bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic Processes Controlling Persistent Changes of Forest Canopy Structure After 2005 Amazon Drought
Authors: Shi Mingjie , Liu Junjie , Zhao Maosheng , Yu Yifan , Saatchi Sassan
Published: December 2017

The long‐term impact of Amazonian drought on canopy structure has been observed in ground and remote sensing measurements. However, it is still unclear whether it is caused by biotic (e.g., plant structure damage) or environmental (e.g., water deficiency) factors. We used the Community Land Model version 4.5 (CLM4.5) and radar backscatter observations from SeaWinds Scatterometer on board QuikSCAT (QSCAT) satellite to investigate the relative role of biotic and environmental factors in controlling the forest canopy disturbance and recovery processes after the 2005 Amazonian drought. We validated the CLM4.5 simulation of the drought impact and the recovery of leaf carbon (C) pool, an indicator of canopy structure, over southwestern Amazonia with QSCAT backscatter observations, which are sensitive to canopy structure change. We found that the leaf C pool simulated by CLM4.5 recovered to the 2000–2009 mean level (343 g C m−2) in 3 years after a sharp decrease in 2005, consistent with the QSCAT observed slow recovery. Through sensitivity experiments, we found that the slow C recovery was primarily due to biotic factors represented by the canopy damage and reduction of plant C pools. The recovery of soil water and the coupling between water and C pools, which is an environmental factor, only contributes ~24% to the leaf C recovery. The results showed (1) the strength of scatterometer backscatter measurements in capturing canopy damage over tropical forests and in validating C cycle models and (2) the biotic factors play the dominant role in regulating the drought induced disturbance and persistent canopy changes in CLM4.5.
Derivation and Solution of the Omega Equation Associated With a Balance Theory on the Sphere
Authors: Dostalek John F. , Schubert Wayne H. , DeMaria Mark
Published: December 2017

The quasi‐geostrophic omega equation has been used extensively to examine the large‐scale vertical velocity patterns of atmospheric systems. It is derived from the quasi‐geostrophic equations, a balanced set of equations based on the partitioning of the horizontal wind into a geostrophic and an ageostrophic component. Its use is limited to higher latitudes, however, as the geostrophic balance is undefined at the equator. In order to derive an omega equation which can be used at all latitudes, a new balanced set of equations is developed. Three key steps are used in the formulation. First, the horizontal wind is decomposed into a nondivergent and an irrotational component. Second, the Coriolis parameter is assumed to be slowly varying, such that it may be moved in and out of horizontal derivative operators as necessary to simplify the derivation. Finally, the mass field is formulated from the nondivergent wind field. The resulting balanced set of equations and the omega equation derived from them take a similar form to the quasi‐geostrophic equations, yet are valid over the whole sphere. A method of solution to the global omega equation using vertical normal modes and spherical harmonics is presented, along with a middle‐latitude and low‐latitude example.
The Heterogeneous Impacts of Groundwater Management Policies in the Republican River Basin of Colorado
Authors: Hrozencik R. A. , Manning D. T. , Suter J. F. , Goemans C. , Bailey R. T.
Published: December 2017

Groundwater is a critical input to agricultural production across the globe. Current groundwater pumping rates frequently exceed recharge, often by a substantial amount, leading to groundwater depletion and potential declines in agricultural profits over time. As a result, many regions reliant on irrigated agriculture have proposed policies to manage groundwater use. Even when gains from aquifer management exist, there is little information about how policies affect individual producers sharing the resource. In this paper, we investigate the variability of groundwater management policy impacts across heterogeneous agricultural producers. To measure these impacts, we develop a hydroeconomic model that captures the important role of well capacity, productivity of water, and weather uncertainty. We use the model to simulate the impacts of groundwater management policies on producers in the High Plains aquifer of eastern Colorado and compare outcomes to a no‐policy baseline. The management policies considered include a pumping fee, a quantity restriction, and an irrigated acreage fee. We find that well capacity and soil type affect policy impacts but in ways that can qualitatively differ across policy type. Model results have important implications for the distributional impacts and political acceptability of groundwater management policies.
A Field‐Scale Sensor Network Data Set for Monitoring and Modeling the Spatial and Temporal Variation of Soil Water Content in a Dryland Agricultural Field
Authors: Gasch C. K. , Brown D. J. , Campbell C. S. , Cobos D. R. , Brooks E. S. , Chahal M. , Poggio M.
Published: December 2017

We describe a soil water content monitoring data set and auxiliary data collected at a 37 ha experimental no‐till farm in the Northwestern United States. Water content measurements have been compiled hourly since 2007 by ECH2O‐TE and 5TE sensors installed at 42 locations and five depths (0.3, 0.6, 0.9, 1.2, and 1.5 m, 210 sensors total) across the R.J. Cook Agronomy Farm, a Long‐Term Agro‐Ecosystem Research Site stationed on complex terrain in a Mediterranean climate. In addition to soil water content readings, the data set includes hourly and daily soil temperature readings, annual crop histories, a digital elevation model, Bt horizon maps, seasonal apparent electrical conductivity, soil texture, and soil bulk density. Meteorological records are also available for this location. We discuss the unique challenges of maintaining the network on an operating farm and demonstrate the nature and complexity of the soil water content data. This data set is accessible online through the National Agriculture Library, has been assigned a DOI, and will be maintained for the long term.
The Importance of Bank Storage in Supplying Baseflow to Rivers Flowing Through Compartmentalized, Alluvial Aquifers
Authors: Rhodes Kimberly A. , Proffitt Tiffany , Rowley Taylor , Knappett Peter S. K. , Montiel Daniel , Dimova Natasha , Tebo Daniel , Miller Gretchen R.
Published: December 2017

