Simultaneous improvement of martensitic phase transition and ductility in Cu-doped and/or alloyed all-d-metal Ni2MnTa Heusler compounds.

Ductile all-d-metal Heusler compounds with tunable martensitic phase transition are desirable for solid-state refrigeration applications. The theoretical investigations on martensitic phase transition and ductile characteristics of novel all-d-metal Ni2MnTa were conducted in this study. By introducing Cu atoms into Ni2MnTa, the improvement of martensitic phase transition and ductility was simultaneously realized. It was found that the substitution of Cu with more valence electrons for Ni, Mn, and Ta atoms resulted in an increase in metallic bonding. Owing to the enhanced metallic bonding, elastic moduli were softened, which improved shear deformation ability and contributed to tailoring the austenite phase stability. Hopefully, the anticipated martensitic phase transition can be tailored to an optimal temperature range. Moreover, the increased metallicity accounted for the simultaneously enhanced ductility. The enhanced metallic characteristics also resulted in contracting lattice sizes of Cu-doped and/or alloyed Ni2MnTa compounds due to the volume effect. Metallic bonding may be described as the mechanism for simultaneously controlling the phase stability and enhancing ductile properties in Cu-doped and/or alloyed Ni2MnTa compounds. The calculated energy, electronic structure, and elastic parameters further verified the occurrence of martensitic phase transition in Cu-doped and/or alloyed Ni2MnTa compounds. Current results suggest that chemical bonding could be employed as a significant tuning factor in the exploration of multipurpose Heusler compounds.

In situ Hg2+ improved the peroxidase-like activity and triggered "ON" the oxidase-like activity of yolk-shell Co3S4 microspheres for the detection of Hg2.

Exploring highly active nanozymes is an important task to realize the real-time detection of some heavy metal ions in water. In this work, yolk-shell Co3S4 microspheres have been verified to possess excellent peroxidase-like activity, which can be further improved by adding Hg2+. Very interestingly, Hg2+ can trigger "ON" the oxidase-like activity of Co3S4 microspheres. The dual peroxidase-/oxidase-like activity of the yolk-shell Co3S4 microspheres is evaluated by using the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB). Furthermore, comprehensive studies verify that the enhanced peroxidase-like activity, together with the "ON" oxidase-like activity of the yolk-shell Co3S4 microspheres, is attributed to the in situ generation of HgS on the surface of Co3S4 microspheres and then the release of more active sites. Importantly, the in situ generated HgS on the surface of Co3S4 microspheres can form a heterojunction, which also accelerates the catalytic process. During the catalytic reaction, some active species (O2- and h+) can be detected by ESR. Thus, a colorimetric sensing platform based on Hg2+-triggered signal amplification has been successfully constructed, which can be validated by the detection of Hg2+ residue in environmental water.

N,N-dicarboxymethyl Perylene-diimide-modified CdV2O6 Nanorods for Colorimetric Sensing of H2O2 and Pyrogallol.

The peroxidase-like activity of CdV2O6 nanorods has been considerably improved by modification with N, N-dicarboxymethyl perylene-diimide (PDI) as a photosensitizer. The peroxidase-like behaviors are evaluated by virtue of the colorless chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB), which is fast changed into blue oxTMB in the presence of H2O2 in only 90 s. PDI-CdV2O6 exhibits high stability at elevated temperatures and PDI-CdV2O6 retains more than 70% of its catalytic activity over a wide range of 15 to 60 °C. The catalytic mechanism of PDI-CdV2O6 is ascribed to the synergistic interaction between PDI and CdV2O6 and the generation of •O2- radicals. Based on the enhanced peroxidase-like activity of PDI-CdV2O6, a selective colorimetric sensor has been constructed for H2O2 and pyrogallol (PG) with detection limits of 36.5 µM and 0.179 µM, respectively. The feasibility of the proposed sensing platform has been validated by detecting H2O2 in milk and pyrogallol in tap water.

Zinc pyrovanadate nanorods with excellent peroxidase-like activity at physiological pH for the colorimetric assay of H2O2 and epinephrine.

