Enhancing Co/Co2VO4 Li-ion battery anode performances via 2D-2D heterostructure engineering.

High-capacity Co2VO4 has become a potential anode material for lithium-ion batteries (LIBs), benefiting from its lower output voltage during cycling than other cobalt vanadates. However, the application of this new conversion-type electrode is still hampered by its inherent large volume variation and poor kinetics. Here, a 2D-2D heterostructure building strategy has been developed to enhance the electrode performance of Co2VO4 through construction of Co/Co2VO4 nanocomposites converted from the in situ phase separation of Co2V2O7·3.3H2O nanosheets. Co/Co2VO4 based on face-to-face contact exhibits the optimized stacking configuration, where Co nanocrystals give gaps of several nanometers between stacked Co2VO4 nanosheets, enabling full contact with the electrolyte, a shorter transport path of lithium ions and more reactive sites. With this design, Co/Co2VO4 anodes deliver outstanding reversible capacity (750 mA h g-1 at 1 A g-1) with ultrahigh capacity retention rate, and excellent cycle stability at high rate (520 mA h g-1 at 5 A g-1 retained after 400 cycles). An "active center's charge transfer-capacity compensation" model was proposed based on capacity analysis, XPS depth analysis and HRTEM observation to uncover the fundamental reason of the excellent cycle performance. This in situ 2D-2D heterostructure constructing strategy may open up the possibility for designing high-performance LIBs.

Metal-organic framework derived amorphous VOx coated Fe3O4/C hierarchical nanospindle as anode material for superior lithium-ion batteries.

Lithium-ion batteries (LIBs) are widely regarded as a promising electrochemical energy storage device, due to their high energy density and good cycling stability. To date, the development of anode materials for LIBs is still confronted with many serious problems, and much effort is required for constructing more ideal anode materials. Herein, starting with metal-organic frameworks (MOFs), an amorphous VOx coated Fe3O4/C hierarchical nanospindle has been successfully synthesized. The obtained Fe3O4/C@VOx nanospindle has a uniform particle size of ∼100 nm in diameter and ∼400 nm in length and consists of ultrafine Fe3O4 nanoparticles (∼5 nm) embedded in a porous carbon matrix as the core and an amorphous VOx layer as the shell. Notably, as the anode material for LIBs, Fe3O4/C@VOx delivers a high coulombic efficiency (74.2%) and a large capacity of 845 mA h g-1 after 500 cycles at 1000 mA g-1. A prominent discharge reversible capacity of 340 mA h g-1 is also still retained at 5000 mA g-1. More importantly, the presented facile MOF-derived route could be easily extended to other functional materials for widespread applications.

Simultaneous eco-toxicity assessment technique using an online monitoring system: effects of different environmental factors on swimming behavior of zebrafish (Danio rerio).

Environmental factors, such as photoperiod and temperature were the main limiting factors for the survival of organisms in the nature environment. Changes in environmental factors are well predicted but determining their effects on organisms are challenging hot topic in the field of eco-toxicology. Thus, technology based eco-toxicity assessment was focused worldwide. In this research, the effects of different temperatures (15 °C, 22 °C, 30 °C, 32 °C, and 35 °C) and photoperiods (dark and light periods) on the continuous behavior responses of Zebrafish (Danio rerio) were investigated using an online monitoring system (OMS). We designed a new fish chamber with sensors to measure the behavior responses of zebrafish under different conditions. Data obtained from the OMS could be assessed for factors such as difference in swimming behavior, circadian rhythm, and avoidance behavior using latest software (MATLAB). The observed behavior anomalies on zebrafish under different temperatures and continuous photoperiods were statically significant (p < 0.05). We conclude that the new designed fish chamber (behavior sensors) is good in sensing behavioral responses of zebrafish under different conditions. The fish behavior strength could be a potential biomarker to assess the effects of environmental factors. The present study would be a basic platform for assessing the effects of different stressors simultaneously on swimming behavior of zebrafish.

A 1D Honeycomb-Like Amorphous Zincic Vanadate for Stable and Fast Sodium-Ion Storage.

Developing nanomaterials with synergistic effects of various structural merits is considered to be an effective strategy to improve the sluggish ion kinetics and severe structural degradation of sodium-ion battery (SIB) anodes. Herein, honeycomb-like amorphous Zn2 V2 O7 (ZVO-AH) nanofibers as SIBs anode material with plentiful defective sites, complex cavities, and good mechanical flexibility are reported. The fabrication strategy relies on the expansive and volatile nature of the organic vanadium source, based on a simple electrospinning with subsequent calcination. Originating from the synergies of amorphous nature and honeycomb-like cavities, ZVO-AH shows increased electrochemical activity, accelerated Na-ion diffusion, and robust structure. Impressively, the ZVO-AH anode delivers superior cycle stability (112% retention at 5 A g-1 after 5000 cycles) and high rate capability (150 mAh g-1 at 10 A g-1 ). The synthetic versatility is able to synergistically promote the practical application of more potential materials in sodium-ion storage.

Potential effects of internal physio-ecological changes on the online biomonitoring of water quality: The behavior responses with circadian rhythms of zebrafish (Danio rerio) to different chemicals.

