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B4C‒15 vol% TiB2 composites were fabricated by in situ reactive spark plasma sintering with B4C, TiC, and amorphous B powders as the raw materials. The size coupling of initial B4C and TiC particles was optimized based on the reaction mechanism to derive B4C‒TiB2 composites with enhanced microstructure and properties. During the reactive sintering, fine B4C–TiB2 particles were firstly formed by an in situ reaction between TiC and B. Then, large B4C particles tended to grow at the cost of small B4C particles. The in situ TiB2 grains gradually grew up and interconnect, distributing around the large B4C grains to form an intergranular TiB2 network. The results showed that the B4C‒15 vol% TiB2 composite prepared from 3.12 μm B4C powder and 0.80 μm TiC powder had the optimal comprehensive properties, with a relative density of 99.50%, a Vickers hardness of 31.84 GPa, a flexural strength of 780 MPa, a fracture toughness of 5.77 MPa·m1/2, as well as an electrical resistivity of 3.01 × 10−2 Ω·cm. [ABSTRACT FROM AUTHOR]

Sintering method greatly affects the sintering behavior, microstructure and properties of the ceramic composites. In the present work, TiB 2 – h -BN composites prepared by reactive spark plasma sintering (RSPS) and conventional spark plasma sintering (CSPS) are compared. Due to the in-situ synthesized TiB 2 and h -BN particles during sintering process, the reactive sintering not only inhibits the orientation of TiB 2 grains but also prevented the formation of the Card-house structure. TiB 2 – h -BN composites obtained by RSPS (R series) exhibit higher sintering activity and finer microstructure, which results in better mechanical performance than those prepared by CSPS (C series). As the SPS temperature is 1600 °C, the relative density of the composite in R series is as high as 97.3%, much higher than that (89.3%) in C series. The composite obtained by RSPS at 1600 °C also exhibits excellent mechanical properties with a bending strength of 205.3 MPa and a Vickers hardness of 2.50 GPa, respectively, which exceeds all composites prepared by CSPS at 1600–2000 °C. When the SPS temperature is 1800 °C or above, for both series, the increase of SPS temperature greatly enhances the Vickers hardness but has litter effect on the strength and electrical resistivity, which is attributed to the comprehensive effect of the density increase and microstructure coarsening. The present work indicates that in-situ reactive sintering has obvious advantages in preparing TiB 2 – h -BN composites with excellent mechanical properties at low temperature. [ABSTRACT FROM AUTHOR]

In this study, Si3N4−Si2N2O composite ceramics were prepared through a two‐step combination of the direct nitriding method and spark plasma sintering method with diamond‐wire saw silicon waste in the photovoltaic industry as raw material. The whole holding time at the constant temperature of the preparing process only lasts 35 min, in which the nitriding time only takes 30 min and the sintering time only takes 5 min. The effects of the Fe2O3 additive on the nitriding and sintering process were investigated in detail. The results show that the Fe2O3 additive accelerates the nitriding process by promoting the formation and diffusion of the gas phase and reducing the apparent activation energy of the reaction between the gas phase containing silicon and N2. Meanwhile, the Fe2O3 additive also promotes the sintering process by lowering the eutectic temperature of the SiO2−Al2O3 and the SiO2−Y2O3 binary system. The optimal technical parameters follow the nitriding temperature of 1400°C, the nitriding time of 30 min, the sintering temperature of 1800°C, and the sintering time of 5 min. The Si3N4−Si2N2O composite ceramic prepared under the above conditions exhibits good performance with an apparent porosity of 2.7%, Vickers hardness of 16.54 GPa, and fracture toughness of 4.1 MPa·m1/2. [ABSTRACT FROM AUTHOR]

Neuronal death occurs during cerebral ischemia. However, when hemoperfusion and oxygen supply are resumed to the ischemic focus of the brain tissue, the brain tissue damage is further aggravated, resulting in cerebral ischemia-reperfusion injury (CIRI) to the patients. Protein kinase C (PKC) plays an important role in CIRI. Through the IP3/DAG/Ca2+ signaling pathway, it promotes the influx of calcium ions in neurons and causes calcium overload, which aggravates the damage. At the same time, when brain cells are hypoxic, hypoxia-inducible factor-1 (HIF-1) is expressed, which regulates the expression of Bcl-2 and Bax through the PI3K/Akt signaling pathway and reduces nerve cell injury. It also fights hypoxic-ischemic injury by increasing the production of vascular endothelial growth factor (VEGF) to promote blood vessel formation. The PKC and HIF-1 signaling pathways are also linked to CIRI. HIF-1 activates the PKC and ERK pathways via the upregulation of VEGF, leading to increased Cx43 phosphorylation and dysfunction and aggravating CIRI. Existing studies have shown that certain traditional Chinese medicine (TCM) compounds regulate the PKC and HIF-1 signaling pathways and alleviate CIRI. These compounds downregulate the PKC and the activity of the PKC-related signaling pathways to alleviate CIRI. They can also promote the expression of HIF-1, increase the content of VEGF in ischemic tissues to promote the generation of blood vessels, and improve microcirculation. TCM compounds can inhibit the cascade of reactions underlying disease occurrence and development by targeting multiple components using different herbal formulations to improve the structural and material changes in the brain cells, which alleviate CIRI and protect the brain tissue. This study briefly describes the role of PKC and HIF-1, their relationship in CIRI, and the effect of TCM on them. [ABSTRACT FROM AUTHOR]

