Search results for "Light"
showing 10 items of 3575 documents
Morphology control in biphasic hybrid systems of semiconducting materials.
2015
Simple blends of inorganic nanocrystals and organic (semiconducting) polymers usually lead to macroscopic segregation. Thus, such blends typically exhibit inferior properties than expected. To overcome the problem of segregation, polymer coated nanocrystals (nanocomposites) have been developed. Such nanocomposites are highly miscible within the polymer matrix. In this Review, a summary of synthetic approaches to achieve stable nanocomposites in a semiconducting polymer matrix is presented. Furthermore, a theoretical background as well as an overview concerning morphology control of inorganic NCs in polymer matrices are provided. In addition, the morphologic behavior of highly anisotropic na…
Highly Defined, Colloid‐Like Ionic Clusters in Solution
2012
Many societal challenges at the beginning of the 21st century lead to an apparent and growing need for functional materials and novel ways of materials synthesis and assembly. Rising to the challenge, the utilization of small, self-assembling building blocks for the bottom-up construction of new types of polymers and nanostructures has enjoyed increasing popularity among materials researchers in the recent past. Supramolecular materials like foldamers, surface films, nanoparticles, etc. are created by exploiting noncovalent forces [1] leading to an ordered arrangement of nanoscale building blocks. [2] In the search for new polymers based on noncovalent molecular forces, we are motivated by …
Biosilica-based immobilization strategy for label-free OWLS sensors
2013
Abstract In the last years, a new group of enzymes, so-called silicateins, have been identified and characterized, which form the axial filaments of the spicules of the siliceous sponges, consisting of amorphous silica. Silicateins are able to catalyze the polycondensation and deposition of silica at mild conditions (low temperature and physiological pH). By means of these enzymes it is possible for the first time to produce silica nanostructures biocatalytically, which opens new ways for construction of biosensors. The cDNAs encoding the responsible enzymes have been isolated and the proteins can be produced in a recombinant way. Here we demonstrate the silicatein-mediated biosilica format…
Porphyrin-Polymer Networks, Worms, and Nanorods: pH-triggerable Hierarchical Self-assembly
2011
In this study, we present a novel, multifaceted pH-triggerable system of self-organized hierarchical nanostructures. The system consists of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and poly(2-vinylpyridine) cylindrical brushes (PVP brushes) and can yield polymer-porphyrin networks, porphyrin loaded polymer brushes and pure porphyrin nanorods. In addition, the polymer influences the pK(a) and the mutual TPPS stacking geometry. Structures were characterized by AFM, dynamic light scattering using an IR laser, UV-Vis spectroscopy and small-angle neutron scattering (SANS). Supramolecular composite porphyrin structures that can be switched through external triggers have potential in photo…
Functionalized halloysite multivalent glycocluster as a new drug delivery system.
2020
A new design for halloysite nanotube materials was obtained by grafting chemically modified cyclodextrin units onto the nanotube surface. In particular, grafted cyclodextrins were decorated with thiosaccharide pendants, in order to mimic the well-known binding of sugars to proteins and the glyco-cluster effect occurring during cellular recognition events. The obtained materials were characterized by using a combination of varied techniques (FT-IR spectroscopy, thermogravimetric analysis, scanning electron microscopy, dynamic light scattering, turbidimetry), and their potential drug-delivery abilities were tested by studying their interactions with the common naturally occurring anticancer a…
Phase Transition of SBN: Ce Studied by Anisotropic Holographic Scattering
1991
Light scattering phenomena in (Sr0.61Ba0.39) Nb2O6:Ce are investigated from room temperature to the phase transition temperature. Temperature dependence and sign of the birefringence are determined from anisotropic holographic scattering at a wavelength of 514.5 nm. The majority charge carriers are electrons. Zwischen Zimmertemperatur und der Phasenubergangstemperatur werden Lichtstreuphanomene in (Sr0,61Ba0,39)Nb2O6:Ce untersucht. Aus der anisotropen holographischen Streuung bei einer Wellenlange von 514,5 nm werden Temperaturabhangigkeit und Vorzeichen der Doppelbrechung bestimmt. Die Majoritatsladungstrager sind Elektronen.
Temperature triggered self-assembly of polypeptides into multivalent spherical micelles.
2007
We report herein thermally responsive elastin-like polypeptides (ELPs) in a linear AB diblock architecture with an N-terminal peptide ligand that self-assemble into spherical micelles when heated slightly above body temperature. A series of 10 ELP block copolymers (ELP(BC)'s ) with different molecular weights and hydrophilic-to-hydrophobic block ratios were genetically synthesized by recursive directional ligation. The self-assembly of these polymers from unimers into micelles was investigated by light scattering, fluorescence spectroscopy, and cryo-TEM. These ELP(BC)'s undergo two phase transitions as a function of solution temperature: a unimer-to-spherical micelle transition at an interm…
Effects of solvent perturbation on gelation driven by spinodal demixing
1999
We study effects of solvent perturbation on kinetic competition between spinodal demixing and gelation in agarose solutions at a concentration of 5 g/l. Two different cosolutes (tert-butyl alcohol and trimethyl amine N-oxide) known for altering in opposite way solvent-mediated interactions are chosen. By rheometry, static and dynamic light scattering experiments, we show that the cosolute presence shifts the boundary of the instability region of solution leaving unaffected temperature and polymer concentration values required for percolation. Results suggest that an appropriate choice of quenching temperature and solvent allows controlling the gelation time and the gel structural properties.
Ligand requirement for LHC I reconstitution
1998
Knowledge of the structure of photosynthetic light harvesting complexes is essential for understanding their function. Reconstitution of light harvesting complexes proved to be a very powerful tool for such structure analyses. In this way evidence was obtained for the central role of lutein and chlorophylls for LHCII structure (1) which was later confirmed by electron crystallographic analyses (2). Employing mutated, bacterial overexpressed LHCII apoproteins, amino acids could be identified which are involved in trimerization of LHCII and probably in binding of phosphatidylglycerol (3).
Photoaffinity labeling of the coupling factor 1 from the thermophilic bacterum PS3 by 8-azido ATP
1984
AbstractTo localize the nucleotide binding sites of the F1ATPase (TF1) from the thermophilic bacterium PS3 we have used 14C-labeled 8-azido ATP (8-N3ATP) as photoaffmity label. 8-N3ATP is hydrolyzed by the F,ATPase in the absence of ultraviolet light. Irradiation by ultraviolet light of the enzyme in the presence of 8-N3ATP results in reduction of ATPase activity and in preferential nucleotide specific labeling of the α subunits (0.8–0.9 mol 8-N3ATP/TF1,α:β = 4:1). Inactivation and labeling do not depend on the presence of Mg2+. Both effects decrease upon addition of various nucleotide di- or triphosphates.