Carbon-Promoted Pt-Single Atoms Anchored on RuO2 Nanorods to Boost Electrochemical Hydrogen Evolution.

While efficient for electrochemical hydrogen evolution reaction (HER), Pt is limited by its cost and rarity. Traditional Pt catalysts and Pt single-atom (aPt) catalysts (Pt-SACs) face challenges in maintaining kinetically favorable HER pathways (Volmer-Tafel) at ultralow Pt loadings. Herein, carbon-promoted aPts were deposited on RuO2 without the addition of reductants. aPts confined on carbon-supported RuO2 nanorods (aPt/RuO2NR/Carbon) promoted "inter-aPts" Tafel. aPt/RuO2NR/Carbon is the Pt-SAC that retained underpotentially deposited H; additionally, its HER onset overpotential was "negative". The aPt/RuO2NR/Carbon exhibited 260-fold higher Pt mass activity (imPt)/turnover frequency (TOF) (522.7 A mg-1/528.4 s-1) than that of commercial Pt/C (1.9 A mg-1/1.9 s-1). In an ultralow Pt loading (0.19 µg cm-2), the HER rate-determining step maintained Volmer-Tafel and the Pt utilization efficiency was 100.3%.

Comparison of Reference-Based Assembly and De Novo Assembly for Bacterial Plasmid Reconstruction and AMR Gene Localization in Salmonella enterica Serovar Schwarzengrund Isolates.

It is well established that plasmids carrying multiple antimicrobial resistance (AMR) genes can be easily transferred among bacterial isolates by horizontal gene transfer. Previous studies have shown that a combination of short- and long-read approaches is effective in reconstructing accurate plasmids. However, high-quality Illumina short reads mapped onto the long reads in the context of an AMR hybrid monitoring strategy have not yet been explored. Hence, this study aimed to improve the reconstruction of plasmids, including the localization of AMR genes, using the above-described parameters on whole-genome sequencing (WGS) results. To the best of our knowledge, this study is the first to use S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) to confirm the number and sizes of plasmids detected by in silico-based predictions in Salmonella strains. Our results showed that de novo assembly did not detect the number of bacterial plasmids more accurately than reference-based assembly did. As this new hybrid mapping strategy surpassed de novo assembly in bacterial reconstruction, it was further used to identify the presence and genomic location of AMR genes among three Salmonella enterica serovar Schwarzengrund isolates. The AMR genes identified in the bacterial chromosome among the three Salmonella enterica serovar Schwarzengrund isolates included: AAC(3)-IV, AAC(6')-Iy, aadA2, APH(4)-Ia, cmlA1, golS, mdsA, mdsB, mdsC, mdtK, qacH, sdiA, sul2, sul3, and TEM-1 genes. Moreover, the presence of TEM-1, AAC(3)-IV, aadA2, APH(4)-Ia, cmlA1, dfrA12, floR, sul1, sul3, and tet(A) genes found within three IncFIB plasmids and one IncX1 plasmid highlight their possible transmission into the environment, which is a public health risk. In conclusion, the generated data using this new hybrid mapping strategy will contribute to the improvement of AMR monitoring and support the risk assessment of AMR dissemination.

Prevalence and risk factors for Salmonella spp. contamination of slaughtered chickens in Taiwan.

The present study was designed to estimate the prevalence of Salmonella contamination in Taiwanese broilers at slaughter and to identify risk factors associated with the presence of Salmonella in processed batches of broilers. Carcass rinse samples from 362 batches of broilers were collected from 45 chicken abattoirs in Taiwan between February 2013 and November 2014. Univariate analyses and multivariable logistic regression analyses were conducted to identify putative risk factors for contamination. Salmonella was detected in 32.6 % (95 % CI: 30.4-34.8) of individual broilers and 56.4 % (95 % CI: 51.1-61.5) of the sampled batches. The multivariable logistic regression model identified season (July to November) (OR = 1.95; 95 % CI: 1.2-3.2) as increasing the risk of infection. Abattoirs in the southern region (Taichung and Kaohsiung) (OR = 0.45; 95 % CI: 0.3-0.8); batches scalded for > 90 s (OR = 0.2; 95 % CI: 0.1-0.3) and batches of commercial white broilers (BR) (OR = 0.21; 95 % CI: 0.1-0.4) all had a decreased risk of contamination compared to abattoirs from the northern region, scalding < 90 s and Taiwan native chickens (TNC), respectively. This study highlights the influence of environmental conditions and poultry breed on the risk of Salmonella contamination of chickens during slaughter.

