bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organic 2D Optoelectronic Crystals: Charge Transport, Emerging Functions, and Their Design Perspective
Authors: Park Sang Kyu , Kim Jin Hong , Park Soo Young 
Published: April 2018

Abstract2D organic semiconductor crystals are emerging as a fascinating platform with regard to their applications in organic field‐effect transistors (OFETs), attributed to their enhanced charge transport efficiency and their new optoelectronic functions, based on their unique morphological features. Advances in material processing techniques have not only enabled easy fabrication of few‐monolayered 2D nanostructures but also facilitated exploration of the interesting properties induced by characteristic 2D morphologies. However, to date, only a limited number of representative organic semiconductors have been utilized in organic 2D optoelectronics. Therefore, in order to further spur this research, an intuitive crystal engineering principle for realizing organic 2D crystals is required. In this regard, here, not only the important implications of applying 2D structures to OFET devices are discussed but also a crystal engineering protocol is provided that first predicts molecular arrangements depending on the molecular factors, which is followed by realizing 2D supramolecular synthon networks for different molecular packing motifs. It is expected that 2D organic semiconductor crystals developed by this approach will pave a promising way toward next‐generation organic 2D optoelectronics.
Real‐Time Observation of Order‐Disorder Transformation of Organic Cations Induced Phase Transition and Anomalous Photoluminescence in Hybrid Perovskites
Authors: Yang Bin , Ming Wenmei , Du Mao‐Hua , Keum Jong K. , Puretzky Alexander A. , Rouleau Christopher M. , Huang Jinsong , Geohegan David B. , Wang Xiaoping , Xiao Kai 
Published: April 2018

AbstractA fundamental understanding of the interplay between the microscopic structure and macroscopic optoelectronic properties of organic‐inorganic hybrid perovskite materials is essential to design new materials and improve device performance. However, how exactly the organic cations affect the structural phase transition and optoelectronic properties of the materials is not well understood. Here, real‐time, in situ temperature‐dependent neutron/X‐ray diffraction and photoluminescence (PL) measurements reveal a transformation of the organic cation CH3NH3
+ from order to disorder with increasing temperature in CH3NH3PbBr3 perovskites. The molecular‐level order‐to‐disorder transformation of CH3NH3
+ not only leads to an anomalous increase in PL intensity, but also results in a multidomain to single‐domain structural transition. This discovery establishes the important role that organic cation ordering has in dictating structural order and anomalous optoelectronic phenomenon in hybrid perovskites.
Extreme Toughening of Soft Materials with Liquid Metal
Authors: Kazem Navid , Bartlett Michael D. , Majidi Carmel 
Published: April 2018

AbstractSoft and tough materials are critical for engineering applications in medical devices, stretchable and wearable electronics, and soft robotics. Toughness in synthetic materials is mostly accomplished by increasing energy dissipation near the crack tip with various energy dissipation techniques. However, bio‐materials exhibit extreme toughness by combining multi‐scale energy dissipation with the ability to deflect and blunt an advancing crack tip. Here, we demonstrate a synthetic materials architecture that also exhibits multi‐modal toughening, whereby embedding a suspension of micron sized and highly deformable liquid metal (LM) droplets inside a soft elastomer, the fracture energy dramatically increases by up to 50x (from 250 ± 50 J m‐2 to 11,900 ± 2600 J m‐2) over an unfilled polymer. For some LM‐embedded elastomer (LMEE) compositions, the toughness is measured to be 33,500 ± 4300 J m‐2, which far exceeds the highest value previously reported for a soft elastic material. This extreme toughening is achieved by (i) increasing energy dissipation, (ii) adaptive crack movement, and (iii) effective elimination of the crack tip. Such properties arise from the deformability of the LM inclusions during loading, providing a new mechanism to not only prevent crack initiation, but also resist the propagation of existing tears for ultra tough, soft materials.
FeS2 Nanoparticles Decorated Graphene as Microbial‐Fuel‐Cell Anode Achieving High Power Density
Authors: Wang Ruiwen , Yan Mei , Li Huidong , Zhang Lu , Peng Benqi , Sun Jinzhi , Liu Da , Liu Shaoqin 
Published: April 2018

