RESUMO
Multishell Y2 O3 :Yb(3+) /Er(3+) hollow spheres with uniform morphologies and controllable inner structures are prepared successfully by using a glucose-template hydrothermal process followed by temperature-programmed calcination. Much enhanced upconverted photoluminescence of these Y2 O3 :Yb(3+) /Er(3+) are observed, which are due to the multiple reflections and the enhanced light-harvesting efficiency of the NIR light resulting from the special features of the multishell structures.
RESUMO
Developing flexible electrodes with high active materials loading and excellent mechanical stability is of importance to flexible electronics, yet remains challenging. Herein, robust flexible electrodes with an encapsulated core-multishell structure are developed via a spraying-hydrothermal process. The multilayer electrode possesses an architecture of substrate/reduced graphene oxide (rGO)/bimetallic complex/rGO/bimetallic complex/rGO from the inside to the outside, where the cellulosic fibers serve as the substrate, namely, the core; and the multiple layers of rGO and bimetallic complex, are used as active materials, namely, the shells. The inner two rGO interlayers function as the cement that chemically bind to two adjacent layers, while the two outer rGO layers encapsulate the inside structure effectively protecting the electrode from materials detachment or electrolyte corrosion. The electrodes with a unique core-multishell structure exhibit excellent cycle stability and exceptional temperature tolerance (-25 to 40 °C) for lithium and sodium storage. A combination of experimental and theoretical investigations are carried out to gain insights into the synergetic effects of cobalt-molybdenum-sulfide (CMS) materials (the bimetallic complex), which will provide guidance for future exploration of bimetallic sulfides. This strategy is further demonstrated in other substrates, showing general applicability and great potential in the development of flexible energy storage devices.