N. Lasemi, Ch. Rentenberger, R. Pospichal, A. Cherevan, M. Pfaffeneder-Kmen, G. Liedl, D. Eder:
"Femtosecond laser-assisted synthesis of Ni/Au BONs in various alcoholic solvents";
Applied Physics A: Materials Science & Processing,
Crystalline Ni/Au bimetallic oxide nanoparticles with various forms of crystallographic systems and defects were generated by femtosecond laser ablation of nickel-gold target in alcoholic solvents. The nature of the liquid can influence the chemical composition, stability, and size distribution of laser-synthesized nanoparticles. In ethanol, bimodal crystalline bimetallic Ni/Au oxide nanoparticles with median size of 15 nm were synthesized. The laser ablation of Ni/Au target in isopropanol and butanol led to nearly monomodal size distribution with median size of 10 and 13 nm, respectively. High-resolution transmission electron microscopy of Ni/Au oxide nanoparticles in butanol, revealed a graphitic shell of a few atomic layers. In this context, two suggested mechanisms were considered. First of all, the high photon intensity of femtosecond laser pulses can induce direct photolysis of liquid media. Secondly, the formation of supercritical temperature solvent due to the interaction of solvent with molten metal layer at liquid-metal interface can trigger pyrolysis of solvent. These mechanisms can contribute to butanol decomposition and encapsulation of Ni/Au oxide bimetallic nanoparticles with graphite shell. Graphite shell can create a better colloidal stability by preventing nanoparticles from further growth and agglomeration.
Ultrafast lasers, nanoparticles
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