Carbonized Polymer Dots for Controlling Construction of MoS2 Flower-Like Nanospheres to Achieve High-Performance Li/Na Storage Devices.

Despite being one of the most promising materials in anode materials, molybdenum sulfide (MoS2 ) encounters certain obstacles, such as inadequate cycle stability, low conductivity, and unsatisfactory charge-discharge (CD) rate performance. In this study, a novel approach is employed to address the drawbacks of MoS2 . Carbon polymer dots (CPDs) are incorporated to prepare three-dimensional (3D) nanoflower-like spheres of MoS2 @CPDs through the self-assembly of MoS2 2D nanosheets, followed by annealing at 700 °C. The CPDs play a main role in the creation of the nanoflower-like spheres and also mitigate the MoS2 nanosheet limitations. The nanoflower-like spheres minimize volume changes during cycling and improve the rate performance, leading to exceptional rate performance and cycling stability in both Lithium-ion and Sodium-ion batteries (LIBs and SIBs). The optimized MoS2 @CPDs-2 electrode achieves a superb capacity of 583.4 mA h g-1 at high current density (5 A g-1 ) after 1000 cycles in LIBs, and the capacity remaining of 302.8 mA h g-1 after 500 cycles at 5 A g-1 in SIBs. Additionally, the full cell of LIBs/SIBs exhibits high capacity and good cycling stability, demonstrating its potential for practical application in fast-charging and high-energy storage.

Twisted lattice nanocavity with theoretical quality factor exceeding 200 billion.

Simultaneous localization of light to extreme spatial and spectral scales is of high importance for testing fundamental physics and various applications. However, there is a longstanding trade-off between localizing a light field in space and in frequency. Here we discover a new class of twisted lattice nanocavities based on mode locking in momentum space. The twisted lattice nanocavity hosts a strongly localized light field in a 0.048 λ3 mode volume with a quality factor exceeding 2.9 × 1011 (∼250 µs photon lifetime), which presents a record high figure of merit of light localization among all reported optical cavities. Based on the discovery, we have demonstrated silicon-based twisted lattice nanocavities with quality factor over 1 million. Our result provides a powerful platform to study light-matter interaction in extreme conditions for tests of fundamental physics and applications in nanolasing, ultrasensing, nonlinear optics, optomechanics and quantum-optical devices.

Magic-angle lasers in nanostructured moiré superlattice.

Conventional laser cavities require discontinuity of material property or disorder to localize a light field for feedback. Recently, an emerging class of materials, twisted van der Waals materials, have been explored for applications in electronics and photonics. Here we propose and develop magic-angle lasers, where the localization is realized in periodic twisted photonic graphene superlattices. We reveal that the confinement mechanism of magic-angle lasers does not rely on a full bandgap but on the mode coupling between two twisted layers of photonic graphene lattice. Without any fine-tuning in structure parameters, a simple twist can result in nanocavities with strong field confinement and a high quality factor. Furthermore, the emissions of magic-angle lasers allow direct imaging of the wavefunctions of magic-angle states. Our work provides a robust platform to construct high-quality nanocavities for nanolasers, nano light-emitting diodes, nonlinear optics and cavity quantum electrodynamics at the nanoscale.

Efficacy of bone marrow stem cells combined with core decompression in the treatment of osteonecrosis of the femoral head: A PRISMA-compliant meta-analysis.

BACKGROUND: This study used the meta-analytic approach to assess the safety and treatment efficacy of bone marrow stem cells (BMSCs) with core decompression (CD) for osteonecrosis of the femoral head (ONFH) based on randomized controlled trials (RCTs). METHODS: Electronic database of PubMed, Embase, Google Scholar, China National Knowledge Infrastructure (CNKI), and Wanfang database was searched up to December 26, 2019 for relevant RCTs about combined utilization of BMSCs and CD versus CD alone for ONFH. Gray literature sources were also searched. We conducted a meta-analysis following the guidelines of the Cochrane Reviewer's Handbook. Two independent reviewers performed the data extraction and assessed study quality. Our outcomes included the Harris hip scores (HHS) at 12 months, HHS at 24 months, necrotic area of femoral head, conversion to total hip arthroplasty (THA), visual analog pain scale at final follow-up, and adverse effects. The meta-analysis was performed with Stata 12.0. RESULTS: A total of 15 published studies with 688 patients fulfilled the requirements of inclusion criteria. Across all populations, participants in combined utilization of BMSCs group showed a statistical significance with higher HHS at 12 months (standard mean difference [SMD] 0.53, 95% confidence interval [CI] 0.29-0.77) and 24 months (SMD 0.57, 95% CI 0.36-0.77). Similarly, participants in combined utilization of BMSCs group had more advantages in reducing necrotic area of femoral head (SMD -1.05, 95% CI -1.73 to -0.38) and the rate of conversion to THA (risk ratio [RR] = 0.53, 95% CI 0.38-0.74, P = .000). No significant differences were identified regarding postoperative adverse effects postoperatively (RR = 1.03, 95% CI 0.64-1.67, P = .893). CONCLUSION: Compared with CD treated alone in the treatment of ONFH, combined utilization of CD and autologous BMSCs implantation has a better pain relief and clinical outcomes and can delay the collapse of the femoral head more effectively.

A high-performance topological bulk laser based on band-inversion-induced reflection.

Topological insulators are materials that behave as insulators in the bulk and as conductors at the edge or surface due to the particular configuration of their bulk band dispersion. However, up to date possible practical applications of this band topology on materials' bulk properties have remained abstract. Here, we propose and experimentally demonstrate a topological bulk laser. We pattern semiconductor nanodisk arrays to form a photonic crystal cavity showing topological band inversion between its interior and cladding area. In-plane light waves are reflected at topological edges forming an effective cavity feedback for lasing. This band-inversion-induced reflection mechanism induces single-mode lasing with directional vertical emission. Our topological bulk laser works at room temperature and reaches the practical requirements in terms of cavity size, threshold, linewidth, side-mode suppression ratio and directionality for most practical applications according to Institute of Electrical and Electronics Engineers and other industry standards. We believe this bulk topological effect will have applications in near-field spectroscopy, solid-state lighting, free-space optical sensing and communication.