Truly form-factor-free industrially scalable system integration for electronic textile architectures with multifunctional fiber devices.

An integrated textile electronic system is reported here, enabling a truly free form factor system via textile manufacturing integration of fiber-based electronic components. Intelligent and smart systems require freedom of form factor, unrestricted design, and unlimited scale. Initial attempts to develop conductive fibers and textile electronics failed to achieve reliable integration and performance required for industrial-scale manufacturing of technical textiles by standard weaving technologies. Here, we present a textile electronic system with functional one-dimensional devices, including fiber photodetectors (as an input device), fiber supercapacitors (as an energy storage device), fiber field-effect transistors (as an electronic driving device), and fiber quantum dot light-emitting diodes (as an output device). As a proof of concept applicable to smart homes, a textile electronic system composed of multiple functional fiber components is demonstrated, enabling luminance modulation and letter indication depending on sunlight intensity.

InP/ZnS quantum dot photoluminescence modulation via in situ H2S interface engineering.

InP quantum dots (QDs) are attracting significant interest as a potentially less toxic alternative to Cd-based QDs in many research areas. Although InP-based core/shell QDs with excellent photoluminescence properties have been reported so far, sophisticated interface treatment to eliminate defects is often necessary. Herein, using aminophosphine as a seeding source of phosphorus, we find that H2S can be efficiently generated from the reaction between a thiol and an alkylamine at high temperatures. Apart from general comprehension that H2S acts as a S precursor, it is revealed that with core etching by H2S, the interface between InP and ZnS can be reconstructed with S2- incorporation. Such a transition layer can reduce inherent defects at the interface, resulting in significant photoluminescence (PL) enhancement. Meanwhile, the size of the InP core could be further controlled by H2S etching, which offers a feasible process to obtain wide band gap InP-based QDs with blue emission.

Optoelectronic system and device integration for quantum-dot light-emitting diode white lighting with computational design framework.

We propose a computational design framework to design the architecture of a white lighting system having multiple pixelated patterns of electric-field-driven quantum dot light-emitting diodes. The quantum dot of the white lighting system has been optimised by a system-level combinatorial colour optimisation process with the Nelder-Mead algorithm used for machine learning. The layout of quantum dot patterns is designed precisely using rigorous device-level charge transport simulation with an electric-field dependent charge injection model. A theoretical maximum of 97% colour rendering index has been achieved with red, green, cyan, and blue quantum dot light-emitting diodes as primary colours. The white lighting system has been fabricated using the transfer printing technique to validate the computational design framework. It exhibits excellent lighting performance of 92% colour rendering index and wide colour temperature variation from 1612 K to 8903 K with only the four pixelated quantum dots as primary.

Smart textile lighting/display system with multifunctional fibre devices for large scale smart home and IoT applications.

Smart textiles consist of discrete devices fabricated from-or incorporated onto-fibres. Despite the tremendous progress in smart textiles for lighting/display applications, a large scale approach for a smart display system with integrated multifunctional devices in traditional textile platforms has yet to be demonstrated. Here we report the realisation of a fully operational 46-inch smart textile lighting/display system consisting of RGB fibrous LEDs coupled with multifunctional fibre devices that are capable of wireless power transmission, touch sensing, photodetection, environmental/biosignal monitoring, and energy storage. The smart textile display system exhibits full freedom of form factors, including flexibility, bendability, and rollability as a vivid RGB lighting/grey-level-controlled full colour display apparatus with embedded fibre devices that are configured to provide external stimuli detection. Our systematic design and integration strategies are transformational and provide the foundation for realising highly functional smart lighting/display textiles over large area for revolutionary applications on smart homes and internet of things (IoT).

Two newly identified Haematococcus strains efficiently accumulated radioactive cesium over higher astaxanthin production.

