The creation of heterostructures based on non-precious metals with platinum-like hydrogen evolution reaction (HER) performance remains a challenge for hydrogen fuel technologies. Motivated by the fascinating properties of heterostructures, we establish here an effective approach to fabricate the heterostructured M−N−Ni 9 S 8 /Nb 2 O 5 ( M = Co, Fe, or Cu) catalysts using spatially separated Ni 9 S 8 nanosheet/Nb 2 O 5 nanobelts that are coupled with nitrogen (N) and metal atoms. Due to its improved intrinsic activity, interface-rich structure, abundant active sites, and large surface area the Co−N−Ni 9 S 8 /Nb 2 O 5 heterostructure achieved a low acidic HER overpotential of −171 mV at −10 mA cm −2 , thereby performing better than existing heterostructures. Moreover, for the alkaline HER, the Cu−N−Ni 9 S 8 /Nb 2 O 5 heterostructure required a low overpotential of −109 mV at −10 mA cm −2 , which is close to the performance of Pt/C catalyst. Density functional theory (DFT) predictions indicate that the local charge distribution and electronic properties at the heterointerface of Ni 9 S 8 /Nb 2 O 5 can be significantly modulated by co-doping of metals with N atoms, resulting in optimal adsorption energy and reduced water dissociation barrier; thereby accelerating the acidic and alkaline HER activity. This work, therefore, provides a new design principle to create advanced heterostructured catalysts.
A sensitive and efficient magnetic amino modified multi-walled carbon nanotubes (m-MWCNT-NH2)-based magnetic dispersive solid-phase extraction (m-dSPE) coupled with hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) strategy is reported for the simultaneous determination of 13 paralytic shellfish toxins (PSTs) in bivalve mollusks. The samples were extracted twice with 1% acetic acid and purified using optimized m-dSPE procedures with Fe3O4 coated MWCNT-NH2 composites as magnetic adsorbents. The adsorbed PSTs on the m-MWCNT-NH2 adsorbents were separated using a Ni-coated neodymium magnet and subsequently eluted with 2 mL water–acetonitrile–acetic acid (80:20:1, v/v/v) and analyzed by HILIC-MS/MS. The correlation coefficients (r) of the targeted toxins obtained in matrix-matched external standard curves were from 0.997 to 0.999. The PSTs were acquired and quantified in the multiple reaction-monitoring mode and the limits of detection and quantitation in bivalve mollusks were 1.10 to 4.51 μg/kg and 3.67 to 13.5 μg/kg, respectively. Spiked recoveries at three concentrations in negative samples were from 73.4% to 92.5% with precision less than 10.6%. The method validation was in accordance with 2002/657/EC guidelines and method application in commercial bivalve mollusk samples. The developed method was rapid, convenient and economical for the determination of the targeted toxins.
Background The emergence of carbapenem and colistin co-resistant Escherichia coli poses a huge challenge to infection control. The purpose of this study was to clarify the mechanism of the carbapenems and colistin co-resistance in E. coli strains.Methods Antimicrobial susceptibility test was carried out by agar dilution methods and colistin resistance was confirmed by broth microdilution methods. Whole genome sequencing was carried out, and resistance genes, sequence types and virulence genes of carbapenems and colistin co-resistance E. coli isolates were analyzed.Results The results showed that among the 176 carbapenem-resistant Enterobacteriaceae strains, 5 multidrug resistant E. coli strains exhibiting coresistance to carbapenem and colistin. The main mechanism of 5 E. coli strains in this study was generating carbapenem. Four E. coli strains were mcr-positive, while one mcr-negative strain had a new MgrB mutation. The blaNDM-5, blaCTX-M-65, blaOXA-10, blaTEM-1 and mcr-1.1 genes were simultaneously detected in E. coli 20IR1127 strain belonging to ST156 lineage. Other antimicrobial resistance genes encoding aminoglycosides-, sulfonamide-, chloramphenicol-, tetracyclines- and macrolides resistance were also detected.Conclusion The main mechanisms of carbapenem and colistin resistance were encoded by blaNDM and mcr1.1, meanwhile mgrB mutations also contribute to colistin resistance. To our knowledge, this study is the first to report of E. coli ST156 strain in which the blaNDM-5, blaCTX-M-65, blaOXA-10, blaTEM-1 and mcr1.1 genes coexist. In addition, there is also an E. coli ST457 strain, which carries blaTEM-1, blaNDM-9, blaCTX-M-199 and is positive for mcr1.1 gene.
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