Nicolas Cheval

Functional hybrid materials

Nanofabrication via self-assembly of hybrid materials into well-defined architectures is essential for the next generation of miniaturized devices. This paper describes our groups achievements towards the development of multifunctional nanostructures via self-assembly of hybrid systems based on the block copolymer PS-b-P4VP and inorganic nanoparticles (NPs) into 0D, 1D, 2D and complex 3D periodic nanostructures. The morphologies of these architectures are adjusted to gain functions via structural control at different dimensions.

Ion-Selective Controlled Assembly of Dendrimer-Based Functional Nanofibers and Their Ionic-Competitive Disassembly

The construction of hierarchical materials through controlled self-assembly of molecular building blocks (e.g., dendrimers) represents a unique opportunity to generate functional nanodevices in a convenient way. Transition-metal compounds are known to be able to interact with cationic dendrimers to generate diverse supramolecular structures, such as nanofibers, with interesting collective properties. In this work, molecular dynamics simulation (MD) demonstrates that acetate ions from dissociated Cd(CH(3)COO)(2) selectively generate cationic PPI-dendrimer functional fibers through hydrophobic modification of the dendrimers surface. The hydrophobic aggregation of dendrimers is triggered by the asymmetric nature of the acetate anions (AcO(-)) rather than by the precise transition metal (Cd). The assembling directionality is also controlled by the concentration of AcO(-) ions in solution. Atomic force (AFM) and transmission electron microscopy (TEM) prove these results. This well-defined directional assembly of cationic dendrimers is absent for different cadmium derivatives (i.e., CdCl(2), CdSO(4)) with symmetric anions. Moreover, since the formation of these nanofibers is controlled exclusively by selected anions, fiber disassembly can be consequently triggered via simple ionic competition by NaCl salt. Ions are here reported as a simple and cost-effective tool to drive and control actively the assembly and the disassembly of such functional nanomaterials based on dendrimers.

Polyamide 66 microspheres metallised with in situ synthesised gold nanoparticles for a catalytic application

A simple concept is proposed to metallise polyamide 66 (PA66) spherulite structures with in situ synthesised gold nanoparticles (Au NPs) using a wet chemical method. This cost-effective approach, applied to produce a PA66/Au NP hybrid material, offers the advantages of controlling the nanoparticle size, the size distribution and the organic-inorganic interactions. These are the key factors that have to be controlled to construct consistent Au nanostructures which are essential for producing the catalytic activities of interest. The hybrid materials obtained are characterised by means of scanning electron microscopy, transmission electron microscopy, attenuated total reflection-Fourier transform infrared spectrometry and X-ray diffraction spectrometry. The results show that PA66 microspheres obtained via the crystallisation process are coated with Au NPs of 13 nm in size. It was found that controlling the metal coordination is the key parameter to template the Au NPs on the spherulite surfaces. The preparation processes and the key factors leading to the formation of PA66 spherulites coated with Au NPs are discussed. Moreover, the efficiency of the coated spherulites as a potential catalyst is proved by demonstrating the reduction of methylene blue via UV-visible spectrometry.

Hybrid one-dimensional nanostructures: one-pot preparation of nanoparticle chains via directed self-assembly of in situ synthesized discrete Au nanoparticles.

The fabrication of well-defined one-dimensional (1D) arrays is becoming a challenge for the development of the next generation of advanced nanodevices. Herein, a simple concept is proposed for the in situ synthesis and self-assembly of gold nanoparticles (AuNPs) into 1D arrays via a one-step process. The results demonstrated the formation of nanoparticle chains (NPC) with high aspect ratio based on discrete Au nanoparticles stabilized by short thiol ligands. A model was proposed to explain the self-assembly based on the investigation of several parameters such as pH, solvent, temperature, and nature of the ligand on the 1D assembly formation. Hydrogen bonding was identified as a key factor to direct the self-assembly of the hybrid organic–inorganic nanomaterials into the well-defined 1D nanostructures. This simple and cost-effective concept could potentially be extended to the fabrication of a variety of hybrid 1D nanostructures possessing unique physical properties leading to a wide range of applications including catalysis, bionanotechnology, nanoelectronics, and photonics.

Hybrid Nanoalloy: Nanofibers Fabricated by Self‐Assembling Dendrimers Mediate In Situ CdSe Quantum Dots and Their Metallization with Discrete Gold Nanoparticles

