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The combination of solution IR spectroscopy measurement, fast cooling crystallization experiments, conformational search, and molecular computation was investigated in detail in this study to explo...

Anion redox chemistry is an essential component of many high energy density electrode materials, while accompanying with voltage hysteresis and fade, which currently hinders its widespread use. Here we demonstrate cation-synergy stabilizing anion redox of Chevrel phase Mo6S8 in aluminum ion battery. EELS and XAS reveal that S is fully reduced, and Mo6 cluster is firstly oxidized and then reduced with Al3+ ions insertion, which originates from the contraction and elongation of Mo-Mo bond in Mo6 cluster verified by atomic-resolved imaging. DFT calculations uncover that the energy level of [Mo-Mo]* antibonding orbitals is lifted and fell by Mo-Mo bond evolution, resulting in the synergetic cationic and anionic redox, which contributes to the stable structure upon cycling. Our work figures out the electrochemical redox mechanism of Mo6S8 in aluminum ion batteries and provides implications generally for the design of materials employing anion redox chemistry.

In this work, a new quantitative analysis method of multi-components analysis via a single marker strategy coupled with high-performance liquid chromatography (HPLC) analysis, was proposed to analyze nine nucleosides (cytidine, uridine, 2'-deoxyuridine, inosine, guanosine, 2'-deoxyguanosine, thymidine, adenosine, and 2'-deoxyadenosine) as quality control markers in Rhizoma Paridis. Guanosine was set as the internal reference substance, whose content in Rhizoma Paridis was determined using conventional external standard method. Then, relative correction factors between guanosine and the other eight nucleosides were measured respectively. The amounts of the other eight components were calculated according to the relative correction factors by the quantitative analysis of multi-components via a single marker method. Finally, the result of vector angle cosine analysis showed that there was no significant difference of the contents between the external standard method and the quantitative analysis of multi-components via a single marker method, indicating that the quantitative analysis of multi-components via a single marker method can be applied for the quality control of Rhizoma Paridis. As far as we know, this is also the first report to analyze nucleosides by the quantitative analysis of multi-components via a single marker method, providing an efficient and promising quality assessment method for other traditional Chinese medicine containing nucleosides.

C-reactive protein (CRP) is an important biomarker for acute inflammation and infection and widely used clinically for the assessment of various diseases and the monitoring of patients’ conditions. At present, the clinical test methods for CRP mainly include immunoturbidimetry, enzyme-linked immunosorbent assays, and lateral flow assays. In recent years, developments in analysis theory and improvements in materials science have resulted in the continual emergence of analytical methods and techniques, such as biosensor technology and microfluidics. In this paper, we summarized the development and application of CRP analytical methods and focus on the developments during the last five years. In addition, we predicted the research directions for novel CRP assays and provide new ideas for the development of CRP analytical methods with high sensitivity and specificity that can meet clinical needs.

Cenospheres are the main component of industrial waste of fly ash and taking full advantage of them has good economic and environmental values. In this paper, cenospheres sensitized emulsion explos...

Natural biomaterials are potential candidates for the next generation of green electronics due to their biocompatibility and biodegradability. On the other hand, the application of biocomposite systems in information storage, photoelectrochemical sensing, and biomedicine has further promoted the progress of environmentally benign bioelectronics. Here, we mainly review recent progress in the development of biocomposites in data storage, focusing on the application of biocomposites in resistive random-access memory (RRAM) and field effect transistors (FET) with their device structure, working mechanism, flexibility, transient characteristics. Specifically, we discuss the application of biocomposite-based non-volatile memories for simulating biological synapse. Finally, the application prospect and development potential of biocomposites are presented., Graphical abstract

Because of the structural complexity and inhomogeneity, the effect of the coordination environment on the catalytic properties is underexplored in heterogeneous catalytic systems. To address this c...

The grand challenge in the development of atomically dispersed metallic catalysts is their low metal-atom loading density, uncontrollable localization and ambiguous interactions with supports, posing difficulty in maximizing their catalytic performance. Here, we achieve an interface catalyst consisting of atomic cobalt array covalently bound to distorted 1T MoS2 nanosheets (SA Co-D 1T MoS2). The phase of MoS2 transforming from 2H to D-1T, induced by strain from lattice mismatch and formation of Co-S covalent bond between Co and MoS2 during the assembly, is found to be essential to form the highly active single-atom array catalyst. SA Co-D 1T MoS2 achieves Pt-like activity toward HER and high long-term stability. Active-site blocking experiment together with density functional theory (DFT) calculations reveal that the superior catalytic behaviour is associated with an ensemble effect via the synergy of Co adatom and S of the D-1T MoS2 support by tuning hydrogen binding mode at the interface., While single-atom catalysis offers an efficient materials usage, the ambiguous interactions with supports poses a difficulty in understanding catalytic performances. Here, authors show an ensemble effect via synergy of Co adatoms and the S of MoS2 supports to boost hydrogen evolution activities.

To better facilitate government management and planning based on public opinion, it is essential to propose a method for extracting public opinion perception features in consideration of an integrated framework, which aims at industry monitoring and decision-making. Based on fundamental characteristics of ordinary traffic incidents, this paper develops a perception features system of public opinion consisting of four modules, where the construction methods have been elaborated. First, mining thematic features is realized via the similarity calculation of text vector. Second, based on summarized Chinese expression patterns, time extraction rules, and a five-layer tree-like spatial feature thesaurus are established to extract spatiotemporal features. Third, the modeling of the emotional features is achieved by a dictionary-based analysis model. Fourth, the evolutional features are extracted by the Exponential Generalized Autoregressive Conditional Heteroscedasticity (EGARCH). In view of the attributes of each module, an integrated framework is built to determine the collaboration relationship of feature indicators. Finally, a case study of Shenzhen public transport has been performed to illustrate the application of proposed methods. Results show that the strong odor in electric buses and a rumor that electric buses have great radiation are two main causes of the decrease in passenger satisfaction in the first quarter of 2017. In contrast, adding new bus lines, increasing service frequency, and guaranteeing the bus-lane right will improve passenger satisfaction, which is basically consistent with the official report. It should be noticed that the developed framework has been validated in the case study of passenger satisfaction analysis, while it can be extensively replicated in other fields. Furthermore, it is important for stakeholders to grasp the public perception of transportation services, in order to enhance public participation in transportation management and decision-making.

