bluuebunny/crossref_metadata_2025 huggingface dataset:
Dune‐Yardang Interactions in Becquerel Crater, Mars
Authors: Urso Anna , Chojnacki Matthew , Vaz David A.
Published: January 2018

Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars' recent history has been dominated by wind‐driven activity. Resultantly, Martian landscapes often exhibit large‐scale aeolian features, including yardang landforms carved from sedimentary‐layered deposits. High‐resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune‐yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16–40 μm yr−1) would yield a formation time of 1.8–4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size‐frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian‐driven landscape evolution on Mars.
Distribution and Characteristics of Boulder Halos at High Latitudes on Mars: Ground Ice and Surface Processes Drive Surface Reworking
Authors: Levy J. S. , Fassett C. I. , Rader L. X. , King I. R. , Chaffey P. M. , Wagoner C. M. , Hanlon A. E. , Watters J. L. , Kreslavsky M. A. , Holt J. W. , Russell A. T. , Dyar M. D.
Published: January 2018

Boulder halos are circular arrangements of clasts present at Martian middle to high latitudes. Boulder halos are thought to result from impacts into a boulder‐poor surficial unit that is rich in ground ice and/or sediments and that is underlain by a competent substrate. In this model, boulders are excavated by impacts and remain at the surface as the crater degrades. To determine the distribution of boulder halos and to evaluate mechanisms for their formation, we searched for boulder halos over 4,188 High Resolution Imaging Science Experiment images located between ~50–80° north and 50–80° south latitude. We evaluate geological and climatological parameters at halo sites. Boulder halos are about three times more common in the northern hemisphere than in the southern hemisphere (19% versus 6% of images) and have size‐frequency distributions suggesting recent Amazonian formation (tens to hundreds of millions of years). In the north, boulder halo sites are characterized by abundant shallow subsurface ice and high thermal inertia. Spatial patterns of halo distribution indicate that excavation of boulders from beneath nonboulder‐bearing substrates is necessary for the formation of boulder halos, but that alone is not sufficient. Rather, surface processes either promote boulder halo preservation in the north or destroy boulder halos in the south. Notably, boulder halos predate the most recent period of near‐surface ice emplacement on Mars and persist at the surface atop mobile regolith. The lifetime of observed boulders at the Martian surface is greater than the lifetime of the craters that excavated them. Finally, larger minimum boulder halo sizes in the north indicate thicker icy soil layers on average throughout climate variations driven by spin/orbit changes during the last tens to hundreds of millions of years.
Large‐Scale Distribution of Molecular Components in Chinese Grassland Soils: The Influence of Input and Decomposition Processes
Authors: Dai Guohua , Ma Tian , Zhu Shanshan , Liu Zongguang , Chen Dima , Bai Yongfei , Chen Litong , He Jin‐Sheng , Zhu Juntao , Zhang Yangjian , Lü Xiaotao , Wang Xiaobo , Han Xingguo , Feng Xiaojuan
Published: January 2018

Chinese grasslands hold a third of the national soil organic carbon (OC) stocks but remain poorly investigated in terms of soil molecular components and their distribution patterns. Such information is important for understanding mechanisms governing grassland soil OC dynamics and its response to global changes. Here employing solvent‐extractable compounds as a group of widely used biomarkers, we present a large‐scale study on the distribution of different soil OC components (including plant‐ and microbial‐derived carbohydrates and aliphatic and cyclic lipids) in the surface soils of Chinese grasslands, spanning from temperate grasslands in the arid/semiarid regions to alpine grasslands on the Qinghai‐Tibetan Plateau. We show that alpine grassland soils are more enriched with carbohydrates and plant‐derived compounds relative to the temperate counterparts due to temperature‐inhibited decomposition. While plant belowground biomass plays a key role in explaining the spatial variation of compounds in the alpine grasslands, climatic variables do in the temperate region. In particular, aliphatic lipids accumulate with increasing mean annual temperature in the temperate grasslands due to a preferential decay of labile soil OC, whereas they decrease in the alpine grasslands owing to dilution by an enhanced plant input of nonlipid components. Collectively, these results demonstrate different mechanisms governing the distribution of solvent‐extractable compounds in grassland soils, with climate‐mediated decomposition processes dominating in the temperate grasslands and plant inputs being more important in the alpine region. In the context of climate change, alterations to soil OC input and decomposition processes may have varied impacts on soil carbon cycling in these two regions.
The roles of trauma exposure, rejection sensitivity, and callous‐unemotional traits in the aggressive behavior of justice‐involved youth: A moderated mediation model
Authors: Mozley Michaela M. , Modrowski Crosby A. , Kerig Patricia K.
Published: January 2018

Research has demonstrated an association between childhood trauma exposure and adolescent aggression. This association may be explained by rejection sensitivity, defined as anger, or anxiety in the anticipation of rejection, which can be a consequence of trauma exposure. Callous‐unemotional (CU) traits also are associated with trauma exposure and aggressive behavior; however, research has not yet investigated the interactive roles that rejection sensitivity and CU traits play in the relation between trauma exposure and aggression. Therefore, this study sought to investigate the role of rejection sensitivity in the association between trauma exposure and aggression, and whether this indirect effect was moderated by CU traits. Participants included 380 detained youth (98 girls, 282 boys) who completed self‐report measures of trauma exposure, angry, and anxious rejection sensitivity, CU traits, and aggression. Results of moderated mediation demonstrated that the relation between trauma exposure and aggression exhibited an indirect effect through angry rejection sensitivity, but only at moderate or high levels of CU traits. This pattern was not found for anxious rejection sensitivity. Results suggest that interventions aimed to decrease aggressive behavior in traumatized adolescents may benefit from considering how youth respond to rejection, as well as whether youth endorse CU traits, as this may help to limit further involvement in the juvenile justice system after release.
High‐Strength, Durable All‐Silk Fibroin Hydrogels with Versatile Processability toward Multifunctional Applications
Authors: Zhu Zhenghua , Ling Shengjie , Yeo Jingjie , Zhao Siwei , Tozzi Lorenzo , Buehler Markus J. , Omenetto Fiorenzo , Li Chunmei , Kaplan David L.
Published: January 2018

