bluuebunny/crossref_metadata_2025_split huggingface dataset:
MXene Ti3C2Tx: A Promising Photothermal Conversion Material and Application in All‐Optical Modulation and All‐Optical Information Loading
Authors: Wang Cong , Wang Yunzheng , Jiang Xiantao , Xu Jiawei , Huang Weichun , Zhang Feng , Liu Jiefeng , Yang Fumei , Song Yufeng , Ge Yanqi , Wu Qing , Zhang Meng , Chen Hong , Liu Jie , Zhang Han 
Published: April 2019

AbstractAll‐optical modulators, where one light modulates the parameters of another light (intensity, phase, frequency, etc.) without external electronic control, have drawn extraordinary attention in all‐optical information processing. In this contribution, by taking advantage of the two‐pass structure of Michelson interferometer and the strong photothermal conversion efficiency of MXene nanomaterials, an all‐optical modulator is demonstrated with a modulation depth of >27 dB, a free spectrum range of 16.8 nm and a pump‐induced phase shift slope of 0.043 π mW−1. Moreover, the all‐optical modulator is successfully employed to switch on/off the intensity of the signal light and load information from one channel to another with comparable response time and baudrate. It is believed that the MXene‐based all‐optical modulator will open a door to practical applications of 2D materials‐based all‐optical devices in all‐optical signal processing.
Memristors for Hardware Security Applications
Authors: Pang Yachuan , Gao Bin , Lin Bohan , Qian He , Wu Huaqiang 
Published: April 2019

AbstractMemristors have recently been explored for hardware security applications such as true random number generators (TRNGs) and physical unclonable functions (PUFs). Several typical designs for memristor‐based PUFs and TRNGs are summarized. PUFs are a novel hardware security primitive utilizing the intrinsic randomness of a physical system, and PUFs have broad potential applications in key protection and authentication. Unlike most conventional PUFs based on manufacturing variations, memristors have both manufacturing variations and intrinsic randomness in their resistance‐switching mechanisms that can be utilized as entropy sources; for instance, device to device (D2D) variation and probabilistic switching behaviors. TRNGs are a cornerstone of hardware security and are widely used in secure chips and encryption protocols. Memristors have random telegraph noise (RTN) and cycle to cycle (C2C) variation characteristics that can be used for high‐quality TRNGs. Here, research progress in memristor‐based PUFs and TRNGs is reviewed, and how these sources of randomness are leveraged to generate security primitives is discussed.
Computation‐Guided Design of LiTaSiO5, a New Lithium Ionic Conductor with Sphene Structure
Authors: Xiong Shan , He Xingfeng , Han Aijie , Liu Zhantao , Ren Zhensong , McElhenny Brian , Nolan Adelaide M. , Chen Shuo , Mo Yifei , Chen Hailong 
Published: April 2019

AbstractThe development of all‐solid‐state Li‐ion batteries requires solid electrolyte materials with many desired properties, such as ionic conductivity, chemical and electrochemical stability, and mechanical durability. Computation‐guided materials design techniques are advantageous in designing and identifying new solid electrolytes that can simultaneously meet these requirements. In this joint computational and experimental study, a new family of fast lithium ion conductors, namely, LiTaSiO5 with sphene structure, are successfully identified, synthesized, and demonstrated using a novel computational design strategy. First‐principles computation predicts that Zr‐doped LiTaSiO5 sphene materials have fast Li diffusion, good phase stability, and poor electronic conductivity, which are ideal for solid electrolytes. Experiments confirm that Zr‐doped LiTaSiO5 sphene structure indeed exhibits encouraging ionic conductivity. The lithium diffusion mechanisms in this material are also investigated, indicating the sphene materials are 3D conductors with facile 1D diffusion along the [101] direction and additional cross‐channel migration. This study demonstrates a novel design strategy of activating fast Li ionic diffusion in lithium sphenes, a new materials family of superionic conductors.
Why are Hot Holes Easier to Extract than Hot Electrons from Methylammonium Lead Iodide Perovskite?
Authors: Dursun Ibrahim , Maity Partha , Yin Jun , Turedi Bekir , Zhumekenov Ayan A. , Lee Kwang Jae , Mohammed Omar F. , Bakr Osman M. 
Published: April 2019