Two-dimensional (2D) metallic transition metal dichalcogenides (MTMDCs) have attracted tremendous interest due to their intriguing physical properties and broad application potential. However, batch production of high-quality 2D MTMDCs based on existing synthesis on 2D surfaces remains a huge challenge. Herein, a universal synthetic route for the scalable synthesis of high-quality 2D MTMDC (e.g., TaS2, V5S8, and NbS2) nanosheets using microcrystalline NaCl crystals as templates via a facile chemical vapor deposition method is reported. Obviously, this synthetic route is perfectly compatible with a facile water dissolution-filtration process for obtaining high-purity MTMDC nanosheet powders. Representatively, a thickness-uniform 1T-TaS2 nanosheet product can be achieved that shows unexceptionable dispersibility in ethanol, which allows its assembly onto arbitrary substrates/electrodes for high-performance energy-related applications, herein serving as a high-performance electrocatalyst for the hydrogen evolution reaction. This work sheds light on the batch production, green transfer, and energy-related application of 2D MTMDC materials.

In this work, we report an element segregation phenomenon in two-dimensional (2D) core-shell nanoplates, subsequently resulting in the formation of yolk-cage nanostructures after selective electrochemical etching. By using PtCu nanoplates as templates, PtCu@Pd core-shell nanoplates are formed. Interestingly, during the growth of Ru on the PtCu@Pd core-shell nanoplates, due to the selective element diffusion, PtCuPd@PdCu@Ru nanoplates are obtained. After selectively etching of PdCu in PtCuPd@PdCu@Ru using electrochemical method, the PtCuPd@Ru yolk-cage nanostructures are obtained. As a proof-of-concept application, this unique nanostructure shows superior electrocatalytic activity and stability toward the methanol oxidation reaction as compared to the PtCu nanoplates and commercial Pt/C catalyst.

Controlled synthesis of transition metal dichalcogenide (TMD) monolayers with unusual crystal phases has attracted increasing attention due to their promising applications in electrocatalysis. However, the facile and large-scale preparation of TMD monolayers with high-concentration unusual crystal phase still remains a challenge. Herein, we report the synthesis of MoX2 (X = Se or S) monolayers with high-concentration semimetallic 1T′ phase by using the 4H/face-centered cubic (fcc)-Au nanorod as template to form the 4H/fcc-Au@MoX2 nanocomposite. The concentrations of 1T′ phase in the prepared MoSe2 and MoS2 monolayers are up to 86% and 81%, respectively. As a proof-of-concept application, the obtained Au@MoS2 nanocomposite is used for the electrocatalytic hydrogen evolution reaction (HER) in acid medium, exhibiting excellent performance with a low overpotential of 178 mV at the current density of 10 mA/cm2, a small Tafel slope of 43.3 mV/dec, and excellent HER stability. This work paves a way for direct synthesis of TMD monolayers with high-concentration of unusual crystal phase for the electrocatalytic application.

As high capacity cathodes, O3-type Na-based oxides always suffer from a series of monoclinic transitions upon sodiation/desodiation, mainly caused by Na+/vacancy ordering and Jahn–Teller (J−T) dist...

The development of high energy electrode materials for lithium ion batteries is challenged by their inherent instabilities, which become more aggravated as the energy densities continue to climb, accordingly causing increasing concerns on battery safety and reliability. Here, taking the high voltage cathode of LiNi0.5Mn1.5O4 as an example, we demonstrate a protocol to stabilize this cathode through a systematic phase modulating on its particle surface. We are able to transfer the spinel surface into a 30 nm shell composed of two functional phases including a rock-salt one and a layered one. The former is electrochemically inert for surface stabilization while the latter is designated to provide necessary electrochemical activity. The precise synthesis control enables us to tune the ratio of these two phases, and achieve an optimized balance between improved stability against structural degradation without sacrificing its capacity. This study highlights the critical importance of well-tailored surface phase property for the cathode stabilization of high energy lithium ion batteries.

The widely distributed unconformity (T7) in Pearl River Mouth Basin, formed at ~ 30 Ma, is one of the most important unconformities of northern South China Sea related to the evolution of basin dynamics. Based on seismic data and logs, this study documents the distribution of the unconformity in Pearl River Mouth Basin (PRMB) and discusses the mechanism of the breakup unconformity in the evolution of the basin. The study verifies that the T7 boundary is a breakup unconformity: (1) most fault tips end at T7 unconformity or the offset diminishes markedly across the unconformity, and (2) these faults control the stratal thickness, reflected by the wedge shape formation. The T7 unconformity can be divided into three zones according to different structures and contact relationships: (1) the angular unconformity zone, (2) the local unconformity and onlap zone, and (3) the conformity zone, these three correspond to strong erosion zone, weak erosion zone, and non-erosion zone respectively. The distribution pattern of the breakup unconformity in this study area is controlled by the tectonic and geomorphology in the different zones of a basin: The angular erosion zone in the north is controlled by fault activity, but in local unconformity and onlap zone the erosion is mainly caused by diapir or local uplift. The conformity zone is located at the depression center in an underwater environment. This pattern indicates that the mechanism of the breakup unconformity is related to the erosion on shoulder uplift structure at the basin margin in rift stage.

Two-dimensional (2D) metal–semiconductor transition-metal dichalcogenide (TMDC) vertical heterostructures play a crucial role in device engineering and contact tuning fields, while their direct integration still challenging. Herein, a robust epitaxial growth method is designed to construct multiple lattice-matched 2D metal–semiconductor TMDC vertical stacks (VSe2/MX2, M: Mo, W; X: S, Se) by a two-step chemical vapor deposition method. Intriguingly, the metallic VSe2 preferred to nucleate and extend from the energy-favorable edge site of the semiconducting MX2 underlayer to form VSe2/MX2 vertical heterostructures. This growth behavior was also confirmed by density functional theory calculations of the initial adsorption of VSe2 adatoms. In particular, the formation of Schottky-diode or Ohmic contact-type band alignments was detected for the stacks between VSe2 and p-type WSe2 or n-type MoSe2, respectively. This work hereby provides insights into the direct integration, band-alignment engineering, and poten...

