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1.
ACS Appl Mater Interfaces ; 11(40): 37051-37059, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31465197

RESUMO

The development of highly sensitive wearable and foldable pressure sensors is one of the central topics in artificial intelligence, human motion monitoring, and health care monitors. However, current pressure sensors with high sensitivity and good durability in low, medium, and high applied strains are rather limited. Herein, a flexible pressure sensor based on hierarchical three-dimensional and porous reduced graphene oxide (rGO) fiber fabrics as the key sensing element is presented. The internal conductive structural network is formed by the rGO fibers which are mutually contacted by interfused or noninterfused fiber-to-fiber interfaces. Thanks to the unique structures, the sensor can show an excellent sensitivity from low to high applied strains (0.24-70.0%), a high gauge factor (1668.48) at an applied compression of 66.0%, a good durability in a wide range of frequencies, a low detection limit (1.17 Pa), and anultrafast response time (30 ms). The dominated mechanism is that under compression, the slide of the graphene fibers through the polydimethylsiloxane matrix reduces the connection points between the fibers, causing a surge in electrical resistance. In addition, because graphene fibers are porous and defective, the change in geometry of the fibers also causes a change in the electrical resistance of the composite under compression. Furthermore, the interfused fiber-to-fiber interfaces can strengthen the mechanical stability under 0.01-1.0 Hz loadings and high applied strains, and the wrinkles on the surface of the rGO fibers increased the sensitivity under tiny loadings. In addition, the noninterfused fiber-to-fiber interfaces can produce a highly sensitive contact resistance, leading to a higher sensitivity at low applied strains.

2.
ACS Appl Mater Interfaces ; 11(24): 21506-21514, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31124648

RESUMO

The rational design of excellent electrocatalysts is significant for triggering the slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable metal-air batteries. Hereby, we report a bifunctional catalytic material with core-shell structure constructed by Co3O4 nanowire arrays as cores and ultrathin NiFe-layered double hydroxides (NiFe LDHs) as shells (Co3O4@NiFe LDHs). The introduction of Co3O4 nanowires could provide abundant active sites for NiFe LDH nanosheets. Most importantly, the deposition of NiFe LDHs on the surface of Co3O4 can modulate the surface chemical valences of Co, Ni, and Fe species via changing the electron donor and/or electron absorption effects, finally achieving the balance and optimization of ORR and OER properties. By this core-shell design, the maximum ORR current densities of Co3O4@NiFe LDHs increase to 3-7 mA cm-2, almost an order of magnitude increases compared to pure NiFe LDH (0.45 mA cm-2). Significantly, an OER overpotential as low as 226 mV (35 mA cm-2) is achieved in the designed core-shell catalyst, which is comparable to and/or even better than those of commercial Ir/C. Hence, the primary zinc-air battery employing Co3O4@NiFe LDH as an air electrode achieves a high specific capacity (667.5 mA h g-1) and first-class energy density (797.6 W h kg-1); the rechargeable battery can show superior reversibility, excellent stability, and voltage gaps of ∼0.8 V (∼60% of round-trip efficiency) in >1200 continuous cycles. Furthermore, the flexible quasi-solid-state zinc-air battery with bendable ability holds practical potential in portable and wearable electronic devices.

