Search results for "Nanoparticle"
showing 10 items of 2198 documents
Interaction between nitroxyl radicals and CdTe quantum dots: Determination of fluorescence-quenching mechanisms in aqueous solution
2019
Abstract The present work characterizes the optical properties of CdTe quantum dots (CdTe QDs) after interaction with nitroxyl radicals based on steady-state and time-resolved fluorescence spectroscopy studies. QDs of different sizes were exposed to 2 different nitroxyl radicals, i.e., TEMPO and 4-amino-TEMPO radicals. A clear dependence of dynamic and static Stern-Volmer constants values, KD and KS, respectively, was observed as a function of the size of QDs used, with a change from a mostly static mechanism (for smaller QD sizes) to a dynamic mechanism predominating as the nanoparticles increase in size. All observed effects are dependent on both the concentration of the radical and the s…
In situ AFM study of proton-assisted electrochemical oxidation/reduction of microparticles of organic dyes
2008
In situ atomic force microscopy (AFM) images of crystals of organic dyes alizarin, indigo and morin have been monitored during the course of their solid-state electrochemical oxidation/reduction in contact with aqueous acetate buffer. Such images indicate that proton-assisted reduction and oxidation processes are localized in a shallow layer in the vicinity of the particle/electrolyte interface, in agreement with expectances from the Lovric and Scholz model with significantly restricted proton diffusion across the solids. Keywords: Voltammetry of nanoparticles, Atomic force microscopy, Organic dyes, Diffusion
Encapsulation of hydrophilic and lipophilized catechin into nanoparticles through emulsion electrospraying
2017
In this work, we investigated the potential of emulsion electrospraying that contained bacterial cellulose and proteins for the encapsulation of epigallocatechin gallate (EGCG). Specifically, two different catechins, hydrophilic (H-EGCG) or lipophilized (L-EGCG), were encapsulated either on the aqueous or the oily phase of the emulsions in order to compare the antioxidants’ stability. Emulsion properties in terms of stability, droplet size, bulk and interfacial viscosity were studied combined with the evaluation of the properties of the produced particles, namely the morphology and size of the particles, the encapsulation efficiency (EE) of catechin and the stability of the EGCG within the …
Structure Sensitivity of 2-Methyl-3-butyn-2-ol Hydrogenation on Pd: Computational and Experimental Modeling
2014
In the frame of DFT paradigms, the adsorption of 2-methyl-3-butyn-2-ol (MBY) and 2-methyl-3-buten-2-ol (MBE) on a Pd-30 cluster, including both {100} and {111} faces, was studied along with the pathways involved in the hydrogenation, taking place on plane and low coordination (corner/edge) sites of given MBY/Pd-30 and MBE/Pd-30 surface configurations. The calculated energetics, further validated by gas-phase and water-assisted gas-phase MBY and MBE hydrogenation, performed on well-defined size and shape-controlled Pd nanoparticles supported on SiO2, were able to explain the origin of the structure sensitivity and the high selectivity characterizing the title reaction when occurring in aqueo…
Application of the Generalized Molar-Ratio Method to the Determination of the Stoichiometry and Apparent Binding Constant of Nanoparticle-Organic Cap…
2015
A generalization of the molar-ratio method is applied to the determination of the stoichiometry and apparent binding constant of metal nanoparticle-organic capping complexes (MmLx) using voltammetric data for the oxygen reduction reaction (ORR) in air-saturated aqueous phosphate buffer solutions. The method is applied to the formation of binary nanohybrids consisting of gold nanoparticles (AuNPs) capped with a rigid spacer, cucurbit[7]uril (CB), termed AuNP@CB, as well as to the formation of their ternary complexes (MmLxBz) with methylene blue (MB), termed AuNP@CB@MB. The obtained stoichiometries correspond to binding of four Au surface atoms for each CB unit.
Preparation of nanostructures composed of dextran sulfate/ruthenium nanoparticles and their interaction with phospholipid monolayers at a liquid–liqu…
2007
Abstract Nanostructures composed of dextran sulfate (DS)/ruthenium (Ru) nanoparticles (NPs) adsorbed on phospholipid monolayers at a liquid–liquid interface were prepared and characterized electrochemically in relation to their potential use in drug delivery systems. First, positively charged Ru NPs were prepared, and then negatively charged DS was adsorbed on the surface of the NPs, thus forming well-defined and organized structures, as observed under the transmission electron microscope, which are referred to composite nanoclusters. The lipid monolayers were formed by depositing either 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphatidylcholine or 1-palmitoyl-2-oleoyl- sn -glycero-3-phospho- …
Halloysite nanotubes filled with MgO for paper reinforcement and deacidification
2021
Abstract A novel material for the deacidification and protection of paper has been designed by using MgO filled halloysite nanotubes (Hal). The ability of MgO loaded nanotubes to control the acidic conditions was evaluated by pH measurements in aqueous solvent. Afterwards, paper was impregnated into hydroxypropyl cellulose dispersions containing the consolidating material. A simulation of strong acidic conditions allowed us to evaluate the deacidification effect of the composite material on the samples. In particular, the paper reaches a pH of 7.7 after 1 h exposition to HNO3 vapours when MgO-Hal nanoparticles are added to the impregnation mixture at a concentration of 10 wt% and it remains…
Expanding the atrane route: Generalized surfactant-free synthesis of mesoporous nanoparticulated xerogels
2008
Abstract A diversity of silica-based and non-silica nanoparticulated mesoporous xerogels have been synthesized from aqueous solution using a surfactant-free strategy, and starting from molecular atrane complexes as precursors. This approach constitutes an extension of the “atrane route” previously described for the surfactant-assisted synthesis of mesoporous materials, and allows us to unify the multiplicity of protocols described for the preparation of conventional xerogels. In fact, we have used exactly the same preparative conditions for obtaining all the compositions reported here. The xerogels synthesized in this way include pure silica (UVM-11), aluminosilicates and titanosilicates (M…
Solid-State Electrochemical Method for Determining Core and Shell Size in Pd@PdO Nanoparticles
2010
Electrochemical characterization of palladium nanoparticles surrounded by a palladium oxide shell (Pd@PdO) is described from a combination of voltammetry plus electrochemical quartz crystal microbalance experiments at nanoparticle deposits on graphite electrodes in contact with aqueous H2SO4 and NaOH solutions. A method for determining the metal core size and oxide shell thickness of the Pd@PdO nanoparticles, based on a combination of conventional voltammetry of nanoparticles in DMSO solution and voltammetry of nanoparticle deposits in contact with 0.10 M aqueous NaOH solution, is described.
Original Supercritical Water Device for Continuous Production of Nanopowders
2011
Well-crystallized ZnO, ZrO2, TiO2, CeO2, Y2O3 and La2O3 nanoparticles are synthesized under supercritical water conditions (T > 647 K and P > 22.1 MPa) using a home-made continuous process. At room temperature, metallic salts with or without aqueous hydroxide solution (KOH or NaOH) are pressurized to 25–30 MPa. Then, the reactant(s) is/are rapidly heated to 673–773 K by mixing with the supercritical water in a patented reactor. Residence time is in the range from 2 to 8 s. XRD, TEM and surface area analyses highlight the production of pure and well-crystallized nanoparticles with a uniform size distribution.