Rational design of electrochemically active polymorphic MnOx/rGO composites for Li+-rechargeable battery electrodes

Electrochemical behavior of different MnO_x @reduced graphene oxide (rGO) composites derived from a MnO₂/GO template are thoroughly investigated. As-prepared MnO₂/GO mixture is gradually converted to MnO₂/rGO and finally to Mn₃O₄/rGO composites under controlled post annealing conditions. The semispherical Mn₃O₄ crystalline compound anchored composite exhibits stable electrode performances, including both the Li⁺ anode and the Li⁺-air cathode catalyst, induced by the electrochemically favorable composite with an effective large contact area between the active materials and the electronic conductive rGO. It is such a meaningful to suggest the facile and controllable synthetic procedures for obtaining Li-rechargeable electrodes with a MnO_x nanoparticle-incorporated composites for the highly reactive lithiation/delithiation electrochemical reactions.     

Enhanced Optical Properties of Bredigite‐Structure Ca13.7Eu0.3Mg2[SiO4]8 Phosphor: Effective Eu Reduction by La Co‐Doping

A green phosphor, La_0.4Ca_13.3Eu_0.3Mg₂Si₈O_31.6+δN_0.4?δ (LaCMSN:Eu²⁺), was prepared by a solid‐state reaction and an efficient green emission was observed at 506 nm under near‐ultraviolet (NUV) excitation. The structural and optical properties of LaCMSN:Eu²⁺ phosphors as well as their thermal quenching were investigated. The partial substitution of La³⁺ and N^3? in Ca_13.7Eu_0.3Mg₂Si₈O₃₂ led to a considerable enhancement in the peak emission intensity by as much as 194%. This demonstrates not only that the total number of Eu²⁺ activators increased, but also that the probability of a nonradiative transition between Eu²⁺ and Eu³⁺ could be reduced as the increase in concentration of the former is at the expense of the later. The white light‐emitting diode (LED) was fabricated using phosphor with a NUV LED chip. The LED showed warm white light with an excellent color rendering index of 91. The LaCMSN:Eu²⁺ is thus a potential green‐emitting phosphor for white LEDs.     

Enhanced Luminescence of Ca14Mg2Si8O28+δN4−δ:Eu2+Phosphors by Codoping Ce3+, Mn2+ for White LEDs and Their Energy‐Transfer Mechanism

The Eu²⁺, M‐codoped(M = Ce³⁺, Mn²⁺) phosphor powders were prepared by a solid‐state reaction. The addition of Ce³⁺ in the Eu²⁺ sites in partially nitridated bredigite‐structure phosphor(CMSN) remarkably enhances the luminescent intensity by ~180% through sensitized luminescence. Dual band emission was observed for Eu, Mn‐codoped CMSN through energy transfer from Eu²⁺ to Mn²⁺. Ce³⁺–Eu²⁺ and Eu²⁺–Mn²⁺ energy‐transfer mechanism was investigated through decay profile analysis using Inokuti–Hirayama model and energy‐transfer parameters are determined. Interaction mechanism was identified as dipole–dipole interaction. In addition, phosphor in glass plates was prepared using the phosphor and its feasibility in white LED application was studied and is presented.