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Reversible and selective ion intercalation through the top surface of few-layer MoS2
摘要： Electrochemical intercalation of ions into the van der Waals gap of two-dimensional (2D) layered materials is a promising low-temperature synthesis strategy to tune their physical and chemical properties. It is widely believed that ions prefer intercalation into the van der Waals gap through the edges of the 2D flake, which generally causes wrinkling and distortion. Here we demonstrate that the ions can also intercalate through the top surface of few-layer MoS2 and this type of intercalation is more reversible and stable compared to the intercalation through the edges. Density functional theory calculations show that this intercalation is enabled by the existence of natural defects in exfoliated MoS2 flakes. Furthermore, we reveal that sealed-edge MoS2 allows intercalation of small alkali metal ions (e.g., Li+ and Na+) and rejects large ions (e.g., K+). These findings imply potential applications in developing functional 2D-material-based devices with high tunability and ion selectivity.
关键词： defects,MoS2,electrochemical control,two-dimensional materials,ion intercalation
更新于2025-09-04 15:30:14
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Searching for exoplanets using a microresonator astrocomb
摘要： Orbiting planets induce a weak radial velocity (RV) shift in the host star that provides a powerful method of planet detection. Importantly, the RV technique provides information about the exoplanet mass, which is unavailable with the complementary technique of transit photometry. However, RV detection of an Earth-like planet in the ‘habitable zone’ requires extreme spectroscopic precision that is only possible using a laser frequency comb (LFC). Conventional LFCs require complex filtering steps to be compatible with astronomical spectrographs, but a new chip-based microresonator device, the Kerr soliton microcomb, is an ideal match for astronomical spectrograph resolution and can eliminate these filtering steps. Here, we demonstrate an atomic/molecular line-referenced soliton microcomb for calibration of astronomical spectrographs. These devices can ultimately provide LFC systems that would occupy only a few cubic centimetres, thereby greatly expanding implementation of these technologies into remote and mobile environments beyond the research lab.
关键词： radial velocity,microresonator,astrocomb,Kerr soliton microcomb,laser frequency comb,exoplanets
更新于2025-09-04 15:30:14
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Estimation of Voxel-Based Above-Ground Biomass Using Airborne LiDAR Data in an Intact Tropical Rain Forest, Brunei
摘要： The advancement of LiDAR technology has enabled more detailed evaluations of forest structures. The so-called “Volumetric pixel (voxel)” has emerged as a new comprehensive approach. The purpose of this study was to estimate plot-level above-ground biomass (AGB) in different plot sizes of 20 m × 20 m and 30 m × 30 m, and to develop a regression model for AGB prediction. Both point cloud-based (PCB) and voxel-based (VB) metrics were used to maximize the efficiency of low-density LiDAR data within a dense forest. Multiple regression model AGB prediction performance was found to be greatest in the 30 m × 30 m plots, with R2, adjusted R2, and standard deviation values of 0.92, 0.87, and 35.13 Mg·ha?1, respectively. Five out of the eight selected independent variables were derived from VB metrics and the other three were derived from PCB metrics. Validation of accuracy yielded RMSE and NRMSE values of 27.8 Mg·ha?1 and 9.2%, respectively, which is a reasonable estimate for this structurally complex intact forest that has shown high NRMSE values in previous studies. This voxel-based approach enables a greater understanding of complex forest structure and is expected to contribute to the advancement of forest carbon quantification techniques.
关键词： LiDAR,voxel,REDD+,volumetric pixel,forest biomass,forest carbon stock,climate change
更新于2025-09-04 15:30:14
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DNA-Based Super-Resolution Microscopy: DNA-PAINT
摘要： Super-resolution microscopies, such as single molecule localization microscopy (SMLM), allow the visualization of biomolecules at the nanoscale. The requirement to observe molecules multiple times during an acquisition has pushed the field to explore methods that allow the binding of a fluorophore to a target. This binding is then used to build an image via points accumulation for imaging nanoscale topography (PAINT), which relies on the stochastic binding of a fluorescent ligand instead of the stochastic photo-activation of a permanently bound fluorophore. Recently, systems that use DNA to achieve repeated, transient binding for PAINT imaging have become the cutting edge in SMLM. Here, we review the history of PAINT imaging, with a particular focus on the development of DNA-PAINT. We outline the different variations of DNA-PAINT and their applications for imaging of both DNA origamis and cellular proteins via SMLM. Finally, we reflect on the current challenges for DNA-PAINT imaging going forward.
关键词： DNA PAINT,SMLM,DNA origami,DNA,fluorescence microscopy,super-resolution microscopy
更新于2025-09-04 15:30:14
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Electronically programmable photonic molecule
摘要： Physical systems with discrete energy levels are ubiquitous in nature and are fundamental building blocks of quantum technology. Realizing controllable artificial atom- and molecule-like systems for light would enable coherent and dynamic control of the frequency, amplitude and phase of photons. In this work, we demonstrate a ‘photonic molecule’ with two distinct energy levels using coupled lithium niobate microring resonators and control it by external microwave excitation. We show that the frequency and phase of light can be precisely controlled by programmed microwave signals, using concepts of canonical two-level systems including Autler–Townes splitting, Stark shift, Rabi oscillation and Ramsey interference. Through such coherent control, we show on-demand optical storage and retrieval by reconfiguring the photonic molecule into a bright–dark mode pair. These results of dynamic control of light in a programmable and scalable electro-optic system open doors to applications in microwave signal processing, quantum photonic gates in the frequency domain and exploring concepts in optical computing and topological physics.
