Gut-brain bidirectional determination in regulating the residual feed intake of small-sized meat ducks.

The gut-brain axis is essential in maintaining the homeostasis of neuronal system, endocrine system, and intestinal microbiota in both the afferent and efferent directions. This axis is considered to be a key mechanism that regulates feed efficiency (FE). This study aimed to investigate the regulatory mechanisms of gut-brain axis-related genes on the residual feed intake (RFI) in H-strain small-sized meat ducks. A total of 500 ducks with similar initial BW (635.2 ± 15.1 g) were selected and reared in the same experimental facility until slaughter at 42 d of age. RFI was calculated from the average daily gain (ADG), average daily feed intake (ADFI), and metabolic body weight (MBW0.75). Thirty high-RFI (H-RFI) and 30 low-RFI (L-RFI) birds were selected for further evaluation of growth performance, carcass characteristics, and blood biochemical parameter measurements. Six L-RFI and 6 H-RFI birds were then subjected to hypothalamic transcriptomic and cecal microbial sequencing analyses. Results indicated that L-RFI birds exhibited lower production performance (ADFI, FCR, and RFI) and blood biochemical indices (total cholesterol and ghrelin content) compared with H-RFI birds (P < 0.05). Gene expression differed significantly between the L-RFI and H-RFI birds, with 70 upregulated and 50 downregulated genes. The bacterial communities of L-RFI birds showed higher abundances of Bacteroides, Bifidobacterium, and Lactococcus, and lower abundances of Erysipelatoclostridium, Parasutterella, Fournierella, and Blautia compared with H-RFI birds (P < 0.05). Interactive analysis revealed bacterial communities associated with FE were significantly correlated with hypothalamic genes (P < 0.05), for example, Bacteroides was positively correlated with DGKH and LIPT2, while negatively correlated with CAPN9, GABRD, and PDE1A. Bifidobacterium showed significant correlations with ATP2A3, CALHM6, and TMEM121B. Overall, RFI was a crucial indicator of FE, regulated by interactions between brain gene expression and gut microbiota through cAMP signaling, neuroactive ligand-receptor interaction, and calcium signaling pathways. Notably, increased expression of hypothalamic genes and abundance of carbohydrate-utilization microbiota in L-RFI meat ducks improved FE by enhancing energy metabolism and volatile fatty acids absorption.

Structural simulation and selective inhibitor discovery study for histone demethylases KDM4E/6B from a computational perspective.

The methylation and demethylation of lysine and arginine side chains are fundamental processes in gene regulation and disease development. Histone lysine methylation, controlled by histone lysine methyltransferases (KMTs) and histone lysine demethylases (KDMs), plays a vital role in maintaining cellular homeostasis and has been implicated in diseases such as cancer and aging. This study focuses on two members of the lysine demethylase (KDM) family, KDM4E and KDM6B, which are significant in gene regulation and disease pathogenesis. KDM4E demonstrates selectivity for gene regulation, particularly concerning cancer, while KDM6B is implicated in inflammation and cancer. The study utilizes specific inhibitors, DA-24905 and GSK-J1, showcasing their exceptional selectivity for KDM4E and KDM6B, respectively. Employing an array of computational simulations, including sequence alignment, molecular docking, dynamics simulations, and free energy calculations, we conclude that although the binding cavities of KDM4E and KDM6B has high similarity, there are still some different crucial amino acid residues, indicating diverse binding forms between protein and ligands. Various interaction predominates when proteins are bound to different ligands, which also has significant effect on selective inhibition. These findings provide insights into potential therapeutic strategies for diseases by selectively targeting these KDM members.

Natural Killer Cells Do Not Attenuate a Mouse-Adapted SARS-CoV-2-Induced Disease in Rag2-/- Mice.