The use of TiO2 as an anode in rechargeable sodium-ion batteries (NIBs) is hampered by intrinsic low electronic conductivity of TiO2 and inferior electrode kinetics. Here, a high-performance TiO2 electrode for NIBs is presented by designing a multichannel porous TiO2 nanofibers with well-dispersed Cu nanodots and Cu2+-doping derived oxygen vacancies (Cu-MPTO). The in-situ grown well-dispersed copper nanodots of about 3 nm on TiO2 surface could significantly enhance electronic conductivity of the TiO2 fibers. The one-dimensional multichannel porous structure could facilitate the electrolyte to soak in, leading to short transport path of Na+ through carbon toward the TiO2 nanoparticle. The Cu2+-doping induced oxygen vacancies could decrease the bandgap of TiO2, resulting in easy electron trapping. With this strategy, the Cu-MPTO electrodes render an outstanding rate performance for NIBs (120 mAh·g−1 at 20 C) and a superior cycling stability for ultralong cycle life (120 mAh·g−1 at 20 C and 96.5% retention over 2,000 cycles). Density functional theory (DFT) calculations also suggest that Cu2+ doping can enhance the conductivity and electron transfer of TiO2 and lower the sodiation energy barrier. This strategy is confirmed to be a general process and could be extended to improve the performance of other materials with low electronic conductivity applied in energy storage systems.

To explore the possible roles of metallothioneins (MTs) played in cadmium (Cd) accumulation of water spinach, three IaMT genes, IaMT1, IaMT2 and IaMT3 in a high-shoot-Cd (T308) and a low-shoot-Cd accumulation cultivar (QLQ) were cloned, characterized, and quantitated. Gene expression analysis suggested that the expression of the IaMTs was differentially regulated by Cd stress in different cultivars, and T308 showed higher MTs expression overall. Furthermore, only shoot IaMT3 expression was cultivar dependent among the three IaMTs. Antioxidant analysis showed that the high production of IaMTs in T308 should be associated with its high oxidation resistance. The role of IaMTs in protecting against Cd toxicity was demonstrated in vitro via recombinant E. coli strains. The results showed that IaMT1 correlated with neither Cd tolerance nor Cd accumulation of E. coli, while IaMT2 conferred Cd tolerance in E. coli, IaMT2 and IaMT3 increased Cd accumulation in E. coli. These findings help to clarify the roles of IaMTs in Cd accumulation, and increase our understanding of the cultivar-dependent Cd accumulation in water spinach.

Cochlear implant (CI) users have been shown to be more susceptible to the variations in speech production encountered in everyday listening, in which speaking rate, amplitude, duration, and voice pitch information may be quite variable, depending on the production context. Such variations may be further enlarged by the background noise, especially dynamic noise. The limited spectral resolution provided by the CI limits perception of voice pitch, which is an important cue for speech prosody and for tonal languages such as Mandarin Chinese. In this study, the effect of varying speaking rates and styles and background noise on speech understanding was investigated in Mandarin-speaking CI and normal-hearing (NH) listeners. Thirteen (5 male and 8 female, age 19–62 years) Mandarin-speaking, post-lingually deafened adult CI patients using their clinical processors and 9 (5 male and 4 female, age 23–59 years) NH subjects listening to unprocessed speech. Five different types of speech variations, including 3 speaking rates (slow, normal, fast) and 2 speaking styles (emotional, shouted) were presented with two masking noises (speech-shaped steady state noise-SSN or six-talker babble). Speech reception threshold, defined as the signal-to-noise ratio producing 50% correct word-in-sentence recognition using Mandarin Speech Perception materials was measured. NH listeners performed significantly better (16.7 dB) than CI patients across all conditions regardless of speech variations and noise types. CI patients’ performance deficit was highly dependent on speech rate and noise type; the deficit was smallest (11.7 dB) when slowly-spoken speech was presented in SSN and largest (20.6 dB) when shouted speech was presented in six-talker speech babble. NH listeners performed significantly better in speech babble than in SSN for all speech variations, while CI patients performed similarly in both noise types. The use of clear and slowly-spoken speech in the laboratory setting may largely underestimate CI patients’ performance deficits in real-world listening conditions, where acoustic variations introduced by speech variations and dynamic noise may present additional challenges.

Rh nanostructures composed of nanosheets embedded with nanodomains adopt vacated Barlow packing with ordered vacancies., Metallic nanostructures are commonly densely packed into a few packing variants with slightly different atomic packing factors. The structural aspects and physicochemical properties related with the vacancies in such nanostructures are rarely explored because of lack of an effective way to control the introduction of vacancy sites. Highly voided metallic nanostructures with ordered vacancies are however energetically high lying and very difficult to synthesize. Here, we report a chemical method for synthesis of hierarchical Rh nanostructures (Rh NSs) composed of ultrathin nanosheets, composed of hexagonal close-packed structure embedded with nanodomains that adopt a vacated Barlow packing with ordered vacancies. The obtained Rh NSs exhibit remarkably enhanced electrocatalytic activity and stability toward the hydrogen evolution reaction (HER) in alkaline media. Theoretical calculations reveal that the exceptional electrocatalytic performance of Rh NSs originates from their unique vacancy structures, which facilitate the adsorption and dissociation of H2O in the HER.

