Abstract
The light–matter interaction in materials is of remarkable interest for various photonic and optoelectronic applications, which is intrinsically determined by the bandgap of the materials ...involved. To extend the applications beyond the bandgap limit, it is of great significance to study the light–matter interaction below the material bandgap. Here, we report the ultrafast transient absorption of monolayer molybdenum disulfide in its sub-bandgap region from ~0.86 µm to 1.4 µm. Even though this spectral range is below the bandgap, we observe a significant absorbance enhancement up to ~4.2% in the monolayer molybdenum disulfide (comparable to its absorption within the bandgap region) due to pump-induced absorption by the excited carrier states. The different rise times of the transient absorption at different wavelengths indicate the various contributions of the different carrier states (i.e., real carrier states in the short-wavelength region of ~<1 µm, and exciton states in the long wavelength region of ~>1 µm). Our results elucidate the fundamental understanding regarding the optical properties, excited carrier states, and carrier dynamics in the technologically important near-infrared region, which potentially leads to various photonic and optoelectronic applications (e.g., excited-state-based photodetectors and modulators) of two-dimensional materials and their heterostructures beyond their intrinsic bandgap limitations.
van der Waals (vdW) heterojunctions enable arbitrary combinations of different layered semiconductors with unique band structures, offering distinctive band engineering for photonic and ...optoelectronic devices with new functionalities and superior performance. Here, an interlayer photoresponse of a few‐layer MoSe2/WSe2 vdW heterojunction is reported. With proper electrical gating and bias, the heterojunction exhibits high‐sensitivity photodetection with the operation wavelength extended up to the telecommunication band (i.e. 1550 nm). The photoresponsivity and normalized photocurrent‐to‐dark current ratio reach up to 127 mA W−1 and 1.9 × 104 mW−1, respectively. The results not only provide a promising solution to realize high‐performance vdW telecommunication band photodetectors, but also pave the way for using sub‐bandgap engineering of two‐dimensional layered materials for photonic and optoelectronic applications.
van der Waals heterostructures are demonstrated as building blocks for photonics and optoelectronics. Herein, a sub‐bandgap photodetection at λ = 1550 nm based on a MoSe2/WSe2 heterojunction is demonstrated. The high responsivity as well as high normalized photocurrent‐to‐dark current ratio indicate that the heterojunction device has promising applications in future optoelectronic.
A confined electronic system can host a wide variety of fascinating electronic, magnetic, valleytronic and photonic phenomena due to its reduced symmetry and quantum confinement effect. For the ...recently emerging one-dimensional van der Waals (1D vdW) materials with electrons confined in 1D sub-units, an enormous variety of intriguing physical properties and functionalities can be expected. Here, we demonstrate the coexistence of giant linear/nonlinear optical anisotropy and high emission yield in fibrous red phosphorus (FRP), an exotic 1D vdW semiconductor with quasi-flat bands and a sizeable bandgap in the visible spectral range. The degree of photoluminescence (third-order nonlinear) anisotropy can reach 90% (86%), comparable to the best performance achieved so far. Meanwhile, the photoluminescence (third-harmonic generation) intensity in 1D vdW FRP is strong, with quantum efficiency (third-order susceptibility) four (three) times larger than that in the most well-known 2D vdW materials (e.g., MoS
). The concurrent realization of large linear/nonlinear optical anisotropy and emission intensity in 1D vdW FRP paves the way towards transforming the landscape of technological innovations in photonics and optoelectronics.
The objective of this study was to investigate the deformation and failure mechanism of silty slates loaded with an angle 0 and 90° between foliation and direction of uniaxial force. For this ...purpose, mineral composition and microstructure test, uniaxial compression test, acoustic emission (AE) monitoring and scanning electron microscope (SEM) were carried out on Silurian silty slates. Based on the results of tests to analyze the deformation and failure mechanism as well as the macroscopic failure modes, microscopic rupture surface characteristics and acoustic emission characteristics of silty slates under different test conditions. Tests results showed that the silty slates are mainly composed of clay minerals (chlorite and illite) and brittle minerals (quartz and feldspar) and in a layered structure. Under the two angles, silty slates specimens exhibited large differences in the deformation and damage process, macroscopic failure modes, microscopic rupture surface characteristics, deformation and failure mechanism. Besides, there are large differences in the relative parameters of AE event. These results reveal that there is a certain relationship between mechanisms of microscopic fractures and macro failure of silty slates.
Graphene has shown intriguing optical properties as a new class of plasmonic material in the terahertz regime. In particular, plasmonic modes in graphene nanostructures can be confined to a spatial ...size that is hundreds of times smaller than their corresponding wavelengths in vacuum. Here, we show numerically that by designing graphene nanostructures in such deep-subwavelength scales, one can obtain plasmonic modes with the desired radiative properties such as radiative and dark modes. By placing the radiative and dark modes in the vicinity of each other, we further demonstrate electromagnetically induced transparency (EIT), analogous to the atomic EIT. At the transparent window, there exist very large group delays, one order of magnitude larger than those offered by metal structures. The EIT spectrum can be further tuned electrically by applying a gate voltage. Our results suggest that the demonstrated EIT based on graphene plasmonics may offer new possibilities for applications in photonics.