This study investigates the roles of T, B, and Natural Killer (NK) cells in the pathogenesis of severe COVID-19, utilizing mouse-adapted SARS-CoV-2-MA30 (MA30). To evaluate this MA30 mouse model, we characterized MA30-infected C57BL/6 mice (B6) and compared them with SARS-CoV-2-WA1 (an original SARS-CoV-2 strain) infected K18-human ACE2 (K18-hACE2) mice. We found that the infected B6 mice developed severe peribronchial inflammation and rapid severe pulmonary edema, but less lung interstitial inflammation than the infected K18-hACE2 mice. These pathological findings recapitulate some pathological changes seen in severe COVID-19 patients. Using this MA30-infected mouse model, we further demonstrate that T and/or B cells are essential in mounting an effective immune response against SARS-CoV-2. This was evident as Rag2-/- showed heightened vulnerability to infection and inhibited viral clearance. Conversely, the depletion of NK cells did not significantly alter the disease course in Rag2-/- mice, underscoring the minimal role of NK cells in the acute phase of MA30-induced disease. Together, our results indicate that T and/or B cells, but not NK cells, mitigate MA30-induced disease in mice and the infected mouse model can be used for dissecting the pathogenesis and immunology of severe COVID-19.

Investigating the impact of elevated urinary trace elements on non-alcoholic fatty liver disease using vibration-controlled transient elastography.

Introduction: Non-alcoholic fatty liver disease (NAFLD) is a global public health concern. However, limited data are available on urinary trace elements and NAFLD caused by various exposure factors. This study aimed to investigate the relationship between the presence of 16 trace elements in urine and NAFLD using data from the National Health and Nutrition Examination Survey (NHANES). Methods: By utilizing the NHANES data from 2017 to 2018, 1613 participants who fulfilled the research criteria were identified from the initial pool of 2979 participants with available urine trace element detection data. Among them, 706 individuals had been diagnosed with NAFLD based on a coefficient of attenuation parameter (CAP) value of at least 274 db/m, determined using vibration-controlled transient elastography (VCTE); whereas the remaining 907 participants were classified as non-NAFLD. The data obtained were used to construct univariate and multivariate logistic regression models and restricted cubic spline models (RCS) analyses. Results: The presence of arsenic, iodine, barium, cesium, molybdenum, lead, tin, and tungsten in the urine of individuals with NAFLD showed a positive correlation with the likelihood of developing NAFLD. The risk of NAFLD had a non-linear dose-dependent relationship with urinary iodine, molybdenum, barium, and cesium. NAFLD was also associated with elevated levels of barium and cesium in urine, which were identified as significant risk factors. Conclusion: These findings suggest a positive association between exposure to trace elements in the urine and the risk of NAFLD. Specifically, urinary barium and cesium appeared to have the greatest impact on the risk of NAFLD. These results provide novel insights into the diagnosis and treatment of NAFLD.

Elucidating the Role of Reduction Kinetics in the Phase-Controlled Growth on Preformed Nanocrystal Seeds: A Case Study of Ru.

This study demonstrates the crucial role of reduction kinetics in phase-controlled synthesis of noble-metal nanocrystals using Ru nanocrystals as a case study. We found that the reduction kinetics played a more important role than the templating effect from the preformed seed in dictating the crystal structure of the deposited overlayers despite their intertwined effects on successful epitaxial growth. By employing two different polyols, a series of Ru nanocrystals with tunable sizes of 3-7 nm and distinct patterns of crystal phase were synthesized by incorporating different types of Ru seeds. Notably, the use of ethylene glycol and triethylene glycol consistently resulted in the formation of Ru shell in natural hexagonal close-packed (hcp) and metastable face-centered cubic (fcc) phases, respectively, regardless of the size and phase of the seed. Quantitative measurements and theoretical calculations suggested that this trend was a manifestation of the different reduction kinetics associated with the precursor and the chosen polyol, which, in turn, affected the reduction pathway (solution versus surface) and packing sequence of the deposited Ru atoms. This work not only underscores the essential role of reduction kinetics in controlling the packing of atoms and thus the phase taken by Ru nanocrystals but also suggests a potential extension to other noble-metal systems.

Characterization of natural co-infection with goose astrovirus genotypes I and II in gout affected goslings.

RESEARCH HIGHLIGHTS: Urate tophi were found in the kidneys, liver, spleen and lungs.IFA confirmed the co-expression of GoAstV-I and II antigens in the same kidney.

COVID-19 and influenza infections mediate distinct pulmonary cellular and transcriptomic changes.