关键词： topological physics,coherent control,optical computing,microring resonators,lithium niobate,optical storage,microwave excitation,photonic molecule,quantum photonics
更新于2025-09-04 15:30:14
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Metasurface with pull
摘要： Using light to manipulate small particles has proven an indispensable tool for ‘tweezing’, sorting and force measurements. To achieve effective optical traps with high ‘stiffness’, researchers often go to great lengths to tailor light fields, for example by using holographic elements. Now, Aliaksandra Ivinskaya and colleagues from Russia, the USA, the UK and Israel predict that small particles can be manipulated using a plane wave of light and a simple flat surface of an anisotropic media supporting hyperbolic modes. Their hyperbolic metamaterial is composed of metal and dielectric layers and is potentially less affected by losses and offers more broadband capability than purely plasmonic approaches. In their theoretical study a small dielectric sphere near a hyperbolic metamaterial is considered. The particle is sufficiently small to provide the required momentum to excite both surface plasmon and bulk hyperbolic waves from incident plane waves. Strong optical pulling forces were predicted over the 400–800 nm wavelength range thanks to the broadband high density of states of hyperbolic modes.
关键词： metasurface,hyperbolic modes,plasmon,nano-optics,optical manipulation
更新于2025-09-04 15:30:14
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Consequences of Ultra-Violet Irradiation on the Mechanical Properties of Spider Silk
摘要： The outstanding combination of high tensile strength and extensibility of spider silk is believed to contribute to the material’s toughness. Thus, there is great interest in engineering silk for biomedical products such as suture or implants. Additionally, over the years, many studies have also sought to enhance the mechanical properties of spider silk for wider applicability, e.g., by irradiating the material using ultra-violet radiation. However, the limitations surrounding the use of ultra-violet radiation for enhancing the mechanical properties of spider silk are not well-understood. Here, we have analyzed the mechanical properties of spider silk at short ultra-violet irradiation duration. Specimens of spider silk were subjected to ultra-violet irradiation (254-nm wavelength, i.e. UVC) for 10, 20, and 30 min, respectively, followed by tensile test to rupture to determine the strength (maximum stress), extensibility (rupture strain), and toughness (strain energy density to rupture). Controls, i.e., specimens that did not received UVC, were also subjected to tensile test to rupture to determine the respective mechanical properties. One-way analysis of variance reveals that these properties decrease significantly (p < 0.05) with increasing irradiation duration. Among the three mechanical parameters, the strength of the spider silk degrades most rapidly; the extensibility of the spider silk degrades the slowest. Overall, these changes correspond to the observed surface modifications as well as the bond rupture between the peptide chains of the treated silk. Altogether, this simple but comprehensive study provides some key insights into the dependence of the mechanical properties on ultra-violet irradiation duration.
关键词： bond crosslinks,bond scission,extensibility,toughness,strength
更新于2025-09-04 15:30:14
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Photodetection probability in quantum systems with arbitrarily strong light-matter interaction
摘要： Cavity-QED systems have recently reached a regime where the light-matter interaction strength amounts to a non-negligible fraction of the resonance frequencies of the bare subsystems. In this regime, it is known that the usual normal-order correlation functions for the cavity-photon operators fail to describe both the rate and the statistics of emitted photons. Following Glauber’s original approach, we derive a simple and general quantum theory of photodetection, valid for arbitrary light-matter interaction strengths. Our derivation uses Fermi’s golden rule, together with an expansion of system operators in the eigenbasis of the interacting light-matter system, to arrive at the correct photodetection probabilities. We consider both narrow- and wide-band photodetectors. Our description is also valid for point-like detectors placed inside the optical cavity. As an application, we propose a gedanken experiment confirming the virtual nature of the bare excitations that enrich the ground state of the quantum Rabi model.
关键词： Cavity-QED,light-matter interaction,ultrastrong coupling,quantum Rabi model,photodetection
更新于2025-09-04 15:30:14
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Creation of Superhydrophobic and Superhydrophilic Surfaces on ABS Employing a Nanosecond Laser
摘要： A nanosecond green laser was employed to obtain both superhydrophobic and superhydrophilic surfaces on a white commercial acrylonitrile-butadiene-styrene copolymer (ABS). These wetting behaviors were directly related to a laser-induced superficial modification. A predefined pattern was not produced by the laser, rather, the entire surface was covered with laser pulses at 1200 DPI by placing the sample at different positions along the focal axis. The changes were related to the laser fluence used in each case. The highest fluence, on the focal position, induced a drastic heating of the material surface, and this enabled the melted material to flow, thus leading to an almost flat superhydrophilic surface. By contrast, the use of a lower fluence by placing the sample 0.8 μm out of the focal position led to a poor material flow and a fast cooling that froze in a rugged superhydrophobic surface. Contact angles higher than 150? and roll angles of less than 10? were obtained. These wetting behaviors were stable over time.
关键词： superhydrophilic,superhydrophobic,surface wettability,nanosecond laser surface modification,ABS (Acrylonitrile-Butadiene-Styrene)
更新于2025-09-04 15:30:14
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Tunnel spectroscopy of localised electronic states in hexagonal boron nitride
摘要： Hexagonal boron nitride is a large band gap layered crystal, frequently incorporated in van der Waals heterostructures as an insulating or tunnel barrier. Localised states with energies within its band gap can emit visible light, relevant to applications in nanophotonics and quantum information processing. However, they also give rise to conducting channels, which can induce electrical breakdown when a large voltage is applied. Here we use gated tunnel transistors to study resonant electron tunnelling through the localised states in few atomic-layer boron nitride barriers sandwiched between two monolayer graphene electrodes. The measurements are used to determine the energy, linewidth, tunnelling transmission probability, and depth within the barrier of more than 50 distinct localised states. A three-step process of electron percolation through two spatially separated localised states is also investigated.
关键词： quantum information processing,hexagonal boron nitride,tunnel spectroscopy,localised electronic states,graphene
更新于2025-09-04 15:30:14