3.
Artigo em Inglês | MEDLINE | ID: mdl-30972672

RESUMO

Soil-exchangeable aluminum (Al) has toxic effects on living organisms in acidic soils. Earthworm presence and activity can alter soil pH, which has a significant influence on Al toxicity. However, the effects of earthworms on soil Al toxicity and fractions are still largely unknown. This laboratory study focused on the effects of three earthworm species (endogeics Pontoscolex corethrurus and Amynthas robustus, anecis Amynthas aspergillum) on soil acidification, Al fraction distribution, and base cation release. Three native earthworm species and a soil (latosolic red soil) collected from a botanical garden in South China were incubated under laboratory conditions. After 40 days of incubation, six Al fractions in soil, namely exchangeable (AlEx), weakly organically bound (AlOrw), organically bound (AlOr), amorphous (AlAmo), Al occluded in crystalline iron oxides (AlOxi), and amorphous aluminosilicate and gibbsite (AlAag) fractions, were extracted using a sequential procedure. Soil pH; organic carbon; total nitrogen; total Al (AlTotal); exchangeable K, Na, Ca, Mg contents; and CEC were determined as well. Compared to control soil, pH values increased by 0.79, 0.41, and 0.57 units in casts in the presence of P. corethrurus, A. robustus, and A. aspergillum, and 0.70, 0.32, and 0.50 units in non-ingested soil, respectively. Compared to control soil, the 61.7%, 30.7%, and 36.1% of AlEx contents in casts and 68.5%, 25.9%, and 39.0% of AlEx in non-ingested soil significantly decreased with the addition of P. corethrurus, A. robustus, and A. aspergillum, respectively. Moreover, compared to control soil, the 78.7%, 37.7%, and 40.1% of exchangeable Ca2+ and 12.3%, 24.7%, and 26.8% of exchangeable Mg2+ contents in casts significantly increased with the presence of P. corethrurus, A. robustus, and A. aspergillum, respectively. Soil treated with P. corethrurus had higher soil pH values, exchangeable Ca2+ contents, and lower AlEx than those with A. robustus and A. aspergillum. Results of principal component analyses showed that P. corethrurus, A. robustus, and A. aspergillum casts and non-ingested soil differ for soil pH, Al fractions, and exchangeable base cations release. These results indicate that earthworms, especially P. corethrurus, can reduce soil Al toxicity, increase soil pH, and affect the release of exchangeable base cations.

4.
Artigo em Inglês | MEDLINE | ID: mdl-30838490

RESUMO

This study focused on the study of earthworm survival, growth, reproduction, enzyme activities, and protein contents to evaluate and predict the effects of different soil pH levels and determine the optimal risk assessment indicators for the effects. Survival rate, growth rate, and cocoon number as well as four enzyme (glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) activities and two proteins (total protein (TP) and metallothionein (MT)) contents in earthworms were determined to characterize the responses of earthworm activity to five soil pH levels. These biological datasets (survival, growth, and reproduction) were compared with biochemical indexes (GSH-PX, SOD, POD, CAT, TP, and MT), mainly using biphasic dose-response models. The results indicated that the soil pH value had significant inhibitory effects on the survival, growth, and reproduction of earthworms beginning with 3.0, 4.0, and 5.2, respectively. The dose-response models (J-shaped and inverted U-shaped curves) statistics indicated that the critical values (ECZEP) of the GSH-PX, SOD, POD, CAT, TP, and MT inhibited by soil acid stress were 3.46, 3.76, 3.35, 3.54, 3.50, and 3.96 (average 3.60), respectively. In the present study, the fitting curve analysis showed that the responses of the CAT activities and TP and MT contents in earthworm in response to soil pH have the behavior of hormesis.

5.
Chemosphere ; 182: 509-516, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28521166

RESUMO

Labile metals in agricultural soils are available to crops and thus pose a great health risk for human beings. Therefore, factors influencing heavy metal activity are of interest to researchers. In this study, a total of 142 soil samples representing 5 typical parent materials in the Pearl River Basin (PRB), China were collected to investigate factors impacting the distribution of labile Cd and Pb in the soils. The results showed that the labile fractions accounted for 0.03%-14.7% for Cd and 0.01%-0.39% for Pb of the total metals, and the labile fractions were linearly correlated to their corresponding total contents. The step regression analyses suggested that the key factors impacting labile Cd and Pb varied in different parent material soils. Pb activity was highly sensitive to pH in alkaline limestone soils. The quartz sand remained in granite-produced soils enhanced Cd activity. And dissolved organic matter (DOM) compositions considerably influenced Cd and Pb activities in sand shale, diluvium, and alluvium soils. Land use impacts heavy metal activities. The labile Cd and Pb in paddy soils were higher than those in non-paddy soils, although total metals in the soils were comparable. It could be ascribed to the long-term equilibrium of metals between the solution and solid phases of the paddy soils. The results provide a theoretical basis for preliminary prediction of heavy metal activity and provide a technical support for heavy metal activity management and pollution control based on soil parent materials.


