Epidemiological and molecular investigations of Salmonella isolated from duck farms in southwest and around area of Shandong, China.

Salmonella is a zoonotic pathogen posing a serious risk to the farming industry and public health due to food animals serving as reservoirs for future contamination and spread of Salmonella. The present study is designed to monitor the contamination status of Salmonella in duck farms and the main control points during breeding. 160 strains of duck-derived Salmonella were isolated from the 736 samples (cloacal swabs, feces, water, feed, soil, and air and dead duck embryos) collected in southwest Shandong Province and the province's surrounding area. The percentage of Salmonella-positive samples collected was 21.74% (160/736), and the greatest prevalence from duck embryo samples (40.00%, 36/90). These Salmonella were classified into 23 serotypes depending on their O and H antigens, in which S. Typhimurium (30.15%), S. Kottbus (13.97%) and S. Enteritidis (10.29%) were the prevailing serotypes. Subsequently, the molecular subtyping was done. Clustered regularly interspaced short palindromic repeats (CRISPR) analysis showed that 41 strains of S. Typhimurium and 14 strains of S. Enteritidis were classified into 13 and 3 genotypes, respectively. 19 S. Kottbus isolates from different sources featured ST1546, ST198, ST321, and ST1690 by multilocus sequence typing (MLST) analysis, among which ST1546 belongs to S. Kottbus was a new ST. The minimum spanning tree analysis based on the two CRISPR loci and seven MLST loci from all S. Typhimurium, S. Enteritidis and S. Kottbus isolates revealed that duck embryos, feed and water were key control points to the spread of Salmonella along the breeding chain. Meanwhile, the emergence of S. Kottbus in duck flocks was considered a potential public health hazard.

Halogen bonds regulating structures and optical properties of hybrid iodobismuthate perovskites.

Successive structural transformations were observed in a methanolic solution containing 4-iodo-1-methylpyridin-1-ium iodide (IPyMe·I) and bismuth iodide (BiI3). When kept in the solution, the amorphous solid (P_1) obtained immediately on mixing would transform to needle crystals (C_1) in hours, which would convert to prismatic crystals (C_2) in around 2 days. In the presence of hydroiodic acid, the hydrothermal reaction of IPyMe·I and BiI3 also gave rise to C_2, and crystals of C_2 in this solution would transform to a third crystalline product C_3 in ca. 3 days. X-ray single crystal diffraction experiments show C_1 containing one-dimensional {BiI4-}n chains, C_2 as a binuclear Bi2I93- structure, and C_3 consisting of a monomeric BiI63- unit, all with IPyMe+ as counter cations. Halogen bonds exist between IPyMe+ and the iodobismuthate, which may play key roles in the structural transformation. By introducing halogen bonding, the hybrids demonstrate excellent water-resistance. A thermal-induced reversible colour change from yellow to dark red occurred from 100 K to 450 K for all three hybrids, in which lattice expansion over the temperature range may be a reason for the thermochromism. The bandgaps derived from the UV-vis diffusion reflectance for the three complexes were 1.80 eV for C_1, 1.84 eV for C_2 and 2.00 eV for C_3. DTF computations followed by electron density topological analysis were applied to explain the structure-optical property relationship for complexes of diverse iodobismuthate types but the same counter cation. It was found that the nature of the Bi-I bonds rather than the dimensionality of the inorganic iodobismuthates is mainly responsible for the light absorption of the materials.

Interface Catalysts of Ni/Co2N for Hydrogen Electrochemistry.

The development of active, durable, and nonprecious electrocatalysts for hydrogen electrochemistry is highly desirable but challenging. In this work, we design and fabricate a novel interface catalyst of Ni and Co2N (Ni/Co2N) for hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). The Ni/Co2N interfacial catalysts not only achieve a current density of -10.0 mA cm-2 with an overpotential of 16.2 mV for HER but also provide a HOR current density of 2.35 mA cm-2 at 0.1 V vs reversible hydrogen electrode (RHE). Furthermore, the electrode couple made of the Ni/Co2N interfacial catalysts requires only a cell voltage of 1.57 V to gain a current density of 10 mA cm-2 for overall water splitting. Hybridizations in the three elements of Ni-3d, N-2p, and Co-3d result in charge transfer in the interfacial junction of the Ni and Co2N materials. Our density functional theory calculations show that both the interfacial N and Co sites of Ni/Co2N prefer to hydrogen adsorption in the hydrogen catalytic activities. This study provides a new approach for the construction of multifunctional catalysts for hydrogen electrochemistry.

Ascorbate-Promoted Surface Iron Cycle for Efficient Heterogeneous Fenton Alachlor Degradation with Hematite Nanocrystals.