Controlling the assembly of individual nanoparticles into welldefi ned nanostructures by self-assembled hybrid materials is a powerful technique to fabricate novel functional nanomaterials. [ 1 ] This type of nanofabrication facilitates the formation of different anisotropic nanostructures. [ 2 ] Among these types of nanostructures, 1D nanostructured hybrid organic–inorganic materials [ 3 ] have attracted signifi cant attention, not only because of their unique physical properties, but also because they can be used as building blocks to achieve a high degree of integral functionality useful for the next generation of miniaturized devices. Herein we report on a simple approach to fabricate metallized high density semiconducting hybrid nanofi bers based on self-assembled dendrimer templated CdSe nanoparticles in situ at room temperature. The dendrimer@CdSe hybrid nanofi bers are prepared by a wet chemical method in aqueous medium and have been used as a scaffold to deposit discrete metallic nanoparticles. Dendrimers are globular macromolecules composed of a core, dendrons, and surface groups. [ 4 ] Dendrimers possess many merits such as well-defi ned molecular structures and monodispersity in molecular weight. [ 5 ] Poly(propyleneimine) (PPI) is a common type of dendrimer consisting of tertiary amine groups in the dendritic scaffold and peripheral primary amine groups (Figure 1-SI, Supporting Information). [ 6 ] The unique dendritic architecture of PPI provides a simple tool to modulate intermolecular interactions by dissimilarity in the protonation state between the dendritic scaffold (core) and peripheral shell. [ 7a ]

Hydroxyl functional polyester dendrimers as stabilizing agent for preparation of colloidal silver particles—a study in respect to antimicrobial properties and toxicity against human cells

The presented study concerns the preparation and investigation of silver particles in presence of hydroxylated polyester dendrimers used as stabilizing agent. Altogether a full series of water soluble and aliphatic bis-MPA dendrimers from first to fifth generation was used as to stabilize silver nanoparticles in situ. A special focus is set on the biological properties. The antibacterial properties of the dendrimer stabilized silver particles are tested against Escherichia coli and the toxicity against human cells is tested with the human epithelial cell line A549. Under the chosen testing arrangement, it was observed that the silver particles contain a significant antibacterial effect against E. coli. Silver particles stabilized in situ with dendrimers of higher generation seem to contain a stronger antibacterial property. No toxicity against human cells was observed for the silver particles even in case of the highest investigated silver concentration. Altogether the here prepared and investigated silver particles could offer a great potential for application as antibacterial agent with low human toxicity.

Cation‐Induced Unidirectional Self‐Assembly of Amino‐Terminated Poly(propylene imine) Dendrimers

Nanofabrication via directed self-assembly of hybrid mate-rials into well-defi ned nanostructures is a powerful tool to produce functional building blocks, which possess unique optical, magnetic, and electronic properties that are essential for the next generation of nanodevices. In particular, hybrid materials based on dendrimers in combination with inorganic components resemble an ideal functional system for nano-structuring via hierarchical self-assembly. Recently, it has been shown that dendrimers can act as unimolecular micelles for the controlled synthesis and stabilization of inorganic nano-particles.

Assembl y of Poly-3-Hexylthiophene Nano-Crystallites into Low Dimensional Structures Using Indandione Derivatives

Conductive polymer poly-3-hexylthiophene (P3HT) needles were self-assembled using a second component (indandione derivatives) as a linking agent to enhance their long range alignment. The morphologies of the hybrid organic/organic materials were characterized by transmission electron microscopy (TEM). Both linear and branched structures could be produced, with the degree of branching depending upon the linker used. Incorporation of indandione derivatives broadened the UV absorbance band of P3HT without significant change to its photoluminescence. This hybrid material could open a promising avenue in photovoltaic applications due to its interesting morphologies and optical properties.

Direct assembly of in situ templated CdSe quantum dots via crystalline lamellae structure of polyamide 66

A simple concept is proposed for templating in situ synthesised CdSe quantum dots (QDs) into an organised nano-pattern using the crystalline lamellae structure of polyamide 66 (PA66). The morphology obtained for PA66 and the hybrid material on Si/SiOx solid substrate was characterised by means of atomic force microscope. Controlling the PA66 concentration in solution and the organic–inorganic interactions are found to be the keys factors to direct the assembly of CdSe QDs along the PA66 linear crystalline structure. This simple approach could be opened a new avenue for a large spectrum of innovative high-tech applications.

Reinforcement of Polyamide 66 with Polyoxometalates Nanoparticles through the In Situ Sol-Gel Method

This paper investigated the influence of the nanoparticles on the thermal and mechanical properties of PA66 and various nanocomposites containing different weight fraction of polyoxometalate nanoparticles were prepared. The structural features of the nanocomposite are characterised using TEM, ATR-FITR, DMA and TGA. The results show that nanoparticles, around 5.5 nm in size are well-dispersed inside the polymer matrix. The physical interaction between PA66 and the POM nanoparticles led to a significant effect on the thermal and mechanical properties of PA66. Dynamic mechanical analysis (DMA) revealed a considerable change in the storage modulus of the nanocomposite. With only 1wt% of POM, the storage modulus of PA66 at 25oC is enhanced by 45%. Furthermore, the thermal stability of the nanocomposite is also enhanced, possibly owing to the absorption of oxygen by the nanoparticles. The results demonstrated that the obtained nanocomposites, via the combination of the excellent mechanical and thermal properties of PA66 with the intriguing optical, electrical and chemical properties of POM, were promising for catalytic, energy storage, memory devices, automobile and construction applications.