SARS-CoV-2 infection can cause persistent respiratory sequelae. However, the underlying mechanisms remain unclear. Here we report that sub-lethally infected K18-human ACE2 mice show patchy pneumonia associated with histiocytic inflammation and collagen deposition at 21 and 45 days post infection (DPI). Transcriptomic analyses revealed that compared to influenza-infected mice, SARS-CoV-2-infected mice had reduced interferon-gamma/alpha responses at 4 DPI and failed to induce keratin 5 (Krt5) at 6 DPI in lung, a marker of nascent pulmonary progenitor cells. Histologically, influenza- but not SARS-CoV-2-infected mice showed extensive Krt5+ "pods" structure co-stained with stem cell markers Trp63/NGFR proliferated in the pulmonary consolidation area at both 7 and 14 DPI, with regression at 21 DPI. These Krt5+ "pods" structures were not observed in the lungs of SARS-CoV-2-infected humans or nonhuman primates. These results suggest that SARS-CoV-2 infection fails to induce nascent Krt5+ cell proliferation in consolidated regions, leading to incomplete repair of the injured lung.

High-sensitivity optical fiber probe for simultaneous measurement of chloride ions and temperature.

A fiber optic probe for the simultaneous measurement of chloride ions and temperature is presented. The Ag/alginate composite film is used as the reflective surface of the Fabry-Perot interferometer (FPI) and is a sensitive film for the adsorption of chloride ions. The experimental results show that the Fabry-Perot (FP) response sensitivity is approximately 1.4689 nm/µM as the chloride ion concentration changes from 1 to 9 µM, but the fiber Bragg grating (FBG) is insensitive to chloride ions. When the temperature is changed from 35°C to 80°C, the response sensitivities of the FP and the FBG are about 0.7 and 0.01115 nm/°C, respectively.

Association of overweight, obesity and risk of urinary incontinence in middle-aged and older women: a meta epidemiology study.

Aims: The aim of this meta-analysis is to evaluate the potential correlation between obesity and overweight, and the vulnerability to urinary incontinence (UI) in women aged middle-aged and above. Methods: We searched PubMed, Cochrane Library, and Embase for observational studies published between the inception of the databases and April 25, 2023. A fixed-effects model was used when the P>0.1 and the I2 ≤ 50%. In cases where I2 ≥ 50% (indicating significant heterogeneity), a random-effects model was applied. For the purpose of evaluating publication bias, a funnel plot and Egger's test were used. Stata 14.0 was used for all statistical analyses. Findings: This meta-analysis includes 16 observational studies, covering29,618 individuals. The pooled analysis shows that being overweight(25 kg/m2≤BMI<30kg/m2) in middle-aged and elderly women is more likely to develop UI (OR=1.27; 95% CI: 1.17-1.37; I2 = 51.8%, P=0.013). Middle-aged and elderly women with obesity(30 kg/m2≤BMI<35 kg/m2) are significantly more likely to develop UI (OR=1.60; 95% CI: 1.42-1.81; I2 = 71.8%, P=0.000). In addition, the results indicated a higher probability of UI in middle-aged and older women with obesity class II (BMI≥35 kg/m2) (OR=1.85; 95% CI: 1.59-2.16; I2 = 48.1%, P=0.103). In subgroup analysis, there is no direct relationship between the obesity in middle-aged and elderly women and an increased risk of stress urinary incontinence (SUI) (OR=1.31; 95% CI: 0.99-1.74; I2 = 63.7%, P=0.011). In middle-aged and elderly women with obesity are more likely to develop urgent urinary incontinence (UUI) (OR=2.11; 95% CI: 1.54-2.89; I2 = 80.2%, P=0.000). Conclusion: In this meta-analysis, overweight and obesity are associated with an increased risk of UI in middle-aged and elderly women. Obesity and overweight are independent risk factors for UI, as demonstrated by this study. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023421986.

Bimetallic core-shell nanocrystals: opportunities and challenges.

