Demonstrative experiments about gold nanoparticles and nanofilms: an introduction to nanoscience

International audienceAn important task of the scientific community is to provide non-specialized audience with explanations about what is nanoscience. Such explanations can be given during public conferences, seminars in high schools or lab work organized with teachers. And very often, the use of an experimental illustration greatly helps to raise the interest and the curiosity of the public. The present article will describe how the authors have used five simple and visual experiments in chemistry and physics to progressively introduce different audiences into the fascination of nanoscience. One experiment is the synthesis of gold nanoparticles with the Turkevich method and shows the progressive appearance of the ruby-red colour of the nanometric gold particles. The second and third experiments describe the way for modulating their colour and how to include them into a polymer and form a ruby-red coloured plastic film. The fourth experiment shows that starting from these nanoparticles, it is possible to turn them back into a yellow golden film. The last experiment is based on the optical properties of ultra-thin gold films. Using the plasmon resonance, it is possible to demonstrate that gold change colours from yellow to orange and green when a white light beam is shone on the gold interface. These visual experiments cannot be fully interpreted in front of a large audience but serve for rising curiosity

Synthèse et caractérisation de nanostructures induites par radiolyse en mésophases hexagonales

Les propriétés (catalytiques, électriques, optiques ou magnétiques) des métaux ultra-divisés sont différentes du métal massif et sont influencées par la forme et la morphologie des nanomatériaux. Parmi les techniques de synthèses des nanomatériaux, la radiolyse est une méthode de choix pour réduire de façon contrôlée des ions métalliques et pour induire la polymérisation de monomères. Une matrice souple auto-assemblée, à partir de molécules de surfactants, a été employée comme nanoréacteur pour synthétiser des nanostructures (bi-)métalliques ou polymères de morphologie contrôlée. Les surfactants forment dans des conditions particulières des mésophases hexagonales quaternaires qui peuvent être gonflées, de façon continue, sur une large gamme. Le dopage des mésophases en sels métalliques ou en monomères peut être réalisé aussi bien en phase aqueuse qu en phase organique, permettant d obtenir des nanostructures de morphologie différentes. En phase aqueuse, la synthèse conduit à la formation de matériaux mésoporeux. Ceux-ci sont d un intérêt tout particulier pour la catalyse en raison de leur très grande surface spécifique. Le contrôle du gonflement de la mésophase permet un ajustement fin de la porosité dans la structure métallique finale. Nous avons également mis en évidence que la composition de ces nanostructures métalliques Pd/Pt poreuses peut être contrôlée. Nous avons également synthétisé des nanostructures 1D dans la phase organique, comme des nanofils de palladium ou des nanofils de polymères.The properties (catalytic, electrical, optical or magnetic) of ultra-divided metals are different from those from bulk and are influenced by the shape and morphology of the nanomaterials. Among the techniques of nanomaterials synthesis, radiolysis is a preferred method to reduce metal ions and to induce the polymerization of monomers. A soft template made of self-assembled surfactant molecules, has been used as nanoreactor to synthesize (bi-)metallic or polymer nanostructures of controlled morphology. Surfactants can form, under certain conditions, quaternary hexagonal mesophases, which can be inflated continuously over a wide range. Mesophases can be doped with metal salts or monomers, in aqueous phase or in organic phase, to obtain different nanostructures morphology. In aqueous phase, the synthesis leads to the formation of mesoporous materials. These are of particular interest for catalysis due to their large surface area. The control of the mesophase swelling allows a fine adjustment of the porosity in the final metal structure. We also demonstrated that the composition of porous bimetallic nanostructures Pd / Pt can be controlled. We also synthesized 1D nanostructures in the organic phase, such as metal (palladium) or polymer nanowires.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Functionalization of gold nanoparticles with Ru-porphyrin and their selectivity in the oligomerization of alkynes

Gold nanoparticles (AuNPs) were functionalized by ruthenium porphyrins through a sulfur/gold covalent bond using a three-steps reaction. The catalyst was characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) in order to control the binding of ruthenium porphyrin on AuNPs’ surface. The catalyst was tested and compared with an analog system not bound to AuNPs in the oligomerization reaction using 1-phenylacetylene as the substrate

TiO₂ Films with Macroscopic Chiral Nematic-Like Structure Stabilized by Copper Promoting Light-Harvesting Capability for Hydrogen Generation

Cellulose nanocrystals (CNCs) have inspired the synthesis of various advanced nanomaterials, opening opportunities for different applications. However, a simple and robust approach for transferring the long-range chiral nematic nanostructures into TiO2 photocatalyst is still fancy. Herein, a successful fabrication of freestanding TiO2 films maintaining their macroscopic chiral nematic structures after removing the CNCs biotemplate is reported. It is demonstrated that including copper acetate in the sol avoids the epitaxial growth of the lamellar-like structure of TiO2 and stabilizes the chiral nematic structure instead. The experimental results and optical simulation demonstrate an enhancement at the blue and red edges of the Fabry-Pérot reflectance peak located in the visible range. This enhancement arises from the light scattering effect induced by the formation of the chiral nematic structure. The nanostructured films showed 5.3 times higher performance in the photocatalytic hydrogen generation, compared to lamellar TiO2, and benefited from the presence of copper species for charge carriers’ separation. This work is therefore anticipated to provide a simple approach for the design of chiral nematic photocatalysts and also offers insights into the electron transfer mechanisms on TiO2/CuxO with variable oxidation states for photocatalytic hydrogen generation.</p

