bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficiency of Light Outcoupling Structures in Organic Light‐Emitting Diodes: 2D TiO2 Array as a Model System
Authors: Will Paul‐Anton , Schmidt Maximilian , Eckhardt Kai , Wisser Florian , Lenk Simone , Grothe Julia , Kaskel Stefan , Reineke Sebastian 
Published: March 2019

AbstractOrganic light‐emitting diodes (OLEDs) are widely used in research and are established in the industry. The building block nature of organic compounds enables a vast variety of materials. On top of that, there exist many strategies to improve the light outcoupling of OLEDs making a direct comparison of outcoupling technologies difficult. Here, a novel approach is introduced for the evaluation of light outcoupling structures. The new defined “efficiency of light outcoupling structures” (ELOS) clearly determines the effectiveness of the light outcoupling structure by weighting the experimental efficiency enhancement over the theoretical outcoupling gain. It neither depends on cavity design nor on the chosen organic material. The methodology is illustrated for red phosphorescent OLEDs comprising internal and external light outcoupling structures. Assumptions and further uses are discussed with respect to experimental and theoretical handling. In addition, the ELOS is calculated for various outcoupling techniques from literature to demonstrate the universality. Finally, most suitable reference OLEDs are discussed for application of light outcoupling structures. The presented approach enables new possibilities for studying light outcoupling structures and improves their comparability in a highly material‐driven research field.
Arbitrarily 3D Configurable Hygroscopic Robots with a Covalent–Noncovalent Interpenetrating Network and Self‐Healing Ability
Authors: Cao Jie , Zhou Changlin , Su Gehong , Zhang Xinxing , Zhou Tao , Zhou Zehang , Yang Yibo 
Published: March 2019

AbstractSoft materials that can reversibly transform shape in response to moisture have applications in diverse areas such as soft robotics and biomedicine. However, the design of a structurally transformable or mechanically self‐healing version of such a humidity‐responsive material, which can arbitrarily change shape and reconfigure its 3D structures remains challenging. Here, by drawing inspiration from a covalent–noncovalent network, an elaborately designed biopolyester is developed that features a simple hygroscopic actuation mechanism, straightforward manufacturability at low ambient temperature (≤35 °C), fast and stable response, robust mechanical properties, and excellent self‐healing ability. Diverse functions derived from various 3D shapes that can grasp, swing, close–open, lift, or transport an object are further demonstrated. This strategy of easy‐to‐process 3D structured self‐healing actuators is expected to combine with other actuation mechanisms to extend new possibilities in diverse practical applications.
Framework‐Porphyrin‐Derived Single‐Atom Bifunctional Oxygen Electrocatalysts and their Applications in Zn–Air Batteries
Authors: Li Bo‐Quan , Zhao Chang‐Xin , Chen Shuangming , Liu Jia‐Ning , Chen Xiao , Song Li , Zhang Qiang 
Published: March 2019

AbstractHigh‐performance bifunctional oxygen electrocatalysis constitutes the key technique for the widespread application of clean and sustainable energy through electrochemical devices such as rechargeable Zn–air batteries. Single‐atom electrocatalysts with maximum atom efficiency are highly considered as an alternative of the present noble‐metal‐based electrocatalysts. However, the fabrication of transition metal single‐atoms is very challenging, requiring extensive attempts of precursors with novel design principles. Herein, an all‐covalently constructed cobalt‐coordinated framework porphyrin with graphene hybridization is innovatively designed and prepared as the pyrolysis precursor to fabricate single‐atom Co–Nx–C electrocatalysts. Excellent electrochemical performances are realized for both bifunctional oxygen electrocatalysis and rechargeable Zn–air batteries with regard to reduced overpotentials, improved kinetics, and prolonged cycling stability comparable with noble‐metal‐based electrocatalysts. Design principles from multiple scales are proposed and rationalized with detailed mechanism investigation. This work not only provides a novel precursor for the fabrication of high‐performance single‐atom electrocatalysts, but also inspires further attempts to develop advanced materials and emerging applications.
Field Effect and Photoconduction in Au25 Nanoclusters Films
Authors: Galchenko Michael , Black Andrés , Heymann Leonard , Klinke Christian 
Published: March 2019