With mastery over the colloidal synthesis of monometallic nanocrystals, a combination of two distinct metals with intricate architectures has emerged as a new direction of innovation. Among the diverse architectures, the one with a core-shell structure has attracted the most scientific endeavors owing to its merits of high controllability and variability. Along with the new hopes arising from the addition of a shell composed of a different metal, there comes unexpected complications for the surface composition, hindering both structural understanding and application performance. In this Focus article, we present a brief overview of the opportunities provided by the bimetallic core-shell nanocrystals, followed by a discussion of the technical challenge to elucidate the true composition of the outermost surface. Some of the promising solutions are then highlighted as well, aiming to inspire future efforts toward this frontier of research.

Growth performance, carcass traits, meat quality, and blood variables of small-sized meat ducks with different feed efficiency phenotypes.

The study investigated the effects of feed efficiency (residual feed intake, RFI and residual intake and gain, RIG) on the production performance of small-sized meat ducks. Ninety ducks with intermediate and extreme (high and low) RFI values were selected from 1,083 male ducks of similar body weight, and the 3 groups were then redivided according to RIG. For both efficiency measures, the feed conversion ratio (FCR) and average daily feed intake (ADFI) of efficient ducks were significantly lower than those of inefficient ducks (P < 0.05), while the residual body weight gain (RG) was significantly higher in efficient ducks (P < 0.05). Inefficient-RFI animals showed greater skin fat yield (P < 0.05), but no other differences in carcass traits were observed (P > 0.05). RIG had positive effects on the pH1 value of the breast muscle (P < 0.05), but feed efficiency did not affect the other meat quality traits (P > 0.05). With regard to blood biochemical parameters, efficient ducks had significantly lower triglycerides (TG) (P < 0.05). Correlation analysis demonstrated that RFI was positively correlated with average daily feed intake and feed conversion ratio (P < 0.05), while RIG exhibited a strong negative correlation with both (P < 0.05). The average daily body weight gain was positively correlated with RIG (P < 0.05). RIG had a positive effect on the pH1 value of the breast muscle (P < 0.05). Furthermore, triglyceride and high-density lipoprotein cholesterol levels correlated with both efficiency classifications (P < 0.05). Overall, the efficiency measures did not affect the carcass and meat quality of small-sized meat ducks but could identify ducks with lower feed consumption and fast growth.

Galvanic Replacement Synthesis of Metal Nanostructures: Bridging the Gap between Chemical and Electrochemical Approaches.

ConspectusGalvanic replacement synthesis involves oxidation and dissolution of atoms from a substrate while the salt precursor to another material with a higher reduction potential is reduced and deposited on the substrate. The driving force or spontaneity of such a synthesis comes from the difference in reduction potential between the redox pairs involved. Both bulk and micro/nanostructured materials have been explored as substrates for galvanic replacement synthesis. The use of micro/nanostructured materials can significantly increase the surface area, offering immediate advantages over the conventional electrosynthesis. The micro/nanostructured materials can also be intimately mixed with the salt precursor in a solution phase, resembling the setting of a typical chemical synthesis. The reduced material tends to be directly deposited on the surface of the substrate, just like the situation in an electrosynthesis. Different from an electrosynthesis where the two electrodes are spatially separated by an electrolyte solution, the cathodes and anodes are situated on the same surface, albeit at different sites, even for a micro/nanostructured substrate. Since the oxidation and dissolution reactions occur at sites different from those for reduction and deposition reactions, one can control the growth pattern of the newly deposited atoms on the same surface of a substrate to access nanostructured materials with diverse and controllable compositions, shapes, and morphologies in a single step. Galvanic replacement synthesis has been successfully applied to different types of substrates, including those made of crystalline and amorphous materials, as well as metallic and nonmetallic materials. Depending on the substrate involved, the deposited material can take different nucleation and growth patterns, resulting in diverse but well-controlled nanomaterials sought for a variety of studies and applications.In this Account, we recapitulate our efforts over the past two decades in fabricating metal nanostructures for a broad range of applications by leveraging the unique capability of galvanic replacement synthesis. We begin with a brief introduction to the fundamentals of galvanic replacement between metal nanocrystals and salt precursors, followed by a discussion of the roles played by surface capping agents in achieving site-selected carving and deposition for the fabrication of various bimetallic nanostructures. Two examples based on the Ag-Au and Pd-Pt systems are selected to illustrate the concept and mechanism. We then highlight our recent work on the galvanic replacement synthesis involving nonmetallic substrates, with a focus on the protocol, mechanistic understanding, and experimental control for the fabrication of Au- and Pt-based nanostructures with tunable morphologies. Finally, we showcase the unique properties and applications of nanostructured materials derived from galvanic replacement reactions for biomedicine and catalysis. We also offer some perspectives on the challenges and opportunities in this emerging field of research.

