Polarization-Sensitive Photodetector Based on High Crystallinity Quasi-1D BiSeI Nanowires Synthesized via Chemical Vapor Deposition.

Bismuth chalcohalides (BiSeI and BiSI), a class of superior light absorbers, have recently garnered great attention owing to their promise in constructing next-generation optoelectronic devices. However, to date, the photodetection application of bismuth chalcohalides is still limited due to the challenge in controllable preparation. Herein, the synthesis of large-scale quasi-1D BiSeI nanowires via chemical vapor deposition growth is reported. By precisely tuning the growth temperature and the Se supply, it can effectively control the growth thermodynamics and kinetics of BiSeI crystal, and thus achieve high purity quasi-1D BiSeI nanowires with high crystal quality, uniform diameter, and tunable domain length. Theory and optical characterizations of the quasi-1D BiSeI nanowires reveal an indirect bandgap of 1.57 eV with prominent optical linear dichroism. As a result, the quasi-1D BiSeI nanowire-based photodetector demonstrates a broadband photoresponse (400-800 nm) with high responsivity of 5880 mA W-1 , fast response speed of 0.11 ms and superior air stability. More importantly, the photodetector displays strong polarization sensitivity (anisotropic ratio = 1.77) under the 532 nm light irradiation. This work will provide important guides to the synthesis of other quais-1D metal chalcohalides and shed light on their potential in constructing novel multifunctional optoelectronic devices.

Coalescence Dynamics of a Droplet Impacting on a Rectangular Pixel for Inkjet Printing.

A droplet impacting on a rectangular pixel with an offset is prone to cause the liquid to spread out of the pixel and adhere to adjacent pixels in organic light-emitting diode (OLED) inkjet printing. Therefore, the coalescence of a droplet impacting on a rectangular pixel is crucial in understanding the reliable OLED inkjet printing. In this paper, an assumption is established that the rectangular coalescence process is divided into the fusion part and spread part. On this basis, a dynamics model is introduced to analyze the coalescence behavior of a droplet impacting on a rectangular pixel. According to the law of conservation of mass and energy, dynamic equations are developed to obtain the maximum spread length as a function of time. In addition, the volume of the fluid method is used to simulate coalescence dynamics of a droplet impacting on a rectangular pixel by using the software of FLUENT, and the analytical solutions are consistent with the simulation results. Furthermore, the effects of the positioning error and initial velocity on the coalescence dynamics are analyzed. The results show that small initial velocity and positioning error of the droplet are helpful for the reliable OLED inkjet printing.

Effect of Image Detection and Analysis and Hospice Nurse Mediated Aromatherapy on Pain in Patients with Advanced Cancer in Intelligent Medical Environment.

Objective: In order to better alleviate the pain symptoms of patients with advanced cancer, this study adopts image detection and analysis and hospice nurse mediated aromatherapy, so as to comprehensively understand the physical condition of patients with advanced cancer and finally implement the nursing scheme of aromatherapy. Methods: Sixty advanced cancer patients admitted to a tertiary and grade A oncology hospital in Jiangxi Province from December 2020 to March 2022 were selected. This study was randomized into trial and control groups. The control group contained 30 regular treatment patients and 30 regular nursing patients for advanced cancer patients, and the trial group performed a 28-day hospice care specialist nurse-mediated aromatherapy based on the control group. Pain and quality of life scores were measured before and after the intervention in both groups. The experimental group consisted of 30 cases, with the mean age of 58.2 years; the control group consisted of 30 cases, with the mean age of 58.6 years. Results: 60 patients with advanced cancer were selected for group comparison. The results showed that the effect of aromatherapy mediated by hospice nurse on pain score, QLQ-C30, index value of patients with advanced cancer (the experimental group) was better than that of patients with advanced cancer (the control group). Conclusion: Through retrospective analysis, we investigated the patients with advanced cancer and discussed the difference between conventional therapy and aromatherapy. The results showed that aromatherapy based on image detection and analysis and mediated by Anning nurses was helpful to alleviate the physical function of patients with advanced cancer and improve their quality of life, which provided a reference for clinical application.

Momentum-Dependent Oscillator Strength Crossover of Excitons and Plasmons in Two-Dimensional PtSe2.