In this study, we investigated the morphological, genomic and bioaccumulation characteristics of two isolated Haematococcus strains (namely Goyang and Sogang), which were newly discovered in South Korea. Morphological analysis revealed that the isolated strains were unicellular and bi-flagellated green microalgae that formed thickened walls at the palmelloid or red-cyst phase. Phylogenetic analysis of 18S rRNA and rbcL gDNA sequences demonstrated that both strains were taxonomically related to the genus Haematococcus. The two strains showed growth pattern that was similar to a typical Haematococcus strain, and accumulated astaxanthin within 48 h of exposure to intensive light. Both red-cyst cells effectively removed radioactive cesium to more than 50% within 48 h from low-level cesium-contaminated water of 5 Bq/ml concentration. The cesium-accumulation mechanism is largely associated with the replacement of cellular potassium in thick cell walls during biouptake, and the cesium-removal rate highly depends on the corresponding astaxanthin accumulation involving the potassium-transporting protein (P-type ATPase).

Room Temperature Wafer-Scale Synthesis of Highly Transparent, Conductive CuS Nanosheet Films via a Simple Sulfur Adsorption-Corrosion Method.

The development of highly conductive electrodes with robust mechanical durability and clear transmittance in the visible to IR spectral range is of great importance for future wearable/flexible electronic applications. In particular, low resistivity, robust flexibility, and wide spectral transparency have a significant impact on optoelectronic performance. Herein, we introduce a new class of covellite copper monosulfide (CuS) nanosheet films as a promising candidate for soft transparent conductive electrodes (TCEs). An atmospheric sulfur adsorption-corrosion phenomenon represents a key approach in our work for the achievement of wafer-scale CuS nanosheet films through systematic control of the neat Cu layer thickness ranging from 2 to 10 nm multilayers at room temperature. These nanosheet films provide outstanding conductivity (∼25 Ω sq-1) and high transparency (> 80%) in the visible to infrared region as well as distinct flexibility and long stability under air exposure, yielding a high figure-of-merit (∼60) that is comparable to that of conventional rigid metal oxide material-based TCEs. Our unique room temperature synthesis process delivers high quality CuS nanosheets on any arbitrary substrates in a short time (< 1 min) scale, thus guaranteeing the widespread use of highly producible and scalable device fabrication.

Technology progress on quantum dot light-emitting diodes for next-generation displays.

Quantum dot light-emitting diodes (QD-LEDs) are widely recognised as great alternatives to organic light-emitting diodes (OLEDs) due to their enhanced performances. This focus article surveys the current progress on the state-of-the-art QD-LED technology including material synthesis, device optimization and innovative fabrication processes. A discussion on the material synthesis of core nanocrystals, shell layers and surface-binding ligands is presented for high photoluminescence quantum yield (PLQY) quantum dots (QDs) using heavy-metal free materials. The operational principles of several types of QD-LED device architectures are also covered, and the recent evolution of device engineering technologies is investigated. By exploring the fabrication process for pixel-patterning of QD-LEDs on an active-matrix backplane for full-colour display applications, we anticipate further improvement in device performance for the commercialisation of next-generation displays.

Robust In-Zn-O Thin-Film Transistors with a Bilayer Heterostructure Design and a Low-Temperature Fabrication Process Using Vacuum and Solution Deposited Layers.

We report on the design, fabrication, and characterization of heterostructure In-Zn-O (IZO) thin-film transistors (TFTs) with improved performance characteristics and robust operation. The heterostructure layer is fabricated by stacking a solution-processed IZO film on top of a buffer layer, which is deposited previously using an electron beam (e-beam) evaporator. A thin buffer layer at the dielectric interface can help to template the structure of the channel. The control of the precursors and of the solvent used during the sol-gel process can help lower the temperature needed for the sol-gel condensation reaction to proceed cleanly. This boosts the overall performance of the device with a significantly reduced subthreshold swing, a four-fold mobility increase, and a two-order of magnitude larger on/off ratio. Atomistic simulations of the a-IZO structure using molecular dynamics (both classical and ab initio) and hybrid density functional theory (DFT) calculations of the electronic structure reveal the potential atomic origin of these effects.

The value of CT, MRI, and PET-CT in detecting retropharyngeal lymph node metastasis of head and neck squamous cell carcinoma.