As water grows scarcer in semiarid and arid regions around the world, new tools are needed to quantify fluxes of water and chemicals between aquifers and rivers. In this study, we quantify the volumetric flux of subsurface water to a 24 km reach of the Brazos River, a lowland river that meanders through the Brazos River Alluvium Aquifer (BRAA), with 8 months of high‐frequency differential gaging measurements using fixed gaging stations. Subsurface discharge sources were determined using natural tracers and End‐Member Mixing Analysis (EMMA). During a 4 month river stage recession following a high stage event, subsurface discharge decreased from 50 m3/s to 0, releasing a total of 1.0 × 108 m3 of water. Subsurface discharge dried up even as the groundwater table at two locations in the BRAA located 300–500 m from the river remained ∼4 m higher than the river stage. Less than 4% of the water discharged from the subsurface during the prolonged recession period resembled the chemical fingerprint of the alluvial aquifer. Instead, the chemistry of this discharged water closely resembled high stage “event” river water. Together, these findings suggest that the river is well connected to rechargeable bank storage reservoirs but disconnected from the broader alluvial aquifer. The average width of discrete bank storage zones on each side of the river, identified with Electrical Resistivity Tomography (ERT), was approximately 1.5 km. In such highly compartmentalized aquifers, groundwater pumping is unlikely to impact the exchange between the river and the alluvium.
EGOFET Peptide Aptasensor for Label‐Free Detection of Inflammatory Cytokines in Complex Fluids
Authors: Berto Marcello , Diacci Chiara , D'Agata Roberta , Pinti Marcello , Bianchini Elena , Lauro Michele Di , Casalini Stefano , Cossarizza Andrea , Berggren Magnus , Simon Daniel , Spoto Giuseppe , Biscarini Fabio , Bortolotti Carlo A.
Published: December 2017

Organic electronic transistors are rapidly emerging as ultrahigh sensitive label‐free biosensors suited for point‐of‐care or in‐field deployed applications. Most organic biosensors reported to date are based on immunorecognition between the relevant biomarkers and the immobilized antibodies, whose use is hindered by large dimensions, poor control of sequence, and relative instability. Here, an electrolyte‐gated organic field effect transistor (EGOFET) biosensor where the recognition units are surface immobilized peptide aptamers (Affimer proteins) instead of antibodies is reported. Peptide aptasensor for the detection of the pro‐inflammatory cytokine tumor necrosis factor alpha (TNFα) with a 1 × 10−12m limit of detection is demonstrated. Ultralow sensitivity is met even in complex solutions such as cell culture media containing 10% serum, demonstrating the remarkable ligand specificity of the device. The device performances, together with the simple one‐step immobilization strategy of the recognition moieties and the low operational voltages, all prompt EGOFET peptide aptasensors as candidates for early diagnostics and monitoring at the point‐of‐care.
Chemotactic Guidance of Synthetic Organic/Inorganic Payloads Functionalized Sperm Micromotors
Authors: Chen Chuanrui , Chang Xiaocong , Angsantikul Pavimol , Li Jinxing , Esteban‐Fernández de Ávila Berta , Karshalev Emil , Liu Wenjuan , Mou Fangzhi , He Sha , Castillo Roxanne , Liang Yuyan , Guan Jianguo , Zhang Liangfang , Wang Joseph
Published: December 2017

The preparation and operation of free swimming functionalized sperm micromotors (FSFSMs) as intelligent self‐guided biomotors with intrinsic chemotactic motile behavior are reported. The natural sperm biomotors are functionalized with a wide variety of synthetic nanoscale payloads, such as CdSe/ZnS quantum dots, doxorubicin hydrochloride drug coated iron‐oxide nanoparticles, and fluorescein isothiocyanate‐modified Pt nanoparticles via endocytosis. The FSFSMs display efficient self‐propulsion in various biological and environmental media with controllable swarming behavior upon exposure to a chemical attractant. As a new class of environmentally responsive smart biomotors, the control of the FSFSM speed is achieved by varying the solution osmolarity that leads to different flagellar lengths. High drug loading capacity and responsive release kinetics are obtained with such sperm biomotors. The transport of synthetic cargo can be guided by the intrinsic chemotaxis of the FSFSMs. The chemotactic characteristics, speed control mechanism, and responsive payload release of the FSFSMs are investigated. Such use of free swimming functionalized sperm cells as intelligent microscale biomotors offers considerable potential for diverse biomedical and environmental applications.
On the Wetting States of Low Melting Point Metal Galinstan® on Silicon Microstructured Surfaces
Authors: Davis Ethan , Ndao Sidy
Published: December 2017

The primary goal of this article is to measure the wetting characteristics of a low melting point metal to determine the efficacy of this type of material for possible use in thermal energy storage applications. Galinstan®, a commercially available alloy consisting of Gallium, Indium, and Tin is subjected to contact angle measurements on various silicon surfaces at varying temperatures. Due to the oxidation characteristics of Galinstan, all experiments are conducted in an inert nitrogen environment (<0.5 ppm oxygen) to maintain fluid‐like properties. This work finds that although contact angle changes with substrate and surface structure, temperature has no observable effect on contact angle. Contact angles range from 141° on smooth silicon to greater than 160° on silicon micropillars. Although a temperature dependence is not observed over the range of temperatures studied, having wetting properties of Galinstan on various surfaces is a step toward better understanding the capabilities of this and similar materials in energy management.
Contrasting Effects of Energy Transfer in Determining Efficiency Improvements in Ternary Polymer Solar Cells
Authors: Li Wei , Yan Yu , Gong Yanyan , Cai Jinlong , Cai Feilong , Gurney Robert S. , Liu Dan , Pearson Andrew J. , Lidzey David G. , Wang Tao
Published: December 2017