If not for its inherently weak opticalabsorption at visible andinfrared wavelengths, graphene would show exceptional promise foroptoelectronic applications. Here we show that by nanopatterning agraphene layer into an array of closely packed graphene nanodisks,its absorption efficiency can be increased from less than 3% to 30%in the infrared region of the spectrum. We examine the dependenceof the enhanced absorption on nanodisk size and interparticle spacing.By incorporating graphene nanodisk arrays into an active device, wedemonstrate that this enhanced absorption efficiency is voltage-tunable,indicating strong potential for nanopatterned graphene as an activemedium for infrared electro-optic devices. [ABSTRACT FROM AUTHOR]

In this article, we reviewed new designs for plasmonic nanostructure and its nanofocusing, coupling, resonance, and waveguide characterizations. With in-plane Fresnel zone plates, a 15 times field enhancement was achieved for the plasmonic nanofocusing. Plasmonic antennas placed at both ends of a single nanowire, consisting of a nanooptical circuit, was successfully realized in an enhanced plasmon coupling and emission. Plasmonic Fano resonance was also observed in a single sliced Ag nanodisk with the structure symmetry breaking. A hybrid plasmonic waveguide with a CdS nanoribbon placed on Ag surface showed an excellent mode confinement and energy low dissipation. More potential applications based on these plasmonic configurations are also discussed in this article. [ABSTRACT FROM AUTHOR]

When an Au nanoparticle in a liquidmedium is illuminated withresonant light of sufficient intensity, a nanometer scale envelopeof vapora “nanobubble”surrounding theparticle, is formed. This is the nanoscale onset of the well-knownprocess of liquid boiling, occurring at a single nanoparticle nucleationsite, resulting from the photothermal response of the nanoparticle.Here we examine bubble formation at an individual metallic nanoparticlein detail. Incipient nanobubble formation is observed by monitoringthe plasmon resonance shift of an individual, illuminated Au nanoparticle,when its local environment changes from liquid to vapor. The temperatureon the nanoparticle surface is monitored during this process, wherea dramatic temperature jump is observed as the nanoscale vapor layerthermally decouples the nanoparticle from the surrounding liquid.By increasing the intensity of the incident light or decreasing theinterparticle separation, we observe the formation of micrometer-sizedbubbles resulting from the coalescence of nanoparticle-“bound”vapor envelopes. These studies provide the first direct and quantitativeanalysis of the evolution of light-induced steam generation by nanoparticlesfrom the nanoscale to the macroscale, a process that is of fundamentalinterest for a growing number of applications. [ABSTRACT FROM AUTHOR]

Nanoscale antennas sandwiched between two graphene monolayersyielda photodetector that efficiently converts visible and near-infraredphotons into electrons with an 800% enhancement of the photocurrentrelative to the antennaless graphene device. The antenna contributesto the photocurrent in two ways: by the transfer of hot electronsgenerated in the antenna structure upon plasmon decay, as well asby direct plasmon-enhanced excitation of intrinsic graphene electronsdue to the antenna near field. This results in a graphene-based photodetectorachieving up to 20% internal quantum efficiency in the visible andnear-infrared regions of the spectrum. This device can serve as amodel for merging the light-harvesting characteristics of opticalfrequency antennas with the highly attractive transport propertiesof graphene in new optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, we propose and simulate the surface plasmon polariton nanofocusing process by using Finite-difference Time-domain (FDTD) method. The maximum enhancement factor at the taper end area is optimized with different wavelength of the excitation laser. With the advantage of SNOM, the SPP nanofocusing is experimentally observed by illuminating the tapered CdS nanoribbon deposited on the Ag film. The SPP dispersion is used to predict the optimal taper angles of the structure. As the emission of the focused SPP at the taper end, the proposed plasmonic structure can be severed as a light nanosource emitter in the future optical integrated circuits. [ABSTRACT FROM AUTHOR]