BACKGROUND: The diagnostic accuracies of the imaging studies should be clearly acknowledged in managing head and neck cancer patients; however, the accuracies of preoperative imaging studies in detecting retropharyngeal lymph node (RPLN) metastasis are still not clarified. This study was to evaluate diagnostic accuracies of computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET-CT) in detecting RPLN metastasis of head and neck squamous cell carcinomas. METHODS: For 123 patients who had performed RPLN dissection during the surgery of their squamous cell carcinoma of the head and neck, preoperative CT, MRI, and/or PET-CT were reviewed for RPLN metastasis in a blinded fashion by one experienced radiologist. Sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of each imaging modality were assessed, by comparing with the histopathologic findings of the resected RPLNs that served as the standard of reference. RESULTS: RPLNs were pathologically positive for metastasis in 43 of the 123 patients (35%). Sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy in detecting metastasis to RPLN were 65, 94, 85, 83, and 84% for CT; 74, 94, 87, 87 and 87% for MRI; 83, 93, 89, 89 and 89% for PET-CT, respectively. When all the three imaging modalities were considered together (n = 74), they offered sensitivity of 90%, specificity of 91%, positive predictive value of 87%, negative predictive value of 93%, and accuracy of 91%. CONCLUSIONS: The preoperative imaging studies offered relatively high specificity rates, but rather low sensitivity rates. The three imaging modalities altogether increased diagnostic accuracies, which highlights the potential of the three studies when used altogether can minimize missed diagnoses of RPLN metastasis.

Enhancement of Drought Tolerance in Cucumber Plants by Natural Carbon Materials.

Stress induced by climate change is a widespread and global phenomenon. Unexpected drought stress has a substantial effect on the growth and productivity of valuable crops. The effects of carbon materials on living organisms in response to abiotic stresses remain poorly understood. In this study, we proposed a new method for enhancing drought tolerance in cucumber (Cucumis sativus L.) using carbon nanotubes and natural carbon materials called shungite, which can be easily mixed into any soil. We analyzed the phenotype and physiological changes in cucumber plants grown under conditions of drought stress. Shungite-treated cucumber plants were healthier, with dark green leaves, than control plants when watering was withheld for 21 days. Furthermore, compared with the control cucumber group, in the shungite-treated plants, the monodehydroascorbate content of the leaf, which is a representative marker of oxidative damage, was 66% lower. In addition, major scavenger units of reactive oxygen species and related drought stress marker genes were significantly upregulated. These results indicate that successive pretreatment of soil with low-cost natural carbon material improved the tolerance of cucumber plants to drought stress.

Direct Epitaxial Synthesis of Selective Two-Dimensional Lateral Heterostructures.

Two-dimensional (2D) heterostructured or alloyed monolayers composed of transition metal dichalcogenides (TMDCs) have recently emerged as promising materials with great potential for atomically thin electronic applications. However, fabrication of such artificial TMDC heterostructures with a sharp interface and a large crystal size still remains a challenge because of the difficulty in controlling various growth parameters simultaneously during the growth process. Here, a facile synthetic protocol designed for the production of the lateral TMDC heterostructured and alloyed monolayers is presented. A chemical vapor deposition approach combined with solution-processed precursor deposition makes it possible to accurately control the sequential introduction time and the supersaturation levels of the vaporized precursors and thus reliably and exclusively produces selective and heterogeneous epitaxial growth of TMDC monolayer crystals. In addition, TMDC core/shell heterostructured (MoS2/alloy, alloy/WS2) or alloyed (Mo1-xWxS2) monolayers are also easily obtained with precisely controlled growth parameters, such as sulfur introduction timing and growth temperature. These results represent a significant step toward the development of various 2D materials with interesting properties.

Surface functionalization-induced photoresponse characteristics of monolayer MoS2 for fast flexible photodetectors.