Hydrogels are the focus of extensive research due to their potential use in fields including biomedical, pharmaceutical, biosensors, and cosmetics. However, the general weak mechanical properties of hydrogels limit their utility. Here, pristine silk fibroin (SF) hydrogels with excellent mechanical properties are generated via a binary‐solvent‐induced conformation transition (BSICT) strategy. In this method, the conformational transition of SF is regulated by moderate binary solvent diffusion and SF/solvent interactions. β‐sheet formation serves as the physical crosslinks that connect disparate protein chains to form continuous 3D hydrogel networks, avoiding complex chemical and/or physical treatments. The Young's modulus of these new BSICT–SF hydrogels can reach up to 6.5 ± 0.2 MPa, tens to hundreds of times higher than that of conventional hydrogels (0.01–0.1 MPa). These new materials fill the “empty soft materials' space” in the elastic modulus/strain Ashby plot. More remarkably, the BSICT–SF hydrogels can be processed into different constructions through different polymer and/or metal‐based processing techniques, such as molding, laser cutting, and machining. Thus, these new hydrogel systems exhibit potential utility in many biomedical and engineering fields.
Two‐Step Targeted Hybrid Nanoconstructs Increase Brain Penetration and Efficacy of the Therapeutic Antibody Trastuzumab against Brain Metastasis of HER2‐Positive Breast Cancer
Authors: He Chunsheng , Li Jason , Cai Ping , Ahmed Taksim , Henderson Jeffrey T. , Foltz Warren D. , Bendayan Reina , Rauth Andrew Michael , Wu Xiao Yu
Published: January 2018

Therapeutic antibodies (e.g., trastuzumab, TRA) against human epidermal growth factor receptor 2 (HER2)‐positive breast cancers have shown benefits in controlling primary tumors, yet are ineffective against brain metastases due to their inability to cross the blood‐brain barrier (BBB). A novel hybrid nanoconstruct system is designed to deliver trastuzumab to brain metastasis of HER2‐positive breast cancer via a two‐step sequential targeting approach. Self‐assembly of a polysorbate 80 (PS 80)‐containing polymer, lipid, and polymer‐conjugated TRA forms hybrid nanoconstructs (TRA–terpolymer nanoparticles (TPN)) with high encapsulation efficiency and bioactivity. The PS 80 moiety enables the first‐step targeting and receptor‐mediated trancytosis across BBB is demonstrated in vitro with a 3D human BBB model in healthy and brain tumor‐bearing mice. The subsequent partial dissociation of the nanoconstructs exposes the encapsulated TRA for the second‐step targeting to HER2‐positive cancer cells in the brain. Intravenously injected TRA–TPN delivers 50‐fold TRA compared to free TRA to the brain metastasis of HER2‐positive breast cancer. Treatment with TRA–TPN increases tumor cell apoptosis by 4‐fold, inhibits tumor growth by 43‐fold, and prolongs median survival by >1.3‐fold compared to free TRA, without causing noticeable organ toxicity. These findings suggest the two‐step targeted nanoconstruct system is promising for shuttling therapeutic antibodies to treat central nervous system diseases.
Artificial Soft–Rigid Protective Layer for Dendrite‐Free Lithium Metal Anode
Authors: Xu Rui , Zhang Xue‐Qiang , Cheng Xin‐Bing , Peng Hong‐Jie , Zhao Chen‐Zi , Yan Chong , Huang Jia‐Qi
Published: January 2018

Lithium (Li) metal has been pursued as “Holy Grail” among various anode materials due to its high specific capacity and the lowest reduction potential. However, uncontrolled growth of Li dendrites and extremely unstable interfaces during repeated Li plating/stripping ineluctably plague the practical applications of Li metal batteries. Herein, an artificial protective layer with synergistic soft–rigid feature is constructed on the Li metal anode to offer superior interfacial stability during long‐term cycles. By suppressing random Li deposition and the formation of isolated Li, such a protective layer enables a dendrite‐free morphology of Li metal anode and suppresses the depletion of Li metal and electrolyte. Additionally, sufficient ionic conductivity is guaranteed through the synergy between soft and rigid structural units that are uniformly dispersed in the layer. Dendrite‐free and dense Li deposition, as well as a greatly reduced interfacial resistance after cycling, is achieved owing to the stabilized interface, accounting for significantly prolonged cycle life of Li metal batteries. This work highlights the ability of synergistic organic/inorganic protective layer in stabilizing Li metal anode and provides fresh insights into the energy chemistry and mechanics of anode in a working battery.
Macroscopic Properties of Biomimetic Ceramics Are Governed by the Molecular Recognition at the Bioorganic–Inorganic Interface
Authors: Kilper Stefan , Facey Sandra J. , Burghard Zaklina , Hauer Bernhard , Rothenstein Dirk , Bill Joachim
Published: January 2018

