SrMoO 4 was studied under compression up to 25 GPa by angle-dispersive xray diffraction. A phase transition was observed from the scheelite-structured ambient phase to a monoclinic fergusonite phase at 12.2(9) GPa with cell parameters a = 5.265 (9) Å, b = 11.191(9) Å, c = 5.195 (5) Å, and β = 90.9°, Z = 4 at 13.1 GPa. There is no significant volume collapse at the phase transition. No additional phase transitions were observed and on release of pressure the initial phase is recovered, implying that the observed structural modifications are reversible. The reported transition appeared to be a ferroelastic second-order transformation producing a structure that is a monoclinic distortion of the low-pressure phase and was previously observed in compounds isostructural to SrMoO 4 . A possible mechanism for the transition is proposed and its character is discussed in terms of the present data and the Landau theory. Finally, the EOS is reported and the anisotropic compressibility of the studied crystal is discussed in terms of the compression of the Sr-O and Mo-O bonds.
A natural wheat straw was used as adsorbent for removal of copper and methylene blue (MB) from aqueous solution. A batch system was applied to study the behavior of Cu2+ and MB adsorption in single and binary systems on wheat straw. In the single systems, there was no significant difference in the quantity of MB adsorbed onto wheat straw within a pH range of 4.0 to 10.0. But for Cu2+, the optimal pH is about 5. Kinetic studies indicate that Cu2+ and MB adsorption on the wheat straw follows the Elovich equation. The Cu2+ adsorption isotherm follows the Langmuir and Redlich−Peterson models, while MB adsorption follows the Redlich−Peterson isotherm. The adsorption capacities of Cu2+ and MB at 273 K and pH 5 are (7.05 and 60.66) mg·g−1, respectively. In the binary system, Cu2+ and MB exhibited competitive adsorption. The adsorption of Cu2+ or MB is considerably reduced with an increasing concentration of the other. The quantity of Cu2+ adsorbed is more strongly influenced by MB due to the higher affinity of wheat straw for the latter. As wheat straw is easily obtained and cheap, it will be promising for removal of metal ions and dyes.
The fabrication of two-dimensional (2D) metal−organic frameworks (MOFs) and Prussian blue analogues (PBAs) combines the advantages of 2D materials, MOFs and PBAs, resolving the poor electronic conductivity and slow diffusion of MOF materials for electrochemical applications. In this work, 2D leaflike zeolitic imidazolate frameworks (Co-ZIF and Fe-ZIF) as sacrificial templates are in situ converted into PBAs, realizing the successful fabrication of PBA/ZIF nanocomposites on nickel foam (NF), namely, CoCo-PBA/Co-ZIF/ NF, FeFe-PBA/Fe-ZIF/NF, CoFe-PBA/Co-ZIF/NF, and Fe/CoCo-PBA/Co-ZIF/NF. Such fabrication can effectively reduce transfer resistance and greatly enhance electron-and masstransfer efficiency due to the electrochemically active PBA particles and NF substrate. These fabricated electrodes as multifunctional sensors achieve highly selective and sensitive glucose and H 2 O 2 biosensing with a very wide detective linear range, extremely low limit of detection (LOD), and good stability. Among them, CoFe-PBA/Co-ZIF/NF exhibits the best sensing performance with a very wide linear range from 1.4 μM to 1.5 mM, a high sensitivity of 5270 μA mM −1 cm −2 , a low LOD of 0.02 μM (S/N = 3), and remarkable stability and selectivity toward glucose. What is more, it can realize excellent detection of glucose in human serum, demonstrating its practical applications. Furthermore, this material as a multifunctional electrochemical sensor also manifests superior detection performance against hydrogen peroxide with a wide linear range of 0.2−6.0 mM, a high sensitivity of 196 μA mM −1 cm −2 , and a low limit of detection of 1.08 nM (S/N = 3). The sensing mechanism for enhanced performance for glucose and H 2 O 2 is discussed and proved by experiments in detail.
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