Detection of chicken carcasses contaminated with Salmonella enterica serovar in the abattoir environment of Taiwan.

Although a nation-wide microbiological screening program of chicken carcasses after chilling in Taiwanese chicken abattoirs has been undertaken since 2006, little is known regarding the potential sources of the Salmonella during the slaughter process. The present study provides data on the detection and serotypes of Salmonella isolated from broilers during processing and from the environment in six abattoirs in Taiwan. Overall, Salmonella were detected in 156 of 622 samples (25.1%; 95% CI: 21.7-28.7) collected. The prevalence of Salmonella varied between sampling sites with 5.8, 17.6, 31.3 and 35.5% of cloacal swabs, environmental samples prior to processing, environmental samples during processing and carcass rinse fluid, respectively, being positive (χ2 = 51.3, p < 0.0001). A total of 15 serotypes were identified from the 156 Salmonella isolates with S. Albany (41.7%) S. Schwarzengrund (20.5%), S. Kentucky (12.8%) and S. Tennessee (5.1%) being the most commonly isolated serotypes. Characterization of 156 isolates by Pulse Field Gel Electrophoresis (PFGE) identified 50 PFGE types. Typing confirmed the presence of the same PFGE type at multiple stages during processing including plucking, evisceration, chilling and post-chilling. The abattoir environment and intestinal contents of chickens are important sources of Salmonella in broiler chicken abattoirs, with the same PFGE types detected at different stages of processing both before and during slaughtering. It is concluded that Salmonella isolates present in the environment and intestinal contents of processed birds survived in the abattoir environment resulting in subsequent carcass contamination along the processing chain including plucking, evisceration, chilling and post-chilling.

Pseudo-atomic-scale metals well-dispersed on nano-carbons as ultra-low metal loading oxygen-evolving electrocatalysts.

Solving challenges for the scaling-up, high metal loadings and low turnover frequency (TOF, defined as mol O2 per mol metal per second), of FeNi catalysts in water electrolysis, we report the first discovery of pH tunable tannic acid single molecular layer formed on nano-sized carbons (NCs), which promotes the gram-production of pseudo-atomic-scale FeNi oxyhydroxide nanoclusters well-dispersed on NCs. It results in ultra-low metal loading (0.42 µg cm-2) and remarkably large TOF of 14.03 s-1 for the oxygen evolution reaction, which is three orders of magnitude higher than that of state-of-the-art FeNi catalysts. A "volcano"-shaped activity trend in specific activity and TOF was found to depend on the Fe content in FeNi oxyhydroxide. The micro-morphologies from the atomic-level exposure of active sites and surface spectra analyses confirm the model of synergism between Ni and Fe centers.

High performance layer-by-layer Pt3Ni(Pt-skin)-modified Pd/C for the oxygen reduction reaction.

Bimetallic Pt-Ni with Pt on the outermost layer and an innermost layer enriched in Ni, referred to as Pt3Ni(Pt-skin), is a promising configuration of an electrocatalyst for the oxygen reduction reaction (ORR) in fuel cells. We prepare a core (Pd)/shell (Pt3Ni(Pt-skin)) catalyst (Pt3Ni(Pt-skin)/Pd/C) from Zn underpotential deposition (UPD) on a Ni UPD modified Pd/C catalyst, facilitating Pt atomic layer-by-layer growth on the Ni surface through the galvanic replacement process. Pt3Ni(Pt-skin)/Pd/C shows the best ORR performance, with a Pt specific activity of 16.7 mA cm-2 and Pt mass activity of 14.2 A mgPt-1, which are 90- and 156- fold improvements over commercial Pt/C catalysts. The Pt3Ni(Pt-skin) structure effectively inhibits Ni leaching to improve the durability in two accelerated durability test modes mimicking the catalyst lifetime and start-up/shut-down cycles.

Electrochemically Identifying Degradation Pathways of Carbon-Supported Pt Catalysts Assists in Designing Highly Durable Catalysts.

Supported Pt catalysts are considered highly efficient in many applications because of their unique catalytic properties. Their poor durability hampers their use in practical applications, particularly in novel energy-conversion devices such as fuel cells. A facile electrochemical procedure that combines the evaluation of the electrochemical surface area with a breakthrough in direct electrochemical quantification of the Pt content was utilized. Catalytic performance-related factors and kinetics of Pt nanoparticle (Ptnano) growth on a carbon substrate were probed under high-temperature annealing and ambient-temperature potential polarization, respectively. Apart from the Pt dissolution/redeposition pathway, we demonstrated that the crystal migration/coalescence pathway in catalyst degradation could not be ignored at ambient temperature. We report the enhanced durability and long-term activity of carbon-supported Pt catalysts, where the Ptnano surface was partially encapsulated by nonspecific noble metal clusters; inhibition of the migration/coalescence pathway and effective exposure of Ptnano surface active sites led to such enhancements.