Bioinspired materials design aims for high‐performing composite materials based on natural biomineralization processes and biomineral architectures. A key component to the research is the bioorganic–inorganic interface, one of the most crucial parameters for controlling the material properties. In this study, genetically engineered phages expressing an inorganic‐binding peptide for the molecular recognition of a ceramic material is exploited to generate thin film multilayer assemblies, with the phage template as minority component. The bioorganic–inorganic interface in the ceramic (zinc oxide, ZnO) multilayer systems is strengthened by the ZnO‐binding motif HSSHH of a peptide to increase Young's modulus and hardness. Applying a point‐mutated version of the peptide, DSSHH, which modulates the interface forces, shows an increased fracture toughness without deteriorating the Young's modulus and the hardness. Molecular matching of the organic phase and its modulation in order to form a specific interface is shown to be important in controlling material properties like in natural biominerals. With this tool in hand, it is not only possible to imitate the structure of biominerals but also to genetically control the molecular recognition of bioorganic molecules to induce macroscopic effects in synthetic composite materials.
Enhanced Thermoelectric Performance in 18‐Electron Nb0.8CoSb Half‐Heusler Compound with Intrinsic Nb Vacancies
Authors: Xia Kaiyang , Liu Yintu , Anand Shashwat , Snyder G. Jeffrey , Xin Jiazhan , Yu Junjie , Zhao Xinbing , Zhu Tiejun
Published: January 2018

Typical 18‐electron half‐Heusler compounds, ZrNiSn and NbFeSb, are identified as promising high‐temperature thermoelectric materials. NbCoSb with nominal 19 valence electrons, which is supposed to be metallic, is recently reported to also exhibit thermoelectric properties of a heavily doped n‐type semiconductor. Here for the first time, it is experimentally demonstrated that the nominal 19‐electron NbCoSb is actually the composite of 18‐electron Nb0.8+δCoSb (0 ≤ δ < 0.05) and impurity phases. Single‐phase Nb0.8+δCoSb with intrinsic Nb vacancies, following the 18‐electron rule, possesses improved thermoelectric performance, and the slight change in the content of Nb vacancies has a profound effect on the thermoelectric properties. The carrier concentration can be controlled by varying the Nb deficiency, and the optimization of the thermoelectric properties can be realized within the narrow pure phase region. Benefiting from the elimination of impurity phases and the optimization of carrier concentration, thermoelectric performance is remarkably enhanced by ≈100% and a maximum zT of 0.9 is achieved in Nb0.83CoSb at 1123 K. This work expands the family of half‐Heusler thermoelectric materials and opens a new avenue for searching for nominal 19‐electron half‐Heusler compounds with intrinsic vacancies as promising thermoelectric materials.
High Rate Magnesium–Sulfur Battery with Improved Cyclability Based on Metal–Organic Framework Derivative Carbon Host
Authors: Zhou Xuejun , Tian Jing , Hu Jiulin , Li Chilin
Published: January 2018

Mg batteries have the advantages of resource abundance, high volumetric energy density, and dendrite‐free plating/stripping of Mg anodes. However the injection of highly polar Mg2+ cannot maintain the structural integrity of intercalation‐type cathodes even for open framework prototypes. The lack of high‐voltage electrolytes and sluggish Mg2+ diffusion in lattices or through interfaces also limit the energy density of Mg batteries. Mg–S system based on moderate‐voltage conversion electrochemistry appears to be a promising solution to high‐energy Mg batteries. However, it still suffers from poor capacity and cycling performances so far. Here, a ZIF‐67 derivative carbon framework codoped by N and Co atoms is proposed as effective S host for highly reversible Mg–S batteries even under high rates. The discharge capacity is as high as ≈600 mA h g−1 at 1 C during the first cycle, and it is still preserved at ≈400 mA h g−1 after at least 200 cycles. Under a much higher rate of 5 C, a capacity of 300–400 mA h g−1 is still achievable. Such a superior performance is unprecedented among Mg–S systems and benefits from multiple factors, including heterogeneous doping, Li‐salt and Cl− addition, charge mode, and cut‐off capacity, as well as separator decoration, which enable the mitigation of electrode passivation and polysulfide loss.
High‐Performance pH‐Switchable Supramolecular Thermosets via Cation–π Interactions
Authors: Chang Guanjun , Yang Li , Yang Junxiao , Stoykovich Mark P. , Deng Xu , Cui Jiaxi , Wang Dapeng
Published: January 2018

Supramolecular chemistry has provided versatile and affordable solutions for the design of intelligent soft materials, but it cannot be applied in stiff materials. This paper describes a new concept for the design of high‐performance supramolecular thermosets by using the noncovalent cation–π interaction as cross‐linking. These supramolecular thermosets are a class of infusible and insoluble stiff polymers having excellent mechanical properties even at temperatures exceeding 300 °C. The cation–π interaction can be locally and reversibly installed and removed by aqueous treatments at high or low pH, respectively. Local manipulation of cross‐linking confers these thermosets with multiple stimuli‐responsive functions, such as recyclability, healability, adhesion, and nondestructive detection of cross‐linking and mechanical properties.
Nociceptive Memristor
Authors: Kim Yumin , Kwon Young Jae , Kwon Dae Eun , Yoon Kyung Jean , Yoon Jung Ho , Yoo Sijung , Kim Hae Jin , Park Tae Hyung , Han Jin‐Woo , Kim Kyung Min , Hwang Cheol Seong
Published: January 2018