Crystallizable, high‐mobility conjugated polymers have been employed as secondary donor materials in ternary polymer solar cells in order to improve device efficiency by broadening their spectral response range and enhancing charge dissociation and transport. Here, contrasting effects of two crystallizable polymers, namely, PffBT4T‐2OD and PDPP2TBT, in determining the efficiency improvements in PTB7‐Th:PC71BM host blends are demonstrated. A notable power conversion efficiency of 11% can be obtained by introducing 10% PffBT4T‐2OD (relative to PTB7‐Th), while the efficiency of PDPP2TBT‐incorporated ternary devices decreases dramatically despite an enhancement in hole mobility and light absorption. Blend morphology studies suggest that both PffBT4T‐2OD and PDPP2TBT are well dissolved within the host PTB7‐Th phase and facilitate an increased degree of phase separation between polymer and fullerene domains. While negligible charge transfer is determined in binary blends of each polymer mixture, effective energy transfer is identified from PffBT4T‐2OD to PTB7‐Th that contributes to an improvement in ternary blend device efficiency. In contrast, energy transfer from PTB7‐Th to PDPP2TBT worsens the efficiency of the ternary device due to inefficient charge dissociation between PDPP2TBT and PC71BM.
Modular Design of Advanced Catalytic Materials Using Hybrid Organic–Inorganic Raspberry Particles
Authors: Shirman Elijah , Shirman Tanya , Shneidman Anna V. , Grinthal Alison , Phillips Katherine R. , Whelan Hayley , Bulger Eli , Abramovitch Marcus , Patil Jatin , Nevarez Rochelle , Aizenberg Joanna
Published: December 2017

Catalysis is one of the most sophisticated areas of materials research that encompasses a diverse set of materials and phenomena occurring on multiple length and time scales. Designing catalysts that can be broadly applied toward global energy and environmental challenges requires the development of universal frameworks for complex catalytic systems through rational and independent (or quasi‐independent) optimization of multiple structural and compositional features. Toward addressing this goal, a modular platform is presented in which sacrificial organic colloids bearing catalytic nanoparticles on their surfaces self‐assemble with matrix precursors, simultaneously structuring the resulting porous networks and fine‐tuning the locations of catalyst particles. This strategy allows combinatorial variations of the material building blocks and their organization, in turn providing numerous degrees of freedom for optimizing the material's functional properties, from the nanoscale to the macroscale. The platform enables systematic studies and rational design of efficient and robust systems for a wide range of catalytic and photocatalytic reactions, as well as their integration into industrial and other real‐life environments.
Polar Elastomers as Novel Materials for Electromechanical Actuator Applications
Authors: Opris Dorina M.
Published: December 2017

Dielectric elastomer actuators are stretchable capacitors capable of a musclelike actuation when charged. They will one day be used to replace malfunctioning muscles supposing the driving voltage can be reduced below 24 V. This focus here is on polar dielectric elastomers and their behavior under an electric field. Emphasis is placed on all the features that are correlated with the molecular structure, its synthetic realization, and its impact on properties. Regarding the polymer class, the focus, to some degree, is on polysiloxanes because of their attractively low glass transition temperatures. This enables introduction of highly polar groups to the backbone while maintaining soft elastic properties. The goal is to provide a few guidelines for future research in this emerging field that may be useful for those considering entering this fascinating endeavor. Because of the large number of materials available, a few restrictions in the selection have to be applied.
Advanced Biomass‐Derived Electrocatalysts for the Oxygen Reduction Reaction
Authors: Borghei Maryam , Lehtonen Janika , Liu Liang , Rojas Orlando J.
Published: December 2017

Recent progress in advanced nanostructures synthesized from biomass resources for the oxygen reduction reaction (ORR) is reviewed. The ORR plays a significant role in the performance of numerous energy‐conversion devices, including low‐temperature hydrogen and alcohol fuel cells, microbial fuel cells, as well as metal–air batteries. The viability of such fuel cells is strongly related to the cost of the electrodes, especially the cathodic ORR electrocatalyst. Hence, inexpensive and abundant plant and animal biomass have become attractive options to obtain electrocatalysts upon conversion into active carbon. Bioresource selection and processing criteria are discussed in light of their influence on the physicochemical properties of the ORR nanostructures. The resulting electrocatalytic activity and durability are introduced and compared to those from conventional Pt/C‐based electrocatalysts. These ORR catalysts are also active for oxygen or hydrogen evolution reactions.
A 3D Self‐Shaping Strategy for Nanoresolution Multicomponent Architectures
Authors: Su Meng , Huang Zhandong , Li Yifan , Qian Xin , Li Zheng , Hu Xiaotian , Pan Qi , Li Fengyu , Li Lihong , Song Yanlin
Published: December 2017

