Trace detection of cadmium (II) ions based on an excessively tilted fiber grating.

Cadmium (Cd2+) ion is one of the most crucial industrial pollutants that cause serious harm to the human body. We proposed and experimentally demonstrated a highly sensitive Cd2+ sensor based on hydrogel coated excessively tilted fiber grating. The hydrogel with the functional monomer of the allyl thiourea can specifically bind to Cd2+, and hence forming a complex. The grating excites high order cladding modes, and ensures a sufficient interaction between the light and hydrogel binding to Cd2+, providing highly sensitive monitoring. The results show that the sensor can detect 0-160 pM Cd2+ in aqueous solution. The maximum sensitivity is 10600 nm/µM, and the minimum detection concentration is 20 pM (about 0.004 ppb), which is much less than that of the international standard (3 ppb). The proposed sensor exhibits high sensitivity, ultra-low detection limit, specificity, and a compact structure, offering potential as a tool for Cd2+ detection in aqueous solution.

Enhanced photocatalytic hydrogen evolution activity of co-catalyst free S-scheme polymer heterojunctions via ultrasonic assisted reorganization in solvent.

In this work, two donor-acceptor linear conjugated polymers were designed and synthesized based on thianthrene-5,5,10,10-tetraoxide (TTO) as the acceptor unit, benzo[1,2-b:4,5-b']dithiophene derivative (Py1) and thiophene (Py2) as the donor units, respectively. The Py1/Py2 composite was prepared by physical ball milling of the two polymers in a mixture, which was further treated with a N-methyl-2-pyrrolidone (NMP)-assisted sonication treatment, and the obtained catalyst was named N-Py1/Py2. Compared with the single polymer or Py1/Py2, the FTIR characteristic peaks of O=S=O have a red shift for N-Py1/Py2, accompanied by a profound change in morphology. Furthermore, N-Py1/Py2 has a broader light response and more efficient separation and transport of charge carriers, and as a result it exhibits a higher photocatalytic hydrogen evolution rate (26.5 mmol g-1 h-1) without the involvement of any co-catalyst than Py1/Py2 catalyst (3.56 mmol g-1 h-1). The underlying mechanism for the enhanced photocatalytic activity by the sonication treatment in NMP is discussed based both on experimental and theoretical calculation data.

Ion-Imprinted Chitosan-Based Localized Surface Plasmon Resonance Sensor for Ni2+ Detection.

Heavy metals are important sources of environmental pollution and cause disease in organisms throughout the food chain. A localized surface plasmon resonance sensor was proposed and demonstrated to realize Ni2+ detection by using ion-imprinted chitosan. Au nanoparticles were coated on the multimode fiber to excite the local surface plasmon resonance, and Ni2+-imprinted chitosan was then functionalized by using the dip coating technique. Ethylene diamine tetra-acetic acid was used to release the Ni2+ ions and hence form countless voids. Ni2+ was refilled into the voids to increase the refractive index of the sensing material, thus realizing the measurement of Ni2+ by monitoring the wavelength shift in the localized surface plasmon resonant peak. The coating thickness of the Ni2+-chitosan gel was optimized to obtain greater sensitivity. Experimental results show that the proposed Ni2+ sensor has a sensitivity of 185 pm/µM, and the limit of detection is 0.512 µM. The comparison experiments indicated that the ion-imprinted chitosan has better selectivity than pure chitosan.

Effect of Nitrogen Atom Introduction on the Photocatalytic Hydrogen Evolution Activity of Covalent Triazine Frameworks: Experimental and Theoretical Study.

