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Natural biomolecules have potential as proton-conducting materials, in which the hydrogen-bond networks can facilitate proton transportation. Herein, a biomolecule/metal–organic framework (MOF) approach to develop hybrid proton-conductive membranes is reported. Single-strand DNA molecules are introduced into DNA@ZIF-8 membranes through a solid-confined conversion process. The DNA-threaded ZIF-8 membrane exhibits high proton conductivity of 3.40 × 10⁻⁴ S cm⁻¹ at 25 °C and the highest one ever reported of 0.17 S cm⁻¹ at 75 °C, under 97% relatively humidity, attributed to the formed hydrogen-bond networks between the DNA molecules and the water molecules inside the cavities of the ZIF-8, but very low methanol permeability of 1.25 × 10⁻⁸ cm² s⁻¹ due to the small pore entrance of the DNA@ZIF-8 membranes. The selectivity of the DNA@ZIF-8 membrane is thus significantly higher than that of developed proton-exchange membranes for fuel cells. After assembling the DNA@ZIF-8 hybrid membrane into direct methanol fuel cells, it exhibits a power density of 9.87 mW cm⁻² . This is the first MOF-based proton-conductivity membrane used for direct methanol fuel cells, providing bright promise for such hybrid membranes in this application.

A DNA-threaded DNA@ZIF-8 membrane demonstrates ultrahigh proton conductivity and low methanol permeability, holding great potential for application in direct methanol fuel cells.

Marjorie Lismont, Laurent Dreesen, and Stephan Wuttke review a new generation of metalo-organic framework based photosensitizers for cancer therapy in article number 1606314. Precise spatial control is required to successfully include an organic photosensitizer as organic component of the framework without encountering aggregation and solubility issues. Overcoming of these obstacles could open new perspectives for photodynamic therapy of cancer.

Resonant tunneling through a 4 nm nanocrystal Ge (nc-Ge) layer and a 2.4 nm monolayer of Si colloidal quantum dots (QD) is achieved with 0.7 nm amorphous Al₂O₃ (a-Al₂O₃) barriers. The nc-Ge resonant tunneling diode (RTD) demonstrates a peak-to-valley current ratio (PVCR) of 8 and a full width at half maximum (FWHM) of 30 mV at 300 K, the best performance among RTDs based on annealed nanocrystals. The Si QD RTD is first achieved with PVCRs up to 47 and FWHMs as small as 10 mV at room temperature, confirming theoretically expected excellences of 3D carrier confinements. The high performances are partially due to the smooth profile of nc-Ge layer and the uniform distribution of Si QDs, which reduce the adverse influences of many-body effects. More importantly, carrier decoherence is avoided in the 0.7 nm a-Al₂O₃ barriers thinner than the phase coherence length (≈1.5 nm). Ultrathin a-Al₂O₃ also passivates well materials and suppresses leakage currents. Additionally, the interfacial bandgap of ultrathin a-Al₂O₃ is found to be similar to the bulk, forming deep potential wells to sharpen transmission curves. This work can be easily extended to other materials, which may enable resonant tunneling in various nanosystems for diverse purposes.

Resonant tunneling is first achieved at room temperature through Ge nanocrystals and freestanding Si quantum dots. The high performance of these devices supports the feasibility of constructing resonant tunneling diodes with ultrathin amorphous insulators and nanoparticles or easily crystallized thin films, greatly expanding the material choice for resonant tunneling devices.

The size of the band gap and the energy position of the band edges make several oxynitride semiconductors promising candidates for efficient hydrogen and oxygen production under solar light illumination. Intense research efforts dedicated to oxynitride materials have unveiled the majority of their most important properties. However, two crucial aspects have received much less attention: One is the critical issue of compositional/structural surface modifications that occur during operation and how these affect photoelectrochemical performance. The second concerns the relation between electrochemical response and the crystallographic surface orientation of the oxynitride semiconductor. These are indeed topics of fundamental importance, since it is exactly at the surface where the visible-light-driven electrochemical reaction takes place.

In contrast to conventional powder samples, thin films represent the best model system for these investigations. This study reviews current state-of-the-art oxynitride thin film fabrication and characterization, before focusing on LaTiO₂N, selected as a representative photocatalyst. An investigation of the initial physicochemical evolution of the surface is reported. Then, it is shown that after stabilization the absorbed photon-to-current conversion efficiency of epitaxial thin films can differ by about 50% for different crystallographic surface orientations, and be up to 5 times larger than for polycrystalline samples.