The 1T-phase layered PtX2 chalcogenide has attracted widespread interest due to its thickness dependent metal-semiconductor transition driven by strong interlayer coupling. While the ground state properties of this paradigmatic material system have been widely explored, its fundamental excitation spectrum remains poorly understood. Here we combine first-principles calculations with momentum (q) resolved electron energy loss spectroscopy (q-EELS) to study the collective excitations in 1T-PtSe2 from the monolayer limit to the bulk. At finite momentum transfer, all the spectra are dominated by two distinct interband plasmons that disperse to higher energy with increasing q. Interestingly, the absence of long-range screening in the two-dimensional (2D) limit inhibits the formation of long wavelength plasmons. Consequently, in the small-q limit, excitations in monolayer PtSe2 are exclusively of excitonic nature, and the loss spectrum coincides with the optical spectrum. The qualitatively different momentum dependence of excitons and plasmons enables us to unambiguously disentangle their spectral fingerprints in the excited state spectrum of layered 1T-PtSe2. This will help to discern the charge carrier plasmon and locally map the optical conductivity and trace the layer-dependent semiconductor to metal transition in 1T-PtSe2 and other 2D materials.

Multiple 2D Phase Transformations in Monolayer Transition Metal Chalcogenides.

Phase transformation lies at the heart of materials science because it allows for the control of structural phases of solids with desired properties. It has long been a challenge to manipulate phase transformations in crystals at the nanoscale with designed interfaces and compositions. Here in situ electron microscopy is employed to fabricate novel 2D phases with different stoichiometries in monolayer MoS2 and MoSe2 . The multiphase transformations: MoS2  â†’ Mo4 S6 and MoSe2  â†’ Mo6 Se6 which are highly localized with atomically sharp boundaries are observed. Their atomic mechanisms are determined as chalcogen 2H ↔ 1T sliding, cation shift, and commensurate lattice reconstructions, resulting in decreasing direct bandgaps and even a semiconductor-metal transition. These results will be a paradigm for the manipulation of multiphase heterostructures with controlled compositions and sharp interfaces, which will guide the future phase engineered electronics and optoelectronics of metal chalcogenides.

Defect Engineering and Anisotropic Modulation of Ionic Transport in Perovskite Solid Electrolyte LixLa(1-x)/3NbO3.

Solid electrolytes, such as perovskite Li3xLa2/1-xTiO3, LixLa(1-x)/3NbO3 and garnet Li7La3Zr2O12 ceramic oxides, have attracted extensive attention in lithium-ion battery research due to their good chemical stability and the improvability of their ionic conductivity with great potential in solid electrolyte battery applications. These solid oxides eliminate safety issues and cycling instability, which are common challenges in the current commercial lithium-ion batteries based on organic liquid electrolytes. However, in practical applications, structural disorders such as point defects and grain boundaries play a dominating role in the ionic transport of these solid electrolytes, where defect engineering to tailor or improve the ionic conductive property is still seldom reported. Here, we demonstrate a defect engineering approach to alter the ionic conductive channels in LixLa(1-x)/3NbO3 (x = 0.1~0.13) electrolytes based on the rearrangements of La sites through a quenching process. The changes in the occupancy and interstitial defects of La ions lead to anisotropic modulation of ionic conductivity with the increase in quenching temperatures. Our trial in this work on the defect engineering of quenched electrolytes will offer opportunities to optimize ionic conductivity and benefit the solid electrolyte battery applications.

Tunable Doping of Rhenium and Vanadium into Transition Metal Dichalcogenides for Two-Dimensional Electronics.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with unique electrical properties are fascinating materials used for future electronics. However, the strong Fermi level pinning effect at the interface of TMDCs and metal electrodes always leads to high contact resistance, which seriously hinders their application in 2D electronics. One effective way to overcome this is to use metallic TMDCs or transferred metal electrodes as van der Waals (vdW) contacts. Alternatively, using highly conductive doped TMDCs will have a profound impact on the contact engineering of 2D electronics. Here, a novel chemical vapor deposition (CVD) using mixed molten salts is established for vapor-liquid-solid growth of high-quality rhenium (Re) and vanadium (V) doped TMDC monolayers with high controllability and reproducibility. A tunable semiconductor to metal transition is observed in the Re- and V-doped TMDCs. Electrical conductivity increases up to a factor of 108 in the degenerate V-doped WS2 and WSe2 . Using V-doped WSe2 as vdW contact, the on-state current and on/off ratio of WSe2 -based field-effect transistors have been substantially improved (from ≈10-8 to 10-5 A; ≈104 to 108 ), compared to metal contacts. Future studies on lateral contacts and interconnects using doped TMDCs will pave the way for 2D integrated circuits and flexible electronics.

Deciphering the Intense Postgap Absorptions of Monolayer Transition Metal Dichalcogenides.

