172 research outputs found
Micellar dye shuttle between water and an ionic liquid
The reversible transfer of poly(2-ethyl-2-oxazoline)-block-poly(2-nonyl-2-oxazoline) nanocarriers comprising encapsulated dyes is demonstrated between water and an ionic liquid. This dye transfer concept is shown to be applicable for loading and delivery of dye molecules as well as to provide a protective environment for the encapsulated dye
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Microwave-Assisted Synthesis of CoreâShell NanoparticlesâInsights into the Growth of Different Geometries
Microwave irradiation is utilized for the rapid synthesis of goldâsilver coreâshell bimetallic nanoparticles (NPs) in a two-step process. A strategy of establishing a bilayer organic barrier around the core using citrate and ascorbic acid as capping agents, providing a means to achieve a well-defined boundary layer between the core and the shell material, is reported. These boundary layers are essential for synthesizing different coreâshell morphologies and the approach results in tunable bimetallic NPs with defined coreâshell structures, both for spherical as well as for triangular seed cores. In addition, theoretical calculations of the plasmonic characteristics based on the boundary element method of different classes of NPs are conducted. These investigations enable conclusions to be drawn on the influence of the core morphology on the tunability of their localized surface plasmon resonances. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
HD DVD substrates for surface enhanced Raman spectroscopy analysis : fabrication, theoretical predictions and practical performance
Commercial HD DVDs provide a characteristic structure of encoding pits which were utilized to fabricate cost efficiently large area SERS substrates for chemical analysis. The study targets the simulation of the plasmonic structure of the substrates and presents an easily accessible fabrication process to obtain highly sensitive SERS active substrates. The theoretical simulation predicted the formation of supermodes under optimized illumination conditions, which were verified experimentally. First tests of the developed SERS substrates demonstrated their excellent potential for detecting vitamin A and pro- vitamin A at low concentration levels
The evolution of the footwall to the Ronda subcontinental mantle peridotites: insights from the Nieves Unit (western Betic Cordillera)
Strongly heterogeneous deformation and extreme metamorphic gradients characterize the dominantly carbonate Nieves Unit in the footwall to the Ronda mantle extrusion wedge in the western Betic Cordillera. A well-developed foliation and mineral lineation, together with isoclinal intrafolial folds, occur in silicate-bearing, calcite or dolomite marbles within a c. 1.5âkm thick metamorphic aureole underlying the peridotites. For the inferred maximum pressure of 300âMPa, petrological investigations allow us to define temperature ranges for the main zones of the metamorphic aureole: >510â°C (probably c. 700â°C) for the forsterite zone; 510â430â°C for the diopside zone; 430â360â°C for the tremolite zone; 360â330â°C for the phlogopite zone. Field structural analysis integrated with petrological, microstructural and electron backscatter diffraction textural data document large finite strains consistent with general shear within the metamorphic aureole, associated with NW-directed thrusting of the peridotites. On the other hand, post-kinematic silicate growth suggests that heat diffusion from the high-temperature peridotites continued after the final emplacement of the Ronda mantle extrusion wedge, leading to final zoning of the metamorphic aureole and to local partial annealing of calcite marble textures, particularly in the highest-temperature zone of the thermally softened footwall carbonates. Following substantial cooling, renewed crustal shortening affected the whole Nieves Unit, resulting in widespread development of NEâSW-trending meso-scale folds
Triazole-Functionalized Mesoporous Materials Based on Poly(styrene- block -lactic acid): A Morphology Study of Thin Films
We report the synthesis of poly(styrene- block -lactic acid) (PS- b -PLA) copolymers with triazole rings as a junction between blocks. These materials were prepared via a âclickâ strategy which involved the reaction between azide-terminated poly(styrene) (PS-N 3 ) and acetylene-terminated poly(D,L-lactic acid) (PLA-Ac), accomplished by copper-catalyzed azide-alkyne cycloaddition reaction. This synthetic approach has demonstrated to be effective to obtain specific copolymer structures with targeted self-assembly properties. We observed the self-assembly behavior of the PS- b -PLA thin films as induced by solvent vapor annealing (SVA), thermal annealing (TA), and hydrolysis of the as-spun substrates and monitored their morphological changes by means of different microscopic techniques. Self-assembly via SVA and TA proved to be strongly dependent on the pretreatment of the substrates. Microphase segregation of the untreated films yielded a pore size of 125 nm after a 45-min SVA. After selectively removing the PLA microdomains, the as-spun substrates exhibited the formation of pores on the surface, which can be a good alternative to form an ordered pattern of triazole functionalized porous PS at the mesoscale. Finally, as revealed by scanning electron microscopyâenergy dispersive X-ray spectroscopy, the obtained triazole-functionalized PS-porous film exhibited some affinity to copper (Cu) in solution. These materials are suitable candidates to further study its metal-caption properties
