Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

We address two aspects of general interest for the chemical synthesis of colloidal semiconductor nanocrystals: (1) the rational design of the synthesis protocol aiming at the optimization of the reaction parameters in a minimum number of experiments; (2) the transfer of the procedure to the gram scale, while maintaining a low size distribution and maximizing the reaction yield. Concerning the first point, the design-of-experiment (DOE) method has been applied to the synthesis of colloidal CdSe nanocrystals. We demonstrate that 16 experiments, analyzed by means of a Taguchi L16 table, are sufficient to optimize the reaction parameters for controlling the mean size of the nanocrystals in a large range while keeping the size distribution narrow (5-10%). The DOE method strongly reduces the number of experiments necessary for the optimization as compared to trial-and-error approaches. Furthermore, the Taguchi table analysis reveals the degree of influence of each reaction parameter investigated (e.g., the nature and concentration of reagents, the solvent, the reaction temperature) and indicates the interactions between them. On the basis of these results, the synthesis has been scaled up by a factor of 20. Using a 2-L batch reactor combined with a high-throughput peristaltic pump, different-sized samples of CdSe nanocrystals with yields of 2-3 g per synthesis have been produced without sacrificing the narrow size distribution. In a similar setup, the gram-scale synthesis of CdSe/CdS/ZnS core/shell/shell nanocrystals exhibiting a fluorescence quantum yield of 81% and excellent resistance of the photoluminescence in presence of a fluorescent quencher (aromatic thiol) has been achieved

Multifunctional hybrid silica nanoparticles based on [Mo₆Br₁₄]²⁻ phosphorescent nanosized clusters, magnetic γ-Fe₂O₃ and plasmonic gold nanoparticles

International audienceWe report on the synthesis, characterization and photophysical study of new luminescent and magnetic hybrid silica nanoparticles. Our method is based on the co-encapsulation of single maghemite γ-Fe2O3 nanoparticles and luminescent molybdenum cluster units [Mo6Br(i)8Br(a)6](2-) through a water-in-oil (W/O) microemulsion technique. The as-prepared core-shell [Cs2Mo6Br14-γFe2O3]@SiO2 nanoparticles (45-53 nm) possess a single magnetic core (6, 10.5 or 15 nm) and the cluster units are dispersed in the entire volume of the silica sphere. The [Cs2Mo6Br14-γFe2O3]@SiO2 nanoparticles have a perfect spherical shape with a good monodispersity and they display red and near-infrared (NIR) emission in water under UV excitation, whose intensity depends on the magnetic core size. The hybrid nanoparticles have been characterized by transmission electron microscopy (TEM), high annular angular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis-NIR spectroscopy and magnetometer SQUID analysis. Small gold nanoparticles were successfully nucleated at the surface of the hybrid silica nanoparticles in order to add plasmonic properties

Polyamine ligand-mediated self-assembly of gold and silver nanoparticles into chainlike structures in aqueous solution: Towards new nanostructured chemosensors

We are grateful to the Scientific Association ProteoMass (Portugal) for financial support. C.N. thanks Xunta de Galicia (Spain) for her postdoctoral contract (I2C program).1D Nanochain formation: The binding ability of a polyamine molecular linker (L)2- bearing different functional groups, which favors the self-assembling of silver (AgNPs) and gold nano-particles (AuNPs) into 1D nanochains in aqueous solution was explored. UV/Vis spectrophotometry and TEM were used to determine time-dependent structural changes associated with these 1D structure formations. Sensing of Hg2+ using AgNPs@ (L) 2- and AuNPs@ (L)2- assemblies was also carried out in aqueous solution. © 2013 The Authors. Published by Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim.publishersversionpublishe

Préparation et études photophysiques d'assemblages de nanoparticules d'or et de molécules organiques fluorescentes