AbstractQuantum‐confined Au nanoclusters exhibit molecule‐like properties, including atomic precision and discrete energy levels. The electrical conductivity of Au nanocluster films can vary by several orders of magnitude and is determined by the strength of the electronic coupling between the individual nanoclusters in the film. Similar to quantum‐confined, semiconducting quantum dots, the electrical coupling in films is dependent on the size and structure of the Au core and the length and conjugation of the organic ligands surrounding it. Unlike quantum dots, however, semiconducting transport has not been reported in Au nanocluster films. Here, it is demonstrated that through a simple yet careful choice of cluster size and organic ligands, stable Au nanocluster films can electronically couple and become semiconducting, exhibiting electric field effect and photoconductivity. The molecule‐like nature of the Au nanoclusters is evidenced by a hopping transport mechanism reminiscent of doped, disordered organic semiconductor films. These results demonstrate the potential of metal nanoclusters as a solution‐processed material for semiconducting devices.
Structure and Charge Transport Properties of Cycloparaphenylene Monolayers on Graphite
Authors: Pérez‐Guardiola Andrés , Pérez‐Jiménez Ángel José , Muccioli Luca , Sancho‐García Juan Carlos 
Published: March 2019

AbstractThe nanoscale organization of cycloparaphenylene molecules when physisorbed on a graphite surface is theoretically investigated by means of atomistic molecular dynamics simulations employing a tailored and benchmarked force field. The landing of a single molecule is first considered, to progressively deposit more molecules to finally reach the full coverage of the surface. This protocol allows to study, consequently, the mechanism and structural pattern of their self‐aggregation. The interfacial morphologies obtained are then analyzed in terms of the electronic coupling between neighboring molecules, allowing thus to provide information about the associated charge‐transfer phenomena which could take place in these highly organized monomolecular layers.
Highly Sensitive and Ultrafast Responding Array Photodetector Based on a Newly Tailored 2D Lead Iodide Perovskite Crystal
Authors: Xu Zhiyun , Li Yaobin , Liu Xitao , Ji Chengmin , Chen Huaixi , Li Lina , Han Shiguo , Hong Maochun , Luo Junhua , Sun Zhihua 
Published: March 2019

Abstract2D organic–inorganic hybrid perovskites are emerging as the promising alternatives in photodetection, due to their unique merits stemming from intrinsic quantum‐confined structures. Despite great ongoing effects, highly sensitive and ultrafast responding photodetectors of 2D hybrid perovskites remain a huge blank. Here, the first nanosecond‐responsive array photodetector based on 2D perovskite crystals of (PA)2(G)Pb2I7 (where PA = n‐pentylaminium and G = guanidinium) is fabricated, which features a newly tailored bilayer motif with large‐size G cation as “perovskiter” inside the distorted PbI3 perovskite framework. This motif creates a new branch of the intriguing 2D hybrid perovskite family. Strikingly, both high photodetectivities (6.3 × 1012 Jones) and responsivities (≈47 A W−1), as well as low dark current (≈2.4 × 10−11 A), are achieved in this array photodetector. Further, its ultrafast response time (τ) of 3.1 ns is one of the record‐fast merits for 2D hybrid perovskites. Such attributes originate from its strong in‐plane photoresponse related to perovskite network and low dark current inhibited by the hopping barriers of insulating PA bilayers. All these characteristics make (PA)2(G)Pb2I7 a promising candidate for photodetection, and pave the way to explore new 2D hybrid perovskite candidates for future high‐performance optoelectronic devices.
Organocatalytic Michael/Michael Cycloaddition Enabled Asymmetric Construction of Hexahydroxanthones with Skeletal Diversity
Authors: Liu Xiong‐Li , Wei Qi‐Di , Zuo Xiong , Xu Sheng‐Wen , Yao Zhen , Wang Jun‐Xin , Zhou Ying 
Published: March 2019

AbstractA highly efficient strategy for stereocontrolled construction of potentially bioactive and structurally rigid isoxazole‐fused spirocyclohexane oxindole‐based hexahydroxanthones via an organocatalytic domino Michael/Michael cycloaddition of multifunctional chromone‐based oxindole as a 4C building block and 3‐methyl‐4‐nitro‐5‐alkenyl‐isoxazole as an activated Michael acceptor is reported. Complex and skeleton‐diversified hexahydroxanthones bearing five continuous stereocenters including one spiro quaternary carton center were smoothly afforded in up to 92% yield, >20:1 d.r. and >99% ee. Further transformation of the product into other potentially bioactive molecules has also been demonstrated. This method could also forge the libraries of medicinally relevant molecules with skeletal diversity, thus to facilitate the search for new bioactive entities.magnified image
Energy Harvesting‐Storage Bracelet Incorporating Electrochemical Microsupercapacitors Self‐Charged from a Single Hand Gesture
Authors: Zhang Steven L. , Jiang Qiu , Wu Zhiyi , Ding Wenbo , Zhang Lei , Alshareef Husam N. , Wang Zhong Lin 
Published: March 2019

