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The on-demand assembly of 2D heterostructures has brought about both novel interfacial physical chemistry and optoelectronic applications; however, existing studies rarely focus on the complementary part—the 2D cavity, which is a new-born area with unprecedented opportunities. In this study, we have investigated the electric field inside a spacer-free 2D cavity consisting of a monolayer semiconductor and a gold film substrate. We have directly captured the built-in electric field crossing a blinking 2D cavity using a Kelvin probe force microscopy–Raman system. The simultaneously recorded morphology (M), electric field (E), and optical spectroscopy (O) mapping profile unambiguously reveals dynamical fluctuations of the interfacial electric field under a constant cavity height. Moreover, we have also prepared non-blinking 2D cavities and analyzed the gap-dependent electric field evolution with a gradual heating procedure, which further enhances the maximum electric field exceeding 109 V/m. Our work has revealed substantial insights into the built-in electric field within a 2D cavity, which will benefit adventures in electric-field-dependent interfacial sciences and future applications of 2D chemical nanoreactors. [ABSTRACT FROM AUTHOR]

Localized excitation in traditional organic photocatalysts typically prevents the generation and extraction of photo‐induced free charge carriers, limiting their activity enhancement under illumination. Here, we enhance delocalized photoexcitation of small molecular photovoltaic catalysts by weakening their electron‐phonon coupling via rational fluoro‐substitution. The optimized 2FBP‐4F catalyst we develop here exhibits a minimized Huang–Rhys factor of 0.35 in solution, high dielectric constant and strong crystallization in the solid state. As a result, the energy barrier for exciton dissociation is decreased, and more importantly, polarons are unusually observed in 2FBP‐4F nanoparticles (NPs). With the increased hole transfer efficiency and prolonged charge carrier lifetime highly related to enhanced exciton delocalization, the PM6 : 2FBP‐4F heterojunction NPs at varied concentration exhibit much higher optimized photocatalytic activity (207.6–561.8 mmol h−1 g−1) for hydrogen evolution than the control PM6 : BP‐4F and PM6 : 2FBP‐6F NPs, as well as other reported photocatalysts under simulated solar light (AM 1.5G, 100 mW cm−2). [ABSTRACT FROM AUTHOR]

Colloidal semiconductor nanocrystals (NCs) have been recognized as promising solution-processable gain media; however, the lasers with state-of-the-art performance exclusively originate from the cadmium- and lead-based NCs. Herein, we for the first time unravel that high-quality heavy-metal-free ZnSe/ZnS NCs show superior optical gain and lasing performance when the sizes exceed the quantum confinement regime. Corroborated by comprehensive transient spectroscopy, we reveal that the optical gain in large ZnSe/ZnS NCs originates from the novel Coulomb-correlated electron–hole plasma (C-EHP) instead of high-order multi-exciton recombination. Thanks to the formation of a four-level system and the suppression of Auger recombination, the C-EHP renders low gain threshold (9.4 μJ/cm2), high gain coefficient (>6500 cm−1), and long gain lifetime (∼4 ns). Such desirable gain properties compete well with those of classic CdSe NCs and enable the construction of a high-performance laser device. This work represents significant progress toward the development of solution-processable non-heavy-metal nanocrystal lasers. [ABSTRACT FROM AUTHOR]

CO2 electroreduction (CO2R) operating in acidic media circumvents the problems of carbonate formation and CO2 crossover in neutral/alkaline electrolyzers. Alkali cations have been universally recognized as indispensable components for acidic CO2R, while they cause the inevitable issue of salt precipitation. It is therefore desirable to realize alkali‐cation‐free CO2R in pure acid. However, without alkali cations, stabilizing *CO2 intermediates by catalyst itself at the acidic interface poses as a challenge. Herein, we first demonstrate that a carbon nanotube‐supported molecularly dispersed cobalt phthalocyanine (CoPc@CNT) catalyst provides the Co single‐atom active site with energetically localized d states to strengthen the adsorbate‐surface interactions, which stabilizes *CO2 intermediates at the acidic interface (pH=1). As a result, we realize CO2 conversion to CO in pure acid with a faradaic efficiency of 60 % at pH=2 in flow cell. Furthermore, CO2 is successfully converted in cation exchanged membrane‐based electrode assembly with a faradaic efficiency of 73 %. For CoPc@CNT, acidic conditions also promote the intrinsic activity of CO2R compared to alkaline conditions, since the potential‐limiting step, *CO2 to *COOH, is pH‐dependent. This work provides a new understanding for the stabilization of reaction intermediates and facilitates the designs of catalysts and devices for acidic CO2R. [ABSTRACT FROM AUTHOR]

