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The realization of room-temperature-operated, high-performance, miniaturized, low-power-consumption and Complementary Metal-Oxide-Semiconductor (CMOS)-compatible mid-infrared photodetectors is highly desirable for next-generation optoelectronic applications, but has thus far remained an outstanding challenge using conventional materials. Two-dimensional (2D) heterostructures provide an alternative path toward this goal, yet despite continued efforts, their performance has not matched that of low-temperature HgCdTe photodetectors. Here, we push the detectivity and response speed of a 2D heterostructure-based mid-infrared photodetector to be comparable to, and even superior to, commercial cooled HgCdTe photodetectors by utilizing a vertical transport channel (graphene/black phosphorus/molybdenum disulfide/graphene). The minimized carrier transit path of tens of nanometers facilitates efficient and fast carrier transport, leading to significantly improved performance, with a mid-infrared detectivity reaching 2.38 × 10 11 cmHz 1/2 W −1 (approaching the theoretical limit), a fast response time of 10.4 ns at 1550 nm, and an ultrabroadband detection range spanning from the ultraviolet to mid-infrared wavelengths. Our study provides design guidelines for next-generation high-performance room-temperature-operated mid-infrared photodetectors. Here, the authors report the realization of room-temperature broadband mid-infrared detectors based on a van der Waals heterostructure with a vertical transport channel, exhibiting specific detectivity and response times comparable or superior to those of commercial cooled HgCdTe photodetectors.

This paper, set against the backdrop of expanding urban rail networks and dynamic urban development, focuses on the distribution and evolution of commercial Points of Interests (POIs) within the central urban rail transit areas of Beijing. The study examines data from four different years—2008, 2013, 2017, and 2020—to observe the temporal evolution of commercial entities. It identifies stable explanatory variables affecting the distribution and evolution of commercial POIs, which include rail transit accessibility, characteristics of the working and residential population distribution around stations, and the construction intensity in the vicinity of station areas. Through statistical analysis and model building, relatively stable linear regression equations were established, with R2 values generally maintained above 0.5 (except for 2017). The study advances our understanding of the influence of rail transit on urban commercial spaces and how this influence shifts with temporal and urban developmental changes. It elucidates the correlation between changes in the number of businesses and spatial configuration, offering insights and information for urban planners and policy makers. This research also serves as a model for exploring the interplay between urban rail transit and commercial spaces in other major cities.

Transition metal oxides exhibit strong structure-property correlations, which has been extensively investigated and utilized for achieving efficient oxygen electrocatalysts. However, high-performance oxide-based electrocatalysts for hydrogen evolution are quite limited, and the mechanism still remains elusive. Here we demonstrate the strong correlations between the electronic structure and hydrogen electrocatalytic activity within a single oxide system Ti 2 O 3 . Taking advantage of the epitaxial stabilization, the polymorphism of Ti 2 O 3 is extended by stabilizing bulk-absent polymorphs in the film-form. Electronic reconstructions are realized in the bulk-absent Ti 2 O 3 polymorphs, which are further correlated to their electrocatalytic activity. We identify that smaller charge-transfer energy leads to a substantial enhancement in the electrocatalytic efficiency with stronger hybridization of Ti 3 d and O 2 p orbitals. Our study highlights the importance of the electronic structures on the hydrogen evolution activity of oxide electrocatalysts, and also provides a strategy to achieve efficient oxide-based hydrogen electrocatalysts by epitaxial stabilization of bulk-absent polymorphs. Converting solar energy to hydrogen fuel requires light-absorbers that well-match the wavelengths of incoming sunlight. Here, authors prepare a broadband visible-light-absorbing molecular complex that efficiently produces hydrogen from water.

Plasmonics has attracted tremendous interests for its ability to confine light into subwavelength dimensions, creating novel devices with unprecedented functionalities. New plasmonic materials are actively being searched, especially those with tunable plasmons and low loss in the visible–ultraviolet range. Such plasmons commonly occur in metals, but many metals have high plasmonic loss in the optical range, a main issue in current plasmonic research. Here, we discover an anomalous form of tunable correlated plasmons in a Mott-like insulating oxide from the Sr 1− x Nb 1− y O 3+ δ family. These correlated plasmons have multiple plasmon frequencies and low loss in the visible–ultraviolet range. Supported by theoretical calculations, these plasmons arise from the nanometre-spaced confinement of extra oxygen planes that enhances the unscreened Coulomb interactions among charges. The correlated plasmons are tunable: they diminish as extra oxygen plane density or film thickness decreases. Our results open a path for plasmonics research in previously untapped insulating and strongly-correlated materials. Conventional plasmons in metals often suffer from high plasmonic loss in the optical range. Here, the authors report a distinct form of tunable correlated plasmons in Mott-like insulating Sr 1− x NbO 3+ δ films, with multiple plasmon frequencies and low loss in the visible-ultraviolet range.

Photoinduced phase transitions in matters have gained tremendous attention over the past few years. However, their ultrashort lifetime makes their study and possible control very challenging. Here, we report on highly anisotropic d-d excitonic excitations yielding photoinduced metal-insulator transitions (MITs) in quasi-one-dimensional metals Sr 1- y NbO x using Mueller-Matrix spectroscopic ellipsometry, transient ultraviolet Raman spectroscopy, transient mid-infrared reflectivity and angular-resolved photoemission spectroscopy supported with density functional theory. Interestingly, the MITs are driven by photo-pumping of d - d excitons, causing the metallic a -axis to become insulating while the insulating b- and c- axis concomitantly become a correlated metal. We assign these effects to an interplay between the melting of charge and lattice orderings along the different anisotropic optical axes and Bose-Einstein-like condensation of the photoinduced excitons. The long lifetime in the order of several seconds of the metastable MITs gives greater flexibility to study and manipulate the transient excitonic state for potential applications in exciton-based optoelectronic devices. Due to recent developments in steady-state and ultrafast spectroscopic techniques there are more readily available methods to excite and observe anisotropic low-dimensional materials in transient states using light-matter interactions. Here, the authors observe photoinduced metal-insulator transitions in a quasi-one-dimensional metal, and analyse the role of d - d excitonic excitations in the transient state.

