Analysis of the formation of $sp$-carbon chains by pulsed laser ablation in liquid through $in situ$ UV resonance Raman spectroscopy.

Polyynes are 1D systems consisting of linear chains made of $sp$-hybridized carbon atoms. Their outstanding predicted properties attracted the interest of material scientists over the last decades. Vibrational spectroscopy emerged as a fundamental tool to investigate these properties. Indeed, polyynes are characterized by a Raman-active collective vibration which is strongly influenced by chain structural and electronic properties. Pulsed laser ablation in liquid (PLAL) turned up as the most efficient and versatile physical method to synthesize polyynes. However, the formation of polyynes during PLAL is still unclear. Thus, we investigated the synthesis of polyyne by PLAL through synchrotron-based $in situ$ UV resonance Raman spectroscopy. Thanks to the resonance condition and the tunability of the synchrotron radiation, we could track the entire evolution of the formation of polyynes with an improved time resolution. We found that the synthesis yield is higher in solvents with a high C/H ratio and low polarity, increases with the laser energy and we discovered a threshold fluence when ablating at $1064 {nm}$. We evaluated the production of single shots and the diffusion mechanisms.