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Bismuth selenide (Bi2Se3) is a novel topological insulator that is promising for broad optical absorption materials on the basis of its large bulk band and well-defined single Dirac cone. Herein, few-layer Bi2Se3 nanoplates of different sizes have been successfully synthesized via the solvothermal method. We present our discovery of optical properties on homojunction Bi2Se3 nanoplates with FTIR measurements. The interface of homojunction Bi2Se3 nanoplates demonstrates an interesting optical modulation in the near-infrared region in contrast to individual bulk Bi2Se3 and other reported 2D hetero-structure materials. It was validated that the unexpected behavior was attributed to the interface between variously stacked nanoplates and its unique zero-wave anti-reflection properties. Our experimental results provide evidence of the Bi2Se3 nanoplate possess high optical absorption in the near-infrared range, promising for photothermal and optical diagnostic therapy application. [ABSTRACT FROM AUTHOR]

The nonlocal spin valve configuration consists of two ferromagnetic and nonmagnetic channels, which is an effective configuration for determining spin injection and accumulation. Here, we report that a reversed nonlocal spin signal was detected by changing the voltage probe configurations in graphene (Py/MgO/graphene/MgO/Py) lateral spin valves. The abnormal reversed spin-dependent nonlocal voltage is attributed to the nonuniform pinhole at the interface of the low-resistance tunnel barrier, which makes the charge current flow through the detection electrode and return to the graphene channel. We demonstrate that the channel-width induced spin-polarized current inhomogeneity significantly contributes to nonlocal resistance. A detailed description and simulated results of the tunnel junctions provide evidence for the reversal of the nonlocal voltage sign induced by the low-resistance tunnel barriers. Our work sheds light on the understanding of the spatial distribution of the spin current and the effect of the tunnel barrier, which are essential for the development of spintronic devices. [ABSTRACT FROM AUTHOR]

Singlet fission (SF), a spin-allowed multiexciton generation process, experienced renewed interest in the last decade due to its potential to increase the efficiency of photovoltaic devices. The hurdles now lie in the limited range of SF-capable materials and demanding morphology requirement for an efficient fission process. Although primary fission to yield triplet pair (1TT) can occur independently of film morphology in intramolecular singlet fission (iSF) materials, the separation of the 1TT state has been shown to be highly dependent on the packing motif and morphologies. In this work, we have demonstrated that both iSF and triplet pair separation processes took place irrelevant of molecular order and/or film morphology in a series of pentalene compounds. With the >180% fission efficiency, the suitable triplet energy levels, and the long lifetime of the triplet excitons, these iSF systems can be integrated into practical photovoltaic application. [ABSTRACT FROM AUTHOR]

We designed and constructed an extensional rheometer for in situ small and wide angle x-ray study on flow-induced crystallization of polymer. Two rotating drums with an axis distance of 20 mm are employed to impose extensional deformation on the samples. With a constant angular velocity, the two drums generate a constant Henkcy strain rate as sample length for testing keeps constant during deformation. An ionic liquid is used as heating medium to prevent polymer melt from bending downward due to gravity, which is excellent in terms of high thermal stability, low viscosity, and relative low adsorption on x-ray. Flow-induced crystallization experiments are conducted with this apparatus on x-ray scattering station in Shanghai Synchrotron Radiation Facility (SSRF), which allows us to collect rheological and structural data simultaneously and may lead to a better understanding on flow-induced crystallization of polymer. [ABSTRACT FROM AUTHOR]

High-symmetry transition-metal dichalcogenides (TMDs) have garnered substantial attention in the fields of sensors, optoelectronics, and valleytronics. However, the inherent C3 rotational symmetry of TMDs engenders highly isotropic properties, impeding their further technological progress. To overcome this limitation, we embarked on a study to investigate the effects of isotropic/anisotropic heterostructures engineering on WS2, aiming to break its C3 rotational symmetry. In this work, we designed and fabricated heterostructures composed of WS2 and ReS2 layers. Our comprehensive investigations revealed a remarkable emergence of anisotropic characteristics in excitons originating from the WS2 layers within the engineered WS2/ReS2 heterostructures. Moreover, we observed an enhancement in the valley polarizations of WS2 layers within the heterostructures, which is attributed to the reduced intervalley scattering facilitated by the WS2/ReS2 heterostructure configuration. This observation indicates the potential for leveraging heterostructure engineering to tailor and optimize anisotropic devices, thereby opening promising avenues for future applications in various technological domains. [ABSTRACT FROM AUTHOR]

Solid-state electrical conducting materials can be roughly categorized as superconductors, conductors, and semiconductors, depending on their conducting carriers, resistance, and band structures. This research reports the discovery of super-semiconductors, whose resistivity is 3–10 orders of magnitude lower than conventional semiconductors at room temperature. In addition, there is a transition from a metal state to a super-semiconducting state at near room temperatures, which is accompanied by an increase in hole carrier density and the mobility increase in electrons. For the first time, a hole-dominated carrier metal is observed in nanostructured bimetallic arrays near room temperature, and no other special conditions are required. Such a behavior is due to the generation of hot electrons and holes induced by metal plasmon resonance in the infrared range in the nanostructured bimetallic arrays. Our research empowers metals with semiconductor features and paves the way to realize ultra-low-power metal-based semiconductor devices. [ABSTRACT FROM AUTHOR]

The excitonic effects in two-dimensional transition metal dichalcogenides and their heterostructures have been extensively investigated. Significantly, the moiré excitons, induced by a moiré superlattice in a twisted heterostructure, have triggered tremendous attention, demonstrating the practicability of artificial excitonic crystals. Besides, recent works have shown that the excitonic states in homostructures also exhibit novel properties worthy of further development. Here, we present a tear-and-stack technique for fabricating a regular or a twisted homostructure. Such a strategy was utilized to reassemble a monolayer WSe2 into a twisted homostructure, and various excitons from this structure have been identified in the photoluminescence spectra. Interestingly, the unusual equidistant splitting was first observed in the defect-bound excitons. It is believed that this phenomenon is attributed to the various defect states and the local stacking patterns. This interpretation is supported by theoretical calculations, which show the dependence of the energy band structure on different defect states and local stacking patterns. These unconventional defect-bound excitons are key building blocks in the research of homostructures that highlight the feasibility of artificially manipulating local excitons for practical applications. [ABSTRACT FROM AUTHOR]