bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors
Authors: Limburg Bart , Thomas James O. , Holloway Gregory , Sadeghi Hatef , Sangtarash Sara , Hou Ian Cheng‐Yi , Cremers Jonathan , Narita Akimitsu , Müllen Klaus , Lambert Colin J. , Briggs G. Andrew D. , Mol Jan A. , Anderson Harry L. 
Published: September 2018

AbstractThe effectiveness of five different anchor groups for non‐covalent interfacing to graphene electrodes are compared. A family of six molecules is tested in single‐molecule junctions: five consist of the same porphyrin core with different anchor groups, and the sixth is a reference molecule without anchor groups. The junction formation probability (JFP) has a strong dependence on the anchor group. Larger anchors give higher binding energies to the graphene surface, correlating with higher JFPs. The best anchor groups tested are 1,3,8‐tridodecyloxypyrene and 2,5,8,11,14‐pentadodecylhexa‐peri‐hexabenzocoronene, with JFPs of 36% and 38%, respectively. Many junctions are tested at 77 K for each molecule by measuring source‐drain current as a function of bias and gate voltages. For each compound, there is wide variation in the strength of the electronic coupling to the electrodes and in the location of Coulomb peaks. In most cases, this device‐to‐device variability makes it impossible to observe trends between the anchor and the charge‐transport characteristics. Tetrabenzofluorene anchors, which are not π‐conjugated with the porphyrin, exhibit different charge transport behavior to the other anchors tested, and they show multiple Coulomb peaks with characteristically small molecular electron‐addition energies of 0.3–0.7 eV, whereas the other compounds give single Coulomb peaks.
Boosting Photovoltaic Output of Ferroelectric Ceramics by Optoelectric Control of Domains
Authors: Bai Yang , Vats Gaurav , Seidel Jan , Jantunen Heli , Juuti Jari 
Published: September 2018

AbstractPhoto‐ferroelectric single crystals and highly oriented thin‐films have been extensively researched recently, with increasing photovoltaic energy conversion efficiency (from 0.5% up to 8.1%) achieved. Rare attention has been paid to polycrystalline ceramics, potentially due to their negligible efficiency. However, ceramics offer simple and cost‐effective fabrication routes and stable performance compared to single crystals and thin‐films. Therefore, a significantly increased efficiency of photo‐ferroelectric ceramics contributes toward widened application areas for photo‐ferroelectrics, e.g., multisource energy harvesting. Here, all‐optical domain control under illumination, visible‐range light‐tunable photodiode/transistor phenomena and optoelectrically tunable photovoltaic properties are demonstrated, using a recently discovered photo‐ferroelectric ceramic (K0.49Na0.49Ba0.02)(Nb0.99Ni0.01)O2.995. For this monolithic material, tuning of the electric conductivity independent of the ferroelectricity is achieved, which previously could only be achieved in organic phase‐separate blends. Guided by these discoveries, a boost of five orders of magnitude in the photovoltaic output power and energy conversion efficiency is achieved via optical and electrical control of ferroelectric domains in an energy‐harvesting circuit. These results provide a potentially supplementary approach and knowledge for other photo‐ferroelectrics to further boost their efficiency for energy‐efficient circuitry designs and enable the development of a wide range of optoelectronic devices.
Impact of 2‐Ethylhexyl Stereoisomers on the Electrical Performance of Single‐Crystal Field‐Effect Transistors
Authors: He Tao , Leowanawat Pawaret , Burschka Christian , Stepanenko Vladimir , Stolte Matthias , Würthner Frank 
Published: September 2018

AbstractMany organic semiconductors (OSCs) inherit chiral alkyl chains, which ensure the desirable high solubility for solution‐processing but may also lead to disorder, inhomogeneous film‐formation, as well as interfacial defects due to the presence of mixtures of stereoisomers or diastereomers, which impair their peak performance. Here, single‐crystal field‐effect transistors (SCFETs) of a diketopyrrolopyrrole‐based organic semiconductor with chiral 2‐ethylhexyl substituents by sublimation in air and organic ribbon mask method are fabricated. Devices of the mesomer (R/S), both enantiomers (R/R, S/S), as well as mixtures of these three stereoisomers measured under ambient conditions exhibit all appreciable p‐channel charge carrier mobilities of > 0.1 cm2 V−1 s−1 despite different packing arrangement in the R/S, R/R (or S/S), and racemate crystal structures. These results suggest a surprising tolerance for isomeric impurities. The highest literature‐reported p‐channel mobility so far for a diketopyrrolopyrrole‐based OSC of 3.4 cm2 V−1 s−1 (Ion/Ioff of 1 × 106) is, however, only obtained for the pure R/S mesomer, illustrating the inherent potential of stereochemical purity. These results on SCFETs are further substantiated by studies on organic thin‐film transistors (OTFTs) of pure and mixed thin films of the different stereoisomers.
Lead‐Free Highly Efficient Blue‐Emitting Cs3Cu2I5 with 0D Electronic Structure
Authors: Jun Taehwan , Sim Kihyung , Iimura Soshi , Sasase Masato , Kamioka Hayato , Kim Junghwan , Hosono Hideo 
Published: September 2018