AbstractCharge‐carriers photoexcited above a semiconductor's bandgap rapidly thermalize to the band‐edge. The cooling of these difficult to collect “hot” carriers caps the available photon energy that solar cells–including efficient perovskite solar cells–may utilize. Here, the dynamics and efficiency of hot carrier extraction from MAPbI3 (MA = methylammonium) perovskite by spiro‐OMeTAD (a hole‐transporting layer) and TiO2 (an electron‐transporting layer) are investigated and explained using both ultrafast electronic spectroscopy and theoretical modeling. Time‐resolved spectroscopy reveals a quasi‐equilibrium distribution of hot carriers forming upon excess‐energy excitation of the perovskite–a distribution largely unaffected by the presence of TiO2. In contrast, the quasi‐equilibrium distribution of hot carriers is virtually nonexistent when spiro‐OMeTAD is present, which is indicative of efficient hot hole extraction at the interface of MAPbI3. Density functional theory calculations predict that deep energy‐levels of MAPbI3 exhibit electronically delocalized character, with significant overlap with the localized valence band charge of the spiro‐OMeTAD molecules lying on the surface of MAPbI3. Consequently, hot holes are easily extracted from the deep energy‐levels of MAPbI3 by spiro‐OMeTAD. These findings uncover the origins of efficient hot hole extraction in perovskites and offer a practical blueprint for optimizing solar cell interlayers to enable hot carrier utilization.
Shape Conformal and Thermal Insulative Organic Solar Absorber Sponge for Photothermal Water Evaporation and Thermoelectric Power Generation
Authors: Zhu Liangliang , Ding Tianpeng , Gao Minmin , Peh Connor Kang Nuo , Ho Ghim Wei 
Published: April 2019

AbstractSolar‐driven interfacial vaporization by localizing solar‐thermal energy conversion to the air–water interface has attracted tremendous attention due to its high conversion efficiency for water purification, desalination, energy generation, etc. However, ineffective integration of hybrid solar thermal devices and poor material compliance undermine extensive solar energy exploitation and practical outdoor use. Herein, a 3D organic bucky sponge that has a combination of desired chemical and physical properties, i.e., broadband light absorbing, heat insulative, and shape‐conforming abilities that render efficient photothermic vaporization and energy generation with improved operational durability is reported. The highly compressible and readily reconfigurable solar absorber sponge not only places less constraints on footprint and shape defined fabrication process but more importantly remarkably improves the solar‐to‐vapor conversion efficiency. Notably, synergetic coupling of solar‐steam and solar‐electricity technologies is realized without trade‐offs, highlighting the practical consideration toward more impactful solar heat exploitation. Such solar distillation and low‐grade heat‐to‐electricity generation functions can provide potential opportunities for fresh water and electricity supply in off‐grid or remote areas.
Advanced Carbon‐Based Anodes for Potassium‐Ion Batteries
Authors: Wu Xuan , Chen Yanli , Xing Zheng , Lam Christopher Wai Kei , Pang Su‐Seng , Zhang Wei , Ju Zhicheng 
Published: April 2019

AbstractThe ever‐increasing demand for large‐scale energy storage systems requires novel battery technologies with low‐cost and sustainable properties. Due to earth‐abundance and cost effectiveness, the development of rechargeable potassium ion batteries (PIBs) has recently attracted much attention. Since carbon‐based materials are abundant, inexpensive, nontoxic, and safe, extensive feasibility investigations have suggested that they can become promising anode materials for PIBs. This review not only attempts to provide better understanding of the potassium storage mechanism, but also summarizes the availability of new carbon‐based materials and their electrochemical performance covering graphite, graphene, and hard carbon materials plus carbon‐based composites. Finally, the critical issues, challenges, and perspectives are discussed to demonstrate the developmental direction of PIBs.
TBHP‐Initiated Transamidation of Secondary Amides via C−N Bond Activation: A Metal‐Free Approach
Authors: Mishra Ankush , Chauhan Swati , Verma Pratibha , Singh Sundaram , Srivastava Vandana 
Published: April 2019

AbstractIn the present study, a facile, efficient, and environmentally benign approach for secondary amide transamidation by using tert‐butyl hydroperoxide (TBHP) as a radical initiator has been developed. The method involves a two‐step approach in which the first step is the C−N bond activation via N‐functionalization with Boc to weaken the amide C−N bond by making amide non‐planar and electronically destabilized. In the second step, an N‐Boc‐activated secondary amides undergoes transamidation with the various primary, secondary, aliphatic, aromatic, as well as the sterically hindered amines, using TBHP as a radical initiator to give the products in good to excellent yields. TBHP is easily available, inexpensive, and an environmentally friendly radical initiator. A broad substrate scope with extensive functional group tolerance, metal and catalyst‐free approach, and operational simplicity are the important characteristics of the present protocol.
Boron‐Catalyzed Hydroamination/Hydroallylation and Hydroamination/Hydrocyanation of Unactivated Alkynes
Authors: Shibuya Masatoshi , Kawano Shohei , Fujita Shoji , Yamamoto Yoshihiko 
Published: April 2019