The surface plasmon polariton (SPP) coupling and enhancement in silver nanowire–nanoantenna structure is proposed and simulated by using finite difference time domain method. The results demonstrate that three-arm antenna can effectively enhance the coupling efficiency at the incident end and the SPP field intensity at the emission end. The enhancement factor, which is defined as the ratio of the SPP field intensity at the emission end with and without the three-arm antenna, for the various antenna arm lengths and incident wavelengths under different incident angles are calculated. The suggested structure can be served as an enhanced plasmonic waveguide for the nanophotonic and plasmonic circuits in the future. [ABSTRACT FROM AUTHOR]

As topological charge constitutes an infinite‐dimensional Hilbert space, vortex beam has numerous applications in optical communications and other fields where signal capacity is a vital requirement. Multifunctional vortex beams, showing up to different controllable responses subjected to separate combinations of polarization states, have significantly exhibited improved capacity of signal transport. Relying on prior physical knowledge, complex requirement brings tremendous challenge to the design of multifunctional vortex beams. Here, a deep‐learning‐based platform for designing metasurfaces is proposed, which can intelligently generate predesigned multifunctional vortex beams. Employing the proposed strategy, the demonstrations of bifunctional and trifunctional vortex beams are consistent with the design targets. Three samples are fabricated and measured by a Michelson interferometer. Clear observed interference patterns revealed the topological nature of the generated vortex beams, unambiguously justifying the design platform. This intelligent design strategy, which may inspire new ideas in other scientific fields, lays a solid foundation for the high‐performance application of multifunctional vortex beams. This work fully exploits the potential of vortex beams for large‐scale dense data communication and quantum optics with high quantum numbers, which may further promote the development of the integrated photonic chip. [ABSTRACT FROM AUTHOR]

Charge transfer introduced by a conductive junction bridging a nanoparticle dimer can have a pronounced effect on the optical properties of the system. We have extended the plasmon hybridization model to include conductive junctions and charge transfer effects. From our model, we are able to derive all the plasmon resonances of the bridged dimer, including the charge transfer plasmon (CTP), and predict their trends when system parameters are varied. In particular, we find that CTP is a result of a sufficiently narrow monopole mode interacting with multipolar (including dipolar) modes. The screening arising from charge transfer induces a blueshift of the hybridized bonding dimer modes and decreases the electric field in the junction. Our model may serve as an important guide for optical properties of bridged nanoparticle aggregates. [ABSTRACT FROM AUTHOR]

[Display omitted] Martynoside (MAR), a bioactive component in several well-known tonic traditional Chinese herbs, exhibits pro-hematopoietic activity during 5-fluorouracil (5-FU) treatment. However, the molecular target and the mechanism of MAR are poorly understood. Here, by adopting the mRNA display with a library of even-distribution (md-LED) method, we systematically examined MAR-protein interactions in vitro and identified the ribosomal protein L27a (RPL27A) as a key cellular target of MAR. Structural and mutational analysis confirmed the specific interaction between MAR and the exon 4,5-encoded region of RPL27A. MAR attenuated 5-FU-induced cytotoxicity in bone marrow nucleated cells, increased RPL27A protein stability, and reduced the ubiquitination of RPL27A at lys92 (K92) and lys94 (K94). Disruption of MAR binding at key residues of RPL27A completely abolished the MAR-induced stabilization. Furthermore, by integrating label-free quantitative ubiquitination proteomics, transcriptomics, and ribosome function assays, we revealed that MAR restored RPL27A protein levels and thus rescued ribosome biogenesis impaired by 5-FU. Specifically, MAR increased mature ribosomal RNA (rRNA) abundance, prevented ribosomal protein degradation, facilitated ribosome assembly, and maintained nucleolar integrity. Collectively, our findings characterize the target of a component of Chinese medicine, reveal the importance of ribosome biogenesis in hematopoiesis, and open up a new direction for improving hematopoiesis by targeting RPL27A. [ABSTRACT FROM AUTHOR]

Smith–Purcell radiation (SPR) with broadly tunable spectra has attracted attention in light emission, and this free‐electron‐driven source shows great potential in illumination fields, such as terahertz sources, ultra‐compact light sources, free‐electron lasers, etc. However, it remains difficult to control the polarization properties of SPR and realize a free‐electron chiral light source. In this work, the chiral SPR with the maximum chirality (>40%) is acquired in a periodic stacked nanosquare light‐well, and the radiation chirality is manipulated by variations of the designed electron beam excitation positions. Furthermore, this work reveals that the chiroptical effect originates in the superposition of SPRs with different phases and polarization, which are derived from adjacent sidewalls. This work may deepen the comprehension of electron‐matter interaction and facilitate the development of compact electron‐driven chirality‐tunable source‐on‐chip, highlighting potential applications in photonic integration and binary data processing. [ABSTRACT FROM AUTHOR]