The biomimetic characteristics of the memristor as an electronic synapse and neuron have inspired the advent of new information technology in the neuromorphic computing. The application of the memristors can be extended to the artificial nerves on condition of the presence of electronic receptors which can transfer the external stimuli to the internal nerve system. In this work, nociceptor behaviors are demonstrated from the Pt/HfO2/TiN memristor for the electronic receptors. The device shows four specific nociceptive behaviors; threshold, relaxation, allodynia, and hyperalgesia, according to the strength, duration, and repetition rate of the external stimuli. Such nociceptive behaviors are attributed to the electron trapping/detrapping to/from the traps in the HfO2 layer, where the depth of trap energy level is ≈0.7 eV. Also, the built‐in potential by the work function mismatch between the Pt and TiN electrodes induces time‐dependent relaxation of trapped electrons, providing the appropriate relaxation behavior. The relaxation time can take from several milliseconds to tens of seconds, which corresponds to the time span of the decay of biosignal. The material‐wise evaluation of the electronic nociceptor in comparison with other material, which did not show the desired functionality, Pt/Ti/HfO2/TiN, reveals the importance of careful material design and fabrication.
High‐Performance Single‐Crystalline Perovskite Thin‐Film Photodetector
Authors: Yang Zhenqian , Deng Yuhao , Zhang Xiaowei , Wang Suo , Chen Huazhou , Yang Sui , Khurgin Jacob , Fang Nicholas X. , Zhang Xiang , Ma Renmin
Published: January 2018

The best performing modern optoelectronic devices rely on single‐crystalline thin‐film (SC‐TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low‐cost solution‐based methods, have achieved substantial success in various optoelectronic devices including solar cells, lasers, light‐emitting diodes, and photodetectors. However, to date, the performance of these perovskite devices based on polycrystalline thin‐film active layers lags behind the epitaxially grown semiconductor devices. Here, a photodetector based on SC‐TF perovskite active layer is reported with a record performance of a 50 million gain, 70 GHz gain‐bandwidth product, and a 100‐photon level detection limit at 180 Hz modulation bandwidth, which as far as we know are the highest values among all the reported perovskite photodetectors. The superior performance of the device originates from replacing polycrystalline thin film by a thickness‐optimized SC‐TF with much higher mobility and longer recombination time. The results indicate that high‐performance perovskite devices based on SC‐TF may become competitive in modern optoelectronics.
Composite of CH3NH3PbI3 with Reduced Graphene Oxide as a Highly Efficient and Stable Visible‐Light Photocatalyst for Hydrogen Evolution in Aqueous HI Solution
Authors: Wu Yaqiang , Wang Peng , Zhu Xianglin , Zhang Qianqian , Wang Zeyan , Liu Yuanyuan , Zou Guizheng , Dai Ying , Whangbo Myung‐Hwan , Huang Baibiao
Published: January 2018

A facile and efficient photoreduction method is employed to synthesize the composite of methylammonium lead iodide perovskite (MAPbI3) with reduced graphene oxide (rGO). This MAPbI3/rGO composite is shown to be an outstanding visible‐light photocatalyst for H2 evolution in aqueous HI solution saturated with MAPbI3. Powder samples of MAPbI3/rGO (100 mg) show a H2 evolution rate of 93.9 µmol h−1, which is 67 times faster than that of pristine MAPbI3, under 120 mW cm−2 visible‐light (λ ≥ 420 nm) illumination, and the composite is highly stable showing no significant decrease in the catalytic activity after 200 h (i.e., 20 cycles) of repeated H2 evolution experiments. The electrochemiluminescence performance of MAPbI3 is investigated to explore the charge transfer process, to find that the photogenerated electrons in MAPbI3 are transferred to the rGO sites, where protons are reduced to H2.
Deformable Organic Nanowire Field‐Effect Transistors
Authors: Lee Yeongjun , Oh Jin Young , Kim Taeho Roy , Gu Xiaodan , Kim Yeongin , Wang Ging‐Ji Nathan , Wu Hung‐Chin , Pfattner Raphael , To John W. F. , Katsumata Toru , Son Donghee , Kang Jiheong , Matthews James R. , Niu Weijun , He Mingqian , Sinclair Robert , Cui Yi , Tok Jeffery B.‐H. , Lee Tae‐Woo , Bao Zhenan
Published: January 2018

Deformable electronic devices that are impervious to mechanical influence when mounted on surfaces of dynamically changing soft matters have great potential for next‐generation implantable bioelectronic devices. Here, deformable field‐effect transistors (FETs) composed of single organic nanowires (NWs) as the semiconductor are presented. The NWs are composed of fused thiophene diketopyrrolopyrrole based polymer semiconductor and high‐molecular‐weight polyethylene oxide as both the molecular binder and deformability enhancer. The obtained transistors show high field‐effect mobility >8 cm2 V−1 s−1 with poly(vinylidenefluoride‐co‐trifluoroethylene) polymer dielectric and can easily be deformed by applied strains (both 100% tensile and compressive strains). The electrical reliability and mechanical durability of the NWs can be significantly enhanced by forming serpentine‐like structures of the NWs. Remarkably, the fully deformable NW FETs withstand 3D volume changes (>1700% and reverting back to original state) of a rubber balloon with constant current output, on the surface of which it is attached. The deformable transistors can robustly operate without noticeable degradation on a mechanically dynamic soft matter surface, e.g., a pulsating balloon (pulse rate: 40 min−1 (0.67 Hz) and 40% volume expansion) that mimics a beating heart, which underscores its potential for future biomedical applications.
A Self‐Powered and Flexible Organometallic Halide Perovskite Photodetector with Very High Detectivity
Authors: Leung Siu‐Fung , Ho Kang‐Ting , Kung Po‐Kai , Hsiao Vincent K. S. , Alshareef Husam N. , Wang Zhong Lin , He Jr‐Hau
Published: January 2018

