Nanocomposite Based on Organic Framework-Loading Transition-Metal Co Ion and Cationic Pillar[6]arene and Its Application for Electrochemical Sensing of l-Ascorbic Acid.

In this study, we constructed a highly sensitive and selective electrochemical sensing strategy for l-ascorbic acid (AA) based on a covalent organic framework (COF)-loading non-noble transition metal Co ion and macrocyclic cationic pillar[6]arene (CP6) nanocomposite (CP6-COF-Co). The COF plays a crucial role in anchoring the Co ion according to its crystalline porous and multiple coordination sites and has an outstanding performance for building an electrochemical sensing platform based on a unique two-dimensional structure. Accordingly, the transition-metal Co ion can be successfully anchored on the framework of COF and shows strong catalytic activity for the determination of AA. Moreover, introduction of host-guest recognition based on CP6 and AA can bring new properties for enhancing selectivity, sensitivity, and practical application in real environment. Host-guest interactions between CP6 and AA were evaluated by the 1H NMR spectrum. When compared with other literatures, our method displayed a lower determination limit and broader linear range. To the best of our knowledge, this is the first study carried out for the non-noble transition-metal Co ion, COF, and pillar[6]arene hybrid material in sensing field, which has a potential value in sensing, catalysis, and preparation of advanced multifunction materials.

Enhancement of the luminescence properties of Sr3 (PO4 )2 :Dy3+ ,Li+ white-light-emitting phosphors by charge compensator Li+ co-doping.

Sr3 (PO4 )2 :Dy3+ ,Li+ phosphors were prepared using a simple high temperature solid method for luminescence enhancement. The structures of the as-prepared samples agreed well with the standard phase of Sr3 (PO4 )2 , even when Dy3+ and Li+ were introduced. Under ultraviolet excitation at 350 nm, the Sr3 (PO4 )2 :Dy3+ sample exhibited two emission peaks at 483 nm and 580 nm, which were due to the 4 F9/2  â†’ 6 H15/2 and 4 F9/2  â†’ 6 H13/2 transitions of Dy3+ ions, respectively. A white light was fabricated using these two emissions from the Sr3 (PO4 )2 :Dy3+ phosphors. The luminescence properties of Sr3 (PO4 )2 :Dy3+ ,Li+ phosphors, including emission intensity and decay time, were improved remarkably with the addition of Li+ as the charge compensator, which would promote their application in near-ultraviolet excited white-light-emitting diodes.

Sol-gel synthesis and luminescence property of Sr4 Al2 O7 :Re3+ ,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors for white LEDs.

Sr4 Al2 O7 :Eu3+ and Sr4 Al2 O7 :Dy3+ phosphors with alkali metal substitution were prepared using a sol-gel method. The effects of a charge compensator R on the structure and luminescence of Sr4 Al2 O7 :Re3+ ,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors were investigated in detail. Upon heating to 1400°C, the structure of the prepared samples was that of the standard phase of Sr4 Al2 O7 . Under ultraviolet excitation, all Sr4 Al2 O7 :Eu3+ ,R+ samples exhibited several narrow emission peaks ranging from 550 to 700 nm due to the 4f â†’ 4f transition of Eu3+ ions. All Sr4 Al2 O7 :Dy3+ ,R+ phosphors showed two emission peaks at 492 and 582 nm, due to the 4 F9/2  â†’ 6 H15/2 and 4 F9/2  â†’ 6 H13/2 transitions of Dy3+ ions, respectively. The luminescence intensity of Sr4 Al2 O7 :Re3+ ,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors improved markedly upon the addition of charge compensators, promoting their application in white light-emitting diodes with a near-ultraviolet chip.