We investigate the effects of ambient gas on the expansion dynamics of laser plume produced during femtosecond laser ablation of a metallic target. We studied experimentally plume propagation for ambient air pressure ranging from 10−6 to 50 mbar, observing that the atomic and nanoparticles plume components experience different effects.We interpret these results with a simplified model of the plume front propagation, which is able to fully reproduce the main experimental features. Our results allow us to estimate quantitatively the nanoparticles plume content up to about 80%, and can help identifying optimal conditions of nanoparticles deposition for thin films production
A Co-catalyzed highly regio- and
enantioselective reductive coupling
of alkynes and aldehydes has been developed under visible light photoredox
dual catalysis. A variety of enantioenriched allylic alcohols have
been obtained by using unsymmetrical internal alkynes and commercially
available catalyst, chiral ligand, and reagents. It is noteworthy
that this approach has considerable advantages, such as excellent
regio- (>95:5 for >40 examples), stereo- (up to >95:5 E/Z), and enantioselectivity (92–99%
ee, >35
examples) control, mild reaction conditions, broad substrate scope,
and good functional group compatibility, making it a great improvement
to enantioselective alkyne–aldehyde reductive coupling reactions.
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