Electrochemical Quantifying, Counting, and Sizing Supported Pt Nanoparticles in Real Time.

Knowledge about controlling the activity and catalyst degradation mechanisms of platinum-based catalysts has been limited by technical impediments. Here we show a facile in situ electrochemical procedure for the simultaneous assessment of the mean size and number of Pt nanoparticles (Ptnano) from an evaluation of the electrochemically surface area (ECSA) and the breakthrough in electrochemical quantification of the Pt content. The electrochemical procedure enables in situ characterization of the factors related to the catalytic activity and monitoring of the changes in Pt content during an accelerated durability test. Surprisingly, the ECSA loss was observed only from the growth of Ptnano mean size even without any Pt loss over the potential range, 0.6-1.0 V vs RHE, at room temperature. These results strongly support the long-standing debate that if the coarsening of Ptnano from crystal migration and coalescence can occur in low temperature fuel cells.

A facile Pt catalyst regeneration process significantly improves the catalytic activity of Pt-organic composites for the O2 reduction reaction.

Combination of the "nano-size" effect and Cl(-) complexation ability causes massive electrodissolution of Pt under acidic conditions to promote the regeneration of Pt-organic composites and to significantly improve the catalytic performance of the O2 reduction reaction.

Potential probiotic attributes of a new strain of Bacillus coagulans CGMCC 9951 isolated from healthy piglet feces.

A new strain of Bacillus coagulans CGMCC 9551, which has a broad range of antibacterial activities against six main pathogenic bacteria including Escherichia coli O8, Staphylococcus aureus, Salmonella enterica subsp. enterica serovar enteritidis, Streptococcus suis, Listeria monocytogenes and Pasteurella multocida, was isolated from healthy piglet feces. In adhesion assay, the isolate exhibited a stronger adhesion to pig intestinal mucus than that of B. subtilis JT143 and L. acidophilus LY24 respectively isolated from BioPlus(®)2B and FloraFIT(®) Probiotics (P < 0.05). The adhesion activity reached 44.5 ± 3.2, 48.9 ± 2.6, 42.6 ± 3.3 and 37.6 ± 2.4% to jejunum, ileum, transverse colon and sigmoid colon, separately. The survival rate of B. coagulans CGMCC 9551 was reduced by only 20% at 4 h exposure under 0.9% w/v bile salt. The strain was fully resistant to pH 2 for 2 h with 90.1 ± 3.5% survival and susceptible to 15 antibiotics commonly used in veterinary medicine. Additionally, the bacteria showed amylase, protease and cellulase activities. The safety assessment demonstrated the lack of toxicity potential in B. coagulans CGMCC 9551 by ligated rabbit ileal loop assay, acute and subchronic toxicity test. These results implied that that the new strain of B. coagulans CGMCC 9951 isolated from healthy piglet feces has promising probiotic characteristics and offers desirable opportunities for its successful commercialization as one excellent candidate probiotic.

EDTA assisted highly selective detection of As(3+) on Au nanoparticle modified glassy carbon electrodes: facile in situ electrochemical characterization of Au nanoparticles.

A facile electrochemical characterization technique of Au nanoparticles (AuNPs) developed by Wang et al. ( Wang, Y.; Laborda, E.; Salter, C.; Crossley, A.; Compton, R. G. Analyst 2012 , 137 , 4693 - 4697 ) was used to track the variation in the particle size and density of AuNPs in situ and to assist in optimizing the conditions of analysis and catalysis. In this method, the combination of total surface area determined by Pb underpotential deposition (UPD) and the amount of Au obtained by anodic stripping of Au in HCl solution was used to evaluate the average diameter of AuNPs and the number of particles on the electrode. The detection of As(3+) in aqueous solution by a AuNP modified glassy carbon electrode (Aunano@GCE) using the electrochemical characterization technique was examined. The AuNPs with a uniform shape and size, deposited onto the GCEs using multiple-scan cyclic voltammetry (MSCV), were suitable for the electrochemical evaluation. The calibration curve for the detection of As(3+) had a dynamic range of 0.1-15.0 µg L(-1) (from 1.30 to 200 nM, y = 0.21x (in µA L µg(-1)) + 0.01 (R(2) = 0.999)) and showed a sensitivity of 0.21 µA L µg(-1) (16.15 µA µM(-1)). A detection limit as low as 0.0025 µg L(-1) (32.5 pM) was achieved. The chelating agent ethylenediaminetetraacetate (EDTA) selectively chelated with the interfering metal ions and effectively inhibited the interfering ions from competing with the ion of interest (As(3+)), in the preconcentration process. The presence of EDTA effectively eliminated interference from several metal ions, especially Cu(2+) and Hg(2+). This method was validated by analyzing the As(3+) content in real water samples.