To meet the growing demand for global electrical energy storage, high‐energy‐density electrode materials are required for Li‐ion batteries. To overcome the limit of the theoretical energy density in conventional electrode materials based solely on the transition metal redox reaction, the oxygen redox reaction in electrode materials has become an essential component because it can further increase the energy density by providing additional available electrons. However, the increase in the contribution of the oxygen redox reaction in a material is still limited due to the lack of understanding its controlled parameters. Here, it is first proposed that Li‐transition metals (TMs) inter‐diffusion between the phases in Li‐rich materials can be a key parameter for controlling the oxygen redox reaction in Li‐rich materials. The resulting Li‐rich materials can achieve fully exploited oxygen redox reaction and thereby can deliver the highest reversible capacity leading to the highest energy density, ≈1100 Wh kg−1 among Co‐free Li‐rich materials. The strategy of controlling Li/transition metals (TMs) inter‐diffusion between the phases in Li‐rich materials will provide feasible way for further achieving high‐energy‐density electrode materials via enhancing the oxygen redox reaction for high‐performance Li‐ion batteries., A new key parameter for fully exploiting the oxygen redox reaction by Li/transition metals (TMs) inter‐diffusion between the two phases in Co‐free Li‐rich materials is first proposed. The resulting Li‐rich materials can achieve fully exploited oxygen redox reaction and thereby can deliver the highest reversible capacity leading to the highest energy density, ≈1100 Wh kg−1 among Co‐free Li‐rich materials.

To keep pace with the upcoming big-data era, the development of a device-level neuromorphic system with highly efficient computing paradigms is underway with numerous attempts. Synaptic transistors based on an all-solution processing method have received growing interest as building blocks for neuromorphic computing based on spikes. Here, we propose and experimentally demonstrated the dual operation mode in poly{2,2-(2,5-bis(2-octyldodecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)dithieno[3,2-b]thiophene-5,5-diyl-alt-thiophen-2,5-diyl}(PDPPBTT)/ZnO junction-based synaptic transistor from ambipolar charge-trapping mechanism to analog the spiking interfere with synaptic plasticity. The heterojunction formed by PDPPBTT and ZnO layers serves as the basis for hole-enhancement and electron-enhancement modes of the synaptic transistor. Distinctive synaptic responses of paired-pulse facilitation (PPF) and paired-pulse depression (PPD) were configured to achieve the training/recognition function for digit image patterns at the device-to-system level. The experimental results indicate the potential application of the ambipolar transistor in future neuromorphic intelligent systems.

Size effect plays a crucial role in catalytic hydrogenation. The highly dispersed ultrasmall clusters with a limited number of metal atoms are one candidate of the next generation catalysts that bridge the single-atom metal catalysts and metal nanoparticles. However, for the unfavorable electronic property and their interaction with the substrates, they usually exhibit sluggish activity. Taking advantage of the small size, their catalytic property would be mediated by surface binding species. The combination of metal cluster coordination chemistry brings new opportunity. CO poisoning is notorious for Pt group metal catalysts as the strong adsorption of CO would block the active centers. In this work, we will demonstrate that CO could serve as a promoter for the catalytic hydrogenation when ultrasmall Pd clusters are employed. By means of DFT calculations, we show that P d n n = 2 ‐ 147 clusters display sluggish activity for hydrogenation due to the too strong binding of hydrogen atom and reaction intermediates thereon, whereas introducing CO would reduce the binding energies of vicinal sites, thus enhancing the hydrogenation reaction. Experimentally, supported Pd 2 CO catalysts are fabricated by depositing preestablished [Pd 2 ( μ -CO) 2 Cl 4 ] 2- clusters on oxides and demonstrated as an outstanding catalyst for the hydrogenation of styrene. The promoting effect of CO is further verified experimentally by removing and reintroducing a proper amount of CO on the Pd cluster catalysts.

Metal–organic frameworks (MOF) have recently emerged as versatile precursors to fabricate functional MOF derivatives for oxygen evolution reactions (OER). Herein, we developed a controlled partial pyrolysis strategy to construct robust NiCo/Fe3O4 heteroparticles within MOF-74 for efficient OER using trimetallic NiCoFe-MOF-74 as precursor. The partial pyrolysis method preserves the framework structure of MOF for effective substrates diffusion while producing highly active nanoparticles. The as-prepared NiCo/Fe3O4/MOF-74 delivered remarkably stable OER current with an overpotential as low as 238 mV at 10.0 mA cm–2 and an Tafel slop of 29 mV/dec, outperforming those of pristine NiCoFe-MOF-74, totally decomposed MOF derivatives, and most reported non-noble metal based electrocatalysts. The key for the formation of NiCo/Fe3O4/MOF-74 nanostructures is that the metals can be decomposed from NiCoFe-MOF-74 in the order of Ni, Co, and Fe under controlled heat treatment. Density functional theory calculations reveal...

Theoretically, Cu2O delivers a poor Li storage capacity ∼373.9 mA h g–1 based on a so-called conversion reaction (Cu2O + 2Li → 2Cu + Li2O). Herein, we broke through the bottleneck and acquired an impressive lithium storage capability (1122 mA h g–1) tripled more than the theoretical one by an in situ surface/interface engineering process for the first time. The surface/interface modification enabled us to fabricate ultrasmall nanocrystals of Cu2O with Cu vacancies (VCu) of high concentration, somewhat like monovalent anion doping. Except for the conversion reaction-type capacity, VCu enhancing intercalation pesudocapacitance in Cu2O and its reduction product-Cu also contributed a lot to the Li-storage capability. First-principles calculation substantiated that intercalation energy of Li was severely lowered for both Cu vacancy-rich Cu2O and Cu comparing with their stoichiometric counterparts. Another important factor for the enhancement was the surface/interface organic species themselves which could reve...

A novel copper-catalyzed cascade cyclization reaction between enamines and electron-deficient terminal alkynes has been developed. The reaction provides a new and efficient strategy for the construction of polysubstituted pyrido[1,2-a]indoles by the formation of two rings, three C–C bonds, and one C–N bond in a single step from readily available acyclic starting materials.

Agricultural innovation is imperative in order to meet global challenges to sustainably feed large urban populations. This paper contributes a modelling framework for urban agriculture, and an implementation in a scenario based on the fast growing mega city of Shenzhen located near Hong Kong in southern China. We also review related work and provide a gap analysis between requirements for modelling modern urban agricultural systems versus related work that looks at agricultural supply chains, production, and land use. The proposed framework will facilitate developing a novel decision support system to coordinate decentralized urban agricultural production units in order to realize, at scale, numerous benefits from co-locating production and consumption in the urban environment.

