Search results for "Catalysis"

Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds

2018

In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively th…

On the biradicaloid nature of long quinoidal oligothiophenes: experimental evidence guided by theoretical studies.

2007

Structure and Photocatalytic Properties of TiO2-WO3Composites Prepared by Electrophoretic Deposition

2015

In this work TiO2-WO3 composite films containing different oxide concentrations were prepared by electrophoretic deposition on steel substrates. Composite coating structures were analyzed by X -ray diffraction, Raman spectra and scanning electron microscopy. The results showed an even distribution of WO3 particles in the entire composite layer. Light absorption measurements were used for photocatalytic properties evaluation. It was found that the removal ratio of methylene blue depends on the (TiO2):(WO3) concentration ratio. The most effective photodegradation was determined for the sample that was electrophoretically deposited from the suspension with the molar content ratio n(TiO2):n(WO3…

A route to simple nonionic surfactants

2016

AbstractA method for the synthesis of nonionic surfactants – N-alkyl-O-(2-hydroxyethyl) carbamates is proposed by acylation of fatty amines with ethylene carbonate without any solvent or catalyst. The surface tension of the prepared surfactants was measured, toxicity and biodegradability were determined for the surfactant with n-dodecyl as a hydrophobic group and N-monosubstituted amide and hydroxyl groups for their hydrophilic part.

An Easy Route Towards Regioselectively Difunctionalized Cyclens and New Cryptands.

2006

Reductive amination of various aldehydes with cyclen represents a very convenient method for the synthesis of a wide range of 1,7-difunctionalized cyclens, as well as new cryptands.

Synthesis and selected properties of metallo and metal-free 2,3,9,10,16,17,23,24-octacarboxyphthalocyanines

2015

This review article reports methods of synthe sis and selected physicochemical properties of metallo and metal-free 2,3,9,10,16,17,23,24–octacarboxyphthalocyanines. The most frequently used methods of synthesis for this class of co mpounds are described in this article. Moreover, aggregation, catalytic and photocatalytic properties of these complexes are presented. Potential applications of metallo and metal-free 2,3,9,10,16,17,23,24–octacarboxyphthalocyanines are also given.

Absolute quantification of noncoding RNA by microscale thermophoresis

2019

Abstract Accurate quantification of the copy numbers of noncoding RNA has recently emerged as an urgent problem, with impact on fields such as RNA modification research, tissue differentiation, and others. Herein, we present a hybridization‐based approach that uses microscale thermophoresis (MST) as a very fast and highly precise readout to quantify, for example, single tRNA species with a turnaround time of about one hour. We developed MST to quantify the effect of tRNA toxins and of heat stress and RNA modification on single tRNA species. A comparative analysis also revealed significant differences to RNA‐Seq‐based quantification approaches, strongly suggesting a bias due to tRNA modifica…

Total Structure and Electronic Structure Analysis of Doped Thiolated Silver [MAg24(SR)18]2– (M = Pd, Pt) Clusters

2015

With the incorporation of Pd or Pt atoms, thiolated Ag-rich 25-metal-atom nanoclusters were successfully prepared and structurally characterized for the first time. With a composition of [PdAg24(SR)18](2-) or [PtAg24(SR)18](2-), the obtained 25-metal-atom nanoclusters have a metal framework structure similar to that of widely investigated Au25(SR)18. In both clusters, a M@Ag12 (M = Pd, Pt) core is capped by six distorted dimeric -RS-Ag-SR-Ag-SR- units. However, the silver-thiolate overlayer gives rise to a geometric chirality at variance to Au25(SR)18. The effect of doping on the electronic structure was studied through measured optical absorption spectra and ab initio analysis. This work d…

Structural Evolution of Atomically Precise Thiolated Bimetallic [Au12+nCu32(SR)30+n]4– (n = 0, 2, 4, 6) Nanoclusters

2014

A series of all-thiol stabilized bimetallic Au-Cu nanoclusters, [Au(12+n)Cu32(SR)(30+n)](4-) (n = 0, 2, 4, 6 and SR = SPhCF3), are successfully synthesized and characterized by X-ray single-crystal analysis and density functional theory (DFT) calculations. Each cluster consists of a Keplerate two-shell Au12@Cu20 core protected by (6 - n) units of Cu2(SR)5 and n units of Cu2Au(SR)6 (n = 0, 2, 4, 6) motifs on its surface. The size and structural evolution of the clusters is atomically controlled by the Au precursors and countercations used in the syntheses. The clusters exhibit similar optical absorption properties that are not dependent on the number of surface Cu2Au(SR)6 units. Although DFT…

Adsorption and Activation of Water on Cuboctahedral Rhodium and Platinum Nanoparticles

2017

Rh and Pt are widely used as the components in heterogeneous catalysts for multiple industrial applications. Because the metals are typically in the form of nanoparticles in real catalysts, it is important to carefully select models for the computational prediction of the catalytic properties. Here we report a first-principles study on the water activation, an important step in numerous catalytic reactions, using the finite-size Rh and Pt nanoparticle models and compare them to the extended surface models. We show that regardless of the model, adsorption and activation of water is practically identical for both metals, whereas the dissociation is energetically more favorable on Rh. The expe…