3D printing or fabrication pursues the essential surface behavior manipulation of droplets or a liquid for rapidly and precisely constructing 3D multimaterial architectures. Further development of 3D fabrication desires a self‐shaping strategy that can heterogeneously integrate functional materials with disparate electrical or optical properties. Here, a 3D liquid self‐shaping strategy is reported for rapidly patterning materials over a series of compositions and accurately achieving micro‐ and nanoscale structures. The predesigned template selectively pins the droplet, and the surface energy minimization drives the self‐shaping processing. The as‐prepared 3D circuits assembled by silver nanoparticles carry a current of 208–448 µA at 0.01 V impressed voltage, while the 3D architectures achieved by two different quantum dots show noninterfering optical properties with feature resolution below 3 µm. This strategy can facilely fabricate micro‐nanogeometric patterns without a modeling program, which will be of great significance for the development of 3D functional devices.
Preparation of Microcellular Epoxy Foams through a Limited‐Foaming Process: A Contradiction with the Time–Temperature–Transformation Cure Diagram
Authors: Wang Lijun , Zhang Chun , Gong Wei , Ji Yubi , Qin Shuhao , He Li
Published: December 2017

3D cross‐linking networks are generated through chemical reactions between thermosetting epoxy resin and hardener during curing. The curing degree of epoxy material can be increased by increasing curing temperature and/or time. The epoxy material must then be fully cured through a postcuring process to optimize its material characteristics. Here, a limited‐foaming method is introduced for the preparation of microcellular epoxy foams (Lim‐foams) with improved cell morphology, high thermal expansion coefficient, and good compressive properties. Lim‐foams exhibit a lower glass transition temperature (Tg) and curing degree than epoxy foams fabricated through free‐foaming process (Fre‐foams). Surprisingly, however, theTgof Lim‐foams is unaffected by postcuring temperature and time. This phenomenon, which is related to high gas pressure in the bubbles, contradicts that indicated by the time–temperature–transformation cure diagram. High bubble pressure promotes the movement of molecular chains under heating at low temperature and simultaneously suppresses the etherification cross‐linking reaction during post‐curing.
Hole‐Transfer Dependence on Blend Morphology and Energy Level Alignment in Polymer: ITIC Photovoltaic Materials
Authors: Eastham Nicholas D. , Logsdon Jenna L. , Manley Eric F. , Aldrich Thomas J. , Leonardi Matthew J. , Wang Gang , Powers‐Riggs Natalia E. , Young Ryan M. , Chen Lin X. , Wasielewski Michael R. , Melkonyan Ferdinand S. , Chang Robert P. H. , Marks Tobin J.
Published: December 2017

Bulk‐heterojunction organic photovoltaic materials containing nonfullerene acceptors (NFAs) have seen remarkable advances in the past year, finally surpassing fullerenes in performance. Indeed, acceptors based on indacenodithiophene (IDT) have become synonymous with high power conversion efficiencies (PCEs). Nevertheless, NFAs have yet to achieve fill factors (FFs) comparable to those of the highest‐performing fullerene‐based materials. To address this seeming anomaly, this study examines a high efficiency IDT‐based acceptor, ITIC, paired with three donor polymers known to achieve high FFs with fullerenes, PTPD3T, PBTI3T, and PBTSA3T. Excellent PCEs up to 8.43% are achieved from PTPD3T:ITIC blends, reflecting good charge transport, optimal morphology, and efficient ITIC to PTPD3T hole‐transfer, as observed by femtosecond transient absorption spectroscopy. Hole‐transfer is observed from ITIC to PBTI3T and PBTSA3T, but less efficiently, reflecting measurably inferior morphology and nonoptimal energy level alignment, resulting in PCEs of 5.34% and 4.65%, respectively. This work demonstrates the importance of proper morphology and kinetics of ITIC → donor polymer hole‐transfer in boosting the performance of polymer:ITIC photovoltaic bulk heterojunction blends.
Structuring of Functional Spider Silk Wires, Coatings, and Sheets by Self‐Assembly on Superhydrophobic Pillar Surfaces
Authors: Gustafsson Linnea , Jansson Ronnie , Hedhammar My , van der Wijngaart Wouter
Published: December 2017

Spider silk has recently become a material of high interest for a large number of biomedical applications. Previous work on structuring of silk has resulted in particles (0D), fibers (1D), films (2D), and foams, gels, capsules, or microspheres (3D). However, the manufacturing process of these structures is complex and involves posttreatment of chemicals unsuitable for biological applications. In this work, the self‐assembly of recombinant spider silk on micropatterned superhydrophobic surfaces is studied. For the first time, structuring of recombinant spider silk is achieved using superhydrophobic surfaces under conditions that retain the bioactivity of the functionalized silk. By tuning the superhydrophobic surface geometry and the silk solution handling parameters, this approach allows controlled generation of silk coatings, nanowires, and sheets. The underlying mechanisms and governing parameters are discussed. It is believed that the results of this work pave the way for fabrication of silk formations for applications including vehicles for drug delivery, optical sensing, antimicrobial coatings, and cell culture scaffolds.
Alumina‐Supported CoFe Alloy Catalysts Derived from Layered‐Double‐Hydroxide Nanosheets for Efficient Photothermal CO2 Hydrogenation to Hydrocarbons
Authors: Chen Guangbo , Gao Rui , Zhao Yufei , Li Zhenhua , Waterhouse Geoffrey I. N. , Shi Run , Zhao Jiaqing , Zhang Mengtao , Shang Lu , Sheng Guiyang , Zhang Xiangping , Wen Xiaodong , Wu Li‐Zhu , Tung Chen‐Ho , Zhang Tierui
Published: December 2017

