Exploration des nanotechnologies ADN pour l'auto-assemblage de nanoparticules d'aluminium et d'oxyde de cuivre : application à la synthèse de matériaux énergétiques

Over the two last decades, DNA technologies have intensively been studied for the organization of matter at the nanoscale. Thanks to the bio recognition of two complementary DNA single-strands and their hybridization into the famous helicoidally structure, self-assembling of gold nanoparticles into highly ordered micrometer scale crystals has been demonstrated. The aim of this thesis is to explore this new nanotechnology for the self-assembly of Al and CuO nanoparticles driven by DNA hybridization into highly energetic nanocomposites by optimizing contact surfaces between reducer (Al) and oxidizer (CuO). We chose Streptavidin-biotin strategy to functionalize nanoparticles with DNA single strands. More precisely, the functionalization process includes four steps: (i) stabilization of Al and CuO nanoparticles into separate colloidal suspensions; (ii) Streptavidin grafting on Al and CuO nanoparticles; (iii) DNA grafting on Al and CuO Streptavidin-modified nanoparticles thanks to the addition of biotin function at the end of the DNA single strands; (iv) mixing of the two colloidal DNA-functionalized suspensions in order to realize the self-assembly. First, we precisely determined, characterized and optimized each step of the functionalization process. Then, we studied more precisely two key points of the process: we analyzed the interaction of DNA bases with technologically relevant oxide surfaces by studying the grafting of Thymidine by theoretical and experimental approaches; and we studied the influence of the coding sequence used for the DNA strands on the quality of the self-assembly, also by theoretical and experimental analyses. Finally, we optimized environmental conditions to realize the self-assembly of DNA-functionalized nanoparticles into energetic nanobiocomposites. Morphologies and energetic properties were established as a function of synthesis conditions, and the control of energetic performances of nanobiocomposites as a function of aggregation process was demonstrated.Les nanotechnologies ADN utilisées pour l’auto-assemblage de nanoparticules d’or ou de métaux nobles ont connu un important développement au cours des vingt dernières années, permettant l’organisation de particules agencées en nano-cristaux, grâce à la reconnaissance biologique inégalable de deux brins complémentaires d’ADN. L’objectif de ces travaux de thèse est d’adapter ces nanotechnologies à l’assemblage de nanoparticules d’Al et de CuO en vue d’élaborer des matériaux composites énergétiques à haute performance, grâce à l’augmentation des surfaces en contact entre réducteur (Al) et oxydant (CuO) par la maîtrise de l’organisation spatiale des nanoparticules. Ainsi, la fonctionnalisation séparée des nanoparticules d’Al et de CuO dispersées en solution colloïdale par des monobrins d’ADN complémentaires doit amener, après mélange des deux solutions colloïdales, à l’agrégation des particules par l’hybridation des brins d’ADN greffés en surface. La stratégie de fonctionnalisation choisie ici est générique : la protéine « Streptavidine » est d’abord greffée sur la nanoparticule, puis le brin d’ADN fonctionnalisé par un groupe biotine à une de ses extrémités, se fixe sur la Streptavidine. Au-delà de l’organisation de la matière à l’échelle nanométrique, l’enjeu double de ces travaux tient dans l’établissement d’un protocole de fonctionnalisation fiable et reproductible, propre aux procédés de micro-électronique, pour envisager un report de ces matériaux sur puce, mais également dans le contrôle des performances énergétiques grâce à l’ADN. Nous avons tout d’abord étudié l’interaction entre les bases de l’ADN et la surface des particules afin d’identifier les interactions non-spécifiques pouvant provoquer une agrégation non-maîtrisée. Dans un second temps, nous nous sommes appliqués à élaborer le protocole en caractérisant précisément chaque étape de fonctionnalisation. Nous avons ensuite étudié l’agrégation des particules fonctionnalisées en fonction de nombreux paramètres expérimentaux telles que la longueur de la chaîne ADN, la séquence de l’oligonucléotide, ou encore la composition saline de la solution. A cause de l’existence d’interactions non-spécifiques, nous avons optimisés ces paramètres de façon à assurer une agrégation dirigée uniquement par l’hybridation des brins d’ADN et améliorer ainsi de façon conséquente l’organisation spatiale des particules et les performances énergétiques des matériaux synthétisés. Enfin, nous avons démontré la possibilité de contrôler les performances énergétiques des nanobiocomposites en maîtrisant leur microstructure grâce à l’ADN

Correlation between DNA Self-Assembly Kinetics, Microstructure, and Thermal Properties of Tunable Highly Energetic Al–CuO Nanocomposites for Micropyrotechnic Applications

International audienceThe association of a metallic fuel (usually aluminum) with an oxidizer (metal oxide or organic compound) creates an exothermic material that can be ignited with an external stimulus such as local heating or spark discharge. These materials with high energetic performances, called nanothermites, have been used to release temperature or pressure waves for civil or military applications (initiators, impact igniters, etc.). However, the energetic performances of these nanothermites are highly dependent on the nanoscale intimacy of the two components. The use of nanoparticles results in an increase of the energy release, but control of their assembly remains particularly challenging. In this work, we demonstrate that the use of DNA to self-organize Al or CuO nanoparticles greatly enhances the energy release of nanothermites by up to 240% compared to classically sonicated nanothermites in hexane, with the heat of reaction prior to Al melting reaching a value of 2.57 kJ·g–1. In particular, we report that the energetic performances can be tuned by controlling the ionic strength during the self-assembly process. These results are supported by ultrafine characterization of the nanocomposite microstructure based on high-resolution transmission electronic microscopy and energy-dispersive X-ray spectroscopy. Besides, we report the surprisingly good energetic performances of randomly mixed nanoparticles dispersed in water, nonetheless 40% lower than DNA-self-assembled nanocomposites. Altogether, our study not only proposes an easy and immediate process for nanocomposites synthesis but also opens the door for opportunities toward large-scale crystalline Al–CuO superlattices with high energetic performances

