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The rapid development of artificial intelligence requires faster information processing capabilities. However, the traditional von Neumann architecture is limited by transmission speed. The combination of neuromorphic structure and photon calculation will break this limitation and effectively improve the calculation efficiency. Here, we demonstrate an optical synaptic device based on GaN/AlN periodic structure that exhibits strong persistent photoconductivity in ultraviolet (UV) detection, which is caused by the strong polarization of GaN/AlN heterojunction. In our devices, photogenerated carriers are trapped in potential wells and then recombine slowly. This physical process alters the initial distribution of the electric field, thus changing the resistance state of the device. Based on this characteristic, the device exhibits optically tunable synaptic behaviors, such as short/long-term memory, excitatory postsynaptic current, and spike-timing-dependent plasticity stimulated by pulsed light. At the same time, our devices exhibit high response and contrast at high bias voltage, making it sensitive to quite weak UV light. Then, it is demonstrated experimentally that the devices can be applied to image information preprocessing, greatly reducing the amount of input information and subsequent training costs in the task of handwritten number recognition. Overall, this work shows an unreported structure of an optical synaptic device with memory and learning behaviors, with great potential for applications in weak UV light detection and neural computing. [ABSTRACT FROM AUTHOR]

Large-areasingle-layer graphenes with high crystallinity are desiredfor electronic applications. Here we demonstrate a continued growthmethod to amplify an existing graphene seed, originally grown by chemicalvapor deposition, by preferentially inducing nucleation at seed edges.More specifically, this approach involves a surface oxidation stepafter the first growth, which leads to the observed formation of oxidesat the vicinity of graphene edges, along with the inevitable formationof cracks due to oxidation, and thus limit growth predominantly atthose edges, as a consequence of the reduced energy barrier of methanedecomposition by oxygen moieties. Consequently, we successfully growmillimeter-size secondary single-crystal graphene structures withthe same lattice structure and orientation as the original seeds.Selected area electron diffraction (SAED), Raman spectroscopy characterization,along with electronic transport measurement confirmed the structurecoherence after the regrowth, even in the seed/regrown grains boundaryregion. This clone-like method provides a venue for production ofgraphene electronics with reproducible properties. [ABSTRACT FROM AUTHOR]

We demonstrate how shape selectivity and optimized surfacecompositionresult in exceptional oxygen reduction activity of octahedral PtNinanoparticles (NPs). The alloy octahedra were obtained by utilizinga facile, completely surfactant-free solvothermal synthesis. We showthat the choice of precursor ligands controls the shape, while thereaction time tunes the surface Pt:Ni composition. The 9.5 nm sizedPtNi octahedra reached a 10-fold surface area-specific (∼3.14mA/cmPt2) aswell as an unprecedented 10-fold Pt mass based (∼1.45 A/mgPt) activity gain over the state-of-art Pt electrocatalyst,approaching the theoretically predicted limits. [ABSTRACT FROM AUTHOR]

Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy line profiles with Ångstrom resolution, we uncover novel core–shell fine structures in a series of catalytically active dealloyed PtxNi1–x core–shell nanoparticles, showing the formation of unusual near-surface Ni-enriched inner shells. The radial location and the composition of the Ni-enriched inner shells were sensitively dependent on the initial alloy compositions. We further discuss how these self-organized Ni-enriched inner shells play a key role in maintaining surface lattice strain and thus control the surface catalytic activity for oxygen reduction. [ABSTRACT FROM AUTHOR]

Candida auris ( C. auris ) was first discovered in Japan in 2009 and has since spread worldwide. It exhibits strong transmission ability, high multidrug resistance, blood infectivity, and mortality rates. Traditional diagnostic techniques for C. auris have shortcomings, leading to difficulty in its timely diagnosis and identification. Therefore, timely and accurate diagnostic assays for clinical samples are crucial. We developed a novel, rapid recombinase-aided amplification (RAA) assay targeting the 18S rRNA, ITS1, 5.8S rRNA, ITS2, and 28S rRNA genes for C. auris identification. This assay can rapidly amplify DNA at 39 °C in 20 min. The analytical sensitivity and specificity were evaluated. From 241 clinical samples collected from pediatric inpatients, none were detected as C. auris -positive. We then prepared simulated clinical samples by adding 10-fold serial dilutions of C. auris into the samples to test the RAA assay's efficacy and compared it with that of real-time PCR. The assay demonstrated an analytical sensitivity of 10 copies/μL and an analytical specificity of 100%. The lower detection limit of the RAA assay for simulated clinical samples was 10 1 CFU/mL, which was better than that of real-time PCR (10 2 -10 3 CFU/mL), demonstrating that the RAA assay may have a better detection efficacy for clinical samples. In summary, the RAA assay has high sensitivity, specificity, and detection efficacy. This assay is a potential new method for detecting C. auris , with simple reaction condition requirements, thus helping to manage C. auris epidemics.