This study reports the H2O2 activation with different hematite nanocrystals and ascorbate ions for the herbicide alachlor degradation at pH 5. We found that hematite nanoplates (HNPs) exposed with {001} facets exhibited better catalytic performance than hematite nanocubes (HNCs) exposed with {012} facets, which was attributed to the formation of inner-sphere iron-ascorbate complexes on the hematite facets. The 3-fold undercoordination Fe cations of {001} facet favors the formation of inner-sphere iron-ascorbate complexes, while the 5-fold undercoordination Fe cations of {012} facet has stereo-hindrance effect, disfavoring the complex formation. The surface area normalized alachlor degradation rate constant (23.3 × 10-4 min-1 L m-2) of HNPs-ascorbate Fenton system was about 2.6 times that (9.1 × 10-4 min-1 L m-2) of HNCs-ascorbate counterpart. Meanwhile, the 89.0% of dechlorination and 30.0% of denitrification in the HNPs-ascorbate Fenton system were also significantly higher than those (60.9% and 13.1%) of the HNCs-ascorbate one. More importantly, the reductive dissolution of hematite by ascorbate was strongly coupled with the subsequent H2O2 decomposition by surface bound ferrous ions through surface iron cycle on the hematite facets in the hematite-ascorbate Fenton systems. This coupling could significantly inhibit the conversion of surface bound ferrous ions to dissolved ones, and thus account for the stability of hematite nanocrystals. This work sheds light on the internal relationship between iron geochemical cycling and contaminants degradation, and also inspires us to utilize surface iron cycle of widely existent hematite for environmental remediation.

Facet-Dependent Cr(VI) Adsorption of Hematite Nanocrystals.

In this study, the adsorption process of Cr(VI) on the hematite facets was systematically investigated with synchrotron-based Cr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, density-functional theory calculation, and surface complexation models. Structural model fitting of EXAFS spectroscopy suggested that the interatomic distances of Cr-Fe were, respectively, 3.61 Å for the chromate coordinated hematite nanoplates with exposed {001} facets, 3.60 and 3.30 Å for the chromate coordinated hematite nanorods with exposed {001} and {110} facets, which were characteristic of inner-sphere complexation. In situ ATR-FTIR spectroscopy analysis confirmed the presence of two inner-sphere surface complexes with C3ν and C2ν symmetry, while the C3ν and C2ν species were assigned to monodentate and bidentate inner-sphere surface complexes with average Cr-Fe interatomic distances of 3.60 and 3.30 Å, respectively. On the basis of these experimental and theoretical results, we concluded that HCrO4(-) as dominated Cr(VI) species was adsorbed on {001} and {110} facets in inner-sphere monodentate mononuclear and bidentate binuclear configurations, respectively. Moreover, the Cr(VI) adsorption performance of hematite facets was strongly dependent on the chromate complexes formed on the hematite facets.

Protocatechuic Acid Promoted Alachlor Degradation in Fe(III)/H2O2 Fenton System.

In this study, we demonstrate that protocatechuic acid (PCA) can significantly promote the alachlor degradation in the Fe(III)/H2O2 Fenton oxidation system. It was found that the addition of protocatechuic acid could increase the alachlor degradation rate by 10 000 times in this Fenton oxidation system at pH = 3.6. This dramatic enhancement of alachlor degradation was attributed to the complexing and reduction abilities of protocatechuic ligand, which could form stable complexes with ferric ions to prevent their precipitation and also accelerate the Fe(III)/Fe(II) cycle to enhance the ·OH generation. Meanwhile, the Fe(III)/PCA/H2O2 system could also work well at near natural pH even in the case of PCA concentration as low as 0.1 mmol/L. More importantly, both alachlor and PCA could be effectively mineralized in this Fenton system, suggesting the environmental benignity of PCA/Fe(III)/H2O2 Fenton system. We employed gas chromatography-mass spectrometry to identify the degradation intermediates of alachlor and then proposed a possible alachlor degradation mechanism in this novel Fenton oxidation system. This study provides an efficient way to remove chloroacetanilide herbicides, and also shed new insight into the possible roles of widely existed phenolic acids in the conversion and the mineralization of organic contaminants in natural aquatic environment.

Insight into core-shell dependent anoxic Cr(VI) removal with Fe@Fe2O3 nanowires: indispensable role of surface bound Fe(II).

In this study, we investigated the anoxic Cr(VI) removal with core-shell Fe@Fe2O3 nanowires. It was found the surface area normalized Cr(VI) removal rate constants of Fe@Fe2O3 nanowires first increased with increasing the iron oxide shell thickness and then decreased, suggesting that Fe@Fe2O3 nanowires possessed an interesting core-shell structure dependent Cr(VI) removal property. Meanwhile, the Cr(VI) removal efficiency was positively correlated to the amount of surface bound Fe(II). This result revealed that the core-shell structure dependent Cr(VI) removal property of Fe@Fe2O3 nanowires was mainly attributed to the reduction of Cr(VI) by the surface bound Fe(II) besides the reduction of Cr(VI) adsorbed on the iron oxide shell via the electrons transferred from the iron core. The indispensable role of surface bound Fe(II) was confirmed by Tafel polarization and high-resolution X-ray photoelectron spectroscopic depth profiles analyses. X-ray diffraction patterns and scanning electron microscope images of the fresh and used Fe@Fe2O3 nanowires revealed the formation of Fe(III)/Cr(III)/Cr(VI) composite oxides during the anoxic Cr(VI) removal process. This study sheds a deep insight into the anoxic Cr(VI) removal mechanism of core-shell Fe@Fe2O3 nanowires and also provides an efficient Cr(VI) removal method.