Effect of Temperature on Green Synthesis of Silver Nanoparticles Using Vitex Agnus-castus Extract

Silver nanoparticles colloids were prepared using the extract from the leaves of Vitex agnus-castus. The effect of temperature on the reduction of silver ions and on the growth of silver nanoparticles was followed by measuring the intensity of the surface plasmon resonance band in the UV spectra. It was found that fast reduction of silver ions occurs even at 40°C, while effective synthesis of silver nanoparticles requires elevated temperatures of 60-80°

Biosecurity measures to control hepatitis E virus on European pig farms

Hepatitis E virus (HEV) genotype 3 is a prevalent zoonotic pathogen in European pig farms, posing a significant public health risk primarily through the foodborne route. The study aimed to identify effective biosecurity measures for controlling HEV transmission on pig farms, addressing a critical gap in current knowledge. Utilizing a cross-sectional design, fecal samples from gilts, dry sows, and fatteners were collected on 231 pig farms of all farm types across nine European countries. Real-time RT-PCR was employed to test these samples for HEV. Simultaneously, a comprehensive biosecurity questionnaire captured data on various potential measures to control HEV. The dependent variable was HEV risk, categorized as lower or higher based on the percentage of positive pooled fecal samples on each farm (25% cut-off). The data were analyzed using generalized linear models (one for finisher samples and one for all samples) with a logit link function with country and farm type as a priori fixed factors. The results of the final multivariable models identified key biosecurity measures associated with lower HEV risk, which were the use of a hygienogram in the breeding (OR: 0.06, p = 0.001) and/or fattening area after cleaning (OR: 0.21, p = 0.019), the presence of a quarantine area (OR: 0.29, p = 0.025), testing and/or treating purchased feed against Salmonella (OR: 0.35, p = 0.021), the presence of other livestock species on the farm, and having five or fewer persons in charge of the pigs. Contrary to expectations, some biosecurity measures were associated with higher HEV risk, e.g., downtime of 3 days or longer after cleaning in the fattening area (OR: 3.49, p = 0.005) or mandatory handwashing for farm personnel when changing barn sections (OR: 3.4, p = 0.026). This novel study unveils critical insights into biosecurity measures effective in controlling HEV on European pig farms. The identification of both protective and risk-associated measures contributes to improving strategies for managing HEV and underscores the complexity of biosecurity in pig farming

Nanoparticle-Supported Molecular Polymerization Catalysts

Homogeneous molecular catalysts are immobilzed in a well-defined fashion on individual silica nanoparticles with a narrow particle size distribution by covalent attachment. This synthetic methodology is demonstrated with modified salicylaldiminato-substituted titanium(IV) complexes incorporating a trimethoxysilane-terminated linker: dichloro-bis[κ2-N,O-6-(3-(trimethoxysilyl)propoxyphenylimino)-2-tert-butyl-phenolato]titanium(IV) (3) and dichlorobis[κ2-N,O-6-(4-(trimethoxysilyl)propoxy-2,3,5,6-tetrafluorophenylimino)-2-tert-butylphenolato]titanium(IV) (4). 3 and 4 were bound covalently to silica nanoparticles via direct condensation of the alkoxysilane with residual silanol groups on the lipophilically modified particle surface. The resulting nonaggregated individual silica nanoparticles (ca. 50 nm diameter) with catalyst bound to the outer surface have been characterized by CP-MAS NMR, FT-IR spectroscopy and by electron microscopy (TEM, ESI). These supported catalysts exhibit single site characteristics for the polymerization of ethylene, affording ultra high molecular weight polyethylene. Polymer particles with a uniform spherical morphology and a particle size in the submicron regime are formed. TEM analyses of cross-sections of single particles formed at different polymerization times revealed a complete fragmentation of the nanoparticle support to fragments of ca. 10 nm size homogeneously distributed in the polymer matrix