The majority of Chinese people who are nearing the end of their lives prefer to receive home-based palliative care. Telehealth, as a new service model, has the potential to meet the increasing demand ...for this service, especially in remote areas with limited resources. However, nurse-led telehealth-based palliative care services are still in the pilot implementation phase. Assessing the telehealth readiness among palliative care specialist nurses and identifying associated factors is crucial to facilitate the successful implementation of telehealth services. Therefore, this study aimed to examine TH readiness and its related factors among Chinese palliative care specialist nurses.
Four hundred nine Chinese palliative care specialist nurses from 28 provinces or municipalities participated in this study between July and August 2022. The Chinese version of Telehealth Readiness Assessment Tools (TRAT-C), and Innovative Self-Efficacy Scale (ISES-C) were used to assess the degree of TH readiness and the levels of innovative self-efficacy.
The total score of the TRAT-C was 65.31 ± 9.09, and the total score of ISES was 29.27 ± 5.78. The statistically significant factors that influenced telehealth readiness were the experience of using telehealth platforms or services, the willingness to provide telehealth to patients, and the level of nurses' innovative self-efficacy. The innovative self-efficacy is positively correlated to telehealth readiness (r = 0.482, P < 0.01). These related factors could explain 27.3% of the difference in telehealth readiness.
The telehealth readiness of Chinese palliative care specialist nurses are at a moderate level. Measures such as providing incentives to promote nurses' innovation self-efficacy by nurse managers, and establishing a comprehensive telehealth training system for palliative care specialist nurses should be taken to facilitate the implementation of telehealth services in the field of palliative care.
The control of optical properties by electric means is the key to optoelectronic applications. For atomically thin two-dimensional (2D) materials, the natural advantage lies in that the carrier ...doping could be readily controlled through the electric gating effect, possibly affecting the optical properties. Exploiting this advantage, here we report the gate switching of the ultrafast upconverted photoluminescence from monolayer graphene. The luminescence can be completely switched off by the Pauli-blocking of one-photon interband transition in graphene with an on/off ratio exceeding 100, which is remarkable compared to other 2D semiconductors and 3D bulk counterparts. The chemical potential and pump fluence dependences of the luminescence are nicely described by a two-temperature model, including both the hot carrier dynamics and carrier-optical phonon interaction. This gate switchable and background-free photoluminescence can open up new opportunities for graphene-based ultrafast optoelectronic applications.
Abstract
Light modulation is of paramount importance for photonics and optoelectronics. Here we report all-optical coherent modulation of third-harmonic generation (THG) with chiral light via the ...symmetry enabled polarization selectivity. The concept is experimentally validated in monolayer materials (MoS
2
) with modulation depth approaching ~100%, ultra-fast modulation speed (<~130 fs), and wavelength-independence features. Moreover, the power and polarization of the incident optical beams can be used to tune the output chirality and modulation performance. Major performance of our demonstration reaches the fundamental limits of optical modulation: near-unity modulation depth, instantaneous speed (ultra-fast coherent interaction), compact footprint (atomic thickness), and unlimited operation bandwidth, which hold an ideal optical modulation solution for emerging and future nonlinear optical applications (e.g., interconnection, imaging, computing, and quantum technologies).
Soft rot causes significant economic losses in the kiwifruit industry. This study isolated strain CTXW 7-6-2 from healthy kiwifruit tissue; this was a gram-positive bacterium that produced the red ...pigment pulcherrimin. The phylogenetic tree based on 16S ribosomal RNA,
, and
gene sequences identified CTXW 7-6-2 as a strain of
. CTXW 7-6-2 inhibited hyphal growth of pathogenic fungi that cause kiwifruit soft rot, namely,
,
sp., and
, by 81.76, 69.80, and 32.03%, respectively. CTXW 7-6-2 caused the hyphal surface to become swollen and deformed. Volatile compounds (VOC) produced by the strain inhibited the growth of
and
sp. by 65.74 and 54.78%, respectively. Whole-genome sequencing revealed that CTXW 7-6-2 possessed a single circular chromosome of 4,221,676 bp that contained 4,428 protein-coding genes, with a guanine and cytosine (GC) content of 43.41%. Gene functions were annotated using the National Center for Biotechnology Information (NCBI) non-redundant protein, Swiss-Prot, Kyoto Encyclopedia of Genes and Genomes, Clusters of Orthologous Groups of proteins, Gene Ontology, Pathogen-Host Interactions, Carbohydrate-Active enZYmes, and Rapid Annotations using Subsystem Technology databases, revealing non-ribosomal pathways associated with antifungal mechanisms, biofilm formation, chemotactic motility, VOC 3-hydroxy-2-butanone, cell wall-associated enzymes, and synthesis of various secondary metabolites. antiSMASH analysis predicted that CTXW 7-6-2 can produce the active substances bacillaene, bacillibactin, subtilosin A, bacilysin, and luminmide and has four gene clusters of unknown function. Quantitative real-time PCR (qRT-PCR) analysis verified that
and
, key genes involved in the production of pulcherrimin, were highly expressed in CTXW 7-6-2. This study elucidates the mechanism by which
strain CTXW 7-6-2 inhibits pathogenic fungi that cause kiwifruit soft rot, suggesting the benefit of further studying its antifungal active substances.
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