AbstractMicrobial fuel cells (MFCs) have received great attention worldwide due to their potential in recovering electrical energy from waste and inexhaustible biomass. Unfortunately, the difficulty of achieving the high power, especially in real samples, remains a bottleneck for their practical applications. Herein, FeS2 nanoparticles decorated graphene is fabricated via a simple hydrothermal reaction. The FeS2 nanoparticles decorated graphene anode not only benefits bacterial adhesion and enrichment of electrochemically active Geobacter species on the electrode surface but also promotes efficient extracellular electron transfer, thus giving rise to a fast start‐up time of 2 d, an unprecedented power density of 3220 mW m−2 and a remarkable current density of 3.06 A m−2 in the acetate‐feeding and mixed bacteria‐based MFCs. Most importantly, the FeS2 nanoparticles decorated graphene anode successfully achieves a power density of 310 mW m−2 with simultaneous removal of 1319 ± 28 mg L−1 chemical oxygen demand in effluents from a beer factory wastewater. The characteristics of improved power generation and enhanced pollutant removal efficiency opens the door toward development of high‐performance MFCs via rational anode design for practical application.
Impact of High Valence State Cation Ti/Ta Surface Doping on the Stabilization of Spinel LiNi0.5Mn1.5O4 Cathode Materials: A Systematic Density Functional Theory Investigation
Authors: Chen Yuyang , Ben Liubin , Chen Bin , Zhao Wenwu , Huang Xuejie 
Published: April 2018

AbstractSurface modification of a high‐voltage spinel LiNi0.5Mn1.5O4 cathode is a common method to improve its cycling performance for next generation lithium‐ion batteries, but the exact surface structural stabilization mechanism is not well‐understood. Here, detailed density function theory investigations based on the first‐principles calculations of high valence state Ti‐/Ta‐surface‐doped LiNi0.5Mn1.5O4 are reported. The migration of Ni/Mn ions is simulated into the surface structure of bare and Ti‐/Ta‐coated LiNi0.5Mn1.5O4. The calculation results suggest that Ti/Ta doping promotes Ni/Mn migration toward the formation of the rocksalt phase. Integrated net spin suggests that the valence state of transition metal ions, especially Ni, around Ti/Ta are slightly reduced in the fully charged state, resulting in a weakened surface oxidative property toward electrolyte. Both Ti/Ta doping and the consequent formation of the rocksalt phase not only stabilizes the oxygen frame of LiNi0.5Mn1.5O4 by forming stronger metal‐O bonds but also suppresses the oxygen evolution during cycling. The stabilized anion frame of oxygen further mitigates the dissolution of Mn ions from the lattice into the electrolyte. These computer simulations are in good accordance with experimental observations. The surface structural stabilization mechanism of the high valence state cation Ti‐/Ta‐coated LiNi0.5Mn1.5O4 can certainly be expanded to improve other cathode electrode materials.
Failure of Fermi Level in Referencing Chemical Shift of Molecules on Solid Surfaces
Authors: Li Yiying , Lu Zheng‐Hong 
Published: April 2018

AbstractCore level chemical shifts using Fermi level as an orthodox reference level are extensively used to detect the forming/breaking of bonds (i.e., change in oxidation states) during chemical reactions and are broadly used as an experimental proof of charge transfers across organic interfaces by several research communities for many decades. Based on core level and valence photoemission experimental measurements a paradoxical relationship between core‐level shift and charge transfer is shown, demonstrating the failure of conventional practice of using Fermi level to measure chemical shifts of molecules on solid surfaces. Thus, great care needs to be taken when interpreting experimentally observed shifts in core level binding energies as well as assigning core level energy peaks associated with certain oxidation states. To resolve this paradoxical problem, it is shown that measurement of interface dipoles is essential in investigating the charge transfers of molecules to/from solid surfaces.
Lotus Seedpod Inspired SERS Substrates: A Novel Platform Consisting of 3D Sub‐10 nm Annular Hot Spots for Ultrasensitive SERS Detection
Authors: Jin Binbin , He Junhui , Li Jing , Zhang Yue 
Published: April 2018

