“Rigid” Luminescent Soft Materials: Europium-Containing Lyotropic Liquid Crystals Based on Polyoxyethylene Phytosterols and Ionic Liquids

Soft materials of europium β-diketonate complexes constructed in lyotropic liquid crystals (LLCs) mediated by ionic liquids (ILs) are impressive for their excellent luminescence performance and stability. For the aim to further improve their mechanical processability and luminescent tunablility, the polyoxyethylene phytosterols (BPS-<i>n</i>) were introduced here as structure directing agents to prepare relatively “rigid” lamellar luminescent LLCs in 1-butyl-3-methyl-imidazolium hexafluorophosphate by doping europium β-diketonate complexes with different imidazolium counterions. As a result of the solvophobic sterol ring structure of BPS-<i>n</i>, the more effective isolation and confinement effects of europium complexes could be achieved. The longest fluorescence lifetime and the highest quantum efficiency reported so far for europium containing lyotropic organized soft materials were thus obtained. Changing the molecular structures of BPS-<i>n</i> with different oxyethylene chains or doped complexes with imidazolium counterions of different alkyl chain lengths, the spacings of lamellar LLC matrixes and position of dispersed complexes became tunable. The measured luminescent and rheological properties for such composite LLCs showed a dependence on the rigidity and isolation capability afforded by sterol molecules. It was also found that the increase of counterion alkyl chain length would weaken the LLC matrix’s confinement and isolation effects and therefore exhibit the deteriorated luminescence performance. The enhanced luminescence efficiency and stability of doped BPS-<i>n</i> LLCs reflected the excellent segregation of europium complexes from each other and therefore the reduced self-quenching process. The obtained results here present the designability of LLC matrixes and their great potential to promote achieving the luminescence tunability of soft materials

Rationally Incorporated MoS₂/SnS₂ Nanoparticles on Graphene Sheets for Lithium-Ion and Sodium-Ion Batteries

Herein, we have designed and first synthesized a unique ternary hybrid structure by simultaneously growing SnS₂ and MoS₂ particles on graphene sheets (denoted as MoS₂/SnS₂-GS) via one-pot hydrothermal route. The charge incompatibility between MoO₄^2– and graphene oxide with negative charged functional groups on surface can be compromised with the aid of Sn⁴⁺ cations, which renders the final formation of SnS₂ and MoS₂ on GS surface. This is the first report of the cohybridization of MoS₂ and SnS₂ with GS matrix from anionic and cationic precursors in the absence of premedication of graphene surface. When MoS₂/SnS₂-GS acts as anodes for lithium-ion batteries, the hybrids exhibit much better cycling stability than MoS₂-GS and SnS₂-GS counterparts. The compact adhesion of MoS₂/SnS₂ nanoparticles helps offset the undesired result of destruction of electrode materials resulting from volume expansion during repeated cycles. Furthermore, by combination with their synergetic effect on interface and the presence of discrepant asynchronous electrochemical reactions for SnS₂ and MoS₂, MoS₂/SnS₂-GS hybrids are endowed with improvement of electrochemical capabilities. Besides, they also showed outstanding Na-storage ability