Zobrazení zdroje stránky Spencerholck4992

The probes can selectively stain mitochondria, while probe D was employed to detect pH changes in HeLa cells and Drosophila melanogaster first-instar larvae.The rapid development of drug nanocarriers has benefited from the surface hydrophilic polymers of particles, which has improved the pharmacokinetics of the drugs. Polyethylene glycol (PEG) is a kind of polymeric material with unique hydrophilicity and electrical neutrality. PEG coating is a crucial factor to improve the biophysical and chemical properties of nanoparticles and is widely studied. Protein adherence and macrophage removal are effectively relieved due to the existence of PEG on the particles. This review discusses the PEGylation methods of nanoparticles and related techniques that have been used to detect the PEG coverage density and thickness on the surface of the nanoparticles in recent years. The molecular weight (MW) and coverage density of the PEG coating on the surface of nanoparticles are then described to explain the effects on the biophysical and chemical properties of nanoparticles.Yolk-shell nanoparticles based on mesoporous SiO2 (mSiO2) coating of Au nanoparticles (Au NPs) hold great promise for many applications in e.g., catalysis, biomedicine, and sensing. Here, we present a single-step coating approach for synthesizing Au NP@mSiO2 yolk-shell particles with tunable size and tunable hollow space between yolk and shell. The Au NP-mSiO2 structure can be manipulated from core-shell to yolk-shell by varying the concentration of cetyltrimethylammonium chloride (CTAC), tetraethyl orthosilicate (TEOS), Au NPs, and NaOH. The growth mechanism of the yolk-shell particles was investigated in detail and consists of a concurrent process of growth, condensation, and internal etching through an outer shell. We also show by means of liquid-cell transmission electron microscopy (LC-TEM) that Au nanotriangle cores (Au NTs) in yolk-shell particles that are stuck on the mSiO2 shell, can be released by mild etching thereby making them mobile and tumbling in a liquid-filled volume. Due to the systematical investigation of the reaction parameters and understanding of the formation mechanism, the method can be scaled-up by at least an order of magnitude. This route can be generally used for the synthesis of yolk-shell structures with different Au nanoparticle shapes, e.g., nanoplatelets, nanorods, nanocubes, for yolk-shell structures with other metals at the core (Ag, Pd, and Pt), and additionally, using ligand exchange with other nanoparticles as cores and for synthesizing hollow mSiO2 spheres as well.Electrolyzing water technology to prepare high-purity hydrogen is currently an important field in energy development. However, the preparation of efficient, stable, and inexpensive hydrogen production technology from electrolyzed water is a major problem in hydrogen energy production. The key technology for hydrogen production from water electrolysis is to prepare highly efficient catalytic, stable and durable electrodes, which are used to reduce the overpotential of the hydrogen evolution reaction and the oxygen evolution reaction of electrolyzed water. The main strategies for preparing catalytic electrodes include (i) choosing cheap, large specific surface area and stable base materials, (ii) modulating the intrinsic activity of the catalytic material through elemental doping and lattice changes, and (iii) adjusting the morphology and structure to increase the catalytic activity. Based on these findings, herein, we review the recent work in the field of hydrogen production by water electrolysis, introduce the preparation of catalytic electrodes based on nickel foam, carbon cloth and new flexible materials, and summarize the catalytic performance of metal oxides, phosphides, sulfides and nitrides in the hydrogen evolution and oxygen evolution reactions. Secondly, parameters such as the overpotential, Tafel slope, active site, turnover frequency, and stability are used as indicators to measure the performance of catalytic electrode materials. Finally, taking the material cost of the catalytic electrode as a reference, the successful preparations are comprehensively compared. The overall aim is to shed some light on the exploration of high-efficiency and economical electrodes in energy chemistry and also demonstrate that there is still room for discovering new combinations of electrodes including base materials, composition lattice changes and morphologies.To investigate the effect of the number of propylene oxide (PO) units on the wettability of surfactants, the wettability of isomeric dodecyl(polyoxyisopropyl)7 sulfate (S-C12PO7S) and isomeric dodecyl(polyoxyisopropyl)13 sulfate (S-C12PO13S) on the surface of polymethylmethacrylate (PMMA) was investigated. The adsorption behavior on the PMMA surface was analyzed by measuring the surface tension and the contact angle. It is found that the PO group may form hydrogen bonds with the PMMA surface, thus facilitating the hydrophobic tails pointing to the aqueous phase. Moreover, the steric effect of the PO group benefits the formation of semi-micelles above the critical micelle concentration (CMC). Surfactant molecules adsorb on the PMMA surface by polar adsorption below the CMC with hydrophobic tails towards the water. Therefore, the PMMA surface is modified to be more hydrophobic. However, the sodium dodecyl sulfate (SDS) surfactant with no PO unit does not have hydrophobic modification ability on the PMMA surface. Below the CMC, the adsorption amounts of the S-C12PO7S and S-C12PO13S surfactants at the solid-liquid interface were approximately 1/3 of those at the air-liquid interface. Interestingly, the adsorption behavior changes when the concentration