A series of novel CoFe‐based catalysts are successfully fabricated by hydrogen reduction of CoFeAl layered‐double‐hydroxide (LDH) nanosheets at 300–700 °C. The chemical composition and morphology of the reaction products (denoted herein as CoFe‐x) are highly dependent on the reduction temperature (x). CO2 hydrogenation experiments are conducted on the CoFe‐x catalysts under UV–vis excitation. With increasing LDH‐nanosheet reduction temperature, the CoFe‐x catalysts show a progressive selectivity shift from CO to CH4, and eventually to high‐value hydrocarbons (C2+). CoFe‐650 shows remarkable selectivity toward hydrocarbons (60% CH4, 35% C2+). X‐ray absorption fine structure, high‐resolution transmission electron microscopy, Mössbauer spectroscopy, and density functional theory calculations demonstrate that alumina‐supported CoFe‐alloy nanoparticles are responsible for the high selectivity of CoFe‐650 for C2+ hydrocarbons, also allowing exploitation of photothermal effects. This study demonstrates a vibrant new catalyst platform for harnessing clean, abundant solar‐energy to produce valuable chemicals and fuels from CO2.
Fine‐Tuning the Energy Levels of a Nonfullerene Small‐Molecule Acceptor to Achieve a High Short‐Circuit Current and a Power Conversion Efficiency over 12% in Organic Solar Cells
Authors: Kan Bin , Zhang Jiangbin , Liu Feng , Wan Xiangjian , Li Chenxi , Ke Xin , Wang Yunchuang , Feng Huanran , Zhang Yamin , Long Guankui , Friend Richard H. , Bakulin Artem A. , Chen Yongsheng
Published: December 2017

Organic solar cell optimization requires careful balancing of current–voltage output of the materials system. Here, such optimization using ultrafast spectroscopy as a tool to optimize the material bandgap without altering ultrafast photophysics is reported. A new acceptor–donor–acceptor (A–D–A)‐type small‐molecule acceptor NCBDT is designed by modification of the D and A units of NFBDT. Compared to NFBDT, NCBDT exhibits upshifted highest occupied molecular orbital (HOMO) energy level mainly due to the additional octyl on the D unit and downshifted lowest unoccupied molecular orbital (LUMO) energy level due to the fluorination of A units. NCBDT has a low optical bandgap of 1.45 eV which extends the absorption range toward near‐IR region, down to ≈860 nm. However, the 60 meV lowered LUMO level of NCBDT hardly changes the Voc level, and the elevation of the NCBDT HOMO does not have a substantial influence on the photophysics of the materials. Thus, for both NCBDT‐ and NFBDT‐based systems, an unusually slow (≈400 ps) but ultimately efficient charge generation mediated by interfacial charge‐pair states is observed, followed by effective charge extraction. As a result, the PBDB‐T:NCBDT devices demonstrate an impressive power conversion efficiency over 12%—among the best for solution‐processed organic solar cells.
Energy–Structure–Function Maps: Cartography for Materials Discovery
Authors: Day Graeme M. , Cooper Andrew I.
Published: December 2017

Some of the most successful approaches to structural design in materials chemistry have exploited strong directional bonds, whose geometric reliability lends predictability to solid‐state assembly. For example, metal–organic frameworks are an important design platform in materials chemistry. By contrast, the structure of molecular crystals is defined by a balance of weaker intermolecular forces, and small changes to the molecular building blocks can lead to large changes in crystal packing. Hence, empirical rules are inherently less reliable for engineering the structures of molecular solids. Energy–structure–function (ESF) maps are a new approach for the discovery of functional organic crystals. These maps fuse crystal‐structure prediction with the computation of physical properties to allow researchers to choose the most promising molecule for a given application, prior to its synthesis. ESF maps were used recently to discover a highly porous molecular crystal that has a high methane deliverable capacity and the lowest density molecular crystal reported to date (r = 0.41 g cm−3, SABET = 3425 m2 g−1). Progress in this field is reviewed, with emphasis on the future opportunities and challenges for a design strategy based on computed ESF maps.
Laser Irradiation‐Induced SiC@Graphene Sub‐Microspheres: A Bioinspired Core–Shell Structure for Enhanced Tribology Properties
Authors: Luo Ting , Chen Xinchun , Wang Ping , Li Cuncheng , Cao Bingqiang , Zeng Haibo
Published: December 2017

Friction generally happening among all moving material interfaces wastes nearly one‐third of total mechanical energy in the world each year, although different kinds of lubricants are adopted. Particle additives, like diamond, inorganic fullerene, and graphene, can enter tribological contacts to reduce friction and protect surfaces from wear. However, the growth of such additives with spherical morphology and high dispersibility in oil without molecular ligands is a major problem. Inspired by the impressive dispersion stability of Noctiluca scientillans in ocean, one novel core–shell composite constructed with superhard SiC sub‐microsphere as core and exclusive floating flat‐blade graphene sheet as shell (SiC@G) is designed. These core–shell SiC@G sub‐micropheres are synthesized for the first time by in situ pulsed laser irradiating commercial SiC powders in liquid at ambient conditions. Both laser‐stimulated surface tension energy release and photothermal decomposition involved in the laser irradiation process assure the reshaping of SiC particles and the formation of graphene sheets derived from SiC surface. Due to the synergistic effect of SiC spheres changing effectively sliding friction into rolling friction and flexible self‐lubricating graphene forming a tribofilm easily, such composites as additives remain well dispersed in lubricating oil and exhibit enhanced antiwear and friction‐reduction performance.
Achieving Totally Local Anticoagulation on Blood Contacting Devices
Authors: Gbyli Rana , Mercaldi Anna , Sundaram Harihara , Amoako Kagya A.
Published: December 2017

