Pure inorganic nanoparticles without ligands or stabilizers fabricated by laser ablation in liquid are promising materials for energy converting materials like heterogeneous catalysts or hydrogen storage materials [1]. Especially in case of heterogeneous catalysts, common preparation techniques like impregnation or colloidal deposition are usually accompanied by extensive use of chemical precursors, stabilizers and ligands that may result in catalysts poising. In our recent work, we showed how to laser-fabricate colloidal stable and size-controlled nanoparticles made of catalytic active materials (e.g. Pt, Pd, Ni) and its integration to catalytic supports in a subsequent step. For this purpose, an intensive pulsed laser beam is focused onto an immersed target of chosen nanoparticle material (see Fig. 1, left). We show how properties of pure, colloidal nanoparticles like particle size and colloidal stability can be controlled by the use of saline solutions [2,3].

These laser-fabricated particles are supported to carrier structures like metal oxides and carbon allotropes for synthesis of heterogeneous catalysts (see Fig. 1, right). Using the model system of platinum nanoparticles and titania support, we demonstrate that the nanoparticle adsorption is dominantly controlled by electrostatic interactions [4]. This attractive electrostatic interaction even overcompensates steric repulsion by various ligands attached to nanoparticle surface. In addition to electrostatic interactions, colloidal stability given by moderate ionic strengths and pH above isoelectric point of nanoparticles is a prerequisite for colloidal deposition. Further, we show how nanoparticles interact with the support material using X-ray photoelectron spectroscopy. First tests of laser-generated nanomaterials proved its catalytic activity and application potential.  

[1] S. Barcikowski, G. Compagnini, Advanced nanoparticle generation and excitation by lasers in liquids, Phys. Chem. Chem. Phys. 5, 3022 (2013).[2] V. Merk, C. Rehbock, F. Becker, U. Hagemann, H. Nienhaus, S. Barcikowski, In Situ Non-DLVO Stabilization of Surfactant-Free, Plasmonic Gold Nanoparticles: Effect of Hofmeister’s Anions, Langmuir 30, 4213 (2014).[3] G. Marzun, J. Nakamura, X. Zhang, S. Barcikowski, P. Wagener, Size control and supporting of palladium nanoparticles made by laser ablation in saline solution as a facile route to heterogeneous catalysts ,Applied Surface         Science 2015 (accepted, DOI: 10.1016/j.apsusc.2015.01.108) [4] G. Marzun, C. Streich, S. Jendrzej, S. Barcikowski, P. Wagener, Adsorption of Colloidal Platinum Nanoparticles to Supports: ChargeTransfer and Effects of Electrostatic and Steric Interactions, Langmuir 30, 11928 (2014).