AbstractB(C6F5)3‐catalyzed tandem double hydrofunctionalization reactions initiated by intramolecular hydroamination of unactivated alkynes are described herein. In the hydroamination/hydroallylation reaction, in situ preparation of anhydrous B(C6F5)3 from B(C6F5)3 ⋅ nH2O and the use of 2,6‐di‐tert‐butylphenol as a proton source were effective. In the hydroamination/hydrocyanation reaction, a combination of B(C6F5)3 ⋅ nH2O and H2O as the proton source provided good results.
Scandium‐Triflate‐Catalyzed Regioselective Ring Opening of Purines with Aminocyclopropanes
Authors: Liang Tao , Xie Ming‐Sheng , Qu Gui‐Rong , Guo Hai‐Ming 
Published: April 2019

AbstractAn efficient route to acyclic purine nucleoside analogues with an amino group at the C1′ position of the side chains has been reported. Using Sc(OTf)3 as the catalyst, the ring‐opening reaction of purines with aminocyclopropanes afforded acyclic nucleoside analogues with moderate to good yields and in a regioselective manner. Furthermore, phenyl cyclopropane also gave the desired acyclic nucleoside analogue with a phenyl linked at C1′ position. Furthermore, generation of a penciclovir analogue may also occur from the ring‐opening product via a reduction reaction.
Soybean Trypsin Inhibitor Assay: The Sequence Effect of Adding Reagents, Factors Involved, and Mechanistic Explanations
Authors: Liu Keshun 
Published: April 2019

AbstractFor assaying trypsin inhibitor activity (TIA) of protein‐based inhibitors, the sequence of adding enzyme, substrate, and inhibitor has profound effects on measured values. This study systematically investigated this reagents’ sequence effect, with regard to factors involved and mechanistic explanations, using raw and toasted soy flours. When the AOCS standard method (Ba 12‐75), which features adding substrates last, was used, TIA values measured varied greatly with not only the pH and Ca2+ concentration of the premix (the mixture of the first two reagents) and preincubation time, but also extractant, postextraction workup (addition of Tris assay buffer and/or centrifugation), and extract dilution levels. Raw and toasted soy flours showed different TIA changes with these factors. Yet, when the standard method was slightly modified by adding enzyme last, TIA values obtained were unaffected by the premix pH and Ca2+ concentration, preincubation time, and extract dilution levels, and thus remained constant. Strong interactions of some factors also existed, as exemplified by significant suppression of the reagents’ sequence effect by the Ca2+ presence in the premix when the premix was neutral and alkaline, but not acidic. These observations are explainable by three proposed mechanisms: limited hydrolysis of the trypsin inhibitor by trypsin in acidic medium according to a reactive site model of the inhibitor, trypsin autolysis in neutral or alkaline medium, and trypsin protection by Ca2+. This study provided a strong basis for modifying the standard method. Because the reactive site model of soybean trypsin inhibitors is applicable to many other protein‐based proteinase inhibitors, the reagents’ sequence will affect the results when assaying their activities.
MicroRNA‐1225 activates Keap1‐Nrf2‐HO‐1 signalling to inhibit TNFα‐induced osteoclastogenesis by mediating ROS generation
Authors: Reziwan Keyimu , Sun Dalei , Zhang Bo , Zhao Zhihe 
Published: April 2019

