Yajuan Sun

Controlled synthesis and morphology dependent upconversion luminescence of NaYF4:Yb, Er nanocrystals

Size and morphology controlled NaYF4:Yb, Er nanocrystals were synthesized via the hydrothermal method. Polydentate ligands, such as EDTA and citrate, were used in the synthesis of cubic and hexagonal Yb3+, Er3+ codoped NaYF4 nanocrystals as a means of controlling the size and morphology of the nanocrystals. Subsequently, the particle size was found to be dependent on the nucleation rate, which, in turn, was governed by the reactant concentration, molar ratio and choice of ligand. The phase transformation from cubic to hexagonal was found to be sensitive to reaction time and reactant concentration. The upconversion photoluminescence of the nanocrystals demonstrated morphology dependence, which provides a means to characterize their crystalline quality and structure.

Ionothermal synthesis of hexagonal-phase NaYF4:Yb3+,Er3+/Tm3+ upconversion nanophosphors

Water-soluble pure hexagonal-phase NaYF(4):Yb(3+),Er(3+)/Tm(3+) nanoparticles were obtained by an ionothermal method for the first time which offers a new alternative in synthesizing such materials.

Hexanedioic acid mediated surface-ligand-exchange process for transferring NaYF4:Yb/Er (or Yb/Tm) up-converting nanoparticles from hydrophobic to hydrophilic

Water-soluble and carboxyl-functionalized up-converting rare-earth nanoparticles (UCNPs) are obtained via an efficient surface-ligand-exchange procedure. Hexanedioic acid molecules are employed to replace the original hydrophobic ligands in diethylene glycol solvent at high temperature. Various characterizations indicate the ligand-exchange process has negligible adverse effect on the quality of the UCNPs. The resulting hydrophilic UCNPs show small size, strong up-converting emission and high water stability. The specific molecular recognition capacity of avidin-modified hydrophilic UCNPs confirms that hydrophilic UCNPs are suitable for potential biological labeling.

Multi-targeting single fiber-optic biosensor based on evanescent wave and quantum dots

Highly sensitive, multi-analyte assay is a long-standing challenge for a single fiber-optic evanescent wave biosensor (FOB). In this paper, we report the first realization of such kind of FOB using CdSe/ZnS core/shell quantum dots (QDs) as labels. A direct binding assay model between antibody and antigen was employed to demonstrate the advantages of using QDs, instead of conventional fluorescein isothiocyanate (FITC), in lifting the sensitivity. Especially, multiplexed immunoassay was demonstrated in a single fiber FOB constructed with four differently sized QDs. Furthermore, the phenomenon that the affinity of the QD-labeled human IgG (QD-IgG) with goat anti-human IgG (anti-IgG) was lower than that of the FITC-labeled human IgG (FITC-IgG) was investigated and was ascribed to the differences in size and mass of the two. Our study indicates that the affinity could be improved by controlling the amount of IgG binding on QDs.