A New Spin-Correlated Plasmon in Novel Highly Oriented Single-Crystalline Gold Quantum Dots

Highly oriented single-crystalline gold quantum-dot metamaterials as prospective materials for photonics

Miniaturization of optical devices is a modern trend essential for optoelectronics, optical sensing, optical computing and other branches of science and technology. To satisfy this trend, optical materials with a small footprint are required. Here we show that extremely thin, flat, nanostructured gold films made of highly oriented single-crystalline gold quantum-dots can provide elements of topological photonics in visible light and be used as high-index dielectric materials in the infrared part of the spectra. We measure and theoretically confirm the presence of topological darkness and associated phase singularities in studied gold films of thickness of below 10 nm placed on MgO substrates in the red part of the spectrum. At telecom wavelengths, the fabricated gold metasurface behaves as a dielectric with the refractive index of n≈2.75 and the absorption coefficient of k≈0.005.

MoP quantum dots based multifunctional efficient electrocatalyst for stable and long-life flexible lithium-sulfur batteries

The commercialization of lithium-sulfur (Li-S) batteries is challenging, owing to factors like the poor conductivity of S, the 'shuttle effect', and the slow reaction kinetics. To address these challenges, MoP quantum dots were decorated on hollow carbon spheres (MoPQDs/C) in this study and used as an efficient lithium polysulfides (LiPSs) adsorbents and catalysts. In this approach polysulfides are effectively trapped through strong chemisorption and physical adsorption while simultaneously facilitating LiPSs conversion by enhancing the reaction kinetics. MXene serves as a flexible physical barrier (MoPQDs/C@MXene), further enhancing the confinement of LiPSs. Moreover, both materials are conductive, significantly facilitating electron and charge transfer. Additionally, the flexible MoPQDs/C@MXene-S electrode offers a large specific surface area for sulfur loading and withstand volume expansion during electrochemical processes. As a result, the MoPQDs/C@MXene-S electrode exhibits excellent long-term cyclability and maintains a robust specific capacity of 992 mA h g-1 even after 800cycles at a rate of 1.0C (1C = 1675 mA g-1), with a minimal capacity decay rate of 0.034 % per cycle. This work proposes an efficient strategy to fabricate highly efficient electrocatalysts for advanced Li-S batteries.

Application of Inorganic Quantum Dots in Advanced Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have emerged as one of the most attractive alternatives for post-lithium-ion battery energy storage systems, owing to their ultrahigh theoretical energy density. However, the large-scale application of Li-S batteries remains enormously problematic because of the poor cycling life and safety problems, induced by the low conductivity , severe shuttling effect, poor reaction kinetics, and lithium dendrite formation. In recent studies, catalytic techniques are reported to promote the commercial application of Li-S batteries. Compared with the conventional catalytic sites on host materials, quantum dots (QDs) with ultrafine particle size (<10 nm) can provide large accessible surface area and strong polarity to restrict the shuttling effect, excellent catalytic effect to enhance the kinetics of redox reactions, as well as abundant lithiophilic nucleation sites to regulate Li deposition. In this review, the intrinsic hurdles of S conversion and Li stripping/plating reactions are first summarized. More importantly, a comprehensive overview is provided of inorganic QDs, in improving the efficiency and stability of Li-S batteries, with the strategies including composition optimization, defect and morphological engineering, design of heterostructures, and so forth. Finally, the prospects and challenges of QDs in Li-S batteries are discussed.

Anomalous Ferromagnetism of quasiparticle doped holes in cuprate heterostructures revealed using resonant soft X-ray magnetic scattering

We report strong ferromagnetism of quasiparticle doped holes both within the ab-plane and along the c-axis of Cu-O planes in low-dimensional Au/d-La_1.8Ba_0.2CuO₄/LaAlO₃(001) heterostructures (d = 4, 8 and 12 unit-cells) using resonant soft X-ray and magnetic scattering together with X-ray magnetic circular dichroism. Interestingly, ferromagnetism is stronger at a hole doped peak and at an upper Hubbard band of O with spin-polarization degree as high as 40%, revealing strong ferromagnetism of Mottness. For in-ab-plane spin-polarizations, the spin of doped holes in O2p-Cu3d-O2p is a triplet state yielding strong ferromagnetism. For out-of-ab-plane spin-polarization, while the spins of doped holes in both O2p-O2p and Cu3d-Cu3d are triplet states, the spin of doped holes in Cu3d-O2p is a singlet state yielding ferrimagnetism. A ferromagnetic-(002) Bragg-peak of the doped holes is observed and enhanced as a function of d revealing strong ferromagnetism coupling between Cu-O layers along the c-axis.