Single-Step Aerosol-Assisted Atmospheric Pressure Plasma Deposition of Hybrid Nanocomposite Thin Films Containing Gold Nanoparticles

Low-temperature atmospheric pressure plasma technologies offer exciting opportunities for the preparation of hybrid nanocomposite (NC) layers consisting of inorganic nanoparticles (NPs) embedded into an organic matrix [1]. To this end, recently, a growing number of studies have explored the combination of atmospheric pressure plasmas with preformed NPs dispersions in aerosol form. However, this deposition strategy raises various problems, such as the risk associated with NPs handling as well as the severe NPs agglomeration in the NC thin films. Therefore, intense efforts are currently dedicated to optimizing safe-by-design deposition processes in which the nanocomposite constituents are synthesized in a single step in the atmospheric pressure plasma [3].<br/>It is in this context that, as suggested by previous work [3], we propose to combine a parallel-plate dielectric barrier discharge plasma at atmospheric pressure with the aerosol of the solution of a gold salt (tetrachloroauric(III) acid trihydrate, HAuCl₄●3H₂O) in a polymerizable liquid precursor (isopropanol), to be able to synthesize in a single step nanocomposite layers. This innovative process avoids the handling of nanoparticles since the gold salt reduction to form Au nanoparticles occurs in the plasma along with the growth of the organic matrix [3].<br/>The chemical composition, morphology, and optical properties of the resulting NC thin films have been investigated using various techniques, such as Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and UV-visible absorption spectroscopy.<br/>Preliminary results have shown that we can synthesize in a single step a hybrid nanocomposite coating composed of gold nanoparticles embedded in an organic matrix deriving from the plasma polymerization of isopropanol. The influence of different experimental parameters, such as the solution composition and the electrical discharge conditions (applied voltage waveform, excitation frequency, etc.) have been studied. In particular, a dual frequency excitation is used to control the nanocomposite composition and morphology [4]. Indeed, the transport of the nanoparticles to the sample surface is mainly related to the electrostatic forces and therefore requires a low excitation frequency; in contrast, the matrix polymerization and the gold salt reduction need a higher plasma energy and thus a higher frequency.<br/>Overall, these results provide new insights into the possibility of using a single-step aerosol-assisted plasma process to deposit hybrid nanocomposite thin films containing gold nanoparticles and into the ability to finely tune the properties of the layers by varying the process parameters.<br/><br/>Acknowledgments<br/>The authors would like to acknowledge financial support from the Agence Nationale de la Recherche (PLASSEL Project, ANR-21-CE08-0038, France).<br/><br/>References<br/>[1] A. Uricchio and F. Fanelli, Processes 9, 2069 (2021).<br/>[2] J. Profili <i>et al.</i>, Plasma Processes and Polymers 13, 981 (2016).<br/>[3] E. Nadal <i>et al.</i>, Nanotechnology 32, 175601 (2021).<br/>[4] P. Brunet <i>et al.</i>, Plasma Processes and Polymers 14, 1700049 (2017).