The recent years have witnessed an increased activity in biocompatibility research aimed at limiting biomaterial‐induced blood coagulation. From 2008 to 2016, a total of $36 946 764.00 USD has been awarded in grants to 213 research proposals and as large as 50.4% ($18 627 854.00) of that award monies have been distributed to 101 proposals over the fiscal years of FY14 to FY16 alone. However, the complexity in blood responses to biomaterials, variability in blood function between individuals and animal species, and differences in medical device application and test setting all continue to pose difficulties in making a breakthrough in this field. This review focuses on the remaining challenges in the context of biomaterial surface interaction with blood, biomaterial properties and their influence on coagulation, old and new surface anticoagulation methods, main test systems (complement and platelet function) for evaluating those methods, limitations of modification techniques, and the current state of systemic anticoagulation usage as adjunctive therapy for controlling blood coagulation on biomaterials. Finally, ingredients necessary for advancing the field toward achieving totally local surface anticoagulation on blood contacting devices including standardization of in vitro and in‐vivo test methods are proposed. Some highlights of recent forward‐looking work and articles on local anticoagulation are also presented.
Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer
Authors: Salomé Pedro M. P. , Vermang Bart , Ribeiro‐Andrade Rodrigo , Teixeira Jennifer P. , Cunha José M. V. , Mendes Manuel J. , Haque Sirazul , Borme Jêrome , Águas Hugo , Fortunato Elvira , Martins Rodrigo , González Juan C. , Leitão Joaquim P. , Fernandes Paulo A. , Edoff Marika , Sadewasser Sascha
Published: December 2017

Thin film solar cells based in Cu(In,Ga)Se2 (CIGS) are among the most efficient polycrystalline solar cells, surpassing CdTe and even polycrystalline silicon solar cells. For further developments, the CIGS technology has to start incorporating different solar cell architectures and strategies that allow for very low interface recombination. In this work, ultrathin 350 nm CIGS solar cells with a rear interface passivation strategy are studied and characterized. The rear passivation is achieved using an Al2O3 nanopatterned point structure. Using the cell results, photoluminescence measurements, and detailed optical simulations based on the experimental results, it is shown that by including the nanopatterned point contact structure, the interface defect concentration lowers, which ultimately leads to an increase of solar cell electrical performance mostly by increase of the open circuit voltage. Gains to the short circuit current are distributed between an increased rear optical reflection and also due to electrical effects. The approach of mixing several techniques allows us to make a discussion considering the different passivation gains, which has not been done in detail in previous works. A solar cell with a nanopatterned rear contact and a 350 nm thick CIGS absorber provides an average power conversion efficiency close to 10%.
Robust Superhydrophobic Laser‐Induced Graphene for Desalination Applications
Authors: Tittle Collin M. , Yilman Dilara , Pope Michael A. , Backhouse Christopher J.
Published: December 2017

The fabrication of long‐lived, durable, superhydrophobic surfaces using a manufacturable process is an important challenge for material science. Significant advances have been reported; however, many surfaces suffer from fragility, nonmanufacturable fabrication techniques, and temporal instability. Such challenges have limited commercial scale application of superhydrophobic films, including their application to water desalination where long lifetimes and durability are essential. The fabrication of controllably wettable surfaces formed from laser‐induced graphene is demonstrated in atmospheric conditions with contact angle control from 59° to 176°; representing some of the most superhydrophobic carbon surfaces ever reported. This superhydrophobicity is used to engineer a membrane with the largest pores ever reported for the energy efficient water desalination technique of air‐gapped membrane distillation. State‐of‐the‐art production of distilled water is observed, and no membrane failure or loss of superhydrophobicity is observed on a time‐scale of months—suggesting total water production capabilities well beyond anything yet demonstrated.
Visualized UV Photodetectors Based on Prussian Blue/TiO2 for Smart Irradiation Monitoring Application
Authors: Qiu Meijia , Sun Peng , Liu Yujin , Huang Qitong , Zhao Chuanxi , Li Zhaohui , Mai Wenjie
Published: December 2017

The growing needs in monitoring health and environmental risks call for the development of smart ultraviolet (UV) photodetectors with special or multiple functions. Herein, a photoelectrochemical cell based self‐powered and wearable UV photodetector system with high stability, high speed, and an interesting visualization feature is successfully developed. TiO2 nanotubes on flexible Ti foil and Prussian blue on flexible polyethylene terephthalate/indium‐tin oxide are selected as the photoanode and electrochromic counter electrode, respectively. The integrated flexible UV photodetectors can not only function stably for many bending cycles but also exhibit visualized indication of UV exposure by recyclable color change without external power. Moreover, the as‐fabricated visible‐blind photodetectors show excellent UV responsivity (78.3 mA W−1), ultralow UV light detection limit (<10 µW cm−2), and fast response with a rise time and a decay time of 0.04 and 0.06 s, respectively. Our all‐in‐one smart photodetector has demonstrated great application potential in self‐powered smart sensors and wearable healthcare electronics.
Terahertz Modulators Based on Silicon Nanotip Array
Authors: Shi Zhong‐Wei , Cao Xing‐Xing , Wen Qi‐Ye , Wen Tian‐Long , Yang Qing‐Hui , Chen Zhi , Shi Wen‐Sheng , Zhang Huai‐Wu
Published: December 2017