DNA grafting and arrangement on oxide surfaces for self-assembly of Al and CuO nanoparticles

International audienceDNA-directed assembly of nano-objects as a means to manufacture advanced nanomaterial architectures has been the subject of many studies. However, most applications have dealt with noble metals as there are fundamental difficulties to work with other materials. In this work, we propose a generic and systematic approach for functionalizing and characterizing oxide surfaces with single-stranded DNA oligonucleotides. This protocol is applied to aluminum and copper oxide nanoparticles due to their great interest for the fabrication of highly energetic heterogeneous nanocomposites. The surface densities of streptavidin and biotinylated DNA oligonucleotides are precisely quantified combining atomic absorption spectroscopy with conventional dynamic light scattering and fluorimetry, and maximized to provide a basis for understanding the grafting mechanism. First, the streptavidin coverage is consistently below 20% of the total surface for both nanoparticles. Second, direct and unspecific grafting of DNA single strands onto Al and CuO nanoparticles largely dominates the overall functionalization process

General Strategy for the Design of DNA Coding Sequences Applied to Nanoparticle Assembly

International audienceThe DNA-directed assembly of nano-objects has been the subject of many recent studies as a means to construct advanced nanomaterial architectures. Although much experimental in silico work has been presented and discussed, there has been no in-depth consideration of the proper design of single-strand sticky termination of DNA sequences, noted as ssST, which is important in avoiding self-folding within one DNA strand, unwanted strand-to-strand interaction, and mismatching. In this work, a new comprehensive and computationally efficient optimization algorithm is presented for the construction of all possible DNA sequences that specifically prevents these issues. This optimization procedure is also effective when a spacer section is used, typically repeated sequences of thymine or adenine placed between the ssST and the nano-object, to address the most conventional experimental protocols. We systematically discuss the fundamental statistics of DNA sequences considering complementarities limited to two (or three) adjacent pairs to avoid self-folding and hybridization of identical strands due to unwanted complements and mismatching. The optimized DNA sequences can reach maximum lengths of 9 to 34 bases depending on the level of applied constraints. The thermodynamic properties of the allowed sequences are used to develop a ranking for each design. For instance, we show that the maximum melting temperature saturates with 14 bases under typical solvation and concentration conditions. Thus, DNA ssST with optimized sequences are developed for segments ranging from 4 to 40 bases, providing a very useful guide for all technological protocols. An experimental test is presented and discussed using the aggregation of Al and CuO nanoparticles and is shown to validate and illustrate the importance of the proposed DNA coding sequence optimization. ■ INTRODUCTION The interest in DNA nanotechnology to program the assembly of nanoparticles into macroscopic nanocomposites emerged in the 1990s. 1,2 Undoubtedly, the controlled interplay of DNA complementary and noncomplementary strands made DNA nanotechnologies one of the most powerful bottom-up approaches to building hierarchical architectures of nano-objects (noble metals, semiconductors, oxides, and polymers) leading to an almost infinite variety of high-performance programmable DNA/nanoparticles hybrid materials. One mainstream DNA-based assembly approach consists of directing the assembly of colloids of interest, mostly gold nanoparticles, by taking advantage of the thiol/metal chemistry 3 to covalently attach DNA strands to nanoparticle surfaces. Other chemical alternatives have also been investigated , such as antigen/antibody-like binding. 4,5 Since the seminal work by Alavisatos and Mirkin 1,2 on gold nanoparticles, many DNA/nanoparticle assembly processes have been reported, notably by varying the DNA length and processing conditions and with a consideration of other materials for applications in catalytics, 6 spectroscopy, 7−10 optical devices

Role of Alumina Coatings for Selective and Controlled Bonding of DNA on Technologically Relevant Oxide Surfaces

International audienceDNA immobilization on surfaces is crucial to a number of applications. However, detailed understanding of DNA/surface chemistry remains poorly documented, especially on oxide surfaces, due to the complexity of such large molecules. This work focuses on a simpler molecule, 2-deoxythymidine-5-monophosphate (dTMP), which contains all the chemical elements of DNA. It confirms that adsorption of dTMP onto OH-terminated SiO2 surfaces does not result in a chemical bond (dTMP readily washes off) and instead shows that dTMP chemically adsorbs on Al2O3 surfaces. We combine first-principles calculations, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy to determine the bonding configuration of dTMP onto alumina surfaces controllably grown by atomic layer deposition. We demonstrate that dTMP covalently reacts with alumina. Calculations indicate that covalent bonding of all dTMP polar groups (sugar ring, phosphate group, and thymine) is thermodynamically favored. Spectroscopic data and theory-based assignments of vibrational modes show that the bonding takes place primarily through both the thymine and phosphate groups. The reactivity and the tendency for dTMP to lie flat on the surface lead to an irreversible and disorganized dTMP layering. Studies of dTMP adsorption as a function of Al2O3 thickness show that the density of grafted dTMP can be controlled, with measurable amounts even above the Al2O3 monolayer coverage. These findings provide technological directions for DNA-based nanotechnologies to graft DNA on surfaces that would otherwise be unreactive