AbstractHalide perovskites, including CsPbX3 (X = Cl, Br, I), have gained much attention in the field of optoelectronics. However, the toxicity of Pb and the low photoluminescence quantum yield (PLQY) of these perovskites hamper their use. In this work, new halide materials that meet the requirements of: (i) nontoxicity, (ii) high PLQY, and (iii) ease of fabrication of thin films via the solution process are explored. In particular, copper(I) halide compounds with low‐dimensional electronic structures are considered. Cs3Cu2I5 has a 0D photoactive site and exhibits blue emission (≈445 nm) with very high PLQYs of ≈90 and ≈60% for single crystals and thin films, respectively. The large exciton binding energy of ≈490 meV explains well the 0D electronic nature of Cs3Cu2I5. Blue electroluminescence of Pb‐free halides is demonstrated using solution‐derived Cs3Cu2I5 thin films.
Chemical Vapor Deposition Grown Wafer‐Scale 2D Tantalum Diselenide with Robust Charge‐Density‐Wave Order
Authors: Shi Jianping , Chen Xuexian , Zhao Liyun , Gong Yue , Hong Min , Huan Yahuan , Zhang Zhepeng , Yang Pengfei , Li Yong , Zhang Qinghua , Zhang Qing , Gu Lin , Chen Huanjun , Wang Jian , Deng Shaozhi , Xu Ningsheng , Zhang Yanfeng 
Published: September 2018

Abstract2D metallic transition metal dichalcogenides (MTMDCs) are benchmark systems for uncovering the dimensionality effect on fascinating quantum physics, such as charge‐density‐wave (CDW) order, unconventional superconductivity, and magnetism, etc. However, the scalable and thickness‐tunable syntheses of such envisioned MTMDCs are still challenging. Meanwhile, the origin of CDW order at the 2D limit is controversial. Herein, the direct synthesis of wafer‐scale uniform monolayer 2H‐TaSe2 films and thickness‐tunable flakes on Au foils by chemical vapor deposition is accomplished. Based on the thickness‐tunable 2H‐TaSe2, the robust periodic lattice distortions that relate to CDW orders by low‐temperature transmission electron microscopy are directly visualized. Particularly, a phase diagram of the transition temperature from normal metallic to CDW phases with thickness by variable‐temperature Raman characterizations is established. Intriguingly, dramatically enhanced transition temperature from bulk value ≈90 to ≈125 K is observed from monolayer 2H‐TaSe2, which can be explained by the enhanced electron–phonon coupling mechanism. More importantly, an ultrahigh specific capacitance is also obtained for the as‐grown TaSe2 on carbon cloth as supercapacitor electrodes. The results hereby open up novel avenues toward the large‐scale preparation of high‐quality MTMDCs, and shed light on their applications in exploring some fundamental issues.
Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys
Authors: Lu Wenjun , Liebscher Christian H. , Dehm Gerhard , Raabe Dierk , Li Zhiming 
Published: September 2018

AbstractMicrostructural length‐scale refinement is among the most efficient approaches to strengthen metallic materials. Conventional methods for refining microstructures generally involve grain size reduction via heavy cold working, compromising the material's ductility. Here, a fundamentally new approach that allows load‐driven formation and permanent refinement of a hierarchical nanolaminate structure in a novel high‐entropy alloy containing multiple principal elements is reported. This is achieved by triggering both, dynamic forward transformation from a faced‐centered‐cubic γ matrix into a hexagonal‐close‐packed ε nanolaminate structure and the dynamic reverse transformation from ε into γ. This new mechanism is referred to as the “bidirectional transformation induced plasticity” (B‐TRIP) effect, which is enabled through a near‐zero yet positive stacking fault energy of γ. Modulation of directionality in the transformation is triggered by local dissipative heating and local micromechanical fields. The simple thermodynamic and kinetic foundations for the B‐TRIP effect render this approach generally suited for designing metastable strong and ductile bulk materials with hierarchical nanolaminate substructures.
Reduction of Amides to Amines under Mild Conditions via Catalytic Hydrogenation of Amide Acetals and Imidates
Authors: Kadyrov Renat 
Published: September 2018

