bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anomalous Photovoltaic Effect in Centrosymmetric Ferroelastic BiVO4
Authors: Liu Xitao , Zhang Faqiang , Long Peiqing , Lu Teng , Zeng Huarong , Liu Yun , Withers Ray L. , Li Yongxiang , Yi Zhiguo 
Published: September 2018

AbstractThe anomolous photovoltaic (APV) effect is an intriguing phenomenon and rarely observed in bulk materials that structurally have an inversion symmetry. Here, the discovery of such an APV effect in a centrosymmetric vanadate, BiVO4, where noticeable above‐bandgap photovoltage and a steady‐state photocurrent are observed in both ceramics and single crystals even when illuminated under visible light, is reported. Moreover, the photovoltaic voltage can be reversed by the stress modulation, and a sine‐function relationship between the photovoltage and stress directional angle is derived. Microstructure and strain‐field analysis reveal localized asymmetries that are caused by strain fluctuations in bulk centrosymmetric BiVO4. On the basis of the experimental results, a flexoelectric coupling via a strain‐induced local polarization mechanism is suggested to account for the APV effect observed. This work not only allows new applications for BiVO4 in optoelectronic devices but also deepens insights into the mechanisms underlying the APV effect.
Large‐Area Synthesis of Layered HfS2(1−x)Se2x Alloys with Fully Tunable Chemical Compositions and Bandgaps
Authors: Wang Denggui , Zhang Xingwang , Guo Gencai , Gao Shihan , Li Xingxing , Meng Junhua , Yin Zhigang , Liu Heng , Gao Menglei , Cheng Likun , You Jingbi , Wang Ruzhi 
Published: September 2018

AbstractAlloying transition metal dichalcogenides (TMDs) with different compositions is demonstrated as an effective way to acquire 2D semiconductors with widely tunable bandgaps. Herein, for the first time, the large‐area synthesis of layered HfS2(1−x)Se2x alloys with fully tunable chemical compositions on sapphire by chemical vapor deposition is reported, greatly expanding and enriching the family of 2D TMDs semiconductors. The configuration and high quality of their crystal structure are confirmed by various characterization techniques, and the bandgap of these alloys can be continually modulated from 2.64 to 1.94 eV with composition variations. Furthermore, prototype HfS2(1−x)Se2x photodetectors with different Se compositions are fabricated, and the HfSe2 photodetector manifests the best performance among all the tested HfS2(1−x)Se2x devices. Remarkably, by introducing a hexagonal boron nitride layer, the performance of the HfSe2 photodetector is greatly improved, exhibiting a high on/off ratio exceeding 105, an ultrafast response time of about 190 µs, and a high detectivity of 1012 Jones. This simple and controllable approach opens up a new way to produce high‐quality 2D HfS2(1−x)Se2x layers, which are highly qualified candidates for the next‐generation application in high‐performance optoelectronics.
Direct Chirality Recognition of Single‐Crystalline and Single‐Walled Transition Metal Oxide Nanotubes on Carbon Nanotube Templates
Authors: Shen Boyuan , Xie Huanhuan , Gu Lin , Chen Xiao , Bai Yunxiang , Zhu Zhenxing , Wei Fei 
Published: September 2018

AbstractChirality is a significant structural feature for chemistry, biology, physics, and materials science, and especially determines the electrical, mechanical, and optical properties of diverse tubular structures, such as carbon nanotubes (CNTs). To recognize the chirality of nanotubes, templates are introduced as potential tools to obtain crystalline samples with visible chiral fringes under electron microscopes. However, few efforts show optimistic results, and new understanding is desired to control the sample quality with CNT templates. Here, a synthesis strategy of single‐crystalline molybdenum trioxide (α‐MoO3) nanotubes (MONTs) on CNT surfaces is reported to build a 1D van der Waals (vdW) heterostructure. The chirality of the MONTs can be directly “seen” and their structural selectivity is revealed. First, the centralized distribution of the chiral angles of the MONTs indicates a preferential orientation due to the anisotropic bending rigidity of the 2D layers. Then, the interlayer mismatching rejects the radial stacking of α‐MoO3to maintain the single‐walled nature. These results provide a spontaneous strategy for the efficient recognition and control of chirality, and open up a new avenue for CNT‐based functional 1D vdW heterostructures.
A Ternary Ni46Co40Fe14 Nanoalloy‐Based Oxygen Electrocatalyst for Highly Efficient Rechargeable Zinc–Air Batteries
Authors: Nam Gyutae , Son Yeonguk , Park Sung O , Jeon Woo Cheol , Jang Haeseong , Park Joohyuk , Chae Sujong , Yoo Youngshin , Ryu Jaechan , Kim Min Gyu , Kwak Sang Kyu , Cho Jaephil 
Published: September 2018

