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.

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.

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.

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.

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.

Discovery of novel biphenyl derivatives as androgen receptor degraders for the treatment of enzalutamide-resistant prostate cancer.

Second-generation AR antagonists, such as enzalutamide, are the primary therapeutic agents for advanced prostate cancer. However, the development of both primary and secondary drug resistance leads to treatment failures and patient mortality. Bifunctional agents that simultaneously antagonize and degrade AR block the AR signaling pathway more completely and exhibit excellent antiproliferative activity against wild-type and drug-resistant prostate cancer cells. Here, we reported the discovery and optimization of a series of biphenyl derivatives as androgen receptor antagonists and degraders. These biphenyl derivatives exhibited potent antiproliferative activity against LNCaP and 22Rv1 cells. Our discoveries enrich the diversity of small molecule AR degraders and offer insights for the development of novel AR degraders for the treatment of enzalutamide-resistant prostate cancer.

Method for analyzing urban waterlogging mechanisms based on a 1D-2D water environment dynamic bidirectional coupling model.

Urban waterlogging is a significant global issue. To achieve precisely control urban waterlogging and enhance our understanding of its causes, a novel study method was introduced. This method is based on a dynamic bidirectional coupling model that combines 1D-2D hydrodynamic and water quality simulations. The waterlogging phenomenon in densely populated metropolitan areas of Changzhi city, China, was studied. This study focused on investigating the process involved in waterlogging formation, particularly overflow at nodes induced by the design of the topological structure of the pipe network, constraints on the capacity of the underground drainage system, and the surface runoff accumulation. The complex interplay among these elements and their possible influences on waterlogging formation were clarified. The results indicated notable spatial and temporal variation in the waterlogging formation process in densely populated urban areas. Node overflow in the drainage system emerged as the key influencing factor in the waterlogging formation process, accounting for up to 71% of the total water accumulation at the peak time. The peak lag time of waterlogging during events with short return periods was primarily determined by the rainfall peak moment. In contrast, the peak time of waterlogging during events with long return periods was influenced by the rainfall peak moment, drainage capacity and topological structure of the pipe network. Notably, the access of inflow from both upstream and downstream segments of the pipe network drainage system significantly impacted the peak time of waterlogging, with upstream water potentially delaying the peak time substantially. This study not only provides new insights into urban waterlogging mechanisms but also provides practical guidance for optimizing urban drainage systems, urban planning, and disaster risk management.

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.

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.

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.

Estimation of the Annual Effective Dose Due to the Ingestion of 210Pb and 210Po in Crops from a Site of Coal Mining and Processing in Southwest China.

The exploitation of mineral resources may cause the environmental release of radionuclides and their introduction in the human trophic chain, affecting public health in the short and long term. A case study of the environmental radiation impact from coal mining and germanium processing was carried out in southwest China. The coal mines contain germanium and uranium and have been exploited for more than 40 years. The farmlands around the site of the coal mining and germanium processing have been contaminated by the solid waste and mine water to some extent since then. Samples of crops were collected from contaminated farmlands in the research area. The research area covers a radius of 5 km, in which there are two coal mines. 210Pb and 210Po were analyzed as the key radionuclides during the monitoring program. The average activity concentrations of 210Pb and 210Po in the crops were 1.38 and 1.32 Bq/kg in cereals, 4.07 and 2.19 Bq/kg in leafy vegetables and 1.63 and 1.32 Bq/kg in root vegetables. The annual effective doses due to the ingestion of 210Pb and 210Po in consumed crops were estimated for adult residents living in the research area. The average annual effective dose was 0.336 mSv/a, the minimum was 0.171 mSv/a and the maximum was 0.948 mSv/a. The results show that the crops grown on contaminated farmland contained an enhanced level of radioactivity concentration. The ingestion doses of local residents in the research area were significantly higher than the average level of 0.112 mSv/a in China, and the world average level of 0.042 mSv/a through 210Pb and 210Po in crop intake, respectively.

[Analysis and comparison of metabolic processes of salvianolic acid A and salvianolic acid B in rats based on UHPLC-LTQ-Orbitrap MS technology].

The metabolites of salvianolic acid A and salvianolic acid B in rats were analyzed and compared by ultra-high-perfor-mance liquid chromatography with linear ion trap-orbitrap mass spectrometry(UHPLC-LTQ-Orbitrap MS). After the rats were administrated by gavage, plasma at different time points and urine within 24 hours were collected to be treated by solid phase extraction(SPE), then they were gradient eluted by Acquity UPLC BEH C_(18) column(2.1 mm×100 mm, 1.7 µm) and 0.1% formic acid solution(A)-acetonitrile(B) mobile phase system, and finally all biological samples of rats were analyzed under negative ion scanning mode. By obtaining the accurate relative molecular mass and multi-level mass spectrometry information of metabolites, combined with the characteristic cleavage law of the reference standard and literature reports, a total of 30 metabolites, including salvianolic acid A and B, were identified. Among them, there were 24 metabolites derived from salvianolic acid A, with the main metabolic pathways including ester bond cleavage, dehydroxylation, decarboxylation, hydrogenation, methylation, hydroxylation, sulfonation, glucuronidation, and their multiple reactions. There were 15 metabolites of salvianolic acid B, and the main biotransformation pathways were five-membered ring cracking, ester bond cleavage, decarboxylation, dehydroxylation, hydrogenation, methylation, sulfonation, glucuronidation, and their compound reactions. In this study, the cross-metabolic profile of salvianolic acid A and B was elucidated completely, which would provide reference for further studies on the basis of pharmacodynamic substances and the exploration of pharmacological mechanism.