AbstractThe development of wearable electronics and sensing networks has increased the demand for wearable power modules that have steady output, high energy density, and long cycle life. Current power modules, such as batteries, suffer from low energy density due to their limited storage capacity. One solution to avoid the issue is to build a hybrid device consisting of both energy harvesting elements that continuously harvest ambient mechanical energy, and electrochemical energy storage units to store the harvested energy. Here, a hybrid energy harvesting bracelet, which combines a dual electromagnetic and triboelectric nanogenerator to harvest wrist motions, is reported. The bracelet is able to charge the RuO2‐based microsupercapacitor to 2 V with a single shake of human wrist, which allows the supercapacitor to power most electronic devices for minutes, such as a calculator, relative humidity, and temperature sensors.
Capture and Catalytic Conversion of Polysulfides by In Situ Built TiO2‐MXene Heterostructures for Lithium–Sulfur Batteries
Authors: Jiao Long , Zhang Chen , Geng Chuannan , Wu Shichao , Li Huan , Lv Wei , Tao Ying , Chen Zijin , Zhou Guangmin , Li Jia , Ling Guowei , Wan Ying , Yang Quan‐Hong 
Published: March 2019

AbstractThe detrimental shuttle effect in lithium–sulfur batteries mainly results from the mobility of soluble polysulfide intermediates and their sluggish conversion kinetics. Herein, presented is a multifunctional catalyst with the merits of strong polysulfides adsorption ability, superior polysulfides conversion activity, high specific surface area, and electron conductivity by in situ crafting of the TiO2‐MXene (Ti3C2Tx) heterostructures. The uniformly distributed TiO2 on MXene sheets act as capturing centers to immobilize polysulfides, the hetero‐interface ensures rapid diffusion of anchored polysulfides from TiO2 to MXene, and the oxygen‐terminated MXene surface is endowed with high catalytic activity toward polysulfide conversion. The improved lithium–sulfur batteries deliver 800 mAh g−1 at 2 C and an ultralow capacity decay of 0.028% per cycle over 1000 cycles at 2 C. Even with a high sulfur loading of 5.1 mg cm−2, the capacity retention of 93% after 200 cycles is still maintained. This work sheds new insights into the design of high‐performance catalysts with manipulated chemical components and tailored surface chemistry to regulate polysulfides in Li–S batteries.
Dual mechanism model for fluid particle breakup in the entire turbulent spectrum
Authors: Karimi Mohsen , Andersson Ronnie 
Published: March 2019

AbstractThis work provides an in‐depth understanding of different breakup mechanisms for fluid particles in turbulent flows. All the disruptive and cohesive stresses are considered for the entire turbulent energy spectrum and their contributions to the breakup are evaluated. A new modeling framework is presented that bridges across turbulent subranges. The model entails different mechanisms for breakup by abandoning the classical limitation of inertial models. The predictions are validated with experiments encompassing both breakup regimes for droplets stabilized by internal viscosity and interfacial tension down to the micrometer length scale, which covers both the inertial and dissipation subranges. The model performance ensures the reliability of the framework, which involves different mechanisms. It retains the breakup rate for inertial models, improves the predictions for the transition region from inertia to dissipation, and bridges seamlessly to Kolmogorov‐sized droplets.
3D‐Printing of Functionally Graded Porous Materials Using On‐Demand Reconfigurable Microfluidics
Authors: Costantini Marco , Jaroszewicz Jakub , Kozoń Łukasz , Szlązak Karol , Święszkowski Wojciech , Garstecki Piotr , Stubenrauch Cosima , Barbetta Andrea , Guzowski Jan 
Published: March 2019