Monolayered, semiconducting molybdenum disulfide (MoS2) is of considerable interest for its potential applications in next-generation flexible, wearable, and transparent photodetectors because it has outstanding physical properties coupled with unique atomically thin dimensions. However, there is still a lack of understanding in terms of the underlying mechanisms responsible for the photoresponse dynamics, which makes it difficult to identify the appropriate device design strategy for achieving a fast photoresponse time in MoS2 photodetectors. In this study, we investigate the importance of surface functionalization on controlling the charge carrier densities in a MoS2 monolayer and in turn the corresponding behavior of the photoresponse in relation to the position of the Fermi-level and the energy band structure. We find that the p-doping and n-doping, which is achieved through the surface functionalization of the MoS2 monolayer, leads to devices with different photoresponse behavior. Specifically, the MoS2 devices with surface functional groups contributing to p-doping exhibited a faster response time as well as higher sensitivity compared to that observed for the MoS2 devices with surface functional groups contributing to n-doping. We attribute this difference to the degree of bending in the energy bands at the metal-semiconductor junction as a result of shifting in the Fermi-level position, which influences the optoelectronic transport properties as well as the recombination dynamics leading to a low dark and thus high detectivity and fast decay time. Based upon these findings, we have also demonstrated the broad applicability of surface functionalization by fabricating a flexible MoS2 photodetector that shows an outstanding decay time of 0.7 s, which is the fastest response time observed in flexible MoS2 detectors ever reported.

Modeling Electrical Percolation to optimize the Electromechanical Properties of CNT/Polymer Composites in Highly Stretchable Fiber Strain Sensors.

A simulation model of electrical percolation through a three-dimensional network of curved CNTs is developed in order to analyze the electromechanical properties of a highly stretchable fiber strain sensor made of a CNT/polymer composite. Rigid-body movement of the curved CNTs within the polymer matrix is described analytically. Random arrangements of CNTs within the composite are generated by a Monte-Carlo simulation method and a union-find algorithm is utilized to investigate the network percolation. Consequently, the strain-induced resistance change curves are obtained in a wide strain range of the composite. In order to compare our model with experimental results, two CNT/polymer composite fibers were fabricated and tested as strain sensors. Their effective CNT volume fractions are estimated by comparing the experimental data with our simulation model. The results confirm that the proposed simulation model reproduces well the experimental data and is useful for predicting and optimizing the electromechanical characteristics of highly stretchable fiber strain sensors based on CNT/polymer composites.

Biosorption of radioactive cesium from contaminated water by microalgae Haematococcus pluvialis and Chlorella vulgaris.

The biosorption properties of water-soluble radioactive cesium (137Cs) by microalga Haematococcus pluvialis were evaluated with different cell conditions, and its cesium-uptake rate was compared with that by other microalgae, Chlorella vulgaris and Anabaena sp. Photo-induced H. pluvialis red cyst rapidly removed radioactive cesium from the solution by bioaccumulation. We showed that the effectiveness of 137Cs uptake is dependent on the specific cell condition of even the same microalgal species. While the H. pluvialis red cyst removed almost 95% of the soluble 137Cs in 48 h, both H. pluvialis intermediate cells and C. vulgaris showed 90% uptake efficiency of 137Cs with slow uptake rate. The energy dispersive spectrometer data demonstrated that the cesium uptake acceleration by inducing astaxanthin in H. pluvialis red cyst involves the cesium accumulation through the potassium transport channel. The long-term monitoring experiments of the cesium uptake showed that only 40% of 137Cs remained in collapsed H. pluvialis cell fragments after 12 months.

Consecutive Junction-Induced Efficient Charge Separation Mechanisms for High-Performance MoS2/Quantum Dot Phototransistors.

Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel concept involving the modulation of the built-in potential within the QD layers for creating a new hybrid MoS2/PbS QDs phototransistor with consecutive type II junctions. The effects of the built-in potential across the depletion region near the type II junction interface in the QD layers are found to improve the photoresponse as well as decrease the response times to 950 µs, which is the faster response time (by orders of magnitude) than that recorded for previously reported 2D/QD phototransistors. Also, by implementing an electric-field modulation of the MoS2 channel, our experimental results reveal that the detectivity can be as large as 1 × 1011 jones. This work demonstrates an important pathway toward designing hybrid phototransistors and mixed-dimensional van der Waals heterostructures.

Balancing Charge Carrier Transport in a Quantum Dot P-N Junction toward Hysteresis-Free High-Performance Solar Cells.

In a quantum dot solar cell (QDSC) that has an inverted structure, the QD layers form two different junctions between the electron transport layer (ETL) and the other semiconducting QD layer. Recent work on an inverted-structure QDSC has revealed that the junction between the QD layers is the dominant junction, rather than the junction between the ETL and the QD layers, which is in contrast to the conventional wisdom. However, to date, there have been a lack of systematic studies on the role and importance of the QD heterojunction structure on the behavior of the solar cell and the resulting device performance. In this study, we have systematically controlled the structure of the QD junction to balance charge transport, which demonstrates that the position of the junction has a significant effect on the hysteresis effect, fill factor, and solar cell performance and is attributed to balanced charge transport.