Flexible and self‐powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self‐powered and flexible PD based on the methylammonium lead iodide (CH3NH3PBI3) perovskite is demonstrated. Such a self‐powered PD can operate even with irregular motion such as human finger tapping, which enables it to work without a bulky external power source. In addition, with high‐quality CH3NH3PBI3 perovskite thin film fabricated with solvent engineering, the PD exhibits an impressive detectivity of 1.22 × 1013 Jones. In the self‐powered voltage detection mode, it achieves a large responsivity of up to 79.4 V mW−1 cm−2 and a voltage response of up to ≈90%. Moreover, as the PD is made of flexible and transparent polymer films, it can operate under bending and functions at 360 Â° of illumination. As a result, the self‐powered, flexible, 360 Â° omnidirectional perovskite PD, featuring high detectivity and responsivity along with real‐world sensing capability, suggests a new direction for next‐generation optical communications, sensing, and imaging applications.
Cocatalysts in Semiconductor‐based Photocatalytic CO2 Reduction: Achievements, Challenges, and Opportunities
Authors: Ran Jingrun , Jaroniec Mietek , Qiao Shi‐Zhang
Published: January 2018

Ever‐increasing fossil‐fuel combustion along with massive CO2 emissions has aroused a global energy crisis and climate change. Photocatalytic CO2 reduction represents a promising strategy for clean, cost‐effective, and environmentally friendly conversion of CO2 into hydrocarbon fuels by utilizing solar energy. This strategy combines the reductive half‐reaction of CO2 conversion with an oxidative half reaction, e.g., H2O oxidation, to create a carbon‐neutral cycle, presenting a viable solution to global energy and environmental problems. There are three pivotal processes in photocatalytic CO2 conversion: (i) solar‐light absorption, (ii) charge separation/migration, and (iii) catalytic CO2 reduction and H2O oxidation. While significant progress is made in optimizing the first two processes, much less research is conducted toward enhancing the efficiency of the third step, which requires the presence of cocatalysts. In general, cocatalysts play four important roles: (i) boosting charge separation/transfer, (ii) improving the activity and selectivity of CO2 reduction, (iii) enhancing the stability of photocatalysts, and (iv) suppressing side or back reactions. Herein, for the first time, all the developed CO2‐reduction cocatalysts for semiconductor‐based photocatalytic CO2 conversion are summarized, and their functions and mechanisms are discussed. Finally, perspectives in this emerging area are provided.
Citrate Improves Collagen Mineralization via Interface Wetting: A Physicochemical Understanding of Biomineralization Control
Authors: Shao Changyu , Zhao Ruibo , Jiang Shuqin , Yao Shasha , Wu Zhifang , Jin Biao , Yang Yuling , Pan Haihua , Tang Ruikang
Published: January 2018

Biological hard tissues such as bones always contain extremely high levels of citrate, which is believed to play an important role in bone formation as well as in osteoporosis treatments. However, its mechanism on biomineralization is not elucidated. Here, it is found that the adsorbed citrate molecules on collagen fibrils can significantly reduce the interfacial energy between the biological matrix and the amorphous calcium phosphate precursor to enhance their wetting effect at the early biomineralization stage, sequentially facilitating the intrafibrillar formation of hydroxyapatite to produce an inorganic–organic composite. It is demonstrated experimentally that only collagen fibrils containing ≈8.2 wt% of bound citrate (close to the level in biological bone) can reach the full mineralization as those in natural bones. The effect of citrate on the promotion of the collagen mineralization degree is also confirmed by in vitro dentin repair. This finding demonstrates the importance of interfacial controls in biomineralization and more generally, provides a physicochemical view about the regulation effect of small biomolecules on the biomineralization front.
Toxic Reactive Oxygen Species Enhanced Synergistic Combination Therapy by Self‐Assembled Metal‐Phenolic Network Nanoparticles
Authors: Dai Yunlu , Yang Zhen , Cheng Siyuan , Wang Zhongliang , Zhang Ruili , Zhu Guizhi , Wang Zhantong , Yung Bryant C. , Tian Rui , Jacobson Orit , Xu Can , Ni Qianqian , Song Jibin , Sun Xiaolian , Niu Gang , Chen Xiaoyuan
Published: January 2018

Engineering functional nanomaterials with high therapeutic efficacy and minimum side effects has increasingly become a promising strategy for cancer treatment. Herein, a reactive oxygen species (ROS) enhanced combination chemotherapy platform is designed via a biocompatible metal‐polyphenol networks self‐assembly process by encapsulating doxorubicin (DOX) and platinum prodrugs in nanoparticles. Both DOX and platinum drugs can activate nicotinamide adenine dinucleotide phosphate oxidases, generating superoxide radicals (O2•−). The superoxide dismutase‐like activity of polyphenols can catalyze H2O2 generation from O2•−. Finally, the highly toxic HO• free radicals are generated by a Fenton reaction. The ROS HO• can synergize the chemotherapy by a cascade of bioreactions. Positron emission tomography imaging of 89Zr‐labeled as‐prepared DOX@Pt prodrug Fe3+ nanoparticles (DPPF NPs) shows prolonged blood circulation and high tumor accumulation. Furthermore, the DPPF NPs can effectively inhibit tumor growth and reduce the side effects of anticancer drugs. This study establishes a novel ROS promoted synergistic nanomedicine platform for cancer therapy.
Complementary Logic Circuits Based on High‐Performance n‐Type Organic Electrochemical Transistors
Authors: Sun Hengda , Vagin Mikhail , Wang Suhao , Crispin Xavier , Forchheimer Robert , Berggren Magnus , Fabiano Simone
Published: January 2018