Cu+ assisted preparation of mesoporous Pt-organic composites for highly selective and sensitive non-enzymatic glucose sensing.

A Nafion (NF) ionomer was used as a potential new template or scaffold for mesoporous metal composites because intrinsic meso-structures have been found in NF. A facile EC catalytic process, involving a Cu+-mediated Pt reduction (CMPR), was successfully used as a major source of Pt nanoparticles (nPts). We found that Cu+ assisted nPts formation and self-assembly in the micro-framework of NF ionomers applied to prepare Pt-nanoparticle-embedded Nafion composites (NF(Ptnano)) exhibiting two different nanostructure characteristics including a microelectrode array with low Pt loading and mesoporous Pt with high Pt loading. The NF(Ptnano) composites exhibited high catalytic activity and sensing ability without the need for time-consuming template-removing processes. The application of nonenzymatic glucose detection served as a probe to track the micro-morphological variation in NF(Ptnano) composites. It was demonstrated that NF(Ptnano) composites exhibited ultra-high sensitivity and selectivity to glucose sensing.

Gold-nanoparticle-embedded nafion composite modified on glassy carbon electrode for highly selective detection of arsenic(III).

A Cu(I)-ion-mediating Au reduction is proposed for preparing an Au-nanoparticle-embedded nafion (NF(Aunano)) composite. The NF(Aunano) composite consisted of highly dense, well-dispersed, and protecting-agent-free Au nanocrystals with a narrow particle size (4.8±0.1 nm) distribution. The NF(Aunano) composite was characterized as a function of composition and particle size distribution using powder X-ray diffraction, transmission electron microscopy, and electrochemical measurements. It was demonstrated that the NF(Aunano) composite provided high activity in the redox behavior of As(III), and was used as a potential sensing material with low Au loading for As(III) detection. An NF(Aunano)-composite-modified electrode is easy to prepare and regenerate. The dynamic range of a calibration curve from 0.1 to 12.0 µg L(-1) (from 1.3 to 160 nM), y=23.98x (in µA µM(-1))+0.42 (R(2)=0.999), showed linear behavior with a slope of 23.98 µA µM(-1). The detection limit is as low as 0.047 µg L(-1) (0.63 nM). The chelating agent ethylenediaminetetraacetate (EDTA) can selectively chelate with interfering metal ions, forming bulky complexes or bulky anions that are excluded from the NF film. The presence of EDTA effectively eliminated interference from several metal ions, particularly Cu(II) and Hg(II), which are generally considered to be major interferents in the electroanalysis of As(III). This method was applicable to As(III) analysis in three real water samples, namely groundwater, lake, and drinking waters.

Four new lignans from Schisandra sphenanthera.

Three new 7,8-secolignans, schisandlignans A-C (1, 2, and 4), one new dibenzocyclooctadiene lignan, schisandlignan D (5), together with nine known lignans 3',4'-dimethoxybenzoic acid (3″,4″-dimethoxyphenyl)-2-methyl-3-oxobutyl ester (3), gomisin J (6), rubrisandrin A(1b) (7), interiotherin B (8), schisantherin D (9), ( - )-machilusin (10), ganschisandrine (11), henricine A (12), and (+)-1-hydroxy pinoresinol (13), were isolated from the rattan of Schisandra sphenanthera. Their structures were determined by analysis of 1D and 2D NMR spectroscopic data.

Application of a nanoporous gold electrode for the sensitive detection of copper via mercury-free anodic stripping voltammetry.

