bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled Vapor Growth and Nonlinear Optical Applications of Large‐Area 3R Phase WS2 and WSe2 Atomic Layers
Authors: Zeng Zhouxiaosong , Sun Xingxia , Zhang Danliang , Zheng Weihao , Fan Xiaopeng , He Mai , Xu Tao , Sun Litao , Wang Xiao , Pan Anlian 
Published: January 2019

Abstract2D layered 3‐rhombohedral (3R) phase transition metal dichalcogenides (TMDs) have received significantly increased research interest in nonlinear optical applications due to their unique crystal structures and broken inversion symmetry. However, controlled growth of 2D 3R phase TMDs still remains a great challenge. In this work, a direct growth of large‐area WS2 and WSe2 atomic layers with controllable crystal phases via a developed temperature selective physical vapor deposition route is reported. Large‐area triangular 3R phase layers are synthesized at a lower deposition temperature. Steady state and time‐resolved photoluminescence spectroscopy and Raman spectroscopy are used to study the unique properties of 3R phase layers due to different layer stacking and interlayer coupling. More importantly, with broken inversion symmetry, 3R phase layers show a quadratically increased second harmonic generation (SHG) intensity with respect to layer numbers. Furthermore, by polarization‐resolved SHG, a uniform polarization preference is observed in bilayer and trilayer 3R phase WS2, which could be a benefit for practical applications. The results not only contribute to the controlled growth of 2D TMDs layers with different phases but also pave the way to promising nonlinear optical devices.
Engineering Perovskite Nanocrystal Surface Termination for Light‐Emitting Diodes with External Quantum Efficiency Exceeding 15%
Authors: Xiao Zhengguo , Kerner Ross A. , Tran Nhu , Zhao Lianfeng , Scholes Gregory D. , Rand Barry P. 
Published: January 2019

AbstractHybrid organic–inorganic metal halide perovskites are particularly promising for light‐emitting diodes (LEDs) due to their attractive optoelectronic properties such as wavelength tunability, narrow emission linewidth, defect tolerance, and high charge carrier mobility. However, the undercoordinated Pb and halide at the perovskite nanocrystal (NC) surface causes traps and nonradiative recombination. In this work, the external quantum efficiency of iodide‐based perovskite LEDs is boosted to greater than 15%, with an emission wavelength at 750 nm, by engineering the perovskite NC surface stoichiometry and chemical structure of bulky organoammonium ligands. To the stoichiometric precursor solution for the 3D bulk perovskite, 20% molar ratio of methylammonium iodide is added in addition to 20% excess bulky organoammonium iodide to ensure that the NC surface is organoammonium terminated as the crystal size is decreased to 5–10 nm. This combination ensures minimal undercoordinated Pb and halide on the surface, avoids 2D phases, and acts to provide nanosized perovskite grains which allow for smooth and pinhole‐free films. As a result of time‐resolved photoluminescence (PL) and PL quantum yield measurements, it is possible to demonstrate that this surface modification increases the radiative recombination rate while reducing the nonradiative rate.
A Dual‐Retarded Reaction Processed Mixed‐Cation Perovskite Layer for High‐Efficiency Solar Cells
Authors: Mali Sawanta S. , Patil Jyoti V. , Kim Hyungjin , Kim HyunHoon , Hong Chang Kook 
Published: January 2019

AbstractMixed‐cation perovskite solar cells (PSCs) have become of enormous interest because of their excellent efficiency, which is now crossing 23.7%. Their broader absorption, relatively high stability with low fabrication cost compared to conventional single phase ABX3 perovskites (where A: organic cation; B: divalent metal ion; and X: halide anion) are key properties of mixed‐halide mixed‐cation perovskites. However, the controlling reaction rate and formation of extremely dense, textured, smooth, and large grains of perovskite layer is a crucial task in order to achieve highly efficient PSCs. Herein, a new simple dual‐retarded reaction processing (DRP) method is developed to synthesize a high‐quality mixed‐cation (FAPbI3)0.85(MAPbBr3)0.15 (where MAPbBr3 stands for methylammonium lead bromide and FAPbI3 stands for formamidinium lead iodide) perovskite thin film via intermediate phase and incorporation of nitrogen‐doped reduced graphene oxide (N‐rGO). The reaction rate is retarded via two steps: first the formation of intermediate phase and second the interaction of the nitrogen groups on N‐rGO with hydrogen atoms from formamidinium cations. This DRP process allows for the fabrication of PSCs with maximum conversion efficiency higher than 20.3%.
Discovering Hidden Material Properties of MgCl2 at Atomic Resolution with Structured Temporal Electron Illumination of Picosecond Time Resolution
Authors: Kisielowski Christian , Specht Petra , Freitag Bert , Kieft Erik R. , Verhoeven Wouter , van Rens Jasper F. M. , Mutsaers Peter , Luiten Jom , Rozeveld Steve , Kang Joo , McKenna Alyssa J. , Nickias Peter , Yancey David F. 
Published: January 2019