AbstractA simple and general protocol was developed for selective conversion of amides into amines. Amides were converted into amide acetals and imido esters by O‐alkylation and then hydrogenated without isolation into amines under very mild reaction conditions over standard hydrogenation catalysts. Triethyloxonium tertafluoroborate, methyl trifluoromethanesulfonate, dimethyl sulfate and ethyl chloroformate were validated as alkylating agent. The synthetic utility of this approach was demonstrated by the selective carbonyl reduction of peptide groups. Carbonyl reduction of peptide group proceeds chemoselective without racemization of the neighboring chiral center.magnified image
TiS2 as an Advanced Conversion Electrode for Sodium‐Ion Batteries with Ultra‐High Capacity and Long‐Cycle Life
Authors: Tao Hongwei , Zhou Min , Wang Ruxing , Wang Kangli , Cheng Shijie , Jiang Kai 
Published: September 2018

AbstractTitanium disulfide (TiS2) is investigated as an advanced conversion electrode for sodium (Na)‐ion batteries (NIB) in an ether‐based electrolyte (NaPF6/glyme (DME)). The as‐prepared TiS2 demonstrates a high reversible capacity of 1040 mA h g−1 at 0.2 A g−1 with the capacity contribution of 521 mA h g−1 in the voltage region below 1.0 V (vs Na/Na+), remarkable initial coulombic efficiency of 95.9% and superior rate capability of 621 mA h g−1 at 40 A g−1. The high conductivity of the Ti‐based compounds and nanosized particles generated by chemical conversion reactions could minimize the entropic barrier for the reversible conversion, resulting in high reversibility and ultrafast charge/discharge ability of the electrode. Moreover, with its strong ability to adsorb soluble polysulfide intermediates, the as‐prepared TiS2 electrode exhibits superior cycling stability over 9000 cycles, serving as a stable and ultra‐high capacity conversion electrode for NIBs.
A Universal Double‐Side Passivation for High Open‐Circuit Voltage in Perovskite Solar Cells: Role of Carbonyl Groups in Poly(methyl methacrylate)
Authors: Peng Jun , Khan Jafar I. , Liu Wenzhu , Ugur Esma , Duong The , Wu Yiliang , Shen Heping , Wang Kai , Dang Hoang , Aydin Erkan , Yang Xinbo , Wan Yimao , Weber Klaus J. , Catchpole Kylie R. , Laquai Frédéric , De Wolf Stefaan , White Thomas P. 
Published: September 2018

AbstractThe performance of state‐of‐the‐art perovskite solar cells is currently limited by defect‐induced recombination at interfaces between the perovskite and the electron and hole transport layers. These defects, most likely undercoordinated Pb and halide ions, must either be removed or passivated if cell efficiencies are to approach their theoretical limit. In this work, a universal double‐side polymer passivation approach is introduced using ultrathin poly(methyl methacrylate) (PMMA) films. Very high‐efficiency (≈20.8%) perovskite cells with some of the highest open circuit voltages (1.22 V) reported for the same 1.6 eV bandgap are demonstrated. Photoluminescence imaging and transient spectroscopic measurements confirm a significant reduction in nonradiative recombination in the passivated cells, consistent with the voltage increase. Analysis of the molecular interactions between perovskite and PMMA reveals that the carbonyl (CO) groups on the PMMA are responsible for the excellent passivation via Lewis‐base electronic passivation of Pb2+ ions. This work provides new insights and a compelling explanation of how PMMA passivation works, and suggests future directions for developing improved passivation layers.
Origin of Degradation in Si‐Based All‐Solid‐State Li‐Ion Microbatteries
Authors: Chen Chunguang , Oudenhoven Jos F. M. , Danilov Dmitri L. , Vezhlev Egor , Gao Lu , Li Na , Mulder Fokko M. , Eichel Rüdiger‐A. , Notten Peter H. L. 
Published: September 2018