Devices operating with excitons have promising prospects for overcoming the dilemma of response time and integration in current generation of electron‐ or/and photon‐based elements and devices. In combination with the advantages of emerging twistronics and valleytronics, the atomically thin transition metal dichalcogenide semiconductors open up new opportunities for pursuing practical excitonic devices, where the strong exciton binding energy enables operating exciton at room temperature. The essential and foremost step toward exciton devices is the control of spatiotemporal exciton flux, which is density‐dependent and affected by the complex many‐body interactions. It can be effectively controlled by the strain, electric field, electron‐doping, and local dielectric environment. Intriguingly, exotic phenomena such as exciton condensation, electron‐hole liquid, exciton Hall effects, and exciton halo effects can be occurred in 2D exciton system, providing new possibilities for excitonic devices. Up to now, the proof‐of‐principle of room temperature exciton devices, including excitonic switching and transistor, exciton guides, and excitonic nanolaser, have been realized. Here the authors review the recent advances in molding 2D exciton flux from basic principle, manipulation, exotic phenomena to promising applications and discuss the opportunities and challenges in pushing the frontiers of room temperature excitonic devices. [ABSTRACT FROM AUTHOR]

Structural design is an important driving force for technological development in nanophotonics. To achieve better performance of nanophotonic devices, the freedom of structural design space needs to be expanded. Unsupervised learning algorithm in deep learning provides a great platform to expand design freedom of structures and avoid the "curse of dimensionality" effectively. It performs well on extracting important features from high‐dimensional data and excavating potential rules. In this work, an unsupervised convolutional neural network is built to inversely design nanostructures with unidirectional transmission. Near‐field information with high dimensions is recognized and extracted into a 2D feature space which maintains high physical continuity and maps to far‐field transmittance effectively. The feature space is further expanded to the whole space by optimistic Bayesian multisampling, from which nanostructures with transmittance over 95% forward while less than 40% backward are inversely designed. Moreover, the relation between near‐field information and far‐field transmittance is explored. A feasible design method of nanostructures is proposed based on unsupervised learning with design space expanded. This design mentality exhibits a way of extracting near‐field features to analyze far‐field spectra with deep learning algorithms, which is suitable for more abundant physical design and can be extended to other similar systems. [ABSTRACT FROM AUTHOR]

Abstract: CeO2 thin films were prepared via a sol–gel dip-coating process, and used as supports to prepare CuO/CeO2 model catalysts. The catalytic activity of the catalysts for low-temperature CO oxidation was investigated with a micro-reactor-GC system. X-ray diffraction (XRD) patterns indicate that the CeO2 films are of random orientation with dominant (111) texture, and Cu0.2Ni0.8O phase has formed in CuO/CeO2 model catalysts. The scanning electron microscopy (SEM) and scanning tunneling microscopy (STM) images show the CeO2 film surface is uniform and CuO exists in either cluster or crystal forms. CuO/CeO2/Ni has higher catalytic activity compared to CuO/CeO2/NiO/Ni. The synergistic interaction between CuO and CeO2 is the main factor responsible for high catalytic activity of CuO/CeO2 model catalysts. [Copyright &y& Elsevier]

Monolayered transition metal dichalcogenides (TMDs) are one kind of hexagonal 2D semiconductors with a direct bandgap structure. Due to the property of natural broken inversion symmetry in the lattice, the strong spin–orbit coupling of electrons in TMDs can induce degenerate levels with antiparallel spins in K and K′ valleys, which selectively respond with external light excitations. Surface plasmon resonance with efficient electromagnetic enhancement and near‐field coupling provides excellent potential opportunities to modulate valley emission of TMDs. Efforts have been devoted to investigating the interaction principles and applications of this research field. This review focuses on plasmonic modulation of valleytronic emission in TMDs with surface plasmon polaritons (SPP) and localized surface plasmons (LSP) based on different modulation principles, respectively, and discusses possible research directions for future device applications. [ABSTRACT FROM AUTHOR]