In the controlled synthesis of noble metal nanostructures using wet-chemical methods, normally, metal salts/complexes are used as precursors, and surfactants/ ligands are used to tune/stabilize the morphology of nanostructures. Here, we develop a facile electrochemical method to directly convert Pt wires to Pt concave icosahedra and nanocubes on carbon paper through the linear sweep voltammetry in a classic three-electrode electrochemical cell. The Pt wire, carbon paper and Ag/AgCl (3 mol L−1 KCl) are used as the counter, working and reference electrodes, respectively. Impressively, the formed Pt nanostructures exhibit better electrocatalytic activity towards the hydrogen evolution compared to the commercial Pt/C catalyst. This work provides a simple and effective way for direct conversion of Pt wires into well-defined Pt nanocrystals with clean surface. We believe it can also be used for preparation of other metal nanocrystals, such as Au and Pd, from their bulk materials, which could exhibit various promising applications. Ministry of Education (MOE) Nanyang Technological University This work was supported by the Ministry of Education under AcRF Tier 2 (ARC 19/15, No. MOE2014-T2-2-093; MOE2015-T2-2-057; MOE2016-T2-2-103; MOE2017-T2-1-162) and AcRF Tier 1 (2016-T1-001-147; 2016-T1-002-051; 2017-T1-001-150; 2017-T1-002-119), and Nanyang Technological University under Start- Up Grant (M4081296.070.500000) in Singapore. We would like to acknowledge the Facility for Analysis, Characterization, Testing and Simulation, Nanyang Technological University, Singapore, for use of their electron microscopy (and/or X-ray) facilities.

Single noble metal atoms and ultrafine metal clusters catalysts tend to sinter into aggregated particles at elevated temperatures, driven by the decrease of metal surface free energy. Herein, we report an unexpected phenomenon that noble metal nanoparticles (Pd, Pt, Au-NPs) can be transformed to thermally stable single atoms (Pd, Pt, Au-SAs) above 900 °C in an inert atmosphere. The atomic dispersion of metal single atoms was confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption fine structures. The dynamic process was recorded by in situ environmental transmission electron microscopy, which showed competing sintering and atomization processes during NP-to-SA conversion. Further, density functional theory calculations revealed that high-temperature NP-to-SA conversion was driven by the formation of the more thermodynamically stable Pd-N4 structure when mobile Pd atoms were captured on the defects of nitrogen-doped carbon. The thermally stable single atoms (Pd-SAs) exhibited even better activity and selectivity than nanoparticles (Pd-NPs) for semi-hydrogenation of acetylene.

Summary Lithium-ion batteries with high energy density are being intensively pursued to meet the ever-growing demand for energy storage. However, the increase in energy density often comes with an elevated instability of electrode materials, causing major concerns about the reliability and safety of lithium-ion batteries. Here, we report a strategy for stabilizing cathode materials by modulating the vacant lattice sites on the particle surface. Using the high-voltage Li[Ni0.5Mn1.5]O4 as an example, we demonstrate that introduction of a 10-nm epitaxial surface layer with Al3+ in the empty 16c octahedral sites of the spinel Li[Ni0.5Mn1.5]O4 suppresses structural degradation during cycling by increasing the surface stability without interfering with the Li+ diffusion around the Al3+ sites. Control of the Al3+ concentration in the surface region was shown to be a facile process. The process was shown to stabilize long-term cycling of Li[Ni0.5Mn1.5]O4 to 5 V versus Li+/Li0.

Orthorhombic phase of niobium pentoxide (T-Nb2O5) has been considered as a potential anode material for sodium ion batteries (NIBs), because it can intercalate a large amount of sodium ion reversibly and durably without structural disruption. However, the inherent deficiency of low electrical conductivity results in a low reversible capacity and poor cycling stability. Here, we achieved the superior sodium storage performance of Nb2O5 by rational design self-supported 3D porous reticular Nb2O5@Carbon (Nb2O5@3D PRS) thin film with interpenetrating network. The film was prepared by a facial electrostatic spray deposition (ESD) technique. The Nb2O5@3D PRS displays outstanding electrochemical performance, especially long cycle life: it can still deliver a specific capacity of 130 mAh g-1 after 7500 times chare/discharge at high rate of 10 C. Furthermore, Na3V2(PO4)3//Nb2O5 full cells were assembled, the full cell displays a remarkable capacity retention of 105 mAh g-1 after 500 cycles at 10 C. The excellent sodium storage performance of the Nb2O5@3D PRS is ascribed to the synergistic effect of the unique porous structure, the nanosized Nb2O5 particles encapsulated in the carbonaceous matrix, which facilitates the electrochemical kinetics between the Nb2O5 and electrolyte. In addition, the key problems of Na ion insertion in Nb2O5, such as the low degree of reversibility are mitigated. Notably, this method is a general process and can be extended to prepare other electrode materials with 3D porous interpenetrating structure for energy storage application.

Disaster preparedness is critical for reducing potential impact. This paper contributes to current knowledge of disaster preparedness using representative national sample data from China, which faces high earthquake risks in many areas of the country. The adoption of earthquake preparedness activities by the general public, including five indicators of material preparedness and five indicators of awareness preparedness, were surveyed and 3245 respondents from all 31 provinces of Mainland China participated in the survey. Linear regression models and logit regression models were used to analyze the effects of potential influencing factors. Overall, the preparedness levels are not satisfied, with a material preparation score of 3.02 (1–5), and awareness preparation score of 2.79 (1–5), nationally. Meanwhile, residents from western China, which has higher earthquake risk, have higher degrees of preparedness. The concern for disaster risk reduction (DRR) and the concern for building safety and participation in public affairs are consistent positive predictors of both material and awareness preparedness. The demographic and socioeconomic variables' effects, such as gender, age, education, income, urban/rural division, and building size, vary according to different preparedness activities. Finally, the paper concludes with a discussion of the theoretical contribution and potential implementation.