Organic electrochemical transistors (OECTs) have been the subject of intense research in recent years. To date, however, most of the reported OECTs rely entirely on p‐type (hole transport) operation, while electron transporting (n‐type) OECTs are rare. The combination of efficient and stable p‐type and n‐type OECTs would allow for the development of complementary circuits, dramatically advancing the sophistication of OECT‐based technologies. Poor stability in air and aqueous electrolyte media, low electron mobility, and/or a lack of electrochemical reversibility, of available high‐electron affinity conjugated polymers, has made the development of n‐type OECTs troublesome. Here, it is shown that ladder‐type polymers such as poly(benzimidazobenzophenanthroline) (BBL) can successfully work as stable and efficient n‐channel material for OECTs. These devices can be easily fabricated by means of facile spray‐coating techniques. BBL‐based OECTs show high transconductance (up to 9.7 mS) and excellent stability in ambient and aqueous media. It is demonstrated that BBL‐based n‐type OECTs can be successfully integrated with p‐type OECTs to form electrochemical complementary inverters. The latter show high gains and large worst‐case noise margin at a supply voltage below 0.6 V.
Engineered Transport in Microporous Materials and Membranes for Clean Energy Technologies
Authors: Li Changyi , Meckler Stephen M. , Smith Zachary P. , Bachman Jonathan E. , Maserati Lorenzo , Long Jeffrey R. , Helms Brett A.
Published: January 2018

Many forward‐looking clean‐energy technologies hinge on the development of scalable and efficient membrane‐based separations. Ongoing investment in the basic research of microporous materials is beginning to pay dividends in membrane technology maturation. Specifically, improvements in membrane selectivity, permeability, and durability are being leveraged for more efficient carbon capture, desalination, and energy storage, and the market adoption of membranes in those areas appears to be on the horizon. Herein, an overview of the microporous materials chemistry driving advanced membrane development, the clean‐energy separations employing them, and the theoretical underpinnings tying membrane performance to membrane structure across multiple length scales is provided. The interplay of pore architecture and chemistry for a given set of analytes emerges as a critical design consideration dictating mass transport outcomes. Opportunities and outstanding challenges in the field are also discussed, including high‐flux 2D molecular‐sieving membranes, phase‐change adsorbents as performance‐enhancing components in composite membranes, and the need for quantitative metrologies for understanding mass transport in heterophasic materials and in micropores with unusual chemical interactions with analytes of interest.
Ultrahigh Piezoelectric Properties in Textured (K,Na)NbO3‐Based Lead‐Free Ceramics
Authors: Li Peng , Zhai Jiwei , Shen Bo , Zhang Shujun , Li Xiaolong , Zhu Fangyuan , Zhang Xingmin
Published: January 2018

High‐performance lead‐free piezoelectric materials are in great demand for next‐generation electronic devices to meet the requirement of environmentally sustainable society. Here, ultrahigh piezoelectric properties with piezoelectric coefficients (d33 ≈700 pC N−1, d33* ≈980 pm V−1) and planar electromechanical coupling factor (kp ≈76%) are achieved in highly textured (K,Na)NbO3 (KNN)‐based ceramics. The excellent piezoelectric properties can be explained by the strong anisotropic feature, optimized engineered domain configuration in the textured ceramics, and facilitated polarization rotation induced by the intermediate phase. In addition, the nanodomain structures with decreased domain wall energy and increased domain wall mobility also contribute to the ultrahigh piezoelectric properties. This work not only demonstrates the tremendous potential of KNN‐based ceramics to replace lead‐based piezoelectrics but also provides a good strategy to design high‐performance piezoelectrics by controlling appropriate phase and crystallographic orientation.
Shape Memory Polymers for Body Motion Energy Harvesting and Self‐Powered Mechanosensing
Authors: Liu Ruiyuan , Kuang Xiao , Deng Jianan , Wang Yi‐Cheng , Wang Aurelia C. , Ding Wenbo , Lai Ying‐Chih , Chen Jun , Wang Peihong , Lin Zhiqun , Qi H. Jerry , Sun Baoquan , Wang Zhong Lin
Published: January 2018

Growing demand in portable electronics raises a requirement to electronic devices being stretchable, deformable, and durable, for which functional polymers are ideal choices of materials. Here, the first transformable smart energy harvester and self‐powered mechanosensation sensor using shape memory polymers is demonstrated. The device is based on the mechanism of a flexible triboelectric nanogenerator using the thermally triggered shape transformation of organic materials for effectively harvesting mechanical energy. This work paves a new direction for functional polymers, especially in the field of mechanosensation for potential applications in areas such as soft robotics, biomedical devices, and wearable electronics.
An Alkylated Indacenodithieno[3,2‐b]thiophene‐Based Nonfullerene Acceptor with High Crystallinity Exhibiting Single Junction Solar Cell Efficiencies Greater than 13% with Low Voltage Losses
Authors: Fei Zhuping , Eisner Flurin D. , Jiao Xuechen , Azzouzi Mohammed , Röhr Jason A. , Han Yang , Shahid Munazza , Chesman Anthony S. R. , Easton Christopher D. , McNeill Christopher R. , Anthopoulos Thomas D. , Nelson Jenny , Heeney Martin
Published: January 2018