Genome sequencing of the Australian wild diploid species Gossypium australe highlights disease resistance and delayed gland morphogenesis.

The diploid wild cotton species Gossypium australe possesses excellent traits including resistance to disease and delayed gland morphogenesis, and has been successfully used for distant breeding programmes to incorporate disease resistance traits into domesticated cotton. Here, we sequenced the G. australe genome by integrating PacBio, Illumina short read, BioNano (DLS) and Hi-C technologies, and acquired a high-quality reference genome with a contig N50 of 1.83 Mb and a scaffold N50 of 143.60 Mb. We found that 73.5% of the G. australe genome is composed of various repeat sequences, differing from those of G. arboreum (85.39%), G. hirsutum (69.86%) and G. barbadense (69.83%). The G. australe genome showed closer collinear relationships with the genome of G. arboreum than G. raimondii and has undergone less extensive genome reorganization than the G. arboreum genome. Selection signature and transcriptomics analyses implicated multiple genes in disease resistance responses, including GauCCD7 and GauCBP1, and experiments revealed induction of both genes by Verticillium dahliae and by the plant hormones strigolactone (GR24), salicylic acid (SA) and methyl jasmonate (MeJA). Experiments using a Verticillium-resistant domesticated G. barbadense cultivar confirmed that knockdown of the homologues of these genes caused a significant reduction in resistance against Verticillium dahliae. Moreover, knockdown of a newly identified gland-associated gene GauGRAS1 caused a glandless phenotype in partial tissues using G. australe. The G. australe genome represents a valuable resource for cotton research and distant relative breeding as well as for understanding the evolutionary history of crop genomes.

Separation of Metal-N4 Units in Metal-Organic Framework for Preparation of M-Nx/C Catalyst with Dense Metal Sites.

Metal and nitrogen codoped carbon (M-Nx/C) materials with good metal dispersion in a carbon matrix have attracted great attention because they can efficiently catalyze various kinds of chemical/electrochemical reactions. However, the existing strategies for preparing M-Nx/C materials still face the challenge of metal site aggregation when the carbon skeleton in the precursor is substantially lost during pyrolysis. Herein, we propose a general strategy that the increase of metal site density and inhibition of metal aggregation could be realized by separating M-N4 units in metal-organic frameworks (MOFs). The metal sites can be well separated and distributed in carbon materials during the pyrolysis of a metal-coordinated block copolymer, one of the specific MOFs. The strategy can be widely applicable for the synthesis of M-Nx/C materials with dense metal sites, such as Fe-, Mn-, Ni-, and Co-Nx/C materials, which are potentially used as the efficient catalysts for various kinds of reactions. Taking Fe-Nx/C as a model oxygen reduction reaction (ORR) electrocatalyst, it shows the ORR half-wave potentials of 0.90 and 0.81 V vs RHE in alkaline and acidic electrolytes, respectively.

[Enzyme activity of neuraminidase 1 correlated with the biological behavior of prostate cancer PC3 and DU145 cell lines].

OBJECTIVE: To investigate the effects of the enzyme activity of neuraminidase 1 (Neu1) on the biological behavior of prostate cancer PC3 and DU145 cell lines. METHODS: We detected the expression of Neul in the prostate cancer PC3 and DU145 cell lines by Western blot. Using sialidase inhibitors and antibody blocking, we suppressed the enzyme activity of Neu1 and then measured the proliferation and invasiveness of the two cell lines by CCK-8 and Transwell assay, respectively. RESULTS: No statistically significant difference was found in the Neu1 expression between the PC3 and DU145 cell lines. The proliferation and invasiveness of the two types of cells were both increased after inhibition of the Neu1 enzyme activity. CONCLUSIONS: The enzyme activity of Neu1 is correlated with the biological behavior of prostate cancer PC3 and DU145 cells and capable of inhibiting the proliferation and invasiveness of the two types of cells.

[Analysis of carnosic acid metabolites in rats by UHPLC-Q-Exactive MS].