The influence of miRNA‐1225‐5p (miR‐1225) and Keap1‐Nrf2 signalling on in vitro osteoclast differentiation in mouse models was studied along with the underlying mechanism. In differentiated bone marrow–derived macrophages (BMMs), downregulated miR‐1225 and upregulated Keap1 were observed in the course of receptor activator of nuclear factor kappa‐Β ligand (RANKL)–mediated osteoclastogenesis. Bioinformatic analysis and dual‐luciferase reporter assay showed that miR‐1225 targeted the three prime untranslated region (3′‐UTR) of Keap1 mRNA and caused its degradation. Transfection of a miR‐1225 mimic or Keap1 silencing was found to inhibit osteoclastogenesis as evidenced by loss of activity and tartrate‐resistant acid phosphatase (TRAP) staining, decreased expression of osteoclast markers, and associated genes and reduced number of multinuclear cells; in contrast, a miR‐1225 inhibitor or Keap1 overexpression increased this process. In addition, transfection with the miR‐1225 mimic or Keap1 silencing decreased the level of tumour necrosis factor (TNF)α, which was increased after miR‐1225 inhibition and Keap1 overexpression. TNFα overexpression promoted Keap1 depletion–inhibited BMM osteoclastogenesis. Furthermore, reactive oxygen species (ROS) generation that is related to osteoclastogenesis and the Keap‐Nrf2 axis was impaired by the miR‐1225 mimic and Keap1 silencing, whereas it was increased following miR inhibition and overexpression of Keap1 and TNFα. Thus, miR‐1225 inhibits osteoclastogenesis by directly activating the Keap1‐Nrf2‐HO‐1 axis to repress TNFα‐mediated ROS generation.Significance of the studyOur study showed that miR‐1225 is significant in multiple malignancies and other pathological reactions. Transfection of a miR‐1225 mimic or Keap1 silencing inhibits osteoclastogenesis. After miR‐1225 inhibition and Keap1 overexpression, TNF was increased. TNFα overexpression promoted Keap1 depletion–inhibited BMM osteoclastogenesis. miR‐1225 activates Keap1‐Nrf2‐HO‐1 signal to inhibit TNFα‐induced osteoclastogenesis.
Heavy Enzymes and the Rational Redesign of Protein Catalysts
Authors: Scott Alan F. , Luk Louis Y.‐P. , Tuñón Iñaki , Moliner Vicent , Allemann Rudolf K. 
Published: April 2019

AbstractAn unsolved mystery in biology concerns the link between enzyme catalysis and protein motions. Comparison between isotopically labelled “heavy” dihydrofolate reductases and their natural‐abundance counterparts has suggested that the coupling of protein motions to the chemistry of the catalysed reaction is minimised in the case of hydride transfer. In alcohol dehydrogenases, unnatural, bulky substrates that induce additional electrostatic rearrangements of the active site enhance coupled motions. This finding could provide a new route to engineering enzymes with altered substrate specificity, because amino acid residues responsible for dynamic coupling with a given substrate present as hotspots for mutagenesis. Detailed understanding of the biophysics of enzyme catalysis based on insights gained from analysis of “heavy” enzymes might eventually allow routine engineering of enzymes to catalyse reactions of choice.
Unravelling the Mechanism and Selectivity of the NHC‐catalyzed Three‐Membered Ring‐Opening/Fluorination of Epoxy Enals: A DFT Study
Authors: Wang Yang , Qu Ling‐Bo , Lan Yu , Wei Donghui 
Published: April 2019

AbstractRegio‐ and stereo‐divergent construction of carbon‐fluorine bond remains a challenge in fluorine chemistry, especially reactions involving fluorination at the α‐position of a carbonyl group. Herein, we present a detailed study for predicting the origins of regio‐ and stereo‐selectivity for organocatalyst catalyzed fluorination reaction. Possible mechanisms and origins of selectivities of NHC (N‐heterocyclic carbene)‐catalyzed fluorination reaction of epoxy‐enals were investigated by using DFT (density functional theory) method. The computational results show that the C−F bond formation step determines stereoselectivity and regioselectivity. LP⋅⋅⋅π and C−H⋅⋅⋅F interactions were identified as the main contributors for the stereoselectivity control, in which R‐configured product was preferred. It was found that α‐fluorination is more energetically favorable than γ‐fluorination, which is possibly due to higher reactivity of the α‐carbon; deduced by the local reactivity index analysis. This work would provide valuable insights for predicting origin of the selectivity of fluorination reactions and developing of more effective organocatalyst with high selectivity.
Ion Association in Lanthanide Chloride Solutions
Authors: Finney Aaron R. , Lectez Sébastien , Freeman Colin L. , Harding John H. , Stackhouse Stephen 
Published: April 2019