The exploitation of M-N X sites, where M is a transition metal atom, is widely regarded as an effective catalytic strategy to promote the oxygen reduction reaction (ORR). In addition, some studies have shown that transition metal nanoparticles (M-NPs) coated with carbon layers can improve the reactivity of ORR and ameliorate the overpotential of the reaction. In this study, we synthesized carbon nanotubes with single-atom Co-N X active sites, Co-NPs outside the tube, and Co-NPs wrapped in the tube by the complexation-pyrolysis synthesis method and explored the role of the particles and Co-N X sites through different pickling steps. The catalyst synthesized with the new stratagem in this study shows outstanding selectivity and also ORR activity. Furthermore, a natural air diffusion electrode fabricated using this material can produce H 2 O 2 at 323 mg L -1 h -1 under neutral conditions without oxygen aeration.

Parastichy, the spiral arrangement of plant organs, is an example of the long-range apparent order seen in biological systems. These ordered arrangements provide scientists with both an aesthetic challenge and a mathematical inspiration. Synthetic efforts to replicate the regularity of parastichy may allow for molecular-scale control over particle arrangement processes. Here we report the packing of a supramolecular truncated cuboctahedron (TCO) into double-helical (DH) nanowires on a graphite surface with a non-natural parastichy pattern ascribed to the symmetry of the TCOs and interactions between TCOs. Such a study is expected to advance our understanding of the design inputs needed to create complex, but precisely controlled, hierarchical materials. It is also one of the few reported helical packing structures based on Platonic or Archimedean solids since the discovery of the Boerdijk-Coxeter helix. As such, it may provide experimental support for studies of packing theory at the molecular level.

This study aimed to explore the dynamic variations in the phenolic and volatile organic compounds of sugarcane vinegar subjected to different production processes. The determination of phenolic and volatile organic compounds was performed by UPLC-MS and solid phase micro extraction (SPME) coupled with gas chromatography combined with mass spectrometry (GC-MS). The complete fermentation process of sugarcane lasted nine days, and production of vinegar of up to 3.04% (w/v), total acids, and 4.1° alcoholicity was accomplished. Various phenolic compounds of sugarcane juice (non-sterilized) and those of alcoholic and acetic acid fermentation were obtained after nine days of fermentation. These were benzoic acid (2.024, 1.002, and 1.027 mg L -1 ), ferulic acid (0.060, 0.205, and 1.124 mg L -1 ), quinic acid (0.019, 0.074, and 0.031 mg L -1 ), chlorogenic acid (0.349, 1.635, and 1.217 mg L -1 ), apigenin (0.002, 0.099, and 0.004 mg L -1 ), kaempferol (0.003, 0.336, and 0.003 mg L -1 ), caffeic acid (-, 0.005, and 0.005 mg L -1 ), luteolin (0.003, 0.323, and 0.005 mg L -1 ), and p -coumaric acid (0.018, 0.015, and 0.027 mg L -1 ). Forty-five volatile organic compounds were also identified. The sugarcane juice can be commercialized as an alternative to wine as it presents characteristics of an alcoholic fermented beverage., Competing Interests: The authors declare no competing financial interest., (© 2020 The Authors. Published by American Chemical Society.)

Air bubbles formed between layers of two-dimensional (2D) materials not only are unavoidable but also emerge as an important means of engineering their excitonic emission properties, especially as controllable quantum light sources. Measuring the actual spatially resolved optical properties across such bubbles is important for understanding excitonic physics and for device applications; however, such a measurement is challenging due to nanoscale features involved which require spatial resolution beyond the diffraction limit. Additional complexity is the involvement of multiple physical effects such as mechanical strain and dielectric environment that are difficult to disentangle. In this paper, we demonstrate an effective approach combining micro-photoluminescence measurement, atomic force microscope profile mapping, and a theoretical strain model. We succeeded in reconstructing the actual spatial profiles of the emission wavelengths beyond the diffraction limit for bubbles formed by a monolayer tungsten disulfide on boron nitride. The agreements and consistency among various approaches established the validity of our approach. In addition, our approach allows us to disentangle the effects of strain and dielectric environment and provides a general and reliable method to determine the true magnitude of wavelength changes due to the individual effects across bubbles. Importantly, we found that micro-optical measurement underestimates the red and blue shifts by almost 5 times. Our results provide important insights into strain and screening-dependent optical properties of 2D materials on the nanometer scale and contribute significantly to our understanding of excitonic emission physics as well as potential applications of bubbles in optoelectronic devices.