Spontaneous emission can be altered by external electromagnetic environment with the bridge of local density of optical states. Microcavities have been widely integrated to accelerate the irreversible spontaneous decay, known as the Purcell effect. However, the Purcell effect breaks down in the strong coupling regime, where the light‐matter interaction is not a perturbation to Fermi's golden rule. Here, it is found that the emission intensity of plasmon–exciton polaritons is asymmetrically dependent on the spectral detuning, confirming the collapse of Purcell effect in strongly coupled systems. Ultrafast nonradiative decays of polaritons play a significant role in revealing the polariton emission intensity. The nonradiative effect is not affected by the coherent energy exchange since final states of nonradiative decays are optically dark and decoupled from Rabi oscillations. Moreover, the nonradiative effect is still valid under intermediate coupling and agrees with the Purcell effect, which suggests its universality at a variety of coupling regimes. This study opens up a successful approach to investigate spontaneous emission in cavity quantum electrodynamics, which is insightful to photonic and opto‐electronic applications based on exciton‐polaritons. [ABSTRACT FROM AUTHOR]

It has been revealed that inversion symmetry breaking in graphene could induce non-trivial Berry curvature, which leads to topologically protected valleytronic applications. Here, we propose an active controllable way of realizing the inversion symmetry breaking of single layer graphene, which is induced by the contrasted AB sub-lattice charge polarization. Our theory model indicates the split of in-plane optical phonons (iTO/iLO) at Γ point is the direct result of inversion symmetry breaking in single layer graphene. Density functional theory calculation was used to quantify the sub-lattice charge polarization and the split of iTO/iLO phonons under the external in-plane electric field, which was further confirmed by Raman spectroscopy. We believe that the method of symmetry manipulation by external in-plane electric field advances fundamental comprehension for the inner mechanism of topological phase transition of graphene. We propose a controllable method to induce topological phase transition of graphene into topological non-trivial material in the way of symmetry manipulation by inducing sub-lattice contrasted charge polarization in the shape of in-plane external electric field. With Raman spectroscopy, the difference between ITO and ILO phonon can be measured. We demonstrate the split of G-peak is proportional to in-plane electric field strength applied on graphene, which is confirmed by theoretical calculation and experiments. Image 1 [ABSTRACT FROM AUTHOR]

Metasurfaces are made of two-dimensional arrays of subwavelength nanostructures that form a spatially varying optical response, to control the wave fronts of optical waves. As the feature size of its constituent materials is nanoscale, investigation of the light-nanostructure interactions in the near field is critical for understanding the novel properties of metasurfaces. Here, we used a scanning near-field optical microscope (SNOM) to observe the near-field distribution of surface plasmon polaritons (SPPs) from a ring-shaped metasurface under illumination of circularly polarized light. It was found that with an additional degree of freedom of the geometric phase provided by the regularly arranged metamolecules, control over the near-field interference of the SPPs can be achieved, which is governed by the metasurface geometric symmetry that can be tuned by its topological charge. Meanwhile, the planar chiral character of the metamolecules exerts a deep influence on the near-field interference patterns. Our results can pave the way for active control of SPP propagation in near fields and have potential applications in highly integrated optical communication systems. [ABSTRACT FROM AUTHOR]

Graphical abstract We realize the efficient modulation of relaxation channels in MoS 2 monolayers and interfacial electron transfer by forming mixed-dimensional VdW heterostructures with graphene quantum dots (GQDs) and find that the cascaded relaxation of hot electrons in GQDs that originate from the quantum confinement effect is the ultimate reason. With femtosecond pump–probe spectroscopy, the biphasic electron injection model and modified rate equations are employed to quantitatively solve the interfacial dynamics. Abstract Van der Waals (VdW) heterostructures have emerged as promising materials for atomically thin optoelectronic and photovoltaic applications, where the efficient charge separation after photo-excitation is significant to enhance device performances. However, modulating the interfacial charge transfer is still challenging due to the weak interlayer VdW interaction. Revealing electron transfer and relaxation processes in heterostructures lays foundation to tune the interfacial dynamics and optoelectronic properties. Here, we realize the efficient modulation of relaxation channels in MoS 2 monolayers and interfacial electron transfer by forming mixed-dimensional VdW heterostructures with graphene quantum dots (GQDs). With femtosecond pump–probe spectroscopy, the biphasic electron injection model and modified rate equations are employed to quantitatively solve interfacial transfer rates of mixed-dimensional VdW heterostructures. We find that the cascaded relaxation of hot electrons in GQDs that originates from the quantum confinement effect can intensively affect the interfacial dynamics. Our established model is instructive to optimize performances of future photon-harvesting devices based on mixed low-dimensional heterostructures. [ABSTRACT FROM AUTHOR]