The promoting effect of sulfur sources is an intriguing but poorly understood phenomenon. Herein, we studied the treatment of PdCu bimetallic nanoparticles (NPs) with different amounts of sulfur powder. Low-level sulfidation led to the generation of a Pd30Cu10S9 NP catalyst consisting of surface enriched Pd NPs, electron deficient Pd and Cu, as well as zero valence sulfur. The Pd30Cu10S9 NP catalyst showed pronouncedly enhanced activity and selectivity in the semihydrogenation of alkynes. Our study revealed for the first time a possible cause for the promoting effect of sulfur at the atomic level, suggesting a new strategy in catalyst design.

Controlled synthesis of structurally anisotropic rhenium diselenide (ReSe2) with macroscopically uniform and strictly monolayer thickness as well as tunable domain shape/size is of great interest for electronics-, optoelectronics-, and electrocatalysis-related applications. Herein, we describe the controlled synthesis of uniform monolayer ReSe2 flakes with variable morphology (sunflower- or truncated-triangle-shaped) on SiO2/Si substrates using different ambient-pressure chemical vapor deposition (CVD) setups. The prepared polycrystalline ReSe2 flakes were transferred intact onto Au foil electrodes and tested for activity in the hydrogen evolution reaction (HER). Interestingly, compared to the compact truncated-triangle-shaped ReSe2 flakes, their edge-abundant sunflower-shaped counterparts exhibited superior electrocatalytic HER activity, featuring a relatively low Tafel slope of ∼76 mV/dec and an exchange current density of 10.5 μA/cm2. Thus, our work demonstrates that CVD-grown ReSe2 is a promising two-dimensional anisotropic material for applications in the electrocatalytic HER.

The unification of tunable band edge (BE) emission and strong Mn2+ doping luminescence in all-inorganic cesium lead halide perovskite nanocrystals (NCs) CsPbX3 (X = Cl and Br) is of fundamental importance in fine tuning their optical properties. Herein, we demonstrate that benefiting from the differentiation of the cation/anion exchange rate, ZnBr2 and preformed CsPb1–xCl3:xMn2+ NCs can be used to obtain high Br− content Cs(Pb1–x–zZnz)(ClyBr1–y)3:xMn2+ perovskite NCs with strong Mn2+ emission, and the Mn2+ substitution ratio can reach about 22%. More specifically, the fast anion exchange could be realized by the soluble halide precursors, leading to anion exchange within a few seconds as observed from the strong BE emission evolution, whereas the cation exchange instead generally required at least a few hours; moreover, their exchange mechanism and dynamics process have been evaluated. The Mn2+ emission intensity could be further varied by controlling the replacement of Mn2+ by Zn2+ with prolonged ion exc...

Single atoms immobilized on metal-organic frameworks (MOFs) with unique nanostructures have drawn tremendous attention in the application of catalysis but remain a great challenge. Various single noble-metal atoms have now been successfully anchored on the well-defined anchoring sites of the zirconium porphyrin MOF hollow nanotubes, which are probed by aberration-corrected scanning transmission electron microscopy and synchrotron-radiation-based X-ray absorption fine-structure spectroscopy. Owing to the hollow structure and excellent photoelectrochemical performance, the HNTM-Ir/Pt exhibits outstanding catalytic activity in the visible-light photocatalytic H2 evolution via water splitting. The single atom immobilized on MOFs with hollow structures are expected to pave the way to expand the potential applications of MOFs.

Breeding for pollution-safe cultivars (PSCs) can reduce pollutant accumulation in crops. However, the PSC breeding would face the risk of nutritional quality reduction, which is usually ignored in conventional breeding programs targeting to increase crop yield or nutritional quality. Thus, the doubt whether the risk would exist has to be clarified for supporting the PSC breeding. In the present study, a newly bred Cd/Pb-PSC of water spinach (Ipomoea aquatic Forsk.) and its parents (QLQ with low-Cd/Pb accumulation ability and T308 with high yield) of water spinach were employed to clarify the above-mentioned issue. Yields, and concentrations of Cd, Pb, nitrite, and organic and inorganic nutrients in shoots of the three experimental lines were determined. There were no significant differences in Cd/Pb concentration between the new PSC and QLQ, in nitrite content between the new PSC and its two parents and in yield between the new PSC and T308. It is decisively significant that shoot concentrations of organic and inorganic nutrients in the Cd/Pb-PSC were as high as those in one of its parents. It is affirmed that the breeding operations (crossing and consequently continuous selfing) for lowering Cd/Pb accumulation capacity of water spinach would not lower the nutritional values of the obtained Cd/Pb-PSCs from the breeding, which should be a pillar that supports the feasibility to minimize Cd/Pb pollution in vegetables using PSC-breeding method.

Monitoring the dynamic pH changes in vivo remains very essential to comprehend the function of pH in various physiological processes. In this study, we report a high-performance electrochemical pH microneedle based on an acupuncture needle (AN) for real-time monitoring of pH changes in a rat brain. The pH microneedle was prepared by a layer-to-layer assembly of molybdenum disulfide (MoS2) nanosheets and polyaniline (PAN), with an attempt to achieve a highly sensitive detection of hydrogen ions (H+). The as-prepared PAN/MoS2/AN exhibited a high Nernstian response of -51.2 mV per pH over a wide pH range from 3.0 to 9.0, and excellent selectivity toward pH against other potential interfering species in the brain. Moreover, the corresponding open circuit potential rapidly increased and decreased when Na2CO3 or NaH2PO4 was injected into the rat brain, respectively, demonstrating that the PAN/MoS2/AN has an excellent response toward pH changes in vivo. This work provides a new potentiometric method for real-time monitoring of dynamic pH changes in vivo with high reliability and stability.