Acute hyperglycemia compromises the responses of choroidal vessels using swept-source optical coherence tomography during dark and light adaptations.

Purpose: To clarify the effects of acute hyperglycemia on the responses of choroidal structural components and vascularity index during light modulation in healthy participants using techniques including image binarization and artificial intelligence (AI) segmentation based on swept-source optical coherence tomography (SS-OCT). Methods: Twenty-four eyes of 24 healthy participants were imaged at different stages after ambient light, 40 min of dark adaptation, and 5 min of light adaptation in two imaging sessions: control and after receiving 75 g of oral glucose solution. The choroidal structural parameters, including luminal volume (LV), stromal volume (SV), total choroidal volume (TCV), and choroidal vascularity index (CVI) within a 6 mm area were determined using a custom algorithm based on image binarization and AI segmentation of SS-OCT. These measurements were compared among the conditions after adjusting for axial length, age to identify the differences. Results: In the dark, CVI decreased (-0.36 ± 0.09%) significantly in acute hyperglycemia compared to the control condition. During the transition to ambient light, there was an increasing trend in the choroidal parameters compared with the control experiment. However, only TCV (0.38 ± 0.17 mm3) and LV (0.27 ± 0.10 mm3) showed a significant increase at the time point of 5 min after ambient light. Conclusion: Analysis of choroidal structural parameters and CVI based on SS-OCT images is a potentially powerful method to objectively reflect subtle changes in neurovascular coupling between the choroid and photoreceptor during dark adaptation.

Controlling the Nucleation and Growth of Au on a-Se Nanospheres to Enhance Their Cellular Uptake and Cytotoxicity.

We report a method to experimentally control the heterogeneous nucleation and growth of Au nanoparticles on the surface of amorphous Se (a-Se) nanospheres. When a AuIII precursor is added into a colloidal suspension of a-Se nanospheres, galvanic replacement occurs between them and the resultant Au0 atoms then heterogeneously nucleate and grow from the surface of the a-Se nanospheres. As a unique feature of this system, the Au0 atoms can only be produced on the surface of the a-Se nanospheres in the nucleation stage. Once Au nuclei are formed on the surface at the very beginning of a synthesis, they will serve as the preferential sites for further deposition of Au0 atoms, making it possible to control the number of Au nanoparticles on each nanosphere and the morphology of the final product. The dependence of the initial reduction rate on the pH can be used to obtain Se-Au hybrid nanoparticles containing one, two, three, and multiple Au nanoparticles on the surface of each a-Se nanosphere. The presence of Au patches on the hybrid nanoparticles offers an experimental handle to optimize the ligand distribution for the achievement of enhanced cellular uptake and cytotoxicity for the a-Se nanospheres.

Strigolactones positively regulate Verticillium wilt resistance in cotton via crosstalk with other hormones.