Abstract: Plasmonic nanostructures have demonstrated a remarkable ability to control light in ways never observed in nature, as the optical response is closely linked to their flexible geometric design. Due to lack of mirror symmetry, chiral nanostructures allow twisted electric field “hotspots” to form at the material surface. These hotspots depend strongly on the optical wavelength and nanostructure geometry. Understanding the properties of these chiral hotspots is crucial for their applications; for instance, in enhancing the optical interactions with chiral molecules. Here, the results of an elegant experiment are presented: by designing 35 intermediate geometries, the structure is “enantiomorphed” from one handedness to the other, passing through an achiral geometry. Nonlinear multiphoton microscopy is used to demonstrate a new kind of double‐bisignate circular dichroism due to enantiomorphing, rather than wavelength change. From group theory, a fundamental origin of this plasmonic chiroptical response is proposed. The analysis allows the optimization of plasmonic chiroptical materials. [ABSTRACT FROM AUTHOR]

Abstract: Organic–inorganic hybrid perovskite photodetectors have been reported to possess superior optoelectronic properties, such as high sensitivity, ultrafast response, and capability of strongly absorbing the light in the visible range. While in the near‐infrared range, the performances of these photodetectors deteriorate seriously, originating from the weak coupling of infrared light to the perovskites. In this study, an organic–inorganic hybrid perovskite photodetector on arrays of Au nanostructures is fabricated, which exhibits a remarkable photocurrent enhancement in the visible and near‐infrared range, ascribed to the huge localized electric field induced by the surface plasmon resonance of Au nanostructures. The maximum external quantum efficiency of this photodetector is as high as about 65%, 2.5 times that on a usual Si/SiO2 substrate without Au nanostructures. Obviously, by exploiting Au nanostructures, the light harvesting ability of the photodetector breaks through the perovskite absorption edge, and extends to the near‐infrared range. [ABSTRACT FROM AUTHOR]

Abstract: With the evergrowing demand for miniaturization of photonic devices, the integration of different functionalities in a single module is highly desired for the next generation of ultracompact photonic devices. Optical modules based on the near field and scattered far field are both key elements in the construction of nanophotonic devices. However, integrating the near‐ and far‐field functionalities into a single module is a great challenge, which hinders the integration and minimization of optical devices. Here, a bifunctional integrated near‐ and far‐field optical launcher with a single metasurface structure is theoretically proposed and experimentally demonstrated, where the unidirectional launching of surface plasmon polaritons (SPPs) and the focusing of scattered far fields can be simultaneously achieved. Moreover, the SPP propagating direction and the real/virtual focus of the far‐field scattering can be actively controlled by the spin state of the incident light. With the additional degree of freedom provided by the positions of the metasurface elements, the optical performances of this bifunctional structure can be compared to the one with single functionality. The work provides a new platform for the integration and control of different optical components at subwavelength scale, and opens a way to design multifunctional optical devices for the future. [ABSTRACT FROM AUTHOR]

The article focuses on a study regarding controlled growth and shape-directed self-assembly of gold nano arrows. It mentions that superstructures offers notable opportunities to create functional devices and artificial materials with unusual properties. It also mentions that anisotropic nanoparticles with no spherical shapes like rods, plates, polyhedra, and multipods offers range of ordered superlattices.

Double peaks at wavelength of 276 and 290 nm are observed for AlGaN/AlGaN multiple quantum wells (MQWs). Cathodoluminescence (CL) mappings identify that the emission at 290 nm originates from the macrostep edges. Potential minima induced by local variation of QW thickness and Ga incorporation are found along the step edges, where quantum wires (QWRs) are formed. The lateral advance rate of macrostep (∼310 nm/h) is obtained by investigating the distribution of QWRs. Temperature-dependent CL spectrum suggest that thermal quenching for 290 nm emission is dramatically suppressed compared with that for conventional QWs emission, which shows excitonic localization characteristics of QWRs. [ABSTRACT FROM AUTHOR]

Abstract Heterostructures from two-dimensional transition-metal dichalcogenides MX 2 have emerged as a hot topic in recent years due to their various fascinating properties. Here, we investigated the temperature dependent Raman and photoluminescence (PL) spectra in vertical stacked WS 2 /MoS 2 monolayer heterostructures. Our result shows that both E1 2g and A 1g modes of WS 2 and MoS 2 vary linearly with temperature increasing from 300 to 642 K. The PL measurement also reveals strong temperature dependencies of the PL intensity and peak position. The activation energy of the thermal quenching of the PL emission has been found to be equal to 69.6 meV. The temperature dependence of the peak energy well follows the band-gap shrinkage of bulk semiconductor. [ABSTRACT FROM AUTHOR]

