2D and 3D double perovskite with dimensionality-dependent optoelectronic properties: first-principle study on Cs2AgBiBr6and Cs4AgBiBr8.

Recently, the effect of dimensional control on the optoelectronic performance of two-dimensional (2D)/three-dimensional (3D) single perovskites has been confirmed. However, how the dimensional change affects the photoelectric properties of 2D/3D all-inorganic double perovskites remains unclear. In this study, we present a detailed theoretical research on a comparison between the optoelectronic properties of 3D all-inorganic double perovskite Cs2AgBiBr6and recently reported 2D all-inorganic double perovskite Cs4AgBiBr8with Ruddlesden-Popper (RP) structure based on density functional theory calculations. The results demonstrate the charge carrier mobility and absorption coefficients in the visible spectrum of Cs4AgBiBr8(2D) is poorer than Cs2AgBiBr6(3D). Moreover, the value of exciton-binding energy for 2D RP all-inorganic double perovskite Cs4AgBiBr8(720 meV) is 3 times larger than that of 3D all-inorganic double perovskite Cs2AgBiBr6(240 meV). Our works indicate that Cs4AgBiBr8(2D) is a promising material for luminescent device, while Cs2AgBiBr6(3D) may be suitable for photovoltaic applications. This study provides a theoretical guidance for the understanding of 2D RP all-inorganic double perovskite with potential applications in photo-luminescent devices.

[Effects of combined addition of organic materials with zinc fertilizer on zinc availability and transformation in calcareous soil]. / æœ‰æœºç‰©æ–™ä¸Žé”Œè‚¥é æ–½å¯¹çŸ³ç°æ€§åœŸå£¤é”Œæœ‰æ•ˆæ€§åŠå½¢æ€è½¬åŒ–çš„å½±å“.

To investigate the changes of Zn availability and transformation in calcareous soil, orga-nic materials (maize straw, biofertilizer, fulvic acids, and chicken manure) were thoroughly mixed with the soils amended with Zn fertilizer in the nylon net bags and buried in a field. Results showed that compared with control (neither Zn nor organic materials), Zn fertilizer alone and combined addition with organic materials significantly increased soil total Zn concentration (7.2%-13.8%) and DTPA-Zn concentration (2.1-2.8 folds). For the Zn amended treatments, the contributions of organic amendments to soil total Zn and DTPA-Zn concentration decreased in the order of chicken manure > biofertilizer > maize straw > fulvic acids. The highest conversion rate of exogenous Zn into DTPA-Zn occurred in the treatments with straw and biofertilizer. In comparison with single Zn application, combination of Zn fertilizer with organic materials increased soil organic matter and stimulated more Zn weakly bound to organic matter, enhanced mobility factor and reduced distribution index of Zn in soil. The differences in soil Zn availability and transformation among the combinations of Zn fertilizer and organic materials were likely linked to the inherent properties of organic materials such as maturity degree and Zn content. Considering the environment safety and cost reduction, combining Zn fertilizer and straw return was the best practice to enhance Zn availability in the Zn-deficient calcareous soil, although its contribution to Zn availability was less than the combination of biofertilizer or chicken manure with Zn fertilizer.

[Separation of Chlorophyll Fluorescence from Scattering Light of Algal Water Based on the Polarization Technique].

Once chlorophyll molecules within the planktonic algae cells absorb light energy, they will release energy in the form of chlorophyll fluorescence emission. The elastic scattering light of particles in water is partially polarized, while chlorophyll fluorescence is unpolarized, so we can use the properties to separate the fluorescence signal from total scattering spectra for further retrieval the concentration of chlorophyll. But for coastal waters, the approach feasibility is still unclear. Based on this, we conducted the experiment in laboratory to analyze the influence of different concentrations of inorganic particles (IOP) and chlorophyll on the fluorescence extraction using polarization discrimination technique. The results indicate that, for algae water with different concentrations of IOP, the fluorescence peak will decrease while the concentration increase, but the retrieval result is still reliable when the concentration up to 300 mg·L(-1). For algae water with different concentrations of chlorophyll, the concentration of chlorophyll more higher, the efficiency of extracted fluorescence using polarization method is better, for common water, this approach can still work. The study proves that the polarization method is also applicable for complex water; it is of great importance for further detecting the concentration of chlorophyll in coastal waters using remote sensing.

Application of ZnSO4 or Zn-EDTA fertilizer to a calcareous soil: Zn diffusion in soil and its uptake by wheat plants.

BACKGROUND: The objective of this study was to compare the efficiency of two Zn sources and two application methods on (i) Zn diffusion from fertilized soil to unfertilized soil, (ii) grain Zn concentration and (iii) grain Zn bio-accessibility to humans. In the laboratory experiment, 20 mg ZnSO4 or 4 mg Zn-EDTA were applied to a 5 mm and 1 mm-wide space in the soil in the half-cell technique. In the greenhouse experiment, Zn-ZnSO4 or Zn-ethylenediaminetetraacetic acid (Zn-EDTA) was mixed or banded with the soil at a rate of 20 or 4 mg Zn kg(-1) , respectively. RESULTS: The results from the diffusion experiment showed that both the extractability and the diffusion coefficient of Zn were higher when Zn fertilizer was applied to a 1 mm-wide space than when it was applied to a 5 mm-wide space. Zn-EDTA had a greater diffusion distance than ZnSO4 . The greenhouse experiment showed that the mixed ZnSO4 application and the Zn-EDTA application (both mixed and banded) treatments significantly increased grain Zn concentration and bio-accessibility. The positive effect of Zn-EDTA on grain Zn concentrations and bio-accessibility was greater than that of ZnSO4 . The banded application reduced the effectiveness of ZnSO4 but not of Zn-EDTA. CONCLUSION: It was concluded that Zn-EDTA was a better Zn source than ZnSO4 for increasing grain Zn content in a potentially Zn-deficient calcareous soil.

[Near ultraviolet absorption spectral properties of chromophoric dissolved organic matter in the north area of Yellow Sea].

Chromophoric dissolved organic matter (CDOM) near ultraviolet absorption spectra contains CDOM molecular structure, composition and other important physical and chemical information. Based on the measured data of CDOM absorption coefficient in March 2009 in the north area of Yellow Sea, the present paper analyzed near ultraviolet absorption spectral properties of CDOM. The results showed that due to the impact of near-shore terrigenous input, the composition of CDOM is quite different in the north area of Yellow Sea, and this area is a typical case II water; fitted slope with specific range of spectral band and absorption coefficient at specific band can indicate the relative size of CDOM molecular weight, correlation between spectral slope of the Sg,275-300), Sg,300-350, Sg,350-400 and Sg,250-275 and the relative size of CDOM molecular weight indicative parameter M increases in turn and the highest is up to 0.95. Correlation between a(g)(lambda) and M value increases gradually with the increase in wavelength, and the highest is up to 0.92 at 400 nm; being correlated or not between spectral slope and absorption coefficient is decided by the fitting-band wavelength range for the spectra slope and the wavelength for absorption coefficient. Correlation between Sg,275-300 and a(g)(400) is the largest, up to 0.87.