Sample preparation methods for femtosecond electron diffraction experiments

Exploring the dynamics of Charge density wave system 1T-TaS2 via femtosecond electron diffraction demonstrated the power of this technique for studying ultrafast structural phenomena in strongly correlated electron materials [1]. The results revealed first direct information on the order parameter dynamics of Charge Density Waves as well as on their photo-induced phase transition. A prerequisite to perform such experiments on modern quantum materials is the availability of laterally large ( similar to 100 mu m) and sufficiently thin ( < 100 nm) single crystalline samples. Different approaches to reach these specifications have been tried out and their effect on sample integrity has been investigated. Finally, using an ultra-microtome, we were able to prepare 30 nm free standing single crystalline films of 1T-TaS2 with lateral dimensions of 200 mu m x 200 mu m. We have characterized these films with different techniques for their stoichiometric and crystalline integrity, ensuring no measurable alternation of sample properties. The application of this sample thinning technique is expected to find its use in further structural dynamics studies, as well as in optical time-resolved studies where homogeneous excitation profile and/or data in transmission geometry may be required. (c) 2012 Elsevier B.V. All rights reserved

Free-Radical Dispersion Polymerization of Ethylene with Laponite to Polyethylene–Clay Nanocomposite Particles

Composite clay/polymer nanoparticle dispersions have been studied for many different polymers but remained elusive for polyolefins even though polyolefins are an important class of polymers and are also industrially applied in the form of aqueous dispersions. Despite the hydrophobic and apolar nature of polyethylene, aqueous nanocomposite dispersions are formed via heterogeneous free-radical polymerization in the presence of the synthetic smectite clay Laponite-RD at relatively mild conditions (250 atm, 85 °C). The clay nanoplatelets effectively contribute to colloidal stability of the polyolefin particles formed and strongly enhance particle formation during the aqueous polymerization. Evolution of the polymer–clay interaction at an early stage of particle formation is instrumental, and initiator-derived polar end groups are decisively involved. The clay enhances polymerization yields and promotes the formation of smaller particles. Stable dispersions with polymer contents of up to 24% were obtained without the need of additional organic surfactants.publishe

Crystallization as a Means for the Switching of Nanoscale Containers

Melting and crystallization are reported as a means for reversible switching of nanoscale containers. Aqueous dispersions of 10 nm particles of polyethylene with variable branching and crystallinity were prepared by catalytic polymerization with water-soluble Ni(II) complexes. Fluorescence studies of lipophilic probe molecules show that in the low-crystallinity particles they experience a more apolar environment. In crystalline particles, the amorphous portions which can accommodate guest molecules are at the periphery of the particle, such that the probe experiences the water-particle interface to some extent. The polarity experienced by the probe molecules can be switched reversibly by melting and crystallization of the individual dispersed particles. The temperature at which this occurs can be adjusted via the microstructure, that is, degree of branching, of the polymer

Magnetic field-assisted assembly of iron oxide mesocrystals : a matter of nanoparticle shape and magnetic anisotropy

This letter describes the formation and detailed characterization of iron oxide mesocrystals produced by the directed assembly of superparamagnetic iron oxide-truncated nanocubes using the slow evaporation of the solvent within an externally applied homogeneous magnetic field. Anisotropic mesocrystals with an elongation along the direction of the magnetic field can be produced. The structure of the directed mesocrystals is compared to self-assembled mesocrystalline films, which are formed without the influence of a magnetic field. The remarkable structural difference of mesocrystals produced within the external magnetic field from those self-assembled without field indicates that the specific nanoparticle ordering within the superstructure is driven by competing of two types of anisotropic interactions caused by particle shape (i.e., faceting) and orientation of the magnetic moment (i.e., easy axes: magnetite). Hence, these findings provide a fundamental understanding of formation mechanisms and structuring of mesocrystals built up from superparamagnetic nanoparticles and how a magnetic field can be used to design anisotropic mesocrystals with different structures.publishe

Size Control of Spherical and Anisotropic Fluorescent Polymer Nanoparticles via Precise Rigid Molecules

Highly monodisperse block copolymers allow for the preparation of luminescent particles with sizes reflecting the oligomer chain length. Self-organization in tetrahydrofuran/methanol leads to anisotropic nanorods with a thickness corresponding directly to the oligomer length (up to 14 nm for 21-mers). As a prerequisite for the realization of this concept, syntheses of defect-free poly­(phenylene ethynylene)­s with unprecedented chain length up to 43 repeat units were developed. Absorption and emission wavelength in solution continue to increase with increasing chain length, and do not converge until the 43-mer