AbstractReplacing noble‐metal‐based oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is the key to developing efficient Zn–air batteries (ZABs). Here, a homogeneous ternary Ni46Co40Fe14 nanoalloy with a size distribution of 30–60 nm dispersed in a carbon matrix (denoted as C@NCF‐900) as a highly efficient bifunctional electrocatalyst produced via supercritical reaction and subsequent heat treatment at 900 °C is reported. Among all the transition‐metal‐based electrocatalysts, the C@NCF‐900 exhibits the highest ORR performance in terms of half‐wave potential (0.93 V) in 0.1 m KOH. Moreover, C@NCF‐900 exhibits negligible activity decay after 10 000 voltage cycles with minor reduction (0.006 V). In ZABs, C@NCF‐900 outperforms the mixture of Pt/C 20 wt% and IrO2, cycled over 100 h under 58% depth of discharge condition. Furthermore, density functional theory (DFT) calculations and in situ X‐ray absorption spectroscopy strongly support the active sites and site‐selective reaction as a plausible ORR/OER mechanism of C@NCF‐900.
Mechanochemically Assisted Synthesis of a Ru Catalyst for Hydrogen Evolution with Performance Superior to Pt in Both Acidic and Alkaline Media
Authors: Li Feng , Han Gao‐Feng , Noh Hyuk‐Jun , Ahmad Ishfaq , Jeon In‐Yup , Baek Jong‐Beom 
Published: September 2018

AbstractCatalysts are at the heart of the hydrogen evolution reaction (HER) for the production of pure and clean hydrogen. For practical applications, the scalable synthesis of efficient HER catalysts, which work in both acidic and alkaline media, is highly desired. In this work, the mechanochemically assisted synthesis of a Ru catalyst with HER performance surpassing Pt in both acidic and alkaline media is reported. Mass production of this Ru catalyst can be achieved via a two‐step procedure: the mechanochemical reaction between graphite and dry ice produces edge‐carboxylic‐acid‐functionalized graphene nanoplatelets (CGnP); mixing a Ru precursor and the CGnP in an aqueous medium introduces Ru ions, which coordinate on the CGnP. Subsequent annealing results in uniform Ru nanoparticles (≈2 nm) anchored on the GnP matrix (Ru@GnP). The efficient Ru@GnP catalyst can be easily powered by a single silicon solar cell using a wireless integration device. The self‐powered device exhibits robust hydrogen evolution under the irradiation of standard AM 1.5 solar light. This work provides a new opportunity for the low‐cost mass production of efficient and stable catalysts for practical applications.
Flexible Linearly Polarized Photodetectors Based on All‐Inorganic Perovskite CsPbI3 Nanowires
Authors: Zhou Ying , Luo Jiajun , Zhao Yang , Ge Cong , Wang Chong , Gao Liang , Zhang Cheng , Hu Manchen , Niu Guangda , Tang Jiang 
Published: September 2018

AbstractPolarization‐sensitive photodetection has drawn a great deal of research interests, which takes advantage of anisotropy from the lattice structure or the morphology of active material. However, no photodetectors combined these two kinds of anisotropy together for linearly polarized photodetection. Here, a photodetector based on cesium lead iodide (β‐CsPbI3) nanowire array with anisotropic crystal structure is demonstrated. Owing to the crystal structure and morphology anisotropy of the β‐CsPbI3 nanowires, the device exhibited high sensitivity to linearly polarized light with a photocurrent anisotropy ratio of 2.68 and 2.17 on rigid and flexible substrates, respectively, which was much higher than existing linearly polarized photodetectors. In addition, the photocurrent anisotropy ratio of the device on flexible substrate only dropped by 5% after 500 bending cycles, indicating excellent flexibility and folding endurance of flexible CsPbI3 device. The application of anisotropic CsPbI3 nanowires in polarization‐sensitive photodetection might provide new functionalities in novel optoelectronic applications.
Low Temperature Fabrication for High Performance Flexible CsPbI2Br Perovskite Solar Cells
Authors: Jiang Hong , Feng Jiangshan , Zhao Huan , Li Guijun , Yin Guannan , Han Yu , Yan Feng , Liu Zhike , Liu Shengzhong (Frank) 
Published: September 2018