As an attractive applications of terahertz (THz) radiation, imaging with THz technique stands at the focus of current interest. THz spatial modulators are key issue for fast imaging with a single detector. Here, for the first time, the silicon nanotip (SiNT) arrays are reported that can be utilized as antireflection layers for the THz wave to achieve a low‐loss and spectrally broadband optical‐driven THz modulator. Compared with the modulator fabricated with bare silicon, a 2–3‐time larger modulation depth is achieved in SiNT modulator. Moreover, it is found that the intrinsic THz transmission of SiNT is as high as 90%, which is much higher than that of bare silicon. The theoretical simulation results reveal that a strong antireflection effect induced from SiNT layer plays a crucial role in enhancing the properties of modulator. The SiNT‐based optical‐driven THz modulator with low loss and high modulation depth is promising for potential application to THz imaging.
Electroluminescence of Colloidal Quantum Dots in Electrical Contact with Metallic Nanoparticles
Authors: Wang Hongyue , Le‐Van Quynh , Aassime Abdelhanin , Roux Xavier Le , Charra Fabrice , Chauvin Nicolas , Degiron Aloyse
Published: December 2017

The electroluminescence of a carpet of colloidal quantum dots in electrical contact with a metal nanoparticle array is investigated. The properties of the structures spectacularly differ from the well‐known behavior of point sources placed at nonvanishing distances from subwavelength scatterers (robustness to quenching, coupling primarily defined by the electrical contact between the two species, etc.). This regime of short‐range interactions can even be enabled with nonplasmonic inclusions made of platinum, providing an extreme case of enhanced and tailored light emission by quantum emitters in a highly absorptive environment. As a corollary, surface plasmons are not a necessary or sufficient ingredient but add functionalities that nonplasmonic structures do not possess. These findings indicate that the physics of localized light emitters in highly inhomogeneous environments is far from being fully understood and have important implications for the next generation of active metamaterials and advanced optoelectronic devices.
Highly Substituted Cyclohexenes via Phosphine‐Catalyzed [4+2] Annulation of Electron‐deficient Dienes and Vinyl Ketones
Authors: Chen Peng , Zhang Junyou , Zhang Junliang
Published: December 2017

A highly efficient phosphine‐catalyzed [4+2] annulation of electron‐deficient diene and alkyl vinyl ketone was developed for the first time, which provides an easy access to functionalized cyclohexenes. This method has the advantages of mild reaction conditions, widely functional group tolerance, high yields and transition metal free.

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Asymmetric Hybrid Polymer–Lipid Giant Vesicles as Cell Membrane Mimics
Authors: Peyret Ariane , Ibarboure Emmanuel , Le Meins Jean‐François , Lecommandoux Sebastien
Published: December 2017

Lipid membrane asymmetry plays an important role in cell function and activity, being for instance a relevant signal of its integrity. The development of artificial asymmetric membranes thus represents a key challenge. In this context, an emulsion‐centrifugation method is developed to prepare giant vesicles with an asymmetric membrane composed of an inner monolayer of poly(butadiene)‐b‐poly(ethylene oxide) (PBut‐b‐PEO) and outer monolayer of 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine (POPC). The formation of a complete membrane asymmetry is demonstrated and its stability with time is followed by measuring lipid transverse diffusion. From fluorescence spectroscopy measurements, the lipid half‐life is estimated to be 7.5 h. Using fluorescence recovery after photobleaching technique, the diffusion coefficient of 1,2‐dioleoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐(lissamine rhodamine B sulfonyl) (DOPE‐rhod, inserted into the POPC leaflet) is determined to be about D = 1.8 ± 0.50 μm2 s−1 at 25 °C and D = 2.3 ± 0.7 μm2 s−1 at 37 °C, between the characteristic values of pure POPC and pure polymer giant vesicles and in good agreement with the diffusion of lipids in a variety of biological membranes. These results demonstrate the ability to prepare a cell‐like model system that displays an asymmetric membrane with transverse and translational diffusion properties similar to that of biological cells.
Increasing Photovoltaic Performance of an Organic Cationic Chromophore by Anion Exchange
Authors: Gesevičius Donatas , Neels Antonia , Jenatsch Sandra , Hack Erwin , Viani Lucas , Athanasopoulos Stavros , Nüesch Frank , Heier Jakob
Published: December 2017

A symmetrical cyanine dye chromophore is modified with different counteranions to study the effect on crystal packing, polarizability, thermal stability, optical properties, light absorbing layer morphology, and organic photovoltaic (OPV) device parameters. Four sulfonate‐based anions and the bulky bistriflylimide anion are introduced to the 2‐[5‐(1,3‐dihydro‐1,3,3‐trimethyl‐2H‐indol‐2‐ylidene)‐1,3‐pentadien‐1‐yl]‐1,3,3‐trimethyl‐3H‐indolium chromophore using an Amberlyst A26 (OH− form) anion exchanger. Anionic charge distribution clearly correlates with device performance, whereby an average efficiency of 2% was reached in a standard bilayer organic solar. Evidence is given that the negative charge of the anion distributed over a large number of atoms is significantly more important than the size of the organic moieties of the sulfonate charge carrying group. This provides a clear strategy for future design of more efficient cyanine dyes for OPV applications.
Graphene‐Based MicroRNA Transfection Blocks Preosteoclast Fusion to Increase Bone Formation and Vascularization
Authors: Dou Ce , Ding Ning , Luo Fei , Hou Tianyong , Cao Zhen , Bai Yun , Liu Chuan , Xu Jianzhong , Dong Shiwu
Published: December 2017

