Nanostructure synthesis by supersonic cluster beam deposition and non-thermal laser ablation
Nanostructures are strategic in many technologically important areas like heterogeneous catalysis [1-3], photo-assisted oxidation , and medicine . Physical methods alternatives to the wet synthesis of nanoparticles (NP) are pulsed laser deposition (PLD) using nanosecond (ns) laser pulses [6,7] and supersonic cluster beam deposition (SCBD) [8,9]. Very recently, few nm-thick coatings composed of NP have been proposed to limit cross contamination of bacteria in hospital settings . However, in view of obtaining a coating with controlled morphology and properties, several issues on NPs synthesis, composition, NP/substrate interaction and adhesion to substrate have to be solved.
Here we tackle some of the open problems by presenting the results obtained in the synthesis of NP and coating deposition by two physical synthesis methods, SCBD and femtosecond (fs) pulsed laser deposition (fs-PLD) , where the material ablation mechanism is differing from the ns-PLD counterpart . In the former we employed SCBD to synthesize bactericidal coatings based on Ag and Ag/Ti bi-metal NP directly on the surface of different substrates, characterizing the physical and the bactericidal properties of the coating. In the latter we show that ambient pressure fs-PLD allows to obtain fractal TiO2 nanostructures in crystalline form at room temperature on silicon substrates. Moreover, we rationalize the fractal formation mechanism and the role of substrate conductivity by comparing the experimental results with Montecarlo simulations of NP diffusion. The perspectives and possible applications of such methods will be discussed.
 D.W. Flaherty et al. J. Phys. Chem. C 111 (2007) 4765.
 I.N. Remediakis, N. Lopez, J.K. Norskov, Angew. Chem., Int. Ed. 44 (2005) 1824.
 A. Kubacka, M. Fernández-García, G. Colón, Chem. Rev. 112 (2012) 1555.
 C.G. Wu, C.C. Chao, F.T. Kuo, Catalysis Today 97 (2004) 103.
 J.T. Seil, T.J. Webster, Inter. J. Nanomedicine 7 (2012) 2767.
 M. Filipescu et al., Appl. Surf. Sci. 253 (2007) 8258.
 M. Sanz et al., Appl. Phys. A 101 (2010) 639.
 E. Barborini, et al. Appl. Phys. Lett. 81 (2002) 3052.
 M. Chiodi, et al., J. Phys. Chem. C 116 (2012) 311.
 E. Cavaliere et al., Nanomedicine: Nanotech. Biol. and Med. 2015, 11, 1417
 E. Cavaliere, G. Ferrini, P. Pingue, L. Gavioli, J. Phys. Chem. C 117 (2013) 23305-23312.
 P. Lorazo, L. J. Lewis, M. Meunier, Phys. Rev. B 73 (2006) 134108.