  Polyynes are finite chains formed by sp-hybridized carbon atoms with
alternating single and triple bonds and displaying intriguing electronic and
optical properties. Pulsed laser ablation in liquid (PLAL) is a well assessed
technique for the physical synthesis of hydrogen-capped polyynes in solution,
however, their limited stability prevents further exploitation in materials for
different applications. In this work, polyynes in poly(vinyl alcohol) (PVA)
were produced in a single-step PLAL process by ablating graphite directly in
aqueous solution of PVA, investigating the role of polymer concentration. The
presence of PVA solution, as a participating medium for PLAL, is shown to
favour the formation of polyynes. The addition of Ag colloids to the aqueous
PVA/polyynes solution allowed surface-enhanced Raman spectroscopy (SERS)
measurements, carried out both on liquid samples and on free-standing
nanocomposites, obtained after solvent evaporation. We show that polyynes in
the nanocomposite remain stable at least for 11 months, whereas the
corresponding PVA/Ag/polyynes solution displayed a strong polyyne reduction
already after 3 weeks. These results open the view to further characterizations
of the properties of polyyne-based films and materials.
