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In-Situ STEM Analysis of Gold Nanoparticles to Understand Nu-cleation and Crystal Growth

Abstract : Liquid state transmission electron microscopy is a recent te-chnique allowing researchers to visualize the nanoparticles dire-ctly in their liquid environment. Accurate visualization of growth in small nanoparticles is desired yet a challenging process due to limited resolution obtained due to surfactant present in the sys-tem. In this work, by using liquid environmental cell specimen holder (e-cell), developed for scanning transmission electron microscopy, we were able to monitor the formation of anisotropic gold nanoparticles from small precursors (< 7 nm) in surfactant assisted media, under electron beam. Technique offers the possi-bility to probe nanoparticles in-situ and to obtain detailed infor-mation on how nanoparticles grow in solution. However, under electron beam irradiation, due to radiolysis of water, some radicals are produced which can interact with the reactants and modify the chemical processes. Such phenomenon has to be considered during in-situ STEM analysis. In case of gold, this prior drawback can also be used to control the reaction. In our work, the incident electron beam was chosen to achieve two tasks simultaneously; first, as a radiation source to induce the radiolysis of water (whi-ch is responsible for the reduction of gold precursor) and the se-cond, it allows the real time imaging of particles of interest in a thin layer of liquid. Initially, we have described influences of the beam parameters and the chemical conditions on the final shape of nanoparticles. Between these parameters, in case of altering the magnification (i.e. the dose rate), we have observed major diffe-rences in the shape of final nanoparticles obtained. Regarding to these differences, following formation mechanism has been pro-posed; at low dose rate, few number of produced seeds are able to grow into branched nanoparticles due to slow kinetics, caused simultaneously by slow ascorbic acid reduction at the surface of the nanoparticles and low number of radicals induced by electron beam, while at higher dose rate, the concentration of strong redu-cing agent is so high that the alimentation of the seeds will certa-inly proceed initially by fast feeding by pre-reduced Au(0) due to aqueous electrons and strong reducing agent and the slow feeding due to ascorbic acid reduction at the surface of the particles. Additionally, the structure of final nanoparticles obtained by in-situ STEM and by gamma irradiation source (at similar chemical com-positions) is compared to demonstrate the crucial importance of beam parameters on nanoparticle morphology.
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Submitted on : Wednesday, October 23, 2019 - 3:43:57 PM
Last modification on : Monday, September 7, 2020 - 11:44:03 AM
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Cansu Zeliha Canbek Özdil, Fabienne Testard, Damien Alloyeau, Guillome Wang, Christian Ricolleau, et al.. In-Situ STEM Analysis of Gold Nanoparticles to Understand Nu-cleation and Crystal Growth. EuroAnalysis 2019, Sep 2019, Istanbul, Turkey. ⟨10.1016/j.fct.2019.03.030⟩. ⟨cea-02329485⟩



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