AbstractTailoring the morphology of macroporous structures remains one of the biggest challenges in material synthesis. Herein, we present an innovative approach for the fabrication of custom macroporous materials in which pore size varies throughout the structure by up to an order of magnitude. We employed a valve‐based flow‐focusing junction (vFF) in which the size of the orifice can be adjusted in real‐time (within tens of milliseconds) to generate foams with on‐line controlled bubble size. We used the junction to fabricate layered and smoothly graded porous structures with pore size varying in the range of 80–800 μm. Additionally, we mounted the vFF on top of an extrusion printer and 3D‐printed constructs characterized by a predefined 3D geometry and a controlled, spatially varying internal porous architecture, such as a model of a bone. The presented technology opens new possibilities in macroporous material synthesis with potential applications ranging from tissue engineering to aerospace industry and construction.
Continuous‐Flow Electrosynthesis of Benzofused S‐Heterocycles by Dehydrogenative C−S Cross‐Coupling
Authors: Huang Chong , Qian Xiang‐Yang , Xu Hai‐Chao 
Published: March 2019

AbstractReported herein is the synthesis of benzofused six‐membered S‐heterocycles by intramolecular dehydrogenative C−S coupling using a modular flow electrolysis cell. The continuous‐flow electrosynthesis not only ensures efficient product formation, but also obviates the need for transition‐metal catalysts, oxidizing reagents, and supporting electrolytes. Reaction scale‐up is conveniently achieved through extended electrolysis without changing the reaction conditions and equipment.
Enantioselective Synthesis of Biaryl Atropisomers by Pd‐Catalyzed C−H Olefination using Chiral Spiro Phosphoric Acid Ligands
Authors: Luo Jun , Zhang Tao , Wang Lei , Liao Gang , Yao Qi‐Jun , Wu Yong‐Jie , Zhan Bei‐Bei , Lan Yu , Lin Xu‐Feng , Shi Bing‐Feng 
Published: March 2019

AbstractThe discovery of proper ligands to simultaneously modulate the reactivity and effectively control the stereoselectivity is a central topic in the field of enantioselective C−H activation. Herein, we reported the synthesis of axially chiral biaryls by Pd‐catalyzed atroposelective C−H olefination. A novel chiral spiro phosphoric acid, STRIP, was identified as a superior ligand for this transformation. A broad range of axially chiral quinoline derivatives were synthesized in good yields with excellent enantioselectivities (up to 98 % ee). Density functional theory was used to gain a theoretical understanding of the enantioselectivities in this reaction.
Polymerization of rac‐Lactide Using Achiral Iron Complexes: Access to Thermally Stable Stereocomplexes
Authors: Marin Paul , Tschan Mathieu J.‐L. , Isnard Florence , Robert Carine , Haquette Pierre , Trivelli Xavier , Chamoreau Lise‐Marie , Guérineau Vincent , del Rosal Iker , Maron Laurent , Venditto Vincenzo , Thomas Christophe M. 
Published: March 2019

AbstractEnantiopure poly(lactic acid) (PLA) can form stereocomplexes when enantiomeric PLA chains are mixed in equivalent amounts. Such materials provide interesting features that might be suitable for numerous applications. Despite several advantages, the main drawback of PLA is its narrow window of processing, thus limiting its use for industrial applications. Reported herein are achiral iron complexes, that are highly active, productive, and stereoselective under mild reaction conditions for the ring‐opening polymerization of lactide. The corresponding catalytic systems enable the production of stereoblock polymers with high molecular weights, allowing the formation of thermally stable and industrially relevant stereocomplexes.
Building Supramolecular DNA‐Inspired Nanowires on Gold Surfaces: From 2D to 3D
Authors: Gatto Emanuela , Kubitzky Sascha , Schriever Marc , Cesaroni Simona , Mazzuca Claudia , Marafon Giulia , Venanzi Mariano , De Zotti Marta 
Published: March 2019

AbstractThree building blocks have been designed to chemically link to a gold surface and vertically self‐assemble through thymine–adenine hydrogen bonds. Starting from these building blocks, two different films were engineered on gold surface. Film 1 consists of adenine linked to lipoic acid (Lipo–A) to covalently bind to the gold surface, and ZnTPP linked to a thymine (T–ZnTPP). Film 2 has an additional noncovalently linked layer: a helical undecapeptide analogue of the trichogin GA IV peptide, in which four glycines were replaced by four lysines to favor a helical conformation and reduce flexibility and the two extremities were functionalized with thymine and adenine to enable Lipo–A and T–ZnTPP binding, respectively. These films were characterized by electrochemical and spectroscopic techniques, and were very stable over time and when in contact with solution. Under illumination, they could generate current with higher efficiency than similar previously described systems.
Sulfonium, an Underestimated Moiety for Structural Modification, Alters the Antibacterial Profile of Vancomycin Against Multidrug‐Resistant Bacteria
Authors: Guan Dongliang , Chen Feifei , Qiu Yunguang , Jiang Bofeng , Gong Likun , Lan Lefu , Huang Wei 
Published: March 2019

