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Nanostructures hybrides plasmoniques assemblées sur des origamis d’ADN stimulables

Abstract : Combining gold nanoparticles and synthetic DNA nanostructures is particularly attractive: on the one hand, gold particlesexhibit a combination of exceptional optical properties - allowed by their plasmon resonances - and physico-chemicalstability; while DNA nanotechnology provides an extremely rich toolbox to design nanoscale actuators whose morphologycan be actively and specifically modulated. It is then possible to program the assembly of complex hybrid nanostructures whose optical properties are sensitive, at the single structure level, to pre-selected physicochemical stimuli.During this thesis, I developed synthesis methods to produce dimers of 40 nm gold nanoparticles assembled around dynamic DNA origamis; but also, experimental tools to characterize their optical properties at the single nanostructure level. These Y-shaped DNA origamis are designed in such a way that their morphology can be modified by various external stimuli: interaction with specific DNA strands, pH modulation or recognition of a chemical analyte (organicmolecule or specific cation). This conformation change leads to a modification of the distance between the two goldparticles, each placed on one arm of the Y: the modification of the plasmon coupling strength can then be detected, foreach dimer, by scattering spectroscopy or on a simple color camera.These experimental developments have allowed me to study and optimize these hybrid nanostructures in order to correlate their plasmon resonances with the conformation of the DNA origami. In particular, I studied the dependence of these optical properties when modulating the local ionic strength, the pH but also by shifting the shape of the origami. This deformation is produced either by a DNA strand displacement reaction or by folding a DNA quadruplex at low pH (i-motif),demonstrating the versatility of these DNA nanoactuators. In practice, I observed that the morphology of the dimers issensitive both to the conformation of the origami and to interactions between the gold nanoparticles that are probablyof an electrostatic nature. This work opens many perspectives for the design of intelligent optical contrast agents or to develop nanosensors, visible with the naked eye, and compatible with single molecule detection.
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Elise Gayet. Nanostructures hybrides plasmoniques assemblées sur des origamis d’ADN stimulables. Physique [physics]. Université Paris sciences et lettres, 2021. Français. ⟨NNT : 2021UPSLS054⟩. ⟨tel-03361374⟩

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