Plasmon-induced hot-electron generation provides an efficient way to convert light into electric current. The investigation of the optoelectronic response in two-dimensional materials and metallic hybrid nanostructure attracts increasing research interest. Here, we present a tunneling effect of plasmonic hot electrons that is generated from Au nanoparticles, which can vertically tunnel through graphene monolayers. A strong photocurrent induced by the hot electrons was measured in this graphene-based vertical photodetector with its intensity maximum reached at the plasmon resonance wavelength. The tunneling effect of plasmonic hot electrons was investigated by gradually increasing the incident laser power and bias voltage between the top and bottom electrodes. The dynamic attenuation of plasmonic hot electrons in an excited state was further investigated with multilayered graphene sheets. These results show that our vertical hybrid structure can function as an effective design for the tunneling photodetector, and enable the realization of complex nanophotonic devices that are based on graphene and other 2D materials, such as optical transistors and plasmonic hot-electron sensors. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenides are becoming attractive materials for novel photoelectric and photovoltaic applications due to their excellent optoelectric properties and accessible optical bandgap in the near-infrared to visible range. Devices utilizing 2D materials integrated with metal nanostructures have recently emerged as efficient schemes for hot electron-based photodetection. Metal-semiconductor heterostructures with low cost, simple procedure, and fast response time are crucial for the practical applications of optoelectric devices. In this paper, template-based sputtering method is used first to fabricate Au nanoantenna (NA)/MoS2 heterostructures with low cost, simple preparation, broad spectral response, and fast response time. Through the measurement of femtosecond pump-probe spectroscopy, it is demonstrated that plasmon-induced hot electron transfer takes place in the Au NA/MoS2 heterostructure on the order of 200 fs with an injected electron density of about 5.6 × 1012 cm−2. Moreover, the pump-power-dependent photoluminescence spectra confirm that the exciton energy of MoS2 can be enhanced, coupled, and reradiated by the Au NA. Such ultrafast plasmon-induced hot electron transfer in the metal-semiconductor heterostructure can enable novel 2D devices for light harvesting and photoelectric conversion. [ABSTRACT FROM AUTHOR]

Recently, reflectionless or low‐reflection surfaces made of subwavelength structures have been of broad interest in practical engineering. Here, a single‐layer terahertz metasurface is proposed to produce ultralow reflections across a broad‐frequency spectrum and wide incidence angles by controlling the reflection phases of subwavelength structures. To enable full control of the phase range in a continuous band, a combination of two different subwavelength elements are employed, both of which exhibit weak interactions with the incident terahertz waves, thereby showing high local reflectivities near the operating frequency. An optimization method is utilized to determine the array pattern with the minimum overall reflections under the illumination of plane waves. Both numerical simulations and experimental results demonstrate ultralow reflections of terahertz waves by the metasurface over a broad frequency band and wide incidence angles. By using the proposed metasurface, the far‐field scattering patterns of metallic objects can be efficiently controlled, which opens up a new route for low‐reflection surface designs in the terahertz spectrum. [ABSTRACT FROM AUTHOR]

Plasmonic toroidal resonance has attracted growing interests because of its low loss electromagnetic properties and potential high sensitive nanophotonic applications. However, the realization in a metamaterial requires three-dimensional complicated structural design so far. In this paper, we design a simple metal-dielectric-metal (MIM) sandwich nanostructure, which exhibits a strong toroidal dipolar resonance under radially polarized excitation. The toroidal dipole moment as the dominant contribution for the scattering is demonstrated by the mirror-image method and further analyzed by Lagrangian hybridization model. The proposed toroidal configuration also shows a highly tolerant for misalignment between the structure center and the incident light focus. Our study proves the way for the toroidal plasmonic application with the cylindrical vector beams. [ABSTRACT FROM AUTHOR]

Single photon counting compressive imaging, a very efficient implementation of compressed sensing theory in photon counting imaging, offers the advantages of low cost and ultra-high sensitivity. However, when performing high-resolution imaging, single photon counting compressive imaging needs a long imaging time due to a lot of measurements and a large amount of image reconstruction calculations. In this paper, we demonstrate a single-photon counting compressed imaging system based a novel sampling and reconstruction integrated deep network. We call this network BF2C-Net. A binarized fully-connected layer is specially designed as the first layer of the network and trained out as a binary measurement matrix that can be directly loaded on the DMD to perform efficiently compressive sampling. The remaining layers of the network except the first layer are used to quickly reconstruct the compressed sensing image. The effects of compression sampling rate, measurement matrix and reconstruction algorithm on imaging performance are compared. The experimental results show that the BF2C-Net significantly outperforms existing iterative method and most other deep learning-based methods. [ABSTRACT FROM AUTHOR]