AbstractIn the antibiotics arsenal, vancomycin is a last resort for the treatment of intractable infections. However, this situation is under threat because of the increasing appearance of vancomycin‐resistant bacteria (VRB). Herein, we report a series of novel vancomycin derivatives carrying a sulfonium moiety. The sulfonium–vancomycin derivatives exhibited enhanced antibacterial activity against VRB both in vitro and in vivo. These derivatives also exhibited activity against some Gram‐negative bacteria. The sulfonium modification enhanced the interaction of vancomycin with the bacterial cell membrane and disrupts membrane integrity. Furthermore, the in vivo pharmacokinetic profile, stability, and toxicity of these derivatives demonstrated good druggability of the sulfonium–vancomycin analogues. This work provides a promising strategy for combating drug‐resistant bacterial infection, and advances the knowledge on sulfonium derivatives for structural optimization and drug development.
Robust control of wind turbines based on fractional nonlinear disturbance observer
Authors: Muñoz‐Vázquez Aldo Jonathan , Parra‐Vega Vicente , Sánchez‐Orta Anand , Romero‐Galván Gerardo , Lara‐Alabazares David 
Published: March 2019

AbstractIn order to assure maximum energy conversion, the angular velocity of the wind turbine rotor tracks a nominal profile depending on the wind speed. However, conventionally, wind flows present non‐differentiable components due to turbulence and gust winds, which affect the wind energy management. Thus, a fast and robust controller is required to induce such nominal regime for maximum energy transfer. A fractional‐order nonlinear disturbance‐observer (FNDOB) is proposed in this paper to cancel the non‐differentiable components of the wind speed, as well as dynamic uncertainties and other aerodynamic disturbances. The proposed FNDOB is based on continuous fractional sliding modes, assuring that disturbances and uncertainties are exactly compensated in finite‐time. A representative simulation study for a variable‐speed wind turbine is presented to show the reliability of the proposed scheme, and a comparative analysis with respect to a conventional linear disturbance observer based control is presented.
Why the cellulosic biofuels mandate fell short: a markets and policy perspective
Authors: Brown Tristan R. 
Published: March 2019

AbstractThe revised Renewable Fuel Standard's cellulosic biofuels mandate requires the USA to consume 16 000 million gallons of cellulosic biofuel per year by 2022. The cellulosic biofuels industry has fallen far short of reaching the production targets needed to achieve this volume, and it has even struggled to achieve the greatly reduced revised volumes that were created by the US Environmental Protection Agency despite the subsequent inclusion of landfill gas within the mandate. This article examines the underlying causes of this shortfall from the perspectives of markets and policy. It examines how the cellulosic biofuels production environment has not been conducive to the cost‐competitiveness of pioneer, first‐of‐their‐kind facilities and pathway buildout, and how recent techno‐economic analyses have used uncertainty to quantify the impacts of this environment. It further examines how the cellulosic biofuels mandate has actually hindered commercialization despite being intended to support it. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd
Dynamic prediction: A challenge for biostatisticians, but greatly needed by patients, physicians and the public
Authors: Schumacher Martin , Hieke Stefanie , Ihorst Gabriele , Engelhardt Monika 
Published: March 2019

AbstractPrognosis is usually expressed in terms of the probability that a patient will or will not have experienced an event of interesttyears after diagnosis of a disease. This quantity, however, is of little informative value for a patient who is still event‐free after a number of years. Such a patient would be much more interested in the conditional probability of being event‐free in the upcomingtyears, given that he/she did not experience the event in thesyears after diagnosis, called “conditional survival.” It is the simplest form of a dynamic prediction and can be dealt with using straightforward extensions of standard time‐to‐event analyses in clinical cohort studies. For a healthy individual, a related problem with further complications is the so‐called “age‐conditional probability of developing cancer” in the nexttyears. Here, the competing risk of dying from other diseases has to be taken into account. For both situations, the hazard function provides the central dynamic concept, which can be further extended in a natural way to build dynamic prediction models that incorporate both baseline and time‐dependent characteristics. Such models are able to exploit the most current information accumulating over time in order to accurately predict the further course or development of a disease. In this article, the biostatistical challenges as well as the relevance and importance of dynamic prediction are illustrated using studies of multiple myeloma, a hematologic malignancy with a formerly rather poor prognosis which has improved over the last few years.