Few-layer black phosphorus (BP), also known as phosphorene, is poised to be the most attractive graphene analogue owing to its high mobility approaching that of graphene, and its thickness-tunable band gap that can be as large as that of molybdenum disulfide. In essence, phosphorene represents the much sought after high-mobility, large direct band gap two-dimensional layered crystal that is ideal for optoelectronics and flexible devices. However, its instability in air is of paramount concern for practical applications. Here, we demonstrate air-stable BP devices with dielectric and hydrophobic encapsulation. Microscopy, spectroscopy, and transport techniques were employed to elucidate the aging mechanism, which can initiate from the BP surface for bare samples, or edges for samples with thin dielectric coating, highlighting the ineffectiveness of conventional scaled dielectrics. Our months-long studies indicate that a double layer capping of Al2O3 and hydrophobic fluoropolymer affords BP devices and transistors with indefinite air-stability for the first time, overcoming a critical material challenge for applied research and development.

Bacterial infection can cause chronic nonhealing wounds, which may be a great threat to public health. It is highly desirable to develop an injectable wound dressing hydrogel with multifunctions including self‐healing, remodeling, antibacterial, radical scavenging ability, and excellent photothermal properties to promote the regeneration of damaged tissues in clinical practice. In this work, dopamine‐modified gelatin (Gel‐DA) is employed for the first time as a biotemplate for enhancing the biomineralization ability of gelatin to synthesize dopamine‐modified gelatin@Ag nanoparticles (Gel‐DA@Ag NPs). Further, the prepared Gel‐DA@Ag NPs with antioxidant activity and near‐infrared (NIR) laser irradiation synergistic antibacterial behavior are fixed in the guar gum based hydrogels through the formation of borate/didiol bonds to possess remolding, injectable, and self‐healing performance. In addition, the multifunctional hydrogels can completely cover the irregular wound shape to prevent secondary injury. More importantly, these hydrogel platforms under NIR can significantly accelerate wound healing with more skin appendages like hair follicles and blood vessels appearing. Therefore, it is expected that these hydrogels can serve as competitive multifunctional dressings in biomedical field, including bacteria‐derived wound infection and other tissue repair related to reactive oxygen species overexpression.

Synergistic therapeutic strategies for bacterial infection have attracted extensive attentions owing to their enhanced therapeutic effects and less adverse effects compared with monotherapy. Herein, we report a novel synergistic antibacterial platform that integrates the nanocatalytic antibacterial therapy and photothermal therapy (PTT) by hemoglobin-functionalized copper ferrite nanoparticles (Hb-CFNPs). In the presence of a low concentration of hydrogen peroxide (H2O2), the excellent Fenton and Fenton-like reaction activity of Hb-CFNPs can effectively catalyze the decomposition of H2O2 to produce hydroxyl radicals (·OH), rendering an increase in the permeability of the bacterial cell membrane and the sensitivity to heat. With the assistance of NIR irradiation, hyperthermia generated by Hb-CFNPs can induce the death of the damaged bacteria. Additionally, owing to the outstanding magnetic property of Hb-CFNPs, it can improve the photothermal efficiency by about 20 times via magnetic enrichment, which facilitates to realize excellent bactericidal efficacy at a very low experimental dose (20 μg/mL). In vitro antibacterial experiment shows that this synergistic antibacterial strategy has a broad-spectrum antibacterial property against Gram-negative Escherichia coli (E. coli, 100%) and Gram-positive Staphylococcus aureus (S. aureus, 96.4%). More importantly, in vivo S. aureus-infected abscess treatment studies indicate that Hb-CFNPs can serve as an antibacterial candidate with negligible toxicity to realize synergistic treatment of bacterial infections through catalytic and photothermal effects. Accordingly, this study proposes a novel, high-efficiency, and multifunctional therapeutic system for the treatment of bacterial infection, which will open up a new avenue for the design of synergistic antibacterial systems in the future.

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To elaborately construct a novel and efficient photothermal antibacterial nanoplatform is a promising strategy for treating bacterial wound infections. In this work, a composite hydrogel (CS/AM NSs hydrogel) with outstanding antibacterial ability is constructed by incorporating antimonene nanosheets (AM NSs) with extraordinary photothermal properties into the network structure of chitosan (CS). When cultured with bacteria, the CS/AM NSs hydrogel can gather bacteria on the surface through the interaction of CS with the bacterial cell membrane. Subsequently, the intrinsic bactericidal property of CS will kill some of the bacteria. After the introduction of near‐infrared laser, the AM NSs effectively convert light energy into localized heat to eliminate residual bacteria. By virtue of the synergistic action between the capture effect of CS and the photothermal effect of AM NSs, the CS/AM NSs hydrogel shows predominant antibacterial behavior against Escherichia coli and Staphylococcus aureus. In vitro assay and in vivo tests of infected full‐thickness defect wound healing confirm the satisfactory biocompatibility and antibacterial ability. Overall, this work reveals that the CS/AM NSs hydrogel holds great potential as a broad‐spectrum antibacterial wound dressing for treating bacteria‐infected wounds. Additionally, this is the first report of the application of AM NSs in the field of antibacterial treatment.