This article proposes for the first time the preparation of a series of amino acid ionic liquids (AAILs) via one‐step hydrolysis of cheap lactams for the capture of CO2. The structures of the prepared AAILs are confirmed using NMR, FTIR, and ESI‐MS, and their physical properties are also determined. It is found that these AAILs are reversible CO2 absorbents with very high absorption capacities (0.15 to 0.18 g·g−1 at 313.2 K and 1.0 bar), better than almost all task‐specific ionic liquids reported in literatures. The absorption mechanism is also elucidated to be a combination of 1:1 and 2:1 stoichiometric reaction of AAILs with CO2 from NMR, FTIR, reaction equilibrium thermodynamical modeling and quantum calculations. The AAILs have the advantages of simple synthesis, high yield, and using available cheap raw materials. It is believed that this kind of AAILs have great potentials to be used as efficient CO2 absorbents. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage. However, up to now, reversible phase transitions in 2D materials that can be driven by facile nondestructive methods, such as temperature, are still rare. Here, we introduce ultrathin Cu9S5 crystals grown by chemical vapor deposition (CVD) as an exemplary case. For the first time, their basic electrical properties were investigated based on Hall measurements, showing a record high hole carrier density of ∼ 1022 cm−3 among 2D semiconductors. Besides, an unusual and repeatable conductivity switching behavior at ∼ 250 K were readily observed in a wide thickness range of CVD-grown Cu9S5 (down to 2 unit-cells). Confirmed by in-situ selected area electron diffraction, this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonal β phase and low-temperature β′ phase with a superstructure. Our work provides new insights to understand the physical properties of ultrathin Cu9S5 crystals, and brings new blood to the 2D materials family with reversible phase transitions. [ABSTRACT FROM AUTHOR]

Shear phonons are collective atomic-layer motions in layered materials that carry critical information about mechanical, thermal and optoelectronic properties. Phonon branches with co-directional atomic-layer motions carry unique information about the global structure and hidden interfaces in layered crystals and heterostructures, but they are not detectable due to the very limited electron–phonon coupling. Here we utilize the propagating feature and mechanical coupling between shear phonons and localized plasmonic cavities to successfully realize direct characterization of ground-state shear phonons down to 4 cm−1 in energy by introducing mechano-Raman spectroscopy (MRS). MRS has the ability to characterize the global crystal structure with more than 108-fold enhancement and to accurately measure subpicometre displacements under ambient conditions with a thermal-noise-free feature. The propagating behaviour and the capacity of MRS to detect optically hidden interfaces are demonstrated. The broad tunability of plasmons makes the MRS technique a robust tool for extensive applications, including global crystal flaw detection, mechanical sensing and the mechanical modulation of light. Mechano-Raman spectroscopy is demonstrated by using interlayer phonons of atomic-layer vibrators to drive synchronous motion of the metallic plasmonic structure that can then be detected. The modulated light scattering brings out the information that cannot be accessed by optical Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction (CO2R) to ethylene and ethanol enables the long-term storage of renewable electricity in valuable multi-carbon (C2+) chemicals. However, carbon–carbon (C–C) coupling, the rate-determining step in CO2R to C2+ conversion, has low efficiency and poor stability, especially in acid conditions. Here we find that, through alloying strategies, neighbouring binary sites enable asymmetric CO binding energies to promote CO2-to-C2+ electroreduction beyond the scaling-relation-determined activity limits on single-metal surfaces. We fabricate experimentally a series of Zn incorporated Cu catalysts that show increased asymmetric CO* binding and surface CO* coverage for fast C–C coupling and the consequent hydrogenation under electrochemical reduction conditions. Further optimization of the reaction environment at nanointerfaces suppresses hydrogen evolution and improves CO2 utilization under acidic conditions. We achieve, as a result, a high 31 ± 2% single-pass CO2-to-C2+ yield in a mild-acid pH 4 electrolyte with >80% single-pass CO2 utilization efficiency. In a single CO2R flow cell electrolyzer, we realize a combined performance of 91 ± 2% C2+ Faradaic efficiency with notable 73 ± 2% ethylene Faradaic efficiency, 31 ± 2% full-cell C2+ energy efficiency, and 24 ± 1% single-pass CO2 conversion at a commercially relevant current density of 150 mA cm−2 over 150 h. CO2 electroreduction to multi-carbon products in acids remains challenging due to the low efficiency and poor stability of C–C coupling. Here, the authors show that asymmetric CO binding at confined nanointerfaces enhances multi-carbon production, improves CO2 utilization, and limits H2 evolution. [ABSTRACT FROM AUTHOR]