AbstractAll‐inorganic CsPbX3‐based perovskites, such as CsPbI2Br, show much better thermal and illumination stability than their organic–inorganic hybrid counterparts. However, fabrication of high‐quality CsPbI2Br perovskite film normally requires annealing at a high temperature (>250 °C) that is not compatible with the plastic substrate. In this work, a Lewis base adduct‐promoted growth process that makes it possible to fabricate high quality CsPbI2Br perovskite films at low temperature is promoted. The mechanism is attributed to synthesized dimethyl sulfoxide (DMSO) adducts which allow a low activation energy route to form CsPbI2Br perovskite films during the thermal annealing treatment. A power conversion efficiency (PCE) of 13.54% is achieved. As far as it is known, this is the highest efficiency for the CsPbI2Br solar cells fabricated at low temperature (120 °C). In addition, the method enables fabrication of flexible CsPbI2Br PSCs with PCE as high as 11.73%. Surprisingly, the bare devices without any encapsulation maintain 70% of their original PCEs after being stored in ambient air for 700 h. This work provides an approach for preparing other high performance CsPbX3‐based perovskite solar cells (PSCs) at low temperature, particularly for flexible ones.
Sequentially Fluorinated PTAA Polymers for Enhancing VOC of High‐Performance Perovskite Solar Cells
Authors: Kim Youngwoong , Jung Eui Hyuk , Kim Geunjin , Kim Donguk , Kim Bumjoon J. , Seo Jangwon 
Published: September 2018

AbstractThe energy level alignment of the perovskite and hole transporting materials (HTMs) is essential for increasing the open‐circuit voltage (Voc) and enhancing the performance of perovskite solar cells (PSCs). In this work, new sequentially fluorinated poly(triarylamine) polymers (PTAA, 1F‐PTAA, and 2F‐PTAA) with tuned highest occupied molecular orbital (HOMO) energy levels are developed and applied as HTMs into PSCs. The fluorination approach successfully leads to stepwise downshifting of the HOMO levels of PTAA derivatives, resulting in an obvious increase in the Voc and power conversion efficiency (PCE) of the PSCs. In particular, introduction of 1F‐PTAA polymer in (FAPbI3)0.85(MAPbBr3)0.15‐based mesoporous n‐i‐p structure PSCs achieves the high stabilized PCE of 21.2% at the maximum power point with improved Voc of 1.14 V. To elucidate the importance of the optimized degree of fluorination of PTAA polymers on the photovoltaic performances, the optical, electrical, photophysical properties, and doping behaviors of the fluorinated PTAA derivatives are investigated.
Solution‐Processable, Solid State Donor–Acceptor Materials for Singlet Fission
Authors: Masoomi‐Godarzi Saghar , Liu Maning , Tachibana Yasuhiro , Goerigk Lars , Ghiggino Kenneth P. , Smith Trevor A. , Jones David J. 
Published: September 2018

AbstractThe exploitation of singlet fission (SF) materials in optoelectronic devices is restricted by the limited number of SF materials available and developing new organic materials that undergo singlet fission is a significant challenge. Using a new strategy based on conjugating strong donor and acceptor building blocks, the small molecule (BDT(DPP)2) and polymer (p‐BDT‐DPP) systems are designed and synthesized knowing that bisthiophene‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (DPP) has a low lying triplet energy level, which is further confirmed by time‐dependent density functional theory (TD‐DFT) calculations. TD‐DFT and natural transition orbital (NTO) analysis are conducted to gain insight into the photophysical properties and features of excited states in BDT(DPP)2, respectively. Femtosecond and nanosecond transient absorption spectroscopies are used to investigate the excited state kinetics in the synthesized compounds. Fast formation of triplet pairs in thin film of p‐BDT‐DPP and BDT(DPP)2 and the equilibrium formation of correlated triplet pairs and S1 from triplet–triplet annihilation in solution of BDT(DPP)2 are further evidence of SF in these compounds. The short triplet lifetime, as a result of fast biexcitonic recombination, provides additional support for triplet pair formation through singlet fission.
Charge State Manipulation of Cobalt Selenide Catalyst for Overall Seawater Electrolysis
Authors: Zhao Yongqiang , Jin Bo , Zheng Yao , Jin Huanyu , Jiao Yan , Qiao Shi‐Zhang 
Published: September 2018