AbstractA novel lotus seedpod (LSP) like array substrate with tailorable annular nanogaps is reported for surface‐enhanced Raman spectroscopy (SERS). High SERS activity with excellent Raman signal reproducibility is achieved for molecular detection. Finite‐different time‐domain simulation suggests that sub‐10 nm annular nanogaps formed in the LSP array contribute significantly to the electromagnetic field enhancement for SERS measurements. The SERS substrate presents a detection limit as low as 10−12m along with a relative standard deviation as small as 4.1−8.0% in the detection of rhodamine 6G (R6G). Moreover, the linear correlation between Raman intensity and the concentration of R6G indicates the capability of the substrate for quantitative SERS analyses. As a typical example, the SERS substrate is successfully applied to detecting the α‐helical structure of amyloid‐β oligomers at a low concentration of 0.1 × 10−6m, which will be promising for label‐free detection of Alzheimer's disease in its earliest, presymptomatic, and most treatable stages. The as‐fabricated LSP array substrates therefore hold exciting potentials toward SERS‐based chemical and biomedical detections.
Tunable Photoluminescence Including White‐Light Emission Based on Noncovalent Interaction‐Locked N,N′‐Disubstituted Dihydrodibenzo[a,c]phenazines
Authors: Wang Jie , Yao Xuyang , Liu Yang , Zhou Haitao , Chen Wei , Sun Guangchen , Su Jianhua , Ma Xiang , Tian He 
Published: April 2018

AbstractUtilizing supramolecular assembling system to achieve tunable photoluminescence emission has become an important method for the development of light‐emitting materials, which could bring out intriguing photophysical properties out of the luminophores themselves without a demanding design and tedious chemical synthesis. In the last few years, vibration‐induced emission (VIE) molecules, with dual photoluminescence emissions and large Stokes shift, have shown their talent in generating tunable fluorescence and potential in fabricating novel light‐emitting materials. However, little attention has been devoted to explore the attractive properties of VIE molecules in supramolecular self‐assembling systems up to now. Herein, the first example of a supramolecular assembling system composed of a water‐soluble VIE molecule N,N′‐diphenyl‐dihydrodibenzo[a,c]phenazines derivative (DPAC‐AB) and bis‐p‐sulfonatocalix[4]arene (BSC4) is introduced. Based on noncovalent interactions including hydrophobic interaction and host–guest interaction between DPAC‐AB and BSC4, tunable fluorescence emissions from orange‐red to white (Commission Internationale de L'éclairage (CIE) coordinates (0.32, 0.37)) to blue are achieved by simple addition of different amounts of BSC4 to the solution of DPAC‐AB. Additionally, a competitive guest acetylcholine is utilized to recover the nearly orange‐red fluorescence emission. This strategy to efficiently control the emission of VIE molecules through supramolecular assembling based on reversible noncovalent interactions opens new avenues in developing tunable light‐emitting materials.
A General and Robust Strategy for Fabricating Mechanoresponsive Surface Wrinkles with Dynamic Switchable Transmittance
Authors: Jiang Baolai , Liu Luntao , Gao Zongpeng , Wang Wenshou 
Published: April 2018

AbstractPreparation of surface wrinkles on a skin layer/elastomer substrate bilayer film has attracted extensive attention because of their unique and broad applications in flexible electronic devices, tunable diffraction gratings, and smart windows. However, it still remains a great challenge to develop a general strategy for fabricating mechanoresponsive surface wrinkles using various skin layer materials with wide tunability of wrinkles' wavelength and amplitude, large optical modulation range, rapid optical switching rate, and high stability. Here, a general, simple, and cost‐effective strategy is reported, through uniaxially stretching and subsequently releasing skin layer/elastomer substrate bilayer films, for producing highly ordered, crack‐free, 1D surface wrinkles on elastomeric polydimethylsiloxane (PDMS) substrates with various skin layer materials, including polyvinyl alcohol (PVA), chitosan (CS), hydroxyethyl cellulose, and the mixtures of PVA and CS. The surface wrinkles on PVA/PDMS bilayer film exhibit excellent mechanoresponsive optical switching properties, such as large transmittance modulation range (transmittance from ≈6% to 91% at visible region), high optical sensitivity with small mechanical strain (less than 20%), and long optical switching cycles (over 2000 times). It is anticipated that this method will enable a new path to the fabrication of mechanoresponsive surface wrinkles with outstanding performance for applications in dynamic optical switching fields and beyond.
Evaluation of Natural and Synthetic Phosphate Donors for the Improved Enzymatic Synthesis of Phosphate Monoesters
Authors: Tasnádi Gábor , Jud Wolfgang , Hall Mélanie , Baldenius Kai , Ditrich Klaus , Faber Kurt 
Published: April 2018