The online biomonitoring of aquatic accidental pollution is very important to realize the assessment of complex toxicity. However, the monitoring results would be affected greatly by the internal physio-ecological changes of test organisms, and circadian rhythms might contribute greatly to this kind of effects. In the present study, the behavior responses of zebrafish (Danio rerio) to different concentrations of Deltamethrin, Atrazine, and Thallium (Tl) in 15 days were investigated using an online behavior monitoring system. The results showed that the average behavior strength (BS) value of dark period (0.71 ±â€¯0.16) was lower than that of light period (0.88 ±â€¯0.09) in the control group. Similar pattern was observed in all other treatments with negative relationship between exposure concentrations and mean BS values. It is concluded that the 24 h circadian rhythms in the behavior responses of zebrafish (Danio rerio) could be observed clearly in the online biomonitoring system, and the online monitoring results would be affected obviously in the characteristics of behavior periodicity abnormal and time delay. Therefore, it is suggested that internal physio-ecological characteristics of organisms must be considered once they have the chance to play roles in bio-induced technologies. More investigations are warranted to clear the effects of internal physio-ecological changes on the exported results.

The online monitoring and assessment of thallium stress using oxygen consumption rate and carbon dioxide excretion rate of zebrafish (Danio rerio).

An online monitoring and assessment system of metabolism to measure oxygen consumption rate (OC) and carbon dioxide (CO2) excretion rate (CR) of zebrafish (Danio rerio) was used to illustrate changes in stressful states in 15 days' (360 h) 0.1 µg/L Tl exposure. Tl had a significant inhibition on zebrafish OC and CR (p < 0.01). OC was more suitable for Tl stress assessment than CR, considering that the OC response was more stable and discernible from the control comparing with CR. However, CR is a suitable alternative to characterize toxic effects on different metabolic substrates. Both OC and CR were integrated to present the respiratory quotient (RQ) analysis. RQ was efficient in differentiating between CO2 produced by respiration in the control group (RQ less than 0.7) and CO2 used for urination or stored in tissues after Tl exposure (some RQs larger than 1.0). Circadian rhythm was observed in RC and CR in the controls and persisted in 0.1 µg/L Tl treatments. The rhythm was relatively more disordered in CR. OC and CR would be suitable for indicating physiological stress in the online system as sensitive physiological indices.

Toxic responses of zebrafish (Danio rerio) to thallium and deltamethrin characterized in the electrocardiogram.

The electrocardiogram (ECG) has been widely used to objectively address the physical condition as an index of stress. Though a numerous accounts of investigations on aquatic organisms' ECGs have been made, differentiation of ECG parameters in responding to specific toxic chemicals has not been extensively studied. In this research, it is hypothesized that zebrafish (Danio rerio) ECG parameters would differently respond to different types of pollutants, a heavy metal, thallium (Tl, 0.10 and 13.00 µg/L) and an organic chemical, deltamethrin (DM, 0.52 and 2.00 µg/L). Based on the SOM training and statistical analyses, QRS complex could be specified as an indicator of Tl stress, while QT interval might be used to evaluate DM stress. Pearson correlation analysis indicated that QRS complex and QT interval were significantly associated with Tl stress (r = 0.854, p = 0.0002) and DM stress (r = 0.792, p = 0.001), respectively. QRS complex and QT interval had the highest R2, the minimum of SSE and the lowest AIC value in Tl and DM treatments, respectively. Bases on the current experimental results and previous reports, QRS complex and QT interval could be considered as a specific indicator of Tl and DM disturbances in the environment, respectively.

Behavior responses of zebrafish (Danio rerio) to aquatic environmental stresses in the characteristic of circadian rhythms.

As behavior shows a distinct circadian rhythm, it is hypothesized that circadian rhythms based on zebrafish (Danio rerio) behavior responses could be affected by contaminants in this study, and then the behavior strength of zebrafish exposed to 0.005 mg/L Cadmium chloride (CdCl2), 0.01 mg/L Dibasic Sodium Phosphate (Na2HPO4), 0.002 mg/L deltamethrin, and 0.003 mg/L atrazine for 6 days is used to illustrate the possibility of behavior circadian rhythms as an indicator in the environmental stress assessment. Statistical analysis with p < 0.01 shows that a clear difference between average values of BS during dark period (AVD) and those during light period (AVL) could be observed, and 24 h circadian rhythms do exist in zebrafish behavior responses. Both BS values and circadian rhythms of zebrafish can be affected in the aspect of periodicity with clear time delay, which were 1 h delay in CdCl2, 4 h delay in Na2HPO4, 4 h delay in deltamethrin, and 1 h delay in atrazine. Behavior circadian rhythms were disturbed according to the repetitive cycles after autocorrelation analysis, and the toxic effects of different chemicals could be reflected by the profiles of the Self-Organizing Map (SOM), which indicated the circadian rhythm disorder in different degrees. These results deduced from the statistical analysis, autocorrelation and SOM strongly supported that circadian rhythms based on zebrafish BS could be used as an indicator in the environmental stress assessment.