A method of ultra-high performance liquid chromatography coupled with quadrupole/electrostatic field Obitrap high-resolution mass spectrometry(UHPLC-Q-Exactive MS) was established to comprehensively identify the metabolites of carnosic acid in rats. After oral gavage of carnosic acid CMC-Na suspension in rats, urine, plasma and feces samples were collected and pretreated by solid phase extraction(SPE). Acquity UPLC BEH C_(18 )column(2.1 mm×100 mm, 1.7 µm) was used with 0.1% formic acid solution(A)-acetonitrile(B) as the mobile phase for the gradient elution. Biological samples were analyzed by quadrupole/electrostatic field Obitrap high-resolution mass spectrometry in positive and negative ion mode. Based on the accurate molecular mass, fragment ion information, and related literature reports, a total of 28 compounds(including carnosic acid) were finally identified in rat samples. As a result, the main metabolic pathways of carnosic acid in rats are oxidation, hydroxylation, methylation, glucuronide conjugation, sulfate conjugation, S-cysteine conjugation, glutathione conjugation, demethylation, decarbonylation and their composite reactions. The study showed that the metabolism of carnosic acid in rats could be efficiently and comprehensively clarified by using UHPLC-Q-Exactive MS, providing a reference for clarifying the material basis and metabolic mechanism of carnosic acid.

A Comprehensive Screening and Identification of Genistin Metabolites in Rats Based on Multiple Metabolite Templates Combined with UHPLC-HRMS Analysis.

Genistin, an isoflavone belonging to the phytoestrogen family, has been reported to possess various therapeutic effects. In the present study, the genistin metabolites in rats were investigated by UHPLC-LTQ-Orbitrap mass spectrometer in both positive and negative ion modes. Firstly, the data sets were obtained based on data-dependent acquisition method and then 10 metabolite templates were established based on the previous reports. Then diagnostic product ions (DPIs) and neutral loss fragments (NLFs) were proposed to efficiently screen and ascertain the major-to-trace genistin metabolites. Meanwhile, the calculated Clog P values were used to identify the positional isomers with different retention times. Consequently, a total of 64 metabolites, including prototype drug, were positively or putatively characterized. Among them, 40 metabolites were found according to the templates of genistin and genistein, which was the same as the previous research method. After using other metabolite templates, 24 metabolites were added. The results demonstrated that genistin mainly underwent methylation, hydrogenation, hydroxylation, glucosylation, glucuronidation, sulfonation, acetylation, ring-cleavage and their composite reactions in vivo biotransformation. In conclusion, the research not only revealed the genistein metabolites and metabolic pathways in vivo comprehensively, but also proposed a method based on multiple metabolite templates to screen and identify metabolites of other natural compounds.

Hexagonal Boron Nitride-Graphene Core-Shell Arrays Formed by Self-Symmetrical Etching Growth.

The synthesis and integration of core-shell materials have been extensively explored in three-dimensional nanostructures, while they are hardly ever extended into the emerging two-dimensional (2D) research field. Herein, demonstrated by graphene (G) and hexagonal boron nitride (h-BN) and via a sequential chemical vapor deposition method, we succeed for the first time in synthesizing 2D h-BN-G core-shell arrays (CSA), which possess extremely high uniformity in shapes, sizes and distributions. Each of the core-shell units is composed of G ring-shaped shell internally filled with h-BN circular core. In addition, we perform simulations to further explain the self-symmetrical etching growth mechanism of the h-BN-G CSA, demonstrating its potential to be used as an efficient synthetic method suitable for other 2D CSA systems.

Graphene: An Outstanding Multifunctional Coating for Conventional Materials.

As the most significant facilitator of human civilization, materials are eternal jewels in the view of researchers whose brilliance never faded. However, simple conventional materials, which are most commonly used and indispensable today, seem too primitive and insufficiently functional to meet the demands of the future intelligent and informational applications, urging more functions to be integrated. The ideal strategy to achieve the transformations of conventional materials non-destructively is functionalizing the surface and retaining the original properties at the same time. Graphene, a two-dimensional material with only atomic-thickness, has come into the view of the researchers, attributed to its various outstanding properties. In recent years, a large amount of research has been devoted to "wearing" graphene to functionalize the conventional materials, booming a huge "graphene-X" family. In this concept, representative members are illustrated and their improved functions are demonstrated. Also, the prospects and challenges for this dazzling family are discussed.

Construction of Novel Thermosensitive Magnetic Cationic Liposomes as a Drug and Gene Co-Delivery System.

This study aimed to develop a novel system for co-delivery of both drugs and genes to the same cells. We described the construction of thermosensitive magnetic cationic liposomes (TSMCLs). Liposomes were prepared by thin film hydration method, then calcein release assay and DSC were used to determine the thermosensitivity of liposomes, and gel retardation experiment was performed to monitor the formation of Lipoplex (Liposomes and pDNA complex), finally the in vitro transfection experiments were performed to evaluate the transfection efficiency of the liposomes. The results showed that TSMCLs combined the features of physical targeting under magnetic guidance and hyperthermia triggered drug release upon the application of alternating magnetic field. Thus TSMCLs could be used for the co-delivery of drugs and genes and have potential application in combined chemotherapy and gene therapy for cancer.