Grand Séminaire d'Institut

Vendredi 22 Septembre 2017 à 11h00.

Tailoring nanostructures by supersonic cluster beam deposition and non-thermal laser ablation

''Nanostructures are strategic for heterogeneous catalysis [1], medicine [2], or nanojoining [3] and single or multi-element nanoparticles (NPs) provide a wide spectrum of possibilities to tune the system properties [4], also when embedded in a host dielectric matrix. Moreover, when the NPs are synthesized in a wet environment [5], formation of a NP-coating often requires time-consuming multi-step post-synthesis processes, cross-linking growth, colloidal stabilizers, or substrate functionalization. Hence tailoring the properties of such systems is very challenging. Flexible alternative synthesis routes providing direct deposition are pulsed laser ablation [6] and supersonic cluster beam deposition (SCBD) [7]. Recently, NP-based ultrathin films have been proposed to limit cross contamination of bacteria in hospital settings [8,9]. However, tailoring the coating morphology, elemental composition and properties still presents several open issues. In this context SCBD and femtosecond (fs) pulsed laser deposition (fs-PLD) [10] are used to tailor NPs and NP-based coatings. For Ag and Ag/Ti bi-element NPs, SCBD is used to directly grow bactericidal coatings on different substrates. The Ag films are higly bactericidal [7], presenting mechanical properties related to the film porosity. The Ag/Ti bi-element NPs are forming a coating characterized by metallic Ag NP into an amorphous TiO2 matrix, with tunable relative Ag/Ti concentration, coating thickness and Ag NP size. Formation of similar structures with embedded NPs is obtained for the Mg/Cu/Ag tri-element system. Employing ambient pressure fs-PLD, fractal TiO2 crystalline nanostructures are forming at room temperature on silicon, quartz and graphite substrates. Moreover, we rationalize the fractal formation mechanism and the role of substrate conductivity by comparing the experimental results with Monte Carlo simulations of NP diffusion. References [1 ] A. Kubacka, M. Fernández-García, G. Colón, Chem. Rev. 112 (2012) 1555. [2 ] J.T. Seil, T.J. Webster, Inter. J. Nanomedicine 7 (2012) 2767. [3 ] J. Janczak-Rusch, et al., Physical Chemistry Chemical Physics 17, 28228 (2015) [4 ] Hu G, et al., Nat. Commun. 5 (2014) 5253 [5 ] Wang D, Li Y, Adv Mater 23 (2011) 1044 [6 ] M. Sanz et al., Appl. Phys. A 101 (2010) 639. [7 ] M. Chiodi, et al., J. Phys. Chem. C 116 (2012) 311. [8 ] E. Cavaliere et al., Nanomedicine: Nanotech. Biol. and Med. 11 (2015) 1417 [9 ] G. Benetti et al. APL Materials 5, 036105 (2017) [10] E. Cavaliere, G. Ferrini, P. Pingue, L. Gavioli, J. Phys. Chem. C 117 (2013) 23305-23312.''