Assuntos
Cádmio/química , Monitoramento Ambiental , Chumbo/química , Rios/química , Poluentes do Solo/química , Solo/química , Agricultura , China , Produtos Agrícolas , Poluição Ambiental/análise , Humanos , Poluentes Químicos da Água/química
6.
Environ Pollut ; 225: 654-662, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28392241

RESUMO

Correct characterization of metal speciation and reactivity is a prerequisite for the risk assessment and remedial activity management of contaminated soil. To better understand the intrinsic reactivity of Pb and Zn, nine heavily and poorly contaminated soils were investigated using the combined approaches of chemical extractions, multi-element stable isotopic dilution (ID) method, and multi-surface modelling. The ID results show that 0.1-38% of total Pb and 3-45% of total Zn in the studied soils are isotopically exchangeable after a 3-day equilibration. The intercomparison between experimental and modelling results evidences that single extraction with 0.43 M HNO3 solubilizes part of non-isotopically exchangeable fraction of Pb and Zn in the studied soils, and cannot be used as a surrogate for ID to assess labile Pb and Zn pools in soil. Both selective sequential extraction (SSE) and modelling reveal that Mn oxides are the predominant sorption surface for Pb in the studied soils; while Zn is predicted to be mainly associated with soil organic matter in the soil with low pH and Fe/Mn oxides in the soils with high pH. Multi-surface modelling can provide a reasonable prediction of Pb and Zn adsorption onto different soil constituents for the most of the studied soils. The modelling could be a promising tool to decipher the underlying mechanism that controls metal reactivity in soil, but the submodel for Mn oxides should be incorporated and the model parameters, especially for the 2-pK diffuse layer model for Mn oxides, should be updated in the further studies.


Assuntos
Chumbo/análise , Modelos Químicos , Poluentes do Solo/análise , Zinco/análise , Adsorção , Poluição Ambiental , Técnicas de Diluição do Indicador , Isótopos , Chumbo/química , Solo/química , Poluentes do Solo/química , Zinco/química
7.
Ying Yong Sheng Tai Xue Bao ; 23(3): 779-84, 2012 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-22720625

RESUMO

Taking mixed agricultural organic wastes cattle manure and rice straw (C:N = 28.7:1) as the substrate of earthworm Eisenia foetida, an experiment was conducted to study the effects of earthworm on the changes of the chemical and biological properties of wastes during vermi-composting. After 30 days of vermi-composting, the substrate' s pH and C/N decreased while the total P content increased significantly, and the total N, available N, dissolved organic carbon, available P content, microbial biomass-C, respiration rate, and microbial quotient increased by 8.5% , 2.6%, 1.8%, 6.3%, 21.2%, 4.4%, and 30.0% whereas the organic matter content and metabolic quotient decreased by 5.0% and 21.9%, respectively, as compared with natural composting. Vermi-composting made the substrate have higher invertase, acid phosphatase, and alkaline phosphatase activities but lower catalase and urease activities. Principal component analysis and discriminant analysis confirmed the significant differences in the substrate' s chemical and biological properties between vermi-composting and natural composting. This study indicated that vermi-composting was superior to natural composting, which could obviously improve the chemical and biological properties of composted organic materials, being a high efficient technology for the management of agricultural organic wastes.


Assuntos
Carbono/análise , Produtos Agrícolas/crescimento & desenvolvimento , Nitrogênio/análise , Oligoquetos/crescimento & desenvolvimento , Resíduos Sólidos/análise , Ração Animal/análise , Animais , Biodegradação Ambiental , Oligoquetos/fisiologia , Compostos Orgânicos/química , Análise de Componente Principal , Eliminação de Resíduos/métodos
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