Facile fabrication of two-dimensional inorganic nanostructures and their conjugation to nanocrystals

Nanocomposites of two-dimensional (2D) inorganic nanosheets and inorganic nanocrystals are fabricated. Freestanding atomically flat gamma-AlOOH nanosheets (thickness <1 nm) are synthesized from a one-pot hydrothermal reaction. The freestanding and binder-free film composed of the gamma-AlOOH nanosheets is fabricated by sedimentation. Because they have positive zeta potentials in the pH range below ca. 9.3, the gamma-AlOOH nanosheets can function as positively charged 2D inorganic matrices in a broad pH range. By solution phase (pH 7.0) mixing of the gamma-AlOOH nanosheets (zeta potential: 30.7 +/- 0.8 mV) and inorganic nanocrystals with negative surface charge, including Au nanoparticles, Au nanorods, CdSe quantum dots, CdSe/CdS/ZnS quantum dots and CdSe nanorods, the nanocomposites are self-assembled via electrostatic interactions. Negatively charged inorganic nanostructures with a wide range of chemical compositions, shapes, sizes, surface ligands and adsorbates can be used as building blocks for gamma-AlOOH nanocomposites. Adsorption densities of inorganic nanocrystals on the nanocomposites can be controlled by varying concentrations of nanocrystal solutions. Nanocomposite films containing alternating layers of gamma-AlOOH and nanocrystals are obtained by a simple drop casting method.close3

Lung cancer with superior vena cava syndrome diagnosed by intravascular biopsy using EBUS-TBNA

AbstractSince superior vena cava syndrome (SVCS) is a critical condition, immediate diagnostic approach and therapy are imperative to avoid potentially life-threatening complications. Here, we report a case of lung cancer with SVCS, which was diagnosed through intravascular tumor biopsy using endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). EBUS-TBNA enabled us to obtain tissue sufficient for diagnosis, without significant complications. Prompt diagnosis was followed by appropriate anticancer treatment and improvement in the symptoms. For patients suspected of SVCS and requiring prompt pathologic diagnosis, we can consider EBUS-TBNA to diagnose intravascular or mediastinal tumors and provide an accurate diagnosis

Strain-Mediated Interlayer Coupling Effects on the Excitonic Behaviors in an Epitaxially Grown MoS2/WS2 van der Waals Heterobilayer.

van der Waals heterostructures composed of two different monolayer crystals have recently attracted attention as a powerful and versatile platform for studying fundamental physics, as well as having great potential in future functional devices because of the diversity in the band alignments and the unique interlayer coupling that occurs at the heterojunction interface. However, despite these attractive features, a fundamental understanding of the underlying physics accounting for the effect of interlayer coupling on the interactions between electrons, photons, and phonons in the stacked heterobilayer is still lacking. Here, we demonstrate a detailed analysis of the strain-dependent excitonic behavior of an epitaxially grown MoS2/WS2 vertical heterostructure under uniaxial tensile and compressive strain that enables the interlayer interactions to be modulated along with the electronic band structure. We find that the strain-modulated interlayer coupling directly affects the characteristic combined vibrational and excitonic properties of each monolayer in the heterobilayer. It is further revealed that the relative photoluminescence intensity ratio of WS2 to MoS2 in our heterobilayer increases monotonically with tensile strain and decreases with compressive strain. We attribute the strain-dependent emission behavior of the heterobilayer to the modulation of the band structure for each monolayer, which is dictated by the alterations in the band gap transitions. These findings present an important pathway toward designing heterostructures and flexible devices

Thermodynamically Stable Synthesis of Large-Scale and Highly Crystalline Transition Metal Dichalcogenide Monolayers and their Unipolar n-n Heterojunction Devices.

Transition metal dichalcogenide (TMDC) monolayers are considered to be potential materials for atomically thin electronics due to their unique electronic and optical properties. However, large-area and uniform growth of TMDC monolayers with large grain sizes is still a considerable challenge. This report presents a simple but effective approach for large-scale and highly crystalline molybdenum disulfide monolayers using a solution-processed precursor deposition. The low supersaturation level, triggered by the evaporation of an extremely thin precursor layer, reduces the nucleation density dramatically under a thermodynamically stable environment, yielding uniform and clean monolayer films and large crystal sizes up to 500 µm. As a result, the photoluminescence exhibits only a small full-width-half-maximum of 48 meV, comparable to that of exfoliated and suspended monolayer crystals. It is confirmed that this growth procedure can be extended to the synthesis of other TMDC monolayers, and robust MoS2 /WS2 heterojunction devices are easily prepared using this synthetic procedure due to the large-sized crystals. The heterojunction device shows a fast response time (≈45 ms) and a significantly high photoresponsivity (≈40 AW-1 ) because of the built-in potential and the majority-carrier transport at the n-n junction. These findings indicate an efficient pathway for the fabrication of high-performance 2D optoelectronic devices.European Research Council under the the European Union's Seventh Framework Programme (FP/2007-2013)/Grant Agreement no. 340538 (Project ‘UniQDS’) European Union under H2020 programme Grant Agreement no. 685758 (Project ‘1D-NEON’)

Heterojunction Area-Controlled Inorganic Nanocrystal Solar Cells Fabricated Using Supra-Quantum Dots