Many recent efforts on the electrode design for advanced Li-ion batteries (LIBs) are often devoted to increasing the gravimetric capacity, but little attention is paid to the volumetric capacity which is more critical for practical application. Though the alloying-type anode materials are quite attractive, the challenge is that they must be composited with a large amount of carbon materials (e.g., GO, rGO, CNT) to buffer their large volume change, which would undoubtedly sacrifice the volumetric energy density of the whole electrode due to the carbon's low tap density (∼0.05 g/cm 3 ). Herein, we propose the unique layered Sb 2 Te 3 , which possesses high conductivity and a large volumetric capacity (3419 mAh/cm 3 ), to be served as the alternative anode for LIBs. Furthermore, we introduce natural graphite, which is low price and with high density (2.25 g/cm 3 ), into Sb 2 Te 3 to successfully build a novel Sb 2 Te 3 @Gra composite in which the Sb 2 Te 3 particles are wrapped by graphite layers. Interestingly, this modified Sb 2 Te 3 @Gra exhibits much more superior cycle stability (570 mAh/g after 200 cycles, 96% retention) than pure Sb 2 Te 3 (130 mAh/g after 200 cycles, 22% retention), while keeping its original large volumetric capacity output (∼3200 mAh/cm 3 ) at the same time. More specially, it enables a reversible structure recovery of Sb 2 Te 3 , guaranteeing the electrode integrity and cyclability. These extraordinary phenomena are investigated in detail, whose results display that the outer graphite layer plays an important role by facilitating the intimate contact with Sb 2 Te 3 particles and protecting them from pulverization. Besides, such graphite layer greatly promotes the electron-transfer during lithiation, helping to improve the rate capability (372 mAh/g at 2000 mA/g, 60% retention). Consequently, the assembled Sb 2 Te 3 //LiCoO 2 full cell delivers a large capacity of 500 mAh/g, with stable discharge plateau and cycle stability, revealing its high potential for practical application.

Two-dimensional (2D) materials exhibit high sensitivity to structural defects due to the nature of interface-type materials, and the corresponding structural defects can effectively modulate their inherent properties in turn, giving them a wide application range in high-performance and functional devices. 2D γ-Ga 2 S 3 is a defective semiconductor with outstanding optoelectronic properties. However, its controllable preparation has not been implemented yet, which hinders exploring its potential applications. In this work, we introduce nonlayered γ-Ga 2 S 3 into the 2D materials family, which was successfully synthesized via the space-confined chemical vapor deposition method. Its intriguing defective structure are revealed by high-resolution transmission electron microscopy and temperature-dependent cathodoluminescence spectra, which endow the γ-Ga 2 S 3 -based device with a broad photoresponse from the ultraviolet to near-infrared region and excellent photoelectric conversion capability. Simultaneously, the device also exhibits excellent ultraviolet detection ability ( R λ = 61.3 A W -1 , I on /I off = 851, EQE = 2.17× 10 4 %, D* = 1.52× 10 10 Jones @350 nm), and relatively fast response (15 ms). This work provides a feasible way to fabricate ultrathin nonlayered materials and explore the potential applications of a 2D defective semiconductor in high-performance broadband photodetection, which also suggests a promising future of defect creation in optimizing photoelectric properties.

Understanding the role of surfactants or ligands on the growth mechanism of metal/alloy nanoparticles (NPs) is important for controlled synthesis of functional metallic NPs with tailored structures and properties. There have been a number of works showing the significant impact of surfactants/ligands on the shape-controlled synthesis of nanocrystals with well-defined surfaces. Beyond the morphological shape control, impact of the surfactants/ligands on the alloying structure of bimetallic nanocrystals, however, still remains largely unaddressed. We reveal here a significant effect of benzoic acid ligand on the elemental growth and alloying phase structure of octahedral Pt-Ni NPs, a class of highly active electrocatalyst for oxygen reduction reaction in fuel cells. Contrary to previous reports showing the critical role of benzoic acid in directing the growth of octahedral Pt-Ni NPs, we found that benzoic acid played a minor role in forming the octahedral shape; instead, it can strongly coordinate with Ni cation and significantly slows down its reduction rate, leading to a phase separation in the Pt-Ni NP products (a mixture of Pt-rich octahedral NPs and nearly pure Ni NPs). Such phase separation further resulted in a lower catalytic activity and stability. These results help us comprehensively understand the effect of metal-ligand coordination chemistry on the elemental growth mechanism and alloying phase structure of bimetallic NPs, complementing previous emphasis on the role of surfactants in purely morphological shape control., Competing Interests: The authors declare no competing financial interest.