This paper describes how a new mercury-free alternative electrode material, nanoporous gold (NPG), was applied to improve the performance of detecting trace metals in stripping voltammetry. The NPG electrode was obtained by dealloying Zn from Au(x)Zn(1-x) in a 40-60 mol% zinc chloride-1-ethyl-3-methylimidazolium chloride (ZnCl(2)-EMIC) ionic liquid. To prevent electrode fouling from surfactant adsorption, the short carbon-chain organothiol (3-mercaptopropyl)sulfonate (MPS) was selected to modify the NPG electrode through the formation of a self-assembled monolayer (SAM). The MPS-modified NPG (MPS@NPG) electrode not only significantly enhanced the sensitivity in detecting Cu(2+) but also effectively prevented electrode surface fouling from surfactant adsorption. The electrode is easy to prepare and can be readily renewed after each stripping experiment. The dynamic range of calibration curve, y = 58.76x (in microA microM(-1)) + 3.90 (R(2) = 0.999), showed very linear behavior with slope of 58.76 microA microM(-1) (0.1-5 microg L(-1)). The detection limit is as low as 0.002 microg L(-1) (0.031 nM). Non-ionic, anionic, and cationic surfactants were found to have no effect on Cu(2+) detection when using the MPS@NPG electrode as a sensing probe. This method was applied to determining the Cu(2+) in a reference material and three real water samples. The results agreed satisfactorily with the certified values.

Facile preparation of an ultrathin nickel film coated nanoporous gold electrode with the unique catalytic activity to oxidation of glucose.

A facile approach to prepare a Ni coated nanoporous gold (Ni@NPG) electrode with the combination of a UPD monolayer and galvanic displacement is described, which not only conserves the 3-D nanostructure of the NPG electrode but presents unique catalytic activity to the electrode surface to significantly enhance the performance of glucose detection.

Silver UPD ultra-thin film modified nanoporous gold electrode with applications in the electrochemical detection of chloride.

Nanoporous noble metals are usually expected to exhibit much higher surface areas than smooth ones, making them of particular importance in many electrochemical applications. This paper describes a simple electrochemical method to modify a nanoporous Au (NPG) surface by using an under potentially deposited (UPD) Ag adlayer. The NPG electrode was obtained by the dealloying of Zn from Au(x)Zn(1-x) in a 40-60mol% zinc chloride-1-ethyl-3-methylimidazolium chloride (ZnCl(2)-EMIC) ionic liquid. The Ag UPD modified nanoporous gold (NPG/Ag(UPD)) electrode possessed dual properties, including an intrinsic high surface area from the nanoporous structure and the characteristics of the Ag UPD adlayer. The potential utility of using NPG/Ag(UPD) for sensors was demonstrated by its excellent sensitivity and selectivity in the electrochemical determination of chloride ions. An atomic scale metal monolayer obtained in the UPD process was selected as a sensing agent. The long-term storability and operational stability of the electrode were strongly demonstrated. Specifically, two couples of redox waves at approximately 552mV and approximately 272mV, respectively, were observed in the cyclic voltammograms (CVs) of the NPG/Ag(UPD) after the adsorption of chloride ions. The first couple of redox waves was related to the UPD and silver stripping and the second couple of redox waves was induced by the adsorption of Cl(-). The Cl(-) adsorption process on the NPG/Ag(UPD) electrode followed the transient Langmuir adsorption kinetic model. The ratio of the integrated charges for these two anodic stripping peaks was selectively used to determine dilute chloride ion levels. The calibration curve was linear in the Cl(-) concentration range of 0.5-30.0muM.

Multiresidue analysis of beta-agonists in pork by coupling polymer monolith microextraction to electrospray quadrupole time-of-flight mass spectrometry.

A novel method of polymer monolith microextraction (PMME) using poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith combined with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF MS) was developed for the rapid and sensitive determination of beta-agonists in pork samples. The conditions of PMME were optimized for the improvement of extraction efficiency and reduction of the matrix interferences from pork. Under the optimal condition, the eluate solution allowed direct analysis by mass spectrometry. In the positive ion mode and in the multiple reaction monitoring (MRM) mode, the limits of detection (LODs) for beta-agonists were found to be 0.08 ng/g (clenbuterol, CLB), 0.18 ng/g (salbutamol, SBTM) and 0.26 ng/g (terbutaline, TBTL) in pork, respectively, with good inter- and intra-day precisions (2-10% for CLB, 11-23% for SBTM and 4-16% for TBTL). The proposed PMME/ESI-QTOF MS method was successfully applied to the determination of beta-agonist residues in thirteen real samples, and the positive samples were confirmed according to the identification points (IPs) system defined by Commission Decision 2002/657/EC. To investigate the matrix effect, the proposed method was compared with PMME-HPLC/ESI-QTOF MS and the slight decrease in sensitivity of PMME/ESI-QTOF MS was ascribed to the inter-analyte ion suppression.