Controllable vortex lasing arrays in a geometrically frustrated exciton-polariton lattice at room temperature.

Quantized vortices appearing in topological excitations of quantum phase transition play a pivotal role in strongly correlated physics involving the underlying confluence of superfluids, Bose-Einstein condensates and superconductors. Exciton polaritons as bosonic quasiparticles have enabled studies of non-equilibrium quantum gases and superfluidity. Exciton-polariton condensates in artificial lattices intuitively emulate energy-band structures and quantum many-body effects of condensed matter, underpinning constructing vortex lattices and controlling quantum fluidic circuits. Here, we harness exciton-polariton quantum fluids of light in a frustrated kagome lattice based on robust metal-halide perovskite microcavities, to demonstrate vortex lasing arrays and modulate their configurations at room temperature. Tomographic energy-momentum spectra unambiguously reveal massless Dirac bands and quenched kinetic-energy flat bands coexisting in kagome lattices, where polariton condensates exhibit prototypical honeycomb and kagome spatial patterns. Spatial coherence investigations illustrate two types of phase textures of polariton condensates carrying ordered quantized-vortex arrays and π-phase shifts, which could be selected when needed using lasing emission energy. Our findings offer a promising platform on which it is possible to study quantum-fluid correlations in complex polaritonic lattices and highlight feasible applications of structured light.

Higher-order topological polariton corner state lasing.

Unlike conventional laser, the topological laser is able to emit coherent light robustly against disorders and defects because of its nontrivial band topology. As a promising platform for low-power consumption, exciton polariton topological lasers require no population inversion, a unique property that can be attributed to the part-light-part-matter bosonic nature and strong nonlinearity of exciton polaritons. Recently, the discovery of higher-order topology has shifted the paradigm of topological physics to topological states at boundaries of boundaries, such as corners. However, such topological corner states have never been realized in the exciton polariton system yet. Here, on the basis of an extended two-dimensional Su-Schrieffer-Heeger lattice model, we experimentally demonstrate the topological corner states of perovskite polaritons and achieved polariton corner state lasing with a low threshold (approximately microjoule per square centimeter) at room temperature. The realization of such polariton corner states also provides a mechanism of polariton localization under topological protection, paving the way toward on-chip active polaritonics using higher-order topology.

Surface-Adsorbed Carboxylate Ligands on Layered Double Hydroxides/Metal-Organic Frameworks Promote the Electrocatalytic Oxygen Evolution Reaction.

Metal-organic frameworks (MOFs) with carboxylate ligands as co-catalysts are very efficient for the oxygen evolution reaction (OER). However, the role of local adsorbed carboxylate ligands around the in-situ-transformed metal (oxy)hydroxides during OER is often overlooked. We reveal the extraordinary role and mechanism of surface-adsorbed carboxylate ligands on bi/trimetallic layered double hydroxides (LDHs)/MOFs for OER electrocatalytic activity enhancement. The results of X-ray photoelectron spectroscopy (XPS), synchrotron X-ray absorption spectroscopy, and density functional theory (DFT) calculations show that the carboxylic groups around metal (oxy)hydroxides can efficiently induce interfacial electron redistribution, facilitate an abundant high-valence state of nickel species with a partially distorted octahedral structure, and optimize the d-band center together with the beneficial Gibbs free energy of the intermediate. Furthermore, the results of in situ Raman and FTIR spectra reveal that the surface-adsorbed carboxylate ligands as Lewis base can promote sluggish OER kinetics by accelerating proton transfer and facilitating adsorption, activation, and dissociation of hydroxyl ions (OH- ).

Nonlinear Parametric Scattering of Exciton Polaritons in Perovskite Microcavities.

Comparing with pure photons, higher nonlinearity in polariton systems has been exploited in various proof-of-principle demonstrations of efficient optical devices based on the parametric scattering effect. However, most of them demand cryogenic temperatures limited by the small exciton binding energy of traditional semiconductors or exhibit weak nonlinearity resulting from Frenkel excitons. Lead halide perovskites, possessing both a large binding energy and a strong polariton interaction, emerge as ideal platforms to explore nonlinear polariton physics toward room temperature operation. Here, we report the first observation of nonlinear parametric scattering in a lead halide perovskite microcavity with multiple polariton branches at room temperature. Driven by the scattering source from condensation in one polariton branch, correlated polariton pairs are obtained at high k states in an adjacent branch. Our results strongly advocate the ability to reach the nonlinear regime essential for perovskite polaritonics working at room temperature.

Spontaneously coherent orbital coupling of counterrotating exciton polaritons in annular perovskite microcavities.

Exciton-polariton condensation is regarded as a spontaneous macroscopic quantum phenomenon with phase ordering and collective coherence. By engineering artificial annular potential landscapes in halide perovskite semiconductor microcavities, we experimentally and theoretically demonstrate the room-temperature spontaneous formation of a coherent superposition of exciton-polariton orbital states with symmetric petal-shaped patterns in real space, resulting from symmetry breaking due to the anisotropic effective potential of the birefringent perovskite crystals. The lobe numbers of such petal-shaped polariton condensates can be precisely controlled by tuning the annular potential geometry. These petal-shaped condensates form in multiple orbital states, carrying locked alternating π phase shifts and vortex-antivortex superposition cores, arising from the coupling of counterrotating exciton-polaritons in the confined circular waveguide. Our geometrically patterned microcavity exhibits promise for realizing room-temperature topological polaritonic devices and optical polaritonic switches based on periodic annular potentials.