Organic–inorganic tin (Sn)‐based halide perovskites have attracted special attention due to their outstanding photophysical properties and eco‐friendly nature. However, the instability of Sn‐based perovskites is still a pressing issue that needs to be addressed. Here, a new lead‐free hybrid Sn(IV) bromide hybrid (4‐APEA)2SnBr6 (4‐APEA: 2‐(4‐aminophenyl)ethylammonium) is synthesized with remarkable stability. This compound has strong electron–phonon coupling, resulting in excitons self‐trapping and broadband yellow emission with a photoluminescence peak at 566 nm. The bare (4‐APEA)2SnBr6 shows impressive emission stability in the air; maintains 90% of photoluminescence quantum yield under ultraviolet light irradiation over 2000 h (T90 > 2000 h), representing the most stable halide hybrids. The excellent stability is profit from the stable valence state and few defect state densities. The findings show the promising prospect of environment‐friendly organic–inorganic halide perovskites and their usage in optoelectronic applications. [ABSTRACT FROM AUTHOR]

Thermoreceptors can encode thermal stimuli into spikes that are processed by the neural network to endow human with thermal perception. Such energy-efficiency and robust interaction with real-world have inspired the rise of the artificial spiking thermoreceptor (AST). However, monolithic spiking thermoreceptor is still rarely reported, which may due to the lack of device that can simultaneously implement temperature-sensing and spike-encoding functions. Here, we demonstrate an artificial spiking thermoreceptor based on Ag/TaO $_{X}$ /AlO $_{X}$ /ITO threshold switching memristor to achieve human-like thermal perception. The device is able to encode thermal information into spikes at a low power consumption (< 240 nW). These advantages consequently facilitate the demonstration of power efficient and accurate thermography edge detection based on the array of such AST and a pulse coupled neural network (PCNN). [ABSTRACT FROM AUTHOR]

Van der Waals heterojunctions are fast‐emerging quantum structures fabricated by the controlled stacking of two‐dimensional (2D) materials. Owing to the atomically thin thickness, their carrier properties are not only determined by the host material itself, but also defined by the interlayer interactions, including dielectric environment, charge trapping centers, and stacking angles. The abundant constituents without the limitation of lattice constant matching enable fascinating electrical, optical, and magnetic properties in van der Waals heterojunctions toward next‐generation devices in photonics, optoelectronics, and information sciences. This review focuses on the charge and energy transfer processes and their dynamics in transition metal dichalcogenides (TMDCs), a family of quantum materials with strong excitonic effects and unique valley properties, and other related 2D materials such as graphene and hexagonal‐boron nitride. In the first part, we summarize the ultrafast charge transfer processes in van der Waals heterojunctions, including its experimental evidence and theoretical understanding, the interlayer excitons at the TMDC interfaces, and the hot carrier injection at the graphene/TMDCs interface. In the second part, the energy transfer, including both Förster and Dexter types, are reviewed from both experimental and theoretical perspectives. Finally, we highlight the typical charge and energy transfer applications in photodetectors and summarize the challenges and opportunities for future development in this field. [ABSTRACT FROM AUTHOR]