AbstractA better understanding of the solution chemistry of the lanthanide (Ln) salts in water would have wide ranging implications in materials processing, waste management, element tracing, medicine and many more fields. This is particularly true for minerals processing, given governmental concerns about lanthanide security of supply and the drive to identify environmentally sustainable processing routes. Despite much effort, even in simple systems, the mechanisms and thermodynamics of LnIII association with small anions remain unclear. In the present study, molecular dynamics (MD), using a newly developed force field, provide new insights into LnCl3(aq) solutions. The force field accurately reproduces the structure and dynamics of Nd3+, Gd3+ and Er3+ in water when compared to calculations using density functional theory (DFT). Adaptive‐bias MD simulations show that the mechanisms for ion pairing change from dissociative to associative exchange depending upon cation size. Thermodynamics of association reveal that whereas ion pairing is favourable, the equilibrium distribution of species at low concentration is dominated by weakly bound solvent‐shared and solvent‐separated ion pairs, rather than contact ion pairs, reconciling a number of contrasting observations of LnIII–Cl association in the literature. In addition, we show that the thermodynamic stabilities of a range of inner sphere and outer sphere
coordination complexes are comparable and that the kinetics of anion binding to cations may control solution speciation distributions beyond ion pairs. The techniques adopted in this work provide a framework with which to investigate more complex solution chemistries of cations in water.
Phantom walkabouts: A customisable source location privacy aware routing protocol for wireless sensor networks
Authors: Gu Chen , Bradbury Matthew , Jhumka Arshad 
Published: April 2019

SummarySource location privacy (SLP) is an important property for a large class of security‐critical wireless sensor network (WSN) applications such as monitoring and tracking. In the seminal work on SLP, phantom routing was proposed as a viable approach to address SLP. However, recent work has shown some limitations of phantom routing such as poor data yield and low SLP. In this paper, we propose phantom walkabouts, a novel and more general version of phantom routing, which performs phantom routes of variable lengths. Through extensive simulations, we show that phantom walkabouts provides high SLP level than phantom routing under specific network configuration.
Phosphorene‐Supported Transition‐Metal Dimer for Effective N2 Electroreduction
Authors: Tang Qing , Jiang De‐en 
Published: April 2019

AbstractThe electrochemical reduction of N2 to NH3 at ambient conditions is a promising alternative to the energy‐intensive, high‐temperature, high‐pressure Haber‐Bosch process. But it is extremely challenging to find an electrocatalyst that can effectively activate N2 and reduce it to NH3. From first principles density functional theory, we found that the Ti dimer supported on single‐layer phosphorene can be used as a promising electrocatalyst for N2 capture and conversion to NH3. The overpotential (relative to the standard hydrogen electrode) was found to be as low as 0.20, much lower than those predicted on the Ti surface (1 to 1.5 V) or their nitrides (0.5 to 1 V). In addition, we found that hydride is involved in the N2 reduction on the Ti dimer catalyst via formation of Ti2‐H species, and the hydride would favorably transfer onto the adsorbed N2* to form *NNH intermediate and further reduced to NH3. Moreover, we also examined other first‐row transition metal dimers, and found that Sc and Fe dimer to be potential catalysts which could catalyze N2 reduction at a low overpotential of about 0.21 and 0.45 V, respectively. Our predictions hence suggest Ti, Sc and Fe dimer clusters supported on phosphorene as promising electrocatalysts for N2 reduction to NH3.
Thermoelectric Properties of Pure SnSe Single Crystal Prepared by a Vapor Deposition Method
Authors: Jin Min , Jiang Jun , Li Rongbin , Wang Xianghu , Chen Yunxia , Chen Yuqi , Xu Jiayue 
Published: April 2019

AbstractAs a promising eco‐friendly high‐performance thermoelectric material, SnSe single crystal has attracted much attention during the past several years. In this work, SnSe single crystal is prepared through a novel vapor deposition method in which polycrystalline SnSe is volatilized on a hot side (800–850 °C) and single‐crystalline SnSe spontaneously nucleates on the cold side (500–650 °C) based on the inside wall of a quartz ampoule. This crystal growth technique is beneficial for obtaining high‐purity SnSe crystal as some metal ions, such as Li+, Na+, and K+, in the quartz ampoule will be restricted from diffusing into the material. SnSe single crystal along the a‐axis is measured to experience a Pnma–Cmcm phase transition around 800 K where power factor (PF) exhibits the highest value of 6.2 µW cm−1 K−2 and total thermal conductivity ktot shows the lowest value of 0.48 W m−1 K−1. Accordingly, SnSe single crystal reaches a maximum ZT = 0.98 near phase transition temperature. These results not only provide an effective approach for pure SnSe single crystal fabrication, but also reveal the intrinsic electronic and phononic transport properties of thermoelectric SnSe.