Improving proton therapy by metal-containing nanoparticles:Nanoscale insights

The use of nanoparticles to enhance the effect of radiation-based cancer treatments is a growing field of study and recently, even nanoparticle-induced improvement of proton therapy performance has been investigated. Aiming at a clinical implementation of this approach, it is essential to characterize the mechanisms underlying the synergistic effects of nanoparticles combined with proton irradiation. In this study, we investigated the effect of platinum- and gadolinium-based nanoparticles on the nanoscale damage induced by a proton beam of therapeutically relevant energy (150 MeV) using plasmid DNA molecular probe. Two conditions of irradiation (0.44 and 3.6 keV/mu m) were considered to mimic the beam properties at the entrance and at the end of the proton track. We demonstrate that the two metal-containing nanoparticles amplify, in particular, the induction of nanosize damages (&gt;2 nm) which are most lethal for cells. More importantly, this effect is even more pronounced at the end of the proton track. This work gives a new insight into the underlying mechanisms on the nanoscale and indicates that the addition of metal-based nanoparticles is a promising strategy not only to increase the cell killing action of fast protons, but also to improve tumor targeting.</p

Les clusters metalliques moleculaires: synthese radiolytique et caracterisation

INIST T 73502 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Nanoparticules métalliques induites par radiolyse (confinement et auto-assemblage)

La radiolyse est une méthode efficace pour la synthèse de nanoparticules mono et bimétalliques, de taille, de forme et de structure contrôlées en solution et en milieu hétérogène. Nous avons synthétisé par radiolyse (synthèse one pot ) des nanobâtonnets d'or de rapports d'aspect contrôlables. Nous avons étudié les processus de réduction et de nucléation/croissance qui mènent à la formation de ces nanoparticules anisotropes. Ces bâtonnets nanométriques métalliques présentent des propriétés optiques originales et des applications potentielles dans différents domaines notamment en optique et en biologie. Ces nanobâtonnets d'or peuvent être piégés dans des hydrogels induits par la réticulation du polymère par radiolyse. Les propriétés d'anisotropie de ces nanobâtonnets sont aussi très recherchées notamment pour former des systèmes organisés et alignés. Nous nous sommes intéressés, dans un second lieu, à la synthèse par radiolyse de nanoparticules d'or et de platine dans des phases lamellaires de cristaux liquides. Nous avons montré que le confinement permettait de limiter la croissance et la taille des nanoparticules. Des nanobâtonnets d'or ont pu être insérés dans la phase aqueuse confinée de la mésophase, ou induits directement in situ par radiolyse. Dans tous les cas, la structure de la mésophase lamellaire est conservée après la croissance des nanoparticules. Le comportement des nanobâtonnets d'or confinés dans la mésophase a été étudié. D'autre part, nous avons synthétisé par radiolyse des nanoparticules de platine ou à base de platine (Pt/Ru, Pt/Ru/Sn et Pt/Co) en solution et sur des nanotubes de carbone. Les nanoparticules obtenues sont petites et monodisperses. La fonctionnalisation des nanotubes par un tensioactif a permis un assemblage homogène des nanoparticules sur leur surface et un meilleur accrochage. Ces nanocomposites peuvent avoir des applications dans différents domaines : piles à combustible, capteurs, limitation optique ...Radiolysis is a powerful method to synthesize mono and bimetallic nanoparticles of controlled size, shape and structure, in solution and in heterogeneous media. Gold nanorods of controllable aspect ratios were synthesized by radiolysis ("one pot" synthesis). The reduction steps and the nucleation and growth processes leading to the formation of these anisotropic nanoparticles were studied. These nanorods display original optical properties and have potential applications in various fields including optics and biology. These gold nanorods can be trapped in hydrogels induced by the polymer crosslinking under radiolysis. The anisotropic properties of these nanorods are also very attractive for the formation of organized and aligned systems. We were interested, in a second step, to synthesize by radiolysis gold and platinum nanoparticles in liquid crystal lamellar phases. We have shown that the confinement allows limitation of the growth and the size of the nanoparticles. Gold nanorods can be confined in a lamellar phase or induced in situ directly by radiolysis. ln all cases, the structure of the lamellar phase is preserved after the growth of the nanoparticles. The behavior of gold nanorods confined in the mesophase was also studied. On the other hand, we have synthesized by radiolysis platinum based nanoparticles (Pt, Pt/Ru, Pt/Ru/Sn and Pt/Co) in solution and on carbon nanotubes. The formed nanoparticles are small and monodisperse. Functionalization of nanotubes by a surfactant allowed a homogeneous assembly of nanoparticles on their surface and a better anchoring. These nanocomposites may have applications in different fields: fuel cells, sensors, optical limitation...ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Nanoparticules métalliques et rayonnements ionisants : synthèse et applications

International audienceLa radiolyse est une puissante méthode de synthèse des nanoparticules métalliques en solution ou dans des milieux hétérogènes permettant un contrôle de la taille et de la forme. La présence de ligands, polymères ou supports utilisés pour stabiliser les nanoparticules joue un rôle important pour les applications potentielles en biologie, médecine, catalyse, photocatalyse, énergie