  Upgrading the productivity of nanoparticles (NPs), generated by pulsed laser
ablation in liquid (PLAL), still remains challenging. Here a novel variant of
PLAL was developed, where a doubled frequency Nd:YAG laser beam (532 nm, ~ 5
ns, 10 Hz) at different fluences and for different times was directed into a
sealed vessel, toward the interface of the meniscus of ethanol with a tilted
bulk metal target. Palladium, copper and silver NPs, synthesized in the
performed proof of concept experiments, were mass quantified, by an inductively
coupled plasma optical emission spectrometry, and characterized by
ultraviolet-visible extinction spectroscopy, transmission electron microscopy
and X-ray diffraction. The NPs consist of crystalline metals of a few nm size
and their ablation rates and agglomeration levels depend on the employed laser
fluences. The ensuing laser power-specific productivity curves for each metal,
peaked at specific laser fluences, were fitted to the results of a simple model
accounting for plasma absorption and heat transfer. The resulting peaked yields
and concentrations were more than an order of magnitude higher than those
obtained for totally immersed targets. Besides, the measured productivities
showed nearly linear dependencies during time intervals up to 30 min of
ablation, but became saturated at 1 h, due to accumulation of a significant
number of NPs along the laser beam path, reducing the laser intensity reaching
the target. This suggested approach could inspire future studies that will
contribute to further developments of efficient generation of NPs with
controlled characteristics.