Selenium cathodes have attracted much more attention due to their much higher electronic conductivity and comparable volumetric capacity when compared with sulfur cathodes. However, selenium cathodes still suffer from low utilization of active materials, high volume changes and the shuttle effect of polyselenides, resulting in rapid capacity fading. Herein, we prepared selenium–carbon composites as cathodes for sodium–selenium batteries to improve the utilization of selenium by embedding selenium in ZIF-8 derived N-doped microporous carbon polyhedrons (denoted as Se@N-MCPs). The N-MCPs could effectively accommodate the volume change of Se@N-MCPs, and alleviate the shuttle effect of polyselenides. The Se@N-MCP cathodes deliver an excellent discharge capacity of 612 mA h g−1 after 100 cycles at a current density of 0.1 A g−1 and a superior rate capability of 496 mA h g−1 at 5 A g−1 for Na–Se batteries. In addition, they also show a superior cycling life of ∼460 mA h g−1 at the current density of 1 A g−1 after 500 cycles with only 0.049% capacity decline per cycle.

The size and morphology of irregular particles are essential parameters for a variety of industrial processes. The backward interferometric speckle imaging technique can be applied to measure the relevant parameters of opaque irregular particles. To verify the accuracy of the backward interferometric speckle imaging technique, an elaborately designed experimental system was used to combine a backward interferometric speckle imaging system with a digital inline holography (DIH) system to characterise the same pulverised coal particles for quantitative comparison. The results of the backward interferometric speckle imaging were in good agreement with those of DIH in terms of particle size and morphology. In the backward interferometric speckle imaging system, the laser illumination and recording system are configured on the same side, and therefore only one window is required during measurement. This facilitates its instrument integration and provides significant potential for industrial applications involving powder processing.

The self-healing performance with the improved corrosion resistance of novel CeO2-sealed micro-arc oxide (MAO) film on Al alloy was studied in this work for the first time. There are three steps involved, including: (1) Preparing porous film by performing MAO treatment on Al alloy with the average thickness of ~15 μm; (2) loading corrosion inhibitor by soaking MAO sample in Ce(NO3)3 solution to fulfill micropores-sealing process; (3) evaluating the self-healing ability of the sealed MAO film in acidic, alkaline and neutral solutions by scratch tests. The experimental results indicated that the corrosion inhibitor was characterized to be CeO2 which can locally fill the micropores to seal the MAO film. The optimized CeO2-sealed MAO film owned the lower porosity and the improved the corrosion resistance, which can be testified from the corrosion current density (Icorr) decreased by 2 orders of magnitude compared with the MAO film. Furthermore, the micropores in the MAO film acted as microcontainers to hold corrosion inhibitor to make CeO2-sealed MAO film showed self-healing ability. In the acidic environment (pH = 2 (8 mL/L H2SO4 + 20 mL/L H2O2)), the novel CeO2-sealed film exhibited positive self-healing effect morphologically with improved corrosion test result, and the underlying self-healing mechanism was discussed in detail.

Distorted surface regions (5–6 nm) with an unusual layered-like structure on LiMn2O4 cathode material were directly observed after it was cycled (3–4.9 V), indicating a possible spinel-to-layered structural transformation. Formation of these distorted regions severely degrades LiMn2O4 cathode capacity. As we attempt to get a better understanding of the exact crystal structure of the distorted regions, the structural transformation pathways and the origins of the distortion are made difficult by the regions’ nanoscopic size. Inspired by the reduction of Mn4+ to Mn3+ in surface electronic structures that might be associated with oxygen loss during cycling, we further investigated the atomic-level surface structure of LiMn2O4 by heat-treatments between 600 and 900 °C in various atmospheres, finding similar surface spinel-to-layered structural transformation only for LiMn2O4 heat-treated in argon atmosphere for a few minutes (or more). Controllable and measurable oxygen loss during heat-treatments result in M...

Two-dimensional metallic transition metal dichalcogenides are emerging as prototypes for uncovering fundamental physical phenomena, such as superconductivity and charge-density waves, as well as for engineering-related applications. However, the batch production of such envisioned transition metal dichalcogenides remains challenging, which has hindered the aforementioned explorations. Herein, we fabricate thickness-tunable tantalum disulfide flakes and centimetre-sized ultrathin films on an electrode material of gold foil via a facile chemical vapour deposition route. Through temperature-dependent Raman characterization, we observe the transition from nearly commensurate to commensurate charge-density wave phases with our ultrathin tantalum disulfide flakes. We have obtained high hydrogen evolution reaction efficiency with the as-grown tantalum disulfide flakes directly synthesized on gold foils comparable to traditional platinum catalysts. This work could promote further efforts for exploring new efficient catalysts in the large materials family of metallic transition metal dichalcogenides, as well as exploiting their applications towards more versatile applications., Metallic transition metal dichalcogenides are important materials for catalysis, but scalable and controllable preparation methods are scarce. Here, the authors synthesize 2H-TaS2 as centimetre-scale films of tunable thickness and show they are an efficient catalyst for hydrogen evolution.

Nano-thick metallic transition metal dichalcogenides such as VS$_{2}$ are essential building blocks for constructing next-generation electronic and energy-storage applications, as well as for exploring unique physical issues associated with the dimensionality effect. However, such 2D layered materials have yet to be achieved through either mechanical exfoliation or bottom-up synthesis. Herein, we report a facile chemical vapor deposition route for direct production of crystalline VS$_{2}$ nanosheets with sub-10 nm thicknesses and domain sizes of tens of micrometers. The obtained nanosheets feature spontaneous superlattice periodicities and excellent electrical conductivities (~3$\times$10$^{3}$ S cm$^{-1}$), which has enabled a variety of applications such as contact electrodes for monolayer MoS$_{2}$ with contact resistances of ~1/4 to that of Ni/Au metals, and as supercapacitor electrodes in aqueous electrolytes showing specific capacitances as high as 8.6$\times$10$^{2}$ F g$^{-1}$. This work provides fresh insights into the delicate structure-property relationship and the broad application prospects of such metallic 2D materials., 23 pages, 5 figues

Rational design and synthesis of heterostructures based on transition metal dichalcogenides (TMDs) have attracted increasing interests because of their promising applications in electronics, catalysis, etc. However, the construction of epitaxial heterostructures with an interface at the edges of TMD nanosheets (NSs) still remains a great challenge. Here, we report a strategy for controlled synthesis of a new type of heterostructure in which TMD NSs, including MoS2 and MoSe2, vertically grow along the longitudinal direction of one-dimensional (1D) Cu2–xS nanowires (NWs) in an epitaxial manner. The obtained Cu2–xS-TMD heterostructures with tunable loading amount and lateral size of TMD NSs are achieved by the consecutive growth of TMD NSs on Cu2–xS NWs through gradual injection of chalcogen precursors. After cation exchange of Cu in Cu2–xS-TMD heterostructures with Cd, the obtained CdS–MoS2 heterostructures retained their original architectures. Compared to the pure CdS NWs, the CdS–MoS2 heterostructures wi...