The objective of this study is to design a graphene‐based miRNA transfection drug delivery system for antiresorptive therapy. An efficient nonviral gene delivery system is developed using polyethylenimine (PEI) functionalized graphene oxide (GO) complex loaded with miR‐7b overexpression plasmid. GO‐PEI complex exhibits excellent transfection efficiency within the acceptable range of cytotoxicity. The overexpression of miR‐7b after GO‐PEI‐miR‐7b transfection significantly abrogates osteoclast (OC) fusion and bone resorption activity by hampering the expression of an essential fusogenic molecule dendritic cell‐specific transmembrane protein. However, osteoclastogenesis occurs without cell–cell fusion and preosteoclast (POC) is preserved. Through preservation of POC, GO‐PEI‐miR‐7b transfection promotes mesenchymal stem cell osteogenesis and endothelial progenitor cells angiogenesis in the coculture system. Platelet‐derived growth factor‐BB secreted by POC is increased by GO‐PEI‐miR‐7b both in vitro and in vivo. In treating osteoporotic ovariectomized mice, GO‐PEI‐miR‐7b significantly enhances bone mineral density, bone volume as well as bone vascularization through increasing CD31hiEmcnhi cell number. This study provides a cell–cell fusion targeted miRNA transfection drug delivery strategy in treating bone disorders with excessive osteoclastic bone resorption.
Nickel Hydr(oxy)oxide Nanoparticles on Metallic MoS2 Nanosheets: A Synergistic Electrocatalyst for Hydrogen Evolution Reaction
Authors: Zhang Xing , Liang Yongye
Published: December 2017

Molybdenum disulfide (MoS2)‐based materials have been recently identified as promising electrocatalysts for hydrogen evolution reaction (HER). However, little work has been done to improve the catalytic performance of MoS2 toward HER in alkaline electrolytes, which is more suitable for water splitting in large‐scale applications. Here, it is reported that the hybridization of 0D nickel hydr(oxy)oxide nanoparticles with 2D metallic MoS2 nanosheets can significantly enhance the HER activities in alkaline and neutral electrolytes. Impressively, the optimized hybrid catalyst can drive a cathodic current density of 10 mA cm−2 at an overpotential of ≈73 mV for HER in 1 m KOH, about 185 mV smaller than the original MoS2. The improved HER activity is attributed to a bifunctional mechanism adopted in these hybrid catalysts, in which nickel hydr(oxy)oxide promotes the water adsorption and dissociation to supply protons for subsequent reactions occurred on MoS2 to generate H2.
ZnO Nanofiber Thin‐Film Transistors with Low‐Operating Voltages
Authors: Wang Fengyun , Song Longfei , Zhang Hongchao , Meng You , Luo Linqu , Xi Yan , Liu Lei , Han Ning , Yang Zaixing , Tang Jie , Shan Fukai , Ho Johnny C.
Published: December 2017

Although significant progress has been made towards using ZnO nanofibers (NFs) in future high‐performance and low‐cost electronics, they still suffer from insufficient device performance caused by substantial surface roughness (i.e., irregularity) and granular structure of the obtained NFs. Here, a simple one‐step electrospinning process (i.e., without hot‐press) is presented to obtain controllable ZnO NF networks to achieve high‐performance, large‐scale, and low‐operating‐power thin‐film transistors. By precisely manipulating annealing temperature during NF fabrication, their crystallinity, grain size distribution, surface morphology, and corresponding device performance can be regulated reliably for enhanced transistor performances. For the optimal annealing temperature of 500 °C, the device exhibits impressive electrical characteristics, including a small positive threshold voltage (Vth) of ≈0.9 V, a low leakage current of ≈10−12 A, and a superior on/off current ratio of ≈106, corresponding to one of the best‐performed ZnO NF devices reported to date. When high‐κ AlOx thin films are employed as gate dielectrics, the source/drain voltage (VDS) can be substantially reduced by 10× to a range of only 0–3 V, along with a 10× improvement in mobility to a respectable value of 0.2 cm2 V−1 s−1. These results indicate the potential of these nanofibers for use in next‐generation low‐power devices.
Controlled Low‐Frequency Electrical Noise of Monolayer MoS2 with Ohmic Contact and Tunable Carrier Concentration
Authors: Wang Ji‐Wun , Liu Yen‐Po , Chen Po‐Han , Chuang Meng‐Hsi , Pezeshki Atiye , Ling Dah‐Chin , Chen Jeng‐Chung , Chen Yung‐Fu , Lee Yi‐Hsien
Published: December 2017

Semiconducting monolayers of transition metal dichalcogenides (TMDs) are considered as emergent materials for nanodevices and optoelectronic applications. The low‐frequency electrical noise of TMD‐based devices is much higher than Si and other conventional semiconductors. The reduction of this noise along with control of the Ohmic contact and carrier concentration of the such devices remain major challenges. Here, the low‐frequency (1/f) noise and transport properties of chemical‐vapor‐deposition‐grown MoS2 are presented. The high mobility of 20–40 cm2 V−1 s−1 of the monolayer devices is highly reproducible. Reliable methods to induce Ohmic contact and to tune carrier density over a wide range of 1011–1014 cm−2 are presented to study the fundamental mechanism of the 1/f noise. The noise performance in the high carrier concentration regime is explored for the first time with Ohmic contact of the devices and ideal sample quality. A significant reduction of the noise figure of merit is achievable in the high‐density regime. Polymer electrolyte encapsulation provides a practical method to effectively tune carrier density and engineer surface trap states of the monolayer TMDs, which would be helpful for practical applications of 2D atomic layers in nanoelectronics and photonics.