Exploring highly active peroxidase mimics at physiological pH is important for the construction of efficient and convenient colorimetric sensing platforms for detecting small biomolecules. In this work, prepared zinc pyrovanadate (Zn3V2O7(OH)2·2H2O) nanorods exhibit excellent peroxidase-like activity, which is verified by the fast oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into a blue product (oxTMB) by H2O2 at physiological pH (pH = 7) in 2 min. In addition, the catalytic behaviors of Zn3V2O7(OH)2·2H2O as a peroxidase-like nanozyme conform to the Michaelis-Menten equation. Scavenger experiments prove that the catalytic activity of Zn3V2O7(OH)2·2H2O is ascribed to ˙O2- radicals generated in the process of catalysis. Based on the peroxidase-like activity of the Zn3V2O7(OH)2·2H2O nanozyme, a fast and convenient colorimetric sensor has been constructed to detect H2O2 and epinephrine (EP) under physiological pH. The detection limit of EP is as low as 0.26 µM. In addition, the feasibility of the proposed sensor has been validated to detect H2O2 in milk and EP in serum.

Enhanced peroxidase-like activity of 2(3), 9(10), 16(17), 23(24)-octamethoxyphthalocyanine modified CoFe LDH for a sensor array for reducing substances with catechol structure.

Improving the catalytic activity of artificial nanozymes to realize the real-time detection of small molecules becomes an important task. Herein, a highly active nanozyme, 2(3), 9(10), 16(17), 23(24)-octamethoxyphthalocyanine (Pc(OH)8) modified CoFe LDH microspheres (Pc(OH)8-CoFe LDH) have been prepared by the two-step hydrothermal method. The 3,3',5,5'-tetramylbenzidine (TMB), a chromogenic substrate, was fast oxidized into blue oxTMB by H2O2 in the presence of Pc(OH)8-CoFe LDH, indicating that Pc(OH)8-CoFe LDH possesses high peroxidase-like activity rather than pure CoFe LDH. The enhancement peroxidase-like activity of the Pc(OH)8-CoFe LDH is ascribed to the synergistic action between Pc(OH)8 and CoFe LDH. Experimental results of radical scavenger and fluorescence probe verify that superoxide radical (•O2-) plays an important role during the catalytic reaction. Interestingly, the absorption intensity of reaction system has been enhanced largely, due to adding of the reducing substances containing catechol structure. Based on this, the three reducing substances (dopamine, procyanidin B2, catechins) containing catechol structure were distinguished from other reducing substances without catechol structure. Thus, a colorimetric array has been constructed using reaction time as the sensing element to realize the sensitive and selective recognition of catechol structures at a certain concentration.

PBA-MoS2 nanoboxes with enhanced peroxidase activity for constructing a colorimetric sensor array for reducing substances containing the catechol structure.

Some nanoperoxidase-based colorimetric sensors have been used to detect only one molecule at a time. Thus, the simultaneous detection of various molecules coexisting in the same system is a great challenge. In this work, an excellent nanoperoxidase, nickel cobalt Prussian blue analogue-MoS2 nanoboxes (PBA-MoS2), have been successfully prepared by the hydrothermal method and used to construct a colorimetric sensing array to determine a series of reductive substances containing the catechol structure (such as catechol, epinephrine hydrochloride, procyanidin, caffeic acid and dopamine hydrochloride). The excellent peroxidase-like activity of PBA-MoS2 is verified by the chromogenic reaction of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2 in 2 min. The catalytic mechanism of PBA-MoS2 is attributed to generated reactive species including holes (h+) and superoxide radicals (˙O2-) in the process of catalysis. The fast economic H2O2 colorimetric sensing array has been constructed based on the PBA-MoS2 nanoperoxidase. Due to the presence of different reducing substances, the catalytic oxidation of TMB can be restricted to different extents, accompanied by blue colour changes to varying degrees. Therefore, on combining PBA-MoS2 nanoperoxidase with H2O2 and TMB, five reductive substances can be quantitatively distinguished by linear discriminant analysis (LDA) at the 2 mM level.

Calcium ion biorecovery from industrial wastewater by Bacillus amyloliquefaciens DMS6.