Due to the drastically different intralayer versus interlayer bonding strengths, the mechanical, thermal, and electrical properties of two-dimensional (2D) materials are highly anisotropic between the in-plane and out-of-plane directions. The structural anisotropy may also play a role in chemical reactions, such as oxidation, reduction, and etching. Here, the composition, structure, and electrical properties of mechanically exfoliated WSe 2 nanosheets on SiO 2 /Si substrates were studied as a function of the extent of thermal oxidation. A major component of the oxidation, as indicated from optical and Raman data, starts from the nano-sheet edges and propagates laterally towards the center. Partial oxidation also occurs in certain areas at the surface of the flakes, which are shown to be highly conductive by microwave impedance microscopy. Using secondary ion mass spectroscopy, we also observed extensive oxidation at the WSe 2 −SiO 2 interface. The combination of multiple microcopy methods can thus provide vital information on the spatial evolution of chemical reactions on 2D materials and the nanoscale electrical properties of the reaction products.Keywords: Tungsten diselenide, 2D materials, thermal oxidation, microwave impedance microscopy, secondary ion mass spectroscopy 2 Layered van der Waals (vdW) materials, in which the electronic properties are inherently anisotropic, have been studied for a relatively long time [1], and have also attracted renewed interest in recent years [1,2]. This family of materials include elemental atomic sheets (e.g.,, and phosphorene [6,7]) and transition metal dichalcogenides [8] (TMDCs, e.g., MoS 2 and WSe 2 ), among others, presenting a wide array of candidates for research and applications. Given the extensive knowledge obtained on the solidstate chemistry of conventional Group IV elemental semiconductors and III-V compounds, and the potential use of vdW materials in nanoelectronics, it is anticipated that much effort will be devoted to investigate the spatial and temporal evolution of various chemical reactions [9], such as solution or vapor-based synthesis, reduction and oxidation, wet and dry etching, in 2D materials. Specifically, the understanding of these processes from atomic to mesoscopic length scales will provide important insight on their performance at the device level.The oxidation process of TMDCs is of particular interest due to its strong influence on the characteristics of devices that are not hermetically sealed and could potentially be oxidized in ambient environments. In addition, the fully oxidized products, e.g., WO 3 , are semiconducting metal oxides with a band gap in the range of 2.5 -3.7 eV, which may find applications in many areas [10][11][12]. To date, the oxidation of TMDCs has been studied at elevated temperatures [13], under intense laser illumination [14], and upon exposure to oxygen plasma [15] or ozone [16]. In contrast to conventional semiconductors such as silicon, the TMDCs show larger oxidative reactivity at the edges and surfac...

ABSTRACT:The dielectric constant or relative permittivity (r) of a dielectric material, which describes how the net electric field in the medium is reduced with respect to the external field, is a parameter of critical importance for charging and screening in electronic devices. Such a fundamental material property is intimately related to not only the polarizability of individual atoms, but also the specific atomic arrangement in the crystal lattice. In this letter, we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nano-flakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope is employed to simultaneously quantify the number of layers and local electrical properties. The measured r increases monotonically as a function of the thickness and saturates to the bulk value at around 6 ~ 8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed by first-principle calculations. Our results of the dielectric response, being ubiquitously applicable to layered 2D semiconductors, are expected to be significant for this vibrant research field.KEYWORDS: microwave impedance microscopy, layer-dependent dielectric constant, In2Se3 nano-flakes, layered materials, polarization, first-principle calculations 2The rapid rise of graphene in the past decade has led to an active research field on twodimensional (2D) layered materials.1, 2 Of particular interest here are layered semiconductors, such as many metal chalcogenides, for their roles as gate dielectrics or channel materials in nextgeneration electronics. 3 Due to the strong intralayer covalent bonding and weak van der Waals (vdW) interactions, most physical properties are already anisotropic in the bulk form, with a clear 3D-2D crossover when approaching the monolayer thickness. In particular, the number of layers (n) in a thin-film 2D system is expected to strongly influence its dielectric constant, a fundamental electrical property that determines the capacitance and charge screening in electronic devices. 4-6The 2D material in this study is the layered semiconducting chalcogenide In2Se3, a technologically important system for phase-change memory, thermoelectric, and photoelectric applications 7 . The In-Se phase diagram is among the most complex ones in binary compounds.Even at the exact stoichiometry of In:Se = 2:3, multiple phases can occur under different temperatures and pressures. [8][9][10][11] By controlling the synthesis parameters or thermal/electrical pretreatment processes, several phases (superlattice, simple hexagonal -phase, simple hexagonal -phase, and amorphous state) with vastly different electrical conductivity can coexist at the ambient condition, 12-14 which explains the research interest of In2Se3 as a prototypical phasechange material. 7,[12][13][14][15][16][17][18] In addition, the lattice constant of In2Se3 matches well with Bi2Se3, which is heavily investigated for its high thermoelectric figure-of-merit and ...