Oxynitride photoanode thin film heterostructures for solar water splitting based on LaTiO_xN_y are fabricated. Polycrystalline samples are used to probe surface physicochemical evolution induced by photoelectrochemical tests. A comparative analysis of samples with different crystalline properties shows that not only the crystalline quality, but also the crystallographic surface orientation determines the photoelectrochemical response.

Due to the intriguing optical and electronic properties, 2D materials have attracted a lot of interest for the electronic and optoelectronic applications. Identifying new promising 2D materials will be rewarding toward the development of next generation 2D electronics. Here, palladium diselenide (PdSe₂), a noble-transition metal dichalcogenide (TMDC), is introduced as a promising high mobility 2D material into the fast growing 2D community. Field-effect transistors (FETs) based on ultrathin PdSe₂ show intrinsic ambipolar characteristic. The polarity of the FET can be tuned. After vacuum annealing, the authors find PdSe₂ to exhibit electron-dominated transport with high mobility (µ_{e (max)} = 216 cm² V⁻¹ s⁻¹) and on/off ratio up to 10³. Hole-dominated-transport PdSe₂ can be obtained by molecular doping using F₄-TCNQ. This pioneer work on PdSe₂ will spark interests in the less explored regime of noble-TMDCs.

2D palladium diselenide field-effect transistors are fabricated and investigated. The devices show ambipolar behavior with tunable ambipolar transport properties by thermal annealing and chemical doping. The electron and hole mobilities are ≈216 and 12 cm² V⁻¹ s⁻¹, respectively. The results demonstrate that PdSe₂ is promising for 2D electronics applications.

Transition metal oxides having a perovskite structure form a wide and technologically important class of compounds. In these systems, ferroelectric, ferromagnetic, ferroelastic, or even orbital and charge orderings can develop and eventually coexist. These orderings can be tuned by external electric, magnetic, or stress field, and the cross-couplings between them enable important multifunctional properties, such as piezoelectricity, magneto-electricity, or magneto-elasticity. Recently, it has been proposed that additional to typical fields, the chemical potential that controls the concentration of ion vacancies in these systems may reveal an efficient alternative parameter to further tune their properties and achieve new functionalities. In this study, concretizing this proposal, the authors show that the control of the content of oxygen vacancies in perovskite thin films can indeed be used to tune their magnetic properties. Growing PrVO₃ thin films epitaxially on an SrTiO₃ substrate, the authors reveal a concrete pathway to achieve this effect. The authors demonstrate that monitoring the concentration of oxygen vacancies through the oxygen partial pressure or the growth temperature can produce a substantial macroscopic tensile strain of a few percent. In turn, this strain affects the exchange interactions, producing a nontrivial evolution of Néel temperature in a range of 30 K.

The control of the content of oxygen vacancies in PrVO₃ perovskite thin films, epitaxially grown on SrTiO₃, is used to tailor their magnetic properties. Through the oxygen partial pressure or the growth temperature control, a substantial macroscopic tensile strain of a few percent is produced. In turn, this strain affects the exchange interactions, producing a nontrivial evolution of the Néel temperature.

The low utilization of active sites and sluggish reaction kinetics of MoSe₂ severely impede its commercial application as electrocatalyst for hydrogen evolution reaction (HER). To address these two issues, the first example of introducing 1T MoSe₂ and N dopant into vertical 2H MoSe₂/graphene shell/core nanoflake arrays that remarkably boost their HER activity is herein described. By means of the improved conductivity, rich catalytic active sites and highly accessible surface area as a result of the introduction of 1T MoSe₂ and N doping as well as the unique structural features, the N-doped 1T-2H MoSe₂/graphene (N-MoSe₂/VG) shell/core nanoflake arrays show substantially enhanced HER activity. Remarkably, the N-MoSe₂/VG nanoflakes exhibit a relatively low onset potential of 45 mV and overpotential of 98 mV (vs RHE) at 10 mA cm⁻² with excellent long-term stability (no decay after 20 000 cycles), outperforming most of the recently reported Mo-based electrocatalysts. The success of improving the electrochemical performance via the introduction of 1T phase and N dopant offers new opportunities in the development of high-performance MoSe₂-based electrodes for other energy-related applications.

