Jingbin Huang

Facile one-pot synthesis of highly fluorescent nitrogen-doped carbon dots by mild hydrothermal method and their applications in detection of Cr(VI) ions.

Nitrogen-doped carbon dots (N-CDs) with well-distribution size and strong blue emission were successfully synthesized via a simple mild hydrothermal strategy using citric acid and ethylenediamine as co-precursors. The highly fluorescent N-CDs exhibit high fluorescence quantum yield (QY, 58.6%), excitation-independent emission behavior, and good photostability. The experimental results showed that the N-CDs can be served as a fluorescent sensing platform for detection of Cr(VI) ions due to the effective fluorescence quenching effect of Cr(VI) ions. The quenching mechanism probably arises from the inner filter effect (IFE) and the electron transfer due to the strong interactions between functional groups (COOH, OH and NH2 groups) of the N-CDs and Cr(VI) ions. It is also found that the N-CDs showed high sensitivity toward Cr(VI) ions with a detection limit of 0.26 μM. Moreover, the obtained N-CD can be employed as chemsensor to detect Cr (VI) in real river water samples, which have potential applications in the environmental water.

Luminescent mesoporous hybrid materials grafted with lanthanide complexes synthesized by Michael-like addition reaction

New kind of luminescent mesoporous hybrid materials were prepared via Michael-like addition reaction. 4-Vinylpyridine-2,6-dicarboxylic acid was selected as a bifunctional chelating ligand, which contains (1) an electron deficient double bond that can react with the thiol group of mesoporous silica by Michael-like addition reaction, (2) a metal chelating unit. The luminescent hybrid materials [MCM-41-SH-Ln(DPA)3, Ln = Tb, Eu] can be prepared through Michael-like addition reaction of thiol-functional MCM-41 and 4-vinylpyridine-2,6-dicarboxylic acid, and then assembling with lanthanide ions and pyridine-2,6-dicarboxylic acid (DPA). FT-IR, XRD, UV–Vis, TEM, N2 adsorption/desorption and photoluminescence measurements were employed to characterize the mesostructure, composition and optical properties of these hybrids. The results reveal that the lanthanide complexes were successfully grafted onto the functional MCM-41, and the ordered mesoporous structure of MCM-41 were preserved after the grafting procedure. Under the excitation of UV light, the obtained MCM-41-SH-Tb(DPA)3 and MCM-41-SH-Eu(DPA)3 exhibit bright green and red emission, long luminescent lifetimes and high quantum efficiency.

Controlled synthesis of 3D flower-like MgWO4:Eu3+ hierarchical structures and fluorescence enhancement through introduction of carbon dots

3D flower-like MgWO4:Eu3+ hierarchical structures were synthesized via a simple hydrothermal method and characterized by XRD, SEM, TEM, XPS, FTIR and PL. The results show that the as-prepared MgWO4:Eu3+ samples have a tetragonal phase structure and possess a 3D flower-like hierarchical morphology. It is found that the Eu3+ doping concentration (more than 5%) has an obvious effect on the phase structure and the formation of a flower-like morphology, and MgWO4:Eu3+ flowers are probably formed from many layered nanosheets. Moreover, the significantly enhanced fluorescence performance of MgWO4:Eu3+ flowers by introducing carbon dots (CDs) is also studied. The PL emission intensities of CD/MgWO4:Eu3+ composites increase fourfold compared to those of the corresponding MgWO4:Eu3+ samples. The luminescence enhancement mechanism could be attributed to the energy transfer processes from the excited states of CDs to Eu3+ ions in the CD/MgWO4:Eu3+ composites. The as-prepared highly fluorescent materials with hierarchical structures might have potential applications in fluorescent lamps, displays, sensors and so on.