A new synthetic route, to prepare an alkylated indacenodithieno[3,2‐b]thiophene‐based nonfullerene acceptor (C8‐ITIC), is reported. Compared to the reported ITIC with phenylalkyl side chains, the new acceptor C8‐ITIC exhibits a reduction in the optical band gap, higher absorptivity, and an increased propensity to crystallize. Accordingly, blends with the donor polymer PBDB‐T exhibit a power conversion efficiency (PCE) up to 12.4%. Further improvements in efficiency are found upon backbone fluorination of the donor polymer to afford the novel material PFBDB‐T. The resulting blend with C8‐ITIC shows an impressive PCE up to 13.2% as a result of the higher open‐circuit voltage. Electroluminescence studies demonstrate that backbone fluorination reduces the energy loss of the blends, with PFBDB‐T/C8‐ITIC‐based cells exhibiting a small energy loss of 0.6 eV combined with a high JSC of 19.6 mA cm−2.
Ternary System with Controlled Structure: A New Strategy toward Efficient Organic Photovoltaics
Authors: Cheng Pei , Wang Rui , Zhu Jingshuai , Huang Wenchao , Chang Sheng‐Yung , Meng Lei , Sun Pengyu , Cheng Hao‐Wen , Qin Meng , Zhu Chenhui , Zhan Xiaowei , Yang Yang
Published: January 2018

Recently, a new type of active layer with a ternary system has been developed to further enhance the performance of binary system organic photovoltaics (OPV). In the ternary OPV, almost all active layers are formed by simple ternary blend in solution, which eventually leads to the disordered bulk heterojunction (BHJ) structure after a spin‐coating process. There are two main restrictions in this disordered BHJ structure to obtain higher performance OPV. One is the isolated second donor or acceptor domains. The other is the invalid metal–semiconductor contact. Herein, the concept and design of donor/acceptor/acceptor ternary OPV with more controlled structure (C‐ternary) is reported. The C‐ternary OPV is fabricated by a sequential solution process, in which the second acceptor and donor/acceptor binary blend are sequentially spin‐coated. After the device optimization, the power conversion efficiencies (PCEs) of all OPV with C‐ternary are enhanced by 14–21% relative to those with the simple ternary blend; the best PCEs are 10.7 and 11.0% for fullerene‐based and fullerene‐free solar cells, respectively. Moreover, the averaged PCE value of 10.4% for fullerene‐free solar cell measured in this study is in great agreement with the certified one of 10.32% obtained from Newport Corporation.
A Universal Strategy for Hollow Metal Oxide Nanoparticles Encapsulated into B/N Co‐Doped Graphitic Nanotubes as High‐Performance Lithium‐Ion Battery Anodes
Authors: Tabassum Hassina , Zou Ruqiang , Mahmood Asif , Liang Zibin , Wang Qingfei , Zhang Hao , Gao Song , Qu Chong , Guo Wenhan , Guo Shaojun
Published: January 2018

Yolk–shell nanostructures have received great attention for boosting the performance of lithium‐ion batteries because of their obvious advantages in solving the problems associated with large volume change, low conductivity, and short diffusion path for Li+ ion transport. A universal strategy for making hollow transition metal oxide (TMO) nanoparticles (NPs) encapsulated into B, N co‐doped graphitic nanotubes (TMO@BNG (TMO = CoO, Ni2O3, Mn3O4) through combining pyrolysis with an oxidation method is reported herein. The as‐made TMO@BNG exhibits the TMO‐dependent lithium‐ion storage ability, in which CoO@BNG nanotubes exhibit highest lithium‐ion storage capacity of 1554 mA h g−1 at the current density of 96 mA g−1, good rate ability (410 mA h g−1 at 1.75 A g−1), and high stability (almost 96% storage capacity retention after 480 cycles). The present work highlights the importance of introducing hollow TMO NPs with thin wall into BNG with large surface area for boosting LIBs in the terms of storage capacity, rate capability, and cycling stability.
Stirring Up Acceptor Phase and Controlling Morphology via Choosing Appropriate Rigid Aryl Rings as Lever Arms in Symmetry‐Breaking Benzodithiophene for High‐Performance Fullerene and Fullerene‐Free Polymer Solar Cells
Authors: Liu Deyu , Wang Junyi , Gu Chunyang , Li Yonghai , Bao Xichang , Yang Renqiang
Published: January 2018

Two series of new polymers with medium and wide bandgaps to match fullerene (PC71BM) and fullerene‐free 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (ITIC) acceptors are designed and synthesized, respectively. For constructing the key donor building blocks, the effective symmetry‐breaking strategy is employed. Two common aromatic rings (thiophene and benzene) are chosen as one side substituted groups in the asymmetric benzodithiophene (BDT) monomers. In addition, another rigid benzene ring is inserted between aryl and thioether in the side chains, which results in larger twisting and destroying the aggregation and forming longer lever arms. As a result, highly ordered polymers (PBDTsTh‐FBT and PBDTsPh‐FBT) with strong aggregation properties can blend well with roughly spherical PC71BM, while amorphous polymers (PBDTsThPh‐BDD and PBDTsPhPh‐BDD) with long and rigid aryl rings show good miscibility with elongated ITIC, and finally, both devices exhibit excellent power conversion efficiencies over 10%. Thus, it clearly shows that the asymmetric BDT unit is an excellent donor building block to construct highly efficient photovoltaic polymers. Meanwhile, this work demonstrates that it is not necessary that high‐performance fullerene‐free polymer solar cells (PSCs) require highly ordered microstructures in the blending films, different from the fullerene‐based PSCs.
Achieving the Widest Range of Syngas Proportions at High Current Density over Cadmium Sulfoselenide Nanorods in CO2 Electroreduction
Authors: He Rong , Zhang An , Ding Yilun , Kong Taoyi , Xiao Qing , Li Hongliang , Liu Yan , Zeng Jie
Published: January 2018