The construction of high-performance photocatalyst has always been explored. Covalent organic frameworks (COFs), especially keto-amine-linked COFs, have many advantages, such as adjustable bandgaps, π-π stacking structure, excellent response ability to visible light, high specific surface area, high mobility of carrier carriers, good physical and chemical stability, and so on, showing strong potential applications in photocatalytic solar energy conversion and hydrogen production. Two analogous covalent triazine frameworks (CTFs), T3H-CTF and T3N-CTF, have been synthesized via Schiff-base condensation reactions between 2,4,6-trihydroxybenzene-1,3,5-tricarbalehyde (MOP) and the corresponding triazine-based aromatic amines under solvothermal condition. For T3N-CTF, the peripheral aromatic linker to the central triazine unit was the pyridine unit, instead of the benzene unit in the T3H-CTF unit. T3N-CTF had a hydrogen production rate (HPR) of 6485.05 µmol g-1 h-1 , much higher than that of T3H-CTF (2028.06 µmol g-1 h-1 ). Accordingly, T3N-CTF had a much higher apparent quantum yield (AQY) of 12.2 % than that of T3H-CTF (4.12 %) at 405 nm. The experimental and theoretical results showed that the extended light absorption range, enlarged surface area, and enhanced separation and transportation efficiencies of charge carriers of T3N-CTF compared with T3H-CTF were uniformly induced by the introduction of peripheral nitrogen atoms into the skeleton of former CTF, which eventually boosted the visible-light induced hydrogen evolution reaction (HER). The work suggests a new method for enhancing the intrinsic HER activity by modulating the electronic features of the conjugated COFs by the introduction of pyridinic N atoms.

Triazine-Based Conjugated Microporous Polymers With Different Linkage Units for Visible Light-Driven Hydrogen Evolution.

Conjugated microporous polymers (CMPs), as a kind of two-dimensional material, have attracted extensive attention due to their advantages in visible light-driven photocatalytic splitting of water for hydrogen evolution. However, improving the microstructure and electronic structure of the material to enhance their photocatalytic performance for hydrogen evolution remains a challenge. We designed and reported two analogous CMPs including CMP-1 and CMP-2 that contain triazine and dibenzothiophene-S,S-dioxide units, which were prepared by Pd-catalyzed Suzuki-Miyaura coupling reaction. The main difference of two CMPs is that the triazine units are connected to benzene unit (CMP-1) or thiophene unit (CMP-2). Both of the CMPs exhibit excellent light capture capability, and compared with CMP-2, CMP-1 has faster separation rates and lower recombination rates for the charge carriers (electron/hole), and then, a higher hydrogen evolution rate was obtained from water decomposition reaction. We find the H2 production rate of CMP-1 can be up to 9,698.53 µmol g-1h -1, which is about twice of that of CMP-2. This work suggests that molecular design is a potent method to optimize the photocatalytic performance toward hydrogen evolution of the CMPs.

Manipulation of composting oxygen supply to facilitate dissolved organic matter (DOM) accumulation which can enhance maize growth.

Promotion of crop yield by compost application is generally thought to be ascribed to a better supply of macro and micronutrients, however the importance of compost DOM on plant growth has not been well demonstrated. In this study, composting of chicken manure, spent mushroom and sawdust was conducted under aerobic or anaerobic condition to determine the effects of compost DOM on plant growth. It was found that dissolved organic matter (DOM) first increased and then decreased in compost, and DOM of anaerobic compost was slightly higher than that of aerobic compost. When compost extract was applied to maize, among N, P, K and DOM content, it was DOM content that was most significantly and strongly related to plant biomass (r = 0.843, p＜0.001). Compost DOM was also strongly related to soil properties, the improvement of which can also promote plant growth. Compost application confirmed that higher compost DOM results in greater plant biomass. In order to facilitate compost DOM accumulation, we designed a novel composting process which combined aerobic and anaerobic treatments, and the resulting compost (A-Ana compost) with the highest amount of DOM displayed the best performance in promotion of plant growth. A-Ana compost was able to increase maize biomass by 32.71% and 12.40% compared with only anaerobic or aerobic compost, respectively. Therefore, DOM is a critical factor determining compost quality and it is feasible to manipulate composting oxygen supply condition to increase compost DOM, which will lead to increased plant yield.

Computational investigation of a switchable emulsion stabilized by the mixture of a surfactant and tertiary amine.