Verticillium wilt caused by Verticillium dahliae is a serious vascular disease in cotton (Gossypium spp.). V. dahliae induces the expression of the CAROTENOID CLEAVAGE DIOXYGENASE 7 (GauCCD7) gene involved in strigolactone (SL) biosynthesis in Gossypium australe, suggesting a role for SLs in Verticillium wilt resistance. We found that the SL analog rac-GR24 enhanced while the SL biosynthesis inhibitor TIS108 decreased cotton resistance to Verticillium wilt. Knock-down of GbCCD7 and GbCCD8b genes in island cotton (Gossypium barbadense) decreased resistance, whereas overexpression of GbCCD8b in upland cotton (Gossypium hirsutum) increased resistance to Verticillium wilt. Additionally, Arabidopsis (Arabidopsis thaliana) SL mutants defective in CCD7 and CCD8 putative orthologs were susceptible, whereas both Arabidopsis GbCCD7- and GbCCD8b-overexpressing plants were more resistant to Verticillium wilt than wild-type (WT) plants. Transcriptome analyses showed that several genes related to the jasmonic acid (JA)- and abscisic acid (ABA)-signaling pathways, such as MYELOCYTOMATOSIS 2 (GbMYC2) and ABA-INSENSITIVE 5, respectively, were upregulated in the roots of WT cotton plants in responses to rac-GR24 and V. dahliae infection but downregulated in the roots of both GbCCD7- and GbCCD8b-silenced cotton plants. Furthermore, GbMYC2 suppressed the expression of GbCCD7 and GbCCD8b by binding to their promoters, which might regulate the homeostasis of SLs in cotton through a negative feedback loop. We also found that GbCCD7- and GbCCD8b-silenced cotton plants were impaired in V. dahliae-induced reactive oxygen species (ROS) accumulation. Taken together, our results suggest that SLs positively regulate cotton resistance to Verticillium wilt through crosstalk with the JA- and ABA-signaling pathways and by inducing ROS accumulation.

Goose surfactant protein A inhibits the growth of avian pathogenic Escherichia coli via an aggregation-dependent mechanism that decreases motility and increases membrane permeability.

Pulmonary collectins have been reported to bind carbohydrates on pathogens and inhibit infection by agglutination, neutralization, and opsonization. In this study, surfactant protein A (SP-A) was identified from goose lung and characterized at expression- and agglutination-functional levels. The deduced amino acid sequence of goose surfactant protein A (gSP-A) has two characteristic structures: a shorter, collagen-like region and a carbohydrate recognition domain. The latter contains two conserved motifs in its Ca2+-binding site: EPN (Glu-Pro-Asn) and WND (Trp-Asn-Asp). Expression analysis using qRT-PCR and fluorescence IHC revealed that gSP-A was highly expressed in the air sac and present in several other tissues, including the lung and trachea. We went on to produce recombinant gSP-A (RgSP-A) using a baculovirus/insect cell system and purified using a Ni2+ affinity column. A biological activity assay showed that all bacterial strains tested in this study were aggregated by RgSP-A, but only Escherichia coli AE17 (E. coli AE17, O2) and E. coli AE158 (O78) were susceptible to RgSP-A-mediated growth inhibition at 2-6 h. Moreover, the swarming motility of the two bacterial strains were weakened with increasing RgSP-A concentration, and their membrane permeability was compromised at 3 h, as determined by flow cytometry and laser confocal microscopy. Therefore, RgSP-A is capable of reducing bacterial viability of E. coli O2 and O78 via an aggregation-dependent mechanism which involves decreasing motility and increasing the bacterial membrane permeability. These data will facilitate detailed studies into the role of gSP-A in innate immune defense as well as for development of antibacterial agents.

CX3CR1 deficiency exacerbates immune-mediated hepatitis by increasing NF-κB-mediated cytokine production in macrophage and T cell.

Immune-mediated hepatitis is marked by liver inflammation characterized by immune cell infiltration, chemokine/cytokine production, and hepatocyte injury. C-X3C motif receptor 1 (CX3CR1), as the receptor of chemokine C-X3C motif ligand 1 (CX3CL1)/fractalkine, is mainly expressed on immune cells including monocytes and T cells. Previous studies have shown that CX3CR1 protects against liver fibrosis, but the exact role of CX3CL1/CX3CR1 in acute immune-mediated hepatitis remains unknown. Here, we investigate the role of the CX3CL1/CX3CR1 axis in immune-mediated hepatitis using concanavalin A (ConA)-induced liver injury model in CX3CR1-deficient (Cx3cr1-/-) mice. We observed that Cx3cr1-/- mice had severe liver injury and increased pro-inflammatory cytokines (tumor necrosis factor-alpha [TNF-α], interferon-gamma [IFN-γ], interleukin-1 beta [IL-1ß], and IL-6) in serum and liver compared to wild-type (Cx3cr1+/+) mice after ConA injection. The deficiency of CX3CR1 did not affect ConA-induced immune cell infiltration in liver but led to elevated production of TNF-α in macrophages as well as IFN-γ in T cells after ConA treatment. On the contrary, exogenous CX3CL1 attenuated ConA-induced cytokine production in wild type, but not CX3CR1-deficient macrophages and T cells. Furthermore, in vitro results showed that CX3CR1 deficiency promoted the pro-inflammatory cytokine expression by increasing the phosphorylation of nuclear factor kappa B (NF-κB) p65 (p-NF-κB p65). Finally, pre-treatment of p-NF-κB p65 inhibitor, resveratrol, attenuated ConA-induced liver injury and inflammatory responses, especially in Cx3cr1-/- mice. In conclusion, our data show that the deficiency of CX3CR1 promotes pro-inflammatory cytokine production in macrophages and T cells by enhancing the phosphorylation of NF-κB p65, which exacerbates liver injury in ConA-induced hepatitis.