AbstractUndesired product hydrolysis along with large amounts of waste in form of inorganic monophosphate by‐product are the main obstacles associated with the use of pyrophosphate in the phosphatase‐catalyzed synthesis of phosphate monoesters on large scale. In order to overcome both limitations, we screened a broad range of natural and synthetic organic phosphate donors with several enzymes on a broad variety of hydroxyl‐compounds. Among them, acetyl phosphate delivered stable product levels and high phospho‐transfer efficiency at the lower functional pH‐limit, which translated into excellent productivity. The protocol is generally applicable to acid phosphatases and compatible with a range of diverse substrates. Preparative‐scale transformations using acetyl phosphate synthesized from cheap starting materials yielded multiple grams of various sugar phosphates with up to 433 g L−1 h−1 space‐time yield and 75% reduction of barium phosphate waste.magnified image
Synthesis of Benzo[4,5]imidazo[2,1‐b]thiazole by Copper(II)‐Catalyzed Thioamination of Nitroalkene with 1H‐Benzo[d]imidazole‐2‐thiol
Authors: Jana Sourav , Chakraborty Amrita , Shirinian Valerii Z. , Hajra Alakananda 
Published: April 2018

AbstractA Copper(II)‐catalyzed thioamination of β‐nitroalkene with 1H‐benzo[d]imidazole‐2‐thiol has been developed for the synthesis of benzo[4,5]imidazo[2,1‐b]thiazole derivatives. A variety of N‐fused benzoimidazothiazole derivatives are obtained in high yields through successive C−N and C−S bond formations. This protocol is also applicable to β‐substituted β‐nitroalkenes to afford 2,3‐disubstituted benzoimidazothiazoles.magnified image
In situ polymerized poly(acrylic acid)/alumina nanocomposites for Pb2+ adsorption
Authors: Wang Ya‐Ping , Zhou Peng , Luo Shi‐Zhong , Guo Sijie , Lin Jing , Shao Qian , Guo Xingkui , Liu Zhongqing , Shen Jun , Wang Bin , Guo Zhanhu 
Published: April 2018

AbstractIn this study, two poly(acrylic acid)/alumina (PAA/alumina) nanocomposites with varied polymer loadings were prepared via in situ polymerization of preadsorbed acrylic acid. One composite would have a ~1/4‐monolayer polymer coverage, while the other had a ~2‐monolayer coverage. The produced composite materials were characterized in the adsorptive behavior of Pb2+ from aqueous solution. When there was less PAA produced in a nanocomposite sample, there was higher Pb2+ sorption capacity due to potentially less blocked alumina pores by in situ formed PAA. Isothermal and kinetic models for Pb2+ sorption were applied by considering the effects of the initial Pb2+ concentration and the contact time. The adsorption kinetics was best expressed using the pseudo‐second‐order equation. Through the isothermal studies, the maximum Pb2+ monolayer adsorption capacity of 167.79 mg/g was recorded for the composite with higher PAA loading.
Large Built‐In Fields Control the Electronic Properties of Nanoscale Molecular Devices with Dipolar Structures
Authors: Van Dyck Colin , Bergren Adam J. 
Published: April 2018

AbstractLarge area molecular junctions are nanoscale materials made of a molecular layer sandwiched between two metal electrodes. In this study, a fundamental property of these systems is demonstrated: the emergence of a large built‐in field, typically as high as 109 V m−1, and susceptible to appear in any junction possessing an asymmetry. This field originates from permanent dipoles in the contacted molecular layer and is responsible for a large renormalization of the band alignment in the junction. To illustrate this effect, a predictive theoretical characterization of two realistic gold‐thiolate‐based organic layers is carried out. The parameters leading to the emergence of the built‐in field are given and the very large renormalization effect is interpreted in terms of an applied voltage drop. Despite a high significance, this generic feature of molecular junctions has widely been neglected hitherto in the design and interpretation of molecular device characteristics. Built‐in fields provide a powerful way to achieve structure–property relationships in molecular junctions, by taking advantage of dipolar nanometric building blocks.
Electrochemical Oxidation of Hf–Nb Alloys as a Valuable Route to Prepare Mixed Oxides of Tailored Dielectric Properties
Authors: Zaffora Andrea , Di Quarto Francesco , Kura Chiharu , Sato Yuki , Aoki Yoshitaka , Habazaki Hiroki , Santamaria Monica 
Published: April 2018