Calcium ions in industrial wastewater needs to be removed to prevent the production of limescale, which can have negative consequences. Biomineralization has become the focus due to its lower costs than traditional methods of remediation. In this study, calcium ions were bio-precipitated under the action of free and immobilized Bacillus amyloliquefaciens DMS6 bacteria, and the calcium ion removal efficiency was also compared. The results show that it only needed 3 days to decrease the calcium ion concentration to an ideal level of 76-116 mg/L under the action of DMS6 bacteria immobilized by activated carbon fiber, with calcium ion removal ratios reaching 99%-95% by the 7th day. DMS6 bacteria immobilized by activated carbon fiber were superior to free bacteria and bacteria immobilized by sodium alginate in calcium ion removal. Calcium ions are biomineralized into calcite, Mg-rich calcite, aragonite and monohydrocalcite with abundant organic functional groups, 4 types of secondary protein structures, amino acids, phospholipids, negative stable carbon isotope δ13CPDB values (-16.68‰ to-17.25‰) and negatively charged biomineral surface. Calcium ions were diffused into cells and took part in the intracellular biomineralization of monohydrocalcite, also facilitating calcium ion removal. The formation of intracellular monohydrocalcite has rarely been reported. This study demonstrates an economic and environmentally friendly method to remove calcium ions from industrial wastewater.

A lipopeptide biosurfactant from Bacillus sp. Lv13 and their combined effects on biodesulfurization of dibenzothiophene.

The process of using biodesulfurization (BDS) to remove sulfur compounds in petroleum has limitations such as low efficiency and low mass transfer. Therefore, it is important to study the combined effects of biosurfactant and the strain on BDS. A thermophilic desulfurization strain, Bacillus sp. Lv13, was isolated from the oilfield and used to produce biosurfactant (BS). The strain was identified as Bacillus licheniformis, a moderate thermophilic bacterium. Its BS was identified as lipopeptide using thin-layer chromatography (TLC), gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FT-IR). The emulsification efficiency after 24 h (E 24) and critical micelle concentration (CMC) were determined to be 46.93% and 30 mg L-1, respectively. The combined effects of biosurfactant and the strain on BDS was confirmed using the Gibbs assay, GC-MS and BaCl2 test. Results showed that the yield of 2-hydroxybiphenyl (2-HBP) from dibenzothiophene significantly increased after the addition of lipopeptide into the reaction system. This could be illustrated by the stabilization of emulsion, lower CMC value, higher mass transfer rate with the addition of lipopeptide, and the enhancement in the capacity of BDS as well as the catalytic ability of the microbial cell.

Ab initio investigation of competing antiferromagnetic structures in low Si-content FeMn(PSi) alloy.

The antiferromagnetic structures of a low Si-content FeMn(PSi) alloy were investigated by first principles calculations. One possible antiferromagnetic structure in supercell along the c-axis was revealed in FeMnP0.75Si0.25 alloy. It was found that atomic disorder occupation between Fe atom on 3f and Mn atoms on 3g sites is responsible for the formation of antiferromagnetic structures. Furthermore the magnetic competition and the coupling between possible AFM supercells along the c and a-axis can promote a non-collinear antiferromagnetic structure. These theoretical investigations help to deeply understand the magnetic order in FeMn(PSi) alloys and benefit to explore the potential magnetocaloric materials in Fe2P-type alloys.

Stable magnetostructural coupling with tunable magnetoresponsive effects in hexagonal ferromagnets.

The magnetostructural coupling between the structural and the magnetic transition has a crucial role in magnetoresponsive effects in a martensitic-transition system. A combination of various magnetoresponsive effects based on this coupling may facilitate the multifunctional applications of a host material. Here we demonstrate the feasibility of obtaining a stable magnetostructural coupling over a broad temperature window from 350 to 70 K, in combination with tunable magnetoresponsive effects, in MnNiGe:Fe alloys. The alloy exhibits a magnetic-field-induced martensitic transition from paramagnetic austenite to ferromagnetic martensite. The results indicate that stable magnetostructural coupling is accessible in hexagonal phase-transition systems to attain the magnetoresponsive effects with broad tunability.