Colloidal Synthesis of Metal Nanocrystals: From Asymmetrical Growth to Symmetry Breaking.

Nanocrystals offer a unique platform for tailoring the physicochemical properties of solid materials to enhance their performances in various applications. While most work on controlling their shapes revolves around symmetrical growth, the introduction of asymmetrical growth and thus symmetry breaking has also emerged as a powerful route to enrich metal nanocrystals with new shapes and complex morphologies as well as unprecedented properties and functionalities. The success of this route critically relies on our ability to lift the confinement on symmetry by the underlying unit cell of the crystal structure and/or the initial seed in a systematic manner. This Review aims to provide an account of recent progress in understanding and controlling asymmetrical growth and symmetry breaking in a colloidal synthesis of noble-metal nanocrystals. With a touch on both the nucleation and growth steps, we discuss a number of methods capable of generating seeds with diverse symmetry while achieving asymmetrical growth for mono-, bi-, and multimetallic systems. We then showcase a variety of symmetry-broken nanocrystals that have been reported, together with insights into their growth mechanisms. We also highlight their properties and applications and conclude with perspectives on future directions in developing this class of nanomaterials. It is hoped that the concepts and existing challenges outlined in this Review will drive further research into understanding and controlling the symmetry breaking process.

Facet-Controlled Synthesis of Platinum-Group-Metal Quaternary Alloys: The Case of Nanocubes and {100} Facets.

We report a robust method for the facet-controlled synthesis of nanocrystals with an ultrathin shell made of a nearly equimolar RuRhPdPt quaternary alloy. Our strategy involves the use of well-defined Rh cubic seeds, halide-free precursors, and a method for precisely controlling the reaction kinetics of different precursors. In the setting of dropwise addition, the precursors with different reactivities can be reduced at about the same pace for the generation of an alloy with a uniform and well-controlled composition. The core-shell nanocubes show greatly enhanced activity toward ethanol oxidation when benchmarked against Pd and Pt counterparts. Combining in situ and ex situ electron microscopy studies, we also demonstrate that the core-shell nanocubes possess good thermal and electrochemical stability in terms of both geometrical shape and elemental composition, with their cubic shape and alloy composition retained when annealing at 500 °C or after long-term electrochemical cycling. It is expected that the synthetic approach can be further extended to fabricate multimetallic catalysts with enhanced activities toward a variety of thermal and electrochemical reactions.

Sequestration of Ruthenium Residues via Efficient Fluorous-enyne Termination.

The creation of polymers without metal contamination remains a significant challenge for metathesis-based polymerization techniques and has complicated applications in biomedical and electronic applications. This communication reports a new approach for the removal of ruthenium byproducts through the design of an enyne terminator for metathesis polymerization that contains a fluorous tag. Upon reaction of a living polymer chain with the enyne, the ruthenium center is captured as a stable sulfur-chelated complex that can be efficiently removed after a single filtration through a fluorous cartridge. Levels of ruthenium residues as determined by ICP-MS were found to depend on the monomer structure, eluting solvent, and the degree of polymerization targeted. Ruthenium residues were minimized to low ppm levels (4-75 ppm) for most samples examined and also led to the improved thermal stability of the final materials. This represents the most efficient single method for removal of ruthenium residues from metathesis polymerization products.