AbstractA combination of atomic resolution phase contrast electron microscopy and pulsed electron beams reveals pristine properties of MgCl2 at 1.7 Å resolution that were previously masked by air and beam damage. Both the inter‐ and intra‐layer bonding in pristine MgCl2 are weak, which leads to uncommonly large local orientation variations that characterize this Ziegler–Natta catalyst support. By delivering electrons with 1–10 ps pulses and ≈160 ps delay times, phonons induced by the electron irradiation in the material are allowed to dissipate before the subsequent delivery of the next electron packet, thus mitigating phonon accumulations. As a result, the total electron dose can be extended by a factor of 80–100 to study genuine material properties at atomic resolution without causing object alterations, which is more effective than reducing the sample temperature. In conditions of minimal damage, beam currents approach femtoamperes with dose rates around 1 eÅ−2 s−1. Generally, the utilization of pulsed electron beams is introduced herein to access genuine material properties while minimizing beam damage.
Composition and Energy Band–Modified Commercial FTO Substrate for In Situ Formed Highly Efficient Electron Transport Layer in Planar Perovskite Solar Cells
Authors: Sun Haoxuan , Zhou Yu , Xin Yu , Deng Kaimo , Meng Linxing , Xiong Jie , Li Liang 
Published: January 2019

AbstractPerovskite solar cells (PSCs) have received much attention and with them a power conversion efficiency (PCE) of over 22% has been achieved. Electron transport layers (ETLs) based on metal oxide materials play an important role in transferring electrons and reducing back recombination. However, existing fabrication approaches are generally waste too many materials and consume too much energy for commercial application. Here, a brand new plasma preannealing procedure is proposed that can replace the traditional ETL preparation process and alleviate the above‐mentioned problems. A pure SnO2 phase in situ formed on the fluorine‐doped tin oxide (FTO) surface can be obtained at room temperature by only 15 min oxygen plasma assisted reaction without postheating treatment. It enables the precise control of compositions, defects, and energy levels of band at the surface of FTO substrate, resulting in a prominent PCE of 20.39% with excellent stability and reproducibility. This simple and efficient source‐free fabrication technology provides a versatile platform for the manufacture of PSCs in the future.
Epitaxial Growth of h‐BN on Templates of Various Dimensionalities in h‐BN–Graphene Material Systems
Authors: Chen Xin , Yang He , Wu Bin , Wang Lifeng , Fu Qiang , Liu Yunqi 
Published: January 2019

AbstractEpitaxy traditionally refers to the growth of a crystalline adlayer on a crystalline surface, and has been demonstrated in several simple material systems over decades. Beyond this, it is not clear whether the growth of 2D materials on templates of various dimensionalities is possible, and no effective theory or model is available for describing the complex epitaxial growth kinetics. Here a library of hexagonal boron nitride epitaxy is presented on graphene–hexagonal boron nitride templates of various dimensionalities, including 2D homo/heteromaterial surface and 1D interfaces of homo/heteromaterials. A framework that allows the description of various kinetic growth by combined geometric and structural modeling is developed. Using these tools, the underlying mechanisms for the complex merging process, grain boundary formation, edge‐configuration‐dependent growth difference, position‐dependent size difference, and the correlation among epilayer orientation, crystal structure and geometry are elucidated. This work provides a general viewpoint for understanding epitaxial growth in complex systems.
Defect Engineering and Surface Functionalization of Nanocarbons for Metal‐Free Catalysis
Authors: Ortiz‐Medina Josue , Wang Zhipeng , Cruz‐Silva Rodolfo , Morelos‐Gomez Aaron , Wang Feng , Yao Xiangdong , Terrones Mauricio , Endo Morinobu 
Published: January 2019

