigated. The binding of LF-UCNPs with BSA was confirmed by the static quenching of intrinsic fluorescence of BSA upon addition of LF-UCNPs. The spectra of synchronous fluorescence and circular dichroism (CD) of BSA in the absence and presence of LF-UCNPs revealed that the presence of LF-UCNPs led to a slight conformational change of BSA, suggesting a minor nanotoxicity of LF-UCNPs toward BSA.

In this paper, a novel fluorescent nanoswitch based on carbon dots (CDs) was developed for the sensitive and selective determination of Hg${}^{2+}$ and I${}^{-}$. The CDs were obtained by simple hydrothermal process and had a strong fluorescence emission at 440nm. The fluorescence of the CDs can be selectively quenched by Hg${}^{2+}$ ion, and then the I${}^{-}$ was added into the system, which can interact with Hg${}^{2+}$ and recover fluorescence of the CDs. Under optimal conditions, the quenching fluorescence intensity on addition of Hg${}^{2+}$ has obtained a satisfactory linear relationship covering the linear range of 0–50$\mu$M with the linear relationship ($R_1^2=0.9991$), and the limit of detection is 0.047$\mu$M. The additions of I${}^{-}$ could lead to the fluorescence intensity of the solution of CDs and Hg${}^{2+}$ (50$\mu$M) recover rapidly, which is linearly related ($R_2^2=0.9957$) to the concentration of I${}^{-}$ in the range from 0 to 70$\mu$M, the detection limit for I${}^{-}$ was calculated to be 0.084$\mu$M. Moreover, the developed method to detect Hg${}^{2+}$ and I${}^{-}$ was evaluated in real examples, and the fluorescence switching can sensitively and selectively detect Hg${}^{2+}$ and I${}^{-}$ over some potentially interfering ions, the recoveries were up to 97.8–107.0% and 96.7–106.6%, respectively.