Tris[2-(pyrrol-2-ylmethyl­eneamino)eth­yl]amine

The title compound, C21H27N7, was synthesized by reaction of tris­(2-amino­ethyl)amine and pyrrole-2-carbaldehyde in ethanol at room temperature. The structure is stabilized by intra- and inter­molecular C—H⋯N and N—H⋯N hydrogen-bonding inter­actions

Reconfigurable two-dimensional optoelectronic devices enabled by local ferroelectric polarization.

Ferroelectric engineered pn doping in two-dimensional (2D) semiconductors hold essential promise in realizing customized functional devices in a reconfigurable manner. Here, we report the successful pn doping in molybdenum disulfide (MoS2) optoelectronic device by local patterned ferroelectric polarization, and its configuration into lateral diode and npn bipolar phototransistors for photodetection from such a versatile playground. The lateral pn diode formed in this way manifests efficient self-powered detection by separating ~12% photo-generated electrons and holes. When polarized as bipolar phototransistor, the device is customized with a gain ~1000 by its transistor action, reaching the responsivity ~12 A W-1 and detectivity over 1013 Jones while keeping a fast response speed within 20 μs. A promising pathway toward high performance optoelectronics is thus opened up based on local ferroelectric polarization coupled 2D semiconductors

Large-surface-area BN nanosheets and their utilization in polymeric composites with improved thermal and dielectric properties

High-throughput few-layered BN nanosheets have been synthesized through a facile chemical blowing route. They possess large lateral dimensions and high surface area, which are beneficial to fabricate effectively reinforced polymeric composites. The demonstrated composites made of polymethyl methacrylate and BN nanosheets revealed excellent thermal stability, 2.5-fold improved dielectric constant, and 17-fold enhanced thermal conductivity. The results indicate multifunctional practical applications of such polymeric composites in many specific fields, such as thermoconductive insulating long-lifetime packaging for electrical circuits

Ultrafast and Sensitive Self-Powered Photodetector Featuring Self-Limited Depletion Region and Fully Depleted Channel with van der Waals Contacts

Self-powered photodetectors with great potential for implanted medical diagnosis and smart communications have been severely hindered by the difficulty of simultaneously achieving high sensitivity and fast response speed. Here, we report an ultrafast and highly sensitive self-powered photodetector based on two-dimensional (2D) InSe, which is achieved by applying a device architecture design and generating ideal Schottky or ohmic contacts on 2D layered semiconductors, which are difficult to realize in the conventional semiconductors owing to their surface Fermi-level pinning. The as-fabricated InSe photodiode features a maximal lateral self-limited depletion region and a vertical fully depleted channel. It exhibits a high detectivity of 1.26 × 1013 Jones and an ultrafast response speed of ∼200 ns, which breaks the response speed limit of reported self-powered photodetectors based on 2D semiconductors. The high sensitivity is achieved by an ultralow dark current noise generated from the robust van der Waals (vdW) Schottky junction and a high photoresponsivity due to the formation of a maximal lateral self-limited depletion region. The ultrafast response time is dominated by the fast carrier drift driven by a strong built-in electric field in the vertical fully depleted channel. This device architecture can help us to design high-performance photodetectors utilizing vdW layered semiconductors

A Comprehensive Review of One-Dimensional Metal-Oxide Nanostructure Photodetectors

One-dimensional (1D) metal-oxide nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating size and dimensionality dependence of nanostructure properties for potential applications. The construction and integration of photodetectors or optical switches based on such nanostructures with tailored geometries have rapidly advanced in recent years. Active 1D nanostructure photodetector elements can be configured either as resistors whose conductions are altered by a charge-transfer process or as field-effect transistors (FET) whose properties can be controlled by applying appropriate potentials onto the gates. Functionalizing the structure surfaces offers another avenue for expanding the sensor capabilities. This article provides a comprehensive review on the state-of-the-art research activities in the photodetector field. It mainly focuses on the metal oxide 1D nanostructures such as ZnO, SnO2, Cu2O, Ga2O3, Fe2O3, In2O3, CdO, CeO2, and their photoresponses. The review begins with a survey of quasi 1D metal-oxide semiconductor nanostructures and the photodetector principle, then shows the recent progresses on several kinds of important metal-oxide nanostructures and their photoresponses and briefly presents some additional prospective metal-oxide 1D nanomaterials. Finally, the review is concluded with some perspectives and outlook on the future developments in this area

Does a Higher Density of Active Sites Indicate a Higher Reaction Rate?

A consensus view in catalysis is that a higher density of catalytically active sites indicates a higher reaction rate. Using molecular dynamics simulations capable of mimicking the electrochemical formation of gas molecules, we herein demonstrate that this view is problematic for electrocatalytic gas production. Our simulation results show that a higher density of catalytic active sites does not necessarily indicate a higher reaction ratea high density of active sites could lead to a reduction in the rate of reaction. Further analysis reveals that this abnormal phenomenon is ascribed to aggregation of the produced gas molecules near catalytic sites. This work challenges the consensus view and lays the groundwork for better developing gas-producing reaction electrocatalysts

Crystal organometal halide perovskites with promising optoelectronic applications

Organometal halide perovskites AMX(3) (A = organic cation, M = metal cation, and X = halogen anion) have been dominating the photovoltaic fields with an unexpected sharp efficiency enhancement to 20.1% in the past five years. Furthermore, the extraordinary properties of optical absorption, photoluminescence and low non-radiative recombination rates extend their applications into optoelectronic fields beyond photovoltaic devices. This review briefly outlines the state-of-the-art research activities of crystal perovskite AMX3, describes the fundamental optoelectronic properties, specific morphologies and related synthesis techniques, and summarizes their functions in optoelectronic fields such as solar cells, lasers, light-emitting diodes and photodetectors. Finally, the general challenges and the potential future directions of this exciting research area are highlighted