AbstractFacile and controllable fabrication of highly active and stable bifunctional electrocatalysts for water electrolysis is important for hydrogen production. 3D cobalt selenide electrodes with CoSe and Co9Se8 phases are synthesized by one‐step calcination of Co foil with Se powder in a vacuum‐sealed ampoule. The charge state of Co species and the electrocatalytic performance of the prepared catalysts are manipulated by controlling Co to Se mass ratio. Mechanistic studies show that a high Co charge state favors oxygen evolution reaction performance and a low Co charge state promotes hydrogen evolution reaction activity for as‐prepared cobalt selenide electrocatalysts. The resultant materials can act as free‐standing bifunctional electrocatalytic electrodes for oxygen evolution reaction and hydrogen evolution reaction in alkaline media. Moreover, a 10.3 mA cm−2 current density at 1.8 V is achieved for overall seawater electrolysis through exploiting as‐synthesized cobalt selenide electrodes as both anode and cathode, which is three times higher than that for novel‐metal‐based seawater electrolyzer at the same voltage (2.9 mA cm−2). Experimental results reveal that the cobalt selenide electrodes show significantly higher electrocatalytic performance than that of integrated Ni/Ir–C and Ni/Pt–C electrodes. Consequently, these novel bifunctional electrodes are promising candidates for realistic large‐scale water electrolysis.
Edge‐Nitrogen‐Rich Carbon Dots Pillared Graphene Blocks with Ultrahigh Volumetric/Gravimetric Capacities and Ultralong Life for Sodium‐Ion Storage
Authors: Liu Zheng , Zhang Longhai , Sheng Lizhi , Zhou Qihang , Wei Tong , Feng Jing , Fan Zhuangjun 
Published: September 2018

AbstractThe development of stable electrode materials for sodium‐ion batteries (NIBs) with excellent rate capacity, high volumetric/gravimetric capacity, and ultralong‐term cycling stability still remains a challenge. Herein, a novel strategy for the synthesis of edge‐nitrogen‐rich carbon dots pillared graphene blocks (N‐CDGB) through self‐polymerization of aniline into graphene oxide blocks, and subsequent carbonization is developed. Due to high bulk density (1.5 g cm−3) and integrated lamellar structure with large edge‐interlayer spacing (4.2 Å) pillared by nitrogen‐doped carbon dots (95% edge‐nitrogen content), the dense N‐CDGB shows robust structural stability, fast ion/electron transfer pathways, and more active sites for sodium storage. As a result, the N‐CDGB electrode exhibits ultrahigh reversible volumetric and gravimetric capacities (780 mAh cm−3/520 mAh g−1 at 0.02 A g−1) far exceeding those of graphene (108 mAh cm−3/290 mAh g−1) and hard carbon (297 mAh cm−3/311 mAh g−1), excellent rate capability (118 mAh g−1/177 mAh cm−3 at 10 A g−1), and superior cycling stability up to 10 000 cycles with almost no capacity loss at 10 A g−1. This work signifies the superiority of densely pillared structure in the future development of NIBs with high volumetric/gravimetric capacity and ultralong‐term cycling stability.
Intermolecular Exchange Boosts Efficiency of Air‐Stable, Carbon‐Based All‐Inorganic Planar CsPbIBr2 Perovskite Solar Cells to Over 9%
Authors: Zhu Weidong , Zhang Qianni , Chen Dazheng , Zhang Zeyang , Lin Zhenhua , Chang Jingjing , Zhang Jincheng , Zhang Chunfu , Hao Yue 
Published: September 2018

AbstractAmong all inorganic halide perovskite photovoltaic materials, CsPbIBr2 exhibits the most balanced features in terms of bandgap and stability. However, the poor quality of solution‐processed CsPbIBr2 films impedes further optimization of cells performance. Herein, a facile intermolecular exchange strategy for CsPbIBr2 film is demonstrated, wherein an optimized methanol solution of CsI is spin‐coated on CsPbIBr2 precursor film in conventional one‐step solution route. It surprisingly produces full‐coverage and pure‐phase CsPbIBr2 films featured with average grain size of ≈0.65 µm, few grain boundaries, high crystallinity, preferable (100) orientation, stoichiometric composition along with favorable electronic structures for effective dissociation and transfer of carriers. Hence, the cost‐effective, carbon‐based all‐inorganic planar perovskite solar cells based on them, yield an optimized efficiency of 9.16% with a stabilized value of 8.46% in ambient air conditions that highlight a particularly superb open‐circuit voltage of 1.245 V, all of which represent the highest values reported in pure CsPbIBr2 based cells so far. Moreover, the optimized cell without encapsulation shows excellent long‐term stability because it can retain 90% over 60 days and 97% over 7 days of its initial efficiency, when is stored controllably in ≈45% relative humidity at 25 or 85 °C at zero humidity, respectively.
Shifts in pollen release envelope differ between genera with non‐uniform climate change
Authors: Panchen Zoe A. , Johnston Mark O. 
Published: September 2018