L'intérêt croissant des scientifiques pour les nanosciences a suscité une forte activité au sein de divers domaines tel que celui des nanoparticules métalliques et des monocouches auto-assemblées sur des surfaces. En effet, le design, la synthèse et la caractérisation de surfaces modifiées de nanoparticules se révèlent être d'une importance fondamentale pour le contrôle des propriétés de nouveaux matériaux utilisables dans des domaines aussi variés que l'optoélectronique, l'imagerie du vivant ou encore la reconnaissance moléculaire. Actuellement, les nanoparticules d'or apparaissent comme une méthode de choix pour l'organisation supramoléculaire. C'est dans cet objectif que nous avons choisi d'étudier les propriétés photophysiques d'assemblages de nanoparticules d'or et de molécules organiques fluorescentes. Des stratégies différentes ont été adoptées afin de réaliser ces assemblages : les monocouches auto-assemblées et le dépôt de polyélectrolytes à la surface métallique.Metallic nanoparticles and Self Assembled Monolayers (SAM's) play key roles in the emerging field of nanosciences. Chemists are playing an important role in the design, synthesis and the characterisation of nanoparticles modified surfaces. This leads to control the properties of new class of materials with potential applications in optoelectronic, bioimaging and molecular recognition. Actually, gold nanoparticles are very important objects for the supramolecular organisation. In this context, we have chosen to study the photophysicals properties of gold nanoparticles functionalized by fluorescent organic molecules. Differents srategies have been used to make this nanomaterials : the technique of Self Assembled Monolayers and the Layer-by-Layer deposition of polyélectrolytes around the metallic surface.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

International audienc

Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

International audienc

Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

<p>Abstract</p> <p>We address two aspects of general interest for the chemical synthesis of colloidal semiconductor nanocrystals: (1) the rational design of the synthesis protocol aiming at the optimization of the reaction parameters in a minimum number of experiments; (2) the transfer of the procedure to the gram scale, while maintaining a low size distribution and maximizing the reaction yield. Concerning the first point, the design-of-experiment (DOE) method has been applied to the synthesis of colloidal CdSe nanocrystals. We demonstrate that 16 experiments, analyzed by means of a Taguchi L₁₆table, are sufficient to optimize the reaction parameters for controlling the mean size of the nanocrystals in a large range while keeping the size distribution narrow (5-10%). The DOE method strongly reduces the number of experiments necessary for the optimization as compared to trial-and-error approaches. Furthermore, the Taguchi table analysis reveals the degree of influence of each reaction parameter investigated (e.g., the nature and concentration of reagents, the solvent, the reaction temperature) and indicates the interactions between them. On the basis of these results, the synthesis has been scaled up by a factor of 20. Using a 2-L batch reactor combined with a high-throughput peristaltic pump, different-sized samples of CdSe nanocrystals with yields of 2-3 g per synthesis have been produced without sacrificing the narrow size distribution. In a similar setup, the gram-scale synthesis of CdSe/CdS/ZnS core/shell/shell nanocrystals exhibiting a fluorescence quantum yield of 81% and excellent resistance of the photoluminescence in presence of a fluorescent quencher (aromatic thiol) has been achieved.</p> <p> <b>PACS: </b>81.20.Ka, 81.07.Bc, 78.67.Bf</p

Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

International audienc

Quenching of molecular fluorescence on the surface of monolayer-protected gold nanoparticles investigated using place exchange equilibria.

International audienc

Hydrophilic monolayer-protected gold nanoparticles and their functionalisation with fluorescent chromophores

International audienceThe efficient implementation of metal nanoparticles in bioanalytical detection schemes, biological imaging and phototherapy requires these particles to be stable against aggregation and chemical desintegration. The functionalisation of these particles with specific (bio)molecular units is a further necessity. These requirements may be met by covering the particle surface with self-assembled monolayers of functional thiols and disulfides. We have synthesised organic disulfides carrying alkyl-oligoethylene glycol chains that self-assemble into a molecular monolayer on the surface of gold nanoparticles to give rise to robust water-soluble nano-objects. These monolayer-protected gold nanoparticles can be purified using centrifugation, dialysis and gel permeation chromatography. The number of available disulfide binding sites on the gold nanoparticles was determined experimentally, and found to be in reasonable agreement with theoretical estimates, indicative of the formation of a dense protecting monolayer. The introduction of molecular functions through amino-terminated oligoethylene glycol disulfides is exemplified using a fluorescent chromophore, fluorescein. The quenching of the fluorescence of fluorescein by the metal nanoparticle core is investigated quantitatively, and employed as a fluorimetric tool for the investigation of the monolayer chemistry of these water-soluble functionalised gold nanoparticles