| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThA |
| Session: | Plasma Processing of Nanoparticles and Nanomaterials |
| Presenter: | Caroline De Vos, Université libre de Bruxelles, Belgium |
| Authors: | C. De Vos, Université libre de Bruxelles, Belgium J. Baneton, Université libre de Bruxelles, Belgium J. Dille, Université libre de Bruxelles, Belgium S. Godet, Université libre de Bruxelles, Belgium M. Sankaran, Case Western Reserve University F.A.B. Reniers, Université libre de Bruxelles, Belgium |
| Correspondent: | Click to Email |
Microscale plasmas are electrical discharges where at least one geometrical dimension is sub-millimetric. In consequence, they present a remarkable stability at high pressure as reducing the size of the plasma allows keeping breakdown voltages sufficiently low to avoid the glow-to-arc transition. [1] The development of non-thermal atmospheric pressure microplasmas facilitates the coupling with the liquid phase and offers new potential applications in water treatment, medicine and material synthesis. [2]
This study focuses on the synthesis of silver and gold nanoparticles in aqueous solution. The plasma, supplied with argon, is initiated at the surface of silver nitrate or chloroauric acid solution. The electrons from the discharge lead to electrochemical reactions and reduction of the metal cations. Different stabilizers such as polyvinyl alcohol and sodium dodecyl sulfate are mixed with the solution to prevent uncontrolled particle growth.
X-ray photoelectron spectroscopy (XPS) spectra exhibit the metallic nature of the Ag and Au nanoparticles and particles growth is monitored by ultraviolet-visible absorbance spectroscopy. The two plasmon bands, characteristic of spherical Ag and Au nanoparticles, can be observed at 415 and 530 nm respectively. The morphology and the size of as-grown colloidal metal nanoparticles are evaluated by transmission electron microscopy (TEM). For silver nanoparticles, the average size rises from 10 to 20 nm when the discharge current increases from 2 to 5 mA. Moreover, bigger nanoparticles are observed at higher concentration and reaction times. For gold experiments, particles about 10 nm in diameter are synthesized at higher current than for silver experiments. Lower precursor concentration is necessary to avoid aggregates formation. In both cases, particles below 20 nm are spherical whereas at larger diameters, various shapes such as triangle, hexagon, appear.
In the project continuity, a comparison of the reduction mechanisms is performed for the two studied metals. At first, the proportion of reduced metal cations is quantified by potentiometric analyzes. Thereafter, the active species involved in the reduction process (e.g., H2O2, electrons) are discriminated. Finally, a bimetallic synthesis is studied to help the comprehension of the fundamental mechanisms. Indeed, metal ratio and alloy formation provide information about the reduction kinetic of both metals.
This work is supported by PSI-IAP 7 (plasma surface interactions) from the Belgian Federal Government BELSPO agency.
References
[1] D. Mariotti, Appl. Phys. Lett. 92 (2008) 151505.
[2] D. Mariotti, R. M. Sankaran, J. of Phys. D: Appl. Phys. 44 (2011), 174023.