Emulsion polymerizations for a sustainable preparation of efficient TEMPOâbased electrodes
Organic polymerâbased batteries represent a promising alternative to presentâday metalâbased systems and a valuable step toward printable and customizable energy storage devices. However, most scientific work is focussed on the development of new redoxâactive organic materials, while straightforward manufacturing and sustainable materials and production will be a necessary key for the transformation to mass market applications. Here, a new synthetic approach for 2,2,6,6âtetramethylâ4âpiperinidylâ N âoxyl (TEMPO)âbased polymer particles by emulsion polymerization and their electrochemical investigation are reported. The developed emulsion polymerization protocol based on an aqueous reaction medium allowed the sustainable synthesis of a redoxâactive electrode material, combined with simple variation of the polymer particle size, which enabled the preparation of nanoparticles from 35 to 138â
nm. Their application in cell experiments revealed a significant effect of the size of the activeâpolymer particles on the performance of poly(2,2,6,6âtetramethylâ4âpiperinidylâ N âoxyl methacrylate) (PTMA)âbased electrodes. In particular rate capabilities were found to be reduced with larger diameters. Nevertheless, all cells based on the different particles revealed the ability to recover from temporary capacity loss due to application of very high charge/discharge rates.Sustainable and efficient organic electrode : A new synthetic approach for polymers for organic batteries includes an emulsion polymerization with adjustable particle sizes in aqueous dispersions and allows the sustainable manufacturing of active materials and composite electrodes. The electrochemical investigation shows that the influence of particle sizes and the resulting morphologies of composite films on the cell performance is as important as the active material itself
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Stealth Effect of Short Polyoxazolines in Graft Copolymers: Minor Changes of Backbone End Group Determine Liver Cell-Type Specificity
Dye-loaded micelles of 10 nm diameter formed from amphiphilic graft copolymers composed of a hydrophobic poly(methyl methacrylate) backbone and hydrophilic poly(2-ethyl-2-oxazoline) side chains with a degree of polymerization of 15 were investigated concerning their cellular interaction and uptake in vitro as well as their interaction with local and circulating cells of the reticuloendothelial system in the liver by intravital microscopy. Despite the high molar mass of the individual macromolecules (Mn â 20 kg mol-1), backbone end group modification by attachment of a hydrophilic anionic fluorescent probe strongly affected the in vivo performance. To understand these effects, the end group was additionally modified by the attachment of four methacrylic acid repeating units. Although various micelles appeared similar in dynamic light scattering and cryo-transmission electron microscopy, changes in the micelles were evident from principal component analysis of the Raman spectra. Whereas an efficient stealth effect was found for micelles formed from polymers with anionically charged or thiol end groups, a hydrophobic end group altered the micelles' structure sufficiently to adapt cell-type specificity and stealth properties in the liver. © 2021 The Authors. Published by American Chemical Society
Targeted delivery of a phosphoinositide 3-kinase Îł inhibitor to restore organ function in sepsis
Jaundice, the clinical hallmark of infection-associated liver dysfunction, reflects altered membrane organization of the canalicular pole of hepatocytes and portends poor outcomes. Mice lacking phosphoinositide 3-kinase-Îł (PI3KÎł) are protected against membrane disintegration and hepatic excretory dysfunction. However, they exhibit a severe immune defect that hinders neutrophil recruitment to sites of infection. To exploit the therapeutic potential of PI3KÎł inhibition in sepsis, a targeted approach to deliver drugs to hepatic parenchymal cells without compromising other cells, in particular immune cells, seems warranted. Here, we demonstrate that nanocarriers functionalized through DY-635, a fluorescent polymethine dye, and a ligand of organic anion transporters can selectively deliver therapeutics to hepatic parenchymal cells. Applying this strategy to a murine model of sepsis, we observed the PI3KÎł-dependent restoration of biliary canalicular architecture, maintained excretory liver function, and improved survival without impairing host defense mechanisms. This strategy carries the potential to expand targeted nanomedicines to disease entities with systemic inflammation and concomitantly impaired barrier functionality
Nanospiral Formation by Droplet Drying: One Molecule at a Time
We have created nanospirals by self-assembly during droplet evaporation. The nanospirals, 60â70 nm in diameter, formed when solvent mixtures of methanol and m-cresol were used. In contrast, spin coating using only methanol as the solvent produced epitaxial films of stripe nanopatterns and using only m-cresol disordered structure. Due to the disparity in vapor pressure between the two solvents, droplets of m-cresol solution remaining on the substrate serve as templates for the self-assembly of carboxylic acid molecules, which in turn allows the visualization of solution droplet evaporation one molecule at a time
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