Electroreduction of CO2 is a sustainable approach to produce syngas with controllable ratios, which are required as specific reactants for the optimization of different industrial processes. However, it is challenging to achieve tunable syngas production with a wide ratio of CO/H2, while maintaining a high current density. Herein, cadmium sulfoselenide (CdSxSe1−x) alloyed nanorods are developed, which enable the widest range of syngas proportions ever reported at the current density above 10 mA cm−2 in CO2 electroreduction. Among CdSxSe1−x nanorods, CdS nanorods exhibit the highest Faradaic efficiency (FE) of 81% for CO production with a current density of 27.1 mA cm−2 at −1.2 V vs. reversible hydrogen electrode. With the increase of Se content in CdSxSe1−x nanorods, the FE for H2 production increases. At −1.2 V vs. RHE, the ratios of CO/H2 in products vary from 4:1 to 1:4 on CdSxSe1−x nanorods (x from 1 to 0). Notably, all proportions of syngas are achieved with current density higher than ≈25 mA cm−2. Mechanistic study reveals that the increased Se content in CdSxSe1−x nanorods strengthens the binding of H atoms, resulting in the increased coverage of H* and thus the enhanced selectivity for H2 production in CO2 electroreduction.
Broadband MoS2 Field‐Effect Phototransistors: Ultrasensitive Visible‐Light Photoresponse and Negative Infrared Photoresponse
Authors: Wu Jing‐Yuan , Chun Young Tea , Li Shunpu , Zhang Tong , Wang Junzhan , Shrestha Pawan Kumar , Chu Daping
Published: January 2018

Inverse photoresponse is discovered from phototransistors based on molybdenum disulfide (MoS2). The devices are capable of detecting photons with energy below the bandgap of MoS2. Under the illumination of near‐infrared (NIR) light at 980 and 1550 nm, negative photoresponses with short response time (50 ms) are observed for the first time. Upon visible‐light illumination, the phototransistors exhibit positive photoresponse with ultrahigh responsivity on the order of 104–105 A W−1 owing to the photogating effect and charge trapping mechanism. Besides, the phototransistors can detect a weak visible‐light signal with effective optical power as low as 17 picowatts (pW). A thermally induced photoresponse mechanism, the bolometric effect, is proposed as the cause of the negative photocurrent in the NIR regime. The thermal energy of the NIR radiation is transferred to the MoS2 crystal lattice, inducing lattice heating and resistance increase. This model is experimentally confirmed by low‐temperature electrical measurements. The bolometric coefficient calculated from the measured transport current change with temperature is −33 nA K−1. These findings offer a new approach to develop sub‐bandgap photodetectors and other novel optoelectronic devices based on 2D layered materials.
Memristor‐Based Analog Computation and Neural Network Classification with a Dot Product Engine
Authors: Hu Miao , Graves Catherine E. , Li Can , Li Yunning , Ge Ning , Montgomery Eric , Davila Noraica , Jiang Hao , Williams R. Stanley , Yang J. Joshua , Xia Qiangfei , Strachan John Paul
Published: January 2018

Using memristor crossbar arrays to accelerate computations is a promising approach to efficiently implement algorithms in deep neural networks. Early demonstrations, however, are limited to simulations or small‐scale problems primarily due to materials and device challenges that limit the size of the memristor crossbar arrays that can be reliably programmed to stable and analog values, which is the focus of the current work. High‐precision analog tuning and control of memristor cells across a 128 × 64 array is demonstrated, and the resulting vector matrix multiplication (VMM) computing precision is evaluated. Single‐layer neural network inference is performed in these arrays, and the performance compared to a digital approach is assessed. Memristor computing system used here reaches a VMM accuracy equivalent of 6 bits, and an 89.9% recognition accuracy is achieved for the 10k MNIST handwritten digit test set. Forecasts show that with integrated (on chip) and scaled memristors, a computational efficiency greater than 100 trillion operations per second per Watt is possible.
Switching the Proton Conduction in Nanoporous, Crystalline Materials by Light
Authors: Müller Kai , Helfferich Julian , Zhao Fangli , Verma Rupal , Kanj Anemar Bruno , Meded Velimir , Bléger David , Wenzel Wolfgang , Heinke Lars
Published: January 2018

Proton conducting nanoporous materials attract substantial attention with respect to applications in fuel cells, supercapacitors, chemical sensors, and information processing devices inspired by biological systems. Here, a crystalline, nanoporous material which offers dynamic remote‐control over the proton conduction is presented. This is realized by using surface‐mounted metal–organic frameworks (SURMOFs) with azobenzene side groups that can undergo light‐induced reversible isomerization between the stable trans and cis states. The trans–cis photoisomerization results in the modulation of the interaction between MOF and guest molecules, 1,4‐butanediol and 1,2,3‐triazole; enabling the switching between the states with significantly increased (trans) and reduced (cis) conductivity. Quantum chemical calculations show that the trans‐to‐cis isomerization results in the formation of stronger hydrogen bridges of the guest molecules with the azo groups, causing stronger bonding of the guest molecules and, as a result, smaller proton conductivity. It is foreseen that photoswitchable proton‐conducting materials may find its application in advanced, remote‐controllable chemical sensors, and a variety of devices based on the conductivity of protons or other charged molecules, which can be interfaced with biological systems.