Hierarchical porous Ni, Fe-codoped Co-hydroxide arrays derived from metal-organic-frameworks for enhanced oxygen evolution.

The multi metal organic frameworks (BTC-CoNiFeZn) were used as the precursors of in situ structure reconstruction in alkaline solution, and we synthesized hierarchical porous Ni,Fe-codoped Co-hydroxide nanowire array (Ni0.8Fe0.2/Co-H NAs/NF) catalyst for the oxygen evolution reaction (OER). Benefiting from the rational micro-structure, rich ion-accessible nanopores, and abundant defect sites, the target catalysts possess enhanced intrinsic activity. The obtained Ni0.8Fe0.2/Co-H NAs/NF catalysts show superior OER catalytic activity with a low overpotential of 231 mV at 10 mA cm-2, a small Tafel slope of 32.9 mV dec-1, and high cycle stability for 135 h with performance degradation of only about 4.4%.

Transient circular dichroism and exciton spin dynamics in all-inorganic halide perovskites.

All-inorganic metal halides perovskites (CsPbX3, X = Br or Cl) show strong excitonic and spin-orbital coupling effects, underpinning spin-selective excitonic transitions and therefore exhibiting great promise for spintronics and quantum-optics applications. Here we report spin-dependent optical nonlinearities in CsPbX3 single crystals by using ultrafast pump-probe spectroscopy. Many-body interactions between spin-polarized excitons act like a pseudo-magnetic field and thus lift the degeneracy of spin states resulting in a photoinduced circular dichroism. Such spontaneous spin splitting between "spin-up" and "spin-down" excitons can be several tens of milli-electron volts under intense excitations. The exciton spin relaxation time is ~20 picoseconds at very low pump fluence, the longest reported in the metal halides perovskites family at room temperature. The dominant spin-flip mechanism is attributed to the electron-hole exchange interactions. Our results provide essential understandings towards realizing practical spintronics applications of perovskite semiconductors.

Structural evolution from a fence-like to pillared-layer metal-organic framework for the stable oxygen evolution reaction.

A stable pillared-layer metal-organic framework (MOF) was obtained through post-synthesis modification from an unstable fence-like MOF for the first time. By virtue of high exposure of active sites on the layers, the evolved MOF with Fe doping exhibits an ultralow overpotential of 238 mV at 10 mA cm-2 during the oxygen evolution reaction (OER). Moreover, it shows a superior electrocatalytic stability with almost no attenuation for more than 168 h.

Evaluation of menopausal status among breast cancer patients with chemotherapy-induced amenorrhea.

OBJECTIVE: In patients with chemotherapy-induced amenorrhea (CIA), the menopausal status is ambiguous and difficult to evaluate. This study aimed to establish a discriminative model to predict and classify the menopausal status of breast cancer patients with CIA. METHODS: This is a single center hospital-based study from 2013 to 2016. The menopausal age distribution and accumulated incidence rate of CIA are described. Multivariate models were adjusted for established and potential confounding factors including age, serum concentration of estradiol (E2) and follicle-stimulating hormone (FSH), feeding, pregnancy, parity, abortions, and body mass index (BMI). The odds ratio (OR) and 95% confidence interval (95% CI) of different risk factors were estimated. RESULTS: A total of 1,796 breast cancer patients were included in this study, among whom, 1,175 (65.42%) were premenopausal patients and 621 (34.58%) were post-menopause patients. Five hundred and fifty patients were included in CIA analysis, and a cumulative CIA rate of 81.64% was found in them. Age (OR: 1.856, 95% CI: 1.732-1.990), serum concentration of E2 (OR: 0.976, 95% CI: 0.972-0.980) and FSH (OR: 1.060, 95% CI: 1.053-1.066), and menarche age (OR: 1.074, 95% CI: 1.009-1.144) were found to be associated with the patients' menopausal status. According to multivariate analysis, the discriminative model to predict the menopausal status is Logit (P)=-28.396+0.536Age-0.014E2+0.031FSH. The sensitivities for this model were higher than 85%, and its specificities were higher than 89%. CONCLUSIONS: The discriminative model obtained from this study for predicting menstrual state is important for premenopausal patients with CIA. This model has high specificity and sensitivity and should be prudently used.

Efficient Hydrogen Evolution on Cu Nanodots-Decorated Ni3S2 Nanotubes by Optimizing Atomic Hydrogen Adsorption and Desorption.

Low-cost transition-metal dichalcogenides (MS2) have attracted great interest as alternative catalysts for hydrogen evolution. However, a significant challenge is the formation of sulfur-hydrogen bonds on MS2 (S-Hads), which will severely suppress hydrogen evolution reaction (HER). Here we report Cu nanodots (NDs)-decorated Ni3S2 nanotubes (NTs) supported on carbon fibers (CFs) (Cu NDs/Ni3S2 NTs-CFs) as efficient electrocatalysts for HER in alkaline media. The electronic interactions between Cu and Ni3S2 result in Cu NDs that are positively charged and can promote water adsorption and activation. Meanwhile, Ni3S2 NTs are negatively charged and can weaken S-Hads bonds formed on catalyst surfaces. Therefore, the Cu/Ni3S2 hybrids can optimize H adsorption and desorption on electrocatalysts and can promote both Volmer and Heyrovsky steps of HER. The strong interactions between Cu and Ni3S2 cause the Cu NDs/Ni3S2 NTs-CFs electrocatalysts to exhibit the outstanding HER catalytic performance with low onset potential, high catalytic activity, and excellent stability.