Metal-organic frameworks (MOFs) have been used to detect uric acid (UA), but still very challenging to achieve a low detection limit due to the low inferior conductivity of MOFs. Herein, three different N-doped ZIF-67-derived carbons were synthesized for the first time by one-step co-pyrolysis of 2-methylimidazole with cobalt nitrate (CN), cobalt acetate (CA) or cobalt chloride (CC) toward UA sensing. Afterwards, the cobalt nitrate-derived Co particle (Co/CN) supported by N-doped ZIF-67-derived carbon displays extremely low detection limit and high sensitivity for UA, outperformed all reported MOFs-based UA sensors. More interestingly, it was discovered that the high valence Co4+ within the Co/CN sample produced in high-acidic environment can intercalate in the frame for a bridge adsorption between two reaction sites, which boosted simultaneous 2-electron transfer, while Co3+ only allows an end-adsorption structure for one-electron transfer being the rate determining step. Furthermore, the bridge adsorption mode of UA on Co4+ -based catalyst was also verified by theoretical DFT calculations and XPS experiment. This work holds great promise for a selective and sensitive UA sensor for practical bioscience and clinic diagnostic applications while shedding lights in fundamental research for innovative designs and developments of high-sensitive electrochemical sensors.
Brackish water resource is widely distributed in the North China Plain, which has not been effectively utilized. Using brackish water for irrigation can alleviate water resource conflict in the well-irrigated area and solve the problem of groundwater over-exploitation of the North China Plain. A long-term experiment (since 2006) was conducted to investigate the effects of brackish water irrigation on the quality and yield of winter wheat in the North China Plain. There were five salinity degrees of irrigation water, i.e. 1, 2, 4, 6, and 8 g·L-1, respectively. The results showed that higher salinity degree of irrigation water (4-8 g·L-1) significantly increased water absorption, development time, sedimentation, wet gluten content, and protein content, but decreased the stabilization time, flour yield, and gluten index. There was no significant difference between the treatments of 1 g·L-1 and 2 g·L-1 on grain yield and yield components, but the treatment of 2 g·L-1 significantly improved grain quality, including water absorption, development time, sedimentation, wet gluten, and protein content. Higher salinity degree of irrigation water (4-8 g·L-1) treatments significantly decreased spike number (44.0%-60.7%) and grain yield (35.6%-64.7%), compared with 1 g·L-1 treatment. Results of principal component analysis showed that 2 g·L-1 treatment had the best overall effect with no significant decrease in grain yield and quality of grain. This study could provide theoretical basis and technical support for use of brackish water in the North China Plain.
Agricultural Irrigation , Triticum , Agricultural Irrigation/methods , Biomass , China , Edible Grain , Glutens/metabolism , Saline Waters , Water
It is of great importance to explore the effects of saline-water furrow irrigation on soil water-stable aggregates for safe and efficient utilization of saline water resources. We conducted a long-term cotton experiment with six levels of saline-water furrow irrigation (1, 2, 4, 6, 8, 10 g·L-1) since 2006 and analyzed the variations of soil salinity and water-stable aggregates in the 10th and 15th years under saline irrigation. The results showed that soil salinity in the 0-30 cm layer at the ditch increased with increasing salinity level of irrigation water. There were significant differences between the 6, 8, 10 g·L-1 and 1 g·L-1 treatments. Soil salinity in each treatment increased gradually with increasing soil depth. Saline-water furrow irrigation tended to reduce the stability of soil water-stable aggregates. When the salinity level of the irrigation water was ≥6 g·L-1, the mass fraction of macroaggregates (>0.25 mm), the mean weight diameter and geometric mean diameter of water-stable aggregates significantly decreased. In contrast, the fractal dimension and mean weight specific surface area increased significantly. The stability of soil water-stable aggregates decreased with soil depth in all treatments. Under the condition of saline-water furrow irrigation for several years, there was no accumulation of soil salinity and instability of water-stable aggregates in the 0-30 cm soil layer at the ditch with each passing year. With the irrigation scheduling of this study, saline-water furrow irrigation with salinity ≤4 g·L-1 did not affect soil salinity and water-stable aggregate stability of cotton field in this area.
Saline Waters , Soil , Agricultural Irrigation/methods , Salinity
The muttagenic H-13 strain which was injected by ionic beam and screened from Trichoderma hamzlaiarum, can promote the growth of rice remarkably. In the experiment, we use zymolytic liquid of H-13 strain sprinkle on the seedling of rice, and determine nitrate reductase activity and N, P, K content. The results suggest that the effect of promoting plant growth of the strain has a relation to the enhance of nitrate reductase activity and the increase of N, P and K absorption.
Trichoderma harziaiarum plays a role of antagonic ability to pathogenic micr obes and of inducing plant to produce a resistivity of disease. In this paper, afte r the rice was sprinkled by zymolytic liquid of Trichoderma harziaiarum, the changes on the activities and isoenzymes of polyphenol oxidase (PPO) and pe roxidase (POD) were investigated. The results indicated that Trichoderma harz iarum could increase the activities of PPO and POD and produce new pattern of isoe nzymes; the different concentration of zymotic liquid had a different effects on the PPO and POD that were caused by the liquid; the 50 times diluted liquid had a greatly positive relation to the POD activity; and the higher concentration o f the liquid had a tendency that made the PPO activity inhibition and then incre ase, which denoted that the liquid took a scheduled adjustment play of the PPO a ctivity.