Rich valleytronics and diverse defect-induced or interlayer pre-bandgap excitonics have been extensively studied in transition metal dichalcogenides (TMDCs), a system with fascinating optical physics. However, more intense high-energy absorption peaks (∼3 eV) above the bandgaps used to be long ignored and their underlying physical origin remains to be unveiled. Here, we employ momentum resolved electron energy loss spectroscopy to measure the dispersive behaviors of the valley excitons and intense higher-energy peaks at finite momenta. Combined with accurate Bethe-Salpeter equation calculations, non-band-nesting transitions at the Q valley and at the midpoint of KM are found to be responsible for the high-energy broad absorption peaks in tungsten dichalcogenides and present spin polarizations similar to A excitons, in contrast with the band-nesting mechanism in molybdenum dichalcogenides. Our experiment-theory joint research will offer insights into the physical origins and manipulation of the intense high-energy excitons in TMDC-based optoelectronic devices.

Seamlessly Splicing Metallic Sn x Mo1- x S2 at MoS2 Edge for Enhanced Photoelectrocatalytic Performance in Microreactor.

Accurate design of the 2D metal-semiconductor (M-S) heterostructure via the covalent combination of appropriate metallic and semiconducting materials is urgently needed for fabricating high-performance nanodevices and enhancing catalytic performance. Hence, the lateral epitaxial growth of M-S Sn x Mo1- x S2/MoS2 heterostructure is precisely prepared with in situ growth of metallic Sn x Mo1- x S2 by doping Sn atoms at semiconductor MoS2 edge via one-step chemical vapor deposition. The atomically sharp interface of this heterostructure exhibits clearly distinguished performance based on a series of characterizations. The oxygen evolution photoelectrocatalytic performance of the epitaxial M-S heterostructure is 2.5 times higher than that of pure MoS2 in microreactor, attributed to the efficient electron-hole separation and rapid charge transfer. This growth method provides a general strategy for fabricating seamless M-S lateral heterostructures by controllable doping heteroatoms. The M-S heterostructures show increased carrier migration rate and eliminated Fermi level pinning effect, contributing to their potential in devices and catalytic system.

Fabricating Dual-Atom Iron Catalysts for Efficient Oxygen Evolution Reaction: A Heteroatom Modulator Approach.

Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal-organic framework encapsulating a trinuclear FeIII 2 FeII complex (denoted as Fe3 ) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of FeII by other metal(II) ions (e.g., ZnII /CoII ) via synthesizing isostructural trinuclear-complex precursors (Fe2 Zn/Fe2 Co), namely the "heteroatom modulator approach", is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal-nitrogen moiety, clearly identified by direct transmission electron microscopy and X-ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal-metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities.

Nanoheterostructures of Partially Oxidized RuNi Alloy as Bifunctional Electrocatalysts for Overall Water Splitting.

Electrocatalytic water splitting, as one of the most promising methods to store renewable energy generated by intermittent sources, such as solar and wind energy, has attracted tremendous attention in recent years. Developing efficient, robust, and green catalysts for the hydrogen and oxygen evolution reactions (HER and OER) is of great interest. This study concerns a facile and green approach for producing RuNi/RuNi oxide nanoheterostructures by controllable partial oxidation of RuNi nanoalloy, which is characterized and confirmed by various techniques, including high-resolution transmission electron microscopy and synchrotron-based X-ray absorption spectroscopy. This nanoheterostructure demonstrates outstanding bifunctional activities for catalyzing the HER and OER with overpotentials that are both among the lowest reported values. In a practical alkali-water-splitting electrolyzer, it also achieves a record-low cell voltage of 1.42 V at 10 mA cm-2 , which is significantly superior to the commercial RuO2 //Pt/C couple and other reported bifunctional water-splitting electrocatalysts. Density functional theory calculations are employed to elaborate the effect of Ni incorporation. This simple catalyst preparation approach is expected to be transferrable to other electrocatalytic reactions.

Probing Exciton Dispersions of Freestanding Monolayer WSe_{2} by Momentum-Resolved Electron Energy-Loss Spectroscopy.

Excitons, as bound electron-hole paired quasiparticle, play an essential role in the energy transport in the optical-electric properties of semiconductors. Their momentum-energy dispersion relation is a fundamental physical property of great significance to understand exciton dynamics. However, this dispersion is seldom explored especially in two-dimensional transition metal dichalcogenides with rich valleytronic properties. In this work, momentum resolved electron energy-loss spectroscopy was used to measure the dispersions of excitons in freestanding monolayer WSe_{2}. Besides the parabolically dispersed valley excitons, a subgap dispersive exciton was observed at nonzero momenta for the first time, which can be introduced by the prolific Se vacancies. Our work provides a paradigm to directly probe exciton dispersions in 2D semiconductors and could be generalized to many low-dimensional systems.

Fabrication of a Spherical Superstructure of Carbon Nanorods.

