Lithium ion as growth-controlling agent of ZnO nanoparticles prepared by organometallic synthesis

ZnO nanoparticles were synthesized by adding solid Zn(c-C6H11)2 to a THF solution of the lithium (sodium) precursor and octylamine (OA) as stabilizer. The proportion of Li (Na) was varied from 1 to 10 mol% compared to Zn. Two different lithium precursors namely Li[N(CH3)2] (series 1) and Li[N(Si(CH3)3)2] (series 2) and one sodium precursor namely Na[N(Si(CH3)3)2] (series 3) were used. Interestingly, Li precursors induce a modification of the growth of the particles while, no effect is observed when Na precursors is used. Indeed, isotropic nanoparticles were obtained when Li precursors were used while nanorods were formed with Na precursor as already observed in the same experimental conditions without alkali-metal precursor. Observations by TEM show that as the Li/Zn molar ratio increases, the mean diameters of the nanoparticles vary from 3.7 ± 0.7 nm to 2.5 ± 0.4 nm, and from 4.3 ± 1.0 nm to 3.1 ± 0.8 nm for series 1 and series 2, respectively, while the length and the diameter of the nanorods are ca. 11 × 4 nm, for series 3. Interestingly, the consequence of the lithium induced size variation leads to a shift of the emission band in the visible range, from yellow to blue through white as a function of increasing concentration of lithium precursor. The intensity of this emission is strong enough to be clearly seen by the human eye

Généralisation d'une approche de synthèse par voie organométallique, à température ambiante, de nanoparticules monocristallines d'oxydes métalliquess (étude de leurs propriétés optiques ou magnétiques)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Study of the role of the ligands coordinated at the surface of pure Wüstite nanoparticles prepared following a room temperature organometallic method: Evidence of ferromagnetic – in shell- and antiferromagnetic – in core magnetic behaviors

International audienc

An organometallic approach for very small maghemite nanoparticles: Synthesis, characterization, and magnetic properties

Maghemite (gamma-Fe2O3) nanoparticles stabilized by long-alkyl-chain amines are synthesized by using an orgonometallic approach. This method consists of the hydrolysis and oxidation of an organometallic precursor, Fe[N(SiMe3)(2)](2), in the presence of amine ligands as stabilizing agent in an organic solvent, namely tetrohydrofuron or toluene. Whatever the experimental conditions, particles with a diameter of 2.8 nm are obtained. The use of high-resolution transmission electron microscopy and wide-angle X-ray scattering, together with Mossbauer spectroscopy and SQuld magnetometry, allows a complete characterization of these particles. Herein, we show that their structure is composed of a well-ordered core surrounded by a more disordered shell. The size of the latter varies from 0.65 to 0.50 nm depending on the experimental conditions and is of prime importance for the understanding of the magnetic properties. We demonstrate that the shorter the alkyl chain length of the amine 1) the better the crystallinity of the particle's core and 2) the stronger the interparticle interactions

Deciphering ligands’ interaction with Cu and Cu2O nanocrystal surfaces by NMR solution tools

International audienceThe hydrogenolysis of [Cu2(iPrN)2(CCH3)2] in the presence of hexadecylamine (HDA) or tetradecylphosphonic acid (TDPA) in toluene leads to 6–9 nm copper nanocrystals. Solution NMR spectroscopy has been used to describe the nanoparticle surface chemistry during the dynamic phenomenon of air oxidation. The ligands are organized as multilayered shells around the nanoparticles. The shell of ligands is controlled by both their intermolecular interactions and their bonding strength on the nanocrystals. Under ambient atmosphere, the oxidation rate of colloidal copper nanocrystals closely relies on the chemical nature of the employed ligands (base or acid). Primary amine molecules behave as soft ligands for Cu atoms, but are even more strongly coordinated on surface CuI sites, thus allowing a very efficient corrosion protection of the copper core. On the contrary, the TDPA ligands lead to a rapid oxidation rate of Cu nanoparticles and eventually to the re-dissolution of CuII species at the expense of the nanocrystals

Understanding the Role of ω‑End Groups and Molecular Weight in the Interaction of PNIPAM with Gold Surfaces

Modification of nanoparticle surfaces by adsorption or grafting of polymers allows fine control of hybrid materials properties for diverse applications. To obtain such a control, it is of paramount importance to understand the impact of the polymer structure on the nature and strength of its interaction with the nanoparticle. We investigated here a simple model of hybrid materials made of poly­(<i>N</i>-isopropylacrylamide) of different molar masses and end groups interacting with gold surfaces. A series of poly­(<i>N</i>-isopropylacrylamide) with number-average molar masses ranging from 3700 to 10000 g·mol^–1 were synthesized by reversible addition–fragmentation chain transfer/macromolecular design by interchange of xanthates (RAFT/MADIX). The terminal xanthate group was then reduced into either a thiol or a hydrogen group. Quartz crystal microbalance adsorption/desorption experiments demonstrated that the polymer termini have a strong impact on the mechanism of polymer adsorption on flat gold surfaces. These differences in polymer structure have, in return, a strong influence on the colloidal stability and growth mechanism of nanoparticles when directly synthesized in polymer solution. For those properties, the effect of xanthate group compared very favorably to the conventional thiol moiety. Interestingly, the properties of nanohybrids were poorly affected by the molar mass of the polymer

Remarkable Decrease in the Oxidation Rate of Cu Nanocrystals Controlled by Alkylamine Ligands

Colloidal solutions of copper nanoparticles (7.2 ± 1.1 nm diameter), stabilized by alkylamine ligands, show a remarkably long persistence (several months) of the localized surface plasmon resonance (LSPR) when exposed to ambient air at room temperature. The oxidation kinetics of these nanoparticles have been investigated by optical spectroscopy and modeled using numerical simulations. Three distinct oxidation regimes are evidenced: (i) A fast regime in which oxygen is adsorbed and dissociated on the nanoparticle to form preoxide islands; (ii) a slower regime where the coalescence of the oxide islands takes place up to the formation of a complete Cu₂O shell; (iii) and finally an extremely slow oxidation of the residual copper core and eventually the formation of hollow Cu₂O nanoparticles. The adsorption rate of oxygen on copper nanoparticles is controlled by the amount of alkylamine ligands in solution (from 0.1 to 2 mol equiv)

Biocompatible inorganic nanoparticles for [F-18]-fluoride binding with applications in PET imaging

A wide selection of insoluble nanoparticulate metal salts was screened for avid binding of [(18)F]-fluoride. Hydroxyapatite and aluminium hydroxide nanoparticles showed particularly avid and stable binding of [(18)F]-fluoride in various biological media. The in vivo behaviour of the [(18)F]-labelled hydroxyapatite and aluminium hydroxide particles was determined by PET-CT imaging in mice. [(18)F]-labelled hydroxyapatite was stable in circulation and when trapped in various tissues (lung embolisation, subcutaneous and intramuscular), but accumulation in liver via reticuloendothelial clearance was followed by gradual degradation and release of [(18)F]-fluoride (over a period of 4 h) which accumulated in bone. [(18)F]-labelled aluminium hydroxide was also cleared to liver and spleen but degraded slightly even without liver uptake (subcutanenous and intramuscular). Both materials have properties that are an attractive basis for the design of molecular targeted PET imaging agents labelled with (18)F