Tailoring the photoluminescence (PL) of semiconductors through spatiotemporal manipulation of dynamics of photoexcited carriers is of paramount importance for understanding the emitting mechanism and developing high‐performance devices. Herein, fluorescence recovery after photobleaching (FRAP) microscopy, a powerful tool in biology, is first utilized to simultaneously manipulate and monitor the dynamics of photoexcited carrier in attractive 2D transition metal dichalcogenide monolayers (1L‐TMDs). This allows on‐demand access to the PL dark state of 1L‐TMDs, based on the triggered exciton–exciton annihilation by pump beam‐initiated photodoping. Using a 0.7‐µm‐diametered pump laser, the PL dark region can be facilely tailored from ≈0.5 to ≈5 µm over a 10‐µm‐1L‐WS2 flake. An interesting photoinduced dedoping effect in 1L‐TMDs after photodoping is discovered by FRAP, which has not been observed before and might account for the non‐blinking emission of 1L‐TMDs. The revealed mono‐exponential photo‐dedoping can also be kinetically tailored by ≈170‐fold (k: 0.11–19.00 s‐1) by humidity, power of incident laser and type of 1L‐TMDs. This study demonstrates the power of FRAP microscopy in exploring the effect of photoexcited carrier dynamics on the PL property of semiconductors, holding promises for understanding light‐emitting mechanism and optimizing operational parameters for optoelectronic devices. [ABSTRACT FROM AUTHOR]

The construction of a heterointerface by structure-induced partial phase transformation is an effective strategy to synchronously boost conductivity and regulate the ion diffusion kinetics of TiO2 considered as an anode material for sodium ion batteries. However, construction of a highly conductive heterostructure in well-crystallized TiO2 is still a great challenge. Herein, a structure-induced partial phase transformation method is reported to synthesize hierarchical hollow TiO2/TiN heterostructure fibers (HTTFs) with a high specific surface area for use as an anode. The interfacial effect of the heterostructures for the anode materials could improve charge transfer capability. The improvement of the conductivity is due to the electric field generated inside the nanocrystals, which greatly reduces the ion diffusion resistance of nanocrystals and promotes the interfacial electron transport. Density functional theory calculations and experimental results demonstrate that HTTFs greatly facilitated the mobility of holes and ion diffusion, which result in excellent rate capability (270.9 and 113.1 mA h g−1 at 50 and 10 000 mA g−1, respectively) and excellent cycling stability (132.5 mA h g−1 with an average capacity fading of only 0.002% per cycle at 5000 mA g−1 over 10 000 cycles). Such improvements signify that suitable heterogeneous interface design provides an innovative and versatile approach for achieving advanced battery materials. [ABSTRACT FROM AUTHOR]

Metal aerogels (MAs) are emerging all‐nanometal‐structured self‐standing porous materials featuring exceptional performances in diverse fields. They have recently been adopted as 3D surface‐enhanced Raman scattering (SERS) substrates, while the less utilization of the unique porous structure leads to limited performance. Here, a fascinating compression‐mediated regulation strategy is presented to largely boost the SERS performance of Au–Ag aerogels. By gently pressing, both the density of hot spots and the inter‐ligament distance can be efficiently modulated, thus enabling to flexibly manipulate the SERS properties of MAs. On this basis, a record‐high misfocus tolerance (∼8.8 mm), low detection limit (down to 0.1 nM), high stability (>1 month), reusability, and multiplex detection ability are concurrently realized. This study may point out a new direction for engineering 3D SERS substrates with tunable and exceptional performance. [ABSTRACT FROM AUTHOR]

The excellent mechanical properties of carbon nanotube (CNT) and low effective modulus of its forest makes CNT forest (CNTF) promising in dry adhesives. However, the low contact efficiency of buckled nanotube segments on the surface of the CNTF weakened its adhesion strength, which is far below the theoretical value. To improve the orientation, density, and arrangement of these nanotube segments, a layer of patterned aluminum was added to the conventional catalyst. Thus, a CNTF with densely-packed, horizontally-aligned surface nanotube segments was obtained. Nanoindentation results showed that the adhesion force of this CNTF could reach up to 13.69 mN under optimized conditions, nearly 5.5 times the best results of similar works. The results of coarse-grained (CG) simulations revealed the lateral stretching of these nanotube segments induced bond energy variation made a major contribution to the superior adhesion performance. The formation mechanism of these surface nanotube segments was also thoroughly analyzed. [Display omitted] • A patterned aluminum layer was introduced to the conventional CNT growth catalyst. • Buckled CNTs were turned into densely-packed, horizontally-aligned CNT segments. • This morphology change was a result of patterned aluminum regulating the catalyst. • The adhesion force was ∼6.9 times of regular forest and ∼5.5 times of similar works. • The coarse-grained simulation revealed the reason for this adhesion performance. [ABSTRACT FROM AUTHOR]