A new powerful strategy to remarkably boost the electrocatalytic activity of MoSe₂/graphene nanoflakes by introducing 1T MoSe₂ and a N dopant simultaneously is demonstrated. These N-doped MoSe₂/graphene nanoflakes show outstanding hydrogen evolution reaction performance, with a small overpotential of 98 mV, a low Tafel slope of around 49 mV dec⁻¹, and an excellent long-term durability.

Two-dimensional (2D) organic–inorganic hybrid perovskite nanosheets (NSs) are attracting increasing research interest due to their unique properties and promising applications. Here, for the first time, we report the facile synthesis of single- and few-layer free-standing phenylethylammonium lead halide perovskite NSs, that is, (PEA)₂PbX₄ (PEA=C₈H₉NH₃, X=Cl, Br, I). Importantly, their lateral size can be tuned by changing solvents. Moreover, these ultrathin 2D perovskite NSs exhibit highly efficient and tunable photoluminescence, as well as superior stability. Our study provides a simple and general method for the controlled synthesis of 2D perovskite NSs, which may offer a new avenue for their fundamental studies and optoelectronic applications.

Ultrathin perovskite nanosheets: Single- and few-layer free-standing phenylethylammonium lead halide perovskite nanosheets with controlled lateral sizes were synthesized by a facile and fast crystallization method. These as-prepared nanosheets show bright, tunable light emission (see picture) as well as enhanced stability.

Z-scheme water splitting is a promising approach based on high-performance photocatalysis by harvesting broadband solar energy. Its efficiency depends on the well-defined interfaces between two semiconductors for the charge kinetics and their exposed surfaces for chemical reactions. Herein, we report a facile cation-exchange approach to obtain compounds with both properties without the need for noble metals by forming Janus-like structures consisting of γ-MnS and Cu₇S₄ with high-quality interfaces. The Janus-like γ-MnS/Cu₇S₄ structures displayed dramatically enhanced photocatalytic hydrogen production rates of up to 718 μmol g⁻¹ h⁻¹ under full-spectrum irradiation. Upon further integration with an MnO_x oxygen-evolution cocatalyst, overall water splitting was accomplished with the Janus structures. This work provides insight into the surface and interface design of hybrid photocatalysts, and offers a noble-metal-free approach to broadband photocatalytic hydrogen production.

Janus-like structures consisting of γ-MnS and Cu₇S₄ with high-quality interfaces were obtained by facile cation exchange. The hybrid structures exhibit broadband light absorption and improved charge separation, which led to a hydrogen production rate of 718 μmol g⁻¹ h⁻¹ under full-spectrum irradiation.

Silicene, a single-layer-thick silicon nanosheet with a honeycomb structure, is successfully fabricated by the molecular-beam-epitaxy (MBE) deposition method on metallic substrates and by the solid-state reaction method. Here, recent progress on the features of silicene that make it a prospective anode for lithium-ion batteries (LIBs) are discussed, including its charge-carrier mobility, chemical stability, and metal–silicene interactions. The electrochemical performance of silicene is reviewed in terms of both theoretical predictions and experimental measurements, and finally, its challenges and outlook are considered.

Silicene, single-layer-thick silicon nanosheets with a honeycomb structure, has been successfully fabricated very recently. Recent progress on the features of silicene that make it a promising anode for lithium-ion batteries (LIBs), including its charge-carrier mobility, chemical stability, and metal–silicene interaction are discussed.

Quantum Hall conductance in monolayer graphene on an epitaxial SrTiO₃ (STO) thin film is studied to understand the role of oxygen vacancies in determining the dielectric properties of STO. As the gate-voltage sweep range is gradually increased in the device, systematic generation and annihilation of oxygen vacancies, evidenced from the hysteretic conductance behavior in the graphene, are observed. Furthermore, based on the experimentally observed linear scaling relation between the effective capacitance and the voltage sweep range, a simple model is constructed to manifest the relationship among the dielectric properties of STO with oxygen vacancies. The inherent quantum Hall conductance in graphene can be considered as a sensitive, robust, and noninvasive probe for understanding the electronic and ionic phenomena in complex transition-metal oxides without impairing the oxide layer underneath.

A sensitive, robust, and noninvasive probing of dielectric properties in epitaxial SrTiO₃ thin film with oxygen vacancies is presented, based on the scalable hysteretic quantum conductance of graphene. The device concept, composed of 2D layered materials and transition-metal oxides, provides an interesting opportunity for understanding the fundamental physical properties of materials that would otherwise not be possible.