of the surfactants is around the CMC. The hydrophilic heads of the surfactant molecules will point to water, and the surfactant molecules will form semi-micellar aggregates on the PMMA surface. Therefore, the PMMA surface is modified to be hydrophilic above the CMC. What's more, both the hydrophilic modification ability and hydrophobic modification ability of the S-C12PO13S surfactant are stronger than those of the S-C12PO7S surfactant. This means that the number of PO units will affect the wettability ability of the surfactants. Therefore, the S-C12PO13S surfactant possesses smaller contact angles than the S-C12PO7S surfactant at high concentrations.Glycosyltransferases (GTs) from the GT1 family are responsible for the glycosylation of various important organic structures such as terpenes, steroids and peptide antibiotics, making it one of the most intensely studied families of GTs. The target of our study, LanGT2, is a member of the GT1 family that uses an inverting mechanism for transferring olivose from TDP-olivose, the donor substrate, to the natural product tetrangulol (Tet), the precursor of the antibiotic landomycin A. X-ray crystallography in conjunction with mutagenesis experiments has revealed the catalytic significance of 3 amino acids (Ser10, Ser219 and Asp137), suggesting Asp137 as the base catalyst. In the absence of X-ray structures that include the acceptor substrate Tet, in silico experiments and MD simulations that have modeled ternary complexes propose that Asp137 could recruit a water molecule to facilitate the nucleophilic activation of Tet, since the distance between Asp137 and the nucleophile is too long to directly deprotonate then the TS. This is the first computational insight into the inverting mechanism of an antibiotic natural product GT, and its implications may serve to guide the design of new biocatalysts for natural product glycodiversification.Large-scale Ni-based nano-sized coordination polymers (Ni-nCPs) are facilely constructed by a self-assembled approach at room temperature and atmosphere pressure. In this strategy, we use only the environmentally friendly solvents of water and ethanol, and the synthesis of 2D Ni-nCPs via a self-assembly route appears close to the "green chemistry" concept. In addition, the morphologies of the Ni-nCPs can be easily adjusted by the water/ethanol ratio. Owing to its unique 2D ultrathin nature and large specific surface area, Ni-nCPs-1 achieves a great number of channels for the transport of electrons and ions and electrochemically redox active sites for a faradaic reaction. Therefore, battery-type Ni-nCPs-1 electrodes have a bright prospect in energy storage, and can reach an outstanding specific capacitance value as high as 1066.9 F g-1 at 1 A g-1. Additionally, the asymmetric supercapacitor (Ni-nCPs-1//active carbon) displays a high energy density of 47.9 W h kg-1 at a power density of 440 W kg-1 and an excellent long-term cycle stability. This work may open up a new path in advanced electrode materials for efficient and real-time energy storge applications.With its ability to enable solvent-free chemical reactions, mechanochemistry promises to open new and greener synthetic routes to chemical products of industrial interest. [https://www.selleckchem.com/products/kt-474.html Selleck KT 474] Its practical exploitation requires understanding the relationships between processing variables, powders' mechanical behaviour, and chemical reactivity. To this aim, rationalizing experimental kinetics is of paramount importance. In this work, we propose a phenomenological kinetic model that could help experimentalists to disentangle the mechanical, chemical, and statistical factors underlying mechanochemical reactions. The model takes into account the statistical nature of ball milling and relates the global kinetic curve that can be obtained experimentally to the deformation and chemical processes that occur on the mesoscopic and microscopic scales during individual impacts. We show that our model equations can satisfactorily best fit experimental datasets, providing information on the underlying mechanochemistry.The mechanism of the recently discovered enhancement of dielectric properties in dilute polymer-nanoparticle composites is investigated by experiments and computer simulations. We show that the weakening of the hydrogen bonds between the nanoparticles and the polymer chains reduces the polymer-nanoparticle composite's dielectric enhancement. The subsequent multiscale simulations investigate the attachment of solvated highly dipolar polymers to oxide nanoparticles, which leads to deposition of nanoparticle-polymer blobs during solution casting and a reduced density compared to a neat polymer film. Coarse-grained simulations of nanocomposite morphology are followed by molecular dynamics and density functional theory calculations of permittivities. The increased free volume in the nanocomposite enables easier reorientation of monomer dipoles with an applied electric field, and thus a higher dielectric permittivity. The numerical results are in excellent agreement with experimental data for PEEU and PEI nanocomposites.Polar organic-inorganic hybrid materials have been applied in ferroelectricity, as well as in devices based on nonlinear optical and piezoelectricity properties. Here, we used a rectangular pyramid structure of [VOCl4]2- to construct a polar compound (C5NH13Cl)2VOCl4 (1). Compound 1 crystallized in the monoclinic P21 space group. Coexistence of nonlinear optical switching behavior (space-group change from P21 to P21/n) and two-staged thermosensitive dielectric switching properties could be achieved under the stimulus of temperature. Our findings provide an effective approach for construction of polar materials.