Enhancing the rate of reverse intersystem crossing ( k risc ) and the rate of radiative transition ( k r ) has been regarded as the key to improve molecular design strategy in the field of thermally activated delayed fluorescence (TADF) materials. Herein, two sky-blue donor-acceptor (D-A)-type TADF materials, namely, CzDCNPy and tBuCzDCNPy, were designed following a strategy of controlling the energy difference among the charge-transfer singlet state ( 1 CT), local exciton triplet state ( 3 LE), and charge-transfer triplet state ( 3 CT). Significantly different from most previously reported TADF materials, large values of k r and k risc and a nearly 100% exciton utilization efficiency were simultaneously achieved despite nonobvious delayed fluorescence and a large value of the singlet-triplet energy difference (Δ E ST ) being observed. This work presents a view that photoinduced delayed fluorescence and a small Δ E ST are sufficient but not necessary for TADF materials. It also provides a reference that the high-energy 3 LE state plays a key role in the RISC process in electroluminescence.

Conductive rubber composites usually suffer a large filler content and relatively low conductivity because the uniform dispersion of conductive nanofillers in rubbers is probably inhibited by the cross-link networks. However, by establishing a double-network model of cross-link and conductive networks, we found the connection of one-dimensional nanofillers could be improved by cross-link networks, which stabilized the conductive network. The percolation value of nanofillers could reduce to 0.06 wt % in experiments, using carbon nanotubes (CNTs) with 9.5 nm diameter and 1.5 μm length as nanofillers and poly(dimethylsiloxane) as the matrix. Moreover, the conductive network owned a critical exponent of 5.63, which was higher than that of conventional conductive networks (ca. 2). This feature proved that the connection between CNTs was improved by the poly(dimethylsiloxane) cross-link network. This work subverted the fundamental conception that cross-link networks in rubbers should make fillers aggregate, and we believed it would conduce to the development of sensors and flexible devices of rubber composites.

As a direct-band-gap transition metal dichalcogenide (TMD), atomic thin MoS 2 has attracted extensive attention in photodetection, whereas the hitherto unsolved persistent photoconductance (PPC) from the ungoverned charge trapping in devices has severely hindered their employment. Herein, we demonstrate the realization of ultrafast photoresponse dynamics in monolayer MoS 2 by exploiting a charge transfer interface based on surface-assembled zinc phthalocyanine (ZnPc) molecules. The formed MoS 2 /ZnPc van der Waals interface is found to favorably suppress the PPC phenomenon in MoS 2 by instantly separating photogenerated holes toward the ZnPc molecules, away from the traps in MoS 2 and the dielectric interface. The derived MoS 2 detector then exhibits significantly improved photoresponse speed by more than 3 orders (from over 20 s to less than 8 ms for the decay) and a high responsivity of 430 A/W after Al 2 O 3 passivation. It is also demonstrated that the device could be further tailored to be 2-10-fold more sensitive without severely sacrificing the ultrafast response dynamics using gate modulation. The strategy presented here based on surface-assembled organic molecules may thus pave the way for realizing high-performance TMD-based photodetection with ultrafast speed and high sensitivity.

Active oxide nanolayers can be stabilized on noble metal surfaces through interface confinement effect in oxide/metal inverse catalysts. Here, using normal metal/oxide catalysts we show that Fe oxide nanolayers can be confined on Pt nanoparticles (NPs) when treating a Pt/FeO x catalyst in Ar or H 2 /O 2 atmospheres at elevated temperatures. Pt NPs partially covered with Fe oxide nanopatches are more active in CO oxidation than bare Pt NPs, while those with fully encapsulated Fe oxide shells in strong metal-support interaction (SMSI) state show much lower activity. Characterization results indicate that three steps play an important role in the formation of Fe oxide overlayers: Pt-aided reduction of interfacial Fe oxide, Pt alloying of interfacial Fe atoms, and surface segregation of alloyed Fe atoms onto surface of Pt NPs. Active surface oxides in so-called support-metal interface confinement (SMIC) state and fully encapsulated oxide layers in the SMSI state can be sequentially produced which depend on the treatment conditions.