Hierarchical superstructures in nano/microsize have attracted great attention owing to their wide potential applications. Herein, a self-templated strategy is presented for the synthesis of a spherical superstructure of carbon nanorods (SS-CNR) in micrometers through the morphology-preserved thermal transformation of a spherical superstructure of metal-organic framework nanorods (SS-MOFNR). The self-ordered SS-MOFNR with a chestnut-shell-like superstructure composed of 1D MOF nanorods on the shell is synthesized by a hydrothermal transformation process from crystalline MOF nanoparticles. After carbonization in argon, the hierarchical SS-MOFNR transforms into SS-CNR, which preserves the original chestnut-shell-like superstructure with 1D porous carbon nanorods on the shell. Taking the advantage of this functional superstructure, SS-CNR immobilized with ultrafine palladium (Pd) nanoparticles (Pd@SS-CNR) exhibits excellent catalytic activity for formic acid dehydrogenation. This synthetic strategy provides a facile method to synthesize uniform spherical superstructures constructed from 1D MOF nanorods or carbon nanorods for applications in catalysis and energy storage.

Synthesis of Large-Size 1T' ReS2x Se2(1-x) Alloy Monolayer with Tunable Bandgap and Carrier Type.

Chemical vapor deposition growth of 1T' ReS2x Se2(1-x) alloy monolayers is reported for the first time. The composition and the corresponding bandgap of the alloy can be continuously tuned from ReSe2 (1.32 eV) to ReS2 (1.62 eV) by precisely controlling the growth conditions. Atomic-resolution scanning transmission electron microscopy reveals an interesting local atomic distribution in ReS2x Se2(1-x) alloy, where S and Se atoms are selectively occupied at different X sites in each Re-X6 octahedral unit cell with perfect matching between their atomic radius and space size of each X site. This structure is much attractive as it can induce the generation of highly desired localized electronic states in the 2D surface. The carrier type, threshold voltage, and carrier mobility of the alloy-based field effect transistors can be systematically modulated by tuning the alloy composition. Especially, for the first time the fully tunable conductivity of ReS2x Se2(1-x) alloys from n-type to bipolar and p-type is realized. Owing to the 1T' structure of ReS2x Se2(1-x) alloys, they exhibit strong anisotropic optical, electrical, and photoelectric properties. The controllable growth of monolayer ReS2x Se2(1-x) alloy with tunable bandgaps and electrical properties as well as superior anisotropic feature provides the feasibility for designing multifunctional 2D optoelectronic devices.

Inversion Domain Boundary Induced Stacking and Bandstructure Diversity in Bilayer MoSe2.

Interlayer rotation and stacking were recently demonstrated as effective strategies for tuning physical properties of various two-dimensional materials. The latter strategy was mostly realized in heterostructures with continuously varied stacking orders, which obscure the revelation of the intrinsic role of a certain stacking order in its physical properties. Here, we introduce inversion-domain-boundaries into molecular-beam-epitaxy grown MoSe2 homobilayers, which induce uncommon fractional lattice translations to their surrounding domains, accounting for the observed diversity of large-area and uniform stacking sequences. Low-symmetry stacking orders were observed using scanning transmission electron microscopy and detailed geometries were identified by density functional theory. A linear relation was also revealed between interlayer distance and stacking energy. These stacking sequences yield various energy alignments between the valence states at the Γ and K points of the Brillouin zone, showing stacking-dependent bandgaps and valence band tail states in the measured scanning tunneling spectroscopy. These results may benefit the design of two-dimensional multilayers with manipulable stacking orders.

Health-related quality of life of cancer patients with peripherally inserted central catheter: a pilot study.

INTRODUCTION: This pilot exploratory study aimed to compare the health-related quality of life (HRQOL) among patients diagnosed with different types of cancer receiving peripherally inserted central catheters (PICCs). METHODS: A multicenter cross-section study of cancer patients with PICCs was performed from February 1, 2013 to April 24, 2014. The primary objective of this study was to compare HRQOL in different cancer type patients with PICC. HRQOL was examined based on European Organisation for Research and Treatment of Cancer Quality-of-Life Questionnaire-Core 30 (EORTC QLQ-C30). Multiple linear regression models were conducted for coping with potential confounding variables. We also examined PICC-related quality of daily life with a self-made questionnaire. RESULTS: Three hundred and fifty-seven cancer patients with PICC completed the survey in nine teaching hospitals. Lung cancer patients with PICC reported the worst dyspnea. Digestive tract cancer patients reported the worst appetite loss. Patients with hematologic malignancy reported the worst emotional, social function, fatigue and financial impact. Breast cancer patients reported better HRQOL. Baseline variables were proven not significant predictors of EORTC QLQ-C30 global health status. In self-made survey, pain after PICC insertion was null or a little in 98.6% of cancer patients. Limitation of upper extremity activity was null or a little in 94.1% of patients. CONCLUSIONS: HRQOL varies in different types of cancer patients with PICC. PICC may have a low impact on cancer patients' HRQOL. Further large sample studies are needed.