AbstractLike all rechargeable battery systems, conventional Li‐ion batteries (LIB) inevitably suffer from capacity losses during operation. This also holds for all‐solid‐state LIB. In this contribution an in operando neutron depth profiling method is developed to investigate the degradation mechanism of all‐solid‐state, thin film Si–Li3PO4–LiCoO2batteries. Important aspects of the long‐term degradation mechanisms are elucidated. It is found that the capacity losses in these thin film batteries are mainly related to lithium immobilization in the solid‐state electrolyte, starting to grow at the anode/electrolyte interface during initial charging. The Li‐immobilization layer in the electrolyte is induced by silicon penetration from the anode into the solid‐state electrolyte and continues to grow at a lower rate during subsequent cycling. X‐ray photoelectron spectroscopy depth profiling and transmission electron microscopy analyses confirm the formation of such immobilization layer, which favorably functions as an ionic conductor for lithium ions. As a result of the immobilization process, the amount of free moveable lithium ions is reduced, leading to the pronounced storage capacity decay. Insights gained from this research shed interesting light on the degradation mechanisms of thin film, all‐solid‐state LIB and facilitate potential interfacial modifications which finally will lead to substantially improved battery performance.
Elucidating the Catalytic Activity of Oxygen Deficiency in the Polysulfide Conversion Reactions of Lithium–Sulfur Batteries
Authors: Lin Haibin , Zhang Shengliang , Zhang Tianran , Ye Hualin , Yao Qiaofeng , Zheng Guangyuan Wesley , Lee Jim Yang 
Published: September 2018

AbstractThe accelerated conversion of soluble lithium polysulfides (the intermediate products in the charging and discharging of lithium–sulfur batteries) to insoluble sulfur and lithium sulfide is an effective method to suppress the “polysulfide shuttle” that is detrimental to the battery performance. The results of this study show that oxygen‐deficient tungsten oxide (WO3−x) nanoplate is an effective bidirectional electrocatalyst for the polysulfide conversion reactions. Two different designs of asymmetric cells are used to elucidate the catalysis of the polysulfide conversion reactions and to confirm the role of oxygen deficiency on the conversion kinetics. The fast polysulfide conversion prevents the accumulation of polysulfides in the sulfur cathode and their ensuing loss to the electrolyte. Consequently, a sulfur cathode with WO3−x nanoplates is able to improve the cycle stability from a fade rate of 0.49% per cycle (over 100 cycles) to 0.13% per cycle (over 300 cycles) at the 0.5 C rate. In addition, the WO3−x nanoplates also improve the high rate performance of the sulfur cathode (at the 4 C rate) from a capacity of 444.1 to 693.2 mAh g−1. The results of this study provide the first direct experimental proof of the beneficial effects of oxygen deficiency in polysulfide conversion reactions.
Self‐Assembled Binary Organic Granules with Multiple Lithium Uptake Mechanisms toward High‐Energy Flexible Lithium‐Ion Hybrid Supercapacitors
Authors: Hu Zhongli , Sayed Shah , Jiang Tao , Zhu Xingyu , Lu Chen , Wang Gulian , Sun Jingyu , Rashid Arif , Yan Chenglin , Zhang Li , Liu Zhongfan 
Published: September 2018

AbstractLithium‐ion hybrid supercapacitors (Li‐HSCs), by virtue of synergizing the merits of batteries and supercapacitors, have attracted considerable attention for high‐energy/‐power energy storage applications. Inorganic transition‐metal compounds with pseudocapacitive characteristics have been widely investigated as promising anodes for use in advanced Li‐HSCs. Nevertheless, the concept of using eco‐friendly and naturally abundant organic compounds as anodes for Li‐HSCs has rarely been realized so far, due to their inferior electrical and ionic conductivity and low capacitive activity. Herein, an innovative self‐assembly strategy to synthesize uniform binary organic granules as high‐capacitive and durable anodes for the construction of high‐energy flexible Li‐HSCs is reported. The unique architecture of maleic acid@polyvinylidene fluoride (MA@PVDF) granules consisting of ultrafine MA nanocrystals within a PVDF network offers multiple lithium storage mechanisms including two‐electron lithiation/delithiation, Li+‐ion intercalation/deintercalation within the MA (020) planes, and Li+‐ion adsorption/desorption at the MA nanocrystals/electrolyte interface. The as‐constructed 4.3 V Li‐HSC full cell comprising a MA@PVDF anode and an activated carbon cathode delivers high energy/power densities (158.4 Wh kg−1/107.5 W kg−1 and 70.9 Wh kg−1/10750 W kg−1), outperforming those of organic anode–based Li/Na‐HSCs and the state‐of‐the‐art inorganic hybrid capacitors. The deriving prototype flexible Li‐HSC devices manifest exceptional energy output under various deformed conditions and bent–release cycling.
Similarities and differences in intrapopulation trait correlations of co‐occurring tree species: consistent water‐use relationships amid widely different correlation patterns
Authors: Messier Julie , Violle Cyrille , Enquist Brian J. , Lechowicz Martin J. , McGill Brian J. 
Published: September 2018