AbstractWith the advent of carbon nanotechnology, which initiated significant research efforts more than two decades ago, novel materials for energy harvesting and storage have emerged at an amazing pace. Nevertheless, some fundamental applications are still dominated by traditional materials, and it is especially evident in the case of catalysis, and environmental‐related electrochemical reactions, where precious metals such as Pt and Ir are widely used. Several strategies are being explored for achieving competitive and feasible metal‐free carbon nanomaterials, among which doping and defect engineering approaches within nanocarbons are recurrent and promising. Here, the most recent efforts regarding the control of doping and defects in carbon nanostructures for catalysis, and in particular for energy‐related applications, are addressed. Finally, an overview of alternative proposals that can make a difference when enabling carbon nanomaterials as efficient and emerging catalysts is presented.
Doping Nanoscale Graphene Domains Improves Magnetism in Hexagonal Boron Nitride
Authors: Fan Mengmeng , Wu Jingjie , Yuan Jiangtan , Deng Liangzi , Zhong Ning , He Liang , Cui Jiewu , Wang Zixing , Behera Sushant Kumar , Zhang Chenhao , Lai Jiawei , Jawdat BenMaan I. , Vajtai Robert , Deb Pritam , Huang Yang , Qian Jieshu , Yang Jiazhi , Tour James M. , Lou Jun , Chu Ching‐Wu , Sun Dongping , Ajayan Pulickel M. 
Published: January 2019

AbstractCarbon doping can induce unique and interesting physical properties in hexagonal boron nitride (h‐BN). Typically, isolated carbon atoms are doped into h‐BN. Herein, however, the insertion of nanometer‐scale graphene quantum dots (GQDs) is demonstrated as whole units into h‐BN sheets to form h‐CBN. The h‐CBN is prepared by using GQDs as seed nucleations for the epitaxial growth of h‐BN along the edges of GQDs without the assistance of metal catalysts. The resulting h‐CBN sheets possess a uniform distrubution of GQDs in plane and a high porosity macroscopically. The h‐CBN tends to form in small triangular sheets which suggests an enhanced crystallinity compared to the h‐BN synthesized under the same conditions without GQDs. An enhanced ferromagnetism in the h‐CBN emerges due to the spin polarization and charge asymmetry resulting from the high density of CN and CB bonds at the boundary between the GQDs and the h‐BN domains. The saturation magnetic moment of h‐CBN reaches 0.033 emu g−1 at 300 K, which is three times that of as‐prepared single carbon‐doped h‐BN.
Enzymes Immobilized on Carbon Nitride (C3N4) Cooperating with Metal Nanoparticles for Cascade Catalysis
Authors: Wang Yangxin , Zhang Ningning , Hübner René , Tan Deming , Löffler Markus , Facsko Stefan , Zhang En , Ge Yan , Qi Zhenhui , Wu Changzhu 
Published: January 2019

AbstractThe exploration of effective platforms for immobilizing chemo‐ and biocatalysts to develop biohybrid catalysts is an attractive subject of practical interest. In this work, carbon nitride (C3N4) is used for the first time as a platform for the immobilization of metal catalyst (Pd nanoparticles) and biocatalyst (Candida antarctica lipase B, CalB) in a facile manner to prepare biohybrid catalyst. The optimal biohybrid catalyst inherits the intrinsic performance of both Pd nanoparticles and CalB, and shows high activity in the one‐pot cascade reaction converting benzaldehyde to benzyl hexanoate at room temperature. With this proof of concept, it is expected that C3N4 can be utilized for immobilizing more types of chemo‐ and biocatalysts for perspective applications.
UV and Visible Light Induced Photocatalytic Degradation on p–n Cu2O/ZnO Nanowires Decorated with Au–Pd Alloy Nanoparticles
Authors: Hsu Cheng‐Liang , Chuo Yen‐Cheng , Hsu Liang‐Wei , Pan Yen‐Liang , Liu Yi‐Hung 
Published: January 2019

AbstractChemical solutions are applied to synthesize Au–Pd alloy nanoparticles (NPs) and ZnO/Cu2O core–shell nanowires (NWs) on ITO/glass substrates by the photochemical, electrochemistry, and hydrothermal methods. The Cu2O cubic structures and ZnO hexagonal wurtzite structures are verified as being polycrystalline and single crystalline, respectively, by X‐ray diffraction and high‐resolution transmission electron microscopy (HR‐TEM). The p‐Cu2O/n‐ZnO NWs samples exhibit rectification properties that confirm the p–n heterojunction interface. The diameter range of the Au–Pd alloy NPs is around 2–15 nm and the Au/Pd ratio is 27:28, according to HR‐TEM and X‐ray photoelectron spectroscopy. The p‐Cu2O/n‐ZnO core–shell NWs feature higher UV photocatalytic degradation of methylene blue than do the ZnO NWs. Deposited Au, Pd, Au–Pd alloy NPs on the p‐Cu2O/n‐ZnO core–shell NWs improve the photocatalytic degradation efficiency under UV and blue light. The Au–Pd alloy NPs/p‐Cu2O/n‐ZnO core–shell NWs offer the best photocatalytic properties under UV‐ and blue‐light‐emitting diode (LED) illumination.
On Untethered, Dual Magneto‐ and Photoresponsive Liquid Crystal Bilayer Actuators Showing Bending and Rotating Motion
Authors: Pilz da Cunha Marina , Foelen Yari , Engels Tom A. P. , Papamichou Kleopatra , Hagenbeek Michiel , Debije Michael G. , Schenning Albert P. H. J. 
Published: January 2019