Molybdenum ditelluride (MoTe2), which is an important transition-metal dichalcogenide, has attracted considerable interest owing to its unique properties, such as its small bandgap and large Seebeck coefficient. However, the batch production of monolayer MoTe2 has been rarely reported. In this study, we demonstrate the synthesis of large-domain (edge length exceeding 30 μm), monolayer MoTe2 from chemical vapor deposition-grown monolayer MoS2 using a chalcogen atom-exchange synthesis route. An in-depth investigation of the tellurization process reveals that the substitution of S atoms by Te is prevalently initiated at the edges and grain boundaries of the monolayer MoS2, which differs from the homogeneous selenization of MoS2 flakes with the formation of alloyed Mo−S−Se hybrids. Moreover, we detect a large compressive strain (approximately −10%) in the transformed MoTe2 lattice, which possibly drives the phase transition from 2H to 1T’ at the reaction temperature of 500 °C. This phase change is substantiated by experimental facts and first-principles calculations. This work introduces a novel route for the templated synthesis of two-dimensional layered materials through atom substitutional chemistry and provides a new pathway for engineering the strain and thus the intriguing physics and chemistry.

We report a method for in situ atomic-scale observation of electrochemical delithiation in a working all-solid-state battery using a state-of-the-art chip based in situ transmission electron microscopy (TEM) holder and focused ion beam milling to prepare an all-solid-state lithium-ion battery sample. A battery consisting of LiCoO2 cathode, LLZO solid state electrolyte and gold anode was constructed, delithiated and observed in an aberration corrected scanning transmission electron microscope at atomic scale. We found that the pristine single crystal LiCoO2 became nanosized polycrystal connected by coherent twin boundaries and antiphase domain boundaries after high voltage delithiation. This is different from liquid electrolyte batteries, where a series of phase transitions take place at LiCoO2 cathode during delithiation. Both grain boundaries become more energy favorable along with extraction of lithium ions through theoretical calculation. We also proposed a lithium migration pathway before and after polycrystallization. This new methodology could stimulate atomic scale in situ scanning/TEM studies of battery materials and provide important mechanistic insight for designing better all-solid-state battery.

The emission colors of cesium lead halide perovskite nanocrystals (NCs) can be controlled by dynamic ion exchange and Mn2+ doping. Herein we report a novel strategy for the synthesis of Cs(PbxMn1−x)(ClyBr1−y)3 NCs via a post-synthetic cation–anion cosubstitution exchange reaction to tailor their optical properties in a wide range. Colloidal CsPbBr3 and CsPb1−xMnxCl3 NCs are firstly prepared, separately, and then mixed together in hexane solution. The Pb2+ and Br− ions in the CsPbBr3 NCs are simultaneously exchanged for the Mn2+ and Cl− ions in the CsPb1−xMnxCl3 NCs, resulting in homogeneous Cs(PbxMn1−x)(ClyBr1−y)3, with preservation of the shape and crystal structure of the initial NCs. This in situ ion exchange method avoids the degradation of photoluminescence originating from the additional purification process of the NCs, and in situ Mn2+ substitution also greatly enhances the emission intensity and quantum yield of the as-obtained NCs, which is found to be related to the bound exciton effect.

For studying the mechanism related to the microscopic internal structure of porous carbon additives in lead-carbon batteries, we conducted the electrochemical experiments with a three-electrode system on a lead-doped mesopore-dominated porous carbon (Pb@MC) composite in a Pb2+ containing H2SO4 electrolyte. Through the electrochemical measures, lead particles on the external surface of carbon could be not only electrodeposited into the nano-sized pores of carbon, but also attached on the pore wall with atomic state, which was observed for the first time by using High Resolution Transmission Electron Microscopy (HRTEM) and Aberration Corrected Scanning Transmission Electron Microscopy (ABF-STEM) with the help of ultrathin sectioning. The nano-lead electrodeposits on the internal surface of carbon didn’t grow up because they were confined by the nano-sized pores of carbon. These nano-lead deposits could not only effectively inhibit the hydrogen evolution, but also contribute the pseudocapacitance and enhance the reversible reaction of Pb/PbSO4, and thus result in the longer cycle performance of lead-carbon batteries.

Cultivar-dependent cadmium (Cd) accumulation was principal in developing Cd-pollution safe cultivars (PSCs). Proteins related to different Cd accumulations of the low-Cd-accumulating (SJ19) and high-Cd-accumulating (CX4) cultivars were investigated by iTRAQ analysis. Higher Cd bioaccumulation factors and translocation factor in CX4 than in SJ19 were consistent with the cultivar-dependent Cd accumulations. The Cd uptake was promoted in CX4 due to its higher expression of Cd-binding proteins and the lower expression of Cd-efflux proteins in roots. What's more, significantly elevated thiol groups (PC2 and PC3) in CX4 under Cd stress might contribute to the high Cd accumulation in roots and the root-to-shoot translocation of Cd-PC complex. Up-regulated proteins involved in cellulose biosynthesis and pectin de-esterification in SJ19 enhanced the Cd sequestration of root cell walls, which was considered as the predominant strategy for reducing Cd accumulation in shoots. The present study provided novel insights in the cultivar-dependent Cd accumulation in shoots of B. parachinensis.