A supra-quantum dot (SQD) is a three-dimensional structure formed by the attachment of quantum dots. The SQDs have sizes of tens of nanometer and they maintain the characteristics of the individual quantum dots fairly well. Moreover, their sizes and elemental compositions can be tuned precisely. On the basis of their unique features, in this work, SQDs are used as constituents of the interpenetrating photoactive layers of inorganic nanocrystal p-n heterojunction solar cells to control the p-type and n-type domain sizes (i.e., p-n heterojunction areas) for optimizing the charge-carrier collection. SQD-containing p-n heterojunction solar cells exhibit improved charge transport and thereby higher power conversion efficiency (PCE) (3.03%) owing to their intermediate p-type and n-type domain sizes, which are between those of a bilayer nanorod p-n heterojunction solar cell (PCE: 1.21%) and an interpenetrating nanorod p-n heterojunction solar cell (PCE: 2.40%). This work demonstrates that the self-assembly of nanoscale materials can be utilized for tailoring the spatial distributions of charge carriers, which is beneficial for obtaining an enhanced device performance

p-Type Conductivity of Hydrated Amorphous V2O5 and Its Enhanced Photocatalytic Performance in ZnO/V2O5/rGO

Vanadium pentoxide (V2O5) is known to have natural n-type conductivity but transitions from n- to p-type conductivity when grown in a hydrated amorphous phase via atomic layer deposition. Compared with the intrinsic n-type character of V2O5, the hydrated amorphous V2O5 with artificial p-type conductivity has an increased work function difference, which can build stronger interface electric fields in ZnO/V2O5 heterojunction structures. This increased internal electric field strengthens the electron-hole separation across the heterojunction interface, which in turn improves the photocatalytic and photoelectrochemical performance of the structure. Using first-principles calculations, we found that when H2O molecules are incorporated into the amorphous V2O5 matrix, delocalized empty states are freshly formed above the valence band maximum in the hydrated amorphous V2O5, playing a crucial role in the transition of electrical conductivity within V2O5 This approach provides a simple and efficient way to discover new p-type materials and apply them to future p-n junction devices in terms of process simplicity and cost effectiveness

Experimental and Numerical Investigation of Solar Panels Deployment with Tape Spring Hinges Having Nonlinear Hysteresis with Friction Compensation

In this work, experimental and numerical investigation on the deployment of solar panels with tape spring (TS) hinges showing complex nonlinear hysteresis behavior caused by the snap-through buckling was conducted. Subsequently, it was verified by comparing simulation results by multi-body dynamics (MBD) analysis with test results on ground-based deployment testing considering gravity compensation, termed zero-gravity (Zero-G) device. It has been difficult to predict the folding and unfolding behavior of TS hinges because their moment–rotation relationship showed a nonlinear hysteresis behavior. To realize this attribute, an algorithm that checks the sign of angular velocity of the revolute joints was used to distinguish folding from unfolding. The nonlinear hysteresis was implemented in terms of two path-dependent nonlinear moment–rotation curves with the aid of the expression function (a kind of user subroutine) in MBD software RecurDyn. Finally, it was found that the results of the deployment analysis were in excellent agreement with those of the test when the friction torques of the revolute joints were properly identified by an inverse analysis with the test frames, thus validating the MBD model

Ultrafast Cation Exchange in Supra-Quantum Dots through Nanoporous Internal Structure

Cation exchange (CE) can convert the chemical composition of nanocrystals while it preserves their size, shape, and crystal phase. Here, we report a CE reaction in a porous nanostructure of supra-quantum dots (SQDs), which are threedimensional stepwise self-assembly of quantum dots (QDs) with several tens of nm size. It shows ultrafast and complete CE reactions in the SQDs from CdSe to Cu2-xSe or Ag2Se, conserving their size and shape. The complete suppression of the 1S excitonic peak of CdSe SQD and the complete conversion of their crystal structure and chemical composition dictate the complete CE reaction in SQDs even if it has near 100 nm diameter size. The conservation of size and shape after CE reactions reveals the existence of the internal void in porous SQDs which could compensate for the expected shrinkage or expansion due to the lattice constant change before and after CE reaction. The CE reaction rate of SQDs is estimated using temporal absorbance spectra in the course of CE reaction. The CE reaction rate of SQDs showed size-independent dynamics among the SQDs with various sizes from 63 to 83 nm. Their CE reaction rate was around 0.057 s-1 which is comparable to that of 4.8 nm sized QDs. For QDs, the reaction rate was critically size-dependent, showing slower CE reaction rate as their size increases. On the other hand, SQDs showed the CE reaction rate similar to those observed by QDs of 4-5 nm in size, which is phenomenal considering the size of SQDs at least 13 times larger than the QDs. Fully accessible external cations into the porous internal structure of SQDs and their direct interaction with the internal surface of SQDs can accelerate the CE reaction. The comparable primary unit size of SQDs, similar to 4 nm, to the size of QDs explains the ultrafast and size-independent CE reaction rate of SQDs.11Nsciescopu

Classification Model for Diabetic Foot, Necrotizing Fasciitis, and Osteomyelitis

Diabetic foot ulcers (DFUs) and their life-threatening complications, such as necrotizing fasciitis (NF) and osteomyelitis (OM), increase the healthcare cost, morbidity and mortality in patients with diabetes mellitus. While the early recognition of these complications could improve the clinical outcome of diabetic patients, it is not straightforward to achieve in the usual clinical settings. In this study, we proposed a classification model for diabetic foot, NF and OM. To select features for the classification model, multidisciplinary teams were organized and data were collected based on a literature search and automatic platform. A dataset of 1581 patients (728 diabetic foot, 76 NF, and 777 OM) was divided into training and validation datasets at a ratio of 7:3 to be analyzed. The final prediction models based on training dataset exhibited areas under the receiver operating curve (AUC) of the 0.80 and 0.73 for NF model and OM model, respectively, in validation sets. In conclusion, our classification models for NF and OM showed remarkable discriminatory power and easy applicability in patients with DFU