Molecular dynamics simulations were performed to investigate the CO2-responsiveness of an oil-in-water (O/W) emulsion stabilized by sodium oleate (NaOA) with a tertiary amine additive, named pentamethyl diethylenetriamine (PMA). The simulated results were in accordance with the experimental observations. That is, the surfactant NaOA itself can stabilize dodecane/water emulsions in aqueous solution, while the CO2-reponsiveness was strongly related to the added PMA. The electroneutral PMA molecules preferred to be located in the core region of the droplets. Thus, under the same conditions, the size of the droplet containing PMA is predictably larger than that without PMA. The increased extent of the charged surfactant headgroups distribution can increase the electrostatic repulsion between the droplets in the emulsion solution, which is the important reason why a much more stable emulsion is obtained by adding PMA. When PMA molecules were protonated to PMA2+ by bubbling CO2, they migrated from the interior to the surface of the droplets under electrostatic attraction, forming ion pairs with OA-. The binding between PMA2+ and OA- made the distribution of the surfactants very concentrated on the droplet surface, leading to large hydrophobic areas exposed to water. Besides, the hydration interactions of OA- headgroups decreased because they were covered by PMA2+. The calculated potential of mean force (PMF) confirmed that the electrostatic repulsion between droplets was crucial for the emulsion stabilization.

[Research on the Risk Prevention and Quality Control of Public Hospital Procurement].

Through the functional combination of relevant departments involved in hospital procurement, to simplify and unify the work process, we establish a standardized procurement system, to realize the pre-procurement budget and approval, power balance, strengthen the fairness and openness of procurement process. By introducing the closed-loop process of in-process supervision to ensure the impartiality of review and post-evaluation control, it comprehensively strengthens the internal control of procurement management, and finally realizes the purpose of strengthening procurement risk prevention and procurement quality management.

Genome-wide Analysis of Phosphoenolpyruvate Carboxylase Gene Family and Their Response to Abiotic Stresses in Soybean.

Phosphoenolpyruvate carboxylase (PEPC) plays an important role in assimilating atmospheric CO2 during C4 and crassulacean acid metabolism photosynthesis, and also participates in various non-photosynthetic processes, including fruit ripening, stomatal opening, supporting carbon-nitrogen interactions, seed formation and germination, and regulation of plant tolerance to stresses. However, a comprehensive analysis of PEPC family in Glycine max has not been reported. Here, a total of ten PEPC genes were identified in soybean and denominated as GmPEPC1-GmPEPC10. Based on the phylogenetic analysis of the PEPC proteins from 13 higher plant species including soybean, PEPC family could be classified into two subfamilies, which was further supported by analyses of their conserved motifs and gene structures. Nineteen cis-regulatory elements related to phytohormones, abiotic and biotic stresses were identified in the promoter regions of GmPEPC genes, indicating their roles in soybean development and stress responses. GmPEPC genes were expressed in various soybean tissues and most of them responded to the exogenously applied phytohormones. GmPEPC6, GmPEPC8 and GmPEPC9 were significantly induced by aluminum toxicity, cold, osmotic and salt stresses. In addition, the enzyme activities of soybean PEPCs were also up-regulated by these treatments, suggesting their potential roles in soybean response to abiotic stresses.

Genome-Wide Identification of Soybean U-Box E3 Ubiquitin Ligases and Roles of GmPUB8 in Negative Regulation of Drought Stress Response in Arabidopsis.

Plant U-box (PUB) E3 ubiquitin ligases play important roles in hormone signaling pathways and response to abiotic stresses, but little is known about them in soybean, Glycine max. Here, we identified and characterized 125 PUB genes from the soybean genome, which were classified into eight groups according to their protein domains. Soybean PUB genes (GmPUB genes) are broadly expressed in many tissues and are a little more abundant in the roots than in the other tissues. Nine GmPUB genes, GmPUB1-GmPUB9, showed induced expression patterns by drought, and the expression of GmPUB8 was also induced by exogenous ABA and NaCl. GmPUB8 was localized to post-Golgi compartments, interacting with GmE2 protein as demonstrated by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) experiments, and showed E3 ubiquitin ligase activity by in vitro ubiquitination assay. Heterogeneous overexpression of GmPUB8 in Arabidopsis showed decreased drought tolerance, enhanced sensitivity with respect to osmotic and salt stress inhibition of seed germination and seedling growth, and inhibited ABA- and mannitol-mediated stomatal closure. Eight drought stress-related genes were less induced in GmPUB8-overexpressing Arabidopsis after drought treatment compared with the wild type and the pub23 mutant. Taken together, our results suggested that GmPUB8 might negatively regulate plant response to drought stress. In addition, Y2H and BiFC showed that GmPUB8 interacted with soybean COL (CONSTANS LIKE) protein. GmPUB8-overexpressing Arabidopsis flowered earlier under middle- and short-day conditions but later under long-day conditions, indicating that GmPUB8 might regulate flowering time in the photoperiod pathway. This study helps us to understand the functions of PUB E3 ubiquitin ligases in soybean.