Premise of THE StudyPlant phenological responses to climate change now constitute one of the best studied areas of the ecological impacts of climate change. Flowering time responses to climate change of wind‐pollinated species have, however, been less well studied. A novel source of flowering time data for wind‐pollinated species is allergen monitoring records.MethodsWe studied the male flowering time response to climatic variables of two wind‐pollinated genera, Betula (Betulaceae) and Populus (Salicaceae), using pollen count records over a 17‐year period.Key ResultsWe found that changes in the pollen release envelope differed between the two genera. Over the study period, the only month with a significant rise in temperature was April, resulting in the duration of pollen release of the April‐flowering Populus to shorten and the start and peak of the May‐flowering Betula to advance. The quantity of pollen released by Betula has increased and was related to increases in the previous year's August precipitation, while the quantity of pollen released by Populus has not changed and was related to the previous year's summer and autumn temperatures.ConclusionsOur findings suggest that taxa differ in the reproductive consequences of environmental change. Differing shifts in phenology among species may be related to different rates of change in climatic variables in different months of the year. While our study only considers two genera, the results underscore the importance of understanding non‐uniform intra‐annual variation in climate when studying the ecological implications of climate change.
Busy Streets Theory: The Effects of Community‐engaged Greening on Violence
Authors: Heinze Justin E. , Krusky‐Morey Allison , Vagi Kevin J. , Reischl Thomas M. , Franzen Susan , Pruett Natalie K. , Cunningham Rebecca M. , Zimmerman Marc A. 
Published: September 2018

AbstractLack of maintenance on vacant neighborhood lots is associated with higher levels of depression, anxiety, and stress for nearby residents. Overgrown grasses and dense brush provide hiding spots for criminals and space to conduct illicit activities. This study builds upon previous research by investigating greening programs that engage community members to conduct routine maintenance on vacant lots within their neighborhoods. The Clean & Green program is a community‐based solution that facilitates resident‐driven routine maintenance of vacant lots in a midsized, Midwestern city. We use mixed effects regression to compare assault and violent crime counts on streets where vacant lot(s) are maintained by community members (N = 216) versus streets where vacant lots were left alone (N = 446) over a 5‐year timeframe (2009–2013). Street segments with vacant lots maintained through the Clean & Green program had nearly 40% fewer assaults and violent crimes than street segments with vacant, abandoned lots, which held across 4 years with a large sample and efforts to test counterfactual explanations. Community‐engaged greening programs may not only provide a solution to vacant lot maintenance, but also work as a crime prevention or reduction strategy. Engaging the community to maintain vacant lots in their neighborhood reduces costs and may increase the sustainability of the program.
Why Name Generators with a Fixed Number of Alters may be a Pragmatic Option for Personal Network Analysis
Authors: Maya Jariego Isidro 
Published: September 2018

AbstractSocial network analysis has grown exponentially in recent years, giving rise to methodological innovations in different scientific disciplines. In psychology, social network analysis has been incorporated into studies of individual personality differences and has generated novel areas, such as network psychometrics and network interventions. In community psychology, a recent review examined the use of network analysis inAmerican Journal of Community Psychologypublications (Neal & Neal,American Journal of Community Psychology, 2017, 60, 279). Based on their study, the authors advise researchers to avoid using the fixed‐choice name generator when possible, as one of the five methodological recommendations proposed. In this essay, I explain how the recent increase of name generators with a fixed number of alters when studying personal networks is originally linked to an interest in describing structural properties. Second, I analyze the pragmatic contributions of this method: establishing a limit of alters a priori can entail advantages in terms of standardization and comparability of personal networks. Finally, to contextualize the methodological debate, I argue that personal networks represent the diversity of contexts in which the individual participates and are naturally integrated into community surveys.