AbstractThe integration of untethered, multi‐stimuli responsive actuation into soft microrobotic devices is a goal in the development of “smart” materials. This manuscript reports on a dual‐stimuli responsive bilayer actuator consisting of a light responsive liquid crystal network (LCN) and a magnetic responsive polydimethylsiloxane (PDMS) composite. This design is of facile fabrication with ample design freedom, using no additional adhesion layers. Untethered control of the bilayer permits motions including bending and rotation, steered individually or in synchronization. Through a systematic study the direct impact of the PDMS layer was elucidated on the light triggered rate of actuation and maximum deformation amplitude of the LCN film. The alignment (homeotropic or planar) of the LCN has a profound effect on the resulting bilayer actuation. It is demonstrated, both experimentally and theoretically, that the rates of sample heating and actuation are directly correlated and highlight the critical role of the PDMS as a heat sink. The maximum amplitude of displacement of the bilayer is tied to the stiffness, being inversely correlated to the PDMS thickness to the third power. These results give insights and provide straightforward design rules to fabricate bilayer actuators with programmed multi‐responsive properties.
A Zero‐Rank, Maximum Nullity Perfect Electromagnetic Wave Absorber
Authors: Suen Jonathan Y. , Fan Kebin , Padilla Willie J. 
Published: January 2019

AbstractElectromagnetic wave absorbers formed from a metamaterial layer are demonstrated and near‐perfect absorption is realized across much of the spectrum. Alternatively, an unpatterned low‐loss dielectric layer forms an absorber of coherent light and shows near‐zero reflectance and high absorption. The latter is termed a coherent perfect absorber (CPA) and may be described as a time‐reversed laser. Here, a more fundamental system of dielectric metasurfaces is experimentally demonstrated, which may achieve either coherent or incoherent absorption. The absorber is viewed as two CPAs with eigenmodes of opposite symmetry, and may achieve incoherent absorption with a null scattering matrix, or coherent absorption with a rank‐1 scattering matrix. Metasurface absorbers are classified based on their scattering matrix rank and nullity. The demonstrated system and theory establish a path to realize a new class of absorbers useful for future novel applications, including hyperspectral imaging and energy harvesting.
Constructing Multi‐Stimuli‐Responsive Luminescent Materials through Outer Sphere Electron Transfer in Ion Pairs
Authors: Ma Yun , Shen Liang , She Pengfei , Hou Yuqi , Yu Yaxin , Zhao Jianzhang , Liu Shujuan , Zhao Qiang 
Published: January 2019

AbstractStimuli‐responsive luminescent materials are of scientific and technological interest due to their wide range of optoelectronic applications. The utilization of photoinduced electron transfer (PET) reactions is an effective strategy to design various stimuli‐responsive luminescent materials. To date, most of these materials are based on the inner sphere electron transfer mechanism, which refers to a redox chemical reaction that proceeds via a covalent bridge. In contrast, the method of using outer sphere electron transfer mechanism is superior to the covalent approach as it does not require tedious synthesis. Ion pairs, which are composed of two oppositely charged components, are ideal for the development of stimuli‐responsive materials based on outer sphere electron transfer mechanism. Here, it is demonstrated that the emission intensity of an ion pair, consisting of an electron‐deficient phosphor ([Ir(ttpy)2]3+, ttpy = 4′‐(p‐tolyl)‐2,2′:6′,2″‐terpyridine) and an electron‐rich quencher (BH4−, tetrabutylammonium borohydride), is significantly enhanced by applying an electrical stimulus or under UV light irradiation. As far as it is known, this work represents the first example of luminescent material showing smart responses to both electrical and light stimuli. The present results indicate that the use of suitable ion pairs can pave the way toward the construction of multi‐stimuli‐responsive smart materials through outer sphere electron transfer mechanism.
Flexible Robust and High‐Density FeRAM from Array of Organic Ferroelectric Nano‐Lamellae by Self‐Assembly
Authors: Guo Mengfan , Jiang Jianyong , Qian Jianfeng , Liu Chen , Ma Jing , Nan Ce‐Wen , Shen Yang 
Published: January 2019