Atomistic dynamics of sulfur-deficient high-symmetry grain boundaries in molybdenum disulfide.

As a common type of structural defect, grain boundaries (GBs) play an important role in tailoring the physical and chemical properties of bulk crystals and their two-dimensional (2D) counterparts such as graphene and molybdenum disulfide (MoS2). In this study, we explore the atomic structures and dynamics of three kinds of high-symmetry GBs (α, ß and γ) in monolayer MoS2. Atomic-resolution transmission electron microscopy (TEM) is used to characterize their formation and evolutionary dynamics, and atomistic simulation based analysis explains the size distribution of α-type GBs observed under TEM and the inter-GB interaction, revealing the stabilization mechanism of GBs by pre-existing sulfur vacancies. The results elucidate the correlation between the observed GB dynamics and the migration of sulfur atoms across GBs via a vacancy-mediated mechanism, offering a new perspective for GB engineering in monolayer MoS2, which may be generalized to other transition metal dichalcogenides.

Direct Imaging of Kinetic Pathways of Atomic Diffusion in Monolayer Molybdenum Disulfide.

Direct observation of atomic migration both on and below surfaces is a long-standing but important challenge in materials science as diffusion is one of the most elementary processes essential to many vital material behaviors. Probing the kinetic pathways, including metastable or even transition states involved down to atomic scale, holds the key to the underlying physical mechanisms. Here, we applied aberration-corrected transmission electron microscopy (TEM) to demonstrate direct atomic-scale imaging and quasi-real-time tracking of diffusion of Mo adatoms and vacancies in monolayer MoS2, an important two-dimensional transition metal dichalcogenide (TMD) system. Preferred kinetic pathways and the migration potential-energy landscape are determined experimentally and confirmed theoretically. The resulting three-dimensional knowledge of the atomic configuration evolution reveals the different microscopic mechanisms responsible for the contrasting intrinsic diffusion rates for Mo adatoms and vacancies. The new insight will benefit our understanding of material processes such as phase transformation and heterogeneous catalysis.

High Mobility 2D Palladium Diselenide Field-Effect Transistors with Tunable Ambipolar Characteristics.

Due to the intriguing optical and electronic properties, 2D materials have attracted a lot of interest for the electronic and optoelectronic applications. Identifying new promising 2D materials will be rewarding toward the development of next generation 2D electronics. Here, palladium diselenide (PdSe2 ), a noble-transition metal dichalcogenide (TMDC), is introduced as a promising high mobility 2D material into the fast growing 2D community. Field-effect transistors (FETs) based on ultrathin PdSe2 show intrinsic ambipolar characteristic. The polarity of the FET can be tuned. After vacuum annealing, the authors find PdSe2 to exhibit electron-dominated transport with high mobility (µe (max) = 216 cm2 V-1 s-1 ) and on/off ratio up to 103 . Hole-dominated-transport PdSe2 can be obtained by molecular doping using F4 -TCNQ. This pioneer work on PdSe2 will spark interests in the less explored regime of noble-TMDCs.

Atomic Defects in Two-Dimensional Materials: From Single-Atom Spectroscopy to Functionalities in Opto-/Electronics, Nanomagnetism, and Catalysis.

Two-dimensional layered graphene-like crystals including transition-metal dichalcogenides (TMDs) have received extensive research interest due to their diverse electronic, valleytronic, and chemical properties, with the corresponding optoelectronics and catalysis application being actively explored. However, the recent surge in two-dimensional materials science is accompanied by equally great challenges, such as defect engineering in large-scale sample synthesis. It is necessary to elucidate the effect of structural defects on the electronic properties in order to develop an application-specific strategy for defect engineering. Here, two aspects of the existing knowledge of native defects in two-dimensional crystals are reviewed. One is the point defects emerging in graphene and hexagonal boron nitride, as probed by atomically resolved electron microscopy, and their local electronic properties, as measured by single-atom electron energy-loss spectroscopy. The other will focus on the point defects in TMDs and their influence on the electronic structure, photoluminescence, and electric transport properties. This review of atomic defects in two-dimensional materials will offer a clear picture of the defect physics involved to demonstrate the local modulation of the electronic properties and possible benefits in potential applications in magnetism and catalysis.