AbstractMetal oxides with high dielectric constant are extensively studied in the frame of substituting SiO2 as gate dielectric in nanoelectronic devices. Here, high‐k mixed HfO2/Nb2O5 oxides are prepared by a facile electrochemical route starting from sputtering‐deposited Hf–Nb alloys with several compositions. Transmission electron microscopy, grazing incidence X‐ray diffraction, and glow discharge optical emission spectroscopy are employed to study the oxide structures, disclosing a crystalline–amorphous transition of the electrochemically prepared oxides by increasing the Nb content. Photo‐electrochemical measurements allow the observation of optical transitions ascribed to localized states inside oxide bandgap induced by the presence of oxygen vacancies for Hf‐rich oxides. Impedance measurements, coupled with withstand voltage and leakage current estimates, provide a comprehensive view of the real dielectric properties of the oxides. The highest ε is estimated for the anodic oxide grown on Hf–39 at% Nb (i.e., 45) but thin film grown on Hf–57 at% Nb alloy shows the best dielectric properties, revealing high dielectric constant, high withstand voltage, and low leakage current. Promising equivalent oxide thickness (down to 0.38 nm) is estimated for the oxide thin layers. The electrochemical oxidation represents a valuable and reliable way to prepare high‐k thin oxide films with tailored and controlled dielectric properties.
Photocurrent, Photovoltage, and Rectification in Large‐Area Bilayer Molecular Electronic Junctions
Authors: Smith Scott R. , McCreery Richard L. 
Published: April 2018

AbstractBilayer donor–acceptor molecular junctions are successfully fabricated with active layer thickness <15 nm to study the mechanism of photo‐induced charge transport. The bilayer devices exhibit lifetimes greater than 1 h with laser irradiation, and a strong dependence of the sign and magnitude of the photovoltage and photocurrent on structure and order of the molecular layers. A distinct feature of the bilayer structure is covalent bonding between the donor and acceptor molecular layers, which permits simultaneous absorption and charge separation across a covalent heterojunction. In addition to providing probes of internal energy levels and charge transport in molecular junctions, photo‐induced currents and voltages may potentially be useful in light‐weight, durable, and flexible photodetectors.
The Effect of Hydrophobicity of Ammonium Salts on Stability of Quasi‐2D Perovskite Materials in Moist Condition
Authors: Zheng Haiying , Liu Guozhen , Zhu Liangzheng , Ye Jiajiu , Zhang Xuhui , Alsaedi Ahmed , Hayat Tasawar , Pan Xu , Dai Songyuan 
Published: April 2018

AbstractWith the potential of achieving high efficiency and low production costs, perovskite solar cells (PSCs) have attracted great attention. However, their unstableness under moist condition has retarded the commercial development. Recently, 2D perovskites have received a lot of attention due to their high moisture resistance. In this work, four quasi 2D quasi perovskites are prepared, then their stability under moist condition is investigated. The surface morphology, crystal structure, optical properties, and photovoltaic performance are measured. Among the four quasi‐2D perovskites, (C6H5CH2NH3)2(FA)8Pb9I28 has the best performance: uniform and dense film, extremely well‐oriented crystal structure, strong absorption, and a high power conversion efficiency (PCE) of 17.40%. The aging tests show that quasi‐2D perovskites are more stable under moist conditions than FAPbI3 is. The (C6H5CH2NH3)2(FA)8Pb9I28 quasi‐2D perovskite devices exhibit high humidity stability, maintaining 80% of the starting PCE after 500 h under 80% relative humidity. Compared with other quasi‐2D perovskites, (C6H5CH2NH3)2(FA)8Pb9I28 has the highest humidity stability, due to their strongest hydrophobicity from C6H5CH2NH3+. This work demonstrates that the properties of perovskite materials can be modified by adding different ammonium salts into FAPbI3. Thus, by introducing ammonium salts with high hydrophobic properties the fabrication of highly efficient and stable 2D PSCs may be possible.
On the Balance of Intercalation and Conversion Reactions in Battery Cathodes
Authors: Hannah Daniel C. , Sai Gautam Gopalakrishnan , Canepa Pieremanuele , Ceder Gerbrand 
Published: April 2018

AbstractA thermodynamic analysis of the driving forces is presented for intercalation and conversion reactions in battery cathodes across a range of possible working ion, transition metal, and anion chemistries. Using this body of results, the importance of polymorph selection as well as chemical composition on the ability of a host cathode to support intercalation reactions is analyzed. It is found that the accessibility of high energy charged polymorphs in oxides generally leads to larger intercalation voltages favoring intercalation reactions, whereas sulfides and selenides tend to favor conversion reactions. Furthermore, it is observed that Cr‐containing cathodes favor intercalation more strongly than those with other transition metals. Finally, it is concluded that two‐electron reduction of transition metals (as is possible with the intercalation of a 2 + ion) will favor conversion reactions in the compositions studied.