Urban parks are one of the most common spaces for social interactions in modern cities. The design of park spaces, especially space configuration, has significant influences on people’s social behaviors in parks. In this study, the associations between space configurational attributes and social interactions were investigated using space syntax theory. An observation analysis of social behaviors was carried out in two urban parks in Beijing, China. Nine space configurational attributes, including depth to the gate, depth to the main road, connectivity, normalized angular integration (NAIN), and normalized angular choice (NACH) with three radii, were calculated using a segment model. The variance analysis and regression analysis reveal the strong joint effect of space type, space scale factors, and space configurational attributes on social interaction behaviors in parks. The personal interaction group contained 23% of the total observed people involved in social interactions. Pathway length, zone area, and NACH-10K (NACH with a radius of 10,000 m) are positively associated with the number of people involved in personal interactions. For the social interaction group (77% of the total observed people), the space scale and depth to main city road were found to have a positive and negative influence on social interaction intensity.

Two-dimensional (2D) materials 1 – 5 offer a unique platform from which to explore the physics of topology and many-body phenomena. New properties can be generated by filling the van der Waals gap of 2D materials with intercalants 6 , 7 ; however, post-growth intercalation has usually been limited to alkali metals 8 – 10 . Here we show that the self-intercalation of native atoms 11 , 12 into bilayer transition metal dichalcogenides during growth generates a class of ultrathin, covalently bonded materials, which we name ic-2D. The stoichiometry of these materials is defined by periodic occupancy patterns of the octahedral vacancy sites in the van der Waals gap, and their properties can be tuned by varying the coverage and the spatial arrangement of the filled sites 7 , 13 . By performing growth under high metal chemical potential 14 , 15 we can access a range of tantalum-intercalated TaS(Se) y , including 25% Ta-intercalated Ta 9 S 16 , 33.3% Ta-intercalated Ta 7 S 12 , 50% Ta-intercalated Ta 10 S 16 , 66.7% Ta-intercalated Ta 8 Se 12 (which forms a Kagome lattice) and 100% Ta-intercalated Ta 9 Se 12 . Ferromagnetic order was detected in some of these intercalated phases. We also demonstrate that self-intercalated V 11 S 16 , In 11 Se 16 and Fe x Te y can be grown under metal-rich conditions. Our work establishes self-intercalation as an approach through which to grow a new class of 2D materials with stoichiometry- or composition-dependent properties. The intercalation of native atoms into bilayer transition metal dichalcogenides during growth generates ultrathin, covalently bonded materials into which ferromagnetic ordering can be introduced.

With the rapid development of economy, heavy metal pollution has brought serious harm to the engineering construction in expansive soil area. The Experimental study are to further reveal its physical and mechanical properties, and better guide the engineering practice. The effects of heavy metal ion concentration on compaction, permeability and unconfined compressive strength of expansive soils were studied by preparing 3 different concentrations of Pb2+ and Zn2+ polluted expansive soils in Nanyang city of Henan Province. The results show that with the increase of heavy metal ion concentration, the maximum dry density and permeability coefficient of contaminated soil increase, and the optimum water content and unconfined compressive strength decrease. At the same heavy metal ion concentration, lead-contaminated soil has a higher permeability coefficient and less unconfined compressive strength than zinc-contaminated soil. Compared with the lead contaminated soil, the maximum dry density of the dyed soil is larger and the optimal water content is smaller. The change of the dry density has a significant effect on the permeability coefficient, and the larger the dry density, the smaller the permeability coefficient. It can be seen that heavy metal pollution can change the physical and mechanical properties of expansive soil.

Heavy metal pollution has received widespread attention at home and abroad as an important environmental engineering problem, and the research on the deformation characteristics of heavy metal contaminated expansive soil under cyclic loading is still in its infancy. According to the Nanyang expansive soil, the effects of a few factors including heavy metal ions concentration, dynamic stress amplitude, vibration frequency and confining pressure on axial cumulative deformation and critical dynamic stress for polluted expansive soil is studied. The results show that the cumulative axial strain has different development modes under different dynamic stress amplitudes, which can be divided into failure type, critical type and stable type. The same cumulative axial strain is achieved with the increase of heavy metal ion concentration, and the amplitude of dynamic stress is smaller. As the vibration frequency increases, the cumulative axial strain of the contaminated expansive soil decreases. The greater the confining pressure, the smaller the cumulative axial strain of the polluted expansive soil. The critical dynamic stress decreases with the increase of the heavy metal ions concentration, and under the same heavy metal ions concentration, the critical dynamic stress increases obviously with the increase of confining pressure.

Depending on the laboratory test of consolidation expansive soil polluted by heavy metal Cd, we can use cement to cure expansive soil artificially polluted by cadmium nitrate in different concentration. The paper discussed how the heavy metal concentration, cement dosage and curing age influence the unconfined compressive strength by solidified expansive soil polluted by heavy metal and micro-structure properties were tested. The study results show that, as the curing age and cement concentration increases, the unconfined compressive strength increases; as the concentration of heavy metal increases, the unconfined compressive strength decreases; the effect of heavy metal concentration on strength is different, the effect of high concentration on strength is greater than the effect of low concentration; Through the change rules of the micro-structure characteristics, the results on micro-structure analyzing show that the reason of strength increases is the porosity decreases after adding cement.