AbstractFerroelectric memories are endowed with high data storage density by nanostructure designing, while the robustness is also impaired. For organic ferroelectrics favored by flexible memories, low Curie transition temperature limits their thermal stability. Herein, a ferroelectric random access memory (FeRAM) is demonstrated based on an array of P(VDF‐TrFE) lamellae by self‐assembly. Written data shows enhanced thermal endurance up to 90 °C and undergoes 12 thermal cycles between 30 and 80 °C with little volatilization. The promoted thermal stability is attributed to pinning effect at interfaces between grain boundaries and lamellae, where charged domain walls and charged defects are coupled. These results provide a strategy for improving robustness of organic flexible FeRAMs, and reveal an attracting coupling effect between different phases of ferroelectric polymer.
Bioinspired Preservation of Natural Killer Cells for Cancer Immunotherapy
Authors: El Assal Rami , Abou‐Elkacem Lotfi , Tocchio Alessandro , Pasley Shannon , Matosevic Sandro , Kaplan David L. , Zylberberg Claudia , Demirci Utkan 
Published: January 2019

AbstractThe ability to cryopreserve natural killer (NK) cells has a significant potential in modern cancer immunotherapy. Current cryopreservation protocols cause deterioration in NK cell viability and functionality. This work reports the preservation of human cytokine‐activated NK cell viability and function following cryopreservation using a cocktail of biocompatible bioinspired cryoprotectants (i.e., dextran and carboxylated ε‐poly‐L‐lysine). Results demonstrate that the recovered NK cells after cryopreservation and rewarming maintain their viability immediately after thawing at a comparable level to control (dimethyl sulfoxide‐based cryopreservation). Although, their viability drops in the first day in culture compared to controls, the cells grow back to a comparable level to controls after 1 week in culture. In addition, the anti‐tumor functional activity of recovered NK cells demonstrates higher cytotoxic potency against leukemia cells compared to control. This approach presents a new direction for NK cell preservation, focusing on function and potentially enabling storage and distribution for cancer immunotherapy.
Combined Amperometry and Electrochemical Cytometry Reveal Differential Effects of Cocaine and Methylphenidate on Exocytosis and the Fraction of Chemical Release
Authors: Zhu Wanying , Gu Chaoyi , Dunevall Johan , Ren Lin , Zhou Xuemin , Ewing Andrew G. 
Published: January 2019

AbstractAmperometry with nanotip electrodes has been applied to show cocaine and methylphenidate not only trigger declines in vesicle content and exocytotic catecholamine release in a model cell line but also differentially change the fraction of transmitter released from each individual vesicle. In addition, cocaine accelerates exocytotic release dynamics while they remain unchanged after methylphenidate treatment. The parameters from pre‐spike feet for the two drugs are also in opposition, suggesting this aspect of release is affected differentially. As cocaine and methylphenidate are psychostimulants with similar pharmacologic action but have opposite effects on cognition, these results might provide a missing link between the regulation of exocytosis and vesicles and the effect of this regulation on cognition, learning, and memory. A speculative chemical mechanism of the effect of these drugs on vesicle content and exocytosis is presented.
A Photoacoustic Probe for the Imaging of Tumor Apoptosis by Caspase‐Mediated Macrocyclization and Self‐Assembly
Authors: Wang Yuqi , Hu Xiaoming , Weng Jianhui , Li Jinbo , Fan Quli , Zhang Yan , Ye Deju 
Published: January 2019

AbstractPhotoacoustic (PA) imaging shows promise in the sensitive detection of caspase‐3 activated in early tumor apoptosis in response to chemotherapy; smart PA probes are thus in high demand. Herein, we report the first smart PA probe (1‐RGD) responsive to caspase‐3, enabling real‐time and high‐resolution imaging of tumor apoptosis. 1‐RGD is designed to leverage the synergetic effect of active delivery and caspase‐3 activation. It is selectively recognized by active caspase‐3 to trigger peptide substrate cleavage and biocompatible macrocyclization‐mediated self‐assembly, leading to an amplified PA imaging signal and prolonged retention in apoptotic tumor cells. Strong, high‐resolution PA images are obtained in chemotherapy‐induced apoptotic tumors in living mice after intravenous administration with 1‐RGD, facilitating sensitive reporting of caspase‐3 activity and distribution within tumor tissues.
Total Synthesis of Actinorhodin
Authors: Ninomiya Mamiko , Ando Yoshio , Kudo Fumitaka , Ohmori Ken , Suzuki Keisuke 
Published: January 2019

AbstractThe enantioselective total synthesis of actinorhodin (1) is described. The synthesis features 1) dual benzyne reactions en route to the monomer, 2) the trans‐selective installation of the side chain, and 3) a regioselective oxidative dimerization.