Search results for "Colloid"

Synthesis of tumor-associated MUC1-glycopeptides and their multivalent presentation by functionalized gold colloids

2014

The mucin MUC1 is a glycoprotein involved in fundamental biological processes, which can be found over-expressed and with a distinctly altered glycan pattern on epithelial tumor cells; thus it is a promising target structure in the quest for effective carbohydrate-based cancer vaccines and immunotherapeutics. Natural glycopeptide antigens indicate only a low immunogenicity and a T-cell independent immune response; however, this major drawback can be overcome by coupling of glycopeptide antigens multivalently to immunostimulating carrier platforms. In particular, gold nanoparticles are well suited as templates for the multivalent presentation of glycopeptide antigens, due to their remarkably…

Single Gold Nanoparticle Growth Monitored in situ

2012

The novel fastSPS setup is used to study the growth process of rodshaped gold nanoparticles in the presence of surfactant molecules. It is observed that the particles grow mainly in the direction of the short rod axis, resulting in a decrease of the aspect ratio. This is, to the best of my knowledge, the first real-time optical observation of nanoparticle growth on a single-particle level (results were published in reference ). In collaboration with Olaf Schubert the nanoparticle growth was also monitored using the novel RotPOL setup. Here a decrease of the average polarization anisotropy \(PA\) is observed.

Palladium-catalyzed dehydrogenative β'-functionalization of β-keto esters with indoles at room temperature.

2012

The dehydrogenative β′-functionalization of α-substituted β-keto esters with indoles proceeds with high regioselectivities (C3-selective for the indole partner and β′-selective for the β-keto ester) and good yields under mild palladium catalysis at room temperature with a variety of oxidants. Two possible mechanisms involving either late or early involvement of indole are presented.

Cross-Dehydrogenative Couplings between Indoles and beta-Keto Esters: Ligand-Assisted Ligand Tautomerization and Dehydrogenation via a Proton-Assiste…

2014

Cross-dehydrogenative coupling reactions between β-ketoesters and electron-rich arenes, such as indoles, proceed with high regiochemical fidelity with a range of β-ketoesters and indoles. The mechanism of the reaction between a prototypical β-ketoester, ethyl 2-oxocyclopentanonecarboxylate, and N-methylindole has been studied experimentally by monitoring the temporal course of the reaction by (1)H NMR, kinetic isotope effect studies, and control experiments. DFT calculations have been carried out using a dispersion-corrected range-separated hybrid functional (ωB97X-D) to explore the basic elementary steps of the catalytic cycle. The experimental results indicate that the reaction proceeds v…

2021

The reaction of :AlAriPr8 (AriPr8 = C6H-2,6-(C6H2-2,4,6-iPr3)2-3,5-iPr2) with ArMe6N3 (ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2) in hexanes at ambient temperature gave the aluminum imide AriPr8AlNArMe6 (1). Its crystal structure displayed short Al-N distances of 1.625(4) and 1.628(3) A with linear (C-Al-N-C = 180°) or almost linear (C-Al-N = 172.4(2)°; Al-N-C = 172.5(3)°) geometries. DFT calculations confirm linear geometry with an Al-N distance of 1.635 A. According to energy decomposition analysis, the Al-N bond has three orbital components totaling -1350 kJ mol-1 and instantaneous interaction energy of -551 kJ mol-1 with respect to :AlAriPr8 and ArMe6N:. Dispersion accounts for -89 kJ mol-1, w…

Graphene-type sheets of Nb(1-x)W(x)S2: synthesis and in situ functionalization.

2013

Enlightened by the discovery of graphenes, a variety of inorganic analogues have been synthesized and characterized in recent years. Solvated Nb1−xWxS2 analogues of graphene-type sheets were prepared by lithiation and exfoliation of multistacked Nb1−xWxS2 coin roll nanowires (CRNWs), followed by in situ functionalization with gold nanoparticles to synthesize gold-loaded Nb1−xWxS2/Au nanocomposites. The Nb1−xWxS2 nanosheets and the corresponding Nb1−xWxS2/Au nanocomposites were characterized by high resolution electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM), dynamic light scattering (DLS) and scanning force microscopy …

Surface Chemistry Directs the Tunable Assembly of TiO 2 Anatase Nanocubes into Three‐Dimensional Mesocrystals

2019

Surface complexation modeling of arsenate adsorption by akagenéite (β-FeOOH)-dominant granular ferric hydroxide

2014

Abstract A surface complexation model has been set up for the first time with akaganeite (β-FeOOH), a major compound of granular ferric hydroxide (GFH) used in groundwater purification units worldwide for arsenic and other toxic pollutant removal. Unlike the situation for the α-FeOOH polymorph goethite, there is yet no published surface complexation model to predict competing oxyanion effects. This is due to a linked bulk-surface reactivity by which excess protons released in an unknown amount from tunnel sites hamper quantification of surface protonation by acid titration. The measured proton uptake thus exceeds what can be expected from OH groups active in surface protonation. However, ch…

Au deposited on CeO2 prepared by a nanocasting route: A high activity catalyst for CO oxidation

2014

Abstract A set of catalysts comprised of gold on different CeO 2 supports has been prepared by a nanocasting route and characterized by several physicochemical techniques. These catalysts have been tested for CO oxidation and show outstanding catalytic activity. Higher calcination temperatures of the hard template, producing a poorly ordered silica template, have led to a higher amount of oxygen vacancies on the surface of CeO 2 . The presence of surface oxygen defects in the support combined with the deposition of Au nanoparticles ( ca. 3 nm) homogeneously dispersed on the CeO 2 support may explain the excellent behaviour for low temperature CO oxidation. Surprisingly, it has been observed…

Thermally highly stable amorphous zinc phosphate intermediates during the formation of zinc phosphate hydrate.

2015

The mechanisms by which amorphous intermediates transform into crystalline materials are still poorly understood. Here we attempt to illuminate the formation of an amorphous precursor by investigating the crystallization process of zinc phosphate hydrate. This work shows that amorphous zinc phosphate (AZP) nanoparticles precipitate from aqueous solutions prior to the crystalline hopeite phase at low concentrations and in the absence of additives at room temperature. AZP nanoparticles are thermally stable against crystallization even at 400 °C (resulting in a high temperature AZP), but they crystallize rapidly in the presence of water if the reaction is not interrupted. X-ray powder diffract…