Local structure evolution and its connection to thermodynamic and transport properties of 1-butyl-3-methylimidazolium tetrafluoroborate and water mixtures by molecular dynamics simulations.

Our recently developed improved united atom force field shows a good quality to reproduce both the static and transport properties of neat ionic liquids (ILs). Combined with the TIP4P-Ew water model, the force field is used to simulate the mixture of 1-butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF(4)]) and water without further optimization to adjust any cross parameters. Liquid densities of the mixture are well predicted over the entire concentration range at temperatures from 298.15 to 353.15 K. Simulations also reproduce the positive values of excess volumes and excess enthalpies, as well as their increase with temperature. The simulated viscosities are in good agreement with experimental values, especially in the water-rich region. We found three distinct regions by analyzing the concentration dependent self-diffusion coefficients via Stokes-Einstein (SE) relation, indicating the mixture experiences significant microheterogeneity with the adding of water. This observation is well connected to the structure features obtained in simulations, such as radial distribution functions (RDFs), spatial distribution functions (SDFs) and water clustering analysis. At the water mole fraction (x(2)) less than 0.2, most of the water molecules are isolated in the polar cation-anion network in ionic liquids. With the increase of x(2) from 0.2 to 0.8, large water cluster forms and eventually percolates the whole system. When x(2) > 0.8, ionic liquids show a moderate degree of aggregation (with maximum around 0.9 to 0.95) before the cations and anions are fully dissolved in water.

Improved classical united-atom force field for imidazolium-based ionic liquids: tetrafluoroborate, hexafluorophosphate, methylsulfate, trifluoromethylsulfonate, acetate, trifluoroacetate, and bis(trifluoromethylsulfonyl)amide.

A cost-effective, classical united-atom (UA) force field for ionic liquids (ILs) was proposed, which can be used in simulations of ILs composed by 1-alkyl-3-methyl-imidazolium cations ([C(n)mim](+)) and seven kinds of anions, including tetrafluoroborate ([BF(4)](-)), hexafluorophosphate ([PF(6)](-)), methylsulfate ([CH(3)SO(4)](-)), trifluoromethylsulfonate ([CF(3)SO(3)](-)), acetate ([CH(3)CO(2)](-)), trifluoroacetate ([CF(3)CO(2)](-)), and bis(trifluoromethylsulfonyl)amide ([NTf(2)](-)). The same strategy in our previous work (J. Phys. Chem. B 2010, 114, 4572) was used to parametrize the force field, in which the effective atom partial charges are fitted by the electrostatic potential surface (ESP) of ion pair dimers to account for the overall effects of polarization in ILs. The total charges (absolute values) on the cation/anion are in the range of 0.64-0.75, which are rescaled to 0.8 for all kinds of ions by a compromise between transferability and accuracy. Extensive molecular dynamics (MD) simulations were performed over a wide range of temperatures to validate the force field, especially on the enthalpies of vaporization (ΔH(vap)) and transport properties, including the self-diffusion coefficient and shear viscosity. The liquid densities were predicted very well for all of the ILs studied in this work with typical deviations of less than 1%. The simulated ΔH(vap) at 298 and 500 K are also in good agreement with the measured values by different experimental methods, with a slight overestimation of about 5 kJ/mol. The influence of ΔC(p) (the difference between the molar heat capacity at constant pressure of the gas and that of liquid) on the calculation of ΔH(vap) is also discussed. The transport coefficients were estimated by the equilibrium MD method using 20-60 ns trajectories to improve the sampling. The proposed force field gives a good description of the self-diffusion coefficients and shear viscosities, which is comparable to the recently developed polarizable force field. Although slightly lower dynamics is found in simulations by our force field, the order of magnitude of the self-diffusion coefficient and viscosity are reproduced for all the ILs very well over a wide temperature range. The largest underestimation of the self-diffusion coefficient is about one-third of the experimental values, while the largest overestimation of the viscosity is about two times the experimental values.