With great advances in wet chemical synthesis of nanoparticles (NPs), plasmonic NPs with various sizes and morphologies are easily available nowadays and demonstrate great potentials in optical, electronic, and biomedical applications. Plasmonic circular dichroism (CD), relating to circular dichroism responses at localized surface plasmon resonance of metal nanostructures, has emerged as a research direction of plasmonics with promising prospects in enantioselective catalysis, chiral separation, and ultrasensitive detections. Herein, plasmonic CD responses of gold nanoparticle based nanostructures are summarized. Two kinds of plasmonic CD phenomena are investigated: structural CD and induced CD. Structural CD is the response from chiral assemblies composed of plasmonic NPs with strong dipole–dipole interactions. Induced CD is the response of nonchiral plasmonic NPs with chiral molecules attached at surface. The weak CD is the result of Coulomb interaction between chiral molecules and plasmonic NPs. Efforts on how to achieve strong CD signals for these two configurations by using chiral molecules and Au nanoparticles are reported. The fabrication of chiral nanostructures, tuning and amplification of CD responses, CD‐based biosensors, chiral catalysis, and future perspectives are presented. The importance of the shape anisotropy of gold nanorods in the generation and amplification of CD signals is especially highlighted. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) photodetectors with high responsivity and fast response are crucial for practical applications. Double perovskite Cs2AgBiBr6 has emerged as a promising optoelectronic material due to its excellent physics and photoelectric properties. However, no work is reported based on its film for photodetector applications. Herein, an ITO/SnO2/Cs2AgBiBr6/Au hole‐transport layer free planar heterojunction device is fabricated for photodetector application. The device is self‐powered with two responsivity peaks at 350 and 435 nm, which is suitable for ultraviolet‐A (320–400 nm) and deep‐blue light detecting. A high responsivity of 0.11 A W−1 at 350 nm and a quick response time of less than 3 ms are obtained, which is significantly higher than other semiconductor oxide heterojunction‐based UV detectors. More importantly, the stability is significantly better than most of the hybrid perovskite photodetectors reported so far. Its photocurrent shows no obvious degradation after more than 6 months storage in ambient conditions without any encapsulation. Consequently, the utilization of Cs2AgBiBr6 film is a practical approach for high performance, large‐area lead‐free perovskite photodetector applications. For the mechanism, it is found that photogenerated carriers in Cs2AgBiBr6 film are separated at the Cs2AgBiBr6/SnO2 heterojunction interface by its built‐in field. The low toxicity and high stability of this double perovskite active layer make it very promising for practical applications. A high‐quality lead‐free double perovskite Cs2AgBiBr6 film based self‐powered photo‐detector is successfully demonstrated. The device with Cs2AgBiBr6/SnO2 heterojunction shows good wavelength selectivity for UV‐A and blue light. As an UV detector, its performance is much higher than other semiconductor oxide heterojunction‐based devices. In addition, this device has excellent stability in ambient conditions. It is believed that the double perovskite Cs2AgBiBr6 film based photodetector can be commercialized due to its low toxicity and excellent intrinsic stability. [ABSTRACT FROM AUTHOR]

On page 6394, Z. Y. Fang and co‐workers apply a femtosecond pumping‐probe technique to measure electron transfer of synthesized AU nanoantenna (NA)/MoS2 heterostructures. The results indicate an ultrafast optical response time and a high cutoff frequency for devices based on this heterostructure. Combining the optoelectric properties of MoS2 with the plasmonic properties of Au NAs holds great promise for photodetectors and photovoltaics. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is widely used as light trapping schemes in solar cells, because it can concentrate light fields surrounding metal nanostructures and realize light management at the nanoscale. SPR in photovoltaics generally occurs at the metal/dielectric interfaces. A well-defined interface is therefore required to elucidate interfacial SPR processes. Here, we designed a photovoltaic device (PVD) with an atomically flat TiO2 dielectric/dye/graphene/metal nanoparticle (NP) interface for quantitatively studying the SPR enhancement of the photovoltaic conversion. Theoretical and experimental results indicated that the graphene monolayer was transparent to the electromagnetic field. This transparency led to significant substrate-induced plasmonic hybridization at the heterostructure interface. Combined with interparticle plasmonic coupling, the substrate-induced plasmonics concentrated light at the interface and enhanced the photo-excitation of dyes, thus improving the photoelectric conversion. Such a mechanistic understanding of interfacial plasmonic enhancement will further promote the development of efficient plasmon-enhanced solar cells and composite photocatalysts. [ABSTRACT FROM AUTHOR]

Free-standing graphitic C3N4 nanosheets are prepared by liquid phase exfoliation from graphitic C3N4 powders dispersed in various solvents such as isopropanol, N-methylpyrrolidone, water, ethanol, or acetone (sonication for 10 h). [ABSTRACT FROM AUTHOR]