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.

Red green blue emissive lead sulfide quantum dots: heterogeneous synthesis and applications.

Visible emission colloidal quantum dots (QDs) have shown promise in optical and optoelectronic applications. These QDs are typically composed of relatively expensive elements in the form of indium, cadmium, and gallium since alternative candidate materials exhibiting similar properties are yet to be realized. Herein, for the first time, we report red green blue (RGB) photoluminescences with quantum yields of 18% from earth-abundant lead sulfide (PbS) QDs. The visible emissive property is mainly attributed to a high degree of crystallinity even for the extremely small QD sizes (1-3 nm), which is realized by employing a heterogeneous reaction methodology at high growth temperatures (>170 °C). We demonstrate that the proposed heterogeneous synthetic method can be extended to the synthesis of other metal chalcogenide QDs, such as zinc sulfide and zinc selenide, which are promising for future industrial applications. More importantly, benefiting from the enlarged band gaps, the as-prepared PbS solar cells show an impressive open circuit voltage (∼0.8 V) beyond that reported to date.

Parasellar Extension Grades and Surgical Extent in Endoscopic Endonasal Transsphenoidal Surgery for Pituitary Adenomas : A Single Surgeon's Consecutive Series with the Aspects of Reliability and Clinical Validity.

OBJECTIVE: The inter-rater reliability of the modified Knosp's classification was measured before the analysis. The clinical validity of the parasellar extension grading system was evaluated by investigating the extents of resection and complication rates among the grades in the endoscopic endonasal transsphenoidal surgery (EETS) for pituitary adenomas. METHODS: From November 2008 to August 2015, of the 286 patients who underwent EETS by the senior author, 208 were pituitary adenoma cases (146 non-functioning pituitary adenomas, 10 adrenocorticotropic hormone-secreting adenomas, 31 growth hormone-secreting adenomas, 17 prolactin-secreting adenomas, and 4 thyroid-stimulating hormone-secreting adenomas; 23 microadenomas, 174 macroadenomas, and 11 giant adenomas). Two neurosurgeons and a neuroradiologist independently measured the degree of parasellar extension on the preoperative sellar MRI according to the modified Knosp's classification. Inter-rater reliability was statistically assessed by measuring the intraclass correlation coefficient. The extents of resection were evaluated by comparison of the pre- and post-operative MR images; the neurovascular complications were assessed by reviewing the patients' medical records. The extent of resection was measured in each parasellar extension grade; thereafter, their statistical differences were calculated. RESULTS: The intraclass correlation coefficient value of reliability across the three raters amounted to 0.862. The gross total removal (GTR) rates achieved in each grade were 70.0, 69.8, 62.9, 21.4, 37.5, and 4.3% in Grades 0, 1, 2, 3A, 3B, and 4, respectively. A significant difference in the extent of resection was observed only between Grades 2 and 3A. In addition, significantly higher complication rates were observed in the groups above Grade 3A. CONCLUSION: Although the modified Knosp's classification system appears to be complex, its inter-rater reliability proves to be excellent. Regarding the clinical validity of the parasellar extension grading system, Grades 3A, 3B, and 4 have a negative predictive value for the GTR rate, with higher complication rates.

High Performance PbS Quantum Dot/Graphene Hybrid Solar Cell with Efficient Charge Extraction.

Hybrid colloidal quantum dot (CQD) solar cells are fabricated from multilayer stacks of lead sulfide (PbS) CQD and single layer graphene (SG). The inclusion of graphene interlayers is shown to increase power conversion efficiency by 9.18%. It is shown that the inclusion of conductive graphene enhances charge extraction in devices. Photoluminescence shows that graphene quenches emission from the quantum dot suggesting spontaneous charge transfer to graphene. CQD photodetectors exhibit increased photoresponse and improved transport properties. We propose that the CQD/SG hybrid structure is a route to make CQD thin films with improved charge extraction, therefore resulting in improved solar cell efficiency.