Premise of the StudyGeneral relationships among functional traits have been identified across species, but the forces shaping these relationships remain largely unknown. Adopting an approach from evolutionary biology, we studied similarities and differences in intrapopulation trait correlations among locally co‐occurring tree species to assess the roles of constraints, phylogeny, and the environmental niche in shaping multivariate phenotypes. We tested the hypotheses (1) that intrapopulation correlations among functional traits are largely shaped by fundamental trade‐offs or constraints and (2) that differences among species reflect adaptation to their environmental niches.MethodsWe compared pairwise correlations and correlation matrices of 17 key functional traits within and among temperate tree species. These traits describe three well‐established trade‐off dimensions characterizing interspecific relationships among physiological functions: resource acquisition and conservation; sap transport and mechanical support; and branch architecture.Key ResultsSix trait pairs are consistently correlated within populations. Of these, only one involves dimensionally independent traits:LMA‐δ13C. For all other traits, intrapopulation functional trait correlations are weak, are species‐specific, and differ from interspecific correlations. Species intrapopulation correlation matrices are related to neither phylogeny nor environmental niche.ConclusionsThe results (1) suggest that the functional design of these species is centered on efficient water use, (2) highlight flexibility in plant functional design across species, and (3) suggest that intrapopulation, local interspecific, and global interspecific correlations are shaped by processes acting at each of these scales.
Ultrasound‐Assisted Multicomponent Reactions, Organometallic and Organochalcogen Chemistry
Authors: Penteado Filipe , Monti Bonifacio , Sancineto Luca , Perin Gelson , Jacob Raquel G. , Santi Claudio , Lenardão Eder J. 
Published: September 2018

AbstractIn the last two decades, the search for sustainability in chemical reactions has attached a lot of attention. In this focus review, the use of ultrasound (US) as an alternative energy source in organic synthesis is presented. The improvement of the performance of chemical reactions due to the cavitation effect has been previously studied and described. The use of US guarantees often higher yields than other green methodologies, as microwave or ball milling. The impressive positive effect of US in organic synthesis are demonstrated in this review mainly in organometallic and multi‐component reactions (MCRs), aimed to prepare bioactive compounds. A particular attention is dedicated to the US‐assisted synthesis of valuable organochalcogen compounds with pharmacological activity.
Tandem Regioselective Hydroformylation‐Hydrogenation of Internal Alkynes Using a Supramolecular Catalyst
Authors: Fang Weiwei , Breit Bernhard 
Published: September 2018

AbstractNew supramolecular ligands containing an acyl guanidine function were designed based on the strategy of increasing the π‐acceptor ability of phosphine ligands by introducing electron‐withdrawing groups. By applying this novel catalytic system, a general protocol for the Rh‐catalysed hydroformylation‐hydrogenation of unsymmetrical internal alkynes, functionalized with a carboxylic acid, was found to furnish aliphatic aldehydes in high regio‐ and chemoselectivities. Control experiments confirm the enzyme‐like supramolecular catalyst mode of action.
Chemotaktische Mikro‐ und Nanomaschinen
Authors: Plutnar Jan , Pumera Martin 
Published: September 2018

AbstractDie Herstellung von autonomen chemotaktischen Mikro‐ und Nanomaschinen stellt eine der schwierigsten Herausforderungen der modernen Materialwissenschaften dar. Das Konstruieren einer Funktionseinheit, die das Verhalten von Mikroorganismen nachahmt, die ihre chemotaktischen Eigenschaften über Jahrtausende der Evolution erworben haben, stellt hohe Ansprüche an die Vorstellungskraft und die Fähigkeiten von Forschern. Trotz allem konnten mit den aktuell verfügbaren chemotaktischen Funktionseinheiten viele neuartige und interessante Anwendungen von Mikromaschinen implementiert werden. Die Einführung einer autonomen Navigation, die von einer externen Steuerung durch elektrische, magnetische oder elektromagnetische Felder unabhängig ist, ist zentral entscheidend für Anwendungen in der Umweltsanierung und könnte Vorteile für medizinische Anwendungen bringen. Dieser Kurzaufsatz fasst die Entwicklung im Gebiet der chemotaktischen Mikro‐ und Nanomaschinen zusammen, beschreibt die aktuellen Trends der Herstellungsverfahren und vergleicht die unterschiedlichen Konstruktionsansätze mit Blick auf mögliche Anwendungen.